Machining of titanium metal matrix composites : progress overview

ABSTRACT: The TiC particles in titanium metal matrix composites (TiMMCs) make them difficult to machine. As a specific MMC, it is legitimate to wonder if the cutting mechanisms of TiMMCs are the same as or similar to those of MMCs. For this purpose, the tool wear mechanisms for turning, milling, and grinding are reviewed in this paper and compared with those for other MMCs. In addition, the chip formation and morphology, the material removal mechanism and surface quality are discussed for the different machining processes and examined thoroughly. Comparisons of the machining mechanisms between the TiMMCs and MMCs indicate that the findings for other MMCs should not be taken for granted for TiMMCs for the machining processes reviewed. The increase in cutting speed leads to a decrease in roughness value during grinding and an increase of the tool life during turning. Unconventional machining such as laser-assisted turning is effective to increase tool life. Under certain conditions, a “wear shield” was observed during the early stages of tool wear during turning, thereby increasing tool life considerably. The studies carried out on milling showed that the cutting parameters affecting surface roughness and tool wear are dependent on the tool material. The high temperatures and high shears that occur during machining lead to microstructural changes in the workpiece during grinding, and in the chips during turning. The adiabatic shear band (ASB) of the chips is the seat of the sub-grains’ formation. Finally, the cutting speed and lubrication influenced dust emission during turning but more studies are needed to validate this finding. For the milling or grinding, there are major areas to be considered for thoroughly understanding the machining behavior of TiMMCs (tool wear mechanisms, chip formation, dust emission, etc.)

Fake News i la política catalana

La campanya presidencial de Donald Trump als Estats Units va posicionar les fake news en l'àmbit comunicatiu mundial. Aquest reportatge analitzarà la situació d'aquestes notícies falses dins del territori català i la influència en la celebració del referèndum de l'1 d'octubre del 2017 i les eleccions catalanes del 21 de desembre del mateix any. Per poder realitzar el reportatge s'ha entrevistat els responsables de comunicació de diferents partits polítics amb representació al Parlament de Catalunya, els caps d'informatius dels principals mitjans de comunicació de Catalunya, com també periodistes i fact-checkers.La campaña presidencial de Donald Trump en los Estados Unidos posicionó las fake news en el ámbito comunicativo mundial. Este reportaje analizará la situación de estas noticias falsas en el territorio catalán y la influencia en la celebración del referéndum del 1 de octubre y las elecciones catalanas del 21 de diciembre del mismo año. Para realizar el reportaje se ha entrevistado a responsables de comunicación de distintos partidos políticos con representación en el Parlamento de Cataluña, a responsables de informativos de los principales medios de comunicación de Cataluña y también a periodistas y fact-checkers.The concept: fake news appeared first during Donald Trump's presidency campaign and placed the term in the jornalistic world. This longform piece will analyze the situation these kind of news face in the Catalan territory considering the celebration of the 2017's 1st of October referendum and the Catalan elections held that same year. In order to write the piece we have interviewed the communication's team leader of different political parties at the Catalan Parliament and some heads of news programs from the main media outlets in Catalonia, as well as journalists and fact-checkers

The Bacterial Defensin Resistance Protein MprF Consists of Separable Domains for Lipid Lysinylation and Antimicrobial Peptide Repulsion

Many bacterial pathogens achieve resistance to defensin-like cationic antimicrobial peptides (CAMPs) by the multiple peptide resistance factor (MprF) protein. MprF plays a crucial role in Staphylococcus aureus virulence and it is involved in resistance to the CAMP-like antibiotic daptomycin. MprF is a large membrane protein that modifies the anionic phospholipid phosphatidylglycerol with l-lysine, thereby diminishing the bacterial affinity for CAMPs. Its widespread occurrence recommends MprF as a target for novel antimicrobials, although the mode of action of MprF has remained incompletely understood. We demonstrate that the hydrophilic C-terminal domain and six of the fourteen proposed trans-membrane segments of MprF are sufficient for full-level lysyl-phosphatidylglycerol (Lys-PG) production and that several conserved amino acid positions in MprF are indispensable for Lys-PG production. Notably, Lys-PG production did not lead to efficient CAMP resistance and most of the Lys-PG remained in the inner leaflet of the cytoplasmic membrane when the large N-terminal hydrophobic domain of MprF was absent, indicating a crucial role of this protein part. The N-terminal domain alone did not confer CAMP resistance or repulsion of the cationic test protein cytochrome c. However, when the N-terminal domain was coexpressed with the Lys-PG synthase domain either in one protein or as two separate proteins, full-level CAMP resistance was achieved. Moreover, only coexpression of the two domains led to efficient Lys-PG translocation to the outer leaflet of the membrane and to full-level cytochrome c repulsion, indicating that the N-terminal domain facilitates the flipping of Lys-PG. Thus, MprF represents a new class of lipid-biosynthetic enzymes with two separable functional domains that synthesize Lys-PG and facilitate Lys-PG translocation. Our study unravels crucial details on the molecular basis of an important bacterial immune evasion mechanism and it may help to employ MprF as a target for new anti-virulence drugs

