Combined Arrhenius-Merz Law Describing Domain Relaxation in Type-II Multiferroics.

Electric fields were applied to multiferroic TbMnO_{3} 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.

Switching kinetics of the ferroelectric transition in K2SeO4 studied by stroboscopic γ-ray diffraction.

The kinetics of the ferroelectric lock-in transition in potassium selenate (K2SeO4) was studied on a millisecond timescale using high-resolution γ-ray diffraction. A large change of the line width and wavevector of the first order satellite is observed during the switching process. This is attributed to a loss of long-range order under the influence of the electric field. In addition, the incommensurate phase is stabilized by the pulsed field and the transition to the pure commensurate phase is shifted to lower temperatures. Strains that may build up during the rapid switching process are supposed to be the reason for this behaviour.

Low frequency excitations in multiferroic MnWO4.

Dynamic anomalies have been found in the magnetically ordered phases of multiferroic MnWO(4) using polarized Raman scattering. Strong phonon damping is observed for several B(g) modes within the ferroelectric phase and has been attributed to spin-phonon interactions. Moreover, a new low frequency excitation was detected near 33 cm(-1) that grows in intensity on cooling into the antiferromagnetic phases. It is argued that this signal is most probably due to a two-magnon process.

Field-effect tunneling transistor based on vertical graphene heterostructures.

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.

Switching behaviour of modulated ferroelectrics: the kinetics of the field induced lock-in transition in K2SeO4.

The field induced switching process across the ferroelectric lock-in transition in K(2)SeO(4) has been studied on a millisecond timescale using stroboscopic neutron diffraction. The time evolution of both the first and the third order satellites was examined. The time constants are found to vary with temperature between 0.2 and 1.2 ms. This is an order of magnitude faster than in the isostructural Rb(2)ZnCl(4). Moreover, the time dependence of the satellite's linewidth provides information about the evolution of the coherence of the modulated structure.

Quantitative determination of domain distribution in SrTiO3-competing effects of applied electric field and mechanical stress.

Below its ordering temperature at 105 K, perovskite-type SrTiO(3) exhibits a tetragonal phase with three different structural domains that are strongly influenced by the application of uniaxial mechanical stresses and electric fields. A careful neutron diffraction study of superlattice reflections provides full quantitative information about the varying domain distributions under external loads as a function of temperature. It is shown that electric field and uniaxial stress exhibit competitive effects and the simultaneous application leads to a complex redistribution behaviour of the tetragonal domains. The results are discussed in the context of the formation of a field induced ferroelectric phase at low temperatures. The experimental findings demonstrate that its polarization is always perpendicular to the tetragonal axis and the polar phase has orthorhombic symmetry.

Congress 2000: a continuing medical education summit with implications for the future.

The expectations of attendees, the evaluations of themes, and the implications for continuing medical education (CME) identified by "Congress 2000: A Continuing Medical Education Summit on the Practices, Opportunities and Priorities for the New Millennium" are reviewed. A vision was identified with significant opportunities for CME to become a more valuable partner in and contributor to quality health care. The vision suggests that CME should be linked more closely to physician learning at the point of care and that technology might be used more successfully to address physician-learner needs by helping them to manage volumes of evidence for treating patients more effectively. At the same time, health care outcome data to analyze the need for and measure the effectiveness of educational interventions should become integrated into standards of practice for CME providers. Continuous improvement based on research about effective learning processes and outcomes should become an essential construct of the CME culture. Implications are summarized for the profession, organizational CME providers, individual CME professionals, and CME research from this new vision of CME crafted at Congress 2000.

Clinical variables influencing treatment decisions for agitated dementia patients: survey of physician judgments.

OBJECTIVE: To better understand primary treatment recommendations and the variables that might influence treatment decisions of physicians who treat agitated dementia patients. DESIGN: 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. PARTICIPANTS: 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. RESULTS: 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. CONCLUSIONS: 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.

Four factors of clinical decision making: a teaching model.

For more than 25 years, Bowman Gray has been placing fourth-year students in community-based primary care settings. Upon their return to campus, the students participate in a seminar in which they discuss issues raised by their primary care experiences. In these seminars, the students have consistently identified four key factors of clinical decision making that reflect current trends in medicine: quality, cost, ethics, and legal concerns. These factors influence the practice of medicine and affect the health care of individuals and communities. The authors discuss the nature of these factors and the physician's role and obligation in clinical decision making. Physicians have two responsibilities in this decision-making model: to be the primary advocates for quality health care and to ensure that there be a balance among the weights given the four factors. While physicians must take the lead in ensuring quality care, they must work in partnership with patients, payers, lawyers, ethicists, and the government. It is up to those responsible for the education of future physicians to see that students understand all the factors of clinical decision making and how best to balance them to fulfill their future obligations to patients.

Experimental topical tetracycline-induced neuritis in the rat.

PURPOSE: Recent studies have reported that tetracycline may induce chronic inflammatory responses in the adjacent soft tissues. The purpose of the present study was to determine if dry, powdered tetracycline evoked an inflammatory response in nerve tissue. MATERIALS AND METHODS: Twenty male Sprague-Dawley rats were anesthetized and bilateral mental nerves were exposed. Half of the 40 nerves were intentionally injured by removing the epineurium, and the remaining nerves were uninjured. In a prospective, randomized, double-blind manner, equal volumes of color-matched, precoded tetracycline powder or Gelfoam (Upjohn, Kalamazoo, MI) powder control was placed in intimate contact with the nerves and sealed in polyethylene tubes. Forty-five days later the animals were killed and 5-micron sections of the nerves were prepared for histologic examination. The presence of epineurium, fascicular number, and fascicular area were measured. An inflammatory response in nerve tissue and the intrafascicular and epifascicular inflammatory index was measured by counting darkly stained nuclei with a Jandel Video Analysis System (Jandel Scientific, Corte Madera, CA). RESULTS: Experimental injury (ie, epineurectomy) of nerves resulted in a statistically significant increase in fascicular number (P = .034), but not in fascicular area. For the intrafascicular inflammatory index, there was a significant main effect for drug (P = .002) and injury (P = .002). Experimental injury in both Gelfoam control and tetracycline grouped nerves resulted in an increase in intrafascicular inflammation. There was no significant increase in intrafascicular inflammation in either Gelfoam control or tetracycline grouped nerves when the epineurium was intact. The combination of both tetracycline and epineurectomy resulted in the largest increase in intrafascicular inflammation found among the groups studied. For epifascicular inflammatory index, there was a significant main effect for drug (P = .003) and injury (P = .001) that mirrored the intrafascicular inflammatory pattern. CONCLUSION: The results of the present study suggest that dry, powdered tetracycline accentuates the inflammatory response in intrafascicular and epifascicular nerve tissue following epineurectomy. The maintenance of epineurium inhibited the inflammatory response in intrafascicular and epifascicular nerve tissues. Gel-foam was an inert material when placed against exposed nerve tissue. These findings suggest that tetracycline should not be placed in extraction sockets when injury of the inferior alveolar and/or lingual nerves are present.

Cortical ultrasound velocity as an indicator of bone status.

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.

Velocity of ultrasound and its association with fracture history in a rural population.

The authors set out to determine the distribution of bone quality, as measured by ultrasound, in a rural Nebraska population of women and men. Noninstitutionalized residents of Saunders County, Nebraska, who were age 50 years or older as of January 1, 1992, were enumerated. From this sampling frame, a randomized proportionate stratified sample was selected. The response rate to this random sampling was 58%. Bone quality was measured using the apparent velocity of ultrasound (AVU) through the patella. In addition to demographic information, participants were asked to describe all fractures that had occurred since age 40 years. Fractures were classified as resulting from low or high trauma. Like bone mass, previously studied extensively, AVU was lower among successively older strata for both sexes. AVU discriminated between those with and those without low-trauma or any fractures for both sexes, whether unadjusted or adjusted for nonresponse. AVU is a faster, cheaper, and less time-consuming procedure than bone mass. The measuring device is portable and is well suited for population-based studies. It remains to be determined, by prospective methods, whether AVU is a predictor of low-trauma or osteoporotic fracture in this population.

Evaluations by three graduating classes of a required community health project.

The authors analyzed seniors' evaluations of the first three years of an intensive community health project at the Bowman Gray School of Medicine of Wake Forest University in 1988-89, 1989-90, and 1990-91. The project was designed to provide a public health perspective by having the students select, study, and propose solutions to a community health problem. Of 285 seniors, 240 (84%) completed evaluation questionnaires, using a five-point scale. The students' perceptions of the value of the project became steadily more favorable with each subsequent class; the classes of 1990 and 1991 rated the value of the project as being greater than that of most other experiences in their medical education. The project was more positively evaluated by the 106 responding students (44%) who planned to enter primary care specialties. The students who invested more time in the project also perceived its value to be greater.

The changing paradigm for continuing medical education: impact of information on the teachable moment.

The teachable moment is the time when a learner is ready to accept new information for use conceptually or in practice. Adult educators are always searching for that "moment" and models in which it has been incorporated. This article reviews the changing paradigm for continuing education of the health professional and the impact of information from the context of university-based providers of continuing education and information. Providers of continuing education and information face similar external opportunities and threats. The continuing education provider is a "marginal dweller" in the organization. The information provider (the library), although moving in that direction as technology affects the way information is accessed and managed, is much more a part of the core institutional mission. These parallel conditions provide opportunities for both organizations to work closely together to identify successful models to serve the "teachable moments" of all health care practitioners. A range of new library roles that suggest strong interaction with continuing educators is presented. Workable models are identified as well as characteristics of successful models. Suggestions for survival for continuing educators and librarians in "stalking the teachable moment" are discussed.

A self-supporting library service in a rural region: a new look at hospital consortia.

To meet the informational needs of health care practitioners and trainees in a four-county rural area of northwestern North Carolina, the eleven-member UNIFOUR Consortium was founded as a two-year experimental project from 1978 to 1980. The consortium has several unique features: (1) it is an organization of institutions, not libraries; (2) it employs its own professional librarian who manages a central library, coordinates consortium programs, and makes regular circuit visits to all affiliated institutions; (3) the central library, where the circuit is based, is a developing community hospital library, not an established academic medical center library; and (4) it is ultimately tied to the Northwest Area Health Education Center and that organization's emerging learning resources network, which includes the Bowman Gray School of Medicine, Library, two other subregional libraries, and the libraries of all member institutions. At the end of the experimental period in 1980, member institutions voted unanimously to continue the program and assume their share of the costs.