Free Alternate Bars in Rivers: Key Physical Mechanisms and Simple Formation Criterion

Free alternate bars are large-scale, downstream-migrating bedforms characterized by an alternating sequence of three-dimensional depositional fronts and scour holes that frequently develop in rivers as the result of an intrinsic instability of the erodible bed. Theoretical models based on two-dimensional shallow water and Exner equations have been successfully employed to capture the bar instability phenomenon, and to estimate bar properties such as height, wavelength and migration rate. However, the mathematical complexity of the problem hampered the understanding of the key physical mechanisms that sustain bar formation. To fill this gap, we considered a simplified version of the equations, based on neglecting the deformation of the free surface, which allows us to: (a) provide the first complete explanation of the bar formation mechanism as the result of a simple bond between variations of the water weight and flow acceleration; (b) derive a simplified, physically based formula for predicting bar formation in a river reach, depending on channel width-to-depth ratio, Shields number and relative submergence. Comparison with an unprecedented large set of laboratory experiments reveals that our simplified formula appropriately predicts alternate bar formation in a wide range of conditions. Noteworthy, the hypothesis of negligible free surface effect also implies that bar formation is fully independent of the Froude number. We show that this intriguing property is intimately related to the three-dimensional nature of river bars, which allows for a gentle lateral deviation of the flow without significant deformation of the water surface

On steady alternate bars forced by a localized asymmetric drag distribution in erodible channels

Studying the effect of different in-stream fluvial turbines siting on river morphodynamics allowed us to witness the onset of a time-Averaged, large-scale, alternate distortion of bed elevations, which could not be exclusively related to the turbine rotor blockage. The longitudinal profiles of this two-dimensional bathymetric perturbation resemble those of steady fluvial bars. In this contribution we generalize the problem addressing a spatially impulsive, asymmetric distribution of drag force in the channel cross-section. This is experimentally investigated through the deployment of differently sized grids perpendicular to the flow, and analytically explored as a finite perturbation of an open channel flow over an erodible sediment layer, as described by a coupled flow-sediment shallow water equation. The steady solutions of this fluvial morphodynamic problem, physically represented by alternate bars scaling with the channel width, highlight the importance of the resonant conditions in defining the spatial extent of the bed deformation. The equations further suggest that in very shallow flows any asymmetric obstruction may lead to an upstream propagation of the steady bars, consistent with previous studies on the effects of channel curvature. In broad terms, this study provides the preliminary framework to control the onset of river meandering through imposed finite perturbations of the cross-section. In a more applied sense, it provides a tool to predict non-local scour-deposition patterns associated with the deployment of energy converters or other flow obstructions

Morphometric properties of alternate bars and water discharge: A laboratory investigation

The formation of alternate bars in straightened river reaches represents a fundamental process of river morphodynamics that has received great attention in the last decades. It is well-established that migrating alternate bars arise from an autogenic instability mechanism occurring when the channel width-to-depth ratio is sufficiently large. While several empirical and theoretical relations are available for predicting how bar height and length depend on the key dimensionless parameters, there is a lack of direct, quantitative information about the dependence of bar properties on flow discharge. We performed a series of experiments in a long, mobile-bed flume with fixed and straight banks at different discharges. The self-formed bed topography was surveyed, different metrics were analyzed to obtain quantitative information about bar height and shape, and results were interpreted in the light of existing theoretical models. The analysis reveals that the shape of alternate bars highly depends on their formative discharge, with remarkable variations in the harmonic composition and a strong decreasing trend of the skewness of the bed elevation. Similarly, the height of alternate bars clearly decreases with the water discharge, in quantitative agreement with theoretical predictions. However, the disappearance of bars when discharge exceeds a critical threshold is not as sharp as expected due to the formation of so-called "diagonal bars". This work provides basic information for modeling and interpreting short-term morphological variations during individual flood events and long-term trajectories due to alterations of the hydrological regime

Distribución espacial de posturas de controladores biológicos crisópidos Neuroptera, en cuatro cultivares de olivo en La Rioja.

