633 research outputs found
Diseño de malla de perforación y voladura para mejorar la fragmentación de la roca - Cantera El Pedregal Reque
La investigación que se centra en la cantera El Pedregal ubicada en la ciudad de
Reque. La problemática que presentaba la empresa al realizar la voladura en los
bancos, por ello se tomó como muestra un banco que se estuvo explotando en el
lapso de estudio. Esta investigación tiene un enfoque cuantitativo y un diseño de
investigación no experimental transversal explicativo. Además, se utilizó la técnica
de observación y la técnica de análisis documental con sus respectivos
instrumentos para el recojo de información. Estos instrumentos fueron validados
por expertos. Para el procesamiento de los datos se utilizó el método analíticossintético
y el método de procesos. En el desarrollo de los resultados se comprobó
y analizo la geología regional, local y estructural de la zona concesionada. También
se evaluó la fragmentación de la malla que se estuvo trabajando anteriormente en
la cantera. De igual manera se logró diseñar una malla de perforación que
cumpliera con el objetivo de mejorar la fragmentación haciendo simulaciones
consecutivas en el software JK-Simblast. Finalmente, se evaluó el costo de la nueva
malla propuesta, la cual tuvo un mayor costo de explosivos, pero una mejor
fragmentación
`I make up a silly name': Understanding Children's Perception of Privacy Risks Online
Children under 11 are often regarded as too young to comprehend the
implications of online privacy. Perhaps as a result, little research has
focused on younger kids' risk recognition and coping. Such knowledge is,
however, critical for designing efficient safeguarding mechanisms for this age
group. Through 12 focus group studies with 29 children aged 6-10 from UK
schools, we examined how children described privacy risks related to their use
of tablet computers and what information was used by them to identify threats.
We found that children could identify and articulate certain privacy risks
well, such as information oversharing or revealing real identities online;
however, they had less awareness with respect to other risks, such as online
tracking or game promotions. Our findings offer promising directions for
supporting children's awareness of cyber risks and the ability to protect
themselves online.Comment: 13 pages, 1 figur
Simultaneous Colorimetric Detection of a Variety of Salmonella spp. in Food and Environmental Samples by Optical Biosensing Using Oligonucleotide-Gold Nanoparticles
Optical biosensors for rapid detection of significant foodborne pathogens are steadily gaining popularity due to its simplicity and sensitivity. While nanomaterials such as gold nanoparticles (AuNPs) are commonly used as signal amplifiers for optical biosensors, AuNPs can also be utilized as a robust biosensing platform. Many reported optical biosensors were designed for individual pathogen detection in a single assay and have high detection limit (DL). Salmonella spp. is one of the major causative agents of foodborne sickness, hospitalization and deaths. Unfortunately, there are around 2,000 serotypes of Salmonella worldwide, and rapid and simultaneous detection of multiple strains in a single assay is lacking. In this study, a comprehensive and highly sensitive simultaneous colorimetric detection of nineteen (19) environmental and outbreak Salmonella spp. strains was achieved by a novel optical biosensing platform using oligonucleotide-functionalized AuNPs. A pair of newly designed single stranded oligonucleotides (30-mer) was displayed onto the surface of AuNPs (13 nm) as detection probes to hybridize with a conserved genomic region (192-bases) of ttrRSBCA found on a broad range of Salmonella spp. strains. The sandwich hybridization (30 min, 55°C) resulted in a structural formation of highly stable oligonucleotide/AuNPs-DNA complexes which remained undisturbed even after subjecting to an increased salt concentration (2 M, final), thus allowing a direct discrimination via color change of target (red color) from non-target (purplish-blue color) reaction mixtures by direct observation using the naked eye. In food matrices (blueberries and chicken meat), nineteen different Salmonella spp. strains were concentrated using immunomagnetic separation and then simultaneously detected in a 96-well microplate by oligonucleotide-functionalized AuNPs after DNA preparation. Successful oligonucleotide/AuNPs-DNA hybridization was confirmed by gel electrophoresis while AuNPs aggregation in non-target and control reaction mixtures was verified by both spectrophotometric analysis and TEM images. Results showed that the optical AuNP biosensing platform can simultaneously screen nineteen (19) viable Salmonella spp. strains tested with 100% specificity and a superior detection limit of <10 CFU/mL or g for both pure culture and complex matrices setups. The highly sensitive colorimetric detection system can significantly improve the screening and detection of viable Salmonella spp. strains present in complex food and environmental matrices, therefore reducing the risks of contamination and incidence of foodborne diseases
A census of X-ray nuclear activity in nearby galaxies
We have studied the X-ray nuclear activity of 187 nearby (distance < 15 Mpc)
galaxies observed with Chandra/ACIS. We found that 86 of them have a point-like
