bluuebunny/crossref_metadata_2025 huggingface dataset:
Serenoa repens extract in the treatment of benign prostatic hyperplasia
Authors: Geavlete Petrisor , Multescu Razvan , Geavlete Bogdan
Published: September 2011

We are experiencing a revival of interest in phytotherapeutic agents, both in Europe and North America, especially as a consequence of patients’ dissatisfaction with the adverse effects of the medical alternatives. One of the most frequently prescribed and studied such agents is Serenoa repens extract, derived from the berry of the dwarf palm tree. We aimed to review the most important published data regarding this type of treatment for benign prostatic hyperplasia. A review of the existing articles regarding the use of Serenoa repens extracts for benign prostatic hyperplasia was performed. The articles were analysed with regard to their relevance, scientific value and the size of the evaluated series. Multiple mechanisms of action have been attributed to this extract, including antiandrogenic action, an anti-inflammatory/anti-oedematous effect, prolactin signal modulation, and an antiproliferative effect exerted through the inhibition of growth factors. Regarding efficacy, European Association of Urology guidelines state that Serenoa repens extracts significantly reduce nocturia in comparison with placebo. However, the guideline committee is unable to make specific recommendations about phytotherapy of male lower urinary tract symptoms owing to the heterogeneity of the products and the methodological problems associated with meta-analyses. Most of the published trials regarding Serenoa repens phytotherapy demonstrate a significant improvement of urinary status and a favourable safety profile. Also, some authors have credited it with giving a significant improvement in erectile function and decreasing complications following transurethral resection of the prostate, especially bleeding. The results of phytotherapy with Serenoa repens extracts are very promising. More high-quality, randomized, placebo-controlled studies are required in order to demonstrate without doubt the true therapeutic value of these products. Particular attention must be focused on differentiating between registered preparations, which are regulated as drugs, and those considered to be food supplements.
Modelling materials for fusion power
Authors: Duffy D
Published: September 2011

Fusion has the potential for delivering safe, clean, low carbon power; however, significant scientific and engineering hurdles must first be overcome. One such hurdle is the design of materials that will withstand the harsh conditions. The materials which line the vessel walls will experience exceptionally high heat and particle fluxes, which will gradually erode the materials and contaminate the plasma. The deuterium–tritium fusion reaction will produce high energy neutrons, which will create defects and transmutation reactions in the vessel walls. These defects, along with the transmutation gasses, evolve over time and change the microstructure and properties of the material. In order to design suitable materials for fusion, the radiation damage, and its evolution over time, must be understood and evaluated for a broad class of materials. Modelling has a vital role to play because it can provide details about processes that occur on length and timescales that are inaccessible to experiment. In this review, the challenges that face designers of fusion power plants are discussed. The modelling techniques that are used to model radiation effects are described and the links between modelling and experiment are discussed. The review concludes with a discussion about the future direction for fusion materials research.
A Cycloalkane-based Thermomorphic System for Organocatalytic Cyclopropanation Using Ammonium Ylides
Authors: Kim Shokaku , Ikuhisa Naoki , Chiba Kazuhiro
Published: September 2011

Highly polar ammonium ylide intermediates derived from α-halocarbonyl compounds were successfully trapped by cycloalkane phase-tagged activated alkenes via a cycloalkane-based thermomorphic (CBT) process, which allows for facile product isolation using a single liquid–liquid extraction step to effectively generate cyclopropane libraries in the cyclohexane phase.
A Highly Selective Colorimetric Chemosensor for Mn2+ Based on Bis(N-salicylidene)ethylenediamine in Pure Aqueous Solution
Authors: Gou Chao , Wu Haiqiang , Jiang Sisi , Yi Chenglin , Luo Jing , Liu Xiaoya
Published: September 2011

A novel easily available chemosensor 1 based on bis(N-salicylidene)ethylenediamine was reported, which exhibits highly selective and sensitive recognition toward Mn2+ in pure aqueous solution over a wide range of tested metal ions with a clear naked eye color change from colorless to red. This represents the first reported colorimetric chemosensor capable of detecting Mn2+ in aqueous solution.
Activity of ceria and ceria-supported gold nanoparticles for the carbamoylation of aliphatic amines by dimethyl carbonate
Authors: Juárez Raquel , Corma Avelino , García Hermenegildo
Published: September 2011

Aliphatic amines react sluggishly with dimethyl carbonate (DMC) to give a mixture of N-methylation and carbamoylation. Nanoparticulated ceria as catalyst increases, in general, conversion and selectivity toward carbamoylation. This increase in catalytic activity and selectivity toward carbamoylation is even increased by deposition of Au nanoparticles on ceria. However, in contrast to aromatic amines for which a complete selectivity toward carbamoylation using ceria-supported Au nanoparticles can be achieved, the catalytic carbamoylation of aliphatic amines by ceria-supported Au nanoparticles occurs only with moderate selectivity.
A Gray Zone between Documentary and Fiction: Interview with Janus Metz
Authors: Sim Gerald
Published: September 2011

Janus Metz discusses his award-winning film Armadillo (2010), which he shot while embedded with a platoon of Danish soldiers in Afghanistan's Helmand province. He locates the film within the discourse of the War on Terror, the possibilities of documentary style, and the mythologies of war narratives.
Protecting Participants, Promoting Progress: Public Perspectives on Community Advisory Boards (CABs) in Biobanking
Authors: Simon Christian M. , Newbury Elizabeth , L'Heureux Jamie
Published: September 2011

