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1.
Opt Express ; 23(6): 7300-11, 2015 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-25837073

RESUMO

We present and demonstrate a novel protocol for distributing secret keys between two and only two parties based on N-party single-qubit Quantum Secret Sharing (QSS). We demonstrate our new protocol with N = 3 parties using phase-encoded photons. We show that any two out of N parties can build a secret key based on partial information from each other and with collaboration from the remaining N - 2 parties. Our implementation allows for an accessible transition between N-party QSS and arbitrary two party QKD without modification of hardware. In addition, our approach significantly reduces the number of resources such as single photon detectors, lasers and dark fiber connections needed to implement QKD.

2.
Phys Rev Lett ; 105(25): 253601, 2010 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-21231588

RESUMO

We present results of a bright polarization-entangled photon source operating at 1552 nm via type-II collinear degenerate spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate crystal. We report a conservative inferred pair generation rate of 123,000 pairs/s/mW into collection modes. Minimization of spectral and spatial entanglement was achieved by group velocity matching the pump, signal, and idler modes and through properly focusing the pump beam. By utilizing a pair of calcite beam displacers, we are able to overlap photons from adjacent down-conversion processes to obtain polarization-entanglement visibility of 94.7+/-1.1% with accidentals subtracted.

3.
Caring ; 16(7): 14-6, 1997 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10169878

RESUMO

Technological advances are changing the way the world shares information and conducts daily business, CARING asked home care colleagues around the world to respond to a question about technology's role in home care delivery. Although the degree of technology's involvement differs from country to country, each country is aware of the possibilities and is looking toward the future.


Assuntos
Serviços de Assistência Domiciliar/tendências , Transferência de Tecnologia , Redes de Comunicação de Computadores , Saúde Global , Humanos , Cooperação Internacional , Serviços de Saúde Rural
4.
Opt Lett ; 20(14): 1553-5, 1995 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-19862080

RESUMO

An electro-optic phase modulator in a regenerative mode-locker configuration is demonstrated as the starting mechanism for a Kerr-lens mode-locked Ti:sapphire laser. Mode locking is initiated automatically, and the system is capable of pulses as short as 21 fs.

5.
Am J Physiol ; 265(6 Pt 2): H2066-72, 1993 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-8285245

RESUMO

We describe a method for the noninvasive measurement of left ventricular mass in small animals using two-dimensionally guided M-mode echocardiography. We compared echocardiographic cross-sectional area (CSA) and cubed-based volumetric indexes of left ventricular (LV) mass with postmortem wet weight in renovascular hypertension-induced pressure overload (group I) and acute aortic insufficiency-induced volume overload (group II) models of ventricular hypertrophy. CSA and cubed echocardiographic indexes correlated well with wet weight from a combination of group I and II animals and their controls (r = 0.89, P < 0.001 for both groups). Separate analyses of groups I and II also demonstrated significant relationships between mass indexes and wet weight using CSA and cubed formulas, respectively, in both pressure (r = 0.57, P = 0.01 and r = 0.71, P < 0.001) and volume (r = 0.90 and r = 0.89, P < 0.001) overload models. Echocardiographically predicted LV mass derived from cubed and CSA regression formulas was 89 and 56% sensitive for pressure overload hypertrophy in group I and 100% sensitive (both cubed and CSA methods) for volume overload hypertrophy in group II. Cubed and CSA mass regression formulas were 60 and 80% specific for hypertrophy in group I and 100 and 90% specific in group II. Normalization of predicted LV mass for body weight added little to the overall technique accuracy with measured sensitivities of 83 and 75% and specificities of 92 and 77%, respectively, for cubed and CSA methods. Two-dimensionally guided M-mode echocardiography provides a reasonably accurate method of LV mass determination in rabbits with pressure- or volume-overloaded ventricles.


