Heterogeneous butt welding of copper and AISI type 304L stainless steel was carried out using the electron beam process. Examination by scanning and transmission electron microscopy has indicated the ...possibility of obtaining joints free of cracks and porosity. Energy dispersive microanalysis of the weld bead cross-section has demonstrated the presence of non-equilibrium phases. The results show that the binary Cu-Fe equilibrium diagram is unable to predict the weld microstructure even at the moderate cooling and solidification rates expected under the present welding conditions. The feasibility of the Cu-304L electron beam welding process is therefore hindered by the problem of microstructural stability of the joint because of possible phase transitions during the service life of welded components.
The low frequency facility, a Virgo R&D experiment, is composed by a Fabry–Perot cavity attached and controlled by the Virgo suspension; the goal is to measure the thermal noise of the apparatus ...above 10 Hz, with a displacement sensitivity as high as 10
−18 m
/
Hz
. Since September 2001 the apparatus, located inside the INFN-Pisa experimental area, has been completely built and put into operation. Vacuum facilities and the control loops have been set up. Transfer functions, necessary to control the cavity, absolute test mass displacement and the first demonstration of the cavity locking are reported.
Mo alloying has been carried out on a Fe–Cr alloy by electron beam irradiation. It is shown that a Mo surface enrichment can be obtained in the range 2–8 at %. Scanning and transmission electron ...microscopy, X ray microanalysis and electron energy loss spectroscopy have been used to investigate the microstructures obtained after irradiation. Mo–Cr carbide and intermetallic X phase have been identified after alloying. The intermetallic phase is preferentially formed when the Mo content increases. It is concluded from electrochemical studies and potentiostatic attacks that the active and transpassive dissolution rates are closely related to the Cr content in the ferritic phase. This work must be also regarded as a first step towards the surface preparation of 316 S. S. by Mo incorporation to 304 S. S.
A new type of self-supporting platform for railway vehicles to be produced using innovative CO
2
laser welding technology was studied.
Optimum structures, using simulation with the finite element ...method, were investigated in search of an alternative structure to the conventional solution of aluminium alloy extrusions but which is equivalent in terms of static behaviour and stability.
An appropriate and focused study was made using the relevant research, as well as extensive mechanical, metallurgical and structural tests to identify optimum parameters of the CO
2
laser welding process for lap welding of AISI 304 stainless steel.
Five different structural solutions were pre-selected to produce the various testpieces of structural components, with dimensions of 300 × 700 mm. One of these was produced by laser welding, as a preliminary prototype, to be subjected to successive mechanical tests, still in progress.
Also in progress is the construction of other testpieces with different geometries. Finally, some of the more significant potential applications of this type of structural component are reported.
A new type of self-supporting platform for railway vehicles to be produced using innovative CO sub 2 laser welding technology was studied. Optimum structures, using simulation with the finite element ...method, were investigated in search of an alternative structure to the conventional solution of aluminium alloy extrusions but which is equivalent in terms of static behavior and stability. An appropriate and focused study was made using the relevant research, and extensive mechanical, metallurgical and structural tests to identify optimum parameters of the CO sub 2 laser welding process for lap welding of AISI 304 stainless steel. Five different structural solutions were pre-selected to produce the various testpieces of structural components, with dimensions of 300x700 mm. One of these was produced by laser welding, as a preliminary prototype, to be subjected to successive mechanical tests, still in progress.
Deregulation of intestinal immune responses seems to have a principal function in the pathogenesis of inflammatory bowel disease. The gut epithelium is critically involved in the maintenance of ...intestinal immune homeostasis-acting as a physical barrier separating luminal bacteria and immune cells, and also expressing antimicrobial peptides. However, the molecular mechanisms that control this function of gut epithelial cells are poorly understood. Here we show that the transcription factor NF- B, a master regulator of pro-inflammatory responses, functions in gut epithelial cells to control epithelial integrity and the interaction between the mucosal immune system and gut microflora. Intestinal epithelial-cell-specific inhibition of NF- B through conditional ablation of NEMO (also called I B kinase- (IKK )) or both IKK1 (IKK ) and IKK2 (IKK )-IKK subunits essential for NF- B activation-spontaneously caused severe chronic intestinal inflammation in mice. NF- B deficiency led to apoptosis of colonic epithelial cells, impaired expression of antimicrobial peptides and translocation of bacteria into the mucosa. Concurrently, this epithelial defect triggered a chronic inflammatory response in the colon, initially dominated by innate immune cells but later also involving T lymphocytes. Deficiency of the gene encoding the adaptor protein MyD88 prevented the development of intestinal inflammation, demonstrating that Toll-like receptor activation by intestinal bacteria is essential for disease pathogenesis in this mouse model. Furthermore, NEMO deficiency sensitized epithelial cells to tumour-necrosis factor (TNF)-induced apoptosis, whereas TNF receptor-1 inactivation inhibited intestinal inflammation, demonstrating that TNF receptor-1 signalling is crucial for disease induction. These findings demonstrate that a primary NF- B signalling defect in intestinal epithelial cells disrupts immune homeostasis in the gastrointestinal tract, causing an inflammatory-bowel-disease-like phenotype. Our results identify NF- B signalling in the gut epithelium as a critical regulator of epithelial integrity and intestinal immune homeostasis, and have important implications for understanding the mechanisms controlling the pathogenesis of human inflammatory bowel disease.
In insects, odorant‐binding proteins (OBPs) connect the peripheral sensory system to receptors of olfactory organs. Medfly Ceratitis capitata CcapObp22 shows 37% identity and close phylogenetic ...affinities with Drosophila melanogaster OBP69a/pheromone‐binding protein related protein 1. The CcapObp22 gene is transcribed in the antennae and maxillary palps, suggesting an active role in olfaction. Here, we recombinantly produced CcapObp22, obtaining a 13.5 kDa protein capable of binding multiple strongly hydrophobic terpene compounds, including medfly male pheromone components. The highest binding affinity half maximal effective concentration (EC50) = 0.48 µM was to (E,E)‐α‐farnesene, one of the most abundant compounds in the male pheromone blend. This odorant was used in cocrystallization experiments, yielding the structure of CcapOBP22. The monomeric structure shows the typical OBP folding, constituted by six α‐helical elements interconnected by three disulphide bridges. A C‐terminal seventh α‐helix constitutes the wall of a deep, L‐shaped hydrophobic cavity. Analysis of the electron density in this cavity suggested trapping of farnesene in the crystal structure, although with partial occupancy. Superposition of the CcapOBP22 structure with related seven‐helical OBPs highlights striking similarity in the organization of the C‐terminal segment of these proteins. Collectively, our molecular and physiological data on medfly CcapOBP22 suggest its involvement in intersex olfactory communication.
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