bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatiotemporally Optimal Fractionation in Radiotherapy
Authors: Saberian Fatemeh , Ghate Archis , Kim Minsun 
Published: May 2017

We present a spatiotemporally integrated formulation of the optimal fractionation problem using the standard log-linear-quadratic survival model. Our objective is to choose a fluence map and a number of fractions to maximize the biological effect of tumor dose averaged over its voxels subject to maximum dose, mean dose, and dose-volume constraints for various normal tissues. Constraints are expressed in biologically effective dose equivalents. We propose an efficient convex programming method to approximately solve the resulting computationally difficult model. Through extensive computer simulations on 10 head-and-neck and prostate cancer test cases with a broad range of radiobiological parameters, we compare the biological effect on tumors obtained by our integrated approach relative to that from two other models. The first is a traditional intensity modulated radiation therapy (IMRT) fluence map optimization model that does not optimize the number of fractions. The second assumes that a fluence map is available a priori from a traditional IMRT optimization model and then optimizes the number of fractions, thus separating the spatial and temporal components. The improvements in tumor biological effect over IMRT were 9%–52%, with an average of 22% for head-and-neck, and 53%–108%, with an average of 69% for prostate. The improvements in tumor biological effect over the spatiotemporally separated model were 15%–45%, with an average of 27%, and 17%–23%, with an average of 21%, for head-and-neck and prostate, respectively. This suggests that integrated optimization of the fluence map and the number of fractions could improve treatment efficacy, as measured within the linear-quadratic framework.
Characterization of Flexural and Impact Strength of Jute/Almond Hybrid Biocomposite
Authors: Singh V. K. , Bansal G. , Negi P. , Bisht A. 
Published: May 2017

Abstract
A hybrid composite consisting of jute fiber-almond shell particle reinforced in epoxy resin modified with 1 weight percentage (wt.%) depolymerised natural rubber (DNR) was fabricated using hand lay-up technique. In the present investigation, we modified the composite by fabricating a composite by filling it with a mixture of almond shell particle and jute fiber, keeping total reinforcement wt. % fixed to 20 wt. %, but varying the ratio of jute fiber and almond shell particle in the manner almond/jute: 100/0, 75/25, 50/50, 25/75, 0/100. Through testings and experimentations, it was concluded that flexural strength is improved by 26.75 %. Through SEM, how the particles and fiber are dispersed in the matrix, how they are bonded to matrix or each other, how at higher wt. % fibers or particles form clusters and effect bonding, with increase in length, how fiber defect increases and composite failure due to fiber pull out or splitting of fiber increases, was seen and justified our results. Thus, it was concluded that 15 wt. % almond shell particle and 5 wt. % treated jute fiber having fiber length 10 mm filled in epoxy modified with 1 wt. % DNR gave the optimum results from various combinations. As such, properties have significantly improved for hybrid composite as compared to pure fiber/ pure particle based composite.
LA SIMULACIÓN COMO RECURSO ELECTRÓNICO PARA POTENCIAR LAS HABILIDADES COGNITIVAS DEL ESTUDIANTADO
Authors: SANDÍ DELGADO JUAN CARLOS , CRUZ ALVARADO MAINOR ALBERTO 
Published: May 2017

Este artículo reúne los resultados del proceso de elaboración de un prototipo de recurso electrónico (simulador) que le permitirá al estudiantado activar, adquirir y desarrollar habilidades cognitivas para potenciar la construcción de nuevos conocimientos significativos en el área de la seguridad vial. El público meta fue la población estudiantil a nivel de educación primaria costarricense, específicamente en el Cantón de Pococí de la Provincia de Limón.Para responder a los objetivos de este estudio se utilizó el enfoque de la investigación cualitativa. La información fue recopilada a partir de una revisión bibliográfica y los datos primarios fueron recolectados a través de la realización de consultas telefónicas a responsables de la gestión administrativa de varios centros educativos seleccionados por conveniencia. La información secundaria se obtuvo a través de la recopilación de fuentes documentales encontradas en Internet, como artículos, tesis y memorias de congresos.Se concluye que la simulación o los ambientes simulados de aprendizaje posibilitan al estudiantado activar variedad de habilidades cognitivas: la memoria a corto y largo plazo, la metacognición, el razonamiento, la resolución de problemas y la representación icónica, entre otros.
CARACTERIZACIÓN MORFOLÓGICA DE 15 GENOTIPOS DE PIMIENTO (CAPSICUM ANNUUM) CULTIVADOS BAJO INVERNADERO EN COSTA RICA
Authors: ELIZONDO CABALCETA ESTEBAN , MONGE PÉREZ JOSÉ ELADIO 
Published: May 2017

