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Sample records for constrained acidic alpha-amino

  1. An NMR and ab initio quantum chemical study of acid-base equilibria for conformationally constrained acidic alpha-amino acids in aqueous solution.

    PubMed

    Nielsen, P A; Jaroszewski, J W; Norrby, P O; Liljefors, T

    2001-03-07

    The protonation states of a series of piperidinedicarboxylic acids (PDAs), which are conformationally constrained acidic alpha-amino acids, have been studied by (13)C NMR titration in water. The resulting data have been correlated with theoretical results obtained by HF/6-31+G calculations using the polarizable continuum model (PCM) for the description of water. The PDAs are highly ionizable and contain one or two possible internal hydrogen bonds. In the present study, we show that the PCM model is able to reproduce the relative stabilities of the different protonation states of the PDAs. Furthermore, our results show that prediction of relative pK(a) values for two different types of ionizable functional groups covering a pK(a) range from 1.6 to 12.1 is possible with a high degree of accuracy.

  2. Synthesis of alpha-amino acids

    DOEpatents

    Davis, Jr., Jefferson W.

    1983-01-01

    A method for synthesizing alpha amino acids proceding through novel intermediates of the formulas: R.sub.1 R.sub.2 C(OSOCl)CN, R.sub.1 R.sub.2 C(Cl)CN and [R.sub.1 R.sub.2 C(CN)O].sub.2 SO wherein R.sub.1 and R.sub.2 are each selected from hydrogen monovalent substituted and unsubstituted hydrocarbon radicals of 1 to 12 carbon atoms. The use of these intermediates allows the synthesis steps to be exothermic and results in an overall synthesis method which is faster than the synthesis methods of the prior art.

  3. Synthesis of alpha-amino acids

    DOEpatents

    Davis, Jr., Jefferson W.

    1983-01-01

    A method for synthesizing alpha amino acids proceding through novel intermediates of the formulas: R.sub.1 R.sub.2 C(OSOCl)CN, R.sub.1 R.sub.2 C(Cl)CN and [R.sub.1 R.sub.2 C(CN)O].sub.2 SO wherein R.sub.1 and R.sub.2 are each selected from hydrogen monovalent substituted and unsubstituted hydrocarbon radicals of 1 to 10 carbon atoms. The use of these intermediates allows the synthesis steps to be exothermic and results in an overall synthesis method which is faster than the snythesis methods of the prior art.

  4. Synthesis of alpha-amino acids

    DOEpatents

    Davis, Jr., Jefferson W.

    1983-01-01

    A method for synthesizing alpha amino acids proceeding through novel intermediates of the formulas: R.sub.1 R.sub.2 C(OSOCl)CN, R.sub.1 R.sub.2 C(Cl)CN and [R.sub.1 R.sub.2 C(CN)O].sub.2 SO wherein R.sub.1 and R.sub.2 are each selected from hydrogen monovalent substituted and unsubstituted hydrocarbon radicals of 1 to 12 carbon atoms. The use of these intermediates allows the synthesis steps to be exothermic and results in an overall synthesis method which is faster than the synthesis methods of the prior art.

  5. Synthesis of alpha-amino acids

    DOEpatents

    Davis, J.W. Jr.

    1983-01-25

    A method is described for synthesizing alpha amino acids proceeding through novel intermediates of the formulas: R[sub 1]R[sub 2]C(OSOCl)CN, R[sub 1]R[sub 2]C(Cl)CN and [R[sub 1]R[sub 2]C(CN)O][sub 2]SO wherein R[sub 1] and R[sub 2] are each selected from hydrogen monovalent substituted and unsubstituted hydrocarbon radicals of 1 to 10 carbon atoms. The use of these intermediates allows the synthesis steps to be exothermic and results in an overall synthesis method which is faster than the synthesis methods of the prior art. No Drawings

  6. How to build optically active alpha-amino acids.

    PubMed

    Calmes, M; Daunis, J

    1999-01-01

    Various methodologies published in the literature dealing with alpha-amino carboxylic acid asymmetric synthesis are presented in a digest form. In each case, only some recent or most typical works are mentioned.

  7. An efficient preparation of N-methyl-alpha-amino acids from N-nosyl-alpha-amino acid phenacyl esters.

    PubMed

    Leggio, Antonella; Belsito, Emilia Lucia; De Marco, Rosaria; Liguori, Angelo; Perri, Francesca; Viscomi, Maria Caterina

    2010-03-05

    In this paper we describe a simple and efficient solution-phase synthesis of N-methyl-N-nosyl-alpha-amino acids and N-Fmoc-N-methyl-alpha-amino acids. This represents a very important application in peptide synthesis to obtain N-methylated peptides in both solution and solid phase. The developed methodology involves the use of N-nosyl-alpha-amino acids with the carboxyl function protected as a phenacyl ester and the methylating reagent diazomethane. An important aspect of this synthetic strategy is the possibility to selectively deprotect the carboxyl function or alternatively both amino and carboxyl moieties by using the same reagent with a different molar excess and under mild conditions. Furthermore, the adopted procedure keeps unchanged the acid-sensitive side chain protecting groups used in Fmoc-based synthetic strategies.

  8. ANTIGENICITY OF POLYPEPTIDES (POLY ALPHA AMINO ACIDS)

    PubMed Central

    Pinchuck, Paul; Maurer, Paul H.

    1965-01-01

    The response of mice to synthetic linear polypeptides of known composition but random sequence has been studied. Neither Swiss mice nor a number of inbred strains could respond to copolymers of only 2 amino acids (G60L40, G60A40, G90T10). Upon introduction of as little as 4 mole per cent of a third amino acid, good immune responses were obtained, regardless of the nature of the third amino acid. The level of the immune response to a series of glu-lys-ala polymers increased with increasing alanine content of the polymer. PMID:5849232

  9. ANTIGENICITY OF POLYPEPTIDES (POLY ALPHA AMINO ACIDS)

    PubMed Central

    Maurer, Paul H.; Gerulat, Bernard F.; Pinchuck, Paul

    1964-01-01

    A new group of synthetic random polymers of α-L-amino acids has been studied for immunogenicity. With the glutamic acid and alanine copolymers, those consisting of almost equimolar amounts of the two (G60A40 and G40A60) were effective antigens in rabbits whereas those with higher glutamic acid contents (G75A25, G90A10) were poor antigens. The substitution of alanine by valine or leucine (G75V25 and G80Leu20) produced copolymers which were poor antigens in rabbits but effective in guinea pigs. L70A30, although capable of "non-specifically" precipitating serum proteins, was shown not to be antigenic in either rabbits or guinea pigs. The introduction of alanine into glutamic acid and lysine polymers (GLA series) enhanced the immunogenicity of the terpolymers, i.e., GLA30 > GLA20 > GLA10 > GL. The mechanism by which this may be accomplished is discussed as possibly being related to the reduction of the interactions between glutamyl and lysyl residues which allows the carboxyl groups to act as strong immunogenic determinants. PMID:14176288

  10. Soluble polymer supported synthesis of alpha-amino acid derivatives.

    PubMed

    Sauvagnat, B; Kulig, K; Lamaty, F; Lazaro, R; Martinez, J

    2000-01-01

    A Schiff base activated glycine supported on a soluble polymer (poly(ethylene glycol) (PEG)) was readily alkylated with a wide variety of electrophiles in the presence of a carbonate base in acetonitrile. The presence of the polymer provided a phase-transfer catalysis environment which accelerated the reaction. Effects of various carbonate bases and leaving groups have been also studied. Completion of the PEG-supported reaction was obtained without using a large excess of reagents or an extra phase-transfer catalyst, even in the case of unreactive or hindered electrophiles. After cleavage from the polymer, alpha-amino esters are obtained in good yields.

  11. N-carbamoyl-alpha-amino acids rather than free alpha-amino acids formation in the primitive hydrosphere: a novel proposal for the emergence of prebiotic peptides.

    PubMed

    Taillades, J; Beuzelin, I; Garrel, L; Tabacik, V; Bied, C; Commeyras, A

    1998-02-01

    Our previous kinetic and thermodynamic studies upon the reactional system HCHO/HCN/NH3 in aqueous solutions are completed. In the assumed prebiotic conditions of the primitive earth ([HCHO] and [HCN] near 1 g L-1, T = 25 degrees C, pH = 8, [NH3] very low), this system leads to 99.9% of alpha-hydroxyacetonitrile and 0.1% of alpha-aminoacetonitrile (precursor of the alpha-amino acid). The classical base-catalyzed hydration of nitriles, slow and not selective, can not modify significantly this proportion. On the contrary, we found two specific and efficient reactions of alpha-aminonitriles which shift the initial equilibrium in favor of the alpha-aminonitrile pathway. The first reaction catalyzed by formaldehyde generates alpha-aminoamides, precursors of alpha-aminoacids. The second reaction catalyzed by carbon dioxide affords hydantoins, precursors of N-carbamoyl-alpha-aminoacids. In the primitive hydrosphere, where the concentration in carbon dioxide was estimated to be higher than that of formaldehyde, the formation of hydantoins was consequently more efficient. The rates of hydrolysis of the alpha-aminoacetamide and of the hydantoin at pH 8 being very similar, the synthesis of the N-carbamoyl-alpha-amino acid seems then to be the fatal issue of the HCHO/HCN/NH3 system that nature used to perform its evolution. These N-protected alpha-amino acids offer new perspectives in prebiotic chemistry, in particular for the emergence of peptides on the prebiotic earth.

  12. An Ireland-Claisen approach to beta-alkoxy alpha-amino acids.

    PubMed

    Tellam, James P; Kociok-Köhn, Gabriele; Carbery, David R

    2008-11-20

    A diastereoselective Ireland-Claisen approach to beta-alkoxy alpha-amino acid esters is reported. Amino acid esters of enol ethereal allylic alcohols undergo facile syn-selective [3,3]-sigmatropic rearrangement via silyl ketene acetals. Substrate synthesis, rearrangement development, stereoselectivity, and product elaboration are discussed.

  13. Synthesis and transformations of a pyrazole containing alpha, beta-didehydro-alpha-amino acid derivatives.

    PubMed

    Vranicar, L; Pozgan, F; Polanc, S; Kocevar, M

    2003-04-01

    2H-Pyran-2-ones 1 were transformed with various hydrazines into (E)- or (Z)-alpha, beta-didehydro-alpha-amino acid (DDAA) derivatives 4 (and 7) containing a highly substituted pyrazolyl moiety attached at the beta-position. With heterocyclic hydrazines, the products 4 were accompanied also by decarboxylated enamines E-6. In order to separate (E/Z)-mixtures of acids, they were transformed to the corresponding methyl esters 9 and 10 by the application of diazomethane. Catalytic hydrogenation under high pressures with Pd/C as a catalyst resulted in the formation of racemic alanine derivatives 11.

  14. Amino acids of the Murchison meteorite. III - Seven carbon acyclic primary alpha-amino alkanoic acids

    NASA Technical Reports Server (NTRS)

    Cronin, John R.; Pizzarello, Sandra

    1986-01-01

    All of the eighteen possible seven-carbon acyclic primary alpha-amino alkanoic acids have been positively identified in a hot-water extract of the Murchison meteorite by the combined use of gas chromatography-mass spectrometry, ion exchange chromatography and reversed-phase chromatography. None of these amino acids has previously been found in meteorites or in any other natural material. They range in concentration from less than or equal to 0.5 to 5.3 nmol/g. Configuration assignments were made for 2-amino-3,4-dimethylpentanoic acid and allo-2-amino-3,4-dimethylpentanoic acid and the diasteromer ratio was determined. Fifty-five amino acids have now been positively identified in the Murchison meteorite, 36 of which are unknown in terrestrial materials. This unique suite of amino acids is characterized by the occurrence of all structural isomers within the two major classes of amino acids represented, by the predominance of branched chain isomers, and by an exponential decline in amount with increasing carbon chain length within homologous series. These characteristics of the Murchison amino acids are suggestive of synthesis before incorporation into a parent body.

  15. 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.

  16. Saponification of esters of chiral alpha-amino acids anchored through their amine function on solid support.

    PubMed

    Cantel, Sonia; Desgranges, Stéphane; Martinez, Jean; Fehrentz, Jean-Alain

    2004-06-01

    Anchoring an alpha-amino acid residue by its amine function onto a solid support is an alternative to develop chemistry on its carboxylic function. This strategy can involve the use of amino-acid esters as precursors of the carboxylic function. A complete study on the Wang-resin was performed to determine the non racemizing saponification conditions of anchored alpha-amino esters. The use of LiOH, NaOH, NaOSi(Me)3, various solvents and temperatures were tested for this reaction. After saponification and cleavage from the support, samples were examined through their Marfey's derivatives by reversed phase HPLC to evaluate the percentage of racemization.

  17. Estrogen dissociates Tau and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor subunit in postischemic hippocampus.

    PubMed

    Cardona-Gómez, Gloria Patricia; Arango-Davila, Cesar; Gallego-Gómez, Juan Carlos; Barrera-Ocampo, Alvaro; Pimienta, Hernan; Garcia-Segura, Luis Miguel

    2006-08-21

    During cerebral ischemia, part of the damage associated with the hyperactivation of glutamate receptors results from the hyperphosphorylation of the microtubule-associated protein Tau. Previous studies have shown that estradiol treatment reduces neural damage after cerebral ischemia. Here, we show that transient occlusion of the middle cerebral artery results in the hyperphosphorylation of Tau and in a significant increase in the association of Tau with glycogen synthase kinase-3beta and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid type glutamate receptor subunits 2/3 in the hippocampus. Estradiol treatment decreased hippocampal injury, inhibited glycogen synthase kinase-3beta and decreased the hyperphosphorylation of Tau and the interaction of Tau with glycogen synthase kinase-3beta and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor. These findings suggest that ischemia produces a strong association between Tau and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor, and estradiol can exert at least part of its neuroprotective activity through inhibition of glycogen synthase kinase-3beta.

  18. Surface active molecules: preparation and properties of long chain n-acyl-l-alpha-amino-omega-guanidine alkyl acid derivatives.

    PubMed

    Infante, R; Dominguez, J G; Erra, P; Julia, R; Prats, M

    1984-12-01

    Synopsis A new route for the synthesis of long chain N(alpha)-acyl-l-alpha-amino-omega-guamdine alkyl acid derivatives, with cationic or amphoteric character has been established. The general formula of these compounds is shown below. A physico-chemical and antimicrobial study of these products as a function of the alkyl ester or sodium salt (R), the straight chain length of the fatty acid residue (x) and the number of carbons between the omega-guanidine and omega-carboxyl group (n) has been investigated. The water solubility, surface tension, critical micelle concentration (c.m.c.) and minimum inhibitory concentration (MIC) against Gram-positive and Gram-negative bacteria (including Pseudomonas) has been determined. Dicyclohexylcarbodiimide has been used to condense fatty acids and alpha-amino-omega-guanidine alkyl acids. In these conditions protection of the omega-guanidine group is not necessary. The main characteristic of this synthetic procedure is the use of very mild experimental conditions (temperature, pH) to form the amide linkage which leads to pure optical compounds in high yield in the absence of electrolytes. The results show that some structural modifications, particularly the protection of the carboxyl group, promote variations of the surfactant and antimicrobial properties. Only those molecules with the blocked carboxyl group (cationic molecules, where R = Me, Et or Pr) showed a good surfactant and antimicrobial activity. When the carboxyl group was unprotected (amphoteric molecules, where R = Na(+)) the resulting compounds were inactive.

  19. alpha-Hydroxy and alpha-amino acids under possible Hadean, volcanic origin-of-life conditions.

    PubMed

    Huber, Claudia; Wächtershäuser, Günter

    2006-10-27

    To test the theory of a chemoautotrophic origin of life in a volcanic, hydrothermal setting, we explored mechanisms for the buildup of bio-organic compounds by carbon fixation on catalytic transition metal precipitates. We report the carbon monoxide-dependent formation of carbon-fixation products, including an ordered series of alpha-hydroxy and alpha-amino acids of the general formula R-CHA-COOH (where R is H, CH3,C2H5,orHOCH2 and A is OH or NH2) by carbon fixation at 80 degrees to 120 degrees C, catalyzed by nickel or nickel,iron precipitates with carbonyl, cyano, and methylthio ligands as carbon sources, with or without sulfido ligands. Calcium or magnesium hydroxide was added as a pH buffer. The results narrow the gap between biochemistry and volcanic geochemistry and open a new gateway for the exploration of a volcanic, hydrothermal origin of life.

  20. PfEMP1-DBL1alpha amino acid motifs in severe disease states of Plasmodium falciparum malaria.

    PubMed

    Normark, Johan; Nilsson, Daniel; Ribacke, Ulf; Winter, Gerhard; Moll, Kirsten; Wheelock, Craig E; Bayarugaba, Justus; Kironde, Fred; Egwang, Thomas G; Chen, Qijun; Andersson, Björn; Wahlgren, Mats

    2007-10-02

    An infection with Plasmodium falciparum may lead to severe malaria as a result of excessive binding of infected erythrocytes in the microvasculature. Vascular adhesion is mediated by P. falciparum erythrocyte membrane protein-1 (PfEMP1), which is encoded for by highly polymorphic members of the var-gene family. Here, we profile var gene transcription in fresh P. falciparum trophozoites from Ugandan children with malaria through var-specific DBL1alpha-PCR amplification and sequencing. A method for subsectioning region alignments into homology areas (MOTIFF) was developed to examine collected sequences. Specific PfEMP1-DBL1alpha amino acid motifs correlated with rosetting and severe malaria, with motif location corresponding to distinct regions of receptor interaction. The method is potentially applicable to other families of variant proteins and may be useful in identifying sequence-phenotype relationships. The results suggest that certain PfEMP1 sequences are predisposed to inducing severe malaria.

  1. Efficient synthesis of 1-azadienes derived from alpha-aminoesters. Regioselective preparation of alpha-dehydroamino acids, vinylglycines, and alpha-amino acids.

    PubMed

    Palacios, Francisco; Vicario, Javier; Aparicio, Domitila

    2006-09-29

    An efficient synthesis of 1-azadienes derived from alpha-aminoesters is achieved through an aza-Wittig reaction of phosphazenes with beta,gamma-unsaturated alpha-ketoesters. Regioselective 1,2-reduction of these functionalized 1-azadienes affords vinylglycine derivatives, while conjugative 1,4-reduction gives alpha-dehydroamino acid compounds. Reduction of both the carbon-carbon and the imine-carbon-nitrogen double bonds leads to the formation of alpha-amino acid derivatives.

  2. Cloning, sequence analysis, and expression in Escherichia coli of the gene encoding an alpha-amino acid ester hydrolase from Acetobacter turbidans.

    PubMed

    Polderman-Tijmes, Jolanda J; Jekel, Peter A; de Vries, Erik J; van Merode, Annet E J; Floris, René; van der Laan, Jan-Metske; Sonke, Theo; Janssen, Dick B

    2002-01-01

    The alpha-amino acid ester hydrolase from Acetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing beta-lactam antibiotics, such as cephalexin and ampicillin. N-terminal amino acid sequencing of the purified alpha-amino acid ester hydrolase allowed cloning and genetic characterization of the corresponding gene from an A. turbidans genomic library. The gene, designated aehA, encodes a polypeptide with a molecular weight of 72,000. Comparison of the determined N-terminal sequence and the deduced amino acid sequence indicated the presence of an N-terminal leader sequence of 40 amino acids. The aehA gene was subcloned in the pET9 expression plasmid and expressed in Escherichia coli. The recombinant protein was purified and found to be dimeric with subunits of 70 kDa. A sequence similarity search revealed 26% identity with a glutaryl 7-ACA acylase precursor from Bacillus laterosporus, but no homology was found with other known penicillin or cephalosporin acylases. There was some similarity to serine proteases, including the conservation of the active site motif, GXSYXG. Together with database searches, this suggested that the alpha-amino acid ester hydrolase is a beta-lactam antibiotic acylase that belongs to a class of hydrolases that is different from the Ntn hydrolase superfamily to which the well-characterized penicillin acylase from E. coli belongs. The alpha-amino acid ester hydrolase of A. turbidans represents a subclass of this new class of beta-lactam antibiotic acylases.

  3. Partial molar volumes of some alpha-amino acids in aqueous sodium acetate solutions at 308.15 K.

    PubMed

    Wang, J; Yan, Z; Zhuo, K; Lu, J

    1999-08-30

    The apparent molar volumes V(2,phi) have been determined for glycine, DL-alpha-alanine, DL-alpha-amino-n-butyric acid, DL-valine and DL-leucine in aqueous solutions of 0.5, 1.0, 1.5 and 2.0 mol kg(-1) sodium acetate by density measurements at 308.15 K. These data have been used to derive the infinite dilution apparent molar volumes V(0)(2,phi) for the amino acids in aqueous sodium acetate solutions and the standard volumes of transfer, Delta(t)V(0), of the amino acids from water to aqueous sodium acetate solutions. It has been observed that both V(0)(2,phi) and Delta(t)V(0) vary linearly with increasing number of carbon atoms in the alkyl chain of the amino acids. These linear correlations have been utilized to estimate the contributions of the charged end groups (NH(3)(+), COO(-)), CH(2) group and other alkyl chains of the amino acids to V(0)(2,phi) and Delta(t)V(0). The results show that V(0)(2,phi) values for (NH(3)(+), COO(-)) groups increase with sodium acetate concentration, and those for CH(2) are almost constant over the studied sodium acetate concentration range. The transfer volume increases and the hydration number of the amino acids decreases with increasing electrolyte concentrations. These facts indicate that strong interactions occur between the ions of sodium acetate and the charged centers of the amino acids. The volumetric interaction parameters of the amino acids with sodium acetate were calculated in water. The pair interaction parameters are found to be positive and decreased with increasing alkyl chain length of the amino acids, suggesting that sodium acetate has a stronger dehydration effect on amino acids which have longer hydrophobic alkyl chains. These phenomena are discussed by means of the co-sphere overlap model.

  4. Enantiomerically pure trans-beta-lactams from alpha-amino acids via compact fluorescent light (CFL) continuous-flow photolysis.

    PubMed

    Vaske, Yvette S Mimieux; Mahoney, Maximillian E; Konopelski, Joseph P; Rogow, David L; McDonald, William J

    2010-08-18

    Photolysis of alpha-diazo-N-methoxy-N-methyl (Weinreb) beta-ketoamides derived from enantiomerically pure (EP) alpha-amino acids affords the corresponding EP beta-lactams via an intramolecular Wolff rearrangement. The photochemistry is promoted with either standard UV irradiation or through the use of a 100 W compact fluorescent light; the latter affords a safe and environmentally friendly alternative to standard photolysis conditions. A continuous-flow photochemical reactor made from inexpensive laboratory equipment reduced reaction times and was amenable to scale-up. The diastereoselectivity (cis or trans) of the product beta-lactams has been shown to vary from modest to nearly complete. An extremely facile, atom-economical method for the epimerization of the product mixture to the trans isomer, which is generally highly crystalline, has been developed. Evidence for C3 epimerization of Weinreb amide structures via a nonbasic, purely thermal route is presented. Subsequent transformations of both the Weinreb amide at C3 (beta-lactam numbering) and the amino acid side chain at C4 are well-tolerated, allowing for a versatile approach to diverse beta-lactam structures. The technology is showcased in the synthesis of a common intermediate used toward several carbapenem-derived structures starting from unfunctionalized aspartic acid.

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

    PubMed

    Hill, A R; Böhler, C; Orgel, L E

    1998-06-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    A detailed study on the synthesis of spherical and monodispersed gold nanoparticles (AuNPs) using all of the 20 naturally occurring α-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 α-amino acids as reducing and capping/stabilizing agents serve as a remarkable example of green chemistry.

  8. Novel solid-phase synthesis of thiol-terminated-poly(alpha-amino acid)-drug conjugate.

    PubMed

    Palacios, P; Bussat, P; Bichon, D

    1991-01-01

    A new method using a controlled pore glass solid support for the preparation of a thiol-terminated-polymerdrug, notably poly-L-glutamate-daunomycin having a terminal thiol group, is described. The method consists of first polymerizing an ester-protected glutamic acid onto an amino-disulfide functionalized controlled pore glass support. The ester protecting group is then removed, freeing the gamma-carboxyl groups of the grafted polymer which then allows it to react with daunomycin. Finally, the disulfide bond linking the conjugated polymer-drug to the solid support is broken by thiolysis, thus releasing the desired product. The final product consists of only polymer-drug conjugates with terminal thiol groups (global yield 26%). This novel method is much simpler and more elegant than more conventional preparation methods requiring solution phase techniques.

  9. Thyroid receptor ligands. Part 8: Thyromimetics derived from N-acylated-alpha-amino acid derivatives displaying modulated pharmacological selectivity compared with KB-141.

    PubMed

    Garg, Neeraj; Li, Yi-Lin; Garcia Collazo, Ana Maria; Litten, Chris; Ryono, Denis E; Zhang, Minsheng; Caringal, Yolanda; Brigance, Robert P; Meng, Wei; Washburn, William N; Agback, Peter; Mellström, Karin; Rehnmark, Stefan; Rahimi-Ghadim, Mahmoud; Norin, Thomas; Grynfarb, Marlena; Sandberg, Johnny; Grover, Gary; Malm, Johan

    2007-08-01

    Based on the scaffold of the pharmacologically selective thyromimetic 2b, structurally a close analog to KB-141 (2a), a number of novel N-acylated-alpha-amino acid derivatives were synthesized and tested in a TR radioligand binding assay as well as in a reporter cell assay. On the basis of TRbeta(1)-isoform selectivity and affinity, as well as affinity to the reporter cell assay, 3d was selected for further studies in the cholesterol-fed rat model. In this model 3d revealed an improved therapeutic window between cholesterol and TSH lowering but decreased margins versus tachycardia compared with 2a.

  10. Synthesis of various 3-substituted 1,2,4-oxadiazole-containing chiral beta 3- and alpha-amino acids from Fmoc-protected aspartic acid.

    PubMed

    Hamzé, Abdallah; Hernandez, Jean-François; Fulcrand, Pierre; Martinez, Jean

    2003-09-19

    Various 3-substituted chiral 1,2,4-oxadiazole-containing Fmoc-beta(3)- and -alpha-amino acids were synthesized from Fmoc-(l or d)-Asp(OtBu)-OH and Fmoc-l-Asp-OtBu, respectively, in three steps (i.e., condensation of an aspartyl derivative with differentially substituted amidoximes, formation of the 1,2,4-oxadiazole, and cleavage of the tert-butyl ester). These compounds represent new series of nonnatural amino acids, which could be used in combinatorial synthesis. A simple protocol has been developed to generate the 1,2,4-oxadiazole ring. Indeed, common methods resulted in cleavage of the Fmoc group or required long reaction times. We found that sodium acetate in refluxing ethanol/water (86 degrees C) was a convenient and efficient catalyst to promote conversion of Fmoc-amino acyl amidoximes to 1,2,4-oxadiazoles, and this procedure proved to be compatible with Fmoc protection. It is shown that these compounds can be prepared without significant loss of enantiomerical purity. Furthermore, the alkaline conditions used to cleave the Fmoc protecting group from these compounds did not induce epimerization of their chiral center.

  11. Purification and biochemical characterization of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate-sensitive L-glutamate receptors of pig brain.

    PubMed Central

    Chang, Y C; Wu, T Y; Li, B F; Gao, L H; Liu, C I; Wu, C L

    1996-01-01

    Two preparations of glutamate receptors were purified from the synaptic junctions of pig brain by a combination of detergent solubilization, anion-exchange chromatography, wheat-germ agglutinin affinity chromatography and sedimentation through sucrose gradients. These preparations were enriched in specific L-[3H]glutamate binding activity (> 5000 pmol of glutamate binding sites/mg of protein), and the rank order of ligand affinity for binding to these preparations was: quisqualate > 6-cyano-7- nitroquinoxaline-2,3-dione > alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid (AMPA) > L-glutamate > kainate > > N-methyl-D-aspartate approximately L-2-amino-4-phosphonobutyrate. SDS/PAGE analysis revealed that more than 80% of the protein in either of these preparations appeared as a single protein band of 106 kDa. Two-dimensional gel electrophoresis further revealed that these 106 kDa proteins consisted of a series of acidic proteins which were recognized by antibodies against rat AMPA receptor subunits. These 106 kDa proteins were also recognized by wheatgerm agglutinin and concanavalin A; in addition, peptide N-glycosidase F treatment of these preparations decreased their size to 99 kDa. Our results suggest that the putative glutamate receptors isolated here are likely to belong to the AMPA subtype of glutamate receptors in pig brain. Using the purification procedure reported here, 5 micrograms of AMPA receptor proteins can be isolated from 250 g of pig brain tissue. PMID:8870648

  12. 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. ); Vanderklish, P.; Lynch, G. )

    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.

  13. New chiral didehydroamino acid derivatives from a cyclic glycine template with 3,6-dihydro-2H-1,4-oxazin-2-one structure: applications to the asymmetric synthesis of nonproteinogenic alpha-amino acids.

    PubMed

    Chinchilla, R; Falvello, L R; Galindo, N; Nájera, C

    2000-05-19

    New chiral (Z)-alpha,beta-didehydroamino acid (DDAA) derivatives with 3,5-dihydro-2H-1,4-oxazin-2-one structure 11a-f have been stereoselectively prepared after condensation of chiral glycine equivalent 7 with aldehydes in the presence of K(2)CO(3) under mild solid-liquid phase-transfer catalysis reaction conditions. These new systems have been used in diastereoselective cyclopropanation reactions using Corey's ylide for the asymmetric synthesis of 1-aminocyclopropane-1-carboxylic acids (ACCs) such as allo-corononamic and allo-norcoronamic acids. The hydrogenation reaction of these systems at ambient pressure in the presence of formaldehyde affords saturated oxazinones and N-methylated oxazinones which have been transformed into the N-methyl-alpha-amino acids (N-MAAs) (S)-2-(methylamino)butanoic acid and (S)-N-methylleucine. In addition, the parent alpha, beta-didehydroalanine derivative 11g has been prepared by a direct aminomethylation-elimination sequence from 7 and Eschenmoser's salt and has been used in Diels-Alder cycloaddition with endo selectivity for the synthesis of the enantiomerically pure bicyclic alpha-amino acids (-)-2-aminobicyclo[2.2.1]heptane-2-carboxylic and (-)-2-aminobicyclo[2.2.2]octane-2-carboxylic acids.

  14. DNA cleavage in red light promoted by copper(II) complexes of alpha-amino acids and photoactive phenanthroline bases.

    PubMed

    Patra, Ashis K; Bhowmick, Tuhin; Ramakumar, Suryanarayanarao; Nethaji, Munirathinam; Chakravarty, Akhil R

    2008-12-28

    Ternary copper(II) complexes [Cu(L-trp)(B)(H(2)O)](NO(3)) (1-3) and [Cu(L-phe)(B)(H(2)O)](NO(3)) (4-6) of L-tryptophan (L-trp) and L-phenylalanine (L-phe) having phenanthroline bases (B), viz. 1,10-phenanthroline (phen, 1 and 4), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 2 and 5) and dipyrido[3,2-a:2',3'-c]phenazine (dppz, 3 and 6), were prepared and characterized by physico-chemical techniques. Complexes 3 and 6 were structurally characterized by X-ray crystallography and show the presence of a square pyramidal (4 + 1) CuN(3)O(2) coordination geometry in which the N,O-donor amino acid (L-trp or L-phe) and N,N-donor phenanthroline base bind at the equatorial plane with an aqua ligand coordinated at the elongated axial site. Complex 3 shows significant distortion from the square pyramidal geometry and a strong intramolecular pi-pi stacking interaction between the pendant indole ring of L-trp and the planar dppz aromatic moiety. All the complexes display good binding propensity to the calf thymus DNA giving an order: 3,6 (dppz) > 2,5 (dpq) > 1,4 (phen). The binding constant (K(b)) values are in the range of 2.1 x 10(4)-1.1 x 10(6) mol(-1) with the binding site size (s) values of 0.17-0.63. The phen and dpq complexes are minor groove binders while the dppz analogues bind at the DNA major groove. Theoretical DNA docking studies on 2 and 3 show the close proximity of two photosensitizers, viz. the indole moiety of L-trp and the quinoxaline/phenazine of the dpq/dppz bases, to the complementary DNA strands. Complexes 2 and 3 show oxidative DNA double strand breaks (dsb) of supercoiled (SC) DNA forming a significant quantity of linear DNA along with the nicked circular (NC) form on photoexposure to UV-A light of 365 nm and red light of 647.1 nm (Ar-Kr laser). Complexes 1,5 and 6 show only single strand breaks (ssb) forming NC DNA. The red light induced DNA cleavage involves metal-assisted photosensitization of L-trp and dpq/dppz base resulting in the formation of a reactive

  15. Positive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor modulators have different impact on synaptic transmission in the thalamus and hippocampus.

    PubMed

    Xia, Yan-Fang; Kessler, Markus; Arai, Amy C

    2005-04-01

    Earlier studies showed that positive modulators of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors enhance synaptic responses and facilitate synaptic plasticity. Those studies focused mainly on hippocampal functions. However, AMPA receptors have regionally distinct subunit compositions and thus potencies and efficacies of modulators may vary across the brain. The present study compared the effects of CX546 [1-(1,4-benzodioxan-6-ylcarbonyl) piperidine], a benzamide-type modulator, on synaptic transmission in neurons of the reticular thalamic nucleus (RTN), which regulates the firing mode of relay cells in other thalamic nuclei, and on hippocampal CA1 pyramidal cells. CX546 greatly prolonged synaptic responses in CA1 pyramidal cells, but at the same concentration it had only weak modulatory effects in RTN neurons. Effects on miniature excitatory postsynaptic currents (EPSCs) were similar to those on EPSCs in both regions, suggesting that variations in neuronal morphology and transmitter release kinetics do not account for the differences. Relay cells in the ventrobasal thalamus also exhibited weak modulatory effects that were comparable with those in RTN neurons. Regionally different effects on response duration were also observed with CX516 [BDP-12, 1-(quinoxalin-6-ylcarbonyl)piperidine], a second benzamide drug. In contrast, 100 microM cyclothiazide produced comparable synaptic enhancements in hippocampus and RTN. The regional selectivity of benzamide drugs (ampakines) may be explained, at least in part, by a lower potency at thalamic AMPA receptors, perhaps due to the prevalence of the subunits GluR3 and 4. Although regional preferences of the ampakines were modest in their extent, they may be sufficient to be of relevance when considering future therapeutic applications of such compounds.

  16. Glutamate regulates intracellular calcium and gene expression in oligodendrocyte progenitors through the activation of DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors.

    PubMed Central

    Pende, M; Holtzclaw, L A; Curtis, J L; Russell, J T; Gallo, V

    1994-01-01

    Oligodendrocytes and their progenitors (O-2A) express functional kainate- and DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-preferring glutamate receptors. The physiological consequences of activation of these receptors were studied in purified rat cortical O-2A progenitors and in the primary oligodendrocyte cell line CG-4. Changes in the mRNA levels of a set of immediate early genes were studied and were correlated to intracellular Ca2+ concentration, as measured by fura-2 Ca2+ imaging. Both in CG-4 and in cortical O-2A progenitors, basal mRNA levels of NGFI-A were much higher than c-fos, c-jun, or jun-b. Glutamate, kainate, and AMPA greatly increased NGFI-A mRNA and protein by activation of membrane receptors in a Ca(2+)-dependent fashion. Agonists at non-N-methyl-D-aspartate receptors promoted transmembrane Ca2+ influx through voltage-dependent channels as well as kainate and/or AMPA channels. The influx of Ca2+ ions occurring through glutamate-gated channels was sufficient by itself to increase the expression of NGFI-A mRNA. AMPA receptors were found to be directly involved in intracellular Ca2+ and NGFI-A mRNA regulation, because the effects of kainate were greatly enhanced by cyclothiazide, an allosteric modulator that selectively suppresses desensitization of AMPA but not kainate receptors. Our results indicate that glutamate acting at AMPA receptors regulates immediate early gene expression in cells of the oligodendrocyte lineage by increasing intracellular calcium. Consequently, modulation of these receptor channels may have immediate effects at the genomic level and regulate oligodendrocyte development at critical stages. Images PMID:8159727

  17. Differential effect of beta-N-oxalylamino-L-alanine, the Lathyrus sativus neurotoxin, and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate on the excitatory amino acid and taurine levels in the brain of freely moving rats.

    PubMed

    La Bella, V; Piccoli, F

    2000-05-01

    We studied the effect of beta-oxalylamino-L-alanine, a glutamate analog present in Lathyrus sativus seeds and implicated in the etiopathogenesis of neurolathyrism, and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate on the extracellular levels of aspartate, glutamate and taurine in the primary motor cortex of freely moving rats. We found that while both neurotoxins increase the level of aspartate and glutamate, only (+/-)-alpha(-amino-3-hydroxy-5-methylisoxazole-4-propionate is able to modulate the level of taurine. GYKI-52466, a non-competitive non-NMDA antagonist, inhibited beta-oxalylamino-L-alanine-induced increase of aspartate, but not that of glutamate. Conversely, this antagonist proved to be very efficient in blocking the stimulating effect of (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate on all three amino acids. We suggest that beta-oxalylamino-L-alanine increases the level of glutamate in vivo by a mechanism not connected to its effect on the non-NMDA receptors, which might involve the inhibition of glutamate transport. This would allow the excitatory neurotransmitter to reach a concentration sufficient to stimulate the non-NMDA receptors, which in their turn mediate the specific release of aspartate. Although the role of aspartate as a neurotransmitter is still under discussion, it might indeed amplify the excitotoxic cascade through its action on NMDA receptors. We speculate that this sequence of events might represent an important step in the molecular cascade leading to the appearance of the selective motoneuron degeneration in neurolathyrism.

  18. Neutral penta- and hexacoordinate silicon(IV) complexes containing two bidentate ligands derived from the alpha-amino acids (S)-alanine, (S)-phenylalanine, and (S)-tert-leucine.

    PubMed

    Cota, Smaranda; Beyer, Matthias; Bertermann, Rüdiger; Burschka, Christian; Götz, Kathrin; Kaupp, Martin; Tacke, Reinhold

    2010-06-11

    The neutral hexacoordinate silicon(IV) complex 6 (SiO(2)N(4) skeleton) and the neutral pentacoordinate silicon(IV) complexes 7-11 (SiO(2)N(2)C skeletons) were synthesized from Si(NCO)(4) and RSi(NCO)(3) (R = Me, Ph), respectively. The compounds were structurally characterized by solid-state NMR spectroscopy (6-11), solution NMR spectroscopy (6 and 10), and single-crystal X-ray diffraction (8 and 11 were studied as the solvates 8 x CH(3)CN and 11 x C(5)H(12) x 0.5 CH(3)CN, respectively). The silicon(IV) complexes 6 (octahedral Si-coordination polyhedron) and 7-11 (trigonal-bipyramidal Si-coordination polyhedra) each contain two bidentate ligands derived from an alpha-amino acid: (S)-alanine, (S)-phenylalanine, or (S)-tert-leucine. The deprotonated amino acids act as monoanionic (6) or as mono- and dianionic ligands (7-11). The experimental investigations were complemented by computational studies of the stereoisomers of 6 and 7.

  19. Helix formation in preorganized beta/gamma-peptide foldamers: hydrogen-bond analogy to the alpha-helix without alpha-amino acid residues.

    PubMed

    Guo, Li; Almeida, Aaron M; Zhang, Weicheng; Reidenbach, Andrew G; Choi, Soo Hyuk; Guzei, Ilia A; Gellman, Samuel H

    2010-06-16

    We report the first high-resolution structural data for the beta/gamma-peptide 13-helix (i,i+3 C=O...H-N H-bonds), a secondary structure that is formed by oligomers with a 1:1 alternation of beta- and gamma-amino acid residues. Our characterization includes both crystallographic and 2D NMR data. Previous studies suggested that beta/gamma-peptides constructed from conformationally flexible residues adopt a different helical secondary structure in solution. Our design features preorganized beta- and gamma-residues, which strongly promote 13-helical folding by the 1:1 beta/gamma backbone.

  20. Insights into the mechanisms of ifosfamide encephalopathy: drug metabolites have agonistic effects on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors and induce cellular acidification in mouse cortical neurons.

    PubMed

    Chatton, J Y; Idle, J R; Vågbø, C B; Magistretti, P J

    2001-12-01

    Therapeutic value of the alkylating agent ifosfamide has been limited by major side effects including encephalopathy. Although the underlying biochemical processes of the neurotoxic side effects are still unclear, they could be attributed to metabolites rather than to ifosfamide itself. In the present study, the effects of selected ifosfamide metabolites on indices of neuronal activity have been investigated, in particular for S-carboxymethylcysteine (SCMC) and thiodiglycolic acid (TDGA). Because of structural similarities of SCMC with glutamate, the Ca(2+)(i) response of single mouse cortical neurons to SCMC and TDGA was investigated. SCMC, but not TDGA, evoked a robust increase in Ca(2+)(i) concentration that could be abolished by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), but only partly diminished by the N-methyl-D-aspartate receptor antagonist 10,11-dihydro-5-methyl-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK=801). Cyclothiazide (CYZ), used to prevent AMPA/kainate receptor desensitization, potentiated the response to SCMC. Because activation of AMPA/kainate receptors is known to induce proton influx, the intracellular pH (pH(i)) response to SCMC was investigated. SCMC caused a concentration-dependent acidification that was amplified by CYZ. Since H(+)/monocarboxylate transporter (MCT) activity leads to similar cellular acidification, we tested its potential involvement in the pH(i) response. Application of the lactate transport inhibitor quercetin diminished the pH(i) response to SCMC and TDGA by 43 and 51%, respectively, indicating that these compounds may be substrates of MCTs. Taken together, this study indicates that hitherto apparently inert ifosfamide metabolites, in particular SCMC, activate AMPA/kainate receptors and induce cellular acidification. Both processes could provide the biochemical basis of the observed ifosfamide-associated encephalopathy.

  1. Linking supply to demand: the neuronal monocarboxylate transporter MCT2 and the alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid receptor GluR2/3 subunit are associated in a common trafficking process.

    PubMed

    Pierre, Karin; Chatton, Jean-Yves; Parent, Annabelle; Repond, Cendrine; Gardoni, Fabrizio; Di Luca, Monica; Pellerin, Luc

    2009-05-01

    MCT2 is the major neuronal monocarboxylate transporter (MCT) that allows the supply of alternative energy substrates such as lactate to neurons. Recent evidence obtained by electron microscopy has demonstrated that MCT2, like alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA) receptors, is localized in dendritic spines of glutamatergic synapses. Using immunofluorescence, we show in this study that MCT2 colocalizes extensively with GluR2/3 subunits of AMPA receptors in neurons from various mouse brain regions as well as in cultured neurons. It also colocalizes with GluR2/3-interacting proteins, such as C-kinase-interacting protein 1, glutamate receptor-interacting protein 1 and clathrin adaptor protein. Coimmunoprecipitation of MCT2 with GluR2/3 and C-kinase-interacting protein 1 suggests their close interaction within spines. Parallel changes in the localization of both MCT2 and GluR2/3 subunits at and beneath the plasma membrane upon various stimulation paradigms were unraveled using an original immunocytochemical and transfection approach combined with three-dimensional image reconstruction. Cell culture incubation with AMPA or insulin triggered a marked intracellular accumulation of both MCT2 and GluR2/3, whereas both tumor necrosis factor alpha and glycine (with glutamate) increased their cell surface immunolabeling. Similar results were obtained using Western blots performed on membrane or cytoplasm-enriched cell fractions. Finally, an enhanced lactate flux into neurons was demonstrated after MCT2 translocation on the cell surface. These observations provide unequivocal evidence that MCT2 is linked to AMPA receptor GluR2/3 subunits and undergoes a similar translocation process in neurons upon activation. MCT2 emerges as a novel component of the synaptic machinery putatively linking neuroenergetics to synaptic transmission.

  2. A study of the oligomeric state of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-preferring glutamate receptors in the synaptic junctions of porcine brain.

    PubMed Central

    Wu, T Y; Liu, C I; Chang, Y C

    1996-01-01

    The number of the subunits in an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-preferring L-glutamate receptor in the synaptic junctions of porcine brain was investigated in this study. Upon incubation of the synaptic junctions with three cross-linking regents, dimethyl adipimidate (DMA), dimethyl suberimidate (DMS) and N-succinimidyl-(4-azidophenyl)-1,3'-dithiopropionate (SADP), AMPA receptor subunits in higher-molecular-mass aggregates were detected by immunoblotting. These aggregates migrated as proteins of approx. 200, 300 and 400 kDa. The number and identity of the subunits in a solubilized AMPA receptor were also investigated here. Two samples, W1 and W2, enriched in AMPA receptors were prepared from synaptic junctions by a combination of detergent-solubilization, anion-exchange chromatography and wheatgerm agglutinin affinity chromatography. Hydrodynamic behaviour analyses revealed that the majority of the AMPA receptors in either one of these samples were asymmetrical detergent-surrounded particles with a protein mass around 350 kDa. SDS/PAGE analysis revealed that the majority of AMPA receptors in the W1 sample were comprised of dimers of 106 kDa subunits which were covalently linked by disulphide bonds. Cross-linking these receptors with SADP yielded a new band of approx. 400 kDa. The results obtained here, either from the studies of AMPA receptors embedding in synaptic junctions or from those of detergent-solubilized and partially purified receptors, suggest that AMPA receptors contain a basic core structure comprising of four 106 kDa subunits. PMID:8920974

  3. Synthesis of chiral alpha-amino aldehydes linked by their amine function to solid support.

    PubMed

    Cantel, Sonia; Heitz, Annie; Martinez, Jean; Fehrentz, Jean-Alain

    2004-09-01

    The anchoring of an alpha-amino-acid derivative by its amine function on to a solid support allows some chemical reactions starting from the carboxylic acid function. This paper describes the preparation of alpha-amino aldehydes linked to the support by their amine function. This was performed by reduction with LiAlH4 of the corresponding Weinreb amide linked to the resin. The aldehydes obtained were then involved in Wittig or reductive amination reactions. In addition, the linked Weinreb amide was reacted with methylmagnesium bromide to yield the corresponding ketone. After cleavage from the support, the compounds were obtained in good to excellent yields and characterized.

  4. An easy stereoselective access to beta,gamma-aziridino alpha-amino ester derivatives via mannich reaction of benzophenone imines of glycine esters with N-sulfonyl alpha-chloroaldimines.

    PubMed

    Kiss, Loránd; Mangelinckx, Sven; Sillanpää, Reijo; Fülöp, Ferenc; De Kimpe, Norbert

    2007-09-14

    Mannich-type addition of benzophenone imine glycinates across newly synthesized N-(p-toluenesulfonyl) alpha-chloroaldimines afforded gamma-chloro-alpha,beta-diamino ester derivatives with moderate diastereoselectivity as separable mixtures of anti and syn diastereomers. The gamma-chloro-alpha,beta-diamino esters were efficiently cyclized under basic conditions to the corresponding beta,gamma-aziridino alpha-amino ester derivatives, representing a new class of conformationally constrained heterocyclic alpha,beta-diamino acid derivatives. The relative configuration of the aziridines was determined via X-ray diffraction analysis. Mechanisms and intermediate transition states to explain the stereochemical outcome of the Mannich reaction with different substrates or under different conditions are proposed. The synthetic importance of the beta,gamma-aziridino alpha-amino ester derivatives is demonstrated by their conversion into the corresponding Boc-protected derivatives and ring opening reactions to alpha,beta-diamino esters and a gamma-amino alpha,beta-unsaturated amino ester.

  5. Peptide backbone folding induced by the C(alpha)-tetrasubstituted cyclic alpha-amino acids 4-amino-1,2-dithiolane-4-carboxylic acid (Adt) and 1-aminocyclopentane-1-carboxylic acid (Ac5c). A joint computational and experimental study.

    PubMed

    Aschi, Massimiliano; Lucente, Gino; Mazza, Fernando; Mollica, Adriano; Morera, Enrico; Nalli, Marianna; Paglialunga Paradisi, Mario

    2003-06-07

    The conformational study of a new group of synthetic peptides containing 4-amino-1,2-dithiolane-4-carboxylic acid (Adt), a cysteine-related achiral residue, has been carried out through a joint application of computational and experimental methodologies. Molecular Dynamics simulations clearly suggest the tendency of this molecule to adopt a gamma-turn conformation in vacuum and help in analyzing the complex and crucial conformational behaviour of the dithiolane ring which appears to preferentially adopt a C(S)-like structure. Electronic structure calculations carried out in solution using the Density Functional Theory also indicate the preservation of the gamma-like folding in apolar solvents and the helix-like one in more polar solvents. A comparison with the achiral 1-aminocycloalkane-1-carboxylic acid (Ac5c) has been carried out using the same computational tools. NMR and IR data on dipeptide derivatives containing the Adt or Ac5c residue show that in chloroform solution all the models prefer a gamma-turn structure, centered at the cyclic residue, stabilized by an intramolecular H-bond, whereas in a more polar solvent, i.e. dimethyl sulfoxide, this folding is not maintained. The experimental conformational studies, extended to N-Boc protected tripeptides, clearly indicate the remarkable tendency of both the five-membered C(alpha)-tetrasubstituted cyclic amino acids Adt and Ac5c to induce the gamma-turn structure also in models able to adopt the beta-bend conformation.

  6. Catalytic asymmetric synthesis of {alpha}-amino phosphonates using lanthanoid-potassium-BINOL complexes

    SciTech Connect

    Sasai, Hiroaki; Arai, Shigeru; Shibasaki, Masakatsu

    1995-10-20

    {alpha}-Amino phosphonic acids 3 are interesting compounds in the design of enzyme inhibitors. The concept of mimicking tetrahedral transition states of enzyme-medicated peptide bond hydrolysis previously led to the successful design and synthesis of phosphonamide-containing peptides as a promising new class of proteinase inhibitors. It is not surprising that the absolute configuration of the {alpha}-carbon strongly influences the biological properties of 3. Several methods for the synthesis of optically active {alpha}-aminophosphonic acids have been published. The authors report here the first example of a catalytic asymmetric hydrophosphonylation to imines using lanthanoid-potassium-BINOL heterobimetallic complexes (LnPB, Ln = lanthanoid metal), which gives optically active {alpha}-amino phosphonates in modest to high enantiometric excess. 17 refs., 1 tab.

  7. Methyl 2-((succinimidooxy)carbonyl)benzoate (MSB): a new, efficient reagent for N-phthaloylation of amino acid and peptide derivatives.

    PubMed

    Casimir, J Richard; Guichard, Gilles; Briand, Jean-Paul

    2002-05-31

    A new, efficient, and readily available reagent, methyl 2-((succinimidooxy)carbonyl)benzoate (MSB), for N-phthaloylation of amino acids and amino acid derivatives is described. The phthaloylation procedure is simple and racemization-free and gives excellent results with alpha-amino acids, alpha-amino alcohols, dipeptides, alpha-amino carboxamides, and alpha-amino esters.

  8. The effect of N-substituted alkyl groups on the anticonvulsant activities ofN-Cbz-alpha-amino-N-alkylsuccinimides.

    PubMed

    Lee, J; Son, K; Jung, K; Choi, J; Park, M

    1997-02-01

    For the purpose of defining the effects of theN-substituted alkyl groups on the anticonvulsant activities ofN-Cbz-alpha-aminosuccinimides, various (R)-and(S)-N-alkyl substitutedN-Cbz-alpha-aminosuccinimides (1 and2) were prepared from the corresponding (R)-and(S)-N-Cbz-aspartic acid by using known reaction and were evaluated the anticonvulsant activies in the MES and PTZ tests, including their neurotoxicities. The most active compound in the MES test was(R)-N-Cbz-alpha-amino-N-methylsuccinimide (1b) (ED(50)=52.5 mg/kg, Pl-3.2). And in case of the PTZ test,(R)-N-Cbz-alpha-amino-N-ethylsuccinimide (1c) was the most active compound (ED(50)=32.5 mg/kg, Pl=3.1). The order of anticonvulsant activities of these compounds against the MES test, as judged from the ED(50) values for theR series (1), wasN-methyl >N-isobutyl > non-substituted >N-ethyl,N-allyl >N-benzyl compound; for theS series (2)N-methyl >N-allyl > non-substituted >N-isobutyl >N-ethyl >N-benzyl compound. The anticonvulsant activities in the PTZ tests of these compounds exhibited somewhat different pattern; for theR series (1)N-ethyl >N-methyl >N-isobutyl> non-substituted >N-allyl >N-benzyl compound in order of decreasing activity; forS series (2)N-ethyl >N-allyl, non-substituted >N-isobutyl >N-methyl >N-benzyl compound in order of decreasing activity.

