bluuebunny/crossref_metadata_2025 huggingface dataset:
REFLEXÕES EM TORNO DA CONFIGURAÇÃO MODERNA DA CORRUPÇÃO
Authors: Loureiro Flávia Noversa
Published: June 2019

Disponível em: www.univali.br/periodicos A perceção social, aliada aos fenómenos corruptivos, sofreu, implicativamente, profundas modificações, passando de uma atitude de tolerância ou indiferença para uma posição de recusa, de denúncia pública e, mesmo, de algum alarme. Hoje, quando falamos em corrupção, pretendemos significar um conjunto fenomenológico muito mais lato, coincidente com aquiloa que chamamos «perceção social da corrupção». A corrupção está longede ter apenas uma dimensão jurídico-criminal, pelo que devemos salientar igualmente o envidamento de esforços que têm vindo a desenvolver-se em nível administrativo. A tónica, neste caso, está não já na repressão, mas sobretudo na prevenção de atos corruptivos. Muitos outros aspetos são igualmente relevantes quando falamos de prevenção e repressão da corrupção. Passam pela atitude da sociedade, pelo papel dos media, pelos meios técnicos e capacidades humanas da investigação criminal, quando seja caso dela, entre tantos outros fatores. O que nos parece verdadeiramente intransponível – se bem que não se afigure nada fácil a partir de um enfoque juspenalista – é que compreendamos as múltiplas e interpenetrantes dimensões do fenómeno, sem o que continuaremos com vislumbres fragmentários e pouco produtivos da realidade.
A DISPUTA HEGEMÔNICA BRASILEIRA COM A REPÚBLICA DA ARGENTINA – O CASO DA INGERÊNCIA NA BOLÍVIA
Authors: Souza Eliton Felipe de
Published: June 2019

Este trabalho pretende lançar luz sobre as relações de dependência que subjugaram as populações latino-americanas durante a segunda metade do século XX, destacando que estas não existiram apenas externamente, pelo domínio do imperialismo, mas, também, internamente, em uma lógica política e social subimperialista, tendo como contexto histórico analisado, os 21 anos da ditadura militar brasileira (1964-1985). A pretensão, portanto, é a de evidenciar que entre a exploração imperialista estadunidense e os golpes militares na América Latina, existiam políticas de Estado praticadas pelos ocupantes do poder brasileiro ambicionando garantir-lhes o papel de potência regional em uma disputa direta com a vizinha Argentina, e que essas práticas eram realizadas com a conivência e até mesmo o apoio dos Estados Unidos que tinha no Brasil o ponto de suporte para a difusão dos interesses capitalistas na América do Sul. Para a realização desse trabalho, portanto, foi necessária a profunda análise e comparação de documentos oficiais dos governos brasileiro, argentino, boliviano e estadunidense, produzidos pelas chancelarias desses países e que demonstram a atuação dos chefes militares brasileiros em relação aos países da América Latina, neste artigo especificamente, um estudo das ingerências sobre a Bolívia.
POLICENTRISMO, GOVERNANÇA CLIMÁTICA E CONSTITUCIONALISMO GLOBAL
Authors: Contipelli Ernani
Published: June 2019

A abordagem alternativa e pluralística desempenhada pelo policentrismo tem por finalidade maximizar a convergência de múltiplas unidades de governança, presentando-se como um fator de estimulo à realização de ações coletivas e coordenadas em diferentes escalas de poder, ao resgatar os índices de confiança e cooperação entre cidadãos e comunidades, especialmente, para enfrentar ameaças globais, como o caso da atual crise climática, a qual tem sido objeto de falhas institucionais, em razão de equivocadas estratégias implementadas no plano internacional. O presente estudo pretende discutir a aplicação do policentrismo no âmbito da governança climática multinível, destacando a importância de fatores que promovam um esquema compreensivo de princípios e regras através de modelos institucionais determinados a partir da utilização da teoria do constitucionalismo global, com a função de orientar a coordenação de iniciativas entre diversos níveis de autoridade, para valorizar processos de conhecimento e aprendizado que influenciem a performance de todo sistema climático global.
Study of natural ventilation in a Gothic multi-tunnel greenhouse designed to produce rose (Rosa spp.) in the high-Andean tropic
Authors: Munar Edwin Andres Villagran , Aldana Carlos Ricardo Bojaca
Published: June 2019

In tropical regions the production of ornamentals is developed exclusively in naturally ventilated plastic greenhouses, which sometimes leads to inappropriate microclimates with high temperatures and humidity that limit the productive development of plants. The aim of this work was to study air flows, temperature distribution and relative humidity inside an alternative greenhouse designed to produce rose (Rosa spp.). Three configurations of ventilation, side ventilation (SV), roof ventilation (RC) and combined roof and side ventilation (RSV) were analyzed. The methodological development was based on the use of a previously validated CFD-2D numerical simulation model, which showed an adequate fit between the measured and simulated data, obtaining MAE and RMSE values for temperature and relative humidity of 0.44 and 0.47 °C, 3.99% and 4.04% respectively. The results obtained for the predominant climatic conditions of the study region showed that the highest ventilation rates were obtained for RSV, with values of 0.044 and 0.182 m3 m-2s-1, this ventilation efficiency propitiated the generation of a homogeneous microclimate, with temperature and relative humidity values adequate to produce rose (Rosa spp).
Strength, Elastic Modulus, and Creep of High-Strength Concrete Produced with Bagasse Ash and Recycled Concrete Aggregate
Authors: Rattanachu Pokpong , Tangchirapat Weerachart , Jaturapitakkul Chai , Chindaprasirt Prinya
Published: June 2019

