bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat shocks enhance procollagen type I and III expression in fibroblasts in ex vivo human skin
Authors: Dams S. D. , de Liefde‐van Beest M. , Nuijs A. M. , Oomens C. W. J. , Baaijens F. P. T.
Published: January 2011

Background: The well‐known characteristics of aging skin are the development of fine lines and wrinkles, but changes in skin tone, skin texture, thickness and moisture content are also aspects of aging. Rejuvenation of the skin aims at reversing the signs of aging and can be established in the epidermis as well as in the dermis. Aged dermis, in fact, has a degenerated collagen matrix. To regenerate this matrix, fibroblasts need to be stimulated into synthesizing new collagen.

Aims: In this study, the effects of heat shocks of different temperatures on human dermal fibroblasts in ex vivo skin on the expression of procollagen 1, procollagen 3, heat shock protein (hsp)27, hsp47, and hsp70 are investigated.

Materials and methods: The heat shocks were applied on ex vivo skin samples by immersing the samples in heated phosphate‐buffered saline of 45 °C or 60 °C. Metabolic activity was measured and at similar time points propidium–iodide–calceine staining was performed to establish cell viability. Quantitative polymerase chain reaction (qPCR) was performed after the heat shock to determine gene expression levels relative to the reference temperature. Furthermore, PicroSirius Red and hematoxylin stainings were performed to visualize the collagen network and the cells.

Results: The skin samples were shown to be viable and metabolically active. Histology indicated that the heat shocks did not influence the structure of the collagen network or cell appearance. qPCR results showed that in contrast to the 45 °C heat shock the 60 °C heat shock resulted in significant upregulations of procollagen type I and III, hsp70 and hsp47.

Conclusion: A 60 °C, heat shock stimulates the human dermal fibroblasts in ex vivo skin to upregulate their procollagen type I and type III expression.
Is there any barrier impairment in sensitive skin?: a quantitative analysis of sensitive skin by mathematical modeling of transepidermal water loss desorption curves
Authors: Pinto Pedro , Rosado Catarina , Parreirão Catarina , Rodrigues Luis Monteiro
Published: January 2011

Background/purpose: Sensitive skin is a vague, subjective and difficult to characterize affliction. It affects a large part of the population and is accompanied with great interest by the cosmetic industry. Some studies have suggested that sensitive skin is the result of impaired barrier function, which leads to the exposure of immune system cells and sensitive nerves, resulting in marked cutaneous responses to otherwise harmless stimuli. This study aimed to investigate the cutaneous barrier integrity of individuals with sensitive skin by a novel approach: a plastic occlusion stress test followed by measurement of transepidermal water loss (TEWL) desorption curves.

Methods: The study was conducted in volunteers with sensitive skin in the hands and a control group with no sensitivity complaints. A previously developed mathematical model was adjusted to the TEWL data points and two parameters were calculated: dynamic water mass and the evaporation half‐life period.

Results: Statistically significant differences have been detected in the parameters obtained in the sensitive skin group, which supports the thesis that individuals with an increased skin susceptibility have impaired barrier function.

Conclusion: Whereas in the studies based in basal TEWL measurements only discrete differences were reported, the dynamic approach followed in this study provided unequivocal evidence of barrier impairment. The methodology enabled a more objective characterization of sensitive skin and can potentially be applied to the diagnosis/prediction of sensitivity; as well as the efficacy assessment of cosmetic products that are specifically designed to fulfill the needs of consumers with this skin condition.
The Bacterial SRP Receptor, SecA and the Ribosome Use Overlapping Binding Sites on the SecY Translocon
Authors: Kuhn Patrick , Weiche Benjamin , Sturm Lukas , Sommer Erik , Drepper Friedel , Warscheid Bettina , Sourjik Victor , Koch Hans‐Georg
Published: January 2011

Signal recognition particle (SRP)‐dependent protein targeting is a universally conserved process that delivers proteins to the bacterial cytoplasmic membrane or to the endoplasmic reticulum membrane in eukaryotes. Crucial during targeting is the transfer of the ribosome‐nascent chain complex (RNC) from SRP to the Sec translocon. In eukaryotes, this step is co‐ordinated by the SRβ subunit of the SRP receptor (SR), which probably senses a vacant translocon by direct interaction with the translocon. Bacteria lack the SRβ subunit and how they co‐ordinate RNC transfer is unknown. By site‐directed cross‐linking and fluorescence resonance energy transfer (FRET) analyses, we show that FtsY, the bacterial SRα homologue, binds to the exposed C4/C5 loops of SecY, the central component of the bacterial Sec translocon. The same loops serve also as binding sites for SecA and the ribosome. The FtsY–SecY interaction involves at least the A domain of FtsY, which attributes an important function to this so far ill‐defined domain. Binding of FtsY to SecY residues, which are also used by SecA and the ribosome, probably allows FtsY to sense an available translocon and to align the incoming SRP–RNC with the protein conducting channel. Thus, the Escherichia coli FtsY encompasses the functions of both the eukaryotic SRα and SRβ subunits in one single protein.
Phytochemicals and Antioxidant Activity of Fruits and Leaves of Paprika (Capsicum Annuum L., var. Special) Cultivated in Korea
Authors: Kim Ji‐Sun , Ahn Jiyun , Lee Sung‐Joon , Moon BoKyung , Ha Tae‐Youl , Kim Suna
Published: January 2011

