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1

Synthesis of alpha-amino acids  

DOEpatents

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.

Davis, Jr., Jefferson W. (San Francisco, CA)

1983-01-01

2

Synthesis of alpha-amino acids  

DOEpatents

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.

Davis, Jr., Jefferson W. (San Francisco, CA)

1983-01-01

3

Synthesis of alpha-amino acids  

DOEpatents

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.

Davis, Jr., Jefferson W. (San Francisco, CA)

1983-01-01

4

Synthesis of alpha-amino acids  

DOEpatents

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

Davis, J.W. Jr.

1983-01-25

5

ANTIGENICITY OF POLYPEPTIDES (POLY ALPHA AMINO ACIDS)  

PubMed Central

It has been demonstrated that polymers consisting solely of D-?-amino acids are not immunogenic in rabbits, guinea pigs, man, and mouse, whereas the same polymers of L-?-amino acids are very effective antigens. This has been attributed to the importance of metabolizability of a polymer in contributing to its immunogenicity. In the glu-lys-ala series of polymers, the immunogenicity of a polymer of 2 L-amino acids and a D-amino acid appears to be governed by the immunogenicity of the 2 L-amino acids. However, some of the specificity may be directed towards configurations containing the D-amino acid. It has been noted that injections of rabbits with polymers of D-amino acids has resulted in a reduced response against the isomeric L polymer. PMID:14271319

Maurer, Paul H.

1965-01-01

6

Diastereoselective synthesis of quaternary alpha-amino acids from diketopiperazine templates.  

PubMed

Sequential enolate alkylations of (S)-N(1)-methyl-5-methoxy-6-isopropyl-3,6-dihydropyrazin-2-one and (S)-N(1)-p-methoxybenzyl-5-methoxy-6-isopropyl-3,6-dihydropyrazin-2-one proceed with excellent levels of diastereoselectivity (>90% de) affording quaternary alpha-amino acids in high enantiomeric excess (>98% ee) after deprotection and hydrolysis. PMID:17581658

Davies, Stephen G; Garner, A Christopher; Ouzman, Jaqueline V A; Roberts, Paul M; Smith, Andrew D; Snow, Emma J; Thomson, James E; Tamayo, Juan A; Vickers, Richard J

2007-07-01

7

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

NASA Technical Reports Server (NTRS)

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.

Cronin, John R.; Pizzarello, Sandra

1986-01-01

8

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

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

9

Novel formation of alpha-amino acid from alpha-oxo acids and ammonia in an aqueous medium  

Microsoft Academic Search

In the course of a study of possible mechanisms for chemical evolution in the primeval sea, we found the novel formation of alpha-amino acids and N-acylamino acids from alpha-oxo acids and ammonia in an aqueous medium. Glyoxylic acid reacted with ammonia to form N-oxalylglycine, which gave glycine in a 5 39% yield after hydrolysis with 6N HCl. Pyruvic acid and

Hiroshi Yanagawa; Yumiko Makino; Kazuki Sato; Masato Nishizawa; Fujio Egami

1984-01-01

10

A novel way for the formation of alpha-amino acids and their derivatives in an aqueous medium  

Microsoft Academic Search

In the course of a study of possible mechanism for chemical evolution in the primeval sea, we observed the formation of alpha-amino acids and N-acylamino acids from alpha-oxo acids and ammonia in an aqueous medium. Glyoxylic acid reacted with ammonia to form N-oxalylglycine, which gave glycine in a 5-39% yield after hydrolysis with 6N HCl. Similarly when glyoxylic acid was

H. Yanagawa; Y. Makino; K. Sato; M. Nishizawa; F. Egami

1983-01-01

11

Enthalpic homogeneous pair interaction coefficients of L-alpha-amino acids as a hydrophobicity parameter of amino acid side chains.  

PubMed

Enthalpies of dilution of aqueous solutions of L-alpha-cysteine, L-alpha-histidine, L-alpha-asparagine, L-alpha-glutamine, L-alpha-arginine, L-alpha-tryptophan, and L-alpha-glutamic acid in water at a temperature of 298.15 K have been measured. The values of dilution enthaply were used to determine enthalpic homogeneous pair interaction coefficients which characterize the interactions between zwitterions of the examined L-alpha-amino acids in water. Approachable literature data of hydrophobic scales have been analyzed to obtain average values. The obtained values of enthalpic pair interaction coefficients have been put together with an average hydrophobic scale. PMID:12022833

Palecz, Bartlomiej

2002-05-29

12

alpha-Hydroxy and alpha-Amino Acids Under Possible Hadean, Volcanic Origin-of-Life Conditions  

Microsoft Academic Search

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,

Claudia Huber; Günter Wächtershäuser

2006-01-01

13

KINETICS AND MECHANISMS OF THE DECOMPOSITION OF N-CHLORO-ALPHA-AMINO ACIDS AND DICHLORAMINE IN AQUEOUS SOLUTIONS  

Microsoft Academic Search

The decomposition of N-chloro-(alpha)-amino acids in neutral solutions gives Cl('-); imines, which hydrolyze rapidly to amine and carbonyl products; and CO(,2). The reactions are first order in {N-Cl-amino acid} and independent of pH. At 25.0(DEGREES)C the rate constants (s('-1)) are: N-Cl-glycine, 4.2 x 10('-6); N-Cl-sarcosine, 5.1 x 10('-5); N-Cl-threonine, 2 x 10('-4); N-Cl-alanine, 2.7 x 10('-4); N-Cl-proline, 8.8 x 10('-3);

VINCENT CYRIL HAND

1982-01-01

14

Synthesis of boronic acid analogues of alpha-amino acids by introducing side chains as electrophiles.  

PubMed

A synthetic route has been developed which has allowed us to prepare novel alpha-aminoboronic acids as inhibitors of serine proteases. These compounds were prepared to study the roles of proteases in biological systems. This methodology affords alpha-aminoboronic acids with the general formula R'-NHCH(R)BO(2)-pinanediol, where R = -CH(2)CHF(2), -CH(2)CO(2)tBu, and -(CH(2))(2)CO(2)Me and R' = either H or C(O)R". The latter two compounds are the boronic acid analogues of the natural amino acids aspartic acid and glutamic acid with the side chain carboxylate protected as a tert-butyl or a methyl ester, respectively. Following acylation of the amino group, the side chain tert-butyl ester of boroaspartic acid was removed by treatment with TFA. Boroglutamic acid was obtained as the free boronic acid by hydrolysis with HCl. Prior syntheses of alpha-aminoboronic acids involve the initial addition of an organometallic reagent to a trialkyl borate ester. These conditions do not allow the preparation of compounds with functionalities that are not stable to the strongly basic reaction conditions. The methodology described here allows the preparation of alpha-aminoboronic acids by introducing side chains as electrophiles. This is particularly advantageous for side chains which are prone to elimination or unwanted enolate formation. Specifically, BrCH(2)CHF(2), BrCH(2)COO(t)Bu, and CH(2)=CHCOOMe were allowed to react with the stabilized anion of (phenylthio)methane boronate, PhSCH(2)BO(2)C(6)H(12), to give the substituted boronate. The substituted (phenylthio)methane boronate was converted to the corresponding sulfonium ion by treatment with methyl iodide and subsequently displaced with iodide. The alpha-iodo derivative was converted to the amine by conventional methods. PMID:11559189

Jagannathan, S; Forsyth, T P; Kettner, C A

2001-09-21

15

Dynamic kinetic resolution of amino acid amide catalyzed by D-aminopeptidase and alpha-amino-epsilon-caprolactam racemase.  

PubMed

Amino acid amide racemizing activity was discovered in alpha-amino-epsilon-caprolactam (ACL) racemase (EC 5. 1. 1. 15) from Achromobacter obae. The enzymatic synthesis of d-alanine from l-alanine amide has been demonstrated by use of d-aminopeptidase (DAP; EC 3. 4. 11. 19) from Ochrobactrum anthropi C1-38 and ACL racemase. The conversion of 45 mM l-alanine amide was carried out at 30 degrees C for 7 h; l-alanine amide was completely converted to d-alanine, and no l-alanine was detected. The result of successive enzymatic reaction shows that the combination of ACL racemase and DAP can be applied for dynamic kinetic resolution of dl-amino acid amides to yield d-amino acids. PMID:15913357

Asano, Yasuhisa; Yamaguchi, Shigenori

2005-06-01

16

Quantitation of fourteen urinary alpha-amino acids using isobutane gas chromatography chemical ionization mass spectrometry with 13C amino acids as internal standards.  

PubMed

Isobutane chemical ionization gas chromatography mass spectometry of the N-trifluoroacetyl-carboxy-n-butyl ester derivatives of amino acids, using a commercial per-13C-amino acid mixture as internal standards, provided a sensitive and specific method for quantitative analysis of fourteen urinary alpha-amino acids. A computer controlled quadrupole mass spectrometer was used in a selected ion monitoring mode to record the ion current due to the protonated molecular ions of each alpha-amino acid/13C analogue pair. BASIC programmes located peak maxima, and using previously established standard curves, calculated the amino acid content on the bases of both peak height and peak area ratios. Duplicate amino acid analyses are possible on 5 microliter of urine. Instrumental analysis required 25 minutes, automated data processing 10 minutes, and sample preparation 2 hours. Detection limits approached 1 ng with a typical mean standard deviation of 2% for the instrumental analysis. PMID:6452181

Finlayson, P J; Christopher, R K; Duffield, A M

1980-10-01

17

Bombesin analogs containing alpha-amino-isobutyric acid with potent anticancer activity.  

PubMed

Six octapeptide bombesin (BN) analogs were synthesized by substituting alpha-aminoisobutyric acid (Aib), in place of Ala9 or Gly11, or both, in the [D-Phe6, desMet14]-BN (6-14) sequence: D-Phe6-Gln7-Trp8-Ala9-Val10-Gly11-His12-Leu13-NH2 (P0). Additionally, Leu13 was replaced with isoleucine in two analogs and one of the analogs was butanoylated at the N-terminus. The antiproliferative activity of the analogs was tested in vitro on human pancreatic (MiaPaCa-2) and colon cancer (SW620, HT29 and PTC) cell lines using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The analogs demonstrated anticancer activity in the above cell lines at concentrations ranging from 0.01 nM to 1 microM. One of the analogs, P6, was evaluated for in vivo tumor regression in a xenograft model of human primary colon cancer in athymic nude mice and was found to cause significant reduction in tumor volume. NMR and molecular dynamics (MD) simulation studies for this analog revealed the presence of a mixed 3(10)/alpha-helical structure. This study demonstrates that the designed BN analogs retain their anticancer activity after the incorporation of the constrained amino acid, Aib, and are potential molecules for future use in cancer therapy and drug targeting. PMID:17031871

Prasad, Sudhanand; Mathur, Archna; Gupta, Neena; Jaggi, Manu; Singh, Anu T; Rajendran, Praveen; Sanna, Vinod K; Datta, Kakali; Mukherjee, Rama

2007-01-01

18

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

19

Tautomeric and microscopic protonation equilibria of some alpha-amino acids.  

PubMed

The acid-base equilibria of several amino acids, namely glycine, l-alanine, l-valine, l-leucine, l-phenylalanine, l-serine, l-methionine, and l-isoleucine, have been characterized in terms of microscopic protonation constants and tautomeric ratios. In this study, the microscopic protonation constants and tautomeric ratios of eight amino acids in different ethanol-water mixtures have been determined. The variation of microscopic constants of amino acids is discussed on the basis of solute-solvent interactions, and the ratio of dipolar ionic form to neutral form is determined in ethanol-water mixtures (20/80% ethanol by volume). The dipolar ionic form still greatly predominates, even in 80% ethanol, as estimated from potentiometric titration data. PMID:17416338

Do?an, Alev; Kiliç, Esma

2007-06-01

20

A beta-lactone route to chiral gamma-substituted alpha-amino acids: application to the concise synthesis of (S)-alpha-azidobutyro lactone and a natural amino acid.  

PubMed

[reaction: see text] Beta-lactones are useful synthetic intermediates allowing access to a number of functional arrays. In this report, enantiomerically pure 4-trichloromethyl-2-oxetanone is shown to be a versatile amino acid synthon leading to a variety of gamma-substituted alpha-amino acid precursors. The utility of this methodology was demonstrated by the concise synthesis of a protected homoserine equivalent, alpha-azidobutyro lactone, and a naturally occurring alpha-amino acid from the seeds of Blighia unijugata. PMID:11843584

Tennyson, Reginald L; Cortez, Guillermo S; Galicia, Héctor J; Kreiman, Charles R; Thompson, Christina M; Romo, Daniel

2002-02-21

21

New enzymatic method of chiral amino acid synthesis by dynamic kinetic resolution of amino acid amides: use of stereoselective amino acid amidases in the presence of alpha-amino-epsilon-caprolactam racemase.  

PubMed

D- and L-amino acids were produced from L- and D-amino acid amides by D-aminopeptidase from Ochrobactrum anthropi C1-38 and L-amino acid amidase from Pseudomonas azotoformans IAM 1603, respectively, in the presence of alpha-amino-epsilon-caprolactam racemase from Achromobacter obae as the catalyst by dynamic kinetic resolution of amino acid amides. PMID:17586677

Yamaguchi, Shigenori; Komeda, Hidenobu; Asano, Yasuhisa

2007-08-01

22

A comparison of the alpha-helix forming propensities and hydrogen bonding properties of serine phosphate and alpha-amino-gamma-phosphonobutyric acid.  

PubMed

The ability of serine phosphate (SerP) or alpha-amino-gamma-phosphonobutyric acid (AbuP) and arginine to form a salt bridge between their side chains appears to be much greater when they are spaced i/i+4 than when they are spaced i/i+3. The side chain-side chain interaction between SerP/Arg and AbuP/Arg, positioned i/i+4, contribute 0.45 and 0.62 kcal mol(-1), respectively, toward stabilizing the alpha-helical conformation of a peptide. PMID:10509930

Liehr, S; Chenault, H K

1999-09-20

23

[Intracellular concentration of phenylalanine, tyrosine and alpha-amino butyric acid in 13 homozygotes and 19 heterozygotes for phenylketonuria (PKU) compared with 26 normals (author's transl)].  

PubMed

Intracellular concentrations for phenylalanine, tyrosine, alpha-amino butyric acid and 7 other amino acids (glycine, alanine, valin, cystin, methionine, iso-leucin, leucin) were measured in lymphocytes of 13 homozygotes and 19 heterozygotes for phenylketonuria as well as in lymphocytes of 26 normals. Intracellular concentrations for phenylalanine, tyrosine and alpha-amino butyric acid were significantly higher in homo- and heterozygotes than in normals (p less than 0,001--p less than 0,01). For the other 7 amino acids there were no or only questionable differences. Between homo- and heterozygotes there was no difference in any of the amino acids. Intracellular phenylalanine: tyrosine ratio was essentially the same in all three groups of individuals. There was no correlation between intracellular phenylalanine above or below 10 nmol/10(6) cells and IQ in heterozygotes. The same is true for phenylalanine: tyrosine ratio greater or smaller than 1. In Homozygotes there was no correlation between intracellular phenylalanine and age -- to whom DQ/IQ is correlated. There was no significant difference in intracellular phenylalanine between homozygotes with blood levels above and below 908 mumol/l (15 mg/100 ml) at the time of blood sampling and no correlation between intra- and extra-cellular phenylalanine concentrations. Among the 26 normals there were only 2 with intracellular phenylalanine above 10 nmol/10(6) cells, both showing phenylalanine loading test curves suspicious for heterozygosity. The results are discussed and important functions of the cell wall supposed. An abnormal unknown intracellular metabolite being the real noxious agent could explain the incomparably different degree of brain dysfunction in individuals with equal though elevated intracellular phenylalanine concentrations i.e. homozygotes and heterozygotes for PKU. PMID:7194402

Thalhammer, O; Pollak, A; Lubec, G; Königshofer, H

1980-11-01

24

Iron-bleomycin-deoxyribonucleic acid system. Evidence of deoxyribonucleic acid interaction with the alpha-amino group of the beta-aminoalanine moiety.  

PubMed

The Fe(III) complex of bleomycin (BLM) is, at pH 4, in the high-spin form. At pH 7, the coordination of the alpha-amino group of the beta-aminoalanine moiety of BLM converts it to a low-spin species: BLM X Fe(III) X alpha NH2. The conversion of the high-spin species to the low-spin one can also take place at pH 4 (i) by addition of ligands L such as N3-, S2O3(2-), and SCN- or (ii) through interaction with DNA. Moreover, the addition, at pH 7, of DNA to BLM X Fe(III) that has been previously complexed with one of these ligands L displaces this latter from its position. These results suggest that (i) the ligand L occupies the same site of coordination as the alpha-amino group and (ii) an interaction occurs between the beta-aminoalanine moiety of BLM and DNA that lowers the pKd of the alpha-amino group, promoting its coordination to iron. PMID:6197995

Albertini, J P; Garnier-Suillerot, A

1984-01-01

25

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

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.

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

1991-03-01

26

Carrier-mediated uptake and phloem systemy of a 350-Dalton chlorinated xenobiotic with an alpha-amino acid function.  

PubMed

In a previous paper we have shown that epsilon-(phenoxyalkanecarboxylyl)-L-Lys conjugates are potent inhibitors of amino acid transport systems and that it is possible to modulate the uptake inhibition by hydrophobic or hydrophilic additions in the 4-position of the aromatic ring (J.F. Chollet, C. Delétage, M. Faucher, L. Miginiac, J.L. Bonnemain [1997] Biochem Biophys Acta 1336: 331-341). In this report we demonstrate that epsilon-(2,4-dichlorophenoxyacetyl)-L-Lys (2,4D-Lys), one of the largest molecules of the series and one of the most potent inhibitors, is a highly permeant conjugate. Uptake of 2,4D-Lys by broad bean (Vicia faba) leaf discs is mediated by an active carrier system (Km1 = 0.2 mM; Vmax1 = 2.4 nmol x cm(-2) x h(-1) at pH 5.0) complemented by an important diffusive component. Among the compounds tested (neutral, basic, and acidic amino acids, auxin, glutathione, and sugars), only the aromatic amino acids clearly compete with 2,4D-Lys. The conjugate accumulates in the vein network, is exported toward the growing organs, and exhibits a distribution pattern different from that of the herbicide moiety. However, over time 2,4D-Lys progressively splits into 2,4D and lysine. Analyses by high-performance liquid chromatography and liquid scintillation spectrometry of the phloem sap collected from the castor bean system, used as a systemy test, indicate decreasing capacities of 2,4D, 2,4D-Lys, and glyphosate, respectively, to move from the epidermis cell wall to the sieve element. Our results show that it is possible to design synthesis of large-size xenobiotics (approximately 350 D) with a lipophilic pole, exhibiting high mobility within the vascular system. PMID:11299344

Delétage-Grandon, C; Chollet, J F; Faucher, M; Rocher, F; Komor, E; Bonnemain, J L

2001-04-01

27

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

PubMed

We studied the effect of beta-oxalylamino-L-alanine, a glutamate analog present in Lathyrus sativus seeds and implicated in the etiopathogenesis of neurolathyrism, and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate on the extracellular levels of aspartate, glutamate and taurine in the primary motor cortex of freely moving rats. We found that while both neurotoxins increase the level of aspartate and glutamate, only (+/-)-alpha(-amino-3-hydroxy-5-methylisoxazole-4-propionate is able to modulate the level of taurine. GYKI-52466, a non-competitive non-NMDA antagonist, inhibited beta-oxalylamino-L-alanine-induced increase of aspartate, but not that of glutamate. Conversely, this antagonist proved to be very efficient in blocking the stimulating effect of (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate on all three amino acids. We suggest that beta-oxalylamino-L-alanine increases the level of glutamate in vivo by a mechanism not connected to its effect on the non-NMDA receptors, which might involve the inhibition of glutamate transport. This would allow the excitatory neurotransmitter to reach a concentration sufficient to stimulate the non-NMDA receptors, which in their turn mediate the specific release of aspartate. Although the role of aspartate as a neurotransmitter is still under discussion, it might indeed amplify the excitotoxic cascade through its action on NMDA receptors. We speculate that this sequence of events might represent an important step in the molecular cascade leading to the appearance of the selective motoneuron degeneration in neurolathyrism. PMID:10762089

La Bella, V; Piccoli, F

2000-05-01

28

Pharmacological characterization of cGMP regulation by the biarylpropylsulfonamide class of positive, allosteric modulators of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors.  

PubMed

The biarylpropylsulfonamide class of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) potentiators represented by N-2-(4-(4-cyanophenol)phenol)propyl-2-propanesulfonamide (LY404187) and (R)-4'-[1-fluoro-1-methyl-2-(propane-2-sulfonylamino)-ethyl]-biphenyl-4-carboxylic acid methylamide (LY503430) are positive, allosteric AMPA receptor activators, which enhance AMPA receptor-mediated neurotransmission by reducing desensitization of the ion channel. Although these compounds have efficacy in in vivo rodent models of cognition, depression, and Parkinson's disease, little is known about biochemical pathways activated by these agents. Given the well established regulation of the nitric oxide/cGMP pathway by excitatory neurotransmission, the current study characterized AMPA receptor potentiator-mediated cGMP response in mouse cerebellum. Acute treatment by both LY404187 and LY503430 [2.0, 5.0, or 10 mg/kg subcutaneously (s.c.)] elevated basal cerebellar cGMP levels in a dose-dependent manner. Pretreatment with the noncompetitive, allosteric AMPA receptor-selective antagonist 7H-1,3-dioxolo[4,5-h][2,3]benzodiazepine-7-carboxamide, 5-(4-aminophenyl)-8,9-dihydro-N,8-dimethyl-monohydrochloride-(9CI) (GYKI 53655) [3.0 mg/kg intraperitoneally (i.p.)], completely blocked the effect of LY404187, demonstrating that activation of AMPA receptors induces cGMP levels. Interestingly, pretreatment with the N-methyl-d-aspartate (NMDA) open channel blocker dizocilpine (0.3 and 1.0 mg/kg i.p.) also abolished the AMPA receptor potentiator-mediated cGMP accumulation, indicating that activation of AMPA receptors leads to NMDA receptor-mediated transmission involved in cGMP regulation. Pharmacological augmentation of the endogenous glutamate tone via the alkaloid harmaline (20-60 mg/kg i.p.) synergized with AMPA potentiator activity and provided further direct evidence of in vivo allosteric activation of AMPA receptors by LY404187. The synergism between harmaline and LY404187 was specific, since cGMP accumulation induced by foot-shock stress was not augmented by the AMPA receptor potentiator. Taken together, these data indicate that the cGMP system may play an important role in pharmacological efficacy of the biarylpropylsulfonamide class of AMPA receptor potentiators. PMID:16803862

Ryder, John W; Falcone, Julie F; Manro, Jason R; Svensson, Kjell A; Merchant, Kalpana M

2006-10-01

29

Stimulation of oxytocin release in the lactating rat by central excitatory amino acid mechanisms: evidence for specific involvement of R,S-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid-sensitive glutamate receptors.  

PubMed

To examine whether an excitatory amino acid (EAA) neurotransmitter may influence the secretion of oxytocin (OT), agonists and antagonists selective for three major groups of EAA receptors were microinjected into the area of right supraoptic nucleus (SON) of conscious unrestrained lactating rats. An increase in plasma OT concentration was induced by the EAA receptor agonist R,S-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and kainic acid, but not by agonists at other EAA receptors, such as N-methyl-D-aspartic acid (NMDA) or the metabotropic agonist (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid. Increasing AMPA doses between 0.1-0.8 nmol/SON progressively increased the percentage of animals showing OT discharges to 100% at the highest dose, whereas the responding animals showed similar elevations of plasma OT regardless of dose. OT release induced by intra-SON AMPA was prevented by treatment with the selective non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione, but not by antagonists of the NMDA receptor. Administration of this antagonist in the third ventricle blocked the release of OT and PRL induced by suckling. The L-type Ca2+ channel antagonist nimodipine and the Na+ channel inhibitor 3-amino-N-(aminoiminomethyl)5-(N-ethyl-N-isopropyl)6-chloropyra zinecarboxamide produced an additive blockade of AMPA-induced OT release, whereas the N-type Ca2+ channel-preferring antagonist omega-conotoxin GVIA had no effect. These findings suggest that an EAA, most likely glutamate, participates in the physiological regulation of OT release in the lactating rat via actions at an AMPA/kainate receptor subtype that gates Na+ and Ca2+. PMID:7694846

Parker, S L; Crowley, W R

1993-12-01

30

Sensory-guided identification of N-(1-methyl-4-oxoimidazolidin-2-ylidene)-alpha-amino acids as contributors to the thick-sour and mouth-drying orosensation of stewed beef juice.  

PubMed

Sensory-guided fractionation of stewed beef juice using ultrafiltration, gel permeation chromatography, PFPP-HPLC, and HILIC combined with analytical sensory techniques led to the identification of the dipeptides beta-alanyl-N-methyl-L-histidine and beta-alanyl-L-histidine, as well as the creatinine derivatives N-(1-methyl-4-oxoimidazolidin-2-ylidene)aminopropionic acid, N-(1-methyl-4-oxoimidazolidin-2-ylidene)aminoacetic acid, and N-(1-methyl-4-oxoimidazolidin-2-ylidene)amino-4,5,6-trihydroxyhexanoic acid as taste modulators in stewed beef juice. Model experiments demonstrated for the first time that the latter three N-(1-methyl-4-oxoimidazolidin-2-ylidene)-alpha-amino acids are formed by Maillard-type reactions from creatinine and reducing hexoses. Quantitative analysis, followed by taste recombination and omission experiments, revealed that subthreshold concentrations of these taste modulators enhance the typical thick-sour and mouth-drying orosensation and the mouthfulness imparted by stewed beef juice, although none of these compounds exhibited any significant intrinsic taste when tasted individually in water. PMID:20420435

Sonntag, Tessa; Kunert, Christof; Dunkel, Andreas; Hofmann, Thomas

2010-05-26

31

Search for new anticonvulsant compounds. Part 1: Synthesis, physicochemical and anticonvulsant properties of new derivatives of alpha-amino-gamma-phthalimidobutyric acid.  

PubMed

Synthesis and physicochemical properties of new derivatives of alpha-substituted gamma-phthalimidobutyric acid are described. N-substituted amides of alpha-(4-phenylpiperazine)-gamma- phthalimidobutyric acid were prepared by condensation of the acid with the corresponding derivatives of benzylamine in the presence of BOP reagent. 2-(4-Phenylpiperazine)- or 2-(4-benzylpiperidine)-4-phthalimidobutyric acid were esterified with alkyl bromide in the presence of DBU or tetrabutylammonium bromide as catalyst. The obtained compounds were evaluated for anticonvulsant activity. 2-(4-Phenylpiperazine)-4-phthalimidobutyric acid and three N-substituted amides of this acid displaced protection against MES and scMet-induced seizures. PMID:8570669

Malawska, B; Zejc, A

1995-11-01

32

Synthesis of a new fluorescent macrocyclic [alpha]-amino acid derivative via tandem cross-enyne\\/ring-closing metathesis cascade catalyzed by ruthenium based catalysts  

Microsoft Academic Search

A simple methodology to a unique macrocyclic ?-amino acid (AAA) derivative involving three step synthetic sequence has been reported. In addition, various ruthenium based catalysts were studied to enhance the selectivity of the desired macrocyclic AAA derivative 6. The fluorescence behavior of these AAA derivatives 5 and 6 indicate their potential applications in biological sciences as biomarkers, ion sensors and

Sambasivarao Kotha; Deepti Bansal; Kuldeep Singh; Subhasree Banerjee

2011-01-01

33

Imidazo[1,2-a]pyrazine-3,6-diones derived from alpha-amino acids: a theoretical mechanistic study of their formation via pyrolysis and silica-catalyzed process.  

