bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Pandemic and Seasonal Influenza A (H1N1) Virus Susceptibility to Neuraminidase Inhibitors in Three Enzyme Activity Inhibition Assays
Authors: Nguyen Ha T. , Sheu Tiffany G. , Mishin Vasiliy P. , Klimov Alexander I. , Gubareva Larisa V.
Published: June 2010

The neuraminidase inhibitors (NAIs) zanamivir and oseltamivir are currently the only antiviral drugs effective for the treatment and prophylaxis of 2009 pandemic influenza A (H1N1) virus infections. The proven potential of these viruses to acquire NAI resistance during treatment emphasizes the need to assess their NAI susceptibility. The 50% inhibitory concentrations (IC50s) are known to vary depending on the neuraminidase inhibition (NI) test used; however, few side-by-side comparisons of different NI assays have been done. In the present study, a panel of 11 isolates representing 2009 seasonal and pandemic influenza H1N1 viruses, including oseltamivir-resistant H275Y variants, were tested in three functional NI assays: chemiluminescent (CL), fluorescent (FL), and colorimetric (CM). The sensitivities of the viruses to zanamivir, oseltamivir, and three investigational NAIs (peramivir, R-125489, and A-315675) were assessed. All isolates with the exception of H275Y variants were sensitive to all five NAIs by all three NI assays. The H275Y variants showed substantially elevated IC50s against oseltamivir and peramivir. The three NI assays generally yielded consistent results; thus, the choice of NI assay does not appear to affect conclusions based on drug susceptibility surveillance. Each assay, however, offers certain advantages compared to the others: the CL assay required less virus volume and the FL assay provided the greatest difference in the IC50s between the wild type and the variants, whereas the IC50s obtained from the CM assay may be the most predictive of the drug concentrations needed to inhibit enzyme activity in humans. It would be desirable to develop an NI assay which combines the advantages of all three currently available assays but which lacks their shortcomings.
Improving Quinolone Use in Hospitals by Using a Bundle of Interventions in an Interrupted Time Series Analysis
Authors: Willemsen Ina , Cooper Ben , van Buitenen Carin , Winters Marjolein , Andriesse Gunnar , Kluytmans Jan
Published: June 2010

The objectives of the present study were to determine the effects of multiple targeted interventions on the level of use of quinolones and the observed rates of resistance to quinolones in
Escherichia coli
isolates from hospitalized patients. A bundle consisting of four interventions to improve the use of quinolones was implemented. The outcome was measured from the monthly levels of use of intravenous (i.v.) and oral quinolones and the susceptibility patterns for
E. coli
isolates from hospitalized patients. Statistical analyses were performed using segmented regression analysis and segmented Poisson regression models. Before the bundle was implemented, the annual use of quinolones was 2.7 defined daily doses (DDDs)/100 patient days. After the interventions, in 2007, this was reduced to 1.7 DDDs/100 patient days. The first intervention, a switch from i.v. to oral medication, was associated with a stepwise reduction in i.v. quinolone use of 71 prescribed daily doses (PDDs) per month (95% confidence interval [CI] = 47 to 95 PDDs/month,
P
< 0.001). Intervention 2, introduction of a new antibiotic guideline and education program, was associated with a stepwise reduction in the overall use of quinolones (reduction, 107 PDDs/month [95% CI = 58 to 156 PDDs/month). Before the interventions the quinolone resistance rate was increasing, on average, by 4.6% (95% CI = 2.6 to 6.1%) per year. This increase leveled off, which was associated with intervention 2 and intervention 4, active monitoring of prescriptions and feedback. Trends in resistance to other antimicrobial agents did not change. This study showed that the hospital-wide use of quinolones can be significantly reduced by an active policy consisting of multiple interventions. There was also a stepwise reduction in the rate of quinolone resistance associated with the bundle of interventions.
Different Classes of Antibiotics Differentially Influence Shiga Toxin Production
Authors: McGannon Colleen Marie , Fuller Cynthia Ann , Weiss Alison Ann
Published: June 2010

Shiga toxin (Stx) in
Escherichia coli
O157:H7 is encoded as a late gene product by temperate bacteriophage integrated into the chromosome. Phage late genes, including
stx
, are silent in the lysogenic state. However, stress signals, including some induced by antibiotics, trigger the phage to enter the lytic cycle, and phage replication and Stx production occur concurrently. In addition to the Stx produced by O157:H7, phage produced by O157:H7 can infect harmless intestinal
E. coli
and recruit them to produce Shiga toxin. To understand how antibiotics influence Stx production, Stx lysogens were treated with different classes of antibiotics in the presence or absence of phage-sensitive
E. coli
, and Stx-mediated inhibition of protein synthesis was monitored using luciferase-expressing Vero cells. Growth-inhibitory levels of antibiotics suppressed Stx production. Subinhibitory levels of antibiotics that target DNA synthesis, including ciprofloxacin (CIP) and trimethoprim-sulfamethoxazole, increased Stx production, while antibiotics that target the cell wall, transcription, or translation did not. More Stx was produced when
E. coli
O157:H7 was incubated in the presence of phage-sensitive
E. coli
than when grown as a pure culture. Remarkably, very high levels of Stx were detected even when growth of O157:H7 was completely suppressed by CIP. In contrast, azithromycin significantly reduced Stx levels even when O157:H7 viability remained high.
Porphyromonas gingivalisLipids Inhibit Osteoblastic Differentiation and Function
Authors: Wang Yu-Hsiung , Jiang Jin , Zhu Qiang , AlAnezi Amer Z. , Clark Robert B. , Jiang Xi , Rowe David W. , Nichols Frank C.
Published: June 2010

