bluuebunny/crossref_metadata_2025 huggingface dataset:
Signatures of Adaptation to Obligate Biotrophy in the
Hyaloperonospora arabidopsidis
Genome
Authors: Baxter Laura , Tripathy Sucheta , Ishaque Naveed , Boot Nico , Cabral Adriana , Kemen Eric , Thines Marco , Ah-Fong Audrey , Anderson Ryan , Badejoko Wole , Bittner-Eddy Peter , Boore Jeffrey L. , Chibucos Marcus C. , Coates Mary , Dehal Paramvir , Delehaunty Kim , Dong Suomeng , Downton Polly , Dumas Bernard , Fabro Georgina , Fronick Catrina , Fuerstenberg Susan I. , Fulton Lucinda , Gaulin Elodie , Govers Francine , Hughes Linda , Humphray Sean , Jiang Rays H. Y. , Judelson Howard , Kamoun Sophien , Kyung Kim , Meijer Harold , Minx Patrick , Morris Paul , Nelson Joanne , Phuntumart Vipa , Qutob Dinah , Rehmany Anne , Rougon-Cardoso Alejandra , Ryden Peter , Torto-Alalibo Trudy , Studholme David , Wang Yuanchao , Win Joe , Wood Jo , Clifton Sandra W. , Rogers Jane , Van den Ackerveken Guido , Jones Jonathan D. G. , McDowell John M. , Beynon Jim , Tyler Brett M.
Published: December 2010

From Blight to Powdery Mildew

Pathogenic effects of microbes on plants have widespread consequences. Witness, for example, the cultural upheavals driven by potato blight in the 1800s. A variety of microbial pathogens continue to afflict crop plants today, driving both loss of yield and incurring the increased costs of control mechanisms. Now, four reports analyze microbial genomes in order to understand better how plant pathogens function (see the Perspective by

Dodds

).

Raffaele
et al.

(p.
1540
) describe how the genome of the potato blight pathogen accommodates transfer to different hosts.

Spanu
et al.

(p.
1543
) analyze what it takes to be an obligate biotroph in barley powdery mildew, and

Baxter
et al.

(p.
1549
) ask a similar question for a natural pathogen of
Arabidopsis
.

Schirawski
et al.

(p.
1546
) compared genomes of maize pathogens to identify virulence determinants. Better knowledge of what in a genome makes a pathogen efficient and deadly is likely to be useful for improving agricultural crop management and breeding.
Pathogenicity Determinants in Smut Fungi Revealed by Genome Comparison
Authors: Schirawski Jan , Mannhaupt Gertrud , Münch Karin , Brefort Thomas , Schipper Kerstin , Doehlemann Gunther , Di Stasio Maurizio , Rössel Nicole , Mendoza-Mendoza Artemio , Pester Doris , Müller Olaf , Winterberg Britta , Meyer Elmar , Ghareeb Hassan , Wollenberg Theresa , Münsterkötter Martin , Wong Philip , Walter Mathias , Stukenbrock Eva , Güldener Ulrich , Kahmann Regine
Published: December 2010

From Blight to Powdery Mildew

Pathogenic effects of microbes on plants have widespread consequences. Witness, for example, the cultural upheavals driven by potato blight in the 1800s. A variety of microbial pathogens continue to afflict crop plants today, driving both loss of yield and incurring the increased costs of control mechanisms. Now, four reports analyze microbial genomes in order to understand better how plant pathogens function (see the Perspective by

Dodds

).

Raffaele
et al.

(p.
1540
) describe how the genome of the potato blight pathogen accommodates transfer to different hosts.

Spanu
et al.

(p.
1543
) analyze what it takes to be an obligate biotroph in barley powdery mildew, and

Baxter
et al.

(p.
1549
) ask a similar question for a natural pathogen of
Arabidopsis
.

Schirawski
et al.

(p.
1546
) compared genomes of maize pathogens to identify virulence determinants. Better knowledge of what in a genome makes a pathogen efficient and deadly is likely to be useful for improving agricultural crop management and breeding.
Sex Determination in the Social AmoebaDictyostelium discoideum
Authors: Bloomfield Gareth , Skelton Jason , Ivens Alasdair , Tanaka Yoshimasa , Kay Robert R.
Published: December 2010

Sex Triangle

The model organismDictyostelium discoideumis a social amoeba that has three sexes, or mating types, that do not resemble those in any other eukaryote studied so far. Any two sexes can form a diploid zygote, which will recruit other haploid cells to form a macrocyst.Bloomfieldet al.(p.1533; see the Perspective byKessin) found that sex in this amoeba is determined by several genes at a locus on chromosome 5, with each mating type represented by a different version of the locus. Not all of the genes were directly essential for successful mating, and the master regulators appeared to be two small soluble intracellular proteins, which control mating types I and III, and a combination of homologs of these two proteins that control mating type II.
Science Books for Fun and Learning—Some Good 2010 Choices
Authors: Malcomson Heather , Jasny Barbara , Zahn Laura , Suter Sherman
Published: December 2010

Short notes on the finalists for this year's
Science Books and Films
Excellence in Science Books prizes.
Earth's Second Wind
Authors: Kump Lee R.
Published: December 2010

Studies of molybdenum isotopes in sediments support the idea that increases in atmospheric oxygen in the Devonian period drove increases in animal size.
Cultivating Young Academies
Authors: ter Meulen Volker , Stock Günter
Published: December 2010

