(II) Infrared and X-ray photoelectron spectroscopy of some transition metal dithiocarbamates and xanthates

Measurements are presented for the binding energy variations of (a) (Ni, Cu) 2p_{$\text{3}\text{2}$}, S 2p and N 1s core levels in a series of Ni and Cu disubstituted dithiocarbamates and (b) (Ni, Cu) 2p_{$\text{3}\text{2}$}, and S 2p core levels in a series of Ni xanthates. These shifts, which are observed to be negative and quite large for the S 2p levels, are then correlated with the infrared absorption frequency variations for the associated intramolecular stretching vibrations of the same series. The results are interpreted in terms of a model based on atomic charges and their potential effects on both variations. The functional relationships between the binding energy and infrared frequency variations are shown to be in good agreement with the experimental results.     

Density-of-state effects in the low temperature properties of TiBe2

The importance of exact theoretical and experimental determination of the band structure near E_F for an understanding of the properties of TiBe₂ is pointed out. Precise density-of-state data, obtained from ab-initio self-consistent band calculations, are used to determine low temperature variations in the susceptibility χ and specific heat γ. The influence on the field and temperature variations on χ is striking and qualitative agreement with experiment is possible without invoking spin-fluctuations.The field and temperature variations of γ are important enough to be considered, but are smaller than for χ and considerably smaller than observed experimentally by Stewart et al. Thus evidence of spin-fluctuations are more convincing when extracted from γ-data than from χ-data.     

Photoemission study of UFe2 and UPt3 using synchrotron radiation

The U 5f density of states in UPt₃ and UFe₂ has been determined experimentally using synchrotron radiation. Cross section variations were exploited to separate the valence band contributions. By means of difference spectra, the variations in the U 5f density at the Fermi level have been measured.     

Surface anchoring and temperature variations of the pitch in thin cholesteric layers

The temperature variations of the cholesteric pitch in thin planar layers of cholesterics and their dependence on the surface anchoring force are investigated theoretically. It is shown that the temperature variations of the pitch in a layer are of a universal character. This is manifested in the fact that they depend not separately on the parameters of the sample but only on one dimensionless parameter S _d =K ²²/dW, where K ₂₂ is the torsional modulus in the Frank elastic energy, W is the height of the surface-anchoring potential, and d is the thickness of the layer. The investigation is performed the parameter S _d in a range where the change per unit number of cholesteric half-turns within the thickness of the layer accompanying a change in the temperature is due to the slipping of the director on the surface of the layer through the potential barrier for surface anchoring. The critical values of the parameter S _d (which are most easily attained experimentally by varying the thickness of the layer), determining the region of applicability of the approach employed, are presented. The temperature variations of the free energy of the layer and the pitch of the cholesteric helix in the layer as well as the temperature hysteresis in the variations of the pitch with increasing and decreasing temperature are investigated for the corresponding values of S _d . Numerical calculations of the quantities mentioned above are performed using the Rapini anchoring potential.     

Search for correlations between the solar-flare disturbances of the earth’s magnetosphere and a flux of cosmic rays detected by the RUSALKA setup

The statistical approach has been applied to the search for correlations between the geomagnetic index K _p and the amplitude of daily variations in the station count rate. The upper limit of variations in the rate due to solar activity was ascertained; it is 1.2% (CL = 99%) for K _p = 8.     

On the effect of temperature fluctuations on line intensities

We investigate the effects of temperature fluctuations in a stellar atmosphere on the intensities of the lines emitted by a multilevel atom, by differentiating the coupled set of radiative transfer and statistical equilibrium equations. We propose a numerical method for the fast computation of large sequences of line profiles when the atmospheric temperatures are fluctuating about a mean curve T(z) (oscillations, waves, turbulence, etc…). This method is applied to a three-level atom simulating the formation of Ca(II) lines in the solar atmosphere and the results are compared with those of direct computations. We show how the variations of atomic level populations, line source functions, and emergent intensities may be related to temperature variations by a sum of several terms corresponding to each atomic transition and arising from the variations of collisional excitation rates. Finally, we discuss the possibility of extending the method to compute profile variations when temperatures, densities and velocities are changing simultaneously within the atmosphere.     

