1,404 research outputs found
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Determining the effects of aqueous alteration on the distribution of oxygen isotopes in carbonaceous chondrites
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Evolved gas analysis of hydrated phases in Murchison and Orgueil
To better characterise the hydrated minerals in chondrites Evolved Gas Analysis of Murchison, Orgueil and selected minerals has been carried out. Meteorite water release profiles show significant differences to expected reference minerals
The malaria parasite cyclic GMP-dependent protein kinase plays a central role in blood-stage schizogony
A role for the Plasmodium falciparum cyclic GMP (cGMP)-dependent protein kinase (PfPKG) in gametogenesis in the malaria parasite was elucidated previously. In the present study we examined the role of PfPKG in the asexual blood-stage of the parasite life cycle, the stage that causes malaria pathology. A specific PKG inhibitor (compound 1, a trisubstituted pyrrole) prevented the progression of P. falciparum schizonts through to ring stages in erythrocyte invasion assays. Addition of compound 1 to ring-stage parasites allowed normal development up to 30 h postinvasion, and segmented schizonts were able to form. However, synchronized schizonts treated with compound 1 for ≥6 h became large and dysmorphic and were unable to rupture or liberate merozoites. To conclusively demonstrate that the effect of compound 1 on schizogony was due to its selective action on PfPKG, we utilized genetically manipulated P. falciparum parasites expressing a compound 1-insensitive PfPKG. The mutant parasites were able to complete schizogony in the presence of compound 1 but not in the presence of the broad-spectrum protein kinase inhibitor staurosporine. This shows that PfPKG is the primary target of compound 1 during schizogony and provides direct evidence of a role for PfPKG in this process. Discovery of essential roles for the P. falciparum PKG in both asexual and sexual development demonstrates that cGMP signaling is a key regulator of both of these crucial life cycle phases and defines this molecule as an exciting potential drug target for both therapeutic and transmission blocking action against malaria
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Experimental study of laboratory-heated CM2 chondrites Mighei and Murchison
We conducted experimental heating of two CM2 chondrites, Murchison and Mighei, to study changes in their oxygen isotopic compositions and mineralogy and explore possible genetic relationships between MCCs and normal CMs
Effective String Theory of Vortices and Regge Trajectories
Starting from a field theory containing classical vortex solutions, we obtain
an effective string theory of these vortices as a path integral over the two
transverse degrees of freedom of the string. We carry out a semiclassical
expansion of this effective theory, and use it to obtain corrections to Regge
trajectories due to string fluctuations.Comment: 27 pages, revtex, 3 figures, corrected an error with the cutoff in
appendix E (was previously D), added more discussion of Fig. 3, moved some
material in section 9 to a new appendi
Semiclassical Quantization of Effective String Theory and Regge Trajectories
We begin with an effective string theory for long distance QCD, and evaluate
the semiclassical expansion of this theory about a classical rotating string
solution, taking into account the the dynamics of the boundary of the string.
We show that, after renormalization, the zero point energy of the string
fluctuations remains finite when the masses of the quarks on the ends of the
string approach zero. The theory is then conformally invariant in any spacetime
dimension D. For D=26 the energy spectrum of the rotating string formally
coincides with that of the open string in classical Bosonic string theory.
However, its physical origin is different. It is a semiclassical spectrum of an
effective string theory valid only for large values of the angular momentum.
For D=4, the first semiclassical correction adds the constant 1/12 to the
classical Regge formula.Comment: 65 pages, revtex, 3 figures, added 2 reference
An Expertise-Oriented Evaluation of the Center for Entrepreneurship Development and Vocational Studies, Federal Polytechnic, Ado-Ekiti, Nigeria: Implications for Assessing and Improving the Federal Polytechnic System in Nigeria
An on-campus evaluative study was conducted at Federal Polytechnic’s Center for Entrepreneurship Development and Vocational Studies in Ado-Ekiti, Ekiti State, Nigeria. One of the evaluation objectives was to conduct an intensive on-site program review. Both quantitative and qualitative program-related data were assessed and a process evaluation was conducted. The aquaculture skills enterprise area was in highest demand by full-time students in both diploma programs, while soap making was in highest demand by part-time students. Data revealed that students scored highest on their final exam in the fourth-year skills training course (Practical Skills Training) and lowest in the first year theory course (Introduction to Entrepreneurship). Federal Polytechnic offers a National Diploma and a Higher National Diploma program. The Entrepreneurship Education program offered by the Center is core requirement of every student regardless of major. Students enroll in a theory course followed by a skills acquisition or laboratory course each academic year. Skills acquisition courses are offered in 15 small-business enterprise areas. A number of themes emerged from the qualitative data regarding the curriculum and program management and operations. The authors conclude with a process-based critique of the program review, with implications for future reviews in the Federal Polytechnic system. The Entrepreneurship Education program is in its fourth year and is considered a flagship program by national experts in Nigeri
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