This October, Germany celebrated the 20th anniversary of its reunification. Over the past two decades, the country has worked hard to reestablish its leadership in the sciences, investing heavily in R&D. Today, it allocates 2.7% of its gross domestic product toward this end. This commitment has led to the growth of Germany's research institutions, graduate programs, and international collaborations. The government's Exzellenzinitiative, which commits 2.7 billion Euros over 5 years for German universities that are the most active in research, is just one example. Nevertheless, the nation's growing need for well-trained and highly educated people raises the question of whether Germany is doing enough to support its future scientific leaders. The economic downturn threatens to decrease research career opportunities at a time when building scientific capacity to tackle global challenges has become a high priority.
Australia to Test 'Mosquito Vaccine' Against Human Disease
Authors: Enserink Martin
Published: December 2010

In January, entomologists will start deploying a strange bacterium called
Wolbachia pipientis
in an attempt to halt disease transmission by mosquitoes.
Shanghai Students Lead Global Results on PISA
Authors: Mervis Jeffrey
Published: December 2010

A group of teenagers from Shanghai, China, have posted the top scores on the latest version of an international test of practical knowledge in reading, mathematics, and science.
A Government Niche for Translational Medicine and Drug Development
Authors: Kaiser Jocelyn
Published: December 2010

National Institutes of Health Director Francis Collins has touched a nerve in the biomedical community with a plan to create a new center focused on translational science—his biggest initiative yet.
The Beginning of the End for Africa's Devastating Meningitis Outbreaks?
Authors: Roberts Leslie
Published: December 2010

Last Monday in Burkina Faso, a massive campaign kicked off to immunize 20 million people in three African countries against deadly meningococcal meningitis by the end of December.
A Change of Biblical Proportions Strikes Mideast Archaeology
Authors: Lawler Andrew
Published: December 2010

At the meeting, a series of biblical archaeologists came to the podium for 2 hours of data-rich presentations—and put their colleagues on notice that their field is in the midst of a scientific revolution.
Tracking the Med's Stone Age Sailors
Authors: Lawler Andrew
Published: December 2010

By carefully sorting genetic data from living people, a researcher reported at the meeting that around 6000 B.C.E., Neolithic seafarers spread their seed—both agricultural and genetic—from their homeland in the Near East as far west across the Mediterranean as Marseilles, but no farther.
Hsp110-Mediated Enhancement of CD4
+
T Cell Responses to the Envelope Glycoprotein of Members of the Family
Flaviviridae In Vitro
Does Not Occur
In Vivo
Authors: McLaughlin Kerry , Carr Veronica B. , Iqbal Munir , Seago Julian , Lefevre Eric A. , Robinson Lucy , Prentice Helen , Charleston Bryan
Published: December 2010

The use of heat shock proteins (HSP) to enhance activation of the immune response to chaperoned antigen is being explored for immunotherapy. Hsp110 chaperones large protein substrates more effectively than Hsp70, offering the potential to use complex antigens containing multiple epitopes in HSP-based vaccines. In this study, we investigated the ability of recombinant bovine Hsp110 to chaperone E2 glycoprotein, the major envelope protein of bovine viral diarrhea virus (BVDV) and the dominant target of neutralizing antibodies. Hsp110 formed complexes with E2, as demonstrated by immunoprecipitation. When monocytes from BVDV-immunized cattle were stimulated with these complexes and incubated with autologous CD4
+
T cells, enhanced levels of proliferation were observed. To determine the ability of these complexes to improve immunogenicity
in vivo
, cattle were vaccinated with either Hsp110-E2 complex or E2 only, combined with Quil-A adjuvant. In contrast to the
in vitro
data, cellular and humoral responses to E2 were greater in the E2-only vaccination group, indicating that complex formation had actually reduced the immunogenicity of E2. This study highlights the need for further understanding of the means by which HSP complexes are endocytosed and processed
in vivo
to enable the design of successful vaccine strategies.
Characterization of Equine Humoral Antibody Response to the Nonstructural Proteins of Equine Arteritis Virus
Authors: Go Yun Young , Snijder Eric J. , Timoney Peter J. , Balasuriya Udeni B. R.
Published: December 2010

Equine arteritis virus (EAV) replicase consists of two polyproteins (pp1a and pp1ab) that are encoded by open reading frames (ORFs) 1a and 1b of the viral genome. These two replicase polyproteins are posttranslationally processed by three ORF 1a-encoded proteinases to yield at least 13 nonstructural proteins (nsp1 to nsp12, including nsp7α and 7β). These nsps are expressed in EAV-infected cells, but the equine immune response they induce has not been studied. Therefore, the primary purpose of this study was to evaluate the humoral immune response of horses to each of the nsps following EAV infection. Individual nsp coding regions were cloned and expressed in both mammalian and bacterial expression systems. Each recombinant protein was used in an immunoprecipitation assay with equine serum samples from horses (n= 3) that were experimentally infected with three different EAV strains (VB, KY77, and KY84), from stallions (n= 4) that were persistently infected with EAV, and from horses (n= 4) that were vaccinated with the modified live-virus (MLV) vaccine strain. Subsequently, protein-antibody complexes were subjected to Western immunoblotting analysis with individual nsp-specific rabbit antisera, mouse anti-His antibody, or anti-FLAG tag antibody. Nsp2, nsp4, nsp5, and nsp12 were immunoprecipitated by most of the sera from experimentally or persistently infected horses, while sera from vaccinated horses did not react with nsp5 and reacted weakly with nsp4. However, serum samples from vaccinated horses were able to immunoprecipitate nsp2 and nsp12 proteins consistently. Information from this study will assist ongoing efforts to develop improved methods for the serologic diagnosis of EAV infection in horses.
SpA, ClfA, and FnbA Genetic Variations Lead to Staphaurex Test-Negative Phenotypes in Bovine Mastitis Staphylococcus aureus Isolates
Authors: Stutz Katrin , Stephan Roger , Tasara Taurai
Published: December 2010