In this study, the mechanical properties of a high-strength recycled concrete (HS-RC) incorporating ground bagasse ash (GBA) were evaluated. Recycled coarse aggregate (R-CA) from concrete demolition was used as a full replacement for natural coarse aggregate (N-CA). The GBA was used to partially substitute 20–50 wt. % of the ordinary portland cement cementitious material. The results indicated that the replacement of N-CA by R-CA led to a slight reduction in the compressive strength of the concrete compared with that of conventional high-strength (CT) concrete. However, the R-CA had a clear negative impact on the elastic modulus and creep strain of the HS-RC. The HS-RC mixtures prepared with 20 wt. % GBA had a higher compressive strength than the CT concrete at later ages (90 days or more). Likewise, the GBA slightly reduced the creep strain, whereas the HS-RC with and without GBA had an approximately 20 % lower elastic modulus than the CT concrete. In addition, the creep strain of concretes containing R-CA and GBA was related to their modulus of elasticity and compressive strength, which could be calculated by a proposed equation and were compared with the results from the predicted model given by ACI 209.2R-08, Guide for Modeling and Calculating Shrinkage and Creep in Hardened Concrete.
Cortical Tracking of Complex Sound Envelopes: Modeling the Changes in Response with Intensity
Authors: Drennan Denis P. , Lalor Edmund C.
Published: June 2019

Characterizing how the brain responds to stimuli has been a goal of sensory neuroscience for decades. One key approach has been to fit linear models to describe the relationship between sensory inputs and neural responses. This has included models aimed at predicting spike trains, local field potentials, BOLD responses, and EEG/MEG. In the case of EEG/MEG, one explicit use of this linear modeling approach has been the fitting of so-called temporal response functions (TRFs). TRFs have been used to study how auditory cortex tracks the amplitude envelope of acoustic stimuli, including continuous speech. However, such linear models typically assume that variations in the amplitude of the stimulus feature (i.e., the envelope) produce variations in the magnitude but not the latency or morphology of the resulting neural response. Here, we show that by amplitude binning the stimulus envelope, and then using it to fit a multivariate TRF, we can better account for these amplitude-dependent changes, and that this leads to a significant improvement in model performance for both amplitude-modulated noise and continuous speech in humans. We also show that this performance can be further improved through the inclusion of an additional envelope representation that emphasizes onsets and positive changes in the stimulus, consistent with the idea that while some neurons track the entire envelope, others respond preferentially to onsets in the stimulus. We contend that these results have practical implications for researchers interested in modeling brain responses to amplitude modulated sounds.
Androgen receptor gene methylation related to colorectal cancer risk
Authors: Xia Tingting , Sun Hongru , Huang Hao , Bi Haoran , Pu Rui , Zhang Lei , Zhang Yuanyuan , Liu Ying , Xu Jing , Onwuka Justina Ucheojor , Liu Yupeng , Cui Binbin , Zhao Yashuang
Published: June 2019

According to its incidence patterns, colorectal cancer (CRC) tends to occur more frequently in males than in females, and the evidence shows that CRC is a hormone-related tumor. These findings indicate that androgen receptor (AR) gene methylation might be important for the regulation of the CRC risk in the different sexes. We used a case–control study to investigate the association between AR methylation in peripheral blood (PBL) and CRC risk. A cohort study was conducted to analyze the effect of AR methylation levels in both PBL and tissue on the prognosis of CRC. AR methylation levels were detected using methylation-sensitive high-resolution melting (MS-HRM). The results indicate that the hypomethylation of AR was significantly associated with the risk of CRC (OR = 1.869, 95% CI: 1.629–2.141, P < 0.001), and the results remained similar after adjusting for the propensity score (PS) (OR = 1.344, 95% CI: 1.147–1.575, P < 0.001) and PS matching (OR = 1.138, 95% CI: 1.000–1.292 P = 0.049). The hypomethylation of AR was significantly associated with CRC in males (OR = 2.309, 95% CI: 1.200–4.245; P = 0.012) but not females (OR = 1.000, 95% CI: 0.567–1.765; P = 0.999). The methylation status of AR in PBL and tissue does not seem to be associated with prognosis in colorectal cancer (OR = 1.425, 95% CI: 0.895–2.269, P = 0.135; OR = 0.930, 95% CI: 0.674–1.285, P = 0.661). We conclude that AR hypomethylation in PBL is associated with a high risk of CRC and may serve as a biomarker. Further studies involving large sample sizes are needed to validate the results of this study.
The impact of epididymal proteins on sperm function
Authors: Björkgren Ida , Sipilä Petra
Published: June 2019

The epididymis is necessary for post-testicular sperm maturation as it provides the milieu required for spermatozoa to gain the ability for progressive movement and fertilization. In the epididymis the sperm protein, lipid and small RNA content are heavily modified due to interaction with luminal proteins secreted by the epididymal epithelium and extracellular vesicles, epididymosomes. This review focuses on epididymal proteins demonstrated to have an effect on sperm functions, such as motility, capacitation, acrosome reaction, sperm-zona pellucida binding and sperm-egg binding, as well as on embryonic development.
Patterns of Electrolyte Testing at Children’s Hospitals for Common Inpatient Diagnoses
Authors: Tchou Michael J. , Hall Matt , Shah Samir S. , Johnson David P. , Schroeder Alan R. , Antoon James W. , Genies Marquita C. , Quinonez Ricardo , Miller Christopher W. , Shah Snehal P. , Brady Patrick W. ,   for the Pediatric Research in Inpatient Settings (PRIS) Network
Published: June 2019

BACKGROUND:

Overuse of laboratory testing contributes substantially to health care waste, downstream resource use, and patient harm. Understanding patterns of variation in hospital-level testing across common inpatient diagnoses could identify outliers and inform waste-reduction efforts.

