A genuinely polynomial primal simplex algorithm for the assignment problem

Cataloged from PDF version of article.Akgil, M., A genuinely polynomial primal simplex algorithm for the assignment problem, Discrete Applied Mathematics 45 (1993) 93-l 15. We present a primal simplex algorithm that solves the assignment problem in :n(n+3)-4 pivots. Starting with a problem of size 1, we sequentially solve problems of size 2,3,4,. ..,lt. The algorithm utilizes degeneracy by working with strongly feasible trees and employs Dantdg’s rule for entering edges for the subproblem. The number of nondegenerate simplex pivots is bounded by n-l. The number of consecutive degenerate simplex pivots is bounded by : (n-2)(n+ 1). All three bounds are sharp. The algorithm can be implemented to run in O(ni) time for dense graphs. For sparse graphs, using state of the art data structures, it runs in O(n2 log n+nm) time, where the bipartite graph has 2n nodes and m edges

Environmentally friendly nanocrystals synthesized and processed in ambient conditions for solution-processed solar cells

Due to the continuously increasing energy demand and the environmental concerns about climate changes raised by international community, alternative energy resources have been put under intense investigation for the past decade. As a consequence, different technologies have been proposed, photovoltaics being a promising one among them. Till now, different structures and methods have been employed to fabricate photovoltaics for energy production. Traditionally, vacuum-based deposition methods have been used to form the stacks required for proper photovoltaic operation. Triggered by the advancements in colloidal synthesis methods, thin films of colloidal semiconductor nanocrystals (CNCs) have gained tremendous attention as cheap substitutes for vacuum-deposited layers. Up to date, various colloidal synthesis methods have been developed to produce semiconductor nanocrystals for applications in photovoltaics. Thanks to the high degree of controllability and high material quality, hot injection methods have been the way-to-go for the past decades. However, the application of CNC films in large-scale photovoltaics has been delayed due to the synthesis constraints originating from hot injection methods itself. In this work, we demonstrate that it is possible to eliminate the need for air-free techniques by careful selection of the precursors and oxygen-aware design of reaction conditions. We use the semiconducting compound silver bismuth sulfide (AgBiS2) as the prototype material to demonstrate the easiness and efficiency of the method. This semiconducting compound is selected as the prototype material thanks to its attractive optical properties for photovoltaics and the environmentally friendly nature of the constituent elements. Solar cells fabricated using CNCs synthesized at room temperature have yielded a power conversion efficiency of 5.5 %, demonstrating the promising potential of the method. The application of the method in the synthesis of AgBiS2 CNCs results in a cost reduction of at least 60 % compared to the previous studies reporting similar photovoltaics-grade AgBiS2 CNCs. Another important challenge in employing hot injection methods is the scalability. Due to the difficulties in maintaining the thermal fluctuations within the reaction volume low and in the maintenance of inert atmosphere inside the reaction vessel, hot injection methods impose an inherent scale constraint on the synthesis. On the other hand, with the elimination of scale constraint by the use of an ambient condition synthesis method, the requirement for high temperature reaction and chemically inert reaction environment is eliminated, enabling us to achieve large-scale volume production of CNCs. This, in turn, can lower the production cost of CNCs further, hence the cost of photovoltaics that are based on CNCs. In addition, we show that the ambient condition method can be adapted for the synthesis of another metal chalcogenide, namely silver bismuth selenide CNCs (AgBiSe2) with an extended absorption spectrum further into the near infrared down to ~ 0.9 eV. The resulting AgBiSe2 CNC solar cells achieved a preliminary efficiency up to 2.6 %. Also, thanks to the structural similarity of these two compounds, the two methods that are developed for the synthesis of AgBiS2 and AgBiSe2 CNCs are combined and optimized to obtain alloyed quaternary AgBiSSe CNCs as a facile means of bandgap tuning in silver bismuth chalcogenide semiconductor family. The formation of AgBiSSe CNCs are verified through optical and structural characterization methods to show the formation of quaternary phase and also the phase