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PubMed2006

Pulse shaping for optimal control of molecular processes.

In this paper, a new method is proposed to design optimized control fields with desired temporal and/or spectral properties. The method is based on penalizing the difference between an optimized field obtained from an iterative scheme and a reference field with desired temporal and/or spectral properties. Compared with the standard optimal control theory, the current method allows a simple, experimentally accessible field be found on the fly; while compared with parameter space searching optimization, the iterative nature of this method allows automatic exploration of the intrinsic mechanism of the population transfer. The method is illustrated by examing the optimal control of vibrational excitation of the Cl-O bond with both temporally and spectrally restricted pulses.

Journal Article↗

PubMed2006

Isotope selective photoionization of NaK by optimal control: theory and experiment.

We present a joint theoretical and experimental study of the maximization of the isotopomer ratio (23)Na(39)K(23)Na(41)K using tailored phase-only as well as amplitude and phase modulated femtosecond laser fields obtained in the framework of optimal control theory and closed loop learning (CLL) technique. A good agreement between theoretically and experimentally optimized pulse shapes is achieved which allows to assign the optimized processes directly to the pulse shapes obtained by the experimental isotopomer selective CLL approach. By analyzing the dynamics induced by the optimized pulses we show that the mechanism involving the dephasing of the wave packets between the isotopomers (23)Na (39)K and (23)Na (41)K on the first excited state is responsible for high isotope selective ionization. Amplitude and phase modulated pulses, moreover, allow to establish the connection between the spectral components of the pulse and corresponding occupied vibronic states. It will be also shown that the leading features of the theoretically shaped pulses are independent from the initial conditions. Since the underlying processes can be assigned to the individual features of the shaped pulses, we show that optimal control can be used as a tool for analysis.

Journal Article↗

PubMed2004

Global optimization of cerebral cortex layout.

Functional areas of mammalian cerebral cortex seem positioned to minimize costs of their interconnections, down to a best-in-a-billion optimality level. The optimization problem here, originating in microcircuit design, is: Given connections among components, what is the physical placement of the components on a surface that minimizes total length of connections? Because of unfeasibility of measuring long-range "wire length" in the cortex, a simpler adjacency cost was validated. To deal with incomplete information on brain networks, a size law was developed that predicts optimization patterns in subnetworks. Macaque and cat cortex rank better in this connection optimization than the wiring of comparably structured computer chips, but somewhat worse than the macroeconomic commodity-flow network among U.S. states. However, cortex wiring conforms to the size law better than the macroeconomic patterns, which may indicate cortex optimizing mechanisms involve more global processes.

Animals↗

PubMed2002

A method for optimizing potential-energy functions by a hierarchical design of the potential-energy landscape: application to the UNRES force field.

A method for optimizing potential-energy functions of proteins is proposed. The method assumes a hierarchical structure of the energy landscape, which means that the energy decreases as the number of native-like elements in a structure increases, being lowest for structures from the native family and highest for structures with no native-like element. A level of the hierarchy is defined as a family of structures with the same number of native-like elements (or degree of native likeness). Optimization of a potential-energy function is aimed at achieving such a hierarchical structure of the energy landscape by forcing appropriate free-energy gaps between hierarchy levels to place their energies in ascending order. This procedure is different from methods developed thus far, in which the energy gap and/or the Z score between the native structure and all non-native structures are maximized, regardless of the degree of native likeness of the non-native structures. The advantage of this approach lies in reducing the number of structures with decreasing energy, which should ensure the searchability of the potential. The method was tested on two proteins, PDB ID codes and, with an off-lattice united-residue force field. For, the search of the conformational space with the use of the conformational space annealing method and the newly optimized potential-energy function found the native structure very quickly, as opposed to the potential-energy functions obtained by former optimization methods. After even incomplete optimization, the force field obtained by using located the native-like structures of two peptides, and betanova (a designed three-stranded beta-sheet peptide), as the lowest-energy conformations, whereas for the 46-residue N-terminal fragment of staphylococcal protein A, the native-like conformation was the second-lowest-energy conformation and had an energy 2 kcal/mol above that of the lowest-energy structure.

