Quasi-Classical Trajectory Studies of H + HX → H2 + X (X = Cl,Br, I) Reaction at High Collision Energy

Quasi-classical trajectory calculations have been performed to investigate the dynamics of the H + HX → H₂ + X reactions, where X = Cl, Br, and I. Calculations were performed for two collision energies, 16 and 36 kcal mol⁻¹. The results show that the dynamics of the abstraction reactions at these high collision energies are rather unusual. The product energy and angular distributions can be accounted for by a mechanism that involves an isolated interaction between the two H atoms in the system to form H₂ followed by hard-sphere scattering of this newly formed H₂ off the X atom.     

Effect of carbon nanofibres dispersion on the microwave absorbing properties of CNF/epoxy composites

Since mid-twentieth century filled polymers have been largely studied for electromagnetic (e.m.) applications, including wave absorbing materials, showing good promise. A certain knowledge was gained in the field of carbon particles filled polymers, even if there is still a lack of understanding the relationship between material microstructure and macroscopic electromagnetic performance. Moreover, the recent discover of carbon nanofibres and nanotubes, with their potentiality, introduces new field of investigation. In this work carbon nanofibers were used to increase permittivity of neat resin, in order to achieve better absorbing performance in the 8–20 GHz range. Carbon nanofibers were chosen as a way of lowering filler content, while increasing the dielectric properties of the resulting composite. Key factor is the nanofiller dispersion process: in this paper two different dispersion methods were used, both employing an organic solvent that was removed either via evaporation or filtration. The resulting microstructures, composed of well dispersed CNF as well as of microaggregates, lead to materials that, on equal filler content, present different dielectric properties and absorbing performance. Microstructures were analyzed by SEM.     

Barriers,biases, and beliefs about arteriovenous fistula placement in children: A survey of the International Pediatric Fistula First Initiative (IPFFI) within the Midwest Pediatric Nephrology Consortium (MWPNC)

There has been recent emphasis on increased arteriovenous fistula (AVF) use and decreased central venous catheter use in hemodialysis (HD) patients. The International Pediatric Fistula First Initiative was founded via collaborative effort with the Midwest Pediatric Nephrology Consortium to alert nephrologists, surgeons, and dialysis staff to consider fistulae as the best access in pediatric HD patients. A multidisciplinary educational DVD outlining expectations and strategies to increase AVF placement and usage in children was created. Participants were administered a survey previewing and postviewing to identify barriers to placement and usage of AVF in children. A total of 52 surveys were subdivided as either “dialysis staff” or “proceduralist” at five centers. Thirty‐three percent of respondents were unaware if their practice was following published guidelines. Sixty‐five percent of respondents stated they referred to a dedicated vascular access surgeon at their respective institutions. Methods used to monitor AVF function included physical exam, venous pressure monitoring, and ultrasound dilution. Vascular access was placed within 3 months in only 35% of patients. Interdisciplinary communication problems between surgeons, interventional radiologists, and nephrologists were identified as a major barrier. Lack of AVF usage was often due to maturation failure. Routine access rounds did not occur in any centers. Regarding monitoring, 74% of the respondents use physical exam, 26% use venous pressure monitoring, and 9% use ultrasound dilution. Ninety‐three percent of dialysis staff stated they would change practice patterns following the intervention; however, 12% of surgeons stated they would alter practice patterns. To our knowledge, this is the first report to identify barriers to placement of AVF in children from the perspectives of multidisciplinary team members including pediatric nephrologists, surgeons, interventional radiologists, and multidisciplinary dialysis staff.     

Computer‐aided simulation and testing of spatial linkages with joint mechanical errors

Tolerance allocation influences production costs in a big way. For this reason it is very important to have an accurate study about the effects of manufacturing errors on the functioning and performances of linkages. In this paper, the authors present a computer‐aided methodology based on a 3D geometrical approach using the dual‐algebra fundamentals. The purpose is to give an useful tool which can be integrated into CAD software in order to evaluate the performances of spatial mechanisms with mechanical errors. The proposed methodology has been validated by means of experimental tests on a Cardan joint mechanism with clearances, misalignments and dimensional errors. Copyright © 2005 John Wiley & Sons, Ltd.     

