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Amplitude
Kinds of Amplitude Terms modified by Amplitude Selected AbstractsR-wave Amplitude in Lead II of an Electrocardiograph Correlates with Central Hypovolemia in Human BeingsACADEMIC EMERGENCY MEDICINE, Issue 10 2006John G. McManus MD Abstract Objectives Previous animal and human experiments have suggested that reduction in central blood volume either increases or decreases the amplitude of R waves in various electrocardiograph (ECG) leads depending on underlying pathophysiology. In this investigation, we used graded central hypovolemia in adult volunteer subjects to test the hypothesis that moderate reductions in central blood volume increases R-wave amplitude in lead II of an ECG. Methods A four-lead ECG tracing, heart rate (HR), estimated stroke volume (SV), systolic blood pressure, diastolic blood pressure, and mean arterial pressure were measured during baseline supine rest and during progressive reductions of central blood volume to an estimated volume loss of >1,000 mL with application of lower-body negative pressure (LBNP) in 13 healthy human volunteer subjects. Results Lower-body negative pressure resulted in a significant progressive reduction in central blood volume, as indicated by a maximal decrease of 65% in SV and maximal elevation of 56% in HR from baseline to ,60 mm Hg LBNP. R-wave amplitude increased (p < 0.0001) linearly with progressive LBNP. The amalgamated correlation (R2) between average stroke volume and average R-wave amplitude at each LBNP stage was ,0.989. Conclusions These results support our hypothesis that reduction of central blood volume in human beings is associated with increased R-wave amplitude in lead II of an ECG. [source] Amplitude and Velocity of Mitral Annulus Motion in RabbitsECHOCARDIOGRAPHY, Issue 4 2004Li-ming Gan M.D., Ph.D. Objective: During recent years, the amplitude and the maximal systolic velocity of the mitral annulus motion (MAM) have been established as indices of the left ventricular systolic function and the maximal diastolic velocity of the annulus motion has been suggested as an index of diastolic function. The main aims of the present study were to investigate the feasibility of these techniques in rabbits and to investigate age-related changes concerning these variables. Methods: Twenty-one New Zealand white rabbits were investigated by echocardiographic M-mode and pulsed tissue Doppler. One subgroup (I) included 11 still-growing, 3.0 ± 0.2 month-old, animals and another group (II) included 10 young grown up rabbits, 12.1 ± 1.5 months old. Results: The amplitude (4.8 ± 0.6 and 3.5 ± 0.3 mm, respectively) and maximal systolic (98 ± 14 and 66 ± 7 mm/s, respectively) and diastolic (111 ± 21 and 80 ± 12 mm/s, respectively) velocities of the MAM were significantly (P < 0.001) higher in group I than in group II, despite a bigger heart in the animals in the latter group. A coefficient of variation of <5% was found for both inter- and intraobserver variability for both amplitude and velocities. Conclusions: The amplitude and velocities of MAM are easily recorded in rabbits with excellent reproducibility and the changes with age seem to be very similar to those in humans. These noninvasive M-mode and tissue Doppler methods are therefore suitable for the investigation of left ventricular function in experimental studies in rabbits. (ECHOCARDIOGRAPHY, Volume 21, May 2004) [source] Lithology and fluid prediction from amplitude versus offset (AVO) seismic dataGEOFLUIDS (ELECTRONIC), Issue 4 2003D. J. Davies Abstract Seismic reflection data as used in the oil industry is acquired and processed as multitrace data with source-receiver offsets from a few hundred metres (short offset) to several kilometres (long offset). This set of data is referred to as ,pre-stack'. The traces are processed by velocity analysis, migration and stacking to yield a data volume of traces with ,zero-offset'. The signal-to-noise enhancement resulting from this approach is very significant. However, reflection amplitude changes in the pre-stack domain may also be analysed to yield enhanced rock physics parameter estimates. Pre-stack seismic data is widely used to predict lithology, reservoir quality and fluid distribution in exploration and production studies. Amplitude versus offset (AVO) data, especially anomalous signals, have been used for decades as indicators of hydrocarbon saturation and favourable reservoir development. Recently, enhanced quantification of these types of measurement, using seismic inversion techniques in the pre-stack domain, have significantly enhanced the utility of such measurements. Using these techniques, for example, probability of the occurrence of hydrocarbons throughout the seismic data can be estimated, and as a consequence the many pre-stack volumes acquired in a three-dimensional (3D) can be survey, reduced to a single, more interpretable volume. The possibilities of 4D time lapse observation extend the measurements to changes in fluid content (and pressure) with time, and with obvious benefits in establishing the accuracy of dynamic reservoir models and improvements in field development planning. As an illustration, recent results from the Nelson Field (UK North Sea), are presented where we show the method by which probability volumes for oil sands may be calculated. The oil,sand probability volumes for three 3D seismic datasets acquired in 1990, 1997 and 2000 are compared and production effects in these data are demonstrated. [source] Dynamic T1-weighted monitoring of vascularization in human carcinoma heterotransplants by magnetic resonance imaging,INTERNATIONAL JOURNAL OF CANCER, Issue 1 2003Fabian Kiessling Abstract Studies on tumor angiogenesis and antiangiogenic therapies are commonly performed with tumor heterotransplants in nude mice. To monitor therapeutic effects, improved noninvasive analyses of functional data are required, in addition to the assessment of tumor volume and histology. Here, we report on sequential monitoring of vascularization of human squamous cell carcinomas growing as heterotransplants in nude mice using MRI. Using a custom-developed animal coil in a conventional whole-body 1.5 T MRI scanner, dynamic T1w sequences were recorded after i.v. injection of Gd-DTPA in tumors grown for 17, 21, 25, 29 and 33 days. Amplitude and the exchange rate constant (kep) were calculated according to a 2-compartment model, discriminating intravascular and interstitial spaces, and correlated with tumor size and histology. High-resolution