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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. 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.

  6. 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.

  7. 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.

  8. Synthesis of beta-hydroxy-alpha-amino acids with a reengineered alanine racemase.

    PubMed

    Fesko, Kateryna; Giger, Lars; Hilvert, Donald

    2008-11-15

    The Y265A mutant of alanine racemase (alrY265A) was evaluated as a catalyst for the synthesis of beta-hydroxy-alpha-amino acids. It promotes the PLP-dependent aldol condensation of glycine with a range of aromatic aldehydes. The desired products were obtained with complete stereocontrol at C(alpha) (ee>99%, D) and moderate to high selectivity at C(beta) (up to 97% de). The designed enzyme is thus similar to natural d-threonine aldolases in its substrate specificity and stereoselectivity. Moreover, its ability to utilize alanine as an alternative donor suggests an expanded scope of potential utility for the production of biologically active compounds. PMID:18760921

  9. 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

  10. 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

  11. The stability constants of copper(II) complexes with some alpha-amino acids in dioxan-water mixtures.

    PubMed

    Doğan, A; Köseoğlu, F; Kiliç, E

    2001-08-15

    In this study, the overall stability constants of copper(II) complexes with some alpha-amino acids (glycine, dl-alanine, dl-valine, l-leucine, l-asparagine, l-glutamine) were determined by potentiometric titration in water, 25% dioxan-75% water, 35% dioxan-65% water, 50% dioxan-50% water, and 60% dioxan-40% water. The titrations were performed at 25 degrees C, under nitrogen atmosphere, and the ionic strength of the medium was maintained at 0.10 M by using sodium perchlorate. The formation curves of their complexes (n-p[L]) were obtained by means of the titration data. Then the stability constants were determined in relation to these curves. The mol ratio of copper(II) to alpha-amino acid was also determined and it was found that the complexes were CuL(2) type. Another important result obtained was that the tendency of amino acids to form complexes with copper(II) was greater in dioxan-water mixtures compared to water. PMID:11488627

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

    PubMed

    Huber, Claudia; Wächtershäuser, Günter

    2006-10-27

    To test the theory of a chemoautotrophic origin of life in a volcanic, hydrothermal setting, we explored mechanisms for the buildup of bio-organic compounds by carbon fixation on catalytic transition metal precipitates. We report the carbon monoxide-dependent formation of carbon-fixation products, including an ordered series of alpha-hydroxy and alpha-amino acids of the general formula R-CHA-COOH (where R is H, CH3,C2H5,orHOCH2 and A is OH or NH2) by carbon fixation at 80 degrees to 120 degrees C, catalyzed by nickel or nickel,iron precipitates with carbonyl, cyano, and methylthio ligands as carbon sources, with or without sulfido ligands. Calcium or magnesium hydroxide was added as a pH buffer. The results narrow the gap between biochemistry and volcanic geochemistry and open a new gateway for the exploration of a volcanic, hydrothermal origin of life. PMID:17068257

  13. 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.

  14. 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.

  15. Mapping the X(+1) binding site of the Grb2-SH2 domain with alpha,alpha-disubstituted cyclic alpha-amino acids.

    PubMed

    García-Echeverría, C; Gay, B; Rahuel, J; Furet, P

    1999-10-18

    A series of phosphopeptides containing alpha,alpha-disubstituted cyclic alpha-amino acids (Ac(n)c, 3 < or = n < or = 7; n refers to the number of carbons in the ring) at the X(+1) position of Ac-Tyr(PO3H2)-X(+1)-Asn-NH2 has been synthesised and their inhibitory activity as antagonists of the Grb2-SH2 domain has been determined in competitive binding assays. The SAR data obtained have been interpreted by using models constructed from the X-ray structure of the ligand-bound Grb2-SH2 domain. The used of alpha,alpha-disubstituted cyclic alpha-amino acids to map the binding pockets of proteins expands the classical alanine scan concept and takes advantage of the known conformational preferences of these amino acids. PMID:10571147

  16. The organization of the gene for the functionally dominant alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor subunit GluR-B.

    PubMed

    Köhler, M; Kornau, H C; Seeburg, P H

    1994-07-01

    The murine gene encoding the GluR-B subunit of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors was characterized with respect to exon-intron organization, transcriptional start site, alternatively spliced transcripts, and adenosine to guanosine substitutions between gene and complementary DNA sequence. The GluR-B gene spans > 90 kilobase pairs and harbors 17 exons. Transcription appears to initiate approximately 430 nucleotides upstream of the translational start codon, with no intron in the 5'-untranslated region of the gene. Four alternatively spliced mRNAs are generated from the primary GluR-B transcript, two containing the modules Flip and Flop, and another two with alternate C-terminal coding sequence. The major GluR-B mRNAs in murine brain, 4 and 6 kilobase differ in the length of their 3'-untranslated region. PMID:7545935

  17. Ligand-Enabled β-C–H Arylation of Alpha-Amino Acids Using a Simple and Practical Auxiliary

    PubMed Central

    Chen, Gang; Shigenari, Toshihiko; Jain, Pankaj; Zhang, Zhipeng; Jin, Zhong; He, Jian; Li, Suhua; Mapelli, Claudio; Miller, Michael M.; Poss, Michael A.; Scola, Paul M.; Yeung, Kap-Sun

    2015-01-01

    Pd-catalyzed β-C–H functionalizations of carboxylic acid derivatives using an auxiliary as a directing group have been extensively explored in the past decade. In comparison to the most widely used auxiliaries in asymmetric synthesis, the simplicity and practicality of the auxiliaries developed for C–H activation remains to be improved. We previously developed a simple N-methoxyamide auxiliary to direct β-C–H activation, albeit this system was not compatible with carboxylic acids containing α-hydrogen atoms. Herein we report the development of a pyridine-type ligand that overcomes this limitation of the N-methoxyamide auxiliary, leading to a significant improvement of β-arylation of carboxylic acid derivatives, especially α-amino acids. The arylation using this practical auxiliary is applied to the gram-scale syntheses of unnatural amino acids, bioactive molecules and chiral bis(oxazoline) ligands. PMID:25697780

  18. 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.

  19. Hydrodynamic and pharmacological characterization of putative alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate-sensitive L-glutamate receptors solubilized from pig brain.

    PubMed Central

    Wu, T Y; Chang, Y C

    1994-01-01

    L-[3H]Glutamate binding sites with characteristics resembling that of membrane-bound alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate-subtype L-glutamate receptors have been solubilized from pig brain synaptic junctions by Triton X-114. Binding of [3H]AMPA to these soluble sites in the presence of KSCN results in a curvilinear Scatchard plot that can be resolved into a high-affinity component and a low-affinity component. These Triton-X-114-solubilized sites can be further separated into two species of binding sites by gel-filtration chromatography or sucrose-density-gradient centrifugation. The pharmacological profiles of these two species of binding site are almost identical, and the rank orders of potency for glutamatergic drugs in displacing L-[3H]glutamate binding to these sites are quisqualate > 6,7-dinitroquinoxaline-2,3-dione > 6-cyano-7-nitroquinoxaline-2,3-dione > AMPA > L-glutamate > kainate >> N-methyl-D-aspartate = L-2-amino-4-phosphonobutyrate. Both sites are found to bind [3H]AMPA, and in the presence of KSCN the binding activities are significantly enhanced. Analysis of the hydrodynamic behaviour of these binding sites by sucrose-density-gradient centrifugation in H2O- and 2H2O-based solvents and gel-filtration chromatography has revealed that one of these sites (Stokes radius 8.3 nm, sedimentation coefficient 18.5 S) consists of 562 kDa protein and 281 kDa detergent, and the other site (Stokes radius 9.6 nm, sedimentation coefficient 13.4 S) consists of 352 kDa protein and 569 kDa detergent. Frictional coefficients of these sites indicate that these receptor-detergent complexes are asymmetrical in structure, consistent with large transmembrane proteins. PMID:7516151

  20. Hydrodynamic and pharmacological characterization of putative alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate-sensitive L-glutamate receptors solubilized from pig brain.

    PubMed

    Wu, T Y; Chang, Y C

    1994-06-01

    L-[3H]Glutamate binding sites with characteristics resembling that of membrane-bound alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate-subtype L-glutamate receptors have been solubilized from pig brain synaptic junctions by Triton X-114. Binding of [3H]AMPA to these soluble sites in the presence of KSCN results in a curvilinear Scatchard plot that can be resolved into a high-affinity component and a low-affinity component. These Triton-X-114-solubilized sites can be further separated into two species of binding sites by gel-filtration chromatography or sucrose-density-gradient centrifugation. The pharmacological profiles of these two species of binding site are almost identical, and the rank orders of potency for glutamatergic drugs in displacing L-[3H]glutamate binding to these sites are quisqualate > 6,7-dinitroquinoxaline-2,3-dione > 6-cyano-7-nitroquinoxaline-2,3-dione > AMPA > L-glutamate > kainate > N-methyl-D-aspartate = L-2-amino-4-phosphonobutyrate. Both sites are found to bind [3H]AMPA, and in the presence of KSCN the binding activities are significantly enhanced. Analysis of the hydrodynamic behaviour of these binding sites by sucrose-density-gradient centrifugation in H2O- and 2H2O-based solvents and gel-filtration chromatography has revealed that one of these sites (Stokes radius 8.3 nm, sedimentation coefficient 18.5 S) consists of 562 kDa protein and 281 kDa detergent, and the other site (Stokes radius 9.6 nm, sedimentation coefficient 13.4 S) consists of 352 kDa protein and 569 kDa detergent. Frictional coefficients of these sites indicate that these receptor-detergent complexes are asymmetrical in structure, consistent with large transmembrane proteins. PMID:7516151

  1. Temperature-induced inversion of the elution order of enantiomers in gas chromatography: N-ethoxycarbonyl propylamides and N-trifluoroacetyl ethyl esters of alpha-amino acids on Chirasil-Val-C11 and Chirasil-Dex stationary phases.

