Coherent spectroscopy in dissipative media: time-domain studies of channel phase and signal interferometry

We extend a recently formulated coherence spectroscopy of dissipative media [J. Chem. Phys. 122, 084502 (2005)] from the stationary excitation limit to the time domain. Our results are based on analytical and numerical solutions of the quantum Liouville equation within the Bloch framework. It is shown that the short pulse introduces a new, controllable time scale that allows better insight into the relation between the coherence signal and the phase properties of the material system. We point to the relation between the time-domain coherence spectroscopy and the method of interferometric two-photon photoemission spectroscopy, and propose a variant of the latter method, where the two time-delayed excitation pathways are distinguishable, rather than identical. In particular, we show that distinguishability of the two excitation pathways introduces the new possibility of disentangling decoherence from population relaxation.     

Coherent control approaches to light guidance in the nanoscale

Concepts of coherent control are extended to manipulate light in subdiffraction length scales via nanoparticle arrays. Phase and polarization control are first introduced and applied to control the pathway of electromagnetic energy through multiple branching nanoarray intersections, leading to an ultrafast optical nanoswitch below the diffraction limit. The genetic algorithm is next generalized to provide a systematic design tool, wherein both the properties of the excitation field and the structural parameters of the material system are optimized so as to make nanodevices with desired functionality. The scheme is used to gain insight into the interplay between the interactions that underlies the coherent propagation of electromagnetic energy via nanoparticle arrays. Implications to several research fields, including single molecule spectroscopy, spatially confined chemistry, optical logic, and nanoscale sensing, are envisioned.     

Microbead chemical switches: an approach to detection of reactive organophosphate chemical warfare agent vapors

In this article, we describe the preparation and application of microbeads that exhibit a "turn on" fluorescence response within seconds of exposure to diethyl chlorophosphate (DCP) vapor. This sensing approach is modeled after the mechanism for acetylcholinesterase enzyme activity inhibition and uses a specific and irreversible reaction between phosphoryl halides and a fluorescent indicator. The microbeads are fabricated by adsorbing fluoresceinamine (FLA) onto carboxylate-functionalized polymer microbeads coated with poly(2-vinylpyridine) (PVP). When the microbeads are subjected to DCP vapor, the conversion of FLA into a phosphoramide causes a rapid and intense fluorescence increase. The PVP layer provides a high density of proton-accepting pyridine nitrogen sites that neutralize the HCl released during the reaction, thereby maintaining high product fluorescence, even after vapor exposure. No significant response is observed when the microbeads are subjected to other nerve agent simulants, a mustard gas simulant, and volatile organics. The size, sensitivity, and subsecond response of these microbeads make them suitable for nerve agent vapor detection and inclusion into microbead sensor arrays.     

Nilfactors of ℝ m and configurations in sets of positive upper density in ℝ m

We use ergodic theoretic tools to solve a classical problem in geometric Ramsey theory. LetE be a measurable subset of ℝ ^m , with . LetV = {0,v ₁,...,v _k} ⊂ ℝ^m. We show that fort large enough, we can find an isometric copy oftV arbitrarily close toE. This is a generalization of a theorem of Furstenberg, Katznelson and Weiss [FuKaW] showing a similar property form=k=2.     

Observation of shot noise suppression at optical wavelengths in a relativistic electron beam

Control of collective properties of relativistic particles is increasingly important in modern accelerators. In particular, shot noise affects accelerator performance by driving instabilities or by competing with coherent processes. We present experimental observations of shot noise suppression in a relativistic beam at the Linac Coherent Light Source. By adjusting the dispersive strength of a chicane, we observe a decrease in the optical transition radiation emitted from a downstream foil. We show agreement between the experimental results, theoretical models, and 3D particle simulations.     

The effect of EGTA and Ca++ in regulation of the brain Na/K-ATP-ase by noradrenaline

Background  

The Na/K-ATPase activity of the brain synaptic plasma membranes (SPM) is regulated by noradrenaline (NA) and the synaptosomal factor SF (soluble protein obtained from the synaptosome cytosol). In the absence of SF, NA inhibits Na/K-ATPase, while, on addition of SF to the reaction medium, there is a NA-dependent activation of Na/K-ATPase . On the other hand, EGTA augments the Na/K-ATPase activity and attenuates the ability of NA to inhibit Na/K-ATPase.     

Poly(vinyl alcohol)-Amino Acid Hydrogels Fabricated into Tissue Engineering Scaffolds by Colloidal Gas Aphron Technology

A new class of hydrogels made from poly(vinyl alcohol) (PVA) and amino acid was formed into porous tissue engineering scaffolds by the colloidal gas aphron (CGA) method. CGA microfoams are formed using high speed stirring to generate uniform, micrometer scale bubbles. CGAs offer several advantages over conventional scaffold fabrication techniques including room temperature processing, aqueous conditions and utilization of air bubbles to create uniform pores. This technique eliminates the need for toxic solvents and salt templates. In addition, the novel poly(vinyl alcohol) hydrogels are inherently strong, eliminating the need for crosslinkers.     

Molecular design strategies for biomaterials that heal

Biomaterials are widely used in medical devices with good success. However, the surface chemistries of our present generation of biomaterials are not specifically recognized by living organisms. Thus, biological reactions to biomaterials in use today are primarily influenced by non-specific interactions occurring at their surfaces. This paper develops a hypothesis for the development of a future generation of biomaterials. A discussion of the meaning of biocompatibility is followed by a strategy for developing biomaterials that actively induce healing and reconstruction by turning on specific biologic pathways. Materials strategies for encouraging specific reactions and inhibiting non-specific bioreaction are presented.     

Synthesis and Crystal Structure of (Z)-4-(p-Bromo phenylthio)-3-(p-nitrobenzoyloxy)-3-buten-2-one

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