X-ray core, consistent with an accreting black hole (BH). We argue that the
majority of them are nuclear BHs, rather than X-ray binaries. The fraction of
galaxies with an X-ray detected nuclear BH is higher (~60 per cent) for
ellipticals and early-type spirals (E to Sb), and lower (~30 per cent) for
late-type spirals (Sc to Sm). There is no preferential association of X-ray
cores with a large-scale bar; in fact, strongly barred galaxies appear to have
slightly lower detection fraction and luminosity for their nuclear X-ray
sources, compared with non-barred or weakly barred galaxies of similar Hubble
types. The cumulative luminosity distribution of the nuclear sources in the
0.3-8 keV band is a power-law with slope ~-0.5, from ~2 x 10^{38} erg/s to
~10^{42} erg/s. The Eddington ratio is lower for ellipticals (L_{X}/L_{Edd} ~
10^{-8}) and higher for late-type spirals (up to L_{X}/L_{Edd} ~ 10^{-4}), but
in all cases, the accretion rate is low enough to be in the
radiatively-inefficient regime. The intrinsic NH is generally low, especially
for the less luminous sources: there appear to be no Type-2 nuclear BHs at
luminosities <~ 10^{39} erg/s. The lack of a dusty torus or of other sources of
intrinsic absorption (e.g., an optically-thick disk wind) may be directly
related to the lack of a standard accretion disk around those faint nuclear
BHs. The fraction of obscured sources increases with the nuclear BH luminosity:
2/3 of the sources with L_{X} > 10^{40} erg/s have a fitted NH > 10^{22}
cm^{-2}. This is contrary to the declining trend of the obscured fraction with
increasing luminosities, observed in more luminous AGN and quasars.Comment: 27 pages, 353 kB, accepted by Ap
Nitrate-Dependent Iron Oxidation: A Potential Mars Metabolism
This work considers the hypothetical viability of microbial nitrate-dependent Fe2+ oxidation (NDFO) for supporting simple life in the context of the early Mars environment. This draws on knowledge built up over several decades of remote and in situ observation, as well as recent discoveries that have shaped current understanding of early Mars. Our current understanding is that certain early martian environments fulfill several of the key requirements for microbes with NDFO metabolism. First, abundant Fe2+ has been identified on Mars and provides evidence of an accessible electron donor; evidence of anoxia suggests that abiotic Fe2+ oxidation by molecular oxygen would not have interfered and competed with microbial iron metabolism in these environments. Second, nitrate, which can be used by some iron oxidizing microorganisms as an electron acceptor, has also been confirmed in modern aeolian and ancient sediment deposits on Mars. In addition to redox substrates, reservoirs of both organic and inorganic carbon are available for biosynthesis, and geochemical evidence suggests that lacustrine systems during the hydrologically active Noachian period (4.1–3.7 Ga) match the circumneutral pH requirements of nitrate-dependent iron-oxidizing microorganisms. As well as potentially acting as a primary producer in early martian lakes and fluvial systems, the light-independent nature of NDFO suggests that such microbes could have persisted in sub-surface aquifers long after the desiccation of the surface, provided that adequate carbon and nitrates sources were prevalent. Traces of NDFO microorganisms may be preserved in the rock record by biomineralization and cellular encrustation in zones of high Fe2+ concentrations. These processes could produce morphological biosignatures, preserve distinctive Fe-isotope variation patterns, and enhance preservation of biological organic compounds. Such biosignatures could be detectable by future missions to Mars with appropriate instrumentation
VERITAS Search for VHE Gamma-ray Emission from Dwarf Spheroidal Galaxies
Indirect dark matter searches with ground-based gamma-ray observatories
provide an alternative for identifying the particle nature of dark matter that
is complementary to that of direct search or accelerator production
experiments. We present the results of observations of the dwarf spheroidal
galaxies Draco, Ursa Minor, Bootes 1, and Willman 1 conducted by VERITAS. These
galaxies are nearby dark matter dominated objects located at a typical distance
of several tens of kiloparsecs for which there are good measurements of the
dark matter density profile from stellar velocity measurements. Since the
conventional astrophysical background of very high energy gamma rays from these
objects appears to be negligible, they are good targets to search for the
secondary gamma-ray photons produced by interacting or decaying dark matter
particles. No significant gamma-ray flux above 200 GeV was detected from these
four dwarf galaxies for a typical exposure of ~20 hours. The 95% confidence
upper limits on the integral gamma-ray flux are in the range 0.4-2.2x10^-12
photons cm^-2s^-1. We interpret this limiting flux in the context of pair
annihilation of weakly interacting massive particles and derive constraints on
the thermally averaged product of the total self-annihilation cross section and
the relative velocity of the WIMPs. The limits are obtained under conservative
assumptions regarding the dark matter distribution in dwarf galaxies and are
approximately three orders of magnitude above the generic theoretical
prediction for WIMPs in the minimal supersymmetric standard model framework.
