RESUMO
We present the measurement of entanglement between twin beams generated with a doubly resonant optical parameter oscillator (OPO) based on four-wave mixing in hot ^{85}Rb vapor above threshold. This is the first measurement of entanglement in an OPO with a χ^{(3)} media above threshold. We reconstruct the covariance matrix for several configurations and based on a full picture of the four side band mode state, we study entanglement between all possible bipartitions. We show a robust generation of entanglement with stronger generation for a specific pair of modes. For this system, we show that atomic density is a determinant factor for the generation and loss of quantum correlations. The generation of entangled fields with an atomic OPO operating close to atomic resonance of alkali atoms enables a natural integration into quantum networks.
RESUMO
We present the first measurement of two-mode squeezing between the twin beams produced by a doubly resonant optical parameter oscillator (OPO) in an above threshold operation based on parametric amplification by nondegenerate four wave mixing with rubidium (^{85}Rb). We demonstrate a maximum intensity difference squeezing of -2.7 dB (-3.5 dB corrected for losses) with a pump power of 285 mW and an output power of 12 mW for each beam, operating close to the D1 line of Rb atoms. The use of open cavities combined with the high gain media can provide a strong level of noise compression and the access to new operation regimes that could not be explored by crystal based OPOs. The spectral bandwidth of the squeezed light is broadened by the cavity dynamics, and the squeezing level is robust for strong pump powers. Stable operation was obtained up to 4 times above the threshold. Moreover, operation of the OPO close to the atomic resonances of alkali atoms allows a natural integration into quantum networks, including structures such as quantum memories.
RESUMO
The phenomenon called Electromagnetically Induced Transparency (EIT) may induce different types of correlation between two optical fields interacting with an ensemble of atoms. It is presently well known, for example, that in the vicinity of an EIT resonance the dominant correlations at low powers turn into anti-correlations as power increases. Such correlation spectra present striking power-broadening-independent features, with the best condition for measuring the characteristic linewidth occurring at the highest powers. In the present work we investigate the physical mechanisms responsible for this set of observations. Our approach is first to reproduce these effects in a better controlled experimental setup: a cold atomic ensemble, obtained from a magneto-optical trap. The results from this conceptually simpler system were then compared to a correspondingly simpler theory, which clearly relates the observed features to the interplay between two key aspects of EIT: the transparency itself and the steep normal dispersion near two-photon resonance.
Assuntos
Campos Eletromagnéticos , Modelos Teóricos , Espalhamento de Radiação , Análise Espectral/métodos , Simulação por Computador , Estatística como AssuntoRESUMO
Hyperinsulinemia and impaired insulin action are familial and predictive of Type 2 diabetes onset. Since high levels of insulin are characteristic of our general (venezuelan)hispanic population, the purpose of this investigation was to identify early metabolic defects in a group of healthy first degree relatives of Type 2 diabetic patients. We studied 46 (29 women and 17 men; ages ranging 18-66 y) first degree relatives of Type 2 diabetic patients comparing them with 22 (12 women and 10 men; ages ranging 22-60 y) subjects who had no family history of diabetes. All subjects underwent resting blood pressure and anthropometric measurements; a 75 g oral glucose tolerance test with determination of glucose and insulin and a fasting lipid profile. The relatives of Type 2 diabetic patients had higher tricipital (TC) and subscapular (SC) skinfolds, and elevated DBP in relation to the control group. The skinfolds elevation was more evident in women, while in men the elevation in DBP predominates. None of the relatives had glucose intolerance, however, the glucose-stimulated insulin response was elevated at all points in men as well as in women. No difference was observed in the HOMA values for IR and beta cell function, or in the delta I30/delta G30 ratio. The lipid profile showed a marked elevation in TG levels in men as well as in women, with low HDL-C values in men. No other lipid abnormalities were observed. Correlation analysis revealed strong association between BMI and WHR with skinfolds and several parameters of the carbohydrate metabolism in women, but not in men. IR in women was possitively associated with skinfolds, SBP and lipid parameters and beta cell function with VLDL-C. Adult relatives of Type 2 diabetic venezuelan patients from hispanic origin had, early in their lives, several parameters of the metabolic syndrome as hyperinsulinemia, obesity, dyslipidemia and high blood pressure. These alterations were more prominent in women, group in which the association among BMI, WHR and IR were statistically significant respect to SBP, DBP, basal insulin, insulin/glucose ratio, TG and HDL-C.
