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1.
Mymensingh Med J ; 22(2): 413-6, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23715373

RESUMO

Infection with Burkholderia pseudomallei has been described, albeit rarely, patients in Bangladesh. Infection usually follows percutaneous inoculation or inhalation of the causative bacterium, which is present in soil and surface water in the endemic region. A 35-year-young male farmer presented with prolonged fever and significant weight loss. Patient gradually deteriorated despite getting different antibiotics including intravenous ceftriaxone and metronidazole. Panels of investigations were done which revealed no diagnostic confirmation except uncontrolled diabetes and multiple abscesses in different organs. Melioidosis was suspected and serum samples were positive for Burkholderia pseudomallei antibody. The case illustrates the importance of non-specific nature of the clinical presentation and high index of suspicion of uncommon diseases like melioidosis where the disease has not been considered as an endemic.


Assuntos
Melioidose/diagnóstico , Adulto , Antibacterianos/uso terapêutico , Diagnóstico Diferencial , Quimioterapia Combinada , Humanos , Masculino , Melioidose/tratamento farmacológico
2.
Phys Rev Lett ; 110(15): 152502, 2013 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-25167256

RESUMO

The second J(π)=2+ state of 12C, predicted over 50 years ago as an excitation of the Hoyle state, has been unambiguously identified using the 12C(γ,α0)(8)Be reaction. The alpha particles produced by the photodisintegration of 12C were detected using an optical time projection chamber. Data were collected at beam energies between 9.1 and 10.7 MeV using the intense nearly monoenergetic gamma-ray beams at the HIγS facility. The measured angular distributions determine the cross section and the E1-E2 relative phases as a function of energy leading to an unambiguous identification of the second 2+ state in 12C at 10.03(11) MeV, with a total width of 800(130) keV and a ground state gamma-decay width of 60(10) meV; B(E2:2(2)+→0(1)+)=0.73(13)e(2) fm(4) [or 0.45(8) W.u.]. The Hoyle state and its rotational 2+ state that are more extended than the ground state of 12C presents a challenge and constraints for models attempting to reveal the nature of three alpha-particle states in 12C. Specifically, it challenges the ab initio lattice effective field theory calculations that predict similar rms radii for the ground state and the Hoyle state.

3.
Phys Rev Lett ; 110(20): 202501, 2013 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-25167400

RESUMO

The first measurement of the three-body photodisintegration of longitudinally polarized (3)He with a circularly polarized γ-ray beam was carried out at the High Intensity γ-ray Source facility located at Triangle Universities Nuclear Laboratory. The spin-dependent double-differential cross sections and the contributions from the three-body photodisintegration to the (3)He Gerasimov-Drell-Hearn integrand are presented and compared with state-of-the-art three-body calculations at the incident photon energies of 12.8 and 14.7 MeV. The data reveal the importance of including the Coulomb interaction between protons in three-body calculations.

4.
Phys Rev Lett ; 108(4): 042502, 2012 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-22400829

RESUMO

The two-body photodisintegration cross section of (4)He into a proton and triton was measured with monoenergetic photon beams in 0.5 MeV energy steps between 22 and 30 MeV. High-pressure (4)He-Xe gas scintillators of various (4)He/Xe ratios served as targets and detectors. Pure Xe gas scintillators were used for background studies. A NaI detector together with a plastic scintillator paddle was employed for determining the incident photon flux. Our comprehensive data set follows the trend of the theoretical calculations of the Trento group very well, although our data are consistently lower in magnitude by about 5%. However, they differ significantly from the majority of the previous data, especially from the recent data of Shima et al. The latter data had put into question the validity of theoretical approaches used to calculate core-collapse supernova explosions and big-bang nucleosynthesis abundances of certain light nuclei.


