bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating the hospitalization burden associated with influenza and respiratory syncytial virus in New York City, 2003–2011
Authors: Goldstein Edward , Greene Sharon K. , Olson Donald R. , Hanage William P. , Lipsitch Marc
Published: May 2015

Background

Hospitalization burden associated with influenza and respiratory syncytial virus (RSV) is uncertain due to ambiguity in the inference methodologies employed for its estimation.

Objectives

Utilization of a new method to quantitate the above burden.

Methods

Weekly hospitalization rates for several principal diagnoses from 2003 to 2011 in New York City by age group were regressed linearly against incidence proxies for the major influenza subtypes and RSV adjusting for temporal trends and seasonal baselines.

Results

Average annual rates of influenza‐associated respiratory hospitalizations per 100 000 were estimated to be 129 [95% CI (79, 179)] for age <1, 36·3 (21·6, 51·4) for ages 1–4, 10·6 (7·5, 13·7) for ages 5–17, 25·6 (21·3, 29·8) for ages 18–49, 65·5 (54·0, 76·9) for ages 50–64, 125 (105, 147) for ages 65–74, and 288 (244, 331) for ages ≥75. Additionally, influenza had a significant contribution to hospitalization rates with a principal diagnosis of septicemia for ages 5–17 [0·76 (0·1, 1·4)], 18–49 [1·02 (0·3, 1·7)], 50–64 [4·0 (1·7, 6·3)], 65–74 [8·8 (2·2, 15·6)], and ≥75 [38·7 (25·7, 52·9)]. RSV had a significant contribution to the rates of respiratory hospitalizations for age <1 [1900 (1740, 2060)], ages 1–4 [117 (70, 167)], and ≥75 [175 (44, 312)] [including chronic lower respiratory disease, 90 (43, 140)] as well as pneumonia & influenza hospitalizations for ages 18–49 [6·2 (1·1, 11·3)] and circulatory hospitalizations for ages ≥75 [199 (13, 375)].

Conclusions

The high burden of RSV hospitalizations among young children and seniors age ≥75 suggests the need for additional control measures such as vaccination to mitigate the impact of annual RSV epidemics. Our estimates for influenza‐associated hospitalizations provide further evidence of the burden of morbidity associated with influenza, supporting current guidelines regarding influenza vaccination and antiviral treatment.
Changes in Family Relationships among Substance Abusing Runaway Adolescents: A Comparison between Family and Individual Therapies
Authors: Guo Xiamei , Slesnick Natasha , Feng Xin
Published: May 2015

Eligible adolescents (12–17 years old) were recruited from a short‐term crisis shelter for runaway adolescents in a large Midwestern city. Adolescents (N = 179) were randomly assigned to Ecologically‐Based Family Therapy (EBFT,n = 61), the Community Reinforcement Approach (CRA,n = 57), or brief Motivational Enhancement Therapy (MET,n = 61) with the primary focus on substance abuse. A significant increase in perceived family cohesion and a significant reduction in perceived family conflict were found among all treatment conditions from baseline to the 24‐month follow‐up. Adolescents who receivedEBFTdemonstrated more improvement in family cohesion after treatment than those who receivedCRAorMET, and more reduction in family conflict during treatment than those who receivedMET.
Hippocampal chromatin‐modifying enzymes are pivotal for scopolamine‐induced synaptic plasticity gene expression changes and memory impairment
Authors: Singh Padmanabh , Konar Arpita , Kumar Ashish , Srivas Sweta , Thakur Mahendra K.
Published: May 2015

The amnesic potential of scopolamine is well manifested through synaptic plasticity gene expression changes and behavioral paradigms of memory impairment. However, the underlying mechanism remains obscure and consequently ideal therapeutic target is lacking. In this context, chromatin‐modifying enzymes, which regulate memory gene expression changes, deserve major attention. Therefore, we analyzed the expression of chromatin‐modifying enzymes and recovery potential of enzyme modulators in scopolamine‐induced amnesia. Scopolamine administration drastically up‐regulated DNA methyltransferases (DNMT1) and HDAC2 expression while CREB‐binding protein (CBP), DNMT3a and DNMT3b remained unaffected. HDAC inhibitor sodium butyrate and DNMT inhibitor Aza‐2′deoxycytidine recovered scopolamine‐impaired hippocampal‐dependent memory consolidation with concomitant increase in the expression of synaptic plasticity genes Brain‐derived neurotrophic factor (BDNF) and Arc and level of histone H3K9 and H3K14 acetylation and decrease in DNA methylation level. Sodium butyrate showed more pronounced effect than Aza‐2′deoxycytidine and their co‐administration did not exhibit synergistic effect on gene expression. Taken together, we showed for the first time that scopolamine‐induced up‐regulation of chromatin‐modifying enzymes, HDAC2 and DNMT1, leads to gene expression changes and consequent decline in memory consolidation. Our findings on the action of scopolamine as an epigenetic modulator can pave a path for ideal therapeutic targets.

image

We propose the following putative pathway for scopolamine‐mediated memory impairment; scopolamine up‐regulates hippocampal DNMT1 and HDAC2 expression, induces methylation and deacetylation of BDNF and Arc promoter, represses gene expression and eventually impairs memory consolidation. On the other hand, Aza‐2 and NaB inhibit DNMT1 and HDAC2 respectively, up‐regulate BDNF and Arc expression and recover memory consolidation. We elucidate the action of scopolamine as an epigenetic modulator and hope that DNMT1 and HDAC2 would be ideal therapeutic targets for memory disorders.
Meaning creation and employee engagement in home health caregivers
Authors: Nielsen Mette Strange , Jørgensen Frances
Published: May 2015

