bluuebunny/crossref_metadata_2025 huggingface dataset:
Ageing and cardiorespiratory response to hypoxia
Authors: Lhuissier François J. , Canouï‐Poitrine Florence , Richalet Jean‐Paul
Published: August 2012

Key points

A previous study showed that an older age could be associated with a lower risk of severe altitude‐induced diseases.

This work combines a cross‐sectional study including 4675 subjects and a longitudinal study on 30 subjects.

It shows that ageing is associated with a blunting of cardiac chronotropic function and an increase in ventilatory response leading to maintenance of arterial O2 saturation in hypoxia.

These adaptive responses to hypoxia with ageing are blunted by menopause but can be maintained with endurance training.

The cardiac and ventilatory adaptations allow older people to challenge hypoxia similarly to younger ones when performing moderate exercise.

Abstract  The risk of severe altitude‐induced diseases is related to ventilatory and cardiac responses to hypoxia and is dependent on sex, age and exercise training status. However, it remains unclear how ageing modifies these physiological adaptations to hypoxia. We assessed the physiological responses to hypoxia with ageing through a cross‐sectional 20 year study including 4675 subjects (2789 men, 1886 women; 14–85 years old) and a longitudinal study including 30 subjects explored at a mean 10.4 year interval. The influence of sex, training status and menopause was evaluated. The hypoxia‐induced desaturation and the ventilatory and cardiac responses to hypoxia at rest and exercise were measured. In men, ventilatory response to hypoxia increased (P < 0.002), while desaturation was less pronounced (P < 0.001) with ageing. Cardiac response to hypoxia was blunted with ageing in both sexes (P < 0.001). Similar results were found in the longitudinal study, with a decrease in cardiac and an increase in ventilatory response to hypoxia with ageing. These adaptive responses were less pronounced or absent in post‐menopausal women (P < 0.01). At exercise, desaturation was greater in trained subjects but cardiac and ventilatory responses to hypoxia were preserved by training, especially in elderly people. In conclusion, respiratory response to hypoxia and blood oxygenation improve with ageing in men while cardiac response is blunted with ageing in both sexes. Training aggravates desaturation at exercise in hypoxia, improves the ventilatory response and limits the ageing‐induced blunting of cardiac response to hypoxia. Training limits the negative effects of menopause in cardiorespiratory adaptations to hypoxia.
Mixed Convection Flow of Micropolar Fluid in an Open Ended Arc-Shape Cavity
Authors: Saleem M. , Hossain M. A. , Saha Suvash C.
Published: August 2012

Numerical simulations for mixed convection flow of micropolar fluid in an open ended arc-shape cavity have been carried out in this study. Computation is performed using the alternate direct implicit (ADI) method together with the successive over relaxation (SOR) technique for the solution of governing partial differential equations. The flow phenomenon is examined for a range of values of Rayleigh number 102 ≤ Ra ≤ 106, Prandtl number 7 ≤ Pr ≤ 50, and Reynolds number 10 ≤ Re ≤ 100. The study is mainly focused on how the micropolar fluid parameters affect the fluid properties in the flow domain. It was found that despite the reduction of flow in the core region, the heat transfer rate increases, whereas the skin friction and microrotation decrease with the increase in the vortex viscosity parameter Δ.
Statistical CT noise reduction with multiscale decomposition and penalized weighted least squares in the projection domain
Authors: Tang Shaojie , Tang Xiangyang
Published: August 2012

Purposes:

The suppression of noise in x‐ray computed tomography (CT) imaging is of clinical relevance for diagnostic image quality and the potential for radiation dose saving. Toward this purpose, statistical noise reduction methods in either the image or projection domain have been proposed, which employ a multiscale decomposition to enhance the performance of noise suppression while maintaining image sharpness. Recognizing the advantages of noise suppression in the projection domain, the authors propose a projection domain multiscale penalized weighted least squares (PWLS) method, in which the angular sampling rate is explicitly taken into consideration to account for the possible variation of interview sampling rate in advanced clinical or preclinical applications.

Methods:

The projection domain multiscale PWLS method is derived by converting an isotropic diffusion partial differential equation in the image domain into the projection domain, wherein a multiscale decomposition is carried out. With adoption of the Markov random field or soft thresholding objective function, the projection domain multiscale PWLS method deals with noise at each scale. To compensate for the degradation in image sharpness caused by the projection domain multiscale PWLS method, an edge enhancement is carried out following the noise reduction. The performance of the proposed method is experimentally evaluated and verified using the projection data simulated by computer and acquired by a CT scanner.

Results:

The preliminary results show that the proposed projection domain multiscale PWLS method outperforms the projection domain single‐scale PWLS method and the image domain multiscale anisotropic diffusion method in noise reduction. In addition, the proposed method can preserve image sharpness very well while the occurrence of “salt‐and‐pepper” noise and mosaic artifacts can be avoided.