PubMed

Imidazo[1,2-a]pyrazine-3,6-diones are unusual compounds composed of three alpha-amino acid fragments. These bicyclic amidines (BCAs) form under high temperatures or with the use of strong dehydrating reagents. We gave insight into the mechanisms of BCA formation via gas-phase pyrolytic and silica-catalyzed reactions of glycine (Gly) and alpha-aminoisobutyric acid (AIB) with related diketopiperazines (DKPs), using quantum chemical calculations. The entire process requires four steps: (1) O-acylation of DKP with free or silica-bonded amino acid, (2) acyl transfer from the oxygen to the nitrogen atom, (3) intramolecular condensation of the N-acyl DKP into a cyclol, and (4) elimination of water. To study step (1) at silica surface (modeled by H7Si8O12-OH cluster), we employed two-level ONIOM calculations (AM1:UFF, B3LYP/3-21G:UFF and B3LYP/6-31G(d):UFF); all gas-phase reactions were studied at the AM1, B3LYP/3-21G and B3LYP/6-31G(d) levels. The catalytic effect of silica was observed for both Gly and AIB: the activation energy in the O-acylation at the surface was lower by more than 9 kcal mol(-1) as compared to the gas-phase process. Contrary to the exothermic O-acylation, the gas-phase transfer reaction (step 2) was exothermic in both cases, but more favorable for Gly. The cyclocondensation of N-acylated DKPs into BCAs (steps 3 and 4) is endothermic for Gly and exothermic for AIB. PMID:16759132

Contreras-Torres, Flavio F; Basiuk, Vladimir A

2006-06-15

34

Studies of cationic radicals in. gamma. -irradiated single crystals of. cap alpha. -aminoisobutyric acid and related. cap alpha. -amino acids by electron spin resonance and SCF MO INDO calculation  

Microsoft Academic Search

The cationic radical of the single crystal of ..cap alpha..-aminoisobutyric acid ..gamma.. irradiated at 77°K was identified as the deprotonated cation radical, NHâC(CHâ)âCOO, by X- and Q-band ESR including photobleaching measurement. The eigenvalues of the g tensor were determined to be 2.0052, 2.0021, and 2.0013. The eigenvector of g\\/sub max\\/(2.0052) is perpendicular to the molecular plane and the density axis

Atsuko Minegishi

1977-01-01

35

Comparative study on the use of ortho-phthalaldehyde, naphthalene-2,3-dicarboxaldehyde and anthracene-2,3-dicarboxaldehyde reagents for alpha-amino acids followed by the enantiomer separation of the formed isoindolin-1-one derivatives using quinine-type chiral stationary phases.  

PubMed

Cinchona alkaloid based chiral stationary phases (CSPs) were evaluated and compared for the enantiomer separation of a set of alpha-amino acid derivatives as selectands (SA), using ortho-phthalaldehyde (OPA), naphthalene-2,3-dicarboxaldehyde (NDA) and anthracene-2,3-dicarboxaldehyde (ADA) as reagents in the presence of acetonitrile. Protocols have been developed for the derivatization of most common amino acids in the absence of the usual thiol components (2-mercaptoethanol, mercaptosulphonic acid, sodium sulfite) under acidic and neutral conditions providing the corresponding isoindolin-1-one (phthalimidine) derivatives. They are stable for hours at various reaction conditions compared to thiol or sulfide modified isoindoles resulted by the OPA-thiol reaction type. Among the derivatizing agents, ADA afforded the highest retention factors (k) and for the majority of the analytes also resolution (Rs) and enantioselectivity (alpha) values (i.e. for tryptophan k1 = 23, Rs = 4.93 and alpha = 1.43). Structure variation of the CSPs and selector (SO), respectively indicates that steric arrangement around the binding cleft plays a major role in the enantiodiscriminating events. To provide more detailed information about the derivatization reaction itself, the proposed mechanism for the formation of the OPA derivative (isoindolin-l-one) was further evaluated by deuterium labeling and LC-MS analysis. PMID:16078691

Gyimesi-Forrás, Krisztina; Leitner, Alexander; Akasaka, Kazuaki; Lindner, Wolfgang

2005-08-12

36

Lipase-catalyzed kinetic resolution of cyclic trans-1,2-diols bearing a diester moiety: synthetic application to chiral seven-membered-ring alpha,alpha-disubstituted alpha-amino acid.  

PubMed

Chiral cycloalkane-trans-1,2-diols (+/-)-3 and (+/-)-8 having a diester moiety have been prepared from dimethyl dialkenylmalonate using olefin metathesis by Grubbs catalyst, followed by epoxidation and acidic hydrolysis. Kinetic resolution of racemic cyclopentane-trans-1,2-diol (+/-)-3 by lipase-catalyzed transesterification afforded an optically active monoacetate (-)-5 of 95% ee in 46% yield and the recovered diol (-)-3 of 92% ee in 51% yield, and that of cycloheptane-trans-1,2-diol (+/-)-8 gave a monoacetate (+)-10 of 95% ee in 51% yield and the diol (-)-8 of >99% ee in 43% yield, respectively. The enantiomer selectivity of racemic cyclic trans-1,2-diols bearing a diester moiety by lipases (Amano PS and Amano AK) was opposite to that of the reported simple racemic cycloalkane-trans-1,2-diols. To explain the lipase-catalyzed enantiomer selectivity, computer modeling of lipase-substrate complexes was performed. Furthermore, the optically active diester (-)-8 could be efficiently converted into an optically active seven-membered-ring alpha,alpha-disubstituted amino acid (4R,5R)-(-)-15. PMID:17713957

Tanaka, Masakazu; Demizu, Yosuke; Nagano, Masanobu; Hama, Mariko; Yoshida, Yukio; Kurihara, Masaaki; Suemune, Hiroshi

2007-09-28

37

Overlapping double turn conformations adopted by tetrapeptides containing non-coded alpha-amino isobutyric acid (Aib) and formation of tape-like structures through supramolecular helix mediated self-assembly.  

PubMed

Single crystal X-ray diffraction studies and solvent dependent (1)H NMR titrations reveal that a set of four tetrapeptides with general formula Boc-Xx(1)-Aib(2)-Yy(3)-Zz(4)-OMe, where Xx, Yy and Zz are coded L-amino acids, adopt equivalent conformations that can be described as overlapping double turn conformations stabilized by two 4-->1 intramolecular hydrogen bonds between Yy(3)-NH and Boc C=O and Zz(4)-NH and Xx(1)C=O. In the crystalline state, the double turn structures are packed in head-to-tail fashion through intermolecular hydrogen bonds to create supramolecular helical structures. Field emission scanning electron microscopic (FE-SEM) images of the tetrapeptides in the solid state reveal that they can form flat tape-like structures. The results establish that synthetic Aib containing supramolecular helices can form highly ordered self-aggregated amyloid plaque like human amylin. PMID:19508219

Kar, Sudeshna; Dutta, Arpita; Drew, M G B; Koley, Pradyot; Pramanik, Animesh

2009-01-01

38

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

PubMed

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

Albericio, F

2000-01-01

39

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

PubMed

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

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

2013-02-01

40

Recognition of non-alpha-amino substrates by pyrrolysyl-tRNA synthetase.  

PubMed

Pyrrolysyl-tRNA synthetase (PylRS), an aminoacyl-tRNA synthetase (aaRS) recently found in some methanogenic archaea and bacteria, recognizes an unusually large lysine derivative, L-pyrrolysine, as the substrate, and attaches it to the cognate tRNA (tRNA(Pyl)). The PylRS-tRNA(Pyl) pair interacts with none of the endogenous aaRS-tRNA pairs in Escherichia coli, and thus can be used as a novel aaRS-tRNA pair for genetic code expansion. The crystal structures of the Methanosarcina mazei PylRS revealed that it has a unique, large pocket for amino acid binding, and the wild type M. mazei PylRS recognizes the natural lysine derivative as well as many lysine analogs, including N(epsilon)-(tert-butoxycarbonyl)-L-lysine (Boc-lysine), with diverse side chain sizes and structures. Moreover, the PylRS only loosely recognizes the alpha-amino group of the substrate, whereas most aaRSs, including the structurally and genetically related phenylalanyl-tRNA synthetase (PheRS), strictly recognize the main chain groups of the substrate. We report here that wild type PylRS can recognize substrates with a variety of main-chain alpha-groups: alpha-hydroxyacid, non-alpha-amino-carboxylic acid, N(alpha)-methyl-amino acid, and D-amino acid, each with the same side chain as that of Boc-lysine. In contrast, PheRS recognizes none of these amino acid analogs. By expressing the wild type PylRS and its cognate tRNA(Pyl) in E. coli in the presence of the alpha-hydroxyacid analog of Boc-lysine (Boc-LysOH), the amber codon (UAG) was recoded successfully as Boc-LysOH, and thus an ester bond was site-specifically incorporated into a protein molecule. This PylRS-tRNA(Pyl) pair is expected to expand the backbone diversity of protein molecules produced by both in vivo and in vitro ribosomal translation. PMID:19100747

Kobayashi, Takatsugu; Yanagisawa, Tatsuo; Sakamoto, Kensaku; Yokoyama, Shigeyuki

2009-02-01

41

Sulfinimine-mediated asymmetric synthesis of beta-hydroxy alpha-amino phosphonates.  

PubMed

The addition of potassium dialkyl phosphites to enantiopure O-protected alpha-hydroxy sulfinimine pseudoenantiomers affords beta-hydroxy alpha-amino phosphonates in good yield and de. The reaction exhibits a strong match-mismatch effect. PMID:12968873

Davis, Franklin A; Prasad, Kavirayani R

2003-09-19

42

Catalysis in the formation of /alpha/-amino ketones  

SciTech Connect

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

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

1988-10-20

43

Synthesis and preliminary biological evaluation of new alpha-amino amide anticonvulsants incorporating a dextromethorphan moiety.  

PubMed

Dextromethorphan 1 is an effective neuroprotectant in animal models of epilepsy and ischemia but showed side-effects during clinical trials limiting its potential use in a clinical setting. Here we describe the enantioselective and enantiospecific syntheses and the initial in vitro and in vivo biological evaluation of new hybrid structures between 1 and a previously disclosed alpha-amino amide anticonvulsant (3). PMID:10406642

Pevarello, P; Traquandi, G; Bonsignori, A; McArthur, R A; Maj, R; Caccia, C; Salvati, P; Varasi, M

1999-07-01

44

S(N)1-like reactions of bicyclic alpha-amino ethers with sulfur, nitrogen, and carbon nucleophiles. Synthesis of 1-azabicyclo[3.2.2]nonanes functionalized at carbon C2 and C6 with complete stereocontrol.  

PubMed

[reaction: see text] In the presence of nucleophiles, Lewis acid mediated cleavage of alpha-amino ethers derived from quincorine and quincoridine affords a variety of C2-substituted and C6-vinylated 1-azabicyclo[3.2.2]nonanes. These are enantiopure and are formed in S(N)1-like reactions with complete stereocontrol. There is no leakage into 2-Nu en route to product 1-Nu or vice versa. Me(3)SiCN provides new Strecker-type alpha-amino nitriles. In the presence of TTMPP-BF(3).OEt(2), the ketene acetal Me(2)C=C(OMe)OSiMe(3) delivers enantiopure bicyclic beta-amino acid esters. PMID:12227743

Röper, Stefanie; Wartchow, Rudolf; Hoffmann, H Martin R

2002-09-19

45

Highly constrained proteins contain an unexpectedly large number of amino acid tandem repeats  

E-print Network

Highly constrained proteins contain an unexpectedly large number of amino acid tandem repeats Loris Single-amino-acid tandem repeats are very common in mammalian proteins but their function and evolution are still poorly understood. Here we investigate how the variability and prevalence of amino acid repeats

Mularoni, Loris

46

Inhibition of CO2 Combination and Reduction of the Bohr Effect in Haemoglobin chemically modified at its alpha-Amino Groups  

Microsoft Academic Search

Blocking of the alpha-amino groups by cyanate inhibits the uptake of CO2 by haemoglobin. It also inhibits the influence which changes in pCO2 at constant pH normally have on the oxygen affinity and on the Bohr effect. Blocking the alpha-amino groups of the alpha chain reduces the alkaline Bohr effect by 25 per cent.

J. V. Kilmartin; L. ROSSI-BERNARDI

1969-01-01

47

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

E-print Network

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

Paris-Sud XI, Université de

48

The novel structure of a pyridoxal 5'-phosphate-dependent fold-type I racemase, alpha-amino-epsilon-caprolactam racemase from Achromobacter obae.  

PubMed

Alpha-amino-epsilon-caprolactam (ACL) racemase (ACLR) from Achromobacter obae catalyzes the interconversion of l- and d-ACL. ACLR belongs to the fold-type I group of pyridoxal 5'-phosphate (PLP) dependent enzymes. In this study, the first crystal structures of a fold-type I racemase are solved for the native form and epsilon-caprolactam-complexed form of ACLR at 2.21 and 2.40 A resolution, respectively. Based on the location of epsilon-caprolactam in the complex structure, the substrate-binding site is assigned between Trp49 and Tyr137. The carboxyl group of Asp210 is a reasonable candidate that recognizes the nitrogen atom of a lactam or amide in the substrate. Based on a structural comparison with fold-type III alanine racemase, Tyr137 is potentially the acid/base catalytic residue that is essential for the two-base racemization mechanism. The overall structure of ACLR is similar to that of fold-type I enzymes. A structural comparison with these enzymes explains the different reaction specificities. PMID:19146406

Okazaki, Seiji; Suzuki, Atsuo; Mizushima, Tsunehiro; Kawano, Takeshi; Komeda, Hidenobu; Asano, Yasuhisa; Yamane, Takashi

2009-02-10

49

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

PubMed

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

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

50

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

SciTech Connect

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.

Onstott, T. C. [Princeton University] [Princeton University; Aubrey, A.D. [Jet Propulsion Laboratory, Pasadena, CA] [Jet Propulsion Laboratory, Pasadena, CA; Kieft, T L [New Mexico Institute of Mining and Technology] [New Mexico Institute of Mining and Technology; Silver, B J [Jet Propulsion Laboratory, Pasadena, CA] [Jet Propulsion Laboratory, Pasadena, CA; Phelps, Tommy Joe [ORNL] [ORNL; Van Heerden, E. [University of the Free State] [University of the Free State; Opperman, D. J. [University of the Free State] [University of the Free State; Bada, J L. [Geosciences Research Division, Scripps Instition of Oceanography, Univesity of California San Diego,] [Geosciences Research Division, Scripps Instition of Oceanography, Univesity of California San Diego,

2014-01-01

51

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

PubMed Central

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

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

2012-01-01

52

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

PubMed

An efficient and convergent synthesis has been developed for the production of 3,4-dihydroxy-5-[4-(2-((2Z)-hexenyl)phenyl)-3-(1Z)-but enyl]-2 (5H)-furanone (12d). This hydrophobic antioxidant is a stable conformationally constrained mimic of arachidonic acid (AA) (1) and its respective aci-reductone analogue (2). Pd(0)-catalyzed cross-coupling of 5-(3-butynyl)-3,4-dihydroxy-2(5H)-furanone (7) with 2-((2Z)-hexenyl)iodobenzene (8d) followed by Lindlar catalyzed hydrogenation produces 12d. Butynyl intermediate 7 is prepared from 2-(benzyloxy)-5-deoxyascorbic acid (15) by iodination (I2, PPh3, Imd), iodo substitution with lithium acetylide ethylenediamine complex (LiAEDA, HMPA, -5 degrees C), and benzyl group cleavage (Ac2O, Pyr, BCl3). The utility of this synthetic method was demonstrated by the synthesis of analogues 10e-k. Biological testing revealed that certain of these antioxidants inhibit both cyclooxygenase (COX) and 5-lipoxygenase (5-LO) with comparable efficacy as reported for aspirin and zileuton, respectively. The antioxidant activity of these aci-reductones, measured as a function of their inhibitory effect on CCl4-induced lipid peroxidation of hepatic microsomes, exceeds that produced by alpha-tocopherol. Synthetic routes and initial structure-activity relationships (SAR) for these novel mixed functioning antioxidants are presented. PMID:9484493

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

1998-02-12

53

Mathematical models of diffusion-constrained polymerase chain reactions: basis of high-throughput nucleic acid assays and simple self-organizing systems  

E-print Network

nucleic acid assays and simple self-organizing systems SUPPLEMENTAL INFORMATION John Aach and George M "Mathematical models of diffusion-constrained polymerase chain reactions: basis of high-throughput nucleic acid

Church, George M.

54

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

SciTech Connect

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.

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

2012-10-09

55

Transformation of some hydroxy amino acids to other amino acids  

Microsoft Academic Search

It has been observed that beta-hydroxy-alpha-amino acids are transformed into other amino acids, when heated in dilute solutions with phosphorous acid, phosphoric acid or their ammonium salts. It has been shown that as in the case of previously reported glycine-aldehyde reactions, glycine also reacts with acetone to give beta-hydroxyvaline under prebiologically feasible conditions. It is suggested, therefore, that the formation

A. S. U. Choughuley; A. S. Subbaraman; Z. A. Kazi; M. S. Chadha

1975-01-01

56

Synthesis of conformationally constrained C-glycosyl alpha- and beta-amino acids and sugar-carbamino sugar hybrids via Diels-Alder reaction.  

PubMed

[structure: see text] Sugar-derived dienes undergo Diels-Alder reactions with methyl alpha-nitro acrylate and ethyl beta-nitro acrylate to form the corresponding cycloadducts which have been converted into conformationally constrained C-glycosyl alpha- and beta-amino acids. Further, these beta-amino acids are converted into sugar-carbamino sugar hybrid molecules. PMID:16288526

Jayakanthan, K; Vankar, Yashwant D

2005-11-24

57

OCEANOGRAPHY Stratigraphic Distribution of Amino Acids in Peats from Cedar Creek  

E-print Network

LIMNOLOGY AND OCEANOGRAPHY April 1959 VOLUME IV NUMBER 2 Stratigraphic Distribution of Amino Acids. MILLERS University of Minnesota, Minneapolis ABSTRACT The concentration of several alpha-amino acids. Seven amino acids are consistently present in the natural accumulations: glycine, aspartic acid

Minnesota, University of

58

Design and synthesis of conformationally constrained analogues of cis-cinnamic acid and evaluation of their plant growth inhibitory activity.  

PubMed

1-O-cis-Cinnamoyl-?-D-glucopyranose is known to be one of the most potent allelochemical candidates and was isolated from Spiraea thunbergii Sieb by Hiradate et al. (2004), who suggested that it derived its strong inhibitory activity from cis-cinnamic acid, which is crucial for phytotoxicity. In this study, key structural features and substituent effects of cis-cinnamic acid (cis-CA) on lettuce root growth inhibition was investigated. These structure-activity relationship studies indicated the importance of the spatial relationship of the aromatic ring and carboxylic acid moieties. In this context, conformationally constrained cis-CA analogues, in which the aromatic ring and cis-olefin were connected by a carbon bridge, were designed, synthesized, and evaluated as plant growth inhibitors. The results of the present study demonstrated that the inhibitory activities of the five-membered and six-membered bridged compounds were enhanced, up to 0.27 ?M, and were ten times higher than cis-CA, while the potency of the other compounds was reduced. PMID:24176527

Nishikawa, Keisuke; Fukuda, Hiroshi; Abe, Masato; Nakanishi, Kazunari; Tazawa, Yuta; Yamaguchi, Chihiro; Hiradate, Syuntaro; Fujii, Yoshiharu; Okuda, Katsuhiro; Shindo, Mitsuru

2013-12-01

59

Physiological Adaptation to the Loss of Amino Acid Transport Ability  

PubMed Central

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

DeBusk, Ruth M.; Ogilvie-Villa, Susan

1982-01-01

60

Enantiomeric excesses in meteoritic amino acids  

NASA Technical Reports Server (NTRS)

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.

Cronin, J. R.; Pizzarello, S.

1997-01-01

61

Non-protein amino acids in the design of secondary structure scaffolds.  

PubMed

The use of stereochemically constrained amino acids permits the design of short peptides as models for protein secondary structures. Amino acid residues that are restrained to a limited range of backbone torsion angles (phi-psi) may be used as folding nuclei in the design of helices and beta-hairpins. alpha-Amino-isobutyric acid (Aib) and related Calphaalpha dialkylated residues are strong promoters of helix formation, as exemplified by a large body of experimentally determined structures of helical peptides. DPro-Xxx sequences strongly favor type II' turn conformations, which serve to nucleate registered beta-hairpin formation. Appropriately positioned DPro-Xxx segments may be used to nucleate the formation of multistranded antiparallel beta-sheet structures. Mixed (alpha/beta) secondary structures can be generated by linking rigid modules of helices and beta-hairpins. The approach of using stereochemically constrained residues promotes folding by limiting the local structural space at specific residues. Several aspects of secondary structure design are outlined in this chapter, along with commonly used methods of spectroscopic characterization. PMID:16957333

Mahalakshmi, Radhakrishnan; Balaram, Padmanabhan

2006-01-01

62

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

PubMed

This paper describes the enantiomeric resolution of a series of unsaturated N-methyloxycarbonyl-alpha-H-alpha-amino acids (N-MOC-alpha-amino acids) on macrocyclic glycopeptide stationary phases by means of high-performance liquid chromatography (HPLC). Three types of glycopeptide phases, i.e. Chirobiotic T, V and R, were evaluated in both reversed-phase (RP) and polar ionic mode (PIM). The best results in terms of enantioselectivity and resolution were obtained on Chirobiotic R phase, with the PIM mobile phase giving the highest resolution per min. Investigation of the pH of the reversed-phase mobile phase in the pH range 4.1-5.9 showed little effect on enantioselectivity. The method was applied for monitoring the conversion and product enantiomeric excess of an enzymatic hydrolysis reaction using N-MOC-alpha-H-alpha-amino acid esters as substrate. PMID:16443231

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

2006-03-01

63

Shock Synthesis of Amino Acids in Simulated Primitive Environments  

Microsoft Academic Search

A mixture of gases roughly simulating the primitive terrestrial atmosphere has been subjected to shock heating followed by a rapid thermal quench. Under strictly homogeneous conditions there is a very high efficiency of 5 × 1010 molecules per erg of shock-injected energy for production of alpha-amino acids. Calculations suggest that rapid quenching bypasses the usual thermochemical barrier. The product of

A. Bar-Nun; N. Bar-Nun; S. H. Bauer; Carl Sagan

1970-01-01

64

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

PubMed

In an attempt to provide a rational basis for the optimization of citric acid production by A. niger, we developed a mathematical model of the metabolism of this filamentous fungus when in conditions of citric acid accumulation. The present model is based in a previous one, but extended with the inclusion of new metabolic processes and updated with currently available kinetic data. Among the different alternatives to represent the system behavior we have chosen the S-system representation within power-law formalism. This type of representation allows us to verify not only the ability of the model to exhibit a stable steady state of the integrated system but also the robustness and quality of the representation. The model analysis is shown to be self-consistent, with a stable steady state, and in good agreement with experimental evidence. Moreover, the model representation is sufficiently robust, as indicated by sensitivity and steady-state and dynamic analyses. From the steady-state results we concluded that the range of accuracy of the S-system representation is wide enough to model realistic deviations from the nominal steady state. The dynamic analysis indicated a reasonable response time, which provided further indication that the model is adequate. The extensive assessment of the reliability and quality of the model put us in a position to address questions of optimization of the system with respect to increased citrate production. We carried out the constrained optimization of A. niger metabolism with the goal of predicting an enzyme activity profile yielding the maximum rate of citrate production, while, at the same time, keeping all enzyme activities within predetermined, physiologically acceptable ranges. The optimization is based on a method described and tested elsewhere that utilizes the fact that the S-system representation of a metabolic system becomes linear at steady state, which allows application of linear programming techniques. Our results show that: (i) while the present profile of enzyme activities in A. niger at idiophase steady state yields high rates of citric acid production, it still leaves room for changes and suggests possible optimization of the activity profile to over five times the basal rate synthesis; (ii) when the total enzyme concentration is allowed to double its basal value, the citric acid production rate can be increased by more than 12-fold, and even larger values can be attained if the total enzyme concentration is allowed to increase even more (up to 50-fold when the total enzyme concentration may rise up to 10-fold the basal value); and (iii) the systematic search of the best combination of subsets of enzymes shows that, under all conditions assayed, a minimum of 13 enzymes need be modified if significant increases in citric acid are to be obtained. This implies that improvements by single enzyme modulation are unlikely, which is in agreement with the findings of some investigators in this and other fields. PMID:10940866

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

2000-10-01

65

Constraining credences  

E-print Network

This dissertation is about ways in which our rational credences are constrained: by norms governing our opinions about counterfactuals, by the opinions of other agents, and by our own previous opinions. In Chapter 1, I ...

Moss, Sarah (Sarah E.)

2009-01-01

66

cap alpha. -1,4-thiazine alkanephosphonic acids as corrosion inhibitors  

SciTech Connect

..cap alpha..-1,4-thiazine alkanephosphonic acids are described as corrosion inhibitors. An ..cap alpha..-aminoalkanephosphonic acid is reacted with an equal molar amount of a divinyl sulfur compound to produce the thiazine alkanephosphonic acids. It is preferred to carry out the reaction in a solvent or a mixture of solvents in which the ..cap alpha..-amino phosphonic acid is soluble. To the solution of the ..cap alpha..-amino phosphonic acid, the divinyl sulfone is slowly added. The preferred temperature is 20 to 50 C. A catalyst, such as triethylamine, may be used. Upon cooling, the product precipitates and is purified by recrystallization. In some cases, it is necessary to reduce the final volume in order to isolate the desired product. These products may be used as scale inhibitors, chelating agents or microbiocides. 8 claims.

Quinlan, P.M.

1982-01-19

67

Evolution from amino acids - Lunar occurrence of their precursors.  

NASA Technical Reports Server (NTRS)

Review of the present state of experimentally based concepts of organic evolution from amino acids. Earlier studies of the synthesis of amino acid precursors from meteoritic material, lunar dust, and terrestrial lava are briefly summarized, and laboratory experiments in which polymers of amino acids were obtained either by direct heating of dry amino acids or by heating aqueous solutions of mixtures of amino acids are described. In particular, a process is described by which alpha-amino acids were made to react to form linear chains of proteinoids. It is concluded that a proteinoid microsystem was a common ancestor of all life on earth.

Fox, S. W.

1972-01-01

68

Carboxylic Acids as Indicators of Parent Body Conditions  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

69

Polymerization of beta-amino acids in aqueous solution  

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

70

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

E-print Network

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

García-Risueño, Pablo; Alonso, José Luis

2011-01-01

71

Concepts and schemes for the re-engineering of physical protein modules: generating nanodevices via targeted replacements with constrained amino acids  

NASA Astrophysics Data System (ADS)

Physically building complex multi-molecular structures from naturally occurring biological macromolecules has aroused a great deal of interest. Here we focus on nanostructures composed of re-engineered, natural 'foldamer' building blocks. Our aim is to provide some of the underlying concepts and schemes for crafting structures utilizing such conformationally relatively stable molecular components. We describe how, via chemical biology strategies, it is further possible to chemically manipulate the foldamer building blocks toward specific shape-driven structures, which in turn could be used toward potential-designed functions. We outline the criteria in choosing candidate foldamers from the vast biological repertoire, and how to enhance their stability through selected targeted replacements by non-proteinogenic conformationally constrained amino acids. These approaches combine bioinformatics, high performance computations and mathematics with synthetic organic chemistry. The resulting artificially engineered self-organizing molecular scale structures take advantage of nature's nanobiology toolkit and at the same time improve on it, since their new targeted function differs from that optimized by evolution. The major challenge facing nanobiology is to be able to exercise fine control over the performance of these target-specific molecular machines.

Alemán, Carlos; Zanuy, David; Jiménez, Ana I.; Cativiela, Carlos; Haspel, Nurit; Zheng, Jie; Casanovas, Jordi; Wolfson, Haim; Nussinov, Ruth

2006-03-01

72

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

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

73

Role of Na+ in alpha -aminoisobutyric Acid Uptake by Membrane Vesicles from Mouse Fibroblasts Transformed by Simian Virus 40  

Microsoft Academic Search

The uptake of alpha -amino[3H]isobutyric acid (AIB) was studied in membrane vesicles from mouse fibroblasts transformed by simian virus 40 to examine the features of the Na+-stimulated and Na+-dependent AIB transport process. The simultaneous addition of NaCl and AIB to these vesicles produced a transient accumulation, or ``overshoot,'' of amino acid 3-4 times the equilibrium value. Both the initial rate

Hoyoku Nishino; Robert M. Schiller; Jane R. Parnes; Kurt J. Isselbacher

1978-01-01

74

Substrate specificity of amino acid transport in sheep erythrocytes.  

PubMed Central

The specificity of amino acid transport in normal (high-glutathione) sheep erythrocytes was investigated by studying the interaction of various neutral and dibasic amino acids in both competition and exchange experiments. Apparent Ki values were obtained for amino acids as inhibitors of L-alanine influx. Amino acids previously found to be transported by high-glutathione cells at fast rates (L-cysteine, L-alpha-amino-n-butyrate) were the most effective inhibitors. D-Alanine and D-alpha-amino-n-butyrate were without effect. Of the remaining amino acids studied, only L-norvaline, L-valine, L-norleucine, L-serine and L-2,4-diamino-n-butyrate significantly inhibited L-alanine uptake. L-Alanine efflux from pre-loaded cells was markedly stimulated by extracellular L-alanine. Those amino acids that inhibited L-alanine influx also stimulated L-alanine efflux. In addition, D-alanine, D-alpha-amino-n-biutyrate, L-threonine, L-asparagine, L-alpha, beta-diaminoproprionate, L-ornithine, L-lysine and S-2-aminoethyl-L-cysteine also significantly stimulated L-alanine efflux. L-Lysine uptake was inhibited by L-alanine but not by D-alanine, and the inhibitory potency of L-alanine was not influenced by the replacement of Na+ in the incubation medium with choline. L-Lysine efflux from pre-loaded cells was stimulated by L-alanine but not by D-alanine. It is concluded that these cells possess a highly selective stero-specific amino acid-transport system. Although the optimum substrates are small neutral amino acids, this system also has a significant affinity for dibasic amino acids. PMID:849280

Young, J D; Ellory, J C

1977-01-01

75

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

76

Formation of acrolein from various amino-acids and polyamines under degradation at 100UC  

Microsoft Academic Search

The formation of acrolein from several new sources under common and widely used physico-chemical conditions is quantitatively reported. Methionine, homoserine, homocysteine, and cystathionine in decreasing order, generated significant amounts of acrolein in aerobic interactions at neutral pH and 100°C with compounds capable of producing the Strecker degradation of ..cap alpha..-amino acids. Such decarboxylation and oxidative deamination of the above amino

R. Alarcon

1976-01-01

77

Domino syntheses of bioactive tetronic and tetramic acids.  

