On the mechanism of the (n, 2n) reaction with 14MeV projectiles on127I and209Bi

The angular and spectral distributions of coincident neutrons from the reactions¹²⁷I(n, 2n)¹²⁶I and²⁰⁹Bi(n, 2n)²⁰⁸Bi have been measured with two time-of-flight detectors at the incident energy 14.1 MeV. Neutron emission has been studied for reaction anglesθ _lab between 10° and 150° (relative angles from 60° to 270°). Energy spectra, angular distributions and coincidence yields are compared with statistical model calculations including preequilibrium decay modes, and nuclear level density and spin cut off parameters are derived.     

Two‐step syntheses of 3‐methyl and 3‐phenyl‐1,2,4‐benzotriazines

3‐Methyl‐1,2,4‐benzotriazine and some of its derivatives were prepared in moderate yields (50–70%) via a reductive cyclization by a PtO₂‐catalyzed hydrogenation of the corresponding 2‐nitrophenylhydrazones of the pyruvic acid. The latter compounds were obtained in yields higher than 90% by reacting 2‐nitrophenylhydrazines with sodium pyruvate salt. Three 3‐phenyl‐1,2,4‐benzotriazine compounds were also produced via a reductive cyclization by a Pt/C‐catalyzed hydrogenation of their corresponding 2‐nitrophenylhydrazono‐ethers in high yields (>70%). © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:166–172, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20200     

Strong Converse for the Classical Capacity of Entanglement-Breaking and Hadamard Channels via a Sandwiched Rényi Relative Entropy

A strong converse theorem for the classical capacity of a quantum channel states that the probability of correctly decoding a classical message converges exponentially fast to zero in the limit of many channel uses if the rate of communication exceeds the classical capacity of the channel. Along with a corresponding achievability statement for rates below the capacity, such a strong converse theorem enhances our understanding of the capacity as a very sharp dividing line between achievable and unachievable rates of communication. Here, we show that such a strong converse theorem holds for the classical capacity of all entanglement-breaking channels and all Hadamard channels (the complementary channels of the former). These results follow by bounding the success probability in terms of a “sandwiched” Rényi relative entropy, by showing that this quantity is subadditive for all entanglement-breaking and Hadamard channels, and by relating this quantity to the Holevo capacity. Prior results regarding strong converse theorems for particular covariant channels emerge as a special case of our results.     

Nucleation barriers for the liquid-to-crystal transition in Ni: experiment and simulation

Nucleation in undercooled Ni is investigated by a combination of differential scanning calorimetry (DSC) experiments and Monte Carlo (MC) simulation. By systematically varying the sample size in the DSC experiments, nucleation rates J over a range of 8 orders of magnitude are obtained. Evidence is given that these rates correspond to homogeneous nucleation. Free energy barriers ΔG*, as extracted from the measured J, are in very good agreement with those from the MC simulation. The MC simulation indicates a nonspherical geometry of crystalline clusters, fluctuating between prolate and oblate shape at a given size. Nevertheless, the temperature dependence of ΔG* is well described by classical nucleation theory.     

Imaging the three-dimensional scattering pattern of plasmonic nanodisk chains by digital heterodyne holography

Nanoantennas have the unique ability to affect the emission pattern of a dipole in free space. We present a technique based on full-field heterodyne holography for the mapping of the scattered field of plasmonic gold nanodisk chains in all three dimensions. A spectroscopic study allowed us to determine the resonant and nonresonant wavelengths at which we conducted a full characterization of the scattered field on a chosen nanodisk chain.     

Structure modification in hen egg yolk low density lipoproteins layers between 30 and 45 mN/m observed by AFM

We have studied the structure of films made by low density lipoproteins (LDL) from hen egg yolk, which are composed of apoproteins, neutral lipids and phospholipids. These LDL have been deposited on air–water interface to form a monolayer which has been compressed to measure an isotherm using Langmuir balance. This isotherm presented three transitions (neutral lipid (surface pressure, π = 19 mN/m), apoprotein–lipid (π = 41 mN/m) and phospholipid (π = 51 mN/m) transitions). We have studied only the apoprotein–lipid transition. In order to observe the LDL film structure before (π = 30 mN/m) and after (π = 45 mN/m) the apoprotein–lipid transition, the formed films were transferred and visualised by atomic force microscopy (AFM). Our results have shown that the structures observed in the LDL film were different depending on the surface pressure. The apoproteins and neutral lipids appeared to be miscible up to the apoprotein–lipid transition, when demixing occured. The structures observed after the apoprotein–lipid transition should be due to the demixing between apoproteins and neutral lipids. On the other hand, apoproteins and phospholipids seemed miscible whatever the surface pressure. Hence, the first transition (π = 19 mN/m) should be attributed to the free neutral lipid collapse; the second transition (π = 41 mN/m) should be attributed to the demixing of apoprotein–neutral lipid complexes; and the last transition (π = 51 mN/m) should be attributed to phospholipid collapse or to demixing of apoprotein–phospholipid complexes.     

Ein alternativer Zugang zum PQQ-Triester

An Alternative Approach to the PQQ-Triester A novel approach to triethyl 5-methoxy-1H-pyrrolo[2,3-f]quinoline-2,7,9-tricarboxylate ( 6 ), a close precursor of the redox cofactor PQQ of bacterial dehydrogenases, is described. Diethyl 2-oxopent-3-ynedioate ( 5 ) was used as building block for the annelation of the quinoline unit. The annelation proceeds in two steps via the diastereoselective formation of diethyl (Z)-4-{[2-(ethoxycarbonyl)-5-methoxyindol-6-yl]amiono}-2-oxopent-3-enedioate ((Z)- 7 ) followed by acid-catalyzed cyclocondensation.     

Simulations of Closed Timelike Curves

Proposed models of closed timelike curves (CTCs) have been shown to enable powerful information-processing protocols. We examine the simulation of models of CTCs both by other models of CTCs and by physical systems without access to CTCs. We prove that the recently proposed transition probability CTCs (T-CTCs) are physically equivalent to postselection CTCs (P-CTCs), in the sense that one model can simulate the other with reasonable overhead. As a consequence, their information-processing capabilities are equivalent. We also describe a method for quantum computers to simulate Deutschian CTCs (but with a reasonable overhead only in some cases). In cases for which the overhead is reasonable, it might be possible to perform the simulation in a table-top experiment. This approach has the benefit of resolving some ambiguities associated with the equivalent circuit model of Ralph et al. Furthermore, we provide an explicit form for the state of the CTC system such that it is a maximum-entropy state, as prescribed by Deutsch.