6,343 research outputs found
Epithelial scatter factor and development of the chick embryonic axis.
No full textPerryman M., & Stoker M
Inner-sphere complexation of cations at the rutile-water interface: A concise surface structural interpretation with the CD and MUSIC model
No full textAcid–base reactivity and ion-interaction between mineral surfaces and aqueous solutions is most frequently investigated at the macroscopic scale as a function of pH. Experimental data are then rationalized by a variety of surface complexation models. These models are thermodynamically based which in principle does not require a molecular picture. The models are typically calibrated to relatively simple solid-electrolyte solution pairs and may provide poor descriptions of complex multi-component mineral–aqueous solutions, including those found in natural environments. Surface complexation models may be improved by incorporating molecular-scale surface structural information to constrain the modeling efforts. Here, we apply a concise, molecularly-constrained surface complexation model to a diverse suite of surface titration data for rutile and thereby begin to address the complexity of multi-component systems. Primary surface charging curves in NaCl, KCl, and RbCl electrolyte media were fit simultaneously using a charge distribution (CD) and multisite complexation (MUSIC) model [Hiemstra T. and Van Riemsdijk W. H. (1996) A surface structural approach to ion adsorption: the charge distribution (CD) model. J. Colloid Interf. Sci. 179, 488–508], coupled with a Basic Stern layer description of the electric double layer. In addition, data for the specific interaction of Ca2+ and Sr2+ with rutile, in NaCl and RbCl media, were modeled. In recent developments, spectroscopy, quantum calculations, and molecular simulations have shown that electrolyte and divalent cations are principally adsorbed in various inner-sphere configurations on the rutile 1 1 0 surface [Zhang Z., Fenter P., Cheng L., Sturchio N. C., Bedzyk M. J., Predota M., Bandura A., Kubicki J., Lvov S. N., Cummings P. T., Chialvo A. A., Ridley M. K., Bénézeth P., Anovitz L., Palmer D. A., Machesky M. L. and Wesolowski D. J. (2004) Ion adsorption at the rutile–water interface: linking molecular and macroscopic properties. Langmuir 20, 4954–4969]. Our CD modeling results are consistent with these adsorbed configurations provided adsorbed cation charge is allowed to be distributed between the surface (0-plane) and Stern plane (1-plane). Additionally, a complete description of our titration data required inclusion of outer-sphere binding, principally for Cl- which was common to all solutions, but also for Rb+ and K+. These outer-sphere species were treated as point charges positioned at the Stern layer, and hence determined the Stern layer capacitance value. The modeling results demonstrate that a multi-component suite of experimental data can be successfully rationalized within a CD and MUSIC model using a Stern-based description of the EDL. Furthermore, the fitted CD values of the various inner-sphere complexes of the mono- and divalent ions can be linked to the microscopic structure of the surface complexes and other data found by spectroscopy as well as molecular dynamics (MD). For the Na+ ion, the fitted CD value points to the presence of bidenate inner-sphere complexation as suggested by a recent MD study. Moreover, its MD dominance quantitatively agrees with the CD model prediction. For Rb+, the presence of a tetradentate complex, as found by spectroscopy, agreed well with the fitted CD and its predicted presence was quantitatively in very good agreement with the amount found by spectroscopy
The chick model system: a distinguished past and a great future
No full textWhen I was asked by the Chief Editor of the Int. J. Dev. Biol. to consider editing a Special Issue about “the chick”, I was first hesitant, because I had already edited such an issue for another journal in 2004 (Mech. Dev. volume 121), when the sequence of the chick genome was first released (Stern, 2004, 2005). But at the same time I was surprised that this journal, well known for its Special Issues of which many have become important historical and literary land-marks to the developmental biology literature, had not yet produced a volume on what is probably the oldest developmental model system. Despite this, it is often forgotten that much of what we know (or think we know) about human developmental events is due to extrapolation from chick embryological studies
A role of HGF/SF in neural induction and its expression in Hensen's node during gastrulation.
