1,430 research outputs found

    Radiative capture of polarized neutrons by polarized protons

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    A model-independent irreducible tensor approach to p(n,gamma)d is presented and an explicit form for the spin-structure of the matrix for the reaction is obtained in terms of the Pauli spin-matrices for the neutron and the proton. Expressing the multipole amplitudes in terms of the triplet --> triplet and singlet --> triplet transitions, we point out how the initial singlet and triplet contributions to the differential cross section can be determined empirically.Comment: Revised version; typeset using RevTeX4; 6 pages, no figure

    Phase ambiguity of the threshold amplitude in pp -> pp\pi^0

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    Measurements of spin observables in pp -> {\vec p}{\vec p}\pi^0 are suggested to remove the phase ambiguity of the threshold amplitude. The suggested measurements complement the IUCF data on {\vec p}{\vec p} -> pp\pi^0 to completely determine all the twelve partial wave amplitudes, taken into consideration by Mayer et.al. [15] and Deepak, Haidenbauer and Hanhart [20].Comment: 4 pages, 1 table

    Metal-insulator transitions in tetrahedral semiconductors under lattice change

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    Although most insulators are expected to undergo insulator to metal transition on lattice compression, tetrahedral semiconductors Si, GaAs and InSb can become metallic on compression as well as by expansion. We focus on the transition by expansion which is rather peculiar; in all cases the direct gap at Γ\Gamma point closes on expansion and thereafter a zero-gap state persists over a wide range of lattice constant. The solids become metallic at an expansion of 13 % to 15 % when an electron fermi surface around L-point and a hole fermi surface at Γ\Gamma-point develop. We provide an understanding of this behavior in terms of arguments based on symmetry and simple tight-binding considerations. We also report results on the critical behavior of conductivity in the metal phase and the static dielectric constant in the insulating phase and find common behaviour. We consider the possibility of excitonic phases and distortions which might intervene between insulating and metallic phases.Comment: 12 pages, 8 figure

    Delicate f(R) gravity models with disappearing cosmological constant and observational constraints on the model parameters

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    We study the f(R)f(R) theory of gravity using metric approach. In particular we investigate the recently proposed model by Hu-Sawicki, Appleby - Battye and Starobinsky. In this model, the cosmological constant is zero in flat space time. The model passes both the Solar system and the laboratory tests. But the model parameters need to be fine tuned to avoid the finite time singularity recently pointed in the literature. We check the concordance of this model with the H(z)H(z) and baryon acoustic oscillation data. We find that the model resembles the Λ\LambdaCDM at high redshift. However, for some parameter values there are variations in the expansion history of the universe at low redshift.Comment: 16 pages and 9 figures, typos corrected, few references and minor clarifications added, revised version to appera in PR

    Comparative evaluation of dexmedetomidine with clonidine as premedication for attenuation of hemodynamic responses during laryngoscopy and endotracheal intubation under general anesthesia

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    Background: Direct laryngoscopy and tracheal intubation predictably leads to tachyarrhythmia and hypertension which are usually transient and variable, but these changes may be fatal in high risk patients. These hemodynamic responses can be attenuated by appropriate premedication. Dexmedetomidine and clonidine, alpha- 2 adrenergic agonist, might do so. The present study was aimed to compare these drugs for attenuation of hemodynamic responses. Methods: Sixty adult consented patients of ASA grade I and II between 18-58 yrs of age of either sex were randomly allocated into two equal groups of 30 patients each by computer generated random number table. They were administered either dexmedetomidine (Group A) or clonidine (Group B) in dose of 1μg.kg-1 intravenously as premedication. Hemodynamic changes during laryngoscopy and intubation were primary end points and any side effects due to drugs were observed as secondary end points.Results: After propofol induction there was more fall in heart rate in patients of dexmedetomidine group  as compared to clonidine group but with statistically non-significant difference (p value>0.05). After laryngoscopy and intubation, hemodynamic variations were more in patients of clonidine group than in dexmedetomidine group with statistically significant difference (p value<0.05). Bradycardia (HR<50/min) was observed in one patient of dexmedetomidine group and two patients in clonidine group, five minutes after intubation. Intraoperative hypotension was observed in one patient of dexmedetomidine group and in two patients of clonidine group.Conclusions: Dexmedetomidine premedication in dose of 1 μg.kg-1 provided more stable hemodynamics during induction with propofol and following laryngoscopy and intubation as compared to clonidine.

    Management of adhesive capsulitis of shoulder joint with arthroscopic release vs. manipulation under anaesthesia: a comparative study

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    Background: Shoulder stiffness is a manifestation of various pathologies or clinical scenarios variously described as scapula humeral periarthritis, frozen shoulder and adhesive capsulitis. Frozen shoulder is characterized by significant restriction of active and passive motion of the shoulder that occurs due to unknown factors. Adhesive capsulitis causes contracted, thickened joint capsule that seemed to be drawn tightly around the humeral head with a relative absence of synovial fluid and chronic inflammatory changes within the subsynovial layer of the capsule. In this study we did a comparison of 30 patients treated with arthroscopic release and manipulation under anesthesia. Methods: There were 30 patients in this study with 15 patients in each group of different age groups. All the patients were studied for a period of one year between July 2021 to July 2022. The functional outcomes were assessed using dash scoring system. Results: in this study of 30 patients with different age groups followed for 12 months and assessed by DASH scoring system. We had excellent results in arthroscopic group with postop dash score standard deviation is 5.87. Conclusions: The arthroscopic capsular release of shoulder joint in adhesive capsulitis was found to have a better functional outcome as compared to the manipulation of shoulder joint under anaesthesia. Currently no treatment protocols are universally effective which needs more and more research and developments for proper treatment strategies. Morbidity with this condition has caused significant loss both economically and psychologically

    Partial-wave analysis of ppppπ\vec{p}\vec{p}\to pp\pi^\circ data

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    We present a partial-wave analysis of the polarization data for the reaction ppppπ\vec{p}\vec{p}\to pp\pi^\circ, based solely on the recent measurements at IUCF for this channel. The fit leads to a χ2\chi^2 per degree of freedom of 1.7. Methods for an improved analysis are discussed. We compare the extracted values to those from a meson exchange model.Comment: 14 pages, 11 figure
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