1,125 research outputs found
Interpretation of the Friction Coefficient During Reciprocating Sliding of Ti6Al4V Alloy Against Al2O3
Tribological behaviour of Ti6Al4V alloy, during linear reciprocating sliding against alumina, at nanotribometer (ball-on-flat type of contact) was investigated. Experiments were carried out for sliding in Ringer's solution, over a range of loads (100 - 1000 mN) and speeds (4 - 12 mm/s). Friction behaviour of the contact pairs was investigated by analysis of the dynamic friction coefficient plots and effective root mean square (rms) coefficient of friction, COFrms. Presented mathematical envelopes of dynamic coefficient of friction curves and averaged envelope signals provided additional explanation of one calculated COFrms value. Envelopes of dynamic coefficient of friction enabled easier determination of different periods during sliding, which were further related to wear mechanisms
Towards the production of 50'000 tonnes of low-carbon steel sheet for the LHC superconducting dipole and quadrupole magnets
A total of 50'000 tonnes of low-carbon steel sheet has been ordered for the LHC main magnets. After three years of production, about 10'000 tonnes of steel sheet have been produced by Cockerill-Sambre Groupe Usinor. This paper gives a summary of the manufacturing process and improvements implemented as well as an overview of the difficulties encountered during this production. Preliminary statistics obtained for the mechanical and magnetic steel properties are presented
Microindentation of Polymethyl Methacrylate (PMMA) Based Bone Cement
Characterization of polymethyl methacrylate (PMMA) based bone cement subjected to cyclical loading using microindentation technique is presented in this paper. Indentation technique represents flexible mechanical testing due to its simplicity, minimal specimen preparation and short time needed for tests. The mechanical response of bone cement samples was studied. Realised microindentation enabled determination of the indentation testing hardness HIT and indentation modulus EIT of the observed bone cement. Analysis of optical photographs of the imprints showed that this technique can be effectively used for characterization of bone cements
Stretched chemical bonds in Si6H6: A transition from ring currents to localized pi-electrons?
Motivated by solid-state studies on the cleavage force in Si, and the
consequent stretching of chemical bonds, we here study bond stretching in the,
as yet unsynthesized, free space molecule Si6H6. We address the question as to
whether substantial bond stretching (but constrained to uniform scaling on all
bonds) can result in a transition from ring current behaviour, characteristic
say of benzene at its equilibrium geometry, to localized pi-electrons on Si
atoms. Some calculations are also recorded on dissociation into 6 SiH radicals.
While the main studies have been carried out by unrestricted Hartree-Fock (HF)
theory, the influence of electron correlation has been examined using two forms
of density functional theory. Planar Si6H6 treated by HF is bound to be
unstable, not all vibrational frequencies being real. Some buckling is then
allowed, which results in real frequencies and stability. Evidence is then
provided that the non-planar structure, as the Si-Si distance is increased,
exhibits pi-electron localization in the range 1.2-1.5 times the equilibrium
distance
Probability density functions of work and heat near the stochastic resonance of a colloidal particle
We study experimentally and theoretically the probability density functions
of the injected and dissipated energy in a system of a colloidal particle
trapped in a double well potential periodically modulated by an external
perturbation. The work done by the external force and the dissipated energy are
measured close to the stochastic resonance where the injected power is maximum.