Brillouin zone effects on the critical temperature of superconductors and some related normal metal properties

A Fermi surface passing through a set of Bragg planes gives rise to variations of several normal metal properties, e.g. the electronic density of states N(0), the magnetic susceptibility, the Seebeck coefficient, the Debye temperature and the electron-phonon interaction strength V_ph, and consequently also to variation of the critical temperature for superconductivity, T_c.This behaviour is analysed on the basis of a nearly free electron model and a comparison is made with experimental results in various alloy systems. These systems include alloys of non-transition metals and pseudo-binary alloyed compounds with Cu₃Au- and CuAl₂-type structure.The observed variations of normal metal properties are in reasonable agreement with the theoretical estimates. The variations in T_c indicate that enhancements not only of N(0) but probably also of V_ph occur near Bragg planes.     

Stability criteria for q-expectation values

In statistical physics lately a specific kind of average, called the q-expectation value, has been extensively used in the context of q-generalized statistics dealing with distributions following power laws. In this context q-expectation value appear naturally. Since it was recently shown that this non-linear functional is instable, using a very strong notion of stability, it is therefore of high interest to know sufficient conditions for when the results of q-expectations are robust under small variations of the underlying distribution function and when not. We show that reasonable restrictions on the domain of admissible probability distributions restore uniform continuity for the q-expectation. Bounds on the size of admissible variations can be given. The practical usefulness of the theorems for estimating the robustness of the q-expectation value with respect to small variations is discussed.     

Equilibrium properties of fast-rotating headed nuclei

We report on calculations of the equilibrium deformation in excited heated rotating nuclei. At A ～ 150–200 and temperature t > t_c ≈ 1.2 MeV the shell effects turn out to be small to compete with the variations of the liquid drop component of the energy. The transition from the shape of a “cool” nucleus to that of a “hot” nucleus takes place at t_c and in deformed nuclei resembles a phase transition. The stiffness parameter with respect to shape variations at t_c is anomalously low.     

Experimental determination of intervalley energy gaps as a temperature function for Ga1−xAlxAs

The forward ln i-v characteristic of metal-compound semiconductor contacts shows abrupt variations of the n ideality factor, which can be explained by assuming that the satellite valleys give a bias dependent contribution to the total current. The knee voltage values at which such variations occur allow the determination of intervalley gaps by means of a simple relationship. We have measured such energy gaps for the Ga_1?xAl_xAs over the temperature range 100–300 K.     

Theoretical sequence of s-and t-incommensurate phases in quartz

The sequence of s-and t-incommensurate phases observed with variations of the temperature in quartz is substantiated theoretically.     

Cloud and aerosol contributions to variation in shortwave surface irradiance over East Asia in July during 2001 and 2007

It is important to clarify the contributions of clouds and aerosols to the variation of surface shortwave irradiance (S) for climatological studies. This study examined the contributions of clouds and aerosols to the variation in S over East Asia (75-135°E, 20-55°N) in July during 2001 and 2007 using the index of potential radiative forcing (PRF) to characterize the temporal and geographical variations. After confirming the validity of PRF for multiyear analyses, we performed several temporal analyses of clouds and aerosols over the whole research domain. Changes in the geographical distribution, contribution histograms, and averaged values were studied. In agreement with previous studies that treated single-year cases, we confirmed that the magnitudes of the temporal changes in S variations due to clouds and aerosols were highly variable geographically. As for domain-averaged S variations, we did not observe defined trends for the research period. It was also found that the temporal variation between one parameter and its S variation was negatively correlated, from the point analyses at two locations. Based on these results, we concluded that PRF is a promising tool for research into long-term S variations. This kind of information will be quite valuable as basic data for use in climate modeling.     

Thermal expansion of dysprosium tetraboride

The temperature variations of the interplanar spacings a(T) and c(T) in the crystal lattice of dysprosium tetraboride have been studied using X-ray diffraction in the temperature range 5?C300 K. Anomalous variations of a(T) and c(T) in the temperature range of magnetic transformations, anisotropy of the thermal expansion of DyB₄, and the monoclinic distortion of the crystal structure at low temperatures have been revealed. The magnitudes of the spontaneous magnetostriction, the thermal expansion coefficients ??a and ??c, and the exchange integrals Y _a and Y _c have been determined.     

Observation of cosmic ray and electric field variations in the surface atmosphere

The results of cosmic ray observations by the CARPET instrument at CASLEO (El Leoncito, Argentina, R _c ≈ 11.8 GV) in 2006–2008 are reported. The main attention is paid to CR variations due to electric field variations in the surface atmosphere.     

