200 research outputs found
Soliton solutions in an effective action for SU(2) Yang-Mills theory: including effects of higher-derivative term
The Skyrme-Faddeev-Niemi (SFN) model which is an O(3) model in three
dimensional space upto fourth-order in the first derivative is regarded as a
low-energy effective theory of SU(2) Yang-Mills theory. One can show from the
Wilsonian renormalization group argument that the effective action of
Yang-Mills theory recovers the SFN in the infrared region. However, the thoery
contains an additional fourth-order term which destabilizes the soliton
solution. In this paper, we derive the second derivative term perturbatively
and show that the SFN model with the second derivative term possesses soliton
solutions.Comment: 7 pages, 3 figure
The Semi-Classical Relativistic Darwin Potential for Spinning Particles in the Rest-Frame Instant Form: 2-Body Bound States with Spin 1/2 Constituents
In the semiclassical approximation of Grassmann-valued electric charges for
regularizing Coulomb self-energies, we extract the unique
acceleration-independent interaction hidden in any Lienard-Wiechert solution
for the system of N positive-energy spinning particles plus the electromagnetic
field in the radiation gauge of the rest-frame instant form. With the help of a
semiclassical Foldy-Wouthuysen transformation, this allows us to find the
relativistic semiclassical Darwin potential. In the 2-body case the
quantization of the lowest order reproduces exactly the results from the
reduction of the Bethe-Salpeter equation.Comment: 102 pages, revtex fil
Miscibility studies of two twist-bend nematic liquid crystal dimers with different average molecular curvatures. A comparison between experimental data and predictions of a Landau mean-field theory for the NTB-N phase transition
We report a calorimetric study of a series of mixtures of two twist-bend liquid crystal dimers, the 1'',7''-bis(4-cyanobiphenyl)-4'-yl heptane (CB7CB) and 1''-(2',4-difluorobiphenyl-4'-yloxy)-9''-(4-cyanobiphenyl-4'-yloxy) nonane (FFO9OCB), the molecules of which have different effective molecular curvatures. High-resolution heat capacity measurements in the vicinity of the NTB-N phase transition for a selected number of binary mixtures clearly indicate a first order NTB-N phase transition for all the investigated mixtures, the strength of which decreases when the nematic range increases. Published theories predict a second order NTB-N phase transition, but we have developed a self-consistent mean field Landau model using two key order parameters: A symmetric and traceless tensor for the orientational order and a short-range vector field which is orthogonal to the helix axis and rotates around of the heliconical structure with an extremely short periodicity. The theory, in its simplified form, depends on two effective elastic constants and explains satisfactorily our heat capacity measurements and also predicts a first-order NTB-N phase transition. In addition, as a complementary source of experimental measurements, the splay (K1) and bend (K3) elastic constants in the conventional nematic phase for the pure compounds and some selected mixtures have been determined.Postprint (author's final draft
In-situ high-temperature EXAFS measurements on radioactive and air-sensitive molten salt materials
The development at the Delft University of Technology (TU Delft, The Netherlands) of an experimental set-up dedicated to high-temperature in situ EXAFS measurements of radioactive, air-sensitive and corrosive fluoride salts is reported. A detailed description of the sample containment cell, of the furnace design, and of the measurement geometry allowing simultaneous transmission and fluorescence measurements is given herein. The performance of the equipment is tested with the room-temperature measurement of thorium tetrafluoride, and the Th—F and Th—Th bond distances obtained by fitting of the EXAFS data are compared with the ones extracted from a refinement of neutron diffraction data collected at the PEARL beamline at TU Delft. The adequacy of the sample confinement is checked with a mapping of the thorium concentration profile of molten salt material. Finally, a few selected salt mixtures (LiF:ThF4) = (0.9:0.1), (0.75:0.25), (0.5:0.5) and (NaF:ThF4) = (0.67:0.33), (0.5:0.5) are measured in the molten state. Qualitative trends along the series are discussed, and the experimental data for the (LiF:ThF4) = (0.5:0.5) composition are compared with the EXAFS spectrum generated from molecular dynamics simulations
Occupational exposure to nano-TiO2 in the life cycle steps of new depollutant mortars used in construction
The present work is focused on the measurement of workers exposure to nano-TiO2
in the life cycle steps of depollutant mortars. It has been done in the framework of the
SCAFFOLD project, which aims at the management of potential risks arising from the use of
manufactured nanomaterials in construction. Main findings can be summarized as follows: (1)
The occupational exposure to nano- TiO2 is below 0.3 mg/m3 for all measured scenarios. The
highest concentrations were measured during the cleaning task (in the nano- TiO2
manufacturing process) and during the application (spraying) of depollutant coatings on a wall.
