Search PubMed⌕ Search

Biomedical subjects

A Imamoglu

Publications and source records attributed to A Imamoglu.

At least 19 recordsLinked to original sources
PubMed2000

A quantum dot single-photon turnstile device.

Quantum communication relies on the availability of light pulses with strong quantum correlations among photons. An example of such an optical source is a single-photon pulse with a vanishing probability for detecting two or more photons. Using pulsed laser excitation of a single quantum dot, a single-photon turnstile device that generates a train of single-photon pulses was demonstrated. For a spectrally isolated quantum dot, nearly 100% of the excitation pulses lead to emission of a single photon, yielding an ideal single-photon source.

Journal Article↗
PubMed2000

Quantum correlation among photons from a single quantum dot at room temperature

Maxwell's equations successfully describe the statistical properties of fluorescence from an ensemble of atoms or semiconductors in one or more dimensions. But quantization of the radiation field is required to explain the correlations of light generated by a single two-level quantum emitter, such as an atom, ion or single molecule. The observation of photon antibunching in resonance fluorescence from a single atom unequivocally demonstrated the non-classical nature of radiation. Here we report the experimental observation of photon antibunching from an artificial system--a single cadmium selenide quantum dot at room temperature. Apart from providing direct evidence for a solid-state non-classical light source, this result proves that a single quantum dot acts like an artificial atom, with a discrete anharmonic spectrum. In contrast, we find the photon-emission events from a cluster of several dots to be uncorrelated.

Journal Article↗
PubMed2000

Nonlinear optics and quantum entanglement of ultraslow single photons

Two light pulses propagating with slow group velocities in a coherently prepared atomic gas exhibit dissipation-free nonlinear coupling of an unprecedented strength. This enables a single-photon pulse to coherently control or manipulate the quantum state of the other. Processes of this kind result in generation of entangled states of radiation field and open up new prospectives for quantum information processing.

Journal Article↗
PubMed2000

The use of self-expanding metallic urethral stents in the treatment of recurrent bulbar urethral strictures: long-term results.

OBJECTIVE: To evaluate the effectiveness and long-term results of using a self-expanding metallic urethral stent (Urolumetrade mark, American Medical Systems, Minnetonka, MI, USA) to treat recurrent bulbar urethral strictures. PATIENTS AND METHODS: Between 1990 and 1999, 65 stents were placed in 60 men (mean age 45.2 years, range 20-71) with a urethral stricture (mostly caused by trauma and present for a mean of 4.3 years, range 0.16-26) and who had previously undergone different unsuccessful treatments. RESULTS: During a mean (range) follow-up of 3.8 (1-9) years the strictures in 52 of the 60 patients (87%) were treated successfully. All patients initially had postvoid dribbling incontinence, but this resolved in most within one week; 19 patients remain incontinent. CONCLUSION: The Urolume is a cost-effective alternative to other treatments for recurrent bulbar urethral strictures of whatever cause.

Adult↗
PubMed2000

Echocardiographic, morphologic, and geometric variations of the left ventricular outflow tract: possible role in the pathogenesis of discrete subaortic stenosis.

