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## Free energy composition curves

In the free energy formula of Eq (7.36), nonideality is expressed by the general form gex, the excess free energy. The simplifications used in the prior analyses of ideal melting and phase separation, namely neglecting sex and confining hex to the regular-solution model, are not valid for most binary systems. In order to construct phase diagrams by the common-tangent technique, more elaborate solution models are needed to relate free energy to composition for all likely phases. Figure 8.9 shows plots of g Vs xB for the three phases at six temperatures, with T6 the highest and T1 the lowest. In the six graphs, the curves for each phase keep approximately the same shape but shift relative Fig. 8.9 Free energy composition curves for an A-B binary system with two solid phases (a and P) and a liquid phase (From Ref. 1) Fig. 8.9 Free energy composition curves for an A-B binary system with two solid phases (a and P) and a liquid phase (From Ref. 1) The subsequent rise in free energy of the...

## Excess Gibbs free energy and the entropy of mixing

As in Eq (7.21) for the enthalpy, the molar Gibbs free energy of a solution (g) can be written in terms of pure-component contributions (gA and gB) and an excess value (gex). However, an important contribution needs to be added. For a binary solution, the terms contributing to g are

## Standard Free Energy of Formation

Even though the thermochemical database need contain only AGo (or, equivalently, AHo and ASo), the number of reactions that would have to be included in such a compilation is intractably large. The key to reducing data requirements to manageable size is to provide the standard free energy changes of forming the individual molecular species from their constituent elements. Particular reactions are constructed from these so-called formation reactions. For molecular compounds containing two or more elements, the basic information is the Free energy change for reactions by which the compound is created from its constituent elements, the latter in their normal state at the particular temperature. These reaction free energy changes are called standard free energies of formation of the compound. For example, the methane combustion reaction of Eq (9.1) involves one elemental compound (O2) and three molecular compounds (CH4, CO2, and H2O). The formation reactions for the latter and their...

## Chapter Solar Energy

Enthusiasts for solar power need to be reminded that, through its role in photosynthesis and in powering the atmosphere, the Sun is already our primary source of renewable energy. Or to put it another way solar photons convert naturally into chemical fuel and heat.1 Photosynthesis yields biomass which can serve as fuel and food and it creates ATP, the main source of energy for living things and thus their muscles. In the process it liberates the oxygen required by most kinds of combustion Solar heat sets up the differences in temperature and pressure that propel wind and waves and by providing rainfall and melting snow it generates the mechanical energy that drives water mills and their hydroelectric successors. Yet as a direct source of energy the Sun contributed only 0.04 .The figure probably underestimates current use, especially as many consumers of solar energy are found in isolated locations, such as cattle ranches and the Space Station, where power generation on a small scale...

## Solar power

The design of solar power systems for landers has significantly different constraints from those for conventional satellites. First, environmental disturbances such as gravity mean the gossamer structures used on the large arrays (which often cannot bear their own weight), now common for satellites, cannot be used - there are therefore severe mass penalties for solar arrays with dimensions much larger than the body of the vehicle itself. Secondly, the orientation of the arrays with respect to the Sun is likely to be controlled by the Figure 9.4. Solar power available on an airless planet at 1 AU from the Sun (S 1340 Wm 2) as a function of time, spacecraft latitude (0) and solar declination (< 5, i.e. latitude of the subsolar point). Solid line is for both the Sun and the lander at the equator giving a 12 hour day. The dotted line shows a lander on the equator during summer or winter, with the Sun 25 away from the equator. With a polar lander (0 76 ) the power can be zero all day...

## Passive solar power

Passive solar power refers to the use of the Sun's energy to heat or cool a building without any mechanical or electrical assistance. The key is to use the right materials, to site the building correctly and to plan the layout in order to promote or inhibit air circulation according to the needs of the moment. Growing numbers of modern buildings demonstrate how passive solar power can add flair to and subtract costs from tower blocks as well as family homes. Early practitioners include George Fred Keck and William Keck, who used air vents and wide eaves to ventilate and cool a number of private homes in the Chicago area in the 1930s, 1940s and 1950s. The first commercial office building with solar water heating and passive design is attributed to Frank Bridgers. The building, now known as the Bridgers-Paxton building and erected in Albuquerque, New Mexico, in 1956, was heated by a solar collector angled at 30 and facing S backed by insulated water heaters and heat pumps which could...

## Photovoltaics

The photovoltaic (PV) plant ancillary to the Sanlucar tower, as we saw, also uses solar energy concentrated by tracking mirrors. Photovoltaic (PV) systems are more versatile but at present substantially more expensive to install than solar heating systems. They convert sunlight to electricity directly with the help of semiconductors, typically made of silicon which has been treated chemically to create a positive charge layer and a negative charge layer. When the PV cell is illuminated by sunlight electrons are liberated which give rise to an electric current. Devices for tracking the Sun are expensive.6 But it also observed that solar energy could be useful for cooking in deserts, where firewood is in short supply, and that. That would seem the route to success start where solar energy is plentiful and necessary. Among the first to exploit energy for domestic heat were Greece and Israel. The PV effect was discovered by Alexandre-Edmond Becquerel in 1839 but it was not until the...

## Reactions in solution with two reactive species

To distinguish the two solutions, the metal alloy is termed the melt and the mixed oxide is called the slag. At the temperature of the reaction, the standard free energy changes of the two reactions are AG and AG . Assuming for simplicity that both solutions are ideal, the activities can be replaced by concentrations and the mass action laws for reactions (9.47a) and (9.47b) are Example Recall that the standard free energy changes for the reactions described by Eqs (9.47a) and (9.47b) refer to complete conversion of the pure metals by O2 at 1 atm pressure to pure oxide products. These free energy changes uniquely determine the oxygen pressure if both product and reactants of each metal are pure and unmixed. The temperature is 1000 K, at which AGM -200 kJ mole and AGp -250 kJ mole. The initial charge is 1 mole each of M and PO2 (or any combination of the metals and their oxides with element mole ratios M P 1 and O P 2). From Eq (9.48), the equilibrium constants are Km 2.8x1010 and Kp...

## Physicsbased Force Fields

Compatibility is usually measured as the free energy difference between the target structure and an unfolded conformation. We start this section by defining the free energy of a protein, and then show how it applies to sequence design. The rest of the section discusses various methods of computing the free energy. The stability of a protein sequence P is a thermodynamics quantity. It is measured as the difference AG(P) in free energy between its native state, N, and an unfolded state, U Note that P here refers to the solvated protein, that is, accounts for the protein and its surrounding solvent and ionic atmosphere. G refers to the Gibbs free energy of the system, defined as A native-like, stable sequence has a minimum (negative) AG(P) ideally this is reached when AU(P) is minimum and AS(P) is maximum. However, AU(P) is minimal when the native state has many stabilizing, nonlocal contacts, which requires an organized structure, whereas the entropy is maximal when the structure has a...

Adenosine triphosphate (ATP) is the major provider of energy for all bodily functions. The term energy really means the (negative) standard free energies of the multitude of reactions that take place within the cell. This free energy change, along with the concentrations of reactants and products via the law of mass action, provides useful work for the body's functions. 1 Reaction (11.2) does not proceed to the right because the standard free energy change is positive (14 kJ mole) however, ATP does this job (see Sect. 11.4.2)

## Thermochemical Databases

The reaction analyses in the previous sections required equilibrium constants K that in turn were determined by the free energy changes AGo. Whether the reaction involves gaseous species, condensed phases, or both, the connection between K and AGo is The linear temperature dependence in this equation accounts for the major portion of the variation of reaction free energy change with T. The reaction enthalpy change AHo and the reaction entropy change ASo are much less temperature-sensitive, and in many cases can be taken as constant properties of the reaction (see Sects. 9.2 and 9.3).

## Computational thermodynamics

So far in this chapter, mainly single reactions have been analyzed. The sole exception was the two-reaction problem in Sect. 9.8. Mass-action laws are inherently nonlinear, and almost always require numerical solution. As the number of simultaneous reactions increases, the method of computation based on the mass-action laws becomes prohibitively complex. A new approach is needed. The literature is replete with large codes with names such as THERMOCALC and PHREEQ. All utillize equilibrium determination based on minimization of the free energy of the system, including all possible reactions and all phases.

