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HISTAMINE IN THE POSTERODORSAL MEDIAL AMYGDALA MODULATES CARDIOVASCULAR REFLEX RESPONSES IN AWAKE RATS

QUAGLIOTTO, E.; NECKEL, H.; RIVEIRO, D. F.; CASALI, K. R.; MOSTARDA, C.; IRIGOYEN, M. C.; DALLAGO, P.; RASIA-FILHO, A. A.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
55.53%
Centrally injected histamine (HA) affects heart rate (HR), arterial blood pressure (BP), and sympathetic activity in rats. The posterodorsal medial amygdala (MePD) has high levels of histidine decarboxylase, connections with brain areas involved with the modulation of cardiovascular responses, and is relevant for the pathogenesis of hypertension. However, there is no report demonstrating the role of the MePD histaminergic activity on the cardiovascular function in awake rats. The alms of the present work were: 1) to study the effects of two doses (10-100 nM) of HA microinjected in the MePD on basal cardiovascular recordings and on baroreflex- and chemoreflex-mediated responses; 2) to reveal whether cardiovascular reflex responses could be affected by MePD microinjections of (R)-alpha-methylhistamine (AH(3)), an agonist of the inhibitory autoreceptor H(3); and, 3) to carry out a power spectral analysis to evaluate the contribution of the sympathetic and parasympathetic components in the variability of the HR and BP recordings. When compared with the control group (microinjected with saline, 0.3 mu l), HA (10 nM) promoted an increase in the MAP(50), i.e. the mean value of BP at half of the HR range evoked by the baroreflex response. Histamine (100 nM) did not affect the baroreflex activity...

Synthesis, Structure, and Phosphatase-Like Activity of a New Trinuclear Gd Complex with the Unsymmetrical Ligand H(3)L As a Model for Nucleases

CAMARGO, Maryene A.; NEVES, Ademir; SZPOGANICZ, Bruno; BORTOLUZZI, Adailton J.; FISCHER, Franciele L.; TERENZI, Hernan; CASTELLANO, Eduardo Ernesto
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
45.58%
The new trinuclear gadolinium complex [Gd(3)L(2)(NO(3))(2)(H(2)O)(4)]NO(3)center dot 8H(2)O (1) with the unsymmetrical ligand 2-[N-bis-(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N-bis(2-hydroxy-2-oxoethyl)aminomethyl] phenol (H(3)L) was synthesized and characterized. The new ligand H(3)L was obtained in good yield. Complex I crystallizes in an orthorhombic cell, space group Pcab. Kinetic studies show that complex 1 is highly active in the hydrolysis of the substrate 2,4-bis(dinitrophenyl)phosphate (K(m) = 4.09 mM, V(max) = 2.68 x 10(-2) mM s(-1), and k(cat) = V(max)/[1] = 0.67 s(-1)). Through a potentiometric study and determination of the kinetic behavior of 1 in acetonitrile/water solution, the species present in solution could be identified, and a trinuclear monohydroxo species appears to be the most prominent catalyst under mild conditions. Complex 1 displays high efficiency in DNA hydrolytic cleavage, and complete kinetic studies were carried out (K(m) = 4.57 x 10(-4) M, K(cat)` = 3.42 h(-1), and k(cat)`/K(m) = 7.48 x 10(3) M(-1) h(-1)). Studies with a radical scavenger (dimethyl sulfoxide, DMSO) showed that it did not inhibit the activity, indicating the hydrolytic action of 1 in the cleavage of DNA, and studies on the incubation of distamycin with plasmid DNA suggest that 1 is regio-specific...

A quantum chemical study on a set of non-imidazole H(3) antihistamine molecules

COSTA, Edson Barbosa da; TRSIC, Milan
Fonte: ELSEVIER SCIENCE INC Publicador: ELSEVIER SCIENCE INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.49%
Molecular orbital calculations were carried out on a set of 28 non-imidazole H(3) antihistamine compounds using the Hartree-Fock method in order to investigate the possible relationships between electronic structural properties and binding affinity for H3 receptors (pK(i)). It was observed that the frontier effective-for-reaction molecular orbital (FERMO) energies were better correlated with pK(i) values than highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy values. Exploratory data analysis through hierarchical cluster (HCA) and principal component analysis (PCA) showed a separation of the compounds in two sets, one grouping the molecules with high pK(i) values, the other gathering low pK(i) value compounds. This separation was obtained with the use of the following descriptors: FERMO energies (epsilon(FERMO)), charges derived from the electrostatic potential on the nitrogen atom (N(1)), electronic density indexes for FERMO on the N(1) atom (Sigma((FERMO))c(i)(2)). and electrophilicity (omega`). These electronic descriptors were used to construct a quantitative structure-activity relationship (QSAR) model through the partial least-squares (PLS) method with three principal components. This model generated Q(2) = 0.88 and R(2) = 0.927 values obtained from a training set and external validation of 23 and 5 molecules...

