bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of Contract Design with Screening
Authors: Cvitanić Jakša , Wan Xuhu , Yang Huali
Published: November 2012

We analyze a novel principal–agent problem of moral hazard and adverse selection in continuous time. The constant private shock revealed at time 0 when the agent selects the contract has a long-term impact on the optimal contract. The latter is based not only on the continuation value of the agent who truthfully reports but is also contingent upon the continuation value of the agent who misreports, called the temptation value. The good agent is retired when the temptation value of the bad agent becomes large, because then it is expensive to motivate the good agent. The bad agent is retired when the temptation value of the good agent becomes small, because then the future payment does not provide sufficient incentives. We also compare the efficiency of the shutdown contract and the screening contract and find that the screening contract can bring more profit to the principal only when the agent's reservation utility is sufficiently small.

This paper was accepted by Wei Xiong, finance.
Revisiting Almost Second-Degree Stochastic Dominance
Authors: Tzeng Larry Y. , Huang Rachel J. , Shih Pai-Ta
Published: November 2012

Leshno and Levy [Leshno M, Levy H (2002) Preferred by “all” and preferred by “most” decision makers: Almost stochastic dominance. Management Sci. 48(8):1074–1085] established almost stochastic dominance to reveal preferences for most rather than all decision makers with an increasing and concave utility function. In this paper, we first provide a counterexample to the main theorem of Leshno and Levy related to almost second-degree stochastic dominance. We then redefine this dominance condition and show that the newly defined almost second-degree stochastic dominance is the necessary and sufficient condition to rank distributions for all decision makers excluding the pathological concave preferences. We further extend our results to almost higher-degree stochastic dominance.

This paper was accepted by Peter Wakker, decision analysis.
Steady-State Analysis for Multiserver Queues Under Size Interval Task Assignment in the Quality-Driven Regime
Authors: Zhang Bo , Zwart Bert
Published: November 2012

We study the steady-state behavior of multiserver queues with general job size distributions under size interval task assignment (SITA) policies. Assuming Poisson arrivals and the existence of the αth moment of the job size distribution for some α > 1, we show that if the job arrival rate and the number of servers increase to infinity with the traffic intensity held fixed, the SITA policy parameterized by α minimizes in a large deviation sense the steady-state probability that the total number of jobs in the system is greater than or equal to the number of servers. The optimal large deviation decay rate can be arbitrarily close to the one for the corresponding probability in an infinite-server queue, which only depends on the system traffic intensity but not on any higher moments of the job size distribution. This supports in a many-server asymptotic framework the common wisdom that separating large jobs from small jobs protects system performance against job size variability.
Differentiated thyroid carcinomas may elude the immune system by B7H1 upregulation
Authors: Cunha Lucas Leite , Marcello Marjory Alana , Morari Elaine Cristina , Nonogaki Suely , Conte Fábio Frangiotti , Gerhard René , Soares Fernando Augusto , Vassallo José , Ward Laura Sterian
Published: November 2012

B7H1 is consistently associated with inhibition of the immune system in many solid tumors. However, there is no report about its impact on differentiated thyroid carcinoma (DTC) presentation, aggressiveness, or evolution. Aiming to investigate the role of B7H1 in DTC and correlate this protein with other tumor-infiltrating immune cells, we studied 407 thyroid nodule tissue samples including 293 from DTC patients, all managed according to a same standard protocol. In addition, we obtained 5 normal and 114 benign thyroid lesions. Eighteen out of the 253 papillary thyroid carcinomas were paired with respective metastatic lymph node tissues. B7H1 (CD274) protein expression was assessed by immunohistochemistry and the gene expression was quantified by real-time PCR. Malignant tissues displayed a more intense B7H1 staining and higher mRNA levels than benign tissues (bothP<0.0001). We observed a positive linear correlation between higher age at diagnosis andB7H1mRNA levels (P=0.02896). Elevated levels of B7H1 protein were associated with the presence of CD4+, CD8+, CD20+, and FoxP3+ lymphocytes (allP<0.05); tumor-associated macrophages (P<0.0001); and the presence of myeloid-derived suppressor cells (P=0.03256). Stage II–IV patients presented higherB7H1mRNA levels than stage I cases (P=0.03522). On the contrary, a decreased expression of B7H1 protein was observed in lymph node metastasis (P=0.0152). In conclusion, our data demonstrate that B7H1 expression is associated with features of aggressiveness, suggesting that this is an immune evasion mechanism of DTC cells.
Essential roles of 11β-HSD1 in regulating brown adipocyte function
Authors: Liu Juan , Kong Xiaocen , Wang Long , Qi Hanmei , Di Wenjuan , Zhang Xiao , Wu Lin , Chen Xia , Yu Jing , Zha Juanmin , Lv Shan , Zhang Aisen , Cheng Peng , Hu Miao , Li Yujie , Bi Jianhua , Li Yan , Hu Fang , Zhong Yi , Xu Yong , Ding Guoxian
Published: November 2012

