Monitoring of fatigue crack growth in composite adhesively bonded joints using Fiber Bragg Gratings

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Comet Machholz (C/2004 Q2): morphological structures in the inner coma and rotation parameters

Extensive observations of comet C/2004 Q2 (Machholz) were carried out between August 2004 and May 2005. The images obtained were used to investigate the comet's inner coma features at resolutions between 350 and 1500 km/pixel. A photometric analysis of the dust outflowing from the comet's nucleus and the study of the motion of the morphological structures in the inner coma indicated that the rotation period of the nucleus was most likely around 0.74 days. A thorough investigation of the inner coma morphology allowed us to observe two main active sources on the comet's nucleus, at a latitude of +85{\deg} \pm 5{\deg} and +45{\deg} \pm 5{\deg}, respectively. Further sources have been observed, but their activity ran out quite rapidly over time; the most relevant was at latcom. = 25{\deg} \pm 5{\deg}. Graphic simulations of the geometrical conditions of observation of the inner coma were compared with the images and used to determine a pole orientation at RA=95{\deg} \pm 5{\deg}, Dec=+35{\deg} \pm 5{\deg}. The comet's spin axis was lying nearly on the plane of the sky during the first decade of December 2004.Comment: 29 pages, 8 figures, 3 table

FimL Regulates cAMP Synthesis in Pseudomonas aeruginosa

Pseudomonas aeruginosa, a ubiquitous bacteria found in diverse ecological niches, is an important cause of acute infections in immunocompromised individuals and chronic infections in patients with Cystic Fibrosis. One signaling molecule required for the coordinate regulation of virulence factors associated with acute infections is 3′, 5′-cyclic adenosine monophosphate, (cAMP), which binds to and activates a catabolite repressor homolog, Vfr. Vfr controls the transcription of many virulence factors, including those associated with Type IV pili (TFP), the Type III secretion system (T3SS), the Type II secretion system, flagellar-mediated motility, and quorum sensing systems. We previously identified FimL, a protein with histidine phosphotransfer-like domains, as a regulator of Vfr-dependent processes, including TFP-dependent motility and T3SS function. In this study, we carried out genetic and physiologic studies to further define the mechanism of action of FimL. Through a genetic screen designed to identify suppressors of FimL, we found a putative cAMP-specific phosphodiesterase (CpdA), suggesting that FimL regulates cAMP levels. Inactivation of CpdA increases cAMP levels and restores TFP-dependent motility and T3SS function to fimL mutants, consistent with in vivo phosphodiesterase activity. By constructing combinations of double and triple mutants in the two adenylate cyclase genes (cyaA and cyaB), fimL, and cpdA, we show that ΔfimL mutants resemble ΔcyaB mutants in TM defects, decreased T3SS transcription, and decreased cAMP levels. Similar to some of the virulence factors that they regulate, we demonstrate that CyaB and FimL are polarly localized. These results reveal new complexities in the regulation of diverse virulence pathways associated with acute P. aeruginosa infections

Mechanical calibration and alignment of an aerial photogrammetric film scanner based on a 2d array camera

Mechanical calibration and alignment are fundamental steps in the development of any new aerial photogrammetric scanner. One aim of a film scanner in the digital era is to digitise the accumulated historic archives of images belonging to photogrammetric institutes. The present analysis is centred on a scanner with a translating 2D array camera. Two phases of equal importance can be outlined: the first phase is the alignment of all the mechanical parts inside the scanner, and the second is mechanical calibration, when the systematic effects in the camera positioning are measured and compensated. Among the design requirements of this scanner was to avoid the need for geometrical modification of the scanned images: they should be acquired in the correct position and not require a posteriori correction with a software routine. The proposed solutions lead to a final result of a metrologically satisfactory scanner with a geometric uncertainty of 2 lm or less throughout the frame (250mm· 250 mm), a value definitely smaller than the pixel size (10 lm/pixel

Vibration control of smart structures using an array of Fiber Bragg Grating sensors

Optical strain gauges, such as Fiber Bragg Grating (FBG) sensors, are widely used to monitor the health of structures and their state of deformation. This paper proposes exploiting the measurements of these sensors as feedback for active vibration control applications. The advantages of this solution are the possibility of monitoring a large number of sensors (to approximate distributed measurements) and of embedding them in carbon fiber structures with negligible load effects. Experimental tests confirm that smart structures with embedded FBG sensors can be profitably designed to suppress vibrations