Diagnosis and monitoring of HIV infection

The latest statistics indicate that the number of people infected with human immunodeficiency virus type 1 (HIV-1) worldwide is 40.3 million; 25.8 million of whom live in sub-Saharan Africa. In 2004; 29.5of South African women attending antenatal clinics were infected. The virus infects people of all ages and social classes. A diagnosis of HIV has serious physical; emotional and social implications for the patient. HIV-infected patients are susceptible to numerous opportunistic and other infections; as well as to non-infectious diseases such as tumours. They eventually require lifelong treatment with potentially toxic medication. It is therefore essential that a timeous and correct diagnosis be made. An understanding of the tests available for the diagnosis and monitoring of HIV is essential for all clinicians working in South Africa. Tests available for the diagnosis of HIV in patients older than 18 months include HIV-specific antibody assays; fourth-generation combination antibody-antigen assays and Western Blot. The diagnosis of HIV infection in infants younger than 18 months requires detection of the virus itself by means of p24 antigen detection or HIV DNA PCR. The CD4+ T lymphocyte count and HIV viral load are used for monitoring disease progression and response to therapy

Diagnosis and Monitoring of HIV Infection

The latest statistics indicate that the number of people infected with human immunodeficiency virus type 1 (HIV-1) worldwide is 40.3 million; 25.8 million of whom live in sub-Saharan Africa. In 2004; 29.5 of South African women attending antenatal clinics were infected. The virus infects people of all ages and social classes. A diagnosis of HIV has serious physical; emotional and social implications for the patient. HIV-infected patients are susceptible to numerous opportunistic and other infections; as well as to non-infectious backdiseases such as tumours. They eventually require lifelong treatment with potentially toxic medication. It is therefore essential that a timeous and correct diagnosis be made. An understanding of the tests available for the diagnosis and monitoring of HIV is essential for all clinicians working in South Africa. Tests available for the diagnosis of HIV in patients older than 18 months include HIV-specific antibody assays; fourth-generation combination antibody-antigen assays and Western Blot. The diagnosis of HIV infection in infants younger than 18 months requires detection of the virus itself by means of p24 antigen detection or HIV DNA PCR. The CD4+ T lymphocyte count and HIV viral load are used for monitoring disease progression and response to therapy

Laser induced damage in optical materials: twelfth ASTM symposium.

The twelfth annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 30 Sept.-l Oct., 1980. The symposium was held under the auspices of ASTM Committee F-l, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Projects Agency, the Department of Energy, the Office of Naval Research, and the Air Force Office of Scientific research. Over 150 scientists attended the symposium, including representatives of the United Kingdom, France, Japan, and West Germany. The symposium was divided into sessions concerning materials and measurements, mirrors and surfaces, thin films, and finally fundamental mechanisms. As in previous years, the emphasis of the papers presented at the symposium was directed toward new frontiers and new developments. Particular emphasis was given to materials for high power systems. The wavelength range of prime interest was from 10.6 microm to the UV region. Highlights included surface characterization, thin film-substrate boundaries, and advances in fundamental laser-matter threshold interactions and mechanisms. The scaling of damage thresholds with pulse duration, focal area, and wavelength was discussed in detail. Harold E. Bennett of the Naval Weapons Center, Alexander J. Glass of the Lawrence Livermore National Laboratory, Arthur H. Guenther of the Air Force Weapons Laboratory, and Brian E. Newnam of the Los Alamos National Laboratory were cochairmen of the symposium. The thirteenth annual symposium is scheduled for 17-18 Nov. 1981 at the National Bureau of Standards, Boulder, Colorado.

Laser induced damage in optical materials: eleventh ASTM symposium.

The eleventh Symposium on Optical Materials for High-Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 30-31 October 1979. The symposium was held under the auspices of ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Projects Agency, the Department of Energy, and the Office of Naval Research. About 150 scientists attended the symposium, including representatives of the United Kingdom, France, Canada, Japan, West Germany, and Denmark. The symposium was divided into sessions concerning transparent optical materials and the measurement of their properties, mirrors and surfaces, thin film characteristics, thin film damage, considerations for high-power systems, and finally theory and breakdown. As in previous years, the emphasis of the papers presented at the symposium was directed toward new frontiers and new developments. Particular emphasis was given to materials for high-power apparatus. The wavelength range of prime interest was from 10.6 microm to the UV region. Highlights included surface characterization, thin film-substrate boundaries, and advances in fundamental laser-matter threshold interactions and mechanisms. The scaling of damage thresholds with pulse duration, focal area, and wavelength was discussed in detail. Harold E. Bennett of the Naval Weapons Center, Alexander J. Glass of the Lawrence Livermore Laboratory, Arthur H. Guenther of the Air Force Weapons Laboratory, and Brian E. Newnam of the Los Alamos Scientific Laboratory were cochairpersons. The twelfth annual symposium is scheduled for 30 September-1 October 1980 at the National Bureau of Standards, Boulder, Colorado.