(2) It was found a high release of particles above the background in several tasks as expected
due to the nature of the activities performed. The maximum concentration was measured
during drilling and during adding powder materials (mean total particle concentration up to
5.591E+04 particles/cm3 and 5.69E+04 particles/cm3). However, considering data on total
particle concentration released, no striking differences have been observed when tasks have
been performed using conventional materials in the sector (control) and when using materials
doped with nano-objects.European Commission's FP
Correlates of tobacco cessation counseling among Hispanic physicians in the US: a cross-sectional survey study.
BACKGROUND: Physician advice is an important motivator for attempting to stop smoking. However, physicians\u27 lack of intervention with smokers has only modestly improved in the last decade. Although the literature includes extensive research in the area of the smoking intervention practices of clinicians, few studies have focused on Hispanic physicians. The purpose of this study was to explore the correlates of tobacco cessation counseling practices among Hispanic physicians in the US.
METHODS: Data were collected through a validated survey instrument among a cross-sectional sample of self-reported Hispanic physicians practicing in New Mexico, and who were members of the New Mexico Hispanic Medical Society in the year 2001. Domains of interest included counseling practices, self-efficacy, attitudes/responsibility, and knowledge/skills. Returned surveys were analyzed to obtain frequencies and descriptive statistics for each survey item. Other analyses included: bivariate Pearson\u27s correlation, factorial ANOVAs, and multiple linear regressions.
RESULTS: Respondents (n = 45) reported a low level of compliance with tobacco control guidelines and recommendations. Results indicate that physicians\u27 familiarity with standard cessation protocols has a significant effect on their tobacco-related practices (r = .35, variance shared = 12%). Self-efficacy and gender were both significantly correlated to tobacco related practices (r = .42, variance shared = 17%). A significant correlation was also found between self-efficacy and knowledge/skills (r = .60, variance shared = 36%). Attitudes/responsibility was not significantly correlated with any of the other measures.
CONCLUSION: More resources should be dedicated to training Hispanic physicians in tobacco intervention. Training may facilitate practice by increasing knowledge, developing skills and, ultimately, enhancing feelings of self-efficacy
Cardiovascular Screening Practices and Statin Prescription Habits in Patients with Psoriasis among Dermatologists, Rheumatologists and Primary Care Physicians
Patients with psoriasis have a higher prevalence of cardiovascular risk factors. This study evaluated cardio-vascular screening practices and statin prescribing habits among dermatologists, rheumatologists and primary care physicians (PCPs) through an online questionnaire, which was distributed through the Spanish scientific societies of the above-mentioned specialties. A total of 299 physicians (103 dermatologists, 94 rheumatologists and 102 PCPs) responded to the questionnaire. Of these, 74.6% reported screening for smoking, 37.8% for hypertension, 80.3% for dyslipidaemia, and 79.6% for diabetes mellitus. Notably, only 28.4% performed global screening, defined as screening for smoking, hypertension, dyslipidaemia, and diabetes mellitus by the same physician, and 24.4% reported calculating 10-year cardiovascular disease (CVD) risk, probably reflecting a lack of comprehensive cardiovascular risk assessment in these patients. This study also identified unmet needs for awareness of cardiovascular comorbidities in psoriasis and corresponding screening and treatment recommendations among PCPs. Of PCPs, 61.2% reported not being aware of the association between psoriasis and CVD and/or not being aware of its screening recommendations, and 67.6% did not consider psoriasis as a risk-enhancing factor when deciding on statin prescription. Thirteen dermatologists (12.6%) and 35 rheumatologists (37.2%) reported prescribing statins. Among those who do not prescribe, 49.7% would be willing to start their prescription
On the energy of charged black holes in generalized dilaton-axion gravity
In this paper we calculate the energy distribution of some charged black
holes in generalized dilaton-axion gravity. The solutions correspond to charged
