Catalyst screening: Refinement of the origin of the volcano curve and its implication in heterogeneous catalysis

Understanding the overall catalytic activity trend for rational catalyst design is one of the core goals in heterogeneous catalysis. In the past two decades, the development of density functional theory (DFT) and surface kinetics make it feasible to theoretically evaluate and predict the catalytic activity variation of catalysts within a descriptor-based framework. Thereinto, the concept of the volcano curve, which reveals the general activity trend, usually constitutes the basic foundation of catalyst screening. However, although it is a widely accepted concept in heterogeneous catalysis, its origin lacks a clear physical picture and definite interpretation. Herein, starting with a brief review of the development of the catalyst screening framework, we use a two-step kinetic model to refine and clarify the origin of the volcano curve with a full analytical analysis by integrating the surface kinetics and the results of first-principles calculations. It is mathematically demonstrated that the volcano curve is an essential property in catalysis, which results from the self-poisoning effect accompanying the catalytic adsorption process. Specifically, when adsorption is strong, it is the rapid decrease of surface free sites rather than the augmentation of energy barriers that inhibits the overall reaction rate and results in the volcano curve. Some interesting points and implications in assisting catalyst screening are also discussed based on the kinetic derivation. Moreover, recent applications of the volcano curve for catalyst design in two important photoelectrocatalytic processes (the hydrogen evolution reaction and dye-sensitized solar cells) are also briefly discussed.

Taxonomic status and origin of the shrews (soricidae) from the canary islands inferred from a mtdna comparison with the european crocidura species

[EN] European island shrews are either relicts of the endemic Pleistocene fauna, e.g., Crocidura zimmermanni, or were introduced from continental source populations. In order to clarify the taxonomic status and the origin of the two shrew species from the Canary Islands, a 981 bp fragment of cytochrome b gene was investigated in all European Crocidura species and compared with the Canary shrew (Crocidura canariensis) and the Osorio shrew (Crocidura osorio). The first shares its karyotype with the Sicilian shrew Crocidura sicula (2N = 36), the second with the Greater white-toothed shrew Crocidura russula (2N = 42), suggesting possible sister species relationships.

The Language(s) of the Diaries

A journal of commercial voyages and domestic life on the Tigris River -- the language used in the diaries.

Age an origin of the "Mexican Onyx" at San Antonio Texcala (Puebla, Mexico)

A great variety of color banded CaC03 is known as „Mexican Onyx“, and is extensively used for ornamental purposes. Within the San Antonio Texcala mining district an area of about 24.000 m2 is covered by a thick travertine crust with a calculated volume of at least 2,8 x 1061. It originates from warm waters that emerge on young fissures and faults. It seems to be likely that the travertine formation is related to the hydrothermal activity of the Transmexican Volcanic Belt and to the seismicity of this zone. The deposit is built up by different travertine varieties. The main lithotypes are: (1) dense crystalline laminated travertine; (2) ray crystal travertine; (3) shrub layer travertine; (4) irregular porous travertine; (5) travertine breccia. Textural variation seems to be related to water temperature/distance from the emergence point, rapid or slow degassing of CO, and bacterial influence. At the moment, a light green banded variety (native sulfur impurities) is mined. It is the facture fill of a morphological prominent fissure-ridge travertine. U/Th data indicate, that the travertine has been deposited since at least 52 + 5 ka.

Origin of an enigmatic regional Mio-Pliocene unconformity on the Demerara plateau

The Demerara plateau, located offshore French Guiana and Suriname, is part of a passive transform continental margin particularly prone to develop slope instabilities, probably in relation to the presence of a free distal border along its steep continental slope. Slope failure occurred at different periods (Cretaceous to Neogene) and shows an overall retrogressive evolution through time. Upslope these failure headscarp, an enigmatic regional MioPliocene unconformity has been discovered through the interpretation of new academic and industrial datasets. The aim of this work is to describe and understand the origin of this surface. Our analysis shows that this unconformity is made of a series of valleys that cross-cut sedimentary strata. Each one of these valleys has a short lateral extent and is closed along two perpendicular directions, which suggests that it could correspond to a highly meandering system, or to some sub-circular depressions. The infill of these features is equivalent to the regional stratigraphic strata found outside the structures, but in a subdued position. This seems to imply that the structures have originated by a local loss of sediments at their base or by sliding processes. Furthermore, these depressions intersect each other through time, while migrating progressively downslope. We discuss a series of hypotheses that try to explain the onset and evolution of these depressions forming the Mio-Pliocene unconformity (Canyons? Slope failures? Contourite moats? Hydrate pockmarks?). Having established that these structures are depressions formed by collapse, and have many similarities with structures recently described in the literature as pockmarks associated with gas hydrate dissolution, we favor this hypothesis. We propose that these hydrate pockmarks form with a mass failure that was triggered by fluid-overpressure development at the base of the hydrate stability zone.

Horæ evangelicæ : or, the internal evidence of the Gospel history, being an inquiry into the structure and origin of the four Gospels, their historical consistency, and the characteristic design of each narrative /

Mode of access: Internet.

The origin of vertebrate steroids in molluscs: uptake, metabolism and depuration studies in the common mussel

No abstract available.

