Tailoring the surface chemistry of zeolite templated carbon by electrochemical methods

One option to optimize carbon materials for supercapacitor applications is the generation of surface functional groups that contribute to the pseudocapacitance without losing the designed physical properties. This requires suitable functionalization techniques able to selectively introduce a given amount of electroactive oxygen groups. In this work, the influence of the chemical and electrochemical oxidation methods, on the chemical and physical properties of a zeolite templated carbon (ZTC), as a model carbon material, have been studied and compared. Although both oxidation methods generally produce a loss of the original ZTC physical properties with increasing amount of oxidation, the electrochemical method shows much better controllability and, unlike chemical treatments, enables the generation of a large number of oxygen groups (O = 11000- 3300 μmol/g), with a higher proportion of active functionalities, while retaining a high surface area (ranging between 1900-3500 m2/g), a high microporosity and an ordered 3-D structure.

Psychometric properties of the School Anxiety Inventory-Short Version in Spanish secondary education students

Background: The School Anxiety Inventory (SAI) can be applied in different fields of psychology. However, due to the inventory’s administration time, it may not be useful in certain situations. To address this concern, the present study developed a short version of the SAI (the SAI-SV). Method: This study examined the reliability and validity evidence drawn from the scores of the School Anxiety Inventory-Short Version (SAI-SV) using a sample of 2,367 (47.91% boys) Spanish secondary school students, ranging from 12 to 18 years of age. To analyze the dimensional structure of the SAI-SV, exploratory and confirmatory factor analyses were applied. Internal consistency and test-retest reliability were calculated for SAISV scores. Results: A correlated three-factor structure related to school situations (Anxiety about Aggression, Anxiety about Social Evaluation, and Anxiety about Academic Failure) and a three-factor structure related to the response systems of anxiety (Physiological Anxiety, Cognitive Anxiety, and Behavioral Anxiety) were identified and supported. The internal consistency and test-retest reliability were determined to be appropriate. Conclusions: The reliability and validity evidence based on the internal structure of SAI-SV scores was satisfactory.

The Spanish version of the Prenatal Breast-feeding Self-efficacy Scale: Reliability and validity assessment

Background: Only a minority of infants are exclusively breastfed for the recommended 6 months postpartum. Breast-feeding self-efficacy is a mother's confidence in her ability to breastfeed and is predictive of breastfeeding behaviors. The Prenatal Breast-feeding Self-efficacy Scale (PBSES) was developed among English-speaking mothers to measure breastfeeding self-efficacy before delivery. Objectives: To translate the PBSES into Spanish and assess its psychometric properties. Design: Reliability and validity assessment. Setting: A public hospital in Yecla, Spain. Participants: A convenience sample of 234 pregnant women in their third trimester of pregnancy. Methods: The PBSES was translated into Spanish using forward and back translation. A battery of self-administered questionnaires was completed by participants, including a questionnaire on sociodemographic variables, breastfeeding experience and intention, as well as the Spanish version of the PBSES. Also, data on exclusive breastfeeding at discharge were collected from hospital database. Dimensional structure, internal consistency and construct validity of the Spanish version of PBSES were assessed. Results: Confirmatory factor analysis suggested the presence of one construct, self-efficacy, with four dimensions or latent variables. Cronbach's alpha coefficient for internal consistency was 0.91. Response patterns based on decision to breastfeed during pregnancy provided evidence of construct validity. In addition, the scores of the Spanish version of the PBSES significantly predicted exclusive breastfeeding at discharge. Conclusions: The Spanish version of PBSES shows evidences of reliability, and contrasting group and predictive validity. Confirmatory factor analysis indicated marginal fit and further studies are needed to provide new evidence on the structure of the scale. The Spanish version of the PBSES can be considered a reliable measure and shows validity evidences.

Electrochemical generation of oxygen-containing groups in an ordered microporous zeolite-templated carbon

Zeolite templated carbon (ZTC) was electrochemically oxidized under various conditions, and its chemistry and structural evolution were compared to those produced by conventional chemical oxidation. In both oxidation methods, a general loss of the original structure regularity and high surface area was observed with increasing amount of oxidation. However, the electrochemical method showed much better controllability and enabled the generation of a large number of oxygen functional groups while retaining the original structure of the ZTC. Unlike chemical treatments, highly microporous carbons with an ordered 3-D structure, high surface area (ranging between 1900 and 3500 m2/g) and a large number of oxygen groups (O = 11,000–3300 μmol/g), have been prepared by the electrochemical method. Some insights into the electrooxidation mechanism of carbon materials are proposed from the obtained polarization curves, using ZTC as a model carbon material.

Characterization of soluble and bound EPS obtained from 2 submerged membrane bioreactors by 3D-EEM and HPSEC

This research study deals with the quantification and characterization of the EPS obtained from two 25 L bench scale membrane bioreactors (MBRs) with micro-(MF-MBR) and ultrafiltration (UF-MBR) submerged membranes. Both reactors were fed with synthetic water and operated for 168 days without sludge extraction, increasing their mixed liquor suspended solid (MLSS) concentration during the experimentation time. The characterization of soluble EPS (EPSs) was achieved by the centrifugation of mixed liquor and bound EPS (EPSb) by extraction using a cationic resin exchange (CER). EPS characterization was carried out by applying the 3-dimensional excitation–emission matrix fluorescence spectroscopy (3D-EEM) and high-performance size exclusion chromatography (HPSEC) with the aim of obtaining structural and functional information thereof. With regard to the 3D-EEM analysis, fluorescence spectra of EPSb and EPSs showed 2 peaks in both MBRs at all the MLSS concentrations studied. The peaks obtained for EPSb were associated to soluble microbial by-product-like (predominantly protein-derived compounds) and to aromatic protein. For EPSs, the peaks were associated with humic and fulvic acids. In both MBRs, the fluorescence intensity (FI) of the peaks increased as MLSS and protein concentrations increased. The FI of the EPSs peaks was much lower than for EPSb. It was verified that the evolution of the FI clearly depends on the concentration of protein and humic acids for EPSb and EPSs, respectively. Chromatographic analysis showed that the intensity of the EPSb peak increased while the concentrations of MLSS did. Additionally, the mean MW calculated was always higher the higher the MLSS concentrations in the reactors. MW was higher for the MF-MBR than for the UF-MBR for the same MLSS concentrations demonstrating that the filtration carried out with a UF membrane lead to retentions of lower MW particles.

La conjetura de Poincaré

Con la ayuda de los grupos de homología – que él mismo había definido – Poincaré dio una clasificación completa de las superficies topológicas, y posteriormente intentó clasificar, con ayuda de estos grupos y también del grupo fundamental, las variedades topológicas de cualquier dimensión. Una de las preguntas que se planteó fue si toda variedad topológica 3-dimensional simplemente conexa era homeomorfa a la esfera S3. Esta pregunta – conocida como la conjetura de Poincaré – ha sido objeto de estudio durante casi 100 años, y ha impulsado de modo notable el desarrollo de la Topología Algebraica. La conjetura se extendió a dimensiones arbitrarias y se fue resolviendo en todas las dimensiones salvo en la dimensión 3 que era aquella en la que había sido originariamente planteada. Por fin en el año 2003, Perelman resolvió la famosa conjetura. Los objetivos de este trabajo son los siguientes: hacer un estudio histórico de la Conjetura de Poincaré y de la clasificación de las variedades topológicas, definir con precisión los conceptos que se usan en la clasificación de las variedades topológicas, presentar una selección de los principales resultados, y por último, construir ejemplos de variedades topológicas que justifiquen el desarrollo de esta teoría.