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Sample records for t-wave alternans twa

  1. Clinical utility of T-wave alternans

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    Armoundas, A. A.; Cohen, R. J.

    1997-01-01

    Electrical alternans represents a variation in the morphology of electrocardiographic complexes on an every-other-beat basis in an ABABAB... pattern. Apparent electrical alternans associated with pericardial effusion results from rotation of the heart in the pericardial sac, and not true alternation in electrical conduction patterns. In contrast, true electrical alternans results from an alternation in electrical conduction patterns in the heart itself. Repolarization alternans is true electrical alternans associated with the ST segment and T wave of the electrocardiogram (ECG). Here we will focus on T-wave alternans (TWA) and its association with susceptibility to ventricular tachyarrhythmias. Electrical alternans was reported in the literature as early as 1909. Historically, electrical alternans has been regarded as a fairly rare electrocardiographic abnormality. Case reports of electrical alternans have been associated with a variety of disease states, including acute ischemia, Prinzmetal's angina, a variety of electrolyte abnormalities, and the long QT syndrome. Interestingly, patients born with the prolonged QT syndrome have a very high incidence of sudden cardiac death at an early age. Schwartz and Malliani showed that patients with the prolonged QT syndrome who do not demonstrate alternans at rest, may evidence alternans during stress such as emotional excitement. Thus, over the years electrical alternans has been associated anecdotally with conditions associated with an increased risk of ventricular arrhythmias. In 1948, Kalter reviewed the world literature on electrical alternans and found a total of 41 reported cases. In addition, he reviewed clinical ectrocardiograms from 6059 patients and found five new cases (incidence of less than 1 in 1000 patients). Interestingly, he found a very high mortality, 62%, associated with this condition. Despite the clinical associations reported in the literature, the consensus view of electrical alternans until recent

  2. Differential diagnosis of cardiovascular diseases and T-wave alternans

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    Ramasamy, Mouli; Varadan, Vijay K.

    2016-04-01

    T wave alternans (TWA) is the variation of the T-wave in electrocardiogram that is observed between periodic beats. TWA is one of the important precursors used to diagnose sudden cardiac death (SCD). Several clinical studies have tried to determine the significance of using TWA analysis to detect abnormalities that may lead to Ventricular Arrhythmias, as well as establish metrics to perform risk stratification for cardiovascular patients with prior cardiac episodes. The statistical significance of TWA in predicting ventricular arrhythmias has been established in patients across several diagnoses. Studies have also shown the significance of the predictive value of TWA analysis in post myocardial infarction patients, risk of SCD, congestive heart failure, ischemic cardiomyopathy, and Chagas disease.

  3. Analysis of T-wave alternans using the dominant T-wave paradigm.

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    Mainardi, Luca; Sassi, Roberto

    2011-01-01

    The dominant T wave (DTW) reflects the derivative of the repolarization phase of the transmembrane potential of myocytes. T-wave alternans (TWA) is defined as an alteration of this repolarization that repeats every other beat. We investigate if the DTW can offer new insight on TWA. We first proved that the DTW estimate obtained through singular value decomposition is optimal, because it minimizes the norm of the residuals. Then we suggested an optimal estimate of the vector of lead factors, in the case in which the DTW is given. Finally, we derived a mathematical relationship between observable TWA on electrocardiogram and DTW morphology. The relationship depends on the slope of the repolarization phase of the myocytes' transmembrane potentials and on the dispersion of the repolarization times. Based on this finding, a new index meant to quantify TWA was defined and termed amplitude of dominant T-wave alternans (ADTWA). A preliminary validation of the index was performed using the synthetic records contained in the Computers in Cardiology 2008 data set. They were obtained from 5 electrocardiogram models to which TWA was added at different extents. We found a linear relationship between the TWA amplitude and the ADTWA metric (R(2) = 0.9898 ± 0.100 across all models). Moreover, the root mean square error between actual and estimated TWA amplitudes was 10.9 μV (ADTWA) vs 12.9 μV obtained with the classical spectral method.

  4. T wave alternans during exercise and atrial pacing in humans

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    Hohnloser, S. H.; Klingenheben, T.; Zabel, M.; Li, Y. G.; Albrecht, P.; Cohen, R. J.

    1997-01-01

    INTRODUCTION: Evidence is accumulating that microvolt T wave alternans (TWA) is a marker of increased risk for ventricular tachyarrhythmias. Initially, atrial pacing was used to elevate heart rate and elicit TWA. More recently, a noninvasive approach has been developed that elevates heart rate using exercise. METHODS AND RESULTS: In 30 consecutive patients with a history of ventricular tachyarrhythmias, the spectral method was used to detect TWA during both atrial pacing and submaximal exercise testing. The concordance rate for the presence or absence of TWA using the two measurement methods was 84%. There was a patient-specific heart rate threshold for the detection of TWA that averaged 100 +/- 14 beats/min during exercise compared with 97 +/- 9 beats/min during right atrial pacing (P = NS). Beyond this threshold, there was a significant and comparable increase in level of TWA with decreasing pacing cycle length and increasing exercise heart rates. CONCLUSIONS: The present study is the first to demonstrate that microvolt TWA can be assessed reliably and noninvasively during exercise stress. There is a patient-specific heart rate threshold beyond which TWA continues to increase with increasing heart rates. Heart rate thresholds for the onset of TWA measured during atrial pacing and exercise stress were comparable, indicating that heart rate alone appears to be the main factor of determining the onset of TWA during submaximal exercise stress.

  5. Is T-Wave Alternans Testing Feasible in Candidates for Prophylactic Implantable Defibrillators?

    NARCIS (Netherlands)

    Kraaier, K.; McCracken, T.; Palen, van der J.; Wilde, A.A.M.; Scholten, M.F.

    2011-01-01

    Aims: Previous studies have demonstrated that microvolt T-wave alternans (TWA) screening in patients with ischaemic and dilated cardiomyopathy is effective in identifying patients at high or low risk of sudden cardiac death. It remains unclear which percentage of potential recipients of an implantab

  6. T-wave alternans: lessons learned from a biophysical ECG model.

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    Sassi, Roberto; Mainardi, Luca T

    2012-01-01

    T-wave alternans (TWA) is an alteration of the ECG T-wave which repeats every other beat. An alternating pattern has been also observed at myocytes level, involving both action potential duration and morphology (mainly in phases 2 and 3). While this might happen in a specific region (i.e., myocardial ischemia), it can also involve the entire myocardium. It is still unclear how alternations at the myocytes level are reflected on surface ECG modification of T-waves, especially when in vivo human hearts are considered. We have recently proposed a simple stochastic model of ventricular repolarization (IEEE Trans. Biomed. Eng., 2011), which takes into account both repolarization heterogeneity across the myocardium as well as random beat-to-beat variations in cells' activity. In this work, we generalized that model incorporating a term which describes myocytes alternans related to T-wave variability. Starting from the model and using the electrophysiological formulation developed by van Oosterom, we derived an analytical formula relating surface ECG to variations at the myocytes' level. Several theoretical results were then obtained. First, temporal small random variations in repolarization heterogeneity affect the precision of TWA estimates in a significant way. Second, TWA theoretically differs across leads, but multilead configuration can be used to reduce the effect of noise. Finally, the dependency between TWA and T-wave amplitude was analyzed.

  7. T-wave alternans in LQTS: repolarization-rate dynamics from digital 12-lead Holter data.

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    Brockmeier, K; Aslan, I; Hilbel, T; Eberle, T; Ulmer, H E; Lux, R L

    2001-01-01

    T-wave alternans (TWA) is a harbinger of ventricular vulnerability and an important prognostic indicator for torsade de pointes and likely sudden death in patients with LQTS. We analyzed the occurrence of TWA in 18 patients with LQTS (7 males, 11 females, ages ranging from 6 months to 32 years--median 8.4 years). Analysis was performed with software to investigate dynamics of cycle length mediated repolarization changes. Digital Holter ECG analysis revealed macroscopic, true TWA in 3 of 18 patients. TWA showed a variable morphological expression. One patient had continuous changes of T wave polarity, but not on a periodic beat-to-beat basis. Onsets of macroscopic TWA were preceded by long/short cycle length sequences and tachycardic rates above 130 to 140 bpm. Impact of ventricular premature beats on TWA onset was insignificant. Two of the identified patients with TWA had sudden cardiac death during follow-up (one refused PM therapy). At present, TWA cannot be detected automatically from Holter ECGs and therefore may be missed, despite the potential danger for the individuals. The observation that predominantly high beat rates and not beat rate changes, per se, triggered episodes of TWA renders difficult general therapeutic recommendations for the identified patients at risk.

  8. Clinical value of T-wave alternans assessment.

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    Klingenheben, Thomas; Hohnloser, Stefan H

    2002-09-01

    Microvolt-level T-wave alternans (TWA) is a new arrhythmia risk marker to assess subtle changes in repolarization that has been introduced for arrhythmia risk stratification. Recent experimental studies have demonstrated that it reflects a heartrate dependent increased spatial dispersion of repolarization associated with unidirectional conduction block, and reentry that may result in the occurrence of ventricular fibrillation. Clinical studies have convincingly demonstrated that TWA is closely related to arrhythmia induction in the electrophysiology (EP) laboratory as well as to the occurrence of spontaneous ventricular tachyarrhythmias in patients undergoing EP study. Subsequent studies showed that TWA-assessed noninvasively-is predictive of future arrhythmic events in patients with implanted ICDs as well as for ventricular tachyarrhythmias in patients with congestive heart failure without a prior history of arrhythmias. There is still controversy, however, about the predictive value of TWA in patients following acute myocardial infarction (MI). Several studies which differ in patient selection, pharmacologic treatment of the patients, and endpoint definitions, have reported conflicting results. Therefore, studies with a large number of unselected patients after acute MI on optimal treatment according to contemporary therapeutic guidelines as well as of patients with reduced left ventricular ejection fraction following MI are needed to define its role with regard to identifying patients who may benefit from primary preventive ICD therapy. Future research should also focus on evaluation of alternative methods to increase heart rate (i.e., pharmacological stimulation) in an attempt to reduce the proportion of incomplete tests in patients with insufficient increase in heart rate during exercise testing.

  9. T wave alternans for predicting adverse effects of amiodarone in a patient with dilated cardiomyopathy.

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    Matsuyama, T; Tanno, K; Kobayashi, Y; Obara, C; Ryu, S; Adachi, T; Ezumi, H; Asano, T; Miyata, A; Koba, S; Baba, T; Katagiri, T

    2001-05-01

    An implantable cardioverter defibrillator (ICD) was used in a 62-year-old man with dilated cardiomyopathy (DCM) because of hemodynamically intolerable ventricular tachycardia (VT). Amiodarone was administered after a second episode of ICD discharge. Three weeks later, incessant VT appeared, and DC discharge failed to terminate it. Microvolt T wave alternans (TWA), measured by a spectral method, was observed in this patient with and without amiodarone administration. The onset heart rate with TWA was lower and the alternans voltage was higher with amiodarone than without it. The effects of amiodarone appeared to be related to the exacerbation of VT and an increased defibrillation threshold. TWA might be useful in predicting the proarrhythmic effects of amiodarone in similar cases.

  10. Identification of Gender-Related Normality Regions for T-Wave Alternans

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    Burattini, Laura; Zareba, Wojciech; Burattini, Roberto

    2011-01-01

    Background T-wave alternans (TWA), a harbinger of sudden cardiac death, associates to a broad variety of pathologies. In a previous study, we observed the presence of unstable and low-amplitude TWA also in healthy subjects, and considered it as “physiological TWA.” The possible existence of different TWA characteristics between males and female is investigated in the present work. Methods Resting ECG recordings from 142 control healthy subjects, 77 males and 65 females, were submitted to our adaptive match filter (AMF) based method for TWA detection and characterization in terms of duration, amplitude, and their product. The 99.5th percentile of these parameters distributions over the entire control population and over the male and female subgroups, were used to define thresholds which delimit a gender-independent and male- and female-related TWA normality regions, respectively, out of which abnormal TWA cases (TWA+) are expected to fall. Clinical usefulness of these regions was tested using a population of 151 coronary artery disease (CAD) patients, divided into 128 males and 23 females. Results In our control-female population, TWA duration was significantly longer than in control-male population (65 ± 13 beat vs 52 ± 14 beat; P < 10−6). Our gender-related normality regions allowed identification of 36 (23.8%) TWA+ cases among the CAD patients, 17 more than those obtained from a gender-independent region. All these 17 patients were CAD males with over-threshold TWA duration. Conclusions TWA is a gender-related phenomenon. Definition of gender-related TWA normality regions improves identification of patients at increased TWA stability (i.e., prolonged TWA duration) and, thus, at increased risk of arrhythmic events. PMID:20946555

  11. The clinical value of T-wave alternans derived from Holter monitoring.

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    Lewek, Joanna; Ptaszynski, Pawel; Klingenheben, Thomas; Cygankiewicz, Iwona

    2017-04-01

    Microvolt-level T-wave alternans (TWA) assessed by spectral method during an exercise stress test has been widely studied for risk stratification. Several studies have documented the association of a positive TWA with total mortality and arrhythmic events. Nevertheless, the need to achieve an elevated and stabilized heart rate resulting in a considerable proportion of indeterminate test results constitutes one of the main limitations of this method. It is well recognized that arrhythmic events may be triggered not only by physical but also by mental stress and are not necessarily associated with exercise. Detection of TWA in ambulatory electrocardiogram recordings during daily activities might be a valuable option in risk stratification. This review describes the modified moving average (MMA) technique for detection of TWA and summarizes the results of clinical studies on the prognostic value of MMA-TWA. So far, MMA-TWA has been studied in over 5000 patients including those evaluated during exercise as well as during daily activities with ambulatory ECG recordings. The results of these studies indicate that increased MMA-TWA is associated with higher risk of cardiac mortality and arrhythmic events. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

  12. Cardiac Pacing Suppressed Macroscopic T Wave Alternans in a Patient with Heart Failure Caused by Non-ischemic Cardiomyopathy

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    Kotaro Miyaji, MD

    2008-01-01

    Full Text Available A 67-year-old male with dilated cardiomyopathy and chronic renal failure who received chronic hemodialysis for 9 years admitted with pulmonary edema. Three days after admission, electrocardiogram showed transient prolongation of QT interval which was followed by macroscopic T wave alternans (TWA and ventricular fibrillation (VF. Temporary pacing from right ventricular apex suppressed TWA and VF effectively. Combined cardiac resynchronization therapy and implantable cardioverter defibrillator device was implanted for the secondary prevention of VF. Both prolongation of QT interval and TWA disappeared for 10 days after therapy and no arrhythmic event occurred since then.

  13. Nonparametric signal processing validation in T-wave alternans detection and estimation.

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    Goya-Esteban, R; Barquero-Pérez, O; Blanco-Velasco, M; Caamaño-Fernández, A J; García-Alberola, A; Rojo-Álvarez, J L

    2014-04-01

    Although a number of methods have been proposed for T-Wave Alternans (TWA) detection and estimation, their performance strongly depends on their signal processing stages and on their free parameters tuning. The dependence of the system quality with respect to the main signal processing stages in TWA algorithms has not yet been studied. This study seeks to optimize the final performance of the system by successive comparisons of pairs of TWA analysis systems, with one single processing difference between them. For this purpose, a set of decision statistics are proposed to evaluate the performance, and a nonparametric hypothesis test (from Bootstrap resampling) is used to make systematic decisions. Both the temporal method (TM) and the spectral method (SM) are analyzed in this study. The experiments were carried out in two datasets: first, in semisynthetic signals with artificial alternant waves and added noise; second, in two public Holter databases with different documented risk of sudden cardiac death. For semisynthetic signals (SNR = 15 dB), after the optimization procedure, a reduction of 34.0% (TM) and 5.2% (SM) of the power of TWA amplitude estimation errors was achieved, and the power of error probability was reduced by 74.7% (SM). For Holter databases, appropriate tuning of several processing blocks, led to a larger intergroup separation between the two populations for TWA amplitude estimation. Our proposal can be used as a systematic procedure for signal processing block optimization in TWA algorithmic implementations.

  14. Spinal cord stimulation affects T-wave alternans in patients with ischaemic cardiomyopathy: a pilot study.

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    Ferrero, Paolo; Castagno, Davide; Massa, Riccardo; De Luca, Anna; Castellano, Maddalena; Chirio, Claudio; Grimaldi, Roberto

    2008-04-01

    An antiarrhythmic effect of spinal cord stimulation (SCS) has been recognized in an animal model. The actual mechanism is still mainly unknown. An adrenergic output reduction has been advocated as the main mechanism, although a modulation effect on the arrhythmic substrate has not yet been investigated. We studied T-wave alternans (TWA) modifications to test the hypothesis that SCS affects the arrhythmic substrate. We performed TWA assessment in three high-risk patients who previously had undergone implantation of both implantable cardioverter defibrillator and SCS to treat refractory angina. The test was performed after switching off the SCS and after 2 and 24 h stimulation at the default amplitude. The protocol was executed 2 months apart in order to assess the reproducibility of the results, collecting a total of 18 TWA reports. In all the three patients, we observed a significant reduction of TWA amplitude after 2 h stimulation. All the tests were classified as negative after 24 h stimulation with the nominal parameters. Spinal cord stimulation results in a decrease in the TWA magnitude, and thus it seems to positively affect the arrhythmic substrate in a time-dependent manner.

  15. Ambulatory ECG-based T-wave alternans monitoring for risk assessment and guiding medical therapy: mechanisms and clinical applications.

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    Verrier, Richard L; Ikeda, Takanori

    2013-01-01

    Identification of individuals at risk for sudden cardiac death (SCD), the main cause of adult mortality in developed countries, remains a major challenge. The main contemporary noninvasive marker, left ventricular ejection fraction (LVEF), has not proved adequately reliable, as the majority of individuals who die suddenly have relatively preserved cardiac mechanical function. Monitoring of T-wave alternans (TWA), a beat-to-beat fluctuation in ST-segment or T-wave morphology, on ambulatory electrocardiogram (AECG) is an attractive approach on both scientific and clinical grounds. Specifically, TWA's capacity to assess risk for malignant arrhythmias has been shown to rest on sound electrophysiologic principles and AECG-based TWA monitoring can be performed in the flow of routine clinical evaluation. This review addresses: (1) electrophysiologic and ionic mechanisms underlying TWA's predictivity, (2) principles and practical aspects of AECG-based TWA monitoring, (3) clinical evidence supporting this approach to SCD risk stratification, and (4) current and potential applications in guiding medical therapy.

  16. Detection of T-Wave Alternans in Body Surface ECG%体表心电图中T波交替现象的检测

    Institute of Scientific and Technical Information of China (English)

    许菲; 滕炯华; 张泾周

    2011-01-01

    Detection of T-wave alternans( TWA) is of great significance for prediction of malignant ventricular arrhythmias. Firstly, empirical mode decomposition ( EMD) -based denoising method was used to reduce noises and interference from body surface ECG. Then recognition of ECG characteristic points was achieved using wavelet transform ,and finally a method of extracting T-wave windows around the T-wave peaks was advanced. By analyzing the power spectrums of 128 consequent T-wave windows, it is indicated that the proposed method achieved the detection of microvolt TWA ,and it can be applied to clinical diagnosis of TWA.%T波交替(T-wave alternans,TWA)的检测对于预测室性心律失常有重要意义.本文首先利用基于经验模态分解(empirical mode decomposition,EMD)的降噪方法进行心电信号的降噪,然后采用小波变换进行心电信号特征点的识别,最后给出以T波峰值点为参考点提取T波窗口的方法.通过对连续的128个T波窗口进行功率谱分析证实,上述方法实现了微伏级TWA的检测,可用于TWA的临床诊断.

  17. The Power of Exercise-Induced T-wave Alternans to Predict Ventricular Arrhythmias in Patients with Implanted Cardiac Defibrillator

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    Laura Burattini

    2013-01-01

    Full Text Available The power of exercise-induced T-wave alternans (TWA to predict the occurrence of ventricular arrhythmias was evaluated in 67 patients with an implanted cardiac defibrillator (ICD. During the 4-year follow-up, electrocardiographic (ECG tracings were recorded in a bicycle ergometer test with increasing workload ranging from zero (NoWL to the patient's maximal capacity (MaxWL. After the follow-up, patients were classified as either ICD_Cases (n = 29, if developed ventricular tachycardia/fibrillation, or ICD_Controls (n = 38. TWA was quantified using our heart-rate adaptive match filter. Compared to NoWL, MaxWL was characterized by faster heart rates and higher TWA in both ICD_Cases (12-18 μ V vs. 20-39 μ V; P < 0.05 and ICD_Controls (9-15 μ V vs. 20-32 μ V; P < 0.05. Still, TWA was able to discriminate the two ICD groups during NoWL (sensitivity = 59-83%, specificity = 53-84% but not MaxWL (sensitivity = 55-69%, specificity = 39-74%. Thus, this retrospective observational case-control study suggests that TWA's predictive power for the occurrence of ventricular arrhythmias could increase at low heart rates.

  18. Microvolt T-wave alternans in patients undergoing elective coronary artery bypass grafting: a pilot study.

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    Khoueiry, G; Abdallah, M; Shariff, M; Kowalski, M; Lafferty, J

    2015-01-01

    We designed a prospective observational study targeting a selective population of patients undergoing elective coronary artery bypass grafting with normal systolic function. In this study we looked at the prevalence of pre-operative microvolt T-wave alternans and if it predicts atrial fibrillation after surgery. The inclusion criteria included all patients referred to the cardiothoracic outpatient clinic for elective bypass, who can perform aerobic exercise, with a recent exercise stress test exercising at least to 85% of the maximal predicted heart rate (220 - age) and with non-limiting chest pain at maximal exercise. Twenty patients met the inclusion/exclusion criteria between May 2008 and February 2010. The hospital course of those patients was followed, and in-hospital events were recorded. Nine out twenty (45%) of patients had a non-negative microvolt T-wave alternans tracing. Six patients (30%) developed new onset atrial fibrillation post surgery. Patients with non-negative microvolt level T-wave alternans are more likely to develop atrial fibrillation post coronary artery bypass grafting then patients with negative microvolt level T-wave alternans (p=0.05). This pilot study provides the first clinical evidence that patients with ischemic heart disease and normal systolic function have a high prevalence of abnormal microvolt T-wave alternans and might be at higher risk of sudden cardiac death. In addition our results show that microvolt level T-wave alternans predicts post coronary artery bypass grafting new onset atrial fibrillation.

  19. Scar tissue and microvolt T-wave alternans.

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    Kraaier, Karin; Olimulder, Marlon A G M; Galjee, Michel A; van Dessel, Pascal F H M; van der Palen, Job; Wilde, Arthur A M; Scholten, Marcoen F

    2014-04-01

    Microvolt T-wave alternans (MTWA) is an electrocardiographic marker for predicting sudden cardiac death. In this study, we aimed to study the relation between MTWA and scar assessed with cardiac magnetic resonance imaging (CMR) in patients with ischemic cardiomyopathy (ICM) or dilated cardiomyopathy (DCM). Sixty-eight patients with positive or negative MTWA and analysable CMR examination were included. Using CMR and the delayed enhancement technique, left ventricular ejection fraction (LVEF), volumes, wall motion and scar characteristics were assessed. Overall, positive MTWA (n = 40) was related to male gender (p = 0.04), lower LVEF (p = 0.04) and increased left ventricular end-diastolic volume (LVEDV) (p Scar characteristics (presence, transmurality, and scar score) were not related to MTWA (all p > 0.5). In the patients with ICM (n = 40) scar was detected in 38. Positive MTWA (n = 18) was related to higher LVEDV (p = 0.05). In patients with DCM (n = 28), scar was detected in 11. Trends were found between positive MTWA (n = 15) and male gender (p = 0.10), lower LVEF (p = 0.10), and higher LVEDV (p = 0.09). In both subgroups, the presence, transmurality or extent of scar was not related to MTWA (all p > 0.45). In this small study, neither in patients with ICM or DCM a relation was found between the occurrence of MTWA and the presence, transmurality or extent of myocardial scar. Overall there was a significant relation between heart failure remodeling parameters and positive MTWA.

  20. Prominent J-wave and T-wave alternans associated with mechanical alternans in a patient with takotsubo cardiomyopathy

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    Rintaro Hojo, MD

    2015-02-01

    Full Text Available A 74-year-old woman with takotsubo cardiomyopathy developed polymorphic ventricular tachycardia during the acute phase. She exhibited prominent J-wave and T-wave alternans preceding ventricular tachycardia. These abnormalities disappeared after recovery from myocardial stunning.

  1. T-wave alternans: desempenho clínico, limitações, metodologias de análise

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    Euler V. Garcia

    2011-03-01

    Full Text Available Reconhecer com precisão indivíduos com maior risco imediato de morte súbita cardíaca (MSC ainda é uma questão em aberto. A natureza fortuita dos eventos cardiovasculares agudos não parece se adequar ao conhecido modelo de indução de taquicardia/fibrilação ventricular por um gatilho em sincronia a um substrato arritmogênico estático. Quanto ao mecanismo da MSC, uma instabilidade elétrica dinâmica explicaria melhor a raridade da associação simultânea de um gatilho certo a um substrato cardíaco apropriado. Diversos estudos tentaram medir essa instabilidade elétrica cardíaca (ou um equivalente válido em uma sequência de batimentos cardíacos no ECG. Dentre os mecanismos possíveis podemos citar o prolongamento do QT, dispersão do QT, potenciais tardios, alternância de onda T ou T-wave alternans (TWA, e turbulência da frequência cardíaca. Este artigo se atém em particular ao papel da TWA no panorama atual da estratificação de risco cardíaco. Os achados sobre TWA ainda são heterogêneos, variando de um desempenho prognóstico muito bom até um quase nulo, dependendo da população clínica observada e protocolo clínico usado. Para preencher as atuais lacunas no conhecimento sobre TWA, profissionais médicos e pesquisadores devem explorar melhor as características técnicas das diversas tecnologias disponíveis para a avaliação de TWA e atentar ao fato de que os valores de TWA respondem a diversos outros fatores, além de medicamentos. Informações sobre mecanismos celulares e subcelulares da TWA estão fora do escopo deste artigo, mas são referenciados alguns dos principais trabalhos sobre este tópico, com o intuito de auxiliar no entendimento dos conceitos e fatos cobertos neste artigo.

  2. T-wave alternans: desempenho clínico, limitações, metodologias de análise T-wave alternans: desempeño clínico, limitaciones, metodologías de análisis T-wave alternans: clinical performance, limitations and analysis methodologies

    Directory of Open Access Journals (Sweden)

    Euler V. Garcia

    2011-03-01

    Full Text Available Reconhecer com precisão indivíduos com maior risco imediato de morte súbita cardíaca (MSC ainda é uma questão em aberto. A natureza fortuita dos eventos cardiovasculares agudos não parece se adequar ao conhecido modelo de indução de taquicardia/fibrilação ventricular por um gatilho em sincronia a um substrato arritmogênico estático. Quanto ao mecanismo da MSC, uma instabilidade elétrica dinâmica explicaria melhor a raridade da associação simultânea de um gatilho certo a um substrato cardíaco apropriado. Diversos estudos tentaram medir essa instabilidade elétrica cardíaca (ou um equivalente válido em uma sequência de batimentos cardíacos no ECG. Dentre os mecanismos possíveis podemos citar o prolongamento do QT, dispersão do QT, potenciais tardios, alternância de onda T ou T-wave alternans (TWA, e turbulência da frequência cardíaca. Este artigo se atém em particular ao papel da TWA no panorama atual da estratificação de risco cardíaco. Os achados sobre TWA ainda são heterogêneos, variando de um desempenho prognóstico muito bom até um quase nulo, dependendo da população clínica observada e protocolo clínico usado. Para preencher as atuais lacunas no conhecimento sobre TWA, profissionais médicos e pesquisadores devem explorar melhor as características técnicas das diversas tecnologias disponíveis para a avaliação de TWA e atentar ao fato de que os valores de TWA respondem a diversos outros fatores, além de medicamentos. Informações sobre mecanismos celulares e subcelulares da TWA estão fora do escopo deste artigo, mas são referenciados alguns dos principais trabalhos sobre este tópico, com o intuito de auxiliar no entendimento dos conceitos e fatos cobertos neste artigo.Reconocer con precisión individuos con mayor riesgo inmediato de muerte súbita cardíaca (MSC aun es una cuestión en abierto. La naturaleza fortuita de los eventos cardiovasculares agudos no parece adecuarse al conocido modelo

  3. Novel algorithm for identifying T-wave current density alternans using synthesized 187-channel vector-projected body surface mapping.

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    Nakai, Kenji; Takahashi, Shin; Suzuki, Atsushi; Hagiwara, Nobuhisa; Futagawa, Keisuke; Shoda, Morio; Shiga, Tsuyoshi; Takahashi, Ken; Okabayashi, Hitoshi; Itoh, Manabu; Kasanuki, Hiroshi

    2011-03-01

    The noninvasive evaluation of ventricular T-wave alternans (TWA) in patients with lethal ventricular arrhythmias is an important issue. In this study, we propose a novel algorithm to identify T-wave current density alternans (TWCA) using synthesized 187-channel vector-projected body surface mapping (187-ch SAVP-ECG). We recorded 10 min of 187-ch SAVP-ECG using a Mason-Likar lead system in the supine position. A recovery time (RT) dispersion map was obtained by averaging the 187-ch SAVP-ECG. The TWCA value was determined from the relative changes in the averaged current density in the T-wave zone (Tpeak ± 50 ms) for two T-wave types. We registered 20 ECG recordings from normal controls and 11 ECG recordings from nine subjects with long QT syndrome (LQT). We divided LQT syndrome subjects into two groups: group 1 provided 9 ECG recordings without visually apparent TWAs, and group 2 provided 2 ECG recordings with visually apparent TWAs. The QTc interval values in the LQT groups were higher than those in the control (515 ± 60 ms in LQT G-1, 600 ± 27 ms in LQT G-2 vs. 415 ± 19 ms in control, P < 0.001). The RTendc dispersion values among the LQT subjects were higher than those of the control subjects (48 ± 19 ms in LQT G-1, 65 ± 30 ms in LQT G-2 vs. 24 ± 10 ms in control, P < 0.01). The mean TWCA value was significantly higher in the LQT G-2 group with visually apparent TWCAs (0.5 ± 0.2% in control, 2.1 ± 1.2% in LQT G-1, and 32.3 ± 6.9% in LQT G-2). Interestingly, the two-dimensional distribution of TWCA in LQT was inhomogeneous and correlated with the distribution of increased RT dispersion. We conclude that a novel algorithm using 187-ch SAVP-ECG might provide new insights into body surface TWCA.

  4. Ambulatory ECG-based T-wave alternans and heart rate turbulence can predict cardiac mortality in patients with myocardial infarction with or without diabetes mellitus

    Directory of Open Access Journals (Sweden)

    Li-na Ren

    2012-09-01

    Full Text Available Abstract Background Many patients who survive a myocardial infarction (MI remain at risk of sudden cardiac death despite revascularization and optimal medical treatment. We used the modified moving average (MMA method to assess the utility of T-wave alternans (TWA and heart rate turbulence (HRT as risk markers in MI patients with or without diabetes mellitus (DM. Methods We prospectively enrolled 248 consecutive patients: 96 with MI (post-MI patients; 77 MI with DM (post-MI + DM patients; 75 controls without cardiovascular disease (group control. Both TWA and HRT were measured on ambulatory electrocardiograms (AECGs. HRT was assessed by two parameters ─ turbulence onset (TO and turbulence slope (TS. HRT was considered positive when both TO ≥0% and TS ≤2.5 ms/R-R interval were met. The endpoint was cardiac mortality. Results TWA values differed significantly between MI and controls. Post-MI + DM patients had higher TWA values than post-MI patients (58 ± 21 μV VS 52 ± 18 μV, P = 0.029. Impaired HRT--increased TO and decreased TS were observed in MI patients with or without DM. During follow-up of 578 ± 146 days, cardiac death occurred in ten patients and three of them suffered sudden cardiac death (SCD. Multivariate analysis determined that a HRT-positive outcome [HR (95% CI: 5.01, 1.33–18.85; P = 0.017], as well as the combination of abnormal TWA (≥47 μV and positive HRT had significant association with the endpoint [HR (95% CI: 9.08, 2.21–37.2; P = 0.002]. Conclusion This study indicates that AECGs-based TWA and HRT can predict cardiac mortality in MI patients with or without DM. Combined analysis TWA and HRT may be a convenient and useful method of identifying patients at high risk for cardiovascular death.

  5. T-Wave Alternans, Heart Rate Turbulence, and Ventricular Ectopy in Standard versus Daily Hemodialysis: Results from the FHN Daily Trial.

    Science.gov (United States)

    Kaplan, Rachel M; Herzog, Charles A; Larive, Brett; Subacius, Haris; Nearing, Bruce D; Verrier, Richard; Passman, Rod S

    2016-11-01

    Hemodialysis (HD) patients are at high risk of sudden cardiac death (SCD). HD 6-times/week (6x/wk) may reduce SCD risk compared to usual 3-times/week HD (3x/wk) by mechanisms unknown. T-wave alternans (TWA), heart rate turbulence (HRT), and ventricular ectopy (VE) are elevated in HD patients, but their response to 6x/wk HD has not been assessed. Baseline and 1-year Holter recordings were analyzed from enrollees in the Frequent Hemodialysis Network Daily Trial, a randomized trial comparing 3x/wk to 6x/wk in 245 chronic HD patients. TWA, HRT, and VE were assessed using MARS software. Sixty-eight patients (34 with 6x/wk) had complete baseline and 1-year Holter recordings. Mean age was 50 ± 13 years and 38% were female. Maximum TWA in the 3x/wk and 6x/wk groups were 52.4 μV at baseline and 51.2 μV at 1-year versus 54.0 and 49.9 μV, respectively (P = 0.28). The proportion of abnormal HRT (scores of 1 or 2) in the 3x/wk group decreased from 65% to 56% at 1-year versus 53% to 53% in the 6x/wk group (P = 0.58). Mean %VE changed from 1.6% to 2.9% in the 3x/wk group from baseline to 1-year and from 2.1% to 3.7% in the 6x/wk group (P = 0.85). There were no significant differences in HRT or VE at 1-year in chronic HD patients randomized to 6x/wk versus 3x/wk and a trend in TWA reduction. Additional studies are needed to evaluate the impact and mechanisms of SCD in HD. © 2016 Wiley Periodicals, Inc.

  6. Aerobic exercise affects T-wave alternans and heart rate variability in postmenopausal women.

    Science.gov (United States)

    Shen, T-W; Wen, H-J

    2013-12-01

    The purpose of this study was to investigate the effects of a 10-week high-intermediate exercise intervention on heart rate variability/microscopic T-wave alternans (HRV/MTWA) in healthy postmenopausal women (PMW). 62 healthy PMW were recruited and randomly divided into an exercise group (EG, n=32) or a control group (CG, n=30). The EG attended a progressively high-intermediate intensity (75-85% heart rate reserve, HRR) group-based step aerobic exercise program for 10 weeks, whereas the CG did not receive any intervention. HRV/MTWA, blood chemistry and physical function-related indices were measured before and within 24 h following the 10-week exercise program. Following a 10-week exercise intervention, the EG had significant mean decreases in SDNN (22.4%), CV (21.4%), NN50 (72.6%), LF (ms2; 55.8%), HF (ms2; 39.9%), LF (n.u.; 11.2%), and LF/HF (34.5%). The EG showed a significant increase in HF (n.u.; 40.0%) and CAV (44.4%), whereas there was no significant finding in the CG. The coupling effect of MTWA and HRV after intervention suggests that exercise intervention potentially affects regulation changes of the autonomic nervous system and cardiovascular condition synchronically in PMW. The rebound effect of biomarkers has proven to be a considerable factor on HRV/MTWA measurements. © Georg Thieme Verlag KG Stuttgart · New York.

  7. T Wave Alternans in high arrhythmic risk patients: Analysis in time and frequency domains: A pilot study

    Directory of Open Access Journals (Sweden)

    Hunt Anthony C

    2002-03-01

    Full Text Available Abstract Background T wave alternans (TA is a repolarisation phenomenon manifesting as a microvolt beat to beat change in the amplitude of the T wave and ST segment. TA has been shown to be a predictor of arrhythmic risk in unselected myocardial infarction populations. TA has not been used to differentiate risk within the ischaemic cardiomyopathy population. Methods The subjects investigated comprised, Group 1: 7 stable patients with remote (>20 months extensive myocardial scarring and no arrhythmic events (NYHA 3 and 4. Group2: 9 post infarction patients with malignant arrhythmia and implantable defibrillator. During breath holding, 20 continuous QRST complexes from each patients X, Y and Z leads were digitally recorded. Time domain, resultant absolute difference vectors (ATA, were calculated for alternate resultant T wave sequences. Group differences between the magnitude and temporal distribution of mean ATAs and their spectral and cross-spectral analysis were compared. Results Group 1 v Group 2 mean ATAs were 10.7 (7.17 v 11.7 (8.48 respectively, not significant. Each group had a homogenous temporal distribution of ATAs. Both group's largest mean ATA frequency components were between 0 to 25 Hz, the largest ATA component being at the DC frequency. Cross spectral analysis showed no significant differences in group ATA frequency content. Conclusion The frequency content and microvolt magnitude of T wave alternans was not significantly different in these two groups. The specificity of T wave alternans for differentiating arrhythmic risk in post infarction scarring and heart failure needs investigation.

  8. Ventricular arrhythmias in competitive athletes: risk stratification with T-wave alternans

    Directory of Open Access Journals (Sweden)

    Rita Pizzi

    2009-08-01

    Full Text Available Introduction: Aim of our study is to evaluate the role of TWA to stratify the risk of sudden cardiac death in athletes (Ath with complex ventricular arrhythmias (VA, and to document a possible correlation between TWA and electrophysiological testing (EES results. Methods: We studied 43 Ath with VA (31 M, mean age 34 ± 12 years. In all cases a cardiological evaluation was performed, including TWA and EES. The patients were evaluated during a followup of 25 ± 22 months. The end-point was the occurrence of sudden death or malignant ventricular tachyarrhythmias (VT. Results: TWA was negative in 28 Ath (65%, positive in 8 (19% and indeterminate in 7 (16%. All subjects with negative TWA did not show induction of VT at EES, with significant correlation between negative TWA and negative EES (p<0.001. All Ath with positive TWA also had VT induced by a EES, but without significant correlation between positive TWA and positive EES. In 2 Ath with undetermined TWA (29% VT were induced at EES. Our data did not show significant correlation between indeterminate TWA and positive or negative EES. However, logistic regression analysis showed significant correlation between abnormal TWA test (positive or indeterminate and inducibility of VT at EES (p<0.001. During follow-up we observed a significant difference in end-point occurrence between Ath with negative or positive TWA and between Ath with negative or positive EES. Conclusion: TWA confirm its role as a simple and non-invasive test, and it seems useful for prognostic stratification of Ath with VA. (Heart International 2007; 3: 58-67

  9. Current Status of T-wave Alternans%T波电交替的研究进展

    Institute of Scientific and Technical Information of China (English)

    任莉娜

    2011-01-01

    T波电交替是指在规整的心律时,体表心电图上T波形态、极性和振幅出现逐搏交替变化的现象,其与恶性室性心律失常以及心脏性猝死的发生有着极为密切的联系.T波电交替的检测方法有频域分析和时域分析方法两种.临床试验证实,T波电交替时恶性室性心律失常事件的预测价值与有创的电生理检测价值相似.但微伏级T波电交替检测作为一种无创的检测手段,其对于发生各种致死性心脏病危险分级的作用仍需要临床实验进一步研究证实,现就T波电交替的发生机制、临床意义以及发展现状等进行综述.%T-wave altemans ( TWA) , the beat-to-beat fluctuation in T wave amplitude and morphology , is closely linked to vulnerability to ventricular arrhythmias in vanous experimental and clinical conditions. Clinically, TWA is most commonly measured using the spectral method and time-domain methods . With current instrumentation and detecting condition, TWA represents an inexpensive, convenient,non-invasive testing modality. The future role of TWA testing in non-invasive risk stratification of fatal heart diseases is awaiting results of ongoing clinical trials. This article presents the mechanism, clinical indications, and research status of TWA according to current literature.

  10. Assessment of Microvolt T Wave Alternans in Children with Repaired Tetralogy of Fallot during 24-Hour Holter Electrocardiography.

    Science.gov (United States)

    Doksöz, Önder; Meşe, Timur; Karaarslan, Utku; Ceylan, Gökhan; Demirpençe, Savaş; Tavlı, Vedide; Ünal, Nurettin

    2016-07-01

    We aimed to examine microvolt T wave alternans (MTWA) in 24-hour Holter electrocardiography (ECG) of children with repaired tetralogy of Fallot (TOF) to assess associations of MTWA with ventricular arrhythmias, ECG parameters, and echocardiographic findings. Holter ECG records and archive files of 56 repaired TOF patients (62.5% male) who were analyzed retrospectively. Subjects' ECG parameters and MTWA values were compared with age-sex-matched control group. T wave changes were analyzed by time-domain-modified moving average method from the three channels of 24-hour Holter ECG. Mean age was 123.4 ± 48.3 months. Median MTWA value was 55.5 μV in the control group, whereas 95.5 μV in patients group (P Holter ECG in repaired TOF patients. © 2015 Wiley Periodicals, Inc.

  11. Prognostic capacity of a clinically indicated exercise test for cardiovascular mortality is enhanced by combined analysis of exercise capacity, heart rate recovery and T-wave alternans.

    Science.gov (United States)

    Minkkinen, Mikko; Nieminen, Tuomo; Verrier, Richard L; Leino, Johanna; Lehtimäki, Terho; Viik, Jari; Lehtinen, Rami; Nikus, Kjell; Kööbi, Tiit; Turjanmaa, Väinö; Kähönen, Mika

    2015-09-01

    Exercise capacity, heart rate recovery and T-wave alternans are independent predictors of cardiovascular mortality. We tested whether these parameters contain supplementary prognostic information. A total of 3609 consecutive patients (2157 men) referred for a routine, clinically indicated bicycle exercise test were enrolled in the Finnish Cardiovascular Study (FINCAVAS). Exercise capacity was measured in metabolic equivalents, heart rate recovery as the decrease in heart rate from maximum to one minute post-exercise, and T-wave alternans by time-domain Modified Moving Average method. During 57-month median follow-up (interquartile range 35-78 months), 96 patients died of cardiovascular causes (primary endpoint) and 233 from any cause. All three parameters were independent predictors of cardiovascular mortality when analysed as continuous variables. Adding metabolic equivalents (p heart rate recovery (p = 0.002) or T-wave alternans (p = 0.01) to the linear model improved its predictive power for cardiovascular mortality. The combination of low exercise capacity (heart rate recovery (≤12 beats/min) and elevated T-wave alternans (≥60 μV) yielded the highest hazard ratio for cardiovascular mortality of 16.5 (95% confidence interval 4.0-67.7, p heart rate recovery and ≥60 μV for T-wave alternans). The prognostic capacity of the clinical exercise test is enhanced by combined analysis of exercise capacity, heart rate recovery and T-wave alternans. © The European Society of Cardiology 2014.

  12. T波电交替计算机检测及其临床研究进展%Progress in Computer Detection and Clinical Study of T-wave Alternans

    Institute of Scientific and Technical Information of China (English)

    王娟; 黄忠朝; 刘正春

    2009-01-01

    T波电交替现象可见于长QT综合征、急性心肌缺血、变异型心绞痛、心脏性猝死以及电解质紊乱等.它在预测室性心律失常方面与电生理检查具有高度的一致性,是恶性室性心律失常和心脏性猝死的独立预测指标,是评定恶性心律失常以及心脏性猝死的可信、实用的技术之一.现在,T波电交替已经成为了一种廉价、方便的非侵入式心电检测方法.现综述T波电交替的研究背景、产生机制、检测方法及其临床研究,并简要分析了T波电交替的研究方向和发展前景.%T-wave alternans (TWA) can be found in long QT syndrome, acute myocardial ischemia, variant angina pectoris, sudden cardiac death, electrolyte turbulence, and others. It has a high rate of consistency when used with an electro-physiological examination in detecting ventricular arrhythmia. It is also an independent prognosticating index and a reliable, practical technology accessing to malignant ventricular arrhythmia and sudden cardiac death. TWA represents today an inexpensive, convenient and non-invasive testing modality for electrocardiogram. The research background, mechanism of the onset, detection and its application in clinical investigations of TWA were reviewed in this paper. The study focus and the perspective of TWA were also briefly discussed.

  13. [Positive microvolt T-wave alternans as a marker of ventricular arrhythmia trigering during cardioverter-defibrillator implantation].

    Science.gov (United States)

    Wierzbowski, Robert; Michałkiewicz, Dariusz; Cholewa, Marian; Jacewicz, Katarzyna; Gniłka, Anna; Adamus, Jerzy

    2006-10-01

    Microvolt T-wave alternans (MTWA) is promising method for noninvasive assessment of arrhythmic risk, but its role hasn't established yet. The aim of this study was to establish the MTWA potency to predict the ventricular arrhythmia triggering during implantable cordioverter-defibrillator (ICD) implantation. Material and metods. The study group consisted of 21 patients, aged 63.0+/-8.0 years; EF was 38.0+/-12.8%. Seventeen of them had a history of myocardial infarction and 4 had non-ischemic cardiomyopathy. The reason for ICD implantation were secondary prevention due to nonfatal cardiac arrest caused by VF/VT in nineteen patients and in two patients ICD was implanted because of unexplained syncope and low EF (protocol of 50 Hz BURST and T SHOCK was applied. After ICD implantation the following tests were performed: ECG with HR, QRS and QTc evaluation, 24-hour ECG Holter monitoring with HRV assessment and MTWA evaluation during treadmill exercise test. Results. In the group with VT/VF induced by less aggressive protocol (EPS), group I (n = 10) MTWA was present in nine patients, in one the result of MTWA was indeterminate. In the group with VT/VF induced by more aggressive protocol, group II (n = 11) MTWA was present in four patients, indeterminate in four and absent in three. There was a significant (p = 0.017) difference between group I and II in the frequency of positive result of MTWA. There were no differences between the two groups according to time domain parameters of HRV such as SDNN, RMSSD and PNN50 and QTc. There was a significant difference between the two groups in time duration of QRS complexes, 118.9+/-14.7 vs. 105.6+/-11.5 accordingly (p more easily inducible by electrophysiologic study during ICD implantation. It is easier to induce ventricular arrhythmia when QRS complexes are wider, irrelevant to left ventricular dysfunction and autonomic function of the heart.

  14. Theoretical comments on reproducibility and normalization of TWA measures.

    Science.gov (United States)

    Sassi, Roberto; Mainardi, Luca T

    2013-01-01

    Using a simple stochastic model of ventricular repolarization and the equivalent surface source (ESS) model, an electrophysiological formulation relating surface ECG to variations at the myocytes' level, we recently pointed out a few theoretical results regarding T-wave alternans (TWA). In this paper, stimulated by the comments of John E. Madias on our paper (J Electrocardiol, 2012), we further explored the consequences implied by the theoretical model. First, we verified the reproducibility of TWA measures, in clinically stable patients repeatedly tested. The sensitivity to displacement was evaluated simulating lead mislocations of up to 20mm. The numerical simulations were performed on data obtained solving the inverse electrocardiographically problem from three subjects (ECGSIM). The results showed that TWA sensitivity varies across leads, being maximal in V1 and decreases towards V6. Globally, the maximal percent error found was 6.1%. Thus, TWA measures do not seem to add more stringent requirements on lead placement's precision, than the usual diagnostic practice. Finally, we further discussed the implications of normalizing TWA measures. While clinical studies are necessary to sort out the issue, the theoretical model suggests that normalization might be appropriate only is certain cases.

  15. Prediction of Appropriate Shocks Using 24-Hour Holter Variables and T-Wave Alternans After First Implantable Cardioverter-Defibrillator Implantation in Patients With Ischemic or Nonischemic Cardiomyopathy.

    Science.gov (United States)

    Seegers, Joachim; Bergau, Leonard; Expósito, Pascal Muñoz; Bauer, Axel; Fischer, Thomas H; Lüthje, Lars; Hasenfuß, Gerd; Friede, Tim; Zabel, Markus

    2016-07-01

    In patients treated with implantable cardioverter defibrillator (ICD), prediction of both overall survival and occurrence of shocks is important if improved patient selection is desired. We prospectively studied the predictive value of biomarkers and indexes of cardiac and renal function and spectral microvolt T-wave alternans testing and 24-hour Holter variables in a population who underwent first ICD implantation. Consecutive patients in sinus rhythm with ischemic or dilated cardiomyopathy scheduled for primary or secondary prophylactic ICD implantation were enrolled. Exercise microvolt T-wave alternans and 24-hour Holter for number of ventricular premature contractions (VPCs), deceleration capacity, heart rate variability, and heart rate turbulence were done. Death of any cause and first appropriate ICD shock were defined as end points. Over 33 ± 15 months of follow-up, 36 of 253 patients (14%) received appropriate shocks and 39 of 253 patients (15%) died. Only 3 of 253 patients (1%) died after receiving at least 1 appropriate shock. In univariate analyses, New York Heart Association class, ejection fraction, N-terminal pro brain-type natriuretic peptide (NT-proBNP), renal function, ICD indication, deceleration capacity, heart rate variability, and heart rate turbulence were predictive of all-cause mortality and VPC number and deceleration capacity predicted first appropriate shock. NT-proBNP (≥1,600 pg/ml) was identified as the only independent predictor of all-cause mortality (hazard ratio 3.0, confidence interval 1.3 to 7.3, p = 0.014). In contrast, VPC number predicted appropriate shocks (hazard ratio 2.3, confidence interval 1.0 to 5.5, p = 0.047) as the only independent risk marker. In conclusion, NT-proBNP is a strong independent predictor of mortality in a typical prospective cohort of newly implanted patients with ICD, among many electrocardiographic and clinical variables studied. Number of VPCs was identified as a predictor of appropriate shocks

  16. Clinical Significance of T-wave Alternans Predicting Sudden Cardiac Death in Patients with Ischemic Heart Disease%T波电交替预测缺血性心脏病心脏性猝死的临床意义

    Institute of Scientific and Technical Information of China (English)

    孙溢晗(综述); 张月兰(审校)

    2015-01-01

    中国每年心脏性猝死人数约54.4万人,主要病因为缺血性心脏病所致恶性心律失常,所以及时有效检测减少心脏性猝死发生对降低心血管病病死率有重要意义。2008年AHA/ACC/HRS联合发表了“无创技术对心脏性猝死危险分层的专家共识”,指出用于识别心脏性猝死高危患者的无创检测指标,包括常规心电图、平均信号心电图、动态心电图、心电图运动试验(T波电交替)及压力感受器敏感性等。其中T波电交替为心电图上ST段或T波形态及振幅变化现象,是一种心电活动不稳定现象,具有在临床应用、随访复查方面更为方便灵活,操作简单及较高阳性识别率等特点,成为预测缺血性心脏病致恶性心律失常及心脏性猝死的主要无创性检测指标之一。%The number of sudden cardiac death in China is about 54.4 million people each year, and the main reason is malignant ar-rhythmias caused by ischemic heart disease, so it does significantly to reduce the incidence of sudden cardiac death and cardiovascular mor-tality by predicting timely and effectively.In 2008, AHA/ACC/HRS published ‘Expert consensus on risk stratification of sudden cardiac death through non-invasive techniques’ , which pointed out non-invasive methods were ECG, ventricular late potential, Holter, T-wave alter-nans, and baroneflex sensitivity.T-wave alternans is instability of electrical activity ECG phenomenon, on which ST segment or T wave mor-phology and amplitude changes, which is more convenient and flexible used in clinical or follow-up, and becomes one of major non-invasive detections of indicators of malignant arrhythmias and sudden cardiac death.

  17. Pattern of crescendo TWA may disclose the underlying cardiac pathology.

    Science.gov (United States)

    Nieminen, Tuomo; Verrier, Richard L; Nikus, Kjell; Viik, Jari; Lehtinen, Rami; Lehtimäki, Terho; Kaiser, Willi; Kähönen, Mika

    2010-01-01

    We present an exercise test case in which crescendo TWA preceded ventricular tachycardia (VT). The patient was examined due to suspicion of ischemic heart disease. The ST-segment became elevated simultaneously with a distinct alternation in the ST-segment and the first half of the T-wave, and the patient developed polymorphic VT. Coronary angiography disclosed marked stenoses. Earlier reports of TWA in patients with congenital long QT syndrome show a pattern in which the T wave frequently alternates above and below the isoelectric line without concomitant ST-segment changes. In Brugada syndrome patients, the signature ST-T wave pattern is the locus of alternation. Future investigation should elucidate whether specific TWA morphologies may expose underlying heart disease.

  18. Mechanism of Discordant Alternans in Spatially Homogenoeus Tissue

    CERN Document Server

    Watanabe, M; Evans, S J; Hastings, H; Karma, A; Watanabe, Mari A.; Fenton, Flavio H; Evans, Steven J.; Hastings, Harold; Karma, Alain

    2000-01-01

    Discordant alternans,the phenomenon of 2 separate cardiac tissue locations exhibiting action potential duration (APD) alternans of opposite phase, appears to be a potential mechanism for electrocardiographic T wave alternans, but its initiation mechanism is unknown. We studied behavior of one- and two- dimensional cardiac tissue spatially homogenous in all respects, including APD restitution and conduction velocity restitution, using the Beeler Reuter ion channel model. We found that discordant alternans was initiated when spatial gradients of APD arose dynamically, such as from fixed rate pacing of a cable end (sinus node scenario), or from fixed rate pacing at one site preceded by a single excitation wavefront from another site (ectopic focus scenario). In the sinus node scenario, conduction velocity restitution was necessary to initiate discordant alternans. Alternating regimes of concordant and discordant alternans arose along the length of the cable, with regimes delimited by nodes of fixed APD. The numb...

  19. Additional TWA Members? Spectroscopic verification of kinematically selected TWA candidates

    CERN Document Server

    Song, I; Zuckerman, B; Song, Inseok

    2002-01-01

    We present spectroscopic measurements of the 23 new candidate members of the TW Hydrae Association from Makarov & Fabricius (2000). Based on Halpha and Li 6708 A strengths together with location on a color-magnitude diagram for Hipparcos TWA candidates, we found only three possible new members (TYC 7760-0835-1, TYC 8238-1462-1, and TYC 8234-2856-1) in addition to the already known member, TWA 19. This eliminated most of the candidates more distant than 100 pc. Three Tycho stars, almost certainly members of the Lower Centaurus Crux association, are the most distant members of the TWA. A claim of isotropic expansion of TWA has to be re-evaluated based on our new results. Generally, one cannot identify new members of a diffuse nearby stellar group based solely on kinematic data. To eliminate interlopers with similar kinematics, spectroscopic verification is essential.

  20. An Excel-based implementation of the spectral method of action potential alternans analysis.

    Science.gov (United States)

    Pearman, Charles M

    2014-12-01

    Action potential (AP) alternans has been well established as a mechanism of arrhythmogenesis and sudden cardiac death. Proper interpretation of AP alternans requires a robust method of alternans quantification. Traditional methods of alternans analysis neglect higher order periodicities that may have greater pro-arrhythmic potential than classical 2:1 alternans. The spectral method of alternans analysis, already widely used in the related study of microvolt T-wave alternans, has also been used to study AP alternans. Software to meet the specific needs of AP alternans analysis is not currently available in the public domain. An AP analysis tool is implemented here, written in Visual Basic for Applications and using Microsoft Excel as a shell. This performs a sophisticated analysis of alternans behavior allowing reliable distinction of alternans from random fluctuations, quantification of alternans magnitude, and identification of which phases of the AP are most affected. In addition, the spectral method has been adapted to allow detection and quantification of higher order regular oscillations. Analysis of action potential morphology is also performed. A simple user interface enables easy import, analysis, and export of collated results.

  1. Biventricular Pulsus Alternans

    Directory of Open Access Journals (Sweden)

    Param Vidwan

    2009-01-01

    Full Text Available Pulsus alternans is a rare hemodynamic condition characterized by beat-to-beat variability in systolic pressure. It is attributed to variations in stroke volume with alternate cardiac cycles and is typically seen in patients with advanced myopathic conditions. Left ventricular pulsus alternans is rare, and right ventricular pulsus alternans is even less common. There are only a few reports of biventricular pulsus alternans. We report the case of a 62-year-old female with a recent anterior wall myocardial infarction who had biventricular pulsus alternans at the time of cardiac catheterization.

  2. A class of Monte-Carlo-based statistical algorithms for efficient detection of repolarization alternans.

    Science.gov (United States)

    Iravanian, Shahriar; Kanu, Uche B; Christini, David J

    2012-07-01

    Cardiac repolarization alternans is an electrophysiologic condition identified by a beat-to-beat fluctuation in action potential waveform. It has been mechanistically linked to instances of T-wave alternans, a clinically defined ECG alternation in T-wave morphology, and associated with the onset of cardiac reentry and sudden cardiac death. Many alternans detection algorithms have been proposed in the past, but the majority have been designed specifically for use with T-wave alternans. Action potential duration (APD) signals obtained from experiments (especially those derived from optical mapping) possess unique characteristics, which requires the development and use of a more appropriate alternans detection method. In this paper, we present a new class of algorithms, based on the Monte Carlo method, for the detection and quantitative measurement of alternans. Specifically, we derive a set of algorithms (one an analytical and more efficient version of the other) and compare its performance with the standard spectral method and the generalized likelihood ratio test algorithm using synthetic APD sequences and optical mapping data obtained from an alternans control experiment. We demonstrate the benefits of the new algorithm in the presence of Gaussian and Laplacian noise and frame-shift errors. The proposed algorithms are well suited for experimental applications, and furthermore, have low complexity and are implementable using fixed-point arithmetic, enabling potential use with implantable cardiac devices.

  3. Effects of pacing site and stimulation history on alternans dynamics and the development of complex spatiotemporal patterns in cardiac tissue

    Directory of Open Access Journals (Sweden)

    Alessio eGizzi

    2013-04-01

    Full Text Available Alternans of action potential duration has been associated with T-wave alternans and the development of arrhythmias because it produces large gradients of repolarization. However, little is known about alternans dynamics in large mammalian hearts. Using optical mapping to record electrical activations simultaneously from the epicardium and endocardium of 9 canine right ventricles, we demonstrate novel arrhythmogenic complex spatiotemporal dynamics. (i Alternans predominantly develops first on the endocardium. (ii The postulated simple progression from normal rhythm to concordant to discordant alternans is not always observed; concordant alternans can develop from discordant alternans as the pacing period is decreased. (iii In contrast to smaller tissue preparations, multiple stationary nodal lines may exist and need not be perpendicular to the pacing site or to each other. (iv Alternans has fully three-dimensional dynamics and the epicardium and endocardium can show significantly different dynamics: multiple nodal surfaces can be transmural or intramural and can form concave/convex surfaces resulting in islands of discordant alternans. (v The complex spatiotemporal patterns observed during alternans are very sensitive to both the site of stimulation and the stimulation history. Alternans in canine ventricles not only exhibit larger amplitudes and persist for longer cycle length regimes compared those found in smaller mammalian hearts, but also show novel dynamics not previously described that enhance dispersion and show high sensitivity to initial conditions. This indicate some underlying predisposition to chaos and can help the design of new drugs and devices controlling and preventing arrhythmic events.

  4. Indeterminacy of Spatiotemporal Cardiac Alternans

    CERN Document Server

    Zhao, Xiaopeng

    2007-01-01

    Cardiac alternans, a beat-to-beat alternation in action potential duration (at the cellular level) or in ECG morphology (at the whole heart level), is a marker of ventricular fibrillation, a fatal heart rhythm that kills hundreds of thousands of people in the US each year. Investigating cardiac alternans may lead to a better understanding of the mechanisms of cardiac arrhythmias and eventually better algorithms for the prediction and prevention of such dreadful diseases. In paced cardiac tissue, alternans develops under increasingly shorter pacing period. Existing experimental and theoretical studies adopt the assumption that alternans in homogeneous cardiac tissue is exclusively determined by the pacing period. In contrast, we find that, when calcium-driven alternans develops in cardiac fibers, it may take different spatiotemporal patterns depending on the pacing history. Because there coexist multiple alternans solutions for a given pacing period, the alternans pattern on a fiber becomes unpredictable. Usin...

  5. Application of a New Robust ECG T-Wave Delineation Algorithm for the Evaluation of the Autonomic Innervation of the Myocardium

    DEFF Research Database (Denmark)

    Cesari, Matteo; Mehlsen, Jesper; Mehlsen, Anne-Birgitte

    2016-01-01

    T-wave amplitude (TWA) is a well know index of the autonomic innervation of the myocardium. However, until now it has been evaluated only manually or with simple and inefficient algorithms. In this paper, we developed a new robust single-lead electrocardiogram (ECG) T-wave delineation algorithm...

  6. Posterior reperfusion T-waves: Wellens' syndrome of the posterior wall.

    Science.gov (United States)

    Driver, Brian E; Shroff, Gautam R; Smith, Stephen W

    2017-02-01

    Reperfusion after coronary occlusion (myocardial infarction, MI), as in Wellens' syndrome, is often represented on ECG as T-wave inversion in the leads overlying the affected myocardial wall(s). As an extension of this logic, reperfusion of the posterior wall should manifest on right precordial leads (which are opposite the posterior wall) as enlarged T-waves. We sought to determine whether T-wave amplitude (TWa) in leads V2 and V3 after reperfusion in posterior MI (PMI) is greater than in patients without PMI. Review of ECGs from patients with ST elevation MI of the left circumflex or right coronary artery with post-procedure thrombolysis in MI (TIMI) flow >0 between 2007 and 2009. Blinded experts reviewed admission ECGs to determine the presence of PMI and measure TWa before and after reperfusion. Maximum TWa in V2 and V3 and the difference between maximum and admission V2 and V3 TWa were compared between those with and without PMI. Of 72 patients, 48 had PMI. Values expressed are medians and IQRs. Maximum TWa after reperfusion was greater in PMI than in non-PMI in V2 (5.00 mm (3.5 to 8.25) vs 3.9 mm (2.75 to 5.5), p=0.04), but not in V3 (4.0 mm (2 to 5.5) vs 3.0 mm (1.75 to 4), p=0.09). The increase in TWa in V2 and V3 after reperfusion was greater in PMI compared with non-PMI: (V2, 3.4 mm (2 to 5.25) vs 1.25 mm (-0.25 to 2), p=0.0005; V3, 2 mm (-0.5 to 3.25) vs 0.25 mm (-1 to 1.75), p=0.03). Reperfusion of the posterior wall results in higher right precordial TWa, and an even greater increase in TWa, as measured in leads V2 and V3. This observation has important implications for emergency physicians to accurately identify recent posterior infarction in patients who may be symptom free on presentation but at risk of reocclusion. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  7. Alternans and the influence of ionic channel modifications: Cardiac three-dimensional simulations and one-dimensional numerical bifurcation analysis.

    Science.gov (United States)

    Bauer, S; Röder, G; Bär, M

    2007-03-01

    Cardiac propagation is investigated by simulations using a realistic three-dimensional (3D) geometry including muscle fiber orientation of the ventricles of a rabbit heart and the modified Beeler-Reuter ionic model. Electrical excitation is introduced by a periodic pacing of the lower septum. Depending on the pacing frequency, qualitatively different dynamics are observed, namely, normal heart beat, T-wave alternans, and 2:1 conduction block at small, intermediate, and large pacing frequencies, respectively. In a second step, we performed a numerical stability and bifurcation analysis of a pulse propagating in a one-dimensional (1D) ring of cardiac tissue. The precise onset of the alternans instability is obtained from computer-assisted linear stability analysis of the pulse and computation of the associated spectrum. The critical frequency at the onset of alternans and the profiles of the membrane potential agree well with the ones obtained in the 3D simulations. Next, we computed changes in the wave profiles and in the onset of alternans for the Beeler-Reuter model with modifications of the sodium, calcium, and potassium channels, respectively. For this purpose, we employ the method of numerical bifurcation and stability analysis. While blocking of calcium channels has a stabilizing effect, blocked sodium or potassium channels lead to the occurrence of alternans at lower pacing frequencies. The findings regarding channel blocking are verified within three-dimensional simulations. Altogether, we have found T-wave alternans and conduction block in 3D simulations of a realistic rabbit heart geometry. The onset of alternans has been analyzed by numerical bifurcation and stability analysis of 1D wave trains. By comparing the results of the two approaches, we find that alternans is not strongly influenced by ingredients such as 3D geometry and propagation anisotropy, but depends mostly on the frequency of pacing (frequency of subsequent action potentials). In addition

  8. Orbits and masses in the young triple system TWA 5

    CERN Document Server

    Köhler, R; Petr-Gotzens, M G; Correia, S

    2013-01-01

    We aim to improve the orbital elements and determine the individual masses of the components in the triple system TWA 5. Five new relative astrometric positions in the H band were recorded with the adaptive optics system at the Very Large Telescope (VLT). We combine them with data from the literature and a measurement in the Ks band. We derive an improved fit for the orbit of TWA 5Aa-b around each other. Furthermore, we use the third component, TWA 5B, as an astrometric reference to determine the motion of Aa and Ab around their center of mass and compute their mass ratio. We find an orbital period of 6.03+/-0.01 years and a semi-major axis of 63.7+/-0.2 mas (3.2+/-0.1 AU). With the trigonometric distance of 50.1+/-1.8 pc, this yields a system mass of 0.9+/-0.1 Msun, where the error is dominated by the error of the distance. The dynamical mass agrees with the system mass predicted by a number of theoretical models if we assume that TWA5 is at the young end of the age range of the TW Hydrae association. We fin...

  9. On the physical properties of TWA-2M1207

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    A. Bayo

    2007-01-01

    Full Text Available We have studied some physical properties of 2M1207 (member of TWA. Previously es- timated age for this moving group is 10 Myr. The chronology has been carried out by analysing different properties of this object (Teff, gravity, accretion/activity and lithium in the optical and IR and comparing them with well-known star-forming regions and open clusters, as well as theoretical models.

  10. T-Wave Morphology Restitution Predicts Sudden Cardiac Death in Patients With Chronic Heart Failure.

    Science.gov (United States)

    Ramírez, Julia; Orini, Michele; Mincholé, Ana; Monasterio, Violeta; Cygankiewicz, Iwona; Bayés de Luna, Antonio; Martínez, Juan Pablo; Pueyo, Esther; Laguna, Pablo

    2017-05-19

    Patients with chronic heart failure are at high risk of sudden cardiac death (SCD). Increased dispersion of repolarization restitution has been associated with SCD, and we hypothesize that this should be reflected in the morphology of the T-wave and its variations with heart rate. The aim of this study is to propose an electrocardiogram (ECG)-based index characterizing T-wave morphology restitution (TMR), and to assess its association with SCD risk in a population of chronic heart failure patients. Holter ECGs from 651 ambulatory patients with chronic heart failure from the MUSIC (MUerte Súbita en Insuficiencia Cardiaca) study were available for the analysis. TMR was quantified by measuring the morphological variation of the T-wave per RR increment using time-warping metrics, and its predictive power was compared to that of clinical variables such as the left ventricular ejection fraction and other ECG-derived indices, such as T-wave alternans and heart rate variability. TMR was significantly higher in SCD victims than in the rest of patients (median 0.046 versus 0.039, P<0.001). When TMR was dichotomized at TMR=0.040, the SCD rate was significantly higher in the TMR≥0.040 group (P<0.001). Cox analysis revealed that TMR≥0.040 was strongly associated with SCD, with a hazard ratio of 3.27 (P<0.001), independently of clinical and ECG-derived variables. No association was found between TMR and pump failure death. This study shows that TMR is specifically associated with SCD in a population of chronic heart failure patients, and it is a better predictor than clinical and ECG-derived variables. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.

  11. Spatiotemporal dynamics of calcium-driven cardiac alternans.

    Science.gov (United States)

    Skardal, Per Sebastian; Karma, Alain; Restrepo, Juan G

    2014-05-01

    We investigate the dynamics of spatially discordant alternans (SDA) driven by an instability of intracellular calcium cycling using both amplitude equations [P. S. Skardal, A. Karma, and J. G. Restrepo, Phys. Rev. Lett. 108, 108103 (2012)] and ionic model simulations. We focus on the common case where the bidirectional coupling of intracellular calcium concentration and membrane voltage dynamics produces calcium and voltage alternans that are temporally in phase. We find that, close to the alternans bifurcation, SDA is manifested as a smooth wavy modulation of the amplitudes of both repolarization and calcium transient (CaT) alternans, similarly to the well-studied case of voltage-driven alternans. In contrast, further away from the bifurcation, the amplitude of CaT alternans jumps discontinuously at the nodes separating out-of-phase regions, while the amplitude of repolarization alternans remains smooth. We identify universal dynamical features of SDA pattern formation and evolution in the presence of those jumps. We show that node motion of discontinuous SDA patterns is strongly hysteretic even in homogeneous tissue due to the novel phenomenon of "unidirectional pinning": node movement can only be induced towards, but not away from, the pacing site in response to a change of pacing rate or physiological parameter. In addition, we show that the wavelength of discontinuous SDA patterns scales linearly with the conduction velocity restitution length scale, in contrast to the wavelength of smooth patterns that scales sublinearly with this length scale. Those results are also shown to be robust against cell-to-cell fluctuations due to the property that unidirectional node motion collapses multiple jumps accumulating in nodal regions into a single jump. Amplitude equation predictions are in good overall agreement with ionic model simulations. Finally, we briefly discuss physiological implications of our findings. In particular, we suggest that due to the tendency of

  12. Rate-dependent force, intracellular calcium, and action potential voltage alternans are modulated by sarcomere length and heart failure induced-remodeling of thin filament regulation in human heart failure: A myocyte modeling study.

    Science.gov (United States)

    Zile, Melanie A; Trayanova, Natalia A

    2016-01-01

    Microvolt T-wave alternans (MTWA) testing identifies heart failure patients at risk for lethal ventricular arrhythmias at near-resting heart rates (voltage alternans (APV-ALT), the cellular driver of MTWA. Our goal was to uncover the mechanisms linking APV-ALT and FORCE-ALT in failing human myocytes and to investigate how the link between those alternans was affected by pacing rate and by physiological conditions such as sarcomere length and heart failure induced-remodeling of mechanical parameters. To achieve this, a mechanically-based, strongly coupled human electromechanical myocyte model was constructed. Reducing the sarcoplasmic reticulum calcium uptake current (Iup) to 27% was incorporated to simulate abnormal calcium handling in human heart failure. Mechanical remodeling was incorporated to simulate altered thin filament activation and crossbridge (XB) cycling rates. A dynamical pacing protocol was used to investigate the development of intracellular calcium concentration ([Ca]i), voltage, and active force alternans at different pacing rates. FORCE-ALT only occurred in simulations incorporating reduced Iup, demonstrating that alternans in the intracellular calcium concentration (CA-ALT) induced FORCE-ALT. The magnitude of FORCE-ALT was found to be largest at clinically relevant pacing rates (<110 bpm), where APV-ALT was smallest. We found that the magnitudes of FORCE-ALT, CA-ALT and APV-ALT were altered by heart failure induced-remodeling of mechanical parameters and sarcomere length due to the presence of myofilament feedback. These findings provide important insight into the relationship between heart-failure-induced electrical and mechanical alternans and how they are altered by physiological conditions at near-resting heart rates.

  13. Dependency of calcium alternans on ryanodine receptor refractoriness.

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    Enric Alvarez-Lacalle

    Full Text Available BACKGROUND: Rapid pacing rates induce alternations in the cytosolic calcium concentration caused by fluctuations in calcium released from the sarcoplasmic reticulum (SR. However, the relationship between calcium alternans and refractoriness of the SR calcium release channel (RyR2 remains elusive. METHODOLOGY/PRINCIPAL FINDINGS: To investigate how ryanodine receptor (RyR2 refractoriness modulates calcium handling on a beat-to-beat basis using a numerical rabbit cardiomyocyte model. We used a mathematical rabbit cardiomyocyte model to study the beat-to-beat calcium response as a function of RyR2 activation and inactivation. Bi-dimensional maps were constructed depicting the beat-to-beat response. When alternans was observed, a novel numerical clamping protocol was used to determine whether alternans was caused by oscillations in SR calcium loading or by RyR2 refractoriness. Using this protocol, we identified regions of RyR2 gating parameters where SR calcium loading or RyR2 refractoriness underlie the induction of calcium alternans, and we found that at the onset of alternans both mechanisms contribute. At low inactivation rates of the RyR2, calcium alternans was caused by alternation in SR calcium loading, while at low activation rates it was caused by alternation in the level of available RyR2s. CONCLUSIONS/SIGNIFICANCE: We have mapped cardiomyocyte beat-to-beat responses as a function of RyR2 activation and inactivation, identifying domains where SR calcium load or RyR2 refractoriness underlie the induction of calcium alternans. A corollary of this work is that RyR2 refractoriness due to slow recovery from inactivation can be the cause of calcium alternans even when alternation in SR calcium load is present.

  14. Fast T Wave Detection Calibrated by Clinical Knowledge with Annotation of P and T Waves

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    Mohamed Elgendi

    2015-07-01

    Full Text Available Background: There are limited studies on the automatic detection of T waves in arrhythmic electrocardiogram (ECG signals. This is perhaps because there is no available arrhythmia dataset with annotated T waves. There is a growing need to develop numerically-efficient algorithms that can accommodate the new trend of battery-driven ECG devices. Moreover, there is also a need to analyze long-term recorded signals in a reliable and time-efficient manner, therefore improving the diagnostic ability of mobile devices and point-of-care technologies. Methods: Here, the T wave annotation of the well-known MIT-BIH arrhythmia database is discussed and provided. Moreover, a simple fast method for detecting T waves is introduced. A typical T wave detection method has been reduced to a basic approach consisting of two moving averages and dynamic thresholds. The dynamic thresholds were calibrated using four clinically known types of sinus node response to atrial premature depolarization (compensation, reset, interpolation, and reentry. Results: The determination of T wave peaks is performed and the proposed algorithm is evaluated on two well-known databases, the QT and MIT-BIH Arrhythmia databases. The detector obtained a sensitivity of 97.14% and a positive predictivity of 99.29% over the first lead of the validation databases (total of 221,186 beats. Conclusions: We present a simple yet very reliable T wave detection algorithm that can be potentially implemented on mobile battery-driven devices. In contrast to complex methods, it can be easily implemented in a digital filter design.

  15. Phase relationship between alternans of early and late phases of ventricular action potentials.

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    Linyuan eJing

    2012-06-01

    Full Text Available Background: Alternans of early phase and of duration of action potential (AP critically affect dispersion of refractoriness through their influence on conduction and repolarization. We investigated the phase relationship between the two alternans and its effect on conduction. Methods and Results: Transmembrane potentials recorded from ventricles of 8 swine and 3 canines during paced activation intervals of ≤ 300 ms were used to quantify alternans of maximum rate of depolarization (|dv/dt|max and of APD. Incidence of APD alternans was 62% and 76% in swine and canines. Alternans of APD was frequently accompanied with alternans of |dv/dt|max. Of these, 4 and 26 % were out of phase in swine and canines, i.e. low |dv/dt|max preceded long APD. Computer simulations show that out of phase alternans attenuate variation of wavelength and thus minimize formation of spatially discordant alternans. Conclusions: The spontaneous switching of phase relationship between alternans of depolarization and repolarization suggests that mechanisms underlying these alternans may operate independent of each other. The phase between these alternans can critically impact spatial dispersion of refractoriness and thus stability of conduction, with the in phase relation promoting transition from concord to discord while out of phase preventing formation of discord.

  16. Spatiotemporal control to eliminate cardiac alternans using isostable reduction

    Science.gov (United States)

    Wilson, Dan; Moehlis, Jeff

    2017-03-01

    Cardiac alternans, an arrhythmia characterized by a beat-to-beat alternation of cardiac action potential durations, is widely believed to facilitate the transition from normal cardiac function to ventricular fibrillation and sudden cardiac death. Alternans arises due to an instability of a healthy period-1 rhythm, and most dynamical control strategies either require extensive knowledge of the cardiac system, making experimental validation difficult, or are model independent and sacrifice important information about the specific system under study. Isostable reduction provides an alternative approach, in which the response of a system to external perturbations can be used to reduce the complexity of a cardiac system, making it easier to work with from an analytical perspective while retaining many of its important features. Here, we use isostable reduction strategies to reduce the complexity of partial differential equation models of cardiac systems in order to develop energy optimal strategies for the elimination of alternans. Resulting control strategies require significantly less energy to terminate alternans than comparable strategies and do not require continuous state feedback.

  17. A unified theory of calcium alternans in ventricular myocytes

    Science.gov (United States)

    Qu, Zhilin; Liu, Michael B.; Nivala, Michael

    2016-01-01

    Intracellular calcium (Ca2+) alternans is a dynamical phenomenon in ventricular myocytes, which is linked to the genesis of lethal arrhythmias. Iterated map models of intracellular Ca2+ cycling dynamics in ventricular myocytes under periodic pacing have been developed to study the mechanisms of Ca2+ alternans. Two mechanisms of Ca2+ alternans have been demonstrated in these models: one relies mainly on fractional sarcoplasmic reticulum Ca2+ release and uptake, and the other on refractoriness and other properties of Ca2+ sparks. Each of the two mechanisms can partially explain the experimental observations, but both have their inconsistencies with the experimental results. Here we developed an iterated map model that is composed of two coupled iterated maps, which unifies the two mechanisms into a single cohesive mathematical framework. The unified theory can consistently explain the seemingly contradictory experimental observations and shows that the two mechanisms work synergistically to promote Ca2+ alternans. Predictions of the theory were examined in a physiologically-detailed spatial Ca2+ cycling model of ventricular myocytes. PMID:27762397

  18. Physiology and analysis of the electrocardiographic T wave in mice

    DEFF Research Database (Denmark)

    Speerschneider, T; Thomsen, Morten Bækgaard

    2013-01-01

    The murine electrocardiogram (ECG) is a valuable tool in cardiac research, although the definition of the T wave has been a matter of debate for several years potentially leading to incomparable data. By this study, we seek to make a clear definition of the murine T wave. Moreover, we investigate...