imaging of small heterotransplants from 100 to 1,000 mm3 was achieved, clearly discriminating vital and necrotic areas. Preceding the development of necroses, which were hyperintense in T2w images and confirmed with histology, a local decrease of amplitude and kep values was observed. Significantly higher amplitudes were found in tumor periphery than in central parts, correlating well with the vascular pattern obtained by immunocytochemistry. Tumor size correlated negatively with amplitude, probably as a result of increasing necrotic areas, whereas the reason for the observed increase of kep value with tumor size remains unclear. These data demonstrate that dynamic MRI is an excellent method for noninvasive assessment of tumor vascularization in small animals using a clinical whole-body scanner with little technical modifications. This technique provides functional data characterizing essential features of tumor biology and is thus appropriate for monitoring antiangiogenic therapies. © 2002 Wiley-Liss, Inc. [source] On Selection of the Perturbation Amplitude Required to Avoid Nonlinear Effects in Impedance MeasurementsISRAEL JOURNAL OF CHEMISTRY, Issue 3-4 2008Bryan Hirschorn Numerical simulations of electrochemical systems were used to explore the influence of large-amplitude potential perturbations on the measured impedance response. The amplitude of the input potential perturbation used for impedance measurements, normally fixed at a value of 10 mV for all systems, should instead be adjusted for each experimental system. Guidelines are developed for selection of appropriate perturbation amplitudes. A characteristic transition frequency is defined that can be used to tailor a frequency-dependent input signal to optimize signal-to-noise levels while maintaining a linear response. [source] Evolution of upper airway resistance syndromeJOURNAL OF SLEEP RESEARCH, Issue 3 2009LUIZA JONCZAK Summary The question of whether upper airway resistance syndrome (UARS) is a distinct disease or an initial feature of obstructive sleep apnoea syndrome is still a matter of debate. We evaluated a retrospective group of UARS patients to determine the evolution of UARS over time and the relationship between clinical evolution and subjects' phenotype. Investigations were performed in 30 patients, in whom UARS was diagnosed between 1995 and 2000 by the use of full polysomnography (PSG) without oesophageal pressure (Pes) measurement. The time between initial and follow-up investigations was 6.6 ± 2.6 years. All subjects had full PSG with Pes measurement and completed a sleep questionnaire, including the Epworth Sleepiness Scale. In 19 subjects, PSG results were compatible with UARS. In nine subjects, obstructive sleep apnoea,hypopnoea syndrome (OSAHS) was diagnosed. In two subjects, PSG did not demonstrate breathing abnormalities. The mean ± SD apnoea,hypopnoea index in the UARS group was 1.5 ± 1.7 h,1 and 25.2 ± 19 h,1 in the OSAHS group (P < 0.01). The increase in body mass index (BMI) between initial and follow-up investigations in the UARS group was from 29.4 ± 4 to 31 ± 5.7 kg m,2 (P = 0.014) and in the OSAHS group from 30 ± 4.1 to 32.4 ± 4.7 kg m,2(P = 0.004). Amplitude of Pes swings during respiratory events was significantly higher in OSAHS than that in UARS (P = 0.014). Our results suggest that UARS is part of a clinical continuum from habitual snoring to OSAHS. Progression from UARS to OSAHS seems to be related to an increase in the BMI. [source] INFLUENCE OF WATER ACTIVITY ON THE ACOUSTIC PROPERTIES OF BREAKFAST CEREALSJOURNAL OF TEXTURE STUDIES, Issue 5 2006EWA GONDEK ABSTRACT Corn and wheat bran flakes were compressed in a plastic cylinder and the generated vibrations were measured by a piezoelectric accelerometer. Amplitude,time records were thoroughly analyzed and the total acoustic energy in arbitrary units, number of acoustic events and energy of a single acoustic event were calculated. Relationships between the time of compression, frequency and sound intensity are presented as acoustograms. All parameters, except the energy of a single acoustic event, were strongly dependent on water activity (Aw). The flakes differed essentially in their ability to propagate vibrations. At low Aw's, both types of flakes were alike, but at higher Aw's, corn flakes damped high-frequency waves while wheat bran flakes did not show this property. [source] Leprous neuropathy: a clinical and neurophysiological studyJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2004E Ghiglione Leprosy is one of the most common treatable causes of neuropathy in the world. Peripheral nerves and skin are commonly affected. We reported the clinical features and electrophysiological findings in 46 patients with leprosy. The aim of our study was to evaluate the nature of damage in the nerve fibres, especially in the first phase of disease. Forty-six patients (mean age: 44.8 ± 17.8) with diagnosed leprosy were studied by neurological examination and nerve conduction studies (NCS). Twenty-eight patients were examined for a mean period of 34.8 months. The number of tests for patients varied from 1 to 13 controls. Amplitude of sensory and motor action potentials (SNAP and MAP), sensory-motor conduction velocity of median, ulnar, tibialis, peroneal and sural nerves were evaluated. Abnormalities were found in 282 of 647 nerves investigated (37.56%), sensory nerve abnormalities being more frequent than motor (50.16% 29.45). Of 282 nerves with neurophysiological abnormalities, 123 were clinically asymptomatic (43.62%). A statistically significant correlation between duration of disease and number of electrophysiological abnormalities was demonstrated. In 19 nerves partial "conduction-block"(reduction of cMAP > 50% in the proximal response) was individuated. The first electrophysiological alteration, suggesting segmental demyelination, was detected in 41 nerves of 21 patients (33.3 %). According to this view, our data support the hypothesis that leprosy induces a neuropathy of demyelinating nature in the first phase. [source] Amplitude,shape approximation as an extension of separation of variablesMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 3 2008N. Parumasur Abstract Separation of variables is a well-known technique for solving differential equations. However, it is seldom used in practical applications since it is impossible to carry out a separation of variables in most cases. In this paper, we propose the amplitude,shape approximation (ASA) which may be considered as an extension of the separation of