Algorithms↗

PubMed1996

Optimization of left ventricular fibre orientation of the normal heart for homogeneous sarcomere length during ejection.

UNLABELLED: During the ejection phase of the cardiac cycle, left ventricular muscle fibres shorten while generating force. It was hypothesized that fibres are oriented in the wall such that the amount of shortening is the same for all fibres. We evaluated this hypothesis for the equatorial region of the left ventricle. In a finite element model of left ventricular wall mechanics fibre orientation was quantified by a helix angle which varied linearly from the inner to the outer wall. Fibre length was characterized by sarcomere length, set at 1.95 microns everywhere in the passive state of 0 transmural pressure. For a cavity pressure of 15 kPa, considered representative for ejection, inhomogeneity in mechanical loading was expressed by the variance of the sarcomere length. The variance was minimized by adapting the transmural course of fibre angle. First, only the slope was optimized and in a second optimization this was done for both slope and intercept. Optimal helix fibre angles were 69.6 degrees endocardially, 0 degree at the middle of the wall and -69.6 degrees epicardially for the first optimization and 78.2 degrees, 20.7 degrees and, -36.7 degrees respectively for the second. Sarcomere length changed from 1.95 to 1.975 +/- 0.012 and 1.981 +/- 0.004 microns (mean +/- SD) respectively. CONCLUSION: After optimization calculated helix fibre angles were in the physiological range. Describing the transmural course of fibre angle with slope and intercept significantly improved homogeneity in mechanical load.

Biomechanical Phenomena↗

PubMed2000

Comparison of blood-film microscopy, the OptiMAL dipstick, Rhodamine-123 fluorescence staining and PCR, for monitoring antimalarial treatment.

In an attempt to see if the OptiMAL dipstick (Flow Inc., Portland, OR) can be used to monitor antimalarial treatment, a pilot study of 17 patients with Plasmodium falciparum malaria, admitted to the Hospital for Tropical Diseases in London, U.K., was conducted. Sequential, follow-up, blood specimens were obtained from day 1 to day 3, 4 or 5 post-admission. Thin and thick films prepared from these samples were examined for the presence of malarial parasites, and the intensities of parasitaemia were estimated. In addition, each specimen was tested with the OptiMAL dipstick, Rhodamine-123 fluorescence staining and, on specimens collected on day 1 and the last follow-up before discharge, by a PCR-based test. The results showed that OptiMAL has good sensitivity for the initial diagnosis of P. falciparum malaria and also mirrors the decline in viability of the parasites on treatment, giving the potential to follow the efficacy of drug treatment. The results of the PCR-based tests were still positive when the blood film and OptiMAL result were negative. The OptiMAL dipstick compared well with blood-film microscopy for monitoring antimalarial treatment and could be a useful replacement for microscopy to monitor treatment in places where facilities for microscopy are either lacking or inadequate. In developed countries it could be a useful adjunct to blood-film microscopy, and it might permit a reduction in the duration of hospitalization and give an early warning of treatment failure.

Humans↗

PubMed2005

Effects of antagonistic co-contraction on differences between electromyography based and optimization based estimates of spinal forces.

Estimates of spinal forces are quite sensitive to model assumptions, especially regarding antagonistic co-contraction. Optimization based models predict co-contraction to be absent, while electromyography (EMG) based models take co-contraction into account, but usually assume equal activation of deep and superficial parts of a muscle. The aim of the present study was to compare EMG based and optimization based estimates of spinal forces in a wide range of work tasks. Data obtained from ten subjects performing a total of 28 tasks were analysed with an EMG driven model and three optimization models, which were specifically designed to test the effects of the above assumptions. Estimates of peak spinal forces obtained using the different modelling approaches were similar for total muscle force and its compression component (on average EMG based predictions were 5% higher) and were closely related (R > 0.92), while differences in predictions of the peak shear component of muscle force were more substantial (with up to 39% lower estimates in optimization based models, R > 0.79). The results show that neither neglecting antagonistic co-contraction, nor assuming equal activation of deep and superficial muscles, has a major effect on estimates of spinal forces. The disparity between shear force predictions was due to an overestimation of activity of the lateral part of the internal oblique muscle by the optimization models, which is explained by the cost function preferentially recruiting larger muscles. This suggests that a penalty for active muscle mass should be included in the cost function used for predicting trunk muscle recruitment.