  19. Elevated heart rate triggers action potential alternans and sudden death. translational study of a homozygous KCNH2 mutation.

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    Ulrich Schweigmann

    Full Text Available BACKGROUND: Long QT syndrome (LQTS leads to arrhythmic events and increased risk for sudden cardiac death (SCD. Homozygous KCNH2 mutations underlying LQTS-2 have previously been termed "human HERG knockout" and typically express severe phenotypes. We studied genotype-phenotype correlations of an LQTS type 2 mutation identified in the homozygous index patient from a consanguineous Turkish family after his brother died suddenly during febrile illness. METHODS AND RESULTS: Clinical work-up, DNA sequencing, mutagenesis, cell culture, patch-clamp, in silico mathematical modelling, protein biochemistry, confocal microscopy were performed. Genetic analysis revealed a homozygous C-terminal KCNH2 mutation (p.R835Q in the index patient (QTc ∼506 ms with notched T waves. Parents were I° cousins - both heterozygous for the mutation and clinically unremarkable (QTc ∼447 ms, father and ∼396 ms, mother. Heterologous expression of KCNH2-R835Q showed mildly reduced current amplitudes. Biophysical properties of ionic currents were also only nominally changed with slight acceleration of deactivation and more negative V50 in R835Q-currents. Protein biochemistry and confocal microscopy revealed similar expression patterns and trafficking of WT and R835Q, even at elevated temperature. In silico analysis demonstrated mildly prolonged ventricular action potential duration (APD compared to WT at a cycle length of 1000 ms. At a cycle length of 350 ms M-cell APD remained stable in WT, but displayed APD alternans in R835Q. CONCLUSION: Kv11.1 channels affected by the C-terminal R835Q mutation display mildly modified biophysical properties, but leads to M-cell APD alternans with elevated heart rate and could precipitate SCD under specific clinical circumstances associated with high heart rates.

  20. Cardiac contraction induces discordant alternans and localized block

    Science.gov (United States)

    Radszuweit, M.; Alvarez-Lacalle, E.; Bär, M.; Echebarria, B.

    2015-02-01

    In this paper we use a simplified model of cardiac excitation-contraction coupling to study the effect of tissue deformation on the dynamics of alternans, i.e., alternations in the duration of the cardiac action potential, that occur at fast pacing rates and are known to be proarrhythmic. We show that small stretch-activated currents can produce large effects and cause a transition from in-phase to off-phase alternations (i.e., from concordant to discordant alternans) and to conduction blocks. We demonstrate numerically and analytically that this effect is the result of a generic change in the slope of the conduction velocity restitution curve due to electromechanical coupling. Thus, excitation-contraction coupling can potentially play a relevant role in the transition to reentry and fibrillation.

  1. Sertindole causes distinct electrocardiographic T-wave morphology changes

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Graff, Claus; Hardahl, Thomas Bork;

    2009-01-01

    Sertindole's propensity to prolong the QT interval relates to blockade of the KCNH2 (HERG) encoded Ikr potassium channel, but there has been limited detailed data on T-wave morphology changes. Digital 12-lead ECG was recorded at baseline and at steady-state in 37 patients switched to sertindole....... ECG was analyzed for quantitative T-wave morphology changes and Fridericia-corrected QT duration (QTcF). Prominent T-wave morphology changes occurred during sertindole treatment and in some cases without concomitant prolongation of the QTcF interval. Four patients developed notched T-waves during...... sertindole treatment. Mean QTc prolongation was 19 ms. The mean effect size was higher for T-wave morphology combination score (MCS) (ES=1.92; 95% CI: 1.35-2.49) compared to the mean effect size for QTcF (ES=0.88; 95% CI: 0.52-1.24). The use of T-wave morphology analysis may become clinically relevant...

  2. Generation Mechanism of Alternans in Luo-Rudy Model

    Science.gov (United States)

    Kitajima, Hiroyuki; Ioka, Eri; Yazawa, Toru

    Electrical alternans is the alternating amplitude from beat to beat in the action potential of the cardiac cell. It has been associated with ventricular arrhythmias in many clinical studies; however, its dynamical mechanisms remain unknown. The reason is that we do not have realistic network models of the heart system. Recently, Yazawa clarified the network structure of the heart and the central nerve system in the crustacean heart. In this study, we construct a simple model of the heart system based on Yazawa’s experimental data. Using this model, we clarify that two parameters (the conductance of sodium ions and free concentration of potassium ions in the extracellular compartment) play the key roles of generating alternans. In particular, we clarify that the inactivation gate of the time-independent potassium channel is the most important parameter. Moreover, interaction between the membrane potential and potassium ionic currents is significant for generating alternate rhythms. This result indicates that if the muscle cell has problems such as channelopathies, there is great risk of generating alternans.

  3. Rumen fermentation and acetogen population changes in response to an exogenous acetogen TWA4 strain and Saccharomyces cerevisiae fermentation product.

    Science.gov (United States)

    Yang, Chun-lei; Guan, Le-luo; Liu, Jian-xin; Wang, Jia-kun

    2015-08-01

    The presence of yeast cells could stimulate hydrogen utilization of acetogens and enhance acetogenesis. To understand the roles of acetogens in rumen fermentation, an in vitro rumen fermentation experiment was conducted with addition of acetogen strain (TWA4) and/or Saccharomyces cerevisiae fermentation product (XP). A 2×2 factorial design with two levels of TWA4 (0 or 2×10(7) cells/ml) and XP (0 or 2 g/L) was performed. Volatile fatty acids (VFAs) were increased (P<0.05) in XP and TWA4XP, while methane was increased only in TWA4XP (P<0.05). The increase rate of microorganisms with formyltetrahydrofolate synthetase, especially acetogens, was higher than that of methanogens under all treatments. Lachnospiraceae was predominant in all acetogen communities, but without close acetyl-CoA synthase (ACS) amino acid sequences from cultured isolates. Low-Acetitomaculum ruminis-like ACS was predominant in all acetogen communities, while four unique phylotypes in XP treatment were all amino acid identified low-Eubacterium limosum-like acetogens. It differs to XP treatment that more low-A. ruminis-like and less low-E. limosum-like sequences were identified in TWA4 and TWA4XP treatments. Enhancing acetogenesis by supplementation with an acetogen strain and/or yeast cells may be an approach to mitigate methane, by targeting proper acetogens such as uncultured low-E. limosum-like acetogens.

  4. Evolution of Action Potential Alternans in Rabbit Heart during Acute Regional Ischemia

    Directory of Open Access Journals (Sweden)

    Irma Martišienė

    2015-01-01

    Full Text Available This study investigates the development of the spatiotemporal pattern of action potential alternans during acute regional ischemia. Experiments were carried out in isolated Langendorff-perfused rabbit heart using a combination of optical mapping and microelectrode recordings. The alternans pattern significantly changed over time and had a biphasic character reaching maximum at 6–9 min after occlusion. Phase I (3–11 minutes of ischemia is characterized by rapid increase in the alternans magnitude and expansion of the alternans territory. Phase I is followed by gradual decline of alternans (Phase II in both magnitude and territory. During both phases we observed significant beat-to-beat variations of the optical action potential amplitude (OAPA alternans. Simultaneous microelectrode recordings from subepicardial and subendocardial layers showed that OAPA alternans coincided with intramural 2 : 1 conduction blocks. Our findings are consistent with the modeling studies predicting that during acute regional ischemia alternans can be driven by 2 : 1 conduction blocks in the ischemic region.

  5. Constant DI pacing suppresses cardiac alternans formation in numerical cable models

    Science.gov (United States)

    Zlochiver, S.; Johnson, C.; Tolkacheva, E. G.

    2017-09-01

    Cardiac repolarization alternans describe the sequential alternation of the action potential duration (APD) and can develop during rapid pacing. In the ventricles, such alternans may rapidly turn into life risking arrhythmias under conditions of spatial heterogeneity. Thus, suppression of alternans by artificial pacing protocols, or alternans control, has been the subject of numerous theoretical, numerical, and experimental studies. Yet, previous attempts that were inspired by chaos control theories were successful only for a short spatial extent (sense that the onset of alternans is further shifted to higher activation rates. Overall, these results support the potential clinical applicability of such type of pacing in improving protocols of implanted pacemakers, in order to reduce the risk of life-threatening arrhythmias. Future research should be conducted in order to experimentally validate these promising results.

  6. T-wave amplitude is related to physical fitness status.

    Science.gov (United States)

    Arbel, Yaron; Birati, Edo Y; Shapira, Itzhak; Topilsky, Yan; Wirguin, Michal; Canaani M D, Jonathan

    2012-07-01

    Abnormalities in repolarization may reflect underlying myocardial pathology and play a prominent role in arrhythmogenesis The T-wave amplitude has been associated with cardiovascular outcome in patients with acute myocardial infarction (MI) Additionally, T-wave amplitude is considered a predictor of arrhythmias, as well as being related to an individual's inflammatory status. The combined influence of different variables, such as inflammation, cardiovascular risk factors and physical fitness status, on the T-wave amplitude has not been evaluated to date. The aim of this study was to identify factors that affect the T-wave amplitude. Data from 255 consecutive apparently healthy individuals included in the Tel Aviv Medical Center Inflammation Survey (TAMCIS) were reviewed. All patients had undergone a physical examination and an exercise stress test, and different inflammatory and metabolic biomarkers (fibrinogen, potassium, and high-sensitivity C-reactive protein) were measured. Multivariate stepwise analysis revealed that the body mass index and the resting heart rate were significantly associated with the T-wave amplitude (β=-0.34, P physical fitness and not to his/her inflammatory status. ©2012, Wiley Periodicals, Inc.

  7. Earthquake Source Parameters Inferred from T-Wave Observations

    Science.gov (United States)

    Perrot, J.; Dziak, R.; Lau, T. A.; Matsumoto, H.; Goslin, J.

    2004-12-01

    The seismicity of the North Atlantic Ocean has been recorded by two networks of autonomous hydrophones moored within the SOFAR channel on the flanks of the Mid-Atlantic Ridge (MAR). In February 1999, a consortium of U.S. investigators (NSF and NOAA) deployed a 6-element hydrophone array for long-term monitoring of MAR seismicity between 15o-35oN south of the Azores. In May 2002, an international collaboration of French, Portuguese, and U.S. researchers deployed a 6-element hydrophone array north of the Azores Plateau from 40o-50oN. The northern network (referred to as SIRENA) was recovered in September 2003. The low attenuation properties of the SOFAR channel for earthquake T-wave propagation results in a detection threshold reduction from a magnitude completeness level (Mc) of ˜ 4.7 for MAR events recorded by the land-based seismic networks to Mc=3.0 using hydrophone arrays. Detailed focal depth and mechanism information, however, remain elusive due to the complexities of seismo-acoustic propagation paths. Nonetheless, recent analyses (Dziak, 2001; Park and Odom, 2001) indicate fault parameter information is contained within the T-wave signal packet. We investigate this relationship further by comparing an earthquake's T-wave duration and acoustic energy to seismic magnitude (NEIC) and radiation pattern (for events M>5) from the Harvard moment-tensor catalog. First results show earthquake energy is well represented by the acoustic energy of the T-waves, however T-wave codas are significantly influenced by acoustic propagation effects and do not allow a direct determination of the seismic magnitude of the earthquakes. Second, there appears to be a correlation between T-wave acoustic energy, azimuth from earthquake source to the hydrophone, and the radiation pattern of the earthquake's SH waves. These preliminary results indicate there is a relationship between the T-wave observations and earthquake source parameters, allowing for additional insights into T-wave

  8. Characterizing Spatial Dynamics of Bifurcation to Alternans in Isolated Whole Rabbit Hearts Based on Alternate Pacing

    Directory of Open Access Journals (Sweden)

    Kanchan Kulkarni

    2015-01-01

    Full Text Available Sudden cardiac death instigated by ventricular fibrillation (VF is the largest cause of natural death in the USA. Alternans, a beat-to-beat alternation in the action potential duration, has been implicated as being proarrhythmic. The onset of alternans is mediated via a bifurcation, which may occur through either a smooth or a border-collision mechanism. The objective of this study was to characterize the mechanism of bifurcation to alternans based on experiments in isolated whole rabbit hearts. High resolution optical mapping was performed and the electrical activity was recorded from the left ventricle (LV epicardial surface of the heart. Each heart was paced using an “alternate pacing protocol,” where the basic cycle length (BCL was alternatively perturbed by ±δ. Local onset of alternans in the heart, BCLstart, was measured in the absence of perturbations (δ=0 and was defined as the BCL at which 10% of LV exhibited alternans. The influences of perturbation size were investigated at two BCLs: one prior to BCLstart (BCLprior=BCLstart+20 ms and one preceding BCLprior (BCLfar=BCLstart+40 ms. Our results demonstrate significant spatial correlation of the region exhibiting alternans with smooth bifurcation characteristics, indicating that transition to alternans in isolated rabbit hearts occurs predominantly through smooth bifurcation.

  9. In Silico Investigation into Cellular Mechanisms of Cardiac Alternans in Myocardial Ischemia

    Directory of Open Access Journals (Sweden)

    Jiaqi Liu

    2016-01-01

    Full Text Available Myocardial ischemia is associated with pathophysiological conditions such as hyperkalemia, acidosis, and hypoxia. These physiological disorders may lead to changes on the functions of ionic channels, which in turn form the basis for cardiac alternans. In this paper, we investigated the roles of hyperkalemia and calcium handling components played in the genesis of alternans in ischemia at the cellular level by using computational simulations. The results show that hyperkalemic reduced cell excitability and delayed recovery from inactivation of depolarization currents. The inactivation time constant τf of L-type calcium current (ICaL increased obviously in hyperkalemia. One cycle length was not enough for ICaL to recover completely. Alternans developed as a result of ICaL responding to stimulation every other beat. Sarcoplasmic reticulum calcium-ATPase (SERCA2a function decreased in ischemia. This change resulted in intracellular Ca (Cai alternans of small magnitude. A strong Na+-Ca2+ exchange current (INCX increased the magnitude of Cai alternans, leading to APD alternans through excitation-contraction coupling. Some alternated repolarization currents contributed to this repolarization alternans.

  10. In Silico Investigation into Cellular Mechanisms of Cardiac Alternans in Myocardial Ischemia

    Science.gov (United States)

    Liu, Jiaqi; Zhao, Xiaopeng

    2016-01-01

    Myocardial ischemia is associated with pathophysiological conditions such as hyperkalemia, acidosis, and hypoxia. These physiological disorders may lead to changes on the functions of ionic channels, which in turn form the basis for cardiac alternans. In this paper, we investigated the roles of hyperkalemia and calcium handling components played in the genesis of alternans in ischemia at the cellular level by using computational simulations. The results show that hyperkalemic reduced cell excitability and delayed recovery from inactivation of depolarization currents. The inactivation time constant τf of L-type calcium current (ICaL) increased obviously in hyperkalemia. One cycle length was not enough for ICaL to recover completely. Alternans developed as a result of ICaL responding to stimulation every other beat. Sarcoplasmic reticulum calcium-ATPase (SERCA2a) function decreased in ischemia. This change resulted in intracellular Ca (Cai) alternans of small magnitude. A strong Na+-Ca2+ exchange current (INCX) increased the magnitude of Cai alternans, leading to APD alternans through excitation-contraction coupling. Some alternated repolarization currents contributed to this repolarization alternans. PMID:28070211

  11. T-tubule disruption promotes calcium alternans in failing ventricular myocytes: mechanistic insights from computational modeling.

    Science.gov (United States)

    Nivala, Michael; Song, Zhen; Weiss, James N; Qu, Zhilin

    2015-02-01

    In heart failure (HF), T-tubule (TT) disruption contributes to dyssynchronous calcium (Ca) release and impaired contraction, but its role in arrhythmogenesis remains unclear. In this study, we investigate the effects of TT disruption and other HF remodeling factors on Ca alternans in ventricular myocytes using computer modeling. A ventricular myocyte model with detailed spatiotemporal Ca cycling modeled by a coupled Ca release unit (CRU) network was used, in which the L-type Ca channels and the ryanodine receptor (RyR) channels were simulated by random Markov transitions. TT disruption, which removes the L-type Ca channels from the associated CRUs, results in "orphaned" RyR clusters and thus provides increased opportunity for spark-induced Ca sparks to occur. This effect combined with other HF remodeling factors promoted alternans by two distinct mechanisms: 1) for normal sarco-endoplasmic reticulum Ca ATPase (SERCA) activity, alternans was caused by both CRU refractoriness and coupling. The increased opportunity for spark-induced sparks by TT disruption combined with the enhanced CRU coupling by Ca elevation in the presence or absence of increased RyR leakiness facilitated spark synchronization on alternate beats to promote Ca alternans; 2) for down-regulated SERCA, alternans was caused by the sarcoplasmic reticulum (SR) Ca load-dependent mechanism, independent of CRU refractoriness. TT disruption and increased RyR leakiness shifted and steepened the SR Ca release-load relationship, which combines with down-regulated SERCA to promote Ca alternans. In conclusion, the mechanisms of Ca alternans for normal and down-regulated SERCA are different, and TT disruption promotes Ca alternans by both mechanisms, which may contribute to alternans at different stages of HF.

  12. Comparison of Spot and Time Weighted Averaging (TWA Sampling with SPME-GC/MS Methods for Trihalomethane (THM Analysis

    Directory of Open Access Journals (Sweden)

    Don-Roger Parkinson

    2016-02-01

    Full Text Available Water samples were collected and analyzed for conductivity, pH, temperature and trihalomethanes (THMs during the fall of 2014 at two monitored municipal drinking water source ponds. Both spot (or grab and time weighted average (TWA sampling methods were assessed over the same two day sampling time period. For spot sampling, replicate samples were taken at each site and analyzed within 12 h of sampling by both Headspace (HS- and direct (DI- solid phase microextraction (SPME sampling/extraction methods followed by Gas Chromatography/Mass Spectrometry (GC/MS. For TWA, a two day passive on-site TWA sampling was carried out at the same sampling points in the ponds. All SPME sampling methods undertaken used a 65-µm PDMS/DVB SPME fiber, which was found optimal for THM sampling. Sampling conditions were optimized in the laboratory using calibration standards of chloroform, bromoform, bromodichloromethane, dibromochloromethane, 1,2-dibromoethane and 1,2-dichloroethane, prepared in aqueous solutions from analytical grade samples. Calibration curves for all methods with R2 values ranging from 0.985–0.998 (N = 5 over the quantitation linear range of 3–800 ppb were achieved. The different sampling methods were compared for quantification of the water samples, and results showed that DI- and TWA- sampling methods gave better data and analytical metrics. Addition of 10% wt./vol. of (NH42SO4 salt to the sampling vial was found to aid extraction of THMs by increasing GC peaks areas by about 10%, which resulted in lower detection limits for all techniques studied. However, for on-site TWA analysis of THMs in natural waters, the calibration standard(s ionic strength conditions, must be carefully matched to natural water conditions to properly quantitate THM concentrations. The data obtained from the TWA method may better reflect actual natural water conditions.

  13. T-wave morphology analysis of competitive athletes

    DEFF Research Database (Denmark)

    Hong, L; Andersen, Lars Juel; Graff, Claus;

    2015-01-01

    the characteristics of T-wave morphology features in athletes. METHODS: Eighty male elite athletes, consisting of 40 Tour de France cyclists (age 27±5years), 40 soccer players (age 26±6years) and 40 healthy men (age 27±5years) were included. RESULTS: Sinus bradycardia, left ventricular (LV) hypertrophy, incomplete......BACKGROUND: T-wave morphology has been shown to be more sensitive than QT and QTc interval to describe repolarization abnormalities. The electrocardiogram (ECG) performed in athletes may manifest abnormalities, including repolarization alterations. The aim of this study was to investigate...... right bundle branch block and early repolarization were documented in 25 %, 20%, 13% and 14% of athletes, respectively. ECG criteria for LV hypertrophy in 12-lead ECG were more common in cyclists (35%) than in soccer players (5%), P

  14. The Construction, Enactment, and Maintenance of Power-as-Domination through an Acquisition: The Case of TWA and Ozark Airlines.

    Science.gov (United States)

    Pierce, Tamyra; Dougherty, Debbie S.

    2002-01-01

    Explores how domination was created, enacted, and maintained in the acquisition of Ozark Airlines by TWA. Uses the concepts of resources, hegemony, and resistance from the functionalist, Marxist, and postmodern traditions, respectively, to understand power-as-domination as a complex communication process. Reveals how communication practices were…

  15. Ca(2+)-activated chloride channel activity during Ca(2+) alternans in ventricular myocytes.

    Science.gov (United States)

    Kanaporis, Giedrius; Blatter, Lothar A

    2016-11-01

    Cardiac alternans, defined beat-to-beat alternations in contraction, action potential (AP) morphology or cytosolic Ca transient (CaT) amplitude, is a high risk indicator for cardiac arrhythmias. We investigated mechanisms of cardiac alternans in single rabbit ventricular myocytes. CaTs were monitored simultaneously with membrane currents or APs recorded with the patch clamp technique. A strong correlation between beat-to-beat alternations of AP morphology and CaT alternans was observed. During CaT alternans application of voltage clamp protocols in form of pre-recorded APs revealed a prominent Ca(2+)-dependent membrane current consisting of a large outward component coinciding with AP phases 1 and 2, followed by an inward current during AP repolarization. Approximately 85% of the initial outward current was blocked by Cl(-) channel blocker DIDS or lowering external Cl(-) concentration identifying it as a Ca(2+)-activated Cl(-) current (ICaCC). The data suggest that ICaCC plays a critical role in shaping beat-to-beat alternations in AP morphology during alternans.

  16. Characterization of Electrocardiogram Changes Throughout a Marathon

    Science.gov (United States)

    Callaway, Clifton; Salcido, David; McEntire, Serina; Roth, Ronald; Hostler, David

    2014-01-01

    Purpose There are few data examining cardiovascular physiology throughout a marathon. This study was devised to characterize electrocardiographic activity continuously throughout a marathon. Methods Cardiac activity was recorded from 19 subjects wearing a Holter monitor during a marathon. The 19 subjects (14 men and 5 women) were aged 39 ± 16 years (mean ± SD) and completed a marathon in 4:32:16 ± 1:23:35. Heart rate (HR), heart rate variability (HRV), T-wave amplitude, T-wave amplitude variability, and T-wave alternans (TWA) were evaluated continuously throughout the marathon. Results Averaged across all subjects, HRV, T-wave amplitude variability, and TWA increased throughout the marathon. Increased variability in T-wave amplitude occurred in 86% of subjects, characterized by complex oscillatory patterns and TWA. Three minutes after the marathon, HR was elevated and HRV was suppressed relative to the pre-marathon state. Conclusion HRV and T-wave amplitude variability, especially in the form of TWA, increase throughout a marathon. Increasing TWA as a marathon progresses likely represents a physiologic process as no arrhythmias or cardiac events were observed. PMID:24832192

  17. Calcium Alternans is Due to an Order-Disorder Phase Transition in Cardiac Cells

    Science.gov (United States)

    Alvarez-Lacalle, Enrique; Echebarria, Blas; Spalding, Jon; Shiferaw, Yohannes

    2015-03-01

    Electromechanical alternans is a beat-to-beat alternation in the strength of contraction of a cardiac cell, which can be caused by an instability of calcium cycling. Using a distributed model of subcellular calcium we show that alternans occurs via an order-disorder phase transition which exhibits critical slowing down and a diverging correlation length. We apply finite size scaling along with a mapping to a stochastic coupled map model, to show that this transition in two dimensions is characterized by critical exponents consistent with the Ising universality class. These findings highlight the important role of cooperativity in biological cells, and suggest novel approaches to investigate the onset of the alternans instability in the heart.

  18. Alternans in genetically modified Langendorff-perfused murine hearts modeling catecholaminergic polymorphic ventricular tachycardia

    Directory of Open Access Journals (Sweden)

    Ian N Sabir

    2010-10-01

    Full Text Available The relationship between alternans and arrhythmogenicity was studied in genetically modified murine hearts modeling catecholaminergic polymorphic ventricular tachycardia (CPVT during Langendorff perfusion, before and after treatment with catecholamines and a β-adrenergic antagonist. Heterozygous (RyR2p/s and homozygous (RyR2s/s RyR2-P2328S hearts, and wild-type (WT controls, were studied before and after treatment with epinephrine (100 nM and 1 µM and propranolol (100 nM. Monophasic action potential recordings demonstrated significantly greater incidences of arrhythmia in RyR2s/p and RyR2s/s hearts as compared to WTs. Arrhythmogenicity in RyR2s/s hearts was associated with alternans, particularly at short baseline cycle lengths. Both phenomena were significantly accentuated by treatment with epinephrine and significantly diminished by treatment with propranolol, in full agreement with clinical expectations. These changes took place, however, despite an absence of changes in action potential durations, ventricular effective refractory periods or restitution curve characteristics. Furthermore pooled data from all hearts in which arrhythmia occurred demonstrated significantly greater alternans magnitudes, but similar restitution curve slopes, to hearts that did not demonstrate arrhythmia. These findings thus further validate the RyR2-P2328S murine heart as a model for human CPVT, confirming an alternans phenotype in common with murine genetic models of the Brugada syndrome and the congenital long-QT syndrome type 3. In contrast to these latter similarities, however, this report demonstrates the dissociation of alternans from changes in the properties of restitution curves for the first time in a murine model of a human arrhythmic syndrome.

  19. Hyperthyroidism with dome-and-dart T wave: A case report

    Science.gov (United States)

    Lai, Ping; Yuan, Jing-ling; Xue, Jin-hua; Qiu, Yue-qun

    2017-01-01

    Abstract Rationale: Dome-and-dart T waves (or bifid T waves) are a rare phenomenon in the surface electrocardiogram. These wave forms are mainly observed in patients with congenital heart disease such as atrial septal defect and ventricular septal defect. And hyperthyroidism who presented with an electrocardiogram that had dome-and-dart T waves in a precordial lead is never been reported. Patient concerns: The patient presented with continuous tachycardia, palpitations, chest tightness, and headache for 4 days, and aggravated for 1 day. Diagnoses: Hyperthyroidism. Interventions: Methimazole. Outcomes: All symptoms were alleviated. Lessons: Dome-and-dart or bifid T waves have been reported in the conventional 12-lead electrocardiograms in some patients with congenital heart disease. The case illustrated here, to the best of our knowledge, dome-and-dart or bifid T waves may associate with hyperthyroidism patients. PMID:28178156

  20. Restitution analysis of alternans and its relationship to arrhythmogenicity in hypokalaemic Langendorff-perfused murine hearts.

    Science.gov (United States)

    Sabir, Ian N; Li, Lucia M; Grace, Andrew A; Huang, Christopher L-H

    2008-01-01

    Alternans and arrhythmogenicity were studied in hypokalaemic (3.0 mM K(+)) Langendorff-perfused murine hearts paced at high rates. Epicardial and endocardial monophasic action potentials were recorded and durations quantified at 90% repolarization. Alternans and arrhythmia occurred in hypokalaemic, but not normokalaemic (5.2 mM K(+)) hearts (Plidocaine (10 microM, Plidocaine was associated with decreased slopes. Thus, hypokalaemia significantly increased (Plidocaine had no significant effect (P>0.05) on either maximal gradients (0.78+/-0.27 in the epicardium and 0.83+/-0.45 in the endocardium) or critical DIs (6.06+/-2.10 ms and 7.04+/-3.82 ms in the endocardium), treatment of hypokalaemic hearts with lidocaine reduced (Pmechanism and that these phenomena are abolished by lidocaine, both recapitulating and clarifying clinical findings.

  1. Unidirectional Pinning and Hysteresis of Spatially Discordant Alternans in Cardiac Tissue

    CERN Document Server

    Skardal, Per Sebastian; Restrepo, Juan G

    2011-01-01

    Spatially discordant alternans is a widely observed pattern of voltage and calcium signals in cardiac tissue that can precipitate lethal cardiac arrhythmia. Using spatially coupled iterative maps of the beat-to-beat dynamics, we explore this pattern's dynamics in the regime of a calcium-dominated period-doubling instability at the single cell level. We find a novel nonlinear bifurcation associated with the formation of a discontinuous jump in the amplitude of calcium alternans at nodal lines separating discordant regions. We show that this jump unidirectionally pins nodal lines by preventing their motion away from the pacing site following a pacing rate decrease, but permitting motion towards this site following a rate increase. This unidirectional pinning leads to strongly history-dependent nodal line motion that is strongly arrhythmogenic.

  2. Memory in a fractional-order cardiomyocyte model alters properties of alternans and spontaneous activity

    Science.gov (United States)

    Comlekoglu, T.; Weinberg, S. H.

    2017-09-01

    Cardiac memory is the dependence of electrical activity on the prior history of one or more system state variables, including transmembrane potential (Vm), ionic current gating, and ion concentrations. While prior work has represented memory either phenomenologically or with biophysical detail, in this study, we consider an intermediate approach of a minimal three-variable cardiomyocyte model, modified with fractional-order dynamics, i.e., a differential equation of order between 0 and 1, to account for history-dependence. Memory is represented via both capacitive memory, due to fractional-order Vm dynamics, that arises due to non-ideal behavior of membrane capacitance; and ionic current gating memory, due to fractional-order gating variable dynamics, that arises due to gating history-dependence. We perform simulations for varying Vm and gating variable fractional-orders and pacing cycle length and measure action potential duration (APD) and incidence of alternans, loss of capture, and spontaneous activity. In the absence of ionic current gating memory, we find that capacitive memory, i.e., decreased Vm fractional-order, typically shortens APD, suppresses alternans, and decreases the minimum cycle length (MCL) for loss of capture. However, in the presence of ionic current gating memory, capacitive memory can prolong APD, promote alternans, and increase MCL. Further, we find that reduced Vm fractional order (typically less than 0.75) can drive phase 4 depolarizations that promote spontaneous activity. Collectively, our results demonstrate that memory reproduced by a fractional-order model can play a role in alternans formation and pacemaking, and in general, can greatly increase the range of electrophysiological characteristics exhibited by a minimal model.

  3. Evidence for Variable, Correlated X-ray and Optical/IR Extinction toward the Nearby, Pre-main Sequence Binary TWA 30

    CERN Document Server

    Principe, David A; Kastner, Joel H; Stelzer, Beate; Alcala, Juan

    2016-01-01

    We present contemporaneous XMM-Newton X-ray and ground-based optical/near-IR spectroscopic observations of the nearby ($D \\approx 42$ pc), low-mass (mid-M) binary system TWA 30A and 30B. The components of this wide (separation $\\sim$3400 AU) binary are notable for their nearly edge-on disk viewing geometries, high levels of variability, and evidence for collimated stellar outflows. We obtained XMM-Newton X-ray observations of TWA 30A and 30B in 2011 June and July, accompanied (respectively) by IRTF SpeX (near-IR) and VLT XSHOOTER (visible/near-IR) spectroscopy obtained within $\\sim$20 hours of the X-ray observations. TWA 30A was detected in both XMM-Newton observations at relatively faint intrinsic X-ray luminosities ($L_{X}$$\\sim$$8\\times10^{27}$ $erg$ $s^{-1}$) compared to stars of similar mass and age . The intrinsic (0.15-2.0 keV) X-ray luminosities measured in 2011 had decreased by a factor 20-100 relative to a 1990 (ROSAT) X-ray detection. TWA 30B was not detected, and we infer an upper limit of ($L_{X}...

  4. Elastic parabolic equation solutions for oceanic T-wave generation and propagation from deep seismic sources.

    Science.gov (United States)

    Frank, Scott D; Collis, Jon M; Odom, Robert I

    2015-06-01

    Oceanic T-waves are earthquake signals that originate when elastic waves interact with the fluid-elastic interface at the ocean bottom and are converted to acoustic waves in the ocean. These waves propagate long distances in the Sound Fixing and Ranging (SOFAR) channel and tend to be the largest observed arrivals from seismic events. Thus, an understanding of their generation is important for event detection, localization, and source-type discrimination. Recently benchmarked seismic self-starting fields are used to generate elastic parabolic equation solutions that demonstrate generation and propagation of oceanic T-waves in range-dependent underwater acoustic environments. Both downward sloping and abyssal ocean range-dependent environments are considered, and results demonstrate conversion of elastic waves into water-borne oceanic T-waves. Examples demonstrating long-range broadband T-wave propagation in range-dependent environments are shown. These results confirm that elastic parabolic equation solutions are valuable for characterization of the relationships between T-wave propagation and variations in range-dependent bathymetry or elastic material parameters, as well as for modeling T-wave receptions at hydrophone arrays or coastal receiving stations.

  5. Evidence for variable, correlated X-ray and optical/IR extinction towards the nearby, pre-main-sequence binary TWA 30

    Science.gov (United States)

    Principe, David A.; Sacco, G.; Kastner, J. H.; Stelzer, B.; Alcalá, J. M.

    2016-06-01

    We present contemporaneous XMM-Newton X-ray and ground-based optical/near-IR spectroscopic observations of the nearby (D ≈ 42 pc), low-mass (mid-M) binary system TWA 30A and 30B. The components of this wide (separation ˜3400 au) binary are notable for their nearly edge-on disc viewing geometries, high levels of variability, and evidence for collimated stellar outflows. We obtained XMM-Newton X-ray observations of TWA 30A and 30B in 2011 June and July, accompanied (respectively) by Infrared Telescope Facility SpeX (near-IR) and VLT XSHOOTER (visible/near-IR) spectroscopy obtained within ˜20 h of the X-ray observations. TWA 30A was detected in both XMM-Newton observations at relatively faint intrinsic X-ray luminosities (LX ˜ 8 × 1027 erg s-1) compared to stars of similar mass and age. The intrinsic (0.15-2.0 keV) X-ray luminosities measured in 2011 had decreased by a factor 20-100 relative to a 1990 (ROSAT) X-ray detection. TWA 30B was not detected, and we infer an upper limit on its X-ray Luminosity of LX ≲ 3.0 × 1027 erg s-1. We measured a decrease in visual extinction towards TWA 30A (from AV ≈ 14.9 to AV ≈ 4.7) between the two 2011 observing epochs, and we find evidence for a corresponding significant decrease in X-ray absorbing column (NH). The apparent correlated change in AV and NH is suggestive of variable obscuration of the stellar photosphere by disc material composed of both gas and dust. However, in both observations, the inferred NH to AV ratio is lower than that typical of the interstellar medium, suggesting that the disc is either depleted of gas or is deficient in metals in the gas phase.

  6. Functional data analytic approach of modeling ECG T-wave shape to measure cardiovascular behavior

    CERN Document Server

    Zhou, Yingchun; 10.1214/09-AOAS273

    2010-01-01

    The T-wave of an electrocardiogram (ECG) represents the ventricular repolarization that is critical in restoration of the heart muscle to a pre-contractile state prior to the next beat. Alterations in the T-wave reflect various cardiac conditions; and links between abnormal (prolonged) ventricular repolarization and malignant arrhythmias have been documented. Cardiac safety testing prior to approval of any new drug currently relies on two points of the ECG waveform: onset of the Q-wave and termination of the T-wave; and only a few beats are measured. Using functional data analysis, a statistical approach extracts a common shape for each subject (reference curve) from a sequence of beats, and then models the deviation of each curve in the sequence from that reference curve as a four-dimensional vector. The representation can be used to distinguish differences between beats or to model shape changes in a subject's T-wave over time. This model provides physically interpretable parameters characterizing T-wave sh...

  7. Measuring the mass of a pre-main sequence binary star through the orbit of TWA5A

    Energy Technology Data Exchange (ETDEWEB)

    Konopacky, Q; Ghez, A; Duchene, G; McCabe, C; Macintosh, B

    2007-01-18

    We present the results of a five year monitoring campaign of the close binary TWA 5Aab in the TW Hydrae association, using speckle and adaptive optics on the W.M. Keck 10 m telescopes. These measurements were taken as part of our ongoing monitoring of pre-main sequence (PMS) binaries in an effort to increase the number of dynamically determined PMS masses and thereby calibrate the theoretical PMS evolutionary tracks. Our observations have allowed us to obtain the first determination of this system's astrometric orbit. We find an orbital period of 5.94 {+-} 0.09 years and a semi-major axis of 0.''066 {+-} 0.''005. Combining these results with a kinematic distance, we calculate a total mass of 0.71 {+-} 0.14 M{sub {circle_dot}} (D/44 pc){sup 3}. for this system. This mass measurement, as well as the estimated age of this system, are consistent to within 2{sigma} of all theoretical models considered. In this analysis, we properly account for correlated uncertainties, and show that while these correlations are generally ignored, they increase the formal uncertainties by up to a factor of five and therefore are important to incorporate. With only a few more years of observation, this type of measurement will allow the theoretical models to be distinguished.

  8. A Large X-ray Flare from a Single Weak-lined T Tauri Star TWA-7 Detected with MAXI GSC

    CERN Document Server

    Uzawa, Akiko; Morii, Mikio; Yamazaki, Kyohei; Kawai, Nobuyuki; Matsuoka, Masaru; Nakahira, Satoshi; Serino, Motoko; Matsumura, Takanori; Mihara, Tatehiro; Tomida, Hiroshi; Ueda, Yoshihiro; Sugizaki, Mutsumi; Ueno, Shiro; Daikyuji, Arata; Ebisawa, Ken; Eguchi, Satoshi; Hiroi, Kazuo; Ishikawa, Masaki; Isobe, Naoki; Kawasaki, Kazuyoshi; Kimura, Masashi; Kitayama, Hiroki; Kohama, Mitsuhiro; Kotani, Taro; Nakagawa, Yujin E; Nakajima, Motoki; Negoro, Hitoshi; Ozawa, Hiroshi; Shidatsu, Megumi; Sootome, Tetsuya; Sugimori, Kousuke; Suwa, Fumitoshi; Tsunemi, Hiroshi; Usui, Ryuichi; Yamamoto, Takayuki; Yamaoka, Kazutaka; Yoshida, Atsumasa

    2011-01-01

    We present a large X-ray flare from a nearby weak-lined T Tauri star TWA-7 detected with the Gas Slit Camera (GSC) on the Monitor of All-sky X-ray Image (MAXI). The GSC captured X-ray flaring from TWA-7 with a flux of $3\\times10^{-9}$ ergs cm$^{-2}$ s$^{-1}$ in 2--20 keV band during the scan transit starting at UT 2010-09-07 18:24:30.The estimated X-ray luminosity at the scan in the energy band is 3$\\times10^{32}$ ergs s$^{-1}$,indicating that the event is among the largest X-ray flares fromT Tauri stars.Since MAXI GSC monitors a target only during a scan transit of about a minute per 92 min orbital cycle, the luminosity at the flare peak might have been higher than that detected. At the scan transit, we observed a high X-ray-to-bolometric luminosity ratio, log $L_{\\rm X}/L_{\\rm bol}$ = $-0.1^{+0.2}_{-0.3}$; i.e., the X-ray luminosity is comparable to the bolometric luminosity. Since TWA-7 has neither an accreting disk nor a binary companion, the observed event implies that none of those are essential to gene...

  9. Triangulation of the monophasic action potential causes flattening of the electrocardiographic T-wave

    DEFF Research Database (Denmark)

    Bhuiyan, Tanveer Ahmed; Graff, Claus; Thomsen, Morten Bækgaard

    2012-01-01

    of the action potential under the effect of the IKr blocker sertindole and associated these changes to concurrent changes in the morphology of electrocardiographic T-waves in dogs. We show that, under the effect of sertindole, the peak changes in the morphology of action potentials occur at time points similar...

  10. Validation of a simple model for the morphology of the T wave in unipolar electrograms

    NARCIS (Netherlands)

    Potse, Mark; Vinet, Alain; Opthof, Tobias; Coronel, Ruben

    2009-01-01

    Potse M, Vinet A, Opthof T, Coronel R. Validation of a simple model for the morphology of the T wave in unipolar electrograms. Am J Physiol Heart Circ Physiol 297: H792-H801, 2009. First published May 22, 2009; doi: 10.1152/ajpheart.00064.2009.-Local unipolar electrograms (UEGs) permit assessment of

  11. Supernormal Conduction and Suppression of Spatial Discord in Alternans of Cardiac Action Potentials

    Directory of Open Access Journals (Sweden)

    Linyuan eJing

    2016-01-01

    Full Text Available Spatially discordant alternans (DA of action potential durations (APD is thought to be more pro-arrhythmic than concordant alternans. Super normal conduction (SNC has been reported to suppress formation of DA. An increase in conduction velocity (CV as activation rate increases, i.e. a negative CV restitution, is widely considered as hallmark of SNC. Our aim in this study is to show that it is not an increase in CV for faster rates that prevents formation of DA, rather, it is the ratio of the CV for the short relative to the long activation that is critical in DA suppression. To illustrate this subtlety, we simulated this phenomenon using two approaches; (1 by using the standard, i.e. S1S2 protocol to quantify restitution and disabling the slow inactivation gate j of the sodium current (INa, and (2 by using the dynamic, i.e. S1S1 protocol for quantification of restitution and increasing INa at different cycle lengths (CL. Even though both approaches produced similar CV restitution curves, DA was suppressed only during the first approach, where the CV of the short of the long-short action potential (AP pattern was selectively increased. These results show that negative CV restitution, which is considered characteristic of SNC, per se, is not causal in suppressing DA, rather, the critical factor is a change in the ratio of the velocities of the short and the long APs.

  12. Supernormal Conduction and Suppression of Spatially Discordant Alternans of Cardiac Action Potentials.

    Science.gov (United States)

    Jing, Linyuan; Agarwal, Anuj; Patwardhan, Abhijit

    2015-01-01

    Spatially discordant alternans (DA) of action potential durations (APD) is thought to be more pro-arrhythmic than concordant alternans. Super normal conduction (SNC) has been reported to suppress formation of DA. An increase in conduction velocity (CV) as activation rate increases, i.e., a negative CV restitution, is widely considered as hallmark of SNC. Our aim in this study is to show that it is not an increase in CV for faster rates that prevents formation of DA, rather, it is the ratio of the CV for the short relative to the long activation that is critical in DA suppression. To illustrate this subtlety, we simulated this phenomenon using two approaches; (1) by using the standard, i.e., S1S2 protocol to quantify restitution and disabling the slow inactivation gate j of the sodium current (INa), and (2) by using the dynamic, i.e., S1S1 protocol for quantification of restitution and increasing INa at different cycle lengths (CL). Even though both approaches produced similar CV restitution curves, DA was suppressed only during the first approach, where the CV of the short of the long-short action potential (AP) pattern was selectively increased. These results show that negative CV restitution, which is considered characteristic of SNC, per se, is not causal in suppressing DA, rather, the critical factor is a change in the ratio of the velocities of the short and the long APs.

  13. Mechanisms of arrhythmogenesis related to calcium-driven alternans in a model of human atrial fibrillation

    Science.gov (United States)

    Chang, Kelly C.; Trayanova, Natalia A.

    2016-11-01

    The occurrence of atrial fibrillation (AF) is associated with progressive changes in the calcium handling system of atrial myocytes. Calcium cycling instability has been implicated as an underlying mechanism of electrical alternans observed in patients who experience AF. However, the extent to which calcium-induced alternation of electrical activity in the atria contributes to arrhythmogenesis is unknown. In this study, we investigated the effects of calcium-driven alternans (CDA) on arrhythmia susceptibility in a biophysically detailed, 3D computer model of the human atria representing electrical and structural remodeling secondary to chronic AF. We found that elevated propensity to CDA rendered the atria vulnerable to ectopy-induced arrhythmia. It also increased the complexity and persistence of arrhythmias induced by fast pacing, with unstable scroll waves meandering and frequently breaking up to produce multiple wavelets. Our results suggest that calcium-induced electrical instability may increase arrhythmia vulnerability and promote increasing disorganization of arrhythmias in the chronic AF-remodeled atria, thus playing an important role in the progression of the disease.

  14. T-wave morphology can distinguish healthy controls from LQTS patients.

    Science.gov (United States)

    Immanuel, S A; Sadrieh, A; Baumert, M; Couderc, J P; Zareba, W; Hill, A P; Vandenberg, J I

    2016-09-01

    Long QT syndrome (LQTS) is an inherited disorder associated with prolongation of the QT/QTc interval on the surface electrocardiogram (ECG) and a markedly increased risk of sudden cardiac death due to cardiac arrhythmias. Up to 25% of genotype-positive LQTS patients have QT/QTc intervals in the normal range. These patients are, however, still at increased risk of life-threatening events compared to their genotype-negative siblings. Previous studies have shown that analysis of T-wave morphology may enhance discrimination between control and LQTS patients. In this study we tested the hypothesis that automated analysis of T-wave morphology from Holter ECG recordings could distinguish between control and LQTS patients with QTc values in the range 400-450 ms. Holter ECGs were obtained from the Telemetric and Holter ECG Warehouse (THEW) database. Frequency binned averaged ECG waveforms were obtained and extracted T-waves were fitted with a combination of 3 sigmoid functions (upslope, downslope and switch) or two 9th order polynomial functions (upslope and downslope). Neural network classifiers, based on parameters obtained from the sigmoid or polynomial fits to the 1 Hz and 1.3 Hz ECG waveforms, were able to achieve up to 92% discrimination between control and LQTS patients and 88% discrimination between LQTS1 and LQTS2 patients. When we analysed a subgroup of subjects with normal QT intervals (400-450 ms, 67 controls and 61 LQTS), T-wave morphology based parameters enabled 90% discrimination between control and LQTS patients, compared to only 71% when the groups were classified based on QTc alone. In summary, our Holter ECG analysis algorithms demonstrate the feasibility of using automated analysis of T-wave morphology to distinguish LQTS patients, even those with normal QTc, from healthy controls.

  15. Quantitative Determination of Salicylaldehyde in the Scent Fluid of Calosoma macrum, C. alternans sayi, C. affine, and C. parvicollis (Coleoptera: Carabidae)

    National Research Council Canada - National Science Library

    MCCULLOUGH, THOMAS

    1966-01-01

    ... (McCullough and Weinheimer 1966), I have collected and investigated 4 more species: C. macrum (LeConte), C. alternans sayi (Dejean), C. affine (Chaudoir), and C. parvicollis (Fall). The last named was taken in Lone Pine, Calif...

  16. Flattening of the electrocardiographic T-wave is a sign of proarrhythmic risk and a reflection of action potential triangulation

    DEFF Research Database (Denmark)

    Bhuiyan, Tanveer Ahmed; Graff, Claus; Kanters, J.K.;

    2013-01-01

    Drug-induced triangulation of the cardiac action potential is associated with increased risk of arrhythmic events. It has been suggested that triangulation causes a flattening of the electrocardiographic T-wave but the relationship between triangulation, T-wave flattening and onset of arrhythmia...

  17. Heritability of Tpeak-Tend Interval and T-wave Amplitude: A Twin Study

    DEFF Research Database (Denmark)

    Haarmark, Christian; Kyvik, Kirsten O; Vedel-Larsen, Esben;

    2011-01-01

    BACKGROUND: -Tpeak-Tend interval (TpTe) and T-wave amplitude (Tamp) carry diagnostic and prognostic information regarding cardiac morbidity and mortality. Heart rate and QT interval are known to be heritable traits. The heritability of T-wave morphology parameters such as TpTe and Tamp is unknown....... TpTe and Tamp were evaluated in a large sample of twins. METHODS AND RESULTS: -Twins from the GEMINAKAR study (611 pairs, 246 monozygotic, 365 dizygotic, aged 38±11 years, 49 % men) who had an ECG performed during 1997-2000 were included. Tamp was measured in leads V1 and V5. Duration variables (RR...... are heritable ECG parameters....

  18. Distribution of Action Potential Duration and T-wave Morphology: a Simulation Study

    CERN Document Server

    Ryzhii, Elena; Wei, Daming

    2009-01-01

    The results of a simulation study of the action potential duration (APD) distribution and T-wave morphology taking into account the midmyocardial cells (M-cells) concept are described. To investigate the effect of M-cells we present a computer model in which ion channel action potential formulations are incorporated into three-dimensional whole heart model. We implemented inhomogeneous continuous action potential duration distribution based on different distributions of maximal slow delayed rectifier current conductance. Using the proposed action potential distribution procedure midmural zeniths with longest action potential length were created as islands of model cells in the depth of thickest areas of ventricular tissue. Different spatial functions on layer indexes were simulated and their influences on electrocardiogram waveforms were analyzed. Changing parameters of ion channel model we varied duration of minimal and maximal action potential and investigated T-wave amplitude, Q-Tpeak and QT intervals vari...

  19. A new approach based on the median filter to T-wave detection in ECG signal.

    Science.gov (United States)

    Kholkhal, Mourad; Bereksi Reguig, Fethi

    2014-07-01

    The electrocardiogram (ECG) is one of the most used signals in the diagnosis of heart disease. It contains different waves which directly correlate to heart activity. Different methods have been used in order to detect these waves and consequently lead to heart activity diagnosis. This paper is interested more particularly to the detection of the T-wave. Such a wave represents the re-polarization state of the heart activity. The proposed approach is based on the algorithm procedure which allows the detection of the T-wave using a lot of filter including mean and median filter. The proposed algorithm is implemented and tested on a set of ECG recordings taken from, respectively, the European STT, MITBIH and MITBIH ST databases. The results are found to be very satisfactory in terms of sensitivity, predictivity and error compared to other works in the field.

  20. Effects of bilastine on T-wave morphology and the QTc interval

    DEFF Research Database (Denmark)

    Graff, Claus; Struijk, Johannes; Kanters, Jørgen K.;

    2012-01-01

    The International Conference of Harmonisation (ICH) E14 guideline for thorough QT studies requires assessing the propensity of new non-antiarrhythmic drugs to affect cardiac repolarization. The present study investigates whether a composite ECG measure of T-wave morphology (Morphology Combination...... Score [MCS]) can be used together with the heart rate corrected QT interval (QTc) in a fully ICH E14-compliant thorough QT study to exclude clinically relevant repolarization effects of bilastine, a novel antihistamine....

  1. Beat-to-beat T-wave amplitude variability in the long QT syndrome.

    Science.gov (United States)

    Extramiana, Fabrice; Tatar, Charif; Maison-Blanche, Pierre; Denjoy, Isabelle; Messali, Anne; Dejode, Patrick; Iserin, Frank; Leenhardt, Antoine

    2010-09-01

    Long QT syndrome (LQTS) is a primary electrical disease characterized by QT prolongation and increased repolarization dispersion leading to T-wave amplitude beat-to-beat changes. We aimed to quantify beat-to-beat T-wave amplitude variability from ambulatory Holter recordings in genotyped LQTS patients. Seventy genotyped LQTS patients (mean age 23 +/- 15 years, 42 males, 50% LQT1, 39% LQT2, and 11% LQT3) and 70 normal matched control subjects underwent a 24-h digital Holter recording. Using the Tvar software (Ela Medical, Sorin group), the beat-to-beat variance of the T-wave amplitude (TAV in microV) [corrected] was assessed on 50-ms consecutive clusters during three 1-h periods: one with around average diurnal heart rate (Day Fast), one nocturnal period (Night), and one diurnal period with around average nocturnal heart rate (Day Slow). TAV was increased in LQTS patients during the two diurnal periods but not at night (during the Day Fast period, mean TAV was 34 +/- 20 microV [corrected] in LQTS patients vs. 27 +/- 10 microV [corrected] in controls, P < 0.05). This effect depended on the genotype. In LQT1, TAV was larger when compared with controls for both Day Fast and Slow periods, but in LQT2 only Day Fast shows higher TAV. Oppositely, in LQT3 the TAV was higher than in the control group during the Day slow period (mean TAV = 34 +/- 20 vs. 25 +/- 8 microV [corrected] in controls, P < 0.05). In genotyped LQTS patients beat-to-beat T-wave amplitude variability was increased when compared with control subjects. That pattern was modulated by circadian influences in a gene-dependent manner.

  2. Design of Microvolt T Wave Alternans Detecting System Based on Wireless and USB Communication%基于USB及无线传输的微伏T波电位交替检测系统设计

    Institute of Scientific and Technical Information of China (English)

    黄莉洁; 杨圣; 刘爱军; 王亚军

    2008-01-01

    本文介绍了一个基于无线传输和USB接口相结合的T波电交替检测系统的设计.该系统首先对心电信号进行放大,放大器放大倍数为2000倍,共模抑制比为80db.放大后的信号经过12位AD采样再经过无线传输和USB总线传输到JPC处理端.在处理端,利用谱分析方法对T波交替进行检测.实验结果表明,该系统具有高数据传输速率和实时数据处理能力,能够实现微伏T波电交替的测定.

  3. Coexisting chaotic and multi-periodic dynamics in a model of cardiac alternans

    Energy Technology Data Exchange (ETDEWEB)

    Skardal, Per Sebastian, E-mail: skardals@gmail.com [Departament d' Enginyeria Informàtica i Matemàtiques, Universitat Rovira i Virgili, 43007 Tarragona (Spain); Restrepo, Juan G., E-mail: juanga@colorado.edu [Department of Applied Mathematics, University of Colorado, Boulder, Colorado 80309 (United States)

    2014-12-15

    The spatiotemporal dynamics of cardiac tissue is an active area of research for biologists, physicists, and mathematicians. Of particular interest is the study of period-doubling bifurcations and chaos due to their link with cardiac arrhythmogenesis. In this paper, we study the spatiotemporal dynamics of a recently developed model for calcium-driven alternans in a one dimensional cable of tissue. In particular, we observe in the cable coexistence of regions with chaotic and multi-periodic dynamics over wide ranges of parameters. We study these dynamics using global and local Lyapunov exponents and spatial trajectory correlations. Interestingly, near nodes—or phase reversals—low-periodic dynamics prevail, while away from the nodes, the dynamics tend to be higher-periodic and eventually chaotic. Finally, we show that similar coexisting multi-periodic and chaotic dynamics can also be observed in a detailed ionic model.

  4. Coexisting chaotic and multi-periodic dynamics in a model of cardiac alternans

    CERN Document Server

    Skardal, Per Sebastian

    2014-01-01

    The spatiotemporal dynamics of cardiac tissue is an active area of research for biologists, physicists, and mathematicians. Of particular interest is the study of period-doubling bifurcations and chaos due to their link with cardiac arrhythmogenesis. In this paper we study the spatiotemporal dynamics of a recently developed model for calcium-driven alternans in a one dimensional cable of tissue. In particular, we observe in the cable coexistence in of regions with chaotic and multi-periodic dynamics over wide ranges of parameters. We study these dynamics using global and local Lyapunov exponents and spatial trajectory correlations. Interestingly, near nodes -- or phase reversals -- low-periodic dynamics prevail, while away from the nodes the dynamics tend to be higher-periodic and eventually chaotic.

  5. Observations of Earthquake-Generated T-Waves in the South China Sea: Possible Applications for Regional Seismic Monitoring

    Directory of Open Access Journals (Sweden)

    Bor-Shouh Huang

    2013-01-01

    Full Text Available We present a detailed study of T-waves originating from earthquakes in the South China Sea region, near the Indochina Peninsula and Luzon islands which were recorded by a broadband seismic station at Nansha Island. Most of these T-waves appear to have been the source originating from earthquakes with epicentral distances greater than 600 km from this station. The T-waves in this region were identified via their apparent stable measured velocities of about 1.45 km s-1, and represent the first reported T-waves and the first T-waves observed from an island station in the South China Sea. However, during the period of analysis (November 2004 to December 2005 additional earthquakes also occurred beyond the South China Sea region, but in these instances, any associated T-waves were not picked up by the station at Nansha Island. An analysis of T-wave travel times reveals the possible locations of the P-wave to T-wave transitions at the ocean to crust interface were presumably situated near the earthquake source side. Our results indicate that the Sound Fixing and Ranging (SOFAR channel is well developed in the South China Sea region. Ultimately, developing a solid understanding of the effective transmission of T-waves through the ocean may provide new opportunities for detecting and locating small earthquakes which would be useful for both seismic monitoring and in helping to predict and reduce the damaging effects of earthquakes and tsunamis in the SouthChina Sea region.

  6. Observations of Earthquake-Generated T-Waves in the South China Sea: Possible Applications for Regional Seismic Monitoring

    Directory of Open Access Journals (Sweden)

    Bor-Shouh Huang

    2013-01-01

    Full Text Available We present a detailed study of T-waves originating from earthquakes in the South China Sea region, near the Indochina Peninsula and Luzon islands which were recorded by a broadband seismic station at Nansha Island. Most of these T-waves appear to have been the source originating from earthquakes with epicentral distances greater than 600 km from this station. The T-waves in this region were identified via their apparent stable measured velocities of about 1.45 km s-1, and represent the first reported T-waves and the first T-waves observed from an island station in the South China Sea. However, during the period of analysis (November 2004 to December 2005 additional earthquakes also occurred beyond the South China Sea region, but in these instances, any associated T-waves were not picked up by the station at Nansha Island. An analysis of T-wave travel times reveals the possible locations of the P-wave to T-wave transitions at the ocean to crust interface were presumably situated near the earthquake source side. Our results indicate that the Sound Fixing and Ranging (SOFAR channel is well developed in the South China Sea region. Ultimately, developing a solid understanding of the effective transmission of T-waves through the ocean may provide new opportunities for detecting and locating small earthquakes which would be useful for both seismic monitoring and in helping to predict and reduce the damaging effects of earthquakes and tsunamis in the South China Sea region.

  7. Observing the planet formation time-scale by ground-based direct imaging of planetary companions to young nearby stars Gemini\\/Hokupa'a image of TWA-5

    CERN Document Server

    Neuhäuser, R; Brandner, W; Neuhaeuser, Ralph; Potter, Dan; Brandner, Wolfgang

    2001-01-01

    Many extra-solar planets and a few planetary systems have been found indirectly by small periodic radial velocity variations around old nearby stars. The orbital characteristics of most of them are different from the planets in our solar system. Hence, planet formation theories have to be revised. Therefore, observational constraints regarding young planets would be very valuable. We have started a ground-based direct imaging search for giant planets in orbit around young nearby stars. Here, we will motivate the sample selection and will present our direct imaging observation of the very low-mass (15 to 40 Jupiter masses) brown dwarf companion TWA-5 B in orbit around the nearby young star TWA-5 A, recently obtained with the 36-element curvature-sensing AO instrument Hokupa'a of the University of Hawai'i at the 8.3m Gemini-North telescope on Mauna Kea. We could achieve a FWHM of 64 mas and 25 % Strehl. We find significance evidence for orbital motion of B around A.

  8. Classification of the long-QT syndrome based on discriminant analysis of T-wave morphology

    DEFF Research Database (Denmark)

    Struijk, Johannes; Kanters, J.K.; Andersen, Mads Peter

    2006-01-01

    been shown to be useful discriminators, but no single ECG parameter has been sufficient to solve the diagnostic problem. In this study we present a method for discrimination among persons with a normal genotype and those with mutations in the KCNQ1 (KvLQT1 or LQT1) and KCNH2 (HERG or LQT2) genes...... on the basis of parameters describing T-wave morphology in terms of duration, asymmetry, flatness and amplitude. Discriminant analyses based on 4 or 5 parameters both resulted in perfect discrimination in a learning set of 36 subjects. In both cases cross-validation of the resulting classifiers showed...

  9. New descriptors of T-wave morphology are independent of heart rate

    DEFF Research Database (Denmark)

    Andersen, Mads Peter; Xue, Joel Q; Graff, Claus;

    2008-01-01

    by means of analysis of covariance. The results showed clear heart rate dependence for the QT interval (R(2) = 0.53-0.57) and a moderate degree of heart rate dependence for the basic morphology parameters (amplitude, area, and others) (R(2) = 0.17-0.42). Both the advanced T-wave descriptors (asymmetry......, flatness, and others), ToTe intervals and TpTe intervals, were practically independent of heart rate (R(2) = 0-0.08), making heart rate correction unnecessary for these parameters....

  10. Electrocardiographic differentiation between acute coronary syndrome and acute pulmonary embolism associated with inverted T waves in precordial leads

    Institute of Scientific and Technical Information of China (English)

    ZHAN Zhong-qun; WANG Chong-quan; HE Chao-rong; WANG Zhi-xiao; MAO Shan

    2010-01-01

    Background Inverted T waves in precordial leads are often seen in patients with acute pulmonary embolism (APE) and acute coronary syndrome (ACS). The purpose of this study was to analyze the electrocardiogram (ECG) difference between APE and ACS related inverted T waves in precordial leads. Methods The ECG difference among 62 patients with APE and 125 patients with ACS related inverted T waves in precordial leads were compared. Results Compared with ACS, Patients with APE were more frequently associated with incomplete or complete RBBB or slurred S wave in lead V1, the sum of the depth of inverted T waves in leads V1 and V2 not less than in lead V3 and V4 (inverted TV1 + V2 ≥ inverted TV3 + V4), and inverted T waves in leads V1 and Ⅲ. Conclusions Complete or incomplete RBBB or slurred S wave in lead V1, inverted T waves in leads V1 and III, and inverted TV1 + V2 ≥ inverted TV3 + V4 are useful criteria for predicting APE.

  11. Prognostic Implications of Newly Developed T-Wave Inversion After Primary Percutaneous Coronary Intervention in Patients With ST-Segment Elevation Myocardial Infarction.

    Science.gov (United States)

    Lee, Man-Jong; Jang, Ji-Hoon; Lee, Myung-Dong; Kwon, Sung Woo; Shin, Sung-Hee; Park, Sang-Don; Woo, Seong-Ill; Kim, Dae-Hyeok; Kwan, Jun; Park, Keum-Soo

    2017-02-15

    We investigated the prognostic value of newly developed T-wave inversion after primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction. New T-wave inversion was defined as new onset of T-wave inversion after the primary PCI, without negative T waves on the presenting electrocardiogram. The primary end point was the occurrence of major adverse cardiac events (MACE), which consisted of cardiovascular mortality, nonfatal myocardial infarction, and rehospitalization for heart failure. A total of 271 patients were analyzed and followed up for 24 months in this study. New T-wave inversion was observed in 194 patients (72%), whereas the remaining 77 patients (28%) did not show T-wave inversion after the index PCI. Post-PCI Thrombolysis In Myocardial Infarction flow grade 2 or 3 was observed more frequently in patients with new T-wave inversion (97% vs 90%; p = 0.011). The cumulative MACE rate was significantly lower in patients with new T-wave inversion than in those without new T-wave inversion (8% vs 30%; odds ratio 0.197, 95% confidential interval 0.096 to 0.403; p wave inversion was an independent prognostic factor for MACE (hazard ratio 0.297, 95% confidential interval 0.144 to 0.611; p = 0.001). In conclusion, newly developed T-wave inversion after primary PCI was associated with favorable long-term outcome.

  12. Observations of polarized seismoacoustic T waves at and beneath the seafloor in the abyssal Pacific ocean.

    Science.gov (United States)

    Butler, Rhett

    2006-12-01

    Combined seismic and hydrophone observations show that the traditional T wave propagates as a seismoacoustic polarized interface wave (Ti) coupled to the seafloor. Seismoacoustic Ti waves propagating at the sound speed of water are routinely observed over megameter distances at the deep (4979 m) seafloor Hawaii-2 Observatory (H2O) between Hawaii and California, even though the seafloor site is within a shadow zone for acoustic wave propagation. Ti has also been observed on seismometers 225 km SSW of Oahu at the OSN1 site at the seafloor and within an ODP borehole into the basalt basement. Analyses of timing, apparent velocity, energy, and polarization of these interface waves are presented. At low frequency (waves. At higher frequencies the observed Ti waves dominantly propagate acoustically with characteristics suggesting local scattering. The observation of Ti from an earthquake in Guatemala at OSN1, whose path is blocked by the Island of Hawaii, is consistent with scattering from the vicinity of the Cross Seamount.

  13. New and Improved T-wave Morphology Parameters to Differentiate Healthy Individuals from those with Cardiomyopathy and Coronary Artery Disease

    Science.gov (United States)

    Greco, E. C.; Schlegel, T. T.; Arenare, B.; DePalma, J. L.; Starc, V.; Rahman, M. A.; Delgado, R.

    2007-01-01

    We investigated the ability of several known as well as new ECG repolarization parameters to differentiate healthy individuals from patients with obstructive coronary artery disease (CAD) and cardiomyopathy (CM). Advanced high-fidelity 12-lead ECG tests (approx. 5-min supine) were first performed on a "training set" of 99 individuals: 33 with ischemic or dilated CM and low ejection fraction (EF less than 40%); 33 with catheterization-proven obstructive CAD but normal EF; and 33 age-/gender-matched healthy controls. The following multiple parameters of T-wave morphology (TWM) were derived via signal averaging and singular value decomposition (SVD, which yields 8 eigenvalues, rho(sub 1) greater than rho(sub 2)...greater than rho(sub 8) and studied for their retrospective accuracy in detecting underlying disease: 1) Principal component analysis ratio of the T wave (T-PCA) = 100*rho(sub 2)/rho(sub 1); 2) Relative T-wave residuum (rTWR) = 100* SIGMA (rho(sub 4)(sup 2) +...+ rho(sub 8)(sup 2)); 3) Modified complexity ratio of the T wave (T-mCR) = 100*SIGMA(rho(sub 3)(sup 2) +...+rho(sb 8) (sup 2)); and 4) Normalized 3-dimensional volume of the T wave (nTV) = 100*(rho(sub 2)*rho(sub 3)/rho(sub 1)(sup 2). All TWM parameters significantly differentiated CAD from controls (p less than 0.0001), and also CM from controls (p less than 0.0001). Retrospective areas under the ROC curve were 0.77, 0.81, 0.82, and 0.83 (CAD vs. controls) and 0.93, 0.89, 0.95 and 0.96 (CM vs. controls) for T-PCA, rTWR, T-mCR and nTV respectively. The newer TWM parameters (T-mCR and nTV) thus outperformed the more established parameters (T-PCA and rTWR), presumably by putting a greater emphasis on the third T-wave eigenvalue, which in most healthy subjects has little energy compared to the first two eigenvalues. Subsequent prospective analyses have also yielded similar results, such that we conclude that diagnostic differentiation of pathology from non-pathology may be especially aided by detecting

  14. Assessing common classification methods for the identification of abnormal repolarization using indicators of T-wave morphology and QT interval

    DEFF Research Database (Denmark)

    Shakibfar, Saeed; Graff, Claus; Ehlers, Lars Holger;

    2012-01-01

    volunteers and LQT2 carriers were used to train classification algorithms using measures of T-wave morphology and QTc. The ability to correctly classify a third group of test subjects before and after receiving d,l-sotalol was evaluated using classification rules derived from training. As a single......Various parameters based on QTc and T-wave morphology have been shown to be useful discriminators for drug induced I(Kr)-blocking. Using different classification methods this study compares the potential of these two features for identifying abnormal repolarization on the ECG. A group of healthy...

  15. Islands of spatially discordant APD alternans underlie arrhythmogenesis by promoting electrotonic dyssynchrony in models of fibrotic rat ventricular myocardium

    Science.gov (United States)

    Majumder, Rupamanjari; Engels, Marc C.; de Vries, Antoine A. F.; Panfilov, Alexander V.; Pijnappels, Daniël A.

    2016-04-01

    Fibrosis and altered gap junctional coupling are key features of ventricular remodelling and are associated with abnormal electrical impulse generation and propagation. Such abnormalities predispose to reentrant electrical activity in the heart. In the absence of tissue heterogeneity, high-frequency impulse generation can also induce dynamic electrical instabilities leading to reentrant arrhythmias. However, because of the complexity and stochastic nature of such arrhythmias, the combined effects of tissue heterogeneity and dynamical instabilities in these arrhythmias have not been explored in detail. Here, arrhythmogenesis was studied using in vitro and in silico monolayer models of neonatal rat ventricular tissue with 30% randomly distributed cardiac myofibroblasts and systematically lowered intercellular coupling achieved in vitro through graded knockdown of connexin43 expression. Arrhythmia incidence and complexity increased with decreasing intercellular coupling efficiency. This coincided with the onset of a specialized type of spatially discordant action potential duration alternans characterized by island-like areas of opposite alternans phase, which positively correlated with the degree of connexinx43 knockdown and arrhythmia complexity. At higher myofibroblast densities, more of these islands were formed and reentrant arrhythmias were more easily induced. This is the first study exploring the combinatorial effects of myocardial fibrosis and dynamic electrical instabilities on reentrant arrhythmia initiation and complexity.

  16. Covariate analysis of QTc and T-wave morphology: new possibilities in the evaluation of drugs that affect cardiac repolarization

    DEFF Research Database (Denmark)

    Graff, Claus; Struijk, Johannes J.; Matz, J;

    2010-01-01

    This study adds the dimension of a T-wave morphology composite score (MCS) to the QTc interval-based evaluation of drugs that affect cardiac repolarization. Electrocardiographic recordings from 62 subjects on placebo and 400 mg moxifloxacin were compared with those from 21 subjects on 160 and 320...

  17. Isolated T Wave Inversion in Lead aVL: An ECG Survey and a Case Report

    Directory of Open Access Journals (Sweden)

    Getaw Worku Hassen

    2015-01-01

    Full Text Available Background. Computerized electrocardiogram (ECG analysis has been of tremendous help for noncardiologists, but can we rely on it? The importance of ST depression and T wave inversions in lead aVL has not been emphasized and not well recognized across all specialties. Objective. This study’s goal was to analyze if there is a discrepancy of interpretation by physicians from different specialties and a computer-generated ECG reading in regard to a TWI in lead aVL. Methods. In this multidisciplinary prospective study, a single ECG with isolated TWI in lead aVL that was interpreted by the computer as normal was given to all participants to interpret in writing. The readings by all physicians were compared by level of education and by specialty to one another and to the computer interpretation. Results. A total of 191 physicians participated in the study. Of the 191 physicians 48 (25.1% identified and 143 (74.9% did not identify the isolated TWI in lead aVL. Conclusion. Our study demonstrated that 74.9% did not recognize the abnormality. New and subtle ECG findings should be emphasized in their training so as not to miss significant findings that could cause morbidity and mortality.

  18. T-wave inversions on ECG as primary manifestation of Hashimoto's disease.

    Science.gov (United States)

    Araque, Katherine A; Smith, Michael J; Walsh, Brooks M

    2016-04-07

    A middle-aged Hispanic woman presented to the emergency department (ED) reporting of acute new onset pressure-like chest pain developed at rest. It was radiated to the right arm and associated with malaise. Initial ECG demonstrated T-wave inversions (TWIs) in all anterior and lateral leads. Electrolytes, serial cardiac troponin and D-dimer were all normal. Comprehensive transthoracic echocardiogram and nuclear stress test did not reveal a cardiac cause of her symptoms.Serum thyroid-stimulating hormone was markedly elevated (207 mIU/L) and free thyroxine was low (FT4 0.07 ng/dL), consistent with severe primary hypothyroidism. Thyroperoxidase (TPO) antibodies were positive. Therapy with levothyroxine was started. No other cause of the TWIs was identified. A repeat ECG obtained 8 weeks later showed partial resolution of the TWIs. Our observations indicate that Hashimoto's disease is the most likely primary cause of this patient's extensive and profound TWI, which improved after thyroid replacement therapy. 2016 BMJ Publishing Group Ltd.

  19. T wave amplitude in lead aVR as a novel diagnostic marker for cardiac sarcoidosis.

    Science.gov (United States)

    Tanaka, Yoshihiro; Konno, Tetsuo; Yoshida, Shohei; Tsuda, Toyonobu; Sakata, Kenji; Furusho, Hiroshi; Takamura, Masayuki; Yoshimura, Kenichi; Yamagishi, Masakazu; Hayashi, Kenshi

    2017-03-01

    It is vital to identify cardiac involvement (CI) in patients with sarcoidosis as the condition could initially lead to sudden cardiac death. Although the T wave amplitude in lead aVR (TWAaVR) is reportedly associated with adverse cardiac events in various cardiovascular diseases, only scarce data are available concerning the utility of lead aVR in identifying CI in patients with sarcoidosis. We retrospectively investigated the diagnostic values of TWAaVR in patients with sarcoidosis in comparison with conventional electrocardiography parameters such as bundle branch block (BBB). From January 2006 to December 2014, 93 consecutive patients with sarcoidosis were enrolled (mean age, 55.7 ± 15.7 years; male, 31 %; cardiac involvement, n = 26). TWAaVR showed the greatest sensitivity (39 %) and specificity (92 %) in distinguishing between sarcoidosis patients with and without CI, at a cutoff value of -0.08 mV. The diagnostic value of BBB for cardiac involvement was significantly improved when combined with TWAaVR (sensitivity: 61-94 %, specificity: 97-89 %, area under the curve: 0.79-0.92, p = 0.018). Multivariate logistic regression analysis indicated that TWAaVR and BBB were independent electrocardiography parameters associated with CI. In summary, we observed that sarcoidosis patients exhibiting a high TWAaVR were likely to have CI. Thus, the application of a combination of BBB with TWAaVR may be useful when screening for CI in sarcoidosis patients.

  20. T-wave inversions related to left ventricular basal hypertrophy and myocardial fibrosis in non-apical hypertrophic cardiomyopathy: A cardiovascular magnetic resonance imaging study

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    Chen, Xiuyu, E-mail: cxy0202@126.com [Department of Radiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037 (China); Zhao, Shihua, E-mail: zhaoshihua0202@126.com [Department of Radiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037 (China); Zhao, Tao, E-mail: taozhao0202@126.com [Department of Radiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037 (China); Lu, Minjie, E-mail: lmjkan@126.com [Department of Radiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037 (China); Yin, Gang, E-mail: gangyin0202@126.com [Department of Radiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037 (China); Jiang, Shiliang, E-mail: jiangsl-2011@163.com [Department of Radiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037 (China); Prasad, Sanjay, E-mail: s.prasad@rbht.nhs.uk [NIHR Biomedical Research Unit, Royal Brompton Hospital Sydney Street, London, SW3 6NP (United Kingdom)

    2014-02-15

    Objectives: To investigate the relationship between T-wave inversions and left ventricular (LV) segmental hypertrophy and myocardial fibrosis assessed by cardiovascular magnetic resonance (CMR) in patients with non-apical hypertrophic cardiomyopathy (HCM). Methods: 196 consecutive patients with non-apical HCM underwent late gadolinium enhancement (LGE) CMR and 12-lead electrocardiogram. The distribution and magnitude of LV segmental hypertrophy and LGE were assessed according to the AHA 17-segment model and analyzed in relation to T-wave inversions. Results: Of 196 HCM patients, 144 (73%) exhibited T-wave inversions. 144 (73%) patients had evidence of myocardial fibrosis as defined by LGE, and the prevalence of LGE was significantly higher in patients with T-wave inversions compared with those without T-wave inversions (78% vs. 59%, P = 0.008). T-wave inversions were related to basal anterior and basal anteroseptal LGE (20% vs. 10%, P = 0.04 and 68% vs. 46%, P = 0.005, respectively). In addition, T-wave inversions were associated with greater basal anteroseptal and basal inferior wall thickness (19.5 ± 4.7 mm vs. 16.7 ± 4.5 mm, P < 0.001 and 10.9 ± 3.3 mm vs. 9.6 ± 3.0 mm, P = 0.01, respectively). By logistic regression analysis, basal anteroseptal wall thickness and LGE were independent determinants of T-wave inversions (P = 0.005, P = 0.01, respectively). Conclusions: T-wave inversions in HCM are associated with LGE and wall thickness of the left ventricular basal segments. Moreover, basal anteroseptal wall thickness and LGE are independent determinants of T-wave inversions.

  1. Investigation of parameters highlighting drug induced small changes of the T-wave's morphology for drug safety studies.

    Science.gov (United States)

    Baas, Tobias; Gräfe, Ksenija; Khawaja, Antoun; Dössel, Olaf

    2011-01-01

    In guideline E14, the American Food and Drug Administration (FDA) requests for clinical studies to investigate the prolongation of the heart rate corrected QT-interval (QTc) of the ECG. As drug induced QT-prolongation can be caused by changes in the repolarisation of the ventricles, it is so far a thorough ECG biomarker of risk for ventricular tachyarrhythmias and Torsade de Pointes (TdP). Ventricular repolarisation changes not only change QT but also influence the morphology of the T-wave. In a (400 mg single dose) Moxifloxacin positive control study both, QTc and several descriptors describing the T-wave morphology have been measured. Moxifloxacin is changing two shape dependent descriptors significantly (P<0.05) about 3 to 4 hours after a 400 mg oral single dose of Moxifloxacin.

  2. Effects of noise and filtering on SVD-based morphological parameters of the T wave in the ECG.

    Science.gov (United States)

    Lehtola, L; Karsikas, M; Koskinen, M; Huikuri, H; Seppanen, T

    2008-01-01

    Singular value decomposition (SVD) based electrocardiogram (ECG) morphology analysis is a novel method in the assessment of subtle abnormalities in the T wave morphology of 12-lead ECG. As various types of noise contaminate the ECG signal and create a bias for the morphological analyses, this study was designed to estimate the effects of noise on the SVD method in an experimental setup. Ideal signals were generated by filtering real ECG signals several times with the Savitzky-Golay filter. Random and real noise samples were superimposed on the ideal signals. The noisy signals were filtered with a power line interference filter combined with the Savitzky-Golay or the wavelet filter. Results show that noise increased both the dipolar and non-dipolar components significantly unless filtering was applied. R-TWR (relative T wave residuum) and A-TWR (absolute T wave residuum) were four to eight times higher in noisy signals. The experiments with patient data demonstrated that certain types of noise may even lead to erroneous classification of patients. Filtering brings the median values closer to the correct ones and decreases significantly the variance of the values of parameters.