Se realizó una caracterización morfológica de 15 genotipos de pimiento con frutos de forma cuadrada o rectangular cultivados bajo invernadero, tanto a nivel cualitativo (5 variables) como cuantitativo (8 variables). Se presentaron diferencias estadísticamente significativas entre genotipos para las variables cuantitativas. Los datos muestran una amplia variabilidad en cuanto a la altura de la planta (0,82 – 1,41 m), área foliar (73,91 – 122,26 cm2), diámetro del tallo (12,55 – 16,55 mm), longitud del tallo (11,38 – 31,38 cm), ancho del fruto (6,85 – 9,28 cm), longitud del fruto (7,78 – 13,17 cm), relación largo/ancho del fruto (0,90 – 1,92), y espesor de la pared del fruto (4,84 – 6,31 mm). Esta información es útil para los productores en el proceso de selección del genotipo a utilizar en su sistema productivo, según el nicho de mercado de interés.
Ultrasound Emission from Porous Silicon: Efficient Thermoacoustic Function as a Depleted Nanocrystalline System
Authors: Koshida N. , Nakajima T. , Yoshiyama M. , Ueno K. , Nakagawa T. , Shinoda H. 
Published: May 2017

AbstractIt is demonstrated that luminescent porous silicon (PS) exhibits an efficient thermoacoustic effect owing to its extremely low thermal conductivity. The experimental device is composed of a patterned thin Al film electrode (30 nm thick), a microporous PS layer (10–50 μm thick), and a single-crystalline Si (c-Si) wafer. The PS layer was formed by a conventional anodization technique. When an electrical input is provided to the Al electrode as a sinusoidal current followed by Joule's heating, a significant acoustic pressure is produced in front of the device as a result of an efficient heat exchange between PS and air. The output amplitude is in inverse proportion to the square root of the input frequency (0.1-100 kHz) as predicted by a theoretical analysis. The observed effect is a novel useful function of PS as a completely depleted nanocrystalline system.
Production of Silicon Nanocrystals by Thermal Annealing of Silicon-Oxygen and Silicon-Oxygen-Carbon Alloys: Model Systems for Chemical and Structural Relaxation at Si-SiO2 and Sic-SiO2 Interfaces
Authors: Lucovsky Gerald , Wolfe David , Hinds Bruce 
Published: May 2017

AbstractThis paper discusses the formation of silicon nanocrystals, nc-Si, by thermal annealing of hydrogenated amorphous thin films of SiOx, x<2 and (Si, C)Ox, x<2. Comparisons are made with SiCx films, providing additional insights into pathways for generation of nc-Si. These alloys are used as model systems for understanding chemical and structural relaxations occurring at Si-SiO2 and SiC-SiO2 interfaces during post-oxidation thermal annealing. This then provides important information for optimized processing of Si-SiO2 and SiC-SiO2 interfaces for device applications.
Effects of Various Hydrogen Dilution Ratios on the Performance of Thin Film Nanocrystalline/Crystalline Silicon Solar Cells
Authors: Song Y. J. , Anderson W. A. 
Published: May 2017

AbstractLow temperature growth of hydrogenated nanocrystalline silicon film (nc-Si:H) by microwave electron cyclotron resonance chemical vapor deposition has been performed employing a double dilution of silane, using a He carrier for SiH4 and its subsequent dilution by H2. A series of Raman spectra and AFM pictures has shown that a very thin (<100Å) nc-Si:H layer initially grown with high H2 dilution on a glass substrate can serve as a seed layer for the subsequent growth of the film with lower H2 dilution, which results in a higher crystallinity of the whole film. The role of this thin layer in low temperature junction formation has been examined by the insertion of the layer between the interface of both nc-Si:H (deposited with lower H2 dilution)/c-Si and a-Si:H/c-Si heterojunction type photovoltaic cells. This is to address the knowledge that the device's performance is strongly influenced by the quality of the thin film silicon/crystalline silicon interface. Various thicknesses and H2 dilution ratios have been used to find the optimized condition providing the best performance of the cells. The maximum efficiency of 10.5% (Jsc=35.1mA/cm2, Voc=0.51V and FF=0.59) has been obtained, without an AR coating, by the successive deposition of nc-Si:H film with four different H2 dilution ratios on a crystalline silicon substrate. This is potentially a low-temperature, low-cost solar cell fabrication process.
Nanostructure of Porous Silicon Using Transmission Microscopy
Authors: Nayfeh M. H. , Yamani Z. , Gurdal O. , Alaql A. 
Published: May 2017

