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Sample records for constrained acidic alpha-amino

  1. 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.

  2. 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.

  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 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.

  4. 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

  5. TiCl4-promoted multicomponent reaction: a new entry to functionalized alpha-amino acids.

    PubMed

    Ghosh, Arun K; Xu, Chun-Xiao; Kulkarni, Sarang S; Wink, Donald

    2005-01-01

    TiCl(4)-promoted multicomponent reactions involving N-tosyl imino ester, cyclic enol ether, and silane reagents in a single one-pot operation provide functionalized alpha-amino acids with multiple stereogenic centers in good to excellent yields. Cis/trans selectivities with optically active substituted dihydrofurans have been investigated. PMID:15624964

  6. Potential pancreatic imaging agents. Tellurium-123m labeled DL-alpha-amino-gamma-(phenyltelluro)butyric acid

    SciTech Connect

    Knapp, F.F. Jr.; Ambrose, K.R.; Callahan, A.P.

    1981-07-01

    This report describes the first successful preparation of a 123mTe-labeled alpha-amino acid as a potential pancreatic imaging agent. Tellurium-123m labeled DL-alpha-amino-gamma-(phenyltelluro)butyric acid was prepared by basic hydrolysis of the radiolabeled 5-(beta-(phenyltelluro)ethyl)hydantoin. The hydantoin was prepared by the reacitron of 123mTe-labeled phenyltellurol, generated by sodium borohydride reduction of diphenyl ditelluride, with 5-(beta-bromoethyl)hydantoin. Tissue distribution studies in rats with the 123mTe-labeled amino acid for periods varying from 30 min to 24 h demonstrated only marginal pancreatic accumulation of radioactivity. The significant result of these studies is that a general synthetic method has been developed for the preparation of 123mTe-labeled amino acids.

  7. Interference from alpha-amino acid and protein on determination of formaldehyde in food

    NASA Astrophysics Data System (ADS)

    Lu, Xiumin; Zhang, Xiaofeng; Fu, Yujie; Xiang, Jinxin

    2005-12-01

    The disturbance of alpha-amino acids and proteins on the analysis of formaldehyde content in food was investigated by electrochemical assay. Results show that the pH decreases gradually from 9.91 to 4.36 with increasing aspartic acid concentration. The recovery rate changes from 8% to 100% after different amounts of formaldehyde were added into protein solutions. For edible bamboo shoots, the recovery rate of formaldehyde is 80% to 100%. For shrimp kernel, however, the recovery rate of formaldehyde is 8% to 60%. These results indicate that the consumed quantity of formaldehyde is correlative with the protein concentration in foods. Therefore, the determinate formaldehyde content in food is actually not the totally applied amount, but just the residue after its reaction with the alpha-amino acids or free amino groups on the protein surface.

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

    PubMed

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

    2008-09-17

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

  9. Colorimetric sensing of alpha-amino acids and its application for the "label-free" detection of protease.

    PubMed

    Lou, Xiaoding; Zhang, Liyao; Qin, Jingui; Li, Zhen

    2010-02-01

    A new indirect approach to explore sensitive colorimetric sensors toward alpha-amino acids is proposed: the pink solution of 1 and copper ions changed to colorless immediately upon the addition of alpha-amino acids. As the hydrolysis of bovine serum albumin (BSA) with the aid of trypsin produces alpha-amino acids, the complex of 1/Cu(2+)/BSA could act as a label-free, sensitive, selective sensor toward trypsin. The detection process could be visually observed by naked eyes. PMID:20047345

  10. 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.

  11. 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.

  12. Molecular Basis of Prodrug Activation by Human Valacyclovirase, an [alpha]-Amino Acid Ester Hydrolase

    SciTech Connect

    Lai, Longsheng; Xu, Zhaohui; Zhou, Jiahai; Lee, Kyung-Dall; Amidon, Gordon L.

    2008-07-08

    Chemical modification to improve biopharmaceutical properties, especially oral absorption and bioavailability, is a common strategy employed by pharmaceutical chemists. The approach often employs a simple structural modification and utilizes ubiquitous endogenous esterases as activation enzymes, although such enzymes are often unidentified. This report describes the crystal structure and specificity of a novel activating enzyme for valacyclovir and valganciclovir. Our structural insights show that human valacyclovirase has a unique binding mode and specificity for amino acid esters. Biochemical data demonstrate that the enzyme hydrolyzes esters of {alpha}-amino acids exclusively and displays a broad specificity spectrum for the aminoacyl moiety similar to tricorn-interacting aminopeptidase F1. Crystal structures of the enzyme, two mechanistic mutants, and a complex with a product analogue, when combined with biochemical analysis, reveal the key determinants for substrate recognition; that is, a flexible and mostly hydrophobic acyl pocket, a localized negative electrostatic potential, a large open leaving group-accommodating groove, and a pivotal acidic residue, Asp-123, after the nucleophile Ser-122. This is the first time that a residue immediately after the nucleophile has been found to have its side chain directed into the substrate binding pocket and play an essential role in substrate discrimination in serine hydrolases. These results as well as a phylogenetic analysis establish that the enzyme functions as a specific {alpha}-amino acid ester hydrolase. Valacyclovirase is a valuable target for amino acid ester prodrug-based oral drug delivery enhancement strategies.

  13. Sterically biased 3,3-sigmatropic rearrangement of azides: efficient preparation of nonracemic alpha-amino acids and heterocycles.

    PubMed

    Gagnon, David; Lauzon, Sophie; Godbout, Cédrickx; Spino, Claude

    2005-10-13

    [reaction: see text] Homochiral alpha-amino acids, heterocycles, and carbocycles are efficiently constructed via a short sequence of reactions starting from the chiral auxiliary p-menthane-3-carboxaldehyde. The key feature of the sequence is a highly selective tandem Mitsunobu/3,3-sigmatropic rearrangement of hydrazoic acid that procures enantiomerically enriched allylic azides. The sequence is either terminated by oxidative cleavage to provide amino acids or by ring-closing metathesis to provide heterocycles or carbocycles bearing nitrogen. PMID:16209531

  14. Some characteristics of the mechanism of action of copper (II) complexes with alpha-amino acids

    SciTech Connect

    Treshchalina, E.M.; Gudratov, N.O.; Matueichuk, N.V.; Potapova, G.I.

    1985-06-01

    On the basis of the supposed difference in the mechanisms of action of copper (II) complexes with alpha-amino acids and of alkylating agents, the antitumor activity of Cu-2 when given in conjunction with cis-diamminedichloroplatinum (DDP) is studied. The DNA precursor C 14-thymidine was injected into mice 30 min before sacrifice. Doses of the substances appropriate as regards toxicity were used: Cu-2 9 mg/kg, DPP 4 mg/kg. The antitumor effect was assessed as inhibition of tumor growth, calculated relative to the mean volumes of the tumor in the experimental animals, was compared with the controls over a period of time. Toxicity was recorded as the percentage of mice which died and changes in the mean weight of the spleen. The investigations show that Cu-1 does not induce direct inhibition of DNA synthesis in the tumor cell, unlike DDP and sarcolysin. Combined administration of Cu-2 and DDP leads to summation of their antitumor effect without any increase in toxicity.

  15. Synthesis of all nineteen appropriately protected chiral alpha-hydroxy acid equivalents of the alpha-amino acids for Boc solid-phase depsi-peptide synthesis.

    PubMed

    Deechongkit, Songpon; You, Shu-Li; Kelly, Jeffery W

    2004-02-19

    [reaction: see text] The preparation of depsi-peptides, amide-to-ester-substituted peptides used to probe the role of hydrogen bonding in protein folding energetics, is accomplished by replacing specific l-alpha-amino acid residues by their alpha-hydroxy acid counterparts in a solid-phase synthesis employing a t-Boc strategy. Herein we describe the efficient stereoselective synthesis of all 19 appropriately protected alpha-hydroxy acid equivalents of the l-alpha-amino acids, employing commercially available materials, expanding the number of available alpha-hydroxy acids from 9 to 19. PMID:14961607

  16. 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. PMID:19467126

  17. The hydrolysis of alpha-amino-acid esters in mixed ligand complexes with copper(II)-iminodiacetate.

    PubMed

    Hay, R W; Banerjee, P K

    1981-04-01

    alpha-Amino-acid esters (EH+) interact with [Cu(IMDA)]0 to give mixed ligand complexes according to the equilibrium, [Cu(IMDA)]0 + EH+ in equilibrium with [Cu(IMDA)(E)]0 + H+, where EH+ represents the protonated ester +NH3CH(R)CO2R' and IMDA2- is HN(CH2CO2-)2. The mixed ligand complexes are only formed over a rather narrow pH range (ca. pH 5.8-6.5). At higher pH there is kinetic evidence for the competing equilibrium, [Cu(IMDA)(E)]0 + OH- in equilibrium with [Cu(IMDA)OH]- +E Rate constants kOH have been obtained by pH-stat for the hydrolyses [where A- = NH2CH(R)CO2-] [Cu(IMDA)(E)]0 + OH- kOH leads to [Cu(IMDA)(A)]- + R'OH. The complexed alpha-amino-acid esters undergo base hydrolysis ca. 10(4) times faster than the free esters E. Values of kOH show little dependence on the nature of the alkyl substituent R but the normal leaving group effect of methyl esters hydrolyzing at ca. twice the rate of ethyl esters is observed. Activation parameters have been determined for base hydrolysis of [Cu(IMDA)(glyOMe)]0, and possible mechanisms for the reaction are considered. PMID:7252492

  18. Determination of the enantiomers of alpha-hydroxy- and alpha-amino acids in capillary electrophoresis with contactless conductivity detection.

    PubMed

    Pormsila, Worapan; Gong, Xiao Yang; Hauser, Peter C

    2010-06-01

    The enantiomers of the anions of five alpha-hydroxy acids, namely lactic acid, alpha-hydroxybutyric acid, 2-hydroxycaproic acid, 2-hydroxyoctanoic acid and 2-hydroxydecanoic acid, as well as the two alpha-amino acids aspartic acid and glutamic acid, were baseline separated and detected by CE with contactless conductivity detection. Vancomycin was employed as chiral selector and could be used with conductivity detection without having to resort to a partial filling protocol as needed when this reagent is used with UV absorbance measurements. The procedure was successfully applied to the determination of the lactic acid enantiomers in samples of milk and yogurt. Linearity was achieved in the concentration range of 10-500 micromol/L with good correlation coefficients (0.9993 and 0.9990 for L- and D-lactic acid, respectively). The LODs (3 S/N) for L- and D-lactic acid were determined as 2.8 and 2.4 micromol/L, respectively. PMID:20496346

  19. 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. PMID:16995675

  20. 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.

  1. Human neutrophils employ myeloperoxidase to convert alpha-amino acids to a battery of reactive aldehydes: a pathway for aldehyde generation at sites of inflammation.

    PubMed

    Hazen, S L; Hsu, F F; d'Avignon, A; Heinecke, J W

    1998-05-12

    We have recently demonstrated that activated phagocytes employ the heme protein myeloperoxidase, H2O2, and Cl- to oxidize the aromatic amino acid l-tyrosine to the reactive aldehyde p-hydroxyphenylacetaldehyde. We now present evidence for the generality of this reaction by demonstrating that neutrophils employ the myeloperoxidase-H2O2-Cl- system to oxidize nearly all of the common alpha-amino acids to yield a family of reactive aldehydes. Chemical characterization suggested that reactive carbonyl moieties were generated during amino acid oxidation by myeloperoxidase. The structures of amino-acid-derived aldehydes were confirmed using a variety of mass spectrometric methods. Aldehyde production required myeloperoxidase, H2O2, Cl-, and an amino acid; it was inhibited by heme poisons and catalase. Hypochlorous acid was the apparent oxidizing intermediate because its addition to alpha-amino acids resulted in the formation of the anticipated aldehyde. Stimulated human neutrophils likewise generated aldehydes from all classes of alpha-amino acids by a pathway inhibited by heme poisons and catalase, implicating myeloperoxidase and H2O2 in the cell-mediated reaction. Aldehyde production accounted for a significant fraction of the H2O2 generated by stimulated neutrophils at physiological concentrations of amino acids. Collectively, these results suggest that amino-acid-derived aldehydes represent a product of reactive oxidant species generated by activated phagocytes. PMID:9578573

  2. 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.

  3. Liposome-assisted selective polycondensation of alpha-amino acids and peptides.

    PubMed

    Hitz, T; Luisi, P L

    2000-01-01

    The main question of this paper is whether and to what extend lipid bilayers can aid in the polycondensation of amino acids and peptides. This means in particular how such bilayers can favor the selection of certain sequences out of a large number of theoretical possible ones. In a first series of experiments we started from a library of Trp-containing dipeptides of the type Trp-X where X is an amino acid residue; and we could show that, when adding this mixture to the POPC liposomes containing a hydrophobic quinoline condensing agent (EEDQ), only the hydrophobic Trp-Trp dipeptide is selected out by the liposomes and transformed into a longer oligomer. Trp-oligomers up to 29 monomers long (water insoluble) could be obtained by using the matrix support of liposomes. Mixed POPC/DDAB liposomes (positive charge) were used to produce co-oligopeptides that contain Trp and Glu residues in the same sequence. Arg/Trp and His/Trp containing sequences were obtained in presence of negatively charged liposomes (mixed POPC/DOPA-liposomes). The polycondensation of racemic NCA-amino acids has been studied to clarify if homochiral sequences are produced preferentially in presence or absence of liposomes. LC-MS and isotope labeling of the L-amino acid, participating in the polymerization reaction achieved this on the level of a direct product analysis. So the individual stereoisomer distribution up to a polymerization degree of 10 (in the case of Trp) could be determined. The data for Trp and other amino acids (Leu, Ile) and amino acid mixtures (Trp/Leu, Trp/Ile, Leu/Ile and Trp/Leu/Ile) show that homochiral sequences are produced preferentially if compared with a random (Bernoulli) distribution. PMID:11241213

  4. Development of enantioselective chemiluminescence flow- and sequential-injection immunoassays for alpha-amino acids.

    PubMed

    Silvaieh, Hossein; Schmid, Martin G; Hofstetter, Oliver; Schurig, Volker; Gbitz, Gerald

    2002-01-01

    The development of an enantioselective flow-through chemiluminescence immunosensor for amino acids is described. The approach is based on a competitive assay using enantioselective antibodies. Two different instrumental approaches, a flow-injection (FIA) and a sequential-injection system (SIA), are used. Compared to the flow-injection technique, the sequential injection-mode showed better repeatability. Both systems use an immunoreactor consisting of a flow cell packed with immobilized haptens. The haptens (4-amino-L- or D-phenylalanine) are immobilized onto a hydroxysuccinimide-activated polymer (Affi-prep 10) via a tyramine spacer. Stereoselective antibodies, raised against 4-amino-L- or D-phenylalanine, are labeled with an acridinium ester. Stereoselective inhibition of binding of the acridinum-labeled antibodies to the immobilized hapten by amino acids takes place. Chiral recognition was observed not only for the hapten molecule but also for a series of different amino acids. One assay cycle including regeneration takes 6:30 min in the FIA mode and 4:40 min in the SIA mode. Using D-phenylalanine as a sample, the detection limit was found to be 6.13 pmol/ml (1.01 ng/ml) for the flow-injection immunoassay (FIIA) and 1.76 pmol/ml (0.29 ng/ml ) for the sequential-injection immunoassay (SIIA) which can be lowered to 0.22 pmol/ml (0.036 ng/ml) or 0.064 pmol/ml (0.01 ng/ml) by using a stopped flow system. The intra-assay repeatability was found to be about 5% RSD and the inter-assay repeatability below 6% (within 3 days). PMID:12406581

  5. Structural and NMR investigations of the ternary adducts of twenty alpha-amino acids and selected dipeptides with a chiral, diaqua-ytterbium complex.

    PubMed

    Dickins, Rachel S; Batsanov, Andrei S; Howard, Judith A K; Parker, David; Puschmann, Horst; Salamano, Stefania

    2004-01-01

    A detailed investigation of the nature of the binding of each of the 20 common alpha-amino acids and various selected dipeptides to a chiral, diaqua-ytterbium complex in aqueous solution has been carried out. Analysis of the dipolar 1H NMR paramagnetic shifts suggests that the alpha-amino acids form a common chelated structure within a nine-coordinate mono-capped square antiprismatic coordination environment, with the amine N axially disposed. Crystal structures of nine chelated YbL1-amino acid adducts (Gly, Ala, Ser, Thr, Met) confirm this. The ternary complexes with dipeptides (e.g. Gly-Ala, Gly-Ser, Gly-Met, Gly-Asp, Gly-Asn, Gly-His, Ser-Met, Asp-Phe, His-Gly) also favour the terminal amine as the axial donor with the proximate amide group binding to generate a five-ring chelate. Evidence for chelation through side-chain functionality was found only in the case of N-terminal Asp. The chiral environment about the ytterbium ion upon amino acid binding has also been probed using near-IR circular dichroism spectroscopy. PMID:15356744

  6. Enantiomeric and diastereomeric high-performance liquid chromatographic separation of cyclic beta-substituted alpha-amino acids on a teicoplanin chiral stationary phase.

    PubMed

    Schlauch, M; Frahm, A W

    2000-02-01

    High-performance liquid chromatographic (HPLC) separation of stereomeric cyclic beta-substituted or-quaternary alpha-amino acids was performed on a chiral stationary phase based on the glycopeptide antibiotic teicoplanin. The investigated amino acids are the 1-amino-2-methylcyclohexanecarboxylic acids, the 1-amino-2-hydroxycyclohexanecarboxylic acids, Ala, Cha, Phe and Tle. The effects of the mobile phase composition (type and content of organic modifier, pH) and of the temperature on the enantio- and diastereoselectivity were studied and the conditions were optimised to resolve the four stereomers of one amino acid in a single chromatographic run. The influence of the modifier concentration and the pH of the mobile phase reveal two enantiomeric and diastereomeric discrimination mechanisms based on different interactions with the stationary phase. For optimal separation of diastereomers the column has to be conditioned with an acidic eluent. PMID:10701670

  7. Gas phase attachment of water and methanol to Ag(I) complexes with alpha-amino acids in an ion trap mass spectrometer.

    PubMed

    Perera, B A; Ince, M P; Talaty, E R; Van Stipdonk, M J

    2001-01-01

    Electrospray ionization was used to generate gas phase complexes of Ag+ with selected alpha-amino acids. Following storage (isolation without collisional activation) in an ion trap mass spectrometer, the mass spectra produced from the complexes of Ag+ with alpha-amino acids such as alanine, valine and tert-leucine contained peaks consistent with the formation of water or methanol molecule adduct ions. The same adduct ions were not present, however, in the mass spectra generated from the Ag+ complexes with phenylalanine, tyrosine and tryptophan following isolation and storage under similar conditions. For those complexes that showed reactivity, the uptake of water and methanol increased with longer storage times in the ion trap. A preliminary molecular modeling study using phenylalanine demonstrated that the aromatic ring coordinates the Ag+ ion, and the interaction between the metal ion and pi-system, in part, is assumed to prohibit the binding of water or methanol during isolation in the gas phase. This conclusion is supported by a comparison of the adduct formation by the Ag+ complexes with phenylalanine, 4-fluorophenylalanine and alpha-aminocyclohexanepropionic acid. In addition, collision induced dissociation experiments involving the Ag+ complexes of phenylalanine, tyrosine and tryptophan suggest that limiting the coordination of the Ag ion by the complexing molecule (i.e. by loss of a coordinating functional group and/or change in structure due to dissociation) results in the binding of a water or methanol molecule during storage in the ion trap. Surprisingly, the bare Ag+ ion, when trapped and stored under identical experimental conditions, formed neither adduct species, suggesting that the attachment of water or methanol may be due to interactions with a molecular orbital within the Ag+/molecule complex. PMID:11312512

  8. 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.

  9. The mechanism of action of aniracetam at synaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors: indirect and direct effects on desensitization.

    PubMed

    Lawrence, J Josh; Brenowitz, Stephan; Trussell, Laurence O

    2003-08-01

    The mechanism of action of aniracetam on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors was examined in outside-out patches and at glutamatergic synapses in neurons of the chick cochlear nucleus. A combination of rapid-flow analysis, using glutamate as an agonist, and kinetic modeling indicated that aniracetam slows both the rate of channel closing, and the microscopic rates of desensitization, even for partially liganded receptors. Little effect was observed on the rate of recovery from desensitization or on the response to the weakly desensitizing agonist kainate. Aniracetam's effects on receptor deactivation saturated at lower concentrations than its effects on desensitization, suggesting that cooperativity between homologous binding sites was required to regulate desensitization. Analysis of responses to paired pulses of agonist also indicated that AMPA receptors must desensitize partially even after agonist exposures too brief to permit rebinding. In the presence of aniracetam, evoked excitatory synaptic currents (EPSCs) and miniature EPSCs in low quantal-content conditions had decay times similar to the time course of receptor deactivation. Under these conditions, the time course of both transmitter release and clearance must be <1 to 2 ms. However, in high quantal-content conditions, the evoked EPSC in aniracetam decayed with a time course intermediate between deactivation and desensitization, suggesting that the time course of transmitter clearance is prolonged because of pooling of transmitter in the synaptic cleft. Moreover, by comparing the amounts of paired-pulse synaptic depression and patch desensitization prevented by aniracetam, we conclude that significant desensitization occurs in response to rebinding of transmitter to the AMPA receptors. PMID:12869631

  10. 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. PMID:15626725

  11. Coordination of biologically important alpha-amino acids to calcium(II) at high pH: insights from crystal structures of calcium alpha-aminocarboxylates.

    PubMed

    Fox, Stefan; Büsching, Insa; Barklage, Walter; Strasdeit, Henry

    2007-02-01

    A series of calcium alpha-aminocarboxylates was prepared by refluxing aqueous solutions/suspensions of calcium hydroxide and the respective alpha-amino acid. The colorless, crystalline hydrates Ca(gly)2.H2O (1), Ca(ala)2.3H2O (2), Ca(val)2.H2O (3), Ca(leu)2.3H2O (4), Ca(met)2.nH2O (5, n approximately 2), and Ca(pro)2.H2O (6) have been isolated in yields between 29 and 67% (gly- = glycinate, ala- = rac-alaninate, val- = rac-valinate, leu- = rac-leucinate, met- = rac-methioninate, pro- = rac-prolinate). The compounds 1-6 are readily soluble in water. The 0.10 M solutions have ca. pH 10-11 which is consistent with a noticeable degree of dissociation. The 13C NMR spectra of 1-6 in D2O were measured, and their comparison with those of the corresponding tetramethylammonium alpha-aminocarboxylates point to carboxylate coordination in solution, but no indication of nitrogen coordination was found. Infrared spectra of 1-6 gave similar results for the solid state. Complete single-crystal X-ray structure analyses of 1-4 and preliminary ones of 5 and 6, however, revealed that all aminocarboxylate ligands are N,O-chelating. Crystals of 2 consist of mononuclear complexes, while the other five compounds form three different types of one-dimensional coordination polymers. Structural diversity is also observed with the binding modes of the aminocarboxylate ligands and the calcium environment. Besides terminal aminocarboxylate coordination, there are three different types of aminocarboxylate bridges. The calcium ions are seven- or eight-coordinate in N2O5 and N2O6 coordination environments, respectively; one or three water molecules are part of the first ligand sphere of each metal ion. The crystal structures support conjectures about the existence of the yet undetected solution species [Cax(aa)2x(H2O)n] (aa- = alpha-aminocarboxylate). For example, x = 1 is realized in crystalline [Ca(ala)2(H2O)3] (2), and in 4 [Ca2(leu)4(H2O)4] complexes (x = 2) are linked to infinite chains by bridging aqua ligands. PMID:17257025

  12. Pb(II)-binding capability of aminohydroxamic acids: primary hydroxamic acid derivatives of alpha-amino acids as possible sequestering agents for Pb(II).

    PubMed

    Bátka, Dávid; Farkas, Etelka

    2006-01-01

    Complexes of aminohydroxamic acids, D,L-alpha-alaninehydroxamic acid (alpha-Alaha), sarcosinehydroxamic acid (Sarha), D,L-N-methyl-alpha-alaninehydroxamic acid (N-Me-alpha-Alaha), beta-alaninehydroxamic (beta-Alaha), L-aspartic acid-beta-hydroxamic acid (Asp-beta-ha), L-glutamic acid-gamma-hydroxamic acid (Glu-gamma-ha) and L-histidinehydroxamic acid (Hisha) with lead(II) in aqueous solution were studied by pH-potentiometric, 1H NMR and electrospray ionization mass spectrometric (ESI MS) methods. The results were compared to those of a simple monohydroxamic acid, acetohydroxamic acid and the effects of the amino group, hydroxamate-N, as well as, additional side chain donors on the co-ordination mode and on the stability of the complexes formed were evaluated. It was found that the amino nitrogen atom situating in beta- or in gamma-position (beta-Alaha, Asp-beta-ha, Glu-gamma-ha) does not co-ordinate to Pb(II), only hydroxamate type chelates are formed before the hydrolytic processes. However, the amino-N in alpha-position (alpha-Alaha, Sarha, Hisha) seems to form a stable 5-membered (N,N)-type chelate together with the deprotonated hydroxamate-N above pH 6. On the other hand, the hydroxamate (O,O)-type chelate also exists. Since steric reasons do not allow the coordination of these two chelates of a molecule to the same Pb(II) ion, polynuclear complexes with mixed co-ordination modes are formed with the alpha-derivatives above pH 6. Simple hydroxamate type complexes are formed with N-Me-alpha-Alaha, where the hydroxamate-N is not able to co-ordinate. The co-ordination of the side chain imidazole of Hisha is not measurable, while a weak interaction of the side chain carboxylates of Asp-beta-ha and especially of Glu-gamma-ha can be suggested. PMID:16274742

  13. 3-Nitro-3,4-dihydro-2(1H)-quinolones. Excitatory amino acid antagonists acting at glycine-site NMDA and (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors.

    PubMed

    Carling, R W; Leeson, P D; Moore, K W; Smith, J D; Moyes, C R; Mawer, I M; Thomas, S; Chan, T; Baker, R; Foster, A C

    1993-10-29

    3,4-Dihydro-2(1H)-quinolones, evolved from 2-carboxy-1,2,3,4,- tetrahydroquinolines and 3-carboxy-4-hydroxy-2(1H)-quinolones, have been synthesized and evaluated in vitro for antagonist activity at the glycine site on the NMDA receptor and for AMPA [(RS)-alpha-amino-3- hydroxy-5-methyl-4-isoxazolepropionic acid] antagonist activity. Generally poor potency at the glycine site is observed when a variety of electron-withdrawing substituents are attached to the 3-position of 3,4-dihydro-2(1H)-quinolones. The analogues 5-9 (IC50 values > 100 microM, Table I) exist largely in the 3,4-dipseudoaxial conformation (as evidenced by 1H NMR spectra), whereas the 3-cyano derivative (10, IC50 = 12.0 microM) has a relatively high population of the 3-pseudoequatorial conformer. The 3-nitro analogue (4, IC50 = 1.32 microM) has a pKa approximately 5 and thus exists at physiological pH as an anion with the nitro group planar to the quinolone ring. The general requirement of acidity for high affinity binding at the glycine/NMDA site is supported with the good activity of the other 3-nitro derivatives (13-21), all of which are deprotonated at physiological pH. The 3-nitro-3,4-dihydro-2(1H)-quinolones and 2-carboxy-1,2,3,4-tetrahydroquinolines show quite different structure-activity relationships at the 4-position. The unselective excitatory amino acid activity of 21 is comparable with 6,7-dichloro-quinoxaline-2,3-dione and 6,7-dichloroquinoxalic acid and this suggests similarities in their modes of binding to excitatory amino acid receptors. The broad spectrum excitatory amino acid antagonist activity of the 4-unsubstituted analogue 21 (KbNMDA = 6.7 microM, KbAMPA = 9.2 microM) and the glycine/NMDA selectivity of the other 3-nitro derivatives allows the proposal of a model for AMPA receptor binding which differs from the glycine binding pharmacophore in that there is bulk intolerance adjacent to the 4-position. Compound 21 (L-698,544) is active (ED50 = 13.2 mg/kg) in the DBA/2 mouse anticonvulsant model and is the most potent combined glycine/NMDA-AMPA antagonist yet reported, in vivo, and may prove to be a useful pharmacological tool. PMID:8230130

  14. Animals are dependent on preformed alpha-amino nitrogen as an essential nutrient.

    PubMed

    Katagiri, Masayuki; Nakamura, Masahiko

    2002-02-01

    It has traditionally been thought that animals can utilize ammonia for amino acid biosynthesis, and that for them some amino acids are nutritionally nonessential. Presumably this idea originates from the notions of Schoenheimer (G. L. Foster et al. [1939] J. Biol. Chem. 127, 319-327) and of Rose (W. C. Rose et al. [1948] J. Biol. Chem. 176, 753-762), which we question for the following reasons. First, Schoenheimer's experiments only showed the incorporation of ammonia into amino acids. This may occur simply as an exchange between ammonia and the alpha-amino group of endogenous amino acids and reflects the enzymatic properties of glutamate dehydrogenase, which is a reversible enzyme. Second, Rose's nutritional experiments were concerned with whether carbon skeletons of particular amino acids can (nonessential) or cannot (essential) be synthesized from common intermediates of carbohydrate metabolism. We propose that mammals, living as they do at the top of the food web, are absolutely dependent directly or indirectly on higher plants and microorganisms for preformed alpha-amino nitrogen per se and that the first joining of C- and N-atoms to make glutamate constitutes a basic anabolic system in nature after the fixation of CO2 and N2. PMID:12049195

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

    PubMed

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

    2013-02-01

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

  16. Catalysis in the formation of /alpha/-amino ketones

    SciTech Connect

    Popov, A.F.; Anikeev, A.V.

    1988-10-20

    The kinetics of the reaction of /alpha/-halogenoacetophenones with piperidine and N-methylpiperidine in cyclohexane at 30/degree/C were investigated. The autocatalytic nature of these reactions is due to the formation of catalytically active acidic products from degradation of the /alpha/-aminoacetophenone in the reaction system. The catalytic effect of additions of acetic acid and phenol on the rate of the reactions of /alpha/-halogenoacetophenone with piperidine and N-methylpiperidine is described quantitatively. Catalysis by acetic acid in the reaction of /alpha/-halogenoacetophenones with piperidine has a bifunctional mechanism.

  17. Betidamino acids: versatile and constrained scaffolds for drug discovery.

    PubMed Central

    Rivier, J E; Jiang, G; Koerber, S C; Porter, J; Simon, L; Craig, A G; Hoeger, C A

    1996-01-01

    Betidamino acids (a contraction of "beta" position and "amide") are N'-monoacylated (optionally, N'-monoacylated and N-mono- or N,N'-dialkylated) aminoglycine derivatives in which each N'acyl/alkyl group may mimic naturally occurring amino acid side chains or introduce novel functionalities. Betidamino acids are most conveniently generated on solid supports used for the synthesis of peptides by selective acylation of one of the two amino functions of orthogonally protected aminoglycine(s) to generate the side chain either prior to or after the elongation of the main chain. We have used unresolved Nalpha-tert-butyloxycarbonyl-N'alpha-fluorenylmethoxycarbonyl++ + aminoglycine, and Nalpha-(Nalpha-methyl)-tert-butyloxycarbonyl-N'alpha-fluo renylmethoxycarbonyl aminoglycine as the templates for the introduction of betidamino acids in Acyline [Ac-D2Nal-D4Cpa-D3Pal-Ser-4Aph(Ac)-D4Aph(A c)-Leu-Ilys-Pro-DAla-NH2, where 2Nal is 2-naphthylalanine, 4Cpa is 4-chlorophenylalanine, 3Pal is 3-pyridylalanine, Aph is 4-aminophenylalanine, and Ilys is Nepsilon-isopropyllysine], a potent gonadotropin-releasing hormone antagonist, in order to test biocompatibility of these derivatives. Diasteremneric peptides could be separated in most cases by reverse-phase HPLC. Biological results indicated small differences in relative potencies (<5-fold) between the D and L nonalkylated betidamino acid-containing Acyline derivatives. Importantly, most betide diastereomers were equipotent with Acyline. In an attempt to correlate structure and observed potency, Ramachandran-type plots were calculated for a series of betidamino acids and their methylated homologs. According to these calculations, betidamino acids have access to a more limited and distinct number of conformational states (including those associated with alpha-helices, beta-sheets, or turn structures), with deeper minima than those observed for natural amino acids. PMID:8700880

  18. 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. PMID:20302360

  19. 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+. PMID:16330242

  20. Corroborative cobalt and zinc model compounds of alpha-amino-beta-carboxymuconic-epsilon-semialdehyde decarboxylase (ACMSD).

