Interference Effects Due to Commensurate Electron Trajectories and Topological Crossovers in (TMTSF)2ClO4

We report angle-dependent magnetoresistance measurements on (TMTSF)2ClO4 that provide strong support for a new macroscopic quantum phenomenon, the interference commensurate (IC) effect, in quasi-one dimensional metals. In addition to observing rich magnetoresistance oscillations, and fitting them with one-electron calculations, we observe a clear demarcation of field-dependent behavior at local resistance minima and maxima (versus field angle). Anticipated by a theoretical treatment of the IC effect in terms of Bragg reflections in the extended Brillouin zone, this behavior results from 1D-2D topological crossovers of electron wave functions as a function of field orientation.Comment: 14 page

Interference Commensurate Oscillations in Q1D Conductors

We suggest an analytical theory to describe angular magnetic oscillations recently discovered in quasi-one-dimensional conductor (TMTSF)2PF6 [see Phys. Rev. B, 57, 7423 (1998)] and define the positions of the oscillation minima. The origin of these oscillations is related to interference effects resulting from an interplay of quasi-periodic and periodic ("commensurate") electron trajectories in an inclined magnetic field. We reproduce via calculations existing experimental data and predict some novel effects.Comment: 10 pages, 2 figure

FDI in Space: Spatial Autoregressive Relationships in Foreign Direct Investment

Theoretical models of foreign direct investment (FDI) have only recently begun to model the role of third countries, and the empirical FDI literature has almost exclusively examined bilateral FDI data without recognizing the potential interdependence between FDI decisions to alternative host countries. This paper uses spatial econometric techniques to examine the spatial correlation between FDI to alternative (neighboring) regions. The sign of such correlations can provide evidence for or against alternative theories for FDI motivations. Using data on OECD countries from 1980-2000, we find evidence consistent with export platform FDI in Europe.

Drag Reduction on Blunt-Based Vehicles Using Forebody Surface Roughness

The article of record as published may be found at http://dx.doi.org/10.2514/2.3849Results of wind-tunnel tests that demonstrate a novel drag reduction technique for blunt-based vehicles are presented. For these tests, the forebody roughness of a blunt-based model was modified using micromachined surface overlays. As forebody roughness increases, the boundary layer at the model aft thickens and reduces the shearing effect of external flow on the separated flow behind the base region, resulting in reduced base drag. For vehicle configurations with large base drag, existing data predict that a small increment in forebody friction drag will result in a relatively large decrease in base drag. If the added increment in forebody skin drag is optimized with respect to base drag, reducing the total drag of the configuration is possible. The wind-tunnel tests results conclusively demonstrate the existence of a forebody drag–base drag optimal point. The data demonstrate that the base drag coefficient corresponding to the drag minimum lies between 0.225 and 0.275, referenced to the base area. Most important, the data show a drag reduction of approximately 15% when the drag optimum is reached

QUANTIFYING IMPACTS DURING BEAM AND FLOOR TRAINING IN PREADOLESCENT GIRLS FROM TWO STREAMS OF ARTISTIC GYMNASTICS

The primary aim of this study was to determine the effects of participation level (international and national), apparatus (beam and floor) and training phase (precompetition and competition) on estimates of training load in a convenient sample of gymnasts aged 7 to 13 years. Video analysis of training sessions along with accelerometer and force platform (500 Hz) peak ground reaction force data were used to establish differences between key gymnastic-specific and non-gymnastic-specific variables. International level gymnasts demonstrated higher incidence in hours of training, number of observed impacts, markers of the quality of periodised training program and lower relative injury rates. Marked differences were also observed between the two training phases. The demand for injury prevention strategies may be higher at the national level of gymnastics training