Porphyromonas gingivalisproduces unusual sphingolipids that are known to promote inflammatory reactions in gingival fibroblasts and Toll-like receptor 2 (TLR2)-dependent secretion of interleukin-6 from dendritic cells. The aim of the present study was to examine whetherP. gingivalislipids inhibit osteoblastic function. Total lipids fromP. gingivalisand two fractions, phosphoglycerol dihydroceramides and phosphoethanolamine dihydroceramides, were prepared free of lipid A. Primary calvarial osteoblast cultures derived from 5- to 7-day-old CD-1 mice were used to examine the effects ofP. gingivalislipids on mineralized nodule formation, cell viability, apoptosis, cell proliferation, and gene expression.P. gingivalislipids inhibited osteoblast differentiation and fluorescence expression of pOBCol2.3GFP in a concentration-dependent manner. However,P. gingivalislipids did not significantly alter osteoblast proliferation, viability, or apoptosis. When administered during specific intervals of osteoblast growth,P. gingivalistotal lipids demonstrated inhibitory effects on osteoblast differentiation only after the proliferation stage of culture. Reverse transcription-PCR confirmed the downregulation of osteoblast marker genes, including Runx2, ALP, OC, BSP, OPG, and DMP-1, with concurrent upregulation of RANKL, tumor necrosis factor alpha, and MMP-3 genes.P. gingivalistotal lipids and lipid fractions inhibited calvarial osteoblast gene expression and functionin vivo, as determined by the loss of expression of another osteoblast differentiation reporter, pOBCol3.6GFPcyan, and reduced uptake of Alizarin complexone stain. Finally, lipid inhibition of mineral nodule formationin vitrowas dependent on TLR2 expression. Our results indicate that inhibition of osteoblast function and gene expression byP. gingivalislipids represents a novel mechanism for altering alveolar bone homeostasis at periodontal disease sites.
Plasmodium vivax
Ookinete Surface Protein Pvs25 Linked to Cholera Toxin B Subunit Induces Potent Transmission-Blocking Immunity by Intranasal as Well as Subcutaneous Immunization
Authors: Miyata Takeshi , Harakuni Tetsuya , Tsuboi Takafumi , Sattabongkot Jetsumon , Kohama Hideyasu , Tachibana Mayumi , Matsuzaki Goro , Torii Motomi , Arakawa Takeshi
Published: June 2010

The nontoxic cholera toxin B subunit (CTB) was evaluated as a potential delivery molecule for the
Plasmodium vivax
ookinete surface protein, Pvs25. Recombinant Pvs25 was expressed as a secreted protein in the yeast
Pichia pastoris
, as a mixture of isoforms including multimers and the A and B monomers. The A isoform with the presumed native protein fold was the most abundant, accounting for more than 40% of all expressed protein. The molecularly uniform A isoform was chemically conjugated to CTB via its primary amines, and the fusion protein, retaining GM1-ganglioside affinity, was administered to BALB/c mice by the subcutaneous (s.c.) or intranasal (i.n.) route. Immunization of mice with conjugated Pvs25 without supplemental adjuvant induced antisera that specifically recognized
P. vivax
ookinetes
in vitro
. Furthermore, the antisera, when mixed with parasitized blood isolated from
P. vivax
patients from Thailand, was found to reduce parasite transmission to mosquitoes, conferring a 93 to 98% (s.c.) or a 73 to 88% (i.n.) decrease in oocyst number. Unconjugated Pvs25 alone conferred only a 23 to 60% (s.c.) or a 0 to 6% (i.n.) decrease in oocyst number. Coadministration of extraneous adjuvants, however, further enhanced the vaccine efficacy up to complete blockade. Taken together, we conclude that a weakly immunogenic Pvs25 by itself, when linked to CTB, transforms into a potent transmission-blocking antigen in both i.n. and s.c. routes. In addition, the present study is, to the best of our knowledge, the first demonstration of the immune potentiating function of CTB for a vaccine antigen delivered by the s.c. route.
T-Cell-Independent Immune Responses Do Not Require Cxc Ligand 13-Mediated B1 Cell Migration
Authors: Colombo Matthew J. , Sun Guizhi , Alugupalli Kishore R.
Published: June 2010

