Quaternary Stratigraphy in Northwestern Maine: A Progress Report

A preliminary Quaternary stratigraphy for northwestern Maine can be assembled from interpretation of ice-flow indicators (dispersal and erosional), exposed sections, and drill-hole logs. Evidence from the ice-flow indicators delineates at least four regions each with different ice-flow histories. The distribution of these regions may result from an eastward invasion of Laurentide source ice during the early portion of the late Wisconsinan and subsequent development of a local ice dome during the closing portion of the Late Wisconsinan substage. Exposed sections contribute the following probable sequence of events to the stratigraphy: 1) deposition of alluvial fans, 2) deposition of a gray compact till beneath eastward flowing (Laurentide) ice, 3) deposition of a brown till beneath northward flowing local ice, 4) deglaciation by a southward retreating ice margin. These events appear continuous and have all been provisionally assigned a Late Wisconsinan age. Drill-hole logs confirm the sequence derived from the exposed sections and allow extension of the Quaternary stratigraphy. The drill-log data show three associated groups of sediments that may in turn result from at least three separate ice margin advances and recessions. The uppermost group of sediments is correlated with those found in exposed sections. The position of the drill-hole logs in an over-deepened basin suggest erosion by at least one even earlier glaciation.À partir de l'interprétation des indicateurs de l'écoulement glaciaire (de dispersion et d'érosion), des coupes naturelles et des résultats des forages, on a tenté d'établir la stratigraphie préliminaire du Quaternaire pour le nord du Maine. Les renseignements tirés des indicateurs de l'écoulement glaciaire ont permis de circonscrire au moins quatre régions, chacune d'elles présentant un processus différent d'écoulement glaciaire. La répartition des régions est probablement le résultat de la progression vers l'est des glaces laurentidiennes au début du Wisconsinien supérieur et de la formation subséquente d'un dôme local à la fin du Wisconsinien supérieur. Les coupes naturelles ont permis de reconstituer la séquence d'événements suivante : 1 ) formation de cônes de déjection; 2) dépôt d'un till gris compact sous une des glaces laurentidiennes s'écoulant vers l'est; 3) dépôt d'un till brun sous les glaces locales s'écoulant vers le nord; 4) déglaciation résultant du retrait de la marge glaciaire vers le sud. Ces événements semblent s'être déroulés de façon continue; on les attribue du moins provisoirement au Wisconsinien supérieur. Les résultats des forages confirment la séquence reconstituée grâce aux coupes naturelles et permettent même de prolonger la stratigraphie du Quaternaire. Les données de forage démontrent la présence de trois groupes associés de sédiments qui, à leur tour, sont le résultat d'au moins trois récurrences et trois récessions de la marge glaciaire. Le groupe supérieur correspond aux sédiments observés dans les coupes. Les résultats de forage dans un bassin surcreusé laissont croire qu'au moins une glaciation antérieure y a laissé des traces d'érosion.Eine vorlàufige Stratigraphie fur Nord-West Maine im Quatemar kann durch Interpretation der Eis-FluB Indikatoren (Dispersion und Erosion), der natùrlichen Schnitte und der Bohrergebnisse erstellt werden. Durch die Eis-RuB Indikatoren ergeben sich mindestens vier Gebiete mit jeweils unterschiedlicher Eis-FluB Vergangenheit. Die Verteilung dieser Gebiete hat wohl ihren Ursprung im Eindringen von Laurentischem Quell-Eis in ôstlicher Richtung wàhrend des Beginns des spàten Wisconsin und der darauf folgenden Entwicklung eines lokalen Eis-Doms wàhrend der AbschluBphase des spâten Wisconsin. Die natùrlichen Schnitte ergeben die folgende môgliche Abfolge der Ereignisse fur die Stratigraphie; 1) Ablagerung von Alluvialkegeln, 2) Ablagerung eines grauen kompakten Tills unter ostwàrts flieBendem (Laurentischem) Eis, 3) Ablagerung eines braunen Tills unter nordwârts flieBendem lokalem Eis, 4) Enteisung durch die sùdwàrts zurùckweichende Eisgrenze. Dièse Ereignisse scheinen kontinuierlich abgelaufen zu sein und sind aile vorlàufig dem spâten Wisconsin zugeschrieben worden. Die Bohrergebnisse bestàtigen die aus den natùrlichen Schnitten gewonnene Abfolge und erlauben eine Ausdehnung der Stratigraphie des Quatemar. Die Bohrdaten zeigen drei Gruppen von Sedimenten, die ihrerseits ihren Ursprung in mindestens drei unterschiedlichen VorstoB- und Rùckzugs-Phasen der Eisgrenze haben. Die oberste Gruppe der Sedimente steht in Wechselbeziehung mit den in den natùrlichen Schnitten gefundenen Sedimenten. Bohrergebnissg in einom ùbGrtieften Becken lassen vermuten, daB zumindest eine frùhre Vereisung Erosionsspuren hinterlassen hat

Wetting and energetics in nanoparticle etching of graphene

Molten metallic nanoparticles have recently been used to construct graphene nanostructures with crystallographic edges. The mechanism by which this happens, however, remains unclear. Here, we present a simple model that explains how a droplet can etch graphene. Two factors possibly contribute to this process: a difference between the equilibrium wettability of graphene and the substrate that supports it, or the large surface energy associated with the graphene edge. We calculate the etching velocities due to either of these factors and make testable predictions for evaluating the significance of each in graphene etching. This model is general and can be applied to other materials systems as well. As an example, we show how our model can be used to extend a current theory of droplet motion on binary semiconductor surfaces

