5,222,783 research outputs found

    Frequency-dependent anti arrhythmic effects of crataegus monogyna on the extracellular field potential recordings in the rabbit atrioventricular node, an experimental model of AF

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    Introduction: Despite extensive studies that have been performed on the effects of Crataegus monogyna in cardiovascular diseases, only few investigations have addressed the antiarrhythmic properties of this plant. Aims of the present study were: 1) To determine the protective role of methanolic extract of C. monogyna on the rate-dependent model and the concealed conduction of the AV node. 2) To explore the role of Na+-K+ ATPase in the protective role of C. monogyna Methods: Male New Zealand rabbits (1.5-2kg) were used in all experiments. Stimulation protocols were used to measure basic and rate-dependent AV nodal properties (recovery, atrial fibrilation and zone of concealment) in two groups (N=14). In the first group, all the stimulation protocols were performed before and after the administration of different concentrations of C. monogyna extract (n=7), while in the second group (n=7), all stimulation protocols were carried out in the presence of ouabaine (0.05 μM) and the plant extract. Results: Basic and rate-dependent properties of the AV node were inhibited after the addition of the extract of C. monogyna to Kerebs Henselite solution. At the maximum concentration of C. monogyna (30 mg/l), WBCL cycle length was significantly increased from 156.5±3.4 to 173±5.8 ms and the nodal functional refractory period was prolonged from 164.4±4.1 to 182.7±3.8 ms (P<0.05). Significant decreases of ventricular rhythm were recorded in both selective concentrations of the plant extract. The depressant electrophysiological effect of C. monogyna on the AV node was not abolished by ouabaine, a selective inhibitor of Na+-K+ ATPase enzyme. Conclusion: The results showed a potential anti-arrhythmic and protective effect for C. monogyna. The effect of the plant extract in increasing nodal refractory period and widening of the concealment zone might be the major mechanisms involved. The protective role of C. monogyna was not related to the Na+-K+ ATPase activity

    Meaningful Categorisation of Novice Programmer Errors

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    The frequency of different kinds of error made by students learning to write computer programs has long been of interest to researchers and educators. In the past, various studies investigated this topic, usually by recording and analysing compiler error messages, and producing tables of relative frequencies of specific errors diagnostics produced by the compiler. In this paper, we improve on such prior studies by investigating actual logical errors in student code, as opposed to diagnostic messages produced by the compiler. The actual errors reported here are more precise, more detailed and more accurate than the diagnostic produced automatically

    Frequency Dependent Specific Heat from Thermal Effusion in Spherical Geometry

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    We present a novel method of measuring the frequency dependent specific heat at the glass transition applied to 5-polyphenyl-4-ether. The method employs thermal waves effusing radially out from the surface of a spherical thermistor that acts as both a heat generator and thermometer. It is a merit of the method compared to planar effusion methods that the influence of the mechanical boundary conditions are analytically known. This implies that it is the longitudinal rather than the isobaric specific heat that is measured. As another merit the thermal conductivity and specific heat can be found independently. The method has highest sensitivity at a frequency where the thermal diffusion length is comparable to the radius of the heat generator. This limits in practise the frequency range to 2-3 decades. An account of the 3omega-technique used including higher order terms in the temperature dependency of the thermistor and in the power generated is furthermore given.Comment: 17 pages, 15 figures, Substantially revised versio

    NPN 9 GHz wideband transistor

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    excellent reliability

    CMOS OTA-C high-frequency sinusoidal oscillators

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    Several topology families are given to implement practical CMOS sinusoidal oscillators by using operational transconductance amplifier-capacitor (OTA-C) techniques. Design techniques are proposed taking into account the CMOS OTA's dominant nonidealities. Building blocks are presented for amplitude control, both by automatic gain control (AGC) schemes and by limitation schemes. Experimental results from 3- and 2- mu m CMOS (MOSIS) prototypes that exhibit oscillation frequencies of up to 69 MHz are obtained. The amplitudes can be adjusted between 1 V peak to peak and 100 mV peak to peak. Total harmonic distortions from 2.8% down to 0.2% have been measured experimentally.Comisión Interministerial de Ciencia y Tecnología ME87-000

    Rain Effect Frequency of Infiltration Rate and Infiltration Capacity in Common Soil: Laboratory Test with Rainfall Simulator

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    Analyzing the Influence of Rain Frequency Infiltration Rate and Infiltration Capacity in Common Soil Type (Laboratory Testing Study With Rainfall Simulator). Infiltration is the flow of water into the ground through the soil surface. This process is a very important part of the hydrological cycle and in the process of transferring rain into the flow of water in the soil before reaching the river. Infiltration (infiltration rate and capacity) is influenced by various variables, including soil type, slope inclination, density and type of vegetation, soil moisture content, and rainfall intensity. This study aims to determine the effect of rainfall frequency on the infiltration rate and infiltration capacity on common soil types. This research is a type of laboratory experimental research, using rainfall simulator tool. The soil used in this study is common soil type. Furthermore, artificial rain was provided with intensity I5, I15, and I25 and performed infiltration rate reading on the Drain Rainfall Simulator. The rate and capacity of infiltration in common soils increase proportionally to the increased intensity of rainfall, the higher the intensity of rainfall the higher the infiltration occurring at the same level of rain frequency. The rate and capacity of infiltration in common soils decrease proportionally to the increasing frequency of rain, the more the frequency of rain the smaller the infiltration occurring at the same level of rainfall intensit

    Frequency of Clinical Symptoms of Gastroesophageal Reflux Disease in Asthmatic Patients

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    Background: Gastroesophageal reflex is known as an acid reflex, is long term condition where stomach contents back into the oesophagus resulting in either symptoms or complications. GERD disease is caused by weakness or failure of the lower oesophageal sphincter. Symptoms include the acidic taste behind the mouth, heart burn, chest pain, difficult breathing and vomiting. Complication includes esophagitis, oesophageal strictures and barrettes oesophagus. Objective: The aim of this research was to introduce the symptoms of GERD disease in asthmatic patients and how these symptoms worsen the symptoms of asthma disease and what clinical pictures present with the asthmatic disease. Methodology: A designed performa was used to collect the data and after filling the performa, results were drawn and conclusion through the facts and the information given by patients. Results: In the present study among all 164 asthmatic patients, 70 (42.7%) patients showed dyspepsia, 58 (35.4%) were with chest burning, 23 (14%) were asking about chest pain, with acidic mouth taste were 39 (23.8%), 22 (13.4%) were feeling sore throat and 44 (26.8%) showed regurgitation reflex. Among these 164 patients 16 (9.8%) were smokers and 148 (90.2 %) were non-smokers. 47 (28.7%) were males and 117 (71.3%) were females. Conclusion: It is concluded that gastroesophageal reflux disease in asthmatic patients present symptoms of acidic mouth taste, chest burning, chest pain, dyspepsia, regurgitation reflex and sore throat
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