bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamics of Congruent Oxidation
Authors: Jacob K.T. , Adharsh R. 
Published: September 2012

AbstractCongruent oxidation occurs when an alloy oxidizes at constant oxygen chemical potential and temperature to an oxide in which the ratio of metallic components is the same as in the alloy. In alloys that undergo congruent oxidation concentration gradients near the surface are minimized. In this work thermodynamic conditions for congruent oxidation of binary and ternary alloys are formulated using the regular solution model to describe thermodynamic mixing properties. The conditions under which congruent oxidation can occur are identified. Congruent oxidation of a binary alloy X-Y will occur only if difference in oxygen potential for the oxidation of the two pure metals is less than twice the difference in regular solution parameters for the oxide and alloy phases (Ω0 − ΩA). In the case of ternary alloys, congruency requirements for both two-phase and three-phase equilibria are discussed. Since the conditions for congruent oxidation of ternary alloy X-Y-Z depends on many parameters, the effect of systematic variation of the binary sets of regular solution parameters on the congruent composition is explored by numerical solution of the governing equations.
Thermodynamic Properties of Solid Solutions between Di-calcium Silicate and Tri-calcium Phosphate
Authors: Hasegawa M. , Kashiwaya Y. , Iwase M. 
Published: September 2012

AbstractFor a better understanding of phosphorus removal from hot metal, the Gibbs free energies of solid solutions between di-calcium silicate and tri-calcium phosphate were derived through applications of solutions models. The regular solution model with the parameters determined in this study gave the activities of the components thermodynamically consistent with the literature data and the phase diagrams.
Electronic Cigarette Use Among Teenagers and Young Adults in Poland
Authors: Goniewicz Maciej Lukasz , Zielinska-Danch Wioleta 
Published: September 2012

BACKGROUND:
Electronic cigarettes (e-cigarettes) are battery-powered devices developed with the goal of mimicking the action of smoking, including nicotine delivery, without the toxic effects of tobacco smoke. Little is known about the uptake of e-cigarettes among young people.

METHODS:
A survey was conducted with a cluster sample of 20 240 students enrolled at 176 nationally representative Polish high schools and universities between September 2010 and June 2011. We estimated national e-cigarette prevalence among various demographic groups by using population weights. Multiple logistic regression was used to evaluate which demographic factors were independent predictors of 2 outcomes: ever use of e-cigarettes and use in the previous 30 days.

RESULTS:
Among high school students, aged 15 to 19 years, 23.5% had ever used e-cigarettes and 8.2% had done so within the previous 30 days. Among those in universities, aged 20 to 24 years, 19.0% had ever used an e-cigarette and 5.9% had done so in the previous 30 days. In multivariate analyses that controlled for covariates, smoking cigarettes, male gender, living in an urban area, and having parents who smoke were associated with ever use of e-cigarettes. Overall, 3.2% of never smoking students reported ever use of e-cigarettes.

CONCLUSIONS:
About one-fifth of Polish youth have tried e-cigarettes; most of them had previously smoked cigarettes. It is unclear whether e-cigarettes are just a novelty that young people try only once or whether they have potential to compete in the marketplace with conventional cigarettes.
Pediatric Residents’ Knowledge, Use, and Comfort With Expedited Partner Therapy for STIs
Authors: Hsii Anne , Hillard Paula , Yen Sophia , Golden Neville H. 
Published: September 2012

OBJECTIVE:
We examined California pediatric residents' knowledge, practices, and comfort of providing expedited partner therapy (EPT) for sexually transmitted infections, by postgraduate year of training and presence of an adolescent medicine fellowship. We hypothesized that few residents are aware of EPT, and fewer are comfortable providing it; knowledge, practices, and comfort increase during residency; and presence of an adolescent medicine fellowship increases knowledge, practices, and comfort.

METHODS:
Online anonymous questionnaires were completed by pediatric residents from 14 California programs.

