Effect of cutting tool assisted with vibrations on turning machined C45 samples

This thesis aims to analyse the effect of a cutting tool assisted (VAM) with 40-kHz vibration on C45 steel samples. It exposes the improvement of surface finish through vibration application and the different effects thus generated while machining process. The vibratory movement of the cutting tool is one-dimensional, and cutting tests are performed on a lathe machine. The study is mainly divided into two stages: the analyses of the effect of vibration assistance, feed and tool angle on the cutting force and roughness by means of a design of experiment. Then, the observation and characterisation of the chips removal mechanism with a high-speed camera to characterize the influence of the vibratory effect on its formation. The state of art section provide knowledge to understand the subject by exposing all the research and studies similar from our topic to justify the experiments that will be carried out. All procedures to achieve the research objectives are described, including the experimental design, experimental setup and the materials used to conduct them. It is concluded that one dimensional vibration assisted machining (VAM) offers distinct advantages over conventional machining (NVAM). The surface quality is improved when the cutting parameters are carefully implemented; adding vibration is the most significant effect on the surface quality providing lower Ra values than NVAM. VAM has demonstrated that applying vibration as a significative influence on the chip removal mechanism. Indeed, the chip fragmentation is facilitated by the VAM process by forming arc loose chips which ultimately improve the surface quality and tool wear resistance by limiting the friction due to enhanced evacuation of the chip. The texturization effects of VAM to obtain specific surface texture are also observed. From VAM to NVAM, two different patterns are easily detected (linear and mesh shape), the level intensity depends mainly on the feed rate

Size dependent phase diagrams of Nickel-Carbon nanoparticles

The carbon rich phase diagrams of nickel-carbon nanoparticles, relevant to catalysis and catalytic chemical vapor deposition synthesis of carbon nanotubes, are calculated for system sizes up to about 3 nanometers (807 Ni atoms). A tight binding model for interatomic interactions drives the Grand Canonical Monte Carlo simulations used to locate solid, core/shell and liquid stability domains, as a function of size, temperature and carbon chemical potential or concentration. Melting is favored by carbon incorporation from the nanoparticle surface, resulting in a strong relative lowering of the eutectic temperature and a phase diagram topology different from the bulk one. This should be taken into account in our understanding of the nanotube growth mechanisms

Entropy driven stability of chiral single-walled carbon nanotubes

Single-walled carbon nanotubes are hollow cylinders, that can grow centimeters long by carbon incorporation at the interface with a catalyst. They display semi-conducting or metallic characteristics, depending on their helicity, that is determined during their growth. To support the quest for a selective synthesis, we develop a thermodynamic model, that relates the tube-catalyst interfacial energies, temperature, and the resulting tube chirality. We show that nanotubes can grow chiral because of the configurational entropy of their nanometer-sized edge, thus explaining experimentally observed temperature evolutions of chiral distributions. Taking the chemical nature of the catalyst into account through interfacial energies, structural maps and phase diagrams are derived, that will guide a rational choice of a catalyst and growth parameters towards a better selectivity

Influence of Travelling Speed on the Risk of Injury Accident: a Matched Case-Control Study

This matched case-control study deals with the effect of the individual travelling speed on the risk of involvement in a road accident. The cases were cars involved in injury accidents dealt with within the framework of an in-depth accident investigation programme. The matched controls were cars passing the same road site as the crash-involved car, in the same conditions but without being involved in an accident. Only normal weather, daytime and free-flow conditions were considered. Overall, 52 cases and 817 controls were used. The speeds were obtained from kinematic reconstructions for the crash-involved cars, and using a laser speed gun for the controls. A significant positive relationship is found between the individual travelling speed and the risk of injury accident. Nevertheless, this study has limitations, due to the relatively small number of cases and to the data used (kinematic reconstructions always involve some degree of interpretation)

SIMONE: a realistic neural network simulator to reproduce MEA-based recordings

International audienceContemporary multielectrode arrays (MEAs) used to record extracellular activity from neural tissues can deliver data at rates on the order of 100 Mbps. Such rates require efficient data compression and/or preprocessing algorithms implemented on an application specific integrated circuit (ASIC) close to the MEA. We present SIMONE (Statistical sIMulation Of Neuronal networks Engine), a versatile simulation tool whose parameters can be either fixed or defined by a probability distribution. We validated our tool by simulating data recorded from the first olfactory relay of an insect. Different key aspects make this tool suitable for testing the robustness and accuracy of neural signal processing algorithms (such as the detection, alignment, and classification of spikes). For instance, most of the parameters can be defined by a probabilistic distribution, then tens of simulations may be obtained from the same scenario. This is especially useful when validating the robustness of the processing algorithm. Moreover, the number of active cells and the exact firing activity of each one of them is perfectly known, which provides an easy way to test accuracy

Changes in plant metabolism and accumulation of fungal metabolites in response to Esca proper and apoplexy expression in the whole grapevine

Trunk diseases have become among the most important grapevine diseases worldwide. They are caused by fungal pathogens that attack the permanent woody structure of the vines and cause various symptoms in woody and annual organs. This study examined modifications of plant responses in green stem, cordon and trunk of grapevines expressing Esca proper (E) or apoplexy (A) event, which are the most frequent grapevine trunk disease symptoms observed in Europe. Transcript expression of a set of plant defense- and stress-related genes was monitored by quantitative RT-PCR while plant phytoalexins and fungal metabolites were quantified by HPLC-MS in order to characterize the interaction between the grapevine and trunk disease agents. Expression of genes encoding enzymes of the phenylpropanoid pathway and trans-resveratrol content were altered in the three organs of diseased plants, especially in the young tissues of A plants. PR proteins and the antioxidant system were severely modulated in A plants, which indicates a drastic stress effect. In the meantime, fungal polyketides 6-MSA, (R)-mellein and (3R,4R)-4-hydroxymellein, were accumulated in A plants that suggests their potential effect on plant metabolism during the appearance of foliar symptoms

