Mass Spectrometry of Some Benzylidene Imidazolidinediones and Thiazolidinediones. II- chlorobenzyl imidazolidinedione and Fluoro or Chlorobenzyl Thiazolidinedione Compounds

In the present investigation, a study of the electron impact mass spectrometry data is reported for seven compounds of a series of some 3-(4-chlorobenzyl)-5-benzylidene-imidazolidine-2, 4-diones and 3-(4-fluoro or chlorobenzyl)-5-benzylidene-thiazolidine-2, 4-diones previously synthesized.     

Microwave-assisted digestion with a single reaction chamber for mineral fertilizer analysis by inductively coupled plasma optical emission spectrometry

A systematic approach is proposed to evaluate microwave-assisted digestion in a single reaction chamber for the simultaneous determination of elements in the mineral fertilizer and raw material by inductively coupled plasma optical emission spectrometry. A reference material was digested using 12 acid mixtures containing nitric, hydrochloric, orthophosphoric, hydrofluoric or boric acid. Principal components analysis was applied for data treatment. Three digestion procedures based on diluted acids exhibited the most accurate results, with relative errors for reference values ranging from ?15% to +?9%. Limits of quantification were in the range of 0.2?mg cadmium kg^?1 up to 1000?mg aluminum kg^?1.     

Multiple scattering of ultrasound in weakly inhomogeneous media: application to human soft tissues

Waves scattered by a weakly inhomogeneous random medium contain a predominant single-scattering contribution as well as a multiple-scattering contribution which is usually neglected, especially for imaging purposes. A method based on random matrix theory is proposed to separate the single- and multiple-scattering contributions. The experimental setup uses an array of sources/receivers placed in front of the medium. The impulse responses between every couple of transducers are measured and form a matrix. Single-scattering contributions are shown to exhibit a deterministic coherence along the antidiagonals of the array response matrix, whatever the distribution of inhomogeneities. This property is taken advantage of to discriminate single- from multiple-scattered waves. This allows one to evaluate the absorption losses and the scattering losses separately, by comparing the multiple-scattering intensity with a radiative transfer model. Moreover, the relative contribution of multiple scattering in the backscattered wave can be estimated, which serves as a validity test for the Born approximation. Experimental results are presented with ultrasonic waves in the megahertz range, on a synthetic sample (agar-gelatine gel) as well as on breast tissues. Interestingly, the multiple-scattering contribution is found to be far from negligible in the breast around 4.3 MHz.     

Structural and spectroscopic properties of the diazocarbene radical (CNN) and its ions CNN+ and CNN−: a high-level theoretical investigation

The diazocarbene radical, CNN, and the ions CNN⁺ and CNN^? were investigated at a high level of theory. Very accurate structural parameters for the states X ³Σ^? and A ³Π of CNN, and X ²Π of both CNN⁺ and CNN^? were obtained with the UCCSD(T) method using correlated-consistent basis functions with extrapolations to the complete basis set limit, with valence only and also with all electrons correlated. Harmonic and anharmonic frequencies were obtained for all species and the Renner parameter and average frequencies evaluated for the Π states. At the UCCSD(T)/CBS_T-5 level of theory, Δ_f H(0 K) = 138.89 kcal/mol and Δ_f H(298 K) = 139.65 kcal/mol were obtained for diazocarbene; for the ionization potential and the electron affinity of CNN, 10.969 eV (252.95 kcal/mol), and 1.743 eV (40.19 kcal/mol), respectively, are predicted. Geometry optimization was also carried out with the CASSCF/MRCI/CBS_T-5 approach for the states X ³Σ^?, A ³Π, and a ¹Δ of CNN, and with the CASSCF/MRSDCI/aug-cc-pVTZ approach for the states b ¹Σ⁺, c ¹Π, d ¹Σ^?, and B ³Σ^?, and excitation energies (T_e) evaluated. Vertical energies were calculated for 15 electronic states, thus improving on the accuracy of the five transitions already described, and allowing for a reliable overview of a manifold of other states, which is expected to guide future spectroscopic experiments. This study corroborates the experimental assignment for the vertical transition X ³Σ^? ← E ³Π.     

