bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic factors in evolution of sleep length – a longitudinal twin study in Finnish adults
Authors: Hublin Christer , Partinen Markku , Koskenvuo Markku , Kaprio Jaakko
Published: March 2013

Genetic factors affect many aspects of sleep, such as sleep length. We investigated the contribution of genetic factors to stability and change of sleep length among adults over a 15‐year period. In this representative follow‐up study we used the Finnish Twin Cohort as the study population. Questionnaire surveys were performed in 1975 (response rate 89%, 11 041 twin pairs; age ≥18 years), 1981 (84%, 9323; ≥24 years) and 1990 (77%, 4507; 33–60 years). Sleep was categorized as short (<7 h), average or long (>8 h). Pairwise similarity in monozygotic and dizygotic pairs was examined at each survey by age group and sex. Quantitative genetic modelling was used to estimate cross‐sectional and longitudinal genetic effects. The proportion of variance in sleep length at one point in time that was accounted for by genetic effects was very stable over the study period, being 0.31 in 1975, 0.32 in 1981 and 0.30 in 1990. Longitudinal genetic modelling indicated that the correlations of genetic effects between the three measurement points were high: 0.85 between 1975 and 1981; 0.93 between 1981 and 1990; and 0.76 between 1975 and 1990. Despite a high contribution of environmental effects, their correlations over time were modest: 0.31 between 1975 and 1981; 0.33 between 1981 and 1990; and 0.18 between 1975 and 1990. In conclusion, genetic factors have a modest but stable effect on the evolution of sleep length over a long time span in adults. Multiple measures are a more robust basis for genetic analyses than a single cross‐sectional measure.
Phylogenetic Analysis of Feline Coronavirus Strains in an Epizootic Outbreak of Feline Infectious Peritonitis
Authors: Barker E.N. , Tasker S. , Gruffydd‐Jones T.J. , Tuplin C.K. , Burton K. , Porter E. , Day M.J. , Harley R. , Fews D. , Helps C.R. , Siddell S.G.
Published: March 2013

Background

Feline coronavirus (FCoV) infection is common. In a small percentage of cats, FCoV infection is associated with the fatal disease feline infectious peritonitis (FIP). Genetically distinct virulent and avirulent strains of FCoV might coexist within a cat population.

Objectives

To determine whether the strains of FCoV in FIP‐affected cats are closely related or genetically distinct from the fecally derived strains of FCoV in contemporary‐asymptomatic cats during an epizootic outbreak of FIP.

Animals

Four cats euthanized because of FIP and 16 asymptomatic cats.

Methods

This prospective outbreak investigation was initiated during an outbreak of FIP in cats within or rehomed from a rescue/rehoming center. Postmortem samples were collected from cats with FIP and contemporaneous fecal samples from asymptomatic cats. RNA was purified from tissue and fecal samples, FCoV gene fragments were reverse transcribed, PCR‐amplified using novel primers, and sequenced. Sequences were aligned with ClustalW and compared with published FCoV sequences.

Results

FCoV RNA was detected in all 4 FIP cat postmortem samples and in 9 of the 16 fecal samples from contemporary‐asymptomatic cats. Novel primers successfully amplified fragments from 4 regions of the genome for all FCoV‐positive samples. Phylogenetic analysis showed that the FIP‐associated strains of FCoV from the outbreak were very closely related to the fecally derived strains of FCoV from contemporary‐asymptomatic cats.

Conclusions and Clinical Importance

Sequence analysis provided no evidence that genetically distinct virulent and avirulent strains of FCoV were present during this FIP outbreak.
The curious case of Hermodice carunculata (Annelida: Amphinomidae): evidence for genetic homogeneity throughout the Atlantic Ocean and adjacent basins
Authors: Ahrens Joseph B. , Borda Elizabeth , Barroso Rômulo , Paiva Paulo C. , Campbell Alexandra M. , Wolf Alexander , Nugues Maggy M. , Rouse Greg W. , Schulze Anja
Published: March 2013

Over the last few decades, advances in molecular techniques have led to the detection of strong geographic population structure and cryptic speciation in many benthic marine taxa, even those with long‐lived pelagic larval stages. Polychaete annelids, in particular, generally show a high degree of population divergence, especially in mitochondrial genes. Rarely have molecular studies confirmed the presence of ‘cosmopolitan’ species. The amphinomid polychaete Hermodice carunculata was long considered the sole species within its genus, with a reported distribution throughout the Atlantic and adjacent basins. However, recent studies have indicated morphological differences, primarily in the number of branchial filaments, between the East and West Atlantic populations; these differences were invoked to re‐instate Hermodice nigrolineata, formerly considered a junior synonym of H. carunculata. We utilized sequence data from two mitochondrial (cytochrome c oxidase subunit I, 16S rDNA) markers and one nuclear (internal transcribed spacer) marker to examine the genetic diversity of Hermodice throughout its distribution range in the Atlantic Ocean, including the Mediterranean Sea, the Caribbean Sea, the Gulf of Mexico and the Gulf of Guinea. Our analyses revealed generally low genetic divergences among collecting localities and between the East and West Atlantic, although phylogenetic trees based on mitochondrial data indicate the presence of a private lineage in the Mediterranean Sea. A re‐evaluation of the number of branchial filaments confirmed differences between East and West Atlantic populations; however, the differences were not diagnostic and did not reflect the observed genetic population structure. Rather, we suspect that the number of branchial filaments is a function of oxygen saturation in the environment. Our results do not support the distinction between H. carunculata in the West Atlantic and H. nigrolineata in the East Atlantic. Instead, they re‐affirm the older notion that H. carunculata is a cohesive species with a broad distribution across the Atlantic Ocean.
Recognition of bacterial plant pathogens: local, systemic and transgenerational immunity
Authors: Henry Elizabeth , Yadeta Koste A. , Coaker Gitta
Published: March 2013

