Efficiency Enhancement in Organic Photovoltaic Cells: Consequences of Optimizing Series Resistance

Here, means to enhance power conversion efficiency (PCE or η) in bulk‐heterojunction (BHJ) organic photovoltaic (OPV) cells by optimizing the series resistance (R_s)—also known as the cell internal resistance—are studied. It is shown that current state‐of‐the‐art BHJ OPVs are approaching the limit for which efficiency can be improved via R_s reduction alone. This evaluation addresses OPVs based on a poly(3‐hexylthiophene):6,6‐phenyl C₆₁‐butyric acid methyl ester (P3HT:PCBM) active layer, as well as future high‐efficiency OPVs (η > 10%). A diode‐based modeling approach is used to assess changes in R_s. Given that typical published P3HT:PCBM test cells have relatively small areas (～0.1 cm²), the analysis is extended to consider efficiency losses for larger area cells and shows that the transparent anode conductivity is then the dominant materials parameter affecting R_s efficiency losses. A model is developed that uses cell sizes and anode conductivities to predict current–voltage response as a function of resistive losses. The results show that the losses due to R_s remain minimal until relatively large cell areas (>0.1 cm²) are employed. Finally, R_s effects on a projected high‐efficiency OPV scenario are assessed, based on the goal of cell efficiencies >10%. Here, R_s optimization effects remain modest; however, there are now more pronounced losses due to cell size, and it is shown how these losses can be mitigated by using higher conductivity anodes.     

A Long‐Cycle‐Life Lithium–CO2 Battery with Carbon Neutrality

Lithium–CO₂ batteries are attractive energy‐storage systems for fulfilling the demand of future large‐scale applications such as electric vehicles due to their high specific energy density. However, a major challenge with Li–CO₂ batteries is to attain reversible formation and decomposition of the Li₂CO₃ and carbon discharge products. A fully reversible Li–CO₂ battery is developed with overall carbon neutrality using MoS₂ nanoflakes as a cathode catalyst combined with an ionic liquid/dimethyl sulfoxide electrolyte. This combination of materials produces a multicomponent composite (Li₂CO₃/C) product. The battery shows a superior long cycle life of 500 for a fixed 500 mAh g^?1 capacity per cycle, far exceeding the best cycling stability reported in Li–CO₂ batteries. The long cycle life demonstrates that chemical transformations, making and breaking covalent C? O bonds can be used in energy‐storage systems. Theoretical calculations are used to deduce a mechanism for the reversible discharge/charge processes and explain how the carbon interface with Li₂CO₃ provides the electronic conduction needed for the oxidation of Li₂CO₃ and carbon to generate the CO₂ on charge. This achievement paves the way for the use of CO₂ in advanced energy‐storage systems.     

Natural and artificial radioactivity distribution in soil of Fars Province, Iran

Fars province is a large populated large province located in the southwest of Iran. This work presents a study of natural and radioactivity levels in soil samples of this province. For this purpose, 126 samples were gathered from different regions of the province and analysed by gamma spectroscopy to quantify radioactivity concentrations of radionuclides using a high-purity germanium detector and spectroscopy system. The results of this investigation show the average concentrations of 271 ± 28 Bq kg(-1), 6.37 ± 0.5 Bq kg(-1), 14.9 ± 0.9 Bq kg(-1) and 26.3 ± 1.9 Bq kg(-1) for (40)K, (137)Cs, (232)Th and (238)U in soil, respectively. Finally, baseline maps were established for the concentrations of each of the radionuclides in different regions. The absorbed dose rate and the annual effective dose (AED) were also calculated for the radionuclides according to the guidelines of UNSCEAR 2000. The average AED from the radioactivity content of soil in this province was found to be 39.9 ± 1.8 μSv.     

Cardiac Disease Alters Myocardial Tissue Levels of Epoxyeicosatrienoic Acids and Key Proteins Involved in Their Biosynthesis and Degradation

CYP2J2 is the main epoxygenase in the heart that is responsible for oxidizing arachidonic acid to cis-epoxyeicosatrienoic acids (EETs). Once formed, EETs can then be hydrolyzed by soluble epoxide hydrolase (sEH, encoded by EPHX2) or re-esterified back to the membrane. EETs have several cardioprotective properties and higher levels are usually associated with better cardiac outcomes/prognosis. This study investigates how cardiovascular disease (CVD) can influence total EET levels by altering protein expression and activity of enzymes involved in their biosynthesis and degradation. Diseased ventricular cardiac tissues were collected from patients receiving Left Ventricular Assist Device (LVAD) or heart transplants and compared to ventricular tissue from controls free of CVD. EETs, and enzymes involved in EETs biosynthesis and degradation, were measured using mass spectrometric assays. Terfenadine hydroxylation was used to probe CYP2J2 activity. Significantly higher cis- and trans-EET levels were observed in control cardiac tissue (n = 17) relative to diseased tissue (n = 24). Control cardiac tissue had higher CYP2J2 protein levels, which resulted in higher rate of terfenadine hydroxylation, compared to diseased cardiac tissues. In addition, levels of both NADPH-Cytochrome P450 oxidoreductase (POR) and sEH proteins were significantly higher in control versus diseased cardiac tissue. Overall, alterations in protein and activity of enzymes involved in the biosynthesis and degradation of EETs provide a mechanistic understanding for decreased EET levels in diseased tissues.     

