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PubMed2003

The C7-C10 cycloalkanes revisited.

The conformers of cycloheptane through cyclodecane have been examined at the B3LYP/6-311+G* and MP2/6-311+G* theoretical levels, with some additional calculations at the CCD/6-311+G* and CCSD(T)/6-311++G** levels. With cyclooctane, B3LYP predicts that the boat-chair and crown conformers have similar energies, whereas MP2 and CCSD(T) predict that the crown conformer is 2 kcal/mol higher in energy. The latter is in agreement with the electron diffraction data. With cyclononane, B3LYP predicts that two of the higher-energy conformers found in molecular mechanics calculations should convert to one of the lower-energy conformers. However, MP2/6-311+G* optimizations find them to be true minima on the potential energy surface. B3LYP systematically predicts larger C-C-C bond angles for these compounds than either MP2 or CCD. The results of molecular mechanics MM4 calculations are generally in good agreement with those obtained using MP2.

Journal Article↗

PubMed1992

Feasibility of using intracardiac impedance measurements for capture detection.

Energy consumption and longevity of modern pacemakers are determined by the controlling electronic circuitry and by the stimulation energy. While with technological progress the electronics' energy consumption has been reduced significantly, clinical practice shows that many cardiac pacemakers are programmed to suboptimal settings with regard to minimization of pacing energy consumption. Several methods for optimizing pacemaker output settings have been proposed in the past. The most promising concept is an output parameter optimizing pacemaker with automatic capture detection. We examined whether it is possible to distinguish between effective and ineffective pacemaker stimulus capture by analyzing high pass filtered intracardiac impedance signals that are derived from standard bipolar pacing leads. In one series of 11 patients undergoing replacement or implantation of chronic bipolar pacemakers, four patients during electrophysiology studies, and eight volunteers undergoing invasive electrophysiology trials, we examined intracardiac impedance signals obtained with various stimulation rates and output parameter settings. Additionally we analyzed a series of five patients with implanted pacemakers that can measure and telemeter intracardiac impedance signals. Several evaluation concepts have been analyzed regarding their ability to discriminate between effective and ineffective stimuli. We developed an adequate algorithm that detects capture or loss of capture at different output parameter settings based on intracardiac impedance analysis. The sensitivity is 98.5% and specificity is 91% to loss of capture for the currently investigated algorithm and this can be used to determine the optimal setting of pulse width and amplitude with regard to energy consumption. This concept is currently under realization in the external programmer and in the future an implementation of these algorithms within the pacemaker itself is intended.

Algorithms↗

PubMed2002

Folding free energy function selects native-like protein sequences in the core but not on the surface.

An automatic protein design procedure is used to select amino acid sequences that optimize the folding free energy function for a given protein. The only information used in designing the sequences is a set of known backbone structures for each protein, a rotamer library, and a well established classical empirical force field, which relies on basic physical chemical principles that underlie molecular interactions and protein stability, and has not been adjusted to yield native-like sequences. Applying the procedure to 7 different known protein folds, representing a total of 45 different native protein structures, yields ensembles of designed sequences displaying remarkable similarity to their natural counterparts in the protein core, but which are distinctly non-native on the protein surface. We show that natural and designed sequences for a given fold score significantly higher than random sequences against profiles derived from both, designed and natural sequence ensembles. Furthermore, we find that designed sequence profiles can be used to retrieve the native sequences for many of the analyzed proteins using standard PSI-BLAST searches in sequence databases. These findings may have important implications for our understanding the selection pressures operating on natural protein sequences and hold promise for improving fold recognition.

Amino Acid Sequence↗

PubMed2003

Biphasic shocks compared with monophasic damped sine wave shocks for direct ventricular defibrillation during open heart surgery.