Brown adipose tissue (BAT) increases energy expenditure and is an attractive therapeutic target for obesity. 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1), an amplifier of local glucocorticoid activity, has been shown to modulate white adipose tissue (WAT) metabolism and function. In this study, we investigated the roles of 11β-HSD1 in regulating BAT function. We observed a significant increase in the expression of BAT-specific genes, includingUCP1,Cidea,Cox7a1, andCox8b, in BVT.2733 (a selective inhibitor of 11β-HSD1)-treated and 11β-HSD1-deficient primary brown adipocytes of mice. By contrast, a remarkable decrease in BAT-specific gene expression was detected in brown adipocytes when 11β-HSD1 was overexpressed, which effect was reversed by BVT.2733 treatment. Consistent with thein vitroresults, expression of a range of genes related to brown fat function in high-fat diet-fed mice treated with BVT.2733. Our results indicate that 11β-HSD1 acts as a vital regulator that controls the expression of genes related to brown fat function and as such may become a potential target in preventing obesity.
Characterization of tyramine β-hydroxylase, an enzyme upregulated by stress in Periplaneta americana
Authors: Châtel Amélie , Murillo Laurence , Bourdin Céline Michelle , Quinchard Sophie , Picard Damien , Legros Christian
Published: November 2012

Octopamine (OA) is an important neuroactive substance that modulates several physiological functions and behaviors of various invertebrate species. This biogenic monoamine, structurally related to noradrenaline, acts as a neurotransmitter, a neuromodulator, or a neurohormone in insects. The tyramine β-hydroxylase (TBH) catalyzes the last step in OA biosynthesis and thus plays a key role in the regulation of synthesis and secretion of OA in neurons. The aim of this study was to characterize TBH in the cockroach Periplaneta americana and to get a better understanding of its regulation under stress conditions in this insect. First of all, five full-length cDNAs encoding TBH isoforms were cloned from the nerve cord of the physiological model P. americana. PaTBH transcripts were found mainly expressed in nervous tissues and in octopaminergic dorsal unpaired median neurons. In addition, a new ELISA assay was developed so as to allow determination of both OA level and TBH activity in stressed cockroaches. Mechanical stressful stimulation led to a significant increase in TBH activity after 1 and 24 h, with a higher induction after 1 h than after 24 h. Thus, TBH could be considered as a promising biomarker of stress in insects rather than OA.
MKP1-dependent PTH modulation of bone matrix mineralization in female mice is osteoblast maturation stage specific and involves P-ERK and P-p38 MAPKs
Authors: Mahalingam Chandrika D , Sampathi Bharat Reddy , Sharma Sonali , Datta Tanuka , Das Varsha , Abou-Samra Abdul B , Datta Nabanita S
Published: November 2012

Limited information is available on the role of MAPK phosphatase 1 (MKP1) signaling in osteoblasts. We have recently reported distinct roles for MKP1 during osteoblast proliferation, differentiation, and skeletal responsiveness to parathyroid hormone (PTH). As MKP1 regulates the phosphorylation status of MAPKs, we investigated the involvement of P-ERK and P-p38 MAPKs in MKP1 knockout (KO) early and mature osteoblasts with respect to mineralization and PTH response. Calvarial osteoblasts from 9–14-week-old WT and MKP1 KO male and female mice were examined. Western blot analysis revealed downregulation and sustained expressions of P-ERK and P-p38 with PTH treatment in differentiated osteoblasts derived from KO males and females respectively. Exposure of early osteoblasts to p38 inhibitor, SB203580 (S), markedly inhibited mineralization in WT and KO osteoblasts from both genders as determined by von Kossa assay. In osteoblasts from males, ERK inhibitor U0126 (U), not p38 inhibitor (S), prevented the inhibitory effects of PTH on mineralization in early or mature osteoblasts. In osteoblasts from KO females, PTH sustained mineralization in early osteoblasts and decreased mineralization in mature cells. This effect of PTH was attenuated by S in early osteoblasts and by U in mature KO cells. Changes in matrix Gla protein expression with PTH in KO osteoblasts did not correlate with mineralization, indicative of MKP1-dependent additional mechanisms essential for PTH action on osteoblast mineralization. We conclude that PTH regulation of osteoblast mineralization in female mice is maturation stage specific and involves MKP1 modulation of P-ERK and P-p38 MAPKs.
Human chorionic gonadotropin regulates gastric emptying in ovariectomized rats
Authors: Seow Kok-Min , Lee Jyun-Lin , Doong Ming-Luen , Huang Seng-Wong , Hwang Jiann-Loung , Huang Wei-Ju , Chang Full-Young , Ho Low-Tone , Juan Chi-Chang
Published: November 2012

Prolongation of gastrointestinal transit resulting in nausea and vomiting in pregnancy (NVP) is the most common phenomenon during the first trimester of pregnancy. Increased human chorionic gonadotropin (hCG) concentration during the first trimester is the most likely cause of NVP. The aim of this study was to investigate the effect of hCG on gastrointestinal transit and plasma concentrations of cholecystokinin (CCK) in ovariectomized (Ovx) rats. I.p. injection of hCG was used to evaluate the dose effect of hCG on gastrointestinal transit in Ovx rats. The CCK antagonist lorglumide was used to clarify the role of CCK in regulating gastrointestinal transit. Gastrointestinal transit was assessed 15 min after intragastric gavage of a mixture of 10% charcoal and Na251CrO4(0.5 μCi/ml). After i.p. administration of hCG, gastric emptying was inhibited in Ovx rats, but intestinal transit was not affected. Plasma CCK concentrations were increased in a dose-dependent manner after hCG treatment, and gastric emptying showed a significant negative correlation with CCK concentrations (P=0.01,r2=−0.5104). Peripheral administration (i.p.) of lorglumide, a selective CCK1receptor antagonist, attenuated the hCG-induced inhibition of gastric emptying in Ovx rats, whereas central administration via the i.c.v. route did not. hCG treatment of Ovx rats inhibits gastric emptying in a dose-dependent manner via a peripheral mechanism of CCK hypersecretion and activation of CCK1receptors.
Educational Perspectives
Authors: Dukhovny Dmitry , Aschner Judy L.
Published: November 2012

