Dual-phase digital lock-in implementation based on Nyquist rate and sampling subtraction.

Lock-in amplifiers (LIA) are widely used in laboratory environments to detect low-amplitude signals buried in noise as well as real and imaginary parts of a complex quantity. They are based on the technique of synchronous detection, where the signal of interest is modulated into a desired frequency, sent to the medium or device to be analyzed, and captured by a detector. The detector scheme relies on the concept of phase-sensitive detection, generally resulting in two components: in-phase and quadrature. This article shows a very simple and low computational-cost way to implement a dual-phase LIA, using readily available microcontrollers, running a simple and fast algorithm. Three examples of signal detection are presented (sound wave signal, impedance meter, and weak signal recovery) to point out the flexibility and capabilities of the proposed methodology.

Real-time FMR lorentzian visualization through a novel synchronous VNA-FMR measurement apparatus.

It is shown in this work that a synchronous measurement setup is able to conveniently and accurately retrieve ferromagnetic resonance's (FMR) main physical properties from a permalloy sample. The apparatus used comprises a vector network analyzer (VNA), coupled with external DC coils, driven by a controllable power supply. A permalloy thin film sample was subjected to a microwave signal through a grounded coplanar waveguide. A square wave signal generated by an Arduino microcontroller drives the coils to a triangular, 65.4 ms period magnetic field. This field's half-cycle is synchronized to match a zero-span sampling time at the VNA. The system has the advantage of fast results, as the typical FMR lorentzian curve is completed in a few seconds and shown immediately on the VNA's scattering parameter S21 trace graph. The system showed an improved signal-to-noise ratio of 51.7 at 10 GHz over 24.3 for the 100 nm thick permalloy- sample used in this work. A magnetic field resonance point, collected at 10 GHz, showed a five-fold improvement in the standard-error.

Rotavirus analyses by SYBR Green real-time PCR and microbiological contamination in bivalves cultivated in coastal water of Amazonian Brazil.

The contamination of mussels and oysters by viruses and bacteria is often associated with water contamination and gastroenteritis in humans. The present study evaluated viral and bacterial contamination in 380 samples, from nine mollusk-producing regions in coastal water north of the Brazilian Amazon. Rotavirus contamination was studied for groups A to H, using a two-step SYBR Green RT-qPCR (quantitative reverse transcription polymerase chain reaction), and bacterial families Enterobacteriaceae, Vibrionaceae, and Aeromonadaceae by classical and molecular methods. From the 19 pools analyzed, 26.3% (5/19) were positive for group A Rotavirus, I2 genotype for VP6 region, without amplifications for groups B-H. Bacteriological analysis identified Escherichia coli isolates in 89.5% (17/19) with identification of atypical enteropathogenic E. coli aEPEC in 10.5% (2/19), Salmonella (Groups C1 and G) (10.5%, 2/19), Vibrio alginolyticus (57.9%, 11/19) V. parahaemolyticus (63.2%, 12/19), V. fluvialis (42.1%, 8/19), V. vulnificus (10.5%, 2/19), V. cholerae non-O1, non O139(10.5%, 2/19) and Aeromonas salmonicida (52.6%, 10/19). All the samples investigated presented some level of contamination by enterobacteria, rotavirus, or both, and these results may reflect the level of contamination in the Northern Amazon Region, due to the natural maintenance of some of these agents or by the proximity with human populations and their sewer.

Velocity asymmetry of Dzyaloshinskii domain walls in the creep and flow regimes.

We have carried out measurements of domain wall dynamics in a Pt/Co/GdOx(t) wedge sample with perpendicular magnetic anisotropy. When driven by an easy-axis field Hz in the presence of an in-plane field Hx, the domain wall propagation is different along [Formula: see text]x, as expected for samples presenting Dzyaloshinskii-Moriya (DMI) interaction. In the creep regime, the sign and the value of the domain wall velocity asymmetry changes along the wedge. We show that in our samples the domain wall speed versus Hx curves in the creep regime cannot be explained simply in terms of the variation of the domain wall energy with Hx, as suggested by previous works. For this reason the strength and the sign of the DMI cannot be extracted from these measurements. To obtain reliable information on the DMI strength using magnetic field-induced domain wall dynamics, measurements have been performed with high fields, bringing the DW close to the flow regime of propagation. In this case we find large values of the DMI, consistent in magnitude and sign with those obtained from Brillouin light scattering measurements.

