Characterizing 15 Years of Saharan-like, Dry, Well-Mixed Air Layers in North Africa

The Saharan Air Layer (SAL) is a dry, well-mixed layer (WML) of warm and sometimes dusty air of nearly constant water vapor mixing ratio generated by the intense surface heating and strong, dry convection in the Sahara Desert, which has notable downstream impacts on the surface energy balance, organized convective system development, seasonal precipitation, and air quality. Characterizing both WMLs and SALs from the existing rawinsonde network has proven challenging because of its sparseness and inconsistent data reporting. Spurred on by this challenge, we previously created a detection methodology and supporting software to automate the identification and characterization of WMLs from multiple data sources including rawinsondes, remote sensing platforms, and model products. We applied our algorithm to each dataset at both its native and at a common (most coarse data product) vertical resolution to detect WMLs and their characteristics (temperature, mixing ratio, AOD, etc.) at each of the 53 rawinsonde launch sites in north Africa

Electron-electron interaction effects in quantum point contacts

We consider electron-electron interaction effects in quantum point contacts on the first quantization plateau, taking into account all scattering processes. We compute the low-temperature linear and nonlinear conductance, shot noise, and thermopower, by perturbation theory and a self-consistent nonperturbative method. On the conductance plateau, the low-temperature corrections are solely due to momentum-nonconserving processes that change the relative number of left- and right-moving electrons. This leads to a suppression of the conductance for increasing temperature or voltage. The size of the suppression is estimated for a realistic saddle-point potential, and is largest in the beginning of the conductance plateau. For large magnetic field, interaction effects are strongly suppressed by the Pauli principle, and hence the first spin-split conductance plateau has a much weaker interaction correction. For the nonperturbative calculations, we use a self-consistent nonequilibrium Green's function approach, which suggests that the conductance saturates at elevated temperatures. These results are consistent with many experimental observations related to the so-called 0.7 anomaly

Imaging Ca2+ concentration changes at the secretory vesicle surface with a recombinant targeted cameleon

AbstractRegulated exocytosis involves the Ca2+-triggered fusion of secretory vesicles with the plasma membrane, by activation of vesicle membrane Ca2+-binding proteins [1]. The Ca2+-binding sites of these proteins are likely to lie within 30 nm of the vesicle surface, a domain in which changes in Ca2+ concentration cannot be resolved by conventional fluorescence microscopy. A fluorescent indicator for Ca2+ called a yellow ‘cameleon’ (Ycam2) – comprising a fusion between a cyan-emitting mutant of the green fluorescent protein (GFP), calmodulin, the calmodulin-binding peptide M13 and an enhanced yellow-emitting GFP – which is targetable to specific intracellular locations, has been described [2]. Here, we generated a fusion between phogrin, a protein that is localised to secretory granule membranes [3], and Ycam2 (phogrin–Ycam2) to monitor changes in Ca2+ concentration ([Ca2+]) at the secretory vesicle surface ([Ca2+]gd) through alterations in fluorescence resonance energy transfer (FRET) between the linked cyan and yellow fluorescent proteins (CFP and YFP, respectively) in Ycam2. In both neuroendocrine PC12 and MIN6 pancreatic β cells, apparent resting values of cytosolic [Ca2+] and [Ca2+]gd were similar throughout the cell. In MIN6 cells following the activation of Ca2+ influx, the minority of vesicles that were within ∼1 μm of the plasma membrane underwent increases in [Ca2+]gd that were significantly greater than those experienced by deeper vesicles, and greater than the apparent cytosolic [Ca2+] change. The ability to image both global and compartmentalised [Ca2+] changes with recombinant targeted cameleons should extend the usefulness of these new Ca2+ probes

Accidental blood exposure: risk and prevention in interventional radiology

There is a growing concern about the transmission of bloodborne pathogens during medical procedures among health care workers and patients. Over the last three decades, radiological services have undergone many changes with the introduction of new modalities. One of these new disciplines is interventional radiology (IR) which deals with procedures such as arteriography, image-guided biopsies, intravascular catheter insertions, angioplasty and stent placements. Despite these developments, the potential for accidental blood exposure and exposure to other infectious material continues to exist. Therefore, it is important for all radiologists who perform invasive procedures to observe specific recommendations for infection control. In this review, we look at the different policies for protection and universal standards on infection control

The impact of perceptual complexity on road crossing decisions in younger and older adults.