Laser induced damage in optical materials: tenth ASTM symposium.

The tenth annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 12-14 September 1978. The symposium was held under the auspices of ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Department of Energy, and the Office of Naval Research. About 175 scientists attended, including representatives of the United Kingdom, France, Canada, Japan, West Germany, and the Soviet Union. The symposium was divided into sessions concerning the measurement of absorption characteristics, bulk material properties, mirrors and surfaces, thin film damage, coating materials and design, and breakdown phenomena. As in previous years, the emphasis of the papers presented was directed toward new frontiers and new developments. Particular emphasis was given to materials for use from 10.6 microm to the UV region. Highlights included surface characterization, thin film-substrate boundaries, and advances in fundamental laser-matter threshold interactions and mechanisms. The scaling of damage thresholds with pulse duration, focal area, and wavelength was also discussed. In commemoration of the tenth symposium in this series, a number of comprehensive review papers were presented to assess the state of the art in various facets of laser induced damage in optical materials. Alexander J. Glass of Lawrence Livermore Laboratory and Arthur H. Guenther of the Air Force Weapons Laboratory were co-chairpersons. The eleventh annual symposium is scheduled for 30-31 October 1979 at the National Bureau of Standards, Boulder, Colorado.

Laser induced damage in optical materials: ninth ASTM symposium.

The Ninth Annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 4-6 October 1977. The symposium was under the auspices of ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Department of Energy (formerly ERDA), and the Office of Naval Research. About 185 scientists attended, including representatives of the United Kingdom, France, Canada, Australia, Union of South Africa, and the Soviet Union. The Symposium was divided into sessions concerning Laser Windows and Materials, Mirrors and Surfaces, Thin Films, Laser Glass and Glass Lasers, and Fundamental Mechanisms. As in previous years, the emphasis of the papers was directed toward new frontiers and new developments. Particular emphasis was given to materials for use from 10.6 microm to the uv region. Highlights included surface characterization, thin film-substrate boundaries, and advances in fundamental laser-matter threshold interactions and mechanisms. The scaling of damage thresholds with pulse duration, focal area, and wavelength were also discussed. Alexander J. Glass of Lawrence Livermore Laboratory and Arthur H. Guenther of the Air Force Weapons Laboratory were co-chairpersons. The Tenth Annual Symposium is scheduled for 12-14 September 1978 at the National Bureau of Standards, Boulder, Colorado.

Laser induced damage in optical materials: 8th ASTM symposium.

The Eighth Annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was hosted by the National Bureau of Standards in Boulder, Colorado, from 13 to 15 July 1976. The Symposium was held under the auspices of ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Energy Research and Development Administration, and the Office of Naval Research. About 160 scientists attended the Symposium, including representatives of the United Kingdom, France, Canada, and Brazil. The Symposium was divided into five half-day sessions concerning Bulk Material Properties and Thermal Behavior, Mirrors and Surfaces, Thin Film Properties, Thin Film Damage, and Scaling Laws and Fundamental Mechanisms. As in previous years, the emphasis of the papers presented at the Symposium was directed toward new frontiers and new developments. Particular emphasis was given to new materials for use at 10.6 microm in mirror substrates, windo s, and coatings. New techniques in film deposition and advances in diamond-turning of optics were described. The scaling of damage thresholds with pulse duration, focal area, and wavelength were discussed. Alexander J. Glass of Lawrence Livermore Laboratory and Arthur H. Guenther of the Air Force Weapons Laboratory were co-chairpersons of the Symposium. The Ninth Annual Symposium is scheduled for 4-6 October 1977 at the National Bureau of Standards, Boulder, Colorado.

Laser induced damage in optical materials: 7th ASTM symposium.

The Seventh ERDA-ASTM-ONR-NBS Symposium on Laser Induced Damage in Optical Materials was held at the National Bureau of Standards in Boulder, Colorado, on 29-31 July 1975. These Symposia are held as part of the activities in ASTM Subcommittee II on Lasers and Laser Materials, which is charged with the responsibilities of formulating standards and test procedures for laser materials, components, and devices. The Chairman of Subcommittee II is Haynes Lee, of Owens-Illinois, Inc. Co-chairmen for the Damage Symposia are Arthur Guenther of the Air Force Weapons Laboratory and Alexander J. Glass of Law-rence Livermore Laboratory. Over 150 attendees at the Symposium heard forty-five papers on topics relating fabrication procedures to laser induced damage in optical materials; on metal mirrors; in ir window materials; the multipulse, wavelength, and pulse length dependence of damage thresholds; damage in dielectric films and at exposed surfaces; as well as theoretical discussions on avalanche ionization and multiphoton processes of importance at shorter wavelengths. Of particular importance were the scaling relations developed from several parametric studies relating fundamental properties (refractive index, surface roughness etc.) to the damage threshold. This year many of the extrinsic influences tending to reduce a materials damage resistance were isolated such that measures of their egregious nature could be quantified. Much still needs to be accomplished to improve processing and fabrication procedures to allow a measurable approach to a materials intrinsic strength to be demonstrated.