## Liquidliquid extraction

Another common phase-distribution system is the partitioning of a solute species between two immiscible solvents, designated as phases I and II. At equilibrium, the chemical potentials of solute A in the two phases, as given by Eq (8.3), are equal. The common pure-A molar free energy cancels, leading to the equilibrium relation

## Problems for Chap

9.2 A mixture of H2 and CH4 establishes a carbon activity, defined as the ratio of the carbon partial pressure generated by the reaction C(g) + 2H2(g) CH4(g) to the vapor pressure of solid carbon (graphite). The standard free energy change for the above reaction is AGo(g). For the reaction with solid carbon, C(s) + 2H2(g) CH4(g), the standard free energy change is AGo(s). For graphite sublimation, C(s) C(g) the free energy change is AGo(sub). 9.3 Consider the gas phase reaction PCl3(g) + Cl2(g) PCl5(g) at equilibrium at 400 K and 1 atm total pressure. The closed system is initially charged with 1 mole of PCl3 and 2 moles of Cl2. The standard free energy change of this reaction is -3.53 kJ mole. What is the mole fraction of PCl5 at equilibrium

## Principles of Protein Carbohydrate Recognition

Basically, typical contributions to the Gibbs' free energy of ligand binding originate from hydrogen bonding, van der Waals forces and the consequences of the hydrophobic effect. Factors to be reckoned with to predict the affinity of a ligand further include any alterations of the geometry and motional dynamics of the receptor and or the ligand and or the solvent molecules. As experimentally readily accessible parameters by calorimetric techniques, the determination of the reaction enthalpy and entropy delineates the global driving force towards complex formation. These parameters have, for example, been measured for an array of mono- and disaccharides in the cases of a plant and an animal lectin sharing specificity to D-galactose (Bharadwaj et al., 1999), and the plot of the data (Fig. 5) according to the equation

## Vaporliquid equilibria

GA is the molar free energy of pure A and yA is the activity coefficient of A in the A-B solution. The chemical potential of A in the gas phase is given by Eq (7.44) where gA(g) is the molar free energy of pure gaseous A at one atm pressure (indicated by the superscript o). The corresponding quantity for the condensed phase, gA, does not need an indication of 1 atm because it is essentially pressure-insensitive. Both molar free energies are at the same temperature T.

## Fig Protein foldingunfolding equilibrium

Because of the huge number of atoms in protein molecules, the heat capacities of both forms are extremely large. Consequently, the ACp term is important in both the enthalpy and entropy changes of the reaction. The standard free energy change of reaction (11.9) is expressed by

## Nonstandard solidstate electrochemical cells

When one or more of the constitutents in the half-cells are not in their standard states (i.e., are nonstandard), Eq (10.5a) relates AG, the free-energy change of the overall reaction, to the cell EMF. The first step in making the connection between the cell voltage and the component concentrations is to relate AG to the chemical potentials of the constituents in the half-cells. Generalizing the analysis in Sect. 9.4, the version of Eq (9.16) for a nonequilibrium reaction is

## Teslas Amazing Inventions

According to some, Tesla's greatest inventions are being kept from us by powerful government and capitalistic interests. For example, it is believed that Tesla's discovery of free energy has the potential to transform the world and usher in a new age, yet this technology is kept under wraps by the authorities, who are afraid that it will destroy their economic interests. One of the most passionate defenders of free, or 'zero-point,' energy is Tom Bearden. In his article 'The New Tesla Electromagnetics and the Secrets of Free Electrical Energy,' Bearden describes the importance of Tesla's discoveries. According to Bearden, Tesla's electromagnetic (EM) theory drastically changes quantum mechanics, quantum electrodynamics, and relativity theory. Indeed, our present EM theory is really 'just a special case of a much more fundamental electromagnetics discovered by Nikola Tesla, just as Newtonian physics is a special case of the relativistic physics. But in the new electromagnetics case,...

## Some Necessary Conditions for Systemic Chemical Self Organization

Life is dissipative, or biologically speaking, metabolic. Thus, for self-organization free energy flow must be provided from the beginning onward. At an already-organized state this would not cause a problem, the energy provided either by chemical energy (nutrients) or by solar photons. However, if there were, by chance, all necessary chemicals already present, life could not start, because this would establish near thermody-namic equilibrium. Thus precursors that react exothermally to building blocks can give the initial energetic kick into this nonequilibrium stage.

## A role for thermodynamics

The ranking can be interpreted on thermodynamic grounds. Amend and Shock (1998) have calculated the free energy of formation of the amino acids from CO2, NH+, and H2 in two sets of conditions. AGsurf in Table 4.2 corresponds to surface seawater conditions (18 C, 1 atm), and AGhydro corresponds to deep-sea hydrothermal conditions (100 C, 250 atm). Figure 4.3 shows thatRobs is closely related to AGsurf. For the ten early amino acids, there is a strong correlation between the two (r 0.96). Fig. 4.3. Relationship between the rank of the amino acid and the free energy of formation circles - early amino acids triangles - late amino acids. The line is the linear regression for the early amino acids. Fig. 4.3. Relationship between the rank of the amino acid and the free energy of formation circles - early amino acids triangles - late amino acids. The line is the linear regression for the early amino acids. All the formation reactions are endergonic (AGsurf > 0). The amino acids with the...

## The RNA world and the origin of the genetic code

Early versions of the code probably used a smaller repertoire of amino acids, each with a larger number of codons. The codon table was divided up into progressively smaller blocks as successive amino acids were added. This idea goes as far back as Crick (1968). Each addition would have opened up a whole new world of protein possibilities. Thus, there is a selective drive for adding new amino acids in the early stages of code development. This brings us back to question of the order of addition of amino acids to the genetic code. We have shown above that the early group of amino acids can be identified based on their appearance in meteorites, the Miller-Urey experiment, and a variety of other chemical syntheses designed to simulate prebiotic conditions. The strong correlation between the ranking, Robs, that we derive and the free energy of formation, AGsurf, suggests that this ranking is a meaningful prediction of the relative frequencies of abiotically synthesized amino acids that...

## Whilst This Planet Has Gone Cycling On According To The Fixed Law Of Gravity

The Second Law of Thermodynamics states that, although energy can be neither created nor destroyed, it can - must, in a closed system - become more impotent to do useful work that is what it means to say that 'entropy' increases. 'Work' includes things like pumping water uphill or - the chemical equivalent -extracting carbon from atmospheric carbon dioxide and using it in plant tissues. As already spelled out in Chapter 12, both those feats can be achieved only if energy is fed into the system, for example electrical energy to drive the water pump, or solar energy to drive the synthesis of sugar and starch in a green plant. Once the water has been pumped to the top of the hill, it will then tend to flow downhill, and some of the energy of its downward flow can be used to drive a water wheel, which can generate electricity, which can drive an electric motor to pump some of the water uphill again but only some Some of the energy is always lost - though never destroyed. Perpetual motion...

## Energy Requirements For Life

Given a biomass of 6 x 1017 g carbon (C), the area of the earth, 5 x 1018 cm2, and the minimal energy requirement of a resting cell, 10-3 W (gC)-1, 10 times less than that of a quiescent yeast cell, an energy flux of 10-4 W cm-2 is required to support present life on Earth. Alternatively, given the energy needed to fix a mole of carbon 500 kJ (mole)-1 and a long cellular reproduction time of 2 years, one again reaches the requirement of 10-4 W cm-2. Based on isotopic ratios of carbon and sulfur, Schidlowski et al. (1983) argue that the biomass has been roughly constant for 3.5 billion years. Only solar energy at 0.1 W cm-2 can supply this source of energy. The next most prevalent source, lightning, fails by more than two orders of magnitude (Miller and Orgel 1974). Cells are little black holes for energy. Broda (1975) has pointed this out along with the fact that the sun generates less than one hundred thousandth of the energy consumed by living cells per gram of material. This is a...

