Página 1 dos resultados de 42710 itens digitais encontrados em 0.126 segundos

Study of copper complexes adsorbed on a silica gel surface chemically modified with 2-amino-1,3,4-thiadiazole

Dias, N. L.; Gushikem, Y.; Franco, D. W.; Schultz, M. S.; Vasconcellos, LCG
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 181-187
Português
Relevância na Pesquisa
551.37195%
The isotherms of adsorption of CuX2 (X=Cl-, Br-, ClO4-) by silica gel chemically modified with 2-amino-1,3,4-thiadiazole were studied in acetone and ethanol solutions: at 298 K. The following equilibria constants (in 1 mol(-1)) were determined: (a) CuCl2: 3.5 x 10(3) (ac), 2.0 x 10(3) (eth); (b) CuBr2: 2.8 x 10(3) (ac), 2.0 x 10(3) (eth); (c) Cu(ClO4)(2): 1.8 x 10(3) (ac), 1.0 x 10(3) (eth); ac = acetone, eth = ethanol. The electron spin resonance spectra of the surface complexes indicated a tetragonal distorted structure in the case of lower degrees of metal loading on the chemically modified surface. The d-d electronic transition spectra showed that for the ClO4-, complex, the peak of absorption did not change for any degree of metal loading, and for Cl- and Br- complexes, the peak maxima shifted to a higher energy region with a lower metal loading. (C) 1998 Elsevier B.V. B.V. All rights reserved.

Timed artificial insemination programs during the summer in lactating dairy cows: Comparison of the 5-d Cosynch protocol with an estrogen/progesterone-based protocol

Pereira, M. H C; Rodrigues, A. D P; Martins, T.; Oliveira, W. V C; Silveira, P. S A; Wiltbank, M. C.; Vasconcelos, J. L M
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
556.08715%
The objective of this study was to compare a GnRH-based to an estrogen/progesterone (E2/P4)-based protocol for estrous cycle synchronization and fixed timed artificial insemination (TAI), both designed for synchronization of ovulation and to reduce the period from follicular emergence until ovulation in cows with a synchronized follicular wave. A total of 1,190 lactating Holstein cows (primiparous: n = 685 and multiparous: n = 505) yielding 26.5 ± 0.30 kg of milk/d at 177 ± 5.02 d in milk were randomly assigned to receive one of the following programs: 5-d Cosynch protocol [d -8: controlled internal drug release (CIDR) + GnRH; d -3: CIDR removal + PGF2α; d -2: PGF2α; d 0: TAI + GnRH] or E2/P4 protocol (d -10: CIDR + estradiol benzoate; d -3: PGF2α; d -2: CIDR removal + estradiol cypionate; d 0: TAI). Rectal temperature and circulating progesterone (P4) were measured on d -3, -2, 0 (TAI), and 7. The estrous cycle was considered to be synchronized when P4 was ≥1.0 ng/mL on d 7 in cows that had luteolysis (P4 ≤0.4 ng/mL on d 0). To evaluate the effects of heat stress, cows were classified by number of heat stress events: 0, 1, and 2-or-more measurements of elevated body temperature (≥39.1°C). Pregnancy success (pregnancy per artificial insemination...

Measurement of intracellular Ca2+ in single aequorin-injected and suspensions of fura-2-loaded ROS 17/2.8 cells and normal human osteoblasts. Effect of parathyroid hormone.

Schöfl, C; Cuthbertson, K S; Gallagher, J A; Pennington, S R; Cobbold, P H; Brabant, G; Hesch, R D; von zur Mühlen, A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/02/1991 Português
Relevância na Pesquisa
552.75266%
It is known that parathyroid hormone (PTH) activates the cyclic AMP (cAMP) signalling pathway in osteoblasts. In recent years it has been suggested that an elevation of the intracellular free Ca2+ concentration ([Ca2+]i) may also be involved in the regulation of osteoblast function by PTH. However, this remains controversial. Here we investigated the effect of PTH on the [Ca2+]i of ROS 17/2.8 cells and normal human osteoblasts. The [Ca2+]i was measured in single aequorin-injected cells and in suspensions of cells loaded with fura-2. Human PTH-(1-38)-peptide (1-300 nM) had no effect on the [Ca2+]i in single aequorin-injected ROS 17/2.8 cells (n = 17) measured at various times after injection (1-20 h), or in suspensions of fura-2-loaded ROS 17/2.8 cells (n = 9). Ionomycin (1 microM) increased the [Ca2+]i in fura-2-loaded and single aequorin-injected ROS 17/2.8 cells by 285 +/- 60 nM (n = 9) and 312 +/- 99 nM (n = 6) respectively, indicating that both methods detect changes in [Ca2+]i with equal sensitivity. In contrast, human PTH-(1-38) (10-100 nM) markedly stimulated cAMP accumulation in ROS 17/2.8 cells. In single aequorin-injected normal human osteoblasts there was no change in the [Ca2+]i in response to 100 nM human PTH-(1-38) or 100 nM bovine PTH-(1-84) (n = 18). In contrast...

