Late Wisconsinan Deglaciation and Champlain Sea Invasion in the St. Lawrence Valley, Québec

Champlain Sea history is directly linked to Late Wisconsinan deglacial episodes. Champlain Sea Phase I (Charlesbourg Phase) began in the Québec area at about 12.4 ka. It represented a western extension of the Goldthwait Sea between remnant Appalachian ice masses and the Laurentide Ice Sheet. Further south, at about the same time, in the Appalachian uplands and piedmont, high-level glacial lakes were impounded by the ice-front during glacial retreat toward NNW: lakes Vermont, Memphrémagog and Mégantic. Lowlands of the Upper St. Lawrence and Lake Champlain valleys were progressively deglaciated and inundated by Lake Iroquois and Lake Vermont. At about 12.1 ka, these two lakes coalesced and formed a single water-body, here referred to as Lake Candona. After the Ulverton-Tingwick Moraine was constructed, this lake extended northeastward onto the Appalachian piedmont where varved sediments containing Candona subtriangulata underlie marine clays. Current data and interpretations bring into question the former concept of the Highland Front Moraine System. The invasion of the main basin, or Champlain Sea Phase II, began around 12 ka. Replacement of Lake Candona by the sea resulted in a fall of about 60 m in water levels. Champlain Sea Phase III began at the end of the Saint-Narcisse episode, at about 10.8 ka. At this time marine waters were able to enter valleys of the Laurentian Highlands where brackish or fresh paramarine basins developed.L'histoire de la Mer de Champlain est directement liée à la déglaciation du Wisconsinien supérieur. La phase I de la Mer de Champlain (Phase de Charlesbourg) débute dans la région de Québec vers 12,4 ka. Elle représente le prolongement de la Mer de Goldthwait entre l'Inlandsis laurentidien et les glaces résiduelles appalachiennes. Plus au sud et approximativement en même temps, le retrait glaciaire vers le NNW sur les plateaux et le piémont appalachiens est marqué par des moraines et les lacs proglaciaires Vermont, Memphrémagog et Mégantic; les terres basses du haut Saint-Laurent et du lac Champlain étaient progressivement déglacées et inondées par les lacs Iroquois et Vermont. Vers 12,1 ka, ces deux lacs forment par coalescence Ie Lac Candona. Après l'épisode de la Moraine d'Ulverton-Tingwick, ce lac inondait le piémont appalachien vers le NE, où des varves à Candona subtriangulata reposent sous les argiles marines. Ces données remettent en question le concept de Highland Front Moraine System. L'invasion du bassin principal (Phase II de la Mer de Champlain) débute vers 12 ka. Le remplacement du Lac Candona par la mer provoque une chute d'environ 60 m du niveau du plan d'eau. La Phase III de la Mer de Champlain commence à la fin de l'épisode de Saint-Narcisse, vers 10,8 ka; les eaux marines pénètrent dans les vallées des Laurentides et sont coalescentes à des bassins paramarins saumâtres ou non salés.Die Geschichte des Meeres von Champlain ist direkt mit Enteisungs-Episoden im spàten Wisconsin verknùpft. Die Phase I des Champlains-Meeres (Charlesbourg Phase) began im Gebiet von Québec um etwa 12.4 ka. Sie stellt eine westliche Ausdehnung des Goldwaith-Meeres dar, zwischen restlichen Eismassen der Appalachen und der laurentidischen Eisdecke. Wàhrend des glazialen Rùckzugs nach NNW wurden weiter sûdlich etwa zur selben Zeit im Hochland und am Fuss der Appalachen glaziale Seen mit hohem Wasserspiegel durch die Eisfront geformt: der Vermont-, Memphrémagog-, und der Mégantic-See. Das Tiefland und die oberen Sankt-Lorenz- und Champlainsee-Tàler wurden allmâhlich enteist und durch den Iroquois-See und den Vermont-See ùberschwemmt. Um etwa 12.1 ka vereinigten sich dièse beiden Seen und bildeten einen einzigen See, der hier Candona-See genannt wird. Nachdem die Ulverton-Tingwick-Moràne geformt war, dehnte sich dieser See nach Nordosten aus bis zum Fuss der Appalachen, wo sich Warwen-Sedimente, die Candona subtriangulata enthalten, unter marinem Ton befinden. Dièse Daten und Interpretationen stellen das frùhere Konzept des Highland-Front-Morâne-Systems in Frage. Der Einbruch des Hauptbeckens oder die Phase II des Meeres von Champlain begann etwa um 12 ka. AIs der Candona-See durch das Meer ersetzt wurde, senkte sich das Wasserniveau um etwa 60 m. Die Phase III des Champlain-Meeres begann am Ende der Episode von Saint-Narcisse, um etwa 10.8 ka. Zu diesem Zeitpunkt konnten marine Wasser in die Tâler des laurentidischen Hochlands eindringen, wo sich mit Salzwasser gemischte oder frische paramarine Becken bildeten

