426 research outputs found
Where's the recovery?
Federal Reserve District, 12th ; Business cycles ; Employment (Economic theory)
First quarter bank results: good news, bad news
Banks and banking - West ; Banks and banking - California
The Use of Feeder Cells in the Cultivation of the Asexual Erythrocytic Stages of Plasmodium falciparum
While the technique of Trager and Jensen (1976) allows the in vitro cultivation of the asexual erythrocytic stages of P. falciparum, this method does have a number of limitations. Most isolates of P. falciparum grow poorly during the first weeks of cultivation and only some new isolates can eventually be established in culture. Methods to increase the proportion of isolates, and also the number of individual parasites within an isolate which could be established in long term culture were studied. Cultures of P. falciparum showed increased multiplication rates in the presence of a feeder cell layer of mouse peritoneal wash cells and within this population the adherent (macrophage enriched) population was the most important in promoting this increase. New isolates of P. falciparum adapted to culture more readily in the presence of a feeder cell layer of PWCS. Thirteen isolates were tested and only 3 were established in culture in the absence of PWCS. A further 6, however were adapted when cultured with PWCS. Three of the 4 isolates which were not established in culture with PWCS were known to have been taken from patients who had been treated with antimalarials and therefore the viability of these parasites at the time of culture was questionable. This was confirmed by the fact that these parasites did not complete a single asexual cycle. The effect of PWCS in the adaptation of new isolates of P. falciparum to long term culture was examined. It was found that the presence of PWCS led to the preservation of a greater degree of parasite diversity than that which was achieved under standard culture conditions. The presence of a feeder cell layer of mouse PWCS when cloning new isolates of P. falciparum (by limiting dilution) led to greatly increased cloning efficiency. Sixteen clones were produced from isolate AF using this method. These clones were examined using a panel of monoclonal antibodies and three different antigenic types were observed. In an attempt to streamline this cloning technique the feasibility of using cryopreserved PWCS was investigated. This was not, however, successful as the ability of cryopreserved PWCS to promote an increase in parasite growth declined rapidly during storage at -7
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"Don't Mind the Gap!" Reflections on Improvement Science as a Paradigm.
Responding to this issue's invitation to bring new disciplinary insights to the field of improvement science, this article takes as its starting point one of the field's guiding metaphors: the imperative to "mind the gap". Drawing on insights from anthropology, history, and philosophy, the article reflects on the origins and implications of this metaphoric imperative, and suggests some ways in which it might be in tension with the means and ends of improvement. If the industrial origins of improvement science in the twentieth century inform a metaphor of gaps, chasms, and spaces of misalignment as invariably imperfect and potentially dangerous, and therefore requiring bridging or closure, other currents that feed the discipline of improvement science suggest the potential value and uses of spaces of openness and ambiguity. These currents include the science of complex adaptive systems, and certain precepts of philosophical pragmatism acknowledged to inform improvement science. Going a step further, I reflect on whether or not these two contrasting approaches within improvement science should be treated as incommensurable paradigms, and what each approach tells us about the very possibility of accommodating seemingly irreconcilable or incommensurable approaches within improvement science
Anti-malarial drugs: how effective are they against Plasmodium falciparum gametocytes?
<p>Abstract</p> <p>Background</p> <p>Recent renewed emphasis on the eradication of malaria has highlighted the need for more tools with which to achieve this ambitious goal. One high priority area is the need to determine the gametocytocidal activity of both currently used anti-malarial drugs and those in the development pipeline. However, testing the activity of compounds against <it>Plasmodium falciparum </it>gametocytes is technically challenging both <it>in vivo </it>and <it>in vitro</it>.</p> <p>Methods</p> <p>Here the use of a simple robust assay to screen a panel of currently used and experimental anti-malarial drugs against mature <it>P. falciparum </it>gametocytes is described.</p> <p>Results</p> <p>Eight of 44 compounds tested reduced gametocyte viability by at least 50% and three showed IC<sub>50 </sub>values in nM range.</p> <p>Conclusions</p> <p>There is a need to identify new compounds with activity against late stage gametocytes and the information provided by this <it>in vitro </it>assay is a valuable first step, which can guide future clinical studies.</p
Metal-organic frameworks for platinum group metal extraction
This Thesis describes the synthesis and characterisation of a variety of functionalised metal-organic frameworks (MOFs). These MOFs have been used for the extraction of platinum group metal (PGM) compounds from aqueous and organic solvents and for the storage of gases such as CO2, CH4 and the C2 hydrocarbons.
Chapter 1 contains an introduction to PGM properties and uses with specific focus on the chemical properties which allow for separation of PGMs from base metal compounds and for separation between different PGM compounds. The synthesis and structure prediction of MOFs is then introduced, leading into an overview of the use of functionalised MOFs, especially those used for the encapsulation and extraction of metal ions from solution. General experimental techniques and details are described, as is the theory behind inductively coupled plasma optical emission spectrometry (ICP-OES), the most widely used analytical technique reported in this work.