Effects of arachidonic acid upon the volume-sensitive chloride current in rat osteoblast-like (ROS 17/2.8) cells.

Gosling, M; Poyner, D R; Smith, J W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/06/1996 Português
Relevância na Pesquisa
548.82133%
1. The effects of arachidonic acid upon the volume-sensitive Cl- current present in cultured osteoblastic cells (ROS 17/2.8) was studied using the whole-cell patch-clamp technique. 2. Arachidonate produced two distinct phases of inhibition, a rapid phase occurring within 10-15 s of application, preceding a slower phase that occurred 2 min after onset of arachidonate superfusion. Accompanying the slower inhibitory phase was an acceleration of the time-dependent inactivation exhibited by the current at strongly depolarized potentials (> + 50 mV). The half-maximal inhibitory concentrations (IC50) were 177 +/- 31 and 10 +/- 4 microM for the two phases, respectively. 3. Arachidonate was still effective in the presence of inhibitors of cyclo-oxygenase (indomethacin, 10 microM), lipoxygenase (nordihydroguaretic acid, 10-100 microM) and cytochrome P450 (SKF525A, 100 microM; ethoxyresorufin, 10 microM; metyrapone, 500 microM; piperonyl butoxide, 500 microM; cimetidine, 1 mM). The effects of arachidonate could not be produced by another cis unsaturated fatty acid, oleic acid. 4. Measurements of cell volume showed that arachidonate effectively inhibited the regulatory volume decrease elicited by ROS 17/2.8 cells in response to a reduction in extracellular osmolarity. 5. It is concluded that the volume-sensitive Cl- conductance in ROS 17/2.8 cells is directly modulated by arachidonate and may represent a physiological mechanism by which volume regulation can be controlled in these cells.

Steric interactions of valines 1, 5, and 7 in [valine 5, D-alanine 8] gramicidin A channels.

Jude, A R; Greathouse, D V; Leister, M C; Koeppe, R E
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1999 Português
Relevância na Pesquisa
556.22832%
When the central valine residues 6, 7, and 8 of gramicidin A (gA) are shifted by one position, the resulting [Val(5), D-Ala(8)]gA forms right-handed channels with a single-channel conductance and average duration somewhat less than gA channels. The reduction in channel duration has been attributed to steric conflict between the side chains of Val(1) and Val(5) in opposing monomers (Koeppe, R. E. II, D. V. Greathouse, A. Jude, G. Saberwal, L. L. Providence, and O. S. Andersen. 1994. J. Biol. Chem. 269:12567-12576). To investigate the orientations and motions of valines in [Val(5), D-Ala(8)]gA, we have incorporated (2)H labels at Val 1, 5, or 7 and recorded (2)H-NMR spectra of oriented and nonoriented samples in hydrated dimyristoylphosphatidylcholine. Spectra of nonoriented samples at 4 degrees C reveal powder patterns that indicate rapid side chain "hopping" for Val(5), and an intermediate rate of hopping for Val(1) and Val(7) that is somewhat slower than in gA. Oriented samples of deuterated Val(1) and Val(7) show large changes in the methyl and C(beta)-(2)H quadrupolar splittings (Deltanu(q)) when Ala(5) in native gA is changed to Val(5). Three or more peaks for the Val(1) methyls with Deltanu(q) values that vary with the echo delay...

Effects of N-butyldeoxynojirimycin and the Lec3.2.8.1 mutant phenotype on N-glycan processing in Chinese hamster ovary cells: application to glycoprotein crystallization.

