692 research outputs found
Bulk etch rate measurements and calibrations of CR39 and Makrofol nuclear track detectors
We developed a new method for determining the bulk etch rate velocity based
on both cone height and base diameter measurements of the etched tracks. This
method is applied here for the calibration of CR39 and Makrofol nuclear track
detectors exposed to 158 A GeV In^{49+} and Pb^{82+} ions, respectively. For
CR39 the peaks corresponding to indium ions and their different fragments are
well separated from Z/beta = 7 to 49: the detection threshold is at REL ~ 50
MeV cm^2 g^{-1}, corresponding to a nuclear fragment with Z/beta = 7. The
calibration of Makrofol with Pb^{82+} ions has shown all peaks due to lead ions
and their fragments from Z/beta ~ 51 to 83 (charge pickup). The detection
threshold of Makrofol is at REL ~ 2700 MeV cm^2 g^{-1}, corresponding to a
nuclear fragment with Z/beta = 51.Comment: 4 pages, 6 eps figures. Talk given at the 24th ICNTS, Bologna, Italy
(1-5 Sept. 2008
The effect of sulfide on -glucosidases: implications for starch degradation in anaerobic bioreactors
Membrane associated α-glucosidase activity was investigated in a methanogenic bioreactor (MR) and a biosulfidogenic bioreactor (SR). Temperature and pH optima studies showed temperature optima of 50 °C and pH optima of 8.0 for the α-glucosidases from both the MR and SR. Sulfide (at a concentration of 150 mg l[superscript (−1)]) resulted in the complete loss of all α-glucosidase activity in both the MR and SR. β-Glucosidase activities in our bioreactors were previously shown to be stimulated in the presence of sulfide. α-Glucosidases, in contrast, are inhibited by sulfide. This differential effect of sulfide on α-glucosidase and β-glucosidase activities is highlighted and is of crucial consequence to the respective degradation and utilization of starch and cellulose substrates in natural anaerobic environments and anaerobic bioreactors specifically designed for the accelerated digestion of wastewater sludge under biosulfidogenic conditions
The effect of physico-chemical parameters and chemical compounds on the activity of β-d-galactosidase (B-GAL), a marker enzyme for indicator microorganisms in water
The presence of coliforms in polluted water was determined enzymatically (in situ) by directly monitoring the activity of beta-d-galactosidase (B-GAL) through the hydrolysis of the yellow chromogenic subtrate, chlorophenol red beta-d-galactopyranoside (CPRG), which produced a red chlorophenol red (CPR) product. The objectives of this study were to monitor the effect of compounds commonly found in the environment and used in water treatment on a B-GAL CPRG assay and to investigate the differences between the environmental B-GAL enzyme and the pure commercial enzyme. Environmental B-GAL was optimally active at pH 7.8. Two temperature optima were observed at 35 and 55 degrees C, respectively. B-GAL activity was strongly inhibited by silver and copper ions. While calcium and ferrous ions at lower concentrations (50-100mgl(-1)) increased the enzyme activity, a reduction was observed at higher concentrations (200mgl(-1)). Sodium hypochlorite, normally used in rural areas to disinfect water gradually decreased B-GAL activity at concentrations between 0 and 5600ppm for both the commercial and environmental enzymes. B-GAL from the environment behaved differently from its commercially available counterpart
Comparison of the direct enzyme assay method with the membrane filtration technique in the quantification and monitoring of microbial indicator organisms - seasonal variations in the activities of coliforms and E.coli, temperature and pH
The aim of this project was to monitor variations and relationships between coliform and E. coli counts, the activities of their marker enzymes GAL and GUD, and temperature and pH over a period of 12 months in river samples obtained from the Eastern Cape, South Africa. Several polluted water samples were collected for direct coliform β-D-galactosidase (B-GAL) and Escherichia coli β-D-glucuronidase (B-GUD) assays and the membrane filtration technique. While all the samples showed enzyme activities, not all exhibited growth on CM1046 media. Variation in B-GAL activity (40%) was observed between November (highest activity month) and May (lowest activity month). The highest and lowest B-GUD activities were observed in the months of September and May/June, respectively. The sensitivity of the spectrophotometric assay method was indicated by a limit of detection (LOD) of 1 coliform forming unit (CFU)/100 mℓ and 2 CFU/100 mℓ for coliforms and E. coli, respectively. There was a significant (P < 0.05) positive correlation between E. coli counts and GUD activity (R2 = 0.8909). A correlation of R2 = 0.9151 was also observed between total coliforms and B-GAL activity, even though the CFUs were not evenly distributed. Direct enzyme assays were also shown to be more sensitive than the membrane filtration (MF) technique
Fragmentation of very high energy heavy ions
A stack of CR39 (C12H18O7)n nuclear track detectors with a Cu target was
exposed to a 158 A GeV lead ion beam at the CERN-SPS, in order to study the
fragmentation properties of lead nuclei.
Measurements of the total, break-up and pick-up charge-changing cross
sections of ultrarelativistic Pb ions on Cu and CR39 targets are presented and
discussed.Comment: 4 pages, 3 EPS figures included with epsf, uses article.sty Talk
presented by M. Giorgini at the Int. Conf. on Structure of the Nucleus at the
Dawn of the Century, Bologna (Italy), May 29-June 3, 200
Fragmentation cross sections of Fe^{26+}, Si^{14+} and C^{6+} ions of 0.3-10 A GeV on CR39, polyethylene and aluminum targets
New measurements of the total and partial fragmentation cross sections in the
energy range 0.3-10 A GeV of Fe^{26+}, Si^{14+} and C^{6+} beams on
polyethylene, CR39 and aluminum targets are presented. The exposures were made
at Brookhaven National Laboratory (BNL), USA, and Heavy Ion Medical Accelerator
in Chiba (HIMAC), Japan. The CR39 nuclear track detectors were used to identify
the incident and survived beams and their fragments. The total fragmentation
cross sections for all targets are almost energy independent while they depend
on the target mass. The measured partial fragmentation cross sections are also
discussed.Comment: 4 pages, 5 eps figures. Talk given at the 24th International
Conference on Nuclear Tracks in Solids, Bologna, Italy, 1-5 September 200
A novel biosensor for the detection and monitoring of -d-galactosidase of faecal origin in water
A voltammetric sensor prepared by the immobilization of metallophthalocyanine complexes onto a glassy carbon electrode has been developed for the detection of β-d-galactosidase (B-GAL) of faecal origin in water. Electrooxidation of chlorophenol red, a breakdown product of the chromogenic substrate chlorophenol red β-d-galactopyranoside, was used as a measure of β-d-galactosidase activity. At metallophthalocyanine modified electrodes, in particular copper(II) phthalocyanine, a decrease in electrode fouling was observed. The sensor was sensitive to fluctuations in pH, not significantly affected by temperature variations and could detect one colony forming unit/100 mL in 15 min. Loss of 40% sensitivity was observed over a period of 30 days. A strong correlation between sensor sensitivity and colony forming units was observed. The sensor is capable of detecting viable but nonculturable bacteria, overcoming this drawback of the use of culture media for detection of coliforms
Time variations in the deep underground muon flux measured by MACRO
More than 30 million of high-energy muons collected with the MACRO detector
at the underground Gran Sasso Laboratory have been used to search for flux
variations of different natures. Two kinds of studies were carried out: search
for periodic variations and for the occurrence of clusters of events. Different
analysis methods, including Lomb-Scargle spectral analysis and Scan Test
statistics have been applied to the data.Comment: 6 pages, 4 EPS figures. Talk given at the 29th ICRC, Pune, India,
3-10 August 200
- …