Abstract:  The phytochemical composition of carotenoids, tocopherols, free sugars, organic acids, L‐ascorbic acid, capsaicinoids, and flavonoids in green and red paprika (GP and RP), and paprika leaves (PL) cultivated in Korea were analyzed. The ethanolic extracts of GP, RP, and PL were obtained with 80% ethanol, and their antioxidative activities were determined by measuring their ABTS and DPPH radical scavenging activities. RP showed the highest contents of capsanthin (58.33 ± 3.91 mg/100 g dry weight) and L‐ascorbic acid (1987.25 ± 19.64 mg/100 g dry weight), and main compounds of PL were lutein, chlorophyll, and γ‐tocopherol (96.91 ± 14.58, 2136.71 ± 21.11, and 723.49 ± 54.10 mg/100 g dry weight, respectively). RP showed the strongest antioxidant activity (IC50= 55.23 ± 6.77 μg/mL in a 2, 2′‐azino‐di‐[3‐ethylbenzthiazoline sulphonate] assay and 150.40 ± 8.07 μg/mL in a 2, 2‐diphenyl‐2‐picrylhydrazyl assay), and the antioxidant activity of PL was higher than β‐carotene but lower than RP. The results indicate that the amounts of capsanthin and L‐ascorbic acid in RP correlate well with antioxidant activity. PL, which has various phytochemicals such as lutein, chlorophyll, and γ‐tocopherol, might be used in nutraceuticals and pharmaceuticals for improving human health.
DNA‐methylation profiling distinguishes malignant melanomas from benign nevi
Authors: Conway Kathleen , Edmiston Sharon N. , Khondker Zakaria S. , Groben Pamela A. , Zhou Xin , Chu Haitao , Kuan Pei Fen , Hao Honglin , Carson Craig , Berwick Marianne , Olilla David W. , Thomas Nancy E.
Published: January 2011

DNA methylation, an epigenetic alteration typically occurring early in cancer development, could aid in the molecular diagnosis of melanoma. We determined technical feasibility for high‐throughput DNA‐methylation array‐based profiling using formalin‐fixed paraffin‐embedded tissues for selection of candidate DNA‐methylation differences between melanomas and nevi. Promoter methylation was evaluated in 27 common benign nevi and 22 primary invasive melanomas using a 1505 CpG site microarray. Unsupervised hierarchical clustering distinguished melanomas from nevi; 26 CpG sites in 22 genes were identified with significantly different methylation levels between melanomas and nevi after adjustment for age, sex, and multiple comparisons and with β‐value differences of ≥0.2. Prediction analysis for microarrays identified 12 CpG loci that were highly predictive of melanoma, with area under the receiver operating characteristic curves of >0.95. Of our panel of 22 genes, 14 were statistically significant in an independent sample set of 29 nevi (including dysplastic nevi) and 25 primary invasive melanomas after adjustment for age, sex, and multiple comparisons. This first report of a DNA‐methylation signature discriminating melanomas from nevi indicates that DNA methylation appears promising as an additional tool for enhancing melanoma diagnosis.
Effect of the duration of immunomodulatory therapy on the clinical features of recurrent episodes in Vogt–Koyanagi–Harada disease
Authors: Errera Marie‐Hélène , Fardeau Christine , Cohen David , Navarro Audrey , Gaudric Alain , Bodaghi Bahram , Westcott Mark , LeHoang Phuc
Published: January 2011

Purpose:  To evaluate the duration of immunomodulatory therapy (corticosteroids, immunosuppressive drugs) with regard to the rate of relapses and clinical features (exudative retinal detachment or anterior uveitis) in inflammatory episodes of Vogt–Koyanagi–Harada disease.

Methods:  Data of all 42 patients diagnosed with acute uveitis associated with VKH disease during the period of January 2005 to December 2008 at the Pitié‐Salpêtrière Hospital or at the Lariboisière Hospital in Paris, France were extracted by chart review.

Results:  There were 31 patients (73.8%) with episodes of recurrence and were included in the study. At the first recurrence, 81% (13 patients) of exudative retinal detachments (ERD) were associated with an initial immunomodulatory treatment conducted ≤6 months (3.76 months ± 2.67). Conversely, an initial treatment duration of >6 months was associated with anterior uveitis signs for 66% of patients (eight patients) with anterior first recurrence (p = 0.0061). On second episode of recurrence, 75% of patients (three patients) who developed exudative retinal detachment had been managed by immunomodulatory therapy for ≤6 months with the total duration of immunomodulatory treatment ≤6 months during previous inflammatory episodes. Conversely, all 16 patients who presented anterior uveitis with additional manifestations (optic disc oedema, macular oedema, vitritis and/or ‘Sunset glow’ fundus) have been treated for more than 6 months or treated during the initial occurrence lasting more than 9 months (p = 0.0035).