The occurrence of orthoreovirus, rotavirus and chicken anemia virus in chickens of the poultry industry in Minas Gerais, Brazil / Ocorrência de orthoreovirus, rotavirus e vírus da anemia das galinhas em frangos de corte da indústria avícola de Minas Gerais

Fifty-four fecal samples taken from broiler chickens from 1 to 45 days of age, and of pullets from 10 to 13 weeks of age, original from eight different poultry regions in the state of Minas Gerais, Brazil, were collected from March 2008 to January 2010 for avian Orthoreovirus (ARV) and avian Rotavirus (AvRV) analyses. For the assay of ARV, RNA was immediately extracted (Trizolâ) and transcribed into cDNA for assaying in a nested-PCR with ARV-specific primers. For AvRV, polyacrylamide gel electrophoresis (PAGE) was performed with RNA extracts obtained by phenol-chloroform extraction. CAV was additionally investigated through a nested-PCR of thymus and spleen. Results found 5.55% positive for ARV and 9.25% for AvRV. Also, CAV and ARV genomes were detected in co-infection, in a highly prostrated and claudicating chicken flock. No ARV or AvRV infections were detected in pullets. Material of a clinically affected flock was inoculated into SPF embryos, resulting in embryonic hemorrhage, whitish foci in the chorio-allantoic membrane and death. Sequencing of ARV amplicons and isolate cDNA grouped local strains with the ARV S1133 strain, historically used in live vaccines, suggesting the continued circulation of this vaccine virus strain in intensive poultry regions. Detection rates for ARV and AvRV, as well as the presence of CAV, were additionally indicative of failing biosecurity strategies for the intensive poultry regions examined.

Avaliou-se a ocorrência de Orthoreovirus (ARV) e Rotavirus (AvRV) aviários na avicultura industrial de Minas Gerais. Foram colhidas cinquenta e quatro amostras de fezes de frangos de corte entre um e 45 dias e de frangas de postura de 10 a 13 semanas de idade. Para análise de ARV, o RNA foi imediatamente extraído (Trizol), transcrito em cDNA e avaliado em uma PCR com oligonucleotídeos iniciadores específicos para ARV. Para a investigação de AvRV, os extratos de RNA foram obtidos por fenol-clorofórmio e submetidos à eletroforese em gel de poliacrilamida. Todas as amostras foram também avaliadas para o DNA do vírus da anemia das galinhas (CAV) em uma nested-PCR específica. Em frangos de corte, a positividade encontrada para ARV foi de 5,55% e para AvRV de 9,25%. CAV foi detectado em coinfecção em um plantel com refugagem, claudicação e prostração. Nenhuma amostra de poedeiras foi positiva para ARV ou AvRV. Material de plantel com sinais clínicos foi purificado e inoculado em ovos SPF embrionados, sendo obtidas lesões hemorrágicas e focos brancos na membrana cório-alantóide. O sequenciamento dos produtos de PCR e de embrião agrupou os isolados de ARV com a estirpe S1133, historicamente usada como vacina viva. Os resultados sugerem a continuada circulação da infecção por estirpes assemelhadas a ARV S1133 nas regiões de avicultura industrial. Os índices de detecção de ARV, AvRV e CAV indicam que a intensificação nas regiões produtoras tem resultado em falhas de biosseguridade.

Direct observation of massless domain wall dynamics in nanostripes with perpendicular magnetic anisotropy.

Domain wall motion induced by nanosecond current pulses in nanostripes with perpendicular magnetic anisotropy (Pt/Co/AlO(x)) is shown to exhibit negligible inertia. Time-resolved magnetic microscopy during current pulses reveals that the domain walls start moving, with a constant speed, as soon as the current reaches a constant amplitude, and no or little motion takes place after the end of the pulse. The very low "mass" of these domain walls is attributed to the combination of their narrow width and high damping parameter α. Such a small inertia should allow accurate control of domain wall motion by tuning the duration and amplitude of the current pulses.

20 T portable bipolar magnetic pulser.

High magnetic fields are required for the study of hard magnetic materials and, in many cases, the reversal of these fields is essential. This paper describes a portable pulse generator capable of producing bipolar magnetic fields up to 20 T into a copper coil. The peak current around 7 kA is achieved by discharging two capacitor banks through a combination of thyristors and fast diodes. Each pulse polarity has a semisinusoidal shape with 18 mus base width. Pulse triggering is computer controlled and magnetic measurements are done by an induction coil or Kerr effect acquired by a sampling oscilloscope. The whole apparatus weighs less than 2 kg. Hysteresis loops of NdFeB magnets were done to demonstrate the viability of the system.

