Sample records for constrained acidic alpha-amino

  1. Synthesis of bicyclic tertiary alpha-amino acids.

    PubMed

    Strachan, Jon-Paul; Whitaker, Regina C; Miller, Craig H; Bhatti, Balwinder S

    2006-12-22

    Novel bicyclic alpha-amino acids, exo and endo-1-azabicyclo[2.2.1]heptane-2-carboxylic acid, 1-azabicyclo[2.2.1]heptane-7-carboxylic acid, and 1-azabicyclo[3.2.2]nonane-2-carboxylic acid have been readily synthesized for the generation of neuronal nicotinic receptor ligands. Alkylation of glycine-derived Schiff bases or nitroacetates with cyclic ether electrophiles, followed by acid-induced ring opening and cyclization in NH4OH, allowed for the preparation of substantial quantities of the three tertiary bicyclic alpha-amino acids. PMID:17168622

  2. Using enantioselective indicator displacement assays to determine the enantiomeric excess of alpha-amino acids.

    PubMed

    Leung, Diana; Folmer-Andersen, J Frantz; Lynch, Vincent M; Anslyn, Eric V

    2008-09-17

    Enantioselective indicator displacement assays (eIDAs) were used for the determination of enantiomeric excess (ee) of alpha-amino acids as an alternative to the labor-intensive technique of chromatography. In this study, eIDAs were implemented by the use of two chiral receptors [(Cu(II)(1)](2+), [Cu(II)(2)](2+)) in conjunction with the indicator chrome azurol S. The two receptors were able to enantioselectively discriminate 13 of the 17 analyzed alpha-amino acids. Enantiomeric excess calibration curves were made using both receptors and then used to analyze true test samples to check the system's ability to determine ee accurately. The proposed method uses a conventional UV-vis spectrophotometer to monitor the colorimetric signal, which allows for a potential high-throughput screening (HTS) method for determining ee. The techniques created consistently produced results accurate enough for rapid preliminary determination of ee. PMID:18714996

  3. Amino acids of the Murchison meteorite. I - Six carbon acyclic primary alpha-amino alkanoic acids

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.; Gandy, W. E.; Pizzarello, S.

    1981-01-01

    Six of the seven chain isomers of six-carbon acyclic primary alpha-amino alkanoic acids (leucine isomers) have been either identified or confirmed in hot-water extracts of the Murchison meteorite using combined gas chromatography-mass spectrometry (GC-MS) and ion exchange chromatography. 2-Amino-2-ethylbutyric acid, 2-amino-2,3-dimethylbutyric acid, pseudoleucine, and 2-methylnorvaline were positively identified by GC-MS. These amino acids have not been previously reported to occur in natural materials and may be uniquely meteoritic in origin. The presence of leucine and isoleucine (including the diastereoisomer, alloisoleucine) was confirmed. Peaks corresponding to norleucine were seen by ion-exchange and gas chromatography but characteristic mass spectra were not obtained. The alpha-branched chain isomers in this series are quantitatively the most significant. These results are compared with literature data on amino acid synthesis by electrical discharge and Fischer-Tropsch-type catalysis. Neither model system produces an amino acid suite that is completely comparable to that found in the Murchison meteorite.

  4. Protein design with L- and D-alpha-amino acid structures as the alphabet.

    PubMed

    Durani, Susheel

    2008-10-01

    Summarizing the implications of homochiral structures in interpeptide interactions, not only in the topology but also possibly in the physics of protein folding, this Account provides an overview of the concept of shape-specific protein design using D- and L-(alpha)amino acid structures as the alphabet. The molecular shapes accessible in de novo protein design are stereochemically defined. Indeed, the defining consideration for shape specificity in proteins to be alpha-helix/beta-sheet composites is the L configuration of the alpha-amino acid structures. The stereospecificity in shapes implies that protein shapes may be diversifiable stereochemically, that is, designable de novo, using D and L structures as the alphabet. Indeed, augmented with D enantiomers, Nature's alphabet will expand greatly in the diversity of polypeptide stereoisomers, for example, from 1(30) to 2(30)--that is, from one to ca. one billion--for a modestly sized 30-residue polypeptide. Furthermore, with each isomer having conformers stereospecific to its structure, molecular folds of specific shapes may be approachable sequentially when D and L structures are used as the alphabet. Illustrating the promise, 14-20-residue bracelet-, boat-, canoe-, and cup-shaped molecular folds were designed stereochemically or implemented as specific sequence plans in the D- and L-alpha-amino acid alphabet. In practical terms, canonical poly-L peptide folds were modified to the desired shapes via stereochemical mutations invoking enantiomer symmetries in the Ramachandran phi,psi space as the logic. For example, in designing the boat-shaped fold, the canonical beta-hairpin was reengineered in its flat planar structure via multiple coordinated L-to-D mutations in its position specific cross-strand neighbor residues, upturning its ends enclosing six side chains in a molecular cleft. While affirming the generality of the approach, the 20-residue molecular canoe and the 14-residue molecular cup are also presented as examples of the scope of functional design. The canoe, possessing alkali cation-specific catgrips in its main chain, and the cup, featuring an organic cation-specific aromatic triad in its side chains, do indeed display desired specificities in their ligand binding. Stereochemistry is, therefore, the crucial specifier of protein shapes and valuable as the tool for shape-specific protein design. Proteins in general, whether poly-L or mixed-D,L, require sequence effects of amino acid side chain structures for their stability, if not also for specifying them conformationally. The principles underlying these phenomena remain a puzzle, but studies invoking a stereochemical mutation approach to the problem have suggested that the poly-L structure may be crucial to the principles of sequential encoding of protein structures in amino acid side chains as the alphabet. PMID:18642934

  5. Polymerization on the rocks: negatively-charged alpha-amino acids

    NASA Technical Reports Server (NTRS)

    Hill, A. R. Jr; Bohler, C.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    Oligomers of the negatively-charged amino acids, glutamic acid, aspartic acid, and O-phospho-L-serine are adsorbed by hydroxylapatite and illite with affinities that increase with oligomer length. In the case of oligo-glutamic acids adsorbed on hydroxylapatite, addition of an extra residue results in an approximately four-fold increase in the strength of adsorption. Oligomers much longer than the 7-mer are retained tenaciously by the mineral. Repeated incubation of short oligo-glutamic acids adsorbed on hydroxylapatite or illite with activated monomer leads to the accumulation of oligomers at least 45 units long. The corresponding reactions of aspartic acid and O-phospho-L-serine on hydroxylapatite are less effective in generating long oligomers, while illite fails to accumulate substantial amounts of long oligomers of aspartic acid or of O-phospho-L-serine.

  6. One pot, rapid and efficient synthesis of water dispersible gold nanoparticles using alpha-amino acids.

    PubMed

    Wangoo, Nishima; Kaur, Sarabjit; Bajaj, Manish; Jain, D V S; Sharma, Rohit K

    2014-10-31

    A detailed study on the synthesis of spherical and monodispersed gold nanoparticles (AuNPs) using all of the 20 naturally occurring ?-amino acids has been reported. The synthesized nanoparticles have been further characterized using various techniques such as absorbance spectroscopy, transmission electron microscopy, dynamic light scattering and nuclear magnetic resonance. Size control of the nanoparticles has been achieved by varying the ratio of the gold ion to the amino acid. These monodispersed water soluble AuNPs synthesized using non-toxic, naturally occurring ?-amino acids as reducing and capping/stabilizing agents serve as a remarkable example of green chemistry. PMID:25300279

  7. Cyclic enkephalin analogues containing alpha-amino-beta-mercapto-beta,beta-pentamethylenepropionic acid at positions 2 or 5.

    PubMed

    Bryan, W M; Callahan, J F; Codd, E E; Lemieux, C; Moore, M L; Schiller, P W; Walker, R F; Huffman, W F

    1989-02-01

    Analogues of the highly potent and delta-receptor-selective enkephalins 1-4 were prepared with alpha-amino-beta-mercapto-beta,beta-pentamethylenepropionic acid (Apmp) replacing the beta,beta-dimethylcysteine (Pen) at positions 2 or 5. The peptides 5-8 were prepared by employing D,L-Apmp and, following oxidative cyclization, the resulting diastereomeric peptides were separated and purified by preparative high performance liquid chromatography. Compounds 7 and 8, with D- or L-Apmp substituted at position 5 are approximately 5 orders of magnitude more potent in the MVD assay than analogues 5 or 6 with D- or L-Apmp at position 2. While displaying less delta-receptor selectivity than the corresponding Pen-containing compounds, 7 and 8 are an order of magnitude more potent. All the analogues showed diminished delta-receptor selectivity in the rat brain binding assay. Compounds 7 and 8 displayed delta-receptor affinity comparable to the corresponding Pen-containing analogues. PMID:2536436

  8. Simulation of organismic morphology and behavior by synthetic poly-alpha-amino acids.

    PubMed

    Fox, S W; McCauley, R; Joseph, D; Windsor, C R; Yuyama, S

    1966-01-01

    Experiments imitating spontaneous geothermal occurrences have yielded most of the amino acids found in protein. All of the amino acids found in protein are simultaneously condensed, by heating in a range of appropriate conditions, to polymers which have many of the properties of proteins. These properties include molecular weights of many thousand, digestibility by proteolytic enzymes, and catalytic activities. One of the other properties is the tendency to form structured units; these units have many of the attributes of biocells. The processes indicated, and others, comprise a conceptual continuum which, according to accumulated information, must have occurred under the conditions existing in regions of the primitive Earth. PMID:11915883

  9. Transitioning enantioselective indicator displacement assays for alpha-amino acids to protocols amenable to high-throughput screening.

    PubMed

    Leung, Diana; Anslyn, Eric V

    2008-09-17

    Enantioselective indicator displacement assays (eIDAs) for alpha-amino acids were conducted in a 96-well plate format to demonstrate the viability of the technique for the high-throughput screening (HTS) of enantiomeric excess (ee) values. Chiral receptors [Cu(II)(1)](2+) and [Cu(II)(2)](2+) with the indicator chrome azurol S were implemented for the eIDAs. Enantiomeric excess calibration curves were made using both receptors and then used to analyze true test samples. These results were compared to those previously obtained with a conventional UV-vis spectrophotometer, and they showed little to no loss of accuracy, while the speed of analysis was increased. A sample of valine of unknown ee was synthesized through an asymmetric reaction to produce a realistic reaction sample, which was analyzed using receptor [Cu(II)(1)](2+). The experimentally determined ee using our eIDA was compared to that obtained by chiral HPLC and (1)H NMR chiral shift reagent analysis. This gave errors of 4.7% and 12.0%, respectively. In addition to the use of ee calibration curves, an artificial neural network (ANN) was used to determine the % L-amino acid of the test samples and of the sample of valine of unknown ee from the asymmetric reaction. This method obtained errors of 5.9% and 2.2% compared to chiral HPLC and (1)H NMR chiral shift reagent analysis, respectively. The technique using calibration curves for the determination of ee on a 96-well plate allows one to determine 96 ee values in under a minute, enabling its use for HTS of asymmetric reactions with acceptable accuracy. PMID:18714993

  10. Highly diastereoselective addition of nitromethane anion to chiral alpha-amidoalkylphenyl sulfones. Synthesis of optically active alpha-amino acid derivatives.

    PubMed

    Foresti, Elisabetta; Palmieri, Gianni; Petrini, Marino; Profeta, Roberto

    2003-12-01

    Optically active syn-alpha-amidoalkylphenyl sulfones can be prepared from chiral aldehydes in anhydrous conditions using benzenesulfinic acid. These sulfones in basic conditions give N-acylimines that react with sodium methanenitronate to afford the corresponding nitro adducts with high anti diastereoselectivity. PM3 semiempirical calculations provide a rationale for the observed opposite stereoselectivity. The obtained nitro derivatives undergo a Nef reaction followed by a methylation giving optically active beta-hydroxy-alpha-amino acid and alpha,beta-diamino acid esters in good yield. These amino acid derivatives are important building blocks for the preparation of biologically active compounds. PMID:14685331

  11. Quantum-chemical analysis of thermodynamics of two-dimensional cluster formation of alpha-amino acids at the air/water interface.

    PubMed

    Vysotsky, Yu B; Fomina, E S; Belyaeva, E A; Aksenenko, E V; Vollhardt, D; Miller, R

    2009-12-31

    The semiempirical quantum-chemical PM3 method is used to calculate the thermodynamic parameters of clusterization of the S-form of alpha-amino acids with the general composition C(n)H(2n+1)CHNH(2)COOH (n = 5-15) at 278 and 298 K. It is shown that six stable conformations of monomers exist, for which the thermodynamic parameters (enthalpy and Gibbs' energy) of the formation and absolute entropy are calculated. The correlation dependencies of the calculated parameters on the alkyl chain length are found to be linear. The structures of the monomers are used to build larger clusters (dimers, tetramers, hexamers). For all small clusters (comprised of two to six molecules), the thermodynamic parameters of formation and clusterization are calculated. It is shown that for tetramers and hexamers the enthalpy, entropy, and Gibbs' energy of clusterization are linearly dependent on the alkyl chain length, whereas for the dimers these dependencies are stepwise. The thermodynamic characteristics of clusterization of associates tilted by angles of 9 and 30 degrees with respect to the normal to the interface are calculated. It is shown that the 30 degrees angle orientation is more energetically advantageous for this class of compounds. The geometric parameters of the unit cell characteristic for the infinite 2D film which corresponds to the most advantageous conformation of the monomer were calculated using the PM3 parametrization to be a = 4.57-4.71 A and b = 5.67-5.75 A, with the angle between the axes theta = 100-103 degrees . These values agree well with the available experimental data. Spontaneous clusterization of alpha-amino acids at the air/water interface at 278 K takes place if the alkyl chain length exceeds 11-12 carbon atoms, whereas for 298 K this clusterization threshold corresponds to 13-14 carbon atoms in the alkyl chain, also in agreement with the experimental data. PMID:19924883

  12. Synthesis and characterization of a lipidic alpha amino acid: solubility and interaction with serum albumin and lipid bilayers.

    PubMed

    Filipe, Hugo A L; Coreta-Gomes, Filipe M; Velazquez-Campoy, Adrian; Almeida, Ana R; Peixoto, Andreia F; Pereira, Mariette M; Vaz, Winchil L C; Moreno, Maria J

    2013-04-01

    The lipidic ?-amino acid with 11 carbons in the alkyl lateral chain (?-aminotridecanoic acid) was synthesized via multicomponent hydroformylation/Strecker reaction, which is a greener synthetic approach to promote this transformation relative to previously described methods. Its solubility and aggregation behavior in aqueous solutions was characterized, as well as the interaction with lipid bilayers. Lipidic amino acids are very promising molecules in the development of prodrugs with increased bioavailability due to the presence of the two polar functional groups and nonpolar alkyl chain. They are also biocompatible surfactants that may be used in the food and pharmaceutical industry. In this work we have conjugated the lipidic amino acid with a fluorescent polar group (7-nitrobenz-2-oxa-1,3-diazol-4-yl), to mimic drug conjugates, and its association with serum proteins and lipid bilayers was characterized. The results obtained indicate that conjugates of polar molecules with lipidic ?-amino acid, via covalent attachment to the amine group, have a relatively high solubility in aqueous solutions due to their negative global charge. They bind to serum albumin with intermediate affinity and show a very high partition coefficient into lipid bilayers in the liquid-disordered state. The attachment of the polar group to the lipidic amino acid increased strongly the aqueous solubility of the amphiphile, although the partition coefficient into lipid membranes was not significantly reduced. Conjugation of polar drugs with lipidic amino acids is therefore an efficient approach to increase their affinity for biomembranes. PMID:23477590

  13. Modulation of DL-. alpha. -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/quisqualate receptors by phospholipase A sub 2 : A necessary step in long-term potentiation

    SciTech Connect

    Massicotte, G.; Baudry, M. (Univ. of Southern California, Los Angeles (United States)); Vanderklish, P.; Lynch, G. (Univ. of California, Irvine (United States))

    1991-03-01

    The effects of kainate (KA)-induced epileptic seizures on the binding properites of hippocampal glutamate receptors, on the modulation of DL-{alpha}-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/quisqualate receptor by phospholipase A{sub 2} (PLA{sub 2}), and on the formation of long-term potentiation (LTP) were studied in hippocampal membranes and hippocampal slices. Systemic administration of KA produced specific changes in the binding properties of the AMPA/quisqualate receptors and its regulation. Whereas the binding of various ligands to the N-methyl-D-aspartate receptors was not modified by KA treatment, there was a singificant decrease in the maximal number of binding sites for ({sup 3}H)AMPA. The loss of LTP was not due to changes in postsynaptic responses elicited by the bursts that trigger the potentiation effect, thus suggesting that KA treatment disrupts processes that follow N-methyl-D-aspartate receptor activation. Systemic administration of KA was associated with calpain activation as the amount of spectrin breakdown products was increased severalfold in hippocampus but not in cerebellum. Pretreatment of telencephalic membranes with calpain greatly reduced the PLA{sub 2}-induced increase in ({sup 3}H)AMPA binding. The results provide evidence in favor of an essential role of PLA{sub 2} in the development of LTP and suggest that the order of activation of different calcium-dependent processes is critical for producing the final changes underlying LTP.

  14. LY503430, a novel alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor potentiator with functional, neuroprotective and neurotrophic effects in rodent models of Parkinson's disease.

    PubMed

    Murray, Tracey K; Whalley, Katherine; Robinson, Christine S; Ward, Mark A; Hicks, Caroline A; Lodge, David; Vandergriff, Jim L; Baumbarger, Polly; Siuda, Edward; Gates, Mary; Ogden, Ann M; Skolnick, Phil; Zimmerman, Dennis M; Nisenbaum, Eric S; Bleakman, David; O'Neill, Michael J

    2003-08-01

    Glutamate is the major excitatory transmitter in the brain. Recent developments in the molecular biology and pharmacology of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) subtype of glutamate receptors have led to the discovery of selective, potent, and systemically active AMPA receptor potentiators. These molecules enhance synaptic transmission and play important roles in plasticity and cognitive processes. In the present study, we first characterized a novel AMPA receptor potentiator, (R)-4'-[1-fluoro-1-methyl-2-(propane-2-sulfonylamino)-ethyl]-biphenyl-4-carboxylic acid methylamide (LY503430), on recombinant human GLUA1-4 and native preparations in vitro and then evaluated the potential neuroprotective effects of the molecule in rodent models of Parkinson's disease. Results indicated that submicromolar concentrations of LY503430 selectively enhanced glutamate-induced calcium influx into human embryonic kidney 293 cells transfected with human GLUA1, GLUA2, GLUA3, or GLUA4 AMPA receptors. The molecule also potentiated AMPA-mediated responses in native cortical, hippocampal, and substantia nigra neurons. We also report here that LY503430 provided dose-dependent functional and histological protection in animal models of Parkinson's disease. The neurotoxicity after unilateral infusion of 6-hydroxydopamine into either the substantia nigra or the striatum of rats and that after systemic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice were reduced. Interestingly, LY503430 also had neurotrophic actions on functional and histological outcomes when treatment was delayed until well after (6 or 14 days) the lesion was established. LY503430 also produced some increase in brain-derived neurotrophic factor in the substantia nigra and a dose-dependent increases in growth associated protein-43 (GAP-43) expression in the striatum. Therefore, we propose that AMPA receptor potentiators offer the potential of a new disease modifying therapy for Parkinson's disease. PMID:12730350

  15. Effects of 5'-alkyl-benzothiadiazides on (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor biophysics and synaptic responses.

    PubMed

    Arai, Amy C; Xia, Yan-Fang; Kessler, Markus; Phillips, Dean; Chamberlin, Richard; Granger, Richard; Lynch, Gary

    2002-09-01

    Alkyl-substituted benzothiadiazides (BTDs) were tested for their effects on (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors. In excised patches, the 5'-ethyl derivative "D1" blocked the desensitization of AMPA receptor currents during prolonged application of glutamate (EC(50), 36 microM), and it slowed deactivation of responses elicited by 1-ms glutamate pulses greater than 10-fold. [(3)H]Fluorowillardiine binding to rat synaptic membranes was increased by D1 by a factor of 3.6 (EC(50), 17 microM) with a Hill coefficient near 2. In hippocampal slices, the compound reversibly increased excitatory postsynaptic currents and field excitatory postsynaptic potentials (EPSPs) with thresholds around 10 microM. The size of the alkyl substituent influenced both the potency and nature of the drug effect on synaptic currents: 5'-methyl compounds had a 2-fold greater effect on response amplitude than on response duration, whereas 5'-ethyl compounds like D1 caused greater increases in duration than amplitude. In tests with recombinantly expressed AMPA receptor subunits, D1 preferred the glutamate receptor (GluR) subunit GluR4 flip (0.64 microM) over GluR4 flop (5.3 microM); similar affinities but with smaller flip-flop differences were obtained for GluR1 through 3. These results show that D1 and congeners are significantly more potent than the parent compound IDRA-21 and that they differ in two fundamental aspects from cyclothiazide, the most widely studied BTD: 1) D1 markedly increases the agonist affinity of AMPA receptors and 2) it has immediate and large effects on field EPSPs. The large gain in potency conferred by alkyl substitution suggests that the 5' substituent is in intimate contact with the receptor, with the size of the substituent determining the way in which receptor kinetics is changed. PMID:12181433

  16. Comparative effects of tumour necrosis factor-alpha (cachectin), interleukin-1-beta and tumour growth on amino acid metabolism in the rat in vivo. Absorption and tissue uptake of alpha-amino[1-14C]isobutyrate.

    PubMed

    Argilés, J M; López-Soriano, F J; Wiggins, D; Williamson, D H

    1989-07-15

    The effects of acute administration of either tumour necrosis factor-alpha (cachectin) (TNF) or interleukin-1-beta (IL-1), or of tumour growth (Walker-256 carcinosarcoma), on blood amino acid concentrations and tissue alpha-amino[1-14C]isobutyrate (AIB) uptake in virgin and lactating rats were compared. Both monokines decreased the blood concentrations of those amino acids (serine, glycine, alanine and proline) transported via the A system. Tumour growth decreased the blood concentrations of serine, proline and histidine, whereas the concentrations of glutamine and leucine were increased. IL-1 decreased the intestinal absorption of AIB in all groups studied; TNF or tumour growth had no effect. Tissue AIB uptake was increased (1.5-2.5-fold) in liver, whereas it was decreased in heart and skeletal muscle of the three treatment groups (except skeletal muscle of the IL-1-treated rats). Lactating rats had lower hepatic uptake of AIB compared with livers of virgin rats. IL-1 increased the hepatic uptake of AIB in lactating rats, but not to the values seen in virgin rats treated with IL-1; there was no effect of the cytokine on muscle or mammary-gland uptake. In adrenalectomized rats, the stimulatory effect of IL-1 on hepatic AIB uptake was diminished, whereas that of TNF still persisted. IL-1 caused a marked decrease of AIB uptake in muscle and heart of adrenalectomized rats, which was accompanied by an increase in the blood concentrations of branched-chain amino acids. These effects did not occur with TNF. It is concluded that the effects of the cytokines on tissue amino acid metabolism may depend on a differential endocrine response involving glucagon and/or glucocorticoids. PMID:2789041

  17. Infrared spectra and molar absorption coefficients of the 20 alpha amino acids in aqueous solutions in the spectral range from 1800 to 500 cm -1

    NASA Astrophysics Data System (ADS)

    Wolpert, Martina; Hellwig, Petra

    2006-07-01

    In this work, we present the absorption spectra and molar coefficients of all 20 amino acids in aqueous solutions down to 500 cm -1. The spectral region between 1200 and 500 cm -1 was yet disregarded for protein infrared spectroscopy, mainly due to the strong H 2O absorption. Absorption spectra were obtained mainly for physiological relevant pH region. Intense bands for aromatic amino acids, histidine and such with OH group could clearly be identified throughout the given spectral region. For sulfur-containing amino acids cysteine and methionine some strong bands besides the weak carbon-sulfur stretching vibration was shown. Effects of aqueous solution environment, pH, protonation states were discussed, together with previously reported data from theoretical approaches. With this complete set of spectral information application to proteins in the whole mid infrared region could be described precise and the potential of the lower spectral region to study typical cofactor ligands like histidine, shown.

  18. Effect of DNA interaction involving antioxidative 4-aminoantipyrine incorporating mixed ligand complexes having alpha-amino acid as co-ligand

    NASA Astrophysics Data System (ADS)

    Raman, Natarajan; Sakthivel, Arunagiri; Selvaganapathy, Muthusamy; Mitu, Liviu

    2014-02-01

    Few new mixed ligand transition metal complexes of the stoichiometry [ML(A)2], where M = Co(II), Ni(II), Cu(II) and Zn(II), L = FFAP (furfurylidene-4-aminoantipyrine) and A = amino acid (glycine/alanine/valine), have been designed, synthesized and characterized. The molar conductivity of the complexes in DMF at 10-3 M concentration shows that they are non-electrolytes. The interaction of these complexes with CT-DNA indicates that the valine mixed ligand complexes are having higher binding constant than alanine and glycine mixed ligand complexes. This analysis reveals that binding constant depends on the size of the alkyl group present in the amino acid. The binding constants of valine mixed ligand complexes are in the order of 104 to 105 M-1 revealing that the complexes interact with DNA through moderate intercalation mode. The metal complexes exhibit effective cleavage of pUC19 DNA but it is not preceded via radical cleavage and superoxide anion radical. They are good antimicrobial agents than the free ligand. On comparing the IC50 values, [Ni(L)(Gly)2] is considered as a potential drug to eliminate the hydroxyl radical.

  19. Chiral separation of phosphine-containing alpha-amino acid derivatives using two complementary cellulosic stationary phases in supercritical fluid chromatography.

    PubMed

    West, Caroline; Bouet, Alexis; Gillaizeau, Isabelle; Coudert, Gerard; Lafosse, Michel; Lesellier, Eric

    2010-02-01

    Enantiomeric separations of six amino-acid derivatives have been studied using packed-column supercritical fluid chromatography with two polysaccharide-based enantioselective stationary phases: cellulose tris(3,5-dimethylphenylcarbamate) and cellulose tris(3-chloro-4-methylphenylcarbamate) (Lux Cellulose-1 and -2). The effect of analyte structure on retention and separation was studied. Varied mobile phase compositions were investigated: alcohol modifier percentage was increased from 3 to 40% but smaller amounts were most effective in separating these compounds. Besides, ethanol was preferred to methanol or isopropanol as it proved to be a good compromise to achieve sufficient resolution in a reasonable analysis time. Moreover, a carbon dioxide-ethanol mixture allows performing analyses in safe and green conditions. The effect of temperature at constant mobile phase composition was explored between 10 and 40 degrees C. In most cases, increasing the temperature improved the chiral separation, up to an optimum temperature. The results are discussed in line with the structure variation of the racemic derivatives analyzed and the two columns are compared. The two columns were shown to provide complementary selectivities for the investigated solutes: whereas Lux 1 provided separation for five of the six racemates, Lux 2 could resolve the last racemic mixture. Finally, optimized conditions of separation are defined. PMID:19551878

  20. Role of spinal cord alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors in complete Freund's adjuvant-induced inflammatory pain

    PubMed Central

    Park, Jang-Su; Yaster, Myron; Guan, Xiaowei; Xu, Ji-Tian; Shih, Ming-Hung; Guan, Yun; Raja, Srinivasa N; Tao, Yuan-Xiang

    2008-01-01

    Spinal cord ?-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) mediate acute spinal processing of nociceptive and non-nociceptive information, but whether and how their activation contributes to the central sensitization that underlies persistent inflammatory pain are still unclear. Here, we examined the role of spinal AMPARs in the development and maintenance of complete Freund's adjuvant (CFA)-induced persistent inflammatory pain. Intrathecal application of two selective non-competitive AMPAR antagonists, CFM-2 (25 and 50 ?g) and GYKI 52466 (50 ?g), significantly attenuated mechanical and thermal hypersensitivities on the ipsilateral hind paw at 2 and 24 h post-CFA injection. Neither CFM-2 nor GYKI 52466 affected the contralateral basal responses to thermal and mechanical stimuli. Locomotor activity was not altered in any of the drug-treated animals. CFA-induced inflammation did not change total expression or distribution of AMPAR subunits GluR1 and GluR2 in dorsal horn but did alter their subcellular distribution. The amount of GluR2 was markedly increased in the crude cytosolic fraction and decreased in the crude membrane fraction from the ipsilateral L4–5 dorsal horn at 24 h (but not at 2 h) post-CFA injection. Conversely, the level of GluR1 was significantly decreased in the crude cytosolic fraction and increased in the crude membrane fraction from the ipsilateral L4–5 dorsal horn at 24 h (but not at 2 h) post-CFA injection. These findings suggest that spinal AMPARs might participate in the central spinal mechanism of persistent inflammatory pain. PMID:19116032

  1. Orthogonal protecting groups for N(alpha)-amino and C-terminal carboxyl functions in solid-phase peptide synthesis.

    PubMed

    Albericio, F

    2000-01-01

    For the controlled synthesis of even the simplest dipeptide, the N(alpha)-amino group of one of the amino acids and the C-terminal carboxyl group of the other should both be blocked with suitable protecting groups. Formation of the desired amide bond can now occur upon activation of the free carboxyl group. After coupling, peptide synthesis can be continued by removal of either of the two protecting groups and coupling with the free C-terminus or N(alpha)-amino group of another protected amino acid. When three functional amino acids are present in the sequence, the side chain of these residues also has to be protected. It is important that there is a high degree of compatibility between the different types of protecting groups such that one type may be removed selectively in the presence of the others. At the end of the synthesis, the protecting groups must be removed to give the desired peptide. Thus, it is clear that the protection scheme adopted is of the utmost importance and makes the difference between success and failure in a given synthesis. Since R. B. Merrifield introduced the solid-phase strategy for the synthesis of peptides, this prerequisite has been readily accepted. This strategy is usually carried out using two main protection schemes: the tert-butoxycarbonyl/benzyl and the 9-flourenylmethoxycarbonyl/tert-butyl methods. However, for the solid-phase preparation of complex or fragile peptides, as well as for the construction of libraries of peptides or small molecules using a combinatorial approach, a range of other protecting groups is also needed. This review summarizes other protecting groups for both the N(alpha)-amino and C-terminal carboxyl functions. PMID:11074410

  2. Four-component reaction for the preparation of alpha-amino phosphonates from methyleneaziridines.

    PubMed

    Mumford, Peter M; Tarver, Gary J; Shipman, Michael

    2009-05-01

    Alpha-amino phosphonates can be rapidly assembled in moderate to good yields (42-65%) via a "one-pot" process that brings together four components through the construction of three new intermolecular bonds. PMID:19351179

  3. Synthesis of a conformationally constrained ?-amino acid building block.

    PubMed

    O'Reilly, Elaine; Pes, Lara; Ortin, Yannick; Müller-Bunz, Helge; Paradisi, Francesca

    2013-02-01

    Conformationally restricted amino acids are important components in peptidomimetics and drug design. Herein, we describe the synthesis of a novel, non-proteinogenic constrained delta amino acid containing a cyclobutane ring, cis-3(aminomethyl)cyclobutane carboxylic acid (ACCA). The synthesis of the target amino acid was achieved in seven steps, with the key reaction being a base induced intramolecular nucleophilic substitution. A small library of dipeptides was prepared through the coupling of ACCA with proteinogenic amino acids. PMID:22851051

  4. a,b-D-Constrained Nucleic Acids Are Strong Terminators of Thermostable DNA Polymerases in Polymerase Chain

    E-print Network

    Paris-Sud XI, Université de

    a,b-D-Constrained Nucleic Acids Are Strong Terminators of Thermostable DNA Polymerases, RP) a,b-D- Constrained Nucleic Acids (CNA) are dinucleotide building blocks that can feature either B. Citation: Marti´nez O, Ecochard V, Mahe´o S, Gross G, Bodin P, et al. (2011) a,b-D-Constrained Nucleic

  5. Evidence from Meteorites for Multiple Possible Amino Acid Alphabets for the Origins of Life

    NASA Technical Reports Server (NTRS)

    Burton, A. S.; Elsila, J. E.; Callahan, M. P.; Glavin, D. P.; Dworkin, J. P.

    2015-01-01

    A key question for the origins of life is understanding which amino acids made up the first proteins synthesized during the origins of life. The canonical set of 20 - 22 amino acids used in proteins are all alpha-amino, alpha-hydrogen isomers that, nevertheless, show considerable variability in properties including size, hydrophobicity, and ionizability. Abiotic amino acid synthesis experiments such as Miller-Urey spark discharge reactions produce a set of up to 23 amino acids, depending on starting materials and reaction conditions, with significant abundances of both alpha- and non-alpha-amino acid isomers. These two sets of amino acids do not completely overlap; of the 23 spark discharge amino acids, only 11 are used in modern proteins. Furthermore, because our understanding of conditions on the early Earth are limited, it is unclear which set(s) of conditions employed in spark discharge or hydrothermal reactions are correct, leaving us with significant uncertainty about the amino acid alphabet available for the origins of life on Earth. Meteorites, the surviving remnants of asteroids and comets that fall to the Earth, offer the potential to study authentic samples of naturally-occurring abiotic chemistry, and thus can provide an alternative approach to constraining the amino acid library during the origins of life.

  6. Stereospecific Synthesis of Conformationally Constrained ?-Amino Acids: New Foldamer Building Blocks that Support Helical Secondary Struture

    PubMed Central

    Guo, Li; Chi, Yonggui; Almeida, Aaron M.; Guzei, Ilia A.; Parker, Brian K.; Gellman, Samuel H.

    2010-01-01

    A highly stereoselective synthesis of novel cyclically constrained ?-amino acid residues is presented. The key step involves organocatalytic Michael addition of an aldehyde to 1-nitrocyclohexene. After aldehyde reduction, this approach provides optically active ?-substituted-?-nitro alcohols (96–99% e.e.), which can be converted to ?-amino acid amino acid residues with a variety of substituents at the ?-position. We have used these new building blocks to prepare ?/?-peptide foldamers that adopt a specific helical conformation in solution and in the solid state. PMID:19886693

  7. Oxygen Consumption Constrains Food Intake in Fish Fed Diets Varying in Essential Amino Acid Composition

    PubMed Central

    Saravanan, Subramanian; Geurden, Inge; Figueiredo-Silva, A. Cláudia; Nusantoro, Suluh; Kaushik, Sadasivam; Verreth, Johan; Schrama, Johan W.

    2013-01-01

    Compromisation of food intake when confronted with diets deficient in essential amino acids is a common response of fish and other animals, but the underlying physiological factors are poorly understood. We hypothesize that oxygen consumption of fish is a possible physiological factor constraining food intake. To verify, we assessed the food intake and oxygen consumption of rainbow trout fed to satiation with diets which differed in essential amino acid (methionine and lysine) compositions: a balanced vs. an imbalanced amino acid diet. Both diets were tested at two water oxygen levels: hypoxia vs. normoxia. Trout consumed 29% less food under hypoxia compared to normoxia (p<0.001). Under both hypoxia and normoxia trout significantly reduced food intake by 11% and 16% respectively when fed the imbalanced compared to the balanced amino acid diet. Oxygen consumption of the trout per unit body mass remained identical for both diet groups not only under hypoxia but also under normoxia (p>0.05). This difference in food intake between diets under normoxia together with the identical oxygen consumption supports the hypothesis that food intake in fish can be constrained by a set-point value of oxygen consumption, as seen here on a six-week time scale. PMID:23991148

  8. Thiopeptide synthesis. {alpha}-amino thionoacid derivatives of nitrobenzotriazole as thioacylating agents

    SciTech Connect

    Shalaby, M.A.; Grote, C.W.; Rapoport, H. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States)

    1996-12-13

    There has been considerable interest recently in the synthesis and properties of thiopeptides in which the -CSNH- group replaces one or more peptide bonds. These modified peptides have demonstrated increased activity in vivo as biological response modifiers, neuro-effectors, and immunomodulators due to the stability of their thioamide bonds toward enzymatic degradation as compared to that of their oxygenated counterpart. Synthetic routes employed to prepare these thiopeptides included replacement of oxygen by sulfur using P{sub 4}S{sub 10} or Lawesson`s phosphetane disulfide reagent, and thioesters or dithioesters of N-protected amino acids. Several procedures also have been reported for monothionation of peptides using N-protected amino monothioacids and benzotriazolyloxytris(pyrrolidino) phosphonium hexafluorophosphate (PYBOP) and some of its derivatives. Unfortunately, these methods displayed lack of reaction site specificity, low yields and purity because of side reactions, and loss of enantiomeric integrity in the final product, apparently because of racemization induced by the thioacylating agents. Recently, major improvement was described for the site specific incorporation of thioamide linkages into a growing peptide under mild conditions using thioacylbenzimidazolinones of amino acid derivatives as thioacylating agents. This method proceeds with about 2% loss of enantiomeric purity, as demonstrated by HPLC analysis of the reaction product 10a, formed in reaction with {alpha}-methylbenzylamine. This procedure, although superior to previous methods, still suffers from the formation of benzimidazole 2 as a significant byproduct, and the overall yield for the four-step process was only about 20%. Furthermore, recent attempt to use this procedure failed due to the limited reactivity of the benzimidazolinone 4 as a thioacylating agent. To overcome these limitations, the authors have developed a new method for thiopeptide synthesis. 12 refs.

  9. Insertion of multiple alpha-amino gamma-lactam (Agl) residues into a peptide sequence by solid-phase synthesis on synphase lanterns.

    PubMed

    Ronga, Luisa; Jamieson, Andrew G; Beauregard, Kim; Quiniou, Christiane; Chemtob, Sylvain; Lubell, William D

    2010-01-01

    The insertion of lactams into peptide analogs can enhance potency and improve receptor selectivity. The synthesis of lactam-bridged peptide sequences has been accomplished by a solid-phase approach on SynPhase lanterns using cyclic (R)- and (S)-oxathiazinane ester (2) to annulate the amino lactam residue onto the peptide chain. Parallel synthesis of alpha-amino gamma-lactam analogs of the allosteric modulator of IL-1 receptor 101.10 (D-Arg-D-Tyr-D-Thr-D-Val-D-Glu-D-Leu-D-Ala: rytvela) was performed by split-mix chemistry on the lanterns. In particular, the double insertion of alpha-amino gamma-lactams in the same peptide sequence has been accomplished by this effective method for the solid-supported combinatorial synthesis of lactam-bridged peptides. Peptides bearing an Agl residue exhibited curve shapes indicative of turn conformations in their circular dichroism spectra. PMID:20225301

  10. Synthesis of homochiral tris(2-alkyl-2-aminoethyl)amine derivatives from chiral alpha-amino aldehydes and their application in the synthesis of water soluble chelators.

    PubMed

    Hajela, S P; Johnson, A R; Xu, J; Sunderland, C J; Cohen, S M; Caulder, D L; Raymond, K N

    2001-06-18

    A novel synthesis of 3-fold symmetric, homochiral tris(2-alkyl-2-aminoethyl)amine (TREN) derivatives is presented. The synthesis is general in scope, starting from readily prepared chiral alpha-amino aldehydes. The optical purity of the N-BOC protected derivatives of tris(2-methyl-2-aminoethyl)amine and tris(2-hydroxymethyl-2-aminoethyl)amine has been ascertained by polarimetry and chiral NMR chemical shift experiments. An X-ray diffraction study of the L-alanine derivative (tris(2-methyl-2-aminoethyl)amine.3 HCl, L-Ala(3)-TREN) is presented: crystals grown from ether diffusion into methanol are cubic, space group P2(1)3 with unit cell dimensions a = 11.4807(2) A, V = 1513.23(4) A(3), and Z = 4. Attachment of the triserine derived backbone tris(2-hydroxymethyl-2-aminoethyl)amine (L-Ser(3)-TREN) to three 3-hydroxy-1-methyl-2(1H)-pyridinonate (3,2-HOPO) moieties, followed by complexation with Gd(III) gives the complex Gd(L-Ser(3)-TREN-Me-3,2-HOPO)(H(2)O)(2), which is more water soluble than the parent Gd(TREN-Me-3,2-HOPO)(H(2)O)(2) and a promising candidate for magnetic resonance imaging (MRI) applications. Crystals of the chiral ferric complex Fe(L-Ser(3)-TREN-Me-3,2-HOPO) grown from ether/methanol are orthorhombic, space group P2(1)2(1)2(1), with unit cell dimensions a = 13.6290(2) A, b = 18.6117(3) A, c = 30.6789(3) A, V = 7782.0(2) A(3), and Z = 8. The solution conformation of the ferric complex has been investigated by circular dichroism spectroscopy. The coordination chemistry of this new ligand and its iron(III) and gadolinium(III) complexes has been studied by potentiometric and spectrophotometric methods. Compared to the protonation constants of previously studied polydentate 3,2-HOPO-4-carboxamide ligands, the sum of protonation constants (log beta(014)) of L-Ser(3)-TREN-Me-3,2-HOPO (24.78) is more acidic by 1.13 log units than the parent TREN-Me-3,2-HOPO. The formation constants for the iron(III) and gadolinium(III) complexes have been evaluated by spectrophotometric pH titration to be (log K) 26.3(1) and 17.2(2), respectively. PMID:11399194

  11. Dioxaphosphorinane-Constrained Nucleic Acid Dinucleotides as Tools for Structural Tuning of Nucleic Acids

    PubMed Central

    Catana, Dan-Andrei; Renard, Brice-Loïc; Maturano, Marie; Payrastre, Corinne; Tarrat, Nathalie; Escudier, Jean-Marc

    2012-01-01

    We describe a rational approach devoted to modulate the sugar-phosphate backbone geometry of nucleic acids. Constraints were generated by connecting one oxygen of the phosphate group to a carbon of the sugar moiety. The so-called dioxaphosphorinane rings were introduced at key positions along the sugar-phosphate backbone allowing the control of the six-torsion angles ? to ? defining the polymer structure. The syntheses of all the members of the D-CNA family are described, and we emphasize the effect on secondary structure stabilization of a couple of diastereoisomers of ?,?-D-CNA exhibiting wether B-type canonical values or not. PMID:23150809

  12. Structural Analysis of a ?-Helical Protein Motif Stabilized by Targeted Replacements with Conformationally Constrained Amino Acids

    PubMed Central

    Ballano, Gema; Zanuy, David; Jiménez, Ana I.; Cativiela, Carlos; Nussinov, Ruth; Alemán, Carlos

    2009-01-01

    Here we study conformational stabilization induced in a ?-helical nanostructure by position-specific mutations. The nanostructure is constructed through the self-assembly of the ?-helical building block excised from E. coli galactoside acetyltransferase (PDB code 1krr, chain A; residues 131-165). The mutations involve substitutions by cyclic, conformationally constrained amino acids. Specifically, a complete structural analysis of the Pro-Xaa-Val sequence [with Xaa being Gly, Ac3c (1-aminocyclopropane-1-carboxylic acid) and Ac5c (1-aminocyclopentane-1-carboxylic acid)], corresponding to the 148-150 loop region in the wild-type (Gly) and mutated (Ac3c and Ac5c) 1krr, has been performed using Molecular Dynamics simulations and X-ray crystallography. Simulations have been performed for the wild-type and mutants of three different systems, namely the building block, the nanoconstruct and the isolated Pro-Xaa-Val tripeptide. Furthermore, the crystalline structures of five peptides of Pro-Xaa-Val or Xaa-Val sequences have been solved by X-ray diffraction analysis and compared with theoretical predictions. Both the theoretical and crystallographic studies indicate that the Pro-Acnc-Val sequences exhibit a high propensity to adopt turn-like conformations, and this propensity is little affected by the chemical environment. Overall, the results indicate that replacement of Gly149 by Ac3c or Ac5c significantly reduce the conformational flexibility of the target site enhancing the structural specificity of the building block and the nanoconstruct derived from the 1krr ?-helical motif. PMID:18811190

  13. Strict reagent control in the asymmetric allylboration of N-TIPS-alpha-amino aldehydes with the B-allyl-10-TMS-9-borabicyclo[3.3.2]decanes.

    PubMed

    Soto-Cairoli, Buddy; Soderquist, John A

    2009-01-15

    The allylboration of enantiomerically pure N-triisopropylsilyl-alpha-amino aldehydes (2) with B-allyl-10-trimethylsilyl-9-borabicyclo[3.3.2]decanes (1) proceeds cleanly at -78 degrees C, exhibiting essentially complete reagent control. After an oxidative workup, an HOAc-mediated N-->O TIPS rearrangement facilitates the clean formation of stable O-TIPS protected beta-amino alcohol derivatives 3 which are isolated in 60-83% yields in > or = 96% de and > 99% ee. For the leucinal series (R = i-Bu), an efficient entry to either statine (8aSS) or epi-statine (8aRS) is reported illustrating the versatility of this potent 1/2 combination. PMID:19128190

  14. Conformationally constrained farnesoid X receptor (FXR) agonists: Naphthoic acid-based analogs of GW 4064.

    PubMed

    Akwabi-Ameyaw, Adwoa; Bass, Jonathan Y; Caldwell, Richard D; Caravella, Justin A; Chen, Lihong; Creech, Katrina L; Deaton, David N; Jones, Stacey A; Kaldor, Istvan; Liu, Yaping; Madauss, Kevin P; Marr, Harry B; McFadyen, Robert B; Miller, Aaron B; Iii, Frank Navas; Parks, Derek J; Spearing, Paul K; Todd, Dan; Williams, Shawn P; Wisely, G Bruce

    2008-08-01

    Starting from the known FXR agonist GW 4064 1a, a series of stilbene replacements were prepared. The 6-substituted 1-naphthoic acid 1b was an equipotent FXR agonist with improved developability parameters relative to 1a. Analog 1b also reduced the severity of cholestasis in the ANIT acute cholestatic rat model. PMID:18621523

  15. Discovery of Azetidinone Acids as Conformationally-Constrained Dual PPARalpha/gamma Agonists

    SciTech Connect

    Wang, W.; Devasthale, P; Farrelly, D; Gu, L; Harrity, T; Cap, M; Chu, C; Kunselman, L; Morgan, N; et. al.

    2008-01-01

    A novel class of azetidinone acid-derived dual PPAR{alpha}/{gamma} agonists has been synthesized for the treatment of diabetes and dyslipidemia. The preferred stereochemistry in this series for binding and functional agonist activity against both PPARa and PPAR? receptors was shown to be 3S,4S. Synthesis, in vitro and in vivo activities of compounds in this series are described. A high-yielding method for N-arylation of azetidinone esters is also described.

  16. Design and synthesis of conformationally constrained 3-( N-alkylamino)propylphosphonic acids as potent agonists of sphingosine-1-phosphate (S1P) receptors

    Microsoft Academic Search

    Lin Yan; Jeffrey J. Hale; Christopher L. Lynch; Richard Budhu; Amy Gentry; Sander G. Mills; Richard Hajdu; Carol Ann Keohane; Mark J. Rosenbach; James A. Milligan; Gan-Ju Shei; Gary Chrebet; James Bergstrom; Deborah Card; Hugh Rosen; Suzanne M. Mandala

    2004-01-01

    A series of conformationally constrained 3-(N-alkylamino)propylphosphonic acids were systematically synthesized and their activities as S1P receptor agonists were evaluated. Several pyrrolidine and cyclohexane analogs had S1P receptor profiles comparable to the acyclic lead compound, 3-(N-tetradecylamino)propylphosphonic acid (3), lowered circulating lymphocytes in mice after iv administration and were thus identified as being suitable for further investigations.

  17. A new stereoselective synthesis of sterically constrained uncommon ?,??-dialkylated ?-amino acids. Part 2 1 Ref. 1 is considered to be Part 1. 1

    Microsoft Academic Search

    Gianni Porzi; Sergio Sandri

    1998-01-01

    The alkylation of the diastereomeric mixture of the chiral morpholinone derivatives 5 and 6 occurs with good yield and a prevalence of the cis isomer. Cleavage of the alkylated intermediates 7b,c yields enantiomerically pure sterically constrained uncommon ?,??-dialkylated ?-amino acids. The absolute configuration of the new stereocentres has been assigned on the basis of the 1H NMR spectra and NOE

  18. An investigation of vitamin B-6 catalyzed reactions of some aminophosphonic acids in model systems

    E-print Network

    Langohr, Michael Frederick

    1975-01-01

    , and love this work would not have been possible. TABLE OP CONTEKTS Introduction Transamination Racemization Beta-elimination Gamma-elimination Carbon-carbon Bond CleavaEe Decarboxylation Oxidative Deamination Aminophosphonic Acids 8 13 15... of an Optically Active Amino acid The Mechanism of Beta-elimination 6 A Mechansim for Gamma-elimination 7 The Mechanism of Degradation (or synthesis) of Beta-hydroxy-alpha Amino Acids 8 A Mechanism for Decarboxylation of an Amino Acid 16 18 20 23 9...

  19. Reasons for the occurrence of the twenty coded protein amino acids

    NASA Technical Reports Server (NTRS)

    Weber, A. L.; Miller, S. L.

    1981-01-01

    Factors involved in the selection of the 20 protein L-alpha-amino acids during chemical evolution and the early stages of Darwinian evolution are discussed. The selection is considered on the basis of the availability in the primitive ocean, function in proteins, the stability of the amino acid and its peptides, stability to racemization, and stability on the transfer RNA. It is concluded that aspartic acid, glutamic acid, arginine, lysine, serine and possibly threonine are the best choices for acidic, basic and hydroxy amino acids. The hydrophobic amino acids are reasonable choices, except for the puzzling absences of alpha-amino-n-butyric acid, norvaline and norleucine. The choices of the sulfur and aromatic amino acids seem reasonable, but are not compelling. Asparagine and glutamine are apparently not primitive. If life were to arise on another planet, it would be expected that the catalysts would be poly-alpha-amino acids and that about 75% of the amino acids would be the same as on the earth.

  20. Carboxylic Acids as Indicators of Parent Body Conditions

    NASA Astrophysics Data System (ADS)

    Lerner, N. R.

