共查询到20条相似文献，搜索用时 31 毫秒
1.
Samodurov V. A. Tyul’bashev S. A. Toropov M. O. Logvinenko S. V. 《Astronomy Reports》2022,66(4):341-347
Astronomy Reports - A search for pulse signals was carried out in a new sky area included in the monitoring program for the search for pulsars and transients. Processing of several months data... 相似文献
2.
V. M. Tereshchenko 《Astronomy Reports》2001,45(12):1002-1011
The second stage in our program to compile a list of regional intermediate-brightness spectrophotometric standards has been completed. We have obtained spectral energy distributions for 24 stars with magnitudes $7\mathop m\limits_. 0 - 8\mathop m\limits_. 5$ near +40° declination. The range λλ3100–7600 Å was studied with a spectral resolution of 50 Å. The relative rms error of our results in the visible is 1–2%, increasing to 3–5% toward the edges of the studied wavelength interval. All the stars are referenced to a single standard, the circumpolar star HD 221525. The energy distributions were used to compute color indices in the UBV, WBVR, and UPXY ZV S systems, as well as in the system of the TYCHO catalog. The computed and observed values for stars in common with the TYCHO catalog are compared. 相似文献
3.
V. G. Klochkova E. L. Chentsov N. S. Tavolzhanskaya V. E. Panchuk 《Astronomy Reports》2007,51(8):642-674
Based on high-resolution observations (R = 60 000 and 75 000), we have studied the optical spectral variability of the star BD + 48°1220, identified with the IR source IRAS 05040+4820. We have measured the equivalent widths of numerous absorption lines of neutral atoms and ions at wavelengths from 4500 Å to 6760 Å, as well as the corresponding radial velocities. We use model atmospheres to determine the effective temperature T eff = 7900 K, surface gravity log g = 0.0, microturbulence velocity ξ t = 6.0, and the abundances for 16 elements. The star’s metallicity differs little from the solar value: [Fe/H] = ?0.10 dex. The main peculiarity of the chemical composition of the star is a large helium excess, derived from the Hel λ 5876 Å absorption, [He/H] = +1.04, and the equally large oxygen excess, [O/Fe] = +0.72 dex. The carbon excess is small, [C/Fe] = +0.09 dex, and the ratio [C/O] < 1. We obtained an altered relation for the light-metal abundances: [Na/Fe] = +0.87 dex with [Mg/Fe] = ?0.31 dex. The barium abundance is low, [Ba/Fe] = ?0.84 dex. It is concluded that the selective separation of elements onto dust grains of the envelope is probably efficient. The radial velocity of the star measured from photospheric absorption lines over three years of observations varies in the interval V ⊙ = ?(7–15) km/s. Time-variable differential line shifts have been revealed. The entire set of available data (the luminosity M v ≈ ?5 m , velocity V lsr ≈ ?20 km/s, metallicity [Fe/H] = ?0.10, and peculiarities of the optical spectrum and chemical composition) confirms the status of BD + 48°1220 as a post-AGB star with He and O excesses belonging to the Galactic disk. 相似文献
4.
David A. Crerar N.J. Susak M. Borcsik S. Schwartz 《Geochimica et cosmochimica acta》1978,42(9):1427-1437
In the design of hydrothermal solubility studies it is important that the system be completely defined chemically. If the solubilities of minerals containing m metallic elements are to be determined in hydrothermal NaCl solutions, the phase rule requires that a total of m + 6 independent intensive parameters be controlled or measured in order to determine completely the system.In this study the solubility of the univariant assemblage pyrite + pyrrhotite + magnetite has been determined in vapor saturated hydrothermal solutions from 200 to 350°C for NaCl concentrations ranging from 0.0 to 5.0 molal. At any temperature, oxygen and sulfur fugacities were buffered by the chosen assemblage. System pH was determined from excess CO2 partial pressures and computed ionic equilibria. Equilibrium constants were calculated by regression analysis of solubility data. The results show that more than 10 ppm of each mineral can dissolve in typical hydrothermal solutions under geologically realistic conditions. Solubilities were best represented by the species Fe2+ and FeCl+ at 200 and 250°C; Fe2+, FeCl+ and FeCl20 at 300°C; and Fe2+ and FeCl20 at 350°C. Ore deposition would occur by lowering temperature, diluting chloride concentration, or by raising pH through wall rock alteration reactions. 相似文献
5.