A dual function TAR Decoy serves as an anti-HIV siRNA delivery vehicle

The TAR RNA of HIV was engineered as an siRNA delivery vehicle to develop a combinatorial therapeutic approach. The TAR backbone was found to be a versatile backbone for expressing siRNAs. Upon expression in human cells, pronounced and specific inhibition of reporter gene expression was observed with TARmiR. The resulting TARmiR construct retained its ability to bind Tat and mediate RNAi. TARmiR was able to inhibit HIV gene expression as a TAR decoy and by RNA interference when challenged with infectious proviral DNA. The implications of this dual function therapeutic would be discussed

Targeting virulence not viability in the search for future antibacterials

New antibacterials need new approaches to overcome the problem of rapid antibiotic resistance. Here we review the development of potential new antibacterial drugs that do not kill bacteria or inhibit their growth, but combat disease instead by targeting bacterial virulence

Capsaicin Protects Mice from Community-Associated Methicillin-Resistant Staphylococcus aureus Pneumonia

BACKGROUND: α-toxin is one of the major virulence factors secreted by most Staphylococcus aureus strains, which played a central role in the pathogenesis of S. aureus pneumonia. The aim of this study was to investigate the impact of capsaicin on the production of α-toxin by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain USA 300 and to further assess its performance in the treatment of CA-MRSA pneumonia in a mouse model. METHODOLOGY/PRINCIPAL FINDINGS: The in vitro effects of capsaicin on α-toxin production by S. aureus USA 300 were determined using hemolysis, western blot, and real-time RT-PCR assays. The influence of capsaicin on the α-toxin-mediated injury of human alveolar epithelial cells was determined using viability and cytotoxicity assays. Mice were infected intranasally with S. aureus USA300; the in vivo protective effects of capsaicin against S. aureus pneumonia were assessed by monitoring the mortality, histopathological changes and cytokine levels. Low concentrations of capsaicin substantially decreased the production of α-toxin by S. aureus USA 300 without affecting the bacterial viability. The addition of capsaicin prevented α-toxin-mediated human alveolar cell (A549) injury in co-culture with S. aureus. Furthermore, the in vivo experiments indicated that capsaicin protected mice from CA-MRSA pneumonia caused by strain USA 300. CONCLUSIONS/SIGNIFICANCE: Capsaicin inhibits the production of α-toxin by CA-MRSA strain USA 300 in vitro and protects mice from CA-MRSA pneumonia in vivo. However, the results need further confirmation with other CA-MRSA lineages. This study supports the views of anti-virulence as a new antibacterial approach for chemotherapy

Bile Acid-Induced Virulence Gene Expression of Vibrio parahaemolyticus Reveals a Novel Therapeutic Potential for Bile Acid Sequestrants

Vibrio parahaemolyticus, a bacterial pathogen, causes human gastroenteritis. A type III secretion system (T3SS2) encoded in pathogenicity island (Vp-PAI) is the main contributor to enterotoxicity and expression of Vp-PAI encoded genes is regulated by two transcriptional regulators, VtrA and VtrB. However, a host-derived inducer for the Vp-PAI genes has not been identified. Here, we demonstrate that bile induces production of T3SS2-related proteins under osmotic conditions equivalent to those in the intestinal lumen. We also show that bile induces vtrA-mediated vtrB transcription. Transcriptome analysis of bile-responsive genes revealed that bile strongly induces expression of Vp-PAI genes in a vtrA-dependent manner. The inducing activity of bile was diminished by treatment with bile acid sequestrant cholestyramine. Finally, we demonstrate an in vivo protective effect of cholestyramine on enterotoxicity and show that similar protection is observed in infection with a different type of V. parahaemolyticus or with non-O1/non-O139 V. cholerae strains of vibrios carrying the same kind of T3SS. In summary, these results provide an insight into how bacteria, through the ingenious action of Vp-PAI genes, can take advantage of an otherwise hostile host environment. The results also reveal a new therapeutic potential for widely used bile acid sequestrants in enteric bacterial infections

Le rôle du contrôle dans l'acceptabilité a priori d'une voiture automatisée

International audienceL’objectif de l’étude est de déterminer si le degré d’automatisation d’une voiture influence son acceptabilité a priori. Les participants visionnaient une vidéo présentant une voiture équipée d’un dispositif dont le degré d’automatisation variait, puis répondaient à des questions relatives à l’intention d’usage du dispositif et à ses déterminants selon le Technology Acceptance Model 3 (Venkatesh & Bala, 2008). Le contrôle perçu et l’intention d’usage diminuent avec le degré d’automatisation alors que l’anxiété perçue augmente. Par ailleurs, l’auto-efficacité perçue et l’intention d’usage sont négativement corrélées avec l’anxiété perçue et positivement corrélées avec le contrôle perçu, lui-même négativement corrélé avec l'anxiété perçue

Fabienne Maillard, Gilles Moreau (dir.), Le bac pro. Un baccalauréat comme les autres ?

Cet ouvrage collectif, issu d’un colloque organisé par le Centre interuniversitaire de recherche sur l’éducation de Lille, est consacré à « un diplôme très mal connu » (p. 18) : le baccalauréat professionnel (bac pro). Créé en 1985, ce diplôme de niveau 4 se prépare aujourd’hui en trois ans, le plus souvent par voie scolaire. Instrument majeur de la « démocratisation ségrégative » impulsée au début des années 1980, le deuxième baccalauréat de France en termes d’effectifs demeure un « étrange ..