Search for efficient,near UV lasing dyes. I. Substituent effects on bicyclic dyes

Methods of blue-shifting the lasing wavelengths of coumarin and quinolone-2 dyes are examined and are evaluated by new synthetic materials. Methoxy substitution at the 4 position is found to be effective. This study was supported under contract SANL 284 from the Lawrence Livermore Laboratory.     

Search for efficient,near UV lasing dyes. III. Monocyclic and miscellaneous dyes

A potential new class of “monocyclic” lasing dyes is discussed and four families out of nine within the class are examined. The 2,6-diaminopyridines in acid are found to lase under flashlamp excitation but show low slope efficiencies and lower stabilities than the “bicyclic” dyes described previously. Other, miscellaneous dyes show oxygen quenching of laser action rather than enhancement and the best of these produces short pulses under long pulse excitation. This study was supported under contract SANL 284 from the Lawrence Livermore Laboratory.     

Eigenmode analysis for the radiating stationary state of N two-level atoms in a slab geometry near threshold

We explore steady states of an open, no end-mirrors, low-Q cw laser pumped above the threshold for laser oscillations. We find that the spatial field profile of the steady state just above the threshold is the same as that of the eigenmode that dominates superradiance in the late linear regime from an initially inverted state without continued pumping. The threshold pumping rate and emission frequency are related to the real and imaginary parts of the eigenvalue of this dominant mode.     

Simple sonochemical synthesis,characterization of TmVO4 nanostructure in the presence of Schiff-base ligands and investigation of its potential in the removal of toxic dyes

Thulium vanadate (TmVO4) nanorods were successfully prepared by a simple sonochemical approach using Schiff-base ligands. Additionally, TmVO₄ nanorods were employed as a photocatalyst. The most optimal crystal structure and morphology of TmVO4 have been determined and optimized by varying Schiff-base ligands, the molar ratio of H2Salen, the sonication time and power, and the calcination time. A Eriochrome Black T (EBT) analysis revealed that the specific surface area was 24.91 m2/g. A bandgap of 2.3 eV was determined by diffuse reflectance spectroscopy (DRS) spectroscopy, which makes this compound suitable for visible photocatalytic applications. In order to assess the photocatalytic performance under visible light, two anionic dyes (EBT) and cationic dyes (Methyl Violet (MV)) were used as models. A variety of factors have been studied in order to improve the efficiency of the photocatalytic reaction, including dye type, pH, dye concentration, and catalyst loading. Under visible light, the highest efficiency was achieved (97.7%) when 45 mg TmVO4 nanocatalysts were present in 10 ppm Eriochorome Black T at pH = 10.     

Point-defect properties of,and sputtering events in,the {001} surfaces of Ni3Al. II. Sputtering events at and near surfaces

Atomic recoil events at and near {001} surfaces of Ni₃Al due to elastic collisions between electrons and atoms have been simulated by molecular dynamics to obtain the sputtering threshold energy as a function of atomic species, recoil direction and atomic layer of the primary recoil atom. The minimum sputtering energy occurs for adatoms and is 3.5 and 4.5?eV for Al and Ni adatoms on the Ni–Al surface (denoted ‘M’), respectively, and 4.5?eV for both species on the pure Ni surface (denoted ‘N’). For atoms within the surface plane, the minimum sputtering energy is 6.0?eV for Al and Ni atoms in the M plane and for Ni atoms in the N surface. The sputtering threshold energy increases with increasing angle, θ, between the recoil direction and surface normal, and is almost independent of azimuthal angle, ?, if θ<60°; it varies strongly with ? when θ>60°, with a maximum at ??=?45° due to ?{110}? close-packed atomic chains in the surface. The sputtering threshold energy increases significantly for subsurface recoils, except for those that generate efficient energy transfer to a surface atom by a replacement collision sequence. The implications of the results for the prediction of the mass loss due to sputtering during microanalysis in a FEG STEM are discussed.     

