Capsule implosions for continuum x-ray backlighting of opacity samples at the National Ignition Facility.

Direct drive implosions of plastic capsules have been performed at the National Ignition Facility to provide a broad-spectrum (500-2000 eV) X-ray continuum source for X-ray transmission spectroscopy. The source was developed for the high-temperature plasma opacity experimental platform. Initial experiments using 2.0 mm diameter polyalpha-methyl styrene capsules with ∼20 µm thickness have been performed. X-ray yields of up to ∼1 kJ/sr have been measured using the Dante multichannel diode array. The backlighter source size was measured to be ∼100 µm FWHM, with ∼350 ps pulse duration during the peak emission stage. Results are used to simulate transmission spectra for a hypothetical iron opacity sample at 150 eV, enabling the derivation of photometrics requirements for future opacity experiments.

Design of the opacity spectrometer for opacity measurements at the National Ignition Facility.

Recent experiments at the Sandia National Laboratory Z facility have called into question models used in calculating opacity, of importance for modeling stellar interiors. An effort is being made to reproduce these results at the National Ignition Facility (NIF). These experiments require a new X-ray opacity spectrometer (OpSpec) spanning 540 eV-2100 eV with a resolving power E/ΔE > 700. The design of the OpSpec is presented. Photometric calculations based on expected opacity data are also presented. First use on NIF is expected in September 2016.

High quantum efficiency photocathode simulation for the investigation of novel structured designs.

A computer model in CST Studio Suite has been developed to evaluate several novel geometrically enhanced photocathode designs. This work was aimed at identifying a structure that would increase the total electron yield by a factor of two or greater in the 1-30 keV range. The modeling software was used to simulate the electric field and generate particle tracking for several potential structures. The final photocathode structure has been tailored to meet a set of detector performance requirements, namely, a spatial resolution of <40 µm and a temporal spread of 1-10 ps. We present the details of the geometrically enhanced photocathode model and resulting static field and electron emission characteristics.

High bandwidth differential amplifier for shock experiments.

We developed a high bandwidth differential amplifier for gas gun shock experiments of low-resistance metals. The circuit has a bandwidth up to 1 GHz, and is capable of measuring signals of ≤1.5 V with a common mode rejection of 250 V. Conductivity measurements of gas gun targets are measured by flowing high currents through the targets. The voltage is measured across the target using a technique similar to a four-point probe. Because of the design of the current source and load, the target voltage is ∼250 V relative to ground. Since the expected voltage change in the target is <1 V, the differential amplifier must have a large common mode rejection. Various amplifying designs are shown, although the increased amplification decreases bandwidth. Bench tests show that the amplifier can withstand significant common mode dc voltage and measure 10 ns, and 50 mV signals.

Integrated x-ray reflectivity measurements of elliptically curved pentaerythritol crystals.

The elliptically curved pentaerythritol (PET) crystals used in the Supersnout 2 x-ray spectrometer on the National Ignition Facility at Lawrence Livermore National Laboratory have been calibrated photometrically in the range of 5.5-16 keV. The elliptical geometry provides broad spectral coverage and minimizes the degradation of spectral resolution due to the finite source size. The reflectivity curve of the crystals was measured using a x-ray line source. The integrated reflectivity (R(I)) and width of its curve (ΔΘ) were the measurements of major interest. The former gives the spectrometer throughput, and the latter gives the spectrometer resolving power. Both parameters are found to vary considerably with the radius of curvature of the crystal and with spectral energy. The results are attributed to an enhanced mosaic effect due to the increase in curvature. There are also contributions from the crystal cleaving and gluing processes.

Respiratory tract toxicity in rats exposed to Mexico City air.

The rat has been used extensively as a health sentinel, indicator, or monitor of environmental health hazards, but this model has not been directly validated against human exposures. Humans in Mexico City show upper respiratory tract lesions and evidence of pulmonary damage related to their environmental inhalation exposure. In this study, male and female F344 rats were exposed (23 hr/day) in Mexico City to local Mexico City air (MCA)* for up to seven weeks. Controls were maintained at the same location under filtered air. Prior to these exposures, several steps were taken. First, the nasal passages of normal male rats shipped from the United States and housed in Mexico City were examined for mycoplasma infection; no evidence of infection was found. In addition, a mobile exposure and monitoring system was assembled and, with an ozone (O3) exposure atmosphere, was tested along with supporting histopathology techniques and analysis of rat nasal and lung tissues. Last, the entire exposure model (equipment and animals) was transported to Mexico City and validated for a three-week period. During the seven-week study there were 18 one-hour intervals during which the average O3 concentration of MCA in the exposure chamber exceeded the US National Ambient Air Quality Standard (NAAQS) of 0.120 ppm 03 (hourly average, not to be exceeded more than once per year). This prolonged exposure of healthy F344 rats to MCA containing episodically low to moderate concentrations of 03 (as well as other urban air pollutants) did not induce inflammatory or epithelial lesions in the nasal airways or lung as measured by qualitative histologic techniques or quantitative morphometric techniques. These findings agree with those of previous controlled O3 inhalation studies, but they are in contrast to reports indicating that O3-polluted MCA causes significant nasal mucosal injury in adults and children living in southwestern Mexico City. Taken together, these findings may suggest that human airways are markedly more susceptible to the toxic effects of MCA than are the airways of the F344 rat.