RESULTS:
Two hundred eighty-nine pediatric residents (41% response; mean age, 29.4 ± 2.7 years; 78% female) responded. Twenty-two percent reported being moderately or very familiar with EPT. Most correctly identified several EPT methods. Incorrectly identified as EPT included patient (55%), health department (42%), and provider (37%) referrals. Only 8% were aware of California’s legal status regarding EPT. Sixty-nine percent knew that California law allows EPT for chlamydia and gonorrhea, but 38% incorrectly stated that EPT can be used to treat trichomoniasis. Fifty-two percent reported ever providing EPT, but 30% of them were uncomfortable doing so. Postgraduate year 1 residents were significantly more likely to report lack of experience as a barrier to prescribing EPT. Residents in programs with the presence of an adolescent medicine fellowship had significantly higher global knowledge scores and were more likely to practice EPT with fewer concerns.

CONCLUSIONS:
California pediatric residents have knowledge gaps and discomfort providing EPT, and the presence of adolescent medicine fellowship is associated with increased EPT knowledge, use, and comfort among residents. Our findings demonstrate a need to improve EPT education in pediatric residencies.
Sexually Explicit Cell Phone Messaging Associated With Sexual Risk Among Adolescents
Authors: Rice Eric , Rhoades Harmony , Winetrobe Hailey , Sanchez Monica , Montoya Jorge , Plant Aaron , Kordic Timothy 
Published: September 2012

OBJECTIVES:
Sexting (sending/receiving sexually explicit texts and images via cell phone) may be associated with sexual health consequences among adolescents. However, to date, no published data from a probability-based sample has examined associations between sexting and sexual activity.

METHODS:
A probability sample of 1839 students was collected alongside the 2011 Youth Risk Behavior Survey in Los Angeles high schools. Logistic regressions were used to assess the correlates of sexting behavior and associations between sexting and sexual risk-taking.

RESULTS:
Fifteen percent of adolescents with cell phone access reported sexting, and 54% reported knowing someone who had sent a sext. Adolescents whose peers sexted were more likely to sext themselves (odds ratio [OR] = 16.87, 95% confidence interval [CI]: 9.62–29.59). Adolescents who themselves sexted were more likely to report being sexually active (OR = 7.17, 95% CI: 5.01–10.25). Nonheterosexual students were more likely to report sexting (OR = 2.74, 95% CI: 1.86–4.04), sexual activity (OR = 1.52, 95% CI: 1.07–2.15), and unprotected sex at last sexual encounter (OR = 1.84, 95% CI: 1.17–2.89).

CONCLUSIONS:
Sexting, rather than functioning as an alternative to “real world” sexual risk behavior, appears to be part of a cluster of risky sexual behaviors among adolescents. We recommend that clinicians discuss sexting as an adolescent-friendly way of engaging patients in conversations about sexual activity, prevention of sexually transmitted infections, and unwanted pregnancy. We further recommend that discussion about sexting and its associated risk behavior be included in school-based sexual health curricula.
Elastic Self-Sealing Cement and Swellable Packer Tool Provides Competent Zonal Isolation to Withstand the Stress Regimes during the Life of the Well: Ecuador Case History
Authors: Carrión Carlos , Astudillo Leonardo , Cayo Marco 
Published: September 2012

Abstract
Highly deviated or horizontal wells are usually drilled to improve the productivity of a field where long-term zonal isolation is essential to helping ensure the economic viability for the life of the well. This paper describes the use of two new technologies designed to help improve zonal isolation in extreme conditions of the well:Cement with elastic and self-sealing properties to help prevent the formation of a microannulus and help ensure complete zonal isolation. This is accomplished either by resilient deformation while the cement is under stress or by swelling of additives in the cement when in the presence of hydrocarbons, depending on the situation of the well.A swellable packer tool (water swellable), located just below the upper aquifers.
This paper discusses the application of cementing technologies that can be used to minimize interventions for maintenance, and possibly prevent the need to repair unwanted communication between zones. This study also is complemented with simulations based on finite element analysis (FEA), which helps predict the various stresses that the cement sheath will be subjected to during the life of the well and help identify the mechanical properties that the cement sheath will need to prevent cement failure in the stages of curing, pressure testing, hydraulic fracturing, completion, and during production of the well.
Differing Relations to Early Atherosclerosis between Vitamin C from Supplements vs. Food in the Los Angeles Atherosclerosis Study: A Prospective Cohort Study
Authors: Agarwal Megha , Mehta Puja K , Dwyer James H , Dwyer Kathleen M , Shircore Anne M , Nordstrom Cheryl K , Sun Ping , Paul-Labrador Maura , Yang Yuching , Merz C. Noel Bairey 
Published: September 2012

