On the self-shift and broadening of doppler-free Rydberg 2S spectral lines in alkali atoms

The shift and broadening of Doppler-free, two-photon transitions to Rydberg states of alkali atoms are analyzed for the case of Rb in the framework of a molecular approach to collisions of ground state and Rydberg atoms. The overall features of the observed spectra are determined by the electrostatic interactions between the two atoms and are calculated using the impact theory of spectral line-shapes. The superimposed oscillations in the widths and shifts as functions of the Rydberg quantum number can be understood in terms of resonance electron-ground state atom scattering. The corresponding contributions to the spectra are determined by the energy and lifetime of a ³P autoionizing state of the negative alakali ion.     

Inclusive ϱ0 production in γp interactions at 2.8, 4.7, and 9.3 GeV

Inclusive ?⁰ production in γp → ?⁰ + anything is studied at 2.8, 4.7, and 9.3 GeV, using the SLAC linearly polarized backscattered laser photon beam and the 82 inch hydrogen bubble chamber. Over this energy range the inclusive inelastic ?⁰ cross section rises from 6.0 μb to 20.5 μb. The multiplicity, i.e. the average number of μ⁰ mesons per inelastic hadronic event, has an energy dependence consistent with 1n s.The inclusive cross section is studied as a function of Feynman x, c.m. rapidity, and p_T² variables, and is also broken down into exclusive channels. At 9.3 GeV a forward inelastic peak is observed in the x distribution, containing mainly polarized ?⁰ mesons. The cross section for this inealastic diffractive component is 2.7 ± 0.6 μb. The p_T² distributions are exponential with a slope of 3 ? 4 (GeV/c)^?2, similar to that found in inclusive ?⁰ production in pp and μp reactions.     

Electron impact ionization of silver clusters Ag n,n≦36

Electron impact ionization of gas phase silver clusters Ag _n ,n≦36 has been achieved in the threshold region. The vertical ionization potentials in this region clearly demonstrate the evidence of shell effects as well as a distinct even-odd oscillation up ton?20. Their general size dependence is somewhat different from that of the alkali metal clusters due to the presence of thed-electrons.     

Distribution functions for filaments under tension

We develop a biased Monte Carlo simulation technique to measure the distribution functions of the extension and the end-to-end distance of fluctuating filaments stretched by external force. The method is applicable for arbitrary ratio of the persistence length to the contour length and for arbitrary forces, and also for the case of steric constraints, such as an external wall. The fundamental idea underlying the algorithm is to account explicitly for the length-scale dependence of the effective elastic moduli. We find that orientational fluctuations and wall effects produce non-Gaussian distributions for nearly rigid filaments in the small to intermediate force regime. The simulation results are tested against analytic expressions for the force-extension curves, both in the semiflexible and nearly stiff limits.     

The geometry of the super KP flows

A supersymmetric generalization of the Krichever map is used to construct algebro-geometric solutions to the various super Kadomtsev-Petviashvili (SKP) hierarchies. The geometric data required consist of a suitable algebraic supercurve of genusg (generallynot a super Riemann surface) with a distinguished point and local coordinates (z, ) there, and a generic line bundle of degreeg–1 with a local trivialization near the point. The resulting solutions to the Manin-Radul SKP system describe coupled deformations of the line bundle and the supercurve itself, in contrast to the ordinary KP system which deforms line bundles but not curves. Two new SKP systems are introduced: an integrable Jacobian system whose solutions describe genuine Jacobian flows, deforming the bundle but not the curve; and a nonintegrable maximal system describing independent deformations of bundle and curve. The Kac-van de Leur SKP system describes the same deformations as the maximal system, but in a different parametrization.     

A New Device for Mechanical Testing of Blood Vessels at Cryogenic Temperatures

As part of an ongoing program to study the thermo-mechanical effects associated with cryopreservation via vitrification (vitreous in Latin means glassy), the current study focuses on the development of a new device for mechanical testing of blood vessels at cryogenic temperatures. This device is demonstrated on a bovine carotid artery model, permeated with the cryoprotectant cocktail VS55 and a reference solution of 7.05M DMSO, below glass transition. Results are also presented for crystallized specimens, in the absence of cryoprotectants. Results indicate that the elastic modulus of a specimen with no cryoprotectant, at about −140°C (8.6 and 15.5°C below the glass transition temperature of 7.05M DMSO and VS55, respectively), is 1038.8 ± 25.2 MPa, which is 8 and 3% higher than that of a vitrified specimen permeated with 7.05M DMSO and VS55, respectively. The elastic modulus of a crystallized material at −50°C is lower by ∼20% lower from that at −140°C.     

Three-dimensional noncommutative bosonization

We consider the extension of the (2+1)-dimensional$(2+1)\text{-dimensional}$ bosonization process in noncommutative (NC) spacetime. We show that the large mass limit of the effective action obtained by integrating out the fermionic fields in NC spacetime leads to the NC Chern–Simons action. The present result is valid to all orders in the noncommutative parameter θ. We also discuss how the NC Yang–Mills action is induced in the next to leading order.     

Hawking radiation,effective actions and covariant boundary conditions

From an appropriate expression for the effective action, the Hawking radiation from charged black holes is derived, using only covariant boundary conditions at the event horizon. The connection of our approach with the Unruh vacuum and the recent analysis [S.P. Robinson, F. Wilczek, Phys. Rev. Lett. 95 (2005) 011303, gr-qc/0502074; S. Iso, H. Umetsu, F. Wilczek, Phys. Rev. Lett. 96 (2006) 151302, hep-th/0602146; R. Banerjee, S. Kulkarni, arXiv: 0707.2449 [hep-th]] of Hawking radiation using anomalies is established.     

Model of DNA bending by cooperative binding of proteins

We present a model of nonspecific cooperative binding of proteins to DNA in which the binding of isolated proteins generates local bends but binding of proteins at neighboring sites on DNA straightens the polymer. We solve the statistical mechanical problem and calculate the effective persistence length, site occupancy, and cooperativity. Cooperativity leads to nonmonotonic variation of the persistence length with protein concentration, and to an unusual shape of the binding isotherm. The results are in qualitative agreement with recent single molecule experiments on nucleoid protein HU-DNA complexes.