METHODS:

We conducted a multicenter retrospective cohort study of pediatric inpatients at 41 children’s hospitals using administrative data from 2010 to 2016. Initial electrolyte testing was defined as testing occurring within the first 2 days of an encounter, and repeat testing was defined as subsequent testing within an encounter in which initial testing occurred. To examine if testing rates correlated across diagnoses at the hospital level, we compared risk-adjusted rates for gastroenteritis with a weighted average of risk-adjusted rates in other diagnosis cohorts. For each diagnosis, linear regression was performed to compare initial and subsequent testing.

RESULTS:

In 497 719 patient encounters, wide variation was observed across hospitals in adjusted, initial, and repeat testing rates. Hospital-specific rates of testing in gastroenteritis were moderately to strongly correlated with the weighted average of testing in other conditions (initial: r = 0.63; repeat r = 0.83). Within diagnoses, higher hospital-level initial testing rates were associated with significantly increased rates of subsequent testing for all diagnoses except gastroenteritis.

CONCLUSIONS:

Among children’s hospitals, rates of initial and repeat electrolyte testing vary widely across 8 common inpatient diagnoses. For most diagnoses, hospital-level rates of initial testing were associated with rates of subsequent testing. Consistent rates of testing across multiple diagnoses suggest that hospital-level factors, such as institutional culture, may influence decisions for electrolyte testing.
Sistematización de experiencias: proyecto de formación continua para profesionales en Orientación
Authors: Jiménez Espinoza Ericka , Valenciano Canet Grettel
Published: June 2019

En este artículo se presenta la sistematización de las experiencias de cuatro cursos impartidos como parte del proyecto de Acción Social de la Universidad de Costa Rica ED- 3138 Formación continua para profesionales en Orientación. Se utilizó el modelo de sistematización propuesto por Oscar Jara; con el objetivo de fortalecer el proyecto de formación continua a partir de la experiencia vivida en los cursos impartidos, dar cuenta de los aciertos y desaciertos de estas experiencias de aprendizaje para mejorar tanto el proyecto de formación continua, como para divulgar los resultados obtenidos hasta el momento. Uno de los puntos de llegada más importantes con la elaboración de esta sistematización es que facilitó en las personas participantes, la construcción y reconstrucción de conocimientos relacionados con las distintas temáticas abordadas.
Prolonged second stage labour and consequences of hypoxia in the neonate: A review
Authors: Martz P. , Georgiev P. , Wehrend A.
Published: June 2019

Hypoxia due to dystocia and its repercussions are serious issues concerning the health of neonates. In order to gain a better understanding of the cause and especially the effects and potential long-term disorders, a critical analysis of peer-reviewed literature was made. As shown by many authors, initially the most devastating peripartal cause of ill health in neonates is associated with the serious effects of prolonged and severe acidosis. Other life threatening complications are related to disorders such as meconium aspiration syndrome (MAS), neonatal respiratory distress syndrome, hypoxic ischaemic encephalopathy and necrotising enterocolitis. Despite the astonishing ability of neonates to compensate mixed metabolic and respiratory acidosis with breathing onset directly postpartum, the longer second stage labour takes and the more extreme the acidosis is, the more detrimental its consequences. Lungs are especially vulnerable in this phase of life, aspired meconium can result in increased expression of pro-inflammatory chemotactic cytokines, phospholipase A2 and PGE2 levels , exacerbating inflammatory reactions of lung tissue and exerting a deleterious effect on alveolar cells. Neonates experiencing dystocia could greatly benefit from administration of buffering substances and non-steroidal anti-inflammatory drugs.
The Structural Characterization of a Series of Uranium-containing Gadolinium Zirconates
Authors: Gregg Daniel J. , Zhang Yingjie , Zhang Zhaoming , Karatchevtseva Inna , Blackford Mark G. , Triani Gerry , Lumpkin Gregory R. , Vance Eric R.
Published: June 2019

A series of uranium-containing gadolinium zirconate samples have been fabricated at 1723 K in air. X-ray diffraction and Raman spectroscopy have confirmed pyrochlore or defect fluorite structures, while diffuse reflectance, X-ray absorption near edge structure and X-ray photoelectron spectroscopies indicate a predominantly U6+oxidation state, even when Ca2+was added to charge balance for U4+. The results demonstrate the potential of gadolinium zirconates as host materials for actinides.
UO2 dissolution in high pH conditions of the Belgian Supercontainer
Authors: Mennecart Th. , Cachoir C. , Lemmens K.
Published: June 2019

