46 research outputs found
Braiding groups of automorphisms and almost-automorphisms of trees
No full textWe introduce "braided" versions of self-similar groups and
R\"over--Nekrashevych groups, and study their finiteness properties. This
generalizes work of Aroca and Cumplido, and the first author and Wu, who
considered the case when the self-similar groups are what we call
"self-identical". In particular we use a braided version of the Grigorchuk
group to construct a new group called the braided R\"over group, which we prove
is of type . Our techniques involve using so called -ary cloning
systems to construct the groups, and analyzing certain complexes of embedded
disks in a surface to understand their finiteness properties.Comment: 39 pages, 7 figures, v2: accepted version, Canad. J. Mat
Biocatalytic reduction of alkenes in micro-aqueous organic solvent catalysed by an immobilised ene reductase
No full textBiocatalytic asymmetric reduction of alkenes in organic solvent is attractive for enantiopurity and product isolation, yet remains under developed. Herein we demonstrate the robustness of an ene reductase immobilised on Celite for the reduction of activated alkenes in micro-aqueous organic solvent. Full conversion was obtained in methyl t-butyl ether, avoiding hydrolysis and racemisation of products. The immobilised ene reductase showed reusability and a scale-up demonstrated its applicability.BT/Biocatalysi
Reforming Cote d'Ivoire's cocoa marketing and pricing system
No full textCote d'Ivoire has historically taxed cocoa producers. Market reforms over the past 10 years have somewhat succeeded in making domestic and foreign marketing more transparent and competitive. But they have not done much to raise producer prices in real terms or as a share of the FOB (free on board) price. Maintaining fixed producer prices and marketing costs and margins has encouraged rent-seeking and led to efficiency losses. New reform will fully liberalize the country's export marketing system by eliminating public management of exports. This means the end of mandatory export authorization, of public forward sales, and of fixed minimum producer prices and marketing margins. The new reform is expected to improve producers'incomes. The authors find that the benefits from the new reform (in terms of lower implicit taxes, lower marketing costs and margins, and higher producer prices) will outweigh the costs from eliminating public forward sales and fixed producer prices. Results from a general equilibrium model indicate that reducing export taxes would have a small negative effect on aggregate income but would improve income distribution for poorer rural areas. The fact that Cote d'Ivoire has market power in the world cocoa market justifies a higher optimal export tax than the current one. But raising export taxes may eventually reduce its market share and worsen income distribution, at the expense of the poorer rural sector.Payment Systems&Infrastructure,Economic Theory&Research,Environmental Economics&Policies,Markets and Market Access,Labor Policies,Consumption,Markets and Market Access,Access to Markets,Economic Theory&Research,Environmental Economics&Policies
Denervación renal en hta resistente. Reporte de los primeros siete casos en Colombia con dispositivo multielectrodo enlightn y seguimiento a 6 meses
No full textLa hipertensión resistente es un problema clínico por la dificultad de su tratamiento y el aumento de morbimortalidad que conlleva. Se ha demostrado que la denervación renal por catéter mejora el control de estos pacientes. Se describen los primeros 7 casos en colombia con dispositivo multideelectrodo enligHTN (St. Jude) y seguimiento a 6 meses.Metodología: Se incluyeron 7 pacientes consecutivos (5 varones y 2 mujeres) hospitalizados por HTA esencial resintente al tratamiento médico a pesar de la toma de tres o más fármacos. Se realizó monitoreo ambulatorio de presión arterial a todos los pacientes. Un equipo compuesto por cardiólogos, nefrólogos e internistas se encargó de la selección de los pacientes para terapia de denervacion renal. A todos los pacientes se les realizó aortograma y se verifico una adecuada anatomia de las arterias renales para la terapia (Diámetro >4mm y Longidud >20mm). Durante el procedimiento se requirio sedacion consciente para todos los pacientes. El dispositivo utilizado fue el enligHTN (St.jude) femoral 8fr (Cateter multielectrodo con 4 puntos de ablacion). El tiempo de denervacion renal por cada arteria fue de 8 min. No se presentaron complicaciones mayores, solo se presento un espasmo de la arteria renal derecha que se manejó con vasodilatadores intra arterial, y se logró la ablación en todos los casos.Resultados: De los 7 pacientes que se diagnóstico HTA resistente al tratamiento médico, todos recibían 4 fármacos en promedio. La presión arterial promedio previo al procedimiento valorada por el MAPA fue de PAS 190 +/-10mmHg y PAD 110 +/-5mmHg. La terapia de denervacion renal logró descensos sostenidos de la presión rrterial en el seguimiento a los 6 meses y se consiguió reducir el número de fármacos.La terapia de denervacion renal para la HTA resistente, con el dispositivo enligHTN es segura y efectiva como terapia coayudante en la población evaluada
Galileo was wrong: The geometrical design of masonry arches