variables method for ordinary differential equations. The main idea of the ASA is to write the solution as a product of an amplitude function and a shape function, both depending on time, and may be viewed as an incomplete separation of variables. In fact, it will be seen that such a separation exists naturally when the method of lines is used to solve certain classes of coupled partial differential equations. We derive new conditions which may be used to solve the shape equations directly and present a numerical algorithm for solving the resulting system of ordinary differential equations for the amplitude functions. Alternatively, we propose a numerical method, similar to the well-established exponential time differencing method, for solving the shape equations. We consider stability conditions for the specific case corresponding to the explicit Euler method. We also consider a generalization of the method for solving systems of coupled partial differential equations. Finally, we consider the simple reaction diffusion equation and a numerical example from chemical kinetics to demonstrate the effectiveness of the method. The ASA results in far superior numerical results when the relative errors are compared to the separation of variables method. Furthermore, the method leads to a reduction in CPU time as compared to using the Rosenbrock semi-implicit method for solving a stiff system of ordinary differential equations resulting from a method of lines solution of a coupled pair of partial differential equations. The present amplitude,shape method is a simplified version of previous ones due to the use of a linear approximation to the time dependence of the shape function. Copyright © 2007 John Wiley & Sons, Ltd. [source] Relationship between Amplitude and Timing of Heart Sounds and Endocardial AccelerationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2009AUDE TASSIN M.D. Objective: To study the correlation between heart sounds and peak endocardial acceleration (PEA) amplitudes and timings, by modulation of paced atrioventricular (AV) delay in recipients of dual chamber pacemakers. Methods: Ten recipients of dual chamber pacemakers implanted for high-degree AV block were studied. Endocardial acceleration (EA) and phonocardiographic and electrocardiographic signals were recorded during performance of an AV delay scan in VDD and DDD modes. Results: First PEA (PEA I) and first heart sound (S1) changed similarly with the AV delay. A close intrapatient correlation was observed between S1 and PEA I amplitudes in all patients (P < 0.0001). The interpatient normalized PEA I to S1 amplitudes correlation was r = 0.89 (P < 0.0001) in DDD mode, and r = 0.81 (P < 0.0001) in VDD mode. The mean cycle-by-cycle PEA I to S1 delay was ,4.3 ± 22 ms and second PEA (PEA II) to second heart sound (S2) delay was ,7.7 ± 15 ms. Conclusions: A close correlation was observed between PEA I and S1 amplitudes and timings, and between PEA II and S2 timings. These observations support the hypothesis that PEA and heart sounds are manifestations of the same phenomena. EA might be a useful tool to monitor cardiac function. [source] Atrial Electrogram Amplitude and Efficacy of Cavotricuspid Isthmus Ablation for Atrial FlutterPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2003MEHMET OZAYDIN Large atrial electrogram amplitudes recorded in the cavotricuspid isthmus (CTI) may reflect thick atrial musculature. For this reason, in patients with atrial flutter, the efficacy of an application of conventional radiofrequency energy may be related to the amplitude of the local atrial electrogram. In 100 consecutive patients (mean age 59 ± 13 years) with atrial flutter, contiguous applications of radiofrequency energy were delivered in the CTI. The criterion for complete CTI block was the presence of widely split double potentials (>110 ms) along the entire ablation line during pacing from the coronary sinus and posterolateral right atrium. The atrial electrogram amplitude was measured before and after applications of radiofrequency energy at sites of gaps in the ablation line. Complete CTI block was achieved in 90 (90%) of the 100 patients. The mean atrial electrogram amplitudes at gap sites where an application of radiofrequency energy did and did not result in complete block were 0.36 ± 0.42 and 0.67 ± 0.62 mV, respectively (P < 0.01). The positive and negative predictive values (for complete block) of a ,50% decrease in electrogram amplitude after an application of radiofrequency energy were 100% and 35%, respectively. The mean atrial electrogram amplitude is larger at CTI sites where complete isthmus block cannot be achieved with conventional radiofrequency energy. The efficacy of conventional radiofrequency ablation may be improved by identifying areas in the CTI where the voltage is relatively low. (PACE 2003; 26:1859,1863) [source] The Defibrillation Efficacy of High Frequency Alternating Current Sinusoidal Waveforms in Guinea PigsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2p1 2003SCOTT J. ROBERTS ROBERTS, S.J., et al.: The Defibrillation Efficacy of High Frequency Alternating Current Sinusoidal Waveforms in Guinea Pigs. There have been few basic studies of alternating current (AC) defibrillation, despite growing interest in the ability of AC to terminate or alter ongoing fibrillation. Based on fibrillation threshold testing, it has been suggested that cardiac tissue is most sensitive to long duration, low strength AC stimulation at around 50 Hz. This has not been directly tested for defibrillation. Two subcutaneous electrodes were placed 40 mm apart on opposing aspects of the guinea pig thorax. Seven seconds were allowed to elapse between fibrillation initiation and defibrillation. The tested waveforms were at 50, 100, 200, 500, and 1000 Hz with 2, 4, 8, 16, and 32-cycles. The efficacy of every waveform was measured using a single stimulus in a large population of animals. Forty-one guinea pigs were used in the fixed energy group. Thirty-three guinea pigs were used in the fixed amplitude group with additional 1-cycle waveforms tested. The 200-Hz and the 2-cycle waveforms were significantly more efficacious than those at other frequencies(P < 0.02)and other durations(P < 0.001). The 50-Hz waveforms were the least successful. Amplitude, not duration or energy, was the determinate of efficacy for 2-cycle (the most efficacious) waveforms. Unlike low strength stimulation, defibrillation strength stimuli are most effective with high frequency (200 Hz) pulses (2 cycles). (PACE 2003; 