The purpose of this study is to contribute to an understanding on how home health caregivers experience engagement in their work, and specifically, how aspects of home healthcare work create meaning associated with employee engagement. Although much research on engagement has been conducted, little has addressed how individual differences such as worker orientation influence engagement, or how engagement is experienced within a caregiving context. The study is based on a qualitative study in two home homecare organisations in Denmark using a think‐aloud data technique, interviews and observations. The analysis suggests caregivers experience meaning in three relatively distinct ways, depending on their work orientation. Specifically, the nature of engagement varies across caregivers oriented towards being ‘nurturers’, ‘professionals’, or ‘workers’, and the sources of engagement differ for each of these types of caregivers. The article contributes by (i) advancing our theoretical understanding of employee engagement by emphasising meaning creation and (ii) identifying factors that influence meaning creation and engagement of home health caregivers, which should consequently affect the quality of services provided home healthcare patients.
Semantic Search in the Remote Associates Test
Authors: Davelaar Eddy J.
Published: May 2015

Searching through semantic memory may involve the use of several retrieval cues. In a verbal fluency task, the set of available cues is limited and every candidate word is a target. Individuals exhibit clustering behavior as predicted by optimal foraging theory. In another semantic search task, the remote associates task (RAT), three cues are presented and a single target word has to be found. Whereas the task has been widely studied as a task of creativity or insight problem solving, in this article, the RAT is treated as a semantic retrieval task and assessed from the perspective of information foraging theory. Experiments are presented that address the superadditive combination of cues and the anti‐clustering behavior in the recall sequence. A new type of search behavior in the RAT is put forward that involves maximizing the difference in activation between target and distractors. This type of search is advantageous when the target is weak and cue patches are contaminated with strong competitors.
Effect of the division between early and late reflections on intelligibility of ideal binary-masked speech
Authors: Li Junfeng , Xia Risheng , Fang Qiang , Li Aijun , Pan Jielin , Yan Yonghong
Published: May 2015

The ideal binary mask (IBM) that was originally defined in anechoic conditions has been found to yield substantial improvements in speech intelligibility in noise. The IBM has recently been extended to reverberant conditions where the direct sound and early reflections of target speech are regarded as the desired signal. It is of great interest to know how the division between early and late reflections impacts on the intelligibility of the IBM-processed noisy reverberant speech. In this present study, the division between early and late reflections in three rooms was first determined by four typical estimation approaches and then used to compute the IBMs in reverberant conditions. The IBMs were then applied to the noisy reverberant mixture signal for segregating the desired signal, and the segregated signal was further presented to normal-hearing listeners for word recognition. Results showed that the IBMs with different divisions between early and late reflections provided substantial improvements in speech intelligibility over the unprocessed mixture signals in all conditions tested, and there were small, but statistically significant, differences in speech intelligibility between the different IBMs in some conditions tested.
Ground cross-modal impedance as a tool for analyzing ground/plate interaction and ground wave propagation
Authors: Grau L. , Laulagnet B.
Published: May 2015

An analytical approach is investigated to model ground–plate interaction based on modal decomposition and the two-dimensional Fourier transform. A finite rectangular plate subjected to flexural vibration is coupled with the ground and modeled with the Kirchhoff hypothesis. A Navier equation represents the stratified ground, assumed infinite in the x- and y-directions and free at the top surface. To obtain an analytical solution, modal decomposition is applied to the structure and a Fourier Transform is applied to the ground. The result is a new tool for analyzing ground–plate interaction to resolve this problem: ground cross-modal impedance. It allows quantifying the added-stiffness, added-mass, and added-damping from the ground to the structure. Similarity with the parallel acoustic problem is highlighted. A comparison between the theory and the experiment shows good matching. Finally, specific cases are investigated, notably the influence of layer depth on plate vibration.
Critical flow and dissipation in a quasi–one-dimensional superfluid
Authors: Duc Pierre-François , Savard Michel , Petrescu Matei , Rosenow Bernd , Del Maestro Adrian , Gervais Guillaume
Published: May 2015

The slowdown of a superflow through a nanoscale pipe is measured and quantified.
Influence of Land Use, Nutrients, and Geography on Microbial Communities and Fecal Indicator Abundance at Lake Michigan Beaches
Authors: Cloutier Danielle D. , Alm Elizabeth W. , McLellan Sandra L.
Published: May 2015

Microbial communities within beach sand play a key role in nutrient cycling and are important to the nearshore ecosystem function.
Escherichia coli
and enterococci, two common indicators of fecal pollution, have been shown to persist in the beach sand, but little is known about how microbial community assemblages are related to these fecal indicator bacteria (FIB) reservoirs. We examined eight beaches across a geographic gradient and range of land use types and characterized the indigenous community structure in the water and the backshore, berm, and submerged sands. FIB were found at similar levels in sand at beaches adjacent to urban, forested, and agricultural land and in both the berm and backshore. However, there were striking differences in the berm and backshore microbial communities, even within the same beach, reflecting the very different environmental conditions in these beach zones in which FIB can survive. In contrast, the microbial communities in a particular beach zone were similar among beaches, including at beaches on opposite shores of Lake Michigan. The differences in the microbial communities that did exist within a beach zone correlated to nutrient levels, which varied among geographic locations. Total organic carbon and total phosphorus were higher in Wisconsin beach sand than in beach sand from Michigan. Within predominate genera, fine-scale sequence differences could be found that distinguished the populations from the two states, suggesting a biogeographic effect. This work demonstrates that microbial communities are reflective of environmental conditions at freshwater beaches and are able to provide useful information regarding long-term anthropogenic stress.
Destruction of the Capsid and Genome of GII.4 Human Norovirus Occurs during Exposure to Metal Alloys Containing Copper
Authors: Manuel C. S. , Moore M. D. , Jaykus L. A.
Published: May 2015

