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Results for “model predictive control”

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PubMed1999

Monte Carlo based protocol for cell survival and tumour control probability in BNCT.

A mathematical model to calculate the theoretical cell survival probability (nominally, the cell survival fraction) is developed to evaluate preclinical treatment conditions for boron neutron capture therapy (BNCT). A treatment condition is characterized by the neutron beam spectra, single or bilateral exposure, and the choice of boron carrier drug (boronophenylalanine (BPA) or boron sulfhydryl hydride (BSH)). The cell survival probability defined from Poisson statistics is expressed with the cell-killing yield, the 10B(n,alpha)7Li reaction density, and the tolerable neutron fluence. The radiation transport calculation from the neutron source to tumours is carried out using Monte Carlo methods: (i) reactor-based BNCT facility modelling to yield the neutron beam library at an irradiation port; (ii) dosimetry to limit the neutron fluence below a tolerance dose (10.5 Gy-Eq); (iii) calculation of the 10B(n,alpha)7Li reaction density in tumours. A shallow surface tumour could be effectively treated by single exposure producing an average cell survival probability of 10(-3)-10(-5) for probable ranges of the cell-killing yield for the two drugs, while a deep tumour will require bilateral exposure to achieve comparable cell kills at depth. With very pure epithermal beams eliminating thermal, low epithermal and fast neutrons, the cell survival can be decreased by factors of 2-10 compared with the unmodified neutron spectrum. A dominant effect of cell-killing yield on tumour cell survival demonstrates the importance of choice of boron carrier drug. However, these calculations do not indicate an unambiguous preference for one drug, due to the large overlap of tumour cell survival in the probable ranges of the cell-killing yield for the two drugs. The cell survival value averaged over a bulky tumour volume is used to predict the overall BNCT therapeutic efficacy, using a simple model of tumour control probability (TCP).

Boron Neutron Capture Therapy↗

PubMed2004

Contrasting effects of dopamine and glutamate receptor antagonist injection in the nucleus accumbens suggest a neural mechanism underlying cue-evoked goal-directed behavior.

Discriminative stimuli (DSs) inform animals that reward can be obtained contingent on the performance of a specific behavior. Such stimuli reinstate drug-seeking behavior, evoke dopamine release in the nucleus accumbens (NAc) and excite and inhibit specific subpopulations of NAc neurons. Here we show in rats that DSs can reinstate food-seeking behavior. In addition, we compare the effects of injecting dopamine receptor antagonists into the NAc with those of general NAc inactivation on the performance of a DS task. Selective antagonism of D1 receptors reduced responding to the DS and increased the latency to respond, whereas general inactivation of NAc neuronal activity increased the latency to respond to the DS and increased behaviors extraneous to the task, such as responding in the absence of cues and responding on the inactive lever. Based on these results and our previous findings that NAc neuronal responses to DSs are dependent on the ventral tegmental area, we propose a model for the functional role of NAc neurons in controlling behavioral responses to reward-predictive stimuli.

Animals↗

PubMed1996

A post mortem study on neurochemical markers of dopaminergic, GABA-ergic and glutamatergic neurons in basal ganglia-thalamocortical circuits in Parkinson syndrome.

Functional models of the circuitry of the basal ganglia have recently been proposed to account for the vast spectrum of motor disorders associated with the loss of anatomical or neurochemical integrity within the basal ganglia. On the basis of these hypothetical models, hypokinetic disorders such as Parkinson's disease, are thought to be associated with excessive tonic and phasic inhibition of the output from the basal ganglia to the thalamus. In the present study we have attempted to determine the validity of the proposed model by measuring neurochemical markers of inhibitory and excitatory neurotransmission in post mortem human brain tissue. We have determined the concentrations of the excitatory neurotransmitters aspartate/glutamate and of the inhibitory neurotransmitter GABA in 18 relevant regions of the thalamocortical circuits of the basal ganglia of patients who had manifested Parkinsonian symptoms, and compared them with controls of individuals who had died without any history of neurological or psychiatric disorders and had no neuropathological abnormalities. Additionally, the receptor subtype for the excitatory amino acid N-methyl-D-aspartate (NMDA) was studied in the same brain tissue in which neurotransmitter concentrations had been analysed as neurochemical markers of post-synaptic excitatory neurotransmission. In patients who had manifested Parkinsonian symptoms, glutamate and aspartate levels were found to be unchanged in all examined brain regions. In contrast, the binding of [3H]MK-801, which identifies the NMDA receptor, was reduced in the head (-42%) and body (-38%) of the caudate nucleus. In parkinsonian patients, GABA levels were diminished by 36% in the centromedial thalamus, compared to control values. These results do not confirm the changes in neurotransmitter concentrations predicted according to the model, although we cannot rule out that the predicted changes might have been observed if the Parkinsonian group had been further subdivided into groups diagnosed on the basis of the patients' clinical picture (akinetic-rigid, tremor-dominant, equivalent type) and compared with the control group.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1996

Estimating local-area needs for psychiatric care: a case study.