The maximum depth from which volatile ices sublimate to the surface is determined by the penetration depth of solar energy into the nucleus. Despite the uncertainties in our knowledge of nucleus parameters, we can make some crude estimates of the skin depth for penetration of solar energy into the nucleus over the diurnal and orbital cycle. The orbital skin depth is 174

## Albedo and color Albedo

Albedo measures the fraction of sunlight reflected by a body. A perfectly reflecting body has an albedo of 1.0 while a perfectly absorbing body has zero albedo. Two common types of albedo which are used in planetary studies are the bond albedo (Ab) and the geometric albedo (A 0). The value of A b depends on the incident solar energy and how much of that flux the planet reflects. The solar flux (F) at some distance r from the Sun is related to the Sun's luminosity (LSolar 3.9X1026 W)

## The Appearance of Life on the Primitive Earth Favourable Conditions

We may note that the Earth's geological record appears to show that the planet has, in the past, suffered from almost complete glaciation. The cooling process is one that is self-reinforcing if the surface temperature decreases, the area of the polar caps increases, which increases the planet's overall albedo. So the planet absorbs less solar energy and its temperature tends to decrease even farther, which increases the glaciation. It seems that several episodes of global glaciation took place between 750 and 580 million year BP. It was probably a violent volcanic episode that reestablished the greenhouse effect by injecting a large amount of carbon dioxide into the atmosphere.

## Life on the Atlantic midOcean Ridge

The deep oceans were beginning to be explored, to a large extent for military purposes. The thermal vents of the mid-Atlantic Ridge were surprisingly found to be populated by complex life forms evolved for life in that environment. The vents are ejecting very hot superheated water with minerals in black plumes which give the vents the name smoky chimneys. Around this hot water are giant sea worms, crabs and shrimp-like creatures. All are blind because sunlight does penetrate to the depths of the Atlantic ocean some 3 kilometres down. Bacteria are present and the driving energy appears to be sulphates. This ecosystem has evolved without the help of solar energy, the independent source instead being the heat arriving from the mantle through the vents system. As one vent becomes dormant the whole system moves, unaccountably, to another.

## Oast A Technology Testbed

The TES experiment consisted of two GAS canisters affixed to the Hitchhiker bridge, one of which contained a 'salt' of lithium fluoride and the other of lithium fluoride and calcium difluoride eutectic. After activation by Mission Specialist Pierre Thuot early on 5 March, TES collected and stored solar energy which was converted into electricity while in Earth's shadow. As the salts in the GAS canisters absorbed thermal energy, they slowly melted and expanded by up to 30 . Then, when cooled, they solidified and shrank, creating 'voids' in the salts which affected their heat-absorption rates.

## Representative Space Transfer Vehicles

Each OMV has approximately the same OEW as indicated in Figures 5.6, 5.7 and 5.9. But each has a different configuration that is determined by the characteristics of the individual propulsion system, as depicted in Figure 5.18. The two chemical rocket-powered OMVs are similar and conventional. Although having different gross weights, they are similarly sized. The satellite attaches to an equipment module mounted on the front end of the propellant tank, where the guidance and control systems and all subsystems are housed. There would be a stowed communications antenna and solar panels for power in the equipment module (not shown). The solar electric propulsion system would require much larger solar panels than shown. Current communications satellites have solar panels in the 25 to 30 m (82 to 98 ft) total span for thrusters with less than one-tenth the thrust required for the solar electric OMV. Some of the limitations of this system are the current low thrust levels the continuously...

## Cutting Edge Technology

The satellite system provides the structure and the equipment necessary for the telescope and the scientific instruments to operate. A propulsion system gradually puts the spacecraft into its final orbit, which is elliptical and extends far from Earth. In order to control the critical temperature of its components, Chandra has a special system of radiators and thermostats. The temperature near the X-ray mirrors has to be maintained at the proper temperature to keep the mirrors in focus. The electrical energy of the satellite comes from solar panels and is stored in three batteries. SOLAR PANEL

## Mars Reconnaissance Orbiter M RO

The MRO spacecraft has a height of 21 feet (6.5 m) and is topped by a 10-foot- (3-m-) diameter radio frequency antenna dish. The spacecraft has a width of 45 feet (13.6 m) from the tip of one extended solar panel to the tip of the other. The solar panels contain about 220 square feet (20 m2) of solar cells for electric power generation. At launch, MRO had a mass of

## Chandra Ready To Open Its Xray Eyes

An hour later, at 1 47 pm, with Columbia about 50 km 'behind' the Chandra IUS combination, the first-stage engine fired for just over two minutes. Approximately 60 seconds later, it was jettisoned and the second-stage took over for another couple of minutes. The booster's next job was to keep the observatory properly oriented as its two solar panels unfurled. Shortly before the second-stage separation, after insertion into a preliminary elliptical orbit, at 2 22 pm Chandra's solar panels unfolded perfectly. The separation of the second stage went without incident at 2 49 pm.

## Making Superman Jealous

''Eager is not the word,'' Weisskopf added, after spending two decades preparing for the mission. ''Slavering at the mouth comes to mind '' The spacecraft at the centre of this praise looked like a tapering, 13.8-m-long metallic cigar with two solar panels at its base to provide electrical power. At the opposite end, mounted in the telescope's primary focus, were its two scientific instruments the High Resolution Camera and the CCD Imaging Spectrometer. The telescope's cylindrical mirrors were coated with reflective iridium, giving Chandra 10 times the resolution of existing X-ray astronomical detectors and 50 times the sensitivity.

## The Lost Pictures of Mars

No anastamosis was performed the final playback was not accomplished. Sitting there still on the Mariner 9 tape recorder are fifteen vital photographs of the planet. They will never be returned under Mariner 9's own power. It has now also lost solar lock sunlight is no longer being converted to electricity on its four great solar panels, and there is no way to reactivate it. We may never know what Tharsis and Syrtis Major looked like around the beginning of November 1972 from the vantage point of Martian orbit.

## Image Not Available

White splotches on the dark outcrops looked like talc deposits but were actually exposed calcrete nodules. Apparently the local soil was being lost to erosion no surprise on this steep and poorly vegetated slope. Continuing on, we passed schistose Gariep metamorphics, a bathhouse topped by solar panels, and a gravel road with white-knuckle blind curves.

## A The terrestrial planets

The terrestrial planets are almost in energy balance, that is, thermal emission nearly equals absorbed solar power. On Earth only a small internal heat source exists, which manifests itself by a vertical temperature gradient in the outer layers of the crust. Early measurements, mostly from a few deep mines and bore holes, indicated a temperature increase with depth of 10-40 K km-1. With reasonable assumptions on the thermal conductivity of rocks this corresponds to an internal heat source of approximately 2.6 x 1013 W (Bullard, 1954). More recent estimates, including data from deep sea drillings, yield a slightly higher value of 4.3 0.6 x 1013 W (Williams & von Herzen, 1974). In contrast, solar radiation absorbed by the Earth amounts to approximately 1.2 x 1017 W. The internal heat flux is, therefore, only 3.5 x 10 4 of the absorbed solar radiation and, consequently, the energy balance of the Earth is approximately 1.000 35.

Most of the energy in the Sun's electromagnetic spectrum is contained within wavelengths ranging from about 0.2 to 3 m (see Figure 6.2), ranging from short wavelength ultraviolet radiation, through visible light, to longer wavelength infrared (heat) radiation. The most obvious effect of this radiation on an orbiting spacecraft is the thermal heating that it causes. For an Earth-orbiting spacecraft, the solar power falling on every square meter of surface presented to the Sun is about 1.4 kilowatts, so that the heat input to the spacecraft surfaces is substantial. By contrast, a spacecraft in a LEO usually enters Earth's shadow on each orbit, and when this happens the vehicle's surface temperature drops drastically. Management of this thermal cycling is a critical job to be done by the thermal control subsystem engineer (see Chapter 9) to ensure that the equipment inside the spacecraft does not suffer a damaging level of temperature variation.

## Small body surface missions

Missions to small bodies differ from those to larger worlds because the low surface gravity means that an orbiter (or rendezvous) spacecraft can approach close enough to perform a surface mission while hovering (with little or no thrust) and the speed of a landing can be very low. This blurs the distinction between orbiters and landers, and may enable orbiter spacecraft to survive landing, as shown by the landing of NEAR on asteroid Eros. Low gravity also means that a landing vehicle may risk being lost entirely on rebound from the surface, or ejected by outgassing in the case of a comet nucleus. Anchoring systems may thus be required. On the positive side, the low gravity also makes it easy to achieve mobility by jumping, and to perform 'touch and go' surface-sampling manoeuvres (e.g. Yano et al., 2003 Sears et al., 2004). Most small bodies are highly irregular, and their gravitational fields can be challenging environments in which to navigate. Dust thrown up from the surface...

