The swept angle retarding mass spectrometer: Initial results from the Michigan auroral probe sounding rocket

Data from a sounding rocket flight of the swept angle retarding ion mass spectrometer (SARIMS) are presented to demonstrate the capability of the instrument to make measurements of thermal ions which are differential in angle, energy, and mass. The SARIMS was flown on the Michigan auroral probe over regions characterized first by discrete auroral arcs and later by diffuse precipitation. The instrument measured the temperature, densities, and flow velocities of the ions NO(+) and O(+). Measured NO(+) densities ranged from 10 to the 5th power up to 3 x 10 to the 5th power ions/cu cm, while the measured O(+) densities were a factor of 5-10 less. Ion temperatures ranged from 0.15 up to 0.33 eV. Eastward ion flows approximately 0.5 km/sec were measured near the arcs, and the observed flow magnitude decreased markedly inside the arcs

Paramètres gouvernant la prolifération bactérienne dans les réseaux de distribution

L'étude a permis de suivre l'évolution des caractéristiques physico-chimiques et microbiologiques des eaux dans un réseau de distribution expérimental de taille industrielle, afin de comparer d'une part l'effet du chlore et de la monochloramine sur la biomasse présente dans le système à l'équilibre et d'autre part d'établir des relations quantitatives entre prolifération bactérienne, oxydant et matière organique biodégradable.Dès les premières heures de transit dans le réseau, une consommation des oxydants est constatée, avec toutefois une plus grande stabilité de la monochloramine (vitesse de consommation de 0,05 mgCl2 l-1h-1 et 0,02 mgCl2 l-1h-1 respectivement pour le chlore et la monochloramine).Même en présence d'un désinfectant résiduel, il est possible de noter une accumulation de bactéries-à ta surface des tuyaux de distribution (105 à 106 cellules. cm-2, dont environ 1 % est cultivable sur gélose) qui augmente avec la diminution de concentration du désinfectant résiduel. Les relations logarithmiques entre densité cellulaire (phase eau ou biofilm) et oxydant résiduel montrent d'une part que pour inactiver totalement les bactéries en suspension dans l'eau il convient de maintenir une chloration en continu avec un résiduel constant supérieur ou égal à 0,5 mgCl2 l-1 et, d'autre part que les chloramines sont au moins 2,5 fois moins efficaces que le chlore, même vis-à-vis des bactéries fixées.La présence de matière organique biodégradable dans les eaux explique la prolifération des bactéries dans le système de distribution. Ainsi une concentration additionnelle de 100 µg.l-1 de carbone organique dissous biodégradable (CODB) dans l'eau entrant dans le réseau de distribution occasionne en 24 heures et à 20°C une augmentation du nombre de bactéries fixées (+7,5.105 cellules.cm-2) ou en suspension (+ 4.104 cellules.ml-1) dans le réseau de distribution, à l'équilibre, déjà largement colonisé par des micro-organismes.Ainsi le contrôle de la fraction biodégradable de la matière organique apparaît toujours comme un objectif primordial.This study was carried out in order to evaluate the variations in the physicochemical characteristics of the water in an experimental distribution system.The primary objectives of the study were :- to compare the disinfectant efficiency of chlorine and monochloramine- to establish quantitative correlations among bacterial density, concentration of residual disinfectant, and concentration of biodegradable organic matter.The finished waters were obtained from a water treatment pilot plant characterized by : prechlorination (average treatment rate : 1.4 mgCl2 l-1 and residual alter sand filtration : 0.08 mgCl2 l-1), coagulation-flocculation-sedimentation (FeCl3 treatment rate : 30 to 60 mg l-1 adjusted to the raw water turbidity below 0.3 NTU), sand filtration (filtration rate : 6 h-1) and post-disinfection with chloramine (average treatment rate : 1.8 mgCl2 l-1) or chloramine (average treatment rate : 1.66 mgCl2 l-1). The concentrations of post-disinfectant used were chosen in order to maintain chlorine at 0.2 to 0.5 mgCl2 l-1 and monochloramine at 1 mgC2 l-1 after the first 24 hours residence time in the experimental distribution system.The experimental distribution system is composed of three parallel loops connected in series (31 m length, 100 mm diameter, cement lined cast iron, water velocity : 1m s-1). The configuration and operation of the system permitted a residence time of 24 hours in each loop (that is 72 hours for the whole system). Appropriate sample tap locations facilitated removal of bulk water samples. Special sampling parts also permitted sampling of cement coupons for determination of attached biofilm.The measured parameters were : residual oxidant (DPD method), DOC, BDOC (28 days of incubation at 28 °C with a bacterial inoculum), cell density in the bulk water phase (CFU ml-1) and in the biofilm (CFU cm-2) after 15 days of incubation at 20-22 °C. Total cells were enumerated using the epifluorescence direct count technique.For each experiment, all the sampling sequences were carried out on each of three days, after quasi steady-state was achieved in the system (4 to 6 weeks after starting each experiment). The data were analysed