Two-way sequential time synchronization: Preliminary results from the SIRIO-1 experiment

A two-way time synchronization experiment performed in the spring of 1979 and 1980 via the Italian SIRIO-1 experimental telecommunications satellite is described. The experiment was designed and implemented to precisely monitor the satellite motion and to evaluate the possibility of performing a high precision, two-way time synchronization using a single communication channel, time-shared between the participating sites. Results show that the precision of the time synchronization is between 1 and 5 ns, while the evaluation and correction of the satellite motion effect was performed with an accuracy of a few nanoseconds or better over a time interval from 1 up to 20 seconds

The Complex Way to Laser Diode Spectra: Example of an External Cavity Laser With Strong Optical Feedback

An external cavity laser with strong grating-filtered feedback to an antireflection-coated facet is studied with a time-domain integral equation for the electric field, which reproduces the modes of the oscillation condition as steady-state solutions. For each mode, the stability and spectral behavior is determined by analysis of the location of side modes in the complex frequency plane. The complex frequency diagrams are shown to be a useful tool to determine the self-stabilization effect of mode coupling and its dependence on laser parameters and external cavity design. The model is used to simulate the large signal time evolution after start from unstable mode

Prospects for high accuracy time dissemination and synchronization using coded radar pulses from a low-earth orbiting spacecraft

The radar (an acronym for radio detection and ranging) is an instrument developed just before the WW-II to precisely measure the position of an object (target) in space. This is done by emitting a narrow pulse of electromagnetic energy in the RF spectrum, receiving the return echo and measuring the time of flight in the two-way path from the emitter to the target. The propagation delay provides a measure of the range to the target, which is not in itself sufficient to uniquely locate the position of the same in space. However, if a directional antenna is used, the direction of the echo can be assessed by the antenna pointing angles. In this way the position of the target can be uniquely determined in space. How well this can be done is a function of the resolution of the measurements performed (range and direction, i.e.: angles); in turn, the resolution will dictate the time and frequency requirements of the reference oscillator

Poesia contemporanea: «L'attimo dopo» di Massimo Gezzi

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Myricetin: A Naturally Occurring Regulator of Metal-Induced Amyloid-β Aggregation and Neurotoxicity

No AbstractPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/84385/1/1198_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/84385/2/cbic_201000790_sm_miscellaneous_information.pd

Insights on Metal Ions and Misfolded Proteins in Alzheimer's Disease Using Flavonoid Derivatives and X-ray Fluorescence Microscopy.

The incidence of Alzheimer’s disease (AD) worldwide has been accelerating at a staggering rate, demonstrating the need to understand its origins clearly. Misfolded proteins such as amyloid-beta have been believed to contribute to the disease. Additionally, it has been suggested that the normal functions and localization of metal ions such as Fe(II/III), Cu(I/II), and Zn(II) could be disrupted in the AD brain. There has been evidence to support the possible interplay between Cu(II) and/or Zn(II) with amyloid-beta-related pathology (i.e., metal–amyloid hypothesis); however, this relationship has yet been to be fully elucidated. A growing interest this possible association with AD pathology has led to new strategies for interrogating the metal– amyloid-beta relationship using small molecule metal chelators. Flavonoids are abundant plant-derived molecules that have been known to bind metal ions and interact with amyloid-beta peptides; however, the synergism of these properties toward metal-associated amyloid-beta has previously received little attention. In this thesis, selected flavonoid derivatives were investigated to formulate a structure-interaction-reactivity relationship among chemical structures, metal ions, and amyloid-beta/metal–amyloid-beta species. The molecules myricetin and luteolin, found in fruits and vegetables, were initially screened and found to influence the reactivity of metal–amyloid-beta species. Building upon these initial observations, the interaction and reactivity of the well-known green tea polyphenol (−)-epigallocatechin-3-gallate (EGCG) were explored at the molecular level through biochemical and biophysical investigations. These findings suggest that metal–amyloid-beta–flavonoid species can be generated and possibly lead to off-pathway aggregation in vitro. We further identified the specific contributions of structural features by synthetic manipulation of the flavonoid framework to aminoisoflavone derivatives. Appropriate tuning of hydrophilic and hydrophobic properties within the structural backbone can modify the balance of metal binding and amyloid-beta interaction, which may account for their reactivity toward amyloid-beta and/or metal–amyloid-beta. Taken together, the studies presented herein demonstrate the utility of flavonoids as a source of structures for direct use and/or synthetic modification from which a structure-interaction-reactivity relationship can be formulated for metal-free and metal-associated amyloid-beta species, which will provide insight into development of chemical tools to uncover the involvement of metal–amyloid species in AD.PHDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/100100/1/detoma_1.pd

