Far-infrared induced current in a ballistic channel -- potential barrier structure

We consider electron transport in a ballistic multi-mode channel structure in the presence of a transversely polarized far-infrared (FIR) field. The channel structure consists of a long resonance region connected to an adiabatic widening with a potential barrier at the end. At frequencies that match the mode energy separation in the resonance region we find distinct peaks in the photocurrent, caused by Rabi oscillations in the mode population. For an experimental situation in which the width of the channel is tunable via gates, we propose a method for reconstructing the spectrum of propagating modes, without having to use a tunable FIR source. With this method the change in the spectrum as the gate voltage is varied can be monitored.Comment: Submitted to Phys. Rev.

Clinical vignette: Zero in 60 in 48 hours

Cirrhosis is a known cause of thrombocytopenia but it is important to consider other etiologies when the degree of thrombocytopenia is severe, especially in light of impending life-threatening bleeding. One must always maintain a low threshold for additional diagnostic entities when patients present acutely and confirmatory testing reveals profound thrombocytopenia. A 34-year-old man with cirrhosis secondary to Hepatitis C and alcohol abuse presented with persistent bleeding from preexisting oral ulcers and hematuria. Patient denied melena, hematemesis or hematochezia. His past medical history was significant for pancytopenia secondary to cirrhosis, active hepatitis C infection and hypersplenism. He denied any recent change in his medications nor taking any herbal medications or supplements. Vital signs were normal on admission. Physical examination was positive for dried blood on the lips and hepatosplenomegaly. Lab work revealed a platelet count of 0 with chronic leukopenia and anemia. His baseline platelet count is approximately 35,000. Urine analysis indicated gross blood. Coagulation workup was not suggestive of Disseminated Intravascular Coagulation (DIC). Peripheral smear was significant for complete lack of platelets without schistocytes. He was started on daily platelet transfusions with minimal change in his platelet count. A diagnosis of secondary Immune Thrombocytopenic Purpura (ITP) was made and therapy was initiated with intravenous immunoglobulin (IVIG) and dexamethasone. His platelet count failed to improve with worsening hematuria. He also received Rituximab, Romiplostim infusions and high dose methylprednisolone. The patient underwent splenic artery embolization three times. In spite of all efforts he continued to have hematuria and bleeding from intravenous lines with only transient rise in counts. He was taken for laparoscopic splenectomy with a platelet count of 35,000; following which the bleeding subsided and his platelet count improved to 100,000. Patient had a complicated hospital course but was eventually discharged home and currently his platelet counts are within normal limits. This patient appeared to have developed secondary ITP from his active Hepatitis C. Though he had chronic thrombocytopenia from cirrhosis and splenomegaly, it would be unusual to see this degree of platelet drop from these causes alone. ITP is a diagnosis of exclusion and bleeding is usually not proportionate to level of thrombocytopenia as in this patient. This case illustrates the fact that a clinician must have a low threshold for expanding the differential diagnosis of thrombocytopenia, especially diagnoses that are likely to harm the patient such as Thrombotic Thrombocytopenic Purpura, Disseminated Intravascular Coagulation and ITP. This case also demonstrates the challenging nature of managing severe refractory ITP. Splenectomy is the preferred therapy for patients with ITP who are refractory to first-line therapy with glucocorticoids or IVIG and is shown to cause sustained remission in two-thirds of patients

A PRELIMINARY INVESTIGATION OF HTR1A GENE EXPRESSION LEVELS IN AUTISM SPECTRUM DISORDERS

Objective: This study was conducted to explore the expression levels of HTR1A gene in a sample of Egyptian autistic children. Methods: Thirty autistic patients (18 boys, 12 girls) and 20 controls were enrolled in the study. From each child, we isolated RNA samples from whole blood. Quantitative Real-Time PCR (qRT-PCR) was used to measure the gene expressions of HTR1A and normalized to the house keeping gene, beta-actin. Results: The HTR1A gene expression of healthy controls and ASD subjects were varied significantly (p =0.0062). As compared to control healthy subjects, the HTR1A expressions were greatly reduced in samples of ASD. Conclusion: HTR1A gene expression level is a candidate gene for further studies to explore its potential roles in ASD related pathways

