Unique spin dynamics and unconventional superconductivity in the layered heavy fermion compound CeIrIn5: NQR evidence

We report measurements of the 115In nuclear spin-lattice relaxation rate ( 1/T1) between T = 0.09 and 100 K in the new heavy fermion (HF) compound CeIrIn5. At 0.4 < or = T< or = 100 K, 1/T1 is strongly T-dependent, which indicates that CeIrIn5 is much more itinerant than known Ce-based HFs. We find that 1/T1T, subtracting that for LaIrIn5, follows a (1 / T+straight theta)3/4 variation with straight theta = 8 K. We argue that this novel feature points to anisotropic, due to a layered crystal structure, spin fluctuations near a magnetic ordering. The bulk superconductivity sets in at 0.40 K below which the coherence peak is absent and 1/T1 follows a T3 variation, which suggests unconventional superconductivity with line-node gap.     

Thermal plumes and convection in highly compressible fluids

We present simple hydrodynamic equations of supercritical fluids close to the gas-liquid critical point. We numerically solve them to examine plume generation and convection under gravity. These results are in good agreement with the experiment [A. B. Kogan and H. Meyer, Phys. Rev. E 63, 056310 (2001)]. This Letter is a first study of transient behavior of convection, which is unique in compressible fluids due to the piston effect.     

Electrochemically Predicting Phenolic Substrates’ Suitability for Detection by Amperometric Laccase Biosensors

In this article, a rapid, simple method of electrochemically predicting a given phenolic substrate’s ability to be detected via amperometric laccase biosensors is proposed. Ten selected substrates were analysed by cyclic voltammetry and the relevant electrochemical parameters compared to biosensor kinetic parameters produced through amperometric detection of these substrates. The two major findings of this study were that biosensor detection sensitivities were found to correlate to: (1) peak oxidation potential of a substrate at unmodified electrodes and (2) the apparent Michaelis? Menten constant, K_m, of the biosensor‐substrate system, once corrections accounting for the relative differences in electroreducible product yield are made.     

Impact of the state of water on the dispersion stability of a skin cream formulation elucidated by magnetic resonance techniques

This study investigated the relationship between the state of water and the dispersion stability of a skin cream formulation. Hydrophilic ointments treated with a high-pressure wet-type jet mill were used as model formulations. Spin-lattice relaxation times (T(1)) were measured by magnetic resonance techniques to estimate the state of water in samples. A shorter T(1) relaxation time was obtained from samples with higher surfactant content, whereas the processing pressure of the jet mill and 1-week storage at 40 °C did not influence the T(1) relaxation time. Observations using scanning electron microscopy (SEM) showed that coalescence occurred in samples with lower surfactant contents (1.0% by weight) following 1-week storage at 40 °C. We also investigated samples prepared using a hydrophilic surfactant with a short polyethylene glycol (PEG) chain and with PEG-4000. From the change in T(1) relaxation times after removing the oil phase from samples by centrifugation, it was clarified that most of the surfactant was located on the surface of oil droplets. Furthermore, SEM observations showed that phase separation was facilitated as the PEG chain length of the surfactant shortened. Thus, a thin water layer over oil droplets is the most important factor for stabilizing their dispersion. This study provides proof-of-principle results on the contribution of the state of water to the dispersion stability of a skin cream formulation.     

Construction of a disorder variable from Steinhardt order parameters in binary mixtures at high densities in three dimensions

Using molecular dynamics simulation, we investigate the structural disorder in crystal, polycrystal, and glass in a Lennard-Jones binary mixture composed of N(1) + N(2) = 4096 particles at a low temperature in three dimensions. The size ratio σ(2)/σ(1) between the large and small particles is either 1.2 or 1.4. The crossovers among these states occur, as the composition of the large particles c = N(2)/(N(1) + N(2)) is varied. We define a disorder variable D(j) for each particle j in terms of local bond order parameters based on spherical harmonics (Steinhardt order parameters). Stacking faults and grain boundaries in fcc polycrystal and mesoscopic structural heterogeneity in glass are then visualized. At small c, disturbances of large particles is stronger for larger σ(2)/σ(1). At large c, the transition between glass and polycrystal occurs nearly discontinuously at c = c(c) ~ 0.8. At σ(2)/σ(1) = 1.4, microphase separation occurs in polycrystal states with c > c(c), where fcc crystal grains comprising the large particles are enclosed by amorphous layers composed of the two particle species.     

Improved Synthesis of the Biologically Active Methionine Analog,L-2-Amino-4-methoxy-cis-but-3-enoic Acid (L-cis-amb) Using an Electrophilic Glycinate Synthon

An improved synthesis of the methionine analog L-cis-AMB, is reported. The key step involves condensation of cis-methoxyvinyllithium with N-acetyl-α-bromoglycine methyl ester to give N-acetyl-DL-cis-AMB methyl ester, the penultimate intermediate of L-cis-AMB synthesis.     

Sheared solid materials

We present a time-dependent Ginzburg-Landau model of nonlinear elasticity in solid materials. We assume that the elastic energy density is a periodic function of the shear and tetragonal strains owing to the underlying lattice structure. With this new ingredient, solving the equations yields formation of dislocation dipoles or slips. In plastic flow high-density dislocations emerge at large strains to accumulate and grow into shear bands where the strains are localized. In addition to the elastic displacement, we also introduce the local free volumem. For very smallm the defect structures are metastable and long-lived where the dislocations are pinned by the Peierls potential barrier. However, if the shear modulus decreases with increasingm, accumulation ofm around dislocation cores eventually breaks the Peierls potential leading to slow relaxations in the stress and the free energy (aging). As another application of our scheme, we also study dislocation formation in two-phase alloys (coherency loss) under shear strains, where dislocations glide preferentially in the softer regions and are trapped at the interfaces.     

Nmr Structural Characterization of Oligo-N-Substituted Glycine Lead Compounds from a Combinatorial Library

Synthesis and screening of combinatorial librariesfor pharmaceutical lead discovery is a rapidlyexpanding field. Oligo-N-substituted glycines (NSGs)were one of the earliest sources of moleculardiversity in combinatorial libraries. In one of thefirst demonstrations of the power of combinatorialchemistry, two NSG trimers, CHIR-2279 and CHIR-4531,were identified as nM ligands for two 7-transmembraneG-protein-coupled receptors. The NMR characterizationof these two lead compounds was undertaken to verifycovalent connectivity and to determine solutionconformations, if any. The sequential chemical shiftassignments were performed using a new strategy forassigning ¹H and ¹³C resonances of NSGs. The conformational preferences were then determined inboth an aqueous co-solvent system and an organicsolvent to probe the effects of hydrophobic collapse. NSGs are expected to be more flexible than peptidesdue to the tertiary amide, with both cis andtrans amide bond conformations being accessible. Solution NMR studies indicate that although CHIR-2279and CHIR-4531 have identical backbones and termini,and very similar side chains, they do not display thesame solution conformational characteristics.     

A decision procedure using discrete geometry

A decision procedure is given which makes essential use of concepts in discrete geometry. The procedure decides for any one-state Turing machine with three-dimensional tape, whether or not it has an immortal configuration, i.e., it solves the uniform halting problem for such devices. The history and significance of the problem is examined. The solution is given with the main motivation of showing how traditional mathematical concepts can be used in decision procedures. The paper is introductory in the sense that all notions are carefully defined.