A search for evolutionary period variations of Cepheids using the harvard plate stacks: II Carinae

We obtained 380 photographic brightness estimates for the long-period classical Cepheid II Car (P = 64.4 days) from the plate stacks of the Harvard College Observatory. Combined with the published photoelectric and CCD observations, these data enable the construction of an O-C diagram covering 120 years. The O-C diagram is parabolic, making it possible for the first time to determine the quadratic light-curve elements and calculate the evolutionary rate of increase of the period, dP/dt = 719(±15) s/year (log(Ṗ/P) = −4.64), in agreement with theoretical computations for the third crossing of the instability strip. The available data, reduced using the method described by Eddington and Plakidis, demonstrate the presence of small random period fluctuations that do not distort the evolutionary changes of the O-C residuals.     

A search for evolutionary period variations of Cepheids using the Harvard plates: V396 Cyg

We obtained 503 photographic brightness estimates for the long-period classical Cepheid V396 Cyg (P = 33.3 days) from the plates of the Harvard Observatory and the Sternberg Astronomical Institute (SAI). Combined with published photoelectric observations, these data were used to plot an O-C diagram covering a time interval of 108 years. The O-C diagram is parabolic in shape, enabling the first determination of quadratic light elements and calculation of the evolutionary rate of decrease of the period, dP/dt = 14.1(±0.8) s per year (log(?/P) = ?6.35), in agreement with theoretical computations for the second crossing of the instability strip. The available data, reduced using the method introduced by Eddington and Plakidis, demonstrate the presence of small random period fluctuations that do not distort the evolutionary changes of the O-C residuals.     

A search for evolutionary period variations of Cepheids using the Harvard plate stacks: FF Aql

Photographic plates of the Harvard Observatory stacks have been used to obtain 1261 brightness estimates for the low-amplitude Cepheid FF Aql (P = 4.47 days). Combined with published visual, photoelectric, and CCD observations, these data enable the construction of an O-C diagram spanning 122 years. The resulting O-C diagram is parabola-shaped, enabling the determination of quadratic brightness elements for the first time. The evolutionary rate of increase of the period, dP/dt = 0.072 ± 0.011 s/year, is in agreement with theoretical computations for the third crossing of the instability strip. The available data, reduced using the technique of by Eddington and Plakidis, reveal the presence of small, random period fluctuations, ? = 0.0061^d ± 0.0044^d, that do not distort the evolutionary trend of the O-C residuals.     

IR photometry and a model of a dust shell in V2108 Ophiuchi

We present the results of JHKLM photometry of the oxygen Mira variable V2108 Oph acquired in 2000–2004. The period of brightness variations is refined (570 ± 3 days), and light and color curves in the near-IR are presented. The mean fluxes, color temperatures, and sizes for two blackbodies representing the combined radiation of the star and dust shell at minimum and maximum brightness are estimated. Additional IRAS data were used to compute a model with a spherically symmetric dust shell of silicate grains; the best-fit model has a radius for its inner boundary of 2.4 × 10¹⁴ cm, a dust temperature at this boundary of 1150 K, an optical depth of the shell at 0.55 μm of 16.8, and implies a distance to the star of 980 pc. We estimate the mass-loss rate for V2108 Oph to be 1.2 × 10⁻⁵ M _⊙/yr. Original Russian Text ? M.B. Bogdanov, O.G. Taranova, V.I. Shenavrin, 2006, published in Astronomicheskiĭ Zhurnal, 2006, Vol. 83, No. 5, pp. 437–442.     

Relationship between the Elemental Abundances and the Kinematics of Galactic-Field RR Lyrae Stars