purity of the obtained product. Overall, it is shown that the proposed ambient condition synthesis method is capable of providing photovoltaics-grade RoHS-compliant materials at a lower cost and higher throughput compared to the hot-injection based methods, opening a novel way for low-cost environmentally friendly photovoltaics.Debido al continuo aumento de la demanda de energía y las preocupaciones ambientales sobre el cambio climático planteadas por la comunidad internacional, los recursos energéticos alternativos han sido objeto de una intensa investigación durante la última década. Como consecuencia, se han propuesto diferentes tecnologías, siendo la fotovoltaica una prometedora entre ellas. Hasta ahora, se han empleado diferentes estructuras y métodos para fabricar células solares para la producción de energía. Tradicionalmente, se han utilizado métodos de deposición basados en vacío para formar las capas necesarias para el funcionamiento fotovoltaico adecuado. Debido a los avances en los métodos de síntesis coloidal, las películas finas de nanocristales semiconductores en solución coloidal (CNCs) han ganado una gran atención como sustitutos baratos de las capas depositadas al vacío. Hasta la fecha, se han desarrollado varios métodos de síntesis coloidal para producir nanocristales semiconductores para aplicaciones en energía fotovoltaica. Gracias al alto grado de controlabilidad y la alta calidad del material, los métodos de inyección en caliente han sido el camino a seguir durante las últimas décadas. Sin embargo, la aplicación de películas de CNCs en fotovoltaica a gran escala se ha retrasado debido a las propias limitaciones de estos métodos de síntesis. En este trabajo, demostramos que es posible eliminar la necesidad de técnicas inertes mediante la selección cuidadosa de los precursores y el diseño de las condiciones de reacción conscientes del oxígeno. Usamos el compuesto semiconductor sulfuro de bismuto y plata (AgBiS2) como material prototipo para demostrar la facilidad y eficiencia del método. Este compuesto semiconductor se ha seleccionado como material prototipo gracias a sus atractivas propiedades ópticas para la energía fotovoltaica y la naturaleza ecológica de los elementos constituyentes. Las células solares fabricadas con CNCs sintetizadas a temperatura ambiente han arrojado una eficiencia de conversión de energía del 5,5 %, lo que demuestra el potencial prometedor del método. La aplicación del método en la síntesis de CNCs de AgBiS2 da como resultado una reducción de costes de al menos un 60 % en comparación con los estudios anteriores que reportaron CNCs de AgBiS2 de una calidad fotovoltaica similar. Otro desafío importante al emplear métodos de inyección en caliente es la escalabilidad. Debido a las dificultades para mantener bajas las fluctuaciones térmicas y la atmósfera inerte dentro del recipiente de reacción, los métodos de inyección en caliente imponen una restricción de escala inherente a la síntesis. Por otro lado, con la eliminación de la restricción de escala mediante el uso de un método de síntesis en condiciones ambientales, se elimina también el requisito de reacción a alta temperatura y entorno de reacción químicamente inerte, lo que nos permite lograr una producción en volumen a gran escala de CNCs. Esto, a su vez, puede reducir aún más el coste de producción de los CNCs, y en consecuencía el coste de las células fotovoltaicas que se basan en CNCs. Además, mostramos que el método en condiciones ambientales se puede adaptar para la síntesis de otro calcogenuro metálico, por ejemplo, CNCs de seleniuro de bismuto y plata (AgBiSe2) con un espectro de absorción más extendido en el infrarrojo cercano, hasta ~ 0.9 eV . Las células solares de CNCs de AgBiSe2 alcanzaron una eficiencia preliminar de hasta el 2,6 %. Además, gracias a la similitud estructural de estos dos compuestos, los dos métodos desarrollados para la síntesis de CNCs de AgBiS2 y AgBiSe2 se combinan y optimizan para obtener CNCs de la aleación cuaternaria AgBiSSe como un medio fácil de sintonización de bandgap en familia de semiconductores de calcogenuro de bismuto y plata.La formación de AgBiSSe CNCs se verifica mediante métodos de caracterización óptica y estructural para mostrar la formación de fase cuaternaria y también la pureza de fase del producto obtenido. En general, se demuestra que el método de síntesis de condiciones ambientales propuesto es capaz de proporcionar materiales fotovoltaicos compatibles con RoHS a un costo menor y un mayor rendimiento en comparación con los métodos basados en inyección en caliente, lo que abre un camino novedoso para la energía fotovoltaica ecológica de bajo costo. .Postprint (published version

