1,125 research outputs found
Direct Experimental Evidence for Differing Reactivity Alterations of Minerals following Irradiation: The Case of Calcite and Quartz
Concrete, a mixture formed by mixing cement, water, and fine and coarse
mineral aggregates is used in the construction of nuclear power plants (NPPs),
e.g., to construct the reactor cavity concrete that encases the reactor
pressure vessel, etc. In such environments, concrete may be exposed to
radiation (e.g., neutrons) emanating from the reactor core. Until recently,
concrete has been assumed relatively immune to radiation exposure. Direct
evidence acquired on Ar-ion irradiated calcite and quartz indicates, on the
contrary, that, such minerals, which constitute aggregates in concrete, may be
significantly altered by irradiation. Specifically, while quartz undergoes
disordering of its atomic structure resulting in a near complete lack of
periodicity, i.e., similar to glassy silica, calcite only experiences random
rotations, and distortions of its carbonate groups. As a result, irradiated
quartz shows a reduction in density of around 15%, and an increase in chemical
reactivity, described by its dissolution rate, similar to a glassy silica;
i.e., an increase of around 3 orders of magnitude. Calcite however, shows
little change in dissolution rates - although its density noted to reduce by
around 9%. These differences are correlated with the nature of bonds in these
minerals, i.e., being dominantly ionic or covalent, and the rigidity of the
mineral's atomic network that is characterized by the number of topological
constraints (n) that are imposed on the atoms in the network. The outcomes
are discussed within the context of the durability of concrete structural
elements formed with calcitic/quartzitic aggregates in nuclear power plants
The self-assembling growth of copper nanowires for transparent electrodes
Long (15 - 40 μm), thin (diameter of 20 ± 5 nm), and well-dispersed CuNWs Cu nanowires were prepared. The high-resolution TEM and selected area electron diffraction showed that the CuNWs were single-crystalline. To investigate the growth mechanism, we examined the microstructure of these CuNWs at different reaction time. It was found that the CuNWs were actually formed through the self-assembling of Cu nanoparticles along the [110] direction. The transparent electrodes fabricated using the CuNWs achieved a high transparency of 76 % at 31±5 Ω/□
Magnetic structure and Ising-like antiferromagnetism in the bilayer triangular lattice compound NdZnPO
The complex interplay of spin frustration and quantum fluctuations in
low-dimensional quantum materials leads to a variety of intriguing phenomena.
This research focuses on a detailed analysis of the magnetic behavior exhibited
by NdZnPO, a bilayer spin-1/2 triangular lattice antiferromagnet. The
investigation employs magnetization, specific heat, and powder neutron
scattering measurements. At zero field, a long-range magnetic order is observed
at . Powder neutron diffraction experiments show the
Ising-like magnetic moments along the -axis, revealing a stripe-like
magnetic structure with three equivalent magnetic propagation vectors.
Application of a magnetic field along the -axis suppresses the
antiferromagnetic order, leading to a fully polarized ferromagnetic state above
. This transition is accompanied by notable enhancements
in the nuclear Schottky contribution. Moreover, the absence of spin frustration
and expected field-induced plateau-like phases are remarkable observations.
Detailed calculations of magnetic dipolar interactions revealed complex
couplings reminiscent of a honeycomb lattice, suggesting the potential
emergence of Kitaev-like physics within this system. This comprehensive study
of the magnetic properties of NdZnPO highlights unresolved intricacies,
underscoring the imperative for further exploration to unveil the underlying
governing mechanisms.Comment: 11 pages, 6 figure
ATP Synthase β
HDL cholesterol is known to be inversely correlated with cardiovascular disease due to its diverse antiatherogenic functions. SR-BI mediates the selective uptake of HDL-C. SR-BI knockout diminishes but does not completely block the transport of HDL; other receptors may be involved. Ectopic ATP synthase β-chain in hepatocytes has been previously characterized as an apoA-I receptor, triggering HDL internalization. This study was undertaken to identify the overexpression of ectopic ATP synthase β-chain on DIL-HDL uptake in primary hepatocytes in vitro and on plasma HDL levels in SR-BI knockout mice. Human ATP synthase β-chain cDNA was delivered to the mouse liver by adenovirus and GFP adenovirus as control. The adenovirus-mediated overexpression of β-chain was identified at both mRNA and protein levels on mice liver and validated by its increasing of DiL-HDL uptake in primary hepatocytes. In response to hepatic overexpression of β-chain, plasma HDL-C levels and cholesterol were reduced in SR-BI knockout mice, compared with the control. The present data suggest that ATP synthase β-chain can serve as the endocytic receptor of HDL, and its overexpression can reduce plasma HDL-C
An Updated Search of Steady TeV Ray Point Sources in Northern Hemisphere Using the Tibet Air Shower Array
Using the data taken from Tibet II High Density (HD) Array (1997
February-1999 September) and Tibet-III array (1999 November-2005 November), our
previous northern sky survey for TeV ray point sources has now been
updated by a factor of 2.8 improved statistics. From to
in declination (Dec) range, no new TeV ray point
sources with sufficiently high significance were identified while the
well-known Crab Nebula and Mrk421 remain to be the brightest TeV ray
sources within the field of view of the Tibet air shower array. Based on the
currently available data and at the 90% confidence level (C.L.), the flux upper
limits for different power law index assumption are re-derived, which are
approximately improved by 1.7 times as compared with our previous reported
limits.Comment: This paper has been accepted by hepn
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at TeV
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb
collisions at = 2.76 TeV have been measured by the ALICE
Collaboration at the LHC. The data are presented for central and peripheral
collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross
section. The measured charged particle spectra in and GeV/ are compared to the expectation in pp collisions at the same
, scaled by the number of underlying nucleon-nucleon
collisions. The comparison is expressed in terms of the nuclear modification
factor . The result indicates only weak medium effects ( 0.7) in peripheral collisions. In central collisions,
reaches a minimum of about 0.14 at -7GeV/ and increases
significantly at larger . The measured suppression of high- particles is stronger than that observed at lower collision energies,
indicating that a very dense medium is formed in central Pb-Pb collisions at
the LHC.Comment: 15 pages, 5 captioned figures, 3 tables, authors from page 10,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/98
N-Glycosylation of ß4 Integrin Controls the Adhesion and Motility of Keratinocytes
α6ß4 integrin is an essential component of hemidesmosomes and modulates cell migration in wound healing and cancer invasion. To elucidate the role of N-glycosylation on ß4 integrin, we investigated keratinocyte adhesion and migration through the re-expression of wild-type or N-glycosylation-defective ß4 integrin (ΔNß4) in ß4 integrin null keratinocytes. N-glycosylation of ß4 integrin was not essential for the heterodimer formation of ß4 integrin with α6 integrin and its expression on a cell surface, but N-glycosylation was required for integrin-mediated cell adhesion and migration. Concomitantly with the reduction of ß4 integrin in the membrane microdomain, the intracellular signals of Akt and ERK activation were decreased in cells expressing ΔNß4 integrin. Forced cross-linking of ß4 integrin rescued the decreased ERK activation in ΔNß4 integrin-expressing cells to a similar extent in wild-type ß4 integrin-expressing cells. Surprisingly, compared with cells expressing wild-type ß4 integrin, an alternation in N-glycan structures expressed on epidermal growth factor receptor (EGFR), and the induction of a stronger association between EGFR and ß4 integrin were observed in ΔNß4 integrin-expressing cells. These results clearly demonstrated that N-glycosylation on ß4 integrin plays an essential role in keratinocyte cellular function by allowing the appropriate complex formation on cell surfaces
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