Human norovirus (HuNoV) represents a significant public health burden worldwide and can be environmentally transmitted. Copper surfaces have been shown to inactivate the cultivable surrogate murine norovirus, but no such data exist for HuNoV. The purpose of this study was to characterize the destruction of GII.4 HuNoV and virus-like particles (VLPs) during exposure to copper alloy surfaces. Fecal suspensions positive for a GII.4 HuNoV outbreak strain or GII.4 VLPs were exposed to copper alloys or stainless steel for 0 to 240 min and recovered by elution. HuNoV genome integrity was assessed by reverse transcription-quantitative PCR (RT-qPCR) (without RNase treatment), and capsid integrity was assessed by RT-qPCR (with RNase treatment), transmission electron microscopy (TEM), SDS-PAGE/Western blot analysis, and a histo-blood group antigen (HBGA) binding assay. Exposure of fecal suspensions to pure copper for 60 min reduced the GII.4 HuNoV RNA copy number by ∼3 log
10
units when analyzed by RT-qPCR without RNase treatment and by 4 log
10
units when a prior RNase treatment was used. The rate of reduction of the HuNoV RNA copy number was approximately proportional to the percentage of copper in each alloy. Exposure of GII.4 HuNoV VLPs to pure-copper surfaces resulted in noticeable aggregation and destruction within 240 min, an 80% reduction in the VP1 major capsid protein band intensity in 15 min, and a near-complete loss of HBGA receptor binding within 8 min. In all experiments, HuNoV remained stable on stainless steel. These results suggest that copper surfaces destroy HuNoV and may be useful in preventing environmental transmission of the virus in at-risk settings.
Prey-Specific Growth Responses of Freshwater Flagellate Communities Induced by Morphologically Distinct Bacteria from the Genus Limnohabitans
Authors: Grujčić Vesna , Kasalický Vojtěch , Šimek Karel
Published: May 2015

Because their large growth potential is counterbalanced with grazing by heterotrophic nanoflagellates (HNF), bacteria of the genus
Limnohabitans
, which are common in many freshwater habitats, represent a valuable model for examining bacterial carbon flow to the grazer food chain. We conducted experiments with natural HNF communities taken from two distinct habitats, the meso-eutrophic Římov Reservoir and the oligo-mesotrophic Lake Cep (South Bohemia). HNF communities from each habitat at distinct seasonal phases, a late April algal bloom and a late May clear water phase, were each fed 3
Limnohabitans
strains of differing cell sizes. Water samples were prefiltered (5 μm) to release natural HNF communities from zooplankton control and then amended with the
Limnohabitans
strains
L. planktonicus
II-D5 (medium sized, rod shaped),
Limnohabitans
sp. strain T6-5 (thin, long, curved rod), and
Limnohabitans
sp. strain 2KL-3 (large solenoid). Using temporal sampling and prey treatment, we determined HNF growth parameters such as doubling time, growth efficiency, and length of lag phase prior starting to exponential growth. All three
Limnohabitans
strains supported HNF growth but in significant prey-, site-, and season-dependent fashions. For instance, addition of the moderately large T6-5 strain yielded very rapid HNF growth with a short lag phase. In contrast, the curved morphology and larger cell size of strain 2KL-3 made this prey somewhat protected against grazing by smaller HNF, resulting in slower HNF growth and longer lag phases. These trends were particularly pronounced during the late May clear-water phase, which was dominated by smaller HNF cells. This may indicate a longer “adaptation time” for the flagellate communities toward the large prey size offered.
Fungal Bioweathering of Mimetite and a General Geomycological Model for Lead Apatite Mineral Biotransformations
Authors: Ceci Andrea , Kierans Martin , Hillier Stephen , Persiani Anna Maria , Gadd Geoffrey Michael
Published: May 2015

Fungi play important roles in biogeochemical processes such as organic matter decomposition, bioweathering of minerals and rocks, and metal transformations and therefore influence elemental cycles for essential and potentially toxic elements, e.g., P, S, Pb, and As. Arsenic is a potentially toxic metalloid for most organisms and naturally occurs in trace quantities in soil, rocks, water, air, and living organisms. Among more than 300 arsenic minerals occurring in nature, mimetite [Pb
5
(AsO
4
)
3
Cl] is the most stable lead arsenate and holds considerable promise in metal stabilization for
in situ
and
ex situ
sequestration and remediation through precipitation, as do other insoluble lead apatites, such as pyromorphite [Pb
5
(PO
4
)
3
Cl] and vanadinite [Pb
5
(VO
4
)
3
Cl]. Despite the insolubility of mimetite, the organic acid-producing soil fungus
Aspergillus niger
was able to solubilize mimetite with simultaneous precipitation of lead oxalate as a new mycogenic biomineral. Since fungal biotransformation of both pyromorphite and vanadinite has been previously documented, a new biogeochemical model for the biogenic transformation of lead apatites (mimetite, pyromorphite, and vanadinite) by fungi is hypothesized in this study by application of geochemical modeling together with experimental data. The models closely agreed with experimental data and provided accurate simulation of As and Pb complexation and biomineral formation dependent on, e.g., pH, cation-anion composition, and concentration. A general pattern for fungal biotransformation of lead apatite minerals is proposed, proving new understanding of ecological implications of the biogeochemical cycling of component elements as well as industrial applications in metal stabilization, bioremediation, and biorecovery.
In Vivo
Programmed Gene Expression Based on Artificial Quorum Networks
Authors: Chu Teng , Huang Yajun , Hou Mingyu , Wang Qiyao , Xiao Jingfan , Liu Qin , Zhang Yuanxing
Published: May 2015