Assuntos
Cardiomegalia/diagnóstico por imagem , Cardiomegalia/etiologia , Ecocardiografia , Ventrículos do Coração/diagnóstico por imagem , Hiperemia/complicações , Hipertensão/complicações , Animais , Coelhos , Valores de Referência , Sensibilidade e Especificidade
6.
Circ Res ; 68(2): 466-81, 1991 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-1991351

RESUMO

Current therapy of myocardial infarction may include early reperfusion. We simulated myocardial perfusion conditions during evolving myocardial infarction in isolated, normothermic, isovolumic rabbit hearts perfused with buffer containing bovine red blood cells (hematocrit of 40%), and we assessed the effects of high levels of glucose and insulin as "therapy" during prolonged (150-minute) severe underperfusion and reperfusion. Protocol 1 consisted of underperfusion at a constant coronary perfusion pressure of 8 mm Hg. The control group (n = 8) received 5.5 mmol/l glucose and 15 microunits/ml insulin; the group treated with high levels of glucose and insulin (G + I) (n = 8) received 19.5 mmol/l glucose and 250 microunits/ml insulin during both underperfusion and reperfusion. Relative to the control group, the G + I group experienced 1) greater developed pressure during underperfusion and increased recovery during reperfusion, 2) preserved diastolic function during underperfusion and reperfusion, 3) lower coronary resistance and greater coronary flow during the underperfusion period, 4) increased glycolytic flux and preserved glycogen stores and high energy phosphate levels, and 5) less loss of myocyte enzymes (creatine kinase and alanine aminotransferase). In protocol 2, coronary flow was kept identical in control (n = 8) and G + I hearts (n = 8) during the underperfusion period, and left ventricular end-diastolic pressure was kept below 10 mm Hg in both groups to minimize subendocardial damage and vascular compression. In this protocol, the effect of the G + I intervention in the prevention of an increase in coronary resistance during the underperfusion period was distinguished from its myocellular metabolic effects; the high G + I substrate had protective effects on mechanical and metabolic function that were less marked than, but similar to, those in protocol 1, indicating that its mechanisms of protection during underperfusion affected both cardiac function and coronary resistance. We conclude that the G + I intervention, in clinically relevant concentrations, markedly protected severely underperfused myocardium for 150 minutes and may be a beneficial intervention in combination with reperfusion therapy in acute myocardial infarction.


Assuntos
Vasos Coronários/fisiopatologia , Eritrócitos , Glicólise , Infarto do Miocárdio/fisiopatologia , Reperfusão Miocárdica , Resistência Vascular , Animais , Circulação Coronária , Diástole , Hematócrito , Técnicas In Vitro , Infarto do Miocárdio/metabolismo , Perfusão , Pressão , Coelhos , Sístole , Fatores de Tempo , Função Ventricular Esquerda
7.
Hypertension ; 13(6 Pt 1): 598-606, 1989 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-2737708

RESUMO

Acute pulmonary edema during hypertensive crisis has been attributed to acute left ventricular systolic failure secondary to increased afterload. We tested the hypothesis that the increase in coronary artery perfusion pressure associated with systemic hypertension could also contribute to increased left ventricular filling pressures by acutely increasing coronary intravascular volume and decreasing left ventricular diastolic compliance. Isolated isovolumic (balloon in left ventricle) normal rabbit hearts (n = 13) with pericardium removed and right ventricle vented were blood perfused at an initial coronary artery perfusion pressure of 100 mm Hg; left ventricular balloon volume was adjusted to produce an initial left ventricular end-diastolic pressure of 15 +/- 1 mm Hg; left ventricular systolic pressure was 102 +/- 3 mm Hg. When coronary perfusion pressure was increased to 130 +/- 1 mm Hg to simulate a hypertensive crisis, coronary flow increased from 2.0 +/- 0.2 to 3.0 +/- 0.2 ml/min/g left ventricle (p less than 0.001), left ventricular systolic pressure increased to 116 +/- 4 mm Hg, and isovolumic left ventricular end-diastolic pressure increased to 21 +/- 1 mm Hg (p less than 0.001), which indicated a decrease in left ventricular diastolic compliance. When coronary perfusion pressure was decreased to a physiological level of 70 mm Hg, coronary flow rate decreased to 1.4 +/- 0.1 ml/min/g left ventricle (p less than 0.001), left ventricular systolic pressure fell to 82 +/- 4 mm Hg, and left ventricular end-diastolic pressure fell to 14 +/- 1 mm Hg (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Diástole , Hipertensão/fisiopatologia , Contração Miocárdica , Animais , Aorta/fisiologia , Pressão Sanguínea , Coração , Ventrículos do Coração/fisiopatologia , Masculino , Perfusão , Coelhos
8.
Hypertension ; 13(4): 361-70, 1989 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-2522416

