bluuebunny/crossref_metadata_2025_split huggingface dataset:
[PSI+] Prion Transmission Barriers Protect Saccharomyces cerevisiae from Infection: Intraspecies 'Species Barriers'
Authors: Bateman David A , Wickner Reed B 
Published: November 2011

Abstract
[PSI+] is a prion of Sup35p, an essential translation termination and mRNA turnover factor. The existence of lethal [PSI+] variants, the absence of [PSI+] in wild strains, the mRNA turnover function of the Sup35p prion domain, and the stress reaction to prion infection suggest that [PSI+] is a disease. Nonetheless, others have proposed that [PSI+] and other yeast prions benefit their hosts. We find that wild Saccharomyces cerevisiae strains are polymorphic for the sequence of the prion domain and particularly in the adjacent M domain. Here we establish that these variations within the species produce barriers to prion transmission. The barriers are partially asymmetric in some cases, and evidence for variant specificity in barriers is presented. We propose that, as the PrP 129M/V polymorphism protects people from Creutzfeldt–Jakob disease, the Sup35p polymorphisms were selected to protect yeast cells from prion infection. In one prion incompatibility group, the barrier is due to N109S in the Sup35 prion domain and several changes in the middle (M) domain, with either the single N109S mutation or the group of M changes (without the N109S) producing a barrier. In another, the barrier is due to a large deletion in the repeat domain. All are outside the region previously believed to determine transmission compatibility. [SWI+], a prion of the chromatin remodeling factor Swi1p, was also proposed to benefit its host. We find that none of 70 wild strains carry this prion, suggesting that it is not beneficial.
Film Bulk Acoustic Resonators for Parallel Mass Sensing
Authors: Chen Shih-Jui , Lin Anderson , Baumgartel Lukas , Kim Eun Sok 
Published: November 2011

ABSTRACTThis paper describes the principle of array sensing with film bulk acoustic resonators (FBARs) for combinatory mass sensing and the use of the arrayed FBAR resonant mass sensor for parallel detection of protein-ligand reactions in liquid environment. Various ligands were immobilized on the gold layer on the FBAR’s sensing surface for selective protein detection. The FBARs of the arrayed FBAR were fabricated to have different resonant frequencies from one another by adding slightly varied amount of mass loading on the resonators. Results showed that the arrayed FBAR could detect specific bindings on its surfaces as the concentration of the target ligand was varied.
Development of Non-acidic Poly(ethylene dioxythiophene):poly(styrene sulfonate) for Organic and Hybrid Photovoltaic Devices
Authors: Lee Yun-Ju , Ferreira Summer R. , Copeland R. Guild , Moore Diana L. , Hsu Julia W. P. 
Published: November 2011

ABSTRACTWe demonstrate improved compatibility of poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole transport layer with acid-sensitive materials by addition of a simple base, NaOH or NH4OH, to the aqueous suspension to increase pH. Addition of NaOH to the acidic PEDOT:PSS allowed the deposition of PEDOT:PSS on top of an inverted poly(3-hexylthiophene):ZnO nanoparticle blend hybrid photovoltaic device, and improved device performance due to preservation of the ZnO electron acceptor. To quantitatively investigate the impact of base addition to hole transport layer properties and device performance, we deposited PEDOT:PSS with different pH values on inverted poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester bulk heterojunction devices. We find that NaOH modification results in a substantial work function decrease and series resistance increase. In contrast, the volatile NH4OH leaves PEDOT:PSS with minimal changes in film properties and device performance.
In Vivo Studies of a Nanostructured Titanium Alloy Knee Plate and Pin
Authors: Mirza Rosca Julia C. , Herrera Santana Eladio D. , Vasilescu C. , García Llorente José A. 
Published: November 2011

