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We suggest a new mechanism to account for the loss of angular momentum in binaries with non-conservative mass exchange. It is shown that in some cases the loss of matter can result in increase of the orbital angular momentum of a binary. If included into consideration in evolutionary calculations, this mechanism appreciably extends the range of mass ratios of components for which mass exchange in binaries is stable. It becomes possible to explain the existence of some observed cataclysmic binaries with high donor/accretor mass ratio, which was prohibited in conservative evolution models.

Triplet-sensitized photolysis of 2,3-diazabicyclo[2.2.1]hept-2-ene (1) in argon- or oxygen- saturated acetonitrile-d3 solutions results in the formation of bicyclo[2.1.0]pentane (3), a ring closure product arising from an intermediate 1,3-cyclopentanediyl triplet biradical (2). Time-resolved infrared (TRIR) spectroscopy was used to monitor the kinetics of bicyclopentane 3 production. This analysis provides a measurement of the triplet biradical lifetime and an estimate of the bimolecular reaction rate between biradical 2 and oxygen, both in good agreement with previous investigations. Our studies also indicate that certain IR bands due to 3 in the C–H stretching region overlap with corresponding bands in biradical 2. This interpretation is supported by computational investigations.Copyright © 2000 John Wiley & Sons, Ltd.

1H-NMR spectra of DBH (1), DBO (2) and of the synthetic precursor to 1, 1,4-phenyl-2,4,6-triazatricyclo[5.2.1.02,6]heplanc-3,5-dione (3), were recorded in acetone-d6 and C6D6 at 500 MHz. Assignment was aided by complete resolution of signals of 1 and 3 in C6D6 by aromatic solvent-induced shifts (ASIS). The effect of the change from phenyllriazolinedione to a diazene functional group on the chemical shifts of the exo,endo and syn,anti protons was investigated. The chemical shifts of the exo,endo protons of 1 are exceptionally sensitive to the functional group at the hetero substituted bridge in the DBH skeleton. However, the relative chemical shift of the syn,anti proton pair is independent of the nature of the functional group. The role of stereochemical effects on these chemical shifts is discussed.

1. Voles undergo pronounced oscillations over periods of 3–5 years in northern Europe. A latitudinal gradient of cycle periods and amplitudes has been reported for Fennoscandia, with periods and amplitudes increasing towards northern latitudes. 2. This study formulates a discrete time model based on maternal effects to explain the density fluctuation patterns of microtine rodents. The phenotypic transmission of quality from mothers to offspring generates delayed density dependence, which produces cyclic behaviour in the model. 3. The dynamic patterns predicted by the maternal effect model agree with data. We conclude that the maternal effect hypothesis is a plausible, parsimonious explanation for vole-density cycles in northern Europe.

Using a population-synthesis code, we calculate the expected nova rate in stellar systems with different star formation histories for a variety of input parameters concerning the initial binary population. We show that the current nova rate in a galaxy is determined by the galaxy's star formation history. We show that in irregular and spiral galaxies, the currently observed nova rates are determined mainly by the present disk star formation rate, while in elliptical galaxies the rate depends mainly on the mass of the galaxy. This offers an explanation for the suspected differences in the observed nova rates per unit of K luminosity in different galaxies. The differences between bulge and disk novae in the Galaxy are probably also related to the respective ages of the parent populations.

Low-temperature photolysis of α-HNIW (2,4,6,8,10,12-hexanitrohexaazatetracyclo[5.5.05,9.03,11]dodecane) generated three 15NO2/15NO2 radical pairs that were studied by single-crystal electron paramagnetic resonance spectroscopy at 80 K. In two of the pairs, A and B, the two NO2 molecules occupy solvent cavities that are related by unit translation along the a-axis of the α-HNIW unit cell (radical pair separations of 9.26 and 9.67 A). In the third pair, C, they occupy cavities related by translation along the b-axis (∼13 A). Pair formation was highly specific since no pairs were trapped in cavities related by the b-glide (8.14 A). All three observed pairs survived annealing to 215 K, but from 220 to 294 K they decayed, one by one, without interconverting or separating to isolated radicals. Positive and negative exchange couplings as large as 0.004 cm-1 were estimated through approximate simulation of the position and intensity of transitions involving the nuclear states with hyperfine-induced So−To mixing. ...

