Compression of Martian atmosphere for production of oxygen

The compression of CO2 from the Martian atmosphere for production of O2 via an electrochemical cell is addressed. Design specifications call for an oxygen production rate of 10 kg per day and for compression of 50 times that mass of CO2. Those specifications require a compression rate of over 770 cfm at standard Martian temperature and pressure (SMTP). Much of the CO2 being compressed represents waste, unless it can be recycled. Recycling can reduce the volume of gas that must be compressed to 40 cfm at SMTP. That volume reduction represents significant mass savings in the compressor, heating equipment, filters, and energy source. Successful recycle of the gas requires separation of CO (produced in the electrochemical cell) from CO2, N2, and Ar found in the Martian atmosphere. That aspect was the focus of this work

Gravitational radiation from a particle in circular orbit around a black hole. VI. Accuracy of the post-Newtonian expansion

A particle of mass $\mu$ moves on a circular orbit around a nonrotating black hole of mass $M$. Under the assumption $\mu \ll M$ the gravitational waves emitted by such a binary system can be calculated exactly numerically using black-hole perturbation theory. If, further, the particle is slowly moving, then the waves can be calculated approximately analytically, and expressed in the form of a post-Newtonian expansion. We determine the accuracy of this expansion in a quantitative way by calculating the reduction in signal-to-noise ratio incurred when matched filtering the exact signal with a nonoptimal, post-Newtonian filter.Comment: 5 pages, ReVTeX, 1 figure. A typographical error was discovered in the computer code used to generate the results presented in the paper. The corrected results are presented in an Erratum, which also incorporates new results, obtained using the recently improved post-Newtonian calculations of Tanaka, Tagoshi, and Sasak

Colliding Black Holes: The Close Limit

The problem of the mutual attraction and joining of two black holes is of importance as both a source of gravitational waves and as a testbed of numerical relativity. If the holes start out close enough that they are initially surrounded by a common horizon, the problem can be viewed as a perturbation of a single black hole. We take initial data due to Misner for close black holes, apply perturbation theory and evolve the data with the Zerilli equation. The computed gravitational radiation agrees with and extends the results of full numerical computations.Comment: 4 pages, Revtex, 3 postscript figures included, CGPG-94/2-

Espiguetas de dois grãos no milho

1 - The morphology, occurrence use and genetics of functional lower flowers in spikelets of maize are discussed briefly. Normally only the upper flower in each spikelet of a maize ear develops and bears a grain but in the examples discussed the lower flower develops as well as the upper. 2 - The embryo in maize is usually turned toward the tip of the ear while that of the grain produced from the lower flower is turned toward the base. 3 - In North and Central America and most of South America ears in which grains are borne in the lower flower of the spikelets are rare. One exception is the sweet corn, "Country Gentleman", which bears grains in both flowers of most spikelets. In Brasil and Bolivia, however, ears with two grained spikelets are more common. If maize originated in South America, one would expect to find more varieties, and more primitive types near the center of origin. 4 - In Pointed Sao Paulo (Brazil) Pop Corn, Dr. BRIEGER found ears in which both flowers developed in some spikelets. In some spikelets both grains were of normal size, but more often either the lower or the upper grain was much smaller. 5 - In ears found by Dr. MARTIN CARDENAS some spikelets bear only grains from the lower flowers., a condition characteristic of the "Poaceae" and not the "Panicaceae", to which maize belogns. 6 - Many genes which influence tassel characters also influence the ears. Some of these control the formation of grains in the lower flower of the female spikelet. Most of the known genes affecting the lower spikelets are recessive, as are those in the Bolivian and Brazilian ears studied, and in "Country Gentleman". 7 - An example of paired spikelets was found in Dr. Brieger's tunicate material. In this case two complete spikelets appear where normally there would be only one. They are symetrical, and one of them thus is in a position opposite to the normal. The grains in both are borne in the upper flower. 8 - Studies on the maize spikelet are being continued. Dr. Gonçalves Drumond of the Escola Superior de Viçosa, Minas Gerais, recently found some ears of "Cateto", the common Brazilian orange flint, in which the lower flower was functional and he is studying this line. The most interesting material for further study appears to be that found by Dr. Brieger in his Pipoca Pontudo Paulista, for here there are varying degrees of development of both the upper and lower grains.A morfologia, ocorrência, utilidade e genética das flores funcionais inferiores em espiguetas de milho, são examinadas ligeiramente. Em regra, somente a flor superior em cada espigueta numa espiga de milho se desenvolve e contém um grão, porém nos exemplos em foco a flor inferior se desenvolve tão bem como a superior. O embrião no milho geralmente se acha voltado na mesma direção que a ponta da espiga, ao passo que o embrião do grão proveniente da flor inferior se volta na direção da base. São raras, não só na América do Norte e Central, como na maior parte da América do Sul, as espigas nas quais os grãos provêm da flor inferior das espiguetas, constituindo uma exceção o milho doce Country Gentleman, no qual se encontram grãos em ambas as flores na maioria das espiguetas. No Brasil e na Bolívia, entretanto, são mais comuns as espigas com espiguetas de dois grãos. Sendo o milho proveniente da América do Sul, é de esperar-se que se encontrem mais variedades e tipos mais primitivos próximo do centro de origem. No milho Pipoca Pontudo Paulista, o Dr. BRIEGER encontrou espigas com ambas as flores funcionais em algumas espiguetas. Em alguns casos, ambos os grãos eram de tamanho normal, porém, mais comumente, um dos dois grãos era bem menor que o outro. Em espigas encontradas pelo Dr. MARTIN CARDENAS, algumas espiguetas apresentam grãos provindos somente das flores inferiores, uma circunstância característica do grupo "Poaceae", e não do "Panicaceae" a que pertence o milho. Muitos gens que influenciam os característicos do pendão, também influenciam os das espigas. Alguns destes controlam a formação de grãos na flor inferior da espigueta-fêmea. A maioria dos gens conhecidos como afetando as espiguetas inferiores, são recessivos, tal como no caso das espigas brasileira e boliviana estudadas, e no Country Gentleman. Um exemplo de espiguetas gêmeas foi encontrado entre o material tunicata do Dr. BRIEGER. Aí, em vez de uma só espi-gueta, o que é o normal, havia duas espiguetas completas, simétricas, sendo uma em posição oposta ao normal. Os grãos, em ambas, achavam-se na flor superior. Prosseguem os estudos sobre a espigueta do milho. O Dr. GONÇALVES DRUMOND, da Escola Superior de Viçosa, Minas Gerais, encontrou recentemente algumas espigas de "Cateto", nas quais a flor inferior é funcional e está estudando as mesmas. Parece que o mais interessante material para os novos estudos é o que o Dr. BRIEGER encontrou no seu milho "Pipoca Pontudo Paulista, pois há ai graus variáveis de desenvolvimento tanto superiores como inferiores