Few studies have explored public perspectives on community advisory board (CAB) involvement in biobank-based research. This study held focus groups (n = 7) with 48 individuals residing in the catchment of an emerging comprehensive tissue and DNA biobank in the state of Iowa. Participants recognized benefits of bringing CABs into biobank oversight, including additional levels of protection they could afford research participants. Yet, CAB goals of protecting participants were also seen as potentially antithetical to research and medical progress. Participants expressed uncertainty about the relationship of CABs to IRBs, communities, and industry. Findings suggest members of the public are in principle supportive of CAB involvement in biobanking, yet anticipate a range of problems and concerns. These perceptions will need to be proactively addressed.
Perceptions of Reimbursement for Clinical Trial Participation
Authors: Breitkopf Carmen Radecki , Loza Melissa , Vincent Kathleen , Moench Thomas , Stanberry Lawrence R. , Rosenthal Susan L.
Published: September 2011

A greater understanding of participant views regarding reimbursement will help investigators plan studies that have better potential for reaching target enrollment, maximize efficient recruitment, maintain scientific integrity, and enhance retention over time. As part of a clinical trial in the area of sexual health, healthy women's perceptions of reimbursement for research participation were investigated. Semi-structured, audio-recorded, qualitative interviews were conducted immediately upon women's completion of the clinical trial to enable a participant-driven understanding of perceptions about monetary reimbursement. Audio-recordings were transcribed and analyzed using framework analysis. Women (N = 30) had a mean age of 29.5 ± 5.7 years (range 22–45 years). Sixty-three percent of participants (n = 19) were non-Hispanic (white n = 13, black n = 4, and Asian n = 2), while the remaining were Hispanic (n = 11). Seventy-three percent (n = 22) reported previous participation in research. In general, women viewed reimbursement as a benefit to research participation, the amount of which should reflect time, the inconvenience to the research subject, and the potential for unknown risks in the short- and long-term. They believed reimbursement should take into account the degree of risk of the study, with investigations of experimental products offering greater reimbursement. Women believed that monetary reimbursement is unlikely to coerce an individual to volunteer for a study involving procedures or requirements that they found unacceptable. The results of this study can be used to provide guidance to those planning and evaluating reimbursement for research participation.
What Research Participants Want to Know About Genetic Research Results: The Impact of “Genetic Exceptionalism”
Authors: Ruiz-Canela Miguel , Valle-Mansilla J. Ignacio , Sulmasy Daniel P.
Published: September 2011

The disclosure of individual genetic results has generated an ongoing debate about which rules should be followed. We aimed to identify factors related to research participants' preferences about learning the results of genomic studies using their donated tissue samples. We conducted a cross-sectional survey of 279 patients from the United States and Spain who had volunteered to donate a sample for genomic research. Our results show that 48% of research participants would like to be informed about all individual results from future genomic studies using their donated tissue, especially those from the U.S. (71.4%) and those believing that genetic information poses special risks (69.7%). In addition, 16% of research participants considered genetic information to be riskier than other types of personal medical data. In conclusion, our study demonstrates that a high proportion of participants prefer to be informed about their individual results and that there is a higher preference among those research subjects who perceive their genetic information as riskier than other types of personal medical data.
High efficiency front-illuminated nanotube-based dye-sensitized solar cells
Authors: Li Kangle , Adams Stefan
Published: September 2011

A highly reproducible two-step anodization method is reported to fabricate anatase TiO2 nanotube layers. The nanotube membrane fabricated by this method is highly uniform and crack-free. Large area nanotube membranes can be transferred completely onto transparent FTO electrodes without the need for damaging ultrasonic agitation or acid treatment for application in front-illuminated nanotube-based dye-sensitized solar cells. A 16 μm thin front-illuminated nanotube-based dye-sensitized solar cell produced using this method reaches an efficiency of 6.3% under 1 sun illumination AM1.5.
Nanosecond response organic photodiodes: From device physics towards biosensor applications
Authors: Valouch S. , Kettlitz S. W. , Christ N. , Züfle S. , Ögün C. M. , Nintz M. , Lemmer U.
Published: September 2011

In this work we investigate polymer photodiodes based on a blend system consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and the fullerene derivative (6,6)-phenyl C-butyric acid methyl ester (PCBM). An optimized low source impedance architecture allows measurements in the GHz range with minimum distortion, while at the same time allowing to probe the favourable sandwich device structure. We have studied the underlying device physics and investigated the influence of parameters such as active layer thickness and bias voltage on the transient photocurrent response. Using a numerical simulation software combining a self-consistent drift-diffusion model in conjunction with an optical model based on the transfer matrix method we model the transient photocurrent of polymer photodiodes. Transient photocurrent measurements utilizing this low impedance device architecture excited by 1.6 ns short laser pulses show very good correlation between simulated and measured results. Furthermore we have developed an encapsulation technique to integrate high-speed organic photodiodes onto standard printed circuit boards (PCBs) to avoid the degradation of the devices by humidity or oxygen.
Fluorescent Nanodiamond – A Novel Nanomaterial forIn VivoApplications
Authors: Mohan Nitin , Zhang Bailin , Chang Cheng-Chun , Yang Liling , Chen Chao-Sheng , Fang Chia-Yi , Hsieh Hsiao-Han , Cho Chun-Yi , Wu Yi-Chun , Weng Jui-Hsia , Chung Bon-chu , Chang Huan-Cheng
Published: September 2011

