RDF-TR: Exploiting structural redundancies to boost RDF compression

The number and volume of semantic data have grown impressively over the last decade, promoting compression as an essential tool for RDF preservation, sharing and management. In contrast to universal compressors, RDF compression techniques are able to detect and exploit specific forms of redundancy in RDF data. Thus, state-of-the-art RDF compressors excel at exploiting syntactic and semantic redundancies, i.e., repetitions in the serialization format and information that can be inferred implicitly. However, little attention has been paid to the existence of structural patterns within the RDF dataset; i.e. structural redundancy. In this paper, we analyze structural regularities in real-world datasets, and show three schema-based sources of redundancies that underpin the schema-relaxed nature of RDF. Then, we propose RDF-Tr (RDF Triples Reorganizer), a preprocessing technique that discovers and removes this kind of redundancy before the RDF dataset is effectively compressed. In particular, RDF-Tr groups subjects that are described by the same predicates, and locally re-codes the objects related to these predicates. Finally, we integrate RDF-Tr with two RDF compressors, HDT and k2-triples. Our experiments show that using RDF-Tr with these compressors improves by up to 2.3 times their original effectiveness, outperforming the most prominent state-of-the-art techniques

Van der Waals spin valves

We propose spin valves where a 2D non-magnetic conductor is intercalated between two ferromagnetic insulating layers. In this setup, the relative orientation of the magnetizations of the insulating layers can have a strong impact on the in-plane conductivity of the 2D conductor. We first show this for a graphene bilayer, described with a tight-binding model, placed between two ferromagnetic insulators. In the anti-parallel configuration, a band gap opens at the Dirac point, whereas in the parallel configuration, the graphene bilayer remains conducting. We then compute the electronic structure of graphene bilayer placed between two monolayers of the ferromagnetic insulator CrI$_3$, using density functional theory. Consistent with the model, we find that a gap opens at the Dirac point only in the antiparallel configuration.Comment: 5 pages, 4 figure

Compressed k2-Triples for Full-In-Memory RDF Engines

Current "data deluge" has flooded the Web of Data with very large RDF datasets. They are hosted and queried through SPARQL endpoints which act as nodes of a semantic net built on the principles of the Linked Data project. Although this is a realistic philosophy for global data publishing, its query performance is diminished when the RDF engines (behind the endpoints) manage these huge datasets. Their indexes cannot be fully loaded in main memory, hence these systems need to perform slow disk accesses to solve SPARQL queries. This paper addresses this problem by a compact indexed RDF structure (called k2-triples) applying compact k2-tree structures to the well-known vertical-partitioning technique. It obtains an ultra-compressed representation of large RDF graphs and allows SPARQL queries to be full-in-memory performed without decompression. We show that k2-triples clearly outperforms state-of-the-art compressibility and traditional vertical-partitioning query resolution, remaining very competitive with multi-index solutions.Comment: In Proc. of AMCIS'201

An Empirical Study of Real-World SPARQL Queries

Understanding how users tailor their SPARQL queries is crucial when designing query evaluation engines or fine-tuning RDF stores with performance in mind. In this paper we analyze 3 million real-world SPARQL queries extracted from logs of the DBPedia and SWDF public endpoints. We aim at finding which are the most used language elements both from syntactical and structural perspectives, paying special attention to triple patterns and joins, since they are indeed some of the most expensive SPARQL operations at evaluation phase. We have determined that most of the queries are simple and include few triple patterns and joins, being Subject-Subject, Subject-Object and Object-Object the most common join types. The graph patterns are usually star-shaped and despite triple pattern chains exist, they are generally short.Comment: 1st International Workshop on Usage Analysis and the Web of Data (USEWOD2011) in the 20th International World Wide Web Conference (WWW2011), Hyderabad, India, March 28th, 201