Chapter 2 describes the synthesis of chemically stable amine-functionalised Zr(IV) MOFs; UiO-68-NH2 and UiO-66-NH2, for extraction of PGM anions from aqueous and acidic solutions. ICP-OES was used to show that both materials exhibit close to 100% uptake of PtCl62- when present in just 3.5 equivalents per anion, comparable to the best materials reported for PtCl62- extraction. Furthermore, UiO-66-NH2 exhibited consistently higher PtCl62- uptake from aqueous solutions than four industrially used materials supplied by Johnson Matthey. Back-extraction of PtCl62- was demonstrated simply by heating the doped MOF in 4 M HCl, removing 99% of the PGM while maintaining the phase and crystallinity of UiO-66-NH2. Separation of PdCl62- from PtCl62- from acidic HCl solutions was exhibited by UiO-66-NH2, showing an exceptional selectivity of 20:1 for Pd:Pt from 2 M HCl. Likewise, 100% selectivity for PtCl62- and PdCl62- over CuCl2 and CuSO4 from acidic solutions was demonstrated, even in cases in which Cu was in 100-fold excess. Solid state NMR was employed to confirm the interaction between the framework and the PGM anions, with XPS results suggesting that the encapsulated Pt species within UiO-66-NH2 may be PtCl3(NH2)3 or PtCl4(NH2)2.
Chapter 3 describes the synthesis and characterisation of a series of functionalised Cu(II) MOFs, NOTT-151, -155, -125 and -150, for the removal of neutral PGM complexes, Pd(OAc)2, PtCl4 and Rh2(OAc)4, from THF. The design of the MOFs allowed for an investigation into the effect of different topologies (ssa and fof), cage sizes and functional groups (amine, oxamide and methyl) on the uptake of each PGM complex. ICP-OES analysis showed that the MOFs were capable of extracting each PGM complex. The oxamide-functionalised NOTT-125 exhibited the most consistent uptake of Pd(OAc)2 with a maximum capacity of 35 mg g-1 (7 NH(CO)2NH groups per PtCl4). The amine-functionalised NOTT-155 showed the highest uptake of PtCl4, with a maximum capacity of 73 mg g-1 (4 NH2 groups per PtCl4). Uptake of Rh2(OAc)4 was generally low, however NOTT-125 showed a maximum extraction of 87 mg g-1 (3 NH(CO)2NH groups per PGM). The larger pore fof MOFs, NOTT-155 and NOTT-125, were more effective for each extraction than the MOFs of ssa topology, NOTT-151 and NOTT-150. However, of the ssa MOFs, amine-functionalised NOTT-151 was shown to give higher uptake of each PGM than the isostructural methyl-functionalised NOTT-150. This demonstrated the importance of incorporating a functional group capable of coordinating to the metal complex.
Chapter 4 introduces the use of a nitrogen-rich triazine core in the synthesis of a variety of organic linkers to prepare MOFs for gas storage applications. The preparation of a novel 3,24-connected Cu(II) MOF of rht topology, denoted NOTT-160, is described and the structure characterised using X-ray crystallography. The material is shown to exhibit good uptake of C2 hydrocarbons with uptake of 128 cc g-1, 115 cc g-1, 110 cc g-1 for C2H2, C2H4, C2H6 respectively at 298 K and 1 bar (this becomes 212 cc g-1, 175 cc g-1 and 201 cc g-1 at 273 K and 1 bar). The selectivities of 79:1 and 70:1 calculated using Henry’s law for the separations of C2H2:CH4 and C2H4:CH4 respectively at 298 K are the third and second highest reported values for a MOF under these conditions. Ideal adsorbed solution theory (IAST) was also employed to calculate and predict these selectivities and shows agreement with the results obtained using Henry’s law. In addition, NOTT-160 shows an exceptional volumetric working capacity for CH4 of 221 cm3 cm-3 at 80 bar and 298 K. This is the second highest working capacity reported for a MOF under these conditions, with the excellent performance attributed to the high porosity and comparatively high crystal density of the material.
Chapter 5 contains a summary of the work presented in this thesis
Aqua/Aura Inclination Adjust Maneuver Series Spring 2018 Planning
This will be presented at the International Earth Science Constellation Mission Operations Working Group meeting on December 6-8, 2017 to discuss the Aqua/Aura Spring 2018 Inclination Adjust Maneuver series planning. Presentation has been reviewed and approved by Eric Moyer, ESMO (Earth Science Mission Operations) Deputy Project Manager
Properties of serendipitous X-ray flares discovered in XMM-Newton observations
We present the results of a search of the XMM-Newton public data archive for
stellar X-ray flares. We find eight flaring sources for which we identify 7
optical counterparts. Three of these sources have distance estimates which
allow us to determine their luminosities. Based on the decay time of the flares
and their luminosity we derive loop half-lengths of ~2-7x10^10 cm and emission
measures of ~10^54 cm^-3: these are similar to values derived for other stellar
flaring sources. One of the stars shows two flares in close succession. We
discuss the likelihood of this double event being either sympathetic or
homologous in nature. A comparison to a pair of similar flares on the Sun
suggests that homology is the more likely process driving the flare event.Comment: Accepted MNRAS, 7 page
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Modeling for deformable mirrors and the adaptive optics optimization program
We discuss aspects of adaptive optics optimization for large fusion laser systems such as the 192-arm National Ignition Facility (NIF) at LLNL. By way of example, we considered the discrete actuator deformable mirror and Hartmann sensor system used on the Beamlet laser. Beamlet is a single-aperture prototype of the 11-0-5 slab amplifier design for NIF, and so we expect similar optical distortion levels and deformable mirror correction requirements. We are now in the process of developing a numerically efficient object oriented C++ language implementation of our adaptive optics and wavefront sensor code, but this code is not yet operational. Results are based instead on the prototype algorithms, coded-up in an interpreted array processing computer language
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