Fluorescent nanodiamonds (FNDs) with a size in the range of 10 – 100 nm have been produced by ion irradiation and annealing, and isolated by differential centrifugation. Single particle spectroscopic characterization with confocal fluorescence microscopy and fluorescence correlation spectroscopy indicates that they are photostable and useful as an alternative to far-red fluorescent proteins for bioimaging applications. We demonstrate the application by performingin vivoimaging of bare and bioconjugated FND particles (100 nm in diameter) inC. elegansand zebrafishes and exploring the interactions between this novel nanomaterial and the model organisms. Our results indicate that FNDs can be delivered to the embryos of both organisms by microinjection and eventually into the hatched larvae in the next generation. No deleterious effects have been observed for the carbon-based nanoparticlesin vivo. The high fluorescence brightness, excellent photostability, and nontoxic nature of the nanomaterial have allowed long-term imaging and tracking of embryogenesis in the organisms.
Method for Fabricating Arrays of Graphene Nanoribbons
Authors: Khokhlov Pavel , Lazarev Pavel , Morozov Evgeny
Published: September 2011

This paper discusses recent progress made in developing an advanced sp2 carbon-based materials that can be produced by wet coating as a thin layer and processed to form highly ordered arrays of Graphene Nanoribbons (GNRs) that attach to the substrate on edge with their planes parallel to each other. The fabrication method is based on carbonization of organic molecules spatially preordered in crystalline film on the substrate. This material, named Ribtan, can be used to fabricate GNRs films over large areas that exhibit a very smooth film surface and can form strong covalent bonds to the substrate. The width (film thickness) of Ribtan GNRs can be controlled precisely down to a few nanometers. We demonstrated advantage of Ribtan material for application in supercapacitors as well as feasibility for use in transparent electrodes, solid tribological coatings, and thin film transistors.
Hydrogen from bioethanol: Catalytic honeycombs loaded with Co-Fe/ZnOfor small-scale energy applications
Authors: Ledesma Cristian , Roig Maria , Llorca Jordi
Published: September 2011

Catalytic monoliths loaded with ZnO-supported Co-Fe catalysts were prepared in one step by the in situ urea method and tested in the ethanol steam reforming reaction to produce hydrogen. The most active and selective formulation was attained with a Fe/Co molar ratio between 0.05 and 0.1, which showed negligible amounts of methane among the reaction products, thus offering an active and selective material for the low-temperature steam reforming of ethanol for small-scale energy applications.
Scaling Challenges for NAND and Replacement Memory Technology
Authors: Prall Kirk
Published: September 2011

Planar NAND technology is rapidly approaching its fundamental limits and will likely transition to a three dimensional structure. The scaling challenges facing NAND will be reviewed. Emerging memory technologies, such as the cross-point, will be discussed. The materials challenges facing emerging memories will be reviewed.
Lanthanum Oxide Capping Layer for Solution-Processed Ferroelectric-Gate Thin-Film Transistors
Authors: Phan Tue T. , Bui Trinh N. Q. , Miyasako Takaaki , Pham Thanh V. , Tokumitsu Eisuke , Shimoda Tatsuya
Published: September 2011

We report on the use of La2O3 (LO) as a capping layer for ferroelectric-gate thin-film transistors (FGTs) with solution-processed indium-tin-oxide (ITO) channel and Pb(Zr,Ti)O3 (PZT) gate insulator. The fabricated FGT exhibited excellent performance with a high “ON/OFF” current ratio (ION/IOFF) and a large memory window (∆Vth) of about 108 and 3.5 V, respectively. Additionally, a significantly improved data retention time (more than 16 hours) as compared to the ITO/PZT structure was also obtained as a result of good interface properties between the ITO channel and LO/PZT stacked gate insulator. We suggest that the LO capping layer acts as a barrier to prevent the interdiffusion and provides atomically flat ITO/LO/PZT interface. This all-oxide FGT device is very promising for future ferroelectric memories.
Inner composition, defects and morphology of AlGaAs nanowires grown by Au-catalyzed MOVPE
Authors: Prete P. , Buick B. , Speiser E. , Lovergine N. , Richter W.
Published: September 2011

The inner composition, defect content and morphology of AlGaAs nanowires (NWs) grown on (111)B-GaAs by Au-catalyzed MOVPE is reported. The NWs grow tapered with their [111] axis normal to the substrate. The Raman spectra of single AlGaAs NWs were measured in non-resonant conditions with sub-μ-meter spatial resolution, allowing determination of the Al content. NWs consist of GaAs for TG<475°C, but show a two-fold compositional structure for TG >475°C, namely an AlxGa1-xAs core surrounded by an AlyGa1-yAs (y<x) shell, ascribed to the combination of Au-catalyzed (axial) and conventional (sidewall) growth. The cross-sectional shape of AlGaAs NWs changes from triangular (for TG=500÷525°C) to almost hexagonal (for TG=550°C), due to an exchange between $\left\{ {\bar 211} \right\}$ and {110} planes as the slowest to grow. The NWs have free-electron concentrations ∼1018 cm-3, due to Si contamination of the Al source.
ZnO-based transparent anodes for organic light-emitting devices
Authors: Sivaramakrishnan K. , Bakken N. , Alford T. L.
Published: September 2011