Para determinar la presencia de los Neuroptera: Chrysopidae en el cultivo de olivo, se realizó una prospección de posturas de “crisópidos” el día 9 de abril de 2011, en la etapa fenológica de precosecha, en el banco de germoplasma de olivo ex situ de la Universidad Nacional de La Rioja. Se escogieron tres árboles de cada una de los cultivares “Arauco”, “Arbequina”, “Frantoio” y “Manzanilla”. En cada árbol se observó ramas por 5 minutos, en cada una de las cuatro orientaciones (N, S, E y O). En los 12 árboles estudiados, se encontró un total de 54 huevos colectados, 23 estaban en el haz de la hoja, 30 en el envés de la hoja y un huevo en el fruto. El cultivar “Frantoio” presentó el mayor número (n = 23) de huevos. Los otros cultivares de olivo presentaron un menor número (50%), y no mostrando diferencias entre ellos ("Arauco” = 10, “Arbequina” = 11, “Manzanilla”= 10). La ubicación de las posturas en relación a la orientación en el árbol, mostró una tendencia por la orientación Norte (n = 17), Oeste (n = 16) y Este (n = 14), mientras que la orientación Sur tuvo el menor número de posturas (n = 7). Estos resultados contribuyen a definir estrategias de control biológico aumentativo en el cultivo.Spatial distribution of eggs of beneficial lacewings Insecta: Neuroptera in four cultivars of olive trees in La Rioja.AbstractFor determined the presence of the Neuroptera: Chrysopidae in olive crops, conducted a survey of eggs of lacewings on April 9, 2011, at the time of pre-harvest, in the germoplasm collections of olive ex situ of the National University of La Rioja. They chose three trees of the “Arauco”, "Arbequina", "Frantoio" and "Manzanilla" cultivars. Each tree found branches for 5 minutes, in each of the four orientations (N, S, E and W). The 54 collected eggs, 23 were on the upper side of the road, 30 on the underside of the leaf and an egg in the fruit. The cultivar "Frantoio" presented the greatest number (n = 23) eggs. Other cultivars of olive tree presented a lower number (50%), and not showing differences between them (“Arauco” = 10, "Arbequina" = 11, "Manzanilla" = 10). The location of the eggs in relation to the guidance in the tree, showed a trend for the North direction (n = 17), West (n = 16) and East (n = 14), while the South direction had the lowest number of eggs (n = 7). These results help define strategies of augmentative biological control in crops.Key words: Eggs distribution; Chrysopidae; Biological control; Oliv

Introduction of WO3 Layer in a Cu-Based Al2O3 Conductive Bridge RAM System for Robust Cycling and Large Memory Window

In this paper, we optimize a WO3\Al2O3 bilayer serving as the electrolyte of a conductive bridge RAM device using a Cu-based supply layer. By introducing a WO3 layer formed by thermal oxidation of a W plug, the hourglass shape of the conductive filament is desirably controlled, enabling excellent switching behavior. We demonstrate a clear improvement of the microstructure and density of the WO3 layer by increasing the oxidation time and temperature, resulting in a strong increase of the high-resistance-state breakdown voltage. The high quality WO3 microstructure allows thus the use of a larger reset pulse amplitude resulting both in larger memory window and failure-free write cycling.1197Ysciescopu

A first assessment of genetic variability in the longhorn beetle Rosalia alpina (Coleoptera: Cerambycidae) from the Italian Apennines

The Rosalia longicorn (Rosalia alpina) is a strictly protected saproxylic beetle, widely distributed in Central and Southern Europe and mainly associated with ancient beech forests. To improve knowledge about the conservation status of R. alpina in Italy, available molecular markers (microsatellites and mitochondrial cytochrome c oxidase I(COI)) were tested for the first time on Italian populations. The study was performed in four sampling sites distributed in two areas placed in Northern (“Foreste Casentinesi” National Park) and Central Apennines (“Abruzzo, Lazio and Molise” National Park) where populational data about Rosalia longicorn were collected in the framework of the European LIFE MIPP Project. The genetic relationship among Apennine and Central/South-eastern European populations was explored by a comparison with mitochondrial DNA (mtDNA) data from literature. Microsatellite markers were only partially informative when applied to R. alpina Italian individuals, although providing some preliminary indication on an extensive gene flow among populations from the Apennines and local ongoing processes of genetic erosion. Genetic data are consistent with previous ecological data suggesting that the maintenance of variability in this species could be related to both habitat continuity and preservation of large senescent or standing dead trees in forests. Finally, a peculiar origin of the Apennine populations of R. alpina from a putative “Glacial Refugium” in Italy was inferred through COI data. The high genetic distance scored among the analysed populations and those from Central and South-eastern Europe indicates that the R. alpina deme from Apennine Mountains might represent a relevant conservation unit in Europe. Further genetic analyses will allow assessing other possible conservation units of R. alpina and, thus, defining large-scale conservation strategies to protect this endangered longhorn beetle in Europe

Diversidad específica de controladores biológicos crisópidos (Neuroptera: Chrysopidae) en el germoplasma olivícola en la Plaza Solar, La Rioja, Argentina.

