Chirality in Bare and Passivated Gold Nanoclusters

Chiral structures have been found as the lowest-energy isomers of bare (Au$_{28}$ and Au$_{55}) and thiol-passivated (Au$_{28}(SCH$_{3})$_{16}$and Au$_{38}(SCH_{3})_{24}) gold nanoclusters. The degree of chirality existing in the chiral clusters was calculated using the Hausdorff chirality measure. We found that the index of chirality is higher in the passivated clusters and decreases with the cluster size. These results are consistent with the observed chiroptical activity recently reported for glutahione-passivated gold nanoclusters, and provide theoretical support for the existence of chirality in these novel compounds.Comment: 5 pages, 1 figure. Submitted to PR

Adaptive optimization for OpenCL programs on embedded heterogeneous systems

Heterogeneous multi-core architectures consisting of CPUs and GPUs are commonplace in today’s embedded systems. These architectures offer potential for energy efficient computing if the application task is mapped to the right core. Realizing such potential is challenging due to the complex and evolving nature of hardware and applications. This paper presents an automatic approach to map OpenCL kernels onto heterogeneous multi-cores for a given optimization criterion – whether it is faster runtime, lower energy consumption or a trade-off between them. This is achieved by developing a machine learning based approach to predict which processor to use to run the OpenCL kernel and the host program, and at what frequency the processor should operate. Instead of hand-tuning a model for each optimization metric, we use machine learning to develop a unified framework that first automatically learns the optimization heuristic for each metric off-line, then uses the learned knowledge to schedule OpenCL kernels at runtime based on code and runtime information of the program. We apply our approach to a set of representative OpenCL benchmarks and evaluate it on an ARM big.LITTLE mobile platform. Our approach achieves over 93% of the performance delivered by a perfect predictor.We obtain, on average, 1.2x, 1.6x, and 1.8x improvement respectively for runtime, energy consumption and the energy delay product when compared to a comparative heterogeneous-aware OpenCL task mapping scheme

COMBUSTION MODEL FOR SPARK IGNITION ENGINES OPERATING ON GASOLINE-ETHANOL BLENDS

This article presents a phenomenological combustion model using turbulent flame propagation theory developed by Keck and coworkers, 1974. The model was adapted to work with gasoline-ethanol blends, following correlations presented by Bayraktar,2005. New sub-models were introduced for intake valve velocity and combustion efficiency. These allow simulating the effect of compression ratio, spark timing and fuel change. Results show good agreement with the ones in the original work as well as with experimental results in a Cooperative Fuels Research (CFR) engine

Variation of Fault Creep Along the Overdue Istanbul-Marmara Seismic Gap in NW Türkiye

Strain energy from tectonic loading can be partly released through aseismic creep. Earthquake repeaters, repeatedly activated brittle fault patches surrounded by creep, indicate steady-state creep that affects the amount of seismic energy available for the next large earthquake along a plate contact. The offshore Main Marmara Fault (MMF) of the North Anatolian Fault Zone represents a seismic gap capable of generating a M > 7 earthquake in direct vicinity to the mega-city Istanbul. Based on a newly compiled seismicity catalog, we identify repeating earthquakes to resolve the spatial creep variability along the MMF during a 15-year period. We observe a maximum of seismic repeaters indicating creep along the central and western MMF segments tapering off toward the locked onshore Ganos fault in the west, and the locked offshore Princes Islands segment immediately south of Istanbul in the east. This indicates a high degree of spatial creep variability along the Istanbul-Marmara seismic gap

Secondary School Students’ Construction and Interpretation of Statistical Tables

Research project PID2019-105601GB-I00/AEI/10.13039/501100011033 (Ministerio de Ciencia e Innovacion) research group FQM-126 (Junta de Andalucia, Spain), and scholarship ANID Number: 72190280.Understanding statistical tables is a main component of statistical literacy, although related research dealing with secondary school students is scarce. The purpose of this study was to investigate secondary school students’ performance when translating graphs to tables and then interpreting the resulting table. Using content analysis of the responses to a questionnaire given to a sample of Spanish students, we analysed the correctness of the constructed table, the semiotic conflicts that appeared in their construction, the interpretation of the table elements, the ability to argue on the basis of the information in the table, and the reading level exhibited by the student in this task. Most students correctly translated a pictogram to a frequency table, and a half of them a double bar graph to a two-way table. The main semiotic conflicts were misinterpretation of the icon in the pictogram and incorrect computation of marginal frequencies. About 40% of the sample correctly justified a statement using the data in the graph and then reached the upper reading level of the graph and table, but only a minority achieved that level when the question required knowledge of the context. The findings of the study suggested points to reinforce the teaching of statistical graphs and tables.Ministerio de Ciencia e Innovacion research group FQM-126 (Junta de Andalucia, Spain) PID2019-105601GB-I00/AEIANID 7219028

