1,225 research outputs found
Apparatus for sensor failure detection and correction in a gas turbine engine control system
A gas turbine engine control system maintains a selected level of engine performance despite the failure or abnormal operation of one or more engine parameter sensors. The control system employs a continuously updated engine model which simulates engine performance and generates signals representing real time estimates of the engine parameter sensor signals. The estimate signals are transmitted to a control computational unit which utilizes them in lieu of the actual engine parameter sensor signals to control the operation of the engine. The estimate signals are also compared with the corresponding actual engine parameter sensor signals and the resulting difference signals are utilized to update the engine model. If a particular difference signal exceeds specific tolerance limits, the difference signal is inhibited from updating the model and a sensor failure indication is provided to the engine operator
Membrane traffic in the secretory pathway: The life cycle of a transport vesicle
Abstract.: Vesicular transport is the basic communication mechanism between different compartments in a cell and with the environment. In this review I discuss the principles of vesicle generation and consumption with particular emphasis on the different types of coat proteins and the timing of the shedding of the coat proteins from transport containers. In recent years it has become clear that there are more coat complexes than the classical COPI, COPII and clathrin coats. These additional coats may generate vesicles that transport cargo in a temporally and/or spatially controlled manner. Work over the last years suggests that GTP hydrolysis occurs early during vesicle biogenesis, destabilizing the coat perhaps before fission of the vesicle from the donor membrane occurs. Recent findings imply, however, that tethers at the receiving compartment specifically detect the coat on vesicle. (Part of a Multi-author Review
Dissection of GTPase activating proteins reveals functional asymmetry in the COPI coat of budding yeast.
The Arf GTPase controls formation of the COPI vesicle coat. Recent structural models of COPI revealed the positioning of two Arf1 molecules in contrasting molecular environments. Each of these pockets for Arf1 is expected to also accommodate an Arf GTPase-activating protein (ArfGAP). Structural evidence and protein interactions observed between isolated domains indirectly suggests that each niche may preferentially recruit one of the two ArfGAPs known to affect COPI, Gcs1/ArfGAP1 and Glo3/ArfGAP2/3, although only partial structures are available. The functional role of the unique non-catalytic domain of either ArfGAP has not been integrated into the current COPI structural model. Here, we delineate key differences in the consequences of triggering GTP hydrolysis via the activity of one versus the other ArfGAP. We demonstrate that Glo3/ArfGAP2/3 specifically triggers Arf1 GTP hydrolysis impinging on the stability of the COPI coat. We show that the yeast homologue of AMP kinase, Snf1, phosphorylates the region of Glo3 that is critical for this effect and thereby regulates its function in the COPI-vesicle cycle. Our results revise the model of ArfGAP function in the molecular context of COPI
Object Tracking Using Local Binary Descriptors
Visual tracking has become an increasingly important topic of research in the
field of Computer Vision (CV). There are currently many tracking methods based on the
Detect-then-Track paradigm. This type of approach may allow for a system to track a
random object with just one initialization phase, but may often rely on constructing
models to follow the object. Another limitation of these methods is that they are
computationally and memory intensive, which hinders their application to resource
constrained platforms such as mobile devices. Under these conditions, the
implementation of Augmented Reality (AR) or complex multi-part systems is not
possible.
