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1.
Results of spectral observations of the unique eclipsing binary ? Aur obtained during its recent eclipse are presented. Profile variations of many spectral lines at different eclipse phases can be traced. These variations are partly due to absorption of the stellar radiation in a rotating disk of gas and dust around the second component and partly due to geometric screening of the stellar photosphere and circumstellar region by the disk. A comparison of these results with analogous results obtained by Lambert and Sawyer during the previous (1982–1984) eclipse of ? Aur indicates good agreement, suggesting stability of the gas-dust disk surrounding the invisible component in the binary. The masses of the binary components are estimated using new observational data.  相似文献   

2.
The results of a search for maser emission in the methanol lines 8?1-70 E at 229.8 GHz, 3?2-4?1 E at 230.0 GHz, 00-1?1 E at 108.9 GHz, and in the J 1-J 0 E series near 165 GHz in star-forming regions are reported. At least two masers and two candidates have been detected at 229.8 GHz. Thus, methanol masers have been detected in the 1-mm band for the first time. At 108.9 GHz, masers have been detected toward G345.01+1.79 and possibly toward M8E as well. Thermal emission was found toward 28 objects. The 229.8-GHz sources are class I masers, whereas the 108.9-GHz sources are class II masers. An analysis using a large velocity-gradient method shows that the 229.8-GHz masers can appear at densities of about 3×104 cm?3. The ratios of the flux densities in different class I lines toward DR 21(OH) and DR 21 West can be approximated in models with gas kinetic temperatures of about 50 K. Detection of the 108.9 GHz masers toward G345.01+1.79 and M8E may provide information about the geometry of these objects.  相似文献   

3.
The results of photoelectric observation of the occultation of the visual binary star SAO 79361 = ADS 6038 by the Moon during the total lunar eclipse of January 9, 1982 are presented. The upper limit of the angular diameter of the brighter component A is estimated to be dul ? 0.0011″ based on direct measurements, which is in agreement with indirect estimates. Accurate estimates for the magnitude difference between components A and B, their angular separation, p ? 3.2″, and the inclination of the Moon’s edge’s at the point of occultation to the mean lunar horizon, θ ? +25°, are obtained. The time of the geometrical occultation of the center of the stellar disk of component A is determined with an accuracy of 1 ms. The results obtained for this star are unique among observations worldwide.  相似文献   

4.
The color and spectroscopic properties of ironbearing tourmalines (elbaite, dravite, uvite, schorl) do not vary smoothly with iron concentration. Such behavior has often been ascribed to intervalence charge transfer between Fe2+ and Fe3+ which produces a new, intense absorption band in the visible portion of the spectrum. In the case of tourmaline, an entirely different manifestation of the interaction between Fe2+ and Fe3+ occurs in which the Fe2+ bands are intensified without an intense, new absorption band. At low iron concentrations, the intensity of light absorption from Fe2+ is about the same for E∥c and E⊥c polarizations, but at high iron concentrations, the intensity of the E⊥c polarization increases more than ten times as much as E∥c. This difference is related to intensification of Fe2+ absorption by adjacent Fe3+. Extrapolations indicate that pairs of Fe2+-Fe3+ have Fe2+ absorption intensity ～200 times as great as isolated Fe2+. Enhanced Fe2+ absorption bands are recognized in tourmaline by their intensity increase at 78 K of up to 50%. Enhancement of Fe2+ absorption intensity provides a severe limitration on the accuracy of determinations of Fe2+ concentration and site occupancy by optical spectroscopic methods. Details of the assignment of tourmaline spectra in the optical region are reconsidered.  相似文献   

