Laser photolysis study of the triplet states of phthalocyanines on the surface of silica nanoparticles in aqueous solutions

Aluminum and zinc phthalocyanines (AlPc and ZnPc, respectively) adsorbed on the surface of silica nanoparticles (60 nm in diameter) in aqueous solutions have been found to form H-aggregates, which possess characteristic absorption spectra with bands (having a maximum at 640 nm) in a shorter wavelength region with respect to the main Q-band of the monomer (having a maximum at 670 nm). For AlPc on the surface, J-aggregates of two types (long-wavelength bands with maximums at 740 and 770 nm) are also observed. Using nanosecond laser photolysis (with the excitation wavelength of 337 nm) in deoxygenated solutions of AlPc on the surface, the formation of the triplet electronically excited states of J-aggregates has been detected, which are characterized by a broad absorption spectrum in the region of 400–800 nm and a lifetime of 360 μs. No intermediate products have been detected during the photolysis of H-aggregates of ZnPc on the surface.     

Engineering strategy to improve peptide analogs: from structure-based computational design to tumor homing

We present a chemical strategy to engineer analogs of the tumor-homing peptide CREKA (Cys-Arg-Glu-Lys-Ala), which binds to fibrin and fibrin-associated clotted plasma proteins in tumor vessels (Simberg et al. in Proc Natl Acad Sci USA 104:932–936, 2007) with improved ability to inhibit tumor growth. Computer modeling using a combination of simulated annealing and molecular dynamics were carried out to design targeted replacements aimed at enhancing the stability of the bioactive conformation of CREKA. Because this conformation presents a pocket-like shape with the charged groups of Arg, Glu and Lys pointing outward, non-proteinogenic amino acids α-methyl and N-methyl derivatives of Arg, Glu and Lys were selected, rationally designed and incorporated into CREKA analogs. The stabilization of the bioactive conformation predicted by the modeling for the different CREKA analogs matched the tumor fluorescence results, with tumor accumulation increasing with stabilization. Here we report the modeling, synthetic procedures, and new biological assays used to test the efficacy and utility of the analogs. Combined, our results show how studies based on multi-disciplinary collaboration can converge and lead to useful biomedical advances.     

Particle-hole symmetry and the Pfaffian state

We show that the particle-hole conjugate of the Pfaffian state-or "anti-Pfaffian" state-is in a different universality class from the Pfaffian state, with different topological order. The two states can be distinguished easily by their edge physics: their edges differ in both their thermal Hall conductance and their tunneling exponents. At the same time, the two states are exactly degenerate in energy for a nu=5/2 quantum Hall system in the idealized limit of zero Landau level mixing. Thus, both are good candidates for the observed sigma_{xy}=5/2(e;{2}/h) quantum Hall plateau.     

Tensor renormalization group approach to two-dimensional classical lattice models

We describe a simple real space renormalization group technique for two-dimensional classical lattice models. The approach is similar in spirit to block spin methods, but at the same time it is fundamentally based on the theory of quantum entanglement. In this sense, the technique can be thought of as a classical analogue of the density matrix renormalization group method. We demonstrate the method - which we call the tensor renormalization group method - by computing the magnetization of the triangular lattice Ising model.     

Spectral Standards Based on Glasses Activated with Rare-Earth Element Ions for the Calibration of Fluorescence and Raman Spectrometers

Optics and Spectroscopy - The results of development of fluorescence calibration standards based on phosphate matrix glass activated with ions of rare-earth metals are presented. The calibration...     

Current Status and Objectives of Modernizing the Engineering,Physical, and Energy Infrastructure of the SFT Facility for the Implementation of the Ignitor Project

Physics of Atomic Nuclei - The Ignitor tokamak nuclear fusion research project is one of the most ambitious initiatives undertaken under the long-term scientific cooperation program between the...     

Parallelization of matrix algorithms for Gröbner basis computation

Sequential and parallel implementations of the F4 algorithm for computing Gröbner bases of polynomial ideals are discussed.     

Numerical simulation of spinning detonation in circular section channels

Numerical simulation of three-dimensional structures of gas detonation in circular section channels that emerge due to the instability when the one-dimensional flow is initiated by energy supply at the closed end of the channel is performed. It is found that in channels with a large diameter, an irregular three-dimensional cellular detonation structure is formed. Furthermore, it is found that in channels with a small diameter circular section, the initially plane detonation wave is spontaneously transformed into a spinning detonation wave, while passing through four phases. A critical value of the channel diameter that divides the regimes with the three-dimensional cellular detonation and spinning detonation is determined. The stability of the spinning detonation wave under perturbations occurring when the wave passes into a channel with a greater (a smaller) diameter is investigated. It is found that the spin is preserved if the diameter of the next channel (into which the wave passes) is smaller (respectively, greater) than a certain critical value. The computations were performed on the Lomonosov supercomputer using from 0.1 to 10 billions of computational cells. All the computations of the cellular and spinning detonation were performed in the whole long three-dimensional channel (up to 1 m long) rather than only in its part containing the detonation wave; this made it possible to adequately simulate and investigate the features of the transformation of the detonation structure in the process of its propagation.