    PubMed

    Gtjens, Jessica; Mullins, Christopher S; Kampf, Jeff W; Thury, Pierre; Pecoraro, Vincent L

    2009-01-01

    We have synthesised and characterised a series of new Co(II) complexes (1-4, 6, 7) and one new Zn(II) complex (5) employing N(3)- and N(3)O-donor ligands [biap: N,N-bis(2-ethyl-5-methyl-imidazol-4-ylmethyl)amino-propane, KBPZG: potassium N,N-bis(3,5-dimethylpyrazolylmethyl) glycinate, KBPZA: potassium N,N-bis(3,5-dimethylpyrazolylmethyl) alaninate, KB(i)PrPZG: potassium N,N-bis(3,5-di-iso-propylpyrazolylmethyl) glycinate, and KB((t)BuM)PZG: potassium N,N-bis(3-methyl-5-tert-butyl-pyrazolylmethyl)glycinate] as structural models of the metalloenzyme alpha-amino-beta-carboxymuconic-epsilon-semialdehyde decarboxylase (ACMSD). These complexes were characterised by several techniques including X-ray crystallographic analysis, X-band EPR, and mass spectrometry (ESI-MS). The crystal structures of 1, 2, 6,7 revealed that they exist as mononuclear Co(II) complexes with trigonal-bipyramidal geometry in the solid state. Compounds 3 and 5 form infinite polymeric chains of Co(II) or Zn(II) complexes, respectively, linked by the pendant carboxylate arms of the BPZG(-) ligand. By comparing the degree of distortion in the penta-coordinate complexes, defined by the Addison-parameter tau, with the value determined for the five-coordinate centres found in the active site of ACMSD, it could be seen that complexes 5 and 7 are very good matches for the geometry of the zinc(II) centre in monomer A of the native enzyme. All complexes could be seen as model compounds for the active site of the enzyme ACMSD, where the Co(II) complexes reflected the structural flexibility found in case of two histidine (His177 and His228) residues found in the active site of the enzyme. PMID:19081971

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

    PubMed Central

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

    2013-01-01

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

  2. 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. PMID:24289240

  3. 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.

  4. 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.

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

    PubMed Central

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

    2012-01-01

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

  6. Functionalization of aromatic amino acids via direct C-H activation: generation of versatile building blocks for accessing novel peptide space.

    PubMed

    Meyer, Falco-Magnus; Liras, Spiros; Guzman-Perez, Angel; Perreault, Christian; Bian, Jianwei; James, Keith

    2010-09-01

    Functionalized alpha-amino acid building blocks have been prepared in good yield with high regiocontrol and preservation of stereochemistry via iridium-catalyzed borylation of suitably protected aromatic alpha-amino acid derivatives. The utility of these systems in peptide couplings and Suzuki reactions has been demonstrated. PMID:20695449

  7. The stability of some selected amino acids under attempted redox constrained hydrothermal conditions.

    PubMed

    Andersson, E; Holm, N G

    2000-02-01

    In order to evaluate the stability of aspartic acid, serine, leucine, and alanine under redox buffered hydrothermal conditions, a series of experiments have been performed. The pyrite-pyrrhotite-magnetite (PPM) mineral assemblage was used in the experimental systems in order to constrain the oxygen fugacity. Likewise, the K-feldspar-muscovite-quartz (KMQ) assemblage was added to control the hydrogen ion activity during the experiments. The purpose was to compare the relative stabilities in buffered and unbuffered experiments. The experiments were conducted at 200 degrees C and 50 bar in Teflon coated autoclaves. Glycine, which was not present initially, started to appear at an early stage in the experimental systems and is believed to be the result of decomposition of serine. Similarly, the increase in relative abundance of alanine is likely to be the result of decomposition of serine. Decomposition rates of leucine, alanine and aspartic acid were found to be lower in experiments containing the redox buffer assemblage pyrite-pyrrhotite-magnetite than in non-redox buffered experiments. The decomposition rate of serine was higher in buffered experiments, which indicates that a transformation pathway via dehydration of serine to dehydroalanine followed by reduction to alanine is promoted by reducing conditions. PMID:10836261

  8. Bifunctional mechanism of catalysis in reactions leading to formation of /alpha/-amino ketones

    SciTech Connect

    Popov, A.F.; Anikeev, A.V.

    1988-10-20

    The kinetics of the reaction of /alpha/-bromoacetophenone and benzyl bromide with aniline and pyridine in the presence of additions of acetic acid and phenol in benzene at 30/degree/C were investigated. The catalytic effects due to the activity of the uncombined forms of the catalyst, their dimers, and their 1:1 complexes with the amines were separated quantitatively. The change in the catalytic activity of the respective particles in the solutions with variation in the structure of the reagents is examined, and possible mechanisms for the catalytic reactions are discussed on this basis. It is concluded that there is a bifunctional mechanism of catalysis by acetic acid in the reaction of /alpha/-bromoacetophenone with aniline.

  9. 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.

  10. 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.

  11. Poly(ethylene-co-acrylic acid) stationary phases for the separation of shape-constrained isomers.

    PubMed

    Wegmann, J; Albert, K; Pursch, M; Sander, L C

    2001-04-15

    A new approach for the synthesis of long alkyl chain length stationary phases for use in reversed-phase liquid chromatography is described. Poly(ethylene-co-acrylic acid) copolymers (i.e., (-CH2CH2-)x[CH2CH(CO2H)-]y) with different levels of acrylic acid were covalently bonded to silica via glycidoxypropyl or aminopropyl linkages. 13C cross polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy was used to characterize the new reversed-phase materials. Aspects of shape selectivity were evaluated for six different columns with Standard Reference Material (SRM) 869a, Column Selectivity Test Mixture for Liquid Chromatography. Selectivity for isomer separations was enhanced for stationary phases prepared with poly(ethylene-co-acrylic acid) containing a mass fraction of 5% acrylic acid. The relationship between alkyl conformation and chromatographic properties was studied by 13C magic angle spinning (MAS) NMR measurements, and correlations were made with the composition of the polymer. Finally, the effectiveness of this phase is demonstrated by the separation of several beta-carotene isomers. PMID:11338596

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

    SciTech Connect

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

    2008-01-01

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

  13. Conformational studies of γ-turn in pseudopeptides containing α-amino acid and conformationally constrained meta amino benzoic acid/meta nitro aniline

    NASA Astrophysics Data System (ADS)

    Dutt Konar, Anita

    2013-03-01

    Reverse turns (commonly β-turns and γ-turns), a common motif in proteins and peptides, have attracted attention due to their relevance in a wide variety of biological processes. In an attempt to artificially imitate and stabilize these turns in short acyclic peptides, a series of N-terminally protected pseudopeptides comprising of an α-amino acid and conformationally constrained meta amino benzoic acid (mABA)/meta nitro aniline (mNA) (peptides I-VI) have been synthesized. The molecules were well characterized by various spectroscopic techniques and subjected to a systematic conformational analysis. Our experimental results reveal that only pseudopeptides I and II with methyl as the sidechain, tertiary butyloxy carbonyl as the N-terminal protecting group and (mABA)/(mNA) at the C-terminus adopt γ-turn conformations in solid state as well as in solution. Even slight modification of any of the stated conditions donot support the formation of this γ-turn architecture in the solid state. Interestingly, the peptides III-V which displays extended conformation in solid state forms γ-turn structure in solution. Thus this result reflects the importance of co-operative steric interactions amongst various amino acid residues in stabilizing a particular conformation in peptides in different phases (solid and solution). This report may open a new avenue in introducing γ-turn motifs within the bioactive conformation of selected peptides.

  14. Constrained poststratification.

    PubMed

    Moise, A; Salamon, R; Raissis, M; Nanopoulos, P; Clement, B

    1986-08-01

    Adjustment for covariates (or poststratification) is frequently used in the analysis of randomized clinical trials. The purpose of such analysis is mainly to eliminate some residual bias resulting from any imbalance between treatment groups for some important covariates. Usually, covariate effect is modeled with the data at hand. In this paper, we present a new method of poststratification ("constrained poststratification") which consists of estimating the prognostic significance of covariates in a large historical data base, transferring the model's coefficients into the (smaller) randomized trial data set, and estimating treatment effects conditional on this a priori information. In a simulated experiment, constrained poststratification allowed not only reduction of the bias but also enhancement of the efficiency of the estimation of treatment effect. PMID:3731761

  15. 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.

  16. Long-term increase of GluR2 alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor subunit in the dispersed dentate gyrus after intrahippocampal kainate injection in the mouse.

    PubMed

    Suzuki, F; Hirai, H; Onteniente, B; Riban, V; Matsuda, M; Kurokawa, K

    2000-01-01

    Intrahippocampal injection of a subtoxic dose of kainate in mice has been shown to induce a dispersion of granule cells of the dentate gyrus, which is a characteristic morphological change often seen in human hippocampal sclerosis. In addition, it has been shown recently that such injections lead to recurrent hippocampal seizures and changes in glucose metabolism, which are reminiscent of temporal lobe epilepsy. Previous reports on human hippocampal sclerosis have shown an increase of the expression of the GluR2 alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate subunits in the dispersed granule cell somata. However, no such changes have been observed so far in animal models of epilepsy with hippocampal sclerosis. In this study, the expression of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor subunits was examined by immunohistochemistry following intrahippocampal injection of kainate in mice and rats. In mice, such injection induced a persistent increase of GluR2 immunoreactivity in the granule cells for up to 180 days. By contrast, GluR1 immunoreactivity was transiently increased during the first four days after the injection and progressively decreased thereafter. By contrast, intrahippocampal injection of kainate in rats did not result in granule cell dispersion and no changes in GluR1 immunoreactivity or GluR2 immunoreactivity were observed. These results show that, in addition to morphological, clinical and metabolical similarities, intrahippocampal injection of kainate results in a persistent increase of GluR2 associated with granule cell dispersion, as in human hippocampal sclerosis. These data suggest the existence of common mechanisms between granule cell dispersion and regulation of GluR2 subunits associated with hippocampal sclerosis. PMID:11068135

  17. 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.

  18. 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.

  19. 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.

  20. Characterization of a broad-scope amino acid transport system in sand dollars

    SciTech Connect

    Davis, J.P.; Bellis, S.; Stephens, G.C. )

    1988-03-01

    Both echinoderm embryos and adults take up {sup 14}C-labelled-{alpha}-amino acids by an apparent broad-scope transport system. This transporter can be characterized as follows: alanine transport is not blocked by {alpha}-(methylamino)isobutyric acid. Leucine and other lipophilic neutral amino acids are preferentially transported. Transport is sodium dependent and blocked by 2-aminobicyclo-(2,2,1)heptane-2-carboxyclic acid. Lysine and aspartate transport is inhibited by lipophilic neutral amino acids. Taurine, a {beta}-neutral amino acid is translocated via a second and independent carrier.

  1. Asymmetric synthesis of beta-hydroxy amino acids via aldol reactions catalyzed by chiral ammonium salts.

    PubMed

    Mettath, Sashikumar; Srikanth, G S C; Dangerfield, Benjamin S; Castle, Steven L

    2004-09-17

    The Cinchona alkaloid derived chiral ammonium salt developed by Park and Jew functions as an effective catalyst for the synthesis of beta-hydroxy alpha-amino acids via asymmetric aldol reactions under homogeneous conditions. The syn diastereomers are obtained in good ee, and aryl-substituted aliphatic aldehydes are the best substrates for the reaction. These results represent the highest ee's obtained to date in direct aldol reactions of glycine equivalents catalyzed by inexpensive, readily prepared chiral ammonium salts. PMID:15357616

  2. Stereocontrolled formation of amino acids and N-heterocycles bearing a quaternary chiral carbon.

    PubMed

    Roy, Stéphanie; Spino, Claude

    2006-03-01

    Stereocontrolled formation of tertiary or quaternary chiral carbons bearing nitrogen was achieved using the [3,3]-sigmatropic rearrangement of cyanate to isocyanate as a key element. A short and highly selective sequence of reactions, starting from p-menthane-3-carboxaldehyde, was developed leading to alpha,alpha-dialkylated alpha-amino acids or N-heterocycles, depending on the method of cleavage of the auxiliary. PMID:16494479

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  4. Pyrolysis of amino acids - Mechanistic considerations

    NASA Technical Reports Server (NTRS)

    Ratcliff, M. A., Jr.; Medley, E. E.; Simmonds, P. G.

    1974-01-01

    Pyrolysis of several structurally different amino acids in a column at 500 C showed differences in the mechanisms and final products. The aliphatic protein amino acids decompose mainly by simple decarboxylation and condensation reactions, while the beta amino acids undergo deamination to unsaturated acids. Alpha amino acids with alpha alkyl substituents undergo an unusual intramolecular SN1 reaction with the formation of an intermediate alpha lactone which decomposes to yield a ketone. The alpha alkyl substituents appear to stabilize the developing negative charge formed by partial heterolytic cleavage of the alpha carbon - NH3 bond. The gamma and delta amino acids give 2-pyrrolidinone and 2-piperidone respectively, while the epsilon acids yield mixed products.

  5. 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. PMID:19822174

  6. Unusual temperature-induced retention behavior of constrained β-amino acid enantiomers on the zwitterionic chiral stationary phases ZWIX(+) and ZWIX(-).

    PubMed

    Ilisz, István; Pataj, Zoltán; Gecse, Zsanett; Szakonyi, Zsolt; Fülöp, Ferenc; Lindner, Wolfgang; Péter, Antal

    2014-08-01

    The effects of temperature on the chiral recognition of cyclic β-amino acid enantiomers on zwitterionic [Chiralpak ZWIX(+) and ZWIX(-)] chiral stationary phases were investigated. Experiments were performed at different mobile phase compositions and under 10°C column temperature increments in the temperature range 10-50°C. Apparent thermodynamic parameters and T(iso) values were calculated from plots of ln k and ln α versus 1/T, respectively. Unusual temperature behavior was observed, especially on the ZWIX(-) column, where the application of MeOH/MeCN (50/50 v/v) containing 25 mM triethylamine and 50 mM formic acid as mobile phase led to nonlinear van't Hoff plots and increasing retention time with increasing temperature. On both columns, both enthalpically and entropically driven separations were observed. PMID:24839210

  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. Phylogenies Constrained by the Crossover Process as Illustrated by Human Hemoglobins and a Thirteen-Cycle, Eleven-Amino-Acid Repeat in Human Apolipoprotein a-I

    PubMed Central

    Fitch, Walter M.

    1977-01-01

    Examination of human apolipoprotein A-I revealed a segment of eleven amino acids that repeated itself 13 times in succession without any additional intervening amino acids between the beginning of the repeats (amino acid 93) and their end at the carboxyl terminus of the sequence. The segments are not identical, but the pattern of their physical and chemical properties is highly conserved. The pattern is shown to be suitable to the formation of alpha helices with an amphipathic character consistent with the formation of a micellar structure, a process entirely appropriate to the protein's known function in the blood stream as a lipid carrier. The simplest hypothesis to account for repeated segments is a series of unequal crossovers. But such a series implies that some segments are more closely related to each other than they are to others, that is, they have a "phylogenetic" relationship. It is shown that only a small fraction of all possible phylogenies are consistent with a set of segments arising by simple unequal crossing over. Nevertheless, it is shown that the apolipoprotein A-I segments are readily interpretable as the result of simple unequal crossing over. Moreover, the crossover constraint applies with as much force to segments larger than a gene as to segments within a gene, and this is shown to require that the human gamma (Gly) hemoglobin gene lie to the left, rather than to the right, of the other non-alpha human hemoglobin genes, a conclusion for which there is no direct genetic evidence currently available. PMID:892425

  9. Suitability of teicoplanin-aglycone bonded stationary phase for simulated moving bed enantioseparation of racemic amino acids employing composition-constrained eluents.

    PubMed

    Bechtold, Matthias; Heinemann, Matthias; Panke, Sven

    2006-04-28

    The suitability of a teicoplanin-aglycone based chiral stationary phase for the simulated moving bed (SMB) enantioseparation of amino acids under enzyme-compatible conditions was shown following a procedure that is based solely on model-based simulations and HPLC experiments. A set of eight amino acids could be separated employing aqueous solvent containing only 10% (v/v) methanol, five of them with baseline resolution. The impact of type and concentration of organic modifier and pH modifier and pH on the separation characteristics of racemic methionine was investigated. Invariant elution profiles of repetitive adsorption/desorption of large amounts of methionine representing SMB-like conditions suggest stable adsorption behavior. Competitive loading capacity (20 mg of methionine per g of chiral stationary phase (CSP)) and SMB productivity (1 g of D-methionine per g of CSP per day) were predicted. The applied transport-dispersive model based on a competitive Bi-Langmuir isotherm was validated and its parameter estimated by model-based experimental analysis. PMID:16500665

  10. 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.

  11. 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

  12. 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.

  13. 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).

  14. Constrained superfields in supergravity

    NASA Astrophysics Data System (ADS)

    Dall'Agata, Gianguido; Farakos, Fotis

    2016-02-01

    We analyze constrained superfields in supergravity. We investigate the consistency and solve all known constraints, presenting a new class that may have interesting applications in the construction of inflationary models. We provide the superspace Lagrangians for minimal supergravity models based on them and write the corresponding theories in component form using a simplifying gauge for the goldstino couplings.

  15. Prompt transgression and gradual salinisation of the Black Sea during the early Holocene constrained by amino acid racemization and radiocarbon dating

    NASA Astrophysics Data System (ADS)

    Nicholas, William Anthony; Chivas, Allan R.; Murray-Wallace, Colin V.; Fink, David

    2011-12-01

    The restricted environment of the Black Sea is particularly sensitive to climatic and oceanographic fluctuations, owing to its connection with the Mediterranean Sea via the narrow Bosphorus Strait. The exact mechanism and timing of the most recent connection between these water bodies is controversial with debate on the post-glacial history of the Black Sea being dependent on radiocarbon dating for numerical ages. Here we present new 23 accelerator mass spectrometer (AMS) radiocarbon ages on peat and bivalve molluscs, supported by the first amino acid racemization (AAR) dating of bivalve molluscs ( n = 66) in the Black Sea. These data indicate infilling of the Black Sea during the early Holocene from an initial depth 107 m below sea-level, and 72 m below that of the Bosphorus Sill. These data combined with a review of previous radiocarbon ages has enabled a unique perspective on the post-glacial Black Sea. A sea-level curve based on conventional and AMS radiocarbon ages on peat and AMS-based ages on Dreissena sp. shells indicate the water-level in the earlier lake phase continued, until the early Holocene, to be lower than the Bosphorus Sill after the Younger Dryas ended. However, the absence of AMS-dated mollusc ages from the shelves of this basin older than the Younger Dryas is suggestive of sub-aerial exposure of the shelves, and comparatively lower water-levels when the Younger Dryas began. Thus post-glacial outflow from the Black Sea occurred through a lowered or open Bosphorus seaway. Basin-wide radiocarbon ages on peat indicate a prompt increase in water-level from that of the pre-existing and unconnected palaeo-lake during the earliest Holocene (9600-9200 cal a BP). Mass colonisation of the Black Sea by Mediterranean taxa did not occur until salinity had risen sufficiently, a process which took 1000 a or more from the initial transgressive event. This gradual change in salinity contrasts with the prompt transgression which would have taken ˜400 a to occur.

  16. Splice junctions are constrained by protein disorder

    PubMed Central

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

    2015-01-01

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

  17. Nitramino acids. Synthesis and biological evaluation of 1-nitroproline, 1-nitropipecolic acid, and N-nitrosarcosine.

    PubMed

    Nagasawa, H T; Muldoon, W P; Shirota, F N

    1977-12-01

    The N-nitro derivatives of secondary alpha-amino acids, viz., 1-nitroproline (1a) (L and D), 1-nitro-DL-pipecolic acid (2a), and N-nitrosarcosine (3a), were prepared by the oxidation of the corresponding nitrosamino acids with peroxytrifluoroacetic acid. These nitramino acids (1a-3a) were not active against Escherichia coli, Candida albicans, Pseudomonas aeruginosa, or Mycobacterium smegmatis, and 1a and 2a did not show mutagenic activity in a Salmonella typhimurium TA-100 system, with or without added rat liver 9000g supernatant fraction. The marginal mutagenicity of 3a in this system suggests that additional work should be done to assess its carcinogenic-mutagenic potential. PMID:338899

  18. 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.

  19. Constraining entropic cosmology

    SciTech Connect

    Koivisto, Tomi S.; Mota, David F.; Zumalacárregui, Miguel E-mail: d.f.mota@astro.uio.no

    2011-02-01

    It has been recently proposed that the interpretation of gravity as an emergent, entropic phenomenon might have nontrivial implications to cosmology. Here several such approaches are investigated and the underlying assumptions that must be made in order to constrain them by the BBN, SneIa, BAO and CMB data are clarified. Present models of inflation or dark energy are ruled out by the data. Constraints are derived on phenomenological parameterizations of modified Friedmann equations and some features of entropic scenarios regarding the growth of perturbations, the no-go theorem for entropic inflation and the possible violation of the Bekenstein bound for the entropy of the Universe are discussed and clarified.

  20. 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.

  1. 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.

  2. 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.

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

    PubMed

    Zuilhof, Han; Morokuma, Keiji

    2003-08-21

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

  4. 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. Adaptive power balancing efficiently predicts where critical paths are likely to occur and distributes power to those paths. Greater power, in turn, allows increased thread concurrency levels, CPU frequency/voltage, or both. We describe these techniques in detail and show that, compared to the state-of-the-art technique of using statically predetermined, per-node power caps, Conductor leads to a best-case performance improvement of up to 30%, and an average improvement of 19.1%. At the node level, an accurate power/performance model will aid in selecting the right configuration from a large set of available configurations. We present a novel approach to generate such a model offline using kernel clustering and multivariate linear regression. Our model requires only two iterations to select a configuration, which provides a significant advantage over exhaustive search-based strategies. We apply our model to predict power and performance for different applications using arbitrary configurations, and show that our model, when used with hardware frequency-limiting in a runtime system, selects configurations with significantly higher performance at a given power limit than those chosen by frequency-limiting alone. When applied to a set of 36 computational kernels from a range of applications, our model accurately predicts power and performance; our runtime system based on the model maintains 91% of optimal performance while meeting power constraints 88% of the time. When the runtime system violates a power constraint, it exceeds the constraint by only 6% in the average case, while simultaneously achieving 54% more performance than an oracle. Through the combination of the above contributions, we hope to provide guidance and inspiration to research practitioners working on runtime systems for power-constrained environments. We also hope this dissertation will draw attention to the need for software and runtime-controlled power management under power constraints at various levels, from the processor level to the cluster level.

  5. 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.

  6. 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.

  7. 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.

  8. Electronic structure and coordination to DNA fragments for coordination compounds of Cu(II) with amino-acids of composition CuA'A''

    SciTech Connect

    Budnikov, S.S.; Donu, S.V.; Chapurina, L.F.; Bersuker, I.B.; D'yakon, I.A.

    1985-11-01

    The MWH method has been used in calculations on the electronic structures of compounds of copper(II) with ..cap alpha..-amino-acids CuGLY(L-Ser), Cu(L-Alan) (L-Ser), CuGly/sub 2/ x H/sub 2/O, as well as for the free amino-acids: alanine, glycine, and serine. The proper energies and eigenvectors have been derived together with the charges on the atoms, which indicate the mode of coordination in these systems with DNA fragments involving the formation of sandwich complexes, and this provides a qualitative explanation of the differences in antitumor activity between these compounds.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Amino acid analogs for tumor imaging

    DOEpatents

    Goodman, Mark M. (Atlanta, GA); Shoup, Timothy (Decatur, GA)

    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.

  15. Amino acid analogs for tumor imaging

    DOEpatents

    Goodman, Mark M. (Atlanta, GA); Shoup, Timothy (Decatur, GA)

    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.

  16. Symplectic Quantization of Constrained Systems

    NASA Astrophysics Data System (ADS)

    Barcelos-Neto, J.; Wotzasek, C.

    It is shown that the symplectic two-form, which defines the geometrical structure of a constrained theory in the Faddeev-Jackiw approach, may be brought into a non-degenerated form, by an iterative implementation of the existing constraints. The resulting generalized brackets coincide with those obtained by the Dirac bracket approach, if the constrained system under investigation presents only second-class constraints. For gauge theories, a symmetry breaking term must be supplemented to bring the symplectic form into a non-singular configuration. At present, the singular symplectic two-form provides directly the generators of the time independent gauge transformations.

  17. Generalized Constrained Canonical Correlation Analysis.

    ERIC Educational Resources Information Center

    Takane, Yoshio; Hwang, Heungsun

    2002-01-01

    Proposes a method for generalized constrained canonical correlation analysis (GCCANO) that incorporates external information on both rows and columns of data matrices. In this method, each set of variables is first decomposed into the sum of several submatrices according to the external information, and then canonical correlation analysis is…

  18. Generalized Constrained Multiple Correspondence Analysis.

    ERIC Educational Resources Information Center

    Hwang, Heungsun; Takane, Yoshio

    2002-01-01

    Proposes a comprehensive approach, generalized constrained multiple correspondence analysis, for imposing both row and column constraints on multivariate discrete data. Each set of discrete data is decomposed into several submatrices and then multiple correspondence analysis is applied to explore relationships among the decomposed submatrices.…

  19. Influence of Murchison Minerals on Hydrogen-Deuterium Exchange of Amino Acids

    NASA Astrophysics Data System (ADS)

    Lerner, N. R.

    1993-07-01

    The amino acids found on the Murchison meteorite are deuterium enriched. For the glycine-alanine fraction, delta D = +2448 per mil, and for the alpha-amino isobutyric acid fraction, delta D = +149 per mil [1]. In order to retain such levels of deuterium enrichment, the amino acids found in Murchison must have not only retained the deuterium enrichment of their interstellar precursors (delta D > +1500 per mil [2]) during synthesis, as has been recently shown [3], but they must have also retained their deuterium label during the aqueous alteration phase [4]. By measuring the rates of deuterium exchange of amino acids with D(sub)2O, limits can be set on the length of time and the conditions under which the Murchison parent body experienced an aqueous environment. The rates of hydrogen-deuterium exchange of nondeuterated glycine, alanine, alpha-amino isobutyric acid, and amino diacetic acid have been measured in D(sub)2O as a function of temperature, pH, and the presence of Murchison minerals. In addition to the amino and carboxylic hydrogens, only the alpha- hydrogens of glycine, alanine, and amino diacetic acid are found to exchange. Even for solutions maintained for weeks at temperatures as high as 120 degrees C, no exchange was observed with the hydrogens of the methyl groups of alanine or alpha-amino isobutyric acid. The rate of exchange for alpha-hydrogens of amino acids is first-order with respect to the amino acid concentration. Increasing the pH of the solution markedly increases the rate of exchange. For example, at 115 degrees C and pH 4.0, 7.0, and 10 the rates are 14, 30, and 125 yr^-1 respectively for glycine and 2.0, 3.5, and 14 yr^-1 respectively for alanine. In a pH-6.0 D(sub)2O solution of amino acids containing Murchison dust the rates are 135 yr^-1 for glycine and 32 yr^-1 for alanine, rates close to those for the pH 10 solution. Activation energies for exchange were obtained from Arrhenius plots constructed from measurements made between 70 degrees C and 155 degrees C in solutions containing Murchison dust. For both glycine and alanine the activation energy is -25 kcal/mole. Using this value, we have calculated the half-lives for complete exchange of the alpha-hydrogens of glycine and alanine for the temperature range thought to have existed on the parent body during aqueous alteration [5]. The half-lives at 0 degrees C and 20 degrees C are 7500 yr and 300 yr respectively for glycine and 55,000 yr and 2100 yr respectively for alanine. Murchison amino acid fraction IV [1] was known to contain impurities and hence the measured delta D value represents a lower limit for alpha-amino isobutyric acid. Assuming that all the deuterium recovered from fraction IV came from alpha-amino isobutryric acid, and that one atom of nitrogen is recovered for each molecule of alpha-amino isobutyric acid, a maximum delta D value of +2600 per mil can be calculated for this amino acid. This is comparable to delta D for the glycine-alanine fraction, which is mainly glycine [6]. In an aqueous environment glycine loses deuterium relatively rapidly while alpha-amino isobutyric acid does not undergo exchange. Hence the similarity in the delta D values of both fractions indicates that the period of aqueous alteration is less than the half-life for hydrogen-deuterium exchange of glycine. References: [1] Pizzarello S. et al. (1991) GCA, 55, 905-910. [2] Zinner E. (1988) In Meteorites and the Early Solar System (J. R. Kerridge and M. S. Matthews, eds.), 956-983, Univ. of Arizona. [3] Lerner N. R. et al. (1993) GCA, in press. [4] Bunch T. E. and Chang S. (1980) GCA, 44, 1543-1577. [5] Clayton R. N. and Mayeda T. K. (1984) EPSL, 67, 151-161. [6] Shock E. L. and Shulte M. D. (1990) GCA, 54, 3159-3173.

  20. Solid-Phase Synthesis of Tetrahydropyridazinedione-Constrained Peptides

    PubMed Central

    2015-01-01

    The design and solid-phase synthesis of tetrahydropyridazine-3,6-dione (Tpd) peptidomimetics derived from backbone-aminated peptides is reported. The described protocol features the synthesis of chiral α-hydrazino acids suitable for chemoselective incorporation into growing peptide chains. Acid-catalyzed cyclization to form the Tpd ring during cleavage affords the target peptidomimetics in good yield and purity. The scope of Tpd incorporation is demonstrated through the synthesis of constrained peptides featuring nucleophilic/electrophilic side chains and sterically encumbered α-substituted hydrazino acid residues. PMID:25295511

  1. Constrained Multiobjective Biogeography Optimization Algorithm

    PubMed Central

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

    2014-01-01

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

  2. Constrained multiobjective biogeography optimization algorithm.

    PubMed

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

    2014-01-01

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

  3. Diameter-Constrained Steiner Tree

    NASA Astrophysics Data System (ADS)

    Ding, Wei; Lin, Guohui; Xue, Guoliang

    Given an edge-weighted undirected graph G = (V,E,c,w), where each edge e ∈ E has a cost c(e) and a weight w(e), a set S ⊆ V of terminals and a positive constant D 0, we seek a minimum cost Steiner tree where all terminals appear as leaves and its diameter is bounded by D 0. Note that the diameter of a tree represents the maximum weight of path connecting two different leaves in the tree. Such problem is called the minimum cost diameter-constrained Steiner tree problem. This problem is NP-hard even when the topology of Steiner tree is fixed. In present paper we focus on this restricted version and present a fully polynomial time approximation scheme (FPTAS) for computing a minimum cost diameter-constrained Steiner tree under a fixed topology.

