Paramagnetic Meissner effect in superconductors from self-consistent solutions of Ginzburg-Landau equations

The paramagnetic Meissner effect (PME) is observed in small superconducting samples, and a number of controversial explanations of this effect are proposed, but there is as yet no clear understanding of its nature. In the present paper PME is considered on the base of the Ginzburg-Landau theory (GL). The one-dimensional solutions are obtained in a model case of a long superconducting cylinder for different cylinder radii R, the GL-parameters \kappa and vorticities m. Acording to GL-theory, PME is caused by the presence of vortices inside the sample. The superconducting current flows around the vortex to screeen the vortex own field from the bulk of the sample. Another current flows at the boundary to screen the external field H from entering the sample. These screening currents flow in opposite directions and contribute with opposite signs to the total magnetic moment (or magnetization) of the sample. Depending on H, the total magnetization M may be either negative (diamagnetism), or positive (paramagnetism). A very complicated saw-like dependence M(H) (and other characteristics), which are obtained on the base of self-consistent solutions of the GL-equations, are discussed.Comment: 6 pages, 5 figures, RevTex, submitted to Phys. Rev.

Gene therapy for pain: Results of a phase I clinical trial

Objective: Preclinical evidence indicates that gene transfer to the dorsal root ganglion using replication‐defective herpes simplex virus (HSV)‐based vectors can reduce pain‐related behavior in animal models of pain. This clinical trial was carried out to assess the safety and explore the potential efficacy of this approach in humans. Methods: We conducted a multicenter, dose‐escalation, phase I clinical trial of NP2, a replication‐defective HSV‐based vector expressing human preproenkephalin ( PENK ) in subjects with intractable focal pain caused by cancer. NP2 was injected intradermally into the dermatome(s) corresponding to the radicular distribution of pain. The primary outcome was safety. As secondary measures, efficacy of pain relief was assessed using a numeric rating scale (NRS), the Short Form McGill Pain Questionnaire (SF‐MPQ), and concurrent opiate usage. Results: Ten subjects with moderate to severe intractable pain despite treatment with >200mg/day of morphine (or equivalent) were enrolled into the study. Treatment was well tolerated with no study agent‐related serious adverse events observed at any point in the study. Subjects receiving the low dose of NP2 reported no substantive change in pain. Subjects in the middle‐ and high‐dose cohorts reported pain relief as assessed by NRS and SF‐MPQ. Interpretation: Treatment of intractable pain with NP2 was well tolerated. There were no placebo controls in this relatively small study, but the dose‐responsive analgesic effects suggest that NP2 may be effective in reducing pain and warrants further clinical investigation. ANN NEUROL 2011Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86983/1/22446_ftp.pd

Nebulized heparin is associated with fewer days of mechanical ventilation in critically ill patients: a randomized controlled trial

INTRODUCTION: Prolonged mechanical ventilation has the potential to aggravate or initiate pulmonary inflammation and cause lung damage through fibrin deposition. Heparin may reduce pulmonary inflammation and fibrin deposition. We therefore assessed whether nebulised heparin improved lung function in patients expected to require prolonged mechanical ventilation. METHODS: Fifty patients expected to require mechanical ventilation for more than 48 hours were enrolled in a double-blind randomised placebo-controlled trial of nebulised heparin (25,000 U) or placebo (normal saline) 4 or 6 hourly, depending on patient height. The study drug was continued while the patient remained ventilated to a maximum of 14 days from randomisation. RESULTS: Nebulised heparin was not associated with a significant improvement in the primary end-point, the average daily partial pressure of oxygen to inspired fraction of oxygen ratio while mechanically ventilated, but was associated with improvement in the secondary end-point ventilator free days amongst survivors at day 28 (22.6 4.0 versus 18.0 7.1, treatment difference 4.6 days, 95% CI 0.9 to 8.3, P = 0.02). Heparin administration was not associated with any increase in adverse events. CONCLUSIONS: Nebulised heparin was associated with fewer days of mechanical ventilation in critically ill patients expected to require prolonged mechanical ventilation. Further trials are required to confirm these findings. Trial registration: The Australian Clinical Trials Registry (ACTR-12608000121369

