1,179 research outputs found
Distribution of Deroceras reticulatum (Müller, 1774) (Pulmonata Stylommatophora) in Argentina with first record of the Reserva de Usos Múltiples Isla Martin Garcia, RÃo de la Plata superior
Deroceras reticulatum is a misanthropic European species spread widely throughout South America. At the moment this species is considered a ‘pest’ in direct sowing such as maize, soybean, sunflower, wheat, alfalfa and clovers, among others. The aim of this paper is to report the first record of D. reticulatum in the Reserva de Usos Multiples Isla MartÃn GarcÃa, Buenos Aires province and to provide information about this species distribution in five Argentina provinces.Deroceras reticulatum é uma espécie sinantrópica oriunda da Europa e com grande dispersão na América do Sul. Esta espécie é considerada atualmente praga dos cultivos de semeadura direta de milho, soja, trigo, girassol, alfafa e trevos, entre outros. O presente trabalho tem por objetivo comunicar o primeiro achado do agriolimácido D. reticulatum na Reserva de usos múltiplos Ilha MartÃn GarcÃa, provÃncia de Buenos Aires e proporcionar informação sobre a distribuição desta espécie em cinco provÃncias argentinas
Prediction of coffee sensory quality through MSenose as analytical decision maker for routine controls: possibilities and limitations.
Divide-and-Conquer Semiclassical Dynamics: A Viable Method for Vibrational Spectra Calculations of High Dimensional and Anharmonic Molecular Systems
The prediction of accurate vibrational frequencies is often necessary for the interpretation of experimental outcomes, especially when sources of strong anharmonic effects such as hydrogen bonding are present. Unfortunately, the most relevant stumbling block to fill in the gap between theory and experiment is usually represented by dimensionality problems, when quantum mechanical effects like Zero Point Energy, quantum anharmonicities, and overtones cannot be neglected. In this circumstance quantum applications are generally limited to small and medium sized molecules. One possible alternative is represented by Semiclassical theory, which allows to recover accurate spectral densities by taking advantage of quantities arising from classical mechanics simulations. [1-5] In particular, here we present a method, called Semiclassical \u201cDivide-and-Conquer\u201d, able to reproduce spectra of high-dimensional molecular systems accurately. [6,7] The method is first validated by performing spectra of small and medium sized molecules, and then it is used to calculate the spectra of benzene and a C 60 model, which is made of 174 degrees of freedom. Then, we show results of variously sized-water clusters characterized by strong hydrogen-bonding that red shifts the involved OH stretches. [8] Finally, the method is combined with ab-initio molecular dynamics to abandon the necessity to employ pre-fitted Potential Energy Surfaces, and applied to study supramolecular systems like the protonated glycine dimer and hydrogen-tagged protonated glycine. [9] [1] W. H. Miller, J. Chem. Phys. 1970, 53, 3578;
[2] E. J. Heller, J. Chem. Phys. 1981, 75, 2923; M. F. Herman and E. Kluk, Chem. Phys. 1984, 91, 27.
[3] K. G. Kay, J. Chem. Phys. 1994, 101, 2250; W. H. Miller, J. Phys. Chem. A 2001, 105, 2942.
[4] A. L. Kaledin and W. H. Miller, J. Chem. Phys. 2003, 118, 7174.
[5] R. Conte, A. Aspuru-Guzik, and M. Ceotto, J. Phys. Chem. Lett. 2013, 4, 3407.
[6] M. Ceotto, G. Di Liberto, and R. Conte, Phys. Rev. Lett. 2017, 119, 010401.
[7] G. Di Liberto, R. Conte, and M. Ceotto, J. Chem. Phys. 2018, 148, 014307.
[8] G. Di Liberto, R. Conte, and M. Ceotto, J. Chem. Phys. 2018, 148, 104302.