After about a decade of graduate and postgraduate medical training, many long hours, and personal sacrifices, perhaps carrying significant debt, you are about to land that long-awaited first job out of fellowship. Coming from the perspective of a fellow’s salary, attending salaries may look like the Promised Land. Starting salaries in neonatology vary from region to region and by type of practice, but the once wide gap between private practice and academic salaries has shrunk in recent years, just as job descriptions have blurred in both venues. Although starting salary is important and often sets the baseline for future raises, there are many factors beyond salary that will influence your lifestyle, career opportunities, job satisfaction, and lifetime finances. This article is intended to educate graduating fellows and other junior faculty or recent graduates about a myriad of factors that should be considered, along with base salary, when negotiating your first (or subsequent) position out of fellowship.
Neonatal Cardiomyopathy
Authors: Wallis Gonzalo , Fricker Frederick Jay
Published: November 2012

Cardiomyopathy is a disease that affects the myocardium and causes mechanical or electrical cardiac dysfunction. The clinical presentation of neonates who have cardiomyopathies is varied, as are the possible causes of the condition and the severity of disease presentation. In our experience, the best approach for evaluating a neonate who has a potential cardiomyopathy is to identify the possible type of cardiomyopathy and subsequently determine the potential cause(s). This review provides a summary of the clinical, laboratory, radiographic, and electrocardiac findings of an infant who has hypertrophic or dilated cardiomyopathy. This summary also provides a detailed overview of the diseases and syndromes associated with both types of cardiomyopathy.
Interference in quorum sensing signal transmission amongst microbial species
Authors: Varga Zoltán , Szabó Mira , Kerényi Monika , Molnár Joseph
Published: November 2012

Antibiotics are usually studied on pure cultures of a single bacterial strain, whereas multi-species communities that inhabit human niches and the biosphere are generally ignored. The modification of quorum sensing (QS) is investigated in a system involving a co-existing signal producer and sensor bacterial cells. A pure culture of merely one bacterial species is quite rare in any niche. The interactions of different bacterial species may therefore be of special importance in pathogenicity, antibiotic resistance and signal transmission.In the present study the authors investigated the QS in model experiments involving several Gram-positive and Gram-negative bacterial species isolated from human infections or laboratory strains. The effects of various compounds on QS were studied in mixed bacterial populations during the incubation period of 24–48 h. As the simplest example of co-existing cell populations, the N-acyl homoserine lactone producing Ezf 10–17 was applied with Chromobacterium violaceum 026 as sensor.The signal of QS transmission between the co-existing QS system and pathogenic bacteria isolated from various patients was found to be modified by certain bacterial cells. The bacterial-bacterial interactions in a mixed flora can change the classical signal transmission in the microbial community and should therefore be taken into consideration in rational chemotherapy.
SWOT analyses of geothermal investment projects — case studies
Authors: Jenei T.
Published: November 2012

The SWOT analyses of two projects are presented in this study, one in the stage of planning, the other in that of operation already. The study points out that while certain traits will emerge as opportunities in the stage of planning, the very same traits will lend themselves to an interpretation as strengths in the operational stage.
GIS-based analysis of renewable energy potentials in urban space
Authors: David T. , Haselmayr T.
Published: November 2012

GIS-based analysis of energy demand facilitates the planning and implementation of renewable energies in urban space. The process of preparing an urban energy concept concerns many actors and facilities, but increases also the acceptance of the energy transition in the proximity. A calculation of energy potentials in the city of Augsburg (Germany) illustrates an usual way of spatial energy planning.
Simulation of a low-reynolds number flow around a cylinder following a figure-8-path
Authors: Baranyi L.
Published: November 2012

This numerical study investigates a circular cylinder placed in a uniform stream and moving along a slender figure-8-path, using a 2D computational method based on the finite difference method. The effects of in-line amplitude of oscillation and of frequency ratio are investigated. Computations for varying amplitude values were carried out at Re = 150, 200 and 250 for a clockwise orbit (in the upper loop). Time-mean and rms values of force coefficients yielded smooth curves and tended to increase with amplitude.

The effect of frequency ratio was investigated at Re = 200, 250 and 300 in the lock-in domain for both clockwise (CW) and anticlockwise (ACW) orientation. Results differ substantially depending on the direction of orientation. Mechanical energy transfer was always positive in ACW direction, which may lead to vortex-induced vibration, and always negative for CW orientation. The time-mean of drag was much lower for CW over the whole frequency ratio domain investigated. For the CW orbit vortex switches were found at specific frequency ratios at Re = 250 and 300. Limit cycle curves for the CW orbit before and after a jump were symmetric, mirror images, and quite complex, while vorticity contours were close to symmetry. These results indicate the possibility of symmetry-breaking bifurcation.
Susceptibility of E. coli, P. aeruginosa, S. aureus and S. epidermidis to Different Bismuth Compounds.
Authors: Vega-Jiménez Alejandro L. , Berea-Montes Edgardo , Almaguer-Flores Argelia
Published: November 2012

