Influence of machining parameters on part geometrical error in abrasive waterjet offset-mode turning

Geometrical error in abrasive waterjet turned parts is an important challenge toward the commercialization of abrasive waterjet turning process. A systematic study has not been done yet to investigate the effects of process parameters on geometrical error in abrasive waterjet offset-mode turning. In this article, a comprehensive study has been performed to investigate the influence of several machining parameters on the geometrical error (part diameter percent error) in turning AA2011-T4 aluminum alloy round bars. Water pressure, cutting head traverse speed, workpiece rotational speed, abrasive mass flow rate and depth of cut were considered as the main machining parameters in a five-level statistical experimental design. Based on central composite rotatable design, a total of 52 experiments were carried out. The main effects of the parameters and interactions among them were analyzed based on the analysis of variance technique, and the response contours for the part geometrical error were obtained using a quadratic regression model (i.e. response surface methodology). The model predictions were found to be in good agreement with experimental data. Furthermore, among the significant parameters, water pressure, depth of cut and traverse speed are the most influential parameters, with percent contribution of almost 25% each. Abrasive mass flow rate is the least influential parameter with a percent contribution of 4%

Experimental investigation of two-side heat transfer in spacer-filled channels

In Membrane Distillation (MD), spacers support the membranes and promote mixing, thus reducing temperature polarization. Their efficient design requires a knowledge of the distribution of the local heat transfer coefficient h and of its dependence on Reynolds number, spacer geometry and flow-spacer relative orientation. In previous work, we applied Thermochromic Liquid Crystals (TLC) and digital image processing to the measurement of h distributions for different spacer configurations; data were used to validate CFD simulations and select turbulence models. For constructive reasons, the test section allowed only one-side heat transfer, while in most MD configurations (e.g. spiral-wound modules) heat transfer occurs from both sides of the feed water channels. Analytical and numerical solutions show that changing from one-side to two-side heat transfer deeply affects h values. This motivated the design and construction of an improved test section in which a hot channel is sandwiched between two cold channels, and twin cameras and lighting equipment allow the simultaneous acquisition of TLC images on both walls. This paper describes this new test section and the experimental technique, discusses measurement uncertainty, and presents preliminary results

The role of healthcare professionals in encouraging parents to see and hold their stillborn baby: a meta-synthesis of qualitative studies.

Background: Globally, during 2013 there were three million recorded stillbirths. Where clinical guidelines exist some recommend that professionals do not encourage parental contact. The guidance is based on quantitative evidence that seeing and holding the baby is not beneficial for everyone, but has been challenged by bereaved parents' organisations. We aim to inform future guideline development through a synthesis of qualitative studies reporting data relevant to the research question; how does the approach of healthcare professionals to seeing and holding the baby following stillbirth impact parents views and experiences? Methods/Findings: Using a predetermined search strategy of PubMed and PsychINFO we identified robust qualitative studies reporting bereaved parental views and/or experiences relating to seeing and holding their stillborn baby (final search 24 February, 2014). Eligible studies were English language, reporting parental views, with gestational loss >20weeks. Quality was independently assessed by three authors using a validated tool. We used meta-ethnographic techniques to identify key themes and a line of argument synthesis. We included 12 papers, representing the views of 333 parents (156 mothers, 150 fathers, and 27 couples) from six countries. The final themes were: "[Still]birth: Nature of care is paramount", "Real babies: Perfect beauties, monsters and spectres", and "Opportunity of a lifetime lost." Our line-of-argument synthesis highlights the contrast between all parents need to know their baby, with the time around birth being the only time memories can be made, and the variable ability that parents have to articulate their preferences at that time. Thus, we hypothesised that how health professionals approach contact between parents and their stillborn baby demands a degree of active management. An important limitation of this paper is all included studies originated from high income, westernised countries raising questions about the findings transferability to other cultural contexts. We do not offer new evidence to answer the question "Should parents see and hold their stillborn baby?", instead our findings advance understanding of how professionals can support parents to make appropriate decisions in a novel, highly charged and dynamic situation. Conclusions: Guidelines could be more specific in their recommendations regarding parental contact. The role of healthcare professionals in encouraging parents to see and hold their stillborn baby is paramount. Parental choice not to see their baby, apprehension, or uncertainty should be continuously revisited in the hours after birth as the opportunity for contact is fleeting and final

