Oral treatment with a zinc complex of acetylsalicylic acid prevents diabetic cardiomyopathy in a rat model of type-2 diabetes: activation of the Akt pathway.

BACKGROUND: Type-2 diabetics have an increased risk of cardiomyopathy, and heart failure is a major cause of death among these patients. Growing evidence indicates that proinflammatory cytokines may induce the development of insulin resistance, and that anti-inflammatory medications may reverse this process. We investigated the effects of the oral administration of zinc and acetylsalicylic acid, in the form of bis(aspirinato)zinc(II)-complex Zn(ASA)2, on different aspects of cardiac damage in Zucker diabetic fatty (ZDF) rats, an experimental model of type-2 diabetic cardiomyopathy. METHODS: Nondiabetic control (ZL) and ZDF rats were treated orally with vehicle or Zn(ASA)2 for 24 days. At the age of 29-30 weeks, the electrical activities, left-ventricular functional parameters and left-ventricular wall thicknesses were assessed. Nitrotyrosine immunohistochemistry, TUNEL-assay, and hematoxylin-eosin staining were performed. The protein expression of the insulin-receptor and PI3K/AKT pathway were quantified by Western blot. RESULTS: Zn(ASA)2-treatment significantly decreased plasma glucose concentration in ZDF rats (39.0 +/- 3.6 vs 49.4 +/- 2.8 mM, P < 0.05) while serum insulin-levels were similar among the groups. Data from cardiac catheterization showed that Zn(ASA)2 normalized the increased left-ventricular diastolic stiffness (end-diastolic pressure-volume relationship: 0.064 +/- 0.008 vs 0.084 +/- 0.014 mmHg/microl; end-diastolic pressure: 6.5 +/- 0.6 vs 7.9 +/- 0.7 mmHg, P < 0.05). Furthermore, ECG-recordings revealed a restoration of prolonged QT-intervals (63 +/- 3 vs 83 +/- 4 ms, P < 0.05) with Zn(ASA)2. Left-ventricular wall thickness, assessed by echocardiography, did not differ among the groups. However histological examination revealed an increase in the cardiomyocytes' transverse cross-section area in ZDF compared to the ZL rats, which was significantly decreased after Zn(ASA)2-treatment. Additionally, a significant fibrotic remodeling was observed in the diabetic rats compared to ZL rats, and Zn(ASA)2-administered ZDF rats showed a similar collagen content as ZL animals. In diabetic hearts Zn(ASA)2 significantly decreased DNA-fragmentation, and nitro-oxidative stress, and up-regulated myocardial phosphorylated-AKT/AKT protein expression. Zn(ASA)2 reduced cardiomyocyte death in a cellular model of oxidative stress. Zn(ASA)2 had no effects on altered myocardial CD36, GLUT-4, and PI3K protein expression. CONCLUSIONS: We demonstrated that treatment of type-2 diabetic rats with Zn(ASA)2 reduced plasma glucose-levels and prevented diabetic cardiomyopathy. The increased myocardial AKT activation could, in part, help to explain the cardioprotective effects of Zn(ASA)2. The oral administration of Zn(ASA)2 may have therapeutic potential, aiming to prevent/treat cardiac complications in type-2 diabetic patients

Thermally annealed Ni/n-GaAs(Si)/In Schottky barrier diodes

We have identically prepared as many as eight Ni/n-GaAs/In Schottky barrier diodes (SBDs) using an n-type GaAs substrate with a doping density of about 7.3 x 10(15) cm(-3). The thermal stability of the Ni/n-GaAs/In Schottky diodes has been investigated by means of current-voltage (I-V) techniques after annealed for 1 min in N-2 atmosphere from 200 to 700 degrees C. For Ni/n-GaAs/In SBDs, the Schottky barrier height Phi(b) and ideality factor it values range from 0.853 +/- 0.012 eV and 1.061 +/- 0.007 (for as-deposited sample) to 0.785 +/- 0.002 eV and 1.209 +/- 0.005 (for 600 degrees C annealing). The ideality factor values remained about unchanged up to 400 degrees C annealing. The I-V characteristics of the devices deteriorated at 700 degrees C annealing. (C) 2007 Elsevier B.V. All rights reserved