ZnO/Au/ZnO (ZAZ) electrodes grown on flexible PEN substrates were evaluated as transparent electrodes for organic light-emitting devices (OLEDs). OLEDs fabricated with the ZAZ electrodes showed reduced leakage in contrast to control OLEDs on ITO and reduced ohmic losses at high current densities. At a luminance of 25000 cd/m2, the lum/W efficiency of the ZAZ electrode based device was 5% greater than for the device on ITO. The ZAZ electrodes also allow for a broader spectral output in the green wavelength region of peak photopic sensitivity compared to ITO. The results have implications for electrode choice in display technology.
Partially Hydrogenated Graphene: Semiconductor Material with a Tunable Gap and Its Non-Destructive Optical Characterization
Authors: Gaspari F. , Shkrebtii A.I. , McNelles P. , Cabellos J.L. , Mendoza B.S.
Published: September 2011

We report first principles modeling of partially hydrogenated graphene, with a variety of hydrogen induced superstructures. The dependence of the optical gap on hydrogen content and coverage is examined, to assess the best configurations suitable for optoelectronic applications. Electron and optical DFT LDA gaps in the range between 0.2 and 1.5 eV were obtained for low hydrogen coverage. For such systems, hydrogen clustering (by saturating neighbouring C dangling bonds at the opposite sides of the graphene sheet) is energetically most favourable and generally produces larger gap. More homogeneous H distribution one-side bonded to C-host atoms is, in contrast, less energetically favourable or even structurally unstable and generally produces smaller gap. In addition, ordering of hydrogen was observed at 50% of H, that offers a possibility of transforming 2D graphene to an array of 1D nanowires Calculated linear optical anisotropy and nonlinear second harmonic generation (this will be discussed in a forthcoming paper) indicate these are not only gap sensitive, but can provide an access to microscopic details of the 2D nano-sheets such as symmetry, hydrogen induced structure, degree of hydrogenation, chemical bonding and many others, all promising for device application. The approach developed can be used for graphene/ graphane single layer or bilayer, formed on top of various substrates, where experimental geometries may not provide conditions for complete hydrogenation of the 2D nano-sheet(s).
Biofuels: The Role of Biodiesel and Improving Its Performance
Authors: Knothe Gerhard
Published: September 2011

Concerns about the availability and long-term supply of petroleum-derived fuels have caused the search for alternative sources of energy. Liquid fuels will for some applications be necessary for an indefinite period of time. Therefore, defining relevant feedstocks, producing fuels from these feedstocks and the properties of these fuels are critical issues. Fuels powering compression-ignition (diesel) and turbine (jet) engines are among these liquid energy sources. Biodiesel, defined as the mono-alkyl esters of vegetable oils, animal fats or other triacylglycerol-based feedstocks plays a prominent role in this connection as alternative to petrodiesel fuels. Important issues facing biodiesel are feedstock supply as not enough vegetable oil is available to replace the whole petrodiesel market and the issue of fuel properties, especially cold flow and oxidative stability. The search for additional feedstocks coupled with the food vs fuel issue has increased interest in inedible oils derived from sources such as used cooking oils, jatropha and algae. However, biodiesel from these sources, as biodiesel derived from classical sources such as commodity vegetable oils, must meet performance criteria and this is not necessarily the case. Therefore, modifying the composition of biodiesel, i.e., its fatty ester profile, is a critical issue to enhance its use in the marketplace. Esters of specific fatty acids impart improved properties to biodiesel with esters of decanoic and palmitoleic acid displaying favorable properties for enrichment in biodiesel feedstocks. Renewable diesel is another fuel that can be obtained from triacylglycerol-based feedstocks. In its composition, i.e. alkane-type hydrocarbons, it more closely resembles petrodiesel fuel. While biodiesel is obtained from triacylglycerol-based feedstocks via a transesterification reaction using an alcohol in presence of a catalyst under mild conditions, renewable diesel can be obtained from such feedstocks via a hydrodeoxygenation reaction using hydrogen in presence of a catalyst under more severe conditions. Biodiesel and renewable diesel are compared regarding their production and properties and it is suggested that each fuel has a role to play in an alternative energy mix based on its properties.
DNA as an Engineering Material: From Assembly to Computation on Silicon
Authors: Akin Hayri E. , Zhong Jiebin , Penchev Miroslav , Ozkan Cengiz S. , Ozkan Mihrimah
Published: September 2011

DNA possesses inherent recognition and self-assembly capabilities, making it attractive templates for constructing functional material structures as building blocks for nanoelectronics. Here we report the use of DNA towards the assembly and electronic functionality of nanoarchitectures based on conjugates of carbon nanotubes (CNTs), nanowires (NWs) and DNA computing on Si-CMOS platform. First, assembly of CNTs with DNA is demonstrated and electrical measurements of these nanoarchitectures demonstrate negative differential resistance in the presence of CNT/DNA interfaces, which indicates a biomimetic route to fabricating resonant tunneling diodes. End-to-end assembly of NWs is realized with designed DNA sequences and process is carried on silicon CMOS based microarray platform. Second, this microarray platform is adopted to perform DNA computing. To begin with, the information present in an image is encoded through the concentrations of various DNA strands via selective hybridization and decoded on microarray to recreate the original image. Lately, various satisfiability (SAT) problems, which has long served as a benchmark problem in DNA computing, are solved on this platform via DNA. The goal in a SAT Problem is to determine appropriate assignments of a set of Boolean variables with values of either “true” or “false” such that the output of the whole Boolean formula is true. Other than making 1st time silicon compatible DNA computing, our studies make us understand bio molecules, especially DNA has various advantages for future hybrid technologies.
Synergistic effects on band gap-narrowing in titania by doping from first-principles calculations: density functional theory studies
Authors: Long Run , English Niall J.
Published: September 2011