    1995-09-01

    Alpha-hydroxy and alpha-amino carboxylic acids found on the Murchison meteorite are deuterium enriched [1]. It is postulated that they arose from a common interstellar source: the reaction of carbonyl compounds in an aqueous mixture containing HCN and NH3. Carbonyl compounds react with HCN to form alph-hydroxy nitriles, RR'CO + HCN <--> RR'C(OH)CN. If ammonia is also present, the alpha-hydroxy nitriles will exist in equilibirum with the alpha-amino nitriles, RR'C(OH)CN +NH3 .<--> RRCNH2CN + H2O. Both nitriles are hydrolyzed by water to form carboxylic acids: RR'C(OH)CN + H2O --> RR'C(OH)CO2H and RR'C(NH2)CN + H2O --> RR'C(NH2)CO2H. Carbonyl compounds observed in the interstellar medium have been shown to be deuterium enriched [2]. The combined alpha-amino acids found on Murchison have deltaD = +1751 o/oo while the combined alpha-hydroxy acids have deltaD = +573. o/oo [1]. This large discrepancy in deltaD values does not preclude common precursors for the alpha-amino acids and the alpha-hydroxy acids. Different relative amounts of specific alpha-amino and alpha-hydroxy acids could lead to quite different combined D/H ratios. If the alpha-hydroxy acids lose significantly more deuterium during synthesis than the alpha-amino acids or if they have a higher rate of H/D exchange with liquid water than alpha-amino acids, the alpha-hydroxy acids would be isotopically lighter than the alpha-amino acids, because the water responsible for the aqueous alteration of the Murchison parent body was deuterium depleted with deltaD = -100. o/oo [3]. To determine between these alternative mechanisms we measured the rates of hydrogen-deuterium exchange of glycolic acid (the alpha-hydroxy analog of glycine), lactic acid (the alpha-hydroxy analog of alanine), and alpha-hydroxy isobutyric acid have been measured in D2O as a function of pH, temperature and the presence of Allende or Murchison minerals. No detectable H/D exchange was observed. Glycine subjected to similar conditons exchanged as much as 80% of its carbon-bonded deuterium, and alanine 43% [4]. Evidently, the relative deuterium content of the alpha-amino acids and alpha-hydroxy acids found on the Murchison meteorite was not determined by H/D exchange with water. In order to determine if deuterium retention is less for alpha-hydroxy acids than it is for alpha-amino carboxylic acids during synthesis a solution was prepared containing: KCN, 0.005M; NH4Cl, 0.002 M; CD2O, 0.0007M; CD3CDO, 0.0008 M; and (CD3)2CO 0.0006 M, and divided into aliquots which were maintained at 263 K and at 295 K. At the end of one month the carbonyls, alpha-amino acids and alpha-hydroxy acids were separated from the mixture and their deuterium content determined from their mass spectra (see Table 1). The retention of deuterium during synthesis varies significantly between the alpha-hydroxy acids and the alpha-amino acids with common precursors. Only comparisons of D/H ratios of specific acids with a postulated common precursor are meaningful. References: [1] Cronin J. R. et al. (1993) GCA, 57, 4745-4752. [2] Zinner E. (1988) in Meteorites and the Early Solar System (J. R. Kerridge and M. S. Matthews, eds.), 956-983, Univ. of Arizona. [3] Robert F. and Epstein S. (1982) GCA, 46, 81-95. [4] Lerner N. R. (1995) GCA, 59, 1623-1631. Table 1 shows D/(D+H) of carbon-bonded hydrogen in compounds separated after one month from a simulated meteorite solution.

  1. Carboxylic Acids as Indicators of Parent Body Conditions

    NASA Technical Reports Server (NTRS)

    Lerner N. R.; Chang, Sherwood (Technical Monitor)

    1995-01-01

    Alpha-hydroxy and alpha-amino carboxylic acids found on the Murchison meteorite are deuterium enriched. It is postulated that they arose from a common interstellar scurce: the reaction of carbonyl compounds in an aqueous mixture containing HCN and NH3. Carbonyl compounds react with HCN to form alpha-hydroxy nitriles, RR'CO + HCN right and left arrow RR'C(OH)CN. If ammonia is also present, the alpha-hydroxy nitriles will exist in equilibrium with the alpha-amino nitriles, RR'C(OH)CN + NH3 right and left arrow - RRCNH2CN + H2O. Both nitrites are hydrolyzed by water to form carboxylic acids: RR'C(OH)CN + H2O yields RR'C(OH)CO2H and RR'C(NH2)CN + H2O yields RR'C(NH2)CO2H.

  2. Influence of phospholids on liver damage. I. Carbontetrachloride poisoning and alterations in amino acid uptake, peroxidation, sialic acid content, and lysosomal enzymes.

    PubMed

    Gerber, G B; Bartsch, G G; Deroo, J

    1975-06-01

    Changes in peroxidation, amino acid uptake [alpha-amino isobutyrate (AIB)], sialic acid content and lysosomal enzymes were followed in rats after carbon-tetrachloride enzymes were followed in rats after carbontetrachloride poisoning and treatment with phospholipids (EPL). Uptake and retention of AIB by liver and brain increased after CCI4 poisoning. EPL had no effect on these changes. EPL diminished markedly, however, the excessive peroxidation caused by CC14. PMID:1220510

  3. The Southern Ocean silicon trap: Data-constrained estimates of regenerated silicic acid, trapping efficiencies, and global transport paths

    NASA Astrophysics Data System (ADS)

    Holzer, Mark; Primeau, François W.; DeVries, Timothy; Matear, Richard

    2014-01-01

    We analyze an optimized model of the global silicon cycle embedded in a data-assimilated steady ocean circulation. Biological uptake is modeled by conditionally restoring silicic acid in the euphotic zone to observed concentrations where the modeled concentrations exceed the observational climatology. An equivalent linear model is formulated to which Green-function-based transport diagnostics are applied. We find that the models' opal export through 133 m depth is 166 ± 24 Tmol Si/yr, with the Southern Ocean (SO) providing ˜70% of this export, ˜50% of which dissolves above 2000 m depth. The global-scale gradients of the opal dissolution rate are primarily meridional, while the global-scale gradients of phosphate remineralization are primarily vertical. The mean depth of the temperature-dependent silicic-acid regeneration reaches 2300 m in the SO, compared to 600 m for phosphate remineralization. Silicic acid is stripped out of the euphotic zone far more efficiently than phosphate, with only (34 ± 5)% of the global silicic-acid inventory being preformed, compared to (61 ± 7)% for phosphate. Subantarctic and tropical waters contribute most of the ocean's regenerated silicic acid, while Antarctic waters provide most of the preformed silicic acid. About half of the global silicic-acid inventory is trapped in transport paths connecting successive SO utilizations, with silicic acid last utilized in the SO having only a (5 ± 2)% chance of being next utilized outside the SO. This trapping depletes subantarctic mode waters of silicic acid relative to phosphate, which has a (44 ± 2)% probability of escaping successive SO utilization.

  4. Innershell absorption spectroscopy of amino acids at all relevant absorption edges.

    PubMed

    Zubavichus, Yan; Shaporenko, Andrey; Grunze, Michael; Zharnikov, Michael

    2005-08-18

    The C, N, and O K-edge near-edge X-ray absorption fine structure spectra of the 22 most common proteinogenic alpha-amino acids in the zwitterionic form collected from solvent-free polycrystalline powder films in the partial electron yield mode are reported. Spectral features common to all amino acids, as well as distinctive fingerprints of specific subgroups of these compounds, are presented and discussed. PMID:16834062

  5. N-halo derivatives III: stabilization of nitrogen-chlorine bond in N-chloroamino acid derivatives.

    PubMed

    Kaminski, J J; Bodor, N; Higuchi, T

    1976-04-01

    The chlorination of alpha-amino acids and their related derivatives was investigated. A kinetic study of the stability of these N-chlorinated products led to an elucidation of the factors that significantly influence the stability and reactivity of the nitrogen-chlorine bond in these N-chloramines. From the kinetic investigations, a series of low chlorine potential, soft antimicrobial N-chloramines was developed based on derivatives of alpha-aminoisobutyric acid and related compounds. PMID:1271254

  6. Effects of metabolic intermediates on sugar and amino acid uptake in rabbit renal tubules and brush border membranes.

    PubMed Central

    Kippen, I; Klinenberg, J R; Wright, E M

    1980-01-01

    1. The effects of tricarboxylic acid cycle intermediates on the renal transport of alpha-methyl-D-glucoside and alpha-amino-isobutyric acid were examined using separated renal tubules of the rabbit. 2. The effect of citrate on alpha-methyl-D-glucoside and alpha-amino-isobutyric acid uptake was markedly biphasic with maximum stimulation of transport occurring at a citrate concentration of 0.64 mM. Biphasic effects were also apparent for L-malate, succinate, fumarate, alpha-ketoglutarate and oxaloacetate. 3. The route of uptake of alpha-methyl-D-glucoside into separated renal tubules is primarily across the brush border (luminal) membrane. 4. Tricarboxylic acid cycle intermediates produced significant stimulation of renal O2 consumption; however, the effects on O2 consumption were not biphasic suggesting that reduced stimulation of transport at high substrate concentration was not caused by a reduction in the supply of metabolic energy. 5. In purified renal cortical brush border membrane vesicles, citrate and alpha-ketoglutarate inhibited the uptake of alpha-methyl-D-glucoside and alpha-amino-isobutyric acid indicating that inhibition of their transport in respiring renal tubules by high concentrations of tricarboxylic acid cycle intermediates occurs via an effect at the membrane level. PMID:7441540

  7. Amino Acid Chemistry as a Link Between Small Solar System Bodies and Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Ehrenfreund, Pascale; Botta, Oliver; Cooper, George; Bada, Jeffrey L.

    2000-01-01

    Establishing chemical links between meteorites and small solar system bodies, such as comets and asteroids, provides a tool for investigating the processes that occurred during the formation of the solar system. Carbonaceous meteorites are of particular interest, since they may have seeded the early Earth with a variety of prebiotic organic compounds including amino acids, purines and pyrimidines, which are thought to be necessary for the origin of life. Here we report the results of high-performance liquid chromatography (HPLC) based amino acid analyses of the acid-hydrolyzed hot water extracts from pristine interior pieces of the CI carbonaceous chondrites Orgueil and Ivuna and the CM meteorites Murchison and Murray. We found that the CI meteorites Orgueil and Ivuna contained high abundances of beta-alanine and glycine, while only traces of other amino acids like alanine, alpha-amino-n-butryic acid (ABA) and alpha-aminoisobutyric acid (AIB) were detected in these meteorites. Carbon isotopic measurements of beta-alanine and glycine in Orgueil by gas chromatography combustion-isotope ratio mass spectrometry clearly indicate an extraterrestrial origin of these amino acids. The amino acid composition of Orgueil and Ivuna was strikingly different from the CM chondrites Murchison and Murray. The most notable difference was the high relative abundance of B-alanine in Orgueil and Ivuna compared to Murchison and Murray. Furthermore, AIB, which is one of the most abundant amino acids found in Murchison and Murray, was present in only trace amounts in Orgueil and Ivuna. Our amino acid data strongly suggest that the CI meteorites Orgueil and Ivuna came from a different type of parent body than the CM meteorites Murchison and Murray, possibly from an extinct comet. It is generally thought that carbonaceous meteorites are fragments of larger asteroidal bodies delivered via near Earth objects (NEO). Orbital and dynamic studies suggest that both fragments of main belt asteroids and comets replenish the NEO population, therefore extinct comets may contribute up to half of all NEO's. A comparison of an amino acid analysis of a returned NEO sample to CI and CM carbonaceous chondrites would help establish a link between small solar system bodies and meteorites. Based on our amino acid measurements of CI and CM chondrites, amino acid chemistry can be included as an additional set of criteria to constrain the nature of meteorite parent bodies.

  8. Exact and efficient calculation of Lagrange multipliers in constrained biological polymers: Proteins and nucleic acids as example cases

    E-print Network

    García-Risueño, Pablo; Alonso, José Luis

    2011-01-01

    In order to accelerate molecular dynamics simulations, it is very common to impose holonomic constraints on their hardest degrees of freedom. In this way, the time step used to integrate the equations of motion can be increased, thus allowing, in principle, to reach longer total simulation times. The imposition of such constraints results in an aditional set of Nc equations (the equations of constraint) and unknowns (their associated Lagrange multipliers), that must be solved in one way or another at each time step of the dynamics. In this work it is shown that, due to the essentially linear structure of typical biological polymers, such as nucleic acids or proteins, the algebraic equations that need to be solved involve a matrix which is banded if the constraints are indexed in a clever way. This allows to obtain the Lagrange multipliers through a non-iterative procedure, which can be considered exact up to machine precision, and which takes O(Nc) operations, instead of the usual O(Nc3) for generic molecular...

  9. Kinetics and mechanism of decomposition of N-chloroamino acids. II: conformationally restricted models.

    PubMed

    Awad, R; Hussain, A; Crooks, P A

    1990-12-01

    The kinetics of decomposition of the following conformationally restricted N-chloro-alpha-amino acids were studied: 1-amino-1-cyclopentanecarboxylic acid (2), 1-amino-1-cyclohexanecarboxylic acid (4), 2-amino-2-norbornanecarboxylic acid (6), and 2-amino-2-benzonorbornanecarboxylic acid (8). The first-order rate constants obtained were 0.520, 5.197, 0.198, and 0.078, respectively, which correlated with the ring strain in the structurally related cyclic ketones cyclopentanone, cyclohexanone, norborane-2-one, and benzonorbornane-2-one. The data are supportive of a concerted mechanism for the decomposition reaction involving an imine-like transition state. PMID:2079660

  10. An investigation of vitamin B-6 catalyzed reactions of some aminophosphonic acids in model systems 

    E-print Network

    Langohr, Michael Frederick

    1975-01-01

    Imine Formation Constants for the Imine Derived from PL and 2-AEP 25 54 58 LIST OF FIGURES FIGURE PAGE 1 Formation of an Aldimine Chelate 2 Bis-terdentate Chelate of Pyridox- ylidene Amino Acid 3 The Mechanism of Transamination 4 Racemization... of an Optically Active Amino acid The Mechanism of Beta-elimination 6 A Mechansim for Gamma-elimination 7 The Mechanism of Degradation (or synthesis) of Beta-hydroxy-alpha Amino Acids 8 A Mechanism for Decarboxylation of an Amino Acid 16 18 20 23 9...

  11. Characteristics and formation of amino acids and hydroxy acids of the Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.; Cooper, G. W.; Pizzarello, S.

    1995-01-01

    Eight characteristics of the unique suite of amino acids and hydroxy acids found in the Murchison meteorite can be recognized on the basis of detailed molecular and isotopic analyses. The marked structural correspondence between the alpha-amino acids and alpha-hydroxy acids and the high deuterium/hydrogen ratio argue persuasively for their formation by aqueous phase Strecker reactions in the meteorite parent body from presolar, i.e., interstellar, aldehydes, ketones, ammonia, and hydrogen cyanide. The characteristics of the meteoritic suite of amino acids and hydroxy acids are briefly enumerated and discussed with regard to their consonance with this interstellar-parent body formation hypothesis. The hypothesis has interesting implications for the organic composition of both the primitive parent body and the presolar nebula.

  12. The spark discharge synthesis of amino acids from various hydrocarbons

    NASA Technical Reports Server (NTRS)

    Ring, D.; Miller, S. L.

    1984-01-01

    The spark discharge synthesis of amino acids using an atmosphere of CH4+N2+H2O+NH3 has been investigated with variable pNH3. The amino acids produced using higher hydrocarbons (ethane, ethylene, acetylene, propane, butane, and isobutane) instead of CH4 were also investigated. There was considerable range in the absolute yields of amino acids, but the yields relative to glycine (or alpha-amino-n-butyric acid) were more uniform. The relative yields of the C3 to C6 aliphatic alpha-amino acids are nearly the same (with a few exceptions) with all the hydrocarbons. The glycine yields are more variable. The precursors to the C3-C6 aliphatic amino acids seem to be produced in the same process, which is separate from the synthesis of glycine precursors. It may be possible to use these relative yields as a signature for a spark discharge synthesis provided corrections can be made for subsequent decomposition events (e.g. in the Murchison meteorite).

  13. Thermal copoly/amino acids/ as inhibitors of glyoxalase I

    NASA Technical Reports Server (NTRS)

    Fox, S. W.; Syren, R. M.; Windsor, C. R.

    1979-01-01

    A number of copoly(alpha-amino acids) have been prepared thermally; some have been found to function as inhibitors of glyoxalase I, an enzyme which occupies a central position in Szent-Gyorgyi's theory of tumour genesis. These polymers are also of interest in the search for synthetic peptides having carcinostatic activity, since many natural peptides are active. The way in which the inhibitory activity varies with composition of the synthetic polymers has been investigated. Various properties (hydrophobicity, molecular weight, UV absorption, kinetic type) have been examined in a search for correlates of inhibitory activity.

  14. Selective tert-butyl ester deprotection in the presence of acid labile protecting groups with use of ZnBr2.

    PubMed

    Kaul, Ramesh; Brouillette, Yann; Sajjadi, Zohreh; Hansford, Karl A; Lubell, William D

    2004-09-01

    Chemoselective hydrolysis of tert-butyl esters in the presence of other acid-labile groups has been explored by employing alpha-amino esters and ZnBr(2) in DCM. Although N-Boc and N-trityl groups were found to be labile, PhF protected amines were compatible with these Lewis acid deprotection conditions such that a variety of N-(PhF)amino acids were prepared in good yields from their corresponding tert-butyl esters. PMID:15373501

  15. Copper(II) diamino acid complexes: quantum chemical computations regarding diastereomeric effects on the energy of complexation.

    PubMed

    Zuilhof, Han; Morokuma, Keiji

    2003-08-21

    [reaction: see text] Quantum chemical calculations were used to rationalize the observed enantiodifferentiation in the complexation of alpha-amino acids to chiral Cu(II) complexes. Apart from Cu(II)[bond]pi interactions and steric repulsions between the anchoring cholesteryl-Glu moiety and an aromatic amino acid R group, hydrogen bonding also plays a role. In fact, in the case of tryptophan, C[double bond]O...H[bond]N hydrogen bonding between the glutamate moiety and the tryptophan N[bond]H group compensates for the loss of intramolecular hydrogen-bonding and diminished Cu(II)[bond]pi interactions. PMID:12916986

  16. Characterization of the cereulide NRPS alpha-hydroxy acid specifying modules: activation of alpha-keto acids and chiral reduction on the assembly line.

    PubMed

    Magarvey, Nathan A; Ehling-Schulz, Monika; Walsh, Christopher T

    2006-08-23

    Several nonribosomal peptide natural products are composites of alpha-hydroxy acid and alpha-amino acid monomers. Cereulide, the emetic toxin from the human pathogen Bacillus cereus, and valinomycin, from Streptomyces spp., are closely related macrocyclic K+ ionophores. The macrocyclic core of each natural product contains alternating peptide (six) and ester (six) bonds, and their cyclododecadepsipeptide structures consist of a tetradepsipeptide unit repeated three times. Here we overexpress the cereulide NRPS alpha-hydroxy acid specifying modules from CesA and CesB and demonstrate that each contains an alpha-keto acid activating adenylation domain and a chiral alpha-ketoacyl-S-carrier protein reductase (alpha-KR). The logic used by the cereulide NRPS is likely at work in the valinomycin NRPS and may be the general strategy used in bacterial NRPSs to form alpha-hydroxy acid containing natural products. PMID:16910662

  17. The Strecker synthesis from interstellar precursors as a source of amino acids in carbonaceous chondrites: Deuterium retention during synthesis. [Abstract only

    NASA Technical Reports Server (NTRS)

    Lerner, N. R.; Peterson, E.; Chang, S.

    1994-01-01

    Amino acids in the Murchison carbonaceous chondrite are anomalously enriched in deuterium. Synthesis in Strecker reactions from D-enriched interstellar precursors during low temperature aqueous alteration of the parent body has been proposed by Cronin et al. (1988) to account for the isotopic observations. To test this hypothesis, we have measured the retention of deuterium in the glycine, alanine, and alpha-amino isobutyric acid produced, respectively, by reactions of formaldehyde-D2, acetaldehyde-D4, and acetone-D6 with HCN and NH3 in water.

  18. Splice junctions are constrained by protein disorder

    PubMed Central

    Smithers, Ben; Oates, Matt E.; Gough, Julian

    2015-01-01

    We have discovered that positions of splice junctions in genes are constrained by the tolerance for disorder-promoting amino acids in the translated protein region. It is known that efficient splicing requires nucleotide bias at the splice junction; the preferred usage produces a distribution of amino acids that is disorder-promoting. We observe that efficiency of splicing, as seen in the amino-acid distribution, is not compromised to accommodate globular structure. Thus we infer that it is the positions of splice junctions in the gene that must be under constraint by the local protein environment. Examining exonic splicing enhancers found near the splice junction in the gene, reveals that these (short DNA motifs) are more prevalent in exons that encode disordered protein regions than exons encoding structured regions. Thus we also conclude that local protein features constrain efficient splicing more in structure than in disorder. PMID:25934802

  19. A reexamination of amino acids in lunar soil

    NASA Technical Reports Server (NTRS)

    Brinton, K. L. F.; Bada, J. L.; Arnold, J. R.

    1993-01-01

    Amino acids in lunar soils provide an important indicator of the level of prebiotic organic compounds on the moon. The results provide insight into the chemistry of amino acid precursors, and furthermore, given the flux of carbonaceous material to the moon, we can evaluate the survival of organics upon impact. The amino acid contents of both hydrolyzed and unhydrolyzed hot-water extracts of Apollo 17 lunar soil were determined using ophthaldialdehyde/N-acetyl cysteine (OPA/NAC) derivatization followed by HPLC analysis. Previous studies of lunar amino acids were inconclusive, as the technique used (derivatization with ninhydrin followed by HPLC analysis) was unable to discriminate between cosmogenic amino acids and terrestrial contaminants. Cosmogenic amino acids are racemic, and many of the amino acids found in carbonaceous meteorites such as Murchison, i.e., alpha-amino-i-butyric acid (aib), are extremely rare on Earth. The ninhydrin method does not distinguish amino acid enantiomers, nor does it detect alpha-alkyl amino acids such as aib, whereas the OPA/NAC technique does both.

  20. Interaction of metal ions and amino acids - Possible mechanisms for the adsorption of amino acids on homoionic smectite clays

    NASA Technical Reports Server (NTRS)

    Gupta, A.; Loew, G. H.; Lawless, J.

    1983-01-01

    A semiempirical molecular orbital method is used to characterize the binding of amino acids to hexahydrated Cu(2+) and Ni(2+), a process presumed to occur when they are adsorbed in the interlamellar space of homoionic smectite clays. Five alpha-amino acids, beta-alanine, and gamma-aminobutyric acid were used to investigate the metal ion and amino acid specificity in binding. It was assumed that the alpha, beta, and gamma-amino acids would bind as bidentate anionic ligands, forming either 1:1 or 1:2 six-coordinated five, six, and seven-membered-ring chelate complexes, respectively. Energies of complex formation, optimized geometries, and electron and spin distribution were determined; and steric constraints of binding of the amino acids to the ion-exchanged cations in the interlamellar spacing of a clay were examined. Results indicate that hexahydrated Cu(2+) forms more stable complexes than hexahydrated Ni(2+) with all the amino acids studied. However, among these amino acids, complex formation does not favor the adsorption of the biological subset. Calculated energetics of complex formation and steric constraints are shown to predict that 1:1 rather than 1:2 metal-amino acid complexes are generally favored in the clay.

  1. Maternal nutrient restriction reduces concentrations of amino acids and polyamines in ovine maternal and fetal plasma and fetal fluids.

    PubMed

    Kwon, Hyukjung; Ford, Stephen P; Bazer, Fuller W; Spencer, Thomas E; Nathanielsz, Peter W; Nijland, Mark J; Hess, Bret W; Wu, Guoyao

    2004-09-01

    Amino acids and polyamines are essential for placental and fetal growth, but little is known about their availability in the conceptus in response to maternal undernutrition. We hypothesized that maternal nutrient restriction reduces concentrations of amino acids and polyamines in the ovine conceptus. This hypothesis was tested in nutrient-restricted ewes between Days 28 and 78 (experiment 1) and between Days 28 and 135 (experiment 2) of gestation. In both experiments, ewes were assigned randomly on Day 28 of gestation to a control group fed 100% of National Research Council (NRC) nutrient requirements and to an nutrient-restricted group fed 50% of NRC requirements. Every 7 days beginning on Day 28 of gestation, ewes were weighed and rations adjusted for changes in body weight. On Day 78 of gestation, blood samples were obtained from the uterine artery and umbilical vein for analysis. In experiment 2, nutrient-restricted ewes on Day 78 of gestation either continued to be fed 50% of NRC requirements or were realimented to 100% of NRC requirements until Day 135. Fetal weight was reduced in nutrient-restricted ewes at both Day 78 (32%) and Day 135 (15%) compared with controls. Nutritional restriction markedly reduced (P < 0.05) concentrations of total alpha-amino acids (particularly serine, arginine-family amino acids, and branched-chain amino acids) and polyamines in maternal and fetal plasma and in fetal allantoic and amniotic fluids at both mid and late gestation. Realimentation of nutrient-restricted ewes increased (P < 0.05) concentrations of total alpha-amino acids and polyamines in all the measured compartments and prevented intrauterine growth retardation. These novel findings demonstrate that 50% global nutrient restriction decreases concentrations of amino acids and polyamines in the ovine conceptus that could adversely impact key fetal functions. The results have important implications for understanding the mechanisms responsible for both intrauterine growth retardation and developmental origins of adult disease. PMID:15140798

  2. Softly Constrained Films

    E-print Network

    Luca Giomi

    2013-04-03

    The shape of materials is often subject to a number of geometric constraints that limit the size of the system or fix the structure of its boundary. In soft and biological materials, however, these constraints are not always hard, but are due to other physical mechanisms that affect the overall force balance. A capillary film spanning a flexible piece of wire or a cell anchored to a compliant substrate by mean of adhesive contacts are examples of these softly constrained systems in the macroscopic and microscopic world. In this article I review some of the important mathematical and physical developments that contributed to our understanding of shape formation in softly constrained films and their recent application to the mechanics of adherent cells.

  3. Constraining Entropic Cosmology

    E-print Network

    Koivisto, Tomi S; Zumalacarregui, Miguel

    2010-01-01

    It has been recently proposed that the interpretation of gravity as an emergent, entropic force might have nontrivial implications to cosmology. Here two approaches are investigated: in one, the Friedman equation receives entropic contributions from the usually neglected surface terms, and in another, the extra terms are derived from quantum corrections to the entropy formula. UV terms may drive inflation, avoiding a recently derived no-go theorem, though in some cases leading to a graceful exit problem. IR terms can generate dark energy, alleviating the cosmological constant problem. The quantum corrections are bounded by their implications to the BBN, and the surface terms are constrained in addition by their effect upon the behavior of matter. Likelihood analyses are performed to constrain the modifications by the SNeIa, BAO and CMB data. It is found that a monomial correction to the area-entropy formula results in late acceleration in very good agreement with observations, which then turn out to be compat...

  4. Polynomial and Constrained Eigenproblems

    E-print Network

    Vorst, Henk A.

    a so­called constrained eigenprob­ lem. In Section 56 we will pay attention to the important class of quadratic eigenproblems, with a small sidestep to higher order polynomial eigenprob­ lems. These quadratic the quadratic eigenvalue prob­ lem (QEP) of the form (â?? 2 M + â??C +K)x = 0 and y \\Lambda (â?? 2 M + â??C +K) = 0; (56

  5. Constrained Sintering Stress -Review

    NASA Astrophysics Data System (ADS)

    Taub, Samuel; Kim, Jung-Sik

    When a thin film is sintered on a rigid substrate, the film will become constrained in its plane. Densification can therefore only occur in one direction, that being perpendicular to the plane of the substrate. The constraint will lead to the development of an in-plane tensile stress in the film, which exactly opposes the tendency for shrinkage in the plane. The magnitude of these stresses has been of much technological interest.

  6. Constrained noninformative priors

    SciTech Connect

    Atwood, C.L.

    1994-10-01

    The Jeffreys noninformative prior distribution for a single unknown parameter is the distribution corresponding to a uniform distribution in the transformed model where the unknown parameter is approximately a location parameter. To obtain a prior distribution with a specified mean but with diffusion reflecting great uncertainty, a natural generalization of the noninformative prior is the distribution corresponding to the constrained maximum entropy distribution in the transformed model. Examples are given.

  7. Constraining Entropic Cosmology

    E-print Network

    Tomi S. Koivisto; David F. Mota; Miguel Zumalacarregui

    2011-02-24

    It has been recently proposed that the interpretation of gravity as an emergent, entropic force might have nontrivial implications to cosmology. Here two approaches are investigated: in one, the Friedman equation receives entropic contributions from the usually neglected surface terms, and in another, the extra terms are derived from quantum corrections to the entropy formula. UV terms may drive inflation, avoiding a recently derived no-go theorem, though in some cases leading to a graceful exit problem. IR terms can generate dark energy, alleviating the cosmological constant problem. The quantum corrections are bounded by their implications to the BBN, and the surface terms are constrained in addition by their effect upon the behavior of matter. Likelihood analyses are performed to constrain the modifications by the SNeIa, BAO and CMB data. It is found that a monomial correction to the area-entropy formula results in late acceleration in very good agreement with observations, which then turn out to be compatible with positive curvature. The evolution of perturbations is deduced by assuming the Jebsen-Birkhoff theorem. Distinct signatures can then be identified in the large scale structure formation. Furthermore, it is shown that the visible universe satisfies the Bekenstein bound.

  8. Time-Constrained Machine Translation

    Microsoft Academic Search

    Janine Toole; Davide Turcato; Fred Popowich; Dan Fass; Paul Mcfetridge

    1998-01-01

    This paper defines the class of time-constrained applications: applications in which the user has limited time to process the system output. This class is differentiated\\u000a from real-time systems, where it is production time rather than comprehension time that is constrained. Examples of time-constrained MT\\u000a applications include the translation of multi-party dialogue and the translation of closed-captions. The constraints on comprehension

  9. Emission constrained economic dispatch

    SciTech Connect

    Ramanathan, R. (ESCA Corp., Bellevue, WA (United States))

    1994-11-01

    This paper presents a methodology to include emission constraints in classical Economic Dispatch (ED), which contains an efficient weights estimation technique. Also, a partial closed form technique is presented to implement the Emission Constrained Economic Dispatch (ECED). A simple technique is proposed to identify the binding constraints. The methods proposed do not need any user-supplied tuning or conversion factors. Dispatch quality is not compromised, and any practical sized problem can be solved efficiently. The proposed methods have rapid and consistent convergence to the Kuhn-Tucker optimality conditions. Different methods of including emissions as well as their advantages and disadvantages are discussed. Sample test results are presented. The proposed two methodologies have potential for on-line implementation.

  10. Density constrained TDHF

    E-print Network

    V. E. Oberacker; A. S. Umar

    2015-02-13

    In this manuscript we provide an outline of the numerical methods used in implementing the density constrained time-dependent Hartree-Fock (DC-TDHF) method and provide a few examples of its application to nuclear fusion. In this approach, dynamic microscopic calculations are carried out on a three-dimensional lattice and there are no adjustable parameters, the only input is the Skyrme effective NN interaction. After a review of the DC-TDHF theory and the numerical methods, we present results for heavy-ion potentials $V(R)$, coordinate-dependent mass parameters $M(R)$, and precompound excitation energies $E^{*}(R)$ for a variety of heavy-ion reactions. Using fusion barrier penetrabilities, we calculate total fusion cross sections $\\sigma(E_\\mathrm{c.m.})$ for reactions between both stable and neutron-rich nuclei. We also determine capture cross sections for hot fusion reactions leading to the formation of superheavy elements.

  11. Constrained space camera assembly

    DOEpatents

    Heckendorn, Frank M. (Aiken, SC); Anderson, Erin K. (Augusta, GA); Robinson, Casandra W. (Trenton, SC); Haynes, Harriet B. (Aiken, SC)

    1999-01-01

    A constrained space camera assembly which is intended to be lowered through a hole into a tank, a borehole or another cavity. The assembly includes a generally cylindrical chamber comprising a head and a body and a wiring-carrying conduit extending from the chamber. Means are included in the chamber for rotating the body about the head without breaking an airtight seal formed therebetween. The assembly may be pressurized and accompanied with a pressure sensing means for sensing if a breach has occurred in the assembly. In one embodiment, two cameras, separated from their respective lenses, are installed on a mounting apparatus disposed in the chamber. The mounting apparatus includes means allowing both longitudinal and lateral movement of the cameras. Moving the cameras longitudinally focuses the cameras, and moving the cameras laterally away from one another effectively converges the cameras so that close objects can be viewed. The assembly further includes means for moving lenses of different magnification forward of the cameras.

  12. Synthesis and chromatographic resolution of conformationally constrained analogues of homotaurine

    Microsoft Academic Search

    Maria Carmela Fulco; Maura Marinozzi; Burcu Çaliskan Ergün; Roccaldo Sardella; Benedetto Natalini; Roberto Pellicciari

    2009-01-01

    The first series of conformationally constrained analogues of homotaurine is reported. The partial constriction of the skeleton was realized through the insertion of a cyclopropyl ring, between the ?,?- and ?,?-positions, thus affording, respectively, trans- and cis-2-aminomethylcyclopropane-1-sulfonic acids and trans- and cis-(2-aminocyclopropyl)methanesulfonic acids. The resolution of all four racemic mixtures was accomplished using HPLC system carrying the polysaccharide-based Chiralpak® IB®

  13. Constraining neutrinoless double beta decay

    E-print Network

    L. Dorame; D. Meloni; S. Morisi; E. Peinado; J. W. F. Valle

    2011-11-23

    A class of discrete flavor-symmetry-based models predicts constrained neutrino mass matrix schemes that lead to specific neutrino mass sum-rules (MSR). We show how these theories may constrain the absolute scale of neutrino mass, leading in most of the cases to a lower bound on the neutrinoless double beta decay effective amplitude.

  14. Constraining Anisotropic Baryon Oscillations

    E-print Network

    Nikhil Padmanabhan; Martin White

    2008-04-05

    We present an analysis of anisotropic baryon acoustic oscillations and elucidate how a mis-estimation of the cosmology, which leads to incorrect values of the angular diameter distance, d_A, and Hubble parameter, H, manifest themselves in changes to the monopole and quadrupole power spectrum of biased tracers of the density field. Previous work has focused on the monopole power spectrum, and shown that the isotropic "dilation" combination d_A^2/H is robustly constrained by an overall shift in the scale of the baryon feature. We extend this by demonstrating that the quadrupole power spectrum is sensitive to an anisotropic "warping" mode d_A H, allowing one to break the degeneracy between d_A and H. We describe a method for measuring this warping, explicitly marginalizing over the form of redshift space distortions. We verify this method on N-body simulations and estimate that d_A H can be measured with a fractional accuracy of ~ 3/sqrt(V) % where the survey volume is estimated in (Gpc/h)^3.

  15. Constrained Vapor Bubble

    NASA Technical Reports Server (NTRS)

    Huang, J.; Karthikeyan, M.; Plawsky, J.; Wayner, P. C., Jr.

    1999-01-01

    The nonisothermal Constrained Vapor Bubble, CVB, is being studied to enhance the understanding of passive systems controlled by interfacial phenomena. The study is multifaceted: 1) it is a basic scientific study in interfacial phenomena, fluid physics and thermodynamics; 2) it is a basic study in thermal transport; and 3) it is a study of a heat exchanger. The research is synergistic in that CVB research requires a microgravity environment and the space program needs thermal control systems like the CVB. Ground based studies are being done as a precursor to flight experiment. The results demonstrate that experimental techniques for the direct measurement of the fundamental operating parameters (temperature, pressure, and interfacial curvature fields) have been developed. Fluid flow and change-of-phase heat transfer are a function of the temperature field and the vapor bubble shape, which can be measured using an Image Analyzing Interferometer. The CVB for a microgravity environment, has various thin film regions that are of both basic and applied interest. Generically, a CVB is formed by underfilling an evacuated enclosure with a liquid. Classification depends on shape and Bond number. The specific CVB discussed herein was formed in a fused silica cell with inside dimensions of 3x3x40 mm and, therefore, can be viewed as a large version of a micro heat pipe. Since the dimensions are relatively large for a passive system, most of the liquid flow occurs under a small capillary pressure difference. Therefore, we can classify the discussed system as a low capillary pressure system. The studies discussed herein were done in a 1-g environment (Bond Number = 3.6) to obtain experience to design a microgravity experiment for a future NASA flight where low capillary pressure systems should prove more useful. The flight experiment is tentatively scheduled for the year 2000. The SCR was passed on September 16, 1997. The RDR is tentatively scheduled for October, 1998.

  16. Phenomenology of Constrained Supersymmetry

    NASA Astrophysics Data System (ADS)

    Wells, James Daniel

    1995-01-01

    Supersymmetry, the symmetry which connects bosons to fermions, has matured into the most elegant and natural extension to the Standard Model of electroweak and strong interactions. This thesis is a study of several low energy experimental signatures of supersymmetry which derives from a high scale origin. First, the Higgs boson mass in supersymmetry is calculated. It is found that there is an upper bound on the lightest Higgs boson of 150 GeV in general supersymmetric theories if one imposes "perturbative validity"--couplings do not go strong below the high scale, taken to be 10 ^{16}GeV. Signatures at high energy colliders are next detailed. It is found that the observable Br(b to sgamma ) is not in the position to significantly constrain or detect supersymmetry. However, a calculation of higher order QCD corrections could make Br(b to sgamma) one of the most sensitive probes of supersymmetry available. The experimentally measured ratio of b-quarks to hadrons produced at LEP is about 2 sigma higher than the Standard Model prediction. The supersymmetric corrections to the Z to | bb decay width are calculated, and it is shown that supersymmetry derived from minimal supergravity boundary conditions cannot account for this anomaly. However, a general low-scale supersymmetric Lagrangian could account for this anomaly if the chargino or stop mass is below the W mass. Finally, the lightest supersymmetric partner (the LSP) is studied. Current theoretical understanding of Planck/GUT scale physics strongly suggests that the LSP is absolutely stable. This has cosmological consequences which are studied. Specifically, the calculated relic density of the particles demonstrates that the LSP might constitute a substantial fraction of the cold dark matter of the universe. If so, then LSPs should interact with table top experiments, capture and annihilate in the sun, and annihilate in the galactic halo making positrons, protons, and photons. All of these observables are studied. It is also argued that colliders might be the best dark matter detectors of them all.

  17. Entropy of Constrained Gravitational Instanton

    E-print Network

    Wu Zhong Chao

    1998-12-17

    The seeds for quantum creations of universes are constrained gravitational instantons. For all compact constrained instantons with U(1) isometry, the period $\\beta$ of the group parameter $\\tau$ is identified as the reciprocal of the temperature. If $\\beta$ remains a free parameter under the constraints, then the Euclidean action becomes the negative of the "entropy". As examples, we perform the calculations for the Taub-NUT and Taub-bolt-type models and study the quantum creation of the Taub-NUT universe.

  18. Convenient synthesis of N-methylamino acids compatible with Fmoc solid-phase peptide synthesis.

    PubMed

    Biron, Eric; Kessler, Horst

    2005-06-24

    N(alpha)-Methylamino acid containing peptides exhibit interesting therapeutic profiles and are increasingly recognized as potentially useful therapeutics. Unfortunately, their synthesis is hampered by the high price and unavaibility of many N(alpha)-methylamino acids. An efficient and practical preparation of N(alpha)-methyl-N(alpha)-(o-nitrobenzenesulfonyl)-alpha-amino acids without extensive purification is described. The procedure is based on the well-known N-alkylation of N(alpha)-arylsulfonylamino esters which was improved by using dimethyl sulfate and DBU as base. Ester cleavage is efficiently achieved by using an S(N)2-type saponification with lithium iodide, avoiding racemization observed with lithium hydroxide hydrolysis. Compatibility of the synthesized N(alpha)-methylamino acids with Fmoc solid-phase peptide synthesis is demonstrated by using normal coupling conditions to efficiently prepare N-methyl dipeptides. The described procedure allows the preparation of N(alpha)-methylamino acids in a very short period of time and a rapid synthesis of N-methyl peptides using Fmoc solid-phase peptide synthesis. PMID:15960522

  19. Edge-Constrained Marching Triangles

    Microsoft Academic Search

    Neil H. Mccormick; Robert B. Fisher

    2002-01-01

    Marching triangles is a method for producing a polygon mesh surface approximation composed of triangular facets which are approximately equilateral. This paper improves the Marching Triangles algorithm where the inputs are multiple range images of scenes. C1 discontinuities (fold edges) are detected and used to constrain the final triangulation, thus increasing the accuracy of the mesh at sharp edges and

  20. A constrained theory of magnetoelasticity

    Microsoft Academic Search

    Antonio DeSimone; Richard D. James

    2002-01-01

    A simple variational theory for the macroscopic behavior of materials with high anisotropy is derived rigorously from micromagnetics. The derivation leads to a constrained theory in which the state of strain and magnetization lies very near the ‘energy wells’ on most of the body. When specialized to ellipsoidal specimens and constant applied field and stress, the theory becomes a finite

  1. INVERSION BASED CONSTRAINED TRAJECTORY OPTIMIZATION

    E-print Network

    to find a trajectory of (1), i.e. [t0, tf ] t (x, u)(t) Rn+1 , that minimizes the performance index JINVERSION BASED CONSTRAINED TRAJECTORY OPTIMIZATION Nicolas Petit, Mark B. Milam, Richard M. Murray Control and Dynamical Systems Mail Code 107-81 California Institute of Technology Pasadena, CA 91125

  2. INVERSION BASED CONSTRAINED TRAJECTORY OPTIMIZATION

    E-print Network

    Murray, Richard M.

    the Nonlinear Trajectory Generation (NTG) software package. Keywords: Real-time optimization, optimal control and functions are real-analytic. It is desired to find a trajectory of (1), i.e. [t0, tf ] t (x, u)(t) Rn+1INVERSION BASED CONSTRAINED TRAJECTORY OPTIMIZATION Nicolas Petit, Mark B. Milam, Richard M. Murray

  3. Steroselective synthesis and application of L-( sup 15 N) amino acids

    SciTech Connect

    Unkefer, C.J. (Los Alamos National Lab., NM (United States)); Lodwig, S.N. (Centralia Coll., WA (United States). Div. of Science)

    1991-01-01

    We have developed two general approaches to the stereoselective synthesis of {sup 15}N- and {sup 13}C-labeled amino acids. First, labeled serine, biosynthesized using the methylotrophic bacterium M. extorquens AM1, serves as a chiral precursor for the synthesis of other amino acids. For example, pyridoxal phosphate enzymes can be used for the conversion of L-({alpha}-{sup 15}N)serine to L-({alpha}-{sup 15}N)tyrosine, L-({alpha}-{sup 15}N)tryptophan, and L-({alpha}-{sup 15}N)cysteine. In the second approach, developed by Oppolzer and Tamura, an electrophilic amination'' reagent, 1-chloro-1-nitrosocyclohexane, was used to convert chiral enolates into L-{alpha}-amino acids. We prepared 1-chloro-1-({sup 15}N) nitrosocyclohexane and used it to aminate chiral enolates to produce L-({alpha}-{sup 15}N)amino acids. The stereoselectivity of this scheme using the Oppolzer sultam chiral auxiliary is remarkable, producing enantiomer ratios of 200 to 1. 22 refs., 4 figs.

  4. NCAD, a database integrating the intrinsic conformational preferences of non-coded amino acids.

    PubMed

    Revilla-López, Guillem; Torras, Juan; Curcó, David; Casanovas, Jordi; Calaza, M Isabel; Zanuy, David; Jiménez, Ana I; Cativiela, Carlos; Nussinov, Ruth; Grodzinski, Piotr; Alemán, Carlos

    2010-06-01

    Peptides and proteins find an ever-increasing number of applications in the biomedical and materials engineering fields. The use of non-proteinogenic amino acids endowed with diverse physicochemical and structural features opens the possibility to design proteins and peptides with novel properties and functions. Moreover, non-proteinogenic residues are particularly useful to control the three-dimensional arrangement of peptidic chains, which is a crucial issue for most applications. However, information regarding such amino acids--also called non-coded, non-canonical, or non-standard--is usually scattered among publications specialized in quite diverse fields as well as in patents. Making all these data useful to the scientific community requires new tools and a framework for their assembly and coherent organization. We have successfully compiled, organized, and built a database (NCAD, Non-Coded Amino acids Database) containing information about the intrinsic conformational preferences of non-proteinogenic residues determined by quantum mechanical calculations, as well as bibliographic information about their synthesis, physical and spectroscopic characterization, conformational propensities established experimentally, and applications. The architecture of the database is presented in this work together with the first family of non-coded residues included, namely, alpha-tetrasubstituted alpha-amino acids. Furthermore, the NCAD usefulness is demonstrated through a test-case application example. PMID:20455555

  5. Amino acid conjugated sophorolipids: A new family of biologically active functionalized glycolipids.

    PubMed

    Azim, Abul; Shah, Vishal; Doncel, Gustavo F; Peterson, Nicholas; Gao, Wei; Gross, Richard

    2006-01-01

    Sophorolipids (SLs) are extra cellular glycolipids produced by Candida bombicola ATCC 22214 when grown in the presence of glucose and fatty acids. These compounds have a disaccharide head group connected to a long-chain hydroxyl-fatty acid by a glycosidic bond. To explore structure-activity of modified SLs, a new family of amino acid-SL derivatives was prepared. Synthesized analogs consist of amino acids linked by amide bonds formed between their alpha-amino moiety and the carboxyl group of ring-opened SL fatty acids. Their preparation involved the following: (i) hydrolysis of a natural SL mixture with aqueous alkali to give SL free acids, (ii) coupling of free acids to protected amino acids using dicarbodiimide, and (iii) removing amino acid carboxyl protecting groups. These conjugates were evaluated for their antibacterial, anti-HIV, and spermicidal activity. All tested analogs showed antibacterial activity against both gram +ve and gram -ve organisms. Leucine-conjugated SL was most efficient. For example, the minimum inhibitory concentrations (MIC) for Moraxella sp. and E. coli were 0.83 and 1.67 mg/mL, respectively. Among the alkyl esters of amino acid conjugated SLs, the ethyl ester of leucine-SLs was most active. Against Moraxella sp., S. sanguinis, and M. imperiale, MIC values are 7.62 x 10(-4), 2.28 x 10-(3) and 1.67 mg/mL, respectively. All compounds displayed virus-inactivating activity with 50% effective concentrations (EC50) below 200 microg/mL. The EC50 of leucine-SL ethyl ester was 24.1 microg/mL, showing that it is more potent than commercial spermicide nonoxynol-9 (EC50 approximately 65 microg/mL). PMID:17105232

  6. Constrained Multiobjective Biogeography Optimization Algorithm

    PubMed Central

    Mo, Hongwei; Xu, Zhidan; Xu, Lifang; Wu, Zhou; Ma, Haiping

    2014-01-01

    Multiobjective optimization involves minimizing or maximizing multiple objective functions subject to a set of constraints. In this study, a novel constrained multiobjective biogeography optimization algorithm (CMBOA) is proposed. It is the first biogeography optimization algorithm for constrained multiobjective optimization. In CMBOA, a disturbance migration operator is designed to generate diverse feasible individuals in order to promote the diversity of individuals on Pareto front. Infeasible individuals nearby feasible region are evolved to feasibility by recombining with their nearest nondominated feasible individuals. The convergence of CMBOA is proved by using probability theory. The performance of CMBOA is evaluated on a set of 6 benchmark problems and experimental results show that the CMBOA performs better than or similar to the classical NSGA-II and IS-MOEA. PMID:25006591

  7. COBS: COnstrained B-Splines

    NASA Astrophysics Data System (ADS)

    Ng, Pin T.; Maechler, Martin

    2015-05-01

    COBS (COnstrained B-Splines), written in R, creates constrained regression smoothing splines via linear programming and sparse matrices. The method has two important features: the number and location of knots for the spline fit are established using the likelihood-based Akaike Information Criterion (rather than a heuristic procedure); and fits can be made for quantiles (e.g. 25% and 75% as well as the usual 50%) in the response variable, which is valuable when the scatter is asymmetrical or non-Gaussian. This code is useful for, for example, estimating cluster ages when there is a wide spread in stellar ages at a chosen absorption, as a standard regression line does not give an effective measure of this relationship.

  8. Constrained multiobjective biogeography optimization algorithm.

    PubMed

    Mo, Hongwei; Xu, Zhidan; Xu, Lifang; Wu, Zhou; Ma, Haiping

    2014-01-01

    Multiobjective optimization involves minimizing or maximizing multiple objective functions subject to a set of constraints. In this study, a novel constrained multiobjective biogeography optimization algorithm (CMBOA) is proposed. It is the first biogeography optimization algorithm for constrained multiobjective optimization. In CMBOA, a disturbance migration operator is designed to generate diverse feasible individuals in order to promote the diversity of individuals on Pareto front. Infeasible individuals nearby feasible region are evolved to feasibility by recombining with their nearest nondominated feasible individuals. The convergence of CMBOA is proved by using probability theory. The performance of CMBOA is evaluated on a set of 6 benchmark problems and experimental results show that the CMBOA performs better than or similar to the classical NSGA-II and IS-MOEA. PMID:25006591

  9. Constrained minimization for monotonic reconstruction

    SciTech Connect

    Rider, W.J.; Kothe, D.B.

    1996-08-20

    The authors present several innovations in a method for monotonic reconstructions. It is based on the application of constrained minimization techniques for the imposition of monotonicity on a reconstruction. In addition, they present extensions of several classical TVD limiters to a genuinely multidimensional setting. In this case the linear least squares reconstruction method is expanded upon. They also clarify data dependent weighting techniques used with the minimization process.

  10. Entropy-constrained vector quantization

    Microsoft Academic Search

    PHILIP A. CHOU; TOM LOOKABAUGH; ROBERT M. GRAY

    1989-01-01

    An iterative descent algorithm based on a Lagrangian formulation for designing vector quantizers having minimum distortion subject to an entropy constraint is discussed. These entropy-constrained vector quantizers (ECVQs) can be used in tandem with variable-rate noiseless coding systems to provide locally optimal variable-rate block source coding with respect to a fidelity criterion. Experiments on sampled speech and on synthetic sources

  11. Optimizing Budget Constrained Spend in Search Advertising

    E-print Network

    Tomkins, Andrew

    Optimizing Budget Constrained Spend in Search Advertising Chinmay Karande Aranyak Mehta are budget constrained, i.e., if al- lowed to participate in every auction that they bid on, they would spend such budget constrained spend. The system is designed be deployed in a large search engine, with hundreds

  12. Cervical screening strategies in resourced and resource-constrained countries.

    PubMed

    Cronjé, H S

    2011-10-01

    Screening for cervical cancer is well established in resourced countries, but in resource-constrained countries, it is almost non-existent at national level. In resourced countries, the Pap test forms the hallmark of screening, with the human papillomavirus DNA test a recent adjunct. In many resourced countries, however, screening for cervical cancer is still far from ideal. A coverage around 50% prevails in some countries, and few have reached the target of 80% or more. Furthermore, the human papillomavirus test and newly developed biomarkers may lead to the development of a 'super test', which could be applied less frequently compared with present-day cytological screening. In resource-constrained countries, the movement is towards a 'screen and treat' approach. The main screening methods under investigation are the visual inspection after diluted acetic acid application test and the human papillomavirus test. Cryotherapy and large loop excision of the transformation zone have been used most often as treatment methods. The ideal seems to be the human papillomavirus test with large loop excision of the transformation zone, provided a low-cost human papillomavirus test becomes available. Coverage is even a greater problem in resource-constrained countries, a problem in need of urgent attention. Resource-constrained countries, however, must curtail the high incidence of cervical cancer, which is often a lower priority than other pressing healthcare needs. PMID:21689987

  13. 8.8 Constrained LS Why Constrain? Because sometimes we know (or believe!)