In this thesis, we explore a variety of interest point descriptors for generic object
tracking. The SIFT descriptor is considered a benchmark and will be compared with
binary descriptors such as BRIEF, ORB, BRISK, and FREAK. The accuracy of these
descriptors is benchmarked against the ground truth of the object\u27s location. We use
dictionaries of descriptors to track regions with small error under variations due to
occlusions, illumination changes, scaling, and rotation. This is accomplished by using
Dense-to-Sparse Search Pattern, Locality Constraints, and Scale Adaptation. A
benchmarking system is created to test the descriptors\u27 accuracy, speed, robustness, and
distinctness. This data offers a comparison of the tracking system to current state of the
art systems such as Multiple Instance Learning Tracker (MILTrack), Tracker Learned
Detection (TLD), and Continuously Adaptive MeanShift (CAMSHIFT)
The variable stellar wind of Rigel probed at high spatial and spectral resolution
We present a spatially resolved, high-spectral resolution (R=12000) K-band
temporal monitoring of Rigel using AMBER at the VLTI. Rigel was observed in the
Bracket Gamma line and its nearby continuum in 2006-2007, and 2009-2010. These
unprecedented observations were complemented by contemporaneous optical
high-resolution spectroscopy. We analyse the near-IR spectra and visibilities
with the 1D non-LTE radiative-transfer code CMFGEN. The differential and
closure phase signal exhibit asymmetries that are interpreted as perturbations
of the wind. A systematic visibility decrease is observed across the Bracket
Gamma. During the 2006-2007 period the Bracket Gamma and likely the continuum
forming regions were larger than in the 2009-2010 epoch. Using CMFGEN, we infer
a mass-loss rate change of about 20% between the two epochs. We further find
time variations in the differential visibilities and phases. The 2006-2007
period is characterized by noticeable variations of the differential
visibilities in Doppler position and width and by weak variations in
differential and closure phase. The 2009-2010 period is much more quiet with
virtually no detectable variations in the dispersed visibilities but a strong
S-shape signal is observed in differential phase coinciding with a strong
ejection event discernible in the optical spectra. The differential phase
signal that is sometimes detected is reminiscent of the signal computed from
hydrodynamical models of corotating interaction regions. For some epochs the
temporal evolution of the signal suggests the rotation of the circumstellar
structures.Comment: Paper accepted in the A&A journa
Functions of the novel RhoGAP proteins RGA-3 and RGA-4 in the germ line and in the early embryo of C. elegans
We have identified two redundant GTPase activating proteins (GAPs) – RGA-3 and RGA-4 – that regulate Rho GTPase function at the plasma membrane in early Caenorhabditis elegans embryos. Knockdown of both RhoGAPs resulted in extensive membrane ruffling, furrowing and pronounced pseudo-cleavages. In addition, the non-muscle myosin NMY-2 and RHO-1 accumulated on the cortex at sites of ruffling. RGA-3 and RGA-4 are GAPs for RHO-1, but most probably not for CDC-42, because only RHO-1 was epistatic to the two GAPs, and the GAPs had no obvious influence on CDC-42 function. Furthermore, knockdown of either the RHO-1 effector, LET-502, or the exchange factor for RHO-1, ECT-2, alleviated the membrane-ruffling phenotype caused by simultaneous knockdown of both RGA-3 and RGA-4 [rga-3/4 (RNAi)]. GFP::PAR-6 and GFP::PAR-2 were localized at the anterior and posterior part of the early C. elegans embryo, respectively showing that rga-3/4 (RNAi) did not interfere with polarity establishment. Most importantly, upon simultaneous knockdown of RGA-3, RGA-4 and the third RhoGAP present in the early embryo, CYK-4, NMY-2 spread over the entire cortex and GFP::PAR-2 localization at the posterior cortex was greatly diminished. These results indicate that the functions of CYK-4 are temporally and spatially distinct from RGA-3 and RGA-4 (RGA-3/4). RGA-3/4 and CYK-4 also play different roles in controlling LET-502 activation in the germ line, because rga-3/4 (RNAi), but not cyk-4 (RNAi), aggravated the let-502(sb106) phenotype. We propose that RGA-3/4 and CYK-4 control with which effector molecules RHO-1 interacts at particular sites at the cortex in the zygote and in the germ line
Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER
Thanks to their large angular dimension and brightness, red giants and
supergiants are privileged targets for optical long-baseline interferometers.