We present a scenario model of the population of close binaries in which the brighter component is a helium or a carbon-oxygen white dwarf. The other, dimmer component can be a helium white dwarf, a carbon-oxygen white dwarf, or a low-mass (≤0.3 M☉) main-sequence star. The model takes into account the effects of observational selection related to the cooling of white dwarfs and the relative brightness of components. The total birthrate of such binaries in our Galaxy is estimated to be ~0.17 yr-1. In the model, in 63% of all cases, the dimmer component is also a white dwarf. In 82% of the systems that consist of two close white dwarfs, the brighter component is a helium white dwarf. This explains why, in at least seven out of the eight white dwarf pairs found in recent years, the primary is composed of helium. We estimate that close white dwarf pairs may constitute of the total sample of observed white dwarfs. Systems that have a total mass exceeding 1.4 M☉ and in which the components are close enough to merge in a Hubble time may constitute ~1/40 of all close white dwarf pairs. This means that the sample of observed white dwarf pairs must be at least quadrupled before one may hope to find a hypothetical Type Ia supernova (SN Ia) precursor. The total number of SN Ia precursors is estimated to exceed the observable number by a factor of about 20. The merger frequency of close binary helium white dwarfs in the Galaxy is estimated to be ~0.02 yr-1. This number is consistent with the fact that, in the total sample of known white dwarf pairs, there are three in which the components are close enough to merge in a Hubble time. In one system (WD 1101+364), the merger may result in the formation of a helium subdwarf (nondegenerate helium star), and in two others (WD 2331+290 and WD 0957-666), probably in the formation of a hydrogen-deficient subgiant and possibly later of an R CrB star. The predicted merger frequency is also consistent with the fact that two out of seven white dwarfs selected for their low mass are apparently single, while five are in close binaries.

To preserve privacy, the original data points (with exact values) are replaced by boxes containing each (inaccessible) data point. This privacy-motivated uncertainty leads to uncertainty in the statistical characteristics computed based on this data. In a previous paper, we described how to minimize this uncertainty under the assumption that we use the same standard statistical estimates for the desired characteristics. In this paper, we show that we can further decrease the resulting uncertainty if we allow fuzzy-motivated weighted estimates, and we explain how to optimally select the corresponding weights.

To understand the influence of orthogonal conjugation pathways fused directly to π-conjugated polymer backbones, we synthesized and studied three series of thiophene-based model compounds containing benzene, naphthalene, and anthracene peri-substituted central cores as representative acenes. These models were functionalized with methyl groups at the reactive thiophene positions in order to generate and observe oxidized species without complications from follow-up polymerization. The neutral monomers and their oxidized charged counterparts were subjected to cyclic voltammetry, spectroelectrochemistry, and EPR spectroscopy as appropriate, and these results were further corroborated with thorough density functional theory studies. This joint experimental and theoretical analysis allowed us to determine that benzene-based conjugated linkers led to more delocalized charge carriers on account of the quinoidal character maintained within the benzene core. In contrast, anthracene-based linkers displayed very localized carriers due to torsional strain between the adjacent aryl groups and to the local evolution of formal aromatic sextets on the benzo-fused rings orthogonal to the backbone in the quinoidal state. In some cases, the electronics of the thiophene-based substituent dominated the electronic properties of the oxidized species regardless of the nature of the central acene linker. These results highlight the dramatic influence that orthogonal conjugation pathways can exert on the electronic properties of π-conjugated materials.

