1,886 research outputs found
Tree level spontaneous R-symmetry breaking in O'Raifeartaigh models
We show that in O'Raifeartaigh models of spontaneous supersymmetry breaking,
R-symmetries can be broken by non-zero values of fields at tree level, rather
than by vacuum expectation values of pseudomoduli at loop level. As a
complement of the recent result by Shih, we show that there must be a field in
the theory with R-charge different from zero and two in order for R-symmetry
breaking to occur, no matter whether the breaking happens at tree or loop
level. We review the example by CDFM, and construct two types of tree level
R-symmetry breaking models with a wide range of parameters and free of runaway
problem. And the R-symmetry is broken everywhere on the pseudomoduli space in
these models. This provides a rich set of candidates for SUSY model building
and phenomenology.Comment: 8 pages; v2: major revision to section 6; v3: minor revision and
typos; v4: typos, published version; v5: fix Latex syntax error, published
versio
Competitive adsorption of phenolic compounds from aqueous solution using sludgeābased activated carbon.
Preparation of activated carbon from sewage sludge is a promising approach to produce cheap and efficient adsorbent for pollutants removal as well as to dispose of sewage sludge. The first objective of this study was to investigate the physical and chemical properties (BET surface area, ash and elemental content, surface functional groups by Boehm titration and weight loss by thermogravimetric analysis) of the sludgeābased activated carbon (SBAC) so as to give a basic understanding of its structure and to compare to those of two commercial activated carbons, PICA S23 and F22. The second and main objective was to evaluate the performance of SBAC for single and competitive adsorption of four substituted phenols (pānitrophenol, pāchlorophenol, pāhydroxy benzoic acid and phenol) from their aqueous solutions. The results indicated that, despite moderate micropore and mesopore surface areas, SBAC had remarkable adsorption capacity for phenols, though less than PICA carbons. Uptake of the phenolic compound was found to be dependent on both the porosity and surface chemistry of the carbons. Furthermore, the electronegativity and the hydrophobicity of the adsorbate have significant influence on the adsorption capacity. The Langmuir and Freundlich models were used for the mathematical description of the adsorption equilibrium for singleāsolute isotherms. Moreover, the LangmuirāFreundlich model gave satisfactory results for describing multicomponent system isotherms. The capacity of the studied activated carbons to adsorb phenols from a multiāsolute system was in the following order: pānitrophenol > pāchlorophenol > PHBA > phenol
Laboratory based X-ray absorption spectroscopy of iron phosphate glasses for radioactive waste immobilisation: a preliminary investigation.
We report the application of laboratory based X-ray absorption spectroscopy to the speciation of Fe in iron phosphate glasses prepared by conventional and microwave melting. Analysis of the weak pre-edge features in Fe K-edge XANES data demonstrated glasses produced by microwave melting to have a higher fraction of reduced Fe2+ species, since microwave melts do not have sufficient time to equilibrate with the prevailing oxygen partial pressure, compared to counterparts produced by conventional melting. Furthermore, our laboratory XANES data are consistent with the formation of octahedral Fe2+ at the expense of tetrahedral Fe3+ species, with increasing Fe2+ content. These findings are consistent with the previous findings of our 57Fe Mossbauer study, synchrotron XANES data, and current understanding of the structure of iron phosphate glasses, and demonstrate the utility of laboratory based XANES for routine speciation of Fe in these and other materials
Bacterial diversity in the intestine of sea cucumber Stichopus japonicus
The intestinal bacterial diversity of Stichopus japonicus was investigated using 16S ribosomal RNA gene (rDNA) clone library and Polymerase Chain Reaction/Denaturing Gradient Gel Electrophoresis (PCR-DGGE). The clone library yielded a total of 188 clones, and these were sequenced and classified into 106 operational taxonomic units (OTUs) with sequence similarity ranging from 88 to 100%. The coverage of the library was 77.4%, with approximately 88.7% of the sequences affiliated to Proteobacteria. Gammaproteobacteria and Vibrio sp. were the predominant groups in the intestine of S. japonicus. Some bacteria such as Legionella sp., Brachybacterium sp., Streptomyces sp., Propionigenium sp. and Psychrobacter sp were first identified in the intestine of sea cucumber
Synchronization of fractional order chaotic systems
The chaotic dynamics of fractional order systems begin to attract much
attentions in recent years. In this brief report, we study the master-slave
synchronization of fractional order chaotic systems. It is shown that
fractional order chaotic systems can also be synchronized.Comment: 3 pages, 5 figure
Multipartite entangled states in coupled quantum dots and cavity-QED
We investigate the generation of multipartite entangled state in a system of
N quantum dots embedded in a microcavity and examine the emergence of genuine
multipartite entanglement by three different characterizations of entanglement.
At certain times of dynamical evolution one can generate multipartite entangled
coherent exciton states or multiqubit states by initially preparing the
cavity field in a superposition of coherent states or the Fock state with one
photon, respectively. Finally we study environmental effects on multipartite
entanglement generation and find that the decay rate for the entanglement is
proportional to the number of excitons.Comment: 9 pages, 4 figures, to appear in Phys. Rev.
Crystal chemical design, synthesis and characterisation of U(IV)-dominant betafite phases for actinide immobilisation
Crystal chemical design principles were applied to synthesise novel U4+ dominant and titanium excess betafite phases
Ca1.15(5)U0.56(4)Zr0.17(2)Ti2.19(2)O7 and Ca1.10(4)U0.68(4)Zr0.15(3)Ti2.12(2)O7, in high yield (85ā95 wt%), and ceramic density reaching 99% of theoretical. Substitution of Ti on the A-site of the pyrochlore structure, in excess of full B-site occupancy, enabled the radius ratio (rA/rBā=ā1.69) to be tuned into the pyrochlore stability field, approximately 1.48 ā² rA/rB ā² 1.78, in contrast to the archetype composition CaUTi2O7 (rA/rBā=ā1.75). U L3-edge XANES and U 4f7/2 and U 4f5/2 XPS data evidenced U4+ as the dominant speciation, consistent with the determined chemical compositions. The new betafite phases, and further analysis reported herein, point to a wider family of actinide betafite pyrochlores that could be stabilised by application of the underlying crystal chemical principle applied here
Quantum coherence in a degenerate two-level atomic ensemble: for a transition
For a transition driven by a linearly polarized
light and probed by a circularly light, quantum coherence effects are
investigated. Due to the coherence between the drive Rabi frequency and Zeeman
splitting, electromagnetically induced transparency, electromagnetically
induced absorption, and the transition from positive to negative dispersion are
obtained, as well as the populations coherently oscillating in a wide spectral
region. At the zero pump-probe detuning, the subluminal and superluminal light
propagation is predicted. Finally, coherent population trapping states are not
highly sensitive to the refraction and absorption in such ensemble.Comment: 9 pages, 6 figure
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