Apoptosis of CD4؉ T lymphocytes, induced by contact between human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (gp120) and its receptors, could contribute to the cell depletion observed in HIV-infected individuals. CXCR4 appears to play an important role in gp120-induced cell death, but the mechanisms involved in this apoptotic process remain poorly understood. To get insight into the signal transduction pathways connecting CXCR4 to apoptosis following gp120 binding, we used different cell lines expressing wild-type CXCR4 and a truncated form of CD4 that binds gp120 but lacks the ability to transduce signals. The present study demonstrates that (i) the interaction of cell-associated gp120 with CXCR4-expressing target cells triggers a rapid dissipation of the mitochondrial transmembrane potential resulting in the cytosolic release of cytochrome c from the mitochondria to cytosol, concurrent with activation of caspase-9 and -3; (ii) this apoptotic process is independent of Fas signaling; and (iii) cooperation with a CD4 signal is not required. In addition, following coculture with cells expressing gp120, a Fas-independent apoptosis involving mitochondria and caspase activation is also observed in primary umbilical cord blood CD4 ؉ T lymphocytes expressing high levels of CXCR4. Thus, this gp120-mediated apoptotic pathway may contribute to CD4 ؉ T-cell depletion in AIDS.

Stand-alone photovoltaic (PV) systems are becoming increasingly viable and cost-effective for remote and/or offutility grid power requirements. Thousands of PV systems are being installed annually in the United States and abroad with typical applications including lighting, telecommunications, and other battery charging requirements. In general, a standalone PV system consists of a PV array, which converts sunlight to direct-current electricity, energy storage in the form of secondary batteries, loads or appliances, and a control system, which regulates battery charging and operation of the load. While PV module development over the past decade has resulted in a highly reliable product, the performance of battery and charge controller sub-systems have indicated a need for improvement. These deficient areas include proper specification of charging requirements and control set points for the battery type and environment. A better understanding of how batteries (less than 220 Ah) operate in PV systems is essential for the success of this market. Specifications applicable to the low charge/discharge rates typical in PV systems need to be published in the battery technical literature. This paper presents typical strategies for battery charge regulation and load control used in stand alone PV systems. Several charge algorithms (methods of controlling current to the battery) are presented, along with terminology used by the PV industry for battery charge controllers. Information gained from an extensive evaluation of commercially available charge controllers is discussed along with data collected from tests on PV systems in the field. Finally, an overview of battery performance characteristics needed for the successful design and long-term operation of PV systems is presented with the

In this paper, we report the results of long-term tests on 14 separate small stand-alone PV systems. These tests were carried out at two separate laboratories in Albuquerque, New Mexico and in Cape Canaveral, Florida. The systems were heavily instrumented to help determine what effects voltage regulation set points have on system water loss, battery capacity lifetime and system reliability. We find that under the proper conditions, the flooded lead-acid batteries in these PV systems can achieve cycle-lifetimes comparable to manufacturer's expectations for conventional battery applications. We also find that both the overcharge and overdischarge protection provided by the system charge controllers were necessary for proper operation of these systems. Details of the data and a number of conclusions for system designers are presented. I NTRO D UCTlO NEarly loss of battery capacity is one of the most common problems restricting the use of small stand-alone PV systems, both in developed countries and in third world applications. 12,3,4 A better understanding of how charge controller settingsand algorithms affect specific types of batteries would allow users to improve PV system reliability and achieve more predictable battery lifetimes.In this paper we report the results of two separate long-term tests of flooded lead-acid batteries and charge controllers in fourteen separate PV systems. Previous papers 56,7 have reported shorter term experiments involving batteries and charge controllers and given an interim report on the tests reported in this paper. The tests reported here, which were designed to evaluate what parameters affect a battery's stateof-charge, lifetime, and water loss, were performed at Sandia National Laboratories (Sandia) in Albuquerque, New Mexico and at the Florida Solar Energy Center (FSEC) in Cape Canaveral, Florida. Seven complete stand-alone PV systems were tested at each location. The tests lasted slightly less than two years at each location, with the systems operating at Sandia from

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The performance of 21 PV-powered low pressure sodium lighting systems on a multi-use pathway has been documented in this paper. Specific areas for evaluation include the vandal resistant PV modules, constant voltage and onloff PV charge controllers, flooded deep-cycle leadantimony and valve regulated lead-acid (VRIA) gel batteries, and low pressure sodium ballasts and lights. The PV lighting system maintenance intervals and lessons learned have been documented over the past 2.5-years. The above performance data has shown that with careful hardware selection, installation, and maintenance intervals the PV lighting systems will operate reliability.