X-ray standing wave analysis of the effect of isotopic composition on the lattice constants of Si and Ge

The x-ray standing wave (XSW) technique is used to measure the isotopic mass dependence of the lattice constants of Si and Ge. Backreflection allows substrates of moderate crystallinity to be used while high order reflection yields high accuracy. The XSW, generated by the substrate, serves as a reference for the lattice planes of an epilayer of different isotopic composition. Employing XSW and photoemission, the position of the surface planes is determined from which the lattice constant difference Deltaa is calculated. Scaled to DeltaM = 1 amu we find (Deltaa/a) of -0.36x10(-5) and -0.88x10(-5) for Ge and -1.8x10(-5) and -3.0x10(-5) for Si at 300 and 30 K, respectively.     

Measurements of the exclusive decays of the upsilon(5S) to meson final states and improved B(s)* mass measurement

Using 420 pb(-1) of data collected on the upsilon(5S) resonance with the CLEO III detector, we reconstruct B mesons in 25 exclusive decay channels to measure or set upper limits on the decay rate of upsilon(5S) into B meson final states. We measure the inclusive B cross section to be sigma(upsilon(5S) --> BB(X)) = (0.177 +/- 0.030 +/- 0.016) nb and make the first measurements of the production rates of sigma(upsilon(5S) --> B*B*) = (0.131 +/- 0.025 +/- 0.014) nb and sigma(upsilon(5S) --> BB*) = (0.043 +/- 0.016 +/- 0.006) nb, respectively. We set 90% confidence level limits of sigma(upsilon(5S) -->BB) < 0.038 nb, sigma(upsilon(5S) --> B(*)B(*)pi) < 0.055 nb and sigma(upsilon(5S) --> BBpipi) < 0.024 nb. We also extract the most precise value of the B(s)* mass to date, M(B(s)*) = (5411.7 +/- 1.6 +/- 0.6) MeV/c2.     

On the normalization of Gamow functions

It is proved that the definitions of the norm given by Berggren and Romo are identical. Regularization in ref. ¹) with any convergence factor of the form

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leads to the same result. The existence of the norm is also established for the proton. The norm for neutrons is analytically given.     

Measurement of the absolute energy level and hyperfine structure of the 87Rb 4D5/2 state

We have measured the absolute frequency of the excited state transition 5P(3/2)-4D(5/2) in a (87)Rb atom with a femtosecond frequency comb, utilizing the recently developed spectroscopic technique of the double resonance optical pumping method. The absolute energy level of the 4D(5/2) state is determined by measuring the absolute frequency of the 5S(1/2)-5P(3/2) transition simultaneously. The hyperfine structure constants of the 4D(5/2) state are obtained by using the measured frequency. The magnetic dipole constant, A, is determined to be (-16.747+/-0.010) MHz with an uncertainty reduced 60-fold compared with a previous result. The electric quadrupole constant, B, is determined, for what is to our knowledge the first time, to be (4.149+/-0.059) MHz.     

The effect of cold acclimation on the water relations and freezing tolerance of Hordeum vulgare L

During a 5 degree C and a 5/-1 degree C cold acclimation (CA) regime there was a significant decline in the water potential of winter barley, and a concurrent decline in tissue water content of the 5/-1 degree C CA plants. Results of carbohydrate analysis illustrated a significant (P < 0.001) accumulation of sucrose, fructose and glucose in the 5/-1 degree C CA plants, which was inversely correlated to water potential. Using an infrared imaging radiometer during a convection frost test the water release time (WRT) of 5/-1 degree C CA was demonstrated to be significantly (P < 0.001) longer than that observed in non-cold acclimated plants. This observation is consistent with visual analysis of exotherm curves where the rate of cellular water release to extracellular ice is reduced in the 5/-1 degree C CA plants, compared to the non-cold acclimated plants. These biochemical and physiological changes were correlated to increased plant health following a non-lethal freezing test to -5 degree C, where non-cold acclimated plants produced 2.3 +/- 0.3 tillers and 5 degree C and 5/-1 degree C CA plants produced 2.4 +/- 0.3 and 4.7 +/- 0.7 tillers, respectively. Results from this study imply that cold acclimation leads to changes in the physical state of water that result in a less osmotically responsive cellular environment and subsequently significantly less damage to meristematic tissue.     

