Experimental characterization of friction coefficients at the tool-chip-workpiece interface in cutting: Evaluation of lubrication efficiency of mineral oil

Collaboration avec le LTDS/ENISEThe characterization of friction coefficients at the tool-chip-workpiece interface remains an issue. This paper presents a new experimental set-up able to simulate similar tribological phenomena as the ones occurring at the tool-chip-workpiece interface. Especially, this system aims to reach contact pressures up to 3 GPa and sliding velocities between 0 to 1000 m/min, and to obtain an open-tribosystem (continuous regeneration of the tool-workmaterial contact). This system has been applied to the characterization of the tool-chip-workpiece interface during the cutting of an AISI4142 treated steel with TiN coated tools. Two environments have been tested: dry cutting, lubrication with a basic mineral oil. The effect of the mineral oil has been investigated

Experimental characterization of friction coefficients at the tool-chip-workpiece interface in cutting: Evaluation of lubrication efficiency of mineral oil

Collaboration avec le LTDS/ENISEThe characterization of friction coefficients at the tool-chip-workpiece interface remains an issue. This paper presents a new experimental set-up able to simulate similar tribological phenomena as the ones occurring at the tool-chip-workpiece interface. Especially, this system aims to reach contact pressures up to 3 GPa and sliding velocities between 0 to 1000 m/min, and to obtain an open-tribosystem (continuous regeneration of the tool-workmaterial contact). This system has been applied to the characterization of the tool-chip-workpiece interface during the cutting of an AISI4142 treated steel with TiN coated tools. Two environments have been tested: dry cutting, lubrication with a basic mineral oil. The effect of the mineral oil has been investigated

Tidal influence on particulate organic carbon export fluxes

his study was supported through grant NE/G006415/1 of the UK’s Natural Environment Research Council (NERC) and grant 669947 of the European Research Council (ERC).As tall seamounts may be ‘stepping stones’ for dispersion and migration of deep open ocean fauna, an improved understanding of the productivity at and food supply to such systems needs to be formed. Here, the 234Th/238U approach for tracing settling particulate matter was applied to Senghor Seamount – a tall sub-marine mountain near the tropical Cape Verde archipelago – in order to elucidate the effects of topographically-influenced physical flow regimes on the export flux of particulate organic carbon (POC) from the near-surface (topmost ⩽ 100 m) into deeper waters. The comparison of a suitable reference site and the seamount sites revealed that POC export at the seamount sites was ∼2–4 times higher than at the reference site. For three out of five seamount sites, the calculated POC export fluxes are likely to be underestimates. If this is taken into account, it can be concluded that POC export fluxes increase while the passing waters are advected around and over the seamount, with the highest export fluxes occurring on the downstream side of the seamount. This supports the view that biogeochemical and biological effects of tall seamounts in surface-ocean waters might be strongest at some downstream distance from, rather than centred around, the seamount summit. Based on measured (vessel-mounted ADCP) and modelled (regional flow field: AVISO; internal tides at Senghor: MITgcm) flow dynamics, it is proposed that tidally generated internal waves result in a ‘screen’ of increased rates of energy dissipation that runs across the seamount and leads to a combination of two factors that caused the increased POC export above the seamount: (1) sudden increased upward transport of nutrients into the euphotic zone, driving brief pulses of primary production of new particulate matter, followed by the particles’ export into deeper waters; and (2) pulses of increased shear-driven aggregation of smaller, slower-settling into larger, faster-settling particles. This study shows that, under certain conditions, there can be an effect of a tall seamount on aspects of surface-ocean biogeochemistry, with tidal dynamics playing a prominent role. It is speculated that these effects can control the spatiotemporal distribution of magnitude and nutritional quality of the flux of food particles to the benthic and benthic-pelagic communities at and near tall seamounts.Publisher PDFPeer reviewe

Les objets en plomb découverts sur le site portuaire médiéval de Taillebourg – port d’Envaux