No full textSince antiquity master builders have used always simple geometrical rules for designing arches. Typically, for a certain form, the thickness is a fraction of the span. This is a proportional design independent of the scale: the same ratio thickness/span applies for spans of 10 m or 100 m. The same kind of rules was also used for more complex problems, like the design of a buttress for a spatial cross-vault. Galileo attacked this kind of proportional design in his Dialogues. He stated the so-called square-cube law: internal stresses grow linearly with scale and therefore the elements of the structures must become thicker in proportion. This law has been accepted many times uncritically for engineering historians, who have considered the traditional geometrical design as unscientific and incorrect. In fact, Galileo’s law applies only to strength problems. Stability problems, such as the masonry arch problem, are governed by geometry. Therefore, Galileo was wrong in applying his reasoning to masonry buildings
Uso das tecnologias da informação e comunicação para o desenvolvimento das inteligências múltiplas a partir da formação docente
No full textThe research aimed to characterize the use of information and communication technologies for the development of multiple intelligences through playful and creative integration in a degree program in Early Childhood Education. The research employed a qualitative approach with an action research design. The study population consisted of ten teachers from private and public educational institutions and ten student teachers. The following categories were used in a survey and a grid: tools, resources, contributions of ICT to multiple intelligences, digital competence, purposes, and limitations of ICT use in learning environments. As a result, the shortage of digital tools and resources in classrooms was identified as a limiting factor in the implementation of teaching strategies that explore new ways of learning and develop students’ digital skills. Trainee teachers demonstrated remarkable adaptability and flexibility by creatively adjusting their activities to meet the needs of the educational context. Although ICT enriches the educational process, the lack of continuous internet access and scarce resources limit teaching innovation. However, teachers can mitigate these challenges and generate learning opportunities adapted to the context through creativity and the use of available resources.Keywords: educational resources, educational strategies, educational technology, intelligence, pedagogical practice.La investigación tuvo como objetivo caracterizar el uso de las tecnologías de la información y la comunicación para el desarrollo de las inteligencias múltiples en la práctica de integración lúdica y creativa de un programa de Licenciatura en Educación Infantil. La metodología se enmarcó en un enfoque cualitativo con un diseño de investigación-acción. La población objeto de estudio estuvo conformada por diez profesores de instituciones educativas privadas y oficiales y diez estudiantes practicantes. Se aplicó una encuesta y una rejilla con las siguientes categorías: herramientas, recursos, aportes de las TIC a las inteligencias múltiples, competencia digital y propósitos y limitaciones del uso de las TIC en los ambientes de aprendizaje. Como resultado, se identificó escasez de herramientas y recursos digitales en las aulas, lo que limita la implementación de estrategias didácticas que exploren nuevas formas de aprendizaje y desarrollen competencias digitales en los estudiantes. Los profesores en formación demostraron una notable capacidad de adaptación y flexibilidad, ya que ajustan creativamente sus actividades para responder a las necesidades del contexto educativo. Se concluye que, aunque las TIC enriquecen el proceso educativo, la falta de acceso continuo a internet y recursos limita la innovación docente. Sin embargo, la creatividad y el aprovechamiento de los recursos disponibles pueden mitigar estos desafíos y generar oportunidades de aprendizaje adaptadas al contexto.A pesquisa teve como objetivo caracterizar o uso das tecnologias da informação e comunicação para o desenvolvimento de inteligências múltiplas por meio da integração lúdica e criativa em um curso de licenciatura em Educação Infantil. A pesquisa empregou uma abordagem qualitativa com um desenho de pesquisa-ação. A população do estudo consistiu em dez professores de instituições de ensino privadas e públicas e dez professores estagiários. As seguintes categorias foram utilizadas numa pesquisa e numa grelha: ferramentas, recursos, contribuições das TIC para as inteligências múltiplas, competência digital, objetivos e limitações do uso das TIC em ambientes de aprendizagem. Como resultado, foi identificada a falta de ferramentas e recursos digitais nas salas de aula, como um fator limitante na implementação de estratégias de ensino que exploram novas formas de aprendizagem e desenvolvem as habilidades digitais dos alunos. Os professores estagiários demonstraram notável adaptabilidade e flexibilidade, ajustando criativamente suas atividades para atender às necessidades do contexto educacional. Embora as TIC enriquecem o processo educacional, a falta de acesso contínuo à internet e a escassez de recursos limitam a inovação no ensino. No entanto, os professores podem mitigar esses desafios e gerar oportunidades de aprendizagem adaptadas ao contexto por meio da criatividade e do uso dos recursos disponíveis
Cysteine and cysteine-related signaling pathways in arabidopsis thaliana
