Measurement of the Properties of a Plasma Column Used as a Radiating Element

This paper presents two test benches for the characterization of a plasma column used as a radiating element. In particular, the main parameters to be quantified are the efficiency of the plasma antenna, the turn-on time of the column, and the conductivity of the plasma. The first two parameters are evaluated by measuring the field radiated by the plasma antenna compared with that of an equivalent copper antenna. For the conductivity, a reflectometric technique is used, wherein the plasma column is inserted inside a waveguide. The accuracy of the method is limited by the ill-conditioned relationship between the reflection coefficient and the plasma conductivity; nevertheless, it is sufficient to subdivide the range of the conductivity values into three regions (i.e., low, medium, and high conductivities) to determine the best operating conditions of the antenna.     

Use of the nitrification inhibitor dicyandiamide (DCD) does not mitigate N2O emission from bovine urine patches under Oxisol in Northwest Brazil

Nutrient Cycling in Agroecosystems - Animal production systems are important sources of greenhouse gases (GHGs), especially methane (CH4) and nitrous oxide (N2O). GHG emissions from urine patches...     

Damage and plastic flow in a Al-Si-Cu thixocast alloy

Thixocast samples of an Al-Si-Cu alloy were solution treated at 500°C for 4 h, aged at 170°C for different times and tensile tested at room temperature. Statistical analysis on the fractured Si particles has pointed out how the fraction of damaged particles is influenced by the ageing treatments performed before deformation. The damage accumulation per unit of strain decreases with increasing ductility of the samples. The Considére criterion for plastic instability shows no significative necking.     

Mometasone furoate decreases adhesion molecule expression in psoriasis

This study was performed to clarify the possibility of visualization and quantification with 99mTc-tetrofosmin (Tf) myocardial scintigraphy in cases with a large atrium demonstrated by trans-thoracic echocardiography (TTE). Myocardial SPECT was evaluated in 4 patients with mitral stenosis and 15 patients with mitral regurgitation. Left atrium was identified in 12 out of 19 cases from an antero-posterior projection. The Tf uptake ratio of the left atrium, which was defined as the ratio of ROI count of the left atrium divided by the ROI count of the left ventricle, showed a good correlation with the left atrial area obtained by both trans-thoracic and trans-esophageal echocardiography (r = 0.88 and 0.91, respectively), These data suggest that Tf myocardial SPECT is a useful method of evaluating left atrial enlargement.     

The relationship between microstructural and plastic instability in AI-4.0 Wt Pct Cu alloy

The investigation of the effect of plastic deformation on the stability of theθ′ precipitates in an aluminum-4.0 wt pct copper alloy was performed. The alloy was produced by directional solidification, with Ti added as a grain refiner. Hot compression tests were performed at 200 °C in the strain rate range of 10_-3 to 10_-5 s₁ and equivalent strain up to 0.7 on specimens that had been initially heat treated, also at 200 °C, in order to obtain a uniform distribution of theθ0′ precipitates within the matrix. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of the plastically deformed specimens revealed a very heterogeneous distribution of strain. Also, the regions with localized strain contained randomly distributedθ precipitates of nearly equiaxed shape without any preferred orientation relationships to the matrix. Thus, the plastic deformation initiated the transformationθ′ →θ. The flow stress was reduced in the regions in which this transformation had occurred, which further accentuated the localization tendency of the strain. The combined process,θ′ →θ transformation/strain localization, thus developed in an avalanching way.     

''Dual positivity'' for neural tube defects and down syndrome at maternal serum screening: gestational outcome

The pattern of anatomical features of the brain revealed by magnetic resonance imaging (MRI) is described in six patients incidentally identified as having acallosal brains. The complex of morphological features associated with complete agenesis of the corpus callosum included lateral displacement of slitlike anterior horns of the lateral ventricles (bullhorn-like shape), dilatation of the posterior horns of the lateral ventricles, absence of the septum pellucidum, lateral displacement of the cingulate gyri, complete separation of fornices and the presence of the anterior commissure and longitudinal callosal bundles (Probst's bundles). No compensatory enlargement of the anterior commissure was seen in the patients. The planimetrically measured cross-sectional areas of the anterior commissures were between 2.0 and 4.2 mm2 (mean 3.1) (in ten normal subjects they were 4.5, SD 0.4; range 3.8-5.2 mm2) and were reduced in four and normal in two patients. Inconstant morphological features were an absence of the posterior commissure and a radial pattern of the sulci and gyri on the medial aspect of the hemispheres. Conventional clinical testing revealed no abnormalities except a slight impairment of walking heel-to-toe in two patients. None of the patients had subjective restrictions of activities of daily life, which shows the efficacy of unknown compensatory processes.     

Evaluation of electromagnetic power deposition in a spherical multilayer head in the near field of a linear antenna

The canonical problem of the radiation of an elementary dipole close to a stratified sphere representing a simplified model of human head is investigated in this paper. The proposed approach is a flexible method of investigation about the influence on Specific Absorption Rate (S.A.R.) evaluation of tissue dielectric parameters and geometry as well as a useful tool to test numerical codes. The solution of the electromagnetic (e.m.) problem is achieved in a closed form; results highlight the position of maximum S.A.R. values and their dependence on frequency: for particular layer thicknesses and dielectric parameters, the maximum absorption can occur in the frequency range of cellular phones.