## Solar Radiative and Particle Forcing of the Earth Like Planets

The solar wind input power for the Earth is obtained by assuming a limited (1-2 ) transfer of energy through the magnetopause. An interesting and important aspect of the input power is the six order of magnitude difference between solar power of the solar irradiation and the solar wind power. The difference intuitively suggests that solar irradiation is the main driver for ionospheric and atmospheric processes. This is certainly the case for heating expansion and dayside ionization of the atmosphere. However, this difference is not the case for the outflow escape of matter. As already noted in Sect. 1, accelerated ionospheric O+ dominates the escaping mass flux from the Earth. As indicated by the title of this report, our focus is on the implications of a planetary magnetic field for solar forcing. Our

## Nuclear Propulsion Current Scenarios

Much as missions to the outer planets are of interest to scientists (witness the enthusiasm after the Huygens landing on Titan), the public is far more sensitive to Mars explorations, hoping that some form of life may be found there. It is apparent that chemical propulsion for a manned mission to Mars would not be just risky, but also extremely expensive Donahue and Cupples, 2000 . For a short period around 1999-2000 solar electric propulsion (SEP), riding high on its high performance in applications to commercial GEO satellites was, if not the favorite, at least one of the alternatives. However, solar-powered propulsion has inherently low thrust, and is hardly suited to explore the outer planets and their satellites, since solar power In fact, the status of propulsion for a Mars mission can be summarized as follows technology-wise, alternatives to nuclear propulsion consist only of SEP or chemical rockets. Both were analyzed in depth, see, for instance Donahue and Cupples, 2000 ....

## The Electrical Power Subsystem

In the same way that the spacecraft has primary and secondary propulsion (see the previous section), the spacecraft also has primary and secondary power systems. The primary power system is the main source of electrical energy for example, for Earth-orbiting satellites this is often the conversion of sunlight into electricity using a solar panel (or array). As you have read through the previous chapters in this book, you've seen numerous pictures of spacecraft, and the majority of them are equipped with solar arrays. The secondary power system comprises electrical storage devices. In the vast majority of spacecraft, this implies the use of battery technology. However, there are other possibilities, although they are rarely used. For example, a fly wheel can be installed as an alternative electrical storage device. While the spacecraft is in sunlight, solar panel power can be supplied to a torque motor to spin a large wheel. When the spacecraft is in darkness, and the primary power...

## B Photoconductors and photodiodes

Photon detectors can be classified as either photoconductive (PC) or photovoltaic (PV) devices. In photoconductors the resistance of the material is lowered when impinging photons generate free charge carriers. The signal is measured as a change in voltage across the detector when it is connected to a constant current source or as a change in current when it is connected to a constant voltage source. Photoconductors In photovoltaic detectors, also called photodiodes, electrons and holes generated by photons are separated by an electric field formed at a potential barrier within the device. This field is formed at a specifically introduced interface in the material, for instance a p-n junction. Photodiodes used in astronomy are almost always made of intrinsic material. When an electron-hole pair is created at the junction by a photon the electron drifts to the n-region and the hole to the p-region. The separation of charge causes a voltage to be generated across the detector terminals,...

## E Circuits for photon detectors

The matched pair of Johnson field-effect transistors (JFETs) provide a high impedance input to the operational amplifier. The JFETs are usually placed close to the detector and feedback resistor to minimize the lengths of wire leads, thereby reducing the capacitance between the signal wire and ground. A large capacitance would greatly limit the maximum modulation frequency of the system. With very high impedances even a small stray capacitance can have a noticeable effect. This circuit can also be used with photovoltaic detectors, with or without bias.

## Transformation of Graphite to Diamond

Another notable solid-solid equilibrium is the graphite-to-diamond transition in the element carbon. Graphite is fairly common in the earth's crust but the rarity of diamond is the origin of its value. Under normal terrestrial conditions (300 K, 1 atm) the two forms of carbon are not in equilibrium and so, thermodynamically speaking, only one form should exist. The stable form is the one with the lowest Gibbs free energy. At 300 K, the enthalpy difference between diamond and graphite is Ahd-g 1900 J mole, with diamond less stable than graphite in this regard. Being a highly ordered structure, diamond has a molar entropy lower than that of graphite, and Asd-g -3.3 J mole-K (see Fig. 3.6). This difference also favors the stability of graphite. The combination of the enthalpy and entropy effects produces a free-energy difference of Since the phase with the lowest free energy (graphite) is stable, diamond is a metastable phase. It exists only because the kinetics of transformation to...

## Insects Were The First Domesticators

Well, the answer's no secret that's exactly what happens. The story is in some cases highly complex and in all cases fascinating. Many flowers use a bribe of food, usually nectar. Maybe bribe is too loaded a word. Would you prefer 'payment for services rendered' I'm happy with both, so long as we don't misunderstand them in a human way. Nectar is sugary syrup, and it is manufactured by plants specifically and only for paying, and fuelling, bees, butterflies, hummingbirds, bats and other hired transport. It is costly to make, funnelling off a proportion of the sunshine energy trapped by the leaves, the solar panels of the plant. From the point of view of the bees and hummingbirds, it is high-energy aviation fuel. The energy locked up in the sugars of nectar could have been used elsewhere in the economy of the plant, perhaps to make roots, or to fill the underground storage magazines that we call tubers, bulbs and corms, or even to make huge quantities of pollen for broadcasting to the...

## Formulation of the Bauer Principle in Elementary Sentences

Regular compensation of equilibration processes with uphill ones requires a systematic work on the internal structure of the organism. In order to initiate uphill processes, regenerating nonequilibrium structures, gradients and potentials, living organisms must be able to work continuously against the thermodynamic equilibrium that otherwise ultimately would be reached given the actual instantaneous state of the organism on the basis of physical laws. This simplified chain of thoughts points towards the Bauer principle. The Bauer principle in its full form tells that The living and only the living systems are never in equilibrium, and, on the debit of their free energy, they continuously invest work against the realization of the equilibrium which should occur within the given outer conditions on the basis of the physical and chemical laws. Bauer had shown that this is the first principle of biology, since all the fundamental phenomena of life can be derived from it (Bauer, 1935 1967,...

## Thermospheric Heat Balance and Composition Modelling

The thermospheres of the terrestrial planets are heated mainly, as was noted above, by the absorption of the solar X-ray and extreme ultraviolet (EUV) radiation. In photoionization most of the excess solar photon energy is carried away by the electrons produced. These photoelectrons may cause secondary and further ionization, dissociation and excitation of electronic states of molecules and atoms. In photodissociation the excess energy can go into internal energy of the products, or it may be released as kinetic energy. To calculate the thermospheric heating rate due to the solar XUV radiation, it is conventional to introduce into heat balance models the solar heating efficiency, which is the fraction of the solar energy absorbed that appears locally as heat. Among many other authors, notably Torr et al. (1979, 1980), Fox and Dalgarno (1981) and Fox (1988) have contributed to the present understanding of this key parameter for the terrestrial planets. For the Earth's thermosphere it...

## Electrostatic Ion Thrusters

Because ion engines have already been installed on geostationary commercial satellites, most manned interplanetary missions have been studied or planned around nuclear-powered ion propulsion. This engine technology is mature and space-qualified, but has been always used, by necessity, at low power. For the JIMO mission planned by NASA the xenon propellant ion thruster was in the 16-25 kW class Randolph and Polk, 2004 Scina et al., 2004 , a veritable jump over what was possible in the past using solar cells. The robotic Venus mission being investigated at NASA-Glenn (the so-called RASC Venus mission in McGuire et al., 2004 ), also assumes a nuclear ion engine, even though near Venus photovoltaic power would be twice that available near Earth (the so-called solar constant'', is 1,300 W m2 near Earth, about half of that near Venus).

## Gas Initially At Temperature Ti And Pressure Pi Is Expanded Isentropically. What Is Its Final Final Temperature

In the right-hand graph of Fig. 3.7, the solid experiences a phase transition prior to melting. The solid-solid transition is a consequence of free-energy minimization just as is the melting process. Solid phase SI has a lower entropy than SII, and so is stable at low temperature. These two curves cross at the SI-SII phase-transition temperature, Ttr. The SII phase remains stable up to the melting temperature, where its free energy curve crosses the liquid curve.