    E-print Network

    Fowler, Mark

    1 8.8 Constrained LS Why Constrain? Because sometimes we know (or believe!) certain values a strong signal from the left-side antennas and a weak one from the right-side antennas) LS^Thus, when finding you want to constrain it to satisfy these conditions #12;2 Constrained LS Problem Statement Say

  14. Constraining disformally coupled scalar fields

    NASA Astrophysics Data System (ADS)

    Brax, Philippe; Burrage, Clare

    2014-11-01

    Light scalar fields can naturally couple disformally to matter fields. Static, nonrelativistic sources do not generate a classical field profile for a disformally coupled scalar, and so such scalars are free from the constraints on the existence of fifth forces that are so restrictive for conformally coupled scalars. In this paper we show that disformally coupled scalars can still be studied and constrained through their microscopic interactions with fermions and photons, both in terrestrial laboratories and from observations of stars. The strongest constraint on the coupling scale comes from mono-photon searches at the LHC and requires M ?102 GeV .

  15. Constraining Modified Gravity with Euclid

    E-print Network

    Matteo Martinelli; Erminia Calabrese; Francesco De Bernardis; Alessandro Melchiorri; Luca Pagano; Roberto Scaramella

    2010-10-27

    Future proposed satellite missions as Euclid can offer the opportunity to test general relativity on cosmic scales through mapping of the galaxy weak lensing signal. In this paper we forecast the ability of these experiments to constrain modified gravity scenarios as those predicted by scalar-tensor and $f(R)$ theories. We found that Euclid will improve constraints expected from the PLANCK satellite on these modified gravity models by two orders of magnitude. We discuss parameter degeneracies and the possible biases introduced by modified gravity.

  16. Constrained ballistics and geometrical optics

    E-print Network

    Epstein, Marcelo

    2014-01-01

    The problem of constant-speed ballistics is studied under the umbrella of non-linear non-holonomic constrained systems. The Newtonian approach is shown to be equivalent to the use of Chetaev's rule to incorporate the constraint within the initially unconstrained formulation. Although the resulting equations are not, in principle, obtained from a variational statement, it is shown that the trajectories coincide with those of geometrical optics in a medium with a suitably chosen refractive index, as prescribed by Fermat's principle of least time. This fact gives rise to an intriguing mechano-optical analogy. The trajectories are further studied and discussed.

  17. Label image constrained multiatlas selection.

    PubMed

    Yan, Pingkun; Cao, Yihui; Yuan, Yuan; Turkbey, Baris; Choyke, Peter L

    2015-06-01

    Multiatlas based method is commonly used in medical image segmentation. In multiatlas based image segmentation, atlas selection and combination are considered as two key factors affecting the performance. Recently, manifold learning based atlas selection methods have emerged as very promising methods. However, due to the complexity of prostate structures in raw images, it is difficult to get accurate atlas selection results by only measuring the distance between raw images on the manifolds. Although the distance between the regions to be segmented across images can be readily obtained by the label images, it is infeasible to directly compute the distance between the test image (gray) and the label images (binary). This paper tries to address this problem by proposing a label image constrained atlas selection method, which exploits the label images to constrain the manifold projection of raw images. Analyzing the data point distribution of the selected atlases in the manifold subspace, a novel weight computation method for atlas combination is proposed. Compared with other related existing methods, the experimental results on prostate segmentation from T2w MRI showed that the selected atlases are closer to the target structure and more accurate segmentation were obtained by using our proposed method. PMID:25415994

  18. Characterization of a dual specificity aryl acid adenylation enzyme with dual function in nikkomycin biosynthesis.

    PubMed

    Moon, Mary; Van Lanen, Steven G

    2010-09-01

    Nikkomycin Z is a dipeptide antifungal antibiotic characterized by two nonproteinogenic amino acids, nikkomycin C(Z) and 4-(4'-hydroxy-2'-pyridinyl)-homothreonine (HPHT). The HPHT scaffold is assembled by an aldol reaction between 2-oxobutyrate and picolinaldehyde, the latter of which is derived from picolinic acid that is activated and loaded to coenzyme A by the aryl-activating adenylation enzyme, NikE. We now provide evidence that NikE is also involved in the activation and loading of the alpha-keto acid precursor, 4-(2'-pyridinyl)-2-oxo-4-hydroxyisovalerate (POHIV), to a phosphopantetheinyl group of an acyl carrier protein domain of NikT. POHIV was synthesized using Escherichia coli 2-dehydro-3-deoxy-phosphogluconate aldolase, and phenylalanine dehydrogenase from Bacillus sp. NRRL B-14911 was used to prepare the alpha-amino acid, 4-(2'-pyridinyl)-homothreonine (PHT). Using the carboxylic acid-dependent, ATP-[(32)P]PP(i) exchange assay, NikE is shown to activate both picolinic acid and POHIV but not PHT. Furthermore, NikE loads POHIV to holo-NikT to generate a new thioester-linked intermediate, which was not observed using a NikT(S33A) mutant. Thus, NikE activates two distinct carboxylic acids to form two new thioester intermediates, one of which is subsequently reduced to the aldehyde and the other that likely serves as a substrate for the aminotransferase domain of NikT prior to condensation with nikkomycin C(Z) to yield the dipeptide. PMID:20577996

  19. Formal language constrained path problems

    SciTech Connect

    Barrett, C.; Jacob, R.; Marathe, M.

    1997-07-08

    In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.

  20. MRI-constrained spectral imaging of benzodiazepine modulation of spontaneous neuromagnetic activity in human cortex

    E-print Network

    statistical parametric maps of drug effects. The distributed MRI-constrained MEG source estimates demonstrated of these rhythms (alpha 8­12 Hz, beta 15­25 Hz, gamma 30­80 Hz) correlates with the state of the consciousness the ionotropic gamma-aminobutyric acid (GABAA) receptors, result in an increase of beta and decrease of alpha

  1. Compensating Mass Matrix Potential Constrained Molecular Dynamics

    E-print Network

    .Jain@jpl.nasa.gov Journal of Computational Physics, Jul, '97 (in press) Subject classification: 65P99, 82A71. KeywordsCompensating Mass Matrix Potential for Constrained Molecular Dynamics Abhinandan Jain Jet: Molecular dynamics, algorithms, simulation. #12; Running head: Compensating Potential for Constrained

  2. CONSTRAINED REGULARIZATION OF DIGITAL TERRAIN ELEVATION DATA

    E-print Network

    Minnesota, University of

    CONSTRAINED REGULARIZATION OF DIGITAL TERRAIN ELEVATION DATA By Anish Mohan and Guillermo Sapiro: 612/626-7370 URL: http://www.ima.umn.edu #12;1 Constrained Regularization of Digital Terrain Elevation in this paper. The framework takes into account errors in the data, which form part of standard elevation maps

  3. Using ecological restoration to constrain biological invasion

    Microsoft Academic Search

    JONATHAN D. BAKKER; SCOTT D. WILSON

    Summary 1. Biological invasion can permanently alter ecosystem structure and function. In- vasive species are difficult to eradicate, so methods for constraining invasions would be ecologically valuable. We examined the potential of ecological restoration to constrain invasion of an old field by Agropyron cristatum , an introduced C 3 grass. 2. A field experiment was conducted in the northern Great

  4. Constrained Wiki: an Oxymoron? Angelo Di Iorio

    E-print Network

    Zacchiroli, Stefano - Laboratoire Preuves, Programmes et Systèmes, Université Paris 7

    Constrained Wiki: an Oxymoron? Angelo Di Iorio Department of Computer Science University of Bologna@cs.unibo.it ABSTRACT In this paper we propose a new wiki concept -- light con- straints -- designed to encode community of constraining user editing of wiki con- tent seems to inherently contradict "The Wiki Way", it is well

  5. MPC for tracking of constrained nonlinear systems

    Microsoft Academic Search

    Antonio Ferramosca; Daniel Limón; Ignacio Alvarado; Teodoro Alamo; Eduardo F. Camacho

    2009-01-01

    This paper deals with the tracking problem for constrained nonlinear systems using a model predictive control (MPC) law. MPC provides a control law suitable for regulating constrained linear and nonlinear systems to a given target steady state. However, when the target operating point changes, the feasibility of the controller may be lost and the controller fails to track the reference.

  6. BICEP2 constrains composite inflation

    NASA Astrophysics Data System (ADS)

    Channuie, Phongpichit

    2014-07-01

    In light of BICEP2, we re-examine single field inflationary models in which the inflation is a composite state stemming from various four-dimensional strongly coupled theories. We study in the Einstein frame a set of cosmological parameters, the primordial spectral index ns and tensor-to-scalar ratio r, predicted by such models. We confront the predicted results with the joint Planck data, and with the recent BICEP2 data. We constrain the number of e-foldings for composite models of inflation in order to obtain a successful inflation. We find that the minimal composite inflationary model is fully consistent with the Planck data. However it is in tension with the recent BICEP2 data. The observables predicted by the glueball inflationary model can be consistent with both Planck and BICEP2 contours if a suitable number of e-foldings are chosen. Surprisingly, the super Yang-Mills inflationary prediction is significantly consistent with the Planck and BICEP2 observations.

  7. Constrained navigation for unmanned systems

    NASA Astrophysics Data System (ADS)

    Vasseur, Laurent; Gosset, Philippe; Carpentier, Luc; Marion, Vincent; Morillon, Joel G.; Ropars, Patrice

    2005-05-01

    The French Military Robotic Study Program (introduced in Aerosense 2003), sponsored by the French Defense Procurement Agency and managed by Thales as the prime contractor, focuses on about 15 robotic themes which can provide an immediate "operational add-on value". The paper details the "constrained navigation" study (named TEL2), which main goal is to identify and test a well-balanced task sharing between man and machine to accomplish a robotic task that cannot be performed autonomously at the moment because of technological limitations. The chosen function is "obstacle avoidance" on rough ground and quite high speed (40 km/h). State of the art algorithms have been implemented to perform autonomous obstacle avoidance and following of forest borders, using scanner laser sensor and standard localization functions. Such an "obstacle avoidance" function works well most of the time, BUT fails sometimes. The study analyzed how the remote operator can manage such failures so that the system remains fully operationally reliable; he can act according to two ways: a) finely adjust the vehicle current heading; b) take the control of the vehicle "on the fly" (without stopping) and bring it back to autonomous behavior when motion is secured again. The paper also presents the results got from the military acceptance tests performed on French 4x4 DARDS ATD.

  8. Constrained exceptional supersymmetric standard model

    SciTech Connect

    Athron, P. [Institut fuer Kern und Teilchenphysik, TU Dresden, Dresden, D-01062 (Germany); King, S. F. [School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ (United Kingdom); Miller, D. J.; Nevzorov, R. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Moretti, S. [School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ (United Kingdom); Dipartimento di Fisica Teorica, Universita degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino (Italy)

    2009-08-01

    We propose and study a constrained version of the exceptional supersymmetric standard model (E{sub 6}SSM), which we call the cE{sub 6}SSM, based on a universal high energy scalar mass m{sub 0}, trilinear scalar coupling A{sub 0} and gaugino mass M{sub 1/2}. We derive the renormalization group (RG) Equations for the cE{sub 6}SSM, including the extra U(1){sub N} gauge factor and the low-energy matter content involving three 27 representations of E{sub 6}. We perform a numerical RG analysis for the cE{sub 6}SSM, imposing the usual low-energy experimental constraints and successful electroweak symmetry breaking. Our analysis reveals that the sparticle spectrum of the cE{sub 6}SSM involves a light gluino, two light neutralinos, and a light chargino. Furthermore, although the squarks, sleptons, and Z{sup '} boson are typically heavy, the exotic quarks and squarks can also be relatively light. We finally specify a set of benchmark points, which correspond to particle spectra, production modes, and decay patterns peculiar to the cE{sub 6}SSM, altogether leading to spectacular new physics signals at the Large Hadron Collider.

  9. Gyrification from constrained cortical expansion

    E-print Network

    Tallinen, Tuomas; Biggins, John S; Mahadevan, L

    2015-01-01

    The exterior of the mammalian brain - the cerebral cortex - has a conserved layered structure whose thickness varies little across species. However, selection pressures over evolutionary time scales have led to cortices that have a large surface area to volume ratio in some organisms, with the result that the brain is strongly convoluted into sulci and gyri. Here we show that the gyrification can arise as a nonlinear consequence of a simple mechanical instability driven by tangential expansion of the gray matter constrained by the white matter. A physical mimic of the process using a layered swelling gel captures the essence of the mechanism, and numerical simulations of the brain treated as a soft solid lead to the formation of cusped sulci and smooth gyri similar to those in the brain. The resulting gyrification patterns are a function of relative cortical expansion and relative thickness (compared with brain size), and are consistent with observations of a wide range of brains, ranging from smooth to highl...

  10. Production of poly-gamma-glutamic acid by Bacillus subtilis and Bacillus licheniformis with different growth media.

    PubMed

    Kedia, Gopal; Hill, David; Hill, Robert; Radecka, Iza

    2010-09-01

    Poly gamma-glutamic acid is a naturally occurring homo-polyamide that is made of D- and L-glutamic acid units connected by amide linkages between alpha-amino and gamma-carboxylic groups. Many strains have been studied for the production of poly y-glutamic acid, B. licheniformis 9945a and B. subtilis natto are the two most widely studied strains due to their higher yield. Both of these strains require L-glutamic acid for poly gamma-glutamic acid production. This paper describes investigations on the biosynthesis of poly y-glutamic acid by B. licheniformis 9945a and B. subtilis natto in an automated pH-controlled fermenter. The effect of the growth media such as medium E, F, C and GS was investigated. Medium E produced poly gamma-glutamic acid both with and without MnSO4 in the medium when fermented by B. licheniformis. Presence of MnSO4 in the medium affected both the yield and biomass production. The yield was 12 g/l for the medium containing 2.46 mM MnSO4 whereas it was only 4-5 g/l for the medium without MnSO4 with molecular weight (Mw) of 321,000. Different media such as medium C, F and GS were used for production of poly gamma-glutamic acid by B. subtilis natto. The yield from GS medium was highest and it produced about 26-28 g/l with molecular weight (Mw) of 627,000. PMID:21133130

  11. 21 CFR 888.3720 - Toe joint polymer constrained prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 2013-04-01 false Toe joint polymer constrained prosthesis. 888.3720...Prosthetic Devices § 888.3720 Toe joint polymer constrained prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a...

  12. Adaptable search neighborhoods for Resource Constrained Scheduling 

    E-print Network

    Balakrishnan, Ramamoorthy

    1993-01-01

    Resource Constrained Scheduling problem (RCSP) is a scheduling problem in which each activity may require more than one resource and resources may not be available in the same quantity throughout the planning period. This thesis describes a...

  13. Ecological and Biogeochemical Interactions Constrain Planktonic

    E-print Network

    Pace, Michael L.

    Ecological and Biogeochemical Interactions Constrain Planktonic Nitrogen Fixation in Estuaries nitrogen (N) is strongly limiting to primary production. Estuaries generally fit this pat- tern-limited estuaries. Heterocystic cyanobacteria capable of N2 fixation are seldom observed in estuaries where

  14. Constrained crosstalk resistant adaptive noise canceller

    NASA Astrophysics Data System (ADS)

    Parsa, V.; Parker, P.

    1994-08-01

    The performance of an adaptive noise canceller (ANC) is sensitive to the presence of signal `crosstalk' in the reference channel. The authors propose a novel approach to crosstalk resistant adaptive noise cancellation, namely the constrained crosstalk resistant adaptive noise canceller (CCRANC). The theoretical analysis of the CCRANC along with the constrained algorithm is presented. The performance of the CCRANC in recovering somatosensory evoked potentials (SEPs) from myoelectric interference is then evaluated through simulations.

  15. Convex Duality in Constrained Portfolio Optimization

    Microsoft Academic Search

    Jaksa Cvitanic; Ioannis Karatzas

    1992-01-01

    We study the stochastic control problem of maximizing expected utility from terminal wealth and\\/or consumption, when the portfolio is constrained to take values in a given closed, convex subset of $\\\\mathscr{R}^d$. The setting is that of a continuous-time, Ito process model for the underlying asset prices. General existence results are established for optimal portfolio\\/consumption strategies, by suitably embedding the constrained

  16. Nonlinear wave equations and constrained harmonic motion

    Microsoft Academic Search

    P. Deift; F. Lund; E. Trubowitz

    1980-01-01

    Moser and Trubowitz [7] showed that the study of the Korteweg-deVries equation is simply the study of constrained harmonic motion. Here we show the same is true for the nonlinear Schr6dinger, sine-Gordon and Toda lattice equations. Briefly, we have found a change of variables under which these integrable wave equations become a system of free oscillators constrained to an intersection

  17. MPC for Tracking of Constrained Nonlinear Systems

    Microsoft Academic Search

    D. Limon; A. Ferramosca; I. Alvarado; T. Alamo; E. Camacho

    This paper deals with the tracking problem for constrained nonlinear systems using a model predictive control (MPC) law. MPC\\u000a provides a control law suitable for regulating constrained linear and nonlinear systems to a given target steady state. However,\\u000a when the target operating point changes, the feasibility of the controller may be lost and the controller fails to track the\\u000a reference.

  18. The current 15N-leucine infusion technique is not suitable for quantitative measurements of ileal endogenous amino acid flows in pigs.

    PubMed

    Leterme, P; Sève, B; Théwis, A

    1998-11-01

    The current 15N-leucine infusion technique may overestimate the ileal endogenous nitrogen losses in pigs. To determine the reason, we infused four cannulated pigs intravenously, fed them a pea-based diet with 15N-leucine, and examined some methodological variables. Neither the blood sampling time nor the choice of precursor pool (total N or amino acid N of deproteinized plasma) or the method of estimation of the isotopic equilibrium level significantly affected the results. On the other hand, the 15N-enrichment of purified mucin, isolated from ileal digesta, was higher than that of the plasma amino acid pool (0.114 vs. 0.077 atom % excess). The endogenous proportion of the labeled amino acids (Ala, Gly, Ile, Leu and Val) in the ileal digesta ranged from 23 (Leu) to 74% (Ala), compared with 70% for total N. The low value of leucine was ascribed to the constant marker infusion condition. In pigs infused with 13C-leucine, a similar endogenous proportion was obtained for lumenal leucine with 13C-leucine and 15N-leucine infusion. However, the 13C-enrichment of the leucine bound to mucin was markedly lower than that of plasma leucine (38%). The endogenous amino acid flows were also estimated by combining the ileal N flow measured with 15N and the endogenous amino acid profile obtained by means of an N-free diet. They were different from those obtained with the 15N-amino acid dilution technique. We conclude that the precursor pool currently used (plasma total N or total alpha-amino acid N pools) is a poor indicator of the enrichment of the secretions and that the infusion of one labeled amino acid is not sufficient to extend the method at the amino acid level. PMID:9808650

  19. Alpha-aminoxy acids: new possibilities from foldamers to anion receptors and channels.

    PubMed

    Li, Xiang; Wu, Yun-Dong; Yang, Dan

    2008-10-01

    Naturally occurring peptides serve important functions as enzyme inhibitors, hormones, neurotransmitters, and immunomodulators in many physiological processes including metabolism, digestion, pain sensitivity, and the immune response. However, due to their conformational flexibility and poor bioavailability, such peptides are not generally viewed as useful therapeutic agents in clinical applications. In an effort to solve these problems, chemists have developed peptidomimetic foldamers, unnatural oligomeric molecules that fold into rigid and well-defined secondary structures mimicking the structures and biological functions of these natural peptides. We have designed peptidomimetic foldamers that give predictable, backbone-controlled secondary structures irrespective of the nature of the side chains. This Account presents our efforts to develop a novel class of peptidomimetic foldamers comprising alpha-aminoxy acids and explore their applications in the simulation of ion recognition and transport processes in living systems. Peptides constructed from alpha-aminoxy acids fold according to the following rules: (1) A strong intramolecular eight-membered-ring hydrogen bond forms between adjacent alpha-aminoxy acid residues (the alpha N-O turn). The chirality of the alpha-carbon, not the nature of the side chains, determines the conformation of this chiral N-O turn. (2) While homochiral oligomers of alpha-aminoxy acids form an extended helical structure (1.8 8 helix), heterochiral ones adopt a bent reverse turn structure. (3) In peptides of alternating alpha-amino acids and alpha-aminoxy acids, the seven-membered-ring intramolecular hydrogen bond, that is, the gamma-turn, is initiated by a succeeding alpha N-O turn. Thus, this type of peptide adopts a novel 7/8 helical structure. In investigating the potential applications of alpha-aminoxy acids, we have found that the amide NH units of alpha-aminoxy acids are more acidic than are regular amide NH groups, which makes them better hydrogen bond donors when interacting with anions. This property makes alpha-aminoxy acids ideal building blocks for the construction of anion receptors. Indeed, we have constructed both cyclic and acyclic anion receptors that have strong affinities and good (enantio-)selectivities toward chloride (Cl(-)) and chiral carboxylate ions. Taking advantage of these systems' preference for Cl(-) ions, we have also employed alpha-aminoxy acid units to construct a synthetic Cl(-) channel that can mediate the passage of Cl(-) ions across cell membranes. Continued studies of these peptidomimetic systems built from alpha-aminoxy acids should lead to a broad range of applications in chemistry, biology, medicine, and materials science. PMID:18785763

  20. Kainic acid triggers oligodendrocyte precursor cell proliferation and neuronal differentiation from striatal neural stem cells.

    PubMed

    Redondo, Carolina; López-Toledano, Miguel A; Lobo, Maria V T; Gonzalo-Gobernado, Rafael; Reimers, Diana; Herranz, Antonio S; Paíno, Carlos L; Bazán, Eulalia

    2007-05-01

    Glutamate is an excitatory amino acid that serves important functions in mammalian brain development through alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/ kainate receptor stimulation. Neural stem cells with self-renewal and multilineage potential are a useful tool to study the signals involved in the regulation of brain development. We have investigated the role played by AMPA/kainate receptors during the differentiation of neural stem cells derived from fetal rat striatum. The application of 1 and 10 microM kainic acid increased significantly the phosphorylation of the cyclic AMP response element binding protein (CREB), raised bromodeoxyuridine incorporation in O4-positive oligodendrocyte precursors, and increased the number of O1-positive cells in the cultures. Increased CREB phosphorylation and proliferation were prevented by the AMPA receptor antagonist 4-4(4-aminophenyl)-1,2-dihydro-1-methyl-2-propylcarbamoyl-6,7-methylenedioxyphthalazine (SYM 2206) and by protein kinase A and protein kinase C inhibitors. Cultures treated with 100 microM kainic acid showed decreased proliferation, a lower proportion of O1-positive cells, and apoptosis of O4-positive cells. None of these effects were prevented by SYM 2206, suggesting that kainate receptors take part in these events. We conclude that AMPA receptor stimulation by kainic acid promotes the proliferation of oligodendrocyte precursors derived from neural stem cells through a mechanism that requires the activation of CREB by protein kinase A and C. In the neurons derived from these cells, either AMPA or kainate receptor stimulation produces neuritic growth and larger cell bodies. PMID:17342781

  1. Rapid complexing of oxoacylglycerols with amino acids, peptides and aminophospholipids.

    PubMed

    Kurvinen, J P; Kuksis, A; Ravandi, A; Sjövall, O; Kallio, H

    1999-03-01

    We prepared model Schiff bases from 2-[9-oxo]nonanoyl glycerol (2-MAG-ALD) and various amino compounds. 2-MAG-ALD was obtained by pancreatic lipase hydrolysis of trioleoyl glycerol and reductive ozonolysis of the resulting 2-monooleoyl glycerol. The reaction products were purified by thin-layer chromatography. Schiff bases were synthesized in greater than 50% yield by reacting 2-MAG-ALD with twofold molar excess of valine, Nalpha-acetyl-L-lysine methyl ester and the tripeptides glycyl-glycyl-glycine, glycyl-glycyl-histidine, and glycyl-histidyl-lysine in aqueous methanol and with 1-palmitoyl-2-stearoyl glycerophosphoethanolamine (PE) in chloroform/methanol for 16 h at room temperature. Prior to analysis the bases were reduced with sodium cyanoborohydride in methanol for 30 min at 4 degrees C. Reaction products were analyzed by high-performance liquid chromatography/electrospray ionization/mass spectrometry (HPLC/ESI/MS). Reduced Schiff bases of 2-MAG-ALD with PE and amino acids were analyzed by normal-phase HPLC/ESI/MS and those with peptides by reversed-phase HPLC/ESI/MS. Single adducts were obtained in all cases and both the alpha-amino group of valine and the epsilon-amino group of Nalpha-acetyl-L-lysine methyl ester were reactive. Molecular ions of reaction products were the only detected ions in the negative ionization mode, whereas in the positive ion mode sodiated molecular ions were also detected. The present study suggests that 2-MAG-ALD may form Schiff base adducts with amino compounds in other aqueous media, such as the intestinal lumen and in the hydrophobic environment of cell membranes. PMID:10230725

  2. Geochemical Processes Constraining Iron Uptake in Strategy II Fe Acquisition

    PubMed Central

    2014-01-01

    Phytosiderophores (PS) are natural chelating agents, exuded by graminaceous plants (grasses) for the purpose of Fe acquisition (Strategy II). They can form soluble Fe complexes with soil-Fe that can be readily taken up. PS are exuded in a diurnal pulse release, and with the start of PS release a “window of iron uptake” opens. In the present study we examined how this window is constrained in time and concentration by biogeochemical processes. For this purpose, a series of interaction experiments was done with a calcareous clay soil and the phytosiderophore 2?-deoxymugineic acid (DMA), in which metal and DMA speciation were examined as a function of time and DMA concentration. Various kinetically and thermodynamically controlled processes affected the size of the window of Fe uptake. Adsorption lowered, but did not prevent Fe mobilization by DMA. Microbial activity depleted DMA from solution, but not on time scales jeopardizing Strategy II Fe acquisition. Complexation of competing metals played an important role in constraining the window of Fe uptake, particularly at environmentally relevant PS concentrations. Our study provides a conceptual model that takes into account the chemical kinetics involved with PS-mediated Fe acquisition. The model can help to explain how success or failure of PS-mediated Fe acquisition depends on environmental conditions. PMID:25275965

  3. On Shor's channel extension and constrained channels

    E-print Network

    A. S. Holevo; M. E. Shirokov

    2004-02-24

    In this paper we give several equivalent formulations of the additivity conjecture for constrained channels, which formally is substantially stronger than the unconstrained additivity. To this end a characteristic property of the optimal ensemble for such a channel is derived, generalizing the maximal distance property. It is shown that the additivity conjecture for constrained channels holds true for certain nontrivial classes of channels. Recently P. Shor showed that conjectured additivity properties for several quantum information quantities are in fact equivalent. After giving an algebraic formulation for the Shor's channel extension, its main asymptotic property is proved. It is then used to show that additivity for two constrained channels can be reduced to the same problem for unconstrained channels, and hence, "global" additivity for channels with arbitrary constraints is equivalent to additivity without constraints.

  4. Constraining Ceres' interior from its Rotational Motion

    E-print Network

    Rambaux, Nicolas; Dehant, Véronique; Kuchynka, Petr

    2011-01-01

    Context. Ceres is the most massive body of the asteroid belt and contains about 25 wt.% (weight percent) of water. Understanding its thermal evolution and assessing its current state are major goals of the Dawn Mission. Constraints on internal structure can be inferred from various observations. Especially, detailed knowledge of the rotational motion can help constrain the mass distribution inside the body, which in turn can lead to information on its geophysical history. Aims. We investigate the signature of the interior on the rotational motion of Ceres and discuss possible future measurements performed by the spacecraft Dawn that will help to constrain Ceres' internal structure. Methods. We compute the polar motion, precession-nutation, and length-of-day variations. We estimate the amplitudes of the rigid and non-rigid response for these various motions for models of Ceres interior constrained by recent shape data and surface properties. Results. As a general result, the amplitudes of oscillations in the r...

  5. Pattern Search Methods for Linearly Constrained Minimization

    NASA Technical Reports Server (NTRS)

    Lewis, Robert Michael; Torczon, Virginia

    1998-01-01

    We extend pattern search methods to linearly constrained minimization. We develop a general class of feasible point pattern search algorithms and prove global convergence to a Karush-Kuhn-Tucker point. As in the case of unconstrained minimization, pattern search methods for linearly constrained problems accomplish this without explicit recourse to the gradient or the directional derivative. Key to the analysis of the algorithms is the way in which the local search patterns conform to the geometry of the boundary of the feasible region.

  6. A conformation-constrained peptide library based on insect defensin A

    Microsoft Academic Search

    An Zhao; Yanning Xue; Jie Zhang; Bo Gao; Jiannan Feng; Canquan Mao; Li Zheng; Nongle Liu; Fang Wang; Huixin Wang

    2004-01-01

    Here, we reported a conformation-constrained peptide library, that was constructed based on the scaffold of a 29 amino acids peptide derived from insect defensin A. The peptide scaffold was designed utilizing the InsightII molecular modeling software and then displayed on M13 filamentous bacteriophage by fusion with coat protein III. The library was constructed by randomization of seven positions located within

  7. Rhythmic Grouping Biases Constrain Infant Statistical Learning

    ERIC Educational Resources Information Center

    Hay, Jessica F.; Saffran, Jenny R.

    2012-01-01

    Linguistic stress and sequential statistical cues to word boundaries interact during speech segmentation in infancy. However, little is known about how the different acoustic components of stress constrain statistical learning. The current studies were designed to investigate whether intensity and duration each function independently as cues to…

  8. Symmetries and dynamics in constrained systems

    E-print Network

    Xavier Bekaert; Jeong-Hyuck Park

    2009-04-03

    We review in detail the Hamiltonian dynamics for constrained systems. Emphasis is put on the total Hamiltonian system rather than on the extended Hamiltonian system. We provide a systematic analysis of (global and local) symmetries in total Hamiltonian systems. In particular, in analogue to total Hamiltonians, we introduce the notion of total Noether charges. Grassmannian degrees of freedom are also addressed in details.

  9. Haptic Interaction With Constrained Dynamic Systems

    E-print Network

    MacIver, Malcolm A.

    Haptic Interaction With Constrained Dynamic Systems Eric L. Faulring, Kevin M. Lynch, J. Edward the operator of a haptic display to interact with virtual systems having significant inertial dynamics is implemented on the Cobotic Hand Controller, an admittance- type haptic display, and two examples are discussed

  10. CRYPTANALYSIS OF RSA WITH CONSTRAINED KEYS

    E-print Network

    Nitaj, Abderrahmane

    CRYPTANALYSIS OF RSA WITH CONSTRAINED KEYS Abderrahmane Nitaj Univerist´e de Caen, France September 30, 2005 A. Nitaj, Cryptanalysis of RSA ­ p.1/29 #12;Outline The RSA cryptosystem The continued, Cryptanalysis of RSA ­ p.2/29 #12;RSA Cryptosystem (1978) The modulus : n = pq, with p and q primes. Euler

  11. Research Articles Exomoon Habitability Constrained by Illumination

    E-print Network

    Barnes, Rory

    Research Articles Exomoon Habitability Constrained by Illumination and Tidal Heating Rene´ Heller1 their habitability will emerge. Exomoons are likely to be tidally locked to their planet and hence experience days evolved outside Earth has prompted scientists to consider habitability of the terres- trial planets

  12. Constrained CP-nets Steve Prestwich

    E-print Network

    Walsh, Toby

    Constrained CP-nets Steve Prestwich , Francesca Rossi ¡ , Kristen Brent Venable ¡, Toby Walsh 1, soft constraints, and CP-nets. We construct a set of hard constraints whose solutions are the optimal to represent preferences, we will consider CP-nets [6, 3], which is a quali- tative approach where preferences

  13. Constrained CP-nets Steve Prestwich1

    E-print Network

    Rossi, Francesca

    Constrained CP-nets Steve Prestwich1 , Francesca Rossi2 , Kristen Brent Venable2 , Toby Walsh1 1, soft constraints, and CP nets. We construct a set of hard constraints whose solutions are the optimal. Among the many existing approaches to represent preferencess, we will consider CP nets [5,3], which

  14. Constraining Ceres' interior from its rotational motion

    Microsoft Academic Search

    N. Rambaux; J. Castillo-Rogez; V. Dehant; P. Kuchynka

    2011-01-01

    Context. Ceres is the most massive body of the asteroid belt and contains about 25 wt.% (weight percent) of water. Understanding its thermal evolution and assessing its current state are major goals of the Dawn mission. Constraints on its internal structure can be inferred from various types of observations. In particular, detailed knowledge of the rotational motion can help constrain

  15. Nonlinear Wave Equations and Constrained Harmonic Motion

    Microsoft Academic Search

    Percy Deift; Fernando Lund; Eugene Trubowitz

    1980-01-01

    The study of the Korteweg-deVries, nonlinear Schrodinger, Sine-Gordon, and Toda lattice equations is simply the study of constrained oscillators. This is likely to be true for any nonlinear wave equation associated with a second-order linear problem.

  16. Globally Convergent Evolution Strategies for Constrained Optimization

    E-print Network

    2014-07-10

    Jul 10, 2014 ... In the literature of direct-search methods (of directional type) for constraints, one finds ..... lms1b, lms2, lms3, lms5 due to library linkage and the linearly constrained problems ..... Comparison of public-domain software for black ...

  17. Statistically Constrained Decimation of a Turbulence Model

    Microsoft Academic Search

    Timothy Joe Williams

    1988-01-01

    The constrained decimation scheme (CDS) is applied to a turbulence model. The CDS is a statistical turbulence theory formulated in 1985 by Robert Kraichnan; it seeks to correctly describe the statistical behavior of a system using only a small sample of the actual dynamics. The full set of dynamical quantities is partitioned into groups, within each of which the statistical

  18. Silent networking for energy-constrained nodes

    Microsoft Academic Search

    Tao Zhang; Provin Gurung; Eric Van Den Berg; Sunil Madhani; Anish Muttreja

    2006-01-01

    This paper proposes Silent Networking – a new method to significantly increase the lifetimes of energy-constrained nodes, networks, and mobile user devices. With Silent Networking, each network element powers off some or all of its radio interfaces during their naturally occurring silent periods, i.e., time periods when it does not expect to originate, receive, or relay traffic through those interfaces

  19. A sequential equality constrained quadratic programming algorithm for inequality constrained optimization

    NASA Astrophysics Data System (ADS)

    Zhu, Zhibin

    2008-02-01

    In this paper, the feasible type SQP method is improved. A new SQP algorithm is presented to solve the nonlinear inequality constrained optimization. As compared with the existing SQP methods, per single iteration, in order to obtain the search direction, it is only necessary to solve equality constrained quadratic programming subproblems and systems of linear equationsE Under some suitable conditions, the global and superlinear convergence can be induced.

  20. Blockade of Lysosomal Acid Ceramidase Induces GluN2B-Dependent Tau Phosphorylation in Rat Hippocampal Slices

    PubMed Central

    Laurier-Laurin, Marie-Elaine; Attiori Essis, Suzanne; Cyr, Michel

    2014-01-01

    The lysosomal acid ceramidase, an enzyme known to limit intracellular ceramide accumulation, has been reported to be defective in neurodegenerative disorders. We show here that rat hippocampal slices, preincubated with the acid ceramidase inhibitor (ACI) d-NMAPPD, exhibit increased N-methyl-D-aspartate (NMDA) receptor-mediated field excitatory postsynaptic potentials (fEPSPs) in CA1 synapses. The ACI by itself did not interfere with either paired pulse facilitation or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor-mediated fEPSPs, indicating that its influence on synaptic transmission is postsynaptic in origin and specific to the NMDA subtype of glutamate receptors. From a biochemical perspective, we observed that Tau phosphorylation at the Ser262 epitope was highly increased in hippocampal slices preincubated with the ACI, an effect totally prevented by the global NMDA receptor antagonist D/L(?)-2-amino-5-phosphonovaleric acid (AP-5), the calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N?,N?-tetraacetic acid (BAPTA), and the GluN2B (but not the GluN2A) receptor antagonist RO25-6981. On the other hand, preincubation of hippocampal slices with the compound KN-62, an inhibitor known to interfere with calcium/calmodulin-dependent protein kinase II (CaMKII), totally abolished the effect of ACI on Tau phosphorylation at Ser262 epitopes. Collectively, these results provide experimental evidence that ceramides play an important role in regulating Tau phosphorylation in the hippocampus via a mechanism dependent on GluN2B receptor subunits and CaMKII activation. PMID:25276436

  1. Blockade of lysosomal acid ceramidase induces GluN2B-dependent Tau phosphorylation in rat hippocampal slices.

    PubMed

    Laurier-Laurin, Marie-Elaine; De Montigny, Audrée; Attiori Essis, Suzanne; Cyr, Michel; Massicotte, Guy

    2014-01-01

    The lysosomal acid ceramidase, an enzyme known to limit intracellular ceramide accumulation, has been reported to be defective in neurodegenerative disorders. We show here that rat hippocampal slices, preincubated with the acid ceramidase inhibitor (ACI) d-NMAPPD, exhibit increased N-methyl-D-aspartate (NMDA) receptor-mediated field excitatory postsynaptic potentials (fEPSPs) in CA1 synapses. The ACI by itself did not interfere with either paired pulse facilitation or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor-mediated fEPSPs, indicating that its influence on synaptic transmission is postsynaptic in origin and specific to the NMDA subtype of glutamate receptors. From a biochemical perspective, we observed that Tau phosphorylation at the Ser262 epitope was highly increased in hippocampal slices preincubated with the ACI, an effect totally prevented by the global NMDA receptor antagonist D/L(-)-2-amino-5-phosphonovaleric acid (AP-5), the calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), and the GluN2B (but not the GluN2A) receptor antagonist RO25-6981. On the other hand, preincubation of hippocampal slices with the compound KN-62, an inhibitor known to interfere with calcium/calmodulin-dependent protein kinase II (CaMKII), totally abolished the effect of ACI on Tau phosphorylation at Ser262 epitopes. Collectively, these results provide experimental evidence that ceramides play an important role in regulating Tau phosphorylation in the hippocampus via a mechanism dependent on GluN2B receptor subunits and CaMKII activation. PMID:25276436

  2. Behavioral effects of alpha-alkylated amino acid analogs in the C57BL/6J mouse.

    PubMed

    Sase, Ajinkya; Brückner, Hans; Höger, Harald; Pollak, Arnold; Lubec, Gert

    2013-09-01

    Although a series of amino acid analogs have been shown to modulate brain function, information on the pharmacology of alpha-alkylated amino acids (AAAA) is limited. In particular there is no information on the effect of these amino acid analogs (AAA) on the elevated plus maze, the tail suspension test and the forced swim test. It was therefore the aim of the study to test a series of AAAA in these paradigms in order to explore behavioral activities of this compound class. 10 male mice per group aged between 10 and 14 weeks were used. Vehicle-treated controls were used in addition to intraperitoneal injections of 1, 10 and 100mg/kg body weight of each, alpha-amino-isobutyic acid (AIB), isovaline (IVA), alpha-propyl-alanine (APA), alpha-butyl-alanine (ABA), alpha-pentyl-alanine (APnA), alpha-ethylphenylglycine (AEPG) and alpha-methyl-valine (AMV). The elevated plus maze (EPM), the tail suspension test (TST) and forced swim test (FST) were used for behavioral testing. There were dose-dependent results: all compounds increased time and pathlength in the open arm of the EPM at least at one dose administered. In the TST and in the FST only the 100mg dose was showing an effect. The results show pharmacological activity modifying the EPM in low doses suggesting the use in treatment of behavioral traits and symptoms represented by or linked to the EPM including anxiety-related behavior including depression. Compounds acting at higher doses may be used to induce behavioral changes and thus serve as neurobiological-neuropharmacological tools. PMID:23756141

  3. Variance constrained control of maneuvering helicopters with sensor failure

    E-print Network

    Sultan, Cornel

    Variance constrained control of maneuvering helicopters with sensor failure Tugrul Oktay constrained controllers and maneuvering helicopters when also some helicopter sensors fail. For this purpose complex, control oriented, physics based helicopter models are used. A nonlinear model of the helicopter

  4. Ocean Acidification-Induced Food Quality Deterioration Constrains Trophic Transfer

    PubMed Central

    Hauss, Helena; Schulz, Kai G.; Riebesell, Ulf; Sommer, Ulrich; Winder, Monika

    2012-01-01

    Our present understanding of ocean acidification (OA) impacts on marine organisms caused by rapidly rising atmospheric carbon dioxide (CO2) concentration is almost entirely limited to single species responses. OA consequences for food web interactions are, however, still unknown. Indirect OA effects can be expected for consumers by changing the nutritional quality of their prey. We used a laboratory experiment to test potential OA effects on algal fatty acid (FA) composition and resulting copepod growth. We show that elevated CO2 significantly changed the FA concentration and composition of the diatom Thalassiosira pseudonana, which constrained growth and reproduction of the copepod Acartia tonsa. A significant decline in both total FAs (28.1 to 17.4 fg cell?1) and the ratio of long-chain polyunsaturated to saturated fatty acids (PUFA:SFA) of food algae cultured under elevated (750 µatm) compared to present day (380 µatm) pCO2 was directly translated to copepods. The proportion of total essential FAs declined almost tenfold in copepods and the contribution of saturated fatty acids (SFAs) tripled at high CO2. This rapid and reversible CO2-dependent shift in FA concentration and composition caused a decrease in both copepod somatic growth and egg production from 34 to 5 eggs female?1 day?1. Because the diatom-copepod link supports some of the most productive ecosystems in the world, our study demonstrates that OA can have far-reaching consequences for ocean food webs by changing the nutritional quality of essential macromolecules in primary producers that cascade up the food web. PMID:22509351

  5. An autonomous vehicle: Constrained test and evaluation

    NASA Astrophysics Data System (ADS)

    Griswold, Norman C.

    1991-11-01

    The objective of the research is to develop an autonomous vehicle which utilizes stereo camera sensors (using ambient light) to follow complex paths at speeds up to 35 mph with consideration of moving vehicles within the path. The task is intended to demonstrate the contribution to safety of a vehicle under automatic control. All of the long-term scenarios investigating future reduction in congestion involve an automatic system taking control, or partial control, of the vehicle. A vehicle which includes a collision avoidance system is a prerequisite to an automatic control system. The report outlines the results of a constrained test of a vision controlled vehicle. In order to demonstrate its ability to perform on the current street system the vehicle was constrained to recognize, approach, and stop at an ordinary roadside stop sign.

  6. Constraining the Braneworld with Gravitational Wave Observations

    NASA Technical Reports Server (NTRS)

    McWilliams, Sean T.

    2011-01-01

    Some braneworld models may have observable consequences that, if detected, would validate a requisite element of string theory. In the infinite Randall-Sundrum model (RS2), the AdS radius of curvature, L, of the extra dimension supports a single bound state of the massless graviton on the brane, thereby reproducing Newtonian gravity in the weak-field limit. However, using the AdS/CFT correspondence, it has been suggested that one possible consequence of RS2 is an enormous increase in Hawking radiation emitted by black holes. We utilize this possibility to derive two novel methods for constraining L via gravitational wave measurements. We show that the EMRI event rate detected by LISA can constrain L at the approximately 1 micron level for optimal cases, while the observation of a single galactic black hole binary with LISA results in an optimal constraint of L less than or equal to 5 microns.

  7. Constraining the braneworld with gravitational wave observations.

    PubMed

    McWilliams, Sean T

    2010-04-01

    Some braneworld models may have observable consequences that, if detected, would validate a requisite element of string theory. In the infinite Randall-Sundrum model (RS2), the AdS radius of curvature, l, of the extra dimension supports a single bound state of the massless graviton on the brane, thereby reproducing Newtonian gravity in the weak-field limit. However, using the AdS/CFT correspondence, it has been suggested that one possible consequence of RS2 is an enormous increase in Hawking radiation emitted by black holes. We utilize this possibility to derive two novel methods for constraining l via gravitational wave measurements. We show that the EMRI event rate detected by LISA can constrain l at the approximately 1 microm level for optimal cases, while the observation of a single galactic black hole binary with LISA results in an optimal constraint of l < or = 5 microm. PMID:20481929

  8. Constraining the Braneworld with Gravitational Wave Observations

    NASA Astrophysics Data System (ADS)

    McWilliams, Sean T.

    2010-04-01

    Some braneworld models may have observable consequences that, if detected, would validate a requisite element of string theory. In the infinite Randall-Sundrum model (RS2), the AdS radius of curvature, ?, of the extra dimension supports a single bound state of the massless graviton on the brane, thereby reproducing Newtonian gravity in the weak-field limit. However, using the AdS/CFT correspondence, it has been suggested that one possible consequence of RS2 is an enormous increase in Hawking radiation emitted by black holes. We utilize this possibility to derive two novel methods for constraining ? via gravitational wave measurements. We show that the EMRI event rate detected by LISA can constrain ? at the ˜1?m level for optimal cases, while the observation of a single galactic black hole binary with LISA results in an optimal constraint of ??5?m.

  9. Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

    PubMed Central

    Koopmanschap, Gijs; Ruijter, Eelco

    2014-01-01

    Summary In the recent past, the design and synthesis of peptide mimics (peptidomimetics) has received much attention. This because they have shown in many cases enhanced pharmacological properties over their natural peptide analogues. In particular, the incorporation of cyclic constructs into peptides is of high interest as they reduce the flexibility of the peptide enhancing often affinity for a certain receptor. Moreover, these cyclic mimics force the molecule into a well-defined secondary structure. Constraint structural and conformational features are often found in biological active peptides. For the synthesis of cyclic constrained peptidomimetics usually a sequence of multiple reactions has been applied, which makes it difficult to easily introduce structural diversity necessary for fine tuning the biological activity. A promising approach to tackle this problem is the use of multicomponent reactions (MCRs), because they can introduce both structural diversity and molecular complexity in only one step. Among the MCRs, the isocyanide-based multicomponent reactions (IMCRs) are most relevant for the synthesis of peptidomimetics because they provide peptide-like products. However, these IMCRs usually give linear products and in order to obtain cyclic constrained peptidomimetics, the acyclic products have to be cyclized via additional cyclization strategies. This is possible via incorporation of bifunctional substrates into the initial IMCR. Examples of such bifunctional groups are N-protected amino acids, convertible isocyanides or MCR-components that bear an additional alkene, alkyne or azide moiety and can be cyclized via either a deprotection–cyclization strategy, a ring-closing metathesis, a 1,3-dipolar cycloaddition or even via a sequence of multiple multicomponent reactions. The sequential IMCR-cyclization reactions can afford small cyclic peptide mimics (ranging from four- to seven-membered rings), medium-sized cyclic constructs or peptidic macrocycles (>12 membered rings). This review describes the developments since 2002 of IMCRs-cyclization strategies towards a wide variety of small cyclic mimics, medium sized cyclic constructs and macrocyclic peptidomimetics. PMID:24605172

  10. Fast features for time constrained object detection

    Microsoft Academic Search

    Gary Overett; Lars Petersson

    2009-01-01

    This paper concerns itself with the development and design of fast features suitable for time constrained object detection. Primarily we consider three aspects of feature design; the form of the precomputed datatype (e.g. the integral image), the form of the features themselves (i.e. the measurements made of an image), and the models\\/weak- learners used to construct weak classifiers (class, non-class

  11. On finding multi-constrained paths

    Microsoft Academic Search

    Shigang Chen; K. Nahrstedt

    1998-01-01

    New emerging distributed multimedia applications provide guaranteed end-to-end quality of service (QoS) and have stringent constraints on delay, delay-jitter, cost, etc. The task of QoS routing is to find a route in the network which has sufficient resources to satisfy the constraints. The delay-cost-constrained routing problem is NP-complete. We propose a heuristic algorithm for this problem. The idea is to

  12. On Finding Multi-constrained Paths

    Microsoft Academic Search

    Shigang Chen Klara Nahrstedt

    1998-01-01

    New emerging distributed multimedia applications provideguaranteed end-to-end quality of service (QoS) and havestringent constraints on delay, delay-jitter, cost, etc. Thetask of QoS routing is to find a route in the network whichhas sufficient resources to satisfy the constraints. The delaycost-constrained routing problem is NP-complete. We proposea heuristic algorithm for this problem. The idea is tofirst reduce the NP-complete problem to

  13. Quantum annealing in a kinetically constrained system

    Microsoft Academic Search

    Arnab Das; Bikas K. Chakrabarti; Robin B. Stinhcombe

    2005-01-01

    Classical and quantum annealing is discussed for a kinetically constrained\\u000achain of $N$ non-interacting asymmetric double wells, represented by Ising\\u000aspins in a longitudinal field $h$. It is shown that in certain cases, where the\\u000akinetic constraints may arise from infinitely high but vanishingly narrow\\u000abarriers appearing in the relaxation path of the system, quantum annealing\\u000aexploiting the quantum-mechanical penetration

  14. Waves in Constrained Linear Elastic Materials

    Microsoft Academic Search

    Maria Luisa Tonon

    2002-01-01

    This paper deals with the propagation of acceleration waves in constrained linear elastic materials, within the framework\\u000a of the so-called linearized finite theory of elasticity, as defined by Hoger and Johnson in [12, 13]. In this theory, the\\u000a constitutive equations are obtained by linearization of the corresponding finite constitutive equations with respect to the\\u000a displacement gradient and significantly differ from

  15. Constrained C1 Interpolation on Rectangular Grids

    Microsoft Academic Search

    E. S. Chan; V. P. Kong; B. H. Ong

    2004-01-01

    This paper is concerned with the range restricted interpolation of 'data on rectangular grids. The interpolant is constrained to lie on the same side of the constraint surface as the data. Sufficient non-negativity conditions on the Bezier ordinates are derived to ensure the non-negativity ofa bicubic Bezier patch. The method modifies Bezier ordinates locally to fulfill the sufficient non-negativity conditions.