Data of our compiled catalog containing the positions, velocities, and metallicities of 415 RR Lyrae variable stars and the relative abundances [el/Fe] of 12 elements for 101 RR Lyrae stars, including four α elements (Mg, Ca, Si, and Ti), are used to study the relationships between the chemical and spatial–kinematic properties of these stars. In general, the dependences of the relative abundances of α elements on metallicity and velocity for the RR Lyrae stars are approximately the same as those for field dwarfs. Despite the usual claim that these stars are old, among them are representatives of the thin disk, which is the youngest subsystem of the Galaxy. Attention is called to the problem of lowmetallicity RR Lyrae stars. Most RR Lyrae stars that have the kinematic properties of thick disk stars have metallicities [Fe/H] < ?1.0 and high ratios [α/Fe] ≈ 0.4, whereas only about 10% of field dwarfs belonging to the so-called “low-metallicity tail” have this chemical composition. At the same time, there is a sharp change in [α/Fe] in RR Lyrae stars belonging just to the thick disk, providing evidence for a long period of formation of this subsystem. The chemical compositions of SDSS J1707+58, V455 Oph, MACHO176.18833.411, V456 Ser, and BPSCS 30339–046 do not correspond to their kinematics.While the first three of these stars belong to the halo, according to their kinematics, the last two belong to the thick disk. It is proposed that they are all most likely extragalactic, but the possible appearance of some of them in the solar neighborhood as a result of the gravitational action of the bar on field stars cannot be ruled out.     

Use of an Analytical Theory for the Physical Libration of the Moon to Detect Free Nutation of the Lunar Core

A brief review of modern observational achievements and the theoretical basis of physical libration of the Moon is presented. Special attention is given to the inferred existence of a lunar core and determination of its parameters. The creation of a theory of physical libration of the Moon, which requires analyses of semi-empirical series of long-term laser observations and the use of the highly accurate DE421 dynamical ephemeris, is related to this. A large role in this area has been played by the analytical theory of physical libration of the Moon constructed by Yu.V. Barkin, which made it possible for the first time to derive parameters of the free nutation of the lunar core from observations. This paper is based on a talk given at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017).

     

Moon—An albite depleted giant Skaergaard?

The chemical composition of 2188 terrestrial igneous rocks ranging from ultrabasic to granitic composition was analyzed statistically using the method of factor analysis (principal components). The resultant first and second factors were: $$\begin{gathered} {\text{ }}F_1 = 0.933{\text{ Na}}_{\text{2}} {\text{O + 0}}{\text{.143 SiO}}_{\text{2}} + 0.206{\text{ K}}_{\text{2}} {\text{O}} - 0.346{\text{ CaO}} - 0.263{\text{ MgO}} - \hfill \\ .203{\text{ FeO}} \pm \cdot \cdot \cdot \hfill \\ {\text{ }}F_2 = 0.979{\text{ Al}}_{\text{2}} {\text{O}}_{\text{3}} - 0.269{\text{ MgO}} - 0.151{\text{ SiO}}_{\text{2}} - 0.112{\text{ FeO}} \pm \cdot \cdot \cdot \hfill \\ \end{gathered} $$ where oxides are in weight percent. A plot of the first factor against the second results in a useful igneous variation diagram. When the compositions of the 2188 terrestrial rocks and 604 lunar rocks are plotted on this diagram, the two groups of rocks are clearly separated within an albite-anorthite-forsterite-fayalite-quartz polygon. None of the terrestrial differentiation trends are significant for lunar rocks. The major difference in the chemistry of lunar and terrestrial rocks lies in the former being albite poor. Removal of most of the albite from the compositions of terrestrial layered intrusives such as the Skaergaard results in an excellent match between the compositions of the two groups of rocks. Albite subtracted compositions of Skaergaard rocks in particular cover the entire range of chemical variation in the lunar rocks. The statistical results prompt us to speculate further on the similarity of the moon and Skaergaard. We note that the average composition of the moon (Wanke et al., 1974) is similar to the albite subtracted composition of the Skaergaard magma. The lunar crust and a significant part of the lunar interior may match the albite subtracted and somewhat Mg enriched Skaergaard magma.     

First approximation sea-level dependent mathematical model for volume eroded and submarine profile development in a semienclosed sea: Kiel Bay,Western Baltic