## Astroengineering and Supercivilizations

In the 1960 paper that Dyson prepared for the professional audience of the journal Science, he did not reveal the source of his idea of artificial spheres. However, he was more open about its origins in his memoirs published two decades later. There he acknowledged that he got the idea from an old science fiction novel, Star Maker (1937) by Olaf Stapledon. In Star Maker, Dyson read that in the future a gauze of light traps focused escaping solar energy for intelligent use.18 Whole galaxies grew dim as Stapledon's aliens built light traps around stars. Kardashev's ancient and technologically superior civilizations fall into two classes. A Type II supercivilization is able to capture all the radiant energy emitted by its sun for its own technological purposes. In essence this civilization has constructed a Dyson sphere to ensure that almost no solar energy escapes into space. Energy consumption in this case is roughly 4 x 1033 ergs per second.

## Activity and Activity Coefficient

The definition has been chosen so that the activity tends to unity for pure i that is, gi, the molar free energy of pure i. Activity varies monotonically with concentration. Therefore, when component i approaches infinite dilution ai 0 and - ot. This inconvenient behavior of the chemical potential at zero concentration is avoided by using the activity in practical thermodynamic calculations involving species in solution. Another reason for the choice of the mathematical form of the relation between and ai embodied in Eq (7.29) is that the activity is directly measurable as the ratio of the equilibrium pressure exerted by a component in solution to the vapor pressure of the pure substance. This important connection is discussed in Chap. 8. Problem 7.7 shows how this equation can be used to assess the validity of formulas for hex. In an equally important application, the above equation can be integrated to give the Gibbs free energy analog of Eq (7.19) for the enthalpy

## Binary phase diagrams by the graphical method

The cases of melting of two-component ideal solutions and of phase separation in a regular solution described in the Sect. 8.4 were easily treated by analytical methods. However, as the nonideal behavior of the liquid and solid solutions become more complicated (i.e., do not follow regular solution theory), the analytical methods based on Eq (8.2) as the starting point quickly become sufficiently complex to preclude derivation of simple formulae such Eqs (8.12) and (8.21). The graphical method does not have this restriction. Provided only that the free energy Vs composition curves can be drawn for each phase, construction of the phase diagram is straightforward. Moreover, the graphical method provides a qualitative understanding of the process that would be lost in complex mathematical analysis. The graphical procedure is based on minimizing the free energy of the system at a fixed temperature (and total pressure). Per mole of solution, the free energy is given by Eq (7.36) with gex...

## Equilibrium between two phases

The equilibrium criterion of minimum Gibbs free energy (Sect. 1.11) can be applied to any of the phase transitions described in the previous section. At fixed pressure and temperature, let the system contain nI moles of phase I and nII moles of phase II, with molar Gibbs free energies of gI and gII, respectively. The total Gibbs free energy of the two-phase mixture is This is an expression of chemical equilibrium. It complements the conditions of thermal equilibrium (TI TII) and mechanical equilibrium (pI pII). Since the Gibbs free energy is defined by g h - Ts, another form of Eq (5.2) is

## Mysterious Flashing Satellite

More recently, it has come to light that STS-28's payload was most likely a member of the second-generation Satellite Data System (SDS)-B family of US Air Force military communications satellites. Doubts over whether it was a KH-12 were raised within weeks of its launch, when ground-based observers noted that it 'flashed' - as sunlight reflected from its solar panels - at regular intervals, a phenomenon not usually consistent with a spying platform.

## The Nikola Tesla Story

To Matthews that Tesla had entrusted two of his greatest inventions prior to his death - the Tesla interplanetary communications set and the Tesla anti-war device. Tesla also left special instructions to Otis T. Carr of Baltimore, who used this information to develop free-energy devices capable of 'powering anything from a hearing aid to a spaceship.' (73) Tesla's technology, through Carr's free-energy device, will revolutionize the world. Instead of purchasing power from the large corporations, which is then delivered to our homes via wires and cables, the new technology consists of nothing more than a small antenna that will be attached to the roof of every building

## Prebiotic Photochemistryuv And Oceanic Photochemistry

Sources of reducing and oxidizing agents are required to establish a free energy gradient necessary to form the required biomolecules and sustain the organization of living things. The oceanic photoreactions could kick-start the chemical evolution that preceded the origin of self-duplicating entities. Once these entities were established

## Chemical Potentials in Gas Mixtures

The analysis in Sect. 7.2.2 of the entropy change associated with mixing of ideal gases at fixed T and p was based on the absence of an entropy change if the pure gases are at the partial pressures that they will have in the mixture. Since the gases are ideal, neither is there an enthalpy change in the mixing process. With both the enthalpy and entropy of each species unaltered, the Gibbs free energy must also remain constant during this mode of mixing. Since the partial molar Gibbs free energy of a species in a solution or a gas mixture is the same as its chemical potential, the above argument can be summarized by the equation Contrary to condensed phases, the Gibbs free energy of a pure gas is pressure-dependent. In order to provide a common pressure reference for all pure gases (arbitrarily chosen at 1 atm), gi in the above equation is expressed in terms of g , which is the molar Gibbs free energy of species i at temperature T and 1 atm pressure. The effect of the difference in...

## Criterion of Chemical Equilibrium

As in any system constrained to constant temperature and pressure, the equilibrium of a chemical reaction is attained when the free energy is a minimum. Specifically, this means that dG 0, where the differential of G is with respect to the composition of the mixture. In order to convert this criterion to an equation relating the equilibrium concentrations of the reactants and products, the chemical potentials are the essential intermediaries. At equilibrium, Eq (7.27) provides the equation

## Eutectic Phase Diagram

Irrespective of the complexity of the nonideal behavior of the phases involved, the phase diagram can always be constructed if the free energy Vs composition curves for each phase can be drawn. The link between the two graphical representations is the common-tangent rule. Because of the wide variations in the shapes of free-energy curves, the types of phase diagrams deduced from them reaches zoological proportions. In this section, a common variety called the eutectic phase diagram5 is developed by the graphical method.

## Binary phase diagrams analytical construction

The structure of a phase diagram is determined by the condition of chemical equilibrium. As shown in Sect. 8.2, this condition can be expressed in one of two ways either the total free energy of the system (Eq (8.1)) is minimized or the chemical potentials of the each component (Eq (8.2)) in coexisting phases are equated. The choice of the manner of expressing equilibrium is a matter of convenience and varies with the particular application. Free-energy minimization is usually used with the graphical method and chemical-potential equality is the method of choice for the analytic approach.

## The Chemical Potential

The chemical potential is directly related to the Gibbs free energy of a system. For a one-component system, the chemical potential is identical to the molar Gibbs free energy of the pure substance. In solutions or mixtures, the chemical potential is simply another name for the partial molar Gibbs free energy. The discussion in Sect. 7.3, in which enthalpy was used to illustrate partial molar and excess properties, applies to the Gibbs free energy one need only replace h everywhere by g. The reason that the partial molar Gibbs free energy (g) is accorded the special name chemical potential is not only to shorten a cumbersome five-word designation. More important is the role of the chemical potential in phase equilibria and chemical equilibria when the restraints are constant temperature and pressure. Instead of the symbol g, the chemical potential is designated by The connection between the Gibbs free energy of a system at fixed T and p and the equilibrium state is shown in Fig. 1.18....

## Paul Boynton Testing the fireball hypothesis

By the time I arrived at Princeton in the fall of 1962, I was thoroughly pumped up to join the quest for controlled fusion at PPL. My under-grad senior thesis on an obscure plasma instability led to working in Jim Drummond's Plasma Physics Group at the Boeing Scientific Research Laboratories in my hometown, Seattle, during the year following graduation. In fact, this millennial dream of realizing a virtually limitless source of pollution-free energy was largely my motivation for applying to grad school, and only to Princeton.

