An obstacle to the use of graphene as an alternative to silicon electronics has been the absence of an energy gap between its conduction and valence bands, which makes it difficult to achieve low ...power dissipation in the OFF state. We report a bipolar field-effect transistor that exploits the low density of states in graphene and its one-atomic-layer thickness. Our prototype devices are graphene heterostructures with atomically thin boron nitride or molybdenum disulfide acting as a vertical transport barrier. They exhibit room-temperature switching ratios of ≈50 and ≈10,000, respectively. Such devices have potential for high-frequency operation and large-scale integration.
Electric fields were applied to multiferroic TbMnO3 single crystals to control the chiral domains, and the domain relaxation was studied over 8 decades in time by means of polarized neutron ...scattering. A surprisingly simple combination of an activation law and the Merz law describes the relaxation times in a wide range of electric field and temperature with just two parameters, an activation-field constant and a characteristic time representing the fastest possible inversion. Over the large part of field and temperature values corresponding to almost 6 orders of magnitude in time, multiferroic domain inversion is thus dominated by a single process, the domain wall motion. Only when approaching the multiferroic transition other mechanisms yield an accelerated inversion.
The domain structure of SrTiO3 below its cubic to tetragonal phase transition depends not only on the stress-state of a particular sample but can also be modified very efficiently by the application ...of electric fields. Hence, the interpretation of field induced phenomena needs a careful consideration of the domain distribution which is often neglected in existing studies. In this paper, it is shown that the strong variation of polarized Raman spectra under external fields observed within both the paraelectric tetragonal phase and the field induced ferroelectric phase, is a direct consequence of the redistribution of domains. Raman data can therefore be used to characterize the domain structure of a particular sample.
Four grades of hexagonal boron nitride are investigated by terahertz time-domain spectroscopy. The refractive indices and loss coefficients at terahertz frequencies are measured and are related to ...aspects of material fabrication and properties.
To better understand primary treatment recommendations and the variables that might influence treatment decisions of physicians who treat agitated dementia patients.
A written cross-sectional survey ...of three physician groups (geriatric psychiatrists, primary care physicians, and neurologists) who typically treat agitated dementia patients in community settings. We used a written clinical vignette describing a home-bound, agitated dementia patient to ask respondents to provide information regarding their primary treatment recommendation and to estimate the degree to which clinically relevant variables might influence their treatment recommendation. Using principal component analysis, the original set of clinical variables was collapsed into a smaller set of composite factors that better defined the fundamental constructs of the variables that influenced decision making. Analyses compared primary treatment recommendations and factors influencing treatment recommendations by physician groups.
The pool of survey respondents consisted of a random selection of 207 primary care physicians from western North Carolina, 147 geriatric psychiatrists obtained from the roster of the 1991 American Association for Geriatric Psychiatry, and 120 neurologists obtained from the roster of the American Board of Medical Specialties. The response rate was 65% for geriatric psychiatrists, 38% for primary care physicians, and 33% for neurologists.
Differences in primary treatment recommendations by physician group were not found. Physicians, regardless of specialty, recommended neuroleptic medications as their primary intervention. When medication classes were collapsed into a single category, medications as a primary intervention exceeded 55% for all physician groups. Twenty-two percent of all respondents recommended psychosocial interventions as primary treatment strategies. The principal component analysis of clinical variables influencing treatment recommendations solved for five components that accounted for 64% of the variance. Comparing the five components by specialty groups failed to find significant differences, except for Factor 5, the "Hassle Factor." Primary care physicians were more likely to indicate that this component influenced their decision making than were the other physician groups.
The findings indicate that physicians, regardless of specialty, are likely to use medication and to weight clinically relevant information in a similar fashion when managing agitated dementia patients.
The domain structure of SrTiO sub(3) below its cubic to tetragonal phase transition depends not only on the stress-state of a particular sample but can also be modified very efficiently by the ...application of electric fields. Hence, the interpretation of field induced phenomena needs a careful consideration of the domain distribution which is often neglected in existing studies. In this paper, it is shown that the strong variation of polarized Raman spectra under external fields observed within both the paraelectric tetragonal phase and the field induced ferroelectric phase, is a direct consequence of the redistribution of domains. Raman data can therefore be used to characterize the domain structure of a particular sample.
The THz optical properties and material structure of pyrolytic boron nitride (PBN), highly oriented pyrolytic boron nitride (HOPBN), and pressed boron nitride powder are investigated by THz ...time-domain spectroscopy. PBN, HOPBN and powder are confirmed as highly oriented structures; the degree of misalignment of hot-pressed boron nitride is indicated. Suitability of PBN for THz optical applications is discussed.
Normative population data are reported here for velocity of ultrasound in tibial cortical bone in a population-based sample of both men and women (n = 371). The cortical measurement is highly precise ...with reproducibility of the order of 0.5%. As with heel and patellar trabecular velocity, tibial cortical velocity declines with age from the fourth through the ninth decades. The rate is 1.7 m/s per year in men and 4.1 m/s per year in women. Tibial cortical velocity values correlate with patellar velocity and with forearm mineral, with correlation coefficients ranging from + 0.46 to + 0.54 in women and + 0.27 to + 0.43 in men (P < 0.002 for all). Tibial velocity averaged 77-104 m/s lower (2-3%: equal to about 1 SD of the young adult normal distribution) in individuals with a history of low-energy appendicular fractures (P < 0.05), and the difference remained significant after adjusting for age. However, there were no perceptible differences in tibial velocity for those with and without vertebral fractures. Odds ratios derived from logistic regression showed an approximate twofold increase in likelihood of low-energy appendicular fracture for every standard deviation decrement in velocity. Comparison of tibial velocity with patellar velocity and forearm density in the same individuals revealed tibial velocity to be more strongly associated with appendicular fractures than patellar velocity for women and about the same for men, and less strongly associated than patellar velocity for vertebral fractures. We conclude that tibial cortical velocity provides useful information about bone status in populations at risk for osteoporosis, and seems particularly well suited for assessing appendicular fracture risk.
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