Dual-wavelength operation diffractive phase elements for pattern formation

We report on the design and fabrication of novel diffractive phase elements that reconstruct distinct intensity patterns in the far-field on illumination with two specific wavelengths. The elements contain deep surface-relief structures that represent phase-delays of greater than 2p radians. The design process incorporates a modified version of the iterative Fourier transform algorithm. A 16 phase-level element for dual wavelength (blue and red) operation, with high diffraction efficiency, is demonstrated experimentally.

Multilevel phase-only array generators with a trapezoidal phase topology

The implementation of a two-stage design process for the design of diffractive optical elements for array illumination is described. Results are presented for on-axis two-dimensional array illuminators for which this method is used. The final designs are theoretically within 5% of the calculated diffraction efficiency upper bound, and theoretical signal reconstruction error is below 1%. Experimental verification of the design theory is given, with experimental diffraction efficiencies within 4% of design values and signal reconstruction error below 6%.

Components for the implementation of free-space optical crossbars

We describe an optical system developed to form the basis of a 64 × 64 free-space optical matrix-matrix crossbar switch. The design and performance of each of the main optical components is discussed: lenses, diffractive optical elements, and polarizing beamsplitters, together with the optomechanical hardware design. For these components, throughput levels of -6.9 dB have been achieved, which is compatible with full system operation at 10(-12) bit error rates at ≥270 Mbits s(-1).

A study of bereavement care after a sudden and unexpected death

Bereaved parents' perceptions of care after the sudden, unexpected death of their child (from 1 week to 12 years), and the care that was or could be offered by statutory and voluntary agencies, was assessed in 11 health districts in seven regions of England and Wales. In these 11 districts, 185 families were identified who met the criteria of the study. Permission to contact these families was given by only 72 general practitioners. Of these, 42 families responded (58%). Sudden infant death syndrome accounted for 43% of the deaths. The results from postal questionnaires sent to both parents showed that hospital care was perceived as good on the whole, although parents would like more choices. Most parents felt that community care was inadequate, leaving many feeling isolated. In contrast, questionnaires from health visitors and general practitioners in the same health districts showed that they believed that they were the most appropriate professionals to give follow up care, but as there were few policies to guide them and little training provided, felt unable to offer support.

Disease in the scurfy (sf) mouse is associated with overexpression of cytokine genes

The murine X-linked lymphoproliferative disease scurfy is similar to the Wiskott-Aldrich syndrome in humans. Disease in scurfy (sf) mice is mediated by CD4+ T cells. Based on similarities in scurfy mice and transgenic mice that overexpress specific cytokine genes, we evaluated the expression of cytokines in the lesions of sf mice by Northern blotting, quantitative reverse-transcription polymerase chain reaction (RT-PCR) and by hybridization in situ. Overall, the phenotypic characteristics of scurfy disease correlated well with increased interleukin (IL)-4 (lymphadenopathy), IL-6 (B cell proliferation, hypergammaglobulinemia), IL-7 (dermal inflammatory cell infiltration), and high levels of tumor necrosis factor-alpha (wasting).

The mouse homolog of the Wiskott-Aldrich syndrome protein (WASP) gene is highly conserved and maps near the scurfy (sf) mutation on the X chromosome

The mouse WASP gene, the homolog of the gene mutated in Wiskott-Aldrich syndrome, has been isolated and sequenced. the predicted amino acid sequence is 86% identical to the human WASP sequence. A distinct feature of the mouse gene is an expanded polymorphic GGA trinucleotide repeat that codes for polyglycine and varies from 15 to 17 triplets in different Mus musculus strains. The genomic structure of the mouse WASP gene is expressed as an approximately 2.4-kb mRNA in thymus and spleen. Chromosomal mapping in an interspecific M. Musculus/M. spretus backcross placed the Wasp locus near the centromere of the mouse X chromosome, inseparable from Gata1, Tcfe3, and scurfy (sf). This localization makes Wasp a candidate for involvement in scurfy, a T cell-mediated fatal lymphoreticular disease of mice that has previously been proposed as a mouse homolog of Wiskott-Aldrich syndrome. Northern analysis of sf tissue samples indicated the presence of WASP mRNA in liver and skin, presumably as a consequence of lymphocytic infiltration, but non abnormalities in the amount or size of mRNA present.

High-efficiency binary fan-out gratings by modulation of a high-frequency carrier grating

A modulation scheme that uses pulse-position modulation of a high-frequency binary grating to increase the diffraction efficiency of the elements is presented. These elements are designed and fabricated with both one- and two-dimensional signals for operation in transmission or reflection modes in the visible and the infrared regions of the spectrum. A direct electron-beam lithography fabrication process capable of realizing features of ∼280 nm with a resolution of 15 nm is described in detail. Experimental results show that diffraction efficiencies of >80% are attainable.

