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A field of applied statistics called survival analysis has been developed over several decades to deal with censored data, which occur in astronomical surveys when objects are too faint to be detected. How these methods can assist in the statistical interpretation of astronomical data are reviewed.
A logical place to search for surviving pristine nebular material is in the fine-grained matrices of ordinary and carbonaceous chondrites of petrographic type 3. Unfortunately, many of these chondrites have experienced brecciation, thermal metamorphism, and aqueous alteration, so that interpreting individual features in terms of specific nebular conditions and/or processes is difficult. It follows that the origin and evolutionary history of such matrix phases are controversial, and a consensus is difficult to define. In this chapter, therefore, after summarizing the salient mineralogical, petrographic, chemical, and isotopic features of matrix in apparently primitive chondrites, an attempt is made to provide an overview both of areas of agreement and of topics that are currently in dispute.
Experiments are discussed in which the cell-cycle dependency of the repair deficiency of the S/S variant of the L5178Y murine leukemic lymphoblast was examined by treatment with the heavy ions, Ne-20, Si-28, Ar-40, Fe-56, and Nb-93. Evidence from those studies provide support for the notion that as the linear energy transfer of the incident radiation increases the ability of the S/S cell to repair radiation damage decreases until it is eliminated around 500 keV/micron. In the region of the latter linear energy transfer value, the behavior of the S/S cell approximates the ideal case of target theory where post-irradiation metabolism does not influence cell survival.
With and without bioconvective pattern formation, a theoretical model predicts growth in light-limited cultures of motile algae. At the critical density for pattern formation, the resulting doubly exponential population curves show an inflection. Such growth corresponds quantitatively to experiments in mechanically unstirred cultures. This attaches survival value to synchronized pattern formation.
The Architecture for Survivable System Processing (ASSP) Program is a multi-phase effort to implement Department of Defense (DOD) and commercially developed high-tech hardware, software, and architectures for reliable space avionics and ground based systems. System configuration options provide processing capabilities to address Time Dependent Processing (TDP), Object Dependent Processing (ODP), and Mission Dependent Processing (MDP) requirements through Open System Architecture (OSA) alternatives that allow for the enhancement, incorporation, and capitalization of a broad range of development assets. High technology developments in hardware, software, and networking models, address technology challenges of long processor life times, fault tolerance, reliability, throughput, memories, radiation hardening, size, weight, power (SWAP) and security. Hardware and software design, development, and implementation focus on the interconnectivity/interoperability of an open system architecture and is being developed to apply new technology into practical OSA components. To insure for widely acceptable architecture capable of interfacing with various commercial and military components, this program provides for regular interactions with standardization working groups (e.g.) the International Standards Organization (ISO), American National Standards Institute (ANSI), Society of Automotive Engineers (SAE), and Institute of Electrical and Electronic Engineers (IEEE). Selection of a viable open architecture is based on the widely accepted standards that implement the ISO/OSI Reference Model.
A number of methods for providing adequate protection from meteoroid and orbital debris impact are available to space vehicle designers. Several techniques to reduce the risks from meteoroid and debris (M&D) impact are presented and assessed in the context of Space Station Freedom (SSF) applications. Evaluations of these options were made using BUMPER, a computer program to perform M&D analyses. M&D survivability can be improved by conducting an in-depth analysis of spacecraft penetration risks to reveal weak areas of the design and to determine optimal distribution of shielding and/or protection capability around the space vehicle. This paper compares enhanced hypervelocity impact shielding techniques that are more weight efficient than conventional shielding approaches. Other design and operational strategies to reduce meteoroid and debris risks are also discussed.
Infrared spectra of dusty galactic environments often contain emission features attributed to polycyclic aromatic hydrocarbons or PAHs, which can be considered to be very small grains or very large molecules. Although IR spectra of starburst galaxies almost always show these emission features, similar spectra of active galaxies are usually featureless. Even in those active galaxies that do exhibit PAH emission, the PAHs still appear to be eradicated from the nuclear region. This dichotomy suggests that PAHs are destroyed by the intense hard radiation field from an AGN. Laboratory experiments show that certain PAHs are, in fact, so effectively destroyed by individual EUV and X-ray photons that they cannot survive even at kiloparsec distances from active nuclei. Regions within active galaxies that do show PAH emission must therefore be shielded from the central X-ray source by a substantial column density of X-ray absorbing gas.