Staphylococcus aureus
encodes many proteins that act as virulence factors, leading to a variety of diseases, including mastitis in cows. Among these virulence factors, SpA, ClfA, ClfB, FnbA, and FnbB are important for the ability of
S. aureus
to adhere to and invade host cells as well as to evade host immune responses. The interaction between these
S. aureus
surface proteins and human immunoglobulin G and fibrinogen that are coupled to latex particles is utilized to induce latex agglutination reactions, which are used widely in diagnostic kits for confirmation of presumptive
S. aureus
isolates. In this study, the Staphaurex latex agglutination test was performed on a collection of confirmed bovine mastitis
S. aureus
isolates. Notably, 54% (43/79 isolates) of these isolates exhibited latex agglutination-negative phenotypes (Staphaurex-negative result). To gain insights into the reasons for the high frequency of Staphaurex-negative bovine mastitis
S. aureus
isolates, the
spa
,
clfA
,
clfB
,
fnbA
, and
fnbB
genes were examined. Specific genetic changes in
spa
,
clfA
, and
fnbA
, as well as a loss of
fnbB
, which may impair SpA, ClfA, FnbA, and FnbB functions in latex agglutination reactions, were detected in Staphaurex-negative
S. aureus
isolates. The genetic changes included a premature stop codon in the
spa
gene, leading to a truncated SpA protein that is unable to participate in
S. aureus
cell-mediated agglutination of latex particles. In addition,
clfA
and
fnbA
genetic polymorphisms were detected that were linked to ClfA and FnbA amino acid changes that may significantly reduce fibrinogen-binding activity. The genetic variations in these
S. aureus
isolates might also have implications for their bovine mastitis virulence capacity.
recA
-Based PCR Assay for Accurate Differentiation of Streptococcus pneumoniae from Other Viridans Streptococci
Authors: Zbinden A. , Köhler N. , Bloemberg G. V.
Published: December 2010

Proper identification of
Streptococcus pneumoniae
by conventional methods remains problematic. The discriminatory power of the 16S rRNA gene, which can be considered the “gold standard” for molecular identification, is too low to differentiate
S. pneumoniae
from closely related species such as
Streptococcus pseudopneumoniae
,
Streptococcus mitis
, and
Streptococcus oralis
in the routine clinical laboratory. A 313-bp part of
recA
was selected on the basis of variability within the
S. mitis
group, showing <95.8% interspecies homology. In addition, 6 signature nucleotides specific for
S. pneumoniae
were identified within the 313-bp
recA
fragment. We show that
recA
analysis is a useful tool for proper identification to species level within the
S. mitis
group, in particular, for pneumococci.
Identification of Variable-Number Tandem-Repeat (VNTR) Sequences in Acinetobacter baumannii and Interlaboratory Validation of an Optimized Multiple-Locus VNTR Analysis Typing Scheme
Authors: Pourcel Christine , Minandri Fabrizia , Hauck Yolande , D'Arezzo Silvia , Imperi Francesco , Vergnaud Gilles , Visca Paolo
Published: December 2010

Acinetobacter baumannii
is an important opportunistic pathogen responsible for nosocomial outbreaks, mostly occurring in intensive care units. Due to the multiplicity of infection sources, reliable molecular fingerprinting techniques are needed to establish epidemiological correlations among
A. baumannii
isolates. Multiple-locus variable-number tandem-repeat analysis (MLVA) has proven to be a fast, reliable, and cost-effective typing method for several bacterial species. In this study, an MLVA assay compatible with simple PCR- and agarose gel-based electrophoresis steps as well as with high-throughput automated methods was developed for
A. baumannii
typing. Preliminarily, 10 potential polymorphic variable-number tandem repeats (VNTRs) were identified upon bioinformatic screening of six annotated genome sequences of
A. baumannii
. A collection of 7 reference strains plus 18 well-characterized isolates, including unique types and representatives of the three international
A. baumannii
lineages, was then evaluated in a two-center study aimed at validating the MLVA assay and comparing it with other genotyping assays, namely, macrorestriction analysis with pulsed-field gel electrophoresis (PFGE) and PCR-based sequence group (SG) profiling. The results showed that MLVA can discriminate between isolates with identical PFGE types and SG profiles. A panel of eight VNTR markers was selected, all showing the ability to be amplified and good amounts of polymorphism in the majority of strains. Independently generated MLVA profiles, composed of an ordered string of allele numbers corresponding to the number of repeats at each VNTR locus, were concordant between centers. Typeability, reproducibility, stability, discriminatory power, and epidemiological concordance were excellent. A database containing information and MLVA profiles for several
A. baumannii
strains is available from
http://mlva.u-psud.fr/
.
Comprehensive Characterization of Interaction Complexes of Herpes Simplex Virus Type 1 ICP22, UL3, UL4, and UL20.5
Authors: Xing Junji , Wang Shuai , Lin Fusen , Pan Weiwei , Hu Chang-Deng , Zheng Chunfu
Published: December 2010

