Este artículo estudia el caso de la empresa Uber Technologies Inc. y su oferta a nivel internacional, abordando cómo su incursión transforma la forma de transporte de personas y mercancías, a pesar ...de las brechas en las regulaciones nacionales (caso de Costa Rica) e internacionales. La investigación es exploratoria, descriptiva, transversal y cualitativa, con enfoque en el comercio transfronterizo de servicios y en la economía del transporte, provocada por este tipo de plataformas tecnológicas. El resultado es una propuesta de tres escenarios prospectivos, dos de tendencia (servicio público innovador y transporte privado colaborativo) y uno de ruptura (transporte multicarga) para vislumbrar la posibilidad de optimizar el modelo de negocio, a través de catorce variables identificadas y determinadas por cuatro factores: tiempo, costo, social y ambiental.
Selective epoxidation of the (R) and (S) isomers of limonene by dioxomolybdenum
(VI)
complexes anchored covalently on TiO
2
nanotubes using UV–Vis light and O
2
as the oxidizing agent was evaluated. ...It is interesting to study the effect of the ligands: bipyridine, terpyridine, and Schiff base on the stereoselective epoxidation of limonene through photostimulated oxygen atom transfer (OAT). OAT activity observed to increase in the following order: Mo
(VI)
O
2
(Schiff base)/TiO
2
-NT < Mo
(VI)
Cl
2
O
2
(bipyridine)/TiO
2
-NT < Mo
(VI)
Cl
2
O
2
(terpyridine)/TiO
2
-NT. Moderate diastereoselectivity to the
cis
-isomer of complexes with “non-chiral” ligands like bipyridine and terpyridine was displayed. Contrary to the complex with the Schiff base as “chiral” ligand, it showed an increase in diastereoisomeric excess (52%), associated to an asymmetric double induction, assuming a complex metal-oxo sideway interaction with the trisubstituted olefins at the transition state.
Graphic Abstract
La arteriopatía autosómica dominante cerebral con infartos subcorticales y leucoencefalopatía es una enfermedad autosómica dominante de pequeños vasos causada por mutaciones del gen NOTCH3. ...Típicamente se presenta con migraña, eventos isquémicos cerebrales recurrentes y trastornos cognitivos. Las crisis epilépticas son inusuales como manifestación inicial, pero aún más infrecuente es su presentación como status epilepticus no convulsivo1. Se presenta una serie familiar de 3casos con esta arteriopatía, entre los cuales 2de ellos tuvieron status epilepticus como manifestación de la enfermedad.
Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal dominant small-vessel disease caused by mutations of the NOTCH3 gene. It typically presents with migraine, recurrent brain ischaemia, and cognitive disorders. Seizures rarely present as the initial manifestation, with non-convulsive status epilepticus being even less frequent. We present a series of 3 related patients with this arteriopathy, 2 of whom presented status epilepticus as a manifestation of the disease.
As a consequence of increasing atmospheric CO₂, the world's oceans are warming and slowly becoming more acidic (ocean acidification, OA) and profound changes in marine ecosystems are certain. ...Calcification is one of the primary targets for studies of the impact of CO₂-driven climate change in the oceans and one of the key marine groups most likely to be impacted by predicted climate change events are the echinoderms. Echinoderms are a vital component of the marine environment with representatives in virtually every ecosystem, where they are often keystone ecosystem engineers. This paper reviews and analyses what is known about the impact of near-future ocean acidification on echinoderms. A global analysis of the literature reveals that echinoderms are surprisingly robust to OA and that important differences in sensitivity to OA are observed between populations and species. However, this is modulated by parameters such as (1) exposure time with rare longer term experiments revealing negative impacts that are hidden in short or midterm ones; (2) bottlenecks in physiological processes and life-cycle such as stage-specific developmental phenomena that may drive the whole species responses; (3) ecological feedback transforming small scale sub lethal effects into important negative effects on fitness. We hypothesize that populations/species naturally exposed to variable environmental pH conditions may be pre-adapted to future OA highlighting the importance to understand and monitor environmental variations in order to be able to to predict sensitivity to future climate changes. More stress ecology research is needed at the frontier between ecotoxicology and ecology, going beyond standardized tests using model species in order to address multiple water quality factors (e.g. pH, temperature, toxicants) and organism health. However, available data allow us to conclude that near-future OA will have negative impact on echinoderm taxa with likely significant consequences at the ecosystem level.