Given a marine basin of near homogeneous lithology, a known sea level curve, and known submarine abrasion rates, a model is developed to estimate the volume of material eroded by marine action. Assumptions of the model are that erosion is effected solely by submarine abrasion, which is assumed known and uniform through time, and that the volume eroded is small relative to the total volume of the basin. The basis of the model is that the volume eroded V, between time limits t₁ andt ₂,is essentially a function of the perimeter length l of the basin, which in turn is time-dependent on the sea level curve, so that $$V = k\int_{t1}^{t2} {l(t)dt} $$ where k is an abrasion rate constant. The model was tested on Kiel Bay, Western Baltic, a shallow semienclosed, essentially nontidal sea, for which considerable data is available. Critical for numerical integration of the model is the k value, representing the volume eroded from the shore normal profile per unit length of shoreline per year. A number of possible k values were utilized, the most likely realizing a total volume eroded over the past 9000 y, since the sea first entered Kiel Bay, of 2.60×10⁹ m ³. From this model, long-term average vertical submarine abrasion rates for Kiel Bay can be deduced as being between 0.001 and 0.0004 m/y. An extension to the model analyzes the effect of sea level transgression rate on whether cliffs develop and predicts the theoretical form of the submarine profile based on varying abrasion rates summarized as $$y_B (x) = \left\{ {\begin{array}{*{20}c} {h({x \mathord{\left/ {\vphantom {x {V_c }}} \right. \kern-\nulldelimiterspace} {V_c }}) - a_T (x) for x > 0;} \\ {x\tan \theta - a_T (x) for x > 0.} \\ \end{array} } \right.$$ Here the origin x=0, y_B=0 is chosen horizontally at the position where cliff formation first occurs, and vertically at the sea level at that time. The coordinate x measures distance inshore from the origin, y_B(x) is the vertical position of the sea floor, a_T(x) is the total depth abraded, tanθ is the original land surface slope, V_c the rate of cliff retreat, and h(t) the sea-level at time t. The synthetic profiles are compared to actual erosional profiles from representative sectors of Kiel Bay. The model predicts cliff development began at about 5800 yB.P., resulting in submarine abrasion profile lengths of about 1740 m and cliff heights of about 17.4 m for original land surface slopes of 0.01. This agrees to within about 10% of mean values obtained from bathymetric and topographic maps.     

钦州市降雨及入海河流径流演变规律与趋势分析

依据钦州市58a平均降雨量和3条入海河流控制站径流量长序列资料,采用滑动平均、线性回归、Spearman、M-K及R/S法综合分析降雨径流的趋势性及突变特征。结果表明,钦州市降雨量总体呈弱增加趋势,增加率为0.742mm/10a,而茅岭江、钦江、大风江流域径流量存在总体减少趋势,减少率分别为0.2×108m~3/10a、1.1×108m~3/10a、0.4×108m~3/10a。运用复Molet小波分析多时间尺度周期性,降雨量序列存在5个时间尺度,22a和15a时间尺度分别为序列第一、三主周期;径流量序列存在3个时间尺度,其中22a和8a时间尺度分别为径流量序列第一、二主周期。     

Effects of straw mulching on soil evaporation during the soil thawing period in a cold region in northeastern China

To study the effect of straw mulching on soil water evaporation, it is necessary to measure soil water evaporation under different conditions of straw mulching during the soil thawing period. A field experiment was conducted in winter, and soil evaporation was measured using a microlysimeter on bare land (LD) and 4500 (GF4500), 9000 (GF9000) and 13500 \(\hbox {kg/hm}^{2}\) (GF13500) straw mulch. The influence of different quantities of straw mulch on soil water evaporation during the thawing period was analyzed using the Mallat algorithm, statistical analysis and information cost function. The results showed that straw mulching could delay the thawing of the surface soil by 3–6 d, decrease the speed at which the surface soil thaws by 0.40–0.80 cm/d, delay the peak soil liquid water content, increase the soil liquid water content, reduce the cumulative evaporation by 2.70–7.40 mm in the thawing period, increase the range of soil evaporation by 0.04–0.10 mm in the early stage of the thawing period, and reduce the range of soil evaporation by 0.25–0.90 mm in the late stage of the thawing period. Straw mulching could reduce the range of and variation in soil evaporation and can reduce the effect of random factors on soil evaporation. When the amount of straw mulch exceeded 9000 \(\hbox {kg/hm}^{2}\), the effect of increasing the amount of straw mulch on daily soil water evaporation was small.     

