115 research outputs found
Determination of fire and explosion characteristics of dust
The aim of this paper is to approximate danger of dust clouds normally occur by determining their explosion characteristics. Nowadays, dusty environment is phenomenon in the industry. In general, about 70% of dust produced is explosive. Dust reduction in companies is the main purpose of the national and European legislative. Early identification and characterization of dust in companies may reduce the risk of explosion. It could be used to identify hazards in industrial production where an explosive dust is produced. For this purpose several standards for identification and characterization of explosion characteristics of industrial dust are being used
Graphene and graphene oxide on Ir(111) are transparent to wetting but not to icing
Anti-icing coatings reduce the freezing onset temperature for water by changing the chemical and physical environment at the water-substrate interface to prevent ice nucleation and growth. Graphene oxide has several attributes that make it attractive as an anti-icing coating and it has been theoretically predicted that graphene oxide has a lower freezing onset temperature than pristine graphene. Here, we test this hypothesis using carefully prepared, well-characterized graphene oxide substrates. We compare the water contact angle for graphene and graphene oxide coatings, both prepared on iridium(111) surfaces. The results show both materials to be transparent to wetting, but indicate a lower freezing onset temperature for graphene oxide than for pristine graphene. The measured water contact angles are dominated by the properties of the underlying Ir(111) substrate while the freezing onset temperature is dictated by the functional groups present on the graphene basal plane. We suggest that the lowering of the freezing onset temperature is caused by the formation of a viscous water layer on the surface. Scanning tunneling microscopy and x-ray photoelectron spectroscopy data are used to evaluate the robustness of the coating material and suggest ways to improve the long-term performance, namely by advancing strategies to avoid water intercalation.publishedVersio
Savor the Cryosphere
This article provides concise documentation of the ongoing retreat of glaciers, along with the implications that the ice loss presents, as well as suggestions for geoscience educators to better convey this story to both students and citizens. We present the retreat of glaciers—the loss of ice—as emblematic of the recent, rapid contraction of the cryosphere. Satellites are useful for assessing the loss of ice across regions with the passage of time. Ground-based glaciology, particularly through the study of ice cores, can record the history of environmental conditions present during the existence of a glacier. Repeat photography vividly displays the rapid retreat of glaciers that is characteristic across the planet. This loss of ice has implications to rising sea level, greater susceptibility to dryness in places where people rely upon rivers delivering melt water resources, and to the destruction of natural environmental archives that were held within the ice. Warming of the atmosphere due to rising concentrations of greenhouse gases released by the combustion of fossil fuels is causing this retreat. We highlight multimedia productions that are useful for teaching this story effectively. As geoscience educators, we attempt to present the best scholarship as accurately and eloquently as we can, to address the core challenge of conveying the magnitude of anthropogenic impacts, while also encouraging optimistic determination on the part of students, coupled to an increasingly informed citizenry. We assert that understanding human perturbation of nature, then choosing to engage in thoughtful science-based decision-making, is a wise choice. This topic comprised “Savor the Cryosphere,” a Pardee Keynote Symposium at the 2015 Annual Meeting in Baltimore, Maryland, USA, for which the GSA recorded supporting interviews and a webinar
Self-assembly of ordered graphene nanodot arrays (vol 8, 47, 2017)
Change History: A correction to this article has been published and is linked from the HTML version of this article
Disease status in human and experimental arthritis, and response to TNF blockade, is associated with MHC class II invariant chain (CD74) isoform expression
Splice variants of CD74 differentially modulate the activity of cathepsin L (CTSL). As CD74 and CTSL participate in the pathogenesis of inflammatory diseases such as rheumatoid arthritis (RA), we determined whether splice variants of CD74 could be biomarkers of disease activity. Gene expression was measured in mice with collagen-induced arthritis using quantitative PCR (qPCR). In vitro studies using murine macrophage/DC-lineage cells determined the relative influence of macrophage phenotype on isoform expression and the potential to produce CTSL in response to TNF. CD74 splice variants were measured in human RA synovium and RA patients' monocytes. In arthritic mice, the expression of the p41 CD74 isoform was significantly higher in severely affected paws compared with unaffected paws or the paws of naïve mice; the p41 isoform significantly correlated with the expression of TNF in arthritic paws. Compared with M2-like macrophages, M1-like macrophages expressed increased levels of CD74 and had higher expression, secretion and activity of CTSL. RA patients that responded to TNF blockade had significantly higher expression levels of CD74 in circulating monocytes after treatment, compared with non-responders. The expression of the human CD74 isoform a was significantly higher in RA synovia, compared with osteoarthritis synovia, and was associated with CSTL enzymatic activity. This study is the first to demonstrate differential expression of the CD74 p41 isoform in an auto-immune disorder and in response to therapy. The differential expression of CD74 splice variants indicates an association, and potentially a mechanistic role, in the pathogenesis of RA