The location problem for color subjectivism.

According to color subjectivism, colors are mental properties, processes, or events of visual experiences of color. I first lay out an argument for subjectivism founded on claims from visual science and show that it also relies on a philosophical assumption. I then argue that subjectivism is untenable because this view cannot provide a plausible account of color perception. I describe three versions of subjectivism, each of which combines subjectivism with a theory of perception, namely sense datum theory, adverbialism, and the virtual color proposal, and argue that each version faces serious objections. Considering these three theories of perception to be exhaustive of those available to the subjectivist, I conclude that subjectivism is untenable and that the scientifically motivated argument for this view is unsound. I then offer the diagnosis that the philosophical assumption on which this argument relies is mistaken.

Color science and spectrum inversion: a reply to Nida-Rümelin.

Martine Nida-Rümelin (1996) argues that color science indicates that behaviorally undetectable spectrum inversion is possible and raises this possibility as an objection to functionalist accounts of visual states of color. I show that her argument does not rest solely on color science, but also on a philosophically controversial assumption, namely, that visual states of color supervene on physiological states. However, this assumption, on the part of philosophers or vision scientists, has the effect of simply ruling out certain versions of functionalism. While Nida-Rümelin is quite right to search for empirical tests for claims about the nature of visual states, philosophical issues remain pivotal in determining the correctness of these claims.

Randomised trial of erythromycin on the development of chronic lung disease in preterm infants.

AIMS: To determine if erythromycin given from birth reduces the inflammatory response and the incidence and severity of chronic lung disease. METHODS: Seventy five infants less than 30 weeks of gestation and ventilated from birth for lung disease were randomly assigned to receive erythromycin intravenously for 7 days or to no treatment. Ureaplasma urealyticum was detected in tracheal secretions by culture and polymerase chain reaction. Differential cell counts were obtained from bronchoalveolar lavage fluid collected daily for 5 days and concentrations of the cytokines interleukins IL-1 beta and IL-8, and tumour necrosis factor alpha (TNF-alpha) were measured. Chronic lung disease (CLD) was defined as oxygen dependency at 36 weeks of gestation. RESULTS: Nine infants (13%) were positive for U urealyticum. The inflammatory cytokines in the lungs increased over the first 5 days of life in all babies, but no association was found between their concentrations and the development of CLD. Those treated with erythromycin showed no significant differences from the non-treated group in the differential cell counts or concentrations of the cytokines. The two groups had a similar incidence of CLD. Babies infected with U urealyticum did not have a more pronounced cytokine response than those without infection. Chorioamnionitis was associated with significantly higher concentrations of IL-1 beta and IL-8 on admission: these babies had less severe acute lung disease and developed significantly less CLD. CONCLUSIONS: U urealyticum in the trachea was not associated with an increased inflammatory response in preterm infants. Erythromycin did not reduce the incidence or severity of CLD.

Comparison of culture with the polymerase chain reaction for detection of Ureaplasma urealyticum in endotracheal aspirates of preterm infants.

Polymerase chain reaction (PCR) amplification of the urease genes of Ureaplasma urealyticum was compared with culture for detection of the organism in 100 endotracheal aspirates from 54 ventilated preterm infants. Ninety specimens gave negative results by both culture and PCR and three specimens gave positive results by both culture and PCR. Six specimens were negative by culture but positive by PCR. The one specimen positive by culture and negative by PCR was interpreted as a false-positive culture result. Overall agreement between results obtained by culture and PCR was 93%. PCR is a sensitive and reliable method for the detection of U. urealyticum in neonatal endotracheal secretions. Detection by PCR (1-2 days) is more rapid than culture (2-5 days) and this will be important if early therapeutic intervention is shown to be effective.

Use of rapid carbohydrate utilisation test for identifying "Streptococcus milleri group".