BACKGROUND: Biphasic waveform shocks are more effective than monophasic shocks for transchest ventricular defibrillation, atrial cardioversion, and defibrillation with implantable defibrillators but have not been studied for open chest, intraoperative defibrillation. This prospective, blinded, randomized clinical study compares biphasic and monophasic shock effectiveness and establishes intraoperative energy dose-response curves. METHODS: Patients undergoing cardiothoracic surgery with bypass cardioplegia were randomly assigned to the monophasic or biphasic shock group. Ventricular fibrillation occurring after aortic clamp removal was treated with escalating energies of 2, 5, 7, 10, and 20 J until defibrillation occurred. If ventricular fibrillation persisted, a 20-J crossover shock of the other waveform was used. RESULTS: Cumulative defibrillation success at 5 J, the primary end point of the study, was higher in the biphasic group than in the monophasic group (25 of 50 vs. 9 of 41 defibrillated; P = 0.011). In addition, the biphasic group required lower threshold energy (6.8 vs. 11.0 J; P = 0.003), less cumulative energy (12.6 vs. 23.4 J; P = 0.002), and fewer shocks (2.5 vs. 3.5; P = 0.002). Crossover-shock effectiveness did not differ between groups. Dose-response curves show biphasic shocks to have higher cumulative success rates at all energies tested. CONCLUSIONS: Biphasic shocks are substantially more effective than monophasic shocks for direct defibrillation. The dose-response curve guides selection of first-shock energy for traditional step-up protocols. Starting at 5 J optimizes for lowest threshold and cumulative energy, whereas 10 or 20 J optimizes for more rapid defibrillation and fewer shocks.

Adult↗

PubMed2006

AMANDA observations constrain the ultrahigh energy neutrino flux.

A number of experimental techniques are currently being deployed in an effort to make the first detection of ultrahigh energy cosmic neutrinos. To accomplish this goal, techniques using radio and acoustic detectors are being developed, which are optimally designed for studying neutrinos with energies in the PeV-EeV range and above. Data from the AMANDA experiment, in contrast, have been used to place limits on the cosmic neutrino flux at less extreme energies (up to approximately 10 PeV). In this Letter, we show that by adopting a different analysis strategy, optimized for much higher energy neutrinos, the same AMANDA data can be used to place a limit competitive with radio techniques at EeV energies. We also discuss the sensitivity of the IceCube experiment, in various stages of deployment, to ultrahigh energy neutrinos.

Journal Article↗

PubMed2005

Identification of distributed metabolic objectives in the hypermetabolic liver by flux and energy balance analysis.

A methodology for inferring distributed metabolic objectives from time series flux data is developed by combining metabolic flux analysis, pathway identification, free energy balances, and nested optimization. This methodology is used to investigate the metabolic response of the rat liver to burn injury-induced whole body inflammation. Gibbs free energy changes were computed for stoichiometrically balanced sequences of reactions, or pathways, rather than individual reactions, to account for energetic coupling between reactions. Systematic enumeration of pathways proceeded by elementary flux mode (EFM) analysis. Together with stoichiometric balances and external metabolite flux measurements, the DeltaG(PATH)(o) criterion provided sufficient constraints to solve a series of nested optimization problems on the metabolic goal functions and associated flux distributions of fasted livers during the first-week time course of burn injury. The optimization results suggest that there is a consistent metabolic goal function for the liver that is insensitive to the changing metabolic burdens experienced by the liver during the first-week time course. As defined by the goal function coefficients, the global metabolic objective was to distribute the metabolic resources between amino acid metabolism and ketone body synthesis. These findings point to a role for the time-invariant structure of the metabolic reaction network, expressed as stoichiometric and thermodynamic constraints, in shaping the cellular metabolic objective.

Animals↗

PubMed2003

Association of the Fibonacci Cascade with the distribution of coronary artery lesions responsible for ST-segment elevation myocardial infarction.

This is the first study to demonstrate the appearance of the Fibonacci Cascade within the distribution of coronary artery lesions in the human heart. The propensity for this ratio to appear in nature may also be because this ratio optimizes the efficiency of packing structures in a limited space in such a way that wasted space is minimized and the supply of energy or nutrients is optimized.

