A simplified model of precipitation enhancement over a heterogeneous surface

Soil moisture heterogeneities through the triggering of mesoscale circulations influence the onset of convection and subsequent evolution of thunderstorms producing heavy precipitation. However local evaporation also plays a role in determining precipitation amounts. Here we aim at disentangling the effect of advection and evaporation on precipitation over the course of a diurnal cycle by formulating a simple conceptual model. The derivation of the model is inspired from the results of simulations performed with a high-resolution (250 m) Large-Eddy Simulation model over a surface with varying degrees of heterogeneity. Key element of the model is the representation of precipitation as weighted sum of advection and evaporation, each weighted by its own efficiency. The model is then used to isolate the main parameters that control the variations of precipitation over spatially drier patches. It is found that these changes surprisingly do not depend on soil moisture itself but instead purely on parameters that describe the atmospheric initial state. The likelihood for enhanced precipitation over drier soils is discussed based on these parameters. Additional experiments are used to test the validity of the model

Effect of soil moisture on diurnal convection and precipitation in large-eddy simulations

A determination of the sign and magnitude of the soil moisture-precipitation feedback relies either on observations, where synoptic variability is difficult to isolate, or on model simulations, which suffer from biases mainly related to poorly resolved convection. In this study, a large-eddy simulation model with a resolution of 250m is coupled to a land surface model and several idealized experiments mimicking the full diurnal cycle of convection are performed, starting from different spatially homogeneous soil moisture conditions. The goal is to determine under which conditions drier soils may produce more precipitation than wetter ones. The methodology of previous conceptual studies that have quantified the likelihood of convection to be triggered over wet or dry soils is followed but includes the production of precipitation. Although convection can be triggered earlier over dry soils than over wet soils under certain atmospheric conditions, total precipitation is found to always decrease over dry soils. By splitting the total precipitation into its magnitude and duration component, it is found that the magnitude strongly correlates with surface latent heat flux, hence implying a wet soil advantage. Because of this strong scaling, changes in precipitation duration caused by differences in convection triggering are not able to overcompensate for the lack of evaporation over dry soils. These results are further validated using two additional atmospheric soundings and a series of perturbed experiments that consider cloud radiative effects, as well as the effect of large-scale forcing, winds, and plants on the soil moisture-precipitation coupling

The AGB population of NGC 6822: distribution and the C/M ratio from JHK photometry

NGC 6822 is an irregular dwarf galaxy and part of the Local Group. Its close proximity and apparent isolation provide a unique opportunity to study galactic evolution without any obvious strong external influences. This paper aims to study the spatial distribution of the asymptotic giant branch (AGB) population and metallicity in NGC 6822. Using deep, high quality JHK photometry, taken with WFCAM on UKIRT, carbon- and oxygen-rich AGB stars have been isolated. The ratio between their number, the C/M ratio, has then been used to derive the [Fe/H] abundance across the galaxy. The tip of the red giant branch is located at K0 = 17.41 \pm 0.11 mag and the colour separation between carbon- and oxygen-rich AGB stars is at (J - K)0 = 1.20 \pm 0.03 mag (i.e. (J - K)2MAS S {\guillemotright} 1.28 mag). A C/M ratio of 0.62 \pm 0.03 has been derived in the inner 4 kpc of the galaxy, which translates into an iron abundance of [Fe/H] = -1.29\pm0.07 dex. Variations of these parameters were investigated as a function of distance from the galaxy centre and azimuthal angle. The AGB population of NGC 6822 has been detected out to a radius of 4 kpc giving a diameter of 56 arcmin. It is metal-poor, but there is no obvious gradient in metallicity with either radial distance from the centre or azimuthal angle. The detected spread in the TRGB magnitude is consistent with that of a galaxy surrounded by a halo of old stars. The C/M ratio has the potential to be a very useful tool for the determination of metallicity in resolved galaxies but a better calibration of the C/M vs. [Fe/H] relation and a better understanding of the sensitivities of the C/M ratio to stellar selection criteria is first required

Feeding behaviour of larval European sea bass (Dicentrarchus labrax L.) in relation to temperature and prey density

