Robust Phonon-Plasmon Coupling in Quasifreestanding Graphene on Silicon Carbide.

Using inelastic electron scattering in combination with dielectric theory simulations on differently prepared graphene layers on silicon carbide, we demonstrate that the coupling between the 2D plasmon of graphene and the surface optical phonon of the substrate cannot be quenched by modification of the interface via intercalation. The intercalation rather provides additional modes like, e.g., the silicon-hydrogen stretch mode in the case of hydrogen intercalation or the silicon-oxygen vibrations for water intercalation that couple to the 2D plasmons of graphene. Furthermore, in the case of bilayer graphene with broken inversion symmetry due to charge imbalance between the layers, we observe a similar coupling of the 2D plasmon to an internal infrared-active mode, the LO phonon mode. The coupling of graphene plasmons to vibrational modes of the substrate surface and internal infrared active modes is envisioned to provide an excellent tool for tailoring the plasmon band structure of monolayer and bilayer graphene for plasmonic devices such as plasmon filters or plasmonic waveguides. The rigidity of the effect furthermore suggests that it may be of importance for other 2D materials as well.

Understanding and tuning the epitaxy of large aromatic adsorbates by molecular design.

If the rich functionality of organic molecules is to be exploited in devices such as light-emitting diodes or field-effect transistors, interface properties of organic materials with various (metallic and insulating) substrates must be tailored carefully. In many cases, this calls for well-ordered interfaces. Organic epitaxy-that is, the growth of molecular films with a commensurate structural relationship to their crystalline substrates--relies on successful recognition of preferred epitaxial sites. For some large pi-conjugated molecules ('molecular platelets') this works surprisingly well, even if the substrate exhibits no template structure into which the molecules can lock. Here we present an explanation for site recognition in non-templated organic epitaxy, and thus resolve a long-standing puzzle. We propose that this form of site recognition relies on the existence of a local molecular reaction centre in the extended pi-electron system of the molecule. Its activity can be controlled by appropriate side groups and--in a certain regime--may also be probed by molecularly sensitized scanning tunnelling microscopy. Our results open the possibility of engineering epitaxial interfaces, as well as other interfacial nanostructures for which specific site recognition is essential.

Sliding friction of nanocomposite WC1-x/C coatings: transfer film and its influence on tribology.

The transfer film on steel spheres formed in reciprocating sliding against nanocomposite coatings based on nanocrystalline WC1-x in amorphous carbon matrix is characterized and correlated with the tribological properties measured by a precision microtribometer. With the presence of transfer film, a coefficient of friction approximately 0.13 and a depth wear rate approximately 0.35 x 10(-10) m/N.Pass were obtained. The central zone of the transfer film covering approximately 25% of the Hertz contact area is intact while cracks and wear debris are found in the vast peripheral area. It is also heavily oxidized due to the absence of carbon, which is located at the peripherals and acts as lubricants. We propose that the oxidation of WC and adhesion of the oxides to the surface of sphere is the main mechanism for the buildup of the transfer films. With the thickening of the film, the internal stress increases. Under the shear stress, spalling and cracking of the transfer film take place. The overall tribological performance of the coatings is therefore a competing process of buildup and spalling of transfer films.

Spectrum of selection: new approaches to detecting the scale-dependent response to habitat.

Detecting habitat selection depends on the spatial scale of analysis, but multi-scale studies have been limited by the use of a few, spatially variable, hierarchical levels. We developed spatially explicit approaches to quantify selection along a continuum of scales using spatial (coarse-graining) and geostatistical (variogram) pattern analyses at multiple levels of habitat use (seasonal range, travel routes, feeding areas, and microsites). We illustrate these continuum-based approaches by applying them to winter habitat selection by woodland caribou (Rangifer tarandus caribou) using two key habitat components, Cladina lichens and snow depth. We quantified selection as the reduction in variance in used relative to available sites, thus avoiding reliance on correlations between organism and habitat, for which interpretation can be impeded by cross-scale correlations. By consistently selecting favorable habitat features, caribou experienced reduced variance in these features. The degree to which selection was accounted for by the travel route, feeding area, or microsite levels varied across the scale continuum. Caribou selected for Cladina within a 13-km scale domain and selected shallower snow at all scales. Caribou responded most strongly at the dominant scales of patchiness, implicating habitat heterogeneity as an underlying cause of multi-scale habitat selection. These novel approaches enable a spatial understanding of resource selection behavior.

Temperature-dependent electronic and vibrational structure of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide room-temperature ionic liquid surface: a study with XPS, UPS, MIES, and HREELS.

The near-surface structure of the room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide has been investigated as a function of temperature between 100 and 620 K. We used a combination of photoelectron spectroscopies (XPS and UPS), metastable induced electron spectroscopy (MIES), and high-resolution electron energy loss spectroscopy (HREELS). The valence band and HREELS spectra are interpreted on the basis of density functional theory (DFT) calculations. At room temperature, the most pronounced structures in the HREELS, UPS, and MIES spectra are related to the CF3 group in the anion. Spectral changes observed at 100 K are interpreted as a change of the molecular orientation at the outermost surface, when the temperature is lowered. At elevated temperatures, early volatilization, starting at 350 K, is observed under reduced pressure.

Relative lesion detection ability of Tc-99m HMDP and Tc-99m MDP: concise communication.

To compare the efficacy of Tc-99m HMDP and Tc-99m MDP to define skeletal lesions, 28 adult patients were examined in a double-blind, randomized, crossover study. Each patient was imaged with both agents over a period of 7-14 days. Both quantitative and qualitative evaluations were performed on the resulting images. Both agents detected the same number of skeletal lesions, and the number of lesions detected was the same whether the imaging was performed 2 or 4 hr after injection. Relative uptake of the tracer in the lesion relative to normal bone was also the same for both agents. Lesions were easier to see at 4 hr after injection than at 2 hr, presumably because soft-tissue levels were lower. Retention of tracer in bone compared with soft tissue was greater, and image quality was judged to be better, with Tc-99m HMDP than with Tc-99m MDP.

Ultrastructural characteristics of the brain and blood-brain barrier in experimental seizures.

During experimental seizures, the blood-brain barrier (BBB) is broken; tracer substances such as I131-albumin, Evans blue and horseradish peroxidase (HRP) geographically locate the barrier breakdown primarily in the diencephalon. Using rats, we have induced seizures with electroshocks and demonstrated the breakdown of the BBB with Evans blue and HRP. We have shown that (1) the BBB breakdown is proportional to the number of electroconvulsant shocks (ES) given; (2) the mechanism of increased barrier permeability is primarily by micropinocytosis in the cerebral capillaries, arterioles, and, to a lesser extent, venules; and (3) the stimulus for micropinocytosis and hence BBB breakdown is associated with the abrupt rise in systemic blood pressure and cerebral vasodilatation that accompanies each ES. If the systolic hypertension is abolished via cervical cordotomy, there is little to no breakdown in the BBB.

Winter foraging by muskoxen: a hierarchical approach to patch residence time and cratering behaviour.

We examined the temporal and spatial patterns of feeding behaviours of muskoxen during winter in the High Arctic. Pawing motions (to uncover forages beneath snow cover) were strongly aggregated into temporal bouts. Similarly, feeding stations (areas exploitable without motion of the forelegs) were aggregated into spatial patches. Muskoxen responded to greater snow accumulation at feeding sites by increasing the rates of pawing, rates of pawing bouts, number of pawing strokes per bout, and station residence times. Patch residence times showed little relationship to snow or forage abundance because, as muskoxen increased station residence times, they decreased the number of stations per patch. Muskoxen displaced one another from feeding stations more frequently as snow thickness and group size increased. Time spent at feeding stations was positively correlated to travel costs, in accordance with the marginal value model of patch residence. The model was not supported, however, at the scale of the feeding patch. The results indicate that behavioural responses of muskoxen to foraging conditions differ across scales.

Caribou movement as a correlated random walk.

Movement is a primary mechanism coupling animals to their environment, yet there exists little empirical analysis to test our theoretical knowledge of this basic process. We used correlated random walk (CRW) models and satellite telemetry to investigate long-distance movements of caribou, the most vagile, non-volant terrestrial vertebrate in the world. Individual paths of migratory and sedentary female caribou were quantified using measures of mean move length and angle, and net squared displacements at each successive move were compared to predictions from the models. Movements were modelled at two temporal scales. For paths recorded through one annual cycle, the CRW model overpredicted net displacement of caribou through time. For paths recorded over shorter intervals delineated by seasonal behavioural changes of caribou, there was excellent correspondence between model predictions and observations for most periods for both migratory and sedentary caribou. On the smallest temporal scale, a CRW model significantly overpredicted displacements of migratory caribou during 3 months following calving; this was also the case for sedentary caribou in late summer, and in late winter. In all cases of overprediction there was significant positive autocorrelation in turn direction, indicating that movements were more tortuous than expected. In one case of underprediction, significant negative autocorrelation of sequential turn direction was evident, indicating that migratory caribou moved in straightened paths during spring migration to calving grounds. Results are discussed in light of known migration patterns and possible limiting factors for caribou, and indicate the applicability of CRW models to animal movement at vast spatial and temporal scales, thus assisting in future development of more sophisticated models of population spread and redistribution for vertebrates.

A facilitated early return to work program at a large urban medical center.

