23,489 research outputs found
Measuring dopant concentrations in compensated p-type crystalline silicon via iron-acceptor pairing
We present a method for measuring the concentrations of ionized acceptors and donors in compensated p-type silicon at room temperature.Carrier lifetimemeasurements on silicon wafers that contain minute traces of iron allow the iron-acceptor pair formation rate to be determined, which in turn allows the acceptor concentration to be calculated. Coupled with an independent measurement of the resistivity and a mobility model that accounts for majority and minority impurity scatterings of charge carriers, it is then possible to also estimate the total concentration of ionized donors. The method is valid for combinations of different acceptor and donor species.D.M. is supported by an Australian Research Council
fellowship. L.J.G. would like to acknowledge SenterNovem
for support
Predicting the steady state thickness of passive films in order to prevent degradations of implant
Some implants have approximately a lifetime of 15 years. The femoral stem,
for example, should be made of 316L/316LN stainless steel. Fretting corrosion,
friction under small displacements, should occur during human gait, due to
repeated loadings and un-loadings, between stainless steel and bone for
instance. Some experimental investigations of fretting corrosion have been
practiced. As well known, metallic alloys and especially stainless steels are
covered with a passive film that prevents from the corrosion and degradation.
This passive layer of few nanometers, at ambient temperature, is the key of our
civilization according to some authors. This work is dedicated to predict the
passive layer thicknesses of stainless steel under fretting corrosion with a
specific emphasis on the role of proteins. The model is based on the Point
Defect Model (micro scale) and an update of the model on the friction process
(micro-macro scale). Genetic algorithm was used for finding solution of the
problem. The major results are, as expected from experimental results, albumin
prevents from degradation at the lowest concentration of chlorides; an
incubation time is necessary for degrading the passive film; under fretting
corrosion and high concentration of chlorides the passive behavior is
annihilated
Neonatal weight loss in breast and formula-fed infants
We have observed an increase in the number of breast fed babies presenting with dehydration and/or failure to thrive because of lactation failure and non-recognition of feeding problems. Recent reports1,2 support this experience and recommend monitoring of the weight of infants through the neonatal period. However, these reports acknowledge uncertainty as to what actually constitutes normal neonatal weight loss. Maisels and colleagues published two studies which have been quoted as giving guidance on normal loss. Both studies were designed primarily to study factors that influence breast milk jaundice. The first3 reported a mean weight loss of about 6% in 100 unselected well babies during the first 3 days. The subsequent study4 reported a mean weight loss of 6.86% in 186 infants. The timescale over which babies were weighed was not clearly indicated, although it may have only been 2-3 days. The sample was neither population based nor randomly selected, being largely preselected because of the presence of more pronounced jaundice. The distribution of data points for early neonatal weight loss are likely to be skewed, yet both studies reported the results as mean (SD). Owing to the design and method of data presentation, these studies cannot reliably inform the debate as to what constitutes the norm. Marchini and colleagues published reports also designed primarily to study other issues. One5 indicated a mean early weight loss of 5.7%. Measurements were recorded over a three day period, and no indication is given of the skewness of the data. Another study6 reported a median weight loss of about 6% recorded over a four day period. At least one baby lost > 15% of his/her birth weight during this time, but there is no clear information as to the frequency with which more extreme degrees of weight loss are observed
Michael Simpson. Closet Performances: Political Exhibition and Prohibition in the Dramas of Byron and Shelley
Predicting dissatisfaction following total knee replacement:a prospective study of 1217 patients
Analytic Solutions to the Constraint Equation for a Force-Free Magnetosphere around a Kerr Black Hole
The Blandford-Znajek constraint equation for a stationary, axisymmetric
black-hole force-free magnetosphere is cast in a 3+1 absolute space and time
formulation, following Komissarov (2004). We derive an analytic solution for
fields and currents to the constraint equation in the far-field limit that
satisfies the Znajek condition at the event horizon. This solution generalizes
the Blandford-Znajek monopole solution for a slowly rotating black hole to
black holes with arbitrary angular momentum. Energy and angular momentum
extraction through this solution occurs mostly along the equatorial plane. We
also present a nonphysical, reverse jet-like solution.Comment: 6 pages, accepted for publication in Ap
Effect of Edge Roughness on Electronic Transport in Graphene Nanoribbon Channel Metal Oxide Semiconductor Field-Effect Transistors
Results of quantum mechanical simulations of the influence of edge disorder
on transport in graphene nanoribbon metal oxide semiconductor field-effect
transistors (MOSFETs) are reported. The addition of edge disorder significantly
reduces ON-state currents and increases OFF-state currents, and introduces wide
variability across devices. These effects decrease as ribbon widths increase
and as edges become smoother. However the bandgap decreases with increasing
width, thereby increasing the band-to-band tunneling mediated subthreshold
leakage current even with perfect nanoribbons. These results suggest that
without atomically precise edge control during fabrication, MOSFET performance
gains through use of graphene will be difficult to achieve.Comment: 8 pages, 5 figure
Intrinsic Curie temperature bistability in ferromagnetic semiconductor resonant tunneling diodes
We predict bistability in the Curie temperature-voltage characteristic of
double barrier resonant-tunneling structures with dilute ferromagnetic
semiconductor quantum wells. Our conclusions are based on simulations of
electrostatics and ballistic quantum transport combined with a mean-field
theory description of ferromagnetism in dilute magnetic semiconductors.Comment: 10 pages, 3 figures, submitted to Phys. Rev. B; typo removed in
revised version - spurious eq.12 immediately after eq.1
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