BACKGROUND: Different approaches to estimating local catchment-area needs for psychiatric services are illustrated and compared. METHOD: Data from an epidemiological morbidity survey of a random sample of 496 adults were available, as were actual service utilisation rates. Four types of utilisation were modelled (i.e. overall, out-patient, in-patient, emergency clinic) using social indicators available from Statistics Canada census-tract data. Finally, a case-control study compared out-patients from a deprived and an affluent catchment area, matched case by case for primary diagnosis, age, sex and residential status (n = 52). RESULTS: Modelling proved highly predictive of utilisation, the overall-use model accounting for 73% of the variance. The case-control study indicated a higher rate of Axis II traits, substance abuse and needs for social care in the deprived catchment area. CONCLUSIONS: Resource allocation based on the social indicators modelling method was more consistent with sensible distribution of human resources. None of the methods, however, appear to reflect adequately the severity of caseloads evidenced in the case-control study.

Adolescent↗

PubMed2004

To eat or not to eat: implications of the attentional myopia model for restrained eaters.

The attentional myopia model of behavioral control was tested in a study of food consumption by chronic dieters. According to the model, when individuals' attentional capacity is limited, their behavior will be disproportionately influenced by highly salient internal and external cues to the exclusion of more distal stimuli. In situations that normally feature conflicting behavioral pressures, such a state of narrowed attention is likely to result in abnormally disinhibited behavior when cues promoting action are more salient and to result in abnormally restrained behavior when inhibiting cues are more salient. In addition to supporting the predictions of the model, this study provided the first evidence for enhanced behavioral control under conditions of limited attention. Participants' responses to a thought-reporting measure also provided evidence for the role played by attentional myopia in the control of eating. Implications for a broad array of regulatory successes and failures are discussed.

Adolescent↗

PubMed1993

Dose intensification in curative head and neck cancer radiotherapy--linear quadratic analysis and preliminary assessment of clinical results.

PURPOSE: The feasibility of reducing overall treatment time by 2 weeks in the curative radiotherapeutic management of head and neck cancer patients is reported in a pilot trial of Hyperfractionated, Accelerated Radiotherapy with Dose Escalation (HARDE). This regimen prescribes 76 Gy in 5 weeks to definitive head and neck cancer patients, and 65 Gy in 5 weeks to high-risk postoperative patients. The linear quadratic model is used to compare predicted tumor cell kill with HARDE versus that expected with conventional fractionation (CF). MATERIALS AND METHODS: Between January 1991 and March 1992, 40 head and neck cancer patients were treated with HARDE at the University of Wisconsin Comprehensive Cancer Center. Case-matched controls treated with CF were identified from patients treated at the same institution between 1980-1990, based on tumor site, stage, and extent of prior surgery. Individual patient treatment data (total dose, fraction size, overall time) rather than idealized schedule data from each group were analyzed using the linear quadratic model. RESULTS: Seventy-nine case-matched controls were identified for comparison with HARDE patients. The predicted increase in log cell kill for HARDE patients over case-matched controls was 1.5 and 1.3 logs, respectively, in the definitive and postoperative settings. This difference in log cell kill projects an improvement in locoregional tumor control for HARDE patients of between 10-25%. HARDE patients experience very brisk acute mucosal reactions and moderately prolonged mucosal healing, however, 91% have completed therapy without a treatment break. CONCLUSION: A 2-week reduction in overall treatment time for curative head and neck cancer patients is feasible while maintaining doses > 70 Gy. Based on radiobiologic predictions, such treatment intensification may significantly improve rates of locoregional tumor control. However, intensified acute mucosal reactions accompany such accelerated therapy.

Case-Control Studies↗

PubMed1982

Frequency response of autoregulation.