Splenic littoral cell hemangioendothelioma in a patient with crohn's disease previously treated with immunomodulators and anti-TNF agents: A rare tumor linked to deep immunosuppression

Th e risk of malignancy in Crohn ’ s disease (CD) has been well described. Moreover, immunomodulators, uch as azathioprine (AZA) and 6-mercaptopurine (6-MP), and biological agents, such as infl iximab and adalimumab, may promote carcinogenesis ( 1 – 3 ). Splenic littoral cell tumors are recently described tumors of vascular origin composed of endothelial cells, with typical microscopic and immunohistochemical features of splenic sinus lining cells ( 4 ). Clinical findings are not specific, and outcome is unpredictable but usually benign, although a few cases with a malignant behavior have been reported ( 5,6 ). We report a 58-year-old Caucasian man with a long history of ileocolonic CD

Enhanced flexibility of the O2 + N2 interaction and Its effect on collisional vibrational energy exchange

12 págs.; 8 figs.; 1 app. This article is part of the Piergiorgio Casavecchia and Antonio Lagana Festschrift special issue.Prompted by a comparison of measured and computed rate coefficients of Vibration-to-Vibration and Vibration-to-Translation energy transfer in O2 + N2 nonreactive collisions, extended semiclassical calculations of the related cross sections were performed to rationalize the role played by attractive and repulsive components of the interaction on two different potential energy surfaces. By exploiting the distributed concurrent scheme of the Grid Empowered Molecular Simulator we extended the computational work to quasiclassical techniques, investigated in this way more in detail the underlying microscopic mechanisms, singled out the interaction components facilitating the energy transfer, improved the formulation of the potential, and performed additional calculations that confirmed the effectiveness of the improvement introduced.The authors acknowledge financial support from the Phys4entry FP7/2007-2013 project (Contract No. 242311), ARPA Umbria, INSTM, the EGI-Inspire project (Contract No. 261323), MIUR PRIN 2008 (2008KJX4SN 003) and 2010/2011 (2010ERFKXL_002), the ESA-ESTEC Contract No. 21790/ 08/NL/HE and the Spanish CTQ2012-37404 and FIS2013- 48275-C2-1-P projects. Computations have been supported by the use of Grid resources and services provided by the European Grid Infrastructure (EGI) and the Italian Grid Infrastructure (IGI) through the COMPCHEM Virtual Organization. Thanks are also due to the COST CMST European Cooperative Project CHEMGRID (Action D37) EGI Inspire.Peer reviewe

Efficiency of Collisional O2 + N2 Vibrational Energy Exchange

10 pags.; 6 figs.; 5 tabs. In press.By following the scheme of the Grid Empowered Molecular Simulator (GEMS), a new O2 + N2 intermolecular potential, built on ab initio calculations and experimental (scattering and second virial coefficient) data, has been coupled with an appropriate intramolecular one. On the resulting potential energy surface detailed rate coefficients for collision induced vibrational energy exchanges have been computed using a semiclassical method. A cross comparison of the computed rate coefficients with the outcomes of previous semiclassical calculations and kinetic experiments has provided a foundation for characterizing the main features of the vibrational energy transfer processes of the title system as well as a critical reading of the trajectory outcomes and kinetic data. On the implemented procedures massive trajectory runs for the proper interval of initial conditions have singled out structures of the vibrational distributions useful to formulate scaling relationships for complex molecular simulations.The authors acknowledge financial support from the Phys4- entry FP7/2007-2013 project (Contract 242311), ARPA Umbria, INSTM, the EGI-Inspire project (Contract 261323), MIUR PRIN 2008 (2008KJX4SN 003) and 2010/2011 (2010ERFKXL_002), the ESA-ESTEC contract 21790/08/ NL/HE, and the Spanish CTQ2012-37404 and FIS2013- 48275-C2-1-P projects. Computations have been supported by the use of Grid resources and services provided by the European Grid Infrastructure (EGI) and the Italian Grid Infrastructure (IGI) through the COMPCHEM Virtual Organization. Thanks are also due to the COST CMST European Cooperative Project CHEMGRID (Action D37) EGI Inspire.Peer reviewe