A. J. Gratz W. J. Nellis J. M. Christie W. Brocious J. Swegle P. Cordier 《Physics and Chemistry of Minerals》1992,19(5):267-288
Shock experiments on quartz single crystals with initial temperatures –170 to +1000°C showed that ambient temperature does not affect the type of defects formed but can lower the pressure of complete amorphization. The amount of glass recovered increases with both pressure and temperature, and the shock-induced phase transformation of quartz is temperature-activated with an apparent activation energy of <60 kj/=" mol.=" the=" phase=" transformation=" is=" localized=" along=" three=" types=" of=" transformation=" lamellae=" (narrow,=" s-shaped,=" and=" wide)=" which=" contain=" fractured=" and/or=" high-pressure=" phases.=" transformation=" lamellae=" are=" inferred=" to=" form=" by=" motion=" of=" linear=" collapse=" zones=" propagating=" near=" the=" shock=" front.=" equilibrium=" phases,=" such=" as=" stishovite,=" were=" not=" recovered=" and=" are=" probably=" not=" formed=" at=" high=" shock=" pressures:=" the=" dominant=" transformation=" mechanism=" is=" inferred=" to=" be=" solid-state=" collapse=" to=" a=" dense,=" disordered=" phase.=" melting=" occurs=" separately=" by=" friction=" along=" microfaults,=" but=" no=" high-pressure=" crystal=" phases=" are=" quenched=" in=" these=" zones.=" shock=" of=" quartz=" thus=" produces=" two=" types=" of=" disordered=" material,=" quenched=" melt=" (along=" microfaults)=" and=" diaplectic=" glass=" (in=" transformation=" lamellae);=" the=" quenched=" melt=" expands=" during=" p-t=" release,=" leaving=" it=" with=" a=" density=" lower=" than=" quartz,=" while=" recovered=" diaplectic=" glass=" has=" a=" density=" closer=" to=" that=" of=" quartz.=" at=" low=" pressures=">< 15=" gpa),=" quartz=" transforms=" mostly=" by=" shear=" melting,=" while=" at=" higher=" pressures=" it=" converts=" mostly=" along=" transformation=" lamellae.=" we=" find=" that=" shock=" paleopiezometers=" using=" microstructures=" are=" nominally=" temperature-invariant,=" so=" that=" features=" observed=" at=" impact=" craters=" and=" the=" k/t=" boundary=" require=" in=" excess=" of=" 10=" gpa=" to=" form,=" regardless=" of=" the=" target=" temperature.=" shock=" comminution=" will=" be=" much=" more=" extensive=" for=" impacts=" on=" cold=" surfaces=" due=" to=" lack=" of=" cementation=" of=" fragments=" by=" melt=" glass;=" shock=" on=" hot=" surfaces=" could=" produce=" much=" more=" glass=" than=" estimated=" from=" room-temperature=" experiments.=" because=" of=" the=" shock-impedance=" mismatch=" between=" quartz=" specimen=" and=" steel=" capsule,=" the=" incident=" shock=" wave=" reverberates=" up=" to=" a=" final=" pressure.=" the=" dynamic=" compression=" process=" is=" quasi-isentropic=" with=" high=" strain=" rates.=" preheating=" and=" precooling=" achieves=" final=" shock=" pressures=" and=" temperatures=" representative=" of=" single-shock=" states=" of=" room=" temperature=" quartz=" and=" of=" quartz=" on=" known=" planetary=" surfaces.=" stress=" histories=" were=" calculated=" by=" detailed=" 1-=" and=" 2-dimensional=" computer=" simulations.=" the=" stress=" history=" throughout=" the=" sample=" is=" relatively=" uniform,=" with=" minor=" variations=" during=" unloading.=" significant=" differences=" between=" impact=" pressures=" calculated=" by=" the=" shock-impedance-match=" method=" and=" specimen=" pressures=" calculated=" by=" computer=" simulations=" indicate=" the=" importance=" of=" modeling=" shock=" recovery=" experiments="> 相似文献
6.
Klochkova V. G. Miroshnichenko A. S. Panchuk V. E. Tavolzhanskaya N. S. Yushkin M. V. 《Astronomy Reports》2022,66(5):429-440
Astronomy Reports - The optical spectra of the B-supergiant LS III +52°24 (IRAS 22023+5249) obtained at the 6-m BTA telescope with a resolution $${\text{R}} \geqslant 60{\kern 1pt} {\kern 1pt}... 相似文献
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The results of observations on the Large Phased Array of the Lebedev Physical Institute made as part of a survey of the northern sky at 102.5 MHz are reported. Survey source lists for the declination ranges 27.5°–33.5° and 67.5°–70.5° are given, together with their coordinates, flux densities, and identifications with 4C objects. In total, there are 920 sources with flux densities S 102.5≥3.0 Jy in the two zones, which cover 0.73 star. The observing and data-reduction methods are described, and the reliability and completeness of the catalog are estimated. 相似文献
8.