The quorum sensing (QS) system, as a well-functioning population-dependent gene switch, has been widely applied in many gene circuits in synthetic biology. In our work, an efficient cell density-controlled expression system (QS) was established via engineering of the
Vibrio fischeri luxI-luxR
quorum sensing system. In order to achieve
in vivo
programmed gene expression, a synthetic binary regulation circuit (araQS) was constructed by assembling multiple genetic components, including the quorum quenching protein AiiA and the arabinose promoter P

araBAD

, into the QS system.
In vitro
expression assays verified that the araQS system was initiated only in the absence of arabinose in the medium at a high cell density.
In vivo
expression assays confirmed that the araQS system presented an
in vivo
-triggered and cell density-dependent expression pattern. Furthermore, the araQS system was demonstrated to function well in different bacteria, indicating a wide range of bacterial hosts for use. To explore its potential applications
in vivo
, the araQS system was used to control the production of a heterologous protective antigen in an attenuated
Edwardsiella tarda
strain, which successfully evoked efficient immune protection in a fish model. This work suggested that the araQS system could program bacterial expression
in vivo
and might have potential uses, including, but not limited to, bacterial vector vaccines.
Microbial Diversity in Engineered Haloalkaline Environments Shaped by Shared Geochemical Drivers Observed in Natural Analogues
Authors: Santini Talitha C. , Warren Lesley A. , Kendra Kathryn E.
Published: May 2015

Microbial communities in engineered terrestrial haloalkaline environments have been poorly characterized relative to their natural counterparts and are geologically recent in formation, offering opportunities to explore microbial diversity and assembly in dynamic, geochemically comparable contexts. In this study, the microbial community structure and geochemical characteristics of three geographically dispersed bauxite residue environments along a remediation gradient were assessed and subsequently compared with other engineered and natural haloalkaline systems. In bauxite residues, bacterial communities were similar at the phylum level (dominated by
Proteobacteria
and
Firmicutes
) to those found in soda lakes, oil sands tailings, and nuclear wastes; however, they differed at lower taxonomic levels, with only 23% of operational taxonomic units (OTUs) shared with other haloalkaline environments. Although being less diverse than natural analogues, bauxite residue harbored substantial novel bacterial taxa, with 90% of OTUs nonmatchable to cultured representative sequences. Fungal communities were dominated by
Ascomycota
and
Basidiomycota
, consistent with previous studies of hypersaline environments, and also harbored substantial novel (73% of OTUs) taxa. In bauxite residues, community structure was clearly linked to geochemical and physical environmental parameters, with 84% of variation in bacterial and 73% of variation in fungal community structures explained by environmental parameters. The major driver of bacterial community structure (salinity) was consistent across natural and engineered environments; however, drivers differed for fungal community structure between natural (pH) and engineered (total alkalinity) environments. This study demonstrates that both engineered and natural terrestrial haloalkaline environments host substantial repositories of microbial diversity, which are strongly shaped by geochemical drivers.
Does smoking reduction worsen mental health? A comparison of two observational approaches
Authors: Taylor Gemma , Taylor Amy , Munafò Marcus R , McNeill Ann , Aveyard Paul
Published: May 2015

Objectives

The association between smoking reduction and mental health is of particular interest given that many smokers report that smoking offers mental health benefits. We aimed to assess the association between smoking reduction and change in mental health using two different analytical approaches to determine if there was any evidence of an association. There were no prior hypotheses.

Design

A secondary analysis of prospective individual level patient data from 5 merged placebo-controlled randomised trials of nicotine replacement therapy for smoking reduction.

Participants

All participants were adult smokers, selected because they wanted to reduce but not stop smoking, and had smoked for at least 3 years. Participants were excluded if they were pregnant, breastfeeding, under psychiatric care, deemed to be unfit by a general practitioner, or part of a cessation programme. 2066 participants were enrolled in the trials, 177 participants were biologically validated as prolonged reducers, and 509 as continuing smokers at both 6-week and 18-week follow-ups.

Primary outcome

Change in mental health from baseline to an 18-week follow-up was measured using the emotional well-being subscale on the Short Form Health Survey-36.

Results

After adjustment for confounding variables, the differences for reducers compared with continuing smokers were: regression modelling −0.6 (95% CI −4.4 to 3.2) and propensity score matching 1.1 (95% CI −2.0 to 4.1).

Conclusions

Smoking reduction, sustained for at least 12 weeks, was not associated with change in mental health, suggesting that reducing smoking was no better or worse for mental health than continuing smoking. Clinicians offering smoking reduction as a route to quit can be confident that, on average, smoking reduction is not associated with negative change in mental health.
Human gammaherpesviruses viraemia in HIV infected patients
Authors: Ferraz da Silva Ana Paula , Giron Leila Bertoni , Ramos da Silva Suzane , Naime Barbosa Alexandre , Almeida Ricardo Augusto Monteiro de Barros , Elgui de Oliveira Deilson
Published: May 2015

Background

The Epstein–Barr virus (EBV) and Kaposi's sarcoma associated herpesvirus (KSHV) are consistently associated with lymphoproliferative diseases and cancers in humans, notably in patients with HIV.

