A self excitation and control system for wind tunnel dynamic stability measurements

The paper describes the design and development of a fast acting self-excitation and control system based on the principles of regenerative and negative feedback for phase resonance testing of aerodynamic models in wind tunnels. Simulation tests and analyses using a linearized model of the drive system are carried out, and results indicate that the system would function even if the system damping becomes neutral or negative. Experiments for dynamic stability measurements show that the control system meets all specifications and performs satisfactorily even in the presence of moderate amounts of turbulence in the air flow

Hummingbird: An Energy-Efficient GPS Receiver for Small Satellites

Global positioning system (GPS) is the most widely adopted localization technique for satellites in low earth orbits (LEOs). To enable many state-of-the-art applications on satellites, the exact position of the satellites is necessary. With the increasing demand for small satellites, the need for a low-power GPS for satellites is also increasing. However, building low-power GPS receivers for small satellites poses significant challenges, mainly due to the high speeds (similar to 7.8 km/s) of satellites and low available energy. While duty cycling the receiver is a possible solution, the high relative Doppler shift among the GPS satellites and the small satellite contributes to an increase in Time to First Fix (TTFF), which negatively impacts energy consumption. Further, if the satellite tumbles, the GPS receiver may not be able to receive signals properly from the GPS satellites, thus leading to an even longer TTFF. In the worst case, the situation may result in no GPS fix due to disorientation of the receiver antenna. In this work, we elucidate the design of a low-cost, low-power GPS receiver for small satellites. We also propose an energy optimization algorithm to improve the TTFF. With the extensive evaluation of our GPS receiver on an operational nanosatellite, we show that up to 96.16% of energy savings can be achieved using our algorithm without significantly compromising (similar to 10 m) the positioning accuracy

Argo data quality control based on climatological convex hulls

This report discusses a new method of identifying erroneous data in temperature and salinity (T/S) profiles measured by Argo profiling floats. The proposed method uses World Ocean Atlas 2009 (WOA09) climatology to classify good against bad data. An 'n' sided polygon (convex hull) with least area encompassing all the points is constructed based on the Jarvis March algorithm. The mean and standard deviation fields of temperature and salinity obtained from WOA09 corresponding to each standard depth are used for building these polygons. Subsequently Points In Polygon (PIP) principle which is implemented using ray casting algorithm is used to classify the T/S data as within or without acceptable bounds. It is observed that various types of anomalies in the Argo profile data viz., spikes, bias, sensor drifts etc can be identified using this method

Representations of Double Affine Lie algebras

We study representations of the double affine Lie algebra associated to a simple Lie algebra. We construct a family of indecomposable integrable representations and identify their irreducible quotients. We also give a condition for the indecomposable modules to be irreducible, this is analogous to a result in the representation theory of quantum affine algebras. Finally, in the last section of the paper, we show, by using the notion of fusion product, that our modules are generically reducible

Induction of ER stress in response to oxygen-glucose deprivation of cortical cultures involves the activation of the PERK and IRE-1 pathways and of caspase-12

Disturbance of calcium homeostasis and accumulation of misfolded proteins in the endoplasmic reticulum (ER) are considered contributory components of cell death after ischemia. However, the signal-transducing events that are activated by ER stress after cerebral ischemia are incompletely understood. In this study, we show that caspase-12 and the PERK and IRE pathways are activated following oxygen-glucose deprivation (OGD) of mixed cortical cultures or neonatal hypoxia–ischemia (HI). Activation of PERK led to a transient phosphorylation of eIF2α, an increase in ATF4 levels and the induction of gadd34 (a subunit of an eIF2α-directed phosphatase). Interestingly, the upregulation of ATF4 did not lead to an increase in the levels of CHOP. Additionally, IRE1 activation was mediated by the increase in the processed form of xbp1, which would be responsible for the observed expression of edem2 and the increased levels of the chaperones GRP78 and GRP94. We were also able to detect caspase-12 proteolysis after HI or OGD. Processing of procaspase-12 was mediated by NMDA receptor and calpain activation. Moreover, our data suggest that caspase-12 activation is independent of the unfolded protein response activated by ER stress

Treatment of cardiogenic shock with left ventricular assist device combined with cardiac resynchronization therapy: A case report

Cardiogenic shock has a poor prognosis with established treatment strategies. We report a 62 years old man with heart failure exacerbating into refractory cardiogenic shock successfully treated with the combination of a percutaneous left ventricular assist device (LVAD) and subacute cardiac resynchronization therapy (CRT) implantable cardioverter-defibrillator device (CRT-D)

Relationship between subcellular localisation of Foscan® and caspase activation in photosensitised MCF-7 cells

The present study investigates the relationship between the subcellular localisation of Foscan® and intrinsic apoptotic pathway post Foscan®-based photodynamic therapy (PDT). With this purpose, mammary carcinoma MCF-7 cells were incubated with Foscan® for 3 or 24 h and then subjected to equitoxic light doses. Fluorescence microscopy revealed very good Foscan® co-localization to endoplasmic reticulum (ER) and Golgi apparatus after 3 h incubation with MCF-7 cells. Progressive increase in incubation time shows leakage of Foscan® from Golgi apparatus. Twenty-four hours incubation yielded a fluence-dependent enhanced induction of the ER-resident glucose-regulated protein 78 (Bip/GRP78), along with a weak mitochondrial damage, thus underscoring the ER as the main site of photodamage after prolonged incubation. Analysis of events implicated in apoptotic pathway after 24 h incubation demonstrated photodamage to Bcl-2 protein in total cellular extract, but not in the mitochondrial fraction. We further determined an increase in caspases-7 and -6 activation, which was strongly related to the expression of GRP78. The above findings demonstrate that Foscan® localisation in ER improves the photoactivation of the caspase-7 apoptotic pathway, which is poorly related to mitochondrial damage