Assuntos
Raios gama , Hélio/química , Trítio/química , Modelos Químicos , Processos Fotoquímicos , Radioatividade , Xenônio/química
5.
Phys Rev Lett ; 107(22): 222501, 2011 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-22182024

RESUMO

The intense, nearly monoenergetic, 100% polarized γ-ray beams available at the HIγS facility, along with the realization that the E1-E2 interference term that appears in the Compton scattering polarization observable has opposite signs in the forward and backward angles, make it possible to obtain an order-of-magnitude improvement in the determination of the parameters of the isovector giant quadrupole resonance (IVGQR). Accurate IVGQR parameters will lead to a more detailed knowledge of the symmetry energy in the nuclear equation of state which is important for understanding nuclear matter under extreme conditions such as those present in neutron stars. Our new method is demonstrated for the case of (209)Bi.

6.
Phys Rev Lett ; 88(1): 012502, 2002 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-11800940

RESUMO

The quality and intensity of gamma rays at the High Intensity gamma-ray Source are shown to make nuclear resonance fluorescence studies possible at a new level of precision and efficiency. First experiments have been carried out using an intense (10(7) gamma/s) beam of 100% linearly polarized, nearly monoenergetic, gamma rays on the semimagic nucleus (138)Ba. Negative parity quantum numbers have been assigned to 18 dipole excitations of (138)Ba between 5.5 MeV and 6.5 MeV from azimuthal gamma-intensity asymmetries.

7.
Circulation ; 101(25): 2909-15, 2000 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-10869262

RESUMO

BACKGROUND: Signal-averaged ECG (SAECG) reproducibility is reported to have a component that is independent of residual noise. Methods and Results-In group 1, multiple paired SAECGs were obtained to noise levels of 0.3+/-0.1 and 0.5+/-0.2 microV. For the 0.5- and 0. 3-microV noise recordings, QRS duration (QRSd) was 101.2+/-11.3 and 104.6+/-9.6 ms, respectively (P<0.0001), and the differences in paired QRSd (DeltaQRSd) were normally distributed, with variances of 11.4 and 26.2 ms(2) (P<0.0001). Paired SAECGs were obtained in group 2 patients without and with late potentials; DeltaQRSd variance was 3.3 and 217.9 ms(2) (P<0.0001). In group 3, >/=10 SAECGs were acquired at noise levels of 0.2 to 0.8 microV, in 0.1-microV increments. QRSd increased as noise level decreased. The variance was greater in low-noise (0.2 to 0.4 microV) versus higher-noise (0. 5 to 0.8 microV) recordings. In group 4, SAECGs were analyzed with bidirectional and Bispec filters, with no difference in QRSd between the 2 filters and a normally distributed DeltaQRSd. A computer simulation demonstrated that alterations in the phase relationship of noise to signal results in a normal distribution of signal end points. CONCLUSIONS: Within the acceptable noise range for SAECG, lower noise results in longer QRSd and larger variance, suggesting that more accurate recordings may have less reproducibility. The random timing of noise relative to signal results in the distribution/variance of repeated measurements. Statistical strategies may be used to reduce some of this variance and may enhance the diagnostic utility of SAECG.


Assuntos
Eletrocardiografia/métodos , Adulto , Artefatos , Eletrocardiografia/normas , Feminino , Humanos , Masculino , Reprodutibilidade dos Testes
8.
Pacing Clin Electrophysiol ; 20(8 Pt 1): 1936-46, 1997 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-9272531

