Error thresholds for self- and cross-specific enzymatic replication

The information content of a non-enzymatic self-replicator is limited by Eigen's error threshold. Presumably, enzymatic replication can maintain higher complexity, but in a competitive environment such a replicator is faced with two problems related to its twofold role as enzyme and substrate: as enzyme, it should replicate itself rather than wastefully copy non-functional substrates, and as substrate it should preferably be replicated by superior enzymes instead of less-efficient mutants. Because specific recognition can enforce these propensities, we thoroughly analyze an idealized quasispecies model for enzymatic replication, with replication rates that are either a decreasing (self-specific) or increasing (cross-specific) function of the Hamming distance between the recognition or "tag" sequences of enzyme and substrate. We find that very weak self-specificity suffices to localize a population about a master sequence and thus to preserve its information, while simultaneous localization about complementary sequences in the cross-specific case is more challenging. A surprising result is that stronger specificity constraints allow longer recognition sequences, because the populations are better localized. Extrapolating from experimental data, we obtain rough quantitative estimates for the maximal length of the recognition or tag sequence that can be used to reliably discriminate appropriate and infeasible enzymes and substrates, respectively.Comment: 23 pages, 7 figures; final version as publishe

Human resident liver myeloid cells protect against metabolic stress in obesity

Although multiple populations of macrophages have been described in the human liver, their function and turnover in patients with obesity at high risk of developing non-alcoholic fatty liver disease (NAFLD) and cirrhosis are currently unknown. Herein, we identify a specific human population of resident liver myeloid cells that protects against the metabolic impairment associated with obesity. By studying the turnover of liver myeloid cells in individuals undergoing liver transplantation, we find that liver myeloid cell turnover differs between humans and mice. Using single-cell techniques and flow cytometry, we determine that the proportion of the protective resident liver myeloid cells, denoted liver myeloid cells 2 (LM2), decreases during obesity. Functional validation approaches using human 2D and 3D cultures reveal that the presence of LM2 ameliorates the oxidative stress associated with obese conditions. Our study indicates that resident myeloid cells could be a therapeutic target to decrease the oxidative stress associated with NAFLD

Steam gasification of sewage sludge for synthesis processes

The paper presents measurement results of a gasification test run. Municipal sewage sludge from a digestion tower is gasified in an advanced dual fluidized bed reactor system. Steam is used as gasification agent and an olivine-limestone mixture as bed material. The fuel analysis shows a very high ash content and a low heating value of the dried sewage sludge. In addition, a significant amount of nitrogen in the fuel is present, leading to a high ammonia content in the product gas.Sintering effects caused by the high ash content do not occur. Thus, a gasification process without limitation is achieved. The fuel input is located in the lower gasification reactor operating as bubbling fluidized bed, whereas the upper gasification reactor is designed as a column of turbulent fluidized zones for tar cracking. The results show an efficient in-situ tar reduction. With a look on the product gas composition a comparatively high carbon dioxide and a low carbon monoxide content is surprising. It is obvious that an iron oxide reduction of the initial fuel ash occur in the gasification reactor. In addition, it is assumed that the significant iron content in the fuel ash also leads to a transport of oxygen from the combustion reactor to the gasification reactor. Thus, carbon monoxide and hydrogen are oxidized in the gasification reactor by the circulating iron-rich ash particles (chemical looping effect).FFG - Österr. Forschungsförderungs- gesellschaft mbH4351

Quantifying primaquine effectiveness and improving adherence: a round table discussion of the APMEN Vivax Working Group.