Stable Determination of the Electromagnetic Coefficients by Boundary Measurements

The goal of this paper is to prove a stable determination of the coefficients for the time-harmonic Maxwell equations, in a Lipschitz domain, by boundary measurements

Confirming the high pressure phase diagram of the Shastry-Sutherland model

A Muon Spin Rotation (μ + SR) study was conducted to investigate the magnetic properties of SrCu2(BO3)2 (SCBO) as a function of temperature/pressure. Measurements in zero field and transverse field confirm the absence of long range magnetic order at high pressures and low temperatures. These measurements suggest changes in the Cu spin fluctuations characteristics above 21 kbar, consistent with the formation of a plaquette phase as previously suggested by inelastic neutron scattering measurements. SCBO is the only known realisation of the Shatry-Sutherland model, thus the ground state mediating the dimer and antiferromagnetic phase is likekly to be a plaquette state

Gravitino Dark Matter Scenarios with Massive Metastable Charged Sparticles at the LHC

We investigate the measurement of supersymmetric particle masses at the LHC in gravitino dark matter (GDM) scenarios where the next-to-lightest supersymmetric partner (NLSP) is the lighter scalar tau, or stau, and is stable on the scale of a detector. Such a massive metastable charged sparticle would have distinctive Time-of-Flight (ToF) and energy-loss ($dE/dx$) signatures. We summarise the documented accuracies expected to be achievable with the ATLAS detector in measurements of the stau mass and its momentum at the LHC. We then use a fast simulation of an LHC detector to demonstrate techniques for reconstructing the cascade decays of supersymmetric particles in GDM scenarios, using a parameterisation of the detector response to staus, taus and jets based on full simulation results. Supersymmetric pair-production events are selected with high redundancy and efficiency, and many valuable measurements can be made starting from stau tracks in the detector. We recalibrate the momenta of taus using transverse-momentum balance, and use kinematic cuts to select combinations of staus, taus, jets and leptons that exhibit peaks in invariant masses that correspond to various heavier sparticle species, with errors often comparable with the jet energy scale uncertainty.Comment: 23 pages, 10 figures, updated to version published in JHE

Vortex Dynamics in Dissipative Systems

We derive the exact equation of motion for a vortex in two- and three- dimensional non-relativistic systems governed by the Ginzburg-Landau equation with complex coefficients. The velocity is given in terms of local gradients of the magnitude and phase of the complex field and is exact also for arbitrarily small inter-vortex distances. The results for vortices in a superfluid or a superconductor are recovered.Comment: revtex, 5 pages, 1 encapsulated postscript figure (included), uses aps.sty, epsf.te

Profiling humoral immune responses to Clostridium difficile-specific antigens by protein microarray analysis

Clostridium difficile is an anaerobic, Gram-positive, and spore-forming bacterium that is the leading worldwide infective cause of hospital-acquired and antibiotic-associated diarrhea. Several studies have reported associations between humoral immunity and the clinical course of C. difficile infection (CDI). Host humoral immune responses are determined using conventional enzyme-linked immunosorbent assay (ELISA) techniques. Herein, we report the first use of a novel protein microarray assay to determine systemic IgG antibody responses against a panel of highly purified C. difficile-specific antigens, including native toxins A and B (TcdA and TcdB, respectively), recombinant fragments of toxins A and B (TxA4 and TxB4, respectively), ribotypespecific surface layer proteins (SLPs; 001, 002, 027), and control proteins (tetanus toxoid and Candida albicans). Microarrays were probed with sera from a total of 327 individuals with CDI, cystic fibrosis without diarrhea, and healthy controls. For all antigens, precision profiles demonstrated<10% coefficient of variation (CV). Significant correlation was observed between microarray and ELISA in the quantification of antitoxin A and antitoxin B IgG. These results indicate that microarray is a suitable assay for defining humoral immune responses to C. difficile protein antigens and may have potential advantages in throughput, convenience, and cost