The dynamic movement of B cells increases the probability of encountering specific antigen and facilitates cell-cell interactions required for mounting a rapid antibody response. B1a and B1b cells are enriched in the coelomic cavity, contribute to T-cell-independent (TI) antibody responses, and increase in number upon antigen exposure. B1 cell movement is largely governed by Cxc ligand 13 (Cxcl13), and mice deficient in this chemokine have a severe reduction in peritoneal B1 cells. In this study, we examined the role of Cxcl13-dependent B cell migration using
Borrelia hermsii
infection or intraperitoneal immunization with pneumococcal polysaccharide or 4-hydroxy-3-nitrophenyl-acetyl (NP)-Ficoll, all of which induce robust antibody responses from B1b cells. Surprisingly, we found that antibody responses to
B. hermsii
or to FhbA, an antigenic target of B1b cells, and the resolution of bacteremia were indistinguishable between wild-type and
Cxcl13
−/−
mice. Importantly, we did not observe an expansion of peritoneal B1b cell numbers in
Cxcl13
−/−
mice. Nonetheless, mice that had resolved infection were resistant to reinfection, indicating that the peritoneal B1b cell reservoir is not required for controlling
B. hermsii
. Furthermore, despite a reduced peritoneal B1b compartment, immunization with pneumococcal polysaccharide vaccine yielded comparable antigen-specific antibody responses in wild-type and
Cxcl13
−/−
mice and conferred protection against
Streptococcus pneumoniae
. Likewise, immunization with NP-Ficoll elicited similar antibody responses in wild-type and
Cxcl13
−/−
mice. These data demonstrate that homing of B1 cells into the coelomic cavity is not a requirement for generating protective TI antibody responses, even when antigen is initially localized to this anatomical compartment.
Analyzing the Regulatory Role of the HigA Antitoxin within
Mycobacterium tuberculosis
Authors: Fivian-Hughes Amanda S. , Davis Elaine O.
Published: June 2010

Bacterial chromosomally encoded type II toxin-antitoxin (TA) loci may be involved in survival upon exposure to stress and have been linked to persistence and dormancy. Therefore, understanding the role of the numerous predicted TA loci within the human pathogen
Mycobacterium tuberculosis
has become a topic of great interest. Antitoxin proteins are known to autoregulate TA expression under normal growth conditions, but it is unknown whether they have a more global role in transcriptional regulation. This study focuses on analyzing the regulatory role of the
M. tuberculosis
HigA antitoxin. We first show that the
M. tuberculosis higBA
locus is functional within its native organism, as
higB
,
higA
, and Rv1957 were successfully deleted from the genome together while the deletion of
higA
alone was not possible. The effects of
higB
-Rv1957 deletion on
M. tuberculosis
global gene expression were investigated, and a number of potential HigA-regulated genes were identified. Transcriptional fusion and protein-DNA-binding assays were utilized to confirm the direct role of HigA in Rv1954A-Rv1957 repression, and the
M. tuberculosis
HigA DNA-binding motif was defined as ATATAGG(N
6
)CCTATAT. As HigA failed to bind to the next-most-closely related motif within the
M. tuberculosis
genome, HigA may not directly regulate any other genes in addition to its own operon.
Sense of effort and other unpleasant sensations during exercise: clarifying concepts and mechanisms
Authors: Smirmaul Bruno de Paula Caraça
Published: June 2010

Introduction

The sense of effort is an essential component of all forms of exercise. Although extensively studied, exercise physiologists have failed to reach consensus about whether this sensation is based on afferent sensory feedback or is centrally generated and independent of such feedback. This confusion has led to misunderstandings regarding the neurological mechanisms responsible for the sense of effort as opposed to other specific sensations such as pain and temperature.

Discussion

A mechanism in which the sense of effort is centrally generated and independent of feedback had been proposed more than 150 years ago. However, a more recent concept of sense of effort as a subjective rating of exercise intensity based on various sensations experienced during exercise given by Borg may have caused confusion, especially among exercise physiologists. Many began to use and understand the sense of effort as a sensation that is generated by afferent sensory feedback. The information reviewed in this article, together with the examples given, constitutes a body of evidence in favour of a centrally generated sense of effort. Afferent sensory feedback is important for the conscious awareness of different sensations such as pain and temperature, and plays important roles in the control of homeostasis. However, peripheral sensory feedback does not seem to be important for the generation of the sense of effort.

Conclusion

The sense of effort and other specific sensations such as temperature, pain and other muscular sensations present two separate neurological mechanisms. While the former is centrally generated, the latter is based on afferent sensory feedback. An interaction of these sensations is likely the ultimate regulator of exercise performance. However, further investigation is required to fully understand these phenomena.
Quantifying the effects of promoting smokeless tobacco as a harm reduction strategy in the USA
Authors: Mejia Adrienne B , Ling Pamela M , Glantz Stanton A
Published: June 2010

Background

Snus (a form of smokeless tobacco) is less dangerous than cigarettes. Some health professionals argue that snus should be promoted as a component of a harm reduction strategy, while others oppose this approach. Major US tobacco companies (RJ Reynolds and Philip Morris) are marketing snus products as cigarette brand line extensions. The population effects of smokeless tobacco promotion will depend on the combined effects of changes in individual risk with population changes in tobacco use patterns.

Objective

To quantitatively evaluate the health impact of smokeless tobacco promotion as part of a harm reduction strategy in the US.

Methods

A Monte Carlo simulation of a decision tree model of tobacco initiation and use was used to estimate the health effects associated with five different patterns of increased smokeless tobacco use.

Results

With cigarette smoking having a health effect of 100, the base case scenario (based on current US prevalence rates) yields a total health effect of 24.2 (5% to 95% interval 21.7 to 26.5) and the aggressive smokeless promotion (less cigarette use and increased smokeless, health-concerned smokers switching to snus, smokers in smokefree environments switching to snus) was associated with a health effect of 30.4 (5% to 95%interval25.9 to 35.2). The anticipated health effects for additional scenarios with lower rates of smokeless uptake also overlapped with the base case.

Conclusions

Promoting smokeless tobacco as a safer alternative to cigarettes is unlikely to result in substantial health benefits at a population level.
CONFORMAL BLOCKS AS DOTSENKO–FATEEV INTEGRAL DISCRIMINANTS
Authors: MIRONOV A. , MOROZOV A. , SHAKIROV SH.
Published: June 2010

As anticipated in Ref. 1, elaborated in Refs. 2–4, and explicitly formulated in Ref. 5, the Dotsenko–Fateev integral discriminant coincides with conformal blocks, thus providing an elegant approach to the AGT conjecture, without any reference to an auxiliary subject of Nekrasov functions. Internal dimensions of conformal blocks in this identification are associated with the choice of contours: parameters of the Dijkgraaf–Vafa phase of the corresponding matrix models. In this paper, we provide further evidence in support of this identity for the 6-parametric family of the 4-point spherical conformal blocks, up to level 3 and for arbitrary values of external dimensions and central charges. We also extend this result to multipoint spherical functions and comment on a similar description of the 1-point function on a torus.
SPHERICAL MODEL OF THE STARK EFFECT IN EXTERNAL SCALAR AND VECTOR FIELDS
Authors: YU. LAZUR V. , REITY O. K. , RUBISH V. V.
Published: June 2010

The Bohr–Sommerfeld quantization rule and the Gamow formula for the width of quasistationary level are generalized by taking into account the relativistic effects, spin and Lorentz structure of interaction potentials. The relativistic quasiclassical theory of ionization of the Coulomb system (VC = -ξ/r) by radial-constant long-range scalar (S lr = (1-λ)(σr+V0)) and vector (V lr = λ(σr+V0)) fields is constructed. In the limiting cases, the approximated analytical expressions for the position Er and width Γ of below-barrier resonances are obtained. The strong dependence of the width Γ of below-barrier resonances on both the bound level energy and the mixing constant λ is detected. The simple analytical formulae for asymptotic coefficients of the Dirac radial wave functions at zero and infinity are also obtained.
BARE AND INDUCED LORENTZ AND CPT INVARIANCE VIOLATIONS IN QED
Authors: ALFARO J. , ANDRIANOV A. A. , CAMBIASO M. , GIACCONI P. , SOLDATI R.
Published: June 2010

We consider QED in a constant axial vector background (Æther). Further Lorentz invariance violations (LIV) might occur owing to radiative corrections. The phenomenology of this model is studied, clarifying issues related to the various regularizations employed, with a particular emphasis on the induced photon mass. To this concern, it is shown that in the presence of LIV dimensional regularization may produce a radiatively induced finite photon mass. The possible physical role of the large momentum cutoff is elucidated and the finite temperature radiative corrections are evaluated. Finally, various experimental bounds on the parameters of the model are discussed.
INELASTIC COLLISION OF KINKS AND ANTIKINKS IN THE ϕ6 SYSTEM
Authors: HOSEINMARDY S. , RIAZI N.
Published: June 2010

In this paper, we study the kink–antikink interaction in the ϕ6 system. This system has soliton-like solutions which fall into two categories with opposite topological charges. We consider the interaction of a kink solution with an antikink at different incident energies (velocities) and observe the outcome. In general, the collision is inelastic. There are two critical velocities v1 and v2 in the system, between which there are enormous number of narrow scattering windows. We study the fractal-like structure of the windows. Below v1 the pair are absorbed into each other. Above v1 the pair get separated after the inelastic interaction. Finally, we obtain the internal modes of the kink in this system and address its relevance to the interaction behavior.
A NOVEL METHOD FOR HORIZONTAL EYE LINE DETECTION UNDER VARIOUS ENVIRONMENTS
Authors: JING MIN-QUAN , CHEN LING-HWEI
Published: June 2010

The eye line is defined to be a horizontal line passing the two eyes of a human face. It can be used to help locate the true positions of eyes and face. In this paper, we propose a method to extract the horizontal eye line of a face under various environments. Based on the facts that the eye color is very different from skin color and the gray level variance of an eye is high, some eye-like regions are first located. Then the horizontal eye line is extracted based on the located eye-like regions and some geometric properties in a face. Experimental results are given to show that the proposed method is robust under a wide range of lighting conditions, different poses and races. The detection rate for HHI face database is 95.63%. For Champion face database, the detection rate is 94.27%.
FROM EMPIRICAL DATA TO INTER-INDIVIDUAL INTERACTIONS: UNVEILING THE RULES OF COLLECTIVE ANIMAL BEHAVIOR
Authors: CAVAGNA ANDREA , CIMARELLI ALESSIO , GIARDINA IRENE , PARISI GIORGIO , SANTAGATI RAFFAELE , STEFANINI FABIO , TAVARONE RAFFAELE
Published: June 2010

