200 research outputs found
Fracture strength and fractographic analysis of zirconia copings treated with four experimental silane primers
This study evaluated and compared the effect of new four experimental silane coupling agents on âthe fracture strength of zirconia copings. The findings were supported with fractographic and âfinite element analyses. All together 125 zirconia copings with a wall thickness of 0.6mm were âfabricated on identical nickel-chromium master dies and then divided randomly into five groups ââ(n = 25). Four test groups were prepared according the experimental silane primer (labeled: âOIWA1, OIWA2, OIWA3 and OIWA4) and one ontrol group without silanization. The silane âmonomers used were: 3-methacryloxypropyltrimethoxysilane (in OIWA1), 3-âacryloxypropyltrimethoxysilane (in OIWA2), 3-isocyanatopropyltriethoxysilane (in OIWA3) and âstyrylethyltrimethoxysilane (in OIWA4). Tribochemical sandblasting (silica-coating) treatment âwas performed to the inner surface of the copings in the test groups. All the specimens were âsilanized at the inner surfaces of the zirconia copings. Self-adhesive universal resin cement was âused to cement the copings to the underlying master die. Zirconia copings were vertically loaded âon the cusp area until the first crack failure was occurred using Precision Universal Tester at a âconstant crosshead speed of 1 mm/min. Then, the machine was manually controlled to cause âmore failure to further determine the texture of fracture. Three dimensional finite element âanalysis and fractography were performed to support the fracture strength findings. Based on the âfinite element analysis results, zirconia silanized with 3-acryloyloxypropyltrimethoxysilane âshowed the highest fracture strength with a mean of 963.75N (SD 4.5 N), while zirconia copings âsilanized with 3 methacryloyloxypropyltrimethoxysilane showed a mean fracture strength value âof 925.65N (SD 2.4 N). Styrylethyltrimethoxysilane-silanised zirconia showed mean fracture âstrength of 895.95N (SD 3.5 N). Adding silane coupling agents to the resin-zirconia interface âincreased the fracture strengths significantly (ANOVA, p < 0.05). Silanization with four new âexperimental silane primers in vitro produced significantly greater fracture strength than the âcontrol group not treated with the test silane.
Insights into Spatial Sensitivities of Ice Mass Response to Environmental Change from the SeaRISE Ice Sheet Modeling Project I: Antarctica
Atmospheric, oceanic, and subglacial forcing scenarios from the Sea-level Response to Ice Sheet Evolution (SeaRISE) project are applied to six three-dimensional thermomechanical ice-sheet models to assess Antarctic ice sheet sensitivity over a 500 year timescale and to inform future modeling and field studies. Results indicate (i) growth with warming, except within low-latitude basins (where inland thickening is outpaced by marginal thinning); (ii) mass loss with enhanced sliding (with basins dominated by high driving stresses affected more than basins with low-surface-slope streaming ice); and (iii) mass loss with enhanced ice shelf melting (with changes in West Antarctica dominating the signal due to its marine setting and extensive ice shelves; cf. minimal impact in the Terre Adelie, George V, Oates, and Victoria Land region of East Antarctica). Ice loss due to dynamic changes associated with enhanced sliding and/or sub-shelf melting exceeds the gain due to increased precipitation. Furthermore, differences in results between and within basins as well as the controlling impact of sub-shelf melting on ice dynamics highlight the need for improved understanding of basal conditions, grounding-zone processes, ocean-ice interactions, and the numerical representation of all three
Cross-National Differences in Victimization : Disentangling the Impact of Composition and Context
Varying rates of criminal victimization across countries are assumed to be the outcome of countrylevel structural constraints that determine the supply ofmotivated oÂĄenders, as well as the differential composition within countries of suitable targets and capable guardianship. However, previous empirical tests of these âcompositionalâ and âcontextualâ explanations of cross-national diÂĄerences
have been performed upon macro-level crime data due to the unavailability of comparable individual-level data across countries. This limitation has had two important consequences for cross-national crime research. First, micro-/meso-level mechanisms underlying cross-national differences cannot be truly inferred from macro-level data. Secondly, the eÂĄects of contextual measures (e.g. income inequality) on crime are uncontrolled for compositional heterogeneity. In this
paper, these limitations are overcome by analysing individual-level victimization data across 18 countries from the International CrimeVictims Survey. Results from multi-level analyses on theft and violent victimization indicate that the national level of income inequality is positively related to risk, independent of compositional (i.e. micro- and meso-level) diÂĄerences. Furthermore, crossnational variation in victimization rates is not only shaped by diÂĄerences in national context, but
also by varying composition. More speciÂącally, countries had higher crime rates the more they consisted of urban residents and regions with lowaverage social cohesion.