  9. Minimal genome encoding proteins with constrained amino acid repertoire

    PubMed Central

    Tsoy, Olga; Yurieva, Marina; Kucharavy, Andrey; O'Reilly, Mary; Mushegian, Arcady

    2013-01-01

    Minimal bacterial gene set comprises the genetic elements needed for survival of engineered bacterium on a rich medium. This set is estimated to include 300–350 protein-coding genes. One way of simplifying an organism with such a minimal genome even further is to constrain the amino acid content of its proteins. In this study, comparative genomics approaches and the results of gene knockout experiments were used to extrapolate the minimal gene set of mollicutes, and bioinformatics combined with the knowledge-based analysis of the structure-function relationships in these proteins and their orthologs, paralogs and analogs was applied to examine the challenges of completely replacing the rarest residue, cysteine. Among several known functions of cysteine residues, their roles in the active centers of the enzymes responsible for deoxyribonucleoside synthesis and transfer RNA modification appear to be crucial, as no alternative chemistry is known for these reactions. Thus, drastic reduction of the content of the rarest amino acid in a minimal proteome appears to be possible, but its complete elimination is challenging. PMID:23873957

  10. Phenylalanine ammonia lyase from Arabidopsis thaliana (AtPAL2): a potent enzyme for the synthesis of non-canonical aromatic alpha-amino acids: Part I: Comparative characterization to the enzymes from Petroselinum crispum (PcPAL1) and Rhodosporidium toruloides (RtPAL).

    PubMed

    Dreßen, Alana; Hilberath, Thomas; Mackfeld, Ursula; Billmeier, Arne; Rudat, Jens; Pohl, Martina

    2017-04-06

    Phenylalanine ammonia lyase (PAL) from Arabidopsis thaliana (AtPAL2) was comparatively characterized to the well-studied enzyme from parsley (PcPAL1) and Rhodosporidium toruloides (RtPAL) with respect to kinetic parameters for the deamination and the amination reaction, pH- and temperature optima and the substrate range of the amination reaction. Whereas both plant enzymes are specific for phenylalanine, the bifunctional enzyme from Rhodosporidium toruloides shows KM-values for L-Phe and L-Tyr in the same order of magnitude and, compared to both plant enzymes, a 10-15-fold higher activity. At 30°C all enzymes were sufficiently stable with half-lives of 3.4days (PcPAL1), 4.6days (AtPAL2) and 9.7days (RtPAL/TAL). Very good results for the amination of various trans-cinnamic acid derivatives were obtained using E. coli cells as whole cell biocatalysts in ammonium carbonate buffer. Investigation of the substrate ranges gave interesting results for the newly tested enzymes from A. thaliana and R. toruloides. Only the latter accepts besides 4-hydroxy-CA also 3-methoxy-4-hydroxy-CA as a substrate, which is an interesting intermediate for the formation of pharmaceutically relevant L-Dopa. AtPAL2 is a very good catalyst for the formation of (S)-3-F-Phe, (S)-4-F-Phe and (S)-2-Cl-Phe. Such non-canonical amino acids are valuable building blocks for the formation of various drug molecules.

  11. A straightforward three-component synthesis of alpha-amino esters containing a phenylalanine or a phenylglycine scaffold.

    PubMed

    Haurena, Caroline; Le Gall, Erwan; Sengmany, Stéphane; Martens, Thierry; Troupel, Michel

    2010-04-16

    A range of alpha-amino esters has been synthesized in good to high yields using a straightforward three-component reaction among preformed or in situ generated aromatic or benzylic organozinc reagents, primary or secondary amines, and ethyl glyoxylate. The procedure, which is characterized by its simplicity, allows the concise synthesis of esters bearing a phenylglycine or a phenylalanine scaffold.

  12. Phosphorus constrains accelerated nitrogen cycling in limed acidic forests

    NASA Astrophysics Data System (ADS)

    Deforest, J. L.; Shaw, A. N.; Kluber, L. A.; Burke, D. J.; Carrino-Kyker, S. R.; Smemo, K. A.

    2011-12-01

    Anthropogenic deposition can increase phosphorus (P) limitation by abiotic and biotic means. Soil acidification can remove P from available pools and nitrogen (N) deposition can increase the demand for P. We reason that chronic acidic deposition is promoting P limitation in acidic hardwood forests and thereby altering N cycling. The objectives of this study were to investigate the interactive influence of P availability and soil pH on N and P cycling and availability to determine if the response varies between two physiographic regions experiencing similar chronic acidic deposition. We addressed these objectives by experimentally manipulating soil pH, P, or both in strongly acidic glaciated and unglaciated hardwood forests in eastern Ohio, USA. Our results suggest complex interactions between P, soil pH, and the N cycle. Glaciated soils were found to be more N-saturated with nitrification rates 18 times greater than in unglaciated soils. Elevating pH, with or without added P, doubled nitrification rates in glaciated soils. For unglaciated soils, raising pH increased nitrification 10-fold, but increased nitrification only 5-fold in combination with P. This result suggests raising soil pH lowered the demand of soil N, or directly stimulated nitrifying activity, and that increasing P availability could limit N availability. To various degrees, readily available P was geochemically or biologically immobilized in all treatments, suggesting chronic P deficiency in these ecosystems. Phosphorus immobilization decreased as soil pH was elevated, but elevated P either had no effect (glaciated) or doubled P immobilization rates (unglaciated). These results suggest that raising soil pH reduces microbial P limitation for phosphate, whereas adding P appears to make phosphate scarcer. We suggest that P plays an important role in N transformations and cycling, but appears more important in unglaciated soils than in glaciated soils. Chronic soil acidification may have a greater

  13. Lanthanum(III) and praseodymium(III) derivatives with dithiocarbamates derived from alpha-amino acids.

    PubMed

    Rai, Anita; Sengupta, Soumitra K; Pandey, Om P

    2006-06-01

    Lanthanum(III) and praseodymium(III) complexes with dithiocarbamates have been synthesized by the reactions of lanthanum(III) and praseodymium(III) chloride with barium dithiocarbamate and complexes of type [LnCl(L)H2O]n have been obtained (where Ln=La(III) or Pr(III); L=barium salt of dithiocarbamate derived from glycine, L-leucine, L-valine, DL-alanine). The complexes have been characterized by elemental analysis, molar conductance, electronic absorption and fluorescence, infrared, far infrared, 1H NMR spectral studies. The presence of coordinated water molecule is inferred from thermogravimetric analysis which indicates the loss of one water molecule at 150-170 degrees C. The oscillator strength, Judd-Ofelt intensity parameter, stimulated emission cross-section, etc. have been obtained for different transitions of Pr3+.

  14. CycloPs: generating virtual libraries of cyclized and constrained peptides including nonnatural amino acids.

    PubMed

    Duffy, Fergal J; Verniere, Mélanie; Devocelle, Marc; Bernard, Elise; Shields, Denis C; Chubb, Anthony J

    2011-04-25

    We introduce CycloPs, software for the generation of virtual libraries of constrained peptides including natural and nonnatural commercially available amino acids. The software is written in the cross-platform Python programming language, and features include generating virtual libraries in one-dimensional SMILES and three-dimensional SDF formats, suitable for virtual screening. The stand-alone software is capable of filtering the virtual libraries using empirical measurements, including peptide synthesizability by standard peptide synthesis techniques, stability, and the druglike properties of the peptide. The software and accompanying Web interface is designed to enable the rapid generation of large, structurally diverse, synthesizable virtual libraries of constrained peptides quickly and conveniently, for use in virtual screening experiments. The stand-alone software, and the Web interface for evaluating these empirical properties of a single peptide, are available at http://bioware.ucd.ie .

  15. Does aspartic acid racemization constrain the depth limit of the subsurface biosphere?

    PubMed

    Onstott, T C; Magnabosco, C; Aubrey, A D; Burton, A S; Dworkin, J P; Elsila, J E; Grunsfeld, S; Cao, B H; Hein, J E; Glavin, D P; Kieft, T L; Silver, B J; Phelps, T J; van Heerden, E; Opperman, D J; Bada, J L

    2014-01-01

    Previous studies of the subsurface biosphere have deduced average cellular doubling times of hundreds to thousands of years based upon geochemical models. We have directly constrained the in situ average cellular protein turnover or doubling times for metabolically active micro-organisms based on cellular amino acid abundances, D/L values of cellular aspartic acid, and the in vivo aspartic acid racemization rate. Application of this method to planktonic microbial communities collected from deep fractures in South Africa yielded maximum cellular amino acid turnover times of ~89 years for 1 km depth and 27 °C and 1-2 years for 3 km depth and 54 °C. The latter turnover times are much shorter than previously estimated cellular turnover times based upon geochemical arguments. The aspartic acid racemization rate at higher temperatures yields cellular protein doubling times that are consistent with the survival times of hyperthermophilic strains and predicts that at temperatures of 85 °C, cells must replace proteins every couple of days to maintain enzymatic activity. Such a high maintenance requirement may be the principal limit on the abundance of living micro-organisms in the deep, hot subsurface biosphere, as well as a potential limit on their activity. The measurement of the D/L of aspartic acid in biological samples is a potentially powerful tool for deep, fractured continental and oceanic crustal settings where geochemical models of carbon turnover times are poorly constrained. Experimental observations on the racemization rates of aspartic acid in living thermophiles and hyperthermophiles could test this hypothesis. The development of corrections for cell wall peptides and spores will be required, however, to improve the accuracy of these estimates for environmental samples.

  16. Does aspartic acid racemization constrain the depth limit of the subsurface biosphere?

    SciTech Connect

    Onstott, T. C.; Aubrey, A.D.; Kieft, T L; Silver, B J; Phelps, Tommy Joe; Van Heerden, E.; Opperman, D. J.; Bada, J L.

    2014-01-01

    Previous studies of the subsurface biosphere have deduced average cellular doubling times of hundreds to thousands of years based upon geochemical models. We have directly constrained the in situ average cellular protein turnover or doubling times for metabolically active micro-organisms based on cellular amino acid abundances, D/L values of cellular aspartic acid, and the in vivo aspartic acid racemization rate. Application of this method to planktonic microbial communities collected from deep fractures in South Africa yielded maximum cellular amino acid turnover times of ~89 years for 1 km depth and 27 C and 1 2 years for 3 km depth and 54 C. The latter turnover times are much shorter than previously estimated cellular turnover times based upon geochemical arguments. The aspartic acid racemization rate at higher temperatures yields cellular protein doubling times that are consistent with the survival times of hyperthermophilic strains and predicts that at temperatures of 85 C, cells must replace proteins every couple of days to maintain enzymatic activity. Such a high maintenance requirement may be the principal limit on the abundance of living micro-organisms in the deep, hot subsurface biosphere, as well as a potential limit on their activity. The measurement of the D/L of aspartic acid in biological samples is a potentially powerful tool for deep, fractured continental and oceanic crustal settings where geochemical models of carbon turnover times are poorly constrained. Experimental observations on the racemization rates of aspartic acid in living thermophiles and hyperthermophiles could test this hypothesis. The development of corrections for cell wall peptides and spores will be required, however, to improve the accuracy of these estimates for environmental samples.

  17. Does Aspartic Acid Racemization Constrain the Depth Limit of the Subsurface Biosphere?

    NASA Technical Reports Server (NTRS)

    Onstott, T C.; Magnabosco, C.; Aubrey, A. D.; Burton, A. S.; Dworkin, J. P.; Elsila, J. E.; Grunsfeld, S.; Cao, B. H.; Hein, J. E.; Glavin, D. P.; Kieft, T. L.; Silver, B. J.; Phelps, T. J.; Heerden, E. Van; Opperman, D. J.; Bada, J. L.

    2013-01-01

    Previous studies of the subsurface biosphere have deduced average cellular doubling times of hundreds to thousands of years based upon geochemical models. We have directly constrained the in situ average cellular protein turnover or doubling times for metabolically active micro-organisms based on cellular amino acid abundances, D/L values of cellular aspartic acid, and the in vivo aspartic acid racemization rate. Application of this method to planktonic microbial communities collected from deep fractures in South Africa yielded maximum cellular amino acid turnover times of approximately 89 years for 1 km depth and 27 C and 1-2 years for 3 km depth and 54 C. The latter turnover times are much shorter than previously estimated cellular turnover times based upon geochemical arguments. The aspartic acid racemization rate at higher temperatures yields cellular protein doubling times that are consistent with the survival times of hyperthermophilic strains and predicts that at temperatures of 85 C, cells must replace proteins every couple of days to maintain enzymatic activity. Such a high maintenance requirement may be the principal limit on the abundance of living micro-organisms in the deep, hot subsurface biosphere, as well as a potential limit on their activity. The measurement of the D/L of aspartic acid in biological samples is a potentially powerful tool for deep, fractured continental and oceanic crustal settings where geochemical models of carbon turnover times are poorly constrained. Experimental observations on the racemization rates of aspartic acid in living thermophiles and hyperthermophiles could test this hypothesis. The development of corrections for cell wall peptides and spores will be required, however, to improve the accuracy of these estimates for environmental samples.

  18. Access to enantioenriched alpha-amino esters via rhodium-catalyzed 1,4-addition/enantioselective protonation.

    PubMed

    Navarre, Laure; Martinez, Rémi; Genet, Jean-Pierre; Darses, Sylvain

    2008-05-14

    Conjugate addition of potassium trifluoro(organo)borates 2 to dehydroalanine derivatives 1, mediated by a chiral rhodium catalyst and in situ enantioselective protonation, afforded straightforward access to a variety of protected alpha-amino esters 3 with high yields and enantiomeric excesses up to 95%. Among the tested chiral ligands and proton sources, Binap, in combination with guaiacol (2-methoxyphenol), an inexpensive and nontoxic phenol, afforded the highest asymmetric inductions. Organostannanes have also shown to participate in this reaction. By a fine-tuning of the ester moiety, and using Difluorophos as chiral ligand, increased levels of enantioselectivity, generally close to 95%, were achieved. Deuterium labeling experiments revealed, and DFT calculation supported, an unusual mechanism involving a hydride transfer from the amido substituent to the alpha carbon explaining the high levels of enantioselectivity attained in controlling this alpha chiral center.

  19. 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.

  20. Design, synthesis, and biological evaluation of conformationally constrained aci-reductone mimics of arachidonic acid.

    PubMed

    Hopper, A T; Witiak, D T; Ziemniak, J

    1998-02-12

    An efficient and convergent synthesis has been developed for the production of 3,4-dihydroxy-5-[4-(2-((2Z)-hexenyl)phenyl)-3-(1Z)-but enyl]-2 (5H)-furanone (12d). This hydrophobic antioxidant is a stable conformationally constrained mimic of arachidonic acid (AA) (1) and its respective aci-reductone analogue (2). Pd(0)-catalyzed cross-coupling of 5-(3-butynyl)-3,4-dihydroxy-2(5H)-furanone (7) with 2-((2Z)-hexenyl)iodobenzene (8d) followed by Lindlar catalyzed hydrogenation produces 12d. Butynyl intermediate 7 is prepared from 2-(benzyloxy)-5-deoxyascorbic acid (15) by iodination (I2, PPh3, Imd), iodo substitution with lithium acetylide ethylenediamine complex (LiAEDA, HMPA, -5 degrees C), and benzyl group cleavage (Ac2O, Pyr, BCl3). The utility of this synthetic method was demonstrated by the synthesis of analogues 10e-k. Biological testing revealed that certain of these antioxidants inhibit both cyclooxygenase (COX) and 5-lipoxygenase (5-LO) with comparable efficacy as reported for aspirin and zileuton, respectively. The antioxidant activity of these aci-reductones, measured as a function of their inhibitory effect on CCl4-induced lipid peroxidation of hepatic microsomes, exceeds that produced by alpha-tocopherol. Synthetic routes and initial structure-activity relationships (SAR) for these novel mixed functioning antioxidants are presented.

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

    SciTech Connect

    Shalaby, M.A.; Grote, C.W.; Rapoport, H.

    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.

  2. Evidence for a Dual Role of an Active Site Histidine in [alpha]-Amino-[beta]-carboxymuconate-[epsilon]-semialdehyde Decarboxylase

    SciTech Connect

    Huo, Lu; Fielding, Andrew J.; Chen, Yan; Li, Tingfeng; Iwaki, Hiroaki; Hosler, Jonathan P.; Chen, Lirong; Hasegawa, Yoshie; Que, Jr., Lawrence; Liu, Aimin

    2012-10-09

    The previously reported crystal structures of {alpha}-amino-{beta}-carboxymuconate-{epsilon}-semialdehyde decarboxylase (ACMSD) show a five-coordinate Zn(II)(His){sub 3}(Asp)(OH{sub 2}) active site. The water ligand is H-bonded to a conserved His228 residue adjacent to the metal center in ACMSD from Pseudomonas fluorescens (PfACMSD). Site-directed mutagenesis of His228 to tyrosine and glycine in this study results in a complete or significant loss of activity. Metal analysis shows that H228Y and H228G contain iron rather than zinc, indicating that this residue plays a role in the metal selectivity of the protein. As-isolated H228Y displays a blue color, which is not seen in wild-type ACMSD. Quinone staining and resonance Raman analyses indicate that the blue color originates from Fe(III)-tyrosinate ligand-to-metal charge transfer. Co(II)-substituted H228Y ACMSD is brown in color and exhibits an electron paramagnetic resonance spectrum showing a high-spin Co(II) center with a well-resolved {sup 59}Co (I = 7/2) eight-line hyperfine splitting pattern. The X-ray crystal structures of as-isolated Fe-H228Y (2.8 {angstrom}) and Co-substituted (2.4 {angstrom}) and Zn-substituted H228Y (2.0 {angstrom} resolution) support the spectroscopic assignment of metal ligation of the Tyr228 residue. The crystal structure of Zn-H228G (2.6 {angstrom}) was also determined. These four structures show that the water ligand present in WT Zn-ACMSD is either missing (Fe-H228Y, Co-H228Y, and Zn-H228G) or disrupted (Zn-H228Y) in response to the His228 mutation. Together, these results highlight the importance of His228 for PfACMSD's metal specificity as well as maintaining a water molecule as a ligand of the metal center. His228 is thus proposed to play a role in activating the metal-bound water ligand for subsequent nucleophilic attack on the substrate.

  3. Laboratory and field measurements to constrain atmospheric sources of acetic and formic acids

    NASA Astrophysics Data System (ADS)

    Baasandorj, M.; Hu, L.; Mitroo, D.; Martinez, R.; Walker, M.; Williams, B. J.; Millet, D. B.

    2013-12-01

    Acetic and formic acids are the most abundant organic acids in the atmosphere. They play an important role in atmospheric aqueous chemistry as they can influence the acidity of precipitation, cloud droplets, and atmospheric aerosols. Sources of these acids are highly uncertain, but include secondary production from VOC oxidation, direct emissions, and possibly organic aerosol aging. Here we present measurements of formic and acetic acid, along with a suite of other gas and particle phase species, from a field study in St. Louis during summer 2013. Calibration procedures and results are discussed, and we interpret the ambient formic and acetic acid measurements in terms of patterns of variability and implied constraints on sources. Finally, we present results from oxidative aging experiments on both ambient and test organic aerosol designed to assess the importance of this mechanism as a source of gas-phase carboxylic acids.

  4. Expression of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) GluR2/3 receptors in the developing rat pineal gland.

    PubMed

    Kaur, C; Sivakumar, V; Ling, E A

    2005-10-01

    The expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) type glutamate (GluR2/3) receptors and N-methyl-D-aspartate receptor subtype 1 (NMDAR1) was carried out by immunohistochemistry, double immunofluorescence and real-time RT-PCR analysis in the pineal glands of 1-day to 6-wk-old rats in the present study. GluR2/3 immunopositive cells were distributed throughout the pineal gland and showed branching processes in all age groups. The NMDAR1 immunoreactivity, however, was observed in fewer branched cells. A constitutive mRNA expression of NMDAR1, GluR2 and GluR3 was detected in the pineal glands of various ages and showed no significant difference between the age groups studied. Immunohistochemical and double immunofluorescence results showed that the GluR2/3 were mainly expressed and co-localized with OX-42-positive microglia/macrophages and the glial fibrillary acidic protein (GFAP)-positive astrocytes. Co-localization of NMDAR1 with OX-42- and GFAP-positive cells was much less. The expression of these receptors on the glial cells suggests that they may be involved in the development and growth of the pineal gland in the early postnatal period (1 day to 3 wk) and subsequently in the regulation of melatonin synthesis.

  5. Modulation of N-methyl-D-aspartate and (R,S)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) responses of spinal nociceptive neurons by a N-terminal fragment of substance P.

    PubMed

    Budai, D; Wilcox, G L; Larson, A A

    1992-06-17

    The effects of an N-terminal fragment of substance P, substance P-(1-7) [SP-(1-7)], on the responses of dorsal horn nociceptive neurons to N-methyl-D-aspartate (NMDA) and (R,S)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) were tested by combined single-unit extracellular recordings/microiontophoresis. While SP-(1-7) had no effects when applied by itself, it was a potent and long-lasting modulator of both NMDA- and AMPA-mediated excitation of spinal dorsal horn nociceptive neurons. NMDA responses were transiently decreased (by an average of 36% of control at minimum) by SP-(1-7) followed by a more sustained increase (by 76% at maximum). In contrast, AMP responses were only increased by SP-(1-7) (by 81% at maximum). It is hypothesized that the actions of SP-(1-7) on excitatory amino acid (EAA) responses of dorsal horn nociceptive neurons reflect a novel mechanism by which SP and EAAs interact to modulate pain transmission.

  6. Expedited Phonon Transfer in Interfacially Constrained Polymer Chain along Self-Organized Amino Acid Crystals.

    PubMed

    Mu, Liwen; Li, Yifan; Mehra, Nitin; Ji, Tuo; Zhu, Jiahua

    2017-04-05

    In this work, poly(vinyl alcohol) (PVA)/amino acid (AA) composites were prepared by a self-organized crystallization process. Five different AAs (cysteine, aspartic acid, glutamic acid, ornithine, and lysine) were selected based on their similar functional groups but different molecular structures. The different PVA-AA interactions in the five PVA/AA composites lead to two crystal patterns, i.e., continuous network (cysteine and lysine) and discrete particles (glutamic acid, ornithine, and aspartic acid). Scanning thermal microscopy is then applied to map the distribution of thermal conduction in these composites. It is found that the interface surrounding the crystals plays a dominating role in phonon transport where the polymer chains are greatly restrained by the interfacial confinement effect. Continuous crystal network builds up a continuous interface that facilitates phonon transfer while phonon scattering occurs in discrete crystalline structures. Significantly improved thermal conductivity of ∼0.7 W/m·K is observed in PVA/cysteine composite with AA loading of 8.4 wt %, which corresponds to a 170% enhancement as compared to pure PVA. The strong PVA-AA molecular interaction and self-organized crystal structure are considered the major reasons for the unique interface property and superior thermal conductivity.

  7. The crystal structure of human alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase in complex with 1,3-dihydroxyacetonephosphate suggests a regulatory link between NAD synthesis and glycolysis.

    PubMed

    Garavaglia, Silvia; Perozzi, Silvia; Galeazzi, Luca; Raffaelli, Nadia; Rizzi, Menico

    2009-11-01

    The enzyme alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase (ACMSD) is a zinc-dependent amidohydrolase that participates in picolinic acid (PA), quinolinic acid (QA) and NAD homeostasis. Indeed, the enzyme stands at a branch point of the tryptophan to NAD pathway, and determines the final fate of the amino acid, i.e. transformation into PA, complete oxidation through the citric acid cycle, or conversion into NAD through QA synthesis. Both PA and QA are key players in a number of physiological and pathological conditions, mainly affecting the central nervous system. As their relative concentrations must be tightly controlled, modulation of ACMSD activity appears to be a promising prospect for the treatment of neurological disorders, including cerebral malaria. Here we report the 2.0 A resolution crystal structure of human ACMSD in complex with the glycolytic intermediate 1,3-dihydroxyacetonephosphate (DHAP), refined to an R-factor of 0.19. DHAP, which we discovered to be a potent enzyme inhibitor, resides in the ligand binding pocket with its phosphate moiety contacting the catalytically essential zinc ion through mediation of a solvent molecule. Arg47, Asp291 and Trp191 appear to be the key residues for DHAP recognition in human ACMSD. Ligand binding induces a significant conformational change affecting a strictly conserved Trp-Met couple, and we propose that these residues are involved in controlling ligand admission into ACMSD. Our data may be used for the design of inhibitors with potential medical interest, and suggest a regulatory link between de novo NAD biosynthesis and glycolysis.

  8. Preferential labeling of alpha-amino N-terminal groups in peptides by biotin: application to the detection of specific anti-peptide antibodies by enzyme immunoassays.

    PubMed

    Sélo, I; Négroni, L; Créminon, C; Grassi, J; Wal, J M

    1996-12-15

    Experimental conditions (pH 6.5, 24 h reaction, peptide:biotin ratio 1:5) were defined for preferential incorporation of the biotin molecule in the N-terminal alpha-amino group of peptides. This strategy could be helpful in numerous applications when an entire peptide chain must remain accessible for antibody or receptor binding. We illustrate this advantage in a solid-phase enzyme immunoassay designed to detect antibodies specific for bovine beta-lactoglobulin present in rabbit or human sera. This test involves synthetic peptides biotinylated in different positions and immobilized on a solid phase. The use of biotin/streptavidin interactions permitted more efficient detection of specific anti-peptide antibodies than solid phases prepared using conventional passive-adsorption techniques. The highest levels of antibody binding were measured when biotinylation occurred at the N-terminal extremity of immobilized peptides.

  9. Pyridoxine-dependent seizures caused by alpha amino adipic semialdehyde dehydrogenase deficiency: the first polish case with confirmed biochemical and molecular pathology.

    PubMed

    Kaczorowska, Magdalena; Kmiec, Tomasz; Jakobs, Cornelis; Kacinski, Marek; Kroczka, Slawomir; Salomons, Gajja S; Struys, Eduard A; Jozwiak, Sergiusz

    2008-12-01

    Pyridoxine-dependent seizures are a rare condition recognized when numerous seizures respond to pyridoxine treatment and recur on pyridoxine withdrawal. For decades the diagnosis was confirmed only with pyridoxine treatment withdrawal trial. Recently described biochemical and molecular pathology improved the diagnostic process for those cases in which seizures are caused by alpha amino adipic semialdehyde dehydrogenase deficiency. This article presents a girl with recurrent status epilepticus episodes resistant to phenobarbital and phenytoin and partly responding to midazolam. Eventually the seizures were completely controlled with pyridoxine; however, due to the severe condition of this child when seizing, no trial of withdrawal has been performed. The diagnosis of pyridoxine-dependent seizures was confirmed with biochemical and molecular testing revealing elevated alpha-AASA excretion and the presence of 2 different mutations in the antiquitin ( ALDH7A1) gene. Due to the availability of reliable laboratory testing, confirmation of the diagnosis was made without the life-threatening trial of pyridoxine withdrawal.

  10. Structural Analysis of a β-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 β-helical nanostructure by position-specific mutations. The nanostructure is constructed through the self-assembly of the β-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 β-helical motif. PMID:18811190

  11. Acylation of the alpha-amino group in neuropeptide Y(12-36) increases binding affinity for the Y2 receptor.

    PubMed

    Murase, S; Yumoto, N; Petukhov, M G; Yoshikawa, S

    1996-01-01

    Competition assays using three series of analogs of neuropeptide Y (NPY) ([Xaa11]NPY(11-36), [Xaa12]NPY(12-36), and [Xaa13]NPY(13-36) revealed that the binding affinity for the Y2 receptor was considerably lowered by truncation of residue 11. Upon acetylation or succinylation of the alpha-amino group, the binding affinity of [Xaa12]NPY(12-36) recovered to a level similar to that of [Xaa11]NPY(11-36). No significant difference was observed between the increases caused by acetylation and those caused by succinylation, suggesting that the increase in binding affinity cannot be explained by the change in the net charge at the N-terminus as a consequence of the modification. The scattered data points on a plot of the alpha-helix content vs. IC50 of all these analogs revealed the absence of any apparent relationship, an indication that prior formation of the alpha-helix is not necessary for binding to the Y2 receptor. It has been widely accepted that fewer than 12 residues from the C-terminus are directly involved in binding of NPY to the Y2 receptor, while the remaining part of NPY only assists in the adoption of a favorable conformation by the C-terminal hexapeptide for recognition by the receptor. However, the present results suggest that the region around residue 12 does not project from the Y2 receptor.

  12. Metabolism of citric acid production by Aspergillus niger: model definition, steady-state analysis and constrained optimization of citric acid production rate.

    PubMed

    Alvarez-Vasquez, F; González-Alcón, C; Torres, N V

    2000-10-05

    In an attempt to provide a rational basis for the optimization of citric acid production by A. niger, we developed a mathematical model of the metabolism of this filamentous fungus when in conditions of citric acid accumulation. The present model is based in a previous one, but extended with the inclusion of new metabolic processes and updated with currently available kinetic data. Among the different alternatives to represent the system behavior we have chosen the S-system representation within power-law formalism. This type of representation allows us to verify not only the ability of the model to exhibit a stable steady state of the integrated system but also the robustness and quality of the representation. The model analysis is shown to be self-consistent, with a stable steady state, and in good agreement with experimental evidence. Moreover, the model representation is sufficiently robust, as indicated by sensitivity and steady-state and dynamic analyses. From the steady-state results we concluded that the range of accuracy of the S-system representation is wide enough to model realistic deviations from the nominal steady state. The dynamic analysis indicated a reasonable response time, which provided further indication that the model is adequate. The extensive assessment of the reliability and quality of the model put us in a position to address questions of optimization of the system with respect to increased citrate production. We carried out the constrained optimization of A. niger metabolism with the goal of predicting an enzyme activity profile yielding the maximum rate of citrate production, while, at the same time, keeping all enzyme activities within predetermined, physiologically acceptable ranges. The optimization is based on a method described and tested elsewhere that utilizes the fact that the S-system representation of a metabolic system becomes linear at steady state, which allows application of linear programming techniques. Our results show

  13. Piracetam defines a new binding site for allosteric modulators of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors.

    PubMed

    Ahmed, Ahmed H; Oswald, Robert E

    2010-03-11

    Glutamate receptors are the most prevalent excitatory neurotransmitter receptors in the vertebrate central nervous system and are important potential drug targets for cognitive enhancement and the treatment of schizophrenia. Allosteric modulators of AMPA receptors promote dimerization by binding to a dimer interface and reducing desensitization and deactivation. The pyrrolidine allosteric modulators, piracetam and aniracetam, were among the first of this class of drugs to be discovered. We have determined the structure of the ligand binding domain of the AMPA receptor subtypes GluA2 and GluA3 with piracetam and a corresponding structure of GluA3 with aniracetam. Both drugs bind to GluA2 and GluA3 in a very similar manner, suggesting little subunit specificity. However, the binding sites for piracetam and aniracetam differ considerably. Aniracetam binds to a symmetrical site at the center of the dimer interface. Piracetam binds to multiple sites along the dimer interface with low occupation, one of which is a unique binding site for potential allosteric modulators. This new site may be of importance in the design of new allosteric regulators.

  14. Synthesis of both enantiomers of hemiesters by enantioselective methanolysis of meso cyclic anhydrides catalyzed by alpha-amino acid-derived chiral thioureas.

    PubMed

    Manzano, Rubén; Andrés, José M; Muruzábal, María-Dolores; Pedrosa, Rafael

    2010-08-06

    Both ureas and thioureas derived from L- or D-valine act as bifunctional organocatalysts able to induce the enantioselective alcoholysis of mono-, bi-, and tricyclic meso anhydrides. The desymmetrization occurs in near quantitative yields and excellent enantiomeric ratios (up to >99:<1) under low catalyst loading. Both enantiomers of the hemiesters can be directly obtained by changing the configuration of the catalyst.

  15. Enantioselective high-performance liquid chromatographic separation of N-methyloxycarbonyl unsaturated amino acids on macrocyclic glycopeptide stationary phases.

    PubMed

    Boesten, J M M; Berkheij, M; Schoemaker, H E; Hiemstra, H; Duchateau, A L L

    2006-03-03

    This paper describes the enantiomeric resolution of a series of unsaturated N-methyloxycarbonyl-alpha-H-alpha-amino acids (N-MOC-alpha-amino acids) on macrocyclic glycopeptide stationary phases by means of high-performance liquid chromatography (HPLC). Three types of glycopeptide phases, i.e. Chirobiotic T, V and R, were evaluated in both reversed-phase (RP) and polar ionic mode (PIM). The best results in terms of enantioselectivity and resolution were obtained on Chirobiotic R phase, with the PIM mobile phase giving the highest resolution per min. Investigation of the pH of the reversed-phase mobile phase in the pH range 4.1-5.9 showed little effect on enantioselectivity. The method was applied for monitoring the conversion and product enantiomeric excess of an enzymatic hydrolysis reaction using N-MOC-alpha-H-alpha-amino acid esters as substrate.

  16. Phosphate Stability in Diagenetic Fluids Constrains the Acidic Alteration Model for Lower Mt. Sharp Sedimentary Rocks in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Berger, J. A.; Schmidt, M. E.; Izawa, M. R. M.; Gellert, R.; Ming, D. W.; Rampe, E. B.; VanBommel, S. J.; McAdam, A. C.

    2016-01-01

    The Mars rover Curiosity has encountered silica-enriched bedrock (as strata and as veins and associated halos of alteration) in the largely basaltic Murray Fm. of Mt. Sharp in Gale Crater. Alpha Particle X-ray Spectrometer (APXS) investigations of the Murray Fm. revealed decreasing Mg, Ca, Mn, Fe, and Al, and higher S, as silica increased (Fig. 1). A positive correlation between SiO2 and TiO2 (up to 74.4 and 1.7 wt %, respectively) suggests that these two insoluble elements were retained while acidic fluids leached more soluble elements. Other evidence also supports a silica-retaining, acidic alteration model for the Murray Fm., including low trace element abundances consistent with leaching, and the presence of opaline silica and jarosite determined by CheMin. Phosphate stability is a key component of this model because PO4 3- is typically soluble in acidic water and is likely a mobile ion in diagenetic fluids (pH less than 5). However, the Murray rocks are not leached of P; they have variable P2O5 (Fig. 1) ranging from average Mars (0.9 wt%) up to the highest values in Gale Crater (2.5 wt%). Here we evaluate APXS measurements of Murray Fm. bedrock and veins with respect to phosphate stability in acidic fluids as a test of the acidic alteration model for the Lower Mt. Sharp rocks.

  17. Highly efficient coupling of beta-substituted aminoethane sulfonyl azides with thio acids, toward a new chemical ligation reaction.

    PubMed

    Merkx, Remco; Brouwer, Arwin J; Rijkers, Dirk T S; Liskamp, Rob M J

    2005-03-17

    [reaction: see text] A highly efficient coupling of protected beta-substituted aminoethane sulfonyl azides with thio acids is reported. In the case of peptide thio acids, this method encompasses a new chemoselective ligation method. Furthermore, the resulting alpha-amino acyl sulfonamides can be alkylated with suitable electrophiles to obtain densely functionalized sulfonamide scaffolds.

  18. 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.

  19. 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.

  20. Selective Michael-aldol reaction by use of sterically hindered aluminum aryloxides as Lewis acids: an easy approach to cyclobutane amino acids.

    PubMed

    Avenoza, Alberto; Busto, Jesús H; Canal, Noelia; Peregrina, Jesús M; Pérez-Fernández, Marta

    2005-08-04

    A formal [2 + 2] cycloaddition of 2-amidoacrylates with monosubstituted donor olefins, including its asymmetric version, is described. The stereoselectivity of this reaction can be modulated by the use of sterically hindered aluminum aryloxides or methylaluminoxane as Lewis acids. The reaction was applied to the synthesis of both stereoisomers of 2-benzyloxycyclobutane-alpha-amino acid, which are protected serine analogues c(4)Ser(OBn).

  1. Roles of fragile X mental retardation protein in dopaminergic stimulation-induced synapse-associated protein synthesis and subsequent alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-4-propionate (AMPA) receptor internalization.

    PubMed

    Wang, Hansen; Kim, Susan S; Zhuo, Min

    2010-07-09

    Fragile X syndrome, the most common form of inherited mental retardation, is caused by the absence of the RNA-binding protein fragile X mental retardation protein (FMRP). FMRP regulates local protein synthesis in dendritic spines. Dopamine (DA) is involved in the modulation of synaptic plasticity. Activation of DA receptors can regulate higher brain functions in a protein synthesis-dependent manner. Our recent study has shown that FMRP acts as a key messenger for DA modulation in forebrain neurons. Here, we demonstrate that FMRP is critical for DA D1 receptor-mediated synthesis of synapse-associated protein 90/PSD-95-associated protein 3 (SAPAP3) in the prefrontal cortex (PFC). DA D1 receptor stimulation induced dynamic changes of FMRP phosphorylation. The changes in FMRP phosphorylation temporally correspond with the expression of SAPAP3 after D1 receptor stimulation. Protein phosphatase 2A, ribosomal protein S6 kinase, and mammalian target of rapamycin are the key signaling molecules for FMRP linking DA D1 receptors to SAPAP3. Knockdown of SAPAP3 did not affect surface expression of alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-4-propionate (AMPA) GluR1 receptors induced by D1 receptor activation but impaired their subsequent internalization in cultured PFC neurons; the subsequent internalization of GluR1 was also impaired in Fmr1 knock-out PFC neurons, suggesting that FMRP may be involved in subsequent internalization of GluR1 through regulating the abundance of SAPAP3 after DA D1 receptor stimulation. Our study thus provides further insights into FMRP involvement in DA modulation and may help to reveal the molecular mechanisms underlying impaired learning and memory in fragile X syndrome.

  2. Early continuous white noise exposure alters l-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor subunit glutamate receptor 2 and gamma-aminobutyric acid type a receptor subunit beta3 protein expression in rat auditory cortex.

    PubMed

    Xu, Jinghong; Yu, Liping; Zhang, Jiping; Cai, Rui; Sun, Xinde

    2010-02-15

    Auditory experience during the postnatal critical period is essential for the normal maturation of auditory function. Previous studies have shown that rearing infant rat pups under conditions of continuous moderate-level noise delayed the emergence of adult-like topographic representational order and the refinement of response selectivity in the primary auditory cortex (A1) beyond normal developmental benchmarks and indefinitely blocked the closure of a brief, critical-period window. To gain insight into the molecular mechanisms of these physiological changes after noise rearing, we studied expression of the AMPA receptor subunit GluR2 and GABA(A) receptor subunit beta3 in the auditory cortex after noise rearing. Our results show that continuous moderate-level noise rearing during the early stages of development decreases the expression levels of GluR2 and GABA(A)beta3. Furthermore, noise rearing also induced a significant decrease in the level of GABA(A) receptors relative to AMPA receptors. However, in adult rats, noise rearing did not have significant effects on GluR2 and GABA(A)beta3 expression or the ratio between the two units. These changes could have a role in the cellular mechanisms involved in the delayed maturation of auditory receptive field structure and topographic organization of A1 after noise rearing.

  3. Exogenous amino acids as fuel in shock.

    PubMed

    Daniel, A M; Kapadia, B; MacLean, L D

    1982-01-01

    It has been suggested that in shock branched-chain amino acids are preferentially oxidized resulting in continued proteolysis and stimulated gluconeogenesis. To determine if exogenous amino acids could be used as fuel in shock, dogs rendered hypotensive by controlled cardiac tamponade and normotensive controls were infused with amino acid mixtures and individual amino acids. When Nephramine, a mixture rich in branched-chain amino acids, was infused, plasma alpha-amino nitrogen levels rose but urea output did not increase in either the control state or in shock, suggesting that these amino acids were not rapidly deaminated to serve as fuels. Travasol, which in addition contained large amounts of alanine and glycine, tripled urea output in the controls and doubled it in shock. The limit of urea production was reached in both groups at 35 mumoles urea/minute/kg. In the Travasol-infused animals plasma alpha-amino nitrogen levels were maintained in normotension but rose sharply in shock. When glycine alone was infused into five dogs in shock urea production rate was 30.6 + 2.1 mumoles/minute/kg; with alanine the same value was 22.5 + 2.2 mumoles/minute/kg. In both cases plasma alpha-amino nitrogen levels were high, suggesting that transport of these amino acids into the cell was slow in shock. In four dogs in shock glycine-14C was added to the glycine infusate as a tracer. At radioactive equilibrium 28% of the label infused appeared in CO2; another 22% appeared in glucose. It is concluded that of all the amino acids tested only glycine and alanine are deaminated rapidly enough to serve as exogenous fuels in shock.

  4. Polymerization of beta-amino acids in aqueous solution

    NASA Technical Reports Server (NTRS)

    Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    We have compared carbonyl diimidazole (CDI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as activating agents for the oligomerization of negatively-charged alpha- and beta-amino acids in homogeneous aqueous solution. alpha-Amino acids can be oligomerized efficiently using CDI, but not by EDAC. beta-Amino acids can be oligomerized efficiently using EDAC, but not by CDI. Aspartic acid, an alpha- and beta-dicarboxylic acid is oligomerized efficiently by both reagents. These results are explained in terms of the mechanisms of the reactions, and their relevance to prebiotic chemistry is discussed.

  5. Deuterium Enrichment of Amino and Hydroxy Acids Found in the Murchison Meteorite: Constraints on Parent Body Conditions

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    The alpha-amino and alpha-hydroxy acids found in the Murchison carbonaceous chondrite are deuterium enriched. These compounds are thought to have originated from common deuterium enriched carbonyl precursors, by way of a Strecker synthesis which took place in a solution of HCN, NH3, and carbonyl compounds during the period of aqueous alteration of the meteorite parent body. However, the hydroxy acids found on Murchison are less deuterium enriched than the amino acids. With the objective of determining if the discrepancy in deuterium enrichment between the amino acids and the hydroxy acids found on Murchison is consistent with their formation in a Strecker synthesis, we have measured the deuterium content of alpha-amino and alpha-hydroxy acids produced in solutions of deuterated carbonyl compounds, KCN and NH4Cl, and also in mixtures of such solutions and Allende dust at 263 K and 295 K. Retention of the isotopic signature of the starting carbonyl by both alpha amino acids and alpha hydroxy acids is more dependent upon temperature, concentration and pH than upon the presence of meteorite dust in the solution. The constraints these observations place on Murchison parent body conditions will be discussed.

  6. Elevation of serum levels of beta-aminoisobutyric acid in uremic patients and the toxicity of the amino acid.

    PubMed

    Gejyo, F; Kinoshita, Y; Ikenaka, T

    1977-12-01

    A reliable method for the determination of beta-aminoisobutyric acid in serum was developed utilizing an automated amino acid analyzer. The serum concentrations of beta-aminoisobutyric acid were determined in 20 normal subjects and in 71 uremic patients. The mean serum level of beta-aminoisobutyric acid was markedly increased in the uremic patients to 0.856 +/- 0.910 (mean +/- SD) mg/100 ml as compared with a normal value of 0.026 +/- 0.027 mg/100 ml. The distribution of serum beta-aminoisobutyric acid level in uremic patients was wide-spread, and there was no correlation between the serum levels of the amino acid and those of urea nitrogen, creatinine and uric acid. The toxicity of beta-aminoisobutyric acid on mice with acute renal failure induced by uranyl acetate was investigated and compared with that of alpha-amino-n-butyric acid and gamma-amino-n-butyric acid. All mice given more than 4 g/kg body wt of beta-aminoisobutyric acid showed twitching and cramps, and some of them died. However, the control mice given an equivalent dose of alpha-amino-n-butyric acid or gamma-amino-n-butyric acid showed no change. These results suggest that beta-aminoisobutyric acid might be a factor influencing the development and progression of uremic toxemia.

  7. Constraining Galileon inflation

    SciTech Connect

    Regan, Donough; Anderson, Gemma J.; Hull, Matthew; Seery, David E-mail: G.Anderson@sussex.ac.uk E-mail: D.Seery@sussex.ac.uk

    2015-02-01

    In this short paper, we present constraints on the Galileon inflationary model from the CMB bispectrum. We employ a principal-component analysis of the independent degrees of freedom constrained by data and apply this to the WMAP 9-year data to constrain the free parameters of the model. A simple Bayesian comparison establishes that support for the Galileon model from bispectrum data is at best weak.

  8. 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

  9. Pharmacology of the inhibitory glycine receptor: agonist and antagonist actions of amino acids and piperidine carboxylic acid compounds.

    PubMed

    Schmieden, V; Betz, H

    1995-11-01

    To define structure-activity relations for ligands binding to the inhibitory glycine receptor (GlyR), the agonistic and antagonistic properties of alpha- and beta-amino acids were analyzed at the recombinant human alpha 1 GlyR expressed in Xenopus oocytes. The agonistic activity of alpha-amino acids exhibited a marked stereoselectivity and was highly susceptible to substitutions at the C alpha-atom. In contrast, alpha-amino acid antagonism was not enantiomer dependent and was influenced little by C alpha-atom substitutions. The beta-amino acids taurine, beta-aminobutyric acid (beta-ABA), and beta-aminoisobutyric acid (beta-AIBA) are partial agonists at the GlyR. Low concentrations of these compounds competitively inhibited glycine responses, whereas higher concentrations elicited a significant membrane current. Nipecotic acid, which contains a trans-beta-amino acid configuration, behaved as purely competitive GlyR antagonist. Our data are consistent with the existence of a common binding site for all amino acid agonists and antagonists, at which the functional consequences of binding depend on the particular conformation a given ligand adopts within the binding pocket. In the case of beta-amino acids, the trans conformation appears to mediate antagonistic receptor binding, and the cis conformation appears to mediate agonistic receptor binding. This led us to propose that the partial agonist activity of a given beta-amino acid is determined by the relative mole fractions of the respective cis/trans conformers.

  10. Positive modulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors reverses sub-chronic PCP-induced deficits in the novel object recognition task in rats.

    PubMed

    Damgaard, Trine; Larsen, Dorrit Bjerg; Hansen, Suzanne L; Grayson, Ben; Neill, Jo C; Plath, Niels

    2010-02-11

    Cognitive deficits are a major clinical unmet need in schizophrenia. The psychotomimetic drug phencyclidine (PCP) is widely applied in rodents to mimic symptoms of schizophrenia, including cognitive deficits. Previous studies have shown that sub-chronic PCP induces an enduring episodic memory deficit in female Lister Hooded rats in the novel object recognition (NOR) task. Here we show that positive modulation of AMPA receptor (AMPAR) mediated glutamate transmission alleviates cognitive deficits induced by sub-chronic PCP treatment. Female Lister hooded rats were treated sub-chronically with either vehicle (0.9% saline) or PCP (2mg/kg two doses per day for 7 days), followed by a 7 days washout period. 30 min prior to the acquisition trial of the NOR task animals were dosed with either vehicle, CX546 (10, 40 or 80 mg/kg) or CX516 (0.5, 2.5, 10, 40 or 80 mg/kg). Our results show that sub-chronic PCP treatment induced a significant decrease in the discrimination index (DI) and both ampakines CX546 and CX516 were able to reverse this disruption of object memory in rats in the novel object recognition task. These data suggest that positive AMPAR modulation may represent a mechanism for treatment of cognitive deficits in schizophrenia.

  11. Constraining the dark fluid

    SciTech Connect

    Kunz, Martin; Liddle, Andrew R.; Parkinson, David; Gao Changjun

    2009-10-15

    Cosmological observations are normally fit under the assumption that the dark sector can be decomposed into dark matter and dark energy components. However, as long as the probes remain purely gravitational, there is no unique decomposition and observations can only constrain a single dark fluid; this is known as the dark degeneracy. We use observations to directly constrain this dark fluid in a model-independent way, demonstrating, in particular, that the data cannot be fit by a dark fluid with a single constant equation of state. Parametrizing the dark fluid equation of state by a variety of polynomials in the scale factor a, we use current kinematical data to constrain the parameters. While the simplest interpretation of the dark fluid remains that it is comprised of separate dark matter and cosmological constant contributions, our results cover other model types including unified dark energy/matter scenarios.

  12. Synthesis of constrained analogues of tryptophan

    PubMed Central

    Negrato, Marco; Abbiati, Giorgio; Dell’Acqua, Monica

    2015-01-01

    Summary A Lewis acid-catalysed diastereoselective [4 + 2] cycloaddition of vinylindoles and methyl 2-acetamidoacrylate, leading to methyl 3-acetamido-1,2,3,4-tetrahydrocarbazole-3-carboxylate derivatives, is described. Treatment of the obtained cycloadducts under hydrolytic conditions results in the preparation of a small library of compounds bearing the free amino acid function at C-3 and pertaining to the class of constrained tryptophan analogues. PMID:26664620

  13. Adipic acid increases plasma lysine but does not improve the efficiency of lysine utilization in swine.

    PubMed

    van Kempen, T A; van Heugten, E; Trottier, N L

    2001-09-01

    Adipic acid, upon catabolism, results in intermediates that bear a structural similarity to lysine degradation products. The objectives of this research were to determine whether adipic acid affects lysine concentrations in plasma and to evaluate whether adipic acid improves the efficiency of lysine utilization in pigs. In Exp. 1, nursery pigs (n = 14) were fed (for a period of 7 d) either a standard nursery diet or the same diet supplemented with 1% adipic acid to assess effects on plasma amino acid concentrations (plasma collected on d 7). In Exp. 2, nursery pigs (n = 56) were fed (for a period of 15 d) either a control diet or the same diet but deficient in either lysine, threonine, or tryptophan with or without supplemental adipic acid to assess the effects of adipic acid on the efficiency of amino acid utilization. The results from Exp. 1 showed that adipic acid increased plasma lysine (by 18%) but not alpha-amino adipic acid, an intermediate in lysine degradation. Experiment 2 demonstrated that adipic acid did not increase the efficiency of utilization of lysine, threonine, or tryptophan. The lack of effects on alpha-amino adipic acid in Exp. 1 and the lack of a positive effect on the efficiency of utilization of lysine, threonine, and tryptophan suggest that adipic acid does not inhibit the mitochondrial uptake of lysine and(or) its degradation in the mitochondrion. It is concluded that feeding adipic acid increases plasma lysine but does not improve the efficiency of lysine utilization.

  14. Constrained control allocation

    NASA Technical Reports Server (NTRS)

    Durham, Wayne C.

    1992-01-01

    This paper addresses the problem of the allocation of several flight controls to the generation of specified body-axis moments. The number of controls is greater than the number of moments being controlled, and the ranges of the controls are constrained to certain limits. The controls are assumed to be individually linear in their effect throughout their ranges of motion, and independent of one another in their effects. The geometries of the subset of the constrained controls and of its image in moment space are examined. A direct method of allocating these several controls is presented, that guarantees the maximum possible moment is generated within the constraints of the controls. The results are illustrated by an example problem involving three controls and two moments.

  15. 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.

  16. 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).

  17. 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.

  18. Constrained space camera assembly

    DOEpatents

    Heckendorn, Frank M.; Anderson, Erin K.; Robinson, Casandra W.; Haynes, Harriet B.

    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.

  19. 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.

