1,164 research outputs found
Constant magnetic field and 2d non-commutative inverted oscillator
We consider a two-dimensional non-commutative inverted oscillator in the
presence of a constant magnetic field, coupled to the system in a
``symplectic'' and ``Poisson'' way. We show that it has a discrete energy
spectrum for some value of the magnetic field.Comment: 7 pages, LaTeX file, no figures, PACS number: 03.65.-
A Novel Approach for an Integrated Straw tube-Microstrip Detector
We report on a novel concept of silicon microstrips and straw tubes detector,
where integration is accomplished by a straw module with straws not subjected
to mechanical tension in a Rohacell lattice and carbon fiber
reinforced plastic shell. Results on mechanical and test beam performances are
reported on as well.Comment: Accepted by Transactions on Nuclear Science (2005). 11 pages, 9
figures, uses lnfprep.st
Strong Interactions, (De)coherence and Quarkonia
Quarkonia are the central objects to explore the non-perturbative nature of
non-abelian gauge theories. We describe the confinement-deconfinement phases
for heavy quarkonia in a hot QCD medium and thereby the statistical nature of
the inter-quark forces. In the sense of one-loop quantum effects, we propose
that the "quantum" nature of quark matters follows directly from the
thermodynamic consideration of Richardson potential. Thereby we gain an
understanding of the formation of hot and dense states of quark gluon plasma
matter in heavy ion collisions and the early universe. In the case of the
non-abelian theory, the consideration of the Sudhakov form factor turns out to
be an efficient tool for soft gluons. In the limit of the Block-Nordsieck
resummation, the strong coupling obtained from the Sudhakov form factor yields
the statistical nature of hadronic bound states, e.g. kaons and Ds particles.Comment: 8 pages, Keywords: CPT symmetry, decoherence, Lorentz symmetry
breaking; PACS: 02.40.-k; 14.40.Pq; 12.40.Nn; 14.70.Dj; conference proceeding
of Discrete 2010, 6-11 December 2010, Roma (Italy); the Symposium proceedings
will be published online in a special volume of Journal of Physics:
Conference Serie
Two-Center Black Holes Duality-Invariants for stu Model and its lower-rank Descendants
We classify 2-center extremal black hole charge configurations through
duality-invariant homogeneous polynomials, which are the generalization of the
unique invariant quartic polynomial for single-center black holes based on
homogeneous symmetric cubic special Kaehler geometries. A crucial role is
played by an horizontal SL(p,R) symmetry group, which classifies invariants for
p-center black holes. For p = 2, a (spin 2) quintet of quartic invariants
emerge. We provide the minimal set of independent invariants for the rank-3 N =
2, d = 4 stu model, and for its lower-rank descendants, namely the rank-2 st^2
and rank-1 t^3 models; these models respectively exhibit seven, six and five
independent invariants. We also derive the polynomial relations among these and
other duality invariants. In particular, the symplectic product of two charge
vectors is not independent from the quartic quintet in the t^3 model, but
rather it satisfies a degree-16 relation, corresponding to a quartic equation
for the square of the symplectic product itself.Comment: 1+31 pages; v2: amendments in Sec. 9, App. C added, other minor
refinements, Refs. added; v3: Ref. added, typos fixed. To appear on
J.Math.Phy
Multi-Centered Black Hole Flows
We describe the systematical construction of the first order formalism for
multi-centered black holes with flat three dimensional base-space, within the
so-called model of N=2, D=4 ungauged Maxwell-Einstein supergravity. The
three possible flow classes (BPS, composite non-BPS and almost-BPS) are
analyzed in detail, and various solutions, such as single-centered (static or
under-rotating) and all known multi-centered black holes, are recovered in this
unified framework. We also consider the possibility of obtaining new solutions.
The almost-BPS class is proved to split into two general sub-classes,
corresponding to a positive or negative value of the duality-invariant
polynomial for the total charge; the well known almost BPS system is shown to
be a particular solution of the second sub-class.Comment: 17 pages,no figure
A Note on Exact Solutions and Attractor Mechanism for Non-BPS Black Holes
We obtain two extremal, spherically symmetric, non-BPS black hole solutions
to 4D supergravity, one of which carries D2-D6 charges and the other carries
D0-D2-D4 charges. For the D2-D6 case, rather than solving the equations of
motion directly, we assume the form of the solution and then find that the
assumption satisfies the equations of motion and the constraint. Our D2-D6
solution is manifestly dual to the solution presented in 0710.4967. The
D0-D2-D4 solution is obtained by performing certain
duality transformations on the D0-D4 solution in 0710.4967.Comment: 20 pages, LaTe
Rashba effect in 2D mesoscopic systems with transverse magnetic field
We present semiclassical and quantum mechanical results for the effects of a
strong magnetic field in Quantum Wires in the presence of Rashba Spin Orbit
coupling. Analytical and numerical results show how the perturbation acts in
the presence of a transverse magnetic field in the ballistic regime and we
assume a strong reduction of the backward scattering interaction which could
have some consequences for the Tomonaga-Luttinger transport. We analyze the
spin texture due to the action of Spin Orbit coupling and magnetic field often
referring to the semiclassical solutions that magnify the singular spin
polarization: results are obtained for free electrons in a twodimensional
electron gas and for electrons in a Quantum Wire.
