Unveiling the photophysics of thiourea from CASPT2/CASSCF potential energy surfaces and singlet/triplet excited state molecular dynamics simulations

This work describes the decay mechanism of photoexcited thiourea, both in gas phase and in solution, from the information inferred from the topography of the excited and ground state potential energy surfaces and mixed singlet/triplet quantum classical molecular dynamics simulations. Our gas phase results reveal T1/S0 intersystem crossing as the dominant (49%) intrinsic decay channel to the ground state, which reaches a population of 0.28 at the final time of our simulations (10 ps). Population of the T1, would occur after internal conversion to the S1 from the spectroscopic S2 electronic state, followed by S1->T2 intersystem crossing and T2->T1 internal conversion processes. Minor decay channels occurring exclusively along the singlet manifold, i.e. S2->S0 (33%) and S1->S0 (18%), were also observed to play a role in the relaxation of photoexcited thiourea in the gas phase. The explicit incorporation of water-thiourea interactions in our simulations was found to provoke a very significant delay in the decay to the ground state of the system, with no transitions to the S0 being registered during the first 10 ps of our simulations. Intermolecular vibrational energy redistribution and explicit hydrogen bond interaction established between water molecules and the NH2 group of thiourea were found to structurally or energetically hamper the access to the intersystem crossing or internal conversion funnels with the ground state

Direct interaction between RecA and a CheW-like protein is required for surface-associated motility, chemotaxis and the full virulence of Acinetobacter baumannii strain ATCC 17978

Acinetobacter baumannii is a nosocomial pathogen that causes multi-drug resistant infections mainly in immunocompromised patients. Although this gram-negative species lacks flagella, it is able to move over wet surfaces through a not well characterized type of movement known as surface-associated motility. In this study we demonstrate through the inactivation of the A1S_2813 gene (coding a CheW-like protein) and recA (coding a DNA damage repair and recombination protein) that both genes are involved in the surface-associated motility and chemotaxis of A. baumannii ATCC 17978 strain. In addition, we also point out that the lack of either RecA or CheW-like proteins reduces its virulence in the Caenorhabditis elegans and the Galleria mellonella animal models. Furthermore, we show through co-immunoprecipitation assays that the CheW-like protein and RecA interact and that this interaction is abolished by the introduction of the mutation S97A in one of the domains of CheW-like protein that is structurally conserved in Salmonella enterica and necessary for the RecA-CheW interaction in this bacterial species. Finally, we show that the replacement of the wild-type CheW-like protein by that presenting the S97A mutation impairs surface-associated motility, chemotaxis and virulence of A. baumannii strain ATCC 17978

Twitching and swimming motility play a role in Ralstonia solanacearum pathogenicity

Ralstonia solanacearum is a bacterial plant pathogen causing important economic losses worldwide. In addition to the polar flagella responsible for swimming motility, this pathogen produces type IV pili (TFP) that govern twitching motility, a flagellum-independent movement on solid surfaces. The implication of chemotaxis in plant colonization, through the control flagellar rotation by the proteins CheW and CheA, has been previously reported in R. solanacearum. In this work, we have identified in this bacterium homologues of the Pseudomonas aeruginosa pilI and chpA genes, suggested to play roles in TFP-associated motility analogous to those played by the cheW and cheA genes, respectively. We demonstrate that R. solanacearum strains with a deletion of the pilI or the chpA coding region show normal swimming and chemotaxis but altered biofilm formation and reduced twitching motility, transformation efficiency, and root attachment. Furthermore, these mutants displayed wild-type growth in planta and impaired virulence on tomato plants after soil-drench inoculations but not when directly applied to the xylem. Comparison with deletion mutants for pilA and fliC encoding the major pilin and flagellin subunits, respectively showed that both twitching and swimming are required for plant colonization and full virulence. This work proves for the first time the functionality of a pilus-mediated pathway encoded by pil-chp genes in R. solanacearum, demonstrating that pilI and chpA genes are bona fide motility regulators controlling twitching motility and its three related phenotypes: virulence, natural transformation, and biofilm formation

Statistical similarity between the compression of a porous material and earthquakes

It has been long stated that there are profound analogies between fracture experiments and earthquakes; however, few works attempt a complete characterization of the parallelisms between these so separate phenomena. We study the Acoustic Emission events produced during the compression of Vycor (SiO2). The Gutenberg-Richter law, the modified Omori's law, and the law of aftershock productivity are found to hold for a minimum of 5 decades, are independent of the compression rate, and keep stationary for all the duration of the experiments. The waiting-time distribution fulfills a unified scaling law with a power-law exponent close to 2.45 for long times, which is explained in terms of the temporal variations of the activity rate.Comment: 4 pages and a bit more, 4 figure

Excited state dynamics of some nonsteroidal anti-inflammatory drugs: a surface-hopping investigation

Here we present a computational investigation of the excited state dynamics of 5 different active medical substances (aspirin, ibuprofen, carprofen, suprofen, indomethacin) which belong to the family of nonsteroidal anti-inflammatory drugs (NSAIDs). The nonadiabatic dynamics simulations were performed using the surface hopping method, with electronic energies and couplings evaluated on the fly in a semiempirical framework. For aspirin, the solvent decay dynamics was also considered by inserting it in a cluster of water molecules, following a QM/MM scheme. A quite diverse behavior was observed for the systems considered, going from fast deactivation to the ground state (aspirin and ibuprofen), to ultrafast intersystem crossing to the triplet manifold (carprofen and suprofen), or to the generation of long lived S1 states (indomethacin). To our knowledge, this is the first computational study of the photodynamics of these NSAIDs

