43,124 research outputs found
Handheld-Impedance-Measurement System with seven-decade capability and potentiostatic function
No full textThis paper describes design and test of a new impedance-measurement system for nonlinear devices that exhibits a seven-decade range and works down to a frequency of 0.01 Hz. The system is specifically designed for electrochemical measurements, but the proposed architecture can be employed in many other fields where flexible signal generation and analysis are required. The system employs an unconventional signal generator based on two pulsewidth modulation (PWM) oscillators and an autocalibration system that allows uncertainties of less than 3% to be obtained over a range of 1 kΩ to 100 GΩ. A synchronous demodulation processing allows the noise superimposed to the low-amplitude input signals to be made negligibl
Micrognazia mandibolare e sleep apnea nella sindrome di Pierre Robin: trattamento di un caso
No full textMicrowave induced devulcanization for poly(ethylene–propylene–diene) recycling
No full textThe production of high quantities of end-of-life rubbers is an environmental problem of growing importance. Because of their crosslinked nature, such rubbers cannot be easily reprocessed, and actually, they are mainly wasted or reused after a simple mechanical grinding. In this study, a microwave (MW)-induced thermal treatment at temperatures above 300 C was proposed to obtain partial devulcanization of a poly(ethylene–propylene–diene) (EPDM) rubber filled with carbon black. The use of MWs showed to be a very fast and simple technique, which allowed the production of a treated rubber with a relatively low degree of crosslinking, a slight revulcanization ability, and suitability for reuse in conjunction with virgin rubber. Preliminary mechanical characterization, performed on the revulcanized samples, indicated that the virgin and treated rubber were able to establish a good interface adhesion, which led to performances better than those of similar materials where the recycled part was made of ground untreated EPDM
Evolution of the G+C content frontier in the rat cytomegalovirus genome
No full textWithin the 230138 bp of the rat cytomegalovirus (RCMV) genome, the G+C content changes abruptly at position 142644, constituting a G+C content frontier. To the left of this point, overall G+C content is 69.2%, and to the right it is only 47.6%. A region of extremely low G+C content (33.8%) is found in the 5 kb immediately to the right of the frontier, in which there are no predicted coding sequences. To the right of position 147501, the G+C content rises and predicted coding sequences reappear. However, these genes are much shorter (average 848bp, 50% G+C) than those in the left two-thirds of the genome (average 1462bp, 70% G+C). Whole genome alignment of several viruses indicates that the initial ultra-low G+C region appeared in the common ancestor of the genera Cytomegalovirus and Muromegalovirus, and that the lowering of G+C in the right third has been a subsequent process in the lineage leading to RCMV. The left two-thirds of RCMV has stop codon occurrences at 67.5% of their expected level, based on a modified Markov chain model of stop codon distribution, and the corresponding figure for the right third is 78%. Therefore, despite heavy mutation pressure, selective constraint has operated in the right third of the RCMV genome to maintain a degree of gene length unusual for such low G+C sequences
Microwave treatment of high performance cement-based materials
No full textHigh performance mortars were microwave-cured for different times (45-780 min) at 80°C and their properties compared to those of samples wet-cured at the same temperature for 24 h. The composition was based on a CEM I 52.5 Portland cement, microsilica and fine quartz. The initial water to cement ratio was ~0.24 and an acrylic superfluidifier was used. The compressive strength after wet-cure was ~100 MPa; that after 780 min of microwave exposure varied from ~70 to ~110 MPa, depending on sample confinement during the treatment. A similar trend was found for the flexural strength (~16 MPa and 13-21 MPa, respectively). The sample weight either increased or decreased depending on whether water evaporated or was absorbed during the treatments; the strength was closely related to the water content variation. The bound water, evaluated by thermal analysis, linearly depended on log(time). Mercury intrusion porosimetry indicated that both the pore cumulative volume and the threshold size of microwave cured samples were substantially smaller than those of the wet-cured samples. Finally, DSC runs and SEM analysis suggested that the CSH of microwave treated samples was better structured than that of the samples matured in hot water