Assuntos
Diabetes Mellitus Tipo 2/genética , Saúde da Família , Hiperinsulinismo/genética , Resistência à Insulina/genética , Estado Pré-Diabético/genética , Adulto , Idade de Início , Antropometria , Glicemia/análise , Metabolismo dos Carboidratos , HDL-Colesterol/sangue , Comorbidade , Diabetes Mellitus Tipo 2/metabolismo , Feminino , Predisposição Genética para Doença , Teste de Tolerância a Glucose , Humanos , Hiperinsulinismo/epidemiologia , Hiperinsulinismo/etnologia , Hipertensão/epidemiologia , Hipertensão/etnologia , Hipertensão/genética , Hipertrigliceridemia/epidemiologia , Hipertrigliceridemia/etnologia , Hipertrigliceridemia/genética , Incidência , Insulina/sangue , Insulina/metabolismo , Secreção de Insulina , Ilhotas Pancreáticas/metabolismo , Masculino , Pessoa de Meia-Idade , Obesidade/epidemiologia , Obesidade/etnologia , Obesidade/genética , Estado Pré-Diabético/epidemiologia , Estado Pré-Diabético/etnologia , Fatores de Risco , Fatores Sexuais , Espanha/etnologia , Venezuela/epidemiologiaRESUMO
Insulin resistance and hyperinsulinemia can induce overproduction of triglyceride (TG) rich VLDL in the liver by increasing the availability of free fatty acids (FFA). Conversely, apolipoprotein C-III (apoC-III) is an inhibitor of the catabolism of TG-rich lipoproteins. To explore the relationship among FFA, apo C-III and TG in hyperinsulinemic subjects, we studied 103 individuals (63 women and 40 men) with a body mass index (BMI) 25 Kg/m2: 59 subjects with normal glucose tolerance (NGT), and 44 with newly diagnosed type 2 diabetes. After adjustment for age, BMI, fasting insulin and TG, FFA were significantly higher in women than in men and in subjects with diabetes compared with NGT. Subjects with diabetes had higher apo C-III levels compared to NGT, adjusted for age, sex and BMI, and that was largely accounted for by differences in insulin and TG levels. In addition, regression analysis in subjects with diabetes showed that TG were strongly associated with apo C-III in both men and women (r = 0.90 and 0.79, respectively; p < 0.001), while the association tended to be smaller between TG and FFA (r = 0.48, p < 0.05 in men and r = 0.45, p = 0.06 in women). Conversely, in individuals with NGT fasting TG was strongly associated with apo C-III in men (r = 0.83, p < 0.01) but not with FFA, while in women TG was associated with FFA (r = 0.39, p < 0.05) but not with apo C-III. In summary, elevated apo C-III was a predominant factor associated with elevated TG levels in NGT men and all subjects with type 2 diabetes, while FFA were more closely related with TG levels in NGT women.
Assuntos
Apolipoproteínas C/sangue , Glicemia/análise , Diabetes Mellitus Tipo 2/sangue , Ácidos Graxos não Esterificados/sangue , Triglicerídeos/sangue , Adulto , Fatores Etários , Apolipoproteína C-III , Feminino , Teste de Tolerância a Glucose , Humanos , Masculino , Pessoa de Meia-Idade , Análise de Regressão , Fatores de Risco , Fatores SexuaisAssuntos
Ensaios Clínicos como Assunto/métodos , Ética Médica , Tiazolidinedionas , Anti-Hipertensivos/uso terapêutico , Cromanos/uso terapêutico , Ensaios Clínicos como Assunto/normas , Complicações do Diabetes , Enalapril/uso terapêutico , Hipertensão/complicações , Hipertensão/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Metformina/uso terapêutico , Estudos Multicêntricos como Assunto , Nisoldipino/uso terapêutico , Estado Pré-Diabético/tratamento farmacológico , Estudos Prospectivos , Tiazóis/uso terapêutico , Falha de Tratamento , TroglitazonaRESUMO
This study reports a 7-y-old boy with severe hypertriglyceridaemia who was successfully treated for 6 y with a low glycaemic index-high carbohydrate modified-lipid diet that produced beneficial changes in triglyceride and total cholesterol levels. It is suggested that a selection of a complex digestible carbohydrate and an adequate ratio between polyunsaturated and monounsaturated fat may, in the long term, favourably improve the lipid profile.