ABSTRACTTitanium alloys are among the most used metallic biomaterials, particularly for orthopedic applications. Ever since the pioneer titanium alloy (Ti6Al4V) has been used as biomaterial, lack of biocompatibility has been extensively reported and propelled research on improved materials with appropriate mechanical behavior and adequate biocompatibility. Studies have indicated that vanadium produces oxides harmful to the human body; in order to replace vanadium containing Ti alloys, Ti-6Al-7Nb was developed. Today this alloy is the preferred choice for cementless total joint replacements. It is very important to produce a nanostructured bioactive metal implant with appropriate mechanical properties and we applied a chemical and thermal treatment that converts the surface of titanium alloy into bioactive surface. Therefore, bioactive Ti6Al7Nb might represent an alternative for advanced orthopedic implants under load-bearing conditions.Eleven mini-pigs weighting around 50 kg, with free access to food pellets and water, were the experimental animals for this study. Ten of these pigs (one is the control) were anesthetized and after shaving, disinfection and draping, a straight 3 cm incision was made and the implants (plate and pin) were implanted into the epiphyses of the tibiae. Surgical procedures were performed bilaterally. At 6 months after implantation, the mini-pigs were sacrificed.After sacrifice, the segments of the proximal tibia epiphyses containing the implanted plates and pins were cut of, fixed in phosphate-buffered formalin and dehydrated in serial concentrations of ethanol after which they were embedded in polyester resin and then cutted and grounded to a thickness of 75-100 μm. With these samples a lot of observations were made: Scanning Electron Microscopy observations, histological examination at implant surface and histological examination of the bone-implant surface and SEM-EDX examinations were also made.All the results revealed that the plates and pins are in direct contact with newly formed bone without any intervening soft tissue layer. We regard osteoinductive ability of nanostructured Ti6Al7Nb as one of the advantages of this implant in consideration for clinical applications.
Analysis of Cu(InGa)Se2Alloy Film Optical Properties and the Effect of Cu Off-Stoichiometry
Authors: Paulson P. D. , Stephens S. H. , Shafarman W. N. 
Published: November 2011

AbstractVariable angle spectroscopic ellipsometry has been used to characterize Cu(InGa)Se2 thin films as a function of relative Ga content and to study the effects of Cu off-stoichiometry. Uniform Cu(InGa)Se2films were deposited on Mo-coated soda lime glass substrates by elemental evaporation with a wide range of relative Cu and Ga concentrations. Optical constants of Cu(InGa)Se2were determined over the energy range of 0.75–C4.6 eV for films with 0 ≤ Ga/(In+Ga) ≤ 1 and used to determine electronic transition energies. Further, the changes in the optical constants and electronic transitions as a function of Cu off-stoichiometry were determined in Cu-In-Ga-Se films with Cu atomic concentration varying from 10 to 25 % and Ga/(In+Ga) = 0.3. Films with Cu in the range 16–24 % are expected to contain 2 phases so an effective medium approximation is used to model the data. This enables the relative volume fractions of the two phases, and hence composition, to be determined. Two distinctive features are observed in the optical spectra as the Cu concentration decreases. First, the fundamental bandgaps are shifted to higher energies. Second, the critical point features at higher energies become broader suggesting degradation of the crystalline quality of the material.
Physics of CdTe Photovoltaics: from Front to Back
Authors: Karpov V. G. , Shvydka Diana , Roussillon Yann 
Published: November 2011

AbstractWe discuss physical mechanisms underlying the performance and stability of CdTe based thin-film PV. The processes in (i) photovoltaic junction, (ii) back contact, (iii) nonuniformities, (iv) grain boundaries, and (v) light-induced degradation are addressed including their interactions. The physics of thin film PV turns out to be quite different from that of crystalline PV. High surface-volume ratio and lack of crystallinity result in strong interfacial effects, lateral nonuniformities, and shunting-like and adhesion instabilities in thin film structures. This paper is aimed at presenting a ‘big picture'; also, it suggests practical ways of improving thin-film PV.
Two-Dimensional and Multi-Experimental Modeling of Polycrystalline Cu(In,Ga)Se2 Solar Cells
Authors: Metzger W. K. , Gloeckler M. , Ahrenkiel R. K. 
Published: November 2011

AbstractWe use two-dimensional simulations to explore if charged columnar grain boundaries (GBs) in Cu(In,Ga)Se2 (CIGS) solar cells increase device performance. Although the simulations confirm that charged GBs can increase photocurrent by forming minority-carrier collection channels, this generally occurs at the expense of overall efficiency. Furthermore, improvements in photocurrent require significant GB minority collection beyond a diffusion length of the space-charge region. This collection from deep within the base can be detected by quantum efficiency (QE) spectra, electron-beam-induced current (EBIC) experiments, near-field scanning optical microscopy (NSOM), and fast photoluminescence decay. Simulations of all these experiments indicate that GB charge sufficient to significantly increase photocurrent collection is generally inconsistent with actual observations.
Novel Wide-Band-Gap Ag(In1-xGax)Se2 Thin Film Solar Cells
Authors: Nakada Tokio , Yamada Keiichiro , Arai Ryota , Ishizaki Hiroki , Yamada Naoomi 
Published: November 2011

