Closed-form BER analysis of variable weight MPPM coding under gamma-gamma scintillation for atmospheric optical communications

In this paper, the performance of the variable weight multiple pulse-position modulation (MPPM) coding technique in an atmospheric optical communication environment under gamma-gamma optical scintillation is analyzed, proposing a closed-form expression for the average bit error rate (BER). This study is based on a hyperexponential fitting of the conditional BER in absence of turbulence fluctuations, leading to closed-form expressions that characterize the behavior of this nonlinear coding scheme. Finally, conditional and average BER expressions proposed here are corroborated with Monte Carlo simulations results.     

Extracting Past-Future Vacuum Correlations Using Circuit QED

We propose a realistic circuit QED experiment to test the extraction of past-future vacuum entanglement to a pair of superconducting qubits. The qubit P interacts with the quantum field along an open transmission line for an interval T_{on} and then, after a time-lapse T_{off}, the qubit F starts interacting for a time T_{on} in a symmetric fashion. After that, past-future quantum correlations will have transferred to the qubits, even if the qubits do not coexist at the same time. We show that this experiment can be realized with current technology and discuss its utility as a possible implementation of a quantum memory.     

High-resolution calorimetric study of pb(mg_{1/3}nb_{2/3})o_{3} single crystal

Motivated by the long-standing unresolved enigma of the relaxor ferroelectric ground state, we performed a high-resolution heat capacity and polarization study of the field-induced phase transition in the relaxor ferroelectric single crystal Pb(Mg_{1/3}Nb_{2/3})O_{3} (PMN) oriented along the [110] direction. We show that the discontinuous evolution of polarization as a function of the electric field or temperature is a consequence of a true first order transition from a glassy to ferroelectric state, which is accompanied by an excess heat capacity anomaly and released latent heat. We also find that in a zero field there is no ferroelectric phase transition in bulk PMN at any temperature, indicating that the nonergodic dipolar glass phase persists down to the lowest temperatures.     

Bounds for point recolouring in geometric graphs

We examine a recolouring scheme ostensibly used to assist in classifying geographic data. Given a drawing of a graph with bi-chromatic points, where the points are the vertices of the graph, a point can be recoloured if it is surrounded by neighbours of the opposite colour. The notion of surrounded is defined as a contiguous subset of neighbours that span an angle greater than 180 degrees. The recolouring of surrounded points continues in sequence, in no particular order, until no point remains surrounded. We show that for some classes of graphs the process terminates in a polynomial number of steps. On the other hand, there are classes of graphs with infinite recolouring sequences.     

Eucalyptus nitens: nanomechanical properties of bark and wood fibers

In this study, Eucalyptus nitens species was nano-characterized to determine variability in nanomechanical properties within the cellular ultra-structure between the bark and wood fibers. Three factors, including site (2 levels), family (2 levels) and fiber type (bark and wood) were analyzed using three response variables, including the elastic modulus (E), hardness (H) and ductility ratio (E/H) in the middle lamella (ML) and the cell wall within the S2 layer. The results indicated significant differences for E _S2 and H _S2 when comparing fiber types: E _S2≈12.52 GPa and H _S2≈0.31 GPa for wood fiber and E _S2≈10.81 GPa and H _S2≈0.26 GPa for bark fiber. There is not statistically significant difference in ductility ratio (E/H) in S2 and ML between fiber types. These results indicate that bark and wood fibers can be used together or separately in the development of new composite materials and engineering products.     

Low intensity infrared laser effects on Escherichia coli cultures and plasmid DNA

Biostimulative effect of low intensity laser in tissues has been described on a photobiological basis and clinical protocols are recommended for treatment of various diseases. The aim of this work was to evaluate effects of laser exposure on the survival of Escherichia coli cultures and plasmid topological forms. Escherichia coli cultures and plasmids were exposed to infrared laser to study bacterial survival and electrophoretic profile, respectively. Data indicate low intensity infrared laser: (i) had no effect on E. coli wild type, endonuclease IV, exonuclease III, formamidopyrimidine DNA glycosylase/MutM protein and endonuclease III deficient cultures, but decreased the survival of E. coli UvrA protein deficient cultures; (ii) there was no alteration in the electrophoretic profile of plasmids. Exposure to low intensity infrared laser decreases survival of Escherichia coli cultures deficient in nucleotide excision repair of DNA and this effect could depend on fluences, wavelength and tissues conditions.     

Imaging of nanostructures with sub-100?nm spatial resolution using a desktop EUV microscope

Laser-produced plasma sources of short-wavelength radiation offer an interesting alternative to synchrotron and free-electron laser installations. Recently, we reported on a newly developed desktop EUV microscope based on plasma generated from a gas-puff target and diffractive optics. The half-pitch resolution of the microscope approached 50?nm. Compared to analogous microscopes based on synchrotron sources, our system is compact and cost-effective. In this paper, we present the results of imaging experiments on a thin polycrystalline object that was carried out in order to further examine the applicability of the microscope. We have demonstrated here that EUV microscopy can provide structural information that cannot be accessed by conventional optical microscopy or SEM.     

Heuristic solution approaches for the maximum minsum dispersion problem

The Maximum Minsum Dispersion Problem (Max-Minsum DP) is a strongly NP-Hard problem that belongs to the family of equitable dispersion problems. When dealing with dispersion, the operations research literature has focused on optimizing efficiency-based objectives while neglecting, for the most part, measures of equity. The most common efficiency-based functions are the sum of the inter-element distances or the minimum inter-element distance. Equitable dispersion problems, on the other hand, attempt to address the balance between efficiency and equity when selecting a subset of elements from a larger set. The objective of the Max-Minsum DP is to maximize the minimum aggregate dispersion among the chosen elements. We develop tabu search and GRASP solution procedures for this problem and compare them against the best in the literature. We also apply LocalSolver, a commercially available black-box optimizer, to compare our results. Our computational experiments show that we are able to establish new benchmarks in the solution of the Max-Minsum DP.     

An unexpected Pummerer rearrangement in the synthetic route to ethyl (2′-hydroxy-4′,5′-methylenedioxyphenyl)acetate: An alternative approach to 2,3-dimethylthio benzofurans

The synthesis of ethyl (2′-hydroxy-4′,5′-methylendioxophenyl)acetate, a fragment of the antihyperglycemic natural coumarin subcoriacin, is reported. We found an expeditious route to the title compound in five steps. Final metal catalyzed acid ethanolysis of the vinylic 1,1-methylthio methylsulfoxide derivative afforded the required aryl acetic ester, but in the absence of metal catalyst, an unexpected Pummerer rearrangement produced the 2,3-dimethylthiofuran derivative as the major product. This last result provides an alternative entry to 2,3-dimethlythiobenzofurans.