However significant uncertainty exists in the dark matter distribution as well
as the neutralino cross sections which under favorable assumptions could
further lower the limits.Comment: 21 pages, 2 figures, updated to reflect version published in ApJ.
NOTE: M.D. Wood added as autho
Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis
BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London
The VICI-trial: high frequency oscillation versus conventional mechanical ventilation in newborns with congenital diaphragmatic hernia: an international multicentre randomized controlled trial
Background: Congenital diaphragmatic hernia (CDH) is a severe congenital anomaly of the diaphragm resulting in pulmonary hypoplasia and pulmonary hypertension. It is associated with a high risk of mortality and pulmonary morbidity. Previous retrospective studies have reported high frequency oscillatory ventilation (HFO) to reduce pulmonary morbidity in infants with CDH, while others indicated HFO to be associated with worse outcome. We therefore aimed to develop a randomized controlled trial to compare initial ventilatory treatment with high-frequency oscillation and conventional ventilation in infants with CDH.Methods/design: This trial is designed as a multicentre trial in which 400 infants (200 in each arm) will be included. Primary outcome measures are BPD, described as oxygen dependency by day 28 according to the definition of Jobe and Bancalari, and/or mortality by day 28. All liveborn infants with CDH born at a gestational age of over 34 weeks and no other severe congenital anomalies are eligible for inclusion. Parental informed consent is asked antenatally and the allocated ventilation mode starts within two hours after birth. Laboratory samples of blood, urine and tracheal aspirate are taken at the first day of life, day 3, day 7, day 14 and day 28 to evaluate laboratory markers for ventilator-induced lung injury and pulmonary hypertension.Discussion: To date, randomized clinical trials are lacking in the field of CDH. The VICI-trial, as the first randomized clinical trial in the field of CDH, may provide further insight in ventilation strategies in CDH patient. This may hopefully prevent mortality and morbidity.Trial registration: Netherlands Trial Register (NTR): NTR1310
Systematic optimization of poly(vinyl chloride) surface modification with an aromatic thiol
Abstract The efficient covalent functionalization of poly(vinyl chloride) (PVC), which is widely used in medical device manufacture, allows an array of potential property-enhancing surface modifications to be made. To demonstrate a general method of functionalization via substituted (functional) thiols, we describe a systematic approach to the optimization of PVC surface modification by nucleophilic substitution with 4-aminothiophenol through control of reaction conditions: solvent composition, sonication, reaction time and presence of base and/or phase transfer catalyst (PTC). Efficient thiol attachment was confirmed using solid-state NMR and Raman spectroscopies, and the extent of surface modification was quantified using ATR-FTIR spectroscopy. Sonicated samples exhibited a lower degree of modification than their statically immersed counterparts (21.7 vs 99.6 μg cm-3), and mechanical integrity was compromised. In DMSO/H2O systems with a PTC, resultant degrees of PVC surface modification were up to 12.5% higher when caesium carbonate was employed as the base than in corresponding systems with potassium carbonate
Mutations involving the SRY-related gene SOX8 are associated with a spectrum of human reproductive anomalies.
© The Author(s) 2018. Published by Oxford University Press. All rights reserved. SOX8 is an HMG-box transcription factor closely related to SRY and SOX9. Deletion of the gene encoding Sox8 in mice causes reproductive dysfunction but the role of SOX8 in humans is unknown. Here, we show that SOX8 is expressed in the somatic cells of the early developing gonad in the human and influences human sex determination. We identified two individuals with 46, XY disorders/differences in sex development (DSD) and chromosomal rearrangements encompassing the SOX8 locus and a third individual with 46, XY DSD and a missense mutation in the HMG-box of SOX8. In vitro functional assays indicate that this mutation alters the biological activity of the protein. As an emerging body of evidence suggests that DSDs and infertility can have common etiologies, we also analysed SOX8 in a cohort of infertile men (n=274) and two independent cohorts of women with primary ovarian insufficiency (POI; n=153 and n=104). SOX8 mutations were found at increased frequency in oligozoospermic men (3.5%; P < 0.05) and POI (5.06%; P=4.5×10 -5 ) as compared with fertile/normospermic control populations (0.74%). The mutant proteins identified altered SOX8 biological activity as compared with the wild-type protein. These data demonstrate that SOX8 plays an important role in human reproduction and SOX8 mutations contribute to a spectrum of phenotypes including 46, XY DSD, male infertility and 46, XX POI.Link_to_subscribed_fulltex
- …