Identification and characterization of bioemulsifier-producing yeasts isolated from effluents of a dairy industry.

New bioemulsifier-producing yeasts were isolated from the biological wastewater treatment plant of a dairy industry. Of the 31 bioemulsifier-producing strains, 12 showed emulsifying activity after 2months of incubation, with E(24) values ranging from 7% to 78%. However, only Trichosporon loubieri CLV20, Geotrichum sp. CLOA40, and T. montevideense CLOA70 exhibited high emulsion-stabilizing capacity, with E(24) values of 78%, 67%, and 66%, respectively. These isolates were shown to induce a strong emulsion stabilizing activity rather than the reduction of the interfacial tension. These strains exhibited similar growth rates in the exponential growth phase, with a clear acceleration after 24h and stabilization of the activity after 144h. Emulsification and stability properties of the bioemulsifiers were compared to those of commercial surfactants after the addition of NaCl and exposure to temperature of 100 degrees C. The compounds produced by the isolates appeared to be lipid-polysaccharide complexes. Gas chromatograph analysis of the lipidic fraction of the bioemulsifiers from CLV20, CLOA40, and CLOA70 shows the prevalence of (9Z,12Z)-octadeca-9,12-dienoic acid, in concentrations of 42.8%, 25.9%, and 49.8%, respectively. The carbohydrate composition, as determined by GC-MS of their alditol acetate derivatives, showed a predominance of mannose, galactose, xylose and arabinose.

Pequi is a Host for Pratylenchus zeae in the Brazilian Cerrado Region.

The Brazilian Cerrado Region has many natural resources that have high social economic interest. Pequi (Caryocar brasiliense Camb.), a native species from that area, has an edible fruit, which is highly appreciated by the local population, and also a high-quality wood. In January 2010, pequi root samples were collected near the municipality of Rio Verde, Goiás State, Brazil (17°49'25.76″S, 51°02'10.06″W). Roots were washed with tapwater, dried on absorbent paper, cut in 1-cm2 pieces, and processed for nematode extraction by the blender centrifugal flotation method (2). The specimens were identified by morphological and morphometrical characteristics of six adult females mounted in formaldehyde temporary slides (1). Morphological characters used for identification included female body, stylet, pharyngeal overlapping, pharynges, postvulval uterine sac, tail lengths, stylet knobs, number of labial rings, vulva position in relation to body length, body diameters (high body, vulval, and anus region), and the de Man's ratios (a, b, b', c, and c'). Characters measured were consistent with those described for Pratylenchus zeae Graham, 1951 (1); the labial region showed three annuli, stylet was 14.83 (±0.93) µm long, with broad, anteriorly flattened basal knobs. Vulva position was 71.66% (±0.98) of body length and spermatheca was round, small, and without sperm (males were not found). Postvulval uterine sac was short (31.3 ± 4.03 µm) and tail (26.6 ± 3.61 µm) was conoid, pointed, and unstriated. Pharyngeal overlapping length was 30.5 (±6.5) µm; pharynges were 150.83 (± 28.16) µm long. The de Man's ratios obtained were: a = 24.26 ± 2.31; b = 3.89 ± 0.69; b' = 3.08 ± 0.48; c = 17.17 ± 1.47; and c' = 2.25 ± 0.19. To our knowledge, this is the first report of P. zeae infecting pequi. It is difficult to determine the economic importance of this nematode parasite to pequi production since pequi is not yet a commercial crop in Brazil. This finding, however, has long term importance because researchers have been developing improved cultivars by combining favorable agronomic characteristics with high oilseed content for biofuel production. If these are commercialized, P. zeae could become an important pathogen in pequi plantings. References: (1) P. Castillo and N. Vovlas. Pratylenchus (Nematoda: Pratylenchidae): Diagnosis, Biology, Pathogenicity and Management. Koninklijke Brill NV, Leiden, the Netherlands, 2007. (2) W. A. Coolen and C. J. D'Herde. A Method for the Quantiative Extraction of Nematodes from Plant Tissue. State Agric. Entomol. Res. Stn. Ghent, Belgium, 1972.

Dynamics of magnetic domain wall motion after nucleation: dependence on the wall energy.