Microstructures in phase-inversion membranes. Part I. Formation of macrovoids

A new mechanism for the formation of macrovoids in phase-inversion membranes is proposed. It is based on the observed difference in type of demixing of a thin film of a polymer solution when immersed in a nonsolvent bath: delayed or instantaneous demixing. The explanation for macrovoid formation assumes local conditions of delayed demixing in front of a certain layer of nuclei already formed, due to a change in the interfacial compositions at the advancing coagulation front, as compared to the original composition at the interface film-bath. Effects of variations in membrane formation conditions which can be calculated using the model of diffusive mass transport in thin films of polymeric solutions in combination with phase separation in phase-inversion membranes, completely support the mechanism as proposed

A representation of a compressed de Bruijn graph for pan-genome analysis that enables search

Recently, Marcus et al. (Bioinformatics 2014) proposed to use a compressed de Bruijn graph to describe the relationship between the genomes of many individuals/strains of the same or closely related species. They devised an $O(n \log g)$ time algorithm called splitMEM that constructs this graph directly (i.e., without using the uncompressed de Bruijn graph) based on a suffix tree, where $n$ is the total length of the genomes and $g$ is the length of the longest genome. In this paper, we present a construction algorithm that outperforms their algorithm in theory and in practice. Moreover, we propose a new space-efficient representation of the compressed de Bruijn graph that adds the possibility to search for a pattern (e.g. an allele - a variant form of a gene) within the pan-genome.Comment: Submitted to Algorithmica special issue of CPM201

A baseband wireless spectrum hypervisor for multiplexing concurrent OFDM signals

The next generation of wireless and mobile networks will have to handle a significant increase in traffic load compared to the current ones. This situation calls for novel ways to increase the spectral efficiency. Therefore, in this paper, we propose a wireless spectrum hypervisor architecture that abstracts a radio frequency (RF) front-end into a configurable number of virtual RF front ends. The proposed architecture has the ability to enable flexible spectrum access in existing wireless and mobile networks, which is a challenging task due to the limited spectrum programmability, i.e., the capability a system has to change the spectral properties of a given signal to fit an arbitrary frequency allocation. The proposed architecture is a non-intrusive and highly optimized wireless hypervisor that multiplexes the signals of several different and concurrent multi-carrier-based radio access technologies with numerologies that are multiple integers of one another, which are also referred in our work as radio access technologies with correlated numerology. For example, the proposed architecture can multiplex the signals of several Wi-Fi access points, several LTE base stations, several WiMAX base stations, etc. As it able to multiplex the signals of radio access technologies with correlated numerology, it can, for instance, multiplex the signals of LTE, 5G-NR and NB-IoT base stations. It abstracts a radio frequency front-end into a configurable number of virtual RF front ends, making it possible for such different technologies to share the same RF front-end and consequently reduce the costs and increasing the spectral efficiency by employing densification, once several networks share the same infrastructure or by dynamically accessing free chunks of spectrum. Therefore, the main goal of the proposed approach is to improve spectral efficiency by efficiently using vacant gaps in congested spectrum bandwidths or adopting network densification through infrastructure sharing. We demonstrate mathematically how our proposed approach works and present several simulation results proving its functionality and efficiency. Additionally, we designed and implemented an open-source and free proof of concept prototype of the proposed architecture, which can be used by researchers and developers to run experiments or extend the concept to other applications. We present several experimental results used to validate the proposed prototype. We demonstrate that the prototype can easily handle up to 12 concurrent physical layers

