| General Information | Rome 28/2 - 3/3 1999 | Final Program |
| Plenary Lecture | Invited Lectures | |
| Life Sciences | Materials and Physical Chemistry | |
| Microgravity Technology & Applications | Posters | Participants |
POSTER SESSION
THERMAL RADIATION FORCES IN MICROGRAVITY:
THE DEVELOPMENT OF A FACILITY FOR AN EXPERIMENT ON MASER8 SOUNDIG ROCKET.
C. Albanese, F.Cavaliere, R. Fortezza and F.S. Gaeta
MARS Center – Via Comunale Tavernola 80144 Napoli
The paper introduces the concept of thermal radiation forces and the importance
of their measure in unsteady experimental conditions. After the studies and
experiments which have been conducted on Thermal Radiation Forces (TRF) in
our laboratory at MARS Center, new experiments will be done in a microgravitational
environment. The first experiment will be done on a sounding rocket, the name
of the experiment is TRUE (Thermal Radiation forces in Unsteady condition
Experiment).The aim of this first experiment is to give an accurate measure
of the TRF avoiding all the disturbances present in earth based laboratories.
The paper describes the activities which are currently going on at MARS Center
related to the construction of the facility TRUE, which will fly on MASER
8 sounding rocket at the end of April 1999, some technical details are discussed
. New experiments are proposed which will be done in microgravity environment,
with particular attention to the possibility to mesure the thermal conductivity
of liquids using the TRF.
COMBUSTION SYNTHESIS AND MICROGRAVITY ACTIVITIES OF THE ITALIAN TEAM
U. Anselmi-Tamburini1, V. Buscaglia2, G. Cao3,*,
P. Giuliani4, R. Orru'3, C. Zanotti4
1Department of Physical Chemistry, University of Pavia,
27100 Pavia, Italy
2Institute of Physical Chemistry of Materials, ICFAM-CNR, via de
Marini, 6, 16149 Genova, Italy 3Dipartimento di Ingegneria Chimica
e Materiali, University of Cagliari, Piazza d’Armi, 09123 Cagliari, Italy
4Institute for Materials and Energetic Processes, TEMPE-CNR, via
Cozzi, 53, 20215 Milano, Italy
Combustion synthesis is characterized by highly exothermic reactions which
for example, once the reacting mixture of powders is ignited, may propagate
in a self-sustained manner in the form of a combustion wave without requiring
additional energy. In this case, specific features of the synthesis technique
are: high rate of self-heating, high combustion temperatures, short time of
synthesis, simplicity of technological facilities. Current research on self-propagating
combustion synthesis under microgravity conditions include, among others,
gravity related aspects of phase and microstructure formation of silicide
materials in gasless combustion wave, production of new materials under supercooling
state during microgravity, synthesis of ceramics, metal-matrix composites
and porous materials, etc.
The main activities will be to share the coordination of the work, identify
the current status in the field, assess the microgravity relevance of the
topic, define the needs in terms of microgravity facilities, establish the
contacts with industry. In particular, the proposed areas of interest are
the synthesis of materials with homogeneous microstructure (metal or intermetallic
matrix composites, composites with aluminum or aluminides), the synthesis
of foam materials, the synthesis of powders (nanoparticles, thermal spray
powders) and welding processes.
PROTEIN CRYSTALS GROWTH IN MICROGRAVITY: THE CASE OF (Pro-Pro-Gly)10 POLYPEPTIDE
L. Carotenuto**, R. Berisio*, C. Piccolo**, G. Sorrentino*, L. Vitagliano*
and
A. Zagari*
*Centro di Studio di Biocristallografia, CNR and Dipartimento di Chimica,
Universita’ di Napoli "Federico II", Via Mezzocannone 4, 80134 Naples, Italy
**MARS-Center, Via Comunale Tavernola, 80144 Naples, Italy
As part of our ongoing research on protein crystallization in microgravity,
we successfully performed microgravity experiments during the US Space Shuttle
Missions USML-2 [1], LMS [2] and STS-95. The purpose was to study the influence
of microgravity on transport and kinetic growth mechanism of biological macromolecules
and to obtain crystals of better quality. than on Earth. The experimental
apparatus used aboard the Shuttle was the Advanced Protein Crystallization
Facility (APCF). This was manufactured by Dornier Gmbh, (Germany) and provided
to us by the European Space Agency (ESA).
The protein currently under study is a collagen model polypeptide (PPG)10.
Collagen is the most abundant protein in mammals, which makes it one of the
most widely studied proteins. Unfortunately, since this protein assembles
into fibres and is not able to form single crystals, only limited high resolution
structural information is available. Therefore, the use of peptide models,
which pack into single crystals, has been found to be extremely helpful. We
chose the model, because it folds into a triple helix structure which closely
mimics the natural collagen.
The (PPG)10 crystals that we grew on ground were very small and exhibited
high mosaicity. Their X-ray diffraction pattern was characterised by a large
number of reflections, which are markedly weak, and a smaller number of stronger
reflections, corresponding to a subcell (a=27.01, b=26.42, c=20.42 Å).