26[Pt. I]:599,604) [source] QRS Amplitude and Shape Variability in MagnetocardiogramsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2000MARKUS HUCK In magnetocardiography, averaging of QRS complexes is often used to improve the signal-to-noise ratio. However, averaging of QRS complexes ignores the variation in amplitude and shape of the signals caused, for example, by respiration. This may lead to suppression of signal portions within the QRS complexes. Furthermore, for inverse source, reconstructions of dipoles and of current density distributions errors in the special arrangement may occur. To overcome these problems we developed a method for separating and selective averaging QRS complexes with different shapes and amplitudes. The method is based on a spline interpolation of the QRS complex averaged by a standard procedure. This spline function then is fitted to each QRS complex in the raw data by means of nonlinear regression (Levenberg-Marquardt method). Five regression parameters are applied: a linear amplitude scaling, two parameters describing the baseline drift, a time scaling parameter, and a time shift parameter. We found that both amplitude and shape of the QRS complex are influenced by respiration. The baseline shows a weaker influence of the respiration. The regression parameters of two neighboring measurement channels correlate linearly. Thus, selective averaging of a larger number of sensors can be performed simultaneously. [source] Amplitude- and temperature effects of filler-reinforced rubber: Experiments and ModellingPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008Martin Rendek Rubber,like materials exhibit special mechanical properties in a wide range of technical applications. To achieve a desired behaviour of the end product, the materials are reinforced with active fillers like carbon black. In the focus of this paper are selected cyclic,monofrequent experiments with constant strain amplitudes. Special attention will be focused to the excitation with small dynamic amplitudes. The amplitude dependence of the storage and loss moduli is known as the Payne,effect. We study the amplitude, and temperature dependence of storage and loss modulus as well as dissipation effects. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Modulation of ongoing cognitive processes by emotionally intense wordsPSYCHOPHYSIOLOGY, Issue 2 2008Luis Carretié Abstract Contrary to what occurs with negative pictures, negative words are, in general, not capable of interfering with performance in ongoing cognitive tasks in normal subjects. A probable explanation is the limited arousing power of linguistic material. Especially intense words (insults and compliments), neutral personal adjectives, and pseudowords were presented to 28 participants while they executed a lexical decision task. Insults were associated with the poorest performance in the task and compliments with the best. Amplitude of the late positive component of the event-related potentials, originating at parietal areas, was maximal in response to compliments and insults, but latencies were delayed in response to the latter. Results suggest that intense emotional words modulate ongoing cognitive processes through both bottom-up (attentional capture by insults) and top-down (facilitation of cognitive processing by arousing words) mechanisms. [source] Assessment of Physiological Amplitude, Duration, and Magnitude of ECG T-Wave AlternansANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2009Laura Burattini Ph.D. Background: An association between T-wave alternans (TWA) and malignant ventricular arrhythmias is generally recognized. Because relatively low levels of TWA have also been observed in healthy (H) subjects, the question arises as to whether these are ascribable to noise and artifacts, or can be given the relevance of a physiological phenomenon characterizing a preclinical condition. Methods: To answer this question, in the present study 20-minute not noisy, sinus ECG recordings, from 138 H-subjects and 148 coronary artery diseased (CAD) patients, were submitted to our adaptive match filter (AMF) procedure to identify and parameterize TWA in terms of duration (TWAD), amplitude (TWAA), and magnitude (TWAM, defined as the product of TWAD times TWAA). The 99.5th percentiles of mean values of TWAA, TWAD, and TWAM over 20-minute ECGs were used to define three threshold levels (THRD, THRA, and THRM), which allow discrimination of abnormal TWA levels. Results: Nonstationary TWA was found in all our H-subjects and CAD-patients. TWAD, TWAA, and TWAM levels were classified as being physiological in 99% of H-subjects and 87% of CAD-patients. A linear correlation (r =,0.52, P < 0.001) was found between TWAA and RR interval in the H-population. Conclusions: Our results support the hypothesis of the existence of physiological TWA levels, which are to be considered in the effort to improve reliability of nonphysiological TWA levels discrimination. [source] Effects of excitatory and inhibitory neurotransmission on motor patterns of human sigmoid colon in vitroBRITISH JOURNAL OF PHARMACOLOGY, Issue 7 2008M Aulí Background and purpose: To characterize the in vitro motor patterns and the neurotransmitters released by enteric motor neurons (EMNs) in the human sigmoid colon. Experimental approach: Sigmoid circular strips were studied in organ baths. EMNs were stimulated by electrical field stimulation (EFS) and through nicotinic ACh receptors. Key results: Strips developed weak spontaneous rhythmic contractions (3.67±0.49 g, 2.54±0.15 min) unaffected by the neurotoxin tetrodotoxin (TTX; 1 ,M). EFS induced strong contractions during (on, 56%) or after electrical stimulus (off, 44%), both abolished by TTX. Nicotine (1,100 ,M) inhibited spontaneous contractions. Latency of off-contractions and nicotine responses were reduced by NG -nitro- L -arginine (1 mM) and blocked after further addition of apamin (1 ,M) or the P2Y1 receptor antagonist MRS 2179 (10 ,M) and were unaffected by the P2X antagonist NF279 (10 ,M) or ,-chymotrypsin (10 U mL,1). Amplitude of on- and off-contractions was reduced by atropine (1 ,M) and the selective NK2 receptor antagonist Bz-Ala-Ala-D-Trp-Phe-D-Pro-Pro-Nle-NH2 (1 ,M). MRS 2179 reduced the amplitude of EFS on- and off-contractions without altering direct muscular contractions induced by ACh (1 nM,1 mM) or substance P (1 nM,10 ,M). Conclusions and implications: Latency of EFS-induced off-contractions and inhibition of spontaneous motility by nicotine are caused by stimulation of inhibitory