Cognitive abilities decline with healthy ageing which can have a critical impact on day-to-day activities. One example is road crossing where older adults (OAs) disproportionally fall victim to pedestrian accidents. The current research examined two virtual reality experiments that investigated how the complexity of the road crossing situation impacts OAs (N = 19, ages 65-85) and younger adults (YAs, N = 34, ages 18-24) with a range of executive functioning abilities (EFs). Overall, we found that OAs were able to make safe crossing decisions, and were more cautious than YAs. This continued to be the case in high cognitive load situations. In these situations, safe decisions were associated with an increase in head movements for participants with poorer attention switching than participants with better attention switching suggesting these groups developed compensation strategies to continue to make safe decisions. In situations where participants had less time to make a crossing decision all participants had difficulties making safe crossing decisions which was amplified for OAs and participants with poorer EFs. Our findings suggest more effort should be taken to ensure that road crossing points are clear of visual obstructions and more speed limits should be placed around retirement or care homes, neither of which are legislated for in the UK and Australia

Acoustic oscillations in stars near the tip of the red giant branch

Small amplitude oscillations are observed in red giant branch (RGB) stars. Data on such oscillations are a source of information about the objects, notably about properties of convection in their envelopes and about the systems these objects inhabit. The OGLE-III catalog contains data for about 80 thousand small amplitude variable red giants (OSARGs) in the Large Magellanic Cloud. We want to explain variability in OSARGs as the solar-like oscillation and to associate the peaks in power spectra with frequencies of acoustic modes. We use data on reddening-free magnitudes of the objects and interpret them in terms of stellar physical parameters using tabulated isochrones calculated for ages and composition parameters corresponding to the upper RGB of the LMC. Massive data on the peak frequencies and amplitudes are compared with expectations for stochastically excited oscillations. The frequencies are also compared with those calculated for radial modes in envelope models with parameters taken from the isochrones. In stars close to the tip of the RGB, the peaks in power spectra are found in the 0.1-1.0 $\mu$Hz range, which is consistent with extrapolation of the frequency-luminosity relation for the solar-like oscillation. The dominant peaks occur close to the first two radial overtones. The increase in amplitude with luminosity is slower than linear. The exponent s=0.9 is similar to what is found from recent analysis of CoRoT data on less luminous red giants. Frequency separations between dominant peaks are found to be smaller by about 20% than calculated separations between these modes. After examining various possibilities, we left this discrepancy unexplained. The small amplitude variability of stars at the RGB tip is likely to be caused by a stochastic excitation of acoustic oscillations, but interpreting of individual peaks in power spectra presents a problem.Comment: Accepted for publication in Astronomy and Astrophysics, 6 pages, 6 figure

Confirmation and Analysis of Circular Polarization from Sagittarius A*

Recently Bower et al. (1999b) have reported the detection of circular polarization from the Galactic Center black hole candidate, Sagittarius A*. We provide an independent confirmation of this detection, and provide some analysis on the possible mechanisms.Comment: 14 pages, to appear in Astrophysical Journal Letter

