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PubMed2006

Geometric phase effects in the coherent control of the branching ratio of photodissociation products of phenol.

Optimal control simulation is used to examine the control mechanisms in the photodissociation of phenol within a two-dimensional, three-electronic-state model with two conical intersections. This model has two channels for H-atom elimination, which correspond to the (2)pi and (2)sigma states of the phenoxyl radical. The optimal pulse that enhances (2)sigma dissociation initially generates a wave packet on the S(1) potential-energy surface of phenol. This wave packet is bifurcated at the S(2)-S(1) conical intersection into two components with opposite phases because of the geometric phase effect. The destructive interference caused by the geometric phase effect reduces the population around the S(1)-S(0) conical intersection, which in turn suppresses nonadiabatic transitions and thus enhances dissociation to the (2)sigma limit. The optimal pulse that enhances S(0) dissociation, on the other hand, creates a wave packet on the S(2) potential-energy surface of phenol via an intensity borrowing mechanism, thus avoiding geometric phase effects at the S(2)-S(1) conical intersection. This wave packet hits the S(1)-S(0) conical intersection directly, resulting in preferred dissociation to the (2)pi limit. The optimal pulse that initially prepares the wave packet on the S(1) potential-energy surface (PES) has a higher carrier frequency than the pulse that prepares the wave packet on the S(2) PES. This counterintuitive effect is explained by the energy-level structure and the S(2)-S(1) vibronic coupling mechanism.

Journal Article↗

PubMed1981

Simulation of head movement trajectories: model and fit to main sequence.

A sixth order nonlinear model for horizontal head rotations in humans is presented and investigated using experimental results on head movement trajectories and neck muscle EMG. The controller signals, structured in accordance with time optimal control theory, are parameterized, and controller signal parameter variations show a dominating influence on different aspects of the head movement trajectory. The model fits the common head acceleration types over a wide range of amplitudes, and also less common (dynamic overshoot) trajectories.

Electromyography↗

PubMed2005

Evaluation of two control strategies for a sequencing batch reactor degrading high concentration peaks of 4-chlorophenol.

The operation of a sequencing batch reactor (SBR) exposed to high concentration peaks (shock loads) of a toxic compound (4-chlorophenol, 4CP) was evaluated. Two control strategies based on on-line measurements of the dissolved oxygen concentration were tested. The first strategy, called variable timing control (VTC), detects the end of the reaction period to stop it. In the second control strategy, called observer-based time optimal control (OB-TOC), the automated system tries to maintain the critical specific growth rate by controlling the feed rate, i.e. the maximum growth rate when the substrate is toxic. The system operating under the VTC strategy presented a stable and efficient operation when the acclimated microorganisms (to an initial concentration of 350 mg 4CP/L) were exposed to punctual concentration peaks of 700 mg 4CP/L. A 4CP concentration peak higher than or equal to 1050 mg/L disturbed the system (1 month to recover). A 1400 mg/L peak caused strong inhibition that shut down the metabolic activity of the microorganisms, leading to reactor failure. With the OB-TOC strategy, the system was stable and worked efficiently when punctual concentration peaks of 700, 1050 and 1400 mg 4CP/L were fed. The system controlled by the OB-TOC strategy treated 1400 mg 4CP/L in less than 8h without affecting the operation of the reactor. The conclusion is that the OB-TOC strategy is more efficient than the VTC strategy to control a bioreactor when there are variations of concentrations of toxic organic compounds.

Biodegradation, Environmental↗

PubMed2003

Optimal stochastic correction strategies for rigid-body target motion.

PURPOSE: To derive optimal correction strategies for setup errors, including the uncertainty in their measurement, and to analyze their impact on treatment margins. METHODS AND MATERIALS: New concepts like image-guided radiotherapy aim to provide an increasing amount of targeting information during treatment. Future treatment devices incorporating imaging capabilities will facilitate frequent correction of treatment setup errors. It is, therefore, possible to design new correction protocols that reduce not only systematic but also random setup errors. A novel, very general approach to developing optimal correction strategies in the presence of measurement uncertainties is derived from linear systems theory. In the simplest approach, the state variable of the system, which represents the patient, is the spatial displacement of the center-of-mass of the clinical target volume with respect to the planning CT. This displacement is the sum of a systematic and a random component. Uncertainties in the measured value of the state variable due to the measurement process, image processing technique, or organ deformation are naturally incorporated into a linear system. The true value of the displacement can be estimated from the noisy measurements with a stochastic filter (Kalman filter). These estimates provide an optimal control law for the system and therefore optimal values for the setup corrections. In the case of unknown systematic and random error variances, an adaptive version of the filter was implemented. The statistical properties of the filter were investigated by performing simulations of the state space model and assessed for individual patients and a large patient population subject to different action criteria. RESULTS: Over a patient population, the corrections by the Kalman filter estimates are always advantageous compared with the corrections by the measured values themselves. For a small percentage of individual patients, however, the Kalman corrections worsen the results. For large measurement error, the residual standard deviation of the random setup errors can be reduced by approximately 28% for over 90% of the patients. The uncertainty in the measured value impairs the ability to completely account for uncertainties. CONCLUSIONS: The Kalman estimates provide an effective means to perform daily setup corrections in the presence of measurement errors. The linear system approach is very versatile and can be extended to more general state variables.