Using only the reflections which characterise the subcell, the crystal structure
was already determined at 1.7 Å resolution in our laboratory.
Microgravity and ground reference experiments were conducted in seven crystallisation
reactors [two FID (free interface diffusion) and five DIA (dialysis)] during
the STS-95 Space Shuttle mission (October 1998). The crystal growth was regularly
monitored by a video observation and relatively large crystals were obtained
in all reactors. The images that were recorded aboard the shutthe are now
under investigation. Because of the unusual distribution of the intensities
characterising the diffraction pattern of (PPG)10, synchrotron radiation was
necessary to assess the crystal quality by X-ray analysis. Diffraction data
were collected at DESY (Hamburg, Germany) and at Elettra (Trieste, Italy).
The data analysys is in progress. Here we report a first comparison of the
results obtained on ground and under microgravity condition.
Acknowledgements
We acknowledge ESA for providing the flight opportunity, Prof. C. Betzel for
the warm hospitality he offered in his laboratory, Dornier (Friedrichshafen,
Germany) for assistance filling the reactors and EMBL for funding the access
to the beamline . This work was financially supported by the Agenzia Spaziale
Italiana.
References
[1] Carotenuto L., Sica F., Sorrentino G., Zagari A. (1997) Visualization
of protein crystal growth inside hanging-drop reactors of the Advanced Protein
Crystallisation Facility J. Applied Crystallogr. 30, 393-395.
[2] Esposito, L., Sica, F., Sorrentino, G., Berisio, R., Carotenuto, L., Giordano,
A., Raia, C.A., Rossi, M., Lamzin, V.S., Wilson, K.S. & Zagari, A. (1998)
Protein Crystal Growth in the Advanced Protein Crystallisation Facility on
the LMS Mission: a Comparison of Sulfolobus solfataricus Alcohol Dehydrogenase
Crystals Grown on the Ground and in Space. Acta Crystallographica D54, 386-390
FLUCTUATIONS IN FREE DIFFUSION PROCESSES.
D. Brogioli, A. Vailati and M. Giglio
Dipartimento di Fisica and Istituto Nazionale per la Fisica della Materia,
Università degli Studi di Milano, via Celoria 16, 20133 Milano.
Macroscopic concentration disturbances relax to an homogeneous state via diffusion
processes. Diffusion is caused by random molecular motion, and in the case
of non interacting particles a lot can be understood in terms of a random
walk model. The general belief is that the fluctuations should occur only
on a molecular lengthscale. We show that this picture is wrong, and diffusion
is associated with giant fluctuations that restlessly accompany the decay
to equilibrium conditions.
The typical free diffusion experiment is performed by preparing two miscible
fluids, so that initially a very sharp horizontal meniscus is present between
them. As time goes on, diffusion determines the mixing of the fluids, until
eventually a homogeneous state is reached. The free diffusion process involves
a mass flow in the vertical direction. Usually the process is studied by looking
at the sample along the horizontal direction, so that the time evolution of
the concentration profile can be determined. The novel approach of our experiment
consists in looking at the fluid along the vertical direction, so that we
are sensitive to fluctuations only.
The sample used is a binary mixture non too far from its critical point. The
sample is first brought to a temperature below the critical point (Tc-T=3
K), so that it separates into two phases. Gravity is of great help here, the
denser phase separating below a sharp, stable meniscus formed at midheight
of the cell. After waiting suitable time to let the system equilibrate in
the two phase state, the temperature is brought above the critical temperature
(Tc-T=1.0 deg C), and diffusion starts since the system wants to go to an
homogeneous state.
The fluctuations involved in a diffusion process are so large that we were
able to visualize them by using the shadowgraph projection technique. In order
to give a quantitative characterization of the fluctuations, we used small
angle static light scattering. This technique allows to give a quantitative
estimate of the mean square amplitude of the fluctuations as a function of
their wavevector q. The amplitude of the fluctuations diverges as q-4
for intermediate wavevectors. This divergence is originated by the coupling
of the equilibrium velocity fluctuations with the nonequilibrium concentration
fluctuations, due to the macroscopic concentration gradient. At smaller wavevectors
the fluctuations are stabilized by gravity and their amplitude levels to a
constant value.
We also report here on the observation of giant fluctuations during a free
diffusion process occurring in ordinary fluids. These results provide strong
evidence that giant concentration fluctuations are a genuinely universal phenomenon
associated to diffusion across a macroscopic gradient.
TOWARDS THE UTILISATION OF SELF-LUBRICATED SYSTEMS FOR SPACE APPLICATIONS
P. Dell'Aversana* and G. P. Neitzel †
*MARS Center,via Comunale Tavernola, 80144, Napoli, Italy
E-mail: dellaversana@mars.unina.it
† The George W. Woodruff School of Mechanical Engineering,
Georgia Institute of Technology, Atlanta, GA, 30332-0405
E-mail: paul.neitzel@me.gatech.edu
The permanent inhibition of coalescence between bodies of the same liquid
in thermocapillary convection is explained as a peculiar lubrication effect.
For this reason, in previous works1, 2, non-coalescing (and non-wetting) liquids
were also referred to as 'self-lubricated'. At a first glance, such liquids,
when they undergo some mechanical stress, may appear to behave like elastic
solids. The analysis presented here shows how this idea is unwarranted.
On the other hand, the laboratory tests shown here demonstrate that, in spite
of the weakness of the forces originated by surface tension, a loaded self-lubricated
silicone oil droplet develops a well measurable reaction without undergoing
the lubricating film breakdown. This fact, together with the circumstance
that a self-lubricated drop is absolutely unaffected by static friction, suggests
the idea that non-coalescing and non-wetting liquids could be employed to
conveniently perform some mechanical work in microgravity conditions.
In order to demonstrate how effective self-lubrication can be to carry loads
without static friction, the first, experimental, self-lubricated device is
presented, which is able to work in normal gravity conditions.
References
1 - P. Dell'Aversana, V. Tontodonato and L. Carotenuto: "Suppression of Coalescence
and of Wetting: the Shape of the Interstitial Film " Phys. Fluids, 9, 2475-2485
(1997).
2 - P. Dell'Aversana and G. P. Neitzel: "When liquids stay dry " Physics Today,
51, 1, 38 - 41, January 1998.
FAST ON STS-95. PRELIMINARY MISSION RESULTS ANALYSIS
P. Falciani, M. Tacconi, G. Simoncini
Alenia Difesa - Unità OFFICINE GALILEO-Via A. Einstein, 35 - 50013
Campi Bisenzio (FI)- Italy Phone:+39.55.8950.672, fax: +39.55.8950.613, e-mail:
microg @ galileo-space.it
Many industrial and natural process involve bubbles or droplets where
surface tension effects and, in particular, the dynamic components of these,
play an important role. The FAST (Facility for Adsorption and
Surface Tension studies), manufactured, under ESA contract,
by Officine Galileo, has been designed in order to deepen our understanding
of dynamic surface tension effects. It is a multi-user and multi-mission Facility
capable to perform basic studies in the field of Physical-Chemistry of surfaces
in a Microgravity environment.
FAST is designed to be accommodated in two Spacehab lockers: the first locker
contains two experiment cells with their relevant mechanisms, stimuli, thermal
conditioning, diagnostics and CCD cameras.
The other one contains the electronics that manage, in automatic mode, the
experiments and communications with Spacehab, in which FAST has been flown,
for the first time, during the shuttle mission STS-95 .
The presentation will describe the main technical features and the overall
instrument capabilities of the Facility and will introduce the preliminary
analysis of the technical performance observed during the STS-95 mission.
The standard locker solution could lead, in the future, to an easier accommodation
of the FAST on the International Space Station, either in the European Standard
Drawer Rack or in the US Express Rack.
One of the experimental cells of FAST-SH.
FERROELECTRIC - LIKE PROPERTIES OF HORNET STRUCTURE OR CONSTRUCTION
J. S. Ishay, S. Kirshboim and L. Litinetsky
Department of Physiology and Pharmacology, Sackler Faculty of Medicine,
Tel-Aviv University, Ramat-Aviv, 69978, Tel-Aviv, Israel
Various structures or constructions of the Oriental hornet Vespa Orientalis
(Hymenoptera, Vespinae) such as the cuticle, the spun silk and the comb
cell walls discharge an electric current. In the dark, at a temperature range
of 5 – 33° C, this current increases with rise in the temperature and decreases
as a temperature drops. Betweeen the ascending and descending "lines" of the
current, a broad hysteresis is formed. The created current may attain a level
of up to 700 nanoAmperes (nA). Upon exposure to light of the hornet or its
constructions, the electric current diminishes within minutes to its minimal
values, no hysteresis is formed between the warming and cooling lines and
the voltage increases. The events described suggest that the structures or
constructions mentioned contain polar materials that undergo changes in conformation
and in polarization (i.e. in charge distribution), becoming a capacitor with
layers of opposite polarization. The active components remind that of triglycine
sulfate (TGS). This explains why the voltage rises and the current decreases
during exposure to light, whereas in the dark (at a suitable temperature),
the mentioned materials revert to a state of spontaneous polarization and
gradually release, as electric current, the charge that was picked up under
illumination. The observed phenomena are characteristic of materials that
are semiconductors endowed with ferroelectric properties.
Key words: Spontaneous polarization, Ferroelectric semiconductors, Light polarization,
Triglicine sulfate, Curie temperature, Vespan cuticle, Silk and Comb structure.
POLYAMINE LEVELS IN HUMAN ERYTHROLEUKEMIA K562 CELLS SUBJECTED TO ALTERED
GRAVITY
M. Maccarrone1,2, M. Bari1,2 and A. Finazzi Agrò1
1Department of Experimental Medicine and Biochemical
Sciences and 2Biomedical Space Center, University of Rome "Tor
Vergata", Via di Tor Vergata 135, I-00133 Rome, Italy
In this study, the possible effects of altered gravity on polyamine metabolism
in human erythroleukemia K562 cells was investigated, by subjecting cell cultures
to simulated hypogravity (by clinorotation) or hypergravity (by centrifugation).