Adult↗

PubMedDate not supplied

Optimism and its relationship to depression, coping, anger, and life events in rural adolescents.

Optimism is a stable personality trait that has important implications for behavior, yet little attention has been given to examining optimism in adolescents. This article describes levels of optimism in rural adolescents and the relationship of optimism with depression, coping, anger, and life events. The identification of optimism may be a vulnerability factor when screening adolescent mental health and, as such, has implications for the psychiatric nurse clinician.

Adaptation, Psychological↗

PubMed1996

Optimal length for summary knowledge of results: the influence of task-related experience and complexity.

Because manipulations of knowledge of results (KR) are critical to motor learning, researchers have attempted to establish an optimal length for summary KR. Experiment 1 of the present study investigated the option that optimal summary length may be dependent on a subject's task-related experience. Participants in a summary 1, 5, or 15 condition practiced a simple striking task for one session on three consecutive days with each day followed by a 24-hour no KR retention test. The retention test results indicated that optimal summary length is dependent on task-related experience. Experiment 2 investigated the nature of the relationship between task-related experience and complexity and optimal summary length (summary 1, 5, or 15). Again, striking tasks (simple and complex) were used. There was one practice session with either a simple or complex striking task for either novice or experienced performers, followed by a 24-hour no KR retention test. Data from the two experiments suggest that task complexity and performer experience interact in determining optimal summary length.

Adult↗

PubMed2000

Development of radiation therapy optimization.

The principal radiobiological problems in the treatment of advanced tumors and the solution of many of them by radiobiologically optimized intensity-modulated radiation therapy are presented. Considerable improvements of the treatment outcome using radiobiologically optimized intensity-modulated treatments are achieved by: (a) increasing the tumor dose and dose per fraction; (b) keeping constant or even reducing slightly the dose and dose per fraction to organs at risk, (c) reducing the overall treatment time and the number of treatment fractions. The merits of the new radiation modalities and advanced intensity-modulated treatment techniques are compared in terms of equipment costs per patient cured. It is predicted that the new development of radiobiologically optimized intensity-modulated radiation therapy will rapidly become an important clinical tool, increasing the efficiency of the collaboration between radiation physicists, radiation biologists and radiation oncologists. Not only does it allow the optimal treatment of every patient, but it also promotes an efficient feedback of treatment outcome and complication data to improve the accuracy of known dose response relations to further augment future treatment results. Equipment costs may go up during a transition period until efficient interfaces between new diagnostic equipment, treatment-planning systems and intensity-modulated treatment units are fully developed. From then onwards the cost of high quality biologically optimized intensity-modulated treatments will decrease and so will the treatment time and personnel requirements, at the same time as the treatment quality is greatly improved particularly for more advanced tumors.

Dose Fractionation, Radiation↗

PubMed2004

Efficiency optimization for systems and components in microwave power engineering.

The paper is concerned with one aspect of optimization of microwave thermal processing, namely, with optimization of energy coupling interpreted as a numerical characteristic of system efficiency. Since in computer-aided design coupling can be evaluated through the computed reflections, an optimization scheme is presented that is particularly suitable for minimizing the reflection coefficient in typical systems and elements of microwave power engineering. Based on response surface methodology and the sequential quadratic programming for constrained optimization, the procedure is linked with the full-wave 3-D FDTD electromagnetic simulator QuickWave-3D. Credibility and effectiveness of the method is illustrated by four examples: dimensional optimization is performed for a dry waveguide load, a waveguide T-junction with a partial-height post, a water cylinder in a cavity, and a slotted waveguide-backed radiating element.

Journal Article↗

PubMed1995

Patient predictors of caregiver burden, optimism, and pessimism in rheumatoid arthritis.