  3. Defective T wave combined with incomplete right bundle branch block: a new electrocardiographic index for diagnosing atrial septal defect

    Institute of Scientific and Technical Information of China (English)

    WANG Mu-xuan; Andrew D.Michaels; MA Hong; WU Gui-fu; GU Jing-li; LI Li; LU Kun; YANG Da; CHEN Long; ZHANG Xi; LUO Fu-tian

    2012-01-01

    Background Incomplete right bundle branch block (ICRBBB) is commonly associated with atrial septal defect (ASD),but lacks sufficient diagnostic test characteristics.An abnormal T wave is also often observed in ASD,with horizontal or inverted displacement of the proximal T wave limb in the right precordial leads,termed "defective T wave" (DTW).Methods We examined the diagnostic test characteristics of combining ICRBBB with DTVV as a new index to diagnose ASD.A total of 132 consecutive patients with ASD and 132 cases of age/gender-matched controls without ASD were enrolled.Results Sensitivities of DTW,ICRBBB,and both were 87.1%-87.9%.Specificities were 97.0%,96.2%,and 100%,respectively.Positive predictive values were 1.3%,1.1%,and 100.0% respectively,while negative predictive values were 99.9% for each.Conclusion Combining ICRBBB with DTW in electrocardiogram (ECG) as a new index significantly increased the specificity and positive predictive values while maintaining a high sensitivity in diagnosing ASD.

  4. T-wave ion mobility-mass spectrometry: basic experimental procedures for protein complex analysis.

    Science.gov (United States)

    Michaelevski, Izhak; Kirshenbaum, Noam; Sharon, Michal

    2010-07-31

    Ion mobility (IM) is a method that measures the time taken for an ion to travel through a pressurized cell under the influence of a weak electric field. The speed by which the ions traverse the drift region depends on their size: large ions will experience a greater number of collisions with the background inert gas (usually N(2;)) and thus travel more slowly through the IM device than those ions that comprise a smaller cross-section. In general, the time it takes for the ions to migrate though the dense gas phase separates them, according to their collision cross-section (Omega). Recently, IM spectrometry was coupled with mass spectrometry and a traveling-wave (T-wave) Synapt ion mobility mass spectrometer (IM-MS) was released. Integrating mass spectrometry with ion mobility enables an extra dimension of sample separation and definition, yielding a three-dimensional spectrum (mass to charge, intensity, and drift time). This separation technique allows the spectral overlap to decrease, and enables resolution of heterogeneous complexes with very similar mass, or mass-to-charge ratios, but different drift times. Moreover, the drift time measurements provide an important layer of structural information, as Omega is related to the overall shape and topology of the ion. The correlation between the measured drift time values and Omega is calculated using a calibration curve generated from calibrant proteins with defined cross-sections(1). The power of the IM-MS approach lies in its ability to define the subunit packing and overall shape of protein assemblies at micromolar concentrations, and near-physiological conditions(1). Several recent IM studies of both individual proteins(2,3) and non-covalent protein complexes(4-9), successfully demonstrated that protein quaternary structure is maintained in the gas phase, and highlighted the potential of this approach in the study of protein assemblies of unknown geometry. Here, we provide a detailed description of IMS

  5. T waves in Western Mediterranean Sea after the May 21, 2003 Algerian earthquake

    Directory of Open Access Journals (Sweden)

    C. Eva

    2007-06-01

    Full Text Available Aim of this paper is to discuss on the T phases generated after the mb 6.5 earthquake that shook Algeria on May 21, 2003. The seismograms, recorded by a cluster of seismic stations located on the coast facing the Ligurian Sea, Northern Italy, some 800 km N-NE from the source, represent a good database able to shed some light on the recognition, propagation and characteristics of these quite uncommon phases. The occurrence and the recording of T phases are in fact due to particular conditions, and require both particular characteristics of the bathymetric slope and the existence of a clear path between the instruments and the earthquake’s source: these constraints are exactly realized in the north-western part of the Mediterranean Sea, whose coasts have been affected several times in the past by similar events. The preliminary investigations on the complex recorded seismogram show two different behaviours for stations close the coast and inland. In both cases, two distinct T phases (namely T1 and T2 are observed. In one case they have apparent velocities close to an average SOFAR channel, and are thus the recording of direct T phases. In particular, T1 is probably a precursor due to some scattering, while T2 is the direct T wave. Conversely, the recordings of the stations inland show apparent velocities that suggest back conversion of the original T to P and S waves and a crustal path. The frequency content of the T phases, as derived from the spectral analysis, reveals marked amplitude peaks also in the range 1-3 Hz, conversely to what was proposed by other authors for similar occurrences in other parts of the world. Since the geometry and shape of the SOFAR channel vary, it is highly likely that the spectrum is biased by the water conditions and the frequency content might change in different seas. Finally, the attenuation of the T phase does not depend on the actual distance of the receiver from the source but rather from the

  6. Effect of Loss of Heart Rate Variability on T-Wave Heterogeneity and QT Variability in Heart Failure Patients: Implications in Ventricular Arrhythmogenesis.

    Science.gov (United States)

    Nayyar, Sachin; Hasan, Muhammad A; Roberts-Thomson, Kurt C; Sullivan, Thomas; Baumert, Mathias

    2017-03-03

    Heart rate variability (HRV) modulates dynamics of ventricular repolarization. A diminishing value of HRV is associated with increased vulnerability to life-threatening ventricular arrhythmias, however the causal relationship is not well-defined. We evaluated if fixed-rate atrial pacing that abolishes the effect of physiological HRV, will alter ventricular repolarization wavefronts and is relevant to ventricular arrhythmogenesis. The study was performed in 16 subjects: 8 heart failure patients with spontaneous ventricular tachycardia [HFVT], and 8 subjects with structurally normal hearts (H Norm). The T-wave heterogeneity descriptors [total cosine angle between QRS and T-wave loop vectors (TCRT, negative value corresponds to large difference in the 2 loops), T-wave morphology dispersion, T-wave loop dispersion] and QT intervals were analyzed in a beat-to-beat manner on 3-min records of 12-lead surface ECG at baseline and during atrial pacing at 80 and 100 bpm. The global T-wave heterogeneity was expressed as mean values of each of the T-wave morphology descriptors and variability in QT intervals (QTV) as standard deviation of QT intervals. Baseline T-wave morphology dispersion and QTV were higher in HFVT compared to H Norm subjects (p ≤ 0.02). While group differences in T-wave morphology dispersion and T-wave loop dispersion remained unaltered with atrial pacing, TCRT tended to fall more in HFVT patients compared to H Norm subjects (interaction p value = 0.086). Atrial pacing failed to reduce QTV in both groups, however group differences were augmented (p < 0.0001). Atrial pacing and consequent loss of HRV appears to introduce unfavorable changes in ventricular repolarization in HFVT subjects. It widens the spatial relationship between wavefronts of ventricular depolarization and repolarization. This may partly explain the concerning relation between poorer HRV and the risk of ventricular arrhythmias.

  7. Submarine explosive activity and ocean noise generation at Monowai Volcano, Kermadec Arc: constraints from hydroacoustic T-waves

    Science.gov (United States)

    Grevemeyer, Ingo; Metz, Dirk; Watts, Anthony

    2016-04-01

    Submarine volcanic activity is difficult to detect, because eruptions at depth are strongly attenuated by seawater. With increasing depth the ambient water pressure increases and limits the expansion of gas and steam such that volcanic eruptions tend to be less violent and less explosive with depth. Furthermore, the thermal conductivity and heat capacity of water causes rapid cooling of ejected products and hence erupted magma cools much more quickly than during subaerial eruptions. Therefore, reports on submarine volcanism are restricted to those sites where erupted products - like the presence of pumice rafts, gas bubbling on the sea surface, and local seawater colour changes - reach the sea surface. However, eruptions cause sound waves that travel over far distances through the Sound-Fixing-And-Ranging (SOFAR) channel, so called T-waves. Seismic networks in French Polynesia recorded T-waves since the 1980's that originated at Monowai Volcano, Kermadec Arc, and were attributed to episodic growth and collapse events. Repeated swath-mapping campaigns conducted between 1998 and 2011 confirm that Monowai volcano is a highly dynamic volcano. In July of 2007 a network of ocean-bottom-seismometers (OBS) and hydrophones was deployed and recovered at the end of January 2008. The instruments were located just to the east of Monowai between latitude 25°45'S and 27°30'S. The 23 OBS were placed over the fore-arc and on the incoming subducting plate to obtain local seismicity associated with plate bending and coupling of the subduction megathrust. However, we recognized additional non-seismic sleuths in the recordings. Events were best seen in 1 Hz high-pass filtered hydrophone records and were identified as T-waves. The term T-wave is generally used for waves travelling through the SOFAR channel over large distances. In our case, however, they were also detected on station down to ~8000 m, suggesting that waves on the sea-bed station were direct waves caused by explosive

  8. Investigation of T-Wave Propagation in the Offshore Area East of Taiwan from Early Analog Seismic Network Observations

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    Bor-Shouh Huang

    2011-01-01

    Full Text Available Extant paper records of the early analog seismic network of Taiwan represent a large resource for earthquake studies in several disciplines. In this study, we report on T waves generated from offshore earthquakes, based on analog observations. The T phases were identified from their stable apparent velocity of about 1.5 km s-1 and other observations using data recorded by stations in eastern Taiwan and on two nearby islands. The observed T phases are recorded for the first time from Taiwan, and in particular are observed by the network in the distal range of local earthquakes. Most of the T waves are observed at island stations at epicentral distances greater than 100 km. For earthquakes that occurred a great distance east of Taiwan, the T phases are always the most dominant phases observed at island stations east of Taiwan, and are also seen at some inland stations with smaller amplitudes. No T phases from inland events were observed by stations on Taiwan or on nearby islands. The observations indicate that the amplitude of the T phase is highly attenuated on its land path and that the propagation direction of the T phase is affected by water depth.

  9. Epicardial distribution of ST segment and T wave changes produced by stimulation of intrathoracic ganglia or cardiopulmonary nerves in dogs.

    Science.gov (United States)

    Savard, P; Cardinal, R; Nadeau, R A; Armour, J A

    1991-06-01

    Sixty-three ventricular epicardial electrograms were recorded simultaneously in 8 atropinized dogs during stimulation of acutely decentralized intrathoracic autonomic ganglia or cardiopulmonary nerves. Three variables were measured: (1) isochronal maps representing the epicardial activation sequence, (2) maps depicting changes in areas under the QRS complex and T wave (regional inhomogeneity of repolarization), and (3) local and total QT intervals. Neural stimulations did not alter the activation sequence but induced changes in the magnitude and polarity of the ST segments and T waves as well as in QRST areas. Stimulation of the same neural structure in different dogs induced electrical changes with different amplitudes and in different regions of the ventricles, except for the ventral lateral cardiopulmonary nerve which usually affected the dorsal wall of the left ventricle. Greatest changes occurred when the right recurrent, left intermediate medial, left caudal pole, left ventral lateral cardiopulmonary nerves and stellate ganglia were stimulated. Local QT durations either decreased or did not change, whereas total QT duration as measured using a root-mean-square signal did not change, indicating the regional nature of repolarization changes. Taken together, these data indicate that intrathoracic efferent sympathetic neurons can induce regional inhomogeneity of repolarization without prolonging the total QT interval.

  10. Resurrection of Scolopendra longipes Wood and Scolopendra cubensis Saussure from synonymy with Scolopendra alternans Leach (Chilopoda, Scolopendromorpha, Scolopendridae): an enigmatic species-group needing phylogeographic analysis, with an overview on the origin and distribution of centipedes in the Caribbean region.

    Science.gov (United States)

    Mercurio, Randy J

    2016-05-12

    Resurrection of Scolopendra longipes Wood, 1862, and Scolopendra cubensis Saussure, 1860, from junior synonymy with Scolopendra alternans Leach, 1815, is proposed. A neotype specimen of Scolopendra longipes is designated. Scolopendra longipes has a restricted range from the Dry Tortugas up through the Florida Keys of Monroe County into the mainland Florida counties of Collier and Dade southeast to the Bahamas, while Scolopendra cubensis is endemic to Cuba. Characters distinguishing S. longipes, and S. cubensis from S. alternans are illustrated and compared using digital photography, micrography and morphometric data. It is suggested that what has been considered Scolopendra alternans from southern Florida through the Caribbean and into northern South America is probably an evolving species-group that has undergone major diversification sometime during the Paleocene and early Eocene ~65.5-50 million years ago (Ma), mainly due to geographic isolation caused by a combination of plate tectonics and 100,000 year cycles of glaciation/deglaciation.

  11. Diagnostic Value of Electrocardiographic T Wave Inversion in Lead aVL in Diagnosing Coronary Artery Disease in Patients with Chronic Stable Angina

    Directory of Open Access Journals (Sweden)

    Hatem L. Farhan

    2010-04-01

    Full Text Available Objectives: The clinical value of T wave inversion in lead aVL in diagnosing coronary artery disease (CAD remains unclear. This study aims to investigate the correlation between aVL T wave inversion and CAD in patients with chronic stable angina.Methods: Electrocardiograms (ECGs of 257 consecutive patients undergoing coronary angiography were analyzed. All patients had chronic stable angina. All patients with secondary T wave inversion had been excluded (66 patients. The remaining 191 patients constituted the study population. Detailed ECG interpretation and coronary angiographic findings were conducted by experienced cardiologists.Results: T wave inversion in aVL was identified in 89 ECGs (46.8% with definite ischemic Q-ST-T changes in different leads in 97 ECGs (50.8%. Stand alone aVL T wave inversion was found in 27 ECGs (14.1% while ischemic changes in other leads with normal aVL were identified in 36 ECGs (18.8%. The incidence of CAD was 86.3%. Single, two- and multi-vessel CAD were found in 38.8%, 28.5% and 32.7% of cases respectively. The prevalence of left main, left anterior descending, left circumflex and right coronary arteries were 4.7%, 61.2%, 29.3% and 44.5%, respectively. T wave inversion in aVL was found to be the only ECG variable significantly predicting mid segment left anterior descending artery (LAD lesions (Odds Ratio 2.93, 95% Confidence Interval 1.59-5.37, p=0.001.Conclusion: This study provides new information relating to T wave inversion in lead aVL to mid segment LAD lesions. Implication of this simple finding may help in bedside diagnosis of CAD typically mid LAD lesions. However, further studies are needed to corroborate this finding.

  12. Cardiac and non-cardiac causes of T-wave inversion in the precordial leads in adult subjects: A Dutch case series and review of the literature

    Institute of Scientific and Technical Information of China (English)

    Salah; AM; Said; Rene; Bloo; Ramon; de; Nooijer; Andries; Slootweg

    2015-01-01

    AIM: To describe the electrocardiographic(ECG) phenomena characterized by T-wave inversion in the precordial leads in adults and to highlight its differential diagnosis. METHODS: A retrospective chart review of 8 adult patients who were admitted with ECG T-wave inversion in the anterior chest leads with or without prolongation of corrected QT(QTc) interval. They had different clinical conditions. Each patient underwent appropriate clinical assessment including investigation for myocardial involvement. Single and multimodality noninvasive, semi-invasive and invasive diagnostic approach were used to ascertain the diagnosis. The diagnostic assessment included biochemical investigation, cardiac and abdominal ultrasound, cerebral and chest computed tomography, nuclear medicine and coronary angiography.RESULTS: Eight adult subjects(5 females) with a mean age of 66 years(range 51 to 82) are analyzed. The etiology of T-wave inversion in the precordial leads were diverse. On admission, all patients had normal blood pressure and the ECG showed sinus rhythm. Five patients showed marked prolongation of the QTc interval. The longest QTc interval(639 ms) was found in the patient with pheochromocytoma. Giant T-wave inversion(≥ 10 mm) was found in pheochromocytoma followed by electroconvulsive therapy and finally ischemic heart disease. The deepest T-wave was measured in lead V3(5 ×). In 3 patients presented with mild T-wave inversion(patients 1, 5 and 4 mm), the QTc interval was not prolonged(432, 409 and 424 msec), respectively.CONCLUSION: T-wave inversion associated with or without QTc prolongation requires meticulous history taking, physical examination and tailored diagnostic modalities to reach rapid and correct diagnosis to establish appropriate therapeutic intervention.

  13. Prolonged angina pectoris and persistent negative T waves in the precordial leads: response to atrial pacing and to methoxamine-induced hypertension

    Energy Technology Data Exchange (ETDEWEB)

    Figueras, J.; Cinca, J.; Gutierrez, L.; Segura, R.; Rius, J.

    1983-06-01

    In 18 consecutive patients without a history of myocardial infarction (MI), prolonged angina pectoris with persistent negative T waves in the precordial leads was associated with a high frequency of in-hospital spontaneous angina (14 of 18, 78%), usually accompanied by S-T segment elevation, and occasionally in-hospital MI (4 of 18, 22%). Angina and MI always involved the electrocardiographic leads with negative T waves. Coronary arteriography, performed in 16 patients, revealed greater than or equal to 90% proximal diameter reduction of the left anterior descending (LAD) coronary artery in 14 patients. No patient had severe narrowing of all 3 major coronary arteries, but the 3 who had 100% LAD occlusion lacked collateral circulation. The ejection fraction was greater than or equal to 50% in 13 patients. Atrial pacing performed in 11 patients at an average rate of 142 beats/min produced a 1.0 mm S-T segment change in only 5 patients (45%), 3 of whom had an associated lactate production. Arterial systemic hypertension induced by methoxamine in 14 patients caused reversal of negative T waves without significant S-T segment shifts or chest pain and failed to elicit lactate extraction abnormalities in each of the 5 patients in whom it was determined. Thus, prolonged angina with persistent negative T waves in the precordial leads is almost invariably associated with a critical and proximal LAD obstruction, severe narrowing of 1 or 2 coronary arteries, and poor or absent collateral vessels.

  14. T-wave changes in patients with Wellens syndrome are associated with increased myocardial mechanical and electrical dispersion.

    Science.gov (United States)

    Stankovic, Ivan; Kafedzic, Srdjan; Janicijevic, Aleksandra; Cvjetan, Radosava; Vulovic, Tijana; Jankovic, Milica; Ilic, Ivan; Putnikovic, Biljana; Neskovic, Aleksandar N

    2017-05-27

    Some patients with unstable angina and critical stenosis of the left anterior descending coronary artery (LAD) present with Wellens syndrome (WS), i.e., inverted or biphasic T-waves in the anterior precordial leads. We assessed clinical, angiographic, electro- and echocardiographic characteristic of patients with WS. In this retrospective study, clinical, angiographic, electro- and echocardiographic characteristic of 35 patients with WS were compared to 57 patients with critical LAD stenosis and normal resting electrocardiogram (ECG), and 45 subjects with normal coronary angiogram. QTc dispersion was measured from the 12-lead ECG as the difference between longest and shortest QTc intervals. Mechanical dispersion was defined as the time difference between the longest and shortest contraction durations which were measured as the time from the first deflection of the QRS complex to maximum myocardial shortening of each 18 segmental longitudinal strain curves derived by speckle tracking echocardiography. There were no significant differences in the complexity and location of the LAD lesion, anterograde and collateral flow in LAD and coronary artery dominance between patients with WS and normal ECG (P > 0.05, for all). Patients with WS had lower global longitudinal strain (GLS) and more pronounced both QTc and myocardial mechanical dispersion than patients with critical LAD stenosis and normal ECG, and control subjects (P dispersion. Similar angiographic characteristics of the LAD lesion were seen in patients with WS and normal ECG.

  15. Ultra-Low Voltage Sixth-Order Low Pass Filter for Sensing the T-Wave Signal in ECGs

    Directory of Open Access Journals (Sweden)

    Panagiotis Bertsias

    2014-11-01

    Full Text Available An ultra-low voltage sixth-order low pass filter topology, suitable for sensing the T-wave signal in an electrocardiogram (ECG, is presented in this paper. This is realized using a cascade connection of second-order building blocks constructed from a sinh-domain two-integrator loop. The performance of the filter has been evaluated using the Cadence Analog Design Environment and the design kit provided by the Austria Mikro Systeme (AMS 0.35-µm CMOS process. The power consumption of filters was 7.21 nW, while a total harmonic distortion (THD level of 4% was observed for an input signal of 220 pA. The RMS value of the input referred noise was 0.43 pA, and the simulated value of the dynamic range (DR was 51.1 dB. A comparison with already published counterparts shows that the proposed topology offers the benefits of 0.5-V supply voltage operation and significantly improved power efficiency.

  16. Relationship between T-wave amplitude and oxygen pulse in guinea pigs in hyperbaric helium and hydrogen.

    Science.gov (United States)

    Kayar, S R; Parker, E C; Aukhert, E O

    1998-09-01

    Diving is known to induce a change in the amplitude of the T wave (ATw) of electrocardiograms, but it is unknown whether this is linked to a change in cardiovascular performance. We analyzed ATw in guinea pigs at 10-60 atm and 25-36 degreesC, breathing 2% O2 in either helium (heliox; n = 10) or hydrogen (hydrox; n = 9) for 1 h at each pressure. Core temperature and electrocardiograms were detected by using implanted radiotelemeters. O2 consumption rate was measured by using gas chromatography. In a previous study (S. R. Kayar and E. C. Parker. J. Appl. Physiol. 82: 988-997, 1997), we analyzed the O2 pulse, i.e., the O2 consumption rate per heart beat, in the same animals. By multivariate regression analysis, we identified variables that were significant to O2 pulse: body surface area, chamber temperature, core temperature, and pressure. In this study, inclusion of ATw made a significantly better model with fewer variables. After normalizing for chamber temperature and pressure, the O2 pulse increased with increasing ATw in heliox (P = 0.001) but with decreasing ATw in hydrox (P pulse for animals breathing heliox vs. hydrox.

  17. Precise NMR measurement and stabilization system of magnetic field of a superconducting 7 T wave length shifter

    CERN Document Server

    Borovikov, V M; Karpov, G V; Korshunov, D A; Kuper, E A; Kuzin, M V; Mamkin, V R; Medvedko, A S; Mezentsev, N A; Repkov, V V; Shkaruba, V A; Shubin, E I; Veremeenko, V F

    2001-01-01

    The system of measurement and stabilization of the magnetic field in the superconducting 7 T wave length shifter (WLS), designed at Budker Institute of Nuclear Physics are described. The measurements are performed by nuclear magnetic resonance (NMR) magnetometer at two points of the WLS magnetic field. Stabilization of the field is provided by the current pumping system. The stabilization system is based on precise NMR measurement of magnetic field as a feedback signal for computer code which control currents inside the superconducting coils. The problem of the magnetic field measurements with NMR method consists in wide spread of field in the measured area (up to 50 Gs/mm), wide temperature range of WLS operating, small space for probe and influence of iron hysteresis. Special solid-state probes were designed to satisfy this requirements. The accuracy of magnetic field measurements at probe locations is not worse than 20 ppm. For the WLS field of 7 T the reproducibility of the magnetic field of 30 ppm has be...

  18. Frontal plane T-wave axis orientation predicts coronary events: Findings from the Moli-sani study.

    Science.gov (United States)

    Iacoviello, Licia; Bonaccio, Marialaura; Di Castelnuovo, Augusto; Costanzo, Simona; Rago, Livia; De Curtis, Amalia; Assanelli, Deodato; Badilini, Fabio; Vaglio, Martino; Persichillo, Mariarosaria; Macfarlane, Peter W; Cerletti, Chiara; Donati, Maria Benedetta; de Gaetano, Giovanni

    2017-09-01

    The orientation of the frontal plane T-wave axis (T axis) is a reliable measure of ventricular repolarisation. We investigated the association between T-axis and the risk of coronary heart disease (CHD), heart failure (HF), atrial fibrillation (AF), stroke and cardiovascular (CVD) mortality. A sample of 21,287 Moli-sani participants randomly recruited from the general adult (≥35 y) Italian population, free of CVD disease, were followed for a median of 4.4 years. T-axis was measured from a standard 12-lead resting ECG. After adjusting for CVD risk factors, subjects with abnormal T-axis showed an increase in the risk of both CHD (Hazard Ratio (HR) = 2.65; 95% CI = 1.67-4.21), HF (HR = 2.56; 1.80-3.63), AF (HR = 2.48; 1.56-3.94) and CVD mortality (HR = 2.83; 1.50-5.32). The association with CHD and HF, but not with AF or CVD death, remained significant after further adjustment for ECG abnormalities. Subjects with abnormal T-axis showed higher levels of subclinical inflammation, hs-troponin I and hs-NT-proBNP (p T-axis orientation is associated with an increased risk of both CHD and HF, independently of common CVD risk factors and other ECG abnormalities. This association was partially explained by increased hs-troponin I and hs-NT-proBNP levels. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. 心电图T波交替检测的GUI设计

    Institute of Scientific and Technical Information of China (English)

    安勇; 罗通顶; 李川勇

    2008-01-01

    以Matlab6.5为工具,利用谱分析法和相关分析法来检测心电图TWA (TWaveAlternans, TWA),最终设计出心电图TWA检测的GUI (Graphical User Interfaces),使得TWA检测更为准确、便捷.

  20. The contribution of ventricular apicobasal and transmural repolarization patterns to the development of the T wave body surface potentials in frogs (Rana temporaria) and pike (Esox lucius).

    Science.gov (United States)

    Vaykshnorayte, Marina A; Azarov, Jan E; Tsvetkova, Alena S; Vityazev, Vladimir A; Ovechkin, Alexey O; Shmakov, Dmitry N

    2011-05-01

    The study aimed at the simultaneous determination of the transmural and apicobasal differences in the repolarization timing and the comparison of the contributions of these two repolarization gradients to the development of the body surface T wave potentials in animals with the single heart ventricle (fishes and amphibians). Unipolar potentials were measured on the body surface, epicardium and in the intramural (subepicardial, Epi; midmyocardial; and subendocardial, Endo) ventricular layers of 9 pike and 8 frogs. Activation times, repolarization times and activation-recovery intervals were determined. A transmural gradient in repolarization durations in frogs (Endo>Epi, Ppike that produces a repolarization sequence from Endo to Epi (Endopike and frogs.

  1. Impaired T-wave amplitude adaptation to heart-rate induced by cardiac deconditioning after 5-days of head-down bed-rest

    Science.gov (United States)

    Caiani, Enrico G.; Pellegrini, Alessandro; Bolea, Juan; Sotaquira, Miguel; Almeida, Rute; Vaïda, Pierre

    2013-10-01

    The study of QT/RR relationship is important for the clinical evaluation of possible risk of acquired or congenital ventricular tachyarrhythmias. In the hypothesis that microgravity exposure could induce changes in the repolarization mechanisms, our aim was to test if a short 5-days strict 6° head-down bed-rest (HDBR) could induce alterations in the QT/RR relationship and spatial repolarization heterogeneity. Twenty-two healthy men (mean age 31±6) were enrolled as part of the European Space Agency HDBR studies. High fidelity (1000 Hz) 24 h Holter ECG (12-leads, Mortara Instrument) was acquired before (PRE), the last day of HDBR (HDT5), and four days after its conclusion (POST). The night period (23:00-06:30) was selected for analysis. X, Y, Z leads were derived and the vectorcardiogram computed. Selective beat averaging was used to obtain averages of P-QRS-T complexes preceded by the same RR (10 ms bin amplitude, in the range 900-1200 ms). For each averaged waveform (i.e., one for each bin), T-wave maximum amplitude (Tmax), T-wave area (Tarea), RTapex, RTend, ventricular gradient (VG) magnitude and spatial QRS-T angle were computed. Non-parametric Friedman test was applied. Compared to PRE, at HDT5 both RTapex and RTend resulted shortened (-4%), with a decrease in T-wave amplitude (-8%) and area (-13%). VG was diminished by 10%, and QRS-T angle increased by 14°. At POST, QT duration and area parameters, as well as QRS-T angle were restored while Tmax resulted larger than PRE (+5%) and VG was still decreased by 3%. Also, a marked loss in strength of the linear regression with RR was found at HDT5 in Tmax and Tarea, that could represent a new dynamic marker of increased risk for life-threatening arrhythmias. Despite the short-term HDBR, ventricular repolarization during the night period was affected. This should be taken into account in astronauts for risk assessment during space flight.

  2. T-wave axis deviation is associated with biomarkers of low-grade inflammation. Findings from the MOLI-SANI study.

    Science.gov (United States)

    Bonaccio, Marialaura; Di Castelnuovo, Augusto; Rago, Livia; de Curtis, Amalia; Assanelli, Deodato; Badilini, Fabio; Vaglio, Martino; Costanzo, Simona; Persichillo, Mariarosaria; Cerletti, Chiara; Donati, Maria Benedetta; de Gaetano, Giovanni; Iacoviello, Licia

    2015-11-25

    T-wave axis deviation (TDev) may help identifying subjects at risk for major cardiac events and mortality, but the pathogenesis of TDev is not well established; in particular, the possible association between TDev and inflammation is unexplored and unknown. We aimed at investigating the association between low-grade inflammation and TDev abnormalities by conducting a cross-sectional analysis on 17,507 subjects apparently free from coronary heart and haematological diseases enrolled in the MOLI-SANI study. TDev was measured from a standard 12-lead resting electrocardiogram. High sensitivity (Hs) C-reactive protein (CRP), leukocyte (WBC) and platelet counts, neutrophil or granulocyte to lymphocyte ratios were used as markers of inflammation. In multivariable model subjects reporting high CRP levels had higher odds of having borderline and abnormal TDev (OR=1.70; 95 %CI: 1.53-1.90 and OR=1.72; 95 %CI: 1.23-2.41, respectively); the association was still significant, although reduced, after controlling for body mass index (OR=1.17; 95 %CI: 1.05-1.32, for borderline and OR=1.46; 95 %CI: 1.03-2.08, for abnormal). Similarly, higher neutrophil or granulocyte to lymphocyte ratios were associated with increased odds of having abnormal TDev. Neither platelet nor leukocyte counts were associated with abnormal TDev. The relationship between CRP with TDev abnormalities was significantly stronger in men, in non- obese or normotensive individuals, and in those without metabolic syndrome. In conclusion, C-reactive protein and some cellular biomarkers of inflammation such as granulocyte or neutrophil to lymphocyte ratios were independently associated with abnormal TDev, especially in subjects at low CVD risk. These results suggest that a low-grade inflammation likely contributes to the pathogenesis of T- wave axis deviation.

  3. Analysis of the ST-T complex of the electrocardiogram using the Karhunen--Loeve transform: adaptive monitoring and alternans detection

    Science.gov (United States)

    Laguna, P.; Moody, G. B.; Garcia, J.; Goldberger, A. L.; Mark, R. G.

    1999-01-01

    The Karhunen-Loeve transform (KLT) is applied to study the ventricular repolarisation period as reflected in the ST-T complex of the surface ECG. The KLT coefficients provide a sensitive means of quantitating ST-T shapes. A training set of ST-T complexes is used to derive a set of KLT basis vectors that permits representation of 90% of the signal energy using four KLT coefficients. As a truncated KLT expansion tends to favor representation of the signal over any additive noise, a time series of KLT coefficients obtained from successive ST-T complexes is better suited for representation of both medium-term variations (such as ischemic changes) and short-term variations (such as ST-T alternans) than discrete parameters such as the ST level or other local indices. For analysis of ischemic changes, an adaptive filter is described that can be used to estimate the KLT coefficient, yielding an increase in the signal-to-noise ratio of 10 dB (u = 0.1), with a convergence time of about three beats. A beat spectrum of the unfiltered KLT coefficient series is used for detection of ST-T alterans. These methods are illustrated with examples from the European ST-T Database. About 20% of records revealed quasi-periodic salvos of ischemic ST-T change episodes and another 20% exhibit repetitive, but not clearly periodic patterns of ST-T change episodes. About 5% of ischemic episodes were associated with ST-T alterans.

  4. Contrast Research of the Occurrence Rate of Posture T Wave Variation in Different Patients%不同患者直立性T波改变发生率的分组对比研究

    Institute of Scientific and Technical Information of China (English)

    王玉燕

    2013-01-01

    Objective: To investigate the effect of body posture on T wave in 12-lead electrocardiogram (ECG) and its clinical significance, Methods: The study concluded 180 patients who were divided into three groups:the control group, the coronary heart disease group and the third group with alteration of T wave in the inferior wal . Each group consisted of 60 individuals. The occurrence rate of posture T wave variation and accompanied heart rate of all 12-lead ECG in both supine and standing positions were measured and compared. Results:21.7%of patient in the control group showed T wave variation when changing to standing position, while the occurrence rate of coronary heart disease group and the group with alteration of T wave in inferior wal was 25.4%and 86.7%respectively. Conclusion: Body posture T wave variation is a normal variation, the occurrence rate of Posture T Wave Variation in the third group with alteration of T wave in the inferior wal is the highest among the three group. .%目的:探讨体位改变对常规12导联心电图T 波的影响及其临床意义。方法:取3组共180例患者(正常组,冠心病组,下壁 T 波改变组),每组60人,共180例患者。观察平卧位与直立位时的12导联心电图T波改变和心率变化的发生率。结果:直立性 T 波改变在正常组占21.7%,冠心病组占25.4%,下壁 T 波改变组占86.7%。结论:体位性 T 波改变是一种正常的 T 波变异,在下壁导联T波改变组中发生率更高。

  5. FIRST IMAGES OF DEBRIS DISKS AROUND TWA 7, TWA 25, HD 35650, AND HD 377

    Energy Technology Data Exchange (ETDEWEB)

    Choquet, Élodie; Perrin, Marshall D.; Chen, Christine H.; Soummer, Rémi; Pueyo, Laurent; Hagan, James B.; Gofas-Salas, Elena; Golimowski, David A.; Hines, Dean C.; Mazoyer, Johan; Debes, John; Stark, Christopher C.; N’Diaye, Mamadou [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Rajan, Abhijith [Arizona State University, Phoenix, AZ 85004 (United States); Schneider, Glenn [Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Augereau, Jean-Charles [Univ. Grenoble Alpes, IPAG, F-38000 Grenoble (France); Wolff, Schuyler; Hsiao, Kevin, E-mail: choquet@stsci.edu [Johns Hopkins University, 3400 North Charles Street, Baltimore MD 21218 (United States)

    2016-01-20

    We present the first images of four debris disks observed in scattered light around the young (4–250 Myr old) M dwarfs TWA 7 and TWA 25, the K6 star HD 35650, and the G2 star HD 377. We obtained these images by reprocessing archival Hubble Space Telescope NICMOS coronagraph data with modern post-processing techniques as part of the Archival Legacy Investigation of Circumstellar Environments program. All four disks appear faint and compact compared with other debris disks resolved in scattered light. The disks around TWA 25, HD 35650, and HD 377 appear very inclined, while TWA 7's disk is viewed nearly face-on. The surface brightness of HD 35650's disk is strongly asymmetric. These new detections raise the number of disks resolved in scattered light around M and late-K stars from one (the AU Mic system) to four. This new sample of resolved disks enables comparative studies of heretofore scarce debris disks around low-mass stars relative to solar-type stars.

  6. Computer quantitation of Q-T and terminal T wave (aT-eT) intervals during exercise: methodology and results in normal men.

    Science.gov (United States)

    O'Donnell, J; Knoebel, S B; Lovelace, D E; McHenry, P L

    1981-05-01

    Computer-quantitated measurements of the Q-T intervals, the Q-T/Q-Tc ratio (Q-T/corrected Q-T) and the terminal T wave (apex to end of T [aT-eT] interval) were evaluated in resting and exercise electrocardiograms of 130 normal men with a mean age of 40 years. Pseudo-orthogonal, bipolar X, Y and Z axis leads were recorded during treadmill exercise testing, and 25 consecutive QRS-T complexes from standing rest and three exercise stages were computer-averaged. The Q-T intervals, Q-T/Q-Tc ratio and aT-eT interval measurements were then computed in the X and Z axis leads only, because the Y lead proved to be too noisy for accurate interpretation. A correlation coefficient of 0.9830 resulted between measurements made manually from the plotted, composite QRS-T complexes and those made by computer. No significant differences , in the paired sense, were found between any of the measurements. Measurements made on the Z axis lead; however, the differences in the measurements remained constant across all stages of exercise. A Q-T/Q-Tc ratio of greater than 1.08, previously reported to be a reliable indicator of coronary disease, was observed in the majority of our normal subjects during exercise. Although the Q-T interval is substantially influenced by many factors, the aT-eT interval proved not to be age- or heart rate-dependent. It appears that the aT-eT interval can be measured with a high degree of reliability during exercise and it may prove to be a relatively specific indicator of repolarization alterations that occur with myocardial ischemia.

  7. A vector-free ECG interpretation with P, QRS & T waves as unbalanced transitions between stable configurations of the heart electric field during P-R, S-T & T-P segments

    Science.gov (United States)

    2014-01-01

    Since cell membranes are weak sources of electrostatic fields, this ECG interpretation relies on the analogy between cells and electrets. It is here assumed that cell-bound electric fields unite, reach the body surface and the surrounding space and form the thoracic electric field that consists from two concentric structures: the thoracic wall and the heart. If ECG leads measure differences in electric potentials between skin electrodes, they give scalar values that define position of the electric field center along each lead. Repolarised heart muscle acts as a stable positive electric source, while depolarized heart muscle produces much weaker negative electric field. During T-P, P-R and S-T segments electric field is stable, only subtle changes are detectable by skin electrodes. Diastolic electric field forms after ventricular depolarization (T-P segments in the ECG recording). Telediastolic electric field forms after the atria have been depolarized (P-Q segments in the ECG recording). Systolic electric field forms after the ventricular depolarization (S-T segments in the ECG recording). The three ECG waves (P, QRS and T) can then be described as unbalanced transitions of the heart electric field from one stable configuration to the next and in that process the electric field center is temporarily displaced. In the initial phase of QRS, the rapidly diminishing septal electric field makes measured potentials dependent only on positive charges of the corresponding parts of the left and the right heart that lie within the lead axes. If more positive charges are near the "DOWN" electrode than near the "UP" electrode, a Q wave will be seen, otherwise an R wave is expected. Repolarization of the ventricular muscle is dampened by the early septal muscle repolarization that reduces deflection of T waves. Since the "UP" electrode of most leads is near the usually larger left ventricle muscle, T waves are in these leads positive, although of smaller amplitude and longer

  8. Changes of T wave amplitude in lead aVR of children with vasovagal syncope%血管迷走性晕厥儿童心电图aVR导联T波振幅变化

    Institute of Scientific and Technical Information of China (English)

    王兰梅; 祝立平; 许毅; 王成; 吴礼嘉; 袁鹤立; 曹闽京; 林萍; 崔晓丽; 李芳

    2011-01-01

    Objective To probe the changes of T wave amplitude in lead aVR (TaVR) in supine and erect position of children with vasovagal syncope ( VVS ). Methods Twelve - lead simultaneous body surface electrocardiogram in supine and erect position were taken in 76 cases which were positive in head - up tilt test (HUTT) with VVS ( research group) aged from 4 to 17 [ mean (11.06 ± 2.37) years old ] and 55 healthy children as control group with SR-1000A automated electrocardiography. The T wave amplitudes were tested by hand during 3 clear wave cycles. Results ①There was no statistical difference in TaVR between two groups in supine position ( P > 0. 05 ).Compared with supine position, the lowering of TaVR of research group was significantly obvious in erect position (P <0.05). TaVR of females in both groups was significant lower than boys(P <0.05). ②T wave amplitude difference between supine and erect position was more significantly different in the research group than in the control group ( P < 0.05 ) , and significantly different in female than in male of control group ( P < 0.05 ); there were no gender differences in the research group ( P > 0.05 ) and no statistical difference in the frequency of syncope ( P > 0.05 ). ③There were no statistical differences in TaVR of the erect position, the supine position and in T wave amplitude difference of supine and erect position in vascular suppression type of VVS( P > 0.05 ) , compared with other types (cardiac suppression and mixed type). Conclusion The change of the body posture from supine to erect can lead to the changes of TaVR, which manifests that this method has directive value for the evaluation of autonomic nervous system function, but TaVR has no clear predictive value for VVS recurrence .%目的 探讨血管迷走性晕厥(VVS)儿童卧位、立位心电图aVR导联T波振幅变化的意义.方法 选择直立倾斜试验(HUTT)阳性的VVS患儿76例为研究组,年龄4~17岁,平均(11.06±2

  9. 晚钠电流的魅影--从交感性 T 波到Takotsubo 综合征%The appearance of late sodium current:from sympathetic T wave to Takotsubo syndrome

    Institute of Scientific and Technical Information of China (English)

    贾忠伟

    2016-01-01

    Sympathetic T wave is a kind of cardiac electrophysiological abnormality related to sympathetic stress.Besides cardiac electrophysiological abnormalities,Takotsubo syndrome includes cardiac mechanical dysfunction.They share the same pathogenesis including sympathetic excitation, late sodium current (ⅠNaL )and electrophysiological abnormalities of myocardial cell mediated by calmodulin,etc.However,they may be different clinical manifestations of the same disease.%交感性 T 波是一类与交感应激有关的心脏电生理异常,而 Takotsubo 综合征包含了心电生理异常和心脏机械功能异常两方面。二者有共同的发病机制,包括交感兴奋、晚钠电流(late sodium current,ⅠNaL )及钙调蛋白介导的心肌细胞电生理异常等。它们可能是同一种疾病不同的临床表现形式。

  10. 静息心电图ST-T改变与冠脉造影的相关性分析%The analysis of the relationship between resting electrocardiogram ST-T wave change and the results of coronary angiography

    Institute of Scientific and Technical Information of China (English)

    李邢婷; 张晓刚

    2015-01-01

    目的:探讨静息心电图(ECG)ST-T改变与冠状动脉造影(CAG)检查阳性结果间的相关性。方法对重庆医科大学附属第一医院心内科1173例临床诊断为冠心病(CHD)患者的CAG检查及常规12导联静息ECG检查结果进行对比,分析同一患者两种检查结果的相关性。结果 ECG ST-T改变与CAG检查阳性结果的一致性微弱(Kappa=0.161,P<0.01);两种检查阳性率有显著性差异(P<0.01);冠脉病变支数不同的各组ECG阳性率差异有显著性(P<0.01);随着冠脉病变支数的增加,ECG阳性率有增加的趋势,且这种趋势有统计学意义(P<0.01)。结论ECG ST-T改变可能部分地预测冠状动脉狭窄,并有显著意义,但与CAG检查相比,对诊断CHD的诊断作用有限,所以临床依据ECG ST-T改变诊断CHD时应慎重,需结合临床症状及其他相关辅助检查。%Objective To investigate the relationship of resting electrocardiogram (ECG) ST-T wave change and posi-tive outcome of coronary angiography (CAG). Methods A comparison was made between CAG results and routine 12-channel resting ECG of 1173 patients diagnosed as coronary heart disease (CHD) clinically in cardiovascular depart-ment of internal medicine in the first affiliated hospital of Chongqing medical university ,and their correlation was ana-lyzed. Results ECG ST-T change was not significantly correlated to the CAG positive outcome (Kappa=0.161,P<0.01);There was significant difference of the positive rates between those two examinations(P<0.01);The ECG positive result rates in different coronary artery lesion groups were significantly different (P<0.01); With the increase of coro-nary artery stenosis number, the positive rate of ECG significantly increased. (P<0.01). Conclusion ECG ST-T wave change might partially predict the coronary artery stenosis, but its clinical utility is limited for CHD diagosis compared with CAG. Therefore,it should be

  11. Electrocardiographic Changes in Certain Cardiovascular Physiological and Pathological Settings. Impact on Coronary Artery Bypass Grafting

    Directory of Open Access Journals (Sweden)

    Dimitar Simov

    2016-03-01

    Full Text Available Review on electrocardiographic changes provoked by aging, diagnostic tests, cardiac surgery, hemodialysis, diabetes, etc., is the objective of the current material. Several electrocardiographic (ECG parameters that are well known risk markers of arrhythmias, incidental heart failure and sudden cardiac death (SCD are discussed: QRS amplitude, QRS morphology, QRS duration, QRS alternans, T-wave amplitude, T-wave morphology, T-wave alternans, negative T-waves, 3D-spatial angle between maximal QRS and T vectors of the vectorcardiographic loops, ST-segment elevation, QT-interval dispersion, and heart rate. All reviewed parameters are compared with the results on the ECG-alterations, induced by coronary artery bypass grafting (CABG surgery. Two parameters showed an improvement in the patients' condition: QRS-T angle and cardiac autonomic innervation while two others (T-wave alternans and heart rate indicated deterioration. We tend to assume that the deterioration in this early post-operative period is an effect of the post-surgery trauma. We speculate that this effect will fade away in a period of a month and more after surgery, and we intend to conduct such a research in the future. The analysis of ECG's changes will help to better assess the impact of the CABG surgery.

  12. 缺血性ST段或T波变化及病灶特征与 血小板功能的相关性%Relationship among ischemic ST segment or T wave shifts, angiographic morphology and platelet function in patients with unstable angina

    Institute of Scientific and Technical Information of China (English)

    刘志忠; 段宝祥; 陈绍良; 王自正; 王书奎; 刘玲玲; 常芸

    2001-01-01

    Objective:To determine the relations among specific clinical pictures ,including electrocardiogram (ECG) abnormalities associated with ischemia,angiographic morphology and plate let function. Method:Thirtyeight consecutive patients were divided into two groups according to ST segment or T waves changes associated with ischemia or angiographic morphology. Venous blood samples were measured for ratios of platelet glycoprotein (GP) Ⅱ b/Ⅲ a by flow cytometry. Result:Twenty-two of the 38 patients exhibited reversible ST segment depression (n= 20) or elevation (n= 2) during ischemic episodes, whereas the other 16 exhibited reversible T wave changes. Positive ratios of platelet GP Ⅱ b/Ⅲ a were different significantly between ST segment shift group and T wave change group (4.4±2.1)% vs (2.7± 1.6)%, P <0.01. Angiographic examinationamong the 38 patients showed complex lesions in 13 patients and no significant stenosis (<50%) in 2 patients. The positive ratios of platelet GP Ⅱ b/Ⅲ a in complex lesion group were markedly elevated compared with noncomplex lesion group(4. 6±2.5)% vs (2.2±1.1)%, P <0. 01. Conclusion:The results suggest that the occurrence of reversible ST segment shifts associated with ischemia or complex lesions noted in angiographic examination identifies the increase of platelet activation in patients with unstable angina and who may be beneficial from antiplatelet therapy.%目的:确立不稳定型心绞痛(UAP)患者缺血性ST段或T波变化及冠状动脉(冠脉)造影所示病灶特征与血小板功能的相关性。方法:38例拟诊UAP患者分别依据胸痛发作时心电图(ECG)短暂性的ST段或T波改变及冠脉造影下病灶特征分组,流式细胞仪检测每例患者外周血糖蛋白(GP)Ⅱb/Ⅲ a受体阳性表达的血小板比率,比较组间GPⅡb/Ⅲ a受体表达差异。9例健康成人作对照组。结果:胸痛发作时22例患者ECG有短暂性ST段变化,另16例表现为短暂性T波

  13. 遗传性心律失常患者心脏除颤器植入术中T 波感知测试的研究%T wave sensing test during ICD implantation procedure in inherited arrhythmias patients

    Institute of Scientific and Technical Information of China (English)

    孙雅逊; 金金花; 陆琴; 刘强; 张祖文; 蒋晨阳; 傅国胜

    2014-01-01

    目的探讨遗传性心律失常患者植入式心脏除颤器( ICD)术中可能出现的T波误感知( TWOS)的原因并进行分析。方法2013年2至12月期间入选因遗传性心律失常而植入ICD的患者7例,ICD术中通过主动起搏导线连接体外ICD及调整ICD感知灵敏度的方法,测试其在各种型号ICD中的心室感知情况。根据ICD的相应感知策略画出真实比例的感知曲线,并据此选择ICD型号。自身对照采用配对t检验。结果7例遗传性心律失常中5例Brugada综合征、1例长QT综合征和1例短QT综合征患者进行ICD植入术或ICD更换术中的体外测试,在最大感知灵敏度下(0.15 mV), Virtuoso及Consulta ICD在2例Brugada综合征患者和1例短QT综合征患者中出现TWOS,其余4例患者未出现TWOS;在默认设置下(0.3 mV),Consulta ICD 在1例Brugada 患者中偶尔出现TWOS。Epic ICD在短QT综合征患者中出现TWOS。连接Fortify及Vitality、Teligen ICD在最大感知灵敏度下,7例患者均未出现TWOS。随访8个月,未出现TWOS及误治疗。结论 ICD植入术或更换体外连接ICD进行测试能够对T波感知进行评估,可能有助于避免潜在的TWOS。%Objective To evaluate the T wave sensing in inherited arrhythmias patients during ICD implantation procedure .Methods In ICD implantation or replacement procedure , the T wave amplitude was measured by i-vitro ICD connection .The sensing threshold was programmed to the most sensitive to re-veal the possible TWOS .The threshold of ventricular sensing was plotted according to algorism of different models of ICD .Results Five Brugada syndrome patients , 1 long QT syndrome patient and 1 short QT syn-drome patient were enrolled in the study .With sensing threshold of 0.15mV in Virtuoso and Consulta ICD , TWOS were observed in 2 Brugada syndrome patients and the short QT syndrome patient .With sensing threshold of 0.3mV, TWOS was observed in Consulta ICD

  14. Collisional Cross-Sections with T-Wave Ion Mobility Spectrometry without Experimental Calibration

    Science.gov (United States)

    Mortensen, Daniel N.; Susa, Anna C.; Williams, Evan R.

    2017-07-01

    A method for relating traveling-wave ion mobility spectrometry (TWIMS) drift times with collisional cross-sections using computational simulations is presented. This method is developed using SIMION modeling of the TWIMS potential wave and equations that describe the velocity of ions in gases induced by electric fields. The accuracy of this method is assessed by comparing the collisional cross-sections of 70 different reference ions obtained using this method with those obtained from static drift tube ion mobility measurements. The cross-sections obtained here with low wave velocities are very similar to those obtained using static drift (average difference = 0.3%) for ions formed from both denaturing and buffered aqueous solutions. In contrast, the cross-sections obtained with high wave velocities are significantly greater, especially for ions formed from buffered aqueous solutions. These higher cross-sections at high wave velocities may result from high-order factors not accounted for in the model presented here or from the protein ions unfolding during TWIMS. Results from this study demonstrate that collisional cross-sections can be obtained from single TWIMS drift time measurements, but that low wave velocities and gentle instrument conditions should be used in order to minimize any uncertainties resulting from high-order effects not accounted for in the present model and from any protein unfolding that might occur. Thus, the method presented here eliminates the need to calibrate TWIMS drift times with collisional cross-sections measured using other ion mobility devices.

  15. T-wave oversensing and inappropriate shocks in implantable cardioverter def ibrillators

    Institute of Scientific and Technical Information of China (English)

    GAO Lei; LU Cai-yi; WANG Shi-wen; XUE Qiao; YAN Wei; ZHOU Sheng-hua; CHEN Rui; LIU Peng; ZHAI Jin-yue

    2010-01-01

    @@ The implantable cardioverter defibrillator (ICD) represents today the treatment and prophylaxis of choice for patients at risk for sustained ventricular tachyarrhythmias.1"6 Accurate sensing of ventricular tachyarrhythmias is a critical aspect of the function of ICD.

  16. An SEC/MALS Study of Alternan Degradation During Size-exclusion Chromatographic Analysis

    Science.gov (United States)

    The degradation of high molar mass polymers during size-exclusion chromatography (SEC) analysis has been a topic of interest for several decades. Should a polymer degrade during analysis, the accuracy of the molar mass (M) and architectural information obtained will be compromised. To this effect,...

  17. Design and realization of the AMANDA software trigger for the TWA data readout system; Entwurf und Realisierung des AMANDA-Softwaretriggers fuer das TWR-Datenauslese-System

    Energy Technology Data Exchange (ETDEWEB)

    Messarius, Timo

    2006-07-15

    The thesis begins with a short introduction in the theory of astroparticle physics. Especially the processes, which lead to signal respectively background events in neutrino detectors, are discussed. Thereafter follows the descripotion of the basing detection principle and the detectors AMANDA and IceCube. The following chapter considers the two data-acquisition systems of the AMANDA detector and explains the motivation for the construction of a new data-acquisition system. The newly designed trigger system is then extensively treated. First a completely on software basing system is discussed, and then the implemented version is considered more detailedly. A procedure to detect and to mark events from atmospheric muons directly on trigger level is presented.

  18. Effect of nalmefene 20 and 80 mg on the corrected QT interval and T-wave morphology

    DEFF Research Database (Denmark)

    Matz, Jørgen; Graff, Claus; Vainio, Petri J.

    2011-01-01

    Nalmefene is an orally administered competitive opioid receptor antagonist targeted at reducing alcohol consumption in alcohol-dependent patients. As part of the regulatory requirements for drug approval, the potential of novel compounds for causing unwanted proarrhythmia should be studied...... in a thoroughly designed clinical QT/corrected QT (QTc) study (International Conference on Harmonisation [ICH] E14 guideline)....

  19. Cardiovascular and cortisol reactivity and habituation to a virtual reality version of the Trier Social Stress Test: a pilot study.

    Science.gov (United States)

    Jönsson, Peter; Wallergård, Mattias; Osterberg, Kai; Hansen, Ase Marie; Johansson, Gerd; Karlson, Björn

    2010-10-01

    The Trier Social Stress Test (TSST) is a widely used protocol to induce stress in laboratory settings. Briefly, in the TSST, the test participant is asked to hold a speech and to do an arithmetic task in front of an audience. In the present pilot study, we examined endocrine and autonomic reactivity and habituation to repeated stress provocations using a virtual reality (VR) version of TSST. The VR system was a CAVE™ system with three rear projected walls (4 m×3 m), and one floor projection. The system also included a head tracking system and passive stereoscopy. The virtual audience consisted of one woman, and two men. Ten healthy men, mean age 28.3 years (24-38 years), were confronted with the test twice (1 week between sessions), during which salivary cortisol, heart rate (HR), high frequency heart rate variability (HF-HRV, parasympathetic activity), and T-wave amplitude (TWA, suggested to be related to sympathetic influence on myocardial performance) were assessed. Cortisol secretion showed a marked increase (88% vs. baseline) during the first stress provocation, but habituated in the second session. The magnitude of HR and TWA reactivity during stress provocation was approximately the same at both sessions, implying a stable increase in sympathetic activity. Heart rate showed a maximum increase of 40% at the first session, and 32% at the second. TWA showed a maximum decrease of 42% at the first session, and 39% at the second. The results resemble those obtained in prior studies using the real-life TSST. If these results can be replicated with larger samples, VR technology may be used as a simple and standardized tool for social stress induction in experimental settings.

  20. Exhaustion-related changes in cardiovascular and cortisol reactivity to acute psychosocial stress

    DEFF Research Database (Denmark)

    Jönsson, Peter; Österberg, Kai; Wallergård, Mattias

    2015-01-01

    cortisol samples were collected. In addition, high frequency heart rate variability (HF-HRV), heart rate (HR), t-wave amplitude (TWA), and α-amylase were assessed to examine stress reactivity and habituation in the autonomic nervous system (ANS). The initial analyses showed clear hypothalamic......-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS) activations in both V-TSST sessions, together with habituation of cortisol and heart rate in the second session, but without any significant group differences. However, the former ED patients showed considerable variation in self-reported signs......Prior findings indicate that individuals scoring high on vital exhaustion show a dysfunctional stress response (DSR), that is, reduced cortisol reactivity and habituation to psychosocial stressors. The main aim of the present study was to examine whether a DSR may be a vulnerability factor...

  1. Cardiovascular adjustments and pain during repeated cold pressor test.

    Science.gov (United States)

    Stancák, A; Yamamotová, A; Kulls, I P; Sekyra, I V

    1996-04-01

    The cold pressor test is used in the clinical testing of the autonomic nervous system. However, little is known about changes in the autonomic control of the cardiovascular system during repeated challenge with cold. Heart rate (HR), respiratory sinus arrhythmia (RSA), T-wave amplitude of ECG (TWA), blood pressure, body temperature and perceived pain were recorded in 18 male subjects during three CPTs which consisted of four minutes immersion of the left hand into cold water at 1 degree C. Breathing during CPT was either spontaneous or paced at 0.23 Hz or 0.1 Hz. Pain intensity and HR decreased and TWA increased during the cold immersion and in the resting period preceding cold in the second and third trials. Systolic and pulse blood pressure increased in resting periods in the third trial. RSA increased in the second and third cold challenge during paced breathing at 0.1 Hz only. A decrease in body temperature (0.48 degree C) at the end of the experiment correlated marginally with HR changes. Our study shows that sustained cardiovascular changes are induced by the first challenge with cold, and persist or increase with repeated cold pressor tests.

  2. Quantitative analysis of T-wave morphology increases confidence in drug-induced cardiac repolarization abnormalities: evidence from the investigational IKr inhibitor Lu 35-138

    DEFF Research Database (Denmark)

    Graff, Claus; Matz, Jørgen; Christensen, Ellen B;

    2009-01-01

    to determine a combined measure of repolarization morphology (morphology combination score [MCS]), based on asymmetry, flatness, and notching. Replicate measurements were used to determine reliable change and study power for both measures. Lu 35-138 increased the QTc interval with corresponding changes in T...... was 93%. As a covariate to the assessment of QT interval liability, MCS offered important additive information to the effect of Lu 35-138 on cardiac repolarization....

  3. Structural Characterization of Monomers and Oligomers of D-Amino Acid-Containing Peptides Using T-Wave Ion Mobility Mass Spectrometry

    Science.gov (United States)

    Pang, Xueqin; Jia, Chenxi; Chen, Zhengwei; Li, Lingjun

    2016-11-01

    The D-residues are crucial to biological function of D-amino acid containing peptides (DAACPs). Previous ion mobility mass spectrometry (IM-MS) studies revealing oligomerization patterns of amyloid cascade demonstrated conversion from native soluble unstructured assembly to fibril ß-sheet oligomers, which has been implicated in amyloid diseases, such as Alzheimer's disease and type 2 diabetes. Although neuropeptides are typically present at very low concentrations in circulation, their local concentrations could be much higher in large dense core vesicles, forming dimers or oligomers. We studied the oligomerization of protonated and metal-adducted achatin I and dermorphin peptide isomers with IM-MS. Our results suggested that dimerization, oligomerization, and metal adduction augment the structural differences between D/L peptide isomers compared to protonated monomers. Dimers and oligomers enhanced the structural differences between D/L peptide isomers in both aqueous and organic solvent system. Furthermore, some oligomer forms were only observed for either D- or L-isomers, indicating the importance of chiral center in oligomerization process. The oligomerization patterns of D/L isomers appear to be similar. Potassium adducts were detected to enlarge the structural differences between D/L isomers.

  4. Structural Characterization of Monomers and Oligomers of D-Amino Acid-Containing Peptides Using T-Wave Ion Mobility Mass Spectrometry

    Science.gov (United States)

    Pang, Xueqin; Jia, Chenxi; Chen, Zhengwei; Li, Lingjun

    2017-01-01

    The D-residues are crucial to biological function of D-amino acid containing peptides (DAACPs). Previous ion mobility mass spectrometry (IM-MS) studies revealing oligomerization patterns of amyloid cascade demonstrated conversion from native soluble unstructured assembly to fibril ß-sheet oligomers, which has been implicated in amyloid diseases, such as Alzheimer's disease and type 2 diabetes. Although neuropeptides are typically present at very low concentrations in circulation, their local concentrations could be much higher in large dense core vesicles, forming dimers or oligomers. We studied the oligomerization of protonated and metal-adducted achatin I and dermorphin peptide isomers with IM-MS. Our results suggested that dimerization, oligomerization, and metal adduction augment the structural differences between D/L peptide isomers compared to protonated monomers. Dimers and oligomers enhanced the structural differences between D/L peptide isomers in both aqueous and organic solvent system. Furthermore, some oligomer forms were only observed for either D- or L-isomers, indicating the importance of chiral center in oligomerization process. The oligomerization patterns of D/L isomers appear to be similar. Potassium adducts were detected to enlarge the structural differences between D/L isomers.

  5. Identifying drug-induced repolarization abnormalities from distinct ECG patterns in congenital long QT syndrome: a study of sotalol effects on T-wave morphology

    DEFF Research Database (Denmark)

    Graff, Claus; Andersen, Mads P; Xue, Joel Q

    2009-01-01

    BACKGROUND: The electrocardiographic QT interval is used to identify drugs with potential harmful effects on cardiac repolarization in drug trials, but the variability of the measurement can mask drug-induced ECG changes. The use of complementary electrocardiographic indices of abnormal repolariz......BACKGROUND: The electrocardiographic QT interval is used to identify drugs with potential harmful effects on cardiac repolarization in drug trials, but the variability of the measurement can mask drug-induced ECG changes. The use of complementary electrocardiographic indices of abnormal...... are typical ECG patterns in LQT2. Blinded to labels, the new morphology measures were tested in a third group of 39 healthy subjects receiving sotalol. Over 3 days the sotalol group received 0, 160 and 320 mg doses, respectively, and a 12-lead Holter ECG was recorded for 22.5 hours each day. Drug...... with QTcF, p ECG patterns in LQT2 carriers effectively quantified repolarization changes induced by sotalol. Further studies are needed to validate whether this measure has...

  6. A case report in a patient with hyperkalemia inducing ischemic upright T wave ( no abstract)%高血钾致缺血性T波直立一例

    Institute of Scientific and Technical Information of China (English)

    张雨田

    2007-01-01

    患者女性,68岁,主因:胸憋、气短半年,加重伴夜间不能平卧2个月,于2002年3月12日下午7时入院,既往高血压病史20年,糖尿病16年,2001年10月诊断为糖尿病肾病,肾功能不全;2002年1月出现夜间不能平卧,进行性加重,合并全身浮肿,恶心、呕吐;2002年3月12日心电图提示,下壁、侧壁心肌缺血,胸部CT提示心力衰竭、肺淤血,双侧胸腔积液。2002年3月16日冠状动脉造影示左主干+三支病变,左主干开口处狭窄90%,右冠状动脉近端狭窄90%,建议行冠状动脉旁路移植术。

  7. The development of selected cardiovascular parameters in patients with type 2 diabetes mellitus during a spa treatment.

    Science.gov (United States)

    Fialová, E; Kittnar, O

    2015-01-01

    Diabetes mellitus is not just a simple metabolic disorder, however, it is considered to be a cardiovascular disease of a metabolic origin. This is apparent especially when speaking about type 2 diabetes (DM II). The objective of our study was to determine whether a comprehensive spa treatment (procedures and drinking cure) may affect the level of the sympathetic tone of patients suffering from DM II. As an indicator of the sympathetic tone, selected electrocardiographic parameters derived from the heart rate variability and microwave alternans were chosen. There were 96 patients enrolled in our study: 38 patients with poorly controlled DM II and two control groups: 9 patients with compensated DM II and 49 patients, average age without diabetes or other disorders of the glucose metabolism. All received an identical spa treatment and continued their medical therapy. The electrophysiological examination of patients was performed before and after a three-week spa treatment using the KARDiVAR system. Parameters derived from the analysis of heart rate variability (HRV), microvolt T-wave alternans, and microvolt R-wave alternans were analyzed in order to evaluate the tones of the autonomic nervous system (ANS). The control group showed a slight increase of parameter the index of activity of regulatory systems (IRSA) (4.4+/-1.3 vs. 3.8+/-1.4; p=0.006) after the spa treatment, while increased heart rate (80.9+/-11.0 vs. 74.6+/-9.6; p=0.028), reduced index of centralization (IC) (1.3+/-0.6 vs. 2.9+/-1.4; p=0.027) and reduced index of myocardium (IM) (9.9+/-7.4 vs. 18.0+/-6.3; p=0.041) were found in patients with a compensated DM II. Patients with a poorly compensated DM II showed a decreased IM (10.9+/-8.6 vs. 16.9+/-5.2; p=0.001) and also a reduced IRSA (4.1+/-3.5 vs. 6.3+/-1.9; p=0.001). The results proved favorable changes in ANS cardiovascular control of patients with DM II after a spa treatment, especially in terms of reducing the sympathoadrenal system activity

  8. Gap junction modifier rotigaptide decreases the susceptibility to ventricular arrhythmia by enhancing conduction velocity and suppressing discordant alternans during therapeutic hypothermia in isolated rabbit hearts

    DEFF Research Database (Denmark)

    Hsieh, Yu-Cheng; Lin, Jiunn-Cherng; Hung, Chen-Ying

    2016-01-01

    ) and 30°C (P = .042). Rotigaptide did not change connexin43 expressions and distributions during hypothermia. CONCLUSION: Rotigaptide protects the hearts against ventricular arrhythmias by increasing ventricular CV, delaying the onset of SDA, and reducing repolarization heterogeneity during TH. Enhancing...

  9. Detrended Fluctuation Analysis on Cardiac Pulses in Both, Animal Models and Humans: A Computation for an Early Prognosis of Cardiovascular Disease

    Directory of Open Access Journals (Sweden)

    Toru Yazawa

    2008-04-01

    Full Text Available We analyzed the heartbeat interval by the detrended fluctuation analysis (DFA in models and humans. In models, the myocardium of the healthy heart contracted regularly. The deteriorated heart model, however, showed alternating beats so-called "alternans." The DFA revealed that if the heart is having "alternans" exhibited there is a declined scaling exponent (~0.5. In humans, the heart that had "alternans" also showed a low scaling exponent (~0.6. We consider that the coexistence of "alternans" and a low scaling exponent can be a risk marker in predictive and preventative diagnosis, supporting the idea that "alternans" can be a harbinger of sudden death.

  10. Maternal Sensitivity and Infant Autonomic and Endocrine Stress Responses

    Science.gov (United States)

    Enlow, Michelle Bosquet; King, Lucy; Schreier, Hannah; Howard, Jamie M.; Rosenfield, David; Ritz, Thomas; Wright, Rosalind J.

    2014-01-01

    Background Early environmental exposures may help shape the development of the autonomic nervous system (ANS) and hypothalamic-pituitary-adrenal (HPA) axis, influencing vulnerability for health problems across the lifespan. Little is known about the role of maternal sensitivity in influencing the development of the ANS in early life. Aims To examine associations among maternal sensitivity and infant behavioral distress and ANS and HPA axis reactivity to the Repeated Still-Face Paradigm (SFP-R), a dyadic stress task. Study Design Observational repeated measures study. Subjects Thirty-five urban, sociodemographically diverse mothers and their 6-month-old infants. Outcome Measures Changes in infant affective distress, heart rate, respiratory sinus arrhythmia (RSA), and T-wave amplitude (TWA) across episodes of the SFP-R were assessed. A measure of cortisol output (area under the curve) in the hour following cessation of the SFP-R was also obtained. Results Greater maternal insensitivity was associated with greater infant sympathetic activation (TWA) during periods of stress and tended to be associated with greater cortisol output following the SFP-R. There was also evidence for greater affective distress and less parasympathetic activation (RSA) during the SFP-R among infants of predominantly insensitive mothers. Conclusions Caregiving quality in early life may influence the responsiveness of the sympathetic and parasympathetic branches of the ANS as well as the HPA axis. Consideration of the ANS and HPA axis systems together provides a fuller representation of adaptive versus maladaptive stress responses. The findings highlight the importance of supporting high quality caregiving in the early years of life, which is likely to promote later health. PMID:24794304

  11. Sudden Cardiac Risk Stratification with Electrocardiographic Indices - A Review on Computational Processing, Technology Transfer, and Scientific Evidence

    Directory of Open Access Journals (Sweden)

    Francisco Javier eGimeno-Blanes

    2016-03-01

    Full Text Available Great effort has been devoted in recent years to the development of sudden cardiac risk predictors as a function of electric cardiac signals, mainly obtained from the electrocardiogram (ECG analysis. But these prediction techniques are still seldom used in clinical practice, partly due to its limited diagnostic accuracy and to the lack of consensus about the appropriate computational signal processing implementation. This paper addresses a three-fold approach, based on ECG indexes, to structure this review on sudden cardiac risk stratification. First, throughout the computational techniques that had been widely proposed for obtaining these indexes in technical literature. Second, over the scientific evidence, that although is supported by observational clinical studies, they are not always representative enough. And third, via the limited technology transfer of academy-accepted algorithms, requiring further meditation for future systems. We focus on three families of ECG derived indexes which are tackled from the aforementioned viewpoints, namely, heart rate turbulence, heart rate variability, and T-wave alternans. In terms of computational algorithms, we still need clearer scientific evidence, standardizing, and benchmarking, siting on advanced algorithms applied over large and representative datasets. New scenarios like electronic health recordings, big data, long-term monitoring, and cloud databases, will eventually open new frameworks to foresee suitable new paradigms in the near future.

  12. Sudden Cardiac Risk Stratification with Electrocardiographic Indices - A Review on Computational Processing, Technology Transfer, and Scientific Evidence.

    Science.gov (United States)

    Gimeno-Blanes, Francisco J; Blanco-Velasco, Manuel; Barquero-Pérez, Óscar; García-Alberola, Arcadi; Rojo-Álvarez, José L

    2016-01-01

    Great effort has been devoted in recent years to the development of sudden cardiac risk predictors as a function of electric cardiac signals, mainly obtained from the electrocardiogram (ECG) analysis. But these prediction techniques are still seldom used in clinical practice, partly due to its limited diagnostic accuracy and to the lack of consensus about the appropriate computational signal processing implementation. This paper addresses a three-fold approach, based on ECG indices, to structure this review on sudden cardiac risk stratification. First, throughout the computational techniques that had been widely proposed for obtaining these indices in technical literature. Second, over the scientific evidence, that although is supported by observational clinical studies, they are not always representative enough. And third, via the limited technology transfer of academy-accepted algorithms, requiring further meditation for future systems. We focus on three families of ECG derived indices which are tackled from the aforementioned viewpoints, namely, heart rate turbulence (HRT), heart rate variability (HRV), and T-wave alternans. In terms of computational algorithms, we still need clearer scientific evidence, standardizing, and benchmarking, siting on advanced algorithms applied over large and representative datasets. New scenarios like electronic health recordings, big data, long-term monitoring, and cloud databases, will eventually open new frameworks to foresee suitable new paradigms in the near future.

  13. New real-time heartbeat detection method using the angle of a single-lead electrocardiogram.

    Science.gov (United States)

    Song, Mi-Hye; Cho, Sung-Pil; Kim, Wonky; Lee, Kyoung-Joung

    2015-04-01

    This study presents a new real-time heartbeat detection algorithm using the geometric angle between two consecutive samples of single-lead electrocardiogram (ECG) signals. The angle was adopted as a new index representing the slope of ECG signal. The method consists of three steps: elimination of high-frequency noise, calculation of the angle of ECG signal, and detection of R-waves using a simple adaptive thresholding technique. The MIT-BIH arrhythmia database, QT database, European ST-T database, T-wave alternans database and synthesized ECG signals were used to evaluate the performance of the proposed algorithm and compare with the results of other methods suggested in literature. The proposed method shows a high detection rate-99.95% of the sensitivity, 99.95% of the positive predictivity, and 0.10% of the fail detection rate on the four databases. The result shows that the proposed method can yield better or comparable performance than other literature despite the relatively simple process. The proposed algorithm needs only a single-lead ECG, and involves a simple and quick calculation. Moreover, it does not require post-processing to enhance the detection. Thus, it can be effectively applied to various real-time healthcare and medical devices.

  14. Cardiac autonomic function in patients with myasthenia gravis: analysis of the heart-rate variability in the time-domain

    Directory of Open Access Journals (Sweden)

    Sherifa Ahmed Hamed

    2015-03-01

    Full Text Available Aim: Myasthenia gravis (MG is a neuromuscular transmission disorder caused by acetylcholine receptor autoantibodies. Cardiac autonomic dysfunctions were rarely reported in patients with MG. Functional cardiac abnormalities were variable and reported in patients at severe stages of the disease and with thymoma. We investigated cardiac functions in patients with MG using Ambulatory 24-h electrocardiographic Holter-Monitoring. Methods: This study included 20 patients with MG with a mean age of 28.45 ± 8.89 years and duration of illness of 3.52 ± 1.15 years. The standard Holter reports include data for heart-rate, ventricular ectopies (VEs, supraventricular ectopies (SVEs, heart-rate variability (HRV, ST, QT, atrial fibrillation and T-wave alternans. Results: VEs, SVEs and ST-T changes were reported in 55%, 40% and 20% of patients respectively. Compared with healthy subjects (n = 20, HRV components including SDNN, SDANN, SDNN Index, RMS-SD and pNN50 (P = 0.001 for all were reduced in patients indicating sympathetic and parasympathetic autonomic dysfunctions. HRV abnormalities were reported in 30-60% of patients. No significant correlations were identified between SDNN, RMS-SD, pNN50, and duration of illness. Conclusion: Depressed HRV may be an early manifestation of autonomic neuropathy in patients with MG even in milder stages of the disease. This information is useful in rating disease progression and the efficacy of therapeutic interventions.

  15. Electrophysiologic Study of Exhaustive Exercise

    Directory of Open Access Journals (Sweden)

    MA Babaee Bigi

    2010-12-01

    Full Text Available Background: Exhaustive exercise is well known to pose a variety ofhealth hazards, such as sudden cardiac death reported in ultra-marathon runners.Depressed parasympathetic tone is associated with increased risk of suddencardiac death, thus parasympathetic withdrawal in post-exercise phase may be ahigh risk period for sudden death. To date, the effect on cardiacelectrophysiology after exhaustive strenuous exercise has not been described.The aim of this study was to evaluate the impact of severe exhaustive exerciseon cardiac electrophysiology.Methods: The subjects in ranger training were invited to participatein this prospective study. The parameters measured consisted of PR interval, QRSduration, and macro T wave alternans as well as corrected QT, QTc dispersion,Tpeak –Tend interval and Tpeak –Tend dispersion.Results: The study group consisted of 40 consecutive male rangers whocompleted training and the control group (22 healthy age and height matched malesubjects. In regard to electrocardiographic criteria, no differences were foundbetween rangers before and after training program. In respect of therepolarization markers, there were no significant differences between therangers before and after training program.

  16. Electrophysiologic testing guided risk stratification approach for sudden cardiac death beyond the left ventricular ejection fraction.

    Science.gov (United States)

    Gatzoulis, Konstantinos A; Tsiachris, Dimitris; Arsenos, Petros; Tousoulis, Dimitris

    2016-01-26

    Sudden cardiac death threats ischaemic and dilated cardiomyopathy patients. Anti- arrhythmic protection may be provided to these patients with implanted cardiac defibrillators (ICD), after an efficient risk stratification approach. The proposed risk stratifier of an impaired left ventricular ejection fraction has limited sensitivity meaning that a significant number of victims will remain undetectable by this risk stratification approach because they have a preserved left ventricular systolic function. Current risk stratification strategies focus on combinations of non invasive methods like T wave alternans, late potentials, heart rate turbulence, deceleration capacity and others, with invasive methods like the electrophysiologic study. In the presence of an electrically impaired substrate with formed post myocardial infarction fibrotic zones, programmed ventricular stimulation provides important prognostic information for the selection of the patients expected to benefit from an ICD implantation, while due to its high negative predictive value, patients at low risk level may also be detected. Clustering evidence from different research groups and electrophysiologic labs support an electrophysiologic testing guided risk stratification approach for sudden cardiac death.

  17. Noninvasive risk stratification of lethal ventricular arrhythmias and sudden cardiac death after myocardial infarction

    Directory of Open Access Journals (Sweden)

    Kenji Yodogawa, MD

    2014-08-01

    Full Text Available Prediction of lethal ventricular arrhythmias leading to sudden cardiac death is one of the most important and challenging problems after myocardial infarction (MI. Identification of MI patients who are prone to ventricular tachyarrhythmias allows for an indication of implantable cardioverter-defibrillator placement. To date, noninvasive techniques such as microvolt T-wave alternans (MTWA, signal-averaged electrocardiography (SAECG, heart rate variability (HRV, and heart rate turbulence (HRT have been developed for this purpose. MTWA is an indicator of repolarization abnormality and is currently the most promising risk-stratification tool for predicting malignant ventricular arrhythmias. Similarly, late potentials detected by SAECG are indices of depolarization abnormality and are useful in risk stratification. However, the role of SAECG is limited because of its low predictive accuracy. Abnormal HRV and HRT patterns reflect autonomic disturbances, which may increase the risk of lethal ventricular arrhythmias, but the existing evidence is insufficient. Further studies of noninvasive assessment may provide a new insight into risk stratification in post-MI patients.

  18. Surface Electrocardiogram Predictors of Sudden Cardiac Arrest

    Science.gov (United States)

    Abdelghani, Samy A.; Rosenthal, Todd M.; Morin, Daniel P.