  4. Efficient transport of Am(III) from nitric acid medium using a new conformationally constrained (N,N,N',N'-tetra-2-ethylhexyl)7-oxabicyclo[2.2.1]heptane-2,3-dicarboxamide across a supported liquid membrane.

    PubMed

    Sharma, S; Panja, S; Ghosh, S K; Dhami, P S; Gandhi, P M

    2016-03-15

    Am(III) is one of the most hazardous radionuclide present in nuclear fuel cycle. A new conformationally constrained diamide, (N,N,N',N'-tetra-2-ethylhexyl)7-oxabicyclo[2.2.1]heptane-2,3-dicarboxamide (OBDA) was studied for Am(III) transport from HNO3 medium across a Supported Liquid Membrane. Transport rate was observed to be significantly fast with ∼95% transport of Am(III) within 1h using 0.1M OBDA in the presence of 15% isodecyl alcohol (IDA)/n-dodecane as carrier. The mechanism of transport was investigated by studying various parameters like feed HNO3/NaNO3 concentration, OBDA concentration in the membrane, membrane pore size, membrane thickness etc. From these studies, the mechanism of transport was found to be diffusion controlled with diffusion co-efficient value of 5.1×10(-6)cm(2)/s. The membrane was found to be highly selective for tri- and tetra-valent actinides, and trivalent lanthanides. OBDA based membrane was found to be stable for at least for ten consecutive cycles of operation. PMID:26685064

  5. 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.

  6. 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.

  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 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.

  9. Constrained Stochastic Extended Redundancy Analysis.

    PubMed

    DeSarbo, Wayne S; Hwang, Heungsun; Stadler Blank, Ashley; Kappe, Eelco

    2015-06-01

    We devise a new statistical methodology called constrained stochastic extended redundancy analysis (CSERA) to examine the comparative impact of various conceptual factors, or drivers, as well as the specific predictor variables that contribute to each driver on designated dependent variable(s). The technical details of the proposed methodology, the maximum likelihood estimation algorithm, and model selection heuristics are discussed. A sports marketing consumer psychology application is provided in a Major League Baseball (MLB) context where the effects of six conceptual drivers of game attendance and their defining predictor variables are estimated. Results compare favorably to those obtained using traditional extended redundancy analysis (ERA). PMID:24327066

  10. Constraining Lorentz violation with cosmology.

    PubMed

    Zuntz, J A; Ferreira, P G; Zlosnik, T G

    2008-12-31

    The Einstein-aether theory provides a simple, dynamical mechanism for breaking Lorentz invariance. It does so within a generally covariant context and may emerge from quantum effects in more fundamental theories. The theory leads to a preferred frame and can have distinct experimental signatures. In this Letter, we perform a comprehensive study of the cosmological effects of the Einstein-aether theory and use observational data to constrain it. Allied to previously determined consistency and experimental constraints, we find that an Einstein-aether universe can fit experimental data over a wide range of its parameter space, but requires a specific rescaling of the other cosmological densities. PMID:19113765

  11. 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.

  12. Quantum Annealing for Constrained Optimization

    NASA Astrophysics Data System (ADS)

    Hen, Itay; Spedalieri, Federico M.

    2016-03-01

    Recent advances in quantum technology have led to the development and manufacturing of experimental programmable quantum annealers that promise to solve certain combinatorial optimization problems of practical relevance faster than their classical analogues. The applicability of such devices for many theoretical and real-world optimization problems, which are often constrained, is severely limited by the sparse, rigid layout of the devices' quantum bits. Traditionally, constraints are addressed by the addition of penalty terms to the Hamiltonian of the problem, which, in turn, requires prohibitively increasing physical resources while also restricting the dynamical range of the interactions. Here, we propose a method for encoding constrained optimization problems on quantum annealers that eliminates the need for penalty terms and thereby reduces the number of required couplers and removes the need for minor embedding, greatly reducing the number of required physical qubits. We argue the advantages of the proposed technique and illustrate its effectiveness. We conclude by discussing the experimental feasibility of the suggested method as well as its potential to appreciably reduce the resource requirements for implementing optimization problems on quantum annealers and its significance in the field of quantum computing.

  13. Bayesian Constrained Local Models Revisited.

    PubMed

    Martins, Pedro; Henriques, Jo Ao F; Caseiro, Rui; Batista, Jorge

    2016-04-01

    This paper presents a novel Bayesian formulation for aligning faces in unseen images. Our approach revisits the Constrained Local Models (CLM) formulation where an ensemble of local feature detectors are constrained to lie within the subspace spanned by a Point Distribution Model (PDM). Fitting such a model to an image typically involves two main steps: a local search using a detector, obtaining response maps for each landmark (likelihood term) and a global optimization that finds the PDM parameters that jointly maximize all the detections at once. The so-called global optimization can be posed as a Bayesian inference problem, where the posterior distribution of the shape (and pose) parameters can be inferred in a maximum a posteriori (MAP) sense. This work introduces an extended Bayesian global optimization strategy that includes two novel additions: (1) to perform second order updates of the PDM parameters (accounting for their covariance) and (2) to model the underlying dynamics of the shape variations, encoded in the prior term, by using recursive Bayesian estimation. Extensive evaluations were performed against state-of-the-art methods on several standard datasets (IMM, BioID, XM2VTS, LFW and FGNET Talking Face). Results show that the proposed approach significantly increases the fitting performance. PMID:26959675

  14. Constraining fundamental physics with Planck

    NASA Astrophysics Data System (ADS)

    Rocha, Graca

    2015-08-01

    The Λ CDM model assumes the validity of General Relativity on cosmological scales,as well as the physics of the standard model of particle physics. One possible extension, which mayhave motivations in fundamental physics, is to consider variations of dimensionless constants.Such variations can be constrained through tests on astrophysical scales.A number of physical systems have been used, spanning different time scales, to set constraints on variations of the fundamental constants.These range from atomic clocks in the laboratory at a redshift z = 0 to BBN at z ˜10^8 . However,apart from the claims of varying based on high resolution quasar absorption-line spectra,there is no other evidence for time-variable fundamental constants.CMB temperature anisotropies have been used extensively to constrain the variation of fundamental constants over cosmictimescales. In this talk I will present constraints on the temporal and spatial variation of fundamental constants such as fine structure constant, $\\alpha$, mass of the electron, $m_{e }$. etc. using CMB data with special focus on Planck data. I will also investigate the degeneracies with other cosmological parameters such as $H_{0}$ .

  15. Enhancement of hydroxyl radical generation in the Fenton reaction by alpha-hydroxy acid.

    PubMed

    Ali, M A; Konishi, T

    1998-09-01

    The effect of various organic acids on hydroxyl radical (.OH) generation in the Fenton reaction were examined by the ESR spin trapping technique, where 5,5-dimethyl-1-pyroline-N-nitroxide (DMPO) and alpha-phenyl-tert-butyl nitrone (PBN) were used as the spin trapping reagents. alpha-Hydroxy acids such as lactic acid, glycolic acid and 2-hydroxy isobutyric acid were found to markedly enhance .OH generation in the reaction. In contrast, beta-hydroxy acid, alpha-keto acid, esters of alpha-hydroxy acids, aldehydes and other straight chain organic acids had no such enhancing activity. alpha-Amino acids had also no enhancing effect. The results suggest that the alpha-hydroxy acid moiety is prerequisite for the enhancement of .OH generation in the Fenton reaction. Superoxide dismutase did not inhibit the enhancing effect of alpha-hydroxy acids whereas catalase completely inhibited the .OH generation. Thus, alpha-hydroxy acids directly enhanced the .OH generation via the Fenton reaction but not the Haber-Weiss reaction. Possible role of lactic acid manipulating .OH generation is discussed in relation to the ischemia-reperfusion cell damage. PMID:9784848

  16. 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.

  17. Cyclobutane amino acid analogues of furanomycin obtained by a formal [2 + 2] cycloaddition strategy promoted by methylaluminoxane.

    PubMed

    Avenoza, Alberto; Busto, Jesús H; Canal, Noelia; Corzana, Francisco; Peregrina, Jesús M; Pérez-Fernández, Marta; Rodríguez, Fernando

    2010-02-01

    The synthesis and conformational analysis of a new type of conformationally restricted alpha-amino acid analogue of the amino acid antibiotic furanomycin is presented. The restriction involves the cis-fused cyclobutane and tetrahydrofuran units, generating the unusual 2-oxabicyclo[3.2.0]heptane core, which is found in a great number of biologically active natural products. The synthetic strategy is based on a formal [2 + 2] cycloaddition between 2-(acylamino)acrylates as acceptor alkenes and 2,3-dihydrofuran as a donor alkene, promoted by bulky aluminum-derived Lewis acids, particularly by methylaluminoxane (MAO). Additionally, following the same strategy, the synthesis of furanomycin analogues incorporating the 2-oxabicyclo[4.2.0]octane is reported. PMID:20038109

  18. Enzymes for the resolution of alpha-tertiary-substituted carboxylic acid esters.

    PubMed

    Kallwass, H K; Yee, C; Blythe, T A; McNabb, T J; Rogers, E E; Shames, S L

    1994-07-01

    Aromatic alpha-amino-alpha-methyl acids and alpha-hydrazino-alpha-methyl acids are known aromatic amino acid decarboxylase inhibitors. Specific derivatives such as 2-amino-2-methyl-3-(3,4- dihydroxyphenyl)propanoate, Aldomet, and 2-hydrazino-2-methyl-3-(3,4- dihydroxyphenyl)propanoate, Lodosyn, have been developed as therapeutic agents to treat hypertension and Parkinson's disease, respectively. We recently reported a method for the kinetic resolution of the racemic esters of such compounds using a crude preparation of a novel enzyme catalyst from the yeast Candida lipolytica (Yee, C.; Blythe, T.A., McNabb, T.J.; Walts, A.E. J. Org. Chem. 1992, 57, 3525-3527). Here we report the purification and initial characterization of the active enzyme component, an enzyme given the name Candida lipolytica ester hydrolase (CLEH). CLEH was purified to > 95% homogeneity by chromatography on Matrex Blue B resin. The enzyme was found to be a glycoprotein with M(r) = 80,000-300,000. In addition to esterolytic activity, the enzyme was found to catalyze the hydrolysis of amides, anilides and peptides. Sequence analysis of internal peptides of CLEH revealed striking homology to a number of enzymes belonging to the group of serine carboxypeptidases (E.C. 3.4.16.1). One peptide aligned with the canonical serine carboxypeptidase active site sequence, GESYAG. Based on the structural relationship of CLEH to serine carboxypeptidases, three representative serine carboxypeptidases were evaluated for their utility in resolving racemic alpha-tertiary ester substrates and compared with the activity of CLEH. All enzymes revealed similarly high activity and enantioselectivity towards the alpha-hydrazino-alpha-methyl ester precursor of the Parkinson-drug Carbidopa. However, differences in enantioselectivity were observed with other alpha-tertiary-substituted ester substrates. Serine carboxypeptidase-catalyzed ester resolutions thus offer a new route to many sterically hindered homochiral alpha-amino, alpha-hydrazino and alpha-hydroxy carboxylic acids. PMID:7858960

  19. 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 brainthe cerebral cortexhas 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

  20. Towards spatially constrained gust models

    NASA Astrophysics Data System (ADS)

    Bos, René; Bierbooms, Wim; van Bussel, Gerard

    2014-06-01

    With the trend of moving towards 10-20 MW turbines, rotor diameters are growing beyond the size of the largest turbulent structures in the atmospheric boundary layer. As a consequence, the fully uniform transients that are commonly used to predict extreme gust loads are losing their connection to reality and may lead to gross overdimensioning. More suiting would be to represent gusts by advecting air parcels and posing certain physical constraints on size and position. However, this would introduce several new degrees of freedom that significantly increase the computational burden of extreme load prediction. In an attempt to elaborate on the costs and benefits of such an approach, load calculations were done on the DTU 10 MW reference turbine where a single uniform gust shape was given various spatial dimensions with the transverse wavelength ranging up to twice the rotor diameter (357 m). The resulting loads displayed a very high spread, but remained well under the level of a uniform gust. Moving towards spatially constrained gust models would therefore yield far less conservative, though more realistic predictions at the cost of higher computation time.

  1. 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.

  2. Hydrolysis of Al3+ from constrained molecular dynamics.

    PubMed

    Ikeda, Takashi; Hirata, Masaru; Kimura, Takaumi

    2006-02-21

    We investigated the hydrolysis reactions of Al(3+) in AlCl(3) aqueous solution using the constrained molecular dynamics based on the Car-Parrinello molecular-dynamics method. By employing the proton-aluminum coordination number as a reaction coordinate in the constrained molecular dynamics the deprotonation as well as dehydration processes are successfully realized. From our free-energy difference of DeltaG(0) approximately 8.0 kcal mol(-1) the hydrolysis constant pK(a1) is roughly estimated as 5.8, comparable to the literature value of 5.07. We show that the free-energy difference for the hydrolysis of Al(3+) in acidic conditions is at least 4 kcal mol(-1) higher than that in neutral condition, indicating that the hydrolysis reaction is inhibited by the presence of excess protons located around the hydrated ion, in agreement with the change of the predominant species by pH. PMID:16497053

  3. Photophysics of constrained tryptophan derivatives

    NASA Astrophysics Data System (ADS)

    Barkley, Mary D.; Tilstra, Luanne F.; McMahon, Lloyd P.; Vela, Marco A.; McLaughlin, Mark L.

    1990-05-01

    The aromatic amino acid tryptophan is widely used as an intrinsic fluorescent probe of the solution conformation and dynamics of peptides and proteins. However, its complex photophysics makes it difficult to interpret the fluorescence results. The biexponential fluorescence decay of the tryptophan zwitterion is presumed to be due to ground-state rotamers. Intramolecular proton and electron transfer reactions involving the excited indole ring and amino acid functional groups have been proposed to account for the lifetime differences among rotamers. Excited-state H-D exchange occurs at the C-4 position of indole. In the proposed mechanism for the photosubstitution reaction, the ammonium group loops back over the aromatic ring and assists the proton exchange.

  4. 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

    2016-02-01

    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. PMID:26759834

  5. 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.

  6. 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.

  7. Constrained crosstalk resistant adaptive noise canceller

    NASA Astrophysics Data System (ADS)

    Parsa, V.; Parker, P.

    1994-08-01

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

  8. Linearly constrained band selection for hyperspectral imagery

    NASA Astrophysics Data System (ADS)

    Wang, Su; Chang, Chein-I.

    2006-05-01

    Linearly constrained adaptive beamforming has been used to design hyperspectral target detection algorithms such as constrained energy minimization (CEM) and linearly constrained minimum variance (LCMV). It linearly constrains a desired target signature while minimizing interfering effects caused by other unknown signatures. This paper investigates this idea and further uses it to develop a new approach to band selection, referred to as linear constrained band selection (LCBS) for hyperspectral imagery. It interprets a band image as a desired target signature while considering other band images as unknown signatures. With this interpretation, the proposed LCBS linearly constrains a band image while also minimizing band correlation or dependence caused by other band images. As a result, two different methods referred to as Band Correlation Minimization (BCM) and Band Correlation Constraint (BCC) can be developed for band selection. Such LCBS allows one to select desired bands for data analysis. In order to determine the number of bands required to select, p, a recently developed concept, called virtual dimensionality (VD) is used to estimate the p. Once the p is determined, a set of p desired bands can be selected by LCBS. Finally, experiments are conducted to substantiate the proposed LCBS.

  9. 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

  10. Constrained simultaneous stitching measurement for aspheric surface

    NASA Astrophysics Data System (ADS)

    Wang, Weibo; Fan, Zhigang

    2013-01-01

    Significant errors could be result from multiple data sets due to error transfer and accumulation in each sub-aperture. The constrained simultaneous stitching method with error calibration is proposed to increase the stability of the numerical solution of the stitching algorithm. Global averaging error and constrained optimization are applied to simultaneous stitching after alignment errors calibrated. The goal of optimization and merit function is the minimization of the discrepancy between multiple data sets by including components related to various alignment errors. The values for stitching coefficients that fall within the unit sphere and minimize the mean square difference between and overlapping values can be found by iterative constrained optimization. At last, the full aperture wave-front was reconstructed by simultaneous stitching with the stitching coefficients required to remain within meaningful bounds.

  11. 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.

  12. 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.

  13. 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. PMID:26639411

  14. Continuum damage mechanics of constrained intergranular cavitation

    SciTech Connect

    Dib, M.W.; Rodin, G.J. . Dept. of Aerospace Engineering and Engineering Mechanics)

    1993-05-01

    A three-dimensional micromechanical model for polycrystalline materials undergoing constrained intergranular cavitation is proposed. The model combines advantages of phenomenological and micromechanical approaches, and can be calibrated from standard uniaxial creep data. When applied to creep analysis of two ferritic steels, the model accurately predicts the creep life under multiaxial stresses as well as the amount of creep damage.

  15. Constrained tri-sphere kinematic positioning system

    DOEpatents

    Viola, Robert J

    2010-12-14

    A scalable and adaptable, six-degree-of-freedom, kinematic positioning system is described. The system can position objects supported on top of, or suspended from, jacks comprising constrained joints. The system is compatible with extreme low temperature or high vacuum environments. When constant adjustment is not required a removable motor unit is available.

  16. A Model for Optimal Constrained Adaptive Testing.

    ERIC Educational Resources Information Center

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

    A model for constrained computerized adaptive testing is proposed in which the information in the test at the ability estimate is maximized subject to a large variety of possible constraints on the contents of the test. At each item-selection step, a full test is first assembled to have maximum information at the current ability estimate fixing…

  17. 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…

  18. 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…

  19. 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

  20. Constrained Principal Component Analysis: Various Applications.

    ERIC Educational Resources Information Center

    Hunter, Michael; Takane, Yoshio

    2002-01-01

    Provides example applications of constrained principal component analysis (CPCA) that illustrate the method on a variety of contexts common to psychological research. Two new analyses, decompositions into finer components and fitting higher order structures, are presented, followed by an illustration of CPCA on contingency tables and the CPCA of…

  1. Thermoregulation constrains effective warning signal expression.

    PubMed

    Lindstedt, Carita; Lindström, Leena; Mappes, Johanna

    2009-02-01

    Evolution of conspicuous signals may be constrained if animal coloration has nonsignaling as well as signaling functions. In aposematic wood tiger moth (Parasemia plantaginis) larvae, the size of a warning signal (orange patch on black body) varies phenotypically and genetically. Although a large warning signal is favored as an antipredator defense, we hypothesized that thermoregulation may constrain the signal size in colder habitats. To test this hypothesis, we conducted a factorial rearing experiment with two selection lines for larval coloration (small and large signal) and with two temperature manipulations (high and low temperature environment). Temperature constrained the size and brightness of the warning signal. Larvae with a small signal had an advantage in the colder environment, which was demonstrated by a faster development time and growth rate in the low temperature treatment, compared to larvae with a large signal. Interestingly, the larvae with a small signal were found more often on the plant than the ones with a large signal, suggesting higher basking activity of the melanic (small signal) individuals in the low temperature. We conclude that the expression of aposematic display is not only defined by its efficacy against predators; variation in temperature may constrain evolution of a conspicuous warning signal and maintain variation in it. PMID:19154362

  2. Automation of constrained-value business forms

    SciTech Connect

    Carson, M.L.; Beaumariage, T.G.; Greitzer, F.L.

    1993-05-01

    Expert systems can improve many business tasks. However, the nature of a constrained-value business form can result in a rule base that contains circular reasoning, unsuitable for expert system implementation. A methodology is presented for restructuring such a rule base for compatibility with a backward-chaining expert system.

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

    PubMed Central

    2014-01-01

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

  4. Extraterrestrial amino acids at the Cretaceous-Tertiary boundary

    SciTech Connect

    Lee, N.C.; Bada, J.L.

    1985-01-01

    The Earth has apparently been impacted by numerous large asteroids (>10 km diameter) or comets throughout its history. The rate of these collisions is roughly 2-4 x 10/sup -8/ events yr/sup -1/. The collision of a large asteroid or comet with the Earth could result in the addition of extra-terrestrial organic compounds. Certain types of meteorites (C2-carbonaceous chondrites) contain a vast assortment of organics, including amino acids, aliphatic and aromatic hydrocarbons, carboxylic acids, heterocycles, and various low molecular weight compounds. Molecules important in abiotic organic syntheses are present in comets, and thus these objects are also likely rich inorganics. The authors have investigated whether the amino acid ..cap alpha..-amino isobutyric acid (AIBA) can be used to ascertain whether extraterrestrial amino acids (ETAA) were added to the Earth's surface at the proposed asteroid or comet impact event associated with the Cretaceous-Tertiary (K-T) boundary. AIBA was utilized in these studies since it is a dominant amino acid in C2-carbonaceous meteorites and only rarely occurs in terrestrial organisms. Detection of AIBA was performed using OPA pre-column derivatization-HPLC methodology. Since the AIBA fluorescent yield is increased relative to non ..cap alpha..-methyl substituted amino acids at elevated temperatures, derivatization was carried out at both room temperature and 90/sup 0/C. Ocean sediments of various geological ages were analyzed. The results indicate that only in DSDP Leg 43 K-T boundary samples are detectable levels of AIBA present.

  5. 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.

  6. Constraining the braneworld with gravitational wave observations.

    PubMed

    McWilliams, Sean T

    2010-04-01

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

  7. A constrained supersymmetric left-right model

    NASA Astrophysics Data System (ADS)

    Hirsch, Martin; Krauss, Manuel E.; Opferkuch, Toby; Porod, Werner; Staub, Florian

    2016-03-01

    We present a supersymmetric left-right model which predicts gauge coupling unification close to the string scale and extra vector bosons at the TeV scale. The subtleties in constructing a model which is in agreement with the measured quark masses and mixing for such a low left-right breaking scale are discussed. It is shown that in the constrained version of this model radiative breaking of the gauge symmetries is possible and a SM-like Higgs is obtained. Additional CP-even scalars of a similar mass or even much lighter are possible. The expected mass hierarchies for the supersymmetric states differ clearly from those of the constrained MSSM. In particular, the lightest down-type squark, which is a mixture of the sbottom and extra vector-like states, is always lighter than the stop. We also comment on the model's capability to explain current anomalies observed at the LHC.

  8. Compilation for critically constrained knowledge bases

    SciTech Connect

    Schrag, R.

    1996-12-31

    We show that many {open_quotes}critically constrained{close_quotes} Random 3SAT knowledge bases (KBs) can be compiled into disjunctive normal form easily by using a variant of the {open_quotes}Davis-Putnam{close_quotes} proof procedure. From these compiled KBs we can answer all queries about entailment of conjunctive normal formulas, also easily - compared to a {open_quotes}brute-force{close_quotes} approach to approximate knowledge compilation into unit clauses for the same KBs. We exploit this fact to develop an aggressive hybrid approach which attempts to compile a KB exactly until a given resource limit is reached, then falls back to approximate compilation into unit clauses. The resulting approach handles all of the critically constrained Random 3SAT KBs with average savings of an order of magnitude over the brute-force approach.

  9. 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.

  10. Maximum constrained sparse coding for image representation

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Zhao, Danpei; Jiang, Zhiguo

    2015-12-01

    Sparse coding exhibits good performance in many computer vision applications by finding bases which capture highlevel semantics of the data and learning sparse coefficients in terms of the bases. However, due to the fact that bases are non-orthogonal, sparse coding can hardly preserve the samples' similarity, which is important for discrimination. In this paper, a new image representing method called maximum constrained sparse coding (MCSC) is proposed. Sparse representation with more active coefficients means more similarity information, and the infinite norm is added to the solution for this purpose. We solve the optimizer by constraining the codes' maximum and releasing the residual to other dictionary atoms. Experimental results on image clustering show that our method can preserve the similarity of adjacent samples and maintain the sparsity of code simultaneously.

  11. Elastic Domain Architectures in Constrained Layers

    NASA Astrophysics Data System (ADS)

    Slutsker, J.; Artemev, A.; Roytburd, A. L.

    2002-08-01

    The formation of elastic domains in transforming constrained films is a mechanism of relaxation of internal stresses caused by the misfit between a film and a substrate. The formation and evolution of polydomain microstructure as a result of the cubic-tetragonal transformation in a constrained layer are investigated by phase-field simulation. It has been shown that the three-domain hierarchical structure can be formed in the epitaxial films. With changing a fraction of out-of-plane domain there are two types of morphological transitions: from the three-domain structure to the two-domain one and from the hierarchical three-domain structure to the cellular three-domain structure. The results of the phase-field simulation are compared with available experimental data on 90deg domain structures in epitaxial ferroelectric films.

  12. On the path integral of constrained systems

    SciTech Connect

    Muslih, Sami I.

    2004-10-04

    Constrained Hamiltonian systems are investigated by using Gueler's method. Integration of a set of equations of motion and the action function is discussed. It is shown that the canonical path integral quantization is obtained directly as an integration over the canonical phase-space coordinates without any need to enlarge the initial phase-space by introducing extra- unphysical variables as in the Batalin-Fradkin-Tyutin (BFT) method. The abelian Proca model is analyzed by the two methods.

  13. Hybrid evolutionary programming for heavily constrained problems.

    PubMed

    Myung, H; Kim, J H

    1996-01-01

    A hybrid of evolutionary programming (EP) and a deterministic optimization procedure is applied to a series of non-linear and quadratic optimization problems. The hybrid scheme is compared with other existing schemes such as EP alone, two-phase (TP) optimization, and EP with a non-stationary penalty function (NS-EP). The results indicate that the hybrid method can outperform the other methods when addressing heavily constrained optimization problems in terms of computational efficiency and solution accuracy. PMID:8833746

  14. Constrained simulation of the Bullet Cluster

    SciTech Connect

    Lage, Craig; Farrar, Glennys

    2014-06-01

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

  15. Constraining neutron star matter with quantum chromodynamics

    SciTech Connect

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

    2014-07-10

    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.

  16. Constraining RRc candidates using SDSS colours

    NASA Astrophysics Data System (ADS)

    Banyai, E.; Plachy, E.; Molnar, L.; Dobos, L.; Szabo, R.

    2016-05-01

    The light variations of first-overtone RR Lyrae stars and contact eclipsing binaries can be difficult to distinguish. The Catalina Periodic Variable Star catalog contains several misclassified objects, despite the classification efforts by Drake et al. (2014). They used metallicity and surface gravity derived from spectroscopic data (from the SDSS database) to rule out binaries. Our aim is to further constrain the catalog using SDSS colours to estimate physical parameters for stars that did not have spectroscopic data.

  17. Cosmicflows Constrained Local UniversE Simulations

    NASA Astrophysics Data System (ADS)

    Sorce, Jenny G.; Gottlöber, Stefan; Yepes, Gustavo; Hoffman, Yehuda; Courtois, Helene M.; Steinmetz, Matthias; Tully, R. Brent; Pomarède, Daniel; Carlesi, Edoardo

    2016-01-01

    This paper combines observational data sets and cosmological simulations to generate realistic numerical replicas of the nearby Universe. The latter are excellent laboratories for studies of the non-linear process of structure formation in our neighbourhood. With measurements of radial peculiar velocities in the local Universe (cosmicflows-2) and a newly developed technique, we produce Constrained Local UniversE Simulations (CLUES). To assess the quality of these constrained simulations, we compare them with random simulations as well as with local observations. The cosmic variance, defined as the mean one-sigma scatter of cell-to-cell comparison between two fields, is significantly smaller for the constrained simulations than for the random simulations. Within the inner part of the box where most of the constraints are, the scatter is smaller by a factor of 2 to 3 on a 5 h-1 Mpc scale with respect to that found for random simulations. This one-sigma scatter obtained when comparing the simulated and the observation-reconstructed velocity fields is only 104 ± 4 km s-1, i.e. the linear theory threshold. These two results demonstrate that these simulations are in agreement with each other and with the observations of our neighbourhood. For the first time, simulations constrained with observational radial peculiar velocities resemble the local Universe up to a distance of 150 h-1 Mpc on a scale of a few tens of megaparsecs. When focusing on the inner part of the box, the resemblance with our cosmic neighbourhood extends to a few megaparsecs (<5 h-1 Mpc). The simulations provide a proper large-scale environment for studies of the formation of nearby objects.

  18. 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.

  19. 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.

  20. Diversification on an ecologically constrained adaptive landscape.

    PubMed

    Wellborn, Gary A; Broughton, Richard E

    2008-06-01

    We used phylogenetic analysis of body-size ecomorphs in a crustacean species complex to gain insight into how spatial complexity of ecological processes generates and maintains biological diversity. Studies of geographically widespread species of Hyalella amphipods show that phenotypic evolution is tightly constrained in a manner consistent with adaptive responses to alternative predation regimes. A molecular phylogeny indicates that evolution of Hyalella ecomorphs is characterized by parallel evolution and by phenotypic stasis despite substantial levels of underlying molecular change. The phylogeny suggests that species diversification sometimes occurs by niche shifts, and sometimes occurs without a change in niche. Moreover, diversification in the Hyalella ecomorphs has involved the repeated evolution of similar phenotypic forms that exist in similar ecological settings, a hallmark of adaptive evolution. The evolutionary stasis observed in clades separated by substantial genetic divergence, but existing in similar habitats, is also suggestive of stabilizing natural selection acting to constrain phenotypic evolution within narrow bounds. We interpret the observed decoupling of genetic and phenotypic diversification in terms of adaptive radiation on an ecologically constrained adaptive landscape, and suggest that ecological constraints, perhaps acting together with genetic and functional constraints, may explain the parallel evolution and evolutionary stasis inferred by the phylogeny. PMID:18522695

  1. Constrained Implants in Total Knee Replacement.

    PubMed

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

    2015-05-01

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

  2. 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.

  3. 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

  4. An axiomatic characterization of the strong constrained egalitarian solution

    NASA Astrophysics Data System (ADS)

    Llerena, Francesc; Vilella, Cori

    2012-09-01

    In this paper we axiomatize the strong constrained egalitarian solution (Dutta and Ray, 1991) over the class of weak superadditive games using constrained egalitarianism, order-consistency, and converse order-consistency.

  5. Characterization of neutral amino acid transport in a marine pseudomonad.

    PubMed Central

    Fein, J E; MacLeod, R A

    1975-01-01

    The transport of neutral amino acids in marine pseudomonad B-16 (ATCC 19855) has been investigated. From patterns of competitive inhibition, mutant analysis, and kinetic data, two active transport systems with overlapping substrate specificities were distinguished and characterized. One system (DAG) served glycine, D-alanine, D-serine, and alpha-aminoisobutyric acid (AIB) and, to a lesser extent, L-alanine and possibly other related neutral D- and L-amino acids. The other system (LIV) showed high stereospecificity for neutral amino acids with the L configuration and served primarily to transport L-leucine, L-isoleucine, L-valine, and L-alanine. This system exhibited low affinity for alpha-aminoisobutyric acid. Neither system was able to recognize structural analogues with modified alpha-amino or alpha-carboxyl groups. The kinetic parameters for L-alanine transport by the DAG and LIV systems were determined with appropriate mutants defective in either system. For L-alanine, Kt values of 4.6 X 10(-5) and 1.9 X 10(-4) M and Vmax values of 6.9 and 20.8 nmol/min per mg of cell dry weight were obtained for transport via the DAG and LIV systems respectively. alpha-Aminoisobutyric acid transport heterogeneity was also resolved with the mutants, and Kt values of 2.8 X 10(-5) and 1.4 X 10(-3) M AIB were obtained for transport via the DAG and LIV systems, respectively. Both systems required Na+ for activity (0.3 M Na+ optimal) and in this regard are distinguished from systems of similar substrate specificity reported in nonmarine bacteria. PMID:1194233

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. Quantization of soluble classical constrained systems

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  2. Modular implementations of linearly constrained beamformers

    NASA Astrophysics Data System (ADS)

    Liu, Tsung-Ching; Van Veen, Barry D.