No full textCD-MUSIC-EDL Modeling of Pb<sup>2+</sup> Adsorption on Birnessites: Role of Vacant and Edge Sites
No full textThe
surface complexation modeling of metal adsorption to birnessites
is in its infancy compared to the charge-distribution multisite ion
complexation (CD-MUSIC) models for iron/aluminum (hydr)oxides. Therefore,
using X-ray diffraction with Rietveld refinement to obtain the reactive
sites and their densities, a CD-MUSIC model combined with a Stern–Gouy–Chapman
electrical double layer (EDL) model for the external surface and a
Donnan model for the interlayer surface is developed for birnessites
with different Mn average oxidation state (MnAOS). Proton affinity
constants and the charge distributions of Pb surface complexes were
calculated a priori. By fitting Pb adsorption data to the model the
obtained equilibrium constants (logKPb) of Pb complexes were 6.9–10.9 for the double-corner-sharing
and double-edge-sharing Pb2+ complexes on the edge sites
and 2.2–6.5 for the triple-corner-sharing Pb2+ complex
on the vacancies. The larger logKPb value
was obtained for higher MnAOS. Speciation calculations showed that
with increasing MnAOS from 3.67 to 3.92 the interlayer surface contribution
to the total Pb2+ adsorption increased from 43.2% to 48.6%,
and the vacancy contribution increased from 43.9% to 54.7%. The vacancy
contribution from interlayer surface was predominant. The present
CD-MUSIC-EDL model contributes to understand better the difference
in metal adsorption mechanism between birnessite and iron/aluminum
(hydr)oxides
Author Co-Citation Analysis (ACA): a powerful tool for representing implicit knowledge of scholar knowledge workers
No full textIn the last decade, knowledge has emerged as one of the most important and valuable organizational assets. Gradually this importance caused to emergence of new discipline entitled ―knowledge management‖. However one of the major challenges of knowledge management is conversion implicit or tacit knowledge to explicit knowledge. Thus Making knowledge visible so that it can be better accessed, discussed, valued or generally managed is a long-standing objective in knowledge management. Accordingly in this paper author co- citation analysis (ACA) will be proposed as an efficient technique of knowledge visualization in academia (Scholar knowledge workers)
Computational Analysis of the U.S FTAs with Central America, Australia, And Morocco
No full textWe use the Michigan Model of World Production and Trade to assess the economic effects of the U.S. bilateral FTAs negotiated with Central America, Australia, and Morocco. The model covers 18 economic sectors in each of 22 countries/regions and is based on Version 5.4 of the GTAP database for 1997 together with specially constructed estimates of services barriers and other data on sectoral employment and numbers of firms. The distinguishing feature of the model is that it incorporates monopolistic competition in the manufacturing and services sectors, including increasing returns and product variety. The modeling focus is on the effects of the bilateral removal of tariffs on agriculture and manufactures and services barriers. Rules of origin and other restrictive measures and the non-trade aspects of the FTAs are not taken into account due to data constraints. The computational results indicate that the benefits of bilateral FTAs for the United States and partner countries are rather small in both absolute and relative terms, and that far greater benefits could be realized if the United States and its FTA partners adopted unilateral free trade and especially if multilateral free trade was adopted by all countries/regions in the global trading system.Free Trade Agreements, Unilateral Liberalization, Multilateral Liberalization
Portfolio of recorded performances and exegesis: Messiaen’s musical language for the jazz pianist - an exploration through performance.
No full textMoving beyond Gunther Schuller’s Third Stream amalgamation of classical and jazz, this study explores whether the musical language of Olivier Messiaen can make a valid contribution to jazz piano performance. Initially, my project sought to answer such questions as: What elements of the musical language of Messiaen already exist in the jazz vocabulary? Am I able to extend this further? What are the timbral structures and pianistic effects within Messiaen’s musical language? What will be the most effective application of Messiaen’s musical language to jazz piano performance? Endeavouring to answer the final question led me to consider such aspects as whether the project should be limited to quoting Messiaen motifs, arranging Messiaen melodies, replacing jazz harmonic structures on standards with examples from Messiaen’s musical language or whether it would be better to approach the research conceptually. The work of Hubert Nuss provided encouraging reassurance that this was not an impossible task. In order to articulate this conception, the initial challenge was to decide how the classical and jazz worlds might meet in a ‘Messiaen’ technique. The approach adopted was similar to that used for undergraduate jazz study, namely, immersion in the piano scores and recordings of Messiaen’s music as well as by live performances. This was followed by the development and assessment of a contrived approach when specific techniques, such as tonal colourings or harmonic structures, were developed through prepared exercises and consciously included in my performance. It was then compared with an intuitive approach when no such precise parameters were established. This submission consists of CD recordings of two public recitals and an exegesis. It documents the development of this Messiaen technique and discusses its application in my performances. It also demonstrates the ways that Messiaen’s musical language can be used within jazz piano performance to provide a colour that distinguishes jazz piano performance in a competitive field.Thesis (M.Mus.) -- University of Adelaide, Elder Conservatorium of Music, 201
Computational Analysis of APEC Trade Liberalization
No full textIn this study, we use the Michigan Model of World Production and Trade to analyze the economic welfare effects of APEC free trade, unilateral free trade for individual APEC members, and global free trade for all countries/regions covered in the Michigan Model. The Michigan Model is a multi-country, multi-sectoral computational general equilibrium (CGE) model of the global trading system. The version of the model used includes 31 countries/regions plus the rest-of-world and 27 sectors in each country/region. Nineteen APEC members are covered. The computational results suggest that APEC free trade would result in sizable increases in the economic welfare of the individual APEC members in both absolute terms and as a percentage of GDP. There would be trade diversion effects for non-APEC countries, except for the Rest of Middle East. Unilateral free trade for the APEC members would result in larger welfare gains as compared to APEC free trade for 7 of the 19 APEC members. The welfare benefits of APEC free trade are thus larger for more APEC members than unilateral free trade. Finally, global (multilateral) free trade by all of the countries/regions covered in the Michigan Model suggests much larger benefits for all APEC members compared to APEC free trade and APEC unilateral free trade. While global free trade is a limiting case, the computational results presented are testimony to the significant welfare benefits that could be realized from successful pursuit of future multilateral trade liberalization.APEC, trade
Spinal anaesthesia for brachytherapy for carcinoma of the cervix a comparison of two dose regimes of hypebaric bupivacaine
No full textIncludes abstract.Includes bibliographical references.The main purpose of the study was to help establish the best dose regimen of hyperbaric bupivacaine, when combined with intrathecal fentanyl, for spinal anaesthesia for brachytherapy for carcinoma of the cervix. This procedure is performed as a day case at Groote Schuur Hospital
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