Differential and Integral Cross Sections for Electron Impact Excitation of Lithium

The differential and integral cross sections for electron impact excitation of lithium from the ground state 1s(2)2s to excited states 1s(2)2p, 1s(2)3l (l = s,p,d) and 1s(2)4l (l = s,p,d,f) at incident energies ranging from 5 eV to 25 eV are calculated by using a full relativistic distorted wave method. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbitals are computed in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. A part of the cross sections are compared with the available experimental data and with the previous theoretical values. It is found that, for the integral cross sections, the present calculations are in good agreement with the time-independent distorted wave method calculation, for differential cross sections, our results agree with the experimental data very well.

Calculations of cross sections of resonant two-photon transitions to the second excited 4f5d state in Pr3+: Y3Al5O12 using density matrix theory

The density matrix resonant two-photon absorption (TPA) theory applicable to laser crystals doped with rare earth ions is described. Using this theory, resonant TPA cross sections for transitions from the ground state to the second excited state of the 4f5d configuration in cm(4)s Pr3+:Y3Al5O12 are calculated. The peak value of TPA cross section calculated is 2.75 x 10(-50) cm(4)s which is very close to the previous experimental value 4 x 10(-50) cm(4) s. The good agreement of calculated data with measured values demonstrates that the density matrix resonant TPA theory can predict resonant TPA intensity much better than the standard second-order perturbation TPA theory.

Steady Patterns of Microparticles Formed by Optical Tweezers

In this paper, we propose a method for forming steady patterns of microparticles in a dispersion using optical tweezers. We demonstrate how to control the congregation of particles in a dispersion and to manually fabricate a pattern, The steady pattern (nay be useful for in-depth research, and the method will have applications in biology and nanotechnology.

Feasibility of Laminar Plasma-Jet Hardening of Cast Iron Surface

Nontransferred DC laminar plasma jets of stable flow and low impinging pressure acting on the substrate were used to heat W–Mo–Cu cast iron for phase transfer hardening of the surface layer. Substrates were heated in multipass with or without overlapping or heated with only single-pass. Surface morphologies of the molten trace and microstructure of the cross-section were observed, and the hardness distribution of the treated surface layer was examined. The surface layer of single-pass-heated specimen has an average hardness of about 900 HV0.1, while the specimen treated with multipass shows an average hardness of about 700 HV0.1, because of the heat effect from the neighboring pass treating, compared with the substrate hardness of about 300 HV0.1. The results demonstrate the stable and favorably controlled heating of the laminar plasma jet on the substrate surface and feasibility of using it as a tool for surface hardening of cast iron.

Vibration analysis of laminated shells using a refined shear deformation theory

A previously published refined shear deformation theory is used to analyse free vibration of laminated shells. The theory includes the assumption that the transverse shear strains across any two layers are linearly dependent on each other. The theory has the same dependent variables as first-order shear deformation theory, hut the set of governing differential equations is of twelfth order. No shear correction factors are required. Free vibration of symmetric cross-ply laminated cylindrical shells, symmetric and antisymmetric cross-ply cylindrical panels is calculated. The numerical results are in good agreement with those from three-dimensional elasticity theory.

Computation of turbulent-flow in a square duct - aspects of the secondary flow and its origin

A numerical study of turbulent flow in a straight duct of square cross-section is made. An order-of-magnitude analysis of the 3-D, time-averaged Navier-Stokes equations resulted in a parabolic form of the Navier-Stokes equations. The governing equations, expressed in terms of a new vector-potential formulation, are expanded as a multi-deck structure with each deck characterized by its dominant physical forces. The resulting equations are solved using a finite-element approach with a bicubic element representation on each cross-sectional plane. The numerical integration along the streamwise direction is carried out with finite-difference approximations until a fully-developed state is reached. The computed results agree well with other numerical studies and compare very favorably with the available experimental data. One important outcome of the current investigation is the interpretation analytically that the driving force of the secondary flow in a square duct comes mainly from the second-order terms of the difference in the gradients of the normal and transverse Reynolds stresses in the axial vorticity equation.