  20. Effects of amino acid additives during hemodialysis of children.

    PubMed

    Abitbol, C L; Mrozinska, K; Mandel, S; McVicar, M; Wapnir, R A

    1984-01-01

    The intradialytic losses into the dialysate of free amino acids (AA) and alpha-amino nitrogen were determined during the dialysis of three children. Variations in plasma AA were determined pre- and postdialysis. The effect of these losses with the addition of an Abbott General Amino Acid Mixture to the dialysate in concentrations of 8.5, 17, and 34 mg/100 ml was studied. The major determinant of AA losses was the plasma concentration of the AA before beginning the dialysis treatment. Dialysance of individual AA varied inversely with their molecular weights. A zero flux of alpha-amino nitrogen occurred at a derived concentration of 22 mg/100 ml of the AA additive in the dialysate. Plasma concentrations of nonessential amino acids were little affected by the dialysate additive. In contrast, total essential amino acid nitrogen which fell during baseline dialyses showed significant improvement when the AA solution was added to the dialysate. This study suggests that the addition of AA to the dialysate bath may be effective in decreasing AA nitrogen losses during dialysis.

  1. Constrained space camera assembly

    DOEpatents

    Heckendorn, F.M.; Anderson, E.K.; Robinson, C.W.; Haynes, H.B.

    1999-05-11

    A constrained space camera assembly which is intended to be lowered through a hole into a tank, a borehole or another cavity is disclosed. 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. 17 figs.

  2. Power-constrained supercomputing

    NASA Astrophysics Data System (ADS)

    Bailey, Peter E.

    As we approach exascale systems, power is turning from an optimization goal to a critical operating constraint. With power bounds imposed by both stakeholders and the limitations of existing infrastructure, achieving practical exascale computing will therefore rely on optimizing performance subject to a power constraint. However, this requirement should not add to the burden of application developers; optimizing the runtime environment given restricted power will primarily be the job of high-performance system software. In this dissertation, we explore this area and develop new techniques that extract maximum performance subject to a particular power constraint. These techniques include a method to find theoretical optimal performance, a runtime system that shifts power in real time to improve performance, and a node-level prediction model for selecting power-efficient operating points. We use a linear programming (LP) formulation to optimize application schedules under various power constraints, where a schedule consists of a DVFS state and number of OpenMP threads for each section of computation between consecutive message passing events. We also provide a more flexible mixed integer-linear (ILP) formulation and show that the resulting schedules closely match schedules from the LP formulation. Across four applications, we use our LP-derived upper bounds to show that current approaches trail optimal, power-constrained performance by up to 41%. This demonstrates limitations of current systems, and our LP formulation provides future optimization approaches with a quantitative optimization target. We also introduce Conductor, a run-time system that intelligently distributes available power to nodes and cores to improve performance. The key techniques used are configuration space exploration and adaptive power balancing. Configuration exploration dynamically selects the optimal thread concurrency level and DVFS state subject to a hardware-enforced power bound

  3. 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.

  4. Constraining Dark Energy

    NASA Astrophysics Data System (ADS)

    Abrahamse, Augusta

    2010-12-01

    Future advances in cosmology will depend on the next generation of cosmological observations and how they shape our theoretical understanding of the universe. Current theoretical ideas, however, have an important role to play in guiding the design of such observational programs. The work presented in this thesis concerns the intersection of observation and theory, particularly as it relates to advancing our understanding of the accelerated expansion of the universe (or the dark energy). Chapters 2 - 4 make use of the simulated data sets developed by the Dark Energy Task Force (DETF) for a number of cosmological observations currently in the experimental pipeline. We use these forecast data in the analysis of four quintessence models of dark energy: the PNGB, Exponential, Albrecht-Skordis and Inverse Power Law (IPL) models. Using Markov Chain Monte Carlo sampling techniques we examine the ability of each simulated data set to constrain the parameter space of these models. We examine the potential of the data for differentiating time-varying models from a pure cosmological constant. Additionally, we introduce an abstract parameter space to facilitate comparison between models and investigate the ability of future data to distinguish between these quintessence models. In Chapter 5 we present work towards understanding the effects of systematic errors associated with photometric redshift estimates. Due to the need to sample a vast number of deep and faint galaxies, photometric redshifts will be used in a wide range of future cosmological observations including gravitational weak lensing, baryon accoustic oscillations and type 1A supernovae observations. The uncertainty in the redshift distributions of galaxies has a significant potential impact on the cosmological parameter values inferred from such observations. We introduce a method for parameterizing uncertainties in modeling assumptions affecting photometric redshift calculations and for propagating these

  5. Imino Acids in the Murchison Meteorite: Evidence of Strecker Reactions

    NASA Technical Reports Server (NTRS)

    Lerner, N. R.; Cooper, G. W.

    2003-01-01

    Both alpha-amino acids and alpha-hydroxy acids occur in aqueous extracts of the Murchison carbonaceous meteorite. The Strecker-cyanohydrin reaction, the reaction of carbonyl compounds, cyanide, and ammonia to produce amino and hydroxy acids, has been proposed as a source of such organic acids in meteorites. Such syntheses are consistent with the suggestion that interstellar precursors of meteoritic organic compounds accreted on the meteorite parent body together with other ices. Subsequent internal heating of the parent body melted these ices and led to the formation of larger compounds in synthetic reactions during aqueous alteration, which probably occurred at temperatures between 273K and 298K. In the laboratory, imino acids are observed as important by-products of the Strecker synthesis.

  6. Reappraisal of the 20th-century version of amino acid metabolism.

    PubMed

    Katagiri, Masayuki; Nakamura, Masahiko

    2003-12-05

    In this article, we advocate the radical revision of the 20th-century version of amino acid metabolism as follows. (1) Classic studies on the incorporation of [15N]ammonia into glutamate, once considered to be an epoch-making event, are not distinctive proof of the ability of animals to utilize ammonia for the synthesis of alpha-amino nitrogen. (2) Mammalian glutamate dehydrogenase has been implicated to function as a glutamate-synthesizing enzyme albeit lack of convincing proof. This enzyme, in combination with aminotransferases, is now known to play an exclusive role in the metabolic removal of amino nitrogen and energy production from excess amino acids. (3) Dr. William C Rose's "nutritionally nonessential amino acids" are, of course, essential in cellular metabolism; the nutritional nonessentiality is related to their carbon skeletons, many of which are intermediates of glycolysis or the TCA cycle. Obviously, the prime importance of amino acid nutrition should be the means of obtaining amino nitrogen. (4) Because there is no evidence of the presence of any glutamate-synthesizing enzymes in mammalian tissues, animals must depend on plants and microorganisms for preformed alpha-amino nitrogen. This is analogous to the case of carbohydrates. (5) In contrast, individual essential amino acids, similar to vitamins and essential fatty acids, should be considered important nutrients that must be included regularly in sufficient amounts in the diet.

  7. [The relatioship between decomposition of amino acid chloramines and their structures].

    PubMed

    Roshchupkin, D I; Murina, M A; Petrova, A O; Sergienko, V I

    2009-01-01

    Rate constants of the decomposition of monoamine alpha-amino acid chloramine derivatives were determined by a spectrophotometeric method. Several amino acid chloramines with elevated stability have been found. These included n-chloroglycine, n-chlorovaline, n-chlorothreonine, and n-chloroisoleucine. Their molecular structures are characterized by some characteristic feature at the beta-position. In the case of glycine chloramine, carbon atom at this position is absent, and the chloramine derivatives of three other amino acids possess branched chains. Partial atomic charges of the electrostatic potential (Wang-Ford) for chloramines of alpha-amino acids were computed using the semiempirical quantum-mechanical method AM1. The chloramines with elevated stability have high positive sums of charges of three carbon atoms that are atoms at alpha- and beta-positions and a carboxyl group atom. High partial charge also was obtained for one carbon atom at the beta-position. These computational values may be employed for prediction of the stability of designed amino acid chloramines. One of the important predictions is that the highest atomic charges and stabilities are characteristics of the amino acid chloramines, in which all hydrogen atoms at the beta-position are replaced by carbon-hydrogen chains or hydroxyl groups.

  8. The effect of experimental ischaemia and excitatory amino acid agonists on the GABA and serotonin immunoreactivities in the rabbit retina.

    PubMed

    Osborne, N N; Herrera, A J

    1994-04-01

    The aim of the described experiments was to use immunohistochemistry to visualize the release of GABA from specific retinal amacrine cells following ischaemia and to establish the involvement of defined glutamatergic receptors. In initial experiments, rabbit retinas were exposed in vitro to excitatory amino acid agonists alone or in combination with a putative antagonist, or in physiological solution lacking oxygen and glucose, or in solution containing potassium cyanide for 45 min at 37 degrees C. The nature of the GABA immunoreactivity was then examined by immunohistochemistry. In other in vitro experiments, retinas were first allowed to accumulate exogenous serotonin before exposing the tissues to the combinations as described. These tissues were then processed immunohistochemically for the localization of serotonin. In yet other experiments, the intraocular pressure of a rabbit's eye was raised to about 110 mmHg for 60 min and a reperfusion time of 45 min allowed before dissecting the retina and processing for the localization of GABA immunoreactivity. The other eye served as a control. Of the excitatory amino acid agonists tested, only N-methyl-D-aspartate, kainate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid caused a change in the GABA immunoreactivity. The N-methyl-D-aspartate effect was specifically antagonized by dizocilpine maleate, dextromethorphan and memantine, and was characterized by a reduction in the number of GABA-immunoreactive perikarya. The GABA "staining" in the inner plexiform layer also appeared as four clear bands. The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid- and kainate-induced effects were both antagonized by 6-cyano-2,3-dihydroxy-7-nitroquinoxaline-2,3-dione and partially by kynurenic acid at the concentrations used. Here, the amount of GABA-positive perikarya was greatly reduced and three immunoreactive bands appeared in the inner plexiform layer. However, for low concentrations of alpha-amino-3-hydroxy

  9. Isotopic analyses of amino acids from the Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Pizzarello, S.; Cronin, J. R.; Krishnamurthy, R. V.; Epstein, S.

    1991-01-01

    An account is given of the results of H-2, C-13 isotopic analyses of the Murchison meteorite incorporating an ultrafiltration step to exclude the possibility of fine particulate contaminants. The meteorite's amino acids were chromatographically separated in order to preclude isotopic enrichment by basic compounds other than the amino acids. The results indicate that the Murchison amino acids are isotopically highly unusual; delta-C-13 is elevated by about 40 percent, and delta-D by fully 2500 percent. This high D content of the meteorite's alpha-amino acids may be due to the synthesis of their molecular precursors by low-temperature ion-molecule reactions in an interstellar cloud.

  10. Insulin effect on amino acid uptake by unloaded rat hindlimb muscles

    NASA Technical Reports Server (NTRS)

    Jaspers, S. R.; Tischler, M. E.

    1988-01-01

    The effect of insulin on the uptake of alpha-amino-isobutyric acid (AIB) by unloaded rat hindlimb muscles was investigated using soleus and extensor digitorum longus (EDL) muscles from intact and adrenalectomized (ADX) rats that were tail-casted for six days. It was found that, at insulin levels above 0.00001 units/ml, the in vitro rate of AIB uptake by muscles from intact animals was stimulated more in the weight bearing muscles than in unloaded ones. In ADX animals, this differential response to insulin was abolished.

  11. Extraterrestrial Amino Acids in Orgueil and Ivuna: Tracing the Parent Body of CI Type Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Meyer, Michael (Technical Monitor); Ehrenfreund, Pascale; Glavin, Daniel P.; Bota, Oliver; Cooper, George; Bada, Jeffrey

    2001-01-01

    Amino acid analyses using HPLC of pristine interior pieces of the CI carbonaceous chondrites Orgueil and Ivuna have found that beta-alanine, glycine, and gamma-amino-n-butyric acid (ABA) are the most abundant amino acids in these two meteorites, with concentrations ranging from approx. 600 to 2,000 parts per billion (ppb). Other alpha-amino acids such as alanine, alpha-ABA, alpha-aminoisobutyric acid (AIB), and isovaline are present only in trace amounts (less than 200 ppb). Carbon isotopic measurements of beta-alanine and glycine and the presence of racemic (D/L 1) alanine and beta-ABA in Orgueil suggest that these amino acids are extraterrestrial in origin. In comparison to the CM carbonaceous chondrites Murchison and Murray, the amino acid composition of the CIs is strikingly distinct, suggesting that these meteorites came from a different type of parent body, possibly an extinct comet, than did the CM carbonaceous chondrites.

  12. Optimization of retinotopy constrained source estimation constrained by prior

    PubMed Central

    Hagler, Donald J.

    2015-01-01

    Studying how the timing and amplitude of visual evoked responses (VERs) vary between visual areas is important for understanding visual processing but is complicated by difficulties in reliably estimating VERs in individual visual areas using non-invasive brain measurements. Retinotopy constrained source estimation (RCSE) addresses this challenge by using multiple, retinotopically-mapped stimulus locations to simultaneously constrain estimates of VERs in visual areas V1, V2, and V3, taking advantage of the spatial precision of fMRI retinotopy and the temporal resolution of magnetoencephalography (MEG) or electroencephalography (EEG). Nonlinear optimization of dipole locations, guided by a group-constrained RCSE solution as a prior, improved the robustness of RCSE. This approach facilitated the analysis of differences in timing and amplitude of VERs between V1, V2, and V3, elicited by stimuli with varying luminance contrast in a sample of eight adult humans. The V1 peak response was 37% larger than that of V2 and 74% larger than that of V3, and also ~10–20 msec earlier. Normalized contrast response functions were nearly identical for the three areas. Results without dipole optimization, or with other nonlinear methods not constrained by prior estimates were similar but suffered from greater between-subject variability. The increased reliability of estimates offered by this approach may be particularly valuable when using a smaller number of stimulus locations, enabling a greater variety of stimulus and task manipulations. PMID:23868690

  13. 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.

  14. 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.

  15. Amino acid analogs for tumor imaging

    DOEpatents

    Goodman, Mark M.; Shoup, Timothy

    1998-10-06

    The invention provides novel amino acid compounds of use in detecting and evaluating brain and body tumors. These compounds combine the advantageous properties of 1-amino-cycloalkyl-1-carboxylic acids, namely, their rapid uptake and prolonged retention in tumors with the properties of halogen substituents, including certain useful halogen isotopes including fluorine-18, iodine-123, iodine-125, iodine-131, bromine-75, bromine-76, bromine-77 and bromine-82. In one aspect, the invention features amino acid compounds that have a high specificity for target sites when administered to a subject in vivo. Preferred amino acid compounds show a target to non-target ratio of at least 5:1, are stable in vivo and substantially localized to target within 1 hour after administration. An especially preferred amino acid compound is ›.sup.18 F!-1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC). In another aspect, the invention features pharmaceutical compositions comprised of an .alpha.-amino acid moiety attached to either a four, five, or a six member carbon-chain ring. In addition, the invention features analogs of .alpha.-aminoisobutyric acid.

  16. Amino acid analogs for tumor imaging

    DOEpatents

    Goodman, Mark M.; Shoup, Timothy

    1998-09-15

    The invention provides novel amino acid compounds of use in detecting and evaluating brain and body tumors. These compounds combine the advantageous properties of 1-amino-cycloalkyl-1-carboxylic acids, namely, their rapid uptake and prolonged retention in tumors with the properties of halogen substituents, including certain useful halogen isotopes including fluorine-18, iodine-123, iodine-125, iodine-131, bromine-75, bromine-76, bromine-77 and bromine-82. In one aspect, the invention features amino acid compounds that have a high specificity for target sites when administered to a subject in vivo. Preferred amino acid compounds show a target to non-target ratio of at least 5:1, are stable in vivo and substantially localized to target within 1 hour after administration. An especially preferred amino acid compound is ›.sup.18 F!-1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC). In another aspect, the invention features pharmaceutical compositions comprised of an .alpha.-amino acid moiety attached to either a four, five, or a six member carbon-chain ring. In addition, the invention features analogs of .alpha.-aminoisobutyric acid.

  17. Amino acid analogs for tumor imaging

    DOEpatents

    Goodman, M.M.; Shoup, T.

    1998-09-15

    The invention provides novel amino acid compounds of use in detecting and evaluating brain and body tumors. These compounds combine the advantageous properties of 1-amino-cycloalkyl-1-carboxylic acids, namely, their rapid uptake and prolonged retention in tumors with the properties of halogen substituents, including certain useful halogen isotopes including fluorine-18, iodine-123, iodine-125, iodine-131, bromine-75, bromine-76, bromine-77 and bromine-82. In one aspect, the invention features amino acid compounds that have a high specificity for target sites when administered to a subject in vivo. Preferred amino acid compounds show a target to non-target ratio of at least 5:1, are stable in vivo and substantially localized to target within 1 hour after administration. An especially preferred amino acid compound is [{sup 18}F]-1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC). In another aspect, the invention features pharmaceutical compositions comprised of an {alpha}-amino acid moiety attached to either a four, five, or a six member carbon-chain ring. In addition, the invention features analogs of {alpha}-aminoisobutyric acid.

  18. Amino acid analogs for tumor imaging

    DOEpatents

    Goodman, M.M.; Shoup, T.

    1998-10-06

    The invention provides novel amino acid compounds of use in detecting and evaluating brain and body tumors. These compounds combine the advantageous properties of 1-amino-cycloalkyl-1-carboxylic acids, namely, their rapid uptake and prolonged retention in tumors with the properties of halogen substituents, including certain useful halogen isotopes including fluorine-18, iodine-123, iodine-125, iodine-131, bromine-75, bromine-76, bromine-77 and bromine-82. In one aspect, the invention features amino acid compounds that have a high specificity for target sites when administered to a subject in vivo. Preferred amino acid compounds show a target to non-target ratio of at least 5:1, are stable in vivo and substantially localized to target within 1 hour after administration. An especially preferred amino acid compound is [{sup 18}F]-1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC). In another aspect, the invention features pharmaceutical compositions comprised of an {alpha}-amino acid moiety attached to either a four, five, or a six member carbon-chain ring. In addition, the invention features analogs of {alpha}-aminoisobutyric acid.

  19. Method of constrained global optimization

    NASA Astrophysics Data System (ADS)

    Altschuler, Eric Lewin; Williams, Timothy J.; Ratner, Edward R.; Dowla, Farid; Wooten, Frederick

    1994-04-01

    We present a new method for optimization: constrained global optimization (CGO). CGO iteratively uses a Glauber spin flip probability and the Metropolis algorithm. The spin flip probability allows changing only the values of variables contributing excessively to the function to be minimized. We illustrate CGO with two problems-Thomson's problem of finding the minimum-energy configuration of unit charges on a spherical surface, and a problem of assigning offices-for which CGO finds better minima than other methods. We think CGO will apply to a wide class of optimization problems.

  20. Constraining walking and custodial technicolor

    SciTech Connect

    Foadi, Roshan; Frandsen, Mads T.; Sannino, Francesco

    2008-05-01

    We show how to constrain the physical spectrum of walking technicolor models via precision measurements and modified Weinberg sum rules. We also study models possessing a custodial symmetry for the S parameter at the effective Lagrangian level - custodial technicolor - and argue that these models cannot emerge from walking-type dynamics. We suggest that it is possible to have a very light spin-one axial (vector) boson. However, in the walking dynamics the associated vector boson is heavy while it is degenerate with the axial in custodial technicolor.

  1. Constraining relativistic viscous hydrodynamical evolution

    SciTech Connect

    Martinez, Mauricio; Strickland, Michael

    2009-04-15

    We show that by requiring positivity of the longitudinal pressure it is possible to constrain the initial conditions one can use in second-order viscous hydrodynamical simulations of ultrarelativistic heavy-ion collisions. We demonstrate this explicitly for (0+1)-dimensional viscous hydrodynamics and discuss how the constraint extends to higher dimensions. Additionally, we present an analytic approximation to the solution of (0+1)-dimensional second-order viscous hydrodynamical evolution equations appropriate to describe the evolution of matter in an ultrarelativistic heavy-ion collision.

  2. 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.

  3. Exploring constrained quantum control landscapes

    NASA Astrophysics Data System (ADS)

    Moore, Katharine W.; Rabitz, Herschel

    2012-10-01

    The broad success of optimally controlling quantum systems with external fields has been attributed to the favorable topology of the underlying control landscape, where the landscape is the physical observable as a function of the controls. The control landscape can be shown to contain no suboptimal trapping extrema upon satisfaction of reasonable physical assumptions, but this topological analysis does not hold when significant constraints are placed on the control resources. This work employs simulations to explore the topology and features of the control landscape for pure-state population transfer with a constrained class of control fields. The fields are parameterized in terms of a set of uniformly spaced spectral frequencies, with the associated phases acting as the controls. This restricted family of fields provides a simple illustration for assessing the impact of constraints upon seeking optimal control. Optimization results reveal that the minimum number of phase controls necessary to assure a high yield in the target state has a special dependence on the number of accessible energy levels in the quantum system, revealed from an analysis of the first- and second-order variation of the yield with respect to the controls. When an insufficient number of controls and/or a weak control fluence are employed, trapping extrema and saddle points are observed on the landscape. When the control resources are sufficiently flexible, solutions producing the globally maximal yield are found to form connected "level sets" of continuously variable control fields that preserve the yield. These optimal yield level sets are found to shrink to isolated points on the top of the landscape as the control field fluence is decreased, and further reduction of the fluence turns these points into suboptimal trapping extrema on the landscape. Although constrained control fields can come in many forms beyond the cases explored here, the behavior found in this paper is illustrative of

  4. A reexamination of amino acids in lunar soil

    NASA Astrophysics Data System (ADS)

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

    1993-03-01

    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.

  5. 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.

  6. Constrained photophysics of partially and fully encapsulated charge transfer probe (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester inside cyclodextrin nano-cavities: Evidence of cyclodextrins cavity dependent complex stoichiometry

    NASA Astrophysics Data System (ADS)

    Ghosh, Shalini; Jana, Sankar; Guchhait, Nikhil

    2011-12-01

    The polarity sensitive intra-molecular charge transfer (ICT) emission from (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester (MAPAME) is found to show distinct changes once introduced into the nano-cavities of cyclodextrins in aqueous environment. Movement of the molecule from the more polar aqueous environment to the less polar, hydrophobic cyclodextrin interior is marked by the blue shift of the CT emission band with simultaneous fluorescence intensity enhancement. The emission spectral changes on complexation with the α- and β-CD show different stoichiometries as observed from the Benesi-Hildebrand plots. Fluorescence anisotropy and lifetime measurements were performed to probe the different behaviors of MAPAME in aqueous α- and β-CD solutions.

  7. Heterogeneous Distributions of Amino Acids Provide Evidence of Multiple Sources Within the Almahata Sitta Parent Body, Asteroid 2008 TC(sub 3)

    NASA Technical Reports Server (NTRS)

    Burton, Aaron S.; Glavin, Daniel P.; Callahan, Michael P.; Dworkin, Jason P.; Jenniskens, Peter; Shaddad, Muawia H.

    2011-01-01

    Two new fragments of the Almahata Sitta meteorite and a sample of sand from the related strewn field in the Nubian Desert, Sudan, were analyzed for two to six carbon aliphatic primary amino acids by ultrahigh performance liquid chromatography with UV-fluorescence detection and time-of-flight mass spectrometry (LC-FT/ToF-MS). The distribution of amino acids in fragment #25, an H5 ordinary chondrite, and fragment #27, a polymict ureilite, were compared with results from the previously analyzed fragment #4, also a polymict ureilite. All three meteorite fragments contain 180-270 parts-per-billion (ppb) of amino acids, roughly 1000-fold lower than the total amino acid abundance of the Murchison carbonaceous chondrite. All of the Almahata Sitta fragments analyzed have amino acid distributions that differ from the Nubian Desert sand, which primarily contains L-alpha-amino acids. In addition, the meteorites contain several amino acids that were not detected in the sand, indicating that many of the amino acids are extraterrestrial in origin. Despite their petrological differences, meteorite fragments #25 and #27 contain similar amino acid compositions; however, the distribution of amino acids in fragment #27 was distinct from those in fragment #4, even though both arc polymict ureilites from the same parent body. Unlike in CM2 and CR2/3 meteorites, there are low relative abundances of alpha-amino acids in the Almahata Sitta meteorite fragments, which suggest that Strecker-type chemistry was not a significant amino acid formation mechanism. Given the high temperatures that asteroid 2008 TC3 appears to have experienced and lack of evidence for aqueous alteration on the asteroid, it is possible that the extraterrestrial amino acids detected in Almahata Sitta were formed by Fischer-Tropsch/Haber-Bosch type gas-grain reactions at elevated temperatures.

  8. Constraining the Europa Neutral Torus

    NASA Astrophysics Data System (ADS)

    Smith, Howard T.; Mitchell, Donald; mauk, Barry; Johnson, Robert E.; clark, george

    2016-10-01

    "Neutral tori" consist of neutral particles that usually co-orbit along with their source forming a toroidal (or partial toroidal) feature around the planet. The distribution and composition of these features can often provide important, if not unique, insight into magnetospheric particles sources, mechanisms and dynamics. However, these features can often be difficult to directly detect. One innovative method for detecting neutral tori is by observing Energetic Neutral Atoms (ENAs) that are generally considered produced as a result of charge exchange interactions between charged and neutral particles.Mauk et al. (2003) reported the detection of a Europa neutral particle torus using ENA observations. The presence of a Europa torus has extremely large implications for upcoming missions to Jupiter as well as understanding possible activity at this moon and providing critical insight into what lies beneath the surface of this icy ocean world. However, ENAs can also be produced as a result of charge exchange interactions between two ionized particles and in that case cannot be used to infer the presence of neutral particle population. Thus, a detailed examination of all possible source interactions must be considered before one can confirm that likely original source population of these ENA images is actually a Europa neutral particle torus. For this talk, we examine the viability that the Mauk et al. (2003) observations were actually generated from a neutral torus emanating from Europa as opposed to charge particle interactions with plasma originating from Io. These results help constrain such a torus as well as Europa source processes.

  9. Order-constrained linear optimization.

    PubMed

    Tidwell, Joe W; Dougherty, Michael R; Chrabaszcz, Jeffrey S; Thomas, Rick P

    2017-02-27

    Despite the fact that data and theories in the social, behavioural, and health sciences are often represented on an ordinal scale, there has been relatively little emphasis on modelling ordinal properties. The most common analytic framework used in psychological science is the general linear model, whose variants include ANOVA, MANOVA, and ordinary linear regression. While these methods are designed to provide the best fit to the metric properties of the data, they are not designed to maximally model ordinal properties. In this paper, we develop an order-constrained linear least-squares (OCLO) optimization algorithm that maximizes the linear least-squares fit to the data conditional on maximizing the ordinal fit based on Kendall's τ. The algorithm builds on the maximum rank correlation estimator (Han, 1987, Journal of Econometrics, 35, 303) and the general monotone model (Dougherty & Thomas, 2012, Psychological Review, 119, 321). Analyses of simulated data indicate that when modelling data that adhere to the assumptions of ordinary least squares, OCLO shows minimal bias, little increase in variance, and almost no loss in out-of-sample predictive accuracy. In contrast, under conditions in which data include a small number of extreme scores (fat-tailed distributions), OCLO shows less bias and variance, and substantially better out-of-sample predictive accuracy, even when the outliers are removed. We show that the advantages of OCLO over ordinary least squares in predicting new observations hold across a variety of scenarios in which researchers must decide to retain or eliminate extreme scores when fitting data.

  10. Constraining QGP properties with CHIMERA

    NASA Astrophysics Data System (ADS)

    Garishvili, Irakli; Abelev, Betty; Cheng, Michael; Glenn, Andrew; Soltz, Ron

    2011-10-01

    Understanding essential properties of strongly interacting matter is arguably the most important goal of the relativistic heavy-ion programs both at RHIC and the LHC. In particular, constraining observables such as ratio of shear viscosity to entropy density, η/s, initial temperature, Tinit, and energy density is of critical importance. For this purpose we have developed CHIMERA, Comprehensive Heavy Ion Model Reporting and Evaluation Algorithm. CHIMERA is designed to facilitate global statistical comparison of results from our multi-stage hydrodynamics/hadron cascade model of heavy ion collisions to the key soft observables (HBT, elliptic flow, spectra) measured at RHIC and the LHC. Within this framework the data representing multiple different measurements from different experiments are compiled into single format. One of the unique features of CHIMERA is, that in addition to taking into account statistical errors, it also treats different types of systematic uncertainties. The hydrodynamics/hadron cascade model used in the framework incorporates different initial state conditions, pre-equilibrium flow, the UVH2+1 viscous hydro model, Cooper-Frye freezeout, and the UrQMD hadronic cascade model. The sensitivity of the observables to the equation of state (EoS) is explored using several EoS's in the hydrodynamic evolution. The latest results from CHIMERA, including data from the LHC, will be presented.

  11. 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.

  12. Gyrification from constrained cortical expansion

    PubMed Central

    Tallinen, Tuomas; Chung, Jun Young; Biggins, John S.; Mahadevan, L.

    2014-01-01

    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 highly convoluted. Furthermore, this dependence on two simple geometric parameters that characterize the brain also allows us to qualitatively explain how variations in these parameters lead to anatomical anomalies in such situations as polymicrogyria, pachygyria, and lissencephalia. PMID:25136099

  13. Constrained Allocation Flux Balance Analysis

    PubMed Central

    Mori, Matteo; Hwa, Terence; Martin, Olivier C.

    2016-01-01

    New experimental results on bacterial growth inspire a novel top-down approach to study cell metabolism, combining mass balance and proteomic constraints to extend and complement Flux Balance Analysis. We introduce here Constrained Allocation Flux Balance Analysis, CAFBA, in which the biosynthetic costs associated to growth are accounted for in an effective way through a single additional genome-wide constraint. Its roots lie in the experimentally observed pattern of proteome allocation for metabolic functions, allowing to bridge regulation and metabolism in a transparent way under the principle of growth-rate maximization. We provide a simple method to solve CAFBA efficiently and propose an “ensemble averaging” procedure to account for unknown protein costs. Applying this approach to modeling E. coli metabolism, we find that, as the growth rate increases, CAFBA solutions cross over from respiratory, growth-yield maximizing states (preferred at slow growth) to fermentative states with carbon overflow (preferred at fast growth). In addition, CAFBA allows for quantitatively accurate predictions on the rate of acetate excretion and growth yield based on only 3 parameters determined by empirical growth laws. PMID:27355325

  14. 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.

  15. The genetic code constrains yet facilitates Darwinian evolution.

    PubMed

    Firnberg, Elad; Ostermeier, Marc

    2013-08-01

    An important goal of evolutionary biology is to understand the constraints that shape the dynamics and outcomes of evolution. Here, we address the extent to which the structure of the standard genetic code constrains evolution by analyzing adaptive mutations of the antibiotic resistance gene TEM-1 β-lactamase and the fitness distribution of codon substitutions in two influenza hemagglutinin inhibitor genes. We find that the architecture of the genetic code significantly constrains the adaptive exploration of sequence space. However, the constraints endow the code with two advantages: the ability to restrict access to amino acid mutations with a strong negative effect and, most remarkably, the ability to enrich for adaptive mutations. Our findings support the hypothesis that the standard genetic code was shaped by selective pressure to minimize the deleterious effects of mutation yet facilitate the evolution of proteins through imposing an adaptive mutation bias.

  16. Constrained Peptides as Miniature Protein Structures

    PubMed Central

    Yin, Hang

    2012-01-01

    This paper discusses the recent developments of protein engineering using both covalent and noncovalent bonds to constrain peptides, forcing them into designed protein secondary structures. These constrained peptides subsequently can be used as peptidomimetics for biological functions such as regulations of protein-protein interactions. PMID:25969758

  17. The 3-amino-derivative of gamma-cyclodextrin as chiral selector of Dns-amino acids in electrokinetic chromatography.

    PubMed

    Giuffrida, A; Contino, A; Maccarrone, G; Messina, M; Cucinotta, V

    2009-04-24

    The enantioseparation of the enantiomeric pairs of 10 Dns derivatives of alpha-amino acids was successfully carried out by using for the first time the 3-amino derivative of the gamma-cyclodextrin. The effects of pH and selector concentration on the migration times and the resolutions of analytes were studied in detail. 3-Deoxy-3-amino-2(S),3(R)-gamma-cyclodextrin (GCD3AM) shows very good chiral recognition ability even at very low concentrations at all the three investigated values of pH, as shown by the very large values of selectivity and resolution towards several pairs of amino acids. The role played by the cavity, the substitution site and the protonation equilibria on the observed properties of chiral selectivity, on varying the specific amino acid involved, is discussed.

  18. constrainedKriging: An R-package for customary, constrained and covariance-matching constrained point or block kriging

    NASA Astrophysics Data System (ADS)

    Hofer, Christoph; Papritz, Andreas

    2011-10-01

    The article describes the R-package constrainedKriging, a tool for spatial prediction problems that involve change of support. The package provides software for spatial interpolation by constrained (CK), covariance-matching constrained (CMCK), and customary universal (UK) kriging. CK and CMCK yield approximately unbiased predictions of nonlinear functionals of target quantities under change of support and are therefore an attractive alternative to conditional Gaussian simulations. The constrainedKriging package computes CK, CMCK, and UK predictions for points or blocks of arbitrary shape from data observed at points in a two-dimensional survey domain. Predictions are computed for a random process model that involves a nonstationary mean function (modeled by a linear regression) and a weakly stationary, isotropic covariance function (or variogram). CK, CMCK, and UK require the point-block and block-block averages of the covariance function if the prediction targets are blocks. The constrainedKriging package uses numerically efficient approximations to compute these averages. The article contains, apart from a brief summary of CK and CMCK, a detailed description of the algorithm used to compute the point-block and block-block covariances, and it describes the functionality of the software in detail. The practical use of the package is illustrated by a comparison of universal and constrained lognormal block kriging for the Meuse Bank heavy metal data set.

  19. Compositionally Constraining Elysium Lava Fields

    NASA Astrophysics Data System (ADS)

    Karunatillake, S.; Button, N. E.; Skok, J. R.

    2013-12-01

    Chemical provinces of Mars defined recently [1-3] became possible with the maps of elemental mass fractions generated with Mars Odyssey Gamma and Neutron Spectrometer (GS) data [4,5]. These provide a unique perspective by representing compositional signatures distinctive of the regolith vertically at decimeter depths and laterally at hundreds of kilometer scale. Some provinces overlap compellingly with regions highlighted by other remote sensing observations, such as the Mars Radar Stealth area [3]. The spatial convergence of mutually independent data with the consequent highlight of a region provides a unique opportunity of insight not possible with a single type of remote sensing observation. Among such provinces, previous work [3] highlighted Elysium lava flows as a promising candidate on the basis of convergence with mapped geologic units identifying Elysium's lava fields generally, and Amazonian-aged lava flows specifically. The South Eastern lava flows of Elysium Mons, dating to the recent Amazonian epoch, overlap compellingly with a chemical province of K and Th depletion relative to the Martian midlatitudes. We characterize the composition, geology, and geomorphology of the SE Elysium province to constrain the confluence of geologic and alteration processes that may have contributed to its evolution. We compare this with the North Western lava fields, extending the discussion on chemical products from the thermal evolution of Martian volcanism as discussed by Baratoux et al. [6]. The chemical province, by regional proximity to Cerberus Fossae, may also reflect the influence of recently identified buried flood channels [7] in the vicinity of Orcus Patera. Despite the compelling chemical signature from γ spectra, fine grained unconsolidated sediment hampers regional VNTIR (Visible, Near, and Thermal Infrared) spectral analysis. But some observations near scarps and fresh craters allow a view of small scale mineral content. The judicious synthesis of

  20. Constrained density functional for noncollinear magnetism

    NASA Astrophysics Data System (ADS)

    Ma, Pui-Wai; Dudarev, S. L.

    2015-02-01

    Energies of arbitrary small- and large-angle noncollinear excited magnetic configurations are computed using a highly accurate constrained density functional theory approach. Numerical convergence and accuracy are controlled by the choice of Lagrange multipliers λI entering the constraining conditions. The penalty part Ep of the constrained energy functional at its minimum is shown to be inversely proportional to λI, enabling a simple, robust, and accurate iterative procedure to be followed to find a convergent solution. The method is implemented as a part of ab initio vasp package, and applied to the investigation of noncollinear B2-like and <001 > double-layer antiferromagnetic configurations of bcc iron, Fe2 dimer, and amorphous iron. Forces acting on atoms depend on the orientations of magnetic moments, and the proposed approach enables constrained self-consistent noncollinear magnetic and structural relaxation of large atomic systems to be carried out.

  1. Active constrained clustering by examining spectral Eigenvectors

    NASA Technical Reports Server (NTRS)

    Wagstaff, Kiri L.; desJardins, Marie; Xu, Qianjun

    2005-01-01

    This work focuses on the active selection of pairwise constraints for spectral clustering. We develop and analyze a technique for Active Constrained Clustering by Examining Spectral eigenvectorS (ACCESS) derived from a similarity matrix.

  2. On the Constrained Attitude Control Problem

    NASA Technical Reports Server (NTRS)

    Hadaegh, Fred Y.; Kim, Yoonsoo; Mesbahi, Mehran; Singh, Gurkipal

    2004-01-01

    In this paper, we consider various classes of constrained attitude control (CAC) problem in single and multiple spacecraft settings. After categorizing attitude constraints into four distinct types, we provide an overview of the existing approaches to this problem. We then proceed to further expand on a recent algorithmic approach to the CAC problem. The paper concludes with an example demonstrating the viability of the proposed algorithm for a multiple spacecraft constrained attitude reconfiguration scenario.

  3. Egg Production Constrains Chemical Defenses in a Neotropical Arachnid

    PubMed Central

    Nazareth, Taís M.; Machado, Glauco

    2015-01-01

    Female investment in large eggs increases the demand for fatty acids, which are allocated for yolk production. Since the biosynthetic pathway leading to fatty acids uses the same precursors used in the formation of polyketides, allocation trade-offs are expected to emerge. Therefore, egg production should constrain the investment in chemical defenses based on polyketides, such as benzoquinones. We tested this hypothesis using the harvestman Acutiosoma longipes, which produces large eggs and releases benzoquinones as chemical defense. We predicted that the amount of secretion released by ovigerous females (OFs) would be smaller than that of non-ovigerous females (NOF). We also conducted a series of bioassays in the field and in the laboratory to test whether egg production renders OFs more vulnerable to predation. OFs produce less secretion than NOFs, which is congruent with the hypothesis that egg production constrains the investment in chemical defenses. Results of the bioassays show that the secretion released by OFs is less effective in deterring potential predators (ants and spiders) than the secretion released by NOFs. In conclusion, females allocate resources to chemical defenses in a way that preserves a primary biological function related to reproduction. However, the trade-off between egg and secretion production makes OFs vulnerable to predators. We suggest that egg production is a critical moment in the life of harvestman females, representing perhaps the highest cost of reproduction in the group. PMID:26331946

  4. Constrained Least Absolute Deviation Neural Networks

    PubMed Central

    Wang, Zhishun; Peterson, Bradley S.

    2008-01-01

    It is well known that least absolute deviation (LAD) criterion or L1-norm used for estimation of parameters is characterized by robustness, i.e., the estimated parameters are totally resistant (insensitive) to large changes in the sampled data. This is an extremely useful feature, especially, when the sampled data are known to be contaminated by occasionally occurring outliers or by spiky noise. In our previous works, we have proposed the least absolute deviation neural network (LADNN) to solve unconstrained LAD problems. The theoretical proofs and numerical simulations have shown that the LADNN is Lyapunov-stable and it can globally converge to the exact solution to a given unconstrained LAD problem. We have also demonstrated its excellent application value in time-delay estimation. More generally, a practical LAD application problem may contain some linear constraints, such as a set of equalities and/or inequalities, which is called constrained LAD problem, whereas the unconstrained LAD can be considered as a special form of the constrained LAD. In this paper, we present a new neural network called constrained least absolute deviation neural network (CLADNN) to solve general constrained LAD problems. Theoretical proofs and numerical simulations demonstrate that the proposed CLADNN is Lyapunov stable and globally converges to the exact solution to a given constrained LAD problem, independent of initial values. The numerical simulations have also illustrated that the proposed CLADNN can be used to robustly estimate parameters for nonlinear curve fitting, which is extensively used in signal and image processing. PMID:18269958

  5. Vibrational analysis of amino acids and short peptides in hydrated media. I. L-glycine and L-leucine.

    PubMed

    Derbel, Najoua; Hernández, Belén; Pflüger, Fernando; Liquier, Jean; Geinguenaud, Frédéric; Jaïdane, Nejmeddine; Lakhdar, Zohra Ben; Ghomi, Mahmoud

    2007-02-15

    Raman scattering and Fourier-transform infrared (FT-IR) attenuated transmission reflectance (ATR) spectra of two alpha-amino acids (alpha-AAs), i.e., glycine and leucine, were measured in H2O and D2O (at neutral pH and pD). This series of observed vibrational data gave us the opportunity to analyze vibrational features of both AAs in hydrated media by density functional theory (DFT) calculations at the B3LYP/6-31++G* level. Harmonic vibrational modes calculated after geometry optimization on the clusters containing each AA and 12 surrounding water molecules, which represent primary models for hydration scheme of amino acids, allowed us to assign the main observed peaks.

  6. Genome wide exploration of the origin and evolution of amino acids

    PubMed Central

    2010-01-01

    Background Even after years of exploration, the terrestrial origin of bio-molecules remains unsolved and controversial. Today, observation of amino acid composition in proteins has become an alternative way for a global understanding of the mystery encoded in whole genomes and seeking clues for the origin of amino acids. Results In this study, we statistically monitored the frequencies of 20 alpha-amino acids in 549 taxa from three kingdoms of life: archaebacteria, eubacteria, and eukaryotes. We found that the amino acids evolved independently in these three kingdoms; but, conserved linkages were observed in two groups of amino acids, (A, G, H, L, P, Q, R, and W) and (F, I, K, N, S, and Y). Moreover, the amino acids encoded by GC-poor codons (F, Y, N, K, I, and M) were found to "lose" their usage in the development from single cell eukaryotic organisms like S. cerevisiae to H. sapiens, while the amino acids encoded by GC-rich codons (P, A, G, and W) were found to gain usage. These findings further support the co-evolution hypothesis of amino acids and genetic codes. Conclusion We proposed a new chronological order of the appearance of amino acids (L, A, V/E/G, S, I, K, T, R/D, P, N, F, Q, Y, M, H, W, C). Two conserved evolutionary paths of amino acids were also suggested: A→G→R→P and K→Y. PMID:20230639

  7. Pattern Search Algorithms for Bound Constrained Minimization

    NASA Technical Reports Server (NTRS)

    Lewis, Robert Michael; Torczon, Virginia

    1996-01-01

    We present a convergence theory for pattern search methods for solving bound constrained nonlinear programs. The analysis relies on the abstract structure of pattern search methods and an understanding of how the pattern interacts with the bound constraints. This analysis makes it possible to develop pattern search methods for bound constrained problems while only slightly restricting the flexibility present in pattern search methods for unconstrained problems. We prove global convergence despite the fact that pattern search methods do not have explicit information concerning the gradient and its projection onto the feasible region and consequently are unable to enforce explicitly a notion of sufficient feasible decrease.

  8. 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.

  9. Spacecraft inertia estimation via constrained least squares

    NASA Technical Reports Server (NTRS)

    Keim, Jason A.; Acikmese, Behcet A.; Shields, Joel F.

    2006-01-01

    This paper presents a new formulation for spacecraft inertia estimation from test data. Specifically, the inertia estimation problem is formulated as a constrained least squares minimization problem with explicit bounds on the inertia matrix incorporated as LMIs [linear matrix inequalities). The resulting minimization problem is a semidefinite optimization that can be solved efficiently with guaranteed convergence to the global optimum by readily available algorithms. This method is applied to data collected from a robotic testbed consisting of a freely rotating body. The results show that the constrained least squares approach produces more accurate estimates of the inertia matrix than standard unconstrained least squares estimation methods.

  10. A universal strategy for visual chiral recognition of α-amino acids with L-tartaric acid-capped gold nanoparticles as colorimetric probes.

    PubMed

    Song, Guoxin; Zhou, Fulin; Xu, Chunli; Li, Baoxin

    2016-02-21

    The ability to recognize and quantify the chirality of alpha-amino acids constitutes the basis of many critical areas for specific targeting in drug development and metabolite probing. It is still challenging to conveniently distinguish the enantiomer of amino acids largely due to the lack of a universal and simple strategy. In this work, we report a strategy for the visual recognition of α-amino acids. It is based on the chirality of L-tartaric acid-capped gold nanoparticles (L-TA-capped AuNPs, ca. 13 nm in diameter). All of 19 right-handed α-amino acids can induce a red-to-blue color change of L-TA-capped AuNP solution, whereas all of the left-handed amino acids (except cysteine) cannot. The chiral recognition can be achieved by the naked eye and a simple spectrophotometer. This method does not require complicated chiral modification, and excels through its low-cost, good availability of materials and its simplicity. Another notable feature of this method is its high generality, and this method can discriminate almost all native α-amino acid enantiomers. This versatile method could be potentially used for high-throughput chiral recognition of amino acids.

  11. Inhibited muscle amino acid uptake in sepsis.

    PubMed Central

    Hasselgren, P O; James, J H; Fischer, J E

    1986-01-01

    Amino acid uptake in vivo was determined in soleus (SOL) muscle, diaphragm, heart, and liver following intravenous injection of [3H]-alpha-amino-isobutyric acid ([3H]-AIB) in rats made septic by cecal ligation and puncture (CLP) and in sham-operated controls. Muscle amino acid transport was also measured in vitro by determining uptake of [3H]-AIB in incubated extensor digitorum longus (EDL) and SOL muscles. Results were expressed as distribution ratio between [3H]-AIB in intracellular and extracellular fluid. AIB uptake in vivo was reduced by 90% in SOL and cardiac muscle and by 45% in diaphragm 16 hours after CLP. In contrast, AIB uptake by liver was almost four times higher in septic than in control animals. AIB uptake in vitro was reduced by 18% in EDL 8 hours after CLP but was not significantly altered in SOL at the same time point. Sixteen hours after CLP, AIB uptake was significantly reduced in both muscles, i.e., by 17% in EDL and by 65% in SOL. When muscles from untreated rats were incubated in the presence of plasma from septic animals (16 hours CLP) or from animals injected with endotoxin (2 mg/kg body weight), AIB uptake was reduced. Addition of endotoxin in vitro (2-200 micrograms/ml) to incubated muscles did not affect AIB uptake. The results suggest that sepsis leads to marked impairment of amino acid transport system A in muscle and that this impairment is mediated by a circulating factor that is not endotoxin. Reduced uptake of amino acids by skeletal muscle during sepsis may divert amino acids to the liver for increased gluconeogenesis and protein synthesis. PMID:3963895

  12. Kinetic analysis of the role of histidine chloramines in hypochlorous acid mediated protein oxidation.

    PubMed

    Pattison, David I; Davies, Michael J

    2005-05-17

    Hypochlorous acid (HOCl) is a powerful oxidant generated from H(2)O(2) and chloride ions by the heme enzyme myeloperoxidase (MPO) released from activated leukocytes. In addition to its potent antibacterial effects, excessive HOCl production can lead to host tissue damage, with this implicated in human diseases such as atherosclerosis, cystic fibrosis, and arthritis. HOCl reacts rapidly with biological materials, with proteins being major targets. Chlorinated amines (chloramines) formed from Lys and His side chains and alpha-amino groups on proteins are major products of these reactions; these materials are however also oxidants and can undergo further reactions. In this study, the kinetics of reaction of His side-chain chloramines with other protein components have been investigated by UV/visible spectroscopy and stopped flow methods at pH 7.4 and 22 degrees C, using the chloramines of the model compound 4-imidazoleacetic acid and N-alpha-acetyl-histidine. The second-order rate constants decrease in a similar order (Cys > Met > disulfide bonds > Trp approximately alpha-amino > Lys > Tyr > backbone amides > Arg) to the corresponding reactions of HOCl, but are typically 5-25 times slower. These rate constants are consistent with His side-chain chloramines being important secondary oxidants in HOCl-mediated damage. These studies suggest that formation and subsequent reactions of His side-chain chloramines may be responsible for the targeted secondary modification of selected protein residues by HOCl that has previously been observed experimentally and highlight the importance of chloramine structure on their subsequent reactivity.

  13. A Model for Optimal Constrained Adaptive Testing.

    ERIC Educational Resources Information Center

    van der Linden, Wim J.; Reese, Lynda M.

    1998-01-01

    Proposes a model for constrained computerized adaptive testing in which the information in the test at the trait level (theta) estimate is maximized subject to the number of possible constraints on the content of the test. Test assembly relies on a linear-programming approach. Illustrates the approach through simulation with items from the Law…

  14. 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…

  15. Constrained Subjective Assessment of Student Learning

    ERIC Educational Resources Information Center

    Saliu, Sokol

    2005-01-01

    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…

  16. High-performance liquid chromatography determination of pipecolic acid after precolumn ninhydrin derivatization using domestic microwave.

    PubMed

    Moulin, Michaël; Deleu, Carole; Larher, François Robert; Bouchereau, Alain

    2002-09-15

    A novel procedure to specifically quantify low amounts of pipecolic acid and structurally related compounds in several types of biological materials has been characterized. From crude extracts of various types of biological material, the first step was to clear all low-molecular-weight compounds containing primary amino groups by a treatment of nitrous acid. Using a microwave-assisted reaction, the remaining substances containing secondary amino groups were then derivatized with ninhydrin and made soluble in glacial acetic acid. The derivatives produced were resolved by reverse-phase HPLC and detected by spectrophotometry at 570nm. This procedure allowed more rapid determination of pipecolic acid since microwave heating shortened the time needed for derivatization compared with heating at 95 degrees C in a water bath. The complete analysis of the chromogens for pipecolic acid and related substances was achieved in 20min. Under such conditions, the detection threshold for pipecolic acid was about 20pmol. The suitability of the technique was assessed in various biological matrices known to contain significant amounts of this amino acid. The data obtained are in accordance with those available in the literature. To our knowledge, this is the first method using the ninhydrin reaction in a precolumn, microwave-assisted derivatization procedure for detection and determination of heterocyclic alpha-amino acids.

  17. Cosmogenic photons strongly constrain UHECR source models

    NASA Astrophysics Data System (ADS)

    van Vliet, Arjen

    2017-03-01

    With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR) propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently updated data for the isotropic diffuse gamma-ray background (IGRB) by Fermi LAT, it is now possible to severely constrain UHECR source models. The evolution of the UHECR sources especially plays an important role in the determination of the expected secondary photon spectrum. Pure proton UHECR models are already strongly constrained, primarily by the highest energy bins of Fermi LAT's IGRB, as long as their number density is not strongly peaked at recent times.

  18. 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.

  19. Constraining SUSY GUTs and Inflation with Cosmology

    SciTech Connect

    Rocher, Jonathan

    2006-11-03

    In the framework of Supersymmetric Grand Unified Theories (SUSY GUTs), the universe undergoes a cascade of symmetry breakings, during which topological defects can be formed. We address the question of the probability of cosmic string formation after a phase of hybrid inflation within a large number of models of SUSY GUTs in agreement with particle and cosmological data. We show that cosmic strings are extremely generic and should be used to relate cosmology and high energy physics. This conclusion is employed together with the WMAP CMB data to strongly constrain SUSY hybrid inflation models. F-term and D-term inflation are studied in the SUSY and minimal SUGRA framework. They are both found to agree with data but suffer from fine tuning of their superpotential coupling ({lambda} (less-or-similar sign) 3 x 10-5 or less). Mass scales of inflation are also constrained to be less than M < or approx. 3 x 1015 GeV.