Le niveau marin relatif dans la région de Matane (Québec), de la déglaciation à nos jours

Dans la région de Matane, la côte a été déglacée vers 13 ka et submergée sur une largeur de 3 à 4 km par les eaux de la Mer de Goldthwait. Le front glaciaire a stationné quelque temps sur le rebord septentrional des hautes terres appalachiennes, à quelques kilomètres seulement du littoral actuel. La mer étant en contact avec le front glaciaire, il ne subsiste aucune ligne de rivage témoignant de la phase initiale de la transgression postglaciaire. L'altitude maximale observée de la Mer de Goldthwait est de 105 m, mais la mer a probablement atteint une altitude voisine de 110 m. Un vaste épandage deltaïque a été construit entre 13 et 12 ka, à la sortie de la rivière Matane. La surface supérieure de l'épandage cependant n'excède pas 80 m d'altitude. Des terrasses fluvio-glaciaires de chaque côté des versants de la vallée témoignent de son occupation tardive par une langue glaciaire se retirant vers le sud et retardant ainsi son invasion par les eaux de la Mer de Goldthwait. Des séries de plages, réparties de part et d'autre de la vallée dans la bande côtière, ont été édifiées entre 11 et 9,5 ka, entre 65 et 25 m d'altitude. La terrasse de 15 m était déjà émergée vers 8 ka. Entre 7 et 5 ka, le niveau marin relatif était au moins équivalent au niveau actuel et probablement inférieur de quelques mètres au zéro géodésique. Il a remonté entre 5 et 4 ka (transgression laurentienne) pour redescendre par la suite. Mais il a fluctué légèrement (1-2 m) de nouveau vers 3 ka avant de régresser et de construire les plages du niveau Mitis. L'âge moyen de la terrasse Mitis dans la région de Matane est de 2,2 ka. D'après les données marégraphiques de la station de Sainte-Anne-des-Monts, la côte serait soit en voie d'émersion (taux moyen de 2,2 mm/an pour la période 1970-1980), soit en voie de submersion (taux moyen de 0,55 mm/an). Actuellement l'érosion sévit un peu partout et le front du delta a reculé de plusieurs mètres entre 1950 et 1965.The Matane coastal area was deglaciated around 13 ka and submerged by the Goldthwait Sea. The area submerged was up to 3-4 km from the present coastline. The Appalachian ice front remained stationary for a while along the highland margin, a few kilometres only from the present shoreline. Because the sea was in contact with the ice front, there is no remaining shoreline of the initial phase of the postglacial submergence. The observed maximum altitude of the Goldthwait Sea is approximately 105 m, but it is most likely around 110 m. A wide delta plain was built between 13 to 12 ka at the mouth of the Matane River. The higher surface is, however, only 80 m in altitude. Ice-contact fluvioglacial terraces occurring on both sides of the Matane River valley indicate that the depression was filled by an ice tongue which retreated to the south and delayed the marine invasion within the valley. In the coastal area, flights of raised beaches, spread between 65 and 25 m in altitude and dated 11-9.5 ka, occur in the vicinity of Matane. The 15-m terrace emerged prior to 8 ka. Between 7 and 5 ka, the relative sea level (RSL) was at least similar to the present day level and most likely a few metres lower than the geodetic zero. Between 5 and 4 ka RSL rose again (Laurentian transgression) and was lowered subsequently to the present day level. A minor RSL fluctuation (1-2 m) occurred around 3 ka and, during subsequent emergence, built the Mitis terrace (beaches); this event is dated about 2 ka. According to tide gauge data for the period 1970-1980 at the Ste-Anne-des-Monts station, the shoreline is probably emerging at a mean annual rate of 2.2 mm or is possibly submerged at a mean annual rate of 0.55 mm. Presently shore erosion occurs almost everywhere in the Matane area and the delta front retreated many metres between 1950-1965.In der Gegend von Matane taute die Kuste gegen 13ka auf und wurde uber eine Breite von 3 bis 4 km von den Wassern der Goldtwaith-See uberflutet. Die glaziale Stirn blieb einige Zeit am nôrdlichen Rand der Appalachen-Hochebenen fest stehen, nur wenige Kilometer vom heutigen Kùstenstreifen entfernt. Die festgestellte maximale Hôhe der Goldtwaith-See ist 105 m, aber das Meer hat wahrscheinlich eine Hôhe von nahezu 110 m erreicht. Ein breites Aufschwem-mungsdelta wurde zwischen 13 und 12 ka angelegt, an der Mùndung des Matane-Flusses. Dessen obère Oberflâche ùbersteigt indessen nicht 80 m Hôhe. Fluvioglaziale Terrassen zu beiden Seiten der Abhânge des TaIs bezeugen, daf3 dieses spat von einer glazialen Zunge angefùllt war, die sich nach Sùden zurùckzog und so seine Anfûllung durch die Wasser der Goldtwaith-See verzôgert hat. Zwischen 11 und 9,5 ka wurden Reihen von Strànden, die sich auf beiden Seiten des TaIs auf den Kùstenstreifen verteilten, angelegt, in einer Hôhe zwischen 65 und 25 m. Die Terrasse von 15 m war schon um 8 ka aufgetaucht. Zwischen 7 und 5 ka entsprach das relative Meeresniveau mindestens dem heutigen und war wahrscheinlich einige Meter niedriger als das geodàtische Null. Es ist zwischen 5 und 4 ka wieder angestiegen (laurentidische Transgression), um dann wieder zu sinken. Aber gegen 3 ka hat es wieder leicht geschwankt (1-2 m), bevor es zurùckging und die Strànde von Mitis bildete. Das durchschnittliche Alter der Mitis-Terrasse in der Gegend von Matane ist 2,2 ka. Nach den Gezeiten-messungsdaten der Station Sainte-Anne-des-Monts soil die Kùste entweder im Auftauchen begriffen sein (durchschnittliche Rate von 2,2 mm/Jahr fur den Zeitraum von 1970-1980), oder im Untertauchen (durchschnittliche Rate von 0,55 mm/Jahr)

