Soluble Microbial Products in ABR Treating Low-Strength Wastewater

The chemical composition, molecular weight (MW) distribution, and biodegradability (both aerobic and anaerobic) of soluble microbial products (SMPs) in an anaerobic baffled reactor (ABR) treating low-strength wastewater were investigated. The effect of various process parameters on the production of SMPs was also examined. Results indicated that high MW (>300 kDa) compounds were produced in the middle compartments of the reactor and formed 22% of the effluent chemical oxygen demand (COD). This fraction was found to be 86% degradable under aerobic conditions but only 4% under anaerobic conditions. Low MW (<1 kDa) material represented the highest portion (36%) of the effluent COD and was mainly found in the first compartment of the ABR and in the effluent. This fraction was more easily degraded under anaerobic conditions (33%) than aerobic conditions (17%). Analysis of a hydrolyzed sample of the high MW fraction revealed the presence of several sugars and volatile fatty acids. Therefore, it was concluded that the high MW material contains heteropolysaccharides. Nuclear magnetic resonance analysis of the low MW fraction revealed the possible presence of alcohol, carboxylate, and aromatic chemical groups. SMP production increased with increasing hydraulic retention time (HRT), probably due to enhanced biomass decay at high HRTs, and also increased with decreasing temperature, probably due to increased stress on the biomass and a reduced metabolism of the SMP at low temperatures. Finally, SMP production in an ABR containing higher levels of initial biomass concentration was greater than for an ABR operating at the same conditions but with lower levels of initial biomass.     

Undesirable flow behavior in a proposed validation data set

The next generation nuclear plant (NGNP), whose development is supported by the U.S. Department of Energy, will be a very high temperature reactor (VHTR). The VHTR is a single-phase helium-cooled reactor that will provide helium at up to 1000 °C. The prospect of a coolant at these temperatures circulating in the reactor vessel demands that careful analysis be performed to ensure that excessively hot spots are not created and that sufficient mixing of the coolant is obtained. Computational fluid dynamics (CFD) coupled with heat transfer will be used to perform the desired analyses. However, primarily because of the imperfect nature of modeling turbulent flow, any CFD calculations used to perform nuclear reactor safety analysis must be validated against experimental data. Experimental data have been taken in a scaled section of the lower plenum of a prismatic VHTR at the matched index of refraction (MIR) facility at the Idaho National Laboratory. These data were taken with the intent that they be examined for use as validation data. A series of investigations have been conducted to assess the MIR data. Issues that have already been examined include the extent of the required computational domain, the outlet boundary condition, the inlet data and the effect of the turbulence model. One of the jets that flow into the model impacts on a wedge, which represents a portion of a hexagonal graphite block that lines the inner wall of the lower plenum. The nature of the flow below this particular jet is such that a randomly varying recirculation zone is created. This recirculation zone is seen to change in size, causing a relatively long-time scale of motion or disturbance of the flow in the model. It is concluded that such a feature is undesirable in a validation data set, firstly because of its apparent random nature and, secondly, because to obtain an appropriate long-time average would be impractical because of the compute time required. It is predicted computationally that by eliminating the first of the four inlet jets into the scaled model, the resulting recirculation zone is rendered stable.     

Changes in subarachnoid hemorrhage mortality, incidence, and case fatality in New Zealand between 1981-1983 and 1991-1993

BACKGROUND AND PURPOSE: As with total stroke, mortality rates from subarachnoid hemorrhage (SAH) have declined in New Zealand since the mid-1970s. Data from the Auckland Region Stroke studies allow an understanding of reasons for the change, as SAH incidence and 28-day case fatality rates were measured as part of population-based stroke registers. METHODS: National death registrations were used to describe the trends in mortality rates from SAH (International Classification of Diseases [ICD] code 430) among men and women in New Zealand. Changes in incidence and case fatality rates were determined from 2 large-scale population-based stroke registries carried out in 1981-1983 and 10 years later in Auckland. Similar methodology and case ascertainment techniques were used in both studies. RESULTS: The mortality rates from SAH declined in both men and women after the mid-1970s. The mortality rate remained higher among women than men. The incidence of SAH was lower in 1991-1993 (11.3 per 100,000) compared with 1981-1983 (14.6 per 100,000). In the younger age groups, the decrease was mostly due to a lower incidence among men, whereas in the older age groups women older than 65 years had a lower incidence. There was no consistent change in case fatality rates between the 2 periods in either men or women. CONCLUSIONS: Mortality rates from SAH have decreased in both men and women. This decrease may be explained by a decrease in the incidence of SAH, because case fatality rates showed no change.     

