Self-Aligned Ballistic Molecular Transistors and Electrically Parallel Nanotube Arrays

Carbon nanotube field-effect transistors with structures and properties near the scaling limit with short (down to 50 nm) channels, self aligned geometries, palladium electrodes with low contact resistance and high-k dielectric gate insulators are realized. Electrical transport in these miniature transistors is near ballistic up to high biases at both room and low temperatures. Atomic layer deposited (ALD) high-k films interact with nanotube sidewalls via van der Waals interactions without causing weak localization at 4 K. New fundamental understanding of ballistic transport, optical phonon scattering and potential interfacial scattering mechanisms in nanotubes are obtained.Comment: Nano Letters, in pres

Structural and stereogenic properties of spiro- and ansa-substituted 1,3-propanedioxy derivatives of a spermine-bridged cyclotriphosphazene

Reaction of 1,3-propanediol with the achiral spermine-bridged cyclophosphazene 1 at various molar ratios in THF gives a number of spiro-and ansa-derivatives that exhibit different stereogenic properties, viz. racemic, meso or achiral forms. As expected, spiro forms are preferred (giving mono-, di-, tri- and tetra-substitution), although significant amounts of mono- and di-substituted ansa derivatives also occur. A number of new structures have been characterized by NMR spectroscopy and X-ray crystallography in this work; mono-spiro 2, di-mono-ansa 6 and di-spiro/mono-ansa 8. The mono-ansa compound 3 was observed in solution by NMR spectroscopy but no evidence was found for the monospiro/monoansa 5, a necessary precursor of compound 8. The tri-spiro derivative 7 has been isolated and characterized by 31P NMR spectroscopy, whereas the structures of the di-monospiro 4 (meso) and tetra-spiro 9 have been characterized previously. The stereogenic properties of many of the products have been confirmed by X-ray crystallography and/or by 31P NMR spectroscopy on addition of the chiral solvating agent, (S)-(+)-2,2,2-trifluoro-1-(9-anthryl)ethanol. Although the starting compound 1 is achiral, it is found that unsymmetrically-substituted derivatives with 1,3-propanediol give racemic mixtures for the mono-spiro 2 and tri-spiro 7 derivatives, whereas symmetrically-substituted derivatives such as di-mono-ansa 6 and di-spiro/mono-ansa 8 are meso. It is found that care must taken in interpreting the 'splitting' of 31P NMR signals on addition of CSA in terms of 'chirality' of molecules, because some meso compounds give false positive results due to changes from A2X-like to A2B or ABX spin systems

Early Geometrical Thinking in the Environment of Patterns, Mosaics and Isometries

This book discusses the learning and teaching of geometry, with a special focus on kindergarten and primary education. It examines important new trends and developments in research and practice, and emphasizes theoretical, empirical and developmental issues. Further, it discusses various topics, including curriculum studies and implementation, spatial abilities and geometric reasoning, as well as the psychological roots of geometrical thinking and teacher preparation in geometry education. It considers these issues from historical, epistemological, cognitive semiotic and educational points of view in the context of students' difficulties and the design of teaching and curricula

An Empirical Study of the Mexican Banking System's Network and Its Implications for Systemic Risk

With the purpose of measuring and monitoring systemic risk, some topological properties of the interbank exposures and the payments system networks are studied. We propose non-topological measures which are useful to describe the individual behavior of banks in both networks. The evolution of such networks is also studied and some important conclusions from the systemic risks perspective are drawn. A unified measure of interconnectedness is also created. The main findings of this study are: the payments system network is strongly connected in contrast to the interbank exposures network; the type of exposures and payment size reveal different roles played by banks; behavior of banks in the exposures network changed considerably after Lehmans failure; interconnectedness of a bank, estimated by the unified measure, is not necessarily related with its assets size

Model for replication potential

This report is a deliverable for the REMOURBAN (REgeneration MOdel for accelerating the smart URBAN transformation) project which is a HORIZON 2020 programme project. Deliverable 5.2 was aimed at the development of a model for replication potential

Sustainable Covid-19 Recovery and Circular Economy

This article addresses the circular economy as a response to Covid-19. The discussion provides a literature-based examination of the Covid-19 pandemic focusing on two areas: Human health and the environment and highlights the impact of the pandemic on pollution, waste, and environmental resiliency. © 2022 Mary Ann Liebert, Inc., publishers

Effects of different derivatives of eudragit polymer on entrapment efficiency, in vitro dissolution, release kinetics and cell viability results on extended release flurbiprofen loaded nanomedicines

The purpose of the present investigation was to design and compare the release characteristics of sustained-release formulations of Flurbiprofen (FLB) loaded nanoparticles (NPs) by using spray-dryer technique using Eudragit RLPO (RLPO), Eudragit RSPO (RSPO) and RLPO:RSPO 1:1 ratio. NPs Formulation were prepared by spray-dryer. Structures of nanoparticles were characterized by entrapment efficiency (EE%), dissolution study and release kinetic study with the DDSolver software program, particle size (PS), zeta potential, morphology, DSC, XRD, FTIR and 1H-NMR analyses. Cytotoxicity studies were performed on the NIH/3T3 mouse embryonic fibroblast cells. FLB-loaded NPs demonstrated nanostructural character while in vitro release study showed extended release of FLB-incorporated. The PS of the prepared FLB-NPs was affected by the polymer type and was in the range of 532 and 565 nm. Entrapment efficiency (EE%) varied from 70 to 76%, depending upon the polymer difference to drug ratio. According to the DDSolver criterion used to evaluate release kinetics, Korsmeyer-Peppas model were determined to be the most appropriate kinetic models for NPs. The results obtained in cell viability study indicate a dose and time dependent decrease in viability of NIH/3T3 for FLB and FLB-NPs. As a conclusion of this study; the effect of the polymer type on the PS, EE% and release properties of NPs has been examined and discussed in detail. According to results FLB-NPs seem to be a promising extended release drug delivery system for oral administration. © 2018, Colegio de Farmaceuticos de la Provincia de Buenos Aires. All rights reserved.formulaciones de liberación sostenida de nanopartículas cargadas de flurbiprofeno (FLB) mediante el uso de la técnica de secado por atomización usando Eudragit RLPO (RLPO), Eudragit RSPO (RSPO) y RLPO: RSPO en relación 1:1. La formulación de NP se preparó mediante secado por pulverización. Las estructuras de las nano-partículas se caracterizaron por la eficiencia de procesamiento (EE%), el estudio de disolución y el estudio ciné-tico de liberación con el programa de software DDSolver, tamaño de partícula (PS), potencial zeta, morfología, DSC, XRD, FTIR y análisis 1H-RMN. Se realizaron estudios de citotoxicidad en las células de fibroblastos em-brionarios de ratón NIH/3T3. Las NP cargadas con FLB demostraron el carácter nanoestructural mientras que el estudio de liberación in vitro mostró la liberación prolongada de FLB-incorporado. La PS de las FLB-NP prepa-radas se vio afectada por el tipo de polímero y estaba en el intervalo de 532 y 565 nm. La eficiencia de atrapa-miento (EE%) varió de 70 a 76%, dependiendo de la diferencia de polímero a la relación de fármaco. De acuerdo con el criterio DDSolver utilizado para evaluar la cinética de liberación, se determinó que el modelo de Korsme-yer-Peppas es el modelo cinético más apropiado para las NP. Los resultados obtenidos en el estudio de viabilidad celular indican una disminución dependiente de la dosis y del tiempo en la viabilidad de NIH/3T3 para FLB y FLB-NP. Como conclusión de este estudio; el efecto del tipo de polímero sobre el PS, EE% y las propiedades de liberación de NP se han examinado y discutido en detalle. De acuerdo con los resultados, las NP-FLB parecen ser un prometedor sistema de administración de fármacos de liberación prolongada para administración oral