The authors of the present study investigated the relationship between rheumatoid arthritis (RA) patients' demographic, medical, and functional status and caregivers' burden, optimism, and pessimism. Subjects were 65 RA patients and their caregivers who were recruited from an outpatient rheumatology clinic. Each caregiver completed the Burden Interview to measure caregiver burden and the Life Orientation Test to measure optimism and pessimism. Each RA patient completed the Arthritis Impact Measurement Scale to measure pain and physical disability as well as a number of cognitive measures to assess two summary psychological cognitive factors labeled self-efficacy expectations and distorted cognitions. These cognitive factors were based on the following commonly used measures in RA research: the Cognitive Errors Questionnaire, the Arthritis Self-Efficacy Scale, the Coping Strategies Questionnaire, and the Pain Beliefs and Perceptions Inventory. Correlational analyses indicated that patients' functional and psychological measures (including poor self-efficacy expectations regarding symptoms) were related to caregiver burden, that patient self-efficacy expectations were related to caregiver optimism, and that patient physical disability was related to caregiver pessimism. Regression analyses revealed that, when competing with other demographic and disease severity variables, the relationships between patient self-efficacy expectations and caregiver burden and caregiver optimism, and patient physical function and caregiver pessimism remained significant. Taken together, these findings suggest that patient expectancies about control over arthritis-related symptoms (including pain) are strongly related to caregiver burden and caregiver optimism and that patient physical status is strongly related to caregiver pessimism.

Activities of Daily Living↗

PubMed1984

Optimization methods and available software. Part 1.

Optimization theories and generally applied optimization techniques are reviewed. The versatility and the complexity anticipated in actual problems are simplified to enable the food practitioners interested in the subject to overcome some of the barriers which prevented full utilization of optimization. The paper summarizes the various mathematical methods available for solving problems of product and process optimization and provides information and advice concerning the advantages and limitations of each technique. A compiled list of optimization subroutines, guidelines and criteria for choosing the proper software are furnished.

Computers↗

PubMed2006

Optimal designs in stability studies.

New optimality criteria for stability studies are proposed, and the related optimal designs are investigated. For each optimality criterion, optimal designs are identified within a class of competing designs. The property of the optimal designs for detecting slope differences is discussed.

Drug Industry↗

PubMed2005

Discrepancy between morphologic and functional criteria of optimal stent deployment using intravascular ultrasound and pressure derived myocardial fractional flow reserve.

BACKGROUND: Pressure derived myocardial FFR, a functional index of epicardial stenosis has been proposed for the assessment of optimal stent deployment. The following study evaluated the potential of serial fractional flow reserve (FFR) measurements in comparison to the 'gold standard' intravascular ultrasound (IVUS) for optimal stent deployment and its long-term outcome. METHODS: 35 patients with a single de novo lesion underwent PTCA followed by stent implantation with an initial inflation pressure of 12 atm. If optimal stent expansion using IVUS-criteria were not fulfilled, re-dilatation at 16 atm as well as additional inflations with larger balloon sizes were performed to reach the procedural end-point. IVUS and FFR were performed after each dilatation (n = 136). Angiography was repeated after 6 months. RESULTS: In 30 pts who fulfilled IVUS criteria, mean lumen area (2.9+/-1.3 mm2) increased after PTCA and stent implantation to 10.0+/-3.0 mm2. In six pts, optimum stent deployment according to a value of FFR0.94 was not reached. Four of six pts reached the IVUS criteria at 12 atm and two pts at 16 atm, respectively. Positive and negative predictive values of FFR were 26 and 64%. Three of the 30 pts (10%) revealed a restenosis at three months follow-up. One of these restenosis was seen in a patient with a post-procedural FFR<0.94. CONCLUSIONS: FFR was not valid to predict optimal stent expansion according to IVUS criteria but could delineate under-expanded stents despite a reasonable angiographic appearance. Morphologic (IVUS) and functional criteria (FFR) for optimal stent deployment revealed a comparably low restenosis rate.

Aged↗

PubMed2001

Using point-of-care CD34 enumeration to optimize PBSC collection conditions.