Conclusions:

Since the interview sampling rate is taken into account in the projection domain multiscale decomposition, the proposed method is anticipated to be useful in advanced clinical and preclinical applications where the interview sampling rate varies.
The Path to Chemotaxis and Transcription Is Smoothened
Authors: Lin Chuwen , Nozawa Yoko Inès , Chuang Pao-Tien
Published: August 2012

Distinct outputs of Hedgehog signaling arise from different subcellular localization of the signal transducer Smoothened.
A Focused Small-Molecule Screen Identifies 14 Compounds with Distinct Effects on Toxoplasma gondii
Authors: Kamau Edwin T. , Srinivasan Ananth R. , Brown Mark J. , Fair Matthew G. , Caraher Erin J. , Boyle Jon P.
Published: August 2012

Toxoplasma gondii
is a globally ubiquitous pathogen that can cause severe disease in immunocompromised humans and the developing fetus. Given the proven role of
Toxoplasma
-secreted kinases in the interaction of
Toxoplasma
with its host cell, identification of novel kinase inhibitors could precipitate the development of new anti-
Toxoplasma
drugs and define new pathways important for parasite survival. We selected a small (
n
= 527) but diverse set of putative kinase inhibitors and screened them for effects on the growth of
Toxoplasma
in vitro
. We identified and validated 14 noncytotoxic compounds, all of which had 50% effective concentrations in the nanomolar to micromolar range. We further characterized eight of these compounds, four inhibitors and four enhancers, by determining their effects on parasite motility, invasion, and the likely cellular target (parasite or host cell). Only two compounds had an effect on parasite motility and invasion. All the inhibitors appeared to target the parasite, and interestingly, two of the enhancers appeared to rather target the host cell, suggesting modulation of host cell pathways beneficial for parasite growth. For the four inhibitors, we also tested their efficacy in a mouse model, where one compound proved potent. Overall, these 14 compounds represent a new and diverse set of small molecules that are likely targeting distinct parasite and host cell pathways. Future work will aim to characterize their molecular targets in both the host and parasite.
Early Insights into the Interactions of Different β-Lactam Antibiotics and β-Lactamase Inhibitors against Soluble Forms of Acinetobacter baumannii PBP1a and Acinetobacter sp. PBP3
Authors: Papp-Wallace Krisztina M. , Senkfor Baui , Gatta Julian , Chai Weirui , Taracila Magdalena A. , Shanmugasundaram Veerabahu , Han Seungil , Zaniewski Richard P. , Lacey Brian M. , Tomaras Andrew P. , Skalweit Marion J. , Harris Michael E. , Rice Louis B. , Buynak John D. , Bonomo Robert A.
Published: August 2012

Acinetobacter baumannii
is an increasingly problematic pathogen in United States hospitals. Antibiotics that can treat
A. baumannii
are becoming more limited. Little is known about the contributions of penicillin binding proteins (PBPs), the target of β-lactam antibiotics, to β-lactam–sulbactam susceptibility and β-lactam resistance in
A. baumannii
. Decreased expression of PBPs as well as loss of binding of β-lactams to PBPs was previously shown to promote β-lactam resistance in
A. baumannii
. Using an
in vitro
assay with a reporter β-lactam, Bocillin, we determined that the 50% inhibitory concentrations (IC
50
s) for PBP1a from
A. baumannii
and PBP3 from
Acinetobacter
sp. ranged from 1 to 5 μM for a series of β-lactams. In contrast, PBP3 demonstrated a narrower range of IC
50
s against β-lactamase inhibitors than PBP1a (ranges, 4 to 5 versus 8 to 144 μM, respectively). A molecular model with ampicillin and sulbactam positioned in the active site of PBP3 reveals that both compounds interact similarly with residues Thr526, Thr528, and Ser390. Accepting that many interactions with cell wall targets are possible with the ampicillin-sulbactam combination, the low IC
50
s of ampicillin and sulbactam for PBP3 may contribute to understanding why this combination is effective against
A. baumannii
. Unraveling the contribution of PBPs to β-lactam susceptibility and resistance brings us one step closer to identifying which PBPs are the best targets for novel β-lactams.
Pharmacokinetics and Renal Disposition of Polymyxin B in an Animal Model
Authors: Abdelraouf Kamilia , He Jie , Ledesma Kimberly R. , Hu Ming , Tam Vincent H.
Published: August 2012

The increasing prevalence of multidrug-resistant Gram-negative infections has led to the resurgence of systemic polymyxin B, but little is known about its pharmacokinetics. The objective of this study was to characterize the pharmacokinetics and renal disposition of polymyxin B. Eight female Sprague-Dawley rats (weight, 225 to 250 g) were administered a single intravenous polymyxin B dose (4 mg/kg of body weight). Serial serum samples were collected and assayed for major polymyxin B components using a validated ultraperformance liquid chromatography-tandem mass spectrometry method. The best-fit pharmacokinetic parameters of each component were derived and compared using one-way analysis of variance. Cumulative urine was also collected daily for 48 h and assayed for polymyxin B. Kidney drug concentrations were measured at 6 h (n= 3) and 48 h (n= 3) after the same dose. Additionally, three rats were administered 2 doses of intravenous polymyxin B (4 mg/kg) 7 days apart. Serial serum samples were collected pre- and post-renal insufficiency (induced by uranyl nitrate) and assayed for polymyxin B. The pharmacokinetic parameters of the major components did not appear to be significantly different (P> 0.05). Less than 1% of the dose was recovered unchanged in urine collected over 48 h following administration. Therapeutic drug concentrations persisted in kidney tissue at 48 h. The post-renal insufficiency to pre-renal insufficiency ratio of the area under the serum concentration-time curve from time zero to infinity was 1.33 ± 0.04. Polymyxin B components appear to have similar pharmacokinetics. Polymyxin B preferentially persists in kidneys, which suggests a selective uptake process in renal cells. A mechanism(s) other than renal excretion could be involved in polymyxin B elimination, and dosing adjustment in renal insufficiency may not be necessary.
Early Control of Mycobacterium tuberculosis Infection Requiresil12rb1Expression byrag1-Dependent Lineages
Authors: Miller Halli E. , Robinson Richard T.
Published: August 2012