In this context, also the activity of the polyamine-catabolizing enzyme diamine
oxidase (DAO; E.C. 1.4.3.6) was determined, by means of a radiochromatographic
assay. The free polyamine content was determined in cell extracts by reverse
phase-high performance liquid chromatography (RP-HPLC).
It is shown that treatment of K562 cells at 0.49x10-3g led to a dramatic
decrease in the content of free putrescine, down to 13% of the 1g control
(P<0.01). On the other hand, putrescine level was not significantly affected
by hypergravity at 22g. A similar trend was shown by DAO specific activity,
which decreased down to 60% of the 1g control (P<0.05) under hypogravity
at 0.49x10-3g, but was not affected by hypergravity values up to 22g.
This finding is noteworthy, because putrescine is the purported natural substrate
of DAO (1). Therefore, it can be suggested that not only degradation but also
biosynthesis of putrescine was decreased by the hypogravity stimulus. Unlike
putrescine, the levels of free spermidine and spermine were not significantly
affected by the reduced force of gravity, neither were they changed by hypergravity
at 22g.
In conclusion, the results reported in this investigation suggest that polyamine
metabolism by diamine oxidase might mediate cell sensitivity to simulated
microgravity. These findings might reflect an interaction between polyamines
and arachidonate cascade (2) in microgravity, which in turn might control
cell sensitivity (3).
Acknowledgements
This work was supported by Italian Space Agency (ASI), under contract n. ARS-96-31.
References
1. Maccarrone, M. et al., FEBS Lett. 408 (1997) 241-244.
2. Maccarrone, M. et al., J. Gravit. Physiol. (1998) in press.
3. George, P. et al., FEBS Lett. 425 (1998) 371-375.
FRTL5 CELLS RESPONSES TO THYROTROPIN HORMONE UNDER DIFFERENT GRAVITY CONDITIONS
A. Meli, G. Perrella, F. Curcio, R. Hemmersbach*, J. Neubert*, and F. S. Ambesi
Impiombato
Dipartimento di Patologia e Medicina Sperimentale e Clinica,
P.le S. Maria della Misericordia,33100 – Udine (Italy).
Tel: 39 0432 559203, Fax: 39 0432 545526, ambesi@dpmsc.uniud.it.
*D.L.R. (German Aerospace Center), Institute for Aerospace Medicine, 51140
Cologne, (Germany)
Aim of this investigation was to study the gravity effects on endocrine responses
in differentiated mammalian cultured cells. Thyroid hormones control every
cell in mammals and, as indicated by many hormonal changes in astronauts during
and shortly after space missions, its complex regulation is influenced by
gravity.
Many of the effects reported in vivo have been linked to changes found in
cell proliferation and differentiation in vitro.
To test the consequences of hypergravity on endocrine regulation, our test
system consists of a well characterized clone of differentiated normal follicular
thyroid cell strain in continuous culture, originally derived from adult rat
thyroids, named FRTL5. To establish if modifications of the gravitational
environment may interfere with post receptorial signal transduction mechanisms
in normal mammalian cultured cells, following our previous microgravity experiments,
we exposed Thyrotropin (TSH)-stimulated and unstimulated FRTL5 cells to hypergravity
(5xg and 9xg) in a low-speed centrifuge (German Aerospace Center -DLR-, Institute
of Aerospace Medicine, Division of Biology, Cologne, Germany), especially
designed for such kind of experiments. A full set of controls were also considered:
TSH-stimulated and unstimulated cells were carried in parallel but under the
normal 1xg (on ground) condition. From both 5xg and 9xg treated cells and
from the control 1xg cells, TSH-dose response curves were generated.
In thyroid follicular cells adenylate cyclase activity is under strong positive
TSH regulation. The FRTL5 cells response to acute TSH stimulation (60 min.)
was evaluated by measuring increase in intracellular cAMP.
FRTL5 cells exposed to hypergravity showed a marked increase in hormonally
stimulated cAMP production over the 1xg controls, both at 5xg and 9xg, at
all TSH concentrations tested (10-11 to 10-7M). Considering
the highest TSH concentration tested equal to 10-7M which is known
to generally produce the maximum stimulation in thyroid cells both in vivo
and in vitro, we found significant increases in cAMP production from centrifuged
compared to 1xg static control cells. Increases were 1.5-fold (at 5xg) and
2-fold (at 9xg).
These data obtained in hypergravity, well correlate with those obtained in
microgravity during the MASER-7 sounding rocket mission and strongly suggest
that alteration of the gravitational environment (either microgravity or hypergravity)
has an important impact on hormonal stimulation in terms of intracellular
cAMP production or, more extensively, in terms of post-receptorial signal
transduction mechanisms in normal mammalian cultured cells.
Acknowledgments: This work was supported by a grant from Agenzia Spaziale
Italiana (ASI). We wish to acknowledge the skilful technical assistance of
Ms. Filomena Ciarfaglia.
Key words: Gravitational Biology, Cell Biology, Hypergravity, Thyroid cells,
Thyrotropin.
ESA’S NEW INSTRUMENT TO OBSERVE CRYSTALLISATION OF BIOLOGICAL MACROMOLECULES
ON BOARD THE INTERNATIONAL SPACE STATION : THE PROTEIN CRYSTALLISATION DIAGNOSTICS
FACILITY
V. Pletser, O. Minster (1), J. Stapelmann, L. Potthast, R. Bosch
(2)
(1) ESTEC, European Space Agency
(2) DASA / Dornier
Perfect crystals of proteins and biological macromelecules are needed to reveal
structural information necessary for the understanding of their functions.
Weightless conditions encountered during orbital space flights have been used
for several years to grow better and larger crystals. The facilities and instruments
used so far to grow crystals in space have mostly focused on growing crystals
for post-flight analysis. The Advanced Protein Crystallisation Facility of
the European Space Agency (ESA), equipped with video recording of images and
interferogrammes in some reactors, enabled scientists for the first time to
partially document the events occurring during a space flight and, thereby,
pointed to the need to understand better the phenomena associated with the
crystallisation processes and their impact on crystal quality.
Therefore, a new facility, the Protein Crystallisation Diagnostics Facility
(PCDF), is presently under development at DASA/Dornier under an ESA contract
that will allow monitoring of the crystallisation of proteins with various
diagnostics means (video microscopy, dynamic light scattering and Mach-Zehnder
interferometry) and control the growth conditions. The present design foresees
the implementation of only the batch and the dialysis crystallisation technique.
Process control of each individual reactor in terms of temperature and concentration
can allow optimisation through several crystallisation/dissolution cycles
to be envisioned.
The design will be such as to allow implementation of other sensors in the
future.
The PCDF is intended to be flown on the International Space Station, accommodated
in the European Drawer Rack in ESA's Columbus Laboratory module, in the 2002-2003
timeframe, using the regular up and down capabilities of NASA's Shuttle.
The actual design features of the PCDF will be presented and the foreseen
utilisation scenario will be discussed.
EVALUATION OF SURFACE TENSION GRADIENT OF MOLTEN SILICON AS A
FUNCTION OF OXYGEN PARTIAL PRESSURE
E. Ricci, R. Novakovic, *E.Arato, *M.Ratto and A. Passerone
Istituto di Chimica Fisica Applicata dei Materiali - Consigho Nazionale
delle Ricerche
Via de Marini 6, - 16149, Genova, Italy
*Dipartimento di Ingegneria Ambientale, Universita di Genova
Via Opera Pie 15, 1-16145 Genova, Italy
Silicon crystal growth technologies (Czochralski and Floating zone methods)
are controlled by complex heat and mass transfer pro~esses which include different
flow types. The most important of them are the Marangoni flow and buoyancy
convection. The first one is thought to be the main cau~ of oxygen transfer
into the crystal. However it is difficult to isolate the Maranooni effect,
since buoyancy convection coexists with other flow patterns in molten silicon.
The driving force for the Marangoni flow is the surface tension gradient.
The surface tension mainly depends on temperature and adsorption parameters.
At present, the surface tension of molten silicon is not known accurately,
and the experimental data show a significant degree Of scatter. This can be
attributed to the difficulties in surface tension measurements, which are
mainly due to t~e high melting point of silicon and to its high chemical reactivity.
Simulation models which describe transport of oxygen in the liquid metal-atmosphere
Systems for different fluid-dynamic conditions have been developed by this
Research group. These models, based on the hypothesis of complete absence
of buoyancy-driven convection, help evaluating the surface tension gradients.
Based on thermodynamic analysis of the Si-O system, some preliminary evaluation
of its behaviour1 varying the operating conditions will be reported.
Microgravity conditions will offer the possibility to test these models and
to clarify the key differences with ground based processes.
TEEMING (Telemetic Energy Exchange Measurements IN microGravity )
A. Sacripanti
ASI - CONI (Institute of Sports Sciences) - ENEA- University of Udine
This paper deals with the rationale behind and with the state of the art of
the ASI-CONI-ENEA-University of Udine joint research called TEEMING (Telemetic
Energy Exchange Measurements IN microGravity ).
The complex multidisciplinary feature of the study, which pertains to physics,
physiology, electronics, bioengineering and the basic use of the new bolometric
thermal camera, calls for an actual revision of the experimental constants
in the equation used for quantitative assessments. Moreover, further efforts
have been made to translate into C++ a more advanced energy exchange equation
has been developed and a computer program originally prepared in Fortran:
this is expected to yield the proper set up for suitable comparison of the
measurements obtained on Earth with those performed onboard the International
Space Station.
PLATEAU-EXPERIMENTS ON THERMOCAPILLARY CONVECTION
J. Siekmann*) and M. Pehl**)
*) Fachbereich 12 – Mechanik, Universität-GH Essen,
Schützenbahn 70, D-45127 Essen, Deutschland
**) Lehrstuhl für Fluidmechanik und Prozeßautomation,
Technische Universität München, D-85350 Freising, Deutschland
Investigations on Marangoni-convection in an earthbound laboratory are limited
by the fact that the interfacial forces have a smaller order of magnitude
than volume forces. With the relevant dimensionless numbers: Reynolds-, Marangoni-
and the dynamical Bond number, characteristics are given for physical similarity,
while the static Bond number is a characteristic number for the geometric
similarity of diverse experimental configurations. Interfacial forces are
dominant if the Bond numbers are small with respect to one. Thus experimental
research on interfacial phenomena can be carried out in case of (a) microgravity
experiments, (b) small characteristic dimensions and (c) simulation experiments
using liquids having small density differences (Plateau-simulation). By means
of a Plateau arrangement the thermocapillary convection in a liquid drop has
been dealt with. Observations of photographically documented convective flow
shapes are communicated and discussed.