Conclusions:  The duration of systemic corticosteroids (and/or immunosuppressive drug therapy) for ≤6 months at first and second recurrence was associated with features of further exudative retinal detachment instead of anterior uveitis in VKH disease.
Develop Acceptance Criteria of Pressure Test of Buried Pipeline Using Uncertainty Analysis
Authors: Al-Muslim Husain , Al-Qutub Amro M.
Published: January 2011

Hydrotest is one of the most important inspection activities to assess the integrity of pipelines prior to starting transportation of hazardous liquids. If the pipeline is buried, and welds cannot be inspected visually for leak, it is required that the hydrotest pressure is held for 24 h to ensure that the pipeline is leak free. Ideally the pressure should remain constant, but this is practically impossible due to changes in temperature. Pressure and temperature of the pipelines are recorded continuously and evaluated at the end of the test. The pressure drop should be in line with the temperature drop based on compressibility relationship. However, nonconformance is expected due to accuracy of the individual instruments used to measure the pressure and temperature. It is then ambiguous to the evaluator whether the nonconformance is attributed to small leak or to instrument accuracy. In this paper, general uncertainty analysis with parametric study is used in the planning and designing phase of pressure test. The objective is to develop an appropriate acceptance criterion for the pressure test of buried pipelines. Actual field hydrotests are used to illustrate and validate the outcome of the analysis. The results show that high uncertainty values reduce the validity of the actual hydrotest. This is because the test would most probably pass regardless of the actual pressure drop measured.
Vision-based approach to automated analysis of structure boundaries in scanning electron microscope images
Authors: Kim Nak H. , Lee Soo-Young
Published: January 2011

In this article, a vision-based approach is presented for the automatic measurement of feature dimensions from cross-section scanning electron microscope images of three-dimensional structures. The cross-sections of fabricated structures are represented by a set of boundary points. The geometric distortion incurred during the imaging process is compensated for by matching the cross-section of a target structure to that of the fabricated one. Control points are defined on the boundary of the target structure, and their locations in the cross-section image are estimated using line fitting. The feature dimensions are measured based on the control points. The proposed automatic analysis method has been successfully applied to measuring dimensions of sawtooth and staircase structures transferred onto resist.
DAXX
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ATRX
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MEN1
, and mTOR Pathway Genes Are Frequently Altered in Pancreatic Neuroendocrine Tumors
Authors: Jiao Yuchen , Shi Chanjuan , Edil Barish H. , de Wilde Roeland F. , Klimstra David S. , Maitra Anirban , Schulick Richard D. , Tang Laura H. , Wolfgang Christopher L. , Choti Michael A. , Velculescu Victor E. , Diaz Luis A. , Vogelstein Bert , Kinzler Kenneth W. , Hruban Ralph H. , Papadopoulos Nickolas
Published: January 2011

A rare but deadly form of human pancreatic cancer harbors mutations in chromatin remodeling genes.
Basal plate plaque: a novel organising placental thrombotic process
Authors: Fitzgerald Brendan , Shannon Patrick , Kingdom John , Keating Sarah
Published: January 2011

In contrast to thrombi and haematomas at other body sites, thrombi in the placental intervillous space are not traditionally known to undergo organisation. This report presents 11 examples of a form of organising thrombotic process that develops as a plaque on the foetal aspect of the basal plate. Originally identified in the placenta of a foetus showing severe intrauterine growth restriction, further examples of this lesion, which we term a ‘basal plate plaque’, show a spectrum of placental involvement. Small lesions appear to occur at points of localised stasis at the basal plate (eg, at edges of anchoring villi or in small basal plate depressions). Large areas of involvement, as seen in the original case, may be pathological markers of more generalised disturbances in placental circulation or of hypercoagulability in the intervillous space. Large basal plate plaques may therefore prove to be diagnostically significant and should be reported.
Design-based diagnostics for k-NN estimators of forest resourcesThis article is one of a selection of papers from Extending Forest Inventory and Monitoring over Space and Time.
Authors: Baffetta F. , Corona P. , Fattorini L.
Published: January 2011

The k-nearest neighbours (k-NN) method constitutes a possible approach to improve the precision of the Horvitz–Thompson estimator of a single interest variable using auxiliary information at the estimation stage. Improvements are likely to occur when the neighbouring structure in the space of auxiliary variables is similar to the neighbouring structure in the space of the survey variables. Populations suitable for k-NN can be identified via the scores of the first principal component computed on the variance–covariance matrix of auxiliary variables. If the first principal component explains a large portion of the whole variability, distances among scores provide good approximations of distances in the space of auxiliary variables in such a way that the effectiveness of k-NN can be assessed by plotting the first principal component scores versus the sampled values of each of the interest variables. Monotone relationships with high values of Spearman’s correlation coefficients should denote effectiveness. Otherwise, when the first principal component explains small fractions of the total variation, an index that directly quantifies the similarity between the neighbouring structure in the space of interest and auxiliary variables is proposed. The validity of the proposed diagnostics is theoretically argued and empirically proven by a simulation study performed on a wide range of artificial and real populations.
The evidence of stand development stages in simulations by an individual-tree growth simulator
Authors: Huber Markus O.
Published: January 2011

Individual-tree growth models have often been evaluated at the stand level in terms of stand increment or the development of stand density, but rarely in conceptual terms of natural stand dynamics. This study addresses the stand development stage concept developed for natural forests and shows how individual-tree growth models can be evaluated in this respect. For this purpose, the individual-tree growth simulator PrognAus was used to simulate the development of three sites for 2500 years, and a statistical classification model and a rule-based classification scheme were used to identify development stages in the output of the simulator. A comparison of the simulated stages with stages observed in a natural forest in terms of the stand volume and a comparison of the simulated stages with hypotheses from the literature in terms of volume, change of volume, and stand density were performed to determine if the simulations are consistent with the theory.
Tree species and soil nutrient profiles in old-growth forests of the Oregon Coast Range
Authors: Cross Alison , Perakis Steven S.
Published: January 2011