Palynological analyses in the laminated sediment of Lake Holzmaar (Eifel, Germany): duration of Lateglacial and Preboreal biozones

The laminated sediment of Lake Holzmaar (Germany) has provided a continuous varve chronology for the last 3500 varve years (vy) and beyond that a floating varve chronology back to more than 22500 vy BP. This chronology in calendar years, in combination with palynology, enables us to determine the timing and the magnitude of Lateglacial and Early Holocene environmental changes on land (from 13838 to 10930 vy BP). The palynological diagram has a mean time resolution of 27 vy between samples. This paper establishes for the first time the biozonation for Lake Holzmaar below the Laacher See Tephra. Fifteen pollen subzones grouped in four biozones are defined by cluster analysis. After a period disturbed by microturbidites, only a part of the Bølling is present. Three cold periods have been evidenced by pollen analyses: the Older Dryas (96-vy-long), the Younger Dryas (654-vy-long) and the Rammelbeek phase (237-vy-long). The Allerød (883-vy-long) is bipartite with a first Betula -dominated period followed by a Pinus -dominated one. The Younger Dryas is also bipartite, with first a decrease of winter temperatures along with a change to a more continental climate. It is followed by a drier phase with a second decrease in temperatures, probably this time also affecting summer temperatures. The Preboreal is 702-yr-long. The duration of most phases corresponds to published records, except for that of the Younger Dryas. Cluster and rate-of-change analyses indicate a sharp change in the terrestrial vegetation assemblages that may be caused by a sedimentary hiatus of erosive origin during this cold and dry period. As a result, the chronology of Holzmaar has to be revised most likely below the middle of the Younger Dryas. Comparison with the varve record of Meerfelder Maar, a neighbour maar lake, suggests adding 320 vy below 12025 vy.     

Associations of Mn-bearing minerals as indicators of oxygen fugacity during the metamorphism of metalliferous deposits

The paper summarizes experimental and calculation data on the effect of oxygen fugacity on the origin of mineral assemblages in Mn-bearing rocks and demonstrates the possibility of application of these data to the reconstruction of conditions under which metalliferous deposits were metamorphosed. A new variant of the T-log\(f_{O_2 } \) diagram is proposed for the Mn-Si-O system, which differs from previous ones by the location of the lines for the formation (decomposition) of braunite and tephroite. These two minerals are the most universal indicators of oxygen fugacity during the metamorphism of Mn-bearing deposits, because these minerals are widespread in nature and can be formed in diverse environments: braunite at high \(f_{O_2 } \) values in the pore solution, and tephroite at low \(f_{O_2 } \) values. The occurrence of Mn oxides and rhodonite (pyroxmangite) in a rock makes it possible to constrain the oxygen fugacity range. An original T-log\(f_{O_2 } \) diagram is constructed for the Ca-Mn-Si-O system. As follows from this diagram, a Ca admixture expands the stability field of rhodonite toward higher oxygen fugacity values. Johannsenite can be formed in these rocks at even higher \(f_{O_2 } \). The stability of both minerals is constrained in the region of low \(f_{CO_2 } \). The paper reports data on the Fe-Si-O and Mn-Fe-Si-O systems and discusses the possibility of applying the results of experiments in the Mn-Al-Si-O system to the estimation of conditions under which andalusite, spessartine, and galaxite can be formed in Mn-bearing rocks. Data on the mineralogy of numerous Mn deposits metamorphosed under various PTX parameters indicate that the origin of Mn-bearing mineral assemblages depends not so much on the temperature and pressure as on the oxygen fugacity, which is, in turn, controlled primarily by the composition of the pristine sediments (the presence or absence of organic matter in them) and host rocks and depends on the permeability of the rocks to oxygen, the P-T conditions, and the duration of the metamorphic processes.     

Light scattering in jadeite melt: Strain relaxation measurements by photon correlation spectroscopy

Photon correlation spectroscopy has been applied to the study of longitudinal strain relaxation of vitreous Jadeite (NaAlSi₂O₆) in the temperature range 811–1014° C. The correlation function $\left| {g^{\left( 1 \right)} \left. {\left( t \right)} \right|^2 \propto \exp \left( {\left( { - 2t/\tau _\beta } \right)^\beta } \right)} \right.$ obeys a Kohlrausch type function with β=0.64±0.01. Individual correlation functions fit altogether a master relaxation curve, thus demonstrating thermorheological simplicity (TRS). The temperature dependence of the measured relaxation times shows Arrhenian behaviour with $\log \left( \tau \right) = - 21.4 \pm 0.3{\text{s}} {\text{ + }} {\text{471}}{\text{.6}} \pm {\text{22}} {\text{kJmol}}^{{\text{ - 1}}} /RT$ . The time scale of longitudinal strain relaxation is consistent with the existing data on shear relaxation derived from shear viscosity and structural relaxation calculated from calorimetric C _pmeasurements. Comparison with oxygen diffusion indicates that network forming elements relax at about the same time scale as viscoelastic properties. On the other hand, Na⁺ relaxation times derived from impedance spectroscopy are short compared to viscoelastic relaxation times at low temperatures. This difference is decreasing with increasing temperature and possibly disappearing at approximately 1100° C.     