Butters, T. D.; Sparks, L. M.; Harlos, K.; Ikemizu, S.; Stuart, D. I.; Jones, E. Y.; Davis, S. J.
Fonte: Cold Spring Harbor Laboratory Press Publicador: Cold Spring Harbor Laboratory Press
Tipo: Artigo de Revista Científica
Publicado em /08/1999 Português
Relevância na Pesquisa
549.8382%
Heterologous gene expression in either (1) the glycosylation-defective, mutant Chinese hamster ovary cell line, Lec3.2.8.1, or (2) the presence of the alpha-glucosidase inhibitor, N-butyldeoxynojirimycin facilitates the trimming of N-linked glycans of glycoproteins to single N-acetylglucosamine (GlcNAc) residues with endoglycosidase H (endo H). Both approaches are somewhat inefficient, however, with as little as 12% of the total protein being rendered fully endo H-sensitive under these conditions. It is shown here that the combined effects of these approaches on the restriction of oligosaccharide processing are essentially additive, thereby allowing the production of glycoproteins that are essentially completely endo H-sensitive. The preparation of a soluble chimeric form of CD58, the ligand of the human T-cell surface recognition molecule CD2, illustrates the usefulness of the combined approach when expression levels are low or the deglycosylated protein is unstable at low pH. The endo H-treated chimera produced crystals of space group P3(1)21 or P3(2)21, and unit cell dimensions a = b = 116.4 A, c = 51.4 A alpha = beta = 90 degrees , gamma = 120 degrees , that diffract to a maximum resolution of 1.8 A.

Estudos visando a síntese total da combretastatina D-2

Raysth Martinez, Walter; Henrique Menezes da Silva, Paulo (Orientador)
Fonte: Universidade Federal de Pernambuco Publicador: Universidade Federal de Pernambuco
Tipo: Outros
Português
Relevância na Pesquisa
645.4347%
A Combretastatina D-2 é uma macrolactona isolada em 1989 da árvore sul africana Combretum caffrum. A partir de 77 Kg da casca foram obtidos 5,8 mg do produto natural - um rendimento de 7,5 × 10-6 %. Este composto exibiu atividade antineoplásica sobre células leucêmicas P-388 ao impedir a desmontagem dos microtúbulos durante a mitose celular. O mecanismo de ação incomum tornou a Combretastatina D-2 um alvo de permanente investigação na farmacologia anticâncer. Assim, com o desejo de contribuir com as investigações sobre esta macrolactona, neste trabalho é proposta a investigação de uma nova estratégia de síntese para a preparação deste produto natural. A estratégia sintética proposta foi baseada no acoplamento de dois fragmentos principais: A e B. O fragmento A consistiu em um composto de boro, sintetizado na forma de um ácido borônico ou um trifluoroborato de potássio em rendimentos globais moderados. Para a preparação do fragmento B, um fenol, foram envolvidas reações de acoplamento do tipo Sonogashira e reação de hidrogenação catalítica; Conselho Nacional de Desenvolvimento Científico e Tecnológico

Capriccio italien : pour grand orchestre, op. 45 / composé par P. Tschaikowsky ; [arrangé à 8 mains par E. Langer].; Capriccio italien; arr.

Tchaikovsky, Peter Ilich (1840 - 1893); Langer, Ėduard (1835 - 1905)
Fonte: D. Rahter Publicador: D. Rahter
Tipo: Musical Score
Português
Relevância na Pesquisa
548.79434%
2 parts (31 p. each) ; 33 cm.
Nouv. éd.
For 2 pianos, 8 hands.