The feeding behaviour of larval European sea bass (Dicentrarchus labrax, L.) was analysed in relation to temperature and prey density under controlled laboratory conditions with the aim to assess the ability of larval fish to change the feeding tactic as a response to environmental changes. Larvae were acclimated for 20 days at three different temperatures (19, 22 and 26°C), and their feeding behaviour was then video-recorded in experimental trials, at two prey densities, consisting of swarms of 400/l and 1440/l Artemia nauplii. Results showed that there was a significant effect of the interaction between temperature and prey density on the proportion of swimming activity that was reduced at the high temperature-high prey density combination. This suggested a switching in the larval feeding behaviour from an active to an ambush tactic, when the temperature reached 26°C and the prey density was 1440 /l Artemia nauplii. These results are consistent with the current literature on fish larval behaviour in showing that the foraging tactic can be modulated by the interaction of different abiotic and biotic factors characterising the rearing environment

Stack sorting with increasing and decreasing stacks

We introduce a sorting machine consisting of $k+1$ stacks in series: the first $k$ stacks can only contain elements in decreasing order from top to bottom, while the last one has the opposite restriction. This device generalizes \cite{SM}, which studies the case $k=1$. Here we show that, for $k=2$, the set of sortable permutations is a class with infinite basis, by explicitly finding an antichain of minimal nonsortable permutations. This construction can easily be adapted to each $k \ge 3$. Next we describe an optimal sorting algorithm, again for the case $k=2$. We then analyze two types of left-greedy sorting procedures, obtaining complete results in one case and only some partial results in the other one. We close the paper by discussing a few open questions.Comment: 16 pages, 4 figure

The VISTA near-infrared YJKs public survey of the Magellanic Clouds System (VMC)

The VISTA public survey project VMC targets the Large Magellanic Cloud, the Small Magellanic Cloud, the Bridge and two fields in the Stream. The VMC survey is a uniform and homogeneous survey in the Y, J and Ks near-infrared filters. The main goals are the determination of the star formation history and the three-dimensional structure of the Magellanic system. The survey is therefore designed to reach stars as faint as the oldest main sequence turn-off point and to constrain the mean magnitude of pulsating variable stars such as RR Lyrae and Cepheids. We provide a brief overview of the survey strategy and first science results. Further details are given in Cioni et al. (2011)

Increased creatine demand during pregnancy in Arginine: Glycine Amidino-Transferase deficiency: A case report

Background: Creatine (Cr), an amino acid derivative, is one of the most important sources of energy acting as both a spatial and temporal energy buffer through its phosphorylated analogue phosphocreatine (PCr) and creatine kinase (CK). Maternal Cr biosynthesis and metabolism seem to play an important role in pregnancy, as shown in preclinical and in healthy human pregnancy studies. Patients with Arginine:Glycine Amidino-Transferase deficiency (AGAT-d), due to the deficit of the first enzyme involved in Cr synthesis, are at a disadvantage due to their failure to synthesize Cr and their dependence on external intake, in contrast to normal subjects, where changes in Cr biosynthesis supply their needs. We report the outcomes of a pregnancy in an AGAT-d woman, and the challenge we faced in managing her treatment with oral Cr to ensure optimal conditions for her fetus. Case presentation: A 22-year-old AGAT-d woman referred to our Institute for the management of her first conception at 11 weeks of fetal gestational age. Sonographic monitoring at 20 w GA indicated a reduction of fetal growth, in particular of the head circumference that was below the 3rd centile. Biochemical monitoring of Cr in biological fluids of the mother revealed a decline of the Cr concentrations, in particular in the urine sample, requiring prompt correction of the Cr dose. At 35 weeks of gestation the patient delivered a male infant, heterozygous for GATM mutation, with normal brain Cr levels; at one year the baby achieved typical developmental milestones. Conclusions: This rare pregnancy demonstrates that Cr levels in the blood and urine of the mother with AGAT-d decreased since the first months of gestation. The increase of the Cr daily dose administered to the mother seems to have produced beneficial effects also on the fetus