THE RENEWABLE THERMODYNAMICS OF LIGHT FOR DIRECT SOLAR ENERGY CONVERSION
IN SPACE
T. Sukhodolsky
General Physics Institute, Vavilov street 38 Moscow, Russia
Fax: (095)1352055, Phone(095)1328164, e-mail:sukhodol@kapella.gpi.ru
Mechanical energy is known to convert into thermal form (heat) without any
restriction. Any opposite conversion of heat into mechanical energy owing
to the work produced in the heat engines has been restricted by principle
of Carnot. The thermal efficiency to convert solar energy by any heat engine
is derived in framework of classical reversible thermodynamics and the concept
of entropy. This paper presents introduction into the elements of renewable
thermodynamics for direct conversion of solar light into mechanical power
available without mechanisms. Using non-equilibrium phase transition of first
order in liquids to mechanical power generation is introduced to be a new
trend in solar engineering. This approach originated from laser experiments
is to promote a new set of devices for direct vibration generation and extraction
of water by sunlight. In order to involve solar light under non-equilibrium
with respect to matter as a motive power within thermodynamics, the principle
of Carnot for heat engines is assumed to be also valid for processes (cycles)
of mechanical energy production by light in liquid matter within constant
volume system as a whole. The basic elements of renewable thermodynamics of
light for direct generation mechanical energy of vibrations and motive forces
of extraction can be presented by next figure:
The absorbing part of condensed matter by optical pumping is considered as
a heat source for production of entropy by heat-transfer into dark surrounding
that plays role of heat sink. The principle of Carnot is used together with
common accepted definition of non-equilibrium entropy in order to describe
the excitement of heat source and its next relaxation. The relaxation of heat
source is considered as both spontaneous (idle cycle of entropy production)
and stimulated (work cycle of entropy production). Such model allows involving
the theorem of Carnot into the problem of self-organization of renewable heat
cycles observed in several experiments by phase transition of first order
powered by light in absorbing liquids that is being accompanied by production
of mechanical energy by constant volume of system as a whole. The new formulation
of Carnot theorem and fundamental maximum of renewable conversion have been
derived.
Here T0 is temperature of surroundings, D
T is the temperature difference pumped by solar light. The experiments
on the direct conversion of energy of light into energy of mechanical motion
within dramatic simplicity of necessary equipment are described. The free-piston
actuator to gather non-equilibrium propulsive energy of evaporation into mechanical
energy is described as a prototype of a new mechanical energy source. It is
proposed to join renewable and reversible methods of solar energy conversion.
Non-available for direct conversion heat powered by solar light is able to
be converted by traditional equilibrium heat engines that has definite perspectives
to increase efficiency of solar engines with open heat cycles in order to
combine renewable and reversible processes.
STUDY OF A REGENERATIVE SYSTEM FOR THE LIFE SUPPORT IN THE SPACE
* A. Virzo De Santo, * N. D'Ambrosio, ° S. De Pascale, ^ V. De Chiara
* Dip. Biologia Vegetale, Universita' degli Studi di Napoli "Federico
II" - Napoli (Italy)
Virzo@unina.it, Dambrosi@unina.it
° Dip. Ing. Agraria ed Agronomia del Territorio, Universita' degli Studi di
Napoli "Federico II" - Napoli (Italy) , Depascal@unina.it
^ MARS Center - Napoli (Italy) Dechiara@mars.unina.it
There is a growing interest towards CELSS, as systems devoted to support life
in the space. Within this framework and in the International Space Station
utilization era, the aim of our project is to carry out a preliminary study
on ground, in the perspective to perform the related space experimentation
to verify the results obtained on ground.
The focus of this research is on a plant system able to function as a regenerative
system of oxygen and water, while producing edible matter and removing CO2
from the atmosphere.
Plant cultivation in CELSS may contribute to:
- regenerate ambient air of the pressurized modules (plants uptake CO2 from
air and release O2 by photosynthesis);
- recover water by transpiration;
- recycle liquid waste of the crew;
- meet nutritional and caloric needs of the crew.
The intent is to design and build up an environmentally (i.e. temperature,
humidity, irradiance) controlled growth chamber where the atmospheric concentration
of O2 and CO2 will be constantly monitored by mean of IRGA, and kept at a
constant value. In fact the O2 will be constantly removed from the growth
chamber, simulating the regenerative action of the system, while it will be
enriched with CO2, that for the flight system will be extracted from the ambient
air of the pressurized modules.