Transcriptional Sygernism Between Vitamin D-Rsponsive Elements in the Rat 25-Hyroxyvitamin D-3 24-Hydroxylase (CYP24) Promotor

Kerry, D.; Dwivedi, P.; Morris, H.; Omdahl, J.; May, B.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Artigo de Revista Científica
Publicado em //1996 Português
Relevância na Pesquisa
547.34484%
Transcription of the CYP24 gene is induced by 1,25-(OH)2D3 through a vitamin D receptor-dependent process. The functional activities of three possible vitamin D response elements (VDREs), located on the antisense strand of the rat CYP24 promoter, were investigated by transient expression of native and mutant promoter constructs in COS-1, JTC-12, and ROS 17/2.8 cells. A putative VDRE with a half-site spacing of 6 base pairs at -249/-232 (VDRE-3) did not contribute to 1,25-(OH)2D3 induced expression in the native promoter, although activity has been reported when the element was fused to the heterologous thymidine kinase promoter. Two VDREs with half-site spacings of 3 base pairs at -150/-136 and -258/-244 (VDRE-1 and VDRE-2, respectively), showed transcriptional synergism in COS-1 cells when treated with 1,25-(OH)2D3 (10(-7) to 10(-11) M). The contribution of both VDREs was hormone-concentration dependent from 10(-10) to 10(-12) M, with VDRE-1 demonstrating greatest sensitivity to 1,25-(OH)2D3. Transactivation by VDRE-1 was always greater than VDRE-2, but the converse was observed for the binding of vitamin D receptor-retinoid X receptor complex by each VDRE in gel mobility shift assays. The synergy observed between VDRE-1 and VDRE-2 may have important implications in cellular responses to different circulating levels of 1...

Dipole Strength in the 235U(gamma,gamma') Reaction up to 2.8 MeV

YEVETSKA O.; ENDERS J.; FRITZSCHE M.; VON NEUMANN-COSEL P.; OBERSTEDT Stephan; RICHTER A.; ROMIG C.; SAVRAN D.; SONNABEND K.
Fonte: AMER PHYSICAL SOC Publicador: AMER PHYSICAL SOC
Tipo: Articles in Journals Formato: Printed
Português
Relevância na Pesquisa
547.9099%
Spectra of the 235U(gamma, gamma') reaction were measured at the S-DALINAC at bremsstrahlung endpoint energies E0 = 3:5 MeV and 4.4 MeV and scattering angles of 90± and 135± with respect to the beam axis. Discrete transitions are observed at excitation energies below 2.3 MeV only. The deduced cross sections are in rough agreement with the findings of Bertozzi et al. [Phys. Rev. C 78, 041601(R) (2008)] except for the most prominent transition, where the present result is a factor of about two lower. Evidence for unresolved dipole strength is found in the spectra by means of a fluctuation analysis, which was carried out up to an excitation energy of 2.8 MeV. If this unresolved strength exhibits the same ratio of E1=M1 cross sections as observed in the even-mass neighbor 236U, then the energy centroid Ex = 2:5(3) MeV and total strength SUM[B(M1)¦ = 3.6(1:3) (mu_N)^2 of the M1 part are in good agreement with the systematics of the scissors mode in even-even actinide nuclei.; JRC.D.4-Nuclear physics

A cryptic deletion of 2q35 including part of the PAX3 gene detected by breakpoint mapping in a child with autism and a de novo 2;8 translocation

Borg, I; Squire, M; Menzel, C; Stout, K; Morgan, D; Willatt, L; O'Brien, P; Ferguson-Smith, M; Ropers, H; Tommerup, N; Kalscheuer, V; Sargan, D
Fonte: BMJ Group Publicador: BMJ Group
Tipo: Artigo de Revista Científica
Publicado em /06/2002 Português
Relevância na Pesquisa
548.42062%
We report a de novo, apparently balanced (2;8)(q35;q21.2) translocation in a boy with developmental delay and autism. Cross species (colour) paint (Rx) and SKY FISH, forward and reverse chromosome painting, and FISH with subtelomeric probes were used to examine the patient's karyotype, but further rearrangements were not detected. FISH with region specific clones mapping near 2q35 and 8q21.2 breakpoints and STS mapping performed on the isolated derivative chromosomes were used to refine the location of the breakpoints further. A cryptic deletion of between 4.23 and 4.41 Mb in extent and involving at least 13 complete genes or transcription units was found at the breakpoint on 2q35. The deletion includes the promoter and 5` untranslated region of the paired box 3 (PAX3) gene. The child has very mild dystopia canthorum which may be associated with the PAX3 haploinsufficiency. The 8q21.2 breakpoint is within MMP16 which encodes matrix metalloproteinase 16. We postulate that the cryptic deletion and rearrangement are responsible for the patient's phenotype and that a gene (or genes) responsible for autism lies at 2q35 or 8q21.2. The results present a step towards identifying genes predisposing to autism.