AbstractWe use high resolution transmission electron microscopy (XTEM) to image the nanostructure of (100) p-type porous Si. A network of pore tracks subdivide the material into nanoislands and nanocrystallites are resolved through out the material. With distance from the substrate, electron diffraction develops, in addition to coherent diffraction, amorphous-like patterns that dominates the coherent scattering in the topmost luminescent layer. Also, with distance from the substrate, crystalline island size diminshes to as small as 1 nm in the topmost luminescence material. Although their uppermost layer has the most resolved nano crystallites, it has the strongest diffuse scattering of all regions. This suggests that the diffuse scattering is due to a size reduction effects rather than to an amorphous state. We discuss the relevance of a new dimer restructuring model in ultra small nanocrystallites to the loss of crystalline effects.
Electron and Hole Relaxation Pathways in II-VI Semiconductor Nanocrystals
Authors: Klimov V. I. , Schwarz Ch. , Yang X. , McBranch D. W. , Leatherdale C. A. , Bawendi M. G. 
Published: May 2017

AbstractFemtosecond (fs) broad-band transient absorption (TA) is used to study the intra-band relaxation and depopulation dynamics of electron and hole quantized states in CdSe nanocrystals (NC's) with a range of surface properties. Instead of the drastic reduction in the energy relaxation rate expected due to a 'phonon bottleneck', we observe a fast sub-picosecond 1P-to-1S relaxation, with the rate enhanced in NC's of smaller radius. We use fs IR TA to probe electron and hole intraband transitions, which allows us to distinguish between electron and hole pathways leading to the depopulation of NC quantized states. In contrast to electron relaxation, which is controlled by NC surface passivation, depopulation of hole quantized states is extremely fast (sub-ps-to-ps time scales) in all types samples, independent of NC surface treatment (including NC's overcoated with a ZnS layer). Our results indicate that ultrafast hole dynamics are not due to trapping at surface defects, but rather arise from relaxation into intrinsic NC states.
Nanoparticle Precursors for Electronic Materials
Authors: Ginley D. S. , Curtis C. J. , Ribelin R. , Alleman J. L. , Mason A. , Jones K. M. , Matson R. J. , Khaselev O. , Schulz D. L. 
Published: May 2017

AbstractThe use of nanoparticle precursors for electronic materials including sulfides, selenides, oxides and the elements has potentially wide ranging implications for improving device properties and substantially reducing the deposition costs. To realize this goal the complex interfacial chemistry of these small particles must be controlled. In this paper we present a number of cases demonstrating the complexity of this chemistry. These include CuInSe2where the kinetics of phase formation dominate the sintering process; CdTe where sintering proceeds with and without the sintering enhancement of CdCl2, but produces materials different electronically than bulk materials; and the use of compound and elemental nanoparticles ( Ag, Al, Hg-Cu-Te and Sb-Te) for contacts to elemental and compound semiconductors (Si and CdTe).
Low Temperature ECR -Plasma Assisted MOCVD Microcrystalline and Amorphous GaN Deposition and Characterization for Electronic Devices
Authors: Hassan Z. , Kordesch M. E. , Jadwisienzak W. M. , Lozykowski H. J. , Halverson W. , Colter P. C. 
Published: May 2017

AbstractGaN films have been deposited over a range of temperatures from 50 C to 650 C by ECR plasma MOCVD on silicon (111) and (100), sapphire and quartz using triethylgallium and molecular nitrogen or ammonia as reagents. Growth rates of 2 um/hr are achieved on temperature-controlled substrates (total reactor pressure 0.5 mTorr, 250 watts at 2.45 GHz).Films deposited at 200, 600 and 650 C on sapphire show the GaN(0002) diffraction peak and sharp photoluminescence lines (at 10 K) between 370 and 400 nm and broad emission at 530-550 nm. Broad photoluminescence at 390 nm is observed from GaN/Si( 11). Films deposited at 50 and 100 C show no evidence of a crystalline phase or GaN(0002) diffraction peak. The films are smooth and optically transparent. A broad photoluminescence peak at 520 nm, with a fwhm of about 150 nm is also observed (at 10K). The optical bandgap is measured to be about 2.6-2.7 eV. All of these films show a GaN LO phonon mode at 736 cm-l. IR spectra indicate some hydrocarbon impurities in the low temperature films.Prototype devices (Schottky barrier diodes) have been made from MOCVD GaN and amorphous GaN.
Photoluminescence from Single Porous Silicon Chromophores
Authors: Mason M. D. , Credo G. M. , Weston K. D. , Buratto S. K. 
Published: May 2017