Animal groups represent magnificent archetypes of self-organized collective behavior. As such, they have attracted enormous interdisciplinary interest in the last years. From a mechanistic point of view, animal aggregations remind physical systems of particles or spins, where the individual constituents interact locally, giving rise to ordering at the global scale. This analogy has fostered important research, where numerical and theoretical approaches from physics have been applied to models of self-organized motion. In this paper, we discuss how the physics methodology may provide precious conceptual and technical instruments in empirical studies of collective animal behavior. We focus on three-dimensional groups, for which empirical data have been extremely scarce until recently, and describe novel experimental protocols that allow reconstructing aggregations of thousands of individuals. We show how an appropriate statistical analysis of these large-scale data allows inferring important information on the interactions between individuals in a group, a key issue in behavioral studies and a basic ingredient of theoretical models. To this aim, we revisit the approach we recently used on starling flocks, and apply it to a much larger data set, never analyzed before. The results confirm our previous findings and indicate that interactions between birds have a topological rather than metric nature, each individual interacting with a fixed number of neighbors irrespective of their distances.
A GENERALIZED NORMAL MEAN-VARIANCE MIXTURE FOR RETURN PROCESSES IN FINANCE
Authors: LUCIANO ELISA , SEMERARO PATRIZIA
Published: June 2010

Time-changed Brownian motions are extensively applied as mathematical models for asset returns in Finance. Time change is interpreted as a switch from calendar time to trade-related business time. Time-changed Brownian motions can be generated by infinitely divisible normal mixtures. The standard multivariate mixtures assume a common mixing variable. This corresponds to a multidimensional return process with a unique change of time for all assets under exam. The economic counterpart is uniqueness of trade or business time, which is not in line with empirical evidence. In this paper we propose a new multivariate definition of normal mixtures with a flexible dependence structure, based on the economic intuition of both a common and an idiosyncratic component of business time. We analyze both the distribution and the related process. We use the above construction to introduce a multivariate generalized hyperbolic process with generalized hyperbolic margins. We conclude with a stock market example to show the ease of calibration of the model.
UTILITY MAXIMIZATION IN AFFINE STOCHASTIC VOLATILITY MODELS
Authors: KALLSEN JAN , MUHLE-KARBE JOHANNES
Published: June 2010

We consider the classical problem of maximizing expected utility from terminal wealth. With the help of a martingale criterion explicit solutions are derived for power utility in a number of affine stochastic volatility models.
ASYMPTOTICS OF LINEARIZED COSMOLOGICAL PERTURBATIONS
Authors: ALLEN PAUL T. , RENDALL ALAN D.
Published: June 2010

In cosmology an important role is played by homogeneous and isotropic solutions of the Einstein–Euler equations and linearized perturbations of these. This paper proves results on the asymptotic behavior of scalar perturbations both in the approach to the initial singularity of the background model and at late times. The main equation of interest is a linear hyperbolic equation whose coefficients depend only on time. Expansions for the solutions are obtained in both asymptotic regimes. In both cases, it is shown how general solutions with a linear equation of state can be parametrized by certain functions which are coefficients in the asymptotic expansion. For some nonlinear equations of state, it is found that the late-time asymptotic behavior is qualitatively different from that in the linear case.
A CONTINUOUS, TWO-WAY FREE BOUNDARY IN THE UNSTEADY TRANSONIC SMALL DISTURBANCE EQUATIONS
Authors: TESDALL ALLEN M. , KEYFITZ BARBARA L.
Published: June 2010

We formulate a problem for the unsteady transonic small disturbance equations which describes a situation analogous to the reflection of a weak shock off a wedge, with the incident shock replaced by an incident rarefaction. We linearize this problem and solve it exactly, and we compute a numerical solution of the full nonlinear problem. The solution of this problem has several features in common with the solution of the weak shock reflection problem, known as Guderley Mach reflection. In both cases, a rarefaction wave reflects off a sonic line and forms a transonic shock. There is transonic coupling between the supersonic and subsonic regions across the sonic line and shock. In both situations, this sonic line/shock can be considered a free boundary in the formulation of a new type of free boundary problem which has not previously been formulated or analyzed. The free boundary problem that arises in the context of the problem considered here is, however, simpler than the free boundary problem that arises in the weak shock reflection problem.
A NEW EXPLORATION OF THE LEBESGUE IDENTITY
Authors: ROWELL MICHAEL
Published: June 2010

We introduce a new combinatorial proof of the Lebesgue identity which allows us to find a new finite form of the identity. Using this new finite form we are able to make new observations about special cases of the Lebesgue identity, namely the "little" Göllnitz theorems and Sylvester's identity.
MULTIPLICATIVE ORDER OF GAUSS PERIODS
Authors: AHMADI OMRAN , SHPARLINSKI IGOR E. , VOLOCH JOSÉ FELIPE
Published: June 2010

We obtain a lower bound on the multiplicative order of Gauss periods which generate normal bases over finite fields. This bound improves the previous bound of von zur Gathen and Shparlinski.
Arnoldi versus GMRES for computing pageRank
Authors: Wu Gang , Wei Yimin
Published: June 2010

PageRank is one of the most important ranking techniques used in today's search engines. A recent very interesting research track focuses on exploiting efficient numerical methods to speed up the computation of PageRank, among which the Arnoldi-type algorithm and the GMRES algorithm are competitive candidates. In essence, the former deals with the PageRank problem from an eigenproblem, while the latter from a linear system, point of view. However, there is little known about the relations between the two approaches for PageRank. In this article, we focus on a theoretical and numerical comparison of the two approaches. Numerical experiments illustrate the effectiveness of our theoretical results.
Learning with click graph for query intent classification
Authors: Li Xiao , Wang Ye-Yi , Shen Dou , Acero Alex
Published: June 2010

