Height growth reconstruction of a boreal forest canopy over a period of 58 years using a combination of photogrammetric and lidar models

Field data describing the height growth of trees or stands over several decades are very scarce. Consequently, our capacity of analyzing forest dynamics over large areas and long periods of time is somewhat limited. This study proposes a new method for retrospectively reconstructing plot-wise average dominant tree height based on a time series of high-resolution canopy height maps, termed canopy height models (CHMs). The absolute elevation of the canopy surface, or digital surface model (DSM), was first reconstructed by applying image-matching techniques to stereo-pairs of aerial photographs acquired in 1945, 1965, 1983, and 2003. The historical CHMs were then created by subtracting the bare earth elevation provided from a recent lidar survey from the DSMs. A method for estimating average dominant tree height from these historical CHMs was developed and calibrated for each photographic year. The accuracy of the resulting remote sensing height estimates was compared to ageheight data reconstructed based on dendrometric measurements. The height bias of the remote sensing estimates relative to the verification data ranged from 0.52 m to 1.55 m (1.16 m on average). The corresponding root-mean-square errors varied between 1.49 m and 2.88 m (2.03 m average). Despite being slightly less accurate than historical field data, the quality of the remote sensing estimates is sufficient for many types of forest dynamics studies. The procedures for implementing this method, with the exception of the calibration phase, are entirely automated such that forest height growth curves can be reconstructed and mapped over large areas for which recent lidar data and historical photographs exist

Completing the bedrock mapping of southern Baffin Island, Nunavut; plutonic suites and regional stratigraphy

This paper summarizes the field observations and initial interpretations following eight weeks of regional and targeted bed- rock mapping on south-central Baffin Island, Nunavut. The 2015 field campaign completes a two-decade mission to update the geoscience knowledge for the whole of Baffin Island south of latitude 70°N. The bedrock in the area is dominated by a Paleoproterozoic metaplutonic suite, ranging in composition from gabbro to syenogranite, with crosscutting relations indi- cating a progression from mafic to silicic magmatism. Phase-equilibria modelling reveals that the prevailing upper-amphi- bolite– to lower-granulite–facies metamorphic conditions overlap the stability limits of magnetite and orthopyroxene for a typical granitoid bulk composition, which is consistent with field observations of the discontinuous presence of both phases throughout the map area. This result is also consistent with regional aeromagnetic data that show complex structures within relatively homogeneous map units, which are primarily attributed to variations in the abundance of magnetite. The granitoid rocks are interpreted as part of the middle Paleoproterozoic Cumberland Batholith. Metasedimentary rocks, including quartzite, pelite, marble and metagreywacke, are present as enclaves and screens within and between plutonic bodies. An examination of the ‘ghost’stratigraphy suggests that the metasedimentary rocks through- out most of the map area can be correlated with the middle Paleoproterozoic Lake Harbour Group, except in the northeast, where the unique presence of greywacke suggests a middle Paleoproterozoic Piling Group affinity. This transition in strata is consistent with the proposal that a middle Paleoproterozoic tectonic suture (the Baffin suture) associated with the Trans- Hudson Orogen runs through Cumberland Sound. Completion of the bedrock mapping in southern Baffin Island indicates that the region offers a world-class exposure of a reworked Paleoproterozoic convergent margin, which affords valuable in- sight into a variety of magmatic and tectonic processes that can be applied to younger collisional belt

Ptarmigan Fiord basement-cover thrust imbricates, Baffin Island, Nunavut

The rocks at Ptarmigan Fiord on the Hall Peninsula of Baffin Island underwent midcrustal deformation during the formation of the Paleoproterozoic Trans-Hudson Orogen. The structural style in the region is dominated by imbricate panels of Archean basement orthogneiss and Paleoproterozoic supracrustal strata, interpreted to have been deformed by thick- skinned ductile thrusting. Basement rocks comprise amphibolite-facies metatonalite, metagranodiorite, metaquartz-diorite and metamonzogranite, and cover rocks comprise amphibolite-facies migmatitic pelitic and semipelitic schist, psammitic schist, amphibolite, calcsilicate and quartzite. The S 1a penetrative foliation is variably present in basement rocks and consis- tently present in cover rocks, and is defined by alignment of biotite, sillimanite and leucogranite that formed before and dur- ing the thermal metamorphic peak. The S 1a foliation was deformed by F 1b isoclinal folds with an amplitude of 100 m. These structures are interpreted as forming during a D 1 east-west crustal shortening event. Basement and cover imbrication oc- curred after the thermal metamorphic peak and is interpreted as D 2 thick-skinned ductile thrusting. Ductile thrust faults at the base of seven basement-cover slices are identified on the basis of repetition of units and strain localization, and are inter- preted as predominantly south-to-southeast verging on the basis of shear-sense indicators. There are two structural panels of D 2 thrust imbricates, one in the northwestern part of the map area and one in the eastern part of the map area. Map-scale crosscutting relationships indicate that the northwestern panel overthrusted the eastern panel on a southeasterly T 2c -di- rected thrust fault, following a F 2b folding event that folded the T 2a basement-cover thrust imbricates in the eastern panel. The Ptarmigan Fiord area contains a world-class exposure of thick-skinned structures as they are spectacularly delineated by belts of distinctive grey-weathering Archean basement rocks and brown- to black-weathering Paleoproterozoic supra- crustal rocks

The diabetes-linked transcription factor PAX4 promotes β-cell proliferation and survival in rat and human islets