    2016-01-01

    Background: Heart disease is a major cause of death in industrialized nations, with approximately 50% of these deaths attributable to sudden cardiac arrest. If patients at high risk for sudden cardiac arrest can be identified, their odds of surviving fatal arrhythmias can be significantly improved through prophylactic implantable cardioverter defibrillator placement. This review summarizes the current knowledge pertaining to surface electrocardiogram (ECG) predictors of sudden cardiac arrest. Methods: We conducted a literature review focused on methods of predicting sudden cardiac arrest through noninvasive electrocardiographic testing. Results: Several electrocardiographic-based methods of risk stratification of sudden cardiac arrest have been studied, including QT prolongation, QRS duration, fragmented QRS complexes, early repolarization, Holter monitoring, heart rate variability, heart rate turbulence, signal-averaged ECG, T wave alternans, and T-peak to T-end. These ECG findings have shown variable effectiveness as screening tools. Conclusion: At this time, no individual ECG finding has been found to be able to adequately stratify patients with regard to risk for sudden cardiac arrest. However, one or more of these candidate surface ECG parameters may become useful components of future multifactorial risk stratification calculators. PMID:27660578

  19. Electrophysiologic testing guided risk stratification approach for sudden cardiac death beyond the left ventricular ejection fraction

    Institute of Scientific and Technical Information of China (English)

    Konstantinos A Gatzoulis; Dimitris Tsiachris; Petros Arsenos; Dimitris Tousoulis

    2016-01-01

    Sudden cardiac death threats ischaemic and dilated cardiomyopathy patients. Anti- arrhythmic protection may be provided to these patients with implanted cardiac defibrillators(ICD), after an efficient risk stratification approach. The proposed risk stratifier of an impaired left ventricular ejection fraction has limited sensitivity meaning that a significant number of victims will remain undetectable by this risk stratification approach because they have a preserved left ventricular systolic function. Current risk stratification strategies focus on combinations of non invasive methods like T wave alternans, late potentials, heart rate turbulence, deceleration capacity and others, with invasive methods like the electrophysiologic study. In the presence of an electrically impaired substrate with formed post myocardial infarction fibrotic zones, programmed ventricular stimulation provides important prognostic information for the selection of the patients expected to benefit from an ICD implantation, while due to its high negative predictive value, patients at low risk level may also be detected. Clustering evidence from different research groups and electrophysiologic labs support an electrophysiologic testing guided risk stratification approach for sudden cardiac death.

  20. VAMAS - Versailles project on Advanced Materials and Standards. Technical working area (TWA) 2: surface chemical analysis. Project A4: evaluation of multilayer reference, coatings for quantitative glow discharge, optical emission spectrometry (GD-OES), and other depth profiling techniques. Report on an inter-laboratory comparison

    Energy Technology Data Exchange (ETDEWEB)

    Beck, U.; Fritz, T.; Gamer, N.; Wirth, T.

    2001-06-01

    The main objective was the evaluation of two different reference coating systems, one conducting for the assessment of dc-GD-OES and one non-conducting for the evaluation of rf-GD-OES. Furthermore, the performance of various dc- and rf-systems was to be studied and the trueness of analysis had to be verified. A restriction was made to two different classes of layer materials: one conducting (on conducting substrate) and one non-conducting (on non-conducting substrate). Hence, with respect to conductivity two coating/substrate systems were provided: TiO{sub 2}/SiO{sub 2}-multilayer (on BK7 glass), and Ti/Al-multilayer (on 100Cr6 steel). (orig.)

  1. X-ray Emission from Young Stars in the TW Hya Association

    CERN Document Server

    Brown, Alexander; Ayres, Thomas R; France, Kevin; Brown, Joanna M

    2014-01-01

    The 9 Myr old TW Hya Association (TWA) is the nearest group (typical distances of $\\sim$50 pc) of pre-main-sequence (PMS) stars with ages less than 10 Myr and contains stars with both actively accreting disks and debris disks. We have studied the coronal X-ray emission from a group of low mass TWA common proper motion binaries using the {\\it{Chandra}} and {\\it{Swift}} satellites. Our aim is to understand better their coronal properties and how high energy photons affect the conditions around young stars and their role in photo-exciting atoms, molecules and dust grains in circumstellar disks and lower density circumstellar gas. Once planet formation is underway, this emission influences protoplanetary evolution and the atmospheric conditions of the newly-formed planets. The X-ray properties for 7 individual stars (TWA 13A, TWA 13B, TWA 9A, TWA 9B, TWA 8A, TWA 8B, and TWA 7) and 2 combined binary systems (TWA 3AB and TWA 2AB) have been measured. All the stars with sufficient signal require two-component fits to...

  2. Effect of nalmefene 20 and 80 mg on the corrected QT interval and T-wave morphology: a randomized, double-blind, parallel-group, placebo- and moxifloxacin-controlled, single-centre study

    DEFF Research Database (Denmark)

    Matz, Jørgen; Graff, Claus; Vainio, Petri J;

    2011-01-01

    Nalmefene is an orally administered competitive opioid receptor antagonist targeted at reducing alcohol consumption in alcohol-dependent patients. As part of the regulatory requirements for drug approval, the potential of novel compounds for causing unwanted proarrhythmia should be studied...

  3. The Clinical Sigfificance of QRS-T Waves in Ventricular Premature Beat by Fuzzy Differentiation%模糊差异鉴别对室性早搏QRS-T波形态的临床意义

    Institute of Scientific and Technical Information of China (English)

    吴达; 俞致远; 祝健

    2000-01-01

    Electrocardiograms (ECG)were collected in 895 cases of simple ventricular prematurebeat(VP3) and 18 cases of ventricuiar premature beat with ventricular tachycardia (VT); QRS-Twaves in ECG were measured and then handled by fuzzy set theory and fuzzy differentiationmethod. It was found that a widened QRS complex, especially with the duration of ≥ 0.16 s.indicated a greater possibility of myocardial damage. This finding is in accord with the resultsderived from classical statistical analysis, but shows some differences with the authoriativetraditional differentiation method suggested by Schamroth in the early 1980 s.%根据模糊集理论和模糊差异鉴别方法,对895例单纯室性早搏和18例室性早搏伴室性心动过速心电图的QRS-T波进行测量并作模糊数据处理,发现QRS波增宽,尤其是当时限≥0.16 s时,存在心肌损害的可能性越大.这一结论与用经典数理统计方法处理所得结论一致,但与80年代初由Schamroth所提出的权威的传统鉴别方法的结论有差异.

  4. Renal failure bring on Niagara falls T wave in electrocardiogram%肾功能衰竭致心电图尼亚加拉瀑布样T波改变一例

    Institute of Scientific and Technical Information of China (English)

    弓旭东; 张冰; 陆志华

    2011-01-01

    @@ 本院近期收治1例肾功能衰竭患者,心电图表现为巨大倒置T波,不对称,伴QT间期明显延长,符合尼亚加拉瀑布样T波改变.该心电图改变,临床比较少见,且少有肾功能衰竭致尼亚加拉瀑布样T波改变病例的报道,现报道1例.

  5. Üç Yaşında Kız Hastada Bilateral Pitosiz İle İlişkili Çocukluk Çağı Alternan Hemiplejisi

    OpenAIRE

    KABAKUŞ, Nimet; Kurt, Abdullah; KURT, Ayşegül Neşe ÇITAK

    2006-01-01

    Alternating hemiplegia of childhood=Alternating hemiplegia of childhood is a rare and poorly understood clinical syndrome that has hemiplegia as the major feature. The syndrome has been linked to migraine, epilepsy and familial paroxysmal choreoathetosis. Cranial nerve dysfunctions are very rare in Alternating hemiplegia of childhood. We present a child with Alternating hemiplegia of childhood who had two attacks associated with ptosis . Flunarizine therapy was started to prevent a new attack...

  6. Predicting the onset of period-doubling bifurcations in noisy cardiac systems.

    Science.gov (United States)

    Quail, Thomas; Shrier, Alvin; Glass, Leon

    2015-07-28

    Biological, physical, and social systems often display qualitative changes in dynamics. Developing early warning signals to predict the onset of these transitions is an important goal. The current work is motivated by transitions of cardiac rhythms, where the appearance of alternating features in the timing of cardiac events is often a precursor to the initiation of serious cardiac arrhythmias. We treat embryonic chick cardiac cells with a potassium channel blocker, which leads to the initiation of alternating rhythms. We associate this transition with a mathematical instability, called a period-doubling bifurcation, in a model of the cardiac cells. Period-doubling bifurcations have been linked to the onset of abnormal alternating cardiac rhythms, which have been implicated in cardiac arrhythmias such as T-wave alternans and various tachycardias. Theory predicts that in the neighborhood of the transition, the system's dynamics slow down, leading to noise amplification and the manifestation of oscillations in the autocorrelation function. Examining the aggregates' interbeat intervals, we observe the oscillations in the autocorrelation function and noise amplification preceding the bifurcation. We analyze plots--termed return maps--that relate the current interbeat interval with the following interbeat interval. Based on these plots, we develop a quantitative measure using the slope of the return map to assess how close the system is to the bifurcation. Furthermore, the slope of the return map and the lag-1 autocorrelation coefficient are equal. Our results suggest that the slope and the lag-1 autocorrelation coefficient represent quantitative measures to predict the onset of abnormal alternating cardiac rhythms.

  7. Detection of the fingerprint of the electrophysiological abnormalities that increase vulnerability to life-threatening ventricular arrhythmias.

    Science.gov (United States)

    Cain, Michael E; Arthur, R Martin; Trobaugh, Jason W

    2003-10-01

    Reduction of sudden death requires accurate identification of patients at risk for ventricular tachycardia (VT) and effective therapies. The Multicenter Unsustained Tachycardia Trial and Multicenter Automatic Defibrillator Implantation Trials demonstrate that the implantable cardioverter defibrillator impacts favorably on the incidence of VT in patients with myocardial infarction, underscoring the need to detect the electrophysiologic abnormalities required for the development of VT. Methods used for this purpose include: Holter monitoring, ejection fraction, signal-averaged ECG, heart rate variability, T-wave alternans, baroreflex sensitivity, and programmed stimulation. Performance of each method alone has demonstrated high-negative but low-positive predictive values. Recent studies confirm that their use in combination augments performance.A second approach for improving performance has been to reexamine how well each method detects the electrophysiological derangements that lead to VT. Our recent work has focused on the signal-averaged ECG. Judging from transmural maps of ventricular activation during VT and sinus rhythm obtained from patients, late potentials fail to detect completely signals from myocardium responsible for VT. To obviate this limitation we developed an approach based on inferred epicardial potentials in the frequency domain from 190-surface ECGs using individualized heart-torso models. Torso geometry and electrode positions are measured with a 3-armed digitizer. The location of cardiac structures is determined using echocardiography. The pericardial surface is approximated by a sphere that encloses the heart. Epicardial potentials are inferred using the boundary element method with zero-order Tikhonov regularization and the Composite Residual Smoothing Operator over the QRS complex. Studies are underway to determine if analysis of bioelectrical signals enveloping arrhythmogenic tissue improves identification of patients vulnerable to VT.

  8. Scaling Exponent Determined by a Bio-Signal Computation for the Healthy and Diseased Heartbeat

    Directory of Open Access Journals (Sweden)

    Tomoo Katsuyama

    2009-04-01

    Full Text Available We analyzed heartbeat-intervals by using our own program of detrended fluctuation analysis (DFA. "Alternans" is an arrhythmia exhibiting alternating amplitude or alternating interval from heartbeat to heartbeat, which was first described in 1872 by Traube. Recently, alternans was finally recognized as the harbinger of a cardiac disease because physicians noticed that an ischemic heart exhibits alternans. To quantify irregularity of the heartbeat including alternans, we used the DFA and revealed that the alternans rhythm lowers the scaling exponent. We conclude that the scaling exponent calculated by the DFA reflects a risk for the "failing" heart. The scaling exponents could determine whether the subjects are under sick or healthy conditions on the basis of cardiac physiology.

  9. X-ray Emission from Young Stars in the TW Hya Association

    Science.gov (United States)

    Brown, Alexander; Herczeg, Gregory J.; Ayres, Thomas R.; France, Kevin; Brown, Joanna M.

    2015-01-01

    The 9 Myr old TW Hya Association (TWA) is the nearest group (typical distances of ˜50 pc) of pre-main-sequence (PMS) stars with ages less than 10 Myr and contains stars with both actively accreting disks and debris disks. We have studied the coronal X-ray emission from a group of low mass TWA common proper motion binaries using the Chandra and Swift satellites. Our aim is to understand better their coronal properties and how high energy photons affect the conditions around young stars and their role in photo-exciting atoms, molecules and dust grains in circumstellar disks and lower density circumstellar gas. Once planet formation is underway, this emission influences protoplanetary evolution and the atmospheric conditions of the newly-formed planets. The X-ray properties for 7 individual stars (TWA 13A, TWA 13B, TWA 9A, TWA 9B, TWA 8A, TWA 8B, and TWA 7) and 2 combined binary systems (TWA 3AB and TWA 2AB) have been measured. All the stars with sufficient signal require two-component fits to their CCD-resolution X-ray spectra, typically with a dominant hot (~2 kev (25 MK)) component and a cooler component at ~0.4 keV (4 MK). The brighter sources all show significant X-ray variability (at a level of 50-100% of quiescence) over the course of 5-15 ksec observations due to flares. We present the X-ray properties for each of the stars and find that the coronal emission is in the super-saturated rotational domain.

  10. A Medical Monitoring Program for the Marine Hazardous Chemical Worker. Volume 1

    Science.gov (United States)

    1985-12-01

    Threshold Limit Value (TLV-TWA) 6. Short Term Exposure Limit (STEL) 7.’ Immediately Dangerous to Life or Health (IDLH) Concentration 8. Odor Threshold 9...SXX 0 SULFUR DIOXIDE SF0 0 SUlFURIC ACID SFA 0 SULFURIC ACID, SPENT SAC 0 TAL LOW TLO D TALLOW FATTY ALCOHOL TWA D TALLOW NITRILE D 1,1.2,2

  11. From Theory of Work Adjustment to Person-Environment Correspondence Counseling: Vocational Psychology as Positive Psychology

    Science.gov (United States)

    Eggerth, Donald E.

    2008-01-01

    This article argues that vocational psychology is, and has been, positive psychology. It provides an overview of the theory of work adjustment (TWA), one of the most robust and best validated theories in vocational psychology. It also provides an introduction to person-environment-correspondence (PEC) counseling, an extension of the TWA concepts…

  12. Enflurane, isoflurane and cyclopropane.

    NARCIS (Netherlands)

    Maclaine Pont, M.A.

    1998-01-01

    The committee recommends the following health based occupational exposure limits: - enflurane: 20 ppm (153 mg/m3) TWA 8 h - isoflurane: 20 ppm (153 mg/m3) TWA 8 h. For cyclopropane no exposure limit can be recommended. For simultaneous exposure to a combination of anaesthetic gases the sum of each s

  13. TW Hya Association Membership and New WISE-detected Circumstellar Disks

    CERN Document Server

    Schneider, Adam; Song, Inseok

    2012-01-01

    We assess the current membership of the nearby, young TW Hydrae Association and examine newly proposed members with the Wide-field Infrared Survey Explorer (WISE) to search for infrared excess indicative of circumstellar disks. Newly proposed members TWA 30A, TWA 30B, TWA 31, and TWA 32 all show excess emission at 12 and 22 \\mum providing clear evidence for substantial dusty circumstellar disks around these low-mass, ~8 Myr old stars that were previously shown to likely be accreting from circumstellar material. TWA 30B shows large amounts of self-extinction, likely due to an edge-on disk geometry. We also confirm previously reported circumstellar disks with WISE, and determine a 22 \\mum excess fraction of 42+/- 9% based on our results.

  14. Electrocardiologic and related methods of non-invasive detection and risk stratification in myocardial ischemia: state of the art and perspectives

    Directory of Open Access Journals (Sweden)

    Seeck, Andrea

    2010-01-01

    Full Text Available Background: Electrocardiographic methods still provide the bulk of cardiovascular diagnostics. Cardiac ischemia is associated with typical alterations in cardiac biosignals that have to be measured, analyzed by mathematical algorithms and allegorized for further clinical diagnostics. The fast growing fields of biomedical engineering and applied sciences are intensely focused on generating new approaches to cardiac biosignal analysis for diagnosis and risk stratification in myocardial ischemia. Objectives: To present and review the state of the art in and new approaches to electrocardiologic methods for non-invasive detection and risk stratification in coronary artery disease (CAD and myocardial ischemia; secondarily, to explore the future perspectives of these methods. Methods: In follow-up to the Expert Discussion at the 2008 Workshop on "Biosignal Analysis" of the German Society of Biomedical Engineering in Potsdam, Germany, we comprehensively searched the pertinent literature and databases and compiled the results into this review. Then, we categorized the state-of-the-art methods and selected new approaches based on their applications in detection and risk stratification of myocardial ischemia. Finally, we compared the pros and cons of the methods and explored their future potentials for cardiology. Results: Resting ECG, particularly suited for detecting ST-elevation myocardial infarctions, and exercise ECG, for the diagnosis of stable CAD, are state-of-the-art methods. New exercise-free methods for detecting stable CAD include cardiogoniometry (CGM; methods for detecting acute coronary syndrome without ST elevation are Body Surface Potential Mapping, functional imaging and CGM. Heart rate variability and blood pressure variability analyses, microvolt T-wave alternans and signal-averaged ECG mainly serve in detecting and stratifying the risk for lethal arrythmias in patients with myocardial ischemia or previous myocardial infarctions

  15. Clinical significance of fragmented QRS complex,Tpeak-Tend interval and ischemic T wave about ventricular arrhythmia of myocardial infarction%fQ RS波、T p-e间期及缺血性J波在心肌梗死后室性心律失常中的意义

    Institute of Scientific and Technical Information of China (English)

    黄飞燕; 丁晓梅

    2014-01-01

    Fragmented QRS complex has been regarded as marker of myocardial scar.Myocardial fibrosis causes slow and inhomoge-neous activation.The interval between Tpeak and Tend,a novel marker of heterogeneity of ventricular repolarization,has been recognized as a surrogate diagnostic parameter of transmural dispersion of repolarization.Ischemic J-wave results from increased Ito of cardiac is-chemic.This markers may serve as high-risk warning of malignant ventricular arrhythmia and sudden cardiac death.So a review is made on correlative research in recent years.%fQRS被视为心肌瘢痕的标记,心肌纤维化导致心肌动作电位的缓慢和不均一。心电图T波峰末间期(Tp-e间期)代表心室复极化离散,被公认为反映跨室壁离散度的诊断性指标。缺血性J波是由心肌缺血损伤导致的瞬时外向钾离子流(Ito)增强引起。上述可作为恶性室性心律失常及心脏性猝死的高危预警指标。相关研究综述如下。

  16. Some theoretical results on the observability of repolarization heterogeneity on surface ECG.

    Science.gov (United States)

    Mainardi, Luca; Sassi, Roberto

    2013-01-01

    Assessing repolarization heterogeneity (RH) from surface ECG recording is an open issue in modern electrocardiography, despite the fact that several indexes measured on the T-wave have been proposed and tested. To understand how RH occurring at myocite level is reflected on T-wave shapes, in this paper we propose a mathematical framework that combines a simple statistical model of cardiac repolarization times with the dominant T-wave formalism. Within this framework we compare different T-wave features such as T-wave amplitude, T-wave amplitude variability or QT intervals and we describe mathematically how they are linked to the spatial and temporal components of repolarization heterogeneity.

  17. Exhaustion-related changes in cardiovascular and cortisol reactivity to acute psychosocial stress.

    Science.gov (United States)

    Jönsson, Peter; Österberg, Kai; Wallergård, Mattias; Hansen, Åse Marie; Garde, Anne Helene; Johansson, Gerd; Karlson, Björn

    2015-11-01

    Prior findings indicate that individuals scoring high on vital exhaustion show a dysfunctional stress response (DSR), that is, reduced cortisol reactivity and habituation to psychosocial stressors. The main aim of the present study was to examine whether a DSR may be a vulnerability factor in exhaustion disorder (ED). We examined whether a DSR is present during the early stages of ED, and still is present after recovery. Three groups were studied: 1. Former ED patients (n=14); 2. persons who during the past 6 month had experienced stress at work and had a Shirom-Melamed Burnout Questionnaire (SMBQ) score over 3.75, considered to indicate a pre-stage of ED (n=17); 3. persons who had not experienced stress at work during the past 6 months and had a SMBQ score below 2.75 (n=20). The participants were exposed twice to a virtual version of the Trier Social Stress Test (V-TSST), during which salivary cortisol samples were collected. In addition, high frequency heart rate variability (HF-HRV), heart rate (HR), t-wave amplitude (TWA), and α-amylase were assessed to examine stress reactivity and habituation in the autonomic nervous system (ANS). The initial analyses showed clear hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS) activations in both V-TSST sessions, together with habituation of cortisol and heart rate in the second session, but without any significant group differences. However, the former ED patients showed considerable variation in self-reported signs of exhaustion (SMBQ). This led us to assign former ED patients with lower ratings into the low SMBQ group (LOWS) and those with higher ratings to the high SMBQ group (HIGHS). When repeating the analyses a different picture emerged; the HIGHS showed a lower cortisol response to the V-TSST than did the LOWS. Both groups' cortisol response habituated to the second V-TSST session. The ANS responses did not differ between the two groups. Thus, persons in a pre-stage of ED and

  18. 49 CFR 227.117 - Hearing protector attenuation.

    Science.gov (United States)

    2010-10-01

    ... exposure to an 8-hour TWA of 90 decibels or lower, as required by § 227.115. (c) For employees who have...-weighted average of 85 decibels or lower. (d) The adequacy of hearing protector attenuation shall be...

  19. Occupational Exposure to Carbon Nanotubes and Nanofibers

    Science.gov (United States)

    ... These nanoscale-based products are typically called "first generation" products of nanotechnology. Many of these nanoscale-based ... TWA) concentration, and (4) describes strategies for controlling workplace exposures and implementing a medical surveillance program. The ...

  20. Close Companions to Nearby Young Stars from Adaptive Optics Imaging on VLT and Keck

    Science.gov (United States)

    Haisch, Karl E.; Jayawardhana, Ray; Brandeker, Alexis; Mardones, Diego

    We report the results of VLT and Keck adaptive optics surveys of known members of the η Chamaeleontis, MBM 12, and TW Hydrae (TWA) associations to search for close companions. The multiplicity statistics of η Cha, MBM 12, and TWA are quite high compared with other clusters and associations, although our errors are large due to small number statistics. We have resolved S18 in MBM 12 and RECX 9 in η Cha into triples for the first time. The tight binary TWA 5Aab in the TWA offers the prospect of measuring the dynamical masses of both components as well as an independent distance to the system within a few years. The AO detection of the close companion to the nearby young star χ1 Orionis, previously inferred from radial velocity and astrometric observations, has already made it possible to derive the dynamical masses of that system without any astrophysical assumption.

  1. Close Companions to Nearby Young Stars from Adaptive Optics Imaging on VLT and Keck

    CERN Document Server

    Haisch, K E; Brandeker, A; Mardones, D; Jr., Karl E. Haisch; Jayawardhana, Ray; Brandeker, Alexis; Mardones, Diego

    2003-01-01

    We report the results of VLT and Keck adaptive optics surveys of known members of the Eta Chamaeleontis, MBM 12, and TW Hydrae (TWA) associations to search for close companions. The multiplicity statistics of Eta Cha, MBM 12, and TWA are quite high compared with other clusters and associations, although our errors are large due to small number statistics. We have resolved S18 in MBM 12 and RECX 9 in Eta Cha into triples for the first time. The tight binary TWA 5Aab in the TWA offers the prospect of measuring the dynamical masses of both components as well as an independent distance to the system within a few years. The AO detection of the close companion to the nearby young star Chi^1 Orionis, previously inferred from radial velocity and astrometric observations, has already made it possible to derive the dynamical masses of that system without any astrophysical assumption.

  2. Ullage Compatible Optical Sensor for Monitoring Safety Significant Malfunctions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Significant emphasis has been placed on aircraft fuel tank safety following the TWA Flight 800 accident in July 1996. Upon investigation, the National Transportation...

  3. 14. EXPOSURE AND EFFECT MONITORING OF WORKERS IN THE COBALT/HARD METAL INDUSTRIES: ABSENCE OF SIGNIFICANT GENOTOXIC EFFECTS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@An increased lung cancer risk is associated with occupational exposure to mixtures of cobalt metal and metallic carbide particles, but when exposure is to cobalt metal alone. The current TLV-TWA was established without consideration of carcinogenicity data. The present study was designed to assess whether an increased cancer risk can be detected in workers currently exposed on average to the TLV-TWA (20 μg/m3).

  4. Reference values of electrocardiogram repolarization variables in a healthy population

    DEFF Research Database (Denmark)

    Haarmark, Christian; Graff, Claus; Andersen, Mads P

    2010-01-01

    Reference values for T-wave morphology analysis and evaluation of the relationship with age, sex, and heart rate are lacking in the literature. In this study, we characterized T-wave morphology in a large sample of healthy individuals....

  5. M Stars in the TW Hya Association: Stellar X-rays and Disk Dissipation

    CERN Document Server

    Kastner, Joel H; Punzi, Kristina; Stelzer, Beate; Gorti, Uma; Pascucci, Ilaria; Argiroffi, Costanza

    2016-01-01

    To investigate the potential connection between the intense X-ray emission from young, low-mass stars and the lifetimes of their circumstellar, planet-forming disks, we have compiled the X-ray luminosities ($L_X$) of M stars in the $\\sim$8 Myr-old TW Hya Association (TWA) for which X-ray data are presently available. Our investigation includes analysis of archival Chandra data for the TWA binary systems TWA 8, 9, and 13. Although our study suffers from poor statistics for stars later than M3, we find a trend of decreasing $L_X/L_{bol}$ with decreasing $T_{eff}$ for TWA M stars wherein the earliest-type (M0--M2) stars cluster near $\\log{(L_X/L_{bol})} \\approx -3.0$ and then $\\log{(L_X/L_{bol})}$ decreases, and its distribution broadens, for types M4 and later. The fraction of TWA stars that display evidence for residual primordial disk material also sharply increases in this same (mid-M) spectral type regime. This apparent anticorrelation between the relative X-ray luminosities of low-mass TWA stars and the lo...

  6. Uncovering the dynamics of cardiac systems using stochastic pacing and frequency domain analyses.

    Science.gov (United States)

    Lemay, Mathieu; de Lange, Enno; Kucera, Jan P

    2012-01-01

    Alternans of cardiac action potential duration (APD) is a well-known arrhythmogenic mechanism which results from dynamical instabilities. The propensity to alternans is classically investigated by examining APD restitution and by deriving APD restitution slopes as predictive markers. However, experiments have shown that such markers are not always accurate for the prediction of alternans. Using a mathematical ventricular cell model known to exhibit unstable dynamics of both membrane potential and Ca²⁺ cycling, we demonstrate that an accurate marker can be obtained by pacing at cycle lengths (CLs) varying randomly around a basic CL (BCL) and by evaluating the transfer function between the time series of CLs and APDs using an autoregressive-moving-average (ARMA) model. The first pole of this transfer function corresponds to the eigenvalue (λ(alt)) of the dominant eigenmode of the cardiac system, which predicts that alternans occurs when λ(alt) ≤ -1. For different BCLs, control values of λ(alt) were obtained using eigenmode analysis and compared to the first pole of the transfer function estimated using ARMA model fitting in simulations of random pacing protocols. In all versions of the cell model, this pole provided an accurate estimation of λ(alt). Furthermore, during slow ramp decreases of BCL or simulated drug application, this approach predicted the onset of alternans by extrapolating the time course of the estimated λ(alt). In conclusion, stochastic pacing and ARMA model identification represents a novel approach to predict alternans without making any assumptions about its ionic mechanisms. It should therefore be applicable experimentally for any type of myocardial cell.

  7. Uncovering the dynamics of cardiac systems using stochastic pacing and frequency domain analyses.

    Directory of Open Access Journals (Sweden)

    Mathieu Lemay

    Full Text Available Alternans of cardiac action potential duration (APD is a well-known arrhythmogenic mechanism which results from dynamical instabilities. The propensity to alternans is classically investigated by examining APD restitution and by deriving APD restitution slopes as predictive markers. However, experiments have shown that such markers are not always accurate for the prediction of alternans. Using a mathematical ventricular cell model known to exhibit unstable dynamics of both membrane potential and Ca²⁺ cycling, we demonstrate that an accurate marker can be obtained by pacing at cycle lengths (CLs varying randomly around a basic CL (BCL and by evaluating the transfer function between the time series of CLs and APDs using an autoregressive-moving-average (ARMA model. The first pole of this transfer function corresponds to the eigenvalue (λ(alt of the dominant eigenmode of the cardiac system, which predicts that alternans occurs when λ(alt ≤ -1. For different BCLs, control values of λ(alt were obtained using eigenmode analysis and compared to the first pole of the transfer function estimated using ARMA model fitting in simulations of random pacing protocols. In all versions of the cell model, this pole provided an accurate estimation of λ(alt. Furthermore, during slow ramp decreases of BCL or simulated drug application, this approach predicted the onset of alternans by extrapolating the time course of the estimated λ(alt. In conclusion, stochastic pacing and ARMA model identification represents a novel approach to predict alternans without making any assumptions about its ionic mechanisms. It should therefore be applicable experimentally for any type of myocardial cell.

  8. BANYAN. IX. The Initial Mass Function and Planetary-mass Object Space Density of the TW HYA Association

    Science.gov (United States)

    Gagné, Jonathan; Faherty, Jacqueline K.; Mamajek, Eric E.; Malo, Lison; Doyon, René; Filippazzo, Joseph C.; Weinberger, Alycia J.; Donaldson, Jessica K.; Lépine, Sébastien; Lafrenière, David; Artigau, Étienne; Burgasser, Adam J.; Looper, Dagny; Boucher, Anne; Beletsky, Yuri; Camnasio, Sara; Brunette, Charles; Arboit, Geneviève

    2017-02-01

    A determination of the initial mass function (IMF) of the current, incomplete census of the 10 Myr-old TW Hya association (TWA) is presented. This census is built from a literature compilation supplemented with new spectra and 17 new radial velocities from ongoing membership surveys, as well as a reanalysis of Hipparcos data that confirmed HR 4334 (A2 Vn) as a member. Although the dominant uncertainty in the IMF remains census incompleteness, a detailed statistical treatment is carried out to make the IMF determination independent of binning while accounting for small number statistics. The currently known high-likelihood members are fitted by a log-normal distribution with a central mass of {0.21}-0.06+0.11 M ⊙ and a characteristic width of {0.8}-0.1+0.2 dex in the 12 M Jup–2 M ⊙ range, whereas a Salpeter power law with α ={2.2}-0.5+1.1 best describes the IMF slope in the 0.1–2 M ⊙ range. This characteristic width is higher than other young associations, which may be due to incompleteness in the current census of low-mass TWA stars. A tentative overpopulation of isolated planetary-mass members similar to 2MASS J11472421–2040204 and 2MASS J11193254–1137466 is identified: this indicates that there might be as many as {10}-5+13 similar members of TWA with hot-start model-dependent masses estimated at ∼5–7 M Jup, most of which would be too faint to be detected in 2MASS. Our new radial velocity measurements corroborate the membership of 2MASS J11472421–2040204, and secure TWA 28 (M8.5 γ), TWA 29 (M9.5 γ), and TWA 33 (M4.5 e) as members. The discovery of 2MASS J09553336–0208403, a young L7-type interloper unrelated to TWA, is also presented.

  9. RIESGO DE ARRITMIAS E HIPERTENSIÓN ARTERIAL / Risk of Arrhythmias and hypertension

    Directory of Open Access Journals (Sweden)

    Raimundo Carmona Puerta

    2012-03-01

    the development of arrhythmias in hypertensive patients. The presence of ventricular arrhythmias, from premature ventricular complexes to ventricular tachycardia, has been shown in a 10 to 27% of affected patients, a percentage that decreases with the severity of the arrhythmia. Noninvasive risk markers for ventricular arrhythmias have been summarized as follows: dispersion and variability of the QT interval, presence of late potentials, heart rate variability, abnormal morphology and T-wave alternans. All of these are related to anatomic-structural changes of the ventricular wall, which affect the action potential. The importance of knowing the epidemiology, pathophysiology, and noninvasive risk markers for arrhythmias in hypertensive patients, offers a way for the application of the proper therapeutic in the control of blood pressure and regression of hypertrophy, as has been shown by inhibitor drugs of the renin-angiotensin-aldosterone system, which decrease the risk of arrhythmias.

  10. New Parallaxes and a Convergence Analysis for the TW Hya Association

    CERN Document Server

    Donaldson, Jessica K; Gagné, Jonathan; Faherty, Jacqueline K; Boss, Alan P; Keiser, Sandra A

    2016-01-01

    The TW Hya Association (TWA) is a nearby stellar association with an age of $\\sim$ 5-10 Myr. This is an important age for studying the late stages of star and planet formation. We measure the parallaxes of 14 candidate members of TWA. That brings to 38 the total number of individual stars with fully measured kinematics, i.e. proper motion, radial velocity, and parallax, to describe their motions through the Galaxy. We analyze these kinematics to search for convergence to a smaller volume in the past, but we find the association is never much more compact than it is at present. We show that it is difficult to measure traceback ages for associations such as TWA that have expected velocity dispersions of 1-2 km s$^{-1}$ with typical measurement uncertainties. We also use our stellar distances and pre-main-sequence evolutionary tracks to find the average age of the association of 7.9 $\\pm$ 1.0 Myr. Additionally, our parallax measurement of TWA 32 indicates it should be considered a bona fide member of TWA. Two ne...

  11. Sex-specific positive and negative consequences of avoidance training during childhood on adult active avoidance learning in mice

    Science.gov (United States)

    Spröwitz, Almuth; Bock, Jörg; Braun, Katharina

    2013-01-01

    In humans and animals cognitive training during childhood plays an important role in shaping neural circuits and thereby determines learning capacity later in life. Using a negative feedback learning paradigm, the two-way active avoidance (TWA) learning, we aimed to investigate in mice (i) the age-dependency of TWA learning, (ii) the consequences of pretraining in childhood on adult learning capacity and (iii) the impact of sex on the learning paradigm in mice. Taken together, we show here for the first time that the beneficial or detrimental outcome of pretraining in childhood depends on the age during which TWA training is encountered, indicating that different, age-dependent long-term “memory traces” might be formed, which are recruited during adult TWA training and thereby either facilitate or impair adult TWA learning. While pretraining during infancy results in learning impairment in adulthood, pretraining in late adolescence improved avoidance learning. The experiments revealed a clear sex difference in the group of late-adolescent mice: female mice showed better avoidance learning during late adolescence compared to males, and the beneficial impact of late-adolescent pretraining on adult learning was more pronounced in females compared to males. PMID:24137115

  12. Simulated consumer exposure to propellant HCFC 22 (chlorodifluoromethane) in aerosol personal products.

    Science.gov (United States)

    Hartop, P J; Adams, M G

    1989-02-01

    Summary The potential human exposure to the aerosol propellant HCFC 22 (chlorodifluoromethane) arising from its use in personal products has been assessed. HCFC 22 concentrations were measured in the 'breathing zone' of an experimental manikin and an 'accompanying child' designed to simulate human use of hairsprays, body sprays and antiperspirants in a closed room. Results were expressed as the 10-min time-weighted average concentration in the air (TWA 10) and as the peak concentration in the 'breathing zone' of the 'user'. Following a 10-s use of hairspray containing approximately 20-40% HCFC 22, TWA10 values for an adult user and child were 64-116 ppm and 44-100 ppm, respectively. Use of an aerosol body spray containing 20-65% HCFC 22 for 5-20 s gave rise to TWA10 values of 32-411 ppm for an adult user and 20-395 ppm for a child. A 4-s use of an antiperspirant containing approximately 20-40% HCFC 22 sprayed at a distance of 10-30 cm from the breathing zone of the adult user generated TWA 10 values in the range of 14-34 ppm for both the adult user and child. Opening the door of the room prior to hairspray and antiperspirant spraying slightly reduced these TWA 10 values. The peak values recorded in these studies for the adult user were 208 ppm for hairspray, 1415 ppm for body sprays and 82 ppm for antiperspirants.

  13. Sex-specific positive and negative consequences of avoidance training during childhood on adult active avoidance learning in mice

    Directory of Open Access Journals (Sweden)

    Almuth eSpröwitz

    2013-10-01

    Full Text Available In humans and animals cognitive training during childhood plays an important role in shaping neural circuits and thereby determines learning capacity later in life. Using a negative feedback learning paradigm, the two-way active avoidance (TWA learning, we aimed to investigate in mice (i the age-dependency of TWA learning, (ii the consequences of pretraining in childhood on adult learning capacity and (iii the impact of sex on the learning paradigm in mice. Taken together, we show here for the first time that the beneficial or detrimental outcome of pretraining in childhood depends on the age during which TWA training is encountered, indicating that different, age-dependent long-term memory traces might be formed, which are recruited during adult TWA training and thereby either facilitate or impair adult TWA learning. While pretraining during infancy results in learning impairment in adulthood, pretraining in late adolescence improved avoidance learning.The experiments revealed a clear sex difference in the group of late-adolescent mice: female mice showed better avoidance learning during late adolescence compared to males, and the beneficial impact of late-adolescent pretraining on adult learning was more pronounced in females compared to males.

  14. Presentación

    OpenAIRE

    Tejada Fernández, José

    2015-01-01

    Presentación del volumen «Formación en alternancia en la Educación Superior: Perspectivas y experiencias». Presentació del volum «Formació en alternança a l’Educació Superior: Perspectives i experiències». Presentation of the volume "Alternance training in Higher Education: approaches and experiences".

  15. Cuticular extracts from Acromis sparsa (Coleoptera: Cassidinae) mediate arrestment behavior of the commensal canestriniid mite Grandiella rugosita.

    Science.gov (United States)

    Beran, Franziska; Geiselhardt, Sven; Vargas, Gloria; Windsor, Donald M

    2014-09-01

    Astigmatid mites in the family Canestriniidae are often closely associated with tortoise leaf beetles (Chrysomelidae: Cassidinae). For example, the survival of the commensal canestriniid mite Grandiella rugosita depends on dispersal to the cassidine beetle Acromis sparsa. Here, we tested whether the beetle cuticle provides chemical cues for host recognition for G. rugosita. In two-choice assays with cuticular extracts from A. sparsa and the co-occurring, non-host cassidine Chelymorpha alternans offered simultaneously, mites clearly preferred the area treated with extract from their host. In no-choice assays, G. rugosita spent three times longer and moved three times slower on host cuticular extracts compared to non-host extracts and the solvent control. Analyses of the chemical composition of cuticular extracts from males and females of A. sparsa and C. alternans revealed complex mixtures of mainly methyl branched hydrocarbons, which clearly separated both species in a principal component analysis. We found no qualitative difference between males and females of either species, but in C. alternans quantitative differences between males and females were detected. Our results demonstrate that G. rugosita is able to discriminate between cuticular extracts from its host A. sparsa and the non-host C. alternans. The components eliciting the observed arrestment behavior remain to be determined.

  16. Glucan synthesis in the genus Lactobacillus: Isolation and characterization of glucansucrase genes, enzymes and glucan products from six different strains

    NARCIS (Netherlands)

    Kralj, S.; Geel-Schutten, G.H. van; Dondorff, M.M.G.; Kirsanovs, S.; Maarel, M.J.E.C. van der; Dijkhuizen, L.

    2004-01-01

    Members of the genera Streptococcus and Leuconostoc synthesize various α-glucans (dextran, alternan and mutan). In Lactobacillus, until now, the only glucosyltransferase (GTF) enzyme that has been characterized is gtfA of Lactobacillus reuteri 121, the first GTF enzyme synthesizing a glucan

  17. Expression of different glucansucrases in potato tubers: implications for starch biosynthesis

    NARCIS (Netherlands)

    Kok-Jacon, G.A.

    2005-01-01

    This thesis describes the production of dextran (polymers with -(1→6)-linked glucosyl residues), mutan (polymers with -(1→3)-linked glucosyl residues) and alternan (polymers with alternating -(1→3)/ -(1→6)-linked glucosyl residues) in potato tubers. Modifications of the physicochemical properties of

  18. Lactic Acid Bateria - Friend or Foe? Lactic Acid Bacteria in the Production of Polysaccharides and Fuel Ethanol

    Science.gov (United States)

    Lactic acid bacteria (LAB) have been widely used in the production of fermented foods and as probiotics. Alternan is a glucan with a distinctive backbone structure of alternating alpha-(1,6) and alpha-(1,3) linkages produced by the LAB Leuconostoc mesenteroides. In recent years, improved strains f...

  19. Glucan synthesis in the genus Lactobacillus: Isolation and characterization of glucansucrase genes, enzymes and glucan products from six different strains

    NARCIS (Netherlands)

    Kralj, S.; Geel-Schutten, G.H. van; Dondorff, M.M.G.; Kirsanovs, S.; Maarel, M.J.E.C. van der; Dijkhuizen, L.

    2004-01-01

    Members of the genera Streptococcus and Leuconostoc synthesize various α-glucans (dextran, alternan and mutan). In Lactobacillus, until now, the only glucosyltransferase (GTF) enzyme that has been characterized is gtfA of Lactobacillus reuteri 121, the first GTF enzyme synthesizing a glucan (reutera

  20. Ku-Band Traveling Wave Slot Array Using Simple Scanning Control

    Science.gov (United States)

    Host, Nicholas K.; Chen, Chi-Chih; Volakis, John L.; Miranda, Felix A.

    2015-01-01

    This paper introduces a feeding concept aimed at simplifying the backend (phase shifters) of traditional phased arrays. As an alternative to traditional phased arrays, we employ a traveling wave array (TWA) using a single feedline whose propagation constant is controlled via a single, small mechanical movement without a need for phase shifters to enable scanning. Specifically, a dielectric plunger is positioned within a parallel plate waveguide (PPW) transmission line (TL) that feeds the TWA. By adjusting the position of the dielectric plunger within the PPW feeding the TWA, beam steering is achieved. A 20 element array is designed at 13GHz shown to give stable realized gain across the angular range of -25 deg. less than or equal to theta less than or equal to 25 deg. A proof of concept array is fabricated and measured to demonstrate and validate the concept's operation.

  1. Social Cognitive Career Theory, the Theory of Work Adjustment, and Work Satisfaction of Retirement-Age Adults.

    Science.gov (United States)

    Foley, Pamela F; Lytle, Megan C

    2015-06-01

    Despite a recent increase in the number of adults who work past traditional retirement age, existing theories of vocational behavior have not yet received adequate empirical support. In a large sample of adults age 60-87, we evaluated the relationship between theorized predictors of work satisfaction proposed by Social Cognitive Career Theory (SCCT), work satisfaction as a predictor of continued work, as proposed by the Theory of Work adjustment (TWA), as well as the influence of reported experiences of discrimination on these relationships. While the results supported most of the predicted relationships, the effects of discrimination were stronger than the variables proposed by either SCCT or TWA for the present sample.

  2. Hiring Costs and Temporary Work Agencies. An explication of regional disparities across Spanish provinces

    Directory of Open Access Journals (Sweden)

    Pedro García-del-Barrio

    2014-01-01

    Full Text Available The Temporary Work Agencies (TWA industry experienced continuous growth throughout the 90s, and now represents around 15% of temporary hiring in Spain. More interestingly, are markable regional disparity in this sector exists across Spanish provinces. By developing a simple theoretical model and using panel data methodology, this article examines the Spanish caseand suggests that the costs of recruiting, training and screening could explain a large part of the regional disparity. This result is supported by the empirical fact that the TWA firms have greater success in markets with low unemployment rates, where the average duration of unemploymen tis longer, and in provinces with higher concentrations of urban population, respectively.

  3. Periprosthetic osteolysis after total wrist arthroplasty

    DEFF Research Database (Denmark)

    Boeckstyns, Michel E H; Herzberg, Guillaume

    2014-01-01

    Background and Literature Review Periprosthetic osteolysis (PPO) after second- or third-generation total wrist arthroplasty (TWA), with or without evident loosening of the implant components, has previously been reported in the literature, but rarely in a systematic way. Purpose The purpose....... Conclusion Periprosthetic loosening is frequent following a TWA. In our series it was not necessarily associated with implant loosening and seemed to stabilize within 3 years. Close and continued observation is, however, recommended. Level of Evidence Therapeutic IV....

  4. Characteristics measurement of gain and refractive index of traveling-wave semiconductor optical amplifier

    Institute of Scientific and Technical Information of China (English)

    MIAO Qing-yuan; Huang De-xiu; WANG Tao; KONG Xiao-jian; KE Chang-jian

    2005-01-01

    A novel method to measure the gain and refractive index characteristics of traveling-wave semiconductor optical amplifier(TMA) is presented.In-out fiber ends of TWA are used to construct an external cavity resonator to produce big ripple on amplified spontaneous emission(ASE) spectrum.By this means,Hakki-Paoli method is adopted to obtain the gain spectra of TWA over a wide spectral range.From measured longitudinal mode spacing and peak wavelength shift due to increased bias current,we further calculate the effective refractive index and the refractive index change.Special feature of refractive index change above lasing threshold is revealed and explained.

  5. Orchids inventory in Sintang Regency, West Kalimantan

    Directory of Open Access Journals (Sweden)

    ESTI ENDAH ARIYANTI

    2008-10-01

    Full Text Available Orchid is one of ornamental plants which have commercial value. Therefore most species are becoming threatened or even endangered because of over exploitation. In addition, its natural habitat is also decreasing. Conservation must be done urgently, both by in situ and ex situ conservation, which can be started by orchid inventory. The orchid inventory was done in TWA Bukit Kelam, TWA Baning and several places in Regency of Sintang, West Kalimantan. The result showed that there were 40 species belonged to 27 genera, which 32 species of them (20 genera were epiphytic orchids and 8 species (7 genera were terrestrial orchids.

  6. 空气断路器

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Development of single break 420kV GCB,Development of synchronous switching controller for gas circuit breakers,EMTP simulation of SLF interrupting performance for twa serially connected arcs with different arc parameters,Feasibility study on application of high voltage and high power vacuum circuit breaker.

  7. Teachers' Autonomy in Today's Educational Climate: Current Perceptions from an Acceptable Instrument

    Science.gov (United States)

    Strong, Luman E. G.; Yoshida, Roland K.

    2014-01-01

    This research evaluated the psychometric properties of Friedman's (1999) Teacher Work-Autonomy Scale (TWA) to determine whether it was an acceptable instrument to measure U.S. teacher autonomy in the present educational context. A second purpose was to ascertain the current status of teachers' perceptions of their autonomy from a sample of U.S.…

  8. A Psychometric Study of the Teacher Work-Autonomy Scale with a Sample of U.S. Teachers

    Science.gov (United States)

    Strong, Luman E. G.

    2012-01-01

    The purpose of this research was to evaluate the psychometric properties of Friedman's (1999) Teacher Work-Autonomy Scale (TWA) in order to determine whether it was an acceptable instrument to measure U.S. teachers' autonomy in the present educational context. A second purpose was to ascertain the current status of teachers' perceptions of their…

  9. Teachers' Autonomy in Today's Educational Climate: Current Perceptions from an Acceptable Instrument

    Science.gov (United States)

    Strong, Luman E. G.; Yoshida, Roland K.

    2014-01-01

    This research evaluated the psychometric properties of Friedman's (1999) Teacher Work-Autonomy Scale (TWA) to determine whether it was an acceptable instrument to measure U.S. teacher autonomy in the present educational context. A second purpose was to ascertain the current status of teachers' perceptions of their autonomy from a sample of U.S.…

  10. Can total wrist arthroplasty be an option in the treatment of the severely destroyed posttraumatic wrist?

    DEFF Research Database (Denmark)

    Boeckstyns, Michel E H; Herzberg, Guillaume; Sørensen, Allan Ibsen;

    2013-01-01

    Background Severely destroyed posttraumatic wrists are usually treated by partial or total wrist fusion or proximal row carpectomy. The indications for and longevity of total wrist arthroplasty (TWA) are still unclear. Case Description The aim of this study was to analyze a series in which one la...

  11. 77 FR 33129 - Airworthiness Directives; The Boeing Company Airplanes

    Science.gov (United States)

    2012-06-05

    ... Airlines for America (A4A), and James Hurd on behalf of the Families of TWA Flight 800, to extend the comment period. A4A requested a 60-day extension because of the extensive scope and significant potential... results of prototype efforts. A4A stated that this extension would provide operators additional time...

  12. Protoplanetary Disk Masses from Stars to Brown Dwarfs

    CERN Document Server

    Mohanty, Subhanjoy; Mortlock, Daniel; Pascucci, Ilaria; Scholz, Aleks; Thompson, Mark; Apai, Daniel; Lodato, Giuseppe; Looper, Dagny

    2013-01-01

    We present SCUBA-2 850um observations for 7 very low mass stars (VLMS) and brown dwarfs (BDs): 3 in Taurus, 4 in the TWA, and all classical T Tauri (cTT) analogs. We detect 2 of the 3 Taurus disks, but none of the TWA ones. Our 3sigma limits correspond to a dust mass of 1.2 MEarth in Taurus and a mere 0.2 MEarth in the TWA (3--10x deeper than previous work). We combine our data with other sub-mm/mm surveys of Taurus, rho Oph and the TWA to investigate trends in disk mass and grain growth during the cTT phase. We find : (1) The minimum disk outer radius required to explain the upper envelope of sub-mm/mm fluxes is 100 AU for intermediate-mass stars, solar-types and VLMS, and 20 AU for BDs. (2) While the upper envelope of disk masses increases with Mstar from BDs to VLMS to solar-types, no increase is seen from solar-type to intermediate-mass stars. We propose this is due to enhanced photoevaporation around intermediate masses. (3) Many disks around Taurus and rho Oph intermediate-mass and solar-type stars evin...

  13. A Chandra Observation of the TW Hydrae Association Brown Dwarf 2MASSW J1139511-315921

    CERN Document Server

    Castro, Philip J; Gagné, Marc

    2011-01-01

    We report on a sequence of Chandra X-ray Observatory observations of the TW Hydrae brown dwarf (BD) 2MASSW J1139511-315921 (2M1139). In the combined 31 ks ACIS-S exposure, 2M1139 is detected at the 3-sigma confidence level. We find an X-ray luminosity of L_X = 1.4^(+2.7)_(-1.0) x 10^26 ergs s^-1 or log(L_X/L_bol) = -4.8 +/- 0.3. This object is similar to another TW Hydrae BD member, CD-33 7795B (TWA 5B): both have H-alpha emission, both show no signatures of accretion, and both have comparable ages and spectral types. TWA 5B was previously detected in X-rays with a luminosity of L_X = 4 x 10^27 ergs s^-1 or log(L_X/L_bol) = -3.4, an order of magnitude more luminous in X-rays than 2M1139. We find that the discrepancy between the X-ray luminosity of 2M1139 and TWA 5B is consistent with the spread in X-ray luminosity in the Orion Nebula Cluster (ONC) for BDs of similar spectral types. Though rotation may play a role in the X-ray activity of ultracool dwarfs like 2M1139 and TWA 5B, the discrepancy cannot be expla...

  14. Distance and Kinematics of the TW Hydrae Association from Parallaxes

    CERN Document Server

    Weinberger, Alycia J; Boss, Alan P

    2012-01-01

    From common proper motion and signatures of youth, researchers have identified about 30 members of a putative TW Hydrae Association. Only four of these had parallactic distances from Hipparcos. We have measured parallaxes and proper motions for 14 primary members. We combine these with literature values of radial velocities to show that the Galactic space motions of the stars, with the exception of TWA 9 and 22, are parallel and do not indicate convergence at a common formation point sometime in the last few million years. The space motions of TWA 9 and 22 do not agree with the others and indicate that they are not TWA members. The median parallax is 18 mas or 56 pc. We further analyze the stars' absolute magnitudes on pre-main sequence evolutionary tracks and find a range of ages with a median of 10.1 Myr and no correlation between age and Galactic location. The TWA stars may have formed from an extended and filamentary molecular cloud but are not necessarily precisely coeval.

  15. 75 FR 24509 - Notice of Availability of the Regulatory Flexibility Act Review of the Methylene Chloride Standard

    Science.gov (United States)

    2010-05-05

    ... on the American people, their families, their communities, their State, local, and tribal governments... methylene dichloride or dichloromethane [DCM or MC]) is a common industrial solvent used in a number of....\\2\\ It reduced the permissible exposure limit from an 8-hour-time-weighted-average (TWA) of 500 parts...

  16. Nonequilibrium dynamics of spin-boson models from phase-space methods

    Science.gov (United States)

    Piñeiro Orioli, Asier; Safavi-Naini, Arghavan; Wall, Michael L.; Rey, Ana Maria

    2017-09-01

    An accurate description of the nonequilibrium dynamics of systems with coupled spin and bosonic degrees of freedom remains theoretically challenging, especially for large system sizes and in higher than one dimension. Phase-space methods such as the truncated Wigner approximation (TWA) have the advantage of being easily scalable and applicable to arbitrary dimensions. In this work we adapt the TWA to generic spin-boson models by making use of recently developed algorithms for discrete phase spaces [J. Schachenmayer, A. Pikovski, and A. M. Rey, Phys. Rev. X 5, 011022 (2015), 10.1103/PhysRevX.5.011022]. Furthermore we go beyond the standard TWA approximation by applying a scheme based on the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy of equations to our coupled spin-boson model. This allows us, in principle, to study how systematically adding higher-order corrections improves the convergence of the method. To test various levels of approximation we study an exactly solvable spin-boson model, which is particularly relevant for trapped-ion arrays. Using TWA and its BBGKY extension we accurately reproduce the time evolution of a number of one- and two-point correlation functions in several dimensions and for an arbitrary number of bosonic modes.

  17. The traveling-wave amplifier model of the cochlea adapted to dolphins

    DEFF Research Database (Denmark)

    Andersen, Lars Nonboe; Au, W.W.L.

    1999-01-01

    of a sonar signal discrimination system. The system was tested on a cylinder wall thickness discrimination problem. Broadband echoes from cylinders with different wall thicknesses were aligned using a matched filter and envelope detection. The aligned signals were used as inputs to the TWA model and energy...

  18. Workplace Support, Discrimination, and Person-Organization Fit: Tests of the Theory of Work Adjustment with LGB Individuals

    Science.gov (United States)

    Velez, Brandon L.; Moradi, Bonnie

    2012-01-01

    The present study explored the links of 2 workplace contextual variables--perceptions of workplace heterosexist discrimination and lesbian, gay, and bisexual (LGB)-supportive climates--with job satisfaction and turnover intentions in a sample of LGB employees. An extension of the theory of work adjustment (TWA) was used as the conceptual framework…

  19. Health-based recommended occupational exposure limit for dimethylamine.

    NARCIS (Netherlands)

    Maclaine Pont, M.A.

    1991-01-01

    18 mg/m3 is an adverse effect level, causing minimal local (no systemic) effects in rats and mice. To take this into account a safety factor of 10 is applied which results in a recommended occupational exposure limit of 1.8 mg/m3 (1 ppm) TWA 8 h for DMA.

  20. Respirable silica dust exposure amongst foundry workers in Gauteng, South Africa: A task-based risk assessment

    CSIR Research Space (South Africa)

    Khoza, NN

    2012-09-01

    Full Text Available Centre for Mining Innovation’s Laboratory SANAS accreditation (ISO 17025) for both x-ray powder diffraction (XRD) and particle size analysis methods. The overall TWA mean and median respirable silica dust concentration was 0.184 mg/m³ and 0.167 mg...

  1. Keck Adaptive Optics Observations of TW Hydrae Association Members

    Energy Technology Data Exchange (ETDEWEB)

    Macintosh, B; Max, C; Zuckerman, B; Becklin, E E; Kaisler, D; Lowrance, P; Weinberger, A; Chirstou, J; Schneider, G; Acton, S

    2001-05-30

    Adaptive optics (AO) on 8-10 m telescopes is an enormously powerful tool for studying young nearby stars. It is especially useful for searching for companions. Using AO on the 10-m W.M. Keck II telescope we have measured the position of the brown dwarf companion to TWA5 and resolved the primary into an 0.055{double_prime} double. Over the next several years follow-up astrometry should permit an accurate determination of the masses of these young stars. We have also re-observed the candidate extrasolar planet TWAGB, but measurements of its motion relative to TWA6A are inconclusive. We are carrying out a search for new planetary or brown dwarf companions to TWA stars and, if current giant planet models are correct, are currently capable of detecting a 1 Jupiter-mass companion at {approx} 1.0{double_prime} and a 5 Jupiter-mass companion at {approx} 0.5{double_prime} around a typical TWA member.

  2. Hangar con alas, Los Angeles

    Directory of Open Access Journals (Sweden)

    Editorial, Equipo

    1961-04-01

    Full Text Available Formando parte de su programa, la TWA ha construido recientemente un hangar para servicio y reparaciones de su flota aérea de naves ordinarias y de aviones de reacción en el aeropuerto internacional de Los Angeles (Estados Unidos. El proyecto de esta obra se encargó a la empresa constructora Holmes & Narver, Inc.

  3. U.S. Navy Capstone Strategies and Concepts (1981-1990): Strategy, Policy, Concept, and Vision Documents

    Science.gov (United States)

    2011-12-01

    Hezbollah hijacked TWA flight. USN diver killed (1985) Libyans, PLF hijacked Achille Lauro cruise ship (1985) PRC hostility to Soviets; fear of Soviet...1988) Libyans bombed PANAM flight over Scotland (1988) Arab terror attack on cruise ship south of Athens (1988) Spate of unfavorable USN publicity

  4. Traveling-wave ion mobility mass spectrometry of protein complexes

    DEFF Research Database (Denmark)

    Salbo, Rune; Bush, Matthew F; Naver, Helle

    2012-01-01

    The collision cross-section (Ω) of a protein or protein complex ion can be measured using traveling-wave (T-wave) ion mobility (IM) mass spectrometry (MS) via calibration with compounds of known Ω. The T-wave Ω-values depend strongly on instrument parameters and calibrant selection. Optimization...

  5. 77 FR 6127 - Submission of Extended Digital Electrocardiogram Waveform Data; Notice of Public Meeting

    Science.gov (United States)

    2012-02-07

    ... continuous recordings. We encourage device manufacturers, ECG laboratories, investigators, industry, and... quantified as the increase in the Q wave and T wave (QT) interval, the length of time corresponding to the start of the Q wave and the end of the T wave on the ECG tracing. In 2005, FDA issued a guidance...

  6. Evaluation of an artificial intelligence program for estimating occupational exposures.

    Science.gov (United States)

    Johnston, Karen L; Phillips, Margaret L; Esmen, Nurtan A; Hall, Thomas A

    2005-03-01

    Estimation and Assessment of Substance Exposure (EASE) is an artificial intelligence program developed by UK's Health and Safety Executive to assess exposure. EASE computes estimated airborne concentrations based on a substance's vapor pressure and the types of controls in the work area. Though EASE is intended only to make broad predictions of exposure from occupational environments, some occupational hygienists might attempt to use EASE for individual exposure characterizations. This study investigated whether EASE would accurately predict actual sampling results from a chemical manufacturing process. Personal breathing zone time-weighted average (TWA) monitoring data for two volatile organic chemicals--a common solvent (toluene) and a specialty monomer (chloroprene)--present in this manufacturing process were compared to EASE-generated estimates. EASE-estimated concentrations for specific tasks were weighted by task durations reported in the monitoring record to yield TWA estimates from EASE that could be directly compared to the measured TWA data. Two hundred and six chloroprene and toluene full-shift personal samples were selected from eight areas of this manufacturing process. The Spearman correlation between EASE TWA estimates and measured TWA values was 0.55 for chloroprene and 0.44 for toluene, indicating moderate predictive values for both compounds. For toluene, the interquartile range of EASE estimates at least partially overlapped the interquartile range of the measured data distributions in all process areas. The interquartile range of EASE estimates for chloroprene fell above the interquartile range of the measured data distributions in one process area, partially overlapped the third quartile of the measured data in five process areas and fell within the interquartile range in two process areas. EASE is not a substitute for actual exposure monitoring. However, EASE can be used in conditions that cannot otherwise be sampled and in preliminary

  7. Nonrespiratory Sinus Arrhythmia

    Directory of Open Access Journals (Sweden)

    Barbosa Filho José

    2002-01-01

    Full Text Available We report here 2 cases of sinus arrhythmia considered to be a form of nonrespiratory sinus arrhythmia because they did not have variances in the RR interval sequence within the oscillations modulated by respiration. Because the patients had pulsus alternans similar that observed in bigeminy, and because they did not have signs or symptoms of heart failure, we believe the arrhythmias represent intrinsic alterations of the electric activity of the sinus node

  8. Paradoxical effects of KB-R7943 on arrhythmogenicity in a chronic myocardial infarction rabbit model.

    Science.gov (United States)

    Chang, Po-Cheng; Wo, Hung-Ta; Lee, Hui-Ling; Wen, Ming-Shien; Chou, Chung-Chuan

    2015-07-01

    Na(+)/Ca(2+) exchanger blockade has been reported to be anti-arrhythmic in different models. The effects of KB-R7943, a Na(+)/Ca(2+) exchanger blocker, on arrhythmogenesis in hearts with chronic myocardial infarction (MI) remain unclear. Dual voltage and intracellular Ca(2+) (Cai) optical mapping was performed in nine rabbit hearts with chronic MI and four control hearts. Electrophysiology studies including inducibility of ventricular tachyarrhythmias, ventricular fibrillation dominant frequency, action potential, Cai alternans, Cai decay, and conduction velocity were performed. The same protocol was repeated in the presence of KB-R7943 (0.5, 1, and 5μM) after the baseline studies. KB-R7943 was effective in suppressing afterdepolarizations and spontaneous ventricular tachyarrhythmias in hearts with chronic MI. Surprisingly, KB-R7943 increased the inducibility of ventricular tachyarrhythmias in a dose-dependent manner (11%, 11%, 22%, and 56% at baseline and with 0.5, 1, and 5μM KB-R7943, respectively, p=0.02). Optical mapping analysis revealed that the underlying mechanisms of the induced ventricular tachyarrhythmias were probably spatially discordant alternans with wave breaks and rotors. Further analysis showed that KB-R7943 significantly enhanced both action potential (p=0.033) and Cai (p=0.001) alternans, prolonged Cai decay (tau value) in a dose-dependent manner (p=0.004), and caused heterogeneous conduction delay especially at peri-infarct zones during rapid burst pacing. In contrast, KB-R7943 had insignificant effects in control hearts. In this chronic MI rabbit model, KB-R7943 has contrasting effects on arrhythmogenesis, suppressing afterdepolarizations and spontaneous ventricular tachyarrhythmias, but enhancing the inducibility of tachyarrhythmias. The mechanism is probably the enhanced spatially discordant alternans because of prolonged Cai decay and heterogeneous conduction delay. Copyright © 2014 Japanese College of Cardiology. Published by Elsevier

  9. Control of spiral waves and turbulent states in a cardiac model by travelling-wave perturbations

    Institute of Scientific and Technical Information of China (English)

    王鹏业; 谢平; 尹华伟

    2003-01-01

    We propose a travelling-wave perturbation method to control the spatiotemporal dynamics in a cardiac model.It is numerically demonstrated that the method can successfully suppress the wave instability(alternans in action potential duration) in the one-dimensional case and convert spiral waves and turbulent states to the normal travelling wave states in the two-dimensional case.An experimental scheme is suggested which may provide a new design for a cardiac defibrillator.

  10. Imaging atrial arrhythmic intracellular calcium in intact heart.

    Science.gov (United States)

    Xie, Wenjun; Santulli, Gaetano; Guo, Xiaoxiao; Gao, Melanie; Chen, Bi-Xing; Marks, Andrew R

    2013-11-01

    Abnormalities in intracellular Ca(2+) signaling have been proposed to play an essential role in the pathophysiology of atrial arrhythmias. However, a direct observation of intracellular Ca(2+) in atrial myocytes during atrial arrhythmias is lacking. Here, we have developed an ex vivo model of simultaneous Ca(2+) imaging and electrocardiographic recording in cardiac atria. Using this system we were able to record atrial arrhythmic intracellular Ca(2+) activities. Our results indicate that atrial arrhythmias can be tightly linked to intracellular Ca(2+) waves and Ca(2+) alternans. Moreover, we applied this strategy to analyze Ca(2+) signals in the hearts of WT and knock-in mice harboring a 'leaky' type 2 ryanodine receptor (RyR2-R2474S). We showed that sarcoplasmic reticulum (SR) Ca(2+) leak increases the susceptibility to Ca(2+) alternans and Ca(2+) waves increasing the incidence of atrial arrhythmias. Reduction of SR Ca(2+) leak via RyR2 by acute treatment with S107 reduced both Ca(2+) alternans and Ca(2+) waves, and prevented atrial arrhythmias.

  11. The interrelations among stochastic pacing, stability, and memory in the heart.

    Science.gov (United States)

    Dvir, Hila; Zlochiver, Sharon

    2014-08-19

    Low pacing variability in the heart has been clinically reported as a risk factor for lethal cardiac arrhythmias and arrhythmic death. In ia previous simulation study, we demonstrated that stochastic pacing sustains an antiarrhythmic effect by moderating the slope of the action potential duration (APD) restitution curve, by reducing the propensity of APD alternans, converting discordant to concordant alternans, and ultimately preventing wavebreaks. However, the dynamic mechanisms relating pacing stochasticity to tissue stability are not yet known. In this work, we develop a mathematical framework to describe the APD signal using an autoregressive stochastic model, and we establish the interrelations between stochastic pacing, cardiac memory, and cardiac stability, as manifested by the degree of APD alternans. Employing stability analysis tools, we show that increased stochasticity in the ventricular tissue activation sequence works to lower the maximal absolute eigenvalues of the stochastic model, thereby contributing to increased stability. We also show that the memory coefficients of the autoregressive model are modulated by pacing stochasticity in a nonlinear, biphasic way, so that for exceedingly high levels of pacing stochasticity, the antiarrhythmic effect is hampered by increasing APD variance. This work may contribute to establishment of an optimal antiarrhythmic pacing protocol in a future study. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  12. Sudden cardiac arrest risk stratification based on 24-hour Holter ECG statistics.

    Science.gov (United States)

    Kasahara, Keisuke; Shiobara, Masahito; Nakamura, Saya; Yamashiro, Koichiro; Yana, Kazuo; Ono, Takuya

    2015-08-01

    This study examined the feasibility of using indices obtained from a long term Holter ECG record for sudden cardiac arrest (SCA) risk stratification. The ndices tested were the QT-RR interval co-variability and the alternans ratio percentile (ARP(θ)) which is defined as the θ(th) percentile of alternans ratios over a 24 hour period. The QT-RR interval co-variabilities are evaluated by the serial correlation coefficient between QT and RR trend sequences (QTRC). Previously reported Kalman filter technique and a simple smoothing spline method for the trend estimation are compared. Parameter θ in the alternans ratio percentile index was optimized to achieve the best classification accuracy. These indices were estimated from 26 cardiovascular outpatients for Holter ECG record. Patients were classified into high and low risk groups according to their clinical diagnosis, and the obtained indices were compared with those of 25 control subjects. A risk stratification using the two indices QTRC and ARP(θ) yielded an average sensitivity of 0.812 and a specificity of 0.925. The sensitivities and specificities of all three categories exceeded 0.8 except for the sensitivity to detect the high-risk patient group. Other short-term ECG parameters may need to be incorporated in order to improve the sensitivity.

  13. Working conditions and health effects of ethylene oxide exposure at hospital sterilization sites.

    Science.gov (United States)

    Sobaszek, A; Hache, J C; Frimat, P; Akakpo, V; Victoire, G; Furon, D

    1999-06-01

    Ethylene oxide (EtO) is a powerful disinfectant and sterilant for heat-sensitive surgical items and instruments. Its use in hospitals constitutes an important source of occupational exposure that is sometimes underestimated, such as in cases of EtO device malfunction when the safety rules of procedure are not strictly followed or when individual or collective protective equipment is lacking. We carried out a descriptive study of the health care workers who were assigned to EtO sterilization units of the Lille University Hospital Centre in Lille, France (n = 16). Before the modification of the sterilization units in the development of a single, central sterilization site, we studied the workplaces, occupational conditions, and work procedures of the health care workers exposed to EtO. The aim was to assess the risk of EtO overexposure of the workers in order to improve workers' health and security in the future sterilization center. The study was based on a physical examination, a questionnaire covering each subject's personal and occupational history, and a complete ocular examination. For occupational conditions, the studies of each workplace were also performed by the occupational physician. Area and personal breathing air samplings were performed at each exposure site. Fourteen of the 16 operators had posterior and anterior subcapsular lens opacities, three of which seemed to be directly and primarily related to occupational exposure; the other ten seemed to be rather common and compatible with age. High levels of EtO exposure were reported in the oldest site (90 parts per million [ppm] during the changing of the gas bottle), where exposure often exceeded French threshold limits (permissible exposure limit: 1 ppm 8-hour time-weighted average (TWA) in air; short-term excursion limit: 5 ppm 15-minute TWA in air), or the current US recommended and legal exposure limits for EtO advocated by the Occupational Safety and Health Administration and the American

  14. Respirable crystalline silica - a failure to control exposureexclamation

    Energy Technology Data Exchange (ETDEWEB)

    Cain, J R, E-mail: john.cain@hse.gsi.gov.u [HM Regional Specialist Inspector (Occupational Hygiene), Health and Safety Executive, Marshalls Mill, Marshall Street, Leeds LS11 9YJ (United Kingdom)

    2009-02-01

    Several sites were visited to monitor stonemason exposure to respirable crystalline silica (RCS), inhalable dust and respirable dust. At all sites, exposure to RCS exceeded the Workplace Exposure Limit of 0.1 mg/m{sup 3} 8-hour TWA. There was therefore a continuing high risk of workers developing silicosis unless the appropriate measures were instigated to prevent or control exposure. Exposure control was ineffective at all sites e.g. water wall extraction systems were not well designed. There was evidence that foreign workers were at a greater exposure risk. But even with appropriate controls to mitigate exposure to RCS it may not be possible to sustain exposure to below 0.1 mg/m{sup 3} 8-hour TWA without on-going HSE intervention.

  15. Retrospective exposure assessment of airborne asbestos related to skilled craftsmen at a petroleum refinery in Beaumont, Texas (1940-2006).

    Science.gov (United States)

    Williams, Pamela; Paustenbach, Dennis; Balzer, J LeRoy; Mangold, Carl

    2007-07-01

    Despite efforts over the past 50 or more years to estimate airborne dust or fiber concentrations for specific job tasks within different industries, there have been no known attempts to reconstruct historical asbestos exposures for the many types of trades employed in various nonmanufacturing settings. In this paper, 8-h time-weighted average (TWA) asbestos exposures were estimated for 12 different crafts from the 1940s to the present day at a large petroleum refinery in Beaumont, TX. The crafts evaluated were insulators, pipefitters, boilermakers, masons, welders, sheet-metal workers, millwrights, electricians, carpenters, painters, laborers, and maintenance workers. This analysis quantitatively accounts for (1) the historical use of asbestos-containing materials at the refinery, (2) the typical workday of the different crafts and specific opportunities for exposure to asbestos, (3) industrial hygiene asbestos air monitoring data collected at this refinery and similar facilities since the early 1970s, (4) published and unpublished data sets on task-specific dust or fiber concentrations encountered in various industrial settings since the late 1930s, and (5) the evolution of respirator use and other workplace practices that occurred as the hazards of asbestos became better understood over time. Due to limited air monitoring data for most crafts, 8-h TWA fiber concentrations were calculated only for insulators, while all other crafts were estimated to have experienced 8-h TWA fiber concentrations at some fraction of that experienced by insulators. A probabilistic (Monte Carlo) model was used to account for potential variability in the various data sets and the uncertainty in our knowledge of selected input parameters used to estimate exposure. Significant reliance was also placed on our collective professional experiences working in the fields of industrial hygiene, exposure assessment, and process engineering over the last 40 yr. Insulators at this refinery were

  16. Applying mathematical modeling to create job rotation schedules for minimizing occupational noise exposure.

    Science.gov (United States)

    Tharmmaphornphilas, Wipawee; Green, Benjamin; Carnahan, Brian J; Norman, Bryan A

    2003-01-01

    This research developed worker schedules by using administrative controls and a computer programming model to reduce the likelihood of worker hearing loss. By rotating the workers through different jobs during the day it was possible to reduce their exposure to hazardous noise levels. Computer simulations were made based on data collected in a real setting. Worker schedules currently used at the site are compared with proposed worker schedules from the computer simulations. For the worker assignment plans found by the computer model, the authors calculate a significant decrease in time-weighted average (TWA) sound level exposure. The maximum daily dose that any worker is exposed to is reduced by 58.8%, and the maximum TWA value for the workers is reduced by 3.8 dB from the current schedule.

  17. Comparison of personal diesel and biodiesel exhaust exposures in an underground mine.

    Science.gov (United States)

    Lutz, Eric A; Reed, Rustin J; Lee, Vivien S T; Burgess, Jefferey L

    2017-07-01

    This study aimed to compare personal exposures to diesel fuel and a biodiesel blend exhaust in an underground mine. Personal exposure monitoring was performed in a non-operational, hard rock underground mine during use of a load-haul-dump vehicle. Eight-hour time-weighted average (TWA8) exposure concentrations of ultra-low sulfur diesel and 75% biodiesel/25% diesel blend (B75) fuels were compared.  Compared to diesel, use of B75 was associated with relative percent reductions of 22 and 28% in median respirable (r) diesel particulate matter (DPM) and nitrogen dioxide and 25 and 23% increases in median total DPM and nitric oxide TWA8 exposure concentrations, respectively. Diesel was associated with a slightly greater total geometric mean mass concentration and lower mean surface area concentration.  Although further testing is needed, B75 has the potential to reduce rDPM exposures.

  18. PROTOPLANETARY DISK MASSES FROM STARS TO BROWN DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhanjoy; Mortlock, Daniel [Imperial College London, 1010 Blackett Lab, Prince Consort Rd., London SW7 2AZ (United Kingdom); Greaves, Jane [SUPA, Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom); Pascucci, Ilaria; Apai, Daniel [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, Tucson AZ 85721 (United States); Scholz, Aleks [School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); Thompson, Mark [Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Lodato, Giuseppe [Dipartimento di Fisica, Universita Degli Studi di Milano, Via Celoria 16, I-20133 Milano (Italy); Looper, Dagny, E-mail: s.mohanty@imperial.ac.uk [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822 (United States)

    2013-08-20

    We present SCUBA-2 850 {mu}m observations of seven very low mass stars (VLMS) and brown dwarfs (BDs). Three are in Taurus and four in the TW Hydrae Association (TWA), and all are classical T Tauri (cTT) analogs. We detect two of the three Taurus disks (one only marginally), but none of the TWA ones. For standard grains in cTT disks, our 3{sigma} limits correspond to a dust mass of 1.2 M{sub Circled-Plus} in Taurus and a mere 0.2 M{sub Circled-Plus} in the TWA (3-10 Multiplication-Sign deeper than previous work). We combine our data with other submillimeter/millimeter (sub-mm/mm) surveys of Taurus, {rho} Oph, and the TWA to investigate the trends in disk mass and grain growth during the cTT phase. Assuming a gas-to-dust mass ratio of 100:1 and fiducial surface density and temperature profiles guided by current data, we find the following. (1) The minimum disk outer radius required to explain the upper envelope of sub-mm/mm fluxes is {approx}100 AU for intermediate-mass stars, solar types, and VLMS, and {approx}20 AU for BDs. (2) While the upper envelope of apparent disk masses increases with M{sub *} from BDs to VLMS to solar-type stars, no such increase is observed from solar-type to intermediate-mass stars. We propose this is due to enhanced photoevaporation around intermediate stellar masses. (3) Many of the disks around Taurus and {rho} Oph intermediate-mass and solar-type stars evince an opacity index of {beta} {approx} 0-1, indicating significant grain growth. Of the only four VLMS/BDs in these regions with multi-wavelength measurements, three are consistent with considerable grain growth, though optically thick disks are not ruled out. (4) For the TWA VLMS (TWA 30A and B), combining our 850 {mu}m fluxes with the known accretion rates and ages suggests substantial grain growth by 10 Myr, comparable to that in the previously studied TWA cTTs Hen 3-600A and TW Hya. The degree of grain growth in the TWA BDs (2M1207A and SSPM1102) remains largely unknown. (5) A

  19. Tempo and mode of speciation in Holacanthus angelfishes based on RADseq markers.

    Science.gov (United States)

    Tariel, Juliette; Longo, Gary C; Bernardi, Giacomo

    2016-05-01

    In this study we estimated the timing of speciation events in a group of angelfishes using 1186 RADseq markers corresponding to 94,880 base pairs. The genus Holacanthus comprises seven species, including two clades of Panama trans-Isthmian geminates, which diverged approximately 3-3.5Mya. These clades diversified within the Tropical Eastern Pacific (TEP, three species) and Tropical Western Atlantic (TWA, two species) which our data suggest to have occurred within the past 1.5My in both ocean basins, but may have proceeded via different mechanisms. In the TEP, speciation is likely to have followed a peripatric pathway, while in the TWA, sister species are currently partially sympatric, thus raising the possibility of sympatric speciation. This study highlights the use of RADseq markers for estimating both divergence times and modes of speciation at a 1-3My timescale.

  20. Social Cognitive Career Theory, the Theory of Work Adjustment, and Work Satisfaction of Retirement-Age Adults

    Science.gov (United States)

    Foley, Pamela F.; Lytle, Megan C.

    2015-01-01

    Despite a recent increase in the number of adults who work past traditional retirement age, existing theories of vocational behavior have not yet received adequate empirical support. In a large sample of adults age 60–87, we evaluated the relationship between theorized predictors of work satisfaction proposed by Social Cognitive Career Theory (SCCT), work satisfaction as a predictor of continued work, as proposed by the Theory of Work adjustment (TWA), as well as the influence of reported experiences of discrimination on these relationships. While the results supported most of the predicted relationships, the effects of discrimination were stronger than the variables proposed by either SCCT or TWA for the present sample. PMID:26101456

  1. 玉米核心种质构建中的表型性状选择%Phenotypic Trait Selection in Construction of a Core Collection for Maize (Zea mays L.)

    Institute of Scientific and Technical Information of China (English)

    张婷婷; 王琳; 秦红珍; 李长生; 吴素文; 张春宇

    2012-01-01

    The core collection is the representative of the germplasm collection. The selection of the phenotypic traits is an important prerequisite for constructing a core collection with phenotypic traits. Five data types, i.e. qualitative traits (QT1), quantitative traits (QT2), asterisked traits (AT), traits without asterisk (TWA) and integrated traits (IT), were compared for their efficiency in constructing core collections of 1003 maize inbred lines based on the test parameters of the core collection. The results showed that the genetic diversity of qualitative traits of core was collections constructed based on the five trait data ranked in the following order: IT>AT≈TWA and IT>QT2 ≈QT1, respectively. In the same way, the genetic diversity of quantitative traits of core collections was constructed based on the five trait data ranked in the order of IT≈AT>TWA and IT> QT2>QT1, respectively. By integrating the genetic diversities of qualitative and quantitative traits, the results showed the following order:IT≈AT>TWA,IT>QT2>QT1,and the efficiency of core collections constructed based on AT is close to IT. The number of AT is less than IT, so AT is very convenient for practical applications with better efficiency for the construction of core collection.%核心种质是种质资源的代表群体,表型性状的选用策略对利用表型性状构建核心种质起到至关重要的作用.以1003份玉米育成高代品系为材料,分别选用质量性状(QT1)、数量性状(QT2)、必测性状(AT)、非必测性状(TWA)和综合性状(IT)构建核心种质.通过比较核心种质的检验参数,分别将上述5种性状构建的核心种质对原始种群的代表性进行研究.结果表明:这5种核心种质质量性状的遗传多样性:IT>AT≈TWA,IT>QT2≈QT1;数量性状的遗传多样性:IT≈AT>TWA,IT >QT2>QT1;综合数量性状和质量性状的遗传多样性评价结果为:IT≈AT>TWA,IT >QT2>QT1,AT与IT结果相近.由于AT的性状

  2. The effect of powder properties on sintering, microstructure, mechanical strength and degradability of beta-tricalcium phosphate/calcium silicate composite bioceramics

    Energy Technology Data Exchange (ETDEWEB)

    Lin Kaili; Chang Jiang; Shen Ruxiang, E-mail: jchang@mail.sic.ac.c [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)

    2009-12-15

    The effect of powder properties on sintering, microstructure, mechanical strength and degradability of beta-tricalcium phosphate/Calcium silicate (beta-Ca{sub 3}(PO{sub 4}){sub 2}/CaSiO{sub 3}, beta-TCP/CS) composite bioceramics was investigated. beta-TCP/CS composite powders with a weight ratio of 50:50 were prepared by three different methods: mechanical milling method (TW-A), two-step chemical precipitation method (TW-B) and in situ chemical co-precipitation method (TW-C), and then the three composite powders were uniaxially compacted at 30 MPa, followed by cold isostatic pressing into rectangular-prism-shaped specimens under a pressure of 200 MPa for 15 min, and then sintered at 1150 deg. C for 5 h. The TW-B powders with less agglomerative morphologies and uniform nano-size particles attained 96.14% relative density (RD). A uniform microstructure with about 120 nm grains was observed. Whereas, the samples obtained from TW-A and TW-C powders only reached a RD of 63.08% and 78.86%, respectively. The bending strength of the samples fabricated from TW-B reached 125 MPa, which was more than 3.7 and 1.5 times higher as compared with that of samples obtained from TW-A and TW-C powders, respectively. Furthermore, the degradability of the samples fabricated from TW-B powders was obviously lower than that of the samples fabricated from TW-A and TW-C powders.

  3. An evaluation of short-term exposures of brake mechanics to asbestos during automotive and truck brake cleaning and machining activities.

    Science.gov (United States)

    Richter, Richard O; Finley, Brent L; Paustenbach, Dennis J; Williams, Pamela R D; Sheehan, Patrick J

    2009-07-01

    Historically, the greatest contributions to airborne asbestos concentrations during brake repair work were likely due to specific, short-duration, dust-generating activities. In this paper, the available short-term asbestos air sampling data for mechanics collected during the cleaning and machining of vehicle brakes are evaluated to determine their impact on both short-term and daily exposures. The high degree of variability and lack of transparency for most of the short-term samples limit their use in reconstructing past asbestos exposures for brake mechanics. However, the data are useful in evaluating how reducing short-term, dust-generating activities reduced long-term exposures, especially for auto brake mechanics. Using the short-term dose data for grinding brake linings from these same studies, in combination with existing time-weighted average (TWA) data collected in decades after grinding was commonplace in rebuilding brake shoes, an average 8-h TWA of approximately 0.10 f/cc was estimated for auto brake mechanics that performed arc grinding of linings during automobile brake repair (in the 1960s or earlier). In the 1970s and early 1980s, a decline in machining activities led to a decrease in the 8-h TWA to approximately 0.063 f/cc. Improved cleaning methods in the late 1980s further reduced the 8-h TWA for most brake mechanics to about 0.0021 f/cc. It is noteworthy that when compared with the original OSHA excursion level, only 15 of the more than 300 short-term concentrations for brake mechanics measured during the 1970s and 1980s possibly exceeded the standard. Considering exposure duration, none of the short-term exposures were above the current OSHA excursion level.

  4. Non-Chromate Aluminum Pretreatments

    Science.gov (United States)

    2012-03-01

    chromated areas of the two tail-only demonstrations was Turco AccelagoldTM. All aircraft were deoxidized using Turco 3003 TWATM. All test aircraft...was washed with Turco 5948RTM mildly alkaline cleaner, and then deoxidized with Turco 3003 TWA. During both of these cycles, white Scotch BrightTM...cleaner. ( Turco 4215 NC LTTM – 120 F) Solution was scrubbed lightly onto the components with Scotch-Brite pads. Figure 5.5 shows the cleaning of a

  5. Field Evaluation Of A Novel Exposure Assessment Strategy Using Respirable Coal Dust Exposures During Heat Plant Coal Receiving Operations

    Science.gov (United States)

    2009-03-01

    percentages of the three most common forms of crystalline silica to include quartz, cristobalite and tridymite. ®) threshold limit value (TLV®) booklet...0.025 mg/m3 (note that between 2005 and 2006 ACGIH® withdrew tridymite and tripoli, while combining quartz and cristobalite into one TLV®, i.e. Silica...carcinogen (ACGIH, 2008). In 2006, the ACGIH® combined quartz and cristobalite into a single TLV® TWA under the heading crystalline silica. As part of

  6. Combined Exposure of Methylene Chloride and Carbon Monoxide in Smoking and Nonsmoking Paint Strippers.

    Science.gov (United States)

    1983-12-01

    plateau of about 7% COHb following an eight-hour time-weighted-average (TWA) exposure of approximately 1800 mg/m3 . The smokers dose response curve did...37 5 Dose Response Curve for Nonsmokers Considering Differences in COHb Increases on Both Exposure and Nonexposure Days...contains no human metabolism studies or studies on animals other than the rat. Ott et al. (17) found that the dose - response curve for humans J

  7. Calibration and Application of Passive Sampling in Drinking Water for Perfluoroalkyl Substances

    OpenAIRE

    Persson, Caroline

    2015-01-01

    Perfluoroalkyl substances (PFASs) are global environmental contaminants and a need for monitoring levels has arisen due to their persistency and their ability to bioaccumulate. One relatively novel method of monitoring for both long and short time intervals and generating time-weighted average (TWA) concentrations is passive sampling for which no power, maintenance and supervision is required. The polar organic compound integrative sampler (POCIS) with a weak anion exchange (WAX) sorbent and ...

  8. Wood dust and formaldehyde exposures in the cabinet-making industry.

    Science.gov (United States)

    Sass-Kortsak, A M; Holness, D L; Pilger, C W; Nethercott, J R

    1986-12-01

    Time-weighted average (TWA) personal total and respirable dust exposures were determined gravimetrically for 48 subjects in 4 cabinet-making plants. TWA personal formaldehyde exposures also were obtained, with the use of 3M 3750 passive monitors. Selective area sampling for formaldehyde was undertaken using two methods. The results obtained with the passive monitors were compared to the standard chromotropic acid impinger method. Considerable variation was noted in the dust exposures. Cabinet-makers exposed to softwoods were found to have a mean exposure of approximately one half of the current applicable ACGIH TWA-TLV, while hard-wood exposure was twice the applicable TWA-TLV. The highest dust exposures were recorded for those workers sanding, the mean total dust being 2.91 mg/m3 (S.E. 0.70) and respirable dust 0.63 mg/m3 (S.E. 0.20). Sanding operations also were found to produce a higher proportion of respirable dust (22%) than other woodworking operations (6%-14%). Workers in assembly areas also were found to have higher dust exposures, likely reflecting the fact that conventional dust collection devices for stationary woodworking equipment are not appropriate for hand held tools and hand sanding. The importance of making respirable dust measurements is discussed. The poor correlation between paired total and respirable dust concentrations indicates that both measurements should be made. Some potential limitations to respirable wood dust sampling using 10 mm nylon cyclones are noted, however. Area dust concentrations were found to be significantly lower than personal exposures, emphasizing the importance of personal sampling data. Formaldehyde vapor exposures were very low, with a mean of 0.06 ppm (S.E. 0.01).

  9. Symposium on Commercial Aviation Energy Conservation Strategies, April 2-3, 1981. Papers and Presentations

    Science.gov (United States)

    1981-04-03

    airport and airway system possible. In addition, we believe it is imperative that the appropriate authorities recognize ehe value of aviation to the...TWA, Delta, British Airways , Swissair, 5AS and VIASA to mention but a few carriers have cooperated wherever possible, as has the govern- ments of...corrections to the profile to save fuel? This is the question we asked ourselves in Qantas Plight Operations. This in turn led to a lengthy

  10. Factors Affecting Noise Levels of High-Speed Handpieces

    Science.gov (United States)

    2012-06-01

    office communication and increase patient anxiety. Purpose: To determine if three noise-reducing techniques utilized in larger scale , non- dental...hearing loss may cause confusion, fear, and loneliness , and that sometimes hearing loss is accompanied by dizziness, which would be a handicap in the...employee noise exposures equal or exceed an 8- hour time-weighted average sound level (TWA) of 85 decibels measured on the A scale (slow response) or

  11. The Role of the Government in Perpetrating Genocide: A Comparative Analysis of 1994 Rwanda Genocide and 2003 Sudan Genocide

    Science.gov (United States)

    2013-06-13

    response, to ensure timely action to avert it. In Rwanda, the UN had enough information to show that genocide was happening and they chose to withdraw ...including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and...Twa or pygmoids did their hunting in forests, the majority Hutu cultivated land, while the minority Tutsi reared cattle . The Tutsi group caught the

  12. The effect of powder properties on sintering, microstructure, mechanical strength and degradability of beta-tricalcium phosphate/calcium silicate composite bioceramics.

    Science.gov (United States)

    Lin, Kaili; Chang, Jiang; Shen, Ruxiang

    2009-12-01

    The effect of powder properties on sintering, microstructure, mechanical strength and degradability of beta-tricalcium phosphate/calcium silicate (beta-Ca3(PO4)2/CaSiO3, beta-TCP/CS) composite bioceramics was investigated. beta-TCP/CS composite powders with a weight ratio of 50:50 were prepared by three different methods: mechanical milling method (TW-A), two-step chemical precipitation method (TW-B) and in situ chemical co-precipitation method (TW-C), and then the three composite powders were uniaxially compacted at 30 MPa, followed by cold isostatic pressing into rectangular-prism-shaped specimens under a pressure of 200 MPa for 15 min, and then sintered at 1150 degrees C for 5 h. The TW-B powders with less agglomerative morphologies and uniform nano-size particles attained 96.14% relative density (RD). A uniform microstructure with about 120 nm grains was observed. Whereas, the samples obtained from TW-A and TW-C powders only reached a RD of 63.08% and 78.86%, respectively. The bending strength of the samples fabricated from TW-B reached 125 MPa, which was more than 3.7 and 1.5 times higher as compared with that of samples obtained from TW-A and TW-C powders, respectively. Furthermore, the degradability of the samples fabricated from TW-B powders was obviously lower than that of the samples fabricated from TW-A and TW-C powders.

  13. ECG Changes In Patients On Chronic Psychotropic medication

    African Journals Online (AJOL)

    2006-08-31

    Aug 31, 2006 ... lack of exercise, obesity, substance misuse) and high autonomic ... heart; however, it might precipitate complete heart block in the presence of .... ECG changes such as rate, rhythm, T waves and QT interval changes have ...

  14. Worker exposure standard for phosphine gas.

    Science.gov (United States)

    Pepelko, Bill; Seckar, Joel; Harp, Paul R; Kim, James H; Gray, David; Anderson, Elizabeth L

    2004-10-01

    The 1998 U.S. Environmental Protection Agency Office of Pesticide Programs (OPP) re-registration eligibility decision (RED) for phosphine fumigants has generated much interest in defining safe levels of exposure for workers and worker bystanders. This report summarizes the pertinent literature on phosphine toxicity, including animal inhalation studies and human epidemiology studies, and also describes a margin-of-exposure (MOE) analysis based on available worker exposure data. In addition, a safe occupational exposure limit is estimated using typical OPP assumptions, after determination of appropriate uncertainty factors, based on quality of data in the principal study and pharmacokinetic considerations. While a conservative 8-hour time-weighted average (TWA) of 0.1 ppm was calculated, the overall weight of evidence, from a risk-management perspective, supports a conclusion that an occupational TWA of 0.3 ppm provides adequate health protection. In addition, a 15-minute short-term exposure limit (STEL) of 3 ppm was estimated. Finally, in contrast to the MOE analysis described in the OPP's phosphine RED, the MOE analysis described herein does not indicate that fumigation workers are currently being exposed to unacceptable levels of phosphine. Collectively, these findings support the occupational exposure limits of 0.3 ppm (8-hour TWA) and 1 ppm (STEL) established in the updated applicator's manuals for phosphine-generating products, which recently received approval from OPP.

  15. Alternative Magnetic Field Exposure Metrics: Occupational Measurements in Trolley Workers (invited paper)

    Energy Technology Data Exchange (ETDEWEB)

    Yost, M

    1999-07-01

    Epidemiological studies on extremely low frequency (ELF) magnetic fields have widely used personal or area sampling to evaluate exposures based on the time-weighted averaged flux density magnitude (TWA field). Relatively few studies have evaluated 'alternative' exposure metrics related to field characteristics such as temporal variability, frequency harmonics, vector polarisation, spatial orientation, static fields, high frequency transients, or induced electric fields. These field attributes fall into three major categories: (1) temporal characteristics of exposure intensity and timing, (2) frequency-domain characteristics, (3) spatial characteristics. The first category describes the magnitude and time history of exposure, including the TWA field metric, which most often is the focus of MF exposure assessment. The second category depicts the waveform characteristic (harmonic content), which has been relatively poorly described in most studies. The third category describes the field vector's time-space orientation and relation to static fields. Some examples of 'alternative metrics' that have been proposed based on biological mechanisms and potential measurement techniques are examined. The limited correlation of some alternative metrics with the TWA field metric in available data suggests that substantial exposure misclassification could occur if measurement protocols only focus on average field levels. (author)

  16. Differential effects of wake promoting drug Modafinil in aversive learning paradigms

    Directory of Open Access Journals (Sweden)

    Bharanidharan eShanmugasundaram

    2015-08-01

    Full Text Available Modafinil (MO an inhibitor of the dopamine transporter was initially approved to treat narcolepsy, a sleep related disorder in humans. One interesting side-effect of this drug, which emerged from preclinical and clinical studies, is the facilitation of cognitive performance. So far, this was primarily shown in appetitive learning paradigms, but it is yet unclear whether MO exerts a more general cognitive enhancement effect. Thus, the aim of the present study in rats was to extend these findings by testing the effects of MO in two aversive paradigms, Pavlovian fear conditioning (FC and the operant two-way active avoidance (TWA learning paradigms. We discovered a differential, task-dependent effect of MO. In the FC paradigm MO treated rats showed a dose-dependent enhancement of fear memory compared to vehicle treated rats, indicated by increased context-related freezing. Cue related fear memory remained unaffected. In the TWA paradigm MO induced a slight, but significant decrease of avoidance responses compared to vehicle treated animals, while the number of escape reactions during the acquisition of the TWA task remained unaffected. These findings expand the knowledge in the regulation of cognitive abilities and may contribute to the understanding of the contraindicative effects of MO in anxiety related mental disorders.

  17. The Composite Strain Index (COSI) and Cumulative Strain Index (CUSI): methodologies for quantifying biomechanical stressors for complex tasks and job rotation using the Revised Strain Index.

    Science.gov (United States)

    Garg, Arun; Moore, J Steven; Kapellusch, Jay M

    2016-11-04

    The Composite Strain Index (COSI) quantifies biomechanical stressors for complex tasks consisting of exertions at different force levels and/or with different exertion times. The Cumulative Strain Index (CUSI) further integrates biomechanical stressors from different tasks to quantify exposure for the entire work shift. The paper provides methodologies to compute COSI and CUSI along with examples. Complex task simulation produced 169,214 distinct tasks. Use of average, time-weighted average (TWA) and peak force and COSI classified 66.9, 28.2, 100 and 38.9% of tasks as hazardous, respectively. For job rotation the simulation produced 10,920 distinct jobs. TWA COSI, peak task COSI and CUSI classified 36.5, 78.1 and 66.6% jobs as hazardous, respectively. The results suggest that the TWA approach systematically underestimates the biomechanical stressors and peak approach overestimates biomechanical stressors, both at the task and job level. It is believed that the COSI and CUSI partially address these underestimations and overestimations of biomechanical stressors. Practitioner Summary: COSI quantifies exposure when applied hand force and/or duration of that force changes during a task cycle. CUSI integrates physical exposures from job rotation. These should be valuable tools for designing and analysing tasks and job rotation to determine risk of musculoskeletal injuries.

  18. Applying the Theory of Work Adjustment to Latino Immigrant Workers: An Exploratory Study.

    Science.gov (United States)

    Eggerth, Donald E; Flynn, Michael A

    2012-02-01

    Blustein mapped career decision making onto Maslow's model of motivation and personality and concluded that most models of career development assume opportunities and decision-making latitude that do not exist for many individuals from low income or otherwise disadvantaged backgrounds. Consequently, Blustein argued that these models may be of limited utility for such individuals. Blustein challenged researchers to reevaluate current career development approaches, particularly those assuming a static world of work, from a perspective allowing for changing circumstances and recognizing career choice can be limited by access to opportunities, personal obligations, and social barriers. This article represents an exploratory effort to determine if the theory of work adjustment (TWA) might meaningfully be used to describe the work experiences of Latino immigrant workers, a group living with severe constraints and having very limited employment opportunities. It is argued that there is significant conceptual convergence between Maslow's hierarchy of needs and the work reinforcers of TWA. The results of an exploratory, qualitative study with a sample of 10 Latino immigrants are also presented. These immigrants participated in key informant interviews concerning their work experiences both in the United States and in their home countries. The findings support Blustein's contention that such workers will be most focused on basic survival needs and suggest that TWA reinforcers are descriptive of important aspects of how Latino immigrant workers conceptualize their jobs.

  19. Comparison of five integrative samplers in laboratory for the monitoring of indicator and dioxin-like polychlorinated biphenyls in water.

    Science.gov (United States)

    Jacquet, Romain; Miège, Cécile; Smedes, Foppe; Tixier, Céline; Tronczynski, Jacek; Togola, Anne; Berho, Catherine; Valor, Ignacio; Llorca, Julio; Barillon, Bruno; Marchand, P; Coquery, Marina

    2014-03-01

    This study aimed at evaluating and comparing five integrative samplers for the monitoring of indicator and dioxin-like polychlorinated biphenyls (PCBs) in water: semi-permeable membrane device (SPMD), silicone rubber, low-density polyethylene (LDPE) strip, Chemcatcher and a continuous-flow integrative sampler (CFIS). These samplers were spiked with performance reference compounds (PRCs) and then simultaneously exposed under constant agitation and temperature in a 200 L stainless steel tank for periods ranging from one day to three months. A constant PCB concentration of about 1 ng·L(-1) was achieved by immersing a large amount of silicone rubber sheets ("dosing sheets") spiked with the target PCBs. The uptake of PCBs in the five samplers showed overall good repeatability and their accumulation was linear with time. The samplers SPMD, silicone rubber and LDPE strip were the most promising in terms of achieving low limits of quantification. Time-weighted average (TWA) concentrations of PCBs in water were estimated from uptake of PCBs using the sampling rates calculated from the release of PRCs. Except for Chemcatcher, a good agreement was found between the different samplers and TWA concentrations ranged between 0.4 and 2.8 times the nominal water concentration. Finally, the influence of calculation methods (sampler-water partition coefficients, selected PRCs, models) on final TWA concentrations was studied.

  20. Applying the Theory of Work Adjustment to Latino Immigrant Workers: An Exploratory Study

    Science.gov (United States)

    Eggerth, Donald E.; Flynn, Michael A.

    2015-01-01

    Blustein mapped career decision making onto Maslow’s model of motivation and personality and concluded that most models of career development assume opportunities and decision-making latitude that do not exist for many individuals from low income or otherwise disadvantaged backgrounds. Consequently, Blustein argued that these models may be of limited utility for such individuals. Blustein challenged researchers to reevaluate current career development approaches, particularly those assuming a static world of work, from a perspective allowing for changing circumstances and recognizing career choice can be limited by access to opportunities, personal obligations, and social barriers. This article represents an exploratory effort to determine if the theory of work adjustment (TWA) might meaningfully be used to describe the work experiences of Latino immigrant workers, a group living with severe constraints and having very limited employment opportunities. It is argued that there is significant conceptual convergence between Maslow’s hierarchy of needs and the work reinforcers of TWA. The results of an exploratory, qualitative study with a sample of 10 Latino immigrants are also presented. These immigrants participated in key informant interviews concerning their work experiences both in the United States and in their home countries. The findings support Blustein’s contention that such workers will be most focused on basic survival needs and suggest that TWA reinforcers are descriptive of important aspects of how Latino immigrant workers conceptualize their jobs. PMID:26345693

  1. Simulated consumer exposure to dimethyl ether and propane/butane in hairsprays.

    Science.gov (United States)

    Hartop, P J; Cook, T L; Adams, M G

    1991-08-01

    Synopsis The potential human exposures from use of dimethyl ether (DME) and 'liquefied petroleum gas'(LPG) arising from use in hairsprays have been assessed. DME and LPG concentrations were measured in the 'breathing zone' of an experimental manikin and an 'accompanying child' designed to simulate human use of hairsprays in a domestic situation and in the breathing zone of a 'stylist' and 'customer' under salon conditions. Results were expressed as the 10 min time weighted average in the air (TWA10) and as the peak concentration in the breathing zone of the 'user'. Following a 10s use of hairspray containing 50% DME or 26% LPG, TWA10 values for an adult user in a closed room (volume 21 m(3)) were on average 114 ppm and 73 ppm respectively. The child TWA10 values were 89 ppm (DME) and 80 ppm (LPG). Leaving the door open during spraying did not significantly alter these values. The peak concentrations measured in the user breathing zone were 1577 ppm of DME and 671 ppm of LPG. Simulated salon use of a hairspray gave a calculated value of 55 ppm DME and 88 ppm LPG for the stylist over an 8 h working period.

  2. Right ventricular arrhythmogenesis in failing human heart: the role of conduction and repolarization remodeling

    Science.gov (United States)

    Lou, Qing; Janks, Deborah L.; Holzem, Katherine M.; Lang, Di; Onal, Birce; Ambrosi, Christina M.; Fedorov, Vadim V.; Wang, I-Wen

    2012-01-01

    Increased dispersion of repolarization has been suggested to underlie increased arrhythmogenesis in human heart failure (HF). However, no detailed repolarization mapping data were available to support the presence of increased dispersion of repolarization in failing human heart. In the present study, we aimed to determine the existence of enhanced repolarization dispersion in the right ventricular (RV) endocardium from failing human heart and examine its association with arrhythmia inducibility. RV free wall preparations were dissected from five failing and five nonfailing human hearts, cannulated and coronary perfused. RV endocardium was optically mapped from an ∼6.3 × 6.3 cm2 field of view. Action potential duration (APD), dispersion of APD, and conduction velocity (CV) were quantified for basic cycle lengths (BCL) ranging from 2,000 ms to the functional refractory period. We found that RV APD was significantly prolonged within the failing group compared with the nonfailing group (560 ± 44 vs. 448 ± 39 ms, at BCL = 2,000 ms, P < 0.05). Dispersion of APD was increased in three failing hearts (161 ± 5 vs. 86 ± 19 ms, at BCL = 2,000 ms). APD alternans were induced by rapid pacing in these same three failing hearts. CV was significantly reduced in the failing group compared with the nonfailing group (81 ± 11 vs. 98 ± 8 cm/s, at BCL = 2,000 ms). Arrhythmias could be induced in two failing hearts exhibiting an abnormally steep CV restitution and increased dispersion of repolarization due to APD alternans. Dispersion of repolarization is enhanced across the RV endocardium in the failing human heart. This dispersion, together with APD alternans and abnormal CV restitution, could be responsible for the arrhythmia susceptibility in human HF. PMID:23042951

  3. Role of a 12-lead electrocardiogram in the diagnosis of cardiac tamponade as diagnosed by transthoracic echocardiography in patients with malignant pericardial effusion.

    Science.gov (United States)

    Argula, Rahul G; Negi, Smita I; Banchs, Jose; Yusuf, Syed Wamique

    2015-03-01

    Few studies have looked at the utility of the 12-lead electrocardiogram (ECG) in diagnosing cardiac tamponade in malignant pericardial effusion (PE). The aim of this study was to determine the sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) of 12-lead ECG in diagnosing cardiac tamponade in PE. Abnormalities on a 12 lead ECG can be used to diagnose or exclude cardiac tamponade in patients with malignant PE. Using echocardiography as the gold standard for diagnosis of cardiac tamponade, we determined the Se, Sp, PPV, and NPV for individual and combinations of the 3 ECG abnormalities (low-voltage complexes, electrical alternans, and sinus tachycardia). For PEs of all sizes, the Se, Sp, PPV, and NPV for detecting cardiac tamponade were: low-voltage complexes (56%, 74%, 81%, 46%), electrical alternans (23%, 98%, 95%, 39%), and sinus tachycardia (76%, 60%, 79%, 56%), respectively. Presence of all 3 and any of the 3 ECG abnormalities had a Se, Sp, PPV, and NPV of 8%, 100%, 100%, 36% and 89%, 47%, 77%, 69%, respectively, for cardiac tamponade. The odds ratios for cardiac tamponade in PE were 3.7 (95% confidence interval [CI]: 1.65-8.30) for low-voltage complexes, 12.3 (95% CI: 1.58-95.17) for electrical alternans, and 4.9 (95% CI: 2.22-10.80) for sinus tachycardia. Presence of any of 3 ECG abnormalities had an odds ratio of 7.3 (95% CI: 2.9-18.1) for cardiac tamponade. In malignant PE, combination of ECG abnormalities can supplement clinical examination in the diagnosis of echocardiographic cardiac tamponade. Due to its low NPV, 12-lead ECG cannot be used as a screening tool to exclude cardiac tamponade with malignant PE. © 2015 Wiley Periodicals, Inc.

  4. Futuro de los recursos h??dricos en la cuenca del r??o Guadalfeo bajo supuesto de cambio clim??tico

    OpenAIRE

    Moreno Aranda, Isabel Mar??a; Millares Valenzuela, Agust??n; Herrero Lantar??n, Javier; Polo G??mez, Mar??a Jos??; Losada Rodr??guez, Miguel ??ngel

    2010-01-01

    La gesti??n integral del agua en las cuencas mediterr??neas resulta muy compleja por dos motivos fundamentales: 1) las precipitaciones son bastante escasas y su distribuci??n espacial y temporal es muy irregular. Se alternan periodos prolongados de sequ??a con a??os de precipitaciones moderadas siendo frecuentes los episodios puntuales torrenciales; 2) el desarrollo socioecon??mico est?? dominado por actividades que requieren importantes cantidades de agua en las ??pocas del a??o donde no se ...

  5. La voz de los instrumentos en manos de los juglares

    OpenAIRE

    Villanueva, Carlos

    2012-01-01

    Lo profano y lo religioso en la imago musicae medieval conviven y se alternan con la naturalidad que la retórica y los sermones de la época nos dictan: equilibrio y armonía de la más pura esencia boeciana, por un lado, y desequilibrio y transgresión en el mensaje de la música que los juglares transmiten. La Iglesia no ha dejado nunca de condenar aquellas prácticas en el templo y en la calle, o la intromisión de lo profano dentro de la liturgia, aunque, por la propia curiositas —como recalca S...

  6. Using noise to determine cardiac restitution with memory

    Science.gov (United States)

    Dai, Shu; Keener, James P.

    2012-06-01

    Variation in cardiac pacing cycles, as seen, for example, in heart rate variability, has been observed for decades. Contemporarily, various mathematical models have been constructed to investigate the electrical activity of paced cardiac cells. Yet there has not been a study of these cardiac models when there is variation in the pacing cycles such as noise. We present a method that uses the stochasticity of pacing cycles to determine approximate models of the dynamics of cardiac cells, and use these models to detect bifurcations to alternans.

  7. Developing a novel comprehensive framework for the investigation of cellular and whole heart electrophysiology in the in situ human heart: historical perspectives, current progress and future prospects.

    Science.gov (United States)

    Taggart, Peter; Orini, Michele; Hanson, Ben; Hayward, Martin; Clayton, Richard; Dobrzynski, Halina; Yanni, Joseph; Boyett, Mark; Lambiase, Pier D

    2014-08-01

    Understanding the mechanisms of fatal ventricular arrhythmias is of great importance. In view of the many electrophysiological differences that exist between animal species and humans, the acquisition of basic electrophysiological data in the intact human heart is essential to drive and complement experimental work in animal and in-silico models. Over the years techniques have been developed to obtain basic electrophysiological signals directly from the patients by incorporating these measurements into routine clinical procedures which access the heart such as cardiac catheterisation and cardiac surgery. Early recordings with monophasic action potentials provided valuable information including normal values for the in vivo human heart, cycle length dependent properties, the effect of ischaemia, autonomic nervous system activity, and mechano-electric interaction. Transmural recordings addressed the controversial issue of the mid myocardial "M" cell. More recently, the technique of multielectrode mapping (256 electrodes) developed in animal models has been extended to humans, enabling mapping of activation and repolarisation on the entire left and right ventricular epicardium in patients during cardiac surgery. Studies have examined the issue of whether ventricular fibrillation was driven by a "mother" rotor with inhomogeneous and fragmented conduction as in some animal models, or by multiple wavelets as in other animal studies; results showed that both mechanisms are operative in humans. The simpler spatial organisation of human VF has important implications for treatment and prevention. To link in-vivo human electrophysiological mapping with cellular biophysics, multielectrode mapping is now being combined with myocardial biopsies. This technique enables region-specific electrophysiology changes to be related to underlying cellular biology, for example: APD alternans, which is a precursor of VF and sudden death. The mechanism is incompletely understood but related

  8. Personality disorders and emotional variables in patients with lupus

    OpenAIRE

    Co??n-Mej??as, Mar??a ??ngeles; Peralta-Ram??rez, Mar??a Isabel; Callejas-Rubio, Jos?? Luis; P??rez Garc??a, Miguel

    2007-01-01

    El lupus eritematoso sist??mico (LES) es una enfermedad de car??cter autoinmune que afecta principalmente a mujeres en edad f??rtil. Los s??ntomas m??s comunes de los pacientes incluyen dolor articular, erupciones cut??neas, cansancio o fatiga y dificultad en la respiraci??n. Aunque el curso de la enfermedad es cr??nico, evoluciona normalmente en forma de brotes, que se alternan con periodos de remisi??n relativa. Si bien la etiolog??a es desconocida, se sabe que existe u...

  9. Bases anatómicas del sueño Anatomical basis of sleep

    OpenAIRE

    2007-01-01

    El sueño es un estado biológico activo, periódico, en el que se distinguen las etapas NREM y REM, que se alternan sucesivamente durante la noche. Intervienen los relojes biológicos en la modulación del sistema, así como neurotransmisores específicos. Se trata de una red neuronal compleja, en la que intervienen diversas zonas del sistema nervioso central. Los procesos oníricos están controlados además de forma neural. Se resume la historia de las investigaciones sobre el tema, desde el siglo X...

  10. Las relaciones de los órganos del poder político en el nuevo contexto político mexicano

    OpenAIRE

    2011-01-01

    El declive del presidencialismo hegemónico que México conoció en el seno de sus instituciones durante 71 años fue lento, pero efectivo. Se trata de una evolución paulatina que permitió tanto al poder como a sus oponentes adaptarse a la crítica. Aprendieron en efecto a criticar y a ser criticados de manera pacífica. De manera progresiva el sistema político mexicano se transforma de hegemónico en plural, reuniendo así un elemento importante de la democracia, siguiendo posteriormente la alternan...

  11. 深圳市南山区生产企业化学毒物急性职业病危害风险分析%Analysis on acute occupational hazard of toxicants in enterprises of Nanshan District in Shenzhen City

    Institute of Scientific and Technical Information of China (English)

    姜立民; 黄丽琴; 朱震忠; 郑曼莹

    2012-01-01

    目的 探讨深圳市南山区因生产中接触化学毒物引起急性职业病危害的风险,为职业病防治提供依据.方法 用Excel建立数据库,分析2009年6月-2011年7月深圳市南山区职业病危害申报和职业卫生监督资料,分析2008-2011年生产企业职业病危害因素检测报告中毒物超标的报告.结果 危害企业数、接害人数、超标毒物种类位居首位的是通信设备、计算机及其他电子设备制造业,接害人数位居前3位的毒物是铅及其化合物、苯系物、正己烷,苯系物分布范围最广.毒物检测点超标情况:苯时间加权平均(浓度)(TWA)超标1.30 ~3.93倍,短时间接触浓度(STEL)超标20.50 ~26.60倍;甲苯TWA超标0.04~3.96倍,STEL超标0.01 ~5.41倍;二甲苯TWA超标5.68倍;甲醇TWA超标0.30~1.03倍,STEL超标0.51 ~4.06倍;硫酸及三氧化硫TWA超标0.005 ~0.16倍;氯化氢及盐酸C-MAC超标1.25倍;锰及其无机化合物TWA超标0.07~22.33倍;铅烟TWA超标1.13 ~25.33倍,铅尘TWA超标0.02 ~25.00倍;三氯乙烯TWA超标0.03 ~ 25.10倍;一氧化碳STEL超标0.03~1.06倍,正己烷TWA超标0.05 ~ 6.28倍;STEL超标0.06 ~5.70倍.结论 通信设备、计算机及其他电子设备制造业属于化学毒物急性职业病危害高风险的行业.三氯乙烯、苯、甲苯等有机溶剂属于急性职业病危害高风险的有害因素.二甲苯、甲醇、一氧化碳、正己烷、硫酸及三氧化硫、氯化氢及盐酸、铅烟等化学毒物急性职业病危害风险依然存在.%[Objective]To understand the risk of acute occupational hazard caused by toxicant exposure in Nanshan District of Shenzhen City, and provide evidence for the prevention of occupational disease. [ Methods ] Excel was used to form database in analyzing the data collected from occupational hazardous report and occupational hygienic supervision of Nanshan District during June 2009 - July 2011, collected from toxicant

  12. Youngest Brown Dwarf Yet in a Multiple Stellar System

    Science.gov (United States)

    2000-07-01

    ... and the Sharpest Optical Image (0.18 arcsec) from the VLT so far...! Astronomers are eager to better understand the formation of stars and planets - with an eye on the complex processes that lead to the emergence of our own solar system some 4600 million years ago. Brown Dwarfs (BDs) play a special role in this context. Within the cosmic zoo, they represent a class of "intermediate" objects. While they are smaller than normal stars, they shine by their own energy for a limited time, in contrast to planets. Recent observations with the ESO Very Large Telescope (VLT) of a "young" Brown Dwarf in a multiple stellar system are taking on a particular importance in this connection. An evaluation of the new data by an international team of astronomers [1] shows that it is by far the youngest of only four such objects found in a stellar system so far. The results are now providing new insights into the stellar formation process. This small object is known as TWA-5 B and with a mass of only 15 - 40 times that of Jupiter, it is near the borderline between planets and Brown Dwarfs, cf. the explanatory Appendix to this Press Release. However, visible and infrared VLT spectra unambiguously classify it in the latter category. Accurate positional measurements with the Hubble Space Telescope (HST) and the VLT hint that it is orbiting the central, much heavier and brighter star in this system, TWA-5 A (itself a close double star of which each component presumably has a mass of 0.75 solar masses), with a period that may be as long as 900 years. And, by the way, an (I-band) image of the TWA-5 system is the sharpest delivered by the VLT so far, with an image size of only 0.18 arcsec [2]! Brown Dwarfs: a cool subject In current astronomical terminology, Brown Dwarfs (BDs) are objects whose masses are below those of normal stars - the borderline is believed to be about 8% of the mass of our Sun - but larger than those of planets, cf. [3]. Unlike normal stars, Brown Dwarfs are unable

  13. Utility of 12-lead electrocardiogram for differentiating paroxysmal supraventricular tachycardias in dogs.

    Science.gov (United States)

    Santilli, R A; Perego, M; Crosara, S; Gardini, F; Bellino, C; Moretti, P; Spadacini, G

    2008-01-01

    The 12-lead surface ECG is validated for differentiating supraventricular tachycardias (SVT) in humans. Despite the description of SVT in veterinary medicine, no studies have analyzed the electrocardiographic features of this type of arrhythmias in dogs. To describe the specific electrocardiographic criteria used to differentiate the most common SVT in dogs. Twenty-three dogs examined at Clinica Veterinaria Malpensa for SVT with the mechanism documented by electrophysiologic studies (EPS). Twelve-lead electrocardiographic variables obtained from 14 dogs with orthodromic atrioventricular reciprocating tachycardia (OAVRT) and 9 dogs with focal atrial tachycardia (FAT) were compared. Dogs with FAT had faster heart rates (278 +/- 62 versus 229 +/- 42 bpm; P= .049) and less QRS alternans (33 versus 86%; P= .022). P waves appeared during tachycardia in 22 dogs, with a superior axis in 100% of OAVRT and 22% of FAT (P < .001). OAVRT was characterized by a shorter RP interval (85.0 +/- 16.8 versus 157.1 +/- 37.3 ms; P < .001) and smaller RP/PR ratio (0.60 +/- 0.18 versus 1.45 +/- 0.52; P < .001). Repolarization anomalies were present in 64% of OAVRT and no FAT (P < .001). Multivariate analysis identified QRS alternans and a positive P wave in aVR during tachycardia as independent predictors of arrhythmia type. Electrocardiographic criteria used in people for differentiating SVT can also be applied in dogs.

  14. Applications of control theory to the dynamics and propagation of cardiac action potentials.

    Science.gov (United States)

    Muñoz, Laura M; Stockton, Jonathan F; Otani, Niels F

    2010-09-01

    Sudden cardiac arrest is a widespread cause of death in the industrialized world. Most cases of sudden cardiac arrest are due to ventricular fibrillation (VF), a lethal cardiac arrhythmia. Electrophysiological abnormalities such as alternans (a beat-to-beat alternation in action potential duration) and conduction block have been suspected to contribute to the onset of VF. This study focuses on the use of control-systems techniques to analyze and design methods for suppressing these precursor factors. Control-systems tools, specifically controllability analysis and Lyapunov stability methods, were applied to a two-variable Karma model of the action-potential (AP) dynamics of a single cell, to analyze the effectiveness of strategies for suppressing AP abnormalities. State-feedback-integral (SFI) control was then applied to a Purkinje fiber simulated with the Karma model, where only one stimulating electrode was used to affect the system. SFI control converted both discordant alternans and 2:1 conduction block back toward more normal patterns, over a wider range of fiber lengths and pacing intervals compared with a Pyragas-type chaos controller. The advantages conferred by using feedback from multiple locations in the fiber, and using integral (i.e., memory) terms in the controller, are discussed.

  15. Reduced intrinsic heart rate is associated with reduced arrhythmic susceptibility in guinea-pig heart.

    Science.gov (United States)

    Osadchii, Oleg E

    2014-12-01

    In the clinical setting, patients with slower resting heart rate are less prone to cardiovascular death compared with those with elevated heart rate. However, electrophysiological adaptations associated with reduced cardiac rhythm have not been thoroughly explored. In this study, relationships between intrinsic heart rate and arrhythmic susceptibility were examined by assessments of action potential duration (APD) rate adaptation and inducibility of repolarization alternans in sinoatrial node (SAN)-driven and atrioventricular (AV)-blocked guinea-pig hearts perfused with Langendorff apparatus. Electrocardiograms, epicardial monophasic action potentials, and effective refractory periods (ERP) were assessed in normokalemic and hypokalemic conditions. Slower basal heart rate in AV-blocked hearts was associated with prolonged ventricular repolarization during spontaneous beating, and with attenuated APD shortening at increased cardiac activation rates during dynamic pacing, when compared with SAN-driven hearts. During hypokalemic perfusion, the inducibility of repolarization alternans and tachyarrhythmia by rapid pacing was found to be lower in AV-blocked hearts. This difference was ascribed to prolonged ERP in the setting of reduced basal heart rate, which prevented ventricular capture at critically short pacing intervals required to induce arrhythmia. Reduced basal heart rate is associated with electrophysiological changes that prevent electrical instability upon an abrupt cardiac acceleration.

  16. Frank-Starling mechanism retains recirculation fraction of myocardial Ca(2+) in the beating heart.

    Science.gov (United States)

    Mizuno, J; Araki, J; Mohri, S; Minami, H; Doi, Y; Fujinaka, W; Miyaji, K; Kiyooka, T; Oshima, Y; Iribe, G; Hirakawa, M; Suga, H

    2001-12-01

    Myocardial Ca(2+) handling in excitation-contraction coupling is the second primary determinant of energy or O(2) demand in a working heart. The intracellular and extracellular routes remove myocardial Ca(2+) that was released into the sarcoplasma with different Ca(2+): ATP stoichiometries. The intracellular route is twice as economical as the extracellular route. Therefore the fraction of total Ca(2+) removed via the sarcoplasmic reticulum, i.e., the recirculation fraction of intracellular Ca(2+) (RF), determines the economy of myocardial Ca(2+) handling. RF has conventionally been estimated as the exponential decay rate of postextrasystolic potentiation (PESP). However, we have found that PESP usually decays in alternans, but not exponentially in the canine left ventricle beating above 100 beats/min. We have succeeded in estimating RF from the exponential decay component of an alternans PESP. We previously found that the Frank-Starling mechanism or varied ventricular preload did not affect the economy of myocardial Ca(2+) handling. Then, to account for this important finding, we hypothesized that the Frank-Starling mechanism would not affect RF at a constant heart rate. We tested this hypothesis and found its supportive evidence in 11 canine left ventricles. We conclude that RF at a constant heart rate would remain constant, independent of the Frank-Starling mechanism.

  17. Electrocardiographic manifestations of hyperkalemia in hemodialysis patients

    Directory of Open Access Journals (Sweden)

    Nemati Eghlim

    2010-01-01

    Full Text Available This study was performed to evaluate whether any electrocardiogram (ECG para-meter can predict the presence of hyperkalemia in patients on maintenance hemodialysis (HD. In January 2006, we conducted a cross-sectional study of 80 stable patients with end-stage renal disease from four university-based HD units of Tehran, Iran, receiving conventional thrice-weekly HD. Pre-HD serum electrolyte values and conventional 12-lead ECG were obtained from each pa-tient. Bivariate linear regression was used for assessing relationship of the study variables with hyperkalemia (K + > 5.2 mg/dL. Multivariable logistic regression was used for evaluating inde-pendent relationship between decreased T wave duration (≤ 170 ms and other variables. Bivariate correlation analysis showed a significant inverse correlation between serum potassium concentration and T wave duration (P < 0.05. None of the patients with serum potassium of ≥ 5.6 mg/dL had T wave duration > 200 ms. Multivariate logistic analysis, after adjustment for other factors, also showed a significant relationship between decreased T wave duration (≤ 170 ms and hyper-kalemia. We conclude that although hyperkalemia does not induce the usual ECG changes in HD patients, decreased T wave duration was found to be a good indicator of this lethal condition.

  18. Revisiting TW Hydrae in light of new astrometric data

    Science.gov (United States)

    Teixeira, R.; Ducourant, C.; Galli, P. A. B.; Le Campion, J. F.; Zuckerman, B.; Krone-Martins, A. G. O.; Chauvin, G.; Song, I.

    2014-10-01

    Our efforts in the present work focused mainly on refining and improving the previous description and understanding of the stellar association TW Hydrae (TWA) including a very detailed membership analysis and its dynamical and evolutionary age.To achieve our objectives in a fully reliable way we take advantage of our own astrometric measurements (Ducourant et al. 2013) performed with NTT/EFOSC2 - ESO (La Silla - Chile) spread over three years (2007 - 2010) and of those published in the literature.A very detailed membership analysis based on the convergent point strategy as developed by our team (Galli et al. 2012, 2013) allowed us to define a consistent kinematic group containing 31 stars among the 44 proposed as TWA member in the literature. Assuming that our sample of stars may be contaminated by non-members and to get rid of the particular influence of each star we applied a Jacknife resampling technique generating 2000 random lists of 13 stars taken from our 16 stars and calculated for each the epoch of convergence when the radius is minimum. The mean of the epochs obtained and the dispersion about the mean give a dynamical age of 7.5± 0.7 Myr for the association that is in good agreement with the previous traceback age (De La Reza et al. 2006). We also estimated age for TWA moving group members from pre-main sequence evolutionary models (Siess et al. 2000) and find a mean age of 7.4± 1.2 Myr. These results show that the dynamical age of the association obtained via the traceback technique and the average age derived from theoretical evolutionary models are in good agreement.

  19. N-acetyl-S-(n-propyl)-l-cysteine in urine from workers exposed to 1-bromopropane in foam cushion spray adhesives.

    Science.gov (United States)

    Hanley, Kevin W; Petersen, Martin R; Cheever, Kenneth L; Luo, Lian

    2009-10-01

    1-Bromopropane (1-BP) has been marketed as an alternative for ozone depleting and other solvents; it is used in aerosol products, adhesives, metal, precision, and electronics cleaning solvents. Mechanisms of toxicity of 1-BP are not fully understood, but it may be a neurological and reproductive toxicant. Sparse exposure information prompted this study using 1-BP air sampling and urinary metabolites. Mercapturic acid conjugates are excreted in urine from 1-BP metabolism involving debromination. Research objectives were to evaluate the utility of urinary N-acetyl-S-(n-propyl)-L-cysteine (AcPrCys) for assessing exposure to 1-BP and compare it to urinary bromide [Br((-))] previously reported for these workers. Forty-eight-hour urine specimens were obtained from 30 workers at two factories where 1-BP spray adhesives were used to construct polyurethane foam seat cushions. Urine specimens were also obtained from 21 unexposed control subjects. All the workers' urine was collected into composite samples representing three time intervals: at work, after work but before bedtime, and upon awakening. Time-weighted average (TWA) geometric mean breathing zone concentrations were 92.4 and 10.5 p.p.m. for spraying and non-spraying jobs, respectively. Urinary AcPrCys showed the same trend as TWA exposures to 1-BP: higher levels were observed for sprayers. Associations of AcPrCys concentrations, adjusted for creatinine, with 1-BP TWA exposure were statistically significant for both sprayers (P < 0.05) and non-sprayers (P < 0.01). Spearman correlation coefficients for AcPrCys and Br((-)) analyses determined from the same urine specimens were highly correlated (P < 0.0001). This study confirms that urinary AcPrCys is an important 1-BP metabolite and an effective biomarker for highly exposed foam cushion workers.

  20. Exposure to MRI-related magnetic fields and vertigo in MRI workers.

    Science.gov (United States)

    Schaap, Kristel; Portengen, Lützen; Kromhout, Hans

    2016-03-01

    Vertigo has been reported by people working around magnetic resonance imaging (MRI) scanners and was found to increase with increasing strength of scanner magnets. This suggests an association with exposure to static magnetic fields (SMF) and/or motion-induced time-varying magnetic fields (TVMF). This study assessed the association between various metrics of shift-long exposure to SMF and TVMF and self-reported vertigo among MRI workers. We analysed 358 shifts from 234 employees at 14 MRI facilities in the Netherlands. Participants used logbooks to report vertigo experienced during the work day at the MRI facility. In addition, personal exposure to SMF and TVMF was measured during the same shifts, using portable magnetic field dosimeters. Vertigo was reported during 22 shifts by 20 participants and was significantly associated with peak and time-weighted average (TWA) metrics of SMF as well as TVMF exposure. Associations were most evident with full-shift TWA TVMF exposure. The probability of vertigo occurrence during a work shift exceeded 5% at peak exposure levels of 409 mT and 477 mT/s and at full-shift TWA levels of 3 mT and 0.6 mT/s. These results confirm the hypothesis that vertigo is associated with exposure to MRI-related SMF and TVMF. Strong correlations between various metrics of shift-long exposure make it difficult to disentangle the effects of SMF and TVMF exposure, or identify the most relevant exposure metric. On the other hand, this also implies that several metrics of shift-long exposure to SMF and TVMF should perform similarly in epidemiological studies on MRI-related vertigo. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  1. Time weighted average concentration monitoring based on thin film solid phase microextraction.

    Science.gov (United States)

    Ahmadi, Fardin; Sparham, Chris; Boyaci, Ezel; Pawliszyn, Janusz

    2017-03-02

    Time weighted average (TWA) passive sampling with thin film solid phase microextraction (TF-SPME) and liquid chromatography tandem mass spectrometry (LC-MS/MS) was used for collection, identification, and quantification of benzophenone-3, benzophenone-4, 2-phenylbenzimidazole-5-sulphonic acid, octocrylene, and triclosan in the aquatic environment. Two types of TF-SPME passive samplers, including a retracted thin film device using a hydrophilic lipophilic balance (HLB) coating, and an open bed configuration with an octadecyl silica-based (C18) coating, were evaluated in an aqueous standard generation (ASG) system. Laboratory calibration results indicated that the thin film retracted device using HLB coating is suitable to determine TWA concentrations of polar analytes in water, with an uptake that was linear up to 70 days. In open bed form, a one-calibrant kinetic calibration technique was accomplished by loading benzophenone3-d5 as calibrant on the C18 coating to quantify all non-polar compounds. The experimental results showed that the one-calibrant kinetic calibration technique can be used for determination of classes of compounds in cases where deuterated counterparts are either not available or expensive. The developed passive samplers were deployed in wastewater-dominated reaches of the Grand River (Kitchener, ON) to verify their feasibility for determination of TWA concentrations in on-site applications. Field trials results indicated that these devices are suitable for long-term and short-term monitoring of compounds varying in polarity, such as UV blockers and biocide compounds in water, and the data were in good agreement with literature data.

  2. Real-time measurement and control of waste anesthetic gases during veterinary surgeries

    Energy Technology Data Exchange (ETDEWEB)

    Burkhart, J.E.; Stobbe, T.J. (National Institute for Occupational Safety and Health, Morgantown, WV (USA))

    1990-12-01

    Veterinary clinics are typically small businesses without access to sophisticated occupational safety and health programs that may exist for larger firms or hospitals. Exposures to waste anesthetic gases have been linked to a myriad of adverse health-related conditions. Excessive exposures to anesthetic agents are possible because many of the clinics use portable gas delivery carts that are not designed to capture waste gases. While scavenging systems are available to remove waste anesthetic gases, the cost may be prohibitive for smaller clinics and the effectiveness of these systems has not been fully established in veterinary clinics. The National Institute for Occupational Safety and Health (NIOSH) recommends limiting exposures to nitrous oxide (N2O) to a time-weighted average (TWA) concentration of 25 ppm and halogenated agents to 2 ppm. The NIOSH TWA is based on the weight of the agent collected from a 45-L air sample by charcoal adsorption over a sampling period not to exceed 1 hr. The NIOSH criteria state that, in most situations, control of N2O to the TWA as defined will result in levels of approximately 0.5 ppm of the halogenated agent. At present, no Occupational Safety and Health Administration (OSHA) permissible exposure level (PEL) exists for exposure to anesthetic agents; nor do specific recommendations exist for veterinary scavenging systems. Waste anesthetic gas exposures were determined using a modified MIRAN 1A at five veterinary clinics operating within the Morgantown, West Virginia, vicinity. For unscavenged systems of methoxyflurane and halothane, 1-hr time-weighted average exposures ranged from 0.5 to 45.5 ppm and 0.2 to 105.4 ppm, respectively.

  3. Analysis of trace contaminants in hot gas streams using time-weighted average solid-phase microextraction: proof of concept.

    Science.gov (United States)

    Woolcock, Patrick J; Koziel, Jacek A; Cai, Lingshuang; Johnston, Patrick A; Brown, Robert C

    2013-03-15

    Time-weighted average (TWA) passive sampling using solid-phase microextraction (SPME) and gas chromatography was investigated as a new method of collecting, identifying and quantifying contaminants in process gas streams. Unlike previous TWA-SPME techniques using the retracted fiber configuration (fiber within needle) to monitor ambient conditions or relatively stagnant gases, this method was developed for fast-moving process gas streams at temperatures approaching 300 °C. The goal was to develop a consistent and reliable method of analyzing low concentrations of contaminants in hot gas streams without performing time-consuming exhaustive extraction with a slipstream. This work in particular aims to quantify trace tar compounds found in a syngas stream generated from biomass gasification. This paper evaluates the concept of retracted SPME at high temperatures by testing the three essential requirements for TWA passive sampling: (1) zero-sink assumption, (2) consistent and reliable response by the sampling device to changing concentrations, and (3) equal concentrations in the bulk gas stream relative to the face of the fiber syringe opening. Results indicated the method can accurately predict gas stream concentrations at elevated temperatures. Evidence was also discovered to validate the existence of a second boundary layer within the fiber during the adsorption/absorption process. This limits the technique to operating within reasonable mass loadings and loading rates, established by appropriate sampling depths and times for concentrations of interest. A limit of quantification for the benzene model tar system was estimated at 0.02 g m(-3) (8 ppm) with a limit of detection of 0.5 mg m(-3) (200 ppb). Using the appropriate conditions, the technique was applied to a pilot-scale fluidized-bed gasifier to verify its feasibility. Results from this test were in good agreement with literature and prior pilot plant operation, indicating the new method can measure low

  4. Chemcatcher and DGT passive sampling devices for regulatory monitoring of trace metals in surface water.

    Science.gov (United States)

    Allan, Ian J; Knutsson, Jesper; Guigues, Nathalie; Mills, Graham A; Fouillac, Anne-Marie; Greenwood, Richard

    2008-07-01

    This work aimed to evaluate whether the performance of passive sampling devices in measuring time-weighted average (TWA) concentrations supports their application in regulatory monitoring of trace metals in surface waters, such as for the European Union's Water Framework Directive (WFD). The ability of the Chemcatcher and the diffusive gradient in thin film (DGT) device sampler to provide comparable TWA concentrations of Cd, Cu, Ni, Pb and Zn was tested through consecutive and overlapping deployments (7-28 days) in the River Meuse (The Netherlands). In order to evaluate the consistency of these TWA labile metal concentrations, these were assessed against total and filtered concentrations measured at relatively high frequencies by two teams using standard monitoring procedures, and metal species predicted by equilibrium speciation modeling using Visual MINTEQ. For Cd and Zn, the concentrations obtained with filtered water samples and the passive sampling devices were generally similar. The samplers consistently underestimated filtered concentrations of Cu and Ni, in agreement with their respective predicted speciation. For Pb, a small labile fraction was mainly responsible for low sampler accumulation and hence high measurement uncertainty. While only the high frequency of spot sampling procedures enabled the observation of higher Cd concentrations during the first 14 days, consecutive DGT deployments were able to detect it and provide a reasonable estimate of ambient concentrations. The range of concentrations measured by spot and passive sampling, for exposures up to 28 days, demonstrated that both modes of monitoring were equally reliable. Passive sampling provides information that cannot be obtained by a realistic spot sampling frequency and this may impact on the ability to detect trends and assess monitoring data against environmental quality standards when concentrations fluctuate.

  5. A Principal Component Regression Approach for Estimating Ventricular Repolarization Duration Variability

    Directory of Open Access Journals (Sweden)

    Pasi A. Karjalainen

    2007-01-01

    Full Text Available Ventricular repolarization duration (VRD is affected by heart rate and autonomic control, and thus VRD varies in time in a similar way as heart rate. VRD variability is commonly assessed by determining the time differences between successive R- and T-waves, that is, RT intervals. Traditional methods for RT interval detection necessitate the detection of either T-wave apexes or offsets. In this paper, we propose a principal-component-regression- (PCR- based method for estimating RT variability. The main benefit of the method is that it does not necessitate T-wave detection. The proposed method is compared with traditional RT interval measures, and as a result, it is observed to estimate RT variability accurately and to be less sensitive to noise than the traditional methods. As a specific application, the method is applied to exercise electrocardiogram (ECG recordings.

  6. Evaluation of clinical and electrocardiographic changes during the euthanasia of horses

    DEFF Research Database (Denmark)

    Buhl, Rikke; Andersen, L.O.F.; Karlshøj, M.

    2013-01-01

    The objective of this prospective field study was to investigate whether commonly used criteria for clinical death occurred at the same time as cardiac death, as determined by electrocardiography. Specific ECG changes during euthanasia were also studied. Twenty-nine horses were euthanized...... with pentobarbital at two different dose rates and 15 of the 29 horses also received detomidine hydrochloride for sedation. ECG was recorded prior to and during euthanasia. Time to collapse, cessation of reflexes, heart sounds and asystole were recorded. ECG recordings were used to calculate RR intervals, PQ...... duration, QRS duration, distance from QRS complex to end of T wave corrected for HR (QTc interval), duration of T-wave from peak to end (TpeakTend) and amplitudes of T wave (Tpeak) before and during euthanasia. Differences between groups and ECG changes were evaluated using analysis of variance. Clinical...

  7. Investigation of Electromagnetic Field Threat to Fuel Tank Wiring of a Transport Aircraft

    Science.gov (United States)

    Ely, Jay J.; Nguyen, Truong X.; Dudley, Kenneth L.; Scearce, Stephen A.; Beck, Fred B.; Deshpande, Manohar D.; Cockrell, C. R.

    2000-01-01

    National Transportation Safety Board investigators have questioned whether an electrical discharge in the Fuel Quantity Indication System (FQIS) may have initiated the TWA-800 center wing tank explosion. Because the FQIS was designed to be incapable of producing such a discharge on its own, attention has been directed to mechanisms of outside electromagnetic influence. To support the investigation, the NASA Langley Research Center was tasked to study the potential for radiated electromagnetic fields from external radio frequency (RF) transmitters and passenger carried portable electronic devices (PEDs) to excite the FQIS enough to cause arcing, sparking or excessive heating within the fuel tank.

  8. La construction sociale du travail intérimaire : de ses origines aux États-Unis à son institutionnalisation en France

    OpenAIRE

    Belkacem, Rachid; Kornig, Cathel

    2011-01-01

    Valorisation d'une thèse en économie sur l'histoire du développement de l'intérim en Europe.; National audience; The aim of this paper is the study of the historical development of temporary work. Temporary workers agencies (TWA) appear first at the beginning of the last century in the United States and in the United Kingdom. From the years 1940 on, their fast development carried by large companies of temporary work would be based first of all on the secretarial work needs. Introduced in Fran...

  9. The Evaluation of Relationship between Spirometric Disorders and Methyl methacrylate in Dental Laboratories Personnel

    Directory of Open Access Journals (Sweden)

    E. Nadi

    2010-04-01

    Full Text Available Introduction & Objective: Methyl methacrylate (MMA, as a monomer of acrylic resin that has a wide variety of usages in denture fabrication, is considered as an air pollution indicator in the laboratories. Occupational exposure to these compound vapors can cause respiratory hypersensitivity, occupational asthma, eye and skin irritation and Allergic Contact Dermatitis (ACD. Therefore control of MMA exposure may promote the personnel’s health. The aim of this study was to determine the relationship between spirometric disorders and methyl methacrylate in dental laboratories personnel.. Materials & Methods: In this case control study, exposure of time-weighted average (TWA and short-term exposure level (STEL were measured with MMA vapors in 39 randomly selected male employee (case group in 25 denture fabrication laboratories in Hamadan city. The air samples were collected by sorbent tubes containing chromosorb (XAD2( and analyzed by gas chromatograph equipped with FID detector based on NIOSH method. In addition 30 men whitout occupational exposure to air pollutants (control group were selected to compare the variation of spirometric parameters. Spirometric parameters of the case and control groups such as FVC, FEV1, FEV1/FVC and FEF25-75 were measured by Vitalograph spirometer (model: 2120 on ATS method, after the standard questionnaire of respiratory diseases had been completed during an interview and medical examination..Results: The mean of MMA concentration was 132.87 ± 220.67 ppm for STEL and 1.95 ± 3.59 ppm for TWA.The relationship between MMA concentration in the STEL and TWA exposures was significant (P<0.05 and the relationship between MMA concentration and ventilation was significant just for STEL. In this study no relationship between MMA concentration and spirometric parameters in both STEL and TWA exposures was found. Also there was no significant difference between spirometric parameters of the case group and normal values of the

  10. The instability of wrist joint and total wrist replacement

    Institute of Scientific and Technical Information of China (English)

    Jin-xing Ma; Yong-Qing Xu

    2016-01-01

    Total wrist arthroplasty are not used as widely as total knee and hip replacement.The functional hands are requiring surgeons to design a durable and functional satisfying prosthesis.This article will list the main reasons that cause the failure of the prosthesis.Some remarkable and representative prostheses are listed to show the devolvement of total wrist prosthesis and their individual special innovations to fix the problems,And the second part we will discuss the part that biomechanical elements act in the total wrist replacement (TWA).Summarize and find out what the real problem is and how we can find a way to fix it.

  11. Development of an Environmental Monitoring Program. Volume 1. Marine Hazardous Chemical Worker.

    Science.gov (United States)

    1985-10-01

    Institute, San Antonio, Texas , April, 1985. !..: . 14 on a regular basis. Tow boats haul barges that contain both Subchapter 0 and D chem- icals, but a...Reference Vapor Pressure (mmHG) 100 6 90 (1) TLV-TWA (ppm) 10 50 10 (2) TLV-STEL (ppm) 15 100 20 (2) Odor Threshold (ppm) (40, USA :194 USSR) 0.47 0.28 (3...one cargo tank by the open gauging method. To measure ullage during the final stages of loading the gauger used a Lufkin tape. Because of tall

  12. Utility of nonspecific resting electrocardiographic features for detection of coronary artery stenosis by Computed Tomography in acute chest pain patients: from the ROMICAT trial

    Science.gov (United States)

    Banerji, Dahlia; Ptaszek, Leon M.; Taylor, Carolyn; Fontes, Joao D.; Kriegel, Matthias; Irlbeck, Thomas; Nagurney, John T.; Hoffmann, Udo

    2011-01-01

    Twelve-lead surface electrocardiography (ECG) and computed tomography (CT) are used to evaluate for myocardial ischemia and coronary artery disease (CAD), respectively. We aimed to determine features on resting ECG that predict coronary artery stenosis by cardiac CT. In 309 acute chest pain patients, we compared the initial triage resting ECG to contrast-enhanced 64-slice cardiac CT angiography. We assessed for 6 quantitative (QT interval, QTc interval, QTc > 440 ms, gender-specific QTc, QT dispersion and QRS duration) and 4 qualitative ECG parameters (ST depression >0.05 to ≤0.1 mV, T wave inversion ≥0.1 mV, T wave flattening, and any T wave abnormalities) and for the presence of coronary stenosis by CT (>50% luminal narrowing). Specificities of these ECG parameters were excellent (83.6–97.0%) while sensitivities were poor (12.2–29.3%). For coronary stenosis detection, the ECG features with the greatest performance were the presence of ST depression (positive likelihood ratio [LR+] 4.09) and T wave inversion (LR+ 4.58). In multivariable analyses, the risk for coronary stenosis increased by 33–41% for every 20 ms prolongation of the QTc interval after adjusting for age, gender, and cardiac risk factors or adjustment for Framingham risk score. Similarly, there was an increase of fourfold with the presence of ST depression >0.05 to ≤0.1 mV or T wave inversion ≥0.1 mV. In acute chest pain patients, resting ECG features of QTc interval prolongation, mild ST depression, and T wave inversion are independently associated with the presence of CT coronary stenosis and their presence suggests an increase risk of CAD. PMID:21287278

  13. Phase 2 reentry in man

    DEFF Research Database (Denmark)

    Thomsen, P.E.B.; Jørgensen, R.M.; Kanters, J.K.;

    2005-01-01

    mu V, range 0-1,700) and T-wave changes in the sinus beat prior to ventricular ectopy. In addition, J-point elevation was demonstrated in several cases. In total, significant changes were demonstrated in 15 of the 18 patients studied (83%). CONCLUSION J-point elevation, ST-elevation, and T......-wave changes documented in the last sinus beat prior to ventricular extrasystoles are in agreement with phase 2 reentry, suggesting that this may be the responsible mechanism for ventricular extrasystoles and ventricular tachycardia/fibrillation. The phenomenon has been demonstrated in only animal experiments...

  14. Comparison of corneal topographic measurements and high order aberrations in keratoconus and normal eyes.

    Science.gov (United States)

    Colak, Hatice Nur; Kantarci, Feride Aylin; Yildirim, Aydin; Tatar, Mehmet Gurkan; Goker, Hasan; Uslu, Hasim; Gurler, Bulent

    2016-10-01

    The aim of this report was to compare corneal topographic measurements and anterior high order corneal aberrations in eyes with keratoconus and normal eyes by using Scheimpflug-Placido topography. Eighty cases diagnosed with mild (group 1), moderate (group 2), and advanced (group 3) stage keratoconus (KC) according to Amsler-Krumeich Classification and 81 healthy (control group) cases were retrospectively examined. The mean keratometric measurements (as both diopters (Kavg) and mm values (mmavg)), central corneal thickness values (CCT), high order aberration (HOA), total wavefront aberration (TWA), coma, trefoil, and spherical aberration measurements were performed using Sirius topography equipment. The topographic values were compared between the groups. There were 25 cases in group 1 KC (15.5%), 34 cases in group 2 KC (21.1%), 21 cases in group 3 KC (13.1%), and 81 cases (50.3%) in the control group. In terms of mean age and gender distributions, there was no statistically significant difference between the groups (p>0.05). However, there was significant difference between the groups in terms of Kavg, CCT, HOA, TWA, coma, trefoil, and spherical aberration values (pkeratoconus. Anterior high order corneal aberration measurements are a useful tool to guide the physician in diagnosis and classification of keratoconus. Copyright © 2016 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  15. 1-溴丙烷对接触工人神经毒性的剂量-效应关系%Exposure to 1-bromopropane causes dose-dependent neurological abnormalities in workers

    Institute of Scientific and Technical Information of China (English)

    李卫华; 王强毅; 市原学; 竹内康浩; 丁训诚; 周志俊

    2010-01-01

    Objective To explore the dose-effect relationship between 1-bromopropane (1-BP) exposure and health effects in workers. Methods Occupational field investigations were conducted in 1-BP factories. Ambient 1-BP concentrations were detected with detection tube, and the 8 h time-weighted average individual exposure levels (TWA-8 h) were measured by passive sampler. Workers underwent questionnaire survey, neurological examination, nerve conduction velocity examination, vibration sensation test, routine blood test as well as blood biochemical test. According to TWA values or TWA × duration values, workers were divided into three dose groups for dose-effect relationship analysis. USEPA BMDS 2.1 software was applied to calculate 1-BP benchmark dose (BMD) and its 95% lower limit (BMDL). Results The TWA-8h concentrations ranged from 0.35 to 535.19 mg/m3 (geo-mean 14.08 mg/m3). Dose-dependent analysis showed that the motor nerve distal latency (linear regression coefficient was 0.066 6), vibration sensation of toes (linear regression coefficient were 0.157 2 and 0.193 9), creatine kinase (linear regression coefficient was-1.05) and thyroid stimulating hormone levels (linear regression coefficient was 0.102 4) of 1-BP exposed workers changed in a dose-dependent manner (P<0.05). BMD calculation based on DL as 1-BP toxic effect endpoint showed that TWA-8h of the BMD values and BMDL values were 50.55 mg/m3 and 30.78 mg/m3, respectively. Conclusion 1-BP causes dose-dependent changes in tibial nerve DL, vibration sensation, CK and TSH levels.%目的 探索1-溴丙烷(1-BP)对接触工人神经毒性的剂量-效应关系.方法 对国内1-BP生产工厂进行职业卫生现场调查.按1:1比例选取年龄配对的接触组和对照组女工各71人.作业环境中1-BP的浓度用直读式检气管测定,工人的8 h时间加权平均(TWA)浓度用个体采样器测定.对工人进行问卷调查、神经内科检查、神经传导速度检查、振动觉检查、血常规和血

  16. [Study of the effect of occupational exposure to glyphosate on hepatorenal function].

    Science.gov (United States)

    Zhang, F; Pan, L P; Ding, E M; Ge, Q J; Zhang, Z H; Xu, J N; Zhang, L; Zhu, B L

    2017-07-06

    Objective: To explore the effect of occupational exposure to glyphosate on hepatorenal function. Methods: 526 workers who were occupationally exposed to glyphosate from 5 glyphosate-producing factories were selected as cases; and another 442 administrative staffs who were not exposed to glyphosate were selected as controls from April to November, 2014. All the subjects accepted occupational health examination. The concentration level of glyphosate in the air of workshop was detected and the time weighted average concentration (TWA) was calculated. And analyze the difference of hepatorenal fuction between case group and control group. Result: The age of the subjects in the case and control groups were separately (35.6±10.3), (34.3±9.7) years old, with the length of working for (6.5±5.7), (7.7±6.8) years. The TWA of glyphosate in the case group was between Glyphosate can affect the hepatic and renal function among occupational exposure population, and there was an association between the effect and the exposure dose.

  17. Pharmaceuticals, alkylphenols and pesticides in Mediterranean coastal waters: Results from a pilot survey using passive samplers

    Science.gov (United States)

    Munaron, Dominique; Tapie, Nathalie; Budzinski, Hélène; Andral, Bruno; Gonzalez, Jean-Louis

    2012-12-01

    21 pharmaceuticals, 6 alkylphenols and 27 hydrophilic pesticides and biocides were investigated using polar organic contaminant integrative samplers (POCIS) during a large-scale study of contamination of French Mediterranean coastal waters. Marine and transitional water-bodies, defined under the EU Water Framework Directive were monitored. Our results show that the French Mediterranean coastal waters were contaminated with a large range of emerging contaminants, detected at low concentrations during the summer season. Caffeine, carbamazepine, theophilline and terbutaline were detected with a detection frequency higher than 83% in the coastal waters sampled, 4-nonylphenol (4-NP), 4-tert-octylphenol (4-OP) and 4-nonylphenol diethoxylate (NP2EO) were detected in all coastal waters sampled, and diuron, terbuthylazine, atrazine, irgarol and simazine were detected in more than 77% of samples. For pharmaceuticals, highest time-weighted average (TWA) concentrations were measured for caffeine and carbamazepine (32 and 12 ng L-1, respectively). For alkylphenols, highest TWA concentrations were measured for 4-nonylphenol mono-ethoxylate and 4-nonylphenol (41 and 33 ng L-1, respectively), and for herbicides and biocides, they were measured for diuron and irgarol (33 and 2.5 ng L-1, respectively). Except for Diana lagoon, lagoons and semi-enclosed bays were the most contaminated areas for herbicides and pharmaceuticals, whilst, for alkylphenols, levels of contamination were similar in lagoons and coastal waters. This study demonstrates the relevance and utility of POCIS as quantitative tool for measuring low concentrations of emerging contaminants in marine waters.

  18. Maritime Technologies. International developments on every scale; Maritieme Technologieen. Internationale ontwikkelingen op elke schaal

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2010-01-15

    Next to the Netherlands, many other shipbuilding nations are broadening their capacities and developing new applications. In this special edition of TWA Netwerk a report is provided of these developments and insight is provided in the options for international collaboration for Dutch companies and knowledge institutes. The global driving forces behind maritime development are making shipping cleaner (especially with regard to emissions and water environment), growth of offshore applications (such as Production Storage and Offloading systems or FPSOs), new or more extreme user environment (deeper, colder) and less use (of fuel and materials). In addition there is a growing interest in transport of Liquefied Natural gas (LNG) which is highly relevant. [Dutch] Naast Nederland verbreden diverse scheepsbouwnaties hun kunnen en ontwikkelen nieuwe toepassingen. In deze speciale aflevering van TWA Netwerk wordt gerapporteerd over deze ontwikkelingen en wordt inzicht gegeven in de mogelijkheden voor internationale samenwerking voor de Nederlandse bedrijven en kennisinstellingen. De mondiale drijfveren voor maritieme ontwikkeling zijn het schoner maken van de scheepsgebruik (met name in emissies en watermilieu), groei van offshore toepassingen (zoals windenergie en complete drijvende fabrieken boven boorputten: Floating Production Storage and Offloading systemen of FPSO's), nieuwe of extremer gebruiksomgeving (dieper, kouder) en minder verbruik (in brandstof en materiaal). Daarnaast is de groeiende interesse in vervoer van Liquified Natural Gas (LNG) bijzonder relevant.

  19. Monitoring contaminants of emerging concern from tertiary wastewater treatment plants using passive sampling modelled with performance reference compounds.

    Science.gov (United States)

    Sultana, Tamanna; Murray, Craig; Ehsanul Hoque, M; Metcalfe, Chris D

    2016-12-01

    The Lake Simcoe watershed in Ontario, Canada is an important recreational area and a recharge zone for groundwater resources. Lake Simcoe is a relatively shallow lotic system that has been impacted by urban development, recreation, industry and agriculture. As part of a watershed management plan, six wastewater treatment plants (WWTPs) located in this catchment basin were selected to measure the inputs of contaminants of emerging concern (CECs) of wastewater origin. These WWTPs were recently upgraded to tertiary treatment for phosphorus removal. Polar organic chemical integrative samplers (POCIS) and semipermeable membrane devices (SPMDs) were used to monitor for hydrophilic and hydrophobic CECs, respectively, in treated and untreated wastewater. The passive samplers were calibrated with performance reference compounds (PRCs) by measuring the loss of deuterated beta blocker drugs spiked into POCIS and the loss of PCB congeners spiked into SPMDs over the course of 14-day deployment periods. From the PRC data, field sampling rates of CECs were determined and applied to estimate time-weighted average (TWA) concentrations and mass loadings in mg/day/1000 members of the population serviced. In treated wastewater, TWA concentrations of an antibiotic, sulfamethoxazole, the prescription drugs, carbamazepine, naproxen and gemfibrozil, and the non-prescription drug, ibuprofen, were estimated to be in the low (77 %), possibly because of the tertiary treatment technologies. Therefore, the mass loadings for these personal care products were all <5 mg/day/1000 people. Overall, this study indicates that tertiary treatment technologies designed for phosphorus removal do not entirely remove the target CECs.

  20. Monitoring of 45 pesticides in Lebanese surface water using polar organic chemical integrative sampler (POCIS)

    Science.gov (United States)

    Aisha, Al Ashi; Hneine, Wael; Mokh, Samia; Devier, Marie-Hélène; Budzinski, Hélèn; Jaber, Farouk

    2017-07-01

    The aim of this study is to assess the dissolved concentration of 45 pesticides in the surface waters of the Lebanese Republic using Polar Organic Chemical Integrative Sampler "POCIS". All of the sampling sites are located in the major agricultural land areas in Lebanon. POCIS (n = 3) were deployed at Ibrahim River, Qaraoun Lake and Hasbani River for a duration of 14 days. The total concentration of pesticides ranged from not detected (nd) to 137.66 ng.L-1. Chlorpyrifos, DDE-pp, diazinon and Fenpropathrin were the most abundant compounds. Qaraoun Lake and Hasbani River were found to be more polluted than Ibrahim River, since they receive large amounts of waste water derived from nearby agricultural lands and they had the lowest dilution factor. The aqueous average concentration of the target compounds were estimated using sampling rates obtained from the literature. Comparison between Time Weighed Average concentrations "TWA" using POCIS and spot sampling is presented. Results showed that POCIS TWA concentrations are in agreement with spot sampling concentrations for Ibrahim and Hasbani Rivers. The toxicity of the major detected pesticides on three representative aquatic species (Daphnia magna, Scenedesmus quadricauda and Oncorhynchus mykiss) is also reported.

  1. Passive sampling of wastewater as a tool for the long-term monitoring of community exposure: Illicit and prescription drug trends as a proof of concept.

    Science.gov (United States)

    Baz-Lomba, J A; Harman, Christopher; Reid, Malcolm; Thomas, Kevin V

    2017-09-15

    A passive sampling device, the Polar Organic Chemical Integrative Sampler (POCIS), was calibrated in-situ over a 4-week period in Oslo (Norway) for 10 illicit drugs and pharmaceuticals with the goal of developing an approach for monitoring long-term wastewater drug loads. The calibrations were performed in triplicate using three different overlapping calibration sets under changing environmental conditions that allowed the uncertainty of the sampling rates to be evaluated. All 10 compounds exhibited linear uptake kinetics and provided sampling rates of between 0.023 and 0.192 L d(-1). POCIS were deployed for consecutive 2-week periods during 2012 and 2013 and the calculated time-weighted average (TWA) concentrations used to define different drug use trends. The relative uncertainty related to the POCIS data was approximately 40% and, except for citalopram, 85% of all the long-term measurements of pharmaceuticals were within the confidence interval levels calculated to evaluate the effects of changing environmental conditions on the TWA estimations. POCIS was demonstrated to be sufficiently robust to provide reliable annual drug use estimates with a smaller number of samplers (n = 24) than recommended for active sampling (n = 56) within an acceptable level of sample size related uncertainty POCIS is demonstrated to be a valuable and reliable tool for the long-term monitoring of certain drugs and pharmaceuticals within a defined population. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. High pressure air jet in the endoscopic preparation room: risk of noise exposure on occupational health.