Minimal Dynamical Systems on the Product of the Cantor Set and the Circle

We prove that a crossed product algebra arising from a minimal dynamical system on the product of the Cantor set and the circle has real rank zero if and only if the set of invariant measures of the system come from the associated Cantor minimal system. In the case that cocycles take values in the rotation group, it is also shown that this condition implies tracial rank zero, and in particular, the crossed product algebra is isomorphic to a unital simple AT-algebra of real rank zero. Under the same assumption, we show that two systems are approximately K-conjugate if and only if there exists a sequence of isomorphisms between two associated crossed products which approximately maps      

Observation of the Bc meson in the exclusive decay Bc-->J/psipi

A fully reconstructed Bc-->J/psipi signal is observed with the D0 detector at the Fermilab Tevatron pp[over] collider using 1.3 fb(-1) of integrated luminosity. The signal consists of 54+/-12 candidates with a significance that exceeds 5 standard deviations, and confirms earlier observations of this decay. The measured mass of the Bc meson is 6300+/-14(stat)+/-5(syst) MeV/c2.     

Measurement of inclusive Ds, D0, and J/psi rates and determination of the Bs(*)Bs(*) production fraction in bb Events at the Upsilon(5S) resonance

The inclusive production of D(s), D(0), and J/psi mesons is studied using a 1.86 fb(-1) data sample collected on the Upsilon(5S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The number of bb events in this Upsilon(5S) data sample is determined. We measure the branching fractions B(Upsilon(5S)-->D(s)X)/2=(23.6+/-1.2+/-3.6)%, B(Upsilon(5S)-->D(0)X)/2=(53.8+/-2.0+/-3.4)%, and B(Upsilon(5S)-->J/psiX)/2=(1.030+/-0.080+/-0.067)%. From the D(s) and D(0) inclusive branching fractions the ratio f(s)=(18.0+/-1.3+/-3.2)% of B(s)(*)B(s)(*) to the total bb quark pair production at the Upsilon(5S) energy is obtained in a model-dependent way.     

Incorporation of iodine into the channels of AlPO4-5 crystals

Iodine molecules have been incorporated into the channels of calcined AlPO₄-5 crystals by using vapor-phase diffusion method. XRD results indicate that the iodine-loaded AlPO₄-5 crystals are of similar structure as that of as-synthesized AlPO₄-5 crystals. TG and XRF analyses reveal that the iodine molecules have not compactly filled the channels of AlPO₄-5 crystals, and the desorbing process of adsorbed iodine is quite different from that of adsorbed water. Polarized Raman spectra imply that the iodine exists in the channels of AlPO₄-5 crystals as vapor-like I₂ molecules, and the I₂ molecules orientate randomly.     

Determination of the 17O NMR tensors in potassium hydrogen dibenzoate: a salt containing a short O...H...O hydrogen bond

Solid-state 17O NMR spectra were obtained at 4.70, 11.75 and 19.60T for potassium hydrogen [17O(4)]dibenzoate (PHB) under both magic-angle spinning and stationary conditions. Spectral analyses yielded both the magnitude and orientation of the 17O chemical shift (CS) tensor and the electric field gradient (EFG) tensor for each of the two chemically distinct oxygen sites in PHB. For the oxygen site that is not involved in hydrogen bonding, the experimental 17O NMR tensors are: delta(iso)=287+/-2 ppm, delta(11)=470+/-5 ppm, delta(22)=380+/-5 ppm, delta(33)=10+/-5 ppm, C(Q)=8.30+/-0.02 MHz, eta(Q)=0.23+/-0.05, alpha=0+/-5 degrees, beta=90+/-5 degrees, and gamma=30+/-5 degrees. For the oxygen site in the short O...H...O hydrogen bond, the experimental 17O NMR tensors are: delta(iso)=213+/-2 ppm, delta(11)=370+/-5 ppm, delta(22)=190+/-5 ppm, delta(33)=80+/-5 ppm, C(Q)=5.90+/-0.02 MHz, eta(Q)=0.55+/-0.05, alpha=5+/-5 degrees, beta=90+/-5 degrees, and gamma=90+/-5 degrees. Extensive quantum mechanical calculations at both restricted Hartree-Fock and density functional theory levels were performed to investigate the effects of an effectively symmetrical O...H...O hydrogen bond on 17O CS and EFG tensors.     