Structural and energetic properties of nickel clusters: 2≤N≤1502 \le N \le 150

The four most stable structures of Ni$_N$ clusters with $N$ from 2 to 150 have been determined using a combination of the embedded-atom method in the version of Daw, Baskes and Foiles, the {\it variable metric/quasi-Newton} method, and our own {\it Aufbau/Abbau} method. A systematic study of energetics, structure, growth, and stability of also larger clusters has been carried through without more or less severe assumptions on the initial geometries in the structure optimization, on the symmetry, or on bond lengths. It is shown that cluster growth is predominantly icosahedral with $islands$ of {\it fcc}, {\it tetrahedral} and {\it decahedral} growth. For the first time in unbiased computations it is found that Ni$_{147}$ is the multilayer (third Mackay) icosahedron. Further, we point to an enhanced ability of {\it fcc} clusters to compete with the icosahedral and decahedral structures in the vicinity of N=79. In addition, it is shown that conversion from the {\it hcp}/anti-Mackay kind of icosahedral growth to the {\it fcc}/Mackay one occurs within a transition layer including several cluster sizes. Moreover, we present and apply different analytical tools in studying structural and energetic properties of such a large class of clusters. These include means for identifying the overall shape, the occurrence of atomic shells, the similarity of the clusters with, e.g., fragments of the {\it fcc} crystal or of a large icosahedral cluster, and a way of analysing whether the $N$-atom cluster can be considered constructed from the $(N-1)$-atom one by adding an extra atom. In addition, we compare in detail with results from chemical-probe experiment. Maybe the most central result is that first for clusters with $N$ above 80 general trends can be identified.Comment: 37 pages, 11 figure

Nanoparticle-and liposome-carried drugs: New strategies for active targeting and drug delivery across blood-brain barrier

The blood-brain barrier (BBB), the unusual microvascular endothelial interface between the central nervous system (CNS) and the circulatory system, is a major hindrance to drug delivery in the brain parenchyma. Besides the absence of fenestrations and the abundance of tight junctions, ATP-binding cassette (ABC) transporters critically reduce drug entry within the CNS, as they carry many drugs back into the bloodstream. Nanoparticle-and liposome-carried drugs, because of their increased cellular uptake and reduced efflux through ABC transporters, have been developed in recent times to circumvent the low drug permeability of the BBB. This review discusses the role of ABC transporters in controlling drug penetration into the brain parenchyma, the rationale for using nanoparticle-and liposome-based strategies to increase drug delivery across the BBB and new therapeutic strategies for using nanoparticle-and liposome-carried drugs in different conditions, ranging from CNS tumors and neurodegenerative diseases to viral infections and epilepsy. © 2013 Bentham Science Publishers

Big Defensins, a Diverse Family of Antimicrobial Peptides That Follows Different Patterns of Expression in Hemocytes of the Oyster Crassostrea gigas

Background: Big defensin is an antimicrobial peptide composed of a highly hydrophobic N-terminal region and a cationic C-terminal region containing six cysteine residues involved in three internal disulfide bridges. While big defensin sequences have been reported in various mollusk species, few studies have been devoted to their sequence diversity, gene organization and their expression in response to microbial infections. Findings: Using the high-throughput Digital Gene Expression approach, we have identified in Crassostrea gigas oysters several sequences coding for big defensins induced in response to a Vibrio infection. We showed that the oyster big defensin family is composed of three members (named Cg-BigDef1, Cg-BigDef2 and Cg-BigDef3) that are encoded by distinct genomic sequences. All Cg-BigDefs contain a hydrophobic N-terminal domain and a cationic C-terminal domain that resembles vertebrate beta-defensins. Both domains are encoded by separate exons. We found that big defensins form a group predominantly present in mollusks and closer to vertebrate defensins than to invertebrate and fungi CS alpha beta-containing defensins. Moreover, we showed that Cg-BigDefs are expressed in oyster hemocytes only and follow different patterns of gene expression. While Cg-BigDef3 is non-regulated, both Cg-BigDef1 and Cg-BigDef2 transcripts are strongly induced in response to bacterial challenge. Induction was dependent on pathogen associated molecular patterns but not damage-dependent. The inducibility of Cg-BigDef1 was confirmed by HPLC and mass spectrometry, since ions with a molecular mass compatible with mature Cg-BigDef1 (10.7 kDa) were present in immune-challenged oysters only. From our biochemical data, native Cg-BigDef1 would result from the elimination of a prepropeptide sequence and the cyclization of the resulting N-terminal glutamine residue into a pyroglutamic acid. Conclusions: We provide here the first report showing that big defensins form a family of antimicrobial peptides diverse not only in terms of sequences but also in terms of genomic organization and regulation of gene expression