EMNs coreleasing NO and a purine acting at muscular P2Y1 receptors through apamin-sensitive K+ channels. EFS-induced on- and off-contractions are caused by stimulation of excitatory EMNs coreleasing ACh and tachykinins acting on muscular muscarinic and NK2 receptors. Prejunctional P2Y1 receptors might modulate the activity of excitatory EMNs. P2Y1 and NK2 receptors might be therapeutic targets for colonic motor disorders. British Journal of Pharmacology (2008) 155, 1043,1055; doi:10.1038/bjp.2008.332; published online 1 September 2008 [source] Pulmonary function tests and diaphragmatic compound muscle action potential in patients with sporadic amyotrophic lateral sclerosisACTA NEUROLOGICA SCANDINAVICA, Issue 6 2010T. N. Sathyaprabha Sathyaprabha TN, Pradhan C, Nalini A, Thennarasu K, Raju TR. Pulmonary function tests and diaphragmatic compound muscle action potential in patients with sporadic amyotrophic lateral sclerosis. Acta Neurol Scand: 2010: 121: 400,405. © 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard. Background,,, Respiratory failure is the primary cause of death in patients with amyotrophic lateral sclerosis (ALS). Diaphragmatic compound muscle action potentials (DCMAP) are valid parameters to assess the respiratory muscle innervation. Aim,,, In this study we propose to establish evidence of pulmonary dysfunction in patients with ALS and its relation to DCMAP parameters among patients with sporadic ALS. Materials and methods,,, Twenty nine patients (M-20, F-9) diagnosed to have sporadic ALS by El. Escorial criteria, without symptoms of pulmonary dysfunction, and able to perform the PFT satisfactorily, were studied. Thirty controls (M-20, F-10) were selected from patient's relatives. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow rate (PEFR) and maximum voluntary ventilation (MVV) were measured by spirometry. Maximum expiratory pressure (MEP) was measured by digital peak pressure monitor. Right phrenic nerve conductions (DCMAP) were performed and the latencies and amplitude of diaphragmatic com-pound action potential (DCMAP) was recorded in controls and ALS patients. Results,,, The mean age of patients was 51.41 ± 10.72 years (37,82) and control was 53.57 ± 8.85 years (30,68). None of the patients had symptoms or clinical evidence of respiratory dysfunction. The FVC, FEV1, PEFR, MVV, MIP and MEP were significantly (P < 0.001) reduced in ALS. The mean DCMAP amplitude was reduced among patients (610 ± 506.231 ,v) as compared to controls (1303.33 ± 584.56, P < 0.001) and mean latency was increased in patients (9.73 ± 2.57 ms) compared to controls (7.69 ± 0.87, P = 0.001). There was significant negative correlation between PFTs and latencies of DCMAP. Amplitude of DCMAP did not correlate with PFTs. Conclusion,,, There is significant negative correlation between DCMAP latencies and PFTs suggesting early loss of myelinated fibres and diaphragmatic dysfunction. DCMAP latencies may be a good indicator of early respiratory muscle involvement and also of disease progression in ALS. [source] Einfluss zyklischer Temperaturänderungen auf die mechanische Beanspruchung von RadialstromadsorbernCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 12 2009H. Steinbach Dipl.-Ing. Abstract In chemischen oder kryogenen Industrieanlagen befindet sich häufig ein Anlagenteil für die Adsorption von Stoffen aus Gasströmen. Durch den erforderlichen Wechsel zwischen einer kalten Arbeits- und einer heißen Regenerierungsphase unterliegen die eingebundenen Komponenten einer zyklischen Temperaturbelastung und daraus resultierenden mechanischen Beanspruchungen. Die Berechnung einer Adsorberstation bedarf deshalb aufgrund ihrer hohen Zyklenzahl einer zeitfesten Auslegung mit einer definierten Spannungsschwingbreite (Amplitude). Der Artikel befasst sich mit der experimentellen Erfassung der auftretenden Temperaturprofile und berücksichtigt die dadurch gewonnenen Erkenntnisse bei der Simulation der mechanischen Belastung radialdurchströmter Adsorptionsbehälter. Die Validierung der simulierten Ergebnisse erfolgte an einer Luftzerlegungsanlage. Die Berücksichtigung des Wärmeübergangs in den Behälter bei der Berechnung von mechanischen Belastungen ermöglicht eine weitaus größere Genauigkeit bei der Dimensionierung von Wandstärken und der Berechnung der Lebensdauer. [source] Nasal high-frequency ventilation for premature infantsACTA PAEDIATRICA, Issue 11 2008Tarah T Colaizy Abstract Aim: To assess the use of nasal high-frequency ventilation (HFV) to provide noninvasive ventilatory support for very low birthweight (VLBW) infants. Study Design: VLBW infants, >7 days of age on nasal continuous positive airway pressure (CPAP), were placed on nasal HFV for 2 h using the Infant Star high-frequency ventilator (Mallinckrodt, Inc., St. Louis, MO, USA). Mean airway pressure was set to equal the previous level of CPAP, and amplitude was adjusted to obtain chest wall vibration. Capillary blood was sampled before starting HFV and after 2 h to determine change in pH and partial pressure of carbon dioxide (pCO2). Results: Fourteen subjects were studied, 10 males and 4 females. Gestational age was 26,30 weeks (median 27). Age at study was 18,147 days (median 30). Median birth weight was 955 g; median weight at study was 1605 g. Nasal CPAP pressure was 4,7 cm H2O (mean 5). Amplitude was 30,60 (median 50). After 2 h, PCO2 (mean 45 torr) was significantly lower than initial PCO2 (mean 50 torr) (p = 0.01), and pH had increased significantly (7.40 vs. 7.37, p = 0.04). Conclusions: Nasal HFV is effective in decreasing pCO2 in stable premature infants requiring nasal CPAP support. Long-term use of nasal HFV requires further study. [source] Language-Related Potentials in Temporal Lobe Epilepsy Before and After Surgical TreatmentEPILEPSIA, Issue 2000Toshihiko Ito Purpose: Temporal lobectomy has contributed to treatment for medically intractable epilepsies. However, influence of the surgical treatment on cognitive function is not still clear, especially from the electrophysiological viewpoint. N400, an event related potential (ERP) named for its negative polarity and peak latency of 400 ms, is reported to be an electrophysiological sign of neural activities associated with semantic priming in language perception. In the present study, ERPs are applied to evaluate the cognitive function of temporal lobe epilepsy before and after temporal lobectomy. Methods: Two patients with intractable temporal lobe epilepsy participated in this study. Fifteen normal subjects served as controls. The incongruous