  20. CONSTRAINED SPECTRAL CLUSTERING FOR IMAGE SEGMENTATION

    PubMed Central

    Sourati, Jamshid; Brooks, Dana H.; Dy, Jennifer G.; Erdogmus, Deniz

    2013-01-01

    Constrained spectral clustering with affinity propagation in its original form is not practical for large scale problems like image segmentation. In this paper we employ novelty selection sub-sampling strategy, besides using efficient numerical eigen-decomposition methods to make this algorithm work efficiently for images. In addition, entropy-based active learning is also employed to select the queries posed to the user more wisely in an interactive image segmentation framework. We evaluate the algorithm on general and medical images to show that the segmentation results will improve using constrained clustering even if one works with a subset of pixels. Furthermore, this happens more efficiently when pixels to be labeled are selected actively. PMID:24466500

  1. The totally constrained model: three quantization approaches

    NASA Astrophysics Data System (ADS)

    Gambini, Rodolfo; Olmedo, Javier

    2014-08-01

    We provide a detailed comparison of the different approaches available for the quantization of a totally constrained system with a constraint algebra generating the non-compact group. In particular, we consider three schemes: the Refined Algebraic Quantization, the Master Constraint Programme and the Uniform Discretizations approach. For the latter, we provide a quantum description where we identify semiclassical sectors of the kinematical Hilbert space. We study the quantum dynamics of the system in order to show that it is compatible with the classical continuum evolution. Among these quantization approaches, the Uniform Discretizations provides the simpler description in agreement with the classical theory of this particular model, and it is expected to give new insights about the quantum dynamics of more realistic totally constrained models such as canonical general relativity.

  2. Comparison of intraduodenal and intravenous administration of amino acids on gastric secretion in healthy subjects and patients with duodenal ulcer.

    PubMed Central

    Konturek, S J; Kwiecień, N; Obtułowicz, W; Mikoś, E; Sito, E; Oleksy, J

    1978-01-01

    The ability of an amino acid mixture given intraduodenally or intravenously to stimulate gastric secretion is compared in healthy subjects and in duodenal ulcer patients. Graded amounts of amino acids by both routes produced a similar increase in acid output in healthy subjects, reaching about 30% of the maximal response to pentagastrin. Serum gastrin concentrations remained virtually unchanged but serum alpha amino acid nitrogen levels were about twice as high with intravenous as with intraduodenal administration. Intravenously administered amino acids produced a significantly higher acid output in patients with duodenal ulcer than in healthy subjects, but did not produce a significant increase in gastric acid or pepsin secretion when combined with a pentagastrin infusion as compared with pentagastrin alone. Cimetidine (2 mg/kg/h) added to intravenous amino acid infusions caused almost complete suppression of acid secretion. This study indicates that amino acids are capable of stimulating gastric secretion after intraduodenal and after intravenous administration. The response to the latter is significantly higher in patients with duodenal ulcer than in healthy subjects, does not appear to involve gastrin release, is not affected by pentagastrin, and is strongly suppressed by histamine H2-blocker. PMID:361509

  3. Constraining neutrino decays with CMBR data

    NASA Astrophysics Data System (ADS)

    Hannestad, Steen

    1998-07-01

    The decay of massive neutrinos to final states containing only invisible particles is poorly constrained experimentally. In this letter we describe the constraints that can be put on neutrino mass and lifetime using CMBR measurements. We find that very tight lifetime limits on neutrinos in the mass range 10 eV - 100 keV can be derived using CMBR data from upcoming satellite measurements.

  4. Constraining Neutron Star Matter with Quantum Chromodynamics

    NASA Astrophysics Data System (ADS)

    Kurkela, Aleksi; Fraga, Eduardo S.; Schaffner-Bielich, Jürgen; Vuorinen, Aleksi

    2014-07-01

    In recent years, there have been several successful attempts to constrain the equation of state of neutron star matter using input from low-energy nuclear physics and observational data. We demonstrate that significant further restrictions can be placed by additionally requiring the pressure to approach that of deconfined quark matter at high densities. Remarkably, the new constraints turn out to be highly insensitive to the amount—or even presence—of quark matter inside the stars.

  5. CONSTRAINING SOURCE REDSHIFT DISTRIBUTIONS WITH GRAVITATIONAL LENSING

    SciTech Connect

    Wittman, D.; Dawson, W. A.

    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.

  6. An English language interface for constrained domains

    NASA Technical Reports Server (NTRS)

    Page, Brenda J.

    1989-01-01

    The Multi-Satellite Operations Control Center (MSOCC) Jargon Interpreter (MJI) demonstrates an English language interface for a constrained domain. A constrained domain is defined as one with a small and well delineated set of actions and objects. The set of actions chosen for the MJI is from the domain of MSOCC Applications Executive (MAE) Systems Test and Operations Language (STOL) directives and contains directives for signing a cathode ray tube (CRT) on or off, calling up or clearing a display page, starting or stopping a procedure, and controlling history recording. The set of objects chosen consists of CRTs, display pages, STOL procedures, and history files. Translation from English sentences to STOL directives is done in two phases. In the first phase, an augmented transition net (ATN) parser and dictionary are used for determining grammatically correct parsings of input sentences. In the second phase, grammatically typed sentences are submitted to a forward-chaining rule-based system for interpretation and translation into equivalent MAE STOL directives. Tests of the MJI show that it is able to translate individual clearly stated sentences into the subset of directives selected for the prototype. This approach to an English language interface may be used for similarly constrained situations by modifying the MJI's dictionary and rules to reflect the change of domain.

  7. Constrained inversion of seismo-volcanic events

    NASA Astrophysics Data System (ADS)

    Nocerino, Luciano; D'Auria, Luca; Giudicepietro, Flora; Martini, Marcello

    2014-05-01

    The inversion of seismo-volcanic events is performed to retrieve the source geometry and to determine volumetric budgets of the source. Such observations have shown to be an important tool for the seismological monitoring of volcanoes. We developed a novel technique for the non-linear constrained inversion of low frequency seismo-volcanic events. Unconstrained linear inversion methods work well when a dense network of broadband seismometers is available. We propose a new constrained inversion technique, which has shown to be efficient also in a reduced network configuration and a low signal-noise ratio. The waveform inversion is performed in the frequency domain, constraining the source mechanism during the event to vary only in its magnitude. The eigenvectors orientation and the eigenvalue ratio are kept constant. This significantly reduces the number of parameters to invert, making the procedure more stable. The method has been tested over a synthetic dataset, reproducing realistic very-long-period (VLP) signals Stromboli volcano. We have applied the method to a VLP dataset recorded on Stromboli volcano and to low-frequency earthquakes recorded on Mt.Vesuvius.

  8. Constrained and joint inversion on unstructured meshes

    NASA Astrophysics Data System (ADS)

    Doetsch, J.; Jordi, C.; Rieckh, V.; Guenther, T.; Schmelzbach, C.

    2015-12-01

    Unstructured meshes allow for inclusion of arbitrary surface topography, complex acquisition geometry and undulating geological interfaces in the inversion of geophysical data. This flexibility opens new opportunities for coupling different geophysical and hydrological data sets in constrained and joint inversions. For example, incorporating geological interfaces that have been derived from high-resolution geophysical data (e.g., ground penetrating radar) can add geological constraints to inversions of electrical resistivity data. These constraints can be critical for a hydrogeological interpretation of the inversion results. For time-lapse inversions of geophysical data, constraints can be derived from hydrological point measurements in boreholes, but it is difficult to include these hard constraints in the inversion of electrical resistivity monitoring data. Especially mesh density and the regularization footprint around the hydrological point measurements are important for an improved inversion compared to the unconstrained case. With the help of synthetic and field examples, we analyze how regularization and coupling operators should be chosen for time-lapse inversions constrained by point measurements and for joint inversions of geophysical data in order to take full advantage of the flexibility of unstructured meshes. For the case of constraining to point measurements, it is important to choose a regularization operator that extends beyond the neighboring cells and the uncertainty in the point measurements needs to be accounted for. For joint inversion, the choice of the regularization depends on the expected subsurface heterogeneity and the cell size of the parameter mesh.

  9. Constraining the mass of the Local Group

    NASA Astrophysics Data System (ADS)

    Carlesi, Edoardo; Hoffman, Yehuda; Sorce, Jenny G.; Gottlöber, Stefan

    2017-03-01

    The mass of the Local Group (LG) is a crucial parameter for galaxy formation theories. However, its observational determination is challenging - its mass budget is dominated by dark matter that cannot be directly observed. To meet this end, the posterior distributions of the LG and its massive constituents have been constructed by means of constrained and random cosmological simulations. Two priors are assumed - the Λ cold dark matter model that is used to set up the simulations, and an LG model that encodes the observational knowledge of the LG and is used to select LG-like objects from the simulations. The constrained simulations are designed to reproduce the local cosmography as it is imprinted on to the Cosmicflows-2 data base of velocities. Several prescriptions are used to define the LG model, focusing in particular on different recent estimates of the tangential velocity of M31. It is found that (a) different vtan choices affect the peak mass values up to a factor of 2, and change mass ratios of MM31 to MMW by up to 20 per cent; (b) constrained simulations yield more sharply peaked posterior distributions compared with the random ones; (c) LG mass estimates are found to be smaller than those found using the timing argument; (d) preferred Milky Way masses lie in the range of (0.6-0.8) × 1012 M⊙; whereas (e) MM31 is found to vary between (1.0-2.0) × 1012 M⊙, with a strong dependence on the vtan values used.

  10. 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.

  11. Wastes from bioethanol and beer productions as substrates for l(+) lactic acid production - A comparative study.

    PubMed

    Djukić-Vuković, Aleksandra; Mladenović, Dragana; Radosavljević, Miloš; Kocić-Tanackov, Sunčica; Pejin, Jelena; Mojović, Ljiljana

    2016-02-01

    Waste substrates from bioethanol and beer productions are cheap, abundant and renewable substrates for biorefinery production of lactic acid (LA) and variability in their chemical composition presents a challenge in their valorisation. Three types of waste substrates, wasted bread and wasted potato stillage from bioethanol production and brewers' spent grain hydrolysate from beer production were studied as substrates for the production of l(+) LA and probiotic biomass by Lactobacillus rhamnosus ATCC 7469. The correlation of the content of free alpha amino nitrogen and the production of LA was determined as a critical characteristic of the waste media for efficient LA production by L. rhamnosus on the substrates which contained equal amount of fermentable sugars. A maximal LA productivity of 1.54gL(-1)h(-1) was obtained on wasted bread stillage media, whilst maximal productivities achieved on the potato stillage and brewers' spent grain hydrolysate media were 1.28gL(-1)h(-1)and 0.48gL(-1)h(-1), respectively. A highest LA yield of 0.91gg(-1) was achieved on wasted bread stillage media, followed by the yield of 0.81gg(-1) on wasted potato stillage and 0.34gg(-1) on brewers' spent grain hydrolysate media. The kinetics of sugar consumption in the two stillage substrates were similar while the sugar conversion in brewers' spent grain hydrolysate was slower and less efficient due to significantly lower content of free alpha amino nitrogen. The lignocellulosic hydrolysate from beer production required additional supplementation with nitrogen.

  12. Protein Structure and Evolution: Are They Constrained Globally by a Principle Derived from Information Theory?

    PubMed Central

    Hatton, Leslie; Warr, Gregory

    2015-01-01

    That the physicochemical properties of amino acids constrain the structure, function and evolution of proteins is not in doubt. However, principles derived from information theory may also set bounds on the structure (and thus also the evolution) of proteins. Here we analyze the global properties of the full set of proteins in release 13-11 of the SwissProt database, showing by experimental test of predictions from information theory that their collective structure exhibits properties that are consistent with their being guided by a conservation principle. This principle (Conservation of Information) defines the global properties of systems composed of discrete components each of which is in turn assembled from discrete smaller pieces. In the system of proteins, each protein is a component, and each protein is assembled from amino acids. Central to this principle is the inter-relationship of the unique amino acid count and total length of a protein and its implications for both average protein length and occurrence of proteins with specific unique amino acid counts. The unique amino acid count is simply the number of distinct amino acids (including those that are post-translationally modified) that occur in a protein, and is independent of the number of times that the particular amino acid occurs in the sequence. Conservation of Information does not operate at the local level (it is independent of the physicochemical properties of the amino acids) where the influences of natural selection are manifest in the variety of protein structure and function that is well understood. Rather, this analysis implies that Conservation of Information would define the global bounds within which the whole system of proteins is constrained; thus it appears to be acting to constrain evolution at a level different from natural selection, a conclusion that appears counter-intuitive but is supported by the studies described herein. PMID:25970335

  13. Protein structure and evolution: are they constrained globally by a principle derived from information theory?

    PubMed

    Hatton, Leslie; Warr, Gregory

    2015-01-01

    That the physicochemical properties of amino acids constrain the structure, function and evolution of proteins is not in doubt. However, principles derived from information theory may also set bounds on the structure (and thus also the evolution) of proteins. Here we analyze the global properties of the full set of proteins in release 13-11 of the SwissProt database, showing by experimental test of predictions from information theory that their collective structure exhibits properties that are consistent with their being guided by a conservation principle. This principle (Conservation of Information) defines the global properties of systems composed of discrete components each of which is in turn assembled from discrete smaller pieces. In the system of proteins, each protein is a component, and each protein is assembled from amino acids. Central to this principle is the inter-relationship of the unique amino acid count and total length of a protein and its implications for both average protein length and occurrence of proteins with specific unique amino acid counts. The unique amino acid count is simply the number of distinct amino acids (including those that are post-translationally modified) that occur in a protein, and is independent of the number of times that the particular amino acid occurs in the sequence. Conservation of Information does not operate at the local level (it is independent of the physicochemical properties of the amino acids) where the influences of natural selection are manifest in the variety of protein structure and function that is well understood. Rather, this analysis implies that Conservation of Information would define the global bounds within which the whole system of proteins is constrained; thus it appears to be acting to constrain evolution at a level different from natural selection, a conclusion that appears counter-intuitive but is supported by the studies described herein.

  14. 21 CFR 888.3720 - Toe joint polymer constrained prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Toe joint polymer constrained prosthesis. 888.3720... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3720 Toe joint polymer constrained prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of...

  15. 21 CFR 888.3720 - Toe joint polymer constrained prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Toe joint polymer constrained prosthesis. 888.3720... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3720 Toe joint polymer constrained prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of...

  16. 21 CFR 888.3720 - Toe joint polymer constrained prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Toe joint polymer constrained prosthesis. 888.3720... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3720 Toe joint polymer constrained prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of...

  17. 21 CFR 888.3230 - Finger joint polymer constrained prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Finger joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3230 Finger joint polymer constrained prosthesis. (a) Identification. A finger joint polymer constrained prosthesis is a device...

  18. 21 CFR 888.3720 - Toe joint polymer constrained prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Toe joint polymer constrained prosthesis. 888.3720... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3720 Toe joint polymer constrained prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of...

  19. 21 CFR 888.3230 - Finger joint polymer constrained prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Finger joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3230 Finger joint polymer constrained prosthesis. (a) Identification. A finger joint polymer constrained prosthesis is a device...

  20. 21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Wrist joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3780 Wrist joint polymer constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a device made...

  1. 21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Wrist joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3780 Wrist joint polymer constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a device made...

  2. 21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Wrist joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3780 Wrist joint polymer constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a device made...

  3. 21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Wrist joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3780 Wrist joint polymer constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a device made...

  4. 21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Wrist joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3780 Wrist joint polymer constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a device made...

  5. 21 CFR 888.3720 - Toe joint polymer constrained prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Toe joint polymer constrained prosthesis. 888.3720... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3720 Toe joint polymer constrained prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of...

  6. 21 CFR 888.3230 - Finger joint polymer constrained prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Finger joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3230 Finger joint polymer constrained prosthesis. (a) Identification. A finger joint polymer constrained prosthesis is a device...

  7. 21 CFR 888.3230 - Finger joint polymer constrained prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Finger joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3230 Finger joint polymer constrained prosthesis. (a) Identification. A finger joint polymer constrained prosthesis is a device...

  8. 21 CFR 888.3230 - Finger joint polymer constrained prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Finger joint polymer constrained prosthesis. 888... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3230 Finger joint polymer constrained prosthesis. (a) Identification. A finger joint polymer constrained prosthesis is a device...

  9. HCV management in resource-constrained countries.

    PubMed

    Lim, Seng Gee

    2017-02-21

    With the arrival of all-oral directly acting antiviral (DAA) therapy with high cure rates, the promise of hepatitis C virus (HCV) eradication is within closer reach. The availability of generic DAAs has improved access to countries with constrained resources. However, therapy is only one component of the HCV care continuum, which is the framework for HCV management from identifying patients to cure. The large number of undiagnosed HCV cases is the biggest concern, and strategies to address this are needed, as risk factor screening is suboptimal, detecting <20% of known cases. Improvements in HCV confirmation through either reflex HCV RNA screening or ideally a sensitive point of care test are needed. HCV notification (e.g., Australia) may improve diagnosis (proportion of HCV diagnosed is 75%) and may lead to benefits by increasing linkage to care, therapy and cure. Evaluations for cirrhosis using non-invasive markers are best done with a biological panel, but they are only moderately accurate. In resource-constrained settings, only generic HCV medications are available, and a combination of sofosbuvir, ribavirin, ledipasvir or daclatasvir provides sufficient efficacy for all genotypes, but this is likely to be replaced with pangenetypic regimens such as sofosbuvir/velpatasvir and glecaprevir/pibrentaasvir. In conclusion, HCV management in resource-constrained settings is challenging on multiple fronts because of the lack of infrastructure, facilities, trained manpower and equipment. However, it is still possible to make a significant impact towards HCV eradication through a concerted effort by individuals and national organisations with domain expertise in this area.

  10. Total parenteral nutrition-associated cholestasis in rats: comparison of different amino acid mixtures.

    PubMed

    Belli, D C; Fournier, L A; Lepage, G; Yousef, I; Weber, A M; Tuchweber, B; Roy, C C

    1987-01-01

    It has been suggested that the quantity of amino acids perfused is a pathogenetic factor in total parenteral nutrition (TPN)-associated hepatotoxicity. However, the effect of the qualitative pattern of amino acid solutions has not been studied. Rats on parenteral nutrition for 5 days received 10.2 g of dextrose and 3.4 g of amino acids daily. Bile flow (microliter/min/g liver protein) after administration of Vamin was 16.2 +/- 0.8, which was similar to that in controls given chow and dextrose iv, but it was significantly higher (p less than 0.001) than those on Travasol (12.3 +/- 0.8). The decrease in bile flow was not related to the large concentrations of alanine and glycine present in Travasol. However, the addition to Travasol of serine present only in Vamin increased bile flow significantly. Bile acid secretion rate, biliary lipid constituents, calcium, sodium, and glucose showed little change. In contrast, alpha-amino nitrogen was increased (p less than 0.05) in Vamin-perfused animals. Steatosis was noted in only a few animals in the Travasol group, and was not associated with an increase in the triglycerides content of the liver. Glycogen and protein content of the livers did not differ. The data show that the composition of amino acid solutions may be a determinant of TPN-induced cholestasis and suggest that the presence of methyl donor amino acids may have a protective effect.

  11. Feature and Pose Constrained Visual Aided Inertial Navigation for Computationally Constrained Aerial Vehicles

    NASA Technical Reports Server (NTRS)

    Williams, Brian; Hudson, Nicolas; Tweddle, Brent; Brockers, Roland; Matthies, Larry

    2011-01-01

    A Feature and Pose Constrained Extended Kalman Filter (FPC-EKF) is developed for highly dynamic computationally constrained micro aerial vehicles. Vehicle localization is achieved using only a low performance inertial measurement unit and a single camera. The FPC-EKF framework augments the vehicle's state with both previous vehicle poses and critical environmental features, including vertical edges. This filter framework efficiently incorporates measurements from hundreds of opportunistic visual features to constrain the motion estimate, while allowing navigating and sustained tracking with respect to a few persistent features. In addition, vertical features in the environment are opportunistically used to provide global attitude references. Accurate pose estimation is demonstrated on a sequence including fast traversing, where visual features enter and exit the field-of-view quickly, as well as hover and ingress maneuvers where drift free navigation is achieved with respect to the environment.

  12. Constrained inflaton due to a complex scalar

    SciTech Connect

    Budhi, Romy H. S.; Kashiwase, Shoichi; Suematsu, Daijiro

    2015-09-14

    We reexamine inflation due to a constrained inflaton in the model of a complex scalar. Inflaton evolves along a spiral-like valley of special scalar potential in the scalar field space just like single field inflation. Sub-Planckian inflaton can induce sufficient e-foldings because of a long slow-roll path. In a special limit, the scalar spectral index and the tensor-to-scalar ratio has equivalent expressions to the inflation with monomial potential φ{sup n}. The favorable values for them could be obtained by varying parameters in the potential. This model could be embedded in a certain radiative neutrino mass model.

  13. Constraining nucleon high momentum in nuclei

    NASA Astrophysics Data System (ADS)

    Yong, Gao-Chan

    2017-02-01

    Recent studies at Jefferson Lab show that there are a certain proportion of nucleons in nuclei have momenta greater than the so-called nuclear Fermi momentum pF. Based on the transport model of nucleus-nucleus collisions at intermediate energies, nucleon high momentum caused by the neutron-proton short-range correlations in nuclei is constrained by comparing with π and photon experimental data and considering some uncertainties. The high momentum cutoff value pmax ≤ 2pF is obtained.

  14. Quantization of soluble classical constrained systems

    SciTech Connect

    Belhadi, Z.; Menas, F.; Bérard, A.; Mohrbach, H.

    2014-12-15

    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.

  15. Incomplete Dirac reduction of constrained Hamiltonian systems

    SciTech Connect

    Chandre, C.

    2015-10-15

    First-class constraints constitute a potential obstacle to the computation of a Poisson bracket in Dirac’s theory of constrained Hamiltonian systems. Using the pseudoinverse instead of the inverse of the matrix defined by the Poisson brackets between the constraints, we show that a Dirac–Poisson bracket can be constructed, even if it corresponds to an incomplete reduction of the original Hamiltonian system. The uniqueness of Dirac brackets is discussed. The relevance of this procedure for infinite dimensional Hamiltonian systems is exemplified.

  16. Electrophysiological evidence for acidic, basic, and neutral amino acid olfactory receptor sites in the catfish

    PubMed Central

    1984-01-01

    Electrophysiological experiments indicate that olfactory receptors of the channel catfish, Ictalurus punctatus, contain different receptor sites for the acidic (A), basic (B), and neutral amino acids; further, at least two partially interacting neutral sites exist, one for the hydrophilic neutral amino acids containing short side chains (SCN), and the second for the hydrophobic amino acids containing long side chains (LCN). The extent of cross-adaptation was determined by comparing the electro-olfactogram (EOG) responses to 20 "test" amino acids during continuous bathing of the olfactory mucosa with water only (control) to those during each of the eight "adapting" amino acid regimes. Both the adapting and test amino acids were adjusted in concentrations to provide approximately equal response magnitudes in the unadapted state. Under all eight adapting regimes, the test EOG responses were reduced from those obtained in the unadapted state, but substantial quantitative differences resulted, depending upon the molecular structure of the adapting stimulus. Analyses of the patterns of EOG responses to the test stimuli identified and characterized the respective "transduction processes," a term used to describe membrane events initiated by a particular subset of amino acid stimuli that are intricately linked to the origin of the olfactory receptor potential. Only when the stimulus compounds interact with different transduction processes are the stimuli assumed to bind to different membrane "sites." Four relatively independent L-alpha-amino acid transduction processes (and thus at least four binding sites) identified in this report include: (a) the A process for aspartic and glutamic acids; (b) the B process for arginine and lysine; (c) the SCN process for glycine, alanine, serine, glutamine, and possibly cysteine; (d) the LCN process for methionine, ethionine, valine, norvaline, leucine, norleucine, glutamic acid-gamma-methyl ester, histidine, phenylalanine, and also

  17. Constraining the braking indices of magnetars

    NASA Astrophysics Data System (ADS)

    Gao, Z. F.; Li, X.-D.; Wang, N.; Yuan, J. P.; Wang, P.; Peng, Q. H.; Du, Y. J.

    2016-02-01

    Because of 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 the mean braking indices of eight magnetars with SNRs, and find that they cluster in the range of 1-42. Five magnetars have smaller mean braking indices of 1 < n < 3, and we interpret them within a combination of magneto-dipole radiation and wind-aided braking. The larger mean braking indices of n > 3 for the 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 1 < n < 3, and the dipolar magnetic field decay rates for the magnetars with n > 3, within the updated magneto-thermal evolution models. Although the constrained range of the magnetars' braking indices is tentative, as a result of the uncertainties in the SNR ages due to distance uncertainties and the unknown conditions of the expanding shells, our method provides an effective way to constrain the magnetars' braking indices if the measurements of the SNR ages are reliable, which can be improved by future observations.

  18. 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.

  19. Constraining the halo mass function with observations

    NASA Astrophysics Data System (ADS)

    Castro, Tiago; Marra, Valerio; Quartin, Miguel

    2016-12-01

    The abundances of dark matter haloes in the universe are described by the halo mass function (HMF). It enters most cosmological analyses and parametrizes how the linear growth of primordial perturbations is connected to these abundances. Interestingly, this connection can be made approximately cosmology independent. This made it possible to map in detail its near-universal behaviour through large-scale simulations. However, such simulations may suffer from systematic effects, especially if baryonic physics is included. In this paper, we ask how well observations can constrain directly the HMF. The observables we consider are galaxy cluster number counts, galaxy cluster power spectrum and lensing of Type Ia supernovae. Our results show that Dark Energy Survey is capable of putting the first meaningful constraints on the HMF, while both Euclid and J-PAS (Javalambre-Physics of the Accelerated Universe Astrophysical Survey) can give stronger constraints, comparable to the ones from state-of-the-art simulations. We also find that an independent measurement of cluster masses is even more important for measuring the HMF than for constraining the cosmological parameters, and can vastly improve the determination of the HMF. Measuring the HMF could thus be used to cross-check simulations and their implementation of baryon physics. It could even, if deviations cannot be accounted for, hint at new physics.

  20. Constraining the Mass of A Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    Cemenenkoff, Nicholas; Rines, Kenneth J.; Geller, Margaret J.; Diaferio, Antonaldo

    2017-01-01

    Accurate cluster masses are critical for understanding dark matter and for using clusters to constrain cosmological parameters. We use the observed surface number density profile and velocity dispersion profile of galaxies in the Coma cluster to constrain its mass profile via Jeans analysis. In particular, we evaluate the robustness of the mass estimate M_200 by using different parametric forms for the distribution of mass and galaxies as well as different models of the orbital anisotropy parameter β (r) . Allowing for variation between the scale radii of the mass profile and the galaxy profile (i.e. relaxing the assumption that galaxies trace mass) does not significantly change the estimate of M 200 . We use a Bayesian approach to construct probability distribution functions of M 200, scale radius, and beta via Markov Chain Monte Carlo (MCMC) sampling. We apply this approach to ensemble clusters stacked by either their Sunyaev-Zel'dovich (SZ) signals or X-ray luminosities to measure the scaling relations of dynamical mass estimates with these mass proxies. Specifically, we test the hypothesis that the apparent deficit of SZ clusters (compared to predictions based on observations of the microwave background) can be explained by a bias of ˜ 60% in the normalization of the scaling relation between SZ signal and mass.

  1. Physically constrained maximum likelihood mode filtering.

    PubMed

    Papp, Joseph C; Preisig, James C; Morozov, Andrey K

    2010-04-01

    Mode filtering is most commonly implemented using the sampled mode shapes or pseudoinverse algorithms. Buck et al. [J. Acoust. Soc. Am. 103, 1813-1824 (1998)] placed these techniques in the context of a broader maximum a posteriori (MAP) framework. However, the MAP algorithm requires that the signal and noise statistics be known a priori. Adaptive array processing algorithms are candidates for improving performance without the need for a priori signal and noise statistics. A variant of the physically constrained, maximum likelihood (PCML) algorithm [A. L. Kraay and A. B. Baggeroer, IEEE Trans. Signal Process. 55, 4048-4063 (2007)] is developed for mode filtering that achieves the same performance as the MAP mode filter yet does not need a priori knowledge of the signal and noise statistics. The central innovation of this adaptive mode filter is that the received signal's sample covariance matrix, as estimated by the algorithm, is constrained to be that which can be physically realized given a modal propagation model and an appropriate noise model. Shallow water simulation results are presented showing the benefit of using the PCML method in adaptive mode filtering.

  2. Multiple Manifold Clustering Using Curvature Constrained Path

    PubMed Central

    Babaeian, Amir; Bayestehtashk, Alireza; Bandarabadi, Mojtaba

    2015-01-01

    The problem of multiple surface clustering is a challenging task, particularly when the surfaces intersect. Available methods such as Isomap fail to capture the true shape of the surface near by the intersection and result in incorrect clustering. The Isomap algorithm uses shortest path between points. The main draw back of the shortest path algorithm is due to the lack of curvature constrained where causes to have a path between points on different surfaces. In this paper we tackle this problem by imposing a curvature constraint to the shortest path algorithm used in Isomap. The algorithm chooses several landmark nodes at random and then checks whether there is a curvature constrained path between each landmark node and every other node in the neighborhood graph. We build a binary feature vector for each point where each entry represents the connectivity of that point to a particular landmark. Then the binary feature vectors could be used as a input of conventional clustering algorithm such as hierarchical clustering. We apply our method to simulated and some real datasets and show, it performs comparably to the best methods such as K-manifold and spectral multi-manifold clustering. PMID:26375819

  3. Constraining torsion with Gravity Probe B

    SciTech Connect

    Mao Yi; Guth, Alan H.; Cabi, Serkan; Tegmark, Max

    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.

  4. 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

  5. Ocean acidification-induced food quality deterioration constrains trophic transfer.

    PubMed

    Rossoll, Dennis; Bermúdez, Rafael; 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 (CO(2)) 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 CO(2) 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) pCO(2) 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 CO(2). This rapid and reversible CO(2)-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.

  6. Spatially constrained propulsion in jumping archer fish

    NASA Astrophysics Data System (ADS)

    Mendelson, Leah; Techet, Alexandra

    2016-11-01

    Archer fish jump multiple body lengths out of the water for prey capture with impressive accuracy. Their remarkable aim is facilitated by jumping from a stationary position directly below the free surface. As a result of this starting position, rapid acceleration to a velocity sufficient for reaching the target occurs with only a body length to travel before the fish leaves the water. Three-dimensional measurements of jumping kinematics and volumetric velocimetry using Synthetic Aperture PIV highlight multiple strategies for such spatially constrained acceleration. Archer fish rapidly extend fins at jump onset to increase added mass forces and modulate their swimming kinematics to minimize wasted energy when the body is partially out of the water. Volumetric measurements also enable assessment of efficiency during a jump, which is crucial to understanding jumping's role as an energetically viable hunting strategy for the fish.

  7. Constrained sampling method for analytic continuation.

    PubMed

    Sandvik, Anders W

    2016-12-01

    A method for analytic continuation of imaginary-time correlation functions (here obtained in quantum Monte Carlo simulations) to real-frequency spectral functions is proposed. Stochastically sampling a spectrum parametrized by a large number of δ functions, treated as a statistical-mechanics problem, it avoids distortions caused by (as demonstrated here) configurational entropy in previous sampling methods. The key development is the suppression of entropy by constraining the spectral weight to within identifiable optimal bounds and imposing a set number of peaks. As a test case, the dynamic structure factor of the S=1/2 Heisenberg chain is computed. Very good agreement is found with Bethe ansatz results in the ground state (including a sharp edge) and with exact diagonalization of small systems at elevated temperatures.

  8. Constrained sampling method for analytic continuation

    NASA Astrophysics Data System (ADS)

    Sandvik, Anders W.

    2016-12-01

    A method for analytic continuation of imaginary-time correlation functions (here obtained in quantum Monte Carlo simulations) to real-frequency spectral functions is proposed. Stochastically sampling a spectrum parametrized by a large number of δ functions, treated as a statistical-mechanics problem, it avoids distortions caused by (as demonstrated here) configurational entropy in previous sampling methods. The key development is the suppression of entropy by constraining the spectral weight to within identifiable optimal bounds and imposing a set number of peaks. As a test case, the dynamic structure factor of the S =1 /2 Heisenberg chain is computed. Very good agreement is found with Bethe ansatz results in the ground state (including a sharp edge) and with exact diagonalization of small systems at elevated temperatures.

  9. How alive is constrained SUSY really?

    SciTech Connect

    Bechtle, Philip; Desch, Klaus; Dreiner, Herbert K.; Hamer, Matthias; Kramer, Michael; O'Leary, Ben; Porod, Werner; Sarrazin, Bjorn; Stefaniak, Tim; Uhlenbrock, Mathias; Wienemann, Peter

    2016-05-31

    Constrained supersymmetric models like the CMSSM might look less attractive nowadays because of fine tuning arguments. They also might look less probable in terms of Bayesian statistics. The question how well the model under study describes the data, however, is answered by frequentist p-values. Thus, for the first time, we calculate a p-value for a supersymmetric model by performing dedicated global toy fits. We combine constraints from low-energy and astrophysical observables, Higgs boson mass and rate measurements as well as the non-observation of new physics in searches for supersymmetry at the LHC. Furthermore, using the framework Fittino, we perform global fits of the CMSSM to the toy data and find that this model is excluded at the 90% confidence level.

  10. 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.

  11. Parametric and Combinatorial Problems in Constrained Optimization

    DTIC Science & Technology

    1993-02-28

    1 ).70 0.30 5 . 49 6 i 68 :ý7 3 74 76 76 17~ 7s 1711 0301 F 70 1 86 89 90) 90) 90 91 190 89...AD-A265 595 1 (),% AGE - 3 I F’ KAi/61 MfAR󈨞 Om sEB93 IIPA`ThA?4RXCTKtf COMBINATORIAL PROBLEMS IN CONSTRAINED OPTIMIZATION * ~2304/ 1 )5 AUJBREY B...POORE ~COLORADO STATE UNIVERSITY FORT COLLINS CO 80523 I SP CN SC ý N 1 -% vC iC R;N G A~ -~ S, i,’ S) 1 SCNSOR’NG M1’%C’NC (: AGENCY 4tPURT N~vBLQ

  12. Fluctuation theorem for constrained equilibrium systems.

    PubMed

    Gilbert, Thomas; Dorfman, J Robert

    2006-02-01

    We discuss the fluctuation properties of equilibrium chaotic systems with constraints such as isokinetic and Nosé-Hoover thermostats. Although the dynamics of these systems does not typically preserve phase-space volumes, the average phase-space contraction rate vanishes, so that the stationary states are smooth. Nevertheless, finite-time averages of the phase-space contraction rate have nontrivial fluctuations which we show satisfy a simple version of the Gallavotti-Cohen fluctuation theorem, complementary to the usual fluctuation theorem for nonequilibrium stationary states and appropriate to constrained equilibrium states. Moreover, we show that these fluctuations are distributed according to a Gaussian curve for long enough times. Three different systems are considered here: namely, (i) a fluid composed of particles interacting with Lennard-Jones potentials, (ii) a harmonic oscillator with Nosé-Hoover thermostatting, and (iii) a simple hyperbolic two-dimensional map.

  13. Fluctuation theorem for constrained equilibrium systems

    NASA Astrophysics Data System (ADS)

    Gilbert, Thomas; Dorfman, J. Robert

    2006-02-01

    We discuss the fluctuation properties of equilibrium chaotic systems with constraints such as isokinetic and Nosé-Hoover thermostats. Although the dynamics of these systems does not typically preserve phase-space volumes, the average phase-space contraction rate vanishes, so that the stationary states are smooth. Nevertheless, finite-time averages of the phase-space contraction rate have nontrivial fluctuations which we show satisfy a simple version of the Gallavotti-Cohen fluctuation theorem, complementary to the usual fluctuation theorem for nonequilibrium stationary states and appropriate to constrained equilibrium states. Moreover, we show that these fluctuations are distributed according to a Gaussian curve for long enough times. Three different systems are considered here: namely, (i) a fluid composed of particles interacting with Lennard-Jones potentials, (ii) a harmonic oscillator with Nosé-Hoover thermostatting, and (iii) a simple hyperbolic two-dimensional map.

  14. Sampling Motif-Constrained Ensembles of Networks

    NASA Astrophysics Data System (ADS)

    Fischer, Rico; Leitão, Jorge C.; Peixoto, Tiago P.; Altmann, Eduardo G.

    2015-10-01

    The statistical significance of network properties is conditioned on null models which satisfy specified properties but that are otherwise random. Exponential random graph models are a principled theoretical framework to generate such constrained ensembles, but which often fail in practice, either due to model inconsistency or due to the impossibility to sample networks from them. These problems affect the important case of networks with prescribed clustering coefficient or number of small connected subgraphs (motifs). In this Letter we use the Wang-Landau method to obtain a multicanonical sampling that overcomes both these problems. We sample, in polynomial time, networks with arbitrary degree sequences from ensembles with imposed motifs counts. Applying this method to social networks, we investigate the relation between transitivity and homophily, and we quantify the correlation between different types of motifs, finding that single motifs can explain up to 60% of the variation of motif profiles.

  15. The asymptotics of large constrained graphs

    NASA Astrophysics Data System (ADS)

    Radin, Charles; Ren, Kui; Sadun, Lorenzo

    2014-05-01

    We show, through local estimates and simulation, that if one constrains simple graphs by their densities ɛ of edges and τ of triangles, then asymptotically (in the number of vertices) for over 95% of the possible range of those densities there is a well-defined typical graph, and it has a very simple structure: the vertices are decomposed into two subsets V1 and V2 of fixed relative size c and 1 - c, and there are well-defined probabilities of edges, gjk, between vj ∈ Vj, and vk ∈ Vk. Furthermore the four parameters c, g11, g22 and g12 are smooth functions of (ɛ, τ) except at two smooth ‘phase transition’ curves.

  16. How alive is constrained SUSY really?

    DOE PAGES

    Bechtle, Philip; Desch, Klaus; Dreiner, Herbert K.; ...

    2016-05-31

    Constrained supersymmetric models like the CMSSM might look less attractive nowadays because of fine tuning arguments. They also might look less probable in terms of Bayesian statistics. The question how well the model under study describes the data, however, is answered by frequentist p-values. Thus, for the first time, we calculate a p-value for a supersymmetric model by performing dedicated global toy fits. We combine constraints from low-energy and astrophysical observables, Higgs boson mass and rate measurements as well as the non-observation of new physics in searches for supersymmetry at the LHC. Furthermore, using the framework Fittino, we perform globalmore » fits of the CMSSM to the toy data and find that this model is excluded at the 90% confidence level.« less

  17. Disappearance and Creation of Constrained Amorphous Phase

    NASA Astrophysics Data System (ADS)

    Cebe, Peggy; Lu, Sharon X.

    1997-03-01

    We report observation of the disappearance and recreation of rigid, or constrained, amorphous phase by sequential thermal annealing. Tempera- ture modulated differential scanning calorimetry (MDSC) is used to study the glass transition and lower melting endotherm after annealing. Cold crystallization of poly(phenylene sulfide), PPS, at a temperature just above Tg creates an initial large fraction of rigid amorphous phase (RAP). Brief, rapid annealing to a higher temperature causes RAP almost to disappear completely. Subsequent reannealing at the original lower temperature restores RAP to its original value. At the same time that RAP is being removed, Tg decreases; when RAP is restored, Tg also returns to its initial value. The crystal fraction remains unaffected by the annealing sequence.

  18. Printer model inversion by constrained optimization

    NASA Astrophysics Data System (ADS)

    Cholewo, Tomasz J.

    1999-12-01

    This paper describes a novel method for finding colorant amounts for which a printer will produce a requested color appearance based on constrained optimization. An error function defines the gamut mapping method and black replacement method. The constraints limit the feasible solution region to the device gamut and prevent exceeding the maximum total area coverage. Colorant values corresponding to in-gamut colors are found with precision limited only by the accuracy of the device model. Out-of- gamut colors are mapped to colors within the boundary of the device gamut. This general approach, used in conjunction with different types of color difference equations, can perform a wide range of out-of-gamut mappings such as chroma clipping or for finding colors on gamut boundary having specified properties. We present an application of this method to the creation of PostScript color rendering dictionaries and ICC profiles.

  19. Constrained fits with non-Gaussian distributions

    NASA Astrophysics Data System (ADS)

    Frühwirth, R.; Cencic, O.

    2016-10-01

    Non-normally distributed data are ubiquitous in many areas of science, including high-energy physics. We present a general formalism for constrained fits, also called data reconciliation, with data that are not normally distributed. It is based on Bayesian reasoning and implemented via MCMC sampling. We show how systems of both linear and non-linear constraints can be efficiently treated. We also show how the fit can be made robust against outlying observations. The method is demonstrated on a couple of examples ranging from material flow analysis to the combination of non-normal measurements. Finally, we discuss possible applications in the field of event reconstruction, such as vertex fitting and kinematic fitting with non-normal track errors.

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

    SciTech Connect

    Lewis, Robert Michael; Griffin, Joshua D.; Kolda, Tamara Gibson

    2006-08-01

    Generating set search (GSS) is a family of direct search methods that encompasses generalized pattern search and related methods. We describe an algorithm for asynchronous linearly-constrained GSS, which has some complexities that make it different from both the asynchronous bound-constrained case as well as the synchronous linearly-constrained case. The algorithm has been implemented in the APPSPACK software framework and we present results from an extensive numerical study using CUTEr test problems. We discuss the results, both positive and negative, and conclude that GSS is a reliable method for solving small-to-medium sized linearly-constrained optimization problems without derivatives.

  2. Eulerian Formulation of Spatially Constrained Elastic Rods

    NASA Astrophysics Data System (ADS)

    Huynen, Alexandre

    Slender elastic rods are ubiquitous in nature and technology. For a vast majority of applications, the rod deflection is restricted by an external constraint and a significant part of the elastic body is in contact with a stiff constraining surface. The research work presented in this doctoral dissertation formulates a computational model for the solution of elastic rods constrained inside or around frictionless tube-like surfaces. The segmentation strategy adopted to cope with this complex class of problems consists in sequencing the global problem into, comparatively simpler, elementary problems either in continuous contact with the constraint or contact-free between their extremities. Within the conventional Lagrangian formulation of elastic rods, this approach is however associated with two major drawbacks. First, the boundary conditions specifying the locations of the rod centerline at both extremities of each elementary problem lead to the establishment of isoperimetric constraints, i.e., integral constraints on the unknown length of the rod. Second, the assessment of the unilateral contact condition requires, in principle, the comparison of two curves parametrized by distinct curvilinear coordinates, viz. the rod centerline and the constraint axis. Both conspire to burden the computations associated with the method. To streamline the solution along the elementary problems and rationalize the assessment of the unilateral contact condition, the rod governing equations are reformulated within the Eulerian framework of the constraint. The methodical exploration of both types of elementary problems leads to specific formulations of the rod governing equations that stress the profound connection between the mechanics of the rod and the geometry of the constraint surface. The proposed Eulerian reformulation, which restates the rod local equilibrium in terms of the curvilinear coordinate associated with the constraint axis, describes the rod deformed configuration

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

    SciTech Connect

    Unkefer, C.J. ); Lodwig, S.N. . 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. T Cell Determinants Incorporating [beta]-Amino Acid Residues Are Protease Resistant and Remain Immunogenic In Vivo

    SciTech Connect

    Webb, Andrew I.; Dunstone, Michelle A.; Williamson, Nicholas A.; Price, Jason D.; Kauwe, Andreade; Chen, Weisan; Oakley, Aaron; Perlmutter, Patrick; McCluskey, James; Aguilar, Marie-Isabel; Rossjohn, Jamie; Purcell, Anthony W.

    2010-07-20

    A major hurdle in designing successful epitope-based vaccines resides in the delivery, stability, and immunogenicity of the peptide immunogen. The short-lived nature of unmodified peptide-based vaccines in vivo limits their therapeutic application in the immunotherapy of cancers and chronic viral infections as well as their use in generating prophylactic immunity. The incorporation of {beta}-amino acids into peptides decreases proteolysis, yet its potential application in the rational design of T cell mimotopes is poorly understood. To address this, we have replaced each residue of the SIINFEKL epitope individually with the corresponding {beta}-amino acid and examined the resultant efficacy of these mimotopes. Some analogs displayed similar MHC binding and superior protease stability compared with the native epitope. Importantly, these analogs were able to generate cross-reactive CTLs in vivo that were capable of lysing tumor cells that expressed the unmodified epitope as a surrogate tumor Ag. Structural analysis of peptides in which anchor residues were substituted with {beta}-amino acids revealed the basis for enhanced MHC binding and retention of immunogenicity observed for these analogs and paves the way for future vaccine design using {beta}-amino acids. We conclude that the rational incorporation of {beta}-amino acids into T cell determinants is a powerful alternative to the traditional homologous substitution of randomly chosen naturally occurring {alpha}-amino acids, and these mimotopes may prove particularly useful for inclusion in epitope-based vaccines.

  5. Constraining electromagnetic core-mantle coupling

    NASA Astrophysics Data System (ADS)

    Wicht, J.; Jault, D.

    1999-02-01

    Electromagnetic core-mantle coupling is one candidate for explaining length of day (LOD) variations on decadal time scales. This coupling has traditionally been calculated from models of core surface flow /U-->, but core flow inversions are not unique. Unfortunately, the main torque contribution depends on the toroidal part /∇×r-->Φ of the vector field (U-->Br), which is left undetermined by the radial induction equation that links core flows to magnetic field data under the frozen-flux hypothesis. (Br is the radial magnetic field at the core surface.) We have developed a new method that bypasses flow inversions. Using the vector field (U-->Br) directly, we estimate its toroidal part by imposing that (U-->Br) vanishes where Br=0. The calculation of the electromagnetic torque is also hindered by the uncertainty in the conductivity structure of the lower mantle. However, we conclude that the conductivity of the lower mantle has to be much larger than current estimates derived from diamond anvil cell experiments to make the electromagnetic torque significant. The region beneath Africa and the mid-Atlantic (where there is the most significant (Br=0) curve apart from the magnetic equator) is particularly important. Here, the field Φ is relatively well constrained, and this is the single region that contributes most to the torque. Following Holme [Holme, R., 1998a. Electromagnetic core-mantle coupling 1: explaining decadal changes in the length of day. Geophys. J. Int. (132) 167-180.], we show nevertheless that small changes to Φ suffice to recover the torque ΓLOD required to explain LOD variations provided that the lower mantle conductivity is high enough. We find a value similar to Holme [Holme, R., 1998b. Electromagnetic core-mantle coupling 2: probing deep mantle conductance. In: Gunis, M., Wysession, M.E., Knittel, E., Buffett, B.A. (Eds.), The Core-Mantle Boundary Region. AGU, pp. 139-151.] for the minimum conductance (108 S). However, we were not able to

  6. Sequential unconstrained minimization algorithms for constrained optimization

    NASA Astrophysics Data System (ADS)

    Byrne, Charles

    2008-02-01

    The problem of minimizing a function f(x):RJ → R, subject to constraints on the vector variable x, occurs frequently in inverse problems. Even without constraints, finding a minimizer of f(x) may require iterative methods. We consider here a general class of iterative algorithms that find a solution to the constrained minimization problem as the limit of a sequence of vectors, each solving an unconstrained minimization problem. Our sequential unconstrained minimization algorithm (SUMMA) is an iterative procedure for constrained minimization. At the kth step we minimize the function G_k(x)=f(x)+g_k(x), to obtain xk. The auxiliary functions gk(x):D ⊆ RJ → R+ are nonnegative on the set D, each xk is assumed to lie within D, and the objective is to minimize the continuous function f:RJ → R over x in the set C=\\overline D , the closure of D. We assume that such minimizers exist, and denote one such by \\hat x . We assume that the functions gk(x) satisfy the inequalities 0\\leq g_k(x)\\leq G_{k-1}(x)-G_{k-1}(x^{k-1}), for k = 2, 3, .... Using this assumption, we show that the sequence {f(xk)} is decreasing and converges to f({\\hat x}) . If the restriction of f(x) to D has bounded level sets, which happens if \\hat x is unique and f(x) is closed, proper and convex, then the sequence {xk} is bounded, and f(x^*)=f({\\hat x}) , for any cluster point x*. Therefore, if \\hat x is unique, x^*={\\hat x} and \\{x^k\\}\\rightarrow {\\hat x} . When \\hat x is not unique, convergence can still be obtained, in particular cases. The SUMMA includes, as particular cases, the well-known barrier- and penalty-function methods, the simultaneous multiplicative algebraic reconstruction technique (SMART), the proximal minimization algorithm of Censor and Zenios, the entropic proximal methods of Teboulle, as well as certain cases of gradient descent and the Newton-Raphson method. The proof techniques used for SUMMA can be extended to obtain related results for the induced proximal

  7. Constrained Markovian Dynamics of Random Graphs

    NASA Astrophysics Data System (ADS)

    Coolen, A. C. C.; de Martino, A.; Annibale, A.

    2009-09-01

    We introduce a statistical mechanics formalism for the study of constrained graph evolution as a Markovian stochastic process, in analogy with that available for spin systems, deriving its basic properties and highlighting the role of the `mobility' (the number of allowed moves for any given graph). As an application of the general theory we analyze the properties of degree-preserving Markov chains based on elementary edge switchings. We give an exact yet simple formula for the mobility in terms of the graph's adjacency matrix and its spectrum. This formula allows us to define acceptance probabilities for edge switchings, such that the Markov chains become controlled Glauber-type detailed balance processes, designed to evolve to any required invariant measure (representing the asymptotic frequencies with which the allowed graphs are visited during the process). As a corollary we also derive a condition in terms of simple degree statistics, sufficient to guarantee that, in the limit where the number of nodes diverges, even for state-independent acceptance probabilities of proposed moves the invariant measure of the process will be uniform. We test our theory on synthetic graphs and on realistic larger graphs as studied in cellular biology, showing explicitly that, for instances where the simple edge swap dynamics fails to converge to the uniform measure, a suitably modified Markov chain instead generates the correct phase space sampling.

  8. Proximity Navigation of Highly Constrained Spacecraft

    NASA Technical Reports Server (NTRS)

    Scarritt, S.; Swartwout, M.

    2007-01-01

    Bandit is a 3-kg automated spacecraft in development at Washington University in St. Louis. Bandit's primary mission is to demonstrate proximity navigation, including docking, around a 25-kg student-built host spacecraft. However, because of extreme constraints in mass, power and volume, traditional sensing and actuation methods are not available. In particular, Bandit carries only 8 fixed-magnitude cold-gas thrusters to control its 6 DOF motion. Bandit lacks true inertial sensing, and the ability to sense position relative to the host has error bounds that approach the size of the Bandit itself. Some of the navigation problems are addressed through an extremely robust, error-tolerant soft dock. In addition, we have identified a control methodology that performs well in this constrained environment: behavior-based velocity potential functions, which use a minimum-seeking method similar to Lyapunov functions. We have also adapted the discrete Kalman filter for use on Bandit for position estimation and have developed a similar measurement vs. propagation weighting algorithm for attitude estimation. This paper provides an overview of Bandit and describes the control and estimation approach. Results using our 6DOF flight simulator are provided, demonstrating that these methods show promise for flight use.