    PubMed

    Levkin, Pavel A; Levkina, Anna; Czesla, Harri; Schurig, Volker

    2007-06-15

    Inversion of the elution order of enantiomers caused by enthalpy-entropy compensation at the isoenantioselective temperature (Tiso) was experimentally observed by gas chromatography on the diamide-type chiral stationary phase (CSP), Chirasil-L-Val-C11, with N-ethoxycarbonyl propylamide (ECPA) derivatives of a number of alpha-amino acids. For the first time, a clear visual representation of the increase of the apparent enantioseparation factor alpha app from 1.00 to 1.08 as the temperature is raised from 120 to 170 degrees C is presented. The increase of alpha app is accompanied by a concomitant reduction of the retention factors of the enantiomers. The Tiso values were in the range from 110 to 130 degrees C depending on the nature of the alpha-amino acid. On the contrary, the Tiso values of the N(O)-trifluoroacetyl ethyl ester derivatives (TFA-Et) of the same alpha-amino acids were approximately 80 degrees higher than that of ECPA derivatives. The comprehensive thermodynamic investigation of the enantioseparation of ECPA and TFA-Et derivatives of valine and alanine using the retention increment method showed that the Delta L,D(DeltaH) difference between the diastereomeric selector-selectand associates was almost the same for ECPA and TFA-Et derivatives despite a much stronger bonded selector-selectand association taking place for the ECPA derivatives. On the other hand, the Delta L,D(DeltaS) values were found to be more negative in the case of ECPA derivatives, resulting in the unusually low values of Tiso. A temperature-dependent inversion of the elution order of enantiomers was also observed on the cyclodextrin-type CSP, Chirasil-Dex, with TFA-Et derivatives of several alpha-amino acids. The Tiso values were in the range from 20 to 170 degrees C depending on the nature of the alpha-amino acid. The results obtained demonstrate the necessity to conduct temperature-dependent studies in order to optimize the enantiomeric separation of single racemates isothermally or

  2. DNA cleavage by new oxovanadium(IV) complexes of N-salicylidene alpha-amino acids and phenanthroline bases in the photodynamic therapy window.

    PubMed

    Sasmal, Pijus K; Patra, Ashis K; Nethaji, Munirathinam; Chakravarty, Akhil R

    2007-12-24

    Oxovanadium(IV) complexes [VO(salmet)(B)] (1-3) and [VO(saltrp)(B)] (4-6), where salmet and saltrp are N-salicylidene-l-methionate and N-salicylidene-l-tryptophanate, respectively, and B is a N,N-donor heterocyclic base (viz. 1,10-phenanthroline (phen, 1, 4), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 2, 5), and dipyrido[3,2-a:2',3'-c]phenazine (dppz, 3, 6)) are prepared and characterized and their DNA binding and photoinduced DNA cleavage activity studied. Complexes 1, 2, and 4 are structurally characterized by single-crystal X-ray crystallography. The molecular structure shows the presence of a vanadyl group in the VO3N3 coordination geometry. The dianionic alpha-amino acid Schiff base acts as a tridentate O,N,O-donor ligand in a meridional binding mode. The N,N-donor heterocyclic base displays a chelating mode of bonding with a N-donor site trans to the oxo group. The complexes show a d-d band in the range of 680-710 nm in DMF with a shoulder near 840 nm. They exhibit an irreversible oxidative cyclic voltammetric response near 0.8 V assignable to the V(V)/V(IV) couple and a quasi-reversible V(IV)/V(III) redox couple near -1.1 V vs SCE in DMF-0.1 M TBAP. The complexes show good binding propensity to calf thymus DNA giving binding constant values in the range from 5.2 x 10(4) to 7.2 x 10(5) M(-1). The binding site size, thermal melting, and viscosity data suggest DNA surface and/or groove binding nature of the complexes. The complexes show poor "chemical nuclease" activity in the dark in the presence of 3-mercaptopropionic acid or hydrogen peroxide. The dpq and dppz complexes show efficient DNA cleavage activity on irradiation with UV-A light of 365 nm via a mechanistic pathway involving formation of singlet oxygen as the reactive species. They also show significant DNA cleavage activity on photoexcitation in red light (>750 nm) by (1)O2 species. Observation of red-light-induced cleavage of DNA is unprecedented in the vanadium chemistry. The DNA cleavage activity is

  3. Dehydration of (R)-2-hydroxyacyl-CoA to enoyl-CoA in the fermentation of alpha-amino acids by anaerobic bacteria.

    PubMed

    Kim, Jihoe; Hetzel, Marc; Boiangiu, Clara Dana; Buckel, Wolfgang

    2004-10-01

    Several clostridia and fusobacteria ferment alpha-amino acids via (R)-2-hydroxyacyl-CoA, which is dehydrated to enoyl-CoA by syn-elimination. This reaction is of great mechanistic interest, since the beta-hydrogen, to be eliminated as proton, is not activated (pK 40-50). A mechanism has been proposed, in which one high-energy electron acts as cofactor and transiently reduces the electrophilic thiol ester carbonyl to a nucleophilic ketyl radical anion. The 2-hydroxyacyl-CoA dehydratases are two-component systems composed of an extremely oxygen-sensitive component A, an activator, and component D, the actual dehydratase. Component A, a homodimer with one [4Fe-4S]cluster, transfers an electron to component D, a heterodimer with 1-2 [4Fe-4S]clusters and FMN, concomitant with hydrolysis of two ATP. From component D the electron is further transferred to the substrate, where it facilitates elimination of the hydroxyl group. In the resulting enoxyradical the beta-hydrogen is activated (pK14). After elimination the electron is handed-over to the next incoming substrate without further hydrolysis of ATP. The helix-cluster-helix architecture of component A forms an angle of 105 degrees, which probably opens to 180 degrees upon binding of ATP resembling an archer shooting arrows. Therefore we designated component A as 'Archerase'. Here, we describe 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans, Clostridium symbiosum and Fusobacterium nucleatum, 2-phenyllactate dehydratase from Clostridium sporogenes, 2-hydroxyisocaproyl-CoA dehydratase from Clostridium difficile, and lactyl-CoA dehydratase from Clostridium propionicum. A relative of the 2-hydroxyacyl-CoA dehydratases is benzoyl-CoA reductase from Thauera aromatica. Analogous but unrelated archerases are the iron proteins of nitrogenase and bacterial protochlorophyllide reductase. In anaerobic organisms, which do not oxidize 2-oxo acids, a second energy-driven electron transfer from NADH to ferredoxin, the

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

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

    PubMed

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

    1996-11-01

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

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

    PubMed Central

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

    1996-01-01

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

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

    PubMed

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

    2007-09-14

    Mannich-type addition of benzophenone imine glycinates across newly synthesized N-(p-toluenesulfonyl) alpha-chloroaldimines afforded gamma-chloro-alpha,beta-diamino ester derivatives with moderate diastereoselectivity as separable mixtures of anti and syn diastereomers. The gamma-chloro-alpha,beta-diamino esters were efficiently cyclized under basic conditions to the corresponding beta,gamma-aziridino alpha-amino ester derivatives, representing a new class of conformationally constrained heterocyclic alpha,beta-diamino acid derivatives. The relative configuration of the aziridines was determined via X-ray diffraction analysis. Mechanisms and intermediate transition states to explain the stereochemical outcome of the Mannich reaction with different substrates or under different conditions are proposed. The synthetic importance of the beta,gamma-aziridino alpha-amino ester derivatives is demonstrated by their conversion into the corresponding Boc-protected derivatives and ring opening reactions to alpha,beta-diamino esters and a gamma-amino alpha,beta-unsaturated amino ester. PMID:17705431

  8. 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

  9. Phosphorus constrains accelerated nitrogen cycling in limed acidic forests

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  10. Synthesis of a bicyclic delta-amino acid as a constrained Gly-Asn dipeptide isostere.

    PubMed

    Trabocchi, A; Menchi, G; Danieli, E; Guarna, A

    2008-06-01

    Delta-amino acids are very attractive in drug discovery, especially in the peptidomimetic area, because of their capability to act as dipeptide isosteres and reverse turn mimetics. Herein we report the synthesis of a rigid delta-amino acid constrained by a 3-aza-6,8-dioxabicyclo[3.2.1]octane-based scaffold, which can be considered as a Gly-Asn dipeptide mimetic. Key steps are the condensation of glycidol and tartaric acid derivatives, and the intramolecular trans-acetalization of the oxidized adduct to give the bicyclic delta-amino acid. Starting from L-tartaric acid derivative, it was achieved the corresponding Gly-D-Asn isostere, whereas from the enantiomeric D-tartaric acid derivative the corresponding Gly-L-Asn isostere could be obtained, thus giving access to both enantiomeric dipeptide sequences. PMID:18235990

  11. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  13. 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

  14. Okadaic acid-sensitive protein phosphatases constrain phrenic long-term facilitation after sustained hypoxia.

    PubMed

    Wilkerson, Julia E R; Satriotomo, Irawan; Baker-Herman, Tracy L; Watters, Jyoti J; Mitchell, Gordon S

    2008-03-12

    Phrenic long-term facilitation (pLTF) is a serotonin-dependent form of pattern-sensitive respiratory plasticity induced by intermittent hypoxia (IH), but not sustained hypoxia (SH). The mechanism(s) underlying pLTF pattern sensitivity are unknown. SH and IH may differentially regulate serine/threonine protein phosphatase activity, thereby inhibiting relevant protein phosphatases uniquely during IH and conferring pattern sensitivity to pLTF. We hypothesized that spinal protein phosphatase inhibition would relieve this braking action of protein phosphatases, thereby revealing pLTF after SH. Anesthetized rats received intrathecal (C4) okadaic acid (25 nm) before SH (25 min, 11% O(2)). Unlike (vehicle) control rats, SH induced a significant pLTF in okadaic acid-treated rats that was indistinguishable from rats exposed to IH (three 5 min episodes, 11% O(2)). IH and SH with okadaic acid may elicit pLTF by similar, serotonin-dependent mechanisms, because intravenous methysergide blocks pLTF in rats receiving IH or okadaic acid plus SH. Okadaic acid did not alter IH-induced pLTF. In summary, pattern sensitivity in pLTF may reflect differential regulation of okadaic acid-sensitive serine/threonine phosphatases; presumably, these phosphatases are less active during/after IH versus SH. The specific okadaic acid-sensitive phosphatase(s) constraining pLTF and their spatiotemporal dynamics during and/or after IH and SH remain to be determined. PMID:18337426

  15. 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.

  16. 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.

  17. 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

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

    PubMed

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

    2010-01-01

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

  19. 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.

  20. 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.

  1. Chance-constrained/stochastic linear programming model for acid rain abatement—I. Complete colinearity and noncolinearity

    NASA Astrophysics Data System (ADS)

    Ellis, J. H.; McBean, E. A.; Farquhar, G. J.

