Radiation, optical, power flow, and electrical diagnostics at the Z facility: Layout and techniques utilized to operate in the harsh environment.

The Z machine is a current driver producing up to 30 MA in 100 ns that utilizes a wide range of diagnostics to assess accelerator performance and target behavior conduct experiments that use the Z target as a source of radiation or high pressures. We review the existing suite of diagnostic systems, including their locations and primary configurations. The diagnostics are grouped in the following categories: pulsed power diagnostics, x-ray power and energy, x-ray spectroscopy, x-ray imaging (including backlighting, power flow, and velocimetry), and nuclear detectors (including neutron activation). We will also briefly summarize the primary imaging detectors we use at Z: image plates, x-ray and visible film, microchannel plates, and the ultrafast x-ray imager. The Z shot produces a harsh environment that interferes with diagnostic operation and data retrieval. We term these detrimental processes "threats" of which only partial quantifications and precise sources are known. We summarize the threats and describe techniques utilized in many of the systems to reduce noise and backgrounds.

Additively manufactured electrodes for plasma and power-flow studies in high-power transmission lines on the 1-MA MAIZE facility.

Power-flow studies on the 30-MA, 100-ns Z facility at Sandia National Laboratories have shown that plasmas in the facility's magnetically insulated transmission lines (MITLs) and double post-hole convolute can result in a loss of current delivered to the load. To study power-flow physics on the 1-MA, 100-ns MAIZE facility at the University of Michigan, planar MITL loads and planar post-hole convolute loads have been developed that extend into the lines of sight for various imaging diagnostics on MAIZE. These loads use 3D-printed dielectric support structures lined with thin foils of either aluminum or stainless steel. The metal foils serve as the current-carrying power-flow surfaces, which generate plasma during the current pulse. The foil thickness (50 µm) and widths (11.5-16 mm) are selected to ensure a sufficient linear current density (0.5-0.7 MA/cm) for plasma formation. Laser backlighting (532 nm) and visible-light self-emission imaging capture the overall plasma evolution in the anode-cathode gaps, including the gap closure velocities (1-4 cm/µs).

Zeeman spectroscopy as a method for determining the magnetic field distribution in self-magnetic-pinch diodes (invited).

In the self-magnetic-pinch diode, the electron beam, produced through explosive field emission, focuses on the anode surface due to its own magnetic field. This process results in dense plasma formation on the anode surface, consisting primarily of hydrocarbons. Direct measurements of the beam's current profile are necessary in order to understand the pinch dynamics and to determine x-ray source sizes, which should be minimized in radiographic applications. In this paper, the analysis of the C IV doublet (580.1 and 581.2 nm) line shapes will be discussed. The technique yields estimates of the electron density and electron temperature profiles, and the method can be highly beneficial in providing the current density distribution in such diodes.

Members of the Candidate Phyla Radiation are functionally differentiated by carbon- and nitrogen-cycling capabilities.

BACKGROUND: The Candidate Phyla Radiation (CPR) is a recently described expansion of the tree of life that represents more than 15% of all bacterial diversity and potentially contains over 70 different phyla. Despite this broad phylogenetic variation, these microorganisms appear to feature little functional diversity, with members generally characterized as obligate fermenters. Additionally, much of the data describing CPR phyla has been generated from a limited number of environments, constraining our knowledge of their functional roles and biogeographical distribution. To expand our understanding of subsurface CPR microorganisms, we sampled four separate groundwater wells over 2 years across three Ohio counties. RESULTS: Samples were analyzed using 16S rRNA gene amplicon and shotgun metagenomic sequencing. Amplicon results indicated that CPR members comprised between 2 and 20% of the microbial communities with relative abundances stable through time in Athens and Greene samples but dynamic in Licking groundwater. Shotgun metagenomic analyses generated 71 putative CPR genomes, representing roughly 32 known phyla and 2 putative new phyla, Candidatus Brownbacteria and Candidatus Hugbacteria. While these genomes largely mirrored metabolic characteristics of known CPR members, some features were previously uncharacterized. For instance, nitrite reductase, encoded by nirK, was found in four of our Parcubacteria genomes and multiple CPR genomes from other studies, indicating a potentially undescribed role for these microorganisms in denitrification. Additionally, glycoside hydrolase (GH) family profiles for our 71 genomes and over 2000 other CPR genomes were analyzed to characterize their carbon-processing potential. Although common trends were present throughout the radiation, differences highlighted potential mechanisms that could allow microorganisms across the CPR to occupy various subsurface niches. For example, members of the Microgenomates superphylum appear to potentially degrade a wider range of carbon substrates than other CPR phyla. CONCLUSIONS: CPR members are present across a range of environments and often constitute a significant fraction of the microbial population in groundwater systems, particularly. Further sampling of such environments will resolve this portion of the tree of life at finer taxonomic levels, which is essential to solidify functional differences between members that populate this phylogenetically broad region of the tree of life.

