The vinyl bromide optically pumped far infrared laser: New large offset emissions

We present the results of a study on vinyl bromide for the search for new far infrared (FIR) laser lines. As the pump source, we use a CW waveguide CO2 laser with a tunability of 290 MHz around each line in order to pump large offset vibrational transitions. As a consequence, we obtained 28 new FIR laser emissions; 24 of them have wavelengths greater than 500 mum and are, therefore, suitable to be used in high-field EPR spectroscopy, For each of the new lines, we give the wavelength, the offset of the pumping transition with respect to the center Frequency of the CO2 emission, the polarization relative to that of the pumping laser line, the operating pressure, and the relative intensity. We also present a catalog including data of all of the FIR laser lines observed from this molecule up to now.

Dissipative three-wave structures in stimulated backscattering. I. A subluminous solitary attractor

We present a solitary solution of the three-wave nonlinear partial differential equation (PDE) model - governing resonant space-time stimulated Brillouin or Raman backscattering - in the presence of a cw pump and dissipative material and Stokes waves. The study is motivated by pulse formation in optical fiber experiments. As a result of the instability any initial bounded Stokes signal is amplified and evolves to a subluminous backscattered Stokes pulse whose shape and velocity are uniquely determined by the damping coefficients and the cw-pump level. This asymptotically stable solitary three-wave structure is an attractor for any initial conditions in a compact support, in contrast to the known superluminous dissipative soliton solution which calls for an unbounded support. The linear asymptotic theory based on the Kolmogorov-Petrovskii-Piskunov assertion allows us to determine analytically the wave-front slope and the subluminous velocity, which are in remarkable agreement with the numerical computation of the nonlinear PDE model when the dynamics attains the asymptotic steady regime. © 1997 The American Physical Society.

Running holograms in azopolymer films

We report investigations on running holograms recorded in an azopolymer film made of a poly(methyl methacrylate) matrix doped with Disperse Red 1. Two-wave mixing experiments were carried out in the symmetrical transmission geometry. A stabilization technique was employed for active control of the phase shift between the real-time hologram and the interference pattern. Depending on the imposed phase shift, a running hologram propagates in the material in the form of an isomerization wave created by a continuous erasing-rewriting process. Diffraction efficiencies and the hologram velocities were measured as functions of the holographic phase shift at the wavelengths 515 and 488 nm. The experimental results were compared to theoretical curves obtained from a simplified model of the isomerization kinetics. The selective contributions of the phase and the amplitude gratings to the whole hologram were also determined. © 2013 Springer-Verlag Berlin Heidelberg.

HLA-Bw4-B*57 and Cw*18 alleles are associated with plasma viral load modulation in HIV-1 infected individuals in Salvador, Brazil

Host genetic factors play an important role in mediating resistance to HIV-1 infection and may modify the course of infection. HLA-B alleles (Bw4 epitope; B*27 and B*57) as well as killer cell immunoglobulin-like receptors have been associated with slow progression of HIV-1 infection. OBJECTIVE: To evaluate the association between serological epitopes HLA-Bw4 and HLA-Bw6 and prognostic markers in AIDS. METHODS: 147 HIV-infected individuals in Bahia, Northeast Brazil, were genotyped for HLA class I locus. HLA class I genotyping was performed by hybridization with sequence-specific oligonucleotide probes following amplification of the corresponding HLA-A, HLA-B and HLA-C genes. Statistical analysis was performed using Fisher's exact and ANOVA tests for categorical and continuous variables, respectively. RESULTS: We detected a significant association (χ2 = 4.856; p = 0.018) between the presence of HLA-Bw4 and low levels of viremia. Eighteen out of the 147 HIV-infected individuals presented viremia <1,800 copies/mL and 129 presented viremia > 2,000 copies/mL. Ninety and four percent (17/18) of all individuals with viremia < 1,800 copies/mL carried HLA-Bw4, compared to 67.4% (87/129) of individuals with viremia > 2,000 copies/mL. Additionally, we found a significantly higher frequency of B*57 (OR = 13.94; 95% CI = 4.19-46.38; p < 0.0001) and Cw*18 (OR = 16.15; 95% CI = 3.46-75.43; p < 0.0001) alleles, favoring the group with lower viremia levels, in comparison with those with higher viral load. CONCLUSION: HLA-Bw4-B*57 and Cw*18 alleles are associated with lower level of viral load in HIV-infected Brazilian patients. These findings may help us in understanding the determinants of HIV evolution in Brazilian patients, as well as in providing important information on immune response correlates of protection for such population.

Square-wave voltammetric determination of rutin in pharmaceutical formulations using a carbon composite electrode modified with copper (II) phosphate immobilized in polyester resin

Descreve-se um eletrodo de carbono modificado com fosfato de cobre (II) imobilizado em uma resina de poliéster (Cu₃(PO₄)₂-Poly) para a determinação de rutina em amostras farmacêuticas por voltametria de onda quadrada. O eletrodo modificado permite a determinação de rutina em potencial (0.20 V vs Ag / AgCl (3,0 mol L^-1 KCl)) menor que o observado em um eletrodo não modificado. Verificou-se que a corrente de pico foi linear com a concentração de rutina na faixa de 9,9 × 10^-8 a 2,5 × 10^-6 mol L^-1, com um limite de detecção de 1,2 × 10^-8 mol L^-1. A resposta do eletrodo foi estável, sem variação significativa dentro de várias horas de operação contínua. A morfologia da superfície do eletrodo modificado foi caracterizada por microscopia eletrônica de varredura (MEV) e pelo sistema de energia dispersiva de raios-X (EDX). Os resultados obtidos foram precisos e exatos. Ademais, estes resultados estão de acordo com aqueles obtidos pelo método cromatográfico a um nível de confiança de 95%.

