A study of class II methanol maser condensations in the star-forming region W48

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.     

The methanol emission of isolated maser condensations: Statistical velocity distribution

The distribution of the radial velocities of class I methanol masers relative to the velocities of their parent molecular clouds is analyzed. This analysis is based on catalog data for methanol masers detected up to the present time in both the northern and southern hemispheres, together with catalog data for the CS(2-1) line, which traces dense, quiescent gas. Results for a large sample of sources show that, in contrast to class II methanol masers, which undergo Keplerian motions in protoplanetary disks, class I methanol masers retain their velocities in the local system of rest of the surrounding medium, and do not participate in the ejection of matter in bipolar outflows. They can be adequately described using a model in which matter ejected from active parts of the associated star-forming regions flows around isolated maser condensations. This compresses the maser clumps, enhancing the concentration of methanol and facilitating collisional pumping of the masers.     

Search for class I methanol maser emission toward several supernova remnants

Observations at 44 GHz in the 7₀−6₁ A ⁺ methanol line have been carried out on the 20-m telescope of the Onsala Space Observatory (Sweden) in the directions of the poorly studied region G27.4–0.2 and of several supernova remnants, at the coordinates of the OH(1720) maser satellite emission, with the aim of searching for Class I methanol maser emission in these sources. The region G27.4–0.2 has beenmapped, and contains maser sources and two supernova remnants with similar coordinates and radial velocities, which may accelerate condensation of the ambient gas-dust medium. This may play a role in enhancing the probability of methanol formation and maser emission. This is the first detection of 44 GHz maser emission in this source, and this maser is among the 10% of the strongest Class I methanol masers, within the uncertainties in the integrated flux (of a total of 198 currently knownmasers). A 27′ × 27′ region around the maser has been mapped at 44 GHz in steps of 1′. The 44-GHz emission forms only within the previously known maser region. Further studies in water lines are needed to estimate the influence of shocks from supernovae. No 44-GHz Class I methanol maser emission was detected at the 3σ level at the coordinates of the OH(1720) satellite emission in six supernova remnants; i.e., the presence of OH(1720) emission is not a sufficient condition for the detection of Class I methanol masers.     

Methanol maser groups and class I emission: Flux density distribution

A search for a relationship between class I and class II methanol maser flux densities has been carried out. A large sample of mixed-type sources has been studied, with each source in the sample radiating as a class I and class II maser simultaneously. In methanol maser groups for which the positions of prominent spectral features at different radial velocities coincide at different frequencies, the fluxes are anticorrelated, and are related as log S _6.7+12.2 = (?1.68 ± 0.38) × log S ₄₄ + (4.01 ± 0.60). For group I, which includes sources with preferred pumping for masers emitting at 6.7 GHz, the relationship between the 6.7 GHz masers and 44 GHz masers is less steep than for group II, which contains sources with normal pumping of class II masers. This implies that class I methanol masers that correspond to group I are suppressed more strongly.     

Search for class I methanol maser emission in various types of objects in the interstellar medium

Observations of various types of objects in the northern sky were obtained at 44 GHz in the 7₀-6₁ A ⁺ methanol line on the 20-m Onsala radio telescope (Sweden), in order to search for Class I methanol maser emission in the interstellar medium: regions of formation of high-mass stars, dust rings around HII regions, and protostellar candidates associated with powerful molecular outflows and Galactic HII regions. Seven new Class Imethanolmasers have been discovered toward regions of formation of highmass stars, and the existence of two previously observed masers confirmed. The following conclusions are drawn: (1) neither the association of a bipolar outflow manifest in the wings of CO lines with a highmass protostellar object (HMPO) nor the presence of thermal emission in lines of complex molecules are sufficient conditions for the detection of Class I methanol emission; no association with HMPOs radiating at 44 GHz was found for EGOs (a new class of object tracing bipolar outflows); (2) the existence of H₂O masers and Class II methanol masers in the region of aHMPOenhances the probability of detecting Class I methanol emission toward the HMPO; Class II methanol masers with stronger line fluxes are associated with Class I methanol masers.     

Map of the 6.7 GHz class II methanol maser emission of the protoplanetary disk G23.01-0.41

We present images of the star-forming regionG23.01–0.41 at 6.7GHz in the Class II methanol maser transition 5₁–6₀ A ⁺, produced from archival observations on the European VLBI Network. Our map of the source and its maser spots contains 24 maser components. The data for each spot—absolute coordinates, coordinates relative to the calibration feature, peak flux and flux integrated over the spot, size, position angle, velocity along the line of sight, and line full width at half-maximum—are collected in tabular form. The spatial region occupied by the maser spots is approximated by a 200×130 milliarcsec ellipse in position angle PA = −0.40°, centered on the absolute coordinates α ₀ = 18^h34^m40.282^s, δ ₀ = −09°00′38.27″ (J2000). If the source is a protoplanetary disk, then, for the distance estimate derived from trigonometric parallax, its diameter is 1800 AU, and the mass of the central protostar is 23.5M _⊙.     

Spatial structure of the class I methanol maser DR21(OH) at 44 GHz in 2003

We present the results of VLA observations of the class I methanol maser DR21(OH) at 44 GHz. The observations, retrieved from the NRAO archive (USA), were carried out in 2003. The maser has 18 spatial components, 17 of them confined to two clusters and one isolated component. In general, this spatial structure is similar to the structure observed earlier by other authors; the detected differences are too small to enable us to derive proper motions of the components: no proper motions exceeding the uncertainties were detecting during the 8 years since 1995. Amaser flare was observed in one of the spectral features for the first time. This is the first brightening detected for a class I methanol maser.     

Magnetic fields in methanol maser condensations based on data for related regions. Seven sources: Observational parameters

Results of polarization observations of gas-dust condensations obtained on the Nançay radio telescope in the 1665 and 1667 MHz OH lines in all four Stokes parameters are reported. Seven OH maser sources associated with methanol masers were selected for this study. The goal was to estimate the magnetic fields in methanol condensations from the Zeeman splitting of OH maser lines associated with the methanol masers. The Gaussian parameters of features in the OH spectra are presented, and their polarization parameters are estimated: the degree of circular polarization m _C , flux density in linear polarization p, and degree of linear polarization m _L . The magnetic field intensity B has been estimated from the Zeeman splitting of the OH lines and approximation of the Stokes parameter V from the derivative of Stokes parameter I. B varies from ≤0.5 to 1.4 mG for different sources. The association of OH masers with methanol emission has been analyzed; the magnetic fields of OH masers in interstellar condensations associated with Class I methanol masers can be determined more reliably than the fields in interstellar condensations with OH masers associated with Class II methanol emission, and have higher values. The sizes of the studied regions suggest they may be bound structures such as Bok globules, small IRDC clouds, or protoplanetary disks.     

A statistical analysis of exploration geochemical data for uranium

This paper describes a statistical analysis of reconnaissance exploration geochemical data for uranium. Three sets of data were analyzed, as they related to: (a) Charlotte-Winston-Salem and (b) Charlotte two-degree NTMS quadrangles of the south-eastern U.S.A. The coefficient of variation for uranium in each of the three sets of data was less than unity and hence no transformation of the original variable was needed. These data were subjected to correlogram analysis. A first-order Markovian model of the type: Y₀ exp (-a |p|) was fit by the least-squares method to serial correlation coefficients of these data using the method proposed by Deming (1948). The model was tested by computing the variance-volume relationship for assumed individual blocks of unit length. The noise in the input (record) was eliminated by the application of an optimum bilateral exponential smoothing technique developed by Agterberg. A comparison of spectral density estimates obtained by a maximum entropy method employing Yule-Walker equations and the Burg algorithm was also made. The prediction error coefficients needed to determine the order of the autoregressive process and hence the spectral densities were determined in both cases for the three sets of data.On leave from National Geophysical Research Institute, Hyderabad-7, India.     

