Seroprevalence of human herpesvirus-8 (HHV-8) in countries of Southeast Asia compared to the USA, the Caribbean and Africa

Seroprevalence of HHV-8 has been studied in Malaysia, India, Sri Lanka, Thailand, Trinidad, Jamaica and the USA, in both healthy individuals and those infected with HIV. Seroprevalence was found to be low in these countries in both the healthy and the HIV-infected populations. This correlates with the fact that hardly any AIDS-related Kaposi’s sarcoma has been reported in these countries. In contrast, the African countries of Ghana, Uganda and Zambia showed high seroprevalences in both healthy and HIV-infected populations. This suggests that human herpes virus-8 (HHV-8) may be either a recently introduced virus or one that has extremely low infectivity. Nasopharyngeal and oral carcinoma patients from Malaysia, Hong Kong and Sri Lanka who have very high EBV titres show that only 3/82 (3.7%) have antibody to HHV-8, demonstrating that there is little, if any, cross-reactivity between antibodies to these two gamma viruses. © 1999 Cancer Research Campaig

The Application of Sparse Supernodal Factorization Algorithms for Structurally Symmetric Linear Systems in Semiconductor Device Simulation

It is well known that the solution of sparse linear systems, generally expressed in th

Indirect Model Predictive Control of a Three-Phase Grid-Connected Siwakoti-H Inverter.

The Siwakoti-H flying-capacitor inverter (sFCI) is a potential candidate for photovoltaic applications, specifically for the transformerless grid-connected systems. One of the main challenges in the control of a sFCI is to maintain the flying capacitor voltage within prescribed limits while balancing the voltages on the three flying capacitors. This paper proposes an indirect model predictive control strategy for a three-phase sFCI connected to the grid via an LCL-filter. By linearizing the system model, the nonlinearities introduced due to the dynamics of the flying capacitor are neglected. Moreover, by not directly controlling the switches, but rather manipulating the modulating signal, the optimization problem can be formulated as a quadratic program (QP) and solved in a computationally efficient manner. The explicit solution computed by the controller makes the realtime implementation feasible by employing a carrier-based pulse width modulator (CB-PWM). The presented results illustrate the steady-state and dynamic performance of the controller.acceptedVersionPeer reviewe

Design of state-feedback controller for a single-phase grid-connected Siwakoti-h inverter with LCL filter

© VDE VERLAG GMBH · Berlin · Offenbach. Grid-tied transformerless inverters for photovoltaic (PV) systems have attained a prominent share in the distributed power generation applications on both the domestic and utility scale. This arises the need of a transformerless inverter with less hardware components and complexity. This paper presents a state-feedback current controller (SFCC) for a flying-capacitor based transformerless inverter (Siwakoti-H topology). Compared to the conventional proportional-integral (PI) based control, the state-feedback current control provides a better dynamic performance for a single-phase grid-tied converter equipped with an LCL filter. The controller is designed using pole placement to set the dominant behavior of the converter, which actively damps the resonant frequency of the LCL filter. The controller is extended using dc voltage feedforward compensation (DVFC) to maintain the voltage ripple of the flying capacitor within the limits, and an integral state for improved disturbance rejection. Simulation results illustrate the steady-state and dynamic performance of the controller as well as the inherent damping of the LCL filter resonance. Experimental results are presented to verify the steady-state operation of the system