Agroecología y el diseño de sistemas agrícolas resilientes al cambio climático

Diverse, severe and location-specific impacts on agricultural production are anticipated with climate change.Temperature and water availability remain key factors in determining crop growth and productivity, predicted changes in these factors will lead to reduced crop yields. Climate induced changes in insect pest, pathogen and weed population dynamics and invasiveness could compound such effects. Undoubtedly climate and weather induced instability will affect levels of and access to food supply. Changes that will not radically modify the monoculture nature of dominant agroecosystems may temporarily moderate negative impacts. The biggest and most durable benefits will likely result from more radical agroecological measures that will strengthen the resilience of farmers and rural communities, such as diversification of agroecosytems in the form of polycultures, agroforestry systems and crop-livestock mixed systems accompanied by organic soil management, water conservation and harvesting and general enhancement of agrobiodiversity. Traditional farming systems are repositories of a wealth of principles and measures that can help modern agricultural systems become more resilient to climatic extremes. Many of these agroecological strategies that reduce vulnerabilities to climate variability include, crop diversification, maintaining local genetic diversity, animal integration, soil organic management, water conservation and harvesting, etc. Understanding the agroecological features that underlie the resilience of traditional agroecosystems is an urgent matter, as they can serve as the foundation for the design of adapted agricultural systems. Field surveys and results reported in the literature suggest that agroecosystems are more resilient when inserted in a complex landscape matrix, featuring adapted local germplasm deployed in diversified cropping systems managed with organic matter rich soils and water conservation-harvesting techniques. The identification of systems that have withstood climatic events recently or in the past and understanding the agroecological features of such systems that allowed them to resist and/or recover from extreme events is of increased urgency, as the derived resiliency principles and practices that underlie successful farms can be disseminated to thousands of farmers.Se anticipa que el cambio climático cause impactos sobre la producción agrícola que serán diversos, severos y específicos según la ubicación geográfica. La temperatura y la disponibilidad de agua siguen siendo factores clave que determinan el crecimiento de los cultivos y la productividad. Los cambios predichos en estos factores causarán una baja en el rendimiento de los cultivos. Los cambios inducidos por el clima en cuanto a las dinámicas de población de plagas de insectos, patógenos y malezas y su invasividad podrían agravar los efectos mencionados. Sin duda alguna, la inestabilidad inducida por el clima y el tiempo afectará los niveles de producción de alimentos y el abastecimiento de los mismos. Los cambios para la adaptación que no modifiquen radicalmente la naturaleza dominante del monocultivo podrían moderar temporalmente los impactos negativos. Los beneficios mayores y más duraderos provendrán de medidas agroecológicas más radicales que fortalezcan la resiliencia de los agricultores y las comunidades rurales, tales como la diversificación de los agroecosistemas en forma de policultivos, los sistemas agroforestales y los sistemas que combinen la agricultura con la ganadería, acompañados por el manejo orgánico de los suelos, la conservación y la cosecha de agua y un incremento general de la agrobiodiversidad. Los sistemas agrícolas tradicionales son depósitos de abundantes principios y medidas que pueden ayudar a que los sistemas agrícolas modernos se vuelven más resilientes a los extremos climáticos. Muchas de las estrategias agroecológicas tradicionales que reducen la vulnerabilidad a la variabilidad climática incluyen la diversificación de cultivos, el mantenimiento de la diversidad genética local, la integración de los animales, la adición de materia orgánica al suelo, la cosecha de agua, etc. Urge entender las características agroecológicas que son la base de la resiliencia de los agroecosistemas tradicionales, ya que de ahí se pueden derivar principios útiles que sirvan de base para el diseño de sistemas agrícolas adaptados. Los estudios sobre el terreno y los resultados reportados en la literatura sugieren que los agroecosistemas son más resilientes cuando están insertados en una matriz de paisaje compleja, que incluya germoplasma local adaptado utilizado en sistemas de cultivos diversificados manejados con suelos ricos en materia orgánica y técnicas de conservación-cosecha de agua. Los principios y prácticas de resiliencia en los que se basan las fincas exitosas pueden ser difundidos a miles de agricultores a través de redes campesino a campesino para ampliar las prácticas agroecológicas que incrementan la resiliencia de los agroecosistemas