Magnetic fields in methanol maser condensations based on data for related regions. Seven sources: Astrophysical parameters

The astrophysical parameters of seven OH maser condensations are estimated based on magnetic fields obtained from polarization observations carried out on the Nan cay Radio Telescope (France) in the 1665 and 1667 MHz lines in four Stokes parameters. Regions in the studied sources containing the observed clusters of maser condensations, as well as clusters of Class I and II methanol masers, have been identified. The associations of the masers are real; i.e., the magnetic field in the clusters can also extend to groups of methanol masers. The linear dimensions of these associations have been found. The ratio of the mass to the magnetic flux, ratio of the thermal to the magnetic pressure, and virial relationships between energies (kinetic, magnetic, and gravitational) in the regions containing the OH andmethanol masers have been obtained. In sources whose magnetic fields have been determined fairly reliably, the ratio of the mass to the magnetic flux exceeds a critical value, and the energies of chaotic motions and of the magnetic field are considerably smaller than the gravitational binding energy. On the other hand, in all cases, the ratio of the thermal to the magnetic pressure is <1, suggesting that the clouds may be in amagnetically dominated regime. This inconsistency is related to probable uncertainties in the the magnetic field values and the estimated distances to the sources, which may lead to overestimation of the sizes of the regions studied.     

Class I methanol maser emission in infrared clouds and the third version of the Astro Space Center MMI/SFR catalog

We have revised the Astro Space Center catalog of Class I methanol masers detected in star-forming regions (MMI/SFR), mainly at 44 GHz, and created a new electronic version of the catalog. Currently, the catalog contains 206 objects, selected from publications through 2011 inclusive. The data from the survey of Chen et al. (2011), performed specifically for objects EGO, which form a new specific catalog, are not included. The MMI/SFR objects were identified with emission and absorption objects in the near IR, detected during the MSX and Spitzer space missions. Seventy-one percent of Class I methanol masers that emit at 44 GHz and fall within the Galactic longitude range surveyed by Spitzer (GLIMPSE) are identified with Spitzer Dark Clouds (SDCs), and 42% with Extended Green Objects (EGOs). It is possible that Class I methanol masers arise in isolated, self-gravitating clumps, such as SDCs, at certain stages of their evolution. A sample of SDCs is proposed as a new target list for Class I methanol maser searches. A detailed statistical analysis was carried out, taking into account the characteristics of the regions of MMI/SFR formation presented in the catalog.     

The statistical analysis of geochemical compositions

The analysis and interpretation of compositional data, such as major oxide compositions of rocks, has been traditionally plagued by the so-called constant-sum or closure problem. Particular difficulties have been the lack of a satisfactory, interpretable covariance structure and of rich, tractable, parametric classes of distributions on the simplex sample space. Consideration of logistic and logratio transformations between the simplex and Euclidan space has allowed the introduction of new concepts of covariance structure and of classes of logistic-normal distributions which have now opened up a substantial and meaningful array of statistical methodology for compositional data. From the motivation of a wide variety of practical geological problems we examine the range of possibilities with this new approach to the constant-sum problem.     

能量桩群桩工作特性简化分析方法研究

采用双曲线模型模拟桩土界面上的力学行为,利用剪切位移法反映剪应力在土层中的传递,考虑群桩之间的相互作用,建立了热-力耦合作用下能量桩群桩基础工作特性的简化分析方法。该方法能反映桩土界面上的非线性、桩顶的约束条件和能量桩位置的影响,可直接计算所有桩的位移和轴力。与现有方法相比,计算得到的双桩相互作用因子更加合理。通过与文献中试验数据的对比表明,若只有局部桩经历温度变化,能量桩运行过程中各桩之间存在差异变形,基础出现倾斜,桩顶荷载发生重分布。所建立方法计算方便,能合理模拟能量桩群桩基础的主要工作特性,可用于大规模能量桩群桩基础的设计计算。     

基于扫描图的线性体统计分析方法

对线性体图像进行分析,提出了一种基于扫描图像的线性体统计分析方法。通过对节点及其信息进行提取,快速抓住线性体的总体拓扑结构,并以节点信息为指引对线性体进行跟踪和识别,解决了复杂的线性体交叉问题。对识别出的线性体,通过直线拟合的方法,精确计算得到其长度、方位等信息。算法的主要特点是直接对扫描图进行运算,不需要矢量化,充分利用栅格图像的特点实现信息的快速获取,算法还具有精度高、抗噪性好和适应性强的特点。     

Correlation analysis of statistical facies fault models

Doklady Earth Sciences - This paper addresses seismic imaging of fault zones and analysis of the seismic data with the use of the fault facies model developed at Uni Research CIPR. Simulated and...     

