Dynamics of the transient buildup of emission inNd3+-doped fiber lasers

The two-stage process of the transient buildup of emission in Nd ⁴⁺-doped fiber lasers is described both experimentally and theoretically. After switching on the pump, spontaneous emission increases first until the gain becomes sufficient to compensate for the cavity losses; the laser field then develops and reaches the steady state after more or less regular oscillations. During this second stage, an almost chaotic spiking is obtained either for high pumping rates and/or at low temperatures. The whole set of these dynamical scenarios is not described under the usual assumptions of uniform cavity losses over the whole field spectrum and of pure homogeneous broadening for the transition line, but rather a modified form of the Maxwell-Bloch equations which retains some frequency dependence for the losses in the cavity and the inhomogeneous broadening as well is proposed     

Sequential Compatibility Effects and Cognitive Control: Does Conflict Really Matter?

Although it is widely accepted that control mechanisms are necessary for human behavior to be adapted, very little is known about how such mechanisms are recruited. A suggestion to fill the gap was put forward by M. M. Botvinick, T. S. Braver, C. S. Carter, D. M. Barch, and J. D. Cohen (2001), who proposed the conflict-loop theory. This theory has been successful in accounting for the reduction of compatibility effects after an incompatible trial: The level of conflict being, on average, higher during an incompatible trial, more control occurs after such a trial. The authors have tested this prediction by sorting the trials on the basis of amount of conflict (quantified by the electromyographic activity) they presented. A reduction of the compatibility effect was observed after incompatible trials, but it was independent of the level of conflict on previous trials, suggesting that the conflict does not trigger changes in executive control. Consequences for the conflict monitoring model are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optical sensors for the determination of concentrated hydroxide

An optical sensor system has been developed for the determination of concentrated strong bases ([OH-] = 1-10 M). The base sensors consist of SiO2/ZrO2-organic polymer composites and doped high-pKa indicators. Films were obtained by spin-casting these composite materials on glass substrates and were used as sensor elements for the spectrometric determination of hydroxide. The hydrophilic nature of the mixed oxide SiO2/ZrO2 and its chemical stability in concentrated alkali made it attractive as support in the composites. The organic polymers in the composites either provided better mechanical stability and dye immobilization or enhanced OH- diffusion and sensor response. The composite sensors showed a relative standard deviation of less than 2%. The response time of a SiO2/ZrO2-Nafion composite (sensor 2) was short (5 s), and a small hysteresis was observed during reproducibility measurements with 1-4 M NaOH solutions. The sensors were found to be stable in 4 M NaOH during a 30-day durability test, showing a standard deviation of 3.0-4.7%. The diffusion kinetics and hysteresis performance of the sensors were also evaluated.     

Crown ether-doped sol-gel materials for strontium(II) separation

Hybrid organic/inorganic sol-gel materials containing an encapsulated crown ether ligand were found to selectively remove 91.4 +/- 1.3% of Sr2+ from a solution containing excess of competing ions such as Ca2+. The crown ether ligand, 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-bis(malonate) ligand (Na4oddm), with known high affinity for Sr2+ was encapsulated in hydrophilic SiO2 through a simple sol-gel process. Washing the Sr(2+)-loaded gel with acid or ethylenediaminetetraacetic acid disodium salt recovered the Sr2+ from the sol-gel sorbent and regenerated the doped gel for subsequent Sr2+ intake. The approach reported here is a new alternative to the use of crown ethers in metal ion separation through, for example, solvent extraction or the use of sorbents containing chemically grafted crown ether ligands.     

WAIS performance in unincarcerated groups of MMPI-defined sociopaths and normal controls.