Uncertainty analyses typically recognize separate stochastic and subjective sources of uncertainty, but do not systematically combine the two, although a large amount of data used in analyses is partly stochastic and partly subjective. We have developed methodology for mathematically combining stochastic and subjective sources of data uncertainty, based on new “hybrid number” approaches. The methodology can be utilized in conjunction with various traditional techniques, such as PRA (probabilistic risk assessment) and risk analysis decision support. Hybrid numbers have been previously examined as a potential method to represent combinations of stochastic and subjective information, but mathematical processing has been impeded by the requirements inherent in the structure of the numbers, e.g., there was no known way to multiply hybrids. In this paper, we will demonstrate methods for calculating with hybrid numbers that avoid the difficulties. By formulating a hybrid number as a probability distribution that is only fuzzily known, or alternatively as a random distribution of fuzzy numbers, methods are demonstrated for the full suite of arithmetic operations, permitting complex mathematical calculations. It will be shown how information about relative subjectivity (the ratio of subjective to stochastic knowledge about a particular datum) can be incorporated. Techniques are also developed for conveying uncertainty information visually, so that the stochastic and subjective components of the uncertainty, as well as the ratio of knowledge about the two, are readily apparent. The techniques demonstrated have the capability to process uncertainty information for independent, uncorrelated data, and for some types of dependent and correlated data. Example applications are suggested, illustrative problems are shown, and graphical results are given.

There are two kinds of uncertainty. One kind arises as variability resulting from heterogeneity or stochasticity. The other arises as partial ignorance resulting from systematic measurement error or subjective (epistemic) uncertainty. As most researchers recognize, variability and ignorance should be treated separately in risk analyses. Although a second-order Monte Carlo simulation is commonly employed for this task, this approach often requires unjustified assumptions which may be inappropriate in some circumstances. We argue that the two kinds of uncertainty should be propagated through mathematical expressions with different calculation methods. Basically, interval analysis should be used to propagate ignorance, and probability theory should be used to propagate variability. We demonstrate how using an inappropriate method can yield erroneous results. We also show how ignorance and variability can be represented simultaneously and manipulated in a coherent analysis that does not confound the two forms of uncertainty and distinguishes what is known from what is assumed.

Results from toxicological bioassays can express the likely impact of environmental contamination on biochemical function, histopathology, development, reproduction and survivorship. However, justifying environmental regulatory decisions and management plans requires predictions of the consequent effects on ecological populations and communities. Although extrapolating the results of toxicity bioassays to potential effects on the ecosystem may be beyond the current scientific capacity of ecology, it is possible to make detailed forecasts at the level of a population. We give examples in which toxicological impacts are either magnified or diminished by population-dynamic phenomena and argue that ecological risk assessments should be conducted at a level no lower than the population. Although methods recently proposed by EPA acknowledge that ecological risk evaluations should reflect population-level effects, they adopt approaches from human health risk analysis that focus on individuals.

Thermal decomposition of a primary alkyl diacyl peroxide 2 is investigated. Dependence of product yields on temperature, viscosity, and solvent polarity is examined in a variety of media. The excess of the alkene disproportionation product 4 and the presence of ester 3 and acid 5 is argued to demonstrate the existence of a discrete acyloxy-alkyl geminate radical pair. Stereoselective deuterium labeling of 2 and subsequent (1)H-NMR analysis of the resulting isotopomers of 4 confirm the radical nature of detected decomposition products.

Low-temperature photolysis of HNIW single crystals was investigated by electron paramagnetic resonance spectroscopy. Crystals of the α and β polymorphs, with either fully or selectively 15N-labeled nitro groups, were photolyzed at 15 K, and various species involving paramagnetic oxides of nitrogen (NO, NO2) were observed after annealing between 15 and 300 K. The orientation of NO trapped in the lattice of β-HNIW was inferred from the orientation of its g- and 15N-hfs tensors. Regioselectivity of photodecomposition within the two crystal lattices, monitored by the ratio of 15N and 14N isotopes in the NO and NO2 radicals, showed that no single reaction pathway produced these products and that concerted three-bond fragmention was not a dominant pathway. Analysis of packing similarities and reaction differences between the α and β polymorphs of HNIW confirmed that the cavities that accommodate water in the α hydrate play an important role in its solid-state reactivity.