    1991-12-01

    This paper describes a cascade decomposition of the generalized sidelobe canceller (GSC) implementation for linearly constrained minimum variance beamformers. The GSC is initially separated into an adaptive interference cancellation module followed by a non-adaptive beamformer. We prove that the adaptive interference cancellation module can be decomposed into a cascade of first (or higher) order adaptive interference cancellation modules, where the order corresponds to the number of adaptive degrees of freedom represented in the module. This distributes the computational burden associated with determining the adaptive weights over several lower order problems and facilitates simultaneous implementation of beamformers with differing numbers of adaptive degrees of freedom.

  3. 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.

  4. 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.

  5. Constraining Cosmological Parameters Using the Correlation Function

    NASA Astrophysics Data System (ADS)

    Warrener, Michael

    2016-01-01

    As the ESA prepares to launch the space telescope Euclid in 2020, we are interested in the possibility of using its galaxy clustering observations as a new tool to constrain the cosmological constants ΩM and ΩΛ. In this work, we use data simulated by Magneticum (a high-resolution cosmological structure simulation) to model the correlation functions of both galaxies and clusters at several redshifts. We fit analytic models to the simulated data centered at the baryon acoustic oscillation peak to extract ΩM and ΩΛ. We will report the results of our latest models, and their implication for the validity of the method.

  6. Medical knowledge evolution query constraining aspects.

    PubMed

    Eklund, Ann-Marie

    2011-01-01

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

  7. Newton modified barrier method in constrained optimization

    NASA Technical Reports Server (NTRS)

    Polyak, R.

    1990-01-01

    In this paper, we develop and investigate the Newton method for solving constrained (non-smooth) optimization problems. This approach is based on the modified barrier functions (MBF) theory and on the global converging step-size version of the Newton method for smooth unconstrained optimization. Due to the excellent properties of the MBF near primal-dual solution, the Newton modified barrier method (NMBM) has a better rate of convergence, better complexity bound, and is much more stable in the final stage of the computational process than the methods which are based on the classical barrier functions (CBF).

  8. 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.

  9. Parameter Identification by Iterative Constrained Regularization

    NASA Astrophysics Data System (ADS)

    Zama, Fabiana

    2015-11-01

    Parameter identification from noisy data is an ill-posed inverse problem and data noise leads to poor solutions. Regularization methods are necessary to obtain stable solutions. In this paper we introduce the regularization by means of an iteratively weighted constraint and define an algorithm to compute the weights and solve the constrained problems using as prior information the given measurements. Although this approach is general, in the present work we prove the convergence in the case of least squares data fit with ℓ2 regularization term. The data reported in the numerical experiments prove the efficiency and good quality of the results.

  10. Local structure of equality constrained NLP problems

    SciTech Connect

    Mari, J.

    1994-12-31

    We show that locally around a feasible point, the behavior of an equality constrained nonlinear program is described by the gradient and the Hessian of the Lagrangian on the tangent subspace. In particular this holds true for reduced gradient approaches. Applying the same ideas to the control of nonlinear ODE:s, one can device first and second order methods that can be applied also to stiff problems. We finally describe an application of these ideas to the optimization of the production of human growth factor by fed-batch fermentation.

  11. 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.

  12. 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.

  13. Extraterrestrial amino acids in Cretaceous/Tertiary boundary sediments at Stevns Klint, Denmark.

    PubMed

    Zhao, M; Bada, J L

    1989-06-01

    Since the discovery nearly a decade ago that Cretaceous/Tertiary (K/T) boundary layers are greatly enriched in iridium, a rare element in the Earth's crust, there has been intense controversy on the relationship between this Ir anomaly and the massive extinction of organisms ranging from dinosaurs to marine plankton that characterizes the K/T boundary. Convincing evidence suggests that both the Ir spike and the extinction event were caused by the collision of a large bolide (greater than 10 km in diameter) with the Earth. Alternative explanations claim that extensive, violent volcanism can account for the Ir, and that other independent causes were responsible for the mass extinctions. We surmise that the collision of a massive extraterrestrial object with the Earth may have produced a unique organic chemical signature because certain meteorites, and probably comets, contain organic compounds which are either rare or non-existent on the Earth. In contrast, no organic compounds would be expected to be associated with volcanic processes. Here we find that K/T boundary sediments at Stevns Klint, Denmark, contain both alpha-amino-isobutyric acid [AIB,(CH3)2CNH2COOH] and racemic isovaline [ISOVAL, CH3CH2(CH3)CNH2COOH], two amino acids that are exceedingly rare on the Earth but which are major amino acids in carbonaceous chondrites. An extraterrestrial source is the most reasonable explanation for the presence of these amino acids. PMID:2725679

  14. 3D constrained inversion of geophysical and geological information applying Spatial Mutually Constrained Inversion.

    NASA Astrophysics Data System (ADS)

    Nielsen, O. F.; Ploug, C.; Mendoza, J. A.; Martínez, K.

    2009-05-01

    The need for increaseding accuracy and reduced ambiguities in the inversion results has resulted in focus on the development of more advanced inversion methods of geophysical data. Over the past few years more advanced inversion techniques have been developed to improve the results. Real 3D-inversion is time consuming and therefore often not the best solution in a cost-efficient perspective. This has motivated the development of 3D constrained inversions, where 1D-models are constrained in 3D, also known as a Spatial Constrained Inversion (SCI). Moreover, inversion of several different data types in one inversion has been developed, known as Mutually Constrained Inversion (MCI). In this paper a presentation of a Spatial Mutually Constrained Inversion method (SMCI) is given. This method allows 1D-inversion applied to different geophysical datasets and geological information constrained in 3D. Application of two or more types of geophysical methods in the inversion has proved to reduce the equivalence problem and to increase the resolution in the inversion results. The use of geological information from borehole data or digital geological models can be integrated in the inversion. In the SMCI, a 1D inversion code is used to model soundings that are constrained in three dimensions according to their relative position in space. This solution enhances the accuracy of the inversion and produces distinct layers thicknesses and resistivities. It is very efficient in the mapping of a layered geology but still also capable of mapping layer discontinuities that are, in many cases, related to fracturing and faulting or due to valley fills. Geological information may be included in the inversion directly or used only to form a starting model for the individual soundings in the inversion. In order to show the effectiveness of the method, examples are presented from both synthetic data and real data. The examples include DC-soundings as well as land-based and airborne TEM-soundings. The SMCI here combines the capability of the DC- resistivity method to map resistive areas with the capability of the EM method to map conductive zones in order to produce models that are more in agreement with the expected geological formations. Furthermore, the results from the SMCI inversion are compared with traditional inversion methods. The comparison is made from resistivity maps where the resolution of the method can be evaluated with known lithology, water levels, etc. The results from SMCI inversion demonstrate significant improvement over those derived from standard 2D constrained inversion. The SMCI is applicable in general geological mapping, groundwater surveys, mineral exploration or other surveys where geophysical information of different types can be combined or where geological information is available.

  15. Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

    PubMed Central

    Koopmanschap, Gijs; Ruijter, Eelco

    2014-01-01

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

  16. Constrained Metric Learning by Permutation Inducing Isometries.

    PubMed

    Bosveld, Joel; Mahmood, Arif; Huynh, Du Q; Noakes, Lyle

    2016-01-01

    The choice of metric critically affects the performance of classification and clustering algorithms. Metric learning algorithms attempt to improve performance, by learning a more appropriate metric. Unfortunately, most of the current algorithms learn a distance function which is not invariant to rigid transformations of images. Therefore, the distances between two images and their rigidly transformed pair may differ, leading to inconsistent classification or clustering results. We propose to constrain the learned metric to be invariant to the geometry preserving transformations of images that induce permutations in the feature space. The constraint that these transformations are isometries of the metric ensures consistent results and improves accuracy. Our second contribution is a dimension reduction technique that is consistent with the isometry constraints. Our third contribution is the formulation of the isometry constrained logistic discriminant metric learning (IC-LDML) algorithm, by incorporating the isometry constraints within the objective function of the LDML algorithm. The proposed algorithm is compared with the existing techniques on the publicly available labeled faces in the wild, viewpoint-invariant pedestrian recognition, and Toy Cars data sets. The IC-LDML algorithm has outperformed existing techniques for the tasks of face recognition, person identification, and object classification by a significant margin. PMID:26595920

  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. Constraining dark matter through 21-cm observations

    NASA Astrophysics Data System (ADS)

    Valdés, M.; Ferrara, A.; Mapelli, M.; Ripamonti, E.

    2007-05-01

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

  19. Intersecting transcription networks constrain gene regulatory evolution

    PubMed Central

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

    2015-01-01

    Epistasis—the non-additive interactions between different genetic loci—constrains evolutionary pathways, blocking some and permitting others1–8. For biological networks such as transcription circuits, the nature of these constraints and their consequences are largely unknown. Here we describe the evolutionary pathways of a transcription network that controls the response to mating pheromone in yeasts9. A component of this network, the transcription regulator Ste12, has evolved two different modes of binding to a set of its target genes. In one group of species, Ste12 binds to specific DNA binding sites, while in another lineage it occupies DNA indirectly, relying on a second transcription regulator to recognize DNA. We show, through the construction of various possible evolutionary intermediates, that evolution of the direct mode of DNA binding was not directly accessible to the ancestor. Instead, it was contingent on a lineage-specific change to an overlapping transcription network with a different function, the specification of cell type. These results show that analyzing and predicting the evolution of cis-regulatory regions requires an understanding of their positions in overlapping networks, as this placement constrains the available evolutionary pathways. PMID:26153861

  20. User-constrained guidewire localization in fluoroscopy

    NASA Astrophysics Data System (ADS)

    Mazouer, Philippe; Chen, Terrence; Zhu, Ying; Wang, Peng; Durlak, Peter; Thiran, Jean-Philippe; Comaniciu, Dorin

    2009-02-01

    In this paper we present a learning-based guidewire localization algorithm which can be constrained by user inputs. The proposed algorithm automatically localizes guidewires in fluoroscopic images. In cases where the results are not satisfactory, the user can provide input to constrain the algorithm by clicking on the guidewire segment missed by the detection algorithm. The algorithm then re-localizes the guidewire and updates the result in less than 0.3 second. In extreme cases, more constraints can be provided until a satisfactory result is reached. The proposed algorithm can not only serve as an efficient initialization tool for guidewire tracking, it can also serve as an efficient annotation tool, either for cardiologists to mark the guidewire, or to build up a labeled database for evaluation. Through the improvement of the initialization of guidewire tracking, it also helps to improve the visibility of the guidewire during interventional procedures. Our study shows that even highly complicated guidewires can mostly be localized within 5 seconds by less than 6 clicks.

  1. 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

  2. Group Sparsity Constrained Automatic Brain Label Propagation.

    PubMed

    Liao, Shu; Zhang, Daoqiang; Yap, Pew-Thian; Wu, Guorong; Shen, Dinggang

    2012-01-01

    In this paper, we present a group sparsity constrained patch based label propagation method for multi-atlas automatic brain labeling. The proposed method formulates the label propagation process as a graph-based theoretical framework, where each voxel in the input image is linked to each candidate voxel in each atlas image by an edge in the graph. The weight of the edge is estimated based on a sparse representation framework to identify a limited number of candidate voxles whose local image patches can best represent the local image patch of each voxel in the input image. The group sparsity constraint to capture the dependency among candidate voxels with the same anatomical label is also enforced. It is shown that based on the edge weight estimated by the proposed method, the anatomical label for each voxel in the input image can be estimated more accurately by the label propagation process. Moreover, we extend our group sparsity constrained patch based label propagation framework to the reproducing kernel Hilbert space (RKHS) to capture the nonlinear similarity of patches among different voxels and construct the sparse representation in high dimensional feature space. The proposed method was evaluated on the NA0-NIREP database for automatic human brain anatomical labeling. It was also compared with several state-of-the-art multi-atlas based brain labeling algorithms. Experimental results demonstrate that our method consistently achieves the highest segmentation accuracy among all methods used for comparison. PMID:25328918

  3. A constrained acetabular component for recurrent dislocation.

    PubMed

    Khan, R J K; Fick, D; Alakeson, R; Haebich, S; de Cruz, M; Nivbrant, B; Wood, D

    2006-07-01

    We treated 34 patients with recurrent dislocation of the hip with a constrained acetabular component. Roentgen stereophotogrammetric analysis was performed to assess migration of the prosthesis. The mean clinical follow-up was 3.0 years (2.2 to 4.8) and the radiological follow-up was 2.7 years (2.0 to 4.8). At the latest review six patients had died and none was lost to follow-up. There were four acetabular revisions, three for aseptic loosening and one for deep infection. Another acetabular component was radiologically loose with progressive radiolucent lines in all Gruen zones and was awaiting revision. The overall rate of aseptic loosening was 11.8% (4 of 34). Roentgen stereophotogrammetric analysis in the non-revised components confirmed migration of up to 1.06 mm of translation and 2.32 degrees of rotation at 24 months. There was one case of dislocation and dissociation of the component in the same patient. Of the 34 patients, 33 (97.1%) had no further episodes of dislocation. The constrained acetabular component reported in our study was effective in all but one patient with instability of the hip, but the rate of aseptic loosening was higher than has been reported previously and requires further investigation. PMID:16798987

  4. Trajectory generation and constrained control of quadrotors

    NASA Astrophysics Data System (ADS)

    Tule, Carlos Alberto

    Unmanned Aerial Systems, although still in early development, are expected to grow in both the military and civil sectors. As part of the UAV sector, the Quadrotor helicopter platform has been receiving a lot of interest from various academic and research institutions because of their simplistic design and low cost to manufacture, yet remaining a challenging platform to control. Four different controllers were derived for the trajectory generation and constrained control of a quadrotor platform. The first approach involves the linear version of the Model Predictive Control (MPC) algorithm to solve the state constrained optimization problem. The second approach uses the State Dependent Coefficient (SDC) form to capture the system non-linearities into a pseudo-linear system matrix, which is used to derive the State Dependent Riccati Equation (SDRE) based optimal control. For the third approach, the SDC form is exploited for obtaining a nonlinear equivalent of the model predictive control. Lastly, a combination of the nonlinear MPC and SDRE optimal control algorithms is used to explore the feasibility of a near real-time nonlinear optimization technique.

  5. 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.

  6. 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. PMID:22509351

  7. 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.

  8. Constraining cosmology with the Halo Occupation Distribution

    NASA Astrophysics Data System (ADS)

    Tinker, Jeremy L.

    The bias of galaxies with respect to the underlying matter distribution has long been an obstacle to constraining cosmology from measurements of galaxy clustering. Recent advancements in quantifying bias have made it possible to model galaxy clustering from linear to strongly non-linear scales, creating unique methods through which to constrain cosmological parameters that are complementary to more standard, large-scale techniques. These advances are encapsulated in the Halo Occupation Distribution (HOD), in which the bias of galaxies is described at the level of individual dark matter halos. For a given cosmological model, the parameters that specify the number of galaxies that reside in each halo can be constrained by measurements of the galaxy correlation function. With these HOD parameters, the given cosmology model can be tested through a number of other clustering measures that are more sensitive to the underlying dark matter distribution. The clustering measures I investigate in this thesis are mass-to-light ratios, redshift-space distortions, and galaxy void statistics. Mass-to-light ratios of galaxy clusters are uniquely suited to the halo occupation approach because the HOD can specify the number of galaxies in a halo as a function of luminosity. Galaxy bias directly influences the amount of light per unit mass in a cosmological model. I combine HOD models with observational measurements of cluster M/L ratios to test varying cosmologies. Using the HOD to model galaxy clustering in redshift-space allows one to combine data from small and large scales to break the degeneracies that govern the application of models based on linear theory alone. I use numerical simulations to calibrate a new analytic model and apply this model to observations of the redshift-space correlation function from the Sloan Digital Sky Survey. Galaxy voids prove to be insensitive to the details of halo occupation or the cosmological model assumed. This makes void statistics a sensitive test for the underlying assumption of the HOD, which states that galaxy occupation is a function of halo mass only, and not dependent on larger- scale environment. Quantifying the limits of this assumption are necessary for confidence in the constraints the HOD places on cosmology, and for testing our current picture of galaxy formation.

  9. Constrained KP models as integrable matrix hierarchies

    SciTech Connect

    Aratyn, H.; Ferreira, L.A.; Gomes, J.F.; Zimerman, A.H.

    1997-03-01

    We formulate the constrained KP hierarchy (denoted by cKP {sub K+1,M}) as an affine [cflx sl](M+K+1) matrix integrable hierarchy generalizing the Drinfeld{endash}Sokolov hierarchy. Using an algebraic approach, including the graded structure of the generalized Drinfeld{endash}Sokolov hierarchy, we are able to find several new universal results valid for the cKP hierarchy. In particular, our method yields a closed expression for the second bracket obtained through Dirac reduction of any untwisted affine Kac{endash}Moody current algebra. An explicit example is given for the case [cflx sl](M+K+1), for which a closed expression for the general recursion operator is also obtained. We show how isospectral flows are characterized and grouped according to the semisimple {ital non-regular} element E of sl(M+K+1) and the content of the center of the kernel of E. {copyright} {ital 1997 American Institute of Physics.}

  10. Constraining dark sectors with monojets and dijets

    NASA Astrophysics Data System (ADS)

    Chala, Mikael; Kahlhoefer, Felix; McCullough, Matthew; Nardini, Germano; Schmidt-Hoberg, Kai

    2015-07-01

    We consider dark sector particles (DSPs) that obtain sizeable interactions with Standard Model fermions from a new mediator. While these particles can avoid observation in direct detection experiments, they are strongly constrained by LHC measurements. We demonstrate that there is an important complementarity between searches for DSP production and searches for the mediator itself, in particular bounds on (broad) dijet resonances. This observation is crucial not only in the case where the DSP is all of the dark matter but whenever — precisely due to its sizeable interactions with the visible sector — the DSP annihilates away so efficiently that it only forms a dark matter subcomponent. To highlight the different roles of DSP direct detection and LHC monojet and dijet searches, as well as perturbativity constraints, we first analyse the exemplary case of an axial-vector mediator and then generalise our results. We find important implications for the interpretation of LHC dark matter searches in terms of simplified models.

  11. Constrained optimisation and its application to scintigraphy.

    PubMed

    Boardman, A K

    1979-03-01

    Any instrument that records data will produce a distorted or degraded version of the input signal. For example, imaging equipment will produce a blurred image of the object, and in the case of scintigraphic imaging the blurs may be comparable to the size of the physiological structures being investigated. The process of refocusing is called, in mathematical terms, deconvolution. In scintigraphy most workers have implemented deconvolution based on Wiener filtering. The shortcomings of the Wiener method when applied to scintigraphy are identified and an alternative approach to deconvolution using constrained optimisation is presented. The mathematical derivation of the new restoring filter is given in terms of the discrete Fourier transform. The practical implementation of the method on a digital computer is described and, as an example, the result of deconvolving a brain scan is presented. PMID:450977

  12. Constraining nonstandard neutrino-electron interactions

    SciTech Connect

    Barranco, J.; Miranda, O. G.; Moura, C. A.; Valle, J. W. F.

    2008-05-01

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

  13. Mixed-Strategy Chance Constrained Optimal Control

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  14. Traveltime tomography and nonlinear constrained optimization

    SciTech Connect

    Berryman, J.G.

    1988-10-01

    Fermat's principle of least traveltime states that the first arrivals follow ray paths with the smallest overall traveltime from the point of transmission to the point of reception. This principle determines a definite convex set of feasible slowness models - depending only on the traveltime data - for the fully nonlinear traveltime inversion problem. The existence of such a convex set allows us to transform the inversion problem into a nonlinear constrained optimization problem. Fermat's principle also shows that the standard undamped least-squares solution to the inversion problem always produces a slowness model with many ray paths having traveltime shorter than the measured traveltime (an impossibility even if the trial ray paths are not the true ray paths). In a damped least-squares inversion, the damping parameter may be varied to allow efficient location of a slowness model on the feasibility boundary. 13 refs., 1 fig., 1 tab.

  15. 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.

  16. Perceived visual speed constrained by image segmentation.

    PubMed

    Verghese, P; Stone, L S

    1996-05-01

    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. PMID:8610014

  17. Regions of constrained maximum likelihood parameter identifiability

    NASA Technical Reports Server (NTRS)

    Lee, C.-H.; Herget, C. J.

    1975-01-01

    This paper considers the parameter identification problem of general discrete-time, nonlinear, multiple-input/multiple-output dynamic systems with Gaussian-white distributed measurement errors. Knowledge of the system parameterization is assumed to be known. Regions of constrained maximum likelihood (CML) parameter identifiability are established. A computation procedure employing interval arithmetic is proposed for finding explicit regions of parameter identifiability for the case of linear systems. It is shown that if the vector of true parameters is locally CML identifiable, then with probability one, the vector of true parameters is a unique maximal point of the maximum likelihood function in the region of parameter identifiability and the CML estimation sequence will converge to the true parameters.

  18. Constraining CO emission estimates using atmospheric observations

    NASA Astrophysics Data System (ADS)

    Hooghiemstra, P. B.

    2012-06-01

    We apply a four-dimensional variational (4D-Var) data assimilation system to optimize carbon monoxide (CO) emissions and to reduce the uncertainty of emission estimates from individual sources using the chemistry transport model TM5. In the first study only a limited amount of surface network observations from the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) is used to test the 4D-Var system. Uncertainty reduction up to 60% in yearly emissions is observed over well-constrained regions and the inferred emissions compare well with recent studies for 2004. However, since the observations only constrain total CO emissions, the 4D-Var system has difficulties separating anthropogenic and biogenic sources in particular. The inferred emissions are validated with NOAA aircraft data over North America and the agreement is significantly improved from the prior to posterior simulation. Validation with the Measurements Of Pollution In The Troposphere (MOPITT) instrument shows a slight improved agreement over the well-constrained Northern Hemisphere and in the tropics (except for the African continent). However, the model simulation with posterior emissions underestimates MOPITT CO total columns on the remote Southern Hemisphere (SH) by about 10%. This is caused by a reduction in SH CO sources mainly due to surface stations on the high southern latitudes. In the second study, we compare two global inversions to estimate carbon monoxide (CO) emissions for 2004. Either surface flask observations from NOAA or CO total columns from the MOPITT instrument are assimilated in a 4D-Var framework. In the Southern Hemisphere (SH) three important findings are reported. First, due to their different vertical sensitivity, the stations-only inversion increases SH biomass burning emissions by 108 Tg CO/yr more than the MOPITT-only inversion. Conversely, the MOPITT-only inversion results in SH natural emissions (mainly CO from oxidation of NMVOCs) that are 185 Tg CO/yr higher compared to the stations-only inversion. Second, MOPITT-only derived biomass burning emissions are reduced with respect to the prior which is in contrast to previous (inverse) modeling studies. Finally, MOPITT derived total emissions are significantly higher for South America and Africa compared to the stations-only inversion. This is likely due to a positive bias in the MOPITT V4 product. This bias is also apparent from validation with surface stations and ground-truth FTIR columns. In the final study we present the first inverse modeling study to estimate CO emissions constrained by both surface (NOAA) and satellite (MOPITT) observations using a bias correction scheme. This approach leads to the identification of a positive bias of maximum 5 ppb in MOPITT column-averaged CO mixing ratios in the remote Southern Hemisphere (SH). The 4D-Var system is used to estimate CO emissions over South America in the period 2006-2010 and to analyze the interannual variability (IAV) of these emissions. We infer robust, high spatial resolution CO emission estimates that show slightly smaller IAV due to fires compared to the Global Fire Emissions Database (GFED3) prior emissions. Moreover, CO emissions probably associated with pre-harvest burning of sugar cane plantations are underestimated in current inventories by 50-100%.

  19. Constraining MOND with Solar System Dynamics

    NASA Astrophysics Data System (ADS)

    Iorio, Lorenzo

    2008-02-01

    In this letter we investigate the deep Newtonian regime of the MOND paradigm from a purely phenomenological point of view by exploiting the least-square estimated corrections to the secular rates of the perihelia of the inner and of some of the outer planets of the Solar System by E.V. Pitjeva with the EPM2004 ephemerides. By using μ(x) ≈ 1 - k0(1/x)n for the interpolating MONDian function, and by assuming that k0, considered body-independent so to avoid violations of the equivalence principle, experiences no spatial variations throughout the Solar System we tightly constrain n with the ratios of the perihelion precessions for different pairs of planets. We find that the range 1 ≤ n ≤ 2 is neatly excluded at much more than 3 - σ level. Such a test would greatly benefit from the use of extra-precessions of perihelia independently estimated by other groups as well.

  20. Constraining The Hot Jupiter Kozai Mechanism Connection

    NASA Astrophysics Data System (ADS)

    Croll, Bryce; Murray, N.; Marcy, G. W.; Wright, J. T.; Cumming, A.

    2007-12-01

    We have performed a systematic analysis to search for long-term trends in the radial velocity residuals of more than 120 exoplanetary hosts from the California-Carnegie Planet Search team to confirm or constrain the role that the Kozai mechanism plays in causing the hot Jupiter pile-up (an excess of exoplanets with 3-4 d periods). These long-term linear trends are likely indicative of stellar or substellar companions that could have induced the known exoplanet to migrate to its present position via the Kozai mechanism. Preliminary results suggest that the frequency of long-term linear trends are statistically similar in the hot Jupiter and the rest of the exoplanetary sample, thus suggesting that Kozai migration is not responsible for the majority of hot Jupiters.

  1. Multiplier-continuation algorthms for constrained optimization

    NASA Technical Reports Server (NTRS)

    Lundberg, Bruce N.; Poore, Aubrey B.; Bing, Yang

    1989-01-01

    Several path following algorithms based on the combination of three smooth penalty functions, the quadratic penalty for equality constraints and the quadratic loss and log barrier for inequality constraints, their modern counterparts, augmented Lagrangian or multiplier methods, sequential quadratic programming, and predictor-corrector continuation are described. In the first phase of this methodology, one minimizes the unconstrained or linearly constrained penalty function or augmented Lagrangian. A homotopy path generated from the functions is then followed to optimality using efficient predictor-corrector continuation methods. The continuation steps are asymptotic to those taken by sequential quadratic programming which can be used in the final steps. Numerical test results show the method to be efficient, robust, and a competitive alternative to sequential quadratic programming.

  2. Arithmetic coding with constrained carry operations

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  3. Measuring component effects in constrained mixture experiments

    SciTech Connect

    Piepel, G.F.

    1981-07-01

    In a mixture experiment, the response to a mixture of q components is a function of the proportions of each in the mixture. Experimentation often takes place within a constraint region imposed by economic or theoretic restrictions on proportions of components. The experimenter's goal is usually twofold: (1) to determine which mixture components affect the response and (2) to identify component combinations which yield optimum results. Measures of the effect each component has on the response are helpful in achieving these goals. A new measure of component effects in constrained mixture experiments is compared to two previous suggestions. The three techniques are seen to use varying amounts of information about the size, shape and location of the constraint region and thus may yield different results. A more complete picture of the response surface is given by using all three techniques instead of any one, as is illustrated in an example.

  4. 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.

  5. Constraining Dark Matter with Merging Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Allen, Steven

    2006-10-01

    We propose to observe two extraordinary, high-redshift galaxy clusters from the Massive Cluster Survey (MACS). These targets have been selected as two of the best examples of major mergers in the MACS catalogue, with clear evidence for considerable offset between the hot X-ray emitting gas and optically luminous stellar material. Subaru and Hubble Space Telescope optical data for these systems have been gathered by us and will be used to carry out gravitational lensing reconstructions of the total cluster masses. XMM X-ray data will be used to probe the mass distribution of hot, baryonic gas, and produce detailed maps of its thermodynamic state. The combination of these two mass measurements will be used to constrain the properties of dark matter in these objects.

  6. 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.

  7. Constraining Paleoearthquake Slip Distributions with Coral Microatolls

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  8. Very constrained minimal supersymmetric standard models

    SciTech Connect

    Ellis, John; Olive, Keith A.; Santoso, Yudi; Spanos, Vassilis C.

    2004-09-01

    We consider very constrained versions of the minimal supersymmetric extension of the standard model (VCMSSMs) which, in addition to constraining the scalar masses m{sub 0} and gaugino masses m{sub 1/2} to be universal at some input scale, impose relations between the trilinear and bilinear soft supersymmetry-breaking parameters A{sub 0} and B{sub 0}. These relations may be linear, as in simple minimal supergravity models, or nonlinear, as in the Giudice-Masiero mechanism for generating the Higgs-mixing {mu} term. We discuss the application of the electroweak vacuum conditions in VCMSSMs, which may be used to make a prediction for tan{beta} as a function of m{sub 0} and m{sub 1/2} that is usually unique. We baseline the discussion of the parameter spaces allowed in VCMSSMs by updating the parameter space allowed in the CMSSM for fixed values of tan{beta} with no relation between A{sub 0} and B{sub 0} assumed a priori, displaying contours of B{sub 0} for a fixed input value of A{sub 0}, incorporating the latest CDF/D0 measurement of m{sub t} and the latest BNL measurement of g{sub {mu}}-2. We emphasize that phenomenological studies of the CMSSM are frequently not applicable to specific VCMSSMs, notably those based on minimal supergravity, which require m{sub 0}=m{sub 3/2} as well as A{sub 0}=B{sub 0}+m{sub 0}. We then display (m{sub 1/2},m{sub 0}) planes for selected VCMSSMs, treating in a unified way the parameter regions where either a neutralino or the gravitino is the lightest supersymmetric particle. In particular, we examine in detail the allowed parameter space for the Giudice-Masiero model.

  9. Diversity and plasticity in amino acid receptor subunits in the rat auditory brain stem.

    PubMed

    Sato, K; Shiraishi, S; Nakagawa, H; Kuriyama, H; Altschuler, R A

    2000-09-01

    Glutamate, gamma aminobutyric acid (GABA) and glycine receptors have different properties depending on the specific subunit combination utilized. The subunit composition of amino acid receptors may help to shape the responses of neurons and can provide a diversity of response properties in different neuronal types and regions. This allows a synaptic fine tuning for an optimization of processing requirements and may also allow for changes in response to changes in input. This article reviews the diversity that has been found in the subunit composition of GABA, glycine, alpha amino-3-hydroxy-5-methyl-4 isoxazole propionic acid and N-Methyl, D-aspartate (NMDA) receptors in the mammalian auditory brain stem and provides new data on how the NMDAR1 glutamate receptor subunit changes as a consequence of deafness. In the latter study, quantitative in situ hybridization was used to assess NMDAR1 mRNA expression in six cell types of the rat cochlear nucleus. A unilateral cochlear ablation was performed and expression determined in the ipsilateral and contralateral cochlear nucleus 5 and 20 days later. Significantly decreased expression, compared to normal, was found 5 days following deafness, in ipsilateral spherical bushy cells, octopus cells and shell neurons, but not in fusiform cells, corn cells or granule cells. At 20 days the expression was not significantly different from normal in any of the six cell types. PMID:10962180

  10. 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.