AbstractAg(In1-xGax)Se2 thin films have been deposited on Mo-coated soda-lime glass substrates by the three-stage process using a molecular beam epitaxy (MBE) system. We found a remarkable decrease in the substrate temperature during the 2nd stage in which the film composition changes to a Ag excess. A single phase chalcopyrite AIGS thin film with a slightly Ag poor composition was obtained by using the temperature monitoring composition method. The cell performance of the AIGS thin film solar cell was found to strongly depend on the Ga/(In+Ga) and Ag/(In+Ga) atomic ratios.A high efficiency wide-gap (Eg=1.7eV) Ag(In0.2Ga0.8)Se2 thin film solar cell with a total-area efficiency of 9.3% (10.2% active area efficiency), Voc = 949mV, Jsc = 17.0 mA/cm2, FF = 0.577, and total area = 0.42 cm2 was achieved. The junction formation mechanism of AIGS devices is discussed based on electron beam induced current (EBIC) and scanning capacitance microscopy (SCM) analyses.
Electronic Properties of Modified CuGaSe2 Solar Cells
Authors: AbuShama Jehad A. , Johnston Steve W. , Young David L. , Noufi Rommel 
Published: November 2011

AbstractWe report on the electronic properties of the state-of the art surface-modified CuGaSe2 solar cells. We compare between the 10.2%-efficient surface-modified and the 9.53%-efficient unmodified CuGaSe2 solar cells. We examined our cells using deep level transient spectroscopy (DLTS) and drive level capacitance profiling (DLCP). The DLTS data for the modified CGS exhibits minority traps with activation energies ranging from Ec — 0.3 to Ec — 0.6 eV, whereas that for the pure CGS exhibits minority traps with activation energies ranging from Ec — 0.06 to Ec — 0.1 eV (where Ec is the energy of electrons at the conduction band minimum). While varying the filling pulse duration, we observed the gradual increase in the amplitude of the DLTS signal for these states until it apparently saturates at a pulse duration of ˜1s for the 10.2% cell, and 0.05 s for the 9.53% cell. Increasing the duration of the filling pulse also results in broadening of the DLTS signals and shifting of the maximum of these signals towards lower temperature, whereas the high-temperature sides coincide. Using a model that allows us to distinguish between bandlike states and localized ones based on the dependence of the shape of their DLTS-signal on the filling-pulse duration, we relate the electron trap to bandlike states. The DLCP data shows that the 10.2% cell has a lower carrier concentration, a more uniform defect density profile, a larger depletion width, and a higher drift collection length for photo-generated carriers as compared to our 9.53% CuGaSe2 cell. We also recorded the transient capacitance versus time and found that the 10.2% has responded differently compared with the 9.53% one. The transient capacitance decay curves for these two cells are different.
Current Transients in CdS/CdTe Solar Cells
Authors: Fahrenbruch Alan 
Published: November 2011

AbstractCurrent transient responses to voltage and illumination steps are investigated to elucidate the mechanisms involved in carrier transport in CdS/CdTe cells. For most cells, the response to a dark, forward-bias step after a long dark soak at zero bias is a current growth curve For one such cell, the magnitude of the transient is ≈ 22% of the starting value with half of the growth occurring within ≈ 10 sec, the other half requiring 1000's of seconds. The effect is completely reversible and a mirror-image decay curve at zero bias after dark bias-on equilibration can be measured. Similarly, a complex of growth and decay curves are observed on application of illumination steps with constant bias. Similar transients have been observed by McMahon [1] and del Cueto et al. [2]. This paper is a survey of these effects in cells from 3 different fabricators.These transients, with varying magnitudes and directions, were seen in all the cells studied. In general, the better the cell, the smaller the magnitudes of the transients. They range from changes by factors of 10 for pathological cells to subtle fast transients (1-2%) in excellent cells.Beside the important implications these transients have for accurate measurements of cell efficiency and stability, they provide clues about the carrier transport mechanisms. One of the mechanisms proposed involves the occupation of deep donor traps with small hole cross sections, changing their recombination kinetics. The second hypothesis involves the modulation of the junction barrier profile by changing the charge on deep acceptors and donors by carrier trapping, leading to a change in the effective junction barrier height. A third involves defect mutation such as that of [Cui] donors into [VCd- Cu] acceptor complexes, depending on the position of the quasi-Fermi levels.
Detailed study of metastable effects in the Cu(InGa)Se2 alloys: Test of defect creation models
Authors: Lee JinWoo , Heath Jennifer T. , Cohen J. David , Shafarman William N. 
Published: November 2011