5.
In this study, single crystals of pure enstatite (Mg2Si2O6) were synthesised under water-saturated conditions at 4 and 8 GPa and 1,150°C with variable silica activity, leading to phase assemblages enstatite + forsterite, enstatite or enstatite + coesite. Run products were investigated using an FTIR spectrometer equipped with a focal plane array detector enabling IR imaging with a lateral pixel resolution of 2.7 μm. IR spectra within the OH-absorption region show two different groups of absorption bands: group 1 (wavenumbers at 3,592 and 3,687 cm?1) shows strongest absorptions for E||n β, whereas group 2 (wavenumbers at 3,067 and 3,362 cm?1) shows strongest absorptions for E||n γ. The groups are related to different defect types, group 1 to tetrahedral defects (T-site vacancies) and group 2 to octahedral defects (M-site vacancies). The intensity ratio of the bands within one group (i.e. A 3067/A 3362 and A 3592/A 3687) and the intensity ratio of E||n γ and E||n α in group 2 bands remain constant within error. In contrast, the intensity ratio of group 2 to group 1 absorption bands [e.g. (A 3362)/(A 3687)] is sensitive to the SiO2 activity and pressure. On the basis of the results of this and previous studies, a barometer for pure orthoenstatite coexisting with forsterite can be formulated:\( P\,[{\text{GPa}}] = 1.056 + \sqrt {{\frac{{1.025 - A_{{\left( {3362} \right)/\left[ {(3362) + (3687)} \right]}} }}{0.009}}} , \) where A (3362) and A (3687) are the integral absorbances of the component E||n γ of the absorption bands at 3,362 cm?1 and the component E||n β of the absorption band at 3,687 cm?1, respectively.  相似文献   

6.
This paper presents simplified dilatometer test (DMT)-based methods for evaluation of liquefaction resistance of soils, which is expressed in terms of cyclic resistance ratio (CRR). Two DMT parameters, horizontal stress index (KD) and dilatometer modulus (ED), are used as an index for assessing liquefaction resistance of soils. Specifically, CRR–KD and CRR–ED boundary curves are established based on the existing boundary curves that have already been developed based on standard penetration test (SPT) and cone penetration test (CPT). One key element in the development of CRR–KD and CRR–ED boundary curves is the correlations between KD (or ED) and the blow count (N) in the SPT or cone tip resistance (qc) from the CPT. In this study, these correlations are established through regression analysis of the test results of SPT, CPT, and DMT conducted side-by-side at each of five sites selected. The validity of the developed CRR–KD and CRR–ED curves for evaluating liquefaction resistance is examined with published liquefaction case histories. The results of the study show that the developed DMT-based models are quite promising as a tool for evaluating liquefaction resistance of soils.  相似文献   

7.
We present spectrophotometric (3400–7500 Å) observations of the evolution of a strong outburst of the classical symbiotic star YY Her in 1993 and photoelectric UBV observations of the star’s eclipse in 1997. The duration of the phase of lowest brightness, when the U brightness had decreased by ～1.3m, was ～0.17 P orb (P orb is the orbital period). If this phase is due to the total eclipse of ～70% of the radiation of the circumstellar envelope, this duration implies that the cool component of YY Her fills its Roche lobe, the bulk of the envelope’s volume emission measure is concentrated around the hot component in a region with rather sharp boundaries r R giant (R giant is the giant’s radius), and the line of sight is close to the binary orbital plane. We model fit the spectral energy distribution of YY Her to obtain estimates of the parameters of several structural components of the system. The red giant’s spectral type correlates with its visual brightness and does not correlate with the hot component’s brightness. At minimum brightness, the hot component’s luminosity fluctuates about that of its cool companion (L h, bol /L c, bol ≈0.9), and its temperature is T h ≈(9–11)×104 K. Activity of the hot component of YY Her is accompanied by increased brightness and reduced temperature (L h, bol ∝T h ?5 ), though the relation between these parameters is not unique. At maximum brightness, L h, bol /L c, bol ≈10 and T h ≈6.0×104 K. If the red giant fills its Roche lobe, the hot component’s luminosity is ～3.3 × 104 L ⊙. The active period of YY Her lasted about 5 years, and the activity decrease was not monotonic.  相似文献   