Regional changes in hippocampal T2 relaxation and volume: a quantitative magnetic resonance imaging study of hippocampal sclerosis

OBJECTIVE: The principal MRI features of hippocampal sclerosis are volume loss and increased T2 weighted signal intensity. Minor and localised abnormalities may be overlooked without careful quantitation. Hippocampal T2 relaxation time (HT2) can be quantified, but previously has only been measured on a few thick coronal slices with interslice gaps. In this study HT2 was measured along the entire length of the hippocampus on contiguous slices and used, with quantitative measures of hippocampal volume (HV) and distribution of atrophy, to better define the range of hippocampal sclerosis. METHODS: Thirty patients with temporal lobe epilepsy, 10 patients with extratemporal localisation related epilepsy and extratemporal lesions, and 20 control subjects were studied using MRI T2 relaxometry and volumetry. RESULTS: In controls and patients, HT2 was higher in the anterior than the posterior hippocampus. Using HV, morphometric, and HT2 data, patients with temporal lobe epilepsy were classified as unilateral diffuse hippocampal sclerosis (n=16), unilateral focal (n=6), bilaterally affected (n=6), and normal (n=2). In patients with unilateral hippocampal sclerosis, the anterior hippocampus was always affected. In three patients with normal HV, HT2 measurements disclosed unilateral focal abnormalities that corresponded to the EEG lateralisation of epileptic activity. Patients with bilateral hippocampal involvement had an earlier onset of epilepsy than patients with unilateral hippocampal sclerosis. CONCLUSIONS: Measurement of regional abnormalities of HT2 along the length of the hippocampus provides further refinement to the MRI assessment of the hippocampi in patients with temporal lobe epilepsy and is complementary to volumetric and morphological data.     

Second-site cleavage in sterol regulatory element-binding protein occurs at transmembrane junction as determined by cysteine panning

In response to sterol deprivation, two sequential proteolytic cleavages release the NH2-terminal fragments of sterol regulatory element-binding proteins (SREBPs) from cell membranes. The fragments translocate to the nucleus where they activate genes involved in cholesterol and fatty acid metabolism. The SREBPs are bound to membranes in a hairpin fashion. The NH2-terminal and COOH-terminal domains face the cytoplasm, separated by two membrane spanning segments and a short lumenal loop. The first cleavage occurs at Site-1 in the lumenal loop. The NH2-terminal fragment is then released by cleavage at Site-2, which is believed to lie within the first transmembrane segment. Here, we use a novel cysteine panning method to identify the second cleavage site (Site-2) in human SREBP-2 as the Leu484-Cys485 bond that lies at the junction between the cytoplasmic NH2-terminal fragment and the first transmembrane segment. We transfected cells with cDNAs encoding fusion proteins with single cysteine residues at positions to the NH2-terminal and COOH-terminal sides of cysteine 485. The NH2-terminal fragments were tested for susceptibility to modification with Nalpha-(3-maleimidylpropionyl)biocytin, which attaches a biotin group to cysteine sulfhydryls. Cysteines to the NH2-terminal side of cysteine 485 were retained on the NH2-terminal fragment, but cysteines to the COOH-terminal side of leucine 484 were lost. Leucine 484 is three residues to the COOH-terminal side of the tetrapeptide Asp-Arg-Ser-Arg, which immediately precedes the first transmembrane segment and is required for Site-2 cleavage.     