Regional economic dynamics and convergence in the european union

[eng] Deepening in the European Union (EU) integration process has enhanced the question of economic disparities at a regional level. The convergence process observed until the late seventies was exhausted onwards in coincidence with important changes in the economic activity. The paper showshow these factors would have provoked a regional differenciated response that,despite being important, would have not strengthened the decrease in regional inequalities. We use an alternative and (in our opinion) richer approach to the traditional convergence analysis, where the evolution of the whole regional distribution is what matters and not that of a representative economy. Moreover, when analysing inequalities among regional economies, the geographical space acquire an outstanding role. Hence, we apply spatial association tests and relate them to the convergence analysis[spa] El avance en el proceso de integración ha aumentado el interés por la evolución de las disparidades económicas entre las regiones de la Unión Europea. El proceso de convergencia observado hasta finales de los setenta parece haberse agotado, coincidiendo con importantes cambios en el desarrollo de la actividad económica. El trabajo muestra como estos factores habrían provocado una respuesta regional diferenciada que, pese a ser importante, no habría contribuido a la disminución de las disparidades. En el trabajo se utiliza una aproximación alternativa a la empleada en el tradicional análisis de convergencia, donde lo que se considera es la evolución de la totalidad de la distribución y no unicamente aquélla de una economía representativa. Adicionalmente, cuando se estudian las disparidades entre economías regionales, el espacio adquiere un papel destacado. Por ello se aplican contrastes de asociación espacial y se relacionan con el análisis de convergenci

Importance of twitching and surface-associated motility in the virulence of Acinetobacter baumannii

Acinetobacter baumannii is a pathogen of increasing clinical importance worldwide, especially given its ability to readily acquire resistance determinants. Motile strains of this bacterium can move by either or both of two types of motility: (i) twitching, driven by type IV pili, and (ii) surface-associated motility, an appendage-independent form of movement. A. baumannii strain MAR002 possesses both twitching and surface-associated motility. In this study, we isolated spontaneous rifampin-resistant mutants of strain MAR002 in which point mutations in the rpoB gene were identified that resulted in an altered motility pattern. Transcriptomic analysis of mutants lacking twitching, surface-associated motility, or both led to the identification of deregulated genes within each motility phenotype, based on their level of expression and their biological function. Investigations of the corresponding knockout mutants revealed several genes involved in the motility of A. baumannii strain MAR002, including two involved in twitching (encoding a minor pilin subunit and an RND [resistance nodulation division] component), one in surface-associated motility (encoding an amino acid permease), and eight in both (encoding RND and ABC components, the energy transducer TonB, the porin OprD, the T6SS component TagF, an IclR transcriptional regulator, a PQQ-dependent sugar dehydrogenase, and a putative pectate lyase). Virulence assays showed the reduced pathogenicity of mutants with impairments in both types of motility or in surface-associated motility alone. By contrast, the virulence of twitching-affected mutants was not affected. These results shed light on the key role of surface-associated motility and the limited role of twitching in the pathogenicity of A. baumannii

Biological control of Acanthoscelides obtectus and Zabrotes subfasciatus in stored dried beans

This study assesses the feasibility of using natural enemies for the control of Acanthoscelides obtectus Say and Zabrotes subfasciatus Boheman (Coleoptera: Chrysomelidae), key pests of stored dried beans, Phaseolus vulgaris L. (Fabales: Fabaceae). The predatory mites Blattisocius tarsalis Berlese (Acari: Ascidae) and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) were able to prey on A. obtectus eggs, reducing the bruchid population by more than 60% under both controlled and warehouse conditions. Therefore, they show good potential as biological agents for controlling this pest. The larval parasitoids Anisopteromalus calandrae Howard and Lariophagus distinguendus Förster (Hymenoptera: Pteromalidae) were both moderately effective (34–38% reduction) at suppressing A. obtectus populations, but when A. calandrae was combined with B. tarsalis, a significant improvement in control efficacy (81% reduction in emergence) was observed. Therefore, the release of A. calandrae combined with B. tarsalis seems to be a promising strategy for controlling A. obtectus. Neither B. tarsalis nor A. swirskii were able to prey on Z. subfasciatus eggs. Only the parasitoid A. calandrae was moderately effective (39% reduction) at supressing Z. subfasciatus populations. Further testing is needed to identify other natural enemies that can complement the action of A. calandrae in reducing Z. subfasciatus populations.info:eu-repo/semantics/acceptedVersio

Susceptibility of Rhyzopertha dominica to high CO2 modified atmospheres in packaged chickpeas

Three MAs with 50%, 70% and 90% CO2 in air was tested at different exposure times on all the developmental stages of R. dominica using chickpeas packed with 4% and 96% filling ratio in which there was excess of CO2. At 4% filling ratio the loss of the gas was negligible. The exposure time to reach 50% mortality (LT50) was estimated for each developmental stage and CO2 concentration, ranging from 7 h for larvae with 90% to 2 days for pupae with 50% CO2. At 96% filling ratio and for the intervals of the estimated exposure times (LT50) from the 4% filling ratio, mortality decreased significantly for eggs and adults at the three MAs tested, while for the internal developmental stages, larvae at 50% and 70% CO2 and pupae in all concentrations of CO2, the susceptibility remained the same as with a 4% filling ratio. This decline in mortality of the external developmental stages was possible due to the sorption of CO2 by the chickpeas, which caused a loss of intergranular levels of CO2 between 17% and 29%. This sorption ranged from 0.1955 to 0.3285 g of CO2 per kg of chickpeas and produced a negative pressure of 77.12 to 60.65 kPa. In conclusion, when chickpeas are packed with high CO2 MAs, a decrease in the mortality of eggs and adults of R. dominica could be expected due to pulse sorption.info:eu-repo/semantics/acceptedVersio