Des prospections subaquatiques menées dans la Charente, sur le site de Taillebourg – Port d’Envaux (17), ont révélé la présence de nombreux témoins d’activités liés au fleuve Charente, datés principalement des périodes mérovingienne et carolingienne. Parmi l’abondant mobilier découvert figure un lot d’objets en plomb.Ces plombs ont été trouvés dans un contexte de pratiques halieutiques. Les premières interprétations les définissent comme des lests d’engins de pêche. La découverte d’un tel corpus est déjà en soi un fait intéressant. En effet, la facilité de recyclage de ce matériau de plaide pas pour sa conservation. L’étude de ce matériel a porté à la fois sur la définition de leur typologie et une première interprétation de leur fonction. En plus des méthodes de classement habituellement utilisées, une approche expérimentale a été menée pour mieux appréhender les techniques de mise en forme utilisées. Des analyses de surface par fluorescence X ont pu être également réalisées. Enfin, le contexte chronologique plaçant cette collection au haut Moyen Âge et la découverte de ce matériel dans la zone d’influence de l’atelier monétaire de Melle nous ont conduit à poser la question de l’origine du plomb métal. Pour répondre à cette interrogation, une série d’analyses isotopique du plomb a été réalisée à partir de la série des plombs naviformes.Subaquaeous surveys carried out in the Charente, on the site Taillebourg – Port Envaux (dept. Charente-Maritime, France) revealed the presence of many evidences in activities related to river Charente, dating mainly from Merovingian and Carolingian periods. A lot of lead objects is found among the abundant furniture.These leads were found in a context of fishing practices. The first interpretations defined as fishing gear. The discovery of such a corpus is itself an interesting fact. Indeed, the tendency of recycling this material does not plead for its preservation. The study of these sinkers has focused both on the definition of their type and initial interpretation of their function. In addition to classified methods usually used, an experimental approach was undertaken to better understand the techniques of production. Surface analysis by X-ray fluorescence were also performed. Finally, the historical context, placing the collection in the High Middle Ages and the discovery of this material in the zone of influence of the mint of Melle led us to the question of the origin of lead metal. To answer this question, a series of lead isotope analysis was carried out from the series of boat-form leads

Etude tribologique d'huiles de micro pulvérisation pour l'usinage d'alliages aluminium

The possibility to reduce the amount of cutting fluids from machining processes is actively studied by the industrials and researchers. Minimum Quantity Lubrication (MQL) is a solution towards cutting fluids reduction. This article investigates the consequences on friction coefficient induced by the use of MQL for two prototype oils. A tribometer is used for both oils in order to simulate experimentally the tribological conditions encountered during machining. Results show that even though the oils have the same lubricating performance in full lubrication, their physical properties are responsible for generating different volumes of mist (but similar droplet size). As the cutting speed increases a lower amount of oil is deposited on the rough surfaces. Depending on the MQL operating conditions and sliding velocities it is plausible to reach starvation by leaving the real rough contact partly dry. A model computing a starvation percentage by filling an estimated oil amount in a deformed topography correlates with the experimental results

Describing Nitrogen dilution curve and physiological behavior of Thinopyrum intermedium

editorial reviewedThe perennial grain crop, Thinopyrum intermedium ((Host) Barkworth & D.R. Dewey) can provide various ecosystem services. Among them we can mention preservation services such as the reduction of nitrate leaching, the improving of soil food webs or the carbon pools and sequestration as well as a dual production of grains and forage. Currently, Th. intermedium is characterized by a recent selection history and its resource allocation to grains is low and variable. At the same time, its perenniality leads to large resource allocation to the belowground organs composed of short rhizomes and a deep root system to ensure crop continuity. Consequently, the development of intermediate wheatgrass in cropping system is still impeded by grain yielding capacity and stability, and knowledge gaps about best management practices in fields. To improve yields and crop management, a good description of its physiological behavior and a better understanding of its growing habits are yet required. Through the determination of its critical nitrogen dilution curve, we aimed to characterize its nitrogen (N) requirements and to establish diagnoses of the N status of the crop in different climatic and agronomic conditions which will allow further to inform fertilization practices to optimize crop growth and yields in fields. A field experiment was conducted in Gembloux AgroBio-Tech, Belgium, for three growing seasons with nitrogen fertilization schemes differing in frequency and amount of N. Globally, N fertilization has a positive impact on the dry matter of leaves, stems and ears (P<0,05). The maximization of the aboveground biomass and N uptake was obtained with a fertilization comprised between 100 and 150kg N/ha over the entire growing year. In addition, fall fertilization could be integrated into the N management strategy of the multi-annual Th. intermedium crop. Indeed, a fall nitrogen application combined with an early spring application resulted in relatively similar aboveground production levels of the crop as a full early spring nitrogen application. The total aboveground biomass tended to increase along the crop cycle. At the grain harvest, it ranged from 7,0 to 16,4T DM/ha for a 100kg N/ha fertilization, depending on the growing season. The N content tended to decrease with the evolution of growing stages, as observed with the proposed critical nitrogen dilution curve. It also indicates a reduced level of N nutrition that can be linked to several life traits of the crop. Actually, we observed a strong decrease in the leaves/stems ratio after the beginning of the growing season. In addition, the study of Sprunger et al. (2018) reported that the nitrogen use efficiency of Th. intermedium is high, considering the N content of the whole plant, and the plant seems able to assimilate large quantities of nitrogen and even more than what has been applied. Its deep and dense root system allows an extensive exploration of the soil profile which can further increase the nitrogen use efficiency and reduce nitrate leaching. This combined with the observed decrease of the N amount of the aboveground biomass in the second phase of growth is discussed in relation with the long-term survival strategy of the crop resulting in substantial investments in perennial belowground structures coupled with reduced resource allocations to seeds. Indeed, storage in rhizomes and roots can be part of a resource-conservative strategy of Th. intermedium that could store a part of the N absorbed in its belowground organs, which reduces the amount of N within the aboveground biomass. Sakiroglu et al. (2020) found out that the plant is effectively storing non-structural carbohydrates and proteins in its roots and rhizomes