Bacterial pathogens can cause multiple plant diseases and plants rely on their innate immune system to recognize and actively respond to these microbes. The plant innate immune system comprises extracellular pattern recognition receptors that recognize conserved microbial patterns and intracellular nucleotide binding leucine‐rich repeat (NLR) proteins that recognize specific bacterial effectors delivered into host cells. Plants lack the adaptive immune branch present in animals, but still afford flexibility to pathogen attack through systemic and transgenerational resistance. Here, we focus on current research in plant immune responses against bacterial pathogens. Recent studies shed light onto the activation and inactivation of pattern recognition receptors and systemic acquired resistance. New research has also uncovered additional layers of complexity surrounding NLR immune receptor activation, cooperation and sub‐cellular localizations. Taken together, these recent advances bring us closer to understanding the web of molecular interactions responsible for coordinating defense responses and ultimately resistance.
Probabilistic Causality and Detecting Collections of Interdependence Patterns
Authors: Ramsahai Roland R.
Published: March 2013

Interdependent effects are usually distinguished from statistical interaction by using the sufficient causes framework. This almost always involves expressing probability distributions as deterministic logic functions, where certain conditions invariably produce or prevent an outcome. Using an idea from the philosophy literature, that a cause is defined as an event which increases the probability of an outcome, a probabilistic sufficient causes framework is developed here. It expresses distributions with probabilistic logic functions and is used to define interdependence without determinism. The connections, between probabilistic logic and the inequalities which define convex polytopes in the space of the distribution parameters, are given. Interdependence is defined for the response behaviour of individuals, defined by latent variables, and is not directly observable. It is shown that the formulation of the models as geometric objects enables the use of algebraic tools to compute observable constraints for detecting interdependence. Novel constraints are derived for detecting causal interdependence patterns and the corresponding statistical tests are described.
Conditional Transformation Models
Authors: Hothorn Torsten , Kneib Thomas , Bühlmann Peter
Published: March 2013

The ultimate goal of regression analysis is to obtain information about the conditional distribution of a response given a set of explanatory variables. This goal is, however, seldom achieved because most established regression models estimate only the conditional mean as a function of the explanatory variables and assume that higher moments are not affected by the regressors. The underlying reason for such a restriction is the assumption of additivity of signal and noise. We propose to relax this common assumption in the framework of transformation models. The novel class of semiparametric regression models proposed herein allows transformation functions to depend on explanatory variables. These transformation functions are estimated by regularized optimization of scoring rules for probabilistic forecasts, e.g. the continuous ranked probability score. The corresponding estimated conditional distribution functions are consistent. Conditional transformation models are potentially useful for describing possible heteroscedasticity, comparing spatially varying distributions, identifying extreme events, deriving prediction intervals and selecting variables beyond mean regression effects. An empirical investigation based on a heteroscedastic varying-coefficient simulation model demonstrates that semiparametric estimation of conditional distribution functions can be more beneficial than kernel-based non-parametric approaches or parametric generalized additive models for location, scale and shape.
A novel HLA‐DRB1*14 allele, HLA‐DRB1*14:136, identified from a registered marrow donor in Korea
Authors: Park H. , Lee Y. J. , Han B. Y. , Song E. Y. , Park M. H.
Published: March 2013

The new allele, HLA‐DRB1*14:136, differs from DRB1*14:05:03 by two nucleotide substitutions at codon 74 with a coding change [GAG→CTG (Glu>Leu)].
Identification of a new HLA allele, HLA‐DRB1*03:80, in a Chinese Han ethnic individual
Authors: Zhang Y. , Nie X.‐M. , Zhuang Y.‐L. , Song Y.‐H. , Zhu C.‐F.
Published: March 2013

The new allele DRB1*03:80 has a single nucleotide change at position 239(C→G) in exon 2 from the closest matching allele DRB1*03:06.
Detection of the new HLA‐DRB1*14:129 allele in a voluntary stem cell donor
Authors: Testi M. , Battarra M. , Stellitano C. , Condello R. , Andreani M.
Published: March 2013

The new allele, officially named HLA DRB1*14:129, differs from HLA DRB1*14:54 in exon 2.
In vitro study of the effect of dog food on the adsorptive capacity of activated charcoal
Authors: Wilson Helen E. , Humm Karen R.
Published: March 2013

Objective

To evaluate the effect of dog food on the adsorptive capacity of activated charcoal.

Design

In vitro laboratory study.

Setting

University veterinary teaching hospital.

Animals

None.

Interventions

None.

Materials and Methods

A fixed quantity of acetaminophen (50 mg) was added to a fixed quantity of activated charcoal (1 g), mixed with varying amounts of dog food (2–14 g). The admixture was agitated for 5 minutes, incubated at 38.5°C for 1 hour and then centrifuged for 30 minutes. The concentration of residual, nonadsorbed acetaminophen in the supernatant was quantitatively assayed by reverse phase high‐pressure liquid chromatography with ultraviolet detection. Data were tested by linear regression analysis and statistical significance was set atP< 0.05.

Measurements and Main Results

A statistically significant reduction in the adsorptive capacity of activated charcoal was demonstrated with increasing amounts of dog food (R2= 0.54;P= 0.0018). However, all measurements of residual acetaminophen were less than 100 mg/L, representing a reduction in acetaminophen concentration of more than 98.6%.