It has been reported that herpes simplex virus type 1 UL3, UL4, and UL20.5 proteins are localized to small, dense nuclear bodies together with ICP22 in infected cells. In the present study, we comprehensively characterized these interactions by subcellular colocalization, coimmunoprecipitation, and bimolecular fluorescence complementation assays. For the first time, it was demonstrated that both UL3 and UL20.5 are targeted to small, dense nuclear bodies by a direct interaction with ICP22, whereas UL4 colocalizes with ICP22 through its interaction with UL3 but not UL20.5 or ICP22. There was no detectable interaction between UL3 and UL20.5.
Comparative Analysis of Monkeypox Virus Infection of Cynomolgus Macaques by the Intravenous or Intrabronchial Inoculation Route
Authors: Johnson Reed F. , Dyall Julie , Ragland Dan R. , Huzella Louis , Byrum Russell , Jett Catherine , St. Claire Marisa , Smith Alvin L. , Paragas Jason , Blaney Joseph E. , Jahrling Peter B.
Published: December 2010

Monkeypox virus (MPXV) infection has recently expanded in geographic distribution and can be fatal in up to 10% of cases. The intravenous (i.v.) inoculation of nonhuman primates (NHPs) results in an accelerated fulminant disease course compared to that of naturally occurring MPXV infection in humans. Alternative routes of inoculation are being investigated to define an NHP model of infection that more closely resembles natural disease progression. Our goal was to determine if the intrabronchial (i.b.) exposure of NHPs to MPXV results in a systemic disease that better resembles the progression of human MPXV infection. Here, we compared the disease course following an i.v. or i.b. inoculation of NHPs with 10-fold serial doses of MPXV Zaire. Classical pox-like disease was observed in NHPs administered a high virus dose by either route. Several key events were delayed in the highest doses tested of the i.b. model compared to the timing of the i.v. model, including the onset of fever, lesion appearance, peak viremia, viral shedding in nasal and oral swabs, peak cytokine levels, and time to reach endpoint criteria. Virus distribution across 19 tissues was largely unaffected by the inoculation route at the highest doses tested. The NHPs inoculated by the i.b. route developed a viral pneumonia that likely exacerbated disease progression. Based on the observations of the delayed onset of clinical and virological parameters and endpoint criteria that may more closely resemble those of human MPXV infection, the i.b. MPXV model should be considered for the further investigation of viral pathogenesis and countermeasures.
Capturing the Natural Diversity of the Human Antibody Response against Vaccinia Virus
Authors: Lantto Johan , Haahr Hansen Margit , Rasmussen Søren Kofoed , Steinaa Lucilla , Poulsen Tine R. , Duggan Jackie , Dennis Mike , Naylor Irene , Easterbrook Linda , Bregenholt Søren , Haurum John , Jensen Allan
Published: December 2010

The eradication of smallpox (variola) and the subsequent cessation of routine vaccination have left modern society vulnerable to bioterrorism employing this devastating contagious disease. The existing, licensed vaccines based on live vaccinia virus (VACV) are contraindicated for a substantial number of people, and prophylactic vaccination of large populations is not reasonable when there is little risk of exposure. Consequently, there is an emerging need to develop efficient and safe therapeutics to be used shortly before or after exposure, either alone or in combination with vaccination. We have characterized the human antibody response to smallpox vaccine (VACV Lister) in immunized volunteers and isolated a large number of VACV-specific antibodies that recognize a variety of different VACV antigens. Using this broad antibody panel, we have generated a fully human, recombinant analogue to plasma-derived vaccinia immunoglobulin (VIG), which mirrors the diversity and specificity of the human antibody immune response and offers the advantage of unlimited supply and reproducible specificity and activity. The recombinant VIG was found to display a high specific binding activity toward VACV antigens, potent
in vitro
VACV neutralizing activity, and a highly protective efficacy against VACV challenge in the mouse tail lesion model when given either prophylactically or therapeutically. Altogether, the results suggest that this compound has the potential to be used as an effective postexposure prophylaxis or treatment of disease caused by orthopoxviruses.
Hepatitis C Virus NS2 Coordinates Virus Particle Assembly through Physical Interactions with the E1-E2 Glycoprotein and NS3-NS4A Enzyme Complexes
Authors: Stapleford Kenneth A. , Lindenbach Brett D.
Published: December 2010

The hepatitis C virus (HCV) NS2 protein is essential for particle assembly, but its function in this process is unknown. We previously identified critical genetic interactions between NS2 and the viral E1-E2 glycoprotein and NS3-NS4A enzyme complexes. Based on these data, we hypothesized that interactions between these viral proteins are essential for HCV particle assembly. To identify interaction partners of NS2, we developed methods to site-specifically biotinylate NS2
in vivo
and affinity capture NS2-containing protein complexes from virus-producing cells with streptavidin magnetic beads. By using these methods, we confirmed that NS2 physically interacts with E1, E2, and NS3 but did not stably interact with viral core or NS5A proteins. We further characterized these protein complexes by blue native polyacrylamide gel electrophoresis and identified ≈520-kDa and ≈680-kDa complexes containing E2, NS2, and NS3. The formation of NS2 protein complexes was dependent on coexpression of the viral p7 protein and enhanced by cotranslation of viral proteins as a polyprotein. Further characterization indicated that the glycoprotein complex interacts with NS2 via E2, and the pattern of N-linked glycosylation on E1 and E2 suggested that these interactions occur in the early secretory pathway. Importantly, several mutations that inhibited virus assembly were shown to inhibit NS2 protein complex formation, and NS2 was essential for mediating the interaction between E2 and NS3. These studies demonstrate that NS2 plays a central organizing role in HCV particle assembly by bringing together viral structural and nonstructural proteins.
Angiographically documented hemorrhagic conversion of a left middle cerebral artery embolic stroke during intra-arterial thrombolysis
Authors: Prince Ethan A , Jayaraman Mahesh V , Schirmang Todd , Haas Richard
Published: December 2010

Background and purpose

The clinical benefits of intra-arterial thrombolysis for ischemic stroke must be weighed against the risks, including hemorrhagic conversion.

