Production and identification of new neutron-deficient isotope235Am in region of transuranium

A new transuranium neutron-deficient isotope²³⁵Am was produced by 35 MeV proton to bombard the rare radioactive²³⁸Pu target. The products were transported and collected by the He-jet system. The Am isotopes were separated and purified by radiochemistry method and the y-ray, X-ray and y-X(y) coincidence of the samples was measured. The synthesis of²³⁵Am was definitely identified. Its measured half-life is (15±5) min. Project supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences.     

Mechanism of microwave synthesized BaTiO3

The difference of intermediate products, microstructure and element concentration in the particles between microwave synthesized samples and conventional samples was responsible for the existence of non-thermal effect in the microwave field. The diffusions of Ba²⁺, Ti⁴⁺ in the microwave field were enhanced, so that the diffusion of Ti⁴⁺ could not be neglected as in the conventional solid state reactions. The influences of the microwave field were mainly expressed as diffusion coefficient and the driving force of ionic motion. The intermediate phase Ba₂TiO₄ which occurred in the conventional solid reaction was not found during microwave syntheses. The quantity analyses based on XRD experimental data show that the reaction dynamics in microwave is suitable for the Carter equation. The activity energy for reaction of BaCO₃ and TiO₂ in the microwave field was 42.26 kj/mol, which was only one fifth of the conventional reaction. Project supported by the National Natural Science Foundation of China.     

Study of ion implanted Al0.25Ga0.75As/GaAs by Raman spectroscopy

This paper reported the effect of the weak damage in the Al_0.25Ga_0.75As/GaAs epitaxial layer induced by 0.8 MeV Si ions implantation with ion dose from 1 × 10¹⁴ to 5 × 10¹⁵ cm^-2. The Raman spectra measured on these samples showed that there were two kinds of phonon modes existing in the epitaxial Al_0.25Ga_0.75As films. The strains induced in the implanted layer and the corresponding lattice parameters were also evaluated as a function of the implanted dose. In addition, the Rutherford backscattering spectrometry/channeling (RBS/C) was also measured on these samples. These two measurement techniques all confirmed that the implantation only induced weak damage in the material.     

Study of ion implanted Al0.25Ga0.75As/GaAs by Raman spectroscopy

This paper reported the effect of the weak damage in the Al_0.25Ga_0.75As/GaAs epitaxial layer induced by 0.8 MeV Si ions implantation with ion dose from 1 × 10¹⁴ to 5 × 10¹⁵ cm^-2. The Raman spectra measured on these samples showed that there were two kinds of phonon modes existing in the epitaxial Al_0.25Ga_0.75As films. The strains induced in the implanted layer and the corresponding lattice parameters were also evaluated as a function of the implanted dose. In addition, the Rutherford backscattering spectrometry/channeling (RBS/C) was also measured on these samples. These two measurement techniques all confirmed that the implantation only induced weak damage in the material.     

Optical absorption spectrum of Ni2+ in Garnierite

The results obtained in the study of the absorption spectrum of Ni²⁺ in two samples of Garnierite are described. Both the samples of Garnierite have been studied by preparing their mineral oil mulls. One of these samples could however be studied in its crystal form as well. From the observed features, the absorption bands in both the samples of Garnierite have been attributed to an ion of Ni²⁺ in tetrahedral symmetry. The observed and calculated energies for the bands are found to be in close agreement with one another justifying the assumption that the site symmetry of Ni²⁺ ion is tetrahedral. For one of the Garnierite samples both the crystal and mineral oil mull spectra could be recorded and it is interesting to find that they are identical with one another. It has therefore been suggested that the absorption spectrum of any mineral can be studied by preparing its mineral oil mull in case it cannot be cut and polished into a thin crystal suitable for absorption work. The crystal field parameters derived for the two samples of Garnierite are identical and they are B = 845 cm^?1, C = 3.9 B, Dq = 422 cm^?1 and λ = ? 275 cm^?1.     

Dual frames in connected with generalized sampling in shift-invariant spaces

The aim of this article is to derive stable generalized sampling in a shift-invariant space by using some special dual frames in L²(0,1). These sampling formulas involve samples of filtered versions of the functions in the shift-invariant space. The involved samples are expressed as the frame coefficients of an appropriate function in L²(0,1) with respect to some particular frame in L²(0,1). Since any shift-invariant space with stable generator is the image of L²(0,1) by means of a bounded invertible operator, our generalized sampling is derived from some dual frame expansions in L²(0,1).     

