Properties of the HYSCORE spin echo signal

In hyperfine sublevel correlation spectroscopy (HYSCORE), the finite duration of the microwave pulses leads to an incomplete inversion of the electron spin magnetization by the third pulse, which results in a significant admixture of stimulated ESEEM to HYSCORE ESEEM. This virtually unavoidable contribution of stimulated ESEEM seriously hampers the analysis of the modulation amplitudes in HYSCORE. In this work, we analyze the properties of the spin echo signals contributing to the composite HYSCORE signal. Based on this analysis, we propose the strategies of HYSCORE data acquisition and processing that allow one to practically eliminate the contribution of the stimulated echo and make the HYSCORE ESEEM analyzable in quantitative terms.     

Instability of the free boundary of a water layer accelerated by a Taylor wave

The instability of the free boundary of a thin (1 mm) water layer under the action of a Taylor wave (80 MPa), which is created by a laser pulse, has been experimentally studied. The experimental results demonstrate the capabilities of the laser Doppler method for the continuous recording of a flying object (PDV method) [O. T. Strand, D. R. Goosman, and C. Martinez, Rev. Sci. Instrum. 77, 0831081 (2006)] for studying this problem.     

Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

A generalized Khintchine inequality in rearrangement invariant spaces

Let X be a separable or maximal rearrangement invariant space on [0, 1]. Necessary and sufficient conditions are found under which the generalized Khintchine inequality

$\left\| {\sum\limits_{k = 1}^\infty {f_k } } \right\|_X \leqslant C\left\| {\left( {\sum\limits_{k = 1}^\infty {f_k^2 } } \right)^{1/2} } \right\|_X $

holds for an arbitrary sequence {?_k} _k=1 ^∞ ? X of mean zero independent variables. Moreover, the subspace spanned in a rearrangement invariant space by the Rademacher system with independent vector coefficients is studied.

     

Optoheterodyne Doppler measurements of the ballistic expansion of the products of the shock wave-induced surface destruction: Experiment and theory

The results of optoheterodyne Doppler measurements of the ballistic expansion of the products of surface destruction under shock-wave loading are presented. The possibility of determining the physical characteristics of a rapidly flying dust cloud, including the microparticle velocities, the microparticle sizes, and the areal density of the dust cloud, is shown. A compact stand for performing experiments on shock-wave loading of metallic samples is described. Shock-wave loading is performed by a 100-µm-thick tantalum flyer plate accelerated to a velocity of 2.8 km/s. As the samples, lead plates having various thicknesses and the same surface roughness are used. At a shock-wave pressure of 31.5 GPa, the destruction products are solid microparticles about 50 µm in size. At a pressure of 42 and 88 GPa, a liquid-drop dust cloud with a particle size of 10–15 µm is formed. To interpret the spectral data on the optoheterodyne Doppler measurements of the expansion of the surface destruction products (spalled fragments, dust microparticles), a transport equation for the function of mutual coherence of a multiply scattered field is used. The Doppler spectra of a backscattered signal are calculated with the model developed for the dust cloud that appears when a shock wave reaches the sample surface at the parameters that are typical of an experimental situation. Qualitative changes are found in the spectra, depending on the optical thickness of the dust cloud. The obtained theoretical results are in agreement with the experimental data.     

Intramolecular Hydrogen Bonding Restricts Gd–Aqua-Ligand Dynamics

Aqua ligands can undergo rapid internal rotation about the M−O bond. For magnetic resonance contrast agents, this rotation results in diminished relaxivity. Herein, we show that an intramolecular hydrogen bond to the aqua ligand can reduce this internal rotation and increase relaxivity. Molecular modeling was used to design a series of four Gd complexes capable of forming an intramolecular H-bond to the coordinated water ligand, and these complexes had anomalously high relaxivities compared to similar complexes lacking a H-bond acceptor. Molecular dynamics simulations supported the formation of a stable intramolecular H-bond, while alternative hypotheses that could explain the higher relaxivity were systematically ruled out. Intramolecular H-bonding represents a useful strategy to limit internal water rotational motion and increase relaxivity of Gd complexes.     

Unusual electronic state of tin dopant atoms in surface layers of NiTiO<Subscript>3</Subscript>

The ¹¹⁹Sn Mössbauer spectra of polycrystalline NiTiO₃ samples impregnated with a solution containing 0.3 at % Sn⁴⁺ are evidence that annealing in H₂ converts tin into the state with the electron density |Ψ(0)|² on ¹¹⁹Sn nuclei corresponding to “Sn³⁺” ions. The stabilization of tin atoms in such an untypical formal oxidation state occurs at a depth of no more than 2–3 nm from the surface of titanate crystallites. It was revealed that the Sn³⁺ ions are not subjected to spin polarization even at temperatures considerably lower than the Néel temperature of NiTiO₃, which can be explained by their location in the Ni²⁺ positions. The formation of Sn3+ prevents the further reduction of tin to the divalent state and, hence, precludes localization of ¹¹⁹Sn probe cations in positions at the interface.     

Interpolation of bilinear operators in Marcinkiewicz spaces

A theorem on interpolation of bilinear operators in symmetric Marcinkiewicz spaces is proved. It follows from the general bilinear results for the Peetre and Peetre-Gustavsson interpolation functors. Translated fromMatematicheskie Zametki, Vol. 60, No. 4, pp. 483–494, October, 1996.