We conducted a multi-wavelength study to unveil the properties of the extremely long-period cataclysmic variable V479 And. We performed series of observations, including moderate to high spectral resolution optical spectrophotometry, X-ray observations with Swift, linear polarimetry and near-IR photometry. This binary system is a low-inclination ~ 17^o system with a 0.594093(4) day orbital period. The absorption line complex in the spectra indicate a G8--K0 spectral type for the donor star, which has departed from the zero-age main sequence. This implies a distance to the object of about 4 kpc. The primary is probably a massive 1.1-1.4 Msun magnetic white dwarf, accreting matter at a rate M(dot) > 10^-10 Msun/ yr. This rate can be achieved if the donor star fills its corresponding Roche lobe, but there is little observational evidence for a mass-transfer stream in this system. An alternative explanation is a stellar wind from the donor star, although such a high rate mass loss is not anticipated from a subgiant. If the strongly magnetic white dwarf in V479 And. is confirmed by future observations, the system the polar with the longest observed orbital period. We also discuss the evolutionary state of V479 And., 12 pages, 12 figures, accepted for publication in Astronomy and Astrophysics

Methodology for the practical synthesis of nonnatural amino acids has been developed through the catalytic, asymmetric alkylation of alpha-imino esters and N,O-acetals by enol silanes, ketene acetals, alkenes, and allylsilanes using chiral transition metal-phosphine complexes as catalysts (1-5 mol %). The alkylation products, which are prepared with high enantioselectivity (up to 99% ee) and diastereoselectivity (up to 25:1/anti:syn), are protected nonnatural amino acids that represent potential precursors to natural products and pharmaceuticals. A kinetic analysis of the catalyzed reaction of alkenes with alpha-imino esters is presented to shed light on the mechanism of this reaction.

We present a detailed investigation of SBS1150+599A, a close binary star hosted by the planetary nebula PN G135.9+55.9 (TS01, Stasinska et al, 2009). The nebula, located in the Galactic halo, is the most oxygen-poor one known to date and is the only one known to harbor a double degenerate core. We present XMM-Newton observations of this object, which allowed the detection of the previously invisible component of the binary core, whose existence was inferred so far only from radial velocity and photometric variations. The parameters of the binary system were deduced from a wealth of information via three independent routes using the spectral energy distribution (from the infrared to X-rays), the light and radial velocity curves, and a detailed model atmosphere fitting of the stellar absorption features of the optical/UV component. We find that the cool component must have a mass of 0.54+/-0.2 Msun, an average effective temperature, Teff, of 58000+/-3000 K, a mean radius of 0.43+/-0.3 Rsun, a gravity log g=5.0+/-0.3, and that it nearly fills its Roche lobe. Its surface elemental abundances are found to be: 12 + log He/H = 10.95+/-0.04 dex, 12 + log C/H = 7.20+/-0.3 dex, 12 + log N/H < 6.92 and 12 + log O/H < 6.80, in overall agreement with the chemical composition of the planetary nebula. The hot component has Teff = 160-180 kK, a luminosity of about ~10e4 Lsun and a radius slightly larger than that of a white dwarf. It is probably bloated and heated as a result of intense accretion and nuclear burning on its surface in the past. The total mass of the binary system is very close to Chandrasekhar limit. This makes TS01 one of the best type Ia supernova progenitor candidates. We propose two possible scenarios for the evolution of the system up to its present stage., Accepted for publication in Ap.J., 25 pages, 17 figures

Construction principles are considered for reflectometers with linear frequency modulated (LFM) subcarrier intended for monitoring of fiber-optic communication links. Analysis of energy characteristics for square-law photodetection regime of optical signals was fulfilled. The analysis of photoresistor operation under radio-heterodyning regime was fulfilled and practical schemes for reflectometry with linear frequency modulated subcarrier has been elaborated to realize advantages of continuous-wave sounding methods at infrared spectral band which is especially important for monitoring of fiber-optic communication links. The processes of backscattering signals accumulation were investigated for reflectometers with LFM subcarrier. Energy characteristics of reflectometers with LFM subcarrier were researched and large range of these systems (86.1 km) was confirmed for sounding beam power 1 mW.

