Abstract The phenomenon of revolution pitch was studied on AA 6061-T6 with a square pin tool for friction stir welding (FSW). The tool rotational speed and traverse speed were varied at four levels and selected in a manner so that the revolution pitch could comprise both lower and higher magnitude of variation when compared among them. An attempt was made to investigate the material flow from the macrostructure of both vertical (transverse to welding direction) and horizontal (parallel to the weld surface) cross-section. The study showed a significant amount of variation in terms of spindle torque, forces, material flow, and tensile properties. The increased material flow was noticed in the top surface of the weld from advancing to the retreating side at increased revolution pitch. Whereas an increased material flow was observed in the downward direction through the retreating side of the nugget. At increased revolution pitch a clear division in the onion ring was noticed towards the retreating side. The variation of torque, force and material flow showed a consistent trend for a higher change in revolution pitch. As the revolution pitch increased finer nugget grains were obtained causing increased tensile properties.

Abstract: The current investigation is a preliminary approach proposing the feasibility of a modified joint configuration namely double-butt-lap (DBL) in the field of friction stir welding (FSW). The main scope of adopting this kind of joint configuration is to essentially eliminate the irregularities in material flow and defects (root gap, kissing bond) that are observed while joining by using the commonly followed simple square butt joint configuration (SSB) technique. Two different geometries of the joint configuration are fabricated on 6 mm thick AA6061-T6 plates. FSW is carried out at a parametric combination of 1100 rpm, 75 mm/min and 1.5° tilt angle. The comparison of the macrographs of DBL with SSB reveals a quite distinct cross-sectional macrostructure of DBL from SSB in terms of material flow in the nugget zone (NZ). Sharp material flow lines without any macro defects are observed in the case of DBL 2. Mechanical test analysis reveals remarkable enhancement in the mechanical properties of some joint configuration of DBL over SSB. The current research work may act as a foundation for future research work in the utility of such configurations in the diverse field of FSW.

Sepse - um estado de infecção bacteriana sistêmica - frequentemente leva à falência múltipla de órgãos e associa-se a altos índices de mortalidade, apesar de progressos recentes no manejo de pacientes em unidades de terapia intensiva. Muitos dos efeitos maléficos associados à sepse são atribuídos a uma resposta inflamatória patologicamente ampliada que leva a recrutamento neutrofílico e ativação das moléculas de adesão do grupo das selectinas, durante as fases iniciais do processo . O óxido nítrico e sua diversas isoformas também foram implicados nas diversas manifestações vasculares da sepse como participantes diretos da toxicidade celular. Esta revisão descreve o papel das selectinas e do óxido nítrico em situações clínicas e experimentais de sepse, bem como os respectivos efeitos de processos terapêuticos de bloqueio.

Sepsis-a state of systemic bacterial infection-often leads to multiorgan failure and is associated with high mortality despite the recent advances achieved in intensive care treatment. Many of the ill effects of sepsis are attributed to an abnormally enhanced host inflammatory response that leads to neutrophil recruitment and activation involving selectins, a class of adhesion molecules, in the initial stages. Nitric oxide and its various isoforms have also been implicated in various vascular alterations and directly participate in the cellular toxicity in sepsis. This review briefly describes the role of selectins and nitric oxide in experimental and clinical sepsis as well as the therapeutic outcomes of blocking therapies.