Language Outcomes of the Play and Language for Autistic Youngsters (PLAY) Project Home Consultation model—An Extended Analysis

The current study is a post-hoc analysis of data from the original randomized control trial of the Play and Language for Autistic Youngsters (PLAY) Home Consultation program, a parent-mediated, DIR/Floortime based early intervention program for children with ASD (Solomon, Van Egeren, Mahone, Huber, & Zimmerman, 2014). We examined 22 children from the original RCT who received the PLAY program. Children were split into two groups (high and lower functioning) based on the ADOS module administered prior to intervention. Fifteen-minute parent-child video sessions were coded through the use of CHILDES transcription software. Child and maternal language, communicative behaviors, and communicative functions were assessed in the natural language samples both pre- and post-intervention. Results demonstrated significant improvements in both child and maternal behaviors following intervention. There was a significant increase in child verbal and non-verbal initiations and verbal responses in whole group analysis. Total number of utterances, word production, and grammatical complexity all significantly improved when viewed across the whole group of participants; however, lexical growth did not reach significance. Changes in child communicative function were especially noteworthy, and demonstrated a significant increase in social interaction and a significant decrease in non-interactive behaviors. Further, mothers demonstrated an increase in responsiveness to the child’s conversational bids, increased ability to follow the child’s lead, and a decrease in directiveness. When separated for analyses within groups, trends emerged for child and maternal variables, suggesting greater gains in use of communicative function in both high and low groups over changes in linguistic structure. Additional analysis also revealed a significant inverse relationship between maternal responsiveness and child non-interactive behaviors; as mothers became more responsive, children’s non-engagement was decreased. Such changes further suggest that changes in learned skills following PLAY parent training may result in improvements in child social interaction and language abilities.

How teachers' perceptions affect the academic and language assessment of immigrant children

Recent research evidences inconsistencies in teachers' practice regarding skills assessment of L2 students. Scientific evidence supports that less experienced teachers have lower orientation toward multiple task-tests for non-native students. Research questions: Whether school teachers as having different teaching training and unequal teaching experience with non-native students perceive differently a four-skills scale. Purpose of the study: This study intends to analyse the importance degree between the four skills/tasks: reading, writing, speaking and listening, in the perspective of school teachers. Method: 77 teachers, aged 32-62, with (and without) experience in teaching and adapting materials for immigrant students, divided into six groups according to their scientific domain. Assessment tools included a scale for judgement of four academic tasks adapted from the original “Inventory of Undergraduate and Graduate Level: Reading, Writing, Speaking and Listening Tasks (Rosenfeld, Leung & Ottman, 2001). Main Findings: 1) different degrees of importance attributed by teachers on tasks that should be included in academic and language test for immigrant students; 2) perceptions of teachers are determined by predictors in this order: scientific domain, experience with multicultural classes and lower prediction from teaching service and age; 3) different results between american and portuguese samples answering the same questionnaire.

Asexual origin of brooding in the sea anemones Actinia equina and A. schmidti: Molecular evidence from the portuguese shore

Reproduction by sexual or asexual viviparity is a common phenomenon in some anemone species. In this short communication, the origin of the brooded young of Actinia equina and A. schmidti from the Portuguese shore was investigated. DNA was extracted from 56 brooding adult Actinia sp. and the nuclear gene that codes for the 28S ribosomal subunit was sequenced. Species identity was then assessed using GenBank. In total, 50 individuals were A. schmidti, five were A. equina and one had a hybrid origin. Three adult anemones (the hybrid, one A. equina and one A. schmidti) possessed two different 28S sequences and so their offspring was selected for further analysis using the same molecular procedure. Each brooded polyp was found to possess the exact same sequence as its parent, strongly suggesting the asexual origin of broods in A. equina and A. schmidti.

Origin of and resulting floristic composition from seedbanks in agroforestry systems of Tomé-Açu, Eastern Amazon.

2016

Rare HIV-1 subtype J genomes and a new H/U/CRF02_AG recombinant genome suggests an ancient origin of HIV-1 in Angola

This is the author’s version of a work that was accepted for publication in AIDS Research and Human Retroviruses .

How relevant is the origin of human capital for immigrant wages? Evidence from Spain

The objective of this article is to analyse the role played by the different components of human capital in the wage determination of immigrants in the Spanish labour market. Using microdata from the Encuesta Nacional de Inmigrantes, we find that human capital of immigrants acquired in Spain presents higher returns than human capital obtained in home countries, reflecting the limited international transferability of the latter. This result is reinforced by the strong heterogeneity observed in wage returns to different kinds of human capital across immigrants from different origins and, in particular, by the fact that immigrants with the higher returns to human capital acquired in their home countries are those coming from other developed countries and Latin America, the two regions more similar to Spain in terms of development and/or culture.

Relationship between super antigenicity, antimicrobial resistance and origin of Staphylococcus aureus isolated

Introduction: Staphylococcus aureus is a pathogen that causes food poisoning as well as hospital and community acquired infections. Objective: Establish the profile of superantigen genes among hospital isolates in relation to clinical specimen type, susceptibility to antibiotics and hospital or community acquisition. Methods: Eighty one isolates obtained from patients at Colombian hospital, were classified by antimicrobial susceptibility, specimen type and hospital or community acquired . The PCR uniplex and multiplex was used for detection of 22 superantigen genes (18 enterotoxins, tsst-1 and three exfoliative toxins). Results: Ninety five point one percent of isolates harbored one or more of the genes with an average of 5.6 genes. Prevalence of individual genes was variable and the most prevalent was seg (51.9%). Thirty nine genotypes were obtained, and the genotype gimnou (complete egc cluster) was the most prevalent alone (16.0%) and in association with other genes (13.6%). The correlation between presence of superantigens and clinical specimen or antimicrobial susceptibility showed no significant difference. But there was significant difference between presence of superantigens and the origin of the isolates, hospital or community acquired (p= 0.049). Conclusions: The results show the variability of the superantigen genes profile in hospital isolates and shows no conclusive relationship with the clinical sample type and antimicrobial susceptibility, but there was correlation with community and hospital isolates. The analysis of the interplay between virulence, epidemic and antibiotic resistance of bacterial populations is needed to predict the future of infectious diseases.