Barrier height enhancement and stability of the Au/n-InP Schottky barrier diodes oxidized by absorbed water vapor

We have fabricated the Au/n-InP Schottky barrier diodes (SBDs) with and without an intentionally grown interfacial oxide layer. The oxide layer on chemically cleaned indium phosphide (InP) surface has been obtained by exposure to water vapor at 1 ml/min at 200 degrees C before metal evaporation. The chemical composition of the surface oxides grown on the InP is investigated using x-ray photoelectron spectroscopy. Phosphorus is present as In(Po-3)(3), InPO4, P2O5 and elemental R The influence of the oxide on the Schottky barrier formation and contact stability at the InP (100) surface upon subsequent metal deposition has been investigated. The transport properties of the metal-semiconductor contacts have been observed to be significantly affected by the presence of the interfacial oxide layer. Thus, the barrier height has been increased by similar to 140 meV for the Au/n-InP SBD by means of the interfacial oxide grown by use of absorbed water vapor. Furthermore, in order to observe the effect of the aging in the Au/n-InP SBD with and without the interfacial oxide layer, the current-voltage (I-V) measurements have also been repeated 7, 14, 28, 45, 56, and 70 days after fabrication of these diodes. The obtained diode parameters were examined statistically and it was found that the reference and oxidized Au/n-InP SBDs exhibited stable characteristics 14 days after metal deposition. (c) 2005 American Vacuum Society

The interface state density characterization by temperature-dependent capacitance-conductance-frequency measurements in Au/Ni/n-GaN structures

Wehave fabricated the Au/Ni/n-GaN structures and measured their capacitance-frequency (C-f) and conductance (G/w)-angular frequency (w) characteristics in the temperature range of 60-320 K. The C-f curves for different reverse bias voltages have shown a behavior almost independent of the bias voltage at frequencies above 300 kHz at each measurement temperature. Wehave calculated the temperature-dependent interface state density, N-ss, values from the G/w versus w curves. The N-ss value for the Ni/n-GaN interface ranges from 3.36 x 10(11) cm(-2) eV(-1) at 0.0 V to 2.92 x 10(11) cm(-2) eV(-1) at 0.40 V for 60 K, and 6.63 x 10(11) cm(-2) eV(-1) at 0.0 V to 3.87 x 10(11) cm(-2) eV(-1) at 0.40 V for 320 K. That is, the interface state density value increases with increasing temperature. It has been seen that the values of N-ss obtained from the G/w versus w curves of the device are lower than the given values for metal/n-type GaN interface in the literature

Thermal annealing effects on I-V-T characteristics of sputtered Cr/n-GaAs diodes

Sputtered Cr/n-GaAs Schottky diodes have been prepared and annealed at 200 and 400 degrees C. The current-voltage (I-V) characteristics of the as-deposited and annealed diodes have been measured in the temperature range of 60-320 K with steps of 20 K. The effect of thermal annealing on the temperature-dependent I-V characteristics of the diodes has been investigated experimentally. The ideality factor and barrier height (BH) values for 400 degrees C annealed diode approximately remain unchanged from 120 to 320 K, and those of the as-deposited sample from 160 to 320 K. The departures from ideality at low temperatures have been ascribed to the lateral fluctuations of the BH. The BH values of 0.61 and 0.74 eV for the as-deposited and 400 degrees C annealed diodes were obtained at room temperature, respectively. A Richardson constant value of 9.83 A cm(-2) K-2 for 400 degrees C annealed Schottky diode, which is in close agreement with the known value of 8.16 A cm(-2) K-2 for n-type GaAs. Furthermore, To anomaly values of 15.52, 10.68 and 5.35 for the as-deposited and 200 and 400 degrees C annealed diodes were obtained from the nT versus T plots. Thus, it has been seen that the interface structure and quality improve by the thermal annealing at 400 degrees C. (C) 2009 Elsevier B.V. All rights reserved

Prediction of lateral barrier height in identically prepared Ni/n-type GaAs Schottky barrier diodes