PubMed

Natural products containing tetronic acid or tetramic acid moieties continue to attract the interest of chemists, biologists, and physicians due to their challenging structures and to the wide range of biological activities they display. This review portrays the structural varieties of tetronic and tetramic acids and the spectrum of possible therapeutically relevant effects in man for exemplary derivatives. Their biosynthetic origin from alpha-amino and alpha-hydroxy acids is briefly discussed as is the relationship between their structures and their modes of interaction with biochemical effectors such as metal cations or enzymes. A short overview of laboratory syntheses of the heterocyclic core structures of tetramic and tetronic acids is provided with an emphasis on those emulating the biosynthesis. A synthesis from the alpha-amino or alpha-hydroxy esters and the cumulated phosphorus ylide Ph(3)PCCO based upon a domino addition-intra-Wittig alkenation sequence is presented with applications to the preparation of the antibiotics reutericyclin and tenuazonic acid, the cytotoxic melophlin B, and the enzyme inhibitor RK-682. Procedural advantages of immobilizing either starting component by attaching it to a resin and its exploitation in the parallel synthesis of libraries of potential drug candidates are described. The basic domino reaction can even be extended by further C-C bond forming steps when starting from suitable alpha-hydroxy or alpha-amino allyl esters. Depending on the chosen reaction conditions, bioactive intermediates of formally three to seven step long cascades can be obtained. Among them, herbicidal 3-alkyltetronic acids and lactone endoperoxides with antiplasmodial activity exceeding that of the natural antimalarial lead artemisinin. Hence, this domino reaction gives access to diversely functionalized derivatives of tetronic and tetramic acids. As it can also be ported to solid phase, it is ideally suited for parallel and combinatorial processing. Future developments might include running such domino sequences in continuous mode in arrays of "labs on microchips". PMID:16944091

Schobert, Rainer

2007-01-01

78

Mathematical models of diffusion-constrained polymerase chain reactions: basis of high-throughput nucleic acid assays and simple self-organizing systems  

E-print Network

nucleic acid assays and simple self-organizing systems John Aach and George M. Church* Department-throughput assays for nucleic acid (NA) sequences have become core technologies in molecular biology. While large

Church, George M.

79

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

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

80

The spark discharge synthesis of amino acids from various hydrocarbons  

NASA Technical Reports Server (NTRS)

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).

Ring, D.; Miller, S. L.

1984-01-01

81

Thermal copoly/amino acids/ as inhibitors of glyoxalase I  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

82

Effect of 2'-O-[2-[2-(N,N-dimethylamino)ethoxy]ethyl] modification on activity of gapmer antisense oligonucleotides containing 2',4'-constrained 2'-O-ethyl nucleic acid.  

PubMed

We evaluated the effect of combining 2'-O-[2-[2-(N,N-dimethylamino)ethoxy]ethyl] (2'-O-DMAEOE), a 2'-cationic modification, with a 2',4'-constrained 2'-O-ethyl nucleic acid (cEt BNA) on the activity of an antisense oligonucleotide (ASO) using PTEN as a model target. Our results suggest that replacing one cEt BNA nucleotide with 2'-O-DMAEOE nucleotide at the 5'-end of a 2-10-2 gapmer ASO maintained the potency relative to parent ASO in liver. The cationic 2'-O-DMAEOE modification did not improve the activity of ASO in extra-hepatic tissues. Results from this study provide guidance to design improved antisense oligonucleotide drugs. PMID:25804718

Pandey, Sanjay K; Nowak, Anna; Perkins, Jake; Ferng, Annie; Prakash, Thazha P

2015-04-15

83

Imino Acids in the Murchison Meteorite: Evidence of Strecker Reactions  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

84

Quantizing constrained systems  

NASA Astrophysics Data System (ADS)

We consider quantum mechanics on constrained surfaces which have non-Euclidean metrics and variable Gaussian curvature. The old controversy about the ambiguities involving terms in the Hamiltonian of order ?2 multiplying the Gaussian curvature is addressed. We set out to clarify the matter by considering constraints to be the limits of large restoring forces as the constraint coordinates deviate from their constrained values. We find additional ambiguous terms of order ?2 involving freedom in the constraining potentials, demonstrating that the classical constrained Hamiltonian or Lagrangian cannot uniquely specify the quantization: the ambiguity of directly quantizing a constrained system is inherently unresolvable. However, there is never any problem with a physical quantum system, which cannot have infinite constraint forces and always fluctuates around the mean constraint values. The issue is addressed from the perspectives of adiabatic approximations in quantum mechanics and Feynman path integrals, and semiclassically in terms of adiabatic actions.

Kaplan, L.; Maitra, N. T.; Heller, E. J.

1997-10-01

85

Isotopic analyses of amino acids from the Murchison meteorite  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

86

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

88

Constraining Galileon inflation  

NASA Astrophysics Data System (ADS)

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.

Regan, Donough; Anderson, Gemma J.; Hull, Matthew; Seery, David

2015-02-01

89

Insulin effect on amino acid uptake by unloaded rat hindlimb muscles  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

90

Indigenous amino acids in primitive CR meteorites  

E-print Network

CR meteorites are among the most primitive meteorites. In this paper, we report the first measurements of amino acids in Antarctic CR meteorites, two of which show the highest amino acid concentrations ever found in a chondrite. EET92042, GRA95229 and GRO95577 were analyzed for their amino acid content using high performance liquid chromatography with UV fluorescence detection (HPLC-FD) and gas chromatographymass spectrometry (GC-MS). Our data show that EET92042 and GRA95229 are the most amino acid-rich chondrites ever analyzed, with total amino acid concentrations ranging from 180 parts-per-million (ppm) to 249 ppm. GRO95577, however, is depleted in amino acids. The most abundant amino acids present in the EET92042 and GRA95229 meteorites are the alpha-amino acids glycine, isovaline, alpha-aminoisobutyric acid (alpha-AIB), and alanine, with delta13C values ranging from +31.6per mil to +50.5per mil. The carbon isotope results together with racemic enantiomeric ratios determined for most amino acids strongly indicate an extraterrestrial origin of these compounds. In addition, the relative abundances of alpha-AIB and beta-alanine in the Antarctic CR meteorites analyzed appear to correspond to the degree of aqueous alteration on their respective parent body.

Z. Martins; C. M. O'D. Alexander; G. E. Orzechowska; M. L. Fogel; P. Ehrenfreund

2008-03-10

91

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)

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.

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

1994-01-01

92

Constraining the dark fluid  

SciTech Connect

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.

Kunz, Martin; Liddle, Andrew R.; Parkinson, David [Astronomy Centre, University of Sussex, Brighton BN1 9QH (United Kingdom); Gao Changjun [National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 (China)

2009-10-15

93

Amino acid analogs for tumor imaging  

DOEpatents

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.

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

1998-09-15

94

Amino acid analogs for tumor imaging  

DOEpatents

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.

Goodman, M.M.; Shoup, T.

1998-10-06

95

Amino acid analogs for tumor imaging  

DOEpatents

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.

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

1998-10-06

96

Amino acid analogs for tumor imaging  

DOEpatents

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.

Goodman, M.M.; Shoup, T.

1998-09-15

97

Net metabolism of volatile fatty acids, D-beta-hydroxybutyrate, nonesterifield fatty acids, and blood gasses by portal-drained viscera and liver of lactating Holstein cows.  

PubMed

Net flux of VFA, D-beta-hydroxybutyrate, nonesterified fatty acids, and blood gasses across portal-drained viscera and liver was measured in four lactating Holstein cows fed a 60:40 corn silage: concentrate diet ad libitum and milked at 12-h intervals. Twelve consecutive hourly measurements of net flux (venous-arterial concentration difference times blood flow) were obtained during wk 4 and 8 postpartum for each cow. Milk yield and DM intake averaged 32.2 and 15.6 kg/d. On a net basis, hepatic tissues produced acetate and removed 63 to 101% of other VFA absorbed by portal-drained viscera. Hepatic and portal-drained visceral tissues produced 60 and 40%, respectively, of D-beta-hydroxybutyrate produced by splanchnic tissues. Hepatic tissues removed 9.3% of nonesterified fatty acids in portal vein and hepatic arterial blood. Oxygen use was greater by liver than for portal-drained viscera (3062 vs. 2394 mmol/h). Net portal-drained visceral flux of VFA, D-beta-hydroxybutyrate, alpha-amino nitrogen, L-lactate, and oxygen together accounted for 84.9% of calculated metabolizable energy intake. Net hepatic removal of propionate, L-lactate, and alpha-amino nitrogen maximally accounted for 55.1, 17.4, and 16.5% of carbon in glucose produced by hepatic tissues. PMID:3141488

Reynolds, C K; Huntington, G B; Tyrrell, H F; Reynolds, P J

1988-09-01

98

Classification Constrained Dimensionality Reduction  

Microsoft Academic Search

Dimensionality reduction is a topic of recent interest. In this paper, we\\u000apresent the classification constrained dimensionality reduction (CCDR)\\u000aalgorithm to account for label information. The algorithm can account for\\u000amultiple classes as well as the semi-supervised setting. We present an\\u000aout-of-sample expressions for both labeled and unlabeled data. For unlabeled\\u000adata, we introduce a method of embedding a new

Jose A. Costa; Alfred O. Hero; Steven B. Damelin; Alfred O. Hero III

2008-01-01

99

A reexamination of amino acids in lunar soil  

NASA Astrophysics Data System (ADS)

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.

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

1993-03-01

100

A reexamination of amino acids in lunar soil  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

101

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)

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.

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

2011-01-01

102

Density constrained TDHF  

E-print Network

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

Oberacker, V E

2015-01-01

103

Constrained space camera assembly  

DOEpatents

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.

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

1999-01-01

104

The dual-specific active site of 7,8-diaminopelargonic acid synthase and the effect of the R391A mutation.  

PubMed

7,8-diaminopelargonic acid (DAPA) synthase (EC 2.6.1.62) is a pyridoxal phosphate (PLP)-dependent transaminase that catalyzes the transfer of the alpha-amino group from S-adenosyl-L-methionine (SAM) to 7-keto-8-aminopelargonic acid (KAPA) to form DAPA in the antepenultimate step in the biosynthesis of biotin. The wild-type enzyme has a steady-state kcat value of 0.013 s(-1), and the K(m) values for SAM and KAPA are 150 and <2 microM, respectively. The k(max) and apparent K(m) values for the half-reaction of the PLP form of the enzyme with SAM are 0.016 s(-1) and 300 microM, respectively, while those for the reaction with DAPA are 0.79 s(-1) and 1 microM. The R391A mutant enzyme exhibits near wild-type kinetic parameters in the reaction with SAM, while the apparent K(m) for DAPA is increased 180-fold. The 2.1 A crystal structure of the R391A mutant enzyme shows that the mutation does not significantly alter the structure. These results indicate that the conserved arginine residue is not required for binding the alpha-amino acid SAM, but it is important for recognition of DAPA. PMID:12379100

Eliot, Andrew C; Sandmark, Jenny; Schneider, Gunter; Kirsch, Jack F

2002-10-22

105

Constraining neutrinoless double beta decay  

E-print Network

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

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

2011-11-23

106

Constrained space camera assembly  

DOEpatents

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.

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

1999-05-11

107

Constraining anisotropic baryon oscillations  

SciTech Connect

We present an analysis of anisotropic baryon acoustic oscillations and elucidate how a mis-estimation of the cosmology, which leads to incorrect values of the angular diameter distance, d{sub A}, and Hubble parameter, H, manifest themselves in changes to the monopole and quadrupole power spectrum of biased tracers of the density field. Previous work has focused on the monopole power spectrum, and shown that the isotropic dilation combination d{sub A}{sup 2}H{sup -1} is robustly constrained by an overall shift in the scale of the baryon feature. We extend this by demonstrating that the quadrupole power spectrum is sensitive to an anisotropic warping mode d{sub A}H, allowing one to break the degeneracy between d{sub A} and H. We describe a method for measuring this warping, explicitly marginalizing over the form of redshift-space distortions. We verify this method on N-body simulations and estimate that d{sub A}H can be measured with a fractional accuracy of {approx}(3/{radical}(V))% where the survey volume is estimated in h{sup -3} Gpc{sup 3}.

Padmanabhan, Nikhil [Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); White, Martin [Departments of Physics and Astronomy, 601 Campbell Hall, University of California Berkeley, CA 94720 (United States)

2008-06-15

108

Designing amino acid residues with single-conformations.  

PubMed

Drug design can benefit from the use of non-coded amino acids, such as alpha-amino isobutyric acids (Aib) or sarcosine (N-methyl-glycine). Non-coded amino acids can confer resistance to enzymatic degradation and increase the conformational stability of the peptides. We have simulated the conformational effects of combining N-methylation, bulky groups on the Calpha atom and/or thioamides using the class II CFF91 force field and our thioamide force field parameters. Although single amino acid substitutions (e.g. Aib) can restrict the available conformations, they do not necessarily lead to unique conformers, however, we predict that some of the amino acids described in this report will fold to a single phi, psi conformation (e.g. N-methylated and thioamide penicillamine). Several other amino acid/thiopeptide combinations were designed, which are predicted to prefer only two conformations. Novel amino acids of this type should prove useful for designing peptides with defined conformations. PMID:16799150

Tran, Tran T; Treutlein, Herbert; Burgess, Antony W

2006-09-01

109

Constrained Vapor Bubble  

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

110

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

PubMed

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

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

2010-02-01

111

Constraining fundamental physics from cosmology  

E-print Network

I use mathematical models and numerical simulations to constrain cosmological inflation, the seeds of structure, and the mass of the neutrino. I revisit arguments that simple models of inflation with a small red tilt in the scalar power spectrum...

Bird, Simeon

2011-10-11

112

Line constrained between two curves  

NASA Astrophysics Data System (ADS)

In this paper, the method of finding the line constrained between two quadratic Bezier curves and also finding the line constrained between a quadratic Bezier curve and a circle is presented. The application of the line constrained can be used in the construction of railway tracks between any obstacle or rolling a ball to the other side of a wall in a way that it just touches the wall. The method used is by using equal root properties of a quadratic equation in order to find one point where the line touches the curve. The work examples involved different curve orientations and different circle positions. Mathematica software is used to compute the solutions for the line constrained and present the solutions graphically. By using the method proposed, the number of intersection points obtained is used to determine the number of lines constrained between two curves and between a curve and a circle. The conclusion on whether all lines are acceptable to be considered as the line constrained are depending on the application of the line.

Ahmad, Afida; Ali, Jamaludin Md.

2013-04-01

113

Multiband Phase Constrained Parallel MRI  

PubMed Central

Purpose Parallel MRI methods are typically associated with a degradation of the signal-to-noise ratio (SNR). High scan time reduction factors are therefore restricted to applications with high intrinsic SNR. One possibility to increase the intrinsic SNR is to simultaneously excite several slices by means of multiband radio-frequency (RF) pulses and subsequently separate the slices by parallel MRI reconstruction algorithms. However, the separation of closely spaced slices may suffer from severe noise amplification when there is insufficient coil sensitivity variation along the slice direction. The purpose of this work is to apply a phase-constrained reconstruction for multiband experiments in order to minimize the noise amplification. Methods Pre-defined phase differences between neighboring slices are induced and slice separation is performed by a phase-constrained parallel MRI reconstruction. Phase differences between neighboring slices are tailored to achieve optimal slice separation with minimized noise amplification. The potential of the method is demonstrated through multiband in-vivo experiments. Results Noise amplification in multiband phase-constrained reconstructions is significantly reduced in comparison to standard multiband reconstruction when the phase difference between neighboring slices (distance = 12 mm) is 90°. Conclusions Multiband phase constrained parallel MRI has the potential for accelerated multi-slice imaging with an improved SNR performance. PMID:23440994

Blaimer, Martin; Choli, Morwan; Jakob, Peter M.; Griswold, Mark A.; Breuer, Felix A.

2013-01-01

114

Resource-constrained project scheduling  

Microsoft Academic Search

Resource-constrained project scheduling involves the scheduling of project activities subject to precedence and resource constraints in order to meet the objective(s) in the best possible way. The area covers a wide variety of problem types. The objective of this paper is to provide a survey of what we believe are important recent in the area . Our main focus will

Willy Herroelen; Erik Demeulemeester

1996-01-01

115

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)

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 ?- and ?-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 ?- and ?-CD solutions.

Ghosh, Shalini; Jana, Sankar; Guchhait, Nikhil

2011-12-01

116

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

PubMed

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

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

1998-03-01

117

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

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 ?- and ?-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 ?- and ?-CD solutions. PMID:21996591

Ghosh, Shalini; Jana, Sankar; Guchhait, Nikhil

2011-12-15

118

Constraining spacetime torsion with LAGEOS  

E-print Network

We compute the corrections to the orbital Lense-Thirring effect (or frame-dragging) in the presence of spacetime torsion. We derive the equations of motion of a test body in the gravitational field of a rotating axisymmetric massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi. We calculate the secular variations of the longitudes of the node and of the pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be used to constrain torsion parameters. We report the experimental constraints obtained using both the nodes and perigee measurements of the orbital Lense-Thirring effect. This makes LAGEOS and Gravity Probe B (GPB) complementary frame-dragging and torsion experiments, since they constrain three different combinations of torsion parameters.

Riccardo March; Giovanni Bellettini; Roberto Tauraso; Simone Dell'Agnello

2011-07-12

119

Constrained Multiobjective Biogeography Optimization Algorithm  

PubMed Central

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

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

2014-01-01

120

Entropy-constrained vector quantization  

Microsoft Academic Search

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

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

1989-01-01

121

Constrained minimization for monotonic reconstruction  

SciTech Connect

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

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

1996-08-20

122

Cervical screening strategies in resourced and resource-constrained countries.  

PubMed

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

Cronjé, H S

2011-10-01

123

Constrained Stochastic Extended Redundancy Analysis.  

PubMed

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

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

2013-12-11

124

Constrained ballistics and geometrical optics  

E-print Network

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

Epstein, Marcelo

2014-01-01

125

Evidence for release of glutamic acid, aspartic acid and substance P but not gamma-aminobutyric acid from primary afferent fibres in rat spinal cord.  

PubMed

In vitro superfusion release experiments and autoradiography were carried out on spinal cords of neonatally capsaicin-treated rats. Electrical and chemical stimulations significantly increased the release of aspartate, glutamate and gamma-aminobutyric acid (GABA) from hemisected dorsal horn slices of vehicle-treated animals. In capsaicin-treated rats, the evoked release of aspartate, glutamate and substance P but not GABA, were significantly lower. Capsaicin (1 microM) stimulated the release of aspartate and glutamate, as reported for substance P, in control slices but this effect was not as apparent in tissues from capsaicin-treated rats. Evoked GABA release was not affected in either case. alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), kainate, dizocilpine and GABAB binding sites were highly localised in the substantia gelatinosa. Capsaicin treatment did not affect the affinity of the binding sites in all four cases but significantly reduced the density of kainate, dizocilpine and GABAB binding sites. The data suggest that capsaicin-sensitive primary afferent fibres release aspartate, glutamate and Substance P following high-intensity stimulations and that this release might be modulated by presynaptic glutamate and GABAB receptors present on these terminals. PMID:8790988

Teoh, H; Malcangio, M; Fowler, L J; Bowery, N G

1996-04-29

126

The remarkable stability of chimeric, sialic acid-derived alpha/delta-peptides in human blood plasma.  

PubMed

Peptides are labile toward proteolytic enzymes, and structural modifications are often required to prolong their metabolic half-life and increase resistance. One modification is the incorporation of non-alpha-amino acids into the peptide to deter recognition by hydrolytic enzymes. We previously reported the synthesis of chimeric alpha/delta-peptides from glutamic acids (Glu) and the sialic acid derivative Neu2en. Conformational analyses revealed these constructs adopt secondary structures in water and may serve as conformational surrogates of polysialic acid. Polysialic acid is a tumor-associated polysaccharide and is correlated with cancer metastasis. Soluble polysialic acid is rapidly cleared from the blood limiting its potential for vaccine development. One motivation in developing structural surrogates of polysialic acid was to create constructs with increased bioavailability. Here, we report plasma stability profiles of Glu/Neu2en alpha/delta-peptides. DOTA was conjugated at the peptide N-termini by solid phase peptide synthesis, radiolabeled with (111)In, incubated in human blood plasma at 37 degrees C, and their degradation patterns monitored by cellulose acetate electrophoresis and radioactivity counting. Results indicate that these peptides exhibit a long half-life that is two- to three-orders of magnitude higher than natural alpha-peptides. These findings provide a viable platform for the synthesis of plasma stable, sialic acid-derived peptides that may find pharmaceutical application. PMID:20486931

Saludes, Jonel P; Natarajan, Arutselvan; DeNardo, Sally J; Gervay-Hague, Jacquelyn

2010-05-01

127

Extraterrestrial amino acids at the Cretaceous-Tertiary boundary  

SciTech Connect

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

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

1985-01-01

128

Conformationally constrained analogues of 2-arachidonoylglycerol.  

PubMed

Novel monocyclic analogues of 2-arachidonoylglycerol (2-AG) were designed in order to explore the pharmacophoric conformations of this endocannabinoid ligand at the key cannabinergic proteins. All 2-arachidonoyl esters of 1,2,3-cyclohexanetriol [meso-7 (AM5504), (+/-)-8 (AM5503), and meso-9 (AM5505)] were synthesized by regioselective acylation of 2,3-dihydroxycyclohexanone followed by selective reductions. The optically active isomers (+)-8 (AM4434) and (-)-8 (AM4435) were synthesized from (2S,3S)- and (2R,3R)-2,3-dihydroxycyclohexanone, respectively, via a chemoenzymatic route. These head group constrained and conformationally restricted analogues of 2-AG as well as the 1-keto precursors were evaluated as substrates for the endocannabinoid deactivating hydrolytic enzymes monoacylglycerol lipase (MGL) and fatty acid amide hydrolase (FAAH), and also were tested for their affinities for CB1 and CB2 cannabinoid receptors. The observed biochemical differences between these ligands can help define the conformational requirements for 2-AG activity at each of the above endocannabinoid protein targets. PMID:17826996

Vadivel, Subramanian K; Vardarajan, Sundararaman; Duclos, Richard I; Wood, JodiAnne T; Guo, Jianxin; Makriyannis, Alexandros

2007-11-01

129

Formal language constrained path problems  

SciTech Connect

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

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

1997-07-08

130

Helically constrained phage display library  

Microsoft Academic Search

The library described here is a collection of phages with six degenerate codons in gene VIII, specifying amino acids 12, 13, 15-17 and 19 of the major coat protein. The randomized positions are surface exposed in the wild-type protein and thus might be expected to tolerate a great diversity of side chains without compromising phage viability. In agreement with this

V. A. Petrenko; G. P. Smith; M. M. Mazooji; T. Quinn

2002-01-01

131

Interactive teaching of constrained generalized predictive control  

Microsoft Academic Search

In this paper, an interactive educational tool for teaching the basic concepts of constrained generalized predictive control is described. Students gain insight into the selection of design parameters and discover how controlled system performance and closed-loop stability are influenced by this selection through a user-friendly presentation of constrained and unconstrained cases.

J. L. Guzman; M. Berenguel; S. Dormido

2005-01-01

132

Interoperability of constrained finite state automata  

Microsoft Academic Search

Finite State Automata have been extended in a number of ways with varied additional constraints with an objective of modeling varied real life problems. The current paper commonly refers to such extensions as constrained automata. It aims at defining a generic mathematical model for the constrained automata targeted towards interoperability and possible integration amongst them. The paper proposes and demonstrates

Dipankar Majumdar; Swapan Bhattacharya

2012-01-01

133

Using ecological restoration to constrain biological invasion  

Microsoft Academic Search

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

JONATHAN D. BAKKER; SCOTT D. WILSON

134

Presentations of Constrained Systems with Unconstrained Positions  

E-print Network

1 Presentations of Constrained Systems with Unconstrained Positions Marie-Pierre B´eal, Maxime subsystem of a constrained system S such that any position modulo T in U is unconstrained, where Marie of bit positions unconstrained. Such a construction can be used to build modulation

Paris-Sud XI, Université de

135

T Cell Determinants Incorporating [beta]-Amino Acid Residues Are Protease Resistant and Remain Immunogenic In Vivo  

SciTech Connect

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.

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. (Monash); (Melbourne); (ANU)

2010-07-20

136

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

PubMed

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

Zhao, M; Bada, J L

1989-06-01

137

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

SciTech Connect

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.

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

1991-01-01

138

Gyrification from constrained cortical expansion  

E-print Network

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.

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

2015-03-12

139

Gyrification from constrained cortical expansion  

E-print Network

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

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

2015-01-01

140

Wavelet library for constrained devices  

NASA Astrophysics Data System (ADS)

The wavelet transform is a powerful tool for image and video processing, useful in a range of applications. This paper is concerned with the efficiency of a certain fast-wavelet-transform (FWT) implementation and several wavelet filters, more suitable for constrained devices. Such constraints are typically found on mobile (cell) phones or personal digital assistants (PDA). These constraints can be a combination of; limited memory, slow floating point operations (compared to integer operations, most often as a result of no hardware support) and limited local storage. Yet these devices are burdened with demanding tasks such as processing a live video or audio signal through on-board capturing sensors. In this paper we present a new wavelet software library, HeatWave, that can be used efficiently for image/video processing/analysis tasks on mobile phones and PDA's. We will demonstrate that HeatWave is suitable for realtime applications with fine control and range to suit transform demands. We shall present experimental results to substantiate these claims. Finally this library is intended to be of real use and applied, hence we considered several well known and common embedded operating system platform differences; such as a lack of common routines or functions, stack limitations, etc. This makes HeatWave suitable for a range of applications and research projects.

Ehlers, Johan Hendrik; Jassim, Sabah A.

2007-04-01

141

BICEP2 constrains Composite Inflation  

E-print Network

In light of BICEP2, we reexamine single field inflationary models in which the inflaton 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 $n_{s}$ 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 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.

Phongpichit Channuie

2014-07-14

142

Constrained orbital intercept-evasion  

NASA Astrophysics Data System (ADS)

An effective characterization of intercept-evasion confrontations in various space environments and a derivation of corresponding solutions considering a variety of real-world constraints are daunting theoretical and practical challenges. Current and future space-based platforms have to simultaneously operate as components of satellite formations and/or systems and at the same time, have a capability to evade potential collisions with other maneuver constrained space objects. In this article, we formulate and numerically approximate solutions of a Low Earth Orbit (LEO) intercept-maneuver problem in terms of game-theoretic capture-evasion guaranteed strategies. The space intercept-evasion approach is based on Liapunov methodology that has been successfully implemented in a number of air and ground based multi-player multi-goal game/control applications. The corresponding numerical algorithms are derived using computationally efficient and orbital propagator independent methods that are previously developed for Space Situational Awareness (SSA). This game theoretical but at the same time robust and practical approach is demonstrated on a realistic LEO scenario using existing Two Line Element (TLE) sets and Simplified General Perturbation-4 (SGP-4) propagator.

Zatezalo, Aleksandar; Stipanovic, Dusan M.; Mehra, Raman K.; Pham, Khanh

2014-06-01

143

Towards spatially constrained gust models  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

144

BICEP2 constrains composite inflation  

NASA Astrophysics Data System (ADS)

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.

Channuie, Phongpichit

2014-07-01

145

Penicillin acylase has a single-amino-acid catalytic centre.  

PubMed

Penicillin acylase (penicillin amidohydrolase, EC 3.5.1.11) is widely distributed among microorganisms, including bacteria, yeast and filamentous fungi. It is used on an industrial scale for the production of 6-aminopenicillanic acid, the starting material for the synthesis of semi-synthetic penicillins. Its in vivo role remains unclear, however, and the observation that expression of the Escherichia coli enzyme in vivo is regulated by both temperature and phenylacetic acid has prompted speculation that the enzyme could be involved in the assimilation of aromatic compounds as carbon sources in the organism's free-living mode. The mature E. coli enzyme is a periplasmic 80K heterodimer of A and B chains (209 and 566 amino acids, respectively) synthesized as a single cytoplasmic precursor containing a 26-amino-acid signal sequence to direct export to the cytoplasm and a 54-amino-acid spacer between the A and B chains which may influence the final folding of the chains. The N-terminal serine of the B chain reacts with phenylmethylsulphonyl fluoride, which is consistent with a catalytic role for the serine hydroxyl group. Modifying this serine to a cysteine inactivates the enzyme, whereas threonine, arginine or glycine substitution prevents in vivo processing of the enzyme, indicating that this must be an important recognition site for cleavage. Here we report the crystal structure of penicillin acylase at 1.9 A resolution. Our analysis shows that the environment of the catalytically active N-terminal serine of the B chain contains no adjacent histidine equivalent to that found in the serine proteases. The nearest base to the hydroxyl of this serine is its own alpha-amino group, which may act by a new mechanism to endow the enzyme with its catalytic properties. PMID:7816145

Duggleby, H J; Tolley, S P; Hill, C P; Dodson, E J; Dodson, G; Moody, P C

1995-01-19

146

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

NASA Technical Reports Server (NTRS)

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.

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

2013-01-01

147

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

SciTech Connect

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

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

1985-04-25

148

21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 false Wrist joint polymer constrained prosthesis. 888.3780...Devices § 888.3780 Wrist joint polymer constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a...

2014-04-01

149

21 CFR 888.3720 - Toe joint polymer constrained prosthesis.  

Code of Federal Regulations, 2013 CFR

...false Toe joint polymer constrained prosthesis. 888.3720 Section 888.3720...3720 Toe joint polymer constrained prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of...

2013-04-01

150

21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.  

Code of Federal Regulations, 2011 CFR

... Wrist joint polymer constrained prosthesis. 888.3780 Section 888.3780... Wrist joint polymer constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a device made of...

2011-04-01

151

21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Wrist joint polymer constrained prosthesis. 888.3780...Devices § 888.3780 Wrist joint polymer constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a...

2010-04-01

152

Power-constrained communications using LDLC lattices  

E-print Network

An explicit code construction for using low-density lattice codes (LDLC) on the constrained power AWGN channel is given. LDLC lattices can be decoded in high dimension, so that the code relies on the Euclidean distance ...

Dauwels, Justin H. G.

153

Constrained density functional for noncollinear magnetism  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

154

CONSTRAINED BUNDLE METHODS FOR UPPER INEXACT ...  

E-print Network

Regarding the last item, the role/utility of the penalty in second target (in ?k ...... inexact data, in Proceedings of the XXIV Hungarian Operations Researc Conference .... and physical assets with chance-constrained programming in the electrical ...

2012-12-18

155

Convex Approximations of Chance Constrained Programs  

E-print Network

simulation-based scheme for bounding the optimal value in the chance constrained problem and ...... By shifting .... concerned; the only purpose of the exercise to follow is to link our approach with some previously known constructions. 26 ...

2005-12-20

156

Constrained crosstalk resistant adaptive noise canceller  

NASA Astrophysics Data System (ADS)

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.

Parsa, V.; Parker, P.

1994-08-01

157

The Sun's Interior Metallicity Constrained by Neutrinos  

E-print Network

Observed solar neutrino fluxes are employed to constrain the interior composition of the Sun. Including the effects of neutrino flavor mixing, the results from Homestake, Sudbury, and Gallium experiments constrain the Mg, Si, and Fe abundances in the solar interior to be within a factor 0.89 to 1.34 of the surface values with 68% confidence. If the O and/or Ne abundances are increased in the interior to resolve helioseismic discrepancies with recent standard solar models, then the nominal interior Mg, Si, and Fe abundances are constrained to a range of 0.83 to 1.24 relative to the surface. Additional research is needed to determine whether the Sun's interior is metal poor relative to its surface.

Guillermo Gonzalez

2006-05-25

158

Constraining Ceres' interior from its Rotational Motion  

E-print Network

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

Rambaux, Nicolas; Dehant, Véronique; Kuchynka, Petr

2011-01-01

159

Geochemical Processes Constraining Iron Uptake in Strategy II Fe Acquisition  

PubMed Central

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

2014-01-01

160

Pattern Search Algorithms for Bound Constrained Minimization  

NASA Technical Reports Server (NTRS)

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.

Lewis, Robert Michael; Torczon, Virginia

1996-01-01

161

Pattern Search Methods for Linearly Constrained Minimization  

NASA Technical Reports Server (NTRS)

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.

Lewis, Robert Michael; Torczon, Virginia

1998-01-01

162

Spacecraft inertia estimation via constrained least squares  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

163

Optically pure N-hydroxy-O-triisopropylsilyl-alpha-L-amino acid methyl esters from AlCl3-assisted ring opening of chiral oxaziridines by nitrogen containing nucleophiles.  

PubMed

[reaction: see text] This article reports a straightforward and unprecedented process of AlCl3-assisted oxaziridine ring opening by nitrogen containing nucleophiles, in a totally anhydrous milieu. Under these conditions, nucleophiles exclusively attack the carbon atom of the three-membered heterocycles, obtained from methyl esters of natural alpha-amino acids, generating N-hydroxy-alpha-L-amino acid methyl esters. No nitrones, amides, or other side products, either from unwanted rearrangements or due to the attack of the nucleophile on the N atom of the oxaziridine systems, are formed. The hydroxylamine compounds are recovered in excellent yields, after their site-specific conversion into the corresponding O-triisopropylsilyl derivatives, by exposure to triisopropylsilyl triflate in the presence of 1H-imidazole. Derivatization, performed immediately after the recovery of the N-hydroxylated precursors, allows the chiral integrity of the asymmetric alpha-carbon atoms in the amino acid methyl esters to be retained. It also protects the obtained compounds from frame degradation by disproportionation. N-Hydroxy-O-triisopropylsilyl-alpha-L-amino acid methyl esters are important intermediates in the study of natural alpha-L-amino acid metabolic pathways and are ideal candidates as starting materials in the synthesis of biologically, pharmacologically, and nutritionally important N-hydroxy peptides. PMID:16323863

Di Gioia, Maria Luisa; Leggio, Antonella; Le Pera, Adolfo; Liguori, Angelo; Siciliano, Carlo

2005-12-01

164

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

SciTech Connect

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.

Tremblay, L.; Blanchard, J

2009-01-01

165

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

PubMed

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

Atta, F M

1994-11-01

166

Rhythmic Grouping Biases Constrain Infant Statistical Learning  

ERIC Educational Resources Information Center

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…

Hay, Jessica F.; Saffran, Jenny R.

2012-01-01

167

Stochastic ranking for constrained evolutionary optimization  

Microsoft Academic Search

Penalty functions are often used in constrained op- timization. However, it is very difficult to strike the right balance between objective and penalty functions. This paper introduces a novel approach to balance objective and penalty functions stochas- tically, i.e., stochastic ranking, and presents a new view on penalty function methods in terms of the dominance of penalty and objec- tive

Thomas Philip Runarsson; Xin Yao

2000-01-01

168

Commodity tax competition with Constrained Taxes  

E-print Network

Commodity tax competition with Constrained Taxes Pascal Belan St´ephane Gauthier 6th August 2008 that there can be only two rates of tax on the different commodities, a positive rate and the zero-rate. The main by countries, i.e., the level of the positive rate and the set of taxed commodities. Under the origin principle

Paris-Sud XI, Université de

169

Communication Constrained Task Allocation For Robotic Networks  

E-print Network

Communication Constrained Task Allocation For Robotic Networks Stephen L. Smith Distibuted Robotics Lab CSAIL MIT 2010 TDS Talk March 19, 2010 Joint work with Francesco Bullo Stephen L. Smith Task: robots divide tasks among themselves Stephen L. Smith Task Allocation 2 #12;Task allocation Given

Lynch, Nancy

170

The Constrained Minimum Spanning Tree (Extended Abstract)  

E-print Network

The Constrained Minimum Spanning Tree Problem (Extended Abstract) R. Ravi* M. X. Goemanst Abstract algorithm, minimum spanning trees, La- grangean relaxation, adjacency relations. 1 Introduction Given. In this case, we can specify a budget L on the total length of the spanning tree and require a tree of minimum

Goemans, Michel X.

171

CONSTRAINED DISCOUNTED SEMI-MARKOV DECISION PROCESSES  

E-print Network

Chapter 13 CONSTRAINED DISCOUNTED SEMI- MARKOV DECISION PROCESSES #3; Eugene A. Feinberg Department of Applied Mathematics and Statistics SUNY at Stony Brook Stony Brook, NY 11794-3600 Eugene.Feinberg in studying Continuous Time Jump Markov Decision Processes; Feinberg [7, 8]. 2. De#12;nitions The probability

Feinberg, Eugene A.

172

TrellisConstrained Codes Brendan J. Frey  

E-print Network

Trellis­Constrained Codes Brendan J. Frey Beckman Institute for Advanced Science and Technology University of Illinois at Urbana­Champaign bfrey@turbo.beckman.uiuc.edu David J. C. MacKay Department of Physics, Cavendish Laboratories Cambridge University mackay@mrao.cam.ac.uk B. J. Frey and D. J. C. Mac

MacKay, David J.C.

173

Trellis-Constrained Codes Brendan J. Frey  

E-print Network

Trellis-Constrained Codes Brendan J. Frey Beckman Institute for Advanced Science and Technology University of Illinois at Urbana-Champaign bfrey@turbo.beckman.uiuc.edu David J. C. MacKay Department of Physics, Cavendish Laboratories Cambridge University mackay@mrao.cam.ac.uk B. J. Frey and D. J. C. Mac

Frey, Brendan J.

174

Power Constrained Design of Multiprocessor Interconnection Networks  

Microsoft Academic Search

The paper considers the power constrained design of orthogonal multiprocessor interconnection networks. The authors present a detailed model of message latency as a function of topology, technology architecture, and power. This model is then used to analyze a number of interesting scenarios, providing a sound engineering basis for interconnection network design in these cases. For example, they have observed that

Chirag S. Patel; Sek M. Chai; Sudhakar Yalamanchili; David E. Schimmel

1997-01-01

175

Constrained Synthesis of Textural Motion for Animation  

Microsoft Academic Search

Obtaining high quality, realistic motions of articulated characters is both timeconsumingand expensive, necessitating the development of effective and easy-tousetools for motion editing and reuse. We propose a new simple technique forgenerating constrained variations of different lengths from an existing captured orotherwise animated motion. Our technique is applicable to textural motions, suchas walking or dancing, where the motion sequence can be

Shmuel Moradoff; Dani Lischinski

2003-01-01

176

Stochastic Multiscale Segmentation Constrained by Image Content  

E-print Network

on large 3D data sets. From the pdf, it is possible to obtain the segmentation. The first approach usesStochastic Multiscale Segmentation Constrained by Image Content Luc Gillibert and Dominique Jeulin Centre de Morphologie Mathematique Ecole des Mines de Paris 35, rue Saint Honor´e 77305 Fontainebleau

Paris-Sud XI, Université de

177

Constraining Mercury Oxidation Using Wet Deposition  

E-print Network

Constraining Mercury Oxidation Using Wet Deposition Noelle E. Selin and Christopher D. Holmes mercury oxidation [Selin & Jacob, Atmos. Env. 2008] 30 60 90 120 150 30 60 90 120 150 30 60 90 120 150 30 Influences on Mercury Wet Deposition · Hg wet dep = f(precipitation, [Hg(II)+Hg(P)]) Correlation (r2) between

Selin, Noelle Eckley

178

Constraining Ceres' interior from its rotational motion  

Microsoft Academic Search

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

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

2011-01-01

179

Constrained tri-sphere kinematic positioning system  

DOEpatents

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.

Viola, Robert J (Jackson, WY)

2010-12-14

180

Constrained Optimization using GA Proposed Optimization Flow  

E-print Network

Constrained Optimization using GA Proposed Optimization Flow for Nano-CMOS VCO Design and Polynomial Modeling of VCO Fast Analog Design Optimization using Regression based Modeling and Genetic manual design step. At this stage a netlist is sufficient for the design flow. 50nm current starved VCO

Mohanty, Saraju P.

181

Constrained CP-nets Steve Prestwich1  

E-print Network

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

Rossi, Francesca

182

Constrained CP-nets Steve Prestwich  

E-print Network

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

Walsh, Toby

183

Likelihood constrained smoothing interpolation using segmentation information  

Microsoft Academic Search

Interpolation techniques are required in many areas of medical image analysis. Due to the discrete nature of all medical images, interpolation is a necessary step in resampling, which is required for image registration and all geometric image manipulations. In this paper, a novel smoothing interpolation technique is proposed. This method incorporates segmentation information using statistical approach. The interpolation is constrained

Jonathan Lok-chuen Lo; Michael Brady

2006-01-01

184

Constraining fossil calibrations for molecular clocks  

E-print Network

Constraining fossil calibrations for molecular clocks Sir, In a recent paper, Mu¨ller and Reisz(1) proposed how fossil calibrations should be selected for application in molecular clock studies. The topic molecules. Nonetheless, we believe that these authors have erred both in their proposal of fossil

Kumar, Sudhir

185

Compilation for critically constrained knowledge bases  

SciTech Connect

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.

Schrag, R. [Univ. of Texas, Austin, TX (United States)

1996-12-31

186

Constraining the braneworld with gravitational wave observations.  

PubMed

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

McWilliams, Sean T

2010-04-01

187

Constraining the Braneworld with Gravitational Wave Observations  

NASA Technical Reports Server (NTRS)

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

McWilliams, Sean T.

2011-01-01

188

Constraining the Braneworld with Gravitational Wave Observations  

SciTech Connect

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 {approx}1 {mu}m level for optimal cases, while the observation of a single galactic black hole binary with LISA results in an optimal constraint of l{<=}5 {mu}m.

McWilliams, Sean T. [Gravitational Astrophysics Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt Maryland 20771 (United States)

2010-04-09

189

Constrained minimal Dirac gaugino supersymmetric standard model  

NASA Astrophysics Data System (ADS)

We examine the possibilities for constructing models with Dirac gaugino masses and unification of gauge couplings. We identify one promising model and discuss to what extent it can have a "natural" supersymmetric (SUSY) spectrum. We then determine the low-energy constraints upon it, and propose a constrained set of boundary conditions at the unification scale. We describe the implementation of these boundary conditions in the spectrum-generator generator SARAH and we perform a first exploration of the parameter space, specifically searching for points where the spectrum is relatively light. It is shown that the pattern of the masses of SUSY states is very different compared to any expectations from the constrained minimal supersymmetric Standard Model.

Benakli, K.; Goodsell, M.; Porod, W.; Staub, F.

2014-08-01

190

21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.  

Code of Federal Regulations, 2013 CFR

...polymer constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a device made of polyester-reinforced silicone elastomer intended to be implanted to replace a wrist joint. This generic type of device...

2013-04-01

191

Mass-Additive Vibration Testing Of Constrained Structures  

NASA Technical Reports Server (NTRS)

Report describes study of mass-additive method of modal survey testing of flexible structures that, in normal use, constrained by other structures. Structure normally constrained by another structure is suspended freely and extra masses attached to boundary.

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

1995-01-01

192

Video Personalization and Caching for Resource Constrained Environments  

E-print Network

Video Personalization and Caching for Resource Constrained Environments Siddhartha Chattopadhyay Dept. of Computer Science, The University of Georgia, Athens, Georgia 30602-7404, USA Abstract: Video constrained, various video personalization strategies are used to provide personalized video content

Bhandarkar, Suchendra "Suchi" M.

193

Risk allocation strategies for distributed chance-constrained task allocation  

E-print Network

This paper addresses the issue of allocating risk amongst agents in distributed chance-constrained planning algorithms. Building on previous research that extended chance-constrained planning to stochastic multi-agent ...

Ponda, Sameera S.

194

Variance constrained control of maneuvering helicopters with sensor failure  

E-print Network

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

Sultan, Cornel

195

Towards Constraining Affleck-Dine Baryogenesis  

E-print Network

Affleck-Dine baryogenesis is preconditioned on a certain structure of non-renormalizable operators in the Kahler potential. In this paper, we geometrically characterize the resulting constraint on the field space Kahler geometry and survey the Lagrangian for correlated predictions. The Affleck-Dine field backreacts on the inflaton, and by mapping the backreacted potential to an inflaton potential with a step, we find that current CMB data severely constrain some versions of the scenario.

David Marsh

2012-04-11

196

Constrained Exploration for Studies in Multirobot Coordination  

Microsoft Academic Search

We are interested in the challenges of long-term, long-distance tight multirobot coordination. In this paper, we discuss the Constrained Exploration domain that pushes the boundaries of tightly-coordinated multirobot teams. We formalize this problem and consider the role of intentional coordination approaches in addressing its numerous challenges. Finally, we present three intentional coordination approaches to solving different aspects of the domain.

Nidhi Kalra; Dave Ferguson; Anthony Stentz

2006-01-01

197

The constrained minimum spanning tree problem  

Microsoft Academic Search

Abstract Given an undirected graph,with two different nonnegative,costs associated with every edge e (say, we for the weight and le for the length of edge e) and a budget L, consider the problem of finding a spanning,tree of total edge length at most,L and minimum,total weight under this restriction. This constrained minimum,spanning tree problem,is weakly,NP-hard. We present a polynomial-time,ap- proximation,scheme,for

R. Ravi; M. X. Goemans

1996-01-01

198

On the path integral of constrained systems  

SciTech Connect

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

Muslih, Sami I. [Physics Department, Al-Azhar University, Gaza, Palestine (Country Unknown)

2004-10-04

199

Constrained Simulation of the Bullet Cluster  

NASA Astrophysics Data System (ADS)

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.

Lage, Craig; Farrar, Glennys

2014-06-01

200

? Conservative approximation for probabilistically constrained convex programs  

Microsoft Academic Search

In this paper, we address an approximate solution of a probabilistically constrained convex program (PCCP), where a convex\\u000a objective function is minimized over solutions satisfying, with a given probability, convex constraints that are parameterized\\u000a by random variables. In order to approach to a solution, we set forth a conservative approximation problem by introducing\\u000a a parameter ? which indicates an approximate

Yuichi Takano; Jun-ya Gotoh

2010-01-01

201

An English language interface for constrained domains  

NASA Technical Reports Server (NTRS)

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.

Page, Brenda J.

1989-01-01

202

Haplotype inference constrained by plausible haplotype data.  

PubMed

The haplotype inference problem (HIP) asks to find a set of haplotypes which resolve a given set of genotypes. This problem is important in practical fields such as the investigation of diseases or other types of genetic mutations. In order to find the haplotypes which are as close as possible to the real set of haplotypes that comprise the genotypes, two models have been suggested which are by now well-studied: The perfect phylogeny model and the pure parsimony model. All known algorithms up till now for haplotype inference may find haplotypes that are not necessarily plausible, i.e., very rare haplotypes or haplotypes that were never observed in the population. In order to overcome this disadvantage, we study in this paper, a new constrained version of HIP under the above-mentioned models. In this new version, a pool of plausible haplotypes H is given together with the set of genotypes G, and the goal is to find a subset H ? H that resolves G. For constrained perfect phlogeny haplotyping (CPPH), we provide initial insights and polynomial-time algorithms for some restricted cases of the problem. For constrained parsimony haplotyping (CPH), we show that the problem is fixed parameter tractable when parameterized by the size of the solution set of haplotypes. PMID:20733241

Fellows, Michael R; Hartman, Tzvika; Hermelin, Danny; Landau, Gad M; Rosamond, Frances; Rozenberg, Liat

2011-01-01

203

Effects of exogenous excitatory amino acid neurotransmitters on blood-brain barrier disruption in focal cerebral ischemia.  

PubMed

This study was performed to determine whether exogenous N-methyl-D: -aspartate (NMDA) or alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) would aggravate blood-brain barrier (BBB) disruption in focal cerebral ischemia in rats. Forty-five minutes after middle cerebral artery (MCA) occlusion, one of the following patches was applied to the exposed ischemic cerebral cortex of each rat: normal saline (control), 10(-5) M AMPA, 10(-4) M AMPA, 10(-5) M NMDA, or 10(-4) M NMDA. At 1 h after MCA occlusion, BBB permeability was determined by measuring the transfer coefficient (Ki) of (14)C-alpha-aminoisobutyric acid ((14)C-AIB). In all experimental groups, the Ki of the ischemic cortex (IC) was higher than that of the corresponding contralateral cortex (CC). The Ki of the IC of the animals treated with 10(-4) M AMPA or 10(-4) M NMDA was higher (+41%: P < 0.05 and +33%: P < 0.05, respectively) than that of the control animals. Our data demonstrated that exogenous NMDA or AMPA could further aggravate the BBB disruption in focal cerebral ischemia. Any insult increasing the release of excitatory neurotransmitters could further aggravate BBB disruption and brain edema during the ischemic period. PMID:19127429

Chi, Oak Z; Hunter, Christine; Liu, Xia; Weiss, Harvey R

2009-07-01

204

Autoradiographical analysis of excitatory amino acid binding sites in rat hippocampus during the development of hippocampal kindling.  

PubMed

Binding sites for excitatory amino acids have been determined by autoradiographical procedures in the rat hippocampus and striatum during hippocampal kindling. The binding sites measured were the N-methyl-D-aspartate (NMDA)-sensitive sites for L-[3H]glutamate and [3H]MK-801 sites (transmitter recognition site and ion channel of the NMDA receptor, respectively), [3H]alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) sites (quisqualate receptor), [3H]kainate sites (kainate receptor) and NMDA-insensitive sites for L-[3H]glutamate. In general, little change was apparent in the hippocampus or striatum for any of these binding sites when assessed 48 h after attaining stages 1/2, 3 or 5 of kindling. These results suggest that hippocampal kindling does not bring about a change in the excitatory amino acid receptor binding sites examined, and that the appearance of an NMDA receptor-mediated component to synaptic responses in the hippocampus produced by kindling, cannot be explained on this basis. PMID:1964104

Vezzani, A; Serafini, R; Samanin, R; Foster, A C

1990-08-27

205

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics  

PubMed Central

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

Koopmanschap, Gijs; Ruijter, Eelco

2014-01-01

206

Ocean Acidification-Induced Food Quality Deterioration Constrains Trophic Transfer  

PubMed Central

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

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

2012-01-01

207

Induction of cobalt accumulation by excitatory amino acids within neurons of the hippocampal slice.  

PubMed

Computer-assisted image analysis was used to establish the dose response of excitatory amino acid (EAA) analogs on the induction of cobalt accumulation within pyramidal and granule cell neurons in 400 microns slices of gerbil hippocampus. Slices were incubated 20 min at 22 degrees C in a solution containing 5 mM CoCl2 and 0-1,000 microM EAA analog. The cobalt was visualized by development in (NH4)2S, and the slices were digitized for quantitative densitometry. Kainic acid (KA) had the largest effect and induced cobalt accumulation in the dentate gyrus and CA1, 180% and 150% above control, respectively, with an ED50 = 30 microM. alpha-Amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) induced accumulations of cobalt in CA1 and hilar neurons 130% above control with an ED50 = 30 microM, but had little effect on dentate granule cells. The accumulations induced by KA and AMPA were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), but not by DL-2-amino-5-phosphonovaleric acid (AP5) or voltage-dependent calcium channel blockers. N-Methyl-D-aspartate (NMDA) induced accumulation in the dentate and CA1 150% above control in a pattern similar to KA, but with an ED50 of 100 microM. The accumulation was blocked by both AP5 and CNQX. These data indicate that cobalt-permeable, receptor-activated divalent cation channels are differentially distributed within the gerbil hippocampus, and have differential sensitivities to non-NMDA agonists. The localization of KA-activated, cobalt-permeable channels appears to be coincident with the flop form of the AMPA-selective calcium-permeable glutamate receptor-activated channel.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1382799

Williams, L R; Pregenzer, J F; Oostveen, J A

1992-05-29

208

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

209

Force induced melting of the constrained DNA  

E-print Network

We develop a simple model to study the effects of an applied force on the melting of a double stranded DNA (dsDNA). Using this model, we could study the stretching, unzipping, rupture and slippage like transition in a dsDNA. We show that in absence of an applied force, the melting temperature and the melting profile of dsDNA strongly depend on the constrained imposed on the ends of dsDNA. The nature of the phase boundary which separates the zipped and the open state for the shearing like transition is remarkably different than the DNA unzipping

Amit Raj Singh; D. Giri; S. Kumar

2009-12-12

210

Local structure of equality constrained NLP problems  

SciTech Connect

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.

Mari, J.

1994-12-31

211

Constraining Ceres' interior from its rotational motion  

NASA Astrophysics Data System (ADS)

Context. Ceres is the most massive body of the asteroid belt and contains about 25 wt.% (weight percent) of water. Understanding its thermal evolution and assessing its current state are major goals of the Dawn mission. Constraints on its internal structure can be inferred from various types of observations. In particular, detailed knowledge of the rotational motion can help constrain the mass distribution inside the body, which in turn can lead to information about its geophysical history. Aims: We investigate the signature of internal processes on Ceres rotational motion and discuss future measurements that can possibly be performed by the spacecraft Dawn and will help to constrain Ceres' internal structure. Methods: We compute the polar motion, precession-nutation, and length-of-day variations. We estimate the amplitudes of the rigid and non-rigid responses for these various motions for models of Ceres' interior constrained by shape data and surface properties. Results: As a general result, the amplitudes of oscillations in the rotation appear to be small, and their determination from spaceborne techniques will be challenging. For example, the amplitudes of the semi-annual and annual nutations are around ~364 and ~140 milli-arcseconds, and they show little variation within the parametric space of interior models envisioned for Ceres. Conclusions: Owing to the small amplitudes of the nutation and the very long-period of the precession motion, the measurements of the rotational variations will be challenging to obtain. We also estimate the timescale for Ceres' orientation to relax to a generalized Cassini state, and find that the tidal dissipation within that object has probably been too small to drive any significant damping of its obliquity since formation. However, combining the shape and gravity observations of Dawn offers the prospect to identify departures of non-hydrostaticity on both global and regional scales, which will be instrumental in constraining Ceres' past and current thermal state. We also discuss the existence of a possible Chandler mode in the rotational motion of Ceres, whose potential excitation by endogenic and/or exogenic processes may help us to detect the presence of liquid reservoirs within the asteroid.

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

2011-11-01

212

Amino acids  

MedlinePLUS

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

213

Constraining dark matter through 21-cm observations  

NASA Astrophysics Data System (ADS)

Beyond reionization epoch cosmic hydrogen is neutral and can be directly observed through its 21-cm line signal. If dark matter (DM) decays or annihilates, the corresponding energy input affects the hydrogen kinetic temperature and ionized fraction, and contributes to the Ly? 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 ??Tb = 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.

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

2007-05-01

214

Regular Language Constrained Sequence Alignment Revisited  

NASA Astrophysics Data System (ADS)

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

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

215

Constraining torsion with Gravity Probe B  

SciTech Connect

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.

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

2007-11-15

216

Constraining subleading soft gluon and graviton theorems  

NASA Astrophysics Data System (ADS)

We show that the form of the recently proposed subleading soft graviton and gluon theorems in any dimension are severely constrained by elementary arguments based on Poincaré and gauge invariance as well as a self-consistency condition arising from the distributional nature of scattering amplitudes. Combined with the assumption of a local form as it would arise from a Ward identity the orbital part of the subleading operators is completely fixed by the leading universal Weinberg soft pole behavior. The polarization part of the differential subleading soft operators in turn is determined up to a single numerical factor for each hard leg at every order in the soft momentum expansion. In four dimensions, factorization of the Lorentz group allows us to fix the subleading operators completely.

Broedel, Johannes; de Leeuw, Marius; Plefka, Jan; Rosso, Matteo

2014-09-01

217

Constraining Dark Sectors with Monojets and Dijets  

E-print Network

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 simpli...

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

2015-01-01

218

Constraining Dark Sectors with Monojets and Dijets  

E-print Network

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.

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

2015-03-19

219

Remote gaming on resource-constrained devices  

NASA Astrophysics Data System (ADS)

Games have become important applications on mobile devices. A mobile gaming approach known as remote gaming is being developed to support games on low cost mobile devices. In the remote gaming approach, the responsibility of rendering a game and advancing the game play is put on remote servers instead of the resource constrained mobile devices. The games rendered on the servers are encoded as video and streamed to mobile devices. Mobile devices gather user input and stream the commands back to the servers to advance game play. With this solution, mobile devices with video playback and network connectivity can become game consoles. In this paper we present the design and development of such a system and evaluate the performance and design considerations to maximize the end user gaming experience.

Reza, Waazim; Kalva, Hari; Kaufman, Richard

2010-08-01

220

Constraining Lorentz violations with Gamma Ray Bursts  

E-print Network

Gamma ray bursts are excellent candidates to constrain physical models which break Lorentz symmetry. We consider deformed dispersion relations which break the boost invariance and lead to an energy-dependent speed of light. In these models, simultaneously emitted photons from cosmological sources reach Earth with a spectral time delay that depends on the symmetry breaking scale. We estimate the possible bounds which can be obtained by comparing the spectral time delays with the time resolution of available telescopes. We discuss the best strategy to reach the strongest bounds. We compute the probability of detecting bursts that improve the current bounds. The results are encouraging. Depending on the model, it is possible to build a detector that within several years will improve the present limits of 0.015 m_pl.

