9,854 research outputs found
Experimental studies on twinjet afterbody-nozzle system of combat aircraft configurations
This report highlights the progress of the work carried out in the above project including the statement of expenditure for presentation at AR&DB annual symposium-201
SU(N) Coherent States
We generalize Schwinger boson representation of SU(2) algebra to SU(N) and
define coherent states of SU(N) using bosonic harmonic
oscillator creation and annihilation operators. We give an explicit
construction of all (N-1) Casimirs of SU(N) in terms of these creation and
annihilation operators. The SU(N) coherent states belonging to any irreducible
representations of SU(N) are labelled by the eigenvalues of the Casimir
operators and are characterized by (N-1) complex orthonormal vectors describing
the SU(N) manifold. The coherent states provide a resolution of identity,
satisfy the continuity property, and possess a variety of group theoretic
properties.Comment: 25 pages, LaTex, no figure
Cerebral autoregulation, brain injury, and the transitioning premature infant
Improvements in clinical management of the preterm infant have reduced the rates of the two most common forms of brain injury, such as severe intraventricular hemorrhage and white matter injury, both of which are contributory factors in the development of cerebral palsy. Nonetheless, they remain a persistent challenge and are associated with a significant increase in the risk of adverse neurodevelopment outcomes. Repeated episodes of ischemia–reperfusion represent a common pathway for both forms of injury, arising from discordance between systemic blood flow and the innate regulation of cerebral blood flow in the germinal matrix and periventricular white matter. Nevertheless, establishing firm hemodynamic boundaries, as a part of neuroprotective strategy, has challenged researchers. Existing measures either demonstrate inconsistent relationships with injury, as in the case of mean arterial blood pressure, or are not feasible for long-term monitoring, such as cardiac output estimated by echocardiography. These challenges have led some researchers to focus on the mechanisms that control blood flow to the brain, known as cerebrovascular autoregulation. Historically, the function of the cerebrovascular autoregulatory system has been difficult to quantify; however, the evolution of bedside monitoring devices, particularly near-infrared spectroscopy, has enabled new insights into these mechanisms and how impairment of blood flow regulation may contribute to catastrophic injury. In this review, we first seek to examine how technological advancement has changed the assessment of cerebrovascular autoregulation in premature infants. Next, we explore how clinical factors, including hypotension, vasoactive medications, acute and chronic hypoxia, and ventilation, alter the hemodynamic state of the preterm infant. Additionally, we examine how developmentally linked or acquired dysfunction in cerebral autoregulation contributes to preterm brain injury. In conclusion, we address exciting new approaches to the measurement of autoregulation and discuss the feasibility of translation to the bedside
Heavy light tetraquarks from Lattice QCD
We present preliminary results from a lattice calculation of tetraquark
states in the charm and bottom sector of the type ,
, and . These
calculations are performed on MILC ensembles with lattice
spacing of and . A relativistic
action with overlap fermions is employed for the light and charm quarks while a
non-relativistic action with non-perturbatively improved coefficients is used
in the bottom sector. Preliminary results provide a clear indication of
presence of energy levels below the relevant thresholds of different tetraquark
states. While in double charm sector we find shallow bound levels, our results
suggest deeply bound levels with double bottom tetraquarks.Comment: Corrected threshold for the tetraquark state.
Proceedings of the 35th International Symposium on Lattice Field Theory,
18-24 June 2017, Granada, Spain. TIFR preprint no : TIFR/TH/17-3
Spectroscopy of Charmed and Bottom Hadrons using Lattice QCD
We present preliminary results on the light, charmed and bottom baryon
spectra using overlap valence quarks on the background of 2+1+1 flavours HISQ
gauge configurations of the MILC collaboration. These calculations are
performed on three different gauge ensembles at three lattice spacings (a ~
0.12 fm, 0.09 fm and 0.06 fm) and for physical strange, charm and bottom quark
masses. The SU(2) heavy baryon chiral perturbation theory is used to
extrapolate baryon masses to the physical pion mass and the continuum limit
extrapolations are also performed. Our results are consistent with the well
measured charmed baryons. We predict the masses of many other states which are
yet to be discovered.Comment: 8 pages, Proceedings of the 35th International Symposium on Lattice
Field Theory (Lattice 2017
More on SU(3) Lattice Gauge Theory in the Fundamental--Adjoint Plane
We present further evidence for the bulk nature of the phase transition line
in the fundamental--adjoint action plane of SU(3) lattice gauge theory.
Computing the string tension and some glueball masses along the thermal phase
transition line of finite temperature systems with , which was found to
join onto the bulk transition line at its endpoint, we find that the ratio
remains approximately constant. However, the mass of the
glueball decreases as the endpoint of the bulk transition line is
approached, while the other glueball masses appear unchanged. This is
consistent with the notion that the bulk transition line ends in a critical
endpoint with the continuum limit there being a theory with a
diverging correlation length only in the channel.Comment: 4 pages, uuencoded, gziped postscript file. To appear in the
Proceedings of LATTICE'95, Melbourne, Australia, 11-15 July, 199
Strong light fields coax intramolecular reactions on femtosecond time scales
Energetic H ions are formed as a result of intra-molecular
rearrangement during fragmentation of linear alcohols (methanol, ethanol,
propanol, hexanol, and dodecanol) induced by intense optical fields produced by
100 fs long, infrared, laser pulses of peak intensity 8 W
cm. Polarization dependent measurements show, counterintuitively, that
rearrangement is induced by the strong optical field within a single laser
pulse, and that it occurs before Coulomb explosion of the field-ionized
multiply charged alcohols
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