Old-growth forests of the Pacific Northwest provide a unique opportunity to examine tree species – soil relationships in ecosystems that have developed without significant human disturbance. We characterized foliage, forest floor, and mineral soil nutrients associated with four canopy tree species (Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), western redcedar (Thuja plicata Donn ex D. Don), and bigleaf maple (Acer macrophyllum Pursh)) in eight old-growth forests of the Oregon Coast Range. The greatest forest floor accumulations of C, N, P, Ca, Mg, and K occurred under Douglas-fir, primarily due to greater forest floor mass. In mineral soil, western hemlock exhibited significantly lower Ca concentration and sum of cations (Ca + Mg + K) than bigleaf maple, with intermediate values for Douglas-fir and western redcedar. Bigleaf maple explained most species-based differences in foliar nutrients, displaying high concentrations of N, P, Ca, Mg, and K. Foliar P and N:P variations largely reflected soil P variation across sites. The four tree species that we examined exhibited a number of individualistic effects on soil nutrient levels that contribute to biogeochemical heterogeneity in these ecosystems. Where fire suppression and long-term succession favor dominance by highly shade-tolerant western hemlock, our results suggest a potential for declines in both soil Ca availability and soil biogeochemical heterogeneity in old-growth forests.
Simulating the effectiveness of three potential management options to slow the spread of emerald ash borer (Agrilus planipennis) populations in localized outlier sites
Authors: Mercader Rodrigo J. , Siegert Nathan W. , Liebhold Andrew M. , McCullough Deborah G.
Published: January 2011

The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a devastating, invasive insect pest of ash trees, Fraxinus spp., in North America. Using a simulation model, we evaluated three potential management options to slow the spread of A. planipennis in discrete outlier sites: (i) removing ash trees to reduce available host phloem resource, (ii) girdling ash trees to attract ovipositing female beetles and destroying the trees before larvae complete development, and (iii) applying a highly effective systemic insecticide. Simulations indicate that systemic insecticide applications provided the greatest reduction in the radial spread of A. planipennis. In simulations in which management options were applied only within a 300 m radius from the origin of the infestation, insecticide applications reduced the radial spread by 30% and larval consumption of ash phloem by 40% beyond the treated area. In contrast, girdling ash trees reduced the radial spread by 15% and larval consumption of ash phloem by 20% beyond the treated area. Both of these management options significantly reduced the spread of A. planipennis when treatments were applied 1 to 4 years after infestations were initiated. Reducing ash phloem by removing ash trees decreased population size within treated areas but did not reduce the radial spread, population size, or larval consumption of ash phloem beyond treated areas.
Contrasting the temporal dynamics of stand structure in even- and uneven-sized Picea abies dominated stands
Authors: Zenner Eric K. , Lähde Erkki , Laiho Olavi
Published: January 2011

Although proposed as a means of increasing structural diversity in managed forests, the impact of single-tree selection on the temporal dynamics of three-dimensional structure has not been previously evaluated. Forest structural development in Picea-dominated stands was contrasted over 15 years in stem-mapped randomized plots in southern Finland that underwent either low thinning (creating the even-sized (ES) structure of a bell-shaped diameter distribution) or single-tree selection (maintaining the uneven-sized (UES) structure of a reverse-J-shaped distribution) through multiple harvest entries. Structure was quantified with nonspatial stand attributes (e.g., density) and indices that quantify spatially explicit relationships among neighboring trees (e.g., structural complexity index (SCI)). Over time, three-dimensional structure reflected differential tree growth and mortality, resulting in minor changes in tree composition, spatial pattern, and tree size differentiation and somewhat greater changes in the SCI. The third harvest entry simplified the forest structure in both structure types. However, structural metrics such as the variability of tree diameters, tree size differentiation, and the SCI recovered to preharvest levels within 2–4 years in UES plots, whereas no recovery was seen in the ES structure type. Single-tree selection was demonstrated to perpetuate the uneven-sized structure associated with natural nonpyrogenic Picea-dominated forests.
Predictions of wood density and module of elasticity of balsam fir (Abies balsamea) and black spruce (Picea mariana) from near infrared spectral analyses
Authors: Xu Qinghua , Qin Menghua , Ni Yonghao , Defo Maurice , Dalpke Barbara , Sherson Gail
Published: January 2011

The predictions of properties for wood disc average are seldom reported, and they are important for sorting out logs based on their quality. The minimum near infrared (NIR) spectra required to predict wood disc average properties would also be of critical importance. In this study, calibration and prediction models for wood disc average properties were developed using NIR spectral data for balsam fir (Abies balsamea (L.) Mill.) and black spruce (Picea mariana (Mill.) B.S.P.) samples collected from 14 different sites across Newfoundland, Canada. The calibration was done against area-weighted average wood properties determined by SilviScan. NIR spectra were collected in 18 mm increments from the radial–longitudinal face of green and oven-dried samples. Results showed that using NIR spectra from three spots per wood strip was sufficient for the modeling and prediction for density and module of elasticity (MOE). The coefficients of determination ranged from 0.76 (MOE of green wood samples) to 0.88 (density of oven-dried wood samples). However, the microfibril angle (MFA) cannot be well predicted from either green wood or oven-dried wood NIR spectra. Our results further showed that the NIR spectra collected from oven-dried wood samples gave better calibration and prediction than those collected from green wood samples.
Changes in litter and dead wood loads following tree death beneath subalpine conifer species in northern Colorado
Authors: Bigler Christof , Veblen Thomas T.
Published: January 2011

