Identification of specific gravity sensitive signal transduction pathways in human A431 carcinoma cells.

Epidermal growth factor (EGF) activates a well characterized signal transduction cascade in human A431 epidermoid carcinoma cells. The influence of gravity on EGF-induced EGF-receptor clustering and early gene expression as well as on actin polymerization and actin organization have been investigated. Different signalling pathways induced by the agents TPA, forskolin and A23187 that activate gene expression were tested for sensitivity to gravity. EGF-induced c-fos and c-jun expression were decreased in microgravity. However, constitutive beta-2 microglobulin expression remained unaltered. Under simulated weightlessness conditions EGF- and TPA-induced c-fos expression was decreased, while forskolin- and A23187-induced c-fos expression was independent of the gravity conditions. These results suggest that gravity affects specific signalling pathways. Preliminary results indicate the EGF-induced EGF-receptor clustering remained unaltered irrespective of the gravity conditions. Furthermore, the relative filamentous actin content of steady state A431 cells was enhanced under microgravity conditions and actin filament organization was altered. Under simulated weightlessness actin filament organization in steady state cells as well as in EGF-treated cells was altered as compared to the 1 G reference experiment. Interestingly the microtubule and keratin organization in untreated cells showed no difference with the normal gravity samples. This indicates that gravity may affect specific components of the signal transduction circuitry.     

Vertical profiles of halocarbons in the stratosphere

Stratospheric air samples collected between 10 and 35 km altitude my means of a cryogenic sampler were analyzed by gaschromatography. Thus vertical profiles of source gases for halogen radicals were derived, such as CCl₄, CCl₃F, CCl₂F₂, CClF₃, CF₄, C₂F₃Cl₃, C₂F₄Cl₂, C₂F₅Cl, C₂F₆, CH₃Cl, CH₃CCl₃, CHF₂Cl, CH₃Br, CBrF₃, and CBrCl₂F. Systematic discrepancies between measured and modelled halocarbon profiles point to deficiencies of present one- and two-dimensional models. Measurements of fully halogenated hydrocarbons provide a tool for systematically studying these deficiencies and thus improving the models.     

ELF radio signals produced in the auroral ionosphere by non-linear demodulation of signals from high-power amplitude-modulated transmitters

ELF and VLF radio signals were recorded in the afternoon to early morning (local time) between 24 March and 4 April 1979, in Northern Scandinavia. Apart from signals of natural origin, timing signals, i.e. six pips of equal duration of 105 ± 8 ms, at 1 kHz ± 0.5 Hz, were observed on the hour UT. Such signals only occur on days of relatively high geomagnetic activity during enhanced auroral electrojet activity. They are believed to be generated by non-linear demodulation (self-detection) of signals from two or more amplitude modulated transmitters in the USSR, operating at 173, 200, 236, 263 and 657 kHz. The simplest explanation for the observations is provided by the three transmitters operating at 173 kHz.     

Metallic multilayers: New possibilities in X-UV optics

Reflectivities measured on metallic multilayers obtained by evaporation methods have demonstrated the validity of theoretical predictions. Experimental tests using wavelengths from 1.54 Å to several hundred of angstroems give a firm basis for proposed new designs for X-UV optics. This new kind of Bragg reflector can be tailored for any wavelength and any incidence angle, because the period of evaporation of the layered synthetic medium can be freely chosen. Such artificial Bragg reflectors are more efficient than natural, organic or molecular crystals which have been employed until now in the X-UV, and can overcome the weak luminosity and astigmatism problems encountered in grazing incidence optics. The possibility of evaporating multilayers on shaped substrates will lead to optics with focussing and selectivity fuctions given by a single reflection.     

Software Maintenance Criteria for Small Microprocessor-Based Systems

Criteria is provided for designing and implementing small microprocessor-based programs with the objective of enhancing their maintainability properties. Since microprocessor-based programs typically have relatively short schedules and low budgets. it is necessary to adapt maintainability enhancing practices for these projects in such a manner that their impact in these critical areas is not excessive. Since many of the practices which can be used to enhance maintainability actually coincide with those which improve productivity during software development, application of those practices should incur little or no added cost or duration to a microprocessor-based program. This paper suggests practical steps which can be applied to the software design and implementation activities, to the software documentation, and to the development environment which will enhance the maintainability of the resultant computer programs.     