8.
Mössbauer spectra (MS) of blue, green and yellow beryl (ideally Be3Al2Si6O18) containing approximately 1% of iron were obtained at 295 and 500 K. Room temperature (RT) spectra of both blue and green samples showed the presence of an asymmetric Fe2+ doublet (ΔE Q~2.7 mm/s, δ~1.1 mm/s), with a very broad low-velocity peak. There is no clear evidence for the presence of a ferric component. The MS of the yellow sample at RT consists of an intense central absorption with parameters typical for Fe3+ (ΔE Q~0.4 mm/s, δ~0.29 mm/s), plus an apparently symmetrical Fe2+ doublet. This sample acquires a light-blue shade upon heating in air at about 620 K. Thermal treatments at high temperatures caused no significant changes in the MS, but the green and yellow beryl acquire a blue colour. All these results are interpreted in relation to the existence of channel water and the distribution of iron among the available crystallographic sites.  相似文献   

9.
In this paper, a study on the performance of surface irrigation of date palms in a Tunisian arid area (Douz oasis) is presented. The study is conducted in 16 plots with various sizes and soil textures over a 4-year period (2012–2015). In the first step, an assessment of total water requirements of the date palms is carried out. Then, the surface irrigation performance is analyzed using three indicators, i.e., the relative water supply (RWS) indicator, the uniformity index of water distribution (D U ), and the water application efficiency (E a ). Finally, the irrigation management problems are identified. The results indicate that in the arid Tunisian Saharan oases, the soil texture, plot size, and farmers’ practices (especially irrigation duration) have significant effects on surface irrigation performance. The average annual net irrigation requirements of date palms are about 2400 mm. The RWS increases from 1.8 in the smaller plots (0.5 ha) to 3.6 in the largest plots (2.5 ha), implying that the increase in the plot size requires an excessive water supply. D U decreases from 80.7 in the 0.5 ha plots to 65.4 in the 2.5 ha plots; however, no significant difference in the E a is observed. The results show that the soil texture has no influence on the RWS and D U , but the E a is significantly higher in the loamy-sand soils (46.7%) compared to the sandy soils (36.3%). Overall, RWS indicator is higher than 1 (RWS?=?2.6) implying excessive irrigation supply to the system. Although D U is relatively uniform (>?60%), E a is relatively low (<?50%) indicating that the current irrigation management is inefficient. These findings have a paramount importance for improving irrigation water management in the Tunisian Saharan oases.  相似文献   

10.
We present the results of observations obtained using the MASTER robotic telescope in 2005–2006, including the earliest observations of the optical emission of the gamma-ray bursts GRB 050824 and GRB 060926. Together with later observations, these data yield the brightness-variation law t ?0.55±0.05 for GRB 050824. An optical flare was detected in GRB 060926—a brightness enhancement that repeated the behavior observed in the X-ray variations. The spectrum of GRB 060926 is found to be F E ～ E ?β , where β = 1.0 ± 0.2. Limits on the optical brightnesses of 26 gamma-ray bursts have been derived, 9 of these for the first time. Data for more than 90% of the accessible sky down to 19 m were taken and reduced in real time during the survey. A database has been composed based on these data. Limits have been placed on the rate of optical flares that are not associated with detected gamma-ray bursts, and on the opening angle for the beams of gamma-ray bursts. Three new supernovae have been discovered: SN 2005bv (type Ia)—the first to be discovered on Russian territory, SN 2005ee—one of the most powerful type II supernovae known, and SN 2006ak (type Ia). We have obtained an image of SN 2006X during the growth stage and a light curve that fully describes the brightness maximum and exponential decay. A new method for searching for optical transients of gamma-ray bursts detected using triangulation from various spacecraft is proposed and tested.  相似文献   