The binding of poly(rI) - poly(rC) to human fibroblasts and the induction of interferon.

Human embryonic fibroblasts produce interferon when incubated at 37 degrees C after being treated at 4 degrees C with poly(rI) - poly(rC), either by addition of the double-stranded duplex or by sequential addition of the constitutent single-stranded polynucleotides. Cells which have been incubated with double-stranded poly(rI) - poly(rC) can be prevented from forming interferon by washing the cells with high concentrations of salt, immediately after adsorption of polynucleotides, or by incubation of the cells with single-stranded polynucleotides. The inhibition is probably due to displacement of the inducing molecule from the cell surface. Interferon production by cells treated sequentially with poly(rI) and poly(rC) is not inhibited by either of these treatments and the polynucleotides are not easily displaced from the cell surface.

Evaluation of hydrogen peroxide vapour as a method for the decontamination of surfaces contaminated with Clostridium botulinum spores.

The aim of this study was to evaluate the efficacy of hydrogen peroxide vapour (HPV) against spores of Clostridium botulinum, for use as a method for decontaminating environments where this pathogen has been handled. Spores were dried onto stainless steel slides and exposed to HPV in a sealed glovebox enclosure, transferred to a quenching agent at timed intervals during the exposure period, before survivors were cultured and enumerated. D-values were calculated from graphs of log10 survivors plotted against time and were found to range from 1.41 to 4.38 min. HPV was found to be effective at deactivating spores of toxigenic Cl. botulinum, non-toxigenic Clostridium spp. and Geobacillus stearothermophilus dried onto stainless steel surfaces. HPV could be used to decontaminate cabinets and rooms where Cl. botulinum has been handled. The cycle parameters should be based on studies carried out with relevant spores of this organism, rather than based on inactivation data for G. stearothermophilus spores, which have been used in the past as a standard biological challenge for disinfection and sterilisation procedures. HPV could provide an attractive alternative to other decontamination methods, as it was rapid, residue-free and did not give rise to the health and safety concerns associated with other gaseous decontamination systems.

Generalized identity matching of two-dimensional forms by individuals with moderate to profound mental retardation.

The classic literature suggests that individuals with MAs of less than 5 years may fail tasks that require same/different judgments. In Study 1 we used an assessment procedure that provided minimal instructional programming to determine whether 17 adults with MAs ranging from 2 years, 5 months to 4 years, 11 months would show accurate identity matching-to-sample. Stimuli were letter-like nonsense forms. Eight participants showed highly accurate matching. Eight of the 9 who failed were available for further study. Of these, 5 ultimately demonstrated highly accurate matching after training with standard fading procedures. These data suggest that a greater proportion of individuals with low MAs can exhibit generalized identity matching than previously documented in the literature.

Conditional versus trial-unique delayed matching-to-sample.

We compared performance on conditional and trial-unique delayed identity matching-to-sample procedures. In Experiment 1, participants with moderate to severe mental retardation were exposed to both procedures under a single, brief delay value. Three of 5 subjects showed higher accuracy in the trial-unique sessions. In Experiment 2, participants with mild mental retardation were exposed to delay values of 0, 2, 4, 8, and 16 seconds, randomized within each session. For 3 of 4 subjects, accuracy was highest with trial-unique, and lowest on the conditional matching-to-sample, at longer delays. Across the two studies, 6 of 9 subjects showed lower delayed matching accuracy when fewer rather than more stimuli were included in a session.

Identity matching of consonant-vowel-consonant words by prereaders.

Using an identity matching-to-sample procedure, normally developing prereaders who matched individual letters with high accuracy (e.g., m and s) did not show high accuracy in matching three-letter printed words that differed only in the first letter (e.g., mad and sad). Teachers and researchers should not assume that children who can discriminate individual letters can also discriminate minimally different words that contain those letters.