Characterization of a volume-sensitive chloride current in rat osteoblast-like (ROS 17/2.8) cells.

Gosling, M; Smith, J W; Poyner, D R
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/06/1995 Português
Relevância na Pesquisa
550.11906%
1. During osmotic swelling, cultured osteoblastic cells (ROS 17/2.8) exhibited activation of large amplitude Cl- currents in the whole-cell configuration of the patch-clamp technique. Effects of hypotonic shock on cell volume and membrane conductance were rapidly reversed on return to isotonic conditions. 2. Voltage command pulses in the range -80 to +50 mV produce instantaneous activation of Cl- currents. At potentials more positive than +50 mV the current exhibited time-dependent inactivation. The instantaneous current-voltage relationship was outwardly rectifying. 3. The anion permeability sequence of the induced current was SCN- (2.2) > i- (1.9) > Br- (1.5) > Cl- (1.0) > F- (0.8) > gluconate- (0.2). This corresponds to Eisenman's sequence I. 4. The volume-sensitive Cl- current was effectively inhibited by the Cl- channel blockers 4,4'- diisothiocyanatostilbene-2,2-disulphonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB). Outward currents were more effectively suppressed by DIDS than inward currents. The concentrations for 50% inhibition (IC50) of outward and inward currents were 81 and 298 microM, respectively. NPPB was equally effective at inhibiting outward and inward currents (IC50 of 64 microM). The current was relatively insensitive to diphenylamine-2-carboxylate (DPC)...

Evidence for helical structure in a tetramer of α2-8 sialic acid: unveiling a structural antigen

Battistel, Marcos D.; Shangold, Michael; Trinh, Loc; Shiloach, Joseph; Freedberg, Darón I.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
548.31062%
Characteristic hydrogen bonding (H-bonding) patterns define secondary structure in proteins and nucleic acids. We show that similar patterns apply for α2-8 linked SiA (sialic acid) in H2O; and that H-bonds define its structure. A 15N,13C α2-8 SiA tetramer was used as a model system for the polymer. At 263K, we detected intra-residue through-bond J couplings between 15N and C8 for residues I, II and III of the tetramer, which indicate H-bonds between the 15Ns and the O8s of these residues. Additional J couplings between the 15Ns and C2s of the adjacent residues confirm the putative H-bonds. The NH groups showing this long-range correlation also experience slower 1H/2H exchange rate. Additionally, detection of couplings between H7 and C2 for residues II and III imply that the conformations of the linkers between these residues are different than the monomer's. These structural elements are consistent with two left handed helical models: 1) two residues per turn (24 helix) and 2) four residues per turn (14 helix). To discriminate between models, we resorted to 1H, 1H NOEs. The 24 helical model is in better agreement with the experimental data, for which all of the observed NOEs are predicted. On the other hand, for the 14 helix 87% of the observed intra-residue NOEs are predicted. In this report we provide direct evidence of H-bonding for a tetramer of α2-8 linked SiA and show how H-bonds can be a determining factor for shaping the carbohydrate three-dimensional structure.

Atomic transitions of Rb, $D_{2}$ line in strong magnetic fields: hyperfine Paschen-Back regime

Sargsyan, A.; Tonoyan, A.; Hakhumyan, G.; Leroy, C.; Pashayan-Leroy, Y.; Sarkisyan, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/05/2014 Português
Relevância na Pesquisa
547.4946%
An efficient $\lambda/2$-method ($\lambda$ is the resonant wavelength of laser radiation) based on nanometric-thickness cell filled with rubidium is implemented to study the splitting of hyperfine transitions of $^{85}$Rb and $^{87}$Rb $D_2$ lines in an external magnetic field in the range of $B =3$~kG -- 7~kG. It is experimentally demonstrated that at $B > 3$~kG from 38 (22) Zeeman transitions allowed at low $B$-field in $^{85}$Rb ($^{87}$Rb) spectra in the case of $\sigma^+$ polarized laser radiation there remain only 12 (8) which is caused by decoupling of the total electronic momentum $\textbf{J}$ and the nuclear spin momentum $\textbf{I}$ (hyperfine Paschen-Back regime). Note that at $B > 4.5$~kG in the absorption spectrum these $20$ atomic transitions are regrouped in two completely separate groups of $10$ atomic transitions each. Their frequency positions and fixed (within each group) frequency slopes, as well as the probability characteristics are determined. A unique behavior of the atomic transitions of $^{85}$Rb and $^{87}$Rb labeled $19$ and $20$ (for low magnetic field they could be presented as transitions $F_g=3, m_F=+3 \rightarrow F_e=4, m_F=+4$ and $F_g=2, m_F=+2 \rightarrow F_e=3, m_F=+3$, correspondingly) is stressed. The experiment agrees well with the theory. Comparison of the behavior of atomic transitions for $D_2$ line compared with that of $D_1$ line is presented. Possible applications are described.; Comment: 13 pages...

