Discs and haloes in pre-main-sequence stars     

Dejan Vinkovi&#;  &#;eljko Ivezi&#;  Anatoly S. Miroshnichenko  Moshe Elitzur 《Monthly notices of the Royal Astronomical Society》2003,346(4):1151-1161

We study the infrared (IR) emission from flared discs with and without additional optically thin haloes. Flux calculations of a flared disc in vacuum can be considered a special case of the more general family of models in which the disc is imbedded in an optically thin halo. In the absence of such a halo, flux measurements can never rule out its existence because the disc flaring surface defines a mathematically equivalent halo that produces the exact same flux at all IR wavelengths. When a flared disc with height H at its outer radius R is imbedded in a halo whose optical depth at visual wavelengths is  τ_halo  , the system IR flux is dominated by the halo whenever  τ_halo > (1/4) H / R   . Even when its optical depth is much smaller, the halo can still have a significant effect on the disc temperature profile. Imaging is the only way to rule out the existence of a potential halo, and we identify a decisive test that extracts a signature unique to flared discs from imaging observations.  相似文献   

A simplified analytical method for soil penetration analysis     

David Z. Yankelevsky  Moshe A. Adin 《国际地质力学数值与分析法杂志》1980,4(3):233-254

A new one-dimensional model for penetration analysis of a rigid projectile into a soil target is presented. The soil medium is represented by a set of discs of constant thickness, responding in the radial direction under plain strain regime. When penetration through a typical disc occurs, the projectile displaces soil material and a radial plastic shock wave propagates in the disc. The interaction pressure between the projectile and soil material is compatible with the motion of the contact boundary, between them. The instantaneous resistive force is obtained by summation of the contributions of all the discs which are in contact with the nose surface of the projectile. Soil is considered as a ‘floating’ ideally locking material, in which the locking volumetric strain is adjusted to the physical stress–strain properties of the soil material. Friction between projectile and soil is assumed to be negligible. Comparison is made with both twodimensional computer program results and experimental data, and very good agreement is observed. Comparison with other analytical methods reveals that the present model most closely resembles existing experimental results and permits further analysis of the problem as predictions of target response and of stress distribution on the projectile nose. The calculations require very small amounts of computer time. Analysis with the present model yields an efficient and comprehensive means to analyse penetration and perform parameter analysis.  相似文献   

Application of real-time PCR for quantitative determination of hepatic vitellogenin transcript levels in the striped sea bream, Lithognathus mormyrus     

Bruria Funkenstein  Anna Dyman  Berta Levavi-Sivan  Moshe Tom 《Marine environmental research》2004,58(2-5):659

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James P. Terry and Frank R. Thomas (eds), The Marshall Islands: Environment,History and Society in the Atolls     

Moshe Rapaport 《Singapore journal of tropical geography》2009,30(3):407-409

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Incision of alluvial channels in response to a continuous base level fall: Field characterization, modeling, and validation along the Dead Sea   总被引：5，自引：1，他引：4  

L. Ben Moshe  I. Haviv  Y. Enzel  E. Zilberman  A. Matmon 《Geomorphology》2008,93(3-4):524-536

The dramatic lake level drop of the Dead Sea during the twentieth century ( 30 m) provides a field-scale experiment in transport-limited incision of gravel-bed channels in response to quasi-continuous base level fall at approximately constant rate. We apply a one-dimensional numerical incision model based on a linear diffusion equation to seven ephemeral channels draining into the Dead Sea. The model inputs include the measured twentieth century lake level curve, annual shoreline location (i.e., annual channel lengthening following the lake level drop), reconstructed longitudinal profiles of each of the channels based on mapped and surveyed terraces, and the current profiles of the active channels. The model parameters included the diffusion coefficient and the upstream-derived sediment flux. Both were first calibrated using a set of longitudinal profiles of known ages and then validated using additional sets of longitudinal profiles.The maximum at-station total incision observed at each of the studied channels was significantly less then the total lake level drop and varied in response to both drainage area and lake bathymetry. The model applied predicted degradation rates and the pattern of degradation with high accuracy. This suggests that sediment flux in the modeled channels is indeed linearly dependent on slope. Further support for this linear dependency is provided by a linear correlation between the diffusion coefficient and the mean annual rain volume over each basin (a proxy for discharge). The model presented could be a valuable tool for planning in rapid base level fall environments where incision may risk infrastructure.  相似文献   

Residual Deformation of Real Earth Models with Application to the Chandler Wobble     

Moshe Israel  Ari Ben-Menahem  Sarva Jit Singh 《Geophysical Journal International》1973,32(2):219-247

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A model of a heterogeneous neighborhood   总被引：1，自引：0，他引：1  