sentence task (Kutas and Hillyard 1980) was used to record N400 components in an auditory modality. Two types of sentences (40 Japanese sentences for each type) were prepared, in which the terminal words were either semantically congruent or incongruent. The scntences were randomly presented at approximately 65 dB SPL peak intensity. ERPs were recorded according to the international 10,20 system, with a balanced non-cephalic electrode reference and 2 1 channels. The band-pass filter was set from 0.5 to 30 Hz, and the ERPs were sampled at 500 Hz from 200 ms before the onset of terminal words to 824 ms post-stimulus. Waves were calculated by subtracting ERPs in the congruent condition from those in the incongruent condition. N400 was scored as the most negative point between 250 and 450 ms in the subtraction waves. Amplitudes were measured from the baseline of 100 ms before the terminal words. Motor responses were also measured with a right index finger, to estimate the accuracy of understanding sentences. Results: Case I was a 22-year-old male who had intractable epilepsy for 7 years. Magnetic resonance imaging (MRI) showed high-intensity signals in the right amygdalo-hippocampal region. The epileptic seizures were confirmed to originate from the region hy electroencephalography/closed-circuit television monitoring, and single-photon-emission computed tomography. ERPs were recorded I month before and after the right anterior temporal lobectomy. Before the surgery, the rate of correct responses showed no difference between the patient (96 %) and the controls (96 %). The amplitudes of N400 for the patient reduced in the right frontal and central areas (F4, C4), comparing to 99 % confidence limit for control subjects. After the surgery, the rate of correct responses was 97 %, and the amplitudes reduced in the right central, parietal, and posterior temporal areas (C4, P4, 0 2, T6). Case 2 (37-year-old female) had intractable epilepsy for 30 years. MRI showed brain atrophy in the right hippocampal region. The epileptic seizures were confirmed to originate from the region. N400 was recorded 3 months after the resection. The rate of correct responses was 95 %. The amplitudes of N400 were lower in the right frontal, parietal, and temporal areas (electrodes Fp2, F4, P4, T6, Pz), comparing to 99 % confidence limit of controls. Conclusions: Before the lpbectomy, the reduction of amplitudes of N400 indicated that the pathogenesis of intractable temporal lobe epilepsy would influence the process of semantic priming in language perception. After the resection, it was suggested that the right temporal lobectomy might affect the cognitive function in the brain from electrophysiological aspects. We could benefit from further study including analysis of the discrepancy between the amplitudes of N400 and behavioral responses. [source] Change of Excitability in Brainstem and Cortical Visual Processing in Migraine Exhibiting AllodyniaHEADACHE, Issue 10 2006Koichi Shibata MD Background.,Clinical and neurophysiological manifestations of information processing associated with central sensitization are little known. Allodynic migraine (AM) can be caused by the sensitization of trigeminal neuron, but no study has reported on AM between attacks using blink reflex (BR) and pattern-reversal visual evoked potentials (PVEPs). Objective.,We explored the characteristics of AM between attacks associated with central sensitization using BR and PVEP. Methods.,We recruited 13 patients with interictal AM and 15 patients with nonallodynic migraine (NA), and 30 healthy subjects (HS). BRs were obtained using paired pulses delivered at the interstimulus interval (ISI) of 150, 300, and 500 ms. The ratio of the area in the R2 of the second to R2 of the first shock was measured for each ISI. PVEP were recorded with 2 spatial frequencies (0.5 and 4.0 cpd) and 2 low and high contrasts (29% and 98%, respectively). Amplitudes of P100 were measured. Results.,For BR, there were no significant differences in the ratio of the area of the R2 between the sides of stimulation, and the sides of headache. AM patients had less suppression of the R2 at the ISI of 150 and 300 ms when compared with the NA patients and HS. For PVEP, at 0.5, there were significant differences of amplitude between AM patients and HS, and between NA patients and HS in low and high contrast. At 4.0 cpd, there were significant differences of amplitude between AM patients and HS in low contrast, and between AM patients and HS, and NA patients and HS in high contrast. In AM patients, there was a significant difference of amplitude ratio between 0.5 and 4.0 cpd. Conclusions.,Our BR and PVEP study showed that migraine patients exhibiting allodynia may show central sensitization of brainstem trigeminal neuron and have contrast modulating dysfunction during the cortical visual processing of striate and extrastriate on visual cortex in-between attacks. [source] The surface winds of Sweden during 1999,2000INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2006Christine Achberger Abstract This study aims at increasing our understanding of the regional wind climate in Sweden. Spatial and temporal patterns of the surface winds are presented for the years 1999,2000. Annual mean wind speeds range between 2 and 5 m/s with high values at exposed mountainous sites and on islands off the coast. Combining wind speed and direction into mean wind velocities shows that flow conditions are stronger and more coherent in space in southern Sweden than in central and northern Sweden. The spatial scale, defined as the distance between stations when the correlation for wind speed drops to ,0.37, was determined by pairwise correlations between all possible station pairs. Scales range from 38 to 530 km for wind speed and from 40 to 830 km for wind direction depending on the region. They tend to be smaller in central and northern Sweden, where the more pronounced relief has a larger influence on the local wind conditions. The strength and the timing of the annual and diurnal wind speed cycle have been estimated for each station. Amplitudes of the annual cycle are greater at exposed sites and correlate generally well with annual mean wind speeds. Monthly mean wind speeds peak in winter in southern Sweden, but peak in other seasons in the remaining regions. In winter, weaker pressure gradients over northern Sweden and surface-near temperature inversions contribute to weaker surface winds. Diurnal cycles vary in strength between summer and winter. Compared to the last normal climate