Implementation of an F-statistic all-sky search for continuous gravitational waves in Virgo VSR1 data

We present an implementation of the F-statistic to carry out the first search in data from the Virgo laser interferometric gravitational wave detector for periodic gravitational waves from a priori unknown, isolated rotating neutron stars. We searched a frequency f(0) range from 100 Hz to 1 kHz and the frequency dependent spindown f(1) range from -1.6(f(0)/100 Hz) x 10(-9) Hz s(-1) to zero. A large part of this frequency-spindown space was unexplored by any of the all-sky searches published so far. Our method consisted of a coherent search over two-day periods using the F-statistic, followed by a search for coincidences among the candidates from the two-day segments. We have introduced a number of novel techniques and algorithms that allow the use of the fast Fourier transform (FFT) algorithm in the coherent part of the search resulting in a fifty-fold speed-up in computation of the F-statistic with respect to the algorithm used in the other pipelines. No significant gravitational wave signal was found. The sensitivity of the search was estimated by injecting signals into the data. In the most sensitive parts of the detector band more than 90% of signals would have been detected with dimensionless gravitational-wave amplitude greater than 5 x 10(-24).

First all-sky search for continuous gravitational waves from unknown sources in binary systems

We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to similar to 2,254 h and a frequency-and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semimajor axes of the orbit from similar to 0.6 x 10(-3) ls to similar to 6,500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3 x 10(-24) at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the low-mass x-ray binary Scorpius X-1 between 20 Hz and 57.25 Hz.

Adaptation and penetration of resin-based root canal sealers in root canals irradiated with high-intensity lasers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Proton magnetic resonance with parahydrogen induced polarization : Imaging strategies and continuous generation

A major challenge in imaging is the detection of small amounts of molecules of interest. In the case of magnetic resonance imaging (MRI) their signals are typically concealed by the large background signal of e.g. the tissue of the body. This problem can be tackled by hyperpolarization which increases the NMR signals up to several orders of magnitude. However, this strategy is limited for 1H, the most widely used nucleus in NMR andrnMRI, because the enormous number of protons in the body screen the small amount of hyperpolarized ones.Here, I describe a method giving rise to high 1H MRI contrast for hyperpolarized molecules against a large background signal. The contrast is based on the J-coupling induced rephasing of the NMR signal of molecules hyperpolarized via parahydrogen induce polarization (PHIP) and it can easily be implemented in common pulse sequences.rnrnHyperpolarization methods typically require expensive technical equipment (e.g. lasers or microwaves) and most techniques work only in batch mode, thus the limited lifetime of the hyperpolarization is limiting its applications. Therefore, the second part of my thesis deals with the simple and efficient generation of an hyperpolarization.These two achievements open up alternative opportunities to use the standard MRI nucleus 1H for e.g. metabolic imaging in the future.

Chest pulse-wave velocity: a novel approach to assess arterial stiffness

Pulse-wave velocity (PWV) is considered as the gold-standard method to assess arterial stiffness, an independent predictor of cardiovascular morbidity and mortality. Current available devices that measure PWV need to be operated by skilled medical staff, thus, reducing the potential use of PWV in the ambulatory setting. In this paper, we present a new technique allowing continuous, unsupervised measurements of pulse transit times (PTT) in central arteries by means of a chest sensor. This technique relies on measuring the propagation time of pressure pulses from their genesis in the left ventricle to their later arrival at the cutaneous vasculature on the sternum. Combined thoracic impedance cardiography and phonocardiography are used to detect the opening of the aortic valve, from which a pre-ejection period (PEP) value is estimated. Multichannel reflective photoplethysmography at the sternum is used to detect the distal pulse-arrival time (PAT). A PTT value is then calculated as PTT = PAT - PEP. After optimizing the parameters of the chest PTT calculation algorithm on a nine-subject cohort, a prospective validation study involving 31 normo- and hypertensive subjects was performed. 1/chest PTT correlated very well with the COMPLIOR carotid to femoral PWV (r = 0.88, p < 10 (-9)). Finally, an empirical method to map chest PTT values onto chest PWV values is explored.

Hohlraum Target for Overcoming Refractive Losses in Plasma X-ray Lasers

Refractive losses in laser-produced plasmas used as gain media are caused by electron density gradients, and limit the energy transport range. The pump pulse is thus deflected from the high-gain region and the short wavelength laser signal also steers away, causing loss of collimation. A Hohlraum used as a target makes the plasma homogeneous and can mitigate refractive losses by means of wave-guiding. A computational study combining a hydrodynamics code and an atomic physics code is presented, which includes a ray-tracing modeling based on the eikonal theory of the trajectory equation. This study presents gain calculations based on population inversion produced by free-electron collisions exciting bound electrons into metastable levels in the 3d94d1(J = 0) → 3d94p1(J = 1) transition of Ni-like Sn. Further, the Hohlraum suggests a dramatic enhancement of the conversion efficiency of collisionally excited x-ray lasing for Ni-like Sn.

Fourier optics study of traveling-wave excitation at short- wavelength plasma-lasing

Traveling-wave excitation close to the speed of light implies small-angle target-irradiation. Yet, short-wavelength lasing needs large irradiation angles. Pulse-front back-tilt is considered to overcome such trade-off. Pulse-front tilt by means of compressor misalignment was found effective only if coupled with a strong front-end imaging/focusing component.