Izhak?SchnellEmail author  Moshe?Harpaz 《GeoJournal》2005,64(2):105-115

Tel Aviv is a highly ethnic city in which ethnicity is deeply embedded in people’s perceptions of their social milieus. Shapira, as one of the most heterogeneous neighborhoods in Tel Aviv, supplies a unique demonstration of the inadequacy of the Chicago model, which assumes the emergence of homogeneous neighborhoods. The study shows that ethnicity is exercised as a major force in determining social life in Shapira. Interactive segregation indices reveal that residents of Shapira tend to prefer intra-ethnic social networks although two-thirds of them maintain inter-ethnic networks as well. Despite this, residential and activity spaces are highly heterogeneous. Residential spaces are heterogeneous on all scales from residents’ immediate surroundings to the block and the neighborhood as a whole. In most buildings one may find neighbors from two or three different ethnic groups with only non-Jewish residents excluded from publicly owned buildings. Most residents perform large part of their everyday life outside the neighborhoods in ethnically heterogeneous surroundings, but nonetheless in choosing their more meaningful partners for social networks they choose them from their ethnic groups. The fact that residents tend to perform a large part of their activities out of their neighborhood, and to live in heterogeneous surroundings in social categories that are perceived by them salient to their daily life, does not undermine the relevance of the neighborhood as a socially constituted entity in the urban field. People organize and act in order to improve life conditions in the neighborhood, they feel sense of attachment to the neighborhood and they develop some local social networks in the neighborhood.  相似文献   

Quantifying fish metallothionein transcript by real time PCR for its utilization as an environmental biomarker   总被引：3，自引：0，他引：3  

Tom M  Chen N  Segev M  Herut B  Rinkevich B 《Marine pollution bulletin》2004,48(7-8):705-710

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Imaging the heart of astrophysical objects with optical long-baseline interferometry     

J.-P. Berger  F. Malbet  F. Baron  A. Chiavassa  G. Duvert  M. Elitzur  B. Freytag  F. Gueth  S. H?nig  J. Hron  H. Jang-Condell  J.-B. Le Bouquin  J.-L. Monin  J. D. Monnier  G. Perrin  B. Plez  T. Ratzka  S. Renard  S. Stefl  E. Thiébaut  K. R. W. Tristram  T. Verhoelst  S. Wolf  J. Young 《Astronomy and Astrophysics Review》2012,20(1):1-55

The number of publications of aperture-synthesis images based on optical long-baseline interferometry measurements has recently increased due to easier access to visible and infrared interferometers. The interferometry technique has now reached a technical maturity level that opens new avenues for numerous astrophysical topics requiring milli-arcsecond model-independent imaging. In writing this paper our motivation was twofold: (1) review and publicize emblematic excerpts of the impressive corpus accumulated in the field of optical interferometry image reconstruction; (2) discuss future prospects for this technique by selecting four representative astrophysical science cases in order to review the potential benefits of using optical long-baseline interferometers. For this second goal we have simulated interferometric data from those selected astrophysical environments and used state-of-the-art codes to provide the reconstructed images that are reachable with current or soon-to-be facilities. The image-reconstruction process was ??blind?? in the sense that reconstructors had no knowledge of the input brightness distributions. We discuss the impact of optical interferometry in those four astrophysical fields. We show that image-reconstruction software successfully provides accurate morphological information on a variety of astrophysical topics and review the current strengths and weaknesses of such reconstructions. We investigate how to improve image reconstruction and the quality of the image possibly by upgrading the current facilities. We finally argue that optical interferometers and their corresponding instrumentation, existing or to come, with six to ten telescopes, should be well suited to provide images of complex sceneries.  相似文献   

Geological and pedological aspects of an Early-Paleolithic site: Revadim,Central Coastal Plain,Israel     

Gdaliahu Gvirtzman  Moshe Wieder  Ofer Marder  Hamudi Khalaily  Rivka Rabinovich  Hagai Ron 《Geoarchaeology》1999,14(2):101-126

An Early Paleolithic site was recently discovered within a sequence of paleosols in the Revadim Quarry, central coastal plain of Israel. The section is composed of three superimposed soils in a continuous sequence, but separated by two unconformity surfaces. The uppermost paleosol is a modern Dark Brown Grumusol (Vertisol), the middle is a Quartzic Gray Brown Soil (Haploxeralf), and the lower is a Red Hamra (Rhodoxeralf). Normal magnetic polarity was detected in the two lower soils, indicating that they are younger than the Brunhes–Matuyama boundary (<780 ka). A human occupation bed, enriched in secondary carbonate nodules, forms the lower part of the Quartzic Gray Brown Soil and overlies the Red Hamra. The living floor is located on top of the unconformity surface, separating the Red Hamra from the overlying Quartzic Gray Brown Soil. Middle to Late Acheulian handaxes, choppers, cores, and flake tools, including tools made by the Levallois technique, and man-laid flint pebbles were excavated in the human occupation bed. In addition, two elephant tusks, an elephant pelvis, an elephant tooth (Palaeoloxodon antiquus), tusk splinters, and bones of equid, suid, cervid, bovid, felid, and rodents were also collected. Based on well-documented nearby boreholes and on regional correlation, it appears that the underlying dune sands, the parent materials from which the Red Hamra developed, were deposited probably during a phase of high-stand sea level of Isotope Stage 9. The Red Hamra developed simultaneously with the human occupation of the site, probably during a phase of low-stand sea-level of Isotope Stage 8, before some 300–245 ka. The overlying dune sands, the parent materials from which the Quartzic Gray Brown Soil developed, were deposited probably during a phase of high-stand sea level of Isotope Stage 7. The climate prevailing in the area during Stage 8, as well as during the human habitation, was moist, with a dense vegetation cover of grassland and probably scattered trees. A small lake of trapped fresh water at a junction of two small tributaries of the Soreq River drainage system near the area occupied was available to hominids and animals. © 1999 John Wiley & Sons, Inc.  相似文献