Interaction of indigo carmine dye with silica modified with humic acids at solid/liquid interface

Two distinct humic acids, one extracted from Brazilian peat soil, HA_PS, and another one obtained from commercial source, HA_FL, were attachment onto silica gel modified with aminopropyltrimethoxysilane, producing two material named SiHA_PS and SiHA_FL, respectively. The ability of these materials in removing indigo carmine dye from aqueous solution was followed through series of adsorption isotherms adjusted to modified Langmuir equation. The maximum number of moles adsorbed gave 6.82 ± 0.12 × 10⁻⁴ and 2.15 ± 0.17 × 10⁻⁴ mol g⁻¹ for SiHA_PS and SiHA_FL, respectively. Same interactions were calorimetrically followed and the thermodynamic data showed endothermic enthalpic values: 12.31 ± 0.55 and 24.69 ± 1.05 kJ mol⁻¹ for SiHA_PS and SiHA_FL surfaces, respectively. Gibbs free energies for two adsorption processes of indigo carmine dye presented negative values, reflecting dye/surface interactions must be accompanied by an increased in entropy values, which are 65 ± 3 and 98 ± 5 J mol⁻¹ K⁻¹ for SiHA_PS and SiHA_FL materials, respectively. The adsorption processes for both materials were spontaneous in nature although they presented an endothermic enthalpy for the interaction, resulting in an entropically favored process.     

Effect of aerosil dispersions on the nematic-to-isotropic interface

The effect of silica aerosils on the kinetics of the first-order nematic-isotropic (NI) phase transition is phenomenologically described in the framework of the time-dependent Landau-Ginzburg equation. A steady-state solution to the equation is presented such that the NI interface may propagate with a solitary-like wave profile under constant quenching. The results provide a plausible basis for the interpretation of the dynamical effects of quenched disorder in the liquid-crystal systems, caused by randomly interconnected porous media, such as aerosils. In the low silica aerosil ρ_s ( ≤0.1 g/cm^3) regime, the calculated values of the interface velocity v(T,ρ_s), the interface thickness κ(T,ρ_s), and the critical radius of a spherical nucleus of new nematic phase in a bulk isotropic environment, composed of polar molecules, such as 4-n-octyl- 4^′- cyanobiphenyl and 4-n-heptyl- 4^′- cyanobiphenyl shows that the effect of silica aerosils on the kinetics is reflected in a shifting of the set of temperature-dependent curves to lower temperature values.-1     

Potential energy landscape of monolayer-surface systems governed by repulsive lateral interactions: the case of (3 x 3)-I-Pt(111)

Combined density functional theory (DFT) and Monte Carlo (MC) approach is applied to study the potential energy landscape of four iodine atoms adsorbed on the Pt(111) surface in a (3 x 3) unit cell. Three critical points were identified: (3 x 3)-sym and (3 x 3)-asym, corresponding to structures well known from experimental studies, while the third one (3 x 3)-zigzag is a new structure not reported before. An interaction model fitted to DFT calculations allows us to explain the difference between arrangements of iodine monolayer in vacuum, air, and solution environments as a result of different repulsion regimes.     

Search for a standard model Higgs boson in the H→ZZ→ℓ(+)ℓ(-)νν decay channel with the ATLAS detector

A search for a heavy standard model Higgs boson decaying via H→ZZ→→?(+)?(-)νν, where ?=e, μ, is presented. It is based on proton-proton collision data at √s=7 TeV, collected by the ATLAS experiment at the LHC in the first half of 2011 and corresponding to an integrated luminosity of 1.04 fb(-1). The data are compared to the expected standard model backgrounds. The data and the background expectations are found to be in agreement and upper limits are placed on the Higgs boson production cross section over the entire mass window considered; in particular, the production of a standard model Higgs boson is excluded in the region 340相似文献   

Constrained random walks and vortex filaments in turbulence theory

We consider a simplified model of vorticity configurations in the inertial range of turbulent flow, in which vortex filaments are viewed as random walks in thermal equilibrium subjected to the constraints of helicity and energy conservation. The model is simple enough so that its properties can be investigated by a relatively straightforward Monte-Carlo method: a pivot algorithm with Metropolis weighting. Reasonable values are obtained for the intermittency dimensionD, a Kolmogorov-like exponent , and higher moments of the velocity derivatives. Qualitative conclusions are drawn regarding the origin of non-gaussian velocity statistics and regarding analogies with polymers and with systems near a critical point.This work was supported in part by the Applied Mathematical Sciences Subprogram of the Office of Energy Research, US Department of Energy, under Contract Number DE-AC03-76SF000098