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  • 1
    ISSN: 1432-0428
    Keywords: Type 1 (insulin-dependent) diabetes mellitus ; intraperitoneal insulin ; closed-loop blood glucose control ; hepatic glucose production ; stable isotope labelled glucose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intraperitoneal infusion of insulin should be more physiological than intravenous insulin since part of the insulin is directed toward the portal vein, which allows the liver to retain its major role in glucose homeostasis. The regulation of hepatic glucose production during the intraperitoneal and intravenous infusions of insulin were compared in eight Type 1 (insulin-dependent), C-peptide-deficient diabetic patients. Primed, continuous infusions of [6,6-2H] glucose were given in the postabsorptive state and during continuous infusion of unlabelled glucose at 1.5 and 4 mg/kg· min, while normoglycaemia was maintained by closed-loop intraperitoneal and intravenous insulin delivery. During all three periods, plasma glucose concentrations remained near normal (variations 3.8–6.1%). The insulin infusion rates required for normal plasma glucose concentrations were essentially the same for the intravenous and intraperitoneal routes in all cases, although the variations were greater with intraperitoneal insulin. Plasma free-insulin levels were only slightly, non-significantly lower with intraperitoneal infusion than with intravenous infusion. Hepatic glucose production was significantly lower with intraperitoneal insulin during all three conditions: basal: 1.71±0.14, i.p. vs 2.37±0.26 mg/kg · min, i.v.; 1.5 mg/kg · min glucose infusion: 0.49±0.23, i.p. vs 0.88±0.18 mg/kg · min, i.v.; 4 mg/kg · min glucose infusion: 0.31±0.10, i.p. vs 0.56±0.12 mg/kg · min, i.v. These results, obtained with steady-state conditions for plasma glucose, isotopic plasma glucose enrichments and unlabelled glucose infusion rates, suggest that better control of hepatic glucose production leading to normoglycaemia was achieved with the intraperitoneal infusion.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 38 (1995), S. 726-731 
    ISSN: 1432-0428
    Keywords: Key words Non-invasive test ; detection ; coronary artery disease ; diabetic patients.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Coronary artery disease may be difficult to detect in diabetic patients. This study was designed to determine the specificity and sensitivity of three non-invasive tests. Accordingly, the results of 48-h ambulatory electrocardiogram (ECG) monitoring, maximal ECG exercise test, and intravenous dipyridamole myocardial thallium scintigraphy were compared in 59 middle-aged diabetic patients who were consecutively selected for suspected coronary artery disease. All patients also underwent coronary angiography, which was performed regardless of the results of the non-invasive tests. Twenty patients (34 %) had significant coronary lesions, i. e. stenosis equal to or greater than 70 %, and 16 of these 20 patients (80 %) had double or triple vessel disease. Sensitivity and specificity were, respectively, 25 % and 88 % for ambulatory ECG monitoring, 75 % and 77 % for the exercise test and 80 % and 87 % for thallium myocardial scintigraphy. This observation strongly supports the use of non-invasive tests for the detection of coronary artery disease in those diabetic patients at high risk of such disease. As the exercise test is cheaper and more widely available than thallium myocardial scintigraphy it should be used as a first line examination. Dipyridamole myocardial scintigraphy may provide an alternative solution for those patients who cannot perform maximal exercise, or with atypical clinical presentation. [Diabetologia (1995) 38: 726–731]
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 38 (1995), S. 726-731 
    ISSN: 1432-0428
    Keywords: Non-invasive test ; detection ; coronary artery disease ; diabetic patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Coronary artery disease may be difficult to detect in diabetic patients. This study was designed to determine the specificity and sensitivity of three non-invasive tests. Accordingly, the results of 48-h ambulatory electrocardiogram (ECG) monitoring, maximal ECG exercise test, and intravenous dipyridamole myocardial thallium scintigraphy were compared in 59 middle-aged diabetic patients who were consecutively selected for suspected coronary artery disease. All patients also underwent coronary angiography, which was performed regardless of the results of the non-invasive tests. Twenty patients (34%) had significant coronary lesions, i.e. stenosis equal to or greater than 70%, and 16 of these 20 patients (80%) had double or triple vessel disease. Sensitivity and specificity were, respectively, 25% and 88% for ambulatory ECG monitoring, 75% and 77% for the exercise test and 80% and 87% for thallium myocardial scintigraphy. This observation strongly supports the use of non-invasive tests for the detection of coronary artery disease in those diabetic patients