Between the months of March toAugust of 2011, it was made prospection of lacewings adults and eggs of in germplasm olive trees of the Solar Square of the National University of La Rioja. The adults were collected by means of entomological net in the tree, during the hours of light in the day, and with plastic bottle of 500ml in the hours at night.The eggs were obtained in the leaves of the tree. The eggs entered in the laboratory of the CENIIT, until the obtaining of the adults. Its were prepared in boxes entomology and determined by the Dr. Enrique González Olazo in the Fundación Miguel Lillo.In the six months of sampling (autumn-winter) a total of six species was determined: Ceraeochrysa claveri Navás Chrysoperla asoralis (Banks), C argentina González Olazo y Reguilón, C externa (Hagen), Ungla argentina(Navás) y U binaria (Navás).They are new records for La Rioja and olive crops: C. asoralis, C. claveri, U argentina and U binaria.The most abundant species (n=9) C asoralis was . Present data on the biology and ecology of the species and a key for the determination of the genus and the six species of Chrysopidae.Entre los meses de marzo y agosto de 2011, se realizó prospección de adultos y posturas de crisópidos en el germoplasma olivícola de la Plaza Solar de la Universidad Nacional de La Rioja. Los adultos fueron colectados mediante red entomológica en el árbol, durante las horas de luz, y con botella plástica de 500ml en las horas de oscuridad.Los huevos fueron obtenidos en las hojas del árbol. Las posturas ingresaron a la cría en el laboratorio del CENIIT, hasta la obtención de los adultos, los cuales fueron acondicionados en cajas entomológicas y determinados por el Dr. Enrique González Olazo en la Fundación Miguel Lillo.En los seis meses de muestreo (otoño-invierno) se determinó un total de seis especies: Ceraeochrysa claveri Navás, Chrysoperla asoralis (Banks), C. argentina González Olazo & Reguilón, C. externa (Hagen), Ungla argentina (Navás) y U. binaria (Navás) Son nuevas citas para La Rioja y el cultivo del olivo: C. asoralis, C. claveri, U. argentina y U. binaria. La especie más abundante (n=9) fue C asolaris. Se presentan datos de la biología y ecología de las especies. Se elaboró una clave para la determinación de los géneros y las seis especies de Chrysopidae

What is the remaining status of adaptive servo-ventilation? The results of a real-life multicenter study (OTRLASV-study). Adaptive servo-ventilation in real-life conditions

Backgrounds: As a consequence of the increased mortality observed in the SERVE-HF study, many questions concerning the safety and rational use of ASV in other indications emerged. The aim of this study was to describe the clinical characteristics of ASV-treated patients in real-life conditions. Methods: The OTRLASV-study is a prospective, 5-centre study including patients who underwent ASV-treatment for at least 1 year. Patients were consecutively included in the study during the annual visit imposed for ASV- reimbursement renewal. Results: 177/214 patients were analysed (87.57% male) with a median (IQ25–75) age of 71 (65–77) years, an ASV- treatment duration of 2.88 (1.76–4.96) years, an ASV-usage of 6.52 (5.13–7.65) hours/day, and 54.8% were previously treated via continuous positive airway pressure (CPAP). The median Epworth Scale Score decreased from 10 (6–13.5) to 6 (3–9) (p < 0.001) with ASV-therapy, the apnea-hypopnea-index decreased from 50 (38–62)/h to a residual device index of 1.9 (0.7–3.8)/h (p < 0.001). The majority of patients were classified in a Central-Sleep-Apnea group (CSA; 59.3%), whereas the remaining are divided into an Obstructive-Sleep-Apnea group (OSA; 20.3%) and a Treatment-Emergent-Central-Sleep-Apnea group (TECSA; 20.3%). The Left Ventricular Ejection Fraction (LVEF) was > 45% in 92.7% of patients. Associated comorbidities/etiologies were cardiac in nature for 75.7% of patients (neurological for 12.4%, renal for 4.5%, opioid-treatment for 3.4%). 9.6% had idiopathic central-sleep-apnea. 6.2% of the patients were hospitalized the year preceding the study for cardiological reasons. In the 6 months preceding inclusion, night monitoring (i.e. polygraphy or oximetry during ASV usage) was performed in 34.4% of patients, 25.9% of whom required a subsequent setting change. According to multivariable, logistic regression, the variables that were independently associated with poor adherence (ASV-usage ≤4 h in duration) were TECSA group versus CSA group (p = 0.010), a higher Epworth score (p = 0.019) and lack of a night monitoring in the last 6 months (p < 0.05). Conclusions: In real-life conditions, ASV-treatment is often associated with high cardiac comorbidities and high compliance. Future research should assess how regular night monitoring may optimize devices settings and patient management