Nanoscale strain engineering of giant pseudo-magnetic fields, valley polarization, and topological channels in graphene.

The existence of nontrivial Berry phases associated with two inequivalent valleys in graphene provides interesting opportunities for investigating the valley-projected topological states. Examples of such studies include observation of anomalous quantum Hall effect in monolayer graphene, demonstration of topological zero modes in "molecular graphene" assembled by scanning tunneling microscopy, and detection of topological valley transport either in graphene superlattices or at bilayer graphene domain walls. However, all aforementioned experiments involved nonscalable approaches of either mechanically exfoliated flakes or atom-by-atom constructions. Here, we report an approach to manipulating the topological states in monolayer graphene via nanoscale strain engineering at room temperature. By placing strain-free monolayer graphene on architected nanostructures to induce global inversion symmetry breaking, we demonstrate the development of giant pseudo-magnetic fields (up to ~800 T), valley polarization, and periodic one-dimensional topological channels for protected propagation of chiral modes in strained graphene, thus paving a pathway toward scalable graphene-based valleytronics.

Single-step deposition of high-mobility graphene at reduced temperatures.

Current methods of chemical vapour deposition (CVD) of graphene on copper are complicated by multiple processing steps and by high temperatures required in both preparing the copper and inducing subsequent film growth. Here we demonstrate a plasma-enhanced CVD chemistry that enables the entire process to take place in a single step, at reduced temperatures (<420 °C), and in a matter of minutes. Growth on copper foils is found to nucleate from arrays of well-aligned domains, and the ensuing films possess sub-nanometre smoothness, excellent crystalline quality, low strain, few defects and room-temperature electrical mobility up to (6.0±1.0) × 10(4) cm(2) V(-1) s(-1), better than that of large, single-crystalline graphene derived from thermal CVD growth. These results indicate that elevated temperatures and crystalline substrates are not necessary for synthesizing high-quality graphene.

Measurement of a sign-changing two-gap superconducting phase in electron-doped Ba(Fe(1-x)Co(x))2As2 single crystals using scanning tunneling spectroscopy.

Scanning tunneling spectroscopic studies of Ba(Fe(1-x)Co(x))(2)As(2) (x=0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition T(c). The two-gap nature and the slightly doping- and energy-dependent quasiparticle scattering interferences near the wave vectors (±π, 0) and (0, ±π) are consistent with sign-changing s-wave superconductivity. The excess zero-bias conductance and the large gap-to-T(c) ratios suggest dominant unitary impurity scattering.

Evidence for strain-induced local conductance modulations in single-layer graphene on SiO2.

Graphene has emerged as an electronic material that is promising for device applications and for studying two-dimensional electron gases with relativistic dispersion near two Dirac points. Nonetheless, deviations from Dirac-like spectroscopy have been widely reported with varying interpretations. Here we show evidence for strain-induced spatial modulations in the local conductance of single-layer graphene on SiO(2) substrates from scanning tunneling microscopic (STM) studies. We find that strained graphene exhibits parabolic, U-shaped conductance vs bias voltage spectra rather than the V-shaped spectra expected for Dirac fermions, whereas V-shaped spectra are recovered in regions of relaxed graphene. Strain maps derived from the STM studies further reveal direct correlation with the local tunneling conductance. These results are attributed to a strain-induced frequency increase in the out-of-plane phonon mode that mediates the low-energy inelastic charge tunneling into graphene.

An analysis of the 1990 Public Health Service physical fitness and exercise objectives for older Americans.

As part of the 1990 Health Objectives for the Nation Report, the Public Health Service (PHS) specified a 50% participation of older adults in aerobic activity. A review of national population based surveys indicated that older Americans are very unlikely to attain this objective. The authors' review of epidemiological and empirical literature, however, suggested that both high activity/high fitness and high activity/low fitness physical activities contribute to health. Moreover, the underlying dimension of the health goal for older Americans is to increase or maintain functional independence. Physical activities that emphasize flexibility, strength, and balance are essential components in maintaining activity in daily living skills for older Americans. A recommendation for cardiovascular health, based upon recent empirical studies, is that older adults should optimally attain a leisure time physical activity (LTPA) expenditure of 150 to 400 K-cal per day. The authors' analysis of the 1985 National Health Interview Survey; Health Promotion and Disease Prevention, indicated that only 22 percent of older Americans are attaining the minimal 150 K-cal threshold in LTPA. The authors subsequently argued that the physical fitness goal for older Americans should be revised to include not only aerobic activity but flexibility, strength, and balance.

Comprehensive health assessment: an algorithmic model.

Most professional communities advocate and employ an assessment of some kind before initiating an action of change. The closer that health promotion programs parallel such models, the easier it will be for their products to be accepted in the health community. This article describes such a comprehensive algorithmic health assessment model, applicable to therapeutic recreation. The focus of the model is on the conceptual interplay between health assessment and the design of prescriptive health promotion plans that are tailored to the individual client. References and general recommendations for applying this model to special populations are provided.

Litigation: a growing threat to community centers.

Many therapeutic recreation professionals are employed in community centers (e.g., boarding homes, nursing homes, sheltered workshops). Recently, community centers have become vulnerable to litigious action through negligence lawsuits. The trends toward substantive immunity and least restrictive environment have fueled such law-suits. This article addresses the reasons behind litigious action in community centers. Liability principles and administrative problem areas are then used by the authors for drawing preventive recommendations.