Photometric period and rotational brightness modulation of V833 Tau

Photometric data covering 1994–2009, obtained at the Crimean Astrophysical Observatory or retrieved from the ASAS and SuperWASP catalogs, were used to analyze the brightness variations of the rapidly rotating star V833 Tau, whose activity level is close to saturation. Combined with previously published results, these data represent for the first time all stages in the development of the star’s 19- year activity cycle. The photometric period and rotational-modulation amplitude for different epochs are determined, and the qualitative pattern of the spots is considered. The photometric period is close to the orbital period, but always exceeds it, indicating that surface inhomogeneities are located far from the equatorial plane. With the high spottedness of the star, reaching 28% at the cycle maximum, the rotationalmodulation amplitude is 0.05?0.1 ^m , and increases during the growth and decline phases of the 19-year cycle. The rotational modulation is due to spots with higher latitudes than in the case of the Sun, and concentrating on active longitudes.     

X Per and V725 Tau: infrared variations on timescales longer than fifteen years

The results of infrared observations of the two Be stars X Per and V725 Tau, which are the optical components of X-ray binary systems, obtained in 1994–2016 are presented. The observations cover Be-star phases as well as shell phases. The data analysis shows that the radiation observed from the binaries at 1.25, 3.5, and 5 μm can be explained as the combined radiation from the optical components and variable sources (shells/disks) that emit as blackbodies (BBs). Emission from a source with the color temperature T _c ~1000?1500 K was detected for X Per at λ ≥ 3.5 μm. The highest IR-brightness variation amplitudes for X Per were 0.9?1.2 ^m (JHK magnitudes) and ~1.45 ^m (LM magnitudes); for V725 Tau, they were 1.1?1.4 ^m and ~1.7 ^m (L magnitudes). The parameters of the optical components and interstellar extinction during the Be phases were estimated: the color excesswasE(B?V) = 0.65±0.08 ^m and 0.77 ± 0.03 ^m for X Per and V725 Tau, respectively. Light from the variable sources (disks/shells) was distinguished and their color temperatures, radii, and luminosities estimated for different observation epochs in a BB model. The variations of the binaries’ IR brightness and colors are shown to be due to changing parameters of the variable sources. The mean color temperature of the cool source (disk/shell) and the mean radius and mean luminosity of X Per are 9500± 2630 K, (35 ± 10) R_⊙, and (9100± 540) L_⊙. For V725 Tau, these parameters are 6200 ± 940 K, (27 ± 6) R_⊙, and (980 ± 420) L_⊙. The 1.25–5 μm radiation from X Per at different epochs can be represented as a sum of contributions from at least three sources: the optical component and two objects emitting as BBs. To reproduce the 1.25–3.5 μm radiation from V725 Tau, two components are sufficient: the optical component and a single variable BB object. For both binary systems, orbital variations of the IR brightness can be noted near the Be-star phase. The amplitudes of the J-band variations of X Per and V725 Tau are about 0.3 ^m and 0.1 ^m , respectively.     

Evolution of sea‐surface conditions on the northwestern Greenland margin during the Holocene

Reconstructions of sea‐surface conditions during the Holocene were achieved on two sediment cores from the northwest Greenland margin (AMD14‐204) and Kane Basin (AMD14‐Kane2B) based on dinoflagellate cyst assemblages. On the northwest Greenland margin, sea‐surface conditions were cold with an extended sea ice cover prior to 7750 cal a bp associated with the end of the deglaciation. A major change occurred around ca. 7750 cal a bp with enhanced influence of warmer water from the West Greenland Current, and optimal sea‐surface conditions were observed around 6000 cal a bp . After 3350 cal a bp , results reflect the establishment of the modern assemblages. In the Kane Basin, sea‐surface conditions were not favourable for dinocyst productivity prior to 7880 cal a bp , as the basin was still largely covered by ice. The presence of warmer water is recorded between 7880 and 7200 cal a bp and the highest primary productivity between 5200 and 2100 cal a bp , but sea‐surface conditions remained cold with an extended sea ice cover throughout the Holocene. Overall, the results from this study revealed the strong influence of meltwater discharges and oceanic current variability on the sea‐surface conditions. Copyright © 2019 John Wiley & Sons, Ltd.     