  16. Constrained simulation of the Bullet Cluster

    SciTech Connect

    Lage, Craig; Farrar, Glennys, E-mail: csl336@nyu.edu [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003 (United States)

    2014-06-01

    In this work, we report on a detailed simulation of the Bullet Cluster (1E0657-56) merger, including magnetohydrodynamics, plasma cooling, and adaptive mesh refinement. We constrain the simulation with data from gravitational lensing reconstructions and the 0.5-2 keV Chandra X-ray flux map, then compare the resulting model to higher energy X-ray fluxes, the extracted plasma temperature map, Sunyaev-Zel'dovich effect measurements, and cluster halo radio emission. We constrain the initial conditions by minimizing the chi-squared figure of merit between the full two-dimensional (2D) observational data sets and the simulation, rather than comparing only a few features such as the location of subcluster centroids, as in previous studies. A simple initial configuration of two triaxial clusters with Navarro-Frenk-White dark matter profiles and physically reasonable plasma profiles gives a good fit to the current observational morphology and X-ray emissions of the merging clusters. There is no need for unconventional physics or extreme infall velocities. The study gives insight into the astrophysical processes at play during a galaxy cluster merger, and constrains the strength and coherence length of the magnetic fields. The techniques developed here to create realistic, stable, triaxial clusters, and to utilize the totality of the 2D image data, will be applicable to future simulation studies of other merging clusters. This approach of constrained simulation, when applied to well-measured systems, should be a powerful complement to present tools for understanding X-ray clusters and their magnetic fields, and the processes governing their formation.

  17. Weak shock waves in constrained thermoelastic solids

    Microsoft Academic Search

    T. Gültop

    2002-01-01

    Summary  ?The jumps in Helmholtz free energy and stress across a shock wave front are obtained by using the Taylor's series expansion\\u000a of the corresponding functions of arbitrarily constrained thermoelastic solids. The linear terms in the expressions of jumps\\u000a are considered alone to account for linear weak shock waves. The generalized thermomechanical constraint functions and purely\\u000a mechanical constraint functions are treated

  18. Constrained Implants in Total Knee Replacement.

    PubMed

    Touzopoulos, Panagiotis; Drosos, Georgios I; Ververidis, Athanasios; Kazakos, Konstantinos

    2015-05-01

    Total knee replacement (TKR) is a successful procedure for pain relief and functional restoration in patients with advanced osteoarthritis. The number of TKRs is increasing, and this has led to an increase in revision surgeries. The key to long-term success in both primary and revision TKR is stability, as well as adequate and stable fixation between components and underlying bone. In the vast majority of primary TKRs and in some revision cases, a posterior cruciate retaining or a posterior cruciate substituting device can be used. In some primary cases with severe deformity or ligamentous instability and in most of the revision cases, a more constrained implant is required. The purpose of this paper is to review the literature concerning the use of condylar constrained knee (CCK) and rotating hinge (RH) implants in primary and revision cases focusing on the indications and results. According to this review, although excellent and very good results have been reported, there are limitations of the existing literature concerning the indications for the use of constrained implants, the absence of long-term results, and the limited comparative studies. PMID:26055025

  19. CONSTRAINING SOURCE REDSHIFT DISTRIBUTIONS WITH GRAVITATIONAL LENSING

    SciTech Connect

    Wittman, D.; Dawson, W. A., E-mail: dwittman@physics.ucdavis.edu [Physics Department, University of California, Davis, CA 95616 (United States)

    2012-09-10

    We introduce a new method for constraining the redshift distribution of a set of galaxies, using weak gravitational lensing shear. Instead of using observed shears and redshifts to constrain cosmological parameters, we ask how well the shears around clusters can constrain the redshifts, assuming fixed cosmological parameters. This provides a check on photometric redshifts, independent of source spectral energy distribution properties and therefore free of confounding factors such as misidentification of spectral breaks. We find that {approx}40 massive ({sigma}{sub v} = 1200 km s{sup -1}) cluster lenses are sufficient to determine the fraction of sources in each of six coarse redshift bins to {approx}11%, given weak (20%) priors on the masses of the highest-redshift lenses, tight (5%) priors on the masses of the lowest-redshift lenses, and only modest (20%-50%) priors on calibration and evolution effects. Additional massive lenses drive down uncertainties as N{sub lens}{sup -1/2}, but the improvement slows as one is forced to use lenses further down the mass function. Future large surveys contain enough clusters to reach 1% precision in the bin fractions if the tight lens-mass priors can be maintained for large samples of lenses. In practice this will be difficult to achieve, but the method may be valuable as a complement to other more precise methods because it is based on different physics and therefore has different systematic errors.

  20. Acid Rain.

    ERIC Educational Resources Information Center

    Openshaw, Peter

    1987-01-01

    Provides some background information on acid deposition. Includes a historical perspective, describes some effects of acid precipitation, and discusses acid rain in the United Kingdom. Contains several experiments that deal with the effects of acid rain on water quality and soil. (TW)

  1. Security-constrained reactive power dispatch

    SciTech Connect

    Terra, L.D.B.; Short, M.J. (Imperial Coll. of Science and Technology, London (UK))

    1991-02-01

    This paper presents a new method to solve the preventive security-constrained reactive power (var) dispatch problem. A decomposition-coordination scheme is conceived in order to take advantage of the special structure of the problem. Instead of tearing the network, the problem itself is decomposed into smaller sub-problems. Techniques are presented for contingency simulation and for the handling of these contingencies in the optimization process. The computing procedure is given for the step-by-step solution for on-line implementation. VAR-oriented load flow and optimal power flow methods are described. Numerical testing results are reported.

  2. Medical knowledge evolution query constraining aspects.

    PubMed

    Eklund, Ann-Marie

    2011-01-01

    In this paper we present a first analysis towards better understanding of the query constraining aspects of knowledge, as expressed in the most used public medical bibliographic database MEDLINE. Our results indicate, possibly not surprising, that new terms occur, but also that traditional terms are replaced by more specific ones or even go out of use as they become common knowledge. Hence, as knowledge evolve over time, search methods may benefit from becoming more sensitive to knowledge expression, to enable finding new, as well as older, relevant database contents. PMID:21893809

  3. Utility Constrained Energy Minimization In Aloha Networks

    E-print Network

    Khodaian, Amir Mahdi; Talebi, Mohammad S

    2010-01-01

    In this paper we consider the issue of energy efficiency in random access networks and show that optimizing transmission probabilities of nodes can enhance network performance in terms of energy consumption and fairness. First, we propose a heuristic power control method that improves throughput, and then we model the Utility Constrained Energy Minimization (UCEM) problem in which the utility constraint takes into account single and multi node performance. UCEM is modeled as a convex optimization problem and Sequential Quadratic Programming (SQP) is used to find optimal transmission probabilities. Numerical results show that our method can achieve fairness, reduce energy consumption and enhance lifetime of such networks.

  4. Semiclassical Analysis of Constrained Quantum Systems

    SciTech Connect

    Tsobanjan, Artur [Institute for Gravitation and the Cosmos, Pennsylvania State University, 104 Davey Lab, University Park, PA 16802 (United States)

    2009-12-15

    Exact procedures that follow Dirac's constraint quantization of gauge theories are usually technically involved and often difficult to implement in practice. We overview an 'effective' scheme for obtaining the leading order semiclassical corrections to the dynamics of constrained quantum systems developed elsewhere. Motivated by the geometrical view of quantum mechanics, our method mimics the classical Dirac-Bergmann algorithm and avoids direct reference to a particular representation of the physical Hilbert space. We illustrate the procedure through the example of a relativistic particle in Minkowski spacetime.

  5. Quantum Annealing in a Kinetically Constrained System

    E-print Network

    Arnab Das; Bikas K. Chakrabarti; Robin B. Stinhcombe

    2005-02-07

    Classical and quantum annealing is discussed for a kinetically constrained chain of $N$ non-interacting asymmetric double wells, represented by Ising spins in a longitudinal field $h$. It is shown that in certain cases, where the kinetic constraints may arise from infinitely high but vanishingly narrow barriers appearing in the relaxation path of the system, quantum annealing exploiting the quantum-mechanical penetration of sufficiently narrow barriers may be far more efficient than its thermal counterpart. We have used a semiclassical picture of scattering dynamics to do our simulation for the quantum system.

  6. Quantization of soluble classical constrained systems

    E-print Network

    Zahir Belhadi; Ferhat Ménas; Alain Bérard; Herve Mohrbach

    2014-08-27

    The derivation of the brackets among coordinates and momenta for classical constrained systems is a necessary step toward their quantization. Here we present a new approach for the determination of the classical brackets which does neither require Dirac's formalism nor the symplectic method of Faddeev and Jackiw. This approach is based on the computation of the brackets between the constants of integration of the exact solutions of the equations of motion. From them all brackets of the dynamical variables of the system can be deduced in a straightforward way.

  7. Aristolochic Acids

    MedlinePLUS

    ... Sciences NIH-HHS www.niehs.nih.gov Aristolochic Acids Key Points Report on Carcinogens Status Known to be human carcinogens Aristolochia Clematitis Aristolochic Acids n Known human carcinogens n Found in certain ...

  8. Iron supply constrains producer communities in stream ecosystems.

    PubMed

    Larson, Chad A; Liu, Hongsheng; Passy, Sophia I

    2015-05-01

    The current paradigm that stream producers are under exclusive macronutrient control was recently challenged by continental studies, demonstrating that iron supply constrained diatom biodiversity and energy flows. Using algal abundance and water chemistry data from the National Water-Quality Assessment Program, we determined for the first time community thresholds along iron gradients in non-acidic running waters, i.e. 30-79.5??g?L(-1) and 70-120 ?g L(-1) in oligotrophic and eutrophic streams, respectively. Given that Fe concentrations fell below both thresholds in 50% of US streams, and below the eutrophic threshold in 75% of US streams, we suggest that Fe limitation is potentially widespread and attribute it to the restricted distribution of wetlands. We also report results from the first laboratory experiments on algal-iron interactions in streams, revealing that iron supplementation leads to significant biovolume and biodiversity increase in both nitrogen fixing and non-nitrogen fixing algae. Therefore, the progressive brownification of freshwaters due to rising dissolved organic carbon and iron levels can have a stimulating influence on microbial producers with cascading effects along the trophic hierarchy. Future research in running waters should focus on the role of iron in algal physiology and biofilm functions, including accumulation of biomass, fixing atmospheric nitrogen and improving water quality. PMID:25873463

  9. Constraining the Braking Indices of Magnetars

    E-print Network

    Gao, Z F; Wang, N; Yuan, J P; Peng, Q H; Du, Y J

    2015-01-01

    Due to the lack of long term pulsed emission in quiescence and the strong timing noise, it is impossible to directly measure the braking index $n$ of a magnetar. Based on the estimated ages of their potentially associated supernova remnants (SNRs), we estimate the values of $n$ of nine magnetars with SNRs, and find that they cluster in a range of $1\\sim$41. Six magnetars have smaller braking indices of $13$ for other three magnetars are attributed to the decay of external braking torque, which might be caused by magnetic field decay. We estimate the possible wind luminosities for the magnetars with $13$ within the updated magneto-thermal evolution models. We point out that there could be some connections between the magnetar's anti-glitch event and its braking index, and the magnitude of $n$ should be taken into account when explaining the event. Although the constrained range of the magnetars' braking indices is tentative, our method provides an effective way to constrain the magnetars' braking indices if th...

  10. Rhythmic grouping biases constrain infant statistical learning

    PubMed Central

    Hay, Jessica F.; Saffran, Jenny R.

    2012-01-01

    Linguistic stress and sequential statistical cues to word boundaries interact during speech segmentation in infancy. However, little is known about how the different acoustic components of stress constrain statistical learning. The current studies were designed to investigate whether intensity and duration each function independently as cues to initial prominence (trochaic-based hypothesis) or whether, as predicted by the Iambic-Trochaic Law (ITL), intensity and duration have characteristic and separable effects on rhythmic grouping (ITL-based hypothesis) in a statistical learning task. Infants were familiarized with an artificial language (Experiments 1 & 3) or a tone stream (Experiment 2) in which there was an alternation in either intensity or duration. In addition to potential acoustic cues, the familiarization sequences also contained statistical cues to word boundaries. In speech (Experiment 1) and non-speech (Experiment 2) conditions, 9-month-old infants demonstrated discrimination patterns consistent with an ITL-based hypothesis: intensity signaled initial prominence and duration signaled final prominence. The results of Experiment 3, in which 6.5-month-old infants were familiarized with the speech streams from Experiment 1, suggest that there is a developmental change in infants’ willingness to treat increased duration as a cue to word offsets in fluent speech. Infants’ perceptual systems interact with linguistic experience to constrain how infants learn from their auditory environment. PMID:23730217

  11. Nonstationary sparsity-constrained seismic deconvolution

    NASA Astrophysics Data System (ADS)

    Sun, Xue-Kai; Sam, Zandong Sun; Xie, Hui-Wen

    2014-12-01

    The Robinson convolution model is mainly restricted by three inappropriate assumptions, i.e., statistically white reflectivity, minimum-phase wavelet, and stationarity. Modern reflectivity inversion methods (e.g., sparsity-constrained deconvolution) generally attempt to suppress the problems associated with the first two assumptions but often ignore that seismic traces are nonstationary signals, which undermines the basic assumption of unchanging wavelet in reflectivity inversion. Through tests on reflectivity series, we confirm the effects of nonstationarity on reflectivity estimation and the loss of significant information, especially in deep layers. To overcome the problems caused by nonstationarity, we propose a nonstationary convolutional model, and then use the attenuation curve in log spectra to detect and correct the influences of nonstationarity. We use Gabor deconvolution to handle nonstationarity and sparsity-constrained deconvolution to separating reflectivity and wavelet. The combination of the two deconvolution methods effectively handles nonstationarity and greatly reduces the problems associated with the unreasonable assumptions regarding reflectivity and wavelet. Using marine seismic data, we show that correcting nonstationarity helps recover subtle reflectivity information and enhances the characterization of details with respect to the geological record.

  12. Regular Language Constrained Sequence Alignment Revisited

    NASA Astrophysics Data System (ADS)

    Kucherov, Gregory; Pinhas, Tamar; Ziv-Ukelson, Michal

    Imposing constraints in the form of a finite automaton or a regular expression is an effective way to incorporate additional a priori knowledge into sequence alignment procedures. With this motivation, Arslan [1] introduced the Regular Language Constrained Sequence Alignment Problem and proposed an O(n 2 t 4) time and O(n 2 t 2) space algorithm for solving it, where n is the length of the input strings and t is the number of states in the non-deterministic automaton, which is given as input. Chung et al. [2] proposed a faster O(n 2 t 3) time algorithm for the same problem. In this paper, we further speed up the algorithms for Regular Language Constrained Sequence Alignment by reducing their worst case time complexity bound to O(n 2 t 3/logt). This is done by establishing an optimal bound on the size of Straight-Line Programs solving the maxima computation subproblem of the basic dynamic programming algorithm. We also study another solution based on a Steiner Tree computation. While it does not improve the run time complexity in the worst case, our simulations show that both approaches are efficient in practice, especially when the input automata are dense.

  13. Intersecting transcription networks constrain gene regulatory evolution.

    PubMed

    Sorrells, Trevor R; Booth, Lauren N; Tuch, Brian B; Johnson, Alexander D

    2015-07-16

    Epistasis-the non-additive interactions between different genetic loci-constrains evolutionary pathways, blocking some and permitting others. For biological networks such as transcription circuits, the nature of these constraints and their consequences are largely unknown. Here we describe the evolutionary pathways of a transcription network that controls the response to mating pheromone in yeast. A component of this network, the transcription regulator Ste12, has evolved two different modes of binding to a set of its target genes. In one group of species, Ste12 binds to specific DNA binding sites, while in another lineage it occupies DNA indirectly, relying on a second transcription regulator to recognize DNA. We show, through the construction of various possible evolutionary intermediates, that evolution of the direct mode of DNA binding was not directly accessible to the ancestor. Instead, it was contingent on a lineage-specific change to an overlapping transcription network with a different function, the specification of cell type. These results show that analysing and predicting the evolution of cis-regulatory regions requires an understanding of their positions in overlapping networks, as this placement constrains the available evolutionary pathways. PMID:26153861

  14. Constraining DM through 21 cm observations

    E-print Network

    M. Valdes; A. Ferrara; M. Mapelli; E. Ripamonti

    2007-01-10

    Beyond reionization epoch cosmic hydrogen is neutral and can be directly observed through its 21 cm line signal. If dark matter (DM) decays or annihilates the corresponding energy input affects the hydrogen kinetic temperature and ionized fraction, and contributes to the Ly_alpha background. The changes induced by these processes on the 21 cm signal can then be used to constrain the proposed DM candidates, among which we select the three most popular ones: (i) 25-keV decaying sterile neutrinos, (ii) 10-MeV decaying light dark matter (LDM) and (iii) 10-MeV annihilating LDM. Although we find that the DM effects are considerably smaller than found by previous studies (due to a more physical description of the energy transfer from DM to the gas), we conclude that combined observations of the 21 cm background and of its gradient should be able to put constrains at least on LDM candidates. In fact, LDM decays (annihilations) induce differential brightness temperature variations with respect to the non decaying/annihilating DM case up to Delta_delta T_b=8 (22) mK at about 50 (15) MHz. In principle this signal could be detected both by current single dish radio telescopes and future facilities as LOFAR; however, this assumes that ionospheric, interference and foreground issues can be properly taken care of.

  15. Constraining the Size of the Protosolar Nebula

    NASA Astrophysics Data System (ADS)

    Kretke, Katherine A.; Levison, H. F.; Buie, M. W.

    2011-04-01

    Observations indicate that the gaseous circumstellar disks around young stars vary significantly in size, ranging from 10s to 1000s of AU. Models of planet formation depend critically upon the properties of these primordial disks, yet in general it is impossible to connect an existing planetary system with a observed disk. We present a method to constrain the size of our own protosolar nebula using the properties of small body reservoirs in the solar system. After Jupiter formed, it scattered a significant number of remnant planetesimals into highly eccentric orbits. If there had been a massive, extended protoplanetary disk at that time, then the disk would have excited Kozai oscillations in some of the scattered objects, driving them into high-inclination, low-eccentricity orbits. The dissipation of the gaseous disk would strand a population of objects in these high-inclination orbits; orbits that are stable on Gyr timescales. Surveys placing limits on the presence of these high inclination objects can constrain the size of the gaseous protoplanetary disk at the time of Jupiter's formation.

  16. Constraining the Size of the Protosolar Nebula

    NASA Astrophysics Data System (ADS)

    Kretke, Katherine A.

    2012-01-01

    Observations indicate that the gaseous circumstellar disks around young stars vary significantly in size, ranging from tens to thousands of AU. Models of planet formation depend critically upon the properties of these primordial disks, yet in general it is impossible to connect an existing planetary system with a observed disk. We present a method to constrain the size of our own protosolar nebula using the properties of small body reservoirs in the solar system. After Jupiter formed, it scattered a significant number of remnant planetesimals into highly eccentric orbits. If there had been a massive, extended protoplanetary disk at that time, then the disk would have excited Kozai oscillations in some of the scattered objects, driving them into high-inclination, low-eccentricity orbits. The dissipation of the gaseous disk would strand a population of objects in these high-inclination orbits; orbits that are stable on Gyr time scales. Using limits derived from the non-detection of these high inclination objects in the Deep Ecliptic Sky Survey, we can constrain the size of our gaseous protoplanetary disk at the time of Jupiter's formation to within 50 AU.

  17. Constraining supersymmetric dark matter with synchrotron measurements

    SciTech Connect

    Hooper, Dan [Fermi National Accelerator Laboratory, Theoretical Astrophysics, Batavia, IL 60510 (United States)

    2008-06-15

    The annihilations of neutralino dark matter (or other dark matter candidate) generate, among other standard model states, electrons and positrons. These particles emit synchrotron photons as a result of their interaction with the galactic magnetic field. In this paper, we use the measurements of the Wilkinson Microwave Anisotropy Probe satellite to constrain the intensity of this synchrotron emission and, in turn, the annihilation cross section of the lightest neutralino. We find this constraint to be more stringent than that provided by any other current indirect detection channel. In particular, the neutralino annihilation cross section must be less than {approx_equal}3x10{sup -26} cm{sup 3}/s (1x10{sup 25} cm{sup 3}/s) for 100 GeV (500 GeV) neutralinos distributed with a Navarro-Frenk-White halo profile. For the conservative case of an entirely flat dark matter distribution within the inner 8 kiloparsecs of the Milky Way, the constraint is approximately a factor of 30 less stringent. Even in this conservative case, synchrotron measurements strongly constrain, for example, the possibility of wino or Higgsino neutralino dark matter produced nonthermally in the early universe.

  18. Constraining torsion with Gravity Probe B

    SciTech Connect

    Mao Yi; Guth, Alan H.; Cabi, Serkan [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Tegmark, Max [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); MIT Kavli Institute for Astrophysics and Space Research, Cambridge, Massachusetts 02139 (United States)

    2007-11-15

    It is well-entrenched folklore that all torsion gravity theories predict observationally negligible torsion in the solar system, since torsion (if it exists) couples only to the intrinsic spin of elementary particles, not to rotational angular momentum. We argue that this assumption has a logical loophole which can and should be tested experimentally, and consider nonstandard torsion theories in which torsion can be generated by macroscopic rotating objects. In the spirit of action=reaction, if a rotating mass like a planet can generate torsion, then a gyroscope would be expected to feel torsion. An experiment with a gyroscope (without nuclear spin) such as Gravity Probe B (GPB) can test theories where this is the case. Using symmetry arguments, we show that to lowest order, any torsion field around a uniformly rotating spherical mass is determined by seven dimensionless parameters. These parameters effectively generalize the parametrized post-Newtonian formalism and provide a concrete framework for further testing Einstein's general theory of relativity (GR). We construct a parametrized Lagrangian that includes both standard torsion-free GR and Hayashi-Shirafuji maximal torsion gravity as special cases. We demonstrate that classic solar system tests rule out the latter and constrain two observable parameters. We show that Gravity Probe B is an ideal experiment for further constraining nonstandard torsion theories, and work out the most general torsion-induced precession of its gyroscope in terms of our torsion parameters.

  19. Constrained Optimization by the ? Constrained Differential Evolution with Gradient-Based Mutation and Feasible Elites

    Microsoft Academic Search

    Tetsuyuki Takahama; Setsuko Sakai

    2006-01-01

    While research on constrained optimization using evolutionary algorithms has been actively pursued, it has had to face the problem that the ability to solve multi-modal problems, which have many local solutions within a feasible region, is insufficient, that the ability to solve problems with equality constraints is inadequate, and that the stability and efficiency of searches is low. We proposed

  20. Newton's method for large bound-constrained optimization problems.

    SciTech Connect

    Lin, C.-J.; More, J. J.; Mathematics and Computer Science

    1999-01-01

    We analyze a trust region version of Newton's method for bound-constrained problems. Our approach relies on the geometry of the feasible set, not on the particular representation in terms of constraints. The convergence theory holds for linearly constrained problems and yields global and superlinear convergence without assuming either strict complementarity or linear independence of the active constraints. We also show that the convergence theory leads to an efficient implementation for large bound-constrained problems.

  1. Constrained De Novo Sequencing of Conotoxins

    PubMed Central

    Bhatia, Swapnil; Kil, Yong J.; Ueberheide, Beatrix; Chait, Brian T.; Tayo, Lemmuel; Cruz, Lourdes; Lu, Bingwen; Yates, John R.; Bern, Marshall

    2012-01-01

    De novo peptide sequencing by mass spectrometry (MS) can determine the amino acid sequence of an unknown peptide without reference to a protein database. MS-based de novo sequencing assumes special importance in focused studies of families of biologically active peptides and proteins, such as hormones, toxins, and antibodies, for which amino acid sequences may be difficult to obtain through genomic methods. These protein families often exhibit sequence homology or characteristic amino acid content, yet current de novo sequencing approaches do not take advantage of this prior knowledge and hence search an unnecessarily large space of possible sequences. Here, we describe an algorithm for de novo sequencing that incorporates sequence constraints into the core graph algorithm, and thereby reduces the search space by many orders of magnitude. We demonstrate our algorithm in a study of cysteine-rich toxins from two cone snail species (Conus textile and Conus stercusmuscarum), and report 13 de novo and about 60 total toxins. PMID:22709442

  2. Constraining gravitational and cosmological parameters with astrophysical data

    E-print Network

    Mao, Yi, Ph. D. Massachusetts Institute of Technology

    2008-01-01

    We use astrophysical data to shed light on fundamental physics by constraining parametrized theoretical cosmological and gravitational models. Gravitational parameters are those constants that parametrize possible departures ...

  3. Constraining the Cratering Chronology of Vesta

    E-print Network

    O'Brien, David P; Morbidelli, Alessandro; Bottke, William F; Schenk, Paul M; Russell, Christopher T; Raymond, Carol A

    2014-01-01

    Vesta has a complex cratering history, with ancient terrains as well as recent large impacts that have led to regional resurfacing. Crater counts can help constrain the relative ages of different units on Vesta's surface, but converting those crater counts to absolute ages requires a chronology function. We present a cratering chronology based on the best current models for the dynamical evolution of asteroid belt, and calibrate it to Vesta using the record of large craters on its surface. While uncertainties remain, our chronology function is broadly consistent with an ancient surface of Vesta as well as other constraints such as the bombardment history of the rest of the inner Solar System and the Ar-Ar age distribution of howardite, eucrite and diogenite (HED) meteorites from Vesta.

  4. Constraining the cratering chronology of Vesta

    NASA Astrophysics Data System (ADS)

    O‘Brien, David P.; Marchi, Simone; Morbidelli, Alessandro; Bottke, William F.; Schenk, Paul M.; Russell, Christopher T.; Raymond, Carol A.

    2014-11-01

    Vesta has a complex cratering history, with ancient terrains as well as recent large impacts that have led to regional resurfacing. Crater counts can help constrain the relative ages of different units on Vesta's surface, but converting those crater counts to absolute ages requires a chronology function. We present a cratering chronology based on the best current models for the dynamical evolution of asteroid belt, and calibrate it to Vesta using the record of large craters on its surface. While uncertainties remain, our chronology function is broadly consistent with an ancient surface of Vesta as well as other constraints such as the bombardment history of the rest of the inner Solar System and the Ar-Ar age distribution of howardite, eucrite and diogenite (HED) meteorites from Vesta.

  5. Perceived visual speed constrained by image segmentation

    NASA Technical Reports Server (NTRS)

    Verghese, P.; Stone, L. S.

    1996-01-01

    Little is known about how or where the visual system parses the visual scene into objects or surfaces. However, it is generally assumed that the segmentation and grouping of pieces of the image into discrete entities is due to 'later' processing stages, after the 'early' processing of the visual image by local mechanisms selective for attributes such as colour, orientation, depth, and motion. Speed perception is also thought to be mediated by early mechanisms tuned for speed. Here we show that manipulating the way in which an image is parsed changes the way in which local speed information is processed. Manipulations that cause multiple stimuli to appear as parts of a single patch degrade speed discrimination, whereas manipulations that perceptually divide a single large stimulus into parts improve discrimination. These results indicate that processes as early as speed perception may be constrained by the parsing of the visual image into discrete entities.

  6. Arithmetic coding with constrained carry operations

    NASA Astrophysics Data System (ADS)

    Mahfoodh, Abo-Talib; Said, Amir; Yea, Sehoon

    2015-03-01

    Buffer or counter-based techniques are adequate for dealing with carry propagation in software implementations of arithmetic coding, but create problems in hardware implementations due to the difficulty of handling worst-case scenarios, defined by very long propagations. We propose a new technique for constraining the carry propagation, similar to "bit-stuffing," but designed for encoders that generate data as bytes instead of individual bits, and is based on the fact that the encoder and decoder can maintain the same state, and both can identify the situations when it desired to limit carry propagation. The new technique adjusts the coding interval in a way that corresponds to coding an unused data symbol, but selected to minimize overhead. Our experimental results demonstrate that the loss in compression can be made very small using regular precision for arithmetic operations.

  7. Constraining nonstandard neutrino-electron interactions

    SciTech Connect

    Barranco, J.; Miranda, O. G.; Moura, C. A.; Valle, J. W. F. [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, Apdo. Postal 14-740 07000 Mexico, D.F. (Mexico); AHEP Group, Instituto de Fisica Corpuscular-C.S.I.C./Universitat de Valencia Edificio Institutos de Paterna, Apt 22085, E-46071 Valencia (Spain)

    2008-05-01

    We present a detailed analysis on nonstandard neutrino interactions (NSI) with electrons including all muon and electron (anti)-neutrino data from existing accelerators and reactors, in conjunction with the 'neutrino counting' data (e{sup +}e{sup -}{yields}{nu}{nu}{gamma}) from the four LEP collaborations. First we perform a one-parameter-at-a-time analysis, showing how most constraints improve with respect to previous results reported in the literature. We also present more robust results where the NSI parameters are allowed to vary freely in the analysis. We show the importance of combining LEP data with the other experiments in removing degeneracies in the global analysis constraining flavor-conserving NSI parameters which, at 90% and 95% C.L., must lie within unique allowed regions. Despite such improved constraints, there is still substantial room for improvement, posing a big challenge for upcoming experiments.

  8. Mixed-Strategy Chance Constrained Optimal Control

    NASA Technical Reports Server (NTRS)

    Ono, Masahiro; Kuwata, Yoshiaki; Balaram, J.

    2013-01-01

    This paper presents a novel chance constrained optimal control (CCOC) algorithm that chooses a control action probabilistically. A CCOC problem is to find a control input that minimizes the expected cost while guaranteeing that the probability of violating a set of constraints is below a user-specified threshold. We show that a probabilistic control approach, which we refer to as a mixed control strategy, enables us to obtain a cost that is better than what deterministic control strategies can achieve when the CCOC problem is nonconvex. The resulting mixed-strategy CCOC problem turns out to be a convexification of the original nonconvex CCOC problem. Furthermore, we also show that a mixed control strategy only needs to "mix" up to two deterministic control actions in order to achieve optimality. Building upon an iterative dual optimization, the proposed algorithm quickly converges to the optimal mixed control strategy with a user-specified tolerance.

  9. Constraining MOND with Solar System dynamics

    E-print Network

    Lorenzo Iorio

    2008-02-15

    In this letter we investigate the deep Newtonian regime of the MOND paradigm from a purely phenomenological point of view by exploiting the least-square estimated corrections to the secular rates of the perihelia of the inner and of some of the outer planets of the Solar System by E.V. Pitjeva with the EPM2004 ephemerides. By using $\\mu(x)\\approx 1-k_0(1/x)^n$ for the interpolating MONDian function, and by assuming that $k_0$, considered body-independent so to avoid violations of the equivalence principle, experiences no spatial variations throughout the Solar System we tightly constrain $n$ with the ratios of the perihelion precessions for different pairs of planets. We find that the range $1\\leq n\\leq 2$ is neatly excluded at much more than $3-\\sigma$ level. Such a test would greatly benefit from the use of extra-precessions of perihelia independently estimated by other groups as well.

  10. Stability analysis of constrained multibody systems

    NASA Astrophysics Data System (ADS)

    Ider, S. K.; Amirouche, F. M. L.

    1990-09-01

    Automated algorithms for the dynamic analysis and simulation of constrained multibody systems usually assume the rows of the constraint Jacobian matrix to be linearly independent. But during the motion, at instantaneous configurations, the Jacobian matrix may become less than full rank resulting in singularities. This occurs when the closed-loop goes from 3D to 2D type of configuration. In this paper the linearly dependent rows are identified by an uptriangular decomposition process. The corresponding constraint equations are modified so that the singularities in the numerical procedure are avoided. The conditions for the validity of the modified equations are described. Furthermore, the constraint equations expressed in accelerations are modified by Baumgarte's approach to stabilize the accumulation of the numerical errors during integration. A computational procedure based on Kane's equations is presented. Two and three-link robotic manipulators will be simulated at singular configurations to illustrate the use of the modified constraints.

  11. A Constrained Tectonics Model for Coronal Heating

    E-print Network

    Ng, C S; 10.1086/525518

    2011-01-01

    An analytical and numerical treatment is given of a constrained version of the tectonics model developed by Priest, Heyvaerts, & Title [2002]. We begin with an initial uniform magnetic field ${\\bf B} = B_0 \\hat{\\bf z}$ that is line-tied at the surfaces $z = 0$ and $z = L$. This initial configuration is twisted by photospheric footpoint motion that is assumed to depend on only one coordinate ($x$) transverse to the initial magnetic field. The geometric constraints imposed by our assumption precludes the occurrence of reconnection and secondary instabilities, but enables us to follow for long times the dissipation of energy due to the effects of resistivity and viscosity. In this limit, we demonstrate that when the coherence time of random photospheric footpoint motion is much smaller by several orders of magnitude compared with the resistive diffusion time, the heating due to Ohmic and viscous dissipation becomes independent of the resistivity of the plasma. Furthermore, we obtain scaling relations that su...

  12. On the Capacity of Constrained Systems

    E-print Network

    Böcherer, Georg; Pimentel, Cecilio

    2009-01-01

    In the first chapter of Shannon's "A Mathematical Theory of Communication," it is shown that the maximum entropy rate of an input process of a constrained system is limited by the combinatorial capacity of the system. Shannon considers systems where the constraints define regular languages and uses results from matrix theory in his derivations. In this work, the regularity constraint is dropped. Using generating functions, it is shown that the maximum entropy rate of an input process is upper-bounded by the combinatorial capacity in general. The presented results also allow for a new approach to systems with regular constraints. As an example, the results are applied to binary sequences that fulfill the (j,k) run-length constraint and by using the proposed framework, a simple formula for the combinatorial capacity is given and a maxentropic input process is defined.

  13. A Naturally-Constrained Orthopyroxene Piezometer

    NASA Astrophysics Data System (ADS)

    Speciale, P. A.; Behr, W. M.

    2014-12-01

    The magnitude of stress in the continental lithosphere, particularly the lithospheric mantle, is highly uncertain and frequently debated, but is critical to understanding continental mechanics. Differential stress can be estimated using paleopiezometry, which is a relationship between dynamically recrystallized grainsize and flow stress. This relationship has been quantified experimentally for a wide range of earth materials, including olivine, quartz, plagioclase, calcite, and numerous metals. The empirical piezometer for olivine (Van der Wal et al., 1993) has been used to estimate stress magnitudes for mantle rocks from several regions worldwide. In contrast, piezometers for other minerals commonly recrystallized in mantle/lower crustal rocks, including orthopyroxene (OPX) and clinopyroxene, are poorly constrained. The two existing OPX piezometers are based on experimental studies and predict OPX grain sizes to be larger than olivine at high stresses. Observations from natural rocks, however, show the opposite relationship: OPX grainsizes are smaller than olivine at high stresses. This study explores the stress-grainsize relationship between dynamically recrystallized OPX and olivine in naturally-deformed peridotites derived from a wide range of pressure-temperature conditions. We measure OPX and olivine grainsizes in banded peridotites that appear to have recrystallized under identical stress conditions and are not mixed. Differential stress is estimated using the well constrained olivine piezometer. We establish a stress(?)-grainsize(d) relationship for OPX (? = 406.1d(-.52)) which predicts that recrystallized grains in OPX are smaller than olivine above ~25 MPa (~200 ?m), and larger than olivine for stresses below this value. This piezometer can be used to estimate stress magnitudes in rocks in which OPX is one of the primary recrystallized phases, including granulites, pyroxenites and other mantle/lower crustal rocks in which olivine or plagioclase are unsuitable.

  14. Constraining Paleoearthquake Slip Distributions with Coral Microatolls

    NASA Astrophysics Data System (ADS)

    Lindsay, A.; McCloskey, J.; nic Bhloscaidh, M.; Murphy, S.

    2014-12-01

    Key to understanding the threat posed by large megathrust earthquakes is identifying where the potential for these destructive events exists. Studying extended sequences of earthquakes, Slip Deficit and Stress Evolution modelling techniques may hold the key to locating areas of concern. However, as well as using recent instrumentally constrained slip distributions they require the production of high resolution source models for pre-instrumental events. One place we can attempt this longer term modelling is along the Sunda Trench with its record of large megathrust earthquakes dating back centuries. Coral microatolls populating the intertidal areas of the Sumatran Forearc act as long-term geodetic recorders of tectonic activity. Repeated cycles of stress accumulation and release alter relative sea levels around these islands. Growth of corals, controlled by the level of the lowest tide, exploit interseismic rises in sea level. In turn, they experience die-offs when coseismic drops in sea level lead to subaerially exposure. Examination of coral stratigraphy reveals a history of displacements from which information of past earthquakes can be inferred. We have developed a Genetic Algorithm Slip Estimator (GASE) to rapidly produce high resolution slip distributions from coral displacement data. GASE recombines information held in populations of randomly generated slip distributions, to create superior models, satisfying observed displacements. Non-unique solutions require multiple iterations of the algorithm, producing a suite of models from which an ensemble slip distribution is drawn. Systematic testing of the algorithm demonstrates its ability to reliably estimate both known synthetic and instrumentally constrained slip distributions based on surface displacements. We will present high-resolution source models satisfying published displacement data for a number recent and paleoearthquakes along the Sunda trench, including the great 1797 and 1833 events.

  15. Constrained Simulation of the Bullet Cluster

    NASA Astrophysics Data System (ADS)

    Lage, Craig

    The Bullet Cluster collision is an ongoing collision of two galaxy clusters in the constellation of Carina. In this work, we have built a detailed simulation of this merger, including magnetohydrodynamics, plasma cooling, and adaptive mesh refinement. We constrain the simulation with data from gravitational lensing reconstructions and Chandra X-ray flux maps, then compare the resulting model to plasma temperature maps, Sunyaev-Zel'dovich effect measurements, and cluster halo radio emission. We constrain the initial conditions by minimizing the chi-squared figure of merit between the full 2D observational data sets and the simulation, rather than comparing only a few features such as the location of subcluster centroids, as in previous studies. A simple initial configuration of two triaxial clusters with Navarro-Frenk-White dark matter profiles and physically reasonable plasma profiles gives a good fit to the current observational morphology and X-ray emissions of the merging clusters. There is no need for unconventional physics or extreme infall velocities. The study gives insight into the astrophysical processes at play during a galaxy cluster merger. In addition, the techniques developed here to create realistic, stable, triaxial clusters, and to utilize the totality of the 2D image data, will be applicable to future simulation studies of other merging clusters. This work also highlights the important role of non-thermal pressure in galaxy clusters. A simple model of the non-thermal pressure is primarily used here, but we have investigated a more physical model where the non-thermal pressure is due to fluid turbulence, and have outlined a path for future work based on this more physical model.

  16. Ice Sheet Stratigraphy Can Constrain Basal Slip

    NASA Astrophysics Data System (ADS)

    Wolovick, M.; Creyts, T. T.; Buck, W. R.; Bell, R. E.

    2014-12-01

    Basal slip is an important component of ice sheet mass flux and dynamics. Basal slip varies over time due to variations in basal temperature, water pressure, and sediment cover. All of these factors can create coherent patterns of basal slip that migrate over time. Our knowledge of the spatial variability in basal slip comes from inversions of driving stress, ice thickness, and surface velocity, but these inversions contain no information about temporal variability. We do not know if the patterns in slip revealed by those inversions move over time. While englacial stratigraphy has classically been used to constrain surface accumulation and geothermal flux, it is also sensitive to horizontal gradients in basal slip. Here we show that englacial stratigraphy can constrain the velocity of basal slip patterns. Englacial stratigraphy responds strongly to patterns of basal slip that move downstream over time close to the ice sheet velocity. In previous work, we used a thermomechanical model to discover that thermally controlled slip patterns migrate downstream and create stratigraphic structures, but we were unable to directly control the pattern velocity, as that arose naturally out of the model physics. Here, we use a kinematic flowline model that allows us to directly control pattern velocity, and thus is applicable to a wide variety of slip mechanisms in addition to basal temperature. We find that the largest and most intricate stratigraphic structures develop when the pattern moves at the column-average ice velocity. Patterns that move slower than the column-average ice velocity produce overturned stratigraphy in the lower part of the ice sheet, while patterns moving at the column-average eventually cause the entire ice sheet to overturn if they persist long enough. Based on these forward models, we develop an interpretive guide for deducing moving patterns in basal slip from ice sheet internal layers. Ice sheet internal stratigraphy represents a potentially vast untapped source of information on basal sliding.

  17. Rosmarinic acid.

    PubMed

    Petersen, Maike; Simmonds, Monique S J

    2003-01-01

    Rosmarinic acid is an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid. It is commonly found in species of the Boraginaceae and the subfamily Nepetoideae of the Lamiaceae. However, it is also found in species of other higher plant families and in some fern and hornwort species. Rosmarinic acid has a number of interesting biological activities, e.g. antiviral, antibacterial, antiinflammatory and antioxidant. The presence of rosmarinic acid in medicinal plants, herbs and spices has beneficial and health promoting effects. In plants, rosmarinic acid is supposed to act as a preformed constitutively accumulated defence compound. The biosynthesis of rosmarinic acid starts with the amino acids L-phenylalanine and L-tyrosine. All eight enzymes involved in the biosynthesis are known and characterised and cDNAs of several of the involved genes have been isolated. Plant cell cultures, e.g. from Coleus blumei or Salvia officinalis, accumulate rosmarinic acid in amounts much higher than in the plant itself (up to 36% of the cell dry weight). For this reason a biotechnological production of rosmarinic acid with plant cell cultures has been proposed. PMID:12482446

  18. Basically Acids

    NSDL National Science Digital Library

    University of Houston,

    Students learn the basics of acid/base chemistry in a fun, interactive way by studying instances of acid/base chemistry found in popular films such as Harry Potter and the Prisoner of Azkaban and National Treasure. Students learn what acids, bases and indicators are and how they can be used, including invisible ink. They also learn how engineers use acids and bases every day to better our quality of life. Students' interest is piqued by the use of popular culture in the classroom.

  19. Using Resolution-Constrained Adaptive Meshes for Traveltime Tomography

    E-print Network

    Ajo-Franklin, Jonathan

    Using Resolution-Constrained Adaptive Meshes for Traveltime Tomography Jonathan B. Ajo.B., Urban, J.A., and Harris, J.M. 2006. Using resolution-constrained adaptive meshes for traveltime which exploits a greedy mesh refine- ment algorithm to construct adaptive parametrizations

  20. Digestively constrained predators evade the cost of interference competition

    Microsoft Academic Search

    Jan A. van Gils; Theunis Piersma

    2004-01-01

    Summary 1. Models of functional and aggregative responses generally assume that rates of prey encounter and handling times limit a predator's intake rate (Holling's disc equation). Two different lines of approach build upon this fundamental foraging concept. In the first, mutual interference further constrains intake rate, while in the second, intake rate may be constrained by rate of digestion. By

  1. Spectral Finite-Element Methods for Parametric Constrained Optimization Problems

    Microsoft Academic Search

    Mihai Anitescu

    2009-01-01

    We present a method to approximate the solution mapping of parametric constrained optimization problems. The approximation, which is of the spectral finite element type, is repre- sented as a linear combination of orthogonal polynomials. Its coefficients are determined by solving an appropriate finite-dimensional constrained optimization problem. We show that, under certain conditions, the latter problem is solvable because it is

  2. A PENALTY FUNCTION METHOD FOR CONSTRAINED MOLECULAR DYNAMICS SIMULATION

    E-print Network

    A PENALTY FUNCTION METHOD FOR CONSTRAINED MOLECULAR DYNAMICS SIMULATION By Ajith Gunaratne­000 A PENALTY FUNCTION METHOD FOR CONSTRAINED MOLECULAR DYNAMICS SIMULATION AJITH GUNARATNE AND ZHIJUN WU FOR MOLECULAR DYNAMICS SIMULATION 1 that the new iterate can satisfy the constraints [3]. Depending

  3. Interoperable Services on Constrained Devices in the Internet of Things

    E-print Network

    Paris-Sud XI, Université de

    1 Interoperable Services on Constrained Devices in the Internet of Things Hauke Petersen1--The Internet of Things (IoT) promises billions of constrained devices connected to the Internet in the near of memory usage and power consumption in particular. I. INTRODUCTION THE Internet of Things (Io

  4. Constraining fault constitutive behavior with slip and stress heterogeneity

    E-print Network

    Greer, Julia R.

    Constraining fault constitutive behavior with slip and stress heterogeneity B. T. Aagaard1 and T. H and postshear stress on a fault can be used to constrain fault constitutive behavior beyond that required on a vertical, planar strike-slip fault show that the conditions that lead to slip heterogeneity remain in place

  5. A constrained edit distance algorithm between semi-ordered trees

    Microsoft Academic Search

    Aïda Ouangraoua; Pascal Ferraro

    2009-01-01

    In this paper, we propose a formal definition of a new class of trees called semi-ordered trees and a polynomial dynamic programming algorithm to compute a constrained edit distance between such trees. The core of the method relies on a similar approach to compare unordered [Kaizhong Zhang, A constrained edit distance between unordered labeled trees, Algorithmica 15 (1996) 205–222] and

  6. A Constrained Attitude Control Module for Small Satellites

    E-print Network

    Lightsey, Glenn

    dots) Final trajectory (blue line) Start Goal #12;Step 2: Find rotation quaternion #12;Step 2: RotateA Constrained Attitude Control Module for Small Satellites Henri Kjellberg and E. Glenn Lightsey Constrained Control Methods McInnes, C. R. - "Large Angle Slew Maneuvers with Autonomous Sun Vector Avoidance

  7. Adaptive Medical Feature Extraction for Resource Constrained Distributed Embedded Systems

    Microsoft Academic Search

    Roozbeh Jafari; Hyduke Noshadiyy; Soheil Ghiasi; Majid Sarrafzadehzz

    Tiny embedded systems have not been an ideal outfit for high performance computing due to their constrained resources. Limitations in processing power, battery life, commu- nication bandwidth and memory constrain the applicability of existing complex medical\\/biological analysis algorithms to such platforms. Electrocardiogram (ECG) analysis resembles such algorithm. In this paper, we address the issue of partitioning an ECG analysis algorithm

  8. Feedback Stabilization over Signal-to-Noise Ratio Constrained Channels

    E-print Network

    Braslavsky, Julio H.

    that there are limitations on the ability to stabi- lize an unstable plant over a signal-to-noise ratio constrained channelFeedback Stabilization over Signal-to-Noise Ratio Constrained Channels Julio H. Braslavsky Richard constraints on the available data rate. Signal to noise ratio con- straints are one way in which data

  9. CONSTRAINED MULTISINE INPUTS FOR PLANT-FRIENDLY IDENTIFICATION OF

    E-print Network

    Mittelmann, Hans D.

    the signal to noise ratio of the resulting plant output, contributing to plant-friendliness duringCONSTRAINED MULTISINE INPUTS FOR PLANT-FRIENDLY IDENTIFICATION OF CHEMICAL PROCESSES D.E. Rivera: This paper considers the use of constrained minimum crest factor multisine signals as inputs for plant

  10. Blind CDMA detection and equalization using linearly constrained CMA

    Microsoft Academic Search

    Li Li; H. Howard Fan

    2000-01-01

    A linearly constrained constant modulus algorithm (CMA) for CDMA detection and equalization is proposed in this paper. Multipath propagation is assumed and only the code sequence of a particular desired user is known. The new algorithm overcomes the shortcoming that the unconstrained CMA cannot lock to the desired user, and yields better performance compared to the existing constrained minimum output

  11. Constrained periodic spacecraft relative motion using non-negative polynomials

    E-print Network

    Paris-Sud XI, Université de

    Constrained periodic spacecraft relative motion using non-negative polynomials G. Deaconu, C constrained periodic relative motion between spacecraft on Keplerian orbits is presented. The periodic-definite programming. Keywords-- impulsive orbital rendezvous, periodic relative motion, non-negative polynomials, semi

  12. Online Multicasting for Network Capacity Maximization in Energy-Constrained

    E-print Network

    Liang, Weifa

    optimization, multicasting, broadcasting, network lifetime. Ç 1 INTRODUCTION IN recent years, multihop wirelessOnline Multicasting for Network Capacity Maximization in Energy-Constrained Ad Hoc Networks Weifa new algorithms for online multicast routing in ad hoc networks where nodes are energy- constrained

  13. The Pendulum: From Constrained Fall to the Concept of Potential

    ERIC Educational Resources Information Center

    Bevilacqua, Fabio; Falomo, Lidia; Fregonese, Lucio; Giannetto, Enrico; Giudice, Franco; Mascheretti, Paolo

    2006-01-01

    Kuhn underlined the relevance of Galileo's gestalt switch in the interpretation of a swinging body from constrained fall to time metre. But the new interpretation did not eliminate the older one. The constrained fall, both in the motion of pendulums and along inclined planes, led Galileo to the law of free fall. Experimenting with physical…

  14. Security-constrained optimal generation scheduling for GENCOs

    Microsoft Academic Search

    Hatim Yamin; Salem Al-Agtash; Mohammad Shahidehpour

    2004-01-01

    This paper presents an approach for maximizing a GENCO's profit in a constrained power market. The proposed approach considers the Interior Point Method (IPM) and Benders decomposition for solving the security-constrained optimal generation scheduling (SC-GS) problem. The master problem represents the economic dispatch problem for a GENCO which intends to optimize its profit. The formulation of the master problem does

  15. Observability-constrained Vision-aided Inertial Navigation

    E-print Network

    Plotkin, Joshua B.