  11. Iron supply constrains producer communities in stream ecosystems.

    PubMed

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

    2015-05-01

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

  12. 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 by means of either its relative position with respect to the constraint axis (contact-free segments) or its angular position on the constraint surface (continuous contacts.) This formulation circumvents both drawbacks that afflict the conventional Lagrangian approach associated with the segmentation strategy. As the a priori unknown domain, viz. the rod length, is substituted for the known constraint axis, the free boundary problem and the associated isoperimetric constraints are converted into a classical two-point boundary value problem. Additionally, the description of the rod deflection by means of its eccentricity with respect to the constraint axis trivializes the assessment of the unilateral contact condition. Along continuous contacts, this formulation expresses the strain variables, measuring the rod change of shape, in terms of the geometric invariants of the constraint surface, and emphasizes the influence of the constraint local geometry on the reaction pressure. Formalizing the segmentation strategy, a computational model that exploits the Eulerian formulation of the rod governing equations is devised. To solve the quasi-static deflection of elastic rods constrained inside or around a tube-like surface, this computational model identifies the number of contacts, their nature (either discrete or continuous), and the rod configuration at the connections that satisfies the unilateral contact condition and preserves the rod integrity along the sequence of elementary problems.

  13. 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.

  14. Dynamic Nuclear Polarization as Kinetically Constrained Diffusion.

    PubMed

    Karabanov, A; Wiśniewski, D; Lesanovsky, I; Köckenberger, W

    2015-07-10

    Dynamic nuclear polarization (DNP) is a promising strategy for generating a significantly increased nonthermal spin polarization in nuclear magnetic resonance (NMR) and its applications that range from medicine diagnostics to material science. Being a genuine nonequilibrium effect, DNP circumvents the need for strong magnetic fields. However, despite intense research, a detailed theoretical understanding of the precise mechanism behind DNP is currently lacking. We address this issue by focusing on a simple instance of DNP-so-called solid effect DNP-which is formulated in terms of a quantum central spin model where a single electron is coupled to an ensemble of interacting nuclei. We show analytically that the nonequilibrium buildup of polarization heavily relies on a mechanism which can be interpreted as kinetically constrained diffusion. Beyond revealing this insight, our approach furthermore permits numerical studies of ensembles containing thousands of spins that are typically intractable when formulated in terms of a quantum master equation. We believe that this represents an important step forward in the quest of harnessing nonequilibrium many-body quantum physics for technological applications. PMID:26207453

  15. Equilibrium and transport properties of constrained systems

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Debasish

    2006-10-01

    Systems under external confinement and constraints often show interesting properties. In this thesis, we study some systems under external confinement. We begin by finding out the probability distribution of end-to-end separation of a Worm Like Chain (WLC) polymer whose ends are positionally (and orientationally) constrained. We use Monte-Carlo simulations (MC) and a theoretical mapping of the WLC to a quantum particle moving on the surface of an unit sphere to find multimodality in Helmholtz ensemble as a generic signature of semi-flexibility. Secondly, we study Laser Induced Freezing using a Kosterlitz-Thouless type renormalization group calculation and a restricted MC simulation to obtain phase diagrams for Hard Disk, Soft Disk and DLVO potentials. They show very good agreement with phase diagrams simulated by other groups. Lastly, we study the strain response and failure mechanism of a two-dimensional solid confined within a hard wall channel using MC and molecular dynamics simulations. We find a reversible plastic failure through solid-smectic coexistence and observe layering transitions. Mean field calculations can capture some of these features. We study the heat transport in this system thorugh nonequilibrium molecular dynamics simulations and find strong signatures of the transitions. We propose a simple free volume calculation that reproduces some qualitative features of the strain response of heat current for small strains.

  16. Constrained bounds on measures of entanglement

    SciTech Connect

    Datta, Animesh; Flammia, Steven T.; Shaji, Anil; Caves, Carlton M.

    2007-06-15

    Entanglement measures constructed from two positive, but not completely positive, maps on density operators are used as constraints in placing bounds on the entanglement of formation, the tangle, and the concurrence of 4N mixed states. The maps are the partial transpose map and the phi map introduced by Breuer [H.-P. Breuer, Phys. Rev. Lett. 97, 080501 (2006)]. The norm-based entanglement measures constructed from these two maps, called negativity and phi negativity, respectively, lead to two sets of bounds on the entanglement of formation, the tangle, and the concurrence. We compare these bounds and identify the sets of 4N density operators for which the bounds from one constraint are better than the bounds from the other. In the process, we present a derivation of the already known bound on the concurrence based on the negativity. We compute bounds on the three measures of entanglement using both the constraints simultaneously. We demonstrate how such doubly constrained bounds can be constructed. We discuss extensions of our results to bipartite states of higher dimensions and with more than two constraints.

  17. 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.

  18. Acoustic characteristics of listener-constrained speech

    NASA Astrophysics Data System (ADS)

    Ashby, Simone; Cummins, Fred

    2003-04-01

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

  19. Constrained filter optimization for subsurface landmine detection

    NASA Astrophysics Data System (ADS)

    Torrione, Peter A.; Collins, Leslie; Clodfelter, Fred; Lulich, Dan; Patrikar, Ajay; Howard, Peter; Weaver, Richard; Rosen, Erik

    2006-05-01

    Previous large-scale blind tests of anti-tank landmine detection utilizing the NIITEK ground penetrating radar indicated the potential for very high anti-tank landmine detection probabilities at very low false alarm rates for algorithms based on adaptive background cancellation schemes. Recent data collections under more heterogeneous multi-layered road-scenarios seem to indicate that although adaptive solutions to background cancellation are effective, the adaptive solutions to background cancellation under different road conditions can differ significantly, and misapplication of these adaptive solutions can reduce landmine detection performance in terms of PD/FAR. In this work we present a framework for the constrained optimization of background-estimation filters that specifically seeks to optimize PD/FAR performance as measured by the area under the ROC curve between two FARs. We also consider the application of genetic algorithms to the problem of filter optimization for landmine detection. Results indicate robust results for both static and adaptive background cancellation schemes, and possible real-world advantages and disadvantages of static and adaptive approaches are discussed.

  20. Constraining Carbon Cycle Feedback Using Paleodata

    NASA Astrophysics Data System (ADS)

    Abe-Ouchi, Ayako; Harrison, Sandy P.

    2009-04-01

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

  1. Constraining the Evolution of ZZ Ceti

    NASA Technical Reports Server (NTRS)

    Mukadam, Anjum S.; Kepler, S. O.; Winget, D. E.; Nather, R. E.; Kilic, M.; Mullally, F.; vonHippel, T.; Kleinman, S. J.; Nitta, A.; Guzik, J. A.

    2003-01-01

    We report our analysis of the stability of pulsation periods in the DAV star (pulsating hydrogen atmosphere white dwarf) ZZ Ceti, also called R548. On the basis of observations that span 31 years, we conclude that the period 213.13 s observed in ZZ Ceti drifts at a rate dP/dt 5 (5.5 plus or minus 1.9) x 10(exp -15) ss(sup -1), after correcting for proper motion. Our results are consistent with previous P values for this mode and an improvement over them because of the larger time base. The characteristic stability timescale implied for the pulsation period is |P||P(raised dot)|greater than or equal to 1.2 Gyr, comparable to the theoretical cooling timescale for the star. Our current stability limit for the period 213.13 s is only slightly less than the present measurement for another DAV, G117-B15A, for the period 215.2 s, establishing this mode in ZZ Ceti as the second most stable optical clock known, comparable to atomic clocks and more stable than most pulsars. Constraining the cooling rate of ZZ Ceti aids theoretical evolutionary models and white dwarf cosmochronology. The drift rate of this clock is small enough that we can set interesting limits on reflex motion due to planetary companions.

  2. Dynamic Nuclear Polarization as Kinetically Constrained Diffusion

    NASA Astrophysics Data System (ADS)

    Karabanov, A.; Wiśniewski, D.; Lesanovsky, I.; Köckenberger, W.

    2015-07-01

    Dynamic nuclear polarization (DNP) is a promising strategy for generating a significantly increased nonthermal spin polarization in nuclear magnetic resonance (NMR) and its applications that range from medicine diagnostics to material science. Being a genuine nonequilibrium effect, DNP circumvents the need for strong magnetic fields. However, despite intense research, a detailed theoretical understanding of the precise mechanism behind DNP is currently lacking. We address this issue by focusing on a simple instance of DNP—so-called solid effect DNP—which is formulated in terms of a quantum central spin model where a single electron is coupled to an ensemble of interacting nuclei. We show analytically that the nonequilibrium buildup of polarization heavily relies on a mechanism which can be interpreted as kinetically constrained diffusion. Beyond revealing this insight, our approach furthermore permits numerical studies of ensembles containing thousands of spins that are typically intractable when formulated in terms of a quantum master equation. We believe that this represents an important step forward in the quest of harnessing nonequilibrium many-body quantum physics for technological applications.

  3. Periodic Buckling Patterns On Constrained Elastic Shells

    NASA Astrophysics Data System (ADS)

    Marthelot, Joel; Lee, Anna; Brun, Pierre-Thomas; Lopez Jimenez, Francisco; Reis, Pedro M.

    Thin spherical shells range from nanometer-sized viruses to space vehicles. A pressure differential between the inner and outer part of the shell can result in the buckling and catastrophic failure of the structure. We revisit this classic buckling problem, depressurizing thin elastic shells, which are arrested from within by a concentric spherical mandrel. As a result, buckling is constrained to occur within the gap between the two. Above a critical pressure, dimples appear sequentially on the surface of the shell to form a robust periodic pattern. We perform precision desktop experiments to construct the bifurcation diagram of the process, and explore a range of geometric and material properties. A scaling analysis enables us to rationalize the dependence of the size of the dimples on both the radius of the shell and the radial gap between the shell and the inner rigid mandrel. Moreover, we characterize the process of nucleation and progression of the dimpled pattern front. Particular emphasis is given to the patterns obtained in the strongly nonlinear post-buckling regime where a network of sharp ridges forms.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Testing constrained sequential dominance models of neutrinos

    NASA Astrophysics Data System (ADS)

    Björkeroth, Fredrik; King, Stephen F.

    2015-12-01

    Constrained sequential dominance (CSD) is a natural framework for implementing the see-saw mechanism of neutrino masses which allows the mixing angles and phases to be accurately predicted in terms of relatively few input parameters. We analyze a class of CSD(n) models where, in the flavour basis, two right-handed neutrinos are dominantly responsible for the ‘atmospheric’ and ‘solar’ neutrino masses with Yukawa couplings to ({ν }e,{ν }μ ,{ν }τ ) proportional to (0,1,1) and (1,n,n-2), respectively, where n is a positive integer. These coupling patterns may arise in indirect family symmetry models based on A 4. With two right-handed neutrinos, using a χ 2 test, we find a good agreement with data for CSD(3) and CSD(4) where the entire Pontecorvo-Maki-Nakagawa-Sakata mixing matrix is controlled by a single phase η, which takes simple values, leading to accurate predictions for mixing angles and the magnitude of the oscillation phase | {δ }{CP}| . We carefully study the perturbing effect of a third ‘decoupled’ right-handed neutrino, leading to a bound on the lightest physical neutrino mass {m}1{{≲ }}1 meV for the viable cases, corresponding to a normal neutrino mass hierarchy. We also discuss a direct link between the oscillation phase {δ }{CP} and leptogenesis in CSD(n) due to the same see-saw phase η appearing in both the neutrino mass matrix and leptogenesis.

  9. 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.

  10. 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.

  11. Constraining the Properties of Cold Interstellar Clouds

    NASA Astrophysics Data System (ADS)

    Spraggs, Mary Elizabeth; Gibson, Steven J.

    2016-01-01

    Since the interstellar medium (ISM) plays an integral role in star formation and galactic structure, it is important to understand the evolution of clouds over time, including the processes of cooling and condensation that lead to the formation of new stars. This work aims to constrain and better understand the physical properties of the cold ISM by utilizing large surveys of neutral atomic hydrogen (HI) 21cm spectral line emission and absorption, carbon monoxide (CO) 2.6mm line emission, and multi-band infrared dust thermal continuum emission. We identify areas where the gas may be cooling and forming molecules using HI self-absorption (HISA), in which cold foreground HI absorbs radiation from warmer background HI emission.We are developing an algorithm that uses total gas column densities inferred from Planck and other FIR/sub-mm data in parallel with CO and HISA spectral line data to determine the gas temperature, density, molecular abundance, and other properties as functions of position. We can then map these properties to study their variation throughout an individual cloud as well as any dependencies on location or environment within the Galaxy.Funding for this work was provided by the National Science Foundation, the NASA Kentucky Space Grant Consortium, the WKU Ogden College of Science and Engineering, and the Carol Martin Gatton Academy for Mathematics and Science in Kentucky.

  12. FPGA design for constrained energy minimization

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Chang, Chein-I.; Cao, Mang

    2004-02-01

    The Constrained Energy Minimization (CEM) has been widely used for hyperspectral detection and classification. The feasibility of implementing the CEM as a real-time processing algorithm in systolic arrays has been also demonstrated. The main challenge of realizing the CEM in hardware architecture in the computation of the inverse of the data correlation matrix performed in the CEM, which requires a complete set of data samples. In order to cope with this problem, the data correlation matrix must be calculated in a causal manner which only needs data samples up to the sample at the time it is processed. This paper presents a Field Programmable Gate Arrays (FPGA) design of such a causal CEM. The main feature of the proposed FPGA design is to use the Coordinate Rotation DIgital Computer (CORDIC) algorithm that can convert a Givens rotation of a vector to a set of shift-add operations. As a result, the CORDIC algorithm can be easily implemented in hardware architecture, therefore in FPGA. Since the computation of the inverse of the data correlction involves a series of Givens rotations, the utility of the CORDIC algorithm allows the causal CEM to perform real-time processing in FPGA. In this paper, an FPGA implementation of the causal CEM will be studied and its detailed architecture will be also described.

  13. 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. PMID:26708088

  14. Scheduling Aircraft Landings under Constrained Position Shifting

    NASA Technical Reports Server (NTRS)

    Balakrishnan, Hamsa; Chandran, Bala

    2006-01-01

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

  15. Constraining sterile neutrinos using reactor neutrino experiments

    NASA Astrophysics Data System (ADS)

    Girardi, Ivan; Melon, Davide; Ohlsson, Tommy; Zhang, He; Zhou, Shun

    2014-08-01

    Models of neutrino mixing involving one or more sterile neutrinos have resurrected their importance in the light of recent cosmological data. In this case, reactor antineutrino experiments offer an ideal place to look for signatures of sterile neutrinos due to their impact on neutrino flavor transitions. In this work, we show that the high-precision data of the Daya Bay experiment constrain the 3+1 neutrino scenario imposing upper bounds on the relevant active-sterile mixing angle sin2 2 θ 14 ≲ 0.06 at 3 σ confidence level for the mass-squared difference Δm {41/2} in the range (10-3, 10-1) eV2. The latter bound can be improved by six years of running of the JUNO experiment, sin2 2 θ 14 ≲ 0.016, although in the smaller mass range Δm {41/2} ∈ (10-4, 10-3) eV2. We have also investigated the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters θ 13 and Δm {31/2} (at Daya Bay and JUNO), θ 12 and Δm {21/2} (at JUNO), and most importantly, the neutrino mass hierarchy (at JUNO). We find that, except for the obvious situation where Δm {41/2} ≲ Δm {31/2}, sterile states do not affect these measurements substantially.

  16. Contact symmetries of constrained quadratic Lagrangians

    NASA Astrophysics Data System (ADS)

    Dimakis, N.; Terzis, Petros A.; Christodoulakis, T.

    2016-01-01

    The conditions for the existence of (polynomial in the velocities) contact symmetries of constrained systems that are described by quadratic Lagrangians is presented. These Lagrangians mainly appear in mini-superspace reductions of gravitational plus matter actions. In the literature, one usually adopts a gauge condition (mostly for the lapse N) prior to searching for symmetries. This, however, is an unnecessary restriction which may lead to a loss of symmetries and consequently to the respective integrals of motion. A generalization of the usual procedure rests in the identification of the lapse function N as an equivalent degree of freedom and the according extension of the infinitesimal generator. As a result, conformal Killing tensors (with appropriate conformal factors) can define integrals of motion (instead of just Killing tensors used in the regular gauge fixed case). Additionally, rheonomic integrals of motion - whose existence is unique in this type of singular systems - of various orders in the momenta can be constructed. An example of a relativistic particle in a pp-wave space-time and under the influence of a quadratic potential is illustrated.

  17. A Constrained Tectonics Model for Coronal Heating

    NASA Astrophysics Data System (ADS)

    Ng, C. S.; Bhattacharjee, A.

    2008-03-01

    An analytical and numerical treatment is given of a constrained version of the tectonics model developed by Priest et al.. We begin with a uniform magnetic field B = B0hat z that is line-tied at the surfaces z = 0 and z = L. This initial configuration is twisted by photospheric footpoint motion that is assumed to depend on only one coordinate (x) transverse to the initial magnetic field. The geometric constraints imposed by our assumption preclude the occurrence of reconnection and secondary instabilities but enable us to follow for long times the dissipation of energy due to the effects of resistivity and viscosity. In this limit, we demonstrate that when the coherence time of random photospheric footpoint motion is much smaller by several orders of magnitude compared with the resistive diffusion time, the heating due to ohmic and viscous dissipation becomes independent of the resistivity of the plasma. Furthermore, we obtain scaling relations that suggest that even if reconnection and/or secondary instabilities were to limit the buildup of magnetic energy in such a model, the overall heating rate will still be independent of the resistivity.

  18. 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.

  19. Constraining uncertainties in terrestrial carbon cycle modeling

    NASA Astrophysics Data System (ADS)

    Kvalevg, M.; Myhre, G.

    2011-12-01

    Global climate models differ in their representation of uptake of CO2 in the biosphere. Our study focuses on constraining the uncertainty in terrestrial carbon cycle modeling by comparing climate model results to observed atmospheric CO2 concentrations. The goal is to improve the representations of the seasonal cycle of terrestrial carbon uptake in the land model. We use the NCAR Community Earth System Model (CESM) climate components CLM4CN and CAM4 to run a prognostic version of the coupled land-atmosphere model where the atmospheric CO2 concentration in CAM4 is interactively calculated. Atmospheric CO2 concentrations from the model are compared to observations provided by flux towers in the AMERIFLUX network through the FLUXNET database and from the WDCGG for year 2000. We compare model results from sensitivity studies using different Q10 and Vcmax parameterizations, which are important functions in calculating plant growth. The carbon uptake in the biosphere is also under anthropogenic influence through emission of nitrogen and ozone from air pollution. Whereas nitrogen limitations in the soil reduce land ecosystem response to increasing CO2 concentrations, nitrogen from anthropogenic emissions increases the nitrogen availability and hence stimulates plant growth. These two nitrogen effects as well as the damaging impact on plants due to tropospheric ozone fertilization have been included in this study.

  20. Aspartic acid

    MedlinePlus

    Aspartic acid is a nonessential amino acids . Amino acids are building blocks of proteins. "Nonessential" means that our ... this amino acid from the food we eat. Aspartic acid is also called asparaginic acid. Aspartic acid helps ...

  1. 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,…

  2. Constrained spectral clustering under a local proximity structure assumption

    NASA Technical Reports Server (NTRS)

    Wagstaff, Kiri; Xu, Qianjun; des Jardins, Marie

    2005-01-01

    This work focuses on incorporating pairwise constraints into a spectral clustering algorithm. A new constrained spectral clustering method is proposed, as well as an active constraint acquisition technique and a heuristic for parameter selection. We demonstrate that our constrained spectral clustering method, CSC, works well when the data exhibits what we term local proximity structure.

  3. 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

  4. 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,

  5. 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…

  6. Constraining blazar physics with polarization signatures

    NASA Astrophysics Data System (ADS)

    Zhang, Haocheng; Boettcher, Markus; Li, Hui

    2016-01-01

    Blazars are active galactic nuclei whose jets are directed very close to our line of sight. They emit nonthermal-dominated emission from radio to gamma-rays, with the radio to optical emissions known to be polarized. Both radiation and polarization signatures can be strongly variable. Observations have shown that sometimes strong multiwavelength flares are accompanied by drastic polarization variations, indicating active participation of the magnetic field during flares. We have developed a 3D multi-zone time-dependent polarization-dependent radiation transfer code, which enables us to study the spectral and polarization signatures of blazar flares simultaneously. By combining this code with a Fokker-Planck nonthermal particle evolution scheme, we are able to derive simultaneous fits to time-dependent spectra, multiwavelength light curves, and time-dependent optical polarization signatures of a well-known multiwavelength flare with 180 degree polarization angle swing of the blazar 3C279. Our work shows that with detailed consideration of light travel time effects, the apparently symmetric time-dependent radiation and polarization signatures can be naturally explained by a straight, helically symmetric jet pervaded by a helical magnetic field, without the need of any asymmetric structures. Also our model suggests that the excess in the nonthermal particles during flares can originate from magnetic reconnection events, initiated by a shock propagating through the emission region. Additionally, the magnetic field should generally revert to its initial topology after the flare. We conclude that such shock-initiated magnetic reconnection event in an emission environment with relatively strong magnetic energy can be the driver of multiwavelength flares with polarization angle swings. Future statistics on such observations will constrain general features of such events, while magneto-hydrodynamic simulations will provide physical scenarios for the magnetic field evolution; both can be tested against our model, obtaining further constraints on the particle acceleration mechanism, as well as magnetic field structure and evolution inside the blazar emission region.

  7. 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.

  8. 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.

  9. 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).

  10. Informed constrained spherical deconvolution (iCSD).

    PubMed

    Roine, Timo; Jeurissen, Ben; Perrone, Daniele; Aelterman, Jan; Philips, Wilfried; Leemans, Alexander; Sijbers, Jan

    2015-08-01

    Diffusion-weighted (DW) magnetic resonance imaging (MRI) is a noninvasive imaging method, which can be used to investigate neural tracts in the white matter (WM) of the brain. However, the voxel sizes used in DW-MRI are relatively large, making DW-MRI prone to significant partial volume effects (PVE). These PVEs can be caused both by complex (e.g. crossing) WM fiber configurations and non-WM tissue, such as gray matter (GM) and cerebrospinal fluid. High angular resolution diffusion imaging methods have been developed to correctly characterize complex WM fiber configurations, but significant non-WM PVEs are also present in a large proportion of WM voxels. In constrained spherical deconvolution (CSD), the full fiber orientation distribution function (fODF) is deconvolved from clinically feasible DW data using a response function (RF) representing the signal of a single coherently oriented population of fibers. Non-WM PVEs cause a loss of precision in the detected fiber orientations and an emergence of false peaks in CSD, more prominently in voxels with GM PVEs. We propose a method, informed CSD (iCSD), to improve the estimation of fODFs under non-WM PVEs by modifying the RF to account for non-WM PVEs locally. In practice, the RF is modified based on tissue fractions estimated from high-resolution anatomical data. Results from simulation and in-vivo bootstrapping experiments demonstrate a significant improvement in the precision of the identified fiber orientations and in the number of false peaks detected under GM PVEs. Probabilistic whole brain tractography shows fiber density is increased in the major WM tracts and decreased in subcortical GM regions. The iCSD method significantly improves the fiber orientation estimation at the WM-GM interface, which is especially important in connectomics, where the connectivity between GM regions is analyzed. PMID:25660002

  11. Motor Demands Constrain Cognitive Rule Structures.

    PubMed

    Collins, Anne Gabrielle Eva; Frank, Michael Joshua

    2016-03-01

    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

  12. Carbon-constrained health care enterprise.

    TOXLINE Toxicology Bibliographic Information

    Gell M

    2010-02-01

    RATIONALE: The health economy is a significant part of a national economy accounting typically for about 8% of GDP spent. As national economies respond to the dual challenges of severe economic turbulence on the global scale and climate change mitigation, the health economy is coming under increasing pressure to respond. Indications for sharp reductions in budgets and reductions in greenhouse gas emissions, such as carbon dioxide, are widespread.AIMS: In this paper an analysis is undertaken of the diverse forces acting on a typical health care enterprise. The forces, both economic and carbon related, are investigated in terms of their effects through the enterprise and across its boundaries on the supply, demand and waste sides. The overall aim is to show how the enterprise and whole supply chains may flip synchronously into a low-carbon evolutionary pathway.OBJECTIVES: By illustrating how different elements of the health care enterprise may respond to these developments, diverse opportunities for cost reduction, carbon reduction and product (goods and services) development are identified. These opportunities involve a variety of waste reduction and energy and materials conservation measures as well as new ways of collaborating with other enterprises going through similar transformations. The overall objective is to show that the carbon-constrained health care enterprise and the low-carbon health economy in which it sits may broaden its role in the coming decades to include a degree of responsibility for the health of the environment. This broader role is likely to supplement and entangle with the traditional role of the health economy, currently focused narrowly on human health, and lead to extensive organisational transformation, and infrastructure and product developments.

  13. Optimal control strategies for constrained relative orbits

    NASA Astrophysics Data System (ADS)

    Irvin, David Jonathan, Jr.

    The US Air Force's ability to protect space assets is enhanced by a proficiency in satellite proximity operations and Space Situational Awareness (SSA). In pursuit of that proficiency, this research develops a key capability of interest to mission planners; the ability of a deputy satellite to "hover" within a defined volume fixed in the vicinity of a chief satellite for an extended period of time. Previous research has developed initial methodologies for maintaining restricted teardrop hover orbits that exist in a plane fixed within the chief's local reference frame. These methods use the natural drift of the deputy satellite in the relative frame and impulsive thrust to keep the deputy in a bounded volume relative to the chief, but do not address fuel-optimality. This research extends and enhances that work by finding optimal trajectories, produced with discrete-thrusts, that minimize fuel spent per unit time and stay within the user-defined volume, thus providing a practical hover capability in the vicinity of the chief. The work assumes the Clohessy-Wiltshire closeness assumption between the deputy and chief is valid, however, elliptical chief orbits are allowed. Using the new methodology developed in this work, feasible closed and non-closed relative orbits are found and evaluated based on a fuel criterion and compared to an easily calculated continuous-thrust baseline. It is shown that in certain scenarios the discrete-thrust solution provides the lowest overall fuel cost. These scenarios are generally constrained to a smaller total time-of-flight. A simple check is proposed that enables the mission planner to make the correct strategy choice.

  14. 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

  15. The cost-constrained traveling salesman problem

    SciTech Connect

    Sokkappa, P.R.

    1990-10-01

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

  16. Constrained layer damping of a tennis racket

    NASA Astrophysics Data System (ADS)

    Harms, Michael R.; Gopal, H. S.; Lai, Ming-Lai; Cheng, Po-Jen

    1996-05-01

    When a tennis ball strikes a racket the impact causes vibrations which are distracting and undesirable to the player. In this work a passive damping system used to reduce vibration is described. The damping system uses a viscoelastic material along with a stiff composite constraining layer which is molded on the inner surface of the tennis racket frame. When a ball strikes a racket with this damping system the vibration causes shearing strain in the viscoelastic material. This strain energy is partially dissipated by the viscoelastic material, thereby increasing the racket damping. An analysis of the design was performed by creating a solid CAD model of the racket using Pro/Engineer. A finite element mesh was created and the mesh was then exported to ANSYS for the finite element modal analysis. The technique used to determine the damping ratio is the modal strain energy method. Experimental testing using accelerometers was conducted to determine the natural frequency and the damping ratio of rackets with and without the damping system. The natural frequency of the finite element model was benchmarked to the experimental data and damping ratios were compared. The modal strain energy method was found to be a very effective means of determining the damping ratio, and the frequencies and damping ratios correlated well with the experimental data. Using this analysis method, the effectiveness of the damping ratio to the change in key variables can be studied, minimizing the need for prototypes. This method can be used to determine an optimum design by maximizing the damping ratio with minimal weight addition.

  17. 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.

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

    PubMed

    Moon, Mary; Van Lanen, Steven G

    2010-09-01

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

  19. 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.

  20. 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 species-specific aerosol mass and size that are tracked in aerosol transport and climate models used to assess aerosol forcing and its anthropogenic components. This presentation will summarize where we stand on the development of the SAM-CAAM concept.

  1. Constraining duty cycles through a Bayesian technique

    NASA Astrophysics Data System (ADS)

    Romano, P.; Guidorzi, C.; Segreto, A.; Ducci, L.; Vercellone, S.

    2014-12-01

    The duty cycle (DC) of astrophysical sources is generally defined as the fraction of time during which the sources are active. It is used to both characterize their central engine and to plan further observing campaigns to study them. However, DCs are generally not provided with statistical uncertainties, since the standard approach is to perform Monte Carlo bootstrap simulations to evaluate them, which can be quite time consuming for a large sample of sources. As an alternative, considerably less time-consuming approach, we derived the theoretical expectation value for the DC and its error for sources whose state is one of two possible, mutually exclusive states, inactive (off) or flaring (on), as based on a finite set of independent observational data points. Following a Bayesian approach, we derived the analytical expression for the posterior, the conjugated distribution adopted as prior, and the expectation value and variance. We applied our method to the specific case of the inactivity duty cycle (IDC) for supergiant fast X-ray transients, a subclass of flaring high mass X-ray binaries characterized by large dynamical ranges. We also studied IDC as a function of the number of observations in the sample. Finally, we compare the results with the theoretical expectations. We found excellent agreement with our findings based on the standard bootstrap method. Our Bayesian treatment can be applied to all sets of independent observations of two-state sources, such as active galactic nuclei, X-ray binaries, etc. In addition to being far less time consuming than bootstrap methods, the additional strength of this approach becomes obvious when considering a well-populated class of sources (Nsrc ≥ 50) for which the prior can be fully characterized by fitting the distribution of the observed DCs for all sources in the class, so that, through the prior, one can further constrain the DC of a new source by exploiting the information acquired on the DC distribution derived from the other sources. R-Language, IDL, and C-language programs are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A97

  2. 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.

  3. Amino acid transport by intestinal brush border vesicles of a marine fish, Boops salpa.

    PubMed

    Bogé, Gérard; Roche, Hélène; Balocco, Catherine

    2002-01-01

    The transport of glycine, alanine, methionine and alpha amino-isobutyric acid (AIB) was studied on brush border membrane vesicles of Boops salpa, a marine fish. This transport was Na(+)-, Cl(-)- and pH-dependent. In the presence of NaCl, the uptake decreased as the pH increased from 5.5 to 8.5. With Na2SO4, the transport of the four amino acids was strongly reduced and the pH optimum was 7-8. In the presence of NaCl, amino acid transport was described by high and low affinity kinetics. The K(t) of the high-affinity component was comparable for glycine, alanine and methionine (0.1 mM), and was significantly enhanced for AIB (0.6 mM). The J(max) of the low affinity component was significantly lower for methionine and AIB than for glycine and alanine. Lowering the sodium concentration from 80 to 20 mM significantly increased K(t) and J(max) of the high-affinity component of glycine transport. Moreover, the kinetics of AIB transport under 100 mM Na(+) were similar to glycine kinetics under 40 mM Na(+) and the two amino acids competed for the same carrier(s). These results suggest that chloride ions are essential in neutral amino acid transport in Boops, that multiple saturable components are involved in this process, and that sodium plays an important role in the differences between the transport kinetics of amino acids. PMID:11742754

  4. 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.

  5. 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

    Although available three dimensional models of the lateral heterogeneity of the mantle, based upon the latest advances in seismic tomographic imaging (e.g. Ritsema et al., 2004, JGR) have provided profound insights into aspects of the mantle general circulation that drives continental drift, the compatibility of the tomography with explicit models of mantle mixing has remained illusive. For example, it remains a significant issue as to whether hydrodynamic models of the mixing process alone are able to reconcile the observed detailed pattern of surface plate velocities or whether explicit account must be taken of elastic fracture processes to account for the observed equipartition of kinetic energy between the poloidal and toroidal components of the surface velocity pattern (e.g. Forte and Peltier, 1987, JGR). It is also an issue as to the significance of the role of mantle chemical heterogeneity in determining the buoyancy distribution that drives mantle flow, especially given the expected importance of the spin transition of iron that onsets in the mid-lower mantle, at least in the ferropericlase component of the mineralogy. In this paper we focus upon the application of data assimilation techniques to the development of a model of mantle mixing that is consistent with a modern three dimensional tomography based model of seismic body wave heterogeneity. Beginning with the simplest possible scenario, that chemical heterogeneity is irrelevant to first order, we employ a three dimensional version of the recently published control volume based convection model of Shahnas and Peltier (2010, JGR) as the basis for the assimilation of a three dimensional density field inferred from our preferred tomography model (Ritsema et al., 2004, JGR). The convection model fully incorporates the dynamical influence of the Olivine-Spinel and Spinel-Perovskite+Magnesiowustite solid-solid phase transformations that bracket the mantle transition zone as well as the recently discovered 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.

