Polymer LEDs as a physics tool

We present a systematic experimental and theoretical study of physical mechanisms governing the operation of polymer light-emitting diodes. We show that through self-consistent modeling we can address both charge transport and exciton generation. Electron and hole mobility in several polymers has been characterized experimentally. Characterization of excitons and especially of triplet-excitons is achieved through use of a triplet-emitting molecule.     

Epilepsia partialis continua: a new manifestation of anti-Hu-associated paraneoplastic encephalomyelitis

We report on 3 anti-Hu-positive patients who presented with clinical and electroencephalographic (EEG) features of epilepsia partialis continua (EPC). Two of the patients had an associated small cell carcinoma. Magnetic resonance imaging (MRI) disclosed a hyperintense nonenhancing focal lesion in T2-weighted images in the sensorimotor area in 2 patients. Histopathological analysis of the lesion revealed inflammatory infiltrates and neuronal cell loss. In the patient who had a postmortem study, these neuropathological changes were not observed in other areas of the nervous system. This study emphasizes that the possibility of an anti-Hu-associated paraneoplastic disorder must be considered in patients with cortical encephalitis presenting with EPC when a brain tumor can be excluded.     

Effect of Grain Thermal Expansion Mismatch on Thermal Conductivity of Porous Ceramics

Many ceramics contain microcracks, which are often situated between sintered grains. These microcracks constitute thermal resistances, which may affect heat transfer through the material and its effective thermophysical properties. The thicknesses and the contact areas of the microcracks change with temperature as a result of the thermal expansion mismatch between the grains on opposite sides of the microcracks. This physical mechanism affects changes of the material's thermal conductivity, k , with temperature. The above mechanism usually plays a minor role at atmospheric pressure, where heat may flow via the gas filling the cracks. Hence, the temperature-induced changes of the crack geometry have little effect on heat transfer. However, at low gas pressures, where the heat flow between the grains occurs mainly via the contact areas, the grains' thermal expansion mismatch causes unusual temperature behavior of the material's thermal conductivity observed for several industrial refractories. In this paper, the influence of the above physical mechanism is discussed relative to other heat transfer mechanisms described in the literature. A simple physical model of the thermal expansion of grains bonded by an agent, having different thermal expansion coefficients, is developed. This model allows calculation of the contact area and the average microcrack opening between the grains as functions of the temperature, the characteristic grains sizes and their thermal expansion coefficients, and the permanent crack area. These parameters are evaluated and used to calculate the effective thermal conductivity of ceramic materials containing microcracks that appear as a result of thermal contraction of grains. The calculated thermal conductivity satisfactorily correlates with the experimental data collected for several chrome-magnesite refractories over a wide range of temperatures and gas pressures.     

Conjugates of Unsaturated Fatty Acids with Propylene Glycol as Potentially Less-Irritant Skin Penetration Enhancers

Fatty acids (FA) are well known as efficient enhancers for transdermal delivery of drugs; however, their frequent dermal toxicity limits their regular use. In order to utilize the fatty acid as a safe enhancer devoid of its irritant effect, we have synthesized and evaluated a series of fatty acids conjugated to propylene glycol (FA-PG). Each one of the conjugates was prepared as a mono- or di- acyl ester derivative. The effects of the synthetic enhancers on the porcine skin permeability were evaluated in a diffusion cell system using lidocaine as the model drug. In addition, in vivo examinations in rabbits were preformed for skin toxicological evaluation. The results indicate that among the FA-PG conjugates, oleic acid (C18:1_n–9)-PG, linoleic acid (C18:2_n–6)-PG and α-linolenic acid (C18:3_n–3)-PG, mono- or di-esters, enhance the penetration of lidocaine relatively to the vehicle (without enhancer). The conjugates of oleic acid (C18:1_n–9) and linoleic acid (C18:2_n–6) with PG have demonstrated a similar enhancing effect as the corresponding free fatty acids. Interestingly, although the mono- or the di- conjugates of α-linolenic acid (C18:3_n–3) with PG enhanced the lidocaine flux as the other two fatty acid conjugates, they resulted in a reduced permeability as compared to the action of their free acid. In addition, the mono-conjugates of α-linolenic acid (C18:3_n–3) with PG exhibited elevated skin irritation in rabbits (relative to the fatty acid alone) compared to the significantly reduced irritation of oleate-PG and linoeate-PG mono-conjugates. In conclusion, except saturated FA-PG and α-linolenic acid (C18:3_n–3)—PG mono-conjugates, unsaturated fatty acids (e.g., oleic and linoleic acids) after conjugation to PG may be safe and effective enhancers for delivering topical drugs.     

Sensing of Alkylating Agents Using Organic Field‐Effect Transistors

Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields, such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical warfare agents. The detection and identification of alkylating agent is not a trivial issue because of their high reactivity and simple structure. Here, a novel polythiophene derivative that is capable of reacting with alkylating agents is reported, along with its application in direct electrical sensing of alkylators using an organic field‐effect transistor, OFET, device. Upon reacting with alkylators, the OFET containing the new polythiophene analogue as its channel becomes conductive, and the gate effect is lost; this is in marked contrast to the response of the OFET to “innocent” vapors, such as alcohols and acetone. By following the drain–source current under gate bias, one can easily follow the processes of absorption of the analyte to the polythiophene channel and their subsequent reaction.     

Spin-dependent plasmonics based on interfering topological defects

Observation of spin-dependent plasmonics based on the interference of topological defects in the near-field is presented. We utilize the surface plasmons' scattering dynamics from localized vortex sources to create spinoptical devices as an ensemble of isolated nanoantennas to observe a "giant" spin-dependent plasmonic vortex and a spin-dependent plasmonic focusing lens. The spin-orbit point spread function, a spiral wavefront, is introduced, where the optical spin is a degree of freedom.     

The Pareto managerial principle: when does it apply?

The well-known 80/20 Pareto principle and its refinement into “A”, “B”, and “C” categories give rise to a managerial methodology consisting of three steps: classification; differentiation; and resource allocation. This is an easy-to-implement and extremely effective methodology. It starts with the creation of “Pareto diagrams”, i.e. bar charts of attributes and their relative frequency, presented in descending order. Typically, Pareto diagrams are useful in that they provide managers with a summary of practical information, revealing critical attributes. However, sometimes a Pareto diagram is less informative than it might be, because the relative frequency is almost uniform. The objective of this article is to provide an analytical tool (an index) that employs the above-mentioned methodology to measure the closeness of empirical Pareto diagrams to an “ideal” Pareto diagram. The index developed is based upon entropy.     

A scalable lock-free stack algorithm

The literature describes two high performance concurrent stack algorithms based on combining funnels and elimination trees. Unfortunately, the funnels are linearizable but blocking, and the elimination trees are non-blocking but not linearizable. Neither is used in practice since they perform well only at exceptionally high loads. The literature also describes a simple lock-free linearizable stack algorithm that works at low loads but does not scale as the load increases. The question of designing a stack algorithm that is non-blocking, linearizable, and scales well throughout the concurrency range, has thus remained open.