4,154 research outputs found
Radion production in exclusive processes at CERN LHC
In the Randall-Sundrum (RS) scenario the compactification radius of the extra
dimension is stabilized by the radion, which is a scalar field lighter than the
graviton Kaluza-Klein states. It implies that the detection of the radion will
be the first signature of the stabilized RS model. In this paper we study the
exclusive production of the radion in electromagnetic and diffractive hadron -
hadron collisions at the LHC. Our results demonstrate that the diffractive
production of radion is dominant and should be feasible of study at CERN LHC.Comment: 6 pages, 3 figures, 1 tabl
Mangroves as a source of polyethylene terephthalate (PET) degrading bacteria
Polyethylene terephthalate (PET) is one of the most widely used plastics, and its accumulation in the environment has become an issue of great concern. PET wastes constitute a critical source of pollution to the environment, with important impacts on ecosystems and human health. One possibility to address this problem is to identify microorganisms that may be able to naturally degrade the compound for downstream applications. This study investigated the biodegradation of PET films in soil in the presence or absence of mangrove plants, and with or without bioaugmentation with bacterial isolates of the genus Bacillus and Enterococcus. The experiment was performed in an open garden for ten months. At the end of this period, biodegradation assays of PET monomers and intermediate were further performed using bacterial consortia isolated from the soil of the different treatments. Terephthalic acid (TPA) and bis-2-hydroxyethyl terephthalate (BHET) were added to liquid medium as the sole carbon sources and incubated for 10 days at 30oC. Growth of the consortia was monitored by spectrophotometry, and degradation was followed by HPLC analysis of aliquot samples. The preliminary results from gravimetry analysis showed no significant changes in PET films, regardless of the treatment. On the other hand, total degradation of TPA and BHET was observed for all assays independently of treatment. The results suggest that although direct biodegradation of PET may be challenging to accomplish, bacteria capable of degrading the intermediates and monomers of PET are readily available in the natural environment.info:eu-repo/semantics/publishedVersio
Implications of flexible spacer rotational processes on the liquid crystal behavior of 4,5-dihydroisoxazole benzoate dimers
The synthesis of some novel non-symmetric liquid crystal dimers, {3-[4-(octyloxyphenyl)]-4,5-dihydroisoxazol-5-yl}alkyl 4-(decyloxy)benzoates (5a–d) and 4-{3-[4-(octyloxyphenyl)]-4,5-dihydroisoxazol-5-yl}alkyl 4-{[6-(octyloxy)naphthalen-2-yl]ethynyl}benzoate (9a–d), are reported. The liquid-crystalline properties, theoretical calculations based on the conformational aspects of the flexible alkyl spacer and X-ray experiments are discussed. The syntheses of the key intermediates, 2-{3-[4-(octyloxy)phenyl]-4,5-dihydroisoxazol-5-yl}alkanol (3a–d), presenting the flexible alkyl spacer were achieved through [3+2] cycloaddition reactions between nitrile oxides, which were generated in situ by oxidation of the respective aromatic oximes, and dipolarophile alkenols (CH2[double bond, length as m-dash]CH(CH2)nOH, n = 1, 2, 3, and 4). The benzoates 5a–d were synthesized through esterification of 3a–d and p-n-decyloxybenzoic acid (4). The esters 9a–d were synthesized through derivatization of isoxazolines 3a–d into 4-{3-[4-(octyloxyphenyl)]-4,5-dihydroisoxazol-5-yl}alkyl 4-bromobenzoate (7a–d) followed by a Sonogashira reaction with 2-ethynyl-6-octyloxynaphthalene (8). 5a and 5b showed a monotropic smectic C phase. 9a/c displayed a enantiotropic nematic (N) mesophase, whereas 9b/d showed a monotropic nematic mesophase. No mesophase was observed for 7a–d. An odd–even effect was observed for 5a–d and 9a–d associated with the crystal to isotropic phase transition and crystal to nematic phase, respectively, as the length of the spacer was increased from 1 to 4 carbon atoms. The transitional properties were higher for odd-numbered members (n = 1 and 3) for all of the series studied. The X-ray data of compounds 5a and 5b are in agreement with polarizing optical microscopy observations with the assignment of an SmC mesophase. Density functional theory calculations using the B3LYP hybrid functional with the level 6-311G(d,p) basis set were performed for molecules 5a–d to correlate the conformation of the flexible spacer and the transitional properties. The conformational analysis showed that the most stable conformation for 5a–d is one where all of the carbon atoms of the flexible spacer are orientated at 180° (antiperiplanar orientation) except for 5a because the spacer is too short. The odd-numbered members have a more bent shape and are less elongated molecules than the even-numbered members. Thus, mesomorphic behavior is dictated by the conformational constraint imposed by the flexible spacer on the mesogenic groups