One of the most difficult obstacles to establishing a causal connection between mass extinctions and large body impacts is the existence of what appear to be many more KT survivor species than previously suspected. Though interpretations of 'Cretaceous' faunal elements in lowermost Danian sediments differ, this enigmatic fauna has not been recovered from every biozone-complete boundary section, including the El Kef stratotype. In terms of their potential for providing constraints on scenarios seeking to account for the KT extinction event, the significance of such observations cannot be overstated. Owing to the consistency with which these observations have been made over the last several years, the possibility of widespread trans-KT biotic survivorship can no longer be dismissed. Rather, the survivorship hypothesis must be tested alongside its alternative (the reworking hypothesis) to determine which explains the available data in the most complete yet parsimonious manner. Moreover, valid tests for survivorship cannot be based on negative evidence or on the assumption that only a small cohort of species could have survived the KT boundary event. Several authors have recently proposed various criteria that might be used to test alternative interpretations for this aspect lowermost Danian biotic record.
The Architecture for Survivable Systems Processing (ASSP) program is a two phase program whose objective is the derivation, specification, development and validation of an open system architecture capable of supporting advanced processing needs of space, ground, and launch vehicle operations. The output of the first phase is a set of hardware and software standards and specifications defining this architecture at three levels. The second phase will validate these standards and develop the technology necessary to achieve strategic hardness, packaging density, throughput requirements, and interoperability/interchangeability.
This report documents the research activities for space suit survivability material enhancements. Self-sealing mechanisms for the pressure envelope were addressed, as were improvements in materials for cut, puncture, and hypervelocity impact resistance.
To determine the survivability of ejection from a planet, two uv-resistant spores have been tested for resistance to high acceleration and high change in acceleration, or jerk.
The majority of carbonaceous meteorites studied today are thought to originate in the asteroid belt. Impacts among asteroidal objects generate heat and pressure that may have altered or destroyed pre-existing organic matter in both targets and projectiles to a greater or lesser degree depending upon impact velocities. Very little is known about the shock related chemical evolution of organic matter relevant to this stage of the cosmic history of biogenic elements and compounds. The present work continues our study of the effects of shock impacts on selected classes of organic compounds utilizing laboratory shock facilities. Our approach was to subject mixtures of organic compounds, embedded in a matrix of the Murchison meteorite, to a simulated hypervelocity impact. The molecular compositions of products were then analyzed to determine the degree of survival of the original compounds. Insofar as results associated with velocities < 8 km/sec may be relevant to impacts on planetary surfaces (e.g., oblique impacts, impacts on small outer planet satellites) or grain-grain collisions in the interstellar medium, then our experiments will be applicable to these environments as well.
Footage shows astronaut candidates during land survival training, where they are seen performing such activities as constructing shelters, making nets, and finding food.
An experimental impact study investigating the fragmentation of various projectiles, including meteorite, at speeds up to 1.8 km/s. The results have implications for the survivability of meteorites impacting planetary and asteroidal surfaces. Additional information is contained in the original extended abstract.
Decompression sickness (DCS) is a complex, multivariable problem. A mathematical description or model of the likelihood of DCS requires a large amount of quality research data, ideas on how to define a decompression dose using physical and physiological variables, and an appropriate analytical approach. It also requires a high-performance computer with specialized software. I have used published DCS data to develop my decompression doses, which are variants of equilibrium expressions for evolved gas plus other explanatory variables. My analytical approach is survival analysis, where the time of DCS occurrence is modeled. My conclusions can be applied to simple hypobaric decompressions - ascents lasting from 5 to 30 minutes - and, after minutes to hours, to denitrogenation (prebreathing). They are also applicable to long or short exposures, and can be used whether the sufferer of DCS is at rest or exercising at altitude. Ultimately I would like my models to be applied to astronauts to reduce the risk of DCS during spacewalks, as well as to future spaceflight crews on the Moon and Mars.
