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Search Results: 1 - 10 of 371830 matches for " R. D. Carlini "
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Testing the Standard Model by precision measurement of the weak charges of quarks
Young, R. D.;Carlini, R. D.;Thomas, A. W.;Roche, J.
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevLett.99.122003
Abstract: In a global analysis of the latest parity-violating electron scattering measurements on nuclear targets, we demonstrate a significant improvement in the experimental knowledge of the weak neutral-current lepton-quark interactions at low energy. The precision of this new result, combined with earlier atomic parity-violation measurements, places tight constraints on the size of possible contributions from physics beyond the Standard Model. Consequently, this result improves the lower-bound on the scale of relevant new physics to ~1 TeV.
Extracting nucleon strange and anapole form factors from world data
R. D. Young,J. Roche,R. D. Carlini,A. W. Thomas
Physics , 2006, DOI: 10.1103/PhysRevLett.97.102002
Abstract: The complete world set of parity violating electron scattering data up to Q^2~0.3 GeV^2 is analysed. We extract the current experimental determination of the strange electric and magnetic form factors of the proton, as well as the weak axial form factors of the proton and neutron, at Q^2 = 0.1 GeV^2. Within experimental uncertainties, we find that the strange form factors are consistent with zero, as are the anapole contributions to the axial form factors. Nevertheless, the correlation between the strange and anapole contributions suggest that there is only a small probability that these form factors all vanish simultaneously.
Ureases display biological effects independent of enzymatic activity: Is there a connection to diseases caused by urease-producing bacteria?
Olivera-Severo, D.;Wassermann, G.E.;Carlini, C.R.;
Brazilian Journal of Medical and Biological Research , 2006, DOI: 10.1590/S0100-879X2006000700002
Abstract: ureases are enzymes from plants, fungi and bacteria that catalyze the hydrolysis of urea to form ammonia and carbon dioxide. while fungal and plant ureases are homo-oligomers of 90-kda subunits, bacterial ureases are multimers of two or three subunit complexes. we showed that some isoforms of jack bean urease, canatoxin and the classical urease, bind to glycoconjugates and induce platelet aggregation. canatoxin also promotes release of histamine from mast cells, insulin from pancreatic cells and neurotransmitters from brain synaptosomes. in vivo it induces rat paw edema and neutrophil chemotaxis. these effects are independent of ureolytic activity and require activation of eicosanoid metabolism and calcium channels. helicobacter pylori, a gram-negative bacterium that colonizes the human stomach mucosa, causes gastric ulcers and cancer by a mechanism that is not understood. h. pylori produces factors that damage gastric epithelial cells, such as the vacuolating cytotoxin vaca, the cytotoxin-associated protein caga, and a urease (up to 10% of bacterial protein) that neutralizes the acidic medium permitting its survival in the stomach. h. pylori whole cells or extracts of its water-soluble proteins promote inflammation, activate neutrophils and induce the release of cytokines. in this paper we review data from the literature suggesting that h. pylori urease displays many of the biological activities observed for jack bean ureases and show that bacterial ureases have a secretagogue effect modulated by eicosanoid metabolites through lipoxygenase pathways. these findings could be relevant to the elucidation of the role of urease in the pathogenesis of the gastrointestinal disease caused by h. pylori.
Time machines and the Principle of Self-Consistency as a consequence of the Principle of Stationary Action (II): the Cauchy problem for a self-interacting relativistic particle
A. Carlini,I. D. Novikov
Physics , 1996, DOI: 10.1142/S021827189600028X
Abstract: We consider the action principle to derive the classical, relativistic motion of a self-interacting particle in a 4-D Lorentzian spacetime containing a wormhole and which allows the existence of closed time-like curves. In particular, we study the case of a pointlike particle subject to a `hard-sphere' self-interaction potential and which can traverse the wormhole an arbitrary number of times, and show that the only possible trajectories for which the classical action is stationary are those which are globally self-consistent. Generically, the multiplicity of these trajectories (defined as the number of self-consistent solutions to the equations of motion beginning with given Cauchy data) is finite, and it becomes infinite if certain constraints on the same initial data are satisfied. This confirms the previous conclusions (for a non-relativistic model) by Echeverria, Klinkhammer and Thorne that the Cauchy initial value problem in the presence of a wormhole `time machine' is classically `ill-posed' (far too many solutions). Our results further extend the recent claim by Novikov et al. that the `Principle of self-consistency' is a natural consequence of the `Principle of minimal action.'
Plant Ureases and Related Peptides: Understanding Their Entomotoxic Properties
Fernanda Stanis?uaski,Célia R. Carlini
Toxins , 2012, DOI: 10.3390/toxins4020055
Abstract: Recently, ureases were included in the arsenal of plant defense proteins, alongside many other proteins with biotechnological potential such as insecticides. Isoforms of Canavalia ensiformis urease (canatoxin—CNTX and jack bean urease—JBURE-I) are toxic to insects of different orders. This toxicity is due in part to the release of a 10 kDa peptide from the native protein, by cathepsin-like enzymes present in the insect digestive tract. The entomotoxic peptide, Jaburetox-2Ec, exhibits potent insecticidal activity against several insects, including many resistant to the native ureases. JBURE-I and Jaburetox-2Ec cause major alterations of post-feeding physiological processes in insects, which contribute to, or can be the cause of, their entomotoxic effect. An overview of the current knowledge on plant urease processing and mechanisms of action in insects is presented in this review.