For this system, two edible species could be used, characterized by two different
photosynthetic pathways, C3 and CAM, which will ensure a continuous CO2 uptake
during the day and during the night, without using a 24 h photoperiod.
The species will be grown in closed cycle hydroponic cultures. Growth and
photosynthetic efficiency at both leaf and community levels will be monitored,
and all environmental parameters will be optimized to ensure the higher productivity
rate of the system.
Finally, the O2/CO2 balance of the whole system will be calculated in order
to obtain information on the efficiency of this system in relation to the
crew need.
The present research program is funded by Italian Space Agency (ASI).
NON-NAVIER-STOKES FLUIDYNAMICS IN VAPOUR CRYSTAL GROWTH
A. Viviani, C. Golia
Seconda Università di Napoli, Dipartimento di Ingegneria Aerospaziale
via Roma 29, I-81031 Aversa, Italy. e-mail: viviani@unina.it
The fluid-dynamics of crystal growth from vapour has been recognized as playing
an important role in technological processes employed to grow bulk crystals
or epitaxial films by physical and chemical vapour transport; indeed the final
properties of the crystal are strongly influenced by the thermodynamic conditions
at the vapour-crystal interface and these, in turn, are the result of the
complex physico-chemical mechanisms involved in the vapour transport.
In recent years a new impetus for studying vapour crystal growth fluid-dynamics
has come from the utilization of space microgravity environment, where low-gravity
conditions are expected to reduce gravity-driven disturbances and, therefore,
to enhance the final properties of the crystals, resulting from the complex
physico-chemical phenomena occurring in the vapour phase.
A large number of works, both numerical and experimental, have been performed
on the subject, and different models have been proposed to investigate the
role of natural convection and the interface kinetics in various geometrical
configurations, for different gravity levels. In particular, double-diffusive
vapour transport in idealized geometrical configurations (plane or cylindrical
enclosures with differentially heated end walls) has been extensively investigated
considering Navier-Stokes fluid-dynamics along with no-slip boundary conditions
on the passive boundaries.
However, some "gas-kinetic" effects, usually masked by gravity on Earth, such
as thermal and concentration stresses (volume-driving actions), thermal and
concentration creep (surface-driving actions) may represent important sources
of convection (described by Burnett equations and slip-boundary conditions)
under the conditions encountered in low-gravity crystal growth but also, depending
on the size of the system and temperature/concentration differences, on earth.
The new transport mechanisms have been investigated by theoretical and numerical
methods, demonstrating that these effects have an important role in processes
of vapour crystal growth in space. In this lecture we deal with new possible
sources of convection arising from non-linear irreversible thermodynamic effects
(non-Navier-Stokes fluid-dynamics) and slip boundary conditions during typical
processes of crystal growth from vapour phase. Attention is focused on the
role played by Burnett stresses and side-wall creep in single component gases,
as well as in the case of binary mixtures.
A rigourous non-dimensional order of magnitude analysis has been performed
to compare these effects to the vapour transport mechanisms usually considered
in vapour crystal growth fluid-dynamics, i.e. buoyancy and the so-called Stefan-Nusselt
flow due to the evaporation at the source and condensation at the crystal;
new characteristic velocities, lengths and corresponding new characteristic
non-dimensional numbers are introduced and discussed for the characterization
of the new phenomenologies, by identifying 15 classes of convection, and a
priori conditions for the existence and characterization of all possible
classes of convection and flow regimes, in terms of the problem's data, are
formulated, by drawing the appropriate regime planes.
Then, we present numerical results obtained with the new set of field equations
(Burnett equations with slip conditions) for geometrical configurations of
interest in crystal growth by physical vapour transport. The results are presented
for several combinations of the non-dimensional characteristic parameters,
ranging from microgravity to earth environment conditionsand compared with
the results of the corresponding solution of the Navier-Stokes approximation.
CONTINUOUS CULTIVATION IN A SPACE BIOREACTOR
I. Walther, B. van der Schoot and A. Cogoli
Space Biology, ETHZ, Zurich, Switzerland
On Earth, biotechnology has already been used for centuries. But it is in
the last 30 years that it has really flourished, thanks the use not only
of microorganisms, but also of plants and mammalian cells. In the last years,
the interest in tissue engineering has risen drastically. New devices and
cultivation processes have been developed for the growth of mammalian tissues.
Continuous cultivation in the defined and controlled environment of a bioreactor
is a prerequisite for the quality and the reproducibility of such cultures.
Moreover a very low shear force environment is one of the most important factor
for a successful cultivation of mammalian cells.
Such an environment is provided by microgravity. We present here the technical
data on the performance of a controlled miniaturised space bioreactor, which
has flown aboard the Shuttle in 1994 and 1996. This first instrument was designed
for yeast cells that we chose as a model organism. It is fitting in an ESA
standard container Type II (87x63x63 mm). The cells were provided with fresh
medium at different but fixed dilution rates during the whole experiment (8
days) by means of a piezo-electric pump. A microsensor measured different
parameters (pH, temperature, Redox potential), and the pH of the culture was
regulated electrochemically, so that no concentrated base had to be used.
The technical data were delivered on-line to the ground during the missions.
