8,023 research outputs found
Review on bibliography related to antimicrobials
In this report, a bibliographic research has been done in the field of antimicrobials.In this report, a bibliographic research has been done in the field of antimicrobials. Not all antimicrobials have been included, but those that are being subject of matter in the group GBMI in Terrassa, and others of interest. It includes chitosan and other biopolymers. The effect of nanoparticles is of great interest, and in this sense, the effect of Ag nanoparticles and antibiotic nanoparticles (nanobiotics) has been revised. The report focuses on new publications and the antimicrobial effect of peptides has been considered. In particular, the influence of antimicrobials on membranes has deserved much attention and its study using the Langmuir technique, which is of great utility on biomimetic studies. The building up of antimicrobials systems with new techniques (bottom-up approach), as the Layer-by-Layer technique, can also be found in between the bibliography. It has also been considered the antibiofilm effect, and the new ideas on quorem sensing and quorum quenching.Preprin
Parallel eigensolvers in plane-wave Density Functional Theory
We consider the problem of parallelizing electronic structure computations in
plane-wave Density Functional Theory. Because of the limited scalability of
Fourier transforms, parallelism has to be found at the eigensolver level. We
show how a recently proposed algorithm based on Chebyshev polynomials can scale
into the tens of thousands of processors, outperforming block conjugate
gradient algorithms for large computations
Multiple Scattering Formulation of Two Dimensional Acoustic and Electromagnetic Metamaterials
This work presents a multiple scattering formulation of two dimensional
acoustic metamaterials. It is shown that in the low frequency limit multiple
scattering allows us to define frequency-dependent effective acoustic
parameters for arrays of both ordered and disordered cylinders. This
formulation can lead to both positive and negative acoustic parameters, where
the acoustic parameters are the scalar bulk modulus and the tensorial mass
density and, therefore, anisotropic wave propagation is allowed with both
positive or negative refraction index. It is also shown that the surface fields
on the scatterer are the main responsible of the anomalous behavior of the
effective medium, therefore complex scatterers can be used to engineer the
frequency response of the effective medium, and some examples of application to
different scatterers are given. Finally, the theory is extended to
electromagnetic wave propagation, where Mie resonances are found to be the
responsible of the metamaterial behavior. As an application, it is shown that
it is possible to obtain metamaterials with negative permeability and
permittivity tensors by arrays of all-dielectric cylinders and that anisotropic
cylinders can tune the frequency response of these resonances
New human resource management systems in non-based-knowledge firms: Applications for decision making on the business performance
The aim of this paper is double. First, it provides a conceptual framework and modelling of the relationship between human resource management (HRM) systems and non-based-knowledge firms. Second, using survey data on 1.518 Catalan firms (in Spain, with capital in Barcelona), the paper: 1) identify two system of HRM (in progress HRM system and non-HRM developed system); 2) build a causal model of determinants of HRM systems; and 3) describe the association links between in progress HRM system and firm's performance. Using factor and cluster analysis, we find that only one-third of firms use in progress HRM system. Using logit binomial analysis, we find that features which are structural, technological, strategic, organisational and performance-related explain the adoption of in progress HRM system. Finally, using association analysis, we find that firms that adopt in progress HRM system: 1) are more internationalised and show greater ability to adapt to the changing environment, to innovate and to collaborate; 2) focus on product/service differentiation strategy enhancing quality; 3) apply a greater degree of new forms of work organization; 4) have more technological equipment and use IT more intensively; and 5) invest more in training their employees, than firms with non-HRM system developed
Using problem-based learning for introducing producer theory and market structure in intermediate microeconomics
This paper shows how instructors can use the problem-based learning method to introduce producer theory and market structure in intermediate microeconomics courses. The paper proposes a framework where different decision problems are presented to students, who are asked to imagine that they are the managers of a firm who need to solve a problem in a particular business setting. In this setting, the instructors’ role is to provide both guidance to facilitate student learning and content knowledge on a just-in-time basis.
A new approach to local hardness
The applicability of the local hardness as defined by the derivative of the
chemical potential with respect to the electron density is undermined by an
essential ambiguity arising from this definition. Further, the local quantity
defined in this way does not integrate to the (global) hardness - in contrast
with the local softness, which integrates to the softness. It has also been
shown recently that with the conventional formulae, the largest values of local
hardness do not necessarily correspond to the hardest regions of a molecule.
Here, in an attempt to fix these drawbacks, we propose a new approach to define
and evaluate the local hardness. We define a local chemical potential,
utilizing the fact that the chemical potential emerges as the additive constant
term in the number-conserving functional derivative of the energy density
functional. Then, differentiation of this local chemical potential with respect
to the number of electrons leads to a local hardness that integrates to the
hardness, and possesses a favourable property; namely, within any given
electron system, it is in a local inverse relation with the Fukui function,
which is known to be a proper indicator of local softness in the case of soft
systems. Numerical tests for a few selected molecules and a detailed analysis,
comparing the new definition of local hardness with the previous ones, show
promising results.Comment: 30 pages (including 6 figures, 1 table
Resonant and Non-Local Properties of Phononic Metasolids
We derive a general theory of effective properties in metasolids based on
phononic crystals with low frequency resonances. We demonstrate that in general
these structures need to be described by means of a frequency-dependent and
non-local anisotropic mass density, stiffness tensor and a third- rank coupling
tensor, which shows that they behave like a non-local Willis medium. The effect
of non-locality and coupling tensor manifest themselves for some particular
resonances whereas they become negligible for other resonances. Considering the
example of a two-dimensional phononic crystal, consisting of triangular
arrangements of cylindrical shells in an elastic matrix, we show that its mass
density tensor is strongly resonant and anisotropic presenting both positive
and negative divergent values, while becoming scalar in the quasi-static limit.
Moreover, it is found that the negative value of transverse component of the
mass density is induced by a dipolar resonance, while that of the vertical
component is induced by a monopolar one. Finally, the dispersion relation
obtained by the effective parameters of the crystal is compared with the band
structure, showing a good agreement for the low-wave number region, although
the non-local effects are important given the existence of some resonant values
of the wave number
The Inverse Grating Problem: Efficient Design of Anomalous Flexural Wave Reflectors and Refractors
We present an extensive formulation of the inverse grating problem for exural
waves, in which the energy of each diffracted mode is selected and the grating
configuration is then obtained by solving a linear system of equations. The
grating is designed as a lineal periodic repetition of a unit cell comprising a
cluster of resonators attached at points whose physical properties are directly
derived by inversion of a given matrix. Although both active and passive
attachments can be required in the most general case, it is possible to find
configurations with only passive, i.e. damped, solutions. This inverse design
approach presents an alternative to the design of metasurfaces for exural waves
overcoming the limitations of gradient phase metasurfaces, which require a
continuous variation of the surface's impedance. When the grating is designed
in such a way that all the energy is channeled to a single diffracted mode, it
behaves as an anomalous refractor or re ector. The negative refractor is
analyzed in depth, and it is shown that with only three scatterers per unit
cell is it possible to build such a device with unitary efficiency
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