Sixteen red giants and supergiants have been observed with the VLTI/AMBER
facility over a two-years period, at medium spectral resolution (R=1500) in the
K band. The limb-darkened angular diameters are derived from fits of stellar
atmospheric models on the visibility and the triple product data. The angular
diameters do not show any significant temporal variation, except for one
target: TX Psc, which shows a variation of 4% using visibility data. For the
eight targets previously measured by Long-Baseline Interferometry (LBI) in the
same spectral range, the difference between our diameters and the literature
values is less than 5%, except for TX Psc, which shows a difference of 11%. For
the 8 other targets, the present angular diameters are the first measured from
LBI. Angular diameters are then used to determine several fundamental stellar
parameters, and to locate these targets in the Hertzsprung-Russell Diagram
(HRD). Except for the enigmatic Tc-poor low-mass carbon star W Ori, the
location of Tc-rich stars in the HRD matches remarkably well the
thermally-pulsating AGB, as it is predicted by the stellar-evolution models.
For pulsating stars with periods available, we compute the pulsation constant
and locate the stars along the various sequences in the Period -- Luminosity
diagram. We confirm the increase in mass along the pulsation sequences, as
predicted by the theory, except for W Ori which, despite being less massive,
appears to have a longer period than T Cet along the first-overtone sequence.Comment: 15 pages, 9 figures, 6 table
Evidence of an asymmetrical Keplerian disk in the Br{\gamma} and He I emission lines around the Be star HD 110432
Context. HD 110432 was classified as a "\gamma Cas X-ray analog" since it has
similar peculiar X-ray and optical characteristics, i.e. a hard-thermal X-ray
variable emission and an optical spectrum affected by an extensive disk. Lopes
de Oliveira et al. (2007) suggest that it might be a Be star harboring an
accreting white dwarf or that the X-rays may come from an interaction between
the surface of the star and its disk. Aims. To investigate the disk around this
Be star we used the VLTI/AMBER instrument, which combines high spectral
(R=12000) and high spatial (\theta min =4 mas) resolutions. Methods. We
constrain the geometry and kinematics of its circumstellar disk from the
highest spatial resolution ever achieved on this star. Results. We obtain a
disk extension in the Br{\gamma} line of 10.2 D\ast and 7.8 D\ast in the He I
line at 2.05 \mu m assuming a Gaussian disk model. The disk is clearly
following a Keplerian rotation. We obtained an inclination angle of 55\degree,
and the star is a nearly critical rotator with Vrot /Vc =1.000.2. This
inclination is greater than the value found for \gamma Cas (about 42\degree,
Stee et al. 2012), and is consistent with the inference from optical Fe II
emission profiles by Smith & Balona (2006) that the inclination should be more
than the \gamma Cas value. In the near-IR continuum, the disk of HD 110432 is 3
times larger than \gamma Cas's disk. We have no direct evidence of a companion
around HD 110432, but it seems that we have a clear signature for disk
inhomogeneities as detected for {\zeta} Tau. This asymmetrical disk detection
may be interpreted within the one-armed oscillation viscous disk framework.
Another finding is that the disk size in the near-IR is similar to other Be
stars with different spectral types and thus may be independent of the stellar
parameters, as found for classical Be stars.Comment: 9 page
A short-term in vitro test for tumour sensitivity to adriamycin based on flow cytometric DNA analysis.
A new method to test the sensitivity of tumour cells to chemotherapy is presented. Tumour cells were incubated in vitro on agar, and drug-induced cell cycle perturbation was monitored by flow cytometric DNA analysis. In the present study the method was applied to monitor the effect of adriamycin on an adriamycin-sensitive Ehrlich ascites tumour and two adriamycin-resistant tumours. Adriamycin caused a dose-related accumulation of tumour cells in the G2 + M phase in the sensitive tumour. Drug concentrations greater than or equal to 100-fold higher were required to induce similar changes in the resistant tumours. The dose level causing maximum accumulation in the G2 + M phase is suggested as a parameter for quantifying the sensitivity. The results indicate that the method can be extended to sensitivity testing of human tumours
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