Native Plasmid-Encoded Mercury Resistance Genes Are Functional and Demonstrate Natural Transformation in Environmental Bacterial Isolates.

Plasmid-mediated horizontal gene transfer (HGT) is a major driver of genetic diversity in bacteria. We experimentally validated the function of a putative mercury resistance operon present on an abundant 8-kbp native plasmid found in groundwater samples without detectable levels of mercury. Phylogenetic analyses of the plasmid-encoded mercury reductases from the studied groundwater site show them to be distinct from those reported in proximal metal-contaminated sites. We synthesized the entire native plasmid and demonstrated that the plasmid was sufficient to confer functional mercury resistance in Escherichia coli Given the possibility that natural transformation is a prevalent HGT mechanism in the low-cell-density environments of groundwaters, we also assayed bacterial strains from this environment for competence. We used the native plasmid-encoded metal resistance to design a screen and identified 17 strains positive for natural transformation. We selected 2 of the positive strains along with a model bacterium to fully confirm HGT via natural transformation. From an ecological perspective, the role of the native plasmid population in providing advantageous traits combined with the microbiome's capacity to take up environmental DNA enables rapid adaptation to environmental stresses.IMPORTANCE Horizontal transfer of mobile genetic elements via natural transformation has been poorly understood in environmental microbes. Here, we confirm the functionality of a native plasmid-encoded mercury resistance operon in a model microbe and then query for the dissemination of this resistance trait via natural transformation into environmental bacterial isolates. We identified 17 strains including Gram-positive and Gram-negative bacteria to be naturally competent. These strains were able to successfully take up the plasmid DNA and obtain a clear growth advantage in the presence of mercury. Our study provides important insights into gene dissemination via natural transformation enabling rapid adaptation to dynamic stresses in groundwater environments

Phase separation processes in polymer solutions in relation to membrane formation

This review covers new experimental and theoretical physical research related to the formation of polymeric membranes by phase separation of a polymer solution, and to the morphology of these membranes. Two main phase separation processes for polymeric membrane formation are discussed: thermally induced phase separation and immersion precipitation. Special attention is paid to phase transitions like liquid-liquid demixing, crystallization, gelation, and vitrification, and their relation to membrane morphology. In addition, the mass transfer processes involved in immersion precipitation, and their influence on membrane morphology are discussed