IL12RB1is essential for human resistance toMycobacterium tuberculosisinfection. In the absence of a functionalIL12RB1allele, individuals exhibit susceptibility to disseminated, recurrent mycobacterial infections that are associated with defects in bothRAG1-dependent andRAG1-independent hematopoietic lineages. Despite this well-established association, a causal relationship betweenM. tuberculosissusceptibility andIL12RB1deficiency in eitherRAG1-dependent orRAG1-independent lineages has never been formally tested. Here, we use the low-dose aerosol model of experimental tuberculosis (TB) to both establish that infectedil12rb1−/−mice recapitulate important aspects of TB inIL12RB1null individuals and, more importantly, use radiation bone marrow chimeras to demonstrate that restriction ofil12rb1deficiency solely torag1-dependent lineages (i.e., T and B cells) allows for the full transfer of theil12rb1−/−phenotype. We further demonstrate that the protection afforded by adaptive lymphocyteil12rb1expression is mediated partially throughifngand that, within the same infection,il12rb1-sufficient T cells exhibit dominance overil12rb1-deficient T cells by enhancingifngexpression in the latter population. Collectively, our data establish a basic framework in which to understand howIL12RB1promotes control of this significant human disease.
Persistent Mycoplasma genitalium Infection of Human Endocervical Epithelial Cells Elicits Chronic Inflammatory Cytokine Secretion
Authors: McGowin Chris L. , Annan Rochelle S. , Quayle Alison J. , Greene Sheila J. , Ma Liang , Mancuso Miriam M. , Adegboye David , Martin David H.
Published: August 2012

Infection with
Mycoplasma genitalium
has been associated with male and female urogenital disease syndromes, including urethritis, cervicitis, pelvic inflammatory disease (PID), and tubal factor infertility. Basic investigations of mucosal cytotoxicity, microbial persistence, and host immune responses are imperative to understanding these inflammatory urogenital syndromes, particularly in females, considering the potential severity of upper tract infections. Here, we report that
M. genitalium
can establish long-term infection of human endocervical epithelial cells that results in chronic inflammatory cytokine secretion and increased responsiveness to secondary Toll-like receptor (TLR) stimulation. Using a novel quantitative PCR assay,
M. genitalium
was shown to replicate from 0 to 80 days postinoculation (p.i.), during which at most time points the median ratio of
M. genitalium
organisms to host cells was ≤10, indicating that low organism burdens are capable of eliciting chronic inflammation in endocervical epithelial cells. This observation is consistent with clinical findings in women. Persistently secreted cytokines predominately consisted of potent chemotactic and/or activating factors for phagocytes, including interleukin-8 (IL-8), monocyte chemotactic protein 1 (MCP-1), and macrophage inflammatory protein 1β (MIP-1β). Despite persistent cytokine elaboration, no host cell cytotoxicity was observed except with superphysiologic loads of
M. genitalium
, suggesting that persistent infection occurs with minimal direct damage to the epithelium. However, it is hypothesized that chronic chemokine secretion with leukocyte trafficking to the epithelium could lead to significant inflammatory sequelae. Therefore, persistent
M. genitalium
infection could have important consequences for acquisition and/or pathogenesis of other sexually transmitted infections (STIs) and perhaps explain the positive associations between this organism and human immunodeficiency virus (HIV) shedding.
Syphilis infection among homosexual men reporting contact with syphilis: a case control study
Authors: Weerakoon Ajith P , Fairley Christopher K , Read Tim RH , Bradshaw Catriona , Forrester Catherine , Bissessor Melanie , Denham Ian , Chen Marcus Y
Published: August 2012

Objective

High rates of syphilis have been reported among men who have sex with men (MSM) internationally. Guidelines recommend presumptive treatment of sexual contacts of individuals with syphilis at the point of care. The aim of this study was to determine the proportion who were infected with syphilis and the factors predictive of infection among men reporting contact with a man with syphilis.

Design

Contacts who were syphilis infected (cases) were compared with those who were uninfected (controls).

Setting

This study was conducted at the main public sexually transmitted diseases clinic in Victoria, Australia.

Participants

One hundred and seventy-two MSM presenting as sexual contacts of men with syphilis at a sexual health service in Melbourne, Australia, between July 2007 and October 2011 were assessed for syphilis.

Outcome measures

Proportion of MSM who are infected with syphilis and factors associated with infection.

Results

Of the 172 men who presented reporting contact with syphilis, 26 (15%, 95% CI 10 to 20%) had syphilis. One man had primary syphilis, 4 had secondary syphilis, while the remaining 21 had early latent syphilis. Infection was associated with unprotected anal sex over the prior 3 months (adjusted OR 6.1, 95% CI 1.4 to 26.8).