    Observability-constrained Vision-aided Inertial Navigation Joel A. Hesch, Dimitrios G. Kottas, Sean of Computer Science & Engineering University of Minnesota Multiple Autonomous Robotic Systems Labroratory-0572 URL: http://www.cs.umn.edu/joel #12;#12;Observability-constrained Vision-aided Inertial Navigation

  16. Explaining evolution via constrained persistent perfect phylogeny

    PubMed Central

    2014-01-01

    Background The perfect phylogeny is an often used model in phylogenetics since it provides an efficient basic procedure for representing the evolution of genomic binary characters in several frameworks, such as for example in haplotype inference. The model, which is conceptually the simplest, is based on the infinite sites assumption, that is no character can mutate more than once in the whole tree. A main open problem regarding the model is finding generalizations that retain the computational tractability of the original model but are more flexible in modeling biological data when the infinite site assumption is violated because of e.g. back mutations. A special case of back mutations that has been considered in the study of the evolution of protein domains (where a domain is acquired and then lost) is persistency, that is the fact that a character is allowed to return back to the ancestral state. In this model characters can be gained and lost at most once. In this paper we consider the computational problem of explaining binary data by the Persistent Perfect Phylogeny model (referred as PPP) and for this purpose we investigate the problem of reconstructing an evolution where some constraints are imposed on the paths of the tree. Results We define a natural generalization of the PPP problem obtained by requiring that for some pairs (character, species), neither the species nor any of its ancestors can have the character. In other words, some characters cannot be persistent for some species. This new problem is called Constrained PPP (CPPP). Based on a graph formulation of the CPPP problem, we are able to provide a polynomial time solution for the CPPP problem for matrices whose conflict graph has no edges. Using this result, we develop a parameterized algorithm for solving the CPPP problem where the parameter is the number of characters. Conclusions A preliminary experimental analysis shows that the constrained persistent perfect phylogeny model allows to explain efficiently data that do not conform with the classical perfect phylogeny model. PMID:25572381

  17. Acid Sulfate Soil Assessment And Monitoring - A Simple Robust Kit For Use by Farmers And Other Land Managers - The Acid Test

    Microsoft Academic Search

    P. G Saffigna

    Acid sulfate soil has proved to be a major problem for land managers in coastal eastern Australia. The identification and assessment of acid sulfate soils commonly is constrained by knowledge and equipment. Usually, farmers and other land managers are not in a position to carry out their own soil testing because of the complexity and cost o the testing equipment.

  18. Acid test

    NSDL National Science Digital Library

    Olivia Worland (Purdue University; Biological Sciences)

    2008-06-06

    Baking soda can be used as an indicator of how much acid a substance contains. Lemons and limes have more acid in them than grapefruits and oranges. Indophenol can be used as an indicator of how much vitamin C is in a substance.

  19. Acids (GCMP)

    NSDL National Science Digital Library

    Acids: this is a resource in the collection "General Chemistry Multimedia Problems". We will observe the reaction of sodium bicarbonate with three acid solutions. General Chemistry Multimedia Problems ask students questions about experiments they see presented using videos and images. The questions asked apply concepts from different parts of an introductory course, encouraging students to decompartmentalize the material.

  20. Domoic Acid

    NSDL National Science Digital Library

    Bailey, Christina

    This online student report discusses the chemistry of domoic acid, a biotoxin that is produced by the diatom Psuedo-nitzschia and associated with Amnesiac Shellfish Poisoning (ASP). In addition to a descriptive summary and images, the report links to other areas of interest related to domoic acid poisoning including signs and symptoms, modes of action, and treatment.

  1. Acid rain

    SciTech Connect

    White, J.C. (Cornell University, Ithaca, NY (US))

    1988-01-01

    This book presents the proceedings of the third annual conference sponsored by the Acid Rain Information Clearinghouse (ARIC). Topics covered include: Legal aspects of the source-receptor relationship: an energy perspective; Scientific uncertainty, agency inaction, and the courts; and Acid rain: the emerging legal framework.

  2. Acid Rain

    Microsoft Academic Search

    Gene E. Likens; Richard F. Wright; James N. Galloway; Thomas J. Butler

    1979-01-01

    Measurements of the acidity of rain and snow reveal that in parts of the eastern U.S. and of western Europe precipitation has changed from a nearly neutral solution 200 years ago to a dilute solution of sulfuric and nitric acids today. The trend is a result of the emission of sulfur and nitrogen oxides to the atmosphere accompanying the rise

  3. Acid rain

    SciTech Connect

    Elsworth, S.

    1985-01-01

    This book was written in a concise and readable style for the lay public. It's purpose was to make the public aware of the damage caused by acid rain and to mobilize public opinion to favor the elimination of the causes of acid rain.

  4. Acid Precipitation

    NSDL National Science Digital Library

    Tyser, Jim

    Acid precipitation will be defined. At different points in the lesson students will write balanced reactions for the formation acid precipitation from atmospheric sulfur and nitrogen oxides and the neutralization of acids by limestone. Students will determine which states are most at risk from acid precipitation and assess how that risk has changed from 1996 to 2006. Sources of atmospheric sulfur (burning of high-sulfur coal) and nitrogen oxides (automobile exhaust) will be listed. The buffering effect of limestone soils and its mitigating effect on acid precipitation will be discussed. Students will correlate these areas with sulfur and nitrogen oxide production, population, composition of coal fields, and soil composition. This resource includes both a teaching guide and student worksheets.

  5. Asparagusic acid.

    PubMed

    Mitchell, Stephen C; Waring, Rosemary H

    2014-01-01

    Asparagusic acid (1,2-dithiolane-4-carboxylic acid) is a simple sulphur-containing 5-membered heterocyclic compound that appears unique to asparagus, though other dithiolane derivatives have been identified in non-food species. This molecule, apparently innocuous toxicologically to man, is the most probable culprit responsible for the curious excretion of odorous urine following asparagus ingestion. The presence of the two adjacent sulphur atoms leads to an enhanced chemical reactivity, endowing it with biological properties including the ability to substitute potentially for ?-lipoic acid in ?-keto-acid oxidation systems. This brief review collects the scattered data available in the literature concerning asparagusic acid and highlights its properties, intermediary metabolism and exploratory applications. PMID:24099657

  6. Acoustic characteristics of listener-constrained speech

    NASA Astrophysics Data System (ADS)

    Ashby, Simone; Cummins, Fred

    2003-04-01

    Relatively little is known about the acoustical modifications speakers employ to meet the various constraints-auditory, linguistic and otherwise-of their listeners. Similarly, the manner by which perceived listener constraints interact with speakers' adoption of specialized speech registers is poorly Hypo (H&H) theory offers a framework for examining the relationship between speech production and output-oriented goals for communication, suggesting that under certain circumstances speakers may attempt to minimize phonetic ambiguity by employing a ``hyperarticulated'' speaking style (Lindblom, 1990). It remains unclear, however, what the acoustic correlates of hyperarticulated speech are, and how, if at all, we might expect phonetic properties to change respective to different listener-constrained conditions. This paper is part of a preliminary investigation concerned with comparing the prosodic characteristics of speech produced across a range of listener constraints. Analyses are drawn from a corpus of read hyperarticulated speech data comprising eight adult, female speakers of English. Specialized registers include speech to foreigners, infant-directed speech, speech produced under noisy conditions, and human-machine interaction. The authors gratefully acknowledge financial support of the Irish Higher Education Authority, allocated to Fred Cummins for collaborative work with Media Lab Europe.

  7. Constrained Graph Optimization: Interdiction and Preservation Problems

    SciTech Connect

    Schild, Aaron V [Los Alamos National Laboratory

    2012-07-30

    The maximum flow, shortest path, and maximum matching problems are a set of basic graph problems that are critical in theoretical computer science and applications. Constrained graph optimization, a variation of these basic graph problems involving modification of the underlying graph, is equally important but sometimes significantly harder. In particular, one can explore these optimization problems with additional cost constraints. In the preservation case, the optimizer has a budget to preserve vertices or edges of a graph, preventing them from being deleted. The optimizer wants to find the best set of preserved edges/vertices in which the cost constraints are satisfied and the basic graph problems are optimized. For example, in shortest path preservation, the optimizer wants to find a set of edges/vertices within which the shortest path between two predetermined points is smallest. In interdiction problems, one deletes vertices or edges from the graph with a particular cost in order to impede the basic graph problems as much as possible (for example, delete edges/vertices to maximize the shortest path between two predetermined vertices). Applications of preservation problems include optimal road maintenance, power grid maintenance, and job scheduling, while interdiction problems are related to drug trafficking prevention, network stability assessment, and counterterrorism. Computational hardness results are presented, along with heuristic methods for approximating solutions to the matching interdiction problem. Also, efficient algorithms are presented for special cases of graphs, including on planar graphs. The graphs in many of the listed applications are planar, so these algorithms have important practical implications.

  8. Prospects for constraining the dark energy potential

    NASA Astrophysics Data System (ADS)

    Fernandez-Martinez, Enrique; Verde, Licia

    2008-08-01

    We generalize to non-flat geometries the formalism of Simon et al (2005 Phys. Rev. D 71 123001 [astro-ph/0412269]) to reconstruct the dark energy potential. This formalism makes use of quantities similar to the horizon-flow parameters in inflation, can, in principle, be made non-parametric and is general enough to be applied outside the simple, single-scalar-field quintessence. Since currently available and forthcoming data do not allow a non-parametric and exact reconstruction of the potential, we consider a general parametric description in terms of Chebyshev polynomials. We then consider present and future measurements of H(z), baryon acoustic oscillation (BAO) surveys and supernovae type 1A surveys, and investigate their constraints on the dark energy potential. We find that relaxing the flatness assumption increases the errors in the reconstructed dark energy evolution but does not open up significant degeneracies, provided that a modest prior is imposed on the geometry. Direct measurements of H(z), such as those provided by BAO surveys, are crucially important for constraining the evolution of the dark energy potential and the dark energy equation of state, especially for non-trivial deviations from the standard ?CDM (CDM: cold dark matter) model.

  9. Generating constrained randomized sequences: item frequency matters.

    PubMed

    French, Robert M; Perruchet, Pierre

    2009-11-01

    All experimental psychologists understand the importance of randomizing lists of items. However, randomization is generally constrained, and these constraints-in particular, not allowing immediately repeated items-which are designed to eliminate particular biases, frequently engender others. We describe a simple Monte Carlo randomization technique that solves a number of these problems. However, in many experimental settings, we are concerned not only with the number and distribution of items but also with the number and distribution of transitions between items. The algorithm mentioned above provides no control over this. We therefore introduce a simple technique that uses transition tables for generating correctly randomized sequences. We present an analytic method of producing item-pair frequency tables and item-pair transitional probability tables when immediate repetitions are not allowed. We illustrate these difficulties and how to overcome them, with reference to a classic article on word segmentation in infants. Finally, we provide free access to an Excel file that allows users to generate transition tables with up to 10 different item types, as well as to generate appropriately distributed randomized sequences of any length without immediately repeated elements. This file is freely available from http://leadserv.u-bourgogne.fr/IMG/xls/TransitionMatrix.xls. PMID:19897832

  10. Constraining Carbon Cycle Feedback Using Paleodata

    NASA Astrophysics Data System (ADS)

    Abe-Ouchi, Ayako; Harrison, Sandy P.

    2009-04-01

    Palaeocarbon Modelling Intercomparison Project Kickoff Workshop; Totnes, United Kingdom, 26-28 January 2009; Climate-induced changes in the terrestrial biosphere and the ocean modulate the release and uptake of carbon dioxide (CO2), and this, in turn, alters atmospheric composition and climate in a process called climate/carbon cycle feedback. The Coupled Carbon Cycle Climate Model Intercomparison Project (C4MIP), using models of the terrestrial and ocean carbon cycles in ocean-atmosphere general circulation models, has shown that although the feedback is positive, its magnitude is highly uncertain (P. Friedlingstein et al., J. Clim., 19, 3337, 2006). It is important to quantify this feedback adequately because it affects the CO2 emissions consistent with any atmospheric CO2 stabilization. One approach to reducing this uncertainty is to evaluate carbon cycle models against observations of the contemporary carbon cycle. Attempts to use modern observations to constrain climate sensitivity have had limited success, so additional constraints are being sought from records of past climate change (T. Edwards et al., Prog. Phys. Geogr., 31, 481, 2007).

  11. Constraining groundwater modeling with magnetic resonance soundings.

    PubMed

    Boucher, Marie; Favreau, Guillaume; Nazoumou, Yahaya; Cappelaere, Bernard; Massuel, Sylvain; Legchenko, Anatoly

    2012-01-01

    Magnetic resonance sounding (MRS) is a noninvasive geophysical method that allows estimating the free water content and transmissivity of aquifers. In this article, the ability of MRS to improve the reliability of a numerical groundwater model is assessed. Thirty-five sites were investigated by MRS over a ?5000 km(2) domain of the sedimentary Continental Terminal aquifer in SW Niger. Time domain electromagnetic soundings were jointly carried out to estimate the aquifer thickness. A groundwater model was previously built for this section of the aquifer and forced by the outputs from a distributed surface hydrology model, to simulate the observed long-term (1992 to 2003) rise in the water table. Uncertainty analysis had shown that independent estimates of the free water content and transmissivity values of the aquifer would facilitate cross-evaluation of the surface-water and groundwater models. MRS results indicate ranges for permeability (K = 1 × 10(-5) to 3 × 10(-4) m/s) and for free water content (w = 5% to 23% m(3) /m(3) ) narrowed by two orders of magnitude (K) and by ?50% (w), respectively, compared to the ranges of permeability and specific yield values previously considered. These shorter parameter ranges result in a reduction in the model's equifinality (whereby multiple combinations of model's parameters are able to represent the same observed piezometric levels), allowing a better constrained estimate to be derived for net aquifer recharge (?22 mm/year). PMID:22150349

  12. Constrained Subjective Assessment of Student Learning

    NASA Astrophysics Data System (ADS)

    Saliu, Sokol

    2005-09-01

    Student learning is a complex incremental cognitive process; assessment needs to parallel this, reporting the results in similar terms. Application of fuzzy sets and logic to the criterion-referenced assessment of student learning is considered here. The constrained qualitative assessment (CQA) system was designed, and then applied in assessing a past course in microcomputer system design (MSD). CQA criteria were articulated in fuzzy terms and sets, and the assessment procedure was cast as a fuzzy inference rule base. An interactive graphic interface provided for transparent assessment, student "backwash," and support to the teacher when compiling the tests. Grade intervals, obtained from a departmental poll, were used to compile a fuzzy "grade" set. Assessment results were compared to those of a former standard method and to those of a modified version of it (but with fewer criteria). The three methods yielded similar results, supporting the application of CQA. The method improved assessment reliability by means of the consensus embedded in the fuzzy grade set, and improved assessment validity by integrating fuzzy criteria into the assessment procedure.

  13. Constraining Sterile Neutrinos Using Reactor Neutrino Experiments

    E-print Network

    Ivan Girardi; Davide Meloni; Tommy Ohlsson; He Zhang; Shun Zhou

    2014-08-21

    Models of neutrino mixing involving one or more sterile neutrinos have resurrected their importance in the light of recent cosmological data. In this case, reactor antineutrino experiments offer an ideal place to look for signatures of sterile neutrinos due to their impact on neutrino flavor transitions. In this work, we show that the high-precision data of the Daya Bay experi\\-ment constrain the 3+1 neutrino scenario imposing upper bounds on the relevant active-sterile mixing angle $\\sin^2 2 \\theta_{14} \\lesssim 0.06$ at 3$\\sigma$ confidence level for the mass-squared difference $\\Delta m^2_{41}$ in the range $(10^{-3},10^{-1}) \\, {\\rm eV^2}$. The latter bound can be improved by six years of running of the JUNO experiment, $\\sin^22\\theta_{14} \\lesssim 0.016$, although in the smaller mass range $ \\Delta m^2_{41} \\in (10^{-4} ,10^{-3}) \\, {\\rm eV}^2$. We have also investigated the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters $\\theta_{13}$ and $\\Delta m^2_{31}$ (at Daya Bay and JUNO), $\\theta_{12}$ and $\\Delta m^2_{21}$ (at JUNO), and most importantly, the neutrino mass hierarchy (at JUNO). We find that, except for the obvious situation where $\\Delta m^2_{41}\\sim \\Delta m^2_{31}$, sterile states do not affect these measurements substantially.

  14. Scheduling Aircraft Landings under Constrained Position Shifting

    NASA Technical Reports Server (NTRS)

    Balakrishnan, Hamsa; Chandran, Bala

    2006-01-01

    Optimal scheduling of airport runway operations can play an important role in improving the safety and efficiency of the National Airspace System (NAS). Methods that compute the optimal landing sequence and landing times of aircraft must accommodate practical issues that affect the implementation of the schedule. One such practical consideration, known as Constrained Position Shifting (CPS), is the restriction that each aircraft must land within a pre-specified number of positions of its place in the First-Come-First-Served (FCFS) sequence. We consider the problem of scheduling landings of aircraft in a CPS environment in order to maximize runway throughput (minimize the completion time of the landing sequence), subject to operational constraints such as FAA-specified minimum inter-arrival spacing restrictions, precedence relationships among aircraft that arise either from airline preferences or air traffic control procedures that prevent overtaking, and time windows (representing possible control actions) during which each aircraft landing can occur. We present a Dynamic Programming-based approach that scales linearly in the number of aircraft, and describe our computational experience with a prototype implementation on realistic data for Denver International Airport.

  15. Pairwise constrained concept factorization for data representation.

    PubMed

    He, Yangcheng; Lu, Hongtao; Huang, Lei; Xie, Saining

    2014-04-01

    Concept factorization (CF) is a variant of non-negative matrix factorization (NMF). In CF, each concept is represented by a linear combination of data points, and each data point is represented by a linear combination of concepts. More specifically, each concept is represented by more than one data point with different weights, and each data point carries various weights called membership to represent their degrees belonging to that concept. However, CF is actually an unsupervised method without making use of prior information of the data. In this paper, we propose a novel semi-supervised concept factorization method, called Pairwise Constrained Concept Factorization (PCCF), which incorporates pairwise constraints into the CF framework. We expect that data points which have pairwise must-link constraints should have the same class label as much as possible, while data points with pairwise cannot-link constraints will have different class labels as much as possible. Due to the incorporation of the pairwise constraints, the learning quality of the CF has been significantly enhanced. Experimental results show the effectiveness of our proposed novel method in comparison to the state-of-the-art algorithms on several real world applications. PMID:24413280

  16. Prospects in Constraining the Dark Energy Potential

    E-print Network

    Enrique Fernandez-Martinez; Licia Verde

    2008-08-14

    We generalize to non-flat geometries the formalism of Simon et al. (2005) to reconstruct the dark energy potential. This formalism makes use of quantities similar to the Horizon-flow parameters in inflation, can, in principle, be made non-parametric and is general enough to be applied outside the simple, single scalar field quintessence. Since presently available and forthcoming data do not allow a non-parametric and exact reconstruction of the potential, we consider a general parametric description in term of Chebyshev polynomials. We then consider present and future measurements of H(z), Baryon Acoustic Oscillations surveys and Supernovae type 1A surveys, and investigate their constraints on the dark energy potential. We find that, relaxing the flatness assumption increases the errors on the reconstructed dark energy evolution but does not open up significant degeneracies, provided that a modest prior on geometry is imposed. Direct measurements of H(z), such as those provided by BAO surveys, are crucially important to constrain the evolution of the dark energy potential and the dark energy equation of state, especially for non-trivial deviations from the standard LambdaCDM model.

  17. The cost-constrained traveling salesman problem

    SciTech Connect

    Sokkappa, P.R.

    1990-10-01

    The Cost-Constrained Traveling Salesman Problem (CCTSP) is a variant of the well-known Traveling Salesman Problem (TSP). In the TSP, the goal is to find a tour of a given set of cities such that the total cost of the tour is minimized. In the CCTSP, each city is given a value, and a fixed cost-constraint is specified. The objective is to find a subtour of the cities that achieves maximum value without exceeding the cost-constraint. Thus, unlike the TSP, the CCTSP requires both selection and sequencing. As a consequence, most results for the TSP cannot be extended to the CCTSP. We show that the CCTSP is NP-hard and that no K-approximation algorithm or fully polynomial approximation scheme exists, unless P = NP. We also show that several special cases are polynomially solvable. Algorithms for the CCTSP, which outperform previous methods, are developed in three areas: upper bounding methods, exact algorithms, and heuristics. We found that a bounding strategy based on the knapsack problem performs better, both in speed and in the quality of the bounds, than methods based on the assignment problem. Likewise, we found that a branch-and-bound approach using the knapsack bound was superior to a method based on a common branch-and-bound method for the TSP. In our study of heuristic algorithms, we found that, when selecting modes for inclusion in the subtour, it is important to consider the neighborhood'' of the nodes. A node with low value that brings the subtour near many other nodes may be more desirable than an isolated node of high value. We found two types of repetition to be desirable: repetitions based on randomization in the subtour buildings process, and repetitions encouraging the inclusion of different subsets of the nodes. By varying the number and type of repetitions, we can adjust the computation time required by our method to obtain algorithms that outperform previous methods.

  18. Ductile failure of a constrained metal foil

    NASA Astrophysics Data System (ADS)

    Varias, A. G.; Suo, Z.; Shih, C. F.

    A METAL foil bonded between stiff ceramic blocks may fail in a variety of ways, including de-adhesion of interfaces, cracking in the ceramics and ductile rupture of the metal. If the interface bond is strong enough to allow the foil to undergo substantial plastic deformation dimples are usually present on fracture surfaces and the nominal fracture energy is enhanced. Ductile fracture mechanisms responsible for such morphology include (i) growth of near-tip voids nucleated at second-phase particles and or interface pores, (ii) cavitation and (iii) interfacial debonding at the site of maximum stress which develops at distances of several foil thicknesses ahead of the crack tip. For a crack in a low to moderately hardening bulk metal, it is known that the maximum mean stress which develops at a distance of several crack openings ahead of the tip does not exceed about three times the yield stress. In contrast, the maximum mean stress that develops at several foil thicknesses ahead of the crack tip in a constrained metal foil can increase continuously with the applied load. Mean stress and interfacial traction of about four to six times the yield of the metal foil can trigger cavitation and/or interfacial debonding. The mechanical fields which bear on the competition between failure mechanisms are obtained by a large deformation finite element analysis. Effort is made to formulate predictive criteria indicating, for a given material system, which one of the several mechanisms operates and the relevant parameters that govern the nominal fracture work. The shielding of the crack tip in the context of ductile adhesive joints, due to the non-proportional deformation in a region of the order of the foil thickness, is also discussed.

  19. Mars, Moon, Mercury: Magnetometry Constrains Planetary Evolution

    NASA Astrophysics Data System (ADS)

    Connerney, John E. P.

    2015-04-01

    We have long appreciated that magnetic measurements obtained about a magnetized planet are of great value in probing the deep interior. The existence of a substantial planetary magnetic field implies dynamo action requiring an electrically conducting, fluid core in convective motion and a source of energy to maintain it. Application of the well-known Lowe's spectrum may in some cases identify the dynamo outer radius; where secular variation can be measured, the outer radius can be estimated using the frozen flux approximation. Magnetic induction may be used to probe the electrical conductivity of the mantle and crust. These are useful constraints that together with gravity and/or other observables we may infer the state of the interior and gain insight into planetary evolution. But only recently has it become clear that space magnetometry can do much more, particularly about a planet that once sustained a dynamo that has since disappeared. Mars is the best example of this class: the Mars Global Surveyor spacecraft globally mapped a remanent crustal field left behind after the demise of the dynamo. This map is a magnetic record of the planet's evolution. I will argue that this map may be interpreted to constrain the era of dynamo activity within Mars; to establish the reversal history of the Mars dynamo; to infer the magnetization intensity of Mars crustal rock and the depth of the magnetized crustal layer; and to establish that plate tectonics is not unique to planet Earth, as has so often been claimed. The Lunar magnetic record is in contrast one of weakly magnetized and scattered sources, not easily interpreted as yet in terms of the interior. Magnetometry about Mercury is more difficult to interpret owing to the relatively weak field and proximity to the sun, but MESSENGER (and ultimately Beppi Columbo) may yet map crustal anomalies (induced and/or remanent).

  20. Improved Hamilton-Jacobi Quantization for Nonholonomic Constrained System

    E-print Network

    Soon-Tae Hong; Won Tae Kim; Yong-Wan Kim; Young-Jai Park

    2001-09-06

    The nonholonomic constrained system with second-class constraints is investigated using the Hamilton-Jacobi (HJ) quantization scheme to yield the complete equations of motion of the system. Although the integrability conditions in the HJ scheme are equivalent to the involutive relations for the first-class constrained system in the improved Dirac quantization method (DQM), one should elaborate the HJ scheme by using the improved DQM in order to obtain the first-class Hamiltonian and the corresponding effective Lagrangian having the BRST invariant nonholonomic constrained system.

  1. Onomatopoeia characters extraction from comic images using constrained Delaunay triangulation

    NASA Astrophysics Data System (ADS)

    Liu, Xiangping; Shoji, Kenji; Mori, Hiroshi; Toyama, Fubito

    2014-02-01

    A method for extracting onomatopoeia characters from comic images was developed based on stroke width feature of characters, since they nearly have a constant stroke width in a number of cases. An image was segmented with a constrained Delaunay triangulation. Connected component grouping was performed based on the triangles generated by the constrained Delaunay triangulation. Stroke width calculation of the connected components was conducted based on the altitude of the triangles generated with the constrained Delaunay triangulation. The experimental results proved the effectiveness of the proposed method.

  2. 21 CFR 888.3100 - Ankle joint metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 false Ankle joint metal/composite semi-constrained cemented prosthesis... § 888.3100 Ankle joint metal/composite semi-constrained cemented prosthesis...Identification. An ankle joint metal/composite semi-constrained cemented...

  3. Folic Acid

    MedlinePLUS Videos and Cool Tools

    ... register. I'm interested in: Pregnancy Baby growth & care Research Volunteer opportunities Advocacy in government For health ... acid During your pregnancy Your pregnant body Prenatal care Eating and nutrition Physical activity Emotional and life ...

  4. ACID RAIN

    EPA Science Inventory

    Acid precipitation has become one of the major environmental problems of this decade. It is a challenge to scientists throughout the world. Researchers from such diverse disciplines as plant pathology, soil science, bacteriology, meteorology and engineering are investigating diff...

  5. Carnosic acid.

    PubMed

    Birti?, Simona; Dussort, Pierre; Pierre, François-Xavier; Bily, Antoine C; Roller, Marc

    2015-07-01

    Carnosic acid (salvin), which possesses antioxidative and antimicrobial properties, is increasingly exploited within the food, nutritional health and cosmetics industries. Since its first extraction from a Salvia species (?70years ago) and its identification (?50years ago), numerous articles and patents (?400) have been published on specific food and medicinal applications of Rosmarinus and Salvia plant extracts abundant in carnosic acid. In contrast, relevant biochemical, physiological or molecular studies in planta have remained rare. In this overview, recent advances in understanding of carnosic acid distribution, biosynthesis, accumulation and role in planta, and its applications are summarised. We also discuss the deficiencies in our understanding of the relevant biochemical processes, and suggest the molecular targets of carnosic acid. Finally, future perspectives and studies related to its potential roles are highlighted. PMID:25639596

  6. Acidic precipitation

    SciTech Connect

    Martin, H.C.

    1987-01-01

    At the International Symposium on Acidic Precipitation, over 400 papers were presented, and nearly 200 of them are included here. They provide an overview of the present state of the art of acid rain research. The Conference focused on atmospheric science (monitoring, source-receptor relationships), aquatic effects (marine eutrophication, lake acidification, impacts on plant and fish populations), and terrestrial effects (forest decline, soil acidification, etc.).

  7. CaMKII AMPA Assembly Model of AMPA Receptors Dependent

    E-print Network

    ; . AMPA (alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid) . AMPA AMPA LTP . . AMPA CaMKII (calcium/calmodulin-dependent protein kinase II) Thr286 . CaMKII AMPA , LTP . AMPA - . . AMPA LTP . AMPA NMDA

  8. Estimation Strategies for Constrained and Hybrid Dynamical Systems 

    E-print Network

    Parish, Julie Marie Jones

    2012-10-19

    an equality constraint can be broken. The direct linearization work for constrained systems modeled with quasi-velocities is demonstrated to be particularly useful for systems subject to nonholonomic constraints. Concerning redundant coordinate systems...

  9. Analytic energy gradients for constrained DFT-configuration interaction

    E-print Network

    Kaduk, Benjamin

    The constrained density functional theory-configuration interaction (CDFT-CI) method has previously been used to calculate ground-state energies and barrier heights, and to describe electronic excited states, in particular ...

  10. Constraining Flow Dynamics of Mass Movements on Earth and Mars

    NASA Astrophysics Data System (ADS)

    Barnouin-Jha, O. S.; Bulmer, M. H.

    2004-03-01

    We utilize topographic data of mass movements obtained both on Earth and Mars to estimate their flow velocity. By comparing these estimates with simple flow models, we begin to constrain their flow dynamics.

  11. Constrained Density-Functional Theory--Configuration Interaction

    E-print Network

    Kaduk, Benjamin James

    2012-01-01

    In this thesis, I implemented a method for performing electronic structure calculations, "Constrained Density Functional Theory-- Configuration Interaction" (CDFT-CI), which builds upon the computational strengths of Density ...

  12. Affine Lie Algebraic Origin of Constrained KP Hierarchies

    E-print Network

    H. Aratyn; J. F. Gomes; A. H. Zimerman

    1994-08-18

    We present an affine $sl (n+1)$ algebraic construction of the basic constrained KP hierarchy. This hierarchy is analyzed using two approaches, namely linear matrix eigenvalue problem on hermitian symmetric space and constrained KP Lax formulation and we show that these approaches are equivalent. The model is recognized to be the generalized non-linear Schr\\"{o}dinger ($\\GNLS$) hierarchy and it is used as a building block for a new class of constrained KP hierarchies. These constrained KP hierarchies are connected via similarity-B\\"{a}cklund transformations and interpolate between $\\GNLS$ and multi-boson KP-Toda hierarchies. Our construction uncovers origin of the Toda lattice structure behind the latter hierarchy.

  13. The effect of foot conditions on constrained standing

    E-print Network

    Barlow, Jessica Marie

    1996-01-01

    This study was conducted to find any differences in physiological effects, subjective rankings, or discomfort with respect to foot conditions in constrained standing. Eight healthy subjects, four female and four male, stood using four different...

  14. FXR agonist activity of conformationally constrained analogs of GW 4064

    SciTech Connect

    Akwabi-Ameyaw, Adwoa; Bass, Jonathan Y.; Caldwell, Richard D.; Caravella, Justin A.; Chen, Lihong; Creech, Katrina L.; Deaton, David N.; Madauss, Kevin P.; Marr, Harry B.; McFadyen, Robert B.; Miller, Aaron B.; Navas, III, Frank; Parks, Derek J.; Spearing, Paul K.; Todd, Dan; Williams, Shawn P.; Wisely, G. Bruce; (GSKNC)

    2010-09-27

    Two series of conformationally constrained analogs of the FXR agonist GW 4064 1 were prepared. Replacement of the metabolically labile stilbene with either benzothiophene or naphthalene rings led to the identification of potent full agonists 2a and 2g.

  15. Length Constrained Multiresolution Deformation for Surface Wrinkling Basile Sauvage

    E-print Network

    Paris-Sud XI, Université de

    Length Constrained Multiresolution Deformation for Surface Wrinkling Basile Sauvage LMC this constraint can be integrated into a multiresolution editing tool allowing an intuitive control in approximating the initial length by modifying the multiresolution decomposition at some spe- cified scale

  16. Irreducible Infeasible Subsystem Decomposition for Probabilistically Constrained Stochastic Integer Programs

    E-print Network

    Gallego Arrubla, Julian Andres

    2013-07-25

    This dissertation explores methods for finding irreducible infeasible subsystems (IISs) of systems of inequalities with binary decision variables and for solving probabilistically constrained stochastic integer programs (SIP-C). Finding IISs...

  17. Chance Constrained Mixed Integer Program: Bilinear and Linear ...

    E-print Network

    that aggregate Benders feasibility cuts are developed using the mixing set ..... cally introduced to model decisions with concrete definitions in practice, e.g., ...... J Luedtke, and S Küçükyavuz, Chance-constrained binary packing problems,.

  18. Conical Intersections using Constrained DFT-Configuration Interaction

    E-print Network

    Kaduk, Benjamin J.

    The constrained density functional theory–configuration interaction (CDFT-CI) method has previously been used to calculate ground-state energies and barrier heights. In this work, it is examined for use in computing ...

  19. Learning to Plan for Constrained Manipulation from Demonstrations

    E-print Network

    Likhachev, Maxim

    Learning to Plan for Constrained Manipulation from Demonstrations Mike Phillips mlphilli@andrew.cmu.edu Carnegie Mellon University Victor Hwang vchwang@andrew.cmu.edu Carnegie Mellon University Sachin Chitta

  20. Resource constrained scheduling problem at U.S. Naval Shipyards

    E-print Network

    Nawara, Terrence M. (Terrence Michael)

    2013-01-01

    Submarine repair schedules are some of the most complex schedules seen in project management. Repairs of a nuclear U.S. submarine are resource constrained since resources are divided among approximately thirty shops (e.g. ...

  1. Constructing constrained invariant sets in multiscale continuum systems.

    PubMed

    Morgan, David; Bollt, Erik M; Schwartz, Ira B

    2003-11-01

    We present a method that we name the constrained invariant manifold method, a visualization tool to construct stable and unstable invariant sets of a map or flow, where the invariant sets are constrained to lie on a slow invariant manifold. The construction of stable and unstable sets constrained to an unstable slow manifold is exemplified in a singularly perturbed model arising from a structural-mechanical system consisting of a pendulum coupled to a viscoelastic rod. Additionally, we extend the step and stagger method [D. Sweet, H. Nusse, and J. Yorke, Phys. Rev. Lett. 86, 2261 (2001)] to calculate a delta pseudoorbit on a chaotic saddle constrained to the slow manifold in order to be able to compute the Lyapunov exponents of the saddle. PMID:14682874

  2. Constraining the QSO luminosity function using gravitational lensing statistics

    E-print Network

    Fakhouri, Onsi Joe, 1983-

    2004-01-01

    In this thesis we use gravitational lensing statistics to constrain the QSO luminosity function at a variety of redshifts. We present a theoretical discussion of gravitational lensing statistics and illustrate how high ...

  3. Unified Particle Swarm Optimization for Solving Constrained Engineering Optimization Problems

    E-print Network

    Parsopoulos, Konstantinos

    Unified Particle Swarm Optimization for Solving Constrained Engineering Optimization Problems K investigate the performance of the recently proposed Uni- fied Particle Swarm Optimization method and global variant of Particle Swarm Optimization are re- ported and discussed. 1 Introduction Many

  4. Constraining volcano eruption dynamics with infrasound

    NASA Astrophysics Data System (ADS)

    Johnson, J. B.; Aster, R. C.

    2003-12-01

    Infrasonic airwaves produced by exploding volcanoes provide an indispensable tool for understanding dynamics of diverse eruptions. Unlike the seismicity generated during eruption, which is a complex superposition of internal and surface source and wave propagation processes, the infrasonic pressure field can be unequivocally associated with the flux rate of gas released at the volcanic vent. Because the atmosphere does not support shear waves, and internal scattering, topographic echoes, site, and weather effects are substantially predictable, it is possible to objectively compare the infrasound, and assess degassing from diverse volcanic systems. With its utility for continuously tracking eruptive activity, even when line-of-sight view to the vent is obscured, infrasound greatly enhances the efficacy of volcano monitoring and interpretation of conduit processes / eruption dynamics. We showcase new results from Erebus, Fuego, Villarrica, and Santiaguito volcanoes to demonstrate the utility of infrasound for recovering quantitative parameters, such as eruption duration, source dimensions and mechanism, and explosive gas release. At Erebus, infrasound can constrain the physical dimension of enormous bubbles, with diameters up to 10 m and containing more than 1000 kg gas, that burst individually and infrequently from the lava lake surface. At Villarrica, longer-duration infrasonic transients reveal the eruptive mechanism to be a succession of gas slugs bursting from the free surface, occurring at 60-90 s intervals and representing a stable long-term mode of degassing. At Fuego, the infrasound associated with vigorous explosions is inferred to result from the fragmentation of a bubble foam layer, which continues for tens of seconds until the gas foam is depleted. And at Santiaguito, large eruptions, which generate low intensity infrasound, suggest a diffuse source region with dimensions comparable to the radiated infrasonic wavelength (vent radii > 100 m). The recorded infrasound from these 4 volcanoes complements our infrasound archives for an additional 6 volcanoes, which encompasses a wide range of eruptive behaviors. Infrasound recorded within a few km of a volcanic vent thus provides an ideal tool for objective comparison of associated degassing.

  5. Constrained minimization of smooth functions using a genetic algorithm

    NASA Technical Reports Server (NTRS)

    Moerder, Daniel D.; Pamadi, Bandu N.

    1994-01-01

    The use of genetic algorithms for minimization of differentiable functions that are subject to differentiable constraints is considered. A technique is demonstrated for converting the solution of the necessary conditions for a constrained minimum into an unconstrained function minimization. This technique is extended as a global constrained optimization algorithm. The theory is applied to calculating minimum-fuel ascent control settings for an energy state model of an aerospace plane.

  6. Adaptive Medical Feature Extraction for Resource Constrained Distributed Embedded Systems

    Microsoft Academic Search

    Roozbeh Jafari; Hyduke Noshadi; Majid Sarrafzadeh; Soheil Ghiasi

    2006-01-01

    Abstract— Tiny embedded systems have not been,an ideal outfit for high performance,computing,due to their constrained resources. Limitations in processing power, battery life, communication bandwidth and memory constrain the applicability of existing complex,medical\\/biological analysis algorithms,to such platforms. Electrocardiogram,(ECG) analysis,resembles,such algorithm. In this paper, we address the issue of partitioning an ECG analysis algorithm,while the wireless communication power,consumption,is minimized. Considering the orientation

  7. A hybrid immune PSO for constrained optimization problems

    Microsoft Academic Search

    Aijia Ouyang

    2010-01-01

    Precise Algorithms combining evolutionary algorithms and constraint-handling techniques have shown to be effective to solve constrained optimization problems during the past decade. This paper presents a hybrid immune PSO (HIA-PSO) algorithm with a feasibility-based rule which is employed in this paper to handle constraints in solving global nonlinear constrained optimization problems, and Nelder-Mead simplex search method is used to improve

  8. Acid Stomach

    NSDL National Science Digital Library

    Science Netlinks

    2003-08-07

    This Science NetLinks lesson is intended for a high-school, introductory chemistry class or health class. The lesson begins with an article on the history of the development of aspirin. Students will then complete a lab that compares the reaction of regular aspirin, buffered aspirin, and enteric aspirin in neutral, acidic, and basic solutions. They will then analyze the results of the experiment to gain insight into how this information was used by researchers to solve some of the problems associated with aspirin. To complete the lesson, students must understand acids and bases.

  9. Amino Acid metabolism conflicts with protein diversity.

    PubMed

    Krick, Teresa; Verstraete, Nina; Alonso, Leonardo G; Shub, David A; Ferreiro, Diego U; Shub, Michael; Sánchez, Ignacio E

    2014-11-01

    The 20 protein-coding amino acids are found in proteomes with different relative abundances. The most abundant amino acid, leucine, is nearly an order of magnitude more prevalent than the least abundant amino acid, cysteine. Amino acid metabolic costs differ similarly, constraining their incorporation into proteins. On the other hand, a diverse set of protein sequences is necessary to build functional proteomes. Here, we present a simple model for a cost-diversity trade-off postulating that natural proteomes minimize amino acid metabolic flux while maximizing sequence entropy. The model explains the relative abundances of amino acids across a diverse set of proteomes. We found that the data are remarkably well explained when the cost function accounts for amino acid chemical decay. More than 100 organisms reach comparable solutions to the trade-off by different combinations of proteome cost and sequence diversity. Quantifying the interplay between proteome size and entropy shows that proteomes can get optimally large and diverse. PMID:25086000

  10. Amino Acid Metabolism Conflicts with Protein Diversity

    PubMed Central

    Krick, Teresa; Verstraete, Nina; Alonso, Leonardo G.; Shub, David A.; Ferreiro, Diego U.; Shub, Michael; Sánchez, Ignacio E.

    2014-01-01

    The 20 protein-coding amino acids are found in proteomes with different relative abundances. The most abundant amino acid, leucine, is nearly an order of magnitude more prevalent than the least abundant amino acid, cysteine. Amino acid metabolic costs differ similarly, constraining their incorporation into proteins. On the other hand, a diverse set of protein sequences is necessary to build functional proteomes. Here, we present a simple model for a cost-diversity trade-off postulating that natural proteomes minimize amino acid metabolic flux while maximizing sequence entropy. The model explains the relative abundances of amino acids across a diverse set of proteomes. We found that the data are remarkably well explained when the cost function accounts for amino acid chemical decay. More than 100 organisms reach comparable solutions to the trade-off by different combinations of proteome cost and sequence diversity. Quantifying the interplay between proteome size and entropy shows that proteomes can get optimally large and diverse. PMID:25086000

  11. Stearic Acid

    ERIC Educational Resources Information Center

    Young, Jay A.

    2004-01-01

    A chemical laboratory information profile (CLIP) is presented for the chemical, stearic acid. The profile lists the chemical's physical and harmful characteristics, exposure limits, and symptoms of major exposure, for the benefit of teachers and students, who use the chemical in the laboratory.

  12. Folic Acid

    MedlinePLUS

    ... lifelong disabilities. They may also need many surgeries. Anencephaly (an-en-SEF-uh-lee), which is when most or all of the brain does not develop. Babies with this problem die before or shortly after birth. The results of some studies suggest that folic acid might also help to prevent other types of ...

  13. Acid Rain

    NSDL National Science Digital Library

    This activity is part of Planet Diary and is an online examination into acid rain and sulfur dioxide emissions. Students research which states have succeeded in reducing sulfur dioxide emissions between 1980 and 1999, and which states emissions have increased. This activity is accompanied by a page of websites for further information.

  14. Acid Attack

    NSDL National Science Digital Library

    2014-09-18

    In this activity, students explore the effect of chemical erosion on statues and monuments. They use chalk to see what happens when limestone is placed in liquids with different pH values. They also learn several things that engineers are doing to reduce the effects of acid rain.

  15. On the design of efficient constrained parity-check codes for optical recording

    Microsoft Academic Search

    Kui Cai; Kees A. Schouhamer Immink

    2005-01-01

    This paper proposes a general and systematic way to efficiently combine constrained codes with parity-check (PC) codes for optical recording. The proposed constrained PC code includes two component codes: the normal constrained (NC) code and the parity-related constrained (PRC) code. They are designed based on the same finite state machine (FSM). The code rates are only a few tenths below

  16. A general construction of constrained parity-check codes for optical recording

    Microsoft Academic Search

    Kui Cai; Kees A. Schouhamer Immink

    2008-01-01

    This paper proposes a general and systematic code design method to efficiently combine constrained codes with parity-check (PC) codes for optical recording. The proposed constrained PC code includes two component codes: the normal constrained (NC) code and the parity-related constrained (PRC) code. They are designed based on the same finite state machine (FSM). The rates of the designed codes are

  17. Azelaic acid.

    PubMed

    Nazzaro-Porro, M

    1987-12-01

    This review is an update on the literature accumulated over the past 10 years following the original observation that azelaic acid, a naturally occurring and nontoxic C9 dicarboxylic acid, possesses significant biologic properties and a potential as a therapeutic agent. These studies have shown that azelaic acid is a reversible inhibitor of tyrosinase and other oxidoreductases in vitro and that it inhibits mitochondrial respiration. It can also inhibit anaerobic glycolysis. Both in vitro and in vivo it has an antimicrobial effect on both aerobic and anaerobic (Propionibacterium acnes) microorganisms. In tissue culture it exerts a dose- and time-dependent cytotoxic effect on malignant melanocytes, associated with mitochondrial damage and inhibition of deoxyribonucleic acid (DNA) synthesis. Tumoral cell lines not containing tyrosinase are equally affected. Normal cells in culture exposed to the same concentrations of the diacid that are toxic for tumoral cells are in general not damaged. Radioactive azelaic acid has been shown to penetrate tumoral cells at a higher level than normal cells of the corresponding line. Topically applied (a 20% cream), it has been shown to be of therapeutic value in skin disorders of different etiologies. Its beneficial effect on various forms of acne (comedogenic, papulopustular, nodulocystic) has been clearly demonstrated. Particularly important is its action on abnormal melanocytes, which has led to the possibility of obtaining good results on melasma and highly durable therapeutic responses on lentigo maligna. It is also capable of causing regression of cutaneous malignant melanoma, but its role in melanoma therapy remains to be investigated.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2963038

  18. Pharmacology of oleanolic acid and ursolic acid

    Microsoft Academic Search

    Jie Liu

    1995-01-01

    Oleanolic acid and ursolic acid are triterpenoid compounds that exist widely in food, medicinal herbs and other plants. This review summarizes the pharmacological studies on these two triterpenoids. Both oleanolic acid and ursolic acid are effective in protecting against chemically induced liver injury in laboratory animals. Oleanolic acid has been marketed in China as an oral drug for human liver

  19. Distribution on contingency of alignment of two literal sequences under constrains.

    PubMed

    Jäntschi, Lorentz; Bolboac?, Sorana D

    2015-03-01

    The case of ungapped alignment of two literal sequences under constrains is considered. The analysis lead to general formulas for probability mass function and cumulative distribution function for the general case of using an alphabet with a chosen number of letters (e.g. 4 for deoxyribonucleic acid sequences) in the expression of the literal sequences. Formulas for three statistics including mean, mode, and standard deviation were obtained. Distributions are depicted for three important particular cases: alignment on binary sequences, alignment of trinomial series (such as coming from generalized Kronecker delta), and alignment of genetic sequences (with four literals in the alphabet). A particular case when sequences contain each letter of the alphabet at least once in both sequences has also been analyzed and some statistics for this restricted case are given. PMID:25524134

  20. Domoic Acid

    NSDL National Science Digital Library

    INCHEM

    This highly detailed chemical information page features domoic acid, a toxin associated with Amnesic shellfish poisoning and naturally produced by the red algae Chondria armata and diatoms of the genus Pseudo-nitzschia. Created by the International Programme on Chemical Safety, this web page organizes information under the following sections: Name, Summary, Physio-Chemical Properties, Uses, Routes of Entry, Kinetics, Toxicology, Toxicological and Biomedical Investigations, Clinical Effects, Management, Illustrative Cases, Additional Information, References, and Authors.

  1. Effect of structurally constrained oxime-ether linker on PPAR subtype selectivity: Discovery of a novel and potent series of PPAR-pan agonists.

    PubMed

    Makadia, Pankaj; Shah, Shailesh R; Pingali, Harikishore; Zaware, Pandurang; Patel, Darshit; Pola, Suresh; Thube, Baban; Priyadarshini, Priyanka; Suthar, Dinesh; Shah, Maanan; Giri, Suresh; Trivedi, Chitrang; Jain, Mukul; Patel, Pankaj; Bahekar, Rajesh

    2011-01-15

    A novel series of thaizole and oxazole containing phenoxy acetic acid derivatives is reported as PPAR-pan agonists. Incorporation of structurally constrained oxime-ether based linker in the chemotype of a potent PPAR? selective agonist GW-501516 was adapted as designing strategy. In vitro, selected test compounds 12a, 12c, 17a and 18a showed PPAR-pan agonists activities and among these four compounds tested, 12a emerged as highly potent and efficacious compound, while 17a exhibited moderate and balanced PPAR-pan agonistic activity. In vivo, selected test compounds 12a and 17a exhibited significant anti-hyperglycemic and anti-hyperlipidemic activities in relevant animal models. These results support our hypothesis that the introduction of structurally constrained oxime-ether linker between lipophilic tail and acidic head plays an important role in modulating subtype selectivity and subsequently led to the discovery of potent PPAR-pan agonists. PMID:21215640

  2. Control area performance improvement by extended security constrained economic dispatch

    SciTech Connect

    Barcelo, W.R.; Rastgoufard, P. [Tulane Univ., New Orleans, LA (United States). Dept. of Electrical Engineering] [Tulane Univ., New Orleans, LA (United States). Dept. of Electrical Engineering

    1997-02-01

    An algorithm for solving the extended security constrained economic dispatch (ESCED) problem with real-time economic dispatch grade speed and reliability is presented. The ESCED problem is formulated by adding regulating margin and ramp rate constraints to the network security constrained economic dispatch problem previously solved by the CEDC algorithm. Starting with Newton`s method to optimize the Lagrangian, the ESCED is developed by superimposing on Newton`s method eight major components called Tracking Start Initialization, Hessian Pre-Elimination, Implicit Dual Variable Calculations, Regulating Margin Sensitivity Coefficient Calculations, Traumatic Event Evaluation, Constraint Relaxation, Implicit Ramp Rate Constraint Implementation, and Relaxed Incremental Cost Calculations. Test results are also presented.

  3. Probabilistic constrained load flow based on sensitivity analysis

    SciTech Connect

    Karakatsanis, T.S.; Hatziargyriou, N.D. (National Technical Univ., Athens (Greece))

    1994-11-01

    This paper presents a method for network constrained setting of control variables based on probabilistic load flow analysis. The method determines operating constraint violations for a whole planning period together with the probability of each violation. An iterative algorithm is subsequently employed providing adjustments of the control variables based on sensitivity analysis of the constrained variables with respect to the control variables. The method is applied to the IEEE 14 busbar system and to a realistic model of the Hellenic Interconnected system indicating its suitability for short-term operational planning applications.

  4. Fast Energy Minimization of large Polymers Using Constrained Optimization

    SciTech Connect

    Todd D. Plantenga

    1998-10-01

    A new computational technique is described that uses distance constraints to calculate empirical potential energy minima of partially rigid molecules. A constrained minimuzation algorithm that works entirely in Cartesian coordinates is used. The algorithm does not obey the constraints until convergence, a feature that reduces ill-conditioning and allows constrained local minima to be computed more quickly than unconstrained minima. Computational speedup exceeds the 3-fold factor commonly obtained in constained molecular dynamics simulations, where the constraints must be strictly obeyed at all times.

  5. Pseudo-updated constrained solution algorithm for nonlinear heat conduction

    NASA Technical Reports Server (NTRS)

    Tovichakchaikul, S.; Padovan, J.

    1983-01-01

    This paper develops efficiency and stability improvements in the incremental successive substitution (ISS) procedure commonly used to generate the solution to nonlinear heat conduction problems. This is achieved by employing the pseudo-update scheme of Broyden, Fletcher, Goldfarb and Shanno in conjunction with the constrained version of the ISS. The resulting algorithm retains the formulational simplicity associated with ISS schemes while incorporating the enhanced convergence properties of slope driven procedures as well as the stability of constrained approaches. To illustrate the enhanced operating characteristics of the new scheme, the results of several benchmark comparisons are presented.