    A Linear Programming model is presented for development of acid rain abatement strategies in eastern North America. For a system comprised of 235 large controllable point sources and 83 uncontrolled area sources, it determines the least-cost method of reducing SO 2 emissions to satisfy maximum wet sulfur deposition limits at 20 sensitive receptor locations. In this paper, the purely deterministic model is extended to a probabilistic form by incorporating the effects of meteorologic variability on the long-range pollutant transport processes. These processes are represented by source-receptor-specific transfer coefficients. Experiments for quantifying the spatial variability of transfer coefficients showed their distributions to be approximately lognormal with logarithmic standard deviations consistently about unity. Three methods of incorporating second-moment random variable uncertainty into the deterministic LP framework are described: Two-Stage Programming Under Uncertainty (LPUU), Chance-Constrained Programming (CCP) and Stochastic Linear Programming (SLP). A composite CCP-SLP model is developed which embodies the two-dimensional characteristics of transfer coefficient uncertainty. Two probabilistic formulations are described involving complete colinearity and complete noncolinearity for the transfer coefficient covariance-correlation structure. Complete colinearity assumes complete dependence between transfer coefficients. Complete noncolinearity assumes complete independence. The completely colinear and noncolinear formulations are considered extreme bounds in a meteorologic sense and yield abatement strategies of largely didactic value. Such strategies can be characterized as having excessive costs and undesirable deposition results in the completely colinear case and absence of a clearly defined system risk level (other than expected-value) in the noncolinear formulation.

  2. Physiological Adaptation to the Loss of Amino Acid Transport Ability

    PubMed Central

    DeBusk, Ruth M.; Ogilvie-Villa, Susan

    1982-01-01

    A strain of Neurospora crassa devoid of constitutive amino acid transport ability can utilize arginine as the sole nitrogen source. Nitrogen starvation, presence of arginine, and mutational inactivation of the general permease are key factors in signaling production of an extracellular enzyme which removes the alpha-amino group from the amino acid. PMID:6214547

  3. Hydrogen-bond motifs in the crystals of hydrophobic amino acids.

    PubMed

    Fábián, László; Chisholm, James A; Galek, Peter T A; Motherwell, W D Samuel; Feeder, Neil

    2008-08-01

    A computer program has been developed to survey a set of crystal structures for hydrogen-bond motifs. Possible ring and chain motifs are generated automatically from a user-defined list of interacting molecular fragments and intermolecular interactions. The new program was used to analyse the hydrogen-bond networks in the crystals of 52 zwitterionic alpha-amino acids. All the possible chain motifs (repeating 1-4 molecules) are frequent, while the frequency of ring motifs (2-6 molecules) ranges from 0 to 85% of the structures. The list of motifs displayed by each structure reveals structural similarities and it can be used to compare polymorphs. The motifs formed in cocrystals of alpha-amino acids and in crystals of beta- and gamma-amino acids are similar to those of alpha-amino acids. PMID:18641453

  4. Mechanism of alpha-amino acids decomposition in the gas phase. experimental and theoretical study of the elimination kinetics of N-benzyl glycine ethyl ester.

    PubMed

    Tosta, Maria; Oliveros, Jhenny C; Mora, Jose R; Córdova, Tania; Chuchani, Gabriel

    2010-02-25

    The gas-phase elimination kinetics of N-benzylglycine ethyl ester was examined in a static system, seasoned with allyl bromide, and in the presence of the free chain radical suppressor toluene. The working temperature and pressure range were 386.4-426.7 degrees C and 16.7-40.0 torr, respectively. The reaction showed to be homogeneous, unimolecular, and obeys a first-order rate law. The elimination products are benzylglycine and ethylene. However, the intermediate benzylglycine is unstable under the reaction conditions decomposing into benzyl methylamine and CO(2) gas. The variation of the rate coefficients with temperature is expressed by the following Arrhenius equation: log k(1) (s(-1)) = (11.83 +/- 0.52) - (190.3 +/- 6.9) kJ mol(-1) (2.303RT)(-1). The theoretical calculation of the kinetic parameters and mechanism of elimination of this ester were performed at B3LYP/6-31G*, B3LYP/6-31+G**, MPW1PW91/6-31G*, and MPW1PW91/6-31+G** levels of theory. The calculation results suggest a molecular mechanism of a concerted nonsynchronous six-membered cyclic transition state process. The analysis of bond order and natural bond orbital charges implies that the bond polarization of C(=O)O-C, in the sense of C(=O)O(delta-)...C(delta+), is rate determining. The experimental and theoretical parameters have been found to be in reasonable agreement. PMID:20121282

  5. Enantiomeric excesses in meteoritic amino acids

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.; Pizzarello, S.

    1997-01-01

    Gas chromatographic-mass spectral analyses of the four stereoisomers of 2-amino-2,3-dimethylpentanoic acid (dl-alpha-methylisoleucine and dl-alpha-methylalloisoleucine) obtained from the Murchison meteorite show that the L enantiomer occurs in excess (7.0 and 9.1%, respectively) in both of the enantiomeric pairs. Similar results were obtained for two other alpha-methyl amino acids, isovaline and alpha-methylnorvaline, although the alpha hydrogen analogs of these amino acids, alpha-amino-n-butyric acid and norvaline, were found to be racemates. With the exception of alpha-amino-n-butyric acid, these amino acids are either unknown or of limited occurrence in the biosphere. Because carbonaceous chondrites formed 4.5 billion years ago, the results are indicative of an asymmetric influence on organic chemical evolution before the origin of life.

  6. Aminocarbonylation of 4-iodo-1H-imidazoles with an amino acid amide nucleophile: synthesis of constrained H-Phe-Phe-NH2 analogues.

    PubMed

    Skogh, Anna; Fransson, Rebecca; Sköld, Christian; Larhed, Mats; Sandström, Anja

    2013-12-01

    A simple and an expedient process to prepare 5-aryl-1-benzyl-1H-imidazole-4-carboxamides by the aminocarbonylation of 5-aryl-4-iodo-1H-imidazoles using ex situ generation of CO from Mo(CO)6 with an amino acid amide nucleophile is reported. Furthermore, a microwave-assisted protocol for the direct C-5 arylation of 1-benzyl-1H-imidazole and a regioselective C-4 iodination method to acquire starting material for our aminocarbonylation are presented. The method can be used to prepare imidazole based peptidomimetics, herein exemplified by the synthesis of constrained H-Phe-Phe-NH2 analogues. PMID:24171628

  7. 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.

  8. Origin of Helical Screw Sense Selectivity Induced by Chiral Constrained Cα-Tetrasubstituted α-Amino Acids in Aib-based Peptides.

    PubMed

    Maffucci, Irene; Clayden, Jonathan; Contini, Alessandro

    2015-11-01

    The mechanisms behind the propensity of chiral constrained Cα-tetrasubstituted amino acids (cCTAAs) to induce one particular helical screw sense, when included in the Ac-Aib2-cCTAA-Aib2-NHMe peptide model, were studied through replica exchange molecular dynamics, potential of mean force, and quantum theory of atoms in molecules calculations. We observed that cCTAAs exert their effect on helical screw sense selectivity through the positioning of the side chain to generate steric hindrance in either the (-x, +y, +z) or (+x, +y, -z) sectors of a right-handed 3D Cartesian space, where the z axis corresponds to the axis of the helix and the Cα lies on the +y semiaxis (0, +y, 0). The different strengthening of the noncovalent interactions, also comprising C-H···O interactions, exerted by the cCTAA in the right-handed or left-handed helix was also found important to define the preference of a cCTAA for a particular helix screw sense. PMID:26457452

  9. 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.

  10. 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.

  11. Bispalladacycle-catalyzed Brønsted acid/base-promoted asymmetric tandem azlactone formation-Michael addition.

    PubMed

    Weber, Manuel; Jautze, Sascha; Frey, Wolfgang; Peters, René

    2010-09-01

    Cooperative activation by a soft bimetallic catalyst, a hard Brønsted acid, and a hard Brønsted base has allowed the formation of highly enantioenriched, diastereomerically pure masked alpha-amino acids with adjacent quaternary and tertiary stereocenters in a single reaction starting from racemic N-benzoylated amino acids. The products can, for example, be used to prepare bicyclic dipeptides. PMID:20715774

  12. Exogenous amino acids as fuel in shock.

    PubMed

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

    1982-01-01

    It has been suggested that in shock branched-chain amino acids are preferentially oxidized resulting in continued proteolysis and stimulated gluconeogenesis. To determine if exogenous amino acids could be used as fuel in shock, dogs rendered hypotensive by controlled cardiac tamponade and normotensive controls were infused with amino acid mixtures and individual amino acids. When Nephramine, a mixture rich in branched-chain amino acids, was infused, plasma alpha-amino nitrogen levels rose but urea output did not increase in either the control state or in shock, suggesting that these amino acids were not rapidly deaminated to serve as fuels. Travasol, which in addition contained large amounts of alanine and glycine, tripled urea output in the controls and doubled it in shock. The limit of urea production was reached in both groups at 35 mumoles urea/minute/kg. In the Travasol-infused animals plasma alpha-amino nitrogen levels were maintained in normotension but rose sharply in shock. When glycine alone was infused into five dogs in shock urea production rate was 30.6 + 2.1 mumoles/minute/kg; with alanine the same value was 22.5 + 2.2 mumoles/minute/kg. In both cases plasma alpha-amino nitrogen levels were high, suggesting that transport of these amino acids into the cell was slow in shock. In four dogs in shock glycine-14C was added to the glycine infusate as a tracer. At radioactive equilibrium 28% of the label infused appeared in CO2; another 22% appeared in glucose. It is concluded that of all the amino acids tested only glycine and alanine are deaminated rapidly enough to serve as exogenous fuels in shock. PMID:6814205

  13. Carboranyl amino acids for the specific neutron capture therapy of malignant melanoma

    SciTech Connect

    Kahl, S.B.

    1991-01-15

    We are pleased to summarize the very significant progress made since our last report dated April 6, 1990. Significant progress has been made toward our twin objectives of both the steroselective and non-steroselective synthesis of carborane-containing amino acids for boron neutron capture therapy of malignant melanoma. Additionally, we have developed a new, general procedure for the synthesis of a variety of {alpha}-amino acids which may find wide applicability in this area. 8 refs., 5 figs., 1 tab.

  14. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  16. Nonprotein amino acids from spark discharges and their comparison with the murchison meteorite amino acids.

