Fabrication and characterization of laser pulled platinum microelectrodes with controlled geometry

The development of a reproducible procedure for the fabrication of Pt disk-shaped microelectrodes with characteristic dimensions ranging from 50 nm to 1 μm in diameter was carried out using a laser pulling technique. The governing physical phenomena involved in their fabrication are discussed, and the importance of adding a critical quartz thinning step in the general procedure is demonstrated. The preparation of the microelectrodes involves sealing a platinum wire inside a quartz tubing using a pipet puller, thinning the composite material (platinum/quartz assembly), and laser pulling it to obtain two microelectrodes. The resulting microelectrodes display reproducible well-controlled geometry, which is important to downstream quantitative scanning electrochemical studies and imaging. Mechanical polishing of the microelectrode is required and remains the critical step in the fabrication of nanometer size electrodes. Following production, the microelectrodes are characterized by electron microscopy, scanning electrochemical microscopy, and cyclic voltammetry. Development of these microelectrodes is motivated by their subsequent application to electrocatalysis and their potential in theoretical study because of their well-defined geometry.     

A Direct Approach to Organic/Inorganic Semiconductor Hybrid Particles via Functionalized Polyfluorene Ligands

Controlled Suzuki–Miyaura coupling polymerization of 7′‐bromo‐9′,9′‐dioctyl‐fluoren‐2′‐yl‐4,4,5,5‐tetramethyl‐[1,3,2]dioxaborolane initiated by bromo(4‐tert‐butoxycarbonylamino‐phenyl)(tri‐tert‐butylphosphine)palladium ( 1 ) or bromo(4‐diethoxyphosphoryl‐phenyl)(tri‐tert‐butylphosphine)palladium ( 2 ) yields functionalized polyfluorenes (M_n = 4 × 10³ g mol^?1, M_w/M_n < 1.2) with a single amine or phosphonic acid, respectively, end‐group. High temperature synthesis of cadmium selenide quantum dots with these functionalized polyfluorenes as stabilizing ligands yields hybrid particles consisting of good quality (e.g. emission full width at half maximum of 30 nm; size distribution σ < 10%) inorganic nanocrystals with polyfluorene attached to the surface, as corroborated by transmission electron microscopy analysis and analytical ultracentrifugation. Sedimentation studies on particle dispersions show that a substantial portion (ca. half) of the phosphonic acid terminated polyfluorene ligands is bound to the inorganic nanocrystals, versus ca. 5% for the amino‐functionalized polyfluorene ligands. Single particle micro‐photoluminescence spectroscopy shows an efficient and complete energy transfer from the polyfluorene layer to the inorganic quantum dot.     

ENIG的耐蚀性：一种改进的浸金工艺

为了了解ENIG化学变化对浸金耐蚀性的形响,探讨了浸金电镀溶液的pH值和化学性质与结果所得到的浸金层的耐蚀性之间的关系。     

Individual differences in the subjective effects of the first cigarette of the day: A self-report method for studying tolerance.

Some smokers are more sensitive than others to the subjective effects of cigarettes, especially the first cigarette of the day. This report explored self-reported subjective effects to the first cigarette of the day and examined the extent to which heaviness of smoking and years smoking are associated with subjective effects. In 3 independent samples (ns?=?254, 116, 86), self-reports of light-headedness from the first cigarette of the day decreased with increasing heaviness of smoking and increasing number of years smoking, suggesting that differences in responses were due to differences in chronic tolerance. Because measures of the subjective effects of drugs are useful in the study of drug response variability, this self-report item on light-headedness should be included in further research on individual differences in the subjective effects of cigarette smoking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Forgetting in primed fragment completion.