  9. NUCLEI SEGMENTATION VIA SPARSITY CONSTRAINED CONVOLUTIONAL REGRESSION

    PubMed Central

    Zhou, Yin; Chang, Hang; Barner, Kenneth E.; Parvin, Bahram

    2017-01-01

    Automated profiling of nuclear architecture, in histology sections, can potentially help predict the clinical outcomes. However, the task is challenging as a result of nuclear pleomorphism and cellular states (e.g., cell fate, cell cycle), which are compounded by the batch effect (e.g., variations in fixation and staining). Present methods, for nuclear segmentation, are based on human-designed features that may not effectively capture intrinsic nuclear architecture. In this paper, we propose a novel approach, called sparsity constrained convolutional regression (SCCR), for nuclei segmentation. Specifically, given raw image patches and the corresponding annotated binary masks, our algorithm jointly learns a bank of convolutional filters and a sparse linear regressor, where the former is used for feature extraction, and the latter aims to produce a likelihood for each pixel being nuclear region or background. During classification, the pixel label is simply determined by a thresholding operation applied on the likelihood map. The method has been evaluated using the benchmark dataset collected from The Cancer Genome Atlas (TCGA). Experimental results demonstrate that our method outperforms traditional nuclei segmentation algorithms and is able to achieve competitive performance compared to the state-of-the-art algorithm built upon human-designed features with biological prior knowledge. PMID:28101301

  10. Constrained spheroids for prolonged hepatocyte culture.

    PubMed

    Tong, Wen Hao; Fang, Yu; Yan, Jie; Hong, Xin; Hari Singh, Nisha; Wang, Shu Rui; Nugraha, Bramasta; Xia, Lei; Fong, Eliza Li Shan; Iliescu, Ciprian; Yu, Hanry

    2016-02-01

    Liver-specific functions in primary hepatocytes can be maintained over extended duration in vitro using spheroid culture. However, the undesired loss of cells over time is still a major unaddressed problem, which consequently generates large variations in downstream assays such as drug screening. In static culture, the turbulence generated by medium change can cause spheroids to detach from the culture substrate. Under perfusion, the momentum generated by Stokes force similarly results in spheroid detachment. To overcome this problem, we developed a Constrained Spheroids (CS) culture system that immobilizes spheroids between a glass coverslip and an ultra-thin porous Parylene C membrane, both surface-modified with poly(ethylene glycol) and galactose ligands for optimum spheroid formation and maintenance. In this configuration, cell loss was minimized even when perfusion was introduced. When compared to the standard collagen sandwich model, hepatocytes cultured as CS under perfusion exhibited significantly enhanced hepatocyte functions such as urea secretion, and CYP1A1 and CYP3A2 metabolic activity. We propose the use of the CS culture as an improved culture platform to current hepatocyte spheroid-based culture systems.

  11. 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.

  12. Pressure compensated transducer system with constrained diaphragm

    NASA Astrophysics Data System (ADS)

    Percy, Joseph L.

    1992-08-01

    An acoustic source apparatus has an acoustic transducer that is enclosed in a substantially rigid and watertight enclosure to resist the pressure of water on the transducer and to seal the transducer from the water. The enclosure has an opening through which acoustic signals pass and over which is placed a resilient, expandable and substantially water-impermeable diaphragm. A net stiffens and strengthens the diaphragm as well as constrains the diaphragm from overexpansion or from migrating due to buoyancy forces. Pressurized gas, regulated at slightly above ambient pressure, is supplied to the enclosure and the diaphragm to compensate for underwater ambient pressures. Gas pressure regulated at above ambient pressure is used to selectively tune the pressure levels within the enclosure and diaphragm so that diaphragm resonance can be achieved. Controls are used to selectively fill, as well as vent the enclosure and diaphragm during system descent and ascent, respectively. A signal link is used to activate these controls and to provide the driving force for the acoustic transducer.

  13. 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.

  14. Constrained Graph Optimization: Interdiction and Preservation Problems

    SciTech Connect

    Schild, Aaron V

    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.

  15. 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.

  16. Optimization of input-constrained systems

    NASA Astrophysics Data System (ADS)

    Malki, Suleyman; Spaanenburg, Lambert

    2009-05-01

    The computational demands of algorithms are rapidly growing. The naive implementation uses extended doubleprecision floating-point numbers and has therefore extreme difficulties in maintaining real-time performance. For fixedpoint numbers, the value representation pushes in two directions (value range and step size) to set the applicationdependent word size. In the general case, checking all combinations of all different values on all system inputs will easily become computationally infeasible. Checking corner cases only helps to reduce the combinatorial explosion, as still checking for accuracy and precision to limit word size remains a considerable effort. A range of evolutionary techniques have been tried where the sheer size of the problem withstands an extensive search. When the value range can be limited, the problem becomes tractable and a constructive approach becomes feasible. We propose an approach that is reminiscent of the Quine-Mc.Cluskey logic minimization procedure. Next to the conjunctive search as popular in Boolean minimization, we investigate the disjunctive approach that starts from a presumed minimal word size. To eliminate the occurrence of anomalies, this still has to be checked for larger word sizes. The procedure has initially been implemented using Java and Matlab. We have applied the above procedure to feed-forward and to cellular neural networks (CNN) as typical examples of input-constrained systems. In the case of hole-filling by means of a CNN, we find that the 1461 different coefficient sets can be reduced to 360, each giving robust behaviour on 7-bits internal words.

  17. Constraining the oblateness of Kepler planets

    SciTech Connect

    Zhu, Wei; Huang, Chelsea X.; Zhou, George; Lin, D. N. C.

    2014-11-20

    We use Kepler short-cadence light curves to constrain the oblateness of planet candidates in the Kepler sample. The transits of rapidly rotating planets that are deformed in shape will lead to distortions in the ingress and egress of their light curves. We report the first tentative detection of an oblate planet outside the solar system, measuring an oblateness of 0.22{sub −0.11}{sup +0.11} for the 18 M{sub J} mass brown dwarf Kepler 39b (KOI 423.01). We also provide constraints on the oblateness of the planets (candidates) HAT-P-7b, KOI 686.01, and KOI 197.01 to be <0.067, <0.251, and <0.186, respectively. Using the Q' values from Jupiter and Saturn, we expect tidal synchronization for the spins of HAT-P-7b, KOI 686.01, and KOI 197.01, and for their rotational oblateness signatures to be undetectable in the current data. The potentially large oblateness of KOI 423.01 (Kepler 39b) suggests that the Q' value of the brown dwarf needs to be two orders of magnitude larger than that of the solar system gas giants to avoid being tidally spun down.

  18. Optimization of constrained density functional theory

    NASA Astrophysics Data System (ADS)

    O'Regan, David D.; Teobaldi, Gilberto

    2016-07-01

    Constrained density functional theory (cDFT) is a versatile electronic structure method that enables ground-state calculations to be performed subject to physical constraints. It thereby broadens their applicability and utility. Automated Lagrange multiplier optimization is necessary for multiple constraints to be applied efficiently in cDFT, for it to be used in tandem with geometry optimization, or with molecular dynamics. In order to facilitate this, we comprehensively develop the connection between cDFT energy derivatives and response functions, providing a rigorous assessment of the uniqueness and character of cDFT stationary points while accounting for electronic interactions and screening. In particular, we provide a nonperturbative proof that stable stationary points of linear density constraints occur only at energy maxima with respect to their Lagrange multipliers. We show that multiple solutions, hysteresis, and energy discontinuities may occur in cDFT. Expressions are derived, in terms of convenient by-products of cDFT optimization, for quantities such as the dielectric function and a condition number quantifying ill definition in multiple constraint cDFT.

  19. Distributed Constrained Optimization with Semicoordinate Transformations

    NASA Technical Reports Server (NTRS)

    Macready, William; Wolpert, David

    2006-01-01

    Recent work has shown how information theory extends conventional full-rationality game theory to allow bounded rational agents. The associated mathematical framework can be used to solve constrained optimization problems. This is done by translating the problem into an iterated game, where each agent controls a different variable of the problem, so that the joint probability distribution across the agents moves gives an expected value of the objective function. The dynamics of the agents is designed to minimize a Lagrangian function of that joint distribution. Here we illustrate how the updating of the Lagrange parameters in the Lagrangian is a form of automated annealing, which focuses the joint distribution more and more tightly about the joint moves that optimize the objective function. We then investigate the use of "semicoordinate" variable transformations. These separate the joint state of the agents from the variables of the optimization problem, with the two connected by an onto mapping. We present experiments illustrating the ability of such transformations to facilitate optimization. We focus on the special kind of transformation in which the statistically independent states of the agents induces a mixture distribution over the optimization variables. Computer experiment illustrate this for &sat constraint satisfaction problems and for unconstrained minimization of NK functions.

  20. Joint Chance-Constrained Dynamic Programming

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    This paper presents a novel dynamic programming algorithm with a joint chance constraint, which explicitly bounds the risk of failure in order to maintain the state within a specified feasible region. A joint chance constraint cannot be handled by existing constrained dynamic programming approaches since their application is limited to constraints in the same form as the cost function, that is, an expectation over a sum of one-stage costs. We overcome this challenge by reformulating the joint chance constraint into a constraint on an expectation over a sum of indicator functions, which can be incorporated into the cost function by dualizing the optimization problem. As a result, the primal variables can be optimized by a standard dynamic programming, while the dual variable is optimized by a root-finding algorithm that converges exponentially. Error bounds on the primal and dual objective values are rigorously derived. We demonstrate the algorithm on a path planning problem, as well as an optimal control problem for Mars entry, descent and landing. The simulations are conducted using a real terrain data of Mars, with four million discrete states at each time step.

  1. Constraining Simulated Photosynthesis with Fluorescence Observations

    NASA Astrophysics Data System (ADS)

    Baker, I. T.; Berry, J. A.; Lee, J.; Frankenberg, C.; Denning, S.

    2012-12-01

    The measurement of chlorophyll fluorescence from satellites is an emerging technology. To date, most applications have compared fluorescence to light use efficiency models of Gross Primary Productivity (GPP). A close correspondence between fluorescence and GPP has been found in these comparisons. Here, we 'go the other way' and calculate fluorescence using an enzyme kinetic photosynthesis model (the Simple Biosphere Model; SiB), and compare to spectral retrievals. We utilize multiple representations for model phenology as a sensitivity test, obtaining leaf area index (LAI) and fraction of photosynthetically active radiation absorbed (fPAR) from both MODIS-derived products as well as a prognostic model of LAI/fPAR based on growing season index (PGSI). We find that bidirectional reflectance distribution function (BRDF), canopy radiative transfer, and leaf-to-canopy scaling all contribute to variability in simulated fluorescence. We use our results to evaluate discrepancies between light use efficiency and enzyme kinetic models across latitudinal, vegetation and climatological gradients. Satellite retrievals of fluorescence will provide insight into photosynthetic process and constrain simulations of the carbon cycle across multiple spatiotemporal scales.

  2. String theory origin of constrained multiplets

    NASA Astrophysics Data System (ADS)

    Kallosh, Renata; Vercnocke, Bert; Wrase, Timm

    2016-09-01

    We study the non-linearly realized spontaneously broken supersymmetry of the (anti-)D3-brane action in type IIB string theory. The worldvolume fields are one vector A μ , three complex scalars ϕ i and four 4d fermions λ 0, λ i. These transform, in addition to the more familiar {N}=4 linear supersymmetry, also under 16 spontaneously broken, non-linearly realized supersymmetries. We argue that the worldvolume fields can be packaged into the following constrained 4d non-linear {N}=1 multiplets: four chiral multiplets S, Y i that satisfy S 2 = SY i =0 and contain the worldvolume fermions λ 0 and λ i ; and four chiral multiplets W α , H i that satisfy S{W}_{α }=S{overline{D}}_{overset{\\cdotp }{α }}{overline{H}}^{overline{imath}}=0 and contain the vector A μ and the scalars ϕ i . We also discuss how placing an anti-D3-brane on top of intersecting O7-planes can lead to an orthogonal multiplet Φ that satisfies S(Φ -overline{Φ})=0 , which is particularly interesting for inflationary cosmology.

  3. Constrained Sypersymmetric Flipped SU (5) GUT Phenomenology

    SciTech Connect

    Ellis, John; Mustafayev, Azar; Olive, Keith A.; /Minnesota U., Theor. Phys. Inst. /Minnesota U. /Stanford U., Phys. Dept. /SLAC

    2011-08-12

    We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, Min, above the GUT scale, M{sub GUT}. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino {chi} and the lighter stau {tilde {tau}}{sub 1} is sensitive to M{sub in}, as is the relationship between m{sub {chi}} and the masses of the heavier Higgs bosons A,H. For these reasons, prominent features in generic (m{sub 1/2}, m{sub 0}) planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to Min, as we illustrate for several cases with tan {beta} = 10 and 55. However, these features do not necessarily disappear at large Min, unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses.

  4. Constraining Cosmological Models with Different Observations

    NASA Astrophysics Data System (ADS)

    Wei, J. J.

    2016-07-01

    With the observations of Type Ia supernovae (SNe Ia), scientists discovered that the Universe is experiencing an accelerated expansion, and then revealed the existence of dark energy in 1998. Since the amazing discovery, cosmology has became a hot topic in the physical research field. Cosmology is a subject that strongly depends on the astronomical observations. Therefore, constraining different cosmological models with all kinds of observations is one of the most important research works in the modern cosmology. The goal of this thesis is to investigate cosmology using the latest observations. The observations include SNe Ia, Type Ic Super Luminous supernovae (SLSN Ic), Gamma-ray bursts (GRBs), angular diameter distance of galaxy cluster, strong gravitational lensing, and age measurements of old passive galaxies, etc. In Chapter 1, we briefly review the research background of cosmology, and introduce some cosmological models. Then we summarize the progress on cosmology from all kinds of observations in more details. In Chapter 2, we present the results of our studies on the supernova cosmology. The main difficulty with the use of SNe Ia as standard candles is that one must optimize three or four nuisance parameters characterizing SN luminosities simultaneously with the parameters of an expansion model of the Universe. We have confirmed that one should optimize all of the parameters by carrying out the method of maximum likelihood estimation in any situation where the parameters include an unknown intrinsic dispersion. The commonly used method, which estimates the dispersion by requiring the reduced χ^{2} to equal unity, does not take into account all possible variances among the parameters. We carry out such a comparison of the standard ΛCDM cosmology and the R_{h}=ct Universe using the SN Legacy Survey sample of 252 SN events, and show that each model fits its individually reduced data very well. Moreover, it is quite evident that SLSNe Ic may be useful

  5. Constraining inflation with future galaxy redshift surveys

    SciTech Connect

    Huang, Zhiqi; Vernizzi, Filippo; Verde, Licia E-mail: liciaverde@icc.ub.edu

    2012-04-01

    With future galaxy surveys, a huge number of Fourier modes of the distribution of the large scale structures in the Universe will become available. These modes are complementary to those of the CMB and can be used to set constraints on models of the early universe, such as inflation. Using a MCMC analysis, we compare the power of the CMB with that of the combination of CMB and galaxy survey data, to constrain the power spectrum of primordial fluctuations generated during inflation. We base our analysis on the Planck satellite and a spectroscopic redshift survey with configuration parameters close to those of the Euclid mission as examples. We first consider models of slow-roll inflation, and show that the inclusion of large scale structure data improves the constraints by nearly halving the error bars on the scalar spectral index and its running. If we attempt to reconstruct the inflationary single-field potential, a similar conclusion can be reached on the parameters characterizing the potential. We then study models with features in the power spectrum. In particular, we consider ringing features produced by a break in the potential and oscillations such as in axion monodromy. Adding large scale structures improves the constraints on features by more than a factor of two. In axion monodromy we show that there are oscillations with small amplitude and frequency in momentum space that are undetected by CMB alone but can be measured by including galaxy surveys in the analysis.

  6. Extraterrestrial Amino Acids Identified in Metal-Rich CH and CB Carbonaceous Chondrites from Antarctica

    NASA Technical Reports Server (NTRS)

    Burton, Aaron S.; Elsila, Jamie E.; Hein, Jason E.; Glavin, Daniel P.; Dworkin, Jason P.

    2013-01-01

    Carbonaceous chondrites contain numerous indigenous organic compounds and could have been an important source of prebiotic compounds required for the origin of life on Earth or elsewhere. Extraterrestrial amino acids have been reported in five of the eight groups of carbonaceous chondrites and are most abundant in CI, CM, and CR chondritesbut are also present in the more thermally altered CV and CO chondrites. We report the abundance, distribution, and enantiomeric and isotopic compositions of simple primary amino acids in six metal-rich CH and CB carbonaceous chondrites that have not previously been investigated for amino acids: Allan Hills (ALH) 85085 (CH3), Pecora Escarpment(PCA) 91467 (CH3), Patuxent Range (PAT) 91546 (CH3), MacAlpine Hills (MAC) 02675(CBb), Miller Range (MIL) 05082 (CB), and Miller Range (MIL) 07411 (CB). Amino acid abundances and carbon isotopic values were obtained by using both liquid chromatography time-of-flight mass spectrometry and fluorescence, and gas chromatography isotope ratiomass spectrometry. The (delta D, delta C-13, delta N-15) ratios of multiple amino acids fall outside of the terrestrial range and support their extraterrestrial origin. Extracts of CH chondrites were found to be particularly rich in amino acids (1316 parts per million, ppm) while CB chondrite extracts had much lower abundances (0.22 ppm). The amino acid distributions of the CH and CB chondrites were distinct from the distributions observed in type 2 and 3 CM and CR chondrites and contained elevated levels of beta-, gamma-, and delta-amino acids compared to the corresponding alpha-amino acids, providing evidence that multiple amino acid formation mechanisms were important in CH and CB chondrites.

  7. Analogues of arginine vasopressin modified in position 2 and 3 with conformationally constrained dipeptide fragments.

    PubMed

    Łempicka, Elzbieta; Derdowska, Izabela; Kowalczyk, Wioleta; Dawidowska, Olga; Prahl, Adam; Janecki, Marcin; Jasiński, Tomasz; Trzeciak, Henryk I; Lammek, Bernard

    2005-02-01

    This study describes the synthesis and some pharmacological properties of ten new analogues of arginine vasopressin (AVP) containing a conformationally constrained dipeptide fragment in the N-terminal part of their molecules. Amino acid residues in positions 2 and 3 of AVP and some of its agonistic analogues were replaced with -Phe-Phe and D-Phe-D-Phe, dipeptides having a -CH2-CH2- link bridging two nitrogens. All the new peptides were tested for vasopressor and antidiuretic activities. Four peptides with pA2 values ranging from 5.96 to 7.21 turned out to be weak or moderately potent V1a antagonists. The results supplied new information about the structure-activity relationship of AVP analogues. As some of these were unexpected, they point to the need for caution when extrapolating previously known effects of modifications to analogues having conformationally constrained fragments in their molecules.

  8. Regularized Partial and/or Constrained Redundancy Analysis

    ERIC Educational Resources Information Center

    Takane, Yoshio; Jung, Sunho

    2008-01-01

    Methods of incorporating a ridge type of regularization into partial redundancy analysis (PRA), constrained redundancy analysis (CRA), and partial and constrained redundancy analysis (PCRA) were discussed. The usefulness of ridge estimation in reducing mean square error (MSE) has been recognized in multiple regression analysis for some time,…

  9. 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…

  10. The constrained reinitialization equation for level set methods

    NASA Astrophysics Data System (ADS)

    Hartmann, Daniel; Meinke, Matthias; Schröder, Wolfgang

    2010-03-01

    Based on the constrained reinitialization scheme [D. Hartmann, M. Meinke, W. Schröder, Differential equation based constrained reinitialization for level set methods, J. Comput. Phys. 227 (2008) 6821-6845] a new constrained reinitialization equation incorporating a forcing term is introduced. Two formulations for high-order constrained reinitialization (HCR) are presented combining the simplicity and generality of the original reinitialization equation [M. Sussman, P. Smereka, S. Osher, A level set approach for computing solutions to incompressible two-phase flow, J. Comput. Phys. 114 (1994) 146-159] in terms of high-order standard discretization and the accuracy of the constrained reinitialization scheme in terms of interface displacement. The novel HCR schemes represent simple extensions of standard implementations of the original reinitialization equation. The results evidence the significantly increased accuracy and robustness of the novel schemes.

  11. Constraining the source of mantle plumes

    NASA Astrophysics Data System (ADS)

    Cagney, N.; Crameri, F.; Newsome, W. H.; Lithgow-Bertelloni, C.; Cotel, A.; Hart, S. R.; Whitehead, J. A.

    2016-02-01

    In order to link the geochemical signature of hot spot basalts to Earth's deep interior, it is first necessary to understand how plumes sample different regions of the mantle. Here, we investigate the relative amounts of deep and shallow mantle material that are entrained by an ascending plume and constrain its source region. The plumes are generated in a viscous syrup using an isolated heater for a range of Rayleigh numbers. The velocity fields are measured using stereoscopic Particle-Image Velocimetry, and the concept of the 'vortex ring bubble' is used to provide an objective definition of the plume geometry. Using this plume geometry, the plume composition can be analysed in terms of the proportion of material that has been entrained from different depths. We show that the plume composition can be well described using a simple empirical relationship, which depends only on a single parameter, the sampling coefficient, sc. High-sc plumes are composed of material which originated from very deep in the fluid domain, while low-sc plumes contain material entrained from a range of depths. The analysis is also used to show that the geometry of the plume can be described using a similarity solution, in agreement with previous studies. Finally, numerical simulations are used to vary both the Rayleigh number and viscosity contrast independently. The simulations allow us to predict the value of the sampling coefficient for mantle plumes; we find that as a plume reaches the lithosphere, 90% of its composition has been derived from the lowermost 260-750 km in the mantle, and negligible amounts are derived from the shallow half of the lower mantle. This result implies that isotope geochemistry cannot provide direct information about this unsampled region, and that the various known geochemical reservoirs must lie in the deepest few hundred kilometres of the mantle.

  12. Motor Demands Constrain Cognitive Rule Structures

    PubMed Central

    Collins, Anne Gabrielle Eva; Frank, Michael Joshua

    2016-01-01

    Study of human executive function focuses on our ability to represent cognitive rules independently of stimulus or response modality. However, recent findings suggest that executive functions cannot be modularized separately from perceptual and motor systems, and that they instead scaffold on top of motor action selection. Here we investigate whether patterns of motor demands influence how participants choose to implement abstract rule structures. In a learning task that requires integrating two stimulus dimensions for determining appropriate responses, subjects typically structure the problem hierarchically, using one dimension to cue the task-set and the other to cue the response given the task-set. However, the choice of which dimension to use at each level can be arbitrary. We hypothesized that the specific structure subjects adopt would be constrained by the motor patterns afforded within each rule. Across four independent data-sets, we show that subjects create rule structures that afford motor clustering, preferring structures in which adjacent motor actions are valid within each task-set. In a fifth data-set using instructed rules, this bias was strong enough to counteract the well-known task switch-cost when instructions were incongruent with motor clustering. Computational simulations confirm that observed biases can be explained by leveraging overlap in cortical motor representations to improve outcome prediction and hence infer the structure to be learned. These results highlight the importance of sensorimotor constraints in abstract rule formation and shed light on why humans have strong biases to invent structure even when it does not exist. PMID:26966909

  13. 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).

  14. Constraining Cosmic Evolution of Type Ia Supernovae

    SciTech Connect

    Foley, Ryan J.; Filippenko, Alexei V.; Aguilera, C.; Becker, A.C.; Blondin, S.; Challis, P.; Clocchiatti, A.; Covarrubias, R.; Davis, T.M.; Garnavich, P.M.; Jha, S.; Kirshner, R.P.; Krisciunas, K.; Leibundgut, B.; Li, W.; Matheson, T.; Miceli, A.; Miknaitis, G.; Pignata, G.; Rest, A.; Riess, A.G.; /UC, Berkeley, Astron. Dept. /Cerro-Tololo InterAmerican Obs. /Washington U., Seattle, Astron. Dept. /Harvard-Smithsonian Ctr. Astrophys. /Chile U., Catolica /Bohr Inst. /Notre Dame U. /KIPAC, Menlo Park /Texas A-M /European Southern Observ. /NOAO, Tucson /Fermilab /Chile U., Santiago /Harvard U., Phys. Dept. /Baltimore, Space Telescope Sci. /Johns Hopkins U. /Res. Sch. Astron. Astrophys., Weston Creek /Stockholm U. /Hawaii U. /Illinois U., Urbana, Astron. Dept.

    2008-02-13

    We present the first large-scale effort of creating composite spectra of high-redshift type Ia supernovae (SNe Ia) and comparing them to low-redshift counterparts. Through the ESSENCE project, we have obtained 107 spectra of 88 high-redshift SNe Ia with excellent light-curve information. In addition, we have obtained 397 spectra of low-redshift SNe through a multiple-decade effort at Lick and Keck Observatories, and we have used 45 ultraviolet spectra obtained by HST/IUE. The low-redshift spectra act as a control sample when comparing to the ESSENCE spectra. In all instances, the ESSENCE and Lick composite spectra appear very similar. The addition of galaxy light to the Lick composite spectra allows a nearly perfect match of the overall spectral-energy distribution with the ESSENCE composite spectra, indicating that the high-redshift SNe are more contaminated with host-galaxy light than their low-redshift counterparts. This is caused by observing objects at all redshifts with similar slit widths, which corresponds to different projected distances. After correcting for the galaxy-light contamination, subtle differences in the spectra remain. We have estimated the systematic errors when using current spectral templates for K-corrections to be {approx}0.02 mag. The variance in the composite spectra give an estimate of the intrinsic variance in low-redshift maximum-light SN spectra of {approx}3% in the optical and growing toward the ultraviolet. The difference between the maximum-light low and high-redshift spectra constrain SN evolution between our samples to be < 10% in the rest-frame optical.

  15. 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.

  16. Quasi-optical constrained lens amplifiers

    NASA Astrophysics Data System (ADS)

    Schoenberg, Jon S.

    1995-09-01

    A major goal in the field of quasi-optics is to increase the power available from solid state sources by combining the power of individual devices in free space, as demonstrated with grid oscillators and grid amplifiers. Grid amplifiers and most amplifier arrays require a plane wave feed, provided by a far field source or at the beam waist of a dielectric lens pair. These feed approaches add considerable loss and size, which is usually greater than the quasi-optical amplifier gain. In addition, grid amplifiers require external polarizers for stability, further increasing size and complexity. This thesis describes using constrained lens theory in the design of quasi optical amplifier arrays with a focal point feed, improving the power coupling between the feed and the amplifier for increased gain. Feed and aperture arrays of elements, input/output isolation and stability, amplifier circuitry, delay lines and bias distribution are all contained on a single planar substrate, making monolithic circuit integration possible. Measured results of X band transmission lenses and a low noise receive lens are presented, including absolute power gain up to 13 dB, noise figure as low as 1.7 dB, beam scanning to +/-30 deg, beam forming and beam switching of multiple sources, and multiple level quasi-optical power combining. The design and performance of millimeter wave power combining amplifier arrays is described, including a Ka Band hybrid array with 1 watt output power, and a V Band 36 element monolithic array with a 5 dB on/off ratio.

  17. Constraining the Evolution of Poor Clusters

    NASA Astrophysics Data System (ADS)

    Broming, Emma J.; Fuse, C. R.

    2012-01-01

    There currently exists no method by which to quantify the evolutionary state of poor clusters (PCs). Research by Broming & Fuse (2010) demonstrated that the evolution of Hickson compact groups (HCGs) are constrained by the correlation between the X-ray luminosities of point sources and diffuse gas. The current investigation adopts an analogous approach to understanding PCs. Plionis et al. (2009) proposed a theory to define the evolution of poor clusters. The theory asserts that cannibalism of galaxies causes a cluster to become more spherical, develop increased velocity dispersion and increased X-ray temperature and gas luminosity. Data used to quantify the evolution of the poor clusters were compiled across multiple wavelengths. The sample includes 162 objects from the WBL catalogue (White et al. 1999), 30 poor clusters in the Chandra X-ray Observatory archive, and 15 Abell poor clusters observed with BAX (Sadat et al. 2004). Preliminary results indicate that the cluster velocity dispersion and X-ray gas and point source luminosities can be used to highlight a weak correlation. An evolutionary trend was observed for multiple correlations detailed herein. The current study is a continuation of the work by Broming & Fuse examining point sources and their properties to determine the evolutionary stage of compact groups, poor clusters, and their proposed remnants, isolated ellipticals and fossil groups. Preliminary data suggests that compact groups and their high-mass counterpart, poor clusters, evolve along tracks identified in the X-ray gas - X-ray point source relation. While compact groups likely evolve into isolated elliptical galaxies, fossil groups display properties that suggest they are the remains of fully coalesced poor clusters.

  18. Constrained Inversion of Enceladus Interaction Observations

    NASA Astrophysics Data System (ADS)

    Herbert, Floyd; Khurana, K. K.

    2007-10-01

    Many detailed and sophisticated ab initio calculations of the electrodynamic interaction of Enceladus' plume with Saturn's corotating magnetospheric plasma flow have been computed. So far, however, all such calculations have been forward models, that assume the properties of the plume and compute perturbations to the magnetic (and in some cases, flow velocity) field. As a complement to the forward calculations, work reported here explores the inverse approach, of using simplified physical models of the interaction for computationally inverting the observed magnetic field perturbations of the interaction, in order to determine the cross-B-field conductivity distribution near Enceladus, and from that, the neutral gas distribution. Direct inversion of magnetic field observations to current systems is, of course, impossible, but adding the additional constraint of the interaction physics greatly reduces the non-uniqueness of the computed result. This approach was successfully used by Herbert (JGR 90:8241, 1985) to constrain the atmospheric distribution on Io and the Io torus mass density at the time of the Voyager encounter. Work so far has derived the expected result that there is a cone-shaped region of enhanced cross-field conductivity south of Enceladus, through which currents are driven by the motional electric field. That is, near Enceladus' south pole the cross-field currents are localized, but more widely spread at greater distance. This cross-field conductivity is presumably both pickup and collisional (Pedersen and Hall). Due to enforcement of current conservation, Alfven-wing-like currents north of the main part of the interaction region seem to close partly around Enceladus (assumed insulating) and also to continue northward with attenuated intensity, as though there were a tenuous global exosphere on Enceladus providing additional cross-field conductivity. FH thanks the NASA Outer Planets Research, Planetary Atmospheres, and Geospace Science Programs for

  19. Depolarizing actions of gamma-aminobutyric acid and related compounds on rat superior cervical ganglia in vitro.

    PubMed

    Bowery, N G; Brown, D A

    1974-02-01

    1 Potential changes in rat superior cervical ganglia were recorded in vitro with surface electrodes.2 gamma-aminobutyric acid (GABA) produced a transient, low-amplitude ganglion depolarization at rest, and a transient hyperpolarization in ganglia depolarized by carbachol. Depolarization was not prevented by preganglionic denervation. The log dose-response curve for depolarization was sigmoid with a mean ED(50) of 12.5 muM.3 The ganglion was depolarized in similar manner by the following compounds (mean molar potencies relative to GABA (=1) in brackets): 3-aminopropane sulphonic acid (3.4), gamma-amino-beta-hydroxybutyric acid (0.27), beta-guanidino-propionic acid (0.12), guanidinoacetic acid (0.057), delta-aminovaleric acid (0.048), beta-alanine (0.01), 2,4-diaminobutyric acid, gamma-guanidinobutyric acid, taurine and N-methyl-GABA (all <0.01). The following compounds did not depolarize the ganglion at 10 mM concentrations: alpha- and beta-amino-n-butyric acids, alpha-amino-iso-butyric acid, glycine and glutamic acid.4 Depolarization declined in the continued presence of GABA. Ganglia thus ;desensitized' to GABA showed a diminished response to other amino acids but not to carbachol.5 The effect of GABA was not antagonized by hyoscine and hexamethonium in combination, in concentrations sufficient to block responses to carbachol.6 Responses to GABA were blocked more readily than those to carbachol by bicuculline (IC(50), 14 muM) and picrotoxin (IC(50), 37 muM). Strychnine (IC(50), 73 muM) was a relatively weak and less selective GABA-antagonist.7 It is concluded that sympathetic ganglion cells possess receptors for GABA and related amino acids which are (a) different from the acetylcholine receptors and (b) similar to GABA receptors in the central nervous system.

  20. Role of the alpha-amino group of protein in ubiquitin-mediated protein breakdown.

    PubMed Central

    Hershko, A; Heller, H; Eytan, E; Kaklij, G; Rose, I A

    1984-01-01

    Previous studies suggest that the conjugation of ubiquitin to NH2 groups of proteins is required for protein breakdown. We now show that the selective modification of NH2-terminal alpha-NH2 groups of globin and lysozyme prevents their degradation by the ubiquitin proteolytic system from reticulocytes. The conjugation by ubiquitin of epsilon-NH2 groups of lysine residues, usually seen in multiples, was also inhibited in alpha-NH2-blocked proteins. Naturally occurring N alpha-acetylated proteins are not degraded by the ubiquitin system at a significant rate, while their nonacetylated counterparts from other species are good substrates. This suggests that one function of N alpha-acetylation of cellular proteins is to prevent their degradation by the ubiquitin system. alpha-NH2-blocked proteins can have their activity as substrates for degradation increased by incorporation of alpha-NH2 groups through the introduction of polyalanine side chains. Proteins in which most epsilon-NH2 groups are blocked but the alpha-NH2 group is free are degraded by the ubiquitin system, but at a reduced rate. It is therefore suggested that the exposure of a free NH2 terminus of proteins is required for degradation and probably initiates the formation of ubiquitin conjugates committed for degradation. Images PMID:6095265

  1. Detection and characterization of carrier-mediated cationic amino acid transport in lysosomes of normal and cystinotic human fibroblasts. Role in therapeutic cystine removal

    SciTech Connect

    Pisoni, R.L.; Thoene, J.G.; Christensen, H.N.

    1985-04-25

    The discovery of a trans-stimulation property associated with lysine exodus from lysosomes of human fibroblasts has enabled us to characterize a system mediating the transport of cationic amino acids across the lysosomal membrane of human fibroblasts. The cationic amino acids arginine, lysine, ornithine, diaminobutyrate, histidine, 2-aminoethylcysteine, and the mixed disulfide of cysteine and cysteamine all caused trans-stimulation of the exodus of radiolabeled lysine from the lysosomal fraction of human fibroblasts at pH 6.5. In contrast, neutral and acidic amino acids did not affect the rate of lysine exodus. Trans-stimulation of lysine exodus was observed over the pH range from 5.5 to 7.6, was specific for the L-isomer of the cationic amino acid, and was intolerant to methylation of the alpha-amino group of the amino acid. The lysosomotropic amine, chloroquine, greatly retarded lysine exodus, whereas the presence of sodium ion was without effect. The specificity and lack of Na+ dependence of this lysosomal transport system is similar to that of System y+ present on the plasma membrane of human fibroblasts. An important mechanism by which cysteamine treatment of cystinosis allows cystine escape from lysosomes may be the ability of the mixed disulfide of cysteine and cysteamine formed by sulfhydryl-disulfide exchange to migrate by this newly discovered system mediating cationic amino acid transport.

  2. Inhibitors of metalloendopeptidase EC 3.4.24.15 and EC 3.4.24.16 stabilized against proteolysis by the incorporation of beta-amino acids.

    PubMed

    Steer, David; Lew, Rebecca; Perlmutter, Patrick; Smith, A Ian; Aguilar, Marie-Isabel

    2002-09-03

    The enzyme EC 3.4.24.15 (EP 24.15) is a zinc metalloendopeptidase whose precise function in vivo remains unknown but is thought to participate in the regulated metabolism of a number of specific neuropeptides. The lack of stable and selective inhibitors has hindered the determination of the exact function of EP 24.15. Of the limited number of EP 24.15 inhibitors that have been developed, N-[1-(R,S)-carboxy-3-phenylpropyl]-Ala-Ala-Tyr-p-aminobenzoate (CFP) is the most widely studied. CFP is a potent and specific inhibitor, but it is unstable in vivo due to cleavage between the alanine and tyrosine residues by the enzyme neprilysin (EP 24.11). This cleavage by EP 24.11 generates a potent inhibitor of angiotensin converting enzyme, thereby limiting the use of CFP for in vivo studies. To develop specific inhibitors of EP 24.15 that are resistant to in vitro and potentially in vivo proteolysis by EP 24.11, this study incorporated beta-amino acids replacing the Ala-Tyr scissile alpha-amino acids of CFP. Both C2 and C3 substituted beta-amino acids were synthesized and substituted at the EP 24.11 scissile Ala-Tyr bond. Significant EP 24.15 inhibitory activity was observed with some of the beta-amino acid containing analogues. Moreover, binding to EP 24.11 was eliminated, thus rendering all analogues containing beta-amino acids resistant to degradation by EP 24.11. Selective inhibition of either EP 24.15 or EP 24.16 was also observed with some analogues. The results demonstrated the use of beta-amino acids in the design of inhibitors of EP 24.15 and EP 24.16 with K(i)'s in the low micromolar range. At the same time, these analogues were resistant to cleavage by the related metalloendopeptidase EP 24.11, in contrast to the alpha-amino acid based parent peptide. This study has therefore clearly shown the potential of beta-amino acids in the design of stable enzyme inhibitors and their use in generating molecules with selectivity between closely related enzymes.

  3. How We Can Constrain Aerosol Type Globally

    NASA Technical Reports Server (NTRS)

    Kahn, Ralph

    2016-01-01

    In addition to aerosol number concentration, aerosol size and composition are essential attributes needed to adequately represent aerosol-cloud interactions (ACI) in models. As the nature of ACI varies enormously with environmental conditions, global-scale constraints on particle properties are indicated. And although advanced satellite remote-sensing instruments can provide categorical aerosol-type classification globally, detailed particle microphysical properties are unobtainable from space with currently available or planned technologies. For the foreseeable future, only in situ measurements can constrain particle properties at the level-of-detail required for ACI, as well as to reduce uncertainties in regional-to-global-scale direct aerosol radiative forcing (DARF). The limitation of in situ measurements for this application is sampling. However, there is a simplifying factor: for a given aerosol source, in a given season, particle microphysical properties tend to be repeatable, even if the amount varies from day-to-day and year-to-year, because the physical nature of the particles is determined primarily by the regional environment. So, if the PDFs of particle properties from major aerosol sources can be adequately characterized, they can be used to add the missing microphysical detail the better sampled satellite aerosol-type maps. This calls for Systematic Aircraft Measurements to Characterize Aerosol Air Masses (SAM-CAAM). We are defining a relatively modest and readily deployable, operational aircraft payload capable of measuring key aerosol absorption, scattering, and chemical properties in situ, and a program for characterizing statistically these properties for the major aerosol air mass types, at a level-of-detail unobtainable from space. It is aimed at: (1) enhancing satellite aerosol-type retrieval products with better aerosol climatology assumptions, and (2) improving the translation between satellite-retrieved aerosol optical properties and

  4. Folding of Small Proteins Using Constrained Molecular Dynamics

    PubMed Central

    Balaraman, Gouthaman S.; Park, In-Hee; Jain, Abhinandan; Vaidehi, Nagarajan

    2011-01-01

    The focus of this paper is to examine whether conformational search using constrained molecular dynamics (MD) method is more enhanced and enriched towards “native-like” structures compared to all-atom MD for the protein folding as a model problem. Constrained MD methods provide an alternate MD tool for protein structure prediction and structure refinement. It is computationally expensive to perform all-atom simulations of protein folding because the processes occur on a timescale of microseconds. Compared to the all-atom MD simulation, constrained MD methods have the advantage that stable dynamics can be achieved for larger time steps and the number of degrees of freedom is an order of magnitude smaller, leading to a decrease in computational cost. We have developed a generalized constrained MD method that allows the user to “freeze and thaw” torsional degrees of freedom as fit for the problem studied. We have used this method to perform all-torsion constrained MD in implicit solvent coupled with the replica exchange method to study folding of small proteins with various secondary structural motifs such as, α-helix (polyalanine, WALP16), β-turn (1E0Q), and a mixed motif protein (Trp-cage). We demonstrate that constrained MD replica exchange method exhibits a wider conformational search than all-atom MD with increased enrichment of near native structures. “Hierarchical” constrained MD simulations, where the partially formed helical regions in the initial stretch of the all-torsion folding simulation trajectory of Trp-cage were frozen, showed a better sampling of near native structures than all-torsion constrained MD simulations. This is in agreement with the zipping-and-assembly folding model put forth by Dill and coworkers for folding proteins. The use of hierarchical “freeze and thaw” clustering schemes in constrained MD simulation can be used to sample conformations that contribute significantly to folding of proteins. PMID:21591767

  5. Binding of flexible and constrained ligands to the Grb2 SH2 domain: structural effects of ligand preorganization

    PubMed Central

    Clements, John H.; DeLorbe, John E.; Benfield, Aaron P.; Martin, Stephen F.

    2010-01-01

    Structures of the Grb2 SH2 domain complexed with a series of pseudopeptides containing flexible (benzyl succinate) and constrained (aryl cyclopropanedicarboxylate) replacements of the phosphotyrosine (pY) residue in tripeptides derived from Ac-pYXN-NH2 (where X = V, I, E and Q) were elucidated by X-ray crystallography. Complexes of flexible/constrained pairs having the same pY + 1 amino acid were analyzed in order to ascertain what structural differences might be attributed to constraining the phosphotyrosine replacement. In this context, a given structural dissimilarity between complexes was considered to be significant if it was greater than the corresponding difference in complexes coexisting within the same asymmetric unit. The backbone atoms of the domain generally adopt a similar conformation and orientation relative to the ligands in the complexes of each flexible/constrained pair, although there are some significant differences in the relative orientations of several loop regions, most notably in the BC loop that forms part of the binding pocket for the phosphate group in the tyrosine replacements. These variations are greater in the set of complexes of constrained ligands than in the set of complexes of flexible ligands. The constrained ligands make more direct polar contacts to the domain than their flexible counterparts, whereas the more flexible ligand of each pair makes more single-water-mediated contacts to the domain; there was no correlation between the total number of protein–ligand contacts and whether the phosphotyrosine replacement of the ligand was preorganized. The observed differences in hydrophobic interactions between the complexes of each flexible/constrained ligand pair were generally similar to those observed upon comparing such contacts in coexisting complexes. The average adjusted B factors of the backbone atoms of the domain and loop regions are significantly greater in the complexes of constrained ligands than in the complexes of

  6. Residual flexibility test method for verification of constrained structural models

    NASA Technical Reports Server (NTRS)

    Admire, John R.; Tinker, Michael L.; Ivey, Edward W.

    1992-01-01

    A method is presented for deriving constrained modes and frequencies from a model correlated to a set of free-free test modes and a set of measured residual flexibilities. The method involves a simple modification of the MacNeal and Rubin component mode representation to allow verification of a constrained structural model. Results for two spaceflight structures show quick convergence of constrained modes using an easily measurable set of free-free modes plus the residual flexibility matrix or its boundary partition. This paper further validates the residual flexibility approach as an alternative test/analysis method when fixed-base testing proves impractical.

  7. 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.

  8. Quantum dynamics by the constrained adiabatic trajectory method

    SciTech Connect

    Leclerc, A.; Jolicard, G.; Guerin, S.; Killingbeck, J. P.

    2011-03-15

    We develop the constrained adiabatic trajectory method (CATM), which allows one to solve the time-dependent Schroedinger equation constraining the dynamics to a single Floquet eigenstate, as if it were adiabatic. This constrained Floquet state (CFS) is determined from the Hamiltonian modified by an artificial time-dependent absorbing potential whose forms are derived according to the initial conditions. The main advantage of this technique for practical implementation is that the CFS is easy to determine even for large systems since its corresponding eigenvalue is well isolated from the others through its imaginary part. The properties and limitations of the CATM are explored through simple examples.

  9. Stereochemically constrained complex organic molecules extracted from olivine crystal matrix

    NASA Astrophysics Data System (ADS)

    Gerasimenko, I.; Freund, F. T.; Imanaka, H.; Rodgers, R.

    2011-12-01

    Paradoxically, the dense solid state of magmatic minerals is a medium, in which organic synthesis can take place. The reason is that gas-fluid components such as H2O, CO/CO2/N2 and H2S are omnipresent in terrestrial magmatic environments. Any silicate mineral that crystallizes from such magmas will incorporate small quantities of the fluid-phase components in the form of structurally incompatible low-z impurities. During cooling the solute species undergo a redox conversion, resulting in chemically reduced low-z elements. To the extent that these low-z impurities are diffusively mobile, they will exsolve to the surface and/or to major structural defects inside the crystal matrix such as dislocations. Dislocations provide a 3-D structured environment, where the low-z impurities will tend to form stereochemically constrained polyatomic Cn-H-O-N-S entities, which we call organic protomolecules. In Nature, during weathering, such protomolecules will be released into the environment in the form of complex organic molecules. In our study we crush samples under clean conditions as a way to expose Cn-H-O-N-S entities at the fracture surfaces. We conduct identical experiments with selected large olivine single crystals, mm-sized olivine from peridiotite nodules from the San Carlos Volcanic Field, Arizona, and the vesiculated basalt that had carried the nodules upward in the volcanic conduit. We Soxhlet-extract the crushed powders with water, THF and ethyl acetate. The extracts are analyzed at the FTICR-MS facility at Florida State University using ultrahigh resolution Mass Spectrometry techniques capable of determining the chemical composition of the organic molecules up to 600 amu and more. So far we have found several analog sequences of oxygen-rich aliphatic hydrocarbons, families with up to 34 carbon atoms, probably poly-carboxylic acids, and some families containing sulfur.

  10. Constraining Anthropogenic and Biogenic Emissions Using Chemical Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Spencer, Kathleen M.

    Numerous gas-phase anthropogenic and biogenic compounds are emitted into the atmosphere. These gases undergo oxidation to form other gas-phase species and particulate matter. Whether directly or indirectly, primary pollutants, secondary gas-phase products, and particulate matter all pose health and environmental risks. In this work, ambient measurements conducted using chemical ionization mass spectrometry are used as a tool for investigating regional air quality. Ambient measurements of peroxynitric acid (HO2NO2) were conducted in Mexico City. A method of inferring the rate of ozone production, PO3, is developed based on observations of HO2NO 2, NO, and NO2. Comparison of this observationally based PO3 to a highly constrained photochemical box model indicates that regulations aimed at reducing ozone levels in Mexico City by reducing NOx concentrations may be effective at higher NO x levels than predicted using accepted photochemistry. Measurements of SO2 and particulate sulfate were conducted over the Los Angeles basin in 2008 and are compared to measurements made in 2002. A large decrease in SO2 concentration and a change in spatial distribution are observed. Nevertheless, only a modest reduction in sulfate concentration is observed at ground sites within the basin. Possible explanations for these trends are investigated. Two techniques, single and triple quadrupole chemical ionization mass spectrometry, were used to quantify ambient concentrations of biogenic oxidation products, hydroxyacetone and glycolaldehyde. The use of these techniques demonstrates the advantage of triple quadrupole mass spectrometry for separation of mass analogues, provided the collision-induced daughter ions are sufficiently distinct. Enhancement ratios of hydroxyacetone and glycolaldehyde in Californian biomass burning plumes are presented as are concentrations of these compounds at a rural ground site downwind of Sacramento.

  11. Glycotargeting: the preparation of glyco-amino acids and derivatives from unprotected reducing sugars.

    PubMed

    Monsigny, M; Quétard, C; Bourgerie, S; Delay, D; Pichon, C; Midoux, P; Mayer, R; Roche, A C

    1998-02-01

    Lectins are present on the surface of many cells. Many lectins actively recycle from membrane to endosomes and efficiently take up glycoconjugates in a sugar-dependent manner. On this basis, glycoconjugates, specially those obtained by chemical means, are good candidates as carriers of drugs, oligonucleotides or genes. In this paper, we present a panel of methods suitable to transform unprotected reducing oligosaccharides into glycosynthons designed to be easily linked to therapeutic agents. All the glycosynthons presented here are glycosylamines or derivatives, mainly glyco-amino acids or glycopeptides. Glycosylamines are easy to obtain, but they are very labile in slightly acidic or neutral medium; they must be stabilized, by acylation for instance. The coupling efficiency of a reducing sugar with ammonia as well as an alkylamine or an arylamine is higher at high temperature, however, because of the Amadori rearrangement, special conditions have to be selected to prepare the expected glycosylamine derivative with a high yield. Glycosylamines are easily acylated by N-protected amino acids, or by halogeno acids which can then be transformed into amino acids. Alternatively, unprotected reducing oligosaccharides may very efficiently be transformed into N-glycosyl-amino acids and then protected by N-acylation. With a glutamyl derivative having both the alpha-amino and the gamma-carboxylic groups free, the coupling and the acylation, which is intramolecular, are roughly quantitative. N-oligosaccharyl-amino acid derivatives are interesting glycosynthons, because their sugar moiety bears the specificity towards membrane lectins while the amino acid part has the capacity to easily substitute a therapeutic agent.

  12. Studies on renal adaptation to altered dietary amino acid intake: tissue taurine responses in nursing and adult rats.

    PubMed

    Chesney, R W; Lippincott, S; Gusowski, N; Padilla, M; Zelikovic, I

    1986-10-01

    This study examines the effect of a low sulfur amino acid diet (LTD) and a high taurine diet (HTD), compared with a normal diet, on the plasma, urine, muscle, brain and renal cortex levels of taurine in immature and adult rats. Milk taurine from lactating dams reflected the taurine content of the diet, being low in LTD-fed and high in HTD-fed animals. Nursing pups (7, 14 and 21 d old) often had plasma, urine and tissue--renal cortex, heart, skeletal muscle--levels of taurine related to dietary exposure, a situation also found in adult animals. These diets did not influence the urinary excretion of the sulfur-containing alpha-amino acids methionine and cystine but a sulfur aminoaciduria of immaturity was evident. By contrast, the content of taurine in brain was constant regardless of dietary intake of sulfur amino acids. An age-related decline in brain taurine content was found--as noted by others--but this too was influenced by diet. This dual finding of brain taurine constancy despite wide differences in sulfur amino acid intake and changes in the renal handling of taurine as influenced by diet suggest that the renal adaptive response serves to maintain the stability of brain taurine content.

  13. CONDORR--CONstrained Dynamics of Rigid Residues: a molecular dynamics program for constrained molecules.

    PubMed

    York, William S; Yi, Xiaobing

    2004-08-01

    A computer program CONDORR (CONstrained Dynamics of Rigid Residues) was developed for molecular dynamics simulations of large and/or constrained molecular systems, particularly carbohydrates. CONDORR efficiently calculates molecular trajectories on the basis of 2D or 3D potential energy maps, and can generate such maps based on a simple force field. The simulations involve three translational and three rotational degrees of freedom for each rigid, asymmetrical residue in the model. Total energy and angular momentum are conserved when no stochastic or external forces are applied to the model, if the time step is kept sufficiently short. Application of Langevin dynamics allows longer time steps, providing efficient exploration of conformational space. The utility of CONDORR was demonstrated by application to a constrained polysaccharide model and to the calculation of residual dipolar couplings for a disaccharide. [Figure: see text]. Molecular models (bottom) are created by cloning rigid residue archetypes (top) and joining them together. As defined here, the archetypes AX, HM and BG respectively correspond to an alpha-D-Xyl p residue, a hydroxymethyl group, and a beta-D-Glc p residue lacking O6, H6a and H6b. Each archetype contains atoms (indicated by boxes) that can be shared with other archetypes to form a linked structure. For example, the glycosidic link between the two D-Glc p residues is established by specifying that O1 of the nonreducing beta-D-Glc p (BG) residue (2) is identical to O4 of the reducing Glc p (BG) residue (1). The coordinates of the two residues are adjusted so as to superimpose these two (nominally distinct) atoms. Flexible hydroxymethyl (HM) groups (3 and 4) are treated as separate residues, and the torsional angles (normally indicated by the symbol omega) that define their geometric relationships to the pyranosyl rings of the BG residues are specified as psi3 and psi4, respectively. The torsional angles phi3 and phi4, defined solely to

  14. Mantle Convection Models Constrained by Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Durbin, C. J.; Shahnas, M.; Peltier, W. R.; Woodhouse, J. H.

    2011-12-01

    Perovskite-post-Perovskite transition (Murakami et al., 2004, Science) that appears to define the D" layer at the base of the mantle. In this initial phase of what will be a longer term project we are assuming that the internal mantle viscosity structure is spherically symmetric and compatible with the recent inferences of Peltier and Drummond (2010, Geophys. Res. Lett.) based upon glacial isostatic adjustment and Earth rotation constraints. The internal density structure inferred from the tomography model is assimilated into the convection model by continuously "nudging" the modification to the input density structure predicted by the convection model back towards the tomographic constraint at the long wavelengths that the tomography specifically resolves, leaving the shorter wavelength structure free to evolve, essentially "slaved" to the large scale structure. We focus upon the ability of the nudged model to explain observed plate velocities, including both their poloidal (divergence related) and toroidal (strike slip fault related) components. The true plate velocity field is then used as an additional field towards which the tomographically constrained solution is nudged.

  15. SNAT2 amino acid transporter is regulated by amino acids of the SLC6 gamma-aminobutyric acid transporter subfamily in neocortical neurons and may play no role in delivering glutamine for glutamatergic transmission.