    PubMed

    Wolman, Y; Haverland, W J; Miller, S L

    1972-04-01

    All the nonprotein amino acids found in the Murchison meteorite are products of the action of electric discharge on a mixture of methane, nitrogen, and water with traces of ammonia. These amino acids include alpha-amino-n-butyric acid, alpha-aminoisobutyric acid, norvaline, isovaline, pipecolic acid, beta-alanine, beta-amino-n-butyric acid, beta-aminoisobutyric acid, gamma-aminobutyric acid, sarcosine, N-ethylglycine, and N-methylalanine. In addition, norleucine, alloisoleucine, N-propylglycine, N-isopropylglycine, N-methyl-beta-alanine, N-ethyl-beta-alanine alpha,beta-diaminopropionic acid, isoserine, alpha,gamma-diaminobutyric acid, and alpha-hydroxy-gamma-aminobutyric acid are produced by the electric discharge, but have not been found in the meteorite. PMID:16591973

  17. 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

  18. A multinuclear NMR relaxation study of the interaction of divalent metal ions with L-aspartic acid.

    PubMed

    Khazaeli, S; Viola, R E

    1984-09-01

    Carbon-13 spin-lattice relaxation times, T1, have been measured for aqueous solutions of L-aspartic acid, L-alanine, O-phospho-L-serine, and 2-mercapto-L-succinic acid in the presence of the paramagnetic metal ions, Cu2+ and Mn2+, and Mg2+ as a diamagnetic control, at ambient temperature and neutral pH. Nitrogen-15, oxygen-17 and proton relaxation times were also obtained for L-aspartic acid and phosphorus-31 relaxation times for O-phospho-L-serine under similar conditions. The structures of these complexes in solution were determined from the various metal ion-nuclei distances calculated from the paramagnetically-induced relaxation. These results indicate that the Cu2+ interaction with L-aspartic acid is through alpha-amino and beta-carboxyl groups while Mn2+ coordinates most strongly through alpha- and beta-carboxyl groups, with the possibility of a weak interaction through the amino group. An examination of the coordination of these divalent metal ions to an analog of L-aspartic acid in which the beta-carboxyl group is replaced by a phosphate group (O-phospho-L-serine) indicated that Cu2+ coordination is now probably through the alpha-amino and phosphate groups, while this analog is a monodentate ligand for Mn2+ coordinating through the phosphate group. Removal of the beta-carboxyl group (L-alanine) also results in Cu2+ coordination through the alpha-carboxyl and alpha-amino groups, and the same ligand interactions are observed with Mn2+. Replacement of the alpha-amino group of L-aspartic acid with an -SH group (2-mercapto-L-succinate) is sufficient to eliminate any specific coordination with either Cu2+ or Mn2+. PMID:6491655

  19. 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.

  20. 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

  1. Choosing health, constrained choices.

    PubMed

    Chee Khoon Chan

    2009-12-01

    In parallel with the neo-liberal retrenchment of the welfarist state, an increasing emphasis on the responsibility of individuals in managing their own affairs and their well-being has been evident. In the health arena for instance, this was a major theme permeating the UK government's White Paper Choosing Health: Making Healthy Choices Easier (2004), which appealed to an ethos of autonomy and self-actualization through activity and consumption which merited esteem. As a counterpoint to this growing trend of informed responsibilization, constrained choices (constrained agency) provides a useful framework for a judicious balance and sense of proportion between an individual behavioural focus and a focus on societal, systemic, and structural determinants of health and well-being. Constrained choices is also a conceptual bridge between responsibilization and population health which could be further developed within an integrative biosocial perspective one might refer to as the social ecology of health and disease. PMID:20028669

  2. 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.

  3. 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.

  4. 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).

  5. Constrained Canonical Correlation.

    ERIC Educational Resources Information Center

    DeSarbo, Wayne S.; And Others

    1982-01-01

    A variety of problems associated with the interpretation of traditional canonical correlation are discussed. A response surface approach is developed which allows for investigation of changes in the coefficients while maintaining an optimum canonical correlation value. Also, a discrete or constrained canonical correlation method is presented. (JKS)

  6. Plasma and cerebrosponal fluid amino acid levels in diabetic ketoacidosis before and after corrective therapy.

    PubMed

    Aoki, T T; Assal J-P; Manzano, F M; Kozak, G P; Cahill, G F

    1975-05-01

    To evaluate the effect of insulin-saline-bicarbonate therapy on amino acid metabolism in diabetic ketoacidosis, arterial and venous blood samples as well as cerebrospinal fluid (CSF) were obtained from six patients before and after initiation of corrective therapy. Levels of CSF glutamine were decreased while alanine alpha-amino-n-butyrate, valine, isoleucine and leucine were increased significantly compared to a control group composed of six normal, postabsorptive adults free of any neurologic disease. Following therapy, CSF levels of alanine, alpha-amino-n-butyrate, valine, isoleucine, and leucine declined while glutamine levels did not change. Admission arterial plasma levels of the glycogenic amino acids were lower than normal while the branched-chain amino acids were elevated. Plasma alanine and glutamine arterio-venous (A-V) differences across forearm tissue were larger. After four hours of corrective therapy, arterial plasma levels of most of the amino acids had declined sharply and A-V differences for glutamine and alanine were markedly reduced (p smaller than.025 and p smaller than.01, paired t, respectively). Coincident with the decrease in A-V amino acid differences, plasma glucagon and free fatty acid levels declined significantly. These data suggest that the effect exerted by insulin-saline-bicarbonate therapy on amino acid metabolism is manifested by diminished A-V plasma alanine and glutamine differences across forearm tissue. Thus, the role played by the splanchnic bed both before and following corrective measures may be secondary to substrate availability. PMID:805076

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. Constraining Dark Energy

    NASA Astrophysics Data System (ADS)

    Abrahamse, Augusta

    2010-12-01

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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Amino acid analogs for tumor imaging

    DOEpatents

    Goodman, Mark M.; Shoup, Timothy

    1998-09-15

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

  17. Amino acid analogs for tumor imaging

    DOEpatents

    Goodman, 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.

  18. 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.

  19. 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.

  20. Constrained Clustering With Imperfect Oracles.

    PubMed

    Zhu, Xiatian; Loy, Chen Change; Gong, Shaogang

    2016-06-01

    While clustering is usually an unsupervised operation, there are circumstances where we have access to prior belief that pairs of samples should (or should not) be assigned with the same cluster. Constrained clustering aims to exploit this prior belief as constraint (or weak supervision) to influence the cluster formation so as to obtain a data structure more closely resembling human perception. Two important issues remain open: 1) how to exploit sparse constraints effectively and 2) how to handle ill-conditioned/noisy constraints generated by imperfect oracles. In this paper, we present a novel pairwise similarity measure framework to address the above issues. Specifically, in contrast to existing constrained clustering approaches that blindly rely on all features for constraint propagation, our approach searches for neighborhoods driven by discriminative feature selection for more effective constraint diffusion. Crucially, we formulate a novel approach to handling the noisy constraint problem, which has been unrealistically ignored in the constrained clustering literature. Extensive comparative results show that our method is superior to the state-of-the-art constrained clustering approaches and can generally benefit existing pairwise similarity-based data clustering algorithms, such as spectral clustering and affinity propagation. PMID:25622327

  1. 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.…

  2. 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

  3. 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

  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 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

  9. 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.

  10. Spacetime-constrained oblivious transfer

    NASA Astrophysics Data System (ADS)

    Pitalúa-García, Damián

    2016-06-01

    In 1-out-of-2 oblivious transfer (OT), Alice inputs numbers x0,x1 , Bob inputs a bit b and outputs xb. Secure OT requires that Alice and Bob learn nothing about b and xb ¯, respectively. We define spacetime-constrained oblivious transfer (SCOT) as OT in Minkowski spacetime in which Bob must output xb within Rb, where R0 and R1 are fixed spacelike separated spacetime regions. We show that unconditionally secure SCOT is impossible with classical protocols in Minkowski (or Galilean) spacetime, or with quantum protocols in Galilean spacetime. We describe a quantum SCOT protocol in Minkowski spacetime, and we show it unconditionally secure.

  11. Image compression using constrained relaxation

    NASA Astrophysics Data System (ADS)

    He, Zhihai

    2007-01-01

    In this work, we develop a new data representation framework, called constrained relaxation for image compression. Our basic observation is that an image is not a random 2-D array of pixels. They have to satisfy a set of imaging constraints so as to form a natural image. Therefore, one of the major tasks in image representation and coding is to efficiently encode these imaging constraints. The proposed data representation and image compression method not only achieves more efficient data compression than the state-of-the-art H.264 Intra frame coding, but also provides much more resilience to wireless transmission errors with an internal error-correction capability.

  12. 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

  13. Constraining Lorentz Violation with Cosmology

    SciTech Connect

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  15. Quantum Annealing for Constrained Optimization

    NASA Astrophysics Data System (ADS)

    Hen, Itay; Spedalieri, Federico

    Recent advances in quantum technology have led to the development and manufacturing of experimental programmable quantum annealers that could potentially solve certain quadratic unconstrained binary optimization problems faster than their classical analogues. The applicability of such devices for many theoretical and practical 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 removes many of the obstacles associated with the implementation of these. We argue the advantages of the proposed technique and illustrate its effectiveness. We then conclude by discussing the experimental feasibility of the suggested method as well as its potential to boost the encodability of other optimization problems.

  16. 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.

  17. 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

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

    PubMed

    Ghosh, Shalini; Jana, Sankar; Guchhait, Nikhil

    2011-12-15

    The polarity sensitive intra-molecular charge transfer (ICT) emission from (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester (MAPAME) is found to show distinct changes once introduced into the nano-cavities of cyclodextrins in aqueous environment. Movement of the molecule from the more polar aqueous environment to the less polar, hydrophobic cyclodextrin interior is marked by the blue shift of the CT emission band with simultaneous fluorescence intensity enhancement. The emission spectral changes on complexation with the α- and β-CD show different stoichiometries as observed from the Benesi-Hildebrand plots. Fluorescence anisotropy and lifetime measurements were performed to probe the different behaviors of MAPAME in aqueous α- and β-CD solutions. PMID:21996591

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

    NASA Astrophysics Data System (ADS)

    Ghosh, Shalini; Jana, Sankar; Guchhait, Nikhil

    2011-12-01

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

  20. Covalent protein crosslinks: general detection, quantitation, and characterization via modification with diphenylborinic acid.

    PubMed

    Graham, L; Gallop, P M

    1994-03-01

    Progressive crosslinking of proteins appears to be a general phenomenon in aging cells and tissues. Crosslinked proteins can form insoluble aggregates which become increasingly resistant to proteolysis as more crosslinks form. However, most evidence for progressive crosslinking with age is indirect, and little is known about the chemical mechanisms involved. We have therefore developed a method for detection and isolation of any type of stable covalent crosslink from protein hydrolysates which requires no prior knowledge of the molecular structure of whatever crosslink(s) may be present. It utilizes the specificity of the diphenylborinic acid reagent for alpha-amino acid groups and the chromatographic properties and uv absorbance of the crosslink derivatives. The method is demonstrated using eight different crosslinks from collagen and fibrin, and a general procedure is given for detection of any type of crosslink in a protein hydrolysate. PMID:8203759

  1. 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

  2. Gyrification from constrained cortical expansion

    PubMed Central

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

    2014-01-01

    The exterior of the mammalian brain—the cerebral cortex—has a conserved layered structure whose thickness varies little across species. However, selection pressures over evolutionary time scales have led to cortices that have a large surface area to volume ratio in some organisms, with the result that the brain is strongly convoluted into sulci and gyri. Here we show that the gyrification can arise as a nonlinear consequence of a simple mechanical instability driven by tangential expansion of the gray matter constrained by the white matter. A physical mimic of the process using a layered swelling gel captures the essence of the mechanism, and numerical simulations of the brain treated as a soft solid lead to the formation of cusped sulci and smooth gyri similar to those in the brain. The resulting gyrification patterns are a function of relative cortical expansion and relative thickness (compared with brain size), and are consistent with observations of a wide range of brains, ranging from smooth to highly convoluted. Furthermore, this dependence on two simple geometric parameters that characterize the brain also allows us to qualitatively explain how variations in these parameters lead to anatomical anomalies in such situations as polymicrogyria, pachygyria, and lissencephalia. PMID:25136099

  3. 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.