In the second flight, the bioreactor was outfitted with an additional sensor
to monitor the flow rate. Technically, the bioreactor has functioned according
to expectations. Biological data were gathered by means of samples, taken
at preset intervals (5 times). Two samples of 500 µl were withdrawn per sampling,
one sample was frozen, and the other one was fixed. The biological analyses
were performed post-flight. They included morphological studies (electron
microscope micrographs, budding scars analyses), metabolite measurements (glucose,
EtOH), physiological analyses (optical density, cell cycle, cell size). Biological
analyses and electron microscopy showed that the general metabolism and morphology
of the cells were similar in space as on ground. Interestingly, we observed
that the specific bipolar bud scar positioning was altered under microgravity
conditions. In fact, a statistically significant higher numbers of flight
cells show a random distribution of scars compared to the ground samples where
scars are localised at both poles in the majority of the cells.
In conclusion it can be said that the technology used for this bioreactor
has been proved adequate for the continuous cultivation of cells in space
and can be further used for the development of an instrument adapted to the
cultivation of mammalian cells.
MAGNETIC VARIATION AND COMPENSATION OF EARTH'S
GRAVITY IN HYDROGEN AT LIQUID-VAPOR COEXISTENCE
R. Wunenburger*, D. Chatain**, Y. Garrabos*, D. Beysens**
*Institut de Chimie de la Matière Condensée de Bordeaux
UPR 9048 Centre National de la Recherche Scientifique,
Avenue Dr. A. Schweitzer, 33608 Pessac Cedex, France
** Département de Recherche Fondamentale sur la Matière Condensée
Commissariat à l’Energie Atomique 17, Rue des Martyrs, 38504 Grenoble
Cedex 09, France
Diamagnetic forces are proportional to the density of materials
and can add to or subtract from thc Earh's gravity. Varying the magnetic
field enables the effective gravitational field g*
to be tuned, resulting in a higher effective acceleration field or else exactly
compensating the gravitational field. In order to determine the range of applicability
of such a technique for gas-liquid systems, we study the behavior of the capillary
length of hydrogen on the liquid-vapor coexistence line, for temperatures
T far from and close to the critical point (tempcrature Tc=33K).
The large diamagnetic susceptibility of hydrogen allows the compensation of
gravitational forces to be performed at relatively moderate field gradients,
such as in the field created by a superconducting 10 Tesla magnet near one
of its ends.
We find that the tuning of the magnetic field allows one to vary the effective
gravitational field g* from 2.2 g to -0.2 g. In a cylindrical sample of 3
mm diameter and 2 mm thickness, the capillary length can be expressed within
a few mK from Tc by Ic = (s
/d r
g*)˝ , with s
the surface tension and d
r the difference
between liquid and gas densities. The temperature variation of s
and d r
combines on the coexistence line to give the expected (T -Tc) dependence:
Ic - (Tc-T)0.47.
Preliminary phase separation experirnents at g*=0 are reported. Qualitative
behavior is similar to that obtained in orbit, where gravitational forces
are compensated by centrifugal forces. However, the gravitational forces can
be effectively compensated only to the extent that the field gradient is uniform.
Very near the critical point, where the surface tension is small, the deviation
from a uniforrn gradient is observed as a deformation from the spherical shape
by a central force field (we call it the "banana" effect). This limitation
is expressed as a maximum length which scales as the capillary length and
which corresponds to the scale where gravity cannot be compensated any more.
PHYSICAL VAPOUR TRANSPORT GROWTH OF UROTROPINE CRYSTALS
M. Zha*, L. Zanotti*, C. Salati**, L. Carotenuto***, C. Paorici**
* MASPEC-CNR Institute, Parco Area delle Scienze, 43100 Parma, Italy
**Physics Dept., Univ. of Parma, 43100 Parma, Italy
*** MARS-Center, Via Comunale Tavernola, 80144 Naples, Italy
The MASPEC-CNR Institute of Parma, in collaboration with the Physics Dept.
of the University of Parma and the MARS Center of Naples are interested in
the growth of single crystals of organic materials for application in linear
and non-linear optics.
Growth experiments in microgravity are envisaged in order to investigate some
basic aspects of the growth from vapour phase, in particular the relation
between microcompositional inhomogeneity and convective modes in the vapour.
It is here reported for the first time the growth of urotropine (HMT = hexametylentetramine)
crystals by a semi-open physical vapour transport (SOPVT) technique.
HMT crystals, approximately 1 cm3 in volume, are grown on a glass
pedestal from solution-grown seeds.
The final habit of the crystal is limited by rhomboedrical (111) faces which
develop on an otherwise hemispherical shape.
X-ray diffraction investigations (rocking curves and topographes) point to
a still non-homogeneous crystal structure which very likely originates at
the seed-crystal interface. However, in comparison with solution-grown samples,
the best structural quality was observed in SOPVT-grown samples.
Preliminary mass-transport calculations point to large kinetical limitations
at the growing interface.
As a final remark, this SOPVT process is to be seen as a first technical step
in a vapour growth process, which is developed at MASPEC aimed at the final
growth of high quality HMT cruystals in closed-PVT systems.
