scholarly journals Estimation of Cerebral Oxygen Utilization Rate by Single-Bolus 15O2 Inhalation and Dynamic Positron Emission Tomography

1987 ◽  
Vol 7 (4) ◽  
pp. 403-414 ◽  
Author(s):  
E. Meyer ◽  
J. L. Tyler ◽  
C. J. Thompson ◽  
C. Redies ◽  
M. Diksic ◽  
...  
Keyword(s):  
Cerebral Blood Volume ◽  
Utilization Rate ◽  
Simultaneous Estimation ◽  
Oxygen Utilization ◽  
Oxygen Extraction Ratio ◽  
Time Activity ◽  
Single Bolus ◽  
Positron Emission ◽  
Tomographic Data ◽  
Oxygen Utilization Rate

This study shows that regional CMRO2 can be estimated by means of nonlinear regression using dynamic positron emission tomographic data acquired during 1 min following single-bolus inhalation of 15O2. The feasibility of simultaneous estimation of CBF, cerebral blood volume (CBV), oxygen extraction ratio (OER), and CMRO2 was assessed by simulations using the model of Mintun et al. Four oxygen metabolic measurements, each consisting of a CBF, CBV, and 15O2 bolus study, were carried out on three volunteers. Regional values for CBF, CBV, OER, and CMRO2 were derived in two ways: from the fits of the time-activity curves of the dynamic 15O2 bolus study alone [CMRO2(fit)] and from the three separate studies [CMRO2 (control)]. For the 56 regions of interest analyzed, using a fit interval of 60 s, CMRO2(fit) was 93.4 ± 7.8% of CMRO2(control) (mean ± SD) with a correlation coefficient of r = 0.95. CMRO2(control) ranged from 87 to 290 μmol/min/100 g. Individual simultaneous estimates of CBF, CBV, and OER were not reliable. Finally, we found that the validity of the model was limited in practice to the first minute after tracer inhalation.

Important limitations in the modeling of activated sludge: biased calibration of the hydrolysis process

2002 ◽  
Vol 45 (12) ◽  
pp. 23-36 ◽  
Author(s):  
G. Insel ◽  
Ö. Karahan Gül ◽  
D. Orhon ◽  
P.A. Vanrolleghem ◽  
M. Henze
Keyword(s):  
Activated Sludge ◽  
Hydrolysis Rate ◽  
Utilization Rate ◽  
Oxygen Utilization ◽  
Experimental Assessment ◽  
Experimental Database ◽  
Hydrolysis Process ◽  
Biochemical Mechanisms ◽  
Oxygen Utilization Rate ◽  
Activated Sludge Models

The merit of activated sludge models depends on the accuracy and reliability of the information they contain on the wastewater to be treated and the biochemical mechanisms involved. In most advanced calibration studies, respirometry i.e. the measurement of the oxygen utilization rate, (OUR), provides the majority of the required experimental database. However, currently used procedures still involve a number of basic and practical problems. Model evaluation of the OUR data may generate a distorted image of the processes involved. Hydrolysis is the most important, yet the most vulnerable process as far as the experimental assessment of accurate kinetic parameters is concerned. This study intends to provide an overview of major experimental limitations in the modeling of activated sludge, with emphasis on the appropriate experimental design for the assessment of the hydrolysis rate.

Correct manipulation method of MBR operating parameters in membrane fouling studies

2013 ◽  
Vol 68 (10) ◽  
pp. 2301-2308 ◽  
Author(s):  
N. Kayaalp ◽  
C. Kinaci
Keyword(s):  
Retention Time ◽  
Membrane Fouling ◽  
Organic Loading Rate ◽  
Utilization Rate ◽  
Operating Parameters ◽  
Oxygen Utilization ◽  
Membrane Area ◽  
Membrane Flux ◽  
Oxygen Utilization Rate ◽  
Common Application

