ARS - 2013http://repository.kln.ac.lk/handle/123456789/1712024-03-29T02:25:57Z2024-03-29T02:25:57ZProviding access to public health information via the institutional repository, Faculty of Medicine: A feasibility study based on medical undergraduates.Abeygunasekera, C.M.Marasinghe, M.P.L.R.http://repository.kln.ac.lk/handle/123456789/238612021-12-19T05:06:56Z2013-01-01T00:00:00ZProviding access to public health information via the institutional repository, Faculty of Medicine: A feasibility study based on medical undergraduates.
Abeygunasekera, C.M.; Marasinghe, M.P.L.R.
Community Medicine Clerkship and Community Attachment programs provide opportunity for
medical undergraduates to learn how public health services are provided to the community.
Their knowledge on health promotion, disease prevention, healthcare planning and management,
demography and understanding epidemiology of diseases in the Sri Lankan context are very
important. They are expected to read from diverse information sources to gain this knowledge,
in addition to field based learning. As most of the recommended reading materials are considered
grey literature sources, students are in a difficulty to access those resources within the library.
Students face difficulties in accessing available online materials too, as some of the websites do
not provide the information in a user friendly manner.
With the understanding of possible barriers to access information, the Medical Library,
University of Kelaniya, has developed a repository collection on ‘Public Health Information
Resources,’ which are recommended as student reading materials for Community Medicine
Clerkship and Attachment programs. This is under its online Institutional Repository (IR),
developed using DSpace Software. This repository provides links to access a collection of
resources published by different institutes. This is in addition to university libraries, which
develop online digital repositories to preserve and distribute the intellectual scholarly
information of the parent institute.
A questionnaire and the User Guide to access the repository were given to a sample of fifty (50)
students from Batch 21, who completed the Clerkship programme. Response rate to the
questionnaire was 82% and more than 80% of students who were among the respondents ranked
the collection as a useful resource which fulfilled their public health information needs. Barriers
to information access were also assessed. Respondents have identified a list of difficulties they
had in the past. Based on the feedback received, a resource collection inclusive of students’
suggestions is being planned to be introduced to the next batch of students.
2013-01-01T00:00:00ZThe red shifts of pulses of light which are emitted at a point on the surface of a sphere and at a point inside of the sphere comprising electrically counterpoised dust with constant uniform density as observed by an observer in a large distance away in the exterior regionWimaladharma, N.A.S.N.de Silva, N.Hewageegana, P.S.http://repository.kln.ac.lk/handle/123456789/86002017-08-17T08:28:01Z2013-01-01T00:00:00ZThe red shifts of pulses of light which are emitted at a point on the surface of a sphere and at a point inside of the sphere comprising electrically counterpoised dust with constant uniform density as observed by an observer in a large distance away in the exterior region
Wimaladharma, N.A.S.N.; de Silva, N.; Hewageegana, P.S.
A sphere, comprising a special kind of matter, with electrically counterpoised dust in which all
the elastic forces have been cancelled out has been considered.
A static spherically symmetric solution to Einstein’s field equations has been found using a new
set of boundary conditions. In introducing these new boundary conditions, we assume that the
radial coordinates in and out of the sphere need not be the same and we are guided by the notion
of what may be called proper distances and proper times of two observers on either side of the
sphere .In these new boundary conditions we replace ordinary partial derivatives by generalized
partial derivatives in curvilinear coordinates.
Then the solution takes the form
2 2 2
2
2 2
2
2 1
dr r d
l
r
c dt
l
r
ds
0 r a
2 2 2
2
2 2 2
2
2
2 1
1
1
dR R d
R
A
c dT
R
A
ds R A
where
l
a
l
a
A
2
2 ,
l
r
is the solution of the Lane-Emden equation
y r lx
dx
dy
x
dx
d
x
,
1 2 3
2 , l is a constant of dimension length , a is the coordinate radius of
the sphere.
In our approach r a in the matter-filled region corresponds to R Ain the region without
matter, outside the sphere.
The red shift of a pulse of light emitted at a point on the surface of the sphere as observed by an
observer who is at a large distance in the exterior region of the sphere is calculated. This
valueequals to
l
a
l
a
l
a
l
a
when the observer is at infinity.
The comparison of this value with the value for the red shift obtained using the metric derived
using the standard (Lichernowicz) boundary conditions which says that the metric coefficients
and their partial derivatives are continuous across the boundary of the sphere when the observer
is at infinity is also done. It is shown that the values obtained for the red shifts are the same
irrespective of the boundary conditions used.
The red shift of a pulse of light emitted at a point inside of the surface of the sphere as observed
by an observer who is at a large distance in the exterior region of the sphere is also calculated
and it is shown that the value obtained is different from the value obtained using the metric
derived using standard (Lichernowicz) boundary conditions.