Although the clinical features and natural course of discrete subaortic stenosis (DSS) are well defined, the etiology remains speculative. The purpose of this study was to identify the echocardiographic, morphologic, and geometric variations of the left ventricular outflow tract associated with DSS in children and to determine whether these variations have a role in the pathogenesis of DSS. The aortoseptal angle (ASA), mitral-aortic valve separation (MAS), and the size of the aortic annulus were determined in two groups of children. Group 1 comprised 11 patients with isolated DSS, who were compared with an age- and body surface area- (BSA) matched healthy children (Group 1A, n: 20). Group 2 comprised 10 patients with DSS and ventricular septal defect (VSD). Group 2 was compared with an age- and BSA-matched patients with isolated perimembranous VSD (Group 2A, n: 22). Measurements were carried out from previously recorded echocardiographic studies. The ASA was steeper (119.3 +/- 6.1 degrees vs 137.5 +/- 5.6 degrees , p < 0.001), and the MAS was wider (6.1 +/- 1.6 vs 3.2 +/- 0.7 mm, p < 0.001) in patients with isolated DSS than in healthy control subjects. Similar differences were found between patients in Group 2 and Group 2A; the ASA was steeper (122.2 +/- 6.5 degrees vs 141.3 +/- 5.0 degrees, p < 0.001), and the MAS was wider (5.8 +/- 1.5 vs 3.8 +/- 1.1 mm, p < 0.001). The size of the aortic annulus was not different among the four study groups. Although the MAS was significantly wider in patients with DSS, there was significant overlap in MAS between patients and controls. However, if an ASA < or = 130 degrees was chosen as a predictive variable, it was found to be a highly sensitive, specific, and positive predictive marker for the development of DSS. This study demonstrates that DSS is associated with a steeper ASA, and a wider MAS, in patients with or without associated VSD. These morphologic abnormalities, especially a steeper ASA, may be risk factors for the development of DSS.

Adolescent↗
PubMed1999

QT/corrected QT (QTc) intervals and QT/QTc dispersions in children with chronic renal failure.

UNLABELLED: We aimed to examine QT/corrected QT (QTc) intervals, QT/QTc dispersions (QTD/QTcD) and also the effect of different clinical and laboratory variables on these parameters in children with chronic renal failure. Serum biochemistry, 12-lead electrocardiogram, telecardiogram, and echocardiography were performed in 50 children with chronic renal failure (23 female and 27 male; aged 12.3+/-3.6 years, range 5 to 20 years). None of them had symptoms related to arrhythmias. When compared with a control group (372 children, aged 7 to 18 years, mean 12.4+/-2.6) patients with chronic renal failure had greater QT/QTc intervals and QT/QTc dispersion values (Patient: QT = 360.9+/-53.3; QTc = 438.5+/-33.2; QTD = 42.4+/-20.8; QTcD = 57.5+/-23.8; CONTROL: QT = 325.9+/-24.1; QTc = 398.7+/-19.7; QTD = 29.9+/-10.2; QTcD = 47.3+/-16.6; P<0.01). QT, QTc, and QTcD values were significantly greater in patients who had renal failure duration longer than 2 years. Patients who had impaired left ventricular systolic function on echocardiogram had greater QTc, QTD, and QTcD values. It was found that sex, cardiomegaly on chest X-ray, and left ventricular hypertrophy on echocardiogram were not related to these parameters. It is concluded that, impaired cardiac systolic function and longer renal failure duration are related to an increase in QT, QTc, QTD, and QTcD values and hence these variables may be risk factors for ventricular arrhythmias in uremic patients.

Adolescent↗
PubMed1999

Plasma endothelin-1 levels in patients with left-to-right shunt with or without pulmonary hypertension.

The aim of this study was to evaluate the role of endothelin-1 (ET-1) in pathophysiology of pulmonary hypertension (PH) secondary to congenital heart disease with left-to-right shunt. Twenty-three children (12 male, 11 female) aged 0.58-13 years were enrolled the study. Blood samples were drawn from superior vena cava, right atrium, right ventricle, pulmonary artery and pulmonary wedge or pulmonary vein during cardiac catheterization. Plasma ET-1 levels were assayed by ELISA. Patients were divided into two groups according to the presence or absence of PH. Plasma ET-1 levels of the study group were compared to the peripheral venous and arterial ET-1 levels of 11 healthy infants and children (aged 0.75-13 years). Plasma ET-1 levels in patients with left-to-right shunt were found significantly higher than those of controls. However, plasma ET-1 levels were similar between the two groups of the patients. Pulmonary venous ET-1 levels were higher than the levels of superior vena cava, this suggested an increased production of ET-1 in pulmonary vascular bed in patients with PH. No correlations were found between plasma ET-1 levels and pulmonary arterial pressure, pulmonary vascular resistance and pulmonary blood flow in the patients. Plasma ET-1 levels of the patients with left-to-right shunt were increased independently from pulmonary arterial pressure and pulmonary vascular resistance. This increase was related to the production of ET-1 in pulmonary vascular bed in patients with PH. ET-1 could not be found to be directly related to the development of PH in the patients with left-to-right shunt.