Reproducing Botryosphaeria dieback foliar symptoms in a simple model system

Botryosphaeria dieback is a grapevine trunk disease with a worldwide distribution and associated with Diplodia seriata and Neofusicoccum parvum among several other Botryosphaeriaceae species. The aforementioned xylem-inhabiting fungi cause wood lesions, leaf and berry symptoms and eventually lead to the death of the plant. The aim of this work was to develop a simple model system to reproduce the foliar symptoms caused by D. seriata and N. parvum to better characterize fungal pathogenicity and determine the mechanisms involved in symptom development. Green stems of grafted grapevine cuttings cv. Aragonez were inoculated with three isolates of N. parvum and two isolates of D. seriata with different degrees of virulence and the experiment was repeated four times from 2011 to 2014. Three months after inoculation, the lesions associated with N. parvum were larger than those associated with D. seriata. Similarly, eight months after inoculation the percentage of plants showing foliar symptoms was greater in the N. parvum treatments than in the D. seriata treatments. During the emergence of foliar symptoms, plant stress-related responses were modulated in green stems and leaves, especially a down-regulation of superoxide dismutase (SOD) and fasciclin-like arabinogalactan protein (fascAGP) and an up-regulation of stilbene synthase (STS) with an accumulation of phenolics. In conclusion, the simple model system developed allowed a good characterization of isolate pathogenicity and correlation with foliar symptoms of Botryosphaeria dieback, namely spots on leaf margin and blade

Phytotoxic metabolites from Neofusicoccum parvum, a pathogen of Botryosphaeria dieback of grapevine

Liquid chromatography-diode array screening of the organic extract of the cultures of 13 isolates of the fungus Neofusicoccum parvum, the main causal agent of botryosphaeria dieback of grapevine, showed similar metabolites. One strain was selected for further chemical studies and led to the isolation and characterisation of 13 metabolites. Structures were elucidated through spectroscopic analyses, including one- and two-dimensional NMR and mass spectrometry, and through comparison to literature data. The isolated compounds belong to four different chemical families: five metabolites, namely, ( )-terremutin (1), (+)-terremutin hydrate (2), (+)-epi-sphaeropsidone (3) ( )-4-chloro-terremutin hydrate (4) and(+)-4- hydroxysuccinate-terremutin hydrate (5), belong to the family of dihydrotoluquinones; two metabolites, namely, (6S,7R) asperlin (6) and (6R,7S)-dia-asperlin (7), belong to the family of epoxylactones; four metabolites, namely, (R)-( )-mellein (8), (3R,4R)-4-hydroxymellein (9), (3R,4S)-4-hydroxymellein (10) (R)( )-3-hydroxymellein (11), belong to the family of dihydroisocoumarins; and two of the metabolites, namely, 6-methyl-salicylic acid (12) and 2-hydroxypropyl salicylic acid (13), belong to the family of hydroxybenzoic acids. We determined the phytotoxic activity of the isolated metabolites through a leaf disc assay and the expression of defence-related genes in Vitis vinifera cells cv. Chardonnay cultured with ( )-terremutin (1), the most abundant metabolite. Finally, analysis of the brown stripes of grapevine wood from plants showing botryosphaeria dieback symptoms revealed the presence of two of the isolated phytotoxinsinfo:eu-repo/semantics/publishedVersio

Low-dose hydrocortisone reduces norepinephrine duration in severe burn patients: a randomized clinical trial

INTRODUCTION: The aim of this study was to assess the effect of low-dose corticosteroid therapy in reducing shock duration after severe burn. METHODS: A placebo-controlled, double-blind, randomized clinical trial (RCT) was performed on two parallel groups in the burn intensive care unit (ICU). Patients were randomized to receive either low-dose corticosteroid therapy or placebo for seven days. A corticotropin test was performed at the time of randomization, before the administration of the treatment dose. Thirty-two severely burned patients with refractory shock (>0.5 μg/kg/min of norepinephrine) were prospectively included in the study. RESULTS: We included 12 patients in the hydrocortisone-treated group and 15 patients in the placebo group in the final analysis. Among these patients, 21 were nonresponders to the corticotropin test. Median norepinephrine treatment duration (primary objective) was significantly lower in the corticosteroid-treated versus the placebo group (57 hours versus 120 hours, P = 0.035). The number of patients without norepinephrine 72 hours after inclusion was significantly lower in the treated group (P = 0.003, log-rank test analysis). The total quantities of norepinephrine administered to patients were lower in the hydrocortisone-treated versus the placebo group (1,205 μg/kg (1,079 to 2,167) versus 1,971 μg/kg (1,535 to 3,893), P = 0.067). There was no difference in terms of ICU or hospital length of stay, sepsis incidence, cicatrization or mortality. CONCLUSIONS: In this placebo-controlled, randomized, double-blind clinical trial, we show for the first time that the administration of low-dose hydrocortisone in burn patients with severe shock reduces vasopressor administration. TRIAL REGISTRATION: Clinicaltrial.gov NCT00149123. Registered 6 September 2005. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13054-015-0740-0) contains supplementary material, which is available to authorized users