  6. Minimally-Constrained Canonical Quantization of Geometrodynamics

    NASA Astrophysics Data System (ADS)

    Corne, Matthew Allan

    Finding a quantum theory of gravitation has been a long-standing problem. Einstein's theory of general relativity gives a classical description of gravity as the action of geometry on matter and matter on geometry. A theory of quantum gravity seeks to provide a quantum mechanical treatment of this process. In analogy with canonical quantization which, from classical mechanics and classical field theory, arrives at quantum mechanics and quantum field theory, canonical quantization of gravity is a family of different procedures following from the canonical (Hamiltonian) formulation of general relativity as pioneered by Dirac and Arnowitt, Deser, and Misner. Unfortunately, almost all of them exhibit pathologies, the most significant being "the problem of time evolution." Specifically, the problem arises with the use of a single operator equation both to describe quantization of the superhamiltonian constraint and as a means of enforcement of this constraint; this inhibits a meaningful notion of time-evolution. However, there is an approach that avoids this difficulty entirely: separation of the process of enforcement of constraints from the evolution of the quantum system. We investigate such an approach to gravity quantization known as minimally-constrained canonical (MC2) quantization. It is based on Wheeler's geometrodynamics and the identification of the correct dynamical degrees of freedom of the gravitational field as determined by York. Using MC2 quantization, we quantize only the dynamical degrees of freedom of gravitation. In this manuscript, we provide an exposition of this procedure as well as a presentation of other methods of canonical quantization of gravity with which to compare and contrast our approach. The first result is a justification of the way in which constraints are imposed. The problem of time evolution motivates imposing constraints as expectation values; the classical theory of general relativity---a theory with external gauge symmetry---requires, due to 3-diffeomorphism invariance, that the supermomentum constraints are automatically satisfied with the superhamiltonian constraint not automatically satisfied. In electromagnetism---a theory with internal gauge symmetry---the constraints can be applied at any point of the quantization. Practically, this manifests as selection of a particular field configuration which automatically satisfies the constraint(s). To investigate this result, we review MC2 quantization of anisotropic, homogeneous cosmologies and explore the procedure in at spacetime regarding electromagnetic plane waves, a charged particle in an electromagnetic field, and a scalar field to compare with prior approaches of quantization. The second result is an explicit demonstration that MC 2 quantization produces exactly the same results as previous quantization procedures applied to the plane wave electromagnetic field and to the scalar field. We discuss the charged particle in an electromagnetic field and how it differs, essentially by construction, from other approaches. Finally, we discuss future directions for gravity quantization including problems such as gravitational collapse, cosmology, and alternative theories of gravity.

  7. Affine Lie algebraic origin of constrained KP hierarchies

    SciTech Connect

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

    1995-07-01

    An affine {ital sl}({ital n}+1) algebraic construction of the basic constrained KP hierarchy is presented. This hierarchy is analyzed using two approaches, namely linear matrix eigenvalue problem on hermitian symmetric space and constrained KP Lax formulation and it is shown that these approaches are equivalent. The model is recognized to be the generalized non-linear Schroedinger @(s@Gs@Ns@LsS) hierarchy and it is used as a building block for a new class of constrained KP hierarchies. These constrained KP hierarchies are connected via similarity-Baecklund transformations and interpolate between@ s@Gs@Ns@LsS and multi-boson KP-Toda hierarchies. Our construction uncovers the origin of the Toda lattice structure behind the latter hierarchy. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  8. Faddeev-Jackiw brackets and quantization conditions of constrained systems

    NASA Astrophysics Data System (ADS)

    Müller-Kirsten, H. J. W.; Zhang, Jian-zu

    1995-02-01

    The correspondence between the Faddeev-Jackiw brackets and the quantization conditions of constrained systems is clarified: Only in the reduced phase space of the independent variables do the FJ brackets define the quantization conditions.

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

    SciTech Connect

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

    2010-09-27

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

  10. Constructing constrained invariant sets in multiscale continuum systems.

    PubMed

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

    2003-11-01

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

  11. 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.

  12. 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.

  13. 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.

  14. 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 States will experience some decrease in yield at a brine/USDW ratio of <0.2, due to high salinity (expressed as TDS). As a stand-alone contaminant, boron that is present in brine may pose the most significant problem in irrigation waters due to low boron tolerance of many crops, particularly fruit.

  15. Constrained Local UniversE Simulations: a Local Group factory

    NASA Astrophysics Data System (ADS)

    Carlesi, Edoardo; Sorce, Jenny G.; Hoffman, Yehuda; Gottlöber, Stefan; Yepes, Gustavo; Libeskind, Noam I.; Pilipenko, Sergey V.; Knebe, Alexander; Courtois, Hélène; Tully, R. Brent; Steinmetz, Matthias

    2016-05-01

    Near-field cosmology is practised by studying the Local Group (LG) and its neighbourhood. This paper describes a framework for simulating the `near field' on the computer. Assuming the Λ cold dark matter (ΛCDM) model as a prior and applying the Bayesian tools of the Wiener filter and constrained realizations of Gaussian fields to the Cosmicflows-2 (CF2) survey of peculiar velocities, constrained simulations of our cosmic environment are performed. The aim of these simulations is to reproduce the LG and its local environment. Our main result is that the LG is likely a robust outcome of the ΛCDMscenario when subjected to the constraint derived from CF2 data, emerging in an environment akin to the observed one. Three levels of criteria are used to define the simulated LGs. At the base level, pairs of haloes must obey specific isolation, mass and separation criteria. At the second level, the orbital angular momentum and energy are constrained, and on the third one the phase of the orbit is constrained. Out of the 300 constrained simulations, 146 LGs obey the first set of criteria, 51 the second and 6 the third. The robustness of our LG `factory' enables the construction of a large ensemble of simulated LGs. Suitable candidates for high-resolution hydrodynamical simulations of the LG can be drawn from this ensemble, which can be used to perform comprehensive studies of the formation of the LG.

  16. Constrained Local UniversE Simulations: A Local Group Factory

    NASA Astrophysics Data System (ADS)

    Carlesi, Edoardo; Sorce, Jenny G.; Hoffman, Yehuda; Gottlöber, Stefan; Yepes, Gustavo; Libeskind, Noam I.; Pilipenko, Sergey V.; Knebe, Alexander; Courtois, Hélène; Tully, R. Brent; Steinmetz, Matthias

    2016-02-01

    Near field cosmology is practiced by studying the Local Group (LG) and its neighbourhood. The present paper describes a framework for simulating the "near field" on the computer. Assuming the ΛCDM model as a prior and applying the Bayesian tools of the Wiener filter (WF) and constrained realizations of Gaussian fields to the Cosmicflows-2 (CF2) survey of peculiar velocities, constrained simulations of our cosmic environment are performed. The aim of these simulations is to reproduce the LG and its local environment. Our main result is that the LG is likely a robust outcome of the LCDM scenario when subjected to the constraint derived from CF2 data, emerging in an environment akin to the observed one. Three levels of criteria are used to define the simulated LGs. At the base level, pairs of halos must obey specific isolation, mass and separation criteria. At the second level the orbital angular momentum and energy are constrained and on the third one the phase of the orbit is constrained. Out of the 300 constrained simulations 146 LGs obey the first set of criteria, 51 the second and 6 the third. The robustness of our LG `factory' enables the construction of a large ensemble of simulated LGs. Suitable candidates for high resolution hydrodynamical simulations of the LG can be drawn from this ensemble, which can be used to perform comprehensive studies of the formation of the nature of the LG.

  17. Orthogonal projection-based fully constrained spectral unmixing

    NASA Astrophysics Data System (ADS)

    Song, Meiping; Li, Hsiao-Chi; Li, Yao; Gao, Cheng; Chang, Chein-I.

    2015-05-01

    OSP has been used widely in detection and abundance estimation for about twenty years. But it can't apply nonnegative and sum-to-one constraints when being used as an abundance estimator. Fully constrained least square algorithm does this well, but its time cost increases greatly as the number of endmembers grows. There are some tries for unmixing spectral under fully constraints from different aspects recently. Here in this paper, a new fully constrained unmixing algorithm is prompted based on orthogonal projection process, where a nearest projected point is defined onto the simplex constructed by endmembers. It is much easier, and it is faster than FCLS with the mostly same unmixing results. It is also compared with other two constrained unmixing algorithms, which shows its effectiveness too.

  18. The constrained NMSSM: mSUGRA and GMSB

    SciTech Connect

    Ellwanger, Ulrich

    2008-11-23

    We review different constrained versions of the NMSSM: the fully constrained cNMSSM with universal boundary conditions for gauginos and all soft scalar masses and trilinear couplings, and the NMSSM with soft terms from Gauge Mediated Supersymmetry Breaking. Regarding the fully constrained cNMSSM, after imposing LEP constraints and the correct dark matter relic density, one single parameter is sufficient to describe the entire Higgs and sparticle spectrum of the model, which then contains always a singlino LSP. The NMSSM with soft terms from GMSB is phenomenologically viable if (and only if) the singlet is allowed to couple directly to the messenger sector; then various ranges in parameter space satisfy constraints from colliders and precision observables. Motivations for and phenomenological features of extra U(1)' gauge symmetries are briefly reviewed.

  19. Constrained Potts mean field systems and their electronic implementation.

    PubMed

    Urahama, K; Yamada, T

    1994-09-01

    The Potts mean field approach for solving combinatorial optimization problems subject to winner-takes-all constraints is extended for problems subject to additional constraints. Extra variables corresponding to the Lagrange multipliers are incorporated into the Potts formulation for the additional constraints to be satisfied. The extended Potts equations are solved by using constrained gradient descent differential systems. This gradient system is proven theoretically to always produce a legal local optimum solution of the constrained combinatorial optimization problems. An analog electronic circuit implementing the present method is designed on the basis of the previous Potts electronic circuit. The performance of the present method is theoretically evaluated for the constrained maximum cut problems. The lower bound of the cut size obtained with the present method is proven to be the same as that of the basic Potts scheme for the unconstrained maximum cut problems. PMID:7866628

  20. Level repulsion in constrained Gaussian random-matrix ensembles

    NASA Astrophysics Data System (ADS)

    Papenbrock, T.; Pluhar, Z.; Weidenmüller, H. A.

    2006-08-01

    Introducing sets of constraints, we define new classes of random-matrix ensembles, the constrained Gaussian unitary (CGUE) and the deformed Gaussian unitary (DGUE) ensembles. The latter interpolate between the GUE and the CGUE. We derive a sufficient condition for GUE-type level repulsion to persist in the presence of constraints. For special classes of constraints, we extend this approach to the orthogonal and to the symplectic ensembles. A generalized Fourier theorem relates the spectral properties of the constraining ensembles with those of the constrained ones. We find that in the DGUEs, level repulsion always prevails at a sufficiently short distance and may be lifted only in the limit of strictly enforced constraints.

  1. 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

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

    NASA Technical Reports Server (NTRS)

    Tovichakchaikul, S.; Padovan, J.

    1983-01-01

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

  3. Fast Energy Minimization of large Polymers Using Constrained Optimization

    SciTech Connect

    Todd D. Plantenga

    1998-10-01

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

  4. Robust head pose estimation using locality-constrained sparse coding

    NASA Astrophysics Data System (ADS)

    Kim, Hyunduk; Lee, Sang-Heon; Sohn, Myoung-Kyu

    2015-12-01

    Sparse coding (SC) method has been shown to deliver successful result in a variety of computer vision applications. However, it does not consider the underlying structure of the data in the feature space. On the other hand, locality constrained linear coding (LLC) utilizes locality constraint to project each input data into its local-coordinate system. Based on the recent success of LLC, we propose a novel locality-constrained sparse coding (LSC) method to overcome the limitation of the SC. In experiments, the proposed algorithms were applied to head pose estimation applications. Experimental results demonstrated that the LSC method is better than state-of-the-art methods.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Amino acids

    MedlinePlus

    Amino acids are organic compounds that combine to form proteins . Amino acids and proteins are the building blocks of life. When proteins are digested or broken down, amino acids are left. The human body uses amino acids ...

  10. College Student Perceptions of Leadership: Empowering and Constraining Beliefs

    ERIC Educational Resources Information Center

    Shertzer, John E.; Schuh, John H.

    2004-01-01

    This study investigated college student perceptions of leadership and beliefs that both empower students towards and constrain students from involvement in leadership. Interviews were conducted with student leaders (students who held leadership positions) and disengaged students (students who had not held leadership positions). The student…

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

    NASA Astrophysics Data System (ADS)

    Martin, Jérôme; Ringeval, Christophe; Vennin, Vincent

    2014-10-01

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

  12. 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.…

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

    ERIC Educational Resources Information Center

    Salazar, R.; Tellez, G.

    2012-01-01

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

  14. 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…

  15. Solution of a Complex Least Squares Problem with Constrained Phase.

    PubMed

    Bydder, Mark

    2010-12-30

    The least squares solution of a complex linear equation is in general a complex vector with independent real and imaginary parts. In certain applications in magnetic resonance imaging, a solution is desired such that each element has the same phase. A direct method for obtaining the least squares solution to the phase constrained problem is described. PMID:21076627

  16. Information Retrieval by Constrained Spreading Activation in Semantic Networks.

    ERIC Educational Resources Information Center

    Cohen, Paul R.; Kjeldsen, Rick

    1987-01-01

    Describes GRANT, an expert system for finding sources of funding given research proposals. The architecture of GRANT and the implementation of constrained spreading activation (a modified search algorithm based on semantic memory) are described, and recall and precision rates are analyzed. (Author/LRW)

  17. 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

  18. 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…

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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

  4. 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…

  5. Relationships among Several Methods of Linearly Constrained Correspondence Analysis.

    ERIC Educational Resources Information Center

    Takane, Yoshio; And Others

    1991-01-01

    Formal relationships are explored among several methods of linearly constrained correspondence analysis. The seven methods considered fall within one of two classes corresponding to ways of imposing linear constraints: the reparameterization method, and the null space method. A connection between these classes is established through a lemma by C.…

  6. 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…

  7. 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…

  8. How well do different tracers constrain the firn diffusivity profile?

    NASA Astrophysics Data System (ADS)

    Trudinger, C. M.; Enting, I. G.; Rayner, P. J.; Etheridge, D. M.; Buizert, C.; Rubino, M.; Krummel, P. B.; Blunier, T.

    2013-02-01

    Firn air transport models are used to interpret measurements of the composition of air in firn and bubbles trapped in ice in order to reconstruct past atmospheric composition. The diffusivity profile in the firn is usually calibrated by comparing modelled and measured concentrations for tracers with known atmospheric history. However, in most cases this is an under-determined inverse problem, often with multiple solutions giving an adequate fit to the data (this is known as equifinality). Here we describe a method to estimate the firn diffusivity profile that allows multiple solutions to be identified, in order to quantify the uncertainty in diffusivity due to equifinality. We then look at how well different combinations of tracers constrain the firn diffusivity profile. Tracers with rapid atmospheric variations like CH3CCl3, HFCs and 14CO2 are most useful for constraining molecular diffusivity, while &delta:15N2 is useful for constraining parameters related to convective mixing near the surface. When errors in the observations are small and Gaussian, three carefully selected tracers are able to constrain the molecular diffusivity profile well with minimal equifinality. However, with realistic data errors or additional processes to constrain, there is benefit to including as many tracers as possible to reduce the uncertainties. We calculate CO2 age distributions and their spectral widths with uncertainties for five firn sites (NEEM, DE08-2, DSSW20K, South Pole 1995 and South Pole 2001) with quite different characteristics and tracers available for calibration. We recommend moving away from the use of a firn model with one calibrated parameter set to infer atmospheric histories, and instead suggest using multiple parameter sets, preferably with multiple representations of uncertain processes, to assist in quantification of the uncertainties.

  9. Palliative therapy with I-131 labeled bezylidenediphosphonic acid: In vivo kinetics and response to pain induced by bone metastases

    SciTech Connect

    Eisenhut, M.; Berberich, R.; Kimmig, B.; Oberhausen, E.; Georgi, P.; Zum Winkel, K.

    1985-05-01

    I-131 labeled ..cap alpha..-amino-(4-hydroxybenzylidene)diphosphonic acid (BDP3) was recently suggested as a palliative acting radiopharmaceutical against pain syndromes associated with disseminated bone metastases. Such an application was supported by the in vivo kinetics of I-131-BDP3 in rats. The authors investigated the palliative effectiveness of I-131-BDP3 in 18 patients with typical pain symptoms induced by bone metastases of various primary carcinoma. The blood clearance was rapid. More than 90% disappeared from the blood pool at 4 hr after injection. The excretion of the activity occured solely through the kidneys and the median total body retention at 48 hr was 51% (range 30-64%). The thyroid activity decreased during therapy indicating no cleavage reactions as long as I-131-BDP3 is bound to the bone tissue. The binding of I-131-BDP3 to bone is very long since the effective half life was in the order of magnitude of the physical half life. Additionally the effective half lifes in the metastatic ares (median 182 hr; range 177-205 hr) proved to be longer than in unaffected areas (145 hr; 140-165 hr). The palliative therapies were performed with doses of 6 - 48 mCi. The response amounted to 44% complete pain relief, 6% substantial pain relief, 22% minimal improvement and 28% no change. The duration of response ranged between 1 and 8 weeks.

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

    PubMed

    Jäntschi, Lorentz; Bolboacă, Sorana D

    2015-03-01

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

  11. A second-generation constrained reaction volume shock tube

    NASA Astrophysics Data System (ADS)

    Campbell, M. F.; Tulgestke, A. M.; Davidson, D. F.; Hanson, R. K.

    2014-05-01

    We have developed a shock tube that features a sliding gate valve in order to mechanically constrain the reactive test gas mixture to an area close to the shock tube endwall, separating it from a specially formulated non-reactive buffer gas mixture. This second-generation Constrained Reaction Volume (CRV) strategy enables near-constant-pressure shock tube test conditions for reactive experiments behind reflected shocks, thereby enabling improved modeling of the reactive flow field. Here we provide details of the design and operation of the new shock tube. In addition, we detail special buffer gas tailoring procedures, analyze the buffer/test gas interactions that occur on gate valve opening, and outline the size range of fuels that can be studied using the CRV technique in this facility. Finally, we present example low-temperature ignition delay time data to illustrate the CRV shock tube's performance.

  12. 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.

  13. ConStrains identifies microbial strains in metagenomic datasets.

    PubMed

    Luo, Chengwei; Knight, Rob; Siljander, Heli; Knip, Mikael; Xavier, Ramnik J; Gevers, Dirk

    2015-10-01

    An important fraction of microbial diversity is harbored in strain individuality, so identification of conspecific bacterial strains is imperative for improved understanding of microbial community functions. Limitations in bioinformatics and sequencing technologies have to date precluded strain identification owing to difficulties in phasing short reads to faithfully recover the original strain-level genotypes, which have highly similar sequences. We present ConStrains, an open-source algorithm that identifies conspecific strains from metagenomic sequence data and reconstructs the phylogeny of these strains in microbial communities. The algorithm uses single-nucleotide polymorphism (SNP) patterns in a set of universal genes to infer within-species structures that represent strains. Applying ConStrains to simulated and host-derived datasets provides insights into microbial community dynamics. PMID:26344404

  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. PMID:25966485

  15. Foldover-Free Mesh Warping for Constrained Texture Mapping.

    PubMed

    Ma, Yuewen; Zheng, Jianmin; Xie, Jian

    2015-03-01

    Mapping texture onto 3D meshes with positional constraints is a popular technique that can effectively enhance the visual realism of geometric models. Such a process usually requires constructing a valid mesh embedding satisfying a set of positional constraints, which is known to be a challenging problem. This paper presents a novel algorithm for computing a foldover-free piecewise linear mapping with exact positional constraints. The algorithm begins with an unconstrained planar embedding, followed by iterative constrained mesh transformations. At the heart of the algorithm are radial basis function (RBF)-based warping and the longest edge bisection (LEB)-based refinement. A delicate integration of the RBF-based warping and the LEB-based refinement provides a provably-foldover-free, smooth constrained mesh warping, which can handle a large number of constraints and output a visually pleasing mapping result without extra smoothing optimization. The experiments demonstrate the effectiveness of the proposed algorithm. PMID:26357069

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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.

  17. Constraining the noncommutative spectral action via astrophysical observations.

    PubMed

    Nelson, William; Ochoa, Joseph; Sakellariadou, Mairi

    2010-09-01

    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. PMID:20867510

  18. 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

    2014-01-01

    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. PMID:24739280

  19. Strongly Constrained and Appropriately Normed Semilocal Density Functional

    NASA Astrophysics Data System (ADS)

    Sun, Jianwei; Ruzsinszky, Adrienn; Perdew, John P.

    2015-07-01

    The ground-state energy, electron density, and related properties of ordinary matter can be computed efficiently when the exchange-correlation energy as a functional of the density is approximated semilocally. We propose the first meta-generalized-gradient approximation (meta-GGA) that is fully constrained, obeying all 17 known exact constraints that a meta-GGA can. It is also exact or nearly exact for a set of "appropriate norms," including rare-gas atoms and nonbonded interactions. This strongly constrained and appropriately normed meta-GGA achieves remarkable accuracy for systems where the exact exchange-correlation hole is localized near its electron, and especially for lattice constants and weak interactions.

  20. 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.

  1. ConStrains identifies microbial strains in metagenomic datasets

    PubMed Central

    Luo, Chengwei; Knight, Rob; Siljander, Heli; Knip, Mikael; Xavier, Ramnik J; Gevers, Dirk

    2015-01-01

    An important fraction of microbial diversity is harbored in strain individuality, so identification of conspecific bacterial strains is imperative for improved understanding of microbial community functions. Limitations in bioinformatics and sequencing technologies have to date precluded strain identification owing to difficulties in phasing short reads to faithfully recover the original strain-level genotypes, which have highly similar sequences. We present ConStrains, an open-source algorithm that identifies conspecific strains from metagenomic sequence data and reconstructs the phylogeny of these strains in microbial communities. The algorithm uses single-nucleotide polymorphism (SNP) patterns in a set of universal genes to infer within-species structures that represent strains. Applying ConStrains to simulated and host-derived data sets provides insights into microbial community dynamics. PMID:26344404

  2. Constrained Path Monte Carlo with Matrix Product State trial wavefunctions

    NASA Astrophysics Data System (ADS)

    Chung, Chia-Min; Fishman, Matthew; White, Steven; Zhang, Shiwei

    Constrained path Monte Carlo (CPMC) is a powerful method for simulating strongly correlated systems. By constraining the path with a trial wavefunction, CPMC circumvents the minus sign problem, but at the cost of introducing a bias. The Density Matrix Renormalization Group (DMRG) is an alternative simulation technique, which is immune to the minus sign problem, but which has an analogous ''dimensionality problem'' for two and three dimensions. Here we present a combination of these techniques, where we use a DMRG matrix product state as a trial wavefunction for CPMC. We demonstrate our method in two-dimensional Hubbard model, and show the comparison to DMRG alone and to CPMC with single-determinant trial functions.

  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. A Constrained Multibody System Dynamics Avoiding Kinematic Singularities

    NASA Astrophysics Data System (ADS)

    Huang, Chih-Fang; Yan, Chang-Dau; Jeng, Shyr-Long; Cheing, Wei-Hua

    In the analysis of constrained multibody systems, the constraint reaction forces are normally expressed in terms of the constraint equations and a vector of Lagrange multipliers. Because it fails to incorporate conservation of momentum, the Lagrange multiplier method is deficient when the constraint Jacobian matrix is singular. This paper presents an improved dynamic formulation for the constrained multibody system. In our formulation, the kinematic constraints are still formulated in terms of the joint constraint reaction forces and moments; however, the formulations are based on a second-order Taylor expansion so as to incorporate the rigid body velocities. Conservation of momentum is included explicitly in this method; hence the problems caused by kinematic singularities can be avoided. In addition, the dynamic formulation is general and applicable to most dynamic analyses. Finally the 3-leg Stewart platform is used for the example of analysis.

  5. Morphological transitions of elastic domain structures in constrained layers

    NASA Astrophysics Data System (ADS)

    Slutsker, J.; Artemev, A.; Roytburd, A. L.

    2002-06-01

    The phase transformation in a constrained layer is the subject of this article. The formation and evolution of polydomain microstructure under external stress in the constrained layer are investigated by phase-field simulation and analytically using homogeneous approximation. As a result of simulation, it has been shown that the three-domain hierarchical structure can be formed in the epitaxial films. Under external stress there are two types of morphological transitions: from the three-domain structure to the two-domain one and from the hierarchical three-domain structure to the cellular three-domain structure. The results of phase-field simulation are compared with conclusions of homogenous theory and with available experimental data.

  6. Negative differential conductance in nanojunctions: A current constrained approach

    NASA Astrophysics Data System (ADS)

    Parida, Prakash; Pati, Swapan K.; Painelli, Anna

    2011-04-01

    A current constrained approach is proposed to calculate negative differential conductance in molecular nanojunctions. A four-site junction is considered where a steady-state current is forced by inserting only the two central sites within the circuit. The two lateral sites (representing, e.g., dangling molecular groups) do not actively participate in transport but exchange electrons with the two main sites. These auxiliary sites allow for a variable number of electrons within the junction, while as required by the current constrained approach, the total number of electrons in the system is kept constant. We discuss the conditions for negative differential conductance in terms of cooperativity, variability of the number of electrons in the junction, and electron correlations.

  7. Spectral finite-element methods for parametric constrained optimization problems.

    SciTech Connect

    Anitescu, M.; Mathematics and Computer Science

    2009-01-01

    We present a method to approximate the solution mapping of parametric constrained optimization problems. The approximation, which is of the spectral finite element type, is represented as a linear combination of orthogonal polynomials. Its coefficients are determined by solving an appropriate finite-dimensional constrained optimization problem. We show that, under certain conditions, the latter problem is solvable because it is feasible for a sufficiently large degree of the polynomial approximation and has an objective function with bounded level sets. In addition, the solutions of the finite-dimensional problems converge for an increasing degree of the polynomials considered, provided that the solutions exhibit a sufficiently large and uniform degree of smoothness. Our approach solves, in the case of optimization problems with uncertain parameters, the most computationally intensive part of stochastic finite-element approaches. We demonstrate that our framework is applicable to parametric eigenvalue problems.

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

    PubMed

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

    2014-01-01

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

  9. Constraining Sn Ia Progenitor Scenarios with SNLS Time Series

    NASA Astrophysics Data System (ADS)

    Bianco, Federica; Howell, D. A.; Kasen, D.; Conley, A.; Sullivan, M.; Gonzales-Gaitan, S.

    2011-01-01

    We used 3 years of SuperNova Legacy Survey (SNLS) data to constraint the SN Ia progenitor scenarios. We searched for an excess in the early portion of SNLS lightcurves, signature of shocking by a companion, as predicted in Kasen 2010. We find no evidence of such excess and we are able to constrain the contribution of single degenerate systems with a Red Giant donor to the type Ia SN progenitors to less then 10%.

  10. Reservoir characterization with sequential Gaussian simulation constrained by diffraction tomography

    SciTech Connect

    Lo, T.W.; Bermawi, A.

    1994-12-31

    A geostatistical approach for reservoir characterization that honors both surface seismic data and wireline data is described. It first computes a velocity profiles with seismic diffraction tomography, then, performs kriging with an external drift and sequential Gaussian simulation using the velocity profiles as soft data and the sonic logs as hard data. The product is a velocity profile with a resolution as high as that of the smoothed sonic logs, showing lateral velocity variations constrained by surface seismic data.

  11. Some preliminary thoughts on the invention of constrained Hamiltonian dynamics

    NASA Astrophysics Data System (ADS)

    Salisbury, Donald

    2011-10-01

    I will present some tentative remarks on the origins of constrained Hamiltonian dynamics, based in part on interviews recently conducted by myself and Dean Rickles with several key contributers. These interviews with James Anderson, Stanley Deser, Charles Misner, and Josh Goldberg were partially supported by the Center for the History of Physics of the American Institute of Physics, and will eventually be made available on the Center web page.

  12. 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.

  13. Juno radio science observations to constrain Jupiter's moment of inertia

    NASA Astrophysics Data System (ADS)

    Le Maistre, S.; Folkner, W. M.; Jacobson, R. A.

    2015-10-01

    Through detailed and realistic numerical simulations, the present study assesses the precision with which Juno can measure the normalized polar moment of inertia (MOI) of Jupiter. Based on Ka-band Doppler and range data, this analysis shows that the determination of the precession rate of Jupiter is by far more efficient than the previously proposed Lense-Thirring effect to determine the moment of inertia and therefore to constrain the internal structure of the giant planet with Juno.

  14. Simulations of the Local Universe constrained by observational peculiar velocities

    NASA Astrophysics Data System (ADS)

    Sorce, Jenny G.; Courtois, Hélène M.; Gottlöber, Stefan; Hoffman, Yehuda; Tully, R. Brent

    2014-02-01

    Peculiar velocities, obtained from direct distance measurements, are data of choice to achieve constrained simulations of the Local Universe reliable down to a scale of a few megaparsec. Unlike redshift surveys, peculiar velocities are direct tracers of the underlying gravitational field as they trace both baryonic and dark matter. This paper presents the first attempt to use solely observational peculiar velocities to constrain cosmological simulations of the nearby Universe. In order to set up initial conditions, a Reverse Zel'dovich Approximation (RZA) is used to displace constraints from their positions at z = 0 to their precursors' locations at higher redshifts. An additional new feature replaces original observed radial peculiar velocity vectors by their full 3D reconstructions provided by the Wiener-Filter (WF) estimator. Subsequently, the constrained realization (CR) of Gaussian fields technique is applied to build various realizations of the initial conditions. The WF/RZA/CR method is first tested on realistic mock catalogues built from a reference simulation similar to the Local Universe. These mocks include errors on peculiar velocities, on data point positions and a large continuous zone devoid of data in order to mimic galactic extinction. Large-scale structures are recovered with a typical accuracy of 5 h-1 Mpc in position, the best realizations reaching a 2-3 h-1 Mpc precision, the limit imposed by the RZA linear theory. Then, the method is applied to the first observational radial peculiar velocity catalogue of the project Cosmicflows. This paper is a proof of concept that the WF/RZA/CR method can be applied to observational peculiar velocities to successfully build constrained initial conditions.

  15. 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.

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

    SciTech Connect

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

    2007-04-01

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

  17. 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.

  18. A surface-associated retinol- and fatty acid-binding protein (Gp-FAR-1) from the potato cyst nematode Globodera pallida: lipid binding activities, structural analysis and expression pattern.