Conclusions

The addition of dog food to activated charcoal reduces its total adsorptive capacity for acetaminophen. However, this reduction in adsorptive capacity is unlikely to be clinically significant in the presence of both the formulation of dog food and the ratio of dog food to charcoal used in this study.
Prospective multicentre study of the effect of voluntary plasmapheresis on plasma cholesterol levels in donors
Authors: Rosa‐Bray M. , Wisdom C. , Wada S. , Johnson B. R. , Grifols‐Roura V. , Grifols‐Lucas V.
Published: March 2013

Background and Objectives

LDL apheresis is used to treat patients with familial hypercholesterolaemia, and low‐volume plasmapheresis for plasma donation may similarly lower cholesterol levels in some donors. This study was designed to assess the effect of plasmapheresis on total, LDL and HDL cholesterol levels in a plasma donor population.

Materials and Methods

This was a prospective, unblinded longitudinal cohort study in which a blood sample was obtained for analysis before each donation. Data from 663 donors were analysed using a multivariable repeated measures regression model with a general estimating equations approach with changes in cholesterol as the primary outcome measure.

Results

The model predicted a significant decrease in total and LDL cholesterol for both genders and all baseline cholesterol levels (P < 0·01). The greatest total cholesterol decreases (women, −46·8 mg/dL; men, −32·2 mg/dL) were associated with high baseline levels and 2–4 days between donations. Small but statistically significant increases (P ≤ 0·01) in HDL cholesterol were predicted for donors with low baseline levels.

Conclusions

These results suggest that, in donors with elevated baseline cholesterol levels, total and LDL cholesterol levels may decrease during routine voluntary plasmapheresis.
Advancing Regenerative Medicine the Translational Way
Authors: Horwitz Edwin M.
Published: March 2013

A subset of circulating T cells can impair bone regeneration and fracture healing.
Neurons Themselves May Shy Away from Normal Interactions in Autism
Authors: Sohal Vikaas
Published: March 2013

This study suggests that in some forms of autism, neurons may abnormally retract their dendrites in response to stimulation.
Paramedic perceptions of the feasibility and practicalities of prehospital clinical trials: a questionnaire survey
Authors: Hargreaves Kate , Goodacre Steve , Mortimer Peter
Published: March 2013

Background

Clinical trials are required to strengthen the evidence base for prehospital care. This questionnaire study aimed to explore paramedics’ perceptions of prehospital research and barriers to conducting prehospital clinical trials.

Methods

A self-completed questionnaire was developed to explore paramedic perceptions and barriers to undertaking prehospital trials based upon a review of existing research and semistructured qualitative interviews with five paramedics. The questionnaire was distributed by ‘research champions’ to 300 paramedics at randomly selected ambulance stations in Yorkshire.

Results

Responses were received from 96/300 participants (32%). Interest in clinical trials was reported, but barriers were recognised, including perceptions of poor knowledge and limited use of evidence, that conducting research is not a paramedics’ responsibility, limited support for involvement in trials, concerns about the practicalities of randomisation and consent, and time pressures. No association was found between training route and perceived understanding of trials (p=0.263) or feeling that involvement in trials was a professional responsibility (p=0.838). Previous involvement in prehospital research was not associated with opinions on importance of an evidence base (p=0.934) or gaining consent (p=0.329). The number of years respondents had been practicing was not associated with opinions on personal experience versus scientific evidence (p=0.582) or willingness to receive training for clinical trials (p=0.111). However, the low response rate limited the power of the study to detect potential associations.

Conclusions

Paramedics reported interest and understanding of research, but a number of practical and ethical barriers were recognised that need to be addressed if prehospital clinical trials are to increase.
UNARY PATTERNS WITH INVOLUTION
Authors: BISCHOFF BASTIAN , CURRIE JAMES , NOWOTKA DIRK
Published: March 2013

An infinite word w avoids a pattern p with the involution if there is no substitution for the variables in p and no involution on substituted variables such that the resulting word is a factor of w. An avoidance index of pattern p is the smallest alphabet size for which a word exists such that p is avoided. A pattern is called unary, if only one variable occurs in it. In this paper, we give the avoidance indices for all unary patterns with involution.
PERMUTATION COMPLEXITY AND THE LETTER DOUBLING MAP
Authors: WIDMER STEVEN
Published: March 2013

Given a countable set X (usually taken to be ℕ or ℤ), an infinite permutation π of X is a linear ordering ≺π of X, introduced in [6]. This paper investigates the combinatorial complexity of infinite permutations on ℕ associated with the image of uniformly recurrent aperiodic binary words under the letter doubling map. An upper bound for the complexity is found for general words, and a formula for the complexity is established for the Sturmian words and the Thue-Morse word.
FULL MONOIDS AND MAXIMAL CODES
Authors: BURDERI FABIO
Published: March 2013

In recent years codes that are not Uniquely Decipherable (UD) were studied partitioning them in classes that localize the ambiguities of the code. A natural question is how we can extend the notion of maximality to codes that are not UD. In this paper we give an answer to this question. To do this we introduce a partial order in the set of submonoids of a free monoid showing the existence, in this poset, of maximal elements that we call full monoids. Then a set of generators of a full monoid is, by definition, a maximal set. We show how this definition extends, in a natural way, the existing definition concerning UD codes and we find a characteristic property of a monoid generated by a maximal UD code. Finally we generalize some properties of UD codes.
BOUNDED PARIKH AUTOMATA
Authors: CADILHAC MICHAËL , FINKEL ALAIN , MCKENZIE PIERRE
Published: March 2013

The Parikh finite word automaton model (PA) was introduced and studied by Klaedtke and Rueß. Here, we present some expressiveness properties of a restriction of the deterministic affine PA recently introduced, and use them as a tool to show that the bounded languages recognized by PA are the same as those recognized by deterministic PA. Moreover, this class of languages is shown equal to the class of bounded languages with a semilinear iteration set.
CHECKERBOARD JULIA SETS FOR RATIONAL MAPS
Authors: BLANCHARD PAUL , ÇİLİNGİR FİGEN , CUZZOCREO DANIEL , DEVANEY ROBERT L. , LOOK DANIEL M. , RUSSELL ELIZABETH D.
Published: March 2013