Flux transitions in a superconducting ring

We perform a numeric study of the flux transitions in a superconducting ring at fixed temperature, while the applied field is swept at an ideally slow rate. The current around the ring and its free energy are evaluated. We partially explain some of the known experimental features, and predict a considerably large new feature: in the vicinity of a critical field, giant jumps are expected

Optimizing high-flow nasal cannula flow settings in adult hypoxemic patients based on peak inspiratory flow during tidal breathing

Cànula nasal d'alt flux; Hipoxèmia; Flux inspiratori màximCánula nasal de alto flujo; Hipoxemia; Flujo inspiratorio máximoHigh-flow nasal cannula; Hypoxemia; Peak inspiratory flowBackground Optimal flow settings during high-flow nasal cannula (HFNC) therapy are unknown. We investigated the optimal flow settings during HFNC therapy based on breathing pattern and tidal inspiratory flows in patients with acute hypoxemic respiratory failure (AHRF). Methods We conducted a prospective clinical study in adult hypoxemic patients treated by HFNC with a fraction of inspired oxygen (FIO2) ≥ 0.4. Patient’s peak tidal inspiratory flow (PTIF) was measured and HFNC flows were set to match individual PTIF and then increased by 10 L/min every 5–10 min up to 60 L/min. FIO2 was titrated to maintain pulse oximetry (SpO2) of 90–97%. SpO2/FIO2, respiratory rate (RR), ROX index [(SpO2/FIO2)/RR], and patient comfort were recorded after 5–10 min on each setting. We also conducted an in vitro study to explore the relationship between the HFNC flows and the tracheal FIO2, peak inspiratory and expiratory pressures. Results Forty-nine patients aged 58.0 (SD 14.1) years were enrolled. At enrollment, HFNC flow was set at 45 (38, 50) L/min, with an FIO2 at 0.62 (0.16) to obtain an SpO2/FIO2 of 160 (40). Mean PTIF was 34 (9) L/min. An increase in HFNC flows up to two times of the individual patient’s PTIF, incrementally improved oxygenation but the ROX index plateaued with HFNC flows of 1.34–1.67 times the individual PTIF. In the in vitro study, when the HFNC flow was set higher than PTIF, tracheal peak inspiratory and expiratory pressures increased as HFNC flow increased but the FIO2 did not change. Conclusion Mean PTIF values in most patients with AHRF were between 30 and 40 L/min. We observed improvement in oxygenation with HFNC flows set above patient PTIF. Thus, a pragmatic approach to set optimal flows in patients with AHRF would be to initiate HFNC flow at 40 L/min and titrate the flow based on improvement in ROX index and patient tolerance.This study does not have funding/support

Optimization and Dose Estimation of Aerosol Delivery to Non-Human Primates

Background: In pre-clinical animal studies, the uniformity of dosing across subjects and routes of administration is a crucial requirement. In preparation for a study in which aerosolized live-attenuated measles virus vaccine was administered to cynomolgus monkeys (Macaca fascicularis) by inhalation, we assessed the percentage of a nebulized dose inhaled under varying conditions. Methods: Drug delivery varies with breathing parameters. Therefore we determined macaque breathing patterns (tidal volume, breathing frequency, and inspiratory to expiratory (I:E) ratio) across a range of 3.3-6.5 kg body weight, using a pediatric pneumotachometer interfaced either with an endotracheal tube or a facemask. Subsequently, these breathing patterns were reproduced using a breathing simulator attached to a filter to collect the inhaled dose. Albuterol was nebulized using a vibrating mesh nebulizer and the percentage inhaled dose was determined by extraction of drug from the filter and subsequent quantification. Results: Tidal volumes ranged from 24 to 46 mL, breathing frequencies from 19 to 31 breaths per minute and I: E ratios from 0.7 to 1.6. A small pediatric resuscitation mask was identified as the best fitting interface between animal and pneumotachometer. The average efficiency of inhaled dose delivery was 32.1% (standard deviation 7.5, range 24%-48%), with variation in tidal volumes as the most important determinant. Conclusions: Studies in non-human primates aimed at comparing aerosol delivery with other routes of administration should take both the inter-subject variation and relatively low efficiency of delivery to these low body weight mammals into account

