678 research outputs found
The glypican Dally is a target and mediator of BMP signaling in eggshell patterning
No full textHeparan sulfate proteoglycans (HSPGs) participate in the regulation of numerous cell signaling pathways in tissues throughout animal development. In Drosophila melanogaster, the HSPG Division-abnormally-delayed (Dally) acts as a co-receptor in several signaling pathways, including bone morphogenetic protein (BMP) signaling, during imaginal wing disc development. Previously, it has been shown that dally is patterned in the follicle cells (FCs), a mono-layer of epithelial cells which surrounds the oocyte. These cells derive the formation of the eggshell. We found this pattern to be evolutionary conserved across Drosophila species. Also, dally’s pattern spatially overlaps the BMP signaling domain, which was monitored by phosphorylated-Mothers-against-Dpp (P-MAD). Using genetic perturbations, we determine that in the FCs, dally is a downstream target of BMP signaling. Furthermore, in clones of cells null for dally, P-MAD is lost cell autonomously. When dally was perturbed uniformly throughout the FCs the BMP signaling gradient was expanded or restricted in gain-of-function or loss-of-function, respectively. Consequently, the FCs patterning shifted along the anterior-posterior axis. Perturbing dally in the anterior domain of the FCs resulted in changes of eggshell morphology. Specifically, the depletion of dally results in an overall increase in operculum length. Based upon our results, and consistent with Dally’s role in wing imaginal discs, we propose a model by which Dally contributes to eggshell patterning along the anterior-posterior axis by regulating BMP signaling.M.S.Includes bibliographical referencesby David James Lemo
The glypican Dally shapes follicle cell patterning by regulating the epidermal growth factor receptor ligand Gurken
No full textHeparan sulfate proteoglycans (HSPGs) have been shown to interact with morphogens of many signaling pathway. During Drosophila oogenesis, the major contributors to tissue patterning are the bone morphogenic protein (BMP) and epidermal growth factor receptor (EGFR) signaling pathways. It was previously shown that BMP signaling is regulated by the HSPG, dally (division abnormally delayed), in the wing, and also in patterning of the follicle cells (FCs). The EGFR pathway is responsible for axis determination as well as follicle cell pattering. Using genetic perturbation, we demonstrate that Dally regulates the distribution of EGFR signaling through the restriction of the TGFα-like ligand Gurken (GRK). When dally is perturbed by uniform overexpression or depletion in the FCs, the GRK gradient is either narrowed, or widened, respectively. In these backgrounds, changes in EGFR activation, measured by dpERK, are consistent with the shapes of GRK patterning. These effects on EGFR activation lead to corresponding results on follicle cell pattering where a decrease in midline clearing of BR in overexpression of dally, corresponding to a reduced gap between the dorsal appendages (DAs). Expressing a mutant form of Dally, lacking an anchor to the membrane, perturbed the GRK gradient, leading to tissue patterning and eggshell morphology defects. Based upon these results, we propose that Dally is required for the formation of the GRK gradient for optimal EGFR signaling activation.M.S.Includes bibliographical referencesby Steven Harris Brownstei
Workshop on Sea Level Rise and Coastal Processes
No full textEstimates of sea level rise - Compaction effects - Tidal range effects - Storm surge and wind-wave response - interaction with natural features and constructed works - shoreline response modeling - saltwater intrusion - upriver saltwater penetration - sedimentary processes in the estuarine region - coastal ecosystemsKWP-collectio
Soft Actor-Critic Deep Reinforcement Learning for Fault Tolerant Flight Control
No full textFault-tolerant flight control faces challenges, as developing a model-based controller for each unexpected failure is unrealistic, and online learning methods can handle limited system complexity due to their low sample efficiency. In this research, a model-free coupled-dynamics flight controller for a jet aircraft able to withstand multiple failure types is proposed. An offline trained cascaded Soft Actor-Critic Deep Reinforcement Learning controller is successful on highly coupled maneuvers, including a coordinated 40 degree bank climbing turn with a normalized Mean Absolute Error of 2.64%. The controller is robust to six failure cases, including the rudder jammed at -15 deg, the aileron effectiveness reduced by 70%, a structural failure, icing and a backward c.g. shift as the response is stable and the climbing turn is completed successfully. Robustness to biased sensor noise, atmospheric disturbances, and to varying initial flight conditions and reference signal shapes is also demonstrated.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Control & Simulatio
