The NAIAD experiment for WIMP searches at Boulby mine and recent results     

B. Ahmed  G. J. Alner  H. Araujo  J. C. Barton  A. Bewick  M. J. Carson  D. Davidge  J. V. Dawson  T. Gamble  S. P. Hart  R. Hollingworth  A. S. Howard  W. G. Jones  M. K. Joshi  V. A. Kudryavtsev  T. B. Lawson  V. Lebedenko  M. J. Lehner  J. D. Lewin  P. K. Lightfoot  I. Liubarsky  R. Lüscher  J. E. McMillan  B. Morgan  G. Nicklin  S. M. Paling  R. M. Preece  J. J. Quenby  J. W. Roberts  M. Robinson  N. J. T. Smith  P. F. Smith  N. J. C. Spooner  T. J. Sumner  D. R. Tovey 《Astroparticle Physics》2003,19(6):691-702

The NAIAD experiment (NaI Advanced Detector) for weakly interacting massive particle (WIMP) dark matter searches at Boulby mine (UK) is described. The detector consists of an array of encapsulated and unencapsulated NaI(Tl) crystals with high light yield. Six crystals are collecting data at present. Data accumulated by four of them (10.6 kg × year exposure) have been used to set upper limits on the WIMP–nucleon spin-independent and WIMP–proton spin-dependent cross-sections. Pulse shape analysis has been applied to discriminate between nuclear recoils, as may be caused by WIMP interactions, and electron recoils due to gamma background. Various calibrations of crystals are presented.  相似文献   

Theoretical and experimental lifetime and oscillator strength determination in singly ionized neodymium (Nd ii)     

H. L. Xu  S. Svanberg  R. D. Cowan  P.-H. Lefèbvre  P. Quinet  E. Biémont 《Monthly notices of the Royal Astronomical Society》2003,346(2):433-440

Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 24 levels of Nd  ii in the energy range 20 500–32 500 cm⁻¹. For 17 levels, no previous experimental data exist. These results have allowed the testing of new theoretical calculations with the relativistic Hartree–Fock method taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for this complex ion. A new set of calculated oscillator strengths, accurate within a few per cent for the strongest transitions, is presented for 107 lines of astrophysical interest appearing in the wavelength range 358.0–1100.0 nm. These results will be useful to evaluate abundance values of neodymium in chemically peculiar stars in relation with cosmochronology.  相似文献   

Probing the core and envelope structure of DBV white dwarfs     

T. S. Metcalfe  M. H. Montgomery  S. D. Kawaler 《Monthly notices of the Royal Astronomical Society》2003,344(4):L88-L92

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Dust-enshrouded super star-clusters     

Marc Sauvage  Stéphanie Plante 《Astrophysics and Space Science》2003,284(2):941-944

With the advent of either sensitive space-born infrared cameras, or their high-resolution ground-based siblings, we are uncovering a new category of star clusters: the dust-enshrouded super-star clusters. These manifest themselves only beyond a few microns, as their shroud of dust is able to block all light emitted by the stars themselves. Here we present our results on the spectacular cluster in SBS 0335-052, a very metal-poor galaxy. We also point to the growing number of galaxy analogs to SBS 0335-052, revealing the possibility that these clusters signal a major mode of star formation in starbursts. We conclude by listing a number of open points these clusters raise, in particular with respect to high-redshift counterparts. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Simulation of stellar instabilities with vastly different time-scales using domain decomposition     

M. Grott  S. Chernigovski  W. Glatzel 《Monthly notices of the Royal Astronomical Society》2003,344(4):1119-1130

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Damped Lyman alpha systems and galaxy formation models – II. High ions and Lyman-limit systems     

Ariyeh H. Maller  Jason X. Prochaska  Rachel S. Somerville  Joel R. Primack 《Monthly notices of the Royal Astronomical Society》2003,343(1):268-278

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Book Review: The Iron Oxides von Rochelle M. Cornell und Udo Schwertmann     

S. Peiffer 《洁净——土壤、空气、水》2003,31(6):527-527

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Bond rolling resistance and its effect on yielding of bonded granulates by DEM analyses     

M. J. Jiang  H. S. Yu  D. Harris 《国际地质力学数值与分析法杂志》2006,30(8):723-761

A discrete element modelling of bonded granulates and investigation on the bond effect on their behaviour are very important to geomechanics. This paper presents a two‐dimensional (2‐D) discrete element theory for bonded granulates with bond rolling resistance and provides a numerical investigation into the effect of bond rolling resistance on the yielding of bonded granulates. The model consists of mechanical contact models and equations governing the motion of bonded particles. The key point of the theory is that the assumption in the original bond contact model previously proposed by the authors (55th CSCE‐ASCE Conference, Hamilton, Ont., Canada, 2002; 313–320; J. Eng. Mech. (ASCE) 2005; 131 (11):1209–1213) that bonded particles are in contact at discrete points, is here replaced by a more reliable assumption that bonded particles are in contact over a width. By making the idealization that the bond contact width is continuously distributed with the normal/tangential basic elements (BE) (each BE is composed of spring, dashpot, bond, slider or divider), we establish a bond rolling contact model together with bond normal/tangential contact models, and also relate the governing equations to local equilibrium. Only one physical parameter β needs to be introduced in the theory in comparison to the original bond discrete element model. The model has been implemented into a 2‐D distinct element method code, NS2D. Using the NS2D, a total of 86 1‐D, constant stress ratio, and biaxial compressions tests have been carried out on the bonded granular samples of different densities, bonding strengths and rolling resistances. The numerical results show that: (i) the new theory predicts a larger internal friction angle, a larger yielding stress, more brittle behaviour and larger final broken contact ratio than the original bond model; (ii) the yielding stress increases nonlinearly with the increasing value of β, and (iii) the first‐yield curve (initiation of bond breakage), which define a zone of none bond breakage and which shape and size are affected by the material density, is amplified by the bond rolling resistance in analogous to that predicted by the original bond model. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Modelling of deformation response and chemo‐mechanical coupling in chalk     

S. Pietruszczak  D. Lydzba  J. F. Shao 《国际地质力学数值与分析法杂志》2006,30(10):997-1018

A constitutive relation is derived for describing the mechanical response of chalk. The approach is based on a phenomenological framework which employs chemo‐plasticity. The properties of the material are assumed to be affected by the physico‐chemical processes that occur through the interaction between the skeleton and the pore fluid. The underlying mechanism is discussed by invoking a micromechanical analysis. The performance of the framework is illustrated by examining the evolution of mechanical characteristics in the presence of different pore fluids. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Dynamic modes of propagation and transformation of subsurface gravitational lenses     

A. S. Samodurov 《Physical Oceanography》2006,16(3):129-140

We study the dynamic features of propagation of subsurface gravitational lenses and the conditions of changes in the modes of control over their motion by various internal and external forces. As these forces, we study the action of drag, molecular and turbulent viscosity due to the presence of internal and external forces, and deceleration caused by the effects of double diffusion. We also analyze the modes of propagation of small-scale gravitational lenses. The information about these lenses taken from the literature is supplemented and generalized. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 3–14, May–June, 2006.  相似文献