Aims

Our aim was to evaluate whether EBV and/or KSHV viral loads regularly assessed in peripheral blood mononuclear cells (PBMC) correlate with clinical or laboratorial parameters retrieved for patients living with HIV.

Methods

This was a longitudinal study with a cohort of 157 HIV positive patients attending an academic HIV outpatient clinic in São Paulo State, Brazil. For each patient, up to four blood samples were collected over a 1 year clinical follow-up: on enrolment into the study, and after 4, 8 and 12 months. Total DNA was extracted from PBMC, and EBV and KSHV viral loads were assessed by real time quantitative PCR.

Results

Higher viral loads for EBV were significantly associated with high HIV viraemia, a greater number of circulating T CD8+ cells and lack of virological response to the antiretroviral treatment. KSHV viral load was undetectable in virtually all samples.

Conclusions

EBV viral load in PBMC correlated with the number of circulating T CD8+ lymphocytes and the response to the antiretroviral therapy in HIV infected patients. In contrast, KSHV was undetectable in PBMC, presumably an effect of the antiretroviral treatment. Therefore, either KSHV infection in the population studied was absent or viral load in PBMC was beyond the analytical limit of the assay.
(Invited) Low Loss Power Conversion with Gallium Nitride Based Devices
Authors: Chowdhury Srabanti
Published: May 2015

Saving energy by reducing losses in power conversion effectively adds to the energy resources. Recent progress made in Gallium nitride (GaN) technology has opened up new possibilities where the converter losses and size can be reduced significantly, reducing the converter footprint and potentially its cost. GaN offers power electronic devices in two flavors, Lateral and Vertical. Lateral GaN technology in the form of HEMTs is now fairly matured and has been adopted by several industries to design into medium (1kW-20kW) power conversion applications. The benefits as evidenced by reduction in size of passive components and heat sinks are exciting and cost effective. Vertical GaN technology, currently under development, has the potential to serve the higher power (>20kW) conversion applications. The availability of high quality freestanding bulk GaN material initiated by the lighting market has enabled vertical power device to make substantial progress creating new prospects for GaN in power electronics.
(Invited) GaN High Power Devices and Their Applications
Authors: Mun Jae-Kyoung , Chang Woojin , Kang Dong Min
Published: May 2015

A 100 W-class GaN transistor is developed based on the ETRI’s proprietary 4-inch AlGaN/GaN high electron mobility transistor (HEMT) process and device technologies for the high power of 200 W solid state power amplifier (SSPA) applied to S-band ship radar system. For systematically comparative study of the developed power devices, two SSPA modules based on ETRI’s and Cree’s commercial GaN HEMTs products are fabricated and tested. After a comparison of both measured module results, good radar images for both SSPAs are successfully obtained with almost the same performances. To our best knowledge, this is the first report of SSPA ship radar with GaN power devices in Korea.
Investigating the Effects of Annealing on Off-State Step-Stressed AlGaN/GaN High Electron Mobility Transistors
Authors: Kim Byung-Jae , Ahn Shihyun , Hwang Ya-Hsi , Ren Fan , Pearton Stephen J.
Published: May 2015

The effects of thermal annealing on dc performance of off-state drain-voltage step-stressed AlGaN/GaN high electron mobility transistors were investigated. After stress, reverse gate leakage current increased and drain current on-off ratio decreased. These degradations were fully recovered after thermal annealing process at 450 °C for 10 minutes. Temperature dependent drain-current sub-threshold swing measurements were used for the estimation of trap densities before, after off-state drain-voltage step-stress and followed with thermal annealing. Off-state step-stressed device showed a huge increase of trap density from 2.15 × 1012 to 6.31 × 1012 /cm2-V and reduced to 3.56 × 1012 /cm2-V after thermal annealing.
(Invited) Group-III Nitrides to the Extreme --- from LEDs and Solar Cells to the Transistor
Authors: Bross Adam , Zhao Liang , Elsaesser David , Li Zhongda , Durniak Mark , Detchprohm Theeradetch , Chow Tat-Sing Paul , Wetzel Christian
Published: May 2015

Achieving p-type conduction in GaN has poised the material a power semiconductor on all fronts. Record conversion efficiencies and power densities in LEDs render it a platform of GW installation base. After commercial success as a blue light emitter, the emphasis now rests on the expansion of its capacity as a full spectrum direct emitter --- and absorber. Green and amber LEDs will allow full control of lighting quality and specificity in photochemistry. In early results we find evidence of temperature performance crucially superior to those of the incumbent. Next, we explore the same GaInN/GaN quantum wells as a concentration solar cell converter. While definitely limited to the short wavelength range so far, we find respectably high spectral conversion efficiencies and outstanding temperature stability. Such performance, however, is just early indication of what else lies ahead in terms of power electronics in the form of lateral and vertical transistor. In early results we monolithically integrate LED and transistor.
(Invited) Applications of Electrochemistry for Novel Wide Bandgap GaN Devices
Authors: Park S. H. , Zhang C. , Yuan G. , Chen D. , Han Jung
Published: May 2015

Electrochemical (EC) etching having large selectivity based on the conductivity of n-type GaN was investigated to demonstrate the feasibility of novel wide bandgap GaN devices. The EC etching relies on the generation of holes at the GaN/electrolyte surface for oxidation and chemical dissolution. Depending on the layer conductivity and applied bias, the EC etching may cause no effect, nanoscale porosification, or complete etching of GaN. The EC etching has been applied to different areas of GaN material and device technologies, including layer separation, the preparation of flexible GaN membrane devices, and the formation of distributed Bragg reflector for photonic applications.
(Invited) Fully Porous GaN p-n Junctions Fabricated by Chemical Vapor Deposition: A Green Technology towards More Efficient LEDs
Authors: Carvajal Joan J. , Mena Josue , Bilousov Oleksandr , Martínez Oscar , Jiménez Juan , Zubialevich V.Z. , Parbrook Peter J. , Geaney Hugh , O'Dwyer Colm , Díaz Francesc , Aguiló Magdalena
Published: May 2015