11.
The methanol-line spectra in two maser condensations at velocities ～41 and ～45 km/s in the star-forming region W48 have been studied. The intensity of the 20-3?1 E (12.2 GHz) line is anticorrelated with that of the 51-60 A + (6.7 GHz) line: the intensity of the 51-60 A + (6.7 GHz) line is greater at ～41 km/s than at ～45 km/s, while the opposite is true of the 20-3?1 E (12 GHz) line. The remaining class II methanol lines in this source demonstrate the same behavior as the 20-3?1 E (12 GHz) line. This contradicts current concepts about the maser line intensities in various methanol transitions: according to model calculations, the intensities of all class II lines should vary in phase. This effect is confirmed for a large homogeneous sample of 67 sources. Possible explanations of the observed effect are proposed; one suggests the possible role of “transpumping” of the methanol-level populations in the maser condensations. The relationships between the variations of the 20-3?1 E (12 GHz) and 51-60 A + (6.7 GHz) line intensities, which are present for all 67 sources considered, may indicate that the condensations are at different distances from the pumping source. The presence of condensations at various distances from the pumping source in all 67 sources can be understood if they are ice planets revolving in different orbits around massive stars or protostars.  相似文献   

12.
The temperature dependence of diffusion is usually found to follow the Arrhenius law: D = D0e?E/RT Winchell (1969) showed that there is commonly an inter-dependence between D0 and E (for diffusion in silicate glasses), such that diffusion of different species show a positive correlation on a log D0 vs E plot. A similar effect was noted by Hofmann (1980) for cation diffusion in basalt. This implies that diffusion rates of different species tend to converge at a particular temperature; this effect is known as the ‘compensation effect’. I will show that this effect is also present for diffusion in feldspars and olivines. The equations for the compensation lines (with E given in kcal/mol) are: basalt—E = 50 + 7.5 log D0 feldspar—E = 50.7 + 3.4 log D0 olivine—E = 78.0 + 7.5 log D0 The convergence, or crossover, temperatures for diffusion in various materials are: obsidian—3400°C basalt—1370°C olivine—1360°C feldspar—460°C Compensation plots are useful for evaluating and comparing experimental diffusion data (though of limited usefulness in a predictive sense) and for understanding ‘closure temperatures’ for diffusion in petrogenetic processes (since closure temperature, the temperature at which natural diffusion processes are frozen in, is dependent on E, log d0, and cooling rate). I show that most diffusing species in feldspar have a closure-temperature close to the crossover or convergence temperature, implying that all species in feldspars can be expected to ‘freeze-in’ simultaneously at temperatures in the range 400–600°C (for cooling rates in the range 101–105°C/myr). Closure temperatures of various species in olivine, on the other hand, span a much larger range (800°C) for a similar range in cooling rates, implying that different elements in olivine will record different time-temperature stages in petrogenetic processes.  相似文献   

13.
Theoretical analysis, calculations, and comparison with the results of observations in Lake Baikal, Lake Tanganyika, and the World Ocean are performed for the vertical stability E and the Brunt-Väisäla frequency N in the form of N 2 with regard to all components (at the constant temperature T and the salinity S, the common adiabatic form at T, S Const). The adiabatic stability E ad and the Väisäla frequency N in the form of N ad 2 are always positive; at a change from the inverse to the direct temperature stratification, they have deep minimums reaching 10?16 m?1 and 10?15 s?2 and less; the minimums have the form of a special point, a reversal point of the first kind called a “cusp.” The reality of these reversal points is confirmed by the analysis of the investigation procedure, comparison with the results of previous theoretical (Sherstyankin, et al., 2007), and experimental (observations in Baikal, Shimaraev et al., 1994) works. The features of vertical profiles of E ad , E andN ad 2 , N 2, as well as the layers where the Brunt-Väisäla frequency is less than the inertial frequency, are studied. The analysis with regard to all components of the stability E ad and the Brunt-Väisäla frequency N makes a great contribution to understanding of mixing processes in theoretical and experimental investigations; it is valid in all reservoirs of the Earth with inverse and direct temperature stratification, including Lake Baikal, Lake Tanganyika, and the World Ocean.  相似文献   