Litter and dead wood affect important processes in forest ecosystems such as nutrient and carbon cycling and are key influences on biodiversity and fire behavior. Increased tree mortality rates in western North America associated with climate trends and increased bark beetle activity highlight the need to better understand the dynamics of litter and dead wood following tree death. For eight old-growth stands in a subalpine forest landscape in northern Colorado (USA), we compared litter and dead wood loads beneath more than 200 dead and live Engelmann spruce (Picea engelmannii Parry ex Engelm.), subalpine fir (Abies lasiocarpa (Hook.) Nutt.), and lodgepole pine (Pinus contorta Douglas ex Loudon). The dynamics of litter and dead wood were analyzed using chronosequences of tree death dates over >100 years that we determined from tree rings. Immediately following tree death, high loads of litter accumulated, particularly for the biggest spruces, which accumulated 10 times more litter than live spruces (five times more for fir, two times more for pine). We estimated a higher decay rate of litter for spruce (half-life of four years) than for pine (15 years) and fir (19 years). The accumulation rates for dead wood following tree death were highly variable among trees, but maximum accumulation was attained during the first 50–60 years.
ON STRONG REVERSIBILITY IN P SYSTEMS AND RELATED PROBLEMS
Authors: IBARRA OSCAR H.
Published: January 2011

We consider transition P systems as originally defined in the seminal paper of Gh. Păun, where he introduced the field of membrane computing. We show that it is decidable to determine, given a P system Π, whether it is strongly reversible (i.e., every configuration has at most one direct predecessor), resolving in the affirmative a recent open problem in the field. We also show that the set of all direct predecessors of a given configuration in a P system is an effectively computable semilinear set, which can effectively be expressed as a Presburger formula, strengthening an early result in the literature. We also prove other related results.
COMPUTATION OF RAMSEY NUMBERS BY P SYSTEMS WITH ACTIVE MEMBRANES
Authors: PAN LINQIANG , DÍAZ-PERNIL DANIEL , PÉREZ-JIMÉNEZ MARIO J.
Published: January 2011

Ramsey numbers deal with conditions when a combinatorial object necessarily contains some smaller given objects. It is well known that it is very difficult to obtain the values of Ramsey numbers. In this work, a theoretical chemical/biological solution is presented in terms of membrane computing for the decision version of Ramsey number problem, that is, to decide whether an integer n is the value of Ramsey number R(k, l), where k and l are integers.
ON A PARTIAL AFFIRMATIVE ANSWER FOR A PĂUN'S CONJECTURE
Authors: PÉREZ-HURTADO IGNACIO , PÉREZ-JIMÉNEZ MARIO J. , RISCOS-NÚÑEZ AGUSTÍN , GUTIÉRREZ-NARANJO MIGUEL A. , RIUS-FONT MIQUEL
Published: January 2011

At the beginning of 2005, Gheorghe Păun formulated a conjecture stating that in the framework of recognizer P systems with active membranes (evolution rules, communication rules, dissolution rules and division rules for elementary membranes), polarizations cannot be avoided in order to solve computationally hard problems efficiently (assuming that P ≠ NP ). At the middle of 2005, a partial positive answer was given, proving that the conjecture holds if dissolution rules are forbidden. In this paper we give a detailed and complete proof of this result modifying slightly the notion of dependency graph associated with recognizer P systems.
AN OVERVIEW ON OPERATIONAL SEMANTICS IN MEMBRANE COMPUTING
Authors: BARBUTI ROBERTO , MAGGIOLO-SCHETTINI ANDREA , MILAZZO PAOLO , TINI SIMONE
Published: January 2011

The aim of this paper is to give motivations for the development of operational semantics in membrane computing, and to survey existing proposals. In particular, the definitions are compared of three operational semantics available in the literature, namely a semantics proposed by Andrei, Ciobanu and Lucanu, another proposed by Busi, and another one proposed by the authors of the present paper. These definitions are different since they are given with different aims. However, we show that there is an operational correspondence among the three.
FILTER POSITION IN NETWORKS OF SUBSTITUTION PROCESSORS DOES NOT MATTER
Authors: MONTORO FERNANDO ARROYO , CASTELLANOS JUAN , MITRANA VICTOR , SANTOS EUGENIO , SEMPERE JOSE M.
Published: January 2011

It is known ([4]) that moving the filters from the nodes to the edges in accepting hybrid networks of evolutionary processors does not decrease the computational power of the model which equals that of a Turing machine. A direct and time complexity preserving simulation is presented in [1]. All three types of processors (substitution, insertion, deletion) are essentially used in this simulation.

In this note we prove that such a direct simulation between networks containing substitution nodes only still exists.
POSITIONED AGENTS IN ECO-GRAMMAR SYSTEMS
Authors: LANGER MIROSLAV , KELEMENOVÁ ALICA
Published: January 2011

Positioned eco-grammar systems (PEG systems, for short) were introduced in [9]. Motivation of introducing positioned eco-grammar systems is an attempt to describe interplay between evolving environment and community of agents living in this environment whereas we focus on the positions of agents in the environment. PEG systems bring a new view to investigating interplay between community of agents and environment. Our approach allows to study local changes in evolving environment caused by agents moreover the position of the agent is strictly given by special symbol and we are able to predict its behavior and control the evolution of environment as well. In this paper we compare generative power of the PEG systems with three types of pure (regulated) grammars.
POWER SUMS ASSOCIATED WITH CERTAIN RECURSIVE PROCEDURES ON WORDS
Authors: SALOMAA ARTO
Published: January 2011