Lens and mirror design via the principal surface.

For many laser applications, it is desired to focus a collimated beam with a specified transformation of the intensity distribution. The transformation properties of a lens or mirror system can be specified in terms of the principal surface r(alpha), which maps the height of the incident ray parallel to the optic axis onto a given angle at the focus. The intensity distribution at the focus is then given by the relation I(alpha) = I(r)r(dr/dalpha)/ sinalpha. One aspheric surface in an optical system is sufficient to yield diffraction limited focusing. By means of two aspheric surfaces, diffraction limited performance with a specified principal surface can be achieved. The problem of optical design is stated as follows: Given a principal surface r(alpha) and a maximum focal angle alpham, find the pair of optical surfaces for which diffraction limited focusing is achieved. It is shown that specification of r(alpha) and alpham uniquely determines the lens design to within a scale factor, given the refractive index of the lens. It is further shown that one straightforward Runge-Kutta integration routine generates both surfaces for either a lens or a pair of mirror surfaces. The complete family of aplanatic lenses will be described. Deviation from sphericity will be discussed, as will the possibility of realizing the specified lens designs. The family of lenses that map uniform incident intensity into uniform illumination about the focus will also be described. Extension of the method to off-axis aberrations will be considered.

Laser Induced Damage in Optical Materials: 6th ASTM Symposium.

The Sixth ASTM-ONR-NBS Symposium on Laser Induced Damage in Optical Materials was held at the National Bureau of Standards in Boulder, Colorado on 22-23 May 1974. Over 150 attendees at the Symposium heard thirty-one papers on topics relating to laser induced damage in crystalline and nonlinear optical materials, at dielectric surfaces, and in thin film coatings as well as discussions of damage problems in the ir region due both to cw and pulsed irradiation. In addition, several reports on the theoretical analysis of laser-materials interaction relative to the damage progress were given, along with tabulations of fundamental materials properties of importance in evaluation of optical material response to high-power laser radiation. Attention was given to high-power laser system design considerations that relate to improved system performance and reliability when various damage mechanisms are operable in such systems. A workshop on the machining of optics was held, and nine papers on various facets of the topic were presented dealing with machining procedures, surface characterization of machined elements, coating of machined components, and the polishing and damage resistance of polished, coated, and bare metal reflectors.

Laser induced damage to optical materials, 1973: a conference report.

During the 1973 Symposium on Damage in Laser Materials several specific topics received considerable attention. The papers presented to the approximately 135 specialists in attendance can logically be separated into categories on self-focusing damage, surface damage, coating damage, infrared component damage, and theory and fundamental properties. Highlighting the meeting were papers on small scale self-focusing, the importance of surface or near-surface absorbing impurities as a major extrinsic influence in reducing the intrinsic damage level of coated and uncoated surfaces, development of new instrumental methods for evaluation of material properties important in the damage process, initial attempts at cataloging these important properties, and, finally, several reports on the frequency and temporal aspects of laser-induced damage in a variety of materials, from the visible to the infrared, and from subnanosecond pulsed to continuous wave exposures.

Laser Induced Damage of Optical Elements-a Status Report.

In the application of high-power lasers, damage to active laser materials, and to components of laser system, generally determines the limit of useful laser performance. Accordingly, there is great interest in reducing the susceptibility of optical elements ot damage. Damage in transparent dielectrics arises from three major causes, particulate inclusions or microinhomogeneities in the material, self-focusing within the materials, and surface damage due to plasma formation. The state of understanding of these phenomena, and the thresholds observed, where they have been determined, will be discussed. Dependence on pulse length will also be considered. Although most of the research accomplished to date on laser damage has concentrated on Nd-glass, the advent of very high-powered gas lasers has stimulated interest in the development of damage resistant component materials for use in the ir. Crystalline dielectrics appear to be the most likely candidate materials for ir windows. Nonlinear optics materials are particularly susceptible to damage, since they are generally exposed to high intensity radiation. Asa final item, damage in thin film dielectric coatings are considered.

Damage in laser materials.

The third ASTM symposium on damage in laser materials held at NBS in May 1971 is discussed, and the results are reviewed.