A cluster expansion approach to renormalization group transformations

The renormalization group (RG) approach is largely responsible for the considerable success which has been achieved in developing a quantitative theory of phase transitions. This work treats the rigorous definition of the RG map for classical Ising-type lattice systems in the infinite volume limit at high temperature. A cluster expansion is used to justify the existence of the partial derivatives of the renormalized interaction with respect to the original interaction. This expansion is derived from the formal expressions, but it is itself well-defined and convergent. Suppose in addition that the original interaction is finite-range and translation-invariant. We will show that the matrix of partial derivatives in this case displays an approximate band property. This in turn gives an upper bound for the RG linearization.Comment: 13 page

Nature of the Hydrogen Bond Enhanced Halogen Bond

The factors responsible for the enhancement of the halogen bond by an adjacent hydrogen bond have been quantitatively explored by means of state-of-the-art computational methods. It is found that the strength of a halogen bond is enhanced by ca. 3 kcal/mol when the halogen donor simultaneously operates as a halogen bond donor and a hydrogen bond acceptor. This enhancement is the result of both stronger electrostatic and orbital interactions between the XB donor and the XB acceptor, which indicates a significant degree of covalency in these halogen bonds. In addition, the halogen bond strength can be easily tuned by modifying the electron density of the aryl group of the XB donor as well as the acidity of the hydrogen atoms responsible for the hydrogen bond.Depto. de Química OrgánicaFac. de Ciencias QuímicasTRUEMINECO and MICIINpu

Controlling the Ambiphilic nature of sigma-arylpalladium intermediates in intramolecular cyclization reactions

The reactivity of main group organometallics, such as organolithium compounds (RLi) and Grignard reagents (RMgX), is quite straightforward. In these species the R group usually exhibits nucleophilic reactivity without any possibility of inducing electrophilic character. In contrast, in organopalladium complexes, researchers can switch the reactivity from electrophilic to nucleophilic relatively simply. Although σ-aryl and σ-vinylpalladium complexes are commonly used as electrophiles in C-C bond-forming reactions, recent research has demonstrated that they can also react with carbon-heteroatom multiple bonds in a nucleophilic manner. Nevertheless, researchers have completely ignored the issue of controlling the ambiphilic nature of such species. This Account describes our efforts toward selectively promoting the same starting materials toward either electrophilic α-arylation or nucleophilic addition reactions to different carbonyl groups. We could tune the properties of the σ-arylpalladium intermediates derived from amino-tethered aryl halides and carbonyl compounds to achieve chemoselective transformations. Therefore, chemists can control the ambiphilic nature of such intermediates and, consequently, the competition between the alternative reaction pathways by the adequate selection of the reaction conditions and additives (base, presence/absence of phenol, bidentate phosphines). The nature of the carbonyl group (aldehydes, ketones, esters, and amides) and the length of the tether connecting it to the aniline moiety also play an important role in the outcome of these processes. Our joint computational and experimental efforts to elucidate the reaction mechanism of these palladium-catalyzed transformations suggest that beyond the formation of the four-membered azapalladacycle, two major factors help to control the dual character of the palladium(II) intermediates derived from 2-haloanilines. First, their high nucleophilicity strongly modifies the interaction of the metal center with the carbonyl group. Second, the additive phenol exchanges the iodide ligand to give an arylpalladium(II) phenoxide complex, which has a beneficial effect on the arylation. The formation of this transient intermediate not only stabilizes the arylpalladium moiety, thus preventing the nucleophilic attack at the carbonyl group, but also assists the enolization reaction, which takes place in a more favorable intramolecular manner. The azapalladacycle intermediate is, in the words of J. R. R. Tolkien, "the one ring to bring them all and in the darkness to bind them." With this intermediate, we can easily achieve the synthesis of a variety of heterocyclic systems by selectively promoting electrophilic α-arylation or nucleophilic addition reactions from the same precursors

Chaotic image encryption using hopfield and hindmarsh–rose neurons implemented on FPGA