Searching for a dipole modulation in the large-scale structure of the Universe

Several statistical anomalies in the CMB temperature anisotropies seem to defy the assumption of a homogeneous and isotropic universe. In particular, a dipole modulation has been detected both in WMAP and Planck data. We adapt the methodology proposed by Eriksen et al. (2007) on CMB data to galaxy surveys, tracing the large-scale structure. We analyse the NRAO VLA Sky Survey (NVSS) data at a resolution of ~2 degrees for three different flux thresholds: 2.5, 5.0 and 10.0 mJy respectively. No evidence of a dipole modulation is found. This result suggests that the origin of the dipole asymmetry found in the CMB cannot be assigned to secondary anisotropies produced at redshifts around z = 1. However, it could still have been generated at redshifts higher or lower, such as the integrated Sachs-Wolfe effect produced by the local structures. Other all-sky surveys, like the infrared WISE catalogue, could help to explore with a high sensitivity a redshift interval closer than the one probed with NVSS.Comment: 6 pages, 2 figures. Some minor changes have been done from the original manuscript. This paper is accepted by MNRA

Working Environment in Nursing: Needs Improvement?

Background: Knowing the quality of life of professionals is important because it is related to job performance, better results, and greater productivity, which results in better patient care. Objective: To know the Professional Quality of Life perceived by the nurses at the Geriatric Hospital of Toledo (Spain). Method: A descriptive cross-section study was employed to measure the Professional Quality of Life of all healthcare nurses (69 in total) at the Geriatric Hospital of Toledo. The questionnaire used as a measuring instrument was the Professional Quality of Life - 35. The data obtained was analyzed by means of: descriptive statistics, single-factor ANOVA variance analysis, T Student tests, and simple and multiple regression analysis. The study was approved by both the research commission and the ethics commission at the Hospital Complex of Toledo. Participation in the study on behalf of the nursing staff was voluntary. Results: In total, 45 responses were obtained (65.2%). The overall mean score measured the perceived Professional Quality of Life to be low. In relation to the three dimensions evaluated in the study, the highest average found was in “intrinsic motivation,” followed by “workload”, and then “management support.” In the multivariate analysis, “management support” was shown as the most influential factor in the Professional Quality of Life with a 23% influence (P<0.001), followed by workload with 9% (P = 0.01). Conclusions: The professionals at the participating center perceive their workplace as having an elevated degree of responsibility, a large quantity of work, a high occurrence of rushes and fatigue, and all this with little support on behalf of management. Promotions are scarce or the policies for receiving a promotion are inadequate. The perception of Professional Quality of Life in nursing is low. The obtained results indicate a need for an organizing cultural change based on participation, motivation, and increased management support

C-S-H gels in blended cements: Study by infrared spectroscopy

ICCC 2015, Beijing, China, 13~16 October 2015; http://iccc2015.csp.escience.cn/dct/page/1C-S-H gel is the main product in the Portland cement (PC) hydration. Of their structure and composition depends the cement properties (strength, durability¿). The mixes of others materials with PC provides new cementitious materials with different properties. Understand the changes produces in the hydration products in these blends improves their use. This work studies the changes produced in the C-S-H gel by means Fourier Transform Infrared Spectroscopy (FTIR). Several samples were studied, PC (as reference system), a system formed by PC and calcium aluminate cement (CAC) with a 75/25 ratio, and two system formed by PC, CAC and calcium sulfate (C¿) with an 85/15 ratio of PC/CAC with 3 and 5% of C¿. All samples were cured in two environmental; at the air and under water, in order to observe the influence of curing. The samples were studied at the 6 hours, 7 days, 12 and 32 months of age. Results show in the PC, it changes to lower wavenumbers in the Q2 units positions over time. This fact indicates a little transformation of structure like-tobermorite to structure like-jennite providing a C-S-H less compact. Addition of CAC in PC hydration decreases the migration of Q2 units to lower wavenumbers indicating that C-S-H structure is more compact in this case. When C¿ is included in the system, this migration of Q2 units is lower and the bands are sharper indicating the structure like tobermorite presence. Other effect visible in the spectra is the decrease of bands due to Q1 units with the addition of CAC. The greater presence of aluminates in the system provides substitutions of Si4+ by Al3+ in the C-S-H structure. This fact produces longer chains reducing the units Q1. Different behaviors are observed in the cured conditions showing higher transformation towards structures like-jennite in the samples cured under water. Several conclusions can be drawn of this work. First, it use of infrared spectroscopy as powerful tool in the cement chemistry field. Not only as characterization technique but also it can be used for obtain structural information about cement phases, both hydrated as anhydrous. Regarding addition of other hydraulic materials at PC, the study shows formation of C-S-H more compact that will provide better mechanical properties. Also the cured conditions have influenced about hydrated products structure.Peer Reviewe