  4. Constrained Allocation Flux Balance Analysis.

    PubMed

    Mori, Matteo; Hwa, Terence; Martin, Olivier C; De Martino, Andrea; Marinari, Enzo

    2016-06-01

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

  5. Constrained Allocation Flux Balance Analysis

    PubMed Central

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

    2016-01-01

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

  6. 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

  7. Constrained Peptides as Miniature Protein Structures

    PubMed Central

    Yin, Hang

    2012-01-01

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

  8. Some non-anomerically C-C-linked carbohydrate amino acids related to leucine-synthesis and structure determination.

    PubMed

    Steiner, Bohumil; Micová, Júlia; Koós, Miroslav; Langer, Vratislav; Gyepesová, Dalma

    2003-06-23

    (5'R)-5'-Isobutyl-5'-[methyl (4R)-2,3-O-isopropylidene-beta-L-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione was synthesised starting from methyl 2,3-O-isopropylidene-alpha-D-lyxo-pentodialdo-1,4-furanoside via methyl 6-deoxy-6-isopropyl-2,3-O-isopropylidene-alpha-D-lyxo-hexofuranosid-5-ulose applying the Bucherer-Bergs reaction. Its 5'-R configuration was confirmed by X-ray crystallography. Corresponding alpha-amino acid-methyl (5R)-5-amino-5-C-carboxy-5,6-dideoxy-6-isopropyl-alpha-D-lyxo-hexofuranoside (alternative name: 2-[methyl (4R)-beta-L-erythrofuranosid-4-C-yl]-D-leucine) was obtained from the above hydantoin by acid hydrolysis of the isopropylidene group followed by basic hydrolysis of the hydantoin ring. Analogous derivatives with 5S configuration, formed in a minority, were also isolated and characterised. PMID:12801708

  9. Constrained Deformable-Layer Tomography

    NASA Astrophysics Data System (ADS)

    Zhou, H.

    2006-12-01

    The improvement on traveltime tomography depends on improving data coverage and tomographic methodology. The data coverage depends on the spatial distribution of sources and stations, as well as the extent of lateral velocity variation that may alter the raypaths locally. A reliable tomographic image requires large enough ray hit count and wide enough angular range between traversing rays over the targeted anomalies. Recent years have witnessed the advancement of traveltime tomography in two aspects. One is the use of finite frequency kernels, and the other is the improvement on model parameterization, particularly that allows the use of a priori constraints. A new way of model parameterization is the deformable-layer tomography (DLT), which directly inverts for the geometry of velocity interfaces by varying the depths of grid points to achieve a best traveltime fit. In contrast, conventional grid or cell tomography seeks to determine velocity values of a mesh of fixed-in-space grids or cells. In this study, the DLT is used to map crustal P-wave velocities with first arrival data from local earthquakes and two LARSE active surveys in southern California. The DLT solutions along three profiles are constrained using known depth ranges of the Moho discontinuity at 21 sites from a previous receiver function study. The DLT solutions are generally well resolved according to restoration resolution tests. The patterns of 2D DLT models of different profiles match well at their intersection locations. In comparison with existing 3D cell tomography models in southern California, the new DLT models significantly improve the data fitness. In comparison with the multi-scale cell tomography conducted for the same data, while the data fitting levels of the DLT and the multi-scale cell tomography models are compatible, the DLT provides much higher vertical resolution and more realistic description of the undulation of velocity discontinuities. The constraints on the Moho depth

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

    PubMed

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

    2016-02-01

    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

  11. 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.

  12. Highly specific olfactory receptor neurons for types of amino acids in the channel catfish.

    PubMed

    Nikonov, Alexander A; Caprio, John

    2007-10-01

    Odorant specificity to l-alpha-amino acids was determined electrophysiologically for 93 single catfish olfactory receptor neurons (ORNs) selected for their narrow excitatory molecular response range (EMRR) to only one type of amino acid (i.e., Group I units). These units were excited by either a basic amino acid, a neutral amino acid with a long side chain, or a neutral amino acid with a short side chain when tested at 10(-7) to 10(-5) M. Stimulus-induced inhibition, likely for contrast enhancement, was primarily observed in response to the types of amino acid stimuli different from that which activated a specific ORN. The high specificity of single Group I ORNs to type of amino acid was also previously observed for single Group I neurons in both the olfactory bulb and forebrain of the same species. These results indicate that for Group I neurons olfactory information concerning specific types of amino acids is processed from receptor neurons through mitral cells of the olfactory bulb to higher forebrain neurons without significant alteration in unit odorant specificity. PMID:17686913

  13. 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

  14. Induction of Arabidopsis tryptophan pathway enzymes and camalexin by amino acid starvation, oxidative stress, and an abiotic elicitor.

    PubMed Central

    Zhao, J; Williams, C C; Last, R L

    1998-01-01

    The tryptophan (Trp) biosynthetic pathway leads to the production of many secondary metabolites with diverse functions, and its regulation is predicted to respond to the needs for both protein synthesis and secondary metabolism. We have tested the response of the Trp pathway enzymes and three other amino acid biosynthetic enzymes to starvation for aromatic amino acids, branched-chain amino acids, or methionine. The Trp pathway enzymes and cytosolic glutamine synthetase were induced under all of the amino acid starvation test conditions, whereas methionine synthase and acetolactate synthase were not. The mRNAs for two stress-inducible enzymes unrelated to amino acid biosynthesis and accumulation of the indolic phytoalexin camalexin were also induced by amino acid starvation. These results suggest that regulation of the Trp pathway enzymes under amino acid deprivation conditions is largely a stress response to allow for increased biosynthesis of secondary metabolites. Consistent with this hypothesis, treatments with the oxidative stress-inducing herbicide acifluorfen and the abiotic elicitor alpha-amino butyric acid induced responses similar to those induced by the amino acid starvation treatments. The role of salicylic acid in herbicide-mediated Trp and camalexin induction was investigated. PMID:9501110

  15. Amino acid-containing membrane lipids in bacteria.

    PubMed

    Geiger, Otto; González-Silva, Napoleón; López-Lara, Isabel M; Sohlenkamp, Christian

    2010-01-01

    In the bacterial model organism Escherichia coli only the three major membrane lipids phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin occur, all of which belong to the glycerophospholipids. The amino acid-containing phosphatidylserine is a major lipid in eukaryotic membranes but in most bacteria it occurs only as a minor biosynthetic intermediate. In some bacteria, the anionic glycerophospholipids phosphatidylglycerol and cardiolipin can be decorated with aminoacyl residues. For example, phosphatidylglycerol can be decorated with lysine, alanine, or arginine whereas in the case of cardiolipin, lysine or d-alanine modifications are known. In few bacteria, diacylglycerol-derived lipids can be substituted with lysine or homoserine. Acyl-oxyacyl lipids in which the lipidic part is amide-linked to the alpha-amino group of an amino acid are widely distributed among bacteria and ornithine-containing lipids are the most common version of this lipid type. Only few bacterial groups form glycine-containing lipids, serineglycine-containing lipids, sphingolipids, or sulfonolipids. Although many of these amino acid-containing bacterial membrane lipids are produced in response to certain stress conditions, little is known about the specific molecular functions of these lipids. PMID:19703488

  16. Constraining weak annihilation using semileptonic D decays

    SciTech Connect

    Ligeti, Zoltan; Luke, Michael; Manohar, Aneesh V.

    2010-08-01

    The recently measured semileptonic D{sub s} decay rate can be used to constrain weak annihilation (WA) effects in semileptonic D and B decays. We revisit the theoretical predictions for inclusive semileptonic D{sub (s)} decays using a variety of quark mass schemes. The most reliable results are obtained if the fits to B decay distributions are used to eliminate the charm quark mass dependence, without using any specific charm mass scheme. Our fit to the available data shows that WA is smaller than commonly assumed. There is no indication that the WA octet contribution (which is better constrained than the singlet contribution) dominates. The results constrain an important source of uncertainty in the extraction of |V{sub ub}| from inclusive semileptonic B decays.

  17. Towards weakly constrained double field theory

    NASA Astrophysics Data System (ADS)

    Lee, Kanghoon

    2016-08-01

    We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon) transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X-ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.

  18. 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.

  19. Use of a peptide rather than free amino acid nitrogen source in chemically defined "elemental" diets.

    PubMed

    Silk, D B; Fairclough, P D; Clark, M L; Hegarty, J E; Marrs, T C; Addison, J M; Burston, D; Clegg, K M; Matthews, D M

    1980-01-01

    Previous studies have shown that amino acid (AA) residues are absorbed more rapidly from di- tripeptides than from free AA. In the present study, an intestinal perfusion technique has been used in normal human subjects to compare absorption of AA residues and total alpha-amino nitrogen (N) from 4 partial enzymic hydrolysates of protein (50--80% of the N contents present as small peptides) and their respective equimolar free AA mixtures. alpha-Amino N absorption was greater from 2 casein hydrolytes and a lactalbumin hydrolysate than from the respective free AA mixtures but similar to that from a fish protein hydrolysate and its AA mixture. The considerable variation in absorption of individual AA residues from the AA mixtures was much reduced when the protein hydrolysates were perfused, as a number of AA which were poorly absorbed from the AA mixtures were absorbed to a greater extent from the protein hydrolysates. The casein and lactalbumin hydrolysates had a stimulatory effect on jejunal absorption of water and electrolytes. In contrast, the fish protein hydrolysate appeared to cause a mean net secretion of fluid and electrolytes. The findings indicate that when absorption is limited by diminished luminal hydrolysis or absorptive capacity, serious consideration might be given to using partial enzymic hydrolysates of whole protein rather than free AA mixtures as the N source in "elemental" diets. Care should be taken, however, in ensuring that the preparation of choice does not promote a net secretion of fluid and electrolytes for such a property could have a deleterious effect in the clinical setting. PMID:6780707

  20. 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

  1. 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.

  2. 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.