Climate Change and San Francisco Bay-Delta Tidal Wetlands

Climate change will affect tidal wetlands with higher rates of sea-level rise and higher concentrations of salt in brackish and freshwater tidal systems, in addition to causing increases in atmospheric CO2 concentration, warmer temperatures, and shifts in precipitation. In the San Francisco Bay–Delta, the areas most likely to be affected—brackish and freshwater tidal wetlands—are also the sites with the majority of endemic plant species and the greater biodiversity and productivity. Effects on the San Francisco Bay– Delta estuary are complex and difficult to predict, but a few things are clear. Biodiversity of the tidal wetland system in the San Francisco Bay–Delta region will decline, with subsequent effects on ecosystem functioning and services. Altered plant production, physiological tolerances, and shifts in rates of mortality will modify wetland plant communities in ways not yet predictable. Lower ecosystem productivity from salinity increases will affect both primary and detrital-based food webs. Such changes will cascade via the food webs into invertebrate, bird, and pelagic systems. Tidal wetlands are especially sensitive to processes that climate change will alter. Several of these altered processes are exacerbated by water diversions from the Delta

Differential responses of ecotypes to climate in a ubiquitous arctic sedge: implications for future ecosystem C cycling

The response of vegetation to climate change has implications for the carbon cycle and global climate. It is frequently assumed that a species responds uniformly across its range to climate change. However, ecotypes—locally adapted populations within a species—display differences in traits, which may affect their gross primary productivity (GPP) and response to climate change. To determine if ecotypes are important for understanding the response of ecosystem productivity to climate we measured and modeled growing season GPP in reciprocally transplanted and experimentally warmed ecotypes of the abundant arctic sedge Eriophorum vaginatum. Transplanted northern ecotypes displayed home site advantage in GPP that was associated with differences in leaf area index. Southern ecotypes exhibited a greater response in GPP when transplanted. The results demonstrate that ecotypic differentiation can impact the morphology and function of vegetation with implications for carbon cycling. Moreover they suggest that ecotypic control of GPP may limit the response of ecosystem productivity to climate change. This investigation shows that ecotypes play a substantial role in determining GPP and its response to climate. These results have implications for understanding annual to decadal carbon cycling where ecotypes could influence ecosystem function and vegetation feedbacks to climate change

Thermodynamics of SmCo5 compound doped with Fe and Ni: An ab initio study

SmCo5 permanent magnets exhibit enormous uniaxial magnetocrystalline anisotropy energy and have a high Curie temperature. However, their low energy product is a significant deficiency. To increase the energy product in SmCo5, we propose substituting cobalt with iron, that has a much larger magnetic moment, in a SmCoNiFe3 magnet where nickel is used as a thermodynamic stabilizer

Cohomogeneity one manifolds and selfmaps of nontrivial degree

We construct natural selfmaps of compact cohomgeneity one manifolds with finite Weyl group and compute their degrees and Lefschetz numbers. On manifolds with simple cohomology rings this yields in certain cases relations between the order of the Weyl group and the Euler characteristic of a principal orbit. We apply our construction to the compact Lie group SU(3) where we extend identity and transposition to an infinite family of selfmaps of every odd degree. The compositions of these selfmaps with the power maps realize all possible degrees of selfmaps of SU(3).Comment: v2, v3: minor improvement

Wound healing and hyper-hydration - a counter intuitive model

Winters seminal work in the 1960s relating to providing an optimal level of moisture to aid wound healing (granulation and re-epithelialisation) has been the single most effective advance in wound care over many decades. As such the development of advanced wound dressings that manage the fluidic wound environment have provided significant benefits in terms of healing to both patient and clinician. Although moist wound healing provides the guiding management principle confusion may arise between what is deemed to be an adequate level of tissue hydration and the risk of developing maceration. In addition, the counter-intuitive model ‘hyper-hydration’ of tissue appears to frustrate the moist wound healing approach and advocate a course of intervention whereby tissue is hydrated beyond what is a normally acceptable therapeutic level. This paper discusses tissue hydration, the cause and effect of maceration and distinguishes these from hyper-hydration of tissue. The rationale is to provide the clinician with a knowledge base that allows optimisation of treatment and outcomes and explains the reasoning behind wound healing using hyper-hydration

Brightness, distribution, and evolution of sunspot umbral dots

We present a 106-minute TiO (705.7nm) time series of high spatial and temporal resolution that contains thousands of umbral dots (UDs) in a mature sunspot in the active region NOAA 10667 at $\mu$=0.95. The data were acquired with the 1-m Swedish Solar Telescope on La Palma. With the help of a multilevel tracking (MLT) algorithm the sizes, brightnesses, and trajectories of 12836 umbral dots were found and analyzed. The MLT allows UDs with very low contrast to be reliably identified. Inside the umbra we determine a UD filling factor of 11%. The histogram of UD lifetimes is monotonic, i.e. a UD does not have a typical lifetime. Three quarters of the UDs lived for less than 150s and showed no or little motion. The histogram of the UD diameters exhibits a maximum at 225km, i.e. most of the UDs are spatially resolved. UDs display a typical horizontal velocity of 420m/s and a typical peak intensity of 51% of the mean intensity of the quiet photosphere, making them on average 20% brighter than the local umbral background. Almost all mobile UDs (large birth-death distance) were born close to the umbra-penumbra boundary, move towards the umbral center, and are brighter than average. Notably bright and mobile UDs were also observed along a prominent UD chain, both ends of which are located at the umbra-penumbra boundary. Their motion started primarily at either of the ends of the chain, continued along the chain, and ended near the chain's center. We observed the splitting and merging of UDs and the temporal succession of both. For the first time the evolution of brightness, size, and horizontal speed of a typical UD could be determined in a statistically significant way. Considerable differences between the evolution of central and peripheral UDs are found, which point to a difference in origin