Morphology,structure and density evolution of carbon nano-structures deposited by N-IR pulsed laser ablation of graphite

Carbon films were deposited by pulsed laser ablation on Si <100> substrates, heated at temperatures increasing from RT to 800 °C, from a pure graphite target, operating in vacuum (~ 10^− 4 Pa). The laser ablation was performed by an Nd:YAG laser, operating in the near IR wavelength (λ = 1064 nm).Micro-Raman and grazing incidence X-ray diffraction analysis (GI-XRD) established the progressive formation of ordered nano-sized graphitic structures, increasing substrate temperature. The surface morphology is characterised by macroscopic roughness (SEM, AFM) while the low temperature samples are characterised by very smooth surface. The film density, evaluated by X-ray reflectivity measurements, is also affected by the substrate temperature. This structural property modification induces relevant variation on the emission properties of carbon films, as evidenced by Field Emission measurements. The film structure and texturing is also strongly related to laser wavelength: the low energy associated to the IR laser radiation (1.17 eV) causes an early aromatic cluster formation at T = 400 °C associated to a sensible increase in the aromatic plane stacking distance (d₀₀₂ ~ 0.39 nm), compared to graphite. These density decrease shows a direct correlation with the electron emission properties. Roughness and presence of voids play a negative role both on the threshold electric field E_th and enhancement factor (β) The density decreasing and graphitic layer widening are notably to be ascribed to the very fast out-of-equilibrium growth and to the presence of large activated carbon species in the “plume”.     

Zahnmi?bildungen beim Steinwild in den Karawanken

Ohne Zusammenfassung     

KDDML‐G: a grid‐enabled knowledge discovery system

KDDML‐G is a middleware language and system for knowledge discovery on the grid. The challenge that motivated the development of a grid‐enabled version of the ‘standalone’ KDDML (Knowledge Discovery in Databases Markup Language) environment was on one side to exploit the parallelism offered by the grid environment, and on the other side to overcome the problem of data immovability, a quite frequent restriction on real‐world data collections that has principally a privacy‐preserving purpose. The last question is addressed by moving the code and ‘mining’ the data ‘on the place’, that is by adapting the computation to the availability and localization of the data. Copyright © 2007 John Wiley & Sons, Ltd.     

IV. Referate

Ohne Zusammenfassung     

Lymphocyte proliferative response in brown bears: cytokine role and glucocorticoid effect

There have been many cholera outbreaks in Senegal since 1971. The last outbreak began in the Dakar region in August 1995. It spread to the Diourbel, Fatick, Saint-Louis and Thies regions. In January 1996, the outbreak hit the Niakhar study area in the Fatick region. A team from ORSTOM (the French Institute of Scientific Research for Development in Cooperation) has been recording demographic events in this area for almost 15 years. The geographic approach is based on the automated mapping of cholera in hamlets and villages. Such studies investigate the factors determining the spread of diseases, within the context of land use. Three sets of data were used: demographic data that had been routinely collected and were available from a database, digitized maps and epidemiological data from a surveillance system set up to monitor the outbreak. A series of incidence maps, over time and on various scales, were generated using specialized software. The maps were analyzed and the outbreak was found to be heterogeneous over time. There were two waves of the outbreak and differences according to age and gender. The degree of heterogeneity depended on the place of residence. Heterogeneity was probably determined by village size, roads and the concentration of inhabitants within hamlets, which is roughly equivalent to the number of people per bore hole. These preliminary results suggest that further research is necessary, looking at different geographical scales (e.g. households, districts and regions). Qualitative studies of water use and the organization of the water supply are also required.     

Internationaler Jagdwissenschaftlicher Kongre? in Jugoslawien

Ohne Zusammenfassung