Assuntos
Carboidratos da Dieta/uso terapêutico , Hipertrigliceridemia/dietoterapia , Criança , Dieta Aterogênica , Dieta com Restrição de Gorduras , Humanos , Hipertrigliceridemia/diagnóstico , Hipertrigliceridemia/fisiopatologia , Masculino , Triglicerídeos/sangueRESUMO
Non-insulin-dependent diabetes mellitus (NIDDM), or type II diabetes is rapidly becoming one of the most common chronic disease in the United States and worldwide, with more than 7% of the adult population affected. NIDDM is even more common in the elderly and in minority population including Hispanic Americans, African Americans, Asian and Pacific Island Americans, and Native Americans. In these populations, NIDDM may be present in 10% to as much as 50% of the adult population. However diagnosed NIDDM is only the tip of the iceberg of an epidemic of glucose intolerance. Impaired glucose intolerance (IGT) is even more prevalent that NIDDM; and in addition to be a major risk factor for the development of NIDDM, IGT is associated with an increased risk of macrovascular disease. Recent advances in research into the etiology and natural history of diabetes have increased the knowledge to such an extent that primary prevention of NIDDM is becoming a reality. This primary prevention can be implemented a) through a population strategy, i.e. changing the lifestyle and environmental determinants that are known to be risk factors for diabetes, and b) through high-risk strategy, i.e. targeting preventive measures only at those specific individuals or groups that are at high risk for the future development of NIDDM. The latter is the strategy of the Diabetes Prevention Program (DDP), a clinical study sponsored by the National Institute of Diabetes and Digestive and Kidney Disease in USA. Twenty five centers were selected to participate in this program. The purpose of DPP is prevent or delay the development of NIDDM in those persons who are at high risk because they have IGT. DPP will also evaluate if the interventions selected to prevent the development of NIDDM can decrease the frequency of cardiovascular events and the occurrence and magnitude of the cardiovascular risk factors that accompany NIDDM and IGT. Four thousand volunteers will be recruited from populations known to be at particular high risk fo IGT and NIDDM including the following: elderly, overweight individuals, persons with family history of NIDDM, women with history of gestational diabetes, and minority populations. In order to be eligible, persons who are older than 25 years will have to demonstrate IGT with plasma glucose levels 100-139 mg/dl fasting and 140-199 mg/dL two hours after a 75 g OGTT. Three study intervention were selected based on their potential efficacy in ameliorating abnormal glucose metabolism in IGT and on their safety and tolerable profile of side-effects. The interventions include: intensive lifestyle intervention which focuses on a healthy diet to achieve and maintain at least a 7% loss of body weight and an increase in caloric expenditure of at least 700 kcal per week. The drug therapy interventions include the biguanide metformin and the thiazolidinedione troglizatone. Standard life-style recommendations, which include conventional instructions regarding diet and exercise, will be provided to all participants, including a placebo treated group which will serve as the control group for the study. After randomization, participants will have quarterly evaluations and have, in addition, a fasting plasma glucose at semi-annual visits and a 75 g OGTT at annual visits. All participants will be followed for three years after the study-wide closing date for recruitment, resulting in 3 to 6 years of participant follow-up. The primary outcome is the development of NIDDM according to WHO criteria (fasting plasma glucose level 140 mg/dL or 2-hour plasma glucose 200 mg/dL after a 75 g OGTT). Secondary outcome will focus en cardiovascular disease and its risk factors and change of glycemia, insulin secretion and sensitivity, obesity, physical activity and nutrient intake, quality of life, and the occurrence of adverse events.
Assuntos
Diabetes Mellitus Tipo 2/prevenção & controle , Estado Pré-Diabético/terapia , Tiazolidinedionas , Adulto , Idoso , Cromanos/uso terapêutico , Comorbidade , Análise Custo-Benefício , Diabetes Mellitus Tipo 2/economia , Diabetes Mellitus Tipo 2/epidemiologia , Dieta Redutora , Exercício Físico , Feminino , Teste de Tolerância a Glucose , Humanos , Hipertensão/epidemiologia , Hipoglicemiantes/uso terapêutico , Estilo de Vida , Masculino , Metformina/uso terapêutico , Pessoa de Meia-Idade , National Institutes of Health (U.S.) , Obesidade/epidemiologia , Estado Pré-Diabético/dietoterapia , Estado Pré-Diabético/tratamento farmacológico , Estado Pré-Diabético/epidemiologia , Fatores de Risco , Tiazóis/uso terapêutico , Troglitazona , Estados UnidosRESUMO
To determine the most frequent dyslipidemias among first-degree relatives of NIDDM patients, and its association with their glucose-tolerance status and hyperinsulinemia, we have started to examine members of NIDDM pedigrees, according to American Diabetes Association guidelines for nuclear family studies. In a large family with 2 NIDDM siblings in the 2nd generation, and 4 siblings with NIDDM in the 3rd generation, we have evaluated 14 first degree relatives and also 15 sex and aged matched healthy control subjects without family history of diabetes. The NIDDM relative group presented BMI = 31.8 +/- 3.9 kg/m2, SBP = 128 +/- 18.2 mmHg, DBP = 84 +/- 12.7 mmHg. Both relatives and controls were subjected to a 2h 75g OGTT for glucose and insulin determinations. Although none of NIDDM relatives has IGT, both Glycemic Area (GA) and Insulin Area (IA) were greater (p < 0.01) in the NIDDM relative group. The Insulin/Glucose ratio was also higher (p < 0.01) at 0 and 120 min of OGTT, this might be indirect evidence of Insulin- Resistance. Fasting serum lipids in the NIDDM relatives were TG = 148 +/- 24mg/dl, T-Chol = 244 +/- 10.7mg/dl, HDL-C = 34.2 +/- 2.5mg/dl; lipids in the control group were TG = 84.8 +/- 10.1mg/dl, T-Chol = 167 +/- 10.2mg/dl, HDL-C = 44.4 +/- 2.6mg/dl. Electrophoretic pattern showed type IIa (30.7%) and IIb (61.5%) hyperlipidemias in the NIDDM relatives. In this group, there was a positive and significant association between basal insulin and DBP (r = 0.67; p < 0.01), and between DBP and both TG (r = 0.74; p < 0.01)) and VLDL-C (r = 0.58; p < 0.05). It was also obtained a negative association between basal insulin and HDL-C (r = -0.89; p < 0.001). These data suggest that hyperinsulinemia in association with lipid abnormalities could appear early (before the development of Impaired Glucose Tolerance and Diabetes) in first degree relatives of NIDDM patients.