Formation and optical properties of gold nanoparticles synthesized in the presence of double-hydrophilic block copolymers

In this article, we present a systematic, controlled synthesis of water-dispersed, polymer-stabilized Au nanoparticles with different sizes by either self-reduction or ultraviolet (UV) irradiation-enhanced reduction in the presence of double hydrophilic block copolymers with different functional patterns. The morphology of the particles was found to be spherical, triangular, truncated triangular, and hexagonal under various conditions. In addition, both the particle size and shape could be controlled by variation of the functional group pattern of the block copolymers. With a hexacyclen functional block, we achieved a perfect match to the Au (111) face, resulting in extremely thin free-standing triangular and hexagonal nanoplatelets that show interference patterns in the electron beam due to deformations in the sub-Angstrom range. UV-visible spectra show that the plasmon absorption band can be fine tuned, depending on the type of the polymer and the irradiation power. The influence of the functional polymer groups and the irradiation on the formation of gold nanoparticles was investigated in more detail.     

Thiocyanate Ion Promoted E ⇌ Z Isomerization of a-Bromo-β,β-Diactivated Electrophilic Olefins: An Apparent High Nucleofugality of NCS−

(E)-β-Chloro-α-phenylcinnamaldehyde and (E)- and (Z)-methyl α-tert-butoxycarbonyl-p-nitro-β-bromocinnamates in the presence of NCS⁻ ion in acetonitrile undergo an (E) ⇌ (Z) isomerization which is faster than the vinylic substitution. (E)- and (Z)-methyl α-cyano-β-mesyloxy- (and β-chloro-) p-nitrocinnamates undergo substitution under similar conditions without preceding isomerization. MO calculations gave the energy differences between the eclipsed and the perpendicular conformers of carbanions ⁻CH₂CH₂X and (NC)₂ČH₂X (X = Cl, NCS). These rotational barriers denote the hyperconjugation stabilization energy resulting from interaction of the C-X bond and the 2p(C⁻) orbital. Both HCA values are high, those for X = Cl being 15–20% higher than for X = NCS. The limited literature data on the nucleofugality of NCS⁻ suggests that it can have a nucleofugality which is not much lower than that of Cl⁻ or Br⁻. Consequently, NCS⁻-catalyzed isomerizations of electrophilic vinyl chlorides and bromides, which involve a 180° internal rotation followed by a faster expulsion of NCS⁻ than of Cl⁻ from the initially formed intermediate carbanion Y'Y⁻C-C(R)(Cl)SCN, are not unreasonable, especially if solvation, which was not included in the calculations, plays an important role in the nucleofuge expulsion process.     

Supervisors' role conflict and role ambiguity differential relations with performance ratings of subordinates and the moderating effect of screening ability.

Survey data obtained from two independent samples of supervisors (Ns?=?68 and 109) supported the prediction that supervisors' experience of role conflict would correlate positively with their reported tendency to deliberately inflate subordinates' performance ratings. Contrary to expectation, in neither sample did supervisors' screening ability emerge as a moderator of the relation between role conflict and rating inflation. In a third independent sample of supervisors (N?=?25), in which rating inflation was operationalized on the basis of actual performance ratings of subordinates, strong support was obtained for both the predicted positive association between role conflict and rating inflation as well as the predicted moderating effect of screening ability on this relation. By contrast, the authors did not anticipate that supervisors' experience of role ambiguity would be directly associated with, or interact with screening ability to predict, rating inflation. The data from all three samples were, in general, in line with these expectations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thin semiconductor films for radiative cooling applications

Passive cooling systems use simple low-cost techniques to provide summer comfort in warm climates and can also be used to keep food, liquids and other materials at temperatures below ambient. Radiative cooling devices require a convective shield that should reject solar radiation but be transparent to mid-IR thermal radiation. In this paper, chemical solution deposition of thin semiconductor films (PbS and PbSe) onto polyethylene foils for radiative cooling applications is described. Optical and structural characterizations of the films were performed using UV–Vis, FTIR spectroscopies, X-ray diffraction and electron microscopy. Additionally, pigmented shields, which exhibit good radiation scattering properties, were prepared by incorporation of ZnS or ZnO into polyethylene. We also studied a combination of pigmented polyethylene foils coated with thin films of PbS that show improved optical properties for cooling purpose.     

Modeling the conductance and DNA blockade of solid-state nanopores

We present measurements and theoretical modeling of the ionic conductance G of solid-state nanopores with 5-100 nm diameters, with and without DNA inserted into the pore. First, we show that it is essential to include access resistance to describe the conductance, in particular for larger pore diameters. We then present an exact solution for G of an hourglass-shaped pore, which agrees very well with our measurements without any adjustable parameters, and which is an improvement over the cylindrical approximation. Subsequently we discuss the conductance blockade ΔG due to the insertion of a DNA molecule into the pore, which we study experimentally as a function of pore diameter. We find that ΔG decreases with pore diameter, contrary to the predictions of earlier models that forecasted a constant ΔG. We compare three models for ΔG, all of which provide good agreement with our experimental data.     

Out-of-core solution of linear equations with non-symmetric coefficient matrix

This paper presents a package of FOTRAN IV subroutines for the out-of-core assembly and solution of a system of linear equations with a non-symmetric coefficient matrix, as met in many finite element applications. A skyline block storage mode is used for the coefficient matrix and a direct triangular decomposition method is employed to solve the system of linear equations. The block partitioning and storage mode of the coefficient matrix and the data transfer procedures for the assembly and solution of the system $\text{Ax = b}$ are discussed in detail. Examples from the field of fluid dynamics are presented.     

Superior mesenteric artery blood flow in celiac disease

Measurements of the hemodynamic parameters of the superior mesenteric artery were performed in 18 patients with celiac disease. Ten were studied at the time of diagnosis, when a small bowel biopsy showed a flat mucosa. The remaining eight patients were studied after complete clinical and histological recovery induced by a gluten-free diet. Doppler ultrasound flowmetry was used to measure blood flow in physiological and fasting conditions and after a mixed liquid test meal (Ensure-Plus). The results were compared with those of healthy subjects (N = 7). Mean basal flow was 50% higher in untreated celiac disease patients than in healthy controls and patients with chronic pancreatitis (P = NS). Postprandial mesenteric blood flow was significantly increased (P < 0.002) and delayed in time (P < 0.005) in celiac disease as compared to controls. Successful treatment reduced the mesenteric blood flow in celiac disease to normal values. Our study demonstrates that pathophysiological changes in the small bowel mucosa during the active clinical phase of celiac disease induce an abnormal splanchnic circulation.     

Noninvasive Transcutaneous Monitoring of Arterial Blood Gases

Valuable clinical and physiological data concerning the function of the cardiopulmonary system can be obtained from continuous monitoring of hemoglobin oxygen saturation (SaO2), oxygen tension (PO2), and carbon dioxide tension (PCO2) in blood. While periodic blood sampling is still used clinically to determine arterial blood gases, it is becoming apparent that the recent introduction of continuous noninvasive monitoring of blood gases can offer many advantages. This paper discusses the historical development and significant accomplishments of various techniques available for transcutaneous blood gas monitoring. Four major areas are reviewed: electrochemistry, spectrophotometry, mass spectrometry, and gas chromatography. For each of these techniques, the theoretical basis, instrumentation, and clinical applications are discussed.