Conclusions

One in seven men presenting as contacts of syphilis had syphilis infection, most of whom were latently infected. Contacts reporting recent unprotected anal sex were more likely to have syphilis.
Buried-valley aquifers in the Canadian Prairies: geology, hydrogeology, and origin1Earth Science Sector (ESS) Contribution 20120131.
Authors: Cummings Don I. , Russell Hazen A.J. , Sharpe David R.
Published: August 2012

We review over 100 years of literature on Prairie buried valleys to provide a platform for future research and policy development. Prairie buried-valley fills commonly function as aquifers that yield abundant groundwater. They have distinct geologies and a distinct stratigraphic setting, which imparts them with distinct hydrogeological properties and gives clues as to how they formed and filled. Prairie buried-valley aquifers are commonly encased in low-permeability strata: Cretaceous shale commonly underlies them, and thick (10–300 m) low-permeability Quaternary till tends to overlie them. This reduces recharge, in rare cases nearly completely, while protecting groundwater resources from contamination and drought. It also tends to lead to highly mineralized groundwater chemistries. The stratigraphic position of Prairie buried valleys also speaks to their origin: those that subtend (“hang”) from the bedrock unconformity were likely eroded by preglacial fluvial systems during late Tertiary uplift of the Rocky Mountains, whereas those that subtend from surfaces within the till package are likely glaciofluvial valleys eroded in proglacial spillway or tunnel-valley settings. Another key trait of Prairie buried valleys is that their fills tend to be heterogeneous and architecturally complex. Sand, gravel, mud, and diamicton are common; any one can dominate the fill at a given location. This heterogeneity, in conjunction with irregularity common to buried-valley bedrock floors, commonly causes aquifer compartmentalization and makes prediction of aquifer potential difficult prior to drilling. It also suggests that most Prairie buried valleys filled over time, and likely over multiple glaciations, in multiple depositional environments.
Dehydration decreases saliva antimicrobial proteins important for mucosal immunity
Authors: Fortes Matthew B. , Diment Bethany C. , Di Felice Umberto , Walsh Neil P.
Published: August 2012

The aim of the study was to investigate the effect of exercise-induced dehydration and subsequent overnight fluid restriction on saliva antimicrobial proteins important for host defence (secretory IgA (SIgA), α-amylase, and lysozyme). On two randomized occasions, 13 participants exercised in the heat, either without fluid intake to evoke progressive body mass losses (BML) of 1%, 2%, and 3% with subsequent overnight fluid restriction until 0800 h in the following morning (DEH) or with fluids to offset losses (CON). Participants in the DEH trial rehydrated from 0800 h until 1100 h on day 2. BML, plasma osmolality (Posm), and urine specific gravity (USG) were assessed as hydration indices. Unstimulated saliva samples were assessed for flow rate (SFR), SIgA, α-amylase, and lysozyme concentrations. Posm and USG increased during dehydration and remained elevated after overnight fluid restriction (BML = 3.5% ± 0.3%, Posm = 297 ± 6 mosmol·kg–1, and USG = 1.026 ± 0.002; P < 0.001). Dehydration decreased SFR (67% at 3% BML, 70% at 0800 h; P < 0.01) and increased SIgA concentration, with no effect on SIgA secretion rate. SFR and SIgA responses remained unchanged in the CON trial. Dehydration did not affect α-amylase or lysozyme concentration but decreased secretion rates of α-amylase (44% at 3% BML, 78% at 0800 h; P < 0.01) and lysozyme (46% at 3% BML, 61% at 0800 h; P < 0.01), which were lower than in CON at these time points (P < 0.05). Rehydration returned all saliva variables to baseline. In conclusion, modest dehydration (~3% BML) decreased SFR, α-amylase, and lysozyme secretion rates. Whether the observed magnitude of decrease in saliva AMPs during dehydration compromises host defence remains to be shown.
Estimated times to exhaustion and power outputs at the gas exchange threshold, physical working capacity at the rating of perceived exertion threshold, and respiratory compensation point
Authors: Bergstrom Haley C. , Housh Terry J. , Zuniga Jorge M. , Camic Clayton L. , Traylor Daniel A. , Schmidt Richard J. , Johnson Glen O.
Published: August 2012

The purposes of this study were to compare the power outputs and estimated times to exhaustion (Tlim) at the gas exchange threshold (GET), physical working capacity at the rating of perceived exertion threshold (PWCRPE), and respiratory compensation point (RCP). Three male and 5 female subjects (mean ± SD: age, 22.4 ± 2.8 years) performed an incremental test to exhaustion on an electronically braked cycle ergometer to determine peak oxygen consumption rate, GET, and RCP. The PWCRPEwas determined from ratings of perceived exertion data recorded during 3 continuous workbouts to exhaustion. The estimated Tlimvalues for each subject at GET, PWCRPE, and RCP were determined from power curve analyses (Tlim = axb). The results indicated that the PWCRPE(176 ± 55 W) was not significantly different from RCP (181 ± 54 W); however, GET (155 ± 42 W) was significantly less than PWCRPEand RCP. The estimated Tlimfor the GET (26.1 ± 9.8 min) was significantly greater than PWCRPE(14.6 ± 5.6 min) and RCP (11.2 ± 3.1 min). The PWCRPEoccurred at a mean power output that was 13.5% greater than the GET and, therefore, it is likely that the perception of effort is not driven by the same mechanism that underlies the GET (i.e., lactate buffering). Furthermore, the PWCRPEand RCP were not significantly different and, therefore, these thresholds may be associated with the same mechanisms of fatigue, such as increased levels of interstitial and (or) arterial [K+].
Physical activity level, waist circumference, and mortality
Authors: Staiano Amanda E. , Reeder Bruce A. , Elliott Susan , Joffres Michel R. , Pahwa Punam , Kirkland Susan A. , Paradis Gilles , Katzmarzyk Peter T.
Published: August 2012

