Two-color spatial and temporal temperature measurements using a streaked soft x-ray imager.

A dual-channel streaked soft x-ray imager has been designed and used on high energy-density physics experiments at the National Ignition Facility. This streaked imager creates two images of the same x-ray source using two slit apertures and a single shallow angle reflection from a nickel mirror. Thin filters are used to create narrow band pass images at 510 eV and 360 eV. When measuring a Planckian spectrum, the brightness ratio of the two images can be translated into a color-temperature, provided that the spectral sensitivity of the two images is well known. To reduce uncertainty and remove spectral features in the streak camera photocathode from this photon energy range, a thin 100 nm CsI on 50 nm Al streak camera photocathode was implemented. Provided that the spectral shape is well-known, then uncertainties on the spectral sensitivity limits the accuracy of the temperature measurement to approximately 4.5% at 100 eV.

A new streaked soft x-ray imager for the National Ignition Facility.

A new streaked soft x-ray imager has been designed for use on high energy-density (HED) physics experiments at the National Ignition Facility based at the Lawrence Livermore National Laboratory. This streaked imager uses a slit aperture, single shallow angle reflection from a nickel mirror, and soft x-ray filtering to, when coupled to one of the NIF's x-ray streak cameras, record a 4× magnification, one-dimensional image of an x-ray source with a spatial resolution of less than 90 µm. The energy band pass produced depends upon the filter material used; for the first qualification shots, vanadium and silver-on-titanium filters were used to gate on photon energy ranges of approximately 300-510 eV and 200-400 eV, respectively. A two-channel version of the snout is available for x-ray sources up to 1 mm and a single-channel is available for larger sources up to 3 mm. Both the one and two-channel variants have been qualified on quartz wire and HED physics target shots.

The effect of soil acidification on atmospheric methane uptake by a Maine forest soil(1).

Soil from the zone of maximal methanotrophic activity (approximately 5-8 cm depth) in a mixed coniferous-hardwood forest consumed atmospheric methane over a wide pH range (3.5-7.5) with a broad optimum between 4.8 and 6.0. Methane uptake at native soil pH values (4.4-4.8) was only slightly less rapid than rates at optimal pH values. Addition of mineral acids to intact soil cores in pulsed applications decreased atmospheric methane consumption. The extent of inhibition varied with the type, concentration and volume of acid added: nitric acid was more inhibitory than sulfuric acid at an equivalent soil pH, and methane uptake decreased with increasing volumes and concentrations of added acid. Although ammonium chloride at 1 µmol g fresh weight (gfw) soil(-1) inhibited methane uptake, the extent of inhibition did not vary significantly with decreasing soil pH below values of 4.4.

Balb/c mice as a preclinical model for raltitrexed-induced gastrointestinal toxicity.

Raltitrexed (RTX) is an antifolate thymidylate synthase (TS) inhibitor used for the treatment of advanced colorectal cancer. RTX induces proliferating tissue toxicities that are largely confined to the intestine, with diarrhea being a severe side effect in a small but significant minority of patients. Similarly, weight loss and diarrhea were observed in BALB/c mice, and a maximum tolerated dose (MTD) was determined as approximately 5-10 mg/kg/day x 5 days. At an equivalent dose of 10 mg/kg/day x 5 days (dl-5), DBA2 mice lost considerably less weight, leading to a higher MTD (>500 mg/kg/day x 5 days), and there was no evidence of diarrhea. Histopathological consequences of damage, such as changes in small intestinal crypt architecture and villus atrophy induced by the 10-mg/kg/day dose, were greater and of longer duration in BALB/c mice. A higher dose of RTX (100 mg/kg/day x 5) induced weight loss and histopathological damage similar to that seen in BALB/c mice (10 mg/kg/ day x 5) but was of later onset, nadir, and recovery. Small changes to the colon were only observed in BALB/c mice. Pretreatment levels of plasma thymidine, deoxyuridine (approximately 1 microM), and folate (approximately40 ng/ml) were similar in both mouse strains. A single injection of radiolabeled RTX (5 mg/kg/ day) did not lead to any marked difference 24 h later in the total drug concentration and distribution of polyglutamates (comprising 70-80% of drug extracted) in the liver, kidney, and intestinal epithelium (large and small intestine) between the two mouse strains. Further studies used a RIA to measure RTX polyglutamate formation in tissues at various times and drug doses. This led to the conclusion that, although there was a higher accumulation of RTX in BALB/c small intestinal epithelium (days 4-6), it may be an effect secondary to another undetermined cause of increased drug sensitivity. This model represents a vehicle by which the etiology and treatment of severe clinical toxicity induced by RTX may be evaluated.