  6. Effect of structurally constrained oxime–ether linker on PPAR subtype selectivity: Discovery of a novel and potent series of PPAR-pan agonists

    Microsoft Academic Search

    Pankaj Makadia; Shailesh R. Shah; Harikishore Pingali; Pandurang Zaware; Darshit Patel; Suresh Pola; Baban Thube; Priyanka Priyadarshini; Dinesh Suthar; Maanan Shah; Suresh Giri; Chitrang Trivedi; Mukul Jain; Pankaj Patel; Rajesh Bahekar

    2011-01-01

    A novel series of thaizole and oxazole containing phenoxy acetic acid derivatives is reported as PPAR-pan agonists. Incorporation of structurally constrained oxime–ether based linker in the chemotype of a potent PPAR? selective agonist GW-501516 was adapted as designing strategy. In vitro, selected test compounds 12a, 12c, 17a and 18a showed PPAR-pan agonists activities and among these four compounds tested, 12a

  7. Stereoselective Synthesis of cis-2 and trans-2-(Indol-3-yl) Cyclopropyl Amines, Carboxylic Acids, and Esters

    Microsoft Academic Search

    Tilak T. Raj; Maurice R. Eftink

    1998-01-01

    We report a general route for the synthesis of E and Z isomers of indol-3-yl cyclopropyl amines, carboylic acids, and esters. These cyclopropane containing molecules are of interest as conformationally constrained analogues of tryptamine and indole propionic acid, biologically active indoles. The route involves reaction of vinyl indole with ethyl diazoacetate, chromatographic separation of the E and Z stereoisomers of

  8. Understanding Acid Rain

    ERIC Educational Resources Information Center

    Damonte, Kathleen

    2004-01-01

    The term acid rain describes rain, snow, or fog that is more acidic than normal precipitation. To understand what acid rain is, it is first necessary to know what an acid is. Acids can be defined as substances that produce hydrogen ions (H+), when dissolved in water. Scientists indicate how acidic a substance is by a set of numbers called the pH…

  9. New Bioactive Fatty Acids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many oxygenated fatty acids are bioactive compounds. Nocardia cholesterolicum and Flavobacterium DS5 convert oleic acid to 10 hydroxy stearic acid and linoleic acid to 10-hydroxy-12(Z)-octadecanoic acid. Pseudomonas aeruginosa PR3 converts oleic acid to new compounds, 7,10-dihydroxy-8(E)-octadecen...

  10. Network constrained security control using an interior point algorithm

    Microsoft Academic Search

    C.-N. Lu; M. R. Unum

    1993-01-01

    N. Karmarkar's interior point method (1984), said to perform much faster than the simplex method in solving large scale linear programming problems, has attracted a great deal of attention. The authors present a preliminary implementation of the interior point algorithm and test results on the network constrained security control problem. Test results indicate that when solving various sizes of network

  11. EUROPEAN LARGE LAKES III Identification of factors constraining nitrate assimilation

    E-print Network

    Berges, John A.

    EUROPEAN LARGE LAKES III Identification of factors constraining nitrate assimilation in Lake Science+Business Media Dordrecht 2013 Abstract Despite a well-documented rise in nitrate concentration to assess the influence of light and nutrients (P, Fe) on nitrate assimilation by a Lake Superior

  12. Envelope-constrained H? filter design: An LMI optimization approach

    Microsoft Academic Search

    Zhiqiang Tan; Yeng Chai Soh; Lihua Xie

    2000-01-01

    In this correspondence, we solve the envelope-constrained H? filter design problem by minimizing the H? norm of the filtering error transfer function subject to the constraint that the filter output is contained in a prescribed envelope. The filter design is transformed into a standard linear matrix inequality (LMI) optimization problem

  13. Constraining Perturbative Early Dark Energy with Current Observations

    Microsoft Academic Search

    Ujjaini Alam; Ujjaini

    2010-01-01

    In this work, we study a class of early dark energy (EDE) models, in which, unlike in standard dark energy models, a substantial amount of dark energy exists in the matter-dominated era. We self-consistently include dark energy perturbations, and constrain these models using current observations. We consider EDE models in which the dark energy equation of state is at least

  14. Solving quadratically constrained least squares using black box solvers

    Microsoft Academic Search

    Tony F. Chan; Julia A. Olkin; Donald W. Cooley

    1992-01-01

    We present algorithms for solving quadratically constrained linear least squares problems that do not necessarily require expensive dense matrix factorizations. Instead, only “black box” solvers for certain related unconstrained least squares problems, as well as the solution of two related linear systems involving the coefficient matrixA and the constraint matrixB, are required. Special structures in the problem can thus be

  15. Risk constrained economic load dispatch in interconnected generating systems

    SciTech Connect

    Chowdhury, N.; Billinton, R. (Power Systems Research Group, University of Saskatchewan, Saskatoon (CA))

    1990-11-01

    A risk constrained unit loading technique for interconnected systems is presented in this paper which utilizes a least costly deviation from economic load dispatch to satisfy the risk criteria. The technique is developed on the basis of each area in a multi-area configuration fulfilling two different response risk criteria. The technique is illustrated with numerical examples.

  16. BINARY CONSTRAINED FLOWS AND SEPARATION OF VARIABLES FOR SOLITON EQUATIONS

    E-print Network

    Ma, Wen-Xiu

    of canonical sepa- rated variables with additional N separated equations is introduced. The Jacobi inversion constrained ows leads to the Jacobi inversion problems for soliton equations. 1. Introduction The separation spectral curve. The resulting linearizing map is essentially the Abel map to the Ja- cobi variety

  17. Bearing-Only Localization Using Geometrically Constrained Optimization

    E-print Network

    Mao, Guoqiang

    1 Bearing-Only Localization Using Geometrically Constrained Optimization Adrian N. Bishop, Student Member, IEEE, Brian D.O. Anderson, Life Fellow, IEEE, Baris¸ Fidan, Member, IEEE, Pubudu N. Pathirana simulation. Index Terms-- Angle Measurements, Bearings, Geometric Con- straints, Localization, Optimization

  18. Chance-Constrained Optimal Path Planning with Obstacles

    E-print Network

    Williams, Brian C.

    avoiding obstacles. These trajectories should be optimal with respect to a criterion such as time or fuel1 Chance-Constrained Optimal Path Planning with Obstacles Lars Blackmore, Masahiro Ono and Brian C. Williams Abstract--Autonomous vehicles need to plan trajectories to a specified goal that avoid obstacles

  19. Optimal Constrained Resource Allocation Strategies under Low Risk Circumstances

    Microsoft Academic Search

    Mugurel Ionut Andreica; Madalina Ecaterina Andreica; Costel Visan

    2009-01-01

    In this paper we consider multiple constrained resource allocation problems, where the constraints can be specified by formulating activity dependency restrictions or by using game-theoretic models. All the problems are focused on generic resources, with a few exceptions which consider financial resources in particular. The problems consider low-risk circumstances and the values of the uncertain variables which are used by

  20. Cramer-Rao lower bound for constrained complex parameters

    Microsoft Academic Search

    Aditya K. Jagannatham; Bhaskar D. Rao

    2004-01-01

    An expression for the Cramer-Rao lower bound (CRB) on the covariance of unbiased estimators of a constrained complex parameter vector is derived. The application and usefulness of the result is demonstrated through its use in the context of a semiblind channel estimation problem.

  1. Design of regularity constrained linear phase modulated lapped transforms

    Microsoft Academic Search

    K. M. Abdul Hameed; Elizabeth Elias

    2006-01-01

    The regularity constrained linear phase filter banks reported recently are based on generalized bi-orthogonal lapped transforms. They do not have a modulated structure and hence all the basis functions are to be optimized separately. Design and implementation complexity increases with the size of the block transform. In this paper, a cosine-modulated approach for the design of orthogonal modulated lapped transforms

  2. Regularizing Flows for Constrained Matrix-Valued Images

    Microsoft Academic Search

    Christophe Chefd'Hotel; David Tschumperlé; Rachid Deriche; Olivier D. Faugeras

    2004-01-01

    Nonlinear diffusion equations are now widely used to restore and enhance images. They allow to eliminate noise and artifacts while preserving large global features, such as object contours. In this context, we propose a differential-geometric framework to define PDEs acting on some manifold constrained datasets. We consider the case of images taking value into matrix manifolds defined by orthogonal and

  3. Thermally constrained motor operation for a climbing robot

    Microsoft Academic Search

    Salomon Trujillo; Mark R. Cutkosky

    2009-01-01

    Climbing robots are especially susceptible to ther- mal overload during normal operation, due to the need to op- pose gravity and to frequently apply internal forces for clinging. As an alternative to setting conservative limits on the motor peak and average current, we investigate methods for measuring motor temperatures, predicting motor thermal conditions and generating thermally constrained behavior. A thermal

  4. Probability-One Homotopy Maps for Tracking Constrained Clustering Solutions

    E-print Network

    Ramakrishnan, Naren

    parametrically as varies, (2) how to find and deal with multiple solutions for a fixed and (3) howProbability-One Homotopy Maps for Tracking Constrained Clustering Solutions David R. Easterling of alternatives. Homotopy methods are a promising approach to characterize solution spaces by smoothly tracking

  5. LIFE EXTENDING CONTROL BY A VARIANCE CONSTRAINED MPC APPROACH

    E-print Network

    Marquez, Horacio J.

    for a boiler system is discussed. To reduce the accumulated damage, a variance constrained model predictive in a prescribed region. Finally, we apply the algorithm in a LEC design for a boiler system. Copyright c 2005 IFAC Keywords: Damage, boilers, linear control systems, variance matrices, multivariable control systems. 1

  6. Sufficient Completeness Verification for Conditional and Constrained TRS

    E-print Network

    Paris-Sud XI, Université de

    Sufficient Completeness Verification for Conditional and Constrained TRS Adel Bouhoulaa , Florent (instances This work has been partially supported by the grant INRIA­DGRSRT 10/01. Email addresses: adel.bouhoula@supcom.rnu.tn (Adel Bouhoula), florent.jacquemard@inria.fr (Florent Jacquemard) Preprint submitted to JAL November 21

  7. Flexible composite propeller design using constrained optimization techniques

    Microsoft Academic Search

    Abdul Monuem Khan

    1997-01-01

    An investigation of a conventional propeller, made from composite materials, was conducted in which its characteristics were studied under quasi-static aerodynamic loading. Also, optimized designing of a composite propeller was performed for various constrained and unconstrained design objectives. Only symmetric ply stacking sequences were considered to eliminate the effect of centrifugal force on the propeller. Results show that the ply

  8. Fourth Meeting on Constrained Dynamics and Quantum Gravity

    Microsoft Academic Search

    Mariano Cadoni; Marco Cavaglia; Jeanette E Nelson

    2006-01-01

    The formulation of a quantum theory of gravity seems to be the unavoidable endpoint of modern theoretical physics. Yet the quantum description of the gravitational field remains elusive. The year 2005 marks the tenth anniversary of the First Meeting on Constrained Dynamics and Quantum Gravity, held in Dubna (Russia) due to the efforts of Alexandre T. Filippov (JINR, Dubna) and

  9. Wavelet evolutionary network for complex-constrained portfolio rebalancing

    Microsoft Academic Search

    N. C. Suganya; G. A. Vijayalakshmi Pai

    2011-01-01

    Portfolio rebalancing problem deals with resetting the proportion of different assets in a portfolio with respect to changing market conditions. The constraints included in the portfolio rebalancing problem are basic, cardinality, bounding, class and proportional transaction cost. In this study, a new heuristic algorithm named wavelet evolutionary network (WEN) is proposed for the solution of complex-constrained portfolio rebalancing problem. Initially,

  10. Wavelet evolutionary network for complex-constrained portfolio rebalancing

    Microsoft Academic Search

    N. C. Suganya; G. A. Vijayalakshmi Pai

    2012-01-01

    Portfolio rebalancing problem deals with resetting the proportion of different assets in a portfolio with respect to changing market conditions. The constraints included in the portfolio rebalancing problem are basic, cardinality, bounding, class and proportional transaction cost. In this study, a new heuristic algorithm named wavelet evolutionary network (WEN) is proposed for the solution of complex-constrained portfolio rebalancing problem. Initially,

  11. Acoustic Eavesdropping Attacks on Constrained Wireless Device Pairing -Final

    E-print Network

    Saxena, Nitesh

    1 Acoustic Eavesdropping Attacks on Constrained Wireless Device Pairing - Final Tzipora Halevi the feasibility of eavesdropping over acoustic emanations associated with these methods and conclude transmission/reception can be perceived by one or more of human senses. Due to this property, OOB communication

  12. Shape Space Exploration of Constrained Meshes Yong-Liang Yang

    E-print Network

    Mitra, Niloy J.

    Shape Space Exploration of Constrained Meshes Yong-Liang Yang KAUST Yi-Jun Yang KAUST Helmut shape space exploration Figure 1: Starting from a single input mesh along with a set of non order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration

  13. Constrained Optimization with Genetic Algorithm: Improving Profitability of Targeted Marketing

    Microsoft Academic Search

    Geng Cui; Man Leung Wong; Xiang Wan

    2010-01-01

    Direct marketing forecasting models have focused on estimating the response probabilities of consumer purchases and neglected the profitability of customers. This study proposes a method of constrained optimization using genetic algorithm to maximize the profitability at the top deciles of a customer list. We apply this method to a direct marketing dataset using tenfold cross validation. The results from this

  14. Side Constrained Traffic Equilibrium Models_ Analysis, Computation and Applications

    E-print Network

    Patriksson, Michael

    in terms of generalized travel cos* *ts and an equilibrium queueing delay result; in traffic networks there is so* *me (fixed or elastic) travel demand and, usually, where because of traffic congestion the link Side Constrained Traffic Equilibrium Models_ Analysis, Computation

  15. Ant colony optimization for resource-constrained project scheduling

    Microsoft Academic Search

    Daniel Merkle; Martin Middendorf; Hartmut Schmeck

    2002-01-01

    An ant colony optimization approach (ACO) for the resource-constrained project schedul- ing problem (RCPSP) is presented. Combi- nations of two pheromone evaluation meth- ods are used by the ants to find new solutions. We tested our ACO algorithm on a set of large benchmark problems from the PSPLIB. Compared to several other heuristics for the RCPSP including genetic algorithms, simu-

  16. Speaker Adaptation Using Constrained Estimation of Gaussian Mixtures

    E-print Network

    Digalakis, Vassilis

    Speaker Adaptation Using Constrained Estimation of Gaussian Mixtures V. Digalakis D. Rtischev L generally to the channel and the task. In continuous mixture­density HMMs the number of component densities for Gaussian mixture densities. The algorithm is evaluated on the large­vocabulary Wall Street Journal corpus

  17. The Anytime Reliability of Constrained Packet Erasure Channels with Feedback

    E-print Network

    Sahai, Anant

    of data within the same packet transmission time.3 Since they are a useful abstraction that is actuallyThe Anytime Reliability of Constrained Packet Erasure Channels with Feedback Anant Sahai Department@me.berkeley.edu Abstract We study the anytime reliability of packet erasure channels where the erasures are iid and known

  18. Joint Power Allocation and Scheduling for Deadline Constrained Wireless Traffic

    Microsoft Academic Search

    Aditya Dua; Nicholas Bambos

    2006-01-01

    We study the problem of joint power allocation and scheduling for deadline constrained traffic on the downl ink of a cellular wireless communication system, where multiple users can be scheduled simultaneously on orthogonal spreading codes (HSDPA), or sub-carriers (OFDMA), subject to a sum power constraint. We formulate the problem for a canonical two-user model within a dynamic programming (DP) frame-

  19. An algorithm for linearly constrained adaptive array processing

    Microsoft Academic Search

    OTIS LAMONT FROST

    1972-01-01

    A constrained least mean-squares algorithm has been derived which is capable of adjusting an array of sensors in real time to respond to a signal coming from a desired direction while discriminating against noises coming from other directions. Analysis and computer simulations confirm that the algorithm is able to iteratively adapt variable weights on the taps of the sensor array

  20. Manipulation Planning with Goal Sets Using Constrained Trajectory Optimization

    E-print Network

    Hammerton, James

    Manipulation Planning with Goal Sets Using Constrained Trajectory Optimization Anca D. Dragan continuous sets of goals. This paper describes how to design optimal trajectories that exploit goal sets. We extend CHOMP (Covariant Hamiltonian Optimization for Motion Planning), a recent trajectory optimizer

  1. Least Constrained Slot Allocation in Optical TDM Networks

    E-print Network

    von Bochmann, Gregor

    Least Constrained Slot Allocation in Optical TDM Networks Hassan Zeineddine and Gregor V. Bochmann, Ottawa, ON-K1N 6N5 Abstract - In this paper, we propose a timeslot allocation scheme in all-optical TDM fit and least loaded approaches to reserve timeslots in networks that include buffers and multi-fibers

  2. A constrained adaptive beamformer for medical ultrasound: initial results

    Microsoft Academic Search

    J. A. Mann; W. F. Walker

    2002-01-01

    Adaptive beamforming has been widely used as a way to improve image quality in medical ultrasound applications by correcting phase and amplitude aberration errors resulting from tissue inhomogeneity. A less-studied concern in ultrasound beamforming is the deleterious contribution of bright off-axis targets. This paper describes a new approach, the constrained adaptive beamformer (CAB), which builds on classic array processing methods

  3. Tissue Classification of Noisy MR Brain Images Using Constrained GMM

    E-print Network

    Goldberger, Jacob

    Tissue Classification of Noisy MR Brain Images Using Constrained GMM Amit Ruf1 , Hayit Greenspan1 of noisy, low contrast magnetic resonance (MR) images of the brain. We use a mixture model composed of a large number of Gaussians, with each brain tissue represented by a large number of the Gaussian

  4. How well can future CMB missions constrain cosmic inflation?

    NASA Astrophysics Data System (ADS)

    Martin, Jérôme; Ringeval, Christophe; Vennin, Vincent

    2014-10-01

    We study how the next generation of Cosmic Microwave Background (CMB) measurement missions (such as EPIC, LiteBIRD, PRISM and COrE) will be able to constrain the inflationary landscape in the hardest to disambiguate situation in which inflation is simply described by single-field slow-roll scenarios. Considering the proposed PRISM and LiteBIRD satellite designs, we simulate mock data corresponding to five different fiducial models having values of the tensor-to-scalar ratio ranging from 10-1 down to 10-7. We then compute the Bayesian evidences and complexities of all Encyclopædia Inflationaris models in order to assess the constraining power of PRISM alone and LiteBIRD complemented with the Planck 2013 data. Within slow-roll inflation, both designs have comparable constraining power and can rule out about three quarters of the inflationary scenarios, compared to one third for Planck 2013 data alone. However, we also show that PRISM can constrain the scalar running and has the capability to detect a violation of slow roll at second order. Finally, our results suggest that describing an inflationary model by its potential shape only, without specifying a reheating temperature, will no longer be possible given the accuracy level reached by the future CMB missions.

  5. METHODS FOR COMPARING AND CONSTRAINING MODELS OF DENDRITIC SPINES

    E-print Network

    Boyer, Edmond

    METHODS FOR COMPARING AND CONSTRAINING MODELS OF DENDRITIC SPINES Nathan Skene Cambridge the uncaging of glutamate has proven the existence of excitable calcium ion channels in spine heads, high- lighting the need for reliable models of spines. In this study we compare the three main methods

  6. Reliability-Constrained Latent Structure Peter Westfall and Kevin Henning

    E-print Network

    Westfall, Peter H.

    Reliability-Constrained Latent Structure Models Peter Westfall and Kevin Henning Texas Tech allow you to estimate reliability of your measure of the fuzzy concept · LSMs allow you to estimate cannot identify reliability. · LSMs cannot identify relationships between fuzzy concepts. · LSMs cannot

  7. Constrained Inverse Volume Rendering for Planetary Nebulae Marcus Magnor

    E-print Network

    Utah, University of

    Constrained Inverse Volume Rendering for Planetary Nebulae Marcus Magnor MPI Informatik, Germany, USA Neb Duric Dept. Physics and Astronomy University of New Mexico, USA Figure 1: The planetary nebula Mz-3. Left to right: the nebula's color-composited original image, the same view rendered from

  8. Simulation of magnetohydrodynamic flows - a constrained transport method

    Microsoft Academic Search

    Charles R. Evans; John F. Hawley

    1988-01-01

    An optimal strategy for treating the MHD field transport equation is discussed. The induction equation is shown to assume its simplest form when written in terms of the contravariant forms of velocity and magnetic vector density. The approach places the induction equation in integral form and uses the magnetic flux as a fundamental variable. A new numerical technique called constrained

  9. Application of evolutionary programming to security constrained economic dispatch

    Microsoft Academic Search

    P. Somasundaram; K. Kuppusamy

    2005-01-01

    This paper presents an algorithm, for solving security constrained economic dispatch (SCED) problem, through the application of evolutionary programming (EP). The controllable system quantities in the base case state are optimized, to minimize some defined objective function, subject to the base case operating constraints as well as the contingency case security constraints. Two representative systems: 10-bus [10] and adapted IEEE

  10. ALGORITHMS FOR CONSTRAINED MINIMIZATION OF QUADRATIC FUNCTIONS GEOMETRY AND

    E-print Network

    Pottmann, Helmut

    for the computation of the point p in an m-dimensional surface Rn , which is closest to a given point p Rn. Therefore, the minimizer of F, restricted to , is the closest point p to p, and thus a normal footpoint recently published paper [2] on the design of motions constrained by a contacting surface pair. A central

  11. Force\\/motion control of constrained robots using sliding mode

    Microsoft Academic Search

    Chun-Yi Su; Tin-hi Leung; Qi-Jie Zhou

    1992-01-01

    A sliding mode control algorithm is presented for trajectory tracking of an end-effector on a constrained surface with specified constraint forces by using the theory of variable structure systems. The development of the algorithm is based on a new formulation of the dynamic model and the expansion of sliding surfaces to include the constraint force error. The proposed sliding controller

  12. Force\\/motion control of constrained manipulators without velocity measurements

    Microsoft Academic Search

    Antonio Loria; Elena Panteley

    1999-01-01

    In this paper the authors deal with the problem of force\\/tracking control of constrained manipulators without velocity measurements interacting with an infinitely stiff environment. They use a reduced-order model for which the coordinate space is restricted to a subset R where the Jacobian constraint is guaranteed to be nonsingular. In contrast to other similar approaches, the authors do not assume

  13. Constrained Quantum Mechanics: Chaos in Non-Planar Billiards

    ERIC Educational Resources Information Center

    Salazar, R.; Tellez, G.

    2012-01-01

    We illustrate some of the techniques to identify chaos signatures at the quantum level using as guiding examples some systems where a particle is constrained to move on a radial symmetric, but non-planar, surface. In particular, two systems are studied: the case of a cone with an arbitrary contour or "dunce hat billiard" and the rectangular…

  14. Constraining fault constitutive behavior with slip and stress heterogeneity

    Microsoft Academic Search

    B. T. Aagaard; T. H. Heaton

    2008-01-01

    We study how enforcing self-consistency in the statistical properties of the preshear and postshear stress on a fault can be used to constrain fault constitutive behavior beyond that required to produce a desired spatial and temporal evolution of slip in a single event. We explore features of rupture dynamics that (1) lead to slip heterogeneity in earthquake ruptures and (2)

  15. Constrained connectivity for hierarchical image partitioning and simplification

    Microsoft Academic Search

    Pierre Soille

    2008-01-01

    This paper introduces an image partitioning and simplification method based on the constrained connectivity paradigm. According to this paradigm, two pixels are said to be connected if they satisfy a series of constraints defined in terms of simple measures such as the maximum gray-level differences over well-defined pixel paths and regions. The resulting connectivity relation generates a unique partition of

  16. Neighboring optimization for constrained control problems in real time

    Microsoft Academic Search

    Adam Korytowski; M. Szymkat; A. Turnau

    2002-01-01

    A neighboring trajectory closed-loop control is proposed for fixed-horizon constrained optimal control problems. The lower level of the algorithm adjusts the switching times based on the linearization of the optimal controller and performs reduced optimization with a change of control structure, whereas the upper level finds the optimal control and recalculates the linearization each time the deviation from the optimal

  17. The explicit linear quadratic regulator for constrained systems

    Microsoft Academic Search

    Alberto Bemporad; Manfred Morari; Vivek Dua; Efstratios N. Pistikopoulos

    2002-01-01

    We present a technique to compute the explicit state-feedback solution to both the xnite and inxnite horizon linear quadratic optimal control problem subject to state and input constraints. We show that this closed form solution is piecewise linear and continuous. As a practical consequence of the result, constrained linear quadratic regulation becomes attractive also for systems with high sampling rates,

  18. Sensitivity-based security-constrained OPF market clearing model

    Microsoft Academic Search

    Federico Milano; Claudio A. Cañizares; Antonio J. Conejo

    2005-01-01

    This paper proposes a novel technique for representing system security constraints that properly include voltage stability limits in the operation of competitive electricity markets. The market-clearing algorithm is modeled as a voltage stability constrained optimal power flow (OPF) problem, while the distance to the closest critical power flow solution is represented by means of a loading parameter and evaluated using

  19. Sensitivity-based security-constrained OPF market clearing model

    Microsoft Academic Search

    F. Milano; A. Conejo; C. Canizares

    2006-01-01

    Summary form only given. This paper proposes a novel technique for representing system security constraints that properly include voltage stability limits in the operation of competitive electricity markets. The market clearing algorithm is modeled as a voltage stability constrained optimal power flow (OPF) problem, while the distance to the closest critical power flow solution is represented by means of a

  20. RESTful Service Development for Resource-Constrained Environments

    E-print Network

    Eliassen, Frank

    , such as smartphones, PDAs, Tablet PCs, and Wireless Sensor Networks (WSNs) is spreading rapidly in the business. In this chapter, we discuss the state-of-the-art in applying REST concepts to develop Web services for WSNs and smartphones as two representative resource-constrained platforms, and then we provide a comprehensive survey

  1. Online Learning: Stochastic and Constrained Adversaries Alexander Rakhlin

    E-print Network

    Rakhlin, Alexander "Sasha"

    Online Learning: Stochastic and Constrained Adversaries Alexander Rakhlin Department of Statistics distribution and the second scenario is the online learning, completely adversarial scenario where adversary continue the line of work on the minimax analysis of online learning, initiated in [1, 14, 13

  2. Mechanized Safety Proofs for Disc-Constrained Aircraft

    E-print Network

    Mechanized Safety Proofs for Disc-Constrained Aircraft David Renshaw Sarah M. Loos Andr´e Platzer, formal verification. #12;1 Introduction Safety-critical systems such as aircraft controllers must between aircraft to increase throughput, and on-board collision avoidance systems become ever more

  3. Multiply-Constrained Semantic Search in the Remote Associates Test

    ERIC Educational Resources Information Center

    Smith, Kevin A.; Huber, David E.; Vul, Edward

    2013-01-01

    Many important problems require consideration of multiple constraints, such as choosing a job based on salary, location, and responsibilities. We used the Remote Associates Test to study how people solve such multiply-constrained problems by asking participants to make guesses as they came to mind. We evaluated how people generated these guesses…

  4. Blue Moon sampling, vectorial reaction coordinates, and unbiased constrained dynamics

    E-print Network

    Van Den Eijnden, Eric

    Blue Moon sampling, vectorial reaction coordinates, and unbiased constrained dynamics Giovanni force in terms of a conditional expectation which can be computed by Blue Moon sampling Introduction Fifteen years ago the Blue Moon ensemble method was introduced to sample rare events that occur

  5. TARGET SIGNATURE-CONSTRAINED MIXED PIXEL CLASSIFICATION (TSCMPC): LCMV CLASSIFIERS

    E-print Network

    Chang, Chein-I

    11 TARGET SIGNATURE-CONSTRAINED MIXED PIXEL CLASSIFICATION (TSCMPC): LCMV CLASSIFIERS The target pixel classification which does not need a linear mixture model. Instead, it classifies a mixed pixel. A subpixel detector can detect targets, but does not necessarily imply that it can also classify the targets

  6. Learning through reinforcement for N-person repeated constrained games

    Microsoft Academic Search

    Alexander S. Poznyak; Kaddour Najim

    2002-01-01

    The design and analysis of an adaptive strategy for N-person averaged constrained stochastic repeated game are addressed. Each player is modeled by a stochastic variable-structure learning automaton. Some constraints are imposed on some functions of the probabilities governing the selection of the player's actions. After each stage, the payoff to each player as well as the constraints are random variables.

  7. Segmental order in a uniaxially constrained polydimethylsiloxane network

    E-print Network

    Paris-Sud XI, Université de

    L-763 Segmental order in a uniaxially constrained polydimethylsiloxane network : a deuterium of a polydimethylsiloxane model network exhibit quadrupolar doublets under both elongation and compression. Experiments polydimethylsiloxane network in an uniaxial stress for both elongation and compression. 2. Experimental. - 2. 1 SAMPLES

  8. Estimation Strategies for Constrained and Hybrid Dynamical Systems

    E-print Network

    Parish, Julie Marie Jones

    2012-10-19

    . . . . . . . . . . . . . . . . . . . . . 6 3. Constrained Systems . . . . . . . . . . . . . . . . . . . 7 4. Infinite-Dimensional Systems . . . . . . . . . . . . . . 9 B. Continuous-Discrete Extended Kalman Filter . . . . . . . . 12 III DIRECT LINEARIZATION VIA THE GIBBS FUNCTION . . 15...: y(x 4) ? y(x 6). . . . . . . . . . . . . . . . . . . . . . 131 113 Actual and Reconstructed Measurements Using Linear Assumed Modes, Case 1: y(x 7) ? y(x10). . . . . . . . . . . . . . . . . . . . . . 132 114 Actual and Reconstructed Measurements...

  9. CRYPTANALYSIS OF RSA WITH CONSTRAINED KEYS Abderrahmane Nitaj

    E-print Network

    Nitaj, Abderrahmane

    CRYPTANALYSIS OF RSA WITH CONSTRAINED KEYS Abderrahmane Nitaj Dâ??epartement de math = pq be an RSA modulus with unknown prime factors of equal bit­size. Let e be the public exponent and d, Boneh and Durfee improved the bound to n 0.292 . In this paper we show that instances of RSA with even

  10. CRYPTANALYSIS OF RSA WITH CONSTRAINED KEYS Abderrahmane Nitaj

    E-print Network

    Nitaj, Abderrahmane

    CRYPTANALYSIS OF RSA WITH CONSTRAINED KEYS Abderrahmane Nitaj D´epartement de math = pq be an RSA modulus with unknown prime factors of equal bit-size. Let e be the public exponent and d, Boneh and Durfee improved the bound to n0.292. In this paper we show that instances of RSA with even

  11. Design principles for opportunistic communication in constrained computing environments

    Microsoft Academic Search

    Earl A. Oliver; Srinivasan Keshav

    2008-01-01

    Constrained computing environments, such as smartphones and embedded wireless devices, are becoming increasingly prevalent. Driven by the need to minimize power usage, these devices are characterized by their low-power CPUs, limited memory, slow yet vast amounts of persistent storage, and one or more wireless network interfaces. As the domi- nant form of future computing, understanding and adapting to the trade

  12. Constrained macroeconomic policy development with a separate predictive model

    Microsoft Academic Search

    Ric D. Herbert; Rod D. Bell

    2004-01-01

    This paper examines the issue of the generation of optimal control policies where there are explicit constraints upon the control values and there is limited knowledge of the complex economic system. The paper develops a methodology where the constrained optimal control is based upon a separate model that predicts the policy targets for the economic system. The methodology as applied

  13. CONSTRAINED FORECASTS IN ARMA MODELS: A BAYESIAN APPROACH

    E-print Network

    West, Mike

    CONSTRAINED FORECASTS IN ARMA MODELS: A BAYESIAN APPROACH Enrique de Alba I.T.A.M. Rio Hondo No. 1­ casts in autoregressive­moving average time series models. Both are calculated by formulating the ARMA applied to ARMA time series models is rather limited. It refers mostly for AR models. Early references

  14. Testing a Constrained MPC Controller in a Process Control Laboratory

    ERIC Educational Resources Information Center

    Ricardez-Sandoval, Luis A.; Blankespoor, Wesley; Budman, Hector M.

    2010-01-01

    This paper describes an experiment performed by the fourth year chemical engineering students in the process control laboratory at the University of Waterloo. The objective of this experiment is to test the capabilities of a constrained Model Predictive Controller (MPC) to control the operation of a Double Pipe Heat Exchanger (DPHE) in real time.…

  15. Global marine primary production constrains fisheries catches Emmanuel Chassot1*

    E-print Network

    Paris-Sud XI, Université de

    Global marine primary production constrains fisheries catches Emmanuel Chassot1* , Sylvain and Sustainability, I- 21027 Ispra (VA), Italy. frederic.melin@jrc.ec.europa.eu 5 Sea Around Us project, Fisheries Centre, University of British Columbia, 2202 Main Mall, Vancouver, BC V6T 1Z4, Canada. r.watson@fisheries

  16. Glassy dynamics of kinetically constrained models and P. Sollich2*

    E-print Network

    Ritort, Felix

    of Mathematics, King's College London, Strand, London WC2R 2LS [Received 17 October 2002] Abstract We review 3.3. Lattice gas models 251 Advances in Physics, 2003, Vol. 52, No. 4, 219­342 Advances in Physics;3.3.1. Some results for lattice gas models 253 3.4. Constrained models on hierarchical structures 257 3

  17. Inferring Meaningful Communities from Topology-Constrained Correlation Networks

    PubMed Central

    Hleap, Jose Sergio; Blouin, Christian

    2014-01-01

    Community structure detection is an important tool in graph analysis. This can be done, among other ways, by solving for the partition set which optimizes the modularity scores . Here it is shown that topological constraints in correlation graphs induce over-fragmentation of community structures. A refinement step to this optimization based on Linear Discriminant Analysis (LDA) and a statistical test for significance is proposed. In structured simulation constrained by topology, this novel approach performs better than the optimization of modularity alone. This method was also tested with two empirical datasets: the Roll-Call voting in the 110th US Senate constrained by geographic adjacency, and a biological dataset of 135 protein structures constrained by inter-residue contacts. The former dataset showed sub-structures in the communities that revealed a regional bias in the votes which transcend party affiliations. This is an interesting pattern given that the 110th Legislature was assumed to be a highly polarized government. The -amylase catalytic domain dataset (biological dataset) was analyzed with and without topological constraints (inter-residue contacts). The results without topological constraints showed differences with the topology constrained one, but the LDA filtering did not change the outcome of the latter. This suggests that the LDA filtering is a robust way to solve the possible over-fragmentation when present, and that this method will not affect the results where there is no evidence of over-fragmentation. PMID:25409022

  18. Finite volume schemes for locally constrained conservation laws

    E-print Network

    Boyer, Edmond

    Finite volume schemes for locally constrained conservation laws Boris Andreianov Paola Goatin model proposed by Colombo and Goatin in [CG07]. The model involves a standard conservation law a "green wave" are presented. Key words: Hyperbolic Scalar Conservation Law, Finite Volume Scheme, Entropy

  19. STABILITY AND SINGULAR PERTURBATIONS IN CONSTRAINED MARKOV DECISION PROBLEMS

    E-print Network

    STABILITY AND SINGULAR PERTURBATIONS IN CONSTRAINED MARKOV DECISION PROBLEMS Eitan Altman INRIA alternative sufficient conditions for stability of CMDPs. In Section 5 we investigate singular perturbations of singularities is the extra constraints in the MDP. We use the theory of singular perturbations of LPs [7

  20. Constraining Cosmic Magnetic Fields by a Measurement of

    E-print Network

    Erdmann, Martin

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 7 Energy-Energy-Correlations 51 7.1 Definition of Energy-EnergyConstraining Cosmic Magnetic Fields by a Measurement of Energy-Energy-Correlations with the Pierre Ultra High Energy Cosmic Rays 3 2.1 Cosmic Rays with Energies below 4 Ee

  1. Resolving Over-constrainedTemporal Problems with Uncertain Durations

    E-print Network

    Williams, Brian C.

    -constrained Temporal Problems with Uncertain Durations 11/46 · Duration: Sep 26th ­ Oct 17th. · Vessel: R/V Atlantis. · Location:Along the coast between SF and LA. · Objectives: ­ Find and sample methane seeps near the coast. ­ Locate and sample a 60 year-old DDT dumping site. ­ Recover and replace incubators on the seafloor. #12;A

  2. Applications of a Constrained Mechanics Methodology in Economics

    ERIC Educational Resources Information Center

    Janova, Jitka

    2011-01-01

    This paper presents instructive interdisciplinary applications of constrained mechanics calculus in economics on a level appropriate for undergraduate physics education. The aim of the paper is (i) to meet the demand for illustrative examples suitable for presenting the background of the highly expanding research field of econophysics even at the…

  3. Performance constrained floorplanning based on partial clustering [IC layout

    Microsoft Academic Search

    Yuchun Ma; Xianlong Hong; Sheqin Dong; Song Chen; Chung-kuan Cheng

    2005-01-01

    In this paper, we propose a partial clustered floorplanning method based on a corner block list (CBL) representation. The hierarchical strategies in this paper are designed for localizing the performance-constrained nets. We devise a sub CBL to represent the cluster and embed the sub CBL into the final CBL list. We combine the iterative optimization of the cluster packing into

  4. A grid algorithm for bound constrained optimization of noisy functions

    E-print Network

    Neumaier, Arnold

    Nelder- Mead in the noisy case. If performance is measured solely by the number of function evaluations in the optimization of experiments), the new algorithm is also significantly faster than Nelder-Mead. Revised version, February 1995 KEY WORDS: bound constrained optimization, noisy functions, Nelder-Mead method, quasi

  5. Solving constrained optimization problems with hybrid particle swarm optimization

    Microsoft Academic Search

    Erwie Zahara; Chia-Hsin Hu

    2008-01-01

    Constrained optimization problems (COPs) are very important in that they frequently appear in the real world. A COP, in which both the function and constraints may be nonlinear, consists of the optimization of a function subject to constraints. Constraint handling is one of the major concerns when solving COPs with particle swarm optimization (PSO) combined with the Nelder-Mead simplex search

  6. Automated Design of Pin-Constrained Digital Microfluidic Biochips Under

    E-print Network

    Chakrabarty, Krishnendu

    14 Automated Design of Pin-Constrained Digital Microfluidic Biochips Under Droplet Corporation and KRISHNENDU CHAKRABARTY Duke University Microfluidics-based biochips, also referred to as lab on a microfluidic array. In contrast to the direct-addressing scheme that has been studied thus far

  7. Efficient Particle Filtering for Road-Constrained Target Tracking

    E-print Network

    Singh, Tarunraj

    Efficient Particle Filtering for Road-Constrained Target Tracking Yang Cheng Department characteristic of ground target tracking is that prior nonstandard information such as target speed con- straints of multiple model esti- mators to ground target tracking were presented in Ref. [1], [3], [4], [5], [6

  8. Multiple Target Tracking With Constrained Motion Using Particle Filtering Methods

    E-print Network

    Del Moral , Pierre

    Multiple Target Tracking With Constrained Motion Using Particle Filtering Methods A Qualifying successfully used in target tracking appli- cations when the state and measurement models are nonlinear and the associated noise is non-Gaussian. Among the most difficult scenarios of target tracking, are multiple target

  9. Security Constrained Economic Dispatch Using Interior Point Method

    Microsoft Academic Search

    Kyoung-Shin Kim; Leen-Hark Jung; Seung-Chul Lee; Un-Chul Moon

    2006-01-01

    This paper presents a technique that can obtain an optimal solution for the security-constrained economic dispatch (SCED) problems using the Interior Point Method (IPM) while taking into account of the power flow constraints. The SCED equations are formulated by using only the real power flow equations from the optimal power flow. Then an algorithm is presented that can linearize the

  10. Security Constrained Dispatch at the New York Power Pool

    Microsoft Academic Search

    A. J. Elacqua; S. L. Corey

    1982-01-01

    This paper describes the Security Constrained Economic Dispatch (SCD) System implemented at the New York Power Pool. The Economic Dispatch program uses the differential algorithm coupled with the revised simplex technique with bounding to produce an optimal generation schedule with security constraints. The constraints used in the initial program implementation consist of generator limitations and transmission line constraints selected by

  11. Security Constrained Dispatch at the New York Power Pool

    Microsoft Academic Search

    A. J. Elacqua; S. L. Corey

    1982-01-01

    This paper describes the Security Constrained Economic Dispatch (SCD) System implemented at the New York Power Poo The Economic Dispatch program uses the differential algorithm coupled with the revised simplex technique with bounding to produce an optimal generation schedule with security constraints. The constraints used in the initial program implementation consist of generator limitations and transniission line constraints selected by

  12. Arbovirus evolution in vivo is constrained by host alternation

    Microsoft Academic Search

    Lark L. Coffey; Nikos Vasilakis; Aaron C. Brault; Ann M. Powers; Frédéric Tripet; Scott C. Weaver

    2008-01-01

    The intrinsic plasticity of RNA viruses can facilitate host range changes that lead to epidemics. However, evolutionary processes promoting cross-species transfers are poorly defined, especially for arthropod-borne viruses (arboviruses). In theory, cross species transfers by arboviruses may be constrained by their alternating infection of disparate hosts, where optimal replication in one host involves a fitness tradeoff for the other. Accordingly,

  13. SNOPT: An SQP Algorithm For Large-Scale Constrained Optimization

    Microsoft Academic Search

    Philip E. Gill; Walter Murray; Michael A. Saunders

    1997-01-01

    . Sequential quadratic programming (SQP) methods have proved highly effective forsolving constrained optimization problems with smooth nonlinear functions in the objective andconstraints. Here we consider problems with general inequality constraints (linear and nonlinear).We assume that first derivatives are available, and that the constraint gradients are sparse.We discuss an SQP algorithm that uses a smooth augmented Lagrangian merit function andmakes explicit

  14. How Well Can Future CMB Missions Constrain Cosmic Inflation?

    E-print Network

    Jerome Martin; Christophe Ringeval; Vincent Vennin

    2014-10-29

    We study how the next generation of Cosmic Microwave Background (CMB) measurement missions (such as EPIC, LiteBIRD, PRISM and COrE) will be able to constrain the inflationary landscape in the hardest to disambiguate situation in which inflation is simply described by single-field slow-roll scenarios. Considering the proposed PRISM and LiteBIRD satellite designs, we simulate mock data corresponding to five different fiducial models having values of the tensor-to-scalar ratio ranging from $10^{-1}$ down to $10^{-7}$. We then compute the Bayesian evidences and complexities of all Encyclopaedia Inflationaris models in order to assess the constraining power of PRISM alone and LiteBIRD complemented with the Planck 2013 data. Within slow-roll inflation, both designs have comparable constraining power and can rule out about three quarters of the inflationary scenarios, compared to one third for Planck 2013 data alone. However, we also show that PRISM can constrain the scalar running and has the capability to detect a violation of slow roll at second order. Finally, our results suggest that describing an inflationary model by its potential shape only, without specifying a reheating temperature, will no longer be possible given the accuracy level reached by the future CMB missions.

  15. Rank-Constrained Fundamental Matrix Estimation by Polynomial Global

    E-print Network

    Henrion, Didier

    on input point matches that do not contain mismatches (a pair of points incorrectly associated yet. In its second step, the eight-point algorithm computes the closest rank-deficient matrix to ~F asRank-Constrained Fundamental Matrix Estimation by Polynomial Global Optimization Versus the Eight-Point

  16. Constrained 11 -Layer Hamiltonian Toy Models for Stratospheric

    E-print Network

    Vellekoop, Michel

    Constrained 11 2 -Layer Hamiltonian Toy Models for Stratospheric Dynamics By Onno Bokhove and Control--Twente Summary A two-layer Hamiltonian toy model consisting of two isentropic stratospheric, following a more concise derivation than shown before, when the Rossby number in the upper stratospheric

  17. Acid Ocean

    NSDL National Science Digital Library

    The I2I-Acid Ocean virtual lab is an e-learning activity where students become virtual scientists studying the impact of ocean acidification on sea urchin larval growth. Students recreate a real, up-to-date climate change experiment. They also learn important general scientific principles, such as the importance of sample size and numbers of replicates, and discuss what this research into a specific impact of climate change may mean for the future of our oceans. There is a French translation available.

  18. Brnsted Acids The Strongest Isolable Acid**

    E-print Network

    Reed, Christopher A.

    Brønsted Acids The Strongest Isolable Acid** Mark Juhasz, Stephan Hoffmann, Evgenii Stoyanov, Kee-Chan Kim, and Christopher A. Reed* Acids based on carborane anions as conjugate bases (Figure 1) are a new class of Brønsted (protic) acids, notable for their "strong yet gentle" qualities.[1] For example

  19. Discussion of Void nucleation in constrained silver interlayers'' and Void growth and coalescence in constrained silver interlayers''

    SciTech Connect

    Kassner, M.E.; Tolle, M.C. (Oregon State Univ., Corvallis, OR (United States). Dept. of Mechanical Engineering); Rosen, R.S.; Henshall, G.A.; Elmer, J.W. (Lawrence Livermore Lab., Livermore, CA (United States))

    1993-08-01

    The authors have read with some concern the two articles by Klassen, Weatherly, and Ramaswami (KWR) entitled Void Nucleation in Constrained Silver Interlayers'' and Void Growth and Coalescence in Constrained Silver Interlayers'' published recently in this journal. They have several comments to these articles. First, substantial portions of these articles appear to closely reaffirm experiments and stress analyses on fracture and other mechanical behavior of constrained silver interlayers already published. KWR appeared to be unaware of (or disregarded) much of these works and this communication is partly intended to direct KWR and perhaps others to these works. Next, although there are many scientific aspects of the articles that warrant discussion, they have focused on two principal points. First, there appear to be some odd aspects of the Nucleation (KWR) article. The authors suggest nucleation and unstable growth occur only near the fracture stress (S[sub f]). This clearly is in contradiction to their careful work, where nucleation is shown to occur at very low stress (S[sub f]/5), just above the uniaxial yield stress of the interlayer silver. Second, and more importantly, KWR do not report any void growth. This, also, is in contradiction to earlier work on void growth in constrained silver interlayers. In the case of brazed silver joints, the shrinkage voids are observed to grow until a critical void separation is reached and instability occurs. In their work, voids appear to grow from small to larger cavities with small overall plastic strain in the interlayer, including at the base-metal/silver interface. In summary, although the KWR articles reasonably reproduced some established experimental trends for constrained interlayers and observed some other phenomena particularly relevant to the case with a substantial volume fraction of dispersions, other more basic conclusions relating to final fracture do not appear to consider more reasonable approaches.

  20. Acid rain

    SciTech Connect

    Boyle, R.H.; Boyle, R.A.

    1983-01-01

    Acid rain, says Boyle is a chemical leprosy eating into the face of North America and Europe, perhaps the major ecological problem of our time. Boyle describes the causes and scope of the phenomenon; the effects on man, wildlife, water, and our cultural heritage. He probes the delays of politicians and the frequent self-serving arguments advanced by industry in the face of what scientists have proved. The solutions he offers are to strengthen the Clean Air Act and require emission reductions that can be accomplished by establishing emission standards on a regional or bubble basis, burn low-sulfur coal, install scrubbers at critical plants, and invest in alternative energy sources. 73 references, 1 figure.

  1. Edinburgh Research Explorer Space-based formaldehyde measurements as constrains on

    E-print Network

    Millar, Andrew J.

    Edinburgh Research Explorer Space-based formaldehyde measurements as constrains on volatile organic, 'Space-based formaldehyde measurements as constrains on volatile organic compound emissions in east record in Edinburgh Research Explorer Published In: Journal of Geophysical Research Publisher Rights

  2. 21 CFR 888.3800 - Wrist joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 2010-04-01 false Wrist joint metal/polymer semi-constrained cemented prosthesis...Prosthetic Devices § 888.3800 Wrist joint metal/polymer semi-constrained cemented prosthesis... (a) Identification. A wrist joint metal/polymer...

  3. 21 CFR 888.3100 - Ankle joint metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 2012-04-01 false Ankle joint metal/composite semi-constrained cemented...Prosthetic Devices § 888.3100 Ankle joint metal/composite semi-constrained cemented...a) Identification. An ankle joint metal/composite...

  4. 21 CFR 888.3350 - Hip joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Hip joint metal/polymer semi-constrained...Prosthetic Devices § 888.3350 Hip joint metal/polymer semi-constrained...prosthesis. (a) Identification. A hip joint metal/polymer...

  5. 21 CFR 888.3340 - Hip joint metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Hip joint metal/composite semi-constrained...Prosthetic Devices § 888.3340 Hip joint metal/composite semi-constrained...prosthesis. (a) Identification. A hip joint metal/composite...

  6. A particle swarm pattern search method for bound constrained global optimization

    E-print Network

    Vicente, Luís Nunes

    stationarity mentioned before. The particle swarm optimization algorithm was firstly proposed in [11, 24A particle swarm pattern search method for bound constrained global optimization A. Ismael F. Vaz, pattern search, particle swarm, derivative free optimization, global optimization, bound constrained

  7. Constraining the nuclear equation of state at subsaturation densities

    E-print Network

    E. Khan; J. Margueron; I. Vidana

    2015-05-28

    Only one third of the nucleons in $^{208}$Pb occupy the saturation density area. Consequently nuclear observables related to average properties of nuclei, such as masses or radii, constrain the equation of state (EOS) not at saturation density but rather around the so-called crossing density, localised close to the mean value of the density of nuclei: $\\rho\\simeq$0.11 fm$^{-3}$. This provides an explanation for the empirical fact that several EOS quantities calculated with various functionals cross at a density significantly lower than the saturation one. The third derivative M of the energy at the crossing density is constrained by the giant monopole resonance (GMR) measurements in an isotopic chain rather than the incompressibility at saturation density. The GMR measurements provide M=1110 $\\pm$ 70 MeV (6% uncertainty), whose extrapolation gives K$_\\infty$=230 $\\pm$ 40 MeV (17% uncertainty).

  8. Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids

    PubMed Central

    Tsuboi, Masahito; Gonzalez-Voyer, Alejandro; Kolm, Niclas

    2015-01-01

    Functional coupling, where a single morphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with bi-parental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution. PMID:25948565

  9. On the equivalence between Implicit Regularization and Constrained Differential Renormalization

    E-print Network

    Carlos R. Pontes; A. P. Baêta Scarpelli; Marcos Sampaio; J. L. Acebal; M. C. Nemes

    2007-06-08

    Constrained Differential Renormalization (CDR) and the constrained version of Implicit Regularization (IR) are two regularization independent techniques that do not rely on dimensional continuation of the space-time. These two methods which have rather distinct basis have been successfully applied to several calculations which show that they can be trusted as practical, symmetry invariant frameworks (gauge and supersymmetry included) in perturbative computations even beyond one-loop order. In this paper, we show the equivalence between these two methods at one-loop order. We show that the configuration space rules of CDR can be mapped into the momentum space procedures of Implicit Regularization, the major principle behind this equivalence being the extension of the properties of regular distributions to the regularized ones.