Characterization and evaluation of Paulownia elongota as a raw material for paper production

Paulownia elongota, one of the most fast growing species of the world, was evaluated as raw material for pulp and paper production. The chemical, morphological and anatomical aspects of paulownia woodwere determined. The lignin, holocellulose and ∝-cellulose contents in P. elongota wood were comparable to those of some common non-wood and hardwood raw materials. Different chemical pulping procedures were applied to P. elongota wood to evaluate its pulping potential. Paper strength properties and acidic group content bound to the cell wall were determined. The alkali solubility, water solubility and alcohol-benzene extractive content were higher than those from wood and most nonwoods. The fiber length of 0.83 mm was observed, which is close to low end of the hardwoods but fiber diameter was very wide, similar to that of softwoods. The pulpability of paulownia wood was alsostudied. The pulp yield and viscosity were very low and the kappa numbers were high. The strength properties were comparable to those of some wood and non-wood pulps. Although, paulownia pulpsare considered as low quality materials, it can be used for paper production when mixed with long fibrous materials

Subvalvular membrane on the left ventricular outflow tract: multidetector computerised tomography imaging

In this report, we describe a patient with a subvalvular membrane on the left ventricular outflow tract. Discrete subvalvular membrane is a cause of left ventricular outflow tract narrowing. Multidetector computerised tomography can demonstrate the anatomical three-dimensional view of this region and guide for surgery. (Folia Morphol 2011; 70, 4: 315–317

Characterization of sleep spindles using higher order statistics and spectra

Cataloged from PDF version of article.This work characterizes the dynamics of sleep spindles, observed in electroencephalogram (EEG) recorded from humans during sleep, using both time and frequency domain methods which depend on higher order statistics and spectra. The time domain method combines the use of second- and third-order correlations to reveal information on the stationarity of periodic spindle rhythms to detect transitions between multiple activities. The frequency domain method, based on normalized spectrum and bispectrum, describes frequency interactions associated with nonlinearities occuring in the observed EEG

Effects of shading and covering material application for delaying harvest on gray mold disease severity

To delay the harvest of Sultani Cekirdeksiz grape variety and to reduce pre and post-harvest botrytis bunch rot severity, shading and covering material application were tested in 2009 to 2010 growing periods. In this study, grape vines were shaded with shading materials which had three different shading densities (35, 55, and 75% shading density) from veraison period to harvest. The grape vines were also covered with four different covering materials (transparent polyethylene, mogul, polypropen cross-stich and lifepack) before rainfall, at the end of August until harvest. The gray mold severity was recorded three times (before shading at unriped grape stage, veraison period, shortly after shading and twice at 20 day interval) during growing period. Based on the results of this study, the highest gray mold (Botrytis cinerea) severity was obtained in the control (uncovered and unshaded) treatment and the lowest disease severity was observed in lifepack treatment with or without shading. Since gray mold disease of grape was the main factor affecting harvest date of the crop lifepack, + 35 or 55% shading could be recommended to delay harvest and reduce the gray mold severity of grape in Manisa province-Turkey.Key words: Sultani seedless, table grape, shading, cover material, delaying harvest disease severity, Botrytis cinerea

Chemical composition of the essential oil of bitter fennel (Foeniculum vulgare subsp. piperitum)