Topical query classification, as one step toward understanding users' search intent, is gaining increasing attention in information retrieval. Previous works on this subject primarily focused on enrichment of query features, for example, by augmenting queries with search engine results. In this work, we investigate a completely orthogonal approach—instead of improving feature representation, we aim at drastically increasing the amount of training data. To this end, we propose two semisupervised learning methods that exploit user click-through data. In one approach, we infer class memberships of unlabeled queries from those of labeled ones according to their proximities in a click graph; and then use these automatically labeled queries to train classifiers using query terms as features. In a second approach, click graph learning and query classifier training are conducted jointly with an integrated objective. Our methods are evaluated in two applications, product intent and job intent classification. In both cases, we expand the training data by over two orders of magnitude, leading to significant improvements in classification performance. An additional finding is that with a large amount of training data obtained in this fashion, a classifier based on simple query term features can outperform those using state-of-the-art, augmented features.
Probabilistic models for answer-ranking in multilingual question-answering
Authors: Ko Jeongwoo , Si Luo , Nyberg Eric , Mitamura Teruko
Published: June 2010

This article presents two probabilistic models for answering ranking in the multilingual question-answering (QA) task, which finds exact answers to a natural language question written in different languages. Although some probabilistic methods have been utilized in traditional monolingual answer-ranking, limited prior research has been conducted for answer-ranking in multilingual question-answering with formal methods. This article first describes a probabilistic model that predicts the probabilities of correctness for individual answers in an independent way. It then proposes a novel probabilistic method to jointly predict the correctness of answers by considering both the correctness of individual answers as well as their correlations. As far as we know, this is the first probabilistic framework that proposes to model the correctness and correlation of answer candidates in multilingual question-answering and provide a novel approach to design a flexible and extensible system architecture for answer selection in multilingual QA. An extensive set of experiments were conducted to show the effectiveness of the proposed probabilistic methods in English-to-Chinese and English-to-Japanese cross-lingual QA, as well as English, Chinese, and Japanese monolingual QA using TREC and NTCIR questions.
Setting the Scope of Concept Inventories for Introductory Computing Subjects
Authors: Goldman Ken , Gross Paul , Heeren Cinda , Herman Geoffrey L. , Kaczmarczyk Lisa , Loui Michael C. , Zilles Craig
Published: June 2010

A concept inventory is a standardized assessment tool intended to evaluate a student’s understanding of the core concepts of a topic. In order to create a concept inventory it is necessary to accurately identify these core concepts. A Delphi process is a structured multi-step process that uses a group of experts to achieve a consensus opinion. We present the results of three Delphi processes to identify topics that are important and difficult in each of three introductory computing subjects: discrete mathematics, programming fundamentals, and logic design. The topic rankings can not only be used to guide the coverage of concept inventories, but can also be used by instructors to identify what topics merit special attention.
Distributed error confinement
Authors: Azar Yossi , Kutten Shay , Patt-Shamir Boaz
Published: June 2010

We study error confinement in distributed applications, which can be viewed as an extreme case of various fault locality notions studied in the past. Error confinement means that to the external observer, only nodes that were directly hit by a fault may deviate from their specified correct behavior, and only temporarily. The externally observable behavior of all other nodes must remain impeccable, even though their internal state may be affected. Error confinement is impossible if an adversary is allowed to inflict arbitrary transient faults on the system, since the faults might completely wipe out input values. We introduce a new fault-tolerance measure we call
agility
, which quantifies the fault tolerance of an algorithm that disseminates information against state corrupting faults.

We then propose broadcast algorithms that guarantee error confinement with optimal agility to within a constant factor in synchronous networks. These algorithms can serve as building blocks in more general reactive systems. Previous results in exploring locality in reactive systems were not error confined, or allowed a wide range of behaviors to be considered correct. Our results also include a new technique that can be used to analyze the “cow path” problem.
Balanced families of perfect hash functions and their applications
Authors: Alon Noga , Gutner Shai
Published: June 2010

The construction of perfect hash functions is a well-studied topic. In this article, this concept is generalized with the following definition. We say that a family of functions from [
n
] to [
k
] is a δ-balanced (
n,k
)-family of perfect hash functions if for every
S
⊆ [
n
], |
S
|=
k
, the number of functions that are 1-1 on
S
is between
T
/δ and δ
T
for some constant
T
>0. The standard definition of a family of perfect hash functions requires that there will be at least one function that is 1-1 on
S
, for each
S
of size
k
. In the new notion of balanced families, we require the number of 1-1 functions to be almost the same (taking δ to be close to 1) for every such
S
. Our main result is that for any constant δ > 1, a δ-balanced (
n,k
)-family of perfect hash functions of size 2

O
(
k
log log
k
)

log
n
can be constructed in time 2

O
(
k
log log
k
)

n
log
n
. Using the technique of color-coding we can apply our explicit constructions to devise approximation algorithms for various counting problems in graphs. In particular, we exhibit a deterministic polynomial-time algorithm for approximating both the number of simple paths of length
k
and the number of simple cycles of size
k
for any
k
≤
O
(log
n
/log log log
n
) in a graph with
n
vertices. The approximation is up to any fixed desirable relative error.
A package for solving parametric polynomial systems
Authors: Gerhard Jürgen , Jeffrey D. J. , Moroz Guillaume
Published: June 2010

