► Atomistic thermo-mechanics of nanomachining between diamond and copper. ► High speed MD nanomachining results in significant inertial tool force increases. ► Chip temperature increases most with ...machining velocity at low machined thicknesses. ► Chip temperature boundary layers can only persist at extremely high cutting speeds. ► There isan apparent isothermal to non-isothermal nanomachining transition at ≈50m/s.
The fabrication of high precision miniaturized components in micro- and nano-technologies requires a deep understanding of the physical mechanisms governing the nanomachining process. To aid with this need, the current article employs molecular dynamics to investigate the thermo-mechanical aspects of orthogonal nanometric machining in a copper workpiece. We study the evolution of the material removal process, the effects of machining velocity on the predicted MD response and the variation of the temperature within the chip for different machining velocities and machined thicknesses. As expected, the chip temperature rises with increasing machining velocity but it only noticeably decreases with growing machined thickness for machining velocities ⩾50m/s. The chip temperature indicates the isothermal nature of the machining process for low cutting speeds (⩽10m/s for copper) and the non-isothermal evolution of the process for high cutting speeds (⩾50m/s for copper).
We present a parallel implementation of a multi-scale coupling method for material simulations. We describe the models used for our application and we focus on the design of our numerical simulation, ...which is based on a coupling involving a parallel code for molecular dynamics and a parallel finite element code for continuum mechanics. Data redistribution and atom migration issues are discussed, and an experimental validation on a real crack propagation problem is provided
When sinks become sources Lavigne, F.; Martin, G.; Anciaux, Y. ...
Evolution,
January 2020, Volume:
74, Issue:
1
Journal Article
Peer reviewed
Open access
The establishment of a population into a new empty habitat outside of its initial niche is a phenomenon akin to evolutionary rescue in the presence of immigration. It underlies a wide range of ...processes, such as biological invasions by alien organisms, host shifts in pathogens, or the emergence of resistance to pesticides or antibiotics from untreated areas. We derive an analytically tractable framework to describe the evolutionary and demographic dynamics of asexual populations in a source-sink system. We analyze the influence of several factors on the establishment success in the sink, and on the time until establishment. To this aim, we use a classic phenotype-fitness landscape (Fisher’s geometrical model in n dimensions) where the source and sink habitats have different phenotypic optima. In case of successful establishment, the mean fitness in the sink follows a typical four-phases trajectory. The waiting time to establishment is independent of the immigration rate and has a “U-shaped” dependence on the mutation rate, until some threshold where lethal mutagenesis impedes establishment and the sink population remains so. We use these results to get some insight into possible effects of several management strategies.
This review gives an overview of the current approaches to evaluate drug absorption potential in the different phases of drug discovery and development. Methods discussed include in silico models, ...artificial membranes as absorption models, in vitro models such as the Ussing chamber and Caco-2 monolayers, in situ rat intestinal perfusion and in vivo absorption studies. In silico models such as iDEA can help optimizing chemical synthesis since the fraction absorbed (Fa) can be predicted based on structural characteristics only. A more accurate prediction of Fa can be obtained by feeding the iDEA model with Caco-2 permeability data and solubility data at various pH's. Permeability experiments with artificial membranes such as the filter-IAM technology are high-throughput and offer the possibility to group compounds according to a low and a high permeability. Highly permeable compounds, however, need to be further evaluated in Caco-2 cells, since artificial membranes lack active transport systems and efflux mechanisms such as P-glycoprotein (PgP). Caco-2 and other "intestinal-like" cell lines (MDCK, TC-7, HT29-MTX, 2/4/A1) permit to perform mechanistic studies and identify drug-drug interactions at the level of PgP. The everted sac and Ussing chamber techniques are more advanced models in the sense that they can provide additional information with respect to intestinal metabolism. In situ rat intestinal perfusion is a reliable technique to investigate drug absorption potential in combination with intestinal metabolism, however, it is time consuming, and therefore not suited for screening purposes. Finally, in vivo absorption in animals can be estimated from bioavailability studies (ratio of the plasma AUC after oral and i.v. administration). The role of the liver in affecting bioavailability can be evaluated by portal vein sampling experiments in dogs.
The Energetic Particle Telescope (EPT) is a new compact and modular ionizing particle spectrometer that was launched on 7 May 2013 to a LEO polar orbit at an altitude of 820 km onboard the ESA ...satellite PROBA-V. First results show electron, proton and helium ion fluxes in the South Atlantic Anomaly (SAA) and at high latitudes, with high flux increases during SEP (Solar Energetic Particles) events and geomagnetic storms. These observations help to improve the understanding of generation and loss processes associated to the Van Allen radiation belts.
A randomized trial of hepatic arterial chemoembolization was conducted in 42 patients with unresectable hepatocellular carcinoma. These patients represented 41% of patients with hepatocellular ...carcinoma seen during the inclusion period. In the remaining 59%, 9% had resectable tumours and 50% had unresectable tumours with contraindication for chemoembolization. Patients received either repeated chemoembolization with gelfoam powder and doxorubicin (group 1) or symptomatic treatment (group 2). There was no difference in age, prevalence of cirrhosis or staging according to Okuda between the two groups of patients. A complete tumour response (assessed by arteriography, ultrasonography and serum alphafetoprotein) was observed in four patients, and a partial response in three other patients from group 1. Actuarial survival rates were 33 and 24% in group 1 and 52 and 31% in group 2 at 6 and 12 months, respectively (differences were not significant--logrank test). With the treatment used in our study, chemoembolization did not prolong the survival time of patients with unresectable hepatocellular carcinoma. There were, however, some complete or partial responses. The high spontaneous 1-year survival rate of untreated patients was probably due to the exclusion of the most severely ill patients. Our results do not support the use of this method of chemoembolization in the treatment of hepatocellular carcinoma.
The aim of the present study was to compare the effect of five structural classes of flavonoids on the viability and metabolism of a colonic adenocarcinoma cell line (HT29 cells). The most prominent ...structural features of flavonoids favoring both their cytotoxic activity and their capacity to inhibit lactate release appear to be the desaturation of the 2, 3 bond and the position of attachment of the B ring. Indeed, flavonol and flavone are the most potent and, in both classes, the order of potency can be modulated by hydroxyl or methoxyl substituents. On the other hand, in our model, we did not find any correlation between flavonoid structure and their capacity to modulate cAMP level. This last point is discussed.
People cannot prevent personal information from being collected by various actors. Several security measures are implemented on servers to minimize the possibility of a privacy violation. ...Unfortunately, even the most well defended servers are subject to attacks and however much one trusts a hosting organism/company, such trust does not last forever. We propose a simple and practical degradation model where sensitive data undergoes a progressive and irreversible degradation from an accurate state at collection time, to intermediate but still informative fuzzy states, to complete disappearance. We introduce the data degradation model and identify related technical challenges and open issues.
PDF