The Shaw bomb,an ideal hydrogen sensor

A simple modification was made to the reaction vessel designed by Shaw (1963) in order to use it as a hydrogen sensor instead of a hydrogen source, thereby allowing a continuous record of to be made during an experiment. The advantage of this arrangement is that (reversed) curves for minerals can be generated from a single experimental run. Other applications are possible.This method was successfully used in the determination of the Ni-NiO-H₂O equilibrium between 580 ° and 830 °C at 2 kbar fluid pressure. The corrected 1 atm values are in agreement with electrochemical measurements. An Ag₇₀Pd₃₀ hydrogen permeable membrane was used for the experiment and flow rates of hydrogen through the membrane were calculated by monitoring the rate of increase or decrease in pressure with an induction pressure transducer. These flow rates range up to two times greater than those calculated for a pure platinum membrane.     

A thermodynamic formulation of hydrous cordierite

A thermodynamic formulation of hydrous Mg-cordierite (Mg₂Al₄Si₅O₁₈·nH₂O) has been obtained by application of calorimetric and X-ray diffraction data for hydrous cordierite to the results of hydrothermal syntheses. The data include measurements of the molar heat capacity and enthalpy of hydration and the molar volume. The synthesis data are consistent with a thermodynamic formulation in which H₂O mixes ideally on a single crystallographic site in hydrous cordierite. The standard molar Gibbs free energy of hydration is-9.5±1.0 kJ/mol (an average of 61 syntheses). The standard molar entropy of hydration derived from this value is-108±3 J/mol-K. An equation providing the H₂O content of cordierite as a function of temperature and fugacity of H₂O is as follows (n moles of H₂O per formula unit, n<1): $$\begin{gathered}n = {{f_{{\text{ H}}_{\text{2}} O}^{\text{V}} } \mathord{\left/{\vphantom {{f_{{\text{ H}}_{\text{2}} O}^{\text{V}} } {\left( {f_{{\text{ H}}_{\text{2}} O}^{\text{V}} + {\text{exp}}\left[ { - {\text{3}}{\text{.8389}} - 5025.2\left( {\frac{1}{T} - \frac{1}{{298.15}}} \right)} \right.} \right.}}} \right.\kern-\nulldelimiterspace} {\left( {f_{{\text{ H}}_{\text{2}} O}^{\text{V}} + {\text{exp}}\left[ { - {\text{3}}{\text{.8389}} - 5025.2\left( {\frac{1}{T} - \frac{1}{{298.15}}} \right)} \right.} \right.}} \hfill \\{\text{ }}\left. {\left. { - {\text{ln}}\left( {\frac{T}{{{\text{298}}{\text{.15}}}}} \right) - \left( {\frac{{298.15}}{T} - 1} \right)} \right]} \right) \hfill \\\end{gathered}$$ Application of this formulation to the breakdown reaction of Mg-cordierite to an assemblage of pyrope-sillimanite-quartz±H₂O shows that cordierite is stabilized by 3 to 3.5 kbar under H₂O-saturated conditions. The thermodynamic properties of H₂O in cordierite are similar to those of liquid water, with a standard molar enthalpy and Gibbs free energy of hydration that are the same (within experimental uncertainty) as the enthalpy and Gibbs free energy of vaporization. By contrast, most zeolites have Gibbs free energies of hydration two to four times more negative than the corresponding value for the vaporization of water.     

