Lunar base CELSS: A bioregenerative approach

During the twenty-first century, human habitation of a self-sustaining lunar base could become a reality. To achieve this goal, the occupants will have to have food, water, and an adequate atmosphere within a carefully designed environment. Advanced technology will be employed to support terrestrial life-sustaining processes on the Moon. One approach to a life support system based on food production, waste management and utilization, and product synthesis is outlined. Inputs include an atmosphere, water, plants, biodegradable substrates, and manufacutured materials such as fiberglass containment vessels from lunar resources. Outputs include purification of air and water, food, and hydrogen (H2) generated from methane (CH4). Important criteria are as follows: (1) minimize resupply from Earth; and (2) recycle as efficiently as possible

Terrestrial Consequences of Spectral and Temporal Variability in Ionizing Photon Events

Gamma-Ray Bursts (GRBs) directed at Earth from within a few kpc may have damaged the biosphere, primarily though changes in atmospheric chemistry which admit greatly increased Solar UV. However, GRBs are highly variable in spectrum and duration. Recent observations indicate that short (~0.1 s) burst GRBs, which have harder spectra, may be sufficiently abundant at low redshift that they may offer an additional significant effect. A much longer timescale is associated with shock breakout luminosity observed in the soft X-ray (~10^3 s) and UV (~10^5 s) emission, and radioactive decay gamma-ray line radiation emitted during the light curve phase of supernovae (~10^7 s). Here we generalize our atmospheric computations to include a broad range of peak photon energies and investigate the effect of burst duration while holding total fluence and other parameters constant. The results can be used to estimate the probable impact of various kinds of ionizing events (such as short GRBs, X-ray flashes, supernovae) upon the terrestrial atmosphere. We find that the ultimate intensity of atmospheric effects varies only slightly with burst duration from 10^-1 s to 10^8 s. Therefore, the effect of many astrophysical events causing atmospheric ionization can be approximated without including time development. Detailed modeling requires specification of the season and latitude of the event. Harder photon spectra produce greater atmospheric effects for spectra with peaks up to about 20 MeV, because of greater penetration into the stratosphere.Comment: 30 pages, to be published in ApJ. Replaced for conformity with published version, including correction of minor typos and updated reference

Spatial Scaling in Model Plant Communities

We present an analytically tractable variant of the voter model that provides a quantitatively accurate description of beta-diversity (two-point correlation function) in two tropical forests. The model exhibits novel scaling behavior that leads to links between ecological measures such as relative species abundance and the species area relationship.Comment: 10 pages, 3 figure

Coherent and incoherent atomic scattering: Formalism and application to pionium interacting with matter

The experimental determination of the lifetime of pionium provides a very important test on chiral perturbation theory. This quantity is determined in the DIRAC experiment at CERN. In the analysis of this experiment, the breakup probabilities of of pionium in matter are needed to high accuracy as a theoretical input. We study in detail the influence of the target electrons. They contribute through screening and incoherent effects. We use Dirac-Hartree- Fock-Slater wavefunctions in order to determine the corresponding form factors. We find that the inner-shell electrons contribute less than the weakly bound outer electrons. Furthermore, we establish a more rigorous estimate for the magnitude of the contributions form the transverse current (magnetic terms thus far neglected in the calculations).Comment: Journal of Physics B: Atomic, Molecular and Optical Physics; (accepted; 22 pages, 6 figures, 26 references) Revised version: more detailed description of DIRAC experiment; failure of simplest models for incoherent scattering demonstrated by example

Radiative and Auger decay data for modelling nickel K lines

Radiative and Auger decay data have been calculated for modelling the K lines in ions of the nickel isonuclear sequence, from Ni$^+$ up to Ni$^{27+}$. Level energies, transition wavelengths, radiative transition probabilities, and radiative and Auger widths have been determined using Cowan's Hartree--Fock with Relativistic corrections (HFR) method. Auger widths for the third-row ions (Ni$^+$--Ni$^{10+}$) have been computed using single-configuration average (SCA) compact formulae. Results are compared with data sets computed with the AUTOSTRUCTURE and MCDF atomic structure codes and with available experimental and theoretical values, mainly in highly ionized ions and in the solid state.Comment: submitted to ApJS. 42 pages. 12 figure