14.
We have carried out a detailed identification of lines in the optical spectrum of the post-AGB star V510 Pup associated with the infrared source IRAS 08005-2356 based on observations with high spectral resolution. Absorption lines of the ions FeII, TiII, CrII, and YII are present at wavelengths from 4549 to 8546 Å. The absorption by YII and other s-process elements is anomalously strong, and the absorption is also strong in the circumstellar C2 Swan bands. The profiles of most of the lines (of hydrogen and metals) display P Cygni absorption-emission profiles. All the absorption lines are shifted toward the blue, suggesting an outflow of stellar material. The expansion velocity of the envelope derived from the Swan bands arising there is V exp =42 km/s. The highest wind velocity determined from the absorption wings of the FeII(42) P Cygni profiles reaches 240 km/s. Based on the star’s kinematic characteristics and the amount of interstellar absorption, it is at a distance of d≈3?4 kpc, which corresponds to an absolute magnitude of Mv≈?6m.  相似文献   

15.
Street dust is one of the important indicators that reflect the status of urban environmental pollution. There are many studies of heavy metals contamination of street dust in capital cities; however, little attention has been paid to this kind of study in medium cities, including China. The dust samples were collected in the district of traffic crossroads in Xianyang city, Shaanxi Province. Pb, Cd, Cu, Ni, Zn, Cr and Mn concentrations were determined using atomic absorption spectrometry (AAS). The results indicate that the concentrations of heavy metals are higher than the background values of soils in Shaanxi Province. The contamination level of heavy metals is assessed by potential ecological risk index (E r), geoaccumulation index (I geo), enrichment factor (EF) and pollution index (Pi). The low I geo, EF, E r, Pi and PIn (integrated pollution index) for Mn in street dusts indicate an absence of distinct Mn pollution. The high EF, Pi and PIn of Cu and Zn indicate that there is considerable Cu and Zn pollution. It is suggested that more attention should be paid to heavy metals contamination of Cu and Zn. The assessment results of Pi and PIn suggest that Pb, Ni and Cr present strong pollution; however, their EFs indicate that they cause moderate pollution and their I geo indicates that they are unpolluted to moderately polluted. The contamination class value with different assessing methods is of the order: Pi ≈ PIn > EF > I geo > E r.  相似文献   

16.
Gadolinite, REE2FeBe2Si2O10, is commonly metamict. 57Fe Mössbauer annealing studies of fully metamict gadolinite from Ytterby, Sweden, have been completed in argon atmosphere from 873 to 1473 K. This technique has rarely been employed in studies of metamict minerals. Changes in the experimental parameters of Mössbauer spectra are sensitive indicators of the thermal recrystallization process of metamict gadolinite and revealed two stages of the structural recovery: a major stage from 873 to 1073 K and a slower recovery stage from 1133 to 1473 K. These observations are confirmed by X-ray powder diffraction. In relation to the first stage, the exponential behaviour of the changes in the Mössbauer parameters can be used for deriving the activation energy E a of the recrystallization process. The calculated value E a =1.97 eV in argon atmosphere explains the common occurrence of gadolinite in the fully or partially metamict state. Results of Mössbauer spectroscopy suggest that the recrystallization of metamict gadolinite is a displacive transition that involves rotation and translation of SiO4 and BeO4 to their normal positions associated with removal of OH groups from the structure.  相似文献   

17.
The polarized (E‖a′, E‖b and E‖c) electronic absorption spectra of five natural chromium-containing clinopyroxenes with compositions close to chromdiopside, omphacite, ureyite-jadeite (12.8% Cr2O3), jadeite, and spodumene (hiddenite) were studied. The polarization dependence of the intensities of the Cr3+ bands in the clinopyroxene spectra cannot be explained by the selection rules for the point groups C 2 or C 2v but can be accounted for satisfactorily with the help of the higher order pseudosymmetry model, i.e. with selection rules for the point symmetry group C 3v. The trigonal axis of the pseudosymmetry crystal field forms an angle of 20.5° with the crystallographic direction c in the (010) plane. D q increases from diopside (1542 cm?1) through omphacite (1552 cm?1), jadeite (1574 cm?1) to spodumene (1592 cm?1). The parameter B which is a measure of covalency for Cr3+-O bonds at M1 sites in clinopyroxene depends on the Cr3+ concentration and the cations at M2 sites.  相似文献   