AbstractWe spatially isolate and detect the luminescence from individual porous Si nanoparticles at room temperature. Our experiments show a variety of phenomena not previously observed in the emission from porous Si including a distribution of emission wavelengths, resolved vibronic structure, random spectral wandering, luminescence intermittency and irreversible photobleaching. Our results indicate that the emission from porous Si nanoparticles originates from excitons in quantum confined Si, strongly influenced by the surface passivating layer of the Si nanocrystal.
Giant Anisotropy of Conductivity in Hydrogenated Nanocrystalline Silicon Thin Films
Authors: Pevtsov A. B. , Feoktistov N. A. , Golubev V. G. 
Published: May 2017

AbstractThin (<1000 Å) hydrogenated nanocrystalline silicon films are widely used in solar cells, light emitting diodes, and spatial light modulators. In this work the conductivity of doped and undoped amorphous-nanocrystalline silicon thin films is studied as a function of film thickness: a giant anisotropy of conductivity is established. The longitudinal conductivity decreases dramatically (by a factor of 109 − 1010) as the layer thickness is reduced from 1500 Å to 200 Å, while the transverse conductivity remains close to that of a doped a- Si:H. The data obtained are interpreted in terms of the percolation theory.
Microstructure and Size Distribution of Compound Semiconductor Nanocrystals Synthesized by Ion Implantation
Authors: Meldrum A. , Withrow S. P. , Zuhr R. A. , White C. W. , Boatnerl L. A. , Budail J. D. , Anderson I. M. , Henderson D. O. , Wu M. , Ueda A. , Mu R. 
Published: May 2017

AbstractIon implantation is a versatile technique by which compound semiconductor nanocrystals may be synthesized in a wide variety of host materials. The component elements that form the compound of interest are implanted sequentially into the host, and nanocrystalline precipitates then form during thermal annealing. Using this technique, we have synthesized compound semiconductor nanocrystal precipitates of ZnS, CdS, PbS, and CdSe in a fused silica matrix. The resulting microstructures and size distributions were investigated by cross-sectional transmission electron microscopy. Several unusual microstructures were observed, including a band of relatively large nanocrystals at the end of the implant profile for ZnS and CdSe, polycrystalline agglomerates of a new phase such as γ-Zn 2SiO4, and the formation of central voids inside CdS nanocrystals. While each of these microstructures is of fundamental interest, such structures are generally not desirable for potential device applications for which a uniform, monodispersed array of nanocrystals is required. Methods were investigated by which these unusual microstructures could be eliminated.
Growth Kinetics of Quantum Size ZnO Particles
Authors: Wong E. M. , Bonevich J. E. , Searson P. C. 
Published: May 2017

AbstractColloidal chemistry techniques were used to synthesize ZnO particles in the nanometer size regime. The particle aging kinetics were determined by monitoring the optical band edge absorption and using the effective mass model to approximate the particle size as a function of time. We show that the growth kinetics of the ZnO particles follow the Lifshitz, Slyozov, Wagner theory for Ostwald ripening. In this model, the higher curvature and hence chemical potential of smaller particles provides a driving force for dissolution. The larger particles continue to grow by diffusion limited transport of species dissolved in solution.
Thin films were fabricated by constant current electrophoretic deposition (EPD) of the ZnO quantum particles from these colloidal suspensions. All the films exhibited a blue shift relative to the characteristic green emission associated with bulk ZnO. The optical characteristics of the particles in the colloidal suspensions were found to translate to the films.
Enhanced Photoluminescence for ZnS Nanocrystals Doped with Mn2+ Close to Carboxyl Groups and/or S2− Vacancies
Authors: Isobe T. , Igarashi T. , Konishi M. , Senna M. 
Published: May 2017

AbstractZnS nanocrystals doped with Mn2+ ions are prepared by a solution process and subsequent UV irradiation to produce the samples with different S/(Zn+Mn) ratios and/or surface modification by acrylic acids. Coordination states around Mn2+, ions were examined at 9 and 35 GHz by electron paramagnetic resonance spectroscopy. The Mn2+ sites in the vicinity of 2- vacancies or carboxyl groups are observed at the frequencies more than 9 or 35 GHz, respectively, for nanocrystals, but are not for the bulk sample of 250 nm diameter. Such Mn2+ sites enhance the photoluminescence due to d-d transition of Mn2+ ions through energy transfer from S2- vacancies or carboxyl groups, excited simultaneously by a light of 350 nm for exciting ZnS.
Chemical Solution Deposited Copper-doped CdSe Quantum Dot Films
Authors: Chandrasekharan N. , Gorer S. , Hodes G. 
Published: May 2017

