A dedicated small‐angle X‐ray scattering beamline with a superconducting wiggler source at the NSRRC

At the National Synchrotron Radiation Research Center (NSRRC), which operates a 1.5 GeV storage ring, a dedicated small‐angle X‐ray scattering (SAXS) beamline has been installed with an in‐achromat superconducting wiggler insertion device of peak magnetic field 3.1 T. The vertical beam divergence from the X‐ray source is reduced significantly by a collimating mirror. Subsequently the beam is selectively monochromated by a double Si(111) crystal monochromator with high energy resolution (ΔE/E? 2 × 10^?4) in the energy range 5–23 keV, or by a double Mo/B₄C multilayer monochromator for 10–30 times higher flux (～10¹¹ photons s^?1) in the 6–15 keV range. These two monochromators are incorporated into one rotating cradle for fast exchange. The monochromated beam is focused by a toroidal mirror with 1:1 focusing for a small beam divergence and a beam size of ～0.9 mm × 0.3 mm (horizontal × vertical) at the focus point located 26.5 m from the radiation source. A plane mirror installed after the toroidal mirror is selectively used to deflect the beam downwards for grazing‐incidence SAXS (GISAXS) from liquid surfaces. Two online beam‐position monitors separated by 8 m provide an efficient feedback control for an overall beam‐position stability in the 10 µm range. The beam features measured, including the flux density, energy resolution, size and divergence, are consistent with those calculated using the ray‐tracing program SHADOW. With the deflectable beam of relatively high energy resolution and high flux, the new beamline meets the requirements for a wide range of SAXS applications, including anomalous SAXS for multiphase nanoparticles (e.g. semiconductor core‐shell quantum dots) and GISAXS from liquid surfaces.     

Optical Non‐Linearity from Montmorillonite Intercalated with a Chromophore‐Containing Dendritic Structure: A Self‐Assembly Approach

Chromophore‐containing dendritic structures (G1, G2) are utilized to intercalate layered silicates, which results in a large d‐spacing up to 126 Å. An exfoliated morphology is obtained by mixing the dendritic structure intercalated layered silicates with polyimide in N,N‐dimethylacetamide solution. The dendritic structures attached on the clay template would arrange in a non‐centrosymmetric manner. This self‐assembled arrangement brought about the electro‐optical coefficients of 5–6 pm · V⁻¹ for these relatively low chromophore‐containing organic/inorganic nanocomposites without resorting to poling. Excellent temporal stability (100 °C) is also achieved.

     

Abstract Riccati equations in an L1 space of finite measure and applications to transport theory

We consider operator-valued Riccati initial-value problems of the form R′(t) + TR(t) + R(t)T = TA(t) + TB(t)R(t) + R(t)TC(t) + R(t)TD(t)R(t), R(0) = R₀. Here A to D and R₀ have values as non-negative bounded linear operators in L¹ (μ), where μ is a finite measure, and T is a closed non-negative operator in L¹ (μ) satisfying additional technical conditions. For such problems the notion of strongly mild solutions is defined, and local existence and uniqueness theorems for such solutions are established. The results of the analysis are applied to the reflection kernels with both isotropically scattering homogeneous and anisotropically scattering inhomogeneous medium.     

Growth and properties of GaSb, Ga1-xInxSb and Ga1-xAlxSb epilayers by MOCVD

GaSb-based compound semiconductors are suitable materials for low-noise avalanche photo-diodes(APD's) and long wavelength laser diodes and photodetectors. In this paper, we review the metal organic chemical vapor deposition (MOCVD) growth conditions and the properties of GaSb, GaInSb and AlGaSb epitaxial layers, including the effects of III/V ratio, growth temperature, pressure and growth rate on electrical quality, optical properties, surface morphology and solid distribution coefficients.     

Nonlinear dynamics of self-pulsating laser diodes under external drive

A self-pulsating laser diode under external drive shows the nonlinear dynamical effects of two competing frequencies. One can establish a route to chaos by increasing the modulation current. However, when the modulation frequency is varied, the chaotic state is suddenly destroyed at the harmonic frequencies of the self-pulsating frequency. This approach therefore offers a simple chaotic light source for possible optical chaotic communication.     

