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A period analysis of CCD unfiltered photometry of V4745 Sgr (Nova Sgr 2003 #1) performed during 23 nights in the years 2003–2005 is presented. The photometric data are modulated with a period of 0.20 782 ± 0.00 003 d (4.98 768 ± 0.00 072 h) . Following the shape of the phased light curve and the presence of the periodicity in all data sets with no apparent change in its value, we interpret this periodicity as orbital in nature and this is consistent with a cataclysmic variable above the period gap. We found a probable short-term periodicity of 0.017 238 ± 0.000 037 d (24.82 272 ± 0.05 328 min) which we interpret as the probable spin period of the white dwarf or the beat period between the orbital and spin period. Therefore, we propose that nova V4745 Sgr should be classified as an intermediate polar candidate, supporting the proposed link between transition-oscillation novae and intermediate polars. The mass–period relation for cataclysmic variables yields a secondary mass of about 0.52 ± 0.05 M⊙ . 相似文献
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Ami Nishri Alon Rimmer Udi Wagner Zvi Rosentraub Peter Yeates 《Aquatic Geochemistry》2011,17(3):195-207
High resolution chemical data collected during summer 2003 indicate that the lower water mass (LWM) of the thermally stratified
Lake Kinneret (LK) can be subdivided into three layers: a benthic boundary layer (BBL), overlain by the hypolimnion (HYP),
and on top, the lower part of the metalimnion (ME-L). After onset of thermal stratification, the BBL is the first layer that
turns anoxic, followed shortly afterward by the ME-L, while the HYP remains oxic and has relatively higher pH until later
in summer. Thus, during the early summer, the HYP forms an oxygen-containing layer in-between two DO-deficient layers. Somewhat
later, the HYP is characterized by still having significant levels of nitrate NO3, while in both adjacent layers nitrate is already removed through denitrification. The mechanisms controlling the gradual
decline of dissolved oxygen (DO) in the HYP during the summer were studied. The seasonal mean lake-wide vertical eddy diffusion
coefficient in this layer, evaluated from heat flux measurements, is approximately 4 × 10−6 m2 s−1. The vertical oxygen flux due to diffusion from within the HYP toward its oxygen-deficient upper and lower boundaries accounts
for most of the slow summer decline in DO in this layer. A smaller portion of this decline can be attributed to in-layer respiratory
processes. The low turbidity, relatively high pH, and slow accumulation rate of NH4 in the HYP support the notion that the slower mineralization processes occurring in this layer result from relatively low
ambient concentrations of biodegradable organic matter, most probably due to the short residence time of the particles settling
through this layer. 相似文献
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We argue that all transient searches for planets in globular clusters have a very low detection probability. Planets of low-metallicity stars typically do not reside at small orbital separations. The dependence of planetary system properties on metallicity is clearly seen when the quantity I e ≡ M p [ a (1 − e )]2 is considered; M p , a and e are the planet mass, semimajor axis and eccentricity, respectively. In high-metallicity systems, there is a concentration of systems at high and low values of I e , with a low-populated gap near I e ∼ 0.3 M J au2 , where M J is Jupiter's mass. In low-metallicity systems, the concentration is only at the higher range of I e , with a tail to low values of I e . Therefore, it is still possible that planets exist around main-sequence stars in globular clusters, although at small numbers because of the low metallicity, and at orbital periods of ≳10 d. We discuss the implications of our conclusions on the role that companions can play in the evolution of their parent stars in globular clusters, for example, influencing the distribution of horizontal branch stars on the Hertzsprung–Russell diagram of some globular clusters, and in forming low-mass white dwarfs. 相似文献
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Alon Ziv 《Journal of Seismology》2016,20(4):1123-1129
A major difficulty in inverting geodetic data for fault slip distribution is that measurement errors are mapped from the data space onto the solution space. The amplitude of this mapping is sensitive to the condition number of the inverse problem, i.e., the ratio between the largest and smallest singular value of the forward matrix. Thus, unless the problem is well-conditioned, slip inversions cannot reveal the actual fault slip distribution. In this study, we describe a new iterative algorithm that optimizes the condition of the slip inversion through discretization of InSAR data. We present a numerical example that demonstrates the effectiveness of our approach. We show that the condition number of the reconditioned data sets are not only much smaller than those of uniformly spaced data sets with the same dimension but are also much smaller than non-uniformly spaced data sets, with data density that increases towards the model fault. 相似文献