## Cleaning Up the Belts

Couple of percent of its natural levels within a year. For that, the system requires 24 tethers, each with a length of about 100 km (60 miles) and a 5-kilowatt power supply, to be put into orbit. The individual tethers could be built up from several relatively short tether modules, connected to each other like train wagons. Each module would consist of first a short length of conducting tether acting as an electron-collecting anode, a small satellite bus with a solar power collection system and a tether deployment mechanism, a

## Space Particles And Fields

The earlier probes had been drum-shaped and had rotated several times per minute, both for stability and to sweep their sensors in three-dimensions in order to measure the trajectories of the charged particles caught up in the magnetic field in the immediate vicinity. Although the new spacecraft would undertake similar measurements, the mission requirements obliged a different configuration. In the earlier design, there was an array of photovoltaic cells around the drum to make electricity from sunlight, but as insolation decreases in proportion to the square of

## The Galilean Moons Food for Thought

That an under-ice ocean exists on Europa is remarkable. It is especially remarkable when it is realized that Jupiter sits well outside of the habitable zone (defined in Chapter 5, and see Figure 5.9) and given that the surface temperature of the moon is not much greater than 100 K. How, indeed, can this ocean exist There is not enough solar energy to warm Europa above the freezing point of water, and the moon is so small that it should have cooled off relatively rapidly after formation.19 The possibility of terraforming Europa and, indeed, the other Galilean moons has been discussed by numerous researchers, but in all cases, bar the stellifying of Jupiter option, the biggest hurdle to overcome is that of supplying enough surface heat. At the orbit of Jupiter the solar energy flux is some 27 times smaller than at the Earth, and although the use of orbital mirrors has been proposed to help warm the moons, the required reflector sizes are so large that the whole idea soon becomes...

## Ninety Millimetres From Salyut

Shatalov recalls All the dynamic operations of the ship were conducted without any problems. The only issue appeared at the time that the Igla took control of the approach the ship would oscillate from side to side periodically, requiring the firing of the correction engines. At a distance of 150 metres I took manual control. It was simpler than on the Soyuz 4 mission. The station grew bigger and bigger - in space, it appeared to be much larger than it had on the ground When we were very close, Aleksey and Nikolay carefully inspected its docking mechanism, antennas and solar panels.

## Fig An aqueous electrochemical cell with an active metal halfcell and a hydrogen halfcell

The term on the left is A , the chemical-potential difference of overall reaction (10.21). It is the aqueous equivalent of the free-energy difference AG used in describing nonaqueous cells. The electric potential difference on the right is the cell EMF, s, so the equation is

## Interesting Things Attract Me

When Yeliseyev was launched into space in January 1969 on Soyuz 5, more than 27 months had elapsed since he received the flight engineer assignment. He recalls of his 37-minute spacewalk ''Travel along the external surface of the ships proved to be the easiest and most pleasant part of the transfer. It barely required any effort. The 'landscape' gave the sensation of limitless space and freedom. It was similar to the experience prior to a jump from an aircraft, but in this case there was no wind - and there was no concern about the operation of the parachute I paused in order to memorise what I could see. Below was the ship that we had left. To the left, shaped like the top of a bell, was our descent module. Volynov was inside, alone. Beyond was a module housing the instruments, the engines and the solar panels. To the right was the second ship, of the same type as ours. I could see Khrunov, his torso safely inside the orbital module of Soyuz 4, holding onto my cable. Far, far away,...

## Interphase Equilibrium

The two-headed arrows in Fig. 8.1 indicate chemical equilibrium of components A and B between phases I and II. According to the discussion in Sect.1.11.14, the criterion of chemical equilibrium at fixed T and p is the minimization of the total free energy of the contents of the cylinder-piston in the figure. Since the total free energy is the sum of those of the two phases, this criterion is The free energy of a phase is related to the chemical potentials of its components by Eqs (7.27) Using the latter for components A and B in Eq (8.1) gives The chemical potentials are seen to be analogous to the thermal and mechanical potentials which provide the equilibrium conditions Ti Tn and pI p n. Equation (8.2) is the multicomponent generalization of the equilibrium condition for two coexisting phases of a pure substance, namely gI gII, where g is the molar free energy (Eq (5.2)).

## Electrodynamic Tethers

Propellant to generate electricity is not an efficient way to power a satellite that could use free solar energy instead (by means of solar cells). Nevertheless, electrodynamic tether power generation could be useful for generating short bursts of electrical energy, for instance when needed for high-energy but short duration experiments involving powerful lidars (instruments similar to radar but using laser light instead of short wavelength radio waves).

## Influence Of Hydrogen On The Phase Diagrams

Dissolution of hydrogen reduces the free energy of a material. Experimental studies show that a significantly larger amount of hydrogen can be dissolved in wadsleyite than in olivine (e.g., Kohlstedt etal., 1996 Young etal., 1993). Therefore the dissolution of hydrogen will expand the stability field of wadsleyite relative to that of olivine (the depth of 410-km boundary will be shallower if a large amount of hydrogen is present). A more subtle effect is the change in the width of the 410-km discontinuity with hydrogen content. When the system is considered to be a binary system, i.e., Mg2SiO4-Fe2SiO4, there is a range of pressure (at a fixed temperature) during which the phase transformation is completed. When the upper and the lower boundaries are affected by hydrogen differently, then the width of the boundary will be modified by hydrogen. The degree to which the dissolution of hydrogen affects the free energy depends on the atomistic mechanisms of hydrogen dissolution. In his...

## Albedo Change and Increased Insolation

The amount of solar energy absorbed by Mars is determined according to the albedo of its atmosphere and surface. As indicated by Equation (5.1), the smaller the albedo term, the greater the amount of solar heating that takes place. Table 6.2 below indicates the effect of varying the atmospheric albedo of Mars. In contrast to the surface or atmospheric manipulation of the albedo, the insolation can be increased externally by the means of large space mirrors. Mars intercepts a meager 2 x 10 10 fraction of the total solar energy flux available at a distance of 1.5 AU from the Sun, and the emplacement of large orbital mirrors or solar sails

## Mars Exploration Rovers

'Follow the water' emerged as the mantra for NASA's Mars programme in the late 1990s. The intent of the Mars Exploration Rover (MER) missions was essentially to act as robotic field geologists, to map the rocks and soils around their landing sites with specific attention to minerals and formations that might indicate the presence or history of liquid water. These rovers were considerably larger than Sojourner. Although loss of solar power due to dust deposition on the arrays was expected to limit their lifetime to a few tens of days, both rovers are still operating at the time of writing, over 1.5 Martian years since their arrival, and have traversed a combined total of over 16.2km. Of particular note are the number and quality of images returned (Figure 17.9). For more details, see the case study, Chapter 27.

## Mammals finally arrive

Many changes occurred to the mammal-like reptiles before they eventually evolved into true mammals. But what made the first true mammals different Mammals have larger brains than snakes and lizards, and give birth to live young (except for echidnas and platypuses, which lay eggs). What really makes cats, rats, you and me different from therapsids, lizards and snakes (apart from not usually being especially slithery and scaly) is that we are far more active and create our own high body temperature. We don't need to wear a solar panel on our back. We just need to eat a lot more food, in fact about ten times as much as a reptile of the same size.

Solar panels suffer radiation damage, which causes the amount of power they produce from sunlight to decrease with time. A spacecraft in this type of orbit for many years may suffer a power loss up to 50 of the solar panel's original output. However, the power subsystem engineer is able to predict the likely deterioration for the particular type of orbit flown, and make due allowance in the spacecraft's design. Other electronic components onboard are also subject to radiation damage, but unlike solar panels, they can be shielded to some degree from the energetic particles by increasing the thickness of the walls of the metal boxes (typically made of aluminium) in which they are usually mounted. However, this needs to be done carefully as it will increase the spacecraft's mass, and as we have seen in Chapter 5, an increase in mass means a larger, more expensive launch vehicle. Another way of providing radiation protection, which goes some way toward solving this mass-growth problem, is...

## Observations of Gas Activity Evolution

The evolution of production rates along a cometary orbit depends on the available solar energy, the volatility of the species and the structure, and outgassing processes in the nucleus as outlined above. Key to constrain the nucleus composition and structure are observations of the cometary activity at large heliocentric distances and over a wide range of rh to cover the long-term evolution. In future, in situ measurements from landers will also become available. Unfortunately, observations of gases are often possible only in the water-driven sublimation regime inside rh 3 AU, because at large rh the sublimation rates are low (Fig. 4), and the excitation of line emissions is weak. Only exceptional bright long-period comets allow us to detect gas emissions also in the CO-driven regime at large heliocentric distances. Here we discuss observations of the gas evolution in comets in view of the different model concepts for sublimation.