To assess the long-term behavior of spent fuel in alkaline conditions representative for the Belgian Supercontainer design, static and dynamic dissolution tests were performed with depleted and Pu-doped UO2 , simulating medium burn-up UOX fuels of different fuel ages. The experiments were performed under argon atmosphere at 25 – 30°C in cement waters in the pH range 11.7 – 13.5 and at different SA/V ratios. This paper presents the observed UO2 matrix dissolution rates based on the (238U or 233U) release, and proposes a selection of reference dissolution rates for performance assessment. We demonstrate that the dissolution rates at high pH are equivalent to the dissolution rates reported in the literature for neutral pH conditions. The α-activity threshold below which radiolytical fuel oxidation becomes negligible, seems to be close to the threshold reported for anoxic media at neutral pH.
Preliminary Performance Assessment for Deep Borehole Disposal of High-Level Radioactive Waste
Authors: Swift Peter N. , Arnold Bill W. , Brady Patrick V. , Freeze Geoff , Hadgu Teklu , Lee Joon H.
Published: June 2019

Deep boreholes have been proposed for many decades as an option for permanent disposal of high-level radioactive waste and spent nuclear fuel. Disposal concepts are straightforward, and generally call for drilling boreholes to a depth of four to five kilometers (or more) into crystalline basement rocks. Waste is placed in the lower portion of the hole, and the upper several kilometers of the hole are sealed to provide effective isolation from the biosphere. The potential for excellent long-term performance has been recognized in many previous studies. This paper reports updated results of what is believed to be the first quantitative analysis of releases from a hypothetical disposal borehole repository using the same performance assessment methodology applied to mined geologic repositories for high-level radioactive waste. Analyses begin with a preliminary consideration of a comprehensive list of potentially relevant features, events, and processes (FEPs) and the identification of those FEPs that appear to be most likely to affect long-term performance in deep boreholes. The release pathway selected for preliminary performance assessment modeling is thermally-driven flow and radionuclide transport upwards from the emplacement zone through the borehole seals or the surrounding annulus of disturbed rock. Estimated radionuclide releases from deep borehole disposal of spent nuclear fuel, and the annual radiation doses to hypothetical future humans associated with those releases, are extremely small, indicating that deep boreholes may be a viable alternative to mined repositories for disposal of both high-level radioactive waste and spent nuclear fuel.
Synthesis Design of TiO2 Nanotubes and Nanowires and Photocatalytic Applications in the Degradation of Organic Pollutants in the Presence or not of Microorganisms
Authors: Turki Asma , Ibáñez Pilar Fernández , Ghorbel Abdelhamid , Kochkar Hafedh , Guillard Chantal , Berhault Gilles
Published: June 2019

1 D TiO2 nanomaterials (nanotubes, nanowires) were synthesized through hydrothermal treatment of TiO2 powder (P25) in concentrated alkaline solutions (NaOH for nanotubes, KOH for nanowires) followed by calcination at varying temperatures between 400°C and 700°C. Samples were characterized by HRTEM, XRD, Raman spectroscopy, and N2 adsorption-desorption isotherms. High surface area nanotubular TiO2 materials can maintain their 1D morphology up to a temperature of calcination of 400°C while changing their phase from hydrogenotitanate to anatase. The use of KOH leads to a retarded formation of anatase. Photocatalytic results showed that TiO2 anatase nanotubes calcined at 400°C can degrade formic acid with a rate constant four times higher than for P25. A direct correlation between surface area and photocatalytic activity explains the much higher activity of TiO2 anatase nanotubes. On the opposite, for the degradation of phenol, P25 remains more active. In the disinfection of water, contrary to P25, the high surface area of TiO2 nanotubes allows the simultaneous degradation of formic acid and the inactivation of pathogen fungus showing the interest of such materials for the treatment of wastewater.
Smart Hydrogels Designed for use in Microfabricated Sensor Arrays
Authors: Bates Jeffrey S. , Cho Seung Hei , Tathireddy Prashant , Rieth Loren W. , Magda Jules J.
Published: June 2019

Hydrogels are considered smart materials because they respond to environmental stimuli. Sensors that monitor the body’s pH levels would be helpful for doctors to determine the severity of a patient’s condition, especially if they exhibit signs of shock. The motivation of this project is to create a biomedical device that can be worn sublingually or implanted into the body to help doctors with diagnosing a patient’s condition. The magnitude of the swelling/deswelling behavior can be measured by placing a sample of the hydrogel in a piezoresistive sensor. The degree of swelling/deswelling is directly proportional to the change in pH of the aqueous solution it is placed in. In this study, a variety of compositions of pH responsive hydrogels were designed and tested to determine the response time and magnitude for use in both macro and micro sensor arrays. This pressure sensor has been designed for use with thinner gels than have been used in the past. The results for swelling time and magnitude were compared to determine the effect of the thickness of the hydrogel samples on the swelling/deswelling kinetics of the material in order to find the appropriate composition, thickness and device that will yield the desired response rate and sensitivity.
Dielectric Morphology and RRAM Resistive Switching Characteristics
Authors: Bersuker G. , Butcher B. , Gilmer D. C. , Larcher L. , Padovani A. , Geer R. , Kirsch P. D.
Published: June 2019

The connection between the bi-polar hafnia-based resistive-RAM (RRAM) operational characteristics and dielectric structural properties is considered. Specifically, the atomic-level description of RRAM, which operations involve the repeatable rupture/recreation of a localized conductive path, reveals that its performance is determined by the outcome of the initial forming process defining the structural characteristics of the conductive filament and distribution of the oxygen ions released from the filament region. The post-forming ions spatial distribution in the cell is found to be linked to a degree of dielectric oxygen deficiency, which may either assist or suppress the resistive switching processes.
Aqueous Phase Diffusion in Crystalline Rock
Authors: Bradbury M.H. , Lever D. , Kinsey D.
Published: June 2019

