21,110 research outputs found
Voltage regulator/amplifier is self-regulated
Signal modulated, self-regulating voltage regulator/amplifier controls the output b-plus voltage in modulated regulator systems. It uses self-oscillation with feedback to a control circuit with a discontinuous amplitude action feedback loop
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Idiopathic AIDS enteropathy and treatment of gastrointestinal opportunistic pathogens.
Diarrhea in patients with acquired immune deficiency syndrome (AIDS) has proven to be both a diagnostic and treatment challenge since the discovery of the human immunodeficiency virus (HIV) virus more than 30 years ago. Among the main etiologies of diarrhea in this group of patients are infectious agents that span the array of viruses, bacteria, protozoa, parasites, and fungal organisms. In many instances, highly active antiretroviral therapy remains the cornerstone of therapy for both AIDS and AIDS-related diarrhea, but other targeted therapies have been developed as new pathogens are identified; however, some infections remain treatment challenges. Once identifiable infections as well as other causes of diarrhea are investigated and excluded, a unique entity known as AIDS enteropathy can be diagnosed. Known as an idiopathic, pathogen-negative diarrhea, this disease has been investigated extensively. Atypical viral pathogens, including HIV itself, as well as inflammatory and immunologic responses are potential leading causes of it. Although AIDS enteropathy can pose a diagnostic challenge so too does the treatment of it. Highly active antiretroviral therapy, nutritional supplementation, electrolyte replacements, targeted therapy for infection if indicated, and medications for symptom control all are key elements in the treatment regimen. Importantly, a multidisciplinary approach among the gastroenterologist, infectious disease physician, HIV specialists, oncology, and surgery is necessary for many patients
Improved electrode gives high-quality biological recordings
To obtain high quality waveforms from a subject engaged in physical activity, an improved electrode assembly has been devised. This consists of a cup containing an electrically conductive paste and a silver electrode. The paste maintains contact between the skin and the plate
Computer program samples digital data for CRT display
High volume, multichannel data reduction computer program permits selection of the rates at which digital data is sampled. The program, written in FORTRAN 4 source language, also permits accessibility to the original mass of data
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Modelling commercial vehicle handling and rolling stability
YesThis paper presents a multi-degrees-of-freedom non-linear multibody dynamic
model of a three-axle heavy commercial vehicle tractor unit, comprising a subchassis, front
and rear leaf spring suspensions, steering system, and ten wheels/tyres, with a semi-trailer
comprising two axles and eight wheels/tyres. The investigation is mainly concerned with the
rollover stability of the articulated vehicle. The models incorporate all sources of compliance,
stiffness, and damping, all with non-linear characteristics, and are constructed and simulated
using automatic dynamic analysis of mechanical systems formulation. A constant radius turn
test and a single lane change test (according to the ISO Standard) are simulated. The constant
radius turn test shows the understeer behaviour of the vehicle, and the single lane change
manoeuvre was conducted to show the transient behaviour of the vehicle. Non-stable roll
and yaw behaviour of the vehicle is predicted at test speeds .90 km/h. Rollover stability of
the vehicle is also investigated using a constant radius turn test with increasing speed.
The articulated laden vehicle model predicted increased understeer behaviour, due to higher
load acting on the wheels of the middle and rear axles of the tractor and the influence of the
semi-trailer, as shown by the reduced yaw rate and the steering angle variation during the constant
radius turn. The rollover test predicted a critical lateral acceleration value where complete
rollover occurs. Unstable behaviour of the articulated vehicle is also predicted in the single lane
change manoeuvre
Electrode for biological recording
Electrochemically reversible silver-silver chloride electrode for detecting bioelectric potential differences generated by human muscles and organ
Bimetallic Effects on Ethylene Polymerization in the Presence of Amines: Inhibition of the Deactivation by Lewis Bases
Dinickel complexes supported by terphenyl ligands appended with phenoxy and imine donors were synthesized. Full substitution of the central arene blocks rotation around the aryl–aryl bond and allows for the isolation of atropisomers. The reported complexes perform ethylene polymerization in the presence of amines. The inhibiting effect of polar additives is up to 250 times lower for the syn isomer than the anti isomer. Comparisons with mononuclear systems indicate that the proximity of the metal centers leads to the observed inhibitory effect on the deactivation of the catalysts
THE DEFICIT IN NATURAL RESOURCE RESEARCH
Resource /Energy Economics and Policy,
Dinickel Bisphenoxyiminato Complexes for the Polymerization of Ethylene and α-Olefins
Dinuclear nickel phenoxyiminato olefin polymerization catalysts based on rigid p-terphenyl frameworks are reported. Permethylation of the central arene of the terphenyl unit and oxygen substitution of the peripheral rings ortho to the aryl–aryl linkages blocks rotation around these linkages, allowing atropisomers of the ligand to be isolated. The corresponding syn and anti dinickel complexes (25-s and 25-a) were synthesized and characterized by single-crystal X-ray diffraction. These frameworks limit the relative movement of the metal centers, restricting the metal–metal distance. Kinetics studies of isomerization of a ligand precursor (7-a) allowed the calculation of the activation parameters for the isomerization process (ΔH^‡ = 28.0 ± 0.4 kcal × mol^(–1) and ΔS^‡ = −12.3 ± 0.4 cal mol^(–1) K^(–1)). The reported nickel complexes are active for ethylene polymerization (TOF up to 3700 (mol C_2H_4) (mol Ni)^(−1) h^(–1)) and ethylene/α-olefin copolymerization. Only methyl branches are observed in the polymerization of ethylene, while α-olefins are incorporated without apparent chain walking. These catalysts are active in the presence of polar additives and in neat tetrahydrofuran. The syn and anti isomers differ in polymerization activity, polymer branching, and polymer molecular weight. For comparison, a series of mononuclear nickel complexes (26, 27-s, 27-a, 28, 30) was prepared and studied. The effects of structure and catalyst nuclearity on reactivity are discussed
Delineation of soil temperature regimes from HCMM data
Evaluation of LANDSAT and Heat Capacity Mapping Mission (HCMM) data as input into National Cooperative Soil Survey is discussed. Signature classification techniques were applied to 13 May 76 LANDSAT data. LANDSAT data was overlaid with HCMM data, revealing registration problems caused by a shortage of control points in LANDSAT data, and the WARP program developed to improve registration accuracy. Initial images for control point selection were produced using digital terrain elevation data. Statistical procedures for evaluating data classification and to describe spatial distribution of surface temperature and its correlation with soil surface conditions were investigated
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