Methanol promotes atmospheric methane oxidation by methanotrophic cultures and soils.

Two methanotrophic bacteria, Methylobacter albus BG8 and Methylosinus trichosporium OB3b, oxidized atmospheric methane during batch growth on methanol. Methane consumption was rapidly and substantially diminished (95% over 9 days) when washed cell suspensions were incubated without methanol in the presence of atmospheric methane (1.7 ppm). Methanotrophic activity was stimulated after methanol (10 mM) but not methane (1,000 ppm) addition. M. albus BG8 grown in continuous culture for 80 days with methanol retained the ability to oxidize atmospheric methane and oxidized methane in a chemostat air supply. Methane oxidation during growth on methanol was not affected by methane deprivation. Differences in the kinetics of methane uptake (apparent K(m) and V(max)) were observed between batch- and chemostat-grown cultures. The V(max) and apparent K(m) values (means +/- standard errors) for methanol-limited chemostat cultures were 133 +/- 46 nmol of methane 10 cells h and 916 +/- 235 ppm of methane (1.2 muM), respectively. These values were significantly lower than those determined with batch-grown cultures (V(max) of 648 +/- 195 nmol of methane 10 cells h and apparent K(m) of 5,025 +/- 1,234 ppm of methane [6.3 muM]). Methane consumption by soils was stimulated by the addition of methanol. These results suggest that methanol or other nonmethane substrates may promote atmospheric methane oxidation in situ.

Alteration in plasmid DNA following natural transformation to populations of marine bacteria.

This article examines alterations in a broad-host-range plasmid (pQSR50) that were observed following transfer to indigenous marine bacteria by natural transformation. Plasmid DNA from the transformants had altered restriction profiles. However, with the exception of the EcoRI site from one transformant (BS10), fragments amplified by polymerase chain reaction (PCR) and encompassing the recognition sites were cleaved by the relevant endonucleases, providing the sites were present. Analysis with DpnI and MboI indicated differences in DNA methylation between pQSR50 and the transformants. The missing EcoRI site from BS10 and smaller EcoRI fragments observed in transformants indicated that rearrangements had also occurred. Evolution of novel plasmid molecules following gene transfer may be an important mechanism by which natural genetic diversity is generated.

Spatial and temporal variations of dissolved gases (CH4, CO 2, and O 2) in peat cores.

Spatial and temporal variations in the concentrations of dissolved gases (CH4, CO2, and O2) in peat cores were studied using membrane inlet mass spectrometry (MIMS). Variations in vertical gas profiles were observed between random peat cores taken from hollows on the same peat bog. Methane concentrations in profiles (0-30 cm) generally increased with depth and reached maximum values in the range of 200-450 µM CH4 below about 13-cm depth. In some profiles, a peak of dissolved methane was observed at 7-cm depth. Oxygen penetrated to approximately 2-cm depth in the hollows. The sampling probe was used to continuously monitor CH4, CO2, and O2 concentrations at fixed depths in peat cores over periods of several days. The concentration of dissolved CO2 and O2 at 1-cm depth oscillated over a 24-h period with the maximum of CO2 concentration corresponding with the minimum of 02. Diurnal variations in CO2 but not CH4 were measured at 15-cm depth; dissolved CO2 levels decreased during daylight hours to a constant minimum concentration of 4.85 mm. This report also describes the application of MIMS for the measurement of gaseous diffusion rates in peat using an inert gas (argon); the value of D, the diffusion coefficient, was 2.07 × 10(-8) m(2) s(-1).

Postmortem assay of digoxin by radioimmunoassay.

Analysis of postmortem blood samples from patients previously on maintenance digoxin therapy suggests that the results are of value in assessing the degree of digitalization at the time of death. Control cases gave results within the normal therapeutic range wheras of six cases in which digoxin was suspected of being implicated in the death five had 'serum' digoxin levels above the therapeutic range. Differences in digoxin concentration were noted in blood collected from three sites in the body, and it is suggested that postmortem blood should be collected from the leg veins if assessment of antermortem digitalization is to be made.