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In this paper, several simple antenna designs based on the use of an active dipole placed above a ground plane with an array of parasitic dipoles are presented. The parasitic dipoles are used to modify the pattern of the active dipole yielding a pencil beam of moderate gain. The use of one active element provides a very simple feeding network that reduces the complexity of the antenna. The proposed technique optimizes the geometry and configuration of both active and parasitic elements. It is shown that the performance of the designed antennas is considerably better than that of a similar antenna without parasitic elements. [ABSTRACT FROM AUTHOR]

AbstractA speciation method based on Chelex-100 titration in combination with electrothermal-atomic absorption spectrometry has been developed to study the distribution of Pb among different fractions in coastal seawater. The method allows an accurate determination of total Pb, thereby avoiding the effect of the saline matrix. Additionally, the distribution patterns of Pb among species with different lability can be established in seawater as a function of pH. Four Pb fractions have been obtained in a model seawater and two seawater samples from Ria de Vigo (NE Atlantic ocean), i.e.free Pb ion, inorganic Pb fraction, organic Pb fraction and inert Pb fraction. The inert and labile organic Pb fractions dominate at natural pH (≈8).Complexation mechanisms of Pb were investigated from the sorption curves of lead on Chelex-100 according to the Gibbs–Donnan model. Three complexes were formed, PbL, PbL2and Pb(HL)2with the following intrinsic complexation constants logβ(1np)= −3.25, −10.10 and −1.98, respectively. The formation of the complex PbL is negligible in all range of pH studied, while the complex Pb(HL)2predominates up to pH 4 and PbL2from pH 4.

Soluble amyloid (A) oligomers might trigger early cognitive deficit in Alzheimers Disease (AD) through the impairment of proper neuronal network function. We have recently shown that the short sequence A25-35 affects the spontaneous activity in hippocampal slices, when was added to the bath, at high nanomolar concentrations. In the present study, we aimed to characterize the effects of the oligomerized full length sequence A1-42 on the spontaneous network activity in the CA1 hippocampal area testing whether such effects are age dependent. By performing extracellular field recordings of spontaneous network activity of hippocampal slices, we found that an oligomerized solution of A1-42 (osA) potently inhibit, in a dose-dependent manner, the spontaneous hippocampal network activity with an IC50 of 0.4 ± 3.2 nM and a maximal effect reached around 10 nM. While spontaneous hippocampal network activity is unaffected by age, the sensitivity of spontaneous hippocampal network activity to osA (10 nM) appears to be increased in slices from older animals. Moreover, to see a significant reduction in spontaneous network activity in slices from animals in their second week of life 100nM osA was needed. The osA-induced reduction in hippocampal network activity is accompanied by a presynaptic reduction in both spontaneous and miniature synaptic potentials. Finally, we demonstrated that the effect produced by osA on spontaneous network activity was specific, reversible and unrelated with cell death. In conclusion, our data show that osA alters hippocampal network activity at concentrations commonly observed in AD patients and that such effect of osA increases with age.

Soluble amyloid β (Aβ) oligomers might trigger early cognitive deficit in Alzheimer's Disease (AD) through the impairment of proper neuronal network function. We have recently shown that the short sequence Aβ25-35 affects the spontaneous activity in hippocampal slices, when was added to the bath, at high nanomolar concentrations. In the present study, we aimed to characterize the effects of the oligomerized full length sequence Aβ1-42 on the spontaneous network activity in the CA1 hippocampal area testing whether such effects are age dependent. By performing extracellular field recordings of spontaneous network activity of hippocampal slices, we found that an oligomerized solution of Aβ1-42 (osAβ) potently inhibit, in a dose-dependent manner, the spontaneous hippocampal network activity with an IC50 of 0.4 ± 3.2 nM and a maximal effect reached around 10 nM. While spontaneous hippocampal network activity is unaffected by age, the sensitivity of spontaneous hippocampal network activity to osAβ (10 nM) appears to be increased in slices from older animals. Moreover, to see a significant reduction in spontaneous network activity in slices from animals in their second week of life 100nM osAβ was needed. The osAβ-induced reduction in hippocampal network activity is accompanied by a presynaptic reduction in both spontaneous and miniature synaptic potentials. Finally, we demonstrated that the effect produced by osAβ on spontaneous network activity was specific, reversible and unrelated with cell death. In conclusion, our data show that osAβ alters hippocampal network activity at concentrations commonly observed in AD patients and that such effect of osAβ increases with age.