Utility of Masson’s Trichrome Stain in the Quantification of Mean Vascular Density in Normal Oral Mucosa, Epithelial Dysplasia and Oral Squamous Cell Carcinoma

Indexación: Scopus; Scielo.El objetivo de este estudio fue valuar la utilidad del uso de la tinción de Tricrómico de Masson (TM) en la cuantificación de la densidad media vascular (DMV) en Mucosa Oral Normal (MON), Displasia Epitelial Oral (DEO) y Carcinoma Oral de Células Escamosas (COCE). Estudio descriptivo de serie de casos. Se analizaron 17 muestras de MON, 15 muestras de DEO y 16 de COCE, teñidas con TM. Para determinar su utilidad, se compararon con las mismas muestras analizadas con técnica de inmunohistoquímica contra CD31. La cuantificación de la DMV se realizó en las 3 áreas de mayor vascularización de cada muestra. Se determinó la DMV según diagnóstico mediante la tinción TM e inmunohistoquímica contra CD31, y se calculó la correlación entre ambos. La DMV cuantificada con TM y contra CD31 difiere según el diagnóstico, observándose un aumento de la DMV al malignizarse el diagnóstico. No se encontraron diferencias al comparar la DMV cuantificada con TM y contra CD31. La correlación de la DMV analizado por TM y contra CD31 es significativa y moderada. La cuantificación de vasos sanguíneos es posible mediante la tinción de TM en muestras de MON, DEO y COCE, con una correlación moderada con la inmunohistoquímica contra CD31.The objective of this study was to evaluate the utility of Masson's Trichrome (TM) staining in the quantification of the mean vascular density (DMV) in samples of normal oral mucosa (MON), oral epithelial dysplasia (ODE) and oral squamous cell carcinoma (COCE). The design - a descriptive study of case series. We analyzed 17 samples of MON, 15 samples of DEO and 16 samples of COCE, stained with TM. To determine usefulness, we compared and analyzed the same samples, either stained with TM or with immunohistochemical technique against CD31. Quantification of the DMV was performed in the 3 areas of greatest vascularization in each sample. DMV was determined according to diagnosis by TM staining and immunohistochemistry against CD31, and the correlation between the two was then calculated. DMV quantified with TM and against CD31 differs according to the diagnosis, with an increase in DMV upon malignant diagnosis. No differences were found when comparing DMV quantified with TM and against CD31. The correlation of the DMV analyzed by TM and against CD31 is significant and moderate. Quantification of blood vessels is possible by TM staining in samples of MON, DEO and COCE. TM staining is moderately correlated with immunohistochemistry against CD31.https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0717-95022017000401576&lng=en&nrm=iso&tlng=e

Point defects on graphene on metals

Understanding the coupling of graphene with its local environment is critical to be able to integrate it in tomorrow's electronic devices. Here we show how the presence of a metallic substrate affects the properties of an atomically tailored graphene layer. We have deliberately introduced single carbon vacancies on a graphene monolayer grown on a Pt(111) surface and investigated its impact in the electronic, structural and magnetic properties of the graphene layer. Our low temperature scanning tunneling microscopy studies, complemented by density functional theory, show the existence of a broad electronic resonance above the Fermi energy associated with the vacancies. Vacancy sites become reactive leading to an increase of the coupling between the graphene layer and the metal substrate at these points; this gives rise to a rapid decay of the localized state and the quenching of the magnetic moment associated with carbon vacancies in free-standing graphene layers