RESUMO

Heart rate variability analysis has been used to derive indices of sympathetic tone. As different sympathetic stimuli may give rise to divergent changes in heart rate variability, this study was designed to characterize the factors responsible for these divergent responses. Twelve healthy subjects (7 males, age 24.8 +/- 3.1 years) were evaluated. Five-minute electrocardiographic recordings were obtained at baseline, following upright tilt, and during isoproterenol infusion (25 ng/kg per min) under control conditions and following parasympathetic blockade. Data were acquired during spontaneous respiration and when breathing was timed with a metronome (15 breaths/min). Under control conditions, both upright tilt and isoproterenol infusion resulted in significant decreases in the SD and MSSD from baseline values of 69 +/- 3 ms and 64 +/- 5 ms to 48 +/- 4 ms and 21 +/- 5 ms during tilt and 44 +/- 4 ms and 20 +/- 5 ms during isoproterenol infusion, respectively. LF power also significantly increased from 0.47 +/- 0.17 ln (beats/min)2 at baseline to 1.90 +/- 0.20. In (beats/min)2 and 1.34 +/- 0.18. In (beats/min)2 during tilt and isoproterenol infusion, respectively. No change in HF power was noted. Following parasympathetic blockade, all heart rate variability parameters were significantly decreased. No significant change from baseline in the SD, MSSD, or HF power was noted with either tilt or isoproterenol infusion. The LF power increased only with tilt from a baseline value of -3.17 +/- 0.17 in (beats/min)2 to -0.41 +/- 0.19 in (beats/min)2. Similar changes were noted during spontaneous respiration and metronome breathing. These findings demonstrate that the response of the sinus node to beta-adrenergic stimulation depends on the mode of stimulation. In addition, the associated level of parasympathetic tone affects the observed changes in heart rate variability that are associated with sympathetic stimulation.


Assuntos
Frequência Cardíaca/fisiologia , Sistema Nervoso Simpático/fisiologia , Adulto , Atropina/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Eletrocardiografia , Análise Fatorial , Feminino , Frequência Cardíaca/efeitos dos fármacos , Humanos , Isoproterenol/farmacologia , Modelos Lineares , Masculino , Bloqueio Nervoso , Parassimpatolíticos/farmacologia , Respiração/fisiologia , Sistema Nervoso Simpático/efeitos dos fármacos , Simpatomiméticos/farmacologia , Teste da Mesa Inclinada
9.
Pacing Clin Electrophysiol ; 20(7): 1796-9, 1997 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-9249834

RESUMO

The purpose of this study was to assess the effects of autonomic stimulation and blockade on noise levels and to compare the noise measurements in the ST and TP segments of the signal-averaged ECG. Five-minute electrocardiographic data were recorded in 14 normal volunteers (8 males and 6 females; mean age 28.5 +/- 5.0 years) on two separate days (day 1-baseline, epinephrine infusion, isoproterenol infusion, beta-blockade, and combined adrenergic and parasympathetic blockade; day 2-baseline, phenylephrine infusion, parasympathetic blockade, and during phenylephrine infusion following atropine). Signal averaging was done off-line on 100 beats and noise was measured in both the ST and TP segments as the standard deviation of voltage in the segment of interest. For all conditions tested, the mean noise level measured in the ST segment (0.46 +/- 0.16 microV) was significantly less than that measured in the TP segment (0.52 +/- 0.24 microV; P = 0.0003), but there was good correlation between the noise measured in the ST and the TP segment (R2 = 0.62, P < 0.0001). Noise increased with isoproterenol infusion and decreased following adrenergic blockade. In addition, day 2 baseline noise was less than baseline noise on day 1. Finally, neither parasympathetic stimulation or blockade nor alpha-adrenergic stimulation significantly affected signal-averaged electrocardiography (SAECG) noise levels. Thus, the data support the notion that enhanced sympathetic tone increases noise levels and beta-adrenergic blockade may decrease noise levels, likely due to effects from muscle sympathetic nerve activity. These findings are important since the target population for the SAECG are patients with myocardial infarction and congestive heart failure, conditions associated with increased sympathetic tone, which may in turn impact on the reproducibility or technical aspects of the SAECG. In addition, because noise in the ST and TP segments are highly correlated and the noise measured in the ST segment is less than that in the TP segment, uniform adoption of noise measurement in the ST segment seems most appropriate.