  3. Spacecraft inertia estimation via constrained least squares

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  4. Analytical solutions to constrained hypersonic flight trajectories

    NASA Technical Reports Server (NTRS)

    Lu, Ping

    1992-01-01

    The flight trajectory of aerospace vehicles subject to a class of path constraints is considered. The constrained dynamics is shown to be a natural two-time-scale system. Asymptotic analytical solutions are obtained. Problems of trajectory optimization and guidance can be dramatically simplified with these solutions. Applications in trajectory design for an aerospace plane strongly support the theoretical development.

  5. 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.

  6. 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.

  7. Rhythmic Grouping Biases Constrain Infant Statistical Learning

    ERIC Educational Resources Information Center

    Hay, Jessica F.; Saffran, Jenny R.

    2012-01-01

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

  8. 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…

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

    PubMed

    Caprio, J; Byrd, R P

    1984-09-01

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

  10. Protein biosynthesis with conformationally restricted amino acids

    SciTech Connect

    Mendel, D. Lawrence Berkeley Lab., CA ); Ellman, J.; Schultz, P.G. )

    1993-05-19

    The incorporation of conformationally constrained amino acids into peptides is a powerful approach for generating structurally defined peptides as conformational probes and bioactive agents. The ability to site-specifically introduce constrained amino acids into large polypeptide chains would provide a similar opportunity to probe the flexibility, conformation, folding and stability of proteins. To this end, we have examined the competence of the Escherichia coli protein biosynthetic machinery to incorporate a number of these unnatural amino acids into the 164 residue protein T4 lysozyme (T4L). Results clearly demonstrate that the protein biosynthetic machinery can accommodate a wide variety of conformationally constrained amino acids. The expansion of structural motifs that can be biosynthetically incorporated into proteins to include a large number of conformationally constrained amino acids significantly increases the power of mutagenesis methods as probes of protein structure and function and provides additional insights into the steric requirements of the translational machinery. 13 refs., 2 figs.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Constrained optimization via artificial immune system.

    PubMed

    Zhang, Weiwei; Yen, Gary G; He, Zhongshi

    2014-02-01

    An artificial immune system inspired by the fundamental principle of the vertebrate immune system, for solving constrained optimization problems, is proposed. The analogy between the mechanism of biological immune response and constrained optimization formulation is drawn. Individuals in population are classified into feasible and infeasible groups according to their constraint violations that closely match with the two states, inactivated and activated, of B-cells in the immune response. Feasible group focuses on exploitation in the feasible areas through clonal selection, recombination, and hypermutation, while infeasible group facilitates exploration along the feasibility boundary via location update. Direction information is extracted to promote the interactions between these two groups. This approach is validated by the benchmark functions proposed most recently and compared with those of the state of the art from various branches of evolutionary computation paradigms. The performance achieved is considered fairly competitive and promising. PMID:23757542

  16. 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.

  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. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. Constrained optimum trajectories with specified range

    NASA Technical Reports Server (NTRS)

    Erzberger, H.; Lee, H.

    1980-01-01

    The characteristics of optimum fixed-range trajectories whose structure is constrained to climb, steady cruise, and descent segments are derived by application of optimal control theory. The performance function consists of the sum of fuel and time costs, referred to as direct operating costs (DOC). The state variable is range-to-go and the independent variable is energy. In this formulation a cruise segment always occurs at the optimum cruise energy for sufficiently large range. At short ranges (500 n. mi. and less) a cruise segment may also occur below the optimum cruise energy. The existence of such a cruise segment depends primarily on the fuel flow vs thrust characteristics and on thrust constraints. If thrust is a free control variable along with airspeed, it is shown that such cruise segments will not generally occur. If thrust is constrained to some maximum value in climb and to some minimum in descent, such cruise segments generally will occur. The performance difference between free thrust and constrained thrust trajectories has been determined in computer calculations for an example transport aircraft.

  4. 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.

  5. 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

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  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, 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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.

  1. 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.

  2. Equilibria of three constrained point charges

    NASA Astrophysics Data System (ADS)

    Khimshiashvili, G.; Panina, G.; Siersma, D.

    2016-08-01

    We study the critical points of Coulomb energy considered as a function on configuration spaces associated with certain geometric constraints. Two settings of such kind are discussed in some detail. The first setting arises by considering polygons of fixed perimeter with freely sliding positively charged vertices. The second one is concerned with triples of positive charges constrained to three concentric circles. In each of these cases the Coulomb energy is generically a Morse function. We describe the minima and other stationary points of Coulomb energy and show that, for three charges, a pitchfork bifurcation takes place accompanied by an effect of the Euler's Buckling Beam type.

  3. Constrained inflaton due to a complex scalar

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    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 varphin. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. DeltapH-Dependent Amino Acid Transport into Plasma Membrane Vesicles Isolated from Sugar Beet (Beta vulgaris L.) Leaves: II. Evidence for Multiple Aliphatic, Neutral Amino Acid Symports.

    PubMed

    Li, Z C; Bush, D R

    1991-08-01

    Proton-coupled aliphatic, neutral amino acid transport was investigated in plasma membrane vesicles isolated from sugar beet (Beta vulgaris L., cv Great Western) leaves. Two neutral amino acid symport systems were resolved based on inter-amino acid transport competition and on large variations in the specific activity of each porter in different species. Competitive inhibition was observed for transport competition between alanine, methionine, glutamine, and leucine (the alanine group) and between isoleucine, valine, and threonine (the isoleucine group). The apparent K(m) and K(i) values were similar for transport competition among amino acids within the alanine group. In contrast, the kinetics of transport competition between these two groups of amino acids did not fit a simple competitive model. Furthermore, members of the isoleucine group were weak transport antagonists of the alanine group. These results are consistent with two independent neutral amino acid porters. In support of that conclusion, the ratio of the specific activity of alanine transport versus isoleucine transport varied from two- to 13-fold in plasma membrane vesicles isolated from different plant species. This ratio would be expected to remain relatively stable if these amino acids were moving through a single transport system and, indeed, the ratio of alanine to glutamine transport varied less than twofold. Analysis of the predicted structure of the aliphatic, neutral amino acids in solution shows that isoleucine, valine, and threonine contain a branched methyl or hydroxyl group at the beta-carbon position that places a dense electron cloud close to the alpha-amino group. This does not occur for the unbranched amino acids or those that branch further away, e.g. leucine. We hypothesize that this structural feature of isoleucine, valine, and threonine results in unfavorable steric interactions with the alanine transport system that limits their flux through this porter. Hydrophobicity and

  10. 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

  11. 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.

  12. A stochastic framework for inequality constrained estimation

    NASA Astrophysics Data System (ADS)

    Roese-Koerner, Lutz; Devaraju, Balaji; Sneeuw, Nico; Schuh, Wolf-Dieter

    2012-11-01

    Quality description is one of the key features of geodetic inference. This is even more true if additional information about the parameters is available that could improve the accuracy of the estimate. However, if such additional information is provided in the form of inequality constraints, most of the standard tools of quality description (variance propagation, confidence ellipses, etc.) cannot be applied, as there is no analytical relationship between parameters and observations. Some analytical methods have been developed for describing the quality of inequality constrained estimates. However, these methods either ignore the probability mass in the infeasible region or the influence of inactive constraints and therefore yield only approximate results. In this article, a frequentist framework for quality description of inequality constrained least-squares estimates is developed, based on the Monte Carlo method. The quality is described in terms of highest probability density regions. Beyond this accuracy estimate, the proposed method allows to determine the influence and contribution of each constraint on each parameter using Lagrange multipliers. Plausibility of the constraints is checked by hypothesis testing and estimating the probability mass in the infeasible region. As more probability mass concentrates in less space, applying the proposed method results in smaller confidence regions compared to the unconstrained ordinary least-squares solution. The method is applied to describe the quality of estimates in the problem of approximating a time series with positive definite functions.

  13. Constraining torsion with Gravity Probe B

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    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.

  14. Intersecting transcription networks constrain gene regulatory evolution.

    PubMed

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

    2015-07-16

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

  15. Regular language constrained sequence alignment revisited.

    PubMed

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

    2011-05-01

    Imposing constraints in the form of a finite automaton or a regular expression is an effective way to incorporate additional a priori knowledge into sequence alignment procedures. With this motivation, the Regular Expression Constrained Sequence Alignment Problem was introduced, which proposed an O(n²t⁴) time and O(n²t²) space algorithm for solving it, where n is the length of the input strings and t is the number of states in the input non-deterministic automaton. A faster O(n²t³) time algorithm for the same problem was subsequently proposed. In this article, we further speed up the algorithms for Regular Language Constrained Sequence Alignment by reducing their worst case time complexity bound to O(n²t³)/log t). This is done by establishing an optimal bound on the size of Straight-Line Programs solving the maxima computation subproblem of the basic dynamic programming algorithm. We also study another solution based on a Steiner Tree computation. While it does not improve the worst case, our simulations show that both approaches are efficient in practice, especially when the input automata are dense. PMID:21554020

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Constraining the halo mass function with observations

    NASA Astrophysics Data System (ADS)

    Castro, Tiago; Marra, Valerio; Quartin, Miguel

    2016-08-01

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

  2. 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.

  3. Preparation and evaluation of new Pirkle type chiral stationary phases with long alkyl chains for the separation of amino acid enantiomers derivatized with NBD-F.

    PubMed

    Kato, M; Fukushima, T; Santa, T; Nakashima, K; Nishioka, R; Imai, K

    1998-12-01

    In order to improve the high-performance liquid chromatographic separation of alpha-amino acids derivatized with the fluorogenic reagent 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) on commercially available chiral stationary phases (CSPs) such as SUMICHIRAL OA-2500(S) (CSP 1) and OA-4700 (CSP 3), the preparation of two new CSPs (CSP 2 and CSP 4) having 11-aminoundecanoic acid between the aminopropyl silica gel support and the chiral moiety in CSP 1 and CSP 3 is described. CSP 2 and CSP 4 improved both the mutual and enantiomeric separation of NBD-amino acids compared with CSP 1 and CSP 3. Thus, 17 pairs of NBD-amino acid enantiomers and NBD-glycine were separated on CSP 2 except for six NBD-amino acids (D-Asn, D-Ser, D-Gln, L-Pro, L-Ser and Gly). CSP 2 and CSP 4 also showed better enantiomeric separation of NBD-amino acid esters and amides than CSP 1 and CSP 3. It was considered that the achiral long alkyl chains in the CSPs might form a hydrophobic space which assisted the stereoselective interaction of analytes with the chiral moiety by changing the environment around the chiral moiety. On CSP 1 and CSP 2, NBD-beta-amino acid was also enantiomerically separated. PMID:10435350

  4. 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.

