46 research outputs found
The Space-Time Continuum of Ras Signal Transduction Pathway
No full textDie räumliche Aufteilung periphärer Membran-Proteine, wie GNBP (Ras) moduliert
deren Spezifität der Signalverarbeitung innerhalb der Zelle. Reversible
Palmitoylierung durch Palmitoylacyltransferasen (PATs der DHHC der DHHC
Familie) erzeugt die Verteilung von Ras hin zu der Plasma-Membran (PM) über den
sekretorischen Weg, indem der entropie-getriebenen Gleichverteilung palmitoylierter
Proteine auf alle Zellmembrane entgegenwirkt wird (Rocks et al., 2010). In dieser
Arbeit wird beschrieben, dass DHHC-PATs sich nicht durch Substratspezifität
auszeichnen und es wird postuliert, dass DHHC Proteine die Palmitoylierungsreaktion
nicht katalysieren. Stattdessen verstärken sie die Konzentration des Palmitat-
Thioester-Zwischenproduktes und erzeugen auf diese Weise ein zytosolisches
Reservoir um Palmitoylierung zu vereinfachen.
In dieser Arbeit soll ebenfalls beschrieben werden, wie GSF PDEδ den zügigen
Transfer von Ras Protein zwischen PM, Golgi Apparat, endoplasmatischem
Retikulum (ER) und Zytoplama unterstützt. Weiterhin wird aufgezeigt werden, dass
dies allein solche farnesylierten Ras Proteine betrifft, welche depalmitoyliert oder, im
Fall von Ras mit polykationischem Motiv, PM-desorbiert sind. In Verbindung mit
dem Palmitoylierungskreislauf wirkt PDEδ, indem es die Diffusion von
depalmitoyliertem Ras vereinfacht und erlaubt so dessen kinetisches
Eingefangenwerden am Golgi Apparat ermöglicht. Andererseits erhöht die
Solubilisierung von Kras, welches ein polybasisches Segment auszeichnet, weg von
Endomembranen die Geschwindigkeit, mit der Kras von der PM wieder eingefangen
werden kann, wodurch dessen Equilibriumsverteilung aufrecht erhalten wird. Dies ist
wichtig, da PDEδ auf diese Art die durch Ras vermittelte Signaltransduktion
verstärkt, indem es die Ras-Konzentration an der PM erhöht, und im Gegenzug
bewirkt das Herunterregeln von PDEδ ein Unterdrücken von regulierten und
onkogenischen Ras Signalen. Zusätzlich wird die Regulierung von farnesyliertem
Ras*PDEδ Einheiten via G-Protein Arl2/Arl3 auf eine GTP-abhängige Art
beschrieben. Diese Erkenntnis deckt einen von PDEδ-abhängigen Mechanismus auf,
der für die räumliche Organisation von Ras Proteinen in Zellmembranen
verantwortlich ist und dessen Einfluss auf das Signalverhalten von Ras Wildtyp- bzw.
mutierter Form
Evolution of the pore pressure due to vibratory installation of sheet piles in sand
No full textVibratory installation of sheet piles is the most economic and suitable for the sandy soil because of its mechanism. However, the process induces excess pore pressure in saturated conditions leading to subsidence. This research focuses on the development of a tool-based solution to predict the excess pore pressure due to vibratory installation, which shall be verified by the postdiction of Kademuur Damrak measurements. This tool will help engineers quantify the impact of generated excess pore pressure on adjacent structures. The proposed work attempted to achieve its objective by answering the following main and sub research questions. How can the existing knowledge on generation and evolution of porewater pressure during vibratory installation be effectively integrated into a model/tool, which verified by the postdiction of Kademuur Damrak measurements, can practically estimate the porewater over-pressure during vibratory installations? • What are the parameters that influence the dissipation of the excess pore pressure? • How does the generation and dissipation of excess pore pressure vary in the liquefied zone from non-liquefied? • How can the vibration attenuation affect the generation of excess pore pressure in the sand? • What are the limitations and controlling parameters of this model or tool? The proposed work combines dynamic soil response and transient groundwater flow model to simulate the evolution of pore pressure due to vibratory loading. Based on the degree of modulus degradation due to the vibratory loading the soil, it is zoned into three. This is also termed as a multiscale computational framework. This allows for the formations liquefied and non-liquefied zone. The threshold acceleration of 0.1g - 0.3g must be available for the soil to liquefy [66]. The non- liquefied zone is fed by the groundwater flow from the liquefied zone. According to the Theis equation, head response due to constant pumping in an aquifer is influenced by the rate of discharge (V), storativity(S) and transmissivity(T), distance from the source. This inspired to model the driving of sheet pile with an analogous to the pumping of well. During the constant head loading due to the pumping, there