    PubMed Central

    Prior, A; Jones, J T; Blok, V C; Beauchamp, J; McDermott, L; Cooper, A; Kennedy, M W

    2001-01-01

    Parasitic nematodes produce at least two structurally novel classes of small helix-rich retinol- and fatty-acid-binding proteins that have no counterparts in their plant or animal hosts and thus represent potential targets for new nematicides. Here we describe a protein (Gp-FAR-1) from the plant-parasitic nematode Globodera pallida, which is a member of the nematode-specific fatty-acid- and retinol-binding (FAR) family of proteins but localizes to the surface of this species, placing it in a strategic position for interaction with the host. Recombinant Gp-FAR-1 was found to bind retinol, cis-parinaric acid and the fluorophore-tagged lipids 11-(dansylamino)undecanoic acid and dansyl-D,L-alpha-amino-octanoic acid. The fluorescence emission characteristics of the dansylated analogues indicated that the entire ligand enters the binding cavity. Fluorescence competition experiments showed that Gp-FAR-1 binds fatty acids in the range C(11) to C(24), with optimal binding at C(15). Intrinsic fluorescence analysis of a mutant protein into which a tryptophan residue had been inserted supported computer-based predictions of the position of this residue at the protein's interior and possibly also at the binding site. Of direct relevance to plant defence systems was the observation that Gp-FAR-1 binds two lipids (linolenic and linoleic acids) that are precursors of plant defence compounds and the jasmonic acid signalling pathway. Moreover, Gp-FAR-1 was found to inhibit the lipoxygenase-mediated modification of these substrates in vitro. Thus not only does Gp-FAR-1 function as a broad-spectrum retinol- and fatty-acid-binding protein, the results are consistent with the idea that Gp-FAR-1 is involved in the evasion of primary host plant defence systems. PMID:11368765

  19. 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.

  20. 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

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

    PubMed

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

    2014-01-01

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

  2. 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.

  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. Constrained novelty search: a study on game content generation.

    PubMed

    Liapis, Antonios; Yannakakis, Georgios N; Togelius, Julian

    2015-01-01

    Novelty search is a recent algorithm geared toward exploring search spaces without regard to objectives. When the presence of constraints divides a search space into feasible space and infeasible space, interesting implications arise regarding how novelty search explores such spaces. This paper elaborates on the problem of constrained novelty search and proposes two novelty search algorithms which search within both the feasible and the infeasible space. Inspired by the FI-2pop genetic algorithm, both algorithms maintain and evolve two separate populations, one with feasible and one with infeasible individuals, while each population can use its own selection method. The proposed algorithms are applied to the problem of generating diverse but playable game levels, which is representative of the larger problem of procedural game content generation. Results show that the two-population constrained novelty search methods can create, under certain conditions, larger and more diverse sets of feasible game levels than current methods of novelty search, whether constrained or unconstrained. However, the best algorithm is contingent on the particularities of the search space and the genetic operators used. Additionally, the proposed enhancement of offspring boosting is shown to enhance performance in all cases of two-population novelty search. PMID:24605847

  5. Performance enhancement for GPS positioning using constrained Kalman filtering

    NASA Astrophysics Data System (ADS)

    Guo, Fei; Zhang, Xiaohong; Wang, Fuhong

    2015-08-01

    Over the past decades Kalman filtering (KF) algorithms have been extensively investigated and applied in the area of kinematic positioning. In the application of KF in kinematic precise point positioning (PPP), it is often the case where some known functional or theoretical relations exist among the unknown state parameters, which can be and should be made use of to enhance the performance of kinematic PPP, especially in an urban and forest environment. The central task of this paper is to effectively blend the commonly used GNSS data and internal/external additional constrained information to generate an optimal PPP solution. This paper first investigates the basic algorithm of constrained Kalman filtering. Then two types of PPP model with speed constraints and trajectory constraints, respectively, are proposed. Further validation tests based on a variety of situations show that the positioning performances (positioning accuracy, reliability and continuity) from the constrained Kalman filter are significantly superior to those from the conventional Kalman filter, particularly under extremely poor observation conditions.

  6. Constraining ecosystem processes from tower fluxes and atmospheric profiles.

    PubMed

    Hill, T C; Williams, M; Woodward, F I; Moncrieff, J B

    2011-07-01

    The planetary boundary layer (PBL) provides an important link between the scales and processes resolved by global atmospheric sampling/modeling and site-based flux measurements. The PBL is in direct contact with the land surface, both driving and responding to ecosystem processes. Measurements within the PBL (e.g., by radiosondes, aircraft profiles, and flask measurements) have a footprint, and thus an integrating scale, on the order of 1-100 km. We use the coupled atmosphere-biosphere model (CAB) and a Bayesian data assimilation framework to investigate the amount of biosphere process information that can be inferred from PBL measurements. We investigate the information content of PBL measurements in a two-stage study. First, we demonstrate consistency between the coupled model (CAB) and measurements, by comparing the model to eddy covariance flux tower measurements (i.e., water and carbon fluxes) and also PBL scalar profile measurements (i.e., water, carbon dioxide, and temperature) from Canadian boreal forest. Second, we use the CAB model in a set of Bayesian inversions experiments using synthetic data for a single day. In the synthetic experiment, leaf area and respiration were relatively well constrained, whereas surface albedo and plant hydraulic conductance were only moderately constrained. Finally, the abilities of the PBL profiles and the eddy covariance data to constrain the parameters were largely similar and only slightly lower than the combination of both observations. PMID:21830696

  7. Spherical Hamiltonian Monte Carlo for Constrained Target Distributions

    PubMed Central

    Lan, Shiwei; Zhou, Bo; Shahbaba, Babak

    2015-01-01

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

  8. Acid Rain

    MedlinePlus

    ... damaging to lakes, streams, and forests and the plants and animals that live in these ecosystems. This Web site provides information about the following: What causes acid rain The effects of acid rain How we measure acid rain ...

  9. Folic Acid

    MedlinePlus

    Folic acid is used to treat or prevent folic acid deficiency. It is a B-complex vitamin needed by ... Folic acid comes in tablets. It usually is taken once a day. Follow the directions on your prescription label ...

  10. Folic Acid

    MedlinePlus

    Folic acid is a B vitamin. It helps the body make healthy new cells. Everyone needs folic acid. For women who may get pregnant, it is really important. Getting enough folic acid before and during pregnancy can prevent major birth ...

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

    NASA Astrophysics Data System (ADS)

    Brunner, Stephen T.

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

  12. 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 cycle 23 and find it to be tied to changes in the meridional flow. Finally, by carefully constraining the system through surface magnetic field observations, we find that what is believed to be the primary source of poloidal field (also known as Babckock-Leigthon mechanism) may not be enough to sustain the solar magnetic cycle.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  14. Refinement of the pharmacophore of an agonist ligand of the secretin receptor using conformationally-constrained cyclic hexapeptides

    PubMed Central

    Dong, Maoqing; Narang, Pooja; Pinon, Delia I.; Bordner, Andrew J.; Miller, Laurence J.

    2010-01-01

    There is a compelling need for the development of small molecule agonists acting at family B G protein-coupled receptors. A possible lead for the development of such drugs was reported when it was recognized that sequences endogenous to the amino terminus of the secretin receptor and certain other receptors in this family possess weak full agonist activity (Dong et al., Mol Pharmacol 2006). In the current report, we extended those observations by building the active dipeptide motif found in the secretin receptor (WD) into each position around a conformationally-constrained D-amino acid-containing cyclic hexapeptide, and determining the biological activity of each peptide at the secretin receptor. Indeed, only two positions for WD around this constrained ring resulted in biological activity at the receptor, providing further insights into the structural specificity of this phenomenon. Molecular modeling supported the presence of a unique WD backbone conformation shared only by these active peptides, and provided a more constrained template for future receptor-active agonist drug development. PMID:20214947

  15. Beyond Sulphuric Acid — What else is in the Clouds of Venus?

    NASA Astrophysics Data System (ADS)

    Wilson, C. F.

    2014-05-01

    Venus clouds are apparently composed primarily of sulphuric acid mixed with water - but what else is there? From the UV absorber, to meteoritic dust and volcanic ash, we review evidence constraining particle composition and discuss measurement needs.

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 21 CFR 888.3500 - Knee joint femorotibial metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...-constrained cemented prosthesis. 888.3500 Section 888.3500 Food and Drugs FOOD AND DRUG ADMINISTRATION... § 888.3500 Knee joint femorotibial metal/composite semi-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite semi-constrained cemented prosthesis is a...

  3. 21 CFR 888.3490 - Knee joint femorotibial metal/composite non-constrained cemented prosthesis.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...-constrained cemented prosthesis. 888.3490 Section 888.3490 Food and Drugs FOOD AND DRUG ADMINISTRATION... § 888.3490 Knee joint femorotibial metal/composite non-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite non-constrained cemented prosthesis is a...

  4. 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... constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is a... as cobalt-chromium-molybdenum, and is limited to those prostheses intended for use with bone...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 21 CFR 888.3490 - Knee joint femorotibial metal/composite non-constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...-constrained cemented prosthesis. 888.3490 Section 888.3490 Food and Drugs FOOD AND DRUG ADMINISTRATION... § 888.3490 Knee joint femorotibial metal/composite non-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite non-constrained cemented prosthesis is a...

  12. 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... constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is a... as cobalt-chromium-molybdenum, and is limited to those prostheses intended for use with bone...

  13. 21 CFR 888.3500 - Knee joint femorotibial metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...-constrained cemented prosthesis. 888.3500 Section 888.3500 Food and Drugs FOOD AND DRUG ADMINISTRATION... § 888.3500 Knee joint femorotibial metal/composite semi-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite semi-constrained cemented prosthesis is a...

  14. 21 CFR 888.3500 - Knee joint femorotibial metal/composite semi-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...-constrained cemented prosthesis. 888.3500 Section 888.3500 Food and Drugs FOOD AND DRUG ADMINISTRATION... § 888.3500 Knee joint femorotibial metal/composite semi-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite semi-constrained cemented prosthesis is a...

  15. 21 CFR 888.3490 - Knee joint femorotibial metal/composite non-constrained cemented prosthesis.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...-constrained cemented prosthesis. 888.3490 Section 888.3490 Food and Drugs FOOD AND DRUG ADMINISTRATION... § 888.3490 Knee joint femorotibial metal/composite non-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite non-constrained cemented prosthesis is a...

  16. 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... constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented prosthesis is a... as cobalt-chromium-molybdenum, and is limited to those prostheses intended for use with bone...

  17. 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...

  18. 21 CFR 888.3340 - Hip 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 Hip joint metal/composite semi-constrained... Hip joint metal/composite semi-constrained cemented prosthesis. (a) Identification. A hip joint metal/composite semi-constrained cemented prosthesis is a two-part device intended to be implanted to replace...

  19. 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...

  20. 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...

  1. 21 CFR 888.3340 - Hip 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 Hip joint metal/composite semi-constrained... Hip joint metal/composite semi-constrained cemented prosthesis. (a) Identification. A hip joint metal/composite semi-constrained cemented prosthesis is a two-part device intended to be implanted to replace...

  2. 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. These methods are then applied to the formation of N-spacecraft. Modified Rodrigues Parameters (MRP) are used for attitude representation of the spacecraft because of their advantage of being a minimum parameter representation. Constrained non-linear equations of motion for this system are developed and stabilized using a Proportional-Derivative (PD) controller derived based on Baumgarte's method. A system of 3 spacecraft is simulated and the results for SCT are shown and analyzed. Another problem studied in this research is that of maintaining SCT under unknown external disturbances. We use an adaptive control algorithm to derive control laws for the actuator torques and develop an estimation law for the unknown disturbance parameters to achieve SCT. The estimate of the disturbance is added as a feed forward term in the actual control law to obtain the stabilization of a 3-spacecraft formation. The disturbance estimates are generated via a Lyapunov analysis of the closed loop system. In summary, the constrained dynamics method shows a lot of potential in formation control, achieving stabilization, synchronization, consensus and tracking of a set of dynamical systems.

  3. Responses of solitary retinal horizontal cells from Carassius auratus to L-glutamate and related amino acids.

    PubMed Central

    Ishida, A T; Kaneko, A; Tachibana, M

    1984-01-01

    Effects of L-glutamate and its analogues on membrane potentials of solitary horizontal cells were studied by intracellular recording. L-glutamate depolarized these cells at micromolar concentrations (greater than or equal to 10 microM), while D-glutamate and L-alpha-amino adipic acid produced slight depolarizations only at millimolar concentrations. Neither L- nor D-aspartate, even at millimolar doses, produced any change in solitary horizontal-cell resting potential. Solitary horizontal-cell responses to L-glutamate did not desensitize detectably. Responses to pairs of brief, ionophoretic pulses of L-glutamate were nearly equal in amplitude at inter-pulse intervals as short as 50 ms. Responses to maintained applications of low doses of L-glutamate did not decline for as long as 2 min. Depolarizing responses were produced by ionophoretic applications of L-glutamate near cell somata as well as dendrites. The mean sensitivity was 1.4 +/- 1.5 mV/nC with a maximum of 5.1 mV/nC. Depolarizing responses to L-glutamate reversed in polarity at membrane potentials between 0 and -20 mV, were accompanied by a decrease in membrane slope resistance, and were suppressed by replacement of extracellular sodium ions with choline. These results demonstrate that chemosensitivity of retinal horizontal cells to acidic amino acids persists after dissociation protocols, and in several respects resembles that found in horizontal cells in situ. These findings are consistent with the notion that retinal horizontal cells receive a synaptic input involving L-glutamate or a similar substance. PMID:6143822

  4. 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

  5. Bound constrained bundle adjustment for reliable 3D reconstruction.

    PubMed

    Gong, Yuanzheng; Meng, De; Seibel, Eric J

    2015-04-20

    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

  6. Constrained motion control on a hemispherical surface: path planning.

    PubMed

    Berman, Sigal; Liebermann, Dario G; McIntyre, Joseph

    2014-03-01

    Surface-constrained motion, i.e., motion constraint by a rigid surface, is commonly found in daily activities. The current work investigates the choice of hand paths constrained to a concave hemispherical surface. To gain insight regarding paths and their relationship with task dynamics, we simulated various control policies. The simulations demonstrated that following a geodesic path (the shortest path between 2 points on a sphere) is advantageous not only in terms of path length but also in terms of motor planning and sensitivity to motor command errors. These stem from the fact that the applied forces lie in a single plane (that of the geodesic path). To test whether human subjects indeed follow the geodesic, and to see how such motion compares to other paths, we recorded movements in a virtual haptic-visual environment from 11 healthy subjects. The task comprised point-to-point motion between targets at two elevations (30° and 60°). Three typical choices of paths were observed from a frontal plane projection of the paths: circular arcs, straight lines, and arcs close to the geodesic path for each elevation. Based on the measured hand paths, we applied k-means blind separation to divide the subjects into three groups and compared performance indicators. The analysis confirmed that subjects who followed paths closest to the geodesic produced faster and smoother movements compared with the others. The "better" performance reflects the dynamical advantages of following the geodesic path and may also reflect invariant features of control policies used to produce such a surface-constrained motion. PMID:24259548

  7. Constraining a Possible Variation of G with Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Mould, Jeremy; Uddin, Syed A.

    2014-03-01

    Astrophysical cosmology constrains the variation of Newton's Constant in a manner complementary to laboratory experiments, such as the celebrated lunar laser ranging campaign. Supernova cosmology is an example of the former and has attained campaign status, following planning by a Dark Energy Task Force in 2005. In this paper, we employ the full SNIa data set to the end of 2013 to set a limit on G variation. In our approach, we adopt the standard candle delineation of the redshift distance relation. We set an upper limit on its rate of change |dot{G}/G| of 0.1 parts per billion per year over 9 Gyrs. By contrast, lunar laser ranging tests variation of G over the last few decades. Conversely, one may adopt the laboratory result as a prior and constrain the effect of variable G in dark energy equation of state experiments to δw < 0.02. We also examine the parameterisation G 1 + z. Its short expansion age conflicts with the measured values of the expansion rate and the density in a flat Universe. In conclusion, supernova cosmology complements other experiments in limiting G variation. An important caveat is that it rests on the assumption that the same mass of 56Ni is burned to create the standard candle regardless of redshift. These two quantities, f and G, where f is the Chandrasekhar mass fraction burned, are degenerate. Constraining f variation alone requires more understanding of the SNIa mechanism.

  8. Acid Rain.

    ERIC Educational Resources Information Center

    Openshaw, Peter

    1987-01-01

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

  9. Conformationally constrained peptidomimetic inhibitors of signal transducer and activator of transcription. 3: Evaluation and molecular modeling.

    PubMed

    Mandal, Pijus K; Limbrick, Donald; Coleman, David R; Dyer, Garrett A; Ren, Zhiyong; Birtwistle, J Sanderson; Xiong, Chiyi; Chen, Xiaomin; Briggs, James M; McMurray, John S

    2009-04-23

    Signal transducer and activator of transcription 3 (Stat3) is involved in aberrant growth and survival signals in malignant tumor cells and is a validated target for anticancer drug design. We are targeting its SH2 domain to prevent docking to cytokine and growth factor receptors and subsequent signaling. The amino acids of our lead phosphopeptide, Ac-pTyr-Leu-Pro-Gln-Thr-Val-NH(2), were replaced with conformationally constrained mimics. Structure-affinity studies led to the peptidomimetic, pCinn-Haic-Gln-NHBn (21), which had an IC(50) of 162 nM (fluorescence polarization), compared to 290 nM for the lead phosphopeptide (pCinn = 4-phosphoryloxycinnamate, Haic = (2S,5S)-5-amino-1,2,4,5,6,7-hexahydro-4-oxo-azepino[3,2,1-hi]indole-2-carboxylic acid). pCinn-Haic-Gln-OH was docked to the SH2 domain (AUTODOCK), and the two highest populated clusters were subjected to molecular dynamics simulations. Both converged to a common peptide conformation. The complex exhibits unique hydrogen bonding between Haic and Gln and Stat3 as well as hydrophobic interactions between the protein and pCinn and Haic. PMID:19334714

  10. 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

  11. 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.

  12. Hierarchically parallelized constrained nonlinear solvers with automated substructuring

    NASA Technical Reports Server (NTRS)

    Padovan, J.; Kwang, A.

    1991-01-01

    This paper develops a parallelizable multilevel 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, both sequential, 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 capacity to yield significant reductions in memory utilization and calculational effort due both to updating and inversion.

  13. 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.

  14. Towards vast libraries of scaffold-diverse, conformationally constrained oligomers.

    PubMed

    Kodadek, Thomas; McEnaney, Patrick J

    2016-05-01

    There is great interest in the development of probe molecules and drug leads that would bind tightly and selectively to protein surfaces that are difficult to target with traditional molecules, such as those involved in protein-protein interactions. The currently available evidence suggests that this will require molecules that are larger and have quite different chemical properties than typical Lipinski-compliant molecules that target enzyme active sites. We describe here efforts to develop vast libraries of conformationally constrained oligomers as a potentially rich source of these molecules. PMID:26996593

  15. Impact localization and identification under a constrained optimization scheme

    NASA Astrophysics Data System (ADS)

    Li, Qiaofeng; Lu, Qiuhai

    2016-03-01

    Load identification becomes essential when direct measurement of structure loads is unavailable. In this paper, a method for localization and identification of impact is proposed. The location of impact is first determined with an error functional indicator using the Complex Method. The identification of impact history is then considered a constrained optimization problem. The solution of the problem is found using Gradient Projection Method. Both numerical and experiment results proved the validity of the proposed method. The identification process is faster and more robust with the techniques introduced. Further discussion and advice for implementation are also provided.

  16. 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.

  17. Constraining portals with displaced Higgs decay searches at the LHC

    NASA Astrophysics Data System (ADS)

    Clarke, Jackson D.

    2015-10-01

    It is very easy to write down models in which long-lived particles decaying to standard model states are pair-produced via Higgs decays, resulting in the signature of approximately back-to-back pairs of displaced narrow hadronic jets and/or lepton jets at the LHC. The LHC collaborations have already searched for such signatures with no observed excess. This paper describes a Monte Carlo method to reinterpret the searches. The method relies on (ideally multidimensional) efficiency tables, thus we implore collaborations to include them in any future work. Exclusion regions in mixing-mass parameter space are presented which constrain portal models.

  18. Domain decomposition in time for PDE-constrained optimization

    DOE PAGESBeta

    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.

  19. Positive Scattering Cross Sections using Constrained Least Squares

    SciTech Connect

    Dahl, J.A.; Ganapol, B.D.; Morel, J.E.

    1999-09-27

    A method which creates a positive Legendre expansion from truncated Legendre cross section libraries is presented. The cross section moments of order two and greater are modified by a constrained least squares algorithm, subject to the constraints that the zeroth and first moments remain constant, and that the standard discrete ordinate scattering matrix is positive. A method using the maximum entropy representation of the cross section which reduces the error of these modified moments is also presented. These methods are implemented in PARTISN, and numerical results from a transport calculation using highly anisotropic scattering cross sections with the exponential discontinuous spatial scheme is presented.

  20. 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.

  1. Polar stimulation and constrained cell migration in microfluidic channels†

    PubMed Central

    Agrawal, Nitin; Mitchison, Timothy; Toner, Mehmet

    2010-01-01

    Asymmetrical delivery of stimuli to moving cells for perturbing spatially-heterogeneous intracellular signaling is an experimental challenge not adequately met by existing technologies. Here, we report a robust microfluidic platform allowing localized treatment of the front and/or back of moving cells which crawl through narrow channels that they completely occlude. The enabling technical element for this study is a novel design for precise, passive balancing of flow inside the microfluidic device by contacting two fluid streams before splitting them again. The microchannels constrain cell morphology and induce qualitative and quantitative changes in neutrophil chemotaxis that mimic cells crawling through tissues. PMID:18030401

  2. Novel technique for Constraining r -Process (n , γ ) Reaction Rates

    NASA Astrophysics Data System (ADS)

    Spyrou, A.; Liddick, S. N.; Larsen, A. C.; Guttormsen, M.; Cooper, K.; Dombos, A. C.; Morrissey, D. J.; Naqvi, F.; Perdikakis, G.; Quinn, S. J.; Renstrøm, T.; Rodriguez, J. A.; Simon, A.; Sumithrarachchi, C. S.; Zegers, R. G. T.

    2014-12-01

    A novel technique has been developed, which will open exciting new opportunities for studying the very neutron-rich nuclei involved in the r process. As a proof of principle, the γ spectra from the β decay of 76Ga have been measured with the SuN detector at the National Superconducting Cyclotron Laboratory. The nuclear level density and γ -ray strength function are extracted and used as input to Hauser-Feshbach calculations. The present technique is shown to strongly constrain the 75Ge (n ,γ )76Ge cross section and reaction rate.

  3. Completing constrained flavor violation: Lepton masses, neutrinos, and leptogenesis

    NASA Astrophysics Data System (ADS)

    Cline, James M.; Díaz-Furlong, Alfonso; Ren, Jing

    2016-02-01

    Constrained flavor violation (CFV) is a recent proposal for predicting the down-quark Yukawa matrix in terms of those for up quarks and charged leptons. We study the viability of CFV with respect to its predictions for the lepton mass ratios, showing that this remains a challenge, and suggest some possible means for improving this shortcoming. We then extend CFV to include neutrinos, and show that it leads to interesting predictions for hierachical heavy neutrinos, and leptogenesis dominated by decays of the second heaviest one ("N2 leptogenesis"), as well as the possibility of low-scale leptoquark-mediated exotic decays.

  4. Constrained Task Assignment and Scheduling On Networks of Arbitrary Topology

    NASA Astrophysics Data System (ADS)

    Jackson, Justin Patrick

    This dissertation develops a framework to address centralized and distributed constrained task assignment and task scheduling problems. This framework is used to prove properties of these problems that can be exploited, develop effective solution algorithms, and to prove important properties such as correctness, completeness and optimality. The centralized task assignment and task scheduling problem treated here is expressed as a vehicle routing problem with the goal of optimizing mission time subject to mission constraints on task precedence and agent capability. The algorithm developed to solve this problem is able to coordinate vehicle (agent) timing for task completion. This class of problems is NP-hard and analytical guarantees on solution quality are often unavailable. This dissertation develops a technique for determining solution quality that can be used on a large class of problems and does not rely on traditional analytical guarantees. For distributed problems several agents must communicate to collectively solve a distributed task assignment and task scheduling problem. The distributed task assignment and task scheduling algorithms developed here allow for the optimization of constrained military missions in situations where the communication network may be incomplete and only locally known. Two problems are developed. The distributed task assignment problem incorporates communication constraints that must be satisfied; this is the Communication-Constrained Distributed Assignment Problem. A novel distributed assignment algorithm, the Stochastic Bidding Algorithm, solves this problem. The algorithm is correct, probabilistically complete, and has linear average-case time complexity. The distributed task scheduling problem addressed here is to minimize mission time subject to arbitrary predicate mission constraints; this is the Minimum-time Arbitrarily-constrained Distributed Scheduling Problem. The Optimal Distributed Non-sequential Backtracking Algorithm solves this problem. The algorithm is correct, complete, outputs time optimal schedules, and has low average-case time complexity. Separation of the task assignment and task scheduling problems is exploited here to ameliorate the effects of an incomplete communication network. The mission-modeling conditions that allow this and the benefits gained are discussed in detail. It is shown that the distributed task assignment and task scheduling algorithms developed here can operate concurrently and maintain their correctness, completeness, and optimality properties.

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

    PubMed

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

    2011-01-15

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

  6. 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.

  7. 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.

  8. Butterfly Encryption Scheme for Resource-Constrained Wireless Networks.

    PubMed

    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

  9. 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

  10. Evaluating competing forces constraining glacial grounding-line stability (Invited)

    NASA Astrophysics Data System (ADS)

    Powell, R. D.

    2013-12-01

    Stability of grounding lines of marine-terminating glaciers and ice sheets is of concern due to their importance in governing rates of ice mass loss and consequent sea level rise during global warming. Although processes are similar at tidewater and floating grounding zones their relative magnitudes in terms of their influence on grounding-line stability vary between these two end members. Processes considered Important for this discussion are ice dynamics, ice surface melting and crevassing, ocean dynamics, subglacial sediment and water dynamics, and subglacial bed geometries. Models have continued to improve in their representation of these complex interactions but reliable field measurements and data continue to be hard earned and too few to properly constrain the range of boundary conditions in this complicated system. Some data will be presented covering a range of regimes from Alaska, Svalbard and Antarctica. Certainly more data are required on subglacial sediment/water dynamics and fluxes to fully represent the spectrum of glacial regimes and to assess the significance of grounding-zone sediment systems in counteracting the other processes to force grounding-line stability. Especially important here is constraining the duration of the stability that could be maintained by sediment flux - present data appear to show that it is likely to be a limited period.

  11. Constrained Density Functional Theory by Imaginary Time-Step Method

    NASA Astrophysics Data System (ADS)

    Kidd, Daniel

    Constrained Density Functional Theory (CDFT) has been a popular choice within the last decade for sidestepping the self interaction problem within long-range charge transfer calculations. Typically an inner constraint loop is added within the self-consistent field iterations of DFT in order to enforce this charge transfer state by means of a Lagrange multiplier method. In this work, an alternate implementation of CDFT is introduced, that of the imaginary time-step method, which lends itself more readily to real space calculations in the ability to solve numerically for 3D local external potentials which enforce arbitrary given densities. This method has been shown to reproduce the proper 1 / R dependence of charge transfer systems in real space calculations as well as the ability to generate useful constraint potentials. As an example application, this method is shown to be capable of describing defects within periodic systems using finite calculations by constraining the 3D density to that of the periodically calculated perfect system at the boundaries.

  12. Galactic disk abundance ratios: constraining SNIa stellar yields

    SciTech Connect

    Chiappini, Cristina

    2005-10-21

    Stellar abundance ratios of very good quality are now available for a large number of stars in the solar vicinity. Moreover, for an increasing number of stars informations on kinematics is also available. The combined information on abundance and kinematics enables one to select objects belonging to the different components of our Galaxy (thin disk, thick disk and halo). In this work we show that a careful comparison of our chemical evolution model for the Milky Way with the available abundance ratio measurements for stars in the solar neighborhood can be used to constrain the stellar yields. In particular, yields of Type Ia SNe are constrained by the abundance pattern of thin disk stars. Our results suggest that the 3-D models for SNIa explosion studied here lead to discrepancies once their predicted stellar yields are used as input in our chemical evolution model. These models produce flat Si/O and Mg/O ratios in disagreement with what is observed in thin disk stars. Moreover, our results indicate that larger quantities of Mg (at least a factor of 10 more than current theoretical predictions of either 1-D or multi-D models) need to be produced in SNIa.

  13. Maximum Constrained Directivity of Oversteered End-Fire Sensor Arrays

    PubMed Central

    Trucco, Andrea; Traverso, Federico; Crocco, Marco

    2015-01-01

    For linear arrays with fixed steering and an inter-element spacing smaller than one half of the wavelength, end-fire steering of a data-independent beamformer offers better directivity than broadside steering. The introduction of a lower bound on the white noise gain ensures the necessary robustness against random array errors and sensor mismatches. However, the optimum broadside performance can be obtained using a simple processing architecture, whereas the optimum end-fire performance requires a more complicated system (because complex weight coefficients are needed). In this paper, we reconsider the oversteering technique as a possible way to simplify the processing architecture of equally spaced end-fire arrays. We propose a method for computing the amount of oversteering and the related real-valued weight vector that allows the constrained directivity to be maximized for a given inter-element spacing. Moreover, we verify that the maximized oversteering performance is very close to the optimum end-fire performance. We conclude that optimized oversteering is a viable method for designing end-fire arrays that have better constrained directivity than broadside arrays but with a similar implementation complexity. A numerical simulation is used to perform a statistical analysis, which confirms that the maximized oversteering performance is robust against sensor mismatches. PMID:26066987

  14. Maximum Constrained Directivity of Oversteered End-Fire Sensor Arrays.

    PubMed

    Trucco, Andrea; Traverso, Federico; Crocco, Marco

    2015-01-01

    For linear arrays with fixed steering and an inter-element spacing smaller than one half of the wavelength, end-fire steering of a data-independent beamformer offers better directivity than broadside steering. The introduction of a lower bound on the white noise gain ensures the necessary robustness against random array errors and sensor mismatches. However, the optimum broadside performance can be obtained using a simple processing architecture, whereas the optimum end-fire performance requires a more complicated system (because complex weight coefficients are needed). In this paper, we reconsider the oversteering technique as a possible way to simplify the processing architecture of equally spaced end-fire arrays. We propose a method for computing the amount of oversteering and the related real-valued weight vector that allows the constrained directivity to be maximized for a given inter-element spacing. Moreover, we verify that the maximized oversteering performance is very close to the optimum end-fire performance. We conclude that optimized oversteering is a viable method for designing end-fire arrays that have better constrained directivity than broadside arrays but with a similar implementation complexity. A numerical simulation is used to perform a statistical analysis, which confirms that the maximized oversteering performance is robust against sensor mismatches. PMID:26066987

  15. 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.

  16. Small Molecule Activation by Constrained Phosphorus Compounds: Insights from Theory.

    PubMed

    Pal, Amrita; Vanka, Kumar

    2016-01-19

    An exciting new development in main group chemistry has been the use of a constrained, "flat", phosphorus-based complex to mediate in reactions such as the dehydrogenation of ammonia borane (AB), and the activation of the N-H bond in primary amines. Its importance is based on the fact that it shows that main group compounds, when properly designed, can be as effective as transition metal complexes for doing significant chemical transformations. What the current computational study, employing density functional theory (DFT), reveals is that a common, general mechanism exists that accounts for the behavior of the flat phosphorus compound in the different reactions that have been experimentally reported to date. This mechanism, which involves the mediation by a base as a proton transfer agent, is simpler and energetically more favorable than the previous mechanisms that have been proposed for the same reactions in the literature. It is likely that the knowledge gained from the current work about the chemical behavior of this phosphorus compound can be utilized to design new constrained phosphorus-based compounds. PMID:26700074

  17. How Well do the Mentawai Corals Constrain the 1797 Tsunami?

    NASA Astrophysics Data System (ADS)

    McCloskey, J.; Nalbant, S.; Kelly, C.; Piatanesi, A.; Lorito, S.; Romano, F.; Antonioli, A.; Cocco, M.; Main, I.; Bell, A.; Naylor, M.; Greenhough, J.