Anthropometry↗

PubMed2004

Alpha-linolenic acid and coronary heart disease.

AIM: To summarize our present knowledge about vegetable omega-3 fatty acids. DATA SYNTHESIS: Alpha-linolenic acid (ALA) is one of the two essential fatty acids in humans. Epidemiological studies and dietary trials strongly suggest that this fatty acid is important in relation with the pathogenesis (and prevention) of coronary heart disease. Like other n-3 fatty acids from marine origin, it may prevent cardiac arrhythmias and sudden cardiac death. The optimal dietary intake of alpha-linolenic acid seems to be about 2 g per day or 0.6 to 1% of total energy intake. Obtaining an optimal ratio of the two essential fatty acids, linoleic and alpha-linolenic acids--ie a ratio of less than 4 to 1 in the diet--is a major issue. The main sources of alpha-linolenic acid for the European population should be canola oil (and canola-oil based margarine if available), nuts (English walnut), ground linseeds and green leafy vegetables such as purslane. CONCLUSIONS: Epidemiological studies and dietary trials in humans suggest that alpha-linolenic acid is a major cardio-protective nutrient.

Biomarkers↗

PubMed2005

Empty level structure and dissociative electron attachment cross section in (bromoalkyl)benzenes.

The gas-phase electron transmission (ET) and dissociative electron attachment (DEA) spectra are reported for the series of (bromoalkyl)benzenes C6H5(CH2)nBr (n = 0-3), where the bromine atom is directly bonded to a benzene ring or separated from it by 1-3 CH2 groups, and the dihalo derivative 1-Br-4-Cl-benzene. The relative DEA cross sections (essentially due to the Br- fragment) are reported, and the absolute cross sections are also evaluated. HF/6-31G and B3LYP/6-31G* calculations are employed to evaluate the virtual orbital energies (VOEs) for the optimized geometries of the neutral state molecules. The pi* VOEs, scaled with empirical equations, satisfactorily reproduce the corresponding experimental vertical electron attachment energies (VAEs). According to the calculated localization properties, the LUMO (as well as the singly occupied MO of the lowest lying anion state) of C6H5(CH2)3Br is largely localized on both the benzene ring and the C-Br bond, despite only a small pi*/sigma*C-Br interaction and in contrast to the chlorine analogue where the LUMO is predicted to possess essentially ring pi character. This would imply a less important role of intramolecular electron transfer in the bromo derivative for production of the halogen negative fragment through dissociation of the first resonant state. The VAEs calculated as the anion/neutral energy difference with the 6-31+G* basis set which includes diffuse functions are relatively close to the experimental values but do not parallel their sequence. In addition the SOMO of some compounds is not described as a valence MO with large pi* character but as a diffuse sigma* MO.

Journal Article↗

PubMed2006

Mental energy: Assessing the mood dimension.

Conceptualizing mental energy as a mood is impor tant, because these feelings are important to people and can influence behavior in the real world. If a person feels a lack of energy, for example, he or she is more likely to avoid physical or mental work if it is possible to do so. Alternatively, this person may seek to improve feelings of energy by eating, drinking, taking dietary supplements or drugs, sleeping, or engaging in other behaviors. Thus, the measurement of the mood of energy has importance in numerous ways, including public health, work productivity, and ultimately economic growth and productivity. Mood data have limitations, for example, self aware ness and literacy are necessary and faking is possible. The problem of faking is most salient in situations in which there is a strong motivation to fake, such as when psychological testing is used as part of an employment application. Despite these limitations, overwhelming evidence supports the validity for certain measures of the mood of energy such as the POMS vigor scale. This is not to say that mood measures are error free in all situations. Despite some error, however, validity evidence for mood measures is published in the scientific literature weekly. Future research aimed at determining the biological bases for the mood of energy, and its relationships to overlapping phenomena such as cognitive fatigue, should yield results that ultimately help us to understand how to optimize our feelings of energy.