Effect of wood properties on within-tree variation in ultrasonic wave velocity in softwood

The radial variations in the velocity of longitudinal waves propagating through Japanese cedar and Japanese cypress were experimentally investigated. In addition, the tracheid length (TL), microfibril angle (MFA), air-dried density (AD), and moisture content (MC) were measured in order to determine the effect of wood properties on velocity variations within the wood trunk. For both species, the longitudinal wave velocities measured in the longitudinal direction (V_L) exhibited minimum values near the pith. For Japanese cedar, V_L increased from 3600 m/s toward the bark and soon attained a constant value (=4500 m/s). On the other hand, for Japanese cypress, V_L kept increasing from 4000 m/s near the pith to 4800 m/s at the bark. These radial variations in V_L coincided with those in the tracheid length. V_L exhibited strong correlations with TL and MFA with a significant level of (p < 0.01). These findings suggest that the TL and MFA greatly affect the radial variation in the ultrasonic wave velocity in softwood.     

Evolution of the energy structure of n-InGaAs/GaAs double quantum wells in tilted magnetic fields

Complex variations of a magnetoresistance oscillation pattern with a tilted magnetic field angle are found in a n-In_0.2Ga_0.8As/GaAs double quantum well. These variations reflect the nontrivial behavior of gaps in the calculated magnetic level patterns. Fourier spectra of oscillations in tilted fields also exhibit a complex structure, and the sum of frequencies of peaks is not constant. It is assumed that this is associated with the magnetic breakdown effect.     

Influence of third-order nonlinear and phase variations on third harmonic generation

A theoretical analysis is presented for third-harmonic generation in KDP for type I/type II angle-detuning scheme of high-intensity laser to produce third harmonic radiation near 0.35 μm. The effects of the third-order nonlinearity and the phase variations on the frequency conversion have been discussed. The results shown that the third-order nonlinear interactions decreases the tripling efficiency, and increases of the modulate strength of the output intensity of 3ω radiation. However, adjusting the angular detuning can compensate effectively the effects of third-order nonlinearity. Furthermore, 3ω conversion efficiency will drop with the increase of the degree of phase variations, and the increase 3ω conversion efficiency can decrease the influence of third-order nonlinearity on the conversion of third harmonics.     

Influence of temperature variations on the entropy and correlation of the Grey-Level Co-occurrence Matrix from B-Mode images

In this work, the feasibility of texture parameters extracted from B-Mode images were explored in quantifying medium temperature variation. The goal is to understand how parameters obtained from the gray-level content can be used to improve the actual state-of-the-art methods for non-invasive temperature estimation (NITE). B-Mode images were collected from a tissue mimic phantom heated in a water bath. The phantom is a mixture of water, glycerin, agar-agar and graphite powder. This mixture aims to have similar acoustical properties to in vivo muscle. Images from the phantom were collected using an ultrasound system that has a mechanical sector transducer working at 3.5 MHz. Three temperature curves were collected, and variations between 27 and 44 °C during 60 min were allowed. Two parameters (correlation and entropy) were determined from Grey-Level Co-occurrence Matrix (GLCM) extracted from image, and then assessed for non-invasive temperature estimation. Entropy values were capable of identifying variations of 2.0 °C. Besides, it was possible to quantify variations from normal human body temperature (37 °C) to critical values, as 41 °C. In contrast, despite correlation parameter values (obtained from GLCM) presented a correlation coefficient of 0.84 with temperature variation, the high dispersion of values limited the temperature assessment.     

Effect of background levels on community responses to aircraft noise

The effect of variations in background noise levels on community reactions to aircraft noise has been investigated by using questionnaire and sound level data collected at a stratified random sample of residential sites in the vicinity of Toronto International Airport. The effects of variations in background noise (24 hour L_eq) on both individual and aggregate responses to aircraft noise have been examined. The response variables considered include annoyance, activity interference and complaints. The results of various statistical analyses show that the effect of background level is generally not significant. These findings are consistent with relevant findings from previous laboratory studies, but not with those from previous field studies.     

Experimental investigation of reflection coefficients for lossy liquid-solid-liquid systems

The reflection coefficient for a bounded ultrasonic beam incident on a liquid-solid-liquid system (LSL) is studied. Systematic measurements were carried out to investigate the variations of the amplitude of the reflection modulus ∣R_LSL∣ with incident angle and parameter Fd (frequency-thickness of the plate). The experimental plots confirm the theoretical works of Claeys et al¹ and Bogy and Gracewski². It is shown that the attenuation of the media has a great influence on the variations of this coefficient as has been already mentioned in the literature, for liquid-solid configurations.