Maria Rodriguez Martinez; Tsvi Piran

2006-05-17

221

Constraining MOND with Solar System Dynamics  

NASA Astrophysics Data System (ADS)

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

Iorio, Lorenzo

2008-02-01

222

Constrained sampling method for analytic continuation  

E-print Network

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

Sandvik, Anders W

2015-01-01

223

Constraining the cratering chronology of Vesta  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

224

Traveltime tomography and nonlinear constrained optimization  

SciTech Connect

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.

Berryman, J.G.

1988-10-01

225

Perceived visual speed constrained by image segmentation  

NASA Technical Reports Server (NTRS)

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.

Verghese, P.; Stone, L. S.

1996-01-01

226

Constraining double-parton correlations and interferences  

NASA Astrophysics Data System (ADS)

Double-parton scattering (DPS) has become very relevant as a background to interesting analyses performed by the experiments at the LHC. It encodes knowledge of correlations between the proton constituents not accessible in single-parton scattering. Within perturbative QCD DPS is described in terms of partonic subprocesses and double-parton distributions (DPDs). There exists a large number of different DPDs describing the different possible states of two partons inside a proton. They include correlations between the two partons and interferences between the two hard subprocesses. Taking the probability interpretation of the DPDs as a starting point, we derive limits on the interference DPDs and thereby constrain the size of correlations between two partons inside an unpolarized proton.

Kasemets, Tomas; Mulders, Piet J.

2015-01-01

227

Constrained Aerothermodynamic Design of Hypersonic Vehicles  

NASA Technical Reports Server (NTRS)

An investigation was conducted into possible methods of incorporating a hypersonic design capability with aerothermodynamic constraints into the CDISC aerodynamic design tool. The work was divided into two distinct phases: develop relations between surface curvature and hypersonic pressure coefficient which are compatible with CDISC's direct-iterative design method; and explore and implement possible methods of constraining the heat transfer rate over all or portions of the design surface. The main problem in implementing this method has been the weak relationship between surface shape and pressure coefficient at the stagnation point and the need to design around the surface blunt leading edge where there is a slope singularity. The final results show that some success has been achieved, but further improvements are needed.

Gally, Tom; Campbell, Dick

2002-01-01

228

Disappearance and Creation of Constrained Amorphous Phase  

NASA Astrophysics Data System (ADS)

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

Cebe, Peggy; Lu, Sharon X.

1997-03-01

229

Constrained sampling method for analytic continuation  

E-print Network

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

Anders W. Sandvik

2015-02-21

230

Constraining MOND with Solar System dynamics  

E-print Network

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

Lorenzo Iorio

2008-02-15

231

Constrained Simulation of the Bullet Cluster  

NASA Astrophysics Data System (ADS)

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

Lage, Craig

232

A Path Algorithm for Constrained Estimation  

PubMed Central

Many least-square problems involve affine equality and inequality constraints. Although there are a variety of methods for solving such problems, most statisticians find constrained estimation challenging. The current article proposes a new path-following algorithm for quadratic programming that replaces hard constraints by what are called exact penalties. Similar penalties arise in l1 regularization in model selection. In the regularization setting, penalties encapsulate prior knowledge, and penalized parameter estimates represent a trade-off between the observed data and the prior knowledge. Classical penalty methods of optimization, such as the quadratic penalty method, solve a sequence of unconstrained problems that put greater and greater stress on meeting the constraints. In the limit as the penalty constant tends to ?, one recovers the constrained solution. In the exact penalty method, squared penalties!are replaced by absolute value penalties, and the solution is recovered for a finite value of the penalty constant. The exact path-following method starts at the unconstrained solution and follows the solution path as the penalty constant increases. In the process, the solution path hits, slides along, and exits from the various constraints. Path following in Lasso penalized regression, in contrast, starts with a large value of the penalty constant and works its way downward. In both settings, inspection of the entire solution path is revealing. Just as with the Lasso and generalized Lasso, it is possible to plot the effective degrees of freedom along the solution path. For a strictly convex quadratic program, the exact penalty algorithm can be framed entirely in terms of the sweep operator of regression analysis. A few well-chosen examples illustrate the mechanics and potential of path following. This article has supplementary materials available online. PMID:24039382

Zhou, Hua; Lange, Kenneth

2013-01-01

233

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

SciTech Connect

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

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

1985-05-01

234

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

PubMed

3-Dehydroshikimate dehydratase catalyzes the third reaction in the inducible quinic acid catabolic pathway of Neurospora crassa and is encoded in the qa-4 gene of the qa gene cluster. As part of continuing genetic and biochemical studies concerning the organization and regulation of this gene cluster, 3-dehydroshikimate dehydratase has been purified and characterized biochemically. The enzyme was purified 1650-fold using the following techniques: 1) (NH4)2SO4 fractionation; 2) ion exchange chromatography on DEAE-cellulose; 3) gel filtration on Sephadex G-100; 4) ion exchange chromatography on Cellex QAE (quaternary aminoethyl); and 5) hydroxylapatite chromatography. 3-Dehydroshikimate dehydratase is a monomer with a molecular weight of about 37,000 and a sedimentation coefficient of 3.27 S. It has a Km value of 5.9 X 10(-4) and an average isoelectric point of 4.92. The purified enzyme is extremely sensitive to thermal denaturation but can be significantly stabilized by Mg2+ ions. The purified enzyme also exhibits maximal catalytic activity only when assayed in the presence of certain divalent cations, e.g. magnesium. The NH2-terminal residue of 3-dehydroshikimate dehydratase is proline, and its alpha-amino group is unblocked. PMID:149131

Strøman, P; Reinert, W R; Giles, N H

1978-07-10

235

Isotropic submanifolds and the inverse problem for mechanical constrained systems  

NASA Astrophysics Data System (ADS)

We give a new characterization of the inverse problem of the calculus of variations that is easily extended to constrained systems, both in the autonomous and non-autonomous cases. The transition from unconstrained to constrained systems is given by passing from Lagrangian submanifolds to isotropic ones. If the constrained system is variational we use symplectic techniques to extend these isotropic submanifolds to Lagrangian ones and describe the solutions of the constrained system as solutions of a variational problem without constraints. Mechanical examples such as the rolling disk are provided to illustrate the main results.

Barbero-Liñán, María; Farré Puiggalí, Marta; Martín de Diego, David

2015-01-01

236

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

PubMed Central

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

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

2001-01-01

237

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

PubMed

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

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

2001-06-01

238

Folic Acid  

MedlinePLUS

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

239

Folic Acid  

MedlinePLUS

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

240

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

PubMed Central

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

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

2014-01-01

241

Interoperable Services on Constrained Devices in the Internet of Things  

E-print Network

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

Paris-Sud XI, Université de

242

MODELING, CONTROL DESIGN AND MECHATRONIC IMPLEMENTATION OF CONSTRAINED ROBOTS  

E-print Network

MODELING, CONTROL DESIGN AND MECHATRONIC IMPLEMENTATION OF CONSTRAINED ROBOTS FOR SURFACE FINISHING;MODELING, CONTROL DESIGN AND MECHATRONIC IMPLEMENTATION OF CONSTRAINED ROBOTS FOR SURFACE FINISHING Engineering of Oklahoma State University who, by simply doing their jobs well, contributed to the successful

Pagilla, Prabhakar R.

243

Spatially-constrained sample kernel for sequence classifi cation  

Microsoft Academic Search

1 $ a2 d 2 $, ..., dt 1 ! at (a1 separated by d1 characters from a2 separated by d2 characters from a3 etc.) occurring in the sequence X. Each sample consists of t spatially-constrained probes ai of size k, with the probes spatially constrained to lie no more than d positions away from their neighbors. In the proposed

Pavel P. Kuksa; Pai-Hsi Huang; Vladimir Pavlovi

244

Constrained sequential-block search in simulation experimentation  

Microsoft Academic Search

This paper describes the application of sequential-block search techniques to simulation experimentation with constrained systems. Two basically different approaches are examined. One approach combines designed experiments, multiple regression, and mathematical optimization to predict a constrained optimum solution, which is then checked by further experimentation in the region of the predicted solution. A second approach employs a sequential optimum seeking-technique, such

William E. Biles

1973-01-01

245

Constrained Clipping for Crest Factor Reduction in OFDM  

Microsoft Academic Search

In this paper, we propose a constrained clipping method for reducing the peak to average power ratio (PAR) or crest factor of an orthogonal frequency division multiplexing (OFDM) signal. This is a transmitter-side processing technique that does not impose any modification at the receiver. Specifically, constrained clipping achieves PAR reduction while simultaneously satisfying spectral mask and error vector magnitude (EVM)

Robert J. Baxley; Chunming Zhao; G. Tong Zhou

2006-01-01

246

CONSTRAINING DARK ENERGY WITH GAMMA-RAY BURSTS  

SciTech Connect

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.

Samushia, Lado; Ratra, Bharat, E-mail: lado@phys.ksu.ed, E-mail: ratra@phys.ksu.ed [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, KS 66506 (United States)

2010-05-10

247

Appendix D Offaxis potential for hydrogen abstraction from constrained  

E-print Network

158 Appendix D Off­axis potential for hydrogen abstraction from constrained isobutane D.1­axis geometries near the transition state. The diamond (111) surface is modelled by constrained isobutane diamond surface, the isobutane atoms are fixed at their transition­state positions while the abstracting

Goddard III, William A.

248

Constraining oceanic dust deposition using surface ocean dissolved Al  

E-print Network

Constraining oceanic dust deposition using surface ocean dissolved Al Qin Han,1 J. Keith Moore,1; accepted 7 December 2007; published 12 April 2008. [1] We use measurements of ocean surface dissolved Al (DEAD) model to constrain dust deposition to the oceans. Our Al database contains all available

Zender, Charles

249

Automated Analysis of Concurrent Systems With the Constrained Expression Toolset  

Microsoft Academic Search

The constrained expression approach to analysis of concurrent softwaresystems has several attractive features, including the facts that itcan be used with a variety of design and programming languages and thatit does not require a complete enumeration of the set of reachable statesof the concurrent system. This paper reports on the construction of atoolset automating the main constrained expression analysis techniquesand

George S. Avrunin; Ugo A. Buy; James C. Corbett; Laura K. Dillon; Jack C. Wileden

1991-01-01

250

The Pendulum: From Constrained Fall to the Concept of Potential  

ERIC Educational Resources Information Center

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…

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

2006-01-01

251

Neurotoxicity of domoic Acid in cerebellar granule neurons in a genetic model of glutathione deficiency.  

PubMed

This study investigated the role of cellular antioxidant defense mechanisms in modulating the neurotoxicity of domoic acid (DomA), by using cerebellar granule neurons (CGNs) from mice lacking the modifier subunit of glutamate-cysteine ligase (Gclm). Glutamate-cysteine ligase (Glc) catalyzes the first and rate-limiting step in glutathione (GSH) biosynthesis. CGNs from Gclm (-/-) mice have very low levels of GSH and are 10-fold more sensitive to DomA-induced toxicity than CGNs from Gclm (+/+) mice. GSH ethyl ester decreased, whereas the Gcl inhibitor buthionine sulfoximine increased DomA toxicity. Antagonists of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate receptors and of N-methyl-D-aspartate (NMDA) receptors blocked DomA toxicity, and NMDA receptors were activated by DomA-induced l-glutamate release. The differential susceptibility of CGNs to DomA toxicity was not due to a differential expression of ionotropic glutamate receptors, as evidenced by similar calcium responses and L-glutamate release in the two genotypes. A calcium chelator and several antioxidants antagonized DomA-induced toxicity. DomA caused a rapid decrease in cellular GSH, which preceded toxicity, and the decrease was primarily due to DomA-induced GSH efflux. DomA also caused an increase in oxidative stress as indicated by increases in reactive oxygen species and lipid peroxidation, which was subsequent to GSH efflux. Astrocytes from both genotypes were resistant to DomA toxicity and presented a diminished calcium response to DomA and a lack of DomA-induced L-glutamate release. Because polymorphisms in the GCLM gene in humans are associated with low GSH levels, such individuals, as well as others with genetic conditions or environmental exposures that lead to GSH deficiency, may be more susceptible to DomA-induced neurotoxicity. PMID:17000861

Giordano, G; White, C C; McConnachie, L A; Fernandez, C; Kavanagh, T J; Costa, L G

2006-12-01

252

The constrained reinitialization equation for level set methods  

NASA Astrophysics Data System (ADS)

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

Hartmann, Daniel; Meinke, Matthias; Schröder, Wolfgang

2010-03-01

253

The strongly constrained interacting binary BY Crucis.  

NASA Astrophysics Data System (ADS)

We discuss spectroscopic and photometric observations (UV to IR) of BY Crucis, a new bright member of the interacting binaries of the W Serpentis class. The orbital period is 106.4days, and the mass function amounts to 5.92Msun_. The primary is an early-F supergiant which fills its Roche lobe; the massive secondary is hidden inside a thick accretion disk, which is probably the dominant light source in the ultraviolet. The observed variations in the photometric lightcurves are caused mainly by ellipsoidal variations. It is unlikely that an eclipse occurs. A particularly interesting circumstance is that BY Cru is a probable member of a visual multiple system which contains another evolved star. This circumstance enables us to estimate with some accuracy the age of the interacting binary and the initial mass of the primary. The history of this binary is then much more constrained than for the other W Serpentis stars. Also taking into account the fact that the binary has avoided Case C Roche lobe overflow, we determine upper and lower bounds for the initial and present masses of both components, and conclude that mass transfer has only been moderately non-conservative.

Daems, K.; Waelkens, C.; Mayor, M.

1997-02-01

254

Scheduling Aircraft Landings under Constrained Position Shifting  

NASA Technical Reports Server (NTRS)

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.

Balakrishnan, Hamsa; Chandran, Bala

2006-01-01

255

Constrained Graph Optimization: Interdiction and Preservation Problems  

SciTech Connect

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.

Schild, Aaron V [Los Alamos National Laboratory

2012-07-30

256

Should we still believe in constrained supersymmetry?  

E-print Network

We calculate Bayes factors to quantify how the feasibility of the constrained minimal supersymmetric standard model (CMSSM) has changed in the light of a series of observations. This is done in the Bayesian spirit where probability reflects a degree of belief in a proposition and Bayes' theorem tells us how to update it after acquiring new information. Our experimental baseline is the approximate knowledge that was available before LEP, and our comparison model is the Standard Model with a simple dark matter candidate. To quantify the amount by which experiments have altered our relative belief in the CMSSM since the baseline data we compute the Bayes factors that arise from learning in sequence the LEP Higgs constraints, the XENON100 dark matter constraints, the 2011 LHC supersymmetry search results, and the early 2012 LHC Higgs search results. We find that LEP and the LHC strongly shatter our trust in the CMSSM (with $M_0$ and $M_{1/2}$ below 2 TeV), reducing its posterior odds by a factor of approximately two orders of magnitude. This reduction is largely due to substantial Occam factors induced by the LEP and LHC Higgs searches.

Csaba Balázs; Andy Buckley; Daniel Carter; Benjamin Farmer; Martin White

2013-11-28

257

Constrained inversion for basal and englacial properties  

NASA Astrophysics Data System (ADS)

When inverting for basal slipperiness and (C retrieval) the rate factor in Glen's flow law (A retrieval) using surface data, the inversion needs to be constrained for the retrieved values to be positive. Some other constraints may also have to be imposed on the retrieved fields. There are various ways of enforcing such constraints. Using an adjoint model of the shallow-ice stream equations, several different algorithms are tested and compared with respect to rate of convergence and cost per iteration. These methods included the projected gradient method, the limited-memory projected BFGS method, the interior-point method, and an incomplete Newton iteration using a barrier function. All these methods perform favourably for small problem sizes (O(1000) unknowns). It is shown that for large-scale optimisation problems the convergence rate for A retrieval is generally lower than for C retrieval. Both projection methods suffer from slow convergence for large problem sizes (O(100 000) unknowns.) Interior-point methods, especially when coupled with an incomplete inner iteration of the Newton system appear to give the best large-scale performance.

Gudmundsson, G. H.

2012-04-01

258

Pairwise constrained concept factorization for data representation.  

PubMed

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

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

2014-04-01

259

FPGA design for constrained energy minimization  

NASA Astrophysics Data System (ADS)

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.

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

2004-02-01

260

Constraining stellar magnetic activity with asteroseismology  

NASA Astrophysics Data System (ADS)

Stellar magnetic activity results from the interaction between rotation, convection, and magnetic field. Unfortunately the detailed mechanism of this process is not completely understood. While there is a long history of spectroscopic surveys to tackle this problem, they only provide observables of the stellar surfaces. The fact that different manifestations of magnetic variability can be observed (either a regular cycle, a non-regular variability or no temporal variation) is linked to the internal properties of the stars and raises the following question: Which conditions and properties of the stars govern these different behaviors? To better understand the detailed mechanism driving solar and stellar magnetic activity and better constrain the 3D dynamo models, it is important to know the characteristics of their magnetic field, the property of the convection, and the rotation profile (internal and at the surface) of the stars. This is where asteroseismology has a key role. Indeed, with missions such as CoRoT and Kepler, we have access to high-precision photometric observations where asteroseismology puts strong constraints on the internal structure and dynamics of the stars. Here, I discuss what seismology brings to the big picture of stellar magnetic activity by presenting the recent results obtained with space missions such as CoRoT and Kepler with a focus on solar-like stars.

Mathur, S.

2014-12-01

261

Constraining the Oblateness of Kepler Planets  

NASA Astrophysics Data System (ADS)

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 0.22-0.11+0.11 for the 18 MJ 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.

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

2014-11-01

262

Constrained Sypersymmetric Flipped SU (5) GUT Phenomenology  

SciTech Connect

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.

Ellis, John; /CERN /King's Coll. London; Mustafayev, Azar; /Minnesota U., Theor. Phys. Inst.; Olive, Keith A.; /Minnesota U., Theor. Phys. Inst. /Minnesota U. /Stanford U., Phys. Dept. /SLAC

2011-08-12

263

Constrained bandwidth waveforms with minimal dilation sensitivity  

NASA Astrophysics Data System (ADS)

The sensitivity of a waveform to velocity-induced time dilation is an important consideration when performing replica correlation for coherent echo location or communication. Bandpass waveforms which have envelopes which are insensitive to this effect may be efficiently processed by what are known as narrowband receivers in which envelope dilation is fixed and Doppler tested using simple spectrum analysis (fast Fourier transform (FFT)) processing. The peak level of the waveform ambiguity function (AF) is a measure of signal coherence and may be used to gauge the distortion of the waveform induced by the dilation effect. The degree of AF attenuation is shown to be proportional to the dilation parameter or velocity, waveform traveling wave (TW) product, and a sensitivity parameter which depends upon the envelope function utilized. Classes of symmetric, constrained bandwidth, phase modulated envelope functions are derived which are minimally dilation sensitive (Doppler tolerant). When the resulting waveforms are used with a simple correlation receiver structure and the echo data is derived from slowly fluctuating point scattering in white Gaussian noise, the receiver becomes an uncoupled joint estimator of delay and dilation (Doppler). In the case of the bandpass waveforms, it is shown that only odd symmetry of the phase modulation yields an uncoupled estimator. The envelopes may use various slowly varying even amplitude window functions affording a measure of freedom in the design of specific ambiguity properties.

Ricker, Dennis W.

1993-07-01

264

Distributed Constrained Optimization with Semicoordinate Transformations  

NASA Technical Reports Server (NTRS)

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.

Macready, William; Wolpert, David

2006-01-01

265

4-Amino-2,6-dichlorophenol nephrotoxicity in the Fischer 344 rat: protection by ascorbic acid, AT-125, and aminooxyacetic acid.  

PubMed

A halogenated derivative of 4-aminophenol, 4-amino-2, 6-dichlorophenol (ADCP), is a potent nephrotoxicant and a weak hepatotoxicant in Fischer 344 rats. Although the mechanism of ADCP nephrotoxicity is unknown, ADCP could undergo oxidation to a reactive intermediate, such as a 4-amino-2,6-dichlorophenoxy radical or 2,6-dichloro-1,4-benzoquinoneimine, which can generate additional free radicals and/or covalently bind to cellular proteins. The toxic process might also be mediated by glutathione (GSH) conjugates of ADCP, as suggested for the mechanism of 4-aminophenol nephrotoxicity. In this study, the effects of modulators of oxidation and GSH conjugation-related metabolism or transport on ADCP-induced nephrotoxicity were examined. In one set of experiments, male Fischer 344 rats (four/group) were intraperitoneally (ip) administered ADCP (0.38 mmol/kg) only or coadministered an antioxidant, ascorbic acid (1.14 mmol/kg, ip) with ADCP. Administration of ascorbic acid markedly reduced both functional nephrotoxicity and morphological changes induced by ADCP. Administration of a gamma-glutamyltransferase (GGT) inhibitor, l-(alphaS, 5S)-alpha-amino-3-chloro-4,5-dihydroxy-5-isoxazoleacetic acid (10 mg/kg, ip), or a cysteine conjugate beta-lyase inhibitor, aminooxyacetic acid (0.5 mmol/kg, ip), 1 hr before ADCP (0.38 mmol/kg) challenge partially protected rats against ADCP nephrotoxicity. In contrast, administration of an organic anion transport inhibitor, probenecid (140 mg/kg, ip), 30 min before ADCP had little effect on ADCP nephrotoxicity. The GSH depletor, buthionine sulfoximine (890 mg/kg, ip), was given 2 hr prior to ADCP and only minimal protection was noted. In addition, the nonprotein sulfhydryl (NPSH) contents in renal cortex and liver were determined at 2 hr following the administration of ADCP only or ascorbic acid/ADCP. Ascorbic acid afforded complete prevention of the depletion of NPSH in the kidney and liver caused by ADCP administration and also prevented the elevation of renal glutathione disulfide content induced by ADCP. The results indicate that oxidation of ADCP appears to be essential to ADCP nephrotoxicity and that GSH or GSH-derived conjugates of ADCP may be partly responsible for the nephrotoxic effects of ADCP via a GGT-mediated mechanism. PMID:9356314

Hong, S K; Anestis, D K; Ball, J G; Valentovic, M A; Brown, P I; Rankin, G O

1997-11-01

266

Aspartic acid  

MedlinePLUS

... don't get this amino acid from the food we eat. Aspartic acid is also called asparaginic acid. Aspartic acid helps every cell in the body work. It plays a role in: Hormone production and release Normal nervous system function Plant sources ...

267

Acid Rain.  

ERIC Educational Resources Information Center

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

Openshaw, Peter

1987-01-01

268

Conformationally Constrained Histidines in the Design of Peptidomimetics: Strategies for the ?-Space Control  

PubMed Central

A successful design of peptidomimetics must come to terms with ?-space control. The incorporation of ?-space constrained amino acids into bioactive peptides renders the ?1 and ?2 torsional angles of pharmacophore amino acids critical for activity and selectivity as with other relevant structural features of the template. This review describes histidine analogues characterized by replacement of native ? and/or ?-hydrogen atoms with alkyl substituents as well as analogues with ?, ?-didehydro unsaturation or C?-C? cyclopropane insertion (ACC derivatives). Attention is also dedicated to the relevant field of ?-aminoacid chemistry by describing the synthesis of ?2- and ?3-models (?-hHis). Structural modifications leading to cyclic imino derivatives such as spinacine, aza-histidine and analogues with shortening or elongation of the native side chain (nor-histidine and homo-histidine, respectively) are also described. Examples of the use of the described analogues to replace native histidine in bioactive peptides are also given. PMID:21686155

Stefanucci, Azzurra; Pinnen, Francesco; Feliciani, Federica; Cacciatore, Ivana; Lucente, Gino; Mollica, Adriano

2011-01-01

269

Constraining the Evolution of Poor Clusters  

NASA Astrophysics Data System (ADS)

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.

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

2012-01-01

270

Experimental generation of volcanic pseudotachylytes: Constraining rheology  

NASA Astrophysics Data System (ADS)

Volcanic systems are highly dynamic environments that comprise rocks and magmas, which, in the process of strain localisation (e.g., in catastrophic flank collapse or dome-building events), are candidate materials for the occurrence of frictional melting and the formation of pseudotachylytes. We evaluate the frictional behaviour of a plagioclase-, two-pyroxene- and glass-bearing andesite and introduce an approach to constrain the rheology of frictional melts. Frictional slip at a rate of 1.3 m/s under an axial stress of 1.5 MPa induces heating at a rate approximating 130 °C per metre of slip and frictional melting of the andesite occurs at >1000 °C, which corresponds to a peak in shear stress. With continuing displacement, the shear stress decreases by ˜25% from the peak strength and stabilises while the temperature equilibrates to 1230-1290 °C. The shear stress for the system is congruent with a non-Arrhenian temperature-dependent frictional melt rheology exhibiting a non-Newtonian viscosity evolving from approximately 104.2 to 103.4 Pa s. Post-experiment analysis shows a gradation from 1) the host rock, to 2) an extraordinary zone of unmelted, yet viscously deformed material, to 3) a thin, outer region of chemically heterogeneous protomelts, and to 4) an inner region of chemically homogeneous frictionally generated/modified melt in the core of the slip zone. We discuss the role and identification of frictional melting in volcanic systems and the implication of viscous remobilisation of magmatic plugs during frictional slip of glass-bearing volcanic materials.

Lavallée, Yan; Mitchell, Thomas M.; Heap, Michael J.; Vasseur, Jérémie; Hess, Kai-Uwe; Hirose, Takehiro; Dingwell, Donald B.

2012-05-01

271

The cost-constrained traveling salesman problem  

SciTech Connect

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.

Sokkappa, P.R.

1990-10-01

272

Constraining Cosmic Evolution of Type Ia Supernovae  

SciTech Connect

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.

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

273

Optimal control strategies for constrained relative orbits  

NASA Astrophysics Data System (ADS)

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

Irvin, David Jonathan, Jr.

274

Acidity in bile acid systems  

Microsoft Academic Search

The acidity parameter in bile acid systems was re-examined in an attempt to unify the many contrasting results reported in the literature. Discrepancies originate not only through differences in experimental approaches but mainly through the peculiar behaviour of bile acids and their salts, which can be present in aqueous solution as monomers, or simple and\\/or mixed aggregates. The acidity (and

Adamo Fini; Giorgio Feroci; Aldo Roda

2002-01-01

275

Onomatopoeia characters extraction from comic images using constrained Delaunay triangulation  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

276

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

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Hip joint metal constrained cemented or uncemented prosthesis...Prosthetic Devices § 888.3300 Hip joint metal constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal constrained cemented or...

2014-04-01

277

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

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Hip joint metal constrained cemented or uncemented prosthesis...Prosthetic Devices § 888.3300 Hip joint metal constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal constrained cemented or...

2012-04-01

278

21 CFR 888.3790 - Wrist joint metal constrained cemented prosthesis.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Wrist joint metal constrained cemented prosthesis. ...Devices § 888.3790 Wrist joint metal constrained cemented prosthesis. (a) Identification. A wrist joint metal constrained cemented...

2012-04-01

279

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

Code of Federal Regulations, 2012 CFR

... 2012-04-01 false Finger joint metal/polymer constrained cemented prosthesis...Prosthetic Devices § 888.3220 Finger joint metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer constrained...

2012-04-01

280

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

Code of Federal Regulations, 2014 CFR

... 2014-04-01 false Finger joint metal/polymer constrained cemented prosthesis...Prosthetic Devices § 888.3220 Finger joint metal/polymer constrained cemented prosthesis. (a) Identification. A finger joint metal/polymer constrained...

2014-04-01

281

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

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Hip joint metal constrained cemented or uncemented prosthesis...Prosthetic Devices § 888.3300 Hip joint metal constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal constrained cemented or...

2010-04-01

282

21 CFR 888.3530 - Knee joint femorotibial metal/polymer semi-constrained cemented prosthesis.  

Code of Federal Regulations, 2010 CFR

...false Knee joint femorotibial metal/polymer semi-constrained cemented prosthesis...3530 Knee joint femorotibial metal/polymer semi-constrained cemented prosthesis... A knee joint femorotibial metal/polymer semi-constrained cemented...

2010-04-01

283

21 CFR 888.3480 - Knee joint femorotibial metallic constrained cemented prosthesis.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Knee joint femorotibial metallic constrained cemented...Prosthetic Devices § 888.3480 Knee joint femorotibial metallic constrained cemented...prosthesis. (a) Identification. A knee joint femorotibial metallic constrained...

2010-04-01

284

Constraining duty cycles through a Bayesian technique  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

285

Constraining volcano eruption dynamics with infrasound  

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

286

21 CFR 888.3720 - Toe joint polymer constrained prosthesis.  

Code of Federal Regulations, 2011 CFR

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3720 Toe joint polymer constrained prosthesis. (a) Identification. A toe joint...

2011-04-01

287

21 CFR 888.3720 - Toe joint polymer constrained prosthesis.  

Code of Federal Regulations, 2010 CFR

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3720 Toe joint polymer constrained prosthesis. (a) Identification. A toe joint...

2010-04-01

288

Constraining the QSO luminosity function using gravitational lensing statistics  

E-print Network

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

Fakhouri, Onsi Joe, 1983-

2004-01-01

289

21 CFR 888.3720 - Toe joint polymer constrained prosthesis.  

Code of Federal Regulations, 2012 CFR

...prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of silicone elastomer or polyester reinforced silicone elastomer intended to be implanted to replace the first metatarsophalangeal (big toe) joint....

