Two-photon finite-pulse model for resonant transitions in attosecond experiments

We present an analytical model capable of describing two-photon ionization of atoms with attosecond pulses in the presence of intermediate and final isolated autoionizing states. The model is based on the finite-pulse formulation of second-order time-dependent perturbation theory. It approximates the intermediate and final states with Fano's theory for resonant continua, and it depends on a small set of atomic parameters that can either be obtained from separate \emph{ab initio} calculations, or be extracted from few selected experiments. We use the model to compute the two-photon resonant photoelectron spectrum of helium below the N=2 threshold for the RABITT (Reconstruction of Attosecond Beating by Interference of Two-photon Transitions) pump-probe scheme, in which an XUV attosecond pulse train is used in association to a weak IR probe, obtaining results in quantitative agreement with those from accurate \emph{ab initio} simulations. In particular, we show that: i) Use of finite pulses results in a homogeneous red shift of the RABITT beating frequency, as well as a resonant modulation of the beating frequency in proximity of intermediate autoionizing states; ii) The phase of resonant two-photon amplitudes generally experiences a continuous excursion as a function of the intermediate detuning, with either zero or $2\pi$ overall variation.Comment: 23 pages, 13 figure

The soft-photon approximation in infrared-laser-assisted atomic ionization by extreme-ultraviolet attosecond-pulse trains

We use the soft-photon approximation, formulated for finite pulses, to investigate the effects of the dressing pulse duration and intensity on simulated attosecond pump–probe experiments employing trains of attosecond extremeultraviolet pulses in conjunction with an IR probe pulse.We illustrate the validity of the approximation by comparing the modelled photoelectron distributions for the helium atom, in the photon energy region close to the N = 2 threshold, to the results from the direct solution of the time-dependent Schr¨odinger equation for two active electrons. Even in the presence of autoionizing states, the model accurately reproduces most of the background features of the ab initio photoelectron spectrum in the 1s channel. A splitting of the photoelectron harmonic signal along the polarization axis, in particular, is attributed to the finite duration of the probe pulse. Furthermore, we study the dependence of the sideband integrated signal on the pump–probe time delay for increasing IR field strengths. Starting at IR intensities of the order of 1TWcm−2, overtones in the sideband oscillations due to the exchange of three or more IR photons start to appear. We derive an analytical expression in the frequency-comb limit of the soft-photon model for the amplitude of all the sideband frequency components and show that these amplitudes oscillate as a function of the intensity of the IR field. In particular, we predict that the amplitude of the fundamental component with frequency 2!IR, on which the rabitt optical reconstruction technique is based, changes sign periodicallyWe thank Mare Nostrum BSC and CCC-UAM (Centro de Computación Científica, Universidad Autónoma de Madrid) for allocation of computer time. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement number 290853, the European COST Actions CM0702 and CM1204, the ERA-Chemistry project number PIM2010EEC-00751, the Marie Curie ITN CORINF and the MICINN projects numbers FIS2010-15127 and CSD 2007-00010 (Spain

Evolución histórica del inventario de molinos hidráulicos de Alcalá de Guadaíra

Comunicación presentada a las II Jornadas Andaluzas de Patrimonio Industrial y de la Obra Pública, celebradas en Cádiz, 25-27 Octubre, 2012Posiblemente sea Alcalá de Guadaíra la primera población andaluza en número de molinos de agua. Entre los siglos XV y XVIII, la antigua Alcalá de los Panaderos llegó a contar con 40 molinos, en el siglo XIX se citan 33 y en la actualidad quedan 24. Nombres como Cerrajas, Pelay orrea, Realajeo Piealegre, Arrabal, Algarrobo, la Tapada, las Eras, San Juan,Benaharosa, Aceña Trapera, San José, Rincón, Hundido o San Pedro son una pequeña muestra de la serie de interesantes artefactos que aún puedan visitarse en sus inmediaciones, bien en el mismo río Guadaíra bien en sus afluentes de Marchenilla y Gandul

Validation of the standard method EN ISO 19343:2017 for detection and quantification of histamine in different matrices of fish and fishery products using high performance liquid chromatography

Motivation: Histamine, a biogenic amine produced by bacterial decarboxylation of histidine, is the main cause of scombroid fish poisoning and is strictly regulated by the European Union in fish and fishery products [1]. Therefore, an adequate histamine quantification method is necessary in order to assess current regulations and prevent health problems. In this sense, High Performance Liquid Chromatography (HPLC) have been widely used for the detection of histamine as it provides good specificity and sensitivity when coupled with a highly sensitive detector. The standard protocol EN ISO 19343 is the current in use and it was developed to meet with 2073/2005 European Regulation about microbiological criteria for food products. However, there is still room for improvement in terms of resolution, sensitivity and discrimination and the validation of this protocol is a necessary step in laboratories to prove the reliability of results and a previous step to get ISO certification [2].Methods: In this study, we use the HPLC method-based ISO 19343:2017 to compare the results from different samples of raw fish, canned fish, fish sauce and fishery derived products. This method allows the separation of histamine within the set of biogenic amines from fish and fishery products. The sample is extracted by mixing it with perchloric acid. A derivatization is carried out prior passing through a chromatographic column using dansyl chloride to do histamine detectable under UV light. Biogenic amines and components in the solution are separated by HPLC using a chromatographic column, with UV detection. Histamine concentration is calculated from the ratio between the areas of histamine peaks and internal standard, using a calibration curve.In the validation process, veracity of the method is studied, examining parameters such as accuracy, recovery and correction. The work interval is defined between the lower and upper quantification limit. The specificity / selectivity of the method is studied and verified by performing exercises in different matrices with different compositions and checking that the quality criteria are met independently of the matrix composition. In this way, and if the parameters are within the limits established by the standard, the method would be validated [3]

Molecular Computation Models in ACL2: a Simulation of Lipton’s Experiment Solving SAT

In this paper we present an ACL2 formalization of a molecular computing model: Adleman’s restricted model [2]. This is a first step to formalize unconventional models of computation in ACL2. As an application of this model, an implementation of Lipton’s experiment solving SAT [7] is described, based on the formalization given in [6]. We use ACL2 to make a formal proof of the completeness and soundness properties of the function implementing the experimentMinisterio de Ciencia y Tecnología TIC2000-1368-CO3-0

Hybrid Networks of Evolutionary Processors

A hybrid network of evolutionary processors consists of several processors which are placed in nodes of a virtual graph and can perform one simple operation only on the words existing in that node in accordance with some strategies. Then the words which can pass the output filter of each node navigate simultaneously through the network and enter those nodes whose input filter was passed. We prove that these networks with filters defined by simple random-context conditions, used as language generating devices, are able to generate all linear languages in a very efficient way, as well as non-context-free languages. Then, when using them as computing devices, we present two linear solutions of the Common Algorithmic Problem.Ministerio de Ciencia y Tecnología TIC2002-04220-C03-0