High-power Lyman-alpha source generated with an ArF excimer laser

We report high-power vacuum-ultraviolet (vuv) generation at the Lyman- alpha wavelength of 121.6nm , using a simple experimental system. vuv radiation is produced through two-photon-resonant difference-frequency mixing with a tunable ArF excimer laser and a Nd:YAG-pumped dye laser. Using phase-matched mixtures of Kr and Ar at a total pressure of 650 mbar, we produced 7-microJ energies at Lyman- alpha in approximately 5ns (1.3kW) , as measured directly with a pyroelectric energy probe. Measurements indicate that higher powers are possible with system optimization. A tuning range of 0.1nm was achieved for a fixed gas mole fraction at a total pressure of 650 mbar. Qualitative agreement is found between measured tuning profiles and theoretical predictions.     

Optically addressed droplet-based protein assay

We demonstrate a new method for performing protein assays with very small volumes ( approximately 1.7 muL to 14 pL). Using a laser to modify local surface energy, we manipulate, fuse, and mix droplets containing horseradish peroxidase and its substrates. A detection limit of approximately 30 attomoles of reacting enzyme was measured by optical absorption. We discuss the possibility of extending this lower limit to zeptomoles of enzyme.     

Commutators and self-adjointness of Hamiltonian operators

A time dependent approach to self-adjointness is presented and it is applied to quantum mechanical Hamiltonians which are not semi-bounded. Sufficient conditions are given for self-adjointness of Schrödinger and Dirac Hamiltonians with potentials which are unbounded at infinity. The method is the introduction of an auxiliary operatorN≧0 whose rate of change (commutator with the Hamiltonian) is bounded by a multiple ofN.     

Spin correlation in stochastic mechanics

Stochastic mechanics may be used to described the spin of atomic particles. The spin variables have the same expectations as in quantum mechanics, but not the same distributions. They play the role of hidden variables that influence, but do not determine, the results of Stern-Gerlach experiments involving magnets. During the course of such an experiment spin becomes correlated with position. The case of two particles with zero total spin occurs in Bohm's version of the Einstein-Rosen-Podolsky experiment.This material is based upon work supported by the National Science Foundation under Grant No. MCS-8002945.     

Localization estimates for a random discrete wave equation at high frequency

It is shown that at high frequencies matrix elements of the Green's function of a random discrete wave equation decay exponentially at long distances. This is the input to the proof of dense point spectrum with localized eigenfunctions in this frequency range. The proof uses techniques of Fröhlich and Spencer. A sequence of renormalization transformations shows that large regions where wave propagation is easily maintained become increasingly sparse as resonance is approached.     

Chemokine Receptor 5 Antagonism Causes Reduction in Joint Inflammation in a Collagen-Induced Arthritis Mouse Model

Rheumatoid arthritis (RA) is a chronic inflammatory disease mainly affecting the synovial joints. A highly potent antagonist of C-C chemokine receptor 5 (CCR5), maraviroc (MVC), plays an essential role in treating several infectious diseases but has not yet been evaluated for its potential effects on RA development. This study focused on evaluating the therapeutic potential of MVC on collagen-induced arthritis (CIA) in DBA/1J mice. Following CIA induction, animals were treated intraperitoneally with MVC (50 mg/kg) daily from day 21 until day 35 and evaluated for clinical score and histopathological changes in arthritic inflammation. We further investigated the effect of MVC on Th9 (IL-9, IRF-4, and GATA3) and Th17 (IL-21R, IL-17A, and RORγT) cells, TNF-α, and RANTES in CD8+ T cells in the spleen using flow cytometry. We also assessed the effect of MVC on mRNA and protein levels of IL-9, IL-17A, RORγT, and GATA3 in knee tissues using RT-PCR and western blot analysis. MVC treatment in CIA mice attenuated the clinical and histological severity of inflammatory arthritis, and it substantially decreased IL-9, IRF4, IL-21R, IL-17A, RORγT, TNF-α, and RANTES production but increased GATA3 production in CD8+ T cells. We further observed that MVC treatment decreased IL-9, IL-17A, and RORγt mRNA and protein levels and increased those of GATA3. This study elucidates the capacity of MVC to ameliorate the clinical and histological signs of CIA by reducing pro-inflammatory responses, suggesting that MVC may have novel therapeutic uses in the treatment of RA.     

Near-field Raman spectroscopy of biological nanomaterials by in situ laser-induced synthesis of tip-enhanced Raman spectroscopy tips

We report a new approach in tip-enhanced Raman spectroscopy (TERS) in which TERS-active tips with enhancement factors of ～10(-5)× can be rapidly (1-3 min) produced in situ by laser-induced synthesis of silver nanoparticles at the tip apex. The technique minimizes the risks of tip contamination and damage during handling and provides in situ feedback control, which allows the prediction of the tip performance. We show that TERS tips produced by this technique enable the measurement of spatially resolved TERS spectra of self-assembled peptide nanotubes with a spatial resolution of ～20 nm.     

Raman Scattering at Resonant or Near-Resonant Conditions: A Generalized Short-Time Approximation

We investigate the dynamics of resonant Raman scattering in the course of the frequency de-tuning. The dephasing in the time domain makes the scattering fast when the photon energy is tuned from the absorption resonance. This makes frequency detuning to act as a cam-era shutter with a regulated scattering duration and provides a practical tool of controlling the scattering time in ordinary stationary measurements. The theory is applied to resonant Raman spectra of a couple of few-mode model systems and to trans-1,3,5-hexatriene and guanine-cytosine (G-C) Watson-Crick base pairs (DNA) molecules. Besides some particular physical effects, the regime of fast scattering leads to a simplification of the spectrum as well as to the scattering theory itself. Strong overtones appear in the Raman spectra when the photon frequency is tuned in the resonant region, while in the mode of fast scattering, the overtones are gradually quenched when the photon frequency is tuned more than one vibra-tional quantum below the first absorption resonance. The detuning from the resonant region thus leads to a strong purification of the Raman spectrum from the contamination by higher overtones and soft modes and purifies the spectrum also in terms of avoidance of dissociationand interfering fluorescence decay of the resonant state. This makes frequency detuning a very useful practical tool in the analysis of the resonant Raman spectra of complex systems and considerably improves the prospects for using the Raman effect for detection of foreign substances at ultra-low concentrations.