Cascade-type excitation energy relay in organic thin-film solar cells

We investigated small-molecule-based organic photovoltaic (PV) cells with three different electron-donating material layers, two thiophene/phenylene co-oligomers [α,ω-bis(biphenyl-4-yl)terthiophene (BP3T) and α,ω-diphenyl sexithiophene (P6T)] and copper phthalocyanine (CuPc), and one electron-accepting material layer (C₆₀). A cascade-type energy relay between the three donor layers occurred, and the incident photon-current conversion efficiency improved in the blue light region, where CuPc has very low optical absorption. An increase in P6T photoluminescence intensity in a two-layer sample (BP3T/P6T) on quartz confirmed interlayer excitation transfer (ET) from BP3T and P6T. The bulk heterojunction architecture in our interlayer-ET-based organic PV cell was effective. Moreover, P6T appeared to have a relatively long exciton diffusion length of several tens of nanometers.     

An analytic framework for performance modeling of software transactional memory

Analytic models based on discrete-time Markov chains (DTMC) are proposed to assess the algorithmic performance of Software Transactional Memory (TM) systems. Base STM variants are compared: optimistic STM with inplace memory updates and write buffering and pessimistic STM. Starting from an absorbing DTMC, closed-form analytic expressions are developed, which are quickly solved iteratively to determine key parameters of the considered STM systems, like the mean number of transaction restarts and the mean transaction length. Since the models reflect complex transactional behavior in terms of read/write locking, data consistency checks and conflict management independent of implementation details, they highlight the algorithmic performance advantages of one system over the other, which – due to their at times small differences – are often blurred by implementation of STM systems and even difficult to discern with statistically significant discrete-event simulations.     

On Analyzing the Potential of a Layer-2 Multi-hop Authentication and Credential Delivery Scheme for Vehicular Communications

In this paper we introduce a new security architecture and security mechanisms for vehicular networks providing a layer-2 multi-hop authentication and credential delivery scheme between vehicles and the network operator authentication server. We present a performance analysis of the proposed solution under various vehicles and Access Points (APs) densities, showing the potential of our scheme in providing a more efficient, robust and scalable authentication and credential delivery to vehicles when compared against the classical single-hop scheme.     

New temperature dependent thermal conductivity data for water-based nanofluids

This paper presents effective thermal conductivity measurements of alumina/water and copper oxide/water nanofluids. The effects of particle volume fraction, temperature and particle size were investigated. Readings at ambient temperature as well as over a relatively large temperature range were made for various particle volume fractions up to 9%. Results clearly show the predicted overall effect of an increase in the effective thermal conductivity with an increase in particle volume fraction and with a decrease in particle size. Furthermore, the relative increase in thermal conductivity was found to be more important at higher temperatures. Obtained results compare favorably with certain data sets and theoretical models found in current literature.     

Synthesis and Biological Evaluation of Chromium Bioorganometallics Based on the Antibiotic Platensimycin Lead Structure

The recent discovery of the natural product platensimycin as a new antibiotic lead structure has triggered the synthesis of numerous organic derivatives for structure–activity relationship studies. Herein, we describe the synthesis, characterization and biological evaluation of the first organometallic antibiotic inspired by platensimycin. Two bioorganometallic compounds containing (η⁶‐pentamethylbenzene)Cr(CO)₃ ( 2 ) and (η⁶‐benzene)Cr(CO)₃ ( 3 ), linked by an amide bond to the aromatic part of platensimycin, were synthesized. Their antibiotic activities were tested against B. subtilis 168 (Gram positive) and E. coli W3110 (Gram negative) bacterial strains. Both compounds were found to be inactive against E. coli but derivative 2 inhibits B. subtilis growth at a moderate MIC value of 0.15 mM . To test the intrinsic toxicity of chromium, several chromium salts along with {η⁶‐(3‐pentamethylphenyl propionic acid)}Cr(CO)₃ ( 5 ) and {η⁶‐(3‐phenyl propionic acid)}Cr(CO)₃ ( 6 ) were tested against both bacterial strains. No activity was observed against E. coli for any of the compounds; B. subtilis growth was not inhibited by Cr(NO₃)₃ and only very weakly by 5 , K₂Cr₂O₇ and Na₂CrO₄ at MIC values of 0.5, 0.68 and 1.24 mM , respectively. Compounds 2 , 3 , 5 and 4 (the pure organic analogue of 2 ) show similar cytotoxicity against HeLa, HepG2 and HT‐29 mammalian cell lines. Furthermore, the cellular uptake and the intracellular distribution of compounds 2 , 3 and Cr(NO₃)₃ in B. subtilis were studied using atomic absorption spectroscopy to gain insight in to the possible cellular targets. Compound 2 was found to be readily taken up and distributed almost equally among cytosol, cell debris and cell membrane in B. subtilis.     

Sensortechnik in der Chemie – Status und Trend

Sensor technology in the chemical process industries – status and trends . Sensor technology is used in chemical process industries to provide information on product and process properties. The computerized handling of this information has altered the requirements for sensor systems. New production methods and the automation of existing processes lead to new tasks for sensor systems. The advancement of sensor technology is proceeding on a broad front and in small steps, also exploiting the potential of microelectronics. Model-based measuring methods utilizing a priori knowledge about the process may substantially increase the information gain.     

Polymer electrolytes

Summary The room temperature conductivity of lithium salts dissolved in polyethylene oxide, proposed as polymer electrolytes, is shown to decrease drastically upon storage. The crystallization process, which is responsible for that ageing, can be blocked, if two further components are added : an elastomer copolymer butadiene-acrylonitrile and a macromer of polyoxyethylene. In addition, a crosslinking process must be carried out.