Hydrodynamic forces resulting from liquid motion in capillary tubes

The wetting kinetics of model tubes of different geometrical shape has been investigated theoretically and experimentally under conditions of simulated zero-gravity (earthbound laboratory experiments) and low gravity (sounding rocket experiments within the TEXUS-programme). The present note deals with the hydrodynamic forces (capillary-, friction-, inertia forces, etc.) resulting from capillary rise in cylindrical, conical and sinusoidal tubes. The rôle of these forces is studied numerically in some detail.     

Bars — A dual bistatic auroral radar system for the study of electric fields in the Canadian sector of the auroral zone

One instrument of the Canadian Auroral Network for the Open Program Unified Study (CANOPUS) is a pulsed dual bistatic auroral radar system (BARS) for the mapping of ionospheric electric fields, using the STARE technique originated by R.A. Greenwald [14]. The Canadian system is presently in the specification and design phases, with the objective of being operational by mid-1984. This paper describes the geometry of the BARS system, the design considerations, and the planned data and control network.     

The state experiment — mesospheric dynamics

The $\text{ST}$ructure and $\text{A}$tmospheric $\text{T}$urbulence $\text{E}$nvironment (STATE) experiment was conducted during the second week of June 1983 at Poker Flat Research Range, Alaska. The measurements focus on a study of the middle atmosphere dynamics by comparison between in-situ probe measurements and MST radar measurements. Rocket launchings were conducted at three periods which were selected by monitoring the doppler velocity spectra of the MST radar.The STATE program has included the efforts of several scientists in planning and carrying out the ground-based and rocket measurements. An overview of the program is given together with some preliminary results. The regions in intense backscatter signals detected by the MST radar are shown to correlate with large irregularities in the electron profiles measured.     

Scientific results from the pioneer Saturn infrared radiometer

The Pioneer 11 Infrared Radiometer instrument made observations of Saturn and its rings in broadband channels centered at 20 and 45 μm and obtained whole-disk information on Titan. A planetary average effective temperature of 96.5±2.5 K implies a total emission 2.8 times the absorbed sunlight. Correlation with radio science results implies that the molar fraction of H₂ is 90±3% (assuming the rest is He). Temperatures at the 1 bar level are 137 to 140 K; regions appearing cooler may be overlain by a cloud acting as a 124 K blackbody surface. A minimum temperature averaging 87 K is reached near 0.06 bars. Ring boundaries and optical depths are consistent with those at optical wavelengths. Ring temperatures are 64–86 K on the south (illuminated) side, ～54 K on the north (unilluminated) side, and at least 67 K in Saturn's shadow. There is evidence for a south to north drop in ring temperatures. Titan's 45 μm brightness temperature is 75±5 K.     

Unique biological aspects of radiation hazards--an overview.

Low orbit, geostationary, and deep-space flights differ from one another with respect to particle radiation environment, participating population size, mission duration, and biological risks other than radiation. It is proposed that all of these factors be considered in the setting of safety standards and, in particular, that the rem-dose concept is applicable only to radiations having low and intermediate linear energy transfer (electrons, protons, and helium ions), whereas the incidence of microlesions is a more meaningful indicator of the hazard due to higher-Z, high energy (HZE) particles. A microlesion is the biological injury inflicted in a specific tissue by a single HZE particle, and it is still in need of quantitative biological definition for specific mammalian tissues. If for example, a microlesion is taken as due to a HZE particle track 10 cell diameters long with LET > 200 KeV/micrometer in its core and > 25 rad dose in its penumbra at a distance of 10 micrometers, then the microlesion dose rate in geostationary orbit, for example, is about 9,000 microlesions per cm3 of tissue per month.