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.

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

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

Theory of Thermodynamic Magnetic Oscillations in Quasi-One-Dimensional Conductors

The second order correction to free energy due to the interaction between electrons is calculated for a quasi-one-dimensional conductor exposed to a magnetic field perpendicular to the chains. It is found that specific heat, magnetization and torque oscillate when the magnetic field is rotated in the plane perpendicular to the chains or when the magnitude of magnetic filed is changed. This new mechanism of thermodynamic magnetic oscillations in metals, which is not related to the presence of any closed electron orbits, is applied to explain behavior of the organic conductor (TMTSF)$_2$ClO$_4$.Comment: 11 pages + 5 figures (included

Demonstration of multi-channel 80 Gbit/s integrated transmitter and receiver for wavelength-division multiplexing passive optical network and fronthauling applications

The performance evaluation of a multi-channel transmitter that employs an arrayed reflective electroabsorption modulator-based photonic integrated circuit and a low-power driver array in conjunction with a multi-channel receiver incorporating a pin photodiode array and integrated arrayed waveguide grating is reported. Due to their small footprint, low power consumption and potential low cost, these devices are attractive solutions for future mobile fronthaul and next generation optical access networks. A BER performance of <10(-9) at 10.3 Gbit/s per channel is achieved over 25 km of standard single mode fibre. The transmitter/receiver combination can achieve an aggregate bit rate of 82.4 Gbit/s when eight channels are active

Efficient Replication of Over 180 Genetic Associations with Self-Reported Medical Data

While the cost and speed of generating genomic data have come down dramatically in recent years, the slow pace of collecting medical data for large cohorts continues to hamper genetic research. Here we evaluate a novel online framework for amassing large amounts of medical information in a recontactable cohort by assessing our ability to replicate genetic associations using these data. Using web-based questionnaires, we gathered self-reported data on 50 medical phenotypes from a generally unselected cohort of over 20,000 genotyped individuals. Of a list of genetic associations curated by NHGRI, we successfully replicated about 75% of the associations that we expected to (based on the number of cases in our cohort and reported odds ratios, and excluding a set of associations with contradictory published evidence). Altogether we replicated over 180 previously reported associations, including many for type 2 diabetes, prostate cancer, cholesterol levels, and multiple sclerosis. We found significant variation across categories of conditions in the percentage of expected associations that we were able to replicate, which may reflect systematic inflation of the effects in some initial reports, or differences across diseases in the likelihood of misdiagnosis or misreport. We also demonstrated that we could improve replication success by taking advantage of our recontactable cohort, offering more in-depth questions to refine self-reported diagnoses. Our data suggests that online collection of self-reported data in a recontactable cohort may be a viable method for both broad and deep phenotyping in large populations

Magnetic Determination of Hc2H_{c2} under Accurate Alignment in (TMTSF)2_2ClO4_4

Cantilever magnetometry has been used to measure the upper critical magnetic field $H_{c2}$ of the quasi-one dimensional molecular organic superconductor (TMTSF)$_2$ClO$_4$. From simultaneous resistivity and torque magnetization experiments conducted under precise field alignment, $H_{c2}$ at low temperature is shown to reach 5T, nearly twice the Pauli paramagnetic limit imposed on spin singlet superconductors. These results constitute the first thermodynamic evidence for a large $H_{c2}$ in this system and provide support for spin triplet pairing in this unconventional superconductorComment: Submitted July 1, 2003, Accepted December 9, 2003, Physical Review Letter