Algorithms↗

PubMed2005

Minimizing broadband excitation under dissipative conditions.

Optimal control theory is employed for the task of minimizing the excited-state population of a dye molecule in solution. The spectrum of the excitation pulse is contained completely in the absorption band of the molecule. Only phase control is studied which is equivalent to optimizing the transmission of the pulse through the medium. The molecular model explicitly includes two electronic states and a single vibrational mode. The other degrees of freedom are classified as bath modes. The surrogate Hamiltonian method is employed to incorporate these bath degrees of freedom. Their influence can be classified as electronic dephasing and vibrational relaxation. In accordance with experimental results, minimal excitation is associated with a negatively chirped pulses. Optimal pulses with more complex transient structure are found to be superior to linearly chirped pulses. The difference is enhanced when the fluence is increased. The improvement degrades when dissipative effects become more dominant.

Journal Article↗

PubMed1998

Statistical quality control methods in infection control and hospital epidemiology, part I: Introduction and basic theory.

This article is the first in a two-part series discussing and illustrating the application of statistical process control (SPC) to processes often examined by hospital epidemiologists. The basic philosophical and theoretical foundations of statistical quality control and their relation to epidemiology are emphasized in order to expand mutual understanding and cross-fertilization between these two disciplines. Part I provides an overview of quality engineering and SPC, illustrates common types of control charts, and provides references for further information or statistical formulae. Part II discusses statistical properties of control charts, issues of chart design and optimal control limit widths, alternate possible SPC approaches to infection control, some common misunderstandings, and more advanced issues. The focus of both articles is mostly non-mathematical, emphasizing important concepts and practical examples rather than academic theory and exhaustive calculations.

Humans↗

PubMed2001

Evidence base of incubation periods, periods of infectiousness and exclusion policies for the control of communicable diseases in schools and preschools.

BACKGROUND: The optimal control of communicable diseases requires accurate information on incubation periods, periods of infectiousness and the effectiveness of exclusion. We collected the available evidence for a wide range of infections and infestations and produced evidence-based guidelines for their control in schools and preschools. METHODS: A thorough MEDLINE literature search was conducted on the incubation period, period of infectiousness and effectiveness of exclusion for 41 infections. The quality of the information obtained was indicated by levels of evidence. The information was used to produce guidelines on exclusion, and the recommendations were graded according to the levels of evidence available. Grades A, B and C represented strongly, reasonably and poorly evidence-based recommendations, respectively. RESULTS: The quality of data obtained was highly variable. Information on incubation periods was obtained for all 41 infections and was generally of good quality. Information on periods of infectiousness and effectiveness of exclusion was of a lesser quality and was found for only 11 and 4 conditions, respectively. There were 3 Grade A, 17 Grade B and 21 Grade C recommendations on exclusion. Examples of exclusion periods include: 5 days for chickenpox, measles, mumps, rubella, pertussis and scarlet fever; and 24 h from the cessation of diarrhea for most gastrointestinal diseases In contrast to existing guidelines exclusion was not recommended for school age children with hepatitis A. CONCLUSIONS: We have been able to present the best available data on the incubation periods and periods of infectiousness of 41 childhood infections. It was possible to produce strongly or reasonably evidence-based guidelines on exclusion periods for approximately one-half of the infections.

Child↗

PubMed2006

The effects of insulin glargine treatment and an educational programme on glycaemic control in type 2 diabetes patients in clinical practice.