全球陆地地表水资源演变特征

探究变化环境下全球陆地地表水资源演变特征，是当前水文与水资源学研究关注的热点与难点问题。其中，提高无资料地区水文预报的精度是准确评价全球地表水资源量的重要前提。针对这个问题，本研究在划分全球气候-生态分区的基础上，通过对5种参数移植方法进行比较优选，发现反距离空间插值法与物理相似法相结合的模拟精度最高，进而以此评价了1960—2016年全球、各大洲和重点地区的地表水资源量演变特征。结果表明：在柯本气候分区的基础上，利用生态分区指标进行无监督分类，共获得了229个气候-生态分区；基于全球降水数据和四级水资源区产水系数，获得全球多年平均地表水资源量为41.06万亿m³，与已有研究结果类似；全球、北美洲和非洲的地表水资源量呈现显著下降趋势；地表水资源量呈下降趋势的四级水资源区主要分布在北美洲、南美洲北部和非洲中部等地区。     

全球陆地地表水资源演变特征

探究变化环境下全球陆地地表水资源演变特征，是当前水文与水资源学研究关注的热点与难点问题。其中，提高无资料地区水文预报的精度是准确评价全球地表水资源量的重要前提。针对这个问题，本研究在划分全球气候-生态分区的基础上，通过对5种参数移植方法进行比较优选，发现反距离空间插值法与物理相似法相结合的模拟精度最高，进而以此评价了1960—2016年全球、各大洲和重点地区的地表水资源量演变特征。结果表明:在柯本气候分区的基础上，利用生态分区指标进行无监督分类，共获得了229个气候-生态分区；基于全球降水数据和四级水资源区产水系数，获得全球多年平均地表水资源量为41.06万亿m3，与已有研究结果类似；全球、北美洲和非洲的地表水资源量呈现显著下降趋势；地表水资源量呈下降趋势的四级水资源区主要分布在北美洲、南美洲北部和非洲中部等地区。     

The accretion activity of the Ae Herbig star CQ Tau

Results of spectral observations of the isolated Ae Herbig star CQ Tau obtained in 1995–1998 in the H_α line and near the sodium resonance doublet are presented, together with simultaneous photometric monitoring of the star. CQ Tau is a member of the family of young UX Ori stars with nonperiodic Algol-like brightness decreases. The star is surrounded by an accretion disk, in which its emission-line spectrum and part of its absorption-line spectrum are formed. The strong variability of the H_α, D NaI, and HeI 5876 Å lines testifies that the gaseous disk is appreciably inhomogeneous in both the radial and azimuthal directions. This inhomogeneity probably results from uneven feeding by the circumstellar material from the peripheral regions of the circumstellar disk. Over the four years of observations, we observed the star in deep minima three times (ΔV～2). On these nights, an increase in the H_α equivalent width followed the decrease in radiation flux. In the two deepest minima, the normally two-component line profile had only a single component with a nearly symmetrical profile. This behavior of the H_α line is in good agreement with the results of numerical modeling of Algol-like minima and can be used to estimate the parameters of the dust clouds eclipsing the star and inner accretion disk. These estimates suggest that the circumstellar dust clouds can approach very close to the star and be sublimated there.     

Water and Iron effect on the P-T-x coordinates of the 410-km discontinuity in the Earth upper mantle

We performed multi-anvil experiments in the system MgO-SiO₂ ± H₂O at 13.0–13.7 GPa and 1,025–1,300°C and in the system MgO-FeO-SiO₂ ± H₂O, under reducing conditions, at 11.0–12.7 GPa and 1,200°C, to depict the effect of H₂O on the P-T-x coordinates of the 410-km discontinuity, i.e. the olivine–wadsleyite phase boundary. The charges were investigated with Electron Microprobe (EMP), Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Secondary Ion Mass Spectrometry (SIMS) and Electron Energy Loss Spectroscopy (EELS). We observe in the MgO-SiO₂-H₂O system at 1,200°C a 0.6 GPa shift of the phase boundary to lower pressure compared to dry conditions, due to the stronger water fractionation into wadsleyite (wad) rather than in olivine (ol). In the MgO-FeO-SiO₂-H₂O system, we reproduced the triple point, i.e. observed coexisting hydrous ol, wad and ringwoodite (ring). SIMS H quantifications provided partitioning coefficients for water: D_\textwad/ol^\textwater D_{\text{wad/ol}}^{\text{water}}  ~ 3.7(5) and D_\textring/ol^\textwater D_{\text{ring/ol}}^{\text{water}}  ~ 1.5(2) and D_{\textwad/ring}^\textwater D_{\text{wad/ring}}^{\text{water}}  ~ 2.5(5). For a bulk composition of x _Fe = 0.1, our data indicate only a slight difference in the width of the loop of the two phase field ol–wad under hydrous conditions compared to dry conditions, i.e. no broadening with respect to composition but a shift to lower pressures. For bulk compositions of x _Fe > 0.2, i.e. in regions where wad–ring and ol–ring coexist, we observe, however, an unexpected broadening of the loops with a shift to higher iron contents. In total, the stability field of hydrous wad expands in both directions, to lower and higher pressures. Fe³⁺ concentrations as determined by EELS are very low and are expected to play no role in the broadening of the loops.     