  10. Lilith: a tool for constraining new physics from Higgs measurements

    E-print Network

    Bernon, Jeremy

    2015-01-01

    The properties of the observed Higgs boson with mass around 125 GeV can be affected in a variety of ways by new physics beyond the Standard Model (SM). The wealth of experimental results, targeting the different combinations for the production and decay of a Higgs boson, makes it a non-trivial task to assess the compatibility of a non-SM-like Higgs boson with all available results. In this paper we present Lilith, a new public tool for constraining new physics from signal strength measurements performed at the LHC and the Tevatron. Lilith is a Python library that can also be used in C and C++/ROOT programs. The Higgs likelihood is based on experimental results stored in an easily extensible XML database, and is evaluated from the user input, given in XML format in terms of reduced couplings or signal strengths. The results of Lilith can be used to constrain a wide class of new physics scenarios.

  11. Mutualism meltdown in insects: Bacteria constrain thermal adaptation

    PubMed Central

    Wernegreen, Jennifer J.

    2013-01-01

    Predicting whether and how organisms will successfully cope with climate change presents critical questions for biologists and environmental scientists. Models require knowing how organisms interact with their abiotic environment, as well understanding biotic interactions that include a network of symbioses in which all species are embedded. Bacterial symbionts of insects offer valuable models to examine how microbes can facilitate and constrain adaptation to a changing environment. While some symbionts confer plasticity that accelerates adaptation, long-term bacterial mutualists of insects are characterized by tight lifestyle constraints, genome deterioration, and vulnerability to thermal stress. These essential bacterial partners are eliminated at high temperatures, analogous to the loss of zooanthellae during coral bleaching. Recent field-based studies suggest that thermal sensitivity of bacterial mutualists constrains insect responses. In this sense, highly dependent mutualisms may be the Achilles’ heel of thermal responses in insects. PMID:22381679

  12. Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids.

    PubMed

    Tsuboi, Masahito; Gonzalez-Voyer, Alejandro; Kolm, Niclas

    2015-05-01

    Functional coupling, where a single morphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with bi-parental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution. PMID:25948565

  13. Fractal Dimension of Geologically Constrained Crater Populations of Mercury

    NASA Astrophysics Data System (ADS)

    Mancinelli, Paolo; Pauselli, Cristina; Perugini, Diego; Lupattelli, Andrea; Federico, Costanzo

    2015-07-01

    Data gathered during the Mariner10 and MESSENGER missions are collated in this paper to classify craters into four geo-chronological units constrained to the geological map produced after MESSENGER's flybys. From the global catalogue, we classify craters, constraining them to the geological information derived from the map. We produce a size frequency distribution (SFD) finding that all crater classes show fractal behaviour: with the number of craters inversely proportional to their diameter, the exponent of the SFD (i.e., the fractal dimension of each class) shows a variation among classes. We discuss this observation as possibly being caused by endogenic and/or exogenic phenomena. Finally, we produce an interpretative scenario where, assuming a constant flux of impactors, the slope variation could be representative of rheological changes in the target materials.

  14. Quaternionic Kahler Manifolds, Constrained Instantons and the Magic Square: I

    E-print Network

    Keshav Dasgupta; Veronique Hussin; Alisha Wissanji

    2007-11-08

    The classification of homogeneous quaternionic manifolds has been done by Alekseevskii, Wolf et al using transitive solvable group of isometries. These manifolds are not generically symmetric, but there is a subset of quaternionic manifolds that are symmetric and Einstein. A further subset of these manifolds are the magic square manifolds. We show that all the symmetric quaternionic manifolds including the magic square can be succinctly classified by constrained instantons. These instantons are mostly semilocal, and their constructions for the magic square can be done from the corresponding Seiberg-Witten curves for certain N = 2 gauge theories that are in general not asymptotically free. Using these, we give possible constructions, such as the classical moduli space metrics, of constrained instantons with exceptional global symmetries. We also discuss the possibility of realising the Kahler manifolds in the magic square using other solitonic configurations in the theory, and point out an interesting new sequence of these manifolds in the magic square.

  15. Quaternionic Kahler Manifolds, Constrained Instantons and the Magic Square: I

    E-print Network

    Dasgupta, Keshav; Wissanji, Alisha

    2007-01-01

    The classification of homogeneous quaternionic manifolds has been done by Alekseevskii, Wolf et al using transitive solvable group of isometries. These manifolds are not generically symmetric, but there is a subset of quaternionic manifolds that are symmetric and Einstein. A further subset of these manifolds are the magic square manifolds. We show that all the symmetric quaternionic manifolds including the magic square can be succinctly classified by constrained instantons. These instantons are mostly semilocal, and their constructions for the magic square can be done from the corresponding Seiberg-Witten curves for certain N = 2 gauge theories that are in general not asymptotically free. Using these, we give possible constructions, such as the classical moduli space metrics, of constrained instantons with exceptional global symmetries. We also discuss the possibility of realising the Kahler manifolds in the magic square using other solitonic configurations in the theory, and point out an interesting new sequ...

  16. Lilith: a tool for constraining new physics from Higgs measurements

    E-print Network

    Jeremy Bernon; Beranger Dumont

    2015-03-05

    The properties of the observed Higgs boson with mass around 125 GeV can be affected in a variety of ways by new physics beyond the Standard Model (SM). The wealth of experimental results, targeting the different combinations for the production and decay of a Higgs boson, makes it a non-trivial task to assess the compatibility of a non-SM-like Higgs boson with all available results. In this paper we present Lilith, a new public tool for constraining new physics from signal strength measurements performed at the LHC and the Tevatron. Lilith is a Python library that can also be used in C and C++/ROOT programs. The Higgs likelihood is based on experimental results stored in an easily extensible XML database, and is evaluated from the user input, given in XML format in terms of reduced couplings or signal strengths. The results of Lilith can be used to constrain a wide class of new physics scenarios.

  17. Origin of Constrained Maximal CP Violation in Flavor Symmetry

    E-print Network

    He, Hong-Jian; Xu, Xun-Jie

    2015-01-01

    Current data from neutrino oscillation experiments are in good agreement with $\\delta=-\\pi/2$ and $\\theta_{23} = \\pi/4$. We define the notion of "constrained maximal CP violation" for these features and study their origin in flavor symmetry models. We give various parametrization-independent definitions of constrained maximal CP violation and present a theorem on how it can be generated. This theorem takes advantage of residual symmetries in the neutrino and charged lepton mass matrices, and states that, up to a few exceptions, $\\delta=\\pm\\pi/2$ and $\\theta_{23} = \\pi/4$ are generated when those symmetries are real. The often considered $\\mu$-$\\tau$ reflection symmetry, as well as specific discrete subgroups of $O(3)$, are special case of our theorem.

  18. Network constrained security control using an interior point algorithm

    SciTech Connect

    Lu, C.N. (National Sun Yat-Sen Univ., Kaohsiung (Taiwan, Province of China)); Unum, M.R. (Harris Controls and Composition Div., Melbourne, FL (United States))

    1993-08-01

    Karmarkar's interior point method, said to perform much faster than the simplex method in solving large scale linear programming problems, has attracted a great deal of attention in recent years. In this paper the authors present a preliminary implementation of the interior point algorithm and test results on the network constrained security control problem. Test results indicate that when solving various sizes of the network constrained security control linear programming problems with increasing numbers of controls and constraints, both the total number of iterations and the overall execution time grow at a slower rate in the interior point method than in the simplex method. The number of iterations required by the interior point method is relatively insensitive to problem size and composition, while iteration counts for the simplex method tend to be much higher in the presence of large numbers of control variables and/or constraints.

  19. Multiply-constrained semantic search in the Remote Associates Test.

    PubMed

    Smith, Kevin A; Huber, David E; Vul, Edward

    2013-07-01

    Many important problems require consideration of multiple constraints, such as choosing a job based on salary, location, and responsibilities. We used the Remote Associates Test to study how people solve such multiply-constrained problems by asking participants to make guesses as they came to mind. We evaluated how people generated these guesses by using Latent Semantic Analysis to measure the similarity between the guesses, cues, and answers. We found that people use two systematic strategies to solve multiply-constrained problems: (a) people produce guesses primarily on the basis of just one of the three cues at a time; and (b) people adopt a local search strategy--they make new guesses based in part on their previous guesses. These results inform how people combine constraints to search through and retrieve semantic information from memory. PMID:23587845

  20. The bounds of feasible space on constrained nonconvex quadratic programming

    NASA Astrophysics Data System (ADS)

    Zhu, Jinghao

    2008-03-01

    This paper presents a method to estimate the bounds of the radius of the feasible space for a class of constrained nonconvex quadratic programmingsE Results show that one may compute a bound of the radius of the feasible space by a linear programming which is known to be a P-problem [N. Karmarkar, A new polynomial-time algorithm for linear programming, Combinatorica 4 (1984) 373-395]. It is proposed that one applies this method for using the canonical dual transformation [D.Y. Gao, Canonical duality theory and solutions to constrained nonconvex quadratic programming, J. Global Optimization 29 (2004) 377-399] for solving a standard quadratic programming problem.

  1. Constraining t-T conditions during palaeoseismic events - constraining the viscous brake phenomena in nature.

    NASA Astrophysics Data System (ADS)

    Dobson, Katherine J.; Kirkpatrick, James D.; Mark, Darren F.; Stuart, Finlay M.

    2010-05-01

    Melt generated by frictional heating during an earthquake is generally assumed to act as a lubricant, and decrease the frictional resistance to sliding. However, recent experimental [1] and theoretical [2] studies indicate that this might not always be the case. When the earthquake starts, melts form in isolated small patches along the fault, and only later coalesce into more extensive sheets. While the pockets of melt are isolated they have a high resistance to viscous shear and increase the overall strength of the fault: an effect known as the ‘viscous brake'. The experimental and theoretical data suggest that the melt pockets can actually stop an earthquake. The crucial parameter that controls if the viscous brake can operate is the normal stress working on the system, which is a function of the mass (i.e. the thickness) of rock above the rupture. It is impossible to directly observe or sample the earthquake source in active faults, and natural examples of the viscous brake have yet to be identified. We present a novel study that uses a combination of low temperature thermochronometry techniques to investigate the viscous brake in nature, by taking advantage of exhumed faults that preserve a record of ancient earthquakes; i.e pseudotachylytes. Pseudotachylytes are chilled frictional melts and are the only accepted indicator of ancient seismicity along faults. Pseudotachylytes found in the central part of the Sierra Nevada mountain range, California, are thin (<10 mm thick) and laterally restricted to small parts (a few meters long) of km scale faults. The discontinuous nature of these pseudotachylytes suggests that they be natural examples of earthquakes that terminated prematurely due to melt generation. These samples are therefore a key target for investigating the natural system, and improving our understanding of earthquake processes. The pseudotachylytes yield K/Ar ages of 74.9 ± 1.1 Ma, 78.2 ± 2.8 Ma and 84.5 ± 1.4 Ma, but although microstructural observations of the fault rocks assemblage indicate that the pseudotachylytes formed at temperatures of < 300°C, the depth of formation, and therefore the normal stress are poorly constrained. In this study we exploit the relationship between the normal stress and the mass (i.e. thickness) of the rocks above the earthquake. We present data from standard thermochronological techniques (Ar/Ar, apatite and zircon (U-Th)/He and apatite fission track) applied to a vertical profile through the pseudotachylyte bearing granite. This enables the complete time-temperature cooling path of the host rock to be determined and the geothermal gradient to be assessed, which in turn allows us calculate the depth at which rupture occurred. We use these results to test the hypothesis that the Sierra Nevada pseudotachylyte acted as a viscous brake. This will ultimately improve understanding of earthquake ruptures by identifying an intrinsic control on the magnitude of earthquakes. References 1. Di Toro et al. 2006. Science 311. 647-649 2. Fialko & Khazab, 2005, J geophys. Res. 110 B12407

  2. Penalized interior point approach for constrained nonlinear programming

    Microsoft Academic Search

    Wen-ting Lu; Yi-rong Yao; Lian-sheng Zhang

    2009-01-01

    A penalized interior point approach for constrained nonlinear programming is examined in this work. To overcome the difficulty\\u000a of initialization for the interior point method, a problem equivalent to the primal problem via incorporating an auxiliary variable is constructed. A combined approach of logarithm barrier and quadratic penalty function\\u000a is proposed to solve the problem. Based on Newton’s method, the

  3. Security constrained economic dispatch using nonlinear Dantzig-Wolfe decomposition

    SciTech Connect

    Aganagic, M.; Mokhtari, S. [Siemens Energy and Automation, Inc., Brooklyn Park, MN (United States). Empros Power Systems Control Div.] [Siemens Energy and Automation, Inc., Brooklyn Park, MN (United States). Empros Power Systems Control Div.

    1997-02-01

    This paper proposes a new approach to the Security Constrained Economic Dispatch based on a nonlinear version of the Dantzig-Wolfe decomposition principle. The dispatch problem is formulated using truly nonlinear unit cost functions and a new, detailed representation of reserve curves. The solutions obtained by the method have the equal {lambda} property. The proposed decomposition scheme is more efficient as the number of generating units in the problem is increased. Numerical results obtained on three test cases are presented.

  4. Time-constrained query processing in CASE-DB

    Microsoft Academic Search

    Gultekin Ozsoyoglu; Sujatha Guruswamy; Kaizheng Du; Wen-Chi Hou

    1995-01-01

    CASE-DB is a real-time, single-user, relational prototype DBMS that permits the specification of strict time constraints for relational algebra queries. Given a time constrained nonaggregate relational algebra query and a “fragment chain” for each relation involved in the query, CASE-DB initially obtains a response to a modified version of the query and then uses an “iterative query evaluation” technique to

  5. Social Emotional Optimization Algorithm for Nonlinear Constrained Optimization Problems

    NASA Astrophysics Data System (ADS)

    Xu, Yuechun; Cui, Zhihua; Zeng, Jianchao

    Nonlinear programming problem is one important branch in operational research, and has been successfully applied to various real-life problems. In this paper, a new approach called Social emotional optimization algorithm (SEOA) is used to solve this problem which is a new swarm intelligent technique by simulating the human behavior guided by emotion. Simulation results show that the social emotional optimization algorithm proposed in this paper is effective and efficiency for the nonlinear constrained programming problems.

  6. Optimal Constrained Resource Allocation Strategies under Low Risk Circumstances

    Microsoft Academic Search

    Mugurel Ionut Andreica; Madalina Ecaterina Andreica; Costel Visan

    2009-01-01

    In this paper we consider multiple constrained resource allocation problems,\\u000awhere the constraints can be specified by formulating activity dependency\\u000arestrictions or by using game-theoretic models. All the problems are focused on\\u000ageneric resources, with a few exceptions which consider financial resources in\\u000aparticular. The problems consider low-risk circumstances and the values of the\\u000auncertain variables which are used by

  7. Page 1Page 1 Ch.5 Constrained Optimality Criteria (2)

    E-print Network

    California at Davis, University of

    Page 1Page 1 Ch.5 Constrained Optimality Criteria (2) -Review of the book "Engineering Optimization" Yi Zhang Networks Lab UC Davis July 2, 2010 #12;Page 2Page 2 Outline · 5.6 Saddlepoint Conditions · 5 of Convex Functions · 5.10 Summary #12;Page 3Page 3 #12;Page 4Page 4 #12;Page 5Page 5 #12;Page 6Page 6 #12

  8. Dantzig-Wolfe decomposition for linearly constrained stable set problem

    E-print Network

    Boyer, Edmond

    Dantzig-Wolfe decomposition for linearly constrained stable set problem Virginie Gabrel Résumé Nous considérons l'application d'un schéma de décomposition de Dantzig-Wolfe sur un programme linéaire en variables départ. Mots-clefs : Decomposition de Dantzig-Wolfe, polytope du stable, graphe parfait Abstract We

  9. On adaptive force\\/motion control of constrained robots

    Microsoft Academic Search

    L. Liu; Y. Han; R. Lingarkar; N. K. Sinha; M. A. Elbestawi

    1989-01-01

    An adaptive control algorithm for controlling the trajectory of motion and the contact force of the end-effector for constrained robots simultaneously is presented. The development of the algorithm is based on the nonlinear coordinate transformation of N.H. McClamroch and D. Wang (1988). The passivity-based control scheme of J.J. Slotine and W. Li (1987) is adopted, where the sliding surface is

  10. Dark matter, constrained minimal supersymmetric standard model, and lattice QCD.

    PubMed

    Giedt, Joel; Thomas, Anthony W; Young, Ross D

    2009-11-13

    Recent lattice measurements have given accurate estimates of the quark condensates in the proton. We use these results to significantly improve the dark matter predictions in benchmark models within the constrained minimal supersymmetric standard model. The predicted spin-independent cross sections are at least an order of magnitude smaller than previously suggested and our results have significant consequences for dark matter searches. PMID:20365976

  11. Control of the constrained planar simple inverted pendulum

    NASA Technical Reports Server (NTRS)

    Bavarian, B.; Wyman, B. F.; Hemami, H.

    1983-01-01

    Control of a constrained planar inverted pendulum by eigenstructure assignment is considered. Linear feedback is used to stabilize and decouple the system in such a way that specified subspaces of the state space are invariant for the closed-loop system. The effectiveness of the feedback law is tested by digital computer simulation. Pre-compensation by an inverse plant is used to improve performance.

  12. On the chemical equilibrium concept: Constrained word associations and conception

    Microsoft Academic Search

    Esther Gussarsky; Malka Gorodetsky

    1988-01-01

    The use of the method of constrained word associations to gain knowledge on the conception of the chemical equilibrium concept is reported. The analysis provides information on:(a)A general indication of change in the cognitive structure of students associated with chemical comprehension.(b)The comparison of clusters of concepts at pre- and postinstruction indicating the associated concepts.(c)A graphical representation of the links among

  13. Asynchronous parallel generating set search for linearly-constrained optimization.

    SciTech Connect

    Kolda, Tamara G.; Griffin, Joshua; Lewis, Robert Michael

    2007-04-01

    We describe an asynchronous parallel derivative-free algorithm for linearly-constrained optimization. Generating set search (GSS) is the basis of ourmethod. At each iteration, a GSS algorithm computes a set of search directionsand corresponding trial points and then evaluates the objective function valueat each trial point. Asynchronous versions of the algorithm have been developedin the unconstrained and bound-constrained cases which allow the iterations tocontinue (and new trial points to be generated and evaluated) as soon as anyother trial point completes. This enables better utilization of parallel resourcesand a reduction in overall runtime, especially for problems where the objec-tive function takes minutes or hours to compute. For linearly-constrained GSS,the convergence theory requires that the set of search directions conform to the3 nearby boundary. The complexity of developing the asynchronous algorithm forthe linearly-constrained case has to do with maintaining a suitable set of searchdirections as the search progresses and is the focus of this research. We describeour implementation in detail, including how to avoid function evaluations bycaching function values and using approximate look-ups. We test our imple-mentation on every CUTEr test problem with general linear constraints and upto 1000 variables. Without tuning to individual problems, our implementationwas able to solve 95% of the test problems with 10 or fewer variables, 75%of the problems with 11-100 variables, and nearly half of the problems with100-1000 variables. To the best of our knowledge, these are the best resultsthat have ever been achieved with a derivative-free method. Our asynchronousparallel implementation is freely available as part of the APPSPACK software.4

  14. Energy-Efficient Image Compression for Resource-Constrained Platforms

    Microsoft Academic Search

    Dong-U. Lee; Hyungjin Kim; Mohammad H. Rahimi; Deborah Estrin; John D. Villasenor

    2009-01-01

    One of the most important goals of current and future sensor networks is energy-efficient communication of images. This paper presents a quantitativecomparison between the energy costs associated with 1) direct transmission of uncompressed images and 2) sensor platform-based JPEG compression followed by trans- mission of the compressed image data. JPEG compression compu- tations are mapped onto various resource-constrained platforms using

  15. Constrained geometric simulation of the nicotinic acetylcholine receptor.

    PubMed

    Belfield, William J; Cole, Daniel J; Martin, Ian L; Payne, Mike C; Chau, P-L

    2014-07-01

    Constrained geometric simulations have been performed for the recently published closed-channel state of the nicotinic acetylcholine receptor. These simulations support the theory that correlated motion in the flexible ?-sheet structure of the extracellular domain helps to communicate a "conformational wave", spreading from the acetylcholine binding pocket. Furthermore, we have identified key residues that act at the interface between subunits and between domains that could potentially facilitate rapid communication between the binding site and the transmembrane gate. PMID:24955489

  16. A simulated annealing algorithm for constrained Multi-Objective Optimization

    Microsoft Academic Search

    Hemant Kumar Singh; Amitay Isaacs; Tapabrata Ray; Warren Smith

    2008-01-01

    In this paper, we introduce a simulated annealing algorithm for constrained Multi-Objective Optimization (MOO). When searching in the feasible region, the algorithm behaves like recently proposed Archived Multi-Objective Simulated Annealing (AMOSA) algorithm [1], whereas when operating in the infeasible region, it tries to minimize constraint violation by moving along Approximate Descent Direction (ADD) [2]. An Archive of non-dominated solutions found

  17. Locality-constrained Linear Coding for image classification

    Microsoft Academic Search

    Jinjun Wang; Jianchao Yang; Kai Yu; Fengjun Lv; Thomas S. Huang; Yihong Gong

    2010-01-01

    The traditional SPM approach based on bag-of-features (BoF) requires nonlinear classifiers to achieve good image classification performance. This paper presents a simple but effective coding scheme called Locality-constrained Linear Coding (LLC) in place of the VQ coding in traditional SPM. LLC utilizes the locality constraints to project each descriptor into its local-coordinate system, and the projected coordinates are integrated by

  18. Ceres' evolution and present state constrained by shape data

    Microsoft Academic Search

    Julie C. Castillo-Rogez; Thomas B. McCord

    2010-01-01

    We model Ceres' thermo-physical-chemical evolution by considering a large range of initial conditions as well as various evolutionary scenarios. Models are constrained by available shape measurements, which point to a differentiated interior for Ceres. We address the role played by hydrothermal activity in the long-term evolution of Ceres and especially the evolution of its hydrosphere. We suggest that models with

  19. Force and motion control of a constrained flexible manipulator

    NASA Astrophysics Data System (ADS)

    Hu, Fon-Lin

    1992-01-01

    This dissertation reports the results of a comprehensive research study on the combined joint motion control, vibration control, and force control of a constrained rigid-flexible robot arm. An efficient and accurate approach to modeling for controller design is provided. Both regulation and tracking problems are considered, and a modified version of a Corless-Leitmann controller is developed. Experimental studies, which demonstrate the effectiveness of the proposed methods, are presented. In this work, the dynamic modeling of a constrained spherical coordinate robot arm, whose last link is very flexible, is studied for the purpose of combined force and motion control. The model is derived using a consistent modeling procedure which accounts for the axial force effects due to contract, and the coupling due to the effects of flexible motions on the rigid body motions. These effects are shown to be important in the prediction of the vibration frequencies. Galerkin's method is employed for spatial discretization of the flexible link deflections. A convergence study is presented to evaluate the appropriateness of the spatial approximating functions and to determine the number of modes required for obtaining accurate simulation results. Linear control design methods are shown to be adequate for solving the problem of hybrid force and position regulation for the constrained flexible robot arm. However, nonlinear control strategies show advantages (i.e., good response of the joint motion and contact force, and small magnitude of the structural vibration) in the tracking control of motion and force. A modified Corless-Leitmann controller is presented to enhance the control of the flexible motion using only joint actuators. Finally, an experimental implementation is used to validate the proposed controller designs, to assess the merit of measuring and feeding back the flexible motion and the contact force, and to evaluate the feasibility of combined force and motion control strategies for the constrained flexible robot arm. These experimental results are in good agreement with the theory, and demonstrate the effectiveness of the proposed control strategies.

  20. TCA*-a time-constrained approximate A* search algorithm

    Microsoft Academic Search

    Benjamin W. Wah; Lon-Chan Chu

    1990-01-01

    The authors develop TCA*, a family of problem-independent, time-constrained, approximate A* search algorithms. The algorithms are designed to achieve the best ascertained degree of approximation with the minimum cost under a fixed time constraint, where cost is measured by either the cumulative space-time (CST) product or the maximum space encountered during the search. Only A* searches with admissible heuristic functions

  1. Exact Max-SAT solvers for over-constrained problems

    Microsoft Academic Search

    Josep Argelich; Felip Manyà

    2006-01-01

    We present a new generic problem solving approach for over-constrained problems based on Max-SAT. We first define a Boolean\\u000a clausal form formalism, called soft CNF formulas, that deals with blocks of clauses instead of individual clauses, and that allows one to declare each block either as hard (i.e., must be satisfied by any solution) or soft (i.e., can be violated

  2. Offset-free receding horizon control of constrained linear systems

    Microsoft Academic Search

    Gabriele Pannocchia; Eric C. Kerrigan

    2005-01-01

    Abstract: This paper addresses the design of a dynamic state feedback receding horizon controller, which guaran- tees robust constraint satisfaction, robust stability and offset-free control of constrained linear systems in the presence of time-varying setpoints and unmeasured,disturbances. This objective is obtained by first designing a dynamic,linear offset-free controller and computing,an appropriate domain,of attraction for this controller. The linear (unconstrained) controller

  3. SNOPT: An SQP Algorithm for Large-Scale Constrained Optimization

    Microsoft Academic Search

    Philip E. Gill; Walter Murray; Michael A. Saunders; Denmark Erwin Kalvelagen

    2000-01-01

    Sequential quadratic programming (SQP) methods have proved highly effective for solv- ing constrained optimization problems with smooth nonlinear functions in the objective and constraints.Here we consider problems with general inequality constraints (linear and nonlinear).We assume that first derivatives are available and that the constraint gradients are sparse.Second derivatives are assumed to be unavailable or too expensive to calculate. We discuss

  4. Spherical Hamiltonian Monte Carlo for Constrained Target Distributions

    PubMed Central

    Lan, Shiwei; Zhou, Bo; Shahbaba, Babak

    2015-01-01

    Statistical models with constrained probability distributions are abundant in machine learning. Some examples include regression models with norm constraints (e.g., Lasso), probit models, many copula models, and Latent Dirichlet Allocation (LDA) models. Bayesian inference involving probability distributions confined to constrained domains could be quite challenging for commonly used sampling algorithms. For such problems, we propose a novel Markov Chain Monte Carlo (MCMC) method that provides a general and computationally efficient framework for handling boundary conditions. Our method first maps the D-dimensional constrained domain of parameters to the unit ball B0D(1), then augments it to a D-dimensional sphere SD such that the original boundary corresponds to the equator of SD. This way, our method handles the constraints implicitly by moving freely on the sphere generating proposals that remain within boundaries when mapped back to the original space. To improve the computational efficiency of our algorithm, we divide the dynamics into several parts such that the resulting split dynamics has a partial analytical solution as a geodesic flow on the sphere. We apply our method to several examples including truncated Gaussian, Bayesian Lasso, Bayesian bridge regression, and a copula model for identifying synchrony among multiple neurons. Our results show that the proposed method can provide a natural and efficient framework for handling several types of constraints on target distributions. PMID:25914759

  5. Real-time optimal trajectory generation for constrained dynamical systems

    NASA Astrophysics Data System (ADS)

    Milam, Mark Bradley

    With the advent of powerful computing and efficient computational algorithms, real-time solutions to constrained optimal control problems are nearing a reality. In this thesis, we develop a computationally efficient Nonlinear Trajectory Generation (NTG) algorithm and describe its software implementation to solve, in real-time, nonlinear optimal trajectory generation problems for constrained systems. NTG is a nonlinear trajectory generation software package that combines nonlinear control theory, B-spline basis functions, and nonlinear programming. We compare NTG with other numerical optimal control problem solution techniques, such as direct collocation, shooting, adjoints, and differential inclusions. We demonstrate the performance of NTG on the Caltech Ducted Fan testbed. Aggressive, constrained optimal control problems are solved in real-time for hover-to-hover, forward flight, and terrain avoidance test cases. Real-time trajectory generation results are shown for both the two-degree of freedom and receding horizon control designs. Further experimental demonstration is provided with the station-keeping, reconfiguration, and deconfiguration of micro-satellite formation with complex nonlinear constraints. Successful application of NTG in these cases demonstrates reliable real-time trajectory generation, even for highly nonlinear and non-convex systems. The results are among the first to apply receding horizon control techniques for agile flight in an experimental setting, using representative dynamics and computation.

  6. Constrained TV-minimization image reconstruction for industrial CT system

    NASA Astrophysics Data System (ADS)

    Chen, Buxin; Yang, Min; Zhang, Zheng; Bian, Junguo; Han, Xiao; Sidky, Emil; Pan, Xiaochuan

    2014-02-01

    In this work, we investigate the applicability of the constrained total-variation (TV)-minimization reconstruction method to industrial CT system. In general, industrial CT systems have the same principles of imaging process with clinical CT systems, but different imaging objectives and evaluation metrics. Optimization-based image reconstruction methods have been actively developed to meet practical challenges and extensively tested for clinical CT systems. However, the utility of optimization-based reconstruction methods is task-specific and not necessarily transferrable among different tasks. In this work, we adopt constrained TV-minimization programs together with adaptive-steepest-descent-projection-ontoconvex-sets (ASD-POCS) algorithm for reconstructing images from data of a concrete sample collected using a laboratory industrial CT system developed for non-destructive evaluation. Our results, compared to those reconstructed from FBPbased algorithm, suggest that the constrained TV-minimization program combined with ASD-POCS algorithm can yield images with comparable or improved visual quality and achieve equivalent or better imaging objectives over the currently used FBP-based algorithm under dense sampling data condition.

  7. Constraining the growth of perturbations with lensing of supernovae

    E-print Network

    Luca Amendola; Tiago Castro; Valerio Marra; Miguel Quartin

    2015-03-05

    A recently proposed technique allows one to constrain both the background and perturbation cosmological parameters through the distribution function of supernova Ia apparent magnitudes. Here we extend this technique to alternative cosmological scenarios, in which the growth of structure does not follow the $\\Lambda$CDM prescription. We apply the method first to the supernova data provided by the JLA catalog combined with all the current independent redshift distortion data and with low-redshift cluster data from Chandra and show that although the supernovae alone are not very constraining, they help in reducing the confidence regions. Then we apply our method to future data from LSST and from a survey that approximates the Euclid satellite mission. In this case we show that the combined data are nicely complementary and can constrain the normalization $\\sigma_8$ and the growth rate index $\\gamma$ to within $0.6\\%$ and $7\\%$, respectively. In particular, the LSST supernova catalog is forecast to give the constraint $\\gamma (\\sigma_8/0.83)^{6.7} = 0.55 \\pm 0.1$. We also report on constraints relative to a step-wise parametrization of the growth rate of structures. These results show that supernova lensing serves as a good cross-check on the measurement of perturbation parameters from more standard techniques.

  8. Groundwater availability as constrained by hydrogeology and environmental flows.

    PubMed

    Watson, Katelyn A; Mayer, Alex S; Reeves, Howard W

    2014-01-01

    Groundwater pumping from aquifers in hydraulic connection with nearby streams has the potential to cause adverse impacts by decreasing flows to levels below those necessary to maintain aquatic ecosystems. The recent passage of the Great Lakes-St. Lawrence River Basin Water Resources?Compact has brought attention to this issue in the Great Lakes region. In particular, the legislation requires the Great Lakes states to enact measures for limiting water withdrawals that can cause adverse ecosystem impacts. This study explores how both hydrogeologic and environmental flow limitations may constrain groundwater availability in the Great Lakes Basin. A methodology for calculating maximum allowable pumping rates is presented. Groundwater availability across the basin may be constrained by a combination of hydrogeologic yield and environmental flow limitations varying over both local and regional scales. The results are sensitive to factors such as pumping time, regional and local hydrogeology, streambed conductance, and streamflow depletion limits. Understanding how these restrictions constrain groundwater usage and which hydrogeologic characteristics and spatial variables have the most influence on potential streamflow depletions has important water resources policy and management implications. PMID:23582026

  9. Constraining rooting depths in tropical rainforests using satellite data and ecosystem modeling for accurate

    E-print Network

    Myneni, Ranga B.

    Constraining rooting depths in tropical rainforests using satellite data and ecosystem modeling in tropical forests. In this study, we adopted a new approach to constrain rooting depth in terrestrial to simulating GPP seasonality in tropical forests, and the use of satellite data can help to constrain

  10. 21 CFR 888.3350 - Hip joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 false Hip joint metal/polymer semi-constrained cemented prosthesis...Devices § 888.3350 Hip joint metal/polymer semi-constrained cemented prosthesis...Identification. A hip joint metal/polymer semi-constrained cemented...

  11. Viability principles for constrained optimization using a (1+1)-CMA-ES

    E-print Network

    Floreano, Dario

    Viability principles for constrained optimization using a (1+1)-CMA-ES Andrea Maesani and Dario of constraints. In this work, we test Viability Evolution principles on a modi ed (1+1)-CMA-ES for constrained+1)-CMA-ES for Constrained Optimisation, Genetic and Evol. Comput. Conf. (GECCO'12), pages 297

  12. The Equivalence of Constrained and Weighted Designs in Multiple Objective Design Problems

    E-print Network

    West, Mike

    The Equivalence of Constrained and Weighted Designs in Multiple Objective Design Problems Merlise of Cook and Wong on the equivalence of the weighted and constrained problems also apply much more criteria, Cook and Wong (1994) showed that the constrained and weighted optimal designs are equivalent

  13. Hybrid Nelder-Mead simplex search and particle swarm optimization for constrained engineering design problems

    Microsoft Academic Search

    Erwie Zahara; Yi-tung Kao

    2009-01-01

    Constrained optimization problems are very important in that they frequently appear in the real world. A constrained optimization problem consists of the optimization of a function subject to constraints, in which both the function and constraints may be nonlinear. Constraint handling is one of the major concerns when solving constrained optimization problems by hybrid Nelder–Mead simplex search method and particle

  14. 21 CFR 888.3560 - Knee joint patellofemorotibial polymer/metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...Knee joint patellofemorotibial polymer/metal/polymer semi-constrained cemented prosthesis...Knee joint patellofemorotibial polymer/metal/polymer semi-constrained cemented prosthesis...knee joint patellofemorotibial polymer/metal/polymer semi-constrained...

  15. Free vibrations of a spherical drop constrained at an azimuth

    NASA Astrophysics Data System (ADS)

    Ramalingam, Santhosh; Ramkrishna, Doraiswami; Basaran, Osman A.

    2012-08-01

    Two droplets coupled through a liquid filled (a) hole in a plate or (b) tube is referred to as a double droplet system (DDS) or a capillary switch. Such capillary systems are gaining increasing attention due to their utility in applications. A particularly exciting application is one where a DDS is employed as a liquid lens, one flavor of which entails using a DDS as a variable focus lens by keeping it under sustained oscillations at its natural frequencies. The natural modes of oscillation of a DDS are determined analytically here in the limit in which the plate thickness (or tube length) is vanishingly small and when the effect of gravity is negligible compared to that of surface tension. In this limit, a DDS at rest reduces to two spherical caps that are pinned to and coupled along a common circular ring of contact of negligible thickness. Here, the caps are taken to be complementary pieces of a sphere so that the equilibrium state of the system is a sphere that is constrained by a ring of negligible thickness at an azimuthal angle with respect to the center of the sphere. Both the constrained drop and the fluid exterior to it are taken to be inviscid fluids undergoing irrotational flow. Similar to the linear oscillations of a free drop first studied by Rayleigh, the analytical formulation of the linear oscillations of the constrained drop results in a linear operator eigenvalue problem but with one additional boundary condition, i.e., that which accounts for zero shape perturbation along the circle of contact. Exploiting properties of linear operators, an implicit expression is obtained for the frequency of each mode of oscillation, a feat that appears not to have been accomplished to date in any problem involving oscillations of constrained drops. An extension of a method based on Green's functions that was developed to analyze the linear oscillations of a drop in contact with a spherical bowl [M. Strani and F. Sabetta, "Free-vibrations of a drop in partial contact with a solid support," J. Fluid Mech. 141, 233-247 (1984)], 10.1017/S0022112084000811 is also employed to verify the aforementioned results. Results obtained from these two approaches are then compared to those reported by Bostwick and Steen ["Capillary oscillations of a constrained liquid drop," Phys. Fluids 21, 032108 (2009)], 10.1063/1.3103344. Careful examination of flow fields within drops reveals that by pinning a drop, it should be possible to selectively excite just a portion of a drop's surface.

  16. Prior image constrained image reconstruction in emerging computed tomography applications

    NASA Astrophysics Data System (ADS)

    Brunner, Stephen T.

    Advances have been made in computed tomography (CT), especially in the past five years, by incorporating prior images into the image reconstruction process. In this dissertation, we investigate prior image constrained image reconstruction in three emerging CT applications: dual-energy CT, multi-energy photon-counting CT, and cone-beam CT in image-guided radiation therapy. First, we investigate the application of Prior Image Constrained Compressed Sensing (PICCS) in dual-energy CT, which has been called "one of the hottest research areas in CT." Phantom and animal studies are conducted using a state-of-the-art 64-slice GE Discovery 750 HD CT scanner to investigate the extent to which PICCS can enable radiation dose reduction in material density and virtual monochromatic imaging. Second, we extend the application of PICCS from dual-energy CT to multi-energy photon-counting CT, which has been called "one of the 12 topics in CT to be critical in the next decade." Numerical simulations are conducted to generate multiple energy bin images for a photon-counting CT acquisition and to investigate the extent to which PICCS can enable radiation dose efficiency improvement. Third, we investigate the performance of a newly proposed prior image constrained scatter correction technique to correct scatter-induced shading artifacts in cone-beam CT, which, when used in image-guided radiation therapy procedures, can assist in patient localization, and potentially, dose verification and adaptive radiation therapy. Phantom studies are conducted using a Varian 2100 EX system with an on-board imager to investigate the extent to which the prior image constrained scatter correction technique can mitigate scatter-induced shading artifacts in cone-beam CT. Results show that these prior image constrained image reconstruction techniques can reduce radiation dose in dual-energy CT by 50% in phantom and animal studies in material density and virtual monochromatic imaging, can lead to radiation dose efficiency improvement in multi-energy photon-counting CT, and can mitigate scatter-induced shading artifacts in cone-beam CT in full-fan and half-fan modes.

  17. Structural consequences of beta-amino acid preorganization in a self-assembling alpha/beta-peptide: fundamental studies of foldameric helix bundles.

    PubMed

    Price, Joshua L; Horne, W Seth; Gellman, Samuel H

    2010-09-01

    We report high-resolution crystal structures of six new alpha/beta-peptide foldamers that have a regular alpha-residue/alpha-residue/beta-residue (alphaalphabeta) backbone repeat pattern. All of these foldamers were crystallized from aqueous solution, and all display four-helix bundle quaternary structure in the crystalline state. These oligomers are based on the well-studied 33-residue alpha-peptide GCN4-pLI, which is an engineered derivative of the dimerization domain of GCN4, a yeast transcription factor. GCN4-pLI forms a stable tetramer in solution and crystallizes as a four-helix bundle (Harbury et al. Science 1993, 262, 1401-1407). Previously we described a foldamer (designated 1 here) that was generated from GCN4-pLI by replacing every third alpha-amino acid residue with the homologous beta(3)-amino acid residue; this alphaalphabeta oligomer retains the side chain sequence of the original alpha-peptide, but the backbone contains 11 additional CH(2) units, which are evenly distributed (Horne et al. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 9151-9156). Despite the expanded backbone, 1 was found to retain the ability to form a tetrameric quaternary structure in which the individual molecules adopt an alpha-helix-like conformation. Here we compare nine analogues of 1 that have the same alphaalphabeta backbone but in which one or more of the flexible beta(3)-amino acid residues is/are replaced with an analogous cyclic beta-residue. The motivation for beta(3)-->cyclic replacements is to enhance conformational stability; however, a crystal structure of the one previously reported example (designated 2 here) revealed a "stammer" distortion of the helix-bundle architecture relative to 1. The results reported here suggest that the stammer is a peculiarity of 2, because all six of the new alpha/beta-peptides display undistorted four-helix bundle quaternary structures. More broadly, our results indicate that beta(3)-->cyclic replacements are generally well-accommodated in helix-bundle quaternary structure, but that such replacements can be destabilizing in certain instances. PMID:20718422

  18. sigma-1 receptor modulation of acid-sensing ion channel a (ASIC1a) and ASIC1a-induced Ca2+ influx in rat cortical neurons.

    PubMed

    Herrera, Yelenis; Katnik, Christopher; Rodriguez, Jael D; Hall, Aaron A; Willing, Alison; Pennypacker, Keith R; Cuevas, Javier

    2008-11-01

    Acid-sensing ion channels (ASICs) are proton-gated cation channels found in peripheral and central nervous system neurons. The ASIC1a subtype, which has high Ca2+ permeability, is activated by ischemia-induced acidosis and contributes to the neuronal loss that accompanies ischemic stroke. Our laboratory has shown that activation of sigma receptors depresses ion channel activity and [Ca2+](i) dysregulation during ischemia, which enhances neuronal survival. Whole-cell patch-clamp electrophysiology and fluorometric Ca2+ imaging were used to determine whether sigma receptors regulate the function of ASIC in cultured rat cortical neurons. Bath application of the selective ASIC1a blocker, psalmotoxin1, decreased proton-evoked [Ca2+](i) transients and peak membrane currents, suggesting the presence of homomeric ASIC1a channels. The pan-selective sigma-1/sigma-2 receptor agonists, 1,3-di-o-tolyl-guanidine (100 microM) and opipramol (10 microM), reversibly decreased acid-induced elevations in [Ca2+](i) and membrane currents. Pharmacological experiments using sigma receptor-subtype-specific agonists demonstrated that sigma-1, but not sigma-2, receptors inhibit ASIC1a-induced Ca2+ elevations. These results were confirmed using the irreversible sigma receptor antagonist metaphit (50 microM) and the selective sigma-1 antagonist BD1063 (10 nM), which obtunded the inhibitory effects of the sigma-1 agonist, carbetapentane. Activation of ASIC1a was shown to stimulate downstream Ca2+ influx pathways, specifically N-methyl-D-aspartate and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid/kainate receptors and voltage-gated Ca2+ channels. These subsequent Ca2+ influxes were also inhibited upon activation of sigma-1 receptors. These findings demonstrate that sigma-1 receptor stimulation inhibits ASIC1a-mediated membrane currents and consequent intracellular Ca2+ accumulation. The ability to control ionic imbalances and Ca2+ dysregulation evoked by ASIC1a activation makes sigma receptors an attractive target for ischemic stroke therapy. PMID:18723775

  19. Nucleic Acids Research, 2014 1 doi: 10.1093/nar/gku1050

    E-print Network

    Tian, Weidong

    of interest and constrain their ac- cumulation to the nucleus. Furthermore, these nuclear ex- pressed RNAsNucleic Acids Research, 2014 1 doi: 10.1093/nar/gku1050 SnoVectors for nuclear expression of RNARNAs have not been optimized for the study of nuclear RNAs. We reported recently that sno

  20. Improving the pH-response of pHLIP insertion at tumor acidity for targeted drug delivery against cancer: Biophysical studies in model membranes and evaluations in cells

    NASA Astrophysics Data System (ADS)

    Onyango, Joab Otieno

    pH (Low) Insertion Peptide (pHLIP) possesses unique qualities that can be applied in cancer biology. It is a peptide that lives in three worlds: In State I, pHLIP exists as an unstructured monomer in solution at neutral pH; In State II, pHLIP partitions to the surface of a lipid bilayer at neutral pH; In State III, pHLIP inserts across the lipid bilayer by forming a transmembrane (TM) alpha helix under slightly acidic conditions (pH 6). These properties allow pHLIP to target acidosis (pH 6.5-7.0), a ubiquitous feature of solid tumors. Although pHLIP shows promise as a drug delivery vehicle, insertion properties such as pH50 (i.e. the pH at which 50% of pHLIP are inserted) and Hill coefficient must be tuned to improve tumor targeting and drug delivery in vivo. When TM region D14 and D25 residues were replaced with two glutamic acid residues as well as noncanonical amino acids such as alpha amino adipic acid (Aad) and gamma carboxyglutamic acid (Gla), we discovered pHLIP variants that possess a pH50 that can match tumor extracellular pH. pHLIP variants D25EE, Asp25Aad, and Asp14Gla/Asp25Aad, insert with pH50 of 6.60, 6.74, and 6.79, respectively. We also tuned pH-response (cooperativity of insertion) and we found that the Asp14Gla variant can insert into membrane with the sharpest transition observed so far for a pHLIP (i.e. over half pH unit vs. one pH unit for WT). Furthermore, we used turn-on fluorescence to evaluate the new variants in cancer cells. The most promising Asp25Aad pHLIP gave near theoretical maximum level of dequenching in cancerous A549 cells at pH 6.2 and 6.4, indicating a high level of plasma-membrane insertion. Under the same conditions, the `WT' and D25E pHLIP variants have low levels of plasma-membrane insertion in cells. Dequenching levels were low in non-cancerous HK2 cell line.

  1. Constrained model predictive control, state estimation and coordination

    NASA Astrophysics Data System (ADS)

    Yan, Jun

    In this dissertation, we study the interaction between the control performance and the quality of the state estimation in a constrained Model Predictive Control (MPC) framework for systems with stochastic disturbances. This consists of three parts: (i) the development of a constrained MPC formulation that adapts to the quality of the state estimation via constraints; (ii) the application of such a control law in a multi-vehicle formation coordinated control problem in which each vehicle operates subject to a no-collision constraint posed by others' imperfect prediction computed from finite bit-rate, communicated data; (iii) the design of the predictors and the communication resource assignment problem that satisfy the performance requirement from Part (ii). Model Predictive Control (MPC) is of interest because it is one of the few control design methods which preserves standard design variables and yet handles constraints. MPC is normally posed as a full-state feedback control and is implemented in a certainty-equivalence fashion with best estimates of the states being used in place of the exact state. However, if the state constraints were handled in the same certainty-equivalence fashion, the resulting control law could drive the real state to violate the constraints frequently. Part (i) focuses on exploring the inclusion of state estimates into the constraints. It does this by applying constrained MPC to a system with stochastic disturbances. The stochastic nature of the problem requires re-posing the constraints in a probabilistic form. In Part (ii), we consider applying constrained MPC as a local control law in a coordinated control problem of a group of distributed autonomous systems. Interactions between the systems are captured via constraints. First, we inspect the application of constrained MPC to a completely deterministic case. Formation stability theorems are derived for the subsystems and conditions on the local constraint set are derived in order to guarantee local stability or convergence to a target state. If these conditions are met for all subsystems, then this stability is inherited by the overall system. For the case when each subsystem suffers from disturbances in the dynamics, own self-measurement noises, and quantization errors on neighbors' information due to the finite-bit-rate channels, the constrained MPC strategy developed in Part (i) is appropriate to apply. In Part (iii), we discuss the local predictor design and bandwidth assignment problem in a coordinated vehicle formation context. The MPC controller used in Part (ii) relates the formation control performance and the information quality in the way that large standoff implies conservative performance. We first develop an LMI (Linear Matrix Inequality) formulation for cross-estimator design in a simple two-vehicle scenario with non-standard information: one vehicle does not have access to the other's exact control value applied at each sampling time, but to its known, pre-computed, coupling linear feedback control law. Then a similar LMI problem is formulated for the bandwidth assignment problem that minimizes the total number of bits by adjusting the prediction gain matrices and the number of bits assigned to each variable. (Abstract shortened by UMI.)

  2. Security constrained dispatch at the New York Power Pool

    SciTech Connect

    Elacqua, A.J.; Corey, S.L.

    1982-08-01

    This paper describes the Security Constrained Economic Dispatch (SCD) System implemented at the New York Power Pool. The Economic Dispatch program uses the differential algorithm coupled with the revised simplex technique with bounding to produce an optimal generation schedule with security constraints. The constraints used in the initial program implementation consist of generator limitations and transmission line constraints selected by the power system dispatcher. Generator limitations include megawatt minimums and maximums, response rate and regulation constraints. Currently 228 lines and transformer banks are monitored, operating at voltage levels ranging from 765 kV to 69 kV.

  3. An algorithm for real-time security constrained economic dispatch

    SciTech Connect

    Sanders, C.W.; Monroe, C.A.

    1987-11-01

    The paper presents results from the development and testing of an algorithm for security constrained dispatch calculations wherein closed area MW, line MW and MVA, and line-group MW constraints must be considered to insure system security. An overview of the algorithm and partial results from full-scale benchmark tests using a real-time 1200 bus/1500 line model and an optimal power flow (OPF) are presented in the body of the paper. Several appendices are included to outline the techniques used in the algorithm development.

  4. Multiple paths extraction in images using a constrained expanded trellis.

    PubMed

    Sun, Changming; Appleton, Ben

    2005-12-01

    Single shortest path extraction algorithms have been used in a number of areas such as network flow and image analysis. In image analysis, shortest path techniques can be used for object boundary detection, crack detection, or stereo disparity estimation. Sometimes one needs to find multiple paths as opposed to a single path in a network or an image where the paths must satisfy certain constraints. In this paper, we propose a new algorithm to extract multiple paths simultaneously within an image using a constrained expanded trellis (CET) for feature extraction and object segmentation. We also give a number of application examples for our multiple paths extraction algorithm. PMID:16355660

  5. Two loop divergences studied with one loop constrained differential renormalization

    SciTech Connect

    Seijas, Cesar [Departamento de Fi sica de Parti culas, Universidade de Santiago de Compostela, E-15706 Santiago de Compostela (Spain)]. E-mail: cesar@fpaxp1.usc.es

    2007-08-15

    In the context of differential renormalization, using constrained differential renormalization rules at one-loop, we show how to obtain concrete results in two-loop calculations without making use of Ward identities. In order to do that, we obtain a list of integrals with overlapping divergences compatible with CDR that can be applied to various two-loop background field calculations. As an example, we obtain the two-loop coefficient of the beta function of QED, SuperQED and Yang-Mills theory.

  6. Adaptively Learning an Importance Function Using Transport Constrained Monte Carlo

    SciTech Connect

    Booth, T.E.