AbstractWe have investigated metastable changes to Cu(InGa)Se2 solar cells in response to infrared optical exposure and forward injection current. Using the drive level capacitance profiling and admittance spectroscopy techniques, we are able to distinguish changes in the free hole carrier concentration from those of a deeper bulk trap. For both types of treatment, changes in these concentrations clearly follow a 1:1 ratio, in agreement with recent predictions of a microscopic model proposed by Lany and Zunger. The creation kinetics follow a strongly sub-linear power law at 250K, and we demonstrate that we can account for this using rate equations in which the metastable effect is initiated by electron capture into an empty defect state. The dependence on time and light intensity is (time) 0.22± 0.03 and (intensity) 0.53± 0.06, except at high light intensities where saturation is observed.
Does CdTe Deposition Affect the Impurity Profile in Sputtered CdS Window Layers?
Authors: Emziane Mahieddine , Durose Ken , Halliday Douglas P. , Bosio Alessio , Romeo Nicola 
Published: November 2011

AbstractWe report a multi-element study of impurities in CdS window layers by dynamic and quantitative SIMS. Two CdS/TCO/glass samples, grown separately using nominally the same conditions, were considered. In203:F grown on soda lime glass was used as TCO followed by a sputtered CdS layer. One of the samples was subsequently used as a substrate for growth of CdTe by CSS. SIMS was carried out on both samples, and O, Na, Si, Cl, Sb, In, Zn, Sn, Pb, Cu, Te, S and Cd were depth profiled. It was shown that before CdTe growth, most of the impurity elements showed flat levels in the CdS ranging from 2-3×1020 cm-3 for Zn and O to 2-3×1017 cm-3 for Na, Cl, Sb and Te. Si was found to segregate at the CdS/TCO interface with a maximum level of 1018 cm-3. However, following CdTe growth, the impurities in the CdS layer showed higher concentrations and different profile shape compared to those before CdTe growth. Some of the impurities also showed a diffusion-like profile following the CdTe growth as compared to before. Possible explanations of these changes are discussed in terms of the purity of the starting materials and the growth environments, as well as the diffusion from the TCO and glass.
Properties of Cu(In,Ga)Se2:Fe Thin Films For Solar Cells
Authors: Sakurai Keiichiro , Shibata Hajime , Nakamura Satoshi , Yonemura Minoru , Kuwamori Shinpei , Kimura Yasuyuki , Ishizuka Shogo , Yamada Akimasa , Matsubara Koji , Nakanishi Hisayuki , Niki Shigeru 
Published: November 2011

AbstractWe have fabricated CIGS:Fe polycrystalline thin films using a standard three-stage method, and investigated the effects of Fe doping on cell performances. The Ga / (In+Ga) ratio was varied between 0.3 ˜ 1.0 (= CGS), and the Fe concentration was varied between 0.0 ˜ 1.2 mol%. The films were characterized by various means, including the cell performance. Increment of the grain size with higher Fe content was observed. Redshift with higher Fe content was observed in the absorbance spectra. The spectral response of the fabricated solar cells deteriorated with higher Fe content, from the long wavelength side.
Formation and characterization of the CuIn(S,Se)2/buffer layer interface in electrodeposited solar cells
Authors: Naghavi N. , Hubert C. , Roussel O. , Sapin L. , Lamirand M. , Guillemoles J. F. , Lincot D. , Kessler J. , Kerrec O. 
Published: November 2011

AbstractThis paper presents the influence of the solution chemistry of chemical bath deposition (pH and complexing agents) on the performance of CuIn(S,Se)2 cells after an initial CN treatment. It is shown that it is possible to modify the deposition conditions of the CdS by increasing the pH of the solution and by replacing the complexing agent (ammonia) by citrate ions. Both NH3 based and citrate based process give very homogenous and covering thin films. However, in the case of the citrate based process a decrease of open circuit voltage (Voc) and fill factor (FF) and thus of the cell efficiencies is observed. This points out that the main role of the buffer layer is not only related to the specific properties of the CdS itself but also to the near surface modifications of the CuIn(S,Se)2 caused by the presence of the complexing agent in the bath.
CdSe Thin Film Preparation by Unipolar Current Pulse Electrodeposition Technique
Authors: Jain Kiran , Karar N. , Chandra H. 
Published: November 2011