OBJECTIVE: This retrospective analysis was performed to establish the effect of initiating insulin glargine (LANTUS; sanofi-aventis, Paris, France), a once-daily basal insulin analogue, in combination with an educational programme on glycaemic control and body weight in sub-optimally controlled patients with Type 2 diabetes in clinical practice. RESEARCH DESIGN AND METHODS: We undertook a retrospective review of the medical records of 46 patients (mean age 61.5 +/- 8.6 years) with Type 2 diabetes. These patients had previously been treated with oral antidiabetic agents (OADs; n = 18) or insulin only (n = 28) and had then received insulin glargine in combination with OADs or prandial insulin, for 30 months. Records of metabolic control and body weight data were analysed at 9 and 30 months. Patients had taken part in a diabetes educational programme before initiation of insulin glargine and received continued physician consultations throughout. RESULTS: Following initiation of insulin glargine, patients showed a significant decrease in HbA1c from 8.14 +/- 1.7% to 7.18 +/- 0.9% at 30 months (p < 0.001). When the results were analysed by pre-treatment, patients pre-treated with OADs showed a reduction in HbA1c of 2.3% at 30 months (p < 0.001), while patients pre-treated with insulin only showed a decrease in HbA1c of 0.4% (p < 0.005). There was no significant change in body weight. No unexpected adverse events or episodes of severe hypoglycaemia (blood glucose < 40 mg/dL [< 2.2 mmol/L]) occurred. CONCLUSIONS: Insulin glargine in combination with educational support and close clinical supervision significantly improved metabolic control without significant weight change in patients with Type 2 diabetes in clinical practice over 30 months. Additional studies are required to establish if similar results can be obtained in a larger cohort of patients.

Aged↗

PubMed2002

Regression of left ventricular hypertrophy in hemodialysis patients is possible.

Regression of left ventricular hypertrophy in hemodialysis patients is possible. Left ventricular hypertrophy represents the major risk factor for cardiac morbidity and mortality. Therefore, their regression is mandatory. Since the causes of uremia-associated left ventricular hypertrophy are multifactorial, various therapeutic options can be considered: optimal control of arterial hypertension and volume status, optimal correction of metabolic acidosis, best possible correction of hypoalbuminemia and severe secondary hyperparathyroidism, modern pharmacotherapeutic strategy for the treatment of heart failure (use of angiotensin-converting enzyme inhibitors in combination with angiotensin II receptor blockers and beta-blockers) and total correction of renal anemia. Following the proposed therapeutic strategies we could, by using echocardiography, distinguish in 100 hemodialysis patients the following 3 groups (on the average after 1.5 years): 36 patients with initially normal left ventricular mass index (LVMI (g/m2), F < 110; M < 130) maintained normal (group 1); in 31 patients with moderately increased LVMI full regression resulted (group 2); 33 patients with severely increased LVMI (group 3) had to be further divided into 2 sub-groups: 22 patients with significant improvement of LVMI, 11 patients with no, regression. For the first time we were able to show that it is possible to maintain initially normal LVMI during long-term treatment and to achieve complete regression and significant improvement of LVMI in our patients. However, since LVMI requires a long time to develop, a similarly long time must be estimated for its regression. However, 11 patients remained therapeutically resistant. In this group, severe heart diseases were often combined and highly prevalent, including ischemic heart and valve diseases and end-stage dilatative cardiomyopathy. These patients had to be transferred to cardiac surgery. Anemia is considered to be one of the most important factors for the development of left ventricular hypertrophy. Therefore, total correction of renal anemia has to be strongly recommended in addition to other measures of our therapeutic strategy to maintain full or significant regression of left ventricular hypertrophy.

Adolescent↗

PubMed1989

[The best ways of the control of inflammatory diseases of the lung].

Three approaches to optimal control of inflammatory diseases of the lungs are described. The first approach includes improvement of the diagnostic procedure. The second approach is based on development of new complexes of drug therapy and organization of nondrug therapy. The third approach is prophylactic. The main goals of the approaches are formulated.

Anti-Bacterial Agents↗

PubMed1998

Statistical quality control methods in infection control and hospital epidemiology, Part II: Chart use, statistical properties, and research issues.

This is the second in a two-part series discussing and illustrating the application of statistical process control (SPC) in hospital epidemiology. The basic philosophical and theoretical foundations of statistical quality control and their relation to epidemiology are emphasized in order to expand the mutual understanding and cross-fertilization between these two disciplines. Part I provided an overview of the philosophy and general approach of SPC, illustrated common types of control charts, and provided references for further information or statistical formulae. Part II now discusses alternate possible SPC approaches, statistical properties of control charts, chart-design issues and optimal control limit widths, some common misunderstandings, and more advanced issues. The focus of both articles is mostly nonmathematical, emphasizing important concepts and practical examples rather than academic theory and exhaustive calculations.