The paper investigates classes of words equivalent under different ways of counting subwords. We present a general method of constructing sequences of equivalent words. Apart from obtaining numerical characterizations of words, we also construct sequences of words generating equal arithmetical power sums. Our notions of equivalence include the Parikh equivalence resulting from Parikh matrices, recently widely studied. Consequently, we are able to settle some open problems in this area.
Source–Drain Engineering Using Atomically Controlled Heterojunctions for Next-Generation SiGe Transistor Applications
Authors: Hamaya Kohei , Ando Yuichiro , Sadoh Taizoh , Miyao Masanobu
Published: January 2011

Using low-temperature molecular-beam epitaxy techniques on the (111) plane of Si or Ge, we can realize an atomically controlled Fe3Si/Si or Fe3Si/Ge heterojunction and simultaneously obtain D
O
3-ordered crystal structures of Fe3Si films. First, high-quality Fe3Si/Si(111) Schottky tunnel contacts enable us to inject and detect spin-polarized electrons in Si conduction channels at ∼180 K, where Fe3Si is a ferromagnetic spin injector and detector. This may lead to the accelerated development of next-generation Si-based spin metal–oxide–semiconductor field-effect transistors (MOSFETs). Next, for the atomically controlled Fe3Si/Ge(111) Schottky contacts, we find the unexpected suppression of the Fermi level pinning (FLP) effect. This indicates that there is an influence of extrinsic contributions such as dangling bonds and disorder on the strong FLP effect at metal/Ge interfaces. We expect that the Fe3Si/Ge(111) contacts can be used to control the Schottky barrier height of future ultra scaled Ge-channel MOSFETs. These two novel and interesting results are expected to form the basis of a key technology toward developing next-generation SiGe transistors.
Gas Phase Doping of Arsenic into (100), (110), and (111) Germanium Substrates Using a Metal–Organic Source
Authors: Takenaka Mitsuru , Morii Kiyohito , Sugiyama Masakazu , Nakano Yoshiaki , Takagi Shinichi
Published: January 2011

The gas phase doping of arsenic (As) into (100), (110), and (111) germanium (Ge) substrates at 500 to 700 °C using a metal–organic vapor phase epitaxy (MOVPE) system with tertiarybutylarsine (TBAs) as the As source was investigated for the n-type source/drain formation of Ge metal–oxide–semiconductor field effect transistors (MOSFETs). The surface concentration of As analyzed by secondary ion mass spectroscopy (SIMS) was approximately 1×1019 cm-3 and the diffusion constant was one order of magnitude smaller than that of As induced by ion implantation at 700 °C. The diffusion constant was linearly dependent on the As concentration, and the activation energy and pre-exponential factor of the As diffusion constant were found to be 1.9 eV and 6.2×10-3 cm2/s, respectively. The electron carrier concentration profiles were also evaluated by spreading resistance profiling (SRP) to confirm dopant activation.
Thermal Robustness and Improved Electrical Properties of Ultrathin Germanium Oxynitride Gate Dielectric
Authors: Kutsuki Katsuhiro , Hideshima Iori , Okamoto Gaku , Hosoi Takuji , Shimura Takayoshi , Watanabe Heiji
Published: January 2011

Robustness of ultrathin germanium oxynitrides (GeON) formed by plasma nitridation of thermal oxides (GeO2) on Ge(100) substrates [K. Kutsuki et al.: Appl. Phys. Lett. 95 (2009) 022102] was investigated by means of physical and electrical measurements. The decomposition temperature of a 3.7-nm-thick GeON layer was found to increase up to 550 °C by plasma nitridation, which was about 100 °C higher than that of pure GeO2. While the insulating property of GeON dielectrics begins to degrade just below the decomposition temperature, i.e., at around 540 °C, thermal treatment up to 520 °C effectively improves the electrical properties of the ultrathin GeON dielectrics, such as recovery of bulk defects and quite low interface state density (D
it) even for the ultrathin gate dielectrics. The advantage of GeON dielectrics in designing a fabrication process for Ge-based devices and the physical origins of the improved properties will be discussed.
Monte Carlo Study of the Coulomb Interaction in Nanoscale Silicon Devices
Authors: Sano Nobuyuki
Published: January 2011

Three-dimensional Monte Carlo simulations coupled self-consistently with the Poisson equation are carried out under the double-gate metal–oxide–semiconductor field-effect-transistor (MOSFET) structures with various channel lengths. The Coulomb force experienced by an electron inside the device is directly evaluated by performing the Monte Carlo simulations with or without the full Coulomb interaction and the plasmon excitation represented by dynamical potential fluctuations in the source and drain regions by the channel electrons is demonstrated. The drain current and transconductance are greatly degraded below the channel length of 20 nm if the self-consistent potential fluctuations are taken into account and, thus, the Coulomb interaction is indeed a key ingredient for reliable predictions of device properties.
Evaluation of Strained-Silicon by Electron Backscattering Pattern Measurement: Comparison Study with UV-Raman Measurement and Edge Force Model Calculation
Authors: Tomita Motohiro , Kosemura Daisuke , Takei Munehisa , Nagata Kohki , Akamatsu Hiroaki , Ogura Atsushi
Published: January 2011

We demonstrate the results of strain (stress) evaluation obtained from electron backscattering pattern (EBSP) measurement for samples of a strained Si-on-insulator (SSOI) and a Si substrate with a patterned SiN film. Two-dimensional stress distributions were obtained in 40×40 µm2 areas of the SSOI. The biaxial stress state was also obtained in the SSOI. Furthermore, clear cross-hatch contrast was observed, especially in the distribution of shear stress S

x
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, in contrast to with the other distributions of normal stress S

