Quantum ground state of self-organized atomic crystals in optical resonators

Cold atoms, driven by a laser and simultaneously coupled to the quantum field of an optical resonator, may self-organize in periodic structures. These structures are supported by the optical lattice, which emerges from the laser light they scatter into the cavity mode and form when the laser intensity exceeds a threshold value. We study theoretically the quantum ground state of these structures above the pump threshold of self-organization by mapping the atomic dynamics of the self-organized crystal to a Bose-Hubbard model. We find that the quantum ground state of the self-organized structure can be the one of a Mott insulator, depending on the pump strength of the driving laser. For very large pump strengths, where the intracavity-field intensity is maximum and one would expect a Mott-insulator state, we find intervals of parameters where the phase is compressible. These states could be realized in existing experimental setups.

Structural phase transitions in low-dimensional ion crystals

A chain of singly charged particles, confined by a harmonic potential, exhibits a sudden transition to a zigzag configuration when the radial potential reaches a critical value, depending on the particle number. This structural change is a phase transition of second order, whose order parameter is the crystal displacement from the chain axis. We study analytically the transition using Landau theory and find full agreement with numerical predictions by Schiffer [Phys. Rev. Lett. 70, 818 (1993)] and Piacente [Phys. Rev. B 69, 045324 (2004)]. Our theory allows us to determine analytically the system's behavior at the transition point.

Platelet Redox Balance in Diabetic Patients with Hypertension improved by n-3 fatty acids

OBJECTIVE:
Patients with type 2 diabetes mellitus (T2DM) are at increased risk of developing cardiovascular disease, largely as a result of defective production of cardioprotective nitric oxide and a concomitant rise in oxidative stress. Dietary interventions that could reverse this trend would be extremely beneficial. Here we investigated whether dietary n-3 polyunsaturated fatty acid (n-3 PUFA) supplementation positively affected platelet nitroso-redox imbalance.
RESEARCH DESIGN AND METHODS:
We randomized hypertensive T2DM patients (T2DM HT; n = 22) and age-and-sex matched hypertensive study participants without diabetes (HT alone; n = 23) in a double-blind, crossover fashion to receive 8 weeks of n-3 PUFAs (1.8 g eicosapentaenoic acid and 1.5 g docosahexaenoic acid) or identical olive oil capsules (placebo), with an intervening 8-week washout period. Platelet nitrite and superoxide were measured and compared before and after treatment; 8-isoprostane was determined by ELISA and subcellular compartmentalization of the NAD(P)H oxidase subunit p47-phox examined by Western blotting.
RESULTS:
The n-3 PUFA supplementation reduced 8-isoprostane and superoxide levels in platelets from T2DM HT, but not HT alone, participants, without effect on nitrite production. This coincided with a significant decrease in p47-phox membrane localization and a similar reduction in superoxide to that achieved with apocynin. At baseline, a subcohort of T2DM HT and HT alone participants showed evidence of nitric oxide synthase (NOS)-derived superoxide production, indicating defective enzymatic activity. This was reversed significantly in T2DM HT participants after treatment, demonstrating improved NOS function.
CONCLUSIONS:
Our finding that n-3 PUFAs diminish platelet superoxide production in T2DM HT patients in vivo suggests a therapeutic role for these agents in reducing the vascular-derived oxidative stress associated with diabetes.

Verification of McCabe's Delta L Law for Growth of Lysozyme Crystals by Hanging Drop Method

Lysozyme is a naturally occurring enzyme in egg white and has high commercial importance due to its antimicrobial properties. The main objective of this work was to study the growth rate of lysozyme crystals isolated from egg for the first 72 hours and verify the results with McCabe’s constant crystal growth theory. Hanging drop crystallization method was used to form high purity lysozyme crystals from the embryonic stage. To this end, this work differs from an earlier work of Forsythe et al., who used seed crystals in the size range of 10 µm - 40 µm for face growth measurements at different pH values. The maximum crystal size recorded in the present work was 392.86 µm, which is within the typical size range of 50 µm - 500 µm for which constant crystal growth is expected to hold according to McCabe’s ?L law. Electron micrographs (SEM) revealed the structure and dimensions of the crystals while SDS-Page was used to measure the purity of the crystals. The SEM results showed that that lysozyme growth rate was linear and agreed with McCabe’s constant growth theory, producing a growth rate of 1.77 x 10-3 µm .s-1

Method for the in situ preparation of a single layer of zeolite Beta crystals on a molybdenum substrate for microreactor applications

A method for the hydrothermal synthesis of a single layer of zeolite Beta crystals on a molybdenum substrate for microreactor applications has been developed. Before the hydrothermal synthesis, the surface of the substrate was modified by an etching procedure that increases the roughness at the nanoscale level without completely eliminating the surface lay structure. Then, thin films of Al2O3 (170 nm) and TiO2 (50 nm) were successively deposited by atomic layer deposition (ALD) on the substrate. The internal Al2O3 film protects the Mo substrate from oxidation up to 550 degrees C in an oxidative environment. The high wettability of the external TiO2 film after UV irradiation increases zeolite nucleation on its surface. The role of the metal precursor (TiCl4 vs TiI4), deposition temperature (300 vs 500 degrees C), and film thickness (50 vs 100 nm) was investigated to obtain titania films with the slowest decay in the superhydrophilic behavior after UV irradiation. Zeolite Beta coatings with a Si/Al ratio of 23 were grown at 140 degrees C for 48 It. After ion exchange with a 10(-4) M cobalt acetate solution, the activity of the coatings was determined in the ammoxidation of ethylene to acetonitrile in a microstructured reactor. A maximum reaction rate of 220 mu mol C2H3N g(-1) s(-1) was obtained at 500 degrees C, with 42% carbon selectivity to acetonitrile. (C) 2007 Elsevier Inc. All rights reserved.