A new Maple package for solving parametric systems of polynomial equations and inequalities is described. The main idea for solving such a system is as follows. The parameter space Rd is divided into two parts: the discriminant variety
W
and its complement R

d

nW
. The discriminant variety is a generalization of the well-known discriminant of a univariate polynomial and contains all those parameter values leading to non-generic solutions of the system. The complement R

d

nW
can be expressed as a finite union of open cells such that the number of real solutions of the input system is constant on each cell. In this way, all parameter values leading to generic solutions of the system can be described systematically. The underlying techniques used are Gröbner bases, polynomial real root finding, and cylindrical algebraic decomposition. This package offers a friendly interface for scientists and engineers to solve parametric problems, as illustrated by an example from control theory.
Toward high-performance polynomial system solvers based on triangular decompositions
Authors: Li Xin
Published: June 2010

This thesis is devoted to the design and implementation of polynomial system solvers based on symbolic computation. Solving systems of non-linear, algebraic or differential equations, is a fundamental problem in mathematical sciences. It has been studied for centuries and still stimulates many research developments, in particular on the front of high-performance computing.

Triangular decompositions are a highly promising technique with the potential to produce high-performance polynomial system solvers. This thesis makes several contributions to this effort.

We propose asymptotically fast algorithms for the core operations on which triangular decompositions rely. Complexity results and comparative implementation show that these new algorithms provide substantial performance improvements.

We present a fundamental software library for polynomial arithmetic in order to support the implementation of high-performance solvers based on triangular decompositions. We investigate strategies for the integration of this library in high-level programming environments where triangular decompositions are usually implemented.

We obtain a high performance library combining highly optimized C routines and solving procedures written in the Maple computer algebra system. The experimental result shows that our approaches are very effective, since our code often outperforms pre-existing solvers in a significant manner.
Numerical and symbolic computation of the Lambert W function in C
nxn
Authors: Ding Hui
Published: June 2010

The Lambert W function is a multivalued complex function, first named in the computer algebra system Maple. We present iterative schemes and strategies for the numerical evaluation of all branches of the scalar complex Lambert W function to hardware precision with high computational efficiency, and present a set of rules for the simplification of special symbolic arguments. We also extend the numerical and symbolic computations to the Lambert W function in C
nxn
, for n > 1. In order to achieve high precision and computational efficiency, we evaluate a series of high order and classical iterative methods and strategies for the evaluation of the scalar Lambert W function. We then construct optimal iterative schemes for the evaluation of the complex Lambert W function in the IEEE oating point model. The schemes consist of variations on Newton and Halley iterations together with initial estimates generated using a variety of series approximations. We also study several classes of exact simplifications for the Lambert W function for symbolic arguments and give rules for their application. Finally, we consider the solutions of the matrix equation S exp(S) = A, where S and A are
n x n
matrices. The solutions are expressed in terms of extensions of the scalar Lambert W function to C
nxn
. The solutions of the matrix equations consist not only of the matrix functions W(A); other solutions also exist. We focus first on solving the matrix equation in C
3x3
, and implement solutions in the floating-point case, and the symbolic case, using Maple.
Deletion of Nck1 attenuates hepatic ER stress signaling and improves glucose tolerance and insulin signaling in liver of obese mice
Authors: Latreille Mathieu , Laberge Marie-Kristine , Bourret Geneviève , Yamani Lama , Larose Louise
Published: June 2010

Obesity has been shown to create stress in the endoplasmic reticulum (ER), and that initiates the activation of the unfolded protein response (UPR). This has been reported to cause insulin resistance in selective tissues through activation of the inositol-requiring enzyme 1α (IRE1α)-c-Jun NH2-terminal kinase (JNK) pathway, which results in the phosphorylation of the insulin receptor substrate-1 (IRS-1) at an inhibitory site and blocks insulin receptor signaling. In this study, we report that the Src homology domain-containing adaptor protein Nck1, previously shown to modulate the UPR, is of functional importance in obesity-induced ER stress signaling and inhibition of insulin actions. We have examined obese Nck1−/− and Nck1 +/+ mice for glucose tolerance, insulin sensitivity, and signaling as well as for ER stress markers and IRS-1 phosphorylation at Ser307. Our findings show that obese Nck1-deficient mice display improved glucose disposal accompanied by enhanced insulin signaling in liver. This correlates with attenuated IRE1α and JNK activation and IRS-1 phosphorylation at Ser307 compared with obese wild-type mice. Consistent with our in vivo data, we report that downregulation of Nck1 using siRNA in HepG2 cells results in decreased thapsigargin-induced IRE1α activation and signaling and IRS-1 phosphorylation at Ser307, whereas it markedly enhances insulin signaling. Overall, in liver and in cultured cells, we show that depletion of Nck1 attenuates the UPR signal and its inhibitory action on insulin signaling. Taken all together, our findings implicate Nck1 in regulating the UPR, which secondary to obesity impairs glucose homeostasis and insulin actions.
On the Importance of the Aromatic Ring Parameter in Studies of the Solvolyses of Cinnamyl and Cinnamoyl Halides
Authors: D'Souza Malcolm J. , Darrington Anthony M. , Kevill Dennis N.
Published: June 2010