in order to characterize the treated and distributed waters; the results discussed here are based on the averages of the measured parameters tram the water samples and biofilm samples taken after the system achieved quasi steady-state.Characteristics of the treated watersThe treated waters were characterized by important variations at the DOC, BDOC and cell density. For example, the concentrations of DOC showed a seasonal variation ranging from 0.8 to 1.3 mg Cl-1 in winter to 1.6 to 2.6 mg Cl-1 in summer.The treated waters contained approximately the same concentrations of residual disinfectant, averaging 1.6 mgCl2 l-1 for chlorine and 1.5 mgCl2 l-1 for monochloramine.However, a significant difference cell density was found between the two post-disinfectants. Cell densities by the epifluorescence direct count technic were 1.6 x 103 ml-1 (0.3 % of CFU ml-1) with chlorine and 6.3 x 104 ml-1 (0.03 % of CFU ml-1) with monochloramine. The difference on cell density between the post-chlorination and the post-chloramination treatments has been observed systematically, and may be explained either as cellular lysis with chlorine or an interference when using epifluorescence counting for chlorinated waters.Characteristics of the distributed watersWhatever the season, depletion of oxidant (chlorine or monochloramine), and elimination of dissolved organic matter (DOC, BDOC) occured during the first hours of circulation of water in the distribution system. The net result was an increase in bacterial cell density.During the first hours of circulation of the waters in the distribution system, depletion of the disinfectant occured. Depletion was more rapid for chlorine (-0.05 mgCl2 l-1 h-1) titan for monochloramine (-0.02 mgCl2 l-1 h-1), winch is considered more stable titan chlorine.Even in the presence of a residual disinfectant in the distribution system, microorganisms are present in the water phase (104 to 106 cells ml-1 by epifluorescence direct count; 1 % CFU ml-1 after 15 days of incubation at 20-22 °C) and in the biofilm (105 to 106 cells cm-2 by epifluorescence direct count; 1 % CFU ml-1 after 15 days of incubation at 20-22 °C). The bacterial density increased white the disinfectant residual decreased. The apparent growth rate of the attached biomass (µfix) in loop 2 of the chlorinated distribution system (equivalent to 48 hours detention), was close to the µfix calculated for loop 2 of the chloraminated distribution system : the values were 0.0043 h-1 and 0.005 h-1 respectively.In addition, the change in the organic matter (expressed as DOC) occured in two steps :- a slight increase in DOC during the 24 first hours of residence time (loop 1), when increased residual disinfectant were present.- a bacterial consumption of DOC after 24 hours of residence time (loops 2 and 3), even in the presence of small concentrations of disinfectants.In loop 2 (48 hours residence time of the water in the system; chlorine : 0.01 mgCl2 l-1, chloramine : 0.3 mgCl2 l-1 h-1), the rates of DOC elimination averaged 13 mgCl2 l-1 h-1 and 0.42, mgCl2 l-1 h-1, respectively in the chlorinated and chloraminated distribution systems. This decrease in DOC concentrations was related to the increase in bacterial density.Relationships between cell density, oxidant and organic matterLinear relationships between the concentration of residual oxidant (chlorine or monochloramine) and the cell density in the water phase or in the biofilm show that :- whichever oxidant was used, the pipe loop sections without residual disinfectants were characterized by about 5 x 106 attached cells per cm2 (4 to 10% were able to grow on agar medium in 15 days at 20-22 °C) and by 4 x 105 planktonic cells per ml (1 % CFU ml-1);- consistently, in the sections of the system with a residual disinfectant, the bacteria (CFU and epilluorescence counting) in the water phase were more sensitive to the residual disinfectant (chlorine or monochloramine) than the bacteria attached to the pipe walls (biofilm).However, there was a difference in effectiveness between the two disinfectants; chlorine was more efficient in controlling planktonic bacteria and biofilm bacteria than was monochloramine.For example, to achieve complete inactivation of the planktonic bacteria (CFU ml-1) a constant chlorine residual of 0.5 mgCl2 l-1 was required throughout the whole distribution system, compared to 2.5 times more chloramine to achieve the same efficiency.Finally, with equivalent concentrations of residual disinfectant, the microbiological quality of the chlorinated distribution waters was better than that of the chloraminated distribution waters.From loop to loop, linear relationships between ∆DOC and cell density pointed out that the presence of biodegradable organic matter can explain the bacterial proliferation in the distribution system. For example, a concentration of BDOC as low as 0.1 mgC l-1 resulted in an increase in the cell density : an additional accumulation of 7.5 x 105 attached cells cm-2 and 4 x 104 planktonic cells ml-1 was observed in the experimental distribution system at quasi steady-state.Consequently, the control of the biodegradable organic carbon remains one of the prime objectives in order to achieve biologically stable distribution waters

