Search

Hydrogen sulfide production by sulfate reducing bacteria (SRB) is the primary cause of oil reservoir souring. Amending environments with chlorate or perchlorate [collectively denoted (per)chlorate] represents an emerging technology to prevent the onset of souring. Recent studies with perchlorate reducing bacteria (PRB) monocultures demonstrated that they have the innate capability to enzymatically oxidize sulfide, thus PRB may offer an effective means of reversing souring. (Per)chlorate may be effective by (i) direct toxicity to SRB; (ii) competitive exclusion of SRB by PRB; or (iii) reversal of souring through re-oxidation of sulfide by PRB. To determine if (per)chlorate could sweeten a soured column system and assign a quantitative value to each of the mechanisms we treated columns flooded with San Francisco bay water with temporally decreasing amounts (50, 25, and 12.5 mM) of (per)chlorate. Geochemistry and the microbial community structure were monitored and a reactive transport model was developed, Results were compared to columns treated with nitrate or untreated. Souring was reversed by all treatments at 50 mM but nitrate-treated columns began to re-sour when treatment concentrations decreased (25 mM). Re-souring was only observed in (per)chlorate-treated columns when concentrations were decreased to 12.5 mM and the extent of re-souring was less than the control columns. Microbial community analyses indicated treatment-specific community shifts. Nitrate treatment resulted in a distinct community enriched in genera known to perform sulfur cycling metabolisms and genera capable of nitrate reduction. (Per)chlorate treatment enriched for (per)chlorate reducing bacteria. (Per)chlorate treatments only enriched for sulfate reducing organisms when treatment levels were decreased. A reactive transport model of perchlorate treatment was developed and a baseline case simulation demonstrated that the model provided a good fit to the effluent geochemical data. Subsequent simulations teased out the relative role that each of the three perchlorate inhibition mechanisms played during different phases of the experiment. These results indicate that perchlorate addition is an effective strategy for both souring prevention and souring reversal. It provides insight into which organisms are involved, and illuminates the interactive effects of the inhibition mechanisms, further highlighting the versatility of perchlorate as a sweetening agent.

Microbial sulfate reduction is a primary cause of oil reservoir souring. Here we show that amendment with chlorate or perchlorate [collectively (per)chlorate] potentially resolves this issue. Triplicate packed columns inoculated with marine sediment were flushed with coastal water amended with yeast extract and one of nitrate, chlorate, or perchlorate. Results showed that although sulfide production was dramatically reduced by all treatments, effluent sulfide was observed in the nitrate (10 mM) treatment after an initial inhibition period. In contrast, no effluent sulfide was observed with (per)chlorate (10 mM). Microbial community analyses indicated temporal community shifts and phylogenetic clustering by treatment. Nitrate addition stimulated Xanthomonadaceae and Rhizobiaceae growth, supporting their role in nitrate metabolism. (Per)chlorate showed distinct effects on microbial community structure compared with nitrate and resulted in a general suppression of the community relative to the untreated control combined with a significant decrease in sulfate reducing species abundance indicating specific toxicity. Furthermore, chlorate stimulated Pseudomonadaceae and Pseudoalteromonadaceae, members of which are known chlorate respirers, suggesting that chlorate may also control sulfidogenesis by biocompetitive exclusion of sulfate-reduction. Perchlorate addition stimulated Desulfobulbaceae and Desulfomonadaceae, which contain sulfide oxidizing and elemental sulfur-reducing species respectively, suggesting that effluent sulfide concentrations may be controlled through sulfur redox cycling in addition to toxicity and biocompetitive exclusion. Sulfur isotope analyses further support sulfur cycling in the columns, even when sulfide is not detected. This study indicates that (per)chlorate show great promise as inhibitors of sulfidogenesis in natural communities and provides insight into which organisms and respiratory processes are involved.

Exercise may be beneficial to older persons living with peripheral neuropathy (PN), but maintaining an exercise program is challenging. After participating in a 12-week tai chi (TC) study, 12 participants requested classes continue. A mixed-methods design was used to explore long-term engagement of older persons with bilateral PN enrolled in a TC class for 18 months beyond the original 3-month study. Pre- and posttest measures of functional status and quality of life (QOL) were conducted. Focus groups were held after 18 months of twice-weekly classes. Psychosocial support was critical to participants’ long-term commitment to exercise. Participants reported, and objective assessments confirmed, increased strength, balance, and stamina beyond that experienced in the original 12-week study. Changes in QOL scores were nonsignificant; however, qualitative data supported clinical significance across QOL domains. Results from this study support psychosocial and physical benefits of TC to older persons.