Bedarfsgerechte ökologische Fütterung von Geflügel-Schwerpunkt: Neue Quelle für Riboflavin (Verbundvorhaben)

Gegenstand war die Entwicklung eines Verfahrens zur Produktion eines Riboflavin-reichen Einzelfuttermittels aus ökologischer Erzeugung, das den ökologischen Landbau von der Supplementierung mit konventionellen Produkten unabhängig macht. Das Produkt wurde durch Fermentation von Bio-Rohstoffen mit dem Hefe-Pilz Ashbya gossypii hergestellt. Während der Fermentation bildet A. gossypii neben einer proteinreichen Biomasse auch Vitamin B2. Das Material aus der Fermentation konnte zu einer bio-zertifizierten, verkaufsfähigen Ware, die in flüssiger und pulverförmiger Form angeboten wird, entwickelt werden. Das Produkt EcoVit R wurde in flüssiger Form als Fermentations-Suspension an Masthühnern und Masthühner-Elterntieren getestet. Es zeigte sich, dass das Produkt bei gleicher Dosierungshöhe als Alternative zu konventionell erzeugtem Riboflavin eingesetzt werden kann. Bei den Masthühner-Elterntieren zeigten sich beim Vergleich der Fermentations-Suspension mit konventionell erzeugtem Riboflavin keine Unterschiede hinsichtlich Leistungs- und Brutparameter. In weiteren Versuchen wurde das Trockenprodukt aus der A. gossypii-Fermentation bei Masthühnern, Mastputen und Legehennen untersucht. Sowohl bei den Masthühnern als auch bei den Mastputen reichte die Fütterung ohne Riboflavin-Supplementierung und mit ausschließlich natürlichen Riboflavin-Gehalten der Futterkomponenten nicht aus, um den physiologischen Bedarf der Tiere zu decken. Stark erhöhte Riboflavin-Supplementierungen hingegen führten nicht zu verbesserten Leistungen oder Vorteilen hinsichtlich Tierwohlindikatoren. Bei Legehennen konnten keine leistungssteigernden Effekte durch eine zusätzliche Vitamin B2-Zulage in Form des Fermentations-Trockenproduktes nachgewiesen werden. Zusammenfassend wurde die Notwendigkeit der Riboflavin-Supplementierung vor allem in den ersten Lebenswochen des Mastgeflügels gezeigt. Die entwickelten Fermentations-Produkte zeigten ihre Wirksamkeit, den Riboflavin-Bedarf beim Geflügel abzudecken

Selenium biochemistry and its role for human health

Despite its very low level in humans, selenium plays an important and unique role among the (semi)metal trace essential elements because it is the only one for which incorporation into proteins is genetically encoded, as the constitutive part of the 21st amino acid, selenocysteine. Twenty-five selenoproteins have been identified so far in the human proteome. The biological functions of some of them are still unknown, whereas for others there is evidence for a role in antioxidant defence, redox state regulation and a wide variety of specific metabolic pathways. In relation to these functions, the selenoproteins emerged in recent years as possible biomarkers of several diseases such as diabetes and several forms of cancer. Comprehension of the selenium biochemical pathways under normal physiological conditions is therefore an important requisite to elucidate its preventing/therapeutic effect for human diseases. This review summarizes the most recent findings on the biochemistry of active selenium species in humans, and addresses the latest evidence on the link between selenium intake, selenoproteins functionality and beneficial health effects. Primary emphasis is given to the interpretation of biochemical mechanisms rather than epidemiological/observational data. In this context, the review includes the following sections: (1) brief introduction; (2) general nutritional aspects of selenium; (3) global view of selenium metabolic routes; (4) detailed characterization of all human selenoproteins; (5) detailed discussion of the relation between selenoproteins and a variety of human diseases