Discovery of a novel synthetic phosphatase from a bead-bound combinatorial library

Using split/pool encoded synthesis and a colorimetric catalysis assay, a number of synthetic phosphatase catalysts were developed.     

Decay of dipolar order in diamagnetic and paramagnetic proteins and protein gels

Magnetic relaxation in solids may be complicated by the creation and loss of dipolar order at finite rates. In tissues the molecular and spin dynamics may be significantly different because of the relatively high concentration of water. We have applied a modified Jeneer-Broekaert pulse sequence to measure dipolar relaxation rates in both dry and hydrated protein systems that may serve as magnetic models for tissue. In lyophilized and dry serum albumin, the dipolar relaxation time, T(1D) is on the order of 1 ms and is consistent with earlier reports. When hydrated by deuterium oxide, the dipolar relaxation times measured were on the order of tens of microseconds. When paramagnetic centers are included in the protein, the Jeneer-Broekaert echo decay times became the order of the decay time for transverse magnetization, i.e., the order of 10 micros or less. In the hydrated or paramagnetic systems, the dipolar relaxation times are too short to require inclusion in the quantitative analysis of magnetization transfer experiments.     

Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films

We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La_0.7Ca_0.3MnO₃ (LCMO) and YBa₂Cu₃O_7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO₃ (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on the LAO (control) and LCMO side of the substrate. Critical current, I _c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed that while the control side showed a J _c of ∼ 2 × 10⁶ A/cm², the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J _c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of J _c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length has been quantified. A control experiment carried out with LaNiO₃ deposited by PLD on YBCO did not show any evidence of self-injection.     

Statistical and Numerical Considerations of Backus-Average Product Approximation

In this paper, we examine the applicability of the approximation, \(\overline{f g}\approx \overline{f}\,\overline{g}\), within Backus (J. Geophys. Res. 67(11):4427–4440, 1962) averaging. This approximation is a crucial step in the method proposed by Backus (J. Geophys. Res. 67(11):4427–4440, 1962), which is widely used in studying wave propagation in layered Hookean solids. According to this approximation, the average of the product of a rapidly varying function and a slowly varying function is approximately equal to the product of the averages of those two functions.Considering that the rapidly varying function represents the mechanical properties of layers, we express it as a step function. The slowly varying function is continuous, since it represents the components of the stress or strain tensors. In this paper, beyond the upper bound of the error for that approximation, which is formulated by Bos et al. (J. Elast. 127:179–196, 2017), we provide a statistical analysis of the approximation by allowing the function values to be sampled from general distributions.Even though, according to the upper bound, Backus (J. Geophys. Res. 67(11):4427–4440, 1962) averaging might not appear as a viable approach, we show that—for cases representative of physical scenarios modelled by such an averaging—the approximation is typically quite good. We identify the cases for which there can be a deterioration in its efficacy.In particular, we examine a special case for which the approximation results in spurious values. However, such a case—though physically realizable—is not likely to appear in seismology, where Backus (J. Geophys. Res. 67(11):4427–4440, 1962) averaging is commonly used. Yet, such values might occur in material sciences, in general, for which Backus (J. Geophys. Res. 67(11):4427–4440, 1962) averaging is also considered.     

Magnetoelectric effect in cobalt ferrite-barium titanate composites and their electrical properties

CoFe₂O₄-BaTiO₃ composites were prepared using conventional ceramic double sintering process with various compositions. Presence of two phases in the composites was confirmed using X-ray diffraction. The dc resistivity and thermoemf as a function of temperature in the temperature range 300 K to 600 K were measured. Variation of dielectric constant (ɛ′) with frequency in the range 100 Hz to 1 MHz and also with temperature at a fixed frequency of 1 kHz was studied. The ac conductivity was derived from dielectric constant (ɛ′) and loss tangent (tan δ). The nature of conduction is discussed on the basis of small polaron hopping model. The static value of magnetoelectric conversion factor has been studied as a function of magnetic field.     

Energy dependence of multiplicity in proton-nucleus collisions and models of multiparticle production

This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR _em = 〈n _s〉/〈n _ch〉, where 〈n _ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R _em = 1·71 implies an effectiveA-dependence ofR _A =A ^0.18,i.e., a very weak dependence. Predictions ofR _em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production.     

Magnetic Fe doped ZnO nanofibers obtained by electrospinning

We demonstrate structural and room temperature magnetic properties of Fe doped ZnO nanofibers (NFs) obtained by electrospinning followed by calcination. The observed NFs, formed from crystalographically oriented, approximately 4.5?nm particles conglomerates, were approximately 200?nm in diameter. The reported synthesis of room temperature ferromagnetic Fe doped ZnO NFs is both facile and economical, and is therefore suggested as a generic method of fabricating biocompatible magnetic materials. The major substrates selected for the NFs synthesis (Zn, Fe) comprised of relatively low toxicity materials. Incorporating 10% Fe into ZnO does not modify the wurtzite crystal structure of the host material. No evidence of impurity phase was detected by either X-ray or electron diffraction. Magnetometry studies and Magnetic Force Microscopy imaging reveal a local ferromagnetic order that persists up to room temperature. We suggest that the observed phenomenon is either due to a mechanism mediated by presence of oxygen vacancies and/or is related to iron-rich precipitates.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.