Twisted N=8, D=2 super Yang-Mills theory as example of a Hodge-type cohomological theory

Geyer, B.; M"ulsch, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/08/2001 Português
Relevância na Pesquisa
553.9435%
It is shown that the dimensional reduction of the N_T=2, D=3 Blau-Thompson model to D=2, i.e., the novel topological twist of N=8, D=2 super Yang-Mills theory, provides an example of a Hodge-type cohomological theory. In that theory the generators of the topological shift, co-shift and gauge symmetry, together with a discrete duality operation, are completely analogous to the de Rham cohomology operators and the Hodge *-operation.; Comment: 8 pages, Latex

N_T=8, D=2 Hodge-type cohomological gauge theory with global SU(4) symmetry

Geyer, B.; Mülsch, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/10/2002 Português
Relevância na Pesquisa
549.11812%
We show that the partially topological twisted N=16, D=2 super Yang-Mill theory gives rise to a N_T=8 Hodge-type cohomological gauge theory with global SU(4) symmetry.; Comment: 8 pages, LATEX2e, Contribution to 3. Int. A. Sakharov Conference, Moscaow, June 23 - 29, 2002

Higher dimensional analogue of the Blau-Thompson model and N_T=8, D=2 Hodge-type cohomological gauge theories

Geyer, B.; Mülsch, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
556.5893%
The higher dimensional analogue of the Blau-Thompson model in D=5 is constructed by a N_T=1 topological twist of N=2, D=5 super Yang-Mills theory. Its dimenional reduction to D=4 and D=3 gives rise to the B-model and N_T=4 equivariant extension of the Blau-Thompson model, respectively. A further dimensional reduction to D=2 provides another example of a N_T=8 Hodge-type cohomological theory with global symmetry group SU(2) \otimes \bar SU(2). Moreover, it is shown that this theory possesses actually a larger global symmetry group SU(4) and and that it agrees with the N_T=8 topological twisting of N+16, D=2 super Yang-Mills theory.; Comment: 20 pages, Latex, final version as appearing in Nucl. Phys. B

A new spin-2 self-dual model in $D=2+1$

Dalmazi, D.; Mendonca, E. L.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
551.7384%
There are three self-dual models of massive particles of helicity +2 (or -2) in $D=2+1$. Each model is of first, second, and third-order in derivatives. Here we derive a new self-dual model of fourth-order, $\cL {SD}^{(4)}$, which follows from the third-order model (linearized topologically massive gravity) via Noether embedment of the linearized Weyl symmetry. In fact, each self-dual model can be obtained from the previous one $ \cL {SD}^{(i)} \to \cL {SD}^{(i+1)}, i=1,2,3$ by the Noether embedment of an appropriate gauge symmetry, culminating in $\cL {SD}^{(4)}$. The new model may be identified with the linearized version of $\cL {HDTMG} = \epsilon^{\mu\nu\rho} \Gamma_{\mu\gamma}^\epsilon (\p_\nu\Gamma_{\epsilon\rho}^\gamma + (2/3)\Gamma_{\nu\delta}^\gamma \Gamma_{\rho\epsilon}^\delta) /8 m + \sqrt{-g}(R_{\mu\nu} R^{\nu\mu} - 3 R^2/8) /2 m^2 $. We also construct a master action relating the third-order self-dual model to $\cL {SD}^{(4)}$ by means of a mixing term with no particle content which assures spectrum equivalence of $\cL {SD}^{(4)}$ to other lower-order self-dual models despite its pure higher derivative nature and the absence of the Einstein-Hilbert action. The relevant degrees of freedom of $\cL {SD}^{(4)}$ are encoded in a rank-two tensor which is symmetric...