Affect↗

PubMedDate not supplied

[The energy characteristics of cardiorespiratory system function in patients with chronic bronchitis under graded physical loads].

On the basis of 38 spiroveloergometries performed in 20 patients with chronic bronchitis (ChB) there have been calculated energy characteristics of the function of the cardiorespiratory system (power of the heart, respiratory muscles and erythron, effectiveness of capturing of oxygen in the cardiac, pulmonary, erythron links and in the oxygen transport system as a whole) while they were doing their graded exercise. Mathematical simulation (factor analysis) permitted identification of two levels of work load (> and < 80 Wt) differing widely in their physiological and energy maintenance. A conclusion is substantiated and validated that loads under 80 Wt appear to be preferable, corresponding to the area of optimal, in terms of energy maintenance, functioning of the cardiorespiratory system of ChB patients (strategy of increasing the oxygen consumption at the expense of the predominant augmentation of the adequate volume in proportion to enlargement of the stroke volume).

Adult↗

PubMed2006

Optimal selection of wavelet-packet-based features using genetic algorithm in pathological assessment of patients' speech signal with unilateral vocal fold paralysis.

Unilateral vocal fold paralysis (UVFP) is one of the most severe types of neurogenic laryngeal disorder in which the patients, due to their vocal cords malfunction, are confronted by some serious problems. As the effect of such pathologies would be significantly evident in the reduced quality and feature variation of dysphonic voices, this study is designed to scrutinize the piecewise variation of some specific types of these features, known as energy and entropy, all over the frequency range of pathological speech signals. In order to do so, the wavelet-packet coefficients, in five consecutive levels of decomposition, are used to extract the energy and entropy measures at different spectral sub-bands. As the decomposition procedure leads to a set of high-dimensional feature vectors, genetic algorithm is invoked to search for a group of optimal sub-band indexes for which the extracted features result in the highest recognition rate for pathological and normal subjects' classification. The results of our simulations, using support vector machine classifier, show that the highest recognition rate, for both optimized energy and entropy measures, is achieved at the fifth level of wavelet-packet decomposition. It is also found that entropy feature, with the highest recognition rate of 100% vs. 93.62% for energy, is more prominent in discriminating patients with UVFP from normal subjects. Therefore, entropy feature, in comparison with energy, demonstrates a more efficient description of such pathological voices and provides us a valuable tool for clinical diagnosis of unilateral laryngeal paralysis.

Adolescent↗

PubMed1987

Free energy differences between enzyme bound states.

A theory is presented that describes the free energy difference between the enzyme-substrate (ES) and enzyme-product (EP) complexes that is expected in enzymes optimized for catalytic efficiency. In such enzymes, the free energy drop between ES and EP complexes reflects a portion of the chemical potential difference between substrates and products outside the active site under physiological conditions. Qualitative and quantitative predictions of the model are discussed and compared with experimental data. The controversy over the kinetically optimal free energy profile for an enzymatic reaction operating under constraints set forward by Albery & Knowles (1976) is resolved.

Enzymes↗

PubMed1996

The determinants of pKas in proteins.

Although validation studies show that theoretical models for predicting the pKas of ionizable groups in proteins are increasingly accurate, a number of important questions remain: (1) What factors limit the accuracy of current models? (2) How can conformational flexibility of proteins best be accounted for? (3) Will use of solution structures in the calculations, rather than crystal structures, improve the accuracy of the computed pKas? and (4) Why does accurate prediction of protein pKas seem to require that a high dielectric constant be assigned to the protein interior? This paper addresses these and related issues. Among the conclusions are the following: (1) computed pKas averaged over NMR structure sets are more accurate than those based upon single crystal structures; (2) use of atomic parameters optimized to reproduce hydration energies of small molecules improves agreement with experiment when a low protein dielectric constant is assumed; (3) despite use of NMR structures and optimized atomic parameters, pKas computed with a protein dielectric constant of 20 are more accurate than those computed with a low protein dielectric constant; (4) the pKa shifts in ribonuclease A that result from phosphate binding are reproduced reasonably well by calculations; (5) the substantial pKa shifts observed in turkey ovomucoid third domain result largely from interactions among ionized groups; and (6) both experimental data and calculations indicate that proteins tend to lower the pKas of Asp side chains but have little overall effect upon the pKas of other ionizable groups.