RESUMO

Hearts with advanced pressure-overload hypertrophy from systemic hypertension have been shown to have an increased susceptibility to the development of diastolic dysfunction in response to tissue hypoxia and ischemia. It is not known if this propensity to develop diastolic dysfunction in response to ischemia is dependent on the presence of a substantial increase in left ventricular mass, or alternatively, is characteristic of hearts subjected to mild chronic hypertension early in the development of cardiac hypertrophy. We tested the hypothesis that systemic hypertension associated with mild left ventricular hypertrophy increases the susceptibility to the development of diastolic dysfunction in response to demand ischemia. The effects of demand ischemia (6 minutes) were studied in hearts from New Zealand white rabbits with chronic systemic hypertension produced by the one-kidney, one-wrap method (n = 15) and compared with age-matched, sham-operated control rabbits (n = 11) with similar left ventricular mass (5.4 +/- 0.2 vs. 5.4 +/- 0.3 g, respectively). The hearts were studied using an isolated, isovolumic (balloon in left ventricle) preparation with absent pericardium that was perfused with fresh whole blood. At baseline, coronary perfusion pressure was 100 mm Hg with comparable coronary flow per gram left ventricular weight; the hearts were paced at a physiological rate of 3 Hz, and the left ventricular balloon volume was adjusted to achieve a left ventricular end-diastolic pressure of 15 mm Hg in both groups. Left ventricular balloon volume was similar in both groups and volume was thereafter held constant. At baseline, left ventricular systolic pressure (114 +/- 4 vs. 95 +/- 3 mm Hg, p less than 0.001) and developed pressure (18.9 +/- 1.2 vs. 15.1 +/- 0.9 mm Hg/g, p less than 0.05) were higher in the hearts from the hypertensive group in comparison with the control group. During the first minute of global ischemia produced by reducing coronary perfusion pressure from 100 to 20 mm Hg, there was an immediate fall in left ventricular systolic pressure in both groups without an increase in diastolic pressure. In response to the superimposition of pacing tachycardia (heart rate, 6 Hz) during the remaining 5 minutes of the period of ischemia, left ventricular developed pressure was comparable. However, isovolumic left ventricular end-diastolic pressure (measured during long diastoles obtained with transient cessation of pacing) rose to a significantly higher level in the hearts from hypertensive rabbits than in those from the control rabbits (29 +/- 3 vs. 18 +/- 2 mm Hg, p less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)


Assuntos
Cardiomegalia/fisiopatologia , Doença das Coronárias/fisiopatologia , Diástole , Hipertensão/fisiopatologia , Contração Miocárdica , Esforço Físico , Animais , Circulação Coronária , Técnicas In Vitro , Masculino , Perfusão/instrumentação , Perfusão/métodos , Coelhos , Taquicardia/fisiopatologia
9.
Jpn Circ J ; 53(3): 261-9, 1989 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-2746841