Determination of the branching fractions for $\psi(3770) \to D^0 \bar D^0, D^+D^-,D\bar D$ and $\psi(3770) \to {\rm non-}D\bar D$

Rong, G.; Zhang, D. H.; Chen, J. C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/06/2005 Português
Relevância na Pesquisa
558.7904%
The branching fractions for $\psi(3770) \to D^0 \bar D^0, D^+D^-,D\bar D$ and $\psi(3770) \to {\rm non-}D\bar D$ are determined based on the cross sections for $\psi(3770)$ and $D \bar D$ production measured by BES Collaboration. From its recent publications we determine the branching fractions for $\psi(3770) \to D^0 \bar D^0, D^+D^-$ and $\psi(3770) \to D\bar D$ to be $(52.2\pm 4.8\pm 5.5)%$, $(37.0 \pm 5.0 \pm 4.3)%$ and $(89.1 \pm 6.9 \pm 9.2)%$, respectively. The latter one implies the branching fraction for $\psi(3770) \to {\rm non-}D\bar D$ to be $(10.9 \pm 6.9 \pm 9.2)%$, corresponding the inclusive ${\rm non-}D \bar D$ partial width $\Gamma(\psi(3770) \to {\rm non-}D\bar D) = (2.8 \pm 1.8 \pm 2.4)$ MeV. Meanwhile we determine the observed cross section for $non-D\bar D$ event production from $\psi(3770)$ decays to be $\sigma^{\rm obs}(\psi(3770)\to non-D\bar D) = (0.72 \pm 0.46 \pm 0.62)$ nb.; Comment: 6 pages, 2 figures

Measurement of branching fractions and CP-violating charge asymmetries for B-meson decays to D^(*)D^(*), and implications for the Cabibbo-Kobayashi-Maskawa angle γ

Aubert, B.; Albert, J.; Chen, E.; Dvoretskii, A.; Hitlin, D. G.; Narsky, I.; Piatenko, T.; Porter, F. C.; Ryd, A.; Samuel, A.
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 01/06/2006 Português
Relevância na Pesquisa
559.95887%
We present measurements of the branching fractions and charge asymmetries of B decays to all D^(*)D^(*) modes. Using 232×10^6 BB pairs recorded on the Υ(4S) resonance by the BABAR detector at the e^+e^- asymmetric B factory PEP-II at the Stanford Linear Accelerator Center, we measure the branching fractions B(B^0→D^(*+)D^(*-))=(8.1±0.6±1.0)×10^(-4), B(B^0→D^(*±)D^∓)=(5.7±0.7±0.7)×10^(-4), B(B^0→D^+D^-)=(2.8±0.4±0.5)×10^(-4), B(B^+→D^(*+)D^(*0))=(8.1±1.2±1.2)×10^(-4), B(B^+→D^*+D^0)=(3.6±0.5±0.4)×10^(-4), B(B^+→D^+D^(*0))=(6.3±1.4±1.0)×10^(-4), and B(B^+→D^+D^(0))=(3.8±0.6±0.5)×10^(-4), where in each case the first uncertainty is statistical and the second systematic. We also determine the limits B(B^0→D^(*0)D^(*0))<0.9×10^(-4), B(B^0→D^(*0)D^0)<2.9×10^(-4), and B(B^0→D^0D^0)<0.6×10^(-4), each at 90% confidence level. All decays above denote either member of a charge-conjugate pair. We also determine the CP-violating charge asymmetries A(B^0→D^(*±)D^∓)=0.03±0.10±0.02, A(B^+→D^(*+)D^(*0))=-0.15±0.11±0.02, A(B^+→D^(*+)D^0)=-0.06±0.13±0.02, A(B^+→D^+D^(*0))=0.13±0.18±0.04, and A(B^+→D^+D^0)=-0.13±0.14±0.02. Additionally, when we combine these results with information from time-dependent CP asymmetries in B^0→D^((*)+)D^((*)-) decays and world-averaged branching fractions of B decays to D_s^(*)D^(*) modes...