Quantum Template Matching
M. Sasaki,A. Carlini,R. Jozsa
Physics , 2001, DOI: 10.1103/PhysRevA.64.022317
Abstract: We consider the quantum analogue of the pattern matching problem, which consists of classifying a given unknown system according to certain predefined pattern classes. We address the problem of quantum template matching in which each pattern class ${\cal C}_i$ is represented by a known quantum state $\hat g_i$ called a template state, and our task is to find a template which optimally matches a given unknown quantum state $\hat f$. We set up a precise formulation of this problem in terms of the optimal strategy for an associated quantum Bayesian inference problem. We then investigate various examples of quantum template matching for qubit systems, considering the effect of allowing a finite number of copies of the input state $\hat f$. We compare quantum optimal matching strategies and semiclassical strategies and demonstrate an entanglement assisted enhancement of performance in the general quantum optimal strategy.
Quantum versions of Carlini-Miji? wormholes
A. Carlini,D. H. Coule,D. M. Solomons
Physics , 1994,
Abstract: We consider the quantum analogues of wormholes obtained by Carlini and Miji\'c (CM), who analytically continued closed universe models. To obtain wormholes when the strong energy condition ($\gamma>2/3$) is satisfied, we are able to simplify the Wheeler-DeWitt (WDW) equation by using an equivalent scalar potential which is a function of the scale factor. Such wormholes are found to be consistent with the Hawking-Page (HP) conjecture for quantum wormholes as solutions of the WDW equation. In addition to the CM type wormholes, for a scalar field realization of the potential in the WDW equation we also obtain quantum wormholes when the strong energy condition is violated. This violation can be up to an arbitrary large distance from the wormhole throat, before the violation eventually has to be relaxed in order to have a flat Euclidean space time. These results give support to the claim of HP that wormhole solutions are a fairly general property of the WDW equation. However, by allowing such solutions one might be precluding other more important properties such as a Lorentzian behaviour and a possible inflationary earlier stage of our universe.
The lead-glass electromagnetic calorimeters for the magnetic spectrometers in Hall C at Jefferson Lab
H. Mkrtchyan,R. Carlini,V. Tadevosyan,J. Arrington,A. Asaturyan,M. E. Christy,D. Dutta,R. Ent,H. C. Fenker,D. Gaskell,T. Horn,M. K. Jones,C. E. Keppel,D. J. Mack,S. P. Malace,A. Mkrtchyan,M. I. Niculescu,J. Seely,V. Tvaskis,S. A. Wood,S. Zhamkochyan
Physics , 2012, DOI: 10.1016/j.nima.2013.03.070
Abstract: The electromagnetic calorimeters of the various magnetic spectrometers in Hall C at Jefferson Lab are presented. For the existing HMS and SOS spectrometers design considerations, relevant construction information, and comparisons of simulated and experimental results are included. The energy resolution of the HMS and SOS calorimeters is better than $\sigma/E \sim 6%/\sqrt E $, and pion/electron ($\pi/e$) separation of about 100:1 has been achieved in energy range 1 -- 5 GeV. Good agreement has been observed between the experimental and simulated energy resolutions, but simulations systematically exceed experimentally determined $\pi^-$ suppression factors by close to a factor of two. For the SHMS spectrometer presently under construction details on the design and accompanying GEANT4 simulation efforts are given. The anticipated performance of the new calorimeter is predicted over the full momentum range of the SHMS. Good electron/hadron separation is anticipated by combining the energy deposited in an initial (preshower) calorimeter layer with the total energy deposited in the calorimeter.
x- and xi-scaling of the Nuclear Structure Function at Large x
J. Arrington,C. S. Armstrong,T. Averett,O. K. Baker,L. de Bever,C. W. Bochna,W. Boeglin,B. Bray,R. D. Carlini,G. Collins,C. Cothran,D. Crabb,D. Day,J. A. Dunne,D. Dutta,R. Ent,B. W. Filippone,A. Honegger,E. W. Hughes,J. Jensen,J. Jourdan,C. E. Keppel,D. M. Koltenuk,R. Lindgren,A. Lung,D. J Mack,J. McCarthy,R. D. McKeown,D. Meekins,J. H. Mitchell,H. G. Mkrtchyan,G. Niculescu,I. Niculescu,T. Petitjean,O. Rondon,I. Sick,C. Smith,B. Terburg,W. F. Vulcan,S. A. Wood,C. Yan,J. Zhao,B. Zihlmann
Physics , 2001, DOI: 10.1103/PhysRevC.64.014602
Abstract: Inclusive electron scattering data are presented for ^2H and Fe targets at an incident electron energy of 4.045 GeV for a range of momentum transfers from Q^2 = 1 to 7 (GeV/c)^2. Data were taken at Jefferson Laboratory for low values of energy loss, corresponding to values of Bjorken x greater than or near 1. The structure functions do not show scaling in x in this range, where inelastic scattering is not expected to dominate the cross section. The data do show scaling, however, in the Nachtmann variable \xi. This scaling may be the result of Bloom Gilman duality in the nucleon structure function combined with the Fermi motion of the nucleons in the nucleus. The resulting extension of scaling to larger values of \xi opens up the possibility of accessing nuclear structure functions in the high-x region at lower values of Q^2 than previously believed.
Enteroquistoma del ombligo con inclusión de mucosa gástrica
Revista chilena de pediatría , 1946,
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