Resonant mode analysis in toroidal cavities with elliptic cross-sections

Resonant cavity modes in a torus with elliptical cross section are studied by means of a direct variational method. The nonlinear effects of toroidicity and ellipticity on the frequency of the basic mode are analyzed simply and systematically without the restriction of linear theory. It is shown that the toroidicity effect on the m = 0 transverse magnetic mode is less-than-or-equal-to 11%. The frequency of the mode shifts approximately 11-29% when the elongation of the cross section changes from 1 to 2. The effects of toroidicity and ellipticity differ for each resonant mode.

Atomistic Simulation On Size-Dependent Yield Strength And Defects Evolution Of Metal Nanowires

A simple derivation based on continuum mechanics is given, which shows the surface stress is critical for yield strength at ultra-small scales. Molecular dynamics (MD) simulations with modified embedded atom method (MEAM) are employed to investigate the mechanical behaviors of single-crystalline metal nanowires under tensile loading. The calculated yield strengths increasing with the decrease of the cross-sectional area of the nanowires are in accordance with the theoretical prediction. Reorientation induced by stacking faults is observed at the nanowire edge. In addition. the mechanism of yielding is discussed in details based on the snapshots of defects evolution. The nanowires in different crystallographic orientations behave differently in stretching deformation. This study on the plastic properties of metal nanowires will be helpful to further understanding of the mechanical properties of nanomaterials. (C) 2009 Elsevier B.V. All rights reserved.

Cross spectral purity and its influence on ghost imaging experiments

Pseudo-thermal light has been widely used in ghost imaging experiments. In order to understand the differences between the pseudo-thermal source and thermal source, we propose a method to investigate whether a light source has cross spectral purity (CSP), and experimentally measure the cross spectral properties of the pseudo-thermal light source in near-field and far-field zones. Moreover we present a theoretical analysis of the cross spectral influence on ghost imaging. (c) 2006 Elsevier B.V. All rights reserved.

Laser-induced damage of Ti O2 Si O2 high reflector at 1064 nm

A high laser-induced damage threshold (LIDT) TiO2/SiO2 high reflector (HR) at 1064 nm is deposited by e-beam evaporation. The HR is characterized by optical properties, surface, and cross section structure. LIDT is tested at 1064 nm with a 12 ns laser pulse in the one-on-one mode. Raman technique and scanning electron Microscope are used to analyze the laser-induced modification of HR. The possible damage mechanism is discussed. It is found that the LIDT of HR is influenced by the nanometer precursor in the surface, the intrinsic absorption of film material, the compactness of the cross section and surface structure, and the homogeneity of TiO2 layer. Three typical damage morphologies such as flat-bottom pit, delamination, and plasma scald determine well the nanometer defect initiation mechanism. The laser-induced crystallization consists well with the thermal damage nature of HR. (C) 2008 American Institute of Physics.

A new species of Amolops (Anura : Ranidae) from Yunnan, China, with a discussion of karyological diversity in Amolops

We describe a new species, Amolops tuberodepressus, from the mountainous regions of Jingdong County, Yunnan Province, China. This species differs from all other congeners in a combination of both karyological and morphological characteristics. Morphologically, the new species resembles A. mantzorum, A. kangtingensis, A. jinjiangensis, and A. liangshanensis occurring in southern Sichuan and northern Yunnan and may easily be confused with those species. However, Amolops tuberodepressus differs from those species by the presence of a distinct tympanum, flatter supratympanic fold, flatter tubercles on the flanks, and absence of a dorsolateral Fold. Karyological evidence also strongly supports the distinctness of the new species. A consideration of one Karyological character demonstrates that species of Amolops in southwestern China all share secondary constrictions on chromosome pair six. In view of the morphological similarity among species df Amolops in southwestern China, these species may have only recently diverged from a common ancestral species.

