161 research outputs found
A synopsis on the effects of anthropogenic greenhouse gases emissions from power generation and energy consumption
Despite the looming difficult energy context in the majority of countries in the world, global change in environmental dignity resulting from power generation and energy consumption scenario is rapidly becoming a globally disturbing phenomenon. Stakeholders and environmental activists alike have been clamouring for adoption of reduction procedures using sustainable means because ignominious environmental practices have associated disastrous consequences. Increasing essential strategies are needed to fortify the pursuit for the reduction in the emissions from power generation and energy consumption. Therefore, this article presents an overview of the effects of anthropogenic energy generation and consumption practices capable of ejecting emissions of greenhouse gases into the atmosphere. It also endeavors to identify some greenhouse gas emission reduction and control measures
Off-shell supergravity-matter couplings in three dimensions
We develop the superspace geometry of N-extended conformal supergravity in
three space-time dimensions. General off-shell supergravity-matter couplings
are constructed in the cases N=1,2,3,4.Comment: 73 pages; V5: typos in eqs. (3.4b), (3.17) and (4.24) correcte
Six-dimensional Supergravity and Projective Superfields
We propose a superspace formulation of N=(1,0) conformal supergravity in six
dimensions. The corresponding superspace constraints are invariant under
super-Weyl transformations generated by a real scalar parameter. The known
variant Weyl super-multiplet is recovered by coupling the geometry to a
super-3-form tensor multiplet. Isotwistor variables are introduced and used to
define projective superfields. We formulate a locally supersymmetric and
super-Weyl invariant action principle in projective superspace. Some families
of dynamical supergravity-matter systems are presented.Comment: 39 pages; v3: some modifications in section 2; equations (2.3),
(2.14b), (2.16) and (2.17) correcte
A Novel View on the Physical Origin of E8
We consider a straightforward extension of the 4-dimensional spacetime
to the space of extended events associated with strings/branes, corresponding
to points, lines, areas, 3-volumes, and 4-volumes in . All those objects
can be elegantly represented by the Clifford numbers . This leads to the
concept of the so-called Clifford space , a 16-dimensional manifold
whose tangent space at every point is the Clifford algebra . The latter space besides an algebra is also a vector space whose
elements can be rotated into each other in two ways: (i) either by the action
of the rotation matrices of SO(8,8) on the components or (ii) by the left
and right action of the Clifford numbers exp [\alpha^A \gam_A] and
exp [\beta^A \gam_A] on . In the latter case, one does not recover all
possible rotations of the group SO(8,8). This discrepancy between the
transformations (i) and (ii) suggests that one should replace the tangent space
with a vector space whose basis elements are
generators of the Clifford algebra , which contains the Lie
algebra of the exceptional group E as a subspace. E thus arises from
the fact that, just as in the spacetime there are -volumes generated
by the tangent vectors of the spacetime, there are -volumes,
, in the Clifford space , generated by the tangent
vectors of .Comment: 14 page
D-branes in PP-wave light cone string field theory
The cubic interaction vertex and the dynamical supercharges are constructed
for open strings ending on D7-branes, in light-cone superstring field theory in
PP-wave background. In this context, we write down the symmetry generators in
terms of the relevant group structure: SU(2) x SU(2) x SO(2) x SO(2),
originating from the eight transverse directions in the PP-wave background and
use the expressions to explicitly construct the vertex at the level of stringy
zero modes. The results are further generalized to include all the stringy
excitations as well.Comment: 30 pages, correction in eqn. (4.28), few equations (appendix),
Comments (p.17-18) and a reference (no. 58) added, typo is corrected in eqn.
(4.5
SOME ABSTRACT PROPERTIES OF SEMIGROUPS APPEARING IN SUPERCONFORMAL THEORIES
A new type of semigroups which appears while dealing with
superconformal symmetry in superstring theories is considered. The ideal series
having unusual abstract properties is constructed. Various idealisers are
introduced and studied. The ideal quasicharacter is defined. Green's relations
are found and their connection with the ideal quasicharacter is established.Comment: 11 page
Three-dimensional (p,q) AdS superspaces and matter couplings
We introduce N-extended (p,q) AdS superspaces in three space-time dimensions,
with p+q=N and p>=q, and analyse their geometry. We show that all (p,q) AdS
superspaces with X^{IJKL}=0 are conformally flat. Nonlinear sigma-models with
(p,q) AdS supersymmetry exist for p+q4 the target space geometries
are highly restricted). Here we concentrate on studying off-shell N=3
supersymmetric sigma-models in AdS_3. For each of the cases (3,0) and (2,1), we
give three different realisations of the supersymmetric action. We show that
(3,0) AdS supersymmetry requires the sigma-model to be superconformal, and
hence the corresponding target space is a hyperkahler cone. In the case of
(2,1) AdS supersymmetry, the sigma-model target space must be a non-compact
hyperkahler manifold endowed with a Killing vector field which generates an
SO(2) group of rotations of the two-sphere of complex structures.Comment: 52 pages; V3: minor corrections, version published in JHE
Can agricultural cultivation methods influence the healthfulness of crops for foods
The aim of the current study was to investigate if there are any health effects of long-term consumption of organically grown crops using a rat model. Crops were retrieved over two years from along-term field trial at three different locations in Denmark, using three different cultivation systems(OA, organic based on livestock manure; OB, organic based on green manure; and C, conventional with mineral fertilizers and pesticides)with two field replicates. The cultivation system had an impact on the nutritional quality, affecting γ-tocopherol, some amino acids, and fatty acid composition. Additionally, the nutritional quality was affected by harvest year and location. However, harvest year and location rather than cultivation system affected the measured health biomarkers. In conclusion, the differences in dietary treatments composed of ingredients from different cultivation systems did not lead to significant differences in the measured health biomarkers, except for a significant difference in plasma IgGl evels
Discrete approaches to quantum gravity in four dimensions
The construction of a consistent theory of quantum gravity is a problem in
theoretical physics that has so far defied all attempts at resolution. One
ansatz to try to obtain a non-trivial quantum theory proceeds via a
discretization of space-time and the Einstein action. I review here three major
areas of research: gauge-theoretic approaches, both in a path-integral and a
Hamiltonian formulation, quantum Regge calculus, and the method of dynamical
triangulations, confining attention to work that is strictly four-dimensional,
strictly discrete, and strictly quantum in nature.Comment: 33 pages, invited contribution to Living Reviews in Relativity; the
author welcomes any comments and suggestion
Xyloglucan endotransglucosylase and cell wall extensibility
Transgenic tomato hypocotyls with altered levels of an XTH gene were used to study how XET activity could affect the hypocotyl growth and cell wall extensibility. Transgenic hypocotyls showed significant over-expression (line 13) or co-suppression (line 33) of the SlXTH1 in comparison with the wild type, with these results being correlated with the results on specific soluble XET activity, suggesting that SlXTH1 translates mainly for a soluble XET isoenzyme. A relationship between XET activity and cell wall extensibility was found, and the highest total extensibility was located in the apical hypocotyl segment of the over-expressing SlXTH1 line, where the XET-specific activity and hypocotyl growth were also highest compared with the wild line
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