Search

It has been found that solar bursts exhibit one unexpected spectral component with fluxes increasing with frequency in the sub-THz range, which is distinct from the well-known microwave emission that peaks at a few to some tens of GHz. This component has been found to extend into the THz range of frequencies by recent 30 THz solar flare observations of impulsive bursts with flux intensities considerably higher than fluxes at sub-THz and microwaves frequencies. High-cadence solar observations at 30 THz (continuum) are therefore an important tool for the study of active regions and flaring events. We report the recent installation of a new 30 THz solar telescope in São Paulo, located at the top of one of the University's buildings. The instrument uses a Hale-type coelostat with two 20 cm diameter flat mirrors sending light to a 15 cm mirror Newtonian telescope. Radiation is directed to a microbolometer array camera that is kept at room temperature. Observations are usually obtained with $5~\mbox{frames}\,\mbox{s}^{-1}$ cadence. One 60 mm refractor has been added to observe $\mathrm{H}\upalpha$ images simultaneously. We describe our new telescopes and the new observatory examples of the first results obtained. [ABSTRACT FROM AUTHOR]

Study design:Review article.Objectives:To review the literature regarding treatment approaches in cases of gunshot wounds (GSWs) affecting the spine.Setting:Brazil.Methods:Narrative review of medical literature.Results:GSWs are an increasing cause of morbidity and mortality. Most patients with spinal GSW have complete neurological deficit. The injury is more common in young men and is frequently immobilizing. The initial approach should follow advanced trauma life support, and broad-spectrum antibiotic therapy should be initiated immediately, especially in patients with perforation of the gastrointestinal tract. The indications for surgery in spinal GSW are deterioration of the neurologic condition in a patient with incomplete neurological deficit, the presence of liquor fistula, spinal instability, intoxication by the metal from the bullet or risk of bullet migration.Conclusion:Surgical treatment is associated with a higher complication rate than conservative treatment. Therefore, the surgeon must know the treatment limitations and recognize patients who would truly benefit from surgery. [ABSTRACT FROM AUTHOR]

Study design:Experimental, controlled, animal study.Objectives:To evaluate the influences of antidepressant treatment, treadmill gait training and a combination of these therapies in rats with experimental, acute spinal cord injury (SCI).Setting:Brazil.Methods:48 Wistar rats were given standardized SCI; rats were then randomly assigned to four treatment groups: (1) motor rehabilitation therapy for 1 hour daily (gait training); (2) daily treatment with the antidepressant, fluoxetine (0.3 ml per 100 g intraperitoneally), beginning 24 h after the trauma; (3) combined fluoxetine treatment and gait training, or (4) untreated (controls). Neurological recovery was tested with the Basso, Beattie and Bresnahan (BBB) scale at 2, 7, 14, 21, 28 ,35 and 42 days after injury. Moreover, on day 42, all rats underwent a motor-evoked potential test (MEP); then, after euthanasia, histopathological evaluation was conducted in the area of SCI.Results:Based on the BBB scale, the combined treatment group showed significantly greater improvement compared with the other three groups, from the 14th to the 42nd day of observation. The MEP revealed that all treated groups showed significant improvement compared with the control group (P<0.02 for latency and P<0.01 for amplitude).Conclusion:Our results indicated that a combination of antidepressant and treadmill gait training was superior to either treatment alone for improving functional deficits in rats with experimental, acute SCI. [ABSTRACT FROM AUTHOR]

Study design:Experimental, controlled, animal study.Objectives:To evaluate the functional effect of hyperbaric oxygen therapy administered shortly, one day after, and no intervention (control) in standardized experimental spinal cord lesions in Wistar rats.Setting:São Paulo, Brazil.Methods:In all, 30 Wistar rats with spinal cord lesions were divided into three groups: one group was submitted to hyperbaric oxygen therapy beginning half an hour after the lesion and with a total of 10 one-hour sessions, one session per day, at 2 atm; the second received the same treatment, but beginning on the day after the lesion; and the third received no treatment (control). The Basso, Beattie and Bresnahan scales were used for functional evaluation on the second day after the lesion and then weekly, until being killed 1 month later.Results:There were no significant differences between the groups in the functional analysis on the second day after the lesion. There was no functional difference comparing Groups 1 and 2 (treated shortly after or one day after) in any evaluation moment. On the 7th day, as well as on the 21st and 28th postoperative days, the evaluation showed that Groups 1 and 2 performed significantly better than the control group (receiving no therapy).Conclusion:Hyperbaric chamber therapy is beneficial in the functional recovery of spinal cord lesions in rats, if it is first administered just after spinal cord injury or within 24 h. [ABSTRACT FROM AUTHOR]