In this study, various parameter manipulation methods, variable sludge retention time (SRT)–variable mixed liquor suspended solids (MLSS) concentration, constant SRT–variable MLSS concentration and variable SRT–constant MLSS concentration, were compared based on the interrelationships among the following membrane bioreactor operating parameters: SRT, food to microorganisms (biomass) (F/M) ratio, MLSS concentration, volumetric organic loading rate (OLR) and membrane flux. Although it is the most applied method, concurrent change of SRT (or F/M ratio) and MLSS concentration is not a good parameter manipulation method because it causes unnecessary changes in many other parameters such as viscosity, oxygen transfer efficiency and oxygen utilization rate. The method of constant SRT–variable MLSS concentration has similar disadvantages to the method of variable SRT–variable MLSS concentration. The best alternative parameter manipulation method to study membrane fouling is the method of variable SRT–constant MLSS concentration because this method eliminates unnecessary changes in other parameters. In addition, while changing OLR or hydraulic retention time (HRT), contrary to the common application, membrane flux should be kept constant because any change in flux overrides changes in other parameters. Accordingly, required changes in OLR or HRT should be made by adjusting membrane area rather than membrane flux.

Activated Sludge Process Control Using Dissolved Oxygen Measurements

1984 ◽  
Vol 16 (5-7) ◽  
pp. 613-620 ◽  
Author(s):  
S Marsili-Libelli
Keyword(s):  
Dissolved Oxygen ◽  
Simulation Analysis ◽  
Dynamic Balance ◽  
Utilization Rate ◽  
Oxygen Utilization ◽  
Output Controller ◽  
Combined Estimation ◽  
Aerobic Reactor ◽  
Oxygen Utilization Rate ◽  
Oxygen Measurements

This paper describes a combined estimation/control scheme conceived to handle unmeasurable process quantities, such as viable mass in the aerobic reactor. Starting with the well known dissolved oxygen dynamic balance, an algorithm for the reconstruction of the oxygen utilization rate is derived, which in turn is used to mechanize a nonlinear state observer for the process variables. Eventually this cascaded double observer is coupled to a digital PID controller, thus forming an overall output controller based solely on dissolved oxygen measurements. Simulation analysis is used to assess the composite output controller performance and sensitivity.

An assessment of sewage sludge stability with a specific oxygen utilization rate (SOUR) test method

2000 ◽  
Vol 42 (9) ◽  
pp. 37-40 ◽  
Author(s):  
K. A. Samson ◽  
G. A. Ekama
Keyword(s):  
Organic Matter ◽  
Sewage Sludge ◽  
Test Method ◽  
Utilization Rate ◽  
Oxygen Utilization ◽  
Sewage Sludges ◽  
Indirect Measure ◽  
Oxygen Utilization Rate ◽  
Specific Oxygen Utilization Rate ◽  
Biodegradable Organic Matter

Sewage sludge treatment systems are intended to stabilize the sludge so that its disposal or reuse can be environmentally acceptable. However, stabilized sludges may still contain residual biodegradable organic matter that can be environmentally a nuisance. This paper presents a specific oxygen utilization rate [SOUR, mgO2/(gVSS·h)] batch reactor test method to quantify the residual biodegradable organic matter content of the treated (stabilized) sewage sludges. The results of the study, in which 37 SOUR batch tests were done on 10 different sewage sludges, show that the SOUR, when determined over a prolonged period (4 to 5 days), gives an indirect measure of sludge stability defined as the % soluble and particulate residual biodegradable organics in the sludge; to determine % sludge stability, it is necessary to simulate the experimental SOUR data by means of a general activated sludge model. The % sludge stability obtained for the 10 different sludges, taking due account of their soluble and particulate constituents, was consistent with that expected from the stabilization treatment systems to which the sludges were subjected.

Dive behavior and estimated energy expenditure of foraging humpback whales in southeast Alaska

1987 ◽  
Vol 65 (2) ◽  
pp. 354-362 ◽  
Author(s):  
William Ford Dolphin
Keyword(s):  
Energy Expenditure ◽  
Dive Duration ◽  
Humpback Whales ◽  
Utilization Rate ◽  
Strongly Correlated ◽  
Oxygen Utilization ◽  
Southeast Alaska ◽  
Use Of Time ◽  
Oxygen Utilization Rate ◽  
Time And Energy