Dynamics of free and H-3-labelled glutamine concentrations during zygotic and somatic embryogenesis of Feijoa [Acca sellowiana (O. Berg.) Burret]

Pescador, R.; Kerbauy, Gilberto Barbante; Fraga, H. P. F.; Hamasaki, R. M.; Tavares, L. B. B.; Guerra, M. P.
Fonte: HEADLEY BROTHERS LTD; ASHFORD Publicador: HEADLEY BROTHERS LTD; ASHFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
55.53%
Amino acids play fundamental roles in plant morphogenesis. Among sources of organic nitrogen (N), glutamine has frequently been used during the establishment and maintenance of cell and tissue cultures. The aim of this study was analyse endogenous levels of glutamine during somatic and zygotic embryogenesis of Acca sellowiana (Feijoa or pineapple guava). The in vitro absorption of H-3-labelled glutamine was investigated. Zygotic embryos and embryogenic cultures (EC) were evaluated at 30 d and 70 d after explant inoculation onto the medium. Endogenous levels of glutamine were similar during zygotic and somatic embryogenesis, and showed a gradual decline until day-24 in culture. The highest rates of H-3-labelled glutamine uptake were observed during the first 2 h of incubation, resulting in values of 6.29 mu mol g(-1) fresh weight (FW) for zygotic embryos, 14.43 mu mol g(-1) FW for EC after 30 d, and 13.85 mu mol g(-1) FW for EC after 70 d. These results showed that the decreased levels of glutamine observed during the initial phase of development may be related to de novo protein synthesis and mobilisation during embryo maturation. The absorption of glutamine in the first 2 h of incubation also emphasises its involvement as an important source of N during morphogenesis of somatic and zygotic embryos.

TeV γ-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S.; TeV gamma-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S.

H.E.S.S. Collaboration; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A.G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher,
Fonte: Published by Oxford University Press on behalf of the Royal Astronomical Society Publicador: Published by Oxford University Press on behalf of the Royal Astronomical Society
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
45.6%
The non-thermal nature of the X-ray emission from the shell-type supernova remnants (SNRs) G1.9+0.3 and G330.2+1.0 is an indication of intense particle acceleration in the shock fronts of both objects. This suggests that the SNRs are prime candidates for very-high-energy (VHE; E > 0.1 TeV) γ-ray observations. G1.9+0.3, recently established as the youngest known SNR in the Galaxy, also offers a unique opportunity to study the earliest stages of SNR evolution in the VHE domain. The purpose of this work is to probe the level of VHE γ-ray emission from both SNRs and use this to constrain their physical properties. Observations were conducted with the H.E.S.S. (High Energy Stereoscopic System) Cherenkov Telescope Array over a more than six-year period spanning 2004–2010. The obtained data have effective livetimes of 67 h for G1.9+0.3 and 16 h for G330.2+1.0. The data are analysed in the context of the multiwavelength observations currently available and in the framework of both leptonic and hadronic particle acceleration scenarios. No significant γ-ray signal from G1.9+0.3 or G330.2+1.0 was detected. Upper limits (99 per cent confidence level) to the TeV flux from G1.9+0.3 and G330.2+1.0 for the assumed spectral index Γ = 2.5 were set at 5.6 × 10−13 cm−2 s−1 above 0.26 TeV and 3.2 × 10−12 cm−2 s−1 above 0.38 TeV...