Study design:Experimental, controlled, animal study.Objectives:To evaluate the effect of GM1 ganglioside, hyperbaric oxygen and both in combination, in the treatment of experimental spinal cord lesions in rats.Setting:Brazil.Methods:Thirty-two Wistar rats with spinal cord lesions were divided into four groups: one group received GM1 ganglioside, one was submitted to hyperbaric oxygen therapy (HBOT), the third received both treatments and the fourth received no treatment (control).Results:There were no significant differences between the groups in the histological analysis, for any of the variables (necrosis, hemorrhage, hyperemia, cystic degeneration, P>0.06). Neither were there any significant differences in the comparison of left and right sides in the functional tests (P>0.06 for all). No significant differences were found in the locomotor ratings, in the comparison of groups at 2, 7, 21 and 28 days after the surgical procedure. However, in the evaluation on day 14, group 3, which received the combined therapy, showed a significantly higher Basso Beattie and Bresnahan score than the other groups (P=0.015).Conclusion:The therapeutic effect of GM1 in locomotor evaluation of rats submitted to spinal cord lesion is anticipated by HBOT. [ABSTRACT FROM AUTHOR]

Study design:A prospective, non-randomized clinical series trial.Objective:To evaluate the effect of autogenous undifferentiated stem cell infusion for the treatment of patients with chronic spinal cord injury (SCI) on somatosensory evoked potentials (SSEPs).Setting:A public tertiary hospital in São Paulo, Brazil.Methods:Thirty-nine consecutive patients with diagnosed complete cervical and thoracic SCI for at least 2 years and with no cortical response in the SSEP study of the lower limbs were included in the trial. The trial patients underwent peripheral blood stem cell mobilization and collection. The stem cell concentrate was cryopreserved and reinfused through arteriography into the donor patient. The patients were followed up for 2.5 years and submitted to SSEP studies to evaluate the improvement in SSEPs after undifferentiated cell infusion.Results:Twenty-six (66.7%) patients showed recovery of somatosensory evoked response to peripheral stimuli after 2.5 years of follow-up.Conclusion:The 2.5-year trial protocol proved to be safe and improved SSEPs in patients with complete SCI.Sponsorship:None. [ABSTRACT FROM AUTHOR]

Introduction:Some studies have made use of the antioxidative capabilities of high doses of vitamins C and E with the aim of neutralizing the noxious effects of free radicals following spinal cord lesion.Objectives:To evaluate the effects of vitamins C and E, separately and together, on the functional performance of rats that were subjected to standardized spinal cord contusion.Materials and methods:Forty male Wistar rats were used, divided into four groups of 10 animals each. Group 3 received vitamin C 100 mg kg−1 day−1 intraperitoneally; Group 2 received vitamin E 100 mg kg−1 day−1 orally; Group 1 received vitamins C and E, at the same dosages; and Group 4 was the control. The vitamin therapy was administered for 1 month and then the animals were killed. A direct contusional injury was caused and functional evaluation was performed using the Basso, Beattie and Bresnahan rating scale. The rats were evaluated on the second postoperative day and weekly thereafter, until the end of the experiment.Results:The results were evaluated by means of the one-tailed, non-paired and non-parametric Mann-Whitney test, comparing the groups two by two. No significant difference in functional performance was observed between the groups.Conclusion:The use of vitamins C and E in these rats did not improve their neurological performance. However, histopathological examination showed that the inflammatory response was less intense following administration of the combination of vitamins C and E.Spinal Cord (2009) 47, 458–463; doi:10.1038/sc.2008.155; published online 9 December 2008 [ABSTRACT FROM AUTHOR]

We present the design and realization of cylindrical dielectric resonators operating in the 40–60 GHz frequency range, designed for the measurement of the surface resistance and of the surface reactance shift in High- T c Superconductors (HTS) thin films in a dc magnetic field. The resonators are single tone, based on the TE 011 mode, and multiple tone, the latter allowing in principle to exploit the simultaneous determination of the surface impedance at different frequencies. As an application example, we report the temperature and field dependencies of the effective surface impedance of some cuprate superconductors thin films. The results are compared with those obtained through the use of a standard metal cavity with a similar Q-factor and operating in the same frequency range. The comparison highlights a superior stability and a higher sensitivity, resulting in an increase of about two orders of magnitude in the resolution of the surface impedance measurement. By contrast, the dissipative part of the superconducting transition (above T/ T c = 0.97) is better studied with the metal cavity. We also present measurements in the vortex state in YBaCa2Cu3O7−δ and Tl2Ba2CaCu2O8+ x that show significantly different physics. [ABSTRACT FROM AUTHOR]

We present measurements of the field induced changes in the 47 GHz complex resistivity, Δρ~( H, T), in Tl2Ba2CaCu2O8+ x (TBCCO) thin films with T c ≃ 105 K, prepared on CeO2 buffered sapphire substrates. At low fields (μ0 H < 10 mT) a very small irreversible feature is present, suggesting a little role of intergranular phenomena. Above that level Δρ~( H, T exhibits a superlinear dependence with the field, as opposed to the expected (at high frequencies) quasilinear behaviour. We observe a crossover between predominantly imaginary to predominantly real (dissipative) response with increasing temperature and/or field. In addition, we find the clear scaling property Δρ~( H, T = Δρ~[ H/ H * ( T)], where the scaling field H ∗ ( T) maps closely the melting field measured in single crystals. We discuss our microwave results in terms of loss of flux lines rigidity. [ABSTRACT FROM AUTHOR]