On the <Emphasis Type="Italic">L</Emphasis><Superscript><Emphasis Type="Italic">p</Emphasis></Superscript>-consistency of wavelet estimators

This paper deals with the L ^p -consistency of wavelet estimators for a density function based on size-biased random samples. More precisely, we firstly show the L ^p -consistency of wavelet estimators for independent and identically distributed random vectors in R ^d . Then a similar result is obtained for negatively associated samples under the additional assumptions d = 1 and the monotonicity of the weight function.     

Esr of CaS:Mn2+: A case with zero cubic field splitting

Electron spin resonance studies on powdered samples of CaS:Mn²⁺ and SrS:Mn²⁺ at 300° and 77° K reveal the usual six-line hyperfine structure due to Mn⁵⁵. CaS:Mn²⁺ exhibits additional fine structure satellites which have been analysed on the basis of a near zero cubic field splitting.     

Features of thermomechanical properties of radiation-modified blends of high-density polyethylene with liquid-crystalline copolyester

The present paper surveys the investigation results of gamma-irradiated blends of high-density polyethylene (PE) with thermotropic liquid-crystalline polymer (LCP). The LCP used was a liquid crystalline copolyester of 40% poly(ethyleneterephthalate) with 60% p-(hydroxybenzoic acid). The LCP content in the blends was 0,5, and 10 wt.%. The constituents were blended with the use of a single-screw extruder. The samples were prepared by compression molding and irradiated by a Co⁶⁰ -radiation source in an inert atmosphere (argon) to relatively low absorbed doses (up to 200 kGy; 1 Mrad=10 kGy). Morphological, thermal, and mechanical properties in a wide temperature range were investigated for the irradiated and nonirradiated samples. The effects of gamma-irradiation and LCP addition on the thermomechanical behavior of PE are discussed. It was found that the LCP addition affected significantly the stress-strain behavior of PE at temperatures above the melting point. The features of thermorelaxation properties of the PE/LCP blends previously irradiated and oriented, particularly thermorelaxation and residual shrinkage stresses at isometric heating and cooling, were also established. The results obtained testify that the LCP addition makes it possible to improve considerably the thermosetting properties of irradiated PE.Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 1, pp. 124–139, January–February, 1998.     

Radon concentration of air over the Eastern Arabian Sea

The radon concentrations of air samples collected during the South West monsoon period at altitudes up to 4 km over the Arabian Sea at two locations,i.e., 0–50 km and 300–400 km west of Bombay, are reported. Radon was extracted from air, using a simple single stage apparatus. The concentration of radon in the monsoon air mass was found to range around 80–100 dpm/m³ STP, indicative of its recent continental origin. The results suggest that the coastal monsoon air mass, up to 400 km west of Bombay coast, is generally homogeneous and vertically well mixed. During the post-monsoon condition, a strong gradient in the radon concentration in the vertical is observed. The concentration of radon decreases from 157 dpm/m³ at sea level to 35 dpm/m³ at about 3·7 km altitude, suggesting a vertical turbulent diffusion coefficient of ～6×10⁴ cm²/sec. In contrast, the near absence of vertical gradient of radon in the monsoon air mass indicates that the vertical turbulence is much stronger during the monsoon period.     

Testing random number generators by numerical modeling of an exactly solvable problem

Monte Carlo numerical modeling of a problem with a known exact solution is used to test linear multiplicative generators with modulus M = 2³¹ ? 1 for their applicability in parallel computing. The deviations of the calculated values of the rotational temperature from the known theoretical values are compared with the possible errors of the Monte Carlo method due to the finiteness of statistical samples. In addition, sample correlation coefficients are used to estimate true correlation coefficients between the values of the rotational temperature obtained on different processors with different multipliers, as well as in the case where additional samples were drawn at the terminal state on each processor in order to increase the size of the total sample. For this purpose, by means of special partial averaging, the random values of the rotational temperature were transformed into approximately normally distributed variables; then, for the variables obtained, true correlation coefficients were estimated by sample correlation coefficients. It was discovered that 204 different multipliers suggested by G.S. Fishman, L.R. Moore exhibit the best performance when used in a parallel implementation of the Monte Carlo method: all deviations are less than the theoretical Monte Carlo errors. Moreover, no correlations between the random variables produced by generators with different multipliers were detected. This suggests that generators with different multipliers produce independent sequences of pseudorandom numbers. However, drawing additional samples on each processor, which is frequently done to increase the size of the total sample, gives rise to correlations. Moreover, in many such cases, the theoretical errors of the Monte Carlo method for multipliers in the bottom part of the list proposed by Fishman and Moore are less than the values of temperature deviations and, therefore, should not be used in this way.     

An Elementary Derivation of the Distribution of the Variance in Normal Samples

In normal samples, the sample variance and sample mean are independent random variables, and the sample variance has, when properly normalized, a X²‐distribution. This paper gives elementary proofs by induction for these two facts.     