C3-halogenation of cytisine generates potent and efficacious nicotinic receptor agonists

Cassels, Bruce K.; Bermúdez, Isabel; Dajas, Federico; Barik, Jacques; Durand, Claudia; Voutilainen, Merja H.; Iturriaga Vásquez, Patricio; Wonnacott, Susan; Abin Carriquiry, Juan Andrés
Fonte: ELSEVIER Publicador: ELSEVIER
Tipo: Artículo de revista
EN
Relevância na Pesquisa
55.57%
Neuronal nicotinic acetylcholine receptors subserve predominantly modulatory roles in the brain, making them attractive therapeutic targets. Natural products provide key leads in the quest for nicotinic receptor subtype-selective compounds. Cytisine, found in Leguminosae spp., binds with high affinity to alpha 4 beta 2* nicotinic receptors. We have compared the effect of C3 and C5 halogenation of cytisine and methylcytisine (MCy) on their interaction with native rat nicotinic receptors. 3-Bromocytisine (3-BrCy) and 3-iodocytisine (3-ICy) exhibited increased binding affinity (especially at alpha 7 nicotinic receptors; K-1 similar to 0.1 mu M) and functional potency, whereas C5-halogenation was detrimental. 3-BrCy and 3-ICy were more potent than cytisine at evoking [H-3]dopamine release from striatal slices (EC50 similar to 11 nM), [H-3]noradrenaline release from hippocampal slices (EC50 similar to 250 nM), increases in intracellular Ca2+ in PC12 cells and inward currents in Xenopus oocytes expressing human alpha 3 beta 4 4 nicotinic receptor (EC50 similar to 2 mu M). These compounds were also more efficacious than cytisine. C3-halogenation of cytisine is proposed to stabilize the open conformation of the nicotinic receptor but does not enhance subtype selectivity.

Production of H$_3^+$ via photodissociation of organic molecules in interstellar clouds

Pilling, S.; Andrade, D. P. P.; Neves, R.; Ferreira-Rodrigues, A. M.; Santos, A. C. F.; Boechat-Roberty, H. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/12/2006
Relevância na Pesquisa
55.62%
We present experimental results obtained from photoionization and photodissociation processes of abundant interstellar CH$_3$-X type organic molecules like methanol (CH$_3$OH), methylamine (CH$_3$NH$_2$) and acetonitrile (CH$_3$CN) as alternative route for the production of H$_3^+$ in interstellar and star forming environments. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS), employing soft X-ray photons with energies between 200 and 310 eV and time of flight mass spectrometry. Mass spectra were obtained using the photoelectron-photoion coincidence techniques. Absolute averaged cross sections for H$_3^+$ production by soft X-rays were determined. We have found that, among the channels leading to molecular dissociation, the H$_3^+$ yield could reach values up to 0.7% for single photoionization process and up to 4% for process involving double photoionization. The H$_3^+$ photoproduction cross section due to the dissociation of the studied organic molecules by photons over the C1s edge (200-310 eV) were about 0.2-1.4 $\times$ 10$^{-18}$ cm$^2$. Adopting the typical X-ray luminosity $L_X \gtrsim 10^{31}$ erg s$^{-1}$ which best fit the observational data for AFGL 2591 (Stauber et al. 2005) we derive an estimative for the H$_3^+$ photoproduction rate due to methyl-compounds dissociation process. The highest value for the H$_3^+$ column density from methanol dissociation by soft X-rays...

Deuterated H$_3^+$ in proto-planetary disks

Ceccarelli, Cecilia; Dominik, Carsten
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/06/2005
Relevância na Pesquisa
45.59%
Probing the gas and dust in proto-planetary disks is central for understanding the process of planet formation. In disks surrounding solar type protostars, the bulk of the disk mass resides in the outer midplane, which is cold ($\leq$20 K), dense ($\geq 10^7$ cm$^{-3}$) and depleted of CO. Observing the disk midplane has proved, therefore, to be a formidable challenge. Ceccarelli et al. (2004) detected H$_2$D$^+$ emission in a proto-planetary disk and claimed that it probes the midplane gas. Indeed, since all heavy-elements bearing molecules condense out onto the grain mantles, the most abundant ions in the disk midplane are predicted to be H$_3^+$ and its isotopomers. In this article, we carry out a theoretical study of the chemical structure of the outer midplane of proto-planetary disks. Using a self-consistent physical model for the flaring disk structure, we compute the abundances of H$_3^+$ and its deuterated forms across the disk midplane. We also provide the average column densities across the disk of H$_3^+$, H$_2$D$^+$, HD$_2^+$ and D$_3^+$, and line intensities of the ground transitions of the ortho and para forms of H$_2$D$^+$ and HD$_2^+$ respectively. We discuss how the results depend on the cosmic ray ionization rate...

