Detection of d-serine in neural samples by saccharide enhanced chiral capillary electrophoresis

Highly fluorescent enantiomeric derivatives of d/l-serine from naphthalene-2,3-dicarboxaldehyde were resolved by hydroxypropyl-γ-cyclodextrin modified capillary electrophoresis using a saccharide as an enhancing chiral selector. Four saccharides, i.e. d-(+)-glucose, d-(−)-fructose, β-lactose, and sucrose were tested. Similar enhancing effects were observed. Coupled with laser induced fluorescence detection, this separation was applied to the determination of d-serine in neural samples including rat brain tissues, Aplysia ganglia, microdialysates from rat brain, and Aplysia individual neurons. High levels of d-serine were found in certain rat brain sections including hippocampus and striatum. d-Serine was also found to occur in Aplysia ganglia, but interestingly, it was not detected in single neurons isolated from Aplysia ganglia.     

Calculations of the axial and azimuthal fluxes contained in a type II superconducting cylinder in a force-free configuration

The force free equation, J∧ B = 0, is expressed in an undimensionalized form for a reversible, Type II, superconducting cylinder carrying a transport current in a longitudinal magnetic field. Using a simple model, the form of the current distribution inside the specimen is varied, and this equation is solved to yield the total axial and azimuthal fluxes. For fixed values of the transport current and applied field it is shown that the total axial flux insensitive to the current distribution, whilst the total azimthal flux varies considerably. It is concluded, therefore, that measurements of the axial magnetization alone cannot discriminate between various force-free models.     

Dynamics of a tunable superfluid junction

We study the population dynamics of a Bose-Einstein condensate in a double-well potential throughout the crossover from Josephson dynamics to hydrodynamics. At barriers higher than the chemical potential, we observe slow oscillations well described by a Josephson model. In the limit of low barriers, the fundamental frequency agrees with a simple hydrodynamic model, but we also observe a second, higher frequency. A full numerical simulation of the Gross-Pitaevskii equation giving the frequencies and amplitudes of the observed modes between these two limits is compared to the data and is used to understand the origin of the higher mode. Implications for trapped matter-wave interferometers are discussed.     

Isotope-Labeled RNA Building Blocks for NMR Structure and Dynamics Studies

RNA structural research lags behind that of proteins, preventing a robust understanding of RNA functions. NMR spectroscopy is an apt technique for probing the structures and dynamics of RNA molecules in solution at atomic resolution. Still, RNA analysis by NMR suffers from spectral overlap and line broadening, both of which worsen for larger RNAs. Incorporation of stable isotope labels into RNA has provided several solutions to these challenges. In this review, we summarize the benefits and limitations of various methods used to obtain isotope-labeled RNA building blocks and how they are used to prepare isotope-labeled RNA for NMR structure and dynamics studies.     

Photocaged pendent thiol polymer brush surfaces for postpolymerization modifications via thiol‐click chemistry

In this work, a postpolymerization surface modification approach is reported that provides pendent thiol functionality along the polymer brush backbone using the photolabile protection chemistry of both o‐nitrobenzyl and p‐methoxyphenacyl thioethers. Poly(2‐hydroxyethyl methacrylate) (pHEMA) brushes were synthesized via surface‐initiated atom transfer radical polymerization, after which the pHEMA hydroxyl groups were esterified with 3‐(2‐nitrobenzylthio)propanoic acid or 3‐(2‐(4‐methoxyphenyl)‐2‐oxoethylthio)propanoic acid to provide the photolabile protected pendent thiols. Addressing the protecting groups with light not only affords spatial control of reactive thiol functionality but enables a plethora of thiol‐mediated transformations with isocyanates and maleimides providing a modular route to create functional polymer surfaces. This concept was extended to block copolymer brush architectures enabling the modification of the chemical functionality of both the inner and outer blocks of the block copolymer surface. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Three-wave interactions between fast-ion modes in the National Spherical Torus Experiment

Simultaneous bursts of energetic particle mode (EPM) and toroidicity-induced Alfvén eigenmode (TAE) activity that correlate with significant fast-ion loss are observed in beam heated plasmas. Three-wave interactions between these modes are conclusively identified, indicating fixed phase relationships. This nonlinear coupling concentrates the energy of the TAEs into a toroidally localized perturbation frozen in the frame of a rigid, toroidally rotating structure formed by the EPMs. This redistribution of energy is significant because it will modify the effect of the TAEs on fast-ion loss.     

Determination of the field dependence of the intergranular critical current in a YBCO tube by horizontal traversals

The magnetic flux density in the cavity of a sintered tube of Yttrium Barium Copper Oxide (YBCO) is measured as a function of H, the axial magnetic field impressed and removed after zero field cooling (ZFC). We note that, in a short thick-walled hollow cylinder of a weak-linked polycrystalline high-T_c superconductor, the magnetic field in the cavity of the tube, H_z hole, rises above the applied field H when it is initially increasing. Consequently the standard approach to determine the critical current density from an ascending sweep of H alone, or a descending sweep alone cannot be exploited. However the field dependence of the intergranular critical current density J_cm can be reliably obtained from the horizontal traversals of H_z hole vs H. Comparison of the experimental data with model calculations for the horizontal traversals of the hysteresis curves show that the intergranular critical current density in the YBCO tube has a Kim-like field dependence. The magnetization of the grains has a significant influence on the flux density in the cavity of the tube.