period (1961,1990), 1999,2000 is characterized by the increased occurrence of westerly and southerly geostrophic flow. Copyright © 2005 Royal Meteorological Society. [source] Climate of the seasonal cycle in the North Pacific and the North Atlantic oceansINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2001Igor M. Yashayaev Abstract Time series of monthly sea-surface temperature (SST), air temperature (AT) and sea level pressure (SLP) were constructed from merged releases of the Comprehensive Ocean-Atmosphere Data Set (COADS). The time series were decomposed into seasonal and non-seasonal (short and long-term) components. The contribution of the seasonal cycle to the total variance of SST and AT exceeds 80% in the mid and in some high latitude locations and reaches its peak (>95%) in the centres of subtropical gyres. In most cases, a combination of annual and semiannual harmonics accounts for more than 95% of the seasonal variability. Amplitudes of SST and AT annual cycles are highest near the western boundaries of the oceans; annual phases of SST and AT increase toward the eastern tropical oceans, revealing a southeastern propagation of the annual cycle over the Northern Hemisphere oceans. The annual cycle of AT leads that of SST by 1,3 weeks. The largest phase differences are observed in the regions of western boundary currents in the North Pacific and the North Atlantic oceans. This is consistent with spatial patterns of integral air,sea heat fluxes. Annual phases of SST increase along the Gulf Stream and the Kuroshio Current. This points to the importance of signal transport by the major ocean currents. The lowest annual amplitudes of SLP are observed along the equator (0°,10°N) in both oceans. There are three distinct areas of high annual amplitudes of SLP in the North Pacific Ocean: Asian, Aleutian and Californian. Unlike the North Pacific, only one such area exists in the North Atlantic centred to the west of Iceland. A remarkable feature in the climate of the North Pacific is a maximum of semiannual SLP amplitudes, centred near 40°N and 170°W. It is also an absolute maximum in the entire Northern Hemisphere. Analysis of phases of harmonics of SLP seasonal cycle has revealed the trajectories of propagation of the annual and semiannual cycles. Analysis of semiannual to annual amplitudes ratio has revealed the regions of semiannual cycle dominance. Copyright © 2001 Royal Meteorological Society [source] Fourier transformation of arterial Doppler waveforms of the lower extremityJOURNAL OF CLINICAL ULTRASOUND, Issue 6 2004Hong Gi Lee MD Abstract Purpose Although it is well known that the normal, triphasic pulsatile arterial Doppler waveform changes in shape as flow is impaired, interpretation of the waveform has largely been subjective. We aimed to describe the Doppler waveforms of the lower extremity objectively using Fourier transformation. Methods Sixty-eight zero-crossing detector arterial recordings from 25 lower extremities were grouped as follows: group 1, no ischemic symptoms with an ankle-brachial index (ABI) > 0.9 (n = 17, 8 limbs); group 2, no ischemic symptoms with ABI < 0.9 (n = 18, 5 limbs); group 3, symptoms of claudication (n = 19, 7 limbs); group 4, rest pain or tissue loss (n = 14, 5 limbs). The waveforms were Fourier transformed and their amplitudes and phases were compared up to the third harmonic (H3). Results Amplitudes of both the fundamental (H1) and second harmonic (H2) were predominant in group 1. In contrast, amplitudes of the H2 and H3 decreased with altered flow (p < 0.0001 for group 1 versus others). The phases of the H1 and H2 were delayed with altered flow (p < 0.05 for group 1 versus others). Phases of the H1 were different between group 2 and 4 (p < 0.05). The difference of phase between the H3 and H1 was shortened with altered flow (p < 0.05 for group 1 or 2 versus group 4). Multivariate analysis revealed that the relative amplitudes of the H2 and H3, the phases of the H1 and H2, and the relative phase of the H3 were significant discriminators among the groups. Conclusion Abnormal waveforms could be characterized by the predominant amplitude of the H1, phase delay of the H1 and H2, and shortening of the relative phase of the H3. These parameters may be useful in the evaluation of Doppler waveforms in patients with peripheral arterial disease. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:277,285, 2004 [source] CMT1A Associated With The 17p11.2 Duplication: Differential Features And CorrelationJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 1 2001D Pareyson A duplication on chromosome 17p11.2 encompassing the gene coding for the peripheral myelin protein-22 (PMP22) is the most common genetic abnormality underlying Charcot-Marie-Tooth disease (CMT). We report clinical and electrophysiologic features of our series of CMT1A patients harboring the duplication. There were 92 patients from 53 families representing 42% of all CMT index cases (n = 125) and 64% of CMT1 probands (n = 83). In CMT1A patients, mean age at onset was 9.7 ± 11.4 and was significantly lower than in non-duplicated CMT1 cases (12.6 ± 9.7, p < 0.01) and CMT2 cases (21.5 ± 17, p < 0.001). Clinical severity was similar to that of CMT2 patients, but significantly milder than in non-duplicated CMT1 cases. Pes cavus, upper limb involvement, deep tendon reflexes abnormalities, and sensory loss were more frequent compared to CMT2. Electrophysiologic examination revealed motor and sensory conduction velocity (MCV, SCV) slowing below 32 m/s in upper limbs. MCV and SCV were significantly lower than in non-duplicated CMT1 patients. Amplitudes of upper limb compound muscle action potentials (CMAPs) and of upper and lower limb sensory action potentials (SAPs) were significantly lower than in CMT2, paralleling clinical differences. Clinical severity correlated with CMAP amplitudes and with disease duration. On the other hand, MCV slowing was not correlated with either severity or duration of the disease. We found a direct correlation between age at onset and upper limb MCV slowing. Conclusions: CMT1A is an early-onset but slowly progressive disorder, on average milder than other CMT1. Axonal loss rather than demyelination per se underlies disease progression. [source] Click and Low-, Middle-, and High-Frequency Toneburst Stimulation of the Canine CochleaJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 3 2002G. Ter Haar A method was developed to deliver tonebursts ranging in frequency from 1 to 32 kHz for frequency-specific assessment of the canine