No full textCysteine occupies a central position in plant metabolism because it is a reduced sulfur donor molecule involved in the synthesis of essential biomolecules and defense compounds. Moreover, cysteine per se and its derivative molecules play roles in the redox signaling of processes occurring in various cellular compartments. Cysteine is synthesized during the sulfate assimilation pathway via the incorporation of sulfide to O-acetylserine, catalyzed by O-acetylserine(thiol)lyase (OASTL). Plant cells contain OASTLs in the mitochondria, chloroplasts, and cytosol, resulting in a complex array of isoforms and subcellular cysteine pools. In recent years, significant progress has been made in Arabidopsis, in determining the specific roles of the OASTLs and the metabolites produced by them. Thus, the discovery of novel enzymatic activities of the less-abundant, like DES1 with L-cysteine desulfhydrase activity and SCS with S-sulfocysteine synthase activity, has provided new perspectives on their roles, besides their metabolic functions. Thereby, the research has been demonstrated that cytosolic sulfide and chloroplastic S-sulfocysteine act as signaling molecules regulating autophagy and protecting the photosystems, respectively. In the cytosol, cysteine plays an essential role in plant immunity; in the mitochondria, this molecule plays a central role in the detoxification of cyanide, which is essential for root hair development and plant responses to pathogens. © 2013 © The Author 2013. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.Peer Reviewe
Politics, transaction costs, and the design of regulatory institutions
No full textProviding a more complete framework for assessing the efficiency of government intervention requires moving away from the idealistic perspective typically found in the normative approach to traditional public economics, contend the authors. Such a move requires viewing the government not as a monolithic entity but as many different government bodies, each with its own constituency and regulatory tools. Not only is the"multitiered"government limited in its ability to commit, but interest groups influence the regulatory process and impose significant transaction costs on government interventions and on their outcome. The authors discuss the nature of those transaction costs and argue that the overall design of the government is the result of their minimization. Among the points they make in their conclusions: 1) Safeguards built into regulatory contracts sometimes reflect and sometimes imply transactions costs which influence, or should influence, the optimal tradeoff between rent and efficient in ways practitioners sometimes ignore. 2) Most of the literature on transaction costs arising from government failures would agree that to be sustainable, regulatory institutions should be independent, autonomous, and accountable. How these criteria are met is determined by the way transaction costs are minimized, which in turn drives the design of the regulatory framework. In practice, for example, if there at commitment problems, short-term institutional contracts between players are more likely to ensure autonomy and independence. This affects the duration of the nomination of the regulators. Short-term contracts may be best, but contracts for regulators typically last four to eight years and are often renewable. The empirical debate about the design of regulators'jobs is a possible source of tension. Practitioners typically recommend choosing regulators based on professional rather than political criteria, but that may not be the best way to minimize regulatory capture. Professional experts are likely to come from the sector they are supposed to regulate and are likely to return to it sooner or later (as typically happens in developing countries). On the other hand, electedregulators are unlikely to be much more independent than professional regulators; they will simply represent different interests. Practitioners and theorists alike emphasize different sources of capture and agree that one way to deal with its risk is to make sure the selection process involves both executive and legislative branches.Environmental Economics&Policies,Economic Theory&Research,Labor Policies,Decentralization,Banks&Banking Reform,Economic Theory&Research,Environmental Economics&Policies,National Governance,Administrative&Regulatory Law,Banks&Banking Reform
Author response: Type III CRISPR-Cas systems can provide redundancy to counteract viral escape from type I systems
No full textManagement of vitreous floaters: an international survey the European VitreoRetinal Society Floaters study report
No full textBackground/objectives: To evaluate the efficacy and safety of pars plana vitrectomy for symptomatic floaters. Subjects/methods: Forty-eight vitreoretinal surgeons from 16 countries provided information on 581 eyes who underwent vitrectomy for floaters in this retrospective survey study conducted by European VitreoRetinal Society. Percentage symptomatic improvement, incidence of retinal tears/detachment and post-vitrectomy cataract surgery, and the factors associated with satisfaction and complications were investigated. Results: Ninety-two percent were satisfied with the results, with 86.3% reporting complete resolution of daily-life symptoms. Overall satisfaction was lower in patients with smaller vitreous opacities at presentation (OR:0.4). Iatrogenic retinal breaks occurred in 29 eyes (5%). Core vitrectomy and cut rates of 1500–4000 or >4000 cuts/min were associated with lower risk of retinal breaks than complete vitrectomy (OR:0.05) and cut rates < 1500 cuts/min (OR: 0.03, 0.12, respectively). Fourteen eyes (2.4%) developed retinal detachment at a median of 3 months; and 84 (48.6%) developed cataract at a median of 16 months post-vitrectomy. Conclusions: Pars plana vitrectomy resulted in high patient satisfaction with relatively low rate of severe complications in a large group of patients. The procedure may be safer when core vitrectomy and cut rates > 1500 cuts/min are favoured. Proper patient selection and informed consent are the most important aspects of surgery. © 2020, The Author(s), under exclusive licence to The Royal College of Ophthalmologists