Ultrametricity indices for the Euclidean and Boolean hypercubes

Motivated by Murtagh’s experimental observation that sparse random samples of the hypercube become more and more ultrametric as the dimension increases, we consider a strict version of his ultrametricity coefficient, an index derived from Rammal’s degree of ultrametricity, and a topological ultrametricity index. First, we prove that the three ultrametricity indices converge in probability to one as dimension increases, if the sample size remains fixed. This is done for uniformly and normally distributed samples in the Euclidean hypercube, and for uniformly distributed samples in F₂ ^N with Hamming distance, as well as for very general probability distributions. Further, this holds true for random categorial data in complete disjunctive form. A second result is that the ultrametricity indices vanish in the limit for the full hypercube F₂ ^N as dimensionN increases,whereby Murtagh’s ultrametricity index is largest, and the topological ultrametricity index smallest, if N is large.     

Sard-optimal prefilters for the Fast Wavelet Transform

A direct input of function samples into the Fast Wavelet Transform often gives inaccurate results. We use the refinement equation for the construction of prefiltering quadrature formulas which are optimal in Sard's sense, i.e.,in the standard class of functions with ‖ f ^(p)‖₂ < ∞. A detailed analysis of the error and several applications are given. This revised version was published online in August 2006 with corrections to the Cover Date.     

A clinically applicable method for assessing lung permeability in the non-steady-state

A clinically applicable method for assessing the permeability of the alveolar-capillary barrier under non-steady-state conditions has been developed. Following deposition of a suitable tracer in the lungs, its rate of entry into the blood can be measured using blood samples alone, without the necessity for external monitoring. A second reference tracer must be infused in order to compensate for renal excretion and for redistribution of tracer in the extravascular space. Tracers of any convenient molecular weight and physical properties can be used, either unlabelled, or labelled with stable or radioactive isotopes.The method was examined by computer simulation in order to assess its sensitivity to measurement “noise”. In contrast to other non-steady-state tracer techniques, it is markedly less sensitive to experimental uncertainty, and measurements to an accuracy of 1–2% (coefficient of variation) should suffice for most purposes. The method was also validated by in vivo experiment in the pig, using a constant intravenous infusion of ⁵¹Cr-EDTA as the reference tracer and a variable intravenous infusion of ^99mTc-DTPA to simulate entry from the alveoli. Good agreement was obtained between the calculated entry rate of the ^99mTc-DTPA and the true entry rate known from the infusion pump rate.     

Fast perfect sampling from linear extensions

In this paper, we study the problem of sampling (exactly) uniformly from the set of linear extensions of an arbitrary partial order. Previous Markov chain techniques have yielded algorithms that generate approximately uniform samples. Here, we create a bounding chain for one such Markov chain, and by using a non-Markovian coupling together with a modified form of coupling from the past, we build an algorithm for perfectly generating samples. The expected running time of the procedure is O(n³lnn), making the technique as fast as the mixing time of the Karzanov/Khachiyan chain upon which it is based.     

Concentration estimates for learning with unbounded sampling

The least-square regression problem is considered by regularization schemes in reproducing kernel Hilbert spaces. The learning algorithm is implemented with samples drawn from unbounded sampling processes. The purpose of this paper is to present concentration estimates for the error based on ?²-empirical covering numbers, which improves learning rates in the literature.     

Influence of Fe3+ on perovskite oxides: La2/3Ca1/3Mn1-x Fe x O3

The structure and magnetoresistance properties in sintered samples of La_2/3Ca_1/3Mn_1-x Fe _x O₃(0≤x≤0.84) are studied by using Mössbauer spectroscopy, XRD and magnetic measurement. There are antiferromagnetic interactions between Fe and its nearest neighbors (Fe, Mn) when 0 <x ≤0.67, which are important factors influencing the double-exchange between Mn³⁺ and Mn⁴⁺, Curie temperature, magnetic moment and GMR. It is suggested that the Mn³⁺ (Fe³⁺) /Mn⁴⁺ system also consists of magnetic clusters with different sizes.     

Efficient Reconstruction of Functions on the Sphere from Scattered Data

Recently, fast and reliable algorithms for the evaluation of spherical harmonic expansions have been developed. The corresponding sampling problem is the computation of Fourier coefficients of a function from sampled values at scattered nodes. We consider a least squares approximation and an interpolation of the given data. Our main result is that the rate of convergence of the two proposed iterative schemes depends only on the mesh norm and the separation distance of the nodes. In conjunction with the nonequispaced FFT on the sphere, the reconstruction of N² Fourier coefficients from M reasonably distributed samples is shown to take O(N² log² N + M) floating point operations. Numerical results support our theoretical findings.