The isoperimetric problem in Johnson graphs

It has been recently proved that the connectivity of distance regular graphs is the degree of the graph. We study the Johnson graphs $J(n,m)$, which are not only distance regular but distance transitive, with the aim to analyze deeper connectivity properties in this class. The vertex $k$-connectivity of a graph $G$ is the minimum number of vertices that have to be removed in order to separate the graph into two sets of at least $k$ vertices in each one. The isoperimetric function $\mu_G(k)$ of a graph $G$ is the minimum boundary among all subsets of vertices of fixed cardinality $k$. We give the value of the isoperimetric function of the Johnson graph $J(n,m)$ for values of $k$ of the form ${t\choose m}$, and provide lower and upper bounds for this function for a wide range of its parameter. The computation of the isoperimetric function is used to study the $k$-connectivity of the Johnson graphs as well. We will see that the $k$-connectivity grows very fast with $k$, providing much sensible information about the robustness of these graphs than just the ordinary connectivity. In order to study the isoperimetric function of Johnson graphs we use combinatorial and spectral tools. The combinatorial tools are based on compression techniques, which allow us to transform sets of vertices without increasing their boundary. In the compression process we will show that sets of vertices that induce Johnson subgraphs are optimal with respect to the isoperimetric problem. Upper bounds are obtained by displaying nested families of sets which interpolate optimal ones. The spectral tools are used to obtain lower bounds for the isoperimetric function. These tools allow us to display completely the isoperimetric function for Johnson graphs $J(n,3)$. . Distance regular graphs form a structured class of graphs which include well-known families, as the n-cubes. Isoperimetric inequalities are well understood for the cubes, but for the general class of distance regular class it has only been proved that the connectivity of these graphs equals the degree. As another test case, the project suggests to study the family of so-called Johnson graphs, which are not only distance regular but also distance transitive. Combinatorial and spectral techniques to analyze the problem are available

Equivalent characterizations of the spectra of graphs and applications to measures of distance-regularity

The spectrum of a graph usually provides a lot of information about its combinatorial structure. Moreover,from the spectrum, the so-called predistance polynomials can be defined, as a generalization, for any graph, of the distancepolynomials of a distance-regular graph. Going further, the preintersection numbers generalize the intersection numbers ofa distance-regular graph. This paper describes, for any graph, the closed relationships between its spectrum, predistancepolynomials, and preintersection numbers. Then, some applications to derive combinatorial properties of the given graph,most of them related to some fundamental characterizations of distance-regularity, are presented. In particular, the so-called‘spectral excess theorem’ is revisited. This result states that a connected regular graph is distance-regular if and only if itsspectral excess, which is a value computed from the spectrum, equals the average excess, that is, the mean of the numbers ofvertices at maximum distance from every vertex.Peer ReviewedPostprint (author's final draft

Locality-Sensitive Hashing for large scale image retrieval

En este artículo proporcionamos una descripción general del hash sensible a la ubicación (LSH) utilizado para la recuperación de imágenes a gran escala y para resolver el problema del vecino más cercano. El objetivo es experimentar con diferentes configuraciones de parámetros de LSH sobre un conjunto de huellas dactilares de video para ver cuál es la mejor en términos de precisión e indexación para que luego, dado un objeto de consulta, devuelva los objetos (vecinos más cercanos) que sean más similares a la consulta. Los parámetros de configuración que ofrecieron mejores resultados fueron un tamaño de cubo de 24 con 15 tablas y tamaños de hash de 15 bits, obteniendo aproximadamente el 50% de las coincidencias correctas con los métodos de recuperación P @ 4 y P @ 6

Efecto del tratamiento preoperatorio con estatinas sobre los resultados de la cirugía coronaria