A molecular dynamics simulation of hydrogen atoms collisions on an H-preadsorbed silica surface

The interaction of hydrogen atoms and molecules with a silica surface is relevant for many research and technological areas. Here, the dynamics of hydrogen atoms colliding with an H-preadsorbed -cristobalite (001) surface has been studied using a semiclassical collisional method in conjunction with a recently developed analytical potential energy surface based on Density Functional Theory (DFT) calculations. The atomic recombination probability via an Eley-Rideal (E-R) mechanism as well as the probabilities for other competitive molecular surface processes have been determined in a broad range of collision energies (0.04-3.0) eV eV) for off-normal (v=45°) and normal (v=0°) incidence and for two different surface temperatures (TS = 300 and 1000 K). H2,gas molecules form in roto-vibrational excited levels while the energy transferred to the solid surface is below of 10% for all simulated conditions. Finally, the global atomic recombination coefficient (E-R) and vibrational state resolved recombination coefficients (v) were calculated and compared with the available experimental values. The calculated collisional data are of interest in chemical kinetics studies and fluid dynamics simulations of silica surface processes in H-based low-temperature, low-pressure plasmas

Molecular dynamics study of hydrogen atom recombination over silica, based on a new analytical DFT potential energy surface

A new analytical potential energy surface (PES) based on new density functional theory data is constructed for the interaction of atomic hydrogen with both a clean and an H-preadsorbed -cristobalite (001) surface. For the atomic interaction, six adsorption sites have been considered, the Si site (T1') being the most stable one. The PES was developed as a sum of pairwise atom-atom interactions between the gas-phase hydrogen atoms and the Si and O atoms of the -cristobalite surface. A preliminary molecular dynamics semiclassical study of the different heterogeneous processes (e.g., H2 formation via Eley-Rideal reaction, H adsorption) that occur when H collides with an H-preadsorbed beta-cristobalite (001) surface was carried out. The calculations were performed for collisional energy in the range (0.06 ≤ Ekin ≤ 3.0 eV), normal incidence and a surface temperature Tsurf = 1000 K. The recombination probability reaches its maximum value of approximately 0.1 for collisional energies in the range 0.3 ≤ Ekin ≤ 0.8 eV. The H2 molecules are formed in medium-lying vibrational levels, while the energy exchanged with the surface in the recombination process is very low

Balance between the reliability of classification and sampling effort: A multi-approach for thewater Framework Directive (WFD) ecological status applied to the Venice Lagoon (Italy)

The Water Framework Directive (WFD) requires Member States to assess the ecological status of water bodies and provide an estimation of the classification confidence and precision. This study tackles the issue of the uncertainty in the classification, due to the spatial variability within each water body, proposing an analysis of the reliability of classification, using the results of macrophyte WFD monitoring in the Venice Lagoon as case study. The level of classification confidence, assessed for each water body, was also used as reference to optimize the sampling effort for the subsequent monitorings. The ecological status of macrophytes was calculated by the Macrophyte Quality Index at 114 stations located in 11 water bodies. At water body scale, the level of classification confidence ranges from 54% to 100%. After application of the multi-approach (inferential statistics, spatial analyses, and expert judgment), the optimization of the sampling effort resulted in a reduction of the number of stations from 114 to 84. The decrease of sampling effort was validated by assessing the reliability of classification after the optimization process (54-99%) and by spatial interpolation of data (Kernel standard error of 22.75%). The multi-approach proposed in this study could be easily applied to any other water body and biological quality element