The dynamics of magnetic domain wall motion in the FeNi layer of a FeNi/Al2O3/Co trilayer has been investigated by a combination of x-ray magnetic circular dichroism, photoelectron emission microscopy, and a stroboscopic pump-probe technique. The nucleation of domains and subsequent expansion by domain wall motion in the FeNi layer during nanosecond-long magnetic field pulses was observed in the viscous regime up to the Walker limit field. We attribute an observed delay of domain expansion to the influence of the domain wall energy that acts against the domain expansion and that plays an important role when domains are small.

Perpendicular interlayer coupling in Ni80Fe20/NiO/Co trilayers.

An in-plane perpendicular magnetic coupling between Ni80Fe20 and Co has been found in NiFe/NiO/Co trilayers for a NiO thickness ranging from 4 to 25 nm by magneto-optical Kerr effect and x-ray magnetic circular dichroism measurements. In the easy magnetization direction of the Co layer, the Co coercive field H(C) increases when the thickness of the NiO layer t(NiO) increases. Because of the coupling, H(C) is always larger than for NiO/Co bilayers with the same thicknesses. The saturation field of the NiFe layer H(S) decreases when t(NiO) increases, indicating a weakening of the coupling. Numerical simulations show that the presence of interface roughness combined with a small value of the NiO anisotropy can explain the observed 90 degrees coupling.

Element-selective nanosecond magnetization dynamics in magnetic heterostructures.

We have developed a new original technique to study the magnetization reversal dynamics of thin films with element selectivity in the nanosecond time scale. X-ray magnetic circular dichroism measurements in pump-probe mode are carried out taking advantage of the time structure of synchrotron radiation. The dynamics of the magnetization reversal of each of the layers of complex heterostructures (like spin valves or tunnel junctions) can be probed independently. The interlayer coupling in the studied systems has been shown to play a key role in the determination of the magnetization reversal of each individual layer.

[Arterial hypertension and alcoholism among workers in an oil refinery]. / Hipertensão arterial e alcoolismo em trabalhadores de uma refinaria de petróleo.

The role of alcohol ingestion in the incidence of arterial hypertension has not been completely established. In addition, there are few studies addressing this point in relation to populations of workers. The objective of this study was to evaluate the association between alcoholism and arterial hypertension among workers in an oil refinery in Mataripe, Bahia, Brazil, from 1986 to 1993. We designed a retrospective cohort study with a 7-year follow-up in a stratified systematic sample of 335 workers from the refinery. Arterial hypertension was diagnosed based on blood pressure measurements done during routine medical examinations. At the beginning of follow-up, three groups were defined using the CAGE test of alcohol dependency: nondrinkers (n = 121), CAGE-negative workers (n = 116), and CAGE-positive workers (n = 98). In comparison with the CAGE-negative group, the CAGE-positive group had both greater relative risk and greater attributable risk for developing arterial hypertension (RR = 2.58; AR = 24.95 per 1,000 person-years). The CAGE-positive group also had greater risks compared to nondrinkers (RR = 2.06; AR = 20.97 per 1,000 person-years). The attributable fractions for the same two comparisons of groups were 61% and 51%, respectively. Rate standardization by age or smoking habit did not substantially change the results. Alcoholism is an important risk factor for arterial hypertension.

Quarter-wave plates and X-ray magnetic circular dichroism on ID24 at the ESRF.

The first XMCD measurements carried out on the ID24 energy-dispersive XAS beamline at the ESRF are reported. Circular-polarized X-rays are obtained using perfect diamond crystals as quarter-wave plates. The very small source divergence allows circular polarizations close to unity to be obtained.

Nanosecond-resolved XMCD on ID24 at the ESRF to investigate the element-selective dynamics of magnetization switching of Gd-Co amorphous thin film.

The one-bunch filling mode of the ESRF is combined with a microcoil to generate a pulsed-magnetic-field pump phased with respect to the probe that is given by the bunch of photons emitted each turn (357 kHz). Nanosecond-resolved X-ray magnetic circular dichroism (XMCD) is carried out. Besides the microcoil, the two other key-elements are the energy-dispersive XAS spectrometer, which yields parallel data acquisition, and the diamond-based quarter-wave plate, which tunes the helicity of the photon alternatively left and right.

Classic X-linked spondyloepiphyseal dysplasia tarda in a woman with normal karyotype.

A case of classic X-linked SED tarda in a woman with normal karyotype is described. The clinical and radiological findings left no doubts about the diagnosis of classical SED tarda (X-linked). The most probable hypothesis for explaining the clinical manifestation of this pathology in a woman with normal karyotype is random inactivation of all X chromosomes with the normal allele in her cells.