The study of neuroscience has vastly benefited from the use of brain slices. This preparation has been fundamental for the understanding of the cellular basis of nervous system function as well as for the study of the mechanisms involved in neuronal network dysfunction. This experimental model provides flexible access, and control of, specific neural circuits and maintains their basic properties, allowing them to reproduce most of their natural network activities. Brain slices permit the combination of sophisticated techniques such as electrophysiology, fluorescence imaging, pharmacology, molecular biology, etc. More recently, the development of organotypic brain slice cultures has expanded the use of modern technical approaches to the study neuronal networks, while increasing their possibilities of evaluating long-term effects of acute experimental conditions, as well as the effects of chronic treatments on neuronal network function in vitro. Here, I will provide an overview of the use of organotypic cultures to understand neuronal network function and dysfunction, as well as the pharmacological approaches used for these studies. As a final example, I will review the studies performed in organotypic cultures regarding the deleterious effects of long-term amyloid beta application on neuronal networks in vitro, as well as the use of drugs that may prevent or revert their deleterious effects on nervous system function. Overall, this review will provide elements to support the use of organotypic cultures as a very reliable model to explore long-term neuropharmacological studies in vitro.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive and irreversible loss of memory and other cognitive functions. Substantial evidence based on genetic, neuropathological and biochemical data has established the central role of -amyloid protein ( βAP) in this pathology. Although the precise etiology of AD is not well understood yet, strong evidence for some of the molecular events that lead to progressive brain dysfunction and neurodegeneration in AD has been afforded by identification of biochemical pathways implicated in the generation of βAP, development of transgenic models exhibiting progressive disease pathology and by data on the effects of βAP at the neuronal network level. However, the mechanisms by which βAP causes cognitive decline have not been determined, nor is it clear if the degree of dementia correlates in time with the degree of neuronal loss. Hence, it is of interest to understand the biochemical processes involved in the mechanisms of βAP-induced neurotoxicity and the mechanisms involved in electrophysiological effects of this protein on different parameters of synaptic transmission and on neuronal firing properties. In this review we analyze recent evidence suggesting a complex role of βAP in the molecular events that lead to progressive loss of function and eventually to neurodegeneration in AD as well as the therapeutic implications based on βAP metabolism inhibition.

In this paper we prove the existence of a solution for a system of nonlinear parabolic partial differential equations arising from thermoelectric modelling of metallurgical electrodes undergoing a phase change. The model consists of an electromagnetic problem for eddy current computation coupled with a Stefan problem for temperature. The proof uses a regularized problem obtained by truncating the source term in temperature equation. Passing to the limit requires fine a priori estimates leading to compactness.

Attenuation artefacts decrease the specificity of myocardial perfusion single-photon emission computed tomography (SPECT). In this paper, the results of a prospective study evaluating the clinical applicability of attenuation and scatter correction in myocardial perfusion SPECT are presented. Of 607 patients in whom post-stress 99mTc-tetrofosmin myocardial perfusion SPECT was performed due to suspicion of coronary artery disease, 99 also underwent coronary angiography (CAG). A simultaneous emissiontransmission acquisition was performed. A multiple linear array of 153Gd sources and four independent energy windows were used for attenuation and scatter correction. A blind separate analysis of non-corrected (NC) and attenuation- and scatter-corrected (AC-SC) images was performed with scores of zero (no uptake) to three (normal uptake). The final diagnosis was based on CAG findings, and stenoses of 70 were considered to be significant. NC images had a sensitivity of 92 and a specificity of 46. In AC-SC images, the sensitivity decreased to 76, but the specificity increased to 71. The decrease in the sensitivity of AC-SC images was observed in all three coronary regions. Attenuation and scatter correction increased the specificity in the right coronary region, but decreased the specificity in the left anterior descending coronary region. In 13 of the 99 patients, AC-SC images showed false positive findings due to count deficiency in the anterior wall with normal CAG. The size of perfusion defects was decreased in AC-SC images (from 5.01±2.74 to 3.15±2.50 segments). The severity of perfusion defects was higher in NC (1.10±0.60) than in AC-SC (1.28±0.56) images. The combined evaluation of NC and AC-SC images was in agreement with the CAG findings in 79 of patients. It can be concluded that, when compared with NC images, AC-SC images improved the specificity in the right coronary region and decreased the sensitivity in all three coronary regions. Attenuation and scatter correction may generate anterior wall defects with normal CAG. The analysis of AC-SC images cannot be used alone for the diagnosis of coronary artery disease. In the clinical setting, combined NC and AC-SC images are recommended for the evaluation of post-stress myocardial perfusion SPECT.

