Nucleophilic versus electrophilic boryl moieties: activation and application in catalysis

Els compostos de bortrivalent s’han considerat tradicionalment com a àcids de Lewis, preferint acceptar electrons més que donar-los en el curs de les reaccions, peròdarrerament han sorgit exemples a la bibliografia on el compost trivalent de bor presenta una reactivitat insòlita vers posicions electrofíliques. Aquest fet ens suggereix un nou context nucleofílic per als sintonsboril, que pot ser augmentat depenent dels substituents als quals estigui unit el bor. En aquesta tesi, volem mostrar una visió de les reactivitat soposades mitjançantl’estudi teòric de diferents compostos de bortri coordinats. A més a més també ens hem centrat en l’estudi de dues reaccions, la hidroboració trans no convencional on la unitat borilactuacom a electròfil i la -boració organo catalítica amb un diborà mixton la unitat boril actua com a nucleòfil.Boron compounds have been traditionally regarded as “Lewis Acids” preferring to accept electrons rather than donate them in the course of their reactions, but current examples of unusual reactivity between tricoordinatedboranes and electrophilic sites suggest another conceptual context for the boryl moieties, based on their nucleophilic character which can be enhanced depending on the substituents on boron. In this thesis, we aim to show an overview of these opposite reactivities through the computational study of different trivalent boron compounds. Moreover, we have also focused our attention in the study of two reactions, the non-conventional trans-hydroboration where the boryl moiety is acting as an electrophile and the organocatalytic-boration with a mixed diboron reagent where the boryl moiety is acting as a nucleophile

The American Dream: An Illusion or Reality for Latino Immigrants

Many Latinos from Mexico, Central America, and South America have made the decision to immigrate to the United States in recent years—whether legally or illegally. In the literature, stories of immigration and hopes for the American Dream proliferated; however, varying degrees of racism and anti-immigration sentiment were also revealed. Interviews of first-generation Latino immigrants and American citizens that were both attendees of a local Hispanic church in southcentral Virginia showed that Latino immigrants had hopes of achieving what they believed to be the American Dream, while realizing they had a long journey ahead. American citizens were more certain of having achieved at least some portion of the American Dream, and also had hopes of fully attaining what they believed to be the American Dream

Ethnic tourism in El Salvador

Tourism in El Salvador has been leveled in recent years as an industry that can contribute to economic development. This paper tries to give an overview of tourism development from the perspective of Ethnic Tourism, considered as a valuable resource to be incorporated in the tourism field, to search for innovative strategies for promotion and maintenance, whereas sustainable development models provide alternatives to schedule conservation with economic and social aspects that opens tourism. In this paperwork is about the tourism and the importance that this has for the economical situation in El Salvador. Also, Ethnic Tourism is presented as a strategically way for the indigenous groups in the country. All this with the purpose of maintaining the culture and revive the identity of the Salvadoran people. In here, there are different segments like history of tourism in El Salvador, indigenous groups, the role of the society and the government with these peoples and the need to bring to development for these communities. Under this perspective there is the idea that Salvadoran government should give more support to the local indigenous people in order to develop the ethnic tourism in the country

Low coordinate NHC-Zinc-Hydride Complexes Catalyze Alkyne C-H Borylation and Hydroboration using Pinacolborane

Organozinc compounds containing sp, sp², and sp³ C–Zn moieties undergo transmetalation with pinacolborane (HBPin) to produce Zn–H species and organoboronate esters (RBPin). This Zn–C/H–B metathesis step is key to enabling zinc-catalyzed borylation reactions, and it is used in this work to develop both terminal alkyne C–H borylation and internal alkyne hydroboration. These two conversions can be combined in one pot to achieve the zinc-catalyzed conversion of terminal alkynes to 1,1-diborylated alkenes without isolation of the sensitive (to protodeboronation) alkynyl boronate ester intermediates. Mechanistic studies involving the isolation of intermediates, stoichiometric experiments, and DFT calculations all support mechanisms involving organozinc species that undergo metathesis with HBPin. Furthermore, zinc-catalyzed hydroboration can proceed via a hydrozincation step, which does not require any exogenous catalyst in contrast to all previously reported alkyne hydrozincations. Bulky <i>N</i>-heterocyclic carbenes (NHCs) are key for effective catalysis as the NHC steric bulk enhances the stability of the NHC–Zn species present during catalysis and provides access to low-coordinate (NHC)­Zn–H cations that are electrophilic yet Brønsted basic. This work provides an alternative approach to access synthetically desirable pinacol–organoboronate esters using earth-abundant metal-based borylation catalysts

Molecular dynamics modelling of the interaction of a synthetic zinc-finger miniprotein with DNA