Extreme precipitation associated with extratropical cyclones can lead to flooding if cyclones track over land. However, the dynamical mechanisms by which moist air is transported into cyclones is ...poorly understood. In this paper we analyze airflows within a climatology of cyclones in order to understand how cyclones redistribute moisture stored in the atmosphere. This analysis shows that within a cyclone’s warm sector the cyclone-relative airflow is rearwards relative to the cyclone propagation direction. This low-level airflow (termed the feeder airstream) slows down when it reaches the cold front, resulting in moisture flux convergence and the formation of a band of high moisture content. One branch of the feeder airstream turns toward the cyclone center, supplying moisture to the base of the warm conveyor belt where it ascends and precipitation forms. The other branch turns away from the cyclone center exporting moisture from the cyclone. As the cyclone travels, this export results in a filament of high moisture content marking the track of the cyclone (often used to identify atmospheric rivers). We find that both cyclone precipitation and water vapor transport increase when moisture in the feeder airstream increases, thus explaining the link between atmospheric rivers and the precipitation associated with warm conveyor belt ascent. Atmospheric moisture budgets calculated as cyclones pass over fixed domains relative to the cyclone tracks show that continuous evaporation of moisture in the precyclone environment moistens the feeder airstream. Evaporation behind the cold front acts to moisten the atmosphere in the wake of the cyclone passage, potentially preconditioning the environment for subsequent cyclone development.
Flavonoids are a family of polyphenolic compounds which are widespread in nature (vegetables) and are consumed as part of the human diet in significant amounts. There are other types of polyphenols, ...including, for example, tannins and resveratrol. Flavonoids and related polyphenolic compounds have significant antiinflammatory activity, among others. This short review summarizes the current knowledge on the effects of flavonoids and related polyphenolic compounds on inflammation, with a focus on structural requirements, the mechanisms involved, and pharmacokinetic considerations. Different molecular (cyclooxygenase, lipoxygenase) and cellular targets (macrophages, lymphocytes, epithelial cells, endothelium) have been identified. In addition, many flavonoids display significant antioxidant/radical scavenging properties. There is substantial structural variation in these compounds, which is bound to have an impact on their biological profile, and specifically on their effects on inflammatory conditions. However, in general terms there is substantial consistency in the effects of these compounds despite considerable structural variations. The mechanisms have been studied mainly in myeloid cells, where the predominant effect is an inhibition of NF-κB signaling and the downregulation of the expression of proinflammatory markers. At present there is a gap in knowledge of in vitro and in vivo effects, although the pharmacokinetics of flavonoids has advanced considerably in the last decade. Many flavonoids have been studied for their intestinal antiinflammatory activity which is only logical, since the gastrointestinal tract is naturally exposed to them. However, their potential therapeutic application in inflammation is not restricted to this organ and extends to other sites and conditions, including arthritis, asthma, encephalomyelitis, and atherosclerosis, among others.
La estética analítica hizo suyo, entre otros, el problema de la definición del arte y halló en el concepto dantiano de artworld una alternativa de solución eficiente. Motivador de subsecuentes ...propuestas, el costado más contextualista del programa de Arthur Danto debe aún enfrentar el reclamo de una supuesta falta de especificidad. Este escrito busca poner en diálogo dicho aporte teórico con los desarrollos hechos por Nelson Goodman en torno al arte a fin de aportar elementos de efectiva visibilidad frente a tal reclamo. Al hacerlo, se prevé analizar la diferencia introducida por este último a propósito de la ejecución y la implementación como instancias configuradoras de lo artístico de espesor y relevancia para su lectura funcionalista. La articulación de un bloque explicativo afin a ambos planteos supone, así, una alternativa novedosa para el área teórica en que se inserta al tiempo que otorga una ventaja considerable frente al marco contextualista del tratamiento del problema.
It is currently a routine practice to require a measurement of a housekeeping reference, including actin, glyceraldehyde-3-phosphate dehydrogenase, β-tubulin, among others, in Western blots, as it is ...the rule in RNA blots. Reversible Ponceau staining has been applied successfully to check equal loading of gels. Here we test a new technique, with the Stain-Free gels from Bio-Rad, against both Ponceau staining and housekeeping protein immunodetection under different conditions. Our results show that Stain-Free gels outperform Ponceau staining and that both are more consistent than housekeeping proteins as a loading control.
México alberga aproximadamente 393 especies de serpientes, de las cuales 210 son endémicas. Estos reptiles ofrecen servicios ecosistémicos que brindan beneficios a la humanidad como el control de ...plagas. A pesar de que nuestros ancestros las veneraban, actualmente existe repudio hacia ellas por desconocimiento y falsa información. Por medio de una exhaustiva revisión bibliográfica damos a conocer datos sobre la trascendencia de las serpientes y su diversidad en nuestro país, el desconocimiento, los mitos y el conflicto con el humano. Además, se enfatizan las causas que amenazan su existencia, así como la importancia de la educación ambiental para su conservación. Es nuestra responsabilidad divulgar información confiable que genere percepciones correctas para que se puedan preservar estos reptiles.
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