To estimate the frequency response of autoregulation and to test whether macula densa feedback alone mediates renal blood flow (RBF) autoregulation in rats, we imposed sudden increases (10 to 20 mm Hg) in arterial pressure (AP) and compared the time courses of renal vascular resistance (RVR) changes and of flow changes at the macula densa. RVR decreased abruptly after the AP increase, but returned to control levels in less than 1 sec, continued to increase, reaching 50% completion within 3 sec, and achieved final values 15 to 20 sec after AP change. To predict transient changes in tubule flow, we derived a model of pressure and flow and combined it with measurements of tubule pressure made during AP steps. With these measured pressures as inputs, the model predicted a prompt rise in GFR followed by a decline that returned GFR halfway to control values within 3 to 4 sec and more slowly thereafter. Predicted early distal flow increased perceptibly only after 1 sec and rose slowly thenceforth. The disturbance in early distal flow appears to arrive too late to signal the rapid changes in RVR. Some other mechanism, possibly myogenic, must have intervened. The results suggest that two mechanisms mediate autoregulation, each with a different response time. The putative myogenic mechanism is about one order of magnitude faster than the macula densa.

Animals↗

PubMed1992

Classic conditioning and placebo effects in crossover studies.

OBJECTIVE: To find evidence of classically conditioned placebo effects in a placebo-controlled crossover drug study. Specifically, we tested a prediction of the conditioning model that the placebo response will be greater after drug exposure than before. METHODS: Twenty-four patients with mild to moderate essential hypertension and no contraindications to atenolol participated in the study. The study design required randomized assignment to one of three groups: placebo followed by 50 mg atenolol daily, followed by no treatment, each for 1 week; atenolol followed by placebo; and atenolol followed by nothing (to show residual drug effects). Twice-daily blood pressure measurements were made by patients at home; once-weekly measurements of blood pressure and heart rate were made by a research nurse. RESULTS: Before drug treatment, there were no differences in the antihypertensive responses of patients taking placebo and patients taking nothing (difference, 0.98 mm Hg; 95% confidence interval, -0.98 to 2.93). After atenolol treatment, placebo treatment produced a significantly greater antihypertensive response than no treatment (difference, -6.09 mm Hg; 95% confidence interval, -11.81 to -0.38). Thus the placebo response after atenolol administration was more than a residual drug effect. Similar patterns were observed for heart rate but not for blood pressure readings taken in the office. CONCLUSIONS: These observations are consistent with a conditioning model of placebo effects. These findings warrant further investigation in larger studies and in other disease models.

Adult↗

PubMed2005

A slender-body micromechanical model for viscoelasticity of magnetic colloids: comparison with preliminary experimental data.

The storage modulus, G', together with the yield stress, is an essential quantity characterizing the rheological properties of magnetic field-responsive suspensions (magnetorheological fluids or MRF). In this work, we present both experimental and theoretical results on the viscoelastic properties of MRFs. Two MRFs are used: In one the solid phase consists of cobalt ferrite particles + silica gel, with silicone oil as liquid phase. The second system is formed by carbonyl iron + silica gel also dispersed in silicone oil. The cobalt ferrite particles are synthesized as monodisperse colloidal spheres with an average diameter of 850 nm. We describe a new model based on the slender-body approach for hydrodynamic interactions. The predictions of the model are compared to preliminary experimental G' data obtained in a controlled stress plate-plate rheometer. It is found that the model gives the correct order of magnitude for the highest fields in iron suspensions, but underestimates the experimental results obtained in ferrite ones. In the case of high permeability materials such as carbonyl iron, by the inclusion of high-order multipolar interactions and saturation effects we also predict the order of magnitude of the experimental results. When dealing with low permeability cobalt ferrite based MRFs, other effects, such as remanence (at low fields) and saturation (at high fields), must be considered.

Journal Article↗

PubMed2003

The importance of clinical factors in parenteral nutrition-associated hypertriglyceridemia.