In this paper, we consider the family of rational maps [Formula: see text] where n ≥ 2, d ≥ 1, and λ ∈ ℂ. We consider the case where λ lies in the main cardioid of one of the n - 1 principal Mandelbrot sets in these families. We show that the Julia sets of these maps are always homeomorphic. However, two such maps Fλ and Fμ are conjugate on these Julia sets only if the parameters at the centers of the given cardioids satisfy μ = νj(d+1)λ or [Formula: see text] where j ∈ ℤ and ν is an (n - 1)th root of unity. We define a dynamical invariant, which we call the minimal rotation number. It determines which of these maps are conjugate on their Julia sets, and we obtain an exact count of the number of distinct conjugacy classes of maps drawn from these main cardioids.
THE ONSET OF BIFURCATIONS IN THE FORCED DUFFING EQUATION WITH DAMPING
Authors: STEFANESCU ION SABBA
Published: March 2013

The paper presents a complete description of the periodic solutions of the Duffing equation: [Formula: see text] for large values of the forcing Γ and the damping Δ. It contains a proof that the equation admits of an infinite sequence of bifurcation curves in the Γ - Δ plane, alternately of the saddle-node and odd periodic — simply 2π-periodic type, whose maxima lie at large Γ along the line: [Formula: see text] where C(Γ) has a finite limit as Γ → ∞. The positions of the maxima are interlaced in asymptotically equal intervals of Γ1/3, with a spacing of 1.403 units. For Δ > Δc(Γ), the Duffing equation admits of a unique periodic solution if Γ is high enough.

These results are obtained by showing that the half-period Poincaré map offered by the Duffing equation is asymptotically equivalent to a map of a circle into itself, according to: [Formula: see text] where χ is an angular variable and β, Σ depend on Γ, Δ. The numerical constants appearing in the circle map and its corrections are determined in the limit Γ → ∞ by a parameter-free boundary layer equation and its variation.
CHAOS GENERATION FOR A CLASS OF NONLINEAR COMPLEX NETWORKS
Authors: LIU NA , LI JUAN , GUAN ZHI-HONG , DING LI , ZHENG GUILIN
Published: March 2013

Chaos generation is an interesting research topic in the study of coupled complex dynamical networks. In this paper, based on mathematical analysis of Lyapunov exponent and boundedness of networks, the emergence of chaos for a class of nonlinear complex networks is investigated and some new criteria of chaos generation are derived. The effectiveness of theoretical results is verified by a numerical example.
A NOVEL APPROACH FOR CONSTRUCTING HIGH-ORDER CHUA'S CIRCUIT WITH MULTI-DIRECTIONAL MULTI-SCROLL CHAOTIC ATTRACTORS
Authors: WANG CHUN HUA , XU HAO , YU FEI
Published: March 2013

A novel approach for constructing a high-order Chua's circuit is proposed. Based on a dual-port RCL network, a high-order Chua's circuit which can generate multi-directional multi-scroll (MDMS) chaotic attractors can be realized by introducing a RC structure and suitable nonlinear functions. First, a fourth-order Chua's circuit is achieved by adding a capacitor, a resistance and a controlled-source constituted by stair functions in the third-order Chua's circuit. And then, this recursive method can be adopted in higher-order Chua's circuit which can generate multi-scroll chaotic attractors in more directions. Finally, a sixth-order Chua's circuit is designed and its experimental results demonstrate the feasibility of this method.
NON-TURING MECHANISM OF SELF-SUSTAINED STRUCTURE FORMATION
Authors: VERISOKIN ANDREY YU. , VERVEYKO DARYA V.
Published: March 2013

We study the mechanism of experimentally observed phase waves and clusters in yeast extracts (cells with destroyed membranes) placed into the unstirred medium (gel). As a mathematical model, the distributed Selkov system is used, since it describes the key step of glycolytic reaction cascade — the phosphofructokinase-catalyzed reaction. We argue that the emergence of spatial phase clusters does not correspond to the Turing mechanism because diffusion coefficients used for two considered reagents are taken as equal. We show that the actual background of this phenomenon is connected with various local rotation velocities in phase space. In this case, large diffusion coefficients stabilize spatial patterns and small diffusion provides an asynchronous regime only.
MESHLESS COLLOCATION METHOD FOR OPTION PRICING BY VARIANCE GAMMA MODEL
Authors: ZHENG Y. J. , YANG Z. H. , HON Y. C.
Published: March 2013

Based on the use of radial basis functions (RBFs), we present in this paper a meshless collocation method to compute both European and American option prices by solving the variance gamma (VG) model. The valuation of the financial derivatives is performed by solving a corresponding partial integro-differential equation (PIDE). In the case of European option, numerical comparison with the analytical solution shows that the proposed scheme achieves a higher accurate approximation than most existing numerical methods. When analytical solution is not available in the case of American option, we use a dividend process to obtain an alternative characterization of the American option so that solution to the PIDE can be achieved in the entire computational region. Since the RBFs used in this paper are infinitely differentiable, the approximation of the derivatives of option prices can be obtained at no extra interpolation cost. In addition, the leave-one-out cross validation (LOOCV) algorithm is generalized for obtaining a local optimal choice of the shape parameter contained in the RBFs for superior convergence. Several numerical examples are given to verify the efficiency and stability of the proposed method.
A SIMPLIFIED MESHLESS METHODS FOR BRITTLE FRACTURE OF CONCRETE
Authors: SAGARESAN N.
Published: March 2013

