Kinetics and the Theoretical Aspects of Drug Release from PLA/HAp Thin Films

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The theory of dissolution kinetics of gentamicin from polylactic acid-hydroxyapatite thin film composites is spotlighted with the combination of diffusion and polymer degradation modeling. The use of various mathematical models, characterizing diffusion, dissolution or/and erosion prevalence as well as a mix of dissolution-diffusion rate processes were employed in order to compare theory with experimental data. A number of factors influence the release kinetics of gentamicin from medical drug release systems and devices. It is difficult to have a single mathematical model that takes all these factors into account. It is shown that the degradation of the polymer matrix plays the biggest role in the release kinetics of polymer-ceramics thin film composites. It was also observed that multistage drug release form these devices depends also on the degradation kinetics of the polymer matrix. The effect of pH and device sizes were not studied but could also be of interest in future studies

Noncommutative Geometries and Gravity

We briefly review ideas about ``noncommutativity of space-time'' and approaches toward a corresponding theory of gravity.Comment: 18 pages, to appear in the Proceedings of the Third Mexican Meeting on Mathematical and Experimental Physics, Symposium on Gravitation and Cosmology, Mexico City, 10-14 September 200

Laboratory studies of heterogeneous uptake relevant to the troposphere

The reactions and fate of many natural and pollutant species in the atmosphere are influenced by the interaction between gas and liquid phase. Despite the acknowledged significance o f these heterogeneous processes, some factors determining the uptake of gases have still to be elucidated.Although the equilibrium water-air partitioning is characterised by the Henry’s law coefficient, the kinetics of the uptake process are more complicated. The Resistance Model approach describes uptake as a combination of the individual transfer processes, i.e. gas diffusion, mass accommodation, liquid solubility and liquid reaction. The mass accommodation is defined as the probability of incorporation at the phase boundary on collision with the surface.In this work, a new vertical wetted-wall flow reactor was constructed to study the accommodation of gas molecules by aqueous solutions. The trace gas was brought into contact with a liquid surface slowly flowing down the inside of the flow tube using a movable injector. Changes in gas phase concentration due to uptake by the liquid were monitored by wavelength-resolved UV absorption spectroscopy.The apparatus was tested by measuring the reactive uptake of ozone on Na2S203 solutions. The derived mass accommodation coefficient of a = 4.3 x 10'2, with a lower limit of > 2.7 x 10°, at 293 K agrees with previously published data. A rate coefficient of k" = 3 .7 x 10s 1 m of1 s' 1 for the reaction of ozone with Na2S203 in water at 293 K was calculated.The main focus of this work was on phenols since some are phytotoxic and have been observed in the ambient atmosphere in the gas phase as well as in fog and rain water. The uptake was measured on water and bromine water to distinguish between solubility-limited and gas and interface controlled regimes. Mass accommodation coefficients o f phenol, 2-nitrophenol and m-cresol were derived as a function of temperature. At 293 K, measured values of a were 8.3 x 10'3, 9.4 x 10‘4 and6.3 x 1CT3, respectively, for these compounds. These values imply that under tropospheric conditions mass accommodation could be the rate limiting process for transfer across the interface.In the Resistance Model mass accommodation is depicted as a continuous process where only clusters of critical size are taken up by the liquid phase. From the temperature dependence of a it was possible to derive the enthalpy and entropy for the transition (mass accommodation) between gas and solvated state. The size of the critical cluster (defined by N*) was determined for each phenol.A general lack of experimental data regarding the Henry’s law coefficient of 2- nitrophenol necessitated independent measurement of this parameter in this work. A newly built bubble column was used to purge 2-nitrophenol from an aqueous solution. The Henry’s law coefficient was derived from the observed loss in the liquid phase as measured by UV absorption spectroscopy. Highly consistent data as a function of temperature were obtained, ranging from 420 M atm' 1 at 278 K to 60 M atm' 1 at 303 K. The enthalpy and entropy of solubility were determined as -50.0 kJ mol' 1 and -104.0 J mol' 1 K 1, respectively

Conflict-free” governance of mineral extraction—is it compatible with the regulatory pluralism in DR Congo?

