Observation of a topological crystalline insulator phase and topological phase transition in Pb(1-x)Sn(x)Te.

A topological insulator protected by time-reversal symmetry is realized via spin-orbit interaction-driven band inversion. The topological phase in the Bi(1-x)Sb(x) system is due to an odd number of band inversions. A related spin-orbit system, the Pb(1-x)Sn(x)Te, has long been known to contain an even number of inversions based on band theory. Here we experimentally investigate the possibility of a mirror symmetry-protected topological crystalline insulator phase in the Pb(1-x)Sn(x)Te class of materials that has been theoretically predicted to exist in its end compound SnTe. Our experimental results show that at a finite Pb composition above the topological inversion phase transition, the surface exhibits even number of spin-polarized Dirac cone states revealing mirror-protected topological order distinct from that observed in Bi(1-x)Sb(x). Our observation of the spin-polarized Dirac surface states in the inverted Pb(1-x)Sn(x)Te and their absence in the non-inverted compounds related via a topological phase transition provide the experimental groundwork for opening the research on novel topological order in quantum devices.

Topological phase transition and texture inversion in a tunable topological insulator.

The recently discovered three-dimensional or bulk topological insulators are expected to exhibit exotic quantum phenomena. It is believed that a trivial insulator can be twisted into a topological state by modulating the spin-orbit interaction or the crystal lattice, driving the system through a topological quantum phase transition. By directly measuring the topological quantum numbers and invariants, we report the observation of a phase transition in a tunable spin-orbit system, BiTl(S(1-δ)Se(δ))(2), in which the topological state formation is visualized. In the topological state, vortex-like polarization states are observed to exhibit three-dimensional vectorial textures, which collectively feature a chirality transition as the spin momentum-locked electrons on the surface go through the zero carrier density point. Such phase transition and texture inversion can be the physical basis for observing fractional charge (±e/2) and other fractional topological phenomena.

Perceived challenges and priorities in co-morbidity management of older patients with Type 2 diabetes.

AIMS: To explore older patients' perceived impact of chronic co-morbid conditions on Type 2 diabetes self-management. METHODS: We used purposive sampling to select 32 mentally alert community-dwelling adults, aged 60 years or older, diagnosed with Type 2 diabetes and at least one other chronic health condition to participate in focus groups. We summarized the discussions following each focus group and identified codes to describe the overarching themes. RESULTS: We conducted eight 90-min focus groups, each consisting of two to six patients. Three themes emerged. (i) Diabetes complications as a motivator: managing co-morbid conditions made health an important focal point in the lives of older patients. Most patients acknowledged the positive effect complications had on their diabetes self-management by motivating them to pay greater attention to their diabetes to diminish the progression of these complications. (ii) Prioritizing health conditions: patients reported prioritizing health conditions and selectively attending to the management of those conditions based on perceived severity or importance. Further, many patients perceived some conditions as more serious than others and admitted to prioritizing another health condition over their diabetes. (iii) Emotional impact of co-morbidity management: patients described feeling frustrated, confused, and overwhelmed in response to conflicting treatment recommendations, particularly for diet, physical activity and medication regimens. CONCLUSIONS: Complications and co-morbidities may have differential impacts on the diabetes self-management of older patients. Addressing the perceived impact of co-morbidity on diabetes self-management may improve patients' outcomes; however, the most effective method of utilizing this information in clinical practice needs to be examined.

Single-Dirac-cone topological surface states in the TlBiSe(2) class of topological semiconductors.

We investigate several strong spin-orbit coupling ternary chalcogenides related to the (Pb,Sn)Te series of compounds. Our first-principles calculations predict the low-temperature rhombohedral ordered phase in TlBiTe2, TlBiSe2, and TlSbX2 (X=Te, Se, S) to be topologically nontrivial. We identify the specific surface termination that realizes the single Dirac cone through first-principles surface state computations. This termination minimizes effects of dangling bonds, making it favorable for photoemission experiments. In addition, our analysis predicts that thin films of these materials could harbor novel 2D quantum spin Hall states, and support odd-parity topological superconductivity.

Explaining the role of sex on disability: a population-based study.