A simplified meshless methods for brittle fracture and nonlinear material is presented. In this method, the crack is modeled by a set of discrete crack segments crossing the entire domain of influence of the meshless shape functions. The key advantage of this method is its simplicity since no representation of the crack topology is needed. A nonlocal stress tensor around the crack tip is used as fracture criterion. A neo-Hooke material in the bulk material is used and a cohesive zone model is employed once discrete cracks occur. We also present consistent linearization of the cohesive zone model. The method is applied to fracture modeling in concrete that is accompanied by excessive cracking and therefore methods that represent the crack path have major drawbacks. We demonstrate the accuracy of the proposed method for complex problems involving mode-I and mixed mode failure.
RAPID DECAY IS PRESERVED BY GRAPH PRODUCTS
Authors: CIOBANU LAURA , HOLT DEREK F. , REES SARAH
Published: March 2013

We prove that the rapid decay property (RD) of groups is preserved by graph products defined on finite simplicial graphs.
SiC Trench Devices with Ultra Low Ron
Authors: Nakamura Takashi , Aketa Masatoshi , Nakano Yuki , Otake Hirotaka , Otsuka Takukazu , Hanada Toshio
Published: March 2013

SiC devices have the potential to reduce energy losses in high power applications. However SiC devices have yet to achieve ideal performance levels. This paper presents SiC diodes and MOSFETs with advanced trench structures. These devices succeeded in improving performance by reduction of the internal electric field. Trench Schottky diodes are able to reduce forward voltage drop and double-trench MOSFETs show extremely low on-resistance.
Optimization of Si IGBT/SiC JBS Diode Hybrid Modules for Medium Voltage Applications
Authors: Hobart Karl D , Imhoff Eugene , Duong Tam , Hefner Allen
Published: March 2013

The optimization of medium voltage hybrid Si IGBT/SiC junction barrier Schottky diode modules is explored. The primary variant in the study is the active device area of the SiC JBS diodes for a fixed Si IGBT area. The optimization is performed through electro-thermal circuit simulations using validated physics-based device models. Parameters tracked include device switching losses, conduction losses and junction temperature. Finally, reliability issues were considered. SiC JBS diodes were subject to surge conditions and diode surge current was evaluated during module optimization.
On The De-Rating of 4H-Silicon Carbide (SiC) Power Schottky Barrier Diodes
Authors: Shenai K.
Published: March 2013

Silicon Carbide (SiC) is the most promising material among all wide bandgap semiconductors for high-voltage and high-temperature power electronics. A careful analysis of the current state-of-the-art commercial SiC power Schottky Barrier Diodes (SBDs) indicates that these devices are operated well below their true potential. It is shown that the breakdown voltage ratings of commercial SiC power SBDs are lower than a factor of 2 or more compared to their true avalanche breakdown capability. A simple analysis is presented to determine the de-rating factor of SiC power SBDs using the information provided in the manufacturer data sheets. The device de-ratings appear to be primarily due to a high-density of crystal defects in the drift-region of the device.
Degradation Study of Single and Double-Heterojunction InAlN/GaN HEMTs by Two-Dimensional Simulation
Authors: Palankovski Vassil , Donnarumma Gesualdo , Kuzmik Jan
Published: March 2013

We study the concept of double-heterostructure quantum well (DHQW) InAlN/GaN/AlGaN high electron mobility transistor (HEMT) for higher device robustness and less degradation. Physics-based device simulation proves that the back barrier blocks the carrier injection into the device buffer. However, the energy of the injected electrons in the buffer is higher for any quantum well design in InAlN /GaN than in AlGaN/GaN HEMTs. This energy may be sufficient for releasing hydrogen from GaN point defects.
Effect of Stress and Measurement Conditions in Determining the Reliability of SiC Power MOSFETs
Authors: Lelis A. , Green R. , El M. , Habersat D.
Published: March 2013

A review of the threshold-voltage instability effect in SiC MOSFETs and the issues regarding the effect of stress and measurement conditions in determining the reliability of these devices is presented. The complex response of near-interfacial oxide traps, as well as other interfacial charge, to bias and temperature with time is discussed, and how it affects the accuracy of reliability measurements. The strong dependence on measurement speed is also addressed. All these issues point to the need for a separate, appropriate reliability test standard for SiC MOSFETs, rather than using the existing standard based on Si technology.
Broadband Gallium Nitride (GaN) Power Amplifiers
Authors: Leong S. K. , Shenai K.
Published: March 2013

Broadband Gallium Nitride (GaN) power amplifiers (PAs) capable of delivering 100 Watts of continuous power from 225 MHz to 2 GHz are reported using GaN power transistors fabricated with 0.5 micron GaN-on-SiC foundry process. The measured third-order intermodulation distortion (IMD3) signal amplitude is below -28 dBc. The power amplifier design employs two 50 Watt amplifiers combined using baluns to match to 50 ohm load, and is constructed on a hydrocarbon ceramic laminated printed circuit board (PCB) for optimum broadband performance. Further improvement in amplifier performance is feasible by employing improved device design, packaging and thermal management. This GaN power transistor is rated at 120 Watts, 11 dB gain at 2 GHz, and with a typical drain efficiency of 65%.
A Promising New n++-GaN/InAlN/GaN HEMT Concept for High-Frequency Applications
Authors: Palankovski Vassil , Kuzmik Jan
Published: March 2013