The goal to eliminate malaria from the Asia-Pacific by 2030 will require the safe and widespread delivery of effective radical cure of malaria. In October 2017, the Asia Pacific Malaria Elimination Network Vivax Working Group met to discuss the impediments to primaquine (PQ) radical cure, how these can be overcome and the methodological difficulties in assessing clinical effectiveness of radical cure. The salient discussions of this meeting which involved 110 representatives from 18 partner countries and 21 institutional partner organizations are reported. Context specific strategies to improve adherence are needed to increase understanding and awareness of PQ within affected communities; these must include education and health promotion programs. Lessons learned from other disease programs highlight that a package of approaches has the greatest potential to change patient and prescriber habits, however optimizing the components of this approach and quantifying their effectiveness is challenging. In a trial setting, the reactivity of participants results in patients altering their behaviour and creates inherent bias. Although bias can be reduced by integrating data collection into the routine health care and surveillance systems, this comes at a cost of decreasing the detection of clinical outcomes. Measuring adherence and the factors that relate to it, also requires an in-depth understanding of the context and the underlying sociocultural logic that supports it. Reaching the elimination goal will require innovative approaches to improve radical cure for vivax malaria, as well as the methods to evaluate its effectiveness

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Heavy metal separation from incineration ashes by chlorination and thermal treatment