Instrument manual for the retarding ion mass spectrometer on Dynamics Explorer-1

The retarding ion mass spectrometer (RIMS) for Dynamics Explorer-1 is an instrument designed to measure the details of the thermal plasma distribution. It combines the ion temperature determining capability of the retarding potential analyzer with the compositional capabilities of the mass spectrometer and adds multiple sensor heads to sample all directions relative to the spacecraft ram direction. This manual provides a functional description of the RIMS, the instrument calibration, and a description of the commands which can be stored in the instrument logic to control its operation

A survey of assimilable organic carbon, biodegradable organic carbon and coliform growth response in US drinking waters

Les objectifs principaux de cette étude étaient :1) De documenter, par une étude de large envergure, les concentrations en COA de l'eau potable, et des usines de traitement.2) De comparer l'indice de croissance des coliformes (ICC) aux concentrations en COA.3) De comparer les concentrations en CODE et celles de COA.Le COA de l'eau a été mesuré avec un mélange de cultures Pseudomonas fluorescens de souche P17 et de Spirillumsp. de souche NOX. La plupart des échantillons d'eaux ont été transferrés dans des ampoules de 40 ml, stérilisés puis inoculés avec les bactéries Pseudomonas et Spirillum et incubés à 15 °C. Les unités formant colonies représentaient le paramètre de suivi.Le test relatif à l'ICC a été réalisé avec l'eau soumise au test, préalablement stérilisée puis inoculée avec Cloacae enterobacter. Les échantillons ont été incubés à 20 °C pendant 5 jours et la croissance des coliformes mesurée par les unités formant colonies.La mesure de CODB a été exécutée dans des ampoules de 40 ml : l'échantillon à analyser, préalablement filtré sur fibre de verre et pasteurisé, était inoculé avec une microflore indigène de rivière puis incubé pendant 28 jours à l'obscurité à température ambiante.L'étude a porté sur 109 échantillons prélevés en 79 points d'approvisionnement en eau potable répartis sur le territoire des Etats-Unis et du Canada : 26 d'eaux souterraines, et 53 d'eaux de surface.Des flacons de prélèvements pour échantillonner et des instructions pour prélever et pasteuriser les eaux ont été fournis à tous les techniciens.L'eau stérilisée était envoyée à la Stroud Water Research Centre pour les analyses du COA, CODB et COD et au Risk Reduction Laboratory pour l'essai relatif à l'indice de croissance des coliformes. Les densités des bactéries coliformes et des bactéries hétérotrophes sur gélose étaient mesurés par les techniciens eux-mêmes.Les concentrations en COD s'échelonnaient de 203 à 4943 µg/L, celles en COA de 18 à 322 µg/L (représentant ainsi de 2,4 % à 44,0 % du COD).Les valeurs élevées du pH dans 5 échantillons d'eau ont inhibé la croissance des bactéries soumises aux deux essais biologiques (AOC ou BDOC).Les concentrations en CODB se sont échelonnées de 1 à 1521 µg/L (soit 0,4 % à 52,8% du COD).L'essai sur l'indice de croissance des coliformes a montré que 79 % des eaux soumises au test n'ont pas permis la croissance des coliformes alors que 7 % entraînaient une forte croissante (toutes provenant d'eaux de surface) et 14 une croissance modérée.Les services des eaux n'ont mis en évidence aucun coliforme et seulement une faible densité de bactéries hétérotrophes dans les eaux des usines de traitement.La corrélation COA-CODB était significative (P≪0,01) avec un coefficient de corrélation de r = 0,594.Des corrélations significatives COA-COD et CODB-COD ont également été mises en évidence.Par contre, les corrélations ICC-COA ou ICC-CODB n'étaient