Data Display↗

PubMed2003

Alternative dosing for PPI therapy: rationale and options.

The target goal for all acid suppressive therapy is to optimize control of intragastric pH over extended periods of time. A somewhat axiomatic paradigm has been that effective control of gastric acid production is associated with optimal outcome in acid-related diseases. The proton pump inhibitor (PPI) class of therapy has shown superiority for effective control of acid and healing of related diseases. Traditional delivery of PPIs may not be a viable option for all patients. Therefore, a clear understanding of alternative dosing formulations and related efficacies is key in order for the clinician to select the most appropriate agent and strategy to optimize outcomes and cost-effectiveness for each patient.

Antacids↗

PubMed2003

Hypertension in the Parsi community of Bombay: a study on prevalence, awareness and compliance to treatment.

BACKGROUND: Uncontrolled hypertension (HT) is an established risk factor for the development of vascular diseases. Prevalence varies in different communities and no such study has been conducted in the Parsi community living in Bombay, India. The objectives of this study were to determine the prevalence, awareness, compliance to medication and control of HT in this community. METHOD: We used a 1 in 4 random selection of subjects who were > or = 20 years of age. A questionnaire was administered and the blood pressure (BP) was measured by a doctor. HT was defined as diastolic blood pressure (DBP) > or = 90 mm Hg +/- systolic pressure (SBP) > or = 140 mm Hg. Isolated systolic hypertension (ISH) was defined as SBP > or = 160 mm Hg with DBP < 90 mm Hg. Subsequently, we reanalysed the data using current definition of ISH as SBP > or = 140 mm Hg with DBP < 90 mm Hg. RESULTS: 2879 subjects > or = 20 years of age were randomly selected of which 2415 (84%) participated in the study. The overall prevalence of HT in the community was 36.4%, of whom 48.5% were unaware of their hypertensive status. Of those aware of having HT, 36.4% were non-compliant with their anti-hypertensive drugs and only 13.6% had optimally controlled HT. Prevalence of ISH using the present criteria was 19.5% and 73% of hypertensives > or = 60 years had ISH. CONCLUSION: This study shows that prevalence of HT in the Parsi community is high and nearly half are unaware of their hypertensive status. ISH is the dominant form of HT in the elderly. Compliance to treatment is poor and optimal BP control is achieved in only a small minority. The study highlights the need for regular screening coupled with educational programs to detect and optimally treat HT in the community.

Adult↗

PubMed2000

Outcome of pregnancies complicated by pre-gestational diabetes mellitus.

Pregestational diabetes mellitus (DM) is associated with adverse fetal and maternal outcomes. Studies suggest that optimal control of diabetes before and during pregnancy minimises these risks. There are few recent reviews of outcomes of pregnancies complicated by DM in Australia. Ninety-three pregnancies in women with DM at our hospital since 1989 were identified. We collected data for maternal age, type of diabetes, duration of therapy, complications of diabetes, maternal complications of pregnancy and fetal outcomes including malformations. The rate of pregnancy planning with optimal glycaemic control at conception was low in our population, particularly in patients with Type 1 diabetes. Women who smoked had worse glycaemic control, and a higher rate of miscarriage. There was a high rate of Caesarean section, particularly in those women with Type 1 diabetes (77.4%). The rate of Caesarean section was lower in planned pregnancies. There were no perinatal deaths. The number of neonates with major congenital anomalies was high (13%) in the Type 1 population. It is important to increase the rates of prepregnancy planning and to optimise glycaemic control before pregnancy. In many cases there has been a long interval between diagnosis and pregnancy, so all women with diabetes should receive counselling at frequent intervals about pregnancy and the importance of planning. Women who planned their pregnancies had improved outcomes, with decreased rate of Caesarean section, better glycaemic control and better neonatal Apgar scores. Women with diabetes should not smoke during pregnancy because of the increased risk of miscarriage and poorer glycaemic control.

Adult↗

PubMed2005

A novel approach of low-frequency ultrasonic naked plasmid gene delivery and its assessment.