Chaotic systems implemented by artificial neural networks are good candidates for data encryption. In this manner, this paper introduces the cryptographic application of the Hopfield and the Hindmarsh–Rose neurons. The contribution is focused on finding suitable coefficient values of the neurons to generate robust random binary sequences that can be used in image encryption. This task is performed by evaluating the bifurcation diagrams from which one chooses appropriate coefficient values of the mathematical models that produce high positive Lyapunov exponent and Kaplan–Yorke dimension values, which are computed using TISEAN. The randomness of both the Hopfield and the Hindmarsh–Rose neurons is evaluated from chaotic time series data by performing National Institute of Standard and Technology (NIST) tests. The implementation of both neurons is done using field-programmable gate arrays whose architectures are used to develop an encryption system for RGB images. The success of the encryption system is confirmed by performing correlation, histogram, variance, entropy, and Number of Pixel Change Rate (NPCR) tests

Contribution of "Omic" studies to the understanding of CADASIL. A systematic review

Altres ajuts: Generación Project, Maestro Project, INVICTUS+ networkAltres ajuts: Fundació la Marató de TV (Epigenesis Project)CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) is a small vessel disease caused by mutations in NOTCH3 that lead to an odd number of cysteines in the epidermal growth factor (EGF)-like repeat domain, causing protein misfolding and aggregation. The main symptoms are migraines, psychiatric disorders, recurrent strokes, and dementia. Omic technologies allow the massive study of different molecules for understanding diseases in a non-biased manner or even for discovering targets and their possible treatments. We analyzed the progress in understanding CADASIL that has been made possible by omics sciences. For this purpose, we included studies that focused on CADASIL and used omics techniques, searching bibliographic resources, such as PubMed. We excluded studies with other phenotypes, such as migraine or leukodystrophies. A total of 18 articles were reviewed. Due to the high prevalence of NOTCH3 mutations considered pathogenic to date in genomic repositories, one can ask whether all of them produce CADASIL, different degrees of the disease, or whether they are just a risk factor for small vessel disease. Besides, proteomics and transcriptomics studies found that the molecules that are significantly altered in CADASIL are mainly related to cell adhesion, the cytoskeleton or extracellular matrix components, misfolding control, autophagia, angiogenesis, or the transforming growth factor β (TGFβ) signaling pathway. The omics studies performed on CADASIL have been useful for understanding the biological mechanisms and could be key factors for finding potential drug targets

Gold-Catalyzed Reaction of propargyl Esters and alkynylsilanes: Synthesis of vinylallene derivatives thorugh a Twofold 1,2-Rearrangement

The reaction of propargyl esters with alkynylsilanes under gold catalysis provides vinylallene derivatives through consecutive [1,2]-acyloxy/[1,2]-silyl rearrangements. Good yields, full atom-economy, broad substrate scope, easy scale-up and low catalyst loadings are salient features of this novel transformation. Density Functional Theory (DFT) calculations suggest a reaction mechanism involving initial [1,2]-acyloxy rearrangement to generate a gold vinylcarbene intermediate which upon regioselective attack of the alkynylsilane affords a vinyl cation which undergoes a type II-dyotropic rearrangement involving the silyl group and the metal fragment. Preliminary results on the enantioselective version of this transformation are also disclose

Synthesis and Characterization of Bis(pyridylimino)isoindolide Alkali Metal Complexes in Three Redox States

Non-innocent ligands (NILs) like bis(pyridylimino)isoindolide (BPI) play crucial roles in coordination chemistry, biosciences, catalysis and material sciences. Investigating the isolated redox states of NILs is inevitable for understanding their redox-activity and fine-tuning the properties of corresponding metal complexes. The limited number of fundamental studies on the coordination behavior and redox chemistry of reduced BPI species is suggested to hamper further applications of the title compounds. This work describes for the first time the isolation of alkali metal complexes of BPI and Me2BPI in three different oxidation states and their characterization by means of NMR or EPR spectroscopy, DFT calculations, and SC-XRD studies. The latter revealed the connection between bond orders in the ligand scaffold and its oxidation state. The paramagnetic compound Me2BPI-K2 was isolated as a coordination copolymer with 18-crown-6, which enabled the characterization of the dianionic BPI radical. Furthermore, the so-far unknown trianionic state of BPI was reported by the isolation of BPI-K3. This divulges an unprecedented bis(amidinato)isoindolide coordination mode

Quo Vadis CO2_2 Activation: Catalytic Reduction of CO2_2 to Methanol Using Aluminum and Gallium/Carbon‐based Ambiphiles

