ABSTRACT
We report a high-resolution terahertz spectroscopic study of quantum spin dynamics in the antiferromagnetic Heisenberg-Ising spin-chain compound BaCo_{2}V_{2}O_{8} as a function of temperature and longitudinal magnetic field. Confined spinon excitations are observed in an antiferromagnetic phase below T_{N}≃5.5 K. In a field-induced gapless phase above B_{c}=3.8 T, we identify many-body string excitations as well as low-energy fractional psinon or antipsinon excitations by comparing to Bethe ansatz calculations. In the vicinity of B_{c}, the high-energy string excitations are found to have a dominant contribution to the spin dynamics as compared with the fractional excitations.
ABSTRACT
We report on magnetization, sound-velocity, and magnetocaloric-effect measurements of the Ising-like spin-1/2 antiferromagnetic chain system BaCo_{2}V_{2}O_{8} as a function of temperature down to 1.3 K and an applied transverse magnetic field up to 60 T. While across the Néel temperature of T_{N}â¼5 K anomalies in magnetization and sound velocity confirm the antiferromagnetic ordering transition, at the lowest temperature the field-dependent measurements reveal a sharp softening of sound velocity v(B) and a clear minimum of temperature T(B) at B_{â¥}^{c,3D}=21.4 T, indicating the suppression of the antiferromagnetic order. At higher fields, the T(B) curve shows a broad minimum at B_{â¥}^{c}=40 T, accompanied by a broad minimum in the sound velocity and a saturationlike magnetization. These features signal a quantum phase transition, which is further characterized by the divergent behavior of the Grüneisen parameter Γ_{B}â(B-B_{â¥}^{c})^{-1}. By contrast, around the critical field, the Grüneisen parameter converges as temperature decreases, pointing to a quantum critical point of the one-dimensional transverse-field Ising model.
ABSTRACT
BACKGROUND AND OBJECTIVE: In order to achieve points for the CME certificate of the German Medical Council ("Arztekammer") the reader of a CME article in a medical journal has to fill in an evaluation form that includes knowledge assessment. This article summarizes the data of the first ten CME presentations in the "Deutsche Medizinische Wochenschrift". METHODS: 4481 completed data sets were evaluated by chi-square and binomial tests using SPSS version 10.0. RESULTS: 85% of the participants were specialists, mainly in internal medicine or surgery: those working in private practice or a hospital took part. The great majority had received their licence one to 30 years ago. The topics dealt with diseases which were not uniformly often seen in clinical practice. The individually perceived changes in the strategy of diagnosis and therapy, induced by the CME article, was mainly dependent on qualification and specialization of the reader as well as on the frequency, with which the reader had been treating the respective disorder. The articles were appreciated by specialists as well as by non-specialists. Knowledge assessment was largely made on the basis of the article alone and was successfully passed by nearly 90% of the participants. CONCLUSION: For the first time this article provides detailed data on CME activities in a nation-wide available German medical journal and thus forms the basis for discussing further the definition of quality criteria for CME articles in medical journals.
Subject(s)
Certification , Education, Medical, Continuing , Periodicals as Topic , Binomial Distribution , Chi-Square Distribution , Education, Medical, Continuing/standards , Germany , Humans , Medicine , Periodicals as Topic/standards , Physician Executives , SpecializationABSTRACT
Adaptive seating devices (ASDs) are used in the treatment of children with multiple handicaps. This longitudinal study evaluated, through direct observation and parent-guardian assessment, the behavioral changes seen with the use of ASDs and programming. Nineteen individuals with multiple handicaps and developmental disabilities, aged 1 to 6 years, participated as subjects. Data were collected by a trained observer from eight on-site evaluations and from parent-guardian responses to a preequipment and postequipment questionnaire. Evaluations were made every six weeks, starting about three months before and ending about six months after receiving the seating devices. The activities observed were head control, controlled sitting posture, visual tracking, reach, and grasp. Rating scale data were analyzed using an analysis of variance and a Friedman's test. Other data were analyzed descriptively for frequencies and central tendencies. Sitting posture, head control, and grasp improved significantly. Parent perceptions of the equipment indicated that the chairs freed parents from the need to provide support for their children's activities of daily living, which enabled them to participate in other activities with the children and around the home.