This paper explores the relation between transnational governance initiatives for “conflict-free” certification in the eastern provinces of the Democratic Republic of the Congo and the regulatory pluralism one finds on the ground. The author scrutinizes efforts in certifying artisanal gold mining in the DRC’s South Kivu province by analyzing how three different gold mining sites are governed. The “conflict-free” initiative is faced with a mostly ‘informal’ artisanal mining sector, as it is usually referred to. The author introduces the idea of a mode of governing that follows the principle of “débrouillardise”, which combines different rule systems and state and non-state regulators. As some state institutions partly register and tax miners and traders, and collaborate with customary authorities, and sometimes military units, this can be considered a de facto formalization. The paper argues that “conflict-free” governance will need to improvise via ad hoc agreements on the legal status of mining sites between state authorities, economic actors and international monitors. The declaration as legal will provide for a semblance of a “conflict-free” status and of a unitary state system of rule, while in practice, the plurality of regulatory authority will not be reversed

Indigenous Religion in Ghana: an explanation for the persistence of Asante chieftaincy in Kumasi

This thesis is the result of extensive historical and empirical research in the Kumasi Metropolis in Ghana (West Africa). Ghana is a modern nation-state with a secular government. Parallel to this post-colonially rooted political institution, the country is ruled by a number of sacred pre-colonially rooted institutions of chieftaincy. Among them, due to its clear hierarchical structure and great sanctity, the Asante institution is most prominent. Since the pre-colonial era, Asante chiefs and queen mothers have derived their authority from a religious source. Traditionally, they perceive themselves as servants of the ancestral spirits, from whom they receive the divine power to rule by occupying a 'stool' (throne). This power enables them to mediate between the spiritual beings and the community and to take care of their wellbeing. Also, since pre-colonial times, traditional Asante authorities have operated as religious peacekeepers as they have managed both religiously and socially to maintain a relationship of balanced tension between Asante indigenous practitioners, Muslims and Christians within the communityThe two main questions that are raised in this thesis are as follows. First, to what extent do the present day Asante traditional authorities still perceive a religious intermediary role? To answer this question the author looks at characteristics of this role in the pre-colonial and colonial era. She also studies four different Asante indigenous religious rituals that have recently been performed in the Kumasi Metropolis: the Asanteman Adae Kese festival, a royal pre-burial ritual, a ritual of pouring of libation and a chiefs installation ritual. The author researches whether Asante Indigenous Religion is present in these rituals and whether there is a formal or informal relationship with the Asante persistence of chieftaincy. This provides insight into to what extent the role of the Asante traditional authorities is still that of religious intermediation in the performance of those rituals. The second question is how Asante chiefs and queen mothers have operated as religious peacekeepers and how this role still contributes to the persistence of Asante chieftaincy. The answer is given by showing the persistent uniqueness of Asante chieftaincy as a religious pluralistic peacekeeping body in today's Kumasi Metropolisy's Kumasi Metropolis. The author concludes that Asante traditional authorities in the Metropolis still fulfil a significant role as both religious mediators and religious peacekeepers. This phenomenon offers an explanation for the persistence of Asante chieftaincy in this ancient capital of the Asante Kingdom and its surrounding areas. The role of the Asante chiefs and queen mothers as religious peacekeepers also provides a model for peaceful coexistence in more conflicted areas in West Africa, such as Nigeria and the rest of Africa

Relativistic magnetotransport in graphene

We study the thermal and electric transport of a fluid of interacting Dirac fermions as they arise in single-layer graphene. We include Coulomb interactions, a dilute density of charged impurities and the presence of a magnetic field to describe both the static and the low frequency response as a function of temperature T and chemical potential mu. In the critical regime mu << T where both bands above and below the Dirac point contribute to transport we find pronounced deviations from Fermi liquid behavior, universal, collision-dominated values for transport coefficients and a cyclotron resonance of collective nature. In the collision-dominated high temperature regime the linear thermoelectric transport coefficients are shown to obey the constraints of relativistic magnetohydrodynamics which we derive microscopically from Boltzmann theory. The latter also allows us to describe the crossover to disorder-dominated Fermi liquid behavior at large doping and low temperatures, as well as the crossover to the ballistic regime at high fields.Comment: Proceedings of the Landau Memorial Conference 200