Importance of initial momentum rate and air-fuel premixing on moderate or intense low oxygen dilution (MILD) combustion in a recuperative furnace
No full textCopyright © 2009 American Chemical SocietyThis paper reports an investigation on the influences of air−fuel injection momentum rate and the air−fuel premixing on the moderate or intense low oxygen dilution (MILD) combustion in a 20-kW recuperative furnace. Various patterns of partially and fully premixed reactants have proven experimentally to work extremely well in the present furnace. H2 recorded for a variety of equivalence ratios at a firing rate of 10 kW. The present numerical study suggests that there is a critical momentum rate of the inlet fuel−air mixture below which the MILD combustion cannot occur. Also, it is revealed, both experimentally and numerically, that, above the critical rate, both the inlet fuel−air mixedness and momentum rate impose insignificant influence on the stability of and emissions from the MILD combustion.Jianchun Mi, Pengfei Li, Bassam B. Dally, and Richard A. Crai
Deep Reinforcement Learning for Flight Control: Fault-Tolerant Control for the PH-LAB
No full textFault-tolerant flight control faces challenges as developing a model-based controller for each unexpected failure is unrealistic, and online learning methods can handle limited system complexity due to their low sample efficiency. In this research, a model-free coupled-dynamics flight controller for a jet aircraft able to withstand multiple failure types is proposed. An offline-trained cascaded Soft Actor-Critic Deep Reinforcement Learning controller is successful on highly coupled maneuvers, including high-bank coordinated climbing turns. The controller is robust to six unforeseen failure cases, including the rudder jammed at -15°, the aileron effectiveness reduced by 70%, a structural failure, icing and a backward c.g. shift as the response is stable and the climbing turn is completed successfully. Robustness to biased sensor noise, atmospheric disturbances, and to varying initial flight conditions and reference signal shapes is also demonstrated.Aerospace Engineering | Control & Simulatio
Modified vitiation in a moderate or intense low-oxygen dilution (MILD) combustion furnace
No full textThis paper reports on the effects of various operational and geometric parameters on mixing and vitiation in a laboratory-scale furnace operating with natural gas and under the moderate or intense low-oxygen dilution (MILD) regime. The study is carried out through numerical modeling. Seven independent parameters are considered: i.e., mass fraction (f) of fuel diluents (CO 2 and N 2), air preheat temperature (T a), global equivalence ratio (φ), air nozzle exit diameter (D a), fuel nozzle exit diameter (D f), fuel-air nozzles separation distance (S), and fuel injection angle from the furnace floor (α). The modeling is initially verified through a comparison to measurements by Szegö et al. (Szegö, G. G., Dally, B. B., and Nathan, G. J.Combust. Flame 2008, 154, 281-295) in the same furnace geometry. It is shown that varying each of the parameters f, φ, D a, D f, S, and α can considerably influence the fuel-jet penetration distance and the recirculation rate of the exhaust gas, two important quantities for establishing the MILD combustion. Relatively, the geometric parameters D a, D f, S and α play more effective roles in controlling the vitiation rate and, hence, "flame" characteristics. Also, it is revealed that influences of all of the parameters, except S and α, can be represented by that of the ratio of the fuel injection momentum to the air injection momentum. © 2011 American Chemical Society.J. Mi, F. Wang, P. Li and B.B. Dall
MILD combustion under different premixing patterns and characteristics of the reaction regime