This study predicted all-cause mortality based on physical activity level (active or inactive) and waist circumference (WC) in 8208 Canadian adults in Alberta, Manitoba, Nova Scotia, and Saskatchewan, surveyed between 1986–1995 and followed through 2004. Physically inactive adults had higher mortality risk than active adults overall (hazard ratio, 95% confidence interval = 1.20, 1.05–1.37) and within the low WC category (1.51, 1.19–1.92). Detrimental effects of physical inactivity and high WC demonstrate the need for physical activity promotion.
Vaccenic acid in serum triglycerides is associated with markers of insulin resistance in men
Authors: Zulyniak Michael A. , Ralston Jessica C. , Tucker Amy J. , MacKay Kathy A. , Hillyer Lyn M. , McNicholas Paul D. , Graham Terry E. , Robinson Lindsay E. , Duncan Alison M. , Ma David W.L. , Mutch David M.
Published: August 2012

Serum triglyceride levels are associated with metabolic disorders; however, it remains unclear whether the fatty acid (FA) composition of triglycerides is also changed. Although there were no differences in circulating triglyceride levels between normoglycaemic–normoinsulinaemic and hyperglycaemic–hyperinsulinaemic men, inspection of individual FA revealed that vaccenic acid was enriched with hyperglycaemia–hyperinsulinaemia. Moreover, vaccenic acid levels were positively correlated with insulin and HOMA-IR. This reinforces that examination of individual FA in the context of insulin resistance is warranted.
Oxygen uptake and heart rate response of 6 standardized tennis drills
Authors: Bekraoui Nabyl , Fargeas-Gluck Marie-Agnès , Léger Luc
Published: August 2012

The purpose of this study was to compare the oxygen uptake of various on-court tennis drills. Eleven tennis players were monitored with a portable metabolic device to measure oxygen uptake of 6 different tennis drills at low and high speeds. The 6 drills were done with or without striking the ball, over half or full-width of the court, in attack or defense mode, using forehand or backhand strokes. Oxygen uptake values (mean ± SD) ranged from 33.8 ± 4.2 to 42.3 ± 5.1 mL·kg–1·min–1 when running at low speed on the full-width court in defense mode without striking the ball and when running at high speed on the full-width court in attack mode while striking the ball, respectively. Specific differences were observed. Attacking mode requires 6.5% more energy than defensive playing mode. Backhand strokes demand 7% more energy at low speed than forehand ones. Running and striking the ball costs 10% more energy than running without striking the ball. While striking the ball, shuttle running on half-width court costs 14% more energy than running on full-width courts. The specificity of the oxygen uptake responses obtained for these various tennis drills gives an improved representation of their energy cost and could be used to optimize training loads.
On the interaction of electromagnetic waves with conductors
Authors: Paranjape B.V. , Paranjape M.B.
Published: August 2012

We study the interaction of electromagnetic waves with electrons. Our results can be applied to radio waves in the ionosphere or to lasers impinging on metals causing melting. We generalize the classical analysis of Zener to the case, which includes the interactions of the electrons with lattice vibrations or positive ions. We use the induced polarization to give a globally coherent and unifying analysis of the two cases: where collisions are important and where they are negligible.
TOLERANCE OF SCALE-FREE NETWORKS UNDER DEGREE SEGMENT PROTECTION AND REMOVAL
Authors: FU TAO , XU BO , ZHANG YONG-AN , CHEN YINI
Published: August 2012

We study the tolerance of scale-free networks (following a power-law distribution P(k) = c⋅kα) under degree segment protection and removal. We use percolation theory to examine analytically and numerically the critical node removal fraction pc required for the disintegration of the network as well as the critical node protection fraction ppc necessary to immunize the network against the disintegration. We show that when degree segment protection is prior to degree segment removal and 2 ≤ α ≤3, scale-free networks are quite robust due to the extremely low value of ppc. Meanwhile, if we protect a degree segment with a fixed fraction of nodes, the threshold pc has a generally downward trend as the degree sum of the segment decreases, but it is not strictly monotonic.
INTERACTIONS BETWEEN THE TIME-VARYING ELECTROMAGNETIC FIELD AND THE QUANTUM SOLITARY WAVE IN A FERROMAGNETIC CHAIN
Authors: LI DE-JUN , TANG YI
Published: August 2012

Starting with the Heisenberg Hamiltonian of the one-dimensional ferromagnetic chain in external fields, we have studied quantum characteristics of solitary waves and interactions between solitary waves and the time-varying electromagnetic field. It is shown that the energy and magnetic moments of the solitary wave are quantized. Utilizing these novel results, we have obtained the Bloch's equation of the two-level quantum solitary wave in a simple harmonic magnetic field.
ITERATIVE FEATURE PERTURBATION AS A GENE SELECTOR FOR MICROARRAY DATA
Authors: CANUL-REICH JUANA , HALL LAWRENCE O. , GOLDGOF DMITRY B. , KORECKI JOHN N. , ESCHRICH STEVEN
Published: August 2012