Identidad, vida y obra del alquimista Ibn Arfaʿ Raʾs

Ibn Arfaʿ Raʾs is the author of a famous collection of alchemical poems entitled Shudhūr al-dhahab (The Splinters of Gold). In addition to Shudhūr al-dhahab, he authored several other works, including a commentary on Shudhūr, which is discussed here at some length for the first time, and strophic poetry on alchemy. The attribution of other works to him seems to be incorrect, and this applies especially to two works on magic. This contribution focusses on our findings on the identity of Ibn Arfaʿ Raʾs and on his life, challenging the identification of the alchemist Ibn Arfaʿ Raʾs with a Mālikī religious scholar known as Ibn al-Naqirāt. Based both on manuscripts and on bio-bibliographical literature, we argue that from an early period, two different people, both from sixth/twelfth century Morocco, have been fused into one. Considering all sources, we also suggest that Ibn Arfaʿ Raʾs might have left the Islamic west and have written at least some of his works in the east, more specifically in Egypt, thereby explaining the broad reception of Shudhūr al-dhahab throughout the Islamic world, particularly in the Mashriq.Ibn Arfaʿ Raʾs es el autor de una colección famosa de poemas alquímicos titulada Šuḏūr al-ḏahab (Las Esquirlas de Oro). Además de Šuḏūr al-ḏahab compuso otras obras — en particular un comentario de las Šuḏūr que está descrito aquí por primera vez más detalladamente — así como poesía estrófica sobre alquimia. La atribución que se suele hacer de algunas obras a Ibn Arfaʿ Raʾs parece incorrecta, sobre todo en lo que se refiere a dos obras concretas sobre magia. Esta contribución enfoca nuestros hallazgos sobre la identidad de Ibn Arfaʿ Raʾs y su vida, desafiando la identificación del alquimista Ibn Arfaʿ Raʾs con un erudito religioso Mālikī conocido como Ibn al-Naqirāt. Basado tanto en los manuscritos como en la literatura bio-bibliográfica, suponemos que dos personas diferentes, ambas del Marruecos del siglo VI/XII, probablemente han sido fusionadas en una en un período bastante temprano. Considerando todas las fuentes, sugerimos también que Ibn Arfaʿ Raʾs pueda haber dejado el Occidente Islámico y haber escrito por lo menos algunas de sus obras en Oriente, más específicamente en Egipto, lo que explicaría la recepción amplia de Šuḏūr al-ḏahab en todo el Mundo Islámico y especialmente en el Máshreq

Semi-automated curation of protein subcellular localization: a text mining-based approach to Gene Ontology (GO) Cellular Component curation

Background: Manual curation of experimental data from the biomedical literature is an expensive and time-consuming endeavor. Nevertheless, most biological knowledge bases still rely heavily on manual curation for data extraction and entry. Text mining software that can semi- or fully automate information retrieval from the literature would thus provide a significant boost to manual curation efforts. Results: We employ the Textpresso category-based information retrieval and extraction system http://www.textpresso.org webcite, developed by WormBase to explore how Textpresso might improve the efficiency with which we manually curate C. elegans proteins to the Gene Ontology's Cellular Component Ontology. Using a training set of sentences that describe results of localization experiments in the published literature, we generated three new curation task-specific categories (Cellular Components, Assay Terms, and Verbs) containing words and phrases associated with reports of experimentally determined subcellular localization. We compared the results of manual curation to that of Textpresso queries that searched the full text of articles for sentences containing terms from each of the three new categories plus the name of a previously uncurated C. elegans protein, and found that Textpresso searches identified curatable papers with recall and precision rates of 79.1% and 61.8%, respectively (F-score of 69.5%), when compared to manual curation. Within those documents, Textpresso identified relevant sentences with recall and precision rates of 30.3% and 80.1% (F-score of 44.0%). From returned sentences, curators were able to make 66.2% of all possible experimentally supported GO Cellular Component annotations with 97.3% precision (F-score of 78.8%). Measuring the relative efficiencies of Textpresso-based versus manual curation we find that Textpresso has the potential to increase curation efficiency by at least 8-fold, and perhaps as much as 15-fold, given differences in individual curatorial speed. Conclusion: Textpresso is an effective tool for improving the efficiency of manual, experimentally based curation. Incorporating a Textpresso-based Cellular Component curation pipeline at WormBase has allowed us to transition from strictly manual curation of this data type to a more efficient pipeline of computer-assisted validation. Continued development of curation task-specific Textpresso categories will provide an invaluable resource for genomics databases that rely heavily on manual curation

Food demand displaced by global refugee migration influences water use in already water stressed countries

Millions of people displaced by conflicts have found refuge in water-scarce countries, where their perceived effect on water availability has shaped local water security discourses. Using an annual global data set, we explain the effects of refugee migrations on the host countries' water stress through the food demand displaced by refugees and the water necessary to produce that food. The water footprint of refugee displacement increased by nearly 75% globally between 2005 and 2016. Although minimal in most countries, implications can be severe in countries already facing severe water stress. For example, refugees may have contributed up to 75 percentage points to water stress in Jordan. While water considerations should not, alone, determine trade and migration policy, we find that small changes to current international food supply flows and refugee resettlement procedures can potentially ease the effect of refugee displacement on water stress in water-vulnerable countries