Zsfassung in dt. SpracheDie Verbrennung von Abfällen wie Hausmüll oder Klärschlamm wird als umweltfreundliche Entsorgung angesehen. Einer der Verbrennungsrückstände ist Flugasche. Lagerung und Transport von Flugasche aus Hausmüllverbrennungsanlagen (Hausmüllasche) gestaltet sich auf Grund des Auslaugungsverhaltens kompliziert. Klärschlammasche ist eine wichtige Sekundärrohstoffquelle für Phosphor. Die Schwermetallgehalte sind jedoch üblicherweise zu hoch für die direkte Nutzung als Düngemittel gemäß aktueller Düngemittelverordnungen. Schwermetalle können aus Asche durch Mischen mit umweltverträglichen Chloriden (z.B. CaCl2, MgCl2) und anschließender thermischer Behandlung zwischen 900 und 1100°C abgetrennt werden. Um den Austrag großer Staubmengen im thermischen Prozess zu vermeiden, kann die Mischung (nach Zugabe von Wasser) pelletiert werden. Die thermische Behandlung kann in Drehrohr- oder Wirbelschichtreaktoren erfolgen. In der vorliegenden Arbeit wird der Einfluss der Asche (Klärschlammasche und Hausmüllasche), des Chlorids (CaCl2, MgCl2, NaCl), der Menge an zugegebenem Chlorid (0 bis 230 g Cl pro Kilogramm Asche zugegeben), der Pelletisierung, des Reaktors (Drehrohr, Wirbelschicht), der Behandlungstemperatur (800 bis 1200°C), und der Verweilzeit (1 min bis 20 h) auf die Abtrenneffizienz für verschiedene Schwermetalle (Cd, Cr, Cu, Ni, Pb, Zn) untersucht. Zusätzlich werden spezielle Untersuchungen in Muffelofen und Thermogravimetrie durchgeführt. Während der thermischen Behandlung werden flüchtige Schwermetallverbindungen gebildet (v.a. Chloride). Schwermetalle können entweder direkt (z.B. ZnO + 2 NaCl ->ZnCl2 + Na2O) oder indirekt chloriert werden. Bei indirekter Chlorierung reagieren Chloride zuerst mit Wasserdampf oder Sauerstoff zu HCl oder Cl2 (z.B. CaCl2 + H2O -> CaO + 2 HCl); diese Gase chlorieren im nächsten Schritt Schwermetallverbindungen. NaCl chloriert direkt; große Mengen verdampfen jedoch ohne zu reagieren. CaCl2 und MgCl2 sind effizienter für die Schwermetallentfrachtung; sie chlorieren indirekt. Behandelt man Pellets aus Klärschlammasche und CaCl2 (150 g Cl pro Kilogramm Asche zugegeben) in einem Labor-Drehrohrreaktor bei 1050°C, so können nach 25 min mehr als 99% Cd, ca. 97% Cu, 95% Pb, und 95% Zn abgetrennt werden. Mehr als 50% dieser Schwermetalle werden bereits während der Aufheizphase verflüchtigt (d.h. beim Aufheizen von Umgebungstemperatur nach 2 min). Führt man die gleiche Prozedur für Hausmüllasche durch, so werden signifikant geringere Mengen an Schwermetallen entfrachtet: Werden 230 g Cl pro Kilogramm Asche zugegeben, so können nach 45 min bei 1050°C ca.95% Cd, 60% Cu, 97% Pb, und 80% Zn abgetrennt werden.Die auftretenden Unterschiede der Abtrenneffizienz liegen an verschiedenen Schwermetallkonzentrationen, Korngrößen und Matrixzusammensetzungen der beiden Aschen. Ohne Pelletisierung können größere Mengen an Cu und Zn aus Hausmüllasche abgetrennt werden. Mit CaCl2 (150 g Cl pro Kilogramm Asche zugegeben) können bei 1000°C bis zu 80% an Cu und Zn nach 60 min verflüchtigt werden. Pelletiert man vor der thermischen Behandlung, so liegen diese Werte nach 45 min bei 25% Cu und 60% Zn. Eine weitere Verbesserung der Abtrenneffizienz von Hausmüllasche kann durch Zugabe von organischem Material zu der Asche-Chlorid-Mischung erreicht werden, obwohl laut thermodynamischer Gleichgewichtsberechnungen reduzierende Bedingungen der Verflüchtigung von Cu entgegen wirken. Die vorherige Reduzierung und nachfolgende Oxidierung bei Chlorierungsbedingungen führt auch zu höheren Entfrachtungen von Cu. Für die Schwermetallentfrachtung von Klärschlammasche können sowohl Drehrohr als auch Wirbelschicht verwendet werden. Vergleicht man die Abtrenneffizienz von Cu, Pb und Zn in beiden Reaktoren, so können die Limitierungen den Stoffübergang betreffend identifiziert werden: Die Cu-Abtrennung wird von der Verdampfung und/oder der Diffusion des Chlorids, die Pb- und Zn-Abtrennung von der Verfügbarkeit von HCl und Cl2 limitiert.Incineration is considered as an environmentally friendly disposal option for waste such as municipal solid waste (MSW) or sewage sludge. One of the residues from incineration is fly ash. MSW fly ash requires special handling and disposal because of its leaching behavior.Sewage sludge ash is an important secondary resource for phosphorus.However, heavy metals have to be considered carefully for direct utilization as fertilizers because their concentrations are usually too high according to current regulations. Heavy metal removal from fly ash can be performed by mixing the ash with environmentally compatible chlorides (e.g.CaCl2, MgCl2) and treating the mixture at temperatures between 900 and 1100°C. In order to avoid the entrainment of significant amounts of dust in the treatment process, the mixture can be pelletized (after addition of water). The thermal treatment can be conducted in rotary or fluidized bed reactors. In this work, experiments concerning the influence of the ash type (sewage sludge ash and MSW fly ash), chloride type (CaCl2, MgCl2, NaCl), chloride amount (0 to 230 g Cl added per kilogram of ash), pelletization, reactor type (rotary reactor, fluidized bed reactor), treatment temperature (800 to 1200°C), and residence time (1 min to 20 h) on the separation efficiency for different heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) were carried out. In addition, specific tests were performed in a muffle oven and by thermogravimetric analysis. During the treatment process, volatile heavy metal compounds (mainly chlorides) are formed. Depending on the type of chloride added, heavy metals are either directly (e.g.ZnO + 2 NaCl ->ZnCl2 + Na2O) or indirectly chlorinated. When chlorinated indirectly, chlorides react first with water vapor or oxygen to form HCl or Cl2 (e.g.CaCl2 + H2O -> CaO + 2 HCl); these gases subsequently chlorinate. NaCl follows the route of direct chlorination but evaporates in significant amounts without reacting as well. CaCl2 and MgCl2 are more effective for heavy metal removal; they indirectly chlorinate. Treating a pelletized mixture of sewage sludge ash and CaCl2 (150 g Cl added per kilogram of ash) in a laboratory-scale rotary reactor, at 1050°C, more than 99% of Cd, approximately 97% of Cu, 95% of Pb, and 95% of Zn can be removed after 25 min. More than 50% of these heavy metals are already volatilized during the heat-up period (i.e. after 2 min when heating from ambient temperature). For MSW fly ash, the same procedure leads to significantly lower amounts of heavy metals removed; even when using 230 g Cl per kilogram of ash, at 1050°C after 45 min approximately 95% of Cd, 60% Cu, 97% Pb, and 80% Zn can be released. These differences in heavy metal removal are caused by different heavy metal concentrations, different grain sizes, and different matrix compositions of both ashes. Without pelletization, but also depending on other conditions, higher amounts of Cu and Zn can be removed from MSW fly ash. Using CaCl2 (150 g Cl added per kilogram of ash) and a treatment temperature of 1000°C, up to 80% of Cu and Zn are volatilized after 60 min. If pelletized before treating thermally, 25% of Cu and 60% of Zn can be removed after 45 min. Further enhancement of heavy metal removal from MSW fly ash is possible by adding organic material to the ash-chloride mixture, although thermodynamic equilibrium calculations reveal that reducing conditions decrease the amount of Cu removed. Prior reduction and subsequent oxidization under chlorination condition increases the amount of Cu removed as well. For heavy metal removal from sewage sludge ash, both a rotary reactor and a fluidized bed reactor are suitable. By comparing the separation efficiency of Cu, Pb, and Zn in both reactors, the limitations of heavy metal removal concerning the external mass transfer were identified: Cu removal is limited by the evaporation and/or diffusion of its chloride; Pb and Zn removal are limited by the availability of HCl and Cl2.16