Formation of H$_3^-$ by radiative association of H$_2$ and H$^-$ in the interstellar medium

Ayouz, M.; Lopes, Raphael; Raoult, Maurice; Dulieu, Olivier; Kokoouline, V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/02/2011
Relevância na Pesquisa
45.6%
We develop the theory of radiative association of an atom and a diatomic molecule within a close-coupling framework. We apply it to the formation of H$_3^-$ after the low energy collision (below 0.5 eV) of H$_2$ with H$^-$. Using recently obtained potential energy and permanent dipole moment surfaces of H$_3^-$, we calculate the lowest rovibrational levels of the H$_3^-$ electronic ground state, and the cross section for the formation of H$_3^-$ by radiative association between H$^-$ and ortho- and para-H$_2$. We discuss the possibility for the H$_3^-$ ion to be formed and observed in the cold and dense interstellar medium in an environment with a high ionization rate. Such an observation would be a probe for the presence of H$^-$ in the interstellar medium.

A note about the ground state of the ${\rm H}_3^+$ hydrogen molecular ion

Vieyra, J. C. Lopez; Turbiner, A. V.; Cobaxin, H. Medel
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/05/2011
Relevância na Pesquisa
55.51%
Three simple $7-, (7+3)-, 10-$parametric trial functions for the ${\rm H}_3^+$ molecular ion are presented. Each of them provides subsequently the most accurate approximation for the Born-Oppenheimer ground state energy among several-parametric trial functions. These trial functions are chosen following a criterion of physical adequacy and includes the electronic correlation in the exponential form $\sim\exp{(\gamma r_{12})}$, where $\gamma$ is a variational parameter. The Born-Oppenheimer energy is found to be $E=-1.340 34, -1.340 73, -1.341 59$\,a.u., respectively, for optimal equilateral triangular configuration of protons with the equilibrium interproton distance $R=1.65$\,a.u. The variational energy agrees in three significant digits (s.d.) with most accurate results available at present as well as for major expectation values.; Comment: 12 pages, 1 figure, 3 tables

About non-existence of the molecular ion $\bf H_3^{++}$

Medel-Cobaxin, H.; Alijah, A.; Turbiner, A. V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/05/2008
Relevância na Pesquisa
55.46%
It is shown that the molecular ion ${\rm H}^{++}_3$ does not exist in a form of the equilateral triangle. To this end, a compact variational method is presented which is based on a linear superposition of six specially tailored trial functions containing non-linear parameters. Careful optimization of a total of fifteen parameters gives consistently lower variational results for the electronic energy than can be obtained with standard methods of quantum chemistry even with huge basis sets as large as mcc-pV7Z.; Comment: 10 pages, 2 figures, Dedicated to Professor Rudolf Zahradnik on the occasion of his 80th birthday

$H_3^{++}$ molecular ions can exist in strong magnetic fields

Turbiner, Alexander; V., Juan Carlos Lopez; H, Ulises Solis
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
55.46%
Using the variational method it is shown that for magnetic fields $B\geq 10^{11}$ G there can exist a molecular ion $H_3^{++}$.; Comment: LaTeX, 7 pp, 1 table, 4 figures. Title modified. Consideration of the longitudinal size of the system was added

The quantum $H_3$ integrable system

García, Marcos A. G.; Turbiner, Alexander V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/07/2010
Relevância na Pesquisa
45.6%
The quantum $H_3$ integrable system is a 3D system with rational potential related to the non-crystallographic root system $H_3$. It is shown that the gauge-rotated $H_3$ Hamiltonian as well as one of the integrals, when written in terms of the invariants of the Coxeter group $H_3$, is in algebraic form: it has polynomial coefficients in front of derivatives. The Hamiltonian has infinitely-many finite-dimensional invariant subspaces in polynomials, they form the infinite flag with the characteristic vector $\vec \al\ =\ (1,2,3)$. One among possible integrals is found (of the second order) as well as its algebraic form. A hidden algebra of the $H_3$ Hamiltonian is determined. It is an infinite-dimensional, finitely-generated algebra of differential operators possessing finite-dimensional representations characterized by a generalized Gauss decomposition property. A quasi-exactly-solvable integrable generalization of the model is obtained. A discrete integrable model on the uniform lattice in a space of $H_3$-invariants "polynomially"-isospectral to the quantum $H_3$ model is defined.; Comment: 32 pages, 3 figures