OBJECTIVE: To deliver the naked genes into cells through the bioeffects of cell membrane porous produced by low-frequency ultrasound (US) and to investigate the safety by determining the threshold of cell damage and membrane permeability. METHODS: The suspension of red cells from chickens, rabbits, rats, and S180 cells was exposed to calibrated US field with different parameters in still and flowing state. Laser scanning confocal microscopy, fluorescent microscopy, scanning electron microscopy, flow cytometry and spectrophotometry were used to examine cell morphology, membrane permeability, enzymes, free radicals, naked gene expression efficiency, threshold of cell damage and cell viability. RESULTS: The plasmid of green fluorescent protein (GFP) as a reporter gene was delivered into S180 cells under optimal conditions without cell damage and cytotoxicity. The transfection rate was (35.83 +/- 2.53)% (n = 6) in viable cells, and the cell viability was (90.17 +/- 1.47)% (n = 6). Also, malondialdehyde, hydroxyl free radical, alkaline phosphatase, and acid phosphatase showed a S-shaped growth model (r = 0.98 +/- 0.01) in response to the permeability change and alteration of cell morphology. The constant E of energy accumulation in US delivery at 90% cell viability was an optimal control factor, and at 80% cell viability was the damage threshold. CONCLUSION: US under optimal conditions is a versatile gene therapy tool. The intensity of GFP expression in US group has a higher fluorescent peak than that in AVV-GFP group and control group (P < 0.001). The optimal gene uptakes, expression of gene and safety depend on E, which can be applied to control gene delivery efficiency in combination with other parameters. The results are helpful for development of a novel clinical naked gene therapeutic system and non-hyperthermia cancer therapeutic system.

Animals↗

PubMed1999

Inhaled corticosteroid therapy in newly detected mild asthma.

Inhaled corticosteroids are the most effective medications currently available to treat symptomatic asthma, and are free of clinically relevant unwanted effects, when used at the doses needed to provide optimal control in most patients with asthma. Inhaled corticosteroids also improve the physiological abnormalities of variable airflow obstruction and airway hyperresponsiveness that characterise asthma. Inhaled corticosteroids are also cost-beneficial when compared with other treatments, even in patients with milder asthma who are treated in primary care. For these reasons, inhaled corticosteroids are now being considered as first-line therapy for patients with regular daily asthma symptoms. Inhaled corticosteroids are, however, often not utilised until other treatments have been demonstrated not to provide optimal asthma control. Available evidence from both children and adults with asthma suggests that the benefits achieved from inhaled corticosteroids are reduced when their introduction as therapy is delayed for several years after persistent symptoms develop. For this reason, corticosteroids should be started soon after a diagnosis is made and persistent symptoms develop. It is not yet known, however, whether inhaled corticosteroids should be used in asthmatic patients who have very mild and infrequent symptoms and who have normal airway calibre most of the time. The current consensus statements do not recommend regular treatment in such patients. Airway biopsies from these asthmatic patients do show evidence of airway inflammation and structural changes; however, we do not yet know whether they lose lung function more rapidly than individuals without asthma, or whether the morbidity associated with very mild asthma warrants the use of regular treatment. This issue is being addressed in a large, multinational, placebo-controlled trial. The results of this study (available in 3 more years) will resolve this persisting question about inhaled corticosteroid use in mild asthma.

Administration, Inhalation↗

PubMed2000

Influenza: prospects for control.

Influenza is a disease of antiquity that annually imposes a major burden of morbidity and mortality. The available inactivated vaccine is effective for preventing influenza and the serious disease and death that can accompany it. However, annual recommendations for vaccination among persons at risk have never been adequately implemented. This remains the most pressing current need for control of influenza. Amantadine, rimantadine, and the newly available drugs zanamivir and oseltamivir are effective for influenza prevention and treatment (the former two for influenza A only). The availability of four antiviral agents that effectively prevent and treat influenza provides the physician with considerable flexibility for their use in influenza control. Optimal application of the currently available vaccine and antiviral agents should substantially reduce the impact of influenza. Other methods for influenza treatment and control are under development, and a live attenuated vaccine with substantial potential for control is nearing approval. However, better inactivated vaccines, better rapid diagnostic tests, and an increased understanding of options for use of antiviral agents are still needed. When all of these things are available and optimally applied, effective control of influenza should result. The prospect is compelling. Full participation by the practicing physician will be necessary to achieve this goal.

Antiviral Agents↗

PubMed1996

[Methodology of choosing priority parameters of water body pollution with oil-containing waste waters].

The article deals with possibility to optimize control over water pollution with waste waters. The optimization covers definition of priority parameters by using a system of 15-17 hygienic criteria of danger resulting from industrial waste presence in water bodies. The authors recommend lists of parameters to control inflow of waste waters from oil-processing and oil-extracting enterprises into water objects, to evaluate water state after unexpected leakage of oil at the output enterprises and pipelines.

Animals↗