The chemical compositions and surface structures of two roAp stars with lithium spots (HD 83368 and HD 60435)

The spectra of two roAp stars have been analyzed as part of a project to study lithium in magnetic Ap stars. Variability of the Li I 6708 Å resonance doublet and rare-earth lines was detected, which can be explained using an oblique rotator model with the lithium spots located at the magnetic poles. Synthetic spectra obtained at different rotational phases have yielded the first data on the atmospheric chemical compositions of these spotted stars. Using refined atomic data and the most complete line lists has enabled a detailed study of the spectra near the Li I 6708 Å line and computation of the Li I line profile taking into account the spotted distribution of the lithium over the stellar surfaces. The positions of two lithium spots and lithium abundances for each of the spots have been determined.     

影响铁长沟露天煤矿边坡稳定性因素分析

凹陷露天煤矿,由于形成的台阶多,在一定的地质和水文条件下或在外力作用下,当边坡岩体结构面顺层或有弱结构层时,往往形成边坡岩体的滑落,造成重大安全事故.乌鲁木齐矿务局铁长沟露天煤矿井田就属于此类型.该煤矿位于铁长沟河和芦草沟河之间,东西长6km,南北宽1.2km,初步设计基岩边坡角35°,第四系边坡角25°,开采深度+650水平.该矿现开采深度已达到80m,通过对边坡稳定性的分析,指出了边坡滑落的可能以及影响边坡滑落的各种因素,这对于预防边坡的滑落有一定的帮助作用.1影响边坡稳定的地质作用岩石组成岩石中如果含有粘土矿物蒙脱石遇水会膨…     

Lithium lines in the spectra of M dwarfs: UX Tau C

The results of numerical modeling of lithium lines in the spectra of M dwarfs are discussed. The behavior of the lithium lines relative to the local pseudocontinuum formed by molecular bands is analyzed as a function of model atmosphere parameters: effective temperature T _eff, gravity logg, and metallicity μ The molecular opacity was computed using the just overlapping line approximation (JOLA) and “line-by-line” methods. The pseudo-equivalent widths of lithium lines depend appreciably on metallicity μ and weakly on T{nteff}. The lithium abundance in the atmosphere of UX Tau C is redetermined. Previous studies underestimated the lithium abundance in this star as a result of the use of insufficiently accurate molecular-line lists. The new lithium abundance log N (Li)=3.2±0.3was derived by comparing the observed profiles of the 670.8 nm resonance doublet lines with profiles calculated using the new TiO line list of Plez.¹ The new abundance agrees with the atmospheric lithium abundances of the other two components in the stellar system, providing further evidence that the three stars in the UX Tau system have the same age. A comparison of the observed spectra of UX Tau C near the lithium resonance doublet (665–680 nm) with spectra computed using JOLA and line-by-line methods suggests that the list of Plez is the best currently available.     

Physical conditions in the hot spots of the radio galaxy Cygnus A

It is shown that composite radio spectra of the hot spots of the radio galaxy Cygnus A can be fully explained by assuming a nonuniform distribution of the magnetic fields inside the hot spots, without invoking any physical mechanisms other than synchrotron radiation. The magnetic fields are strong (B ?? 10^?2?10^?1 G) at the center of the hot spots, and decreases at the hot-spot edges to the level of the magnetic field of the radio lobes in which the hot spots are embedded (B ?? 10^?4?10^?5 G). The difference in the magnetic field between the hot-spot center and edge decreases during the evolution, while the average magnetic-field intensity increases.     

