23,461 research outputs found
Glassy dynamics in granular compaction
Two models are presented to study the influence of slow dynamics on granular
compaction. It is found in both cases that high values of packing fraction are
achieved only by the slow relaxation of cooperative structures. Ongoing work to
study the full implications of these results is discussed.Comment: 12 pages, 9 figures; accepted in J. Phys: Condensed Matter,
proceedings of the Trieste workshop on 'Unifying concepts in glass physics
Menstrual health management: Knowledge and practices among adolescent girls
Objectives: To assess the knowledge and attitude of adolescent girls regarding menstruation and menstrual hygiene.Material and Methods: After approval by the ethical committee , the study was conducted on 340 adolescent girls aged 12-19 years, belonging to an urban slum area of Delhi. This was a questionnaire based cross-sectional study conducted over a period of 9 months in a tertiary hospital. Confidentiality of the subjects was ensured.Results: Out of 340 girls 69 % were between 16-19 years. Source of information about menstruation in majority of the cases was mother (60%). Only 48% girls knew menstruation before menarche and 24% girls knew uterus as the organ for menstruation. 71 % girls used sterile sanitary napkins as absorbent. Satisfactory changing of pads (>2pads/day) was done by 68 % and 77% girls cleaned the genitalia satisfactorily (>2 times/day). 41% girls were aware of the fact that unhygienic use of pad could be a source of genital infection and 8% girls had associated vaginal discharge. Social restrictions during menses in the form of religious activities, drop out from school, avoiding certain foods etc were practiced in many families.Conclusion: Although the menstrual practices appear to be satisfactory in major percentage of girls but knowledge regarding menstrual hygiene is worrisome, as maximum girls are unaware of menarche and physiology of menstruation. Inclusion of such information in the school curriculum and wider coverage in mass media will help to bridge this gap.Keywords: Adolescence; hygiene; menstruation healt
Chaotic quantum dots with strongly correlated electrons
Quantum dots pose a problem where one must confront three obstacles:
randomness, interactions and finite size. Yet it is this confluence that allows
one to make some theoretical advances by invoking three theoretical tools:
Random Matrix theory (RMT), the Renormalization Group (RG) and the 1/N
expansion. Here the reader is introduced to these techniques and shown how they
may be combined to answer a set of questions pertaining to quantum dotsComment: latex file 16 pages 8 figures, to appear in Reviews of Modern Physic
Smoothing of sandpile surfaces after intermittent and continuous avalanches: three models in search of an experiment
We present and analyse in this paper three models of coupled continuum
equations all united by a common theme: the intuitive notion that sandpile
surfaces are left smoother by the propagation of avalanches across them. Two of
these concern smoothing at the `bare' interface, appropriate to intermittent
avalanche flow, while one of them models smoothing at the effective surface
defined by a cloud of flowing grains across the `bare' interface, which is
appropriate to the regime where avalanches flow continuously across the
sandpile.Comment: 17 pages and 26 figures. Submitted to Physical Review
Moments of a single entry of circular orthogonal ensembles and Weingarten calculus
Consider a symmetric unitary random matrix
from a circular orthogonal ensemble. In this paper, we study moments of a
single entry . For a diagonal entry we give the explicit
values of the moments, and for an off-diagonal entry we give leading
and subleading terms in the asymptotic expansion with respect to a large matrix
size . Our technique is to apply the Weingarten calculus for a
Haar-distributed unitary matrix.Comment: 17 page
Frobenius Splittings
We give a gentle introduction to Frobenius splittings. Then we recall a few
results that have been obtained with the method.Comment: 21 pages, typos correcte
Competition and cooperation:aspects of dynamics in sandpiles
In this article, we review some of our approaches to granular dynamics, now
well known to consist of both fast and slow relaxational processes. In the
first case, grains typically compete with each other, while in the second, they
cooperate. A typical result of {\it cooperation} is the formation of stable
bridges, signatures of spatiotemporal inhomogeneities; we review their
geometrical characteristics and compare theoretical results with those of
independent simulations. {\it Cooperative} excitations due to local density
fluctuations are also responsible for relaxation at the angle of repose; the
{\it competition} between these fluctuations and external driving forces, can,
on the other hand, result in a (rare) collapse of the sandpile to the
horizontal. Both these features are present in a theory reviewed here. An arena
where the effects of cooperation versus competition are felt most keenly is
granular compaction; we review here a random graph model, where three-spin
interactions are used to model compaction under tapping. The compaction curve
shows distinct regions where 'fast' and 'slow' dynamics apply, separated by
what we have called the {\it single-particle relaxation threshold}. In the
final section of this paper, we explore the effect of shape -- jagged vs.
regular -- on the compaction of packings near their jamming limit. One of our
major results is an entropic landscape that, while microscopically rough,
manifests {\it Edwards' flatness} at a macroscopic level. Another major result
is that of surface intermittency under low-intensity shaking.Comment: 36 pages, 23 figures, minor correction
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