    PubMed

    Grewal, Sukhjeevan; Defamie, Norah; Zhang, Xiong; De Gois, Stéphanie; Shawki, Ali; Mackenzie, Bryan; Chen, Chu; Varoqui, Hélène; Erickson, Jeffrey D

    2009-04-24

    System A transporters SNAT1 and SNAT2 mediate uptake of neutral alpha-amino acids (e.g. glutamine, alanine, and proline) and are expressed in central neurons. We tested the hypothesis that SNAT2 is required to support neurotransmitter glutamate synthesis by examining spontaneous excitatory activity after inducing or repressing SNAT2 expression for prolonged periods. We stimulated de novo synthesis of SNAT2 mRNA and increased SNAT2 mRNA stability and total SNAT2 protein and functional activity, whereas SNAT1 expression was unaffected. Increased endogenous SNAT2 expression did not affect spontaneous excitatory action-potential frequency over control. Long term glutamine exposure strongly repressed SNAT2 expression but increased excitatory action-potential frequency. Quantal size was not altered following SNAT2 induction or repression. These results suggest that spontaneous glutamatergic transmission in pyramidal neurons does not rely on SNAT2. To our surprise, repression of SNAT2 activity was not limited to System A substrates. Taurine, gamma-aminobutyric acid, and beta-alanine (substrates of the SLC6 gamma-aminobutyric acid transporter family) repressed SNAT2 expression more potently (10x) than did System A substrates; however, the responses to System A substrates were more rapid. Since ATF4 (activating transcription factor 4) and CCAAT/enhancer-binding protein are known to bind to an amino acid response element within the SNAT2 promoter and mediate induction of SNAT2 in peripheral cell lines, we tested whether either factor was similarly induced by amino acid deprivation in neurons. We found that glutamine and taurine repressed the induction of both transcription factors. Our data revealed that SNAT2 expression is constitutively low in neurons under physiological conditions but potently induced, together with the taurine transporter TauT, in response to depletion of neutral amino acids.

  16. A Constrained Spline Estimator of a Hazard Function.

    ERIC Educational Resources Information Center

    Bloxom, Bruce

    1985-01-01

    A constrained quadratic spline is proposed as an estimator of the hazard function of a random variable. A maximum penalized likelihood procedure is used to fit the estimator to a sample of psychological response times. (Author/LMO)

  17. Vibration control through passive constrained layer damping and active control

    NASA Astrophysics Data System (ADS)

    Lam, Margaretha J.; Inman, Daniel J.; Saunders, William R.

    1997-05-01

    To add damping to systems, viscoelastic materials (VEM) are added to structures. In order to enhance the damping effects of the VEM, a constraining layer is attached. When this constraining layer is an active element, the treatment is called active constrained layer damping (ACLD). Recently, the investigation of ACLD treatments has shown it to be an effective method of vibration suppression. In this paper, the treatment of a beam with a separate active element and passive constrained layer (PCLD) element is investigated. A Ritz- Galerkin approach is used to obtain discretized equations of motion. The damping is modeled using the GHM method and the system is analyzed in the time domain. By optimizing on the performance and control effort for both the active and passive case, it is shown that this treatment is capable of lower control effort with more inherent damping, and is therefore a better approach to damp vibration.

  18. Geometric constrained variational calculus. II: The second variation (Part I)

    NASA Astrophysics Data System (ADS)

    Massa, Enrico; Bruno, Danilo; Luria, Gianvittorio; Pagani, Enrico

    2016-10-01

    Within the geometrical framework developed in [Geometric constrained variational calculus. I: Piecewise smooth extremals, Int. J. Geom. Methods Mod. Phys. 12 (2015) 1550061], the problem of minimality for constrained calculus of variations is analyzed among the class of differentiable curves. A fully covariant representation of the second variation of the action functional, based on a suitable gauge transformation of the Lagrangian, is explicitly worked out. Both necessary and sufficient conditions for minimality are proved, and reinterpreted in terms of Jacobi fields.

  19. Constrained Adaptive Beamforming for Improved Contrast in Breast Ultrasound

    DTIC Science & Technology

    2007-06-01

    us to modify the Spatial Processing Optimized and Constrained algorithm ( SPOC ) toyield the Time-Domain Optimized Near-field Estimator (TONE). In...modified the Spatial Processing Optimized and Constrained ( SPOC ) algorithm [14, 15] to operate on near-field, broadband signals. In the process of writing...about this modified algorithm it became clear that our significant changes to SPOC really made it a new algorithm, deserving a new name. Thus we have

  20. Constrained Adaptive Beamforming for Improved Contrast in Breast Ultrasound

    DTIC Science & Technology

    2006-06-01

    have led us to utilize a recently proposed method, Spatial Processing Optimized and Constrained ( SPOC ). In initial simulations this method not only...6 Summary of First Year Progress……………………………………6 Conventional Beamformer Optimization………….…………….….7 SPOC Progress...and hundreds of papers published in this area, only the SPOC (Spatial Processing Optimized and Constrained) algorithm could be readily modified to meet

  1. Constrained Adaptive Beamforming for Improved Contrast in Breast Ultrasound

    DTIC Science & Technology

    2008-06-01

    us to modify the Spatial Processing Optimized and Constrained algorithm ( SPOC ) to yield the Time-Domain Optimized Near-field Estimator (TONE). In...beamformers - Improvement and evaluation of adaptive imaging algorithms based loosely on SPOC - Invention and testing of the basic TONE algorithm...named the Time-domain Optimized Near-Filed Estimator, or TONE. The novel ABF was developed from Spatial Processing: Optimized and Constrained ( SPOC

  2. Conjugate Gradient Methods for Constrained Least Squares Problems

    DTIC Science & Technology

    1990-01-01

    TINO Hi!AGL . edi"o ar m m Conjugate Gradient Methods for Constrained Least Squares Problems by Douglas James A thesis 3ubmitted to the Graduate Faculty...Methods for Constrained Least uares Problems (directed by Robert J . Plemmons). Nreiw• 1\\ . ’iu 1988, Barlow, Nichols, and Plemmons proposed order...typical). The blocks 13 element j / F __- . F= %.GEi ,,,mo node Figure 2.4: Matrices for Static Structurem Prcblem associated with t’e planar square

  3. 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.

  4. Constraining compartmental models using multiple voltage recordings and genetic algorithms.

    PubMed

    Keren, Naomi; Peled, Noam; Korngreen, Alon

    2005-12-01

    Compartmental models with many nonlinearly and nonhomogeneous distributions of voltage-gated conductances are routinely used to investigate the physiology of complex neurons. However, the number of loosely constrained parameters makes manually constructing the desired model a daunting if not impossible task. Recently, progress has been made using automated parameter search methods, such as genetic algorithms (GAs). However, these methods have been applied to somatically recorded action potentials using relatively simple target functions. Using a genetic minimization algorithm and a reduced compartmental model based on a previously published model of layer 5 neocortical pyramidal neurons we compared the efficacy of five cost functions (based on the waveform of the membrane potential, the interspike interval, trajectory density, and their combinations) to constrain the model. When the model was constrained using somatic recordings only, a combined cost function was found to be the most effective. This combined cost function was then applied to investigate the contribution of dendritic and axonal recordings to the ability of the GA to constrain the model. The more recording locations from the dendrite and the axon that were added to the data set the better was the genetic minimization algorithm able to constrain the compartmental model. Based on these simulations we propose an experimental scheme that, in combination with a genetic minimization algorithm, may be used to constrain compartmental models of neurons.

  5. Reduced amino acid transport in skeletal muscle caused by a circulating factor during endotoxemia.

    PubMed Central

    Warner, B W; Hasselgren, P O; James, J H; Hummel, R P; Rigel, D F; Fischer, J E

    1990-01-01

    The present study was designed to determine whether reduced amino acid uptake in skeletal muscle during endotoxemia is due to associated hypotension or is caused by a factor present in plasma. Three series of experiments were performed. In the first series of experiments, mean arterial pressure (MAP), heart rate, and amino acid uptake in incubated soleus muscles were measured after intravenous injection of endotoxin (1 mg/kg) in male Sprague-Dawley rats (40 to 60 g). Amino acid transport was measured by determining intracellular uptake of [3H]-alpha-amino-isobutyric acid (AIB) during 2 hours of incubation. In the second series of experiments, hypotension was induced by bleeding and muscle amino acid uptake was measured. In the third series of experiments, whole plasma or a low molecular weight fraction (less than 10,000 d) of plasma from endotoxin-injected rats was added in vitro to incubated muscles and amino acid uptake was determined. One hour after injection of endotoxin, MAP was reduced from 80 +/- 2 mmHg to 54 +/- 4 mmHg (p less than 0.05). AIB uptake was reduced by 20% (p less than 0.05) 2 hours after endotoxin injection. When MAP was maintained at 50 mmHg for 1 hour by bleeding, no changes in muscle AIB uptake were noted. When plasma obtained from rats 2 hours after endotoxin injection was added to incubated soleus muscles, AIB uptake was reduced by 22%. This effect was duplicated by a fraction of endotoxic plasma containing substances with a molecular weight less than 10,000 d. The present results suggest that reduced muscle amino acid uptake during endotoxemia is not due to associated hypotension, but may be caused by a circulating factor(s) with a molecular weight less than 10,000 d. PMID:2178567

  6. Soil phosphorus constrains biodiversity across European grasslands.

    PubMed

    Ceulemans, Tobias; Stevens, Carly J; Duchateau, Luc; Jacquemyn, Hans; Gowing, David J G; Merckx, Roel; Wallace, Hilary; van Rooijen, Nils; Goethem, Thomas; Bobbink, Roland; Dorland, Edu; Gaudnik, Cassandre; Alard, Didier; Corcket, Emmanuel; Muller, Serge; Dise, Nancy B; Dupré, Cecilia; Diekmann, Martin; Honnay, Olivier

    2014-12-01

    Nutrient pollution presents a serious threat to biodiversity conservation. In terrestrial ecosystems, the deleterious effects of nitrogen pollution are increasingly understood and several mitigating environmental policies have been developed. Compared to nitrogen, the effects of increased phosphorus have received far less attention, although some studies have indicated that phosphorus pollution may be detrimental for biodiversity as well. On the basis of a dataset covering 501 grassland plots throughout Europe, we demonstrate that, independent of the level of atmospheric nitrogen deposition and soil acidity, plant species richness was consistently negatively related to soil phosphorus. We also identified thresholds in soil phosphorus above which biodiversity appears to remain at a constant low level. Our results indicate that nutrient management policies biased toward reducing nitrogen pollution will fail to preserve biodiversity. As soil phosphorus is known to be extremely persistent and we found no evidence for a critical threshold below which no environmental harm is expected, we suggest that agro-environmental schemes should include grasslands that are permanently free from phosphorus fertilization.

  7. The 1.9 A Structure of the Branched-Chain Amino-Acid Transaminase (IlvE) from Mycobacterium tuberculosis

    SciTech Connect

    Tremblay, L.; Blanchard, J

    2009-01-01

    Unlike mammals, bacteria encode enzymes that synthesize branched-chain amino acids. The pyridoxal 5'-phosphate-dependent transaminase performs the final biosynthetic step in these pathways, converting keto acid precursors into {alpha}-amino acids. The branched-chain amino-acid transaminase from Mycobacterium tuberculosis (MtIlvE) has been crystallized and its structure has been solved at 1.9 {angstrom} resolution. The MtIlvE monomer is composed of two domains that interact to form the active site. The biologically active form of IlvE is a homodimer in which each monomer contributes a substrate-specificity loop to the partner molecule. Additional substrate selectivity may be imparted by a conserved N-terminal Phe30 residue, which has previously been observed to shield the active site in the type IV fold homodimer. The active site of MtIlvE contains density corresponding to bound PMP, which is likely to be a consequence of the presence of tryptone in the crystallization medium. Additionally, two cysteine residues are positioned at the dimer interface for disulfide-bond formation under oxidative conditions. It is unknown whether they are involved in any regulatory activities analogous to those of the human mitochondrial branched-chain amino-acid transaminase.

  8. Constraining condensed-phase formation kinetics of secondary organic aerosol components from isoprene epoxydiols

    NASA Astrophysics Data System (ADS)

    Riedel, T. P.; Lin, Y.-H.; Zhang, Z.; Chu, K.; Thornton, J. A.; Vizuete, W.; Gold, A.; Surratt, J. D.

    2016-02-01

    Isomeric epoxydiols from isoprene photooxidation (IEPOX) have been shown to produce substantial amounts of secondary organic aerosol (SOA) mass and are therefore considered a major isoprene-derived SOA precursor. Heterogeneous reactions of IEPOX on atmospheric aerosols form various aerosol-phase components or "tracers" that contribute to the SOA mass burden. A limited number of the reaction rate constants for these acid-catalyzed aqueous-phase tracer formation reactions have been constrained through bulk laboratory measurements. We have designed a chemical box model with multiple experimental constraints to explicitly simulate gas- and aqueous-phase reactions during chamber experiments of SOA growth from IEPOX uptake onto acidic sulfate aerosol. The model is constrained by measurements of the IEPOX reactive uptake coefficient, IEPOX and aerosol chamber wall losses, chamber-measured aerosol mass and surface area concentrations, aerosol thermodynamic model calculations, and offline filter-based measurements of SOA tracers. By requiring the model output to match the SOA growth and offline filter measurements collected during the chamber experiments, we derive estimates of the tracer formation reaction rate constants that have not yet been measured or estimated for bulk solutions.

  9. Hypochlorous acid-mediated protein oxidation: how important are chloramine transfer reactions and protein tertiary structure?

    PubMed

    Pattison, David I; Hawkins, Clare L; Davies, Michael J

    2007-08-28

    Hypochlorous acid (HOCl) is a powerful oxidant generated from H2O2 and Cl- by the heme enzyme myeloperoxidase, which is released from activated leukocytes. HOCl possesses potent antibacterial properties, but excessive production can lead to host tissue damage that occurs in numerous human pathologies. As proteins and amino acids are highly abundant in vivo and react rapidly with HOCl, they are likely to be major targets for HOCl. In this study, two small globular proteins, lysozyme and insulin, have been oxidized with increasing excesses of HOCl to determine whether the pattern of HOCl-mediated amino acid consumption is consistent with reported kinetic data for isolated amino acids and model compounds. Identical experiments have been carried out with mixtures of N-acetyl amino acids (to prevent reaction at the alpha-amino groups) that mimic the protein composition to examine the role of protein structure on reactivity. The results indicate that tertiary structure facilitates secondary chlorine transfer reactions of chloramines formed on His and Lys side chains. In light of these data, second-order rate constants for reactions of Lys side chain and Gly chloramines with Trp side chains and disulfide bonds have been determined, together with those for further oxidation of Met sulfoxide by HOCl and His side chain chloramines. Computational kinetic models incorporating these additional rate constants closely predict the experimentally observed amino acid consumption. These studies provide insight into the roles of chloramine formation and three-dimensional structure on the reactions of HOCl with isolated proteins and demonstrate that kinetic models can predict the outcome of HOCl-mediated protein oxidation.

  10. Constraining Effects of Brine Leakage from Carbon Sequestration Sites

    NASA Astrophysics Data System (ADS)

    Wunsch, A.; Navarre-Sitchler, A. K.; McCray, J. E.

    2011-12-01

    Research has shown that pressure build up associated with injection of CO2 into a deep saline aquifer has the potential to promote brine leakage into overlying formations. In order to understand and quantify chemical changes in an underground source of drinking water (USDW) invaded by deep saline brines, we analyzed over 90,000 brine geochemical data entries from the NETL NATCARB brine database to identify potential brine constituents of concern. Using a variety of statistical methods and EPA regulatory levels or standards (RLS) we narrowed the list of brine constituents of potential concern to USDWs to TDS, thallium, chloride, sulfate and arsenic. Somewhat surprisingly, the distribution of reported pH had a fairly narrow distribution around a median value of 7.4, with over 78% of values complying with EPA recommended secondary standard for drinking water acidity. The pH distribution implies that unlike pure CO2 leakage, far-field brine leakage (i.e., brine not in contact with CO2) is not expected to bear a low-pH signature, thus suggesting use of other means of geochemical monitoring for brine leakage, such as electrical conductivity. Geochemical mixing models of brine and dilute water were used to constrain mixing ratios where RLS values are exceeded for the TDS, thallium and chloride. TDS and chloride exceed the EPA secondary standards at a brine/USDW mixing ratio of 0.012 and 0.459, respectively. The thallium maximum contaminant level (MCL) is exceeded at a brine/USDW mixing ratio of 0.3753, smaller than the chloride mixing ratio. However, sorption and/or desorption processes may alter thallium concentrations along a leakage pathway resulting in lower concentrations in the aquifer than predicted by simple mixing models. While leakage into USDWs has received considerable attention, brine contamination of groundwater used for irrigation of agricultural crops is also an important area of research. Our calculations suggest that almost all crops grown in the United

  11. Residual flexibility test method for verification of constrained structural models

    NASA Technical Reports Server (NTRS)

    Admire, John R.; Tinker, Michael L.; Ivey, Edward W.

    1994-01-01

    A method is described for deriving constrained modes and frequencies from a reduced model based on a subset of the free-free modes plus the residual effects of neglected modes. The method involves a simple modification of the MacNeal and Rubin component mode representation to allow development of a verified constrained (fixed-base) structural model. Results for two spaceflight structures having translational boundary degrees of freedom show quick convergence of constrained modes using a measureable number of free-free modes plus the boundary partition of the residual flexibility matrix. This paper presents the free-free residual flexibility approach as an alternative test/analysis method when fixed-base testing proves impractical.

  12. Using extracellular action potential recordings to constrain compartmental models.

    PubMed

    Gold, Carl; Henze, Darrell A; Koch, Christof

    2007-08-01

    We investigate the use of extracellular action potential (EAP) recordings for biophysically faithful compartmental models. We ask whether constraining a model to fit the EAP is superior to matching the intracellular action potential (IAP). In agreement with previous studies, we find that the IAP method under-constrains the parameters. As a result, significantly different sets of parameters can have virtually identical IAP's. In contrast, the EAP method results in a much tighter constraint. We find that the distinguishing characteristics of the waveform--but not its amplitude-resulting from the distribution of active conductances are fairly invariant to changes of electrode position and detailed cellular morphology. Based on these results, we conclude that EAP recordings are an excellent source of data for the purpose of constraining compartmental models.

  13. A Novel Approach to Constraining Uncertain Stellar Evolution Models

    NASA Astrophysics Data System (ADS)

    Rosenfield, Philip; Girardi, Leo; Dalcanton, Julianne; Johnson, L. C.; Williams, Benjamin F.; Weisz, Daniel R.; Bressan, Alessandro; Fouesneau, Morgan

    2017-01-01

    Stellar evolution models are fundamental to nearly all studies in astrophysics. They are used to interpret spectral energy distributions of distant galaxies, to derive the star formation histories of nearby galaxies, and to understand fundamental parameters of exoplanets. Despite the success in using stellar evolution models, some important aspects of stellar evolution remain poorly constrained and their uncertainties rarely addressed. We present results using archival Hubble Space Telescope observations of 10 stellar clusters in the Magellanic Clouds to simultaneously constrain the values and uncertainties of the strength of core convective overshooting, metallicity, interstellar extinction, cluster distance, binary fraction, and age.

  14. Constrained modes in control theory - Transmission zeros of uniform beams

    NASA Technical Reports Server (NTRS)

    Williams, T.

    1992-01-01

    Mathematical arguments are presented demonstrating that the well-established control system concept of the transmission zero is very closely related to the structural concept of the constrained mode. It is shown that the transmission zeros of a flexible structure form a set of constrained natural frequencies for it, with the constraints depending explicitly on the locations and the types of sensors and actuators used for control. Based on this formulation, an algorithm is derived and used to produce dimensionless plots of the zero of a uniform beam with a compatible sensor/actuator pair.

  15. Augmented Lagrangian method for constrained nuclear density functional theory

    NASA Astrophysics Data System (ADS)

    Staszczak, A.; Stoitsov, M.; Baran, A.; Nazarewicz, W.

    2010-10-01

    The augmented Lagrangiam method (ALM), widely used in quantum chemistry constrained optimization problems, is applied in the context of the nuclear Density Functional Theory (DFT) in the self-consistent constrained Skyrme Hartree-Fock-Bogoliubov (CHFB) variant. The ALM allows precise calculations of multi-dimensional energy surfaces in the space of collective coordinates that are needed to, e.g., determine fission pathways and saddle points; it improves the accuracy of computed derivatives with respect to collective variables that are used to determine collective inertia; and is well adapted to supercomputer applications.

  16. Value, Cost, and Sharing: Open Issues in Constrained Clustering

    NASA Technical Reports Server (NTRS)

    Wagstaff, Kiri L.

    2006-01-01

    Clustering is an important tool for data mining, since it can identify major patterns or trends without any supervision (labeled data). Over the past five years, semi-supervised (constrained) clustering methods have become very popular. These methods began with incorporating pairwise constraints and have developed into more general methods that can learn appropriate distance metrics. However, several important open questions have arisen about which constraints are most useful, how they can be actively acquired, and when and how they should be propagated to neighboring points. This position paper describes these open questions and suggests future directions for constrained clustering research.

  17. Augmented Lagrangian Method for Constrained Nuclear Density Functiional Theory

    SciTech Connect

    Staszczak, A.; Stoitsov, Mario; Baran, Andrzej K; Nazarewicz, Witold

    2010-01-01

    The augmented Lagrangian method (ALM), widely used in quantum chemistry constrained optimization problems, is applied in the context of the nuclear Density Functional Theory (DFT) in the self-consistent constrained Skyrme Hartree-Fock-Bogoliubov (CHFB) variant. The ALM allows precise calculations of multidimensional energy surfaces in the space of collective coordinates that are needed to, e.g., determine fission pathways and saddle points; it improves accuracy of computed derivatives with respect to collective variables that are used to determine collective inertia and is well adapted to supercomputer applications.

  18. A lexicographic approach to constrained MDP admission control

    NASA Astrophysics Data System (ADS)

    Panfili, Martina; Pietrabissa, Antonio; Oddi, Guido; Suraci, Vincenzo

    2016-02-01

    This paper proposes a reinforcement learning-based lexicographic approach to the call admission control problem in communication networks. The admission control problem is modelled as a multi-constrained Markov decision process. To overcome the problems of the standard approaches to the solution of constrained Markov decision processes, based on the linear programming formulation or on a Lagrangian approach, a multi-constraint lexicographic approach is defined, and an online implementation based on reinforcement learning techniques is proposed. Simulations validate the proposed approach.

  19. Constrained optimization for image restoration using nonlinear programming

    NASA Technical Reports Server (NTRS)

    Yeh, C.-L.; Chin, R. T.

    1985-01-01

    The constrained optimization problem for image restoration, utilizing incomplete information and partial constraints, is formulated using nonlinear proramming techniques. This method restores a distorted image by optimizing a chosen object function subject to available constraints. The penalty function method of nonlinear programming is used. Both linear or nonlinear object function, and linear or nonlinear constraint functions can be incorporated in the formulation. This formulation provides a generalized approach to solve constrained optimization problems for image restoration. Experiments using this scheme have been performed. The results are compared with those obtained from other restoration methods and the comparative study is presented.

  20. Effects of nitric oxide availability on responses of spinal wide dynamic range neurons to excitatory amino acids.

    PubMed

    Budai, D; Wilcox, G L; Larson, A A

    1995-05-04

    The role of nitric oxide (NO) in responses of spinal dorsal horn neurons to excitatory amino acids and to cutaneous mechanical stimuli was examined. Extracellular recordings were made from wide dynamic range neurons excited with iontophoretically applied excitatory amino acid agonists, N-methyl-D-aspartate (NMDA) and (R,S)-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) or kainic acid. Nitric oxide availability was decreased by iontrophoretic application of NO synthase inhibitors, N omega-nitro-L-arginine methyl ester (L-NAME) or L-N5-(1-iminoethyl)ornithine (L-NIO), or elevated by the NO donating compound, S-nitroso-N-penicillamine (SNAP). When cells were excited with successive application of NMDA and non-NMDA excitatory amino acid receptor agonists, application of NO synthase inhibitors led to a decrease in responses to NMDA in 60% of neurons. In more than a third of the cells tested, inhibition of NO synthase caused reciprocal changes in responses to glutamate receptor agonists: NMDA-evoked responses were significantly decreased whereas responses to the non-NMDA receptor agonists (AMPA or kainic acid) were increased. Application of the NO donating compound, S-nitroso-N-penicillamine, revealed an opposite tendency, increasing responses to NMDA in more than half of the neurons tested. In approximately 40% of the cells, reciprocal changes in responses to excitatory amino acid receptor agonists of NMDA versus non-NMDA types were observed after application of S-nitroso-N-penicillamine, such that the increase in NMDA responses was accompanied by decreases in the responses to kainic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

  1. 21 CFR 888.3210 - Finger joint metal/metal constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Finger joint metal/metal constrained cemented... metal/metal constrained cemented prosthesis. (a) Identification. A finger joint metal/metal constrained..., 1996 for any finger joint metal/metal constrained cemented prosthesis that was in...

  2. 21 CFR 888.3210 - Finger joint metal/metal constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Finger joint metal/metal constrained cemented... metal/metal constrained cemented prosthesis. (a) Identification. A finger joint metal/metal constrained..., 1996 for any finger joint metal/metal constrained cemented prosthesis that was in...

  3. 21 CFR 888.3210 - Finger joint metal/metal constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Finger joint metal/metal constrained cemented... metal/metal constrained cemented prosthesis. (a) Identification. A finger joint metal/metal constrained..., 1996 for any finger joint metal/metal constrained cemented prosthesis that was in...

  4. 21 CFR 888.3210 - Finger joint metal/metal constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Finger joint metal/metal constrained cemented... metal/metal constrained cemented prosthesis. (a) Identification. A finger joint metal/metal constrained..., 1996 for any finger joint metal/metal constrained cemented prosthesis that was in...

  5. 21 CFR 888.3300 - Hip joint metal constrained cemented or uncemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Hip joint metal constrained cemented or uncemented... metal constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal constrained... Administration on or before December 26, 1996 for any hip joint metal constrained cemented or...

  6. 21 CFR 888.3210 - Finger joint metal/metal constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Finger joint metal/metal constrained cemented... metal/metal constrained cemented prosthesis. (a) Identification. A finger joint metal/metal constrained..., 1996 for any finger joint metal/metal constrained cemented prosthesis that was in...

  7. Reaction of primary and secondary amines to form carbamic acid glucuronides.

    PubMed

    Schaefer, William H

    2006-12-01

    Glucuronidation is an important mechanism used by mammalian systems to clear and eliminate both endogenous and foreign chemicals. Many functional groups are susceptible to conjugation with glucuronic acid, including hydroxyls, phenols, carboxyls, activated carbons, thiols, amines, and selenium. Primary and secondary amines can also react with carbon dioxide (CO(2)) via a reversible reaction to form a carbamic acid. The carbamic acid is also a substrate for glucuronidation and results in a stable carbamate glucuronide metabolite. The detection and characterization of these products has been facilitated greatly by the advent of soft ionization mass spectrometry techniques and high field NMR instrumentation. The formation of carbamate glucuronide metabolites has been described for numerous pharmaceuticals and they have been identified in all of the species commonly used in drug metabolism studies (rat, dog, mouse, rabbit, guinea pig, and human). There has been no obvious species specificity for their formation and no preference for 1 degrees or 2 degrees amines. Many biological reactions have also been described in the literature that involve the reaction of CO(2) with amino groups of biomolecules. For example, CO(2) generated from cellular respiration is expired in part through the reversible formation of a carbamate between CO(2) and the alpha-amino groups of the alpha- and beta-chains of hemoglobin. Also, carbamic acid products of several amines, such as beta-N-methylamino-L-alanine (BMAA), ethylenediamine, and L-cysteine have been implicated in toxicity. Studies suggested that a significant portion of amino-compounds in biological samples (that naturally contain CO(2)/bicarbonate) can be present as a carbamic acid.

  8. Achieving Procurement Efficiencies in a Budget-Constrained Environment

    DTIC Science & Technology

    2015-05-13

    Copyright © 2015 Boeing. All rights reserved. . Corporate Contracts Darryl Scott Corporate Vice President, Contracts May 13, 2015 Naval...Budget-Constrained Environment T2012 Panel March 12, 2012 Copyright © 2012 Boeing. All rights reserved. Copyright © 2015 Boeing. All rights reserved...Corporate | Contracts Comparison of Commercial and Military Production Satellites Copyright © 2012 Boeing. All rights reserved. $407M ~58 mo

  9. Using Diagnostic Text Information to Constrain Situation Models

    ERIC Educational Resources Information Center

    Dutke, Stephan; Baadte, Christiane; Hahnel, Andrea; von Hecker, Ulrich; Rinck, Mike

    2010-01-01

    During reading, the model of the situation described by the text is continuously accommodated to new text input. The hypothesis was tested that readers are particularly sensitive to diagnostic text information that can be used to constrain their existing situation model. In 3 experiments, adult participants read narratives about social situations…

  10. Joint Force Interdependence for a Fiscally Constrained Future

    DTIC Science & Technology

    2013-03-01

    Army 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Dr. Richard Meinhart ...Joint Force Interdependence For A Fiscally Constrained Future by Colonel Daniel P. Ray United States Army ...United States Army War College Class of 2013 DISTRIBUTION STATEMENT: A Approved for Public Release Distribution is Unlimited

  11. Bayesian Item Selection in Constrained Adaptive Testing Using Shadow Tests

    ERIC Educational Resources Information Center

    Veldkamp, Bernard P.

    2010-01-01

    Application of Bayesian item selection criteria in computerized adaptive testing might result in improvement of bias and MSE of the ability estimates. The question remains how to apply Bayesian item selection criteria in the context of constrained adaptive testing, where large numbers of specifications have to be taken into account in the item…

  12. Hamiltonian dynamics and constrained variational calculus: continuous and discrete settings

    NASA Astrophysics Data System (ADS)

    de León, Manuel; Jiménez, Fernando; Martín de Diego, David

    2012-05-01

    The aim of this paper is to study the relationship between Hamiltonian dynamics and constrained variational calculus. We describe both using the notion of Lagrangian submanifolds of convenient symplectic manifolds and using the so-called Tulczyjew triples. The results are also extended to the case of discrete dynamics and nonholonomic mechanics. Interesting applications to the geometrical integration of Hamiltonian systems are obtained.

  13. Constrained variational calculus for higher order classical field theories

    NASA Astrophysics Data System (ADS)

    Campos, Cédric M.; de León, Manuel; Martín de Diego, David

    2010-11-01

    We develop an intrinsic geometrical setting for higher order constrained field theories. As a main tool we use an appropriate generalization of the classical Skinner-Rusk formalism. Some examples of applications are studied, in particular to the geometrical description of optimal control theory for partial differential equations.

  14. 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…

  15. Extracting electron transfer coupling elements from constrained density functional theory

    NASA Astrophysics Data System (ADS)

    Wu, Qin; Van Voorhis, Troy

    2006-10-01

    Constrained density functional theory (DFT) is a useful tool for studying electron transfer (ET) reactions. It can straightforwardly construct the charge-localized diabatic states and give a direct measure of the inner-sphere reorganization energy. In this work, a method is presented for calculating the electronic coupling matrix element (Hab) based on constrained DFT. This method completely avoids the use of ground-state DFT energies because they are known to irrationally predict fractional electron transfer in many cases. Instead it makes use of the constrained DFT energies and the Kohn-Sham wave functions for the diabatic states in a careful way. Test calculations on the Zn2+ and the benzene-Cl atom systems show that the new prescription yields reasonable agreement with the standard generalized Mulliken-Hush method. We then proceed to produce the diabatic and adiabatic potential energy curves along the reaction pathway for intervalence ET in the tetrathiafulvalene-diquinone (Q-TTF-Q) anion. While the unconstrained DFT curve has no reaction barrier and gives Hab≈17kcal /mol, which qualitatively disagrees with experimental results, the Hab calculated from constrained DFT is about 3kcal /mol and the generated ground state has a barrier height of 1.70kcal/mol, successfully predicting (Q-TTF-Q)- to be a class II mixed-valence compound.

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

    SciTech Connect

    Martin, Jérôme; Vennin, Vincent; Ringeval, Christophe E-mail: christophe.ringeval@uclouvain.be

    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{sup -1} down to 10{sup -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.

  17. 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…

  18. Constrained Adaptive Beamforming for Improved Contrast in Breast Ultrasound

    DTIC Science & Technology

    2005-06-01

    led us to utilize a recently proposed method, Spatial Processing Optimized and Constrained ( SPOC ). In initial simulations this method not only...6 Review of the Adaptive Beamforming Literature ................... 7 SPOC Progress...given the parameters of in vivo ultrasound imaging. SPOC Progress: Most of the Adaptive Beamforming algorithms previously described fail when applied to

  19. Constrained quantum mechanics: chaos in non-planar billiards

    NASA Astrophysics Data System (ADS)

    Salazar, R.; Téllez, G.

    2012-07-01

    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 billiard with an inner Gaussian surface.

  20. Excision technique in constrained formulations of Einstein equations: collapse scenario

    NASA Astrophysics Data System (ADS)

    Cordero-Carrión, I.; Vasset, N.; Novak, J.; Jaramillo, J. L.

    2015-04-01

    We present a new excision technique used in constrained formulations of Einstein equations to deal with black hole in numerical simulations. We show the applicability of this scheme in several scenarios. In particular, we present the dynamical evolution of the collapse of a neutron star to a black hole, using the CoCoNuT code and this excision technique.

  1. Reflections on How Color Term Acquisition Is Constrained

    ERIC Educational Resources Information Center

    Pitchford, Nicola J.

    2006-01-01

    Compared with object word learning, young children typically find learning color terms to be a difficult linguistic task. In this reflections article, I consider two questions that are fundamental to investigations into the developmental acquisition of color terms. First, I consider what constrains color term acquisition and how stable these…

  2. Constrained Hartree-Fock and quasi-spin projection

    NASA Astrophysics Data System (ADS)

    Cambiaggio, M. C.; Plastino, A.; Szybisz, L.

    1980-08-01

    The constrained Hartree-Fock approach of Elliott and Evans is studied in detail with reference to two quasi-spin models, and their predictions compared with those arising from a projection method. It is found that the new approach works fairly well, although limitations to its applicability are encountered.

  3. 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…

  4. 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.…

  5. Constrained optimization schemes for geophysical inversion of seismic data

    NASA Astrophysics Data System (ADS)

    Sosa Aguirre, Uram Anibal

    Many experimental techniques in geophysics advance the understanding of Earth processes by estimating and interpreting Earth structure (e.g., velocity and/or density structure). These techniques use different types of geophysical data which can be collected and analyzed separately, sometimes resulting in inconsistent models of the Earth depending on data quality, methods and assumptions made. This dissertation presents two approaches for geophysical inversion of seismic data based on constrained optimization. In one approach we expand a one dimensional (1-D) joint inversion least-squares (LSQ) algorithm by introducing a constrained optimization methodology. Then we use the 1-D inversion results to produce 3-D Earth velocity structure models. In the second approach, we provide a unified constrained optimization framework for solving a 1-D inverse wave propagation problem. In Chapter 2 we present a constrained optimization framework for joint inversion. This framework characterizes 1-D Earth's structure by using seismic shear wave velocities as a model parameter. We create two geophysical synthetic data sets sensitive to shear velocities, namely receiver function and surface wave dispersion. We validate our approach by comparing our numerical results with a traditional unconstrained method, and also we test our approach robustness in the presence of noise. Chapter 3 extends this framework to include an interpolation technique for creating 3-D Earth velocity structure models of the Rio Grande Rift region. Chapter 5 introduces the joint inversion of multiple data sets by adding delay travel times information in a synthetic setup, and leave the posibility to include more data sets. Finally, in Chapter 4 we pose a 1-D inverse full-waveform propagation problem as a PDE-constrained optimization program, where we invert for the material properties in terms of shear wave velocities throughout the physical domain. We facilitate the implementation and comparison of different

  6. MicroRNA-101 Regulates Multiple Developmental Programs to Constrain Excitation in Adult Neural Networks.

    PubMed

    Lippi, Giordano; Fernandes, Catarina C; Ewell, Laura A; John, Danielle; Romoli, Benedetto; Curia, Giulia; Taylor, Seth R; Frady, E Paxon; Jensen, Anne B; Liu, Jerry C; Chaabane, Melanie M; Belal, Cherine; Nathanson, Jason L; Zoli, Michele; Leutgeb, Jill K; Biagini, Giuseppe; Yeo, Gene W; Berg, Darwin K

    2016-12-21

    A critical feature of neural networks is that they balance excitation and inhibition to prevent pathological dysfunction. How this is achieved is largely unknown, although deficits in the balance contribute to many neurological disorders. We show here that a microRNA (miR-101) is a key orchestrator of this essential feature, shaping the developing network to constrain excitation in the adult. Transient early blockade of miR-101 induces long-lasting hyper-excitability and persistent memory deficits. Using target site blockers in vivo, we identify multiple developmental programs regulated in parallel by miR-101 to achieve balanced networks. Repression of one target, NKCC1, initiates the switch in γ-aminobutyric acid (GABA) signaling, limits early spontaneous activity, and constrains dendritic growth. Kif1a and Ank2 are targeted to prevent excessive synapse formation. Simultaneous de-repression of these three targets completely phenocopies major dysfunctions produced by miR-101 blockade. Our results provide new mechanistic insight into brain development and suggest novel candidates for therapeutic intervention.

  7. Stimulation of cartilage amino acid uptake by growth hormone-dependent factors in serum. Mediation by adenosine 3':5'-monophosphate.

    PubMed

    Drezner, M K; Eisenbarth, G S; Neelon, F A; Lebovitz, H E

    1975-02-13

    The effects of growth hormone-dependent serum factors on amino acid transport and on cartilage cyclic AMP levels in embryonic chicken cartilage were studied in vitro. Cartilages incubated in medium containing rat serum showed a significantly greater uptake of alpha-amino [1-14C] isobutyrate or [1-14C] cycloleucine than control cartilages incubated in medium alone. Normal rat serum (5%) added to the incubation medium also caused an increase in cartilage cyclic AMP content (from as little as 23% to as much as 109%). The factors in serum which increase cartilage cyclic AMP and amino acid uptake are growth hormone dependent, since neither growth hormone itself nor serum from hypophysectomized rats restores these serum factors. Studies comparing the ability of sera with varying amounts of growth hormone-dependent factors to stimulate amino-aminoisobutyrate transport and to increase cartilage cyclic AMP show a striking linear correlation between the two effects (r=0.977). Theophylline and prostaglandin E1, WHICH RAISE CARTILAGE CYCLIC AMP also increase amino-aminoisobutyrate transport. Exogenous cyclic AMP, N6-monobutyryl cyclic AMP and n6, 02'-dibutyryl cyclic AMP increase cartilage amino-aminoisobutyrate transport. The data are compatible with the thesis that growth hormone-dependent serum factors increase cartilage amino acid transport by elevating cartilage cyclic AMP.

  8. J1 acylase, a glutaryl-7-aminocephalosporanic acid acylase from Bacillus laterosporus J1, is a member of the alpha/beta-hydrolase fold superfamily.

    PubMed

    Yau, Ming-Hon; Wang, Jun; Tsang, Paul W K; Fong, Wing-Ping

    2006-02-20

    J1 acylase, a glutaryl-7-aminocephalosporanic acid acylase (GCA) isolated from Bacillus laterosporus J1, has been conventionally grouped as the only member of class V GCA, although its amino acid sequence shares less than 10% identity with members of other classes of GCA. Instead, it shows higher sequence similarities with Rhodococcus sp. strain MB1 cocaine esterase (RhCocE) and Acetobacter turbidans alpha-amino acid ester hydrolase (AtAEH), members of the alpha/beta-hydrolase fold superfamily. Homology modeling and secondary structure prediction indicate that the N-terminal region of J1 acylase has an alpha/beta-hydrolase folding pattern. The catalytic triads in RhCocE and AtAEH were identified in J1 acylase as S125, D264 and H309. Mutations to alanine at these positions were found to completely inactivate the enzyme. These results suggest that J1 acylase is a member of the alpha/beta-hydrolase fold superfamily with a serine-histidine-aspartate catalytic triad.

  9. Uterocalin, a lipocalin provisioning the preattachment equine conceptus: fatty acid and retinol binding properties, and structural characterization.

    PubMed Central

    Suire, S; Stewart, F; Beauchamp, J; Kennedy, M W

    2001-01-01

    The equine conceptus is surrounded by a fibrous capsule that persists until about day 20 of pregnancy, whereupon the capsule is lost, the conceptus attaches to the endometrium and placentation proceeds. Before attachment, the endometrium secretes in abundance a protein of the lipocalin family, uterocalin. The cessation of secretion coincides with the end of the period during which the conceptus is enclosed in its capsule, suggesting that uterocalin is essential for the support of the embryo before direct contact between maternal and foetal tissues is established. Using recombinant protein and fluorescence-based assays, we show that equine uterocalin binds the fluorescent fatty acids 11-(dansylamino)undecanoic acid, dansyl-D,L-alpha-amino-octanoic acid and cis-parinaric acid, and, by competition, oleic, palmitic, arachidonic, docosahexaenoic, gamma-linolenic, cis-eicosapentaenoic and linoleic acids. Uterocalin also binds all-trans-retinol, the binding site for which is coincident or interactive with that for fatty acids. Molecular modelling and intrinsic fluorescence analysis of the wild-type protein and a Trp-->Glu mutant protein indicated that uterocalin has an unusually solvent-exposed Trp side chain projecting from its large helix directly into solvent. This feature is unusual among lipocalins and might relate to binding to, and uptake by, the trophoblast. Uterocalin therefore has the localization and binding activities for the provisioning of the equine conceptus with lipids including those essential for morphogenesis and pattern formation. The possession of a fibrous capsule surrounding the conceptus might be an ancestral condition in mammals; homologues of uterocalin might be essential for early development in marsupials and in eutherians in which there is a prolonged preimplantation period. PMID:11368763

  10. Shared developmental programme strongly constrains beak shape diversity in songbirds.

    PubMed

    Fritz, Joerg A; Brancale, Joseph; Tokita, Masayoshi; Burns, Kevin J; Hawkins, M Brent; Abzhanov, Arhat; Brenner, Michael P

    2014-04-16

    The striking diversity of bird beak shapes is an outcome of natural selection, yet the relative importance of the limitations imposed by the process of beak development on generating such variation is unclear. Untangling these factors requires mapping developmental mechanisms over a phylogeny far exceeding model systems studied thus far. We address this issue with a comparative morphometric analysis of beak shape in a diverse group of songbirds. Here we show that the dynamics of the proliferative growth zone must follow restrictive rules to explain the observed variation, with beak diversity constrained to a three parameter family of shapes, parameterized by length, depth and the degree of shear. We experimentally verify these predictions by analysing cell proliferation in the developing embryonic beaks of the zebra finch. Our findings indicate that beak shape variability in many songbirds is strongly constrained by shared properties of the developmental programme controlling the growth zone.

  11. Image coding using entropy-constrained residual vector quantization

    NASA Technical Reports Server (NTRS)

    Kossentini, Faouzi; Smith, Mark J. T.; Barnes, Christopher F.

    1993-01-01

    The residual vector quantization (RVQ) structure is exploited to produce a variable length codeword RVQ. Necessary conditions for the optimality of this RVQ are presented, and a new entropy-constrained RVQ (ECRVQ) design algorithm is shown to be very effective in designing RVQ codebooks over a wide range of bit rates and vector sizes. The new EC-RVQ has several important advantages. It can outperform entropy-constrained VQ (ECVQ) in terms of peak signal-to-noise ratio (PSNR), memory, and computation requirements. It can also be used to design high rate codebooks and codebooks with relatively large vector sizes. Experimental results indicate that when the new EC-RVQ is applied to image coding, very high quality is achieved at relatively low bit rates.

  12. Moving Forward to Constrain the Shear Viscosity of QCD Matter.

    PubMed

    Denicol, Gabriel; Monnai, Akihiko; Schenke, Björn

    2016-05-27

    We demonstrate that measurements of rapidity differential anisotropic flow in heavy-ion collisions can constrain the temperature dependence of the shear viscosity to entropy density ratio η/s of QCD matter. Comparing results from hydrodynamic calculations with experimental data from the RHIC, we find evidence for a small η/s≈0.04 in the QCD crossover region and a strong temperature dependence in the hadronic phase. A temperature independent η/s is disfavored by the data. We further show that measurements of the event-by-event flow as a function of rapidity can be used to independently constrain the initial state fluctuations in three dimensions and the temperature dependent transport properties of QCD matter.

  13. A Novel Neural Network for Generally Constrained Variational Inequalities.

    PubMed

    Gao, Xingbao; Liao, Li-Zhi

    2016-06-13

    This paper presents a novel neural network for solving generally constrained variational inequality problems by constructing a system of double projection equations. By defining proper convex energy functions, the proposed neural network is proved to be stable in the sense of Lyapunov and converges to an exact solution of the original problem for any starting point under the weaker cocoercivity condition or the monotonicity condition of the gradient mapping on the linear equation set. Furthermore, two sufficient conditions are provided to ensure the stability of the proposed neural network for a special case. The proposed model overcomes some shortcomings of existing continuous-time neural networks for constrained variational inequality, and its stability only requires some monotonicity conditions of the underlying mapping and the concavity of nonlinear inequality constraints on the equation set. The validity and transient behavior of the proposed neural network are demonstrated by some simulation results.

  14. A Projection Neural Network for Constrained Quadratic Minimax Optimization.

    PubMed

    Liu, Qingshan; Wang, Jun

    2015-11-01

    This paper presents a projection neural network described by a dynamic system for solving constrained quadratic minimax programming problems. Sufficient conditions based on a linear matrix inequality are provided for global convergence of the proposed neural network. Compared with some of the existing neural networks for quadratic minimax optimization, the proposed neural network in this paper is capable of solving more general constrained quadratic minimax optimization problems, and the designed neural network does not include any parameter. Moreover, the neural network has lower model complexities, the number of state variables of which is equal to that of the dimension of the optimization problems. The simulation results on numerical examples are discussed to demonstrate the effectiveness and characteristics of the proposed neural network.

  15. Assessing working memory capacity through time-constrained elementary activities.

    PubMed

    Lucidi, Annalisa; Loaiza, Vanessa; Camos, Valérie; Barrouillet, Pierre

    2014-01-01

    Working memory (WM) capacity measured through complex span tasks is among the best predictors of fluid intelligence (Gf). These tasks usually involve maintaining memoranda while performing complex cognitive activities that require a rather high level of education (e.g., reading comprehension, arithmetic), restricting their range of applicability. Because individual differences in such complex activities are nothing more than the concatenation of small differences in their elementary constituents, complex span tasks involving elementary processes should be as good of predictors of Gf as traditional tasks. The present study showed that two latent variables issued from either traditional or new span tasks involving time-constrained elementary activities were similarly correlated with Gf. Moreover, a model with a single unitary WM factor had a similar fit as a model with two distinct WM factors. Thus, time-constrained elementary activities can be integrated in WM tasks, permitting the assessment of WM in a wider range of populations.

  16. Constraining the nuclear equation of state at subsaturation densities.

    PubMed

    Khan, E; Margueron, J; Vidaña, I

    2012-08-31

    Only one-third of the nucleons in 208Pb occupy the saturation density area. Consequently, nuclear observables related to the average properties of nuclei, such as masses or radii, constrain the equation of state not at the saturation density but rather around the so-called crossing density, localized close to the mean value of the density of nuclei: ρ is approximately equal to 0.11 fm(-3). This provides an explanation for the empirical fact that several equation of state quantities calculated with various functionals cross at a density significantly lower than the saturation one. The third derivative M of the energy per unit of volume at the crossing density is constrained by the giant monopole resonance measurements in an isotopic chain rather than the incompressibility at saturation density. The giant monopole resonance measurements provide M=1100±70 MeV (6% uncertainty), whose extrapolation gives K(∞)=230±40 MeV (17% uncertainty).

  17. CONMIN: A FORTRAN program for constrained function minimization: User's manual

    NASA Technical Reports Server (NTRS)

    Vanderplaats, G. N.

    1973-01-01

    CONMIN is a FORTRAN program, in subroutine form, for the solution of linear or nonlinear constrained optimization problems. The basic optimization algorithm is the Method of Feasible Directions. The user must provide a main calling program and an external routine to evaluate the objective and constraint functions and to provide gradient information. If analytic gradients of the objective or constraint functions are not available, this information is calculated by finite difference. While the program is intended primarily for efficient solution of constrained problems, unconstrained function minimization problems may also be solved, and the conjugate direction method of Fletcher and Reeves is used for this purpose. This manual describes the use of CONMIN and defines all necessary parameters. Sufficient information is provided so that the program can be used without special knowledge of optimization techniques. Sample problems are included to help the user become familiar with CONMIN and to make the program operational.

  18. Colorimetric characterization of LCD based on constrained least squares

    NASA Astrophysics Data System (ADS)

    LI, Tong; Xie, Kai; Wang, Qiaojie; Yao, Luyang

    2017-01-01

    In order to improve the accuracy of colorimetric characterization of liquid crystal display, tone matrix model in color management modeling of display characterization is established by using constrained least squares for quadratic polynomial fitting, and find the relationship between the RGB color space to CIEXYZ color space; 51 sets of training samples were collected to solve the parameters, and the accuracy of color space mapping model was verified by 100 groups of random verification samples. The experimental results showed that, with the constrained least square method, the accuracy of color mapping was high, the maximum color difference of this model is 3.8895, the average color difference is 1.6689, which prove that the method has better optimization effect on the colorimetric characterization of liquid crystal display.

  19. Moving Forward to Constrain the Shear Viscosity of QCD Matter

    DOE PAGES

    Denicol, Gabriel; Monnai, Akihiko; Schenke, Björn

    2016-05-26

    In this work, we demonstrate that measurements of rapidity differential anisotropic flow in heavy-ion collisions can constrain the temperature dependence of the shear viscosity to entropy density ratio η/s of QCD matter. Comparing results from hydrodynamic calculations with experimental data from the RHIC, we find evidence for a small η/s ≈ 0.04 in the QCD crossover region and a strong temperature dependence in the hadronic phase. A temperature independent η/s is disfavored by the data. We further show that measurements of the event-by-event flow as a function of rapidity can be used to independently constrain the initial state fluctuations inmore » three dimensions and the temperature dependent transport properties of QCD matter.« less

  20. Moving Forward to Constrain the Shear Viscosity of QCD Matter

    SciTech Connect

    Denicol, Gabriel; Monnai, Akihiko; Schenke, Björn

    2016-05-26

    In this work, we demonstrate that measurements of rapidity differential anisotropic flow in heavy-ion collisions can constrain the temperature dependence of the shear viscosity to entropy density ratio η/s of QCD matter. Comparing results from hydrodynamic calculations with experimental data from the RHIC, we find evidence for a small η/s ≈ 0.04 in the QCD crossover region and a strong temperature dependence in the hadronic phase. A temperature independent η/s is disfavored by the data. We further show that measurements of the event-by-event flow as a function of rapidity can be used to independently constrain the initial state fluctuations in three dimensions and the temperature dependent transport properties of QCD matter.

  1. Bayesian methods for the analysis of inequality constrained contingency tables.

    PubMed

    Laudy, Olav; Hoijtink, Herbert

    2007-04-01

    A Bayesian methodology for the analysis of inequality constrained models for contingency tables is presented. The problem of interest lies in obtaining the estimates of functions of cell probabilities subject to inequality constraints, testing hypotheses and selection of the best model. Constraints on conditional cell probabilities and on local, global, continuation and cumulative odds ratios are discussed. A Gibbs sampler to obtain a discrete representation of the posterior distribution of the inequality constrained parameters is used. Using this discrete representation, the credibility regions of functions of cell probabilities can be constructed. Posterior model probabilities are used for model selection and hypotheses are tested using posterior predictive checks. The Bayesian methodology proposed is illustrated in two examples.