Bismuth has been used as an antimicrobial agent for treating gastrointestinal disorders, and has been used in the eradication of Helicobacter pylori. The aim of the present study was to analyze the antimicrobial activity of different Bi compounds against opportunistic pathogens. Ten bismuth compounds were tested with three different concentrations (60, 30 and 10%), against pure cultures of the following bacterial strains: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis. The results show that Bismuth subsalicylate, Bismuth trioxide and Bismuth subgallate had a good antibacterial activity however, Bismuth subsalicylate was the most effective in the inhibition of the four bacterial strains tested. In this study we confirm the antibacterial properties of Bi-based compounds for other bacteria than H. pylori.
Smart Additives for Self-Sealing and Self-Healing Concrete
Authors: De Belie Nele , Van Tittelboom Kim , Snoeck Didier , Wang Jianyun
Published: November 2012

Like broken bones are able to heal themselves, it would be desirable that damaged concrete may be repaired autonomously as high costs are related to the repair. Actually, concrete already has some self-healing properties; when cracks appear, water enters and reacts with unhydrated cement grains which results in crack healing. However, only small cracks can be healed in this way. Therefore, we want to improve the self-healing efficiency by adapting the concrete matrix. By introducing high amounts of fibers several small cracks appear instead of one large crack. Combination with superabsorbent polymers, also called hydrogels, provides immediate crack sealing. Another methodology is to embed encapsulated polymeric agents in the matrix. When cracks appear, the capsules break and the agent is released. Upon contact of both components, they react and the crack is healed. This technique is also combined with CaCO3precipitation of bacteria. In that case, not only polymers but also bacteria and nutrients are encapsulated and released upon cracking. First the polymer reacts, later the bacteria start to convert the nutrients into CaCO3crystals which make the polymer structure denser and thus seal the cracks completely. As crack healing by means of bacteria uses a repair material which is more compatible with concrete we also try to seal cracks by only using bacterial CaCO3. Therefore, bacteria are embedded inside aggregates. Upon cracking, bacteria are exposed to the air and when water enters the crack bacteria become active and fill the crack with CaCO3. From the first results it was noticed that due to autonomous crack healing, water permeability is reduced and regain in mechanical properties is obtained. This means that more durable concrete structures may be obtained by using the proposed self-healing techniques.
Cementitious Blends of Portland Cement with Calcium Sulphate, Fly Ash and Cupola Slag.
Authors: Rodríguez-Mendoza Yared E. , Fuentes Antonio F , Escalante-García J Iván
Published: November 2012

This investigation is on alternative cementitious materials of low cost, energy and environmental emissions. Portland cement (PC) was replaced by different types of calcium sulphate (hemihydrate HH, or anhydrite AN), fly ash (PFA) and cupola slag (CS) from an iron foundry. Pastes of blends of (HH or AN) – CS – PC and (HH or AN) – PFA – PC were characterized. The compositions varied within the ranges of 0 – 35% PC, 15 – 80% HH or AN, 10 – 80% CS and 10 – 80% PFA. The water/solids ratio was kept at 0.45 for HH blends and 0.37 for those of AN. The pastes were cured in dry and for some time under water. Selected blends of CS were repeated with blast furnace slag (BFS) for comparison. CS showed better results over PFA and less than BFS, perhaps as derived from its chemical composition, phase configuration and physical characteristics. These and other results of microstructural characterization will be discussed. This work is part of a broader research on the development of alternative environment friendly hydraulic composite cements of Portland cement highly replaced by calcium sulphate and industrial byproducts.
Methods for Porosity Characterization of Cement Based Materials
Authors: Canut M.M. , Geiker M. R.
Published: November 2012

Important pore structure parameters related to mechanical properties and durability of cement-based materials can be determined by techniques such as scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and low temperature calorimetry (LTC). The methods provide information on porosity characteristics as pore volume, pore thresholds and/or pore size distribution in different size ranges and do therefore to a large extent supplement each other. Pastes of w/b=0.4 with 0%, 40% or 70% slag by volume were cured saturated at 20ºC for up to two years. The porosity was characterized by LTC, MIP, and SEM. Higher volume of pores was obtained by MIP compared to results obtained using LTC and SEM. Measured porosity was correlated with predicted porosity using information on the density and degree of hydration of the cement and slag. Porosity estimation showed best agreement with the porosity data measured by MIP. The use of slag showed the same trend for all tests: a higher total volume of pores, but a lower threshold pore size when compared with Portland cement paste. The findings illustrate the importance of measuring not only pore volume but also threshold pore sizes when characterizing porosity of cement-based materials with different binder compositions.
Hydrogenated Nanocrystalline Silicon based Solar Cell with 13.6% Stable Efficiency
Authors: Yue Guozhen , Yan Baojie , Sivec Laura , Su Tining , Zhou Yan , Yang Jeff , Guha Subhendu
Published: November 2012

Multi-junction solar cells incorporating hydrogenated nanocrystalline silicon (nc-Si:H) exhibit a high current capability and low light-induced degradation. In this paper, we report our recent progress in developing nc-Si:H solar cells using a modified very-high-frequency glow discharge technique. We achieved a short-circuit current density >30 mA/cm2and 10.6% conversion efficiency from single-junction solar cells. Using the improved nc-Si:H cells in an a-Si:H/nc-Si:H/nc-Si:H triple-junction structure, we attained initial and stabilized efficiencies of 13.9% and 13.6%, respectively. Issues related to improving material properties and device structures are addressed. Besides using the conventional techniques, such as hydrogen dilution profiling, optimized Ag/ZnO back reflector, and buffer layers, we found that compensation from Boron and Oxygen micro-doping is also critical in obtaining the above achievements.
Influence of Ammoniating Temperatures on Microstructures, Morphologies and Optical Properties of GaN/Nb Nanostructures by RF Magnetron Sputtering Technique
Authors: Shi Feng , Xue Chengshan
Published: November 2012

