Spangenberg's words not only reflected the exemplary performance of NIZEMI and its experiments, but also the progress of the IML-2 mission overall. As well as providing an excellent testbed for the kind of research that would be conducted on board the space station, Cabana's crew expanded on the experiments performed during IML-1 in the spring of 1992. One of these was a Canadian study of back pain: for many years, two out of every three astronauts had returned to Earth suffering from what was thought to be a result of the lengthening of the spinal column in the microgravity environment.
Canadian astronaut Roberta Bondar had investigated the phenomenon during IML-1 and follow-up research on the second mission focused on determining whether it could indeed be associated with changes in the function of the spinal cord or spinal nerve 'roots' which branch off from it. Concerns had already been raised about the potential impact of spinal column lengthening on changes in the functioning of astronauts' cardiovascular systems and bladders; it was also considered likely that such 'stretching' of the spinal nerves could cause them not to work properly.
During IML-2, the spacing between discs in the spinal vertebrae was measured to determine if that was the reason for the height increases, or if it was actually due to the 'straightening' of the curvature of the back. Typically, IML-1 had illustrated overall height increases of between five and seven centimetres, as well as 'flattening' of the normal spinal contour. Each day throughout their mission, Cabana and his crewmates filled in questionnaires to describe any occurrences of back pain or symptoms of spinal column 'dysfunction', such as a feeling of numbness. Additionally, the astronauts carefully measured their heights daily.
They also took stereo photographs of themselves in different postures to provide further evidence of changes in spinal contour, height and the range of motion of their vertebral columns. This was followed by MRI scans after landing. To stimulate their sensory nerves, they applied tiny electrical impulses to their ankles and measured the time it took for signals to reach their brains using a nerve stimulation and recording device. They also monitored their autonomic nerves by squeezing hand grips, as electrodes gathered blood pressure and heart rate data, and synchronised their breathing on audio tape for another heart rate study.
Meanwhile, a group of Japanese researchers were more than happy with the results of their investigations in the Animal Aquatic Experiment Unit elsewhere in the Spacelab module. This aquarium-type facility provided them with an opportunity to closely examine the spawning, fertilisation, embryonic stages, vestibular functioning and general behaviour of live fish and small amphibians in space. For IML-2, almost 150 pre-fertilised newt eggs, as well as four adult newts, were carried in cassette-sized containers as part of studies of their development throughout the 14-day mission.
Unfortunately, not all of the newts survived, to which researcher Michael Wiederhold told a disappointed Don Thomas that there was always a chance that some might not make it through the flight. In general, the newts developed at about the same rate as ground-based controls. Other AAEU passengers included Akira Takabayashi's goldfish, which were included as part of an investigation into the causes of space motion sickness; on 17 July, live video downlink from the Spacelab module gave him an excellent view as they reacted to light stimulation inside their tank.
Takabayashi later told journalists that, even a few days into the mission, ''they [the goldfish] appear to have adapted to the weightlessness of space''. Other investigations focused on the adaptation characteristics of Japanese Medaka fish, watched intently by their experiment's Principal Investigator Ken-Ichi Ijiri. The AAEU, which had carried carp on a Japanese-dedicated Spacelab mission two years earlier, performed near-flawlessly during IML-2, providing not only life-support and temperature-control data but also an attachable video system to monitor swimming patterns and fertilisation and embryonic development.
Although life sciences research occupied a significant portion of the crew's time, a large number of facilities were devoted to materials science, processing and fluid physics investigations. One of these was ESA's Critical Point Facility (CPF), which explored the behaviour of certain substances at their so-called 'critical points' - the peculiar stage in which they are technically neither a liquid nor a gas, but rather occupy a limbo world in between. More accurately, the material's properties fluctuate backwards and forwards from a liquid to a gaseous state so that its 'bulk' state is indistinguishable.
On Earth, critical point experiments are difficult to perform because, under our gravity, the weight of the material is 'compressed' to a density greater than its own critical density. Scientists were keen to understand the behaviour of different
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