The large intrinsic band gap in TiO2 has hindered severely its potential application for visible-light irradiation. We have used a passivated approach to modify the band edges of anatase-TiO2 by codoping of X (N, C) with transition metals (TM=W, Re, Os) to extend the absorption edge to longer visible-light wavelengths. It was found that all the codoped systems can narrow the band gap significantly; in particular, (N+W)-codoped systems could serve as remarkably better photocatalysts with both narrowing of the band gap and relatively smaller formation energies and larger binding energies than those of (C+TM) and (N+TM)-codoped systems. Our theoretical calculations help to rationalise experimental results and provide reasonably meaningful guides for experiment to develop more powerful visible-light photocatalysts.
Alloy Oxide Electrocatalysts for Regenerative Hydrogen-Halogen Fuel Cell
Authors: Mondal Sujit K , Rugolo Jason , Aziz Michael J.
Published: September 2011

Stable, catalytically active, and inexpensive halogen electrodes are essential for the success of the regenerative hydrogen-halogen fuel cell as a competitive means of large-scale electricity storage. We report the synthesis and electrochemical testing of two novel electrode materials — ruthenium-cobalt and ruthenium-manganese alloy oxides. These alloys were fabricated by wet chemical synthesis methods as a coating on a titanium metal substrate and tested for chloride and bromide oxidation and for chlorine and bromine reduction. These alloy oxides exhibit high catalytic potency and good electrical conductivity good stability, while having a significantly reduced precious metal composition compared to commercial chloride oxidation electrodes made of the oxide of a ruthenium-titanium alloy. We tested alloys with Ru content as low as 1% that maintained good electrochemical activity. Stability tests indicate immeasurably small mass loss.
Comparison of ion beam and electron beam induced transport of hot charge carriers in metal-insulator-metal junctions
Authors: Hopster Johannes , Diesing Detlef , Wucher Andreas , Schleberger Marika
Published: September 2011

The generation of hot charge carriers within a solid bombarded by charged particles is investigated using biased thin film metal-insulator-metal (MIM) devices. For slow, highly charged ions approaching a metal surface the main dissipation process is electronic excitation of the substrate, leading to electron emission into the vacuum and internal electron emission across the MIM junction. In order to gain a deeper understanding of the distribution and transport of the excited charge carriers leading to the measured device current, we compare ion induced and electron induced excitation processes in terms of absolute internal emission yields as well as their dependence on the applied bias voltage.
First Principles Analysis of Ultra-Thin Silicon Films with Dimer Structures
Authors: Kamiyama Eiji , Sueoka Koji
Published: September 2011

The impact of dimer formations at the surfaces of the internal atoms of silicon (Si) thin film was evaluated by examining silicon-on-insulator (SOI) and plate models. In the SOI models, a dimer formation was modeled at one side of the Si thin film. The plate models had two dimers at each surface, which had been considered as a Si bulk model in previous studies. First principles calculation showed that the deviations of Si atoms from the first to fourth layers of the SOI models did not differ remarkably from those of the plate models. The internal atoms deeper than the fifth layer showed near-zero deviation in some of the SOI models and had evident non-zero deviation in the other SOI models. All the SOI and plate models showed lower Si atom self-energy than in the Si bulk. The layer-to-layer distance of internal atoms in the films became longer than that of atoms in Si bulk. These results indicated that (i) Si films with dimer surfaces are relaxed by deviations in the whole film, and (ii) even the thick plate model with 32 layers dose not reveal the nature of Si bulk.
Semiconducting Polymer and Hydrogenated Amorphous Silicon Heterojunction Solar Cells
Authors: Middya A. R. , Schiff Eric A.
Published: September 2011

In this work, we report on investigation of p-type semiconducting polymer, {poly(3,4 polyethylenedioxythiophene)-poly(styrenesulfonate)} (PEDOT:PSS) as the p-layer in NIP and PIN hydrogenated amorphous silicon (a-Si:H) solar cells. The rectification ratio of solution-casted diode is ∼ 10, it increases to 3×104 when PEDOT:PSS is deposited by Spin Coating technique. We observed additional photovoltaic effect when light is illuminated through polymer side. So far, best solar cells characteristics observed for PEDOT:PSS/a-Si:H hybrid solar cells are Voc ≈ 720 mV and Jsc ≈ 1 - 2 mA/cm2.
Density-Functional Theory Study of Hydrogen Induced Platelets in Silicon
Authors: Bîlteanu Liviu , Crocombette Jean-Paul
Published: September 2011