Assuntos
Artefatos , Sistema Nervoso Autônomo/fisiologia , Eletrocardiografia/métodos , Processamento de Sinais Assistido por Computador , Antagonistas Adrenérgicos/farmacologia , Agonistas alfa-Adrenérgicos/farmacologia , Antagonistas Adrenérgicos beta/farmacologia , Adulto , Atropina/farmacologia , Fármacos do Sistema Nervoso Autônomo/farmacologia , Sistema Nervoso Autônomo/efeitos dos fármacos , Epinefrina/farmacologia , Feminino , Insuficiência Cardíaca/fisiopatologia , Humanos , Isoproterenol/farmacologia , Masculino , Infarto do Miocárdio/fisiopatologia , Bloqueio Nervoso , Parassimpatolíticos/farmacologia , Fenilefrina/farmacologia , Reprodutibilidade dos Testes , Sistema Nervoso Simpático/efeitos dos fármacos , Sistema Nervoso Simpático/fisiologia , Simpatomiméticos/farmacologia
10.
J Cardiovasc Electrophysiol ; 7(7): 594-602, 1996 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-8807405

RESUMO

INTRODUCTION: Time-and frequency-domain measurements of heart rate variability have been used as indices of parasympathetic tone. However, studies of the effect of parasympathetic stimulation on these indices in humans have yielded conflicting results. METHODS AND RESULTS: This study evaluated the effects of parasympathetic stimulation on heart rate variability. Twelve normal subjects (7 males, 5 females; age 24.8 +/- 3.4 years) were evaluated in the Clinical Research Center. Five-minute ECG recordings were obtained at baseline and during graded phenylephrine infusions (0.3 and 0.6 micrograms/kg per min). Recordings were made during spontaneous respiration and when breathing was timed with a metronome at 15 cycles/min. Heart rate variability analysis was performed using standard time- and frequency-domain parameters. Graded phenylephrine infusion resulted in a progressive increase in blood pressure and RR interval but no consistent changes in heart rate variability for the group. The results during normal versus metronome breathing were similar. Stepwise linear regression analysis revealed that the phenylephrine-induced changes in heart rate variability were inversely correlated with the baseline heart rate variability and not related to the baseline RR interval or the phenylephrine-induced change in RR interval. CONCLUSION: These findings suggest that the respiratory variation in "parasympathetic effect" typically observed at the sinus node can be either increased or decreased by parasympathetic stimulation, depending on the initial level of parasympathetic tone and the intensity of stimulation. This resolves the previously conflicting data. Thus, evaluation of parasympathetic tone using heart rate variability techniques should be cautiously undertaken.


Assuntos
Frequência Cardíaca/fisiologia , Sistema Nervoso Parassimpático/fisiologia , Agonistas alfa-Adrenérgicos/farmacologia , Adulto , Pressão Sanguínea/efeitos dos fármacos , Feminino , Frequência Cardíaca/efeitos dos fármacos , Humanos , Masculino , Sistema Nervoso Parassimpático/efeitos dos fármacos , Fenilefrina/farmacologia , Análise de Regressão , Mecânica Respiratória/efeitos dos fármacos , Mecânica Respiratória/fisiologia , Estimulação Química , Nervo Vago/efeitos dos fármacos , Nervo Vago/fisiologia
11.
J Am Coll Cardiol ; 26(2): 497-502, 1995 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-7608455

RESUMO

OBJECTIVES: This study sought to evaluate the effects of autonomic stimulation and blockade on the signal-averaged P wave duration. BACKGROUND: Signal-averaged P wave duration has been shown to have prognostic implications for patients prone to develop atrial fibrillation, but autonomic influences on the signal-averaged P wave duration have not been studied. METHODS: In 14 healthy volunteers (8 men, 6 women; mean [ +/- SD] age 28.5 +/- 4.8 years, range 22 to 38), signal-averaged P wave duration was measured on day 1 at baseline, during sympathetic stimulation with infusions of epinephrine (50 ng/kg body weight per min) and isoproterenol (50 ng/kg per min), beta-blockade with propranolol (0.2 mg/kg) and autonomic blockade with propranolol followed by atropine (0.04 mg/kg). On a second day, 10 of the 14 subjects returned for repeat baseline recordings and recordings during parasympathetic blockade with atropine (0.04 mg/kg). Signal averaging was performed using a P wave template. Both unfiltered and filtered (least-squares fit filter with 100-ms window) P wave durations were measured. Day to day and interobserver variability were assessed by calculation of intraclass correlation coefficients. RESULTS: The mean ( +/- SD) baseline filtered P wave duration on day 1 was 141 +/- 10 ms. Isoproterenol infusion significantly shortened the P wave duration to 110 +/- 16 ms (p < 0.001), and epinephrine resulted in significant prolongation to 150 +/- 10 ms (p < 0.05). Beta-adrenergic blockade increased the P wave duration to 153 +/- 10 ms (p < 0.005). Autonomic blockade shortened the P wave duration to 143 +/- 16 ms (p < 0.05 vs. beta-blockade). On the second day, the mean baseline P wave duration was slightly longer (144 +/- 10 ms, p < 0.02). Parasympathetic blockade with atropine resulted in mild shortening of the P wave duration to 136 +/- 15 ms (p < 0.1). Interobserver reproducibility was excellent (intraclass correlation coefficient 0.99). Day to day reproducibility was good (intraclass correlation coefficient 0.56). CONCLUSIONS: The signal-averaged P wave duration is not a fixed variable because it may change significantly under different autonomic conditions. This has important implications for the application of this test to the heterogeneous population susceptible to atrial fibrillation.