Observations of a unique minimum of RR Tau in the optical and near infrared

We present observations of the UX Ori star RR Tau in the optical (UBVRI)and near infrared (JHKLM)acquired between November 2000 and April 2001. We recorded a uniquely long (about half a year) Algol-like minimum with an amplitude of ΔV≈2.9. The dimming of RR Tau was accompanied by an increase of the linear polarization, typical of UX Ori stars and testifying to the eclipsing nature of the minimum. The J and H infrared fluxes varied synchronously with the optical variations. However, the K and L brightness changes were in the opposite sense: the flux in these two bands increased for the entire duration of the optical minimum. Our analysis suggests that the source of the K and L radiation is the dust cloud itself, moving at a distance of about 1 AU from the star. The flux increase in these bands was not due to an increase in the dust temperature, but instead to an increase in the number of emitting grains in the cloud. This could be associated either with an actual increase in the number of fine grains due to sublimation and the disruption of larger grains or with the distortion and disruption of the cloud due to tidal perturbation, permitting the star’s light to penetrate and heat the densest regions of the cloud. Based on the observed L fluxes, we estimate the mass of the emitting dust in the cloud to be ≈10²³ g. Taking into account the presence of cool dust and a gaseous component in the cloud in addition to the dust heated by the star’s radiation, and adopting a ratio for the masses of the dust and gas components similar to that in the interstellar medium (1:100), we estimate the cloud’s total mass to be ≥10²⁵ g. Judging from this value and the duration of the minimum, we observed an extremely rare episode associated with a giant gas and dust cloud with a total mass on the order of 0.1 lunar mass or higher, which passed very near the young star (and may be falling onto it).     

Analysis of the spectral energy distributions of four cool R CrB stars near the brightness maximum

The effective temperatures T _eff and carbon and nitrogen abundances in the atmospheres of the cool R CrB stars ES Aql, SV Sge, Z UMi, and NSV 11154 have been determined by modeling their spectral energy distributions in the optical and near-infrared. The hydrogen-deficient model atmospheres were computed using the SAM12 code in the classical approximation, taking into account sources of opacity characteristic of the atmospheres of R CrB stars. The influence of the hydrogen deficiency on theoretical stellar spectra is analyzed. The resulting effective-temperature estimates for ES Aql, SV Sge, Z UMi, and NSV 11154 are in the range T _eff = 4600–5200 K. The carbon abundances log n(C) in the atmospheres of ES Aql, SV Sge, and Z UMi are 8.9–10.1, corresponding to [C/Fe] values typical of the atmospheres of R CrB stars. The nitrogen abundances are lower than those determined in other studies, and differ considerably from star to star. The mean [N/Fe] value for these three stars is ≈1.5 dex lowthan the mean [N/Fe] for known warm R CrB stars. Abnormally high estimates were obtained for the atmosphere of NSV 11154: log n(C) = 10.8 and log n(N) = 10.0. The approximate log g estimates agree with the conclusion from photometric observations that cool R CrB stars have lower luminosities than hotter R CrB stars.     

土质滑坡地表倾斜变形特征与基于MEMS的倾斜变形监测技术初探

随着现代信息技术快速发展,人们获取滑坡现场各类监测信息的能力越来越强,积累的现场监测数据也愈来愈多,如何充分、精细化地利用监测数据已成为滑坡监测预警工作中重点关注的问题。为此,本文以土质滑坡为研究对象,采用强度折减有限元方法开展地表倾斜变形时空演化特征理论研究,发现地表倾斜变形在滑动面扩展至贯通期间出现"速率排序跃迁"现象,在滑动面贯通后出现"速率突变"现象。采用地表倾斜变形与内部滑动面之间的这种定量化关联特性,可以为土质滑坡中短期预测预报方法研究提供新的视角和方向。利用理论研究成果,本文进一步开展地表倾斜变形监测关键技术研究,讨论基于MEMS加速度计的倾角传感器的测量原理与测量精度,分析环境温差波动对倾角测量误差的影响,最后介绍基于竖直倾角测量方式研制的普适型滑坡地表倾斜变形监测设备——坡体浅层倾斜变形测量仪。     

关于冰期演变三个问题的讨论

施雅风和李吉均（1994）在总结80年代以来中国冰川学研究的新进展中,提出了3个有待深化和争论的问题：1）不同地区最大冰期出现先后差别的原因尚不清楚;对是否存在一种与季风区相反的模式,即冰期与雨期同步;3）在冰期变化中"气候因素与构造因素何者为主".这3个问题也可以说是本世纪冰川学研究留给下世纪的3个问题．它的解决只有冰川学、气候学和地球动力学等的结合才有可能文章拟对此3个问题提点看法,以期"抛砖引玉"．     

