Doping a correlated band insulator: A new route to half metallic behaviour

We demonstrate in a simple model the surprising result that turning on an on-site Coulomb interaction U in a doped band insulator leads to the formation of a half-metallic state. In the undoped system, we show that increasing U leads to a first order transition between a paramagnetic, band insulator and an antiferomagnetic Mott insulator at a finite value U_{AF}. Upon doping, the system exhibits half metallic ferrimagnetism over a wide range of doping and interaction strengths on either side of U_{AF}. Our results, based on dynamical mean field theory, suggest a novel route to half-metallic behavior and provide motivation for experiments on new materials for spintronics.Comment: 5 pages, 7 figure

Can correlations drive a band insulator metallic?

We analyze the effects of the on-site Coulomb repulsion U on a band insulator using dynamical mean field theory (DMFT). We find the surprising result that the gap is suppressed to zero at a critical Uc1 and remains zero within a metallic phase. At a larger Uc2 there is a second transition from the metal to a Mott insulator, in which the gap increases with increasing U. These results are qualitatively different from Hartree-Fock theory which gives a monotonically decreasing but non-zero insulating gap for all finite U.Comment: 4 pages, 5 figure

Thermo-mechanical properties of sodium chloride and alkali-treated sugarcane bagasse fibre

The experimental characterization of mechanical and thermal properties of treated and raw sugarcane bagasse fibre hasbeen studied. The bagasse fibres are treated with sodium chloride (NaCl) and sodium hydroxide (NaOH) solutions. TheNaOH treated fibres show better structural and thermal properties than other two types. SEM image of alkali-treated fibresreveals that the bundles of fibres are mainly composed of thin parenchyma cell walls. The fibres are joined with each otherwhich improves the mechanical properties. The statistical analysis is also performed using ANOVA one-factor method.From ANOVA, the significant difference between the dependent parameters and the various chemical treatments aredetermined. The results show that the NaCl and NaOH treated fibres significantly improve the mechanical properties andthermal stability

Internet Versus Mailed Questionnaires: A Randomized Comparison (2)

BACKGROUND Low response rates among surgeons can threaten the validity of surveys. Internet technologies may reduce the time, effort, and financial resources needed to conduct surveys. OBJECTIVE We investigated whether using Web-based technology could increase the response rates to an international survey. METHODS We solicited opinions from the 442 surgeon–members of the Orthopaedic Trauma Association regarding the treatment of femoral neck fractures. We developed a self-administered questionnaire after conducting a literature review, focus groups, and key informant interviews, for which we used sampling to redundancy techniques. We administered an Internet version of the questionnaire on a Web site, as well as a paper version, which looked similar to the Internet version and which had identical content. Only those in our sample could access the Web site. We alternately assigned the participants to receive the survey by mail (n=221) or an email invitation to participate on the Internet (n=221). Non-respondents in the mail arm received up to three additional copies of the survey, while non-respondents in the Internet arm received up to three additional requests, including a final mailed copy. All participants in the Internet arm had an opportunity to request an emailed Portable Document Format (PDF) version. RESULTS The Internet arm demonstrated a lower response rate (99/221, 45%) than the mail questionnaire arm (129/221, 58%) (absolute difference 13%, 95% confidence interval 4%-22%, P<0.01). CONCLUSIONS. Our Internet-based survey to surgeons resulted in a significantly lower response rate than a traditional mailed survey. Researchers should not assume that the widespread availability and potential ease of Internet-based surveys will translate into higher response rates.Department of Surgery, McMaster University, Hamilton, Ontario, Canad

Tibial tuberosity fracture in adult as an unusual pattern of injury

Tibial tuberosity avulsion is an uncommon fracture in adults, such lesions typically seen in adolescent male with well-developed quadriceps, ligaments when they are stronger than growth plate. We described a case of 51-year-old gentlemen had direct trauma to left knee, no risk factors were identified, not able to walk, difficulty in straight leg raise test, radiograph of left knee showed tibial tuberosity avulsion fracture. The fracture was treated with open reduction and internal fixation, f/u with successful rehabilitation which results in good range of motion and excellent function at knee joint. The aim of study is present unusual and rare case of tibial tuberosity Avulsion fracture in adult, early diagnosis, surgical mode of treatment, post-surgery rehabilitation and possible complications

p493F12 kinase: A novel MAP kinase expressed in a subset of neurons in the human nervous system

AbstractMonoclonal antibody 31712 identifies a cytoplasmic antigen of 49 kDa in human hippocampus and neocortex. The distribution of 31712 immunoreactive neurons closely matches that of Alzheimer's disease (AD) targeted neurons in these areas. In some hippocampal neurons of AD patients, this antigen colocalizes with ALZ-50, indicating the presence of AD pathology in these neurons. Molecular characterization of the 3F12 cDNA revealed it to be a member of the MAP kinase family, showing 43% amino acid sequence identity to human extracellular related kinase 2 (p42mapk). We have confirmed that p493F12 kinase autophosphorylates both threonine and tyrosine residues, as expected for a MAP kinase. The p49 mRNA is expressed exclusively in the nervous system. In the brain, the distribution of these neurons closely corresponds to 31712 antigenbearing neurons. The p493F12 gene maps to the human chromosome 21q21 region, a region that may be important in the pathogenesis of AD and Down's syndrome

Exciton transition and electronic structure of PbMoO4 crystals studied by polarized light

Published in Physica status solidi. B, Basic solid state physics, Vol. 247, No. 2, pp405-410, 2010.Polarized reflectivity spectra of PbMoO4 crystals have been measured using synchrotron radiation up to 20 eV. The optical constants for the crystallographic axes are derived by using a Kramers-Kronig analysis. It is found that the exciton band at 3.6 eV shows a doublet structure with distinct dichroism. X-ray photoemission spectroscopy (XPS) and the calculation of the elec-tronic structure by a discrete variational Xα method are also carried out. The calculation shows that the va-lence band and the conduction band are mainly com-posed of the O 2p and Mo 4d states, respectively, and the Pb state contributes appreciably to the top of the valence band and the bottom of the conduction band. The valence-band XPS spectrum of PbMoO4 is com-pared with that of PbWO4, which reveals a remarkable difference between them. This difference reflects dif-ferent magnitude of hybridization of Mo 4d or W 5d state to the valence band. The exciton transition is ex-plained in terms of the cationic Pb 6s → 6p excitation model taking into account the crystal-field splitting and the spin-orbit interaction of Pb 6p state. From a comparison of the doublet structure of the exciton band of PbMoO4 and PbWO4, it is suggested that the electron-hole exchange interaction plays an important role for the exciton transitions in both materials.ArticlePhysica status solidi. B, Basic solid state physics. 247(2):405-410 (2010)journal articl

Delay-induced destabilization of entrainment of nerve impulses on ephaptically coupled nerve fibers

We study the effect of delay on the synchronization of two nerve impulses traveling along two ephaptically coupled, unmyelinated nerve fibers. The system is modeled as a pair of delay-coupled Fitzhugh-Nagumo equations. A multiple-scale perturbation approach is used for the analysis of these equations in the limit of weak coupling. In the absence of delay, two pulses with identical speeds are shown to be entrained precisely. However, as the delay is increased beyond a critical value, we show that this precise entrainment becomes unstable. We make quantitative estimates for the actual values of delay at which this can occur in the case of squid giant axons and compare them with the relevant time-scales involved