    Science.gov (United States)

    Chiu, King-Wah; Lu, Lung-Sheng; Wu, Cheng-Kun

    2015-01-01

    After high-level disinfection of gastrointestinal endoscopes, they are hung to dry in order to prevent residual water droplets impact on patient health. To allow for quick drying and clinical reuse, some endoscopic units use a high pressure air jet (HPAJ) to remove the water droplets on the endoscopes. The purpose of this study was to evaluate the excessive noise exposure with the use of HPAJ in endoscopic preparation room and to investigate the risk to occupational health. Noise assessment was taken during 7 automatic endoscopic reprocessors (AERs) and combined with/without HPAJ use over an 8-hour time-weighted average (TWA). Analytical procedures of the NIOSH and the ISO for noise-induced hearing loss were estimated to develop analytic models. The peak of the noise spectrum of combined HPAJ and 7 AERs was significantly higher than that of the 7 AERs alone (108.3 ± 1.36 versus 69.3 ± 3.93 dBA, P risk of hearing loss (HL > 2.5 dB) was 2.15% at 90 dBA, 11.6% at 95 dBA, and 51.3% at 100 dBA. The odds ratio was 49.1 (95% CI: 11.9 to 203.6). The noise generated by the HPAJ to work over TWA seriously affected the occupational health and safety of those working in an endoscopic preparation room.

  3. Wood dust exposure during furniture manufacture--results from an Australian survey and considerations for threshold limit value development.

    Science.gov (United States)

    Pisaniello, D L; Connell, K E; Muriale, L

    1991-11-01

    A survey of time-weighted average (TWA) personal inhalable dust exposures for woodworkers in 15 Australian furniture factories was undertaken. There was significant variation in the individual dust measurements with mean exposures of 3.2, 5.2, and 3.5 mg/m3 for wood machinists, cabinetmakers, and chair framemakers, respectively. Hardwoods, softwoods, and reconstituted woods are used in the industry, but only minor differences in mean exposures or particle size distributions were found for the broad categories. In addition, a modified British Medical Research Council respiratory questionnaire was used to obtain information about work-related symptoms and job activities. Compared with a control group, the woodworkers reported more eye, ear, and nasal problems, with the differences being statistically significant. However, among the woodworkers themselves, with the exception of several nasal symptoms, the prevalences of reported symptoms were poorly correlated with gravimetric measurements of personal dust exposure. The problem of selection bias in cross-sectional studies is discussed. For a mean TWA personal exposure of about 3 mg/m3, hardwood users were more likely to report nasal symptoms than users of reconstituted wood. The question of appropriate exposure standards for woods in general is addressed by reference to those important health effects, besides sino-nasal cancer, that have been investigated. Further exposure guidelines should be formulated for groups of woods that are known to cause a common health effect, such as nasal/respiratory sensitization.

  4. Genotoxic risk for humans due to work place exposure to ethylene oxide: remarkable individual differences in susceptibility.

    Science.gov (United States)

    Fuchs, J; Wullenweber, U; Hengstler, J G; Bienfait, H G; Hiltl, G; Oesch, F

    1994-01-01

    Single strand breaks of DNA of peripheral mononuclear blood cells from 97 male and female workers occupationally exposed to ethylene oxide were analysed by the alkaline elution method. These individuals were occupied with the sterilization of medical devices in hospitals and in commercial plants. Ethylene oxide in the air of the working areas was detected up to a maximal concentration of 16.5 mg/m3 calculated as 4-h time-weighted average (4h TWA). Mean value was 1.47 +/- 0.52 mg/m3 (1 mg/m3 = 0.55 ppm). Compared to the mean elution rate of the DNA from non-smoking workers exposed to air concentrations of ethylene oxide below the detection limit of 0.1 mg/m3 (4h TWA) the non-smokers working in rooms with a concentration of ethylene oxide between 0.5 mg/m3 and 2 mg/m3 showed a statistically significant (P ethylene oxide a statistically significant (P ethylene oxide the non-smoking workers could be classified into two subpopulations. In the majority of the non-smokers (67%) approximately 5-fold more DNA strand breaks were induced by ethylene oxide than in the other non-smokers. A lowest detectable effect level could only be specified for non-smokers. (ABSTRACT TRUNCATED AT 250 WORDS)

  5. Comparative analysis of fourth-harmonic multiplying gyrotron traveling-wave amplifiers operating at different frequency multiplications

    Science.gov (United States)

    Yeh, Y. S.; Kao, W. J.; Li, L. J.; Guo, Y. W.

    2017-01-01

    The harmonic multiplying operation in a gyrotron traveling-wave amplifier (gyro-TWA) permits magnetic field reduction and frequency multiplication. This study presents a comparative analysis of fourth-harmonic multiplying gyro-TWAs with three schemes of operation. An improved mode-selective circuit using circular waveguides with various radii provides the rejection points within the range of operating frequencies to suppress the competing modes of gyro-TWAs. The simulated results reveal that gyro-TWAs are the most susceptible to the fundamental-harmonic TE11 competing mode, regardless of the operating scheme, and that the mode-selective circuit can provide an attenuation of more than 20 dB to suppress the competing modes. The amplification of the waves in a gyro-TWA depends on the lengths of the sections, and the simulated results show that the gain increases for all schemes, as the length of the lossy section or the length of the copper section increases. All schemes exhibit nearly the same saturated output powers and bandwidths; however, the saturated gain of the scheme at a high frequency multiplication ratio is less than that of the scheme at a low frequency multiplication ratio. Extensive numerical calculations of power and gain scaling are conducted for all schemes.

  6. Large X-ray Flares on Stars Detected with MAXI/GSC: A Universal Correlation between the Duration of a Flare and its X-ray Luminosity

    CERN Document Server

    Tsuboi, Yohko; Sugawara, Yasuharu; Kawagoe, Atsushi; Kaneto, Soichiro; Iizuka, Ryo; Matsumura, Takanori; Nakahira, Satoshi; Higa, Masaya; Matsuoka, Masaru; Sugizaki, Mutsumi; Ueda, Yoshihiro; Kawai, Nobuyuki; Morii, Mikio; Serino, Motoko; Mihara, Tatehiro; Tomida, Hiroshi; Ueno, Shiro; Negoro, Hitoshi; Daikyuji, Arata; Ebisawa, Ken; Eguchi, Satoshi; Hiroi, Kazuo; Ishikawa, Masaki; Isobe, Naoki; Kawasaki, Kazuyoshi; Kimura, Masashi; Kitayama, Hiroki; Kohama, Mitsuhiro; Kotani, Taro; Nakagawa, Yujin E; Nakajima, Motoki; Ozawa, Hiroshi; Shidatsu, Megumi; Sootome, Tetsuya; Sugimori, Kousuke; Suwa, Fumitoshi; Tsunemi, Hiroshi; Usui, Ryuichi; Yamamoto, Takayuki; Yamaoka, Kazutaka; Yoshida, Atsumasa

    2016-01-01

    23 giant flares from 13 active stars (eight RS CVn systems, one Algol system, three dMe stars and one YSO) were detected during the first two years of our all-sky X-ray monitoring with the gas propotional counters (GSC) of the Monitor of All-sky X-ray Image (MAXI). The observed parameters of all of these MAXI/GSC flares are found to be at the upper ends for stellar flares with the luminosity of 10^(31-34) ergs s-1 in the 2-20 keV band, the emission measure of 10^(54-57) cm-3, the e-folding time of 1 hour to 1.5 days, and the total radiative energy released during the flare of 10^(34-39) ergs. Notably, the peak X-ray luminosity of 5(3-9)*10^33 ergs s-1 in the 2-20 keV band was detected in one of the flares on II Peg, which is one of the, or potentially the, largest ever observed in stellar flares. X-ray flares were detected from GT Mus, V841 Cen, SZ Psc, and TWA-7 for the first time in this survey. Whereas most of our detected sources are multiple-star systems, two of them are single stars (YZ CMi and TWA-7). ...

  7. 插入双面有三角形翅片的金属带对热交换管中流动和传热特性的影响%Influence of Double-sided Delta-wing Tape Insert with Alternate-axes on Flow and Heat Transfer Characteristics in a Heat Exchanger Tube

    Institute of Scientific and Technical Information of China (English)

    Smith Eiamsa-ard; Pongjet Promvonge

    2011-01-01

    The convective heat transfer and friction behaviors of turbulent tube flow through a straight tape with double-sided delta wings (T-W) have been studied experimentally. In the current work, the T-W formed on the tape was used as vortex generators for enhancing the heat transfer coefficient by breakdown of thermal boundary layer and by mixing of fluid flow in tubes. The T-W characteristics are (1) T-W with forward/backward-wing arrangement, (2) T-W with alternate axis (T-WA), (3) three wing-width ratios and (4) wing-pitch ratios. The experimental result reveals that for using the T-W, the increases in the mean Nusselt number (Nu) and friction factor are, respectively, up to 165% and 14.8 times of the plain tube and the maximum thermal performance factor is 1.19. It is also obvious that the T-W with forward-wing gives higher heat transfer rate than one with backward-wing around 7%.The present investigation also shows that the heat transfer rate and friction factor obtained from the T-WA is higher than that from the T-W. In addition, the flow pattern and temperature fields in the T-W tube with both backward and forward wings were also examined numerically.

  8. Assessment of Occupational Noise Exposure among Groundskeepers in North Carolina Public Universities.

    Science.gov (United States)

    Balanay, Jo Anne G; Kearney, Gregory D; Mannarino, Adam J

    2016-01-01

    Groundskeepers may have increased risk to noise-induced hearing loss due to the performance of excessively noisy tasks. This study assessed the exposure of groundskeepers to noise in multiple universities and determined the association between noise exposure and variables (ie, university, month, tool used). Personal noise exposures were monitored during the work shift using noise dosimetry. A sound level meter was used to measure the maximum sound pressure levels from groundskeeping equipment. The mean Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH) time-weighted average (TWA) noise exposures were 83.0 ± 9.6 and 88.0 ± 6.7 dBA, respectively. About 52% of the OSHA TWAs and 77% of the NIOSH TWAs exceeded 85 dBA. Riding mower use was associated with high TWA noise exposures and with having OSHA TWAs exceeding 85 and 90 dBA. The maximum sound pressure levels of equipment and tools measured ranged from 76 to 109 dBA, 82% of which were >85 dBA. These findings support that groundskeepers have excessive noise exposures, which may be effectively reduced through careful scheduling of the use of noisy equipment/tools.

  9. 江苏省某镍镉电池生产企业镉作业工人尿镉水平调查%Investigation on urinary cadmium levels in workers exposed to cadmium in a nickel-cadmium battery manufacturing enterprise in Jiangsu province

    Institute of Scientific and Technical Information of China (English)

    韩磊; 仲立新; 张恒东

    2012-01-01

    目的 了解镉作业工人的职业危害状况.方法 对江苏省某镍镉电池生产企业进行职业卫生学调查,并对镉作业工人进行尿镉水平检测.结果 个体采样的8个含镉作业岗位空气中镉及其化合物时间加权平均浓度(TWA)有6个岗位超过职业卫生接触限值.1 177名镉作业工人中有18例尿镉水平超标.尿镉超标工人所在岗位空气中镉及其化合物短时间接触浓度( STEL)与时间加权平均浓度(TWA)均超过国家标准限值.不同工龄镉作业工人尿镉水平比较,差异有统计学意义(P<0.05).结论 企业应降低工作场所空气中镉的浓度,减少作业工人的接触时间,将镉对人体的损害降到最低.

  10. A multiyear workplace-monitoring program for refractory ceramic fibers: findings and conclusions.

    Science.gov (United States)

    Maxim, L D; Allshouse, J N; Kelly, W P; Walters, T; Waugh, R

    1997-10-01

    Results of a monitoring program carried out by members of the Refractory Ceramic Fibers Coalition as part of a Consent Agreement with the U.S. Environmental Protection Agency to measure workplace concentrations of refractory ceramic fiber (RCF) are presented. More than 700 personal monitoring samples were collected and analyzed annually from workers in RCF production and processing plants, as well as from those employed by customers/end users. The data indicate that (i) approximately 90% of time-weighted average (TWA) workplace concentrations are below the industry's recommended exposure guideline of 1 fiber per cubic centimeter TWA; (ii) workplace concentrations vary with functional job category; (iii) concentrations are approximately lognormally distributed; (iv) workplace concentrations are generally decreasing; (v) there are significant differences in workplace concentrations among plants operated by both RCF producers and customers; (vi) equations can be developed to interconvert data analyzed using different measurement techniques and counting rules; (vii) usage of respirators varies with the functional job category of the worker and the average fiber concentration; and (viii) workplace samples differ from those used in animal inhalation experiments in terms of the ratio of respirable particles to fibers.

  11. A comparison of exposures to refractory ceramic fibres over multiple work shifts.

    Science.gov (United States)

    Hall, G S; Rice, C H; Lockey, J E; Lemasters, G K; Gartside, P S

    1997-10-01

    As part of an ongoing, industry-wide study in the manufacture of refractory ceramic fibres (RCF), time weighted average (TWA) exposures have been collected at five facilities according to a standardised protocol. Work activities were grouped into dust zones (DZs). Persons to be sampled were randomly selected according to a protocol designed to assure that at least one sample was collected annually from each DZ; each work shift is also sampled at least annually. TWA exposures calculated over a sampling period of at least 360 min were included in the data set. DZs were combined into one of three groups (DZGs): fibre production; vacuum processes; other. The data were analysed to identify any differences by DZG between airborne fibre exposures, by the shift worked at each facility, and across all facilities. There were no statistically significant shift-related differences detected between airborne fibre exposures across the five RCF facilities when analysed as a group. Within four of the facilities, no shift-related differences were detected between airborne fibre exposures; however, at one facility, first and third shift exposures were statistically different. No documentation related to job activities was found to account for the observation. The data generally support the use of a single exposure estimate for each DZG in each of these facilities, regardless of shift worked. Researchers reconstructing exposure and not able to determine the shift worked by study subjects may find these results useful, but are cautioned that substantial differences in exposure across shifts may exist in other types of manufacturing.

  12. Airborne asbestos take-home exposures during handling of chrysotile-contaminated clothing following simulated full shift workplace exposures.

    Science.gov (United States)

    Sahmel, Jennifer; Barlow, Christy A; Gaffney, Shannon; Avens, Heather J; Madl, Amy K; Henshaw, John; Unice, Ken; Galbraith, David; DeRose, Gretchen; Lee, Richard J; Van Orden, Drew; Sanchez, Matthew; Zock, Matthew; Paustenbach, Dennis J

    2016-01-01

    The potential for para-occupational, domestic, or take-home exposures from asbestos-contaminated work clothing has been acknowledged for decades, but historically has not been quantitatively well characterized. A simulation study was performed to measure airborne chrysotile concentrations associated with laundering of contaminated clothing worn during a full shift work day. Work clothing fitted onto mannequins was exposed for 6.5 h to an airborne concentration of 11.4 f/cc (PCME) of chrysotile asbestos, and was subsequently handled and shaken. Mean 5-min and 15-min concentrations during active clothes handling and shake-out were 3.2 f/cc and 2.9 f/cc, respectively (PCME). Mean airborne PCME concentrations decreased by 55% 15 min after clothes handling ceased, and by 85% after 30 min. PCM concentrations during clothes handling were 11-47% greater than PCME concentrations. Consistent with previously published data, daily mean 8-h TWA airborne concentrations for clothes-handling activity were approximately 1.0% of workplace concentrations. Similarly, weekly 40-h TWAs for clothes handling were approximately 0.20% of workplace concentrations. Estimated take-home cumulative exposure estimates for weekly clothes handling over 25-year working durations were below 1 f/cc-year for handling work clothes contaminated in an occupational environment with full shift airborne chrysotile concentrations of up to 9 f/cc (8-h TWA).

  13. Quantum simulation of spin models and the discrete Truncated Wigner Approximation: from Rydberg atoms to trapped ions

    Science.gov (United States)

    Pineiro Orioli, Asier; Berges, Juergen; Signoles, Adrien; Schempp, Hanna; Whitlock, Shannon; Weidemueller, Matthias; Safavi-Naini, Arghavan; Wall, Michael; Schachenmayer, Johannes; Rey, Ana Maria

    2016-05-01

    Accurate description of the dynamics of quantum spin models is a theoretically challenging problem with widespread applications ranging from condensed matter to high-energy physics. Furthermore recent experimental progress in AMO experiments allows for the physical realization of these models in a variety of setups, such as Rydberg systems and trapped ion experiments, with an unprecedented degree of control and flexibility. Therefore, it is vital to develop efficient theoretical methods capable of simulating the many-body dynamics of such systems. In this work, we employ and extend the recently developed discrete Truncated Wigner Approximation (dTWA), an approximation based on the phase space description of quantum mechanics, to compute the dynamics of two types of spin models: the long-range XY model, which can be realized with Rydberg atoms, and a coupled spin-boson model, which is relevant to trapped ion experiments. Comparisons to experimental results and to available exact solutions to benchmark the method show that the dTWA is capable of capturing important features of the spin evolution and can also help uncovering some underlying non-equilibrium processes.

  14. Exposure levels of farmers and veterinarians to particulate matter and gases uring operational tasks in pig-fattening houses

    Directory of Open Access Journals (Sweden)

    Nele Van Ransbeeck

    2014-09-01

    Full Text Available The main objective of the study was to assess particulate matter (PM exposure levels for both the farmer and the veterinarian during different operational tasks in pig-fattening houses, and to estimate their exposure levels on a daily working basis (time-weighted average (TWA. The measured PM fractions were: inhalable and respirable PM, PM10, PM2.5 and PM1. The effects of pig age, pen floor type (conventional or low emission surface and cleaning of the pens on the personal PM exposure were also investigated. Indoor concentrations of NH[sub]3[/sub], CH[sub]4[/sub], and CO[sub]2[/sub] were additionally measured during some operational tasks. The results showed that personal exposure levels can become extremely high during some operational tasks performed by the farmer or veterinarian. The highest concentration levels were observed during feed shovelling and blood sampling, the lowest during the weighing of the pigs. For the farmer, the estimated TWA exposure levels of inhalable and respirable PM were 6.0 and 0.29 mg m[sup] -3[/sup] , respectively. These exposure levels for the veterinarian were, respectively, 10.6 and 0.74 mg m[sup] -3[/sup] . The PM concentration levels were mainly determined by the performed operational tasks. There was no significant effect of pig age, pen floor type, nor cleaning of the pens on the personal exposure levels.

  15. Development of a passive sampler based on a polymer inclusion membrane for total ammonia monitoring in freshwaters.

    Science.gov (United States)

    Almeida, M Inês G S; Silva, Adélia M L; Coleman, Rhys A; Pettigrove, Vincent J; Cattrall, Robert W; Kolev, Spas D

    2016-05-01

    A passive sampler for determining the time-weighted average total ammonia (i.e. molecular ammonia and the ammonium cation) concentration (C TWA) in freshwaters, which incorporated a polymer inclusion membrane (PIM) as a semi-permeable barrier separating the aqueous source solution from the receiving solution (i.e. 0.8 mol L(-1) HCl), was developed for the first time. The PIM was composed of dinonylnaphthalene sulfonic acid (DNNS) as a carrier, poly (vinyl chloride) (PVC) as a base polymer and 1-tetradecanol as a modifier. Its optimal composition was found to be 35 wt% commercial DNNS, 55 wt% PVC and 10 wt% 1-tetradecanol. The effect of environmental variables such as the water matrix, pH and temperature were also studied using synthetic freshwaters. The passive sampler was calibrated under laboratory conditions using synthetic freshwaters and exhibited a linear response within the concentration range 0.59-2.8 mg L(-1) NH4(+) (0.46-2.1 mg N L(-1)) at 20 °C. The performance of the sampler was further investigated under field conditions over 7 days. A strong correlation between spot sampling and passive sampling was achieved, thus providing a proof-of-concept for the passive sampler for reliably measuring the C(TWA) of total ammonia in freshwaters, which can be used as an indicator in tracking sources of faecal contamination in stormwater drains.

  16. A PREDICTIVE STUDY: CARBON MONOXIDE EMISSION MODELING AT A SIGNALIZED INTERSECTION

    Directory of Open Access Journals (Sweden)

    FREDDY WEE LIANG KHO

    2014-02-01

    Full Text Available CAL3QHC dispersion model was used to predict the present and future carbonmonoxide (CO levels at a busy signalized intersection. This study attempted to identify CO “hot-spots” at nearby areas of the intersection during typical A.M. and P.M. peak hours. The CO concentration “hot-spots” had been identified at 101 Commercial Park and the simulated maximum 1-hour Time-Weighted Average (1-h TWA ground level CO concentrations of 18.3 ppm and 18.6 ppm had been observed during A.M. and P.M. peaks, respectively in year 2006. This study shows that there would be no significant increment in CO level for year 2014 although a substantial increase in the number of vehicles is assumed to affect CO levels. It was also found that CO levels would be well below the Malaysian Ambient Air Quality Guideline of 30 ppm (1-h TWA. Comparisons between the measured and simulated CO levels using quantitative data analysis technique and statistical methods indicated that CAL3QHC dispersion model correlated well with measured data.

  17. The release of lindane from contaminated building materials.

    Science.gov (United States)

    Volchek, Konstantin; Thouin, Geneviève; Kuang, Wenxing; Li, Ken; Tezel, F Handan; Brown, Carl E

    2014-10-01

    The release of the organochlorine pesticide lindane (γ-hexachlorocyclohexane) from several types of contaminated building materials was studied to assess inhalation hazard and decontamination requirements in response to accidental and/or intentional spills. The materials included glass, polypropylene carpet, latex-painted drywall, ceramic tiles, vinyl floor tiles, and gypsum ceiling tiles. For each surface concentration, an equilibrium concentration was determined in the vapour phase of the surrounding air. Vapor concentrations depended upon initial surface concentration, temperature, and type of building material. A time-weighted average (TWA) concentration in the air was used to quantify the health risk associated with the inhalation of lindane vapors. Transformation products of lindane, namely α-hexachlorocyclohexane and pentachlorocyclohexene, were detected in the vapour phase at both temperatures and for all of the test materials. Their formation was greater on glass and ceramic tiles, compared to other building materials. An empiric Sips isotherm model was employed to approximate experimental results and to estimate the release of lindane and its transformation products. This helped determine the extent of decontamination required to reduce the surface concentrations of lindane to the levels corresponding to vapor concentrations below TWA.

  18. Correlation Between Toluene Environmental Monitoring and Biological Index of Urinary Hippuric Acid of Workers in the Coke Industry

    Directory of Open Access Journals (Sweden)

    MM Amin

    2007-04-01

    Full Text Available Introduction: Toluene is an organic solvent that it is one of the byproducts in the coke industry. Exposure to toluene causes central nervous system dysfunction and others disorders. Many workers are exposed to toluene due to leakage from tracks. Therefore the aim of this study was to determine the levels of exposure through environmental and biological monitoring of toluene Methods: Air toluene sampling of air inhaled by 36 coke oven workers was done by using activated charcoal tubes and personal sampling pumps. At the end of the shift, urine samples of workers and control group were collected by urine samplers. Air toluene was determined by GC, urinary hippuric acid by HPLC and urine creatinine level was determined by auto analyzer. Results: The mean of air toluene and urinary hippuric acid levels in exposed and control samples were 14.34 ppm, 0.33 and 0.28 g/g creatinine. Air toluene and urinary hippuric acid showed a correlation of r = 0.8. Conclusion: Toluene TWA was lower than the TLV-TWA (p=0.000. Urinary hippuric acid concentration was also lower than the BEI (p=0.008. Difference between exposed and unexposed group was not significant. This study showed that hippuric acid because of its interaction with background factors can not be used as a sensitive biomarker for biomonitoring.

  19. Airborne asbestos exposures associated with gasket and packing replacement: a simulation study of flange and valve repair work and an assessment of exposure variables.

    Science.gov (United States)

    Madl, Amy K; Devlin, Kathryn D; Perez, Angela L; Hollins, Dana M; Cowan, Dallas M; Scott, Paul K; White, Katherine; Cheng, Thales J; Henshaw, John L

    2015-02-01

    A simulation study was conducted to evaluate worker and area exposure to airborne asbestos associated with the replacement of asbestos-containing gaskets and packing materials from flanges and valves and assess the influence of several variables previously not investigated. Additionally, potential of take home exposures from clothing worn during the study was characterized. Our data showed that product type, ventilation type, gasket location, flange or bonnet size, number of flanges involved, surface characteristics, gasket surface adherence, and even activity type did not have a significant effect on worker exposures. Average worker asbestos exposures during flange gasket work (PCME=0.166 f/cc, 12-59 min) were similar to average worker asbestos exposures during valve overhaul work (PCME=0.165 f/cc, 7-76 min). Average 8-h TWA asbestos exposures were estimated to range from 0.010 to 0.062 f/cc. Handling clothes worn during gasket and packing replacement activities demonstrated exposures that were 0.71% (0.0009 f/cc 40-h TWA) of the airborne asbestos concentration experienced during the 5 days of the study. Despite the many variables considered in this study, exposures during gasket and packing replacement occur within a relatively narrow range, are below current and historical occupational exposure limits for asbestos, and are consistent with previously published data.

  20. Exposure levels of farmers and veterinarians to particulate matter and gases during operational tasks in pig-fattening houses.

    Science.gov (United States)

    Van Ransbeeck, Nele; Van Langenhove, Herman; Michiels, Annelies; Sonck, Bart; Demeyer, Peter

    2014-01-01

    The main objective of the study was to assess particulate matter (PM) exposure levels for both the farmer and the veterinarian during different operational tasks in pig-fattening houses, and to estimate their exposure levels on a daily working basis (time-weighted average (TWA)). The measured PM fractions were: inhalable and respirable PM, PM10, PM2.5 and PM1. The effects of pig age, pen floor type (conventional or low emission surface) and cleaning of the pens on the personal PM exposure were also investigated. Indoor concentrations of NH3, CH4, and CO2 were additionally measured during some operational tasks. The results showed that personal exposure levels can become extremely high during some operational tasks performed by the farmer or veterinarian. The highest concentration levels were observed during feed shovelling and blood sampling, the lowest during the weighing of the pigs. For the farmer, the estimated TWA exposure levels of inhalable and respirable PM were 6.0 and 0.29 mg m(-3), respectively. These exposure levels for the veterinarian were, respectively, 10.6 and 0.74 mg m(-3). The PM concentration levels were mainly determined by the performed operational tasks. There was no significant effect of pig age, pen floor type, nor cleaning of the pens on the personal exposure levels.

  1. La noción del tiempo en la cultura maya prehispánica

    Directory of Open Access Journals (Sweden)

    Alexander Wolfgang Voss

    2015-07-01

    Full Text Available La concepción del tiempo de los mayas prehispánicos se estudia mediante el análisis epigráfico y filológico de textos jeroglíficos bajo los planteamientos teóricos de la escuela italiana de historia de las religiones. Los datos indican que el tiempo es animado y formado por unidades discretas tangibles que se representan con un calendario de 365 días. Las características de cada día son fijadas por un oráculo de suertes de 260 unidades que es proyectado sobre el tiempo. El tiempo y el oráculo son pensados como dioses que se alternan en un orden y no como una magnitud física abstracta.

  2. Facies y microfacies de la rampa tithoniana-berriasiana de la cuenca neuquina (Formación Vaca Muerta en la sección del arroyo Loncoche - Malargüe, provincia de Mendoza Facies and microfacies of the Tithonian-Berriasian ramp from the Neuquén basin (Vaca Muerta Formation in the Loncoche creek section - Malargüe, Mendoza

    Directory of Open Access Journals (Sweden)

    Diego A. Kietzmann

    2008-12-01

    Full Text Available La Formación Vaca Muerta (Tithoniano-Berriasiano consiste en una alternancia rítmica de lutitas negras, lutitas grises, margas y limolitas, con mudstones, wackestones, packstones, floatstones y rudstones bioclásticos. La asociación de facies en la sección del arroyo Loncoche, permitió definir 12 litofacies y 8 microfacies, dominadas por moluscos, equinodermos, foraminíferos, braquiópodos, serpúlidos y radiolarios. Se distinguieron cuatro asociaciones de facies correspondientes a los subambientes de cuenca, rampa externa (distal y proximal y rampa media. La utilización de la relación Nassellaria/Spumellaria permitió estimar un rango de profundidades menores a 200 metros. El patrón de apilamiento y la distribución vertical de facies permitió la distinción de tres secuencias depositacionales, y el reconocimiento de un sistema tithoniano de rampa homoclinal y un sistema berriasiano de rampa homoclinal de mayor gradiente. La secuencia depositacional 1 consiste en facies de cuenca y rampa externa distal y se caracteriza por un patrón retrogradacional. Presenta un espesor de 124 m, y se extiende desde la Zona de Virgatosphinctes mendozanus hasta la base de la Zona de Corongoceras alternans. Las secuencias depositacionales 2 y 3 consisten en facies de rampa externa y rampa media. Están caracterizadas por un patrón agradacional y progradacional. El espesor de la secuencia 2 es de 66 m y se asigna a la Zona de Corongoceras alternans, mientras que la secuencia 3 alcanza 78 m y corresponde a las zonas de Substeueroceras koeneni y Spiticeras damesi.Facies association of the Tithonian-Berriasian Vaca Muerta Formation from the Loncoche creek section, Neuquén Basin, west central Argentina, allow the distinction and definition of 12 lithofacies and 8 microfacies, which are dominated by molluscs, echinoderms, foraminifera, brachiopods, serpulids and radiolarians. The Vaca Muerta Formation consists of a rhythmical alternation of black shales

  3. Los paisajes geomorfológicos de la Región de Murcia como recurso turístico

    Directory of Open Access Journals (Sweden)

    Asunción Romero Díaz

    2002-01-01

    Full Text Available En este trabajo se analiza de una forma sucinta los distintos paisajes geomorfológicos de la región de Murcia. En ella alternan todo un conjunto de montañas, valles, depresiones y llanuras, consecuencia principalmente de la historia geológica y de sus características climáticas, por lo que es posible observar una gran variedad de paisajes en la escasa superficie regional. Los paisajes desde una perspectiva geomorfológica se han clasificado en paisajes: de montaña, de costas, fluviales, cárcavas y barrancos, kársticos, y de altiplanos y llanuras. Para cada uno de ellos, se indican cuales son sus características más importantes, sus rasgos de identidad, su localización, y en ocasiones, sus mejores puntos de observación.

  4. Temperature, geometry, and bifurcations in the numerical modeling of the cardiac mechano-electric feedback

    Science.gov (United States)

    Collet, A.; Bragard, J.; Dauby, P. C.

    2017-09-01

    This article characterizes the cardiac autonomous electrical activity induced by the mechanical deformations in the cardiac tissue through the mechano-electric feedback. A simplified and qualitative model is used to describe the system and we also account for temperature effects. The analysis emphasizes a very rich dynamics for the system, with periodic solutions, alternans, chaotic behaviors, etc. The possibility of self-sustained oscillations is analyzed in detail, particularly in terms of the values of important parameters such as the dimension of the system and the importance of the stretch-activated currents. It is also shown that high temperatures notably increase the parameter ranges for which self-sustained oscillations are observed and that several attractors can appear, depending on the location of the initial excitation of the system. Finally, the instability mechanisms by which the periodic solutions are destabilized have been studied by a Floquet analysis, which has revealed period-doubling phenomena and transient intermittencies.

  5. Memory effects, transient growth, and wave breakup in a model of paced atrium

    Science.gov (United States)

    Garzón, Alejandro; Grigoriev, Roman O.

    2017-09-01

    The mechanisms underlying cardiac fibrillation have been investigated for over a century, but we are still finding surprising results that change our view of this phenomenon. The present study focuses on the transition from normal rhythm to spiral wave chaos associated with a gradual increase in the pacing rate. While some of our findings are consistent with existing experimental, numerical, and theoretical studies of this problem, one result appears to contradict the accepted picture. Specifically we show that, in a two-dimensional model of paced homogeneous atrial tissue, transition from discordant alternans to conduction block, wave breakup, reentry, and spiral wave chaos is associated with the transient growth of finite amplitude disturbances rather than a conventional instability. It is mathematically very similar to subcritical, or bypass, transition from laminar fluid flow to turbulence, which allows many of the tools developed in the context of fluid turbulence to be used for improving our understanding of cardiac arrhythmias.

  6. Nonlinear-dynamical arrhythmia control in humans.

    Science.gov (United States)

    Christini, D J; Stein, K M; Markowitz, S M; Mittal, S; Slotwiner, D J; Scheiner, M A; Iwai, S; Lerman, B B

    2001-05-08

    Nonlinear-dynamical control techniques, also known as chaos control, have been used with great success to control a wide range of physical systems. Such techniques have been used to control the behavior of in vitro excitable biological tissue, suggesting their potential for clinical utility. However, the feasibility of using such techniques to control physiological processes has not been demonstrated in humans. Here we show that nonlinear-dynamical control can modulate human cardiac electrophysiological dynamics by rapidly stabilizing an unstable target rhythm. Specifically, in 52/54 control attempts in five patients, we successfully terminated pacing-induced period-2 atrioventricular-nodal conduction alternans by stabilizing the underlying unstable steady-state conduction. This proof-of-concept demonstration shows that nonlinear-dynamical control techniques are clinically feasible and provides a foundation for developing such techniques for more complex forms of clinical arrhythmia.

  7. Usefulness of the presenting electrocardiogram in predicting successful reperfusion with streptokinase in acute myocardial infarction.

    Science.gov (United States)

    Wong, C K; French, J K; Aylward, P E; Frey, M J; Adgey, A A; White, H D

    1999-01-15

    The presenting electrocardiogram may contain information indicating the probability of successful reperfusion. The relation between 3 parameters in the presenting electrocardiogram (pathologic Q waves, T-wave inversion, and the slope of ST elevation) and Thrombolysis in Myocardial Infarction trial (TIMI) grade 3 flow in the infarct-related artery was assessed angiographically 90 minutes after beginning streptokinase in 362 patients. TIMI grade 3 flow was more common in patients without Q waves (55%) than in those with Q waves (35%; p wave inversion (50%) than in those with T-wave inversion (30%; p waves and T-wave inversion had TIMI grade 3 flow, compared with 50% of the remaining patients (p waves (p wave inversion (p = 0.06). Among patients treated after 3 hours, TIMI grade 3 flow was seen in 38% of those without versus 30% of those with Q waves (p = NS), and in 38% of those without versus 23% of those with T-wave inversion (p waves, the time from the onset of chest pain to treatment, and age were independent predictors of TIMI grade 3 flow. Pathologic Q waves in the presenting electrocardiogram provide valuable information as to the probability of achieving successful reperfusion following administration of streptokinase, and may be helpful for triage of patients to alternative reperfusion strategies, including percutaneous revascularization.

  8. Prevalence of electrocardiographic ST-T changes during acute ischemic stroke in patients without known ischemic heart disease

    DEFF Research Database (Denmark)

    Jensen, Jesper K; Bak, Søren; Flemming Høilund-Carlsen, Poul;

    2008-01-01

    We evaluated characteristics and prevalence of ST-segment depression and/or T-wave inversion in the resting electrocardiogram of 244 consecutive patients with acute ischemic stroke, but without ischemic heart disease. The prevalence of ST-T changes ranged from 13% to 16% and this is what to expect...

  9. Electroconvulsive therapy-induced ECG changes simulating a myocardial infarction.

    Science.gov (United States)

    Gould, L; Gopalaswamy, C; Chandy, F; Kim, B

    1983-09-01

    Electroconvulsive therapy (ECT) can produce various cardiac arrhythmias; however, to our knowledge, no other alterations have been described in the ECG. A 75-year-old woman was admitted to the Methodist Hospital in Brooklyn, NY, because of depression. She had had no cardiac symptoms and had been in good health. She was not receiving any medications. Physical examination showed no abnormalities. Findings from the routine laboratory tests, a chest roentgenogram, and the initial ECG were normal. In view of the severe depression, a series of ECTs were given to the patient during a two-week period. A repeated ECG showed deep T-wave inversions in leads I, II, III, aVF, and V1 to V6. The patient was completely asymptomatic. Serial enzyme determinations were normal. A brain scan, gated-pool scan, computed tomography scan of the head, and a technetium Tc 99m pyrophosphate scan were all normal. Serial ECGs showed a persistence of the deep T-wave inversions. There were no QRS changes. There was no evidence of a cerebral vascular accident or pericarditis. The T-wave changes in our patient were not due to a myocardial infarction. Thus, ECT can produce striking T-wave abnormalities in the ECG that can simulate an acute myocardial infarction.

  10. chronic psychotropic medication

    African Journals Online (AJOL)

    2006-08-31

    Aug 31, 2006 ... lack of exercise, obesity, substance misuse) and high autonomic arousal during ... heart; however, it might precipitate complete heart block in the presence of .... desipramine) may impact more on children and the elderly. .... ECG changes such as rate, rhythm, T waves and QT interval ... Type of abnormality.

  11. [Cardiovascular manifestations of pancreatitis. Apropos of 4 cases].

    Science.gov (United States)

    Godeau, P; Derrida, J P; Herreman, G; Devaux, J; Pagniez, G

    1975-10-09

    The authors report four cases of cardiovascular signs in pancreatitis in patients aged between 31 and 42 years. They then consider the main aspects observed. T-wave disorders, pericarditis, myocardial infarction and coronary heart disease and arterio-pancreatic syndrome. They consider the points in common between myocardial infarction and acute pancreatitis and then review the various pathogenic theories proposed.

  12. Left bundle branch block (LBBB) masks changes due to hyperkalemia: a myth.

    Science.gov (United States)

    Kumar, Anil; Shah, Neel; Jesmajian, Stephen

    2010-04-01

    Left bundle branch block masks ischemic changes but not those due to electrolyte imbalance. Peaking of T waves, prolongation of PR interval, diminution/absence of P wave, and widening of QRS complex can still be appreciated if one carefully compares the baseline ECG to the presenting ECG. (c) 2010 Society of Hospital Medicine.

  13. Lesson Seventeen Digitalis Effect and Intoxication on the Electrocardiogram

    Institute of Scientific and Technical Information of China (English)

    鲁端; 王劲

    2006-01-01

    @@ Effect of Digitalis on the Electrocardiogram: ①ST segment depression, ②Decreased amplitude of the T wave,which may become diphasic (negative-positive) or negative,③Shortening of the Q-T interval,④Increase of the U-wave amplitude.

  14. [The influence of GPIIIA gene polymorphism on the variability of standard electrocardiogram in patients with acute coronary syndrome].

    Science.gov (United States)

    Komarova, A G; Zotova, T Iu; Miandina, G I; Kasapova, E N; Zotov, A K; Tarasova, E S; Frolov, V A

    2010-01-01

    The authors analyse effect of GPIIIA gene (PI a allele) polymorphism on the frequency of complicated coronary heart disease in patients with dyslipidemia and hypertensive disease. Specific features of ventricular repolarization (T-wave variability) in patients with acute coronary syndrome are described.

  15. Characterization and mechanisms of action of novel NaV1.5 channel mutations associated with Brugada syndrome

    DEFF Research Database (Denmark)

    Callø, Kirstine; Refaat, Marwan M.; Grubb, Søren

    2013-01-01

    Brugada syndrome is a heterogeneous heart rhythm disorder characterized by an atypical right bundle block pattern with ST-segment elevation and T-wave inversion in the right precordial leads. Loss-of-function mutations in SCN5A encoding the cardiac sodium channel Na(V)1.5 are associated with Brug...

  16. The NO Regular Defibrillation testing In Cardioverter Defibrillator Implantation (NORDIC ICD) trial

    DEFF Research Database (Denmark)

    Bänsch, Dietmar; Bonnemeier, Hendrik; Brandt, Johan

    2015-01-01

    was standardized across all participating centres. After inducing a fast ventricular tachycardia (VT) with a heart rate ≥240 b.p.m. or ventricular fibrillation (VF) with a low-energy T-wave shock, DF was attempted with an initial 15 J shock. If the shock reversed the VT or VF, DF testing was considered successful...

  17. Cardiac effects of sertindole and quetiapine

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Matz, Jørgen; Mittoux, Aurelia;

    2015-01-01

    The QT interval is the most widely used surrogate marker for predicting TdP; however, several alternative surrogate markers, such as Tpeak-Tend (TpTe) and a quantitative T-wave morphology combination score (MCS) have emerged. This study investigated the cardiac effects of sertindole and quetiapin...

  18. Mutation analysis of potassium channel genes KCNQ1 and KCNH2 in patients with long QT syndrome

    Institute of Scientific and Technical Information of China (English)

    刘文玲; 胡大一; 李翠兰; 李萍; 李运田; 李志明; 李蕾; 秦绪光; 董玮; 戚豫; 陈胜寒; 王擎

    2003-01-01

    Objective To determine mutations of two common potassium channel subunit genes KCNQ1, KCNH2 causing long QT syndrome (LQTS) in the Chinese.Methods Thirty-one Chinese LQTS pedigrees were characterized for mutations in the two LQTS genes, KCNQ1 and KCNH2, by sequencing.Results Two novel KCNQ1 mutations, S277L in the S5 domain and G306V in the channel pore, and two novel KCNH2 mutations, L413P in the transmembrane domain S1 and L559H in the transmembrane domain S5 were identified. The triggering factors for cardiac events developed in these mutation carriers included physical exercise and excitation. Mutation L413P in KCNH2 was associated with the notched T wave on ECGs. Mutation L559H in KCNH2 was associated with the typical bifid T wave on ECGs. Mutation S277L in KCNQ1 was associated with a high-amplitude T wave and G306V was associated with a low-amplitude T wave. Two likely polymorphisms, IVS11+18C>T in KCNQ1 and L520V in KCNH2 were also identified in two LQTS patients.Conclusions The mutation rates for both KCNQ1 (6.4%) and KCNH2 (6.4%) are lower in the Chinese population than those from North America or Europe.

  19. Comparative study of T-amplitude features for fitness monitoring using the ePatch® ECG recorder

    DEFF Research Database (Denmark)

    Thorpe, Julia Rosemary; Saida, Trine; Mehlsen, Jesper

    2014-01-01

    This study investigates ECG features, focusing on T-wave amplitude, from a wearable ECG device as a potential method for fitness monitoring in exercise rehabilitation. An automatic T-peak detection algorithm is presented that uses local baseline detection to overcome baseline drift without the need...

  20. Atrial rate and rhythm abnormalities in a patient with hyperkalemia.

    Science.gov (United States)

    Rosman, Jonathan; Thiagarajah, Prashan; Schweitzer, Paul; Rachko, Maurice; Hanon, Sam

    2009-05-15

    A 67 year old man presented with a serum potassium of 7.7 mEq/L and slow atrial flutter with variable A-V block and peaked T waves. Initial treatment for hyperkalemia was followed by an increase in the atrial flutter rate to 300 beats per minute. After hemodialysis the rhythm converted to sinus.

  1. Contenido de Fibra Dietaria de Inflorescencias de Palmas Procesadas Dietary Fiber Content on Processed Palm Inflorescences

    Directory of Open Access Journals (Sweden)

    Dora Centurión-Hidalgo

    2011-01-01

    Full Text Available Se evaluó el efecto del procesamiento y de la madurez en el contenido de fibra dietaria de cuatro inflorescencias de consumo tradicional (Chamaedorea alternans, Chamaedorea tepejilote, Chamaedorea sp y Astrocaryum mexicanum. Se formaron tres grupos de acuerdo a la masa y se aplicaron tres tratamientos: crudo, asado y cocido. Las muestras tratadas se secaron y envasaron para determinar posteriormente el contenido de fibra dietaria. Se aplicó un diseño factorial con una distribución al azar 4x3x3 (cuatro palmas, tres tratamientos y tres grupos. No se encontraron diferencias significativas al comparar el contenido de fibra dietaria total entre los tres grupos. El contenido de fibra dietaria soluble tuvo diferencias significativas (p≤0.05 entre tratamientos siendo el tratamiento crudo el mejor. Se observó diferencias entre especies para fibra dietaria total y fibra dietaria insoluble.Processing effect and maturity stage on dietary fiber content of four traditionally consumed inflorescences (Chamaedorea alternans, Chamaedorea tepejilote, Chamaedorea sp and Astrocaryum mexicanum were evaluated. Three groups were formed according to the mass and three treatments were applied: raw, roasted and boiled. Samples were dried and packed for dietary fiber determination. A randomly distributed factorial analysis 4x3x3 (four palms, three treatments, three groups was used. Total dietary fiber content was not significantly different (p≤0.05 between groups. Soluble dietary fiber content was significantly different between treatments being the raw treatment the best one. It was observed that there were differences in total and insoluble dietary fiber contents between species.

  2. Facies y microfacies de la rampa tithoniana-berriasiana de la cuenca neuquina (Formación Vaca Muerta en la sección del arroyo Loncoche - Malargüe, provincia de Mendoza

    Directory of Open Access Journals (Sweden)

    Diego A. Kietzmann

    2008-12-01

    Full Text Available La Formación Vaca Muerta (Tithoniano-Berriasiano consiste en una alternancia rítmica de lutitas negras, lutitas grises, margas y limolitas, con mudstones, wackestones, packstones, floatstones y rudstones bioclásticos. La asociación de facies en la sección del arroyo Loncoche, permitió definir 12 litofacies y 8 microfacies, dominadas por moluscos, equinodermos, foraminíferos, braquiópodos, serpúlidos y radiolarios. Se distinguieron cuatro asociaciones de facies correspondientes a los subambientes de cuenca, rampa externa (distal y proximal y rampa media. La utilización de la relación Nassellaria/Spumellaria permitió estimar un rango de profundidades menores a 200 metros. El patrón de apilamiento y la distribución vertical de facies permitió la distinción de tres secuencias depositacionales, y el reconocimiento de un sistema tithoniano de rampa homoclinal y un sistema berriasiano de rampa homoclinal de mayor gradiente. La secuencia depositacional 1 consiste en facies de cuenca y rampa externa distal y se caracteriza por un patrón retrogradacional. Presenta un espesor de 124 m, y se extiende desde la Zona de Virgatosphinctes mendozanus hasta la base de la Zona de Corongoceras alternans. Las secuencias depositacionales 2 y 3 consisten en facies de rampa externa y rampa media. Están caracterizadas por un patrón agradacional y progradacional. El espesor de la secuencia 2 es de 66 m y se asigna a la Zona de Corongoceras alternans, mientras que la secuencia 3 alcanza 78 m y corresponde a las zonas de Substeueroceras koeneni y Spiticeras damesi.

  3. Neologia i gramàtica: entre el neologisme lèxic i el neologisme sintàctic

    Directory of Open Access Journals (Sweden)

    Jordi Ginebra

    2015-11-01

    Full Text Available Resum: En aquest treball es mira de contribuir a objectivar el concepte de neologia sintàctica, de manera que pugui ser un recurs classificatori operatiu. La proposta és utilitzar l’expressió neologisme sintàctic per referir-nos als canvis de règim verbal que no són concomitants amb canvis semàntics (ja que llavors haurem de parlar de neologisme semàntic, i que tampoc concorren amb altres procediments neològics. En aquest sentit, un neologisme sintàctic no és un neologisme lèxic, una paraula nova, com sí que ho són els neologismes semàntics. Quan diem que el neologisme sintàctic exclou el canvi semàntic, però, no ens referim al significat relacionat amb les propietats estructurals de tipus temàtic i aspectual que determinen les diverses alternances sintàctiques regulars dels verbs i que els agrupen en classes sintàctiques. Així, l’aparició de l’alternant causatiu transitiu en un verb inacusatiu que no tenia aquest alternant il·lustra un cas de neologia sintàctica. La neologia sintàctica, doncs, reclassifica verbs, però no crea verbs nous. A més, pot fer adquirir a un verb una alternança que el col·loca fora de les classes establertes. Llavors ens acostem a l’àmbit del canvi sintàctic.Paraules clau: neologia, lexicologia, semàntica, canvi sintàctic, alternança verbal.

  4. Sex-related differences in reproductive allocation, growth, defense and herbivory in three dioecious neotropical palms.

    Directory of Open Access Journals (Sweden)

    Verónica Cepeda-Cornejo

    Full Text Available BACKGROUND: Frequently, in dioecious plants, female plants allocate more resources to reproduction than male plants. Therefore it is expected that asymmetrical allocation to reproduction may lead to a reproduction-growth tradeoff, whereby female plants grow less than male plants, but invest more in defenses and thus experience lower herbivory than male plants. METHODOLOGY/PRINCIPAL FINDINGS: We tested these expectations by comparing resource allocation to reproduction, growth and defense and its consequences on herbivory in three sympatric dioecious Chamaedorea palms (C. alternans, C. pinnatifrons and C. ernesti-augusti using a pair-wise design (replicated male/female neighboring plants in a Mexican tropical rain forest. Our findings support the predictions. Biomass allocation to reproduction in C. pinnatifrons was 3-times higher in female than male plants, consistent with what is known in C. alternans and C. ernesti-augusti. Growth (height and leaf production rate and biomass production was higher in male plants of all three species. Female plants of the three species had traits that suggest greater investment in defense, as they had 4-16% tougher leaves, and 8-18% higher total phenolic compounds concentration. Accordingly, female plants sustained 53-78% lower standing herbivory and 49-87% lower herbivory rates than male plants. CONCLUSIONS/SIGNIFICANCE: Our results suggests that resource allocation to reproduction in the studied palms is more costly to female plants and this leads to predictable intersexual differences in growth, defense and herbivory. We conclude that resource allocation to reproduction in plants can have important consequences that influence their interaction with herbivores. Since herbivory is recognized as an important selective force in plants, these results are of significance to our understanding of plant defense evolution.

  5. Noninvasive quantification of blood potassium concentration from ECG in hemodialysis patients

    Science.gov (United States)

    Corsi, Cristiana; Cortesi, Marilisa; Callisesi, Giulia; De Bie, Johan; Napolitano, Carlo; Santoro, Antonio; Mortara, David; Severi, Stefano

    2017-01-01

    Blood potassium concentration ([K+]) influences the electrocardiogram (ECG), particularly T-wave morphology. We developed a new method to quantify [K+] from T-wave analysis and tested its clinical applicability on data from dialysis patients, in whom [K+] varies significantly during the therapy. To elucidate the mechanism linking [K+] and T-wave, we also analysed data from long QT syndrome type 2 (LQT2) patients, testing the hypothesis that our method would have underestimated [K+] in these patients. Moreover, a computational model was used to explore the physiological processes underlying our estimator at the cellular level. We analysed 12-lead ECGs from 45 haemodialysis and 12 LQT2 patients. T-wave amplitude and downslope were calculated from the first two eigenleads. The T-wave slope-to-amplitude ratio (TS/A) was used as starting point for an ECG-based [K+] estimate (KECG). Leave-one-out cross-validation was performed. Agreement between KECG and reference [K+] from blood samples was promising (error: −0.09 ± 0.59 mM, absolute error: 0.46 ± 0.39 mM). The analysis on LQT2 patients, also supported by the outcome of computational analysis, reinforces our interpretation that, at the cellular level, delayed-rectifier potassium current is a main contributor of KECG correlation to blood [K+]. Following a comprehensive validation, this method could be effectively applied to monitor patients at risk for hyper/hypokalemia. PMID:28198403

  6. Assessment of dust exposure in a steel plant in the eastern coast of peninsular Malaysia.

    Science.gov (United States)

    Nurul, Ainun Hamzah; Shamsul, Bahri Mohd Tamrin; Noor Hassim, Ismail

    2016-11-22

    Steel manufacturing produces dust, fumes, and pollutant gases that may give adverse health effects to the respiratory function of workers. Improper occupational hygiene practice in the workplace will affect both workers wellbeing and productivity. To assess the level of particulate matter [(PM2.5, PM10, and Total Particulate Matter (TPM)], and trace metal dust concentrations in different sections of a steel plant and compare with the occupational exposure values. The work environmental parameters of the particulate matters were evaluated using Indoor Air Quality, while metal dust concentrations were measured using portable personal air sampler. A total of 184 personal samples were randomly collected from workers in three major sections; steel making plant, direct reduced plant, and support group. Trace metal dust concentrations were subjected to wet mineral acid mixture digestion and analysed by atomic absorption spectrophotometer (AAS). The overall average PM2.5 concentration observed was varied according to the section: steel making plant was 0.18 mg/m3, direct reduced iron plant was 0.05 mg/m3, and support plant was 0.05 mg/m3. Average PM 10 concentration in steel making shop (SMS) plant, direct reduced (DR) plant, and support plant were 0.70 mg/m3, 0.84 mg/m3, and 0.58 mg/m3, respectively. The average TWA8 of trace metal dusts (cobalt and chromium) in all the sections exceeded 1 to 3 times the ACGIH prescribed values, OSHA PELs, NIOSH RELs as well as USECHH OSHA, whereas TWA8 concentration of nickel for each section did not exceed the occupational exposure values. The average PM2.5, PM10 and TPM did not exceed the prescribed values, while average trace metal dust concentration TWA8 for cobalt and chromium in all plants exceeded occupational exposure prescribed values. However, the nickel found did not exceed the prescribed values in all the plants except for NIOSH RELs.

  7. In situ calibration of polar organic chemical integrative samplers to monitor organophosphate flame retardants in river water using polyethersulfone membranes with performance reference compounds.

    Science.gov (United States)

    Li, Ying; Yang, Cunman; Zha, Daoping; Wang, Li; Lu, Guanghua; Sun, Qin; Wu, Donghai

    2018-01-01

    Passive sampler is an innovative way of monitoring chemicals in different environmental. A modified polar organic chemical integrative sampler (m-POCIS) with a performance reference compound (PRC) was used to evaluate the concentrations of 8 organophosphate flame retardants (OPFRs) under field conditions. The m-POCIS was deployed for 15days under laboratory conditions and 21days under in situ conditions to determine the concentrations of OPFRs. The analytes were trapped in the sorbent and the microporous polyethersulfone (PES) membrane of the m-POCIS. Sampling rates (Rs) were determined for the studied compounds and ranged from 0.02±0.0003L/d (triphenylphosphine oxide, TPPO) to 0.24±0.021L/d (tripropyl phosphate, TPrP) in the laboratory. The membranes accumulation increased with usage and was correlated to the logKow. Among the tested compounds, tripentylphosphate (TPeP) and triphenylphosphate (TPhP) had the highest logKow values and were mostly detected in the membranes. This behavior resulted in a lag-phase, which was measured by extrapolating the data from the last third of the uptake phase (quasilinear) to the x-axis using a linear regression, before the compounds transferred into the sorbent. TPhP was the only compound with a lag-phase of 3.9days during the 15days experiment. Deuteratedtributyl phosphate (TBP-d27) and desisopropyl atrazine-d5 (DIA-d5) were identified through specific experiments as potential PRC. The results from the PRC calibrations suggested that DIA-d5 (ke (in situ)=0.075±0.0048day(-1)) can be used as a PRC for the evaluation of OPFRs using m-POCISs. The time-weighted average (TWA) concentrations estimated by the m-POCIS with or without a PRC were significantly correlated with the corresponding values determined from the grab samples. After the PRC calibration, the TWA concentrations of the tested OPFRs in an aquatic environment were lower than those estimated using the laboratory sampling rates (Rs). The m-POCIS with a PRC correction

  8. Thermal diffusivity of aromatic polyimide thin films by temperature wave analysis

    Science.gov (United States)

    Morikawa, Junko; Hashimoto, Toshimasa

    2009-06-01

    The heat transport properties of aromatic polyimide thin films have become more important in the use for the electric insulation in the microelectronic devices with highly integrated circuits. The various kinds of measuring methods have been applied to obtain the anisotropic thermal conductivity and thermal diffusivity of thin films, however, if the specimens are soft and transparent, the conventional methodology requires highly advanced technology in preparing the specimens for the measurement and the results obtained vary widely. The purpose of this study is to apply the temperature wave analysis (TWA) method to measure the thermal diffusivity of thin films and spin-coated layers of aromatic polyimide in the thickness direction at various temperatures. The TWA is an absolute method to determine the thermal diffusivity by using the phase shift of temperature wave. We have performed measurements on the five different chemical structures of aromatic polyimide, including polyimide isoindoloquinazolinedione (PIQ), pyromellitic dianhydride and 4,4'-oxydianiline (PMDA/ODA), 3,3',4,4',-biphenyltetracarboxylic dianhydride and p-phenylenediamine (BPDA/PPDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride and 4,4'-oxydianiline (BPDA/ODA), and 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 3,3'-diaminobenzophenone (BTDA/DAB). As a result, thermal diffusivity of thin films in a thickness range from 0.1 to 300 μm at a temperature range from 10 to 570 K is obtained. The thickness dependence of thermal diffusivity of spin-coated layers of PIQ exhibits a good coincidence with the tendency of molecular anisotropy observed by attenuated total reflection Fourier transform infrared spectroscopy. In the low temperature below 20 K the amorphous PMDA/ODA film exhibits a substantial increase, which can be understood by considering the phonon mean free path of amorphous systems as first noted by Kittel for inorganic glasses. The glass transition of BTDA/DAB is observed as a rapid

  9. A Comparison of "Total Dust" and Inhalable Personal Sampling for Beryllium Exposure

    Energy Technology Data Exchange (ETDEWEB)

    Carter, Colleen M. [Tulane Univ., New Orleans, LA (United States). School of Public Health and Tropical Medicine

    2012-05-09

    In 2009, the American Conference of Governmental Industrial Hygienists (ACGIH) reduced the Beryllium (Be) 8-hr Time Weighted Average Threshold Limit Value (TLV-TWA) from 2.0 μg/m3 to 0.05 μg/m3 with an inhalable 'I' designation in accordance with ACGIH's particle size-selective criterion for inhalable mass. Currently, per the Department of Energy (DOE) requirements, the Lawrence Livermore National Laboratory (LLNL) is following the Occupational Health and Safety Administration (OSHA) Permissible Exposure Limit (PEL) of 2.0 μg/m3 as an 8-hr TWA, which is also the 2005 ACGIH TLV-TWA, and an Action Level (AL) of 0.2 μg/m3 and sampling is performed using the 37mm (total dust) sampling method. Since DOE is considering adopting the newer 2009 TLV guidelines, the goal of this study was to determine if the current method of sampling using the 37mm (total dust) sampler would produce results that are comparable to what would be measured using the IOM (inhalable) sampler specific to the application of high energy explosive work at LLNL's remote experimental test facility at Site 300. Side-by-side personal sampling using the two samplers was performed over an approximately two-week period during chamber re-entry and cleanup procedures following detonation of an explosive assembly containing Beryllium (Be). The average ratio of personal sampling results for the IOM (inhalable) vs. 37-mm (total dust) sampler was 1.1:1 with a P-value of 0.62, indicating that there was no statistically significant difference in the performance of the two samplers. Therefore, for the type of activity monitored during this study, the 37-mm sampling cassette would be considered a suitable alternative to the IOM sampler for collecting inhalable particulate matter, which is important given the many practical and economic advantages that it presents. However, similar comparison studies would be necessary for this conclusion to be

  10. ANALYSIS OF LARGE LC-MS/MS DATASETS USING AMAZON WEB SERVICES AND THE TRANS-PROTEOMIC PIPELINE

    DEFF Research Database (Denmark)

    Slagel, Joseph; Deutsch, Eric; Mendoza, Luis

    in a timely manner. Compounding the problem is TPP’s iProphet which can significantly improve the confidence of identifications by combining the output of multiple search engines but then requires orders more searches to be performed. We show that cloud computing products like Amazon Web Services (AWS......) provides a viable solution to meet this need. Methods Amazon Web Services provides an especially flexible platform for enabling cloud computing applications by providing virtualized servers that are capable of executing custom virtual machine images, have almost unlimited and secure file storage......, and a queuing system that provides job control and communication across AWS. TPP has been enhanced to utilize these services in either a complete hosted form via the TPP Web Application (TWA) interface, via new functionality in the existing Petunia interface for TPP, or via a command line tool called amztpp...

  11. Divinity and destiny in the religion of Ruanda-Urundi

    Directory of Open Access Journals (Sweden)

    Olof Pettersson

    1967-02-01

    Full Text Available Ruanda and Urundi belong to the Ruanda cluster of the interlactustrine Bantu in the regions surrounded by a great ring of lakes—Tanganyika, Kivu, Edward Albert, Kioga and Victoria. Pygmoid hunters and gatherers still survive among some tribes of the Ruanda cluster, and in both Ruanda and Urundi, people of "Hamitic" (Nilotic origin live side by side with the original tribes. Most of the societies today reveal a sharp stratification into endogamous castes with a ruling aristocracy of herders called Tutsi, a subject agricultural peasanty called Hutu, and often also a depressed caste of Pygmy hunters, called Twa. Even if the beliefs in Ruanda and in Urundi differ in detail, the general religious system is the same among the both peoples. The influences—good or evil—on the life of mankind, on the social orders etc. come from what can be determined as the ultrahuman or superhuman' part of the world.

  12. “Remotion” Total Wrist Arthroplasty: Preliminary Results of a Prospective International Multicenter Study of 215 Cases

    DEFF Research Database (Denmark)

    Herzberg, Guillaume; Boeckstyns, Michel Ernest Henri; Sorensen, Allan Ibsen

    2012-01-01

    preoperative and postoperative reports of "ReMotion" TWA at regular intervals. The cases of 7 centers with more than 15 inclusions were considered for this article. A total of 215 wrists were included. In the rheumatoid arthritis (RA; 129 wrists) and nonrheumatoid arthritis (non-RA; 86 wrists) groups......, there were respectively 5 and 6% complications requiring implant revision with a survival rate of 96 and 92%, respectively, at an average follow-up of 4 years. Within the whole series, only one dislocation was observed in one non-RA wrist. A total of 112 wrists (75 rheumatoid and 37 nonrheumatoid) had more...... than 2 years of follow-up (minimum: 2 years, maximum: 8 years). In rheumatoid and non-RA group, visual analog scale (VAS) pain score improved by 48 and 54 points, respectively, and QuickDASH score improved by 20 and 21 points, respectively, with no statistical differences. Average postoperative arc...

  13. A Technique for Designing Variation Resilient Subthreshold Sram Cell

    Directory of Open Access Journals (Sweden)

    Aminul Islam

    2013-04-01

    Full Text Available This paper presents a technique for designing a variability aware subthreshold SRAM cell. The architecture of the proposed cell is similar to the standard read-decoupled 8-transistor (RD8T SRAM cell with the exception that the access FETS are replaced with transmission gates (TGs. In this work, various design metrics are assessed and compared with RD8T SRAM cell. The proposed design offers 2.14× and 1.75× improvement in TRA (read access time and TWA (write access time respectively compared with RD8T. It proves its robustness against process variations by featuring narrower spread in TRA distribution (2.35× and TWA distribution (3.79× compared with RD8T. The proposed bitcell offers 1.16× higher read current (IREAD and 1.64× lower bitline leakage current (ILEAK respectively compared with RD8T. It also shows its robustness by offering 1.34× (1.58× tighter spread in IREAD (ILEAK compared with RD8T. It exhibits 1.42× larger IREAD to ILEAK ratio. It shows 2.2× higher frequency @ 250 mV with read bitline capacitance of 10 fF. Besides, the proposed bitcell achieves same read stability and write-ability as that of RD8T at the cost of 3 extra transistors. The leakage power of the proposed design is close to that of RD8T.   ABSTRAK: Kertas kerja ini membentangkan teknik merekabentuk sel bawah ambang SRAM yang bolehubah. Senibina sel yang dicadangkan adalah sama dengan sel SRAM 8-transistor (RD8T “pisahan-bacaan” piawai kecuali FET akses  digantikan dengan sel pintu transmisi (TGs. Di dalam kajian ini, beberapa metrik rekabentuk dinilai dan dibandingkan dengan sel RD8T SRAM. Rekabentuk yang dicadangkan menawarkan  peningkatan 2.14× dan 1.75×  dalam TRA (masa akses baca dan TWA (masa akses tulis berbanding dengan RD8T. Ia membuktikan kekukuhan variasi proses dengan menampilkan tebaran yang lebih sempit dalam pengagihan TRA (2.35 × dan pengagihan TWA (3.79 × berbanding dengan RD8T. Sel-Bit yang dicadangkan mempunyai arus baca 1.16

  14. DNA damage in leukocytes of workers occupationally exposed to 1-bromopropane.

    Science.gov (United States)

    Toraason, Mark; Lynch, Dennis W; DeBord, D Gayle; Singh, Narendra; Krieg, Edward; Butler, Mary Ann; Toennis, Christine A; Nemhauser, Jeffrey B

    2006-01-31

    1-bromopropane (1-BP; n-propyl bromide) (CAS No. 106-94-5) is an alternative to ozone-depleting chlorofluorocarbons that has a variety of potential applications as a degreasing agent for metals and electronics, and as a solvent vehicle for spray adhesives. Its isomer, 2-brompropane (2-BP; isopropyl bromide) (CAS No. 75-26-3) impairs antioxidant cellular defenses, enhances lipid peroxidation, and causes DNA damage in vitro. The present study had two aims. The first was to assess DNA damage in human leukocytes exposed in vitro to 1- or 2-BP. DNA damage was also assessed in peripheral leukocytes from workers with occupational exposure to 1-BP. In the latter assessment, start-of- and end-of-work week blood and urine samples were collected from 41 and 22 workers at two facilities where 1-BP was used as a solvent for spray adhesives in foam cushion fabrication. Exposure to 1-BP was assessed from personal-breathing zone samples collected for 1-3 days up to 8h per day for calculation of 8h time weighted average (TWA) 1-BP concentrations. Bromide (Br) was measured in blood and urine as a biomarker of exposure. Overall, 1-BP TWA concentrations ranged from 0.2 to 271 parts per million (ppm) at facility A, and from 4 to 27 ppm at facility B. The highest exposures were to workers classified as sprayers. 1-BP TWA concentrations were statistically significantly correlated with blood and urine Br concentrations. The comet assay was used to estimate DNA damage. In vitro, 1- or 2-BP induced a statistically significant increase in DNA damage at 1mM. In 1-BP exposed workers, start-of- and end-of-workweek comet endpoints were stratified based on job classification. There were no significant differences in DNA damage in leukocytes between workers classified as sprayers (high 1-BP exposure) and those classified as non-sprayers (low 1-BP exposure). At the facility with the high exposures, comparison of end-of-week values with start-of-week values using paired analysis revealed non

  15. A study of the differences in respirator fit factor values between years and masks

    Energy Technology Data Exchange (ETDEWEB)

    Longo, Anastasia [Univ. of Minnesota, Minneapolis, MN (United States)

    1995-08-15

    The work described in this report was carried out at a national laboratory of the Department of Energy, during the time that the author was engaged in a Department of Energy Industrial Hygiene Graduate Fellowship. The national laboratory had a respiratory protection program with approximately 50 employees participating. The program was in place to protect employees from over-exposure to airborne contaminants while engineering and work practice controls were being installed and implemented. It was also in place to protect workers in situations where engineering and work control practices were not feasible, such as during maintenance and repair work, as well as in situations where engineering and work practice controls were not enough to lower the exposure to or below the Permissible Exposure Limit (PEL) as set by the Occupational Safety and Health Association (OSHA) as an eight-hour time weighted average (TWA) or an excursion limit. Respirators were also used for emergencies by the emergency response team.

  16. EFICIÊNCIA DOS DILUIDORES TRIS E BOTU-CRIO® SOBRE OS PARÂMETROS SEMINAIS DE GARANHÕES DAS RAÇAS QUARTO DE MILHA E MANGALARGA MARCHADOR

    Directory of Open Access Journals (Sweden)

    Deyse Naira Mascarenhas Costa

    2014-09-01

    Full Text Available The limiting factor in the cryopreservation process of equine semen is related to the species, as they present a great variability in the ejaculate’s characteristics after thawing. The aim of this study was to evaluate sperm viability after thawing, from Quarter Horse and Mangalarga Marchador stallions using two extenders (Botu-crio and Tris in cryopreservation. To this end, we analyzed the physical characteristics of fresh semen, the sperm membrane functionality by the hypoosmotic swelling test (HOST, total motility and vigor by the Thermoresistance Test (TRT, progressive motility by a computerized system CASA (Computer-Assisted Semen Anlyses and acrosomal membrane integrity and functionality of the mitochondria by epifluorescence microscopy. After thawing, the extender Botu-crio® better preserved motility, vigor and integrity of the plasma membrane. There was no significant difference between breeds for the thermoresistance test after twaing. Quarter Horse showed higher percentage of bigger defects in the sperm pathology analysis.

  17. Chiral fermions in asymptotically safe quantum gravity

    CERN Document Server

    Meibohm, Jan

    2016-01-01

    We study the consistency of dynamical fermionic matter with the asymptotic safety scenario of quantum gravity using the functional renormalisation group. Since this scenario suggests strongly coupled quantum gravity in the UV, one expects gravity-induced fermion self-interactions at energies of the Planck-scale. These could lead to chiral symmetry breaking at very high energies and thus to large fermion masses in the IR. The present analysis which is based on the previous works \\cite{Christiansen:2015rva, Meibohm:2015twa}, concludes that gravity-induced chiral symmetry breaking at the Planck scale is avoided for a general class of NJL-type models, regardless of the number of fermion flavours. This suggests that the phase diagram for these models is topologically stable under the influence of gravitational interactions.

  18. Application of the triolein-embedded cellulose acetate membrane passive sampler for monitoring of polycyclic aromatic hydrocarbons in water.

    Science.gov (United States)

    Tang, Jianfeng; He, Guiying; Li, Gang

    2014-01-01

    Triolein-embedded cellulose acetate membrane (TECAM) can be used as a passive sampler to measure hydrophobic organic contaminants in water. Uptake constant rates (k u ) for polycyclic aromatic hydrocarbons (PAHs) by TECAM sampling were measured under different hydrodynamic conditions. The measured k u values were modeled to enable the quantification of time weighed average (TWA) concentrations of PAHs in the field. An empirical relationship that enables the calculation of in situ k u values of chemicals using performance reference compounds (PRCs) was derived and its application was demonstrated in a field study. The results showed that freely dissolved concentrations of hydrophobic organic compounds (HOCs) can be accurately measured in the field using TECAM method based on empirical uptake models calibrated with PRCs.

  19. Yields of nuclear fragments in the interactions of carbon nuclei with a beryllium target at a projectile energy of 0.6 GeV per nucleon

    Science.gov (United States)

    Abramov, B. M.; Alexeev, P. N.; Borodin, Yu. A.; Bulychjov, S. A.; Gudima, K. K.; Dukhovskoy, I. A.; Krutenkova, A. P.; Kulikov, V. V.; Martemianov, M. A.; Matsyuk, M. A.; Mashnik, S. G.; Turdakina, E. N.; Khanov, A. I.

    2016-09-01

    The yields of long-lived nuclear fragments at an angle of 3.5° that originate fromthe fragmentation of carbon ions with an energy of T 0 = 0.6 GeV per nucleon on a berylliumtarget were measured in the FRAGMexperiment at the ITEP TWA heavy-ion accelerator. The momentum spectra of these fragments cover both the fragmentation-maximum region and the cumulative region. The respective differential cross sections change by about five orders of magnitude. The momentum distributions of fragments in the laboratory frame and their kinetic-energy distributions in the rest frame of the fragmenting nucleus are used to test the predictions of four models of ion-ion interactions: BC, INCL++, LAQGSM03.03, and QMD.

  20. Exposure of firefighters to diesel emissions in fire stations

    Energy Technology Data Exchange (ETDEWEB)

    Froines, J.R.; Hinds, W.C.; Duffy, R.M.; Lafuente, E.J.; Liu, W.C.

    1987-03-01

    Personal sampling techniques were used to evaluate firefighter exposure to particulates from diesel engine emissions. Selected fire stations in New York, Boston and Los Angeles were studied. Firefighter exposure to total particulates increased with the number of runs conducted during an 8-hr period. In New York and Boston where the response level ranged from 7 to 15 runs during an 8-hr shift, the resulting exposure levels of total airborne particulates from diesel exhaust were 170 to 480 ..mu..g/m/sup 3/ (TWA). Methylene chloride extracts of the diesel particulates averaged 24% of the total. The authors' findings suggest that additional research is necessary to assess fire station concentrations of vehicle diesel exhaust that may have adverse health consequences to firefighters.

  1. Pesticide exposure assessment in flowing waters – results for predicted environmental concentrations in some brooks in Germany

    DEFF Research Database (Denmark)

    Trapp, M.T.; Guerniche, D.G.; Bach, M.B.

    2010-01-01

    was to predict initial environmental concentrations in flowing water bodies after spray drift exposure. Based on this the downstream development of these concentrations over space and time with regard to dispersion processes was simulated (PECtwa, Time over Threshold). An adequate GIS-based software......-environment and a functional workflow have been developed which make use of high and medium resolution geodata (water bodies, application areas, mitigating vegetation) and implement results of the relevant scientific work. The observed spatial entity here, as a first step, is a brook in the Hallertau Region, Germany...... TWA strongly correlated to the neighbouring application areas. Differences between the databases can be stated: PECtwa(1h) at 3150 m from the source simulated on ATKIS data amounts to 18 µg/l (Max: 18.5 µg/l at 6000 m), whereby the value calculated on HR-data is 11.7 µg/l (Max: 18 µg/l at 4250 m...

  2. Cool Star Science with the FIRE Spectrograph

    CERN Document Server

    Burgasser, Adam J; Bochanski, John J; Melis, Carl; McMurtry, Craig; Pipher, Judy; Forrest, William; Cushing, Michael C; Looper, Dagny L; Mohanty, Subhanjoy

    2010-01-01

    The Folded-port InfraRed Echellette (FIRE) has recently been commissioned on the Magellan 6.5m Baade Telescope. This single object, near-infrared spectrometer simultaneously covers the 0.85-2.45 micron window in both cross-dispersed (R ~ 6000) or prism-dispersed (R ~ 250-350) modes. FIRE's compact configuration, high transmission optics and high quantum efficiency detector provides considerable sensitivity in the near-infrared, making it an ideal instrument for studies of cool stars and brown dwarfs. Here we present some of the first cool star science results with FIRE based on commissioning and science verification observations, including evidence of clouds in a planetary-mass brown dwarf, accretion and jet emission in the low-mass T Tauri star TWA 30B, radial velocities of T-type brown dwarfs, and near-infrared detection of a debris disk associated with the DAZ white dwarf GALEX 1931+01.

  3. A review of the literature on the toxicity of rare-earth metals as it pertains to the Engineering Demonstration System surrogate testing

    Energy Technology Data Exchange (ETDEWEB)

    Wald, P.H.

    1989-10-01

    A review of data on animal and damaging human exposure to the rare-earth elements has been made. Incidental oral ingestion is considered to be harmless and accidental nonrespiratory uptake does not represent a health risk. Equipment design and operating procedures mitigate against dermatologic or ophthalmologic risk to workers and the public. Animal and human inhalation studies confirm the use of the Threshold Limit Value-Time Weighted Average (TLV-TWA) for yttrium as a conservative measure for evaluation of the Engineering Demonstration System (EDS) emission of the lanthanons. This value (1 mg/m{sup 3}) is also consistent with the OSHA-established permissible exposure limit (PEL). Environmental exposures that are maintained at a level below the TLV/PEL value should result in no health impact to workers, visitors, or the public. 38 refs., 7 tabs.

  4. The UNO Aviation Monograph Series: Aviation Security: An Annotated Bibliography of Responses to the Gore Commission

    Science.gov (United States)

    Carrico, John S.; Schaaf, Michaela M.

    1998-01-01

    This monograph is a companion to UNOAI Monograph 96-2, "The Image of Airport Security: An Annotated Bibliography," compiled in June 1996. The White House Commission on Aviation Safety and Security, headed by Vice President Al Gore, was formed as a result of the TWA Flight 800 crash in August 1996. The Commission's final report included 31 recommendations addressed toward aviation security. The recommendations were cause for security issues to be revisited in the media and by the aviation industry. These developments necessitated the need for an updated bibliography to review the resulting literature. Many of the articles were written in response to the recommendations made by the Gore Commission. "Aviation Security: An Annotated Bibliography of Responses to the Gore Commission" is the result of this need.

  5. Small-angle fragmentation of carbon ions at 0.6 GeV/n: a comparison with models of ion-ion interactions

    Directory of Open Access Journals (Sweden)

    Krutenkova A.P.

    2015-01-01

    Full Text Available Momentum distributions of hydrogen and helium isotopes from 12C fragmentation at 3.5° were measured at 0.6 GeV/nucleon in the FRAGM experiment at ITEP TWA heavy ion accelerator. The fragments were selected by correlated time of flight and dE/dx measurements with a magnetic spectrometer with scintillation counters. The main attention was drawn to the high momentum region where the fragment velocity exceeds the velocity of the projectile nucleus. The momentum spectra of fragments span the region of the fragmentation peak as well as the cumulative region. The differential cross sections cover six orders of magnitude. The distributions measured are compared to the predictions of three ion-ion interaction models: BC, QMD and LAQGSM03.03. The kinetic energy spectra of fragments in the projectile rest frame have an exponential shape with two temperatures, being defined by their slope parameters.

  6. Airborne arsenic and urinary excretion of arsenic metabolites during boiler cleaning operations in a Slovak coal-fired power plant.