## The Curse Of Steve Hawley

Confusingly, the second Satcom, known as 'Ku-2', had already been placed into orbit by Space Shuttle Atlantis in November 1985. After Columbia's delivery of Ku-1, a third member of the series was scheduled to be sent aloft in 1987. Satcom Ku-1 was a three-axis-stabilised satellite, carrying its own electricity-generating solar cells in a pair of deployable solar panels, attitude-control thrusters, thermal-control system and command-and-telemetry equipment. Like the other Satcoms, its 45-watt transponders were considerably more powerful than the 12-30 watts used in C-band transponders. This was expected to allow users to employ dishes as small as a metre across.

## Energy Generation and Transport

The process of energy generation results from the enormous pressure and density at the centre of the Sun, which makes it possible for nuclei to overcome electrostatic repulsion. (Nuclei are positive and thus repel each other.) Once in some billions of years a given proton (1H, in which the superscript represents the mass of the isotope) is close enough to another to undergo a process called inverse beta-decay, in which one proton becomes a neutron and combines with the second to form a deuteron (2D). While this is a rare event, hydrogen atoms are so numerous that it is the main solar energy source. Subsequent encounters proceed much faster the deuteron encounters one of the ubiquitous protons to produce helium-3 (3He), and these in turn form helium-4 (4He). The net result is that four hydrogen atoms are fused into one helium atom. The energy is carried off by gamma-ray photons and neutrinos. Because the nuclei must have enough energy to overcome the electrostatic barrier, the rate of...

## Terrestrial Heat Flow

The vast majority of the heat affecting the Earth's surface comes from the Sun, which accounts for some 99.98 of the Earth's surface energy budget. Most of this thermal energy, however, is reradiated into space, while the rest penetrates only a few hundred meters below the surface. Solar energy consequently has a negligible effect on thermal processes occurring in the interior of the Earth. The geothermal energy loss from heat sources within the Earth constitutes about 0.022 of its surface energy budget. Other sources of energy include the energy generated by the gradual deceleration of the

## Photometric investigations a Introduction

To be well-suited for albedo measurements a radiometer should have a wide spectral range with a flat spectral response to register as much of the reflected solar energy as possible. Polarization information is not required on the contrary, the instrument should be insensitive to polarization. Measurements over a full range of phase and azimuth angles are needed to derive either the local or the global albedo. Examples of such photometers are the instruments of the Earth Radiation Budget Experiment (ERBE) and the IRIS radiometer on Voyager. Both the objective of obtaining the local scattering properties and that of obtaining the Bond albedo require instruments with good radiometric calibration. In each case a well-calibrated spectrometer would be preferable to a radiometer, but only radiometers have been used in space for these purposes so far.

## Lectins Translators of the Sugar Code

Mono-, bi-, and trivalent Gal-terminated oligosaccharides and mammalian asialoglycoprotein receptor, a C-type lectin, has been attributed to the topological complementarity between multiple ligand and receptor sites (Lee and Lee, 1997). Membrane solubilization by detergent treatment will in this case disrupt the essential spatial arrangement. An important caveat for approaches to detect the cluster effect concerns the use of agglutination assays. In contrast to affinity measurements in direct binding assays, the ongoing aggregation of multivalent receptors and ligands in solution can lead to erroneous conclusions. Indeed, under these circumstances isothermal titration calorimetry failed to record enhancements of Gibbs' free energy of binding but measured an endothermic, entropically favored process, its extent correlating with the inhibitory potency (IC50-values) of tetra- and hexavalent ligands (Dimick et al., 1999).

## Life Forms Bridging Up the Gap Between Life and Nonlife

The difference between a physical object and a living organism is that the living organism can select an endpoint for the action principle, like a living bird when dropped from a height, in contrast to a fallen stone which must follow the law of free fall. The fallen stone follows the least action principle, while the living bird follows the most action principle securing the maximum available distance from equilibrium. The selection of the endpoint for the most action principle produces an input for the first principle of physics securing the least action to be consumed. (Grandpierre, 2007) In order that an organism can move its parts like an animal or change its forms as a plant, it must be able to select an endpoint and govern its whole macroscopic structure towards reaching the selected state. In plants and animals, the conditions are such that they are able to realize such hierarchical organization from the global to the microlevel, continuously. It seems to be possible that...

## Volatile Reservoirs and Exchange Processes on Earth and Mars

Habitable planetary environments also must provide sources of energy that living systems can utilize to drive their metabolism. Today's biosphere is dominated by photosyn-thetic biota that can harvest abundant solar energy. However many other organisms are non-photosynthetic and can obtain useful chemical energy by reacting oxidized and reduced chemical compounds in so-called redox reactions. Processes of volatile exchange in the Earth's crust have delivered both oxidized and reduced chemical compounds to habitable environments.

## Launch Vehicle Environment and Its Effects on Spacecraft Design

For launch spectators, one overriding impression is the wall of sound that hits them a few seconds after they see the rocket engines ignite, despite the fact that they are kept at a safe distance from the launch complex. Launch is a very noisy affair, and even more so for the satellite payload sitting on top of the rocket. The acoustic field encountered by the satellite is harsh, despite the satellite being contained within the launcher fairing. Large amplitude and damaging vibrations can be excited in flexible structures, such as solar panels or large antennas, by this level of noise.

## Nuclear Electric Propulsion NEP

Propellant comes from a separate source, and so in principle is unlimited. As the name implies, this separate source is electricity, and this can be generated using sunlight (solar panels) or nuclear energy. The resulting exhaust velocity of the device is typically on the order of 50 km sec (30 miles sec) about 10 times higher than that of a highperformance chemical system but the achievable mass flow rate is much smaller. As a consequence, a typical ion engine has a large specific impulse (which is good), but a low thrust level (which is not so good). Recalling the discussion about specific impulse in Chapter 5, this means that, all other things being equal, the ion engine will produce about 10 times more AV (speed change) for a given mass of fuel than a chemical system. However, the low thrust means that it will take a long time to do so. Fortunately ion engines can operate for thousands of hours, so the tiny accelerations that they produce can build up large A Vs, but one has to be...

## Amyloidosis Interstrand

Circular dichroism (CD) analysis of proteins from the four-helix bundle libraries confirmed that nearly all the proteins were a-helical (Kamtekar et al. 1993 Wei et al. 2003a). CD was also used to monitor thermal or chemical denaturation and to determine the free energy of unfolding. Most of the proteins from the first-generation library have slightly lower stabilities than natural proteins, while proteins from the second library are quite stable and often have melting temperatures near 100 C (Kamtekar et al. 1993 Roy et al. 1997a Roy and Hecht, 2000 Wei et al. 2003a).

## Meltingsolidification of an ideal twocomponent system

All graphical determinations of binary phase diagrams begin with the free energy Vs composition curves for all possible phases in the system. For ideal systems, these curves are given by Eqs (8.22) - (8.24) with hex 0 in both solid and liquid phases In order to construct the free energy - composition curves using these equations, the four pure-component molar free energies must be specified. Equation (8.13) relates the molar free energies of the pure liquids and pure solids As discussed in Sect. 1.6, the free energy (in common with u, h, and h) has no absolute value. Therefore, two molar free energies, say gA(S) and gB(S), can be specified arbitrarily. Of course, this choice affects the shapes and positions of the free energy Plots of Eqs (8.26a) and (8.26b) are shown in Fig. 8.8. The common-tangency points are xBL 0.10 on the liquid curve and xBS 0.17 on the solid curve. For xB < xBL The free energy of the liquid is lower than that of the solid, so the system is a single phase...

## Power Systems for Spaceflight

A spacecraft must be powered, otherwise it can't accelerate or is useless. Electromagnetically driven propulsion systems require a reliable power supply. The ion rocket and VASIMR are likely to be employed over the direct nuclear rocket for reasons of radiation safety. Large spacecraft sent to deep space this will require a power source that is considerably superior to what currently exists. Current power systems are solar photovoltaic generators and weak decay reactors that are not true nuclear reactors. Photovoltaic systems work well for small craft that travel close enough to the sun. The RTG radioactive type of decay reactors have been employed on craft sent to the outer gas giant planets. It is likely that some form of nuclear energy will have to be used to send spacecraft by propulsive means to speeds of 100 km sec or higher to the outer planets. Solar energy may work well for the inner planets. However, the energy requirements for reaching Mercury are comparatively high and a...