GaN nanowires and nanorods have been successfully synthesized on Si (111) substrates by magnetron sputtering through ammoniating Ga2O3/Nb thin films and the effects of ammoniation temperatures on growth of GaN nanowires and nanorods were analyzed in detail. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectra were carried out to characterize microstructures, morphologies, and optical properties of GaN samples. The results demonstrate that sample after ammoniation at 950 °C is single crystal GaN with hexagonal wurtzite structure and high crystalline quality, having the size of 30 - 80 nm in diameter. After ammoniation at 1000 °C, GaN nanorods appear with smooth and clean surface and more than 100 nm in diameter. The optical properties of GaN nanowires grown at 950 °C and nanorods grown at 1000 °C are best with strong emission intensities.
Growth of ZnO Nanostructures on Cellulosic Substrates
Authors: Athauda Thushara J. , Butt Umaiz , Harikumar Parameswar , Ozer Ruya R.
Published: November 2012

ZnO nanostructures such as nanorods and nanoneedles were prepared on both cotton textiles and electrospun cellulosic nanofibers by a simple, two-step hydrothermal process at low temperature in aqueous solution. Commercially available cotton fabrics were used. Cellulosic nanofibers (average diameters of 100 nm) were obtained by electrospinning of cellulose acetate/polyvinyl acetate/polyethylene glycol mixture on glass slides to form non-woven mats.

On cotton textiles, the systematic change of the seed-to-growth solution concentration ratio caused a noticeable variation on the morphology of the nanostructures. The loading ratio of ZnO nanorods and nanoneedles were 37.5% and 18.1 wt%, respectively. Durable superhydrophobicity was achieved with a static water contact angle of 160.7° upon fluorosilane treatment, even after prolonged exposure to UV and plasma irradiation. The surface wettability was found to slightly vary from nanorods (160.7°) to nanoneedles (159.8°). The ZnO nanostructures did not lose their superhydrophobicity after 1 h of agitation in DI water. Excellent UV blocking activities were observed for nanorods and nanoneedles in the wavelength region analyzed. On electrospun cellulosic nanofibers of approximately 100 nm diameter, the loading ratio of ZnO nanorods were found to be 33.3 wt% which are densely and uniformly distributed the entirety of the nanofibers. Although diameters of the nanofibers and cotton fibers are very different in size (around 100 nm and 15-20 micron, respectively) the ZnO loading on electrospun fibers are very close to that of cotton fabric due to the high surface area and coiled nature of electrospun fibers, resulting in high packing density. ZnO nanorods grown on electrospun nanofibers exhibited hydrophilic behavior.
Triiodide Photooxidation and Subsequent Regeneration in UVA Exposed Nano-Structured TiO2 Solar Cell Devices
Authors: Carnie Matthew , Watson Trystan , Worsley David
Published: November 2012

UV exposure of dye-sensitized solar cells (DSCs) results in a loss of triiodide from the electrolyte and this is as a result of direct band gap excitation of the TiO2 semiconductor. The UV stability of a typical electrolyte composition is explored further and the results show that the electrolyte is very stable to UV irradiation in the absence of TiO2 but experiences rapid triiodide loss in its presence. Furthermore, the effect of a periodic triiodide regeneration technique, applied to UV exposed DSCs, is investigated and whilst this treatment does not appear to be able to permanently reverse triiodide loss in UV exposed cells, devices that are periodically regenerated, maintain higher average photocurrents over the UV exposure period.
Intermediate Layers for Thin-Film Polycrystalline Silicon Solar Cells on Glass Formed by Diode Laser Crystallization
Authors: Dore Jonathon , Evans Rhett , Eggleston Bonne D. , Varlamov Sergey , Green Martin A.
Published: November 2012

Intermediate layers between silicon and borosilicate glass are investigated for compatibility with a diode laser crystallization technique for fabrication of thin-film polycrystalline silicon solar cells. SiCx, SiNx and SiOx layers or multilayer stacks of these materials have allowed silicon films of 10μm thickness to be successfully crystallized by diode laser irradiation without dewetting, with each option offering different advantages. SiCx allows the most robust crystallization process, while SiOx is the best barrier to contamination and the most stable layer. SiNx offers the best anti-reflection coating for superstrate configured solar cells. Presently, best device performance is achieved with a SiOxintermediate layer with cells achieving up to ∼540 mV open-circuit voltage.
Formation of Aluminum Oxide Films on Silicon Surface by Aluminum Evaporation in Oxygen Gas Atmosphere
Authors: Nagatomi Y. , Yoshidomi S. , Hasumi M. , Sameshima T. , Kohno A.
Published: November 2012

