A Time Series Model of Multiple Structural changes in Level, Trend and Variance

We consider a deterministically trending dynamic time series model in which multiple changes in level, trend and error variance are modeled explicitly and the number but not the timing of the changes are known. Estimation of the model is made possible by the use of the Gibbs sampler. The determination of the number of structural breaks and the form of structural change is considered as a problem of model selection and we compare the use of marginal likelihoods, posterior odds ratios and Schwarz' BIC model selection criterion to select the most appropriate model from the data. We evaluate the efficacy of the Bayesian approach using a small Monte Carlo experiment. As empirical examples, we investigate structural changes in the U.S. ex-post real interest rate and in a long time series of U.S. GDP.BIC, Gibbs sampling, multiple structural changes, posterior odds ratio

PEP7 is a ligand for receptor kinase SIRK1 to regulate aquaporins and root growth

Receptor kinases constitute the largest protein family in regulating various responses to external and internal biotic and abiotic signals. Functional characterization of this large protein family and particularly the identification of their ligands remains a major challenge in plant biology. Previously, we identified SIRK1 and QSK1 as a receptor / co-receptor pair involved in regulation of aquaporins in response to osmotic changes induced by sucrose. Here, we now identify a member of the Elicitor Peptide (PEP) family, namely PEP7, as a ligand to receptor kinase SIRK1. PEP7 was shown to bind to the extracellular domain of SIRK1 with a binding constant of 19 µM. PEP7 was secreted to the apoplasm specifically in response to sucrose. Formation of a signaling complex involving SIRK1, QSK1 as well as aquaporins as substrates was induced by sucrose or external PEP7 treatment. PEP7 induced aquaporin phosphorylation and water influx activity. The knock-out mutant of receptor SIRK1 was not responsive to external PEP7 treatment. Binding to receptor SIRK1 and induction of physiological responses was specific to PEP7, neither other members of the PEP-family (PEP6, PEP4), nor other small signaling peptides (CLEs, IDA, RALFs) induced SIRK1 kinase activity, aquaporin phosphorylation, or protoplast water influx activity.Rezeptorkinasen sind die größte Proteinfamilie, die verschiedene Reaktionen auf externe und interne biotische und abiotische Signale reguliert. Die funktionelle Charakterisierung dieser großen Proteinfamilie und insbesondere die Identifizierung ihrer Liganden bleibt eine große Herausforderung in der Pflanzenbiologie. Zuvor hatten wir SIRK1 und QSK1 als ein Rezeptor/Co-Rezeptor-Paar identifiziert, das an der Regulierung von Aquaporinen als Reaktion auf osmotische Veränderungen durch Saccharose beteiligt ist. Jetzt haben wir ein Mitglied der Familie der Elicitor-Peptide (PEP), nämlich PEP7, als Liganden für die Rezeptor-Kinase SIRK1 identifiziert. Es wurde gezeigt, dass PEP7 mit einer Bindungskonstante von 19 µM an die extrazelluläre Domäne von SIRK1 bindet. PEP7 wurde speziell als Reaktion auf Saccharose in das Apoplasma sezerniert. Die Bildung eines Signalkomplexes, an dem SIRK1, QSK1 sowie Aquaporine als Substrate beteiligt sind, wurde durch Saccharose oder externe PEP7-Behandlung induziert. PEP7 induzierte die Aquaporin-Phosphorylierung und die Aktivität des Wassereinstroms. Die Knock-out-Mutante des Rezeptors SIRK1 reagierte nicht auf eine externe PEP7-Behandlung. Die Bindung an den Rezeptor SIRK1 und die Induktion physiologischer Reaktionen war spezifisch für PEP7. Weder andere Mitglieder der PEP-Familie (PEP6, PEP4) noch andere kleine Signalpeptide (CLEs, IDA, RALFs) induzierten die Kinaseaktivität von SIRK1, die Aquaporin-Phosphorylierung oder die Wassereinstromaktivität in Protoplasten

Deformation Mapping and Modeling of the Aleutian Volcanoes with InSAR and Numerical Models

Surface deformation mapping is an essential component for comprehensive monitoring of volcanic activities, serving as a vital tool for discerning crucial insights into magma dynamics, storage, and migration for accurate hazard forecasting, assessment, and mitigation. However, monitoring of the volcanic deformation across the Aleutian volcanic arc is usually limited by the lack of terrestrial sensors deployed due to their remote locations and hostile environmental conditions, necessitating alternative methodologies for data acquisition and analysis. My PhD study aims at precisely mapping the crustal deformation for the Aleutian volcanoes and tracking the evolution of the magmatic system with Interferometric Synthetic Aperture Radar (InSAR) and numerical deformation modeling. Advanced timeseries InSAR algorithms are applied to three cases: Okmok, Makushin, and western and central Aleutian. Deformation history since the 2008 eruption at Okmok mapped with PSInSAR unveils several successive inflation episodes with time-dependent rates. Finite Element Models (FEM) updated with Ensemble Kalman Filter (EnKF) find the timeseries deformation can be well explained by a spherical source with temporally steady location about 3.5 km beneath the central caldera, with cumulative volume change about from 2008 to 2021. Deformation mapped from SAR data collected across platforms have detected multiple inflation/deflation cycles characterized by temporally varying rates at Makushin volcano from 2004 to 2021. Inverse models of the crustal deformation suggest a Mogi source located to the northeast of the caldera at a depth ~6 km Beneath Sea Level (BSL). A shallow secondary deformation located to the southeast of the volcano, with rates about half that of the main deformation is also identified. A volatile intrusion/degassing dominated plumbing system is preferred by the inflation/deflation cycles with distinct magnitudes and lifetimes. A new timeseries InSAR framework is developed based on the geocoded unwrapped interferograms produced from Jet Propulsion Laboratory (JPL) Advanced Rapid Imaging and Analysis (ARIA) system. Deformation histories for volcanoes in the western and central Aleutian are retrieved with this framework with Sentinel-1 imageries from 2015 to 2021. Various deformation patterns associated with different volcanic processes have been detected and used to track the evolution of volcanic systems. New deformation patterns are observed from Tanaga, Great Sitkin and Yunaska volcano. Overall higher magmatism, which may be attributed to spatial variation in tectonic environments, is identified in the central Aleutian. To investigate the discrepancy between magmatic sources derived from geodetic deformation and the ones inferred from seismic tomography at Okmok, several numerical magma reservoir models are constructed and analyzed. The single reservoir model with magmatic chamber characterized by low P and S wave velocity (Vp and Vs) and moderate P to S wave velocity (Vp/Vs) ratio produce crustal deformation that fits the geodetic observations better than the distributed reservoir model with magma chambers represented by high Vp and Vp/Vs ratio and low Vs, which likely reconcile the geodetic deformation and seismic tomography observations and highlights the necessity of joint interpretation of geophysical observations over regions with complicated volcanic environments