BACKGROUND: A PBSC graft containing 4-5 x 10(6) CD34(+) cells/kg is considered optimal in terms of durable engraftment. Tracking CD34 kinetics via point-of-care testing during PBSC mobilization could determine which (and when) patients will yield an optimal product. We evaluated whether microvolume fluorimetry (MVF) would be useful in optimizing PBSC mobilization/harvest and if it will shorten our standard 6 h collection. METHODS: Absolute CD34 values were obtained using the IMAGN 2000 and STELLer CD34 assay (50 microL sample volume). Peripheral blood (PB) CD34 values from 30 patients undergoing PBSC mobilization were used to generate a PB CD34-based algorithm that would predict collection day/duration of apheresis. The algorithm was then used prospectively to collect PBSC products on 50 hematologic malignancy (HM) patients. RESULTS: Using the algorithm, patients were assigned to either a 6 (11-20 CD34/microL), 4 (21-49 CD34/microL) or 2 (> or = 50 CD34/microL) h collection. Patients with a CD34 value < or = 10/microL were re-tested. All patients (n = 43) predicted to mobilize reached the optimal CD34 (4-5 x 10(6)/kg) value with 1.0 apheresis procedure; seven patients had < or = 10/microL (nonmobilizers). The majority (75%) had apheresis charges decreased by 33-66%; 47% only required a 2 h procedure and 28% required 4 h. All patients demonstrated rapid trilineage engraftment. DISCUSSION: Absolute PB CD34 measurement using MVF offers a rapid and reliable approach to obtaining optimal PBSC products with minimal technical expertise. Although not a replacement for conventional flow cytometry, it meets the requirements for a point-of-care procedure.

Algorithms↗

PubMed1998

Compromised optimal hybridization temperatures may explain PM plus DQA1 anomalies.

The multiplex DNA typing test kit, PM plus DQA1 relies on 36 different oligonucleotides that all must hybridize correctly for accurate DNA typing. The G + C contents of the probe oligonucleotides range from 47% to 83%. Since G + C content directly affects optimal hybridization temperatures, a wide range of optimal hybridization temperatures is expected. This was verified by two empirically tested formulas. The recommended hybridization temperature is 55 degrees C. The control probe has an estimated optimal temperature of 75 degrees C indicating low stringency of the control. The B allele probe of the GC locus has an estimated optimal hybridization temperature of 70 degrees C. These discrepancies are unexplained by GC clusters or sequence palindromes. The departures from temperature optima may be responsible for observed PM plus DQA1 artifacts and for previously observed, low tolerance of this system to temperature variation. Since optimal temperature and cation concentration are related variables, careful attention to these is recommended as are positive controls demonstrating amplification of all alleles monitored by PM plus DQA1.

Alleles↗

PubMed1983

Optimal design of the chronic animal bioassay.

Optimal experimental designs for carcinogenicity bioassays conducted for the assessment of risks associated with exposure to environmental chemicals are derived. For our purposes, an optimal experimental design is a design that minimizes the mean-squared error of the maximum likelihood estimate of the virtually safe dose from the Armitage-Doll multistage model and maintains a high power for the detection of increased carcinogenic response. Three- and four-dose designs (including control as one of the doses) are discussed for a variety of dose response patterns. Monte Carlo simulation techniques are used to estimate the power and mean-squared error for small samples sizes. Two forms of the multistage model are used to estimate the virtually safe dose: the linear model and the linear-quadratic model. The optimal designs for fitting the linear model used a control group and a group administered the maximum tolerated dose, with about 50% of the animals at each dose. The three- and four-dose optimal designs when fitting the linear-quadratic model were found to be equivalent. However, after considering several biological issues, including overt toxicity, the optimal four-dose designs would use between 150 and 300 animals, with 50 to 60 animals in the control group, and 40 to 60 animals in the group administered the maximum tolerated dose. One-third of the remaining animals would be administered a dose between 10 and 30% of the maximum tolerated dose, and two-thirds of the remaining animals would be administered 50% of the maximum tolerated dose.

Animals↗