4,822 research outputs found
A Hybrid Drift Diffusion Model: Derivation, Weak Steady State Solutions and Simulations
In this paper we derive a new hybrid model for drift di usion equations. This model provides a description of the quantum phenomena in the parts of the device where they are relevant, and degenerates to a semiclassical model where quantum e ects are negligible, so that the system can be considered classically. The study of quantum correction to the equation of state of an electron gas in a semiconductor with the assumption of localized quantum e ects leads to a further condition on the classical-quantum interface. Moreover, we prove the existence of weak solutions for our hybrid model. Finally, we present numerical results for di erent devices, by means of Colsys software
Nutrition and dementia: Evidence for preventive approaches?
In recent years, the possibility of favorably influencing the cognitive trajectory through
promotion of lifestyle modifications has been increasingly investigated. In particular, the relationship
between nutritional habits and cognitive health has attracted special attention. The present review
is designed to retrieve and discuss recent evidence (published over the last 3 years) coming from
randomized controlled trials (RCTs) investigating the efficacy of nutritional interventions aimed
at improving cognitive functioning and/or preventing cognitive decline in non-demented older
individuals. A systematic review of literature was conducted, leading to the identification of 11 studies
of interest. Overall, most of the nutritional interventions tested by the selected RCTs were found
to produce statistically significant cognitive benefits (defined as improved neuropsychological test
scores). Nevertheless, the clinical meaningfulness of such findings was not adequately discussed and
appears controversial. In parallel, only 2 studies investigated between-group differences concerning
incident dementia and mild cognitive impairment cases, reporting conflicting results. Results of
the present review suggest that several dietary patterns and nutritional components may constitute
promising strategies in postponing, slowing, and preventing cognitive decline. However, supporting
evidence is overall weak and further studies are needed
Spatially-resolved spectroscopy of narrow-line Seyfert 1 host galaxies
We present optical integral field spectroscopy for five narrow-line
Seyfert 1 galaxies (NLS1s) host galaxies, probing their host galaxies at
kpc scales. Emission lines in the nuclear AGN spectra and the
large-scale host galaxy are analyzed separately, based on an AGN-host
decomposition technique. The host galaxy gas kinematics indicates large-scale
gas rotation in all five sources. At the probed scales of kpc,
the host galaxy gas is found to be predominantly ionized by star formation
without any evidence of a strong AGN contribution. None of the five objects
shows specific star formation rates exceeding the main sequence of low-redshift
star forming galaxies. The specific star formation rates for MCG-05-01-013 and
WPVS 007 are roughly consistent with the main sequence, while ESO 399-IG20, MS
22549-3712, and TON S180 show lower specific star formation rates, intermediate
to the main sequence and red quiescent galaxies. The host galaxy metallicities,
derived for the two sources with sufficient data quality (ESO 399-IG20 and
MCG-05-01-013), indicate central oxygen abundances just below the low-redshift
mass-metallicity relation. Based on this initial case study, we outline a
comparison of AGN and host galaxy parameters as a starting point for future
extended NLS1 studies with similar methods.Comment: 25 pages, 8 figures, accepted for publication in ApJ on 3 September
201
Weighted Voronoi Region Algorithms for Political Districting
Automated political districting shares with electronic voting the aim of
preventing electoral manipulation and pursuing an impartial electoral
mechanism. Political districting can be modelled as multiobjective partitioning of a graph into connected components, where population equality and compactness must hold if a majority voting rule is adopted. This leads to the formulation of combinatorial optimization problems that are extremely hard to solve exactly. We propose a class of heuristics, based on discrete weighted Voronoi regions, for obtaining compact and balanced districts, and discuss some formal properties of these algorithms. Their performance has been tested on randomly generated rectangular grids, as well as on real-life benchmarks; for the latter instances the resulting district maps are compared with the institutional ones adopted in the Italian political elections from 1994 to 2001
Weighted Voronoi Region Algorithms for Political Districting
Automated political districting shares with electronic voting the aim of
preventing electoral manipulation and pursuing an impartial electoral
mechanism. Political districting can be modelled as multiobjective partitioning of a graph into connected components, where population equality and compactness must hold if a majority voting rule is adopted. This leads to the formulation of combinatorial optimization problems that are extremely hard to solve exactly. We propose a class of heuristics, based on discrete weighted Voronoi regions, for obtaining compact and balanced districts, and discuss some formal properties of these algorithms. Their performance has been tested on randomly generated rectangular grids, as well as on real-life benchmarks; for the latter instances the resulting district maps are compared with the institutional ones adopted in the Italian political elections from 1994 to 2001
Left Ventricular Trabeculations Decrease the Wall Shear Stress and Increase the Intra-Ventricular Pressure Drop in CFD Simulations
The aim of the present study is to characterize the hemodynamics of left ventricular (LV) geometries to examine the impact of trabeculae and papillary muscles (PMs) on blood flow using high performance computing (HPC). Five pairs of detailed and smoothed LV endocardium models were reconstructed from high-resolution magnetic resonance images (MRI) of ex-vivo human hearts. The detailed model of one LV pair is characterized only by the PMs and few big trabeculae, to represent state of art level of endocardial detail. The other four detailed models obtained include instead endocardial structures measuring ≥1 mm2 in cross-sectional area. The geometrical characterizations were done using computational fluid dynamics (CFD) simulations with rigid walls and both constant and transient flow inputs on the detailed and smoothed models for comparison. These simulations do not represent a clinical or physiological scenario, but a characterization of the interaction of endocardial structures with blood flow. Steady flow simulations were employed to quantify the pressure drop between the inlet and the outlet of the LVs and the wall shear stress (WSS). Coherent structures were analyzed using the Q-criterion for both constant and transient flow inputs. Our results show that trabeculae and PMs increase the intra-ventricular pressure drop, reduce the WSS and disrupt the dominant single vortex, usually present in the smoothed-endocardium models, generating secondary small vortices. Given that obtaining high resolution anatomical detail is challenging in-vivo, we propose that the effect of trabeculations can be incorporated into smoothed ventricular geometries by adding a porous layer along the LV endocardial wall. Results show that a porous layer of a thickness of 1.2·10−2 m with a porosity of 20 kg/m2 on the smoothed-endocardium ventricle models approximates the pressure drops, vorticities and WSS observed in the detailed models.This paper has been partially funded by CompBioMed project, under H2020-EU.1.4.1.3 European Union’s Horizon 2020 research and innovation programme, grant agreement n◦ 675451. FS is supported by a grant from Severo Ochoa (n◦ SEV-2015-0493-16-4), Spain. CB is supported by a grant from the Fundació LaMarató de TV3 (n◦ 20154031), Spain. TI and PI are supported by the Institute of Engineering in Medicine, USA, and the Lillehei Heart Institute, USA.Peer ReviewedPostprint (published version
External validity of randomized controlled trials on Alzheimer's disease: the biases of frailty and biological aging
To date, the external validity of randomized controlled trials (RCTs) on Alzheimer's disease (AD) has been assessed only considering monodimensional variables. Nevertheless, looking at isolated and single characteristics cannot guarantee a sufficient level of appreciation of the AD patients' complexity. The only way to understand whether the two worlds (i.e., research and clinics) deal with the same type of patients is to adopt multidimensional approaches more holistically reflecting the biological age of the individual. In the present study, we compared measures of frailty/biological aging [assessed by a Frailty Index (FI)] of a sample of patients with AD resulted eligible and subsequently included in phase III RCTs compared to patients referring to the same clinical service, but not considered for inclusion. The "RCT sample" and the "real world sample" were found to be statistically similar for all the considered sociodemographic and clinical variables. Nevertheless, the "real world sample" was found to be significantly frailer compared to the "RCT sample," as indicated by higher FI scores [0.28 (SD 0.1) vs. 0.17 (SD 0.1);p < 0.001, respectively]. Moreover, when assessing the relationship between FI and age, we found that the correlation was almost null in the "RCT sample" (Spearman'sr = 0.01;p = 0.98), while it was statistically significant in the "real world sample" (r = 0.49;p = 0.02). The application of too rigid designs may result in the poor representativeness of RCT samples. It may even imply the study of a condition biologically different from that observed in the "real world." The adoption of multidimensional measures capable to capture the individual's biological age may facilitate evaluating the external validity of clinical studies, implicitly improving the interpretation of the results and their translation in the clinical arena
Post-Transplant Lymphoproliferative Disease (PTLD) after Allogeneic Hematopoietic Stem Cell Transplantation: Biology and Treatment Options
Inflammation in diabetic nephropathy: moving toward clinical biomarkers and targets for treatment
Polynucleotide: Adenosine glycosidase is the sole activity of ribosome-inactivating proteins on DNA
Polynucleotide: adenosine glycosidases (PNAG) are a class of plant and bacterial enzymes commonly known as ribosome-inactivating proteins (RIP). They are presently classified as rRNA N-glycosidases in the enzyme nomenclature [EC 3.2.2.22]. Several activities on nucleic acids, other than depurination, have been attributed to PNAG: in particular modifications induced in circular plasmids, including linearisation and topological changes, and cleavage of guanidinic residues. Here we describe a chromatographic procedure to obtain nuclease-free PNAG by dye-chromatography onto Procion Red derivatized Sepharose®. Highly purified enzymes depurinate extensively pBR322 circular, supercoiled DNA at neutral pH and exhibit neither DNase nor DNA glycolyase activities, do not cause topological changes, and adenine is the only base released from DNA and rRNA, even at very high enzyme concentrations. A scanning force microscopy (SFM) study of pBR322 treated with saporin-S6 confirmed that (i) this PNAG binds extensively to the plasmid, (ii) the distribution of the bound saporin-S6 molecules along the DNA chain is markedly variable, (iii) plasmids already digested with saporin-S6 do not appear fragmented or topologically modified. The observations here described demonstrate that polynucleotide:adenosine glycosidase is the sole enzymatic activity of the four ribosome-inactivating proteins gelonin, momordin I, pokeweed antiviral protein from seeds and saporin-S6. These proteins belong to different families, suggesting that the findings here described may be generalized to all PNAG
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