Activation of a CH bond in polypyridine systems by acetyl hypofluorite made from F2

Activation of the relatively inactive polypyridine backbone with strong electrophilic fluorine, originating from acetyl hypofluorite (AcOF) enables attack of the acetoxy moiety at the α position to the heteroatom. Derivatives of bipyridine, phenanthroline and terpyridine systems have been acetoxylated or oxygenated within a few minutes usually in very good yields.     

Organic nanoparticles from microemulsions: Formation and applications

Microemulsions have already been recognized as convenient templates for nanoparticle synthesis. Spontaneous formation of the compartmentalized domains within the microemulsions leads to facile and low-cost preparation processes.In the past, microemulsions were mainly explored as precursors for the synthesis of inorganic nanoparticles. However, there is a constantly growing number of publications offering to exploit these systems to produce organic nanoparticles, and in recent years, a variety of methods have emerged in this field. The aim of this review is to survey the methods recently used to produce organic nanomaterials from microemulsions, and to give a perspective on particle design possibilities that can be achieved by various techniques. The structure of the initial microemulsion system, the chemical and technical aspects of preparation, the nature of additives and surface active agents, as well as the possible outcomes in terms of final particle characteristics, will be discussed for the various methods.     

New resonant cavity-enhanced absorber structures for mid-infrared detector applications

A new dielectric Fabry–Perot cavity was designed for a resonant enhancing optical absorption by a thin absorber layer embedded into the cavity. In this cavity, the front mirror is a subwavelength grating with ~ 100% retroreflection. For a HgCdTe absorber in a matching cavity of the new type, the design is shown to meet the combined challenges of increasing the absorbing efficiency of the entire device up to ~ 100?% and reducing its size and overall complexity, compared to a conventional resonant cavity enhanced HgCdTe absorber, while maintaining a fairly good tolerance against the grating’s fabrication errors.     

Universal behavior of optimal paths in weighted networks with general disorder

We study the statistics of the optimal path in both random and scale-free networks, where weights are taken from a general distribution P(w). We find that different types of disorder lead to the same universal behavior. Specifically, we find that a single parameter (S defined as AL(-1/v) for d-dimensional lattices, and S defined as AN(-1/3) for random networks) determines the distributions of the optimal path length, including both strong and weak disorder regimes. Here v is the percolation connectivity exponent, and A depends on the percolation threshold and P(w). We show that for a uniform P(w), Poisson or Gaussian, the crossover from weak to strong does not occur, and only weak disorder exists.     

Surface modification of crosslinked poly(styrene-divinyl benzene) micrometer-sized particles of narrow size distribution by ozonolysis

Micrometer-sized polystyrene template particles of narrow size distribution were prepared by dispersion polymerization of styrene in 2-methoxyethanol. Uniform micrometer-sized polystyrene/crosslinked poly(styrene-divinyl benzene) composite particles were formed by a single-step swelling process of the template particles with styrene, divinyl benzene and benzoyl peroxide, followed by polymerization at 70 degrees C. Uniform micrometer-sized crosslinked poly(styrene-divinyl benzene) particles of higher surface area were produced by dissolution of the template polystyrene part of the former composite particles with N,N-dimethylformamide. Hydroperoxide conjugated crosslinked poly(styrene-divinyl benzene) particles were produced by ozonolysis of these particles. The effect of ozonolysis conditions, such as exposure time and flow rate of the ozone, on the hydroperoxide conjugation to the crosslinked particles was also studied. Functionalization of the crosslinked poly(styrene-divinyl benzene) particles was performed by graft polymerization of vinylic monomers such as acrylonitrile and chloromethylstyrene on the hydroperoxide conjugated crosslinked particles. This was accomplished by raising the temperature (e.g., 70 degrees C) of deairated acetonitrile dispersions containing the hydroperoxide conjugated particles and the vinylic monomers. The influence of various polymerization parameters on the grafting yield, e.g., monomer concentration, conjugated hydroperoxide concentration, and temperature, was also elucidated.     

Current status of equation of state of nuclear matter

The equation of state (EOS) of symmetric nuclear matter (SNM) is a very important ingredient in the study of various phenomena of interest in nuclear physics and astrophysics. Accurate assessment of the value of the SNM incompressibility coefficient, K, which is directly related to the curvature of the EOS, is needed to extend our knowledge of the EOS in the vicinity of the saturation point. We review the current status of K as determined from experimental data on compression modes in nuclei using the mean-field-based random-phase approximation. The text was submitted by the authors in English.     

Performance bounds and cutoff rates of quantum limited OOK withoptical amplification

The bit error probability (BER) and the generalized cutoff rate (GCR) of optically amplified, direct-detection on-off keying (OOK) signaling are addressed utilizing the classical theory of Fredholm integral equations. The approach accounts for the impact of optical bandlimiting and upper bounds on the BER are found via Chernoff techniques, which address the resultant intersymbol interference (ISI) incurred by the linear pulse distortion. Simple rigorous upper bounds on the BER are derived in terms of basic system parameters relaxing the need for solving Fredholm related equations. Random coding is used to obtain the GCR of this channel. The theory is demonstrated for the Lorentzian and finite-duration bandpass optical filters and the optical bandwidth which optimally balances the ISI versus the amplified spontaneous emission noise is found     

Linear time approximation of 3D convex polytopes

We develop algorithms for the approximation of a convex polytope in by polytopes that are either contained in it or containing it, and that have fewer vertices or facets, respectively. The approximating polytopes achieve the best possible general order of precision in the sense of volume-difference. The running time is linear in the number of vertices or facets.