Birefringence in nonlinear anisotropic dielectric media

Light propagation is investigated in the context of local anisotropic nonlinear dielectric media at rest with the dielectric coefficients $\epsilon^\mu{}_\nu = \epsilon^\mu{}_\nu (\vec{E},\vec{B})$ and constant $\mu$, in the limit of geometrical optics. Birefringence was examined and the general conditions for its occurrence were presented. A toy model is exhibited, in which uniaxial birefringent media with nonlinear dielectric properties could be driven by external fields in such way that birefringence may be artificially controlled. The effective geometry interpretation is also addressed.Comment: 5 pages, 1 figur

Water vapor emission from IRC+10216 and other carbon-rich stars: model predictions and prospects for multitransition observations

We have modeled the emission of H2O rotational lines from the extreme C-rich star IRC+10216. Our treatment of the excitation of H2O emissions takes into account the excitation of H2O both through collisions, and through the pumping of the nu2 and nu3 vibrational states by dust emission and subsequent decay to the ground state. Regardless of the spatial distribution of the water molecules, the H2O 1_{10}-1_{01} line at 557 GHz observed by the Submillimeter Wave Astronomy Satellite (SWAS) is found to be pumped primarily through the absorption of dust-emitted photons at 6 $\mu$m in the nu2 band. As noted by previous authors, the inclusion of radiative pumping lowers the ortho-H2O abundance required to account for the 557 GHz emission, which is found to be (0.5-1)x10^{-7} if the presence of H2O is a consequence of vaporization of orbiting comets or Fischer-Tropsch catalysis. Predictions for other submillimeter H2O lines that can be observed by the Herschel Space Observatory (HSO) are reported. Multitransition HSO observations promise to reveal the spatial distribution of the circumstellar water vapor, discriminating among the several hypotheses that have been proposed for the origin of the H2O vapor in the envelope of IRC+10216. We also show that, for observations with HSO, the H2O 1_{10}-1_{01} 557 GHz line affords the greatest sensitivity in searching for H2O in other C-rich AGB stars.Comment: 35 pages, 12 figures, to be published in The Astrophysical Journa

Genotype-Phenotype Correlation in NF1: Evidence for a More Severe Phenotype Associated with Missense Mutations Affecting NF1 Codons 844-848

Neurofibromatosis type 1 (NF1), a common genetic disorder with a birth incidence of 1:2,000–3,000, is characterized by a highly variable clinical presentation. To date, only two clinically relevant intragenic genotype-phenotype correlations have been reported for NF1 missense mutations affecting p.Arg1809 and a single amino acid deletion p.Met922del. Both variants predispose to a distinct mild NF1 phenotype with neither externally visible cutaneous/plexiform neurofibromas nor other tumors. Here, we report 162 individuals (129 unrelated probands and 33 affected relatives) heterozygous for a constitutional missense mutation affecting one of five neighboring NF1 codons—Leu844, Cys845, Ala846, Leu847, and Gly848—located in the cysteine-serine-rich domain (CSRD). Collectively, these recurrent missense mutations affect ∼0.8% of unrelated NF1 mutation-positive probands in the University of Alabama at Birmingham (UAB) cohort. Major superficial plexiform neurofibromas and symptomatic spinal neurofibromas were more prevalent in these individuals compared with classic NF1-affected cohorts (both p \u3c 0.0001). Nearly half of the individuals had symptomatic or asymptomatic optic pathway gliomas and/or skeletal abnormalities. Additionally, variants in this region seem to confer a high predisposition to develop malignancies compared with the general NF1-affected population (p = 0.0061). Our results demonstrate that these NF1 missense mutations, although located outside the GAP-related domain, may be an important risk factor for a severe presentation. A genotype-phenotype correlation at the NF1 region 844–848 exists and will be valuable in the management and genetic counseling of a significant number of individuals

Supporting breast cancer screening decisions for caregivers of older women with dementia: study protocol for a randomized controlled trial

BACKGROUND: Alzheimer's disease and related dementias (ADRD) impact a woman's life expectancy and her ability to participate in medical decision-making about breast cancer screening, necessitating the involvement of family caregivers. Making decisions about mammography screening for women with ADRD is stressful. There are no data that suggest that breast cancer screening helps women with ADRD live longer or better. Decision aids may improve the quality of decision-making about mammography for ADRD patients and may inform family caregivers about the risks, benefits, and need for decision-making around mammography screening. METHODS/DESIGN: The Decisions about Cancer Screening in Alzheimer's Disease (DECAD) trial, a randomized controlled clinical trial, will enroll 426 dyads of older women with ADRD (≥75 years) and a family caregiver from clinics and primary-care practices in Indiana to test a novel, evidence-based decision aid. This decision aid includes information about the impact of ADRD on life expectancy, the benefit of mammograms, and the impact on the quality of life for older women with ADRD. Dyads will be randomized to receive the decision aid or active control information about home safety. This trial will examine the effect on the caregiver's decisional conflict (primary outcome) and the caregiver's decision-making self-efficacy (secondary outcome). A second follow-up at 15 months will include a brief, semi-structured interview with the caregiver regarding the patient's experience with mammograms and decision-making about mammograms. At the same time, a review of the patient's electronic medical record (EMR) will look at discussions about mammography with their primary-care physician and mammogram orders, receipt, results, and burden (e.g., additional diagnostic procedures due to false-positive results, identification of an abnormality on the screening exam but further work-up declined, and identification of a clinically unimportant cancer). A third follow-up at 24 months will extract EMR data on mammogram orders, occurrences, results, and the burden of mammograms. DISCUSSION: We hypothesize that caregivers who receive the decision aid will have lower levels of decisional conflict and higher levels of decision-making self-efficacy compared to the control group. We also hypothesize that the DECAD decision aid will reduce mammography use among older women with ADRD

Magnetoelectric birefringence revisited

Electromagnetic wave propagation inside isotropic material media characterized by dielectric coefficients $\varepsilon_{\mu\nu}(E,B)$ and $\mu_{\mu\nu}(E,B)$ is examined. The regime of the eikonal approximation is considered. The Hadamard method of field disturbances is used and the dispersion relations are obtained by solving the Fresnel equation. Some applications of the formalism are presented. Particularly, birefringence phenomena induced by applied external fields are derived and discussed. It is shown that magnetoelectric birefringence effect can occur even without the presence of Kerr and Cotton-Mouton effects, provided the physical system satisfies certain conditions.Comment: 9 pages, 1 figure, LaTe

Predicting risky choices from brain activity patterns

Previous research has implicated a large network of brain regions in the processing of risk during decision making. However, it has not yet been determined if activity in these regions is predictive of choices on future risky decisions. Here, we examined functional MRI data from a large sample of healthy subjects performing a naturalistic risk-taking task and used a classification analysis approach to predict whether individuals would choose risky or safe options on upcoming trials. We were able to predict choice category successfully in 71.8% of cases. Searchlight analysis revealed a network of brain regions where activity patterns were reliably predictive of subsequent risk-taking behavior, including a number of regions known to play a role in control processes. Searchlights with significant predictive accuracy were primarily located in regions more active when preparing to avoid a risk than when preparing to engage in one, suggesting that risk taking may be due, in part, to a failure of the control systems necessary to initiate a safe choice. Additional analyses revealed that subject choice can be successfully predicted with minimal decrements in accuracy using highly condensed data, suggesting that information relevant for risky choice behavior is encoded in coarse global patterns of activation as well as within highly local activation within searchlights

Lifestyle index for mortality prediction using multiple ageing cohorts in the USA, UK and Europe

Current mortality prediction indexes are mainly based on functional morbidity and comorbidity, with limited information for risk prevention. This study aimed to develop and validate a modifiable lifestyle-based mortality predication index for older adults. Data from 51,688 participants (56% women) aged ≥50 years in 2002 Health and Retirement Study, 2002 English Longitudinal Study of Ageing and 2004 Survey of Health Ageing and Retirement in Europe were used to estimate coefficients of the index with cohort-stratified Cox regression. Models were validated across studies and compared to the Lee index (having comorbid and morbidity predictors). Over an average of 11-year follow-up, 10,240 participants died. The lifestyle index includes smoking, drinking, exercising, sleep quality, BMI, sex and age; showing adequate model performance in internal validation (C-statistic 0.79; D-statistic 1.94; calibration slope 1.13) and in all combinations of internal-external cross-validation. It outperformed Lee index (e.g. differences in C-statistic = 0.01, D-statistic = 0.17, P < 0.001) consistently across health status. The lifestyle index stratified participants into varying mortality risk groups, with those in the top quintile having 13.5% excess absolute mortality risk over 10 years than those in the bottom 50th centile. Our lifestyle index with easy-assessable behavioural factors and improved generalizability may maximize its usability for personalized risk management

Primary Care Providers’ Perceptions of the Acceptability, Appropriateness, and Feasibility of a Mammography Decision Aid for Women Aged 75 and Older

Background. Clinicians need to find decision aids (DAs) useful for their successful implementation. Therefore, we aimed to conduct an exploratory study to learn primary care clinicians? (PCPs) perspectives on a mammography DA for women ≥75 to inform its implementation. Methods. We sent a cross-sectional survey to 135 PCPs whose patients had participated in a randomized trial of the DA. These PCPs practiced at 1 of 11 practices in Massachusetts or North Carolina. PCPs were asked closed-ended and open-ended questions on shared decision making (SDM) around mammography with women ≥75 and on the DA?s acceptability, appropriateness, and feasibility. Results. Eighty PCPs participated (24 [30%] from North Carolina). Most (n = 69, 86%) thought that SDM about mammography with women ≥75 was extremely/very important and that they engaged women ≥75 in SDM around mammography frequently/always (n = 49, 61%). Regarding DA acceptability, 60% felt the DA was too long. Regarding appropriateness, 70 (89%) thought it was somewhat/very helpful and that it would help patients make more informed decisions; 55 (70%) would recommend it. Few (n = 6, 8%) felt they had other resources to support this decision. Regarding feasibility, 53 (n = 67%) thought it would be most feasible for patients to receive the DA before a visit from medical assistants rather than during or after a visit or from health educators. Most (n = 62, 78%) wanted some training to use the DA. Limitations. Sixty-nine percent of PCPs in this small study practiced in academic settings. Conclusions. Although PCPs were concerned about the DA?s length, most found it helpful and informative and felt it would be feasible for medical assistants to deliver the DA before a visit. Implications. Study findings may inform implementation of this and other DAs