Porous GaN based LEDs produced by corrosion etching techniques have demonstrated enhanced light extraction efficiencies in the past. However, these fabrication techniques require further post-growth processing steps, which increase the price of the final device. In this paper, we review the process we developed for the formation of fully porous GaN p-n junctions directly during growth, using a sequential chemical vapor deposition (CVD) process to produce the different layers that form the p-n junction.
Large Gate Swing and High Threshold Voltage Enhancement-Mode AlGaN/GaN HEMTs Using Low Energy Fluorine Ion Implantation in GaN Layer
Authors: Wu Chia-Hsun , Han Ping-Cheng , Chang Edward Yi
Published: May 2015

Enhancement-mode (E-mode) AlGaN/GaN HEMTs with large gate swing and high threshold voltage is demonstrated in this work. The E-mode GaN HEMTs were fabricated by low energy fluorine ion implantation technique. Low energy fluorine ion implantation can provide higher fluorine ion concentration in the AlGaN layer and modulate the fluorine ion distribution in the GaN layer. The ion distribution can be also calculated by SRIM simulation. (The Stopping and Range of Ions in Matter) Without using gate insulator, the enhancement-mode GaN HEMT shows high threshold voltage of 2.5 V, with a current density of 200 mA/mm at a gate bias of 5.5 V. To confirm the implantation damages were removed, thermal stability test was performed in this work. After annealing at 400 °C for 10 minutes, the implanted devices showed no obvious threshold voltage shift.
A Novel Approach to Improve Heat Dissipation of AlGaN/GaN High Electron Mobility Transistors with a Backside Cu Via
Authors: Hwang Ya-Hsi , Kang Tsung-Sheng , Ren Fan , Pearton Stephen J.
Published: May 2015

A novel approach by employing a Cu filled via hole under device active area to improve heat dissipation of AlGaN/GaN high electron mobility transistors (HEMTs) grown on silicon substrate is proposed. In this study, finite element analysis was employed to simulate the temperature distributions of reference HEMT and proposed model. By introducing a Cu filled via underneath the active area and removing a thermal resistive layer resulted from the nucleation layer generated during the HEMT structure grwoth, the maximum junction temperature could be reduced from 147 to 123ºC at a power density of 5W/mm.
Effect of Island Configuration and Neutral Axis Location for Mechanical Bending Strain on a-IGZO Thin Film Transistors
Authors: Park Chang Bum , Kim Jung Jun , Na HyungIl , Moon Tae Hyoung , Yoo Soon Sung , Yang Myoung Su
Published: May 2015

The effect of electromechanical and mechanical strain was studied on amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistor regarding to the structural design of the device as well as the location from neutral plane (N.P) for bending stress. Here we show a highly reliable bending feature of the island structured (IS) device and its backplane against the mechanical strain after being subjected to an extreme tensile cyclic bending stress. The IS TFTs fabricated on polyimide (PI) substrate exhibit an pronounced bendability for an cyclic bending of 100,000 cycles with varying radii to a radius less than 2 mm with the electro-mechanical integrity. The onset of crack strain also closely corresponds to that of the electrical degradation of the device. The backplane array composed of IS TFTs clearly reveals that the island configuration remarkably reduce the bending stress accumulation on the sheets of inorganic stacked layers along to the uniaxial on plastic substrate.
Simulation Comparison of Self-Heating Effects in Junctionless Nanowire Transistors and FinFET Devices
Authors: Mariniello Genaro , Pavanello Marcelo
Published: May 2015

This paper aims at comparing the self-heating effects influence between FinFETs and Junctionless Nanowire Transistors (JNT) based on three-dimensional numerical simulations. The self-heating of JNT made with different materials, Silicon and Silicon Carbide, is also studied. The results show lower impact in JNT compared to FinFETs. Also, the self-heating is lower in silicon devices then silicon carbide.
ALD NiO Thin Films As a Hole Transport-Electron Blocking Layer Material for Photo-Detector and Solar Cell Devices
Authors: Nam Wook Jun , Gray Zachary , Stayancho John , Plotnikov Victor , Kwon Dohyoung , Waggoner Shawn , Shenai-Khatkhate Deodatta V , Pickering Michael , Okano Terumi , Compaan Alvin , Fonash Stephen J
Published: May 2015

ALD NiO was deposited on silicon and glass substrates by applying alternative pulses of Ni(amd) (AccuDEPTM Ni, Dow Chemical), and water. The film deposition rate at 200°C was 0.25-0.45 Å/cycle. The material properties of the NiO films were characterized using FESEM, AFM, UV-Vis-NIR spectrometer, and GIXRD. The optimized thin ALD NiO film was applied to very thin (500nm) CdTe cells in order to evaluate the potential of the ALD NiO film as a HT-EBL layer. The ALD NiO integrated CdTe cells enhanced Voc and FF, and offered 15% improvement in PCE compared with the control cells.
Analysis of Patterned Defects on Graphene Using Micro-Raman Spectroscopy and Liquid Crystals
Authors: Yang Gwangseok , Oh Sooyeoun , Kim JiHyun
Published: May 2015