is an increase in the head radially outward from the source. This resembles the phenomenon of pre-shearing in the field. The driving of the sheet pile was stimulated by the constant head loading. The application of time series analysis (PRIFICT method) [8] provides the first estimation of the pore pressure response from the first of three days of field piezometric data of Kademmur damrak. The semi-empirical model was formulated influenced by the head response of the slug test. The response of the time series analysis helped to calibrate the semi-empirical model. The relationship evolved between the physical and modelling parameters established that the hydraulic conductivity is the key parameter in both the generation and the dissipation of the excess pore pressure. The analysis of the field data establishes the conservative assumption of 1m for the width of the liquefaction zone. The analysis of accelerometer data from the Amsterdam noord zuid metro line tunnel helps to establish the dependency of liquefaction on acceleration amplitude. This bolstered the threshold acceleration for liquefaction to be 0.1 - 0.3g. The simple flow only Plaxis model helped to validate the proposed hypothesis. The hydraulic conductivity was established as the key parameter of the model. The integration of dynamic generation and transient groundwater flow model helped to analyse the evolution of excess pore pressure
Not Available
No full textNot AvailableField experiments were conducted during winter seasons of 2007-08 and 2008-09 at Norman E Borloug Crop Research Centre, Pantnagar on sandy loam soil to assess the impact of seed inoculation with phosphate solubilizing bacteria (PSB) and irrigation schedules with sprinklers on vegetable pea (Pisum sativum L.). Results revealed that yield attributes and green pod yield was not influenced significantly by PSB inoculation while irrigation schedules did. Irrigation scheduled at IW: CPE 1.0 through sprinklers produced at par green pod yield with flood irrigation at vegetative and flowering stages but recorded 19.2 and 30.9% higher green pod yield than 0.8 and 0.6 irrigation schedules. Similarly, values of yield components were also higher under this treatment. PSB inoculated treatment recorded 11.1% higher water-use efficiency than no inoculation. Among the irrigation schedules, maximum WUE was noticed with IW: CPE 0.6 treatment (97.0 kg/ ha-cm) while lowest (51.3 kg/ha-cm) was observed with flood irrigation at vegetative and flowering stages. In terms of gross, net return and B: C ratio, IW: CPE 1.0 was superior to other treatments.Not Availabl
Modulation of Type IV pili phenotypic plasticity through a novel Chaperone-Usher system in <i>Synechocystis sp.</i>
No full textAbstractControlling the transition from a multicellular motile state to a sessile biofilm is an important eco-physiological decision for most prokaryotes, including cyanobacteria. Photosynthetic and bio geochemically significant cyanobacterium Synechocystis sp. PCC6803 (Syn6803) uses Type IV pili (TFP) for surface-associated motility and light-directed phototaxis. We report the identification of a novel Chaperone-Usher (CU) system in Syn6803 that regulate secretion of minor pilins as a means of stabilizing TFP morphology. These secreted minor-pilins aid in modifying TFP morphology to suit the adhesion state by forming cell to surface contacts when motility is not required. This morphotype is structurally distinct from TFP assembled during motile phase. We further demonstrate by examining mutants lacking either the CU system or the minor-pilins, which produce aberrant TFP, that are morphologically and functionally distinct from wild-type (WT). Thus, here we report that in Syn6803, CU system work independent of TFP biogenesis machinery unlike reported for other pathogenic bacterial systems and contributes to provide multifunctional plasticity to TFP. cAMP levels play an important role in controlling this switch. This phenotypic plasticity exhibited by the TFP, in response to cAMP levels would allow cells and cellular communities to adapt to rapidly fluctuating environments by dynamically transitioning between motile and sessile states.Significance of this workHow cyanobacterial communities cope with fluctuating or extreme environments is crucial in understanding their role in global carbon and nitrogen cycles. This work addresses the key question: how do cyanobacteria modulate external appendages, called Type IV pili, to effectively switch between motile and sessile biofilm states? We demonstrate that cells transition between forming strong cell-surface interactions indispensable for biofilm formation to forming cell-cell interactions that allow for coordinated movement crucial for social motility by functional/ structural modification of same TFP appendage. The second messenger, cAMP and a Chaperone-Usher secretion are indispensible to achieve these structural modifications of TFP and control the complex phenotypic transition. We have uncovered a strategy that Syn6803 has evolved to deal with molecular decision-making under uncertainty, which we call phenotypic plasticity. Here we demonstrate how a single motility appendage can be structurally modified to attain two antagonistic functions in order to meet the fluctuating environmental demands.</jats:sec