  5. Constrained least squares estimation incorporating wavefront sensing

    NASA Astrophysics Data System (ADS)

    Ford, Stephen D.; Welsh, Byron M.; Roggemann, Michael C.

    1998-11-01

    We address the optimal processing of astronomical images using the deconvolution from wave-front sensing technique (DWFS). A constrained least-squares (CLS) solution which incorporates ensemble-averaged DWFS data is derived using Lagrange minimization. The new estimator requires DWFS data, noise statistics, optical transfer function statistics, and a constraint. The constraint can be chosen such that the algorithm selects a conventional regularization constant automatically. No ad hoc parameter tuning is necessary. The algorithm uses an iterative Newton-Raphson minimization to determine the optimal Lagrange multiplier. Computer simulation of a 1m telescope imaging through atmospheric turbulence is used to test the estimation scheme. CLS object estimates are compared with the corresponding long exposure images. The CLS algorithm provides images with superior resolution and is computationally inexpensive, converging to a solution in less than 10 iterations.

  6. Arithmetic coding with constrained carry operations

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  7. How alive is constrained SUSY really?

    DOE PAGESBeta

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

    2016-05-31

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

  8. Constraining condensate dark matter in galaxy clusters

    NASA Astrophysics Data System (ADS)

    de Souza, J. C. C.; Ujevic, M.

    2015-09-01

    We constrain scattering length parameters in a Bose-Einstein condensate dark matter model by using galaxy clusters radii, with the implementation of a method previously applied to galaxies. At the present work, we use a sample of 114 clusters radii in order to obtain the scattering lengths associated with a dark matter particle mass in the range - eV. We obtain scattering lengths that are five orders of magnitude larger than the ones found in the galactic case, even when taking into account the cosmological expansion in the cluster scale by means of the introduction of a small cosmological constant. We also construct and compare curves for the orbital velocity of a test particle in the vicinity of a dark matter cluster in both the expanding and the non-expanding cases.

  9. Constraining cosmology with pairwise velocity estimator

    NASA Astrophysics Data System (ADS)

    Ma, Yin-Zhe; Li, Min; He, Ping

    2015-11-01

    In this paper, we develop a full statistical method for the pairwise velocity estimator previously proposed, and apply Cosmicflows-2 catalogue to this method to constrain cosmology. We first calculate the covariance matrix for line-of-sight velocities for a given catalogue, and then simulate the mock full-sky surveys from it, and then calculate the variance for the pairwise velocity field. By applying the 8315 independent galaxy samples and compressed 5224 group samples from Cosmicflows-2 catalogue to this statistical method, we find that the joint constraint on Ωm0.6h and σ8 is completely consistent with the WMAP 9-year and Planck 2015 best-fitting cosmology. Currently, there is no evidence for the modified gravity models or any dynamic dark energy models from this practice, and the error-bars need to be reduced in order to provide any concrete evidence against/to support ΛCDM cosmology.

  10. Statistical mechanics of budget-constrained auctions

    NASA Astrophysics Data System (ADS)

    Altarelli, F.; Braunstein, A.; Realpe-Gomez, J.; Zecchina, R.

    2009-07-01

    Finding the optimal assignment in budget-constrained auctions is a combinatorial optimization problem with many important applications, a notable example being in the sale of advertisement space by search engines (in this context the problem is often referred to as the off-line AdWords problem). On the basis of the cavity method of statistical mechanics, we introduce a message-passing algorithm that is capable of solving efficiently random instances of the problem extracted from a natural distribution, and we derive from its properties the phase diagram of the problem. As the control parameter (average value of the budgets) is varied, we find two phase transitions delimiting a region in which long-range correlations arise.

  11. The asymptotics of large constrained graphs

    NASA Astrophysics Data System (ADS)

    Radin, Charles; Ren, Kui; Sadun, Lorenzo

    2014-05-01

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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. High proportions of deleterious polymorphisms in constrained human genes.

    PubMed

    Subramanian, Sankar

    2011-01-01

    Previous studies on human mitochondrial genomes showed that the ratio of intra-specific diversities at nonsynonymous-to-synonymous positions was two to ten times higher than the ratio of interspecific divergences at these positions, suggesting an excess of slightly deleterious nonsynonymous polymorphisms. However, such an overabundance of nonsynonymous single nucleotide polymorphisms (SNPs) was not found in human nuclear genomes. Here, genome-wide estimates using >14,000 human-chimp nuclear genes and 1 million SNPs from four human genomes showed a significant proportion of deleterious nonsynonymous SNPs (∼ 15%). Importantly, this study reveals a negative correlation between the magnitude of selection pressure and the proportion of deleterious SNPs on human genes. The proportion of deleterious amino acid replacement polymorphisms is 3.5 times higher in genes under high purifying selection compared with that in less constrained genes (28% vs. 8%). These results are explained by differences in the extent of contribution of mildly deleterious mutations to diversity and substitution. PMID:20974690

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

    PubMed Central

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

    1984-01-01

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

  1. 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

  2. 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.

  3. Explaining evolution via constrained persistent perfect phylogeny

    PubMed Central

    2014-01-01

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

  4. 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

  5. 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.

  6. 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.

  7. Constraining Particle Sizes of Saturn's F Ring

    NASA Astrophysics Data System (ADS)

    Becker, T. M.; Colwell, J.; Esposito, L. W.

    2011-12-01

    Saturn's beauty is often attributed to the magnificent rings that encircle the planet. Although admired for hundreds of years, we are now just beginning to understand the complexity of the rings as a result of new data from the Cassini orbiter. Studying occultations of the rings provides information about the distribution and sizes of the particles that define the rings. During one solar occultation, the Ultraviolet Imaging Spectrograph (UVIS) on board Cassini was slightly misaligned with the Sun, decreasing the amount of direct solar signal to ~1% of the normal value. As a result, UVIS detected a peak in photon counts above the non-occulted signal due to forward-scattered light diffracted by the small particles in the F Ring. There is a direct relationship between the size of the particles and the intensity of the light scattered. We utilize this relationship in a model that replicates the misalignment and calculates the amount of light that would be detected as a function of the particle sizes in the ring. We present new results from the model that constrain the size distribution of the dynamically active F Ring, contributing to the study of the origin and evolution of Saturn's ring system.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Optimization of constrained density functional theory

    NASA Astrophysics Data System (ADS)

    O'Regan, David D.; Teobaldi, Gilberto

    2016-07-01

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

  14. 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.

  15. Constraining Binary Stellar Evolution With Pulsar Timing

    NASA Astrophysics Data System (ADS)

    Ferdman, Robert D.; Stairs, I. H.; Backer, D. C.; Burgay, M.; Camilo, F.; D'Amico, N.; Demorest, P.; Faulkner, A.; Hobbs, G.; Kramer, M.; Lorimer, D. R.; Lyne, A. G.; Manchester, R.; McLaughlin, M.; Nice, D. J.; Possenti, A.

    2006-06-01

    The Parkes Multibeam Pulsar Survey has yielded a significant number of very interesting binary and millisecond pulsars. Two of these objects are part of an ongoing timing study at the Green Bank Telescope (GBT). PSR J1756-2251 is a double-neutron star (DNS) binary system. It is similar to the original Hulse-Taylor binary pulsar system PSR B1913+16 in its orbital properties, thus providing another important opportunity to test the validity of General Relativity, as well as the evolutionary history of DNS systems through mass measurements. PSR J1802-2124 is part of the relatively new and unstudied "intermediate-mass" class of binary system, which typically have spin periods in the tens of milliseconds, and/or relatively massive (> 0.7 solar masses) white dwarf companions. With our GBT observations, we have detected the Shapiro delay in this system, allowing us to constrain the individual masses of the neutron star and white dwarf companion, and thus the mass-transfer history, in this unusual system.

  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 the oblateness of Kepler planets

    SciTech Connect

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

    2014-11-20

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

  18. 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.

  19. Computational studies of spatially constrained DNA

    SciTech Connect

    Olson, W.K.; Westcott, T.P.; Liu, Guo-Hua

    1996-12-31

    Closed loops of double stranded DNA are ubiquitous in nature, occurring in systems ranging from plasmids, bacterial chromosomes, and many viral genomes, which form single closed loops, to eukaryotic chromosomes and other linear DNAs, which appear to be organized into topologically constrained domains by DNA-binding proteins. The topological constraints in the latter systems are determined by the spacing of the bound proteins along the contour of the double helix along with the imposed turns and twists of DNA in the intermolecular complexes. As long as the duplex remains unbroken, the linking number Lk, or number of times the two strands of the DNA wrap around one another, is conserved. If one of the strands is nicked and later re-sealed, the change in overall folding that accompanies DNA-protein interactions leads to a change in Lk. The supercoiling brought about by such protein action, in turn, determines a number of key biological events, including replication, transcription, and recombination. 51 refs., 5 figs., 1 tab.

  20. 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.

  1. 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.

  2. Using infrasound to constrain ash plume height

    NASA Astrophysics Data System (ADS)

    Lamb, Oliver; De Angelis, Silvio; Lavallée, Yan

    2016-04-01

    Airborne volcanic ash advisories are currently based on analyses of satellite imagery with relatively low temporal resolution, and numerical simulations of atmospheric plume dispersion. These simulations rely on key input parameters such as the maximum height of eruption plumes and the mass eruption rate at the vent, which remain loosely constrained. In this study, we present a proof-of-concept workflow that incorporates the analysis of volcanic infrasound with numerical modelling of volcanic plume rise in a realistic atmosphere. We analyse acoustic infrasound records from two explosions during the 2009 eruption of Mt. Redoubt, USA, that produced plumes reaching heights of 12-14 km. We model the infrasonic radiation at the source under the assumptions of linear acoustic theory and calculate variations in mass ejection velocity at the vent. The estimated eruption velocities serve as the input for numerical models of plume rise. The encouraging results highlight the potential for infrasound measurements to be incorporated into numerical modelling of ash dispersion, and confirm their value for volcano monitoring operations.

  3. 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.

  4. Autonomy, constraining options, and organ sales.

    PubMed

    Taylor, James Stacey

    2002-01-01

    Although there continues to be a chronic shortage of transplant organs the suggestion that we should try to alleviate it through allowing a current market in them continues to be morally condemned, usually on the grounds that such a market would undermine the autonomy of those who would participate in it as vendors. Against this objection Gerald Dworkin has argued that such markets would enhance the autonomy of the vendors through providing them with more options, thus enabling them to exercise a greater degree of control over their bodies. Paul Hughes and T.L. Zutlevics have recently criticized Dworkin's argument, arguing that the option to sell an organ is unusual in that it is an autonomy-undermining "constraining option" whose presence in a person's choice set is likely to undermine her autonomy rather than enhance it. I argue that although Hughes' and Zutlevics' arguments are both innovative and persuasive they are seriously flawed--and that allowing a market in human organs is more likely to enhance vendor autonomy than diminish it. Thus, given that autonomy is the preeminent value in contemporary medical ethics this provides a strong prima facie case for recognizing the moral legitimacy of such markets. PMID:12747360

  5. 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.