Gene-expression microarray datasets often consist of a limited number of samples with a large number of gene-expression measurements, usually on the order of thousands. Therefore, dimensionality reduction is critical prior to any classification task. In this work, the iterative feature perturbation method (IFP), an embedded gene selector, is introduced and applied to four microarray cancer datasets: colon cancer, leukemia, Moffitt colon cancer, and lung cancer. We compare results obtained by IFP to those of support vector machine-recursive feature elimination (SVM-RFE) and the t-test as a feature filter using a linear support vector machine as the base classifier. Analysis of the intersection of gene sets selected by the three methods across the four datasets was done. Additional experiments included an initial pre-selection of the top 200 genes based on their p values. IFP and SVM-RFE were then applied on the reduced feature sets. These results showed up to 3.32% average performance improvement for IFP across the four datasets. A statistical analysis (using the Friedman/Holm test) for both scenarios showed the highest accuracies came from the t-test as a filter on experiments without gene pre-selection. IFP and SVM-RFE had greater classification accuracy after gene pre-selection. Analysis showed the t-test is a good gene selector for microarray data. IFP and SVM-RFE showed performance improvement on a reduced by t-test dataset. The IFP approach resulted in comparable or superior average class accuracy when compared to SVM-RFE on three of the four datasets. The same or similar accuracies can be obtained with different sets of genes.
ISOGEOMETRIC DIVERGENCE-CONFORMING B-SPLINES FOR THE DARCY–STOKES–BRINKMAN EQUATIONS
Authors: EVANS JOHN A. , HUGHES THOMAS J. R.
Published: August 2012

We develop divergence-conforming B-spline discretizations for the numerical solution of the Darcy–Stokes–Brinkman equations. These discretizations are motivated by the recent theory of isogeometric discrete differential forms and may be interpreted as smooth generalizations of Raviart–Thomas elements. The new discretizations are (at least) patchwise C0 and can be directly utilized in the Galerkin solution of Darcy–Stokes–Brinkman flow for single-patch configurations. When applied to incompressible flows, these discretizations produce pointwise divergence-free velocity fields and hence exactly satisfy mass conservation. In the presence of no-slip boundary conditions and multi-patch geometries, the discontinuous Galerkin framework is invoked to enforce tangential continuity without upsetting the conservation or stability properties of the method across patch boundaries. Furthermore, as no-slip boundary conditions are enforced weakly, the method automatically defaults to a compatible discretization of Darcy flow in the limit of vanishing viscosity. The proposed discretizations are extended to general mapped geometries using divergence-preserving transformations. For sufficiently regular single-patch solutions, we prove a priori error estimates which are optimal for the discrete velocity field and suboptimal, by one order, for the discrete pressure field. Our estimates are in addition robust with respect to the parameters of the Darcy–Stokes–Brinkman problem. We present a comprehensive suite of numerical experiments which indicate optimal convergence rates for both the discrete velocity and pressure fields for general configurations, suggesting that our a priori estimates may be conservative. The focus of this paper is strictly on incompressible flows, but our theoretical results naturally extend to flows characterized by mass sources and sinks.
Discotic liquid crystals of transition metal complexes 46: mesomorphism and antagonist solubility of octaphenoxy-phthalocyaninato copper(II) complex substituted by oligoether chains
Authors: Sato Hiroyuki , Sakagami Yuya , Itoh Eiji , Ohta Kazuchika
Published: August 2012

We synthesized a novel discotic liquid crystalline compound, octakis[3-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)phenoxy]phthalocyaninato copper(II) (abbreviated as [m- MeO(EtO)3PhO]8PcCu ), and established the mesomorphism by using a differential scanning calorimeter, a polarizing optical microscope, and temperature-dependent wide angle X-ray diffraction diffractometer. Very interestingly, this [m- MeO(EtO)3PhO]8PcCu complex showed a hexagonal ordered columnar (Colho) mesophase in the virgin sample, whereas it showed a rectangular ordered columnar (Colro(P21/a)) mesophase in the non-virgin sample. The Colho mesophase gave a dimer stacking distance at 9.26 Å, whereas the Colro mesophase gave a short monomer stacking distance at 3.45 Å. Furthermore, this novel Pc derivative is readily soluble in polar solvents such as acetone, ethanol and methanol. Using antagonist solubilities of the present hydrophilic [m- MeO(EtO)3PhO]8PcCu derivative in a polar solvent and the previous hydrophobic (C10O)16TzCu derivative in the non-polar solvent, a p-n junction layered thin films could be successfully prepared.
IWASAWA THEORY FOR ONE-PARAMETER FAMILIES OF MOTIVES
Authors: BARTH PETER
Published: August 2012

In [A formulation of conjectures on p-adic zeta functions in non-commutative Iwasawa theory, in Proc. St. Petersburg Mathematical Society, Vol. 12, American Mathematical Society Translations, Series 2, Vol. 219 (American Mathematical Society, Providence, RI, 2006), pp. 1–85] Fukaya and Kato presented equivariant Tamagawa number conjectures that implied a very general (non-commutative) Iwasawa main conjecture for rather general motives. In this article we apply their methods to the case of one-parameter families of motives to derive a main conjecture for such families. On our way there we get some unconditional results on the variation of the (algebraic) λ- and μ-invariant. We focus on the results dealing with Selmer complexes instead of the more classical notion of Selmer groups. However, where possible we give the connection to the classical notions.
POLARIZED MORPHISMS BETWEEN ABELIAN VARIETIES
Authors: PAZUKI F.
Published: August 2012