利用连续小波分析和经验模态分解方法,对我国北方地区(33°～41°N,108°～115°E)1470 ～2002年每年夏季降水量指数的时间序列进行了周期成分分析,探索全球气候变暖下的该地区降水量的多尺度变化特征.小波分析表明,降水量指数的可能周期有2.57a,4.83a,10.65a,23.25a,48.56a,68.30a和105.90a的周期,在95％置信水平有统计意义的周期是2.57a和23.25a的周期.这些周期和自然因素导致的周期相联系,不仅包含了气候系统内部(平流层准2a振荡和厄尔尼诺/南方涛动)的非线性作用,还包含了气候系统外(主要是太阳活动)受强迫的周期变化,且二者在原始降水量中所在比重相当,共同反映了原始降水量的绝大部分变化.降水量不只是在百年尺度上受太阳活动的驱动,在数十年尺度上也受到太阳活动的影响.我国北方地区的夏季降水量指数和夏季温度指数同相位反相关,全球增温并没有明显地改变二者之间的反相关关系.近百年来全球变暖期间,夏季降水量出现明显的新特征:短周期成分(小于30a的周期)的振幅比以往要显著大,而长周期成分的振幅比以往要显著小,同时呈现降水量逐年减少的长期变化趋势. 相似文献
9.
A search for extended radio sources with peak flux densities higher than 10 Jy at 110.6 MHz has been carried out, and two giant radio-galaxy candidates found. Data from a 24-hour survey in an area spanning ～8° in declination were used for the search. 相似文献
10.
《Chemical Geology》2004,203(1-2):139-151
Aragonite is precipitated by a new CO2-diffusion technique from a Ca2+–Mg2+–Cl− solution between 10 and 50 °C. Crystallisation of aragonite instead of calcite occurs by maintaining a [Mg2+]/[Ca2+] ratio of 2 in the fluid. The dissolved inorganic carbon (DIC) is received by diffusion of CO2 through a polyethylene membrane (diffusion coefficient: DCO2=10−6.4 cm2 s−1 at 19 °C). It is suggested that significant amounts of DIC may be transferred by diffusion of CO2 in natural systems if the CO2 gradient is high. The CO2-diffusion technique is used as a kind of simple mixed flow reactor for the co-precipitation of barium and strontium with aragonite. The distribution coefficients of Ba2+ and Sr2+ decrease from 10 to 50 °C according to DBa,a*=2.42−0.03595T (°C) and DSr,a*=1.32−0.005091T (°C). At 25 °C, the distribution coefficients are DBa,a*=1.5±0.1 and DSr,a*=1.19±0.03. The effect of temperature on DBa,a* is about one order of magnitude higher versus that on DSr,a*. Thus, Ba2+ may be a potential paleotemperature indicator if the composition of the solution is known. 相似文献
11.
Dhammika A. Tantrigoda M. M. P. M. Fernando 《Journal of the Geological Society of India》2013,82(4):430-434
Satellite free air gravity anomalies over the Indian ocean region 79°E–86°E, 2°S–8°S were obtained from the website http://topex.ucsd.edu and a contour map was compiled. Five profiles of the anomaly have been interpreted in terms of two-dimensional structures in the ocean. Thickness of sediments lying on the oceanic crust determined from the interpretation of gravity profiles were used to compile an isopach map of the region 79°E–86°E, 2°S–8°S. This map in combination with one of the isopach maps compiled by previous workers, provides information regarding the thickness of sediments up to 6° S. According to this map sediment thickness varies from ～600 m over the middle part of the region to ～800 m further south, indicating that thinning of sediments in the middle part of the region is only localized. Information provided by this gravity study may be useful in planning detailed seismological studies to delimit the outer edge of the continental margin of Sri Lanka, defined according to the United Nations Convention of the Law of the Sea (UNCLOS). 相似文献
12.
吉尔吉兹加盟共和国部长会议所属地质保矿管理局的地质勘探队1959年10月钻进90°—75°角的斜孔时,利用了由作者设计的金属轻便钻塔。 相似文献
13.
