8,229 research outputs found
Fractional Hamiltonian analysis of higher order derivatives systems
The fractional Hamiltonian analysis of 1+1 dimensional field theory is
investigated and the fractional Ostrogradski's formulation is obtained. The
fractional path integral of both simple harmonic oscillator with an
acceleration-squares part and a damped oscillator are analyzed. The classical
results are obtained when fractional derivatives are replaced with the integer
order derivatives.Comment: 13 page
Implant Site Nexplanon Reaction?
Nexplanon (Schering-Plough Limited/Merck Sharp & Dohme Limited (MSD)) is a long active reversible contraceptive method that provides effective contraception for 3 years. It consists of a single, flexible, rod-shaped implant, containing 68 mg etonogestrel. It is 4 cm long, consists of an ethylene vinyl acetate copolymer, a non-absorbable material, and also contains 15 mg of barium sulfate, which makes it visible by X-ray. We describe a case of a 39-year-old woman who experienced a local reaction to the barium sulfate in Nexplanon. She was given medical treatment, but only the removal of the implant resolved the symptoms. After removal there was gradual improvement and 72 h later the patient was asymptomatic. Allergic reaction to barium sulfate is extremely rare: until now, there have only been two cases associated with Nexplanon described in the literature
On the renormalization group flow of f(R)-gravity
We use the functional renormalization group equation for quantum gravity to
construct a non-perturbative flow equation for modified gravity theories of the
form . Based on this equation we show that certain
gravitational interactions monomials can be consistently decoupled from the
renormalization group (RG) flow and reproduce recent results on the asymptotic
safety conjecture. The non-perturbative RG flow of non-local extensions of the
Einstein-Hilbert truncation including and interactions is investigated in detail. The inclusion of
such interactions resolves the infrared singularities plaguing the RG
trajectories with positive cosmological constant in previous truncations. In
particular, in some -truncations all physical trajectories emanate from
a Non-Gaussian (UV) fixed point and are well-defined on all RG scales. The RG
flow of the -truncation contains an infrared attractor which drives a
positive cosmological constant to zero dynamically.Comment: 55 pages, 7 figures, typos corrected, references added, version to
appear in Phys. Rev.
The graphene sheet versus the 2DEG: a relativistic Fano spin-filter via STM and AFM tips
We explore theoretically the density of states (LDOS) probed by an STM tip of
2D systems hosting an adatom and a subsurface impurity,both capacitively
coupled to AFM tips and traversed by antiparallel magnetic fields. Two kinds of
setups are analyzed, a monolayer of graphene and a two-dimensional electron gas
(2DEG). The AFM tips set the impurity levels at the Fermi energy, where two
contrasting behaviors emerge: the Fano factor for the graphene diverges, while
in the 2DEG it approaches zero. As result, the spin-degeneracy of the LDOS is
lifted exclusively in the graphene system, in particular for the asymmetric
regime of Fano interference. The aftermath of this limit is a counterintuitive
phenomenon, which consists of a dominant Fano factor due to the subsurface
impurity even with a stronger STM-adatom coupling. Thus we find a full
polarized conductance, achievable just by displacing vertically the position of
the STM tip. To the best knowledge, our work is the first to propose the Fano
effect as the mechanism to filter spins in graphene. This feature arises from
the massless Dirac electrons within the band structure and allows us to employ
the graphene host as a relativistic Fano spin-filter
Lagrangian formulation of classical fields within Riemann-Liouville fractional derivatives
The classical fields with fractional derivatives are investigated by using
the fractional Lagrangian formulation.The fractional Euler-Lagrange equations
were obtained and two examples were studied.Comment: 9 page
The type N Karlhede bound is sharp
We present a family of four-dimensional Lorentzian manifolds whose invariant
classification requires the seventh covariant derivative of the curvature
tensor. The spacetimes in questions are null radiation, type N solutions on an
anti-de Sitter background. The large order of the bound is due to the fact that
these spacetimes are properly , i.e., curvature homogeneous of order 2
but non-homogeneous. This means that tetrad components of are constant, and that essential coordinates first appear as
components of . Covariant derivatives of orders 4,5,6 yield one
additional invariant each, and is needed for invariant
classification. Thus, our class proves that the bound of 7 on the order of the
covariant derivative, first established by Karlhede, is sharp. Our finding
corrects an outstanding assertion that invariant classification of
four-dimensional Lorentzian manifolds requires at most .Comment: 7 pages, typos corrected, added citation and acknowledgemen
Disinfection with neutral electrolyzed oxidizing water to reduce microbial load and to prevent biofilm regrowth in the processing of fresh-cut vegetables
Product decontamination is one of the most important processes of the hygienic practice in food industries such as Minimally Processed Vegetables (MPV) plants and sodium hypochlorite (NaOCl) solutions are commonly used as a biocide for disinfection. Although it may be corrosive and irritating when compared to alternative biocides, this biocide is frequently applied at high concentrations. This work aims at studying the use of lower concentrations of chlorine by testing neutral electrolyzed oxidizing water (NEOW) as a chlorine-source disinfectant in fresh-cut salad processing. Assays were performed at industrial and laboratory scale. Results showed that lower doses of chlorine from NEOW (30 ppm) are as effective as higher concentrations of the traditional chlorine from NaOCl (80 ppm) in the reduction of total microbial population at industrial scale. Moreover, in laboratory studies, the NEOW chlorine was also more effective in biofilm eradication, as well as a biofilm preventive agent. NEOW can thus be a successful alternative water disinfection technique, reducing the free chlorine concentration needed to sanitize salads, also decreasing water consumption whilst taking into account environmental and food quality impacts
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