The mechanism by which the β-cell transcription factor Pax4 influences cell function/mass was studied in rat and human islets of Langerhans. Pax4 transcripts were detected in adult rat islets, and levels were induced by the mitogens activin A and betacellulin. Wortmannin suppressed betacellulin-induced Pax4 expression, implicating the phosphatidylinositol 3-kinase signaling pathway. Adenoviral overexpression of Pax4 caused a 3.5-fold increase in β-cell proliferation with a concomitant 1.9-, 4-, and 5-fold increase in Bcl-xL (antiapoptotic), c-myc, and Id2 mRNA levels, respectively. Accordingly, Pax4 transactivated the Bcl-xL and c-myc promoters, whereas its diabetes-linked mutant was less efficient. Bcl-xL activity resulted in altered mitochondrial calcium levels and ATP production, explaining impaired glucose-induced insulin secretion in transduced islets. Infection of human islets with an inducible adenoviral Pax4 construct caused proliferation and protection against cytokine-evoked apoptosis, whereas the mutant was less effective. We propose that Pax4 is implicated in β-cell plasticity through the activation of c-myc and potentially protected from apoptosis through Bcl-xL gene expression

New linear stability parameter to describe low-β\beta electromagnetic microinstabilities driven by passing electrons in axisymmetric toroidal geometry

In magnetic confinement fusion devices, the ratio of the plasma pressure to the magnetic field energy, $\beta$, can become sufficiently large that electromagnetic microinstabilities become unstable, driving turbulence that distorts or reconnects the equilibrium magnetic field. In this paper, a theory is proposed for electromagnetic, electron-driven linear instabilities that have current layers localised to mode-rational surfaces and binormal wavelengths comparable to the ion gyroradius. The model retains axisymmetric toroidal geometry with arbitrary shaping, and consists of orbit-averaged equations for the mode-rational surface layer, with a ballooning space kinetic matching condition for passing electrons. The matching condition connects the current layer to the large scale electromagnetic fluctuations, and is derived in the limit that $\beta$ is comparable to the square root of the electron-to-ion-mass ratio. Electromagnetic fluctuations only enter through the matching condition, allowing for the identification of an effective $\beta$ that includes the effects of equilibrium flux surface shaping. The scaling predictions made by the asymptotic theory are tested with comparisons to results from linear simulations of micro-tearing and electrostatic microinstabilities in MAST discharge #6252, showing excellent agreement. In particular, it is demonstrated that the effective $\beta$ can explain the dependence of the local micro-tearing mode (MTM) growth rate on the ballooning parameter $\theta_0$ -- possibly providing a route to optimise local flux surfaces for reduced MTM-driven transport.Comment: 29 pages, 14 figure

Murmuration

Murmuration is an outcome of the EU Culture funded EMDL project (EMDL.eu), exhibited at Society for Arts and Technology’s (SAT) Satosphere. The artistic research initiative brought together an international interdisciplinary group to explore the fulldome environment as a platform for creative innovation. Murmuration consolidated research into networked navigation devices for virtual spaces, swarm algorithms for audience participation, 3D scanning (MRI volumetric modelling) and 3D sonification for game engines in performance

Forschendes Lernen. Konzeptuelle Grundlagen und Potenziale digitaler Medien

Im folgenden Artikel wird dargelegt, was unter dem Konzept des forschenden Lernens zu verstehen ist und welche Einsatzmöglichkeiten sich für das forschende Lernen im Kontext Universität ergeben. Dabei werden speziell diejenigen Merkmale theoretisch herausgearbeitet, die aus Lehrendenperspektive Anknüpfungspunkte für einen prozessbegleitenden Medieneinsatz bieten. Exemplarisch wird eine Lehrveranstaltung angeführt, die auf Fallebene zeigt, wie ein forschungsorientiertes Seminar um digitale Medien angereichert werden kann und welche Chancen und Grenzen sich bei der selbstgesteuerten Verwendung digitaler Medienangebote ergeben. Die Evaluation des Seminars zeigt, dass die Studierenden einen großen Lernzuwachs erleben, jedoch teilweise durch die Offenheit des Lernens überfordert sind. Diese und andere Gründe führen dazu, dass die von Lehrenden vorgeschlagenen Medienangebote selten bis kaum genutzt werden. Zudem sehen Lernende die Qualität virtuell distribuierter Inhalte kritisch, was sich auf die Akzeptanz und die Nutzung der vorhandenen digitalen Medienangebote auswirkt. (DIPF/Orig.

The liver receptor homolog-1 (LRH-1) is expressed in human islets and protects β-cells against stress-induced apoptosis

Liver receptor homolog (LRH-1) is an orphan nuclear receptor (NR5A2) that regulates cholesterol homeostasis and cell plasticity in endodermal-derived tissues. Estrogen increases LRH-1 expression conveying cell protection and proliferation. Independently, estrogen also protects isolated human islets against cytokine-induced apoptosis. Herein, we demonstrate that LRH-1 is expressed in islets, including β-cells, and that transcript levels are modulated by 17β-estradiol through the estrogen receptor (ER)α but not ERβ signaling pathway. Repression of LRH-1 by siRNA abrogated the protective effect conveyed by estrogen on rat islets against cytokines. Adenoviral-mediated overexpression of LRH-1 in human islets did not alter proliferation but conferred protection against cytokines and streptozotocin-induced apoptosis. Expression levels of the cell cycle genes cyclin D1 and cyclin E1 as well as the antiapoptotic gene bcl-xl were unaltered in LRH-1 expressing islets. In contrast, the steroidogenic enzymes CYP11A1 and CYP11B1 involved in glucocorticoid biosynthesis were both stimulated in transduced islets. In parallel, graded overexpression of LRH-1 dose-dependently impaired glucose-induced insulin secretion. Our results demonstrate the crucial role of the estrogen target gene nr5a2 in protecting human islets against-stressed-induced apoptosis. We postulate that this effect is mediated through increased glucocorticoid production that blunts the pro-inflammatory response of islet