671 research outputs found
Thermal effects on atomic friction
We model friction acting on the tip of an atomic force microscope as it is
dragged across a surface at non-zero temperatures. We find that stick-slip
motion occurs and that the average frictional force follows ,
where is the tip velocity. This compares well to recent experimental work
(Gnecco et al, PRL 84, 1172), permitting the quantitative extraction of all
microscopic parameters. We calculate the scaled form of the average frictional
force's dependence on both temperature and tip speed as well as the form of the
friction-force distribution function.Comment: Accepted for publication, Physical Review Letter
Nanosized Sodium-Doped Lanthanum Manganites: Role of the Synthetic Route on their Physical Properties
In this paper we present the results of the synthesis and characterisation of
nanocrystalline La1-xNaxMnO3+delta samples. Two synthetic routes were employed:
polyacrylamide-based sol-gel and propellant synthesis. Pure, single phase
materials were obtained with grain size around 35 nm for the sol-gel samples
and around 55 nm for the propellant ones, which moreover present a more broaden
grain size distribution. For both series a superparamagnetic behaviour was
evidenced by means of magnetisation and EPR measurements with peculiar features
ascribable to the different grain sizes and morphology. Preliminary
magnetoresistivity measurements show enhanced low-field (< 1 T)
magnetoresistance values which suggest an interesting applicative use of these
manganites.Comment: 31 Pages 10 Figures to appear in Chem. Mate
Consistent Approximation of Local Flow Behavior for 2D Vector Fields Using Edge Maps
Abstract not provide
Causal attribution of mental illness in south-eastern Nigeria
Background:
Understanding of mental illness in sub-Saharan Africa has remained under-researched in spite of the high and increasing neuropsychiatric burden of disease in the region.
Aims:
This study investigated the causal beliefs that the Igbo people of south-eastern Nigeria hold about schizophrenia, with a view to establishing the extent to which the population makes psychosocial, biological and supernatural attributions.
Method:
Multi-stage sampling was used to select participants (N = 200) to which questionnaires were administered.
Results:
Mean comparison of the three causal models revealed a significant endorsement of supernatural causation. Logistic regressions revealed significant contributions of old age and female gender to supernatural attribution; old age, high education and Catholic religious denomination to psychosocial attributions; and high education to biological attributions.
Conclusions:
It is hoped that the findings would enlighten, augment literature and enhance mental health care service delivery
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Psychosocial aspects of feeding children with neurodisability
The psychosocial support needs of parents considering a gastrostomy feeding tube for their disabled child are often overlooked, yet there is a growing body of evidence that attests to the decisional conflicts parents, often mothers, experience. This may be in addition to the stress associated with feeding a disabled child. The support needs of families and caregivers should be assessed, including the values parents attach to oral and tube feeding. Structured support should be embedded within the care pathway and both professionals, and service users, with appropriate training should be identified to ensure parental information needs, and any emotional, practical and financial issues are addressed
Granular systems in the Coulomb blockade regime
Disordered granular systems, at temperatures where charging effects are
important, are studied, by means of an effective medium approximation. The
intragrain charging energy leads to insulating behavior at low temperatures,
with a well defined Coulomb gap. Non equilibrium effects can give rise to a
zero temperature transition between a metallic, gapless phase, and an
insulating phase
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