PURPOSE: There is no clear consensus about how sex influences prevalent disability and through what mechanisms. We investigated whether sex had a direct independent effect on disability or whether sex had an interactive effect on the relationship between chronic diseases/conditions and disability, and whether these effects differed in middle-aged versus older adults. DESIGN AND METHODS: We used baseline data from two nationally representative health interview surveys, the Health and Retirement Study (HRS) and the Study of Asset and Health Dynamics Among the Oldest Old (AHEAD), and disability and covariate measures that were nearly identical in both surveys. Logistic regression models tested the contributions of diseases, impairments, and demographic and social characteristics on difficulties with prevalent activities of daily living (ADLs), mobility, and strength. RESULTS: Models demonstrated no direct sex effect for ADL disability in either age group after adjusting for key covariates. However, sex did exert an indirect effect on ADL disability in older adults via musculoskeletal conditions and depressive symptoms. In contrast, female sex remained strongly associated with mobility and strength disability in both age groups, net of covariates. Major interactions were also significant, including a female sex/body mass index (BMI) interaction for mobility difficulty and several sex-disease interactions for strength disability in the middle-aged group. IMPLICATIONS: The effect of sex on ADL difficulty is largely explained by social and health-related covariates in middle-aged and older adults. In contrast, the independent association of female sex with decreased strength and mobility in both groups cannot be explained by our models' social or health-related variables. In addition, the positive association of BMI with mobility difficulty is significantly worse for women than for men.

The impact of education and heart attack on smoking cessation among middle-aged adults.

Considerable evidence supports the premise that higher levels of education lead to enhanced health, including protective health behaviors. This paper focuses on how education affects one health behavior known to lead to enhanced health: the cessation of smoking. In particular, the authors examine the extent to which education influences the decision by middle-aged adults to quit smoking following a heart attack, a potentially life-threatening health event. We first hypothesize that middle-aged adults with more formal education will stop smoking more readily than people with less formal education following the experience of a heart attack. Second, we ask what other factors might underlie and explain that hypothesized effect. Using longitudinal data, the authors track changes in individual smoking behaviors after a heart attack among preretirement-age Americans. We control for documented correlates of smoking and heart attack plus other factors associated with education, heart attack, and smoking that may also influence whether a person quits smoking. In addition to confirming evidence on the education-health association as well as the documented connection between heart attack and smoking cessation, this study provides a surprising twist on those links: Our results show that the move to quit smoking following the experience of a heart attack among middle-aged adults is significantly and dramatically moderated by their level of educational attainment.

The role of ethnicity in the disability and work experience of preretirement-age Americans.

Using the 1992 HRS, this study examines the effects of social and demographic risk factors, including ethnicity, as well as health and job characteristics on disability and work status among 8,701 preretirement-age Americans with work history. Analytic results indicated that non-Anglo ethnicity was not a significant predictor of disability status but that being African American was a strong significant predictor of being a past versus current worker. The primary predictors of disability and work status were health behaviors, effects of health conditions, job characteristics, and workplace adaptations, factors that lend themselves to policy manipulation.

The relationship between retirement life cycle changes and older men's labor force participation rates.

This study probes the utility of older men's labor force participation rates (LFPRs) as indicators of the work-to-retirement transition. Specific attention is directed at how shifts in the retirement life cycle are related to LFPRs. Based on Current Population Survey data for the 1970s, a life table modeling approach showed that LFPRs are relatively weak indicators of the work-to-retirement transition. This was demonstrated by the relative stability in older men's age profiles of LFPRs despite significant changes in the timing and "organization" of the work-to-retirement transition. The 1970s evidenced a contraction of the main career and the expansion of both post-retirement work activity and retirement, yet none of these changes substantially altered the age profiles of older men's labor force participation rates.

Funding and policies affecting geriatric rehabilitation.

Policy makers and practitioners are increasingly acknowledging the need to shift health care expenditures toward cost-effective strategies that reduce disability and dependency in older persons. That need is driven by current research on disability and population aging, disability interventions, and the inadequacy of the existing service delivery system for chronic care needs. How disability and dependency should be reduced most effectively and efficiently is a critical yet unanswered policy question.

Health policy and ethnic diversity in older Americans. Dissonance or harmony?

The rapid growth and diversity of the older population have long-term implications for health care policies in the United States. Current policies designed for a homogeneous population are increasingly obsolete. To ameliorate obstacles that handicap many ethnic minority elders and to provide equal access to adequate and acceptable health care, several factors need to be considered. Enhanced data collection and analytic techniques are needed. The effects of race or ethnicity must be separated from other biologic, environmental, socioeconomic, cultural, and temporal factors on health status and behavior. Health care professionals and organizations serving minority elders must continue to expand their advocacy efforts to articulate the findings and their concerns to policymakers. Policymakers must understand and acknowledge the implications of an increasingly diverse society and determine what will constitute adequate, accessible, and acceptable health care within continuing fiscal constrains. Program planning, implementation, and evaluation methods must be revised to meet future health care needs effectively and efficiently.

Public policy implications of an ethnically diverse elderly population.

Social, economic, and health care trends demonstrating the rapid growth and diversity of elderly minority and ethnic groups have long-term repercussions for social support service systems in the United States. Current public policies designed for a homogeneous elderly population must become more flexible and must recognize and accommodate the needs of an increasingly diverse American society.