In vitro and in situ rumen digestion trials were conducted to measure the effect of heat treatment on protein degradation by rumen microbes of cottonseed auotclaved and dry-heated (120, 140, 160 and 180 C) for different lengths of time (20, 40, 60, 90 and 120 min). Autoclaving (120 C, 1 kg/cm2of pressure for 60 min) was effective in reducing ammonia nitrogen concentration in vitro, but dry heat at this temperature was without effect. Dry heating caused a linear decrease of in vitro ammonia concentration as temperature increased from 140 to 180 C and as exposure time increased from 20 to 120 min. The in situ results corroborated the in vitro findings. Crude protein disappearance from dacron bags decreased from 87 to 48% as temperature increased from 140 to 180 C after 20 min of heating.

Six mature Holstein cows in late lactation and fitted with permanent ruminal, duodena) and ideal cannulae were used in a double 3 × 3 Latin-square design to study the effect of roasting or extruding of cottonseed on protein degradation in the rumen and availability of amino acids in the small intestine. Raw whole cottonseed (CS), extruded whole cottonseed (ECS), and roasted whole cottonseed (RCS) were fed in diets containing 17% crude protein and composed of 42% whole cottonseed, 26% corn grain and 29% hay supplemented with dry molasses, vitamins and minerals. The diets were isocaloric and contained 1.86 Mcal NEL/kg. Acid detergent lignin was used as a digesta marker, and diaminopimelic acid as a bacterial marker. Ruminai ammonia concentration was higher (P<.05) for CS than for ECS and RCS (15.7, 12.7 and 10.2 mM). Concentrations of isobutyrate (1.3 vs 0.8 and 0.8 mM) and isovalerate (1.8 vs 1.1 and 1.1 mM) were higher (P<.05) for CS compared with ECS and RCS. Non-ammonia nitrogen flow to the duodenum (g/d) was 248, 300 and 350 for CS, ECS, and RCS, with RCS higher (P<.05) that in CS.Apparent absorption of total amino acids in the small intestine was .80. 1.01, and 1.24 kg/d, for CS, ECS, and RCS, respectively, with RCS higher (P<.05) than CS. Apparent absorption of essential and non-essential amino acids was 376, 425; 458, 548;610 and 628 g/d for CS, ECS and RCS respectively, with RCS higher (P<.05) than CS.

Sequence-specific PCR was used in six laboratories and a ligase detection reaction was used in one laboratory to detect the zidovudine-resistance mutation at codon 215 of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase DNA. The genotypes of 27 different clinical samples, including cultured HIV-1 isolates, peripheral blood mononuclear cells, and plasma, were correctly identified by 140 of 154 (91%) assays. The sensitivity for detecting a mutation was 96% for HIV-1 reverse transcriptase DNA clone mixtures containing 30% mutant DNA and 62% for mixtures containing 6% mutant DNA.

It is shown that shaped beam patterns with acceptable ripple and sidelobe levels can be obtained from circular apertures or arrays with uniform excitation amplitude.

This study presents a numerical and experimental development of a piezo-actuated device used for monitoring the stiffness variations of its support through electromechanical impedance measurements. The piezo-device and its components define a clamped beam system activated dynamically by two piezo-transducers that transmit vibrations to the support (monitoring substrate). An harmonic finite element analysis was carried out to understand the effects of the substrate properties on the dynamics of the piezo-device. Experimental tests corroborated the simulations with the correspondence of modal shapes and frequency response functions (FRFs) when the substrate varies its stiffness. A biomedical application was conducted in a bone specimen with three embedded teeth to monitor the stiffness variations induced by drillings in the bone. Results showed that the bone stiffness monitoring could be possible through the teeth due to that the drillings effect were quantified by electrical impedance signals.

The finite element analysis is useful to predict the displacements and strength of the components of an urban seat bus. However, this analysis has a high computational cost when explicit dynamic technique is applied. This work uses Ansys LS Dyna software to carried out a complete 3D static test of an urban seat bus according with the Regulation No. 80 of the Economic Commission of the United Nations for Europe. To reduce the computational cost, we applied a bidimensional frame analysis (metamodel) using direct matrix method to obtain nodal displacements in 12 different models. The variables of this study were: thickness, sections and length of structural elements in order to optimize the strength of the seat. The results showed a range of variation about 0.1 % to 3.0% between finite elements analysis and metamodels Finally, it was proved that metamodels reduce the time analysis and can be used in a pre-design stage