We report formation of thin aluminum oxide AlOx films on the silicon surface by a simple method of Al metal evaporation in oxygen gas atmosphere. 520 μm thick 30-Ωcm p-type-silicon substrates with a top bare surface and a rear surface coated with 100 nm thick thermally grown SiO2 layers were prepared. AlOx films were formed on the top surfaces by Al metal evaporation up to 20 s in oxygen gas atmosphere at 0.8 Pa with a flow rate of 3 sccm. Samples were subsequently annealed with 9.0x105 Pa H2O vapor at 260°C for 3 h. Measurement of capacitance response to a modulation voltage at 500 kHz as a function of bias gate voltages C-V revealed that AlOx films had the effective oxide thickness ranging from 2.0 and 2.6 nm were formed. C-V measurements also revealed that negative fixed charges were accumulated with a density of 5x1012 cm-2 in AlOx films. Photo-induced carrier microwave absorption measurement resulted in a high minority carrier effective lifetime τeff of 3.6x10-4 s comparable to that of 4.1x10-4 s for thermally grown SiO2 passivation. Field effect passivation was probably caused by negative charges in AlOx so that the surface recombination velocity decreased to 70 cm/s. X-ray reflectivity analysis indicated that the interfacial layer like SiOx was formed between AlOx and Si substrate. High pressure H2O vapor heat annealing caused increase in the density and decrease in the thickness of AlOx layers, although it increased the density and thickness of the interfacial SiOx layer thickness. H2O vapor treatment is effective to improve the quality of nanometer thick AlOxlayer.
SiC multilayer photonic structures with self optical bias amplification
Authors: Vieira M. , Vieira M. A. , Louro P. , Fantoni A. , Silva V. , Barata M.
Published: November 2012

Stacked layered pin a-SiC/a-Si devices based on a filter design are approached from a reconfigurable point of view. This paper shows that a double SiC/Si pin photodiode can be de-composed into two photonic active filters changeable in function. Reconfiguration is provided by optical control signals to the optoelectronic front and back pin building blocks. Depending on the wavelength and irradiation side of the external optical bias the device acts either as a short- and a long- pass band filter or as a band-stop filter, amplifying or rejecting a specific wavelength range. Particular attention is given to the amplification coefficient weights, which allow taking into account the wavelength background effects. We illustrate these effects in detail and discuss the filters transfer function characteristics. We present examples of filters and we propose a reconfigurable device for directed optical logic. An algorithm to decode the information is presented. An optoelectronic model supports the optoelectronic logic architecture.
Atomic Layer Deposition of TiO2 ultrathin films on 3D substrates for energy applications
Authors: Soum-Glaude Audrey , Tian Liang , Blanquet Elisabeth , Brizé Virginie , Cagnon Laurent , Giusti Gaël , Salhi Rached , Daniele Stéphane , Ternon Céline , Bellet Daniel
Published: November 2012

In the present global environmental context, it becomes more and more critical to find efficient solutions to lower our energy consumption on one hand, and to produce energy from clean renewable sources on the other hand. Consequently, research efforts on materials for energy applications are intensifying.

The present work aims at developing optoelectrical components usable for both energy saving (light emitting diodes) and renewable energy production (solar cells) by fabricating p-n heterojunctions based on a single semiconductor, titanium dioxide. TiO2 is indeed a very promising candidate: it is chemically and physically stable under irradiation, transparent to visible and near-infrared light (Eg= 3 – 3.5 eV), presents photocatalytic activity, is non-toxic and low cost, which permits to envisage its large scale use.

In the present paper, the proposed architecture for both solar cells and LEDs is original as well as common for both applications: a three-dimensional architecture based on an anodic alumina nanoporous membrane which serves as nanomask for TiO2 growth in order to enlarge the effective surface of the components. TiO2is synthesized by Atomic Layer Deposition (ALD), a technique particularly well adapted to the deposition of ultrathin films (from one monolayer to few tens of nanometers) on 3D porous substrates patterned with high aspect ratio nanopores.

In this work, the capacity of synthesizing 3D nanostructures is demonstrated. TiO2ultrathin films (10 to 100 nm) were grown by ALD on flat, micropatterned, microporous and nanoporous anodic alumina membranes (AAM) substrates. The films were highly conformal, as confirmed by SEM and TEM imaging. Both EDS and XPS analyses validated the dioxide film stoichiometry.
STUDY OF CO-ASSEMBLED CONDUCTING POLYMERS FOR ENHANCED ETHANOL ELECTRO-OXIDATION REACTION
Authors: Hoa Le Q. , Yoshikawa Hiroyuki , Saito Masato , Tamiya Eiichi
Published: November 2012

Herein, we investigated the effects of polyaniline (PANI) and polypyrrole (PPY) in their native and co-assembled forms as a thin layer on Pt nanoparticle-decorated multi-walled carbon nanotubes (Pt/MWCNTs) toward the ethanol oxidation reaction (EOR). The co-assembled conducting PANI-PPY deposited Pt/MWCNTs was successfully synthesized and demonstrated significant enhancement of the electro-catalytic activity and stability toward EOR as revealed by electrochemical characterizations. The presented results indicate that in the co-assembled form, PANI and PPY retained their own superior effects on the enhancement of stability and catalytic activity via intermediate species removal and ethanol adsorption, respectively. This preliminary result reveals a new strategy for the use of conducting polymers as potential catalyst supports due to its facile fabrication and functionalization, cost effectiveness and environmental friendliness in comparison to alloys and metal oxides, factors which are necessary for the practical application of direct ethanol fuel cells in the near future.
Shape-controlled Synthesis of Silver and Palladium Nanocrystals using β-Cyclodextrin
Authors: Berhault Gilles , Kochkar Hafedh , Ghorbel Abdelhamid
Published: November 2012