black holes arising in a Kalb-Ramond-dilaton background and some existing
non-rotating black hole solutions are recovered in special cases. We focus our
study to asymptotically flat and asymptotically non-flat types of solutions and
resort for this purpose to the M{\o}ller prescription. Various aspects of
energy are also analyzed.Comment: LaTe
Missed opportunities for tobacco use screening and brief cessation advice in South African primary health care: a cross-sectional study
BACKGROUND: Primary health care (PHC) settings offer opportunities for tobacco use screening and brief cessation advice, but data on such activities in South Africa are limited. The aim of this study was to determine the extent to which participants were screened for and advised against tobacco use during consultations. METHODS: This cross-sectional study involved 500 participants, 18 years and older, attended by doctors or PHC nurses. Using an exit-interview questionnaire, information was obtained on participants' tobacco use status, reason(s) for seeking medical care, whether participants had been screened for and advised about their tobacco use and patients' level of comfort about being asked about and advised to quit tobacco use. Main outcome measures included patients' self-reports on having been screened and advised about tobacco use during their current clinic visit and/or any other visit within the last year. Data analysis included the use of chi-square statistics, t-tests and multiple logistic regression analysis. RESULTS: Of the 500 participants, 14.9% were current smokers and 12.1% were smokeless tobacco users. Only 12.9% of the participants were screened for tobacco use during their current visit, indicating the vast majority were not screened. Among the 134 tobacco users, 11.9% reported being advised against tobacco use during the current visit and 35.1% during any other visit within the last year. Of the participants not screened, 88% indicated they would be 'very comfortable' with being screened. A pregnancy-related clinic visit was the single most significant predictor for being screened during the current clinic visit (OR = 4.59; 95%CI = 2.13-9.88). CONCLUSION: Opportunities for tobacco use screening and brief cessation advice were largely missed by clinicians. Incorporating tobacco use status into the clinical vital signs as is done for pregnant patients during antenatal care visits in South Africa has the potential to improve tobacco use screening rates and subsequent cessation
Missed Opportunities: Family History and Behavioral Risk Factors in Breast Cancer Risk Assessment Among a Multiethnic Group of Women
BACKGROUND: Clinician’s knowledge of a woman’s cancer family history (CFH) and counseling about health-related behaviors (HRB) is necessary for appropriate breast cancer care. OBJECTIVE: To evaluate whether clinicians solicit CFH and counsel women on HRB; to assess relationship of well visits and patient risk perception or worry with clinician’s behavior. DESIGN: Cross-sectional population-based telephone survey. PARTICIPANTS: Multiethnic sample; 1,700 women from San Francisco Mammography Registry with a screening mammogram in 2001–2002. MEASUREMENTS: Predictors: well visit in prior year, self-perception of 10-year breast cancer risk, worry scale. Outcomes: Patient report of clinician asking about CFH in prior year, or ever counseling about HRB in relation to breast cancer risk. Multivariate models included age, ethnicity, education, language of interview, insurance/mammography facility, well visit, ever having a breast biopsy/follow-up mammography, Gail-Model risk, Jewish heritage, and body mass index. RESULTS: 58% reported clinicians asked about CFH; 33% reported clinicians ever discussed HRB. In multivariate analysis, regardless of actual risk, perceived risk, or level of worry, having had a well visit in prior year was associated with increased odds (OR = 2.3; 95% CI 1.6, 3.3) that a clinician asked about CFH. Regardless of actual risk of breast cancer, a higher level of worry (OR = 1.9; 95% CI 1.4, 2.6) was associated with increased odds that a clinician ever discussed HRB. CONCLUSIONS: Clinicians are missing opportunities to elicit family cancer histories and counsel about health-related behaviors and breast cancer risk. Preventive health visits offer opportunities for clinicians to address family history, risk behaviors, and patients’ worries about breast cancer
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