In this paper, we will study the dynamical Manin–Mumford problem, focusing on the question of polarizability for endomorphisms of an abelian variety A and on the action of a Frobenius and its Verschiebung on the diagonal subvariety of A × A. We complete the study with different polarizability criteria.
CMOS LC voltage controlled oscillator design using multiwalled and single-walled carbon nanotube wire inductors
Authors: Srivastava Ashok , Xu Yao , Liu Yang , Sharma Ashwani K. , Mayberry Clay
Published: August 2012

We have utilized our Multiwalled Carbon NanoTube (MWCNT) and Single-Walled Carbon NanoTube (SWCNT) bundle interconnects model in a widely used π model to study the performances of MWCNT and SWCNT bundle wire inductors and compared these with copper (Cu) inductors. The calculation results show that the Q-factors of Carbon NanoTube (CNT) wire (SWCNT bundle and MWCNT) inductors are higher than that of the Cu wire inductor. This is mainly due to much lower resistance of CNT and negligible skin effect in carbon nanotubes at higher frequencies. The application of CNT wire inductor in LC VCO is also studied and the Cadence/Spectre simulations show that VCOs with CNT bundle wire inductors have significantly improved performance such as the higher oscillation frequency and lower phase noise due to their smaller resistances and higher Q-factors. It is also noticed that CMOS LC VCO using a SWCNT bundle wire inductor has better performance when compared with the performance of LC VCO using the MWCNT wire inductor due to its lower resistance and higher Q-factor.
Dynamic clock stretching for variation compensation in VLSI circuit design
Authors: Mahalingam Venkataraman , Ranganathan Nagarajan , Hyman Ransford
Published: August 2012

In the nanometer era, process, voltage, and temperature variations are dominating circuit performance, power, and yield. Over the past few years, statistical optimization methods have been effective in improving yield in the presence of uncertainty due to process variations. However, statistical methods overconsume resources, even in the absence of variations. Hence, to facilitate a better performance-power-yield trade-off, techniques that can dynamically enable variation compensation are becoming necessary. In this article, we propose a dynamic technique that controls the instance of data capture in critical path memory flops, by delaying the clock edge trigger. The methodology employs a dynamic delay detection circuit to identify the uncertainty in delay due to variations and stretches the clock in the destination flip-flops. The delay detection circuit uses a latch and set of combinational gates to dynamically detect and create the slack needed to accommodate the delay due to variations. The Clock Stretching Logic (CSL) is added only to paths, which have a high probability of failure in the presence of variations. The proposed methodology improves the timing yield of the circuit without significant overcompensation. The methodology approach was simulated using Synopsys design tools for circuit synthesis and Cadence tools for placement and routing of the design. Extraction of parasitic of timing information was parsed using Perl scripts and simulated using a simulation program generated in C++. Experimental results based on Monte-Carlo simulations on benchmark circuits indicate considerable improvement in timing yield with negligible area overhead.
An efficient heuristic to identify threshold logic functions
Authors: Palaniswamy Ashok Kumar , Tragoudas Spyros
Published: August 2012

A fast method to identify the given Boolean function as a threshold function with weight assignment is introduced. It characterizes the function based on the parameters that have been defined in the literature. The proposed method is capable to quickly characterize all functions that have less than eight inputs and has been shown to operate fast for functions with as many as forty inputs. Furthermore, comparisons with other existing heuristic methods show huge increase in the number of threshold functions identified, and drastic reduction in time and complexity.
Effect of process variations in 3D global clock distribution networks
Authors: Xu Hu , Pavlidis Vasilis F. , De Micheli Giovanni
Published: August 2012

In three-dimensional (3D) integrated circuits, the effect of process variations on clock skew differs from 2D circuits. The combined effect of inter-die and intra-die process variations on the design of 3D clock distribution networks is considered in this article. A statistical clock skew model incorporating both the systematic and random components of process variations is employed to describe this effect. Two regular 3D clock tree topologies are investigated and compared in terms of clock skew variation. The statistical skew model used to describe clock skew variations is verified through Monte-Carlo simulations. The clock skew is shown to change in different ways with the number of planes forming the 3D IC and the clock network architecture. Simulations based on a 45-nm CMOS technology show that the maximum standard deviation of clock skew can vary from 15 ps to 77 ps. Results indicate that simply increasing the number of planes of a 3D IC does not necessarily lead to lower skew variation and higher operating frequencies. A multigroup 3D clock tree topology is proposed to effectively mitigate the variability of clock skew. Tradeoffs between the investigated 3D clock distribution networks and the number of planes comprising a 3D circuit are discussed and related design guidelines are offered. The skew variation in 3D clock trees is also compared with the skew variation of clock grids.
Spatial and temporal thermal characterization of stacked multicore architectures
Authors: Kursun Eren , Wakil Jamil , Farooq Mukta , Hannon Robert
Published: August 2012

