1,788 research outputs found
An anomalous magnetic phase transition at 10 K in Nd7Rh3
The compound, Nd7Rh3, crystallizing in Th7Fe3-type hexagonal structure, has
been shown recently by us to exhibit a signature of magnetic phase-coexistence
phenomenon below 10 K after a field cycling, uncharacteristic of stoichiometric
intermetallic compounds, bearing a relevance to the trends in the field of
electronic phase-separation. In order to characterize this compound further, we
have carried out dc magnetic susceptibility (chi), electrical resistivity,
magnetoresistance and heat-capacity measurements as a function temperature (T=
1.8 to 300 K). The results reveal that this compound exhibits another unusual
finding at the 10K-transition in the sense that the plot of chi(T) shows a
sharp increase in the field-cooled cycle, whereas the zero-field-cooled curve
shows a downturn below the transition. In addition, the sign of
magnetoresistance is negative and the magnitude is large over a wide
temperature range in the vicinity of magnetic ordering temperature, with a
sharp variation at 10 K. The results indicate that the transition below 10 K is
first-order in its character.Comment: Appeared in JPCM (Letters) 18 (2006) L40
Investigation of complete and incomplete fusion in Li+Sn reaction around Coulomb barrier energies
The complete and incomplete fusion cross sections for Li+Sn
reaction were measured using online and offline characteristic -ray
detection techniques. The complete fusion (CF) cross sections at energies above
the Coulomb barrier were found to be suppressed by 26 \% compared to the
coupled channel calculations. This suppression observed in complete fusion
cross sections is found to be commensurate with the measured total incomplete
fusion (ICF) cross sections. There is a distinct feature observed in the ICF
cross sections, i.e., -capture is found to be dominant than
-capture at all the measured energies. A simultaneous explanation of
complete, incomplete and total fusion (TF) data was also obtained from the
calculations based on Continuum Discretized Coupled Channel method with short
range imaginary potentials. The cross section ratios of CF/TF and ICF/TF
obtained from the data as well as the calculations showed the dominance of ICF
at below barrier energies and CF at above barrier energies.Comment: 9 pages, 8 figure
New limit for the half-life of double beta decay of Zr to the first excited state of Mo
Neutrinoless Double Beta Decay is a phenomenon of fundamental interest in
particle physics. The decay rates of double beta decay transitions to the
excited states can provide input for Nuclear Transition Matrix Element
calculations for the relevant two neutrino double beta decay process. It can be
useful as supplementary information for the calculation of Nuclear Transition
Matrix Element for the neutrinoless double beta decay process. In the present
work, double beta decay of Zr to the excited state of
Mo at 871.1 keV is studied using a low background 230 cm HPGe
detector. No evidence of this decay was found with a 232 g.y exposure of
natural Zirconium. The lower half-life limit obtained for the double beta decay
of to the excited state of is y at 90% C.L., an improvement by a factor of
4 over the existing experimental limit at 90\% C.L. The sensitivity is
estimated to be y at 90% C.L. using
the Feldman-Cousins method.Comment: 11 pages, 7 figures, Accepted in Eur. Phys. J.
Orbital Myiasis: Due to Invasion of Larvae of Flesh Fly (Wohlfahrtia magnifica) in a Child; Rare Presentation
Wohlfahrtia magnifica larvae cause myiasis in mammals, mainly in sheep and rarely in human. In human it may infest the ear, eye, mouth or nose, damaging living tissues. We report a case of ocular myiasis in 1.5 years old child belonging to urban slum after history of minor injury on left upper lid due to fall from bed. The purpose of reporting this case is to highlight the ocular association of W. magnifica
Role of friction-induced torque in stick-slip motion
We present a minimal quasistatic 1D model describing the kinematics of the
transition from static friction to stick-slip motion of a linear elastic block
on a rigid plane. We show how the kinematics of both the precursors to
frictional sliding and the periodic stick-slip motion are controlled by the
amount of friction-induced torque at the interface. Our model provides a
general framework to understand and relate a series of recent experimental
observations, in particular the nucleation location of micro-slip instabilities
and the build up of an asymmetric field of real contact area.Comment: 6 pages, 5 figure
Quantitative Nanofriction Characterization of Corrugated Surfaces by Atomic Force Microscopy
Atomic Force Microscopy (AFM) is a suitable tool to perform tribological
characterization of materials down to the nanometer scale. An important aspect
in nanofriction measurements of corrugated samples is the local tilt of the
surface, which affects the lateral force maps acquired with the AFM. This is
one of the most important problems of state-of-the-art nanotribology, making
difficult a reliable and quantitative characterization of real corrugated
surfaces. A correction of topographic spurious contributions to lateral force
maps is thus needed for corrugated samples. In this paper we present a general
approach to the topographic correction of AFM lateral force maps and we apply
it in the case of multi-asperity adhesive contact. We describe a complete
protocol for the quantitative characterization of the frictional properties of
corrugated systems in the presence of surface adhesion using the AFM.Comment: 33 pages, 9 figures, RevTex 4, submitted to Journal of Applied
Physic
An in-situ synchrotron XAS methodology for surface analysis under high temperature, pressure and shear
The complex tribochemical nature of lubricated tribological contacts is inaccessible in real time without altering their initial state. To overcome this issue, a new design of a pin-on-disc tribological apparatus was developed and combined with synchrotron X-ray absorption spectroscopy (XAS). Using the designed apparatus, it is possible to study in situ the transient decomposition reactions of various oil additives on different surfaces under a wide range of realistic operating conditions of contact pressure (1.0–3.0 GPa), temperature (25–120 °C), and sliding speed (30–3000 rpm or 0.15–15 m/s). To test the apparatus, several tribological tests were performed at different shearing times ranging from 2.5 to 60 min. These tests were carried out under helium atmosphere at a temperature of 80 °C, contact pressure of 2.2 GPa, and sliding speed of 50 rpm. The XAS experiments indicate that the zinc dialkyldithiophosphate antiwear additive decomposes in the oil to form a tribofilm on the iron surface at different reaction kinetics from the ones of the thermal film. The tribofilm composition evolves much faster than the one of the thermal film, which confirms that the formation of the tribofilm is a thermally activated process similar to the one of the thermal film but accelerated by shear. Furthermore, the results indicate that the sulfur of the formed film, whether a tribofilm or a thermal film, appears initially in the form of sulfate, with some sulfide, which under heat or shear is reduced into mainly sulfide
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