Propagation model for the Land Mobile Satellite channel in urban environments

This paper presents the major characteristics of a simulation package capable of performing a complete narrow and wideband analysis of the mobile satellite communication channel in urban environments for any given orbital configuration. The wavelength-to-average urban geometrical dimension ratio has required the use of the Geometrical Theory of Diffraction (GTD). For the RF frequency range, the model has been designed to be (1 up to 60 GHz) extended to include effects of non-perfect conductivity and surface roughness. Taking advantage of the inherent capabilities of such a high frequency method, we are able to provide a complete description of the electromagnetic field at the mobile terminal. Using the information made available at the ray-tracer and GTD solver outputs, the Land Mobile Satellite (LMS) urban model can also give a detailed description of the communication channel in terms of power delay profiles, Doppler spectra, channel scattering functions, and so forth. Statistical data, e.g. cumulative distribution functions, level crossing rates or distributions of fades are also provided. The user can access the simulation tool through a Design-CAD user-friendly interface by means of which she can effectively design her own urban layout and run consequently all the envisaged routines. The software is optimized in its execution time so that numerous runs can be achieved in a considerably short time

Drug-eluting Microspheres Compared to Conventional Transarterial Chemoembolization as First Line Treatment for Unresectable Hepatocellular Carcinoma: A Single-center Retrospective Cost-utility Analysis

Purpose: To assess the cost-utility of initial treatment with drug-eluting microspheres (DEM) transarterial chemoembolization (TACE) versus conventional (C)-TACE in patients with hepatocellular carcinoma considering the perspective of a Local Healthcare Authority in Italy. Materials and methods: The economic evaluation is based on a retrospective single-center study and individual patients' data whose details have been previously reported. The impact of initial treatment with DEM-TACE or C-TACE on disease progression, mortality, and direct health costs over a lifetime horizon were simulated and compared in terms of incremental cost-utility ratio expressed as costs per quality adjusted life years (QALY). Costs included direct health costs related to the first chemoembolization procedure and all subsequent follow-up costs associated with health care resources used for disease management. Probabilistic (PSA) sensitivity analysis was used to assess the robustness of the results. Results: A total of 101 patients in each treatment group were considered. All over the time-horizon median costs were €3,145.14 and €2,158.32 in the DEM-TACE and C-TACE group, respectively (p < 0.001); while mean costs were € 24,619 and € 17,001, respectively (p < 0.001). The ICUR was 6,461.86 €/QALY when using median costs derived from the study population as input for the health-economic evaluation and 49,932.15 €/QALY when the mean costs were considered. Results from PSA highlighted that using median costs DEM-TACE was always cost-effective, while using mean costs, it was preferable only 24.7% of times. Conclusions: The higher prices of DEMs are counterbalanced by the positive impact on QALY

Transcranial direct current stimulation (tDCS) in unilateral cerebral palsy: A pilot study of motor effect

Transcranial Direct Current Stimulation (tDCS) is an emerging tool to improve upper limb motor functions after stroke acquired in adulthood; however, there is a paucity of reports on its efficacy for upper limb motor rehabilitation in congenital or early-acquired stroke. In this pilot study we have explored, for the first time, the immediate effects, and their short-term persistence, of a single application of anodal tDCS on chronic upper limb motor disorders in children and young individuals with Unilateral Cerebral Palsy (UCP). To this aim, in a crossover sham-controlled study, eight subjects aged 10-28 years with UCP underwent two sessions of active and sham tDCS. Anodal tDCS (1.5 mA, 20 min) was delivered over the primary motor cortex (M1) of the ipsilesional hemisphere. Results showed, only following the active stimulation, an immediate improvement in unimanual gross motor dexterity of hemiplegic, but not of nonhemiplegic, hand in Box and Block test (BBT). Such improvement remained stable for at least 90 minutes. Performance of both hands in Hand Grip Strength test was not modified by anodal tDCS. Improvement in BBT was unrelated to participants’ age or lesion size, as revealed by MRI data analysis. No serious adverse effects occurred after tDCS; some mild and transient side effects (e.g., headache, tingling, and itchiness) were reported in a limited number of cases. This study provides an innovative contribution to scientific literature on the efficacy and safety of anodal tDCS in UCP