No full textThrough experiment and numerical modeling, this study investigated the establishment of moderate or intense low-oxygen dilution (MILD) combustion in a laboratory-scale furnace when fuel and air are fully premixed (FP), partially premixed (PP), or non-premixed (NP). Experiments were carried out at firing rates from 7.5 to 15 kW and equivalence ratios (Φ) ranging from 0.5 to 1. The furnace thermal fields and exhaust NOx emissions for the three mixing patterns were compared. Validated computational fluid dynamics was used to aid in better understanding the flow and compositional structures in the furnace. Natural gas was used as the fuel. The eddy dissipation concept (EDC) model and the GRI-Mech 3.0 mechanism were used. Additional chemical kinetics calculations were also performed to examine reaction pathways under the MILD combustion regime. Moreover, the characteristics of the reaction regime of MILD combustion were examined and are discussed in detail. Estimation of the initial jet momentum rate (J) showed that JFP > JNP > JPP, and consistently the recirculating rate of internal flue gas (Kv) was found to be in the order Kv,FP > Kv,NP > Kv,PP. Correspondingly, the highest values of both furnace temperature and NOx emission were experimentally measured in the PP case, while the lowest values were found in the FP case. The measured NOx emission was negligibly low for the FP case. Numerical results revealed that in all the three cases of firing natural gas (FP, PP, NP), more than 80% of the total NO formation results from the N2O intermediate route while other NO mechanisms are unimportant. As Φ is increased from 0.5 to 1.0, both the measured and simulated NO emissions in the three cases initially increase and then decrease. Moreover, for Φ > 0.9, the NO-reburning reaction becomes significant and the resulting reduction of NO is notable. The rates of both turbulent mixing and chemical reaction were found to play a significant role in the structure and establishment of MILD combustion, with estimated Damköhler numbers in the range Da = 0.01–5.35.P. Li, F. Wang, J. Mi, B. B. Dally, and Z. Me
MILD oxy-combustion of gaseous fuels in a laboratory-scale furnace
No full textThe present study investigates the characteristics of Moderate or Intense Low-oxygen Dilution (MILD) oxy-combustion in a laboratory-scale furnace. Experiments using natural gas (NG), liquefied petroleum gas (LPG) and ethylene (C₂H₄) are carried out at a firing rate of 13 kW. The furnace temperatures and exhaust emissions are measured for a range of equivalence ratios and external-CO₂ dilution rates. It is observed that MILD combustions occur for the three fuels even when using pure oxygen as oxidant. When diluting oxidant by CO₂ at a fixed rate, the MILD combustion can be established as long as the equivalence ratio (Φ) is sufficiently high. The region of MILD combustion is found to be wider with dilution by CO₂ than by N₂. Notably, also, the operating range of MILD combustion is larger for NG than LPG or C₂H₄ as fuel. Moreover, when Φ < 1, as Φ is increased, the furnace temperature rises slightly but the NO(x) emission decreases. This cannot be explained when using the traditional thermal NO(x) mechanism. Indeed, using various NO mechanism models, our calculations show very low NO emissions resulting from the thermal, prompt and NNH routes but a much higher value from the N₂O-intermediate route. Namely, only the latter mechanism plays a crucial role in forming NO. Also important is that the NO reburning appears to reduce NO emissions notably and so should not be ignored in the MILD combustion.Pengfei Li, Bassam B. Dally, Jianchun Mi, Feifei Wan
Recommended from our members
TDP-43 proteinopathy alters the ribosome association of multiple mRNAs including the glypican Dally-like protein (Dlp)/GPC6
No full textAmyotrophic lateral sclerosis (ALS) is a genetically heterogeneous neurodegenerative disease in which 97% of patients exhibit cytoplasmic aggregates containing the RNA binding protein TDP-43. Using tagged ribosome affinity purifications in Drosophila models of TDP-43 proteinopathy, we identified TDP-43 dependent translational alterations in motor neurons impacting the spliceosome, pentose phosphate and oxidative phosphorylation pathways. A subset of the mRNAs with altered ribosome association are also enriched in TDP-43 complexes suggesting that they may be direct targets. Among these, dlp mRNA, which encodes the glypican Dally like protein (Dlp)/GPC6, a wingless (Wg/Wnt) signaling regulator is insolubilized both in flies and patient tissues with TDP-43 pathology. While Dlp/GPC6 forms puncta in the Drosophila neuropil and ALS spinal cords, it is reduced at the neuromuscular synapse in flies suggesting compartment specific effects of TDP-43 proteinopathy. These findings together with genetic interaction data show that Dlp/GPC6 is a novel, physiologically relevant target of TDP-43 proteinopathy. © 2021, The Author(s).Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
- …