Bragg holograms with binary synthetic surface-relief profile

Synthetic pulse-position-modulated binary surface-relief elements with subwavelength transverse features are designed by using a combination of scalar and rigorous electromagnetic diffraction theories. Theoretically, both reflection- and transmission-type elements achieve nearly 100% diffraction efficiency at Bragg incidence. Using direct-write electron-beam lithography and reactive ion etching, we demonstrate a reflective binary Bragg-type multiple beam splitter for operation at lambda = 1.064 microm.

Selective decontamination of the digestive tract: a stratified, randomized, prospective study in a mixed intensive care unit

To evaluate the use of selective decontamination of the digestive tract (SDD) (polymyxin, amphotericin, tobramycin, and intravenous cefotaxime) in a mixed intensive care unit, we performed a stratified, randomized, prospective study. The 331 patients were recruited over an 18-month period, with 256 patients remaining more than 48 hours. Stratification by acute physiology and chronic health evaluation (APACHE II) preceded randomization to control (standard antibiotic therapy) or treatment (SDD) groups. Nosocomial infection was significantly reduced in the SDD group (16.7%; 21 of 126 patients) compared with the control group (30.8%; 40 of 130 patients; p = 0.008). No difference was found in overall mortality rate or length of stay between the two groups. Those patients with admission APACHE II scores 10 to 19 demonstrated the most significant reduction in nosocomial infection (23 of 70 control vs 13 of 76 SDD; p = 0.03) and mortality (15 of 70 control vs 8 of 76 SDD; p = 0.07). Emergence of multiresistant microorganisms was not a clinical problem, but a definite change occurred in the ecology of environmental and colonizing bacteria. With the exception of cefotaxime, a reduction was noted in systemic antibiotic usage in the SDD group. We conclude that SDD is useful in selected patients in a mixed intensive care unit.

Contribution of ventral blood island mesoderm to hematopoiesis in postmetamorphic and metamorphosis-inhibited Xenopus laevis

In an effort to label very early erythrocyte and lymphocyte populations and to follow their fate in normally developing postmetamorphic frogs and goitrogen-treated permanent larvae, diploid (2N) and triploid (3N) ventral blood island (VBI) mesoderm was exchanged between neurula stage embryos (about 16-22 hr old). Beginning at 15 days of age, half of the 2N or 3N hosts were treated with sodium perchlorate to prevent thyroxine-induced developmental changes. At larval stages 55-59 (41-48 days) and at 1-2 months postmetamorphosis (110-120 days), the untreated control chimeras and age-matched perchlorate-treated chimeras were killed for analysis of the VBI contribution to blood, spleen, and thymus populations by flow cytometry. The data suggest that grafting of ventral blood island mesoderm is an effective way to label an early larval erythrocyte population that declines after metamorphosis. In perchlorate-blocked permanent larvae this early VBI-derived erythrocyte population persists. In contrast, grafting of VBI mesoderm was less useful as a method to label a larvally distinct lymphocyte population in the thymus and spleen. At the late larval stages that we examined, the proportion of VBI-derived cells in thymus and spleen was not different from that observed after metamorphosis. Inhibition of metamorphosis interfered with the thymocyte expansion that normally occurs after metamorphosis, but the proportion of VBI-derived cells in thymus and spleen was not affected. This suggests that lymphopoiesis occurring in late larval life and after metamorphosis uses a stable persisting population of VBI-derived stem cells as well as dorsally derived stem cells.

Organ-specific hematopoietic changes induced by a recombinant human interferon-alpha in mice

Interferon-alpha (IFN-alpha) is a naturally occurring cytokine that mediates numerous biological activities and has demonstrated therapeutic potential in a variety of malignancies. Encouraging activity against HIV-1 replication has also been observed with IFN-alpha in the treatment of AIDS, although hematotoxicity has been a frequently observed side effect. In addition, in vitro studies have suggested that IFN-alpha may function as a down-regulator of myelopoiesis. A recombinant hybrid of subtypes of human IFN-alpha, rHuIFN-alpha A/D, has antiviral activity in murine cells in vitro and in vivo. This study examines the effect of acute and subchronic exposure to rHuIFN-alpha A/D on hemopoietic and immune parameters in C57Bl/6 mice. IFN-alpha was administered ip at 0, 1000, 10,000, and 100,000 units/day for either 1 or 10 consecutive days. Many of the known effects of IFN-alpha in humans such as anemia, leukopenia, and thrombocytopenia were observed in mice following subchronic exposure, with the latter two effects also manifested following acute exposure. Further analysis showed that this leukopenia was not selective. Both splenic and bone marrow cells were examined following 10 days of dosing with the high dose of IFN-alpha. Lymphocytes were reduced in both compartments, while granulocytes were increased in both compartments. Bone marrow cells programmed to differentiate into granulocytes (CFU-G) were suppressed, while macrophage progenitors (CFU-M) were stimulated. Erythroid cells decreased in the marrow but increased in the spleen, suggesting that the microenvironment may play a significant role in the effect of IFN-alpha. The proliferative capacity of both B and T splenic lymphocytes was significantly suppressed in a dose-related fashion following multiple exposure to IFN-alpha. Clinically, IFN-alpha is most often given in multiple doses and the present data suggest that such a regimen is toxic to both erythroid and myeloid cells, as well as being immunotoxic to splenic B and T lymphocytes.