ABSTRACT

Shape-controlled Ag and Pd nanocrystals were synthesized using seed-mediated techniques using β-cyclodextrin (β-CD) as structuring agent. First, seeds were obtained by reacting Na2PdCl4 or AgNO3 with a strong reducing agent, NaBH4 in the presence of sodium citrate dihydrate acting as stabilizing agent. These seeds were then injected into a growth solution containing the same metallic precursor, ascorbic acid (as a weak reducing agent) and β-CD as structuring agent. TEM results emphasize a strong influence of the relative concentration of β-CD on the final morphology. In the case of silver, well-facetted nanocrystals were obtained with a progressive shift from kinetically to thermodynamically-controlled nanoobjects when increasing the β-CD/Ag molar ratio. On palladium, β-CD leads to the formation of dendrites (urchin-like) or multipods through controlled aggregation of primary particles. The use of β-CD does not interfere negatively with the catalytic properties of the Pd nanocrystals in the hydrogenation of cinnamaldehyde.
Fabrication and Characterization of Organic Thin Films for Applications in Tissue Engineering: Emphasis on Cell-Surface Interactions
Authors: Wertheimer Michael R. , St-Georges-Robillard Amélie , Lerouge Sophie , Mwale Fackson , Elkin Bentsian , Oehr Christian , Wirges Werner , Gerhard Reimund
Published: November 2012

In several recent communications from these laboratories, we have described observations that thin organic layers which are rich in primary amine (R-NH2) groups are very efficient surfaces for the adhesion of mammalian cells, even for controlling the differentiation of stem cells. We prepare such deposits by plasma polymerization at low pressure (thin films designated “L-PPE:N”, for “Low-pressure Plasma Polymerized Ethylene containing Nitrogen”), at atmospheric (“High”) pressure (“H-PPE:N”), or by vacuum-ultraviolet photo-polymerization (“UV-PE:N”). More recently, we have also investigated a commercially available material, Parylene diX AM.

In the present communication we shall, first, briefly introduce literature relating to electrostatic interactions between cells, proteins, and charged surfaces. Next, we discuss the comparative results of physico-chemical characterizations of the various organic deposits mentioned above, which deliberately contain varying concentrations of nitrogen, [N], and amine groups, [NH2]. Finally, we present certain selected cell-response results that pertain to applications in orthopedic medicine; we discuss the influence of surface properties on the observed behaviors of various cell lines, with particular emphasis on possible electrostatic attractive forces due to positively charged R-NH3+ groups and negatively charged proteins and cells, respectively.
Porous Alumina Template based Versatile and Controllable Direct Synthesis of Silicon nanowires
Authors: Kim Ki-Hwan , Lefeveure Emmanuel , Châtelet Marc , Cojocaru Costel-Sorin
Published: November 2012

Highly densely packed, self-organized silicon nanowires with very narrow diameter distribution were synthesized within porous anodic alumina templates with electrodeposited catalytic metal nanoparticles. For successful catalytic metal nanoparticle deposition, electrochemical-, and chemical barrier layer thinning process was investigated following anodization process. Controlled pulsed electrodeposition process was carried out for a volume calibration of desired catalytic metal nanoparticle deposition inside nanopore arrays using different metal-ion containing electrolyte. Not only single metal nanoparticles, but also multi metal nanoparticles layers were filled inside PAA to enhance metal filling aspect, and to control the volume of nanoparticles more precisely. Using multilayered metal nanoparticles resulted on different SiNW’s growth behavior depending on the types of underlying metal nanoparticles.

SiNWs were successfully synthesized using hot-filament assisted chemical vapor deposition system. Although silicon precursor gas can generally be dissociated at relatively low temperatures, the use of a hot filament activation help decreasing process temperature, and also, highly activated atomic hydrogen generation via the tungsten hot filament placed at gas inlet helps preventing parasitic amorphous silicon deposition on either the alumina membrane surface or the pore wall which hinders appropriate growth of SiNWs in PAA by nanopores clogging. Such densely packed, self-organized SiNWs are of high interest in many application fields like nanoelectronics, optoelectronics, and energy storage/conversion devices etc.
Probing the Viscoelasticity of Collagen Solutions via Optical-Tweezers-Based Microrheology
Authors: Shayegan Marjan , Forde Nancy R.
Published: November 2012

How the molecular structure of proteins in solution correlates with the mechanical properties of the solution at different length scales is not known. Using optical-tweezers based microrheology, we investigate a key physical property, viscoelasticity, of collagen solutions. To do this, we measure short-range thermal fluctuations of probe particles to obtain elastic and viscous moduli of their surrounding medium, and validate our measurement and analysis techniques using the previously studied system of polyethylene oxide. Probing the concentration dependence of viscoelasticity, we find that collagen solutions exhibit elasticity of comparable strength to viscosity when the concentration reaches ∼5 mg/ml. We also find that the presence of telopeptides alters the viscoelasticity of collagen solutions, particularly at high frequencies
Spatial and Temporal Analysis of Microplasma Light Emission
Authors: Blajan M. , Fukunaga H. , Shimizu K.
Published: November 2012