We have identically prepared Ni/n-GaAs/In Schottky barrier diodes (SBDs) with doping density of 7.3 x 10(15) cm(-3). The barrier height for the Ni/n-GaAs/In SBDs from the current-voltage characteristics have varied from 0.835 to 0.856 eV, and ideality factor n from 1.02 to 1.08. We have determined a lateral homogeneous barrier height value of 0.862 eV for the Ni/n-GaAs/In SBD from the experimental linear relationship between barrier heights and ideality factors. (c) 2007 Elsevier B.V. All rights reserved

Analysis of current-voltage-temperature characteristics and T-0 anomaly in Cr/n-GaAs Schottky diodes fabricated by magnetron sputtering technique

We have fabricated two groups of Cr/n-GaAs Schottky diodes (SDs) by magnetron sputtering technique to determine whether To anomaly varies in similarly fabricated SDs or not. Firstly, the first group diodes were inserted into a vacuum chamber to form the Schottky contacts, then the second group diodes which are held in the clean room medium for 3 In before Schottky metal deposition. The current-voltage (I-V) characteristics of three diodes (the dots of the sample CrD1) from the first group and two diodes (the dots of the sample CrD2) from the second group were measured in temperature range of 60-320 K. The barrier heights increased with increasing temperature in range of 60-160 K, and did not changed in range of 160-320 K. Ideality factory value decreased with increasing temperature in range of 60-160 K and changed between 1.05 and 1.10 in range of 160-320 K. To anomaly values were calculated from straight lines fitted to nT-T plots. The fits to the experimental values of nT-T plots are parallel to the ideal Schottky especially for the dots (Schottky diodes) of the sample CrD1. To anomaly values for the dots contact line, of the sample CrD1 were obtained as 13.9, 11.20 and 13.31 K: and the values of 19.74 and 19.20 K was obtained for the dots of the sample CrD2. It has been concluded that the To anomaly values for the similarly fabricated diodes (the dots of the sample CrD1 or the CrD2) are almost very close to each other within the margins of experimental error. (C) 2008 Elsevier B.V. All rights reserved.The Turkish Scientific and Technological Research Council of Turkey (TUBITAK) [105T487]; Ataturk University [BAP 2006/51]This work was supported by The Turkish Scientific and Technological Research Council of Turkey (TUBITAK) (Project No. 105T487) and Ataturk University (Project No. BAP 2006/51). The authors wish to thank to TUBITAK and Ataturk University

DEPENDENCE OF CHARACTERISTIC DIODE PARAMETERS IN <font>Ni</font>/n-<font>GaAs</font> CONTACTS ON THERMAL ANNEALING AND SAMPLE TEMPERATURE

We have prepared the sputtered Ni /n- GaAs Schottky diodes which consist of as-deposited, and diodes annealed at 200 and 400°C for 2 min. The effect of thermal annealing on the temperature-dependent current–voltage (I–V) characteristics of the diodes has been experimentally investigated. Their I–V characteristics have been measured in the temperature range of 60–320 K with steps of 20 K. It has been seen that the barrier height (BH) slightly increased from 0.84 (as-deposited sample) to 0.88 eV at 300 K when the contact has been annealed at 400°C. The SBH increased whereas the ideality factor decreased with increasing annealing temperature for each sample temperature. The I–V measurements showed a dependence of ideality factor n and BH on the measuring temperature that cannot be explained by the classical thermionic emission theory. The experimental data are consistent with the presence of an inhomogeneity of the SBHs. Therefore, the temperature dependent I–V characteristics of the diodes have been discussed in terms of the multi-Gaussian distribution model. The experimental data good have agree with the fitting curves over whole measurement temperature range indicating that the SBH inhomogeneity of our as-deposited and annealed Ni /n- GaAs SBDs can be well-described by a double-Gaussian distribution. The slope of the nT versus T plot for the samples has approached to unity with increasing annealing temperature and becomes parallel to that of the ideal Schottky contact behavior for the 400°C annealed diode. Thus, it has been concluded that the thermal annealing process translates the metal-semiconductor contacts into thermally stable Schottky contacts. </jats:p