Three-dimensional integration provides a new way of performance growth for microprocessor architectures. While a recent studies report promising performance improvement numbers, majority of the processor stacking options are thermally-limited. Elevated stack temperatures have significant effect on the overall energy efficiency and reliability of the processor; they also limit the potential peak performance improvement from the 3D implementation. Thermal characteristics of 3D stacks differ from 2D processors in various ways including: the nature of heat dissipation throughout the stack, thermal conductivity of the 3D structures such as micro-C4 layers, and hotspot interactions among layers. The intensity of the corresponding thermal problems is highly dependent on the 3D technology, processor and stack parameters. In this study we focus on spatial and temporal thermal characteristics of 3D multicore architectures using high-fidelity technology and processor models. Our experimental results highlight the need for integrating detailed thermal models in the design flow, starting with the early design stages. In addition, the reduced time constants and elevated on-chip temperatures indicate faster response time requirements for dynamic thermal management in processor stacking options.
A brief survey of automatic methods for author name disambiguation
Authors: Ferreira Anderson A. , Gonçalves Marcos André , Laender Alberto H.F.
Published: August 2012

Name ambiguity in the context of bibliographic citation records is a hard problem that affects the quality of services and content in digital libraries and similar systems. The challenges of dealing with author name ambiguity have led to a myriad of disambiguation methods. Generally speaking, the proposed methods usually attempt to group citation records of a same author by finding some similarity among them or try to directly assign them to their respective authors. Both approaches may either exploit supervised or unsupervised techniques. In this article, we propose a taxonomy for characterizing the current author name disambiguation methods described in the literature, present a brief survey of the most representative ones and discuss several open challenges.
SIGCSE symposium Kids' Camp
Authors: Fox Susan , Pulimood Sarah Monisha
Published: August 2012

At the 2012 conference in Raleigh, SIGCSE sponsored the fifth Kids' Camp, a childcare and educational experience provided to SIGCSE conference attendees. Professional caregivers planned games and craft activities for the younger campers. Older ones learned to use kid-oriented software to create animations and games; these computer-oriented activities connect the campers to the overall purpose of the conference.
SIGCSE chair's annual report
Authors: McCauley Renee
Published: August 2012

At the end of each year (July 1- June 30) ACM asks each SIG for information about awards given, significant papers published, significant programs, and key issues the SIG expects to face over the next three years. Here are highlights from the report.
ACM Turing centenary celebration
Authors: Owens Barbara Boucher
Published: August 2012

The ACM held its Turing Centenary Celebration on June 15 and 16 in San Francisco. Thirty-two recipients of the Turing Award, computer science's equivalent of the Nobel Prize, attended the conference, and many of them spoke. To be surrounded by so many heroes and heroines of our discipline was amazing.
NCWIT, from a SIGCSE perspective
Authors: Alvarado Christine
Published: August 2012

The National Center for Women & Information Technology (NCWIT) held its annual summit May 22-24, 2012 in Chicago, IL. As always, the overlap between Summit attendees and SIGCSE members was high, and SIGCSE members got a lot out of their experiences at the Summit. I asked two SIGCSE members to share their experience for those who have never been to an NCWIT Summit.
An Analytical Approach to the Analysis of Inhomogeneous Pipes under External Pressure
Authors: Fraldi Massimiliano , Guarracino Federico
Published: August 2012

Pipes for deep‐water applications possess a diameter‐to‐thickness ratio in a region where failure is dominated by both instability and plastic collapse. This implies that prior to failure the compressive yield strength of the material must be exceeded, followed by ovalisation and further local yielding. This paper presents an investigation into the mechanics of this specific problem and develops an analytical approach that accounts for the effects of geometrical and material data on the collapse pressure of inhomogeneous rings under external hydrostatic pressure. The analytical expressions have been correlated to numerical and experimental test data, proving their accuracy.
New Preconditioners with Two Variable Relaxation Parameters for the Discretized Time‐Harmonic Maxwell Equations in Mixed Form
Authors: Zeng Yuping , Li Chenliang
Published: August 2012

We provide new preconditioners with two variable relaxation parameters for the saddle point linear systems arising from finite element discretization of time‐harmonic Maxwell equations in mixed form. The new preconditioners are of block‐triangular forms and Schur complement‐free. They are extensions of the results in Cheng et al., 2009, Grief and Schötzau, 2007, and Huang et al., 2009. Theoretical analysis shows that all eigenvalues of the preconditioned matrices are tightly clustered, and numerical tests confirm our analysis.
Computerized Segmentation and Characterization of Breast Lesions in Dynamic Contrast-Enhanced MR Images Using Fuzzy c-Means Clustering and Snake Algorithm
Authors: Pang Yachun , Li Li , Hu Wenyong , Peng Yanxia , Liu Lizhi , Shao Yuanzhi
Published: August 2012

This paper presents a novel two-step approach that incorporates fuzzy c-means (FCMs) clustering and gradient vector flow (GVF) snake algorithm for lesions contour segmentation on breast magnetic resonance imaging (BMRI). Manual delineation of the lesions by expert MR radiologists was taken as a reference standard in evaluating the computerized segmentation approach. The proposed algorithm was also compared with the FCMs clustering based method. With a database of 60 mass-like lesions (22 benign and 38 malignant cases), the proposed method demonstrated sufficiently good segmentation performance. The morphological and texture features were extracted and used to classify the benign and malignant lesions based on the proposed computerized segmentation contour and radiologists’ delineation, respectively. Features extracted by the computerized characterization method were employed to differentiate the lesions with an area under the receiver-operating characteristic curve (AUC) of 0.968, in comparison with an AUC of 0.914 based on the features extracted from radiologists’ delineation. The proposed method in current study can assist radiologists to delineate and characterize BMRI lesion, such as quantifying morphological and texture features and improving the objectivity and efficiency of BMRI interpretation with a certain clinical value.