We propose the systems as possible devices for the spin filtering at various
regimes.Comment: 12 pages, 12 figures, to appear in Phys. Rev.
A multibiomarker approach to evaluate the impact of anthropogenic contaminants on the ecotoxicological status of honey bees, Apis mellifera
A rapid decline of Apis mellifera, a keystone pollinator of wild plant species and
agricultural crops, was recorded worldwide in recent years. The massive use of
insecticides and fungicides in agriculture associated with pollution generated by
other human activities and presence of parasites can cause toxicological effects in
bees including a decrease of the immune defences, leading to the collapse of the
colonies. Effective assessment of the ecotoxicological impacts of anthropogenic
contaminants requires an approach that combines different biomarkers that enable
a more precise diagnosis of exposure to environmental stressors through a
combination of different biological responses. The aim of this study was to
develop and apply a set of biomarkers to study the ecotoxicological status of
honey bees. In the first phase, we investigated in the laboratory the effects of
EMS, cadmium and a commercial fungicide (azoxistrobin 18.2% and
ciproconazole 7.3%) in adult honey bees, evaluating eventual variation in
glutathione S-transferase (GST), carboxylesterase (CaE), acetylcholinesterase
(AChE) activities, alkaline phosphatase (ALP), lysozyme, erythrocyte nuclear
abnormalities (ENA) assay and differential haemocytes count (DHC). Genotoxic
effects, as well as alteration of the immune system, were found in bees treated
with EMS, cadmium or the fungicide. Cadmium and the fungicide also inhibited
AChE and CaE activities, GST was induced by all the compounds investigated. In
the second phase, adult honey bees were collected from apiaries located in four
environments characterized by different chemical input: a wooded environment
(low input), an urban site, an orchard and a cultivated countryside site. Honey
bees from the urban site were also collected and analyzed before and after
treatment for parasites. ENA assay showed that bees taken from the countryside
and the orchard had a greater number of abnormalities compared to the forest,
confirming the presence of genotoxic substances in agricultural environments
compared to control environments. GST activity was induced in bees from the
urban environment, AChE was inhibited in the countryside compared to the forest,
suggesting the presence of substances with neurotoxic effect in this environment.
ALP activity was induced in all sites in comparison to wooded one. The bees
collected after the parasites treatment showed an increase for GST activity as well
as AChE inhibition
Designing cascades of electron transfer processes in multicomponent graphene conjugates
A novel family of nanocarbon-based materials was designed, synthesized, and probed within the context of charge-transfer cascades. We integrated electron-donating ferrocenes with light-harvesting/electron-donating (metallo)porphyrins and electron-accepting graphene nanoplates (GNP) into multicomponent conjugates. To control the rate of charge flow between the individual building blocks, we bridged them via oligo-p-phenyleneethynylenes of variable lengths by β-linkages and the Prato-Maggini reaction. With steady-state absorption, fluorescence, Raman, and XPS measurements we realized the basic physico-chemical characterization of the photo- and redox-active components and the multicomponent conjugates. Going beyond this, we performed transient absorption measurements and corroborated by single wavelength and target analyses that the selective (metallo)porphyrin photoexcitation triggers a cascade of charge transfer events, that is, charge separation, charge shift, and charge recombination, to enable the directed charge flow. The net result is a few nanosecond-lived charge-separated state featuring a GNP-delocalized electron and a one-electron oxidized ferrocenium
Etching kinetics of nanodiamond seeds in the early stages of CVD diamond growth
We present an experimental study on the etching of detonation nanodiamond (DND) seeds during typical microwave chemical vapor deposition (MWCVD)conditions leading to ultra-thin diamond film formation, which is fundamental for many technological applications. The temporal evolution of the surface density of seeds on the Si(100) substrate has been assessed by scanning electron microscopy (SEM). The resulting kinetics have been explained in the framework of a model based on the effect of the particle size, according to the Young-Laplace equation,on both chemical potential of carbon atoms in DND and activation energy of the reaction with atomic hydrogen. The model describes the experimental kinetics of seeds' disappearance by assuming that nanodiamond particles with a size smaller than a "critical radius", r*, are etched away while those greater than r* can grow. Finally, the model allows to estimate the rate coefficients for growth and etching from the experimental kinetics
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