RESUMO

We studied the influence of inotropic agents on prompt and transient left ventricular (LV) diastolic relaxation dysfunction produced by superimposition of pacing tachycardia on low-flow ischemia, using an isolated, blood-perfused and isovolumic (balloon-in-LV) rabbit heart preparation. The LV balloon volume was adjusted to produce an LV end-diastolic pressure (EDP) of 15 mmHg and was held constant thereafter. Coronary perfusion pressure was adjusted to 100 mmHg during baseline and to 20 mmHg during low-flow ischemia of 6 min. At baseline, isoproterenol and ouabain were administered to cause moderate and similar rises (14 +/- 3 and 16 +/- 4% above baseline values, respectively) in maximum + dp/dt of LVP with no change in LVEDP. In control hearts which received no drug, superimposition of 5-min pacing tachycardia on low-flow ischemia produced a significant and transient increase in LVEDP under constant LV volume (from 13.4 +/- 0.4 to 24.7 +/- 3.3 mmHg, p less than 0.01). In the hearts which received isoproterenol it did not change LVEDP (from 14.0 +/- 0.4 to 16.2 +/- 1.0 mmHg, NS). In contrast, the ouabain hearts showed a further increase in LVEDP (from 13.7 +/- 0.8 to 29.9 +/- 4.6 mmHg, p less than 0.01). LV developed pressure, myocardial oxygen consumption or myocardial lactate production during pacing tachycardia superimposed on the low-flow ischemia did not differ significantly among the 3 groups. Thus, isoproterenol markedly improved transient LV relaxation dysfunction produced by superimposition of pacing tachycardia on low-flow ischemia, in which an equipotent inotropic dose of ouabain exaggerated the relaxation dysfunction. These results suggest that calcium overload rather than ATP depletion per se contributes to transiently impaired diastolic relaxation by pacing tachycardia and low-flow ischemia.


Assuntos
Isoproterenol/farmacologia , Contração Miocárdica/efeitos dos fármacos , Ouabaína/farmacologia , Taquicardia/fisiopatologia , Animais , Circulação Coronária/efeitos dos fármacos , Diástole/efeitos dos fármacos , Técnicas In Vitro , Lactatos/metabolismo , Masculino , Relaxamento Muscular/efeitos dos fármacos , Miocárdio/metabolismo , Consumo de Oxigênio/efeitos dos fármacos , Pressão , Coelhos , Volume Sistólico/efeitos dos fármacos , Taquicardia/metabolismo
10.
Circ Res ; 63(2): 457-67, 1988 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-3396161

RESUMO

Myocardial ischemia causes both systolic and diastolic dysfunction. A variety of positive inotropic agents with different subcellular mechanisms may be used clinically in an attempt to reverse ischemic contractile failure. We tested the hypothesis that two inotropic agents, isoproterenol (a beta-adrenergic agonist) and ouabain (a sodium pump inhibitor), might have different effects on left ventricular (LV) diastolic function during ischemic failure despite an equivalent inotropic effect. Isolated isovolumic (balloon-in-LV) blood perfused rabbit hearts were paced at constant physiological heart rate (4 Hz), given either no drug (controls, n = 7), isoproterenol (n = 7), or ouabain (n = 7), and then subjected to 6 minutes of low flow ischemia (75% reduction of baseline coronary flow). The doses of isoproterenol and ouabain were selected to produce equivalent modest inotropic effects (15% increase in LV + dP/dt) in each heart during baseline perfusion conditions. During the ischemic period, there was a marked decrease in contractility, and neither isoproterenol nor ouabain demonstrated a positive inotropic effect relative to the control group. However, these agents had markedly different effects on diastolic chamber distensibility (assessed by end-diastolic pressure at constant LV volume) during ischemia. In the control and isoproterenol groups, diastolic chamber distensibility did not change during the ischemic period. In contrast, ouabain treatment resulted in a marked decrease in diastolic chamber distensibility during ischemia; this change was not completely reversible during the 10-minute reperfusion period. The mechanism by which ouabain decreased diastolic chamber distensibility relative to isoproterenol was assessed indirectly. The ouabain and isoproterenol groups were subjected to equivalent degrees of ischemia as assessed by oxygen supply/demand imbalance; during ischemia, each drug group did not differ with regard to myocardial perfusion rates, determinants of myocardial oxygen demand (heart rate, LV developed pressure, LV + dP/dt), myocardial oxygen consumption, lactate production, and ATP and creatine phosphate content. We therefore inferred that the greater decrease in diastolic distensibility in the ouabain group was not due to a greater metabolic severity of ischemia. These observations are consistent with a mechanism of cytosolic calcium overload induced by ouabain, resulting in persistent active myofilament tension development throughout diastole, to cause the observed decrease in diastolic chamber distensibility during ischemia in the ouabain group.(ABSTRACT TRUNCATED AT 400 WORDS)