Motor neuron disease due to neuropathy target esterase gene mutation: Clinical features of the index families

Recently, we reported that mutations in the neuropathy target esterase (NTE) gene cause autosomal recessive motor neuron disease (NTE-MND). We describe clinical, neurophysiologic, and neuroimaging features of affected subjects in the index families. NTE-MND subjects exhibited progressive lower extremity spastic weakness that began in childhood and was later associated with atrophy of distal leg and intrinsic hand muscles. NTE-MND resembles Troyer syndrome, except that short stature, cognitive impairment, and dysmorphic features, which often accompany Troyer syndrome, are not features of NTE-MND. Early onset, symmetry, and slow progression distinguish NTE-MND from typical amyotrophic lateral sclerosis. NTE is implicated in organophosphorus compound–induced delayed neurotoxicity (OPIDN). NTE-MND patients have upper and lower motor neuron deficits that are similar to OPIDN. Motor neuron degeneration in subjects with NTE mutations supports the role of NTE and its biochemical cascade in the molecular pathogenesis of OPIDN and possibly other degenerative neurologic disorders. Muscle Nerve, 2011Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78477/1/21777_ftp.pd

Generation of the millisecond electron beam at forevacuum

The possibility of generation of a quasicontinuous electron beam with pulse duration up to 4.2 ms from arc discharge plasma in the forevacuum pressure range is presented. It is shown, that the voltage-current characteristic of the forevacuum plasma electron source generating millisecond electron beam has a "classical" form for electron sources with a plasma cathode

Giant vortex state in perforated aluminum microsquares

We investigate the nucleation of superconductivity in a uniform perpendicular magnetic field H in aluminum microsquares containing a few (2 and 4) submicron holes (antidots). The normal/superconducting phase boundary T_c(H) of these structures shows a quite different behavior in low and high fields. In the low magnetic field regime fluxoid quantization around each antidot leads to oscillations in T_c(H), expected from the specific sample geometry, and reminiscent of the network behavior. In high magnetic fields, the T_c(H) boundaries of the perforated and a reference non-perforated microsquare reveal cusps at the same values of Phi/Phi_0 (where Phi is the applied flux threading the total square area and Phi_0 is the superconducting flux quantum), while the background on T_c(H) becomes quasi-linear, indicating that a giant vortex state is established. The influence of the actual geometries on T_c(H) is analyzed in the framework of the linearized Ginzburg-Landau theory.Comment: 14 pages, 6 PS figures, RevTex, accepted for publication in Phys. Rev.

Surface Superconductivity in Niobium for Superconducting RF Cavities

A systematic study is presented on the superconductivity (sc) parameters of the ultrapure niobium used for the fabrication of the nine-cell 1.3 GHz cavities for the linear collider project TESLA. Cylindrical Nb samples have been subjected to the same surface treatments that are applied to the TESLA cavities: buffered chemical polishing (BCP), electrolytic polishing (EP), low-temperature bakeout (LTB). The magnetization curves and the complex magnetic susceptibility have been measured over a wide range of temperatures and dc magnetic fields, and also for di erent frequencies of the applied ac magnetic field. The bulk superconductivity parameters such as the critical temperature Tc = 9.26 K and the upper critical field Bc2(0) = 410 mT are found to be in good agreement with previous data. Evidence for surface superconductivity at fields above Bc2 is found in all samples. The critical surface field exceeds the Ginzburg-Landau field Bc3 = 1.695Bc2 by about 10% in BCP-treated samples and increases even further if EP or LTB are applied. From the field dependence of the susceptibility and a power-law analysis of the complex ac conductivity and resistivity the existence of two different phases of surface superconductivity can be established which resemble the Meissner and Abrikosov phases in the bulk: (1) coherent surface superconductivity, allowing sc shielding currents flowing around the entire cylindrical sample, for external fields B in the range between Bc2 and Bcohc3, and (2) incoherent surface superconductivity with disconnected sc domains between Bcohc3 and Bc3. The coherent critical surface field separating the two phases is found to be Bcoh c3 = 0.81Bc3 for all samples. The exponents in the power law analysis are different for BCP and EP samples, pointing to different surface topologies.Comment: 15 pages, 21 figures, DESY-Report 2004-02