Diseño, fabricación y aplicaciones analíticas de nanocelulosa y sus híbridos

El gran avance nanotecnológico que ha experimentado la Química Analítica en los últimos años ha sido un indicador del grado de bienestar de la sociedad. La multidisciplinaridad de la Nanociencia y Nanotecnología ha sido esencial para el avance de los métodos y herramientas analíticas, así como para llevar a cabo la automatización, simplificación y miniaturización de los procesos analíticos integrados en los laboratorios [1]. En este campo, son muchos los nanomateriales explorados por sus propiedades excepcionales (ópticas, eléctricas, magnéticas) como sensores y sorbentes así como su amplio rango de aplicación de interés medioambiental o en bienes de consumo, cosmética, agroalimentación, entre otros. Sin embargo, la nanocelulosa no se ha explorado en química analítica aun siendo postulada como uno de los nanomateriales emergentes del siglo XXI, debido a su carácter biodegradable y su abundancia en la naturaleza, así como a otras fascinantes propiedades que le confieren un sinfín de aplicaciones. No cabe duda que en la búsqueda de los nanomateriales del futuro la nanocelulosa revolucionará las industrias electrónica, textil, farmacéutica y la energética, por su producción a gran escala con bajo coste a partir de un recurso natural renovable. Teniendo en cuenta lo anteriormente expuesto, la Tesis Doctoral tiene como objetivo general el estudio de la nanocelulosa en química analítica, centrándonos en el diseño de nanofibras de celulosa como herramienta en la mejora de los procesos analíticos, así como en la separación de productos farmacéuticos y otros

Periprosthetic Fractures Around a Cementless Hydroxyapatite-coated Implant: A New Fracture Pattern Is Described

Background Periprosthetic fractures can occur both intraoperatively and postoperatively with implantation of cementless tapered stems. Questions/purposes In a large cohort of patients receiving cementless, proximally hydroxyapatite-coated femoral implants, we answered the following questions: What was the incidence of intraoperative and postoperative fractures associated with the implant? What were the fracture patterns as classified by the Vancouver classification system? Did the Vancouver classification represent the fracture patterns found? How were the fractures treated and what were the treatment outcomes; that is, how many fractures healed and did the stems osseointegrate? Methods We evaluated 1039 hips (932 patients) from three prospective studies. The hips were divided into three groups: no fractures, intraoperative fractures, and postoperative fractures. Demographic differences among the groups were noted. Postoperative fractures were classified using the Vancouver classification system. We judged stem stability using Engh’s criteria and fracture union was determined by the treating surgeon and confirmed by the authors. Results We identified 58 periprosthetic fractures in the 1039 hips (5.6%): 38 intraoperative (3.7%) and 20 postoperative (1.9%). Eleven of the postoperative fractures were classifiable by the original Vancouver classification system and nine were of the newly described “clamshell” variety, not classifiable by this system. No intraoperative fractures extended below the lesser trochanter. Twenty-five of these fractures were treated with a single cable or cerclage wire. The remaining received no specific treatment. Of the 20 postoperative fractures, five were treated nonoperatively. All stems osseointegrated. Conclusions Both intraoperative and postoperative fractures can be managed with success when the stem is stabilized or found to be osseointegrated. An adjustment to the Vancouver classification is suggested to include the clamshell fracture, which has not been previously described. Level of Evidence Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence

High Survivorship With a Titanium-encased Alumina Ceramic Bearing for Total Hip Arthroplasty

Background Although ceramic-on-ceramic bearings for total hip arthroplasty (THA) show promising results in terms of bearing-surface wear, fracture of the bearing, insertional chips, and squeaking remain a concern. Questions/purposes Our primary objective of this report was to determine overall survivorship of a titanium- encased ceramic-on-ceramic bearing couple. Our secondary objectives were to evaluate for ceramic fracture, insertional chips, osteolysis, and device squeaking. Methods Six surgeons at six institutions implanted 194 patients (209 hips) with an average age of 52 years with cementless hips and alumina ceramic bearings. One hun- dred thirty-seven patients (146 hips) have 10-year followup (70%). We determined Kaplan-Meier survivorship of the bearing surface and implant system and collected radio- graphic and clinical data to evaluate for osteolysis and squeaking. Results Survivorship using revision for any reason as the end point was 97% at 10 years and survivorship end point bearing surface failure or aseptic loosening of 99%. There was one ceramic insert fracture (0.5%), there were no insertional chips, there was no visible osteolysis on AP and lateral radiographs, and there was a 1% patient- self-reported incidence of squeaking at the last clinical followup. Six hips underwent revision (3.7%). Conclusions Ceramic bearings for THA with a titanium- encased insert have high survivorship at 10 years followup and a fracture risk of 0.5%. We found at last followup on routine radiographs no evidence of osteolysis, and no patient has been revised for squeaking or has reported dissatisfaction with the clinical result because of noise. Level of Evidence Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence