Effects on Rotational Dynamics of Azo and Hydrazodicarboxamide-Based Rotaxanes

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. This manuscript version is made available under the CC-BY 4.0 license https://creativecommons.org/licenses/by/4.0/ This document is the Published Manuscript version of a Published Work that appeared in final form in Molecules. To access the final edited and published work see https://doi.org/10.3390/molecules22071078The synthesis of novel hydrogen-bonded [2]rotaxanes having two pyridine rings in the macrocycle and azo- and hydrazodicarboxamide-based templates decorated with four cyclohexyl groups is described. The different affinity of the binding sites for the benzylic amide macrocycle and the formation of programmed non-covalent interactions between the interlocked components have an important effect on the dynamic behavior of these compounds. Having this in mind, the chemical interconversion between the azo and hydrazo forms of the [2]rotaxane was investigated to provide a chemically-driven interlocked system enable to switch its circumrotation rate as a function of the oxidation level of the binding site. Different structural modifications were carried out to further functionalize the nitrogen of the pyridine rings, including oxidation, alkylation or protonation reactions, affording interlocked azo-derivatives whose rotation dynamics were also analyzed

Tape-tether design for de-orbiting from given altitude and inclination

The product of the tether-to-satellite mass ratio and the probability of tether cuts by small debris must be small to make electrodynamic bare tethers a competitive and useful de-orbiting technology. In the case of a circular orbit and assuming a model for the debris population, the product can be written as a function that just depends on the initial orbit parameters (altitude and inclination) and the tether geometry. This formula, which does not contain the time explicitly and ignores the details of the tether dynamics during the de-orbiting, is used to find design rules for the tape dimensions and the orbit parameter ranges where tethers dominate other de-orbiting technologies like rockets, electrical propulsion, and sails

Optimum sizing of bare-tape tethers for de-orbiting satellites at end of mission

De-orbiting satellites at end of mission would prevent generation of new space debris. A proposed de-orbit technology involves a bare conductive tape-tether, which uses neither propellant nor power supply while generating power for on-board use during de-orbiting. The present work shows how to select tape dimensions for a generic mission so as to satisfy requirements of very small tether-to-satellite mass ratio m(t)/M-s and probability N-f of tether cut by small debris, while keeping de-orbit time t(f) short and product t(f) x tether length low to reduce maneuvers in avoiding collisions with large debris. Design is here discussed for particular missions (initial orbit of 720 km altitude and 63 and 92 inclinations, and 3 disparate M-s values, 37.5, 375, and 3750 kg), proving it scalable. At mid-inclination and a mass-ratio of a few percent, de-orbit time takes about 2 weeks and N-f is a small fraction of 1%, with tape dimensions ranging from 1 to 6 cm, 10 to 54 mu m, and 2.8 to 8.6 km. Performance drop from middle to high inclination proved moderate: if allowing for twice as large m(t)/M-s, increases are reduced to a factor of 4 in tf and a slight one in N-f; except for multi-ton satellites, somewhat more requiring because efficient orbital-motion-limited electron collection restricts tape-width values, resulting in tape length (slightly) increasing too.This work was supported by the European Commission FP7/Space Project 262972 (BETs), the Ministry of Science and Innovation of Spain (BES-2009-013319 FPI Grant), and Universidad Politécnica de Madrid (Research Grant RR01 2009)

Nuevos registros corológicos para Sucre (Sanguaré - Colombia)

We carried out an inventory of plant angiosperm, in the nature reserve Sanguaré (Sucre- Colombia), following the methodology type RAP. The plants was collected and identified after that all the taxa were reviewed in database online herbarium and moreover we used different kind of bibliographic source to determinate if the species found in Sanguaré are a new record to department of Sucre. We found 102 species within which 24 species (distributed in 21 families) are new chorological record to the department.Se realizó un inventario de angiospermas en la Reserva Natural Sanguaré (Sucre- Colombia), con base en la metodología de muestreos RAP; luego de recolectadas e identificadas las especies, se llevaron a cabo revisiones detalladas de bases de datos sobre colecciones taxonómicas en línea y diferentes fuentes bibliográficas, para establecer si las especies encontradas en Sanguaré presentan novedades taxonómicas para el departamento de Sucre. Dentro de los resultados se hallaron 102 especies, de las cuales 24 (distribuidas en 21 familias), son novedades corológicas para el departamento

Fijación de materiales biológicos mediante suturas y adhesivos biológicos

Las suturas son los elementos usados para fijar implantes o velos valvulares de las bioprótesis cardiacas. Tienen gran resistencia, su escasa elasticidad genera tensiones internas en los elementos que fijan. Se han comenzado a utilizar con fines médicos en la cirugía adherentes biológicos como elementos de fijación aunque no hay experiencia en bioprótesis. El objetivo de este trabajo era conocer si las muestras suturadas y pegadas eran capaces de proporcionar resistencia y elasticidad suficiente como para aportar un beneficio a la sutura, en la fijación de implantes o en la construcción de bioprótesis cardiacas. Para ello, hemos diseñado un ensayo de resistencia a tracción de 60 muestras de pericardio de ternera, material que se utiliza para fabricar velos valvulares de bioprótesis, comparando el comportamiento mecánico de 24 muestras suturadas con sutura continua borde a borde, prolene 5/0, a 45º y 90º del eje principal de la carga y otras 24 muestras similares, en las que el ojal del hilo de sutura (o parte del tejido que atraviesa la aguja de sutura) había sido reforzado con un adhesivo de fibrina. Como grupo de control se emplearon doce muestras sin sutura ni adhesivo. Los resultados obtenidos confirman la pérdida de resistencia al esfuerzo de tracción de las muestras suturadas, borde a borde, independientemente de la dirección de la sutura en relación con el eje principal de la carga. Esta forma de sutura no debe ser utilizada. La pérdida de resistencia se manifiesta tras pequeñas deformaciones de las muestras de pericardio. Para un 15% de deformación el estrés medio necesario para el grupo de control fue de 3.15 MPa frente a 0.92 MPa y 1.98 MPa, valores extremos de las series suturadas (p<0.01). Por otra parte, el uso de adherentes de fibrina no mejoró ni la resistencia ni la elasticidad de las muestras, aunque homogenizó el comportamiento mecánico de aquellas muestras suturadas que reforzaron con adherente de fibrina los ojales de paso de los hilos de sutura.Peer Reviewe

A proposed bare-tether experiment on board a sounding rocket

A mission on board a sounding rocket to carry out two bare-tether experiments is proposed: a test of orbital-motion-limited (OML) collection and the proof-of-flight of a technique to determine the (neutral) density vertical profile in the critical E-layer. Since full bias from the motional field will be small (~ 20V), corresponding to a tape 1 km long and V rocket <8 km/s, a power source with a range of supply voltages of few kV would be used. First, the negative terminal of the supply would be connected to the tape, and the positive terminal to a round, conductive boom of length 10 - 20 m; electrons collected by the boom cross the supply into the tape, where they leak out at the rate of ion impact plus secondary emission. Determination of the density profile from measurements of auroral emissions observed from the rocket, as secondaries racing down the magnetic field reach an E-layer footprint, are discussed. Next the positive terminal of the voltage supply is connected to the tape, and the negative terminal to a Hollow Cathode (HC); electrons now collected by the tape cross the supply, and are ejected at the HC. The opposite connections, with current collection operated by tape and boom, and operating on electrons and ions, and through partial switching in the supply, allow testing OML collection in almost all respects it depends on