    Science.gov (United States)

    Yager, J W; Hicks, J B; Fabianova, E

    1997-01-01

    Little information is available on the relationship between occupational exposure to inorganic arsenic in coal fly ash and urinary excretion of arsenic metabolites. This study ws undertaken in a coal-fired power plant in Slovakia during a routine maintenance outage. Arsenic was measured in the breathing zone of workers during 5 consecutive workdays, and urine samples were obtained for analysis of arsenic metabolites--inorganic arsenic (Asi), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA)--prior to the start of each shift. Results from a small number of cascade impactor air samples indicated that approximately 90% of total particle mass and arsenic was present in particle size fractions >/= 3.5 micron. The 8-hr time-weighted average (TWA) mean arsenic air concentration was 48.3 microg/m3 (range 0.17-375.2) and the mean sum of urinary arsenic (SigmaAs) metabolites was 16.9 microg As/g creatinine (range 2.6-50.8). For an 8-hr TWA of 10 microg/m3 arsenic from coal fly ash, the predicted mean concentration of the SigmaAs urinary metabolites was 13.2 microg As/G creatinine [95% confidence interval (CI), 10.1-16.3). Comparisons with previously published studies of exposure to arsenic trioxide vapors and dusts in copper smelters suggest that bioavailability of arsenic from airborne coal fly ash (as indicated by urinary excretion) is about one-third that seen in smelters and similar settings. Arsenic compound characteristics, matrix composition, and particle size distribution probably play major roles in determining actual uptake of airborne arsenic. Images Figure 1. A Figure 1. B Figure 2. PMID:9347899

  7. Evaluation of the toxicity data for peracetic acid in deriving occupational exposure limits: a minireview.

    Science.gov (United States)

    Pechacek, Nathan; Osorio, Magdalena; Caudill, Jeff; Peterson, Bridget

    2015-02-17

    Peracetic acid (PAA) is a peroxide-based chemistry that is highly reactive and can produce strong local effects upon direct contact with the eyes, skin and respiratory tract. Given its increasing prominence in industry, attention has focused on health hazards and associated risks for PAA in the workplace. Occupational exposure limits (OEL) are one means to mitigate risks associated with chemical hazards in the workplace. A mini-review of the toxicity data for PAA was conducted in order to determine if the data were sufficient to derive health-based OELs. The available data for PAA frequently come from unpublished studies that lack sufficient study details, suffer from gaps in available information and often follow unconventional testing methodology. Despite these limitations, animal and human data suggest sensory irritation as the most sensitive endpoint associated with inhalation of PAA. Rodent RD50 data (the concentration estimated to cause a 50% depression in respiratory rate) were selected as the critical studies in deriving OELs. Based on these data, a range of 0.36-0.51mg/m(3) (0.1-0.2ppm) was calculated for a time-weighted average (TWA), and 1.2-1.7mg/m(3) (0.4-0.5ppm) as a range for a short-term exposure limit (STEL). These ranges compare favorably to other published OELs for PAA. Considering the applicable health hazards for this chemistry, a joint TWA/STEL OEL approach for PAA is deemed the most appropriate in assessing workplace exposures to PAA, and the selection of specific values within these proposed ranges represents a risk management decision.

  8. Contribution of solid fuel, gas combustion, or tobacco smoke to indoor air pollutant concentrations in Irish and Scottish homes

    Energy Technology Data Exchange (ETDEWEB)

    Semple, S.; Garden, C. (Univ. of Aberdeen. Scottish Centre for Indoor Air, Div. of Applied Health Sciences (United Kingdom)); Galea, K.S.; Cowie, H.; Hurley, J.F.; Sanchez-Jimenez, A. (Scottish Centre for Indoor Air. Institute of Occupational Medicine, Edinburgh (United Kingdom)); Whelan, P.; Coggins, M. (National Univ. of Ireland Galway (Ireland)); Thorne, P.S. (Univ. of Iowa. Environmental Health Sciences Research Center, Iowa City, IA (United States)); Ayres, J.G. (Univ. of Birmingham. Institute of Occupational and Environmental Medicine (United Kingdom))

    2012-06-15

    There are limited data describing pollutant levels inside homes that burn solid fuel within developed country settings with most studies describing test conditions or the effect of interventions. This study recruited homes in Ireland and Scotland where open combustion processes take place. Open combustion was classified as coal, peat, or wood fuel burning, use of a gas cooker or stove, or where there is at least one resident smoker. Twenty-four-hour data on airborne concentrations of particulate matter <2.5 mu in size (PM{sub 2.5}), carbon monoxide (CO), endotoxin in inhalable dust and carbon dioxide (CO{sub 2}), together with 2-3 week averaged concentrations of nitrogen dioxide (NO{sub 2}) were collected in 100 houses during the winter and spring of 2009-2010. The geometric mean of the 24-h time-weighted-average (TWA) PM{sub 2.5} concentration was highest in homes with resident smokers (99 mu/m3- much higher than the WHO 24-h guidance value of 25 mu/m3). Lower geometric mean 24-h TWA levels were found in homes that burned coal (7 mu/m3) or wood (6 mu/m3) and in homes with gas cookers (7 mu/m3). In peat-burning homes, the average 24-h PM{sub 2.5} level recorded was 11 mu/m3. Airborne endotoxin, CO, CO{sub 2}, and NO{sub 2} concentrations were generally within indoor air quality guidance levels. (Author)

  9. Conceptual study of an ICRH traveling-wave antenna system for low-coupling conditions as expected in DEMO

    Science.gov (United States)

    Ragona, R.; Messiaen, A.

    2016-07-01

    For the central heating of a fusion reactor ion cyclotron radio frequency heating (ICRH) is the first choice method as it is able to couple RF power to the ions without density limit. The drawback of this heating method is the problem of excitation of the magneto-sonic wave through the plasma boundary layer from the antenna located along the wall, without exceeding its voltage standoff. The amount of coupling depends on the antenna excitation and the surface admittance at the antenna output due to the plasma profile. The paper deals with the optimization of the antenna excitation by the use of sections of traveling-wave antennas (TWAs) distributed all along the reactor wall between the blanket modules. They are mounted and fed in resonant ring system(s). First, the physics of the coupling of a strap array is studied by simple models and the coupling code ANTITER II. Then, after the study of the basic properties of a TWA section, its feeding problem is solved by hybrids driving them in resonant ring circuit(s). The complete modeling is obtained from the matrices of the TWA sections connected to one of the feeding hybrid(s). The solution is iterated with the coupling code to determine the loading for a reference low-coupling ITER plasma profile. The resulting wave pattern up to the plasma bulk is derived. The proposed system is totally load resilient and allows us to obtain a very selective exciting wave spectrum. A discussion of some practical implementation problems is added.

  10. Comparisons of discrete and integrative sampling accuracy in estimating pulsed aquatic exposures.

    Science.gov (United States)

    Morrison, Shane A; Luttbeg, Barney; Belden, Jason B

    2016-11-01

    Most current-use pesticides have short half-lives in the water column and thus the most relevant exposure scenarios for many aquatic organisms are pulsed exposures. Quantifying exposure using discrete water samples may not be accurate as few studies are able to sample frequently enough to accurately determine time-weighted average (TWA) concentrations of short aquatic exposures. Integrative sampling methods that continuously sample freely dissolved contaminants over time intervals (such as integrative passive samplers) have been demonstrated to be a promising measurement technique. We conducted several modeling scenarios to test the assumption that integrative methods may require many less samples for accurate estimation of peak 96-h TWA concentrations. We compared the accuracies of discrete point samples and integrative samples while varying sampling frequencies and a range of contaminant water half-lives (t50 = 0.5, 2, and 8 d). Differences the predictive accuracy of discrete point samples and integrative samples were greatest at low sampling frequencies. For example, when the half-life was 0.5 d, discrete point samples required 7 sampling events to ensure median values > 50% and no sampling events reporting highly inaccurate results (defined as sampling only required two samples to prevent highly inaccurate results and measurements resulting in median values > 50% of the true concentration. Regardless, the need for integrative sampling diminished as water half-life increased. For an 8-d water half-life, two discrete samples produced accurate estimates and median values greater than those obtained for two integrative samples. Overall, integrative methods are the more accurate method for monitoring contaminants with short water half-lives due to reduced frequency of extreme values, especially with uncertainties around the timing of pulsed events. However, the acceptability of discrete sampling methods for providing accurate concentration measurements

  11. Laboratory evaluation of a physiologic sampling pump (PSP).

    Science.gov (United States)

    Lin, Ming-I Brandon; Groves, William A; Freivalds, Andris; Lee, Larry; Lee, Eun Gyung; Slaven, James E; Harper, Martin

    2010-07-08

    Recently, physiologic sampling pumps (PSPs), which can adjust their sampling rates in proportion to wearers' minute ventilation (V[combining dot above](E)), have been proposed to better estimate exposure to airborne contaminants in the workplace. A laboratory evaluation was conducted to compare the performance of a new PSP with a traditional sampling pump (TSP) in an exposure chamber. Fifteen subjects (aged 19-36 years) performed two replicate sessions of step-tests for correlated and uncorrelated exposure scenarios on four separate days. When exposed to a scenario in which subject V[combining dot above](E) is highly correlated with m-xylene concentration over the sampling period (r = 0.93), the PSP-measured time-weighted average (TWA) concentrations are higher than TSP-measured concentrations (average ratio of PSP to TSP = 1.18). The ratio of PSP- and TSP-measured TWA concentrations for the uncorrelated scenario (r = 0.02) is closer to one, as expected, with an average value of 0.94. The test results of the linear mixed model further indicate that the performance of the PSP is unaffected by the anthropometric and physiological characteristics of the wearer. Potential differences in exposure estimates resulting from the use of the two instruments were examined in light of various schemes which can potentially occur in the field. With the capability of estimating the total volume of air inhaled over the sampling period with improved accuracy, PSPs show promise in reducing the inherent uncertainty in current risk assessment approaches that entail constant-flow (TSP) sampling approaches.

  12. Aerosol Emission Monitoring and Assessment of Potential Exposure to Multi-walled Carbon Nanotubes in the Manufacture of Polymer Nanocomposites.

    Science.gov (United States)

    Thompson, Drew; Chen, Sheng-Chieh; Wang, Jing; Pui, David Y H

    2015-11-01

    Recent animal studies have shown that carbon nanotubes (CNTs) may pose a significant health risk to those exposed in the workplace. To further understand this potential risk, effort must be taken to measure the occupational exposure to CNTs. Results from an assessment of potential exposure to multi-walled carbon nanotubes (MWCNTs) conducted at an industrial facility where polymer nanocomposites were manufactured by an extrusion process are presented. Exposure to MWCNTs was quantified by the thermal-optical analysis for elemental carbon (EC) of respirable dust collected by personal sampling. All personal respirable samples collected (n = 8) had estimated 8-h time weighted average (TWA) EC concentrations below the limit of detection for the analysis which was about one-half of the recommended exposure limit for CNTs, 1 µg EC/m(3) as an 8-h TWA respirable mass concentration. Potential exposure sources were identified and characterized by direct-reading instruments and area sampling. Area samples analyzed for EC yielded quantifiable mass concentrations inside an enclosure where unbound MWCNTs were handled and near a pelletizer where nanocomposite was cut, while those analyzed by electron microscopy detected the presence of MWCNTs at six locations throughout the facility. Through size selective area sampling it was identified that the airborne MWCNTs present in the workplace were in the form of large agglomerates. This was confirmed by electron microscopy where most of the MWCNT structures observed were in the form of micrometer-sized ropey agglomerates. However, a small fraction of single, free MWCNTs was also observed. It was found that the high number concentrations of nanoparticles, ~200000 particles/cm(3), present in the manufacturing facility were likely attributable to polymer fumes produced in the extrusion process. © The Author 2015. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

  13. Characterization of naturally occurring airborne diacetyl concentrations associated with the preparation and consumption of unflavored coffee

    Directory of Open Access Journals (Sweden)

    Jennifer S. Pierce

    2015-01-01

    Full Text Available Diacetyl, a suspected cause of respiratory disorders in some food and flavorings manufacturing workers, is also a natural component of roasted coffee. We characterized diacetyl exposures that would plausibly occur in a small coffee shop during the preparation and consumption of unflavored coffee. Personal (long- and short-term and area (long-term samples were collected while a barista ground whole coffee beans, and brewed and poured coffee into cups. Simultaneously, long-term personal samples were collected as two participants, the customers, drank one cup of coffee each per h. Air sampling and analyses were conducted in accordance with OSHA Method 1012. Diacetyl was detected in all long-term samples. The long-term concentrations for the barista and area samples were similar, and ranged from 0.013–0.016 ppm; long-term concentrations for the customers were slightly lower and ranged from 0.010–0.014 ppm. Short-term concentrations ranged from below the limit of detection (<0.0047 ppm–0.016 ppm. Mean estimated 8 h time-weighted average (8 h TWA exposures for the barista ranged from 0.007–0.013 ppm; these values exceed recommended 8 h TWA occupational exposure limits (OELs for diacetyl and are comparable to long-term personal measurements collected in various food and beverage production facilities. The concentrations measured based on area sampling were comparable to those measured in the breathing zone of the barista, thus exceedances of the recommended OELs may also occur for coffee shop workers who do not personally prepare coffee (e.g., cashier, sanitation/maintenance. These findings suggest that the practicality and scientific basis of the recommended OELs for diacetyl merit further consideration.

  14. Predicting benzene vapor concentrations with a near field/far field model.

    Science.gov (United States)

    Nicas, Mark; Neuhaus, John

    2008-09-01

    Published data on benzene vapor concentrations in work simulation settings were used to examine the predictive ability of a near field/far field vapor dispersion model with an exponentially decreasing vapor emission rate. A given simulation involved two 15-min periods of applying a known volume of benzene-containing liquid to equipment on a worktable in a room with a measured air exchange rate. Replicate personal breathing zone (15-min time-weighted average, TWA) and room area (1-hr TWA) air samples were collected. In our modeling, the benzene vapor concentration in the near field zone (at the worktable) represented the personal breathing zone exposure level, and the benzene vapor concentration in the far field zone represented the room area concentration. Across 10 simulation combinations of two factors (the mass of benzene applied and the room air exchange rate), the mean of the personal breathing zone exposure levels ranged from 0.2 to 9.9 mg m(-3), and the mean of the room area concentrations ranged from 0.05 to 5.05 mg m(-3). Our model provided reasonably accurate estimates of the measured benzene vapor concentrations. Linear regression of the mean measured personal breathing zone exposure versus the predicted near field concentration yielded slope = 0.93 and r(2) = 0.94; the null hypothesis that the true slope equals one was not rejected (p-value = 0.39). Linear regression of the mean measured room area concentration versus the predicted far field concentration yielded slope = 0.90 and r(2) = 0.94; the null hypothesis that the true slope equals one was not rejected (p-value = 0.20). Other statistical tests showed no significant differences between measured and predicted values. In addition, most predicted concentrations fell within an approximate range of one-half to twofold the respective measured concentrations.

  15. Nanosilver – Occupational exposure limits

    Directory of Open Access Journals (Sweden)

    Anna Maria Świdwińska-Gajewska

    2015-07-01

    Full Text Available Historically, nanosilver has been known as colloidal silver composed of particles with a size below 100 nm. Silver nanoparticles are used in many technologies, creating a wide range of products. Due to antibacterial properties nanosilver is used, among others, in medical devices (wound dressings, textiles (sport clothes, socks, plastics and building materials (paints. Colloidal silver is considered by many as an ideal agent in the fight against pathogenic microorganisms, unlike antibiotics, without side effects. However, in light of toxicological research, nanosilver is not inert to the body. The inhalation of silver nanoparticles have an adverse effect mainly on the liver and lung of rats. The oxidative stress caused by reactive oxygen species is responsible for the toxicity of nanoparticles, contributing to cytotoxic and genotoxic effects. The activity of the readily oxidized nanosilver surface underlies the molecular mechanism of toxicity. This leads to the release of silver ions, a known harmful agent. Occupational exposure to silver nanoparticles may occur in the process of its manufacture, formulation and also usage during spraying, in particular. In Poland, as well as in other countries of the world, there is no separate hygiene standards applicable to nanomaterials. The present study attempts to estimate the value of MAC-TWA (maximum admissible concentration – the time-weighted average for silver – a nano-objects fraction, which amounted to 0.01 mg/m3. The authors are of the opinion that the current value of the MAC-TWA for silver metallic – inhalable fraction (0.05 mg/m3 does not provide sufficient protection against the harmful effects of silver in the form of nano-objects. Med Pr 2015;66(3:429–442

  16. Biological exposure assessment to tetrachloroethylene for workers in the dry cleaning industry

    Directory of Open Access Journals (Sweden)

    Ashley David L

    2008-04-01

    Full Text Available Abstract Background The purpose of this study was to assess the feasibility of conducting biological tetrachloroethylene (perchloroethylene, PCE exposure assessments of dry cleaning employees in conjunction with evaluation of possible PCE health effects. Methods Eighteen women from four dry cleaning facilities in southwestern Ohio were monitored in a pilot study of workers with PCE exposure. Personal breathing zone samples were collected from each employee on two consecutive work days. Biological monitoring included a single measurement of PCE in blood and multiple measurements of pre- and post-shift PCE in exhaled breath and trichloroacetic acid (TCA in urine. Results Post-shift PCE in exhaled breath gradually increased throughout the work week. Statistically significant correlations were observed among the exposure indices. Decreases in PCE in exhaled breath and TCA in urine were observed after two days without exposure to PCE. A mixed-effects model identified statistically significant associations between PCE in exhaled breath and airborne PCE time weighted average (TWA after adjusting for a random participant effect and fixed effects of time and body mass index. Conclusion Although comprehensive, our sampling strategy was challenging to implement due to fluctuating work schedules and the number (pre- and post-shift on three consecutive days and multiplicity (air, blood, exhaled breath, and urine of samples collected. PCE in blood is the preferred biological index to monitor exposures, but may make recruitment difficult. PCE TWA sampling is an appropriate surrogate, although more field intensive. Repeated measures of exposure and mixed-effects modeling may be required for future studies due to high within-subject variability. Workers should be monitored over a long enough period of time to allow the use of a lag term.

  17. Biological exposure assessment to tetrachloroethylene for workers in the dry cleaning industry.

    Science.gov (United States)

    McKernan, Lauralynn T; Ruder, Avima M; Petersen, Martin R; Hein, Misty J; Forrester, Christy L; Sanderson, Wayne T; Ashley, David L; Butler, Mary A

    2008-04-15

    The purpose of this study was to assess the feasibility of conducting biological tetrachloroethylene (perchloroethylene, PCE) exposure assessments of dry cleaning employees in conjunction with evaluation of possible PCE health effects. Eighteen women from four dry cleaning facilities in southwestern Ohio were monitored in a pilot study of workers with PCE exposure. Personal breathing zone samples were collected from each employee on two consecutive work days. Biological monitoring included a single measurement of PCE in blood and multiple measurements of pre- and post-shift PCE in exhaled breath and trichloroacetic acid (TCA) in urine. Post-shift PCE in exhaled breath gradually increased throughout the work week. Statistically significant correlations were observed among the exposure indices. Decreases in PCE in exhaled breath and TCA in urine were observed after two days without exposure to PCE. A mixed-effects model identified statistically significant associations between PCE in exhaled breath and airborne PCE time weighted average (TWA) after adjusting for a random participant effect and fixed effects of time and body mass index. Although comprehensive, our sampling strategy was challenging to implement due to fluctuating work schedules and the number (pre- and post-shift on three consecutive days) and multiplicity (air, blood, exhaled breath, and urine) of samples collected. PCE in blood is the preferred biological index to monitor exposures, but may make recruitment difficult. PCE TWA sampling is an appropriate surrogate, although more field intensive. Repeated measures of exposure and mixed-effects modeling may be required for future studies due to high within-subject variability. Workers should be monitored over a long enough period of time to allow the use of a lag term.

  18. Effect of xinmailong on ischemic cardiac muscle during hemorrhagic shock

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Xinmailong injection solution was invented at 1988 by prof. Li Shunan in Dali medical college. It was made from the material which has high biological activeness to the cardiac and vascular system. During the experimental shock caused by excessive loss of blood in monkey and dog, it was found by ECG that the T-wave of anterion lead on left chest elevated and became high and sharp after acute blood loss. Arterial blood pressure dropped to 8-5.3 kPa for dog and 8-5.3-2.7 kPa for monkey, changes of T-wave all recovered to near normal level after xinmailong solution was injected intravenously (0.05-0.2 mL/kg). These Results implied that xinmailong might improve the ischemia of myocardium induced by hemorrhagic shock.

  19. EL FENÓMENO DE LA MEMORIA ELÉCTRICA: UN GRAN SIMULADOR. PRESENTACIÓN DE DOS CASOS / Electrical memory phenomenon - a great deceiver. Presentation of two cases

    Directory of Open Access Journals (Sweden)

    Raimundo Carmona Puerta

    2010-09-01

    Full Text Available Resumen Presentamos dos pacientes en los que se desarrollaron ondas T negativas que aparecen en el electrocardiograma por la memoria eléctrica cardíaca. Este fenómeno aunque fue descrito hace muchos años es causa de interpretación errónea de ondas T debido a isquemia cardíaca, y puede ser visto en ciertas situaciones clínicas que permiten sospechar su presencia. / Abstract We present two patients in whom negative T waves are developed, and appeared in the electrocardiogram as a result of the electric cardiac memory. Though described many years ago, this phenomenon is the cause for t-wave misinterpretation due to cardiac ischemia. It can be seen in certain clinical situations which lead to suspect its presence.

  20. Clinical Evaluation of Xylazine-Butorphanol-Guaifenesin-Ketamine as Short-Term TIVA in Equines

    Directory of Open Access Journals (Sweden)

    Bhanu Partap Singh Thakur

    2011-01-01

    Full Text Available Xylazine (1.1 mg/kg, butorphanol (0.02 mg/kg, guaifenesin 5% (20 mg/kg, and ketamine (2.2 mg/kg combinations were able to induce short-term surgical anaesthesia for 23.33 ± 2.57 min in Spiti ponies with excellent to good muscle relaxation and analgesia. Urination and neighing was a constant feature during recovery period. Biphasic P wave, biphasic T wave, and depressed PR segment were common electrocardiographic findings. Biochemical attributes were within physiological limits except a significant increase in ALT values during anaesthesia. The values returned to normal during recovery ruling out any renal or hepatic toxicity. Occasionally, negative T wave, notched P wave, and sinus block were noticed. It is recommended that the anaesthetic combinations xylazine-butorphanol-guaifenesin-ketamine can be safely used for short-term total intravenous anaesthesia (TIVA in equines under field conditions.

  1. Clinical Evaluation of Xylazine-Butorphanol-Guaifenesin-Ketamine as Short-Term TIVA in Equines.

    Science.gov (United States)

    Thakur, Bhanu Partap Singh; Sharma, Sandeep Kumar; Sharma, Arvind; Kumar, Adarsh

    2011-01-01

    Xylazine (1.1 mg/kg), butorphanol (0.02 mg/kg), guaifenesin 5% (20 mg/kg), and ketamine (2.2 mg/kg) combinations were able to induce short-term surgical anaesthesia for 23.33 ± 2.57 min in Spiti ponies with excellent to good muscle relaxation and analgesia. Urination and neighing was a constant feature during recovery period. Biphasic P wave, biphasic T wave, and depressed PR segment were common electrocardiographic findings. Biochemical attributes were within physiological limits except a significant increase in ALT values during anaesthesia. The values returned to normal during recovery ruling out any renal or hepatic toxicity. Occasionally, negative T wave, notched P wave, and sinus block were noticed. It is recommended that the anaesthetic combinations xylazine-butorphanol-guaifenesin-ketamine can be safely used for short-term total intravenous anaesthesia (TIVA) in equines under field conditions.

  2. [Supernormal excitability and conduction in the human heart - electrocardiographic myth or reality?].

    Science.gov (United States)

    Jastrzebski, Marek

    2009-09-01

    Three cases of possible supernormal conduction and excitability are described. Case one: subthreshold stimulation with ventricular capture occurring only at the end of the T wave. Case two: advanced atrioventricular block with conduction present only when P waves fell at the downsloping part of the T wave of ventricular escape beats. Case three: 2 : 1 atrioventricular block at atrial pacing rate of 115 bpm with improvement of conduction during higher pacing rates (3 : 2 block at 130 bpm and above; with negligible PR prolongation). Possible alternative mechanisms: gap phenomenon, ventriculophasic modulation of vagal discharge, ventriculophasic pacing lead movement and concealed 2 : 1 atrioventricular block due to superimposed ventricular escape rhythm, are discussed and considered either impossible or unlikely.

  3. Electrocardiographic Predictors of Cardiovascular Mortality

    Directory of Open Access Journals (Sweden)

    Ioana Mozos

    2015-01-01

    Full Text Available Cardiovascular diseases are the main causes of mortality. Sudden cardiac death may also appear in athletes, due to underlying congenital or inherited cardiac abnormalities. The electrocardiogram is used in clinical practice and clinical trials, as a valid, reliable, accessible, inexpensive method. The aim of the present paper was to review electrocardiographic (ECG signs associated with cardiovascular mortality and the mechanisms underlying those associations, providing a brief description of the main studies in this area, and consider their implication for clinical practice in the general population and athletes. The main ECG parameters associated with cardiovascular mortality in the present paper are the P wave (duration, interatrial block, and deep terminal negativity of the P wave in V1, prolonged QT and Tpeak-Tend intervals, QRS duration and fragmentation, bundle branch block, ST segment depression and elevation, T waves (inverted, T wave axes, spatial angles between QRS and T vectors, premature ventricular contractions, and ECG hypertrophy criteria.

  4. Review and management of the dental patient with Long QT syndrome (LQTS).

    Science.gov (United States)

    Rochford, Christopher; Seldin, R David

    2009-01-01

    Long QT syndrome (LQTS) is a unique cardiovascular condition, with both congenital and acquired forms that afflict patients. These patients show a lengthening of the repolarization phase of the cardiac cycle, which can be best visualized on an electrocardiogram (ECG). The ECG changes can include QT interval (the time between the start of the Q wave and the end of the T wave, as seen on an ECG) and T wave abnormalities, as well as progression to torsades de pointes and ventricular fibrillation. The ECG changes are most commonly elicited by physical activity, emotional stress, and certain medications. This condition represents a challenge for the oral and maxillofacial surgeon. Patients with LQTS must receive proper medical management and a controlled and anxiety-free surgical environment. The purpose of this article was to present a review of LQTS and provide recommendations for effective surgical management. Additionally, a case report of a patient with LQTS, treated by one of the authors, has been included.

  5. Incidence of electrocardiographic changes during cytapheresis using an intermittent flow centrifuge, haemonetics V50 and a continuous flow centrifuge, AS104.

    Science.gov (United States)

    Komatsu, F; Kajiwara, M

    1997-03-01

    Electrocardiographic (ECG) monitoring was performed during cytapheresis and the incidence of ECG changes was compared between methods of intermittent flow centrifugation using the Haemonetics V50 with apheresis donors and continuous flow centrifugation with the AS104 for peripheral blood stem cell (PBSC) collection from patients. ST depression, inverted T wave and other ECG changes were found in 49 (14.3%) of the 342 cytaphereses carried out by the intermittent flow centrifugation method and in 8 (4.7%) of the 169 PBSC collections by the continuous flow centrifugation method. This difference was significant (P < 0.05). The hemodynamic changes in the procedure with the AS104 seem to be small. This is considered to be important for prevention of serious ST and T wave changes.

  6. Major rapid weight loss induces changes in cardiac repolarization

    DEFF Research Database (Denmark)

    Vedel-Larsen, Esben; Iepsen, Eva Winning; Lundgren, Julie

    2016-01-01

    INTRODUCTION: Obesity is associated with increased all-cause mortality, but weight loss may not decrease cardiovascular events. In fact, very low calorie diets have been linked to arrhythmias and sudden death. The QT interval is the standard marker for cardiac repolarization, but T-wave morphology...... analysis has been suggested as a more sensitive method to identify changes in cardiac repolarization. We examined the effect of a major and rapid weight loss on T-wave morphology. METHODS AND RESULTS: Twenty-six individuals had electrocardiograms (ECG) taken before and after eight weeks of weight loss......A1c (pweight loss induces changes in cardiac repolarization. Monitoring of MCS during calorie restriction makes it possible to detect repolarization changes with higher discriminative power than the QT-interval during major rapid weight...

  7. Characterization and mechanisms of action of novel NaV1.5 channel mutations associated with Brugada syndrome

    DEFF Research Database (Denmark)

    Callø, Kirstine; Refaat, Marwan M.; Grubb, Søren;

    2013-01-01

    Brugada syndrome is a heterogeneous heart rhythm disorder characterized by an atypical right bundle block pattern with ST-segment elevation and T-wave inversion in the right precordial leads. Loss-of-function mutations in SCN5A encoding the cardiac sodium channel Na(V)1.5 are associated with Brug......Brugada syndrome is a heterogeneous heart rhythm disorder characterized by an atypical right bundle block pattern with ST-segment elevation and T-wave inversion in the right precordial leads. Loss-of-function mutations in SCN5A encoding the cardiac sodium channel Na(V)1.5 are associated...... with Brugada syndrome. We found novel mutations in SCN5A in 2 different families diagnosed with Brugada syndrome and investigated how those affected Na(V)1.5 channel function....

  8. Painless Mini-Wellens Sign 5 Minutes After Exercise in a Man With Previously Undiagnosed Total Occlusion of the Left Anterior Descending and Right Coronary Arteries.

    Science.gov (United States)

    Kawji, Mazen M; Glancy, David Luke

    2017-09-05

    A 60-year-old man with no coronary artery history and a normal resting electrocardiogram came to the hospital with his second stroke and underwent a treadmill exercise test before carotid endarterectomy. He had no chest pain and stopped because of leg pain. Five minutes after exercise he developed terminal T-wave inversion in leads V3 and V4 that lasted 7 minutes. The T-wave pattern resembled the Wellens pattern that has usually been seen after intense preinfarction rest pain and has usually lasted hours, days, or even weeks. Coronary arteriography showed complete occlusion of the left anterior descending and right coronary arteries. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Coding Manual for the U.S. Army Aviation Epidemiology Data Register

    Science.gov (United States)

    1991-01-01

    voltage Ventricular hypertrophies G720 LVH (voltage plus ST-T wave changes) G721 RVH (tall R type) G722 RVH (rSR’ type) G723 Acute cor pulmonale G724...Chronic cor pulmonale G725 Emphysema without cor pulmonale G726 Age related right ventricular preponderance G727 Biventricular enlargement G728 Septal...Diseases Volume 3: Tabular List and Alphabetic Index of Procedures The first volume contains the code numbers and their cor - responding diagnoses. The

  10. A wavelet-based ECG delineation algorithm for 32-bit integer online processing

    OpenAIRE

    Chiari Lorenzo; Di Marco Luigi Y

    2011-01-01

    Abstract Background Since the first well-known electrocardiogram (ECG) delineator based on Wavelet Transform (WT) presented by Li et al. in 1995, a significant research effort has been devoted to the exploitation of this promising method. Its ability to reliably delineate the major waveform components (mono- or bi-phasic P wave, QRS, and mono- or bi-phasic T wave) would make it a suitable candidate for efficient online processing of ambulatory ECG signals. Unfortunately, previous implementati...

  11. Elastic Bottom Propagation Mechanisms Investigated by Parabolic Equation Methods

    Science.gov (United States)

    2014-09-30

    environments in the form of scattering at an elastic interface, oceanic T - waves , and Scholte waves . OBJECTIVES To implement explosive and earthquake...of the the deep ocean where there is no significant sloping bottom. It is believed that ocean bottom roughness scatters the elastic waves up into...Scholte interface waves are excited by seismic sources and have been observed by seismometers at the ocean bottom.[12, 13] Energy from interface waves has

  12. Takotsubo Cardiomyopathy and Catatonia in the Setting of Benzodiazepine Withdrawal

    OpenAIRE

    Peng, Teng J; Patchett, Nicholas D.; Bernard, Sheilah A.

    2016-01-01

    We report two serious and unusual complications of benzodiazepine withdrawal in a single patient: takotsubo cardiomyopathy and catatonia. This 61-year-old female patient was brought to the emergency department with lethargy and within hours had declined into a state of catatonia. Although there was never a complaint of chest pain, ECG showed deep anterior T-wave inversions and cardiac enzymes were elevated. An echocardiogram was consistent with takotsubo cardiomyopathy. She later received 1 m...

  13. Electrical remodelling in patients with iatrogenic left bundle branch block.

    Science.gov (United States)

    Engels, Elien B; Poels, Thomas T; Houthuizen, Patrick; de Jaegere, Peter P T; Maessen, Jos G; Vernooy, Kevin; Prinzen, Frits W

    2016-12-01

    Left bundle branch block (LBBB) is induced in approximately one-third of all transcatheter aortic valve implantation (TAVI) procedures. We investigated electrophysiological remodelling in patients with TAVI-induced LBBB. This retrospective study comprises 107 patients with initially narrow QRS complex of whom 40 did not and 67 did develop persistent LBBB after TAVI. 12-lead electrocardiograms (ECGs) taken before TAVI, within 24 hours ('acute'), and 1-12 months after TAVI ('chronic') were used to reconstruct vectorcardiograms. From these vectorcardiograms, QRS and T-wave area were calculated as comprehensive indices of depolarization and repolarization abnormalities, respectively. TAVI-induced LBBB resulted in significant acute depolarization and repolarization changes while further repolarization changes were observed with longer lasting LBBB. The amount of long-term repolarization changes (remodelling) was highly variable between patients. The change in T-wave area between acute and chronic LBBB ranged from +57% to - 77%. After dividing the LBBB cohort into tertiles based on the change in T-wave area, only baseline QRS area was larger in the tertile with no significant change in T-wave area. During longer lasting LBBB, the spatial vector gradient (SVG) changed orientation towards the direction of the QRS-vector, indicating that later-activated regions developed shorter action potential duration. This study in patients with TAVI-induced LBBB shows that repolarization changes develop within months after onset of LBBB, and that these changes are highly variable between individual patients. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For Permissions, please email: journals.permissions@oup.com.

  14. Unusual case of left ventricular ballooning involving the inferior wall: a case report

    OpenAIRE

    Rognoni, Andrea; Bertolazzi, Marzia; Maccio', Sergio; Reale, Danilo; PROIETTI, RICCARDO; Rognoni, Giorgio

    2009-01-01

    Background Tako – tsubo like syndrome (also named left ventricular apical ballooning) is an unusual cardiomyopathy with an high incidence in Japanese population of female sex, following an emotional stress. The clinical features (typical chest pain), and the electrocardiographic changes (negative T wave and persistent ST elevation in anterior leads), are suggestive of an acute myocardial infarction; nevertheless the coronary angiography show coronary arteries without lesions and the ventricul...

  15. Wellens' syndrome with segmental wall-motion abnormalities

    OpenAIRE

    Bugan, Baris; Celik,Turgay; Celik,Murat; Dermikoh,Sait; Iyisoy,Atila; Serdar ,Firtina

    2010-01-01

    Turgay Celik1, Baris Bugan1, Serdar Firtina1, Murat Celik2, Sait Demirkol1, Atila Iyisoy11Gulhane Military Medical Academy, Department of Cardiology, Ankara, Turkey; 2Van Army District Hospital, Department of Cardiology, Van, TurkeyAbstract: Wellens' syndrome is a pattern of electrocardiographic T-wave changes associated with critical, proximal left anterior descending (LAD) artery stenosis. We herein report 2 cases of Wellens' syndrome with segmental wall-motion abnormalities...

  16. Method for Correction of Consequences of Radiation-Induced Heart Disease using Low-Intensity Electromagnetic Emission under Experimental Conditions.

    Science.gov (United States)

    Bavrina, A P; Monich, V A; Malinovskaya, S L; Yakovleva, E I; Bugrova, M L; Lazukin, V F

    2015-05-01

    Effects of successive exposure to ionizing irradiation and low-intensity broadband red light on electrical activity of the heart and myocardium microstructure were studied in rats. Lowintensity red light corrected some ECG parameters, in particular, it normalized QT and QTc intervals and voltage of R and T waves. Changes in ECG parameters were followed by alterations in microstructure of muscle fi laments in the myocardium of treatment group animals comparing to control group.

  17. Electrocardiographic parameters in captive, clinically healthy, Amazona ochrocephala

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    Claudia Guerrero S

    2015-11-01

    Full Text Available Objective. To stablish the electrocardiographic parameters of individuals of the species Amazona ochrocephala, from the Unidad de Rescate y Rehabilitacion de Animales Silvestres at the Universidad Nacional de Colombia. Materials and methods. The electrocardiographic examination was performed under inhaled anesthesia with isoflurane. Leads I, II, III, aVL, aVR and aVF were measured. Results. Electrocardiographic parameters obtained in Lead II. P wave Duration: 0.015-0.044 s, P wave amplitude: 0.031 to 0.6 mv, R wave duration: 0.015-0.022 s, amplitude R: 0.034-0.038 mv, S wave Duration: 0.019- 0.042 s, amplitude S: 0.194-0.815 mv, T wave Duration: 0.025-0.064 s, T-wave amplitude: 0.010 to 0.5 mv, PQ Duration: 0.021-0.076 s, QRS Duration: 0.036-0.068 s, QT Duration: 0.070-0.015 s, RR Duration: 0.104-0.324 s, EEM: -111° to -80°, FC: 240-600 ppm. Conclusions. The results showed different values for amplitude and duration of the P, R and T waves in comparison to those obtained in other studies. However, they were similar for heart rate, MEA and duration of the PQ/R, QT and QRS segments.

  18. The application of root mean square electrocardiography (RMS ECG for the detection of acquired and congenital long QT syndrome.

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    Robert L Lux

    Full Text Available BACKGROUND: Precise measurement of the QT interval is often hampered by difficulty determining the end of the low amplitude T wave. Root mean square electrocardiography (RMS ECG provides a novel alternative measure of ventricular repolarization. Experimental data have shown that the interval between the RMS ECG QRS and T wave peaks (RTPK closely reflects the mean ventricular action potential duration while the RMS T wave width (TW tracks the dispersion of repolarization timing. Here, we tested the precision of RMS ECG to assess ventricular repolarization in humans in the setting of drug-induced and congenital Long QT Syndrome (LQTS. METHODS: RMS ECG signals were derived from high-resolution 24 hour Holter monitor recordings from 68 subjects after receiving placebo and moxifloxacin and from standard 12 lead ECGs obtained in 97 subjects with LQTS and 97 age- and sex-matched controls. RTPK, QTRMS and RMS TW intervals were automatically measured using custom software and compared to traditional QT measures using lead II. RESULTS: All measures of repolarization were prolonged during moxifloxacin administration and in LQTS subjects, but the variance of RMS intervals was significantly smaller than traditional lead II measurements. TW was prolonged during moxifloxacin and in subjects with LQT-2, but not LQT-1 or LQT-3. CONCLUSION: These data validate the application of RMS ECG for the detection of drug-induced and congenital LQTS. RMS ECG measurements are more precise than the current standard of care lead II measurements.

  19. A Wavelet-Based ECG Delineation Method: Adaptation to an Experimental Electrograms with Manifested Global Ischemia.

    Science.gov (United States)

    Hejč, Jakub; Vítek, Martin; Ronzhina, Marina; Nováková, Marie; Kolářová, Jana

    2015-09-01

    We present a novel wavelet-based ECG delineation method with robust classification of P wave and T wave. The work is aimed on an adaptation of the method to long-term experimental electrograms (EGs) measured on isolated rabbit heart and to evaluate the effect of global ischemia in experimental EGs on delineation performance. The algorithm was tested on a set of 263 rabbit EGs with established reference points and on human signals using standard Common Standards for Quantitative Electrocardiography Standard Database (CSEDB). On CSEDB, standard deviation (SD) of measured errors satisfies given criterions in each point and the results are comparable to other published works. In rabbit signals, our QRS detector reached sensitivity of 99.87% and positive predictivity of 99.89% despite an overlay of spectral components of QRS complex, P wave and power line noise. The algorithm shows great performance in suppressing J-point elevation and reached low overall error in both, QRS onset (SD = 2.8 ms) and QRS offset (SD = 4.3 ms) delineation. T wave offset is detected with acceptable error (SD = 12.9 ms) and sensitivity nearly 99%. Variance of the errors during global ischemia remains relatively stable, however more failures in detection of T wave and P wave occur. Due to differences in spectral and timing characteristics parameters of rabbit based algorithm have to be highly adaptable and set more precisely than in human ECG signals to reach acceptable performance.

  20. QconCAT standard for calibration of ion mobility-mass spectrometry systems.

    Science.gov (United States)

    Chawner, Ross; McCullough, Bryan; Giles, Kevin; Barran, Perdita E; Gaskell, Simon J; Eyers, Claire E

    2012-11-01

    Ion mobility-mass spectrometry (IM-MS) is a useful technique for determining information about analyte ion conformation in addition to mass/charge ratio. The physical principles that govern the mobility of an ion through a gas in the presence of a uniform electric field are well understood, enabling rotationally averaged collision cross sections (Ω) to be directly calculated from measured drift times under well-defined experimental conditions. However, such "first principle" calculations are not straightforward for Traveling Wave (T-Wave) mobility separations due to the range of factors that influence ion motion through the mobility cell. If collision cross section information is required from T-Wave mobility separations, then calibration of the instruments using known standards is essential for each set of experimental conditions. To facilitate such calibration, we have designed and generated an artificial protein based on the QconCAT technology, QCAL-IM, which upon proteolysis can be used as a universal ion mobility calibration standard. This single unique standard enables empirical calculation of peptide ion collision cross sections from the drift time on a T-Wave mobility instrument.

  1. Evaluation of clinical and electrocardiographic changes during the euthanasia of horses.

    Science.gov (United States)

    Buhl, R; Andersen, L O F; Karlshøj, M; Kanters, J K

    2013-06-01

    The objective of this prospective field study was to investigate whether commonly used criteria for clinical death occurred at the same time as cardiac death, as determined by electrocardiography. Specific ECG changes during euthanasia were also studied. Twenty-nine horses were euthanized with pentobarbital at two different dose rates and 15 of the 29 horses also received detomidine hydrochloride for sedation. ECG was recorded prior to and during euthanasia. Time to collapse, cessation of reflexes, heart sounds and asystole were recorded. ECG recordings were used to calculate RR intervals, PQ duration, QRS duration, distance from QRS complex to end of T wave corrected for HR (QTc interval), duration of T-wave from peak to end (TpeakTend) and amplitudes of T wave (Tpeak) before and during euthanasia. Differences between groups and ECG changes were evaluated using analysis of variance. Clinical determination of death occurred before cardiac death (Peuthanasia resulted in a shorter time to asystole and is therefore recommended for the euthanasia of horses. Importantly, the results show that the clinical definition of death occurred significantly earlier than cardiac death (defined as asystole), which indicates that the clinical declaration of death in horses could be premature compared to that used in humans. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Automatic recognition of T and teleseismic P waves by statistical analysis of their spectra: An application to continuous records of moored hydrophones

    Science.gov (United States)

    Sukhovich, Alexey; Irisson, Jean-Olivier; Perrot, Julie; Nolet, Guust

    2014-08-01

    A network of moored hydrophones is an effective way of monitoring seismicity of oceanic ridges since it allows detection and localization of underwater events by recording generated T waves. The high cost of ship time necessitates long periods (normally a year) of autonomous functioning of the hydrophones, which results in very large data sets. The preliminary but indispensable part of the data analysis consists of identifying all T wave signals. This process is extremely time consuming if it is done by a human operator who visually examines the entire database. We propose a new method for automatic signal discrimination based on the Gradient Boosted Decision Trees technique that uses the distribution of signal spectral power among different frequency bands as the discriminating characteristic. We have applied this method to automatically identify the types of acoustic signals in data collected by two moored hydrophones in the North Atlantic. We show that the method is capable of efficiently resolving the signals of seismic origin with a small percentage of wrong identifications and missed events: 1.2% and 0.5% for T waves and 14.5% and 2.8% for teleseismic P waves, respectively. In addition, good identification rates for signals of other types (iceberg and ship generated) are obtained. Our results indicate that the method can be successfully applied to automate the analysis of other (not necessarily acoustic) databases provided that enough information is available to describe statistical properties of the signals to be identified.

  3. The Effects of Nicorandil and Nifekalant, Which Were Injected into the Pericardial Space, for Transmural Dispersion of Repolarization in the Pig

    Directory of Open Access Journals (Sweden)

    Hiroyuki Ito, MD

    2007-01-01

    Full Text Available Introduction: Some studies have reported that transmural dispersion of repolarization (TDR is involved in the onset of ventricular arrhythmia. We investigated the effects of nicorandil (NIC and nifekalant (NIF injected into the pericardial space, on TDR and T waves in the pig. Methods and Results: We injected NIC 4 or 8 mg and NIF 50 or 100 mg at intervals into the pericardial space for eleven pigs. The effects of these drugs were investigated on the effective refractory period (ERP between the endocardial and epicardial myocardial cells, as well as on QT time, QT peak-end (QTcpe as an index of TDR, and T waveforms, respectively. QTcpe increased from 91 ± 21 to 116 ± 19 msec, 2.8 min after injection of NIC (p < 0.01, although corrected QT (QTc interval did not changed. But 5.5 min after injection, QTc decreased while QTcpe recovered. T wave amplitude significantly increased, and epicardium ERP decreased. When NIF was injected, TDR decreased from 55 ± 10 msec to 44 ± 8 msec (p < 0.01 although QTc did not change. In a later phase, QTc increased (p < 0.01 and QTcpe recovered. T wave amplitude rapidly decreased and became negative. Conclusion: Injected into the pericardial space, NIC and NIF brought about certain changes in ERP, QT and T waveform. Furthermore, NIC increased TDR while NIF decreased TDR.

  4. The application of root mean square electrocardiography (RMS ECG) for the detection of acquired and congenital long QT syndrome.

    Science.gov (United States)

    Lux, Robert L; Sower, Christopher Todd; Allen, Nancy; Etheridge, Susan P; Tristani-Firouzi, Martin; Saarel, Elizabeth V

    2014-01-01

    Precise measurement of the QT interval is often hampered by difficulty determining the end of the low amplitude T wave. Root mean square electrocardiography (RMS ECG) provides a novel alternative measure of ventricular repolarization. Experimental data have shown that the interval between the RMS ECG QRS and T wave peaks (RTPK) closely reflects the mean ventricular action potential duration while the RMS T wave width (TW) tracks the dispersion of repolarization timing. Here, we tested the precision of RMS ECG to assess ventricular repolarization in humans in the setting of drug-induced and congenital Long QT Syndrome (LQTS). RMS ECG signals were derived from high-resolution 24 hour Holter monitor recordings from 68 subjects after receiving placebo and moxifloxacin and from standard 12 lead ECGs obtained in 97 subjects with LQTS and 97 age- and sex-matched controls. RTPK, QTRMS and RMS TW intervals were automatically measured using custom software and compared to traditional QT measures using lead II. All measures of repolarization were prolonged during moxifloxacin administration and in LQTS subjects, but the variance of RMS intervals was significantly smaller than traditional lead II measurements. TW was prolonged during moxifloxacin and in subjects with LQT-2, but not LQT-1 or LQT-3. These data validate the application of RMS ECG for the detection of drug-induced and congenital LQTS. RMS ECG measurements are more precise than the current standard of care lead II measurements.

  5. Hypertensive crisis-induced electrocardiographic changes: a case series

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    Farha Khalid Abou

    2009-08-01

    Full Text Available Abstract Introduction Myocardial injury is one of the most notorious complications of a hypertensive crisis. Key electrocardiograph signs used to detect cardiac injury such as ST segment changes and cardiac arrhythmias usually indicate acute ongoing end-organ damage. Lack of early signs to predict end-organ damage might lead to a delay in the initiation of therapy and selection of the incorrect therapeutic strategy. Case presentation We describe five cases of tall, hyper acute symmetrical T-waves alone or accompanied by other electrocardiograph abnormalities in five healthy participants: three women aged 52, 60 and 62-years and two men aged 49 and 66-years, during a tyramine-monoamine oxidase-inhibitor interaction, phase I clinical trial. T-wave changes appeared early during the course of the hypertensive crisis and were attributed to subendocardial ischemia. The changes were transient and reverted to baseline in parallel with a fall in blood pressure. Conclusion Recognition of tall symmetrical T-waves in early phases of hypertensive crisis heralds commencement of myocardial damage. This calls for prompt medical intervention to avoid an impending irreversible myocardial injury. It is our belief that these findings will add new insight into the management of hypertensive crisis and will open avenues of further investigation.

  6. Intra-QT Spectral Coherence as a Possible Noninvasive Marker of Sustained Ventricular Tachycardia

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    Gianfranco Piccirillo

    2014-01-01

    Full Text Available Sudden cardiac death is the main cause of mortality in patients affected by chronic heart failure (CHF and with history of myocardial infarction. No study yet investigated the intra-QT phase spectral coherence as a possible tool in stratifying the arrhythmic susceptibility in patients at risk of sudden cardiac death (SCD. We, therefore, assessed possible difference in spectral coherence between the ECG segment extending from the q wave to the T wave peak (QTp and the one from T wave peak to the T wave end (Te between patients with and without Holter ECG-documented sustained ventricular tachycardia (VT. None of the QT variability indexes as well as most of the coherences and RR power spectral variables significantly differed between the two groups except for the QTp-Te spectral coherence. The latter was significantly lower in patients with sustained VT than in those without (0.508±0.150 versus 0.607±0.150, P<0.05. Although the responsible mechanism remains conjectural, the QTp-Te spectral coherence holds promise as a noninvasive marker predicting malignant ventricular arrhythmias.

  7. Relationship between electrocardiographic features and distribution of hypertrophy in patients with hypertrophic cardiomyopathy

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Tetsuya; Nakamura, Kazufumi; Yamanari, Hiroshi; Ohe, Tohru [Okayama Univ. (Japan). School of Medicine; Yoshinouchi, Takeo

    1998-07-01

    To evaluate the relationship between the distribution of hypertrophy and the electrocardiographic findings in patients with hypertrophic cardiomyopathy (HCM), 54 HCM patients were studied using magnetic resonance imaging. The patients were divided into 4 groups according to hypertrophic patterns: hypertrophy only at the apex (group I, n=12); hypertrophy in both the apex and base (group II, n=20); hypertrophy only at the base with asymmetric septal hypertrophy (ASH) (group IIIa, n=17); and hypertrophy only at the base without ASH (group IIIb, n=5). Abnormal Q waves in leads II, III and aV{sub F} were found in 1/12, 3/20, 10/17 and 0/5, respectively, and in leads I and aV{sub L} they were found in 1/12, 8/20, 4/17 and 1/5, respectively. The largest negative T waves (mm) were found in group I (group I vs group II vs group IIIa vs group IIIb: 15.2{+-}5.3, 8.2{+-}6.1, 1.6{+-}2.0, 0.8{+-}1.3, respectively). The largest positive T waves (mm) were identified in group IIIb (3.8{+-}3.0, 6.8{+-}3.2, 5.8{+-}3.6, 9.3{+-}2.1, respectively). The presence of abnormal Q waves reflected regional hypertrophy in HCM patients but the configuration of T waves represented the difference in the localization of hypertrophy between the basal and apical segments. (author)

  8. Addenda and Corrigenda to the Catalogue of Palaearctic Coleoptera, volumes 7 and 8 (Curculionoidea

    Directory of Open Access Journals (Sweden)

    Alonso-Zarazaga, Miguel A.

    2016-06-01

    Full Text Available Additions, corrections, comments and nomenclatural novelties for the volumes 7 and 8 of the Catalogue of Palaearctic Coleoptera are provided. For the exact authorship of these check the text. One new species is described: Mecinus tavaresi Caldara & Fogato, sp. nov. from Portugal and Spain. New synonymies are: Compsapoderus (Compsapoderus erythropterus (Gmelin, 1790 = Attelabus intermedius Hellwig, 1795, syn. nov.; Paroplapoderus (Erycapoderus angulipennis (Kolbe, 1886 = Paroplapoderus (Erycapoderus angulipennis shaanxinsis Legalov, 2004, syn. nov. (Attelabidae; Aspidapion (Koestlinia aeneum (Fabricius, 1775 = Aspidapion (Koestlinia motschulskyi (Hochhuth, 1847, syn. nov., Taeniapion rufescens (Gyllenhal, 1833 = Taeniapion notatum (Wagner, 1912, syn. nov. (Apionidae; Larinus (Larinomesius scolymi (Olivier, 1807 = Curculio teres Hellwig, 1795, syn. nov. (Curculionidae; Lixus paraplecticus (Linnaeus, 1758 = Curculio phellandrii Linnaeus, 1764, syn. nov. (Curculionidae; Curculio alternans Hellwig, 1795= Curculio alternans Herbst, 1795, syn. nov. (Curculionidae; Sibinia lyrata Faust, 1889= Sibinia attalica var. judea Pic, 1901, syn. nov. (Curculionidae; Phyllobius (Metaphyllobius pomaceus Gyllenhal, 1834= Curculio prasinus Olivier, 1791, syn. nov. (Curculionidae. New homonymies are: Attelabus intermedius Hellwig, 1795 (non Attelabus intermedius Illiger, 1794; Baris marshalli Ramesha & Ramamurthy, 2011 (non Baris marshalli Hustache, 1938. New replacement names are: Baris ramamurthyi Alonso-Zarazaga nom. nov. for Baris bimaculata Pajni & Kohli, 1990 (non Hustache, 1932; Archarius (Archarius kwonleeanus Alonso-Zarazaga nom. nov. for Archarius (Archarius parvus (Kwon & Lee, 1990 (non Archarius (Archarius parvus (Hong & Wang, 1987, a fossil species; Curculio (Curculio zhangianus Alonso-Zarazaga nom. nov. for Curculio (Curculio helleri Pelsue & Zhang, 2002 (non Curculio (Curculio helleri (Voss, 1932; Lixus trichromus Alonso-Zarazaga nom. nov. for Lixus

  9. Intramural optical mapping of V(m) and Ca(i)2+ during long-duration ventricular fibrillation in canine hearts.

    Science.gov (United States)

    Kong, Wei; Ideker, Raymond E; Fast, Vladimir G

    2012-03-15

    Intramural gradients of intracellular Ca(2+) (Ca(i)(2+)) Ca(i)(2+) handling, Ca(i)(2+) oscillations, and Ca(i)(2+) transient (CaT) alternans may be important in long-duration ventricular fibrillation (LDVF). However, previous studies of Ca(i)(2+) handling have been limited to recordings from the heart surface during short-duration ventricular fibrillation. To examine whether abnormalities of intramural Ca(i)(2+) handling contribute to LDVF, we measured membrane voltage (V(m)) and Ca(i)(2+) during pacing and LDVF in six perfused canine hearts using five eight-fiber optrodes. Measurements were grouped into epicardial, midwall, and endocardial layers. We found that during pacing at 350-ms cycle length, CaT duration was slightly longer (by ≃10%) in endocardial layers than in epicardial layers, whereas action potential duration (APD) exhibited no difference. Rapid pacing at 150-ms cycle length caused alternans in both APD (APD-ALT) and CaT amplitude (CaA-ALT) without significant transmural differences. For 93% of optrode recordings, CaA-ALT was transmurally concordant, whereas APD-ALT was either concordant (36%) or discordant (54%), suggesting that APD-ALT was not caused by CaA-ALT. During LDVF, V(m) and Ca(i)(2+) progressively desynchronized when not every action potential was followed by a CaT. Such desynchronization developed faster in the epicardium than in the other layers. In addition, CaT duration strongly increased (by ∼240% at 5 min of LDVF), whereas APD shortened (by ∼17%). CaT rises always followed V(m) upstrokes during pacing and LDVF. In conclusion, the fact that V(m) upstrokes always preceded CaTs indicates that spontaneous Ca(i)(2+) oscillations in the working myocardium were not likely the reason for LDVF maintenance. Strong V(m)-Ca(i)(2+) desynchronization and the occurrence of long CaTs during LDVF indicate severely impaired Ca(i)(2+) handling and may potentially contribute to LDVF maintenance.

  10. A computational model of spatio-temporal cardiac intracellular calcium handling with realistic structure and spatial flux distribution from sarcoplasmic reticulum and t-tubule reconstructions.

    Directory of Open Access Journals (Sweden)

    Michael A Colman

    2017-08-01

    Full Text Available Intracellular calcium cycling is a vital component of cardiac excitation-contraction coupling. The key structures responsible for controlling calcium dynamics are the cell membrane (comprising the surface sarcolemma and transverse-tubules, the intracellular calcium store (the sarcoplasmic reticulum, and the co-localisation of these two structures to form dyads within which calcium-induced-calcium-release occurs. The organisation of these structures tightly controls intracellular calcium dynamics. In this study, we present a computational model of intracellular calcium cycling in three-dimensions (3-D, which incorporates high resolution reconstructions of these key regulatory structures, attained through imaging of tissue taken from the sheep left ventricle using serial block face scanning electron microscopy. An approach was developed to model the sarcoplasmic reticulum structure at the whole-cell scale, by reducing its full 3-D structure to a 3-D network of one-dimensional strands. The model reproduces intracellular calcium dynamics during control pacing and reveals the high-resolution 3-D spatial structure of calcium gradients and intracellular fluxes in both the cytoplasm and sarcoplasmic reticulum. We also demonstrated the capability of the model to reproduce potentially pro-arrhythmic dynamics under perturbed conditions, pertaining to calcium-transient alternans and spontaneous release events. Comparison with idealised cell models emphasised the importance of structure in determining calcium gradients and controlling the spatial dynamics associated with calcium-transient alternans, wherein the probabilistic nature of dyad activation and recruitment was constrained. The model was further used to highlight the criticality in calcium spark propagation in relation to inter-dyad distances. The model presented provides a powerful tool for future investigation of structure-function relationships underlying physiological and pathophysiological

  11. Real-time electrocardiogram P-QRS-T detection-delineation algorithm based on quality-supported analysis of characteristic templates.

    Science.gov (United States)

    Karimipour, Atiyeh; Homaeinezhad, Mohammad Reza

    2014-09-01

    The main objective of this study is to introduce a simple, low-latency, and accurate algorithm for real-time detection of P-QRS-T waves in the electrocardiogram (ECG) signal. In the proposed method, real-time signal preprocessing, which includes high frequency noise filtering and baseline wander reduction, is performed by applying discrete wavelet transform (DWT). A method based on signal first-order derivative and adaptive threshold adjustment is employed for real-time detection of the QRS complex. Moreover, detection and delineation of P- and T-waves are achieved by correlation analysis conducted between signal and their templates. Besides, signal quality is investigated online, and if the quality of the analysis window is unacceptable, then the algorithm will guess (estimate) the locations of P- and T-waves. The operating characteristics of the proposed algorithm are evaluated by its implementation to an artificially generated ECG signal whose quality is adjustable from the best (Quality, 100%) to the worst (Quality, ≤40%) cases based on the random-walk noise theory. The algorithm was applied to the MIT-BIH arrhythmia database, QT database, and Physionet/CinC challenge 2011competition database. The obtained results, which were based on the QT database, showed sensitivity and positive predictivity of Se=99.63% and P+=99.83%, Se=99.83% and P+=99.98%, and Se=99.74% and P+=99.89% for the detection of P-, QRS-, and T-waves, respectively, and the obtained results, which were based on the MIT-BIH arrhythmia database, showed Se=99.81% and P+=99.70% for the detection of the QRS complex. Moreover, it will be shown that the results of the proposed method are reliable for a minimum signal quality value of 70%. According to numerical assessments, 8-ms after the occurrence of R-wave, its location will be identified by the computer code of the proposed algorithm. This parameter is 198-ms and 177-ms for P- and T-waves, respectively.

  12. SEMINARIO INTERNACIONAL “NEUROCIENCIAS Y LA INVESTIGACIÓN DEL SUEÑO” PRODUCTIVIDAD Y DESEMPEÑO EN TODAS LAS ESPECIES ANIMALES ASOCIADA AL SUEÑO VOLUMEN

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    Rojas Manuel

    2009-04-01

    Full Text Available Las neurociencias agrupan un amplio espectro de tópicos de investigación en aéreas básicas y clínicas. El estudio del sistema nervioso ha aportado en las últimas décadas información trascendental que permite a la ciencia entender algunos de los circuitos, mecanismos y funciones neuronales que regulan, modulan e inducen diferentes estados de sueño. En los mamíferos es absolutamente evidente la presencia de ciclos que alternan estados de vigilia y de sueño, tanto así que la mayoría de estas especies consumen alrededor de un tercio de la vida durmiendo. Adicionalmente, los índices de producción, productividad y reproducción, así como en general el desempeño durante la vigilia son estrechamente dependientes de la calidad y la cantidad de sueño de los individuos. En consecuencia, profesionales de las ciencias medicas, biológicas y agropecuarias, encuentran puntos de extremo interés y aplicación a partir del conocimiento generado por las neurociencias en torno al fenómeno biológico del sueño.

  13. Nonlinear physics of electrical wave propagation in the heart: a review

    Science.gov (United States)

    Alonso, Sergio; Bär, Markus; Echebarria, Blas

    2016-09-01

    The beating of the heart is a synchronized contraction of muscle cells (myocytes) that is triggered by a periodic sequence of electrical waves (action potentials) originating in the sino-atrial node and propagating over the atria and the ventricles. Cardiac arrhythmias like atrial and ventricular fibrillation (AF,VF) or ventricular tachycardia (VT) are caused by disruptions and instabilities of these electrical excitations, that lead to the emergence of rotating waves (VT) and turbulent wave patterns (AF,VF). Numerous simulation and experimental studies during the last 20 years have addressed these topics. In this review we focus on the nonlinear dynamics of wave propagation in the heart with an emphasis on the theory of pulses, spirals and scroll waves and their instabilities in excitable media with applications to cardiac modeling. After an introduction into electrophysiological models for action potential propagation, the modeling and analysis of spatiotemporal alternans, spiral and scroll meandering, spiral breakup and scroll wave instabilities like negative line tension and sproing are reviewed in depth and discussed with emphasis on their impact for cardiac arrhythmias.

  14. Medical image of the week: malignant pericardial effusion and cardiac tamponade

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    Yun S

    2014-06-01

    Full Text Available No abstract available. Article truncated after 150 words. A 53 year old woman with history of metastatic breast cancer presented to the emergency department (ED with worsening shortness of breath for 2 weeks. She was initially diagnosed with grade III breast intraductal carcinoma was estrogen receptor, progesterone receptor, and HER2 negative 5 years earlier. A lumpectomy was performed followed by 4 cycles of chemotherapy with cyclophosphamide and taxol as well as radiation therapy. However, follow-up CT and MRI and subsequent biopsy demonstrated metastatic disease in the left adrenal gland, right ovary, and mediastinal lymph nodes, for which additional chemotherapy was started a month prior to presentation. In the ED, the patient was tachycardic and tachypneic. Vital signs showed BP 112/94 mmHg, HR 118 /min, RR 28 /min, temperature 97.5 °F, and SpO2 97 % with room air. EKG showed sinus tachycardia, low QRS voltage with electric alternans (Figure 1, and chest x-ray demonstrated cardiomegaly with a water bottle ...

  15. Depresión en la mujer: ¿expresión de la realidad actual?

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    Carolina Ochoa Gómez

    2015-01-01

    Full Text Available De acuerdo a múltiples estudios realizados a nivel mundial, la depresión podría afectar alrededor de 350 millones de personas en el mundo. En Colombia, y particularmente en Medellín, el fenómeno también se ha manifestado de forma representativa, especialmente en la población femenina, que prácticamente duplica el número de casos de sus pares masculinos. El objetivo de este artículo es presentar una reseña de diferentes estudios realizados en mayor medida en países de habla hispana que validan como proposición inicial la posibilidad de que la población mundial y particularmente la mujer, desarrolle un síntoma que va en aumento, llamado depresión. La metodología utilizada fue el rastreo de fuentes bibliográficas producto de investigación, realizadas en los últimos diez años, especialmente en España y Latinoamérica. Los hallazgos muestran que la búsqueda de equidad de género, los nuevos roles laborales que se alternan con los quehaceres domésticos, los apegos y algunas circunstancias de orden familiar son factores determinantes frente al fenómeno de la depresión en la mujer.

  16. A Biomedical Computation Revealed that an Extra-Systolic Heartbeat Exhibits a Lower Scaling Exponent: DFA as a Beneficial Biomedical Tool

    Directory of Open Access Journals (Sweden)

    Toru Yazawa

    2013-06-01

    Full Text Available We made our own DFA (detrended fluctuation analysis program. We applied it for checking characteristics for the heartbeat of various individuals. Healthy subjects showed a normal scaling exponent, which is near 1.0 (ranging 0.9 to 1.19 in our own temporary guideline. This is in agreement with the original report by Peng et al. long time ago. In the present study, we investigated the person who has an extra-systole heartbeat, and revealed that their arrhythmic heartbeat exhibited a low scaling exponent (around 0.7. Alternans, which is the heart beating in period-2 rhythms, exhibited a much low scaling exponent (around 0.6. We may conclude that if it would be possible to make a device that equips a DFA program, it might be useful to check the heart condition, and contribute not only in nonlinear physics but also in biomedical fields; especially as a device for health check, which is applicable for people who are spending an ordinary life, before they get seriously heart sick.

  17. Concepto actual y aspectos clínicos de la enfermedad de Crohn y la colitis ulcerosa.

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    Luis Ortigosa

    2009-11-01

    Full Text Available La enfermedad inflamatoria intestinal (EII agrupa dos entidades clínicas bien diferenciadas entre sí, la colitis ulcerosa (CU y la enfermedad de Crohn (EC. La CU se caracteriza por una inflamación difusa del colon, con compromiso del recto, que se extiende de manera proximal y continua. El proceso inflamatorio habitualmente se localiza en la mucosa y la submucosa colónica. La EC es una inflamación crónica y transmural, que afecta todas las capas del intestino y puede llegar a incluir a uno o varios segmentos del tracto digestivo, con localización predominante en íleon terminal, colon y región perianal. Los tramos entre zonas afectadas histológicamente son normales. Ambos trastornos se acompañan de manifestaciones tanto digestivas como extradigestivas en ocasiones: articulares, muco-cutáneas, hepatobiliares, nefro-urológicas y oculares principalmente. Tienen un curso crónico, donde se alternan fases de actividad con fases de latencia. Generalmente, con una buena anamnesis, y la ayuda de datos clínicos, analíticos, endoscópicos, histopatológicos y de distintas técnicas de imagen se puede llegar a un diagnóstico diferencial entre CU y EC. Los índices de actividad de la enfermedad son de gran utilidad para el adecuado control evolutivo.

  18. ECG phenomena: pseudopreexcitation and repolarization disturbances resembling ST-elevation myocardial infarction caused by an intraatrial rhabdomyoma in a newborn.

    Science.gov (United States)

    Paech, Christian; Gebauer, Roman Antonin

    2014-01-01

    As is known from other reports, a rhabdomyoma or tumor metastasis may alter intracardiac electrical conduction, producing electrical phenomena like pseudopreexcitation or repolarization disturbances resembling ST-elevation myocardial infarction or Brugada's syndrome. We present a newborn with a giant atrial rhabdomyoma and additionally multiple ventricular rhabdomyomas. He presented with several electrocardiogram (ECG) phenomena due to tumor-caused atrial depolarization and repolarization disturbances. Except from the cardiac tumors, the physical status was within normal range. Initial ECG showed a rapid atrial tachycardia with a ventricular rate of 230 bpm, which was terminated by electrical cardioversion. Afterwards, the ECG showed atrial rhythm with frequent atrial premature contractions and deformation of the PR interval with large, broad P waves and loss of discret PR segment, imposing as pseudopreexcitation. The following QRS complex was normal, with seemingly abnormal ventricular repolarization resembeling ST-elevation myocardial infarction. The atrial tumor was resected with consequent vast atrial reconstruction using patch plastic. The ventricular tumors were left without manipulation. After surgery, pseudopreexcitation and repolarization abnormalities vanished entirely and an alternans between sinus rhythm and ectopic atrial rhythm was present. These phenomena were supposably caused by isolated atrial depolarization disturbances due to tumor-caused heterogenous endocardial activation. The seemingly abnormal ventricular repolarization is probably due to repolarization of the atrial mass, superimposed on the ventricular repolarization. Recognizably, the QRS complex before and after surgical resection of the rhabdomyoma is identical, underlining the atrial origin of the repolarization abnormalities before surgery.

  19. Sialoadenitis bacteriana crónica recurrente de la infancia. Caracterización clínica

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    Carlos Ávila-Sánchez

    2015-03-01

    Full Text Available La sialoadenitis recurrente es el segundo cuadro inflamatorio más frecuente que afecta a la glándula parótida, precedida por la parotiditis viral. Esta afección tiene un cuadro clínico muy similar a la sialoadenitis, motivo por el cual se debe considerar dentro de los  iagnósticos diferenciales. La sialoadenitis recurrente se caracteriza por episodios periódicos de inflamación y aumento de volumen de la glándula parótida acompañados de fiebre y malestar general que alternan con intervalos de remisión en los que la glándula es clínicamente asintomática. En el Instituto Nacional de Pediatría consideramos al concepto Sialoadenitis bacteriana crónica recurrente de la infancia como la definición más específica y completa para referirse a esta enfermedad. Debido a su recurrencia decidimos escribir este artículo para señalar sus características clínicas.

  20. AV nodal dual pathway electrophysiology and Wenckebach periodicity.

    Science.gov (United States)

    Zhang, Youhua; Mazgalev, Todor N

    2011-11-01

    The precise mechanism(s) governing the phenomenon of AV nodal Wenckebach periodicity is not fully elucidated. Currently 2 hypotheses, the decremental conduction and the Rosenbluethian step-delay, are most frequently used. We have provided new evidence that, in addition, dual pathway (DPW) electrophysiology is directly involved in the manifestation of AV nodal Wenckebach phenomenon. AV nodal cellular action potentials (APs) were recorded from 6 rabbit AV node preparations during standard A1A2 and incremental pacing protocols. His electrogram alternans, a validated index of DPW electrophysiology, was used to monitor fast (FP) and slow (SP) pathway conduction. The data were collected in intact AV nodes, as well as after SP ablation. In all studied hearts the Wenckebach cycle started with FP propagation, followed by transition to SP until its ultimate block. During this process complex cellular APs were observed, with decremental foot formations reflecting the fading FP and second depolarizations produced by the SP. In addition, the AV node cells exhibited a progressive loss in maximal diastolic membrane potential (MDP) due to incomplete repolarization. The pause created with the blocked Wenckebach beat was associated with restoration of MDP and reinitiation of the conduction cycle via the FP wavefront. DPW electrophysiology is dynamically involved in the development of AV nodal Wenckebach periodicity. In the intact AV node, the cycle starts with FP that is progressively weakened and then replaced by SP propagation, until block occurs. AV nodal SP modification did not eliminate Wenckebach periodicity but strongly affected its paradigm. © 2011 Wiley Periodicals, Inc.

  1. Benchmarking ventricular arrhythmias in the mouse--revisiting the 'Lambeth Conventions' 20 years on.

    Science.gov (United States)

    Huggins, Catherine E; Bell, James R; Pepe, Salvatore; Delbridge, Lea M D

    2008-12-01

    The isolated Langendorff-mode perfused heart has become a valuable experimental model, used extensively to examine cardiac function, pathophysiology and pharmacology. For the clinical cardiologist an ECG is often a simple practicality, however in experimental circumstances, particularly with ex vivo murine hearts it is not always possible to obtain an ECG due to experimental recording constraints. However, the mechanical record of ventricular contractile function can be highly informative in relation to electrical state. It is difficult though to achieve consistency in these evaluations of arrhythmia as a validated common reference framework is lacking. In 1988, a group of investigators developed the 'Lambeth Conventions'--a standardised reference for the definition and classification of arrhythmias in animal experimental models of ischaemia, infarction and reperfusion in vivo. Now, two decades later it is timely to revisit the Lambeth Conventions, and to update the guidelines in the context of the marked increase in murine heart study in experimental cardiac pathophysiology. Here we describe an adjunct to the Lambeth Conventions for the reporting of ventricular arrhythmias post-ischaemia in ex vivo mouse hearts when ECG recordings are not employed. Of seven discrete and identifiable patterns of mechanical dysrhythmia observed in reperfusion, five could be classified using conventional ECG terminology: ventricular premature beat, bigeminy, trigeminy, ventricular tachycardia and ventricular fibrillation. Two additional rhythm variations detected from the pressure record are described (potentiated contraction and alternans).

  2. A technical review of optical mapping of intracellular calcium within myocardial tissue.

    Science.gov (United States)

    Jaimes, Rafael; Walton, Richard D; Pasdois, Philippe; Bernus, Olivier; Efimov, Igor R; Kay, Matthew W

    2016-06-01

    Optical mapping of Ca(2+)-sensitive fluorescence probes has become an extremely useful approach and adopted by many cardiovascular research laboratories to study a spectrum of myocardial physiology and disease conditions. Optical mapping data are often displayed as detailed pseudocolor images, providing unique insight for interpreting mechanisms of ectopic activity, action potential and Ca(2+) transient alternans, tachycardia, and fibrillation. Ca(2+)-sensitive fluorescent probes and optical mapping systems continue to evolve in the ongoing effort to improve therapies that ease the growing worldwide burden of cardiovascular disease. In this technical review we provide an updated overview of conventional approaches for optical mapping of Cai (2+) within intact myocardium. In doing so, a brief history of Cai (2+) probes is provided, and nonratiometric and ratiometric Ca(2+) probes are discussed, including probes for imaging sarcoplasmic reticulum Ca(2+) and probes compatible with potentiometric dyes for dual optical mapping. Typical measurements derived from optical Cai (2+) signals are explained, and the analytics used to compute them are presented. Last, recent studies using Cai (2+) optical mapping to study arrhythmias, heart failure, and metabolic perturbations are summarized.

  3. Diagnostic accuracy retrospectively of electrocardiographic findings and cancer history for tamponade in patients determined to have pericardial effusion by transthoracic echocardiogram.

    Science.gov (United States)

    Mathur, Atish Pratap; Saini, Abhimanyu; Lucas, Brian P; AlYousef, Tareq; Margeta, Bosko; Mba, Benjamin

    2013-04-01

    Unexpected pericardial effusions are often found by frontline providers who perform computed tomography. To study the hypothesis that electrocardiographic findings and whether cancer is known or suspected importantly change the likelihood of tamponade for such providers, all unique patients with moderate or large pericardial effusions determined by transthoracic echocardiography during a 6-year period were retrospectively identified. Electrocardiograms were evaluated by blinded investigators for electrical alternans (total and QRS), low voltage (limb leads only, precordial leads only, and both), and tachycardia (>100 QRS complexes/min). Medical records were reviewed to determine whether cancer was known or suspected and whether tamponade was diagnosed. Tamponade was present in 66 patients (27% of 241) with moderate or large pericardial effusions. No tachycardia lowered the odds of tamponade the most (likelihood ratio 0.4, 95% confidence interval 0.3 to 0.6) but by a degree less than any single diagnostic element increased it when present. The combined presence of all 3 electrocardiographic findings and cancer increased the odds of tamponade 63-fold (likelihood ratio 63, 95% confidence interval 33 to 150), whereas their combined absence decreased the odds only fivefold (likelihood ratio 0.2, 95% confidence interval 0.2 to 0.3). In conclusion, electrocardiography findings and cancer rule in tamponade better than they rule it out. Combining these diagnostic elements improves their discriminatory power but not sufficiently enough to rule out tamponade in patients with moderate or large pericardial effusions.

  4. Real-time feedback based control of cardiac restitution using optical mapping.

    Science.gov (United States)

    Kulkarni, Kanchan; Tolkacheva, Elena G

    2015-01-01

    Cardiac restitution is the shortening of the action potential duration with an increase in the heart rate. A shorter action potential duration enables a longer diastolic interval which ensures that the heart gets adequate time to refill with blood. At higher rates however, restitution becomes steep and thus, can lead to unstable electrical activity (alternans) in the heart, leading to fatal cardiac rhythms. It has been proposed that maintaining a shallow slope of cardiac restitution could have potentially anti-arrhythmic effects. Previous studies involved the control of action potential duration (APD) or diastolic interval (DI) in isolated tissue samples based on the feedback from single microelectrode recordings. This limited the spatial resolution of the feedback system. Here, we aimed to develop a real time feedback control system that enabled the detection of APDs from various single pixels based on optical mapping recordings. Stimuli were applied after a predefined fixed DI after detection of an APD. We validated our algorithm using optical mapping movies from an ex-vivo rabbit heart. Thus, we provide an optical mapping based approach for the control of cardiac restitution and a potential means to validate its anti-arrhythmic effects.

  5. A molecular phylogenetic investigation of zoothamnium (ciliophora, peritrichia, sessilida).

    Science.gov (United States)

    Clamp, John C; Williams, Daniel

    2006-01-01

    The gene coding for 18S small subunit ribosomal RNA (ssu rRNA) was sequenced in seven free-living, marine species of the sessiline peritrich genus Zoothamnium. These were Zoothamnium niveum, Zoothamnium alternans, Zoothamnium pelagicum, and four unidentified species. The ssu rRNA gene also was sequenced in Vorticella convallaria, Vorticella microstoma, and in an unidentified, freshwater species of Vorticella. Phylogenetic trees were constructed using these new sequences to test a previously published phylogenetic association between Zoothamnium arbuscula, currently in the family Zoothamniidae, and peritrichs in the family Vorticellidae. Trees constructed by means of neighbor-joining, maximum parsimony, maximum likelihood, and Bayesian inference methods all had similar topologies. The seven new sequences of Zoothamnium species grouped into three well-supported clades, each of which contained a diversity of morphological types. The three clades formed a poorly supported, larger clade that was deeply divergent from Z. arbuscula, which remained more closely associated with vorticellid peritrichs. It is apparent that Zoothamnium is a richly diverse genus and that a much more intensive investigation, involving both morphological and molecular data and a wider selection of species, will be necessary to resolve its phylogeny. A greater amount of molecular diversity than is predicted by morphological data exists within all major clades of sessiline peritrichs that have been included in molecular phylogenies, indicating that characteristics of stalk and peristomial structure traditionally used to differentiate taxa at the generic level and above may not be uniformly reliable.