Assuntos
Doença das Coronárias/fisiopatologia , Coração/fisiopatologia , Isoproterenol/farmacologia , Ouabaína/farmacologia , Animais , Sangue , Pressão Sanguínea/efeitos dos fármacos , Circulação Coronária , Doença das Coronárias/metabolismo , Diástole/efeitos dos fármacos , Ventrículos do Coração , Técnicas In Vitro , Miocárdio/metabolismo , Perfusão , Coelhos
11.
Circ Res ; 61(6): 925-33, 1987 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-3677344

RESUMO

It is not clear what factors contribute to the prompt and reversible decrease in left ventricular diastolic chamber distensibility during angina pectoris that is induced by an increase in myocardial energy demand due to exercise or pacing tachycardia. To simulate the demand ischemia that occurs clinically during pacing-induced angina, we used isolated, blood-perfused rabbit hearts with restricted coronary flow and increased myocardial energy demand. A constant left ventricular balloon volume model was used to measure left ventricular diastolic chamber distensibility during 6 minutes of low-flow global ischemia, induced by a reduction in coronary perfusion pressure from 100 to 20 mm Hg. To investigate the influence of different levels of myocardial energy demand, the effects of two different heart rates were studied during low-flow global ischemia; pacing tachycardia (6.4 +/- 0.2 Hz, n = 7) was compared with the rabbit's baseline heart rate of 4 Hz (n = 7). Low-flow ischemia caused a marked decrease in contractile function relative to the baseline preischemic state. In the pacing-tachycardia group, myocardial energy demand, as estimated by the rate X systolic pressure product, was significantly greater than in the constant heart-rate group. When tachycardia was imposed during low-flow global ischemia, there was a transient and reversible increase in isovolumic left ventricular end-diastolic pressure from 14 +/- 1 to 25 +/- 4 mm Hg (measured during long diastoles obtained with transient cessation of pacing) in the pacing-tachycardia group, but there was no increase in left ventricular end-diastolic pressure during low flow ischemia in the constant heart-rate group with lower energy demand (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Angina Pectoris/fisiopatologia , Diástole , Contração Miocárdica , Animais , Circulação Coronária , Doença das Coronárias/fisiopatologia , Metabolismo Energético , Frequência Cardíaca , Ventrículos do Coração/fisiopatologia , Masculino , Miocárdio/metabolismo , Consumo de Oxigênio , Perfusão , Pressão , Coelhos
12.
Circulation ; 76(5 Pt 2): V150-5, 1987 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-3665013

RESUMO

We tested the hypothesis that neonatal myocardium is more sensitive to injury during cardiac surgery than adult myocardium. Groups of neonatal (4 to 5 days old) and adult (3 months old) isolated, blood-perfused rabbit hearts were subjected to periods of ischemic arrest and reperfusion without cardioplegic protection as follows. Protocol I consisted of 30 min of normothermic (37 degrees C) ischemic arrest and reperfusion, protocol II of 60 min of hypothermic (15 degrees C) ischemic arrest and warm (37 degrees C) reperfusion, and protocol III of 120 min of hypothermic ischemic arrest and cool (21 degrees to 25 degrees C) reperfusion. After protocol I, the neonatal hearts recovered 23% greater contractile function than the adult hearts; after protocols II and III the neonatal hearts recovered 51% to 55% more function than the adults. These results suggest that neonatal hearts tolerate the conditions of cardiac surgery better than adult hearts.


Assuntos
Circulação Coronária , Parada Cardíaca Induzida , Coração/fisiologia , Hipotermia Induzida , Fatores Etários , Animais , Pressão Sanguínea , Coração/anatomia & histologia , Masculino , Contração Miocárdica , Tamanho do Órgão , Coelhos , Volume Sistólico
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