《地质科技情报》2016,(1)
为了深入了解西南印度洋中脊调查区表层沉积物的物质来源和沉积环境,对大洋第30航次在该区域获取的21个表层沉积物样品进行了物相鉴定和主量元素、微量元素及稀土元素含量测试,分析结果显示,样品可分为Si质沉积物和Ca质沉积物两类,其中Si质沉积物富含Si、Mg、Fe、Al,稀土元素含量特征、轻重稀土元素分馏特征,以及稀土元素的北美页岩归一化曲线均表明沉积物保留了N-MORB的特征,主要为基性岩、超基性岩的风化产物;而Ca质沉积物富Ca、LOI、Sr,稀土元素以及微量元素之间的分配均指示沉积物物源为生源主导;所有站位均显示了两类沉积物不同程度的混杂,表明物质来源具有一定的多样性,调查区总体为稳定的偏氧化环境。 相似文献
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S. A. Silantyev N. S. Bortnikov K. N. Shatagin V. E. Bel’tenev N. N. Kononkova Ya. V. Bychkova E. A. Krasnova 《Petrology》2016,24(4):336-366
The paper presents petrological and geochemical data on mantle peridotite, basalt, and metamorphic rocks sampled in Cruise 36 of the R/V Professor Logachev at the MAR axial zone between 17° and 20° N. These data are interesting not only as providing new information on the inner structure of the oceanic crust in the still-poorly known axial MAR segment but also in the context of the fundamental problem of interaction between magmatic and hydrothermal systems in slow-spreading mid-oceanic ridges. The MAR axial zone between 17° and 20° N was determined to host both weakly and strongly depleted residual peridodites, which suggests that the degree of mantle source melting significantly varied along the ridge axis in this segment. The MAR crest zone comprises slabs of serpentinized peridotite brought to the seafloor surface at various time. The most strongly depleted mantle peridotites likely uplifted later than the mildly and weakly depleted rocks in the same areas. A mantle reservoir beneath the MAR axial zone at 20° N is not isotopically related to the mantle source of the parental MORB melts, and high-Mg metabasites exposed at 17°56- N were derived from a crustal source that was modified near the root zone of a high-temperature hydrothermal system. The studied area seems to display traces of an extinct hydrothermal field and likely an ore occurrence related to it. 相似文献
19.
Annerose Heydemann 《Contributions to Mineralogy and Petrology》1964,10(2):242-259
The formation of quartz from amorphous silica under hydrothermal conditions has been investigated in the temperature range between 100° and 250°C. In this whole range and in an alkaline environment the conversion from amorphous silica occurs through two steps of intermediate phases. At first a hitherto unknown silica phase is formed: SiO2-X (for X-ray patterns see Table 1). After this step α-cristobalite is crystallizing. The single phases are briefly described. The results of the experiments show a strong but mathematically not simple correlation between the rate of conversion and temperature. At higher temperature silica converts into quartz within several hours or days; at lower temperatures conversion rates measure in months and years. The influence of alkali concentrations and the influence of the type of starting materials on the course of reactions has been tested at several temperatures. With increasing alkali concentration time of reaction decreases always. If quartz fragments occur in the starting material the rate of conversion of all phases increases and the fragments grow in the solution. A certain correspondence between nature and experiments can be observed. 相似文献
20.
《Applied Geochemistry》1998,13(7):905-916
Experiments measuring kaolinite and smectite dissolution rates were carried out using batch reactors at 35° and 80°C. No potential catalysts or inhibitors were present in solution. Each reactor was charged with 1 g of clay of the ≤2 μm fraction and 80, 160 or 240 ml of 0.1–4 M KOH solution. An untreated but sized kaolinite from St. Austell and two treated industrial smectites were used in the experiments. One smectite is a nearly pure montmorillonite, while the second has a significant component of beidellitic charge (35%). The change in solution composition and mineralogy was monitored as a function of time. Initially, the 3 clays dissolved congruently. No new formed phases were observed by XRD and SEM during the pure dissolution stage. The kaolinite dissolution is characterized by a linear release of silica and Al as a function of the log of time. This relationship can be explained by a reaction affinity effect which is controlled by the octahedral layer dissolution. Far from equilibrium, dissolution rates are proportional to a0.56±0.12OH− at 35°C and to a0.81±0.12OH− at 80°C. The activation energy of kaolinite dissolution increases from 33±8 kJ/mol in 0.1 M KOH solutions to 51±8 kJ/mol in 3 M KOH solutions. In contrast to kaolinite, the smectites dissolve at much lower rates and independently of the aqueous silica or Al concentrations. The proportionality of the smectite dissolution rate constant at 35 and 80°C was a0.15±0.06OH−. The activation energy of dissolution appears to be independent of pH for smectite and is found to be 52±4 kJ/mol. The differences in behavior between the two kinds of minerals can be explained by structural differences. The hydrolysis of the tetrahedral and the octahedral layer appears as parallel reactions for kaolinite dissolution and as serial reactions for smectite dissolution. The rate limiting step is the dissolution of the octahedral layer in the case of kaolinite, and the tetrahedral layer in the case of smectite. 相似文献