AbstractCopper doped CdSe quantum dots (QDs) and larger nanocrystals were deposited by chemical solution deposition at two different temperatures (5°C and 80°C) and their morphological, optical and surface properties compared with similarly deposited undoped CdSe. Crystal sizes and structure were investigated by X-ray diffraction and transmission electron microscopy. All the samples exhibited cubic (sphalerite) structure except for the 80°C Cu-doped ones which were substantially hexagonal (wurtzite). For the 5°C samples, the crystal sizes were similar for the doped and undoped samples (ca. 3.4 nm). For the 80°C samples, the crystal size of the doped CdSe was much larger (84 nm) than the undoped one (6.3 nm) and extensive twinning occurred. Optical measurements on the doped samples showed the presence of surface states due to the copper seen as an increase in absorbance in the long wavelength region. Xray photoemission spectroscopy similarly showed tails in the valence band spectra of the doped samples. These tails were dominant in the 5°C samples and less so for the 80°C ones. XPS also showed that the Cu was present predominantly in the univalent state. The copper was found to be located on the QD surface for the 2–3 nm QDs and distributed both on the surface and in the bulk (or at twin boundaries) for the larger nanoparticles.
Amorphous/Microcrystalline Phase Control in Silicon Film Deposition for Improved Solar Cell Performance
Authors: Koh Joohyun , Fujiwara H. , Lee Yeeheng , Wronski C. R. , Collins R. W. 
Published: May 2017

AbstractReal time optical studies have provided insights into the growth of hydrogenated amorphous silicon (a-Si:H) and microcrystalline silicon (μc-Si:H) thin films by plasma-enhanced chemical vapor deposition as a function of the H2-dilution gas flow ratio Research-article=[H2]/[SiH4], the accumulated film thickness db, and the substrate material. Results pertinent to the optimization of a-Si:H-based solar cells have been obtained in studies of Si film growth at moderate to high R on dense amorphous semiconductor film surfaces. For depositions with 15≤Research-article≤80 on freshly-deposited a-Si:H, initial film growth occurs in the amorphous phase. Upon continued growth, however, a transition is observed as crystallites begin to nucleate from the amorphous film. The thickness at which this amorphous-to-microcrystalline (a→μc) transition occurs is found to decrease with increasing R.Based on these results, a deposition phase diagram has been proposed that describes the a–gc transition as a continuous function of R and db. We find that the optimum stabilized a-Si:H p-i-n solar cell performance is obtained in an i-layer growth process that is maintained as close as possible to the phase boundary (but on the amorphous side) versus film thickness.
Preparation and Characterization of Microcrystalline and Epitactially Grown Emitter Layers for Silicon Solar Cells
Authors: Lips K. , Platen J. , Brehme S. , Gall S. , Sieber I. , Elstner L. , Fuhs W. 
Published: May 2017

AbstractWe have deposited thin B- and P-doped Si layers by electron cyclotron resonance CVD on c- Si (4 Ωcm, CZ) and on quartz glass substrates at T=325°C. Films grown on quartz glass are of microcrystalline nature with crystalline volume fractions of about 70 % and a resistivity ranging from 0.01 - 10 (Ωcm)−1 depending on doping concentration. The doping efficiency is close to unity with the carrier mobility being independent of doping concentration for both B- and Pdoping. Films grown on c-Si, on the other hand, exhibit perfect homoepitaxial morphology when the gas phase doping concentration exceeds 1000 ppm and 5000 ppm for P- and B-doping, respectively. The quality of the films is tested by preparing thin film emitter solar cells. We find efficiencies above 11 % for cells without ARC. The result are compared to cells with diffused emitters, otherwise prepared with the same technological steps.
Low Temperature Deposition of Polycrystalline Silicon Thin Films Prepared by Hot Wire Cell Method
Authors: Ichikawa M. , Takeshita J. , Yamada A. , Konagai M. 
Published: May 2017

AbstractHot wire (HW) cell method has been newly developed and successfully applied to grow polycrystalline silicon films at a low temperature with a relatively high growth rate. In the HWcell method, silane is decomposed by reaction with a heated tungsten wire placed near the substrate. It is found that polycrystalline silicon films can be obtained at substrate temperatures of 175-400°C without hydrogen dilution. The film crystallinity is changed from polycrystalline to amorphous with decreasing the total pressure. The X-ray analysis clearly showed that the films grown at the filament temperature of 1700°C have a very strong (220) preferential orientation. The films consist of large grains as well as small grains, and it was found from cross-sectional SEM that the films have columnar structure. These results suggested that the HW-cell method would be a promising candidate to grow device-grade polycrystalline silicon films for photovoltaic application.