Photoinduced Fano-resonance of coherent phonons in zinc

Utilizing femtosecond optical pump-probe technique, we have studied transient Fano-resonance in zinc. At high excitation levels the Fourier spectrum of the coherent E$_{2g}$ phonon exhibits strongly asymmetric line shape, which is well modeled by the Fano function. The Fano parameter (1/Q) was found to be strongly excitation fluence dependent while depending weakly on the initial lattice temperature. We attribute the origin of the Fano-resonance to the coupling of coherent phonon to the electronic continuum, with their transition probabilities strongly renormalized in the vicinity of the photoinduced structural transition.Comment: 5 pages, 3 figures, to be published in Physical Review

Characterization of the enzymatic resistance to β-lactamics in enterobacteria

Detecting the resistance to CTG in severe infections-by enterobacteria guides to successful treatments. The main resistance mechanisms are the production of extended spectrum β-lactamases (BLEE), chromosomal inducible or derepressed β-lactamases Amp-C type or plasmidic Amp-C. The aim of this study was to investigate and characterize the mechanisms involved in the resistance to CTG in clinical isolations of enterobacteria, by phenotypic and genotypic methods. 64 isolations resistant to CTG were studied (K. pneumoniae, E. coli, Enterobacter spp and Proteus spp ). Antimicrobial agents sensibility and phenotypic detection of Amp-C and BLEE enzymes was performed by diffusion and dilution methods. In cefotaxime resistant E. coli and K. pneumoniae strains a possible enzymatic resistance mechanism was detected by Masuda Bioassay. The genes bla CTX-M-2 and bla PER-2 were detected by PCR. Of 64 isolations, 8 strains were presumptively producers of derepressed Amp-C and 56 were BLEE producers (with prevalence of CTX-M-2). Accompanying resistance was observed. Masuda Bioassay was negative and accompanying resistance suggests it is due an impermeability phenomenon. Our results confirm that the resistance to CTG in our strains is mainly caused by enzymes coded in plasmids so that it merit to establish epidemic control measures and to emphasize wise use of β-lactamic agents available.Fil: Castillo, Natalia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Jure, M. A.. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Allori, C.. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Castillo, M.. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaXXIII Jornadas Científicas de la Asociación de Biología de TucumánTucumánArgentinaAsociación de Biología de Tucumá

Colloidal ionic complexes on periodic substrates: ground state configurations and pattern switching

We theoretically and numerically studied ordering of "colloidal ionic clusters" on periodic substrate potentials as those generated by optical trapping. Each cluster consists of three charged spherical colloids: two negatively and one positively charged. The substrate is a square or rectangular array of traps, each confining one such cluster. By varying the lattice constant from large to small, the observed clusters are first rod-like and form ferro- and antiferro-like phases, then they bend into a banana-like shape and finally condense into a percolated structure. Remarkably, in a broad parameter range between single-cluster and percolated structures, we have found stable supercomplexes composed of six colloids forming grape-like or rocket-like structures. We investigated the possibility of macroscopic pattern switching by applying external electrical fields.Comment: 14 pages, 13 figure

Caracterización de la resistencia enzimática a β -lactámicos en enterobacterias

La emergencia de enterobacterias resistentes a los antimicrobianos es una realidad en nuestro medio, el manejo de las infecciones severas por estos microorganismos se realiza con cefalosporinas de 3ra Generación (CTG). Detectar la resistencia a estos antimicrobianos precozmente en el laboratorio orienta el tratamiento según la especie aislada. La producción de β-lactamasas es el principal mecanismo de resistencia. Según su actividad hidrolítica estas enzimas se clasifican en: β-lactamasas plasmídicas de espectro extendido (BLEE), β-lactamasas cromosómica e inducible (Amp-C) y Amp-C plasmídicas. El objetivo de este trabajo fue investigar los mecanismos enzimáticos responsables de la resistencia a CTG en aislamientos clínicos de Enterobacterias, así como caracterizar las ß-lactamasas presentes por métodos fenotípicos y genotípicos. Se estudiaron 64 aislamientos de Enterobacterias (K. pneumoniae, E. coli, Enterobacter spp y Proteus spp) resistentes a CTG. Se ensayó la sensibilidad por difusión y dilución en agar según normas de la NCCLS (actualmente CLSI) frente a los siguientes antimicrobianos: ampicilina, cefalotina, cefoxitina, ceftazidima (CAZ), cefotaxima (CTX), aztreonam, imipenem (IMP), meropenem, ciprofloxacina (CIP), trimetoprima/sulfametoxazol (SXT), gentamicina (GEN), amikacina, cefepime (FEP), amoxicilina/ac.clavulánico y piperacilina/tazobactama (PTAZ). Como control de calidad se utilizaron las cepas ATCC: E. coli 25922 y 35218 y K. pneumoniae 700603. Por difusión con discos se realizó la detección fenotípica de ßlactamasas inducibles y derreprimida y de BLEEs. En las cepas de E. coli y K. pneumoniae resistentes a CXT se detectó la posible resistencia enzimática por el bioensayo de Masuda y se evaluó la resistencia acompañante con discos de tetraciclina (30ug) y cloranfenicol (30ug). Se detectaron los genes bla CTX-M-2 y bla PER-2 por PCR. De los 64 aislamientos de Enterobacterias; 8 cepas fueron presuntivamente productoras de AMPC derreprimida y 56 productoras de BLEE las que fueron resistentes a ampicilina, piperacilina, cefalotina, amoxicilina/clavulánico, el 39% fueron resistentes a P/TAZ y ninguna a Imipenem. Los valores de CIM para CTX fueron >16 ug/ml y para CAZ >32 ug/ml asociados a elevados valores de CIM para FEP >64. Se presentó resistencia acompañante a CIP (85%), GEN (79%) y TMS (64%). La detección de genes bla CTX-M-2 y bla PER-2 indicó un marcado predominio de cepas productoras de CTX-M2. El ensayo de inducción realizado en los aislamientos de Enterobacter sp indica la presencia de AMP-C induclble en 6 cepas también productoras de BLEE. En las cepas resistentes a cefoxitina el bioensayo dio negativo. Se encontró resistencia acompañante a tetraciclina en 1 aislamiento, a cloranfenicol en 2, y a ambos en 8, lo que sugiere que la resistencia a cefoxitina se debe posiblemente a un fenómeno de impermeabilidad. Nuestros resultados confirman que la resistencia a CTG en nuestras cepas está mediada principalmente por enzimas codificadas en plásmidos rápidamente transferibles lo que amerita instaurar medidas de control epidemiológico en las instituciones de salud y enfatizar el uso prudente de los agentes β-lactamicos disponibles.Fil: Castillo, Natalia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Jure, Maria Angela. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Allori, C.. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Castillo, M.. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaXXIII Jornadas Científicas de la Asociación de Biología de TucumánTafí del ValleArgentinaAsociacion de Biologia de Tucuma