Objective:To determine the relationship of vitamin c intake from supplements vs food on early atherosclerosis detected by carotid intima media thickness (IMT).Background:Oxidative stress and endothelial dysfunction play a critical role in the pathogenesis of atherosclerosis. Dietary vitamin C appears to have anti-oxidant properties and beneficial relations to endothelial function, yet vitamin C taken as a vitamin supplement does not appear to protect from cardiovascular events. The impact of vitamin c intake from supplements vs food on progression of atherosclerosis is unknown.Methods:We examined 3-year progression of carotid IMT in a randomly sampled cohort of 573 healthy women and men aged 40-60 years. Progression of carotid IMT was determined bilaterally with B-mode ultrasound at 3 examinations (1.5-year intervals). Intake of dietary vitamin C was measured by six, 24-hour recall interviews. Intake of vitamin C from vitamin supplements was measured by questionnaire in quartiles of supplement intake and no supplement. Vitamin C wasmeasured in plasma as ascorbic acid.Results:Carotid IMT progressed 10.0±16.5 μm/year (mean±SD) among all those with follow-up (n=500; 87%). For those who took vitamin C supplements, carotid IMT progression increased with dose (p-trend=0.0009). Among persons in the highest quartile (857-5000 mg/day) of vitamin C supplement intake compared to those not consuming any vitamin C supplements, carotid IMT progression increased three-fold (20.3±2.6 versus 7.6±1.8 μm/year (mean±SD); p<0.001). The adverse association of vitamin C supplement intake with carotid IMT was two-fold greater in the upper tertile of serum cholesterol compared to the lower two tertiles (p=0.01). In contrast to the adverse association of vitamin C supplements, vitamin C intake from food had a weak protective relationship on carotid IMT progression (reduced progression -5.0±1.9 μm/year; p=0.008).Conclusions:Vitamin C supplementation is associated with accelerated early atherosclerosis measured by carotid IMT compared to a protective association with vitamin C from food. Theadverse association of vitamin C supplementation may be greater in patients with higher serum cholesterol levels. The current results provide a potential mechanistic understanding for the observed differences between Vitamin C in supplements vs food in prior studies. Given these observations,vitamin C supplementation does not appear to be currently advisable for prevention or treatment of atherosclerosis.
Synergistic Effect of TGF-β1 And BMP–7 on Chondrogenesis and Extracellular Matrix Synthesis: An In Vitro Study
Authors: Gokce Alper , Yilmaz Ibrahim , Bircan Rifat , Tonbul Murat , Gokay Nevzat Selim , Gokce Cigdem 
Published: September 2012

Introduction:The purpose of the present study seeks to determine the signal timing of BMP–7 and TGF-β1 from a novel chitosan based hydrogel system that may affect chondrocyte proliferation resulting in the presence of a synergism seen conspicuously in consecutive controlled delivery.Methods:Four groups of cultured chondrocytes were seeded on a novel designed chitosan based hydrogel. The hydrogel was left empty (control) in one group and loaded with BMP–7, TGF-β1 and their combination in the other groups, respectively. Hydrogel structure was analyzed with scanning electron microscope. The release kinetics of Growth Factors (GFs) was determined with ELISA. Chondrocyte viability and toxicity after being tested with MTS and collagen type II synthesis, were quantified with western blotting. Canonical regression analysis was used for measuring statistical evaluation.Results:Chitosan based hydrogel allowed controlled release of GFs in different time intervals for BMP–7 and TGF-β1. Double peak concentration gradient was found to be present in the group loaded with both GFs. In this group, substantially higher chondrocyte growth and collagen synthesis were also detected.Conclusions:We concluded that, chitosan based hydrogel systems may be adjusted to release GFs consecutively during biodegradation at the layers of surface, which may increase the cell number and enhance collagen type II synthesis.
Auditing National HIV Guidelines and Policies: The United Kingdom CD4 Surveillance Scheme
Authors: Brown Alison E , Kall Meaghan M , Smith Ruth D , Yin Zheng , Hunter Alan , Hunter Alan , Delpech Valerie C 
Published: September 2012