Adsorption of tannic acid, humic acid, and dyes from water using the composite of chitosan and activated clay

Chitosan is a well-known excellent adsorbent for a number of organics and metal ions, but its mechanical properties and specific gravity should be enhanced for practical operation. In this study, activated clay was added in chitosan slurry to prepare composite beads. The adsorption isotherms and kinetics of two organic acids (tannic acid, humic acid) and two dyes (methylene blue, reactive dye RR222) using composite beads, activated clay, and chitosan beads were compared. With composite beads as an adsorbent, all the isotherms were better fitted by the Freundlich equation. The adsorption capacities with composite beads were generally comparable to those with chitosan beads but much larger than those with activated clay. The pseudo-first-order and pseudo-second-order equations were then screened to describe the adsorption processes. It was shown that the adsorption of larger molecules such as tannic acid (MW, 1700 g mol(-1)), humic acid, and RR222 from water onto composite beads was better described by the pseudo-first-order kinetic model. The rate parameters of the intraparticle diffusion model for adsorption onto such adsorbents were also evaluated and compared to identify the adsorption mechanisms.     

White light emitting diodes (LEDs) with good color rendering indices (CRI) and high luminous efficiencies by the encapsulation of mixed and double-deck phosphors

In this paper, white light emitting diodes (LEDs) with good color rendering indices (CRI) and high luminous efficiencies have been fabricated by the encapsulation of mixed and double-deck phosphors. Experimental results revealed that white LEDs with the encapsulation of double-deck phosphors exhibited better CRI and higher luminous efficiencies than those with the encapsulation of mixed phosphors because no secondary excitation took place. The hue, CRI, and luminous efficiencies of white LEDs with double-deck phosphors under 200 mA were CIE_x,y = (0.357, 0.348), 90, and 62.3 lm/W, respectively while the hue, CRI, and luminous efficiencies of white LEDs with mixed phosphors under 200 mA were CIE_x,y = (0.366, 0.354), 89, and 56.5 lm/W, respectively.     

Conductive carbon tape as a sample platform for microwave-based MALDI MS detection of proteins and phosphoproteins

In this study, we developed a novel microwave-assisted protein preparation and digestion method for matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry analysis and identification of proteins that involves using conductive carbon tape as a sample platform for sample preparation (reduction and alkylation) and digestion under microwave heating and as a plate for MALDI analysis. This method allows for the enzymatic digestion products of proteins to be directly analyzed by MALDI mass spectrometry and results in a marked reduction in sample loss. Our protocol requires only a small volume (1 μL) of reaction solvent, which increases the frequency of enzyme-to-protein contact, thereby resulting in more efficient digestion of sample than conventional in-solution digestion methods. To test this protocol, we used magnetic iron (II, III) oxide nanoparticles as concentrating probes to enrich phosphopeptides from a mixture of peptides in enzymatically digested protein samples. We found that the one-pot on-tape-based protein preparation and digestion under microwave heating combined with the on-tape-based enrichment method not only dramatically reduced the time required for phosphopeptides analysis but also allowed for the simultaneous identification of phosphoproteins. The advantages of our protocol include ease of use, high digestion efficiency, high specificity, and rapid (15 min) identification of proteins and enrichment of phosphopeptides in a mixture of enzymatically digested protein samples.     

MEMS microwell and microcolumn arrays: novel methods for high-throughput cell-based assays

Although the cell-based assay is becoming more popular for high throughput drug screening and the functional characterization of disease-associated genes, most researchers in these areas do not use it because it is a complex and expensive process. We wanted to create a simple method of performing an on-chip cell-based assay. To do this, we used micro-electro-mechanical systems (MEMS) to fabricate a microwell array chip comprised of a glass substrate covered with a photoresist film patterned to form multiple microwells and tested it in two reverse transfection experiments, an exogenous gene expression study and an endogenous gene knockdown study. It was used effectively in both. Then, using the same MEMS technology, we fabricated a complementary microcolumn array to be used as a drug carrier device to topically apply drugs to cells cultured in the microwell array. We tested the effectiveness of microwell-microcolumn on-chip cell-based assay by using it in experiments to identify epidermal growth factor receptor (EGFR) activity inhibitors, for which it was found to provide effective high throughput and high content functional screening. In conclusion, this new method of cell-based screening proved to be a simple and efficient method of characterizing gene function and discovering drug leads.