Effect of Sb implantation on copper silicides formation and morphology after annealing of Cu/Si structures

In this work, the solid state reaction between a thin film of copper and silicon has been studied using Rutherford backscattering spectroscopy, X-ray diffraction, scanning electron microscopy and microprobe analysis. Cu films of 400 and 900 Å thicknesses are thermally evaporated on Si(1 1 1) substrates, part of them had previously been implanted with antimony ions of 5×10¹⁴ or 5×10¹⁵ at. cm⁻² doses. The samples are heat-treated in vacuum at temperatures in the range 200–700 °C for various times. The results show the growth and formation of Cu₃Si and Cu₄Si silicides under crystallites shape dispatched on the sample surface, independently of the implantation dose. On the other hand, it is established that the copper layer is less and less consumed as the antimony dose increases, resulting in the accumulation of Sb⁺ ions at silicide/Si interface and in the silicide layer close to surface. The exposure of samples to air at room temperature shows the stability of Cu₄Si phase whereas the Cu₃Si silicide disappears to the benefit of the silicon dioxide formation. The observed phenomena are discussed.     

Adenovirus-mediated catalase gene transfer reduces oxidant stress in human, porcine and rat pancreatic islets

Susceptibility of pancreatic islets to oxidant stress may affect islet viability and contribute to primary non function of allo- or xenogenic grafts. We investigated the influence of overexpression of catalase (CAT) on the viability of human, porcine and rat islets, as well as INS-1 beta-cell line. Islets were transfected with a replication-deficient adenovirus vector containing human CAT cDNA under the control of the adenovirus major late promoter (AdCAT) or a vector containing no foreign gene (AdNull) and used as a control. Oxidant stress was induced 48 h later by xanthine oxidase-hypoxanthine (XO 25 mU/ml, HX 0.5 mmol/l) or hydrogen peroxide (100 or 250 micromol/l). Islet cell viability was assessed 72 h after CAT transfer by 4-[3-(4-Idophenyl)-2-(4 nitrophenyl)-2H-5-tetrazolio]-1,2,benzene disulphonate (WST-1) test. Baseline catalase activity was three to fourfold lower in porcine than in human islets. CAT activity was reproducibly increased 2.5- to 7-fold in AdCAT infected islets, at least for 13 days. Overall, AdCAT conferred on human and pig islets a protection of 26.1 +/- 6.1 and 21.2 +/- 9.8% on XOHX injury and 35.4 +/- 4.2 and 57.9 +/- 10.5% on H2O2 stress. Similarly, rat islet cells and INS-1 cells were protected on XOHX stress by 17.8 +/- 2.3 and 30.8 +/- 8.7%, respectively. AdNull had no effect. Basal and stimulated insulin secretion was preserved in AdCAT-transfected human islets despite a XOHX challenge. This study validates adenovirus-mediated catalase gene transfer as a realistic approach to reduce non specific inflammation effects on human or porcine islet grafts. Moreover the relevance of defense mechanisms, previously suggested in human islets, is here illustrated in porcine islets.     

QoS management through service level agreements: a short overview

The Internet protocol (IP) was created as a connectionless network layer protocol that takes no attempt to distinguish between various application types. Hence, the integration of a wide range of telecommunication services over the Internet is the main reason behind the need for the provision of quality of service (QoS) guarantees to end users. In such multiservice networks, resources are managed based on service level agreements (SLA), acknowledging different types of traffic in terms of bandwidth requirements, delay and other QoS parameters. An SLA is the documented result of a negotiation between a customer and a service provider that defines service characteristics, responsibilities and priorities of every party. An SLA may include statements about tariffing and billing, service delivery, and compensations. This paper provides a short overview of some aspects of quality of service, and identifies main issues and problems of defining and managing an SLA, based on its current standardization stage.     

Magnetocaloric Properties of the Perovskite GdCuO3: Monte Carlo Simulation

Journal of Superconductivity and Novel Magnetism - This work aims to examine the magnetocaloric properties of the Perovskite GdCuO3, such as the total magnetization, the susceptibility, and the...     

Elaboration and characterization of a KCl single crystal doped with nanocrystalsof a Sb2O3 semiconductor

Undoped and doped KCl single crystals have been successfully elaborated via the Czochralski（Cz） method.The effects of dopant Sb₂O₃ nanocrystals on structural and optical properties were investigated by a number of techniques,including X-ray diffraction（XRD）,scanning electron microscopy（SEM）,energy dispersive X-ray（EDAX） analysis,UV-visible and photoluminescence（PL） spectrophotometers.An XRD pattern of KCl:Sb₂O₃ reveals that the Sb₂O₃ nanocrystals are in the well-crystalline orthorhombic phase.The broadening of diffraction peaks indicated the presence of a Sb₂O₃ semiconductor in the nanometer size regime.The shift of absorption and PL peaks is observed near 334 nm and 360 nm respectively due to the quantum confinement effect in Sb₂O₃ nanocrystals.Particle sizes calculated from XRD studies agree fairly well with those estimated from optical studies.An SEM image of the surface KCl:Sb₂O₃ single crystal shows large quasi-spherical of Sb₂O₃ crystallites scattered on the surface.The elemental analysis from EDAX demonstrates that the KCl:Sb₂O₃ single crystal is slightly rich in oxygen and a source of excessive quantities of oxygen is discussed.     