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Polysulfides and ammonia are abundant in young depositional environments and play an important role in the formation of macromolecular structures such as protokerogen and humics. In this work, we study the co-incorporation of polysulfides and ammonia into simple carbonyl model compounds, octanal and trans 2-octenal, in order to study their effect on the formation of a cross-linked macromolecule and suggest a feasible mechanism. The reactions, performed in aqueous solutions at ambient temperature and pH ∼6 to 9, simulate formation of S and N cross-linked polymers in the natural environment. The complex S and N containing polymer was studied by 15N enrichment coupled to 2D NMR (1H, 13C, 15N) techniques and chemical degradation of S-S bonds followed by deuterium labeling and GC-MS analyses. In addition, molecular modeling techniques were used to provide theoretical interpretations and important insights at the molecular level. The results indicate that polysulfide out competes ammonia in the formation of Michael adducts while ammonia is equally competitive with polysulfides when the reaction is addition to the carbonyl position. The co-incorporation of ammonia and polysulfides into carbonyls rapidly forms N and S cross-linked polymers. The effects of ammonia and amines on the polymerization processes are by two means: (i) reaction with carbonyls through an imine functionality to form oligomers and polymers and (ii) catalysis of sulfur nucleophiles onto carbonyls by transfer of a proton which enhances the rate of polymerization. A similar catalytic effect is observed when glycine is used instead of ammonia. This mechanism is especially important under basic to neutral conditions like those that prevail in marine environments. The results show that ammonia and glycine or possibly other amino acids and/or peptides are intimately involved with sulfur nucleophiles throughout the polymerization processes that occur at low temperatures and thus are suggested as key reactants in diagenetic formation of protokerogen and humics. 相似文献
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Alon Manor 《Boundary-Layer Meteorology》2014,150(2):327-340
A new approach for estimating concentration fluctuations intensity in dense built-up environments using a Lagrangian stochastic (LS) particle model is described. Following past success in modelling the dynamics of concentration variance as a diffusion-advection process, the ensemble-averaged concentration variance is represented by particles that advect and diffuse throughout the computational domain. The calculation of the concentration variance is addressed by assuming an appropriate distribution of effective variance sources for a given mean concentration field. Dissipation is treated by allowing the variance carried by every particle to decay exponentially with a locally-estimated decay time. The approach has the benefit of easily handling complex boundary conditions. It can also be easily and naturally implemented as an extension to an existing LS model, which is used for mean concentration estimations. The method differs from existing two-particle methods that demand knowledge of the structure function of the flow. It is also more computationally efficient than micro-mixing approaches that involve maintaining high population levels of particles in every grid volume. The model is compared with high frequency concentration measurements, taken as part of the JU2003 (Joint Urban 2003) experiment that was carried out in Oklahoma City. Good agreement is observed. 相似文献
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It has been suggested recently that self-interacting dark matter (SIDM) fits better the observational characteristics of galaxy dynamics. We propose that the SIDM is composed from the glueballs of the hidden sector non-Abelian gauge group, while the hidden matter states exist in vector-like representation and decouple from the light spectrum. It is shown that these glueballs are semi-stable with the lifetime larger than the present age of the Universe, if their mass is 1 GeV or less. The constraint on their abundance today suggests that the energy was stored in the hidden sector soon after inflation. This imposes an upper limit on the reheating temperature. We further study the naturalness of this scenario in the context of the free-fermionic string models and point out a class of such models where the SIDM from the hidden sector is indeed plausible. 相似文献