379 research outputs found
A case study of Caribbean chartered airline services for possible application in the Eastern Cape
Tourism is becoming a vital component of economic development in South Africa. In the light of South Africa having hosted the 2010Football World Cup, it is important to identify sustainable tourism that continues to benefit the economy long after the event is over.The Eastern Cape is identified as a region that has not been entirely successful in attracting large number of tourists, despite its variedtourist attractions. One of the constraints to tourism development is the lack of direct flight connections with northern Europe. As aresult, research into the development of charter services between Port Elizabeth, the largest city in the Eastern Cape, and selectednorthern European destinations is considered. The research looked at the successful tourism development policy in the Caribbeanand aimed to identify how similar policies could work in the Eastern Cape. A comparative case study of the connection between thecharter airline operations and tourism development in the Caribbean, with the focus on the Dominican Republic, was analysed toprovide motivation for such research. Its findings can be related to the Port Elizabeth-based charter airline operation being consideredin this study. A second objective was to identify constraints on the project or market failures which would prevent the implementationof charter services. The comparative case study was followed up by an actual cost benefit analysis of establishing a charterKeywords: airlines, Caribbean, case study, charter, constraints, development, market failures, South Africa, tourism
Lumps and P-branes in Open String Field Theory
We describe numerical methods for constructing lump solutions in open string
field theory. According to Sen, these lumps represent lower dimensional
Dp-Branes and numerical evaluation of their energy can be compared with the
expected value for the tension. We take particular care of all higher
derivative terms inherent in Witten's version of open string field theory. The
importance of these terms for off shell phenomena is argued in the text.
Detailed numerical calculations done for the case of general brane show
very good agreement with Sen's conjectured value. This gives credence to the
conjecture itself and establishes further the usefulness of Witten's version of
SFT .Comment: 11 pages, 1 figure, 1 table; v2: small typos correcte
Construction methods and quality control for concrete shell roofs
p. 177-187Concrete shells are moldable to any shape and can be made aesthetically beautiful. This
paper discusses the suitability of various methods of concrete shell roof construction,
necessary precautions and quality guidelines. Good construction practice for concrete shell roofs is also highlighted.Mihailescu, M.; Sundaram, R. (2009). Construction methods and quality control for concrete shell roofs. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/648
Worldsheet correlators in AdS(3)/CFT(2)
The AdS_3/CFT_2 correspondence is checked beyond the supergravity
approximation by comparing correlation functions. To this end we calculate 2-
and 3-point functions on the sphere of certain chiral primary operators for
strings on AdS_3 x S^3 x T^4. These results are then compared with the
corresponding amplitudes in the dual 2-dimensional conformal field theory. In
the limit of small string coupling, where the sphere diagrams dominate the
string perturbation series, beautiful agreement is found.Comment: 23 page
Elliptic supertube and a Bogomol'nyi-Prasad-Sommerfield D2-brane--anti-D2-brane Pair
An exact solution, in which a D2-brane and an anti-D2-brane are connected by
an elliptically tubular D2-brane, is obtained without any junction condition.
The solution is shown to preserve one quarter of the supersymmetries of the
type-IIA Minkowski vacuum. We show that the configuration cannot be obtained by
"blowing-up" from some inhomogeneously D0-charged superstrings. The BPS bound
tells us that it is rather composed of D0-charged D2-brane-anti-D2-brane pair
and a strip of superstrings connecting them. We obtain the correction to the
charges of the string end points in the constant magnetic background.Comment: v3. 12 pages, journal version; title changed, length trimmed to fit
for Rapid Communication forma
Coded Aperture and Compton Imaging for the Development of Ac-based Radiopharmaceuticals
Targeted alpha-particle therapy (TAT) has great promise as a cancer
treatment. Arguably the most promising TAT radionuclide that has been proposed
is Ac. The development of Ac-based radiopharmaceuticals has
been hampered due to the lack of effective means to study the daughter
redistribution of these agents in small animals at the preclinical stage. The
ability to directly image the daughters, namely Fr and Bi, via
their gamma-ray emissions would be a boon for preclinical studies. That said,
conventional medical imaging modalities, including single photon emission
computed tomography (SPECT) based on pinhole collimation, cannot be employed
due to sensitivity limitations. As an alternative, we propose the use of both
coded aperture and Compton imaging with the former modality suited to the
218-keV gamma-ray emission of Fr and the latter suited to the 440-keV
gamma-ray emission of Bi. This work includes coded aperture images of
Fr and Compton images of Bi in tumor-bearing mice injected with
Ac-based radiopharmaceuticals. These results are the first
demonstration of visualizing and quantifying the Ac daughters in small
animals via coded aperture and Compton imaging and serve as a stepping stone
for future radiopharmaceutical studies
Can Quantum de Sitter Space Have Finite Entropy?
If one tries to view de Sitter as a true (as opposed to a meta-stable)
vacuum, there is a tension between the finiteness of its entropy and the
infinite-dimensionality of its Hilbert space. We invetsigate the viability of
one proposal to reconcile this tension using -deformation. After defining a
differential geometry on the quantum de Sitter space, we try to constrain the
value of the deformation parameter by imposing the condition that in the
undeformed limit, we want the real form of the (inherently complex) quantum
group to reduce to the usual SO(4,1) of de Sitter. We find that this forces
to be a real number. Since it is known that quantum groups have
finite-dimensional representations only for root of unity, this suggests
that standard -deformations cannot give rise to finite dimensional Hilbert
spaces, ruling out finite entropy for q-deformed de Sitter.Comment: 10 pages, v2: references added, v3: minor corrections, abstract and
title made more in-line with the result, v4: published versio
Spectral Flow in AdS(3)/CFT(2)
We study the spectral flowed sectors of the H3 WZW model in the context of
the holographic duality between type IIB string theory in AdS(3)x S^3 x T^4
with NSNS flux and the symmetric product orbifold of T^4. We construct
explicitly the physical vertex operators in the flowed sectors that belong to
short representations of the superalgebra, thus completing the bulk-to-boundary
dictionary for 1/2 BPS states. We perform a partial calculation of the string
three-point functions of these operators. A complete calculation would require
the three-point couplings of non-extremal flowed operators in the H3 WZW model,
which are at present unavailable. In the unflowed sector, perfect agreement has
recently been found between the bulk and boundary three-point functions of 1/2
BPS operators. Assuming that this agreement persists in the flowed sectors, we
determine certain unknown three-point couplings in the H3 WZW model in terms of
three-point couplings of affine descendants in the SU(2) WZW model.Comment: 50 pages, 2 figure
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