Implementación del Algoritmo de Descifrado para un Esquema Criptográfico de Dinámica Distribuida

Este trabajo ha adaptado el Cifrado de Dinámica Distribuida (CDD) a un sistema caótico de baja dimensión para evaluar la debilidad y seguridad de dicha adaptación en un ejemplo realista. Esto debido a que varios autores apuntan a una deficiencia del CDD en el proceso de descifrado. En concreto, se utilizó un mapa logístico acoplado, el cual presenta múltiples atractores caóticos hecho que elimina la deficiencia del mapa logístico simple manifiesta para las aplicaciones criptográficas. Además se exploran optimizaciones al algoritmo de descifrado llegando a rendimientos apreciables para su futura escalabilidad

Modeling the Chemical Looping Reforming Process Operated in a Circulating Fluidized Bed Reactor Consisting of Two Bubbling Bed Units: Model Validation

A transient one-dimensional model is developed for simulation of the chemical looping reforming process in a circulating fluidized bed (CFB). A CFB reactor model consisting of two connected bubbling bed units, namely the fuel reactor (FR) and the air reactor (AR), is proposed, and the simulated results are validated by comparison with experimental data available in the literature. Three cases with different oxygen-carrier-to-fuel ratios are simulated until the equilibrium concentrations are established in the solid phase. The hydrogen conversion and oxygen carrier conversion results from the simulations are then compared with experimental data from the literature, showing that the numerical results are in fair agreement with the experimental results. Model validation against experimental data of the process performance is of paramount importance for future process design and optimization of chemical looping systems via numerical modeling and simulation

Chiral Resolution of <i>RS</i>-Praziquantel via Diastereomeric Co-Crystal Pair Formation with l‑Malic Acid

Praziquantel (PZQ) is an important chiral active pharmaceutical ingredient for the treatment of gastrointestinal parasites, which is commercially available only in the form of its racemate. In this article, on the basis of co-crystallization experiments a convenient two-step protocol for the chiral resolution of <i>RS</i>-PZQ is described. Screening experiments with <i>RS</i>-PZQ using the liquid-assisted grinding technique revealed the formation of a diastereomeric co-crystal pair with l-malic acid (l-MA) of the compositions <i>R</i>-PZA:l-MA and <i>S</i>-PZQ:l-MA. Both co-crystals have been examined by single-crystal X-ray diffraction analysis, revealing similar unit cell parameters but differences in the supramolecular organization. Particularly the analysis of the hydrogen bonding patterns indicated overall stronger intermolecular interactions in the case of <i>R</i>-PZA:l-MA, which was confirmed by thermogravimetric–differential scanning calorimetry analysis giving a substantial difference in the melting point when compared to <i>S</i>-PZA:l-MA. After synthesis of <i>R</i>- and <i>S</i>-PZQ in enantiomerically pure form for the selective preparation of both <i>R</i>-PZA:l-MA and <i>S</i>-PZQ:l-MA, comparative solubilization experiments were carried out. Since significant variations in the solubility were found in some solvents, a procedure could be established allowing for the separation of <i>R</i>-PZA:l-MA by fractional crystallization. In a subsequent reaction step, the biologically active enantiomer <i>R</i>-PZQ was liberated from the co-crystal in the form of its hemihydrate by stirring with water. Comparison of the intrinsic dissolution rates for <i>RS</i>-PZQ, <i>R</i>-PZA·0.5H₂O, and <i>R</i>-PZA:l-MA indicated that the co-crystalline phase exhibits a significantly larger rate constant than praziquantel in its enantiomerically pure form or as a racemate

Self-Assembly of Fluorinated Boronic Esters and 4,4′-Bipyridine into 2:1 N→B Adducts and Inclusion of Aromatic Guest Molecules in the Solid State: Application for the Separation of <i>o</i>,<i>m</i>,<i>p</i>‑Xylene

A series of 2:1 fluorinated arylboronic ester adducts with 4,4′-bipyridine sustained by N→B dative bonds have been synthesized. The degree of fluorination in the arylboronic esters derived from catechol is shown to modulate the molecular conformation of the coordinated boronic ester moieties and the intermolecular interactions by means of C–H···F and F···F contacts that sustain the crystal lattices. The adduct derived from the catechol ester of 2,4-difluorophenylboronic acid was chosen to examine the formation of inclusion complexes with a large number of aromatic guests, affording solvates, cocrystals, and a cocrystal solvate. Six different crystal structure types with 1:1, 1:2, and 1:2:2 N→B adduct–guest ratios were observed, whose supramolecular organization is strongly influenced by the formation of sandwich-type complexes between the host and guest molecules. The host–guest interactions involve π···π interactions with the bipyridine linkers and additional contacts with the catecholate and B-aryl_F substituents, indicating a large flexibility of the N→B adducts to adapt to the guest stereochemistry. The versatility of the crystallization system was employed to isolate <i>o</i>-xylene from an equimolar mixture of <i>o</i>-, <i>m</i>-, and <i>p</i>-xylene

Chiral Resolution of <i>RS</i>-Praziquantel via Diastereomeric Co-Crystal Pair Formation with l‑Malic Acid

Praziquantel (PZQ) is an important chiral active pharmaceutical ingredient for the treatment of gastrointestinal parasites, which is commercially available only in the form of its racemate. In this article, on the basis of co-crystallization experiments a convenient two-step protocol for the chiral resolution of <i>RS</i>-PZQ is described. Screening experiments with <i>RS</i>-PZQ using the liquid-assisted grinding technique revealed the formation of a diastereomeric co-crystal pair with l-malic acid (l-MA) of the compositions <i>R</i>-PZA:l-MA and <i>S</i>-PZQ:l-MA. Both co-crystals have been examined by single-crystal X-ray diffraction analysis, revealing similar unit cell parameters but differences in the supramolecular organization. Particularly the analysis of the hydrogen bonding patterns indicated overall stronger intermolecular interactions in the case of <i>R</i>-PZA:l-MA, which was confirmed by thermogravimetric–differential scanning calorimetry analysis giving a substantial difference in the melting point when compared to <i>S</i>-PZA:l-MA. After synthesis of <i>R</i>- and <i>S</i>-PZQ in enantiomerically pure form for the selective preparation of both <i>R</i>-PZA:l-MA and <i>S</i>-PZQ:l-MA, comparative solubilization experiments were carried out. Since significant variations in the solubility were found in some solvents, a procedure could be established allowing for the separation of <i>R</i>-PZA:l-MA by fractional crystallization. In a subsequent reaction step, the biologically active enantiomer <i>R</i>-PZQ was liberated from the co-crystal in the form of its hemihydrate by stirring with water. Comparison of the intrinsic dissolution rates for <i>RS</i>-PZQ, <i>R</i>-PZA·0.5H₂O, and <i>R</i>-PZA:l-MA indicated that the co-crystalline phase exhibits a significantly larger rate constant than praziquantel in its enantiomerically pure form or as a racemate

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population.The aim of this study was to inform vaccination prioritization by modelling the impact of vaccination on elective inpatient surgery. The study found that patients aged at least 70 years needing elective surgery should be prioritized alongside other high-risk groups during early vaccination programmes. Once vaccines are rolled out to younger populations, prioritizing surgical patients is advantageous