    2008-12-01

    Vertical coseismic displacements recorded in corals on the Sumatran forearc offer a unique opportunity to reconstruct past earthquakes on the Sunda megathrust. These observations not only constrain the time and magnitude of the 1797 event but also place some bounds on possible slip distributions for this great earthquake. Here we explore the range of slip distributions which are consistent with the coral data. We choose a brute-force technique in which the displacements at the corals are computed for many possible, stochastic slip distributions. The technique makes no assumptions about the earthquake other than the geometry of the fault and the autocorrelation function of the slip distribution which limits the post-seismic strain on the megathrust. We expose several internal inconsistencies in the data with respect to a double couple event on a single inclined plane. We also show that while the along strike length of the rupture is reasonably well constrained, the down-dip distribution of slip, a first order control on the tsunamigenic potential of the earthquake, is only poorly resolved. Numerical simulations of tsunamis that would have resulted from possible 1797 earthquakes may help to advise on possible hazard from a near future Mentawai earthquake.

  18. How well do the Mentawai corals constrain great historical earthquakes?

    NASA Astrophysics Data System (ADS)

    McCloskey, J.; Nalbant, S. S.; Bell, A.; Main, I. G.; Naylor, M.; Greenhough, J.; Antonioli, A.

    2009-04-01

    Vertical coseismic displacements recorded in corals on the Sumatran forearc offer a unique opportunity to reconstruct past earthquakes on the Sunda megathrust. These observations not only constrain the time and magnitude of historical earthquakes but also place some bounds on possible slip distributions for them. Here we explore the range of slip distributions which are consistent with the coral data. We choose a brute-force technique in which the displacements at the corals are computed for many possible slip distributions. The technique makes no assumptions about the earthquake other than the geometry of the fault and the autocorrelation function of the slip distribution which limits the post-seismic strain. We expose several internal inconsistencies in the data which may indicate that the displacements suggested by the corals may not have resulted from pure double couple displacement on the megathrust. Movement on splay faults, for example, may be required to reconcile the discrepancies. We also show that while the along-strike length of the rupture is reasonably well constrained, the location of high slip down dip is only poorly resolved. Numerical simulations of tsunamis that would have resulted from possible historical earthquakes may help to advise on possible hazard from a near future Mentawai earthquake.

  19. Weak gravity strongly constrains large-field axion inflation

    NASA Astrophysics Data System (ADS)

    Heidenreich, Ben; Reece, Matthew; Rudelius, Tom

    2015-12-01

    Models of large-field inflation based on axion-like fields with shift symmetries can be simple and natural, and make a promising prediction of detectable primordial gravitational waves. The Weak Gravity Conjecture is known to constrain the simplest case in which a single compact axion descends from a gauge field in an extra dimension. We argue that the Weak Gravity Conjecture also constrains a variety of theories of multiple compact axions including N-flation and some alignment models. We show that other alignment models entail surprising consequences for how the mass spectrum of the theory varies across the axion moduli space, and hence can be excluded if further conjectures hold. In every case that we consider, plausible assumptions lead to field ranges that cannot be parametrically larger than M Pl. Our results are strongly suggestive of a general inconsistency in models of large-field inflation based on compact axions, and possibly of a more general principle forbidding super-Planckian field ranges.

  20. Constraining dark sector perturbations I: cosmic shear and CMB lensing

    NASA Astrophysics Data System (ADS)

    Battye, Richard A.; Moss, Adam; Pearson, Jonathan A.

    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 Script 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.

  1. Constrained camouflage facilitates the evolution of conspicuous warning coloration.

    PubMed

    Merilaita, Sami; Tullberg, Birgitta S

    2005-01-01

    The initial evolution of aposematic and mimetic antipredator signals is thought to be paradoxical because such coloration is expected to increase the risk of predation before reaching a stage when predators associate it effectively with a defense. We propose, however, that constraints associated with the alternative strategy, cryptic coloration, may facilitate the evolution of antipredator signals and thus provide a solution for the apparent paradox. We tested this hypothesis first using an evolutionary simulation to study the effect of a constraint due to habitat heterogeneity, and second using a phylogenetic comparison of the Lepidoptera to investigate the effect of a constraint due to prey motility. In the evolutionary simulation, antipredator warning coloration had an increased probability to invade the prey population when the evolution of camouflage was constrained by visual difference between microhabitats. The comparative study was done between day-active lepidopteran taxa, in which camouflage is constrained by motility, and night-active taxa, which rest during the day and are thus able to rely on camouflage. We compared each of seven phylogenetically independent day-active groups with a closely related nocturnal group and found that antipredator signals have evolved at least once in all the diurnal groups but in none of their nocturnal matches. Both studies lend support to our idea that constraints on crypsis may favor the evolution of antipredator warning signals. PMID:15792225

  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. Constrained optimization framework for joint inversion of geophysical data sets

    NASA Astrophysics Data System (ADS)

    Sosa, A.; Velasco, A. A.; Velazquez, L.; Argaez, M.; Romero, R.

    2013-12-01

    Many experimental techniques in geophysics advance the understanding of Earth processes by estimating and interpreting Earth structure (e.g. velocity and/or density structure). Different types of geophysical data can be collected and analysed separately, sometimes resulting in inconsistent models of the Earth depending on the data used. We present a constrained optimization approach for a joint inversion least-squares (LSQ) algorithm to characterize 1-D Earth's structure. We use two geophysical data sets sensitive to shear velocities: receiver function and surface wave dispersion velocity observations. We study the use of bound constraints on the regularized inverse problem, which are more physical than the regularization parameters required by conventional unconstrained formulations. Specifically, we develop a constrained optimization formulation that is solved with a primal-dual interior-point (PDIP) method, and validate our results with a traditional, unconstrained formulation that is solved with a truncated singular value decomposition (TSVD) for a set of numerical experiments with synthetic crustal velocity models. We conclude that the PDIP results are as accurate as those from the regularized TSVD approach, are less affected by noise, and honour the geophysical constraints.

  4. 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.

  5. Nonlinear wave propagation in constrained solids subjected to thermal loads

    NASA Astrophysics Data System (ADS)

    Nucera, Claudio; Lanza di Scalea, Francesco

    2014-01-01

    The classical mathematical treatment governing nonlinear wave propagation in solids relies on finite strain theory. In this scenario, a system of nonlinear partial differential equations can be derived to mathematically describe nonlinear phenomena such as acoustoelasticity (wave speed dependency on quasi-static stress), wave interaction, wave distortion, and higher-harmonic generation. The present work expands the topic of nonlinear wave propagation to the case of a constrained solid subjected to thermal loads. The origin of nonlinear effects in this case is explained on the basis of the anharmonicity of interatomic potentials, and the absorption of the potential energy corresponding to the (prevented) thermal expansion. Such "residual" energy is, at least, cubic as a function of strain, hence leading to a nonlinear wave equation and higher-harmonic generation. Closed-form solutions are given for the longitudinal wave speed and the second-harmonic nonlinear parameter as a function of interatomic potential parameters and temperature increase. The model predicts a decrease in longitudinal wave speed and a corresponding increase in nonlinear parameter with increasing temperature, as a result of the thermal stresses caused by the prevented thermal expansion of the solid. Experimental measurements of the ultrasonic nonlinear parameter on a steel block under constrained thermal expansion confirm this trend. These results suggest the potential of a nonlinear ultrasonic measurement to quantify thermal stresses from prevented thermal expansion. This knowledge can be extremely useful to prevent thermal buckling of various structures, such as continuous-welded rails in hot weather.

  6. 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.

  7. 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.

  8. Multicomponent Synthesis of a N-Protected Alpha-Amino Ester: Ethyl 2-((4-Methoxyphenyl)Amino)-3-Phenylpropanoate

    ERIC Educational Resources Information Center

    Le Gall, Erwan; Pignon, Antoine

    2012-01-01

    This laboratory experiment describes the preparation of a N-protected phenylalanine ethyl ester by a zinc-mediated Mannich-like multicomponent reaction between benzyl bromide, "p"-anisidine, and ethyl glyoxylate. The one-step reaction involves the in situ metallation of benzyl bromide into a benzylzinc reagent and its addition onto imine (Barbier…

  9. 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. However, for future studies we will need to obtain new coupled mode splitting data and to perform joint analyses with fundamental mode and overtone surface-waves. This will reduce parameter tradeoffs and improve our constraints on the individual elastic parameters and on the depth location of the azimuthal anisotropy.

  10. Constraining the Interior Geophysics of Rubble Pile Asteroids

    NASA Astrophysics Data System (ADS)

    Scheeres, D. J.; Jacobson, S.; McMahon, J.; Hirabayashi, M.

    2013-12-01

    The internal geophysics of small rubble pile asteroids are largely unknown, and standard geophysical theories are not well matched to the extreme environment these bodies exist in. Interior pressures within rapidly spinning rubble piles are predicted to be as small as a few Pascals, a regime in which small non-gravitational forces not considered for larger bodies may become important. Previous research has suggested that the standard geophysical models for internal energy dissipation in this regime require modification (Goldreich and Sari, ApJ 2009), adding additional uncertainty in the geophysics. We report on new theoretical and observational results that suggest a direct way in which fundamental geophysical parameters of small rubble pile asteroids can be constrained. Specifically, we will discuss how the ratio Q/k, tidal dissipation number over tidal Love number, can be inferred and more strictly constrained for primaries in small binary asteroid systems where the secondary is spin-synchronized and the primary is super-synchronous, the most common class of small asteroid binary systems. Jacobson & Scheeres (ApJ 2011) proposed that many of these binary asteroid systems may be in an equilibrium state where contractive Binary YORP forces balance against expansive tidal torques due to tidal distortion of the primary body. The predicted equilibrium semi-major axes for such binary asteroid systems (based on presumed values for the Binary YORP force and Q/k values) has been seen to be consistent with the observed sizes of many of these systems (see figure). Recently, it has also been reported that the spacecraft-accessible binary asteroid 1996 FG3 is in such an equilibrium state (Scheirich et al., Binaries Workshop 2013). The combined detection of such an equilibrium coupled with their theoretical model makes it feasible to sharply constrain the Q/k parameter for the primary asteroid in the 1996 FG3 system and extrapolate its functional form to other such systems. We will review the theory and measurements that make such a determination feasible, and explore other geophysical aspects of such a system that could be determined from a rendezvous space mission. Singly-synchronous binary system primary radii are plotted against their determined value of BQ/k, based on their current semi-major axis. Values of the BYORP coefficient B are on the order of 0.001 with an order of magnitude uncertainty, providing initial estimates on Q/k. Proposed approaches for measuring B, and hence Q/k, will be discussed.

  11. Acid rain

    SciTech Connect

    Stensland, G.J.

    1983-11-01

    A series of definitions for the field of acid rain studies are presented. Protocols for acid rain sampling and monitoring are also presented. A procedure for calculatory precipitation pH is discussed. 11 references, 1 table.

  12. Aminocaproic Acid

    MedlinePlus

    Aminocaproic acid is used to control bleeding that occurs when blood clots are broken down too quickly. This type ... the baby is ready to be born). Aminocaproic acid is also used to control bleeding in the ...

  13. 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.

  14. Surface-Constrained 3D Reconstruction in Cryo-EM.

    PubMed

    Barthel, Andrew C; Tagare, Hemant; Sigworth, Fred J

    2011-01-01

    Random spherically-constrained (RSC) reconstruction is a new form of single particle reconstruction (SPR) using cryo-EM images of membrane proteins embedded in spherical lipid vesicles to generate a 3D protein structure. The method has many advantages over conventional SPR, including a more native environment for protein particles and an initial estimate of the particle's angular orientation. These advances allow us to determine structures of membrane proteins such as ion channels and derive more reliable structure estimates. We present an algorithm that relates conventional SPR to the RSC model, and generally, to projection images of particles embedded with an axis parallel to the local normal of a general 2D manifold. We illustrate the performance of this algorithm in the spherical system using synthetic data. PMID:24477184

  15. Constraining photon mass by energy-dependent gravitational light bending

    NASA Astrophysics Data System (ADS)

    Qian, Lei

    2012-03-01

    In the standard model of particle physics, photons are massless particles with a particular dispersion relation. Tests of this claim at different scales are both interesting and important. Experiments in territory labs and several exterritorial tests have put some upper limits on photon mass, e.g., torsion balance experiment in the lab shows that photon mass should be smaller than 1.2 10-51g. In this work, this claim is tested at a cosmological scale by looking at strong gravitational lensing data available and an upper limit of 8.71 10-39g on photon mass is given. Observations of energy-dependent gravitational lensing with not yet available higher accuracy astrometry instruments may constrain photon mass better.

  16. Forced to be free? Increasing patient autonomy by constraining it

    PubMed Central

    2014-01-01

    It is universally accepted in bioethics that doctors and other medical professionals have an obligation to procure the informed consent of their patients. Informed consent is required because patients have the moral right to autonomy in furthering the pursuit of their most important goals. In the present work, it is argued that evidence from psychology shows that human beings are subject to a number of biases and limitations as reasoners, which can be expected to lower the quality of their decisions and which therefore make it more difficult for them to pursue their most important goals by giving informed consent. It is further argued that patient autonomy is best promoted by constraining the informed consent procedure. By limiting the degree of freedom patients have to choose, the good that informed consent is supposed to protect can be promoted. PMID:22318413

  17. Constraining the nonstandard interaction parameters in long baseline neutrino experiments

    NASA Astrophysics Data System (ADS)

    Huitu, Katri; Kärkkäinen, Timo J.; Maalampi, Jukka; Vihonen, Sampsa

    2016-03-01

    In this article we investigate the prospects for probing the strength of the possible nonstandard neutrino interactions (NSI) in long baseline neutrino oscillation experiments. We find that these experiments are sensitive to NSI couplings down to the level of 0.01-0.1 depending on the oscillation channel and the baseline length, as well as on the detector's fiducial mass. We also investigate the interference of the leptonic C P angle δC P with the constraining of the NSI couplings. It is found that the interference is strong in the case of the νe↔νμ and νe↔ντ transitions but not significant in other transitions. In our numerical analysis we apply the GLoBES software and use the LBNO setup as our benchmark.

  18. Constraining the Satellite Quenching Timescale at z < 1.5

    NASA Astrophysics Data System (ADS)

    Rodriguez Wimberly, M. Katy; Cooper, Michael

    2016-01-01

    Despite remarkable success at modeling the evolution of massive galaxies over cosmic time, modern hydrodynamic and semi-analytic models of galaxy formation generally fail to reproduce the properties of low-mass galaxies. This shortcoming in our theoretical picture is largely driven by an inability to understand the physics of satellite (or "environmental") quenching. Using abundance matching prescriptions to populate large dissipationless N-body simulations, including the Bolshoi Simulation, we study the dependence of satellite properties on cluster-centric distance within massive host halos at z < 1.5, focusing on the potential physical mechanisms that may be at play in suppressing star formation in the satellite population. Our results illustrate the potential power of ongoing cluster surveys, such as the multi-year GOGREEN Survey at Gemini Observatories, to constrain the quenching timescale over more than half of cosmic time.

  19. Position and locality constrained soft coding for human action recognition

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Liu, Yu; Xiao, Wenhua; Xu, Wei; Zhang, Maojun

    2013-10-01

    Although the traditional bag-of-words model has shown promising results for human action recognition, in the feature coding phase, the ambiguous features from different body parts are still difficult to distinguish. Furthermore, it also suffers from serious representation error. We propose an innovative coding strategy called position and locality constrained soft coding (PLSC) to overcome these limitations. PLSC uses the feature position in a human oriented region of interest (ROI) to distinguish the ambiguous features. We first construct a subdictionary for each feature by selecting the bases from their spatial neighbor in human ROI. Then, a modified soft coding with locality constraint is adopted to alleviate the quantization error and preserve the manifold structure of features. This novel coding algorithm increases both the representation accuracy and discriminative power with low computational cost. The human action recognition experimental results on KTH, Weizmann, and UCF sports datasets show that PLSC can achieve a better performance than previous competing feature coding methods.

  20. Location constrained approximate message passing for compressed sensing MRI.

    PubMed

    Sung, Kyunghyun; Daniel, Bruce L; Hargreaves, Brian A

    2013-08-01

    Iterative thresholding methods have been extensively studied as faster alternatives to convex optimization methods for solving large-sized problems in compressed sensing. A novel iterative thresholding method called LCAMP (Location Constrained Approximate Message Passing) is presented for reducing computational complexity and improving reconstruction accuracy when a nonzero location (or sparse support) constraint can be obtained from view shared images. LCAMP modifies the existing approximate message passing algorithm by replacing the thresholding stage with a location constraint, which avoids adjusting regularization parameters or thresholding levels. This work is first compared with other conventional reconstruction methods using random one-dimention signals and then applied to dynamic contrast-enhanced breast magnetic resonance imaging to demonstrate the excellent reconstruction accuracy (less than 2% absolute difference) and low computation time (5-10 s using Matlab) with highly undersampled three-dimentional data (244 × 128 × 48; overall reduction factor = 10). PMID:23042658

  1. Constraining Nonstandard Interactions in Neutrino-Electron Processes

    SciTech Connect

    Moura, C. A.

    2008-07-02

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

  2. 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.

  3. Constraining White Dwarf Structure and Neutrino Physics in 47 Tucanae

    NASA Astrophysics Data System (ADS)

    Goldsbury, R.; Heyl, J.; Richer, H. B.; Kalirai, J. S.; Tremblay, P. E.

    2016-04-01

    We present a robust statistical analysis of the white dwarf cooling sequence in 47 Tucanae. We combine Hubble Space Telescope UV and optical data in the core of the cluster, Modules for Experiments in Stellar Evolution (MESA) white dwarf cooling models, white dwarf atmosphere models, artificial star tests, and a Markov Chain Monte Carlo sampling method to fit white dwarf cooling models to our data directly. We use a technique known as the unbinned maximum likelihood to fit these models to our data without binning. We use these data to constrain neutrino production and the thickness of the hydrogen layer in these white dwarfs. The data prefer thicker hydrogen layers ({q}{{H}}=3.2× {10}-5) and we can strongly rule out thin layers ({q}{{H}}={10}-6). The neutrino rates currently in the models are consistent with the data. This analysis does not provide a constraint on the number of neutrino species.

  4. Constraining recent oscillations in quintessence models with Euclid

    NASA Astrophysics Data System (ADS)

    Lima, N. A.; Viana, P. T. P.; Tereno, I.

    2014-07-01

    Euclid is a future space-based mission that will constrain dark energy with unprecedented accuracy. Its photometric component is optimized for weak lensing studies, while the spectroscopic component is designed for baryon acoustic oscillations (BAO) analysis. We use the Fisher matrix formalism to make forecasts on two quintessence dark energy models with a dynamical equation of state that leads to late-time oscillations in the expansion rate of the Universe. We find that weak lensing will place much stronger constraints than the BAO, being able to discriminate between oscillating models by measuring the relevant parameters to 1σ precisions of 5-20 per cent. The tight constraints suggest that Euclid data could identify even quite small late-time oscillations in the expansion rate of the Universe.

  5. Postural position constrains multimodal object exploration in infants

    PubMed Central

    Soska, Kasey C.; Adolph, Karen E.

    2013-01-01

    Recent research has revealed the important role of multimodal object exploration in infants’ cognitive and social development. Yet, the real time effects of postural position on infants’ object exploration have been largely ignored. In the current study, 5- to 7-month-old infants (N = 29) handled objects while placed in supported sitting, supine, and prone postures, and their spontaneous exploratory behaviors were observed. Infants produced more manual, oral, and visual exploration in sitting compared to lying supine and prone. Moreover, while sitting, infants more often coupled manual exploration with mouthing and visual examination. Infants’ opportunities for learning from object exploration are embedded within a real time postural context that constrains the quantity and quality of exploratory behavior. PMID:24639621

  6. Future fish distributions constrained by depth in warming seas

    NASA Astrophysics Data System (ADS)

    Rutterford, Louise A.; Simpson, Stephen D.; Jennings, Simon; Johnson, Mark P.; Blanchard, Julia L.; Schön, Pieter-Jan; Sims, David W.; Tinker, Jonathan; Genner, Martin J.

    2015-06-01

    European continental shelf seas have experienced intense warming over the past 30 years. In the North Sea, fish have been comprehensively monitored throughout this period and resulting data provide a unique record of changes in distribution and abundance in response to climate change. We use these data to demonstrate the remarkable power of generalized additive models (GAMs), trained on data earlier in the time series, to reliably predict trends in distribution and abundance in later years. Then, challenging process-based models that predict substantial and ongoing poleward shifts of cold-water species, we find that GAMs coupled with climate projections predict future distributions of demersal (bottom-dwelling) fish species over the next 50 years will be strongly constrained by availability of habitat of suitable depth. This will lead to pronounced changes in community structure, species interactions and commercial fisheries, unless individual acclimation or population-level evolutionary adaptations enable fish to tolerate warmer conditions or move to previously uninhabitable locations.

  7. Locality-constrained anomaly detection for hyperspectral imagery

    NASA Astrophysics Data System (ADS)

    Liu, Jiabin; Li, Wei; Du, Qian; Liu, Kui

    2015-12-01

    Detecting a target with low-occurrence-probability from unknown background in a hyperspectral image, namely anomaly detection, is of practical significance. Reed-Xiaoli (RX) algorithm is considered as a classic anomaly detector, which calculates the Mahalanobis distance between local background and the pixel under test. Local RX, as an adaptive RX detector, employs a dual-window strategy to consider pixels within the frame between inner and outer windows as local background. However, the detector is sensitive if such a local region contains anomalous pixels (i.e., outliers). In this paper, a locality-constrained anomaly detector is proposed to remove outliers in the local background region before employing the RX algorithm. Specifically, a local linear representation is designed to exploit the internal relationship between linearly correlated pixels in the local background region and the pixel under test and its neighbors. Experimental results demonstrate that the proposed detector improves the original local RX algorithm.

  8. Active flutter control using discrete optimal constrained dynamic compensators

    NASA Technical Reports Server (NTRS)

    Broussard, J. R.; Halyo, N.

    1983-01-01

    A method for synthesizing digital active flutter suppression controllers using the concept of optimal output feedback is presented. A recently developd convergent algorithm is employed to determine constrained control law parameters that minimize an infinite-time discrete quadratic performance index. Low-order compensator dynamics are included in the control law and the compensator parameters are computed along with the output feedback gain as part of the optimization process. An input noise adjustment procedure is used to improve the stability margins of the digital active flutter controller. Results from investigations into sample rate variation, prefilter pole variation, and effects of varying flight condtions are discussed. The study indicates that a digital control law which accommodates computation delay can stabilize the wing with reasonable rms performance and adequate stability margins.

  9. Constrained independent component analysis approach to nonobtrusive pulse rate measurements

    NASA Astrophysics Data System (ADS)

    Tsouri, Gill R.; Kyal, Survi; Dianat, Sohail; Mestha, Lalit K.

    2012-07-01

    Nonobtrusive pulse rate measurement using a webcam is considered. We demonstrate how state-of-the-art algorithms based on independent component analysis suffer from a sorting problem which hinders their performance, and propose a novel algorithm based on constrained independent component analysis to improve performance. We present how the proposed algorithm extracts a photoplethysmography signal and resolves the sorting problem. In addition, we perform a comparative study between the proposed algorithm and state-of-the-art algorithms over 45 video streams using a finger probe oxymeter for reference measurements. The proposed algorithm provides improved accuracy: the root mean square error is decreased from 20.6 and 9.5 beats per minute (bpm) for existing algorithms to 3.5 bpm for the proposed algorithm. An error of 3.5 bpm is within the inaccuracy expected from the reference measurements. This implies that the proposed algorithm provided performance of equal accuracy to the finger probe oximeter.

  10. Thermally-Constrained Fuel-Optimal ISS Maneuvers

    NASA Technical Reports Server (NTRS)

    Bhatt, Sagar; Svecz, Andrew; Alaniz, Abran; Jang, Jiann-Woei; Nguyen, Louis; Spanos, Pol

    2015-01-01

    Optimal Propellant Maneuvers (OPMs) are now being used to rotate the International Space Station (ISS) and have saved hundreds of kilograms of propellant over the last two years. The savings are achieved by commanding the ISS to follow a pre-planned attitude trajectory optimized to take advantage of environmental torques. The trajectory is obtained by solving an optimal control problem. Prior to use on orbit, OPM trajectories are screened to ensure a static sun vector (SSV) does not occur during the maneuver. The SSV is an indicator that the ISS hardware temperatures may exceed thermal limits, causing damage to the components. In this paper, thermally-constrained fuel-optimal trajectories are presented that avoid an SSV and can be used throughout the year while still reducing propellant consumption significantly.

  11. Constrained random-force model for weakly bending semiflexible polymers.

    PubMed

    Benetatos, Panayotis; Terentjev, Eugene M

    2011-08-01

    The random-force (Larkin) model of a directed elastic string subject to quenched random forces in the transverse directions has been a paradigm in the statistical physics of disordered systems. In this Brief Report, we investigate a modified version of the above model where the total transverse force along the polymer contour and the related total torque, in each realization of disorder, vanish. We discuss the merits of adding these constraints and show that they leave the qualitative behavior in the strong stretching regime unchanged, but they reduce the effects of the random force by significant numerical prefactors. We also show that a transverse random force effectively makes the filament softer to compression by inducing undulations. We calculate the related linear compression coefficient in both the usual and the constrained random-force model. PMID:21929049

  12. Constrained optimization of gradient waveforms for generalized diffusion encoding

    NASA Astrophysics Data System (ADS)

    Sjölund, Jens; Szczepankiewicz, Filip; Nilsson, Markus; Topgaard, Daniel; Westin, Carl-Fredrik; Knutsson, Hans

    2015-12-01

    Diffusion MRI is a useful probe of tissue microstructure. The conventional diffusion encoding sequence, the single pulsed field gradient, has recently been challenged as more general gradient waveforms have been introduced. Out of these, we focus on q-space trajectory imaging, which generalizes the scalar b-value to a tensor valued entity. To take full advantage of its capabilities, it is imperative to respect the constraints imposed by the hardware, while at the same time maximizing the diffusion encoding strength. We provide a tool that achieves this by solving a constrained optimization problem that accommodates constraints on maximum gradient amplitude, slew rate, coil heating and positioning of radio frequency pulses. The method's efficacy and flexibility is demonstrated both experimentally and by comparison with previous work on optimization of isotropic diffusion sequences.

  13. Formation of current singularity in a topologically constrained plasma

    NASA Astrophysics Data System (ADS)

    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.

  14. Phenolate constrained geometry polymerization catalyst and method for preparing

    DOEpatents

    Marks, Tobin J.; Chen, You-Xian

    1999-01-01

    The subject invention involves a method of preparing and the constrained geometry catalyst thereby prepared of the general formula Ar'R4(O)Ar"R'.sub.4 M(CH.sub.2 Ph).sub.2 where Ar' is a phenyl or naphthyl group; Ar" is a cyclopentadienyl or indenyl group, R and R' are H or alkyl substituents (C.ltoreq.10) and M is Ti, Zr or Hf. The synthetic method involves a simple alkane elimination approach which permits a "one-pot" procedure. The catalyst, when combined with a cocatalyst such as Pb.sub.3 C.sup.+ B(Ar.sub.3.sup.F).sub.4 BAr.sub.3.sup.F or methyl alumoxane where Ar.sup.F is a fluoroaryl group, is an effective catalyst for the polymerization of .alpha.-olefins such as ethylene, propylene and styrene.

  15. Magnetospheric plasma analyzer for spacecraft with constrained resources

    SciTech Connect

    Bame, S.J.; McComas, D.J.; Thomsen, M.F.; Barraclough, B.L.; Elphic, R.C.; Glore, J.P.; Gosling, J.T. ); Chavez, J.C.; Evans, E.P.; Wymer, F.J. )

    1993-04-01

    A light-weight, low-power, plasma analyzer is described that can be used for measuring the plasma environments of spacecraft with constrained resources. A unique system using a single electrostatic analyzer coupled to a single array of channel electron multipliers allows measurement of the three-dimensional energy per charge distributions of both ions and electrons over [ital E]/[ital q] ranges from [similar to]1 eV/[ital q] to [gt]40 keV/[ital q]. Particles selected by the analyzer are post-accelerated into the multipliers to maintain sensitivity for the lowest energy particles. An instrument using this concept called the magnetospheric plasma analyzer (MPA) is described. Presently, three MPAs are in geosynchronous orbits (GEO) aboard spacecraft with International Designators of 1989-046, 1990-095, and 1991-080. The MPA and its response characteristics are described, and examples of on-orbit data showing some of the MPA capabilities are presented.

  16. 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. PMID:23193324

  17. 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. PMID:19013054

  18. Constraining f(R) gravity by the Large Scale Structure

    NASA Astrophysics Data System (ADS)

    de Martino, Ivan; De Laurentis, Mariafelicia; Capozziello, Salvatore

    2015-07-01

    Over the past decades, General Relativity and the concordance ΛCDM model have been successfully tested using several different astrophysical and cosmological probes based on large datasets (precision cosmology). Despite their successes, some shortcomings emerge due to the fact that General Relativity should be revised at infrared and ultraviolet limits and to the fact that the fundamental nature of Dark Matter and Dark Energy is still a puzzle to be solved. In this perspective, f(R) gravity have been extensively investigated being the most straightforward way to modify General Relativity and to overcame some of the above shortcomings. In this paper, we review various aspects of f(R) gravity at extragalactic and cosmological levels. In particular, we consider cluster of galaxies, cosmological perturbations, and N-Body simulations, focusing on those models that satisfy both cosmological and local gravity constraints. The perspective is that some classes of f(R) models can be consistently constrained by Large Scale Structure.

  19. Constrained basin stability for studying transient phenomena in dynamical systems

    NASA Astrophysics Data System (ADS)

    van Kan, Adrian; Jegminat, Jannes; Donges, Jonathan F.; Kurths, Jürgen

    2016-04-01

    Transient dynamics are of large interest in many areas of science. Here, a generalization of basin stability (BS) is presented: constrained basin stability (CBS) that is sensitive to various different types of transients arising from finite size perturbations. CBS is applied to the paradigmatic Lorenz system for uncovering nonlinear precursory phenomena of a boundary crisis bifurcation. Further, CBS is used in a model of the Earth's carbon cycle as a return time-dependent stability measure of the system's global attractor. Both case studies illustrate how CBS's sensitivity to transients complements BS in its function as an early warning signal and as a stability measure. CBS is broadly applicable in systems where transients matter, from physics and engineering to sustainability science. Thus CBS complements stability analysis with BS as well as classical linear stability analysis and will be a useful tool for many applications.

  20. Stabilizing model predictive control for constrained nonlinear distributed delay systems.

    PubMed

    Mahboobi Esfanjani, R; Nikravesh, S K Y

    2011-04-01

    In this paper, a model predictive control scheme with guaranteed closed-loop asymptotic stability is proposed for a class of constrained nonlinear time-delay systems with discrete and distributed delays. A suitable terminal cost functional and also an appropriate terminal region are utilized to achieve asymptotic stability. To determine the terminal cost, a locally asymptotically stabilizing controller is designed and an appropriate Lyapunov-Krasoskii functional of the locally stabilized system is employed as the terminal cost. Furthermore, an invariant set for locally stabilized system which is established by using the Razumikhin Theorem is used as the terminal region. Simple conditions are derived to obtain terminal cost and terminal region in terms of Bilinear Matrix Inequalities. The method is illustrated by a numerical example. PMID:21232739