Recommended from our members
The future sea-level contribution of the Greenland ice sheet: A multi-model ensemble study of ISMIP6
The Greenland ice sheet is one of the largest contributors to global mean sea-level rise today and is expected to continue to lose mass as the Arctic continues to warm. The two predominant mass loss mechanisms are increased surface meltwater run-off and mass loss associated with the retreat of marine-terminating outlet glaciers. In this paper we use a large ensemble of Greenland ice sheet models forced by output from a representative subset of the Coupled Model Intercomparison Project (CMIP5) global climate models to project ice sheet changes and sea-level rise contributions over the 21st century. The simulations are part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6).We estimate the sea-level contribution together with uncertainties due to future climate forcing, ice sheet model formulations and ocean forcing for the two greenhouse gas concentration scenarios RCP8.5 and RCP2.6. The results indicate that the Greenland ice sheet will continue to lose mass in both scenarios until 2100, with contributions of 90-50 and 32-17mm to sea-level rise for RCP8.5 and RCP2.6, respectively. The largest mass loss is expected from the south-west of Greenland, which is governed by surface mass balance changes, continuing what is already observed today. Because the contributions are calculated against an unforced control experiment, these numbers do not include any committed mass loss, i.e. mass loss that would occur over the coming century if the climate forcing remained constant. Under RCP8.5 forcing, ice sheet model uncertainty explains an ensemble spread of 40 mm, while climate model uncertainty and ocean forcing uncertainty account for a spread of 36 and 19 mm, respectively. Apart from those formally derived uncertainty ranges, the largest gap in our knowledge is about the physical understanding and implementation of the calving process, i.e. the interaction of the ice sheet with the ocean. © Author(s) 2020
Overexpression of Mitochondrial Uncoupling Protein 2 Inhibits Inflammatory Cytokines and Activates Cell Survival Factors after Cerebral Ischemia
Mitochondria play a critical role in cell survival and death after cerebral ischemia. Uncoupling proteins (UCPs) are inner mitochondrial membrane proteins that disperse the mitochondrial proton gradient by translocating H+ across the inner membrane in order to stabilize the inner mitochondrial membrane potential (ÎΚm) and reduce the formation of reactive oxygen species. Previous studies have demonstrated that mice transgenically overexpressing UCP2 (UCP2 Tg) in the brain are protected from cerebral ischemia, traumatic brain injury and epileptic challenges. This study seeks to clarify the mechanisms responsible for neuroprotection after transient focal ischemia. Our hypothesis is that UCP2 is neuroprotective by suppressing innate inflammation and regulating cell cycle mediators. PCR gene arrays and protein arrays were used to determine mechanisms of damage and protection after transient focal ischemia. Our results showed that ischemia increased the expression of inflammatory genes and suppressed the expression of anti-apoptotic and cell cycle genes. Overexpression of UCP2 blunted the ischemia-induced increase in IL-6 and decrease in Bcl2. Further, UCP2 increased the expression of cell cycle genes and protein levels of phospho-AKT, PKC and MEK after ischemia. It is concluded that the neuroprotective effects of UCP2 against ischemic brain injury are associated with inhibition of pro-inflammatory cytokines and activation of cell survival factors
The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6
The Greenland ice sheet is one of the largest contributors to global mean sea-level rise today and is expected to continue to lose mass as the Arctic continues to warm. The two predominant mass loss mechanisms are increased surface meltwater run-off and mass loss associated with the retreat of marine-terminating outlet glaciers. In this paper we use a large ensemble of Greenland ice sheet models forced by output from a representative subset of the Coupled Model Intercomparison Project (CMIP5) global climate models to project ice sheet changes and sea-level rise contributions over the 21st century. The simulations are part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We estimate the sea-level contribution together with uncertainties due to future climate forcing, ice sheet model formulations and ocean forcing for the two greenhouse gas concentration scenarios RCP8.5 and RCP2.6. The results indicate that the Greenland ice sheet will continue to lose mass in both scenarios until 2100, with contributions of 90±50 and 32±17âmm to sea-level rise for RCP8.5 and RCP2.6, respectively. The largest mass loss is expected from the south-west of Greenland, which is governed by surface mass balance changes, continuing what is already observed today. Because the contributions are calculated against an unforced control experiment, these numbers do not include any committed mass loss, i.e. mass loss that would occur over the coming century if the climate forcing remained constant. Under RCP8.5 forcing, ice sheet model uncertainty explains an ensemble spread of 40âmm, while climate model uncertainty and ocean forcing uncertainty account for a spread of 36 and 19âmm, respectively. Apart from those formally derived uncertainty ranges, the largest gap in our knowledge is about the physical understanding and implementation of the calving process, i.e. the interaction of the ice sheet with the ocean