Improved filters for gravitational waves from inspiralling compact binaries

The order of the post-Newtonian expansion needed, to extract in a reliable and accurate manner the fully general relativistic gravitational wave signal from inspiralling compact binaries, is explored. A class of approximate wave forms, called P-approximants, is constructed based on the following two inputs: (a) The introduction of two new energy-type and flux-type functions e(v) and f(v), respectively, (b) the systematic use of Pade approximation for constructing successive approximants of e(v) and f(v). The new P-approximants are not only more effectual (larger overlaps) and more faithful (smaller biases) than the standard Taylor approximants, but also converge faster and monotonically. The presently available O(v/c)^5-accurate post-Newtonian results can be used to construct P-approximate wave forms that provide overlaps with the exact wave form larger than 96.5% implying that more than 90% of potential events can be detected with the aid of P-approximants as opposed to a mere 10-15 % that would be detectable using standard post-Newtonian approximants.Comment: Latex ([prd,aps,eqsecnum,epsf]{revtex}), 40 pages including 12 encapsulated figures. (The paper, together with all the figures and tables is available from ftp://carina.astro.cf.ac.uk/pub/incoming/sathya/dis97.uu

Measuring black-hole parameters and testing general relativity using gravitational-wave data from space-based interferometers

Among the expected sources of gravitational waves for the Laser Interferometer Space Antenna (LISA) is the capture of solar-mass compact stars by massive black holes residing in galactic centers. We construct a simple model for such a capture, in which the compact star moves freely on a circular orbit in the equatorial plane of the massive black hole. We consider the gravitational waves emitted during the late stages of orbital evolution, shortly before the orbiting mass reaches the innermost stable circular orbit. We construct a simple model for the gravitational-wave signal, in which the phasing of the waves plays the dominant role. The signal's behavior depends on a number of parameters, including $\mu$, the mass of the orbiting star, $M$, the mass of the central black hole, and $J$, the black hole's angular momentum. We calculate, using our simplified model, and in the limit of large signal-to-noise ratio, the accuracy with which these quantities can be estimated during a gravitational-wave measurement. Our simplified model also suggests a method for experimentally testing the strong-field predictions of general relativity.Comment: ReVTeX, 16 pages, 5 postscript figure