[9] F. Gabas, G. Di Liberto, R. Conte, and M. Ceotto In preparation
Divide-and-Conquer Semiclassical Dynamics: A Viable Route for Spectroscopic Calculations of High Dimensional Molecular Systems
The accurate prediction of vibrational spectra has become a very challenging task for theoretical methods. The most relevant stumbling block is represented by the necessity to employ quantum methods, since very often quantum effects, like zero point energy, quantum anharmonicities, and overtones, are not negligible to gain insights into the physics of a molecular system. Unfortunately, quantum mechanical methods are usually affected by the so-called curse of dimensionality problem, which limits their applicability to small and medium sized molecules. A viable alternative is represented by the Semiclassical theory, which is obtained by stationary-phase approximating to the second order of the Feynman Path-Integral representation of the Quantum time evolution operator, and allows to calculate spectral densities. In particular, the Coherent State Representation was shown to be very valid in molecular applications. However, even in this case the curse of dimensionality occurs and the method runs out of steam when the system dimensionality increases to 25-30 degrees of freedom or more. Here, we present a method, called Divide-and-Conquer, able to overcome this issue, and to reproduce spectra of high-dimensional molecular systems, while retaining the typical semiclassical accuracy (20-30 cm-1). The method is tested on simple molecules. Then, it is used to calculate spectra of a C60 model, which is made by 174 degrees of freedom, and of variously sized-water clusters characterized by strong hydrogen-bonding that red shifts the involved OH stretches. Finally, the method is also combined with ab-initio molecular dynamics to abandon the necessity to employ pre-fitted Potential Energy Surfaces, and applied to study supramolecular systems as the protonated glycine dimer and hydrogen-tagged protonated glycine
Semiclassical vibrational spectroscopy : the importance of quantum anharmonicity in supra-molecular systems
Semiclassical (SC) vibrational spectroscopy has been applied successfully to several molecular systems thanks to the possibility to regain quantum effects accurately starting from short-time classical trajectories.[1-5] Larger molecular and supra-molecular systems represent instead an open challenge in the field of semiclassical spectroscopy mainly due to the necessity to work in very high dimensionality.
To start off the talk I will present some recent theoretical advances able to extend the range of applicability of SC vibrational spectroscopy to very high-dimensional systems.[6-7] Then, I will move to applications of semiclassical spectroscopy concerning the vibrational features of water clusters and two supra-molecular systems involving glycine.[8-9] These applications will point out the importance of a multi-reference, dynamical approach able to reproduce quantum anharmonicities without employing any ad-hoc scaling factor.
[1] M. F. Herman, E. Kluk, Chem. Phys. 1984, 91, 27.
[2] A. L. Kaledin, W. H. Miller, J. Chem. Phys. 2003, 118, 7174.
[3] M. Ceotto, S. Atahan, G. F. Tantardini, A. Aspuru-Guzik, J. Chem. Phys. 2009, 130, 234113.
[4] R. Conte, A. Aspuru-Guzik, M. Ceotto, J. Phys. Chem. Lett. 2013, 4, 3407.
[5] F. Gabas, R. Conte, M. Ceotto, J. Chem. Theory Comput. 2017, 13, 2378.
[6] M. Ceotto, G. Di Liberto, R. Conte, Phys. Rev. Lett. 2017, 119, 010401.
[7] G. Di Liberto, R. Conte, M. Ceotto, J. Chem. Phys. 2018, 148, 014307.
[8] G. Di Liberto, R. Conte, M. Ceotto, J. Chem. Phys. 2018, 148, 104302.
[9] F. Gabas, G. Di Liberto, R. Conte, M. Ceotto, to be submitted
On the evolution of decoys in plant immune systems
The Guard-Guardee model for plant immunity describes how resistance proteins
(guards) in host cells monitor host target proteins (guardees) that are
manipulated by pathogen effector proteins. A recently suggested extension of
this model includes decoys, which are duplicated copies of guardee proteins,
and which have the sole function to attract the effector and, when modified by
the effector, trigger the plant immune response. Here we present a
proof-of-principle model for the functioning of decoys in plant immunity,
quantitatively developing this experimentally-derived concept. Our model links
the basic cellular chemistry to the outcomes of pathogen infection and
resulting fitness costs for the host. In particular, the model allows
identification of conditions under which it is optimal for decoys to act as
triggers for the plant immune response, and of conditions under which it is
optimal for decoys to act as sinks that bind the pathogen effectors but do not
trigger an immune response.Comment: 15 pages, 6 figure
Misura tridimensionale dei tempi di rilassamento longitudinali (spin - reticolo) di un dosimetro Fricke mediante una apparecchiatura di diagnostica RMN da 1.5 T
Potential Aroma Chemical Fingerprint of Oxidised Coffee Note by HS-SPME-GC-MS and Machine Learning
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