pas significatives.The primary objectives of this study were : 1) to document concentrations of Assimilable Organic Carbon (AOC) in a survey of a broad range of drinking waters and treatment processes; 2) compare the Colilorm Growth Response (CGR) to AOC concentrations; and 3) compare Biodegradable Dissolved Organic Carbon (BDOC) concentrations to AOC concentrations. AOC was measured with mixed cultures of Pseudomonas fluorescens strain P-17 and Spirillum sp. strain NOX. Test waters were transferred to 40-ml vials, pasteurized, inoculated, and incubated at 15°C. Colony forming units was the test parameter. CGR was performed with pasteurized test water inoculated with Enterobacter cloacae. Samples were incubated at 20°C for 5 days and response determined from colony forming units. The BDOC assay was performed in 40-ml vials, with glass fiber filtered, pasteurized test water, inoculated with the indigenous microflore from a stream, and incubated for 28 days in the dark et room temperature. The survey involved 109 samples from 79 drinking water supplies located throughout the United States and Canada, including 26 groundwater and 53 surface water sources. Utility personnel were supplied with sample bottles and instructions for sampling and pasteurtzing the test waters. Pasteurized water was sent to the Stroud Water Research Center for AOC, BDOC, and DOC analyses, and to the Risk Reduction Engineering Laboratory for the CGR assay. Densities of coliforms and heterotrophic plate count bacteria (HPC) were measured in the test waters by utility personnel. DOC concentrations ranged from 203 to 4943 µg/L. AOC concentrations ranged from 18 to 322 µg/L, or 2.4 % to 44.0 % of the DOC. High pH values in 5 test waters inhibited the growth of both AOC bioassay organisms. BDOC concentrations ranged from 1 to 1521 µg/L, or 0.4% to 52.8 % of DOC. The CGR assay indicated that 79 % of the test waters did not promote coliform growth, 7 % were strongly growth promoting, all from surface water sources, and 14 % were moderately growth promoting. No coliforms and only low densities at HPC organisms were reported by utilities for treatment plant effluents. The correlation of AOC and BDOC was significant (P≪0.01), with a correlation coefficient of r=0.594. Significant correlations were also found for AOC and DOC, and BDOC and DOC. Correlations of CGR and either AOC or BDOC were not statistically significant

DE 1 RIMS operational characteristics

The Retarding Ion Mass Spectrometer (RIMS) on the Dynamics Explorer 1 spacecraft observes both the thermal and superthermal (50 eV) ions of the ionosphere and inner magnetosphere. It is capable of measuring the detailed species distribution function of these ions in many cases. It was equipped with an integral electrometer to permit in-flight calibration of the detector sensitivities and variations thereof. A guide to understanding the RIMS data set is given. The reduction process from count rates to physical quantities is discussed in some detail. The procedure used to establish in-flight calibration is described, and results of a comparison with densities from plasma wave measurements are provided. Finally, a discussion is provided of various anomalies in the data set, including changes of channeltron efficiency with time, spin modulation of the axial sensor heads, apparent potential differences between the sensor heads, and failures of the radial head retarding potential sweep and of the -Z axial head aperture plane bias. Studies of the RIMS data set should be conducted only with a thorough awareness of the material presented here, or in collaboration with one of the scientists actively involved with RIMS data analysis