Low-Pressure Experimental Constraints on the Evolution of Komatiites

Melting experiments were performed on a komatiitic basalt with17 wt% MgO from Munro Township, Ontario, at I-atm pressure andan oxygen fugacity controlled approximately to the fayalite-magnetite-quartzbuffer. The experiments showed that olivine appears at 1344±5°C,spinel at 1334±6°C plagioclase at 1185±5°C,augite at 1176±5°C and pigeonite at 1154±6°C.Compositionally, olivine varies from Fo₉₀ to Fo₇₄ and displaysan average K^Fe/Mg_D (ol/liq) of 0•32. The spinels are chromitesand chromian spinels with Mg/(Mg + Fe²⁺) ratios between 0•66and 0•;32, which show a marked correlation with meltingtemperature. The pyroxenes show an average K^Fe/Mg_D (px/liq)of 0•26, identical for augite and pigeonite. Plagiodaseranges compositionally between An₈₂ and An₇₂ Plotted in thepseudo-quaternary basalt phase diagram, the liquid line of descentis similar to that observed for quartz tholeiitic magmas. Therefore,the low-pressure, late-stage evolution products of komatiiteand basaltic komatiite parental magmas will chemically and mineralogicallybe ferrobasaltic quartz tholeiites. High-temperature and high-pressuremodeling suggests that the main observed compositional variationof Munro komatiites can be explained by low-pressure crystalfractionation and accumulation of olivine into komatiite liquidswith below 21•5–23•5 wt% MgO and eruptive temperaturesbelow 1435–1465°C for oxygen fugacities between thefayalite-magnetite quartz (FMQ) and iron-wiistite (IW) buffers.The maximum magnesium content of liquid komatiites, assumingequilibrium Fo₉₄ olivine, is 27–29 wt% MgO and eruptivetemperatures are between 1515 and 1540°C. KEY WORDS: komatiites; experimental petrology; Munro Township; Ontario     

Morphology of the interaction between the stream and cool accretion disk in a semidetached binary system

We analyze heating and cooling processes in accretion disks in binaries. For realistic parameters of the accretion disks in close binaries (\(\dot M \simeq 10^{ - 12} - 10^7 M_ \odot /yr\) and α?10^?1–10^?2), the gas temperature in the outer parts of the disk is from ～10⁴ to ～10⁶ K. Our previous gas-dynamical studies of mass transfer in close binaries indicate that, for hot disks (with temperatures for the outer parts of the disk of several hundred thousand K), the interaction between the stream from the inner Lagrange point and the disk is shockless. To study the morphology of the interaction between the stream and a cool accretion disk, we carried out three-dimensional modeling of the flow structure in a binary for the case when the gas temperature in the outer parts of the forming disk does not exceed 13 600 K. The flow pattern indicates that the interaction is again shockless. The computations provide evidence that, as is the case for hot disks, the zone of enhanced energy release (the “hot line”) is located beyond the disk and originates due to the interaction between the circumdisk halo and the stream.     

神狐海域扩散型水合物在地震反射剖面上的“亮点”与“暗点”分析

地震"亮点"分析技术在传统油气勘探中已被证明是一种可行有效的方法,但在天然气水合物勘查中还没有得到足够重视。本文基于含水合物层、含气层及含水层的岩石物理属性,利用2015年神狐钻探区地震资料,分析了含天然气水合物的地震振幅响应特征。结果表明:在神狐钻探区天然气水合物稳定域内,扩散型水合物共有三种形成模式,分别为形成于稳定域底界的水合物层,形成于稳定域内部的高饱和度水合物层和形成于稳定域内部的低饱和度水合物层。水合物形成于稳定域底界时,地震剖面上产生BSR,当沉积层中含高饱和度水合物或含气时,会在地震剖面上产生相应"亮点";当沉积层中含低饱和度水合物时,则在地震剖面上产生相应的"暗点"。综合分析,可以利用地震"亮点"与"暗点"在钻前对水合物成矿进行预测。     

烃源岩TOC值变化与其生排烃效率关系的探讨

采用实验模拟和数值模拟相结合的方法揭示了烃源岩有机碳(TOC%)的损失率DTOC=(TOC0-TOC)/TOC0的变化规律.当烃源岩生排烃效率很低时,DTOC都为负值,即在成熟演化过程 TOC是增加的.随着生排烃效率提高,有机碳变化率DTOC逐渐增加(TOC损失率增大),烃源岩逐步由"增碳"进程转变为"减碳"进程.但只有生烃潜力很高的Ⅰ型有机质岩石,在生烃降解率和排烃效率极高的"理想"条件下,DTOC的增加(减碳进程)幅度才十分显著.指出基于有机质原始丰度恢复的碳酸盐岩烃源岩评价标准,可能过分强调了"减碳"的进程,很多情形下会美化原本比较差的烃源岩.