2012-04-01

290

21 CFR 888.3720 - Toe joint polymer constrained prosthesis.  

Code of Federal Regulations, 2014 CFR

...prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of silicone elastomer or polyester reinforced silicone elastomer intended to be implanted to replace the first metatarsophalangeal (big toe) joint....

2014-04-01

291

Constraining climate model properties using optimal fingerprint detection methods  

E-print Network

We present a method for constraining key properties of the climate system that are important for climate prediction (climate sensitivity and rate of heat penetration into the deep ocean) by comparing a model's response to ...

Forest, Chris Eliot.; Allen, Myles R.; Sokolov, Andrei P.; Stone, Peter H.

292

FXR agonist activity of conformationally constrained analogs of GW 4064  

SciTech Connect

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

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

2010-09-27

293

Computational study of a chance constrained portfolio selection ...  

E-print Network

Key words: Chance Constraints, Sample Average Approximation, Portfo- lio Selection ... where an extensive list of references can be found. Applications of chance constrained programming include, e.g., soil management [29], water man

2008-02-01

294

Viscoelastic Dewetting of Constrained Polymer Thin Films SYLVAIN GABRIELE,1  

E-print Network

Viscoelastic Dewetting of Constrained Polymer Thin Films SYLVAIN GABRIELE,1 PASCAL DAMMAN,1 SE the stability and dewetting dynamics of viscoelastic polymer thin films. The dewetting of polystyrene close Keywords: dewetting instability; interfaces; polystyrene; thin films; viscoelasticity INTRODUCTION Thin

Raphael, Elie

295

OPTIMIZATION OF MISSION DESIGN FOR CONSTRAINED LIBRATION POINT SPACE MISSIONS  

E-print Network

OPTIMIZATION OF MISSION DESIGN FOR CONSTRAINED LIBRATION POINT SPACE MISSIONS A DISSERTATION on Graduate Studies: iii #12;iv #12;Abstract Designing space missions to remain in the vicinity where the gravitational and centripetal accelerations exactly cancel; three where the satellite

Stanford University

296

Resource constrained scheduling problem at U.S. Naval Shipyards  

E-print Network

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

Nawara, Terrence M. (Terrence Michael)

2013-01-01

297

21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.  

Code of Federal Regulations, 2012 CFR

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3780 Wrist joint polymer constrained prosthesis. (a) Identification. A wrist joint...

2012-04-01

298

Scaling Up Reinforcement Learning without Sacrificing Optimality by Constraining Exploration  

E-print Network

of learning to solve new tasks and also identified conditions where transferring knowledge may impede learning. I present situations where transfer learning can be used to intelligently constrain the exploration space so that optimality loss can be minimized...

Mann, Timothy 1984-

2012-12-05

299

Irreducible Infeasible Subsystem Decomposition for Probabilistically Constrained Stochastic Integer Programs  

E-print Network

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

Gallego Arrubla, Julian Andres

2013-07-25

300

Constrained Density-Functional Theory--Configuration Interaction  

E-print Network

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

Kaduk, Benjamin James

2012-01-01

301

Constraining North Atlantic circulation with transient tracer observations  

E-print Network

The capability of transient tracers to constrain the ocean circulation in the North Atlantic is explored. Study of an idealized tracer shows that inferences of circulation properties from transient state distributions are ...

Li, Xingwen, 1968-

2003-01-01

302

A Constrained Spline Estimator of a Hazard Function.  

ERIC Educational Resources Information Center

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

Bloxom, Bruce

1985-01-01

303

A Filled Function Method with One Parameter for Rn Constrained ...  

E-print Network

For Rn constrained global optimization problem, a new auxiliary function ... algorithm is designed according to the theoretical analysis and some ..... on several global minimization problems to have an initial feeling of the potential practical ...

2007-06-07

304

An interior point potential reduction method for constrained equations  

Microsoft Academic Search

We study the problem of solving a constrained system of nonlinear equations by a combination of the classical damped Newton\\u000a method for (unconstrained) smooth equations and the recent interior point potential reduction methods for linear programs,\\u000a linear and nonlinear complementarity problems. In general, constrained equations provide a unified formulation for many mathematical\\u000a programming problems, including complementarity problems of various kinds

Tao Wang; Renato D. C. Monteiro; Jong-shi Pang

1996-01-01

305

Box-constrained maximum-likelihood detection in CDMA  

Microsoft Academic Search

The detection strategy usually denoted optimal multiuser detection is equivalent to the solution of a (0,1)-constrained maximum-likelihood (ML) problem, a problem which is known to be NP-complete. In contrast, the unconstrained ML problem can be solved quite easily and is known as the decorrelating detector. In this paper, we consider the box-constrained ML problem and suggest a general iterative solution

Peng Hui Tant; L. K. Rasmussen; Teng Joon Lim

2000-01-01

306

Constrained minimization of smooth functions using a genetic algorithm  

NASA Technical Reports Server (NTRS)

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

Moerder, Daniel D.; Pamadi, Bandu N.

1994-01-01

307

Ascorbic Acid  

MedlinePLUS

Ascorbic acid is used to prevent and treat scurvy, a disease caused by a lack of vitamin C in ... Ascorbic acid comes in extended-release (long-acting) capsules and tablets, lozenges, syrup, chewable tablets, and liquid drops to ...

308

Ethacrynic Acid  

MedlinePLUS

Ethacrynic acid, a 'water pill,' is used to treat swelling and fluid retention caused by various medical problems. It ... Ethacrynic acid comes as a tablet to take by mouth. It is usually taken once or twice a day ...

309

Folic acid  

MedlinePLUS

Folic acid is a water-soluble B vitamin. Since 1998, it has been added to cold cereals, flour, breads, ... law. Foods that are naturally high in folic acid include leafy vegetables (such as spinach, broccoli, and ...

310

Mefenamic Acid  

MedlinePLUS

Mefenamic acid is used to relieve mild to moderate pain, including menstrual pain (pain that happens before or during a menstrual period). Mefenamic acid is in a class of medications called NSAIDs. ...

311

Aristolochic Acids  

Cancer.gov

Aristolochic acids are a group of acids found naturally in many types of plants known as Aristolochia (birthworts or pipevines) and some types of plants known as Asarum (wild ginger), which grow worldwide.

312

Aristolochic Acids  

MedlinePLUS

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

313

Aminocaproic Acid  

MedlinePLUS

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

314

Folic Acid  

MedlinePLUS

... acid. Talk to your doctor about how much folic acid you need if you: Are taking medicines used to treat: Epilepsy Type 2 diabetes Rheumatoid arthritis , lupus , psoriasis , asthma , and inflammatory bowel disease Have kidney disease ...

315

Free and constrained symplectic integrators for numerical general relativity  

E-print Network

We consider symplectic time integrators in numerical General Relativity and discuss both free and constrained evolution schemes. For free evolution of ADM-like equations we propose the use of the Stoermer-Verlet method, a standard symplectic integrator which here is explicit in the computationally expensive curvature terms. For the constrained evolution we give a formulation of the evolution equations that enforces the momentum constraints in a holonomically constrained Hamiltonian system and turns the Hamilton constraint function from a weak to a strong invariant of the system. This formulation permits the use of the constraint-preserving symplectic RATTLE integrator, a constrained version of the Stoermer-Verlet method. The behavior of the methods is illustrated on two effectively 1+1-dimensional versions of Einstein's equations, that allow to investigate a perturbed Minkowski problem and the Schwarzschild space-time. We compare symplectic and non-symplectic integrators for free evolution, showing very different numerical behavior for nearly-conserved quantities in the perturbed Minkowski problem. Further we compare free and constrained evolution, demonstrating in our examples that enforcing the momentum constraints can turn an unstable free evolution into a stable constrained evolution. This is demonstrated in the stabilization of a perturbed Minkowski problem with Dirac gauge, and in the suppression of the propagation of boundary instabilities into the interior of the domain in Schwarzschild space-time.

Ronny Richter; Christian Lubich

2008-11-04

316

Valproic Acid  

MedlinePLUS

Valproic acid is used alone or with other medications to treat certain types of seizures. Valproic acid is also used to treat mania (episodes of ... to relieve headaches that have already begun. Valproic acid is in a class of medications called anticonvulsants. ...

317

Shikimic Acid  

NSDL National Science Digital Library

The molecule for this month comes from the article Isolation of Shikimic Acid from Star Aniseed by Richard Payne and Michael Edmonds. Shikimic acid plays a key role in the biosynthesis of many important natural products including aromatic amino acids, alkaloids, phenolics, and phenylpropanoids. It plays such an important role that one of the key biosynthetic pathways is referred to as the shikimate pathway.

318

Rapid "tea-bag" peptide synthesis using 9-fluorenylmethoxycarbonyl (Fmoc) protected amino acids applied for antigenic mapping of viral proteins.  

PubMed

The role of individual amino acids in binding human and macaque antibodies were determined in the human immunodeficiency virus type 1 (HIV-1) gp41, residues 594-613, and for human antibodies in the hepatitis B (HB) virus core/e antigens (HBc/eAg), residues 121-140. Decapeptides with 9 amino acids (aa) overlap were synthesised using a rapid method for simultaneous multiple peptide synthesis with 9-fluorenylmethoxycarbonyl (Fmoc) protection for the alpha-amino group of the aas. One coupling cycle including washing steps was performed within 60-90 min. The crude products were analysed by reversed-phase HPLC and PD-mass spectrometry. With the 11 decapeptides covering residues 594-613 of HIV-1 gp41, the sequences SGKLI at aa 599-603 was found to be the main recognition site for 19 human anti-HIV positive sera. Two macaques repeatedly immunized with a peptide covering aa 594-613 of gp41, preferentially recognised the sequence CTTAVPW at residues 604-610 after 1-2 months of immunisation. One macaque also recognised the sequence CSGKLI, with sera sampled greater than 10 months after start of immunisation. Out of 9 human sera from patients with chronic HB, and reactive to a peptide covering residues 121-140 of HBc/eAg, 8 were found to recognise the sequence TPPA at residues 128-131, with an individual variation within residues 125-133 in regard to N- and C-terminal ends of the recognised antigenic site. Thus, human recognition of this antigenic site overlaps the reported T- and the B-cell recognition site found in mice. We believe that this simple and rapid approach to obtain large numbers of immunologically active peptides can be useful for most laboratories interested in the immunological characterisation of proteins. PMID:1720419

Sällberg, M; Rudén, U; Magnius, L O; Norrby, E; Wahren, B

1991-09-01

319

Gold nanoclusters protected by conformationally constrained peptides.  

PubMed

The preparation and properties of a series of gold nanoclusters protected by thiolated peptides based on the alpha-aminoisobutyric acid (Aib) unit are described. The peptides were devised to form 0-3 C=O...H-N intramolecular hydrogen bonds, as required by their 3(10)-helical structure. The monolayer-protected clusters (MPCs) were prepared, using a modified version of the two-phase Brust-Schiffrin preparation, and fully characterized with (1)H NMR spectrometry, IR and UV-vis absorption spectroscopies, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The MPCs were obtained with core diameters in the range of 1.1-2.3 nm, depending on the reaction conditions. Structured peptides formed smaller clusters. The smallest MPC obtained is in agreement with the average formula Au(38)Pep(18). The results showed that the chemical integrity of the peptide is maintained upon monolayer formation and that the average number of peptide ligands per gold cluster is typically 75-85% the value calculated for alkanethiolate MPCs of similar sizes. The IR and NMR spectra indicated that in the monolayer the peptides are involved in both intra- and interligand C=O...H-N hydrogen bonds. PMID:16390162

Fabris, Laura; Antonello, Sabrina; Armelao, Lidia; Donkers, Robert L; Polo, Federico; Toniolo, Claudio; Maran, Flavio

2006-01-11

320

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

Microsoft Academic Search

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

Kui Cai; Kees A. Schouhamer Immink

2008-01-01

321

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

Microsoft Academic Search

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

Kui Cai; Kees A. Schouhamer Immink

2005-01-01

322

Constrained Willmore Surfaces: Symmetries of a Moebius Invariant Integrable System  

NASA Astrophysics Data System (ADS)

This work is dedicated to the study of the Moebius invariant class of constrained Willmore surfaces and its symmetries. We define a spectral deformation by the action of a loop of flat metric connections; Baecklund transformations, by applying a dressing action; and, in 4-space, Darboux transformations, based on the solution of a Riccati equation. We establish a permutability between spectral deformation and Baecklund transformation and prove that non-trivial Darboux transformation of constrained Willmore surfaces in 4-space can be obtained as a particular case of Baecklund transformation. All these transformations corresponding to the zero multiplier preserve the class of Willmore surfaces. We verify that, for special choices of parameters, both spectral deformation and Baecklund transformation preserve the class of constrained Willmore surfaces admitting a conserved quantity, and, in particular, the class of CMC surfaces in 3-dimensional space-form.

Casinhas Quintino, Áurea

2009-12-01

323

Constraining Cut-off Physics in the Cosmic Microwave Background  

E-print Network

We investigate the ability to constrain oscillatory features in the primordial power spectrum using current and future cosmic microwave background observations. In particular, we study the observability of an oscillation arising from imprints of physics at the cut-off energy scale. We perform a likelihood analysis on the WMAP data set, and find that the current data set constrains the amplitude of the oscillations to be less than 0.77 at 2-sigma, consistent with a power spectrum without oscillations. In addition, we investigate the fundamental limitations in the measurement of oscillation parameters by studying the constraints from a cosmic variance limited experiment. We find that such an experiment is capable of constraining the amplitude of such oscillations to be below 0.005, implying that reasonable models with cut-off energy scales Lambda>200 H_infl are unobservable through the microwave background.

Takemi Okamoto; Eugene A. Lim

2004-03-23

324

Conserved and nonconserved residues in the substrate binding site of 7,8-diaminopelargonic acid synthase from Escherichia coli are essential for catalysis.  

PubMed

The vitamin B(6)-dependent enzyme 7,8-diaminopelargonic acid (DAPA) synthase catalyzes the antepenultimate step in the synthesis of biotin, the transfer of the alpha-amino group of S-adenosyl-l-methionine (SAM) to 7-keto-8-aminopelargonic acid (KAPA) to form DAPA. The Y17F, Y144F, and D147N mutations in the active site were constructed independently. The k(max)/K(m)(app) values for the half-reaction with DAPA of the Y17F and Y144F mutants are reduced by 1300- and 2900-fold, respectively, compared to the WT enzyme. Crystallographic analyses of these mutants do not show significant changes in the structure of the active site. The kinetic deficiencies, together with a structural model of the enzyme-PLP/DAPA Michaelis complex, point to a role of these two residues in recognition of the DAPA/KAPA substrates and in catalysis. The k(max)/K(m)(app) values for the half-reaction with SAM are similar to that of the WT enzyme, showing that the two tyrosine residues are not involved in this half-reaction. Mutations of the conserved Arg253 uniquely affect the SAM kinetics, thus establishing this position as part of the SAM binding site. The D147N mutant is catalytically inactive in both half-reactions. The structure of this mutant exhibits significant changes in the active site, indicating that this residue plays an important structural role. Of the four residues examined, only Tyr144 and Arg253 are strictly conserved in the available amino acid sequences of DAPA synthases. This enzyme thus provides an illustrative example that active site residues essential for catalysis are not necessarily conserved, i.e., that during evolution alternative solutions for efficient catalysis by the same enzyme arose. Decarboxylated SAM [S-adenosyl-(5')-3-methylthiopropylamine] reacts nearly as well as SAM and cannot be eliminated as a putative in vivo amino donor. PMID:14756557

Sandmark, Jenny; Eliot, Andrew C; Famm, Kristoffer; Schneider, Gunter; Kirsch, Jack F

2004-02-10

325

Basically Acids  

NSDL National Science Digital Library

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

2014-09-18

326

Constrained Selected Reaction Monitoring: Quantification of selected post-translational modifications and protein isoforms  

PubMed Central

Selected reaction monitoring (SRM) is a mass spectrometry method that can target signature peptides to provide for the detection and quantitation of specific proteins in complex biological samples. When quantifying a protein, peptides are generated using a specific protease such as trypsin, allowing the choice of signature peptides with robust signals. In contrast, signature peptide selection can be constrained when the goal is to monitor a specific post-translational modification (PTM) or protein isoform as the signature peptide must include the amino acid residue(s) of PTM attachment or sequence variation. This can force the selection of a signature peptide with a weak SRM response or one that is confounded by high background. In this article, additional steps that can be optimized to maximize peptide selection and assay performance of constrained SRM assays are discussed including tuning instrument parameters, fragmenting product ions, using a different protease, and enriching the sample. Examples are provided for selection of phosphorylated or citrullinated peptides and protein isoforms. PMID:23523700

Liu, Xiaoqian; Jin, Zhicheng; O’Brien, Richard; Bathon, Joan; Dietz, Harry C.; Grote, Eric; Van Eyk, Jennifer E.

2014-01-01

327

A constrained Ensemble Kalman Filter for improved streamflow forecasting  

NASA Astrophysics Data System (ADS)

Data assimilation techniques, such as the Kalman Filter and its variants, are often applied to physically or mathematically constrained hydrological models with little, if any, respect for physical laws. Model states can be adjusted beyond what is physically possible, compromising the integrity of model output. The challenge of constraining state updates, and the extent to which model predictions can be compromised without sensible constraints, has been largely ignored in the past. In this paper, a constrained Ensemble Kalman Filter (EnKF) is applied to a semi-distributed, physically-based conceptual model for the Tauranga-Taupo catchment, New Zealand. Streamflow observations are used to update the soil storage, baseflow, interflow and fastflow model states. Simple mass and flux constraints are placed on the data assimilation framework, encouraging state perturbations to have some physical meaning. The constrained EnKF is evaluated over 30 events between 2008 and 2011. This evaluation is based on model performance over a five day forecasting period, with EnKF state updating (both constrained and unconstrained) applied from 1998 up to the start each forecasting period. Constraining state updates shows significantly better overall performance compared to the unconstrained filter, according to the Kling Gupta Efficiency Index. Summary statistics for the 30 events are presented. For demonstration purposes, we focus on two events - 12 February 2009 and 21 January 2010. In these events, model performance was improved by 64% and 29%, respectively. More specifically, two of the three components of the KGE index, overall volume (bias) and the timing and shape of the hydrograph (correlation), show a better fit to the observations. The range of uncertainty between the five parameter sets applied was also reduced by 85% and 68%, respectively, resulting in more precise and reliable streamflow forecasts.

Maxwell, D. H.; Jackson, B. M.; McGregor, J.

2013-12-01

328

Failure of a constrained acetabular liner without reinforcement ring disruption.  

PubMed

Several risk factors for dislocation after total hip arthroplasty (THA) have been identified including operative-, patient-, and implant-related factors. The following case report describes the dislocation of a revision THA without disruption of the constrained liner or containment ring. The possible mechanisms leading to this type of failure include lever-out impingement and poor abductor function, or tension secondary to prior surgery. Dislocation without disruption of containment ring has not been described for the Pinnacle Acetabular Cup with the Enhanced Stability Constrained Liner (DePuy Orthopaedics, Warsaw, Indiana). PMID:24471147

Arthur, Jeffrey A; Amanatullah, Derek F; Kennedy, Gannon D; Di Cesare, Paul E

2013-12-01

329

Conformationally constrained functional peptide monolayers for the controlled display of bioactive carbohydrate ligands.  

PubMed

In this study, we employed thiolated peptides of the conformationally constrained, strongly helicogenic ?-aminoisobutyric acid (Aib) residue to prepare self-assembled monolayers (SAMs) on gold surfaces. Electrochemistry and infrared reflection absorption spectroscopy support the formation of very well packed Aib-peptide SAMs. The immobilized peptides retain their helical structure, and the resulting SAMs are stabilized by a network of intermolecular H bonds involving the NH groups adjacent to the Au surface. Binary SAMs containing a synthetically defined glycosylated mannose-functionalized Aib-peptide as the second component display similar features, thereby providing reproducible substrates suitable for the controlled display of bioactive carbohydrate ligands. The efficiency of such Aib-based SAMs as a biomolecular recognition platform was evidenced by examining the mannose-concanavalin A interaction via surface plasmon resonance biosensing. PMID:23782319

Kaplan, Justin M; Shang, Jing; Gobbo, Pierangelo; Antonello, Sabrina; Armelao, Lidia; Chatare, Vijay; Ratner, Daniel M; Andrade, Rodrigo B; Maran, Flavio

2013-07-01

330

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

PubMed

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

Jäntschi, Lorentz; Bolboac?, Sorana D

2015-03-01

331

Acid Rain  

Microsoft Academic Search

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

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

1979-01-01

332

Acid rain  

SciTech Connect

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

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

1988-01-01

333

Acid rain  

SciTech Connect

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

Elsworth, S.

1985-01-01

334

Domoic Acid  

NSDL National Science Digital Library

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

Bailey, Christina

335

Acids (GCMP)  

NSDL National Science Digital Library

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

336

Acid Precipitation  

NSDL National Science Digital Library

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

Tyser, Jim

337

Security-constrained unit commitment with AC constraints  

Microsoft Academic Search

In a restructured power market, the independent system operator (ISO) executes the security-constrained unit commitment (SCUC) program to plan a secure and economical hourly generation schedule for the day-ahead market. This paper introduces an efficient SCUC approach with ac constraints that obtains the minimum system operating cost while maintaining the security of power systems. The proposed approach applies the Benders

Yong Fu; Mohammad Shahidehpour; Zuyi Li

2005-01-01

338

Security-Constrained Unit Commitment With AC Constraints  

Microsoft Academic Search

In a restructured power market, the independent system operator (ISO) executes the security-constrained unit commitment (SCUC) program to plan a secure and economical hourly generation schedule for the day-ahead market. This paper introduces an efficient SCUC approach with ac constraints that obtains the minimum system operating cost while maintaining the security of power systems. The proposed approach applies the Benders

Yong Fu; Mohammad Shahidehpour; Zuyi Li

2005-01-01

339

Hierarchical Iterative Algorithm for a Coupled Constrained OSNR Nash Game  

E-print Network

Hierarchical Iterative Algorithm for a Coupled Constrained OSNR Nash Game Lacra Pavel Department@control.toronto.edu Abstract-- This paper develops a hierarchical iterative OSNR algorithm based on a game theory framework signal-to-noise ratio (OSNR). The OSNR game has coupled utilities and coupled constraints

Pavel, Lacra

340

A Distributed Optimization Approach to Constrained OSNR Problem  

E-print Network

A Distributed Optimization Approach to Constrained OSNR Problem Yan Pan Tansu Alpcan Lacra Pavel signal-to-noise ratio (OSNR) problem via a distributed optimization approach. In multi-channel optical to OSNR degradation. Regulating the input optical power at the Source (transmitter) aims to achieve

Pavel, Lacra

341

Optimization of constrained composite absorbers using simulated annealing  

Microsoft Academic Search

Sound reverberation is an important problem in some industrial environments. As indicated by the Occupational Safety and Health Act of 1970, noise is responsible for the psychological and physiological ills of workers. Therefore reduction of reverberation becomes essential. For maintenance and other reasons, the thickness of sound absorbers used for reverberation control may be constrained. Consequently there is interest in

Ying-Chun Chang; Long-Jyi Yeh; Min-Chie Chiu

2005-01-01

342

SECONDORDER RUNGE--KUTTA APPROXIMATIONS IN CONTROL CONSTRAINED OPTIMAL CONTROL #  

E-print Network

SECOND­ORDER RUNGE--KUTTA APPROXIMATIONS IN CONTROL CONSTRAINED OPTIMAL CONTROL # A. L. DONTCHEV and Applied Mathematics Vol. 38, No. 1, pp. 202­226 Abstract. In this paper, we analyze second­order Runge--Kutta a derivative of bounded variation and a coercivity condition holds, we show that for a special class of Runge--Kutta

Hager, William

343

Automated assignment of backbone NMR peaks using constrained bipartite matching  

Microsoft Academic Search

Peak assignment is a key step in solving protein structures using nuclear magnetic resonance. The authors present a new computational framework for automating this process, particularly for backbone resonance peak assignment, as a constrained weighted bipartite matching problem. Although it's NP-hard, they have developed a rigorous algorithm to solve the problem

Ying Xu; Dong Xu; Dongsup Kai; VICTOR OLMAN; JANE RAZUMOVSKAYA; Tao Jiang

2002-01-01

344

Security Constrained Economic Dispatch Using Interior Point Method  

Microsoft Academic Search

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

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

2006-01-01

345

Use of risk premiums in chance-constrained dynamic programing  

Microsoft Academic Search

Stochastic dynamic programing offers a powerful means of deriving optimum operating policies for water resource systems. In order to limit the probability of system failure associated with such policies it is necessary to amend the standard algorithm and use some form of chance-constrained dynamic programing. This technique may involve an iterative search based on variations in such parameters as the

Arthur J. Askew

1975-01-01

346

Constrained Quantum Mechanics: Chaos in Non-Planar Billiards  

ERIC Educational Resources Information Center

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

Salazar, R.; Tellez, G.

2012-01-01

347

Passive Network-Awareness for Dynamic Resource-Constrained Networks  

E-print Network

Passive Network-Awareness for Dynamic Resource-Constrained Networks Agoston Petz1 , Taesoo Jun2 the possibility of col- lecting reasonably accurate context information passively. This paper introduces a framework for defining passively sensed context through network overhearing, defining context metrics

Julien, Christine

348

ORIGINAL ARTICLE Tonic, But Not Phasic Corticosterone, Constrains Stress Activated  

E-print Network

and adrenonocorticotrophic hormone secretion. This tonic CORT inhibition of stress-induced activation of ERK1 / 2 may involveORIGINAL ARTICLE Tonic, But Not Phasic Corticosterone, Constrains Stress Activated Extracellular of Colorado, UCB 345, Boulder, CO, USA. Glucocorticoids potently suppress stress-induced hypothalamic

Spencer, Robert L.

349

A simple elitist genetic algorithm for constrained optimization  

Microsoft Academic Search

In this paper we propose a novel approach for solving constrained optimization problems using genetic algorithms. The main emphasis of this algorithm is to be problem independent and to produce consistent results in terms of the quality of feasible solutions. The basic characteristic of this algorithm is the complete ignorance of the objective function till at least one feasible solution

Sangameswar Venkatraman; Gary G. Yen

2004-01-01

350

Parallel micro genetic algorithm for constrained economic dispatch  

Microsoft Academic Search

This paper proposes a parallel micro genetic algorithm (PMGA) for solving ramp rate constrained economic dispatch (ED) problems for generating units with nonmonotonically and monotonically increasing incremental cost (IC) functions. The developed PMGA algorithm is implemented on the thirty-two-processor Beowulf cluster with ethernet switches network on the systems with the number of generating units ranging from 10 to 80 over

Jarurote Tippayachai; Weerakorn Ongsakul; Issarachai Ngamroo

2002-01-01

351

Finite Satisfiability of UML Class Diagrams with Constrained Class Hierarchy  

E-print Network

24 Finite Satisfiability of UML Class Diagrams with Constrained Class Hierarchy MIRA BALABAN for efficient powerful methods for verifying model correctness. Class diagram is the central language within UML of finite satisfiability of class diagrams with class hierarchy constraints and generalization

Balaban, Mira

352

Parameterized Polyhedra Approach for Robust Constrained Generalized Predictive Control  

Microsoft Academic Search

The paper considers the discrete time-invariant linear systems affected by input disturbances and construct the explicit description of the constrained generalized predictive control (GPC) law taking in account the constraints existence from the design stage. The explicit formulation of the predictive controllers gives a useful insight on the closed loop capabilities. The GPC is a special case of model predictive

Sorin Olaru; Didier Dumur; Sihem Tebbani

2005-01-01

353

SNOPT: An SQP Algorithm For Large-Scale Constrained Optimization  

Microsoft Academic Search

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

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

1997-01-01

354

How Well Can Future CMB Missions Constrain Cosmic Inflation?  