Thermodynamics and phonon dispersion of pyrope and grossular silicate garnets from ab initio simulations

The phonon dispersion and thermodynamic properties of pyrope (\(\hbox {Mg}_3\hbox {Al}_2\hbox {Si}_3\hbox {O}_{12}\)) and grossular (\(\hbox {Ca}_3\hbox {Al}_2\hbox {Si}_3\hbox {O}_{12}\) ) have been computed by using an ab initio quantum mechanical approach, an all-electron variational Gaussian-type basis set and the B3LYP hybrid functional, as implemented in the Crystal program. Dispersion effects in the phonon bands have been simulated by using supercells of increasing size, containing 80, 160, 320, 640, 1280 and 2160 atoms, corresponding to 1, 2, 4, 8, 16 and 27 \(\mathbf {k}\) points in the first Brillouin zone. Phonon band structures, density of states and corresponding inelastic neutron scattering spectra are reported. Full convergence of the various thermodynamic properties, in particular entropy (S) and specific heat at constant volume (\(C_\mathrm{{V}}\)), with the number of \(\mathbf {k}\) points is achieved with 27 \(\mathbf {k}\) points. The very regular behavior of the S(T) and \(C_\mathrm{{V}}(T)\) curves as a function of the number of \(\mathbf {k}\) points, determined by high numerical stability of the code, permits extrapolation to an infinite number of \(\mathbf {k}\) points. The limiting value differs from the 27-\(\mathbf {k}\) case by only 0.40 % at 100 K for S (the difference decreasing to 0.11 % at 1000 K) and by 0.29 % (0.05 % at 1000 K) for \(C_\mathrm{{V}}\). The agreement with the experimental data is rather satisfactory. We also address the problem of the relative entropy of pyrope and grossular, a still debated question. Our lattice dynamical calculations correctly describe the larger entropy of pyrope than grossular by taking into account merely vibrational contributions and without invoking “static disorder” of the Mg ions in dodecahedral sites. However, as the computed entropy difference is found to be larger than the experimental one by a factor of 2–3, present calculations cannot exclude possible thermally induced structural changes, which could lead to further conformational contributions to the entropy.     

Equilibriums between Cu,Fe, and Zn sulfides and oxides in chloride solution: A thermodynamic study

The results of thermodynamic modeling of equilibriums between Cu, Fe, and Zn sulfides and oxides pertaining to the Cu-Fe-Zn-S-O₂ system in water and aqueous chloride solution are presented. The system comprises solid phases of constant composition: pyrite, pyrrhotite, hematite, magnetite, wüstite, γ-iron, chalcocite, covellite, cuprite, native copper, chalcopyrite, and bornite, as well as more than 100 ions, complexes, and molecules in an aqueous solution. The GIBBS program with the UNITHERM thermodynamic dataset used in calculations allows numerical analysis of phase assemblages in a dry system and in equilibrium with an aqueous solution. How the temperature, pressure, and the composition of the solution in the system opened for oxygen and sulfur affects the composition of phase assemblages was considered in temperature and pressure ranges of 50–350 C and 100–1000 bar, respectively. Decrease in temperature leads to a shift in stability fields of the studied phases toward the region of elevated oxygen and sulfur partial pressures. Variation of temperature is an important factor affecting precipitation of ore minerals, primarily, Cu- and Zn-bearing. The calculation results are presented in tables and diagrams. Each point in the $ (\log m_{S_{tot} } - \log f_{O_2 } ) $ (\log m_{S_{tot} } - \log f_{O_2 } ) diagram is characterized by a single possible assemblage of phases equilibrated with a solution of the given composition within the considered temperature and pressure range. Since the composition of the mineral assemblage is controlled by physicochemical conditions at the moment of mineral formation, comparison of the calculation results with mineral assemblages at ore deposits makes it possible to estimate the parameters of ore deposition at the early stage of investigation, including oxygen and sulfur activity and, occasionally, the composition and salinity of the solution. These parameters control the formation of such assemblages.     