Emission spectroscopy analysis was used to study the microplasma phenomena. The microplasma discharge in Ar, N2/Ar and O2/Ar was analyzed in the discharge gap area and spatial distribution of active species was measured also outside the electrodes. Spatial and temporal distribution showed the propagation of light emission from anode towards cathode within a time period of 190 ns. The measurement of OH peak at 308.9 nm proved the existence of this excited species 1 mm outside the electrodes area.
Separated Anode Experiment to Measure Gas Transport and Methane Reforming within Solid-Oxide Fuel Cell Anodes
Authors: Richards Amy E. , Sullivan Neal P. , Zhu Huayang , Kee Robert J.
Published: November 2012

Solid-oxide fuel cell (SOFC) performance depends greatly upon electrode design. The composite anode plays a critical role in fuel reforming, especially when hydrocarbons are included in the fuel mixture. Because direct observation of fuel reforming in a functioning SOFC is difficult, if not impossible, an alternative experimental configuration is needed to evaluate anode performance. The Separated Anode Experiment (SAE) is designed to isolate and study porous-media transport and heterogeneous reforming chemistry in SOFC anodes. Although the experiment does not incorporate a dense electrolyte membrane or a cathode, it is configured to replicate important aspects of anode behavior in a fully operational SOFC. The experiment is also designed to facilitate model-based interpretation of the results. Comparisons of two significantly different anode structures are used to illustrate the experimental and modeling capabilities.
Fragment Size and Planting Depth Affect the Regenerative Capacity of Bushkiller (Cayratia japonica)
Authors: West Amanda M. , Lewis Dustin F. , Richardson Robert J.
Published: November 2012

Bushkiller (Cayratia japonica) is a herbaceous, perennial vine that reproduces from seed and vegetative root structures within its native range. However, this species is considered invasive in the United States due to prolific shoot production, which can overtop surrounding vegetation. Cultural control practices, such as mulching, have been observed to further the spread of this species through regeneration of root fragments. Research was conducted to determine the regenerative capacity of bushkiller root fragments (1 to 7 cm; 2.5 to 18 inches) buried at various depths (0 to 40 cm). Root length and planting depth affected leaf number, shoot number, plant height, and shoot biomass. Bushkiller leaf density, shoot density, plant height, and dry weight increased as root fragment length increased from 1 to 7 cm; conversely, these variables decreased as planting depth increased from 0 to 40 cm. Results indicate bushkiller regeneration capacity from root fragments is extremely high and control practices that fragment roots should be avoided to reduce further spread.
Ecological Characteristics of Sites Invaded by Buffelgrass (Pennisetum ciliare)
Authors: Abella Scott R. , Chiquoine Lindsay P. , Backer Dana M.
Published: November 2012

Understanding the ecological characteristics of areas invaded and not invaded by exotic plants is a priority for invasive plant science and management. Buffelgrass is an invasive perennial species that managers view as a major threat to indigenous ecosystems of conservation lands in Australia, Mexico, the United States, and other locations where the species is not native. At 14 sites in Saguaro National Park in the Arizona Uplands of the Sonoran Desert, we compared the soil, vegetation, and soil seed bank of patches invaded and not invaded by buffelgrass. Abiotic variables, such as slope aspect and soil texture, did not differ between buffelgrass patches and patches without buffelgrass. In contrast, variables under primarily biotic control differed between patch types. Soil nutrients, such as organic C and NO3–N, were approximately twofold greater in buffelgrass compared with nonbuffelgrass patches. Average native species richness was identical (14 species 100 m−2) between patch types, but native plant cover was 43% lower in buffelgrass patches. Unexpectedly, native seed-bank densities did not differ significantly between patch types and were 40% greater than buffelgrass seed density below buffelgrass canopies. Results suggest that (1) soil nutrient status should not be unfavorable for native plant colonization at buffelgrass sites if buffelgrass is treated; (2) at least in the early stages of buffelgrass patch formation (studied patches were about 10 yr old), native vegetation species were not excluded, but rather, their cover was reduced; and (3) native soil seed banks were not reduced in buffelgrass patches.
Repeated Herbicide Application for Control of Old World Climbing Fern (Lygodium microphyllum) and the Effects on Nontarget Vegetation on Everglade Tree Islands
Authors: Hutchinson Jeffrey T. , Langeland Kenneth A.
Published: November 2012

The effects of annual, aerial and ground, herbicide treatments with glyphosate and metsulfuron were evaluated for control of Old World climbing fern (OWCF) and effects on native plants on tree islands in Arthur R. Marshall Loxahatchee National Wildlife Refuge during 2006 to 2009. Initial aerial herbicide treatments reduced OWCF cover by greater than 98% on metsulfuron-treated islands and greater than 88% on glyphosate-treated islands, but there was a concomitant decrease in native ground cover with both herbicides. Follow-up ground treatments, during years two and three of the study, were effective at maintaining low levels of OWCF. OWCF cover at the end of the study was 1 to 2% of pretreatment cover on metsulfuron-treated islands and 8 to 10% on glyphosate-treated islands. At the end of the study (3 yr after treatment), species richness was dominated by ruderal native species not typically found on tree islands. The survival rate of tree and shrubs was 65 to 93% on islands treated with metsulfuron and 6 to 20% on islands treated with glyphosate. Minimum effects were recorded for canopy cover on tree islands treated with metsulfuron compared with glyphosate. These data indicate that the aerial application of metsulfuron can be used for control of OWCF on tree islands. Follow-up ground treatments will be required for OWCF regrowth and new sporelings and should be conducted within 1 yr of the aerial application.