Celestial mechanics in Kerr spacetime

The dynamical parameters conventionally used to specify the orbit of a test particle in Kerr spacetime are the energy $E$, the axial component of the angular momentum, $L_{z}$, and Carter's constant $Q$. These parameters are obtained by solving the Hamilton-Jacobi equation for the dynamical problem of geodesic motion. Employing the action-angle variable formalism, on the other hand, yields a different set of constants of motion, namely, the fundamental frequencies $\omega_{r}$, $\omega_{\theta}$ and $\omega_{\phi}$ associated with the radial, polar and azimuthal components of orbital motion. These frequencies, naturally, determine the time scales of orbital motion and, furthermore, the instantaneous gravitational wave spectrum in the adiabatic approximation. In this article, it is shown that the fundamental frequencies are geometric invariants and explicit formulas in terms of quadratures are derived. The numerical evaluation of these formulas in the case of a rapidly rotating black hole illustrates the behaviour of the fundamental frequencies as orbital parameters such as the semi-latus rectum $p$, the eccentricity $e$ or the inclination parameter $\theta_{-}$ are varied. The limiting cases of circular, equatorial and Keplerian motion are investigated as well and it is shown that known results are recovered from the general formulas.Comment: 25 pages (LaTeX), 5 figures, submitted to Class. Quantum Gra

Gravitational waves from inspiralling compact binaries: Parameter estimation using second-post-Newtonian waveforms

The parameters of inspiralling compact binaries can be estimated using matched filtering of gravitational-waveform templates against the output of laser-interferometric gravitational-wave detectors. Using a recently calculated formula, accurate to second post-Newtonian (2PN) order [order $(v/c)^4$, where $v$ is the orbital velocity], for the frequency sweep ($dF/dt$) induced by gravitational radiation damping, we study the statistical errors in the determination of such source parameters as the ``chirp mass'' $\cal M$, reduced mass $\mu$, and spin parameters $\beta$ and $\sigma$ (related to spin-orbit and spin-spin effects, respectively). We find that previous results using template phasing accurate to 1.5PN order actually underestimated the errors in $\cal M$, $\mu$, and $\beta$. For two inspiralling neutron stars, the measurement errors increase by less than 16 percent.Comment: 14 pages, ReVTe

Neurocardiovascular deficits in the Q175 mouse model of Huntington's disease.

Cardiovascular dysautonomia as well as the deterioration of circadian rhythms are among the earliest detectable pathophysiological changes in individuals with Huntington's disease (HD). Preclinical research requires mouse models that recapitulate disease symptoms and the Q175 knock-in model offers a number of advantages but potential autonomic dysfunction has not been explored. In this study, we sought to test the dual hypotheses that cardiovascular dysautonomia can be detected early in disease progression in the Q175 model and that this dysfunction varies with the daily cycle. Using radiotelemetry implants, we observed a significant reduction in the diurnal and circadian activity rhythms in the Q175 mutants at the youngest ages. By middle age, the autonomically driven rhythms in core body temperature were highly compromised, and the Q175 mutants exhibited striking episodes of hypothermia that increased in frequency with mutant huntingtin gene dosage. In addition, Q175 mutants showed higher resting heart rate (HR) during sleep and greatly reduced correlation between activity and HR HR variability was reduced in the mutants in both time and frequency domains, providing more evidence of autonomic dysfunction. Measurement of the baroreceptor reflex revealed that the Q175 mutant could not appropriately increase HR in response to a pharmacologically induced decrease in blood pressure. Echocardiograms showed reduced ventricular mass and ejection fraction in mutant hearts. Finally, cardiac histopathology revealed localized points of fibrosis resembling those caused by myocardial infarction. Thus, the Q175 mouse model of HD exhibits cardiovascular dysautonomia similar to that seen in HD patients with prominent sympathetic dysfunction during the resting phase of the activity rhythm

Gravitational radiation from a particle in circular orbit around a black hole. V. Black-hole absorption and tail corrections

A particle of mass $\mu$ moves on a circular orbit of a nonrotating black hole of mass $M$. Under the restrictions $\mu/M \ll 1$ and $v \ll 1$, where $v$ is the orbital velocity, we consider the gravitational waves emitted by such a binary system. We calculate $\dot{E}$, the rate at which the gravitational waves remove energy from the system. The total energy loss is given by $\dot{E} = \dot{E}^\infty + \dot{E}^H$, where $\dot{E}^\infty$ denotes that part of the gravitational-wave energy which is carried off to infinity, while $\dot{E}^H$ denotes the part which is absorbed by the black hole. We show that the black-hole absorption is a small effect: $\dot{E}^H/\dot{E} \simeq v^8$. We also compare the wave generation formalism which derives from perturbation theory to the post-Newtonian formalism of Blanchet and Damour. Among other things we consider the corrections to the asymptotic gravitational-wave field which are due to wave-propagation (tail) effects.Comment: ReVTeX, 17 page