Anharmonic effect on the equation of state (EoS) for NaCl

We find clear intrinsic anharmonicity in the NaCl-B1 phase by examining the equation of state (EoS) based on previous ultrasonic velocity data for pressures up to 0.8 GPa and temperatures up to 800 K. The experimental EoS for this phase shows that its specific heat at constant volume (C _V ) is significantly smaller than that based on a harmonic model. Also, the sign of $\left( {{{\partial C_{V} } \mathord{\left/ {\vphantom {{\partial C_{V} } {\partial P}}} \right. \kern-0pt} {\partial P}}} \right)_{T} ,$ which is normally negative in the quasi-harmonic approximation, is unexpectedly positive. The thermodynamic Grüneisen parameter (γ), which has frequently been assumed to be a single-variable function of molar volume, shows not only volume dependence but also negative temperature dependence. To understand these features of C _V and γ, we introduce a thermodynamic model including positive quartic anharmonicity. To make an anharmonic model advancing the ordinarily quasi-harmonic approximation model, we introduce two parameters: anharmonic characteristic temperature (θ _a ) and its volume derivative. In the anharmonic model, the value of C _V is calculated along an isochore using classical statistical mechanics and a harmonic quantum correction. At high temperatures, the decrease in C _V from the Dulong-Petit limit is related to the value of T/θ _a . For infinitely large θ _a , the system is approximately quasi-harmonic. The temperature dependence of γ is related to C _V by the thermodynamic identity $\left( {{{\partial C_{V} } \mathord{\left/ {\vphantom {{\partial C_{V} } {\partial \ln V}}} \right. \kern-0pt} {\partial \ln V}}} \right)_{T} = C_{V} \left( {{{\partial \gamma } \mathord{\left/ {\vphantom {{\partial \gamma } {\partial \ln T}}} \right. \kern-0pt} {\partial \ln T}}} \right)_{V} + \gamma \left( {{{\partial C_{V} } \mathord{\left/ {\vphantom {{\partial C_{V} } {\partial \ln T}}} \right. \kern-0pt} {\partial \ln T}}} \right)_{V}.$ Even though our modification of the quasi-harmonic approximation is simple, our anharmonic model succeeds in reproducing the experimental γ and C _V simultaneously for the NaCl-B1 phase.     

广西龙头山金矿床黄铁矿标型特征及其地质意义

广西龙头山金矿床是大瑶山成矿带内重要的金矿床,矿区发育大量不同类型的黄铁矿。根据黄铁矿的产出特征,将黄铁矿划分为5个世代,对应着5个成矿阶段:电气石-石英-硫化物阶段(Ⅰ)、石英-黄铁矿-黄铜矿阶段(Ⅱ)、石英-多金属硫化物阶段(Ⅲ)、石英-黄铁矿-闪锌矿阶段(Ⅳ)、石英-黄铁矿阶段(Ⅴ)。不同阶段黄铁矿晶形均以{100}为主,少见{210};金含量与{210}含量呈正相关。黄铁矿晶胞参数为5.411 86~5.415 52,变化幅度不大,与钴含量呈正相关,主成矿阶段受金含量影响而变大。形貌及砷含量变化特征表明,{210}和金含量随砷含量降低而升高,说明砷含量降低利于{210}的出现,且金与砷不存在正相关关系。形貌特征及微量元素特征均反映主成矿阶段温度应220℃,且多集中于300℃的范围;δFe—δS图解及矿床地质特征表明,成矿热液主要为岩浆热液。综合分析认为,龙头山金矿床为中-高温岩浆期后热液矿床。     

Butterfly diagram for starspots on LQ Hya

Information on the latitude distribution of starspots and changes in this distribution from year to year is very important for our understanding of the nature of stellar activity and for developing dynamo theory. The concept of butterfly diagrams is introduced for highly spotted stars of late spectral types, by analogy to the Maunder diagrams for the Sun. Our approach is based on the zonal spottedness models constructed by Alekseev and Gershberg. A detailed analysis is given for the single active star LQ Hya, and a comparison is made to similar analyses for several stars with two well-separated spot belts—EK Dra, VY Ari, V775 Her, and V833 Tau. The lower boundary of the butterfly diagram drifts toward the equator during the activity-rise phase, i.e., during years when the relative spotted area increases. This effect is clearly expressed for LQ Hya and other stars whose orientation enables observation of both hemispheres and virtually vanishes for V833 Tau, which is viewed nearly pole-on. The upper boundary of the diagram is virtually unchanged for all the considered spotted stars except V775 Her, for which it moves toward the pole. The drift rate of the lower boundary is ?1 to ?2 deg/yr, a factor of two to three smaller in magnitude than the corresponding solar value. Our analysis provides an independent confirmation of the occurrence of high-latitude spots on stars that are younger than the Sun and whose activity is high but less regular than the solar activity; it also enables the identification of the starting times of stellar cycles.