5,352 research outputs found
Circular dichroism in photoelectron angular distributions from two‐color (1+1) REMPI of NO
A detailed experimental and theoretical study of dichroic effects in photoelectron angular distributions is reported for (1+1), two‐color REMPI of NO via the A^ 2Σ^+, v=0 state. Optically aligned A state rotational levels are probed through ionization by circularly polarized light. Resultant photoelectron angular distributions exhibit significant left–right asymmetry, the phase and magnitude of which are shown to be related to the curvature of the excited state M_J distribution. Theoretical calculations involving a full ab initio treatment of the ionization dynamics result in circularly dichroic angular distribution (CDAD) parameters in good agreement with those derived experimentally. Additional effects including hyperfine depolarization and coherence are also discussed in relation to the observed CDAD data
Computing welfare losses from data under imperfect competition with heterogeneous goods
We study the percentage of welfare losses (PWL) yielded by imperfect competition under
product differentiation. When demand is linear, if prices, outputs, costs and the number of firms
can be observed, PWL is arbitrary in both Cournot and Bertrand equilibria. If in addition, the
elasticity of demand (resp. cross elasticity of demand) is known, we can calculate PWL in
Cournot (resp. Bertrand) equilibrium. When demand is isoelastic and there are many firms, PWL
can be computed from prices, outputs, costs and the number of .rms. In all these cases we find
that price-marginal cost margins and demand elasticities may influence PWL in a
counterintuitive way. We also provide conditions under which PWL increases or decreases with
concentration
Optimal Multi-Modes Switching Problem in Infinite Horizon
This paper studies the problem of the deterministic version of the
Verification Theorem for the optimal m-states switching in infinite horizon
under Markovian framework with arbitrary switching cost functions. The problem
is formulated as an extended impulse control problem and solved by means of
probabilistic tools such as the Snell envelop of processes and reflected
backward stochastic differential equations. A viscosity solutions approach is
employed to carry out a finne analysis on the associated system of m
variational inequalities with inter-connected obstacles. We show that the
vector of value functions of the optimal problem is the unique viscosity
solution to the system. This problem is in relation with the valuation of firms
in a financial market
Z_N Phases in Hot Gauge Theories
We argue that the \zn phases of hot gauge theories cannot be realized as a
real system with an Hermitean density matrix.Comment: 7 page
Photoelectron spectroscopy of excited molecular states
Results of studies of ion rotational and vibrational distributions for resonance enhanced multiphoton ionization are discussed
A theoretical investigation of the low lying electronic structure of poly(p-phenylene vinylene)
The two-state molecular orbital model of the one-dimensional phenyl-based
semiconductors is applied to poly(p-phenylene vinylene). The energies of the
low-lying excited states are calculated using the density matrix
renormalization group method. Calculations of both the exciton size and the
charge gap show that there are both Bu and Ag excitonic levels below the band
threshold. The energy of the 1Bu exciton extrapolates to 2.60 eV in the limit
of infinite polymers, while the energy of the 2Ag exciton extrapolates to 2.94
eV. The calculated binding energy of the 1Bu exciton is 0.9 eV for a 13
phenylene unit chain and 0.6 eV for an infinite polymer. This is expected to
decrease due to solvation effects. The lowest triplet state is calculated to be
at ca. 1.6 eV, with the triplet-triplet gap being ca. 1.6 eV. A comparison
between theory, and two-photon absorption and electroabsorption is made,
leading to a consistent picture of the essential states responsible for most of
the third-order nonlinear optical properties. An interpretation of the
experimental nonlinear optical spectroscopies suggests an energy difference of
ca. 0.4 eV between the vertical energy and ca. 0.8 eV between the relaxed
energy, of the 1Bu exciton and the band gap, respectively.Comment: LaTeX, 19 pages, 7 eps figures included using epsf. To appear in
Physical Review B, 199
Hot Gauge Theories and Phases
In this paper the several aspects of the symmetry in gauge theories
at high temperatures are discussed. The metastable bubbles in the
gauge theories with fermions may have, generically, unacceptable
thermodynamic behavior. Their free energy with a positive
proportionality constant. This leads not only to negative pressure but also to
negative specific heat and, more seriously, to negative entropy. We argue that
although such domains are important in the Euclidean theory, they cannot be
interpreted as physical domains in Minkowski space. The related problem is
connected with the analysis of the high-temperature limit of the confining
phase. Using the two-dimensional QCD with adjoint fermions as a toy model we
shall demonstrate that in the light fermion limit in this theory there is no
breaking of the symmetry in the high-temperature limit and thus there
are no bubbles.Comment: preprint PUPT-1415, 21
Long-term moderate calorie restriction inhibits inflammation without impairing cell-mediated immunity: A randomized controlled trial in non-obese humans
Calorie restriction (CR) inhibits inflammation and slows aging in many animal species, but in rodents housed in pathogen-free facilities, CR impairs immunity against certain pathogens. However, little is known about the effects of long-term moderate CR on immune function in humans. In this multi-center, randomized clinical trial to determine CR's effect on inflammation and cell-mediated immunity, 218 healthy non-obese adults (20-50 y), were assigned 25% CR (n=143) or an ad-libitum (AL) diet (n=75), and outcomes tested at baseline, 12, and 24 months of CR. CR induced a 10.4% weight loss over the 2-y period. Relative to AL group, CR reduced circulating inflammatory markers, including total WBC and lymphocyte counts, ICAM-1 and leptin. Serum CRP and TNF-α concentrations were about 40% and 50% lower in CR group, respectively. CR had no effect on the delayed-type hypersensitivity skin response or antibody response to vaccines, nor did it cause difference in clinically significant infections. In conclusion, long-term moderate CR without malnutrition induces a significant and persistent inhibition of inflammation without impairing key in vivo indicators of cell-mediated immunity. Given the established role of these pro-inflammatory molecules in the pathogenesis of multiple chronic diseases, these CR-induced adaptations suggest a shift toward a healthy phenotype
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