In this contribution we present the results of Density-Functional Theory (DFT) calculations of platelets as modelled by infinite planar arrangements of hydrogen atoms and vacancies in (100) planes of silicon. From the observation of the relaxed platelet structures and the comparison of their energy with the one of hydrogen molecules dissolved in silicon we were able to evidence several features. A planar arrangement of hydrogen atoms inserted in the middle of Si-Si bonds proves unstable and Si bonds must be broken for the platelet to be stable. In the (100) plane the most stable configuration is the one with two Si-H bonds (a so-called SiH2 structure). It is possible to generate SiH3 structures which are more stable than hydrogen dissolved in Si bulk but less than SiH2 structures but SiH1 or SiH4 sometimes observed in experiments prove unstable.
Absorption Enhancement in Plasmonic Solar Cells by Incorporation of Periodic Nanopatterns
Authors: Wang W. , Wu S. , Lu Y.L. , Reinhardt Kitt , Chen S.C.
Published: September 2011

Currently, the performances of thin film solar cells are limited by poor light absorption and carrier collection. In this research, large, broadband, and polarization-insensitive light absorption enhancement was realized via incorporation of different periodic nanopetterns. By studying the enhancement effect brought by different materials, dimensions, coverage, and dielectric environments of the metal nanopatterns, we analyzed the absorption enhancement mechanisms as well as optimization criteria for our designs. A test for totaling the absorption over the solar spectrum shows an up to ∼30% broadband absorption enhancement when comparing to conventional thin film cells.
Wide-spectral-range, Expanded-beam Spectroscopic Ellipsometer and its Application for Imaging/Mapping of Graded Nanocrystalline Si:H Films
Authors: Nemeth A. , Attygalle D. , Dahal L. R. , Aryal P. , Huang Z. , Salupo C. , Petrik P. , Juhasz G. , Major C. , Polgar O. , Fried M. , Pecz B. , Collins R. W.
Published: September 2011

A prototype expanded-beam spectroscopic ellipsometer has been developed that uses uncollimated (non-parallel, diffuse) illumination with a detection system consisting of an angle-of-incidence-sensitive pinhole camera for high-speed, large-area imaging/mapping applications. The performance of this novel instrument is being tested for imaging/mapping of mixed-phase hydrogenated silicon films having graded amorphous (a-Si:H) and nanocrystalline (nc-Si:H) components throughout the film depth. The speed of the measurement system makes the instrument suitable for use on production lines. The precision enables detection of subnanometer thicknesses, and refractive index and extinction coefficient changes of 0.01. Angle-of-incidence and mirror calibrations are made via well-known sample structures. Alternative commercial instrumentation for mapping by spectroscopic ellipsometry must translate the sample or ellipsometer in two dimensions. For this instrumentation, even a 15 × 15 cm2 sample with cm2 resolution requires > 200 measurements and at least 15 min. By imaging along one dimension in parallel, the expanded-beam system can measure with similar resolution in < 2 min. The focus of recent instrumentation efforts is on improving the overall system spectral range and its performance.
Semi reflective biopolymer layers for the detection of biomass hydrolytic enzymatic activities
Authors: Cerclier C. , Moreau C. , Guyomard-Lack A. , Bonnin E. , Bizot H. , Cathala B.
Published: September 2011

Structural colors were obtained by the deposition of plant cell walls biopolymers films on reflective support. Multilayered xyloglucan(XG)/cellulose nanocrystals(CN) thin films were obtained by spin-assisted layer-by-layer assembly while arabinoxylan (AX) thin films were elaborated via the spin-coating of AX/melamine formaldehyde resin followed by a cross-linking step. The effects of aqueous solutions on the stability of the structural colors were evaluated. The films were subsequently used to detect cellulase and xylanase activities by the change in the colors due to the film degradation. This enzymatic assay method appeared to be about 150 more sensitive that a standard method. Moreover due its simplicity, the method could be used to detect other biomass-hydrolyzing enzymes and more generally for other heterocatalytic degradations of solid polymer layers.
Hydrogen Production from Ethanol. Comparing Thermal Catalytic Reactions to Photo-catalytic Reactions.
Authors: Scott M. , Nadeem A.M. , Waterhouse G.I.W. , Idriss H.
Published: September 2011

Hydrogen production from renewables such as bio-ethanol is one of the most promising processes for energy carriers in a sustainable way. In this work we review and compare two catalytic systems: one based on thermal activation over bimetallic catalysts (Rh-Pd/CeO2) and the other over photo-excited semiconductor catalysts (Au/TiO2 anatine, rutile and anatase/rutile). It is found that the hydrogen yield is far higher on the thermally activated catalysts (at 773K) when compared to that of the photo-exited catalysts (at room temperature); about 60 times. However, the photo-excited catalysts are a promising way to create a fully sustainable system for future applications if the complete removal of hydrogen atoms from water and ethanol are obtained at room temperature.
Ab initio Study of the Hydrogen Molecule on ZnO Surfaces
Authors: Liu Po-Liang , Wu Yen-Ting , Siao Yu-Jin
Published: September 2011