Effects of dopaminergic agents on monoamine levels and motor behaviour in planaria
No full text1. Dopamine, serotonin and, in lesser amounts, norepinephrine were detected in Dugesia gonocephala using electrochemical detection coupled with liquid chromatography (LCED). 2. Treatment with L-dopa induced hyperkinesias, and a rise in dopamine, serotonin and norepinephrine content, whereas reserpine reduced motor activity and the concentrations of all three monoamines. 3. Haloperidol reduced motor activity and dopamine and norepinephrine levels. 4. Apomorphine induced hyperkinesias without altering monoamine levels
Fluorescence spectroscopy of synthetic melanin solution
No full textWe report a detailed investigation of fluorescence properties of synthetic eumelanin pigment in solution. A complete set of fluorescence spectra in the near-UV and visible range is analysed. Excitation spectra at a few selected emission energies are also investigated. Our measurements support the hypothesis that fluorescence in eumelanin is related to chemically distinct oligomeric units that can be selectively excited. Fluorescence due to large oligomer systems is spectrally differentiated from that due to monomers and small oligomer systems. Fluorescence excitation measurements show the contribution of 5,6-dihydroxyndole-2-carboxylic acid and 5,6-dihydroxyndole monomers to the emission of small-size oligomers. (C) 2008 Elsevier B.V. All rights reserved
[Analysis of right electrocardiographic leads in 195 normal subjects].
No full textThe aim of the present study was to analyse age-related differences in the morphology of QRS complex and ST-T segment of right-sided chest ECG leads (V3R-V6R) in normal subjects.One hundred ninety-five subjects evaluated for competitive sport training were divided into 2 groups according to age: group A (18-35 years) 77 subjects; group B (36-65 years) 118 subjects. All subjects underwent a complete clinical examination, conventional 12-lead ECG with right-sided chest leads, spirometric tests, a maximal stress-test (Bruce protocol), and a cardiac ultrasound study. None had signs or symptoms of cardiopulmonary disease nor of thoracic abnormalities, and all had normal standard ECGs.An rS morphology in V3R-V4R was observed in 92\%-84\% and 92\%-81\% of subjects in groups A and B, respectively (p = NS). The QS morphology in V6R was observed in 15\% of subjects in group A and in 11\% in group B (p = NS). Negative T-waves in V6R were more often observed in group A than B (94\% vs 85\%, p < 0.03). Isoelectric T-waves in V3R were found in 10\% of subjects in group A and 21\% in group B (p < 0.04). The amplitude of R-wave was always higher in group A (p < 0.01). An upsloping ST-T segment (0.5-1 mm) was observed only in V3R-V4R, with a prevalence of 23\% in group A and 13\% in group B in V3R (p < 0.05).No significant differences were observed between the 2 groups as to QRS complex of the right-sided ECG leads. A QS morphology may be observed even in normal subjects. The polarity of T-wave is quite variable, but in V6R it is most often negative among young people. Elevation of ST-T segment may be observed only in V3R and V4R, and more often in young subjects in the former lead
Polyurethane unimorph bender microfabricated with Pressure Assisted Microsyringe (PAM) for biomedical applications
No full textThis paper describes a new microfabrication technique for bender-type electromechanical actuators made of an elastomeric electroactive polymer. The technique is based on a computer-controlled deposition of the active material with a microsyringe. The paper describes the developed microfabrication system and proposes a simple deposition model. The realization of solid-state unimorph bender actuators made of polyurethane as electrolyte and a mixture of carbon black and polyurethane as electrodes is presented. Prototype actuators fabricated both with the new technique were driven with electrical field of 100 V/μm and showed bending angles higher than 30°. In this way, we have demonstrated that it is possible to fabricate polyurethane based microactuators using a polyurethane/carbon black composite such as device
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