Amino Acid Sequence↗

PubMed1988

Very-low-calorie diets with high and low protein content: impact on triiodothyronine, energy expenditure, and nitrogen balance.

Optimal composition of reducing diets remains controversial. Seventeen obese inpatients received 440 kcal/d, either 41% protein plus 55% carbohydrate (CD) or 95% protein (PP), for 3 wk. There were no significant diet effects (all data CD vs PP) in weight loss (8.88 +/- 1.01 vs 8.74 +/- 0.79 kg), loss of lean mass (2.10 +/- 0.35 vs 1.61 +/- 0.39 kg), metabolic rate reduction (15.3 +/- 2.8 vs 13.0 +/- 5.2%), or meal-stimulated thermogenesis (26.6-37.9 vs 29.0-26.1 net kcal/3 h [time NS also]). Triiodothyronine (T3) responses differed (2.35 +/- 0.11 to 1.57 +/- 0.14 vs 2.43 +/- 0.11 to 1.47 +/- 0.12 nmol/L, p less than 0.01) as did free T3 (3.4 +/- 0.2 to 2.6 +/- 0.2 vs 3.2 +/- 0.2 to 2.0 +/- 0.2 pmol/L, (p less than 0.01]; thyroxine declined similarly in both groups. Subjects fed CD gained no advantage over subjects fed PP. Regression analyses revealed no relationship between thyroid hormones, energy deficit, or lean mass with nitrogen losses, suggesting that other or more complex processes govern endogenous protein metabolism during weight loss.

Adult↗

PubMed2004

Recent advances in light ion radiation therapy.

BACKGROUND: The fast development of energy- and intensity-modulated radiation therapy during the last two decades using photon and electron beams has when implemented resulted in a considerable improvement of radiation therapy, particularly if combined with radiobiologically based treatment optimization techniques. This has made intensity-modulated electron and photon beams as powerful as today's uniform dose proton therapy. To be able to cure also the most advanced hypoxic and radiation-resistant tumors of complex local spread, intensity-modulated light ion beams are really the ultimate tool and in clinical practice 2 to 3 times less expensive per patient treated than proton therapy. This development and the recent development of advanced tumor diagnostics based on PET-CT imaging of the tumor cell density open the field for new powerful radiobiologically based treatment optimization methods. The ultimate step is to use the unique radiobiologic and dose distributional advantages of light ion beams for truly optimized bioeffect planning where the integral three-dimensional dose delivery and tumor cell survival can be monitored by PET-CT imaging and corrected by biologically based adaptive therapy optimization methods. PURPOSE: The main purpose of the present paper is to discuss the principal areas of development of therapy optimization, by considering the therapy chain from tumor diagnostics and the use of three-dimensional predictive assay to biologically based treatment optimization with special focus on the rapid clinical development of advanced light ion therapy. METHODS: Besides the "classical" approaches using low ionization density hydrogen ions (protons, but also possibly deuterons and tritium nuclei) and high ionization density carbon ions, two new approaches will be discussed. In the first one, lithium or beryllium or boron ions, which induce the least detrimental biologic effect to normal tissues for a given biologic effect in a small volume of the tumor, will be key particles. In the second approach, referred patients will be given a high-dose, high-precision "boost" treatment with carbon or oxygen ions during 1 week preceding the final treatment with conventional radiation in the referring hospital. The rationale behind these approaches is to minimize the high ionization density dose to the normal-tissue stroma outside but sometimes also inside the tumor bed and to ensure a more uniform and optimal biologic effectiveness in the tumor, also on the microscopic scale. The present discussion indicates that BIologically Optimized predictive Assay based light ion Radiation Therapy (Bio-Art) is really the ultimate way to perform high-precision radiation therapy using checkpoints of the integral dose delivery and the tumor response and, based on this information, perform compensating corrections of the dose delivery. By using biologically optimized scanned high-energy photon or ion beams, it is possible to measure in vivo the three-dimensional dose delivery using the same PET-CT camera that was used for diagnosing the tumor spread. This method thus opens up the door for truly three-dimensional biologically optimized adaptive radiation therapy, where the measured dose delivery to the true target tissues can be used to fine-adjust the incoming beams, so that possible errors in the integral therapy process are eliminated toward the end of the treatment. Interestingly enough, practically all major error sources--such as organ motion, treatment planning errors, patient setup errors, and dose delivery problems due to gantry, multileaf, or scanning beam errors--can be corrected for in this way. RESULTS AND CONCLUSIONS: Radiobiologically optimized dose delivery using intensity and radiation quality modulation based on high-resolution PET-CT or Magnetic Resonance Spectroscopic Imaging (MRSI)-based tumor and normal-tissue imaging is probably the ultimate development of radiation therapy, taking the unique physical and biologic advantages of light ions fully into account in truly patient-individualized curative treatment schedules. Using recently available biologically based treatment ilable biologically based treatment optimization algorithms, it is possible to improve the treatment outcome for advanced tumors by as much as 10-40%. The adaptive radiotherapy process based both on three-dimensional tumor cell survival and dose delivery monitoring has the potential of percent accuracy in tumor response and dose delivery monitoring, using two-dimensional, narrow high-energy photon beam scanning and three-dimensional (11)C Bragg peak scanning for radiation quality and intensity-modulated dose delivery. There is no doubt that the future of radiation therapy is very promising, and gradually more and more patients may not even need advanced surgery. Instead, they could be cured by biologically optimized electron, photon, or light ion therapy, where the densely ionizing Bragg peak is placed solely in the gross tumor, and a lower ionization density is used in microscopically invasive tumor volumes.