E-print Network

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

Jerome Martin; Christophe Ringeval; Vincent Vennin

2014-10-29

355

Handling Alternative Activities in Resource-Constrained Project Scheduling Problems  

E-print Network

-established framework for the formal description of scheduling problems: Generalizing the production-specific job shopHandling Alternative Activities in Resource-Constrained Project Scheduling Problems J¨urgen Kuster can be assessed by the application of generic scheduling frameworks such as the Resource

Jannach, Dietmar

356

An Opportunistic Batch Bundle Authentication Scheme for Energy Constrained DTNs  

Microsoft Academic Search

Bundle Authentication is a critical security service in Delay Tolerant Networks (DTNs) that ensures authenticity and integrity of bundles during multi-hop transmissions. Public key signatures, which have been suggested in existing bundle security protocol specification, achieve bundle authentication at the cost of an increased computational, transmission overhead and a higher energy consumption, which is not desirable for energy-constrained DTNs. On

Haojin Zhu; Xiaodong Lin; Rongxing Lu; Xuemin Shen; Dongsheng Xing; Zhenfu Cao

2010-01-01

357

Constrained Transport vs. Divergence Cleanser Options in Astrophysical MHD Simulations  

NASA Astrophysics Data System (ADS)

In previous work, we presented results from global numerical simulations of the evolution of black hole accretion disks using the Cosmos++ GRMHD code. In those simulations we solved the magnetic induction equation using an advection-split form, which is known not to satisfy the divergence-free constraint. To minimize the build-up of divergence error, we used a hyperbolic cleanser function that simultaneously damped the error and propagated it off the grid. We have since found that this method produces qualitatively and quantitatively different behavior in high magnetic field regions than results published by other research groups, particularly in the evacuated funnels of black-hole accretion disks where Poynting-flux jets are reported to form. The main difference between our earlier work and that of our competitors is their use of constrained-transport schemes to preserve a divergence-free magnetic field. Therefore, to study these differences directly, we have implemented a constrained transport scheme into Cosmos++. Because Cosmos++ uses a zone-centered, finite-volume method, we can not use the traditional staggered-mesh constrained transport scheme of Evans & Hawley. Instead we must implement a more general scheme; we chose the Flux-CT scheme as described by Toth. Here we present comparisons of results using the divergence-cleanser and constrained transport options in Cosmos++.

Lindner, Christopher C.; Fragile, P.

2009-01-01

358

Constraining magnesium cycling in marine sediments using magnesium isotopes  

E-print Network

Constraining magnesium cycling in marine sediments using magnesium isotopes J.A. Higgins *, D Abstract Magnesium concentrations in deep-sea sediment pore-fluids typically decrease down core due to net and differentiate these processes, we have measured magnesium isotopes in pore-fluids and sediment samples from

Paytan, Adina

359

Computing a Diameter-Constrained Minimum Spanning Tree in Parallel  

Microsoft Academic Search

A minimum spanning tree (MST) with a small diameter is required in numerous practical situations. It is needed, for example, in distributed mutual exclusion algorithms in order to minimize the number of messages communicated among processors per critical section. The Diameter- Constrained MST (DCMST) problem can be stated as follows: given an undirected, edge-weighted graph G with n nodes and

Narsingh Deo; Ayman Abdalla

2000-01-01

360

Tumor localization using diffuse optical tomography and linearly constrained  

E-print Network

Tumor localization using diffuse optical tomography and linearly constrained minimum variance. nehorai@ese.wustl.edu Abstract: We present a tumor localization method for diffuse optical tomography as a possible position of abnormality (e.g., tumor). We then design a spatial filter based on the linearly

Nehorai, Arye

361

STATIONARITY RESULTS FOR GENERATING SET SEARCH FOR LINEARLY CONSTRAINED OPTIMIZATION  

E-print Network

STATIONARITY RESULTS FOR GENERATING SET SEARCH FOR LINEARLY CONSTRAINED OPTIMIZATION TAMARA G. KOLDA, ROBERT MICHAEL LEWIS, AND VIRGINIA TORCZON Abstract. We present a new generating set search (GSS) approach for minimizing functions subject to linear constraints. GSS is a class of direct search

Torczon, Virginia

362

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

Microsoft Academic Search

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

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

1992-01-01

363

Force and position control of manipulators during constrained motion tasks  

Microsoft Academic Search

Trajectory control of a manipulator constrained by the contact of the end-effector with the environment represents an important class of control problems. A method is proposed whereby both contact force exerted by the manipulator, and the position of the end-effector while in contact with the surface are controlled. The controller parameters are derived based on a linearized dynamic model of

J. K. Mills; A. A. Goldenberg

1989-01-01

364

Dynamic state feedback control of constrained robot manipulators  

Microsoft Academic Search

The problem of simultaneous motion and force control of a constrained robot manipulator is studied. It is recognized that the degrees of freedom of the manipulator are reduced in the presence of constraints. A dynamic model suitable for motion and force control is derived. Both motion and force control loops are exactly linearized and decoupled by using a dynamic nonlinear

Xiaoping Yun

1988-01-01

365

Evolution of Visual Resolution Constrained by a Trade-off  

Microsoft Academic Search

The evolution of visual systems is constrained by a trade-off between spatial and temporal resolution. In this paper we aim at identifying the causes of the trade-off at the retinal level in both artificial and natural visual systems. We start by selecting two factors that limit the values of spatial and temporal resolution. Then we show in two experiments on

Rens Kortmann; Eric O. Postma; H. Jaap Van Den Herik

2001-01-01

366

EUROPEAN LARGE LAKES III Identification of factors constraining nitrate assimilation  

E-print Network

-long increase in nitrate levels (Sterner et al., 2007). This trend was initially reported in the years followingEUROPEAN LARGE LAKES III Identification of factors constraining nitrate assimilation in Lake Science+Business Media Dordrecht 2013 Abstract Despite a well-documented rise in nitrate concentration

Berges, John A.

367

Motion Planning of Human-Like Robots using Constrained Coordination  

E-print Network

Motion Planning of Human-Like Robots using Constrained Coordination Liangjun Zhang Jia Pan Dinesh for human-like robots. The planning problem is decomposed into a sequence of low-dimensional sub-like model and generate efficient motion strategies for walking, sitting and grabbing objects in complex CAD

North Carolina at Chapel Hill, University of

368

Solution of a Complex Least Squares Problem with Constrained Phase.  

PubMed

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

Bydder, Mark

2010-12-30

369

Functional Integration on Constrained Function Spaces I: Foundations  

E-print Network

Analogy with Bayesian inference is used to formulate constraints within a scheme for functional integration proposed by Cartier and DeWitt-Morette. According to the analogy, functional counterparts of conditional and conjugate probability distributions are introduced for integrators. The analysis leads to some new functional integration tools and methods that can be applied to the study of constrained dynamical systems.

J. LaChapelle

2014-11-18

370

Heuristic Algorithm in Optimizing Stochastic Resource-Constrained Project Scheduling  

Microsoft Academic Search

This paper presents a newly developed resource constrained project scheduling method in stochastic networks by using critical chain concept. The objective of the presented model is defined as minimizing the multiplication of expected project duration and its variance. This paper suggests a competition routine by implementing a policy to maximize the total contribution of selected activities in reducing the expected

Fang Ming Guo; Li Ma; Min He

2009-01-01

371

Mercury's thermo-chemical evolution from numerical models constrained  

E-print Network

Mercury's thermo-chemical evolution from numerical models constrained by MESSENGER observations Globe de Paris, France #12;Basics facts about Mercury · Semi-major axis: 0.39 AU · 3:2 spin Earth!) · Black body temperature: 440 K #12;Exploration of Mercury Mariner10 ·First spacecraft to use

Cerveny, Vlastislav

372

Learning Adaptive Navigation Strategies for Resource-constrained Systems  

E-print Network

objectives for an autonomous robot. As a precondition for finding the way to a target location, the robotLearning Adaptive Navigation Strategies for Resource-constrained Systems Armin Hornung1 and Maren. The majority of navigation algorithms for mobile robots assume that the robots possess enough computational

Stachniss, Cyrill

373

Bayesian Item Selection in Constrained Adaptive Testing Using Shadow Tests  

ERIC Educational Resources Information Center

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

Veldkamp, Bernard P.

2010-01-01

374

Constrained Signaling for Welfare and Revenue Maximization Shaddin Dughmi  

E-print Network

scores and tran- scripts. Targeted advertising sales in both online and offline media describe viewers in various markets including online advertising, wheat sales, diamond sales, and spectrum auctions. 1 #12;A might be legally constrained to truthfully advertise the item being sold. Each candidate signaling

Immorlica, Nicole

375

Power Allocations in Minimum-Energy SER Constrained Cooperative Networks  

E-print Network

1 Power Allocations in Minimum-Energy SER Constrained Cooperative Networks Behrouz Maham for repetition-based amplify- and-forward (AF) relaying, given a required symbol error rate (SER the total relay power subject to the SER requirement at the destination. Two outstanding features

Paris-Sud XI, Université de

376

Applications of a Constrained Mechanics Methodology in Economics  

ERIC Educational Resources Information Center

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

Janova, Jitka

2011-01-01

377

Distance-Enhancing Constrained Codes for Optical Recording Channels  

Microsoft Academic Search

This paper proposes distance-enhancing con- strained codes for optical recording channels. The repeated minimum transition runlength (RMTR) constraints are first in- vestigated, based on error event analysis and capacity calculation. A new RMTR constrained code is then proposed. Compared with the codes used in standard systems, it imposes the minimum achievable RMTR constraint on the channel bit stream, without introducing

Kui Cai; Kees A. Schouhamer Immink; Zhiliang Qin

2008-01-01

378

PSYCHOACOUSTICALLY CONSTRAINED AND DISTORTION MINIMIZED SPEECH ENHANCEMENT ALGORITHM  

E-print Network

PSYCHOACOUSTICALLY CONSTRAINED AND DISTORTION MINIMIZED SPEECH ENHANCEMENT ALGORITHM Seokhwan Jo minimized speech enhancement algorithm is considered. In general, noise reduction leads to speech distortion, and thus, the goal of an enhancement al- gorithm should reduce noise and speech distortion so that both

Yoo, Chang D.

379

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

E-print Network

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

Van Den Eijnden, Eric

380

An algorithm for linearly constrained adaptive array processing  

Microsoft Academic Search

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

OTIS LAMONT FROST

1972-01-01

381

Constrained Hidden Markov Models roweis@gatsby.ucl.ac.uk  

E-print Network

Constrained Hidden Markov Models Sam Roweis roweis@gatsby.ucl.ac.uk Gatsby Unit, University College London Abstract By thinking of each state in a hidden Markov model as corresponding to some spatial variables. Hidden Markov models (HMMs) can be thought of as dynamic generalizations of discrete state static

Roweis, Sam

382

Inferring Meaningful Communities from Topology-Constrained Correlation Networks  

PubMed Central

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

Hleap, Jose Sergio; Blouin, Christian

2014-01-01

383

Critical transition in the constrained traveling salesman problem  

NASA Astrophysics Data System (ADS)

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

Andrecut, M.; Ali, M. K.

2001-04-01

384

Mechanized Safety Proofs for Disc-Constrained Aircraft  

E-print Network

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

385

Treating 'thooft-Polyakov Monopole as Constrained System  

E-print Network

The 'tHooft-Polyakov monopole is treated as constrained system using the Hamilton-Jacobi method. The set of the Hamilton-Jacobi partial differential equations and the equations of motion are obtained. The quantization of the system is also discussed.

Hatem Widyan

2008-12-29

386

Interactive image segmentation by constrained spectral graph partitioning  

Microsoft Academic Search

This paper proposed an interactive image segmentation algorithm that can tolerate slightly incorrect user constraints. Interactive image segmentation was formulated as a constrained spectral graph partitioning problem. Furthermore, it was proven to equal to a supervised classification problem, where the feature space was formed by rows of the eigenvector matrix that was computed by spectral graph analysis. nu-SVM (support vector

Hao Zhang; Jin He; Hong Zhang; Zhanhua Huang

2010-01-01

387

Shape Space Exploration of Constrained Meshes Yong-Liang Yang  

E-print Network

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

Mitra, Niloy J.

388

Testing a Constrained MPC Controller in a Process Control Laboratory  

ERIC Educational Resources Information Center

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

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

2010-01-01

389

Bursty Traffic in Energy-Constrained Opportunistic Spectrum Access  

E-print Network

Bursty Traffic in Energy-Constrained Opportunistic Spectrum Access Yunxia Chen, Qing Zhao, and Ananthram Swami I. INTRODUCTION Opportunistic spectrum access (OSA) is one of the approaches envisioned with the current spectrum management policy and legacy wireless systems. The basic idea of OSA is to allow

Islam, M. Saif

390

Bursty Traffic in Energy-Constrained Opportunistic Spectrum Access  

E-print Network

Bursty Traffic in Energy-Constrained Opportunistic Spectrum Access Yunxia Chen, Qing Zhao Army Research Laboratory Adelphi, MD 20783 Abstract--We design opportunistic spectrum access strategies for improving spectrum efficiency. In each slot, a secondary user chooses a subset of channels to sense

Islam, M. Saif

391

DISTRIBUTED COGNITIVE MAC FOR ENERGY-CONSTRAINED OPPORTUNISTIC SPECTRUM ACCESS  

E-print Network

DISTRIBUTED COGNITIVE MAC FOR ENERGY-CONSTRAINED OPPORTUNISTIC SPECTRUM ACCESS Yunxia Chen, Qing for opportunistic spectrum access (OSA) under an energy constraint on the secondary users. The objective partially observable Markov decision process (POMDP) and obtain the optimal spectrum sensing and access

Islam, M. Saif

392

A spatially constrained ecological classification: rationale, methodology and implementation  

Microsoft Academic Search

The theory, methodology and implementation for an ecological and spatially constrained classification are pre- sented. Ecological and spatial relationships among several landscape variables are analyzed in order to define a new approach for a landscape classification. Using ecological and geostatistical analyses, several ecological and spatial weights are derived to recreate landscape pattern and structure in a classification model. An ecological

Franz Mora; Louis Iverson

2002-01-01

393

Interior point techniques for the constrained simulation problem  

Microsoft Academic Search

We present a special application of optimization techniques, based on Interior Point methods, in order to cope with the general Constrained Simulation Problem (CSP). A Successive Linear Programming (SLP) method or a Successive Quadratic Programming (SQP) method are alternatively exploited to treat in a robust and efficient way the process simulation problems that are, in general, subject to inequalities to

Dionyssia J. Kyriakopoulou; Boris Kalitventzeff

1998-01-01

394

An Adaptive Penalty Approach for Constrained GeneticAlgorithm Optimization  

E-print Network

). These include: 1. Rejection of infeasible solutions (the death penalty). 2. Using a mapping function so that allAn Adaptive Penalty Approach for Constrained Genetic­Algorithm Optimization Khaled Rasheed shehata@cs.rutgers.edu ABSTRACT In this paper we describe a new adaptive penalty approach for handling

Rasheed, Khaled

395

MPC for tracking piecewise constant references for constrained linear systems  

Microsoft Academic Search

In this paper, a novel model predictive control (MPC) for constrained (non-square) linear systems to track piecewise constant references is presented. This controller ensures constraint satisfaction and asymptotic evolution of the system to any target which is an admissible steady-state. Therefore, any sequence of piecewise admissible setpoints can be tracked without error. If the target steady state is not admissible,

D. Limón; I. Alvarado; T. Alamo; Eduardo F. Camacho

2008-01-01

396

The explicit linear quadratic regulator for constrained systems  

Microsoft Academic Search

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

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

2002-01-01

397

Skeptical Query-Answering in Constrained Default Logic  

Microsoft Academic Search

An approach to skeptical query-answering in Constrained Default Logic based on the Connection Method is presented. We adapt a recently pro- posed general method to skeptical reasoning in Default Logics|a method which does neither strictly require the inspection of all extensions nor the computation of entire extensions to decide whether a formula is skeptically entailed. We com- bine this method

Torsten Schaub; Michael Thielscher

1996-01-01

398

Using Resolution-Constrained Adaptive Meshes for Traveltime Tomography  

E-print Network

- mic dataset with irregular ray coverage collected at a shallow site with groundwater contamination of Geophysics, Stanford University) Jaime A. Urban Department of Geophysics, Stanford University, Rm.360.B., Urban, J.A., and Harris, J.M. 2006. Using resolution-constrained adaptive meshes for traveltime

Ajo-Franklin, Jonathan

399

RESTful Service Development for Resource-Constrained Environments  

E-print Network

community and our daily life. Accessing services from such devices is very common in ubiquitous environments this technology is still heavyweight for resource-constrained devices. The emergence of REST architectural style. In this chapter, we discuss the state-of-the-art in applying REST concepts to develop Web services for WSNs

Eliassen, Frank

400

Constraining Cosmic Magnetic Fields by a Measurement of  

E-print Network

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

Erdmann, Martin

401

Dynamic Resource Management in Energy Constrained Heterogeneous Computing  

E-print Network

Dynamic Resource Management in Energy Constrained Heterogeneous Computing Systems Using Voltage and to a mathematical bound. Index Terms--Ad hoc, distributed heterogeneous computing, dynamic resource allocation/management management system (RMS) takes care of allocating resources of a certain system. The power management aspect

Maciejewski, Anthony A.

402

A CONSTRAINED GROWTH METHOD FOR PROCEDURAL FLOOR PLAN GENERATION  

E-print Network

A CONSTRAINED GROWTH METHOD FOR PROCEDURAL FLOOR PLAN GENERATION Ricardo Lopes1 , Tim Tutenel1, The Hague, the Netherlands KEYWORDS Virtual worlds, procedural modeling, floor plan genera- tion ABSTRACT Modern games often feature highly detailed urban envi- ronments. However, buildings are typically

Bidarra, Rafael

403

College Student Perceptions of Leadership: Empowering and Constraining Beliefs  

ERIC Educational Resources Information Center

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

Shertzer, John E.; Schuh, John H.

2004-01-01

404

Constrained optimization schemes for geophysical inversion of seismic data  

NASA Astrophysics Data System (ADS)

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

Sosa Aguirre, Uram Anibal

405

Synthesis of conformationally-constrained stereospecific analogs of glutamic acid as antagonists of metabotropic receptors  

Microsoft Academic Search

Rigid analogs of ACPD have been synthesized to mimick different potential conformations of ACPD in aqueous solution. One of them, (±)-ABHD-I is a competitive antagonist at mGluR1a receptor with a KB value of 300 ?M.

Frédérique Tellier; Francine Acher; Isabelle Brabet; Jean-Philippe Pin; Joël Bockaert; Robert Azerad

1995-01-01

406

How well do different tracers constrain the firn diffusivity profile?  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

407

Acid Rain  

NSDL National Science Digital Library

Due to the presence of dissolved gases such as carbon dioxide, rainfall is naturally acidic. The release of other gases and chemicals such as sulfur dioxide during the combustion of coal and oil can cause rainfall to become even more acidic, sometimes to the point of toxicity. In this activity, students will measure the pH of local rainfall to see what effect these gases have in their region. They will also check an online resource to see how the releases of acid rain-causing chemicals have varied over the past 20 years, and answer questions about the information they uncover.

Chris Fox

408

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

PubMed

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

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

2011-01-15

409

Changes of extracellular calcium concentration induced by application of excitatory amino acids in the human neocortex in vitro.  

PubMed

The influence of the glutamate subreceptor agonists N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) on cortical field potentials and on changes in extracellular free calcium concentration ([Ca2+]o) was tested on human neocortical slices (eleven from nine different patients). The tissue used was a small portion of that which is normally removed for the treatment of a brain tumor. [Ca2+]o and field potentials were measured by Ca(2+)-selective microelectrodes. Local pressure-microejection of NMDA (100 mumol/l)- and AMPA (1 mmol/l)-induced negative field potentials with maximal amplitudes of 0.9 +/- 0.1 mV (11 slices, mean +/- S.E.M.) and 1.0 +/- 0.1 mV (nine slices), respectively. The negative field potentials induced by NMDA were accompanied by monophasic decreases of [Ca2+]o (0.8 +/- 0.1 mmol/l, nine slices). AMPA elicited no (three slices) or only minor decreases of [Ca2+]o (0.2 +/- 0.1 mmol/l, five slices). The responses to the glutamate subreceptor agonists NMDA and AMPA were reversibly depressed by adding their specific antagonists DL-2-amino-5-phosphonovalerate (APV, 100 mumol/l, six slices) and 6-cyano-7-nitroquinoxalin-2,3-dion (CNQX, 5 mumol/l, four slices), respectively. The results correspond to findings in animal experiments and are consistent with the interpretation that in the human neocortex the Ca2+ permeability of channels gated by NMDA is higher than those gated by AMPA. PMID:7538028

Lücke, A; Köhling, R; Straub, H; Moskopp, D; Wassmann, H; Speckmann, E J

1995-02-13

410

Carboxylic acid-modified polyethylene: a novel support for the covalent immobilization of polypeptides for C-terminal sequencing.  

PubMed Central

We have developed a method for the covalent immobilization of peptides, for the purpose of C-terminal sequencing, to a novel solid support, carboxylic acid-modified polyethylene (PE-COOH) film. The peptides are attached by coupling the N-terminal amino group to the activated carboxyl groups of the film. Reagents for carboxyl group activation, including 1,3-dicyclohexylcarbodiimide (DCC), 1,1'-carbonyldiimidazole (CDI), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), benzotriazol-1-yl-oxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP), and 1,3-diisopropylcarbodiimide (DICD) were compared. The best yields were obtained with DCC for a variety of tested peptides and averaged approximately 50%. The covalent attachment at pH 6.7 of peptides was shown to occur predominantly thorough the alpha-amino group for the peptide, SIGSLAK, which after attachment to the PE-COOH support permitted the C-terminal lysine residue to be sequenced in good yield, indicating that the epsilon-amino group of lysine is not covalently attached. This support offers a number of advantages over other solid supports, such as silica and polyvinylidene difluoride, for C-terminal sequencing including (1) stability to base and the high temperatures (65 degrees C) employed for C-terminal sequencing, (2) wettability with both aqueous and organic solvents, (3) a high capacity (1.6 nmol/mm2) for covalent coupling of polypeptides, and (4) easy divisibility into 1 x 5-mm pieces for use in our continuous flow reactor (CFR), which is also used for automated N-terminal sequencing (Shively, J.E., Miller, P., & Ronk, M., 1987, Anal. Biochem. 163, 517-529). Automated C-terminal sequencing on these supports is described in the companion paper (Bailey, J.M., Shenoy, N.R., Ronk, M., & Shively, J.E., 1992, Protein Sci. 1, 68-80). PMID:1304883

Shenoy, N. R.; Bailey, J. M.; Shively, J. E.

1992-01-01

411

ACID RAIN  

EPA Science Inventory

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

412

Acid Reflux  

MedlinePLUS

... time. This stomach juice consists of acid, digestive enzymes, and other injurious materials. The prolonged contact of ... role in absorption of vitamins (Vitamin B12), the digestion of proteins, and initiation of peristalsis which causes the food ...

413

Acidic precipitation  

SciTech Connect

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

Martin, H.C.

1987-01-01

414

Acidizing wells  

Microsoft Academic Search

A method of increasing the permeability of a rock formation by acidizing is applicable to silicate-bearing formations containing alkaline-earth-metal ions and alkali- metal ions which would have a reducing effect on the permeability of the formation. A carbonate solution is injected into the formation to convert any calcium sulfate to calcium carbonate. This is followed by injecting hydrochloric acid to

1966-01-01

415

Lilith: a tool for constraining new physics from Higgs measurements  

E-print Network

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

Jeremy Bernon; Beranger Dumont

2015-03-05

416

Constraining the characteristics of tsunami waves from deformable submarine slides  

NASA Astrophysics Data System (ADS)

As a marine hazard, submarine slope failures have the potential to directly destroy offshore infrastructure, and, if a tsunami is generated, it also endangers the life of those who live and work at the coastline. The hazard and risk from tsunamis generated by submarine mass failure is difficult to quantify and evaluate due to the problems to constrain the characteristics of the triggered submarine landslide, which introduces unquantifiable uncertainty to hazard assessments based on numerical modelling. To lower the uncertainty, we present a method that determines material parameters for the slide body to constrain the generated tsunami waves. Our method employs the distribution of landslide run-out masses and their comparison with simulations. It assumes that the slide material can be approximated by bulk values during the slide motion. To demonstrate our method, we make use of Valdes slide run-out masses off the Chilean coast.

Weiss, Robert; Krastel, Sebastian; Anasetti, Andreas; Wünnemann, Kai

2013-07-01

417

On constrained and regularized high-dimensional regression *  

PubMed Central

High-dimensional feature selection has become increasingly crucial for seeking parsimonious models in estimation. For selection consistency, we derive one necessary and sufficient condition formulated on the notion of degree-of-separation. The minimal degree of separation is necessary for any method to be selection consistent. At a level slightly higher than the minimal degree of separation, selection consistency is achieved by a constrained L0-method and its computational surrogate–the constrained truncated L1-method. This permits up to exponentially many features in the sample size. In other words, these methods are optimal in feature selection against any selection method. In contrast, their regularization counterparts–the L0-regularization and truncated L1-regularization methods enable so under slightly stronger assumptions. More importantly, sharper parameter estimation/prediction is realized through such selection, leading to minimax parameter estimation. This, otherwise, is impossible in absence of a good selection method for high-dimensional analysis. PMID:24465052

Shen, Xiaotong; Pan, Wei; Zhu, Yunzhang; Zhou, Hui

2013-01-01

418

Mutualism meltdown in insects: Bacteria constrain thermal adaptation  

PubMed Central

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

Wernegreen, Jennifer J.

2013-01-01

419

Assessing working memory capacity through time-constrained elementary activities.  

PubMed

Working memory (WM) capacity measured through complex span tasks is among the best predictors of fluid intelligence (Gf). These tasks usually involve maintaining memoranda while performing complex cognitive activities that require a rather high level of education (e.g., reading comprehension, arithmetic), restricting their range of applicability. Because individual differences in such complex activities are nothing more than the concatenation of small differences in their elementary constituents, complex span tasks involving elementary processes should be as good of predictors of Gf as traditional tasks. The present study showed that two latent variables issued from either traditional or new span tasks involving time-constrained elementary activities were similarly correlated with Gf. Moreover, a model with a single unitary WM factor had a similar fit as a model with two distinct WM factors. Thus, time-constrained elementary activities can be integrated in WM tasks, permitting the assessment of WM in a wider range of populations. PMID:24846786

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

2014-01-01

420

Fractal Dimension of Geologically Constrained Crater Populations of Mercury  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

421

Cone-Constrained Continuous-Time Markowitz Problems  

E-print Network

The Markowitz problem consists of finding in a financial market a self-financing trading strategy whose final wealth has maximal mean and minimal variance. We study this in continuous time in a general semimartingale model and under cone constraints: Trading strategies must take values in a (possibly random and time-dependent) closed cone. We first prove existence of a solution for convex constraints by showing that the space of constrained terminal gains, which is a space of stochastic integrals, is closed in L^2. Then we use stochastic control methods to describe the local structure of the optimal strategy, as follows. The value process of a naturally associated constrained linear-quadratic optimal control problem is decomposed into a sum with two opportunity processes L^{\\pm} appearing as coefficients. The martingale optimality principle translates into a drift condition for the semimartingale characteristics of L^{\\pm} or equivalently into a coupled system of backward stochastic differential equations for...

Czichowsky, Christoph

2012-01-01

422

Image coding using entropy-constrained residual vector quantization  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

423

An Automated Translator for Model Checking Time Constrained Workflow Systems  

NASA Astrophysics Data System (ADS)

Workflows have proven to be a useful conceptualization for the automation of business processes. While formal verification methods (e.g., model checking) can help ensure the reliability of workflow systems, the industrial uptake of such methods has been slow largely due to the effort involved in modeling and the memory required to verify complex systems. Incorporation of time constraints in such systems exacerbates the latter problem. We present an automated translator, YAWL2DVE-t, which takes as input a time constrained workflow model built with the graphical modeling tool YAWL, and outputs the model in DVE, the system specification language for the distributed LTL model checker DiVinE. The automated translator, together with the graphical editor and the distributed model checker, provides a method for rapid design, verification and refactoring of time constrained workflow systems. We present a realistic case study developed through collaboration with the local health authority.

Mashiyat, Ahmed Shah; Rabbi, Fazle; Wang, Hao; Maccaull, Wendy

424

Constraining the Noncommutative Spectral Action via Astrophysical Observations  

SciTech Connect

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

Nelson, William; Ochoa, Joseph; Sakellariadou, Mairi [Institute of Gravitation and the Cosmos, Penn State University, State College, Pennsylvania 16801 (United States); Department of Physics, King's College, University of London, Strand WC2R 2LS, London (United Kingdom)

2010-09-03

425

The SL(2,R) totally constrained model: three quantization approaches  

E-print Network

We provide a detailed comparison of the different approaches available for the quantization of a totally constrained system with a constraint algebra generating the non-compact $SL(2,\\mathbb{R})$ group. In particular, we consider three schemes: the Refined Algebraic Quantization, the Master Constraint Programme and the Uniform Discretizations approach. For the latter, we provide a quantum description where we identify semiclassical sectors of the kinematical Hilbert space. We study the quantum dynamics of the system in order to show that it is compatible with the classical continuum evolution. Among these quantization approaches, the Uniform Discretizations provides the simpler description in agreement with the classical theory of this particular model, and it is expected to give new insights about the quantum dynamics of more realistic totally constrained models such as canonical general relativity.

Rodolfo Gambini; Javier Olmedo

2014-07-22

426

Lilith: a tool for constraining new physics from Higgs measurements  

E-print Network

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

Bernon, Jeremy

2015-01-01

427

Spectral finite-element methods for parametric constrained optimization problems.  

SciTech Connect

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

Anitescu, M.; Mathematics and Computer Science

2009-01-01

428

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

NASA Technical Reports Server (NTRS)

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

Vanderplaats, G. N.