One of the options being considered for the disposal of radioactive waste is deep burial in crystalline rocks such as granite. It is generally recognised that in such rocks groundwater flows mainly through the fracture networks so that these will be the “highways” for the return of radionuclides to the biosphere. The main factors retarding the radionuclide transport have been considered to be the slow water movement in the fissures over the long distances involved together with sorption both in man-made barriers surrounding the waste, and onto rock surfaces and degradation products in the fissures.
Metastable Phase Equilibria in Co-Deposited Ni1−xZrx Thin Films
Authors: Rubin J. B. , Schwarz R. B.
Published: June 2019

We determine the glass forming range (GFR) of co-deposited Ni1−xZrx (0 < x < 1) thin films by measuring their electrical resistance during in situ constant-heating-rate anneals. The measured GFR is continuous for 0.10 < x < 0.87. We calculate the GFR of Ni-Zr melts as a function of composition and cooling rate using homogeneous nucleation theory and a published CALPHAD-type thermodynamic modeling of the equilibrium phase diagram. Assuming that the main competition to the retention of the amorphous structure during the cooling of the liquid comes from the partitionless crystallization of the terminal solid solutions, we calculate that for dT/dt = 1012 K s−1, the GFR extends to x = 0.05 and x = 0.96. Better agreement with the measured values is obtained assuming a lower ‘effective’ cooling rate during the condensation of the films.
Atom Probe Studies of Interfaces in Metallic Multilayers
Authors: Cerezo Alfred , Hyde Jonathon M. , Hetherington Mark G. , Petford-Long Amanda K.
Published: June 2019

The atom probe field-ion microscope has been used to study the diffusion at interfaces in metallic multilayers deposited directly onto field-ion specimens and to develop models for the solid state reactions occuring at the atomic-scale in multilayer systems. Results are presented for the low temperature annealing of a Co-Ni multilayer. Intermixing over about 2 atomic planes is found even in as-deposited samples, extending to mnm after heating at 300°C for 1 hour. Using atom probe results from bulk alloys, a Monte Carlo simulation has been developed for the Fe-Cr system, in which a miscibility gap exists, and is being used in an attempt to model the behaviour of interfaces in Fe-Cr multilayers. Preliminary results are presented, showing that interfaces which are initially mixed over 10 atomic planes become sharper by an ‘interface spinodal’ reaction.
In SituHvem of Crystallization of Amorphous TiNi Thin Films
Authors: Moberly Warren J. , Busch J. D. , Johnson A. D. , Berkson M. H.
Published: June 2019

TiNi alloys have been extensively studied for their shape memory properties, arising from a martensitic transformation between the cubic B2 crystal structure and the monoclinic B19′ structure. However, only recently has the application of TiNi alloys as thin film actuators been considered. Well-controlled thicknesses of TiNi films have been deposited via d.c. magnetron ion sputtering, with as-deposited films exhibiting an amorphous structure. These ductile metallic glass films may be bent into various macroscopic shapes and then heated to crystallize the B2 structure, thereby determining its parent (memory) shape.In situhigh voltage electron microscopy (HVEM) heating and cooling experiments are utilized to observe the crystallization of the B2 structure and the martensitic transformation from B2 to B19∼500°C to ∼600°C. Isothermal annealing determines the kinetics of the crystallization process to be nucleation limited. The nucleation of B2 crystallites in thicker regions of TEM specimens, which occurs prior to nucleation in thinner regions, indicates that nucleation does not occur preferentially at surfaces, but rather homogeneously. After crystallization is completed, the existence of random orientations of B2 grains provides films that will exhibit shape memory in any desired orientation. Video-recording of the crystallization processes has been acquired.
Rapid Thermal-Pulsed Diffusion of Zn into GaAs
Authors: Tiku S.K. , Delaney J.B. , Gabriel N.S. , Yuan H.T.
Published: June 2019

A rapid thermal process for the diffusion of Zn into GaAs has been developed
to fulfill the need for highly doped p type layers in GaAs technology. The
process uses a solid Zn:Si:O source layer and a quartz-halogen lamp system
for the thermal drive-in. Surface concentrations of the order of
1020/cm3 have been achieved with good depth
reproducibility and low lateral diffusion. Specific contact resistance of
Au:Zn/Au alloyed contacts fabricated using this process was in the
10−7 ohm-cm2 range.
Thermodynamic and Kinetic Studies of Pulsed-Laser Annealing from
Transient Conductivity Measurements
Authors: Peercy P.S. , Thompson Michael O.
Published: June 2019

Simultaneous measurements of the transient conductance and time-dependent
surface reflectance of the melt and solidification dynamics produced by
pulsed laser irradiation of Si are reviewed. These measurements demonstrate
that the melting temperature of amorphous Si is reduced 200 ± 50 K from that
of crystalline Si and that explosive crystallization in amorphous Si is
mediated by a thin (≤ 20 nm) molten layer that propagates at ~ 15 m/sec.
Studies with 3.5 nsec pulses permit an estimate of the dependence of the
solidification velocity on undercooling. Measurements of the effect of As
impurities on the solidification velocity demonstrate that high As
concentrations decrease the melting temperature of Si (~ 150 K for 7 at.%),
which can result in surface nucleation to produce buried melts. Finally, the
silicon-germanium alloy system is shown to be an ideal model system for the
study of superheating and undercooling. The Si50Ge50
alloy closely models amorphous Si, and measurements of layered Si-Ge alloy
structures indicate superheating up to 120 K without nucleation of internal
melts. The change in melt velocity with superheating yields a velocity
versus superheating of 17 ± 3 k/m/sec.
Temperature Dependent Orientational Epitaxy of C60 Films on Noble Metal (111) Surfaces; Au, Ag and Cu
Authors: Fartash A.
Published: June 2019