We study enhancement-mode n++-GaN/InAlN/GaN high electron mobility transistors (EHEMTs) by means of two-dimensional numerical device simulation. An introduction of a highly-doped GaN cap layer, which is recessed under the gate, was initially proposed for an improvement of the device performance by diminishing surface traps-related parasitic effects. Our new simulation results reveal that, unlikely to planar transistor structures, the extension of the gate depletion region with drain bias is kept restricted in the presence of a n++-GaN cap layer. This highly-scaled new device concept is very promising for ultra-high frequency performance.
Low Dynamic ON-Resistance in AlGaN/GaN Power HEMTs Obtained by AlN Thin Film Passivation
Authors: Chen Kevin J. , Huang Sen , Jiang Qimeng
Published: March 2013

An effective passivation technique for AlGaN/GaN-on-Si power HEMTs is presented. This technique features AlN ultra-thin film grown by plasma enhanced atomic layer deposition (PEALD). With low-surface-damage in situ remote plasma pretreatments prior to the AlN deposition, an atomically sharp PEALD-AlN/III-nitride interface as well as high-crystal-quality AlN film have been obtained. Effective current collapse suppression and dynamic ON-resistance reduction are demonstrated in the PEALD-AlN passivated AlGaN/GaN HEMTs under high drain bias switching conditions. An output power of 2.64 W/mm and a power added-efficiency of 33% are obtained at 2 GHz on the PEALD-AlN passivated HEMTs without the use of field-plate.
Thickness Dependent Electrical Characteristics of AlGaN/GaN MOSHEMT with La2O3 Gate Dielectrics
Authors: Chen Jiangning , Tsuneishi Kana , Kakushima Kuniyuki , Ahmet Parhat , Kataoka Yoshinori , Nishiyama Akira , Sugii Nobuyuki , Tsutsui Kazuo , Natori Kenji , Hattori Takeo , Iwai H.
Published: March 2013

Thickness dependence of La2O3 gate dielectrics on electrical characteristics for AlGaN/GaN MOSHFET has been investigated. Positive shift in threshold voltage has been observed with thicker La2O3 film thickness. Reduction in leakage current has obtained with thicker film.
Field Control Energy-Band (FCE) Technology for GaN-Based Heterostructure Power Devices
Authors: Chen Wanjun , Wang Zhigang , Deng Xiaochuan , Zhang Bo
Published: March 2013

In this paper, a Field Control Energy-band (FCE) Technology is developed. The two-dimensional electron gas (2DEG) at the AlGaN/GaN interface is determined by the energy-band profiles of AlGaN/GaN interface, which can be controlled by the field distributions. The FCE illustrates the relationship between the energy-band profiles and 2DEG density for AlGaN/GaN interface. Most of the methods for achieving the positive threshold shift can be summarized and unified as the field control energy-band technology. Furthermore, it can be used to calculate the threshold-voltage for both depletion- and enhancement-mode AlGaN/GaN devices. Two power devices based on FCE are presented. Both devices show excellent performance.
Al+ Implanted Anode for 4H-SiC p-i-n Diodes
Authors: Nipoti Roberta , Di Benedetto Luigi , Albonetti Cristiano , Bellone Salvatore
Published: March 2013

Simulations of hole injection and forward current-voltage characteristics of Al+ implanted 4H-SiC p-i-n diodes have been performed for different values of hole densities in the ion implanted anode anddifferent thicknesses of the base. Both the parameters are more elevated for thinner base valuesbecause of a less effective recombination but identical injection and increase with the increasing ofthe anode hole density up saturate because of a reduced effective majority carrier density in theelectrodes with respect to real majority carrier density values due to the 4H-SiC band gap shrinkingup to an effective carrier saturation. For Al p-type doping of 4H-SiC simulations show effectivecarrier of few units 1E18 cm-3 and saturation to 5E18 cm-3 for real hole density > 5E18 cm-3. In Al+ implanted 4H-SiC such hole density values can be obtained for implanted Al concentration of about 2E20 cm-3 and 1950 °C/5 min annealing.
Multilayer Epitaxial Growth and Fabrication of 4H-SiC BJT with Double Base Epilayers
Authors: Zhang Yu-Ming , Yuan Lei , Zhang Yi-Men , Tang Xiao-Yan , Song Qing-Wen , Zhang Xiao-Peng , Zhang Qian
Published: March 2013

Multilayer epitaxial growth (n+/p+/p-/n-) of 4H-SiC including double P-type epilayers was performed in the horizontal low-pressure hot-wall CVD(LP-HW-CVD). With the measurements of secondary ion mass spectroscopy (SIMS), atomic force microscope (AFM), Raman scattering and optical microscope, the doping concentration, surface morphology and crystalline quality of the epitaxial film were characterized. 4H-SiC BJTs with double base were fabricated on the epitaxial wafer. I-V characteristics of the device are presented.
Nanoscale Probing of Interfaces in GaN for Devices Applications
Authors: Giannazzo Filippo , Scuderi Antonino , Greco Giuseppe , Fiorenza Patrick , Lo Nigro Raffaela , Leszczyński Michal , Roccaforte Fabrizio
Published: March 2013

This work reviews some of the results achieved at CNR-IMM in the last years on nanoscale probing of interfaces in gallium nitride (GaN) for devices applications. A special emphasis will be given to the insights obtained using high resolution techniques based on scanning probe microscopy (SPM), often employed in combination with conventional macroscopic measurements. Some aspects related to GaN interfaces that are relevant for devices technology, i.e. Schottky and Ohmic contacts, will be discussed as examples.
Characteristics of GaN Nanowires Produced Using VLS Method on the Growth Temperatures
Authors: Yang Jae Yeol , Lee Ji-myon , Oh Byung Sung , Kim Chang-su , Kim Jae-Kwan , Hong Soon-jik , Yoon Jae Sik
Published: March 2013