The ventilatory and dive behaviors of humpback whales were studied during July–September 1982–1984 in the area of Frederick Sound, Alaska. Oxygen utilization and energy expenditure were estimated based upon observed blow rates and calculated tidal volume during foraging at identified depths between 0 and 120 m. Duration of dive, duration of surfacing, and number of blows per surfacing were all strongly correlated with depth of dive. Dives tended to be short (57.4% were less than 2.8 min in duration) and shallow (84.6% were to depths of less than 60 m). Humpback whales dived and returned to the surface directly, which allowed for calculation of the time spent at depth in different diving situations. The percent of time spent at the surface tended to increase with increasing depth of dive and exhibited a marked increase at depths surpassing 60 m. The lowest oxygen utilization rate was found during dives 41–60 m in depth. Oxygen utilization per ventilation–dive cycle was strongly and positively correlated with depth of dive. It is postulated that dives to depths of 41–60 m (4–6 min in duration) represent the aerobic limit of humpback whales. Dives exceeding these limits result in anaerobic metabolism and, consequently, an inefficient use of time and energy resources.

scholarly journals The Effect of Nimodipine on the Evolution of Human Cerebral Infarction Studied by PET

1989 ◽  
Vol 9 (4) ◽  
pp. 523-534 ◽  
Author(s):  
A. M. Hakim ◽  
A. C. Evans ◽  
L. Berger ◽  
H. Kuwabara ◽  
K. Worsley ◽  
...  
Keyword(s):  
Cerebral Blood Volume ◽  
Statistical Significance ◽  
Treated Group ◽  
Brain Regions ◽  
Normal Brain ◽  
Oxygen Extraction Ratio ◽  
Perfusion Measurement ◽  
Positron Emission ◽  
The Difference ◽  
Cortical Regions

Fourteen patients were studied by positron emission tomography (PET) within 48 h of onset of a hemispheric ischemic stroke and again 7 days later. After the first set of PET scans, the patients were randomized to receive either nimodipine (n = 7) or a carrier solution (n = 7) by intravenous infusion. The infusions were maintained until the end of the second PET studies. CBF, cerebral blood volume (CBV), oxygen extraction ratio (OER), CMRO2, and CMRglc were measured each time. These metabolic and perfusion measurements were performed by standard methods. A surface map of each metabolic and perfusion measurement in the cortical mantle was generated by interpolating between the available slices. The various surface maps representing the physiological characteristics determined in the same or subsequent studies were aligned so that all data sets could be analyzed identically using an array of square regions of interest (ROIs). The functional status of each ROI was recorded at the two intervals following the cerebrovascular accident to characterize the evolution of the infarct, penumbra, and normal brain regions. We presumed the ischemic penumbra to be cortical regions in the proximity of the infarct and perfused at CBF values between 12 and 18 ml/100 g/min on the first PET scan, while densely ischemic regions had CBF of <12 nl/100 g/min and normally perfused brain >18 ml/100 g/min. In the densely ischemic zone, CBF increased more in the nimodipine-treated group than in the carrier group. As well, in this region nimodipine reversed the decline in CMRO2 noted in the carrier group, the difference in the changes being significant. In the penumbra zone, comparable trends were noted in OER and CMRO2 but the difference in the changes between the two groups did not reach statistical significance. Changes in CMRglc and CBV were comparable between the two groups in both cortical regions.

Floc-Load as It Relates to Enzymatic Transfer of Soluble Substrate and Sludge Bulking Control

1988 ◽  
Vol 20 (11-12) ◽  
pp. 481-484
Author(s):  
M. C. Goronszy ◽  
W. W. Eckenfelder
Keyword(s):  
Transfer Process ◽  
Utilization Rate ◽  
Atp Content ◽  
Oxygen Utilization ◽  
Sorptive Capacity ◽  
Substrate Removal ◽  
Sludge Bulking ◽  
Oxygen Utilization Rate ◽  
Soluble Substrate ◽  
Specific Oxygen Utilization Rate

Floc-load and enzymatic transfer of soluble substrate from a wastewater into microorganisms in an activated sludge floe are related. In the absence of other metabolic selectivity pressures, this rapid sequestering of available soluble organics is required for the avoidance of filamentous sludge bulking in various reactor configurations. The specific oxygen utilization rate response to floc-loading is a measure of the magnitude of the enzymatic transfer capacity of a biomass and can be used to determine its maximum sorptive capacity. During the transfer process the biomass Adenosine triphosphate (ATP) content undergoes a rapid depletion for 20-30 minutes before increasing again. Relevant parameters associated with soluble substrate removal and floc-forming selectivity mechanisms are summarized.

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