Using an optically thick inner disk and an extended, optically thin outer disk as described in Mosqueira and Estrada, we compute the torque as a function of position in the subnebula, and show that although the torque exerted on the satellite is generally negative, which leads to inward migration as expected, there are regions of the disk where the torque is positive. For our model these regions of positive torque correspond roughly to the locations of Callisto and Iapetus. Though the outer location of zero torque depends on the (unknown) size of the transition region between the inner and outer disks, the result that Saturn's is found much farther out (at approximately 3r(sub c, sup S) where r(sub c, sup S) is Saturn's centrifugal radius) than Jupiter's (at approximately 2r(sub c, sup J), where r(sub c, sup J) is Jupiter's centrifugal radius) is mostly due to Saturn's less massive outer disk, and larger Hill radius. For a satellite to survive in the disk the timescale of satellite migration must be longer than the timescale for gas dissipation. For large satellites (approximately 1000 km) migration is dominated by the gas torque. We consider the possibility that the feedback reaction of the gas disk caused by the redistribution of gas surface density around satellites with masses larger than the inertial mass causes a large drop in the drift velocity of such objects, thus improving the likelihood that they will be left stranded following gas dissipation. We adapt the inviscid inertial mass criterion to include gas drag, and m-dependent non-local deposition of angular momentum.
Aqueous alteration has played a significant role in the geological evolution of almost all the chondrite groups and attests to the importance of water during the earliest history of the solar system. Among the chondrites that show evidence of aqueous alteration the CM chondrites, in particular, have received considerable attention, because of their primitive composition and the fact that they preserve a record of incomplete hydration. Petrologic studies of this group of meteorites have helped provide important insights into aqueous alteration processes and the nature of the alteration products. However, due to the complex history of these chondrites, important details of the alteration remain enigmatic. Among the major problems to be resolved are the location and timing of aqueous alteration as well as the relationship between alteration and brecciation. Although many authors favor aqueous alteration within a parent body environment, there is also evidence that some of the components of CM chondrites may have experienced aqueous alteration prior to accretion. One of the key lines of evidence for alteration in a pre-accretionary environment is the presence of unaltered metal grains associated with hydrated phases. Low-Ni metal (kamacite) is typically one of the first phases in CM chondrites that alters in the presence of water. However, in some CM chondrites, such as Yamato 791198, micron-sized metal grains are present within the hydrated fine-grained rim material around chondrules. In addition, nanometer-sized grains that have been interpreted as being unaltered metal particles have been reported in the relatively heavily altered CM chondrite, ALH 81002. In most cases, these occurrences have been interpreted as being the result of mixing of anhydrous and hydrous materials prior to accretion. According to this hypothesis, the metal grains remain unaltered because little or no post-accretionary alteration took place. Whilst such a scenario is plausible, no alternative explanations such as the presence of submicron protective layers or a minor element chemistry that might inhibit oxidation have been investigated in detail. During a study of the distribution of carbonaceous material in fine-grained rims on chondrules in Murchison, previously unidentified, nanometer-sized metal grains were observed. These grains were characterized in detail using high resolution TEM and energy filtered TEM (EFTEM) and provide important insights into how metal grains in CM chondrites may survive aqueous alteration.
Between October 16th and November 9th 2002, the first NASA Ames DDF Licancabur multidisciplinary expedition initiated the investigation of the biology and environment for life in the highest lake on Earth located at the summit of the Licancabur volcano (6017 m/20,056 ft) at the boundary of Chile and Bolivia. The low oxygen, low atmospheric pressure, high-UV radiation, average temperature, volcano-tectonic and hydrothermal environment make the site a close analog to Martian paleolakes 3.5 billion years ago. The overall goal of the project is to understand through a series of high altitude scientific expeditions what strategies life is using to defend itself against killer-level UV radiation and environmental extreme conditions at this altitude. Several other lakes are located at 4300 m at the foot of the Licancabur volcano (hereafter named laguna Blanca and Laguna Verde). They were also investigated using identical experiments and methods as for the summit lake in order to compare the results and better understand the evolution of survival strategies at transitioning elevations. The lagunas are geothermally heated and many springs provide water at various temperatures. Sources of heat are also suspected for the summit lake as its surface water temperature was measured during the successful ascent at +6 C in a -9 C ambient crater environment (with a wind chill factor of -25 C with a wind blowing almost constantly). Results of this project are expected to provide critical keys to help searching and identifying potential sites for life (extant/extinct) on Mars and developing instruments, experiments and technologies for future missions.