Filter und filtriertechnisches

Ohne Zusammenfassung     

Synthesis of 1,3,6,8-Tetrabromophenanthrene via a Stoichiometric Ullmann Reaction

1,3,6,8-Tetrabromophenantherene (1) is prepared in four steps from 2,4,6-tribromobenzoic acid (4) in an overall yield of 12%. The key transformation used in the synthesis is a stoichiomteric Ullmann reaction.     

Measurements of the 10B (n,He) reaction rate in zppr

Direct measurements of the ¹⁰B(n, He) reaction rate have been made in ZPPR. The measurements were made by isotope-dilution mass spectrometric analysis of stainless-steel encapsulated samples of enriched ¹⁰B. The results demonstrate that direct measurements of the ¹⁰B reaction rate in ZPPR are obtainable to an accuracy of ～1%. Comparisons with calculations give a predicted-to-experiment value of ～0.93. This value is consistent with earlier Rockwell measurements in benchmark neutron fields and further supports a need for revision in the ENDF/B cross section for ¹⁰B above ～0.1 MeV.     

e+e− → γ + Hadrons

We give the spectrum in momentum and angle of directly produced γ's in e⁺e^? → γ + hadrons, and show that in QCD if p_⊥² of the recoil hadron jet relative to the photon is large, the leading logarithmic corrections to the lowest order result are absent. This process is therefore of great value in learning whether QCD actually governs quark dynamics.     

Development of capacitance-based and impedance-based wireless sensors and sensor nodes for structural health monitoring applications

A field demonstration of a new and hybrid wireless sensing network paradigm for structural health monitoring (SHM) is presented. In this paradigm, both power and data interrogation commands are conveyed via a mobile agent that is sent to each sensor node to perform individual interrogations, which can alleviate several limitations of traditional sensing networks. This paper will discuss such prototype systems, which will be used to interrogate capacitive-based and impedance-based sensors for SHM applications. The capacitive-based wireless sensor node is specifically built to collect peak displacement measurements. In addition, a wireless sensor node for collecting electromechanical impedance data has also been developed. Both sensor nodes are specifically designed to accept various power sources and to be wirelessly triggered on an as-needed basis so that they can be used for the hybrid sensing network approach. The capabilities of these miniaturized and portable devices are demonstrated in the laboratory and the field, which was performed at the Alamosa Canyon Bridge in southern New Mexico.     

Strong CP problem with 10(32) standard model copies

We show that a recently proposed solution to the hierarchy problem simultaneously solves the strong CP problem, without requiring an axion or any further new physics. Consistency of black hole physics implies a nontrivial relation between the number of particle species and particle masses, so that with approximately 10(32) copies of the standard model, the TeV scale is naturally explained. At the same time, as shown here, this setup predicts a typical expected value of the strong-CP parameter in QCD of theta approximately 10(-9). This strongly motivates a more sensitive measurement of the neutron electric dipole moment.     

Identification of 1,3-dialkylimidazolium salt supramolecular aggregates in solution

The nature of the interactions between 1,3-dialkylimidazolium cations and noncoordinating anions such as tetrafluoroborate, hexafluorophosphate, and tetraphenylborate has been studied in the solid state by X-ray diffraction analysis and in solution by (1)H NMR spectroscopy, conductivity, and microcalorimetry. In the solid state, these compounds show an extended network of hydrogen-bonded cations and anions in which one cation is surrounded by at least three anions and one anion is surrounded by at least three imidazolium cations. In the pure form, imidazolium salts are better described as polymeric supramolecules of the type {[(DAI)(3)(X)](2+)[(DAI)(X)(3)](2-)}(n) (where DAI is the dialkylimidazolium cation and X is the anion) formed through hydrogen bonds of the imidazolium cation with the anion. In solution, this supramolecular structural organization is maintained to a great extent, at least in solvents of low dielectric constant, indicating that mixtures of imidazolium ionic liquids with other molecules can be considered as nanostructured materials. This model is very useful for the rationalization of the majority of the unusual behavior of the ionic liquids.     

QCD predictions for γγ annihilation to baryons

QCD predictions for large-momentum transfer cross sections of the type $\text{γγ →}\text{B}\text{B}\text{′}$ are given, for B and B′ any members of the baryon octet or decuplet, and all possible helicity combinations for photons and baryons.