In solvolysis studies using Grunwald-Winstein plots, dispersions were observed for substrates with aromatic rings at theα-carbon. Several examples for the unimolecular solvolysis of monoaryl benzylic derivatives and related diaryl- or naphthyl-substituted derivatives have now been reported, where the application of the aromatic ring parameter(I)removes this dispersion. A recent claim suggesting the presence of an appreciable nucleophilic component to theIscale has now been shown, in a review of the solvolysis of highly-hindered alkyl halides, to be unlikely to be correct. Attention is now focused on the application of thehIterm for the solvolysis of compounds containing a double bond in the vicinity of any developing carbocation. Available specific rates of solvolysis (plus some new values) at25°C of cinnamyl chloride, cinnamyl bromide, cinnamoyl chloride,p-chlorocinnamoyl chloride, andp-nitrocinnamoyl chloride are analyzed using the simple and extended (including thehIterm) Grunwald-Winstein equations.
Genetic Influences on Individual Differences in Exercise Behavior during Adolescence
Authors: van der Aa Niels , De Geus Eco J. C. , van Beijsterveldt Toos C. E. M. , Boomsma Dorret I. , Bartels Meike
Published: June 2010

The aim of this study was to investigate the degree to which genetic and environmental influences affect variation in adolescent exercise behavior. Data on regular leisure time exercise activities were analyzed in 8,355 adolescent twins, from three-age cohorts (13-14, 15-16, and 17–19 years). Exercise behavior was assessed with survey items about type of regular leisure time exercise, frequency, and duration of the activities. Participants were classified as sedentary, regular exercisers, or vigorous exercisers. The prevalence of moderate exercise behavior declined from age 13 to 19 years with a parallel increase in prevalence of sedentary behavior, whereas the prevalence of vigorous exercise behavior remained constant across age cohorts. Variation in exercise behavior was analyzed with genetic structural equation modeling employing a liability threshold model. Variation was largely accounted for by genetic factors (72% to 85% of the variance was explained by genetic factors), whereas shared environmental factors only accounted for a substantial part of the variation in girls aged 13-14 years (46%). We hypothesize that genetic effects on exercise ability may explain the high heritability of exercise behavior in this phase of life.
Permanence of a Discrete Periodic Volterra Model with Mutual Interference and Beddington‐DeAngelis Functional Response
Authors: Wu Runxin
Published: June 2010

This paper discuss a discrete periodic Volterra model with mutual interference and Beddington‐DeAngelis functional response. By using the comparison theorem of difference equation, sufficient conditions are obtained for the permanence of the system. After that,we give an example to show the feasibility of our main result.
Synthesis and Biological Evaluation of New CRH Analogues
Authors: Papazacharias Spyridon , Magafa Vassiliki , Bernad Nicole , Pairas George , Spyroulias Georgios A. , Martinez Jean , Cordopatis Paul
Published: June 2010

A series of 7 new human/rat Corticotropin Releasing Hormone (h/r‐CRH) analogues were synthesized. The induced alterations include substitution of Phe at position 12 with D‐Phe, Leu at positions 14 and 15 with Aib and Met at positions 21 and 38 with Cys(Et) and Cys(Pr). The analogues were tested regarding their binding affinity to the CRH‐1 receptor and their activity which is represented by means of percentage of maximum response in comparison to the native molecule. The results indicated that the introduction of Aib, or Cys derivatives although altering the secondary structure of the molecule, did not hinder receptor recognition and binding.
Genome Size in Diploids, Allopolyploids, and Autopolyploids of Mediterranean Triticeae
Authors: Eilam T. , Anikster Y. , Millet E. , Manisterski J. , Feldman M.
Published: June 2010

Nuclear DNA amount, determined by the flow cytometry method, in diploids, natural and synthetic allopolyploids, and natural and synthetic autopolyploids of the tribe Triticeae (Poaceae) is reviewed here and discussed. In contrast to the very small and nonsignificant variation in nuclear DNA amount that was found at the intraspecific level, the variation at the interspecific level is very large. Evidently changes in genome size are either the cause or the result of speciation. Typical autopolyploids had the expected additive DNA amount of their diploid parents, whereas natural and synthetic cytologically diploidized autopolyploids and natural and synthetic allopolyploids had significantly less DNA than the sum of their parents. Thus, genome downsizing, occurring during or immediately after the formation of these polyploids, provides the physical basis for their cytological diploidization, that is, diploid-like meiotic behavior. Possible mechanisms that are involved in genome downsizing and the biological significance of this phenomenon are discussed.
Parameter Identification of a Class of Economical Models
Authors: Cantó Begoña , Coll Carmen , Sánchez Elena
Published: June 2010

In mathematical modeling of economic problems, it is common to assume that economic laws influence the process and analyze the type of solution obtained. Sometimes these laws have unknown parameters and they worth studying if these parameters can be determined. In this paper, a structured system is considered and the identifiability
is analyzed. In case the parameters can be uniquely identified, an algorithm for obtaining the model parameters is presented and,
finally, the existence of a balanced growth solution is studied.