Strong curvature singularities in quasispherical asymptotically de Sitter dust collapse
We study the occurrence, visibility, and curvature strength of singularities
in dust-containing Szekeres spacetimes (which possess no Killing vectors) with
a positive cosmological constant. We find that such singularities can be
locally naked, Tipler strong, and develop from a non-zero-measure set of
regular initial data. When examined along timelike geodesics, the singularity's
curvature strength is found to be independent of the initial data.Comment: 16 pages, LaTeX, uses IOP package, 2 eps figures; accepted for
publication in Class. Quantum Gra
Early reserve effects linked to small home ranges of a commercial fish, Diplodus sargus, Sparidae
Studies that combine both the ecological responses of marine species and protection measures with movement patterns and habitat use are of major importance in order to better understand the performance of marine protected areas (MPA) and how species respond to their implementation. However, few studies have assessed MPA performance by relating local individual movement patterns and the observed reserve effects. In this study, we combined acoustic telemetry with abundance estimates to study the early effects of a recently established small coastal MPA on the local populations of white seabream. The results show that even small, recently established coastal MPAs can increase the abundance and biomass of commercial fish species, provided that target species have small home ranges and exhibit high site fidelity
Quantum spinor field in the FRW universe with a constant electromagnetic background
The article is a natural continuation of our paper {\em Quantum scalar field
in FRW Universe with constant electromagnetic background}, Int. J. Mod. Phys.
{\bf A12}, 4837 (1997). We generalize the latter consideration to the case of
massive spinor field, which is placed in FRW Universe of special type with a
constant electromagnetic field. To this end special sets of exact solutions of
Dirac equation in the background under consideration are constructed and
classified. Using these solutions representations for out-in, in-in, and
out-out spinor Green functions are explicitly constructed as proper-time
integrals over the corresponding contours in complex proper-time plane. The
vacuum-to-vacuum transition amplitude and number of created particles are found
and vacuum instability is discussed. The mean values of the current and
energy-momentum tensor are evaluated, and different approximations for them are
presented. The back reaction related to particle creation and to the
polarization of the unstable vacuum is estimated in different regimes.Comment: 36 pages, LaTex fil
Hysteretic Optimization For Spin Glasses
The recently proposed Hysteretic Optimization (HO) procedure is applied to
the 1D Ising spin chain with long range interactions. To study its
effectiveness, the quality of ground state energies found as a function of the
distance dependence exponent, , is assessed. It is found that the
transition from an infinite-range to a long-range interaction at
is accompanied by a sharp decrease in the performance . The transition is
signaled by a change in the scaling behavior of the average avalanche size
observed during the hysteresis process. This indicates that HO requires the
system to be infinite-range, with a high degree of interconnectivity between
variables leading to large avalanches, in order to function properly. An
analysis of the way auto-correlations evolve during the optimization procedure
confirm that the search of phase space is less efficient, with the system
becoming effectively stuck in suboptimal configurations much earlier. These
observations explain the poor performance that HO obtained for the
Edwards-Anderson spin glass on finite-dimensional lattices, and suggest that
its usefulness might be limited in many combinatorial optimization problems.Comment: 6 pages, 9 figures. To appear in JSTAT. Author website:
http://www.bgoncalves.co
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