One-dimensional GaN NWs (nanowires) were grown by the VLS (Vapor-liquid-solid) method using MOCVD (Metal organic chemical vapor deposition) equipment on growth temperatures in order to evaluate its characteristics. The growth temperatures ranged from 650¢J to 800¢J at an interval of 50¢J. GaN NWs grown at a temperature of 700¢J was approx. 5 μm in length and 200 nm in a diameter, showing relatively uniform size and highly density. The X-ray diffraction analysis showed that NWs grew as wurtzite GaN. In PL (photoluminescence) the spectrum measured at 4 K, at 3.47 eV, BE (band-edge) emissions were identified and the YL (yellow luminescence) was almost not shown. As a temperature dependant PL, the band structure of n-type GaN NWs was identified and E(0) values of FX and DX were calculated using Varshni's equation of 3.476 eV and 3.470 eV, respectively. The result of calculation by quenching equation showed that the activation energy value of FX was 12.8 meV and the activation energy value of DX was 19.1 meV.
(Invited) ALD Grown Functional Oxide Layers for Nonvolatile Resistive Switching Memory Applications
Authors: Hoffmann-Eifert Susanne , Reiners Marcel , Waser Rainer
Published: March 2013

The significance of atomic layer deposition (ALD) for the growth of transition metal oxide thin films which are to be integrated into metal-oxide-metal structures for future nonvolatile resistive switching memory devices is illustrated. Focus is put to the requirements on transition metal oxide layers with respect to the control of morphology, structure, and defect state. For the representative example of ALD TiO2-x thin films grown from different titanium sources possibilities for a design of thin film properties by means of precise process control are exemplified. The success of this strategy is highlighted by the resistive switching behavior of 8 nm ALD TiO2-x thin films integrated into Pt/ TiO2-x/Ti/Pt cross point junctions of 100 nm x 100 nm lateral size by which it could be demonstrated that a stable SET operation in TiO2 films is possible for compliance currents of about 20 µA.
(Invited) HfO2-Based RRAM for Embedded Nonvolatile Memory: From Materials Science to Integrated 1T1R RRAM Arrays
Authors: Bertaud Thomas , Walczyk Damian , Sowinska Malgorzata , Wolansky Dirk , Tillack Bernd , Schoof Gunter , Stikanov Valery , Wenger Christian , Thiess Sebastian , Schroeder Thomas , Walczyk Christian
Published: March 2013

The Ti/HfO2/TiN-based system is a very promising candidate for Resistance change Random Access Memory (RRAM). By combining material science studies and integration in a Si CMOS technology, we succeeded to give quantitative insight in the resistive switching mechanism and to process a 4 kbit array with 1T1R RRAM devices. In particular, in-operando hard X-ray photoelectron spectroscopy allows to describe the resistive switching mechanism by a push-pull model of oxygen vacancies as a function of voltage polarity. Moreover, the characterization of integrated 600×600 nm2 TiN/Ti/HfO2/TiN 1T1R devices in the pulse-induced mode and the recent realization of a 4 kbit memory array have demonstrated promising performance for embedded non-volatile memory applications.
Resistive Switching of Iron Oxide Nanoparticles in Patterned Array Structure on Flexible Substrate
Authors: Kim Jae-Deuk , Yoo Jae Woo , Baek Yoon-Jae , Kim Hyung Jun , Hu Quanli , Kang Chi Jung , Yoon Tae-Sik
Published: March 2013

Resistive switching characteristics of maghemite (γ-Fe2O3) nanoparticle (NP) assembly were investigated in patterned array structure of Pt/γ-Fe2O3/Pt on a flexible polyethylene terephthalate (PET) substrate. The NPs layer was formed through dip-coating process. The cross-bar array patterned devices with NPs sandwiched between Pt electrodes exhibited memristive switching with hysteresis in current-voltage characteristics with gradually changing resistance with respect to the bias conditions.
Roles of Target Composition on the Dielectric Property of RF Sputtered Bi2O3-ZnO-Nb2O5 Pyrochlore Thin Film
Authors: Lim Minhyuk , Lee B. J. , Lee H. S. , Choi J. O. , Ko K. H.
Published: March 2013

Bi2O3-ZnO-Nb2O5 (BZN) thin films were well formed on a Pt/TiO2/SiO2/Si substrate by RF magnetron sputtering. Process induced nonstoichiometric of BZN yielded two typical crystalline structures i.e. cubic and monoclinic. Due to the low sputtering yield of Bi, BZN cubic phase, could be obtained not only from the sputtering of corresponding target (Bi1.5Zn0.5)(Zn0.5Nb1.5) O7 but also from the target which has Bi-enriched monoclinic composition (Bi2(Zn0.33Nb0.66)2O7). Even film which is deposited from monoclinic BZN has better tunability. It was observed that BZN cubic films were continuously deposited until target composition increased up to (Bi:Zn:Nb = 4.0:1:2) from stoichiometry (Bi:Zn:Nb = 3:1:2) and that tunability maximized with a dielectric constant of 184, loss tangent of 0.008, and maximum tunability of 42% at 1.1MV/cm from 3.2:1:2 composition. In the mid nonstoichiometric range, only Bi5Nb3O15 secondary orthorhombic phases were observed along with cubic phase which showed synergetic effects on BZN cubic films.
Conduction Band-Offset in GeO2/Ge Stack Determined by Internal Photoemission Spectroscopy
Authors: Zhang Wenfeng , Nishimura Tomonori , Nagashio Kosuke , Kita Koji , Toriumi Akira
Published: March 2013

The conduction band offset (CBO) at GeO2/Ge interface has been systematically investigated by using internal photoemission spectroscopy (IPE). Irrespective of the metal gate electrode (Au or Al) and Ge substrate type (p- or n- type) variance, the energy barrier for the electrons of Ge valence band into GeO2 conduction band is determined to be 2.34 ±0.1eV, thus yielding the CBO of 1.65 ± 0.1eV. Such as-obtained >1.5eV CBO agrees well with previous IPE results measured on the ultra-thin GeOx/High-k oxide stacks and theoretical calculation without the valence alternation pair, and gives further support of GeO2 as potential passivation layer for the future Ge-based CMOS devices.
Hydrogen Interaction with HfO2 Films Deposited on Ge(100) and Si(100)
Authors: Soares Gabriel Vieira , Feijó Taís , Baumvol Israel J.R. , Aguzzoli Cesar , Krug Cristiano , Radtke Cláudio
Published: March 2013

In the present work we investigated the thermally-driven hydrogen incorporation in HfO2 films deposited on Si and Ge substrates. Two incorporation regimes were identified, one in the 200-400ºC temperature range and another one in the 400-600ºC temperature range. D incorporation was higher for films deposited on Si for all investigated temperatures, indicating a higher density of sites for D incorporation, probably near the HfO2/Si interface. HfO2 films undergo structural changes during annealing in the high temperature regime, crystallizing in the monoclinic and in the cubic phase. No oxygen or hafnium desorption were observed after annealings, as well as no Ge incorporation in the HfO2 film.
(Invited) Conformal Metal Gate Process Technology for 14nm Logic Node and Below
Authors: Noori Atif M , Brand Adam , Lei Yu , Chen Michael , Tang Wei , Lu Xinliang , Fu Xinyu , Ganguli Seshadri , Anthis Jeffrey , Thompson David , Yoshida Naomi , Xu Min , Allen Miller , Yang Haichun , Gelatos Jerry , Yu San-Ho , Chang Mei , Gandikota Srinivas
Published: March 2013

Emerging 3D transistor structures and continued scaling requires conformal metal gate options with low resistivity, band edge work function and improved barrier properties. Doping ALD TiN with Si improves barrier properties shown with 10X reduced gate leakage. Both valence and conduction band edge work function can be met with low resistivity conformal films. The combination of ALD TiN, CVD Co and CVD Al can be used for low resistivity replacement metal gate fill for sub-15nm trenches.
(Invited) Independent-Double-Gate FinFET SRAM Technology
Authors: Endo Kazuhiko , O'uchi Shin-ichi , Matsukawa Takashi , Liu Yongxun , Masahara Meishoku
Published: March 2013

Double-gate (DG) device technology has been proposed and investigated for many years. However, there are many issues due to the aggressively scaled feature size. Variability of the device due to the various random sources is increasing and will reduce the yield of the circuit. This paper presents the variability issues in the scaled FinFET and focuses on the Vth controllable independent-DG SRAM technology to enhance circuit performance.
(Invited) Electrical Characterization and Reliability Assessment of Double-Gate FinFETs
Authors: Young Chadwin D , Akarvardar Kerem , Matthews Ken , Baykan Mehmet O. , Pater James , Ok Injo , Ngai Tat , Ang Kah-Wee , Minakais Matt , Bersuker Gennadi , Deora S. , Hobbs Chris , Kirsch Paul , Jammy Raj
Published: March 2013

The performance and reliability of doped and undoped (100)<100> and (110)<110> sidewall silicon-on-insulator (SOI) FinFETs with an Hf-based gate dielectric were evaluated. The electron mobility of the (110) FinFET sidewall is comparable to the (100) FinFET sidewall devices, which is opposite of the typical planar MOSFET electron mobility dependence on orientation, wherein (110) degrades significantly. In addition, TiN metal gate-induced strain cannot completely explain the similarity in (110) and (100) electron mobility because, although lower in magnitude, the two orientations with polysilicon electrodes resulted in similar mobility values. When investigating the orientation dependence of negative bias temperature instability (NBTI), (110) was found to cause more degradation than (100), and FinFETs with higher fin body doping demonstrated even more degradation.
(Invited) Current Status of High-k and Metal Gates in CMOS
Authors: Wilk Glen D. , Verghese Mohith , Chen Peijun , Maes Jan Willem
Published: March 2013

Continued scaling of microelectronic devices has driven the change from SiO2 to alternative, Hf-based, high-k gate dielectric materials in recent years. This materials change has enabled device performance scaling without the gate leakage current becoming unacceptably high. The change from doped poly-Si to metal(s) as the gate electrode material also occurred simultaneously with the introduction of high-k materials, as the resulting high-k / metal gate (HKMG) device can effectively overcome depletion effects in poly-Si gate devices. Processing of the metal gate stack is a challenging task in terms of meeting requirements in effective work function for both nMOS and pMOS, as well as enabling low resistivity gate/contact metal fill. The introduction of 3D device structures such as FinFETs serves as an inflection point for novel materials and the transition from PVD to ALD processes.
Area Dependence of Reliability Characteristics for Atomic Layer Deposition HfO2 Film under Static and Dynamic Stress
Authors: Cheng Yi-Lung , Chang You-Ling , Hsieh Cheng-Yang , Lin Jian-Run
Published: March 2013

The reliability characteristics of high-k gate stacks of HfO2 films under static and dynamic stresses have been investigated. Weibull slopes (β), area scaling factor, and lifetime projection model have been checked, in order to further understanding of the breakdown mechanism of HfO2 gate stacks. Irrespective of the static and dynamic stress, the breakdown distributions of HfO2 capacitors with various areas can be merged to a single Weilbull plot, suggesting that the dielectric breakdown is intrinsic for both cases. This study shows that a higher frequency and a lower duty cycle in the bipolar stress resulted in a longer lifetime enhancement. With respect to gate area effect, the amount of lifetime enhancement increases as the gate area decreases. A higher weibull slope is observed on a smaller gate area under dynamic stress.