  6. 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.

  7. [Comparative distribution study of 14C labeled amino acids, glucose-analogue and precursor of nuclei acid, as tumor seeking agents].

    PubMed

    Shiba, K; Mori, H; Hisada, K

    1984-08-01

    As tumor-seeking agents, glucose analogues, natural amino acids, synthetic nonmetabolized amino acids, and precursor of nucleic acids, etc., labeled with positron emitter, such as 11C and 18F have been recently investigated. However, there are very few reports concerning comparative study of tumor uptake and tissue distribution of these agents. This preliminary paper describes comparative distribution and whole-body autoradiography of these agents. 14C labeled deoxy-2-fluoro-D-glucose (FDG), L-, DL-leucine, 1-aminocyclopentane carboxylic acid (ACPC), alpha-amino isobutyric acid (alpha-AIB), and thymidine were intravenously injected through tail vein into separate groups of the experimental animals. As the experimental animals, the mice with Ehrlich tumor and the rats with Hepatoma AH109A were used. Within 30 min after injection, FDG had the highest tumor uptake and tumor to tissue ratios, although FDG was inferior to ACPC and thymidine in related to tumor to heart, lung and brain ratios. However, the time course study indicated that tumor uptake of ACPC, alpha-AIB and D-leucine increased with time, whereas those of other agents decreased with time or reached a plateau. Thus, at 120 min after injection, ACPC had the highest tumor uptake and tumor to tissue ratios, although ACPC was inferior to FDG in related to tumor to blood, liver and pancreas ratios. Autoradiogram of ACPC showed very clear tumor image as well as that of FDG. The above data suggest that synthetic nonmetabolized amino acids, such as ACPC may be promising as tumor-seeking agents, when used with a single photon emission computed tomography, while glucose analogue such as FDG, are the best tumor-seeking agent, when used with a positron emission computed tomography. PMID:6505304

  8. The Constraining of Parameters in Restricted Factor Analysis.

    ERIC Educational Resources Information Center

    Hattie, John; Fraser, Colin

    1988-01-01

    In restricted factor analysis, each element of the matrices of factor loadings and correlations and unique variances and covariances can be constrained. It is argued that the practice of constraining some parameters at zero is not psychologically meaningful. Alternative procedures are presented and illustrated. (TJH)

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

    ERIC Educational Resources Information Center

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

    2006-01-01

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

  10. 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. 888.3230 Section 888.3230 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3230 Finger joint polymer constrained prosthesis. (a) Identification....

  11. Probability Statements Extraction with Constrained Conditional Random Fields.

    PubMed

    Deleris, Léa A; Jochim, Charles

    2016-01-01

    This paper investigates how to extract probability statements from academic medical papers. In previous work we have explored traditional classification methods which led to numerous false negatives. This current work focuses on constraining classification output obtained from a Conditional Random Field (CRF) model to allow for domain knowledge constraints. Our experimental results indicate constraining leads to a significant improvement in performance. PMID:27577439

  12. CONSTRAINING DARK ENERGY WITH GAMMA-RAY BURSTS

    SciTech Connect

    Samushia, Lado; Ratra, Bharat E-mail: ratra@phys.ksu.ed

    2010-05-10

    We use the measurement of gamma-ray burst (GRB) distances to constrain dark energy cosmological model parameters. We employ two methods for analyzing GRB data-fitting luminosity relation of GRBs in each cosmology and using distance measures computed from binned GRB data. Current GRB data alone cannot tightly constrain cosmological parameters and allow for a wide range of dark energy models.

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

    NASA Astrophysics Data System (ADS)

    Connerney, John E. P.

    2015-04-01

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

  14. Constraining 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.

  15. 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.

  16. 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

  17. Laterally constrained inversion for CSAMT data interpretation

    NASA Astrophysics Data System (ADS)

    Wang, Ruo; Yin, Changchun; Wang, Miaoyue; Di, Qingyun

    2015-10-01

    Laterally constrained inversion (LCI) has been successfully applied to the inversion of dc resistivity, TEM and airborne EM data. However, it hasn't been yet applied to the interpretation of controlled-source audio-frequency magnetotelluric (CSAMT) data. In this paper, we apply the LCI method for CSAMT data inversion by preconditioning the Jacobian matrix. We apply a weighting matrix to Jacobian to balance the sensitivity of model parameters, so that the resolution with respect to different model parameters becomes more uniform. Numerical experiments confirm that this can improve the convergence of the inversion. We first invert a synthetic dataset with and without noise to investigate the effect of LCI applications to CSAMT data, for the noise free data, the results show that the LCI method can recover the true model better compared to the traditional single-station inversion; and for the noisy data, the true model is recovered even with a noise level of 8%, indicating that LCI inversions are to some extent noise insensitive. Then, we re-invert two CSAMT datasets collected respectively in a watershed and a coal mine area in Northern China and compare our results with those from previous inversions. The comparison with the previous inversion in a coal mine shows that LCI method delivers smoother layer interfaces that well correlate to seismic data, while comparison with a global searching algorithm of simulated annealing (SA) in a watershed shows that though both methods deliver very similar good results, however, LCI algorithm presented in this paper runs much faster. The inversion results for the coal mine CSAMT survey show that a conductive water-bearing zone that was not revealed by the previous inversions has been identified by the LCI. This further demonstrates that the method presented in this paper works for CSAMT data inversion.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. Synthesis and antibacterial activity of thioglycolic amino acid derivatives and dipeptides containing the 2-methyl-3,4-dihydroquinazolin-4-one moiety.

    PubMed

    Atta, F M

    1994-11-01

    3-(2'-Chloroethyl)-2-methyl-3,4-dihydroquinazolin-4-one (I) was reacted with sodio (sodium thioglycolate) in dry dioxane and yielded compound II. By using thionyl chloride, this compound was converted to the corresponding acid chloride (III). The prepared acyl chloride (III) was allowed to interact with different alpha-amino acids such as Gly, L-Ala, L-B-Phe, DL-Asp, L-Glu, L-Thr and L-Val to give new amino acid derivatives (IVa-g). A selected C-terminal derivative of glycine (IVa) was converted into acid chloride (V). The acid chloride formed was reacted with L-Ala, L-B-Phe, DL-Asp, L-Glu, L-Thr and L-Val and yielded the new dipeptides VIa-f. The structures of the synthesized compounds were elucidated by elemental analysis and IR spectra. The prepared peptides were tested for their antimicrobial activities by comparison with tetra-cycline as a reference compound. PMID:7765582

  5. First total syntheses of aeruginosin 298-A and aeruginosin 298-B, based on a stereocontrolled route to the new amino acid 6-hydroxyoctahydroindole-2-carboxylic acid.

    PubMed

    Valls, N; López-Canet, M; Vallribera, M; Bonjoch, J

    2001-08-17

    The first total syntheses of aeruginosin 298-A (1) and aeruginosin 298-B (3) are described. The syntheses of the alternative putative structures 2 and 4 were also accomplished. The key common strategic element is the stereo-controlled synthesis of (2S,3aS,6R,7aS)-6-hydroxyoctahydroindole-2-carboxylic acid (L-Choi, 5) from L-tyrosine. The synthesis of this new bicyclic alpha-amino acid, which is the core of aeruginosins, involves Birch reduction of O-methyl-L-tyrosine (6) and aminocyclization of the resulting dihydroanisole 7 in acid medium, followed by N-benzylation to give the diastereoisomers 12 and 13. Upon acid treatment with HCl-MeOH, the last two produce an equilibrium mixture in which the endo isomer 13 significantly predominates. Hydrogenation of 13 in the presence of (Boc)2O gives 16, which on reduction with LS-Selectride furnishes the alcohol 22, a protected L-Choi. Successive couplings of 22 with D-leucine, protected (R)-(4-hydroxyphenyl)lactic acid, and L-arginine fragments, followed by reduction to the argininol level and a deprotection end step complete the synthetic sequence to produce aeruginosin 298-A (1). Spectral comparison showed that peptide 2, with the structure previously proposed for aeruginosin 298-A, was different from the natural product. However, synthetic 1 was found to be identical to the isolated natural sample of aeruginosin 298-A. These results unequivocally establish that the absolute stereochemistry of aeruginosin 298-A, formerly assigned incorrectly, is D-Hpla-D-Leu-L-Choi-L-Argol, as shown by structure 1. Aeruginosin 298-B was also synthesized and shown to be a mixture of rotamers of D-Hpla-D-Leu-L-ChoiNH2 (3), rather than an epimeric mixture of 3 and the L-Leu-incorporating 4. PMID:11560314

  6. 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

  7. Vibrational pooling and constrained equilibration on surfaces

    NASA Astrophysics Data System (ADS)

    Boney, E. T. D.

    In this thesis, we provide a statistical theory for the vibrational pooling and fluorescence time dependence observed in infrared laser excitation of CO on an NaCl surface. The pooling is seen in experiment and in computer simulations. In the theory, we assume a rapid equilibration of the quanta in the substrate and minimize the free energy subject to the constraint at any time t of a fixed number of vibrational quanta N(t). At low incident intensity, the distribution is limited to one-quantum exchanges with the solid and so the Debye frequency of the solid plays a key role in limiting the range of this one-quantum domain. The resulting inverted vibrational equilibrium population depends only on fundamental parameters of the oscillator (oe and oeχe) and the surface (oD and T). Possible applications and relation to the Treanor gas phase treatment are discussed. Unlike the solid phase system, the gas phase system has no Debye-constraining maximum. We discuss the possible distributions for arbitrary N-conserving diatom-surface pairs, and include application to H:Si(111) as an example. Computations are presented to describe and analyze the high levels of infrared laser induced vibrational excitation of a monolayer of absorbed 13CO on a NaCl(100) surface. The calculations confirm that, for situations where the Debye frequency limited n domain restriction approximately holds, the vibrational state population deviates from a Boltzmann population linearly in n, a result that we have derived earlier theoretically for a domain of n restricted to one-phonon transfers. This theoretically understood term, linear in n, dominates the Boltzmann term and is responsible for the inversion of the population of vibrational states, Pn We discuss the one-to-one relationship between N and gamma and the examine the state space of the new distribution function for varied gamma. We derive the Free Energy and effective chemical potential for the vibrational pool. We also find the anti

  8. 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

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

    NASA Astrophysics Data System (ADS)

    Spencer, Kathleen M.

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

  10. 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.