We present results of a systematic investigation of the evolution of low-mass (0.35, 0.40, and 0.65 solar mass) helium donors in semidetached binaries with accretors - white dwarfs. In the initial models of evolutionary sequences abundance of helium in the center is between $\simeq 0.1$ and 0.98. Results of computations may be applied to the study of the origin and evolutionary state of AM CVn stars. It is shown that the minimum orbital periods of the systems only weakly depend on the total mass of the system and evolutionary state of the donor at RLOF and are equal to 9-11 min. The scatter in the mass-exchange rates at a given orbital period in the range between period minimum and about 40 min. does not exceed $\sim 2.5$. At orbital periods exceeding about 20 min. mass-losing stars are weakly degenerate homogeneous cooling objects and abundances of He, C, N, O, Ne in the matter lost by them depend on the extent of He-depletion at RLOF. For the systems which are currently considered as the most probable model candidates for AM CVn stars with helium donors these abundances are, approximately, Y$>$0.4, X_C$, Comment: 21 pages, 10 figures, to be published in Astronomy Letters, vol.34, no.9, 2008. Detailed results of computations are available at http://www.inasan.ru/~lry/HELIUM_STARS . P-logR_{He} curves in Fig. 3 corrected

Much of the debate about alternative scaling exponents may result from unawareness of the dimensionality appropriate for different data and questions; in some cases, analysis has to include a fourth temporal dimension, and in others, it does not. Proportional scaling simultaneously applied to an organism and its generation time, treating the latter as a natural fourth dimension, produces a simple explanation for the 3/4 power in large‐scale interspecies comparisons. Analysis of data sets of reduced dimensionality (e.g., data sets constructed such that one or more of the four dimensions are fixed), results in predictably lower metabolic exponents of 2/3 and 1/2 under one and two constraints, respectively. Our space‐lifetime view offers a predictive framework that may be useful in developing a more complete mechanistic theory of metabolic scaling.

We consider evolutionary models for the population of short-period ( 0.35$ at the Roche-lobe overflow (RLOF). Longer period (0.5 - 1) day) SXTs might descend from systems with initial donor masses of about 1 $M_\odot$ and $X_c < 0.35$. Thus, one can explain the origin of short period LMBHB without invoking donors with cores almost totally depleted of hydrogen. Our models suggest that, unless the currently accepted empirical estimates of mass-loss rates by winds for massive O-stars and Wolf-Rayet stars are significantly over-evaluated, a very high efficiency of common-envelope ejection is necessary to form short-period LMBHBs., 9 pages, 6 figures, replaced to match the version accepted by A&A, 2 new figures, Eq. (3) for the upper limit on mass-transfer rates corrected, more extended discussion, conclusions unchanged