Amolops bellulus: A new species of stream-breeding frog from western Yunnan, China (Anura : Ranidae)

We describe a new species of stream-breeding frog of the genus Amolops, Amolops bellulus, from the mountainous region of Lushui County, Yunnan Province, China, near the boundary between Yunnan and Myanmar. This species differs from all its congeners in a combination of morphological characteristics including the absence of a circummarginal groove at the tip of first finger, lack of a supratympanic fold, a white band along the upper jaw extending to shoulder, a black band starting from tip of snout along upper loreal region and extending to anterior flank of body, absence of a vocal sac, tympanum distinct and feebly concave, and the presence of vomerine teeth.

Morphological and molecular phylogenetic analysis of two Saprolegnia sp (Oomycetes) isolated from silver crucian carp and zebra fish

Two Saprolegnia isolates, JY isolated from silver crucian carp (Carassius auratus gibelio Bloch) and BMY isolated from zebra fish (Brachydanio rerio Hamilton) came from infections occurring concurrently in different locations in China. To confirm whether the two isolates were from the same Saprolegnia clone, comparative studies have been carried out based on their morphological, physiological and molecular characteristics. Observations showed that morphologically (both asexual and sexual organs) the two isolates were broadly similar and both isolates under-went repeated zoospore emergence. Comparing 704 base pairs of internal transcribed spacer (ITS) region and the 5.8S rDNA, we found isolates JY and BMY shared an identical ITS sequence with a minor variation (99.6 % similarity). Forty available sequences for representatives Saprolegnia spp. belonged to four phylogenetically separate clades. The two studied isolates fell within clade I that comprised a group of isolates which showed almost an identical ITS sequence but had been identified as a number of different morphological species. our findings suggest that isolates JY and BMY appear to belong to the S. ferax clade and this clade (1) contains a number of closely related phylogenetic species. This is distinct from the more common fish pathogenic isolates, which belong to the S. parasitica clade (III) and are characterized by having cysts decorated by bundles of long hooked hairs and two further clades (II and IV) containing largely saprotrophic or soil born species. (C) 2009 Published by Elsevier Ltd on behalf of The British Mycological Society.

Threatened fishes of the world: Tanichthys albonubes Lin 1932 (Cyprinidae)

The white cloud mountain minnow Tanichthys albonubes Lin is an endemic species to southern China and the genus has two species, Tanichthys albonubes Lin and Tanichthys micagemmae Freyhof et Herder. The distribution range of T. albonubes Lin and T. micagemmae is very narrow and only found in the mountain brooks of Baiyunshan Mountain (White Cloud Mountain), Huaxian Country and the vicinity of Guangzhou in Guangdong Province and Halong, Quang Ninh Province, Vietnam respectively. The wild populations of this fish had already been on the verge of extinction when Shu-Yan Lin first discovered it in 1932 at the Baiyunshan Mountain. It was believed to be extinct in the wild because there were no reports of this fish in the wild since 1980. In September 2003, a small and isolated population of the fish was discovered in a mountain puddle in the north vicinity of Guangzhou. Additional studies are needed to determine the survival and propagation of the released fish. The protection of their natural habitat should be implemented.

Rearing of Procypris rabaudi during early life-history stages

The early life-history of Chinese rock carp Procypris rabaudi was investigated during a 56-day rearing period: 318 artificially propagated P. rabaudi larvae were reared throughout metamorphosis in a small-scale recirculation system (345 L water volume, 10 x 18 L rearing tanks, 150 L storage and filter compartment with bioballs, 20-30 larvae L-1) at the Institute of Hydrobiology, Wuhan, Hubei Province, China. The newly hatched larvae had an initial total length of 8.93 +/- 0.35 mm SD (n = 10) at 3 days post-hatch and reached an average total length of 33.29 mm (+/- 1.88 mm SD, n = 10) 56 days after hatching. Length increment averaged 0.45 mm day(-1), resulting in a mean growth of 24.4 mm within the 56-day period. High mortality rates of up to 92% derived from an introduced fungus infection and subsequent treatment stress with malachite green. Our results indicate that Chinese rock carp can be raised successfully from artificially fertilized eggs. We therefore assume this species to be a candidate for commercial aquaculture.