409,767 research outputs found
Phase behavior and material properties of hollow nanoparticles
Effective pair potentials for hollow nanoparticles like the ones made from
carbon (fullerenes) or metal dichalcogenides (inorganic fullerenes) consist of
a hard core repulsion and a deep, but short-ranged, van der Waals attraction.
We investigate them for single- and multi-walled nanoparticles and show that in
both cases, in the limit of large radii the interaction range scales inversely
with the radius, , while the well depth scales linearly with . We predict
the values of the radius and the wall thickness at which the gas-liquid
coexistence disappears from the phase diagram. We also discuss unusual material
properties of the solid, which include a large heat of sublimation and a small
surface energy.Comment: Revtex, 13 pages with 8 Postscript files included, submitted to Phys.
Rev.
Elastic Interactions of Cells
Biological cells in soft materials can be modeled as anisotropic force
contraction dipoles. The corresponding elastic interaction potentials are
long-ranged ( with distance ) and depend sensitively on elastic
constants, geometry and cellular orientations. On elastic substrates, the
elastic interaction is similar to that of electric quadrupoles in two
dimensions and for dense systems leads to aggregation with herringbone order on
a cellular scale. Free and clamped surfaces of samples of finite size introduce
attractive and repulsive corrections, respectively, which vary on the
macroscopic scale. Our theory predicts cell reorientation on stretched elastic
substrates.Comment: Revtex, 6 pages, 2 Postscript files included, to appear in Phys. Rev.
Let
Neutrino and astroparticle physics : Working group report
The contributions made to the Working Group activities on neutrino and
astroparticle physics are summarised in this article. The topics discussed were
leptogenesis in Left-Right symmetric model, inflationary models in
Raman-Sundrum scenarios, ultra high energy cosmic rays and neutrino
oscillations in 4 flavour and decaying neutrino models.Comment: 11 pages; arXiv copy of contribution to WHEPP-6 proceeding
Deformation and tribology of multi-walled hollow nanoparticles
Multi-walled hollow nanoparticles made from tungsten disulphide (WS) show
exceptional tribological performance as additives to liquid lubricants due to
effective transfer of low shear strength material onto the sliding surfaces.
Using a scaling approach based on continuum elasticity theory for shells and
pairwise summation of van der Waals interactions, we show that van der Waals
interactions cause strong adhesion to the substrate which favors release of
delaminated layers onto the surfaces. For large and thin nanoparticles, van der
Waals adhesion can cause considerable deformation and subsequent delamination.
For the thick WS nanoparticles, deformation due to van der Waals
interactions remains small and the main mechanism for delamination is pressure
which in fact leads to collapse beyond a critical value. We also discuss the
effect of shear flow on deformation and rolling on the substrate.Comment: Latex, 13 pages with 3 Postscript figures included, to appear in
Europhysics Letter
Assessment of Occupational Diseases among Artisans and Factory Workers in Ifo, Nigeria
The ever increasing incidences of occupational diseases among workers have continually
drawn the attention of researchers towards ameliorating the situation. Investigation was
launched to assess occupational diseases among artisans and factory workers in Ifo,
Nigeria. Structured questionnaires with oral interview were employed to complement the
health records of the respondents at the Government accredited health center. Of the one
hundred and fifty six (156) respondents, ninety six (62%) are males and sixty one (38%)
female, sixty one point fifty four percent (61.54%) are youths of age 20 to 39 years, fifty
one (32.69%) are illiterates and one hundred and eight (69.21%) earn N100, 000 ($615)
and below as monthly wages. The diseases prevalent in these workers were evaluated to
include but not limited to disorders of muscles, bones, joints, skin and the respiratory
organs indicating that most of the jobs are such that causes damages to these special
parts of the body and could lead to deformities/incapacitation in old age. Common
amongst these diseases are Pre-patellar bursitis and Eczema (1.92% each),
Tuberculosis, Asthma and Sunburn (5.77% each). Toxic/inflammatory syndrome, hearing
impairment, allergies and computer vision syndrome (7.69% each). Two (1.28% in each
case) have been diagnosed of Lead poisoning, Lung cancer, Carpal tunnel syndrome,
Pulmonary fibrosis, Meniscus lesion and Olecranon bursitis. Upper airway disorders (4.49%), Irritations (3.21%), Post-traumatic stress syndrome (11.54%), skin allergies
(13.46%). Chronic bronchitis; Pneumonia; Pneumoconiosis; Hepatitis and Anthrax-like
infection (0.64 % each). The causes of these diseases/disorders include dusts from
quarry, textile, cotton, metal, paper, mineral, wood, cereals, cement, and chemical fumes
industries, extreme posture of wrist, repetitive movements, inhalations from petrol fuel,
prolonged pressure of the elbow region, prolonged kneeling/ squatting position, forceful
exertions and microorganisms. Adequate occupational health and safety awareness
through training and campaign should be provided. The use of personal protective
equipment among workers should also be encouraged
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