Relationship between release of nitric oxide and CO2 and their dependence on oxidation reduction potential in wastewater treatment.

Nitric oxide (NO) is an intermediate of denitrification process and can be produced by denitrifiers, nitrifiers and other bacteria. In our experiments we measured the dynamic flow of NO depending on oxidation reduction potential (ORP). Different ORP-ranges were related to various carbon loading stages in the wastewater treatment pilot plant. Nitrification and denitrification were achieved by a sequence of aeration and non-aeration periods. Our measurements show that different carbon loading conditions (low feed, balanced and overloaded conditions) did not change the range of the mixing ratio of NO emissions when the aeration conditions like air-flow and temperature were kept constant. Minimum and maximum NO mixing ratios were 34.7 and 91.8 ppbv; 52.3 and 91.3 ppbv; 57.6 and 109 ppbv for low feed, balanced and overloaded conditions, respectively. The curve of the NO graph relied on nitrification/denitrification dynamics. The dependence of NO release on different ORP and CO2-release during the various conditions are shown. Longer aeration times resulted in an increased release of gaseous NO. The net-release of NO g(-1) nitrogen removed was between 0.014% and 0.028%. The NO fluxes to the air were observed between 8.3 and 14.9 mg m(-2) d(-1) NO. The major release occurred during high aeration periods whereas the concentration of dissolved [NOaq] in the wastewater was less than 0.05% of the gaseous release due to very low solubility of the NO.

The impact of peak saturation of the arterial input function on quantitative evaluation of dynamic susceptibility contrast-enhanced MR studies.

PURPOSE: The purpose of this work was to investigate systematic errors in dynamic contrast-enhanced MR perfusion studies due to peak saturation of the arterial input function (AIF) and to introduce a simple correction algorithm. METHOD: Computer simulations were performed to evaluate the influence of AIF peak saturation and to demonstrate the effectiveness of the presented correction algorithm. To compare the computer simulations with real MR data, MR perfusion measurements were performed on volunteers. RESULTS: The computer simulations show that AIF peak saturation leads to a systematic overestimation of cerebral blood volume (CBV) and cerebral blood flow (CBF) values, which was confirmed by comparing the obtained MR data with PET results. With use of an improved calculation algorithm correcting for AIF peak saturation, a significant improvement of the obtained CBV and CBF values could be demonstrated. CONCLUSION: Our results suggest that AIF peak saturation leads to a significant systematic error in the determination of CBV and CBF values and has necessarily to be taken into account for dynamic contrast-enhanced MR perfusion studies.

Effects of hyperoxia and hypocapnia on regional venous oxygen saturation in the primary visual cortex in conscious humans.

Hyperoxia can improve oxygen delivery in patients exposed to hypocapnia for neurosurgical procedures but this effect may be modified by regional differences in the degree of hypocapnic vasoconstriction. Using functional magnet resonance imaging (fMRI), we have investigated the influence of hyperoxia on blood flow and blood oxygenation in the primary visual cortex in hypocapnic volunteers. Consecutive fMRI measurements were performed in 10 awake, male volunteers during hypocapnia (mean PE'CO2 3.3 (SD 0.1) kPa) and normocapnia (PE'CO2 5.3 (0.1) kPa) at FIO2 values of 0.21 and 1.0, respectively. Hypocapnia significantly reduced the pixel count in the primary visual cortex (median 169 (quartiles 34-246) vs 21 (0-40) pixels at an FIO2 of 0.21). Additional hyperoxia had no influence on this reduction in pixel count (16 (0-28) pixels at FIO2 1.0 vs 21 (0-40) pixels at FIO2 0.21). Hyperoxia did not influence hypocapnic vasoconstriction in the primary visual cortex. These data suggest that in the primary visual cortex, administration of oxygen alone may not be sufficient to improve oxygen delivery under hypocapnic conditions.

Collagen membrane barrier therapy to guide regeneration in Class II furcations in humans.

This study was undertaken to evaluate the effectiveness of resorbable collagen membranes in guided tissue regeneration. The study participants were 38 adults with moderate to advanced periodontitis. Each patient had at least one Class II furcation defect which could serve as either a test or control tooth. The cases were randomized prior to selection, so that investigators did not known whether the patient would be a test case or a control case until the time of surgery. Sites were surgically exposed and measurements were recorded from the cemento-enamel junction (CEJ) directly coronal to the furcation area to the alveolar crest, and to the base of the defect. Horizontal furcation measurements were also made, using a color coded furcation probe. The test patients had a trimmed and shaped collagen membrane barrier placed over the prepared furcation area. The control patients received the identical surgical management, except that no collagen membrane barrier was placed. All patients received normal post-surgical care, and at 12 weeks post-surgery, were scheduled for re-entry surgery. The re-entry mucoperiosteal flaps were designed to expose the furcation area for measurements, as described above. There was clinical improvement in all measurements made in both the test and control patients over the 3-month period. The horizontal furcation measurement and the CEJ to base of alveolar defect measurements did yield a statistically significant improvement when comparing the test patients to the controls.

A Veterans Administration Cooperative Study of biphasic calcium phosphate ceramic in periodontal osseous defects.

One hundred thirty-seven V.A. patients were randomized to one of three treatment groups to evaluate the efficacy of biphasic calcium phosphate (BCP) ceramic in the treatment of periodontal osseous defects. This material was tested against both autogenous bone implant and open flap curettage procedures. Baseline probing attachment level, Navy plaque index, and gingival index were recorded for all patients. These parameters were monitored for 3 years. At the end of this period, 101 patients had completed the study. Although the plaque and gingival indices steadily increased with time, there were no statistically significant differences among the treatment groups. Patients in the ceramic group had a gain in attachment level of 1.0 mm; those in the curettage group, 0.9 mm; and 0.4 mm for those in the bone implant group. Although the BCP patients had a greater gain, the difference was not statistically significant. In this veteran population, not only did BCP patients fail to outperform those in the control groups, all three treatment groups were similarly ineffective.

Maxillary sinus lymphoma: a consideration in the diagnosis of odontogenic pain.

A patient with a known history of diffuse large cell histiocytic non-Hodgkin's lymphoma in the neck and left parotid gland presented with acute right maxillary odontogenic pain and swelling. Following endodontic treatment of the nonvital maxillary right second molar, minor masticatory discomfort persisted in the sextant but a dental etiology could not be established. Two months after the onset of symptoms, the right maxilla expanded uncontrollably and biopsy confirmed an antral lymphoma. The patient succumbed to the lymphoma and secondary complications 2 months later.

Prevalence of medical problems in periodontal patients obtained from three different populations.

Data from three different sources of periodontal patients were collected and examined to find if there was a significant difference between these groups relative to the prevalence of medical problems. Data were evaluated to show if age and sex were significantly related to the existence of medical problems and to determine which problems were the most prevalent. A total of 581 periodontal patients' records were obtained. Results of the evaluation showed that the private office group had 27.6% medical problems, the academic dental center had 46.3%, and the hospital dental clinic had 74.1%. Cardiovascular disease was the most prevalent medical problem in all groups and orthopedic disease or injury was second. Within each group, sex was not significantly related to the presence of a medical problem. Age was a highly significant factor, with the prevalence of medical problems increasing with advancing age.