We report on so-called “hidden FLPs” (FLP: frustrated Lewis pair) consisting of a phosphorus ylide featuring a group 13 fragment in the ortho position of a phenyl ring scaffold to form five-membered ring structures. Although the formation of the Lewis acid/base adducts was observed in the solid state, most of the title compounds readily react with carbon dioxide to provide stable insertion products. Strikingly, 0.3–3.0 mol% of the reported aluminum and gallium/carbon-based ambiphiles catalyze the reduction of CO$_2$ to methanol with satisfactory high selectivity and yields using pinacol borane as stoichiometric reduction equivalent. Comprehensive computational studies provided valuable mechanistic insights and shed more light on activity differences

Seguridad operacional y gestión del operador para habilitar el uso de sistemas aéreos no tripulados (UAS) como herramientas geomáticas

[EN] Potential civil applications of Unmanned Aircraft Systems (UAS), commonly known as drones, have risen steeply during the last decade, mainly due to their versatility and capability of spatial data gathering. Nonetheless, real use of UAS is quite restricted nowadays, primarily due to safety and regulatory constraints. This multidisciplinary project aims to perform specific safety assessments using the SORA methodology adopted by the European Aviation Safety Agency (EASA) and develop documentation and procedures for operators to follow, complying with all required safety and regulatory requirements. As a result, DEURPAS-UPV is the first Spanish drone operator belonging to a university to be authorized by Spanish civil aviation agency (AESA-Agencia Estatal de Seguridad Aérea), to perform drone flights in urban areas, in controlled airspace and during the night. In addition, DEURPAS-UPV has performed the first authorized experimental transport operations using drones in Spain. The results from safety assessment and designed procedures have been successfully applied to the operation of Safety and Emergency service providers, such as Valencia Local Police Corps and the Valencian Emergency and Safety Response Agency (AVSRE - Agencia Valenciana de Seguridad y Respuesta a las Emergencias). Overall, this project has served as an enabler for more complex and safer UAS operations, from the operator’s point of view, which will help break the barriers related to the use of these aircraft, with huge potential in geomatics applications.[ES] Las aplicaciones civiles de los sistemas aéreos no tripulados (UAS), comúnmente conocidos como drones, han aumentado considerablemente durante la última década, principalmente debido a su versatilidad y capacidad de recopilación de datos espaciales. Sin embargo, el uso real de los UAS está bastante restringido hoy en día, principalmente debido a las restricciones de seguridad y legislativas. Este proyecto multidisciplinar tiene como objetivo realizar evaluaciones de seguridad específicas utilizando la metodología SORA adoptada por la Agencia Europea de Seguridad Aérea (EASA) y desarrollar documentación y procedimientos para que los operadores los sigan, cumpliendo con todos los requisitos de seguridad y normativos exigidos. Como resultado, DEURPAS-UPV es el primer operador español de drones perteneciente a una universidad que ha sido autorizado por la Agencia Estatal de Seguridad Aérea (AESA), para realizar vuelos con drones en zonas urbanas, en espacio aéreo controlado y durante la noche. Además, DEURPAS-UPV ha realizado las primeras operaciones experimentales de transporte con drones autorizadas en España. Los resultados de la evaluación de seguridad y los procedimientos diseñados se han aplicado con éxito a la operación de proveedores de servicios de Seguridad y Emergencias, como el Cuerpo de Policía Local de Valencia y la Agencia Valenciana de Segurida y Respuesta a las Emergencias (AVSRE). En general, este proyecto ha servido para facilitar operaciones con UAS más complejas y seguras, desde el punto de vista del operador, lo que ayudará a romper las barreras relacionadas con el uso de estas aeronaves, con un enorme potencial en aplicaciones geomáticas.This work was supported by the Generalitat Valenciana under Grant DECRETO 63/2020 and Universitat Politècnica de València under Grant PAID-01-1.Vera, N.; Quintanilla, I.; Vidal, J.; Fernández, B. (2021). Operational safety and operator management to enable the use of unmanned aircraft systems (UAS) as geomatics tools. En Proceedings 3rd Congress in Geomatics Engineering. Editorial Universitat Politècnica de València. 194-200. https://doi.org/10.4995/CiGeo2021.2021.12724OCS19420

The Pauli Repulsion-Lowering Concept in Catalysis

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