Induced Nucleon Polarization and Meson-Exchange Currents in (e,e'p) Reactions

Nucleon recoil polarization observables in $(e,e'\vec{p})$ reactions are investigated using a semi-relativistic distorted-wave model which includes one- and two-body currents with relativistic corrections. Results for the induced polarization asymmetry are shown for closed-shell nuclei and a comparison with available experimental data for $^{12}$C is provided. A careful analysis of meson exchange currents shows that they may affect significantly the induced polarization for high missing momentum.Comment: 7 pages, 9 figures. Revised version with small changes, new curve in Fig. 3. To be published in PR

Gb/s visible light communications with colloidal quantum dot color converters

This paper reports the utilization of colloidal semiconductor quantum dots as color converters for Gb/s visible light communications. We briefly review the design and properties of colloidal quantum dots and discuss them in the context of fast color conversion of InGaN light sources, in particular in view of the effects of self-absorption. This is followed by a description of a CQD/polymer composite format of color converters. We show samples of such color-converting composite emitting at green, yellow/orange and red wavelengths, and combine these with a blueemitting microsize LED to form hybrid sources for wireless visible light communication links. In this way data rates up to 1 Gb/s over distances of a few tens of centimeters have been demonstrated. Finally, we broaden the discussion by considering the possibility for wavelength division multiplexing as well as the use of alternative colloidal semiconductor nanocrystals

An unreported variation of the cervical vagus nerve: anatomical and histological observations

Variations involving the cervical portion of the vagus nerve are seemingly very rare. We report an adult male found to harbour a right cervical vagus nerve that crossed anterior to the right common carotid artery to terminate in the lateral aspect of the thyroid gland. A very small continuation of this nerve was found to continue distally into the thorax. Histologically, this part of the vagus nerve did not contain ganglion or other cell bodies. There were no heterologous inclusions (thyroid, parathyroid, thymus, salivary gland or branchial cleft remnants) present. Although grossly there was a connection into the thyroid gland, this was not observed histologically. No signs of trauma were found to the ipsilateral neck region. We hypothesise that this variation is due to entanglement between the thyroid gland and cervical vagus nerve during development. This rare variation might be considered by the clinician who operates in the cervical region or interprets imaging of the neck. To our knowledge, a vagus nerve with the above described morphology has not been described

Sums over Graphs and Integration over Discrete Groupoids

We show that sums over graphs such as appear in the theory of Feynman diagrams can be seen as integrals over discrete groupoids. From this point of view, basic combinatorial formulas of the theory of Feynman diagrams can be interpreted as pull-back or push-forward formulas for integrals over suitable groupoids.Comment: 27 pages, 4 eps figures; LaTeX2e; uses Xy-Pic. Some ambiguities fixed, and several proofs simplifie

Transport equation for the photon Wigner operator in non-commutative QED

We derive an exact quantum equation of motion for the photon Wigner operator in non-commutative QED, which is gauge covariant. In the classical approximation, this reduces to a simple transport equation which describes the hard thermal effects in this theory. As an example of the effectiveness of this method we show that, to leading order, this equation generates in a direct way the Green amplitudes calculated perturbatively in quantum field theory at high temperature.Comment: 13 pages, twocolumn revtex4 styl

Classical transport equation in non-commutative QED at high temperature

We show that the high temperature behavior of non-commutative QED may be simply obtained from Boltzmann transport equations for classical particles. The transport equation for the charge neutral particle is shown to be characteristically different from that for the charged particle. These equations correctly generate, for arbitrary values of the non-commutative parameter theta, the leading, gauge independent hard thermal loops, arising from the fermion and the gauge sectors. We briefly discuss the generating functional of hard thermal amplitudes.Comment: 11 page

Suppressing cyanobacterial dominance by UV-LED TiO2-photocatalysis in a drinking water reservoir: a mesocosm study.

Cyanobacteria and their toxic secondary metabolites present challenges for water treatment globally. In this study we have assessed TiO2 immobilized onto recycled foamed glass beads by a facile calcination method, combined in treatment units with 365 nm UV-LEDs. The treatment system was deployed in mesocosms within a eutrophic Brazilian drinking water reservoir. The treatment units were deployed for 7 days and suppressed cyanobacterial abundance by 85%, while at the same time enhancing other water quality parameters; turbidity and transparency improved by 40 and 81% respectively. Genomic analysis of the microbiota in the treated mesocosms revealed that the composition of the cyanobacterial community was affected and the abundance of Bacteroidetes and Proteobacteria increased during cyanobacterial suppression. The effect of the treatment on zooplankton and other eukaryotes was also monitored. The abundance of zooplankton decreased while Chrysophyte and Alveolata loadings increased. The results of this proof-of-concept study demonstrate the potential for full-scale, in-reservoir application of advanced oxidation processes as complementary water treatment processes

Micro to nanostructural observations in neutron irradiated nuclear graphites PCEA and PCIB

The neutron irradiation-induced structural changes in nuclear grade graphites PCEA and PCIB were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and electron energy loss spectroscopy (EELS). The graphite samples were irradiated at the Advanced Test Reactor at the Idaho National Laboratory. Received doses ranged from 1.5 to 6.8 displacements per atom and irradiation temperatures varied between 350 °C and 670 °C. XRD and Raman measurements provided evidence for irradiation induced crystallite fragmentation, with crystallite sizes reduced by 39–55%. Analysis of TEM images was used to quantify fringe length, tortuosity, and relative misorientation of planes, and indicated that neutron irradiation induced basal plane fragmentation and curvature. EELS was used to quantify the proportion of sp2 bonding and specimen density; a slight reduction in planar-sp2 content (due to the buckling basal planes and the introduction of non-six-membered rings) agreed with the observations from TEM

Spallation reactions. A successful interplay between modeling and applications

The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie