On improving the iterative convergence properties of an implicit approximate-factorization finite difference algorithm

The iterative convergence properties of an approximate-factorization implicit finite-difference algorithm are analyzed both theoretically and numerically. Modifications to the base algorithm were made to remove the inconsistency in the original implementation of artificial dissipation. In this way, the steady-state solution became independent of the time-step, and much larger time-steps can be used stably. To accelerate the iterative convergence, large time-steps and a cyclic sequence of time-steps were used. For a model transonic flow problem governed by the Euler equations, convergence was achieved with 10 times fewer time-steps using the modified differencing scheme. A particular form of instability due to variable coefficients is also analyzed

Endoscopic scores for inflammatory bowel disease in the era of 'mucosal healing'. old problem, new perspectives

The importance of the endoscopic evaluation in inflammatory bowel disease (IBD) management has been recognized for many years. However, the modalities for reporting endoscopic activity represent an ongoing challenge. To address this, several endoscopic scores have been proposed. Very few have been properly validated, and the use of such tools remains sub-optimal and is mainly restricted to clinical trials. In recent years, a growing emphasis of the concept of 'mucosal healing' as a prognostic marker and therapeutic goal has increased the need for a more accurate definition of endoscopic activity in both ulcerative colitis (UC) and Crohn's Disease (CD). In the present review, the evolution of the challenges related to endoscopic scores in IBD has been analyzed, with particular attention paid to the renewed relevance of endoscopic activity in recent years. Currently, despite the growing relevance of endoscopic activity, evaluating this activity in IBD is still a challenge. The implementation of efficacious endoscopic scores and a better definition of the absence of activity (mucosal healing) are needed.The importance of the endoscopic evaluation in inflammatory bowel disease (IBD) management has been recognized for many years. However, the modalities for reporting endoscopic activity represent an ongoing challenge. To address this, several endoscopic scores have been proposed. Very few have been properly validated, and the use of such tools remains sub-optimal and is mainly restricted to clinical trials. In recent years, a growing emphasis of the concept of 'mucosal healing' as a prognostic marker and therapeutic goal has increased the need for a more accurate definition of endoscopic activity in both ulcerative colitis (UC) and Crohn's Disease (CD). In the present review, the evolution of the challenges related to endoscopic scores in IBD has been analyzed, with particular attention paid to the renewed relevance of endoscopic activity in recent years. Currently, despite the growing relevance of endoscopic activity, evaluating this activity in IBD is still a challenge. The implementation of efficacious endoscopic scores and a better definition of the absence of activity (mucosal healing) are needed

Interpretation of the behaviour of compacted soils using cam-clay extended to unsaturated conditions

This paper is focused on the interpretation of experimental results obtained at the Department of Geotechnical Engineering of the University of Naples Federico II (Italy) to investigate the effects of partial saturation on the volumetric behaviour and the initial shear stiffness of a compacted silt. Tests were performed by using suction-controlled triaxial and resonant column cells. Herein, the compatibility of the results with a Single Stress Model (SSM) is discussed. The SSM allows to highlight that suction can have two effects on the mechanical behaviour of an unsaturated soil: it increases the average volumetric stress acting on the soil skeleton and it has a sort of cementing effect on the soil packing (hardening and cementation)

Application to a compacted soil of a Cam Clay model extended to unsaturated conditions

This paper presents an interpretation of experimental results obtained at the Department of Geotechnical Engineering of the Università di Napoli Federico II. The results are part of an extensive program carried out to investigate the effects of partial saturation on the volumetric behaviour and on the initial shear stiffness of a compacted silt. Tests were performed using two suction-controlled devices, a triaxial cell and a Resonant Column Torsional Shear (RCTS) cell. The compatibility of experimental data with a Bishop Stress Model (BSM) is discussed in the paper. The BSM permits to highlight the two main effects of suction on soil behaviour: the increase of the average stress acting on the soil skeleton and the hardening - cementing of the soil packing. Hydraulic hysteresis is included in the definition of the water retention curve so that its effects, such as the irreversible component of volume change recorded during drying paths, are automatically incorporated in the predictions of the model

Optimisation and application of ICP-MS and alpha-spectrometry for determination of isotopic ratios of depleted uranium and plutonium in samples collected in Kosovo

The determination of environmental contamination with natural and artificial actinide isotopes and evaluation of their source requires precise isotopic determination of actinides, above all uranium and plutonium. This can be achieved by alpha spectrometry or by inductively coupled plasma mass spectrometry (ICP-MS) after chemical separation of actinides. The performance of a sector-field ICP-MS (ICP-SFMS) coupled to a low-flow micronebulizer with a membrane desolvation unit, "Aridus'', was studied with respect to precise isotopic measurements of uranium and plutonium at the ultratrace level. The UH+/U+ formation rate was about 3x10(-5) and a sensitivity for U-238 of up to 4x10(9) counts s(-1) ppm(-1) was achieved. The limit of quantification (LOQ, 10s) for U-236 and Pu-239 using the experimental arrangement described above was 0.6 pg l(-1) in aqueous solution and 0.13 pg g(-1) in soil, respectively. ICP-SFMS was used in comparison to alpha spectrometry to measure the U and Pu concentrations and isotopic compositions in two soil samples and in one penetrator collected in Kosovo. ICP-MS permitted the determination of U and Pu isotope ratios including the U-236 abundance and Pu-240/Pu-239 ratio at ultratrace levels in soil samples of up to 0.1 g. Depleted uranium (U-235/U-238= 0.00202 +/-0.00001) was determined in one penetrator and one soil sample. Pu concentrations of (5.5 +/-0.1) x 10(-13) g g(-1) and (4.4 +/-0.5) x 10(-13) g g(-1) (Pu-240/Pu-239=0.35 +/-0.10 and 0.27 +/-0.07, respectively) were found in both soil samples from Kosovo. Besides plutonium, U-236 (3.1x10(-5) g g(-1)) and Am-241 (1.7x10(-12) g g(-1)) were also detected in the penetrator sample, which indicates the previous existence of neutron-related processes and points to a possible presence of spent reactor uranium in munitions. However, the most probable plutonium contamination sources in analyzed soil samples from Kosovo are mixed fallout including spent reactor fuel due to the Chernobyl nuclear power plant accident in 1986 and plutonium due to nuclear weapon tests. Additional plutonium contamination could not be determined in the Kosovo soil sample containing depleted uranium with a detection limit of about 10(-13) g g(-1)

impact of consumption profile discontinuities on the feasibility of a pv plant

Abstract The revenues of a grid-connected photovoltaic plant are strongly related to the local climatic conditions. In addition, since self-consumed electricity is much more valuable than that traded with the main power grid, also consumption profile plays a key role in the profitability of a PV system. Self-consumption to total PV production ratio depends on the temporal mismatch between energy generation and demand. The amount of energy that is not self-consumed may be very high in the case of a consumption profile with several discontinuities. This study is focused on the analysis of a grid-connected PV system serving a compressed natural gas (CNG) fueling station. These facilities are energy-intensive users, characterized by high variability of electricity demand due to intermittent operation of gas compressors: in a few seconds the total load may change from 100% to 5% and vice versa very frequently during the day. The analysis was based on data acquired on the field for the compression station and those already present in the literature for solar irradiation. The influence on plant design of the time step used for the analysis was studied in detail. The outcomes showed that the typical and well-assessed design approaches of a PV pant may lead to errors when used for the design of systems with several consumption profile discontinuities

Woodchip size effect on combustion temperatures and volatiles in a small-scale fixed bed biomass boiler

Biomass combustion performance is greatly affected by the particle size distribution, which influences heat and mass transport phenomena. The present work investigates the effect of woodchip size distribution on combustion in a 140 kW underfeed stoker boiler. Three different fuel sizes were prepared, and their combustion performance was measured by monitoring temperatures inside and above the fire pit and the gas composition above the fuel bed. The gas composition was then correlated to the particle mean diameter. Although minor effects could be detected in the temperature and composition of the flue gases, a more uniform spatial distribution of volatiles was observed when employing bigger woodchips. The present results can improve the understanding of the impact of fuel size on the performance of woodchip-fired boilers and can be valuably used for numerical model validation

Folate-Functionalization Enhances Cytotoxicity of Multivalent DNA Nanocages on Triple-Negative Breast Cancer Cells

DNA is an excellent programmable polymer for the generation of self-assembled multivalent nanostructures useful for biomedical applications. Herein, we developed (i) folate-functionalized nanocages (Fol-NC), very efficiently internalized by tumor cells overexpressing the alpha isoform of the folate receptor; (ii) AS1411-linked nanocages (Apt-NC), internalized through nucleolin, a protein overexpressed in the cell surface of many types of cancers; and (iii) nanostructures that harbor both folate and AS1411 aptamer functionalization (Fol-Apt-NC). We analyzed the specific miRNA silencing activity of all types of nanostructures harboring miRNA sequestering sequences complementary to miR-21 and the cytotoxic effect when loaded with doxorubicin in a drug-resistant triple-negative breast cancer cell line. We demonstrate that the presence of folate as a targeting ligand increases the efficiency in miR-21 silencing compared to nanocages functionalized with AS1411. Double-functionalized nanocages (Fol-Apt-NC), loaded with doxorubicin, resulted in an increase of over 51% of the cytotoxic effect on MDA-MB-231 cells compared to free doxorubicin, demonstrating, besides selectivity, the ability of nanocages to overcome Dox chemoresistance. The higher efficiency of the folate-functionalized nanocages is due to the way of entrance, which induces more than four times higher intracellular stability and indicates that the folate-mediated route of cell entry is more efficient than the nucleolin-mediated one when both folate and AS1411 modifications are present

Modelling piezoelectric energy harvesters by a finite integration technique formulation for electromechanical coupled problems

A detailed analysis and optimization of piezoelectric devices, which nowadays are of widespread use in electronic applications, requires numerical analysis. Numerical models based on the Finite Element Method (FEM) have already been proposed in literature. The Finite Integration Technique (FIT) provides stable and consistent discretization schemes for coupled multiphysics problems. A FIT formulation with unstructured meshes, for 2-D/3-D coupled electromechanical static or dynamic problems, is presented. Piezoelectric bimorph cantilevers, with a realistic multilayered geometry, can be analyzed. Comparisons with FEM show the validity and the accuracy of the method

ramp rate abatement for wind energy integration in microgrids

Abstract This study analyses the performance of a battery storage system in abating the ramp rates of the power produced by a wind turbine. This approach can reduce the wind power fluctuations that are typical of small size wind farms and promote the wind energy integration in microgrids. Production data was generated from actual wind measurements over one year, and the capability of ramp abatement by varying battery capacity, battery power rating and ramp rate thresholds was investigated. The effect on battery degradation due to charge-discharge cycling required by the smoothing service was also estimated. Results suggest that good smoothing performance can be achieved with a wide range of power-capacity combinations, but the lifetime of the storage system can be as low as one year if its capacity is small