High quality C60 films are grown on surfaces of (111) oriented noble metal substrates (i.e., Au, Ag, and Cu) by using a molecular beam deposition method. The structures of these films are compared with each other on substrates that are prepared to have similar in-plane mosaic widths (σ1.25*) as determined by their x-ray diffraction scans. The in-plane structures of these films are studied for substrate temperatures ranging from σ110 to 290°C. Although most materials grow in high symmetry small-lattice-mismatch in-plane orientations, C60 films (depending on their growth temperatures) grow in orientations that are poorly lattice matched with their Au(111) and Ag(111) substrates. In these orientations, C60 structures can be lattice matched only over large unit cells, forming “long-period ” structures. These “long-period ” structures coexist with “commensurate” structures that are almost perfectly lattice matched on twheitshe osur bpsrterdaotems.i naOten Au(111) substrates, a structural transition is observed between two distinct long-period structures (at Tc, σ150 °C). Although Au and Ag have similar lattice spacings, this transition is absent on Ag(111) substrates. The question of orientational epitaxy for C60 layers is examined in the context of several well-known systems in condensed matter physics.
Electrochemical Synthesis and Processing of Materials: From Fractal Electrodes to Epitaxial Thin Films
Authors: Family Fereydoon
Published: June 2019

Electrochemical processes hold great promise as flexible and effective tools for synthesis and processing of a wide range of materials from fractal electrodes to epitaxial nanostructures. The key to successful application of electrochemical techniques is in understanding the kinetic processes which control the evolution and the morphology of the surface at the solid-liquid interface. This paper provides a review of recent advances made by different electrochemical communities in recent years in studies of the growth and modification of a wide variety of materials. The topics covered include studies of pattern formation and growth of dendritic and fractal structures in electrode-position, kinetic roughening and dynamic scaling of surfaces fluctuations during electrochemical deposition and dissolution, as well as recent progress in electrochemical growth of epitaxial layers and nanostructures.
Molecular Grafting on Si(111) Surfaces: An Electrochemical Approach
Authors: Henry de Villeneuve C. , Pinson J. , Ozanam F. , Chazalviel J. N. , Allongue P.
Published: June 2019

This works addresses the question of the direct attachment of organic molecules on Si(111) by an electrochemical method. Anodic grafting of -OR group is demonstrated by in-situ STM and the LDOS characterized. The grafting of aryl groups, by reduction of aryl diazonium salts in aqueous solution, is also described. This approach leads to well ordered and close-packed thin molecular films with various functionality. Different chemical and structural characterizations conclude to a Si-C binding, between the Si surface and aryl groups. The stability of films is also investigated.
Characterization of the Silicon / Fluoride Solution Interface by In-Situ Microwave Reflectivity
Authors: Natarajan Arun , Oskam Gerko , Oursler Douglas A. , Searson Peter C.
Published: June 2019

Etching of silicon in aqueous fluoride solutions can lead to almost atomically flat surfaces with a low density of surface states and recombination centers. The final quality of the surface, however, is strongly dependent on the solution composition and pH. We have performed electrochemical impedance spectroscopy in combination with potential modulated microwave reflectance spectroscopy (PMMRS) to elucidate the processes occurring at the surface during etching. PMMRS is a novel technique that only probes the free carriers in the conduction and valence bands and is, under certain conditions, not affected by processes involving electrically active surface states or charge transfer. This unique feature allows us to separate the energetics of the semiconductor from surface processes. Microwave reflectivity (δR) versus potential curves in HF solutions demonstrate the variation of the flatband potential as a function of pH. The AR response in the narrow potential region around the flatband potential and at more negative potentials is also discussed.
Influence of a silicon cap on SiGe passivation by anodic oxidation
Authors: Rappich J. , Sieber I. , Schöpke A. , Füssel W. , Glück M. , Hersener J.
Published: June 2019

We applied electrochemical oxidation as a low thermal budget process for the passivation of thin SiGe epilayers on Si substrate and compared the results with those obtained on thermally oxidized layers. The use of a thin silicon cap on the SiGe layer reduces the electrochemical corrosion with dissolution of Ge during oxidation and leads to a higher amount of GeO2 in the oxidized SiGe layer than anodic oxidation without a Si cap. The protected SiGe layer shows a slight Ge enrichment at the interface which is different from the behavior of the non-protected SiGe layer. The highest Ge pile-up is achieved by the thermally oxidized samples where the oxide layer is formed by nearly pure SiO2. Using photoluminescence spectroscopy we showed that the passivation and quality of the interface is best if no Ge enrichment occurs. The results suggest that electrochemical oxidation of SiGe layers is preferable to high temperature processing.
Discrete Metal Deposition on Hydrogen Terminated Silicon Surfaces: Kinetics, Morphologies and Sensor Applications
Authors: Chyan Oliver , Chen Jin-Jian , Wu Junjun , Chien Steve , Liu Min
Published: June 2019