    1998-06-22

    It is well known that a Monte Carlo estimate can be obtained with zero-variance if an exact importance function for the estimate is known. There are many ways that one might iteratively seek to obtain an ever more exact importance function. This paper describes a method that has obtained ever more exact importance functions that empirically produce an error that is dropping exponentially with computer time. The method described herein constrains the importance function to satisfy the (adjoint) Boltzmann transport equation. This constraint is provided by using the known form of the solution, usually referred to as the Case eigenfunction solution.

  7. Hierarchically Parallelized Constrained Nonlinear Solvers with Automated Substructuring

    NASA Technical Reports Server (NTRS)

    Padovan, Joe; Kwang, Abel

    1994-01-01

    This paper develops a parallelizable multilevel multiple constrained nonlinear equation solver. The substructuring process is automated to yield appropriately balanced partitioning of each succeeding level. Due to the generality of the procedure,_sequential, as well as partially and fully parallel environments can be handled. This includes both single and multiprocessor assignment per individual partition. Several benchmark examples are presented. These illustrate the robustness of the procedure as well as its capability to yield significant reductions in memory utilization and calculational effort due both to updating and inversion.

  8. Novel technique for constraining r-process (n, ?) reaction rates.

    PubMed

    Spyrou, A; Liddick, S N; Larsen, A C; Guttormsen, M; Cooper, K; Dombos, A C; Morrissey, D J; Naqvi, F; Perdikakis, G; Quinn, S J; Renstrøm, T; Rodriguez, J A; Simon, A; Sumithrarachchi, C S; Zegers, R G T

    2014-12-01

    A novel technique has been developed, which will open exciting new opportunities for studying the very neutron-rich nuclei involved in the r process. As a proof of principle, the ? spectra from the ? decay of ^{76}Ga have been measured with the SuN detector at the National Superconducting Cyclotron Laboratory. The nuclear level density and ?-ray strength function are extracted and used as input to Hauser-Feshbach calculations. The present technique is shown to strongly constrain the ^{75}Ge(n,?)^{76}Ge cross section and reaction rate. PMID:25526121

  9. Constrained Task Assignment and Scheduling On Networks of Arbitrary Topology

    NASA Astrophysics Data System (ADS)

    Jackson, Justin Patrick

    This dissertation develops a framework to address centralized and distributed constrained task assignment and task scheduling problems. This framework is used to prove properties of these problems that can be exploited, develop effective solution algorithms, and to prove important properties such as correctness, completeness and optimality. The centralized task assignment and task scheduling problem treated here is expressed as a vehicle routing problem with the goal of optimizing mission time subject to mission constraints on task precedence and agent capability. The algorithm developed to solve this problem is able to coordinate vehicle (agent) timing for task completion. This class of problems is NP-hard and analytical guarantees on solution quality are often unavailable. This dissertation develops a technique for determining solution quality that can be used on a large class of problems and does not rely on traditional analytical guarantees. For distributed problems several agents must communicate to collectively solve a distributed task assignment and task scheduling problem. The distributed task assignment and task scheduling algorithms developed here allow for the optimization of constrained military missions in situations where the communication network may be incomplete and only locally known. Two problems are developed. The distributed task assignment problem incorporates communication constraints that must be satisfied; this is the Communication-Constrained Distributed Assignment Problem. A novel distributed assignment algorithm, the Stochastic Bidding Algorithm, solves this problem. The algorithm is correct, probabilistically complete, and has linear average-case time complexity. The distributed task scheduling problem addressed here is to minimize mission time subject to arbitrary predicate mission constraints; this is the Minimum-time Arbitrarily-constrained Distributed Scheduling Problem. The Optimal Distributed Non-sequential Backtracking Algorithm solves this problem. The algorithm is correct, complete, outputs time optimal schedules, and has low average-case time complexity. Separation of the task assignment and task scheduling problems is exploited here to ameliorate the effects of an incomplete communication network. The mission-modeling conditions that allow this and the benefits gained are discussed in detail. It is shown that the distributed task assignment and task scheduling algorithms developed here can operate concurrently and maintain their correctness, completeness, and optimality properties.

  10. A simple SQP algorithm for constrained finite minimax problems.

    PubMed

    Wang, Lirong; Luo, Zhijun

    2014-01-01

    A simple sequential quadratic programming method is proposed to solve the constrained minimax problem. At each iteration, through introducing an auxiliary variable, the descent direction is given by solving only one quadratic programming. By solving a corresponding quadratic programming, a high-order revised direction is obtained, which can avoid the Maratos effect. Furthermore, under some mild conditions, the global and superlinear convergence of the algorithm is achieved. Finally, some numerical results reported show that the algorithm in this paper is successful. PMID:24683318

  11. Polar stimulation and constrained cell migration in microfluidic channels†

    PubMed Central

    Agrawal, Nitin; Mitchison, Timothy; Toner, Mehmet

    2010-01-01

    Asymmetrical delivery of stimuli to moving cells for perturbing spatially-heterogeneous intracellular signaling is an experimental challenge not adequately met by existing technologies. Here, we report a robust microfluidic platform allowing localized treatment of the front and/or back of moving cells which crawl through narrow channels that they completely occlude. The enabling technical element for this study is a novel design for precise, passive balancing of flow inside the microfluidic device by contacting two fluid streams before splitting them again. The microchannels constrain cell morphology and induce qualitative and quantitative changes in neutrophil chemotaxis that mimic cells crawling through tissues. PMID:18030401

  12. Constraining the supply of physicians: effects on black physicians.

    PubMed

    Hanft, R S; White, C C

    1987-01-01

    Although there is still dispute about the "surplus" of physicians, federal policies have begun to constrain the number of new entrants. Black students have been especially affected by retrenchment of federal support to education and by eroding medical school commitments to equity. Such trends undercut the demonstrable preference of black students to practice in geographic and specialty areas of greatest need. Better preparation for entry into medical school, and support through the long educational process, are necessary to preserve and extend the gains in both equity and health begun in the mid-1960s. PMID:3451060

  13. Constraining a Generative Word Alignment Model with Discriminative Output

    NASA Astrophysics Data System (ADS)

    Goh, Chooi-Ling; Watanabe, Taro; Yamamoto, Hirofumi; Sumita, Eiichiro

    We present a method to constrain a statistical generative word alignment model with the output from a discriminative model. The discriminative model is trained using a small set of hand-aligned data that ensures higher precision in alignment. On the other hand, the generative model improves the recall of alignment. By combining these two models, the alignment output becomes more suitable for use in developing a translation model for a phrase-based statistical machine translation (SMT) system. Our experimental results show that the joint alignment model improves the translation performance. The improvement in average of BLEU and METEOR scores is around 1.0-3.9 points.

  14. Preparation and biological evaluation of conformationally constrained BACE1 inhibitors.

    PubMed

    Winneroski, Leonard L; Schiffler, Matthew A; Erickson, Jon A; May, Patrick C; Monk, Scott A; Timm, David E; Audia, James E; Beck, James P; Boggs, Leonard N; Borders, Anthony R; Boyer, Robert D; Brier, Richard A; Hudziak, Kevin J; Klimkowski, Valentine J; Garcia Losada, Pablo; Mathes, Brian M; Stout, Stephanie L; Watson, Brian M; Mergott, Dustin J

    2015-07-01

    The BACE1 enzyme is a key target for Alzheimer's disease. During our BACE1 research efforts, fragment screening revealed that bicyclic thiazine 3 had low millimolar activity against BACE1. Analysis of the co-crystal structure of 3 suggested that potency could be increased through extension toward the S3 pocket and through conformational constraint of the thiazine core. Pursuit of S3-binding groups produced low micromolar inhibitor 6, which informed the S3-design for constrained analogs 7 and 8, themselves prepared via independent, multi-step synthetic routes. Biological characterization of BACE inhibitors 6-8 is described. PMID:26001341

  15. The unreasonable effectiveness of experiments in constraining nova nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Parikh, Anuj

    2014-09-01

    Classical nova explosions arise from thermonuclear ignition in the envelopes of accreting white dwarfs in close binary star systems. Detailed observations of novae have stimulated numerous studies in theoretical astrophysics and experimental nuclear physics. These phenomena are unusual in nuclear astrophysics because most of the thermonuclear reaction rates thought to be involved are constrained by experimental measurements. This situation allows for rather precise statements to be made about which measurements are still necessary to improve the nuclear physics input to astrophysical models. We briefly discuss desired measurements in these environments with an emphasis on recent experimental progress made to better determine key rates.

  16. A nonmonotone filter trust region method for nonlinear constrained optimization

    NASA Astrophysics Data System (ADS)

    Su, Ke; Pu, Dingguo

    2009-01-01

    In this paper, we present a nonmonotone filter trust region algorithm for solving nonlinear equality constrained optimization. Similar to Bryd-Omojokun class of algorithms, each step is composed of a quasi-normal step and a tangential step. This new method has more flexibility for the acceptance of the trial step compared to the filter methods, and requires less computational costs compared with the monotone methods. Under reasonable conditions, we give the globally convergence properties. Numerical tests are presented that confirm the efficiency of the approach.

  17. Constrained optimization of sequentially generated entangled multiqubit states

    E-print Network

    Hamed Saberi; Andreas Weichselbaum; Lucas Lamata; David Pérez-García; Jan von Delft; Enrique Solano

    2009-09-20

    We demonstrate how the matrix-product state formalism provides a flexible structure to solve the constrained optimization problem associated with the sequential generation of entangled multiqubit states under experimental restrictions. We consider a realistic scenario in which an ancillary system with a limited number of levels performs restricted sequential interactions with qubits in a row. The proposed method relies on a suitable local optimization procedure, yielding an efficient recipe for the realistic and approximate sequential generation of any entangled multiqubit state. We give paradigmatic examples that may be of interest for theoretical and experimental developments.

  18. Constraining predictions of the carbon cycle using data.

    PubMed

    Rayner, P J; Koffi, E; Scholze, M; Kaminski, T; Dufresne, J-L

    2011-05-28

    We use a carbon-cycle data assimilation system to estimate the terrestrial biospheric CO(2) flux until 2090. The terrestrial sink increases rapidly and the increase is stronger in the presence of climate change. Using a linearized model, we calculate the uncertainty in the flux owing to uncertainty in model parameters. The uncertainty is large and is dominated by the impact of soil moisture on heterotrophic respiration. We show that this uncertainty can be greatly reduced by constraining the model parameters with two decades of atmospheric measurements. PMID:21502169

  19. A transformation method for constrained-function minimization

    NASA Technical Reports Server (NTRS)

    Park, S. K.

    1975-01-01

    A direct method for constrained-function minimization is discussed. The method involves the construction of an appropriate function mapping all of one finite dimensional space onto the region defined by the constraints. Functions which produce such a transformation are constructed for a variety of constraint regions including, for example, those arising from linear and quadratic inequalities and equalities. In addition, the computational performance of this method is studied in the situation where the Davidon-Fletcher-Powell algorithm is used to solve the resulting unconstrained problem. Good performance is demonstrated for 19 test problems by achieving rapid convergence to a solution from several widely separated starting points.

  20. A Simple SQP Algorithm for Constrained Finite Minimax Problems

    PubMed Central

    2014-01-01

    A simple sequential quadratic programming method is proposed to solve the constrained minimax problem. At each iteration, through introducing an auxiliary variable, the descent direction is given by solving only one quadratic programming. By solving a corresponding quadratic programming, a high-order revised direction is obtained, which can avoid the Maratos effect. Furthermore, under some mild conditions, the global and superlinear convergence of the algorithm is achieved. Finally, some numerical results reported show that the algorithm in this paper is successful. PMID:24683318

  1. Evolutionary laws, initial conditions and gauge fixing in constrained systems

    NASA Astrophysics Data System (ADS)

    Pons, J. M.; Shepley, L. C.

    1995-07-01

    We describe in detail how to eliminate nonphysical degrees of freedom in the Lagrangian and Hamiltonian formulations of a constrained system. Two important and distinct steps in our method are the fixing of ambiguities in the dynamics and the determination of inequivalent initial data. The Lagrangian discussion is novel, and a proof is given that the final number of degrees of freedom in the two formulations agrees. We give applications to reparameterization invariant theories, where we prove that one of the constraints must be explicitly time dependent. We illustrate our procedure with the examples of trajectories in spacetime and with spatially homogeneous cosmological models. Finally, we comment briefly on Dirac's extended Hamiltonian technique.

  2. Formic Acid Mechanical,

    E-print Network

    Illinois at Urbana-Champaign, University of

    Formic Acid Fire Ant Starch Mechanical, Industrial Chemical, Petroleum Biological What Do and engineering. Products will range from starch, to polylactic acid, to corn fiber, to motor fuels. Progressive systems. Fire ants make formic acid. U of I researchers are developing fuel cells that use formic acid (1

  3. Acid Rain Study Guide.

    ERIC Educational Resources Information Center

    Hunger, Carolyn; And Others

    Acid rain is a complex, worldwide environmental problem. This study guide is intended to aid teachers of grades 4-12 to help their students understand what acid rain is, why it is a problem, and what possible solutions exist. The document contains specific sections on: (1) the various terms used in conjunction with acid rain (such as acid

  4. Acids and Bases (Netorials)

    NSDL National Science Digital Library

    Acids and Bases: this is a resource in the collection "Netorials". In this module there is an introduction to the chemical properties of acids and bases. Afterwards, the sections include topics such as Molecular Structures of Acids and Bases, Ionization constants, properties of salts, buffers and Lewis theory of Acids and Bases. The Netorials cover selected topics in first-year chemistry including: Chemical Reactions, Stoichiometry, Thermodynamics, Intermolecular Forces, Acids & Bases, Biomolecules, and Electrochemistry.

  5. Galactic disk abundance ratios: constraining SNIa stellar yields

    NASA Astrophysics Data System (ADS)

    Chiappini, Cristina

    2005-10-01

    Stellar abundance ratios of very good quality are now available for a large number of stars in the solar vicinity. Moreover, for an increasing number of stars informations on kinematics is also available. The combined information on abundance and kinematics enables one to select objects belonging to the different components of our Galaxy (thin disk, thick disk and halo). In this work we show that a careful comparison of our chemical evolution model for the Milky Way with the available abundance ratio measurements for stars in the solar neighborhood can be used to constrain the stellar yields. In particular, yields of Type Ia SNe are constrained by the abundance pattern of thin disk stars. Our results suggest that the 3-D models for SNIa explosion studied here lead to discrepancies once their predicted stellar yields are used as input in our chemical evolution model. These models produce flat Si/O and Mg/O ratios in disagreement with what is observed in thin disk stars. Moreover, our results indicate that larger quantities of Mg (at least a factor of 10 more than current theoretical predictions of either 1-D or multi-D models) need to be produced in SNIa.

  6. Constraining neutron star tidal Love numbers with gravitational wave detectors

    E-print Network

    Eanna E. Flanagan; Tanja Hinderer

    2007-12-07

    Ground-based gravitational wave detectors may be able to constrain the nuclear equation of state using the early, low frequency portion of the signal of detected neutron star - neutron star inspirals. In this early adiabatic regime, the influence of a neutron star's internal structure on the phase of the waveform depends only on a single parameter lambda of the star related to its tidal Love number, namely the ratio of the induced quadrupole moment to the perturbing tidal gravitational field. We analyze the information obtainable from gravitational wave frequencies smaller than a cutoff frequency of 400 Hz, where corrections to the internal-structure signal are less than 10 percent. For an inspiral of two non-spinning 1.4 solar mass neutron stars at a distance of 50 Mpc, LIGO II detectors will be able to constrain lambda to lambda < 2.0 10^{37} g cm^2 s^2 with 90% confidence. Fully relativistic stellar models show that the corresponding constraint on radius R for 1.4 solar mass neutron stars would be R < 13.6 km (15.3 km) for a n=0.5 (n=1.0) polytrope.

  7. Spatially distributed observations in constraining inundation modelling uncertainties

    NASA Astrophysics Data System (ADS)

    Werner, Micha; Blazkova, Sarka; Petr, Jiri

    2005-10-01

    The performance of two modelling approaches for predicting floodplain inundation is tested using observed flood extent and 26 distributed floodplain level observations for the 1997 flood event in the town of Usti nad Orlici in the Czech Republic. Although the one-dimensional hydrodynamic model and the integrated one- and two-dimensional model are shown to perform comparably against the flood extent data, the latter shows better performance against the distributed level observations. Comparable performance in predicting the extent of inundation is found to be primarily as a result of the urban reach considered, with flood extent constrained by road and railway embankments. Uncertainty in the elevation model used in both approaches is shown to have little effect on the reliability in predicting flood extent, with a greater impact on the ability in predicting the distributed level observations. These results show that reliability of flood inundation modelling in urban reaches, where flood risk assessment is of more interest than in more rural reaches, can be improved greatly if distributed observations of levels in the floodplain are used in constraining model uncertainties.

  8. Maximum Constrained Directivity of Oversteered End-Fire Sensor Arrays.

    PubMed

    Trucco, Andrea; Traverso, Federico; Crocco, Marco

    2015-01-01

    For linear arrays with fixed steering and an inter-element spacing smaller than one half of the wavelength, end-fire steering of a data-independent beamformer offers better directivity than broadside steering. The introduction of a lower bound on the white noise gain ensures the necessary robustness against random array errors and sensor mismatches. However, the optimum broadside performance can be obtained using a simple processing architecture, whereas the optimum end-fire performance requires a more complicated system (because complex weight coefficients are needed). In this paper, we reconsider the oversteering technique as a possible way to simplify the processing architecture of equally spaced end-fire arrays. We propose a method for computing the amount of oversteering and the related real-valued weight vector that allows the constrained directivity to be maximized for a given inter-element spacing. Moreover, we verify that the maximized oversteering performance is very close to the optimum end-fire performance. We conclude that optimized oversteering is a viable method for designing end-fire arrays that have better constrained directivity than broadside arrays but with a similar implementation complexity. A numerical simulation is used to perform a statistical analysis, which confirms that the maximized oversteering performance is robust against sensor mismatches. PMID:26066987

  9. A hybrid subgrid-scale model constrained by Reynolds stress

    NASA Astrophysics Data System (ADS)

    Verma, Aman; Park, Noma; Mahesh, Krishnan

    2013-11-01

    A novel constrained formulation for the dynamic subgrid-scale model for large eddy simulation (LES) is proposed. An externally prescribed Reynolds stress is used as the constraint and is imposed in the near-wall region of wall-bounded flows. However, unlike conventional zonal approaches, Reynolds stress is not imposed as the solution, but used as a constraint on the subgrid-scale stress so that the computed Reynolds stress closely matches the prescribed one only in the mean sense. In the absence of an ideal wall model or adequate near-wall resolution, a LES solution at coarse resolution is expected to be erroneous very near the wall while giving reasonable predictions away from the wall. The Reynolds stress constraint is limited to the region where the LES solution is expected to be erroneous. The Germano-identity error is used as an indicator of LES quality such that the Reynolds stress constraint is activated only where the Germano-identity error exceeds a certain threshold. The proposed model is applied to LES of turbulent channel flow at various Reynolds numbers and grid resolutions to obtain significant improvement over the dynamic Smagorinsky model, especially at coarse resolutions. This constrained formulation can be extended to incorporate constraints on the mean of other flow quantities.

  10. Characteristics of constrained optimum trajectories with specified range

    NASA Technical Reports Server (NTRS)

    Erzberger, H.; Lee, H.

    1978-01-01

    Necessary conditions of optimality are derived for trajectories whose structure is limited to climb, steady cruise, and descent segments. The performance function consists of the sum of fuel and time costs, referred to as direct operating cost (DOC). The state variable is range to go and the independent variable is energy. In this formulation a cruise segment always occurs at the optimum cruise energy for sufficiently large range. At short ranges (500 n. mi. and less) a cruise segment may also occur below the optimum cruise energy. The existence of such a cruise segment depends primarily on the fuel flow vs thrust characteristics and on thrust constraints. If thrust is a free control variable along with airspeed, it is shown that such cruise segments will not generally occur. If thrust is constrained to some maximum value in climb and to some minimum in descent, such cruise segments generally will occur. Computer calculations of typical short-range trajectories obtained about a 1% cost penalty for constraining the thrust.

  11. Performance of redirected walking algorithms in a constrained virtual world.

    PubMed

    Hodgson, Eric; Bachmann, Eric; Thrash, Tyler

    2014-04-01

    Redirected walking algorithms imperceptibly rotate a virtual scene about users of immersive virtual environment systems in order to guide them away from tracking area boundaries. Ideally, these distortions permit users to explore large unbounded virtual worlds while walking naturally within a physically limited space. Many potential virtual worlds are composed of corridors, passageways, or aisles. Assuming users are not expected to walk through walls or other objects within the virtual world, these constrained worlds limit the directions of travel and as well as the number of opportunities to change direction. The resulting differences in user movement characteristics within the physical world have an impact on redirected walking algorithm performance. This work presents a comparison of generalized RDW algorithm performance within a constrained virtual world. In contrast to previous studies involving unconstrained virtual worlds, experimental results indicate that the steer-to-orbit keeps users in a smaller area than the steer-to-center algorithm. Moreover, in comparison to steer-to-center, steer-to-orbit is shown to reduce potential wall contacts by over 29%. PMID:24650985

  12. Understanding (sessile/constrained) bubble and drop oscillations.

    PubMed

    Milne, A J B; Defez, B; Cabrerizo-Vílchez, M; Amirfazli, A

    2014-01-01

    The diffuse literature on drop oscillation is reviewed, with an emphasis on capillary wave oscillations of constrained drops. Based on the review, a unifying conceptual framework is presented for drop and bubble oscillations, which considers free and constrained drops/bubbles, oscillation of the surface or the bulk (i.e. center of mass) of the drop/bubble, as well as different types of restoring forces (surface tension, gravity, electromagnetic, etc). Experimental results (both from literature and from a new set of experiments studying sessile drops in cross flowing air) are used to test mathematical models from literature, using a novel whole profile analysis technique for the new experiments. The cause of oscillation (cross flowing air, vibrated surface, etc.) is seen not to affect oscillation frequency. In terms of models, simplified models are seen to poorly predict oscillation frequencies. The most advanced literature models are found to be relatively accurate at predicting frequency. However it is seen that no existing models are reliably accurate across a wide range of contact angles, indicating the need for advanced models/empirical relations especially for drops undergoing the lowest frequency mode of oscillation (the order 1 degree 1 non-axisymmetric 'bending' mode that corresponds to a lateral 'rocking' motion of the drop). PMID:24359696

  13. Electromagnetic imaging of underground targets using constrained optimization

    SciTech Connect

    Chaturvedi, P.; Plumb, R.G. [Univ. of Kansas, Lawrence, KS (United States)] [Univ. of Kansas, Lawrence, KS (United States)

    1995-05-01

    Several high-frequency electromagnetic techniques have been used in recent years to detect and identify buried objects. Post-processing of the collected data is performed in many of these techniques to obtain high-quality images of buried targets. Accurate reconstructions o f the target`s constitutive parameters can be obtained by casting the imaging problem in terms of an inverse electromagnetic scattering problem. A number of techniques have been put forth recently to invert the electromagnetic data to obtain such images. In this paper, the authors use a frequency-domain Born iterative method to reconstruct images of shallow targets. The Born iterative technique requires successive solutions to a forward scattering problem followed by an inverse scattering problem at each iteration step. They use a finite-difference time-domain (FDTD) algorithm to solve the forward scattering problem and constrained optimization for the inverse problem Two-dimensional simulated data for several canonical objects buried in the ground are obtained using the FDTD technique. The same FDTD code is also used in calculating the Green`s function required for solving the constrained optimization problem. Lossy, inhomogeneous ground models are used in several simulations to illustrate the use of this technique for practical situations. The inversion process can be used to reconstruct images for many realistic dielectric contrasts for which a linear Born approximation fails. Moreover, it is also shown that a small number of measurements results in accurate reconstructions with this technique. Use of multiple frequencies is also investigated.

  14. A Method to Constrain the Size of the Protosolar Nebula

    NASA Astrophysics Data System (ADS)

    Kretke, K. A.; Levison, H. F.; Buie, M. W.; Morbidelli, A.

    2012-04-01

    Observations indicate that the gaseous circumstellar disks around young stars vary significantly in size, ranging from tens to thousands of AU. Models of planet formation depend critically upon the properties of these primordial disks, yet in general it is impossible to connect an existing planetary system with an observed disk. We present a method by which we can constrain the size of our own protosolar nebula using the properties of the small body reservoirs in the solar system. In standard planet formation theory, after Jupiter and Saturn formed they scattered a significant number of remnant planetesimals into highly eccentric orbits. In this paper, we show that if there had been a massive, extended protoplanetary disk at that time, then the disk would have excited Kozai oscillations in some of the scattered objects, driving them into high-inclination (i >~ 50°), low-eccentricity orbits (q >~ 30 AU). The dissipation of the gaseous disk would strand a subset of objects in these high-inclination orbits; orbits that are stable on Gyr timescales. To date, surveys have not detected any Kuiper-belt objects with orbits consistent with this dynamical mechanism. Using these non-detections by the Deep Ecliptic Survey and the Palomar Distant Solar System Survey we are able to rule out an extended gaseous protoplanetary disk (RD >~ 80 AU) in our solar system at the time of Jupiter's formation. Future deep all sky surveys such as the Large Synoptic Survey Telescope will allow us to further constrain the size of the protoplanetary disk.

  15. Image registration guided, sparsity constrained reconstructions for dynamic MRI.

    PubMed

    Jin, Jin; Liu, Feng; Crozier, Stuart

    2014-12-01

    It is generally a challenging task to reconstruct dynamic magnetic resonance (MR) images with high spatial and high temporal resolutions, especially with highly incomplete k-space sampling. In this work, a novel method that combines a non-rigid image registration technique with sparsity-constrained image reconstruction is introduced. Employing a multi-resolution free-form deformation technique with B-spline interpolations, the non-rigid image registration accurately models the complex deformations of the physiological dynamics, and provides artifact-suppressed high spatial-resolution predictions. Based on these prediction images, the sparsity-constrained data fidelity-enforced image reconstruction further improves the reconstruction accuracy. When compared with the k-t FOCUSS with motion estimation/motion compensation (MEMC) technique on volunteer scans, the proposed method consistently outperforms in both the spatial and the temporal accuracy with variously accelerated k-space sampling. High fidelity reconstructions for dynamic systolic phases with reduction factor of 10 and cardiac perfusion series with reduction factor of 3 are presented. PMID:25131631

  16. A class of constrained clustering algorithms for object boundary extraction.

    PubMed

    Abrantes, A J; Marques, J S

    1996-01-01

    Boundary extraction is a key task in many image analysis operations. This paper describes a class of constrained clustering algorithms for object boundary extraction that includes several well-known algorithms proposed in different fields (deformable models, constrained clustering, data ordering, and traveling salesman problems). The algorithms belonging to this class are obtained by the minimization of a cost function with two terms: a quadratic regularization term and an image-dependent term defined by a set of weighting functions. The minimization of the cost function is achieved by lowpass filtering the previous model shape and by attracting the model units toward the centroids of their attraction regions. To define a new algorithm belonging to this class, the user has to specify a regularization matrix and a set of weighting functions that control the attraction of the model units toward the data. The usefulness of this approach is twofold: it provides a unified framework for many existing algorithms in pattern recognition and deformable models, and allows the design of new recursive schemes. PMID:18290068

  17. Adaptive ranking mutation operator based differential evolution for constrained optimization.

    PubMed

    Gong, Wenyin; Cai, Zhihua; Liang, Dingwen

    2015-04-01

    Differential evolution (DE) is a powerful evolutionary algorithm (EA) for numerical optimization. Combining with the constraint-handling techniques, recently, DE has been successfully used for the constrained optimization problems (COPs). In this paper, we propose the adaptive ranking mutation operator (ARMOR) for DE when solving the COPs. The ARMOR is expected to make DE converge faster and achieve feasible solutions faster. In ARMOR, the solutions are adaptively ranked according to the situation of the current population. More specifically, the population is classified into three situations, i.e., infeasible situation, semi-feasible situation, and feasible situation. In the infeasible situation, the solutions are ranked only based on their constraint violations; in the semi-feasible situation, they are ranked according to the transformed fitness; while in the feasible situation, the objective function value is used to assign ranks to different solutions. In addition, the selection probability of each solution is calculated differently in different situations. The ARMOR is simple, and it can be easily combined with most of constrained DE (CDE) variants. As illustrations, we integrate our approach into three representative CDE variants to evaluate its performance. The 24 benchmark functions presented in CEC 2006 and 18 benchmark functions presented in CEC 2010 are chosen as the test suite. Experimental results verify our expectation that the ARMOR is able to accelerate the original CDE variants in the majority of test cases. Additionally, ARMOR-based CDE is able to provide highly competitive results compared with other state-of-the-art EAs. PMID:25055390

  18. Cyclic fatty acids from linolenic acid

    Microsoft Academic Search

    R. A. Eisenhauer; R. E. Beal; E. L. Griffin

    1964-01-01

    Linolenic acid of 95% purity was heated with excess alkali in ethylene glycol to produce cyclic fatty acids. Reaction variables,\\u000a which are associated with the cyclization reaction and which were investigated, included solvent-to-fatty-acid ratio, catalyst\\u000a concentration, and reaction temperature, headspace gas (N2 or C2H4), and head-space gas pressure.\\u000a \\u000a Yields of cyclic acids were improved by increasing solvent ratio (1.5–6 wt

  19. Constraining the Interior Geophysics of Rubble Pile Asteroids

    NASA Astrophysics Data System (ADS)

    Scheeres, D. J.; Jacobson, S.; McMahon, J.; Hirabayashi, M.

    2013-12-01

    The internal geophysics of small rubble pile asteroids are largely unknown, and standard geophysical theories are not well matched to the extreme environment these bodies exist in. Interior pressures within rapidly spinning rubble piles are predicted to be as small as a few Pascals, a regime in which small non-gravitational forces not considered for larger bodies may become important. Previous research has suggested that the standard geophysical models for internal energy dissipation in this regime require modification (Goldreich and Sari, ApJ 2009), adding additional uncertainty in the geophysics. We report on new theoretical and observational results that suggest a direct way in which fundamental geophysical parameters of small rubble pile asteroids can be constrained. Specifically, we will discuss how the ratio Q/k, tidal dissipation number over tidal Love number, can be inferred and more strictly constrained for primaries in small binary asteroid systems where the secondary is spin-synchronized and the primary is super-synchronous, the most common class of small asteroid binary systems. Jacobson & Scheeres (ApJ 2011) proposed that many of these binary asteroid systems may be in an equilibrium state where contractive Binary YORP forces balance against expansive tidal torques due to tidal distortion of the primary body. The predicted equilibrium semi-major axes for such binary asteroid systems (based on presumed values for the Binary YORP force and Q/k values) has been seen to be consistent with the observed sizes of many of these systems (see figure). Recently, it has also been reported that the spacecraft-accessible binary asteroid 1996 FG3 is in such an equilibrium state (Scheirich et al., Binaries Workshop 2013). The combined detection of such an equilibrium coupled with their theoretical model makes it feasible to sharply constrain the Q/k parameter for the primary asteroid in the 1996 FG3 system and extrapolate its functional form to other such systems. We will review the theory and measurements that make such a determination feasible, and explore other geophysical aspects of such a system that could be determined from a rendezvous space mission. Singly-synchronous binary system primary radii are plotted against their determined value of BQ/k, based on their current semi-major axis. Values of the BYORP coefficient B are on the order of 0.001 with an order of magnitude uncertainty, providing initial estimates on Q/k. Proposed approaches for measuring B, and hence Q/k, will be discussed.

  20. A New Constrained Multiobjective Optimization Algorithm Based on Artificial Immune Systems

    Microsoft Academic Search

    Hansong Xiao; Jean W. Zu

    2007-01-01

    This paper proposes a new constrained multiobjective optimization algorithm based on artificial immune systems (AIS). To deal with constrained multiobjective optimization problems, the constrained AlS-based multiobjective optimization algorithm is developed by integrating a proposed constraint-handling technique with the unconstrained AIS-based multiobjective optimization algorithm named MOAIS (Xiao and Zu, 2006). We propose the constraint-handling technique by extending a single-objective constraint-handling technique

  1. Nature's starships. I. Observed abundances and relative frequencies of amino acids in meteorites

    SciTech Connect

    Cobb, Alyssa K.; Pudritz, Ralph E., E-mail: cobbak@mcmaster.ca, E-mail: pudritz@physics.mcmaster.ca [Origins Institute, McMaster University, ABB 241, 1280 Main Street, Hamilton, ON L8S 4M1 (Canada)

    2014-03-10

    The class of meteorites called carbonaceous chondrites are examples of material from the solar system which have been relatively unchanged from the time of their initial formation. These meteorites have been classified according to the temperatures and physical conditions of their parent planetesimals. We collate available data on amino acid abundance in these meteorites and plot the concentrations of different amino acids for each meteorite within various meteorite subclasses. We plot average concentrations for various amino acids across meteorites separated by subclass and petrologic type. We see a predominance in the abundance and variety of amino acids in CM2 and CR2 meteorites. The range in temperature corresponding to these subclasses indicates high degrees of aqueous alteration, suggesting aqueous synthesis of amino acids. Within the CM2 and CR2 subclasses, we identify trends in relative frequencies of amino acids to investigate how common amino acids are as a function of their chemical complexity. These two trends (total abundance and relative frequencies) can be used to constrain formation parameters of amino acids within planetesimals. Our organization of the data supports an onion shell model for the temperature structure of planetesimals. The least altered meteorites (type 3) and their amino acids originated near cooler surface regions. The most active amino acid synthesis likely took place at intermediate depths (type 2). The most altered materials (type 1) originated furthest toward parent body cores. This region is likely too hot to either favor amino acid synthesis or for amino acids to be retained after synthesis.

  2. Nature's Starships. I. Observed Abundances and Relative Frequencies of Amino Acids in Meteorites

    NASA Astrophysics Data System (ADS)

    Cobb, Alyssa K.; Pudritz, Ralph E.

    2014-03-01

    The class of meteorites called carbonaceous chondrites are examples of material from the solar system which have been relatively unchanged from the time of their initial formation. These meteorites have been classified according to the temperatures and physical conditions of their parent planetesimals. We collate available data on amino acid abundance in these meteorites and plot the concentrations of different amino acids for each meteorite within various meteorite subclasses. We plot average concentrations for various amino acids across meteorites separated by subclass and petrologic type. We see a predominance in the abundance and variety of amino acids in CM2 and CR2 meteorites. The range in temperature corresponding to these subclasses indicates high degrees of aqueous alteration, suggesting aqueous synthesis of amino acids. Within the CM2 and CR2 subclasses, we identify trends in relative frequencies of amino acids to investigate how common amino acids are as a function of their chemical complexity. These two trends (total abundance and relative frequencies) can be used to constrain formation parameters of amino acids within planetesimals. Our organization of the data supports an onion shell model for the temperature structure of planetesimals. The least altered meteorites (type 3) and their amino acids originated near cooler surface regions. The most active amino acid synthesis likely took place at intermediate depths (type 2). The most altered materials (type 1) originated furthest toward parent body cores. This region is likely too hot to either favor amino acid synthesis or for amino acids to be retained after synthesis.

  3. Acid Thunder: Acid Rain and Ancient Mesoamerica

    ERIC Educational Resources Information Center

    Kahl, Jonathan D. W.; Berg, Craig A.

    2006-01-01

    Much of Mesoamerica's rich cultural heritage is slowly eroding because of acid rain. Just as water dissolves an Alka-Seltzer tablet, acid rain erodes the limestone surfaces of Mexican archaeological sites at a rate of about one-half millimeter per century (Bravo et al. 2003). A half-millimeter may not seem like much, but at this pace, a few…

  4. Global scheduling on temperature-constrained multiprocessor real-time systems 

    E-print Network

    Koo, Ja-Ryeong

    2008-10-10

    -time multiprocessor systems. Additionally, we show how the maximum schedulable utilization (MSU) for partitioning heuristics can be determined on the temperature-constrained multiprocessor real-time systems....

  5. Constraining the Sensitivity of Regional Climate with the Use of Historical Observations

    E-print Network

    Constraining the Sensitivity of Regional Climate with the Use of Historical Observations APOSTOLOS and the way in which Corresponding author address: Apostolos Voulgarakis, NASA Goddard Institute for Space

  6. Lucid Dreaming: Reliable Analog Event Detection for Energy-Constrained Applications

    E-print Network

    Lucid Dreaming: Reliable Analog Event Detection for Energy-Constrained Applications Sasha Jevtic vibrations in buildings and bridges, we have designed, implemented, and evaluated lucid dreaming, a hardware

  7. Helix-constrained nociceptin peptides are potent agonists and antagonists of ORL-1 and nociception.

    PubMed

    Lohman, Rink-Jan; Harrison, Rosemary S; Ruiz-Gómez, Gloria; Hoang, Huy N; Shepherd, Nicholas E; Chow, Shiao; Hill, Timothy A; Madala, Praveen K; Fairlie, David P

    2015-01-01

    Nociceptin (orphanin FQ) is a 17-residue neuropeptide hormone with roles in both nociception and analgesia. It is an opioid-like peptide that binds to and activates the G-protein-coupled receptor opioid receptor-like-1 (ORL-1, NOP, orphanin FQ receptor, kappa-type 3 opioid receptor) on central and peripheral nervous tissue, without activating classic delta-, kappa-, or mu-opioid receptors or being inhibited by the classic opioid antagonist naloxone. The three-dimensional structure of ORL-1 was recently published, and the activation mechanism is believed to involve capture by ORL-1 of the high-affinity binding, prohelical C-terminus. This likely anchors the receptor-activating N-terminus of nociception nearby for insertion in the membrane-spanning helices of ORL-1. In search of higher agonist potency, two lysine and two aspartate residues were strategically incorporated into the receptor-binding C-terminus of the nociceptin sequence and two Lys(i)?Asp(i+4) side chain-side chain condensations were used to generate lactam cross-links that constrained nociceptin into a highly stable ?-helix in water. A cell-based assay was developed using natively expressed ORL-1 receptors on mouse neuroblastoma cells to measure phosphorylated ERK as a reporter of agonist-induced receptor activation and intracellular signaling. Agonist activity was increased up to 20-fold over native nociceptin using a combination of this helix-inducing strategy and other amino acid modifications. An NMR-derived three-dimensional solution structure is described for a potent ORL-1 agonist derived from nociceptin, along with structure-activity relationships leading to the most potent known ?-helical ORL-1 agonist (EC50 40 pM, pERK, Neuro-2a cells) and antagonist (IC50 7 nM, pERK, Neuro-2a cells). These ?-helix-constrained mimetics of nociceptin(1-17) had enhanced serum stability relative to unconstrained peptide analogues and nociceptin itself, were not cytotoxic, and displayed potent thermal analgesic and antianalgesic properties in rats (ED50 70 pmol, IC50 10 nmol, s.c.), suggesting promising uses in vivo for the treatment of pain and other ORL-1-mediated responses. PMID:25677767

  8. Future fish distributions constrained by depth in warming seas

    NASA Astrophysics Data System (ADS)

    Rutterford, Louise A.; Simpson, Stephen D.; Jennings, Simon; Johnson, Mark P.; Blanchard, Julia L.; Schön, Pieter-Jan; Sims, David W.; Tinker, Jonathan; Genner, Martin J.

    2015-06-01

    European continental shelf seas have experienced intense warming over the past 30 years. In the North Sea, fish have been comprehensively monitored throughout this period and resulting data provide a unique record of changes in distribution and abundance in response to climate change. We use these data to demonstrate the remarkable power of generalized additive models (GAMs), trained on data earlier in the time series, to reliably predict trends in distribution and abundance in later years. Then, challenging process-based models that predict substantial and ongoing poleward shifts of cold-water species, we find that GAMs coupled with climate projections predict future distributions of demersal (bottom-dwelling) fish species over the next 50 years will be strongly constrained by availability of habitat of suitable depth. This will lead to pronounced changes in community structure, species interactions and commercial fisheries, unless individual acclimation or population-level evolutionary adaptations enable fish to tolerate warmer conditions or move to previously uninhabitable locations.

  9. Late time CMB anisotropies constrain mini-charged particles

    SciTech Connect

    Burrage, C.; Redondo, J.; Ringwald, A. [Deutsches Elektronen Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Jaeckel, J., E-mail: clare.burrage@desy.de, E-mail: joerg.jaeckel@durham.ac.uk, E-mail: javier.redondo@desy.de, E-mail: andreas.ringwald@desy.de [Institute for Particle Physics and Phenomenology, Durham University, Durham, DH1 3LE (United Kingdom)

    2009-11-01

    Observations of the temperature anisotropies induced as light from the CMB passes through large scale structures in the late universe are a sensitive probe of the interactions of photons in such environments. In extensions of the Standard Model which give rise to mini-charged particles, photons propagating through transverse magnetic fields can be lost to pair production of such particles. Such a decrement in the photon flux would occur as photons from the CMB traverse the magnetic fields of galaxy clusters. Therefore late time CMB anisotropies can be used to constrain the properties of mini-charged particles. We outline how this test is constructed, and present new constraints on mini-charged particles from observations of the Sunyaev-Zel'dovich effect in the Coma cluster.

  10. Constraining the Quasar Contribution to the Reionisation of Cosmic Hydrogen

    E-print Network

    Jhan Srbinovsky; Stuart Wyithe

    2006-10-11

    Absorption spectra of high redshift quasars suggest that the reionisation of cosmic hydrogen was complete near z~6. The dominant sources of ionising photons responsible for this reionisation are generally thought to be stars and quasars. In this paper we make a quantitative estimate of the relative contributions made by these sources. Our approach is to compute the evolution of the post overlap ionising background radiation by combining semi-analytic descriptions of reionisation in a clumpy medium with a model for the quasar luminosity function. Our overall model has two free parameters, the star formation efficiency and the minimum quasar luminosity. By adjusting these parameters, we constrain the relative contributions made by stars and quasars through comparison with reported observations (Fan et al. 2005). We find that the relative quasar contribution (at z=5.7) to the ionising background was between 1.4% and 14.5%. The range of uncertainty is dominated by the unknown minimum quasar luminosity.

  11. The effect of humor on memory: constrained by the pun.

    PubMed

    Summerfelt, Hannah; Lippman, Louis; Hyman, Ira E

    2010-01-01

    In a series of experiments, we investigated the effect of pun humor on memory. In all experiments, the participants were exposed to knock-knock jokes in either the original form retaining the pun or in a modified form that removed the pun. In Experiment 1, the authors found that pun humor improved both recall and recognition memory following incidental encoding. In Experiment 2, they found evidence that rehearsal is not the cause of the humor effect on memory. In Experiments 3 and 4, the authors found that the constraints imposed by puns and incongruity may account for the humor effects observed. Puns constrain and limit the information that can fit in the final line of a joke and thus make recall easier. PMID:21086859

  12. Weak Gravity Strongly Constrains Large-Field Axion Inflation

    E-print Network

    Ben Heidenreich; Matthew Reece; Tom Rudelius

    2015-06-10

    Models of large-field inflation based on axion-like fields with shift symmetries can be simple and natural, and make a promising prediction of detectable primordial gravitational waves. The Weak Gravity Conjecture is known to constrain the simplest case in which a single axion descends from a gauge field in an extra dimension. By supplementing the Weak Gravity Conjecture with considerations of how the mass spectrum of the theory varies across the axion moduli space, we obtain more powerful constraints that apply to a variety of multi-axion theories including N-flation and alignment models. In every case that we consider, plausible assumptions lead to field ranges that cannot be parametrically larger than the Planck scale. Our results are strongly suggestive of a general inconsistency in models of large-field inflation based on axions, and possibly of a more general principle forbidding super-Planckian field ranges.

  13. Weak Gravity Strongly Constrains Large-Field Axion Inflation

    E-print Network

    Heidenreich, Ben; Rudelius, Tom

    2015-01-01

    Models of large-field inflation based on axion-like fields with shift symmetries can be simple and natural, and make a promising prediction of detectable primordial gravitational waves. The Weak Gravity Conjecture is known to constrain the simplest case in which a single axion descends from a gauge field in an extra dimension. By supplementing the Weak Gravity Conjecture with considerations of how the mass spectrum of the theory varies across the axion moduli space, we obtain more powerful constraints that apply to a variety of multi-axion theories including N-flation and alignment models. In every case that we consider, plausible assumptions lead to field ranges that cannot be parametrically larger than the Planck scale. Our results are strongly suggestive of a general inconsistency in models of large-field inflation based on axions, and possibly of a more general principle forbidding super-Planckian field ranges.

  14. Constraining recent oscillations in quintessence models with Euclid

    NASA Astrophysics Data System (ADS)

    Lima, N. A.; Viana, P. T. P.; Tereno, I.

    2014-07-01

    Euclid is a future space-based mission that will constrain dark energy with unprecedented accuracy. Its photometric component is optimized for weak lensing studies, while the spectroscopic component is designed for baryon acoustic oscillations (BAO) analysis. We use the Fisher matrix formalism to make forecasts on two quintessence dark energy models with a dynamical equation of state that leads to late-time oscillations in the expansion rate of the Universe. We find that weak lensing will place much stronger constraints than the BAO, being able to discriminate between oscillating models by measuring the relevant parameters to 1? precisions of 5-20 per cent. The tight constraints suggest that Euclid data could identify even quite small late-time oscillations in the expansion rate of the Universe.

  15. Forced to be free? Increasing patient autonomy by constraining it

    PubMed Central

    2014-01-01

    It is universally accepted in bioethics that doctors and other medical professionals have an obligation to procure the informed consent of their patients. Informed consent is required because patients have the moral right to autonomy in furthering the pursuit of their most important goals. In the present work, it is argued that evidence from psychology shows that human beings are subject to a number of biases and limitations as reasoners, which can be expected to lower the quality of their decisions and which therefore make it more difficult for them to pursue their most important goals by giving informed consent. It is further argued that patient autonomy is best promoted by constraining the informed consent procedure. By limiting the degree of freedom patients have to choose, the good that informed consent is supposed to protect can be promoted. PMID:22318413

  16. Phenolate constrained geometry polymerization catalyst and method for preparing

    DOEpatents

    Marks, T.J.; Chen, Y.X.

    1999-01-05

    The subject invention involves a method of preparing and the constrained geometry catalyst thereby prepared of the general formula Ar{prime}R4(O)Ar{double_prime}R{prime}{sub 4}M(CH{sub 2}Ph){sub 2} where Ar{prime} is a phenyl or naphthyl group; Ar{double_prime} is a cyclopentadienyl or indenyl group, R and R{prime} are H or alkyl substituents (C{<=}10) and M is Ti, Zr or Hf. The synthetic method involves a simple alkane elimination approach which permits a ``one-pot`` procedure. The catalyst, when combined with a cocatalyst such as Pb{sub 3}C{sup +}B(Ar{sub 3}{sup F}){sub 4}BAr{sub 3}{sup F} or methyl alumoxane where Ar{sup F} is a fluoroaryl group, is an effective catalyst for the polymerization of {alpha}-olefins such as ethylene, propylene and styrene. 1 fig.

  17. Phenolate constrained geometry polymerization catalyst and method for preparing

    DOEpatents

    Marks, Tobin J. (Evanston, IL); Chen, You-Xian (Chicago, IL)

    1999-01-01

    The subject invention involves a method of preparing and the constrained geometry catalyst thereby prepared of the general formula Ar'R4(O)Ar"R'.sub.4 M(CH.sub.2 Ph).sub.2 where Ar' is a phenyl or naphthyl group; Ar" is a cyclopentadienyl or indenyl group, R and R' are H or alkyl substituents (C.ltoreq.10) and M is Ti, Zr or Hf. The synthetic method involves a simple alkane elimination approach which permits a "one-pot" procedure. The catalyst, when combined with a cocatalyst such as Pb.sub.3 C.sup.+ B(Ar.sub.3.sup.F).sub.4 BAr.sub.3.sup.F or methyl alumoxane where Ar.sup.F is a fluoroaryl group, is an effective catalyst for the polymerization of .alpha.-olefins such as ethylene, propylene and styrene.

  18. Thermally-Constrained Fuel-Optimal ISS Maneuvers

    NASA Technical Reports Server (NTRS)

    Bhatt, Sagar; Svecz, Andrew; Alaniz, Abran; Jang, Jiann-Woei; Nguyen, Louis; Spanos, Pol

    2015-01-01

    Optimal Propellant Maneuvers (OPMs) are now being used to rotate the International Space Station (ISS) and have saved hundreds of kilograms of propellant over the last two years. The savings are achieved by commanding the ISS to follow a pre-planned attitude trajectory optimized to take advantage of environmental torques. The trajectory is obtained by solving an optimal control problem. Prior to use on orbit, OPM trajectories are screened to ensure a static sun vector (SSV) does not occur during the maneuver. The SSV is an indicator that the ISS hardware temperatures may exceed thermal limits, causing damage to the components. In this paper, thermally-constrained fuel-optimal trajectories are presented that avoid an SSV and can be used throughout the year while still reducing propellant consumption significantly.

  19. Constraining Recent Oscillations in Quintessence Models with Euclid

    E-print Network

    Lima, Nelson A; Tereno, I

    2013-01-01

    Euclid is a future space-based mission that will constrain dark energy with unprecedented accuracy. Its photometric component is optimized for Weak Lensing studies, while the spectroscopic component is designed for Baryon Acoustic Oscillations (BAO) analysis. We use the Fisher matrix formalism to make forecasts on two quintessence dark energy models with a dynamical equation of state that leads to late-time oscillations in the expansion rate of the Universe. We find that Weak Lensing will place much stronger constraints than the BAO, being able to discriminate between oscillating models by measuring the relevant parameters to $1\\sigma$ precisions of 5 to 20%. The tight constraints suggest that Euclid data could identify even quite small late-time oscillations in the expansion rate of the Universe.

  20. Constrained Quadratic Programming, Active Control of Rotating Mass Imbalance

    NASA Astrophysics Data System (ADS)

    Manchala, D. W.; Palazzolo, A. B.; Kascak, A. F.; Montague, G. T.; Brown, G. V.

    1997-09-01

    Jet engines may experience severe vibration due to the sudden imbalance caused by blade failure. The current research investigates employment of piezoelectric actuators to suppress this using active vibration control. This requires identification of the source of the vibrations via an expert system, determination of the required phase angles and amplitudes for the correction forces, and application of the desired control signals to the piezoelectric actuators. Correction forces may exceed the physical limitations of the actuators; hence results of “constrained force” quadratic programming, least squares and multi-point correction algorithms will be compared. It is demonstrated that simply scaling down the least squares predicted correction forces to satisfy the actuator saturation constraints does not necessarily yield optimal reductions in vibration. In this paper test results are shown for sudden imbalance, and the computational time requirements and balancing effectiveness for the various approaches are compared.