Weibull statistical analysis of granite bending strength

Summary  This paper describes and discusses the adequacy of Weibull statistical analysis to analyse the bending strength of granite. The experimental results show that strength variability is related with a specific origin of failure. This conclusion is based on analysing the influence of the surface condition (extrinsic defects) on the bending strength results treated by the Weibull statistics. The conclusions drawn from this study have been validated by analysing the results of the critical flaw dimension estimated by applying the linear elastic fracture mechanics (LEFM) formulae. Results obtained from fractographic examination also have been used to describe the location of the origin of the fracture and understand the distribution of defects; i.e., there is a unimodal distribution of defects (intrinsic defects), despite the fact that some outlier values are normally observed in the fractured surfaces. Correspndence: P. M. Amaral, Department of Materials Engineering, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal     

A method for the analysis of large vertically loaded pile groups

An iterative method is described for the analysis of vertically loaded pile groups with a large number of vertical piles. The individual pile response is modelled using load-transfer (t–z) curves while pile–soil–pile interaction is determined using Mindlin's solution. The present method not only keeps all the advantages of the so-called ‘hybrid method’, but also makes it possible for practising engineers to solve problems of large non-uniformly arranged pile groups in a time-saving way using a personal computer. Good agreement between the present method of analysis and the direct method is observed. A case history is analysed and the computed response of a large pile group compares favourably with the field measurement. Copyright © 1999 John Wiley & Sons, Ltd.     

The statistical study of hydraulic geometry: A new direction for compositional data analysis

Hydraulic exponents and unit hydraulic exponents are unit-sum constrained, which requires that they be analyzed by statistical methods designed for compositional data. Though uncertainties remain regarding selection of the best constraining operation and method of handling departures from the unit-sum constraint, neither category of uncertainty should be an impediment to the selection of the appropriate statistical methodology. In a small sample study, the hydraulic geometry of different types of streams were compared: (1) semi-arid: perennial vs. ephemeral; (2) tropical: Puerto Rico vs. West Malaysia; and (3) semi-arid vs. tropical (by pooling the previous data sets). All three comparisons revealed statistically significant differences in either logratio mean vectorsor logratio covariance matrices but not both. All six categories of data had logistic normal distributions. Because the derivatives at a given discharge of curvilinear hydraulic geometry relationships and hydraulic exponents on either side of the breakpoints of piecewise linear relationships are unit-sum constrained, they also can be studied by compositional methods. However, the compositional approach is limited in cases where distributions have large departures from logistic normality and for streams that have negative hydraulic exponents.     

A magnetized disk around an O star: Polarization of the OH maser emission

W75N is one of the first OH masers in which 100% linear polarization has been observed in several spots. Two spots contain Zeeman pairs, corresponding to magnetic fields of 5.2 and 7.7 mG. Another Zeeman pair consisting of two linearly polarized components was tentatively detected in one spot. The linearly polarized spots are σ components for the case when the magnetic field is perpendicular to the line of sight. For these spots, the magnetic field is perpendicular to the plane of the circumstellar disk, though a correction for Galactic Faraday rotation may considerably modify this conclusion.     

Aspects of the statistical analysis of marine ore deposits

Geostatistical analyses employed in the prospecting and for exploration of marine mineral resources, must be aimed at particular problems and goals. The quality of navigation, sampling, mining technology and the profitability of the project strongly influence such analyses. The studies presented here, have two main objectives, namely, to estimate the reserves of manganese nodules and to determine in what order the explored areas should be mined. Several geostatistical methods were used. These were designed partly to supplement one another, but mostly to create a sequence of analytical steps which could be applied to any typical marine exploration project.

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Zusammenfassung Sollen im Rahmen von Prospektions- und Explorationsvorhaben auf marine Rohstoffe geostatistische Untersuchungen durchgeführt werden, so haben sich diese an den speziellen Problemen und Zielsetzungen zu orientieren. Dabei spielen Fragen der Navigation, der Probennahme, der Förderungstechnik und der Wirtschaftlichkeit eine wichtige Rolle. Im vorliegenden Falle war das Ziel der Untersuchungen nach der Schätzung der Vorräte an Mangan-Knollen die Erstellung einer Rangordnung der Explorations-Areale für den Abbau. Hierzu wurden verschiedene Verfahren der Geostatistik eingesetzt, die sich zum Teil gegenseitig zu ergänzen haben, im Großen gesehen jedoch eine Methoden-Folge bilden, die als typisch für Explorations-Projekte auf marine Rohstoffe angesehen werden kann.