Summary of case

A case of angiographically documented hemorrhagic conversion of an ischemic stroke during intra-arterial thrombolysis is presented. Discussion focuses on recognition and management of risk factors for hemorrhagic conversion during performance of stroke thrombolysis.

Conclusions

Recognition and modification of risk factors for hemorrhagic conversion may not prevent this complication during stroke thrombolysis. Identification of the angiographic appearance of hemorrhagic conversion should alert the interventionalist to the likelihood of a poor clinical outcome regardless of vessel patency status.
HYPERCHAOS GENERATED FROM THE UNIFIED CHAOTIC SYSTEM AND ITS CONTROL
Authors: WANG XING-YUAN , ZHAO GUO-BIN
Published: December 2010

In this paper, a new hyperchaotic system is formulated by introducing an additional state into the third-order unified system. Some of its basic dynamical properties, such as Lyapunov exponent, bifurcation diagram and the Poincáre section are investigated. It was found that the system is hyperchaotic in several different regions of the parameters. The analysis of equilibrium points and stability are also given. Two different methods, i.e., nonlinear hyperbolic function feedback control and tracking control methods, are used to control hyperchaos in the new hyperchaotic system. Based on the Routh–Hurwitz criteria, the conditions suppressing hyperchaos to unstable equilibrium point are discussed. A tracking control method is proposed. It is also proved that the strategy can make the system approach any desired smooth orbit at an exponential rate. Numerical results have shown the effectiveness of the control methods.
EFFECT OF POST-DEPOSITION ANNEALING IN FORMING GAS ON STRUCTURAL AND ELECTRICAL PROPERTIES OF SOL–GEL DERIVED SiO2 THICK FILM ON 4H–SiC
Authors: CHEONG KUAN YEW , KURNIN AZLAN AHMAD
Published: December 2010

The effect of post-deposition annealing in forming gas on the structural and electrical properties of sol–gel derived SiO 2 thick film on n-type 4H–SiC has been systematically investigated. Tetraethylorthosilicate-based precursor with H 2 SO 4 as catalyst was prepared and prior to film deposition, substrate surface was treated by hexamethyldisilizane. The spin-coated film was annealed at 750–950°C for 30 min with an approximately 185-nm thick film. It was found that oxide annealed at the highest temperature revealed the densest film, lowest oxide defects, and lowest total interface trap density. As a result, this oxide had demonstrated the lowest leakage current density if compared with other oxides.
DIELECTRIC PROPERTIES OF CHEMICALLY SYNTHESIZED PbTiO3 NANOCRYSTALS SUITABLE FOR HIGH FREQUENCY DEVICES
Authors: VERMA K. C. , SINGH M. , THAKUR N. , NEGI N. S.
Published: December 2010

PbTiO 3 (PT) nanoparticles have been prepared by chemical route using polyvinyl alcohol (PVA) as an efficient surfactant. The effect of PVA to reduce the particle's sizes of PT has been observed. X-ray diffraction (XRD) pattern shows that the PT nanoparticles are tetragonal with distortion ratio, c/a ~1.061. The average particle's size calculated from XRD and transmission/scanning electron microscopy is ~24 nm for PT powder sintered at 700°C. The nanostructured grains were also observed in PT pellet sintered at 1000°C. The dielectric properties of PT pellet have been measured from room temperature to 200°C and in the frequency range of 0.075 to 10 MHz. The values of room temperature dielectric constant and tanδ are 117 and 0.05 respectively, measured at 0.5 MHz. It is found that the dielectric constant of PT nanoparticles can be controlled up to higher frequency region of 5 MHz.
FORTHCOMING GALLIUM NITRIDE BASED POWER DEVICES IN PROMPTING THE DEVELOPMENT OF HIGH POWER APPLICATIONS
Authors: QUAH H. J. , CHEONG K. Y. , HASSAN Z.
Published: December 2010

Recent advances in silicon technology have pushed the silicon properties to its theoretical limits. Therefore, wide band gap semiconductors, such as silicon carbide ( SiC ) and gallium nitride ( GaN ) have been considered as a replacement for silicon. The discovery of these wide band gap semiconductors have given the new generation power devices a magnificent prospect of surviving under high temperature and hostile environments. The primary focuses of this review are the properties of GaN , the alternative substrates that can be used to deposit GaN and the substitution of SiO 2 gate dielectric with high dielectric constant (k) film. The future perspectives of AlGaN / GaN heterostructures are also discussed, providing that these structures are able to further enhance the performance of high power devices.
ENHANCING MULTISCALE FRACTAL DESCRIPTORS USING FUNCTIONAL DATA ANALYSIS
Authors: FLORINDO JOÃO BATISTA , DE CASTRO MÁRIO , BRUNO ODEMIR MARTINEZ
Published: December 2010