Use of PM6 quantum-chemical calculations in studying the properties of antioxidants in the biological environment

The energies of formation, enthalpies, and entropies of the conformers of 1-(carboxy)-1-(N-methylamide)-2-(3′,5′-di-tert-butyl)-4-hydroxyphenyl)-propionic acid and sodium and potassium 1-(carboxy)-1-(N-methylamide)-2-(3′,5′-di-tert-butyl)-4-hydroxyphenyl)-propionates are calculated by quantum-chemical methods in the PM6 approximation. A doubling of signals in the ¹H NMR spectrum of the first conformer is observed, which merge into singlets when the compound is heated. Changes in the structure of the conformers and donor-acceptor complexes (solvates) occur with the preservation of the metal-ligand coordination bond. Calculations of the characteristics of 1-(carboxy)-1-(N-methylamide)-2-(3′,5′-di-tert-butyl)-4-hydroxyphenyl)-propionic acid and sodium and potassium 1-(carboxy)-1-(N-methylamide)-2-(3′,5′-di-tert-butyl)-4-hydroxyphenyl)-propionates in the PM6 approximation make it possible to predict the structure and properties of the solvated structures. The energies of homolysis of the H-O bond D _(OH) are calculated, and a linear dependence of the antioxidant activity on D _(OH) for the structures of the studied compounds is demonstrated. The results make it possible to predict the properties of antioxidants in the biological environment.     

Wetting and interfacial adsorption in the Blume-Capel model on the square lattice

The structural and electronic properties of Cu_5-1 and Cu_6-1 nanowires with core-shell structures encapsulated inside a series zigzag (n,0) BeONTs denoted by Cu_5-1@(n,0) and Cu_6-1@(n,0) are investigated using the first-principles calculations within the generalized-gradient approximation. For Cu_5-1@(n,0) (10 ? n ? 17) and Cu_6-1@(n,0) (11 ? n ? 18) combined systems, the initial shapes (cylindrical BeONTs and CuNWs) are preserved without any visible change after optimization. The quantum conductances 5G ₀ and 6G ₀ of the most stable Cu_5-1@(12,0) and Cu_6-1@(13,0) combined systems are identical to the corresponding free-standing Cu_5-1 and Cu_6-1 nanowires, respectively. The energy bands crossing the Fermi level in both the Cu_5-1@(12,0) and Cu_6-1@(13,0) combined systems are all originated from the inner CuNWs. Therefore the electron transport will occur only through the inner CuNWs and the outer inert BeONTs serves well as an insulating cable sheath. The robust quantum conductance of the Cu_5-1 and Cu_6-1 nanowires, the insulating protection character of the (12,0) and (13,0) BeONTs and the highest stability of the tube-wire combined systems make the Cu_5-1@(12,0) and Cu_6-1@(13,0) combined systems are top-priority in the ULSI circuits and MEMS devices that demand steady transport of electrons.     

Detecting the ejection of particles from the free surface of a shock-loaded sample

The details of the ejection of 20- to 200-µm particles with a velocity of 1.0-1.5 km/s from the surfaces of lead and steel samples with a roughness of 5-40 µm (Rz 5-Rz 40) when shock waves with an amplitude of 15 and 27 GPa reach them are visualized with a high-speed streak camera with a CCD matrix and pulsed laser illumination at a pulse duration of 4 ns. The size and velocity distributions of the particles are obtained.     

Large scale properties of the Webgraph

In this paper we present an experimental study of the properties of web graphs. We study a large crawl from 2001 of 200M pages and about 1.4 billion edges made available by the WebBase project at Stanford [17]. We report our experimental findings on the topological properties of such graphs, such as the number of bipartite cores and the distribution of degree, PageRank values and strongly connected components.Received: 5 December 2003, Published online: 30 March 2004PACS: 89.20.Hh World Wide Web, Internet - 89.75.Fb Structures and organization in complex systemsPartially supported by the Future and Emerging Technologies programme of the EU under contracts number IST-2001-33555 COSIN Co-evolution and Self-organization in Dynamical Networks and IST-1999-14186 ALCOM-FT Algorithms and Complexity in Future Technologies, and by the Italian research project ALINWEB: Algorithmica per Internet e per il Web, MIUR - Programmi di Ricerca di Rilevante Interesse Nazionale.     