In this work, we report a facile probing method for large-area graphene. Patterned defects in graphene were defined by means of photolithography and oxygen plasma treatment. Defect level was characterized using micro-Raman spectroscopy. Only defined region was exposed to oxygen plasma while almost no change is observed in PR remained region. The patterned defects in graphene were visualized using polarized optical microscopy with nematic liquid crystal. Differently aligned textures of liquid crystal result in distinct optical variations.
Effect of Cu- and Y-Codoping on Structural and Luminescent Properties of Zirconia Based Nanopowders
Authors: Korsunska N. , Stara T. , Khomenkova L. , Poslishchuk Yu. , Kladko V , Michailovska K , Kharchenko M. , Gorban O.
Published: May 2015

The effect of Cu doping and calcination temperatures on photoluminescence (PL) spectra and XRD patterns of Y-stabilized ZrO2 powders was studied. The PL spectra of (Y,Cu) codoped samples showed the presence of two main PL components peaked at about 630 and 540 nm in the most samples. The increase of calcination temperature results in the non-monotonic variation of total PL intensity as well as the somewhat changes in PL spectra. The temperature increase from 500°C to 600°C results in the increase of total PL intensity and can be ascribed to the increase of crystallinity degree. The next PL intensity decrease with temperature rise up to 800-900°C is attributed to the appearance of non-radiative recombination centers, probably Zr3+. Their number decrease after annealing at 900-1000°C due to phase transformation from tetagonal to monoclinc as well as the appearance of additional green band can be the reason of consequence PL intensity increase.
(Invited) The Role of Solid-Gas Electrochemical Interfaces for Mixed Ionic Electronic Conducting Oxygen Transport Membranes
Authors: Baumann Stefan , Niehoff Patrick , Schulze-Küppers Falk , Ramasamy Madhumidha , Meulenberg Wilhelm A. , Guillon Olivier
Published: May 2015

Oxygen transport membranes are of great interest for different applications requiring oxygen due to their high efficiency and infinite selectivity. Potential membrane materials are mixed ionic-electronic conducting (MIEC) ceramics enabling oxygen transport by ion diffusion without creating a voltage due to the electrical conductivity. High performance membranes are developed consisting of thin layers on a porous support. Oxygen transport through such asymmetric membranes can be considered as a series of different processes, each of which can be rate limiting depending on operation conditions. One major resistance is concentration polarization in the support pores, which can be eliminated experimentally by using pure oxygen on the support side of the membrane. By doing so the role of oxygen surface exchange in thin perovskite layers is investigated. Different modelling approaches are described. Finally dual phase MIEC membranes, in which oxygen ions and electrons are conducted through separate phases, are briefly discussed.
Polarization Induced Changes in LSM Thin Film Electrode Composition Observed by In Operando Raman Spectroscopy and TOF-SIMS
Authors: McIntyre Melissa D. , Traulsen Marie Lund , Norrman Kion , Sanna Simone , Walker Robert A
Published: May 2015

Polarization induced changes in LSM electrode composition were investigated by utilizing in operando Raman spectroscopy and post mortem TOF-SIMS depth profiling. Experiments were conducted on cells with 160 nm thick (La0.85Sr0.15)0.9MnO3
±δ thin film electrodes in 10% O2 at 700 °C under various electrical polarizations. Raman spectra recorded during polarization showed shifts in spectral intensities that were both reversible and dependent on the applied potential. Spectral changes were assigned to changes in the LSM electronic structure that resulted from changing oxide concentrations in the near-surface region. Ex situ TOF-SIMS depth profiles were recorded through the LSM electrodes and revealed distinct compositional changes throughout the electrodes. The electrode elements and impurities separated into well-defined layers that were more stratified for stronger applied polarizations. The mechanism(s) behind this layering remain unidentified and highlight important questions about mass transfer and ion migration in conducting metal oxide materials subject to electrical polarization.
Surface Composition of Layered Ruddlesden-Popper Lan+1NinO3n+1 (n = 1, 2 and 3) Epitaxial Films
Authors: Wu Kuan-Ting , Téllez Helena , Druce John , Burriel Mónica , Ishihara Tatsumi , Kilner John A. , Skinner Stephen J.
Published: May 2015

Layered Ruddlesden-Popper (RP) type oxides, formulated Lan+1NinO3n+1 (n = 1, 2 and 3), have recently been suggested as candidates for IT-SOFC cathodes. The oxygen surface exchange activity is strongly influenced by the surface composition and atomic surface structure where the adsorption and dissociation of molecular oxygen take place. It is therefore necessary to understand the surface and near-surface chemical compositions of the cathode materials. In this work, the surface and near-surface composition of epitaxial films in the RP series was systematically investigated using low-energy ion scattering (LEIS).
(Invited) Oxygen Reduction Reaction at Cathodes on Proton Conducting Oxide Electrolytes: Contribution from Three Phase Boundary Compared to Bulk Path
Authors: Merkle Rotraut , Poetzsch Daniel , Maier Joachim
Published: May 2015

The required protonic conductivity of cathodes on proton conducting electrolytes to extend the oxygen reduction reaction beyond the three phase boundary is explored. Experimental results for Ba0.5Sr0.5Fe0.8Zn0.2O3-δ (BSFZ) are discussed in this context. While for thin-film electrodes the effective rate constant k
q of the surface reaction is the most important parameter, for porous thick cathodes k
q and the electrode's proton conductivity are equally influential. The low activation energy of the latter quantity turns out to be particularly advantageous for the targeted lower operation temperatures.
Effect of Gd0.2Ce0.8O2 Sintering Temperature on Formation of a SrZrO3 Blocking Layer between Y0.16Zr0.84O2, Gd0.2Ce0.8O2 and La0.58Sr0.4Co0.2Fe0.8O3
Authors: Wilde Virginia , Störmer Heike , Szász Julian , Wankmüller Florian , Ivers-Tiffée Ellen , Gerthsen Dagmar
Published: May 2015