An Early Return to Work Program was initiated at The Johns Hopkins Hospital and Associated Schools of Medicine, Hygiene and Nursing in Baltimore, Maryland, in April 1992 as part of a comprehensive effort to control the incidence and costs of work-related illnesses and injuries. The program was similar to others that incorporate employee and supervisory training and job accommodation, but it also included an industrial hygienist trained in ergonomics to facilitate the placement of individuals with restrictions. The return to work program was studied over a 10-year period, comparing the number of lost workday cases, lost workdays, and restricted duty days before (1989 to 1992) and after (1993 to 1999) initiation of the program. A significant decrease (55%) was observed in the rate of lost workday cases before versus after the return to work program. Furthermore, the number of lost workdays decreased from an average of 26.3 per 100 employees before, to 12.0 per 100 employees after, the return to work initiative, and the number of restricted duty days went from an average of 0.63 per 100 employees to 13.4 per 100 employees (a twentyfold increase). The study suggests that a well-structured early return to work program is an integral part of a comprehensive effort to control the duration of disability associated with occupational injuries and illness. It also indicates that to be most effective, an early return to work program must include participation by medical providers, safety professionals, injured employees, and supervisors. Our work suggests that even with these elements in place, the effectiveness of return to work programs may be increased by including an individual trained in ergonomics to facilitate the job placement process.

An ergonomics program designed to reduce the incidence of upper extremity work related musculoskeletal disorders.

In 1992, the Johns Hopkins Hospital and University initiated a program aimed at the early diagnosis and treatment of potential upper extremity work related musculoskeletal disorders (UEWMSDs), ergonomic assessment and abatement of work areas where individuals with UEWMSDs are employed, as well as the identification and correction of areas throughout the hospital and university where UEWMSDs could possibly occur. The program resulted in an initial increase in the number and cost for the treatment of UEWMSDs. Subsequently, there was a significant decrease in the number of UEWMSDs reported and virtual elimination of the need to use surgical procedures to correct these conditions. This article suggests that a coordinated program of medical care, ergonomic assessment, and intervention can be efficacious in the primary, secondary, and tertiary prevention of UEWMSD.

An in vitro study of the accuracy and precision of Breathalyzer models 900, 900A, and 1000.

Ninety Breathalyzer instruments (Model 1000) and twenty instruments (Models 900, 900A) were studied using a protocol described by the Department of Transportation's "Standard for Devices to Measure Breath Alcohol." Although the mean of each of three concentrations tested (0.05, 0.10, and 0.15 g/210 L) compared favorably in both series, the standard deviation was consistently higher for the Model 1000 instruments. The Model 1000 instruments also produced a significant number of test results which exceeded the normally expected scientific deviation.

Electronic structure of the surface of the ionic liquid [EMIM][Tf(2)N] studied by metastable impact electron spectroscopy (MIES), UPS, and XPS.

The near-surface electronic structure of the room-temperature ionic liquid (RT-IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf(2)N]) has been investigated with the combination of the electron spectroscopies metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS (HeI and HeII)), and monochromatized X-ray photoelectron spectroscopy (XPS). We find that the top of the valence band states originates from states of the cation (see also ref 1). The ultimately surface-sensitive technique MIES proves that the surface layer consists of both cations and anions. The temperature dependence of the spectra has been measured between about 160 and 610 K. Information on the glass transition and the possibility for low-temperature distillation of [EMIM][Tf(2)N] at reduced pressures is derived from the present results.

Respiratory protection in the health care setting.

Respiratory protection is of increased importance due to the resurgence of tuberculosis. This chapter examines protective devices and regulations and explains how a program can be designed to minimize workplace hazards. Of particular value is a table detailing 12 high-efficiency particulate air respirators that meet criteria set by the Centers for Disease Control and the National Institute of Occupational Safety and Health.

Effects of work stressors and work climate on long-term care staff's job morale and functioning.

Relationships between work stressors and work climate, and job morale and functioning were examined. Initial and 8-month follow-up data were obtained from 405 staff in 14 long-term care facilities. Relationship and workload stressors were related to less job satisfaction and intent to stay in the job, and more job-related distress, depression, and physical symptoms. Patient care task stressors were associated with better outcomes. More positive work climates were linked to higher job morale. Initial work stressors predicted poorer functioning, and coworker cohesion predicted more intent to stay in the job at follow-up.

Epstein-Barr virus in cerebrospinal fluid during infectious mononucleosis encephalitis.

Epstein-Barr virus (EBV) was recovered from cerebrospinal cells (but not from cell-free fluid) of a patient with meningoencephalitis complicating infectious mononucleosis. This finding suggests that virus-altered B lymphocytes can invade the central nervous system and may play a direct role in the pathogenesis of neurologic sequelae of EBV infections. Several mechanisms by which these cells can cause neurologic manifestations are discussed.

Deconvolution method for two-dimensional spatial-response mapping of lithographic infrared antennas.

The spatial impulse response of antenna-coupled infrared detectors with dimensions comparable with the wavelength is obtained from a two-dimensional scan of a tightly focused CO(2)-laser beam. The method uses an experimental setup with submicrometer resolution and an iterative deconvolution algorithm. The measured spatial response is compared with numerically computed near-field distributions of a dipole antenna, with good agreement.