  2. Constraining the Noncommutative Spectral Action via Astrophysical Observations

    SciTech Connect

    Nelson, William; Ochoa, Joseph; Sakellariadou, Mairi

    2010-09-03

    The noncommutative spectral action extends our familiar notion of commutative spaces, using the data encoded in a spectral triple on an almost commutative space. Varying a rather simple action, one can derive all of the standard model of particle physics in this setting, in addition to a modified version of Einstein-Hilbert gravity. In this Letter we use observations of pulsar timings, assuming that no deviation from general relativity has been observed, to constrain the gravitational sector of this theory. While the bounds on the coupling constants remain rather weak, they are comparable to existing bounds on deviations from general relativity in other settings and are likely to be further constrained by future observations.

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

    NASA Astrophysics Data System (ADS)

    Bernon, Jérémy; Dumont, Béranger

    2015-09-01

    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 patibility 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.

  4. Inadequacy of single-impulse transfers for path constrained rendezvous

    NASA Technical Reports Server (NTRS)

    Stern, S. A.; Soileau, K. M.

    1987-01-01

    The use of single-impulse techniques to maneuver from point to point about a large space structure (LSS) with an arbitrary geometrical configuration and spin is examined. Particular consideration is given to transfers with both endpoints on the forbidden zone surface. Clohessy-Wiltshire equations of relative motion are employed to solve path constrained rendezvous problems. External and internal transfers between arbitrary points are analyzed in terms of tangential departure and arrival conditions. It is observed that single-impulse techniques are inadequate for transferring about the exterior of any LSS; however, single-impulse transfers are applicable for transfers in the interior of LSSs. It is concluded that single-impulse transducers are not applicable for path constrained rendezvous guidance.

  5. 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

  6. Matter coupling in partially constrained vielbein formulation of massive gravity

    SciTech Connect

    Felice, Antonio De; Gümrükçüoğlu, A. Emir; Heisenberg, Lavinia; Mukohyama, Shinji

    2016-01-04

    We consider a linear effective vielbein matter coupling without introducing the Boulware-Deser ghost in ghost-free massive gravity. This is achieved in the partially constrained vielbein formulation. We first introduce the formalism and prove the absence of ghost at all scales. As next we investigate the cosmological application of this coupling in this new formulation. We show that even if the background evolution accords with the metric formulation, the perturbations display important different features in the partially constrained vielbein formulation. We study the cosmological perturbations of the two branches of solutions separately. The tensor perturbations coincide with those in the metric formulation. Concerning the vector and scalar perturbations, the requirement of absence of ghost and gradient instabilities yields slightly different allowed parameter space.

  7. 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.

  8. Critical transition in the constrained traveling salesman problem

    NASA Astrophysics Data System (ADS)

    Andrecut, M.; Ali, M. K.

    2001-04-01

    We investigate the finite size scaling of the mean optimal tour length as a function of density of obstacles in a constrained variant of the traveling salesman problem (TSP). The computational experience pointed out a critical transition (at ρc~85%) in the dependence between the excess of the mean optimal tour length over the Held-Karp lower bound and the density of obstacles.

  9. Anti-B-B Mixing Constrains Topcolor-Assisted Technicolor

    SciTech Connect

    Burdman, Gustavo; Lane, Kenneth; Rador, Tonguc

    2000-12-06

    We argue that extended technicolor augmented with topcolor requires that all mixing between the third and the first two quark generations resides in the mixing matrix of left-handed down quarks. Then, the anti-B_d--B_d mixing that occurs in topcolor models constrains the coloron and Z' boson masses to be greater than about 5 TeV. This implies fine tuning of the topcolor couplings to better than 1percent.

  10. 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.

  11. Constraining dark energy through the stability of cosmic structures

    SciTech Connect

    Pavlidou, V.; Tetradis, N.; Tomaras, T.N. E-mail: ntetrad@phys.uoa.gr

    2014-05-01

    For a general dark-energy equation of state, we estimate the maximum possible radius of massive structures that are not destabilized by the acceleration of the cosmological expansion. A comparison with known stable structures constrains the equation of state. The robustness of the constraint can be enhanced through the accumulation of additional astrophysical data and a better understanding of the dynamics of bound cosmic structures.

  12. Constrained and Unconstrained Localization for Automated Inspection of Marine Propellers

    DTIC Science & Technology

    1991-05-01

    5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7...S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT This work ...constrained localization allows a subset of the points to have stronger influence on the transformation. The measured points in the context of this work refer

  13. Image restoration by constrained total variation minimization and variants

    NASA Astrophysics Data System (ADS)

    Chambolle, Antonin; Lions, Pierre-Louis

    1995-09-01

    We study a signal or image restoration method proposed by Rudin and Osher, namely, the constrained total variation (TV) minimization. This very powerful method gives excellent results on nearly piecewise constant signals, but fails on more complicated data. We propose a very general way to combine convex potentials like the TV, and in this setting we introduce a variant that performs better on piecewise regular--but non constant-- signals.

  14. SIALIC ACIDS AND AUTOIMMUNE DISEASE

    PubMed Central

    Mahajan, Vinay S.; Pillai, Shiv

    2016-01-01

    summary An important underlying mechanism that contributes to autoimmunity is the loss of inhibitory signaling in the immune system. Sialic acid-recognizing Ig superfamily lectins or Siglecs are a family of cell surface proteins largely expressed in hematopoietic cells. The majority of Siglecs are inhibitory receptors expressed in immune cells that bind to sialic acid containing ligands and recruit SH2-domain containing tyrosine phosphatases to their cytoplasmic tails. They deliver inhibitory signals that can contribute to the constraining of immune cells and thus protect the host from autoimmunity. The inhibitory functions of CD22/Siglec-2 and Siglec-G and their contributions to tolerance and autoimmunity, primarily in the B lymphocyte context, are considered in some detail in this review. The relevance to autoimmunity and unregulated inflammation of modified sialic acids, enzymes that modify sialic acid, and other sialic acid binding proteins are also reviewed. PMID:26683151

  15. Temporally constrained reconstruction applied to MRI temperature data.

    PubMed

    Todd, Nick; Adluru, Ganesh; Payne, Allison; DiBella, Edward V R; Parker, Dennis

    2009-08-01

    The monitoring of thermal ablation procedures would benefit from an acceleration in the rate at which MRI temperature maps are acquired. Constrained reconstruction techniques have been shown to be capable of generating high quality images using only a fraction of the k-space data. Here, we present a temporally constrained reconstruction (TCR) algorithm applied to proton resonance frequency shift (PRF) data. The algorithm generates images from undersampled data by iteratively minimizing a cost function. The unique challenges of using an iterative constrained reconstruction technique to generate real-time images were addressed. For a set of eight heating experiments on ex vivo porcine tissue, a maximum reduction factor of 4 was achieved while keeping the root mean square error (RMSE) of the temperature below 0.5 degrees C. For a set of three heating experiments on in vivo canine muscle tissue, the maximum reduction factor achieved was 3 while keeping the temperature RMSE below 1.0 degrees C. At these reduction factors, the TCR algorithm underpredicted the thermal dose by an average of 6% for the ex vivo data and 28% for the in vivo data. Compared with sliding window and low resolution reconstructions, the RMSE of the TCR algorithm was significantly lower (P < 0.05 in all cases).

  16. Groundwater availability as constrained by hydrogeology and environmental flows

    USGS Publications Warehouse

    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.

  17. 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.

  18. Short-Term Results of Novel Constrained Total Hip Arthroplasty

    PubMed Central

    Pace, Thomas; Finley, Stephen; Snider, Rebecca; Looper, Jayme; Tanner, Stephanie

    2015-01-01

    Constrained acetabular components have only been recommended as a salvage option for the persistently unstable total hip arthroplasty (THA), due to limited range of motion and less than satisfactory component failure rates. This is a retrospective review of 137 patients with 154 consecutive primary constrained THAs performed between November 2003 and August 2007. We reviewed serial radiographs, postoperative complications, groin/thigh pain, and compared preoperative and postoperative Harris Hip Scores. With a mean follow-up of 6 years, there was 1.9% dislocation rate, 0% component failure rate, and 2.6% infection rate. Seven patients reported continued groin pain, and three had continued thigh pain. One patient showed radiographic evidence of 1 mm polyethylene wear. Radiographic review showed no evidence of osteolysis or stem subsidence. Harris Hip Scores improved from a mean of 68.8 (range 58-87) preoperatively to 98.9 (range 65-100) at final clinical assessment. This constrained acetabular prosthesis had a dislocation rate of less than 2%, with 0% component failure rate at a minimum of 2 years of follow-up suggesting this prosthesis may be a viable alternative for patients at risk for instability or those known to have recurrent instability. PMID:26330992

  19. CONSTRAINING SOLAR FLARE DIFFERENTIAL EMISSION MEASURES WITH EVE AND RHESSI

    SciTech Connect

    Caspi, Amir; McTiernan, James M.; Warren, Harry P.

    2014-06-20

    Deriving a well-constrained differential emission measure (DEM) distribution for solar flares has historically been difficult, primarily because no single instrument is sensitive to the full range of coronal temperatures observed in flares, from ≲2 to ≳50 MK. We present a new technique, combining extreme ultraviolet (EUV) spectra from the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory with X-ray spectra from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), to derive, for the first time, a self-consistent, well-constrained DEM for jointly observed solar flares. EVE is sensitive to ∼2-25 MK thermal plasma emission, and RHESSI to ≳10 MK; together, the two instruments cover the full range of flare coronal plasma temperatures. We have validated the new technique on artificial test data, and apply it to two X-class flares from solar cycle 24 to determine the flare DEM and its temporal evolution; the constraints on the thermal emission derived from the EVE data also constrain the low energy cutoff of the non-thermal electrons, a crucial parameter for flare energetics. The DEM analysis can also be used to predict the soft X-ray flux in the poorly observed ∼0.4-5 nm range, with important applications for geospace science.

  20. Constraining Solar Flare Differential Emission Measures with EVE and RHESSI

    NASA Astrophysics Data System (ADS)

    Caspi, Amir; McTiernan, James M.; Warren, Harry P.

    2014-06-01

    Deriving a well-constrained differential emission measure (DEM) distribution for solar flares has historically been difficult, primarily because no single instrument is sensitive to the full range of coronal temperatures observed in flares, from lsim2 to gsim50 MK. We present a new technique, combining extreme ultraviolet (EUV) spectra from the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory with X-ray spectra from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), to derive, for the first time, a self-consistent, well-constrained DEM for jointly observed solar flares. EVE is sensitive to ~2-25 MK thermal plasma emission, and RHESSI to gsim10 MK together, the two instruments cover the full range of flare coronal plasma temperatures. We have validated the new technique on artificial test data, and apply it to two X-class flares from solar cycle 24 to determine the flare DEM and its temporal evolution; the constraints on the thermal emission derived from the EVE data also constrain the low energy cutoff of the non-thermal electrons, a crucial parameter for flare energetics. The DEM analysis can also be used to predict the soft X-ray flux in the poorly observed ~0.4-5 nm range, with important applications for geospace science.

  1. CONSTRAINING INTRACLUSTER GAS MODELS WITH AMiBA13

    SciTech Connect

    Molnar, Sandor M.; Umetsu, Keiichi; Ho, Paul T. P.; Koch, Patrick M.; Victor Liao, Yu-Wei; Lin, Kai-Yang; Liu, Guo-Chin; Nishioka, Hiroaki; Birkinshaw, Mark; Bryan, Greg; Haiman, Zoltan; Shang, Cien; Hearn, Nathan

    2010-11-10

    Clusters of galaxies have been extensively used to determine cosmological parameters. A major difficulty in making the best use of Sunyaev-Zel'dovich (SZ) and X-ray observations of clusters for cosmology is that using X-ray observations it is difficult to measure the temperature distribution and therefore determine the density distribution in individual clusters of galaxies out to the virial radius. Observations with the new generation of SZ instruments are a promising alternative approach. We use clusters of galaxies drawn from high-resolution adaptive mesh refinement cosmological simulations to study how well we should be able to constrain the large-scale distribution of the intracluster gas (ICG) in individual massive relaxed clusters using AMiBA in its configuration with 13 1.2 m diameter dishes (AMiBA13) along with X-ray observations. We show that non-isothermal {beta} models provide a good description of the ICG in our simulated relaxed clusters. We use simulated X-ray observations to estimate the quality of constraints on the distribution of gas density, and simulated SZ visibilities (AMiBA13 observations) for constraints on the large-scale temperature distribution of the ICG. We find that AMiBA13 visibilities should constrain the scale radius of the temperature distribution to about 50% accuracy. We conclude that the upgraded AMiBA, AMiBA13, should be a powerful instrument to constrain the large-scale distribution of the ICG.

  2. The dynamics of folding instability in a constrained Cosserat medium

    PubMed Central

    Gourgiotis, Panos A.

    2017-01-01

    Different from Cauchy elastic materials, generalized continua, and in particular constrained Cosserat materials, can be designed to possess extreme (near a failure of ellipticity) orthotropy properties and in this way to model folding in a three-dimensional solid. Following this approach, folding, which is a narrow zone of highly localized bending, spontaneously emerges as a deformation pattern occurring in a strongly anisotropic solid. How this peculiar pattern interacts with wave propagation in the time-harmonic domain is revealed through the derivation of an antiplane, infinite-body Green’s function, which opens the way to integral techniques for anisotropic constrained Cosserat continua. Viewed as a perturbing agent, the Green’s function shows that folding, emerging near a steadily pulsating source in the limit of failure of ellipticity, is transformed into a disturbance with wavefronts parallel to the folding itself. The results of the presented study introduce the possibility of exploiting constrained Cosserat solids for propagating waves in materials displaying origami patterns of deformation. This article is part of the themed issue ‘Patterning through instabilities in complex media: theory and applications.’ PMID:28373382

  3. Applications of a constrained mechanics methodology in economics

    NASA Astrophysics Data System (ADS)

    Janová, Jitka

    2011-11-01

    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 undergraduate level and (ii) to enable the students to gain a deeper understanding of the principles and methods routinely used in mechanics by looking at the well-known methodology from the different perspective of economics. Two constrained dynamic economic problems are presented using the economic terminology in an intuitive way. First, the Phillips model of the business cycle is presented as a system of forced oscillations and the general problem of two interacting economies is solved by the nonholonomic dynamics approach. Second, the Cass-Koopmans-Ramsey model of economical growth is solved as a variational problem with a velocity-dependent constraint using the vakonomic approach. The specifics of the solution interpretation in economics compared to mechanics is discussed in detail, a discussion of the nonholonomic and vakonomic approaches to constrained problems in mechanics and economics is provided and an economic interpretation of the Lagrange multipliers (possibly surprising for the students of physics) is carefully explained. This paper can be used by the undergraduate students of physics interested in interdisciplinary physics applications to gain an understanding of the current scientific approach to economics based on a physical background, or by university teachers as an attractive supplement to classical mechanics lessons.

  4. 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

  5. Towards better constrained models of the solar magnetic cycle

    NASA Astrophysics Data System (ADS)

    Munoz-Jaramillo, Andres

    2010-12-01

    The best tools we have for understanding the origin of solar magnetic variability are kinematic dynamo models. During the last decade, this type of models has seen a continuous evolution and has become increasingly successful at reproducing solar cycle characteristics. The basic ingredients of these models are: the solar differential rotation -- which acts as the main source of energy for the system by shearing the magnetic field; the meridional circulation -- which plays a crucial role in magnetic field transport; the turbulent diffusivity -- which attempts to capture the effect of convective turbulence on the large scale magnetic field; and the poloidal field source -- which closes the cycle by regenerating the poloidal magnetic field. However, most of these ingredients remain poorly constrained which allows one to obtain solar-like solutions by "tuning" the input parameters, leading to controversy regarding which parameter set is more appropriate. In this thesis we revisit each of those ingredients in an attempt to constrain them better by using observational data and theoretical considerations, reducing the amount of free parameters in the model. For the meridional flow and differential rotation we use helioseismic data to constrain free parameters and find that the differential rotation is well determined, but the available data can only constrain the latitudinal dependence of the meridional flow. For the turbulent magnetic diffusivity we show that combining mixing-length theory estimates with magnetic quenching allows us to obtain viable magnetic cycles and that the commonly used diffusivity profiles can be understood as a spatiotemporal average of this process. For the poloidal source we introduce a more realistic way of modeling active region emergence and decay and find that this resolves existing discrepancies between kinematic dynamo models and surface flux transport simulations. We also study the physical mechanisms behind the unusually long minimum of

  6. Purification and characterization of 3-dehydroshikimate dehydratase, an enzyme in the inducible quinic acid catabolic pathway of Neurospora crassa.

    PubMed

    Strøman, P; Reinert, W R; Giles, N H

    1978-07-10

    3-Dehydroshikimate dehydratase catalyzes the third reaction in the inducible quinic acid catabolic pathway of Neurospora crassa and is encoded in the qa-4 gene of the qa gene cluster. As part of continuing genetic and biochemical studies concerning the organization and regulation of this gene cluster, 3-dehydroshikimate dehydratase has been purified and characterized biochemically. The enzyme was purified 1650-fold using the following techniques: 1) (NH4)2SO4 fractionation; 2) ion exchange chromatography on DEAE-cellulose; 3) gel filtration on Sephadex G-100; 4) ion exchange chromatography on Cellex QAE (quaternary aminoethyl); and 5) hydroxylapatite chromatography. 3-Dehydroshikimate dehydratase is a monomer with a molecular weight of about 37,000 and a sedimentation coefficient of 3.27 S. It has a Km value of 5.9 X 10(-4) and an average isoelectric point of 4.92. The purified enzyme is extremely sensitive to thermal denaturation but can be significantly stabilized by Mg2+ ions. The purified enzyme also exhibits maximal catalytic activity only when assayed in the presence of certain divalent cations, e.g. magnesium. The NH2-terminal residue of 3-dehydroshikimate dehydratase is proline, and its alpha-amino group is unblocked.

  7. 21 CFR 888.3100 - Ankle joint metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ankle joint metal/composite semi-constrained... Ankle joint metal/composite semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/composite semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  8. 21 CFR 888.3100 - Ankle joint metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ankle joint metal/composite semi-constrained... Ankle joint metal/composite semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/composite semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  9. 21 CFR 888.3100 - Ankle joint metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ankle joint metal/composite semi-constrained... Ankle joint metal/composite semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/composite semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  10. 21 CFR 888.3100 - Ankle joint metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ankle joint metal/composite semi-constrained... Ankle joint metal/composite semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/composite semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  11. Resource-Driven Mission-Phasing Techniques for Constrained Agents in Stochastic Environments

    DTIC Science & Technology

    2010-07-01

    adopted a Lagrangian and dual LP approach to solve constrained MDPs with total cost criteria. Feinberg (2000) analyzed the complexity of constrained...agents mechanically implement mode-transition and resource- reconfiguration actions. 6. Conclusion The work in this paper designed, analyzed, and...lize resource reconfiguration opportunities. It provides a new computationally efficient resource-reconfiguration mechanism for resource-constrained

  12. 21 CFR 888.3110 - Ankle joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ankle joint metal/polymer semi-constrained... Ankle joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  13. 21 CFR 888.3160 - Elbow joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Elbow joint metal/polymer semi-constrained... Elbow joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An elbow joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  14. 21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in...

  15. 21 CFR 888.3800 - Wrist joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Wrist joint metal/polymer semi-constrained... Wrist joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A wrist joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace a wrist...

  16. 21 CFR 888.3310 - Hip joint metal/polymer constrained cemented or uncemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint metal/polymer constrained cemented or... Hip joint metal/polymer constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal/polymer constrained cemented or uncemented prosthesis is a device intended to be implanted...

  17. 21 CFR 888.3310 - Hip joint metal/polymer constrained cemented or uncemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Hip joint metal/polymer constrained cemented or... Hip joint metal/polymer constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal/polymer constrained cemented or uncemented prosthesis is a device intended to be implanted...

  18. 21 CFR 888.3650 - Shoulder joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Shoulder joint metal/polymer non-constrained... Shoulder joint metal/polymer non-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer non-constrained cemented prosthesis is a device intended to be implanted to replace...

  19. 21 CFR 888.3120 - Ankle joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ankle joint metal/polymer non-constrained cemented... metal/polymer non-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer non... December 26, 1996 for any ankle joint metal/polymer non-constrained cemented prosthesis that was...

  20. 21 CFR 888.3120 - Ankle joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ankle joint metal/polymer non-constrained cemented... metal/polymer non-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer non... December 26, 1996 for any ankle joint metal/polymer non-constrained cemented prosthesis that was...

  1. 21 CFR 888.3160 - Elbow joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Elbow joint metal/polymer semi-constrained... Elbow joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An elbow joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  2. 21 CFR 888.3120 - Ankle joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ankle joint metal/polymer non-constrained cemented... metal/polymer non-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer non... December 26, 1996 for any ankle joint metal/polymer non-constrained cemented prosthesis that was...

  3. 21 CFR 888.3110 - Ankle joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ankle joint metal/polymer semi-constrained... Ankle joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  4. 21 CFR 888.3110 - Ankle joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ankle joint metal/polymer semi-constrained... Ankle joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  5. 21 CFR 888.3120 - Ankle joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ankle joint metal/polymer non-constrained cemented... metal/polymer non-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer non... December 26, 1996 for any ankle joint metal/polymer non-constrained cemented prosthesis that was...

  6. 21 CFR 888.3660 - Shoulder joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Shoulder joint metal/polymer semi-constrained... Shoulder joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  7. 21 CFR 888.3510 - Knee joint femorotibial metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Knee joint femorotibial metal/polymer constrained... Knee joint femorotibial metal/polymer constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/polymer constrained cemented prosthesis is a device intended to be implanted to replace...

  8. 21 CFR 888.3800 - Wrist joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Wrist joint metal/polymer semi-constrained... Wrist joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A wrist joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace a wrist...

  9. 21 CFR 888.3110 - Ankle joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ankle joint metal/polymer semi-constrained... Ankle joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  10. 21 CFR 888.3800 - Wrist joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Wrist joint metal/polymer semi-constrained... Wrist joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A wrist joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace a wrist...

  11. 21 CFR 888.3510 - Knee joint femorotibial metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint femorotibial metal/polymer constrained... Knee joint femorotibial metal/polymer constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/polymer constrained cemented prosthesis is a device intended to be implanted to replace...

  12. 21 CFR 888.3310 - Hip joint metal/polymer constrained cemented or uncemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Hip joint metal/polymer constrained cemented or... Hip joint metal/polymer constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal/polymer constrained cemented or uncemented prosthesis is a device intended to be implanted...

  13. 21 CFR 888.3800 - Wrist joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Wrist joint metal/polymer semi-constrained... Wrist joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A wrist joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace a wrist...

  14. 21 CFR 888.3120 - Ankle joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ankle joint metal/polymer non-constrained cemented... metal/polymer non-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer non... December 26, 1996 for any ankle joint metal/polymer non-constrained cemented prosthesis that was...

  15. 21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in...

  16. 21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in...

  17. 21 CFR 888.3650 - Shoulder joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Shoulder joint metal/polymer non-constrained... Shoulder joint metal/polymer non-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer non-constrained cemented prosthesis is a device intended to be implanted to replace...

  18. 21 CFR 888.3310 - Hip joint metal/polymer constrained cemented or uncemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Hip joint metal/polymer constrained cemented or... Hip joint metal/polymer constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal/polymer constrained cemented or uncemented prosthesis is a device intended to be implanted...

  19. 21 CFR 888.3310 - Hip joint metal/polymer constrained cemented or uncemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Hip joint metal/polymer constrained cemented or... Hip joint metal/polymer constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal/polymer constrained cemented or uncemented prosthesis is a device intended to be implanted...

  20. 21 CFR 888.3660 - Shoulder joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Shoulder joint metal/polymer semi-constrained... Shoulder joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  1. 21 CFR 888.3650 - Shoulder joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Shoulder joint metal/polymer non-constrained... Shoulder joint metal/polymer non-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer non-constrained cemented prosthesis is a device intended to be implanted to replace...

  2. 21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in...

  3. 21 CFR 888.3510 - Knee joint femorotibial metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Knee joint femorotibial metal/polymer constrained... Knee joint femorotibial metal/polymer constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/polymer constrained cemented prosthesis is a device intended to be implanted to replace...

  4. 21 CFR 888.3660 - Shoulder joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Shoulder joint metal/polymer semi-constrained... Shoulder joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  5. 21 CFR 888.3650 - Shoulder joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Shoulder joint metal/polymer non-constrained... Shoulder joint metal/polymer non-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer non-constrained cemented prosthesis is a device intended to be implanted to replace...

  6. 21 CFR 888.3800 - Wrist joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Wrist joint metal/polymer semi-constrained... Wrist joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A wrist joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace a wrist...

  7. 21 CFR 888.3160 - Elbow joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Elbow joint metal/polymer semi-constrained... Elbow joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An elbow joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  8. 21 CFR 888.3220 - Finger joint metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Finger joint metal/polymer constrained cemented... metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer..., 1996 for any finger joint metal/polymer constrained cemented prosthesis that was in...

  9. 21 CFR 888.3110 - Ankle joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ankle joint metal/polymer semi-constrained... Ankle joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  10. 21 CFR 888.3510 - Knee joint femorotibial metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Knee joint femorotibial metal/polymer constrained... Knee joint femorotibial metal/polymer constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/polymer constrained cemented prosthesis is a device intended to be implanted to replace...

  11. 21 CFR 888.3160 - Elbow joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Elbow joint metal/polymer semi-constrained... Elbow joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An elbow joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  12. 21 CFR 888.3510 - Knee joint femorotibial metal/polymer constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Knee joint femorotibial metal/polymer constrained... Knee joint femorotibial metal/polymer constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/polymer constrained cemented prosthesis is a device intended to be implanted to replace...

  13. 21 CFR 888.3160 - Elbow joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Elbow joint metal/polymer semi-constrained... Elbow joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An elbow joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an...

  14. 21 CFR 888.3650 - Shoulder joint metal/polymer non-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Shoulder joint metal/polymer non-constrained... Shoulder joint metal/polymer non-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer non-constrained cemented prosthesis is a device intended to be implanted to replace...

  15. 21 CFR 888.3660 - Shoulder joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Shoulder joint metal/polymer semi-constrained... Shoulder joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  16. 21 CFR 888.3660 - Shoulder joint metal/polymer semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Shoulder joint metal/polymer semi-constrained... Shoulder joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A shoulder joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  17. 21 CFR 888.3790 - Wrist joint metal constrained cemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Wrist joint metal constrained cemented prosthesis... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3790 Wrist joint metal constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is...

  18. 21 CFR 888.3200 - Finger joint metal/metal constrained uncemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Finger joint metal/metal constrained uncemented... metal/metal constrained uncemented prosthesis. (a) Identification. A finger joint metal/metal... Administration on or before December 26, 1996 for any finger joint metal/metal constrained uncemented...

  19. 21 CFR 888.3790 - Wrist joint metal constrained cemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Wrist joint metal constrained cemented prosthesis... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3790 Wrist joint metal constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is...

  20. 21 CFR 888.3200 - Finger joint metal/metal constrained uncemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Finger joint metal/metal constrained uncemented... metal/metal constrained uncemented prosthesis. (a) Identification. A finger joint metal/metal... Administration on or before December 26, 1996 for any finger joint metal/metal constrained uncemented...

  1. 21 CFR 888.3790 - Wrist joint metal constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Wrist joint metal constrained cemented prosthesis... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3790 Wrist joint metal constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is...

  2. 21 CFR 888.3200 - Finger joint metal/metal constrained uncemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Finger joint metal/metal constrained uncemented... metal/metal constrained uncemented prosthesis. (a) Identification. A finger joint metal/metal... Administration on or before December 26, 1996 for any finger joint metal/metal constrained uncemented...

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

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ankle joint metal/composite semi-constrained... Ankle joint metal/composite semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/composite semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  4. 21 CFR 888.3200 - Finger joint metal/metal constrained uncemented prosthesis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Finger joint metal/metal constrained uncemented... metal/metal constrained uncemented prosthesis. (a) Identification. A finger joint metal/metal... Administration on or before December 26, 1996 for any finger joint metal/metal constrained uncemented...

  5. 21 CFR 888.3790 - Wrist joint metal constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Wrist joint metal constrained cemented prosthesis... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3790 Wrist joint metal constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is...

  6. 21 CFR 888.3790 - Wrist joint metal constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Wrist joint metal constrained cemented prosthesis... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3790 Wrist joint metal constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is...

  7. 21 CFR 888.3200 - Finger joint metal/metal constrained uncemented prosthesis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Finger joint metal/metal constrained uncemented... metal/metal constrained uncemented prosthesis. (a) Identification. A finger joint metal/metal... Administration on or before December 26, 1996 for any finger joint metal/metal constrained uncemented...

  8. Growth-promoting activity of pyrazinoic acid, a putative active compound of antituberculosis drug pyrazinamide, in niacin-deficient rats through the inhibition of ACMSD activity.

    PubMed

    Fukuwatari, Tsutomu; Sugimoto, Etsuro; Shibata, Katsumi

    2002-07-01

    We have recently reported that the antituberculosis drug, pyrazinamide (PZA), caused a significant increase in the conversion ratio of tryptophan to niacin in rats. In the present work, we investigated whether or not pyrazinoic acid (POA), a putative metabolite of PZA, increased the conversion ratio of tryptophan to niacin. Weaning rats were fed with a niacin-free and tryptophan-limited diet (negative control diet), or with the negative control diet supplemented with 0.003% nicotinic acid (positive control diet) or 1% POA (test diet) for 27 days. The growth rate was almost same between the groups fed on the positive control diet and the test diet. Dietary POA significantly increased the conversion ratio of tryptophan to niacin. Although POA did not directly inhibit the activity of alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase (ACMSD), the rate-limiting enzyme in the tryptophan-niacin pathway, liver ACMSD activity was only not detected in the test diet group. These results suggest that a derivative of POA metabolized by rats inhibited the ACMSD activity.

  9. Excitotoxic death induced by released glutamate in depolarized primary cultures of mouse cerebellar granule cells is dependent on GABAA receptors and niflumic acid-sensitive chloride channels.

    PubMed

    Babot, Zoila; Cristòfol, Rosa; Suñol, Cristina

    2005-01-01

    Excitotoxic neuronal death has been linked to neurological and neurodegenerative diseases. Several studies have sought to clarify the involvement of Cl(-) channels in neuronal excitotoxicity using either N-methyl-D-aspartic acid (NMDA) or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate/kainic acid agonists. In this work we induced excitotoxic death in primary cultures of cerebellar granule cells by means of endogenously released glutamate. Excitotoxicity was provoked by exposure to high extracellular K(+) concentrations ([K(+)](o)) for 5 min. Under these conditions, a Ca(2+)-dependent release of glutamate was evoked. When extracellular glutamate concentration rose to between 2 and 4 microM, cell viability was significantly reduced by 30-40%. The NMDA receptor antagonists (MK-801 and D-2-amino-5-phosphonopentanoic acid) prevented cell death. Exposure to high [K(+)](o) produced a (36)Cl(-) influx which was significantly reduced by picrotoxinin. In addition, the GABA(A) receptor antagonists (bicuculline, picrotoxinin and SR 95531) protected cells from high [K(+)](o)-triggered excitotoxicity and reduced extracellular glutamate concentration. The Cl(-) channel blockers niflumic acid and 5-nitro-2-(3-phenylpropylamino)benzoic acid also exerted a neuroprotective effect and reduced extracellular glutamate concentration, even though they did not reduce high [K(+)](o)-induced (36)Cl(-) influx. Primary cultures of cerebellar granule cells also contain a population of GABAergic neurons that released GABA in response to high [K(+)](o). Chronic treatment of primary cultures with kainic acid abolished GABA release and rendered granule cells insensitive to high [K(+)](o) exposure, even though NMDA receptors were functional. Altogether, these results demonstrate that, under conditions of membrane depolarization, low micromolar concentrations of extracellular glutamate might induce an excitotoxic process through both NMDA and GABA(A) receptors and niflumic acid-sensitive Cl

  10. Constrained dynamics approach for motion synchronization and consensus

    NASA Astrophysics Data System (ADS)

    Bhatia, Divya

    In this research we propose to develop constrained dynamical systems based stable attitude synchronization, consensus and tracking (SCT) control laws for the formation of rigid bodies. The generalized constrained dynamics Equations of Motion (EOM) are developed utilizing constraint potential energy functions that enforce communication constraints. Euler-Lagrange equations are employed to develop the non-linear constrained dynamics of multiple vehicle systems. The constraint potential energy is synthesized based on a graph theoretic formulation of the vehicle-vehicle communication. Constraint stabilization is achieved via Baumgarte's method. The performance of these constrained dynamics based formations is evaluated for bounded control authority. The above method has been applied to various cases and the results have been obtained using MATLAB simulations showing stability, synchronization, consensus and tracking of formations. The first case corresponds to an N-pendulum formation without external disturbances, in which the springs and the dampers connected between the pendulums act as the communication constraints. The damper helps in stabilizing the system by damping the motion whereas the spring acts as a communication link relaying relative position information between two connected pendulums. Lyapunov stabilization (energy based stabilization) technique is employed to depict the attitude stabilization and boundedness. Various scenarios involving different values of springs and dampers are simulated and studied. Motivated by the first case study, we study the formation of N 2-link robotic manipulators. The governing EOM for this system is derived using Euler-Lagrange equations. A generalized set of communication constraints are developed for this system using graph theory. The constraints are stabilized using Baumgarte's techniques. The attitude SCT is established for this system and the results are shown for the special case of three 2-link robotic manipulators

  11. 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

  12. Hygro-thermal mechanical behavior of Nafion during constrained swelling

    NASA Astrophysics Data System (ADS)

    Silberstein, Meredith N.; Boyce, Mary C.

    Durability is a major limitation of current proton exchange membrane fuel cells. Mechanical stress due to hygro-thermal cycling is one failure mechanism of the polymer electrolyte membrane. In previous work the cyclic rate, temperature, and hydration dependent elastic-viscoplastic mechanical behavior of Nafion has been extensively investigated in uniaxial and biaxial tension, serving as a data basis and means of validation for a three-dimensional constitutive model. Here, the important effect of loading via constrained swelling is studied. Specifically, two types of loading are investigated: partially constrained swelling via a bimaterial swelling test and hygro-thermal cycling within a fuel cell. The bimaterial swelling conditions are examined via experiments in conjunction with modeling. Nafion/GDL bimaterial strips were hydrated and observed to curl significantly with the membrane on the convex side due to the large Nafion hygro-expansion coefficient. Upon drying the bimaterial strips developed a slight reverse curvature with the membrane on the concave side due to the plastic deformation which had occurred in the membrane during hydration. Finite element simulations utilizing the Nafion constitutive model successfully predicted the behavior during hydration and drying, providing insight on the constrained swelling physics and the ability of the model to predict such events. Simulations of in situ fuel cell hygro-thermal cycling are performed via a simplified two-dimensional fuel cell model. The simulation results confirm the finding of other studies that a tensile stress develops in the membrane during drying. Further, a concentration of negative hydrostatic pressure is found to develop just inside the channel region in the dried state supporting the theory of hygro-thermal driven mechanical stresses causing pinhole formation in the channel. The amplitude of the pressure cycling is found to be large and sensitive to both hygro-thermal ramp time and hold time

  13. Fast alternating projection methods for constrained tomographic reconstruction.

    PubMed

    Liu, Li; Han, Yongxin; Jin, Mingwu

    2017-01-01

    The alternating projection algorithms are easy to implement and effective for large-scale complex optimization problems, such as constrained reconstruction of X-ray computed tomography (CT). A typical method is to use projection onto convex sets (POCS) for data fidelity, nonnegative constraints combined with total variation (TV) minimization (so called TV-POCS) for sparse-view CT reconstruction. However, this type of method relies on empirically selected parameters for satisfactory reconstruction and is generally slow and lack of convergence analysis. In this work, we use a convex feasibility set approach to address the problems associated with TV-POCS and propose a framework using full sequential alternating projections or POCS (FS-POCS) to find the solution in the intersection of convex constraints of bounded TV function, bounded data fidelity error and non-negativity. The rationale behind FS-POCS is that the mathematically optimal solution of the constrained objective function may not be the physically optimal solution. The breakdown of constrained reconstruction into an intersection of several feasible sets can lead to faster convergence and better quantification of reconstruction parameters in a physical meaningful way than that in an empirical way of trial-and-error. In addition, for large-scale optimization problems, first order methods are usually used. Not only is the condition for convergence of gradient-based methods derived, but also a primal-dual hybrid gradient (PDHG) method is used for fast convergence of bounded TV. The newly proposed FS-POCS is evaluated and compared with TV-POCS and another convex feasibility projection method (CPTV) using both digital phantom and pseudo-real CT data to show its superior performance on reconstruction speed, image quality and quantification.

  14. Pattern recognition constrains mantle properties, past and present

    NASA Astrophysics Data System (ADS)

    Atkins, S.; Rozel, A. B.; Valentine, A. P.; Tackley, P.; Trampert, J.

    2015-12-01

    Understanding and modelling mantle convection requires knowledge of many mantle properties, such as viscosity, chemical structure and thermal proerties such as radiogenic heating rate. However, many of these parameters are only poorly constrained. We demonstrate a new method for inverting present day Earth observations for mantle properties. We use neural networks to represent the posterior probability density functions of many different mantle properties given the present structure of the mantle. We construct these probability density functions by sampling a wide range of possible mantle properties and running forward simulations, using the convection code StagYY. Our approach is particularly powerful because of its flexibility. Our samples are selected in the prior space, rather than being targeted towards a particular observation, as would normally be the case for probabilistic inversion. This means that the same suite of simulations can be used for inversions using a wide range of geophysical observations without the need to resample. Our method is probabilistic and non-linear and is therefore compatible with non-linear convection, avoiding some of the limitations associated with other methods for inverting mantle flow. This allows us to consider the entire history of the mantle. We also need relatively few samples for our inversion, making our approach computationally tractable when considering long periods of mantle history. Using the present thermal and density structure of the mantle, we can constrain rheological and compositional parameters such as viscosity and yield stress. We can also use the present day mantle structure to make inferences about the initial conditions for convection 4.5 Gyr ago. We can constrain initial mantle conditions including the initial concentration of heat producing elements in the mantle and the initial thickness of primordial material at the CMB. Currently we use density and temperature structure for our inversions, but we can

  15. Constrained Spectral Conditioning for spatial sound level estimation

    NASA Astrophysics Data System (ADS)

    Spalt, Taylor B.; Brooks, Thomas F.; Fuller, Christopher R.

    2016-11-01

    Microphone arrays are utilized in aeroacoustic testing to spatially map the sound emitted from an article under study. Whereas a single microphone allows only the total sound level to be estimated at the measurement location, an array permits differentiation between the contributions of distinct components. The accuracy of these spatial sound estimates produced by post-processing the array outputs is continuously being improved. One way of increasing the estimation accuracy is to filter the array outputs before they become inputs to a post-processor. This work presents a constrained method of linear filtering for microphone arrays which minimizes the total signal present on the array channels while preserving the signal from a targeted spatial location. Thus, each single-channel, filtered output for a given targeted location estimates only the signal from that location, even when multiple and/or distributed sources have been measured simultaneously. The method is based on Conditioned Spectral Analysis and modifies the Wiener-Hopf equation in a manner similar to the Generalized Sidelobe Canceller. This modified form of Conditioned Spectral Analysis is embedded within an iterative loop and termed Constrained Spectral Conditioning. Linear constraints are derived which prevent the cancellation of targeted signal due to random statistical error as well as location error in the sensor and/or source positions. The increased spatial mapping accuracy of Constrained Spectral Conditioning is shown for a simulated dataset of point sources which vary in strength. An experimental point source is used to validate the efficacy of the constraints which yield preservation of the targeted signal at the expense of reduced filtering ability. The beamforming results of a cold, supersonic jet demonstrate the qualitative and quantitative improvement obtained when using this technique to map a spatially-distributed, complex, and possibly coherent sound source.

  16. Constraining continuous rainfall simulations for derived design flood estimation

    NASA Astrophysics Data System (ADS)

    Woldemeskel, F. M.; Sharma, A.; Mehrotra, R.; Westra, S.

    2016-11-01

    Stochastic rainfall generation is important for a range of hydrologic and water resources applications. Stochastic rainfall can be generated using a number of models; however, preserving relevant attributes of the observed rainfall-including rainfall occurrence, variability and the magnitude of extremes-continues to be difficult. This paper develops an approach to constrain stochastically generated rainfall with an aim of preserving the intensity-durationfrequency (IFD) relationships of the observed data. Two main steps are involved. First, the generated annual maximum rainfall is corrected recursively by matching the generated intensity-frequency relationships to the target (observed) relationships. Second, the remaining (non-annual maximum) rainfall is rescaled such that the mass balance of the generated rain before and after scaling is maintained. The recursive correction is performed at selected storm durations to minimise the dependence between annual maximum values of higher and lower durations for the same year. This ensures that the resulting sequences remain true to the observed rainfall as well as represent the design extremes that may have been developed separately and are needed for compliance reasons. The method is tested on simulated 6 min rainfall series across five Australian stations with different climatic characteristics. The results suggest that the annual maximum and the IFD relationships are well reproduced after constraining the simulated rainfall. While our presentation focusses on the representation of design rainfall attributes (IFDs), the proposed approach can also be easily extended to constrain other attributes of the generated rainfall, providing an effective platform for post-processing of stochastic rainfall generators.

  17. Bound constrained bundle adjustment for reliable 3D reconstruction

    PubMed Central

    Gong, Yuanzheng; Meng, De; Seibel, Eric J.

    2015-01-01

    Bundle adjustment (BA) is a common estimation algorithm that is widely used in machine vision as the last step in a feature-based three-dimensional (3D) reconstruction algorithm. BA is essentially a non-convex non-linear least-square problem that can simultaneously solve the 3D coordinates of all the feature points describing the scene geometry, as well as the parameters of the camera. The conventional BA takes a parameter either as a fixed value or as an unconstrained variable based on whether the parameter is known or not. In cases where the known parameters are inaccurate but constrained in a range, conventional BA results in an incorrect 3D reconstruction by using these parameters as fixed values. On the other hand, these inaccurate parameters can be treated as unknown variables, but this does not exploit the knowledge of the constraints, and the resulting reconstruction can be erroneous since the BA optimization halts at a dramatically incorrect local minimum due to its non-convexity. In many practical 3D reconstruction applications, unknown variables with range constraints are usually available, such as a measurement with a range of uncertainty or a bounded estimate. Thus to better utilize these pre-known, constrained, but inaccurate parameters, a bound constrained bundle adjustment (BCBA) algorithm is proposed, developed and tested in this study. A scanning fiber endoscope (the camera) is used to capture a sequence of images above a surgery phantom (the object) of known geometry. 3D virtual models are reconstructed based on these images and then compared with the ground truth. The experimental results demonstrate BCBA can achieve a more reliable, rapid, and accurate 3D reconstruction than conventional bundle adjustment. PMID:25969115

  18. Bridled ambition: Why countries constrain their nuclear capabilities

    SciTech Connect

    Reiss, M.

    1995-12-31

    Reiss worked for the National Security Council on nonproliferation issues and thus brings a wealth of inside information to this study. Reiss examines nine countries that have voluntarily constrained, frozen, or eliminated their nuclear weapons programs. These counties are South Africa, Argentina, Brazil, Belarus, Kazakhstan, Ukraine, India, Pakistan, and North Korea. Reiss has added an important contribution to the research of nuclear nonproliferation and shown us that occasionally deproliferation is a viable policy option. At a time when nuclear proliferation is becoming an increasingly ominous threat to global stability, Mitchell Reiss`s book provides the much-needed perspective. Thoroughly researched, systematic and probing in analysis, and significant in its conclusions.

  19. An Algorithm for Linearly Constrained Nonlinear Programming Programming Problems.

    DTIC Science & Technology

    1980-01-01

    ALGORITHM FOR LINEARLY CONSTRAINED NONLINEAR PROGRAMMING PROBLEMS Mokhtar S. Bazaraa and Jamie J. Goode In this paper an algorithm for solving a linearly...distance pro- gramr.ing, as in the works of Bazaraa and Goode 12], and Wolfe [16 can be used for solving this problem. Special methods that take advantage of...34 Pacific Journal of Mathematics, Volume 16, pp. 1-3, 1966. 2. M. S. Bazaraa and J. j. Goode, "An Algorithm for Finding the Shortest Element of a

  20. Domain decomposition in time for PDE-constrained optimization

    SciTech Connect

    Barker, Andrew T.; Stoll, Martin

    2015-08-28

    Here, PDE-constrained optimization problems have a wide range of applications, but they lead to very large and ill-conditioned linear systems, especially if the problems are time dependent. In this paper we outline an approach for dealing with such problems by decomposing them in time and applying an additive Schwarz preconditioner in time, so that we can take advantage of parallel computers to deal with the very large linear systems. We then illustrate the performance of our method on a variety of problems.

  1. QoS-constrained Energy Minimization in Multiuser Multicarrier Systems

    NASA Astrophysics Data System (ADS)

    Bai, Qing; Ivrlač, Michel T.; Nossek, Josef A.

    In this paper the QoS-constrained resource allocation problem in multicarrier systems is considered. Within the established cross-layer framework, parameters for subchannel assignment, adaptive modulation and coding, and ARQ/HARQ protocols are jointly optimized. Instead of the conventional transmit power minimization, the total energy consumption for the successful transmissions of all information bits is set as the optimization goal. The nonconvex primal problem is solved by using Lagrange dual decomposition and the ellipsoid method. Numerical results indicate that the recovered primal solution is well acceptable in performance, and efficient in terms of computational effort.

  2. Constrained blind source extraction of readiness potentials from EEG.

    PubMed

    Ahmadian, Pouya; Sanei, Saeid; Ascari, Luca; González-Villanueva, Lara; Alessandra Umiltà, Maria

    2013-07-01

    One of the changes seen in electroencephalography (EEG) data preceding human voluntary movement is a cortical potential called readiness potential (RP). Detection of this potential can benefit researchers in clinical neurosciences for rehabilitation of malfunctioning brain and those working on brain-computer interfacing to develop a suitable mechanism to detect the intention of movement. Here, a constrained blind source extraction (CBSE) is attempted for detection of RP. A suitable constraint is defined and applied. The results are also compared with those of the traditional blind source separation in terms of true positive rate, false positive rate, and computation time. The results show that the CBSE approach in overall has superior performance.

  3. Hex-dominant mesh generation using 3D constrained triangulation

    SciTech Connect

    OWEN,STEVEN J.

    2000-05-30

    A method for decomposing a volume with a prescribed quadrilateral surface mesh, into a hexahedral-dominated mesh is proposed. With this method, known as Hex-Morphing (H-Morph), an initial tetrahedral mesh is provided. Tetrahedral are transformed and combined starting from the boundary and working towards the interior of the volume. The quadrilateral faces of the hexahedra are treated as internal surfaces, which can be recovered using constrained triangulation techniques. Implementation details of the edge and face recovery process are included. Examples and performance of the H-Morph algorithm are also presented.

  4. Interactive image segmentation by constrained spectral graph partitioning

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; He, Jin; Zhang, Hong; Huang, Zhanhua

    2010-11-01

    This paper proposed an interactive image segmentation algorithm that can tolerate slightly incorrect user constraints. Interactive image segmentation was formulated as a constrained spectral graph partitioning problem. Furthermore, it was proven to equal to a supervised classification problem, where the feature space was formed by rows of the eigenvector matrix that was computed by spectral graph analysis. ν-SVM (support vector machine) was preferred as the classifier. Some incorrect labels in user constraints were tolerated by being identified as margin errors in ν-SVM. Comparison with other algorithms on real color images was reported.

  5. Active Constrained Layer Damping of Thin Cylindrical Shells

    NASA Astrophysics Data System (ADS)

    RAY, M. C.; OH, J.; BAZ, A.

    2001-03-01

    The effectiveness of the active constrained layer damping (ACLD) treatments in enhancing the damping characteristics of thin cylindrical shells is presented. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. Experiments are performed to verify the numerical predictions. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  6. 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

  7. Shared inductor hybrid topology for weight constrained piezoelectric actuators

    NASA Astrophysics Data System (ADS)

    Elliott, A. D. T.; Caccia, A.; Thomas, A.; Astolfi, A.; Mitcheson, P. D.

    2016-11-01

    This paper presents a new circuit topology designed to minimise the weight of the control circuit required to actuate multiple piezoelectric actuators. It can independently set the phase and bias voltage on each piezoelectric actuator through the use of a single inductor. This is highly desirable in weight constrained applications such as unmanned aerial vehicles as the ferroelectric material required for the inductor is heavy. Furthermore, the circuit topology can also use the same inductor to generate the high bias voltage required to drive the actuators. The full system has been verified in PSpice and a pair of piezoelectric actuators have been successfully driven using off the shelf components.

  8. Finding intrinsic rewards by embodied evolution and constrained reinforcement learning.

    PubMed

    Uchibe, Eiji; Doya, Kenji

    2008-12-01

    Understanding the design principle of reward functions is a substantial challenge both in artificial intelligence and neuroscience. Successful acquisition of a task usually requires not only rewards for goals, but also for intermediate states to promote effective exploration. This paper proposes a method for designing 'intrinsic' rewards of autonomous agents by combining constrained policy gradient reinforcement learning and embodied evolution. To validate the method, we use Cyber Rodent robots, in which collision avoidance, recharging from battery packs, and 'mating' by software reproduction are three major 'extrinsic' rewards. We show in hardware experiments that the robots can find appropriate 'intrinsic' rewards for the vision of battery packs and other robots to promote approach behaviors.

  9. 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.

  10. Constraining modified gravitational theories by weak lensing with Euclid

    SciTech Connect

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

    2011-01-15

    Future proposed satellite missions such 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 such as those predicted by scalar-tensor and f(R) theories. We find that Euclid will improve constraints expected from the Planck satellite on these modified theories of gravity by 2 orders of magnitude. We discuss parameter degeneracies and the possible biases introduced by modifications to gravity.

  11. New quasidilaton theory in partially constrained vielbein formalism

    SciTech Connect

    Felice, Antonio De; Gümrükçüoğlu, A. Emir; Heisenberg, Lavinia; Mukohyama, Shinji; Tanahashi, Norihiro

    2016-05-25

    In this work we study the partially constrained vielbein formulation of the new quasidilaton theory of massive gravity, where the quasidilaton field couples to both physical and fiducial metrics simultaneously via a composite effective metric and Lorentz violation is introduced by a constraint on the vielbein. This formalism improves the new quasidilaton model since the Boulware-Deser ghost is removed fully non-linearly at all scales. This also yields crucial implications in the cosmological applications. We derive the governing cosmological background evolution and study the stability of the attractor solution.

  12. 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.

  13. Conformationally Constrained Histidines in the Design of Peptidomimetics: Strategies for the χ-Space Control

    PubMed Central

    Stefanucci, Azzurra; Pinnen, Francesco; Feliciani, Federica; Cacciatore, Ivana; Lucente, Gino; Mollica, Adriano

    2011-01-01

    A successful design of peptidomimetics must come to terms with χ-space control. The incorporation of χ-space constrained amino acids into bioactive peptides renders the χ1 and χ2 torsional angles of pharmacophore amino acids critical for activity and selectivity as with other relevant structural features of the template. This review describes histidine analogues characterized by replacement of native α and/or β-hydrogen atoms with alkyl substituents as well as analogues with α, β-didehydro unsaturation or Cα-Cβ cyclopropane insertion (ACC derivatives). Attention is also dedicated to the relevant field of β-aminoacid chemistry by describing the synthesis of β2- and β3-models (β-hHis). Structural modifications leading to cyclic imino derivatives such as spinacine, aza-histidine and analogues with shortening or elongation of the native side chain (nor-histidine and homo-histidine, respectively) are also described. Examples of the use of the described analogues to replace native histidine in bioactive peptides are also given. PMID:21686155

  14. Modeling active constrained-layer damping using Golla-Hughes-McTavish approach

    NASA Astrophysics Data System (ADS)

    Lam, Margaretha J.; Saunders, William R.; Inman, Daniel J.