Recent Development of Bifunctional Small Molecules to Study Metal-Amyloid-β Species in Alzheimer's Disease

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease related to the deposition of aggregated amyloid-β (Aβ) peptides in the brain. It has been proposed that metal ion dyshomeostasis and miscompartmentalization contribute to AD progression, especially as metal ions (e.g., Cu(II) and Zn(II)) found in Aβ plaques of the diseased brain can bind to Aβ and be linked to aggregation and neurotoxicity. The role of metal ions in AD pathogenesis, however, is uncertain. To accelerate understanding in this area and contribute to therapeutic development, recent efforts to devise suitable chemical reagents that can target metal ions associated with Aβ have been made using rational structure-based design that combines two functions (metal chelation and Aβ interaction) in the same molecule. This paper presents bifunctional compounds developed by two different design strategies (linkage or incorporation) and discusses progress in their applications as chemical tools and/or potential therapeutics

Effects of hydroxyl group variations on a flavonoid backbone toward modulation of metal-free and metal-induced amyloid-?? aggregation

Amyloid-?? (A??) and metal ions are suggested to be involved in the pathogenesis of Alzheimer???s disease(AD). Cu(II) and Zn(II) can interact with A?? and facilitate peptide aggregation producing toxic oligomeric peptide species. Additionally, redox-active metal-bound A?? is shown to generate reactive oxygen species(ROS). Although the interaction of metal ions with A?? and the reactivity of metal-associated A?? (metal-A??) are indicated, the relationship between metal-A?? and AD etiology is still unclear. Some naturally occurring flavonoids capable of redirecting metal-A?? peptides into nontoxic, off-pathway A?? aggregates have been presented as valuable tools for elucidating the role of metal-A?? in AD. The structural moieties of the flavonoids responsible for their reactivity toward metal-A?? are not identified, however. To determine a structure-interaction-reactivity relationship between flavonoids and metal-free A?? or metal-A??, four flavonoids (morin, quercetin, galangin, and luteolin) were rationally selected based on structural variations(i.e., number and position of hydroxyl groups). These four flavonoids could noticeably modulate metal-A?? aggregation over metal-free analogue to different extents. Moreover, nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) studies reveal that the direct interactions of the flavonoids with metal-free and/or metal-bound A?? are distinct. Overall, our studies demonstrate that alternation of the hydroxyl groups on the B and C rings of flavonoids (structure) could differentiate their metal/metal-free A??/metal-A?? interactions (interaction) and subsequently direct their effects on metal-free A?? and metal-A?? aggregation in vitro and A??-/metal-A??-triggered toxicity in living cells (reactivity), suggesting a structure-interaction-reactivity relationship.open

BAAD - Baja Altura Alta Densidad

Trabajo Final de GradoSituados en el Barrio Güemes de la Ciudad de Córdoba, Argentina, buscamos una respuesta a la problemática de la ciudad dispersa y las complicaciones que la misma trae aparejada, como el aumento del tráfico, la necesidad de extender las redes de servicios y la segregación social en algunos casos. Planteamos una alternativa a la densificación en altura mediante torres y proponemos la inserción de pequeñas viviendas distribuidas de manera atomizada sobre el tejido preexistente, con el objetivo de brindar el acceso a una vivienda en la ciudad y mejorar la calidad ambiental de la misma mediante pequeñas intervenciones sobre los espacios públicos intermedios y privados. Con esta intervención se pretende mantener la identidad del barrio, reforzando las actividades mediante la generación de espacios que las contengan, tanto públicos como privados. Analizando los resultados obtenidos, de completarse el proyecto permitiría aumentar la densidad poblacional del sector en un 56,5%, pensamos que toda la ciudad de Córdoba podría aumentar la cantidad de habitantes un 50% sin expandir su mancha urbana y sin eliminar su tejido preexistente, manteniendo una escala que no supere los 12 metros de altura, lo que consideramos contribuye a una mejor calidad ambiental que el desarrollo de edificios en altura