Variable renewal rate and growth properties of cell populations in colon crypts.

A nonlinear mathematical model is used to investigate the time evolution of the cell populations in colon crypts (stem, semidifferentiated and fully differentiated cells). To mimic pathological alteration of the biochemical pathways leading to abnormal proliferative activity of the population of semidifferentiated cells their renewal rate is assumed to be dependent on the population size. Then, the effects of such perturbation on the population dynamics are investigated theoretically. Using both theoretical methods and numerical simulations it is shown that the increase in the renewal rate of semidifferentiated cells strongly impacts the dynamical behavior of the cell populations.

The characteristics required for a Sendai virus preparation to induce high levels of interferon in human lymphoblastoid cells.

The capacity of an egg-grown Sendai virus preparation to induce interferon in the human lymphoblastoid cell Namalwa is dependent on its passage history. Virus which has been serially passaged at high dilution is a poor inducer, whereas virus serially passaged undiluted is a good inducer. Such a good induce preparation has a low infectivity to haemagglutination ratio as the result of a high content of defective-interfering (DI) particles. Using DI particles purified on glycerol gradients, it is shown that for the induction of maximum interferon titres both infectious and DI particles are required. DI particles alone induce little or no interferon. Addition of DI particles to fully infectious Sendai virus preparations increased the interferon yield obtained from Namalwa cells some 60- to 100-fold.

Enhanced production of interferon from human lymphoblastoid (Namalwa) cells pre-treated with sodium butyrate.

Pre-treatment of Namalwa cells with 1 mM-sodium butyrate enhanced interferon production induced by Sendai virus. This enhancement was reversed if the cells were incubated in butyrate-free medium. Butyrate treatment increased the rate of interferon production but not its duration. Yields of interferon from Namalwa cells were also enhanced in response to other inducers including the synthetic dsRNA, poly(rI) . poly(rC). Butyrate pre-treatment also increased interferon yields from cells of the vervet monkey kidney cell line, V3, but cells of the human diploid fibroblast line, MRC-5, did not respond.

The effect of interfering substances on the disinfection process: a mathematical model.

AIMS: To gain a greater understanding of the effect of interfering substances on the efficacy of disinfection. METHODS AND RESULTS: Current kinetic disinfection models were augmented by a term designed to quantify the deleterious effect of soils such as milk on the disinfection process of suspended organisms. The model was based on the assumption that inactivation by added soil occurred at a much faster rate than microbial inactivation. The new model, the fat-soil model, was also able to quantify the effect of changing the initial inoculum size (1 x 10(7)-5 x 10(7) ml(-1) of Staphylococcus aureus) on the outcome of the suspension tests. Addition of catalase to the disinfection of Escherichia coli by hydrogen peroxide, resulted in changes to the shape of the log survivor/time plots. These changes were modelled on the basis of changing biocide concentration commensurate with microbial inactivation. CONCLUSIONS: The reduction in efficacy of a disinfectant in the presence of an interfering substance can be quantified through the use of adaptations to current disinfection models. SIGNIFICANCE AND IMPACT OF THE STUDY: Understanding the effect of soil on disinfection efficacy allows us to understand the limitations of disinfectants and disinfection procedures. It also gives us a mechanism with which to investigate the soil tolerance of new biocides and formulations.

Disinfection kinetics: a new hypothesis and model for the tailing of log-survivor/time curves.

A new hypothesis for the understanding of chemical disinfection, which we have termed the Intrinsic Quenching hypothesis, is presented. This mechanistic treatment of disinfection kinetics is based on the hypothesis that the biocide concentration may not be in vast excess over the microbes, as is normally assumed. A mathematical model was developed and found to be useful in describing the observed kinetics of several disinfectants. The model suggested that the reason for the observation of non-linear, log-survivor curves was due to the ability of the microbes, in clean, soil-free conditions, to intrinsically quench the bulk concentration of biocide.

An investigation into the changed physiological state of Vibrio bacteria as a survival mechanism in response to cold temperatures and studies on their sensitivity to heating and freezing.