IntroducciónEl uso de estatinas se asocia a una reducción de accidentes coronarios en prevención primaria y secundaria y después de angioplastia primaria.ObjetivoInvestigar si el empleo de estatinas en pacientes sometidos a cirugía de revascularización coronaria (CRC) se asocia a beneficio clínico.MétodosSe incluyeron 102 pacientes consecutivos con enfermedad coronaria para CRC electiva y aislada. En el momento de la inclusión se registró el tratamiento preoperatorio y las variables clínicas basales. En el seguimiento se registró la aparición de muerte de origen cardíaco e infarto agudo de miocardio (IAM) en los primeros 30 días.ResultadosRecibían estatinas 61 pacientes (60%) frente a 41 (40%) que no las recibían. No se encontraron diferencias significativas entre ambas poblaciones respecto a las características basales. A los 30 días se produjo una muerte cardíaca (1,6%) en el grupo que recibió estatinas, frente a cinco (12,2%) en el grupo que no las recibían (p=0,02), el IAM ocurrió en cuatro (6,6%) frente a 8 (19,5%) (p=0,04) y el resultado compuesto de muerte cardíaca o IAM ocurrió en cinco (8,2%) frente a 10 (24,4%) (p=0,02). En un modelo multivariado, el tratamiento preoperatorio con estatinas se mantuvo como un factor independiente de predicción (p=0,01; odds ratio [OR]: 3,6) de la aparición de muerte de causa cardíaca o IAM durante los primeros 30 días después de la intervención.ConclusiónEl tratamiento previo con estatinas se asocia de forma significativa e independiente a un menor riesgo de IAM o muerte de origen cardíaco en pacientes sometidos a CRC.IntroductionStatin treatment diminishes adverse cardiac events both in primary and secondary prevention and also after percutaneous coronary intervention.ObjectiveTo study if preoperative statin treatment is associated with any clinical advantage after coronary artery surgery.MethodsWe enrolled 102 consecutive patients with coronary artery disease, scheduled for elective coronary artery surgery. Combined procedures were excluded. Preoperative treatment and the clinical baseline characteristics were recorded in all patients at inclusion. Cardiac death and acute myocardial infarction (AMI) were recorded during the first 30 days.ResultsSixty one patients (60%) were on preoperative statin treatment vs. 41 (40%) who were not. There were no differences at baseline level between both groups. There was one cardiac death at 30 days (1.6%) in the statin-treatment group vs. five deaths (12.2%) in the nostatin group (p=0.02). Acute myocardial infarction presented in four (6.6%) vs. eight (19.5%) (p=0.04). The primary combined cardiac endpoint made of cardiac death or AMI occurred in five (8.2%) vs. 10 (24.4%) (p=0.02). In a multivariate model, preoperative statin treatment remained an independent predictor (p=0.01; odds ratio [OR] 3.6) of cardiac death or AMI during the first 30 days after surgery.ConclusionPreoperative statin-treatment was significative and independently associated with less risk of AMI or cardiath death in patients who underwent coronary artery bypass grafting

Síntesis de nuevos híbridos indol-1,2,3-triazol-carbohidrato

En este trabajo se presenta la síntesis y caracterización de tres nuevos derivados de 1,2,3-triazoles 1,4-disustituidos que contienen un fragmento indol y un carbohidrato. Los híbridos indol-1,2,3-triazol-carbohidrato se prepararon mediante una reacción de cicloadición alquino-azida catalizada por cobre (I) (CuAAC) entre el N-propargil indol y tres diferentes glucosil azidas, a saber: 2,3,4,6-tetra-O-acetil-β-D-glucopiranosil azida, 3-desoxi-3-azido-1,2:5,6-di-O-isopropiliden-a-D-gluco furanosa y su diasterómero la 3-desoxi-3-azido-1,2:5,6-di-O-isopropiliden-a-D-alofuranosa. Se encontró que con el sistema CuI/DIPEA/EtOH:H2O y calentamiento por microondas, los glicoconjugados esperados se obtienen en buenos rendimientos. Estos nuevos compuestos fueron caracterizados adecuadamente por técnicas espectroscópicas convencionales.In this work, the synthesis and characterization of three new 1,4-disubstituted 1,2,3-triazole derivatives containing an indole fragment and a carbohydrate moiety is described. The indole-1,2,3-triazole-carbohydrate hybrids were prepared by a copper (I)-catalyzed azide-alkyne cycloaddition reaction (CuAAC) between the N-propargyl indole and three different glucosyl azides, namely: 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl azide, 3-deoxy-3-azido-1,2:5,6-di-O-isopropylidene-a-D-gluco furanose and its diastereomer 3-deoxy-3-azido-1,2: 5,6-di-O-isopropylidene- -allofuranose. It was found that with the CuI/DIPEA/EtOH:H2O system and microwave heating, the expected glycoconjugates were obtained in good yields. These new compounds were adequately characterized by conventional spectroscopic techniques

Evaluación de la actividad catalítica de MCM-41-Zn en la reacción de oxidación de benzaldehído utilizando O₂ como agente oxidante

En el presente trabajo se describe el diseño y la síntesis del material mesoporoso MCM-41 dopado con Zn, obtenido mediante la técnica de co¬precipitación, así como su aplicación como modulador de la reactividad en la reacción de oxidación de benzaldehído a ácido benzoico, empleando oxígeno molecular como agente oxidante. El catalizador mesoporoso MCM-41-Zn promueve la formación del producto de oxidación con una conversión del 90% y rendimientos del 100% en condiciones de reacción moderadas y tiempos de reacción cortos. Se presenta la comparación y optimización de las condiciones de reacción empleando diversas metodologías: síntesis con calentamiento convencional, síntesis asistida por microondas, así como mecanosíntesis.The present work describes the design and synthesis of a Zn doped MCM-41 mesoporous material, obtained by co-precipitation technique, and its application as a reactivity modulator in the oxidation reaction of benzaldehyde to benzoic acid, by using molecular oxygen as oxidant reagent. Mesoporous catalyst MCM-41-Zn promotes the formation of the oxidation product with conversions of 90% and yields of 100% in moderated reaction conditions and short reaction times. A comparison and optimization of the reaction conditions of diverse synthetic methodologies is presented: Conventional heating, Microwave assisted and mechanosynthesis