Assuntos
Sistema Nervoso Autônomo/efeitos dos fármacos , Sistema de Condução Cardíaco/efeitos dos fármacos , Adulto , Atropina/farmacologia , Sistema Nervoso Autônomo/fisiologia , Eletrocardiografia/efeitos dos fármacos , Epinefrina/farmacologia , Feminino , Sistema de Condução Cardíaco/fisiologia , Humanos , Isoproterenol/farmacologia , Masculino , Propranolol/farmacologia , Valores de Referência , Reprodutibilidade dos Testes , Processamento de Sinais Assistido por Computador
12.
J Am Coll Cardiol ; 24(4): 1082-90, 1994 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-7930202

RESUMO

OBJECTIVES: The aim of this study was to evaluate and compare the effects of physiologic and pharmacologic sympathetic stimulation on time and frequency domain indexes of heart rate variability. BACKGROUND: Measurements of heart rate variability have been used as indexes of sympathetic tone. To date, the effects of circulating catecholamines on heart rate variability have not been evaluated. METHODS: Fourteen normal subjects (eight men, six women, mean [+/- SD] age 28.5 +/- 4.8 years) were evaluated. Five-minute electrocardiographic recordings were obtained in triplicate after physiologic and pharmacologic sympathetic stimulation: during upright tilt, after maximal exercise, during epinephrine and isoproterenol infusions at 50 ng/kg body weight per min, during beta-adrenergic blockade and during combined beta-adrenergic and parasympathetic blockade. RESULTS: Beta-adrenergic stimulation resulted in a significant decrease in time domain measures of heart rate variability. The frequency domain indexes showed variable responses, depending on the individual stimulus. Tilt caused an increase in low frequency power and in the ratio of low to high frequency power. These changes were not necessarily observed with other conditions of beta-adrenergic stimulation. Double blockade suppressed baseline heart rate variability, but beta-adrenergic blockade had no significant effect. Time domain measures of heart rate variability demonstrated excellent reproducibility over the three recordings, but the frequency domain variables demonstrated fair to excellent reproducibility. CONCLUSIONS: These findings suggest that different modes of beta-adrenergic stimulation may result in divergent heart rate variability responses. Thus, current heart rate variability techniques cannot be used as general indexes of "sympathetic" tone. Studies utilizing heart rate variability to quantify sympathetic tone need to consider this.


Assuntos
Adrenérgicos/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Adulto , Atropina/farmacologia , Catecolaminas/sangue , Eletrocardiografia , Epinefrina/farmacologia , Teste de Esforço , Feminino , Coração/inervação , Humanos , Isoproterenol/farmacologia , Masculino , Sistema Nervoso Parassimpático/efeitos dos fármacos , Propranolol/farmacologia , Reprodutibilidade dos Testes , Estimulação Química , Sistema Nervoso Simpático/efeitos dos fármacos , Sistema Nervoso Simpático/fisiologia
13.
Am J Physiol ; 266(5 Pt 2): H2152-7, 1994 May.
Artigo em Inglês | MEDLINE | ID: mdl-8203614