Examined WAIS performance by 32 sociopaths and 33 normal controls, as defined by MMPI criteria. The 2 groups showed no differences in overall intellectual functioning. Differences in performance on some measures, however, challenge the idea that sociopaths are attentive only to aspects of the environment that lead to immediate gratification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Production of Carbopol 974P and Carbopol 971P pellets by extrusion-spheronization: optimization of the processing parameters and water content

Pellets obtained by extrusion-spheronization represent multiparticulate dosage forms whose interest in intestinal drug delivery can be potentiated and targeted through bioadhesive properties. However, adhesion itself makes the process difficult or even impossible. The problem of tackiness encountered with bioadhesive wet masses was previously eliminated by the use of electrolytes such as CaCl₂. This approach is known to reduce the viscosity of polyacrylic acids by disturbing the interactions between carboxylate groups on adjacent polymer molecules, thereby decreasing their bioadhesive properties. The present study aimed at producing pellets containing carbomers without addition of electrolytes in order to maintain their bioadhesive potentiality at its maximum. Carbopol® 974P (10%, 15% and 20%) and Carbopol® 971P (10%) were used in combination with Avicel® PH101. The extrusion speed (30, 45, 60, 90, and 150 rpm), spheronizer speed (350, 700, 960, 1000, and 1300 rpm), spheronization time (5, 10, 15, and 20 minutes) and amount of water (45%, 50%, 54%, and 58%) were optimized in order to obtain the highest yield of spherical pellets ranging 710-1000 µm in diameter. For pellets containing 10%, 15% Carbopol® 974P or 10% Carbopol® 971P and 45% water content, 30 rpm extrusion speed, 960 rpm, and 10 minutes spheronization speed and time led to the highest yields and sphericities, respectively, 72% and 0.91, 67% and 0.78, and 76% and 0.80. Production of pellets with 20% Carbopol® 974P could be achieved through the increase of the water content up to 58% and implementation of 30 rpm extrusion speed, 1300 rpm, and 10 minutes spheronization speed and time. The yield and sphericity were 42% and 0.78 respectively.     

Surface-enhanced Raman scattering substrate based on a self-assembled monolayer for use in gene diagnostics

The development of surface-enhanced Raman scattering (SERS)-active substrates for cancer gene detection is described. The detection method uses Raman active dye-labeled DNA gene probes, self-assembled monolayers, and nanostructured metallic substrates as SERS-active platforms. The mercaptohexane-labeled single-stranded DNA (SH-(CH(2))(6)-ssDNA)/6-mercapto-1-hexanol system formed on a silver surface is characterized by atomic force microscopy. The surface-enhanced Raman gene (SERGen) probes developed in this study can be used to detect DNA targets via hybridization to complementary DNA probes. The probes do not require the use of radioactive labels and have a great potential to provide both sensitivity and selectivity. The effectiveness of this approach and its application in cancer gene diagnostics (BRCA1 breast cancer gene) are investigated.     

Unexpected Formation of a Doubly Bridged Cyclo-1,2-dithian 1D Coordination Cu<Subscript>2</Subscript>I<Subscript>2</Subscript>-Containing Luminescent Polymer

Abstract  

CuI reacts instantaneously with butanedithiol in MeCN solution to form a sparingly soluble and thermally stable colorless polymeric material 1 of composition [(Cu₂I₂){HS(CH₂)₄SH}] _n . Raman and IR spectroscopy confirm the presence of Cu(I) bound S–H functions. Furthermore, small amounts of the yellow compound [{Cu(μ₂-I)₂Cu}(C₄H₈S₂)₂] _n 2 co-crystallize after several days. If the reaction mixture is exposed to air, polymeric 2 is isolated as the main product. An X-ray diffraction study reveals that 1D polymer 2 is assembled by rhomboid Cu(μ₂-I)₂Cu clusters (d Cu···Cu 2.6843(18) ?), which are linked through the S-atoms of six-membered 1,2-dithian heterocycles, thus generating an infinite ribbon. The low-frequency region in the Raman spectra show a striking similarity suggesting that polymers 1 and 2 bear the same cluster rhomboid Cu(μ₂-I)₂Cu clusters. The photophysics and luminescence properties of 2 have been studied experimentally and by means of DFT/TDDFT calculations.