Adolescent↗
PubMed1999

Quantitation of Doppler color flow jet areas for mitral regurgitation in children: angiographic correlation.

Eighteen patients with chronic isolated rheumatic mitral regurgitation aged between 7 and 19 years (mean age +/-SD, 12.69+/-3.47 years) were analyzed with color Doppler imaging. Sixteen patients were performed cardiac catheterization within 24 h. Jets were classified as eccentric and central. Regurgitant jet area and its ratio to left atrial area and body surface area were measured by Doppler color flow imaging. Regurgitant volume and regurgitant fractions were calculated with angiography. There was a good correlation between regurgitant jet area and angiographic grade of mitral regurgitation (P<0.01). The correlation between regurgitant jet area/left atrial area ratios and angiographic grade of mitral regurgitation was limited (P<0.01). There was excellent correlation between regurgitant jet area/body surface area and angiographic regurgitant fraction (r = 0.85; P<0.001). There was also a good correlation between regurgitant jet area and regurgitant fraction (r = 0.82; P<0.001). However, the relation of regurgitant jet area/left atrial area to regurgitant fraction was weak (r = 0.72; P<0.01). In conclusion, the measurement of regurgitant fraction and its ratios to left atrial area and body surface area by color Doppler flow imaging can predict the angiographic severity in children who have even eccentric regurgitant jets.

Adolescent↗
PubMed1998

Dispersion of QT and QTc interval in healthy children, and effects of sinus arrhythmia on QT dispersion.

OBJECTIVE: To determine the normal values of QT and QTc dispersion and the effects of sinus arrhythmia on QT dispersion in healthy children. PATIENTS AND SETTING: The study was carried out in a university hospital on 372 local schoolchildren (200 male, 172 female), aged seven to 18 years. METHODS: The QT and preceding RR intervals of at least one sinus beat were measured manually in a range of nine to 12 leads on standard 12 lead surface ECGs. The corrected QT interval was computed by the method of Bazett. Dispersion of QT and QTc were defined as (1) the difference between the maximum and minimum QT and QTc intervals occurring in any of the 12 leads (QTD and QTcD), (2) the standard deviation of the QT and QTc interval in the measurable leads (QT-SD and QTc-SD). RESULTS: There was no significant difference in QT, QTc, and RR dispersion between girls and boys. Overall 53% of children had sinus arrhythmia. Although QTD and QT-SD were not affected by sinus arrhythmia, both QTcD and QTc-SD were significantly greater in children with sinus arrhythmia than in those without (QTcD: 52.9 (17.4) v 40.9 (13.1); QTc-SD: 17.5 (5.9) v 13.2 (4.0); p < 0.001). CONCLUSIONS: As calculation of QTc dispersion is affected by sinus arrhythmia, which is common in childhood, we suggest that QT dispersion should not be corrected for heart rate in children.

Adolescent↗
PubMed1995

Mitral valve and left ventricular thrombi in an infant with acquired protein C deficiency. A case report.

The authors present an infant with left ventricular and mitral valve thrombi diagnosed by cross-sectional echocardiography. Thrombosis was due to acquired transient protein C deficiency, which was caused by impaired liver function due to sepsis. Because the thombi were very large and mobile, urgent surgery was performed. Eight weeks later, the patient's protein C level returned to normal ranges. The authors suggest that in all cases with intracardiac thrombosis, protein C deficiency should be investigated.

Echocardiography↗