Structural, Morphological and Optical Characterization of X80Y10Cu10 and Y80X10Cu10 (X = Se, Y,Te) Chalcogenide Thin Films
No full textSimulation of maturity duration and productivity of two rice varieties under system of rice intensification using DSSAT v 4.5/CERES-Rice model
No full textCrop growth models have been considered as potential tools for simulating growth and yield of crops. Hence, Decision Support System for Agro-technology Transfer/Crop Estimation through Resource and Environment Synthesis (DSSAT v 4.5/CERES-Rice) model was applied to the data recorded in two years (2008 and 2009). The field experiment included two rice varieties (‘Pant Dhan 4’ and ‘Hybrid 6444’) cultivated with system of rice intensification (SRI) method, under three irrigation schedules (irrigation at 1, 3 and 5 day after disappearance of ponded water) and two planting spacings (20 cm x 20 cm and 25 cm x 25 cm). The model was calibrated using data of 2009 and validated with the data of 2008. For ‘Pant Dhan 4’ maturity was slightly under predicted (gap 2-6 days) by the model with an overall gap between observed and predicted values being 2%, during 2009. However, model predictions were closer (gap 1-2 days) during 2008. The predicted maturity of ‘Hybrid 6444’ was close to the observed one (gap 1 day) but it was over predicted for the year 2008. The model predicted the yield of both the varieties with fair accuracy. The overall gap between predicted and observed yield was 5% for ‘Pant Dhan 4’ and 11.4 % for ‘Hybrid 6444’. Hence the model can be used for predicting maturity and yield of these rice varieties
grown with SRI method.
Modelling and Verification of CoAP over Routing Layer Using SPIN Model Checker
No full textAbstractMany of the communication protocols developed for the resource constrained devices are rarely subjected to protocol verification. Design flaws like deadlocks, livelocks, non-progressive cycles etc. may come into view during the realization and can cause catastrophic effects in safety-critical applications. Formal specification of the protocol represented as a model helps to describe and analyse the conformability of the implementation to its specification and subsequently reveal design flaws, if any in the system. The formal model is subject to verification by inserting correctness and safety properties of the protocol and validating logical correctness using a model checking tool. All model checkers suffer from state explosion problem due to enormous states of the model being created. The key contribution of the present work is the introduction of a method to develop a compact verification model which is amenable to full state space search by abstracting the key elements of a protocol. Moreover, many protocol verification works presented in the existing literature consider only a single layer of a communication protocol. To correctly model the overall behaviour of a protocol, interactions between the layers have to be incorporated. The proposed method has been proven useful by considering verification of an application protocol, CoAP for constrained devices by abstracting out the aspects of the underlying routing protocol RPL. Reliable message exchanges among various entities are modeled and its safety and correctness properties were analysed and verified. The results obtained show that the model performs the full state space search by considering all possible routing paths and are free from design flaws. The method described has been implemented by building a validation model in PROMELA and the model is verified by using SPIN model checker. The methodology used in this paper can be used to verify any application layer protocol for constrained devices in IoT scenario that run on top of routing layer
Conduction Mechanism and Charge Transporting Property of Te 90-x Se 10 Cd x Chalcogenides by AC Conductivity and Dielectric Analysis
No full textIntravascular large B-cell lymphoma with primary bone marrow involvement – Report of a rare disease
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