Endogenous ADP-ribosylation of eukaryotic elongation factor 2 and its 32 kDa tryptic fragment.

Eukaryotic elongation factor 2 (eEF-2) can undergo ADP-ribosylation in the absence of diphtheria toxin. The binding of free ADP-ribose and endogenous transferase-dependent ADP-ribosylation were distinct reactions for eEF-2, as indicated by different findings. Incubation of eEF-2 tryptic fragment 32/33 kDa (32F) with NAD was ADP-ribosylated and gave rise to the covalent binding of ADP-ribose to eEF-2. 32F was revealed to be at the C-terminal by Edman degradation sequence analysis. In our study, the elution of 32F from SDS-PAGE was ADP-ribosylated both in the presence and absence of diphtheria toxin. These results suggest that endogenous ADP-ribosylation of 32F might be related to protein synthesis. This modification appears to be important for the cell function.     

Angiosarcoma (angioendothelioma) of the scalp. An unusual case of scarring alopecia

Angiosarcoma with initial involvement of the scalp is a rare, malignant neoplasm. We present the case of a 77-year-old woman in whom extensive scarring alopecia developed that was proved histologically to be due to angiosarcoma. She had a good initial response to treatment with electron-beam therapy, but after seven months, extensive nodules and indurated areas on the face beyond the borders of the radiation field developed. Subsequently, massive cervical adenopathy and metastases to the lungs, liver, and spleen developed. Angiosarcoma must be differentiated from other malignant blood vessel tumors and should be considered in the differential diagnosis of scarring alopecia of the scalp in elderly patients.     

Dual-Antenna RF CMOS Front-End for Interferer Removal in Ultra-Wideband Systems

Many ultra-wideband (UWB) systems are challenged by strong jammers and narrowband interferers. Using two antennas, we demonstrate a robust UWB radio frequency (RF) front-end design in a 0.25 μm mixed-signal complementary metal oxide semiconductor (CMOS) technology. The proposed realization is capable of adaptively removing a high-power, narrowband interferer early in the receiver chain avoiding front-end saturation and preserving UWB signal power. The early interferer removal resulting in interferer-free demodulation is based on the least mean squares (LMS) algorithm and achieved through a novel combiner low-noise amplifier and noise optimized filtering. Circuit level RF simulations of the proposed circuitry indicate a maximum improvement in signal-to-interference ratio of 39.6 dB.     

Fungal strains isolated from cork stoppers and the formation of 2,4,6-trichloroanisole involved in the cork taint of wine

Cork taint is mainly due to 2,4,6-trichloroanisole (TCA) produced through the activity of undesirable fungal strains. We observed that CFU mould number in TCA-containing stoppers was not quantitatively different to that of the stoppers not containing TCA (ca. 10(5)CFU/g). In contrast more fungi diversity was observed in TCA-containing stoppers. Penicillium spp (Penicillium chrysogenum, Penicillium glabrum), Aspergillus spp (Aspergillus niger and Aspergillus oryzae), Chrysonilia sitophila, Mucor racemosus, Paecilomyces sp. and Trichoderma viride were found in TCA-containing stoppers, while C. sitophila and Penicillium sp. were the main fungi in the stoppers devoid of TCA. Conidia were numerous close to the lenticels and present from the lateral surface through to the centre of the stoppers. Strains of Aspergillus, Mucor, Paecilomyces, Penicillium and Trichoderma isolated from TCA-containing stoppers were able to convert 2,4,6-trichlorophenol (TCP) in TCA in resting cell or growing conditions. The best yields of conversion were obtained by green fungi Paecilomyces sp. and P. chrysogenum, 17% and 20%, respectively. Chysonilia sitophila and Penicillium sp. did not produce TCA from TCP in our conditions.     

Influence of edge velocity on flame front position and displacement speed in turbulent premixed combustion

Using a novel concept, the present study experimentally investigates underlying physics pertaining to statistics of the flame front position and the flame front velocity in turbulent premixed V-shaped flames. The concept is associated with characteristics of the reactants velocity at the vicinity of the flame front, referred to as the edge velocity. The experiments are performed using simultaneous Mie scattering and Particle Image Velocimetry techniques. Three mean streamwise exit velocities of: 4.0, 6.2, and 8.6 m/s along with three fuel–air equivalence ratios of: 0.7, 0.8, and 0.9 are examined. The results show that fluctuations of the flame front position and the flame front velocity are induced by the fluctuations of the component of the edge velocity transverse to the mean flow direction. Analysis of the results show that the mean of the flame front velocity in the normal direction to the flame front is significantly dependent on the vertical distance from the flame-holder. Relatively close to the flame-holder, the mean of the flame front velocity in the direction normal to the flame front is about zero; however, it increases to values several times larger than the laminar flame speed by increasing the vertical distance from the flame-holder.