AIMS: To induce pathogenic Vibrio bacteria into a changed physiological state, in response to cold temperatures in sea water, and assess their sensitivity to heating and freezing, as compared with normal cells. METHODS AND RESULTS: Cells of exponential phase Vibrio vulnificus, V. cholerae and V. parahaemolyticus were washed and inoculated into flasks of sea water, which were stored at 20 and 4 degrees C. Cells stored at 20 degrees C could be recovered after 60 d on non-selective agar (heart infusion agar; HIA) and on the selective agar (thiosulphate citrate bile salts agar) which is used in most Vibrio detection methodology. At 4 degrees C cells became non-culturable on both agars over time. The non-culturable cells appeared to be metabolically active and maintained their membrane integrity, whilst undergoing a change in morphology from rod-shaped to coccoid cells. Resuscitation was possible, in some cases, by an upshift in temperature before plating and the addition of catalase to HIA plates was found to increase recovery. Studies were carried out to assess the sensitivity of the non-culturable cells to heating and freezing compared with the normal cells. Vibrio organisms, whether culturable or in the non-culturable form, were not inactivated by freezing to -20 degrees C. Heating studies showed that V. parahaemolyticus was very heat resistant at low temperatures. However, a pasteurization regime of 2 min at 70 degrees C was found to be effective against all three strains. Experiments showed that the non-culturable cells of all three strains were similar in their heat resistance or, in some cases, were more heat sensitive than cells in the normal form. CONCLUSIONS: Cells in the changed physiological form would not be detected in fish or seafood products by the current Vibrio detection methods. Freezing had no effect in reducing cell numbers. Vibrio parahaemolyticus was very heat resistant in the low temperature pasteurization studies. The higher pasteurization regime of 70 degrees C for 2 min was effective against all three pathogens. Non-culturable cells had similar heat sensitivity or were more heat sensitive than cells in the normal state. SIGNIFICANCE OF IMPACT OF THE STUDY: The study has highlighted a need for the development of better Vibrio detection methods. The low temperature pasteurization of oysters, which has been recommended in the USA, would not be adequate against the strain of V. parahaemolyticus used in this study. Heating regimes which were found to control cells in the normal form will also be effective for the control of the cells with changed physiology.

One explanation for the variability of the bacterial suspension test.

Disinfection kinetic studies of sodium dodecyl sulphate, benzalkonium chloride and sodium hypochlorite against Staphylococcus aureus revealed that when a higher inoculum level of Staph. aureus than normal was used (approximately 1 log higher), the efficacy of disinfection was severely attenuated. Kinetic analysis using the Hom model for experiments carried out on tests using 3 x 108 organisms ml-1 were unable to account for the large increase in disinfection power observed when smaller inoculum levels were used. Since the inoculum was the same in every way except for the numbers used, the large variations in the log reduction/time curves could not be explained by a variation in the resistance of the population to the biocide, as identical log reduction-time curves should have resulted. The level of disinfection achieved for a given concentration of biocide was found to be approximately linearly related to the cell number ml-1 of test solution and not to the log number. The variation observed is believed to occur due to intrinsic self-quenching of the biocide by the microbes during the course of the disinfection test. As the level of free biocide decreases, the rate of reaction decreases, giving the tails of the log reduction/time curves. Such intrinsic self-quenching could explain the large variations known to occur in the legally required disinfection suspension tests.

A kinetic study of the effect of hydrogen peroxide and peracetic acid against Staphylococcus aureus and Pseudomonas aeruginosa using the bioscreen disinfection method.

Hydrogen peroxide and peracetic acid at pH 4 were examined against Staphylococcus aureus and Pseudomonas aeruginosa using the published 'Bioscreen' technique of biocide analysis. The data were examined using either classical Chick-Watson (CW) log-linear disinfection kinetics or the empirical, non-linear time Hom model. In some cases, modelling the data with the classical CW method gave good linear correlations, in others, however, deviations from this model were observed. In such cases the Hom model proved an adequate descriptor of the data. The Bioscreen technique therefore gives data which can be analysed using the normal mechanistic and empirical models currently available.

Disinfectant testing: use of the Bioscreen Microbiological Growth Analyser for laboratory biocide screening.

A new method is described for screening potential biocides based on the traditional suspension test using the Bioscreen optical plate reader. This new method is rapid, reproducible, quantitative and cost effective. Data obtained by this new method are not directly equivalent to the log reduction normally quoted, but give a measurement of the total effect of the biocide on the microbe population, measuring the effect of injury as well as death (non-viability). The method allows for the routine examination of disinfection kinetics, the study of which leads to greater scientific insight into disinfection than that achieved by the standard 5 min, one-point, disinfection tests currently employed.