This work presents a novel approach in order to increase the recognition power of Multiscale Fractal Dimension (MFD) techniques, when applied to image classification. The proposal uses Functional Data Analysis (FDA) with the aim of enhancing the MFD technique precision achieving a more representative descriptors vector, capable of recognizing and characterizing more precisely objects in an image. FDA is applied to signatures extracted by using the Bouligand–Minkowsky MFD technique in the generation of a descriptors vector from them. For the evaluation of the obtained improvement, an experiment using two datasets of objects was carried out. A dataset was used of characters shapes (26 characters of the Latin alphabet) carrying different levels of controlled noise and a dataset of fish images contours. A comparison with the use of the well-known methods of Fourier and wavelets descriptors was performed with the aim of verifying the performance of FDA method. The descriptor vectors were submitted to Linear Discriminant Analysis (LDA) classification method and we compared the correctness rate in the classification process among the descriptors methods. The results demonstrate that FDA overcomes the literature methods (Fourier and wavelets) in the processing of information extracted from the MFD signature. In this way, the proposed method can be considered as an interesting choice for pattern recognition and image classification using fractal analysis.
BORDER COLLISION BIFURCATIONS IN 1D PWL MAP WITH ONE DISCONTINUITY AND NEGATIVE JUMP: USE OF THE FIRST RETURN MAP
Authors: GARDINI LAURA , TRAMONTANA FABIO
Published: December 2010

The aim of this work is to study discontinuous one-dimensional maps in the case of slopes and offsets having opposite signs. Such models represent the dynamics of applied systems in several disciplines. We analyze in particular attracting cycles, their border collision bifurcations and the properties of the periodicity regions in the parameter space. The peculiarity of this family is that we can make use of the technical instrument of the first return map. With this, we can rigorously prove properties which were known numerically, as well as prove new ones, giving a complete characterization of the overlapping periodicity regions.
LIMIT SET DICHOTOMY AND CONVERGENCE OF SEMIFLOWS DEFINED BY COOPERATIVE STANDARD CNNs
Authors: DI MARCO MAURO , FORTI MAURO , GRAZZINI MASSIMO , PANCIONI LUCA
Published: December 2010

The paper analyzes some fundamental properties of the solution semiflow of nonsymmetric cooperative standard (S) cellular neural networks (CNNs) with a typical three-segment piecewise-linear (pwl) neuron activation. Two relevant subclasses of SCNNs, corresponding to one-dimensional circular SCNNs with two-sided or single-sided positive interconnections between nearest neighboring neurons only, are considered. For these subclasses it is shown that the associated solution semiflow satisfies the fundamental properties of the CONVERGENCE CRITERION, the NONORDERING OF LIMIT SETS and the LIMIT SET DICHOTOMY, and that this is true although the semiflow is not eventually strongly monotone. As a consequence such CNNs are almost convergent, i.e., almost all solutions converge toward an equilibrium point as time tends to infinity. To the authors' knowledge the paper is the first rigorous investigation on the geometry of limit sets and convergence properties of cooperative SCNNs with a pwl neuron activation. All available convergence results in the literature indeed concern a modified cooperative CNN model where the original pwl activation of the SCNN model is replaced by a continuously differentiable strictly increasing sigmoid function. The main results in the paper are established by conducting a deep analysis of the properties of the omega-limit sets of the solution semiflow defined by the considered subclasses of SCNNs. In doing so the paper exploits and extends some mathematical tools for monotone systems in order that they can be applied to pwl vector fields that govern the dynamics of SCNNs. By using some transformations and referring to specific examples it is also shown that the treatment in the paper can be extended to other subclasses of SCNNs.
EQUATION-FREE MULTISCALE COMPUTATIONS IN SOCIAL NETWORKS: FROM AGENT-BASED MODELING TO COARSE-GRAINED STABILITY AND BIFURCATION ANALYSIS
Authors: TSOUMANIS A. C. , SIETTOS C. I. , BAFAS G. V. , KEVREKIDIS I. G.
Published: December 2010

We focus on the "trijunction" between multiscale computations, bifurcation theory and social networks. In particular, we address how the Equation-Free approach, a recently developed computational framework, can be exploited to systematically extract coarse-grained, emergent dynamical information by bridging detailed, agent-based models of social interactions on networks, with macroscopic, systems-level, continuum numerical analysis tools. For our illustrations, we use a simple dynamic agent-based model describing the propagation of information between individuals interacting under mimesis in a social network with private and public information. We describe the rules governing the evolution of the agents' emotional state dynamics and discover, through simulation, multiple stable stationary states as a function of the network topology. Using the Equation-Free approach we track the dependence of these stationary solutions on network parameters and quantify their stability in the form of coarse-grained bifurcation diagrams.
BIFURCATION IN WIND ENERGY GENERATION SYSTEMS
Authors: LI ZHEN , WONG SIU-CHUNG , TSE CHI K. , CHU GRACE
Published: December 2010

This letter reveals the possibility of Hopf bifurcation in a grid-connected wind energy generation system which handles an unbalanced loading. The wind energy generation system consists of a typical doubly fed induction generator (DFIG) which allows variable speed operation by using partially rated back-to-back quadruple active and reactive power PWM converters. Many control schemes reported in the literature are designed to solve some specific control problems associated with DFIG and have rarely been tested for general stability. Specifically, bifurcation analysis of the system has not been reported so far. We study the system stability in terms of the magnitude of some unwanted oscillation of the voltage link capacitor under a practical scenario where the system interacts indirectly with unbalanced single-phase constant power loads through the power grid. In this letter, the rotor speed of the DFIG is used as a variation parameter for bifurcation analysis. Bifurcation diagram of the voltage link capacitor indicates a Hopf-like bifurcation of the system in super-synchronous operation. This clearly explains the instability phenomenon of the practical DFIG system when unbalanced single-phase constant power loads are connected to the connecting grid.
A PARRONDO'S PARADOX GAME DEPENDING ON CAPITAL PARITY
Authors: WANG CHAO , XIE NENG-GANG , WANG LU , YE YE , XU GANG
Published: December 2010