We show a good agreement between the probability density functions exactly
computed from a Langevin dynamics and the measured ones. The probability
density function of the work done on the particle satisfies the fluctuation
theorem
Novel microstructured fibres for supercontinuum generation
We report recent progress on the fabrication of photonic crystal fibre from ZBLAN and tellurite glasses and their application to generating broadband supercontinua
A sticky situation: CCN1 promotes both proliferation and apoptosis of cancer cells
Members of the CCN family of matricellular signaling regulators promote cell adhesion through integrins and heparan sulfate-containing proteoglycans. A paradox of the CCN field is that, depending on the set of circumstances examined, individual CCN molecules can have quite different, and often opposing, effects. In a recent report, Franzen and colleagues (Mol Cancer Res. 7:1045–1055, 2009) show using siRNA knockdown that CCN1 (cyr61) is essential for the proliferation of prostate cancer cells. Intriguingly, on the other hand, CCN1 also enhances TRAIL-induced apoptosis. Thus the utility of anti-CCN1 therapy in cancer needs to be carefully considered in light of these divergent results. The significance of this paper is discussed
Impaired Retromer Function in Niemann-Pick Type C Disease Is Dependent on Intracellular Cholesterol Accumulation
Niemann-Pick type C disease (NPC) is a rare inherited neurodegenerative disorder characterized by an accumulation of intracellular cholesterol within late endosomes and lysosomes due to NPC1 or NPC2 dysfunction. In this work, we tested the hypothesis that retromer impairment may be involved in the pathogenesis of NPC and may contribute to increased amyloidogenic processing of APP and enhanced BACE1-mediated proteolysis observed in NPC disease. Using NPC1-null cells, primary mouse NPC1-deficient neurons and NPC1-deficient mice (BALB/cNctr-Npc1m1N), we show that retromer function is impaired in NPC. This is manifested by altered transport of the retromer core components Vps26, Vps35 and/or retromer receptor sorLA and by retromer accumulation in neuronal processes, such as within axonal swellings. Changes in retromer distribution in NPC1 mouse brains were observed already at the presymptomatic stage (at 4-weeks of age), indicating that the retromer defect occurs early in the course of NPC disease and may contribute to downstream pathological processes. Furthermore, we show that cholesterol depletion in NPC1-null cells and in NPC1 mouse brains reverts retromer dysfunction, suggesting that retromer impairment in NPC is mechanistically dependent on cholesterol accumulation. Thus, we characterized retromer dysfunction in NPC and propose that the rescue of retromer impairment may represent a novel therapeutic approach against NPC
Mass-Varying Neutrinos from a Variable Cosmological Constant
We consider, in a completely model-independent way, the transfer of energy
between the components of the dark energy sector consisting of the cosmological
constant (CC) and that of relic neutrinos. We show that such a cosmological
setup may promote neutrinos to mass-varying particles, thus resembling a
recently proposed scenario of Fardon, Nelson, and Weiner (FNW), but now without
introducing any acceleronlike scalar fields. Although a formal similarity of
the FNW scenario with the variable CC one can be easily established, one
nevertheless finds different laws for neutrino mass variation in each scenario.
We show that as long as the neutrino number density dilutes canonically, only a
very slow variation of the neutrino mass is possible. For neutrino masses to
vary significantly (as in the FNW scenario), a considerable deviation from the
canonical dilution of the neutrino number density is also needed. We note that
the present `coincidence' between the dark energy density and the neutrino
energy density can be obtained in our scenario even for static neutrino masses.Comment: 8 pages, minor corrections, two references added, to apear in JCA
Tsunami-Related Data: A Review of Available Repositories Used in Scientific Literature
Various organizations and institutions store large volumes of tsunami-related data, whose
availability and quality should benefit society, as it improves decision making before the tsunami
occurrence, during the tsunami impact, and when coping with the aftermath. However, the existing
digital ecosystem surrounding tsunami research prevents us from extracting the maximum benefit
from our research investments. The main objective of this study is to explore the field of data
repositories providing secondary data associated with tsunami research and analyze the current
situation. We analyze the mutual interconnections of references in scientific studies published in the
Web of Science database, governmental bodies, commercial organizations, and research agencies. A
set of criteria was used to evaluate content and searchability. We identified 60 data repositories with
records used in tsunami research. The heterogeneity of data formats, deactivated or nonfunctional
web pages, the generality of data repositories, or poor dataset arrangement represent the most
significant weak points. We outline the potential contribution of ontology engineering as an example
of computer science methods that enable improvements in tsunami-related data management
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