利用CARS技术研究激发态Rb2和H2的碰撞转移

利用相干反斯托克斯拉曼光谱(coherent anti-stokes Raman spectroscopy,CARS)探测技术,研究了激发态Rb2与H<,2>间的电子-振转能级的碰撞转移.扫描CARS谱确认了H<,2>分子仅在v=1,J=1,2及v=2,J=0,1,2能级上有布居,用n1,n2,n3,n4,n5分别表示...     

Effect of spectral resolution on the intelligibility of ideal binary masked speech

Most binary-mask studies assume a fine time-frequency representation of the signal that may not be available in some applications (e.g., cochlear implants). This study assesses the effect of spectral resolution on intelligibility of ideal-binary masked speech. In Experiment 1, speech corrupted in noise at -5 to 5 dB signal-to-noise ratio (SNR) was filtered into 6-32 channels and synthesized using the ideal binary mask. Results with normal-hearing listeners indicated substantial improvements in intelligibility with 24-32 channels, particularly in -5 dB SNR. Results from Experiment 2 indicated that having access to the ideal binary mask in the F1/F2 region is sufficient for good performance.     

Experimental constraints on the spin and parity of the Lambdac(2880)+

We report the results of several studies of the Lambda(c)(+)pi(+)pi(-)X final state in continuum e(+)e(-) annihilation data collected by the Belle detector. An analysis of angular distributions in Lambda(c)(2880)(+)-->Sigma(c)(2455)(0,++)pi(+,-) decays strongly favors a Lambda(c)(2880)(+) spin assignment of 5/2 over 3/2 or 1/2. We find evidence for Lambda(c)(2880)(+)-->Sigma(c)(2520)(0,++)pi(+,-) decay and measure the ratio of Lambda(c)(2880)(+) partial widths Gamma(Sigma(c)(2520)pi)/Gamma(Sigma(c)(2455)pi)=0.225+/-0.062+/-0.025. This value favors the Lambda(c)(2880)(+) spin-parity assignment of 5/2(+) over 5/2(-). We also report the first observation of Lambda(c)(2940)(+)-->Sigma(c)(2455)(0,++)pi(+,-) decay and measure Lambda(c)(2880)(+) and Lambda(c)(2940)(+) mass and width parameters. These studies are based on a 553 fb(-1) data sample collected at or near the Upsilon(4S) resonance at the KEKB collider.     

Cs(8S)态的碰撞转移和高位原子态的激发

在Cs蒸气中,二步激发Cs原子至8S态,研究了其碰撞转移和高位原子态的产生过程.在1016～1017 cm-3密度范围内,测量了碰撞激发转移8S 6S→6D 6S的速率系数.由测得的荧光强度随密度的变化关系,得到k6D=(2.4±0.5)×10-10 cm3·s-1.同时研究了碰撞能量合并过程5D 5D→nL 6S(nL=9D,11S,7F),5D态是由8S→7P→5D的辐射跃迁产生的.由以前测量过的6P 5D 6S 7D的转移速率系数以及6P态的原子密度,结合荧光强度比得到碰撞能量合并过程的速率系数,对于9D,11S和7F各态,其平均值分别为(6.4±3.2)×10-10,(1.0±0.5)×10-10和(8.4±4.2)×10-10 cm3·s-1.     

Radiative transition probabilities in ions of the silver isoelectronic sequence

The wave functions of one-electron states above the 4d ¹⁰ core have been calculated within the relativistic perturbation theory with a zero-order model potential. The wavelengths and probabilities of electric dipole transitions in an Ag-like ion have been calculated for the 5s-5p, 5p-5d, 5d-5f, and 4f-5d transitions. The data obtained are compared with the results of calculations by the relativistic Hartree-Fock method and within the relativistic many-body perturbation theory. The theoretical results are compared with experimental data on the lifetimes of energy levels in Ag-like ions.     

Holographic multivergence target for subjective measurement of the spherical power error of the human eye

We have fabricated a single hologram with which to determine the spherical refractive error of the human eye in the range 5 to -2.5 diopters (D) with an accuracy of +/-0.25 D in a single step. The amplitude of accommodation is determined at the same time. The hologram is a record of 16 targets, each of which has a different image vergence in the range 5 to -2.5 D in steps of 0.5 D. This idea can be applied readily to any dioptric range. The measurement method is simple, fast, and reliable.