5,945 research outputs found
Preparation of thermally stable phenylpolysiloxane fused silica capillary columns : optimization and evaluation of the deactivation by capillary GC and solid state 29Si NMR
The deactivation of fused silica capillary columns with a laboratory-made poly-diphenylvinylmethylhydrosiloxane copolymer has been investigated. The deactivation obtained at different temperatures and reaction times is characterized with a dual column capillary GC system [1]. In parallel, the effect of the silylation temperatures and reaction times on the nature, the structure, and the chemical properties of the deactivation layer has also been studied by solid-state 29Si NMR spoctroscopy. A fumed silica, Cab-O-Sil M5, was used as a model substrate for these spectroscopic studies. The deactivated fused silica capillaries show an excellent thermal stability (up to 400°C), a high resistance to solvolysis, and a minimal interaction to various critical test components. A good wettability of the fused silica capillary columns deactivated with this reagent was confirmed by successful subsequent coating with polysiloxanes with different phenyl content
Penta-quark states with hidden charm and beauty
More and more hadron states are found to be difficult to be accommodated by
the quenched quark models which describe baryons as 3-quark states and mesons
as antiquark-quark states. Dragging out an antiquark-quark pair from the gluon
field in hadrons should be an important excitation mechanism for hadron
spectroscopy. Our recent progress on the penta-quark states with hidden charm
and beauty is reviewed.Comment: Plenary talk at the 5th Asia-Pacific Conference on Few-Body Problems
in Physics 2011 (APFB2011), 22-26 Aug., 2011, Seoul, Kore
Unambiguous discrimination between two unknown qudit states
We consider the unambiguous discrimination between two unknown qudit states
in -dimensional () Hilbert space. By equivalence of unknown
pure states to known mixed states and with the Jordan-basis method, we
demonstrate that the optimal success probability of the discrimination between
two unknown states is independent of the dimension . We also give a scheme
for a physical implementation of the programmable state discriminator that
unambiguously discriminate between two unknown states with optimal probability
of success.Comment: 8 pages, 3 figure
Quantum-classical correspondence for local density of states and eigenfunctions of a chaotic periodic billiard
Classical-quantum correspondence for conservative chaotic Hamiltonians is
investigated in terms of the structure of the eigenfunctions and the local
density of states, using as a model a 2D rippled billiard in the regime of
global chaos. The influence of the observed localized and sparsed states in the
quantum-classical correspondence is discussed.Comment: 8 pages, 4 figure
Perturbative Formulation and Non-adiabatic Corrections in Adiabatic Quantum Computing Schemes
Adiabatic limit is the presumption of the adiabatic geometric quantum
computation and of the adiabatic quantum algorithm. But in reality, the
variation speed of the Hamiltonian is finite. Here we develop a general
formulation of adiabatic quantum computing, which accurately describes the
evolution of the quantum state in a perturbative way, in which the adiabatic
limit is the zeroth-order approximation. As an application of this formulation,
non-adiabatic correction or error is estimated for several physical
implementations of the adiabatic geometric gates. A quantum computing process
consisting of many adiabatic gate operations is considered, for which the total
non-adiabatic error is found to be about the sum of those of all the gates.
This is a useful constraint on the computational power. The formalism is also
briefly applied to the adiabatic quantum algorithm.Comment: 5 pages, revtex. some references adde
Two-dimensional non-commutative Yang-Mills theory: coherent effects in open Wilson line correlators
A perturbative calculation of the correlator of three parallel open Wilson
lines is performed for the U(N) theory in two non-commutative space-time
dimensions. In the large-N planar limit, the perturbative series is fully
resummed and asymptotically leads to an exponential increase of the correlator
with the lengths of the lines, in spite of an interference effect between lines
with the same orientation. This result generalizes a similar increase occurring
in the two-line correlator and is likely to persist when more lines are
considered provided they share the same direction.Comment: 22 pages, 1 figure, typeset in JHEP styl
Transport and the Order Parameter of Superconducting UPt3
We calculate the ultrasonic absorption and the thermal conductivity in the
superconducting state of UPt as functions of temperature and direction of
propagation and polarization. Two leading candidates for the superconducting
order parameter are considered: the and representations. Both
can fit the data except for the ultrasonic absorption in the phase. To do
that, it is necessary to suppose that the system has only a single domain, and
that must be chosen as the most favorable one. However, the theory
requires fine-tuning of parameters to fit the low temperature thermal
conductivity. Thus, transport data favor the theory. Measurements of
the thermal conductivity as a function of pressure at low temperature could
help to further distinguish the two theories.Comment: 7 pages, 4 figure
On the general structure of gauged Wess-Zumino-Witten terms
The problem of gauging a closed form is considered. When the target manifold
is a simple Lie group G, it is seen that there is no obstruction to the gauging
of a subgroup H\subset G if we may construct from the form a cocycle for the
relative Lie algebra cohomology (or for the equivariant cohomology), and an
explicit general expression for these cocycles is given. The common geometrical
structure of the gauged closed forms and the D'Hoker and Weinberg effective
actions of WZW type, as well as the obstructions for their existence, is also
exhibited and explained.Comment: Some changes. 23 pages; latex2e file. To appear in Nucl. Phys.
Endophthalmitis after pars plana vitrectomy: Results of the pan American collaborative retina study group
Purpose: To determine the incidence of endophthalmitis after 20-, 23-, and 25-gauge pars plana vitrectomies (PPVs). Methods: Retrospective comparative case series of consecutive patients who underwent 20-, 23-, or 25-gauge PPV at 11 centers from Latin America between 2005 to 2009. Pars plana vitrectomy cases were identified through a search of the billing records of each institution. Cases of PPV performed in the management of trauma, endophthalmitis, and combined PPV phacoemulsification cases were excluded. Endophthalmitis was diagnosed by clinical criteria regardless of the microbiologic results. The incidence of post-PPV endophthalmitis was compared between 20-, 23-, and 25-gauge PPVs. Results: A total of 35,427 cases of PPV were identified during the study period (n = 19,865 for 20 gauge, n = 10,845 for 23 gauge, and n = 4,717 for 25 gauge). The 5-year post-PPV endophthalmitis incidence rates were 0.020% (4 of 19,865), 0.028% (3 of 10,845), and 0.021% (1 of 4,717) for 20 gauge, 23 gauge, and 25 gauge, respectively (P = 0.9685). Conclusion: Small-gauge transconjunctival PPV does not appear to increase the rates of post-PPV endophthalmitis. © The Ophthalmic Communications Society, Inc
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