Hydrogen sulfide production by sulfate reducing bacteria (SRB) is the primary cause of oil reservoir souring. Amending environments with chlorate or perchlorate [collectively denoted (per)chlorate] represents an emerging technology to prevent the onset of souring. Recent studies with perchlorate reducing bacteria (PRB) monocultures demonstrated that they have the innate capability to enzymatically oxidize sulfide, thus PRB may offer an effective means of reversing souring. (Per)chlorate may be effective by (i) direct toxicity to SRB; (ii) competitive exclusion of SRB by PRB; or (iii) reversal of souring through re-oxidation of sulfide by PRB. To determine if (per)chlorate could sweeten a soured column system and assign a quantitative value to each of the mechanisms we treated columns flooded with San Francisco bay water with temporally decreasing amounts (50, 25, and 12.5 mM) of (per)chlorate. Geochemistry and the microbial community structure were monitored and a reactive transport model was developed, Results were compared to columns treated with nitrate or untreated. Souring was reversed by all treatments at 50 mM but nitrate-treated columns began to re-sour when treatment concentrations decreased (25 mM). Re-souring was only observed in (per)chlorate-treated columns when concentrations were decreased to 12.5 mM and the extent of re-souring was less than the control columns. Microbial community analyses indicated treatment-specific community shifts. Nitrate treatment resulted in a distinct community enriched in genera known to perform sulfur cycling metabolisms and genera capable of nitrate reduction. (Per)chlorate treatment enriched for (per)chlorate reducing bacteria. (Per)chlorate treatments only enriched for sulfate reducing organisms when treatment levels were decreased. A reactive transport model of perchlorate treatment was developed and a baseline case simulation demonstrated that the model provided a good fit to the effluent geochemical data. Subsequent simulations teased out the relative role that each of the three perchlorate inhibition mechanisms played during different phases of the experiment. These results indicate that perchlorate addition is an effective strategy for both souring prevention and souring reversal. It provides insight into which organisms are involved, and illuminates the interactive effects of the inhibition mechanisms, further highlighting the versatility of perchlorate as a sweetening agent.

INTRODUCTION: We reviewed our experience with the use of gabapentin to treat symptoms of overactive bladder (OAB) and nocturia in patients who have failed conventional anticholinergic therapy. METHODS: Thirty-one patients referred to us with refractory (OAB) and/or nocturia were treated with oral gabapentin. All the patients had tried or remained on antimuscarinic drugs during treatment. Twenty-four of 31 complained of bothersome symptoms during day and night and the other seven had primary complaints of nocturia. Initial gabapentin doses ranged from 100-300 mg at bedtime. Dose was slowly titrated up to 3,000 mg based on patients' symptomatology and tolerability. RESULTS:The mean age was 51 years old (range 27-78). There were 13 men and 18 women. The median steady state dose chosen by the patient after initial titration was 600 mg/day. Fourteen of 31 patients reported subjective improvement of their frequency and 8 have been on the medication for over 12 months with persistent efficacy. For the 14 improved patients, mean frequency/24 hours decreased from 14.1 ± 2.2 to10.0 + 2.1. Three patients with primary nocturia reported improvement from a mean of 4.0 ± 1.3 to 1.0 ± 0.3 episodes/night. Six patients stopped taking the drug within one month due to side effects mostly described as drowsiness or lethargy. CONCLUSION: Fourteen of 31 patients with refractory (OAB) and nocturia improved with oral gabapentin. Gabapentin was generally well tolerated and can be considered in selective patients when conventional modalities have failed.

A cDNA clone encoding GLORF-C4 was isolated from the WB strain, an assemblage A Giardia intestinalis. Interestingly, GLORF-G4 has been previously reported as an assemblage B-specific gene. Using two primers based on GLORF-C4 of the GS strain, a prototype assemblage B, GLORFG4 gene was amplified from all the groups of G. intestinalis, and applied to detect the presence of cysts of G. intestinalis from faecal samples of cyst-passers. RFLP analysis of this PCR product successfully classified G. intestinalis into two distinct groups, assemblages A and B.