Parrondo's Paradox has pointed out that combined losing strategies can win. In Parrondo's Paradox games, the design of game B is critical. Currently there are mainly three versions, which depend on capital, history and space. We devise a new version of game B which depends on the capital parity and draw on the structure of the benefit matrix in the Prisoner's Dilemma game model. Theoretical analysis and computer simulation results both demonstrate the establishment of this paradox version.
PPAR-γ agonist ameliorates kidney and liver disease in an orthologous rat model of human autosomal recessive polycystic kidney disease
Authors: Yoshihara Daisuke , Kurahashi Hiroki , Morita Miwa , Kugita Masanori , Hiki Yoshiyuki , Aukema Harold M. , Yamaguchi Tamio , Calvet James P. , Wallace Darren P. , Nagao Shizuko
Published: December 2010

In autosomal recessive polycystic kidney disease (ARPKD), progressive enlargement of fluid-filled cysts is due to aberrant proliferation of tubule epithelial cells and transepithelial fluid secretion leading to extensive nephron loss and interstitial fibrosis. Congenital hepatic fibrosis associated with biliary cysts/dilatations is the most common extrarenal manifestation in ARPKD and can lead to massive liver enlargement. Peroxisome proliferator-activated receptor γ (PPAR-γ), a member of the ligand-dependent nuclear receptor superfamily, is expressed in a variety of tissues, including the kidneys and liver, and plays important roles in cell proliferation, fibrosis, and inflammation. In the current study, we determined that pioglitazone (PIO), a PPAR-γ agonist, decreases polycystic kidney and liver disease progression in the polycystic kidney rat, an orthologous model of human ARPKD. Daily treatment with 10 mg/kg PIO for 16 wk decreased kidney weight (% of body weight), renal cystic area, serum urea nitrogen, and the number of Ki67-, pERK1/2-, and pS6-positive cells in the kidney. There was also a decrease in liver weight (% of body weight), liver cystic area, fibrotic index, and the number of Ki67-, pERK1/2-, pERK5-, and TGF-β-positive cells in the liver. Taken together, these data suggest that PIO inhibits the progression of polycystic kidney and liver disease in a model of human ARPKD by inhibiting cell proliferation and fibrosis. These findings suggest that PPAR-γ agonists may have therapeutic value in the treatment of the renal and hepatic manifestations of ARPKD.
Maintained tubuloglomerular feedback responses during acute inhibition of P2 purinergic receptors in mice
Authors: Schnermann Jurgen
Published: December 2010

Tubuloglomerular feedback (TGF), the change of afferent arteriolar resistance initiated by changes of luminal NaCl concentration, is thought to be related to NaCl-dependent release of ATP by macula densa cells. In the present study, we have explored the possibility that the released ATP may directly interact with vasoconstrictor P2 purinergic receptors in the vicinity of the glomerular vascular pole. In two different strains of wild-type mice (SWR/J and FVB), TGF responses were determined in vivo by measuring the stop flow pressure (PSF) change caused by a saturating increase in loop of Henle flow rate before and during the administration of the P2 receptor inhibitors PPADS (12 mg/kg + 35 mg·kg−1·h−1 iv) or suramin (50 mg/kg + 150 mg·kg−1·h−1). Both agents significantly reduced the blood pressure response to the P2X agonist α,β-methylene ATP. In SWR/J and FVB mice, elevating flow to 30 nl/min reduced PSF by 16.4 ± 2.2 and 17.1 ± 1.8%. During infusion of PPADS, PSF fell by 18.8 ± 2 ( P = 0.4) and 16.5 ± 1.5% ( P = 0.82) in the two strains of mice. During suramin infusion, PSF decreased by 14.7 ± 2.4 ( P = 0.62) and 15 ± 1.3% ( P = 0.4) in SWR/J and FVB mice, respectively. Including PPADS (10−4 M) in the loop perfusate did not significantly alter the PSF response (18.9 ± 1.8%; P = 0.54). Arterial blood pressure was not systematically affected by the P2 inhibitors. As measured by free-flow micropuncture, PPADS significantly reduced proximal tubular fluid reabsorption in both fractional and absolute terms. These results indicate that the direct activation of P2 purinergic receptors by ATP is not a major cause of TGF-induced vasoconstriction in vivo.
Lung and vascular function during chronic severe pulmonary ischemia
Authors: Wagner Elizabeth M. , Jenkins John , Perino Maria Grazia , Sukkar Adlah , Mitzner Wayne
Published: December 2010

Bronchial vascular angiogenesis takes place in a variety of lung inflammatory conditions such as asthma, cystic fibrosis, lung cancer, and chronic pulmonary thromboembolic disease. However, it is unclear whether neovascularization is predominantly appropriate and preserves lung tissue or whether it contributes further to lung pathology through edema formation and inflammation. In the present study we examined airway and lung parenchymal function 14 days after left pulmonary artery ligation. In rats as well as higher mammals, severe pulmonary ischemia results in bronchial vascular proliferation. Using labeled microspheres, we demonstrated an 18-fold increase in systemic blood flow to the ischemic left lung. Additionally, vascular remodeling extended to the tracheal venules, which showed an average 28% increase in venular diameter. Despite this increase in vascularity, airways resistance was not altered nor was methacholine responsiveness. Since these measurements include the entire lung, we suggest that the normal right lung, which represented 78% of the total lung, obscured the ability to detect a change. When functional indexes such as diffusing capacity, in situ lung volume, and vascular permeability of the left lung could be separated from right lung, significant changes were observed. Thus when comparing average left lung values of rats 14 days after left pulmonary artery ligation to left lungs of rats undergoing sham surgery, diffusing capacity of the left lung decreased by 72%, left lung volume decreased by 38%, and the vascular permeability to protein increased by 58%. No significant differences in inflammatory cell recruitment were observed, suggesting that acute ischemic inflammation had resolved. We conclude that despite the preservation of lung tissue, the proliferating bronchial neovasculature may contribute to a sustained decrement in pulmonary function.
Subliminal Gamma Flicker Draws Attention Even in the Absence of Transition-Flash Cues
Authors: Cheadle Samuel W. , Parton Andrew , Müller Hermann J. , Usher Marius
Published: December 2010