at high risk of such disease. As the exercise test is cheaper and more widely available than thallium myocardial scintigraphy it should be used as a first line examination. Dipyridamole myocardial scintigraphy may provide an alternative solution for those patients who cannot perform maximal exercise, or with atypical clinical presentation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2173-2175 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate high-speed performance of InGaAs barrier-enhanced metal-semiconductor-metal (M-S-M) Schottky barrier photodetectors monolithically integrated with double-heterostructure InP/InGaAsP/InP waveguides. Pulse response widths of 77 ps are recorded, with an associated 3 dB power bandwidth of 1.7 GHz. Photodetectors acting as both "taps'' of the waveguided signal and as "terminal'' devices were fabricated. These detectors have application in receivers which are integrated with semiconductor waveguides for on-chip optical signal processing.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first measurement of two-photon absorption (TPA) and self-phase modulation in an InGaAsP/InP multi-quantum-well waveguide. The TPA coefficient, β2, was found to be 60±10 cm/GW at 1.55 μm. Despite operating at 200 nm from the band edge, self-phase modulation as high as 8±2 rad was observed for 30-ps optical pulses at 3.8-W peak input power. A theoretical calculation indicates that this enhanced phase modulation is primarily due to bandfilling in the quantum wells and the free-carrier plasma effect.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of two photon absorption which is strongly dependent on the applied electric field and the optical polarization. At 1.55 μm wavelength, the two-photon absorption coefficient of the GaAs/AlGaAs multiquantum well (MQW) waveguides for transverse-magnetic light is about seven times lower than for transverse-electric polarized light and changes by a factor of approximately 4 for a change in applied direct-current electric field of ∼140 kV/cm. Ultrafast nonlinear refraction causing phase changes of over π radians without appreciable excess loss is observed. These measurements demonstrate that GaAs/AlGaAs MQW waveguides could be successfully used for subpicosecond all-optical switching near half-band gap, at wavelengths corresponding to the 1.55 μm optical communications band.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1949-1951 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a two-dimensional grating spectrometer implemented in an InP/InGaAsP/InP planar waveguide for use in the low-loss 1.5 μm wavelength fiber band. The spectrometer uses a single vertical-walled focusing reflection grating to disperse 78 channels, spaced at 1 nm intervals, with diffraction-limited resolution (∼0.3 nm) and a high channel isolation ((approximately-greater-than)19 dB). The spectrometer may be used such that it is insensitive to the state of the input polarization.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1518-1520 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the monolithic integration of an InGaAs metal-semiconductor-metal Schottky barrier photodetector with a butt-coupled InP/InGaAsP/InP waveguide, where the latter is formed by selective area regrowth using organometallic chemical vapor deposition. A fast pulse response (60–65 ps full width at half maximum, with no discernible tail) and a high quantum efficiency (∼80%) were observed for 1.3 μm guided light with the detector biased at 7 V. A thin InAlAs Schottky barrier enhancement layer limited the dark current to ∼28 nA at this bias.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 729-731 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The high-speed performance of InGaAs interdigitated metal-semiconductor-metal (M-S-M) photodetectors illuminated with 1.55 and 1.3 μm wavelength radiation is modeled using a two-dimensional transit time calculation. Excellent agreement is found with the experimental pulse response of detectors with interdigital spacings of 2 and 3 μm. We study the dependence of the bandwidth on the device dimensions, and also examine the quantum efficiency. The results should aid the design of InGaAs M-S-M detectors with the optimum combination of bandwidth and efficiency for a given application.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a novel coupling geometry for integrated waveguide photodetectors−a hybrid vertical coupling/butt coupling scheme that allows the integration of fast, efficient, photodetectors with conventional double heterostructure waveguides. It can be employed to yield a planar, or pseudo-planar, surface that supports further levels of integration. The approach is demonstrated with a 25-μm-long p-i-n detector integrated with an InP/InGaAsP/InP waveguide, which displays a high (∼90%) efficiency and large (∼15 GHz) bandwidth. This is the fastest high-efficiency integrated waveguide photodetector reported to date.
    Type of Medium: Electronic Resource
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