3,079 research outputs found
Real-time pcr method combined with a matrix lysis procedure for the quantification of listeria monocytogenes in meat products
In this study a real-time PCR method has been developed for the specific quantification of the foodborne pathogen Listeria monocytogenes on meat products through the gene hlyA. The PCR was combined with a matrix lysis that allowed the obtaining of the microorganisms without sample dilution and the elimination the PCR inhibitors from dry-cured ham. The qPCR method calibration curve had an efficiency of 100.4%, limits of detection and quantification were 30.1 ± 6.2 CFU/g which is under the legal limit of L. monocytogenes in ready-to-eat products, and an analytical variability <0.25 log hlyA gene copies/reaction. The analysis was performed simultaneously with the reference method ISO 11290-2. The comparison of the qPCR-matrix lysis results with the reference method showed an excellent correspondence, with a relative accuracy between 95.83â105.20%. Finally, the method was applied to commercial derived meat samples and the pathogen was quantified in one of the commercial samples assayed in 69.1 ± 13.9 CFU/g while the reference method did not quantify it. The optimized qPCR showed higher precision and sensitivity than the reference method at low concentrations of the microorganism in a shorter time. Therefore, qPCR-matrix lysis shows a potential application in the meat industry for L. monocytogenes routine control. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
Improving reality. An analysis of Spanish makeover reality television
The main aim of this paper is to identify the values conveyed by Spanish makeover reality television. There are two aspects that make these programmes relevant study objects: first, their widespread presence in Spanish television schedules, and second, the role they play in constructing the social imaginary due to their didactic and prescriptive nature. We analysed six Spanish makeover reality shows, Cambio Radical, Desnudas, Esta casa era una ruina, Supernanny, Hermano Mayor and Ajuste de Cuentas, using a methodology that combines narrative semiotics and the analysis of narrative form (plot/syhuzet) and audiovisual style. This paper summarises the main research results and conclusions of a doctoral thesis presented in September 2010
Scalar Field Oscillations Contributing to Dark Energy
We use action-angle variables to describe the basic physics of coherent
scalar field oscillations in the expanding universe. These analytical mechanics
methods have some advantages, like the identification of adiabatic invariants.
As an application, we show some instances of potentials leading to equations of
state with , thus contributing to the dark energy that causes the
observed acceleration of the universe.Comment: 17 pages, 6 figures, Latex file. Sec.II reduced, discussion on sound
speed added in Sec.IV, new references added. Accepted for publication in
Physical Review
Condensate fraction in liquid 4He at zero temperature
We present results of the one-body density matrix (OBDM) and the condensate
fraction n_0 of liquid 4He calculated at zero temperature by means of the Path
Integral Ground State Monte Carlo method. This technique allows to generate a
highly accurate approximation for the ground state wave function Psi_0 in a
totally model-independent way, that depends only on the Hamiltonian of the
system and on the symmetry properties of Psi_0. With this unbiased estimation
of the OBDM, we obtain precise results for the condensate fraction n_0 and the
kinetic energy K of the system. The dependence of n_0 with the pressure shows
an excellent agreement of our results with recent experimental measurements.
Above the melting pressure, overpressurized liquid 4He shows a small condensate
fraction that has dropped to 0.8% at the highest pressure of p = 87 bar.Comment: 12 pages. 4 figures. Accepted for publication on "Journal of Low
Temperature Physics
Urban Heat Island (UHI) risk maps as innovative tool for urban regeneration strategies. The case of Parma
For the purposes of regeneration of the consolidated city it is increasingly important
to have the knowledge of the micro-scale distribution of the vulnerability of the population to
the consequences of climate change and increasing urbanization. The work to be presented starts
with the creation of maps of the risk classification induced by the heat islands in the city of
Parma, and aims to investigate which are the most effective strategies that a Public
Administration can adopt. The maps that have been created allow to assess the risk for the fragile
population at the level of the single building. They relate the climatic datum of thermal variation
with the population residing within each building, and verify the causal relationship with the soil
sealing and with the morphology of the urban fabric. The results of the study can help to identify
the thermal hot spot, receivers of specific mitigation actions. The risk map is itself a tool to
develop multilevel actions, designed according to the peculiarities of the sites, where the possible
adaptive solutions are compared with the physical and morphological characteristics of the
places. The positive function of green infrastructures (contrast of overheating, flood mitigation,
creation of places and services with a recreational function) is acquired by research and urban
planning practice. It is equally well known the difficulty faced by Local Authorities in the
maintenance and increase of unbuilt public areas, fundamental for the connection of ecological
networks
Mixable Shuffles, Quasi-shuffles and Hopf Algebras
The quasi-shuffle product and mixable shuffle product are both
generalizations of the shuffle product and have both been studied quite
extensively recently. We relate these two generalizations and realize
quasi-shuffle product algebras as subalgebras of mixable shuffle product
algebras. As an application, we obtain Hopf algebra structures in free
Rota-Baxter algebras.Comment: 14 pages, no figure, references update
Generalized shuffles related to Nijenhuis and TD-algebras
Shuffle and quasi-shuffle products are well-known in the mathematics
literature. They are intimately related to Loday's dendriform algebras, and
were extensively used to give explicit constructions of free commutative
Rota-Baxter algebras. In the literature there exist at least two other
Rota-Baxter type algebras, namely, the Nijenhuis algebra and the so-called
TD-algebra. The explicit construction of the free unital commutative Nijenhuis
algebra uses a modified quasi-shuffle product, called the right-shift shuffle.
We show that another modification of the quasi-shuffle product, the so-called
left-shift shuffle, can be used to give an explicit construction of the free
unital commutative TD-algebra. We explore some basic properties of TD-operators
and show that the free unital commutative Nijenhuis algebra is a TD-algebra. We
relate our construction to Loday's unital commutative dendriform trialgebras,
including the involutive case. The concept of Rota-Baxter, Nijenhuis and
TD-bialgebras is introduced at the end and we show that any commutative
bialgebra provides such objects.Comment: 20 pages, typos corrected, accepted for publication in Communications
in Algebr
Spitzer's Identity and the Algebraic Birkhoff Decomposition in pQFT
In this article we continue to explore the notion of Rota-Baxter algebras in
the context of the Hopf algebraic approach to renormalization theory in
perturbative quantum field theory. We show in very simple algebraic terms that
the solutions of the recursively defined formulae for the Birkhoff
factorization of regularized Hopf algebra characters, i.e. Feynman rules,
naturally give a non-commutative generalization of the well-known Spitzer's
identity. The underlying abstract algebraic structure is analyzed in terms of
complete filtered Rota-Baxter algebras.Comment: 19 pages, 2 figure
Heteroclinic structure of parametric resonance in the nonlinear Schr\"odinger equation
We show that the nonlinear stage of modulational instability induced by
parametric driving in the {\em defocusing} nonlinear Schr\"odinger equation can
be accurately described by combining mode truncation and averaging methods,
valid in the strong driving regime. The resulting integrable oscillator reveals
a complex hidden heteroclinic structure of the instability. A remarkable
consequence, validated by the numerical integration of the original model, is
the existence of breather solutions separating different Fermi-Pasta-Ulam
recurrent regimes. Our theory also shows that optimal parametric amplification
unexpectedly occurs outside the bandwidth of the resonance (or Arnold tongues)
arising from the linearised Floquet analysis
- âŠ