Bibliothek

Notizen: Supersonic fluid flow and the interaction of strong shock waves to produce jets of material are ubiquitous features of inertial confinement fusion (ICF), astrophysics, and other fields of high energy-density science. The availability of large laser systems provides an opportunity to investigate such hydrodynamic systems in the laboratory, and to test their modeling by radiation hydrocodes. We describe experiments to investigate the propagation of a structured shock front within a radiation-driven target assembly, the formation of a supersonic jet of material, and the subsequent interaction of this jet with an ambient medium in which a second, ablatively driven shock wave is propagating. The density distribution within the jet, the Kelvin–Helmholz roll-up at the tip of the jet, and the jet's interaction with the counterpropagating shock are investigated by x-ray backlighting. The experiments were designed and modeled using radiation hydrocodes developed by Los Alamos National Laboratory, AWE, and Lawrence Livermore National Laboratory. The same hydrocodes are being used to model a large number of other ICF and high energy-density physics experiments. Excellent agreement between the different simulations and the experimental data is obtained, but only when the full geometry of the experiment, including both laser-heated hohlraum targets (driving the jet and counter-propagating shock), is included. The experiments were carried out at the University of Rochester's Omega laser [J. M. Soures et al., Phys. Plasmas 3, 2108 (1996)]. © 2002 American Institute of Physics.

Notizen: The Fuping Complex and the adjoining Wutai and Hengshan Complexes are located in the central zone of the North China craton. The dominant rock types in the Fuping Complex are high-grade tonalitic–trondhjemitic–granodioritic (TTG) gneisses, with minor amounts of mafic granulites, syntectonic granitic rocks and supracrustal rocks. The petrological evidence from the mafic granulites indicates three stages of metamorphic evolution. The M1 stage is represented by garnet porphyroblasts and matrix plagioclase, quartz, orthopyroxene, clinopyroxene and hornblende. Orthopyroxene+plagioclase symplectites and clinopyroxene+plagioclase±orthopyroxene coronas formed in response to decompression during M2 following the peak metamorphism at M1. Hornblende+plagioclase symplectites formed as a result of further isobaric cooling and retrograde metamorphism during M3. The P–T  estimates using TWQ thermobarometry are: 900–950 °C and 8.0–8.5 kbar for the peak assemblage (M1), based on the core compositions of garnet, matrix pyroxene and plagioclase; 700–800 °C and 6.0–7.0 kbar for the pyroxene+plagioclase symplectites or coronas (M2); and 550–650 °C and 5.3–6.3 kbar for the hornblende+plagioclase symplectites (M3), based on garnet rim and corresponding symplectic mineral compositions. These P–T  estimates define a clockwise P–T  path involving near-isothermal decompression for the Fuping Complex, similar to the P–T  path estimated for the metapelitic gneisses. The inferred P–T  path suggests that the Fuping Complex underwent initial crustal thickening, subsequent exhumation, and finally cooling and retrogression. This tectonothermal path is similar to P–T  paths inferred for the Wutai and Hengshan Complexes and other tectonic units in the central zone of the North China craton, but different from anti-clockwise P–T paths estimated for the basement rocks in the eastern and western zones of the craton. Based on lithological, structural, metamorphic and geochronological data, the eastern and western zones of the craton are considered to represent two different Archean to Paleoproterozoic continental blocks that amalgamated along the central zone at the end of Paleoproterozoic. The P–T paths of the Fuping Complex and other tectonic units in the central zone record the collision between the eastern and western zones that led to the final assembly of the North China craton at c. 1800 Ma.

Notizen: Abstract  A nursing clinic for homeless men was developed by a faculty member and her senior community health nursing students in a city mission over a 2.5-year period. The development of this clinic and a conceptualization of their nursing roles are described. Nursing care focused on promoting access to primary care through screening and referral and through nursing interventions of education, counseling, advocacy, and collaboration. Because the Student Nurses' Clinic was instrumental in clarifying and conceptualizing what nurses can do to promote primary care, mission administrators and staff gained insights about nursing and are better prepared to plan programs for the health care needs of the homeless men—the “guests” at the mission.

