13,909 research outputs found
An investigation of the beneficial effects of adding carbon nanotubes to standard injection grout
Mortar grouting is often used in masonry constructions to mitigate structural decay and repair damage by filling cracks and voids, resulting in an improvement in mechanical properties. This paper presents an original experimental investigation on grout with added carbon nanotubes (CNTs). The samples were prepared with different percentages of CNTs, up to 1.2 wt% with respect to the binder, and underwent three‐point bending tests in crack mouth opening displacement mode and compressive tests. The results showed that very small additions (up to 0.12 wt% of CNTs) increased not only flexural and compressive strengths (+73% and 35%, respectively, in comparison with plain mortar) but also fracture energy (+80%). These results can be explained on the basis of a reduction in porosity, as evidenced by mercury intrusion porosimetry, as well as by a crack bridging mechanism and by the probable formation of nucleation sites for hydration products, as observed through scanning electron microscopy
Variable stars in the globular cluster NGC 7492. New discoveries and physical parameters determination
We have performed a photometric V, R, I CCD time-series analysis with a
baseline of ~8 years of the outer-halo globular cluster NGC 7492 with the aim
of searching for new variables and using these (and the previously known
variables) to determine the physical parameters of interest for the cluster
(e.g. metallicity, absolute magnitude of the horizontal branch, distance,
etc.).
We use difference image analysis (DIA) to extract precise light curves in the
relatively crowded star field, especially towards the densely populated central
region. Several approaches are used for variability detection that recover the
known variables and lead to new discoveries. We determine the physical
parameters of the only RR0 star using light curve Fourier decomposition
analysis.
We find one new long period variable and two SX Phe stars in the blue
straggler region. We also present one candidate SX Phe star which requires
follow-up observations. Assuming that the SX Phe stars are cluster members and
using the period-luminosity relation for these stars, we estimate their
distances as ~25.2+-1.8 and 26.8+-1.8 kpc, and identify their possible modes of
oscillation. We refine the periods of the two RR Lyrae stars in our field of
view. We find that the RR1 star V2 is undergoing a period change and possibly
exhibits the Blazhko effect. Fourier decomposition of the light curve of the
RR0 star V1 allows us to estimate the metallicity [Fe/H]_ZW-1.68+-0.10 or
[Fe/H]_UVES-1.64+-0.13, log-luminosity ~1.76+-0.02, absolute magnitude
~0.38+-0.04 mag, and true distance modulus of ~16.93+-0.04 mag, which is
equivalent to a distance of ~24.3+-0.5 kpc. All of these values are consistent
with previous estimates in the literature.Comment: 12 pages, 13 figures, 6 tables, accepted for publication in A&
Reduced lysosomal acid lipase activity: A new marker of liver disease severity across the clinical continuum of non-alcoholic fatty liver disease?
Lysosomal acid lipase (LAL) plays a key role in intracellular lipid metabolism. Reduced LAL activity promotes increased multi-organ lysosomal cholesterol ester storage, as observed in two recessive autosomal genetic diseases, Wolman disease and Cholesterol ester storage disease. Severe liver steatosis and accelerated liver fibrosis are common features in patients with genetic LAL deficiency. By contrast, few reliable data are available on the modulation of LAL activity in vivo and on the epigenetic and metabolic factors capable of regulating its activity in subjects without homozygous mutations of the Lipase A gene. In the last few years, a less severe and non-genetic reduction of LAL activity was reported in children and adults with non-alcoholic fatty liver disease (NAFLD), suggesting a possible role of LAL reduction in the pathogenesis and progression of the disease. Patients with NAFLD show a significant, progressive reduction of LAL activity from simple steatosis to non-alcoholic steatohepatitis and cryptogenic cirrhosis. Among cirrhosis of different etiologies, those with cryptogenic cirrhosis show the most significant reductions of LAL activity. These findings suggest that the modulation of LAL activity may become a possible new therapeutic target for patients with more advanced forms of NAFLD. Moreover, the measurement of LAL activity may represent a possible new marker of disease severity in this clinical setting
Foreword
This work reports on the performances of ohmic contacts fabricated on highly p-type doped 4H-SiC epitaxial layer selectively grown by vapor-liquid-solid transport. Due to the very high doping level obtained, the contacts have an ohmic behavior even without any annealing process. Upon variation of annealing temperatures, it was shown that both 500 and 800 °C annealing temperature lead to a minimum value of the Specific Contact Resistance (SCR) down to 1.3×10−6 Ω⋅cm2. However, a large variation of the minimum SCR values has been observed (up to 4×10−4 Ω⋅cm2). Possible sources of this fluctuation have been also discussed in this paper
How to Evaluate your Question Answering System Every Day and Still Get Real Work Done
In this paper, we report on Qaviar, an experimental automated evaluation
system for question answering applications. The goal of our research was to
find an automatically calculated measure that correlates well with human
judges' assessment of answer correctness in the context of question answering
tasks. Qaviar judges the response by computing recall against the stemmed
content words in the human-generated answer key. It counts the answer correct
if it exceeds agiven recall threshold. We determined that the answer
correctness predicted by Qaviar agreed with the human 93% to 95% of the time.
41 question-answering systems were ranked by both Qaviar and human assessors,
and these rankings correlated with a Kendall's Tau measure of 0.920, compared
to a correlation of 0.956 between human assessors on the same data.Comment: 6 pages, 3 figures, to appear in Proceedings of the Second
International Conference on Language Resources and Evaluation (LREC 2000
Constraining the parameters of globular cluster NGC 1904 from its variable star population
We present the analysis of 11 nights of V and I time-series observations of
the globular cluster NGC 1904 (M 79). Using this we searched for variable stars
in this cluster and attempted to refine the periods of known variables, making
use of a time baseline spanning almost 8 years. We use our data to derive the
metallicity and distance of NGC 1904. We used difference imaging to reduce our
data to obtain high-precision light curves of variable stars. We then estimated
the cluster parameters by performing a Fourier decomposition of the light
curves of RR Lyrae stars for which a good period estimate was possible. We also
derive an estimate for the age of the cluster by fitting theoretical isochrones
to our colour-magnitude diagram (CMD). Out of 13 stars previously classified as
variables, we confirm that 10 are bona fide variables. We cannot detect
variability in one other within the precision of our data, while there are two
which are saturated in our data frames, but we do not find sufficient evidence
in the literature to confirm their variability. We also detect a new RR Lyrae
variable, giving a total number of confirmed variable stars in NGC 1904 of 11.
Using the Fourier parameters, we find a cluster metallicity [Fe/H]_ZW=-1.63 +-
0.14, or [Fe/H]_UVES=-1.57 \pm 0.18, and a distance of 13.3 +- 0.4 kpc (using
RR0 variables) or 12.9 kpc (using the one RR1 variable in our sample for which
Fourier decomposition was possible).Comment: 14 pages, 11 figures, accepted for publication in A&
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