The United Kingdom’s CD4 surveillance scheme monitors CD4 cell counts among HIV patients and is a national resource for HIV surveillance. It has driven public health policy and allowed auditing of national HIV testing, treatment and care guidelines.We demonstrate its utility through four example outputs: median CD4 count at HIV diagnosis; late HIV diagnosis and short-term mortality; the timing of first CD4 count to indicate entry into HIV care; and the proportion of patients with CD4 counts <350 cells/mm3 receiving anti-retroviral therapy (ARV).In 2009, 95% (61,502/64,420) of adults living with diagnosed HIV infection had CD4 counts available. The median CD4 count at diagnosis increased from 276 to 335 cells/mm3 between 2000 and 2009, indicating modest improvements in HIV testing. In 2009, 52% of patients were diagnosed at a late stage of HIV infection (CD4 <350 cells/mm3); these individuals had a ten-fold risk of dying within a year of their diagnosis compared to those diagnosed promptly. In 2008, the national target of performing a CD4 count within 14 days of diagnosis was met for 61% of patients. National treatment guidelines have largely been met with 83% patients with CD4 <350 cells/mm3receiving ARV.The monitoring of CD4 counts is critical to HIV surveillance in the United Kingdom enabling the close monitoring of efforts to reduce morbidity and mortality associated with late diagnosis and underpins the auditing of policies and guidelines. These routine surveillance outputs can be generated at national and local levels to drive and monitor public health policy and prevention efforts.
Regional Differences Among HIV Patients in Care: California Medical Monitoring Project Sites, 2007-2008
Authors: Scheer Susan , Hughes Alison J , Tejero Judith , Damesyn Mark A , Mark Karen E , Arguello Tyler M , Wohl Amy R 
Published: September 2012

Introduction:
The Medical Monitoring Project (MMP) is a national, multi-site population-based supplemental HIV/AIDS surveillance project of persons receiving HIV/AIDS care. We compared California MMP data by region. Demographic characteristics, medical care experiences, HIV treatment, clinical care outcomes, and need for support services are described.

Methods:
HIV-infected patients 18 years or older were randomly selected from medical care facilities. In person structured interviews from 2007 - 2008 were used to assess sociodemographic characteristics, self-reported clinical outcomes, and need for supportive services. Pearson chi-squared, Fisher’s exact and Kruskal-Wallis p-values were calculated to compare regional differences.

Results:
Between 2007 and 2008, 899 people were interviewed: 329 (37%) in San Francisco (SF), 333 (37%) in Los Angeles (LA) and 237 (26%) in other California counties. Significant regional sociodemographic differences were found. Care received and clinical outcomes for patients in MMP were positive and few regional differences were identified. HIV case management (36%), mental health counseling (35%), and dental services (29%) were the supportive services patients most frequently needed. Unmet needs for supportive services were low overall. Significant differences by region in needed and unmet need services were identified.

Discussion:
The majority of MMP respondents reported standard of care CD4 and viral load monitoring, high treatment use, undetectable HIV viral loads and CD4 counts indicative of good immune function and treatment efficacy. Information from MMP can be used by planning councils, policymakers, and HIV care providers to improve access to care and prevention. Identifying regional differences can facilitate sharing of best practices among health jurisdictions.
The Cardiac Anxiety Questionnaire: Cross-Validation among Cardiac Inpatients
Authors: Van Beek M. H. C. T. , Voshaar R. C. Oude , Van Deelen F. M. , Van Balkom A. J. L. M. , Pop G. , Speckens A. E. M. 
Published: September 2012