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y
y
. One- and two-dimensional stress distributions in the Si substrate with the patterned SiN film were also obtained from EBSP measurement. Moreover, the results were compared with those of UV-Raman measurement and edge force model calculation, and were found to have a good correlation with each other. EBSP measurement was used to measure the complicated biaxial stress including the shear stress in a sample with a 150-nm-wide space pattern. We can conclude that EBSP measurement is a useful method for precisely measuring stress with high spatial resolution.
Characterization of Indium Segregation in Metalorganic Vapor Phase Epitaxy-Grown InGaP by Schottky Barrier Height Measurement
Authors: Ichikawa Osamu , Fukuhara Noboru , Hata Masahiko , Nakano Takayuki , Sugiyama Masakazu , Nakano Yoshiaki , Shimogaki Yukihiro
Published: January 2011

Surface/interface segregation of indium in InGaP layers grown by metalorganic vapor phase epitaxy has been studied. Al/InGaP Schottky barrier height (ΦB) measurement was used for the evaluation of the segregation. It is shown that ΦB of GaAs/InGaP/GaAs double heterostructure (DH) is larger than that of InGaP/GaAs single heterostructure (SH), suggesting the diffusion of indium into upper GaAs layer. It is shown that the indium segregation progresses at the initial stage of InGaP growth and saturates when the InGaP thickness reaches about 15 nm. Using the segregation model, we calculated the exchange coefficient of indium as 0.76 at 620 °C.
Near-Infrared Polarizer with Tungsten Silicide Wire Grids
Authors: Yamada Itsunari , Fukumi Kohei , Nishii Junji , Saito Mitsunori
Published: January 2011

We fabricated a near-infrared wire-grid polarizer consisting of a 230-nm-pitch tungsten silicide (WSi) grating on a SiO2 substrate using two-beam interference lithography and dry etching. The transverse magnetic (TM) polarization transmittance of the fabricated polarizer exceeded 80% in the 1000–1600-nm wavelength range. The extinction ratio was higher than 20 dB in the 650–1500-nm wavelength range. We also measured the extinction coefficient κ of WSi and verified that WSi is a suitable polarizing material in the near-infrared range.
Distributed Bragg Reflector Using Nanoporous TiO2 Thin Films
Authors: Park Si-Hyun , Lee Duck-Hee , Kim Chang-Sik , Jeong Hyun-Dam
Published: January 2011

Distributed Bragg reflectors (DBRs) were successfully fabricated with nanoporous TiO2 thin films using the surfactant-templated method. Nanoporous TiO2 thin films with various film refractive indices and thicknesses were spin-coated onto silicon substrates using titanium(IV) butoxide Ti(OC4H9)4 as the inorganic precursor, n-butanol as the solvent, and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) block copolymer EO20PO70EO20 as the templating agent, and were characterized using Fourier-transform infrared spectroscopy (FT-IR), capacitance–voltage (C–V) measurements, spectroscopic ellipsometry (SE), and transmission electron microscopy (TEM). We designed and fabricated DBRs using the nanoporous TiO2 thin films, whose refractive indices and thicknesses were controlled by varying the amounts of solute and solvent, respectively. The measured reflectance for the fabricated DBRs was over 96% at a center wavelength of ∼430 nm with a flat band of about 50 nm in the resonant region and typical interference patterns in the off-resonant region for a DBR with six pairs of TiO2 thin films.
Fabrication of Magnetic Tunnel Junctions with a Synthetic Ferrimagnetic Free Layer for Magnetic Field Sensor Applications
Authors: Fujiwara Kousuke , Oogane Mikihiko , Kou Futoyoshi , Watanabe Daisuke , Naganuma Hiroshi , Ando Yasuo
Published: January 2011

Magnetic tunnel junctions (MTJs) with a CoFeB/Ru/Ni80Fe20 synthetic ferrimagnetic free layer and an MgO barrier layer were fabricated. The effect of the shape and thickness of the free layer on the magnetic field sensor characteristics was systematically investigated. We achieved a high sensitivity of 4.8%/Oe in the MTJ with a 70-nm-thick Ni80Fe20 layer and an aspect ratio of 1.0. Here, sensitivity is defined as TMR/(2H
k), where TMR is tunnel magnetoresistance ratio in the MTJ and H
k is a magnetic anisotropy field of the free layer. Furthermore, we successfully increased the detection field range up to 230 Oe while keeping high sensitivity and linearity.
Design Feasibility of High-Performance Si Wire Gate-All-Around Metal–Oxide–Semiconductor Field-Effect Transistor in Sub-30-nm-Channel Regime
Authors: Omura Yasuhisa
Published: January 2011

In this paper we propose a simple model to examine the design feasibility of Si wire gate-all-around (GAA) metal–oxide–semiconductor field-effect transistor (MOSFET) having a sub-30-nm channel. Although the model has one fitting parameter, it successfully reproduces previous simulation results. The practical value of the fitting parameter is examined under physical consideration. It is strongly suggested that the fitting parameter is almost independent of device parameters; thus, the feasibility of the proposed model is verified.
An Analysis of the Field Dependence of Interface Trap Generation under Negative Bias Temperature Instability Stress using Wentzel–Kramers–Brillouin with Density Gradient Method
Authors: Choi SeongWook , Baek Chang-Ki , Park Sooyoung , Park Young June
Published: January 2011