AIMS: The purpose of this study was to establish the relevance of several clinical factors associated with parenteral nutrition (PN) hypertriglyceridemia and to construct a predictive model for this complication. METHOD: This multicenter study included all patients with initial serum triglyceridemia <3 mmol and receiving a minimum of 7 days' PN therapy. The study ended for each patient when hypertriglyceridemia developed or PN was terminated. Two multivariate models were constructed, one to study the clinical factors and the second to predict plasma triglyceridemia. A total of 22 clinical factors studied as independent variables were included in the multiple-step regression models only when they showed a P-value over 0.1. Statistical significance was determined by the confidence interval of the odds ratio (OR) and the partial regression coefficient (b). RESULTS: The study included 260 patients from 14 hospitals. Lipid administration was 0.83+/-0.37 g/kg/day. Among the total, 68 patients (26.2%) showed hypertriglyceridemia. Variables included in both models were serum glucose (OR, 2.63; b, 0.06), renal failure (OR, 10.56; b, 1.70), corticoid administration >0.5 mg/kg (OR, 7.98; b, 0.97), pancreatitis (OR, 4.38; b, 0.64), sepsis (OR, 4.48; b, 0.24), lipids infused (OR, 3.03; b, 0.24) and heparin administration >3 mg/kg/day (OR, 0.11; b, -1.21). CONCLUSION: Although the rate of lipid infusion was low, certain clinical factors modified triglyceridemia. Nevertheless, relatively fast plasma clearance of lipids infused indicates that a reduction in lipid supply could be a quick, effective measure for controlling hypertriglyceridemia. Thus, careful monitoring of patients with clinical factors predicting risk in the model studied, with adjustment of lipid perfusion rates accordingly, is suggested to avoid hypertriglyceridemia.

Adult↗

PubMed2005

Effects of inhaled nitric oxide administration on early postoperative mortality in patients operated for correction of atrioventricular canal defects.

OBJECTIVE: Postoperative pulmonary hypertension (POPH) substantially increases mortality after repair of congenital heart diseases. Inhaled nitric oxide (NO) has been reported as an effective and specific means of controlling POPH crisis. No randomized, placebo-controlled study has addressed the ability of NO administration to reduce mortality. Such a trial could raise ethical questions. DESIGN: Observational study with historical control subjects based on multivariate confounder scores. SETTING: Surgical pediatric ICU in a university hospital. PATIENTS: Two hundred ninety-four records of patients operated on for atrioventricular (AV) canal between 1984 and 1994 who presented with severe POPH. INTERVENTIONS: All variables found to be predictive for death by univariate tests were entered in a multivariate forward stepwise logistic regression model. Two paired groups regarding risk factors for death and only differing for POPH treatment (NO or conventional treatment) were constructed on the basis of predicted values obtained from this model. Twenty-five patients received NO, and 39 control patients, operated on between 1984 and 1994, received conventional treatment for POPH. MEASUREMENTS AND RESULTS: Postoperative pulmonary pressure, date of operation, and occurrence of an infectious complication were retained in the model. The comparison between the two paired groups showed a significant difference in mortality (24%; 95% confidence interval [CI], 7 to 41%; vs 56%; 95% CI, 37 to 75%, respectively; p = 0.02). CONCLUSIONS: This study suggests that there is a high probability for postoperative mortality reduction associated with administration of inhaled NO when severe POPH occurs in children operated for complete repair of AV canal.

Adolescent↗

PubMed1999

Predictivity of an in vitro model for acute and chronic skin irritation (SkinEthic) applied to the testing of topical vehicles.

An in vitro human reconstructed epidermis model (SkinEthic) used for screening acute and chronic skin irritation potential was validated against in vivo data from skin tolerability studies. The irritation potential of sodium lauryl sulfate (SLS), calcipotriol and trans-retinoic acid was investigated. The in vitro epidermis-like model consists of cultures of keratinocytes from human foreskin on a polycarbonate filter. The modulation of cell viability, the release and gene expression of proinflammatory cytokines, interleukins 1alpha and 8, and morphological changes were evaluated during 3 days as endpoints representative for an inflammatory reaction. The cumulative irritation potential of the topical products was evaluated in a human clinical study by visual scoring and biophysical measurement of inflammatory skin reaction after repeated 24 h applications over 3 weeks under Finn chamber patches. All topical products that were nonirritating in the human study were noncytotoxic and did not induce cytokine expression in the in vitro acute model (day 1 exposure). All irritating controls exhibited specific cell viability and cytokine patterns, which were predictive of the in vivo human data. The ranking of mild to moderate skin irritation potential was based on the lack of cytotoxicity and the presence of cytokine patterns including gene expression specific for each irritant, using the chronic in vitro model (up to 3 days exposure). The human reconstructed epidermis model SkinEthic was shown to be a reliable preclinical tool predicting the irritation potential of topical products. Moreover, it is a useful model in a two-step tiered strategy for screening acute and chronic irritation potential for the selection of vehicles for new topical drugs.