18.
We have performed spectroscopy and photometry of eclipses of the pre-cataclysmic variable UUSge using the 6-m telescope of the Special AstrophysicalObservatory and the 1.5-mRussian-Turkish telescope. Our analysis of variations of the B-V and V-R color indices during the eclipses indicates that the temperature of the secondary is T eff,2 = 6000?6300 K. A similar value, T eff,2 = 6200 ± 200 K, follows from our comparison of the observed spectrum of UU Sge at the total eclipse phase and theoretical spectra of late-type stars. We identify 27 absorption lines of 11 chemical elements in the secondary??s spectrum. Their abnormal intensities indicate possible high-velocity turbulent motions (up to ?? turb = 10.0 km/s) in the atmosphere of the star and the presence of hot gas above its surface.  相似文献   

19.
《Quaternary Science Reviews》2003,22(10-13):1279-1285
Three sediment samples were collected from a soil profile at the Lagoa do Bordoal site, Algarve, Portugal. Quartz extracted from soil horizons within the profile, was optically dated using the single-aliquot regenerative-dose (SAR) protocol outlined by Murray and Wintle (Radiation Measurements 5 (2000) 523). The optically stimulated luminescence (OSL) emitted by quartz within the 90–150 μm size range was measured using three aliquot sizes. The equivalent doses (DE) that were obtained show an asymmetric distribution. As the numbers of grains in each aliquot are reduced, the distribution of doses is clearly shifted to lower DE values including zero doses on single grain aliquots. This shift is accompanied by an increase in the asymmetry of the distribution. These patterns indicate that as the aliquot size decreases, the distributions are increasingly characterized by aliquots with lower DE's. With respect to the present day modern surface, this shift is most evident in the sample collected from a depth of 37 cm, within an ancient B-horizon. It is least evident in the sample located only 10 cm below it, within a sand unit. An asymmetric distribution of DE's can be a result of a large number of grains that were well bleached at burial being mixed with a small number of grains that were partially bleached at that time (Radiation Measurements 30 (1999) 207). However, the shift in DE's that is seen in the Lagoa East samples is most likely due to the postburial downward movement of fully and partially bleached grains from the surface, with possible contributions from the downward movement of grains that received low doses while buried in overlying horizons. The simplest explanation for our results is that grains carrying zero or small DE's have been moved downward during bioturbation events. These results suggest that downward bioturbation in ancient soil profiles can be identified based on the OSL characteristics of quartz grains. We are also able to provide a minimum age of 24.4±3.2 ka for the Upper Palaeolithic lithic assemblage at the site.  相似文献   

20.
New empirical models were developed to predict the soil deformation moduli using gene expression programming (GEP). The principal soil deformation parameters formulated were secant (Es) and reloading (Er) moduli. The proposed models relate Es and Er obtained from plate load-settlement curves to the basic soil physical properties. The best GEP models were selected after developing and controlling several models with different combinations of the influencing parameters. The experimental database used for developing the models was established upon a series of plate load tests conducted on different soil types at depths of 1–24 m. To verify the applicability of the derived models, they were employed to estimate the soil moduli of a part of test results that were not included in the analysis. The external validation of the models was further verified using several statistical criteria recommended by researchers. A sensitivity analysis was carried out to determine the contributions of the parameters affecting Es and Er. The proposed models give precise estimates of the soil deformation moduli. The Es prediction model provides considerably better results in comparison with the model developed for Er. The simplified formulation for Es significantly outperforms the empirical equations found in the literature. The derived models can reliably be employed for pre-design purposes.  相似文献   

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