Objective: General anxiety symptoms are common in patients with cardiac disease and considered to have an adverse effect on cardiac prognosis. The role of specific cardiac anxiety, however, is still unknown. The aim of this study is to examine the factor structure, reliability, and validity of the Dutch version of the Cardiac Anxiety Questionnaire (CAQ), which was specifically designed to assess heart focused anxiety. Methods: Two hundred thirty-seven patients admitted for an acute coronary syndrome (ACS) and a control group of 49 patients admitted for an exacerbation of rheumatoid arthritis (RA) completed the CAQ, the Agoraphobic Cognitions Questionnaire, Mobility Inventory, Beck Depression Inventory, Beck Anxiety Inventory, and the State-Trait Anxiety Inventory. Results: Although the original three-factor solution (fear, avoidance, and attention) was acceptable (model fit parameters: CFI=0.89 and TLI=0.87), our data were best explained by a four-factor model including safety seeking behaviors. Internal consistency and test-retest reliability were good. The CAQ had moderate correlations with the other anxiety and depression questionnaires. Recently admitted ACS patients had significantly higher scores than RA patients, even after controlling for general anxiety and depressive symptoms ( p < 0.001). Conclusion: The CAQ is a reliable and valid instrument to assess cardiac anxiety in patients hospitalized with ACS. These results enable longitudinal studies to examine the relationship of heart-focused anxiety with cardiac prognosis and to evaluate interventions specifically targeted at anxiety in cardiac patients.
Estimation of Stiffness and Energy Dissipation for the Models of Reinforced-Concrete Composite Slabs Based on the Investigations of Statically Loaded Slabs
Authors: Gromysz K. 
Published: September 2012

Abstract Reinforced concrete composite slab consists of a thin prefabricated slab in which span reinforcement is located and of concrete joined with the slab, with such concrete being laid on site.The existence of a joint of two concretes in such floors is interpreted as introducing a contact layer into a monolithic slab. In the paper parameters of two models are estimated. The first is a model of a contact layer and the second is a model of a composite slab with a single degree of freedom. The models consider that the contact has elastic properties and inelastic properties causing energy dissipation. Experimental investigations are discussed further based on which the parameters values of the contact layer model were determined.Delamination was experienced for the slabs characterised by low contact layer stiffness after applying a maximum load. In addition, the strains of a contact layer having low stiffness are accompanied by lower energy dissipation than of a layer with high stiffness.The smaller stiffness of composite floors, as compared to monolithic floors, occurs as a consequence of the existence of a joint. Such decrease for a composite slab is interpreted in the model with a single degree of freedom as the serial connection of stiffness of a monolithic slab and an element considering the existence of a contact layer.The stiffness of an element considering the existence of a contact layer decreases along with a load, and the elements corresponding to the higher stiffness of the contact layer are characterised by higher energy dissipation.The aforementioned results of the investigations confirm the assumptions of the contact layer model and a composite slab model with a single degree of freedom. The findings made represent a basis for establishing a method of evaluating the condition of a joint in composite slabs according to statistical investigations.
Performance of a Voltage Step-Up/Step-Down Transformerless DC/DC Converter: Analytical Model
Authors: Suskis P. , Rankis I. 
Published: September 2012

Performance of a Voltage Step-Up/Step-Down Transformerless DC/DC Converter: Analytical Model
The authors present an analytical model for a voltage step-up/step-down DC/DC converter without transformers. The proposed topology is a combination of classic buck and boost converters in one single circuit but with differing operational principles. The converter is developed for a wind power autonomous supply system equipped with a hydrogen electrolytic tank and a fuel cell for energy stabilization. The main power source of the hydrogen-based autonomous supply system is energized by a synchronous generator operating on permanent magnets and equipped with a diode bridge. The input voltage of the converter in this case varies in the range 0-700 V, while its output DC voltage must be 540 V according to the demand of other parts of the system. To maintain the rated voltage, a special electrical load regulation is introduced. The calculations of the converter, the generator (equipped with a diode bridge) as element of the power system supply joint, and the load replaced by resistance are verified with PSIM software.
Reducing Oscillations During Positioning of A Servomechanism Having Flexibility
Authors: Hubinský Peter , Häuptle Peter 
Published: September 2012

Reducing Oscillations During Positioning of A Servomechanism Having FlexibilityThis contribution describes the method of harmonic modulation of a velocity set-point signal in control to reduce undesirable oscillations. Especially the combination of this method with the well known input shaping method is of interest. Such a solution seeks for instance to a control structure used for servomechanisms equipped with a gear-box or namely mechatronic drives (MDs); where undesirable oscillations in transient- as well as semi-steady-states could arise. The combination of the methods has been proofed under real conditions in an experimental setup. Based on this, simulations regarding different industry demands and the proper choice of the modulation signal types will be introduced. Further it will be discussed which modulation signal should be used for the correspondingieindustrial demands. Both proposed methods are in the category of feed-forward-control which led to a practical implementation where no additional sensor (for measuring these undesirable effects) is needed to improve the system dynamics.