The Thermal Ion Dynamics Experiment and Plasma Source Instrument

The Thermal Ion Dynamics Experiment (TIDE) and the Plasma Source Instrument (PSI) have been developed in response to the requirements of the ISTP Program for three-dimensional (3D) plasma composition measurements capable of tracking the circulation of low-energy (0-500 eV) plasma through the polar magnetosphere. This plasma is composed of penetrating magnetosheath and escaping ionospheric components. It is in part lost to the downstream solar wind and in part recirculated within the magnetosphere, participating in the formation of the diamagnetic hot plasma sheet and ring current plasma populations. Significant obstacles which have previously made this task impossible include the low density and energy of the outflowing ionospheric plasma plume and the positive spacecraft floating potentials which exclude the lowest-energy plasma from detection on ordinary spacecraft. Based on a unique combination of focusing electrostatic ion optics and time of flight detection and mass analysis, TIDE provides the sensitivity (seven apertures of about 1 cm squared effective area each) and angular resolution (6 x 18 degrees) required for this purpose. PSI produces a low energy plasma locally at the POLAR spacecraft that provides the ion current required to balance the photoelectron current, along with a low temperature electron population, regulating the spacecraft potential slightly positive relative to the space plasma. TIDE/PSI will: (a) measure the density and flow fields of the solar and terrestrial plasmas within the high polar cap and magnetospheric lobes; (b) quantify the extent to which ionospheric and solar ions are recirculated within the distant magnetotail neutral sheet or lost to the distant tail and solar wind; (c) investigate the mass-dependent degree energization of these plasmas by measuring their thermodynamic properties; (d) investigate the relative roles of ionosphere and solar wind as sources of plasma to the plasma sheet and ring current

Space experiments with particle accelerators (SEPAC): Description of instrumentation

SEPAC (Space Experiments with Particle Accelerators) flew on Spacelab 1 (SL 1) in November and December 1983. SEPAC is a joint U.S.-Japan investigation of the interaction of electron, plasma, and neutral beams with the ionosphere, atmosphere and magnetosphere. It is scheduled to fly again on Atlas 1 in August 1990. On SL 1, SEPAC used an electron accelerator, a plasma accelerator, and neutral gas source as active elements and an array of diagnostics to investigate the interactions. For Atlas 1, the plasma accelerator will be replaced by a plasma contactor and charge collection devices to improve vehicle charging meutralization. This paper describes the SEPAC instrumentation in detail for the SL 1 and Atlas 1 flights and includes a bibliography of SEPAC papers

Proposal for a method to estimate nutrient shock effects in bacteria

Plating methods are still the golden standard in microbiology; however, some studies have shown that these techniques can underestimate the microbial concentrations and diversity. A nutrient shock is one of the mechanisms proposed to explain this phenomenon. In this study, a tentative method to assess nutrient shock effects was tested. Findings To estimate the extent of nutrient shock effects, two strains isolated from tap water (Sphingomonas capsulata and Methylobacterium sp.) and two culture collection strains (E. coli CECT 434 and Pseudomonas fluorescens ATCC 13525) were exposed both to low and high nutrient conditions for different times and then placed in low nutrient medium (R2A) and rich nutrient medium (TSA). The average improvement (A.I.) of recovery between R2A and TSA for the different times was calculated to more simply assess the difference obtained in culturability between each medium. As expected, A.I. was higher when cells were plated after the exposition to water than when they were recovered from high-nutrient medium showing the existence of a nutrient shock for the diverse bacteria used. S. capsulata was the species most affected by this phenomenon. This work provides a method to consistently determine the extent of nutrient shock effects on different microorganisms and hence quantify the ability of each species to deal with sudden increases in substrate concentration. <br/

Developing an ecologically relevant heterogeneous biofilm model for dental-unit waterlines

This study monitored the biodiversity of microbes cultured from a heterogeneous biofilm which had formed on the lumen of a section of dental waterline tubing over a period of 910 days. By day two bacterial counts on the outlet-water showed that contamination of the system had occurred. After 14 days, a biofilm comparable to that of clinical waterlines, consisting of bacteria, fungi and amoebae had formed. This showed that the proprietary silver coating applied to the lumenal surface of the commercial waterline tubing failed to prevent biofilm formation. Molecular barcoding of isolated culturable microorganisms showed some degree of the diversity of taxa in the biofilm, including the opportunistic pathogen Legionella pneumophila. Whilst the system used for isolation and identification of contaminating microorganisms may underestimate the diversity of organisms in the biofilm, their similarity to those found in the clinical environment makes this a promising test-bed for future biocide testing