Moment–curvature measurement in thin sheet—part II: yielding and kinking in aged steel sheet

The measurement of the moment–curvature characteristic for thin sheet metal in the elastic–plastic range provides important information which is not readily obtained from the tensile test. Steel sheet which is roll-formed to products such as roofing typically contains a residual stress distribution and is subject to strain ageing; these conditions can be identified from bend tests. The accurate determination of the moment–curvature diagram is not easy as the limiting elastic curvature is large and the magnitude of the moment is small.Part I of this paper describes equipment and data processing which have been developed for this purpose and in Part II, results obtained in sheet which has been progressively aged and stress-relieved are presented.     

Fatty acid composition and intramolecular structure of triglycerides from adipose tissue of the red deer and the reindeer

Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB Triglycerides extracted from perinephric, omental and subcutaneous adipose tissue of six female red deer and of two male and one female reindeer were analysed for the composition and intramolecular disposition of their component fatty acids. In their overall fatty acid composition, the triglycerides of normal and pregnant red deer were similar and resembled those of domesticated ruminants; trans-unsaturated acids were present and the perinephric triglycerides contained a relatively high proportion of stearic acid compared with triglycerides from other bodily sites. The triglycerides from corresponding adipose tissue of lactating hinds contained much less stearic acid and relatively more myristic, palmitic and palmitoleic acids, suggesting that fatty acids of exogenous origin were not being deposited because they were in demand for milk fat synthesis. The adipose tissue triglycerides of the reindeer were unusual in that they were, apparently, mainly of endogenous origin and showed a notable resemblance to the triglycerides of lambs reared on a virtually lipid-free diet. This was reflected in a comparatively low content of stearic acid in the perinephric triglycerides, and the absence of trans-unsaturated acids from all the triglycerides. Analysis of the principal feed (‘reindeer moss’, Cladonia) showed that, compared with normal herbage, it is a very poor source of exogenous fatty acids. Regardless of their fatty acid composition, the intramolecular structure of the triglycerides of the red deer and the reindeer conformed to the general distribution pattern common to most animals. Stearic acid was, for the most part, esterified to the primary alcoholic groups of the glycerol moiety (positions 1 and 3), as was palmitic acid, except when it was present in lower overall proportion than stearic acid. Unsaturated acids and the medium-chain acid, myristic acid, were mainly esterified to the secondary alcohol group (position 2).     

Studies on nucleotides and related compounds in plants. V. Isolation and identification of bracken nucleotides

The presence of acid-soluble nucleotides was demonstrated in bracken rhizomes. Cold trichloroacetic acid extracts of bracken had to be submitted to some eight purification steps prior to analysis. Of the nucleotide material held by an anion exchange resin uridine derivatives (UMP, UDP-glucose, UDP-galactose, UDP-xylose, UDP-arabinose, UDP-glucuronic acid and a trace of UDP) accounted for some 80% of the total. The remainder comprised guanosine (12%; GMP, GDP-mannose and GDP-fucose) and adenosine (8%; mainly ATP) compounds. A comparison of the sugar composition of the nucleotide material with that of associated soluble carbohydrates present in the rhizome (mucilage, glycoside and sucrose) is also included.     

Studies on nucleotides and related compounds in plants. II. An adenyl-cleaving enzyme system in potato tubers

Adenyl-cleaving activity was demonstrated in clarified potato juice. A stock freezedried enzyme preparation, obtained after (NH₄)₂SO₄ fractionation, hydrolysed adenosine and deoxyadenosine but had no effect on other possible nucleoside substrates including cytidine, deoxycytidine, guanosine, deoxyguanosine, inosine, hypoxanthosine, uridine and thymidine. The rate of adenine release for adenosine was some 60% of that for deoxyadenosine under the conditions of the digest. AMP, ADP, ATP and dAMP were all susceptible to hydrolysis releasing adenine. Evidence is produced to show that dephosphorylation is a necessary prerequisite to adenine release. The adenine nucleosidase has an optimum pH 4.1–4.6 and an apparent temperature optimum of 50 °C.