The presence of ultra-trace (as low as 1010 – 1013 atoms/cm2) quantities of metal contaminants on silicon substrates is well known to adversely affect the electrical properties of the silicon based microelectronic devices. In this paper, we report our most recent experimental findings on the trace metal deposition mechanisms and its interplays with silicon substrate surface properties at specific chemical environments. The emphases were on the deposition kinetics and morphology, especially at the early stage of metal out-plating process. For instance, our atomic force microscopy results revealed that the Cu deposition on H-Si(100) surface was dominated by nucleation of nanometer-sized Cu nuclei at the initial stage (less than 60 seconds). The growth of the existing Cu nuclei was suppressed for the initial nucleation period until all the nucleation sites were consumed. The number of nucleation sites were found to closely relate to wafer intrinsic properties and solution compositions. A novel sensor which provides direct detection of part-per-trillion level of metal ion impurities in wet cleaning solutions will also be presented.
Electrodeposition of Copper / Cuprous Oxide Nanocomposites
Authors: Swrrzer Jay A. , Bohannan Eric W. , Golden Teresa D. , Hung Chen-Jen , Huang Ling-Yuang , Shumsky Mark
Published: June 2019

Nanocomposite films of copper metal and cuprous oxide were electrodeposited at room temperature from an alkaline copper(11) lactate solution. The electrode potential oscillated spontaneously during constant-current deposition of the composites. The oscillations were periodic in a stirred solution, but became chaotic in unstirred solution. For a given current density the phase composition was a strong function of solution pH. As the pH was increased, the cuprous oxide content increased. At pH 12, no oscillations were observed, and pure cuprous oxide was deposited. At pH 9, the phase composition varied from pure cuprous oxide at current densities below 0.1 mA/cm2 to 96 mole percent copper at 2.5 mA/cm2.
Nanowires Grown Electrochemically in Porous Templates
Authors: Schönenberger C. , Van Der Zande B. M. I. , Fokkink L. G. J.
Published: June 2019

Metallic nanowires are synthesized by electrochemical growth in nanopores of either track-etched polycarbonate membranes or anodized aluminum films. The potentiostatic growth is systematically investigated for track-etched membranes with nominal pore diametersdN between 10 and 80 nm. For this model system, the cross-section of the metallic wires is found to vary: the wire diameter, which is argued to directly reflect the pore diameter, is observed to be substantially larger in the middle than at both ends. Therefore, the pores are not cylindrical with constant cross-section, but appear to be ‘cigar-like’. Inside the membranes, the pores are wider by up to a factor 3.

The aluminum oxide template has successfully been used to prepare a colloidal suspension of gold needles (anisotropie metallic colloid) by growing Au wires in the pores, dissolving the aluminum oxide and finally stabilizing and dispersing the ‘nano-rods’ in water. Visible near-infrared absorption spectroscopy reveal two absorption maxima caused by the anisotropy of these scatterers. The maxima can be assigned to a longitudional and transversal plasma resonance.
Defect Structure and Crystallographic Texture of Polycrystalline Electrodeposits
Authors: Merchant H. D. , Girin O. B.
Published: June 2019

The polycrystalline electrodeposits of metals and alloys are characterized by exceptionally fine, equiaxed grain structure; the grain sizes two to four orders of magnitude smaller than those encountered in the bulk metals are generally obtained. Under the conditions of high cation discharge rate, twins accommodate interface growth; elongated grains and columnar morphology then become the common features. The dislocation density can be very high; the dislocations reside primarily as complex substructural configurations which are inherently unstable to thermal or mechanical stimuli. Vacancies, microvoids and vacancy/impurity complexes are endemic to deposits. The defect structure infrastructure (dislocation density and configuration, twinning frequency and hydrogen bubbles) is controlled by the deposition overpotential which also determines the preferred crystallographic texture. When the texture axis is parallel to the twin plane, anisotropie grain structure and columnar morphology are promoted; when the texture axis is perpendicular to the twin plane, a layered structure forms. The textured electrodeposit generates a duplex grain and subgrain structure. The random grains are small and defect saturated; the oriented grains are much larger and relatively free from crystal defects. The incidence of random grains, their size and defect concentration also depend upon the melting temperature of the metal.
Composite Films of Copper / Boron Nitride and Nickel / Boron Nitride
Authors: Hepel Maria , Tannatoli Tania , Baxter Christopher , Stephenson Richard
Published: June 2019

The formation and characterization of composite films of copper/boron nitride (Cu/BN) and nickel/boron nitride (Ni/BN) are described. Composite Cu/BN and Ni/BN films were synthesized by a metal electrodeposition from suspensions of boron nitride particles on carbon steel substrates. The effects of concentration of boron nitride in the solution, temperature, potential and various additives on the morphology of composite films have been investigated. The morphology of these films was examined using Scanning Electron Microscopy. The elemental analysis for boron, nitrogen, copper and nickel was performed using Energy Dispersive X-ray Spectroscopy (EDS), and a Microprobe X-ray Analyzer. The Vickers hardness of Cu/BN and Ni/BN films prepared under different conditions was also investigated. It has been found that the composite Cu/BN and Ni/BN films have an increased microhardness as compared to the respective pure metal films. The effects of deposition potential, temperature, concentration of BN and presence of various additives on the microhardness of Cu/BN and Ni/BN films have been investigated.
Time-Resolved Measurements of Overlayer Ordering in Electrodeposition
Authors: Finnefrock A. C. , Bullert L. J. , Ringland K. L. , Tingi P. D. , Abruña H. D. , Brock J. D.
Published: June 2019

