Espectroscopía IR de sulfatos en clínkeres y cementos

Infrared spectroscopy is a very useful technique in Cement Chemistry. This work is devoted to the study of a large number of sulphates that should have an incidence in false set phenomena, and they are qualitative and semi-quantitatlvely studied when they are in some degree in the clinker or in the portland cement.La espectroscopía infrarroja es una técnica de gran utilidad en la Química del Cemento. En el presente trabajo se aplica al estudio de numerosos sulfatos que pueden tener incidencia en el fenómeno de falso fraguado, y se estudian cualitativa y semicuantitativamente cuando forman parte del clinker o cemento portland

The LIL for UU-statistics in Hilbert spaces

We give necessary and sufficient conditions for the (bounded) law of the iterated logarithm for $U$-statistics in Hilbert spaces. As a tool we also develop moment and tail estimates for canonical Hilbert-space valued $U$-statistics of arbitrary order, which are of independent interest

A first-principles study of superconductivity on RbH by doping without applied pressure

The structural, electronic, lattice dynamics, electron-phonon coupling, and superconducting properties of the alkali-metal hydride RbH, metalized through electron-doping by the construction of the solid-solution Rb$_{1-x}$Sr$_x$H, are systematically analyzed as a function of Sr-content within the framework of density functional perturbation and Migdal-Eliashberg theories, taking into account the effect of zero-point energy contribution by the quasi-harmonic approximation. For the entire studied range of Sr-content, steady increments of the electron-phonon coupling constant and the superconducting critical temperature are found with progressive alkaline-earth metal content through electron-doping, reaching the values of $\lambda=1.92$ and $T_c=51.3(66.1)$~K with $\mu^*$=0.1(0). The steady rise of such quantities as a function of Sr-content is consequence of the metallization of the hydride as an increase of density of states at the Fermi level is observed, as well as the softening of the phonon spectrum, mainly coming from H-optical modes. Our results indicate that electron-doping on metal-hydrides is an encouraging alternative to look for superconductivity without applied pressure.Comment: 8 pages, 6 figure

The Relationship Between Childhood Physical and Sexual Abuse and Adolescent Cannabis Use: A Systematic Review

Background: Among adolescents, cannabis use is a health concern due to associations with drug addiction and mental health disorders across the life course. It has been shown that childhood maltreatment is associated with drug addiction in adulthood. However, a better understanding of the relationship between maltreatment and drug use may improve targeted prevention and interventions. The aim of this systematic review is to describe the association between exposure to childhood maltreatment, specifically physical and sexual abuse, with adolescent cannabis use. Methods: A systematic search strategy was applied to Embase, PsycINFO, and Ovid MEDLINE(R) databases. Methods followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Abstract and title screening was performed to identify papers which reported an estimate of the association between childhood physical or sexual abuse and adolescent cannabis use. Full text screening of each paper was performed, and data were extracted and study quality assessed. Weighted means meta-analysis was performed on studies reporting odds ratios as effect estimates. Results: Of 8,780 screened articles, 13 were identified for inclusion. Eight papers received a quality rating score indicating lower risk of bias. Eleven papers reported the relationship between childhood sexual abuse and adolescent cannabis use; effect estimates ranged from AOR 0.53-AOR 2.18 (weighted mean OR 1.29, 95% CI 1.08-1.49). The relationship between childhood physical abuse and adolescent cannabis use was reported in 7 papers; effect estimates ranged from AOR 1.25-AOR 1.87 (weighted mean OR 1.39, 95% CI 1.12-1.66). Differences in the strength of the evidence were observed by the method of exposure ascertainment, and there was some evidence of differences in association by gender, age of cannabis initiation, and the severity of the abuse. Conclusions: This systematic review indicates childhood physical or sexual abuse may increase risk of adolescent-onset cannabis use. Few studies considered variation in timing of onset, or by gender. Adolescent cannabis use precedes is strongly associated with increased risk of negative mental health outcomes; further exploration of adolescent cannabis use's place on the causal pathway between childhood abuse and adult mental health problems is warranted to improve intervention

Cycle-finite module categories

We describe the structure of module categories of finite dimensional algebras over an algebraically closed field for which the cycles of nonzero nonisomorphisms between indecomposable finite dimensional modules are finite (do not belong to the infinite Jacobson radical of the module category). Moreover, geometric and homological properties of these module categories are exhibited

A Graphene Acid - TiO2 Nanohybrid as Multifunctional Heterogeneous Photocatalyst for the Synthesis of 1,3,4-Oxadiazoles

The immobilization of TiO2 nanoparticles on graphene acid (GA), a conductive graphene derivative densely functionalized with COOH groups, is presented. The interaction between the carboxyl groups of the surface and the titanium precursor leads to a controlled TiO2 heterogenization on the nanosheet according to microscopic and spectroscopic characterizations. Electronic communication shared among graphene and semiconductor nanoparticles shifts the hybrid material optical features toward less energetic radiation but maintaining the conductivity. Therefore, GA-TiO2 is employed as heterogeneous photocatalyst for the synthesis of 2,5-disubstituted 1,3,4-oxadiazoles using ketoacids and hydrazides as substrates. The material presented enhanced photoactivity compared to bare TiO2, being able to yield a large structural variety of oxadiazoles in reaction times as fast as 1 h with full recyclability and stability. The carbocatalytic character of GA is the responsible for the substrates condensation and the GA-TiO2 light interaction ability is able to photocatalyze the cyclization to the final 1,3,4-oxadiazoles, demonstrating the optimal performance of this multifunctional photocatalytic materialFinancial support was provided by the Spanish Government (RTI2018-095038-B-I00), FotoaArt “Comunidad de Madrid”, and European Structural Funds (S2018/NMT-4367) proyectos sinérgicos I+D (Y2020/NMT-6469) and Comunidad Autónoma de Madrid (SI1/PJI/2019-00237). M.B. and M.B. thank the Spanish MICINN for the Juan de la Cierva Incorporación contracts (IJC2019-042157-I and IJC2019- 042430-I). We also acknowledge the electron microscopy analysis from CNME. This work was supported by the national project NovaCO2 (PID2020-118593RB-C22) funded by MCIN/AEI/10.13039/50110001103