## Gas Sublimation and Nucleus Differentiation

* Dust particles too large to be accelerated by the gas flow can accumulate at the surface and build a crust covering the volatile icy interior. This dust crust inhibits surface sublimation, because the dust heated by solar energy re-radiates most of the energy at thermal wavelengths. It depends strongly on the porosity of the crust how much sublimated water vapor can pass from below through the crust into the coma.

## Glucose

In order to maintain optimum body temperature, mammals need thermal energy acquired from internal chemical reactions to make up for heat loss to the environment. Additionally, the free energy of the body's chemistry sustains functions ranging from muscle contraction to the thought processes and instinctual responses of the brain. Thermal energy and free energy, represented by AH and AG respectively, are supplied mainly by reaction of oxygen with food- Here hv stands for photons from the sun that provide the free energy that overcomes the highly unfavorable energy (enthalpy) difference between the products and the reactants. C6H12O6 is the chemical formula for the glucose molecule that is shown in a structural representation in Fig. 11.2. The oxygen product of photosynthesis is returned to the atmosphere. The radiant energy that drives this reaction is stored in the glucose molecule, to be released after vegetable matter has been consumed by humans (and other mammals) and its charge of...

## Info

FIGURE 12.1 Schematic representation of the thermodynamics involved in computational protein design. We assume a first-order folding for a protein sequence P1. The stability AG(P1) of P1 in the native conformation N is the difference in free energy between N and the unfolded state AG(P1) GN(P1) - GU(P1). When a new sequence P2 is tested against the target structure N, we need to take into account the changes in sequence at both ends of the folding process, that is, for the folded and the unfolded state. Equation 12.5 requires computing the free energy of a sequence in the unfolded state, which is usually taken to be the fully extended structure. The denatured state of a protein is known to be a distribution of different molecular conformations for review, see (Dill and Shortle 1991) . Though distant residue contacts do exist in the denatured states, their free energies are dominated by local interactions within the protein and by interactions with the solvent. Therefore, the free...

## Negative Design

Positive design aims to design a molecule to perform a desired function. Negative design seeks to ensure the specificity of function by minimizing unintended side effects. Biological molecules and systems exhibit great specificity precisely because nature is proficient in both positive and negative design. Computational protein modeling today is still in the process of developing and optimizing positive design, with most efforts focused on engineering macromolecules to perform specific target functions. To that end, recent years have seen significant progress in macromolecule structural modeling and recognition. In particular, protein sequences that fold into novel structures, bind novel ligands (e.g., small molecules, nucleic acids), and catalyze nonbiological reactions have been designed (Dahiyat and Mayo 1997 Kuhlman et al. 2003 Looger et al. 2003 Ashworth et al. 2006 Jiang et al. 2008 Rothlisberger et al. 2008). The core of positive design used in these problems involves setting a...

## MicroRNAs

There is a growing number of reports on miRNA-regulated genes, yet, for most miRNAs, their functions and role in molecular mechanisms are not known. Known examples of verified miRNA-mRNA pairs has allowed for the derivation of certain rules, including free energy and the extent of complementarity of RNA duplexes that may help in identification of putative miRNA binding sites (Doench and Sharp 2004). An analysis of 3'-UTRs of human mR-NAs demonstrated that over 2,000 genes show conservation of miRNA target sites with other mammalian species. Furthermore, about 10 of human genes have two or more potential miRNA binding sequences. A majority of miRNAs targets a limited number of genes, but there are miRNA species that may be involved in the regulation of hundreds of mRNAs. It is also evident that some of the mRNAs maybe regulated by more than one miRNA (John et al. 2004). These features resemble transcriptional regulation by transcription factors (Hobert 2004). In both cases, gene...

## A modest solution

James Martin's acclaimed The Meaning of the 21st Century, published in 2006, devotes less than two pages out of a total 526 to solar power. It considers the fact that solar panels covering the area of the Nellis Air Force Base and its Nevada Test site could generate about twice the electricity needed by the entire USA - and then declares 'Nobody ' s suggesting this is a good idea.' If Martin is so dismissive, Of course, cool, small countries are unlikely to embrace solar power as the primary, let alone the sole solution the UK would have to sacrifice 12 of its territory to PV devices, Belgium 24 . The answer must lie in the trading of energies. A cooperative scheme has been proposed for the European Union and the countries of the Middle East and North Africa, the TREC (Trans-Mediterranean Renewable Energy Cooperation) grid, which draws on solar, wind, geothermal, hydropower, biomass and conventional energy sources (Fig. 8.72 . It foresees that by 2050, for instance, transmission lines...

## Energy balance

Where a is the Stefan-Boltzmann constant and Teff the effective planetary temperature. This is the temperature of a blackbody with the same spectrally integrated power as the planet. The first term on the right represents the absorbed solar power A is the planetary Bond albedo, n S the solar constant at Earth, and D is the heliocentric distance of the planet in Astronomical Units. The last term in Eq. (9.4.1) is the power released by internal heat sources. (4) Heat generated by absorption of solar energy, On the outer planets the internal heat is found by measuring the thermal emission and subtracting the term representing absorbed solar power. Consequently, careful measurements of the effective planetary temperatures and the Bond albedos are required. The quantities R and D in Eq. (9.4.1) are relatively well known for each planet, as is S. On Earth the internal power is small in comparison with the other terms of Eq. (9.4.1). Thus it would be difficult to find the internal heat by...

## C The outer planets

The outer planets provide the opportunity for the study of significantly different meteorological regimes than those of Mars and Earth. Their atmospheres are composed primarily of hydrogen with smaller amounts of helium and traces of other species, including methane and ammonia, and extend to great depths before major phase boundaries are encountered. With the exception of Uranus, the giant planets possess significant internal heat sources, comparable in magnitude to the solar energy absorbed in their atmospheres. A major problem in the dynamics of these atmospheres is to understand how the two energy sources conspire to drive the atmospheric motions.

## Gravitys Reign

Revealed a living, evolving planetary system. The unanticipated activity and youthfulness of these worlds implies that gravitational energy may be of equal or even greater importance than solar energy in fueling life in our universe. The belief that water is necessary and sufficient rests on the assumption that suitable energy sources will be common. How reasonable is this Well, the presence of liquid water actually implies some kind of energy source, so the two requirements aren't completely separate. Our two examples of oceanic planets are Earth and Europa. Earth is wet because it is in the right place to soak up plenty of solar energy. Europa is wet because of the release of tidal energy. So, both ways that we know of for a planet to stay watery also come with built-in, long-term energy supplies.

## Springer

Book cover The Earth system consists of 6 sub-systems (1) growth tectonics in the core (2) plume tectonics in the lower mantle (3) plate tectonics in the upper mantle (4) Solar-driven hydro-biosphere (5) atmosphere and (6) magnetosphere, penetrating through all of these domains. The Earth behaves as a nonlinear system in response to either external or internal forcing. The surface environment of (4) and (5) is controlled by the solar energy in a daily time span, whereas the solid Earth is driven by internal heating over a much longer time span, up to a time scale of billions of years. With a cooling Earth, the Earth system has changed with catastrophic events due to the linked subsystem, and drastically affected the evolution of the surface environment and of life. The superplume sits atop the hot liquid outer core to drive the Earth as a main heat engine in maintaining geodynamics. (graphics by Shio Watanabe)

## The Opening Salvo

Schematic illustration of the Martian orbit and spin-axis orientation. Since the orbit of Mars is appreciably eccentric, it receives a slightly greater solar energy flux when it is at perihelion. The northern winter currently takes place, however, at this time. The dashed, arrowed line shows the present orientation of Mars' spin axis. Some 25,000 years from the present, the northern summer will take place when the planet is at perihelion, and this is the time and spin-axis orientation, Sagan argued, when the northern polar cap will melt. Figure 6.12. Schematic illustration of the Martian orbit and spin-axis orientation. Since the orbit of Mars is appreciably eccentric, it receives a slightly greater solar energy flux when it is at perihelion. The northern winter currently takes place, however, at this time. The dashed, arrowed line shows the present orientation of Mars' spin axis. Some 25,000 years from the present, the northern summer will take place when the planet is...

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## Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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