    1995-05-01

    Viscoelastic material (VEM) adds damping to structures. In order to enhance the damping effects of the viscoelastic material, a constraining layer is attached. If this constraining layer is a piezoelectric patch, the system is said to have active constrained layer damping (ACLD). In this paper, the damping effects due to viscoelastic material which has an active constraining layer is modeled using the Golla-Hughes-McTavish (GHM) damping method. The piezoelectric patch and structure are modeled using a Galerkin approach in order to account for the effect of the constraining layer on the beam.

  15. Butterfly Encryption Scheme for Resource-Constrained Wireless Networks †

    PubMed Central

    Sampangi, Raghav V.; Sampalli, Srinivas

    2015-01-01

    Resource-constrained wireless networks are emerging networks such as Radio Frequency Identification (RFID) and Wireless Body Area Networks (WBAN) that might have restrictions on the available resources and the computations that can be performed. These emerging technologies are increasing in popularity, particularly in defence, anti-counterfeiting, logistics and medical applications, and in consumer applications with growing popularity of the Internet of Things. With communication over wireless channels, it is essential to focus attention on securing data. In this paper, we present an encryption scheme called Butterfly encryption scheme. We first discuss a seed update mechanism for pseudorandom number generators (PRNG), and employ this technique to generate keys and authentication parameters for resource-constrained wireless networks. Our scheme is lightweight, as in it requires less resource when implemented and offers high security through increased unpredictability, owing to continuously changing parameters. Our work focuses on accomplishing high security through simplicity and reuse. We evaluate our encryption scheme using simulation, key similarity assessment, key sequence randomness assessment, protocol analysis and security analysis. PMID:26389899

  16. Constraining the North Pacific carbon sink: biological and physical processes

    NASA Astrophysics Data System (ADS)

    Ayers, J.; Lozier, M.

    2010-12-01

    The transition zone region of the North Pacific is a notably large sink for atmospheric carbon dioxide on a mean annual basis, though seasonally the region varies between strong wintertime uptake and weak summertime outgassing. Because the direction of air-sea carbon flux is effectively set by the sea surface pCO2, we seek to identify and quantify those processes most responsible for its variability in this region. While changes in temperature, salinity, dissolved inorganic carbon, and alkalinity are all factors that impact sea surface pCO2 on a seasonal basis, on a mean annual basis the region must be maintained as a sink by processes that remove carbon from surface waters: biological drawdown as well as the result of advection/mixing. In this work we constrain the quantitative contribution of each of these processes throughout an annual cycle. The least constrained of these processes is the biological pump, which we estimate in two independent ways: bottom-up, using satellite data-based primary productivity models coupled with export estimates from literature; and top-down, by determining what the biological pump would need to be to maintain the observed sea surface pCO2 values in the region, given our estimates of all the other regulatory processes.

  17. Accurate de novo design of hyperstable constrained peptides

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Gaurav; Mulligan, Vikram Khipple; Bahl, Christopher D.; Gilmore, Jason M.; Harvey, Peta J.; Cheneval, Olivier; Buchko, Garry W.; Pulavarti, Surya V. S. R. K.; Kaas, Quentin; Eletsky, Alexander; Huang, Po-Ssu; Johnsen, William A.; Greisen, Per, Jr.; Rocklin, Gabriel J.; Song, Yifan; Linsky, Thomas W.; Watkins, Andrew; Rettie, Stephen A.; Xu, Xianzhong; Carter, Lauren P.; Bonneau, Richard; Olson, James M.; Coutsias, Evangelos; Correnti, Colin E.; Szyperski, Thomas; Craik, David J.; Baker, David

    2016-10-01

    Naturally occurring, pharmacologically active peptides constrained with covalent crosslinks generally have shapes that have evolved to fit precisely into binding pockets on their targets. Such peptides can have excellent pharmaceutical properties, combining the stability and tissue penetration of small-molecule drugs with the specificity of much larger protein therapeutics. The ability to design constrained peptides with precisely specified tertiary structures would enable the design of shape-complementary inhibitors of arbitrary targets. Here we describe the development of computational methods for accurate de novo design of conformationally restricted peptides, and the use of these methods to design 18-47 residue, disulfide-crosslinked peptides, a subset of which are heterochiral and/or N-C backbone-cyclized. Both genetically encodable and non-canonical peptides are exceptionally stable to thermal and chemical denaturation, and 12 experimentally determined X-ray and NMR structures are nearly identical to the computational design models. The computational design methods and stable scaffolds presented here provide the basis for development of a new generation of peptide-based drugs.

  18. Constraining Modern and Historic Mercury Emissions From Gold Mining

    NASA Astrophysics Data System (ADS)

    Strode, S. A.; Jaeglé, L.; Selin, N. E.; Sunderland, E.

    2007-12-01

    Mercury emissions from both historic gold and silver mining and modern small-scale gold mining are highly uncertain. Historic mercury emissions can affect the modern atmosphere through reemission from land and ocean, and quantifying mercury emissions from historic gold and silver mining can help constrain modern mining sources. While estimates of mercury emissions during historic gold rushes exceed modern anthropogenic mercury emissions in North America, sediment records in many regions do not show a strong gold rush signal. We use the GEOS-Chem chemical transport model to determine the spatial footprint of mercury emissions from mining and compare model runs from gold rush periods to sediment and ice core records of historic mercury deposition. Based on records of gold and silver production, we include mercury emissions from North and South American mining of 1900 Mg/year in 1880, compared to modern global anthropogenic emissions of 3400 Mg/year. Including this large mining source in GEOS-Chem leads to an overestimate of the modeled 1880 to preindustrial enhancement ratio compared to the sediment core record. We conduct sensitivity studies to constrain the level of mercury emissions from modern and historic mining that is consistent with the deposition records for different regions.

  19. Butterfly Encryption Scheme for Resource-Constrained Wireless Networks.

    PubMed

    Sampangi, Raghav V; Sampalli, Srinivas

    2015-09-15

    Resource-constrained wireless networks are emerging networks such as Radio Frequency Identification (RFID) and Wireless Body Area Networks (WBAN) that might have restrictions on the available resources and the computations that can be performed. These emerging technologies are increasing in popularity, particularly in defence, anti-counterfeiting, logistics and medical applications, and in consumer applications with growing popularity of the Internet of Things. With communication over wireless channels, it is essential to focus attention on securing data. In this paper, we present an encryption scheme called Butterfly encryption scheme. We first discuss a seed update mechanism for pseudorandom number generators (PRNG), and employ this technique to generate keys and authentication parameters for resource-constrained wireless networks. Our scheme is lightweight, as in it requires less resource when implemented and offers high security through increased unpredictability, owing to continuously changing parameters. Our work focuses on accomplishing high security through simplicity and reuse. We evaluate our encryption scheme using simulation, key similarity assessment, key sequence randomness assessment, protocol analysis and security analysis.

  20. Constraining the level density using fission of lead projectiles

    NASA Astrophysics Data System (ADS)

    Rodríguez-Sánchez, J. L.; Benlliure, J.; Álvarez-Pol, H.; Audouin, L.; Ayyad, Y.; Bélier, G.; Boutoux, G.; Casarejos, E.; Chatillon, A.; Cortina-Gil, D.; Gorbinet, T.; Heinz, A.; Kelić-Heil, A.; Laurent, B.; Martin, J.-F.; Paradela, C.; Pellereau, E.; Pietras, B.; Ramos, D.; Rodríguez-Tajes, C.; Rossi, D. M.; Simon, H.; Taïeb, J.; Vargas, J.; Voss, B.

    2015-10-01

    The nuclear level density is one of the main ingredients for the statistical description of the fission process. In this work, we propose to constrain the description of this parameter by using fission reactions induced by protons and light ions on 208Pb at high kinetic energies. The experiment was performed at GSI (Darmstadt), where the combined use of the inverse kinematics technique with an efficient detection setup allowed us to measure the atomic number of the two fission fragments in coincidence. This measurement permitted us to obtain with high precision the partial fission cross sections and the width of the charge distribution as a function of the atomic number of the fissioning system. These data and others previously measured, covering a large range in fissility, are compared to state-of-the-art calculations. The results reveal that total and partial fission cross sections cannot unambiguously constrain the level density at ground-state and saddle-point deformations and additional observables, such as the width of the charge distribution of the final fission fragments, are required.

  1. Maximum Constrained Directivity of Oversteered End-Fire Sensor Arrays.

    PubMed

    Trucco, Andrea; Traverso, Federico; Crocco, Marco

    2015-06-09

    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.

  2. Vibration control of cylindrical shells using active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Ray, Manas C.; Chen, Tung-Huei; Baz, Amr M.

    1997-05-01

    The fundamentals of controlling the structural vibration of cylindrical shells treated with active constrained layer damping (ACLD) treatments are presented. The effectiveness of the ACLD treatments in enhancing the damping characteristics of thin cylindrical shells is demonstrated theoretically and experimentally. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. The FEM is used to predict the natural frequencies and the modal loss factors of shells which are partially treated with patches of the ACLD treatments. The predictions of the FEM are validated experimentally using stainless steel cylinders which are 20.32 cm in diameter, 30.4 cm in length and 0.05 cm in thickness. The cylinders are treated with ACLD patches of different configurations in order to target single or multi-modes of lobar vibrations. The ACLD patches used are made of DYAD 606 visco-elastic layer which is sandwiched between two layers of PVDF piezo-electric films. Vibration attenuations of 85% are obtained with maximum control voltage of 40 volts. Such attenuations are attributed to the effectiveness of the ACLD treatment in increasing the modal damping ratios by about a factor of four over those of conventional passive constrained layer damping (PCLD) treatments. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  3. 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.

  4. A Collective Neurodynamic Approach to Constrained Global Optimization.

    PubMed

    Yan, Zheng; Fan, Jianchao; Wang, Jun

    2016-04-01

    Global optimization is a long-lasting research topic in the field of optimization, posting many challenging theoretic and computational issues. This paper presents a novel collective neurodynamic method for solving constrained global optimization problems. At first, a one-layer recurrent neural network (RNN) is presented for searching the Karush-Kuhn-Tucker points of the optimization problem under study. Next, a collective neuroydnamic optimization approach is developed by emulating the paradigm of brainstorming. Multiple RNNs are exploited cooperatively to search for the global optimal solutions in a framework of particle swarm optimization. Each RNN carries out a precise local search and converges to a candidate solution according to its own neurodynamics. The neuronal state of each neural network is repetitively reset by exchanging historical information of each individual network and the entire group. Wavelet mutation is performed to avoid prematurity, add diversity, and promote global convergence. It is proved in the framework of stochastic optimization that the proposed collective neurodynamic approach is capable of computing the global optimal solutions with probability one provided that a sufficiently large number of neural networks are utilized. The essence of the collective neurodynamic optimization approach lies in its potential to solve constrained global optimization problems in real time. The effectiveness and characteristics of the proposed approach are illustrated by using benchmark optimization problems.

  5. Accurate de novo design of hyperstable constrained peptides

    PubMed Central

    Bhardwaj, Gaurav; Mulligan, Vikram Khipple; Bahl, Christopher D.; Gilmore, Jason M.; Harvey, Peta J.; Cheneval, Olivier; Buchko, Garry W.; Pulavarti, Surya V.S.R.K.; Kaas, Quentin; Eletsky, Alexander; Huang, Po-Ssu; Johnsen, William A.; Greisen, Per; Rocklin, Gabriel J.; Song, Yifan; Linsky, Thomas W.; Watkins, Andrew; Rettie, Stephen A.; Xu, Xianzhong; Carter, Lauren P.; Bonneau, Richard; Olson, James M.; Coutsias, Evangelos; Correnti, Colin E.; Szyperski, Thomas; Craik, David J.; Baker, David

    2016-01-01

    Summary Naturally occurring, pharmacologically active peptides constrained with covalent crosslinks generally have shapes evolved to fit precisely into binding pockets on their targets. Such peptides can have excellent pharmaceutical properties, combining the stability and tissue penetration of small molecule drugs with the specificity of much larger protein therapeutics. The ability to design constrained peptides with precisely specified tertiary structures would enable the design of shape-complementary inhibitors of arbitrary targets. Here we describe the development of computational methods for de novo design of conformationally-restricted peptides, and the use of these methods to design 15–50 residue disulfide-crosslinked and heterochiral N-C backbone-cyclized peptides. These peptides are exceptionally stable to thermal and chemical denaturation, and twelve experimentally-determined X-ray and NMR structures are nearly identical to the computational models. The computational design methods and stable scaffolds presented here provide the basis for development of a new generation of peptide-based drugs. PMID:27626386

  6. Multiple Sclerosis Lesion Detection Using Constrained GMM and Curve Evolution

    PubMed Central

    Freifeld, Oren; Greenspan, Hayit; Goldberger, Jacob

    2009-01-01

    This paper focuses on the detection and segmentation of Multiple Sclerosis (MS) lesions in magnetic resonance (MRI) brain images. To capture the complex tissue spatial layout, a probabilistic model termed Constrained Gaussian Mixture Model (CGMM) is proposed based on a mixture of multiple spatially oriented Gaussians per tissue. The intensity of a tissue is considered a global parameter and is constrained, by a parameter-tying scheme, to be the same value for the entire set of Gaussians that are related to the same tissue. MS lesions are identified as outlier Gaussian components and are grouped to form a new class in addition to the healthy tissue classes. A probability-based curve evolution technique is used to refine the delineation of lesion boundaries. The proposed CGMM-CE algorithm is used to segment 3D MRI brain images with an arbitrary number of channels. The CGMM-CE algorithm is automated and does not require an atlas for initialization or parameter learning. Experimental results on both standard brain MRI simulation data and real data indicate that the proposed method outperforms previously suggested approaches, especially for highly noisy data. PMID:19756161

  7. Constrained Large Eddy Simulation of Separated Turbulent Flows

    NASA Astrophysics Data System (ADS)

    Xia, Zhenhua; Shi, Yipeng; Wang, Jianchun; Xiao, Zuoli; Yang, Yantao; Chen, Shiyi

    2011-11-01

    Constrained Large-eddy Simulation (CLES) has been recently proposed to simulate turbulent flows with massive separation. Different from traditional large eddy simulation (LES) and hybrid RANS/LES approaches, the CLES simulates the whole flow domain by large eddy simulation while enforcing a RANS Reynolds stress constraint on the subgrid-scale (SGS) stress models in the near-wall region. Algebraic eddy-viscosity models and one-equation Spalart-Allmaras (S-A) model have been used to constrain the Reynolds stress. The CLES approach is validated a posteriori through simulation of flow past a circular cylinder and periodic hill flow at high Reynolds numbers. The simulation results are compared with those from RANS, DES, DDES and other available hybrid RANS/LES methods. It is shown that the capability of the CLES method in predicting separated flows is comparable to that of DES. Detailed discussions are also presented about the effects of the RANS models as constraint in the near-wall layers. Our results demonstrate that the CLES method is a promising alternative towards engineering applications.

  8. Understanding the Toothbrush Merging Galaxy Cluster to Constrain Dark Matter

    NASA Astrophysics Data System (ADS)

    Dawson, William; Brüggen, M.; Van Weeren, R. J.; Wittman, D. M.

    2014-01-01

    Merging galaxy clusters have proven to be one of the most important probes of dark matter self-interaction properties. If their full dark matter constraining power is to be realized though, we must accurately quantify the properties of these dissociative mergers. Some properties such as mass and relative line of sight velocity can be directly measured and sufficiently constrained, but there remains considerable uncertainty on indirect properties of the mergers. Indirect properties such as the angle of the merger axis with the plane of the sky and collision velocity are crucial to translating the gravitational lensing measurements of the mass, X-ray measurements of the cluster gas and optical measurements of the galaxies into constraints on the dark matter properties. By utilizing multi-wavelength measurements (X-ray to radio), of the Toothbrush radio relic dissociative merger (1RXS J0603+4212) we show that we can improve the constraints on the indirect parameters of the merger by up to an order of magnitude vs. traditional approaches. By utilizing multi-wavelength measurements (X-ray to radio), of the Toothbrush radio relic dissociative merger we show that we can improve the constraints on the indirect parameters of the merger by up to an order of magnitude vs. traditional approaches.

  9. Constraining extra neutral gauge bosons with atomic parity violation measurements

    NASA Astrophysics Data System (ADS)

    Diener, Ross; Godfrey, Stephen; Turan, Ismail

    2012-12-01

    The discovery of a new neutral gauge boson Z' could provide the first concrete evidence of physics beyond the standard model. We explore how future parity violation experiments, especially atomic parity violation experiments, can be used to constrain Z' bosons. We use the recent measurement of the Cs133 nuclear weak charge to estimate lower bounds on the mass of Z' bosons for a number of representative models and to put constraints on the couplings of a newly discovered Z' boson. We also consider how these constraints might be improved by future atomic parity violation experiments that will measure nuclear weak charges of multiple isotopes. We show how measurements of a single isotope and combining measurements into ratios and differences can be used to constrain the couplings of a Z' and discriminate between models. We include in our results the constraints that can be obtained from the experiments Qweak and P2 that measure the proton weak charge. We find that current and future parity violation experiments could potentially play an important role in unravelling new physics if a Z' were discovered.

  10. Constrained low-rank gamut completion for robust illumination estimation

    NASA Astrophysics Data System (ADS)

    Zhou, Jianshen; Yuan, Jiazheng; Liu, Hongzhe

    2017-02-01

    Illumination estimation is an important component of color constancy and automatic white balancing. According to recent survey and evaluation work, the supervised methods with a learning phase are competitive for illumination estimation. However, the robustness and performance of any supervised algorithm suffer from an incomplete gamut in training image sets because of limited reflectance surfaces in a scene. In order to address this problem, we present a constrained low-rank gamut completion algorithm, which can replenish gamut from limited surfaces in an image, for robust illumination estimation. In the proposed algorithm, we first discuss why the gamut completion is actually a low-rank matrix completion problem. Then a constrained low-rank matrix completion framework is proposed by adding illumination similarities among the training images as an additional constraint. An optimization algorithm is also given out by extending the augmented Lagrange multipliers. Finally, the completed gamut based on the proposed algorithm is fed into the support vector regression (SVR)-based illumination estimation method to evaluate the effect of gamut completion. The experimental results on both synthetic and real-world image sets show that the proposed gamut completion model not only can effectively improve the performance of the original SVR method but is also robust to the surface insufficiency in training samples.

  11. Hummingbird: Ultra-Lightweight Cryptography for Resource-Constrained Devices

    NASA Astrophysics Data System (ADS)

    Engels, Daniel; Fan, Xinxin; Gong, Guang; Hu, Honggang; Smith, Eric M.

    Due to the tight cost and constrained resources of high-volume consumer devices such as RFID tags, smart cards and wireless sensor nodes, it is desirable to employ lightweight and specialized cryptographic primitives for many security applications. Motivated by the design of the well-known Enigma machine, we present a novel ultra-lightweight cryptographic algorithm, referred to as Hummingbird, for resource-constrained devices in this paper. Hummingbird can provide the designed security with small block size and is resistant to the most common attacks such as linear and differential cryptanalysis. Furthermore, we also present efficient software implementation of Hummingbird on the 8-bit microcontroller ATmega128L from Atmel and the 16-bit microcontroller MSP430 from Texas Instruments, respectively. Our experimental results show that after a system initialization phase Hummingbird can achieve up to 147 and 4.7 times faster throughput for a size-optimized and a speed-optimized implementations, respectively, when compared to the state-of-the-art ultra-lightweight block cipher PRESENT[10] on the similar platforms.

  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).

  13. Longitudinal wave motion in width-constrained auxetic plates

    NASA Astrophysics Data System (ADS)

    Lim, Teik-Cheng

    2016-05-01

    This paper investigates the longitudinal wave velocity in auxetic plates in comparison to conventional ones, in which the plate is constrained from motion in the width direction. By taking into account the thickness change of the plate and its corresponding change in density, the developed wave velocity is casted not only as a function of Young’s modulus and density, but also in terms of Poisson’s ratio and longitudinal strain. Results show that density and thickness variations compensate for one another when the Poisson’s ratio is positive, but add up when the Poisson’s ratio is negative. Results also reveal that the classical model of longitudinal wave velocity for the plate is accurate when the Poisson’s ratio is about 1/3; at this Poisson’s ratio the influence from density and thickness variations cancel each other. Comparison between the current corrected model and the density-corrected Rayleigh-Lamb model reveals a number of consistent trends, while the discrepancies are elucidated. If the plate material possesses a negative Poisson’s ratio, the deviation of the actual wave velocity from the classical model becomes significant; auxeticity suppresses and enhances the wave velocity in compressive and tensile impacts, respectively. Hence the use of the corrected model is proposed when predicting longitudinal waves in width-constrained auxetic plates, and auxetic materials can be harnessed for effectively controlling wave velocities in thin-walled structures.

  14. Security-constrained unit commitment with flexible operating modes

    NASA Astrophysics Data System (ADS)

    Lu, Bo

    The electricity industry throughout the world, which has long been dominated by vertically integrated utilities, is facing enormous challenges. To enhance the competition in electricity industry, vertically integrated utilities are evolving into a distributed and competitive industry in which market forces drive the price of electricity and possibly reduce the net cost of supplying electrical loads through increased competition. To excel in the competition, generation companies (GENCOs) will acquire additional generating units with flexible operating capability which allows a timely response to the continuous changes in power system conditions. This dissertation considers the short-term scheduling of generating units with flexible modes of operation in security-constrained unit commitment (SCUC). Among the units considered in this study are combined cycle units, fuel switching/blending units, photovoltaic/battery system, pumped-storage units, and cascaded hydro units. The proposed security-constrained unit commitment solution will include a detailed model of transmission system which could impact the short-term scheduling of units with flexible operation modes.

  15. Constraining dark sector perturbations I: cosmic shear and CMB lensing

    SciTech Connect

    Battye, Richard A.; Moss, Adam; Pearson, Jonathan A. E-mail: adam.moss@nottingham.ac.uk

    2015-04-01

    We present current and future constraints on equations of state for dark sector perturbations. The equations of state considered are those corresponding to a generalized scalar field model and time-diffeomorphism invariant L(g) theories that are equivalent to models of a relativistic elastic medium and also Lorentz violating massive gravity. We develop a theoretical understanding of the observable impact of these models. In order to constrain these models we use CMB temperature data from Planck, BAO measurements, CMB lensing data from Planck and the South Pole Telescope, and weak galaxy lensing data from CFHTLenS. We find non-trivial exclusions on the range of parameters, although the data remains compatible with w=−1. We gauge how future experiments will help to constrain the parameters. This is done via a likelihood analysis for CMB experiments such as CoRE and PRISM, and tomographic galaxy weak lensing surveys, focussing in on the potential discriminatory power of Euclid on mildly non-linear scales.

  16. Thermodynamic-kinetic simulation of constrained dendrite growth in steels

    SciTech Connect

    Miettinen, J.

    2000-04-01

    A model of constrained dendritic growth for steels, based on thermodynamic and kinetic theory, is presented. The model links thermodynamic chemical potential-equality equations to an existing, approximate treatment of constrained dendritic growth in multicomponent steels, taking into account the deviation from the local thermodynamic equilibrium of the phase interface caused by interface friction, capillarity, and solute trapping. Due to the thermodynamic approach, with a thermodynamic model and recently assessed data, the present treatment yields a more accurate determination of phase stabilities than the earlier methods. Depending on the steel composition and the growth conditions (growth rate and temperature gradient), the model determines the dendrite tip undercooling, the primary solid phase (ferrite or austenite), the stability of that phase, certain dimensions of the microstructure, and the solute accumulation ahead of the dendrite tip. A special optional calculations is that of the equally probable formation of ferrite and austenite in stainless steels. Calculations for testing the model and for validation it with experimental data are presented.

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

    NASA Astrophysics Data System (ADS)

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

    2006-08-01

    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 pendulums and assuming the impossibility of perpetual motion Huygens obtained a law of conservation of vis viva at specific positions, beautifully commented by Mach. Daniel Bernoulli generalised Huygens results introducing the concept of potential and the related independence of the ‘work’ done from the trajectories (paths) followed: vis viva conservation at specific positions is now linked with the potential. Feynman’s modern way of teaching the subject shows striking similarities with Bernoulli’s approach. A number of animations and simulations can help to visualise and teach some of the pendulum’s interpretations related to what we now see as instances of energy conservation.

  18. Accurate de novo design of hyperstable constrained peptides.

    PubMed

    Bhardwaj, Gaurav; Mulligan, Vikram Khipple; Bahl, Christopher D; Gilmore, Jason M; Harvey, Peta J; Cheneval, Olivier; Buchko, Garry W; Pulavarti, Surya V S R K; Kaas, Quentin; Eletsky, Alexander; Huang, Po-Ssu; Johnsen, William A; Greisen, Per Jr; Rocklin, Gabriel J; Song, Yifan; Linsky, Thomas W; Watkins, Andrew; Rettie, Stephen A; Xu, Xianzhong; Carter, Lauren P; Bonneau, Richard; Olson, James M; Coutsias, Evangelos; Correnti, Colin E; Szyperski, Thomas; Craik, David J; Baker, David

    2016-10-20

    Naturally occurring, pharmacologically active peptides constrained with covalent crosslinks generally have shapes that have evolved to fit precisely into binding pockets on their targets. Such peptides can have excellent pharmaceutical properties, combining the stability and tissue penetration of small-molecule drugs with the specificity of much larger protein therapeutics. The ability to design constrained peptides with precisely specified tertiary structures would enable the design of shape-complementary inhibitors of arbitrary targets. Here we describe the development of computational methods for accurate de novo design of conformationally restricted peptides, and the use of these methods to design 18-47 residue, disulfide-crosslinked peptides, a subset of which are heterochiral and/or N-C backbone-cyclized. Both genetically encodable and non-canonical peptides are exceptionally stable to thermal and chemical denaturation, and 12 experimentally determined X-ray and NMR structures are nearly identical to the computational design models. The computational design methods and stable scaffolds presented here provide the basis for development of a new generation of peptide-based drugs.

  19. Constraining the Symmetry Energy Using Radioactive Ion Beams

    NASA Astrophysics Data System (ADS)

    Stiefel, Krystin; Kohley, Zachary; Morrissey, Dave; Thoennessen, Michael; MoNA Collaboration

    2016-09-01

    Calculations from the constrained molecular dynamics (CoMD) model have shown that the N/Z ratio of the residue fragments and neutron emissions from projectile fragmentation reactions is sensitive to the form of the symmetry energy, a term in the nuclear equation of state. In order to constrain the symmetry energy using the N/Z ratio observable, an experiment was performed using the MoNA-LISA and Sweeper magnet arrangement at the NSCL. Beams of 30S and 40S impinged on 9Be targets and the heavy residue fragments were measured in coincidence with fast neutrons. Comparison of the new experimental data with theoretical models should provide a constraint on the form of the symmetry energy. Some of the data from this experiment will be presented and discussed. This work is partially supported by the National Science Foundation under Grant No. PHY-1102511 and the Department of Energy National Nuclear Security Administration under Award No. DE-NA0000979.

  20. 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%.

  1. Targeting kinase signaling pathways with constrained peptide scaffolds.

    PubMed

    Hanold, Laura E; Fulton, Melody D; Kennedy, Eileen J

    2017-02-07

    Kinases are amongst the largest families in the human proteome and serve as critical mediators of a myriad of cell signaling pathways. Since altered kinase activity is implicated in a variety of pathological diseases, kinases have become a prominent class of proteins for targeted inhibition. Although numerous small molecule and antibody-based inhibitors have already received clinical approval, several challenges may still exist with these strategies including resistance, target selection, inhibitor potency and in vivo activity profiles. Constrained peptide inhibitors have emerged as an alternative strategy for kinase inhibition. Distinct from small molecule inhibitors, peptides can provide a large binding surface area that allows them to bind shallow protein surfaces rather than defined pockets within the target protein structure. By including chemical constraints within the peptide sequence, additional benefits can be bestowed onto the peptide scaffold such as improved target affinity and target selectivity, cell permeability and proteolytic resistance. In this review, we highlight examples of diverse chemistries that are being employed to constrain kinase-targeting peptide scaffolds and highlight their application to modulate kinase signaling as well as their potential clinical implications.

  2. Adaptive windowed range-constrained Otsu method using local information

    NASA Astrophysics Data System (ADS)

    Zheng, Jia; Zhang, Dinghua; Huang, Kuidong; Sun, Yuanxi; Tang, Shaojie

    2016-01-01

    An adaptive windowed range-constrained Otsu method using local information is proposed for improving the performance of image segmentation. First, the reason why traditional thresholding methods do not perform well in the segmentation of complicated images is analyzed. Therein, the influences of global and local thresholdings on the image segmentation are compared. Second, two methods that can adaptively change the size of the local window according to local information are proposed by us. The characteristics of the proposed methods are analyzed. Thereby, the information on the number of edge pixels in the local window of the binarized variance image is employed to adaptively change the local window size. Finally, the superiority of the proposed method over other methods such as the range-constrained Otsu, the active contour model, the double Otsu, the Bradley's, and the distance-regularized level set evolution is demonstrated. It is validated by the experiments that the proposed method can keep more details and acquire much more satisfying area overlap measure as compared with the other conventional methods.

  3. X-ray Constrained Extremely Localized Molecular Orbitals: Theory and Critical Assessment of the New Technique.

    PubMed

    Genoni, Alessandro

    2013-07-09

    Following the X-ray constrained wave function approach proposed by Jayatilaka, we have devised a new technique that allows to extract molecular orbitals strictly localized on small molecular fragments from sets of experimental X-ray structure factors amplitudes. Since the novel strategy enables to obtain electron distributions that have quantum mechanical features and that can be easily interpreted in terms of traditional chemical concepts, the method can be also considered as a new useful tool for the determination and the analysis of charge densities from high-resolution X-ray experiments. In this paper, we describe in detail the theory of the new technique, which, in comparison to our preliminary work, has been improved both treating the effects of isotropic secondary extinctions and introducing a new protocol to halt the fitting procedure against the experimental X-ray scattering data. The performances of the novel strategy have been studied both in function of the basis-sets flexibility and in function of the quality of the considered crystallographic data. The tests performed on four different systems (α-glycine, l-cysteine, (aminomethyl)phosphonic acid and N-(trifluoromethyl)formamide) have shown that the achievement of good statistical agreements with the experimental measures mainly depends on the quality of the crystal structures (i.e., geometry positions and thermal parameters) used in the X-ray constrained calculations. Finally, given the reliable transferability of the obtained Extremely Localized Molecular Orbitals (ELMOs), we envisage to exploit the novel approach to construct new ELMOs databases suited to the development of linear-scaling methods for the refinement of macromolecular crystal structures.

  4. Simultaneous inhibition of key growth pathways in melanoma cells and tumor regression by a designed bidentate constrained helical peptide.

    PubMed

    Dhar, Amlanjyoti; Mallick, Shampa; Ghosh, Piya; Maiti, Atanu; Ahmed, Israr; Bhattacharya, Seemana; Mandal, Tapashi; Manna, Asit; Roy, Koushik; Singh, Sandeep; Nayak, Dipak Kumar; Wilder, Paul T; Markowitz, Joseph; Weber, David; Ghosh, Mrinal K; Chattopadhyay, Samit; Guha, Rajdeep; Konar, Aditya; Bandyopadhyay, Santu; Roy, Siddhartha

    2014-07-01

    Protein-protein interactions are part of a large number of signaling networks and potential targets for drug development. However, discovering molecules that can specifically inhibit such interactions is a major challenge. S100B, a calcium-regulated protein, plays a crucial role in the proliferation of melanoma cells through protein-protein interactions. In this article, we report the design and development of a bidentate conformationally constrained peptide against dimeric S100B based on a natural tight-binding peptide, TRTK-12. The helical conformation of the peptide was constrained by the substitution of α-amino isobutyric acid--an amino acid having high helical propensity--in positions which do not interact with S100B. A branched bidentate version of the peptide was bound to S100B tightly with a dissociation constant of 8 nM. When conjugated to a cell-penetrating peptide, it caused growth inhibition and rapid apoptosis in melanoma cells. The molecule exerts antiproliferative action through simultaneous inhibition of key growth pathways, including reactivation of wild-type p53 and inhibition of Akt and STAT3 phosphorylation. The apoptosis induced by the bidentate constrained helix is caused by direct migration of p53 to mitochondria. At moderate intravenous dose, the peptide completely inhibits melanoma growth in a mouse model without any significant observable toxicity. The specificity was shown by lack of ability of a double mutant peptide to cause tumor regression at the same dose level. The methodology described here for direct protein-protein interaction inhibition may be effective for rapid development of inhibitors against relatively weak protein-protein interactions for de novo drug development.

  5. Coexpression of striatal dopamine receptor subtypes and excitatory amino acid subunits.

    PubMed

    Ariano, M A; Larson, E R; Noblett, K L; Sibley, D R; Levine, M S

    1997-08-01

    The striatal cellular coexpression patterns for the D(1A) and D2 dopamine (DA) receptor subtypes and the ionotropic excitatory amino acid (EAA) subunits of the N-methyl-D-aspartate (NMDA-R1) and the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) (GluR1 and GluR2/3) receptor subunits were examined morphologically. Their coincidence was assessed by visualization of mRNA transcripts, localization of encoded receptor proteins, and binding analysis using concurrently paired methods of fluorescence detection. The findings indicated that 1) mRNA transcripts for both receptor systems were detected in the medium-sized neuron population, and the distribution of receptor message closely reflected protein and binding patterns, with the exception of the GluR1 subunit; 2) both DA receptor mRNA transcripts were coexpressed with each ionotropic EAA receptor subunit examined and with each other, and NMDA and AMPA receptor subunits also showed coincident expression; 3) D(1A) DA receptor protein was detected in neurons which coexpressed EAA subunit proteins; and 4) GluR2/3 and NMDA-R1 subunit proteins were coexpressed in medium-sized neurons which also demonstrated D2 DA receptor binding sites. These findings suggest morphological receptor "promiscuity" since the coexpression patterns between DA and EAA receptors were found in all permutations. The results provide a spatial framework for physiological findings describing functional interactions between the two DA receptor types and between specific DA and EAA receptors in the striatum.

  6. On size-constrained minimum s–t cut problems and size-constrained dense subgraph problems

    SciTech Connect

    Chen, Wenbin; Samatova, Nagiza F.; Stallmann, Matthias F.; Hendrix, William; Ying, Weiqin

    2015-10-30

    In some application cases, the solutions of combinatorial optimization problems on graphs should satisfy an additional vertex size constraint. In this paper, we consider size-constrained minimum s–t cut problems and size-constrained dense subgraph problems. We introduce the minimum s–t cut with at-least-k vertices problem, the minimum s–t cut with at-most-k vertices problem, and the minimum s–t cut with exactly k vertices problem. We prove that they are NP-complete. Thus, they are not polynomially solvable unless P = NP. On the other hand, we also study the densest at-least-k-subgraph problem (DalkS) and the densest at-most-k-subgraph problem (DamkS) introduced by Andersen and Chellapilla [1]. We present a polynomial time algorithm for DalkS when k is bounded by some constant c. We also present two approximation algorithms for DamkS. In conclusion, the first approximation algorithm for DamkS has an approximation ratio of n-1/k-1, where n is the number of vertices in the input graph. The second approximation algorithm for DamkS has an approximation ratio of O (nδ), for some δ < 1/3.

  7. On size-constrained minimum s–t cut problems and size-constrained dense subgraph problems

    DOE PAGES

    Chen, Wenbin; Samatova, Nagiza F.; Stallmann, Matthias F.; ...

    2015-10-30

    In some application cases, the solutions of combinatorial optimization problems on graphs should satisfy an additional vertex size constraint. In this paper, we consider size-constrained minimum s–t cut problems and size-constrained dense subgraph problems. We introduce the minimum s–t cut with at-least-k vertices problem, the minimum s–t cut with at-most-k vertices problem, and the minimum s–t cut with exactly k vertices problem. We prove that they are NP-complete. Thus, they are not polynomially solvable unless P = NP. On the other hand, we also study the densest at-least-k-subgraph problem (DalkS) and the densest at-most-k-subgraph problem (DamkS) introduced by Andersen andmore » Chellapilla [1]. We present a polynomial time algorithm for DalkS when k is bounded by some constant c. We also present two approximation algorithms for DamkS. In conclusion, the first approximation algorithm for DamkS has an approximation ratio of n-1/k-1, where n is the number of vertices in the input graph. The second approximation algorithm for DamkS has an approximation ratio of O (nδ), for some δ < 1/3.« less

  8. Constraining the Ensemble Kalman Filter for improved streamflow forecasting

    NASA Astrophysics Data System (ADS)

    Maxwell, Deborah; Jackson, Bethanna; McGregor, James

    2016-04-01

    Data assimilation techniques such as the Kalman Filter and its variants are often applied to hydrological models with minimal state volume/capacity constraints. Flux constraints are rarely, if ever, applied. Consequently, model states can be adjusted beyond physically reasonable limits, compromising the integrity of model output. In this presentation, we investigate the effect of constraining the Ensemble Kalman Filter (EnKF) on forecast performance. An EnKF implementation with no constraints is compared to model output with no assimilation, followed by a 'typical' hydrological implementation (in which mass constraints are enforced to ensure non-negativity and capacity thresholds of model states are not exceeded), and then a more tightly constrained implementation where flux as well as mass constraints are imposed to limit the rate of water movement within a state. A three year period (2008-2010) with no significant data gaps and representative of the range of flows observed over the fuller 1976-2010 record was selected for analysis. Over this period, the standard implementation of the EnKF (no constraints) contained eight hydrological events where (multiple) physically inconsistent state adjustments were made. All were selected for analysis. Overall, neither the unconstrained nor the "typically" mass-constrained forecasts were significantly better than the non-filtered forecasts; in fact several were significantly degraded. Flux constraints (in conjunction with mass constraints) significantly improved the forecast performance of six events relative to all other implementations, while the remaining two events showed no significant difference in performance. We conclude that placing flux as well as mass constraints on the data assimilation framework encourages physically consistent state updating and results in more accurate and reliable forward predictions of streamflow for robust decision-making. We also experiment with the observation error, and find that this

  9. Constraining the volatile fraction of planets from transit observations

    NASA Astrophysics Data System (ADS)

    Alibert, Y.

    2016-06-01

    Context. The determination of the abundance of volatiles in extrasolar planets is very important as it can provide constraints on transport in protoplanetary disks and on the formation location of planets. However, constraining the internal structure of low-mass planets from transit measurements is known to be a degenerate problem. Aims: Using planetary structure and evolution models, we show how observations of transiting planets can be used to constrain their internal composition, in particular the amount of volatiles in the planetary interior, and consequently the amount of gas (defined in this paper to be only H and He) that the planet harbors. We first explore planets that are located close enough to their star to have lost their gas envelope. We then concentrate on planets at larger distances and show that the observation of transiting planets at different evolutionary ages can provide statistical information on their internal composition, in particular on their volatile fraction. Methods: We computed the evolution of low-mass planets (super-Earths to Neptune-like) for different fractions of volatiles and gas. We used a four-layer model (core, silicate mantle, icy mantle, and gas envelope) and computed the internal structure of planets for different luminosities. With this internal structure model, we computed the internal and gravitational energy of planets, which was then used to derive the time evolution of the planet. Since the total energy of a planet depends on its heat capacity and density distribution and therefore on its composition, planets with different ice fractions have different evolution tracks. Results: We show for low-mass gas-poor planets that are located close to their central star that assuming evaporation has efficiently removed the entire gas envelope, it is possible to constrain the volatile fraction of close-in transiting planets. We illustrate this method on the example of 55 Cnc e and show that under the assumption of the absence of

  10. Constraining Upper Mantle Azimuthal Anisotropy With Free Oscillation Data (Invited)

    NASA Astrophysics Data System (ADS)

    Beghein, C.; Resovsky, J. S.; van der Hilst, R. D.

    2009-12-01

    We investigate the potential of Earth's free oscillations coupled modes as a tool to constrain large-scale seismic anisotropy in the transition zone and in the bulk of the lower mantle. While the presence of seismic anisotropy is widely documented in the uppermost and the lowermost mantle, its observation at intermediate depths remains a formidable challenge. We show that several coupled modes of oscillations are sensitive to radial and azimuthal anisotropy throughout the mantle. In particular, modes of the type 0Sl-0T(l+1) have high sensitivity to shear-wave radial anisotropy and to six elastic parameters describing azimuthal anisotropy in the 200 km-1000 km depth range. The use of such data enables us thus to extend the sensitivity of traditionally used fundamental mode surface waves to depths corresponding to the transition zone and the top of the lower mantle. In addition, these modes have the potential to provide new and unique constraints on several elastic parameters to which surface waves are not sensitive. We attempted to fit degree two splitting measurements of 0Sl-0T(l+1) coupled modes using previously published isotropic and transversely isotropic mantle models, but we could not explain the entire signal. We then explored the model space with a forward modeling approach and determined that, after correction for the effect of the crust and mantle radial anisotropy, the remaining signal can be explained by the presence of azimuthal anisotropy in the upper mantle. When we allow the azimuthal anisotropy to go below 400 km depth, the data fit is slightly better and the model space search leads to better-resolved model than when we force the anisotropy to lie in the top 400 km of the mantle. Its depth extent and distribution are, however, still not well constrained by the data due to parameter tradeoffs and a limited coupled mode data set. It is thus clear that mode coupling measurements have the potential to constrain upper-mantle azimuthal anisotropy

  11. 4-Amino-2,6-dichlorophenol nephrotoxicity in the Fischer 344 rat: protection by ascorbic acid, AT-125, and aminooxyacetic acid.

    PubMed

    Hong, S K; Anestis, D K; Ball, J G; Valentovic, M A; Brown, P I; Rankin, G O

    1997-11-01

    A halogenated derivative of 4-aminophenol, 4-amino-2, 6-dichlorophenol (ADCP), is a potent nephrotoxicant and a weak hepatotoxicant in Fischer 344 rats. Although the mechanism of ADCP nephrotoxicity is unknown, ADCP could undergo oxidation to a reactive intermediate, such as a 4-amino-2,6-dichlorophenoxy radical or 2,6-dichloro-1,4-benzoquinoneimine, which can generate additional free radicals and/or covalently bind to cellular proteins. The toxic process might also be mediated by glutathione (GSH) conjugates of ADCP, as suggested for the mechanism of 4-aminophenol nephrotoxicity. In this study, the effects of modulators of oxidation and GSH conjugation-related metabolism or transport on ADCP-induced nephrotoxicity were examined. In one set of experiments, male Fischer 344 rats (four/group) were intraperitoneally (ip) administered ADCP (0.38 mmol/kg) only or coadministered an antioxidant, ascorbic acid (1.14 mmol/kg, ip) with ADCP. Administration of ascorbic acid markedly reduced both functional nephrotoxicity and morphological changes induced by ADCP. Administration of a gamma-glutamyltransferase (GGT) inhibitor, l-(alphaS, 5S)-alpha-amino-3-chloro-4,5-dihydroxy-5-isoxazoleacetic acid (10 mg/kg, ip), or a cysteine conjugate beta-lyase inhibitor, aminooxyacetic acid (0.5 mmol/kg, ip), 1 hr before ADCP (0.38 mmol/kg) challenge partially protected rats against ADCP nephrotoxicity. In contrast, administration of an organic anion transport inhibitor, probenecid (140 mg/kg, ip), 30 min before ADCP had little effect on ADCP nephrotoxicity. The GSH depletor, buthionine sulfoximine (890 mg/kg, ip), was given 2 hr prior to ADCP and only minimal protection was noted. In addition, the nonprotein sulfhydryl (NPSH) contents in renal cortex and liver were determined at 2 hr following the administration of ADCP only or ascorbic acid/ADCP. Ascorbic acid afforded complete prevention of the depletion of NPSH in the kidney and liver caused by ADCP administration and also prevented

  12. Failure of the constrained equilibrium hypothesis in nucleation

    NASA Astrophysics Data System (ADS)

    Bartell, Lawrence S.

    2009-11-01

    The purpose of this investigation is to find whether solutions of the Becker-Döring-Tunitskii coupled differential equations can yield results closely paralleling those found in molecular dynamics (MD) simulations of freezing. What is investigated, in particular, is the validity of the constrained equilibrium hypothesis (CEH). It is shown that the MD results cannot be reproduced unless the CEH is violated. A physically plausible reason for the violation is proposed. In addition, methods for determining the size of critical nuclei are examined. It is found that a new criterion for identifying that size, a criterion incorporating the CEH, can be significantly in error. Methods for avoiding the use of the CEH are briefly discussed.

  13. Lifetime of the solar nebula constrained by meteorite paleomagnetism

    NASA Astrophysics Data System (ADS)

    Wang, Huapei; Weiss, Benjamin P.; Bai, Xue-Ning; Downey, Brynna G.; Wang, Jun; Wang, Jiajun; Suavet, Clément; Fu, Roger R.; Zucolotto, Maria E.

    2017-02-01

    A key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the lifetime of the nebular magnetic field and nebula are poorly constrained. We present paleomagnetic analyses of volcanic angrites demonstrating that they formed in a near-zero magnetic field (<0.6 microtesla) at 4563.5 ± 0.1 million years ago, ~3.8 million years after solar system formation. This indicates that the solar nebula field, and likely the nebular gas, had dispersed by this time. This sets the time scale for formation of the gas giants and planet migration. Furthermore, it supports formation of chondrules after 4563.5 million years ago by non-nebular processes like planetesimal collisions. The core dynamo on the angrite parent body did not initiate until about 4 to 11 million years after solar system formation.

  14. Formation of current singularity in a topologically constrained plasma.

    PubMed

    Zhou, Yao; Huang, Yi-Min; Qin, Hong; Bhattacharjee, A

    2016-02-01

    Recently a variational integrator for ideal magnetohydrodynamics in Lagrangian labeling has been developed. Its built-in frozen-in equation makes it optimal for studying current sheet formation. We use this scheme to study the Hahm-Kulsrud-Taylor problem, which considers the response of a 2D plasma magnetized by a sheared field under sinusoidal boundary forcing. We obtain an equilibrium solution that preserves the magnetic topology of the initial field exactly, with a fluid mapping that is non-differentiable. Unlike previous studies that examine the current density output, we identify a singular current sheet from the fluid mapping. These results are benchmarked with a constrained Grad-Shafranov solver. The same signature of current singularity can be found in other cases with more complex magnetic topologies.

  15. An approach to constrained aerodynamic design with application to airfoils

    NASA Technical Reports Server (NTRS)

    Campbell, Richard L.

    1992-01-01

    An approach was developed for incorporating flow and geometric constraints into the Direct Iterative Surface Curvature (DISC) design method. In this approach, an initial target pressure distribution is developed using a set of control points. The chordwise locations and pressure levels of these points are initially estimated either from empirical relationships and observed characteristics of pressure distributions for a given class of airfoils or by fitting the points to an existing pressure distribution. These values are then automatically adjusted during the design process to satisfy the flow and geometric constraints. The flow constraints currently available are lift, wave drag, pitching moment, pressure gradient, and local pressure levels. The geometric constraint options include maximum thickness, local thickness, leading-edge radius, and a 'glove' constraint involving inner and outer bounding surfaces. This design method was also extended to include the successive constraint release (SCR) approach to constrained minimization.

  16. Nonlinear hyperspectral unmixing based on constrained multiple kernel NMF

    NASA Astrophysics Data System (ADS)

    Cui, Jiantao; Li, Xiaorun; Zhao, Liaoying

    2014-05-01

    Nonlinear spectral unmixing constitutes an important field of research for hyperspectral imagery. An unsupervised nonlinear spectral unmixing algorithm, namely multiple kernel constrained nonnegative matrix factorization (MKCNMF) is proposed by coupling multiple-kernel selection with kernel NMF. Additionally, a minimum endmemberwise distance constraint and an abundance smoothness constraint are introduced to alleviate the uniqueness problem of NMF in the algorithm. In the MKCNMF, two problems of optimizing matrices and selecting the proper kernel are jointly solved. The performance of the proposed unmixing algorithm is evaluated via experiments based on synthetic and real hyperspectral data sets. The experimental results demonstrate that the proposed method outperforms some existing unmixing algorithms in terms of spectral angle distance (SAD) and abundance fractions.

  17. Longitudinal force distribution using quadratically constrained linear programming

    NASA Astrophysics Data System (ADS)

    Klomp, M.

    2011-12-01

    In this paper, a new method is presented for the optimisation of force distribution for combined traction/braking and cornering. In order to provide a general, simple and flexible problem formulation, the optimisation is addressed as a quadratically constrained linear programming (QCLP) problem. Apart from fast numerical solutions, different driveline configurations can be included in the QCLP problem in a very straightforward fashion. The optimisation of the distribution of the individual wheel forces using the quasi-steady-state assumption is known to be useful for the study of the influence of particular driveline configurations on the combined lateral and longitudinal grip envelope of a particular vehicle-driveline configuration. The addition of the QCLP problem formulation makes another powerful tool available to the vehicle dynamics analyst to perform such studies.

  18. Membrane-constrained acoustic metamaterials for low frequency sound insulation

    NASA Astrophysics Data System (ADS)

    Wang, Xiaole; Zhao, Hui; Luo, Xudong; Huang, Zhenyu

    2016-01-01

    We present a constrained membrane-type acoustic metamaterial (CMAM) that employs constraint sticks to add out-of-plane dimensions in the design space of MAM. A CMAM sample, which adopts constraint sticks to suppress vibrations at the membrane center, was fabricated to achieve a sound transmission loss (STL) peak of 26 dB at 140 Hz, with the static areal density of 6.0 kg/m2. The working mechanism of the CMAM as an acoustic metamaterial is elucidated by calculating the averaged normal displacement, the equivalent areal density, and the effective dynamic mass of a unit cell through finite element simulations. Furthermore, the vibration modes of the CMAM indicate that the eigenmodes related to STL dips are shifted into high frequencies, thus broadening its effective bandwidth significantly. Three samples possessing the same geometry and material but different constraint areas were fabricated to illustrate the tunability of STL peaks at low frequencies.

  19. Total energy control system autopilot design with constrained parameter optimization

    NASA Technical Reports Server (NTRS)

    Ly, Uy-Loi; Voth, Christopher

    1990-01-01

    A description is given of the application of a multivariable control design method (SANDY) based on constrained parameter optimization to the design of a multiloop aircraft flight control system. Specifically, the design method is applied to the direct synthesis of a multiloop AFCS inner-loop feedback control system based on total energy control system (TECS) principles. The design procedure offers a structured approach for the determination of a set of stabilizing controller design gains that meet design specifications in closed-loop stability, command tracking performance, disturbance rejection, and limits on control activities. The approach can be extended to a broader class of multiloop flight control systems. Direct tradeoffs between many real design goals are rendered systematic by proper formulation of the design objectives and constraints. Satisfactory designs are usually obtained in few iterations. Performance characteristics of the optimized TECS design have been improved, particularly in the areas of closed-loop damping and control activity in the presence of turbulence.

  20. Computational strategies in the dynamic simulation of constrained flexible MBS

    NASA Technical Reports Server (NTRS)

    Amirouche, F. M. L.; Xie, M.

    1993-01-01

    This research focuses on the computational dynamics of flexible constrained multibody systems. At first a recursive mapping formulation of the kinematical expressions in a minimum dimension as well as the matrix representation of the equations of motion are presented. The method employs Kane's equation, FEM, and concepts of continuum mechanics. The generalized active forces are extended to include the effects of high temperature conditions, such as creep, thermal stress, and elastic-plastic deformation. The time variant constraint relations for rolling/contact conditions between two flexible bodies are also studied. The constraints for validation of MBS simulation of gear meshing contact using a modified Timoshenko beam theory are also presented. The last part deals with minimization of vibration/deformation of the elastic beam in multibody systems making use of time variant boundary conditions. The above methodologies and computational procedures developed are being implemented in a program called DYAMUS.