Halo globular clusters observed with AAOmega: dark matter content, metallicity and tidal heating
Globular clusters have proven to be essential to our understanding of many
important astrophysical phenomena. Here we analyse spectroscopic observations
of ten Halo globular clusters to determine their dark matter content, their
tidal heating by the Galactic disc and halo, describe their metallicities and
the likelihood that Newtonian dynamics explain their kinematics. We analyse a
large number of members in all clusters, allowing us to address all these
issues together, and we have included NGC 288 and M30 to overlap with previous
studies. We find that any flattening of the velocity dispersion profiles in the
outer regions of our clusters can be explained by tidal heating. We also find
that all our GCs have M/L_V < 5, therefore, we infer the observed dynamics do
not require dark matter, or a modification of gravity. We suggest that the lack
of tidal heating signatures in distant clusters indicates the Halo is not
triaxial. The isothermal rotations of each cluster are measured, with M4 and
NGC 288 exhibiting rotation at a level of 0.9 +/- 0.1 km/s and 0.25 +/- 0.15
km/s, respectively. We also indirectly measure the tidal radius of NGC 6752,
determining a more realistic figure for this cluster than current literature
values. Lastly, an unresolved and intriguing puzzle is uncovered with regard to
the cooling of the outer regions of all ten clusters.Comment: 12 pages, 8 figures, 1 table. Accepted for publication in MNRAS
Testing Newtonian Gravity with AAOmega: Mass-To-Light Profiles and Metallicity Calibrations From 47 Tuc and M55
Globular clusters are an important test bed for Newtonian gravity in the
weak-acceleration regime, which is vital to our understanding of the nature of
the gravitational interaction. Recent claims have been made that the velocity
dispersion profiles of globular clusters flatten out at large radii, despite an
apparent paucity of dark matter in such objects, indicating the need for a
modification of gravitational theories. We continue our investigation of this
claim, with the largest spectral samples ever obtained of 47 Tucanae and M55.
Furthermore, this large sample allows for an accurate metallicity calibration
based on the equivalent widths of the calcium triplet lines and K band
magnitude of the Tip of the Red Giant Branch. Assuming an isothermal
distribution, the rotations of each cluster are also measured with both
clusters exhibiting clear rotation signatures. The global velocity dispersions
of NGC 121 and Kron 3, two globular clusters in the Small Magellanic Cloud, are
also calculated. By applying a simple dynamical model to the velocity
dispersion profiles of 47 Tuc and M55, we calculate their mass-to-light
profiles, total masses and central velocity dispersions. We find no
statistically significant flattening of the velocity dispersion at large radii
for M55, and a marked increase in the profile of 47 Tuc for radii greater than
approximately half the tidal radius. We interpret this increase as an
evaporation signature, indicating that 47 Tuc is undergoing, or has undergone,
core-collapse, but find no requirement for dark matter or a modification of
gravitational theories in either cluster.Comment: 11 pages, 12 figures, 4 tables. Accepted by MNRA
TLR expression profiles are a function of disease status in rheumatoid arthritis and experimental arthritis
The role of the innate immune system has been established in the initiation and perpetuation of inflammatory disease, but less attention has been paid to its role in the resolution of inflammation and return to homeostasis. Toll-like receptor (TLR) expression profiles were analysed in tissues with differing disease status in rheumatoid arthritis (RA), ankylosing spondylitis (AS), and in experimental arthritis. TLR gene expression was measured in whole blood and monocytes, before and after TNF blockade. In RA and osteoarthritis synovia, the expression of TLRs was quantified by standard curve qPCR. In addition, four distinct stages of disease were defined and validated in collagen-induced arthritis (CIA), the gold standard animal model for RA - pre-onset, early disease, late disease and immunised mice that were resistant to the development of disease. TLR expression was measured in spleens, lymph nodes, blood cells, liver and the paws (inflamed and unaffected). In RA whole blood, the expression of TLR1, 4 and 6 was significantly reduced by TNF blockade but the differences in TLR expression profiles between responders and non-responders were less pronounced than the differences between RA and AS patients. In RA non-responders, monocytes had greater TLR2 expression prior to therapy compared to responders. The expression of TLR1, 2, 4 and 8 was higher in RA synovium compared to control OA synovium. Circulating cytokine levels in CIA resistant mice were similar to naïve mice, but anti-collagen antibodies were similar to arthritic mice. Distinct profiles of inflammatory gene expression were mapped in paws and organs with differing disease status. TLR expression in arthritic paws tended to be similar in early and late disease, with TLR1 and 2 moderately higher in late disease. TLR expression in unaffected paws varied according to gene and disease status but was generally lower in resistant paws. Disease status-specific profiles of TLR expression were observed in spleens, lymph nodes, blood cells and the liver. Notably, TLR2 expression rose then fell in the transition from naïve to pre-onset to early arthritis. TLR gene expression profiles are strongly associated with disease status. In particular, increased expression in the blood precedes clinical manifestation
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