Implicit Geometry and Interaction Embeddings Improve Few-Shot Molecular Property Prediction

Few-shot learning is a promising approach to molecular property prediction as supervised data is often very limited. However, many important molecular properties depend on complex molecular characteristics -- such as the various 3D geometries a molecule may adopt or the types of chemical interactions it can form -- that are not explicitly encoded in the feature space and must be approximated from low amounts of data. Learning these characteristics can be difficult, especially for few-shot learning algorithms that are designed for fast adaptation to new tasks. In this work, we develop molecular embeddings that encode complex molecular characteristics to improve the performance of few-shot molecular property prediction. Our approach leverages large amounts of synthetic data, namely the results of molecular docking calculations, and a multi-task learning paradigm to structure the embedding space. On multiple molecular property prediction benchmarks, training from the embedding space substantially improves Multi-Task, MAML, and Prototypical Network few-shot learning performance. Our code is available at https://github.com/cfifty/IGNITE

Ultrafast dynamics of coherent optical phonons and nonequilibrium electrons in transition metals

The femtosecond optical pump-probe technique was used to study dynamics of photoexcited electrons and coherent optical phonons in transition metals Zn and Cd as a function of temperature and excitation level. The optical response in time domain is well fitted by linear combination of a damped harmonic oscillation because of excitation of coherent $E_{2g}$ phonon and a subpicosecond transient response due to electron-phonon thermalization. The electron-phonon thermalization time monotonically increases with temperature, consistent with the thermomodulation scenario, where at high temperatures the system can be well explained by the two-temperature model, while below $\approx$ 50 K the nonthermal electron model needs to be applied. As the lattice temperature increases, the damping of the coherent $E_{2g}$ phonon increases, while the amplitudes of both fast electronic response and the coherent $E_{2g}$ phonon decrease. The temperature dependence of the damping of the $E_{2g}$ phonon indicates that population decay of the coherent optical phonon due to anharmonic phonon-phonon coupling dominates the decay process. We present a model that accounts for the observed temperature dependence of the amplitude assuming the photoinduced absorption mechanism, where the signal amplitude is proportional to the photoinduced change in the quasiparticle density. The result that the amplitude of the $E_{2g}$ phonon follows the temperature dependence of the amplitude of the fast electronic transient indicates that under the resonant condition both electronic and phononic responses are proportional to the change in the dielectric function.Comment: 10 pages, 9 figures, to appear in Physical Review

The impact of crop management regime on oil content and fatty acid composition in hulless and covered spring barley

Received: November 11th, 2021 ; Accepted: January 30th, 2022 ; Published: March 17th, 2022 ; Correspondence: [email protected] are a minor nutritional component of barley (Hordeum vulgare L.) grain and have not been as widely explored as the major components. The aim of this study was to investigate the effect of genotype and environment, including conventional farming system with three crop management regimes, differing in agrochemical input, and organic farming system, on oil content and fatty acid composition in grain of two covered and four hulless spring barley genotypes during two growing seasons. Genotype significantly affected oil content and it was on average 4.26% and ranged in individual barley samples from 2.87 to 5.53%. We found linoleic, oleic, palmitic, α-linolenic, stearic and capric fatty acids in average proportions of 55.6; 21.3; 18.6; 3.7; 0.6 and 0.4%, respectively. Higher average oil content and proportion of α-linolenic acid was found in covered barley. Crop management regime did not significantly affect oil content but had some effect on the proportion of linoleic, α-linolenic, oleic and stearic acid. Decrease of chemical inputs was in favour of oil content and proportion of α-linolenic, oleic and stearic acids but did not promote linoleic acid. Waxy hulless barley line with high oil content and a very high proportion of linoleic acid was identified

Designing stimulus-sensitive colloidal walkers.

Colloidal particles with DNA "legs" that can bind reversibly to receptors on a surface can be made to 'walk' if there is a gradient in receptor concentration. We use a combination of theory and Monte Carlo simulations to explore how controllable parameters, e.g. coating density and binding strength, affect the dynamics of such colloids. We find that competition between thermodynamic and kinetic trends imply that there is an optimal value for both the binding strength and the number of "legs" for which transport is the fastest. Using available thermodynamic data on DNA binding, we indicate how directionally reversible, temperature-controlled transport of colloidal walkers can be achieved. In particular, the present results should make it possible to design a chromatographic technique that can be used to separate colloids with different DNA functionalizations