Expression of class II major histocompatibility complex antigens on adult T cells in Xenopus is metamorphosis-dependent

Class II major histocompatibility complex (MHC) antigens are expressed predominantly on B lymphocytes and macrophages of tadpoles of the South African clawed frog, Xenopus laevis, as is the pattern in lymphocyte populations of most mammals. However, unlike most mammals, young postmetamorphic frogs show expression of class II MHC antigens on a high proportion of thymocytes and most peripheral T and B lymphocytes. Using the J-strain of Xenopus and the anticlass II monoclonal antibody, 14A2, we have studied, by indirect immunofluorescence, whether inhibition of metamorphosis would alter the pattern of expression of class II antigens during ontogeny. In control animals, class II antigens were virtually absent from thymic lymphocytes and peripheral T cells of normal untreated larvae, but could be found in increasing numbers in both populations after metamorphosis (10-12 weeks of age). In contrast, larvae, whose metamorphosis was inhibited by treatment with sodium perchlorate, had relatively few class II+ thymic lymphocytes throughout the 6-month period of study, and the proportion of class II+ splenic lymphocytes was approximately equal to that of IgM+ B lymphocytes. Thus, perchlorate-treated animals retained the larval pattern of class II expression, suggesting that emergence of class II+ T cells is dependent on metamorphosis.

Evaluation of amino-oxyacetic acid as a palliative in tinnitus

Amino-oxyacetic acid (AOAA) was evaluated as a palliative in tinnitus. Sixty-six patients with tinnitus presumed to be of cochlear origin were given either a placebo or 75 mg of AOAA four times a day for 1 week. Response was evaluated by both audiometric measurement of tinnitus loudness and subjective rating by patients of change or no change in tinnitus severity. Because loudness measurements and self-rating have not been shown to be independent, and since the aim of clinical treatment of tinnitus is the alleviation of subjective distress, greater weight was given to the patient's self-rating. A total of 21% of all patients reported a subjective decrease in tinnitus severity, usually within 3 to 4 days after the start of AOAA use. Patients with tinnitus caused by presbycusis or Meniere's disease were the most likely to respond to AOAA treatment with a reduction in tinnitus severity, whereas those with drug-induced tinnitus were the least likely to respond. Nausea and dysequilibrium were the most common side effects of AOAA use. Of the 21% of patients who responded to AOAA, 71% developed some type of side effect. Amino-oxyacetic acid produces a reduction in the severity of tinnitus in about 20% of patients; however, the incidence of side effects makes the drug unacceptable for clinical use.

Toxicology studies of a chemical mixture of 25 groundwater contaminants. II. Immunosuppression in B6C3F1 mice

Concern over the potential adverse health effects of chemically contaminated groundwater has existed for many years. In general, these studies have focused on retrospective epidemiological studies for cancer risk. In the present studies, immune function was monitored in female B6C3F1 mice exposed to a chemical mixture in drinking water for either 14 or 90 days. The mixture consisted of 25 common groundwater contaminants frequently found near toxic waste dumps, as determined by EPA surveys. None of the animals developed overt signs of toxicity such as body or liver weight changes. Mice exposed to the highest dose of this mixture for 14 or 90 days showed immune function changes which could be related to rapidly proliferating cells, including suppression of hematopoietic stem cells and of antigen-induced antibody-forming cells. Some of these responses, e.g., granulocyte-macrophage colony formation, were also suppressed at lower concentrations of the chemical mixture. There were no effects on T cell function or T and B cell numbers in any of the treatment groups. Altered resistance to challenge with an infectious agent also occurred in mice given the highest concentration, which correlated with the immune function changes. Paired-water studies indicated that the immune effects were related to chemical exposure and not to decreased water intake. These results suggest that long-term exposure to contaminated groundwater may represent a risk to the immune system in humans.

Identification of the sigma 1S protein in reovirus serotype 2-infected cells with antibody prepared against a bacterial fusion protein

A bacterial expression vector, pATH 3, was used to produce high levels of a fusion protein composed of a portion of the trpE protein of Escherichia coli and the putative sigma 1S coding region from the S1 gene of reovirus serotype 2. The fusion protein was purified and injected into rabbits to prepare antisera. This antibody was able to detect sigma 1S being synthesized in L929 cells infected with reovirus serotype 2 by means of immunoprecipitation and immunoblotting techniques. The peak of sigma 1S accumulation in type 2-infected cells was shown to occur approximately 20 hr after infection. This report represents the first description of sigma 1S production in reovirus serotype 2-infected cells.