We study the effects of semiconductor substrates on the surface impedance of high- T c Superconductor (HTS) YBa2Cu3O7−δ (YBCO) films. The characteristic impedance of silicon (Si) (for different doping levels and for different charge carrier scattering times) is evaluated. In particular, the most relevant features of Si electrodynamics are highlighted by the introduction of suitable normalized quantities. The effective surface impedance of the YBCO films on Si substrates is then calculated and discussed for different temperatures and frequencies in the microwave range, comparing the obtained results to their limiting expressions for bulk and thin-film HTS. Our analysis shows how the widely used thin-film approximation for the surface impedance can fail, critically highlighting the conditions it requires to be correctly used. We show that substrate contributions can heavily influence the overall response. [ABSTRACT FROM AUTHOR]

We report measurements of the magnetic field induced microwave complex resistivity in REBa2Cu3O7−δ thin films, with RE = Y, Sm. Measurements are performed at 48 GHz by means of a resonant cavity in the end-wall-replacement configuration. The magnetic field dependence is investigated by applying a moderate (0.8 T) magnetic field along the c-axis. The measured vortex-state complex resistivity in YBa2Cu3O7−δ and SmBa2Cu3 7−δ is analyzed within the well-known models for vortex dynamics. It is shown that attributing the observed response to vortex motion alone leads to inconsistencies in the as-determined vortex parameters (such as the vortex viscosity and the pinning constant). By contrast, attributing the entire response to field-induced pair breaking leads to a nearly quantitative description of the data. [ABSTRACT FROM AUTHOR]

Presents the results of a study on microwave fluctuational conductivity in YBa2Cu3O7-α. Relationship between temperature and fluctuational excess conductivity; Response of the fluctuations upon its approach to the transition temperature; Background on the modified Gaussian Theory for finite-frequency fluctuational conductivity.

We present measurements of the real part of the microwave resistivity at 48 GHz in YBa2 Cu3 O7−δ and Bi2 Sr2 CaCu2 O8+x films, as a function of the temperature and of the static magnetic field. In zero field, the resistivity above the critical temperature is well described by the frequency-dependent fluctuational excess conductivity. In a static magnetic field and below Tc , the resistivity in YBa2 Cu3 O7−δ can be fully described by a simple flux-flow model, while in Bi2 Sr2 CaCu2 O8+x this model applies only partially. We discuss possible alternative models. [ABSTRACT FROM AUTHOR]

Measurements of the real part of the resistivity at 23 and 48 GHz are performed in Bi2 Sr2 CaCu2 O8+x thin films as a function of the temperature. The experimental behavior above Tc is analyzed in the frame of the time dependent Ginzburg-Landau theory for the excess conductivity. We show that the observed resistivity can be interpreted by the 2D gaussian theory due to the high anisotropy of this compound. The validity of the theory is extended up to the high temperature region with the introduction of a phenomenogical cut-off on the order parameter spectrum. Approaching Tc , data depart from the predicted behavior; this departure can be ascribed either to a dimensional crossover or to the effects of interacting fluctuations. [ABSTRACT FROM AUTHOR]

Copyright of Il Nuovo Cimento: B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Il Nuovo Cimento: B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We report measurements of the magnetic field dependent microwave dissipation at 21 GHz in BiSrCaCuO epitaxial films and in oriented YBaCuO films, by means of the end-wall-replacement cavity technique. The power reflected by the tuned cavity is measured as a function of the external magnetic field H and of the angle ε between H and the ( a, b), planes, at fixed temperatures. In BiSrCaCuO, apart from a narrow (Δε≈0.5°) angular range close to the parallel orientation, the strongly anisotropic dissipation exhibits striking scaling properties: all the data at fixed temperature can be made to collapse on a single curve with a simple angular scaling of the magnetic field: H→H/f(ε). It is found that the anisotropy ratio f(0°)/ f(90°) increases with temperature. It is shown that the scaling function f(ε) and its temperature evolution are in agreement with the model for a quasi-2D superconductor. In YBaCuO the presence of the flux-flow dissipation prevents the application of a scaling procedure, and a specific model must be applied. We obtain that the anisotropy is almost constant with the temperature, as predicted for a three-dimensional, anisotropic superconductor. [ABSTRACT FROM AUTHOR]

We present some experimental facts which suggest that fluctuational phenomena dictate the dissipative behaviour in a wide region of fields and temperatures across the critical temperature T . In particular, we discuss resistivity data on an YBCO thin film as a function of the field orientation ϑ with respect to the crystallographic axes of the sample. We also compare our data with those taken on an untwinned single crystal. Both analyses define a temperature T ( H) marking the onset of extrinsic effects on the dissipation. Finally, the comparison of the data with the predictions of the interacting fluctuations theory and with the Bardeen-Stephen flux-flow expression is used to clarify whether the intrinsic behaviour is due to fluctuations of the order parameter or to the free motion of vortex lines. [ABSTRACT FROM AUTHOR]

Copyright of Il Nuovo Cimento della Societa Italiana di Fisica: B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Il Nuovo Cimento della Societa Italiana di Fisica: B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)