Tool wear monitoring in milling using aZIBO shape descriptor

En este documento, se lleva a cabo un proceso de monitoreo del desgaste de la herramienta para determinar la condición de desgaste y para asegurar el uso óptimo de las herramientas antes de su reemplazo durante las operaciones de mecanizado de metales. El conjunto de datos se compone de 53 inserciones de corte. Todos ellos fueron preprocesados y el desgaste de los bordes fue segmentado, resultando 212 bordes establecidos. Para describir la forma de desgaste, se usó un descriptor de forma aZIBO y sus resultados se compararon con dos descriptores clásicos, Hu y Flusser. La clasificación se llevó a cabo utilizando kNN con 1, 3, 5, 7, 9 y 11 vecinos y seis distancias: Cosine, Euclidean, IntersetcDist, ChiSquare, SqDist y Cityblock. Se han llevado a cabo dos clasificaciones: una de ellas con tres clases diferentes (baja, media y alta wexar -L, M y H, respectivamente) y la otra con solo dos clases: baja (L) y alta (H). El descriptor aZIBO ofrece mejores resultados que los clásicos, con una tasa de aciertos del 60,84% y un 81,13% utilizando las etiquetas L-M-H y L-H, respectivamente

Síntesis de nuevos triazolil-glicoconjugados con un fragmento carbazol

En este trabajo se presenta la síntesis de tres nuevos híbridos carbazol-triazol-carbohidrato los cuales podrían ser de potencial utilidad como inhibidores de la enzima -glucosidasa. Los derivados de 1,2,3-triazoles 1,4-disustituidos fueron preparados mediante una reacción de cicloadición alquino-azida catalizada por cobre (I) (CuAAC) entre glucosilazidas (derivadas de la glucosa y de los diacetónidos de la gluco- y alofuranosa) y el 9-propargil-9H-carbazol. Los triazolil-glicoconjugados con un fragmento carbazol se obtuvieron en buenos rendimientos empleando condiciones de microondas y en cortos tiempos de reacción. Estos productos fueron caracterizados adecuadamente por técnicas espectroscópicas convencionales.In this work, the synthesis of three new carbazole-triazole-carbohydrate hybrids is presented, which could be potentially useful as inhibitors of the enzyme -glucosidase. The 1,4-disubstituted 1,2,3-triazole derivatives were prepared by a copper (I) catalyzed alkyne-azide cycloaddition reaction (CuAAC) between glucosylazides (derived from glucose and from the diacetonides of gluco- and alofuranose) and 9-propargyl-9H-carbazole. Triazolyl-glycoconjugates with a carbazole fragment were obtained in good yields using microwave conditions and in short reaction times. These products were adequately characterized by conventional spectroscopic techniques

Sequential oral antibiotic in uncomplicated Staphylococcus aureus bacteraemia: a propensity-matched cohort analysis

Objectives: We aimed to analyse the efficacy and safety of oral sequential therapy (OST) in uncomplicated Staphylococcus aureus bacteraemia (SAB). Methods: Single-centre observational cohort at a tertiary hospital in Spain, including all patients with the first SAB episode from January 2015 to December 2020. We excluded patients with complicated SAB and those who died during the first week. Patients were classified into the OST group (patients who received oral therapy after initial intravenous antibiotic therapy [IVT]), and IVT group (patients who received exclusively IVT). We performed a propensity-score matching to balance baseline differences. The primary composite endpoint was 90-day mortality or microbiological failure. Secondary endpoints included 90-day SAB relapse. Results: Out of 407 SAB first episodes, 230 (56.5%) were included. Of these, 112 (n = 48.7%) received OST and 118 (51.3%) IVT exclusively. Transition to oral therapy was performed after 7 days (interquartile range, 4–11). The primary endpoint occurred in 10.7% (11/112) in OST vs. 30.5% (36/118) in IVT (p < 0.001). SAB relapses occurred in 3.6% (4/112) vs. 1.7% (2/118) (p 0.436). None of the deaths in OST were related to SAB or its complications. After propensity-score matching, the primary endpoint was not more frequent in the OST group (relative risk, 0.42; 95% CI, 0.22–0.79). Ninety-day relapses occurred similarly in both groups (relative risk, 1.35; 95% CI, 0.75–2.39). Discussion: After an initial intravenous antibiotic, patients with uncomplicated SAB can safely be switched to oral antibiotics without apparent adverse outcomes. This strategy could save costs and complications of prolonged hospital stays. Prospective randomized studies are needed