The composition of the essential oil obtained by steam distillation from seeds of bitter fennel (Foeniculum vulgare subsp. piperitum) was analysed by GC/MS. The presence of atleast seventeen compounds was demonstrated. They correspond to 99.95% of the oil. Methyl chavicol was the main constituent of the oil (47.09%), followed by limonene (29.07%), fenchone 03.43%), a-terpinene (2.5%), fenchyl acetate (exo) 0.95%) and cis-b-ocimene (1.41%). Trans-anethole was not detected. Therefore, it is concluded that the oil of Turkish bitter fennel is rich in methyl chavicol. &nbsp

Macrocrystals of Colloidal Quantum Dots in Anthrancene: Exciton Trannsfer and Polarized Emission

Cataloged from PDF version of article.In this work, centimeter-scale macrocrystals of nonpolar colloidal quantum dots (QDs) incorporated into anthracene were grown for the first time. The exciton transfer from the anthracene host to acceptor QDs was systematically investigated, and anisotropic emission from the isotropic QDs in the anthracene macrocrystals was discovered. Results showed a decreasing photoluminescence lifetime of the donor anthracene, indicating a strengthening energy transfer with increasing QD concentration in the macrocrystals. With the anisotropy study, QDs inside the anthracene host acquired a polarization ratio of similar to 1.5 at 0 degrees collection angle, and this increases to similar to 2.5 at the collection angle of 60 degrees. A proof-of-concept application of these excitonic macrocrystals as tunable color converters on light-emitting diodes was also demonstrated

Determination of cadmium accumulation capabilities of aquatic macrophytes Ceratophyllum demersum, Bacopa monnieri and Rotala rotundifolia

In the present study, cadmium (Cd) accumulation capabilities of aquatic macrophytes Ceratophyllum demersum, Bacopa monnieri and Rotala rotundifolia were determined after treating both individual and triple macrophytes. The macrophytes were treated with Cd at 0, 0.1, 1 and 10 mg/L concentrations in a controlled chamber for 12-days. Cadmium accumulations increased with increasing Cd concentrations in all macrophytes. Bioconcentration factor (BCF), which indicates the efficiency of the macrophyte to accumulate Cd, decreased with increased external Cd concentrations. When compared to single macrophyte applications, reductions were observed in Cd accumulation of the combined macrophyte treatments. The maximum Cd accumulation was recorded in R. rotundifolia followed by C. demersum and B. monnieri in both single and combined macrophyte applications. Consequently, the macrophytes in both applications proved highly effective in the accumulation of Cd. Thus, they may be used especially in the abatement and monitoring of Cd pollution

Study on determination of bioactive potentials of certain lichens

Lichens are symbiotic associations that are formed by fungi and algae or cyanobacteria. The number of lichen species investigated pharmaceutically is still very low at present. The present study aims to determine the antioxidant activities, antibacterial activities, DNA protective activities, and oxidative stress status of Bryoria fuscescens (Gyeln.) Brodo & D. Hawksw., Parmelina tiliacea (Hoffm.) Hale, and Umbilicaria decussata (Vill.) Zahlbr. Lichens were extracted with ethanol in the Soxhlet device. The DPPH method was used to determine antioxidant activities. DNA protective activity was determined using pBR322 supercoil DNA. Antibacterial activity was determined with dilution test on 5 different species of bacteria (Enterocossus faecalis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus). Total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) were defined with Rel Assay Diagnostics kits. It was observed that DPPH free radical scavenging activities in lichen ethanol extracts increased with increasing concentration. The highest antioxidant activity was observed in B. fuscescens and the lowest activity was determined in U. decussata. It was also determined that the ethanol extracts of all lichen samples had DNA-protective activity. The highest antibacterial activity was detected in B. fuscescens, while the lowest activity was detected in U. decussata. It was determined that B. fuscescens had the highest oxidative stress index and U. decussata had the lowest value. It appears that the ethanol extracts of the lichen samples utilized in the study could be used as an alternative and complementary resource in medical treatment