Photofragmentation of the H_3 molecule, including Jahn-Teller coupling effects

Kokoouline, Viatcheslav; Greene, Chris H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/01/2004
Relevância na Pesquisa
55.54%
We have developed a theoretical method for interpretation of photoionization experiments with the H_3 molecule. In the present study we give a detailed description of the method, which combines multichannel quantum defect theory, the adiabatic hyperspherical approach, and the techniques of outgoing Siegert pseudostates. The present method accounts for vibrational and rotation excitations of the molecule, deals with all symmetry restrictions imposed by the geometry of the molecule, including vibrational, rotational, electronic and nuclear spin symmetries. The method was recently applied to treat dissociative recombination of the H_3^+ ion. Since H_3^+ dissociative recombination has been a controversial problem, the present study also allows us to test the method on the process of photoionization, which is understood better than dissociative recombination. Good agreement with two photoionization experiments is obtained.; Comment: 10 figures

Photoproduction of H$_3^+$ from gaseous methanol inside dense molecular clouds

Pilling, S.; Andrade, D. P. P.; Santos, A. C. F.; Boechat-Roberty, H. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/03/2008
Relevância na Pesquisa
55.58%
We present experimental results obtained from photoionization and photodissociation processes of abundant interstellar methanol (CH$_3$OH) as an alternative route for the production of H$_3^+$ in dense clouds. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS) employing soft X-ray and time-of-flight mass spectrometry. Mass spectra were obtained using the photoelectron-photoion coincidence techniques. Absolute averaged cross sections for the production of H$_3^+$ due to molecular dissociation of methanol by soft X-rays (C1s edge) were determined. The H$_3^+$'s photoproduction rate and column density were been estimated adopting a typical soft X-ray luminosity inside dense molecular and the observed column density of methanol. Assuming a steady state scenario, the highest column density value for the photoproduced H$_3^+$ was about 10$^{11}$ cm$^2$, which gives the ratio photoproduced/observed of about 0.05%, as in the case of dense molecular cloud AFGL 2591. Despite the small value, this represent a new and alternative source of H$_3^+$ into dense molecular clouds and it is not been considered as yet in interstellar chemistry models.; Comment: To be published in the Proceedings of IAU-251 Symposium - Organic Matter in Space...

The D/H ratio at z = 3.57 toward Q 1937-1009

Levshakov, Sergei A.; Kegel, Wilhelm H.; Takahara, Fumio
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/02/1998
Relevância na Pesquisa
45.59%
Deuterium abundance re-measurements by Burles and Tytler (1998; hereafter BT) yielded D/H = (3.3 +/- 0.3) 10^{-5} and the robust upper limit D/H < 3.9 10^{-5} from the z_a = 3.572 system toward Q1937-1009. In this new analysis BT adopted multicomponent microturbulent models together with the possibility to vary freely the local continuum level around each HI line to improve the fit. The procedure failed, however, to fit adequately D Ly-beta without recourse to an additional H Ly-alpha contamination at the position of D Ly-beta. We show that this obstacle may be successfully overcome within the framework of the mesoturbulent model accounting (in contrast to the microturbulent approximation) for a correlated structure of the large scale velocity field. Using the same observational data and the original continuum as determined by Tytler et al. (1996), we obtained good fits. The one-component mesoturbulent models provide D/H in the range (3.2 - 4.8) 10^{-5} and the total hydrogen column density N(HI) = (5.6 - 7.0) 10^{17} cm^{-2}. This result is consistent with that found by us from the z_a = 2.504 and z_a = 0.701 systems toward Q1009+2956 and Q1718+4807, respectively. The range for D/H common to all three analyses is D/H = (4.1 - 4.6) 10^{-5}. This value is consistent with standard big bang nucleosynthesis [SBBN] if the baryon-to-photon ratio...