Efecto sobre la calidad de la leche, características tecnológicas y producción quesera de la raza merina de grazalema frente al cruce con razas mejoradas

En los últimos años se están incorporando masivamente en España, en general y Andalucía en particular, razas ovinas foráneas de aptitud lechera, fundamentalmente las razas Assaf, Awassi y Lacaune. Su introducción está fomentando asimismo, la realización de cruces indiscriminados con nuestras razas ovinas autóctonas, de aptitud lechera pero de menor especialización, al menos cuantitativamente (Casas et al., 2005). El objetivo de este estudio ha sido analizar en dos grupos de animales de un mismo rebaño (ovejas puras de raza Merina de Grazalema, y ovejas cruzadas Merina de Grazalema x Awassi) las características de la producción lechera, y proceder a la elaboración de quesos para estudiar las posibles Consejería de Agricultura y Pesca 34 diferencias tecnológicas de los quesos derivados de ambas elaboraciones. A través del mismo se ha comprobado una mayor producción lechera de las ovejas cruzadas (167,35±13,20 kg frente a 136,84±4,25 kg) pero con un porcentaje de grasa (6,25±0,34 % frente a 8,27±0,22 %), proteína (4,71±0,14 % frente a 5,80±0,09 %) y extracto seco (10,97±0,46 % frente a 14,07±0,28 %) estadísticamente inferior. En cuanto a los parámetros de aptitud tecnológica, los valores de tiempo de coagulación medio (24,70±0,77 minutos), dureza media (dureza del coágulo a los 30 minutos) de 25,03±2,27 mm, y el rendimiento en cuajada (327,50±5,70 g/l), mostraron cifras inferiores a las referenciadas por Casas et al. (2005) para la raza ovina Merina de Grazalema. Finalmente, la velocidad de endurecimiento resultó mayor a los valores obtenidos en el trabajo citado anteriormente (4,59±0,54 min). Por otro lado, estos mismos parámetros mostraron valores inferiores en el tiempo de coagulación (19,60±0,62 minutos), velocidad de endurecimiento (3,97±0,38 min) y rendimiento en cuajada (290,55±6,67), mientras que la dureza media (32,85±2,03 mm) fue superior en las ovejas cruzadas, respecto a los valores encontrados en esta misma explotación para los animales puros. Como consecuencia de todo ello, el rendimiento quesero real fue del 30,25 % para las ovejas puras frente al 23,70 % de las cruzadas. Esto determina que la producción quesera real que se obtiene por oveja pura, sea superior al de la cruzada (41,38 kg queso fresco/ lactación frente a los 39,70 de la cruzada).Proyecto INIA. Ministerio de Educación y Ciencia

Mixed Ti-Zr metal-organic-frameworks for the photodegradation of acetaminophen under solar irradiation

Mixed Ti-Zr metal-organic-frameworks (MOFs)have been synthesized and tested as photocatalysts under solar-simulated radiation using acetaminophen (ACE)as target pollutant. These materials were obtained upon partial substitution of Ti by Zr atoms in the crystalline structure of NH2-MIL-125(Ti)MOF. The effect of the Ti:Zr molar ratio on their characteristics and catalytic behaviour has been analysed. Materials with high Zr relative amount (60–80%)showed amorphous structure and low solar-photocatalytic activity. In contrast, lower Zr proportions resulted in new MOFs with well-defined crystalline structure and high activity for the solar photocatalytic degradation of ACE, even higher than that of the bare Ti MOF. Results with scavengers allowed concluding that O2[rad]− radicals are the main reactive species, although photogenerated [rad]OH radicals and electrons also contribute to the degradation. The stability of the most active photocatalyst was confirmed upon three successive runsThe authors acknowledge the financial support from Spanish MINECO (project CTQ2016-78576-R). M. Peñas-Garzón thanks Spanish MECD for FPU16/00576 grant. Authors thank the Research Support Services of the University of Extremadura (SAIUEx) for its technical and scientific support. We also thank to Dr. Juan Cabanillas for his help with PL measurement