Untersuchungen zur Relation zwischen Struktur und Dynamik in glasbildenden metallischen Schmelzen

Die Untersuchung der Struktur-Dynamik-Relation in glasbildenden metallischen Schmelzen ist von besonderem Interesse in Bezug auf ein besseres Verständnis des Glasbildungsprozesses in diesen Materialien. Deshalb wurden die atomare Dynamik und die Nahordnung in metallischen Hf-/Zr-Ni Schmelzen mittels Neutronenstreuung untersucht. Mit Hilfe der Modenkopplungstheorie des Glasübergangs konnte die Beziehung zwischen dem dynamischen Verhalten der einzelnen atomaren Spezies und der Schmelzstruktur direkt analysiert werden, indem lediglich zeitlich- und räumlich gemittelte strukturelle Informationen als Eingangsparameter verwendet werden, um die Selbstdiffusionskoeffizienten zu berechnen. Hierdurch konnten verschiedene Effekte wie die zusammensetzungsabhängige dynamische Entkopplung der Selbstdiffusionskoeffizienten, Unterschiede im Hinblick auf die Temperaturabhängigkeit der atomaren Dynamik und der Einfluss von Mischungseffekten strukturell erklärt werden

Thermal and hydrometallurgical recovery methods of heavy metals from municipal solid waste fly ash

Heavy metals in fly ash from municipal solid waste incinerators are present in high concentrations. Therefore fly ash must be treated as a hazardous material. On the other hand, it may be a potential source of heavy metals. Zinc, lead, cadmium, and copper can be relatively easily removed during the thermal treatment of fly ash, e.g. in the form of chlorides. In return, wet extraction methods could provide promising results for these elements including chromium and nickel. The aim of this study was to investigate and compare thermal and hydrometallurgical treatment of municipal solid waste fly ash. Thermal treatment of fly ash was performed in a rotary reactor at temperatures between 950 and 1050 °C and in a muffle oven at temperatures from 500 to 1200 °C. The removal more than 90% was reached by easy volatile heavy metals such as cadmium and lead and also by copper, however at higher temperature in the muffle oven. The alkaline (sodium hydroxide) and acid (sulphuric acid) leaching of the fly ash was carried out while the influence of temperature, time, concentration, and liquid/solid ratio were investigated. The combination of alkaline-acidic leaching enhanced the removal of, namely, zinc, chromium and nickel.Web of Science33112327232