Magnetic susceptibility and ESR studies of three complexes of chromium(III) and L-histidine. Ferromagnetic interactions in the dimeric complex [Cr(L-histidine)2(OH)]2

Three complexes of chromium(III) and histidine were investigated by variable temperature magnetic susceptibility and ESR. Two monomeric stereosoimers of Cr(L-histidine)₂(NO₃) were studied; the trans(imidazole) and trans(carboxylate)isomers exhibited Curie-Weiss behaviour in the 6–300 K temperature region. The magnetic susceptibility of the related binuclear complex, [Cr(L-histidine)₂(OH)]₂, showed ferromagnetic behaviour at low temperature (J/k = +0.15 K) lending strong support to the proposed hydroxo-bridged structure.     

Λ and K0 production in p↑p interactions at 6 GeV/c

Results on K⁰ and Λ production in p↑p interactions at 6 GeV are presented. The data are from an exposure of the Argonne 12 ft bubble chamber to a 60% transversely polarized proton beam. Results include data on Λ and K⁰ inclusive production, and on the reactions p↑p → pΛK⁺(pΣ⁰K⁺). The beam asymmetry parameter for $\text{p}\text{↑}\text{p}\text{→}\text{K}{}^0\text{(}\text{K}{}^0\text{) +}\text{X}$ is determined to be (?0.52 ± 0.12).     

Incoherent neutral pion photoproduction on 12C

We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The 12C(gamma,pi(0))(12)C*(4.4 MeV) reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a pi(0) spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the Delta in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a Delta-hole model.     

Modulation of the absorption coefficient at 1.3 μm in Ge/SiGe multiple quantum well heterostructures on silicon

We report modulation of the absorption coefficient at 1.3?μm in Ge/SiGe multiple quantum well heterostructures on silicon via the quantum-confined Stark effect. Strain engineering was exploited to increase the direct optical bandgap in the Ge quantum wells. We grew 9?nm-thick Ge quantum wells on a relaxed Si0.22Ge0.78 buffer and a contrast in the absorption coefficient of a factor of greater than 3.2 was achieved in the spectral range 1290-1315?nm.     

THE PHOTOADDITION OF NUCLEOPHILES TO URACIL

Abstract— Quantum yields for 254 nm ultraviolet photoaddition of the nucleophiles hydrazine, HCN, HSO₃^-, methyl amine, and BH₄^- to uracil have been measured; the quantum yields for hydrazine, HCN, and HSO₃^- additions are pH-dependent. The nucleophiles sulfide, azide, chloride, bromide, iodide, nitrite and thiocyanate failed to photo–add under similar conditions. These reactions are interpreted as 1,4-additions to the conjugated enone system of the anti-aromatic compound, uracil; as suggested by S. Y. Wang (Wang and Nnadi, 1968). The nuclear magnetic resonance (NMR) spectrum of the photohydrate of uracil-5-d-showed that the proton was added to the 5-position in a stereochemically random manner. The photoaddition of HSO₃^- takes place at much lower concentrations than required for the thermal addition of this anion and is also stereochemically random.     

Cartilage‐Specific Near‐Infrared Fluorophores for Biomedical Imaging

A novel class of near‐infrared fluorescent contrast agents was developed. These agents target cartilage with high specificity and this property is inherent to the chemical structure of the fluorophore. After a single low‐dose intravenous injection and a clearance time of approximately 4 h, these agents bind to all three major types of cartilage (hyaline, elastic, and fibrocartilage) and perform equally well across species. Analysis of the chemical structure similarities revealed a potential pharmacophore for cartilage targeting. Our results lay the foundation for future improvements in tissue engineering, joint surgery, and cartilage‐specific drug development.     

连续波锁模P_r~（3＋）：YLF激光器

本文报导了采用氩离子激光器来泵浦Ｒｒ￣（３＋）：ＹＬＦ晶体，应用声光调制器实现了主动锁模；同时应用振动─高反射平面镜也实现了被动锁模，两种锁模均得到了ｐｓ光脉冲。据作者了解这是这种晶体材料的第一次锁模运转。     

Kinetic models for dilute solutions of dumbbells in non-homogeneous flows revisited

We propose a two-fluid theory to model a dilute polymer solution assuming that it consists of two phases, polymer and solvent, with two distinct macroscopic velocities. The solvent phase velocity is governed by the macroscopic Navier–Stokes equations with the addition of a force term describing the interaction between the two phases. The polymer phase is described on the mesoscopic level using a dumbbell model and its macroscopic velocity is obtained through averaging. We start by writing down the full phase-space distribution function for the dumbbells and then obtain the inertialess limits for the Fokker–Planck equation and for the averaged friction force acting between the phases from a rigorous asymptotic analysis. The resulting equations are relevant to the modelling of strongly non-homogeneous flows, while the standard kinetic model is recovered in the locally homogeneous case.     

A non-homogeneous constitutive model for human blood: Part II. Asymptotic solution for large Péclet numbers

In tube flow of healthy human blood the formed elements typically migrate away from vessel walls, leaving a plasma-rich, cell-depleted region there. In larger tubes (corresponding in size to arteries, for example) and at physiologically realistic flow rates, very thin wall boundary layers may develop which, nonetheless, have an impact upon the bulk flow properties. In this paper the non-homogeneous blood model of Moyers-Gonzalez et al. [M. Moyers-Gonzalez, R.G. Owens and J. Fang, A non-homogeneous constitutive model for human blood. Part I. Model derivation and steady flow, submitted for publication] is used in combination with a novel matched asymptotic method, to study the boundary layer behaviour of the steady tube flow of blood at high Péclet numbers Pe$Pe$ and in vessels of diameters corresponding to those of small arteries. A boundary layer thickness of O(Pe^−1/2)$O(P{\text{e}}^{-1/2})$ is predicted. In the absence of stress diffusion (the homogeneous case, with Pe=∞$Pe=\infty$) no cell migration takes place and the size and number density of red cell aggregates along the axis of symmetry remains constant at all flow rates. In the non-homogeneous case, however, even at very high values of Pe$Pe$, particles migrate, introducing a thin apparent slip layer next to the wall and affecting the aggregate distribution throughout the flow, even on the axis of symmetry.