Seven experiments examined the time course of primed fragment-completion performance. A pilot experiment and Experiment 1 showed that rapid forgetting occurs immediately after study for a period of approximately 5 min. The rate of this immediate forgetting is independent of the length of the list. Experiment 2 showed that priming effects were still present after 16 months. Experiments 3 and 4 provided further evidence of forgetting over 1 week. Experiment 5 showed that retention performance after 20 min is unaffected by the interpolated study and recall of other lists of words. Experiment 6 showed that 10-min retention performance was substantially reduced as list length was increased from 10 to 100 words; but it showed no evidence of intralist proactive interference. The combined results of the seven experiments illustrate some similarities and differences between forgetting in primed fragment completion and in episodic memory tasks such as recall and recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Kinetics for unidirectional endwise chain depolymerizations. Experiments with amylose in aqueous alkaline solutions

A kinetic model for the unidirectional endwise chain-propagated depolymerization of a linear polymer is described in terms of three pseudo-first-order rate constants: k₁ for the unzipping itself; k₂ for termination through the formation of stable endgroups; and k₃ for termination through complete degradation of polymer chains. It is shown that the calculated zip length, ν = k₁/(k₂ + k₃), will decrease as the initial substrate D.P. is reduced. For the dimer, a maximum value of ν = 1 is expected. During the anaerobic degradation of potato amylose in aqueous alkaline solutions, k₁ decreases and k₂ increases in value as the initial amylose concentration is raised. As a result, quantitative depolymerization occurs at low substrate concentrations, while at raised starch levels an alkali-stable residue is formed. It is proposed that intermolecular association between polymer chains causes these kinetic differences. For amylose, the constants k₁, k₂, and k₃ are approximately related by the ratio 1000:1:1 or 1000:0:1; and for the homologous disaccharide, the ratio is 10:1:10. The relevance of these findings to the kinetics of cellulose decomposition in aqueous alkali is discussed.     

Oligomerization and Nitration of the Grass Pollen Allergen Phl p 5 by Ozone,Nitrogen Dioxide,and Peroxynitrite: Reaction Products,Kinetics, and Health Effects

The allergenic and inflammatory potential of proteins can be enhanced by chemical modification upon exposure to atmospheric or physiological oxidants. The molecular mechanisms and kinetics of such modifications, however, have not yet been fully resolved. We investigated the oligomerization and nitration of the grass pollen allergen Phl p 5 by ozone (O₃), nitrogen dioxide (NO₂), and peroxynitrite (ONOO^–). Within several hours of exposure to atmospherically relevant concentration levels of O₃ and NO₂, up to 50% of Phl p 5 were converted into protein oligomers, likely by formation of dityrosine cross-links. Assuming that tyrosine residues are the preferential site of nitration, up to 10% of the 12 tyrosine residues per protein monomer were nitrated. For the reaction with peroxynitrite, the largest oligomer mass fractions (up to 50%) were found for equimolar concentrations of peroxynitrite over tyrosine residues. With excess peroxynitrite, the nitration degrees increased up to 40% whereas the oligomer mass fractions decreased to 20%. Our results suggest that protein oligomerization and nitration are competing processes, which is consistent with a two-step mechanism involving a reactive oxygen intermediate (ROI), as observed for other proteins. The modified proteins can promote pro-inflammatory cellular signaling that may contribute to chronic inflammation and allergies in response to air pollution.     

Novel BQCA- and TBPB-Derived M1 Receptor Hybrid Ligands: Orthosteric Carbachol Differentially Regulates Partial Agonism

Recently, investigations of the complex mechanisms of allostery have led to a deeper understanding of G protein-coupled receptor (GPCR) activation and signaling processes. In this context, muscarinic acetylcholine receptors (mAChRs) are highly relevant due to their exemplary role in the study of allosteric modulation. In this work, we compare and discuss two sets of putatively dualsteric ligands, which were designed to connect carbachol to different types of allosteric ligands. We chose derivatives of TBPB [1-(1′-(2-tolyl)-1,4′-bipiperidin-4-yl)-1H-benzo[d]imidazol-2(3H)-one] as M₁-selective putative bitopic ligands, and derivatives of benzyl quinolone carboxylic acid (BQCA) as an M₁ positive allosteric modulator, varying the distance between the allosteric and orthosteric building blocks. Luciferase protein complementation assays demonstrated that linker length must be carefully chosen to yield either agonist or antagonist behavior. These findings may help to design biased signaling and/or different extents of efficacy.