We recently reported evidence indicating that selective attention is deployed to a target location in a multi-object display, when the target event (a change of one of the objects) is preceded by subliminal flicker in the gamma range. However, concerns have been raised regarding the stimuli used in this study and the possible contribution of an artifactual cue: a “transition flash” between pretarget flicker offset and target onset. Here, we report a series of experiments investigating the existence and potential contribution to selective attention of this transition-flash cue under different presentation conditions. We find that, although the transition flash is a real phenomenon (detection rates ≃ 15% > chance), it cannot, on its own, explain the original effects of gamma flicker on the response time to target detection. Even after eliminating this flash, detection was significantly faster, or more accurate, for targets preceded (vs. not preceded) by flicker. This congruency effect (≈15 ms) demonstrates that gamma flicker on its own is sufficient to engage selective attention. This interpretation is further strengthened by a reevaluation of 1) experiment 7 reported by van Diepen and colleagues and 2) the validity effect experiment reported by Bauer and colleagues. Possible reasons for the discrepant results are also discussed.
Coding of Amplitude Modulation in Primary Auditory Cortex
Authors: Yin Pingbo , Johnson Jeffrey S. , O'Connor Kevin N. , Sutter Mitchell L.
Published: December 2010

Conflicting results have led to different views about how temporal modulation is encoded in primary auditory cortex (A1). Some studies find a substantial population of neurons that change firing rate without synchronizing to temporal modulation, whereas other studies fail to see these nonsynchronized neurons. As a result, the role and scope of synchronized temporal and nonsynchronized rate codes in AM processing in A1 remains unresolved. We recorded A1 neurons' responses in awake macaques to sinusoidal AM noise. We find most (37–78%) neurons synchronize to at least one modulation frequency (MF) without exhibiting nonsynchronized responses. However, we find both exclusively nonsynchronized neurons (7–29%) and “mixed-mode” neurons (13–40%) that synchronize to at least one MF and fire nonsynchronously to at least one other. We introduce new measures for modulation encoding and temporal synchrony that can improve the analysis of how neurons encode temporal modulation. These include comparing AM responses to the responses to unmodulated sounds, and a vector strength measure that is suitable for single-trial analysis. Our data support a transformation from a temporally based population code of AM to a rate-based code as information ascends the auditory pathway. The number of mixed-mode neurons found in A1 indicates this transformation is not yet complete, and A1 neurons may carry multiplexed temporal and rate codes.
Transcranial Magnetic Stimulation in Different Current Directions Activates Separate Cortical Circuits
Authors: Ni Zhen , Charab Samer , Gunraj Carolyn , Nelson Aimee J. , Udupa Kaviraja , Yeh I-Jin , Chen Robert
Published: December 2010

Transcranial magnetic stimulation (TMS) to the primary motor cortex (M1) produces a series of corticospinal descending waves, with a direct (D) wave followed by several indirect (I) waves. TMS inducing posterior–anterior (PA) current in the brain predominantly recruits the early I1-wave, whereas anterior–posterior (AP) directed current preferentially recruits the late I3-wave. However, it is not known whether I-waves elicited by different current directions are mediated by the same neuronal populations. We studied the neuronal mechanisms mediating I-waves by examining the influence of short-latency afferent inhibition (SAI) on various I-waves. SAI was tested with electrical median nerve stimulation at the wrist followed by TMS to the contralateral M1 at different current directions. Surface electromyograms and single motor units were recorded from the first dorsal interosseous muscle. SAI was weaker for the AP compared with that for the PA current direction. With increasing median nerve stimulation intensities, SAI increased for the PA direction but showed a U-shaped relationship for the AP direction. SAI produced more inhibition of late I-waves generated by PA than those generated by AP current direction. We conclude that late I-waves generated by PA and AP current directions are mediated by different neuronal mechanisms.
Integration of Visual and Tactile Signals From the Hand in the Human Brain: An fMRI Study
Authors: Gentile Giovanni , Petkova Valeria I. , Ehrsson H. Henrik
Published: December 2010

In the non-human primate brain, a number of multisensory areas have been described where individual neurons respond to visual, tactile and bimodal visuotactile stimulation of the upper limb. It has been shown that such bimodal neurons can integrate sensory inputs in a linear or nonlinear fashion. In humans, activity in a similar set of brain regions has been associated with visuotactile stimulation of the hand. However, little is known about how these areas integrate visual and tactile information. In this functional magnetic resonance imaging experiment, we employed tactile, visual, and visuotactile stimulation of the right hand in an ecologically valid setup where participants were looking directly at their upper limb. We identified brain regions that were activated by both visual and tactile stimuli as well as areas exhibiting greater activity in the visuotactile condition than in both unisensory ones. The posterior and inferior parietal, dorsal, and ventral premotor cortices, as well as the cerebellum, all showed evidence of multisensory linear (additive) responses. Nonlinear, superadditive responses were observed in the cortex lining the left anterior intraparietal sulcus, the insula, dorsal premotor cortex, and, subcortically, the putamen. These results identify a set of candidate frontal, parietal and subcortical regions that integrate visual and tactile information for the multisensory perception of one's own hand.