Notizen: Pacemaker Treatment in LQT3 and Brugada Syndrome. Introduction: We recently identified a novel mutation of SCN5A (1795insD) in a large family with features of both long QT syndrome type 3 and the Brugada syndrome. The purpose of this study was to detail the clinical features and efficacy of pacemaker therapy in preventing sudden death in this family. Methods and Results: The study group consisted of 116 adult family members: 60 carriers (29 males) and 56 noncarriers (28 males) of the mutant gene. Investigations included 24-hour Holter monitoring, ergometry, and electrophysiologic studies. Mean, lowest, and highest heart rate were lower in the carriers, but heart rate variability was comparable. In carriers, disproportional QT prolongation was present during bradycardia. No complex ventricular ectopy was recorded, and there were fewer isolated premature beats (both ventricular and atrial) in carriers. All patients were asymptomatic, except for two individuals who experienced syncope; in one of these patients, asystolic episodes (up to 9 sec) were repeatedly recorded. Prolonged HV intervals were present in 5 of 6 patients. Thirty carriers received a prophylactic backup pacemaker. During median follow-up of 4.5 years (range 0.0 to 22.6), their survival rate was 100%. There were five sudden deaths among the remaining 30 carriers without a pacemaker (P = 0.019). Conclusion: This family with a high incidence of nocturnal sudden death is characterized by bradycardia-dependent QT prolongation, intrinsic sinus node dysfunction, and generalized conduction abnormalities. There is a striking absence of complex ventricular ectopy, and pacemaker implantation was effective in preventing sudden death. These findings raise the possibility of a bradycardic rather than tachycardic mode of death.

Notizen: Background: Recently, we identified a novel mutation of SCN5A (1795insD) in a large family with LQTS3. The aim of this study was to assess whether the various proposed corrections of the QT interval to heart rate help to improve the identification of carriers of the mutant gene. Methods: The study group consisted of 101 adult family members: 57 carriers and 44 noncarriers (mean age 44.6 ± 14.6 and 40.3 ± 12.8 years, respectively). In all individuals a 12-lead ECG, exercise ECG, and 24-hour Holter ECG were obtained. Results: Correction for heart rate significantly improved the diagnostic performance of the QT interval. Diagnostic performance of the Bazett formula was similar to that of the newer formulas (Fridericia, Hodges, Framingham, and a logarithmic formula). At a cut-off value of 440 ms, the Bazett corrected QT interval was associated with a sensitivity and specificity of 90% and 91%, respectively. Using the 24-hour Holter ECG, a prolonged QTc at heart rates less than 60 beats/min was almost pathognomonic for genetic mutation (sensitivity and specificity both 99%), whereas the QTc calculated at the lowest heart rate using Bazett's formula provided full discrimination. Conclusion: In the present family, the resting ECG gave a good indication about the presence or absence of genetic mutation but a 24-hour Holter recording was mandatory to ascertain the diagnosis. In the diagnosis of this form of LQTS3, Bazett's formula was at least as good as other proposed corrections of the QT interval to heart rate.

Notizen: Calorimetric, thermomechanical, and rheological properties of undercooled liquid Pd40Ni40P20 were determined within a wide temperature range above the glass transition. The concept of the limiting fictive temperature was applied to the entire set of measurements to compare the different properties adequately. It was found that an equilibrium state of a sample that is defined by its calorimetric glass temperature corresponds to a similar equilibrium state for the specific volume and for the shear viscosity as well. The Kauzmann temperature as one of the most important material characteristics concerning the glass transition could be determined with high accuracy leading to the evaluation of the free volume persistent in the samples. Viscosity values of the liquid extending over a range of about nine orders in magnitude could be described best by the free volume theory evaluated by Cohen and Grest, provided that experimentally obtained parameters were used for the calculations. The comparison between nonequilibrium measurements at isochronous heating and model calculations in the framework of bimolecular reaction kinetics shows that good agreement can be achieved using thermodynamic parameters that have been obtained from equilibrium measurements. However, systematic deviations indicate also the limitations of the model that are related to the intrinsic dynamic heterogeneity of the vitreous state. © 2000 American Institute of Physics.

Notizen: This study examined two screening instruments designed to measure phonemic awareness (Test of Auditory Analysis Skills-TAAS and Yopp-Singer Test of Phoneme Segmentation). Participants included 25 second-semester kindergarten children who were administered both instruments. The dependent measure (the STAR Reading Test) was administered in February of their First-Grade year. The investigation was designed to determine if these instruments are both evaluating the same skills and identify which was more effective in predicting success in reading near the end of First Grade. The children's scores from the Yopp-Singer and the TAAS were correlated (r=0.56, p〈0.01) and so were the scores between the TAAS and STAR (r=0.51, p〈0.01). Comparison of scores between the Yopp and the STAR produced non-significant results (r=0.31). Although the TAAS produced a higher correlation with reading achievement than the Yopp-Singer, the difference between these two measures failed to reach significance (t=1.16). Implications of these findings, along with possible explanations of the results, are discussed.

Notizen: Modulated-temperature calorimetry measurements on the bulk glass-forming Pd40Ni40P20 alloy yielded the complex specific heat response of the deeply undercooled melt near the static glass transition. The imaginary contributions to the complex signal give direct access to the spectrum of slow α-relaxation modes of the undercooled liquid state that are frozen in upon vitrification. The results are discussed with respect to the kinetics of the glass transition and compared to results obtained from static equilibrium measurements. © 2001 American Institute of Physics.