RESUMO

Time and frequency domain measurements of heart rate variability have been used as indexes of parasympathetic tone. This study evaluates the effects of parasympathetic stimulation on these indexes. Ten normal subjects (5 females, 5 males; age 27.4 +/- 5.1 yr) were evaluated in the Clinical Research Center. Five-minute electrocardiographic recordings were obtained at baseline and during 1) combined alpha-adrenergic stimulation with baroreflex-increased cardiac parasympathetic activity produced by phenylephrine infusion; 2) parasympathetic blockade (atropine 0.04 mg/kg); and 3) isolated alpha-adrenergic stimulation produced by phenylephrine infusion after parasympathetic blockade. The infusion rate of phenylephrine was titrated to increase the systolic blood pressure by 20-30 mmHg. Heart rate variability analysis was performed using standard time and frequency domain parameters. Phenylephrine infusion resulted in a decrease in the time domain measures and in the high-frequency power. After parasympathetic blockade, alpha-adrenergic stimulation had no significant effect on the heart rate variability parameters. These findings suggest that the heart rate variability parameters traditionally associated with parasympathetic tone do not always reliably measure parasympathetic tone, since they decrease with baroreflex parasympathetic stimulation.


Assuntos
Atropina/farmacologia , Eletrocardiografia/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Sistema Nervoso Parassimpático/fisiologia , Fenilefrina/farmacologia , Adulto , Feminino , Frequência Cardíaca/efeitos dos fármacos , Humanos , Infusões Intravenosas , Masculino , Sistema Nervoso Parassimpático/efeitos dos fármacos , Fenilefrina/administração & dosagem , Receptores Adrenérgicos alfa/efeitos dos fármacos , Receptores Adrenérgicos alfa/fisiologia
14.
Circulation ; 89(4): 1656-64, 1994 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-8149533

RESUMO

BACKGROUND: Signal-averaged ECG is a noninvasive test designed to detect "late potentials." The effects of alterations in autonomic tone on the signal-averaged ECG have not been evaluated systematically. METHODS AND RESULTS: The effects of autonomic stimulation and blockade on the signal-averaged ECG were evaluated in 14 healthy subjects (8 men and 6 women; age, 28.5 +/- 4.8 years) on 2 separate days. The signal-averaged ECG was recorded at baseline and after physiological and pharmacologic beta-adrenergic stimulation (tilt, exercise, and epinephrine and isoproterenol infusions), sequential and combined beta-adrenergic and parasympathetic blockade, and alpha-adrenergic stimulation before and after parasympathetic blockade. Analysis was performed with a bidirectional filter (40-Hz high-pass). Significant changes in the signal-averaged QRS duration from baseline (105.1 +/- 12.0 milliseconds) were noted with tilt (96.8 +/- 8.8 milliseconds), tilt after double blockade (97.5 +/- 9.0 milliseconds), epinephrine (110.5 +/- 11.8 milliseconds), and isoproterenol (99.6 +/- 12.6 milliseconds). Changes in the root-mean-square voltage of the terminal 40 milliseconds and the low-amplitude (< 40 microV) signal duration paralleled the changes in the QRS duration. CONCLUSIONS: The signal-averaged ECG does not measure only "fixed" parameters but rather is altered under a variety of physiological and pharmacologic conditions. Upright tilt leads to shortening of the QRS duration before and after autonomic blockade; thus, the decrease in QRS duration with tilt may be related to factors other than changes in autonomic tone. These findings have implications for interpretation of the results of signal-averaged ECG.


Assuntos
Sistema Nervoso Autônomo/fisiologia , Eletrocardiografia/métodos , Coração/fisiologia , Processamento de Sinais Assistido por Computador , Adulto , Atropina , Sistema Nervoso Autônomo/efeitos dos fármacos , Epinefrina , Teste de Esforço , Feminino , Coração/efeitos dos fármacos , Humanos , Isoproterenol , Masculino , Fenilefrina , Postura/fisiologia , Propranolol , Reprodutibilidade dos Testes
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