Autophagy Impairment Induces Premature Senescence in Primary Human Fibroblasts
BACKGROUND:Recent studies have demonstrated that activation of autophagy increases the lifespan of organisms from yeast to flies. In contrast to the lifespan extension effect in lower organisms, it has been reported that overexpression of unc-51-like kinase 3 (ULK3), the mammalian homolog of autophagy-specific gene 1 (ATG1), induces premature senescence in human fibroblasts. Therefore, we assessed whether the activation of autophagy would genuinely induce premature senescence in human cells. METHODOLOGY/PRINCIPAL FINDINGS:Depletion of ATG7, ATG12, or lysosomal-associated membrane protein 2 (Lamp2) by transfecting siRNA or infecting cells with a virus containing gene-specific shRNA resulted in a senescence-like state in two strains of primary human fibroblasts. Prematurely senescent cells induced by autophagy impairment exhibited the senescent phenotypes, similar to the replicatively senescent cells, such as increased senescence associated ÎČ-galactosidase (SA-ÎČ-gal) activity, reactive oxygen species (ROS) generation, and accumulation of lipofuscin. In addition, expression levels of ribosomal protein S6 kinase1 (S6K1), p-S6K1, p-S6, and eukaryotic translation initiation factor 4E (eIF4E) binding protein 1 (4E-BP1) in the mammalian target of rapamycin (mTOR) pathway and beclin-1, ATG7, ATG12-ATG5 conjugate, and the sequestosome 1 (SQSTM1/p62) monomer in the autophagy pathway were decreased in both the replicatively and the autophagy impairment-induced prematurely senescent cells. Furthermore, it was found that ROS scavenging by N-acetylcysteine (NAC) and inhibition of p53 activation by pifithrin-α or knockdown of p53 using siRNA, respectively, delayed autophagy impairment-induced premature senescence and restored the expression levels of components in the mTOR and autophagy pathways. CONCLUSION:Taken together, we concluded that autophagy impairment induces premature senescence through a ROS- and p53-dependent manner in primary human fibroblasts
Recommended from our members
Future Sea Level Change Under Coupled Model Intercomparison Project Phase 5 and Phase 6 Scenarios From the Greenland and Antarctic Ice Sheets
Projections of the sea level contribution from the Greenland and Antarctic ice sheets (GrIS and AIS) rely on atmospheric and oceanic drivers obtained from climate models. The Earth System Models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6) generally project greater future warming compared with the previous Coupled Model Intercomparison Project phase 5 (CMIP5) effort. Here we use four CMIP6 models and a selection of CMIP5 models to force multiple ice sheet models as part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We find that the projected sea level contribution at 2100 from the ice sheet model ensemble under the CMIP6 scenarios falls within the CMIP5 range for the Antarctic ice sheet but is significantly increased for Greenland. Warmer atmosphere in CMIP6 models results in higher Greenland mass loss due to surface melt. For Antarctica, CMIP6 forcing is similar to CMIP5 and mass gain from increased snowfall counteracts increased loss due to ocean warming
Magnetic Fields toward Ophiuchus-B Derived from SCUBA-2 Polarization Measurements
We present the results of dust emission polarization measurements of Ophiuchus-B (Oph-B) carried out using the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) camera with its associated polarimeter (POL-2) on the James Clerk Maxwell Telescope in Hawaii. This work is part of the B-fields in Star-forming Region Observations survey initiated to understand the role of magnetic fields in star formation for nearby star-forming molecular clouds. We present a first look at the geometry and strength of magnetic fields in Oph-B. The field geometry is traced over ~0.2 pc, with clear detection of both of the sub-clumps of Oph-B. The field pattern appears significantly disordered in sub-clump Oph-B1. The field geometry in Oph-B2 is more ordered, with a tendency to be along the major axis of the clump, parallel to the filamentary structure within which it lies. The degree of polarization decreases systematically toward the dense core material in the two sub-clumps. The field lines in the lower density material along the periphery are smoothly joined to the large-scale magnetic fields probed by NIR polarization observations. We estimated a magnetic field strength of 630 ± 410 ÎŒG in the Oph-B2 sub-clump using a DavisâChandrasekharâFermi analysis. With this magnetic field strength, we find a mass-to-flux ratio λ = 1.6 ± 1.1, which suggests that the Oph-B2 clump is slightly magnetically supercritical
- âŠ