2013-01-01T00:00:00ZThe velocity of a particle relative to an observer instantaneously at rest coinciding with the point through which the particle passes in a spherical distribution of matter comprising electrically counterpoised dust with constant uniform densityWimaladharma, N.A.S.N.de Silva, N.Hewageegana, P.S.http://repository.kln.ac.lk/handle/123456789/85992017-08-17T08:29:27Z2013-01-01T00:00:00ZThe velocity of a particle relative to an observer instantaneously at rest coinciding with the point through which the particle passes in a spherical distribution of matter comprising electrically counterpoised dust with constant uniform density
Wimaladharma, N.A.S.N.; de Silva, N.; Hewageegana, P.S.
A sphere comprising a special kind of matter, electrically counterpoised dust in which all the
elastic forces have been cancelled out, has been considered.
A static spherically symmetric solution to Einstein’s field equations has been found using a new
set of boundary conditions. In introducing these new boundary conditions, we assume that the
radial coordinates in and out of the sphere need not be the same and we are guided by the notion
of what may be called proper distances and proper times of two observers on either side of the
sphere. In these new boundary conditions we replace ordinary partial derivatives by generalized
partial derivatives in curvilinear coordinates.
Then the solution takes the form
2 2 2
2
2 2
2
2 1
dr r d
l
r
c dt
l
r
ds
0 r a
2 2 2
2
2 2 2
2
2
2 1
1
1
dR R d
R
A
c dT
R
A
ds
R A
where
l
a
l
a
A
2
2 ,
l
r
is the solution of the Lane-Emden equation
y r lx
dx
dy
x
dx
d
x
,
1 2 3
2 , l is a constant of dimension length , a is the coordinate radius of
the sphere .
In our approach r a in the matter-filled region corresponds to R A in the region without
matter, outside the sphere.The velocity of a particle relative to an observer instantaneously at rest coinciding with the point
through which the particle passes has been calculated for this metric.
Using these values, a minimum value for a measure of energy with which the particle has to be
projected at the center of the sphere, to reach infinity has been calculated to be
l
a
l
a
l
a
c
where c is the velocity of the light.
A minimum value for a measure of energy with which the particle has to be projected at the
center of the sphere, to reach infinity has also been calculated for metric derived using standard
(Lichernowicz) boundary conditions which says that the metric coefficients and their partial
derivatives are continuous across the boundary of the sphere.
It is shown that we have the same value irrespective of boundary conditions used.
Also a minimum value for a measure of energy with which the particle has to be projected at the
center of the sphere, to reach the exterior region of the sphere has been calculated to be
l
a
c
.
The comparison of this value with the value obtained for the metric derived using standard
(Lichernowicz) boundary conditions is also done and it is shown that these two values are the
same irrespective of the boundary conditions used.
2013-01-01T00:00:00ZThetanulls of cyclic curves of genus 4Wijesiri, G.S.http://repository.kln.ac.lk/handle/123456789/85982023-04-26T06:38:44Z2013-01-01T00:00:00ZThetanulls of cyclic curves of genus 4
Wijesiri, G.S.
Let
be an irreducible smooth projective cyclic curve of genus
defined over the complex field
. These are by definition compact Riemann surfaces of genus
(unless we allow singular points) admitting an automorphism
such that
and
generates a normal subgroup of the automorphism group
of
When the curve is hyperelliptic, then the curve has extra automorphisms, in particular
is not the hyperelliptic involution. The condition implies to having an equation
for the curve, where
is an affine coordinate on
and
has order
. The branch points of
together with the signature of the cover provide algebraic coordinates for the curve in moduli. Choosing a symplectic homology basis
for a given curve
of genus
such that the intersection products
and
where
is the Kronecker delta and a basis
for the space of holomorphic 1- forms such that
we can define the period matrix
of
It can be shown that
is an element of the Siegel upper-half space
. For any
and any
the Riemann’s theta function is defined as
Any point
where
is the Jacobian of the curve
can be written uniquely as
, where
For any
the theta function with rational characteristics is defined as
When the entries of column vectors
are from the set
, then the corresponding theta functions with rational characteristics are known as theta characteristics. A scalar obtained by evaluating a theta characteristics at
is called a thetanull.
The problem of expressing branch points
in terms of transcendentals (period matrix, thetanulls, etc.,) is classical. This is an old problem that goes back to Riemann, Jacobi, Picard and Rosenhein. We do not aim here at a complete account of the classical or contemporary work on these problems. We determine the curves of genus 4 in terms of thetanulls and further study relations among the classical thetanulls of cyclic curves
(of genus 4) with an automorphisms. In our work we use formulas for small genus curves introduced by Rosenhein, Thomae’s formulas for hyperelliptic curves, some recent results of Hurwitz space theory, and symbolic manipulation. Inverting the period map has an application in fast genus two curves arithmetic incryptography. We determine similar formulas for genus 4 hyperelliptic curves as the one used in cryptography using genus 2 algebraic curves.
2013-01-01T00:00:00Z