Adult↗

PubMed2006

Effect of 1-year dairy product intervention on fat mass in young women: 6-month follow-up.

OBJECTIVE: Previous results from this laboratory suggest that a 1-year dairy intake intervention in young women does not alter fat mass. The objective of this study was to determine the impact of the 1-year dairy intervention 6 months after completion of the intervention. RESEARCH METHODS AND PROCEDURES: Previously, normal-weight young women (n = 154) were randomized to one of three calcium intake groups: control (<800 mg/d), medium dairy (1000 to 1100 mg/d), or high dairy (1300 to 1400 mg/d) for a 1-year trial (n = 135 completed). In the current study, 51 women were assessed 6 months after completion of the intervention trial. Body compositions (body fat, lean mass) were measured using DXA. Self-report questionnaires were utilized to measure activity and dietary intake (kilocalories, calcium). RESULTS: The high-dairy group (n = 19) maintained an elevated calcium intake (1027 +/- 380 mg/d) at 18 months compared with the control group (n = 18, 818 +/- 292; p = 0.02). Mean calcium intake over the 18 months predicted a negative change in fat mass (p = 0.04) when baseline BMI was controlled in regression analysis (model R(2) = 0.11). 25-Hydroxyvitamin D levels were correlated with fat mass at each time-point (baseline, r = -0.41, p = 0.003; 12 months, r = -0.42, p = 0.002; 18 months, r = -0.32, p = 0.02) but did not predict changes in fat mass. DISCUSSION: Dietary calcium intake over 18 months predicted a negative change in body fat mass. Thus, increased dietary calcium intakes through dairy products may prevent fat mass accumulation in young, healthy, normal-weight women.

Absorptiometry, Photon↗

PubMedDate not supplied

Functional CT perfusion imaging in predicting the extent of cerebral infarction from a 3-hour middle cerebral arterial occlusion in a primate stroke model.

BACKGROUND AND PURPOSE: Our purpose was to determine whether cerebral perfusion functional CT (fCT), performed after endovascular middle cerebral artery (MCA) occlusion, can be used to predict final cerebral infarction extent in a primate model. METHODS: fCT with bolus tracking was performed before and 30 and 150 minutes after 3-hour digital subtraction angiography (DSA)-guided endovascular MCA occlusion in five baboons. Parametric cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) maps were constructed by voxel-by-voxel gamma variate fitting and used to determine lesion sizes. Animals were sacrificed 48 hours after the occlusion, and ex vivo MR imaging was performed. Lesion sizes on fCT and MR images were compared. RESULTS: Hypoperfusion was clearly identified on all images obtained after MCA occlusion. Thirty and 150 minutes after occlusion onset, respectively, mean lesion sizes were 737 mm(2) +/- 33 and 737 mm(2) +/- 44 for CBF, 722 mm(2) +/- 32 and 730 mm(2) +/- 43 for CBV, and 819 mm(2) +/- 14 and 847 mm(2) +/- 11 for MTT. Mean outcome infarct size on MR images was 733 mm(2) +/- 30. Measurements based on CBV and CBF (R(2) = 0.97 and 0.96, P <.001), but not MTT (R(2) = 0.40, P >.5), were highly correlated with final lesion size. CONCLUSION: An endovascular approach to MCA occlusion provides a minimally invasive, reproducible animal model for controlled studies of cerebral ischemia and infarction. Derived cerebral perfusion maps closely predict the 48-hour infarct size after 3-hour MCA occlusion.

Angiography, Digital Subtraction↗

PubMed1982

Viscosity dependence of the kinetics of the diffusion-controlled reaction of carbon monoxide and myoglobin.

The kinetics of the reaction of CO with myoglobin have been studied by laser flash photolysis in glycerol-water as a function of solvent viscosity and temperature. At high viscosities and low temperatures the second-order rate constant is inversely proportional to the viscosity raised to approximately the 0.5 power. This result parallels the behavior of the oxygen diffusion coefficient in glycerol-water. It is concluded that the reaction kinetics in high viscosity glycerol-water are largely diffusion controlled. At higher temperatures, though, the effect of simultaneous chemical activation control of the reaction is observed. The diffusion-controlled rate constant is 1.4 X 10(-3) of that predicted from simple von Smoluchowski theory based on diffusion coefficients and molecular radii. Several models with steric requirements for diffusion-controlled reactions are examined.