Search for Uranium Source in Warcha Sandstone, Salt Range, Pakistan, using SSNTD Technique

The similarity in sedimentary depositional characteristics of the Warcha Sandstone of Nilawahan Group in the Salt Range to the uranium bearing sandstones of Siwalik Group in the foot hills of Himalaya and Sulaiman Ranges, Pakistan, tempted geologists to investigate the former group for the occurrence of uranium deposits in it. Like volcanic ash beds in Siwaliks, phosphatic nodules may be a possible source of uranium mineralization in Warcha Sandstone. Samples of phosphatic nodules occurring in the Warcha sandstone near Chakwal were collected and subjected to the solid state nuclear track detection technique for the determination of their uranium concentration. The uranium concentration in these samples ranges from (434±32) to (964±74) with an average of . The high uranium content indicates that the phosphatic nodules may be the possible source of uranium mineralization in Warcha Sandstone. These results are quite encouraging and favor the idea of exploring the area in detail for any possible occurrence of uranium deposits.     

Surface‐enhanced Raman spectroscopy (SERS) on silver colloids for the identification of ancient textile dyes. Part II: pomegranate and sumac

The effectiveness of surface‐enhanced Raman spectroscopy (SERS) spectrocsopy on Ag colloids has been successfully demonstrated for the identification of a yellow dye in two ancient wool threads found in the Royal Tumulus of In Aghelachem, Libyan Sahara, belonging to the Garamantian period (2nd–3rd century A.D.). High‐performance liquid chromatography (HPLC) highlighted the presence of ellagic acid in the extracts from the threads, excluding other chromophores. This result, together with the abundance of malic acid detected by gas chromatography‐mass spectrometry (GC‐MS), suggested the possible use of pomegranate rind or sumac berries as source of the yellow dye, both plants being documented in the Fezzan area during the Garamantian period. HPLC analyses and SERS spectra acquired on the extracts of the ancient threads were therefore compared with those obtained from pomegranate and sumac extracts of the corresponding fruits and reference dyed wool samples, allowing us to identify the yellow dye as deriving from pomegranate (Punica granatum L.). SERS spectra of ellagic acid and dyes extracted from pomegranate rind and sumac berries are reported here for the first time. A methodological improvement is also presented, based on the use of NaClO₄ as aggregating agent, that leads to a significant increase of the signal‐to‐noise ratio in the SERS spectra. Copyright © 2010 John Wiley & Sons, Ltd.     

Point defect generation,nano-void formation and growth. II. Criterion for ductile failure

Using the derived relation for point defect generation according to a new constitutive relation, the notion of nano-void formation at grown-in nano-particles is examined and its consequences deduced as the nano-voids grow in size with continued deformation. Assuming that void growth is due only to point defect accumulation, the analysis of fracture strains in tension of natural-aged AA6111 suggests that coalescence by micro-plastic activity occurs when the void diameter becomes about one third of the evolving inter-void spacing. Hence, the derived limit strain to incipient void-coalescence is inversely proportional to the square root of point defect generation as determined from the stress–strain data. Using this criterion, failure prediction maps can be constructed for strain modes of plane-strain and balanced bi-axial to result in the outer bounds of the forming limit diagram. Trial examinations with AA5754 and AA3003 show great promise.     

Artificial compressibility, characteristics-based schemes for variable-density, incompressible, multispecies flows: Part II. Multigrid implementation and numerical tests

The paper presents an investigation of the accuracy and efficiency of artificial compressibility, characteristics-based (CB) schemes for variable-density incompressible flows. The CB schemes have been implemented in conjunction with a multigrid method for accelerating numerical convergence and a fourth-order, explicit Runge–Kutta method for the integration of the governing equations in time. The implementation of the CB schemes is obtained in conjunction with first-, second- and third-order interpolation formulas for calculating the variables at the cell faces of the computational volume. The accuracy and efficiency of the schemes are examined against analytical and experimental results for diffusion broadening in two- and three-dimensional microfluidic channels, a problem that has motivated the development of the present methods. Moreover, unsteady, inviscid simulations have been performed for variable-density mixing layer. The computations revealed that accuracy and efficiency depend on the CB scheme design. The best multigrid convergence rates were exhibited by the conservative CB scheme, which is obtained by the fully conservative formulation of the variable-density, incompressible equations.     