In this paper, the Si–H bond dissociation rate is calculated under a negative bias temperature instability (NBTI) condition that considers the quantum effect on the hole density in the inversion layer of a metal–oxide–semiconductor field-effect transistor (MOSFET). The physical model used in this study is composed of two terms: the number of holes in that Si–H bond, and the polarization of the Si–H bond under an external electric field. By adopting a density-gradient (DG) method with a penetration boundary condition and the Wentzel–Kramers–Brillouin (WKB) approximation, the penetrated hole density profile in the gate oxide and the tendency towards the hole amount in the Si–H bond according to the electric field have been identified and compared with other works. The results show that the NBTI field dependence and the lifetime of the devices under NBTI stress correlate to the power-law dependency.
Gas Detection of Volatile Organic Compounds Using Trigonal Selenium Nanowires
Authors: Akiyama Norio , Ohtani Tsukio
Published: January 2011

The conductivity of random networks of trigonal selenium (t-Se) nanowires has been investigated under the presence of various kinds of evaporated organic gases. The conductivity shows a characteristic response for an individual organic gas at room temperature without heating t-Se. These results indicate that recognizable detection of organic gases is possible using simple-to-fabricate t-Se nanowire devices.
Thin Single-Walled Carbon Nanotubes with Narrow Diameter Distribution Grown by Cold-Wall Chemical Vapor Deposition Combined with Co Nanoparticle Deposition
Authors: Ishii Satoshi , Ohno Yutaka , Kishimoto Shigeru , Mizutani Takashi
Published: January 2011

We have grown thin single-walled carbon nanotubes (SWNTs) with a narrow diameter distribution using the arc-discharge plasma (ADP) technique for Co catalyst metal deposition and a cold-wall chemical vapor deposition (CVD) system for SWNT growth. The diameters of the SWNTs ranged from 0.79 to 1.07 nm. In addition to depositing small and uniform-sized metal catalyst nanoparticles by the ADP technique, decreasing the growth temperature using the cold-wall CVD system seemed to suppress the aggregation of the metal catalyst nanoparitcles leading to SWNTs with small diameters of narrow distribution.
Formation and Magnetic Properties of Ultrahigh Density Fe3Si Nanodots Epitaxially Grown on Si(111) Substrates Covered with Ultrathin SiO2 Films
Authors: Nakamura Yoshiaki , Amari Shogo , Cho Sung-Pyo , Tanaka Nobuo , Ichikawa Masakazu
Published: January 2011

The epitaxial growth technique of ultrahigh density (>1012 cm-2) Fe3Si nanodots (NDs) on Si(111) substrates was developed using an ultrathin SiO2 film technique. Low temperature (<300 °C) growth of the Fe3Si NDs was needed to suppress the interdiffusion between Fe atoms deposited on the sample surface and Si atoms in the substrate. The ND shape changed drastically from sphere to discontinuous films as the Fe content was increased slightly from a stoichiometric ratio of Fe:Si of 3:1. For almost-spherical NDs with the ultrahigh density, a transition from superparamagnetism to ferromagnetism was observed at specific temperatures, the ferromagnetism of which included the magnetic dipole interactions in ultrahigh density ND system. These ND structures with ND size dependence of the coercive force were expected to be selectively used as both magnetically fixed and free layers in magnetic tunneling junction structures only by changing the ND size.
Microscopy and Electrical Properties of Ge/Ge Interfaces Bonded by Surface-Activated Wafer Bonding Technology
Authors: Watanabe Kentaroh , Wada Kensuke , Kaneda Hidehiro , Ide Kensuke , Kato Masahiro , Wada Takehiko
Published: January 2011

We have performed microscopy and electric measurements of the Ge/Ge interfaces bonded by surface-activated wafer bonding (SAB) technology. Similarly to the case of Si wafer bonding, two Ge wafers of 50 mm in diameter, both doped by Ga with a concentration of 2.2×1014 cm-3, were bonded by SAB at room temperature. The SAB process was performed in a high-vacuum chamber (10-4 Pa) at room temperature. The bonding was achieved by attaching and pressing the two wafers, the contact surfaces of which were activated by argon ion beam irradiation. The cross-sectional scanning electron microscopy (SEM) image of the Ge/Ge bonded sample apparently shows an interface that seems to be caused by crystallographic discontinuity. The measurement by transmission electron microscope (TEM) reveals an atomic-disordered layer structure of about 3 nm in thickness at the interface of the bonded Ge/Ge. The resistivity of bonded Ge/Ge samples across the interfaces was measured at 300 and 77 K. As compared with the result of similar measurements for non bonded bulk Ge samples, we find no significant difference in resistivity between the bulk Ge and bonded Ge/Ge samples.
Novel Fabrication Method of a Round Microtip Based on Aluminum Spike Phenomenon
Authors: Kim Geunyoung , Kim Kangil , Park Tae-Gyu , Yang Sang Sik
Published: January 2011

In this paper, we present a new method of fabricating microtips based on the aluminum spike phenomenon. Silicon dissolves in aluminum at high temperatures above 400 °C, and normally this is an undesirable effect in integrated circuit (IC) processing. However, in this study, this phenomenon is exploited, with which a round tip is fabricated by a simple process involving the annealing of aluminum at 800 °C; a major advantage of the method is that the apex of the fabricated tip is round. The penetration depth of aluminum increases with annealing time, and the height of the fabricated tip can be controlled by adjusting annealing time. The height and width of the tip, annealed for 25 min using (100) silicon wafer, are 40 and 80 µm, respectively.