  6. Retazos de Historias a Manera de Segunda Piel. Magdalena, una Mujer Abusada y Maltratada

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    Cecilia Muñoz Vila

    2012-01-01

    Full Text Available Objetivo: Explorar el funcionamiento psíquico de una mujer abusada y maltratada desde niña. Desarrollo: Los autores hicieron una revisión sistemática con observación de segundo grado sobre seis sesiones de psicoterapia de orientación psicoanalítica llevadas a cabo por una estudiante de Maestría de Psicología Clínica de la Universidad Javeriana. Conclusiones: Los autores encontraron en la paciente un funcionamiento bidimensional, con atención y conciencia exclusivamente sensorial, con estados pasivos de desmentalización y desmantelamiento, con una ruptura del plan de funcionamiento sensorial en múltiples pedazos que solo se conectan por contigüidad o contraste verbal, y que se alternan en su aparición, sin que el tiempo, ni el espacio, ni los objetos intervengan como factores organizadores, porque la violenta irrupción de la violación en el cuerpo ha roto la conexión inicial entre el cuerpo y el psiquismo, y se ha dañado el desarrollo de la feminidad normal. Se desarrolla así un estado mental de segunda piel donde todos esos trozos de historias narradas una y otra vez la mantienen temporalmente unida, pero al hacerse cada vez más pequeños y desarticulados la dejan en el vacío de su existencia.

  7. A Biomedical Computation Revealed that an Extra-Systolic Heartbeat Exhibits a Lower Scaling Exponent: DFA as a Beneficial Biomedical Tool

    Directory of Open Access Journals (Sweden)

    Toru Yazawa

    2013-06-01

    Full Text Available We made our own DFA (detrended fluctuation analysis program. We applied it for checking characteristics for the heartbeat of various individuals. Healthy subjects showed a normal scaling exponent, which is near 1.0 (ranging 0.9 to 1.19 in our own temporary guideline. This is in agreement with the original report by Peng et al. long time ago. In the present study, we investigated the person who has an extra-systole heartbeat, and revealed that their arrhythmic heartbeat exhibited a low scaling exponent (around 0.7. Alternans, which is the heart beating in period-2 rhythms, exhibited a much low scaling exponent (around 0.6. We may conclude that if it would be possible to make a device that equips a DFA program, it might be useful to check the heart condition, and contribute not only in nonlinear physics but also in biomedical fields; especially as a device for health check, which is applicable for people who are spending an ordinary life, before they get seriously heart sick.

  8. Tiempo y aspeczo en la poesía de Federico García Lorca y en su traducción Eslovena

    Directory of Open Access Journals (Sweden)

    Jasmina Markič

    2001-12-01

    Full Text Available En el Romancero Gitano , y también en el Llanto por Ignacio Sánchez Mejías3, obras a las que dedicamos este estudio, Federico García Lorca recurre a la poesía popular y emplea algunos recursos típicos de los antiguos romances españoles, como por ejemplo el uso singular de los tiempos verbales del romancero tradicional para crear un mundo poético especial. La mezcla de los tiempos verbales en el Romancero Gitana es un rasgo característico que llama mucho la atención. Parece que existe un juego entre los tiempos verbales que más frecuentemente aparecen en estos poemas: el presente, el pretérito simple 4 y el imperfecto. Los tres tiempos verbales alternan en el mismo nivel temporal formando curiosas combinaciones que contribuyen a la creación del misterioso mundo del Romancero Gitana, ese mundo mítico de los gitanos que el mismo poeta denomina retablo de Andalucia (García Lorca, 1978, 106, un mundo que no se ve, pero que se siente palpitar.

  9. Computational modeling and numerical methods for spatiotemporal calcium cycling in ventricular myocytes

    Directory of Open Access Journals (Sweden)

    Michael eNivala

    2012-05-01

    Full Text Available Intracellular calcium (Ca cycling dynamics in cardiac myocytes is regulated by a complex network of spatially distributed organelles, such as sarcoplasmic reticulum (SR, mitochondria, and myofibrils. In this study, we present a mathematical model of intracellular Ca cycling and numerical and computational methods for computer simulations. The model consists of a coupled Ca release unit (CRU network, which includes a SR domain and a myoplasm domain. Each CRU contains 10 L-type Ca channels and 100 ryanodine receptor channels, with individual channels simulated stochastically using a varient of Gillespie’s method, modified here to handle time-dependent transition rates. Both the SR domain and the myoplasm domain in each CRU are modeled by 5x5x5 voxels to maintain proper Ca diffusion. Advanced numerical algorithms implemented on graphical processing units were used for fast computational simulations. For a myocyte containing 100x20x10 CRUs, a one-second heart time simulation takes about 10 minutes of machine time on a single NVIDIA Tesla C2050. Examples of simulated Ca cycling dynamics, such as Ca sparks, Ca waves, and Ca alternans, are shown.

  10. Chitinoidellids from the Early Tithonian-Early Valanginian Vaca Muerta Formation in the Northern Neuquén Basin, Argentina

    Science.gov (United States)

    Kietzmann, Diego A.

    2017-07-01

    As part of microfacies studies carried out on the Tithonian - Valanginian carbonate ramp of the Neuquén Basin, two stratigraphic sections of the Vaca Muerta Formation (Arroyo Loncoche and Río Seco de la Cara Cura) were chosen in order to analyze the chitinoidellid content and distribution. Calpionellids in the studied sections are relatively poorly preserved; hyaline calcite walls are often recrystallized making the systematic determination difficult. However, microgranular calcite walls seem to have resisted better the incipient neomorphism presented by the limestones of the Vaca Muerta Formation. Seven known species of Chitinoidellidae and four known species of Calpionellidae are recognized. The distribution of calpionellid species allows recognizing the Chitinoidella and Crassicollaria Zones in the Neuquén Basin. The Chitinoidella Zone correlates with the Virgatosphinctes mendozanus-Windhauseniceras internispinosum Andean ammonite Zones, and can be divided into two subzones. The lower one is poorly defined, while the upper one can be assigned to the Boneti Subzone. The Crassicollaria Zone in the Neuquén basin needs a detailed revision, but data provided in this work enable its correlation at least with the Corongoceras alternans ammonite Zone. Similar associations were reported in Mexico and Cuba, showing good consistency between these regions. However, in the Neuquén Basin unlike the Tethys, chitinoidellids persist until the lower Berriasian.

  11. Autoridade e educação: o desafio em face do ocaso da tradição

    Directory of Open Access Journals (Sweden)

    JOSÉ SÉRGIO FONSECA DE CARVALHO

    2015-01-01

    Full Text Available La discusión sobre el lugar de la autoridad en el proceso educativo escolar ha movilizado intelectuales, profesores y responsables políticos. Los dis - cursos se alternan entre la queja y el lamento, entre el rechazo de las rela - ciones fundadas en la autoridad y la búsqueda de la restauración de una supuesta autoridad perdida. Este artículo pretende aclarar que, a pesar de las diferencias teóricas y programáticas entre estas dos tendencias de los discursos, ambas tienen un aspecto común: no distinguen la obediencia producida por una relación de autoridad –siempre fundada en la confianza– de otras forma de obediencia, como las que son producidas por la violen - cia, la coacción o la adhesión a normas legales. Por lo tanto, el debate sobre los dilemas y dificultades relacionadas con la disminución de la autoridad en las relaciones educativas del mundo moderno requiere la comprensión de la especificidad de este tipo de relación y de los regímenes temporales que rigen los nexos que las sociedades establecen entre presente, pasado y futuro.

  12. Mud and silk in the dark: A new type of millipede moulting chamber and first observations on the maturation moult in the order Callipodida.

    Science.gov (United States)

    Reboleira, Ana Sofia P S; Enghoff, Henrik

    2016-05-01

    The postembryonic development of millipedes includes a series of stadia separated by moults, a process known as anamorphosis. The moulting process and especially the moulting into maturity, i.e., with fully developed copulatory organs, remains unknown for most millipede species. We have kept specimens of Lusitanipus alternans (Verhoeff, 1893) in the laboratory for one year and studied its moulting process, including the first study of the maturation moult in the order Callipodida. Unlike the typical silk cocoon reported for other callipodidans, this species builds a new type of solid moulting chamber, using the available substrate reinforced by a silken web. We present the detailed ultrastructure of the moulting chamber and silk. It takes five days to build the moulting chamber and between 29 (female) and 35 (male) days to shed the exuviae. The male maturation moult is preceded by an evagination of a gonopodal sac between the 6th and 7th body rings, in which the gonopods are developed. Females evaginated completely their vulval sacs, retracting them after shedding the exuviae. Vulval sac size seems to increase with the progressive reduction of the second pair of legs.

  13. Formas pronominales de tratamiento y cortesía en el habla de Tunja, Colombia

    Directory of Open Access Journals (Sweden)

    Gloria Smith Avendaño de Barón

    2014-01-01

    Full Text Available Este artículo presenta resultados de una investigación orientada hacia los siguientes propósitos: determinar la frecuencia de uso de las formas pronominales de tratamiento cortés sumercé, usted y tú, según variables sociales de género, edad y nivel de instrucción en hablantes de Tunja; describir las variaciones sociodiscursivas y explicar la relación de ese uso con la cortesía. Se utilizó la metodología del Proyecto para el Estudio Sociolingüístico del Español de España y de América (PRESEEA y la muestra se conformó con 54 hablantes. Los resultados indican que la forma pronominal más empleada en Tunja es sumercé, para expresar cordialidad y afecto, seguida de usted y tú; las mujeres y los hombres de distintas generaciones y niveles de instrucción alternan el empleo de esas tres formas en el contexto de discursos de tipo narrativo, descriptivo, argumentativo y expositivo.

  14. Oligosaccharides in Food and Agriculture

    Science.gov (United States)

    Collins, Michelle E.; Rastall, Robert A.

    Oligosaccharides are an integral part of the daily diet for humans and animals. They are primarily used for their nutritional properties, however they are currently receiving much attention due to their physiological effect on the microflora of the gastrointestinal tract. Galacto-oligosaccharides and the fructan-type oligosaccharides, namely FOS and inulin are well established as beneficial to the host and are classified as prebiotic based on data from clinical studies. These compounds dominate this sector of the market, although there are oligosaccharides emerging which have produced very interesting in vitro results in terms of prebiotic status and human trials are required to strengthen the claim. Such compounds include pectic oligosaccharides, gluco-oligosaccharides, gentio-oligosaccharides, kojio-oligosaccharides, and alternan oligosaccharides. The raw materials for production of these prebiotic compounds are derived from natural sources such as plants but also from by products of the food processing industry. In addition to being prebiotic these compounds can be incorporated into foodstuffs due to the physiochemical properties they possess.

  15. The survey of environmental pollution in denture producing center%义齿制作中心工作环境污染状况的调查

    Institute of Scientific and Technical Information of China (English)

    梁翠云; 王跃进; 陈健钊; 黄哲云; 邝婉容

    2014-01-01

    In order to provide theoretical evidence about management of denture production as well as prevention of technicians’ occupational disease, daily operations in denture producing center are detected which consist of noise and dust situation, etc. The noise and dust which were from polished mental, plastic and porcelain were respectively detected. In the meantime, the result was compared with national hygiene standard. The result of the noise from polished mental, plastic and porcelain is gradually going up, while some data reach to high point, over standard rate is 63.3%. Precisely, the PC-TWA(permissible concentration-time weighted average) of dust from polished mental and plastic are 10.75 mg/m3、and 9.07 mg/m3 respectively. In other words, the result is completely over the standard level. Meanwhile, the PC-TWA of polished porcelain is 8.84 mg/m3,which is over standard around 40% . Noise pollution and air pollution in denture producing center should be paid high attention. In order to guarantee the health issues of technicians, effective measurements should be proceeded, consisting of pollution prevention and personal protection of staff.%目的:通过对义齿制作中心一些常用操作项目所产生的噪声、粉尘达标情况进行检测,为规范义齿制作中心管理和技师职业病防控提供理论依据。方法分别对打磨金属、塑料、瓷体产生的噪声、粉尘进行监测,与国家卫生标准对照分析。结果打磨金属、塑料、瓷体产生的噪声,测定值呈渐进性增高,个别为高频,超标率达63.3%。打磨金属、塑料产生粉尘时间加权平均容许浓度平均值(PC-TWA)分别是10.75 mg/m3、9.07 mg/m3,超标率达100%;打磨瓷体的 PC-TWA 为8.84 mg/m3,超标率为40%。结论义齿制作中心噪声和粉尘污染问题需引起重视,应采取有效的防尘降噪措施和个人防护措施,从而保障技师的健康。

  16. GSTM1和GSTT1基因多态性对苯乙烯接触工人苯乙烯代谢的影响%Influence of Genetic Polymorphisms of GSTM1 and GSTT1 on Metabolism of Styrene in Styrene-exposed Workers

    Institute of Scientific and Technical Information of China (English)

    张放; 籍继颖; 邵华; 张志虎

    2011-01-01

    目的 探讨GSTM1和GSTT1基因多态性对苯乙烯接触工人苯乙烯代谢的影响.方法于2006年11月选择山东省某玻璃钢游艇生产企业喷漆车间工龄在1年以上、防护情况基本相同的全部工人共计56人作为研究对象.分别测定个体苯乙烯接触剂量、尿中代谢产物——苯乙烯巯基尿酸的浓度,采用多重PCR技术检测GSTM1和GSTT1基因多态性.结果 工人尿中苯乙烯巯基尿酸浓度均值为(19.80±13.25) mg/g Cr,苯乙烯8h时间加权平均浓度(8 h-TWA)均值为(133.28±95.81) mg/m3,两者间呈正相关(r=0.937,P<0.05).高暴露组(苯乙烯浓度>50 mg/m3)和低暴露组(苯乙烯浓度≤50 mg/m3)工人年龄、工龄、吸烟率、饮酒率以及GSTM1、GSTT1基因型的构成比间比较,差异均无统计学意义.无论在低暴露组还是高暴露组,携带GSTM1(+)基因型受试工人尿中的苯乙烯巯基尿酸浓度均高于携带GSTM1(-)基因型受试工人,差异均有统计学意义(P<0.05);但是在携带GSTT1不同基因型受试工人之间中未发现同等差异.结论CSTM1是苯乙烯的主要代谢酶之一,其基因多态性可影响苯乙烯在体内的代谢过程.%Objective To explore the influence of genetic polymorphisms of GSTM1 and GSTT1 on metabolism of styrene in styrene-exposed workers. Methods In November 2006,fifty-six styrene-exposed workers were chosen as the study subjects. Personal passive samplers were used to determine personal 8 -hour -time -weighted average (8h -TWA). The concentration of the phenyl-hydroxyethyl-mercapturic-acid (PHEMA) in urine was determined by Ellman spectrophotometry. The genetic polymorphisms of GSTT1 and GSTMl were detected by multiple PCR method. Results The mean concentration of PHEMA in urine,8-hour-TWA of styrene were (19.80±13.25) mg/g Cr,(133.28±95.81) mg/m3,respectively, with a positive correlation (r=0.937,P50 mg/m3) or low-exposed group (8h-TWAs≤50 mg/m3), there was a significant association between

  17. Energy Reductions Using Next-Generation Remanufacturing Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Sordelet, Daniel; Racek, Ondrej

    2012-02-24

    supported the Industrial Technologies Program's initiative titled 'Industrial Energy Efficiency Grand Challenge.' To contribute to this Grand Challenge, we. pursued an innovative processing approach for the next generation of thermal spray coatings to capture substantial energy savings and green house gas emission reductions through the remanufacturing of steel and aluminum-based components. The primary goal was to develop a new thermal spray coating process that yields significantly enhanced bond strength. To reach the goal of higher coating bond strength, a laser was coupled with a traditional twin-wire arc (TWA) spray gun to treat the component surface (i.e., heat or partially melt) during deposition. Both ferrous and aluminum-based substrates and coating alloys were examined to determine what materials are more suitable for the laser-assisted twin-wire arc coating technique. Coating adhesion was measured by static tensile and dynamic fatigue techniques, and the results helped to guide the identification of appropriate remanufacturing opportunities that will now be viable due to the increased bond strength of the laser-assisted twin-wire arc coatings. The feasibility of the laser-assisted TWA (LATWA) process was successfully demonstrated in this current effort. Critical processing parameters were identified, and when these were properly controlled, a strong, diffusion bond was developed between the substrate and the deposited coating. Consequently, bond strengths were nearly doubled over those typically obtained using conventional grit-blast TWA coatings. Note, however, that successful LATWA processing was limited to ferrous substrates coated with steel coatings (e.g., 1020 and 1080 steel). With Al-based substrates, it was not possible to avoid melting a thin layer of the substrate during spraying, and this layer re-solidified to form a band of intermetallic phases at the substrate/coating interface, which significantly diminished the coating adhesion. The

  18. Assessment of suspended dust from pipe rattling operations

    Science.gov (United States)

    Park, Ju-Myon

    Six types of aerosol samplers were evaluated experimentally in a test chamber with polydisperse fly ash. The Andersen sampler overestimates the mass of small particles due to particle bounce between stages and therefore provides a conservative estimate of respirable particulate mass and thoracic particulate mass. The TSP sampler provides an unbiased estimate of total particulate mass. TSP/CCM provides no information below ESD 2 mum and therefore underestimates respirable particulate mass. The PM10 sampler provides a reasonable estimate of the thoracic particulate fraction. The RespiCon sampler provides an unbiased estimate of respirable, thoracic, and inhalable fractions. DustTrak and SidePak monitors provide relative particle concentrations instead of absolute concentrations because it could not be calibrated for absolute particle concentrations with varying particle shape, composition, and density. Six sampler technologies were used to evaluate airborne dust concentrations released from oilfield pipe rattling operations. The task sampled was the removal of scale deposited on the inner wall of the pipe before it was removed from service in a producing well. The measured mass concentrations of the aerosol samplers show that a Gaussian plume model is applicable to the data of pipe rattling operations for finding an attainment area. It is estimated that workers who remain within 1 m of the machine centerline and directly downwind have an 8-hour TWA exposure opportunity of (13.3 +/- 9.7) mg/m3 for the Mud Lake pipe scale and (11.4 +/- 9.7) mg/m3 for the Lake Sand pipe scale at 95% confidence. At distances more than 4 m downwind from the machine centerline, dust concentrations are below the TWA-TLV of 10 mg/m3 for the worker in both scales. At positions crosswind or upwind from the machine centerline there is no measurable exposure. Available data suggest that the attainment area for the public starts at about 9 m downwind from the machine centerline in both scales, as

  19. Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity

    Science.gov (United States)

    Tsuboi, Yohko; Yamazaki, Kyohei; Sugawara, Yasuharu; Kawagoe, Atsushi; Kaneto, Soichiro; Iizuka, Ryo; Matsumura, Takanori; Nakahira, Satoshi; Higa, Masaya; Matsuoka, Masaru; Sugizaki, Mutsumi; Ueda, Yoshihiro; Kawai, Nobuyuki; Morii, Mikio; Serino, Motoko; Mihara, Tatehiro; Tomida, Hiroshi; Ueno, Shiro; Negoro, Hitoshi; Daikyuji, Arata; Ebisawa, Ken; Eguchi, Satoshi; Hiroi, Kazuo; Ishikawa, Masaki; Isobe, Naoki; Kawasaki, Kazuyoshi; Kimura, Masashi; Kitayama, Hiroki; Kohama, Mitsuhiro; Kotani, Taro; Nakagawa, Yujin E.; Nakajima, Motoki; Ozawa, Hiroshi; Shidatsu, Megumi; Sootome, Tetsuya; Sugimori, Kousuke; Suwa, Fumitoshi; Tsunemi, Hiroshi; Usui, Ryuichi; Yamamoto, Takayuki; Yamaoka, Kazutaka; Yoshida, Atsumasa

    2016-10-01

    Twenty-three giant flares from thirteen active stars (eight RS CVn systems, one Algol system, three dMe stars, and one young stellar object) were detected during the first two years of our all-sky X-ray monitoring with the gas propotional counters (GSC) of the Monitor of All-sky X-ray Image (MAXI). The observed parameters of all these MAXI/GSC flares are found to be at the upper ends for stellar flares with the luminosity of 1031-34 erg s-1 in the 2-20 keV band, the emission measure of 1054-57 cm-3, the e-folding time of 1 hr to 1.5 d, and the total radiative energy released during the flare of 1034-39 erg. Notably, the peak X-ray luminosity of 5^{+4}_{-2} × 10^{33}erg s-1 in the 2-20 keV band was detected in one of the flares on II Peg, which is one of the, or potentially the, largest-ever-observed in stellar flares. X-ray flares were detected from GT Mus, V841 Cen, SZ Psc, and TWA-7 for the first time in this survey. Whereas most of our detected sources are multiple-star systems, two of them are single stars (YZ CMi and TWA-7). Among the stellar sources within 100 pc distance, the MAXI/GSC sources have larger rotation velocities than the other sources. This suggests that the rapid rotation velocity may play a key role in generating large flares. Combining the X-ray flare data of nearby stars and the sun, taken from literature and our own data, we discovered a universal correlation of τ ∝ L_X^{0.2} for the flare duration τ and the intrinsic X-ray luminosity LX in the 0.1-100 keV band, which holds for 5 and 12 orders of magnitude in τ and LX, respectively. The MAXI/GSC sample is located at the highest ends of the correlation.

  20. Recent advances in physics and technology of ion cyclotron resonance heating in view of future fusion reactors

    Science.gov (United States)

    Ongena, J.; Messiaen, A.; Kazakov, Ye O.; Koch, R.; Ragona, R.; Bobkov, V.; Crombé, K.; Durodié, F.; Goniche, M.; Krivska, A.; Lerche, E.; Louche, F.; Lyssoivan, A.; Vervier, M.; Van Eester, D.; Van Schoor, M.; Wauters, T.; Wright, J.; Wukitch, S.

    2017-05-01

    Ion temperatures of over 100 million degrees need to be reached in future fusion reactors for the deuterium-tritium fusion reaction to work. Ion cyclotron resonance heating (ICRH) is a method that has the capability to directly heat ions to such high temperatures, via a resonant interaction between the plasma ions and radiofrequency waves launched in the plasma. This paper gives an overview of recent developments in this field. In particular a novel and recently developed three-ion heating scenario will be highlighted. It is a flexible scheme with the potential to accelerate heavy ions to high energies in high density plasmas as expected for future fusion reactors. New antenna designs will be needed for next step large future devices like DEMO, to deliver steady-state high power levels, cope with fast variations in coupling due to fast changes in the edge density and to reduce the possibility for impurity production. Such a new design is the traveling wave antenna (TWA) consisting of an array of straps distributed around the circumference of the machine, which is intrinsically resilient to edge density variations and has an optimized power coupling to the plasma. The structure of the paper is as follows: to provide the general reader with a basis for a good understanding of the later sections, an overview is given of wave propagation, coupling and RF power absorption in the ion cyclotron range of frequencies, including a brief summary of the traditionally used heating scenarios. A special highlight is the newly developed three-ion scenario together with its promising applications. A next section discusses recent developments to study edge-wave interaction and reduce impurity influx from ICRH: the dedicated devices IShTAR and Aline, field aligned and three-strap antenna concepts. The principles behind and the use of ICRH as an important option for first wall conditioning in devices with a permanent magnetic field is discussed next. The final section presents ongoing

  1. Exposure to static and time-varying magnetic fields from working in the static magnetic stray fields of MRI scanners: a comprehensive survey in the Netherlands.

    Science.gov (United States)

    Schaap, Kristel; Christopher-De Vries, Yvette; Crozier, Stuart; De Vocht, Frank; Kromhout, Hans

    2014-11-01

    Clinical and research staff who work around magnetic resonance imaging (MRI) scanners are exposed to the static magnetic stray fields of these scanners. Although the past decade has seen strong developments in the assessment of occupational exposure to electromagnetic fields from MRI scanners, there is insufficient insight into the exposure variability that characterizes routine MRI work practice. However, this is an essential component of risk assessment and epidemiological studies. This paper describes the results of a measurement survey of shift-based personal exposure to static magnetic fields (SMF) (B) and motion-induced time-varying magnetic fields (dB/dt) among workers at 15 MRI facilities in the Netherlands. With the use of portable magnetic field dosimeters, >400 full-shift and partial shift exposure measurements were collected among various jobs involved in clinical and research MRI. Various full-shift exposure metrics for B and motion-induced dB/dt exposure were calculated from the measurements, including instantaneous peak exposure and time-weighted average (TWA) exposures. We found strong correlations between levels of static (B) and time-varying (dB/dt) exposure (r = 0.88-0.92) and between different metrics (i.e. peak exposure, TWA exposure) to express full-shift exposure (r = 0.69-0.78). On average, participants were exposed to MRI-related SMFs during only 3.7% of their work shift. Average and peak B and dB/dt exposure levels during the work inside the MRI scanner room were highest among technical staff, research staff, and radiographers. Average and peak B exposure levels were lowest among cleaners, while dB/dt levels were lowest among anaesthesiology staff. Although modest exposure variability between workplaces and occupations was observed, variation between individuals of the same occupation was substantial, especially among research staff. This relatively large variability between workers with the same job suggests that exposure classification

  2. Avaliação da exposição a metais numa oficina de recuperação de armamento de uma organização militar Exposure assessment to metals in an armament repair shop of a military organization

    Directory of Open Access Journals (Sweden)

    Eduardo Borba Neves

    2009-12-01

    Full Text Available O objetivo deste estudo foi a avaliação da exposição ocupacional ao chumbo e manganês dos trabalhadores de uma oficina de recuperação de armamento de uma organização militar. O ar do ambiente de trabalho foi avaliado no monitoramento ambiental e os indicadores biológicos de dose interna, para chumbo e manganês, em sangue e na urina, foram utilizados no monitoramento biológico. A concentração de manganês e chumbo nos filtros e fluidos biológicos foi determinada por espectrometria de absorção atômica eletrotérmica. Os resultados do monitoramento ambiental indicaram níveis de Pb e Mn acima do TLV-TWA durante o processo de pintura (313,33 μg m-3 e solda (951 μg m-3. Os indicadores biológicos revelaram que cinco dos nove trabalhadores apresentam níveis de Pb-S que sugerem exposição ambiental ao chumbo (valores entre 5 e 10 μg dL-1. Pode-se concluir que existe uma pequena exposição ocupacional ao chumbo e ao manganês na oficina de tratamento superficial. Tal exposição é influenciada pelas condições meteorológicas e pela demanda variável de trabalho.The aim of this study was the occupational exposure assessment to lead and manganese of workers in an armament repair shop of a military organization. The air of the working environment was assessed in the environmental monitoring while the internal dose biological indicators for lead and manganese, in blood and urine, were used in biological monitoring. Metals concentration in filters and biological fluids were determined by electrothermal atomic absorption spectrometry. The results of the environmental monitoring showed lead and manganese levels above the TLV-TWA during the process of painting (313.33 g m-3 and solder (951 μg m-3. The biological indicators revealed that five of the nine employees presented Pb-S levels that suggested an environmental exposure to lead (values between 5 and 10 μg dL-1. It can be concluded that there is a small occupational exposure to

  3. Refinements on the age-dependent half-life model for estimating child body burdens of polychlorodibenzodioxins and dibenzofurans.

    Science.gov (United States)

    Kerger, Brent D; Leung, Hon-Wing; Scott, Paul K; Paustenbach, Dennis J

    2007-04-01

    We modified our prior age-dependent half-life model to characterize the range of child (ages 0-7) body burdens associated with dietary and environmental exposure to polychlorodibenzodioxins and furans (PCDD/Fs). Several exposure scenarios were evaluated. Infants were assumed to be either breast-fed or formula-fed from birth to 6 months of age. They then received intakes of PCDD/Fs through age 7 from foods based on weighted means estimates [JECFA, 2001. Joint FAO/WHO Committee on Food Additives. Fifty-seventh meeting, Rome, June 5-14 , 2001, pp. 24-40], and with or without exposures (ingestion and dermal) to urban residential soils at 1ppb TCDD toxic equivalents (TEQ). A one-compartment (adipose volume) toxicokinetic model for TCDD described by Kreuzer [Kreuzer, P.F., Csanady, Gy.A., et al., 1997. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and congeners in infants. A toxicokinetic model of human lifetime body burden by TCDD with special emphasis on its uptake by nutrition. Arch. Toxicol. 71, 383-400] was expanded to include the key non-TCDD congeners in human breast milk and adipose tissues, and two model parameter refinements were examined: (1) use of updated and more detailed age-correlated body fat mass data [CDC, 2000. Centers for Disease Control. CDC Growth Charts: United States. Advance Data from Vital and Health Statistics of the Centers for Disease Control and Prevention, National Center for Health Statistics, Number 314, December 2000]; (2) use of breast milk PCDD/F concentration data from sampling completed in 2000-2003 [Wittsiepe, J., Fürst, P., et al., 2004. PCDD/F and dioxin-like PCB in human blood and milk from German mothers. Organohalogen Compd. 66, 2865-2872]. The updated body fat mass data nearly halved the predicted peak body burden for breast-feeding and lowered the time-weighted average (TWA) body burdens from ages 0-7 by 30-40% for breast-fed and formula-fed infants. Combined use of the updated breast milk PCDD/F concentration and body fat

  4. Contribution of solid fuel, gas combustion, or tobacco smoke to indoor air pollutant concentrations in Irish and Scottish homes.

    Science.gov (United States)

    Semple, S; Garden, C; Coggins, M; Galea, K S; Whelan, P; Cowie, H; Sánchez-Jiménez, A; Thorne, P S; Hurley, J F; Ayres, J G

    2012-06-01

      There are limited data describing pollutant levels inside homes that burn solid fuel within developed country settings with most studies describing test conditions or the effect of interventions. This study recruited homes in Ireland and Scotland where open combustion processes take place. Open combustion was classified as coal, peat, or wood fuel burning, use of a gas cooker or stove, or where there is at least one resident smoker. Twenty-four-hour data on airborne concentrations of particulate matter<2.5 μm in size (PM2.5), carbon monoxide (CO), endotoxin in inhalable dust and carbon dioxide (CO2), together with 2-3 week averaged concentrations of nitrogen dioxide (NO2) were collected in 100 houses during the winter and spring of 2009-2010. The geometric mean of the 24-h time-weighted-average (TWA) PM2.5 concentration was highest in homes with resident smokers (99 μg/m3--much higher than the WHO 24-h guidance value of 25 μg/m3). Lower geometric mean 24-h TWA levels were found in homes that burned coal (7 μg/m3) or wood (6 μg/m3) and in homes with gas cookers (7 μg/m3). In peat-burning homes, the average 24-h PM2.5 level recorded was 11 μg/m3. Airborne endotoxin, CO, CO2, and NO2 concentrations were generally within indoor air quality guidance levels. Little is known about indoor air quality (IAQ) in homes that burn solid or fossil-derived fuels in economically developed countries. Recent legislative changes have moved to improve IAQ at work and in enclosed public places, but there remains a real need to begin the process of quantifying the health burden that arises from indoor air pollution within domestic environments. This study demonstrates that homes in Scotland and Ireland that burn solid fuels or gas for heating and cooking have concentrations of air pollutants generally within guideline levels. Homes where combustion of cigarettes takes place have much poorer air quality. © 2011 John Wiley & Sons A/S.

  5. KONDISI TERUMBU KARANG DI PULAU WEH PASCA BENCANA MEGA TSUNAMI (Coral Reef Condition in Weh Island after Mega Tsunami Disaster

    Directory of Open Access Journals (Sweden)

    Dini Purbani

    2015-01-01

    Full Text Available ABSTRAK Penelitian ini bertujuan untuk mengetahui kondisi terumbu karang pasca tsunami sebagai langkah awal dalam upaya rehabilitasi terumbu karang. Metode yang digunakan adalah dengan membandingkan kondisi terumbu karang tahun 2002 sebelum tsunami dan tahun 2009 pasca tsunami menggunakan citra satelit Landsat ETM7 melalui analisis Lyzenga. Pengamatan langsung di lapangan menggunakan metode LIT (Line Intercept Transect dan pengukuran kualitas perairan. Lokasi pengamatan berada di Ujung Seurawan,  Sea Garden di Pulau Rubiah,  Sea Garden 1, Rubiah Channel 2 dan  Loh Weng. Kondisi terumbu karang yang berada di Taman Wisata Alam (TWA Pulau Weh ini berada pada kondisi yang buruk sampai baik. Terumbu karang kondisi baik terdapat di lokasi Sea Garden 1 (54,26 %, kondisi sedang di Rubiah Channel 2 (26,32% dan Sea Garden 2 (39,5% sedangkan kondisi buruk terdapat di Ujung Seurawan (19,28 % dan Loh Weng (15,14%. Bentuk kerusakan terumbu karang antara lain patah, terbalik dan hanyut. Jenis terumbu karang yang rusak terdapat di sebelah timur Pulau Weh yaitu sekitar Pulau Rubiah dan sekitar Teluk Loh Pria Laot. Kisaran kondisi perairan berupa pH, salinitas, suhu dan DO menunjukkan bahwa kualitas perairan berada pada kondisi baik untuk perencanaan kegiatan rehabilitasi terumbu karang. ABSTRACT This study aims to determine the condition of coral reefs after the tsunami as the first step in the rehabilitation of coral reefs. The methods used are of comparing the condition of coral reefs between pre-tsunami in 2002 and post-tsunami in 2009 using Landsat satellite imagery ETM7 through Lyzenga analysis, direct observe of the coral reefs in the field have been done using the LIT (Line Intercept Transect and measurement of water quality. Locations of observations are in Ujung Seurawan, Sea Garden in Rubiah Island, Sea Garden 1, Rubiah Channel 2 and Loh Weng. The condition of coral reefs in the Natural Park (TWA Weh Island is generally in the range between poor and

  6. ENGLISH FOLK BALLADS COLLECTED BY CECIL JAMES SHARP IN THE SOUTHERN APPALACHIANS: GENESIS, TRANSFORMATION AND UKRAINIAN PARALLELS

    Directory of Open Access Journals (Sweden)

    Oksana Karbashevska

    2015-04-01

    Full Text Available The purpose of this research, presented at the Conference sectional meeting, is to trace peculiarities of transformation of British folk medieval ballads, which were brought to the Southern Appalachians in the east of the USA by British immigrants at the end of the XVIIIth – beginning of the XIXth century and retained by their descendants, through analyzing certain texts on the levels of motifs, dramatis personae, composition, style and artistic means, as well as to outline relevant Ukrainian parallels. The analysis of such ballads, plot types and epic songs was carried out: 1 British № 10: “The Twa Sisters” (21 variants; American “The Two Sisters”(5 variants and Ukrainian plot type I – C-5: “the elder sister drowns the younger one because of envy and jealousy” (8 variants; 2 British № 26: The Three Ravens” (2, “The Twa Corbies” (2; American “The Three Ravens” (1, “The Two Crows”(1 and Ukrainian epic songs with the motif of lonely death of a Cossack warrior on the steppe (4. In our study British traditional ballads are classified according to the grouping worked out by the American scholar Francis Child (305 numbers, Ukrainian folk ballads – the plot-thematic catalogue developed by the Ukrainian folklorist Оleksiy Dey (here 288 plots are divided into 3 spheres, cycles and plot types. The investigation and comparison of the above indicated texts witness such main tendencies: 1 the American counterparts, collected in the Appalachian Mountains, preserve the historic-national memory and cultural heritage of the British immigrant bearers on the level of leading motifs, dramatis personae, composition peculiarities, traditional medieval images, epithets, similes, commonplaces; 2 some motifs, characters, images, artistic means, archaic and dialectal English of the Child ballads are reduced or substituted in the Appalachian texts; 3 realism of American ballad transformations, which overshadows fantasy and

  7. A test chamber for experimental hydrogen fluoride exposure in humans.

    Science.gov (United States)

    Søstrand, P; Kongerud, J; Eduard, W; Nilsen, T; Skogland, M; Boe, J

    1997-07-01

    An inhalation chamber was built to perform experimental studies with hydrogen fluoride (HF), other gases, and particulate matter. The present study sought to describe a new gas delivery system and the distribution and concentration of HF gas in the chamber. The aluminum chamber has a volume of 19.2 m3 and a variable ventilation rate of about 1 to 10 air changes per hour. The negative pressure difference between the chamber and outside air can be regulated from 0 to 300 Pa. HF was fed at concentrations of up to 4000 mg/m3 directly into the ventilation duct feeding the chamber through openings with diameters as small as 50 microns, oriented opposite to the airflow. Gas flow was varied from about 0.1 dm3/min at a pressure of 4 atm. The dilution factor of HF concentration from cylinder to chamber was on the order of 10(3) to 10(4). The standard deviation (SD) of the HF concentrations at a fixed measurement point during a 1-hour test was typically 0.05 mg/m3 at a time-weighted average (TWA) concentration of 2.66 mg/m3. The SD of the TWA HF concentrations at six locations in the chamber was typically 0.05 mg/m3 and 0.29 mg/m3 at 0.61 and 3.46 mg/m3, respectively. Human exposure could be predicted from calculations based on ventilation data, gas flow, and observed ratio between calculated and measured concentrations. When the target exposure concentration was 1.5 mg/m3, the measured mean exposure concentration was typically 1.54 mg/m3 (range: 1.4-1.7 mg/m3, SD 0.09 mg/m3, n = 8). The chamber is well-suited for inhalation studies in humans. Chamber atmosphere was controlled and has proved to be stable and homogeneous, even in tests with HF, a highly reactive gas in the class of superacids.

  8. Assessment and evaluation of noise controls on roof bolting equipment and a method for predicting sound pressure levels in underground coal mining

    Science.gov (United States)

    Matetic, Rudy J.

    Over-exposure to noise remains a widespread and serious health hazard in the U.S. mining industries despite 25 years of regulation. Every day, 80% of the nation's miners go to work in an environment where the time weighted average (TWA) noise level exceeds 85 dBA and more than 25% of the miners are exposed to a TWA noise level that exceeds 90 dBA, the permissible exposure limit (PEL). Additionally, MSHA coal noise sample data collected from 2000 to 2002 show that 65% of the equipment whose operators exceeded 100% noise dosage comprise only seven different types of machines; auger miners, bulldozers, continuous miners, front end loaders, roof bolters, shuttle cars (electric), and trucks. In addition, the MSHA data indicate that the roof bolter is third among all the equipment and second among equipment in underground coal whose operators exceed 100% dosage. A research program was implemented to: (1) determine, characterize and to measure sound power levels radiated by a roof bolting machine during differing drilling configurations (thrust, rotational speed, penetration rate, etc.) and utilizing differing types of drilling methods in high compressive strength rock media (>20,000 psi). The research approach characterized the sound power level results from laboratory testing and provided the mining industry with empirical data relative to utilizing differing noise control technologies (drilling configurations and types of drilling methods) in reducing sound power level emissions on a roof bolting machine; (2) distinguish and correlate the empirical data into one, statistically valid, equation, in which, provided the mining industry with a tool to predict overall sound power levels of a roof bolting machine given any type of drilling configuration and drilling method utilized in industry; (3) provided the mining industry with several approaches to predict or determine sound pressure levels in an underground coal mine utilizing laboratory test results from a roof bolting

  9. Evaluation of take-home exposure and risk associated with the handling of clothing contaminated with chrysotile asbestos.

    Science.gov (United States)

    Sahmel, J; Barlow, C A; Simmons, B; Gaffney, S H; Avens, H J; Madl, A K; Henshaw, J; Lee, R J; Van Orden, D; Sanchez, M; Zock, M; Paustenbach, D J

    2014-08-01

    The potential for para-occupational (or take-home) exposures from contaminated clothing has been recognized for the past 60 years. To better characterize the take-home asbestos exposure pathway, a study was performed to measure the relationship between airborne chrysotile concentrations in the workplace, the contamination of work clothing, and take-home exposures and risks. The study included air sampling during two activities: (1) contamination of work clothing by airborne chrysotile (i.e., loading the clothing), and (2) handling and shaking out of the clothes. The clothes were contaminated at three different target airborne chrysotile concentrations (0-0.1 fibers per cubic centimeter [f/cc], 1-2 f/cc, and 2-4 f/cc; two events each for 31-43 minutes; six events total). Arithmetic mean concentrations for the three target loading levels were 0.01 f/cc, 1.65 f/cc, and 2.84 f/cc (National Institute of Occupational Health and Safety [NIOSH] 7402). Following the loading events, six matched 30-minute clothes-handling and shake-out events were conducted, each including 15 minutes of active handling (15-minute means; 0.014-0.097 f/cc) and 15 additional minutes of no handling (30-minute means; 0.006-0.063 f/cc). Percentages of personal clothes-handling TWAs relative to clothes-loading TWAs were calculated for event pairs to characterize exposure potential during daily versus weekly clothes-handling activity. Airborne concentrations for the clothes handler were 0.2-1.4% (eight-hour TWA or daily ratio) and 0.03-0.27% (40-hour TWA or weekly ratio) of loading TWAs. Cumulative chrysotile doses for clothes handling at airborne concentrations tested were estimated to be consistent with lifetime cumulative chrysotile doses associated with ambient air exposure (range for take-home or ambient doses: 0.00044-0.105 f/cc year).

  10. Preliminary Study on the Standards of Operation Ventilation of Diesel Traction in High- altitude Tunnel%高海拔隧道内燃牵引运营通风标准研究

    Institute of Scientific and Technical Information of China (English)

    孙三祥; 张云霞; 李国良; 杨国柱; 谢君泰

    2011-01-01

    Research purposes: In order to solve the problem of standards about allowable concentration of harmful emission gases to operation ventilation of diesel traction in high - altitude ( >3 000 m) tunnel. Based on the comparison results of operation ventilation standards and allowable concentrations of harmful emission gases, CO, NO2 control of the maximum allowable concentration, the suggestion standards of operation ventilation control of diesel traction in high altitude tunnel is presented.Research conclusions: The national standards is more stringent than the developed countrie' s. The suggestion standards of operation ventilation control of diesel traction in high altitude tunnel are that time weightd average ( TWA) of Noχ (nitragen dioxide level) is 10 mg/m3 in workday, short term(30 min)exposure limit of Noχ≤30 mg/m3. TWA of CO is 30 mg/m3 in workday, short term(30 min)exposure limit of CO≤90 mg/m3.%目前国内高海拔地区(海拔>3 000 m)隧道内燃牵引运营通风设计中,有害气体容许浓度没有相应的规范可参照.通过国内外高、低海拔地区CO、NO2最高容许浓度的比较,国内外隧道运营通风与环境控制标准检索、分析,提出高海拔隧道内燃牵引运营通风控制标准建议值.研究结论:国内相关规范(标准)规定的有害气体最高容许浓度比国外发达国家的标准要求高.初步建议高海拔运营隧道内空气中内燃机车废气的容许浓度:NOx(以NO2计):工作日内平均容许浓度为10 mg/m3,工作日内任何一次30 min内接触废气的平均浓度不超过30 mg/m3.CO:工作日内平均容许浓度为30 mg/m3,工作日内任何一次30 min内接触废气的平均浓度不超过90 mg/m3.

  11. Airborne total gaseous mercury and exposure in a Venezuelan mining area.

    Science.gov (United States)

    Garcia-Sanchez, Antonio; Contreras, Felicia; Adams, Meliton; Santos, Fernando

    2006-10-01

    This paper presents a short-term monitoring study of total gaseous mercury (TGM) in air, and exposure to airborne mercury. The evaluation was carried out in polluted mining sites (El Callao, Venezuela), where for decades mercury has been used in diverse stages of gold mining activities. The contamination is mainly due to emission of Hg0 during gold amalgamation and burning, which can cause direct human health risks. Total gaseous mercury (TGM) in air was analysed in mill, jewellery and indoor house sites, and at different heights (height profiles near the surface) at polluted and not polluted sites. Mercury concentration in air was measured with a portable mercury analyser (Lumex Ra-915+). Time weighted average mercury (TWA) was calculated for the evaluation of mercury exposure. TWA values ranged between 0.28 microg m(-3) and >100 microg m(-3). These measurements were done during sunny and dry days. In the case of mills and gold workshops, the values were over the limit recommended by the World Health Organization to exposure (25 microg m(-3)) and NIOSH limit (50 microg m(-3)). Indoors in a house, the air Hg average value was 2.58 microg m(-3) exceeding EPA (0.3 microg m(-3)) and ATSDR (1 microg m(-3)) guidelines. The mercury concentration at different height profiles, varied between 1766 microg m(-3) and 0.014 microg m(-3). Mercury height profiles were described by a power function model of the form c(Hg) = ah(-b), where a parameter describes the magnitude of Hg emission. For polluted sites there was a significant correlation between a and Hg in soil or Hg emission from soil to air, while b is only significantly correlated with air temperature. An air and soil mercury measurement transect was carried out at a mill site up to a distance of 1000 m, and it was observed that the air mercury concentration decreases with increasing distance from the mill site, and inversely to Hg soil content.

  12. Asbestos exposures of mechanics performing clutch service on motor vehicles.

    Science.gov (United States)

    Cohen, Howard J; Van Orden, Drew R

    2008-03-01

    and frequency of this task, the incremental contribution of this task to mechanics' 8-hr time-weighted average (TWA) asbestos exposures was 0.0016 flcc. Using the range of data inputs that were obtained, the authors calculated a range of TWA exposures of 3.75 x 10(-5) flcc to 0.03 flcc. The mean value of 0.0016 flcc is below background levels of asbestos that have been reported in garages during this time and below the current OSHA PEL of 0.1 flcc.

  13. High Power Diode Laser-Treated HP-HVOF and Twin Wire Arc-Sprayed Coatings for Fossil Fuel Power Plants

    Science.gov (United States)

    Mann, B. S.

    2013-08-01

    This article deals with high power diode laser (HPDL) surface modification of twin wire arc-sprayed (TWAS) and high pressure high velocity oxy-fuel (HP-HVOF) coatings to combat solid particle erosion occurring in fossil fuel power plants. To overcome solid particle impact wear above 673 K, Cr3C2-NiCr-, Cr3C2-CoNiCrAlY-, and WC-CrC-Ni-based HVOF coatings are used. WC-CoCr-based HVOF coatings are generally used below 673 K. Twin wire arc (TWA) spraying of Tafa 140 MXC and SHS 7170 cored wires is used for a wide range of applications for a temperature up to 1073 K. Laser surface modification of high chromium stainless steels for steam valve components and LPST blades is carried out regularly. TWA spraying using SHS 7170 cored wire, HP-HVOF coating using WC-CoCr powder, Ti6Al4V alloy, and high chromium stainless steels (X20Cr13, AISI 410, X10CrNiMoV1222, 13Cr4Ni, 17Cr4Ni) were selected in the present study. Using robotically controlled parameters, HPDL surface treatments of TWAS-coated high strength X10CrNiMoV1222 stainless steel and HP-HVOF-coated AISI 410 stainless steel samples were carried out and these were compared with HPDL-treated high chromium stainless steels and titanium alloy for high energy particle impact wear (HEPIW) resistance. The HPDL surface treatment of the coatings has improved the HEPIW resistance manifold. The improvement in HPDL-treated stainless steels and titanium alloys is marginal and it is not comparable with that of HPDL-treated coatings. These coatings were also compared with "as-sprayed" coatings for fracture toughness, microhardness, microstructure, and phase analyses. The HEPIW resistance has a strong relationship with the product of fracture toughness and microhardness of the HPDL-treated HP-HVOF and TWAS SHS 7170 coatings. This development opens up a possibility of using HPDL surface treatments in specialized areas where the problem of HEPIW is very severe. The HEPIW resistance of HPDL-treated high chromium stainless steels and

  14. Electrocardiogram in pneumonia.

    Science.gov (United States)

    Stein, Paul D; Matta, Fadi; Ekkah, Maan; Saleh, Tarek; Janjua, Muhammad; Patel, Yash R; Khadra, Helmi

    2012-12-15

    Findings on electrocardiogram may hint that pulmonary embolism (PE) is present when interpreted in the proper context and lead to definitive imaging tests. However, it would be useful to know if electrocardiographic (ECG) abnormalities also occur in patients with pneumonia and whether these are similar to ECG changes with PE. The purpose of this investigation was to determine ECG findings in patients with pneumonia. We retrospectively evaluated 62 adults discharged with a diagnosis of pneumonia who had no previous cardiopulmonary disease and had electrocardiogram obtained during hospitalization. The most prevalent ECG abnormality, other than sinus tachycardia, was minor nonspecific ST-segment or T-wave changes occurring in 13 of 62 (21%). Right atrial enlargement occurred in 4 of 62 (6.5%). QRS abnormalities were observed in 24 of 62 (39%). Right-axis deviation and S(1)S(2)S(3) were the most prevalent QRS abnormalities, which occurred in 6 of 62 (9.7%). Complete right bundle branch block and S(1)Q(3)T(3) pattern occurred in 3 of 62 (4.8%). ECG abnormalities that were not present within 1 month previously or abnormalities that disappeared within 1 month included left-axis deviation, right-axis deviation, right atrial enlargement, right ventricular hypertrophy, S(1)S(2)S(3), S(1)Q(3)T(3), low-voltage QRS complexes, and nonspecific ST-segment or T-wave abnormalities. In conclusion, electrocardiogram in patients with pneumonia often shows QRS abnormalities or nonspecific ST-segment or T-wave changes. ECG findings are similar to ECG abnormalities in PE and electrocardiogram cannot assist in the differential diagnosis.

  15. A comparison of two-dimensional techniques for converting magnetocardiogram maps into effective current source distributions.

    Science.gov (United States)

    Ogata, K; Kandori, A; Miyashita, T; Sekihara, K; Tsukada, K

    2011-01-01

    The aim of this study was to develop a method for converting the pseudo two-dimensional current given by a current-arrow map (CAM) into the physical current. The physical current distribution is obtained by the optimal solution in a least mean square sense with Tikhonov regularization (LMSTR). In the current dipole simulation, the current pattern differences (ΔJ) between the results of the CAM and the LMSTR with several regularization parameters (α = 10(-1)-10(-15)) are calculated. In magnetocardiographic (MCG) analysis, the depth (z(d)) of a reconstruction plane is chosen by using the coordinates of the sinus node, which is estimated from MCG signals at the early p-wave. The ΔJs at p-wave peaks, QRS-complex peaks, and T-wave peaks of MCG signals for healthy subjects are calculated. Furthermore, correlation coefficients and regression lines are also calculated from the current values of the CAM and the LMSTR during p-waves, QRS-complex, and T-waves of MCG signals. In the simulation, the ΔJs (α ≈ 10(-10)) had a minimal value. The ΔJs (α = 10(-10)) at p-wave peaks, QRS-complex peaks, and T-wave peaks of MCG signals for healthy subjects also had minimal value. The correlation coefficients of the current values given by the CAM and the LMSTR (α = 10(-10)) were greater than 0.9. Furthermore, slopes (y) of the regression lines are correlated with the depth (z(d)) (r = -0.93). Consequently, the CAM value can be transformed into the LMSTR current value by multiplying it by the slope (y) obtained from the depth (z(d)). In conclusion, the result given by the CAM can be converted into an effective physical current distribution by using the depth (z(d)).

  16. Study on the relationship between the changes of electrocardiogram and quality of life in patients after interventional treatment of acute coronary syndrome%急性冠脉综合征介入术后心电图的变化情况与患者生活质量的关系研究

    Institute of Scientific and Technical Information of China (English)

    严颖; 魏丽萍

    2015-01-01

    Objective To investigate the acute coronary syndrome (ACS) and the relationship between changes of quali-ty of life in patients with ECG after PCI. Methods 124 cases of PCI intervention in ACS patients in Traditional Chi-nese Medical Hospital of Hangzhou City from November 2011 to November 2014 were selected as the research objects, and they were divided into two groups according to the postoperative 1 h ST down more than 50% and the 24 h T wave inversion respectively. 80 patients of postoperative 1 h ST segment elevation ≥ 50% was 1 h ST segment elevation ≥50% group, and 44 cases patients of postoperative 1 h ST segment elevation < 50% was 1 h ST segment elevation <50% group; 85 patients of 24 h inverted T wave was T wave inversion group, and 39 patients with T wave non-inver-sion was T wave non-inversion group. The quality of life postoperative 3 months of patients in the four groups was e-valuated by the SF-36 scale, the relation between the changes of the electrocardiogram and life quality of patients with ACS after PCI was discussed;and the cardiac function of 3 months with postoperative of patients in the four groups was determined. Results According to the SF-36 scale, each dimension (physiological function, psychological function, body pain, general health, vitality, social function, emotional function, mental health, physical health-related quality of life, psychological quality of life score and total score) of 1 h ST segment elevation ≥ 50% group were significantly higher than that of 1 h ST segment < 50% group (P< 0.05), the scores of T wave inversion group were significantly higher than that of T wave non-inversion group (P < 0.05);LVEF, Em/Am, LVED of the 1 h ST segment elevation ≥50%group after 3 months were significantly higher than that of the 1 h ST segment<50% group (P<0.05), above indexes of T wave inversion group were significantly higher than T wave non-inversion group (P<0.05); LVDD of the 1 h ST segment elevation ≥ 50% group was

  17. Non-invasive electrocardiogram detection of in vivo zebrafish embryos using electric potential sensors

    Science.gov (United States)

    Rendon-Morales, E.; Prance, R. J.; Prance, H.; Aviles-Espinosa, R.

    2015-11-01

    In this letter, we report the continuous detection of the cardiac electrical activity in embryonic zebrafish using a non-invasive approach. We present a portable and cost-effective platform based on the electric potential sensing technology, to monitor in vivo electrocardiogram activity from the zebrafish heart. This proof of principle demonstration shows how electrocardiogram measurements from the embryonic zebrafish may become accessible by using electric field detection. We present preliminary results using the prototype, which enables the acquisition of electrophysiological signals from in vivo 3 and 5 days-post-fertilization zebrafish embryos. The recorded waveforms show electrocardiogram traces including detailed features such as QRS complex, P and T waves.

  18. Cerebrogenic tachyarrhythmia in acute stroke

    Directory of Open Access Journals (Sweden)

    A S Praveen Kumar

    2012-01-01

    Full Text Available The electrocardiac abnormalities following acute stroke are frequent and seen in both ischemic and hemorrhagic stroke. The changes seen in electrocardiogram (ECG consist of repolarization abnormalities such as ST elevation, ST depression, negative T waves, and QT prolongation. Among tachyarrhythmias, atrial fibrillation is the most common and occurrence of focal atrial tachycardia is very rare though any cardiac arrhythmias can follow acute stroke. We report a case of focal atrial tachycardia following acute ischemic stroke in 50-year-old female without structural heart disease, and their mechanisms and clinical implications.

  19. Electrocardiographic surrogates of structural myocardial alterations in the Dorper sheep heart

    Directory of Open Access Journals (Sweden)

    J. Ker

    2005-09-01

    Full Text Available In this study we evaluated the validity of well-known human electrocardiographic markers of myocardial pathology in Dorper sheep. These markers include: the duration of the QRS complex of premature ventricular complexes (PVCs, the presence of notching of the QRS complex of PVCs and change of the ST-segment of PVCs. It was shown that these three electrocardiographic phenomena correlate with myocardial pathology in the hearts of Dorper sheep. We also describe a new electrocardiographic indicator of myocardial pathology, namely an increase in the frequency of cardiac memory T waves as a new electrocardiographic surrogate for myocardial pathology in the hearts of Dorper sheep.

  20. Clinical Evaluation of Xylazine-Butorphanol-Guaifenesin-Ketamine as Short-Term TIVA in Equines

    OpenAIRE

    Bhanu Partap Singh Thakur; Sandeep Kumar Sharma; Arvind Sharma; Adarsh Kumar

    2011-01-01

    Xylazine (1.1 mg/kg), butorphanol (0.02 mg/kg), guaifenesin 5% (20 mg/kg), and ketamine (2.2 mg/kg) combinations were able to induce short-term surgical anaesthesia for 23.33 ± 2.57 min in Spiti ponies with excellent to good muscle relaxation and analgesia. Urination and neighing was a constant feature during recovery period. Biphasic P wave, biphasic T wave, and depressed PR segment were common electrocardiographic findings. Biochemical attributes were within physiological limits except a si...

  1. The fifth takotsubo variant.

    Science.gov (United States)

    Bridgman, Paul G; Chan, Christina W

    2017-01-01

    We document the fifth pattern of takotsubo cardiomyopathy, in which the mid-LV is hyperdynamic but the apex and base are akinetic or hypokinetic. This is a reverse mid-ventricular takotsubo. The patient is a 79-year-old woman admitted with chest pain and initially a normal EKG. Her troponin I rose to 5.4 μg/L (0.02-0.03 μg/L) and she developed QT prolongation and widespread T-wave inversion. Coronary angiography showed only very mild atheroma. Follow-up echocardiogram six weeks later showed normal left ventricular function. © 2016, Wiley Periodicals, Inc.

  2. Coexistence of Wolff-Parkinson-white and Brugada syndrome: mere curiosity?

    Science.gov (United States)

    Kaiser, Elisabeth; Sacilotto, Luciana; Darrieux, Francisco; Sosa, Eduardo

    2014-09-01

    The association between Brugada syndrome (BS) and ventricular preexcitation is a rare condition, with sporadic cases already reported. We report the case of a 29-year-old man, with palpitation unrelated to physical or emotional stress. The electrocardiogram of the first visit revealed a ventricular preexcitation pattern and an end-conduction delay, with negative T wave in V1 and intraventricular conduction disturbance in V2 (atypical for BS). The typical aspect of BS occurred after introduction of propafenone for the prevention of atrioventricular tachycardia. We discuss the recognition of this rare association, the proarrhythmic effects of some drugs, treatment options, and prognosis.

  3. Pancreatitis with Electrocardiographic Changes Mimicking Acute Myocardial Infarction

    Directory of Open Access Journals (Sweden)

    Paul Khairy

    2001-01-01

    Full Text Available A 64-year-old woman with mild acute pancreatitis presented with epigastric pain, nausea and vomiting while undergoing hemodialysis for chronic renal insufficiency. Serial electrocardiograms revealed new onset ST segment elevations in leads V2 to V4 mimicking an anterior myocardial infarction, followed by diffusely inverted deep T waves. No cardiac pathology was demonstrated by echocardiography or coronary angiography. A review of the literature and possible pathophysiological mechanisms of electrocardiographic changes in acute pancreatitis, such as metabolic abnormalities, hemodynamic instability, vasopressors, pericarditis, myocarditis, a cardiobiliary reflex, exacerbation of underlying cardiac pathology, coagulopathy and coronary vasospasm, are discussed.

  4. A rare form of extremely wide QRS complex due to reversed homologous electrical ventricular separation of acute heart failure.

    Science.gov (United States)

    Yan, Sujuan; Yu, Jianhua; Xia, Zhen; Zhu, Bo; Hu, Jinzhu; Li, Juxiang

    2017-06-29

    Electrical ventricular separation, as a special complete intraventricular block, denotes that ventricles be electrically separated into two or more parts caused by severe and wide damage of myocardium and conduction. Electrical ventricular separation can be divided into homologous and heterologous, homologous electrical ventricular separation is a rare phenomenon, literally the excitement of whole ventricle originate from supraventricle, on ECG, there are two different QRS waves which connect with an isoelectric line, one ST segment and T wave. We report a valve heart disease presented with complicated electrophysiological characteristics, which has reversed complex homologous electrical ventricular separation with second degree intraventricular block. © 2017 Wiley Periodicals, Inc.

  5. The genetic basis of long QT and short QT syndromes: a mutation update

    DEFF Research Database (Denmark)

    Hedley, Paula L; Jørgensen, Poul; Schlamowitz, Sarah;

    2009-01-01

    Long QT and short QT syndromes (LQTS and SQTS) are cardiac repolarization abnormalities that are characterized by length perturbations of the QT interval as measured on electrocardiogram (ECG). Prolonged QT interval and a propensity for ventricular tachycardia of the torsades de pointes (TdP) type...... are characteristic of LQTS, while SQTS is characterized by shortened QT interval with tall peaked T-waves and a propensity for atrial fibrillation. Both syndromes represent a high risk for syncope and sudden death. LQTS exists as a congenital genetic disease (cLQTS) with more than 700 mutations described in 12 genes...

  6. Tuberous sclerosis and cardiac tumors: new electrocardiographic finding in an infant.

    Science.gov (United States)

    Aslan, Eyup; Sap, Fatih; Sert, Ahmet; Odabas, Dursun

    2014-10-01

    Cardiac rhabdomyoma, the primary cardiac tumor most often diagnosed in children, is frequently present in patients with tuberous sclerosis. Most pediatric patients with rhabdomyoma are asymptomatic; however, various electrocardiographic abnormalities can be detected, such as Wolff-Parkinson-White syndrome, ectopic atrial tachycardia, and atrioventricular node dysfunction. We describe the case of a 10-month-old infant girl who had tuberous sclerosis and multiple cardiac rhabdomyomas. Her electrocardiographic presentation was notable for dome-shaped T waves and no ST segment in some leads. To our knowledge, this electrocardiographic finding has not been described in patients with tuberous sclerosis and cardiac masses.

  7. Evolutionary change mimicking apical hypertrophic cardiomyopathy in a patient with takotsubo cardiomyopathy.

    Science.gov (United States)

    Hwang, Hui-Jeong; Lee, Hyae-Min; Yang, In-Ho; Kim, Dong-Hee; Byun, Jong-Kyu; Sohn, Il Suk

    2014-11-01

    In this report, we introduce a case of thickening of the involved left ventricular apical segment on echocardiography and deep T-wave inversions in precordial leads on electrocardiography transiently seen in the course of recovery from biventricular takotsubo cardiomyopathy, mimicking apical hypertrophic cardiomyopathy. This result suggests that the echocardiographic finding of transient myocardial edema can be identified by cardiac magnetic resonance imaging in takotsubo cardiomyopathy. Additionally, it persisted a few weeks after full functional recovery. We believe that this case will contribute in part toward clarifying the pathophysiology of takotsubo cardiomyopathy.

  8. Mid-ventricular hypertrophic obstructive cardiomyopathy (MVHOCM)complicated with coronary artery disease: a case report

    Institute of Scientific and Technical Information of China (English)

    Haoming Song; Cuimei Zhao; Jinfa Jiang; Yang Liu; Yihan Chen

    2008-01-01

    Mid-ventricular hypertrophic obstructive cardiomyopathy (MVHOCM) is a rare type of cardiomyopathy thatcan be accompanied by apical aneurysm.We presented here a case report of MVHOCM with cornary artery disease.The sixty-fouryears old man was sent to hospital because of ventricular tachycardia.Large inversion T wave was showed on electrocardiography in the presence of abnormal coronary arteries and normal cardiac enzyme.Echoeardiogmphy showed an hourglass appearance of the leftventricle with an aneurysm in the apex and a pressure gradient between the outflow tract of left ventricle and the middle of the leftventricle was revealed by left-heart catheterization.

  9. A dangerous twist of the ‘T’ wave: A case of Wellens’ Syndrome

    Directory of Open Access Journals (Sweden)

    Kavitha Balasubramanian

    2013-03-01

    Full Text Available Wellens’ syndrome is a condition in which electrocardiographic (ECG changes indicate critical proximal left anterior descending artery narrowing occurring during the chest pain-free period. Due to the severity of the obstruction, if such cases are managed by early invasive revascularisation therapy, a major threat in the form of a massive myocardial infarction or sudden death may be averted. We present the case of a patient with previous chest pain, whose ECG showing subtle ischemic changes was initially overlooked. A repeat ECG taken during the painless period showed a biphasic T wave, suggestive of Wellen’s’ syndrome. This was confirmed by an immediate coronary angiogram.

  10. Left bundle branch block: a rare ECG manifestation of hyperkalemia

    Directory of Open Access Journals (Sweden)

    Venkata Madhav M

    2015-04-01

    Full Text Available A 20-year-old female patient with chronic kidney disease was brought to our emergency medical department with symptoms of pain in chest and abdomen, vomitings. Laboratory testing revealed serum potassium 7.7 mEq/L, serum creatinine 9.1 mg/dL. Electrocardiogram (ECG showed left bundle branch block (LBBB pattern with left axis deviation, tall T waves and ST elevation. Among ECG alterations in hyperkalemia, LBBB is rare and is being reported in our case.

  11. EL FENÓMENO DE LA MEMORIA ELÉCTRICA: UN GRAN SIMULADOR. PRESENTACIÓN DE DOS CASOS / Electrical memory phenomenon - a great deceiver. Presentation of two cases

    OpenAIRE

    Raimundo Carmona Puerta; Ramiro R. Ramos Ramírez; Arnaldo Rodríguez León; Gustavo Padrón Peña; Elibet Chávez González; Juan Miguel Cruz Elizundia

    2010-01-01

    Resumen Presentamos dos pacientes en los que se desarrollaron ondas T negativas que aparecen en el electrocardiograma por la memoria eléctrica cardíaca. Este fenómeno aunque fue descrito hace muchos años es causa de interpretación errónea de ondas T debido a isquemia cardíaca, y puede ser visto en ciertas situaciones clínicas que permiten sospechar su presencia. / Abstract We present two patients in whom negative T waves are developed, and appeared in the electrocardiogram as a result of the ...

  12. Organic Membranes for Selectivity Enhancement of Metal Oxide Gas Sensors

    Directory of Open Access Journals (Sweden)

    Thorsten Graunke

    2016-01-01

    Full Text Available We present the characterization of organic polyolefin and thermoplastic membranes for the enhancement of the selectivity of metal oxide (MOX gas sensors. The experimental study is done based on theoretical considerations of the membrane characteristics. Through a broad screening of dense symmetric homo- and copolymers with different functional groups, the intrinsic properties such as the mobility or the transport of gases through the matrix were examined in detail. A subset of application-relevant gases was chosen for the experimental part of the study: H2, CH4, CO, CO2, NO2, ethanol, acetone, acetaldehyde, and water vapor. The gases have similar kinetic diameters and are therefore difficult to separate but have different functional groups and polarity. The concentration of the gases was based on the international indicative limit values (TWA, STEL. From the results, a simple relationship was to be found to estimate the permeability of various polar and nonpolar gases through gas permeation (GP membranes. We used a broadband metal oxide gas sensor with a sensitive layer made of tin oxide with palladium catalyst (SnO2:Pd. Our aim was to develop a low-cost symmetrical dense polymer membrane to selectively detect gases with a MOX sensor.

  13. Assessment of airborne asbestos exposure during the servicing and handling of automobile asbestos-containing gaskets.

    Science.gov (United States)

    Blake, Charles L; Dotson, G Scott; Harbison, Raymond D

    2006-07-01

    Five test sessions were conducted to assess asbestos exposure during the removal or installation of asbestos-containing gaskets on vehicles. All testing took place within an operative automotive repair facility involving passenger cars and a pickup truck ranging in vintage from late 1960s through 1970s. A professional mechanic performed all shop work including engine disassembly and reassembly, gasket manipulation and parts cleaning. Bulk sample analysis of removed gaskets through polarized light microscopy (PLM) revealed asbestos fiber concentrations ranging between 0 and 75%. Personal and area air samples were collected and analyzed using National Institute of Occupational Safety Health (NIOSH) methods 7400 [phase contrast microscopy (PCM)] and 7402 [transmission electron microscopy (TEM)]. Among all air samples collected, approximately 21% (n = 11) contained chrysotile fibers. The mean PCM and phase contrast microscopy equivalent (PCME) 8-h time weighted average (TWA) concentrations for these samples were 0.0031 fibers/cubic centimeters (f/cc) and 0.0017 f/cc, respectively. Based on these findings, automobile mechanics who worked with asbestos-containing gaskets may have been exposed to concentrations of airborne asbestos concentrations approximately 100 times lower than the current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) of 0.1 f/cc.

  14. Fugitive emissions from nanopowder manufacturing

    Science.gov (United States)

    Trompetter, W. J.; Ancelet, T.; Davy, P. K.; Kennedy, J.

    2016-07-01

    In response to health and safety questions and concerns regarding particulate matter emissions from equipment used for synthesizing NiFe and TiO2 nanopowders, a study was undertaken to assess their impact on the air quality inside and outside a laboratory where the manufacturing equipment is operated. Elemental concentrations determined by ion beam analysis (IBA) of air particulate matter (PM) samples collected hourly with a StreakerTM sampler were used to identify possible sources and estimate contributions from nanopowder production and other sources. The fugitive nanopowder emissions were the highest at the indoor sampling location when powders were being manufactured. Average fugitive emissions of 210 ng m-3 (1-h average) (maximum 2163 ng m-3 1-h average) represented 2 % (maximum 20 %) of the average PM collected (9359 ng m-3 1-h average). The measured NiFe alloy or TiO2 PM concentrations were much smaller than the 8-h time-weighted average (TWA) workplace exposure standards (WES) for these materials (≥1,000,000 ng m-3). Most PM was found to be from infiltrated outdoor ambient sources. This suggests that nanopowder production in the laboratory is not likely to have adverse health effects on individuals using the equipment, although further improvements can be made to further limit exposure.

  15. Beyond Conflict and Spoilt Identities: How Rwandan Leaders Justify a Single Recategorization Model for Post-Conflict Reconciliation

    Directory of Open Access Journals (Sweden)

    Sigrun Marie Moss

    2014-08-01

    Full Text Available Since 1994, the Rwandan government has attempted to remove the division of the population into the ‘ethnic’ identities Hutu, Tutsi and Twa and instead make the shared Rwandan identity salient. This paper explores how leaders justify the single recategorization model, based on nine in-depth semi-structured interviews with Rwandan national leaders (politicians and bureaucrats tasked with leading unity implementation conducted in Rwanda over three months in 2011/2012. Thematic analysis revealed this was done through a meta-narrative focusing on the shared Rwandan identity. Three frames were found in use to “sell” this narrative where ethnic identities are presented as a an alien construction; b which was used to the disadvantage of the people; and c non-essential social constructs. The material demonstrates the identity entrepreneurship behind the single recategorization approach: the definition of the category boundaries, the category content, and the strategies for controlling and overcoming alternative narratives. Rwandan identity is presented as essential and legitimate, and as offering a potential way for people to escape spoilt subordinate identities. The interviewed leaders insist Rwandans are all one, and that the single recategorization is the right path for Rwanda, but this approach has been criticised for increasing rather than decreasing intergroup conflict due to social identity threat. The Rwandan case offers a rare opportunity to explore leaders’ own narratives and framing of these ‘ethnic’ identities to justify the single recategorization approach.

  16. Polar organic chemical integrative samplers for pesticides monitoring: impacts of field exposure conditions.

    Science.gov (United States)

    Lissalde, Sophie; Mazzella, Nicolas; Mazellier, Patrick

    2014-08-01

    This study focuses on how Polar Organic Chemical Integrative Samplers (POCIS) work in real environmental conditions. A selection of 23 polar pesticides and 8 metabolites were investigated by exposure of triplicates of integrative samplers in two rivers in France for successive 14-day periods. The pesticides and metabolites were trapped not only in Oasis HLB sorbent but also in the polyethersulfone (PES) membrane of the POCIS. The distribution of pesticides depended on the molecular structure. The use of the Performance Reference Compound (PRC) is also discussed here. The impact of some environmental parameters and exposure setup on the transfer of pesticides in POCIS sorbent was studied: river flow rate, biofouling on membranes, sampler holding design and position in the stream. Results show a significant impact of river flow velocity on PRC desorption, especially for values higher than 4 cm·s(-1). Some fouling was observed on the PES membrane which could potentially have an impact on molecule accumulation in the POCIS. Finally, the positioning of the sampler in the river did not have significant effects on pesticide accumulation, when perpendicular exposures were used (sampler positioning in front of the water flow). The POCIS with PRC correction seems to be a suitable tool for estimating time-weighted average (TWA) concentrations, for all the molecules except for one of the nine pesticides analyzed in these two French rivers.

  17. Metal Dust Exposure and Respiratory Health of Male Steel Work¬ers in Terengganu, Malaysia

    Directory of Open Access Journals (Sweden)

    Nurul Ainun HAMZAH

    2015-10-01

    Full Text Available Background: This cross sectional study was carried out to determine the relationship between metal dust exposure and respiratory health in male steel workers in Terengganu, Malaysia.Methods: Subjects were interviewed using a structured questionnaire from British Medical Research Council (BMRC Questionnaire regarding respiratory symptoms and were examined their lung function using spirometer.Results: The mean trace metal dusts concentration TWA8 for cobalt and chromium in most of work unit exceeded occupational exposure prescribed values. Prevalence of chest tightness, chronic phlegm, and shortness of breath was 28.0%, 26.8%, 24.1%, and 20.2% respectively. Age and smoking were among the factors associated with respiratory symptoms (OR: 0.92 – 1.78. Smoking and cumulative respirable metal dust were negatively associated with FEV1.Conclusion: The mean metal dust for cobalt and chromium were 1 to 2 times higher than permissible exposure limit (PEL. This study found that respirable cumulative metal dust exposure is one of the contributing factors to lung function values among steel workers. Keywords: Respiratory symptoms, Lung function, Metal dust, Questionnaire

  18. Monitoring tylosin and sulfamethazine in a tile-drained agricultural watershed using polar organic chemical integrative sampler (POCIS).

    Science.gov (United States)

    Washington, Maurice T; Moorman, Thomas B; Soupir, Michelle L; Shelley, Mack; Morrow, Amy J

    2017-08-27

    This study evaluated the influence of temporal variation on the occurrence, fate, and transport of tylosin (TYL) and sulfamethazine (SMZ); antibiotics commonly used in swine production. Atrazine (ATZ) was used as a reference analyte to indicate the agricultural origin of the antibiotics. We also assessed the impact of season and hydrology on antibiotic concentrations. A reconnaissance study of the South Fork watershed of the Iowa River (SFIR), was conducted from 2013 to 2015. Tile drain effluent and surface water were monitored using polar organic integrative sampler (POCIS) technology. Approximately 169 animal feeding operations (AFOs) exist in SFIR, with 153 of them being swine facilities. All analytes were detected, and detection frequencies ranged from 69 to 100% showing the persistence in the watershed. Antibiotics were detected at a higher frequency using POCIS compared to grab samples. We observed statistically significant seasonal trends for SMZ and ATZ concentrations during growing and harvest seasons. Time weighted average (TWA) concentrations quantified from the POCIS were 1.87ngL(-1) (SMZ), 0.30ngL(-1) (TYL), and 754.2ngL(-1) (ATZ) in the watershed. SMZ and TYL concentrations were lower than the minimum inhibitory concentrations (MIC) for E. coli. All analytes were detected in tile drain effluent, confirming tile drainage as a pathway for antibiotic transport. Our results identify the episodic occurrence of antibiotics, and highlights the importance identifying seasonal fate and occurrence of these analytes. Published by Elsevier B.V.

  19. Chapter 8 Tool for monitoring hydrophilic contaminants in water: polar organic chemical integrative sampler (POCIS)

    Science.gov (United States)

    Alvarez, David A.; Huckins, James N.; Petty, Jimmie D.; Jones-Lepp, Tammy L.; Stuer-Lauridsen, Frank; Getting, Dominic T.; Goddard, Jon P.; Gravell, Anthony

    2007-01-01

    The development of the polar organic chemical integrative sampler (POCIS) provides environmental scientists and policy makers a tool for assessing the presence and potential impacts of the hydrophilic component of these organic contaminants. The POCIS provides a means for determining the time-weighted average (TWA) concentrations of targeted chemicals that can be used in risk assessments to determine the biological impact of hydrophilic organic compounds (HpOCs) on the health of the impacted ecosystem. Field studies have shown that the POCIS has advantages over traditional sampling methods in sequestering and concentrating ultra-trace to trace levels of chemicals over time resulting in increased method sensitivity, ability to detect chemicals with a relatively short residence time or variable concentrations in the water, and simplicity in use. POCIS extracts can be tested using bioassays and can be used in organism dosing experiments for determining toxicological significance of the complex mixture of chemicals sampled. The POCIS has been successfully used worldwide under various field conditions ranging from stagnant ponds to shallow creeks to major river systems in both fresh and brackish water.

  20. The young binary HD 102077: Orbit, spectral type, kinematics, and moving group membership

    CERN Document Server

    Wöllert, Maria; Reffert, Sabine; Schlieder, Joshua E; Mohler-Fischer, Maren; Köhler, Rainer; Henning, Thomas

    2014-01-01

    The K-type binary star HD 102077 was proposed as a candidate member of the TW Hydrae Association (TWA) which is a young (5-15 Myr) moving group in close proximity (~50 pc) to the solar system. The aim of this work is to verify this hypothesis by different means. We first combine diffraction-limited observations from the ESO NTT 3.5m telescope in SDSS-i' and -z' passbands and ESO 3.6m telescope in H-band with literature data to obtain a new, amended orbit fit, estimate the spectral types of both components, and reanalyse the Hipparcos parallax and proper motion taking the orbital motion into account. Moreover, we use two high-resolution spectra of HD 102077 obtained with the fibre-fed optical echelle spectrograph FEROS at the MPG/ESO 2.2m telescope to determine the radial velocity and the lithium equivalent width of the system. The trajectory of HD 102077 is well constrained and we derive a total system mass of $2.6 \\pm 0.8\\,$ M$_{\\odot}$ and a semi-major axis of $14.9 \\pm 1.6\\,$AU. From the i'-z' colours we i...