Information criteria for inhomogeneous spatial point processes

The theoretical foundation for a number of model selection criteria is established in the context of inhomogeneous point processes and under various asymptotic settings: infill, increasing domain, and combinations of these. For inhomogeneous Poisson processes we consider Akaike information criterion and the Bayesian information criterion, and in particular we identify the point process analogue of sample size needed for the Bayesian information criterion. Considering general inhomogeneous point processes we derive new composite likelihood and composite Bayesian information criteria for selecting a regression model for the intensity function. The proposed model selection criteria are evaluated using simulations of Poisson processes and cluster point processes.Comment: 6 figure

Experimental study of photon beam polarimeter based on nuclear e+e- pair production in an amorphous target

The experimental method of the linearly polarized photons polarimetry,using incoherent e+e- pair production process has been investigated on the beam of coherent bremsstrahlung (CB) photons in the energy range of 0.9-1.1 GeV at the Yerevan synchrotron.Comment: 6 pages (text),10 figure

Ecological equivalence: a realistic assumption for niche theory as a testable alternative to neutral theory

Hubbell's 2001 neutral theory unifies biodiversity and biogeography by modelling steady-state distributions of species richness and abundances across spatio-temporal scales. Accurate predictions have issued from its core premise that all species have identical vital rates. Yet no ecologist believes that species are identical in reality. Here I explain this paradox in terms of the ecological equivalence that species must achieve at their coexistence equilibrium, defined by zero net fitness for all regardless of intrinsic differences between them. I show that the distinction of realised from intrinsic vital rates is crucial to evaluating community resilience. An analysis of competitive interactions reveals how zero-sum patterns of abundance emerge for species with contrasting life-history traits as for identical species. I develop a stochastic model to simulate community assembly from a random drift of invasions sustaining the dynamics of recruitment following deaths and extinctions. Species are allocated identical intrinsic vital rates for neutral dynamics, or random intrinsic vital rates and competitive abilities for niche dynamics either on a continuous scale or between dominant-fugitive extremes. Resulting communities have steady-state distributions of the same type for more or less extremely differentiated species as for identical species. All produce negatively skewed log-normal distributions of species abundance, zero-sum relationships of total abundance to area, and Arrhenius relationships of species to area. Intrinsically identical species nevertheless support fewer total individuals, because their densities impact as strongly on each other as on themselves. Truly neutral communities have measurably lower abundance/area and higher species/abundance ratios. Neutral scenarios can be parameterized as null hypotheses for testing competitive release, which is a sure signal of niche dynamics. Ignoring the true strength of interactions between and within species risks a substantial misrepresentation of community resilience to habitat los

Coulomb corrections to bremsstrahlung in electric field of heavy atom at high energies

The differential and partially integrated cross sections are considered for bremsstrahlung from high-energy electrons in atomic field with the exact account of this field. The consideration exploits the quasiclassical electron Green's function and wave functions in an external electric field. It is shown that the Coulomb corrections to the differential cross section are very susceptible to screening. Nevertheless, the Coulomb corrections to the cross section summed up over the final-electron states are independent of screening in the leading approximation over a small parameter $1/mr_{scr}$ ($r_{scr}$ is a screening radius, $m$ is the electron mass, $\hbar=c=1$). Bremsstrahlung from an electron beam of the finite size on heavy nucleus is considered as well. Again, the Coulomb corrections to the differential probability are very susceptible to the beam shape, while those to the probability integrated over momentum transfer are independent of it, apart from the trivial factor, which is the electron-beam density at zero impact parameter. For the Coulomb corrections to the bremsstrahlung spectrum, the next-to-leading terms with respect to the parameters $m/\epsilon$ ($\epsilon$ is the electron energy) and $1/mr_{scr}$ are obtained.Comment: 13 pages, 4 figure