The probability of extinction is sensitive to the presence and character of density dependence controlling the dynamics of a population. This means that our capacity to estimate a population's risks of extinction under varying environmental conditions or competing management re- gimes is linked to our ability to reconstruct from data the density-dependence relationships governing the natural dy- namics, especially when data do not reveal a trend of pop- ulation growth or decline. In an example using Gadus morhua, we show that even 10- or 20-year data sets are too short to make precise estimates of these risks. We also ob- serve, however, that under moderate or weak density depen- dence, the computed risks are lower than when density de- pendence is not included in the model. We propose, therefore, that when available data sets are insufficient for recon- structing reliable measurements of density dependence, con- servative estimates of extinction probabilities can be made from models that simply omit density dependence. Resumen: La probabilidad de extinci6n es sensible a la presencia y al cardcter de la dependencia de densidad que controla la dinamica de una poblaci6n. Esto significa que nuestra capacidad para estimar los riesgos de extinci6n de una poblacion bajo condiciones ambientales cambiantes, o diferentes regimenes de manejo, esta relacionada a nuestra capacidad de reconstruir, en base a datos, las relaciones de dependencia de densidad que gobiernan la dinamica natu- ral de poblaciones, especialmente cuando no se dispone de informaci6n que revele tendencias de crecimiento o decli- naci6n de poblaciones. En un ejemplo, utilizando Gadus morhua, demostramos que aun los datos sobre un periodo de 10 6 20 anios son insuficientes para hacer estimaciones pre- cisas sobre estos riesgos. Sin embargo, observamos que in- cluso en una situaci6n de dependencia de densidad mo- derada o debil, los riesgos calculados son mas bajos que cuando la dependencia de densidad no es incluida en el modelo. Por ello proponemos, que, cuando no se dispone de datos suficientes para reconstruir estimados confiables de dependencia de densidad, se pueden hacer estimaciones con- servadoras de probabilidades de extinci6n a partir de mo- delos que simplemente omiten los aspectos de dependencia de densidad.

Consumer-resource system dynamics hinge upon the rate at which consumers capture, consume, and convert resources into biomass. In classical functional and numerical response theory, this rate is assumed to depend on resource density but not on consumer density (reviewed in Jeschke et al. [2002]). In assuming that both densities determine this rate, consumer-dependent func tional responses (e.g., Hassell and Varley 1969, Bed dington 1975, DeAngelis et al. 1975, Arditi and Ginzburg 1989) challenge the resource-dependent tradi tion. This challenge has produced a long-standing debate (reviewed in Abrams and Ginzburg 2000). The traditional approach of fitting functional response models to time series data has yielded equivocal results (e.g., Jost and Arditi 2001) and may not be capable of resolving the debate (Lundberg and Fryxell 1995). In a recent issue of Ecology, Fussmann et al. (2005) tried to enrich the debate with empirical data. They described functional response experiments in the rotifer-algae system Brachionus calyciflorus-Monoraphidium minutum that detected consumer dependence only at unnaturally high Brachionus densities and concluded that consumer dependence plays only a minor rule for planktonic rotifers in natural environments. Here, we outline why this conclusion is an over-interpretation of their results. Their experimental approach only considers direct physical interference between Brachionus and excludes all other and more important forms of consumer dependent effects (e.g., chemically mediated interfer

This report addresses the characterization of measurements that include epistemic uncertainties in the form of intervals. It reviews the application of basic descriptive statistics to data sets which contain intervals rather than exclusively point estimates. It describes algorithms to compute various means, the median and other percentiles, variance, interquartile range, moments, confidence limits, and other important statistics and summarizes the computability of these statistics as a function of sample size and characteristics of the intervals in the data (degree of overlap, size and regularity of widths, etc.). It also reviews the prospects for analyzing such data sets with the methods of inferential statistics such as outlier detection and regressions. The report explores the tradeoff between measurement precision and sample size in statistical results that are sensitive to both. It also argues that an approach based on interval statistics could be a reasonable alternative to current standard methods for evaluating, expressing and propagating measurement uncertainties.

We study the evolution and fate of solar composition supermassive stars in the mass range 60 - 1000 Msun. Our study is relevant both for very massive objects observed in young stellar complexes as well as supermassive stars that may potentially form through runaway stellar collisions. We predict the outcomes of stellar evolution employing a mass-loss prescription that is consistent with the observed Hertzsprung-Russell Diagram location of the most massive stars. We compute a series of stellar models with an appropriately modified version of the Eggleton evolutionary code. We find that super-massive stars with initial masses up to 1000 Msun end their lives as objects less massive than ~150 Msun. These objects are expected to collapse into black holes (with M < 70 Msun) or explode as pair-instability supernovae. We argue that if ultraluminous X-ray sources (ULXs) contain intermediate-mass black holes, these are unlikely to be the result of runaway stellar collisions in the cores of young clusters., 26 pages, 15 figures, accepted by A&A. small language corrections