A short series of biochemical and serological tests were developed for the rapid presumptive identification of "Streptococcus milleri group" isolates. One hundred and seventy seven streptococcal isolates were recovered from the mouths of 10 out of 12 healthy adult volunteers by use of a simple sampling procedure and a single selective medium. In all, 127 oral "S milleri group" isolates were identified by biochemical and serological tests, confirming the indigenous nature of these streptococci in the mouth. Most (70.1%) of "S milleri group" isolates were non-haemolytic, 26% were alpha-haemolytic, and 3.9% beta-haemolytic. Fifty four (42.5%) were serologically typable, of which 46 were Lancefield group F, suggesting that the mouth is an important source of Lancefield group F streptococci. A collection of group F streptococci from a range of sources was indistinguishable from a collection of oral "S milleri group" isolates on the basis of the tests used, supporting the general synonymity of group F streptococcus with the broader "S milleri group". The battery of tests was cheap and simple to perform, and was capable of identifying "S milleri group" isolates from a range of sources, including variants with wide sugar fermentation patterns.

Urologic syndrome associated with wire caging in AKR mice.

Individually housed male AKR/NCrlBR mice used in a chronic inhalation experiment were noted to develop a severe obstructive genitourinary condition. The mouse urologic syndrome (MUS) had one or more of the following features: bladder distension; peripreputial urine staining, alopecia, and edema; paraphimosis; urethral blockage; ulcerative balanophosthitis; hydronephrosis; pyelonephritis; rectal prolapse; and perineal ulcerative dermatitis. MUS was less severe and less prevalent in similarly housed B6C3F1/CrlBR and NIH-Swiss mice used in the same experiment. Epidemiologic evidence within the animal facility restricted the syndrome to the inhalation toxicology area. The effects of intermittent water deprivation as well as wire caging on the development of MUS were studied because these conditions were only utilized in the inhalation facility. Male AKR/NCrlBR mice, caged individually in suspended wire caging or kept isolated in polystyrene shoebox style cages containing wire floorwalk bottoms, all developed MUS within 16 weeks. Mice which were housed directly on hardwood bedding in identical plastic caging remained free of the syndrome, as did castrated males which were kept in suspended wire cages. Water deprivation was not found to be a major contributing factor to the development of the condition, but was found to augment its severity. We concluded that although MUS is probably multifactorial in etiology, housing susceptible animals on wire bottom caging may exacerbate the incidence and severity of the condition in certain strains of male mice.

Effect of a purified diet on dystrophic cardiac calcinosis in mice.

Male and female C3H/HeNCrl mice were divided into test groups and fed either a purified diet (AIN-76A) or a natural ingredient diet (NIH-07). Lesions of dystrophic cardiac calcinosis (DCC) were found to be more prevalent and more severe in mice fed the purified diet. The cardiac changes, which were similar in nature in both groups of mice, consisted of randomly distributed foci of myocardial mineralization and fibrosis. These lesions were not associated with clinical disease or significant alterations in serum calcium, lactic dehydrogenase, aspartate aminotransferase, alkaline phosphatase or creatine kinase levels. We conclude that AIN-76A purified diet should be utilized with caution in toxicology studies which use mice as experimental subjects, especially if the heart is a potential target organ.

Analysis of EDTA-soluble cell surface components of gram-positive anaerobic cocci.

The protein content of EDTA extracts from 76 strains of Gram-positive anaerobic cocci was examined using SDS-PAGE. Strains of Peptostreptococcus anaerobius produced almost identical profiles; greater heterogeneity was observed within the species Peptococcus magnus, Peptococcus prevotii and Peptococcus asaccharolyticus, but several strains within each biotype produced similar patterns. Serological investigation of these extracts by ELISA revealed numerous cross-reactions among the different biotypes. Immunoblot transfers from polyacrylamide gels demonstrated two common antigens within strains of the species, Ps. anaerobius, but these were not species-specific.

Immunochemical characterization of the cell surface carbohydrate antigens of Peptostreptococcus anaerobius.

Two carbohydrate antigens were isolated from the cell surface of Peptostreptococcus anaerobius. One, extracted from purified cell walls with NaOH, contained glucose and phosphorus, with traces of galactosamine and glucosamine. Serological activity was detected by a 'dot blot' procedure. The second antigen, extracted from cell membranes with phenol and purified by chromatography on Sepharose 6B and an immunoadsorbent column, contained glucose, glycerol phosphate, phosphorus and fatty acids. Antigenicity of this extract could also be demonstrated by an ELISA technique.

Survival of gram positive anaerobic cocci on swabs and their isolation from the mouth and vagina.

The survival of Gram positive anaerobic cocci on plain cotton wool and albumin coated swabs held in various transport media was investigated. Results suggested that in most cases Amies', Stuart's and VMGII media do not offer any more protection to the bacteria than storing swabs dry in their containers. A technique was developed for the isolation and identification of Gram positive anaerobic cocci from the mouth and vagina, incorporating bicozamycin in the medium as a selective agent. Few strains were recovered from the oral cavity, but larger numbers were isolated from the vagina. Using a minimum number of antibiotic sensitivity and biochemical tests, including analysis of end products by gas-liquid chromatography, most isolates were identified to species level.