This study focuses on the microstructural characterization of LSCF(La0.58Sr0.4Co0.2Fe0.8O3-δ )-GDC (Gd0.2Ce0.8O2-δ) and GDC-YDZ (8 mol% Y2O3-doped ZrO2) interfaces in solid oxide fuel cells (SOFCs) using transmission electron microscopy (TEM). In particular, the influence of the GDC sintering temperature on microstructure evolution is studied. As a result, an interdiffusion layer between GDC and YDZ is observed. In case of lower GDC sintering temperatures (1100 ℃) the YDZ/GDC interface region consists of two different layers with distinct elemental composition. The layer adjoined to the GDC layer is rich in Sr and Zr, indicating SrZrO3 (SZO) formation; the layer adjoined to YDZ is rich in Gd. With higher GDC sintering temperature the Gd-rich layer increases in thickness, whereas SZO formation is reduced. In this case, only disconnected regions of SZO are formed.
Interfaces and Durability for Different LSCF/CGO/YSZ Systems for IT-SOFC
Authors: Rossignol Cécile , Constantin Guillaume , Briois Pascal , Billard Alain , Djurado Elisabeth , Dessemond Laurent
Published: May 2015

Ageing investigations of LSCF/CGO/YSZ systems were performed at 700°C in air at OCV up to 530h with different thicknesses of CGO layer (0, 0.11, 0.45, 1.1 and 2 µm). After 530 h, a low series resistance variation is observed and becomes weaker with CGO layer due to a better contact. The polarization resistance evolution is strongly reduced when the CGO layer is added, and the minimum is observed with a CGO thickness of only 0.11 µm. The increase of the polarisation resistance was related to the high frequency contribution which corresponds to the degradation of the ionic transfer at the electrode / electrolyte interface. X-ray microanalyses have shown the diffusion and segregation of Sr at this interface only in the sample without CGO layer.
(Invited) Determination of Effective Reaction Area in a Mixed-Conducting SOFC Cathode
Authors: Amezawa Koji , Fujimaki Yoshinobu , Nakamura Takashi , Bagarinao Katherine Develos- , Yamaji Katsuhiro , Nitta Kiyofumi , Terada Yasuko , Iguchi Fumitada , Yashiro Keiji , Yugami Hiroo , Kawada Tatsuya
Published: May 2015

For the quantitative determination of the effective reaction area in an SOFC cathode, a new type of model patterned electrode was proposed and fabricated with La0.6Sr0.4CoO3-δ
(LSC). In situ micro X-ray absorption spectroscopy (XAS) measurements were performed in 1 bar of p(O2) at 973 K under open circuit and cathodic polarization. Absorption spectra were taken at different positions with the position resolution of less than 1 μm. The increase in the absorbance, i.e. the decrease in the oxygen potential, was observed near the electrod/electrolyte interface, when the electrode was cathodically polarized. The characteristic length of the effective reaction area for the patterned LSC electrode was estimated approximately 20 μm from the interface. Electrochemical impedance spectroscopy (EIS) measurements were also carried out with the patterned LSC electrode. The characteristic length of the effective reaction area estimated by EIS was close to one by XAS.
(Invited) Capabilities of Analytical Transmission Electron Microscopy for the Analysis of Structural, Chemical and Electronic Properties Exemplified by the Study of Y-Doped (Ba,Sr)(Co,Fe)O3-δ
Authors: Meffert Matthias , Störmer Heike , Gerthsen Dagmar
Published: May 2015

The effect of Y-doping on secondary phase formation was studied in (Ba0.5Sr0.5)(Co0.8Fe0.2)O3-δ to avoid degradation of the oxygen permeation in this material. B-site cations were substituted by up to 10 % Yttrium. The microstructure was studied by analytical transmission electron microscopy. This also includes the investigation of A- and B-site occupation by Y-cations using atom location by channeling enhanced microanalysis (ALCHEMI).
(Invited) Enhancement of Surface Oxygen Exchange Kinetics for Pr0.1Ce0.9O2-
δ with Deposition of La or Sm Oxide
Authors: Zhao Liang , Perry Nicola H. , Sasaki Kazunari , Bishop Sean R.
Published: May 2015

Rapid oxygen transport across the gas/solid interface (oxygen exchange) is critical for solid oxide fuel cell electrode performance. In this work, La and Sm are shown to dramatically improve the oxygen exchange rate on Pr0.1Ce0.9O2-δ thin films (>50 x at 450 oC) as compared to a freshly deposited film without La or Sm oxide. A surface cleaning effect from the La and Sm is suspected as the source of the enhancement, though catalytic activity from La and Sm may also play a role.
Modeling Water Reduction on 10 Mole% Gadolinia-Doped Ceria (GDC10) Porous Electrodes
Authors: Valdes-Espinosa Honorio , Stuve Eric M. , Adler Stuart B.
Published: May 2015

In this work, non-linear electrochemical impedance spectroscopy in conjunction with a macrohomogeneous model has been used to study water reduction on a 10 mole% gadolinia-doped ceria porous electrode. Comparison between two different proposed mechanisms of a 1D semi-infinite diffusion scenario provided poor agreement with the experimental results. Such failures were attributed to an observed deviation from semi-infinite diffusion under some of the experimental conditions.