On Convergence to Equilibrium Distribution, II. The Wave Equation in Odd Dimensions, with Mixing

The paper considers the wave equation, with constant or variable coefficients in ⁿ , with odd n3. We study the asymptotics of the distribution _t of the random solution at time t as t . It is assumed that the initial measure ₀ has zero mean, translation-invariant covariance matrices, and finite expected energy density. We also assume that ₀ satisfies a Rosenblatt- or Ibragimov–Linnik-type space mixing condition. The main result is the convergence of _t to a Gaussian measure as t , which gives a Central Limit Theorem (CLT) for the wave equation. The proof for the case of constant coefficients is based on an analysis of long-time asymptotics of the solution in the Fourier representation and Bernstein's room-corridor argument. The case of variable coefficients is treated by using a version of the scattering theory for infinite energy solutions, based on Vainberg's results on local energy decay.     

A unified approach for deriving kinetic equations in nonequilibrium statistical mechanics. II. Approximate results

The exact form for the kinetic equation derived by Mori, Fujisaka, and Shigematsu (MFS) is used to obtain several approximations better suited to be compared with macroscopic transport equations. Three approximations are discussed, namely, those known as the diagonal, the slow process, and the Markovian. The corresponding results are emphasized and their relationship is established. In particular, the Kramers-Moyal expansion for the Markovian kinetic equation is obtained from a microscopic basis.     

Cross-section prediction for isotopes near neutron drip line in ~(70, 80)Zn projectile fragmentation reactions

The cross sections for ~(59,60)Ca, recently measured in the 345 A MeV ~(70)Zn+~9 Be reaction,were estimated using the FRACS parametrization and an empirical formula,which are in good agreement.The FRACS parametrization and the empirical formula are combined to predict the cross sections for extreme calcium isotopes ~(66,70)Ca in the~(70,80)Zn+~9 Be reactions at the incident energies of ~(60,80),and 345 A MeV.The dependence of emperical formula parameters on the reaction system,as well as the incident energy,are discussed.The results indicate that ~(66,70)Ca can be discovered in reactions of ~(60,80)A MeV ~(80)Zn+~9 Be.The predicted binding energy for extreme neutron-rich isotopes by the spherical relativistic continuum Hartree-Bogoliubov theory was adopted in the calculation.Hence,the planned Beijing Isotope-Separation-On Line Neutron-Rich Beam Facility(BISOL),which is a third generation radioactive ion beam facility,could provide the opportunity to discover ~(66,70) Ca and neighboring neutron-drip line nuclei.     

Surface crystallography by LEED: II. Matrix formalisms for fast LEED intensity calculations: bare substrate,surface barrier,superstructure

Starting from the generalized Darwin theory of McRae we present several approximations for LEED intensity calculations using matrix formalisms. A layer by layer method is derived, applicable to a general case. We then present a multiple order perturbation method for the clean substrate case. Next, the formulation is extended to include the case of a surface barrier and of an overlayer. Finally, our approximations are discussed in connexion with other perturbation methods.     

Multispectroscopic studies for the identification of archaeological frankincense excavated in the underground palace of Bao'en Temple,Nanjing: near infrared,midinfrared, and Raman spectroscopies

Five resinous incense materials excavated from the underground palace of Bao'en Temple, Nanjing, were studied by a multianalytical approach of near infrared, midinfrared, and Fourier transform Raman spectroscopies. By comparing the multispectroscopic features of five specimens, these incense materials were identified to the same substance. Subsequent analysis and comparison of the ancient incense materials and three modern reference specimens were carried out, and the results indicated that the excavated incense materials were frankincense, with its major component of triterpenoids. This work performs, for the first time, a comprehensive spectroscopic study for the Chinese excavated incense materials, demonstrating that a combined use of near infrared, midinfrared, and Fourier transform Raman spectroscopies is an efficient technique to identify an excavated incense. Copyright © 2012 John Wiley & Sons, Ltd.     

Theory of irreversible processes in nonequilibrium quantum systems. II. Cluster expansions with contraction for homogenous systems

On the basis of a method developed in a previous paper, a systematic rule for obtaining a symmetrized collision superoperator of the Van Hove generalized master equation including an arbitrary number of particles is given. In the formalism, the quantum statistical effect is taken into account through the use of contractions (internal and external contractions) on the basis of the cluster expansion. As an application of this general rule, a symmetrized collision superoperator including the effect of three-particle collisions is obtained.