Cell Cycle↗

PubMed1979

Controlled transcutaneous powering of a chronically implanted telemetry device.

Radiofrequency (RF) powered subcutaneous transmitter devices offer the unique possibility of very long-term measurements from sites within the body under a variety of normal living conditions without percutaneous connections and concomitant dangers such as local tissue infection. Disturbances in the energy transport across the cutaneous barrier may, however, give rise to output data signal fluctuations, which are perceived as transients or drift. A RF-powered implanted biotelemetry device is proposed where the energy transport is controlled by continually optimizing the emission frequency and the duration of energy transfer.

Animals↗

PubMed1983

Influence of precursors of biosyntheses on the energy metabolism of the liver cell.

The influence of variable energy demand on both the total ATP/ADP ratio and the rate of respiration was investigated in isolated hepatocytes. For hepatocytes respiring at the same rate, different ATP/ADP ratios were observed when the energy drain was caused either by ureogenesis and gluconeogenesis or by partial uncoupling. These differences were provoked by an additional effect of the precursors of syntheses studied, i.e. lactate or ornithine, on the hydrogen supply of the respiratory chain, as was reflected in terms of the reduction degree of cytochrome c in isolated mitochondria. For a fixed hydrogen supply there exists a defined characteristic ATP/ADP ratio versus rate of respiration. It is concluded that the respiratory rate, the mitochondrial redox state and the phosphorylation potential (transmitted into the extramitochondrial one by the adenine nucleotide translocator) represent a system of three interdependent parameters. The presence of metabolic precursors such as ornithine and lactate enhances the load of the cellular energy metabolism as well as the energy supply of the cell, the latter through improvement of substrate utilization. The ambivalent character of the precursors makes possible a kind of forward optimization of the hepatic energy metabolism which allows the cell to perform syntheses at a relatively high ATP/ADP ratio and, unless syntheses take place, to save energy by avoiding higher ATP/ADP ratios.

Adenosine Diphosphate↗