Hyperovals of $H(3,q^2)$ when $q$ is even

Cossidente, Antonio; King, Oliver H.; Marino, Giuseppe
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/11/2012
Relevância na Pesquisa
55.56%
For even $q$, a group $G$ isomorphic to $PSL(2,q)$ stabilizes a Baer conic inside a symplectic subquadrangle ${\cal W}(3,q)$ of ${\cal H}(3,q^2)$. In this paper the action of $G$ on points and lines of ${\cal H}(3,q^2)$ is investigated. A construction is given of an infinite family of hyperovals of size $2(q^3-q)$ of ${\cal H}(3,q^2)$, with each hyperoval having the property that its automorphism group contains $G$. Finally it is shown that the hyperovals constructed are not isomorphic to known hyperovals.; Comment: Submitted

Quantum-defect analysis of $np$ and $nd$ $\rm{H_3}$ Rydberg energy levels

Wang, Jia; Greene, Chris H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
55.54%
In this work, Rydberg energy levels of the triatomic hydrogen molecule ($\rm{H_3}$) are studied with multichannel quantum-defect theory. We extract the body-frame p-wave quantum defects from highly accurate \emph{ab initio} electronic potential surfaces and calculate the quantum defects of higher momentum states by using the long-range multipole potential model. To obtain laboratory-frame quantum defects, we perform a rovibrational-frame transformation with accurate rovibrational states of $\rm{H_3^+}$. Finally, we use the laboratory-frame quantum defects to calculate Rydberg energy levels for the fundamental neutral triatomic molecule $\rm{H_3}$.

Antimatter $^4_{\Lambda}$H Hypernucleus Production and the $^3_{\Lambda}$H/$^3$He Puzzle in Relativistic Heavy-Ion Collisions

Sun, Kai-Jia; Chen, Lie-Wen
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/12/2015
Relevância na Pesquisa
45.59%
We show that the measured much larger yield ratio $^3_{\Lambda}$H/$^3$He ($^3_{\overline{\Lambda}}\overline{\text{H}}$/$^3\overline{\text{He}}$) in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV than that in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV can be understood within a covariant coalescence model if (anti-)$\Lambda$ particles freeze out earlier than (anti-)nucleons but their relative freezeout time is closer at $\sqrt{s_{NN}}=2.76$ TeV than at $\sqrt{s_{NN}}=200$ GeV. The earlier (anti-)$\Lambda$ freezeout can significantly enhance the yield of (anti)hypernucleus $^4_{\Lambda}$H ($^4_{\overline{\Lambda}}\overline{\text{H}}$), leading to that $^4_{\overline{\Lambda}}\overline{\text{H}}$ has an even larger abundance than $^4\overline{\text{He}}$ and provides an easily measured antimatter heavier than $^4\overline{\text{He}}$. The future measurement on $^4_{\Lambda}$H ($^4_{\overline{\Lambda}}\overline{\text{H}}$) would be very useful to understand the (anti-)$\Lambda$ freezeout dynamics and the production mechanism of (anti)hypernuclei in relativistic heavy-ion collisions.; Comment: 5 pages, 2 figures, 2 tables

Structure-Based Prediction of Subtype Selectivity of Histamine H_3 Receptor Selective Antagonists in Clinical Trials

Kim, Soo-Kyung; Fristrup, Peter; Abrol, Ravinder; Goddard, William A., III
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /12/2011
Relevância na Pesquisa
45.6%
Histamine receptors (HRs) are excellent drug targets for the treatment of diseases, such as schizophrenia, psychosis, depression, migraine, allergies, asthma, ulcers, and hypertension. Among them, the human H_3 histamine receptor (hH3HR) antagonists have been proposed for specific therapeutic applications, including treatment of Alzheimer’s disease, attention deficit hyperactivity disorder (ADHD), epilepsy, and obesity. However, many of these drug candidates cause undesired side effects through the cross-reactivity with other histamine receptor subtypes. In order to develop improved selectivity and activity for such treatments, it would be useful to have the three-dimensional structures for all four HRs. We report here the predicted structures of four HR subtypes (H_1, H_2, H_3, and H_4) using the GEnSeMBLE (GPCR ensemble of structures in membrane bilayer environment) Monte Carlo protocol, sampling ~35 million combinations of helix packings to predict the 10 most stable packings for each of the four subtypes. Then we used these 10 best protein structures with the DarwinDock Monte Carlo protocol to sample ~50 000 × 10^(20) poses to predict the optimum ligand–protein structures for various agonists and antagonists. We find that E206^(5.46) contributes most in binding H3 selective agonists in agreement with experimental mutation studies. We also find that conserved E5.46/S5.43 in both of hH_(3)HR and hH_(4)HR are involved in H_(3)/ H_(4) subtype selectivity. In addition...