Effect of substrate temperature on the structural and magnetic properties of Fe/Ag superlattices

In the present work, Fe/Ag superlattices were grown by molecular beam epitaxy (MBE) on MgO(001) single crystal substrates maintained at room temperature or at 423 K during the deposition. The structural properties were carried out using small and high angle X-ray diffraction techniques. The magnetic hysteresis loops with the magnetic field applied parallel or perpendicular to the plane of the films were measured by a superconducting quantum interference device (SQUID) magnetometer in the temperature range 5–300 K. A comparison of the obtained results showed that the heating of MgO substrates leads to a strong interdiffusion and causes a significant modification of structural and magnetic properties of Fe/Ag superlattices.     

Formation de “whiskers” et de “hillocks” sur la surface des couches minces de Cu/Sn

The external morphology of free surfaces of Cu/Sn thin films was studied using scanning electron microscopy, electron microprobe analysis and X-ray diffraction. It was shown that the aging of samples of type A (films deposited at room temperature) and type B (copper underlayer deposited at 623 K) at room temperature leads to the formation of hillocks and whiskers; however, the annealing of as-prepared samples at temperatures in the range 363–483 K leads to hillock formation only. The density of hillocks and whiskers in type A samples is two times higher than that in type B samples. The length of the whiskers in type A films (about 4 × 10^-6 m) is one order of magnitude lower than that of the whiskers in type B samples (about 3 × 10^-5 m). This large difference is due to the texture {200} of tin films in type B samples. In type C samples, after aging at room temperature, we observed only hillocks whose diameter could reach 10 × 10^-6 m. Whiskers and hillocks are composed essentially of tin, and the matrix is composed of the Cu₆Sn₅ phase.     

Contrasting renal effects of nicotine in smokers and non-smokers

BACKGROUND: Cigarette smoking is associated with acute increase in arterial pressure due to systemic vasoconstriction and decreased skin and coronary blood flow. Virtually all cardiovascular effects of cigarette smoking are due to nicotine. However, whether nicotine also affects the renal circulation and function in humans is at present unknown. METHODS: In the current study the acute effects of a 4-mg nicotine gum on arterial pressure, heart rate as well as renal haemodynamics and function were assessed in non-smokers and chronic smokers. RESULTS: In non-smokers, mean arterial pressure (+8 +/- 1 mmHg, P<0.001) and heart rate (+13 +/- 3 beats/min, P<0.001) increased whereas effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) decreased by 15 +/- 4% and 14 +/- 4% respectively; in addition, urinary cyclic GMP decreased by 51 +/- 12% in response to nicotine administration. In smokers, mean arterial pressure and heart rate increased similarly; however, in contrast with non-smokers, ERPF and GFR remained unchanged whereas urinary cyclic GMP rose by 87 +/- 43%. Changes in ERPF induced by nicotine were positively correlated with changes in urinary cyclic GMP. CONCLUSIONS: These findings indicate that nicotine administration is associated with renal vasoconstriction in healthy non-smokers, possibly through alteration of a cyclic-GMP-dependent vasoactive mechanism. Tolerance to the renal effect of nicotine was observed in chronic smokers, despite the maintenance of the systemic response to nicotine.     

GMPLS and ASON for automatic switched transport networks

In automatic switched transport networks (ASTN), transport services of different granularity can be set up, modified and released on demand, using mechanisms in the control plane. Currently, this novel provisioning paradigm is being standardized under the umbrella of the automatic switched optical network (ASON) and the generalized multiprotocol label switching (GMPLS) framework. This paper gives an overview of the concepts and open issues of ASON and GMPLS at the current stage of their development.     

Overview on MPLS Virtual Private Networks

The basic idea, features, and necessity of multiprotocol label switching (MPLS) are given in this paper, with a special focus on virtual private networks (VPN) as one of the most important features that MPLS as technology enables and supports. In this context, we first describe the general VPN models, the overlay and the peer model, and than analyze different models, such as the BGP/MPLS virtual private networks and the layer-2 MPLS virtual private networks. All over the paper, the benefits provided by using MPLS for different VPN models are emphasized, with particular attention to improved scalability, management, and quality of service (QoS).