We conduct first-principles total-energy density functional calculations to study the interaction of H2 on ZnO surfaces. Four surface models of Zn-terminated (0001)-, O-terminated (0001)-, $(10{\bar 1}0)-$, and $(2{\bar 1}{\bar 1}0)-$oriented ZnO planes in the presence of H2 are evaluated. The relative stability of four different surface models is examined as a function of the chemical potentials of oxygen and hydrogen. We find that only surfaces of O-terminated (0001)-oriented ZnO models exhibit active sites for the dissociation of H2, which in turn enables the formation of water from dissociative chemisorption of 2H on the O-terminated ZnO(0001) surface. The surface energy of O-terminated ZnO(0001) surface in the presence of water was found to be negative under the O-rich and H-rich condition. The findings agree with the experimental observations that ZnO epitaxial layers are easily etched by hydrogen at typical growth temperatures.
Control of Crystal Orientation of Epitaxial Si nanowires on Si Substrate Using AAO template
Authors: Shimizu Tomohiro , Wang Qi , Wang Chonge , Inoue Fumihiro , Koto Makoto , Jeon Minsung , Shingubara Shoso
Published: September 2011

Control of crystal orientation of vertically grown epitaxial Si (111) and (110) nanowire arrays on Si substrate has been demonstrated using a combination of an anodic aluminum oxide (AAO) template and vapor – liquid – solid (VLS) growth method. The crystal orientation of the nanowire was investigated by transmission electron microscopy. A growth direction of the nanowire arrays was guided perpendicular to the surface of the substrate by the AAO template, and the crystal orientation of the nanowire arrays was selected using the single crystal Si substrate properly cut in desired orientation.
Behavior of Two Titanium Alloys in Simulated Body Fluid
Authors: Mirza Rosca Julia C. , Herrera Santana Eladio D. , Drob S. , Martinez Ortigosa Agurtzane
Published: September 2011

Titanium possesses an excellent corrosion resistance in biological environments because the titanium dioxide formed on its surface is extremely stable. When aluminium and vanadium are added to titanium in small quantities, the alloy achieves considerably higher tensile properties than of pure titanium and this alloy is used in high stress-bearing situations. But these metals may also influence the chemostatic mechanisms that are involved in the attraction of biocells. V presence can be associated with potential cytotoxic effects and adverse tissue reactions. The alloys with aluminium and iron or with aluminium and niobium occur to be more suitable for implant applications: it possesses similar corrosion resistance and mechanical properties to those of titanium-aluminium-vanadium alloy; moreover, these alloys have no toxicity.

In this paper, pure Ti, Ti-6Al-7Nb and Ti-6Al-4Fe with a nanostructured surface were studied. Data about mechanical behavior are presented. The mechanical behavior was determined using optical metallography, tensile strength and Vickers microhardness.

For the electrochemical measurements a conventional three-electrode cell with a Pt grid as counter electrode and saturated calomel (SCE) as reference electrode was used. AC impedance data were obtained at open circuit potential using a PAR 263A potentiostat connected with a PAR 5210 lock-in amplifier. The ESEM and EDAX observation were carried out with an environmental scanning electronic microscope Fei XL30 ESEM with LaB6-cathode attached with an energy-dispersive electron probe X-ray analyzer (EDAX Sapphire). After 3 days of immersion in simulated body fluid the nucleation of the bone growth was observed on the implant surface.

It resulted that the tested oxide films presented passivation tendency and a very good stability and no form of local corrosion was detected. The mechanical data confirm the presence of an outer porous passive layer and an inner compact and protective passive layer. EIS confirms the mechanical results. The thicknesses of these layers were measured. SEM photographs of the surface and EDX profiles for the samples illustrate the appearance of a microporous layer made up of an alkaline titanate hydrogel. The apatite-forming ability of the metal is attributed to the amorphous sodium titanate that is formed on the metal during the surface treatment.

The results emphasized that the surface treatment increases the passive layer adhesion to the metal surface and improves the biocompatibility of the biomedical devices inducing the bone growth on the implant surface.
Bone-Inspired Multicomponent Bionanocomposites with a Simple Drop-Cast Processing Strategy
Authors: Biswas Abhijit , Biris Alexandru S. , Bayer Ilker S.
Published: September 2011

We describe an innovative and simple drop-cast processing strategy to create bonelike multicomponent bionanocomposite materials that consist of an organic poly(ε-caprolactone) (PCL) matrix, minerals such as hydroxyapatite (HAP) and CaCO3, and collagen fibers. The process allows morphological and structural control to achieve the desired nanostructure of the bone mimics. The fabrication method involves adding inorganic and organic components sequentially followed by controlling the growth conditions and composition. This enables organization of collagen nanofibers (∼ 100 nm) into scaffolds while simultaneously allowing nucleation and co-alignment of hydroxyapatite spheres (∼ 100 – 500 nm) within aligned, thermally stable collagen fibers in the porous PCL matrix. We achieved high calcium (26%) and oxygen (17%) within the bioscaffold and adequate phosphorous compositions comparable to the levels of bone tissues. Adequate mineralization along with high oxygen content may help maintain the required bone mineral density and revascularization for nutrient and compensate for the loss of oxygen delivered to the bone cells. Furthermore, since the bionanocomposite scaffold is made of natural materials (calcium, phosphorous and collagen) found in bone tissue, the formulation makes it an excellent biocompatible/biodegradable material. Our preliminary results suggest huge potential of these advanced bionanocomposite scaffolds for bone substitutes and tissue engineering applications.
Assessment of marine biofilm attachment and growth for antifouling surfaces under static and controlled hydrodynamic conditions
Authors: Salta Maria , Wharton Julian A. , Stoodley Paul , Wood Robert J.K. , Stokes Keith R.
Published: September 2011

