Discharge studies in micromegas detectors in a 150 GeV/c pion beam

A detailed study of several Micromegas detectors prototyped for the COMPASS and CLAS12 experiments is presented. Using a 150 GeV/c pion beam, the discharge probability was measured for several detector variants including bulk and non-bulk Micromegas. A detector equipped with an additional GEM foil as pre-amplification stage was also tested. A resistive coating of the readout strips was found to reduce the amplitude of the discharge by at least two orders of magnitude which was below the detection limit of the experimental setup. The effects of the micro-mesh type and material were investigated as well as the influence of the drift gap. Response in the presence of a 1.5 T transverse magnetic field was also studied. The measurements presented were performed during a RD51 beam test period.     

Advances in Modeling Completely Mixed Flow Reactors for Ion Exchange

This work advances the mathematical modeling of ion exchange treatment in completely mixed flow reactors in which there is recycle and regeneration of the ion exchange resin. The most common application of this process is magnetic ion exchange resin to remove dissolved organic carbon from raw drinking water. The motivation for this work was the complex distribution of resin particle ages and sizes that result from the recycle and regeneration processes. The newly developed model uses a single “age-averaged” diffusion equation to represent resin particle age as compared with the previous Monte Carlo model that uses a large number of diffusion equations to represent various resin particle ages. Advantages of the age-averaged model over the Monte Carlo model include a closed-form analytical solution for the steady-state case of the model, advanced numerical techniques used for the nonsteady-state case of the model, and model simulations require much less computational time and yield more accurate results. The age-averaged model is a robust numerical tool that can be used to evaluate a range of treatment scenarios as a result of these advancements.     

Phosphate recovery using hybrid anion exchange: Applications to source-separated urine and combined wastewater streams

There is increasing interest in recovering phosphorus (P) from various wastewater streams for beneficial use as fertilizer and to minimize environmental impacts of excess P on receiving waters. One such example is P recovery from human urine, which has a high concentration of phosphate (200–800 mg P/L) and accounts for a small volume (∼1%) of total wastewater flow. Accordingly, the goal of this study was to evaluate the potential to recover P from source-separated and combined wastewater streams that included undiluted human urine, urine diluted with tap water, greywater, mixture of urine and greywater, anaerobic digester supernatant, and secondary wastewater effluent. A hybrid anion exchange (HAIX) resin containing hydrous ferric oxide was used to recover P because of its selectivity for phosphate and the option to precipitate P minerals in the waste regeneration solution. The P recovery potential was fresh urine > hydrolyzed urine > greywater > biological wastewater effluent > anaerobic digester supernatant. The maximum loading of P on HAIX resin was fresh urine > hydrolyzed urine > anaerobic digester supernatant ≈ greywater > biological wastewater effluent. Results indicated that the sorption capacity of HAIX resin for phosphate and the total P recovery potential were greater for source-separated urine than the combined wastewater streams of secondary wastewater effluent and anaerobic digester supernatant. Dilution of urine with tap water decreased the phosphate loading on HAIX resin. The results of this work advance the current understanding of nutrient recovery from complex wastewater streams by sorption processes.     

Disseminated tuberculosis of unusual locations

We report a case of disseminated tuberculosis involving the middle ear, the central nervous system, the spine and the lung. The tuberculous epidural abscess and otomastoiditis don't have any specific imaging features. But their coexistence with an other tuberculous involvement might suggest their tuberculous nature. The epidural abscess may result from direct extension from otomastoiditis.     

Mutation rate of a microsatellite sequence in normal human fibroblasts

Dinucleotide repeats, because of their repetitive nature, are prone to frameshift mutations, most likely via a DNA-polymerase slippage mechanism. Mutation rates in microsatellite DNA sequences are high in mismatch repair-defective cells. In normal cells, only estimates of maximal rates of mutation in microsatellites have been possible previously, because of the low sensitivity of screening assays for mutations in endogenous sequences. We have measured the spontaneous mutation rate of a dinucleotide repeat in diploid human foreskin fibroblasts. In our system, the mutation target is a (CA)17 repeat contained within a stably integrated plasmid. The repeat disrupts the reading frame of a neomycin (neo) resistance gene within the plasmid. Cells containing frameshift mutations in the CA repeat that correct the reading frame of the neo gene are selected using the neo analogue G418. This system of measuring microsatellite mutation rates is highly sensitive, because there is a specific target within which mutations can be selected. Fluctuation analysis of cells containing the target DNA yielded mutation rates of <3.1 x 10(-8) to 44.8 x 10(-8) mutations/cell/generation. This is the first report of a direct measurement of a spontaneous mutation rate of a microsatellite sequence in normal human cells.     

A Proof of the Security of Quantum Key Distribution

We prove the security of theoretical quantum key distribution against the most general attacks which can be performed on the channel, by an eavesdropper who has unlimited computation abilities, and the full power allowed by the rules of classical and quantum physics. A key created that way can then be used to transmit secure messages such that their security is also unaffected in the future.     

Use of health services for anxiety disorders: a multisite study in Quebec

OBJECTIVE: We investigated patient characteristics and use of services for anxiety disorders among patients seeking care from participating clinicians at 7 anxiety clinics in Quebec: 3 general hospital clinics, 3 psychologist-run clinics, and one psychiatric hospital clinic. METHODS: Persons eligible for the study were those who were visiting the clinics for the first time, had a current diagnosis of an anxiety disorder, and could communicate in French or English. Subjects recruited through advertisements were excluded. Data, collected by a self-administered questionnaire, included demographics, treatment history, use of services for anxiety, and the Beck Anxiety Inventory (BAI). RESULTS: The sample comprised 235 subjects: 146 seen at 3 general hospital clinics, 54 at 3 psychologist-run clinics, and 35 at a psychiatric hospital clinic. There were statistically significant differences by clinic type in the prevalence of specific anxiety diagnoses, BAI score, referral source, antidepressant use, and use of services. High-intensity use (10 or more consultations during the previous year) was reported by 23.4% of the sample for medical services and 19.6% for mental health services. Multiple logistic regression identified variables associated with high-intensity use of medical services (higher BAI score, 1 to 4 years since first sought treatment, and less than 12 years of education) and high-intensity use of mental health services (clinic type, obsessive-compulsive disorder [OCD], and 5 or more years since first sought treatment). CONCLUSIONS: The patient populations seen at different types of anxiety clinics differ in several respects, including referral source, previous treatment, and severity of symptoms. Regardless of type of clinic, patients with a longer time since they first sought treatment use more services, particularly mental health services. Those with less education use more medical services than those with greater education.