Carbon Monoxide↗

PubMed2005

Timing of induction of osmotically controlled genes in Salmonella enterica Serovar Typhimurium, determined with quantitative real-time reverse transcription-PCR.

The signals that control the transcription of osmoregulated genes are not understood satisfactorily. The "turgor control model" suggested that the primary osmoregulatory signal in Enterobacteriaceae is turgor loss, which induces the kdp K+ transport operon and activates the Trk K+ permease. The ensuing increase in cytoplasmic K+ concentration was proposed to be the signal that turns on all secondary responses, including the induction of the proU (proline-glycine betaine transport) operon. The "ionic strength model" proposed that the regulatory signal for all osmotically controlled responses is the increase in the cytoplasmic ionic strength or macromolecular crowding after an osmotic upshift. The assumption in the turgor control model that the induction of kdp is a primary response to osmotic shock predicts that this response should precede all secondary responses. Both models predict that the induction of all osmotically activated responses should be independent of the chemical nature of the solute used to impose osmotic stress. We tested these predictions by quantitative real-time reverse transcription-PCR analysis of the expression of six osmotically regulated genes in Salmonella enterica serovar Typhimurium. After shock with 0.3 M NaCl, proU was induced at 4 min, proP and rpoS were induced at 4 to 6 min, kdp was induced at 8 to 9 min, and otsB and ompC were induced at 10 to 12 min. After an equivalent osmotic shock with 0.6 M sucrose, proU was induced with kinetics similar to those seen with NaCl, but induction of kdp was reduced 150-fold in comparison to induction by NaCl. Our results are inconsistent with both the turgor control and the ionic strength control models.

Amino Acid Transport Systems↗

PubMed2005

Proton MR spectroscopic imaging depicts diffuse axonal injury in children with traumatic brain injury.

BACKGROUND AND PURPOSE: Diffuse axonal injury (DAI) after traumatic brain injury (TBI) is important in patient assessment and prognosis, yet they are underestimated with conventional imaging techniques. We used MR spectroscopic imaging (MRSI) to detect DAI and determine whether metabolite ratios are accurate in predicting long-term outcomes and to examine regional differences in injury between children with TBI and control subjects. METHODS: Forty children with TBI underwent transverse proton MRSI through the level of the corpus callosum within 1-16 days after injury. T2-weighted, fluid-attenuated inversion recovery, and susceptibility-weighted MR imaging was used to identify voxels as normal-appearing or as nonhemorrhagic or hemorrhagic injury. Neurologic outcome was evaluated at 6-12 months after injury. Metabolite ratios for total (all voxels), normal-appearing, and hemorrhagic brain were compared and used in a logistic regression model to predict long-term outcome. Total and regional metabolite ratios were compared with control data. RESULTS: A significant decrease in N-acetylaspartate (NAA)/creatine (Cr) and increase in choline (Cho)/Cr (evidence of DAI) was observed in normal-appearing (P < .05) and visibly injured (hemorrhagic) brain (P < .001) compared with controls. In normal-appearing brain NAA/Cr decreased more in patients with poor outcomes (1.32 +/- 0.54) than in those with good outcomes (1.61 +/- 0.50, P = .01) or control subjects (1.86 +/- 0.1, P = .00). In visibly injured brains, ratios were similarly altered in all patients. In predicting outcomes, ratios from normal-appearing and visibly-injured brain were 85% and 67% accurate, respectively. CONCLUSION: MRSI can depict injury in brain that appears normal on imaging and is useful for predicting long-term outcomes.

Adolescent↗

PubMed2002

Modelling and control of potable water chlorination.

The Umgeni Water Wiggins water treatment plant feeds the southern areas of Durban in South Africa and has a maximum treatment capacity of about 350 Ml/d. Two interconnected reservoirs at this facility hold treated water before it enters the distribution network. Because of the variable demand, the reservoir levels and residence times undergo considerable variation. This has a strong influence on the free chlorine concentration in the water leaving the reservoir, which should be 0.8 to 1.2 mg/l, to ensure an adequate disinfection potential within the network. This paper describes a model which accounts for the observed variations of chlorine concentration, and will form the basis of a predictive controller for the chlorine concentration in the outlet.

Chlorine Compounds↗