This investigation has assessed natural product antifouling performance of an isolated compound from a terrestrial source against marine biofilm forming bacteria, Cobetia marina and Marinobacter hydrocarbonoclasticus. Novel bioassay protocols using the hydrodynamic system and its well plate microfluidics capability were developed to test the in situ antifouling efficacy of the natural product against biofilm attachment under two shear stresses (0.07 and 0.3 Pa). The hydrodynamic results allowed for the first time the direct observation of the natural product influence on newly attached marine biofilms and the evolution of the antifouling affect with time. Biofilm attachment behaviour appeared to be markedly different in the presence of the natural product, illustrated by limited cluster and extracellular polymeric substance formation which suggests an interference of the bacterial attachment mechanisms. Ultimately, this is fundamental in developing greater understanding of the biofilm kinetics. These observations were confirmed using epifluoresence and confocal microscopy, with the additional corroborative data on bacterial cell integrity using the LIVE / DEAD nucleic acid kit.
Chemical functionalization of carbon nanotubes with aryl diazonium salts
Authors: Golosova Anastasia A. , Papadakis Christine M. , Jordan Rainer
Published: September 2011

We describe a facile and direct method for the functionalization of single-walled carbon nanotubes with4’-substituted phenyls and biphenyls. By means of Raman spectroscopy and thermogravimetric analysis we demonstrate that a simple protocol of a direct chemical grafting in acetonitrile solution of the corresponding diazonium salts at room temperature results in a formation of stable aryl monolayers on carbon nanotubes.
Morphology control of copper indium disulfide nanocrystals
Authors: Kruszynska Marta , Borchert Holger , Parisi Jürgen , Kolny-Olesiak Joanna
Published: September 2011

In this report, we present a hot-injection strategy for the synthesis of CuInS2 (CIS) nanocrystals with hexagonal, pyramidal and nanorod shapes. For that purpose copper (I) and indium (III) acetates were dissolved in oleylamine as a high-boiling solvent. Tert-dodecanethiol (t-DDT) was used as a sulfur source. It was mixed with 1-dodecanothiol (1-DDT) and injected at a high temperature. The presence of the second dodecanethiol was necessary to control the growth of the synthesized nanocrystals. We observed a strong influence of the t-DDT amount on the morphology of the CIS nanocrystals. By the variation of the injected solution uniform CIS nanorods with different aspect ratio and size were obtained.
Wafer Bonded Ge-Si Heterostructure for Avalanche Photodiode Application
Authors: Byun Ki Yeol , Hayes John , Gity Farzan , Corbett Brian , Colinge Cindy
Published: September 2011

In this study, we investigate directly bonded germanium-silicon interfaces to facilitate the development of high quality germanium silicon integration for Avalanche photodiode application. Angle resolved x-ray photoelectron spectroscopy data is presented which provides the chemical composition of the germanium surfaces as a function of the surface passivation. The hetero-structure is characterized by measuring forward and reverse current and comparing the measured results to TCAD simulation. The physical structure of hetero-junction is supported by high resolution transmission electron microscopy.
Ion implantation of Carbon and Silicon into Ge2Sb2Te5: Ion Profiles and Post Crystallization Redistribution
Authors: Cohen Guy M. , Raoux Simone , Hopstaken Marinus , Maurer Siegfried
Published: September 2011

Ion implantation of Ge2Sb2Te5 (GST) enables localized doping of the film by using conventional lithography. Although the doped region dimensions and the doping concentration profile are defined by the opening in the mask and the ion energy, longitudinal and lateral straggling of implanted ions leads to a spread in the ions final location. Additionally, a thermal treatment such as one that induces a phase transition may lead to redistribution of the implanted dopants and further increase the spread. In this work we demonstrate doping of GST by ion implantation. Using Secondary Ion Mass Spectrometry (SIMS) we studied the as-implanted doping profiles obtain by ion implantation of carbon and silicon into GST. We also investigated by SIMS the dopant redistribution following a recrystallization annealing. The as-implanted ion profiles were found to be in fair agreement with TRIM simulation. The dopants profiles show little change after a crystallization annealing at 200°C for silicon doping and at 350°C for carbon doping.
Electro-migration of Zinc during current-assisted pressure sintering of β-Zn4Sb3 – effect of process parameters and its influence on the thermoelectric properties
Authors: Dasgupta T. , Stiewe C. , Boettcher L. , Yin H. , Iversen B.B. , Mueller E.
Published: September 2011

Compaction of β-Zn4Sb3 was carried out by current-assisted short term sintering under pressure (STS) using different material and process parameters. Surface Seebeck mapping (PSM) of the compacted specimens (along the uniaxial pressing direction) shows a wide gradation ranging from ∼40–180 μV/K due to electro-migration of Zinc along the current direction. The wide distribution of S corresponds to a mixture of Zn-Sb phases [1] which arise depending on the extent of Zinc migration during the STS process. Variation in the material and process parameters (average particle size, heating rate, compaction time/temperature) results in different spatial distribution of S. Measurements of electrical (σ), thermal (κ) conductivities and Seebeck (S) coefficients between room temperature and 523 K were carried out on two specimens having different average S values and distributions as observed by the PSM. The results indicate an increase in the lattice thermal conductivity (κL) and subsequent lower ZT in the specimens compared to the reported values for β-Zn4Sb3.