AbstractCdSe thin films were prepared using unipolar current pulse electrodeposition technique on fluorine doped SnO2 coated glass plates. The electrodeposition bath consisted of aqueous solution including CdSO4, SeO2 and pH was adjusted using H2SO4. Growth of CdSe was accomplished under wide range of variables like current density, pulse on and off time in order to elucidate the effect on crystalline structure, grain size and optical properties. A low current density and increased off time favored grain orientation and crystallinity. Increased current density and on time favored grain size reduction.
Optimization of RF-Sputtered ITO Films for High NIR Transparency at Low Deposition Temperature
Authors: Zhou J. , Wu X. , Gessert T.A. , Yan Y. , Teeter G. , Moutinho H.R. 
Published: November 2011

AbstractSn-doped indium oxide (ITO) films deposited at temperatures <250°C by r.f. magnetron sputtering are investigated for use as transparent back-contact electrodes to CdS/CdTe top cells in two-junction, mechanically stacked tandem-cell designs. Results show that carrier mobility increases with substrate temperature while beneficial changes in carrier activation occurs at a substrate temperature ~230°C. Small additions of oxygen to the sputtering environment are effective at reducing near infrared (NIR) absorption. Control of these deposition parameters has produced ITO films with NIR absorption (860–1300 nm) < 10%, and electrical resistivity of <1x10-3 ohm-cm.
Optical, Structural and Electronic Properties of CuInS2 Solar Cells Deposited by Reactive Magnetron Sputtering
Authors: Unold T. , Enzenhofer T. , Ellmer K. 
Published: November 2011

AbstractCuInS2 thin films have been prepared by reactive magnetron sputtering from metallic targets in an Ar/H2S atmosphere. The Cu/In ratio and substrate temperature have been varied and absorber layers were processed to solar cell devices using the HMI baseline process. Device efficiencies up to 8.8 % have been achieved. The electronic and optical properties of the solar cell devices were analyzed by Scanning Electron Microscopy, Raman, photoluminescence, current-voltage and quantum efficiency measurements. Raman measurements indicate that Cu-Au defect ordering is present in some of the films, which can be eliminated by appropriate choice of the growth parameters. Photoluminescence measurements show spectra very similar to the spectra found for cells from the two-step sequential process indicating a similar defect structure in these films. No principle obstacles to establishing a one-step reactive magnetron sputtering process for CuInS2 solar cell absorbers have been identified.
Synchrotron-based spectroscopy for the characterization of surfaces and interfaces in chalcopyrite solar cells
Authors: Lauermann Iver , Pistor Paul , Kötschau Immo , Bär Marcus 
Published: November 2011

AbstractIn this paper we describe synchrotron based, state-of-the-art spectroscopic methods for the analysis of surfaces and interfaces in thin film photovoltaic devices, their merits and their limitations. Using results obtained with the “CISSY” end station at the BESSY synchrotron in Berlin, Germany, we show how surface sensitive Synchrotron excitedX-rayPhotoelectronSpectroscopy(SXPS)andSoftX-rayEmissionSpectroscopy (SXES), which yields compositional and chemical depth information in the ten to hundred nm scale, have increased our knowledge of the chemistry of surfaces and buried interfaces of these systems.
A comparison of in situ As doping with ex situ CdCl2 treatment of CdTe solar cells
Authors: Barrioz Vincent , Rowlands Rachael L. , Jones Eurig W. , Irvine Stuart J. C. , Zoppi Guillaume , Durose Ken 
Published: November 2011

AbstractA comparison has been made of MOCVD grown CdTe/CdS solar cells processed either by ex situ annealing with CdCl2 or doping with arsenic, in situ, together with various optional anneals. A materials comparison was made of both routes using Jsc measurements on arrays of gold contacts to the CdTe. The Jsc increased from around 1 mA cm-2 for undoped and unannealed layers to a range of 25-30 mA cm-2 for CdCl2 annealed layers. In situ arsenic doping resulted in Jsc values up to 18 mA cm-2. The annealing characteristics were very different for these films, compared with the CdCl2 annealed films, with annealing at 500°C dramatically reducing the Jsc. Only annealing under nitrogen at 400°C produced an improvement in Jsc and further evidence from SIMS analysis suggests that hydrogen passivation of the arsenic dopant may have a significant effect on the dopant activity.