We report the modelling of the DNA complex of an artificial miniprotein composed of two zinc finger modules and an AT-hook linking peptide. The computational study provides for the first time a structural view of these types of complexes, dissecting interactions that are key to modulate their stability. The relevance of these interactions was validated experimentally. These results confirm the potential of this type of computational approach for studying peptide–DNA complexes and suggest that they could be very useful for the rational design of non-natural, DNA binding miniproteinsThis work has received financial support from Spanish grants (IJC2019-040358-I funded by MCIN/AEI/10.13039/501100011033 to J. R., PID2019-108624RB-I00 funded by MCIN/AEI/10.13039/501100011033 to J. L. M. and RTI2018-096704-B-100 and PID2021-122478NB-I00 to M. O.), the Consellería de Cultura, Educación e Ordenación Universitaria (Grants 2015-CP082, ED431C-2017/19, ED431C-2021/ 25 and ED431G 2019/03: Centro Singular de Investigación de Galicia accreditation 2019–2022 to J. L. M.) and the European Union (European Regional Development Fund-ERDF corresponding to the multiannual financial framework 2014–2020 to J. L. M.). This work was also supported by the BioExcel-2. Centre of Excellence for Computational Biomolecular Research” (823830, M. O.) and the Instituto de Salud Carlos III–Instituto Nacional de Bioinformática (ISCIII PT 17/0009/0007 co-funded by the Fondo Europeo de Desarrollo Regional, M. O.)S

Factores asociados a malestar psicológico durante la pandemia de COVID-19 en personal de salud de un hospital público de Ecuador

Fundamento: La pandemia por el coronavirus SARS-CoV-2, genera afectaciones en las esferas social, económica y sanitaria de un país, y de manera particular, consecuencias psicológicas negativas en el personal sanitario de hospitales públicos, considerados como la primera línea de atención a pacientes con esta enfermedad. Objetivo: Describir factores asociados a la presencia de malestar psicológico en el personal sanitario de un hospital general público en Ecuador, durante la pandemia de COVID-19. Metodología: Estudio no experimental, de corte transversal, con alcance descriptivo-correlacional. Los datos correspondieron a 276 funcionarios de la salud que respondieron un instrumento online, con un módulo de datos sociodemográficos y una escala de tamizaje de malestar psicológico, estos se aplicaron después de una intervención en salud dirigida al personal de salud realizada al inicio de la pandemia, en mayo del año 2020. Se realizaron análisis descriptivos y de asociación, mediante el software SPSS 25.0. Resultados: La muestra estuvo compuesta por 76.1 % de mujeres, 23.9 % de hombres, con una media de edad de 36 años, en mayor cantidad con profesionales de Enfermería (33.7 %), seguido de Medicina (24.3 %). El 70.7 % del personal de salud presentó malestar psicológico, de estos, el 26.1 % con indicativo de trastorno mental. Se encontraron tres variables asociadas a la presencia de malestar psicológico: clima laboral, teletrabajo y convivir con grupos de riesgo. Conclusiones: El personal de Salud ha presentado afectación en su salud mental asociado a las condiciones sociolaborales durante la pandemia

Observation of the Ξ−b→J/ψΛK−decay

The observation of the decay Ξ−b→J/ψΛK−is reported, using a data sample corresponding to an integrated luminosity of 3 fb−1, collected by the LHCb detector in ppcollisions at centre-of-mass energies of 7and 8 TeV. The production rate of Ξ−bbaryons detected in the decay Ξ−b→J/ψΛK−is measured relative to that of Λ0bbaryons using the decay Λ0b→J/ψΛ. Integrated over the b-baryon transverse momentum pT<25 GeV/cand rapidity 2.0 <y <4.5, the measured ratio is fΞ − b fΛ0 b B(Ξ − b → J/ψΛK− ) B(Λ0 b → J/ψΛ) = (4.19±0.29 (stat)± 0.15 (syst))×10−2, where fΞ−band fΛ0bare the fragmentation fractions of b →Ξ−band b →Λ0btransitions, and Brepresents the branching fraction of the corresponding b-baryon decay. The mass difference between Ξ−band Λ0bbaryons is measured to be M(Ξ − b )− M(Λ0 b ) = 177.08±0.47 (stat)± 0.16 (syst)MeV/c2.S

Measurement of the J/ψ pair production cross-section in pp collisions at √s=13 TeV

The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of √s=13 TeV, corresponding to an integrated luminosity of 279 ±11 pb−1. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y < 4.5. The production cross-section is measured to be 15.2 ± 1.0 ± 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions.S

Measurements of prompt charm production cross-sections in pp collisions at √s=5 TeV

Production cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5 TeV. The data sample corresponds to an integrated luminosity of 8.60 ± 0.33 pb−1 collected by the LHCb experiment. The production cross-sections of D 0, D +, D +s, and D ∗+ mesons are measured in bins of charm meson transverse momentum, p T, and rapidity, y. They cover the rapidity range 2.0 < y < 4.5 and transverse momentum ranges 0 < p T < 10 GeV/c for D 0 and D + and 1 < p T < 10 GeV/c for D +s and D ∗+ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of 1 < p T < 8 GeV/c are determined to be σ(pp→D0X)=1004±3±54μb,σ(pp→D+X)=402±2±30μb,σ(pp→D+sX)=170±4±16μb,σ(pp→D∗+X)=421±5±36μb, where the uncertainties are statistical and systematic, respectively.S