Alfredo García

Bio: Alfredo García is an academic researcher from University of Zaragoza. The author has contributed to research in topics: Planar graph & General position. The author has an hindex of 15, co-authored 54 publications receiving 808 citations. Previous affiliations of Alfredo García include University College London Hospitals NHS Foundation Trust.

Lower bounds on the number of crossing-free subgraphs of K N

Abstract: We improve previous lower bounds on the number of simple polygonizations, and other kinds of crossing-free subgraphs, of a set of N points in the plane by analyzing a suitable configuration. We also prove that the number of crossing-free perfect matchings and spanning trees is minimum when the points are in convex position.

Syntheses of mesoporous zirconia with anionic surfactants

Abstract: Synthesis of mesoporous zirconia has been performed by slowly hydrolyzing zirconium propoxide in the presence of anionic surfactants: dodecyl phosphate or sulfate (P12 and Sf12) and hexadecyl sulfonate (So16). t-Plot surface areas >400 m2 g–1 and diffraction lines corresponding to spacings near 45 A were measured for solids outgassed at 140–150 °C. This treatment does not remove the surfactant. After calcination in air at 500 °C and combustion of the surfactant the spacing increases to ca. 70 A and the mesoporous volume is reduced by a factor of about 2, whereas the pore wall material crystallizes in the tetragonal phase. A schematic model in which the surfactant is a scaffold component is suggested in order to explain these results. It is very different from the templating mechanisms reported for zirconia by others. The high resolution electron microscopic study reveals the presence of a disorganized network of polygonal pores in the solids obtained through the mediation of surfactant. It is suggested that the chemistry of the hydrolysis solution is instrumental in the organization of the pore structure and in determining the thickness of the walls. In agreement with others, the fixation of PO4 or SO4 in the walls may help to preserve the porous structure.

Incidence and predictors of anti-bradycardia pacing in patients with Anderson-Fabry disease.

Abstract: Background Anderson-Fabry disease (AFD) is an X-linked lysosomal storage disorder associated with bradyarrhythmias. We sought to examine the nature of conduction system abnormalities and the indications and determinants of anti-bradycardia pacing in patients with AFD. Methods and results We studied 204 patients with AFD (49% male, mean age 42 years) in an observational, longitudinal, retrospective cohort study. At baseline, 5 (2.5%) patients had pacemakers for the treatment of bradycardias [4/5 (80%) for atrioventricular disease; 1/5 (20%) for sinus node disease]. PR interval 200 ms in 6 (3%); QRS interval >120 ms 18 (9%); left QRS axis deviation in 16 (8%); and right-axis deviation in 2 (1%). Age was an independent determinant of prolonged PR interval, QRS duration and left QRS axis deviation. During follow-up (189 patients; 899 patient-years), 12 (6%) had a device implanted to treat spontaneously occurring bradyarrhythmias [5/12 (42%) for atrioventricular disease; 7/12 (58%) sinus node disease] with 8% 5-year cumulative incidence. Two independent predictors of future anti-bradycardia pacing were identified in a multivariable Cox model: QRS duration [hazard ratio (HR) 1.05, 95% confidence intervals (CI) 1.02-1.09, P= 0.001; receiver operating characteristic (ROC) curve c-statistic 0.726] and PR interval duration (HR 1.03, 95% CI 1.004-1.060, P = 0.023; ROC curve c-statistic 0.548). QRS duration ≥110 ms at baseline had a sensitivity of 64%, specificity of 84%, 49% positive predictive value, and 91% negative predictive value for identifying patients likely to require anti-bradycardia pacing. Conclusion In patients with AFD increasing age is associated with PR and QRS interval prolongation and left QRS axis deviation. Pacing for atrioventricular and sinus node disease is common and patients with QRS≥110 ms should be closely monitored for bradyarrhythmias.

Augmenting the connectivity of geometric graphs

Abstract: Let G be a connected plane geometric graph with n vertices. In this paper, we study bounds on the number of edges required to be added to G to obtain 2-vertex or 2-edge connected plane geometric graphs. In particular, we show that for G to become 2-edge connected, 2n3 additional edges are required in some cases and that 6n7 additional edges are always sufficient. For the special case of plane geometric trees, these bounds decrease to n2 and 2n3, respectively.

Chemical strategies to design textured materials: from microporous and mesoporous oxides to nanonetworks and hierarchical structures.

Abstract: 3.

Block Copolymer Templating Syntheses of Mesoporous Metal Oxides with Large Ordering Lengths and Semicrystalline Framework

Abstract: A simple and general procedure has been developed for the syntheses of ordered largepore (up to 14 nm) mesoporous metal oxides, including TiO2, ZrO2 ,N b 2O5 ,T a 2O5 ,A l 2O3, SiO2, SnO2 ,W O 3, HfO2, and mixed oxides SiAlOy ,A l 2TiOy, ZrTiOy, SiTiOy, ZrW2Oy. Amphiphilic poly(alkylene oxide) block copolymers were used as structure-directing agents in nonaqueous solutions for organizing the network-forming metal oxide species. Inorganic salts, rather than alkoxides or organic metal complexes, were used as soluble and hydrolyzable precursors to the polymerized metal oxide framework. These thermally stable mesoporous oxides have robust inorganic frameworks and thick channel walls, within which high densities of nanocrystallites can be nucleated. These novel mesoporous metal oxides are believed to be formed through a mechanism that combines block copolymer self-assembly with alkylene oxide complexation of the inorganic metal species.

Ordered mesoporous materials

Abstract: About six years after the first publication, ordered mesoporous oxides can be prepared by a variety of procedures and over a wide range of compositions using various different surfactant templates. The mechanisms of formation, although still a matter of discussion, are understood in principle, and the macroscopic morphology as well as the orientation of the pores can be controlled in fortunate cases. However, still lacking are groundbreaking developments in the field of applications, either in catalysis or other areas. The state-of-the-art in the synthesis, characterization and application of ordered mesoporous oxides will be covered in this review.

2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

Abstract: Glenn N. Levine, MD, FACC, FAHA, Chair Patrick T. O’Gara, MD, MACC, FAHA, Chair-Elect Jonathan L. Halperin, MD, FACC, FAHA, Immediate Past Chair [‡‡][1] Sana M. Al-Khatib, MD, MHS, FACC, FAHA Joshua A. Beckman, MD, MS, FAHA Kim K. Birtcher, PharmD, MS, AACC Biykem Bozkurt, MD, PhD,

Perspectives in catalytic applications of mesostructured materials

Abstract: This review paper deals with proven and potential applications of mesoporous molecular sieves in catalysis. In addition to introduction and conclusion, the text is divided into two parts, respectively, dedicated to the design of solid catalysts and catalyst supports and to some relevant examples of catalytic processes.