1973-01-01

429

Topoisomerase V relaxes supercoiled DNA by a constrained swiveling mechanism  

PubMed Central

Topoisomerase V is a type I topoisomerase without structural or sequence similarities to other topoisomerases. Although it belongs to the type I subfamily of topoisomerases, it is unrelated to either type IA or IB enzymes. We used real-time single-molecule micromechanical experiments to show that topoisomerase V relaxes DNA via events that release multiple DNA turns, employing a constrained swiveling mechanism similar to that for type IB enzymes. Relaxation is powered by the torque in the supercoiled DNA and is constrained by friction between the protein and the DNA. Although all type IB enzymes share a common structure and mechanism and type IA and type II enzymes show marked structural and functional similarities, topoisomerase V represents a different type of topoisomerase that relaxes DNA in a similar overall manner as type IB molecules but by using a completely different structural and mechanistic framework. PMID:17804808

Taneja, Bhupesh; Schnurr, Bernhard; Slesarev, Alexei; Marko, John F.; Mondragón, Alfonso

2007-01-01

430

Effect of surface induced nucleation of ferroelastic domains on polarization switching in constrained ferroelectrics  

E-print Network

Effect of surface induced nucleation of ferroelastic domains on polarization switching polarization switching in constrained ferroelectrics is investigated using the time-dependent Ginzburg. A square-shaped finite sized constrained ferroelectric system with vanishing surface polarization

Cao, Wenwu

431

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

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Finger joint metal/metal constrained uncemented prosthesis. 888.3200 Section...DEVICES Prosthetic Devices § 888.3200 Finger joint metal/metal constrained uncemented prosthesis. (a)...

2011-04-01

432

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

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Finger joint metal/metal constrained cemented prosthesis. 888.3210 Section...DEVICES Prosthetic Devices § 888.3210 Finger joint metal/metal constrained cemented prosthesis. (a)...

2013-04-01

433

21 CFR 888.3550 - Knee joint patellofemorotibial polymer/metal/metal constrained cemented prosthesis.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Knee joint patellofemorotibial polymer/metal/metal constrained cemented prosthesis. 888.3550 Section...888.3550 Knee joint patellofemorotibial polymer/metal/metal constrained cemented prosthesis. (a)...

2013-04-01

434

21 CFR 888.3550 - Knee joint patellofemorotibial polymer/metal/metal constrained cemented prosthesis.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 false Knee joint patellofemorotibial polymer/metal/metal constrained cemented prosthesis. 888.3550 Section...888.3550 Knee joint patellofemorotibial polymer/metal/metal constrained cemented prosthesis. (a)...

2014-04-01

435

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

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Finger joint metal/metal constrained cemented prosthesis. 888.3210 Section...DEVICES Prosthetic Devices § 888.3210 Finger joint metal/metal constrained cemented prosthesis. (a)...

2014-04-01

436

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

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Finger joint metal/metal constrained uncemented prosthesis. 888.3200 Section...DEVICES Prosthetic Devices § 888.3200 Finger joint metal/metal constrained uncemented prosthesis. (a)...

2012-04-01

437

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

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Finger joint metal/metal constrained cemented prosthesis. 888.3210 Section...DEVICES Prosthetic Devices § 888.3210 Finger joint metal/metal constrained cemented prosthesis. (a)...

2010-04-01

438

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

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Knee joint femorotibial metal/composite non-constrained...DEVICES Prosthetic Devices § 888.3490 Knee joint femorotibial metal/composite non-constrained...prosthesis. (a) Identification. A knee joint femorotibial...

2014-04-01

439

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

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Knee joint femorotibial metal/composite semi-constrained...DEVICES Prosthetic Devices § 888.3500 Knee joint femorotibial metal/composite semi-constrained...prosthesis. (a) Identification. A knee joint femorotibial...

2014-04-01

440

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

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Knee joint femorotibial metal/composite semi-constrained...DEVICES Prosthetic Devices § 888.3500 Knee joint femorotibial metal/composite semi-constrained...prosthesis. (a) Identification. A knee joint femorotibial...

2012-04-01

441

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

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Knee joint femorotibial metal/composite non-constrained...DEVICES Prosthetic Devices § 888.3490 Knee joint femorotibial metal/composite non-constrained...prosthesis. (a) Identification. A knee joint femorotibial...

2013-04-01

442

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

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Knee joint femorotibial metal/composite non-constrained...DEVICES Prosthetic Devices § 888.3490 Knee joint femorotibial metal/composite non-constrained...prosthesis. (a) Identification. A knee joint femorotibial...

2012-04-01

443

Edinburgh Research Explorer Space-based formaldehyde measurements as constrains on  

E-print Network

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

Millar, Andrew J.

444

21 CFR 888.3530 - Knee joint femorotibial metal/polymer semi-constrained cemented prosthesis.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Knee joint femorotibial metal/polymer semi-constrained...Devices § 888.3530 Knee joint femorotibial metal/polymer semi-constrained...Identification. A knee joint femorotibial metal/polymer...

2011-04-01

445

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

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Knee joint femorotibial metal/composite non-constrained...Devices § 888.3490 Knee joint femorotibial metal/composite non-constrained...Identification. A knee joint femorotibial metal/composite...

2011-04-01

446

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

Code of Federal Regulations, 2011 CFR

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

2011-04-01

447

21 CFR 888.3520 - Knee joint femorotibial metal/polymer non-constrained cemented prosthesis.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Knee joint femorotibial metal/polymer non-constrained...Devices § 888.3520 Knee joint femorotibial metal/polymer non-constrained...Identification. A knee joint femorotibial metal/polymer...

2011-04-01

448

EFFICIENT ALGORITHMS FOR SEVERAL CONSTRAINED RESOURCE ALLOCATION, MANAGEMENT AND DISCOVERY PROBLEMS  

E-print Network

EFFICIENT ALGORITHMS FOR SEVERAL CONSTRAINED RESOURCE ALLOCATION, MANAGEMENT AND DISCOVERY PROBLEMS for several constrained resource allocation, management and discovery problems. We consider new types, business planning, distributed computing, and so on. Many resource allocation, management and discovery

Paris-Sud XI, Université de

449

A Distributed Optimization Approach to Constrained OSNR Problem  

Microsoft Academic Search

This paper studies constrained optical signal-to-noise ratio (OSNR) problem via a distributed optimization approach. In multi-channel optical systems, the signal over an optical link can be regarded as an interfering noise for others, which leads to OSNR degradation. Regulating the input optical power at the Source (transmitter) aims to achieve satisfactory OSNR level at the Destination (receiver) for each channel.

Yan Pan; Tansu Alpcan; Lacra Pavel

2008-01-01

450

Constrained Protein Docking with Chemera 3.0  

Microsoft Academic Search

Chemera 3.0 is a molecular modelling software package that includes BiGGER (Bimolecular complex Generation with Global Evaluation and Ranking), a protein docking algorithm (1,2). This paper focuses on new features of Chemera 3.0, specially constrained docking, which allows the user to restrict the search for protein-protein complex models in a manner consistent with the ambiguity of some experimental data. This

Ludwig Krippahl; Pedro Barahona; José J. G. Moura

451

The delay-constrained minimum spanning tree problem  

Microsoft Academic Search

We formulate the problem of constructing broadcast trees for real-time traffic with delay constraints in networks with asymmetric link loads as a delay-constrained minimum spanning tree (DCMST) problem in directed networks. Then, we prove that this problem is NP-complete, and we propose an efficient heuristic to solve the problem based on Prim's algorithm for the unconstrained minimum spanning tree problem.

Hussein F. Salama; Douglas S. Reeves; Yannis Viniotis

1997-01-01

452

Constraining Sn Ia Progenitor Scenarios with SNLS Time Series  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

453

Jamming transition in kinetically constrained models with reflection symmetry  

E-print Network

A class of kinetically constrained models with reflection symmetry is proposed as an extension of the Fredrickson-Andersen model. It is proved that the proposed model on the square lattice exhibits a freezing transition at a non-trivial density. It is conjectured by numerical experiments that the known mechanism of the singular behaviors near the freezing transition in a previously studied model (spiral model) is not responsible for that in the proposed model.

Hiroki Ohta; Shin-ichi Sasa

2014-04-30

454

Jamming Transition in Kinetically Constrained Models with Reflection Symmetry  

NASA Astrophysics Data System (ADS)

A class of kinetically constrained models with reflection symmetry is proposed as an extension of the Fredrickson-Andersen model. It is proved that the proposed model on the square lattice exhibits a freezing transition at a non-trivial density. It is conjectured by numerical experiments that the known mechanism of the singular behaviors near the freezing transition in a previously studied model (spiral model) is not responsible for that in the proposed model.

Ohta, Hiroki; Sasa, Shin-ichi

2014-06-01

455

An algorithm for solving control constrained optimal control problems  

Microsoft Academic Search

An algorithm, with an approach similar to the Han-Powell method in finite-dimensional optimization, is devised to solve continuous-time optimal control problems where the control variables are constrained. The algorithm is based on a second-order approximation to the change of the cost functional due to a change in the control. Further approximation of that summation produces a simple convex functional. It

Baoming Ma; W. S. Levine

1993-01-01

456

An Array Beampattern Synthesis Using Partial Constrained Adaptive Optimization  

NASA Astrophysics Data System (ADS)

One of the prominent studies conducted on the beamforming method is the Zhou and Ingram weighting function method. This method adaptively adjusts the weights of an array to meet the desired mainlobe beamwidth and sidelobe level. However, with the Zhou and Ingram method, it took up a considerably long computation time to adjust the desired sidelobe level. Therefore, in this paper, we propose a new algorithm using partially constrained adaptation which allows us to circumvent this problem and easily meet the design specification.

Jun, Byung Doo; Lim, Jun-Seok; Sung, Koeng-Mo

2007-07-01

457

On the chemical equilibrium concept: Constrained word associations and conception  

Microsoft Academic Search

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

Esther Gussarsky; Malka Gorodetsky

1988-01-01

458

Hybrid quantum-classical models as constrained quantum systems  

E-print Network

Constrained Hamiltonian description of the classical limit is utilized in order to derive consistent dynamical equations for hybrid quantum-classical systems. Starting with a compound quantum system in the Hamiltonian formulation conditions for classical behavior are imposed on one of its subsystems and the corresponding hybrid dynamical equations are derived. The presented formalism suggests that the hybrid systems have properties that are not exhausted by those of quantum and classical systems.

M. Radonjic; S. Prvanovic; N. Buric

2012-06-07

459

Asynchronous parallel generating set search for linearly-constrained optimization.  

SciTech Connect

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

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

2007-04-01

460

Constraining Models of Postglacial Rebound Using Space Geodesy  

NASA Astrophysics Data System (ADS)

We are using observations from five space techniques (VLBI, SLR, GPS, DORIS, and GRACE) to (1) determine the character of Earth's viscous response to unloading of the ice sheets 5 to 20 thousand years ago, and (2) constrain models of postglacial rebound determined primarily from Holocene estimates of relative sea level and geophysical observations of Earth's spin and shape. The horizontal estimates of site velocity are constraining the postglacial rebound model. Places along the margins of the former Laurentide and Fennoscandia ice sheets are moving horizontally away from the centers at about 1 millimeter per year, at the speed predicted by the model of Peltier [1994], but significantly slower than the speeds predicted by the models of Peltier [1996] and Peltier [2004]. The parts of Antarctic, Eurasian, and North American plate interiors neither beneath nor along the margins of the former ice sheets are hardly deforming at all, allowing the angular velocity of the plates to be estimated meaningfully. The vertical estimates of site velocity are also constraining the postglacial rebound model. Algonquin Park (Ontario) is rising at 2.5 millimeters per year and Yellowknife (Northwest Territories) at 6 millimeters per year, constraining the thickness of the Laurentia ice sheet 20 thousand years ago. The eastern and central United States is subsiding at 1 to 2 millimeter per year, at about the speeds predicted by the models of Peltier [1994], Peltier [1996], and Peltier [2004]. We are attempting to modify the ice sheet thickness, mantle viscosity, and elastic lithospheric thickness in the model to fit all geodetic and geologic observations. We are furthermore quantifying the uncertainty in estimates of vertical velocity due to uncertainty in the velocity of Earth's center.

Argus, D. F.; Peltier, W.

2008-12-01

461

Bound constrained quadratic programming via piecewise quadratic functions  

Microsoft Academic Search

1  , the smallest eigenvalue of a symmetric, positive definite matrix, and is solved by Newton iteration with line search. The\\u000a paper describes the algorithm and its implementation including estimation of ?1, how to get a good starting point for the iteration, and up- and downdating of Cholesky factorization. Results of extensive\\u000a testing and comparison with other methods for constrained QP

Kaj Madsen; Hans Bruun Nielsen; Mustafa Ç. P?nar

1999-01-01

462

Constraining effective rheology through parallel joint geodynamic inversion  

NASA Astrophysics Data System (ADS)

The dynamics of crust and lithosphere is to a large extent controlled by its effective viscosity. Unfortunately, extrapolation of laboratory experiments indicates that viscosity is likely to vary over many orders of magnitude. Additional methods are thus required to constrain the effective viscosity of the present-day lithosphere using more direct geophysical observations. Here we discuss a method, which couples 3D geodynamic models with observations (surface velocities and gravity anomalies) and with a Bayesian inversion scheme on massively parallel high performance computers. We illustrate that the basic principle of a joint geodynamic and gravity inversion works well with a simple analytical example. In a next step, we test our approach using a synthetic 3D model of salt tectonics with erosion and sedimentation, and check how much noise conditions, model resolution, and sparse data coverage affect the resolving power of the method. Results show that it is possible to constrain the effective viscosity and density of layers that contribute to the large-scale dynamics, provided that those layers are numerically well resolved. The properties of thin layers that do not contribute much to the overall dynamics cannot be constrained, but noise or sparse data sampling does not significantly affect the inversion results. This thus illustrates that a joint geodynamic and gravity inversion is a potentially powerful method to constrain the dynamics of the crust and lithosphere. Having better constraints on the structure of the present-day crust and lithosphere will help to narrow the parameter space for models that aim to unravel lithosphere dynamics on a geological time scale.

Baumann, Tobias S.; Kaus, Boris J. P.; Popov, Anton A.

2014-09-01

463

Simulations of the Local Universe constrained by observational peculiar velocities  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

464

Constrained geometric simulation of the nicotinic acetylcholine receptor.  

PubMed

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

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

2014-07-01

465

Anti-B-B Mixing Constrains Topcolor-Assisted Technicolor  

SciTech Connect

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

Burdman, Gustavo; Lane, Kenneth; Rador, Tonguc

2000-12-06

466

Control of the constrained planar simple inverted pendulum  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

467

Constrained TV-minimization image reconstruction for industrial CT system  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

468

Groundwater availability as constrained by hydrogeology and environmental flows.  

PubMed

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

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

2014-01-01

469

Constrained novelty search: a study on game content generation.  

PubMed

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

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

2015-01-01

470

Robust initialization of a Jordan network with recurrent constrained learning.  

PubMed

In this paper, we propose a robust initialization of a Jordan network with a recurrent constrained learning (RIJNRCL) algorithm for multilayered recurrent neural networks (RNNs). This novel algorithm is based on the constrained learning concept of the Jordan network with a recurrent sensitivity and weight convergence analysis, which is used to obtain a tradeoff between the training and testing errors. In addition to using classical techniques for the adaptive learning rate and the adaptive dead zone, RIJNRCL employs a recurrent constrained parameter matrix to switch off excessive contributions from the hidden layer neurons based on weight convergence and stability conditions of the multilayered RNNs. It is well known that a good response from the hidden layer neurons and proper initialization play a dominant role in avoiding local minima in multilayered RNNs. The new RIJNRCL algorithm solves the twin problems of weight initialization and selection of the hidden layer neurons via a novel recurrent sensitivity ratio analysis. We provide the detailed steps for using RIJNRCL in a few benchmark time-series prediction problems and show that the proposed algorithm achieves superior generalization performance. PMID:21965202

Song, Qing

2011-12-01

471

Constraining Solar Flare Differential Emission Measures with EVE and RHESSI  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

472

Uric acid - urine  

MedlinePLUS

The urine uric acid test measures the level of uric acid in urine. Uric acid level can also be checked using a blood ... to choose the best medicine to lower uric acid level in the blood. Uric acid is a ...

473

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

Code of Federal Regulations, 2014 CFR

... 2014-04-01 false Ankle joint metal/polymer non-constrained cemented prosthesis...Prosthetic Devices § 888.3120 Ankle joint metal/polymer non-constrained cemented prosthesis...a) Identification. An ankle joint metal/polymer non-constrained...

2014-04-01

474

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

Code of Federal Regulations, 2012 CFR

... 2012-04-01 false Ankle joint metal/polymer non-constrained cemented prosthesis...Prosthetic Devices § 888.3120 Ankle joint metal/polymer non-constrained cemented prosthesis...a) Identification. An ankle joint metal/polymer non-constrained...

2012-04-01

475

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

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Ankle joint metal/polymer semi-constrained... § 888.3110 Ankle joint metal/polymer semi-constrained...Identification. An ankle joint metal/polymer semi-constrained...that have a talar resurfacing component made of alloys, such as...

2013-04-01

476

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

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Ankle joint metal/polymer semi-constrained... § 888.3110 Ankle joint metal/polymer semi-constrained...Identification. An ankle joint metal/polymer semi-constrained...that have a talar resurfacing component made of alloys, such as...

2012-04-01

477

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

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Hip joint metal/composite semi-constrained...Devices § 888.3340 Hip joint metal/composite semi-constrained...Identification. A hip joint metal/composite semi-constrained...prostheses that consist of a femoral component made of alloys, such as...

2011-04-01

478

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

Code of Federal Regulations, 2014 CFR

...2014-04-01 false Ankle joint metal/polymer semi-constrained... § 888.3110 Ankle joint metal/polymer semi-constrained...Identification. An ankle joint metal/polymer semi-constrained...that have a talar resurfacing component made of alloys, such as...

2014-04-01

479

MC2: High-Performance Garbage Collection for Memory-Constrained Environments  

E-print Network

for memory-constrained con- sumer devices such as PDAs and cellular phones, because it provides safetyMC2: High-Performance Garbage Collection for Memory-Constrained Environments Narendran Sachindran J and portability. Since Java uses garbage collection, efficient garbage collectors that run in constrained memory

Berger, Emery

480

A Gibbs sampler for inequality-constrained geostatistical interpolation and inverse modeling  

E-print Network

A Gibbs sampler for inequality-constrained geostatistical interpolation and inverse modeling Anna M. M. (2008), A Gibbs sampler for inequality-constrained geostatistical interpolation and inverse to inequality-constrained data and parameters. The approach is to be applicable with any variogram or covariance

Michalak, Anna M.

481

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

E-print Network

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

West, Mike

482

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

Code of Federal Regulations, 2010 CFR

... 2010-04-01 false Ankle joint metal/polymer non-constrained cemented prosthesis...Prosthetic Devices § 888.3120 Ankle joint metal/polymer non-constrained cemented prosthesis...a) Identification. An ankle joint metal/polymer non-constrained...

2010-04-01

483

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

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Ankle joint metal/polymer semi-constrained cemented prosthesis...Devices § 888.3110 Ankle joint metal/polymer semi-constrained cemented prosthesis...Identification. An ankle joint metal/polymer semi-constrained cemented...

2010-04-01

484

Cost function for neutralizing acidic Adirondack surface waters  

SciTech Connect

A cost function for neutralizing acidic surface waters by base addition (liming) is derived based upon constrained cost minimization. The model is estimated using a sample of 547 acidic Adirondack lakes with total costs projected for neutralizing each lake to one of six possible target alkalinity levels. Empirical findings indicate that relatively accurate forecasts of lake neutralization costs can be obtained given target alkalinity levels and various limnological characteristics. The results provide a model for predicting lake neutralization costs which can potentially be used in evaluating the relative merits of alternative strategies for reducing acidic deposition damages. 13 references.

Dutkowsky, D.; Menz, F.C.

1985-09-01

485

Salicylic acids  

PubMed Central

Salicylic acid is well known phytohormone, emerging recently as a new paradigm of an array of manifestations of growth regulators. The area unleashed yet encompassed the applied agriculture sector to find the roles to strengthen the crops against plethora of abiotic and biotic stresses. The skipped part of integrated picture, however, was the evolutionary insight of salicylic acid to either allow or discard the microbial invasion depending upon various internal factors of two interactants under the prevailing external conditions. The metabolic status that allows the host invasion either as pathogenesis or symbiosis with possible intermediary stages in close systems has been tried to underpin here. PMID:22301975

Hayat, Shamsul; Irfan, Mohd; Wani, Arif; Nasser, Alyemeni; Ahmad, Aqil

2012-01-01

486

Acid Stomach  

NSDL National Science Digital Library

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

Science Netlinks

2003-08-07

487

Prior image constrained image reconstruction in emerging computed tomography applications  

NASA Astrophysics Data System (ADS)

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

Brunner, Stephen T.

488

Amino Acid Metabolism Conflicts with Protein Diversity  

PubMed Central

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

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

2014-01-01

489

21 CFR 888.3640 - Shoulder joint metal/metal or metal/polymer constrained cemented prosthesis.  

Code of Federal Regulations, 2013 CFR

...Shoulder joint metal/metal or metal/polymer constrained cemented prosthesis. 888...Shoulder joint metal/metal or metal/polymer constrained cemented prosthesis. ...shoulder joint metal/metal or metal/polymer constrained cemented...

2013-04-01

490

21 CFR 888.3640 - Shoulder joint metal/metal or metal/polymer constrained cemented prosthesis.  

Code of Federal Regulations, 2010 CFR

...Shoulder joint metal/metal or metal/polymer constrained cemented prosthesis. 888...Shoulder joint metal/metal or metal/polymer constrained cemented prosthesis. ...shoulder joint metal/metal or metal/polymer constrained cemented...

2010-04-01

491

Acid Rain  

NSDL National Science Digital Library

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

492

Acid rain  

SciTech Connect

An overview is presented of acid rain and the problems it causes to the environment worldwide. The acidification of lakes and streams is having a dramatic effect on aquatic life. Aluminum, present in virtually all forest soils, leaches out readily under acid conditions and interferes with the gills of all fish, some more seriously than others. There is evidence of major damage to forests in European countries. In the US, the most severe forest damage appears to be in New England, New York's Adirondacks, and the central Appalachians. This small region is part of a larger area of the Northeast and Canada that appears to have more acid rainfall than the rest of the country. It is downwind from major coal burning states, which produce about one quarter of US SO/sub 2/ emissions and one sixth of nitrogen oxide emissions. Uncertainties exist over the causes of forest damage and more research is needed before advocating expensive programs to reduce rain acidity. The President's current budget seeks an expansion of research funds from the current $30 million per year to $120 million.

Not Available

1984-06-01

493

Amino Acids  

NSDL National Science Digital Library

The Featured Molecules this month are the 20 standard ?-amino acids found in proteins and serve as background to the paper by Barone and Schmidt on the Nonfood Applications of Proteinaceous Renewable Materials. The molecules are presented in two formats, the neutral form and the ionized form found in solution at physiologic pH.

494

Acid Attack  

NSDL National Science Digital Library

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

Integrated Teaching and Learning Program,

495

Pharmacology of oleanolic acid and ursolic acid  

Microsoft Academic Search

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

Jie Liu

1995-01-01

496

CONSTRAINING PERTURBATIVE EARLY DARK ENERGY WITH CURRENT OBSERVATIONS  

SciTech Connect

In this work, we study a class of early dark energy (EDE) models, in which, unlike in standard dark energy models, a substantial amount of dark energy exists in the matter-dominated era. We self-consistently include dark energy perturbations, and constrain these models using current observations. We consider EDE models in which the dark energy equation of state is at least w{sub m} {approx_gt} -0.1 at early times, which could lead to an EDE density of up to {Omega}{sub DE}(z{sub CMB})= 0.03{Omega}{sub m}(z{sub CMB}). Our analysis shows that marginalizing over the non-DE parameters such as {Omega}{sub m}, H{sub 0}, andn{sub s} , current CMB observations alone can constrain the scale factor of transition from EDE to late-time dark energy to a{sub t} {approx_gt} 0.44 and width of transition to {Delta}{sub t} {approx_lt} 0.37. The equation of state at present is somewhat weakly constrained to w{sub 0} {approx_lt} -0.6, if we allow H{sub 0} < 60 km s{sup -1} Mpc{sup -1}. Taken together with other observations, such as SNe, Hubble Space Telescope, and Sloan Digital Sky Survey luminous red galaxies, w{sub 0} is constrained much more tightly to w{sub 0} {approx_lt} -0.9, while redshift of transition and width of transition are also tightly constrained to a{sub t} {approx_lt} 0.19 and{Delta}{sub t} {approx_lt} 0.21. The evolution of the equation of state for EDE models is thus tightly constrained to {Lambda}CDM-like behavior at low redshifts. Incorrectly assuming dark energy perturbations to be negligible leads to different constraints on the equation of state parameters-w{sub 0} {approx_lt} -0.8, a{sub t} {approx_lt} 0.33, and{Delta}{sub t} {approx_lt} 0.31, thus highlighting the necessity of self-consistently including dark energy perturbations in the analysis. If we allow the spatial curvature to be a free parameter, then the constraints are relaxed to w{sub 0} {approx_lt} -0.77, a{sub t} {approx_lt} 0.35, and{Delta}{sub t} {approx_lt} 0.35 with -0.014 < {Omega}{sub {kappa}} < 0.031 for CMB + other observations. For perturbed EDE models, the 2{sigma} lower limit on {sigma}{sub 8} ({sigma}{sub 8} {>=} 0.59) is much lower than that in {Lambda}CDM ({sigma}{sub 8} {>=} 0.72), thus raising the interesting possibility of discriminating EDE from {Lambda}CDM using future observations such as halo mass functions or the Sunyaev-Zeldovich power spectrum.

Alam, Ujjaini [ISR-1, ISR Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2010-05-10

497

Constrained dynamics approach for motion synchronization and consensus  

NASA Astrophysics Data System (ADS)

In this research we propose to develop constrained dynamical systems based stable attitude synchronization, consensus and tracking (SCT) control laws for the formation of rigid bodies. The generalized constrained dynamics Equations of Motion (EOM) are developed utilizing constraint potential energy functions that enforce communication constraints. Euler-Lagrange equations are employed to develop the non-linear constrained dynamics of multiple vehicle systems. The constraint potential energy is synthesized based on a graph theoretic formulation of the vehicle-vehicle communication. Constraint stabilization is achieved via Baumgarte's method. The performance of these constrained dynamics based formations is evaluated for bounded control authority. The above method has been applied to various cases and the results have been obtained using MATLAB simulations showing stability, synchronization, consensus and tracking of formations. The first case corresponds to an N-pendulum formation without external disturbances, in which the springs and the dampers connected between the pendulums act as the communication constraints. The damper helps in stabilizing the system by damping the motion whereas the spring acts as a communication link relaying relative position information between two connected pendulums. Lyapunov stabilization (energy based stabilization) technique is employed to depict the attitude stabilization and boundedness. Various scenarios involving different values of springs and dampers are simulated and studied. Motivated by the first case study, we study the formation of N 2-link robotic manipulators. The governing EOM for this system is derived using Euler-Lagrange equations. A generalized set of communication constraints are developed for this system using graph theory. The constraints are stabilized using Baumgarte's techniques. The attitude SCT is established for this system and the results are shown for the special case of three 2-link robotic manipulators. These methods are then applied to the formation of N-spacecraft. Modified Rodrigues Parameters (MRP) are used for attitude representation of the spacecraft because of their advantage of being a minimum parameter representation. Constrained non-linear equations of motion for this system are developed and stabilized using a Proportional-Derivative (PD) controller derived based on Baumgarte's method. A system of 3 spacecraft is simulated and the results for SCT are shown and analyzed. Another problem studied in this research is that of maintaining SCT under unknown external disturbances. We use an adaptive control algorithm to derive control laws for the actuator torques and develop an estimation law for the unknown disturbance parameters to achieve SCT. The estimate of the disturbance is added as a feed forward term in the actual control law to obtain the stabilization of a 3-spacecraft formation. The disturbance estimates are generated via a Lyapunov analysis of the closed loop system. In summary, the constrained dynamics method shows a lot of potential in formation control, achieving stabilization, synchronization, consensus and tracking of a set of dynamical systems.

Bhatia, Divya

498

Constraining a Possible Variation of G with Type Ia Supernovae  

NASA Astrophysics Data System (ADS)

Astrophysical cosmology constrains the variation of Newton's Constant in a manner complementary to laboratory experiments, such as the celebrated lunar laser ranging campaign. Supernova cosmology is an example of the former and has attained campaign status, following planning by a Dark Energy Task Force in 2005. In this paper, we employ the full SNIa data set to the end of 2013 to set a limit on G variation. In our approach, we adopt the standard candle delineation of the redshift distance relation. We set an upper limit on its rate of change |dot{G}/G| of 0.1 parts per billion per year over 9 Gyrs. By contrast, lunar laser ranging tests variation of G over the last few decades. Conversely, one may adopt the laboratory result as a prior and constrain the effect of variable G in dark energy equation of state exp