We report in situ time-resolved surface x-ray scattering measurements of the underpoten-tial deposition of Cu2+ on Pt(111) in the presence of Cl− in HClO4 solution. Chronoamperometric (current vs. time) measurements indicate that after a potential step, the electrode-position current decays to 1/e of its initial value in at most 0.12 seconds. In contrast, our simultaneous time-resolved surface x-ray scattering data reveal that the overlayer requires on the order of two seconds to develop long-range periodic order. These results demonstrate that the kinetics of surface ordering can be significantly different from the kinetics of charge-transfer and illustrate the power of time-resolved surface x-ray scattering for in situ studies of electrodeposition.
Lattice-Gas Models of Electrochemical Adsorption: Static and Dynamic Aspects
Authors: Rikvold Per Arne , Wieckowski Andrzej , Ramos Raphael A.
Published: June 2019

We discuss applications of statistical-mechanical lattice-gas models to electrochemical adsorption. Our strategy to describe specific systems includes microscopic model formulation, calculation of zero-temperature phase diagrams, numerical simulation of thermody-namic and structural quantities at nonzero temperatures, and estimation of effective, lateral interactions. We report applications to adsorption on single-crystal electrodes, presenting simulated and experimental coverages and voltammetric currents for urea on Pt(100) and the underpotential deposition of Cu on Au(111) in sulfuric acid. We also discuss an extension of the method to study time-dependent phenomena far from equilibrium.
Dynamical Processes at the Solid / Liquid Interface
Authors: Giesen M. , Dietterle M. , Stapel D. , Ibach H. , Kolb D. M.
Published: June 2019

We have investigated transport processes on a stepped Ag(111) surface in an aqueous electrolyte by analyzing the equilibrium step fluctuations as a function of the electrode potential. No influence of the electrolyte and the potential was found in the regime of negative potentials with respect to the saturated calomel electrode. As the potential becomes positive and approaches the dissolution limit, the increasing magnitude of the step fluctuations and the change in the time dependence indicate a rapid exchange of silver atoms with the electrolyte long before the silver begins to dissolve.
An in Situ Small Angle Neutron Scattering Investigation of Ag0.7Au0.3 Dealloying Under Potential Control
Authors: Corcoran Sean G. , Wiesler David G. , Sieradzki Karl
Published: June 2019

In situ small angle neutron scattering (SANS) was used to characterize the formation of the random 3-dimensional porous structure created during the dealloying of a Ag0.7Au0.3 alloy under potential control. Using a model developed by N.F. Berk (Phys. Rev. Lett., 58 (1987) 2718) for the scattering properties of random porous media, we were able to characterize the average ligament width as a function of time during the dealloying process. We find that the coarsening of the average ligament width is strongly dependent upon the value of the applied potential. Our results represent the first in situ nanoscale characterization of the 3-dimensional formation of porosity in a dealloying system under potential control.
Planar Ferrite Materials for Millimeter-Wave Applications
Authors: McKnight Stephen W. , Oliver Steven A. , How Hoton , Vittoria Carmine
Published: June 2019

Transferred-film technology provides a path to the integration of self-biased hexaferrite film devices into MMIC circuits. While progress is being made on the growth of thick oriented films of barium hexaferrite doped with aluminum and scandium by pulsed laser deposition or liquidphase epitaxy, we have demonstrated prototype devices using available yttrium-iron-garnet films and thinned bulk hexaferrites. Insertion losses less than 2dB and isolation greater than 20dB have been demonstrated, and theoretical modeling indicates that insertion losses less than 0.5 dB are accessible with optimized materials and through matching the active circuit components to the ferrite device. The prospects of accessing ferrite non-reciprocal, non-linear, and tunable functions at frequencies up to and exceeding 100 GHz through devices integrated onto microwave IC substrates without the use of DC biasing magnets are the driving force of this research.
Controlled Injection of Holes into ALQ3 Based Oleds by Means of An Oxidized Transport Layer
Authors: Mathai Mathew K. , Higginson Keith A. , Hsieh Bing R. , Papadimitrakopoulos Fotios
Published: June 2019

In this paper we report a method for tuning the extent of hole injection into the active light emitting tris- (8-hydroxyquinoline) aluminum (Alq3) layer in organic light emitting diodes (OLEDs). This is made possible by modifying the indium tin oxide (ITO) anode with an oxidized transport layer (OTL) comprising a hole transporting polycarbonate of N,N'-bis(3-hydroxymethyl)-N,N'-bis(phenyl) benzidine and diethylene glycol (PC-TPB-DEG) doped with varying concentrations of antimonium hexafluoride salt of N,N,N',N'-tetra-p-tolyl-4,4'-biphenyldiamine (TMTPD+ SbF6-). The conductivity of the OTL can be changed over three orders of magnitude depending on salt loading. The analysis of hole and electron current variations in these devices indicates that optimizing the conductivity of the OTL enables the modulation of hole injection into the Alq3 layer. The bipolar charge transport properties for OLEDs in which the interfacial carrier injection barriers have been minimized, are governed by the conductivities of the respective layers and in this case it is shown that the variable conductivity of the OTL does allow for better control of the same. Accordingly, varying the concentration of holes in the device indicates that beyond an optimum concentration of holes, further hole injection results in the formation of light quenching cationic species and the initiation of oxidative degradation processes in the Alq3 layer, thus accelerating the intrinsic degradation of these devices. The variable conductivity of the OTL can hence be used to minimize the occurrence of these processes.