cochlea. Brainstem auditory-evoked responses (early latency responses, 0,10 ms) to a click (CS) and to 1-, 2-, 4-, 8-, 12-, 16-, 24-, and 32-kHz toneburst stimulations (TS) were compared at 80-dB sound pressure level stimulus (SPL) intensity in 10 adult dogs. All stimulations yielded a 5,7 positive wave pattern, with the exception of the 1-kHz TS, which evoked a frequency-following response (FFR). Thresholds were lowest for the CS and the 12- and 16-kHz TS. All individual peak latencies for TS were significantly (P, .05) longer than for CS. Peak I latencies were significantly (P,.05) shorter for the 12- and 16-kHz TS than for the other TS. Interpeak latencies I-V were significantly (P, .05) longer for the 4- to 32-kHz TS than for CS. Differences in interpeak latencies I,III were not significant. Amplitudes of waves I and V were significantly (P, .05) lower for TS than for CS, except for higher wave V amplitude (P, .05) at 2- and 32-kHz TS. Peak I-V amplitude ratios were significantly (P, .05) higher for the 2-, 4-, 16-, 24-, and 32-kHz TS and lower for the 8- and 12-kHz TS, compared to CS. We conclude that reproducible information on frequency specificity of the canine cochlea can be obtained by TS. This report provides a normative database for parameters needed to evaluate frequency-specific hearing loss in dogs. [source] Sensory potentials evoked by tactile stimulation of different indentation velocities at the finger and palmMUSCLE AND NERVE, Issue 9 2001Masayuki Baba MD Abstract Previous studies suggest that the rate of indentation of a tactile probe determines which skin mechanoreceptors are activated. To further investigate this possibility, indentations of 300 ,m at velocities of 100 (T100) and 400 ,m/ms (T400) were applied to the tip (FT) and the proximal phalanx of digit III (PP) and the thenar eminence (Pm) of ten healthy volunteers, and compared with responses after electrical stimulation at the FT. Compound sensory action potentials (CSAPs) were recorded from the median nerve through needle electrodes at the wrist and elbow. The maximal sensory conduction velocities (SNCVs) between wrist and elbow were similar with electrical and T400 stimulation, but on average were 15% lower with T100 stimulation (P < 0.001). With both indentation velocities, SNCVs were similar regardless of stimulation sites. Amplitudes of tactile CSAPs with FT stimulation were 1,2 ,V at T400 and 0.3,0.4 ,V at T100. The CSAP areas evoked by T100 stimulation showed a reduction from fingertip to proximal finger to palm (P < 0.05,0.005), whereas those obtained with T400 stimulation showed a reduction only at the palm (P < 0.05). The results support previous studies indicating that fast indentation at 400 ,m/ms activated deeply placed Pacinian corpuscles as well as superficially situated Meissner corpuscles, whereas slower indentation at 100 ,m/ms activated primarily Meissner corpuscles. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1213,1218, 2001 [source] Effects of Natriuretic Peptides on Intracavernous Pressure and Blood Pressure in Conscious RatsTHE JOURNAL OF SEXUAL MEDICINE, Issue 10 2008Naoki Aizawa PhD ABSTRACT Introduction., Natriuretic peptides activate particulate guanylyl cyclases and have been shown to induce penile erection in rats, rabbits, and humans. Aim., We investigated the effects of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) on intracavernous pressure (ICP) and systemic blood pressure (BP) in conscious, free-moving rats. Methods., ICP and BP were measured in male Sprague,Dawley rats after catheters were inserted into the crus corpus cavernosum and carotid artery, respectively. Natriuretic peptides were given by intravenous bolus (3, 10, and 30 nmol/kg) or continuous (0.1 and 1 nmol/kg/minute) administration. Main Outcome Measures., The number of animals with increases in ICP were determined. Amplitudes and durations of ICP responses and changes in BP were also evaluated. Results., More animals had multiple transient increases of ICP in response to ANP and BNP than to CNP. The increases in ICP were transient and appeared to be an "all or none" response. ANP and BNP decreased BP more than CNP, especially with bolus administration. Conclusions., These findings show that in rats, erectile responses can be initiated by ANP, BNP, and less effectively, by CNP. ANP and BNP have a high affinity for the natriuretic peptide receptor-A, suggesting that this receptor is involved in the responses. Aizawa N, Ishizuka O, Ogawa T, Mizusawa H, Igawa Y, Nishizawa O, and Andersson K-E. Effects of natriuretic peptides on intracavernous pressure and blood pressure in conscious rats. J Sex Med 2008;5:2312,2317. [source] Changes of Extremity and Laryngeal Muscle Electromyographic Amplitudes After Intravenous Administration of Vecuronium,THE LARYNGOSCOPE, Issue 12 2008Yongbing Shi MD Abstract Objectives: To compare electromyographic (EMG) amplitude changes in extremity and laryngeal muscles after vecuronium administration and study the effects of topical lidocaine on laryngeal EMG in a swine model. Study Design: Prospective animal study. Methods: Electrically evoked EMG activities were recorded from the vocalis muscles (directly and via an EMG endotracheal tube) and from the flexor digitorum muscles before and after intravenous vecuronium administration. EMG amplitudes were followed for 30 minutes after vecuronium injection together with monitoring of limb twitches to train-of-four stimulation. The testing was repeated after a 30-minute wash-out period and with topical lidocaine. Results: EMG amplitude recovery occurred sooner and more quickly in flexor digitorum muscle than in vocalis muscles. Reappearance of four twitches corresponded to EMG amplitude recovery to about 80% of the baseline in flexor digitorum muscles and to about half-baseline size in vocalis muscles. EMG amplitudes were generally lower at the start of the second round testing than the first round, with somewhat slower recovery in vocalis muscles. Conclusions: In contrast to reports by others in human studies, extremity muscles seem to be more resistant to vecuronium at 0.1 mg/kg than laryngeal muscles in the swine. Reappearance of four twitches corresponds to 50% of laryngeal EMG recovery and indicates adequate condition for monitoring electrically evoked laryngeal EMG activities. This study is inconclusive regarding the effects of topically applied lidocaine on laryngeal EMG amplitudes. Translation of these data to humans should be done with caution. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||