Regional Stratigraphic Framework of Surficial Sediments and Bedrock Beneath Lake Ontario

Approximately 2550 km of single-channel high-resolution seismic reflection profiles have been interpreted and calibrated with lithological and geochronological information from four representative piston cores and one grab sample to provide a regional stratigraphie framework for the subbottom deposits of Lake Ontario. Five units overlying Paleozoic bedrock were identified and mapped. These are classified as informal units and represent, from oldest to youngest: (A) subglacial till (?) deposited by the Port Huron ice at the end of the Wisconsin glaciation; (B) an ice-marginal (?) unit confined to the western part of the lake that was probably deposited during retreat of the Port Huron ice shortly after 13 ka; (C) a regionally extensive unit of laminated glacio-lacustrine clay that accumulated until about 11 ka; (D) a weakly laminated to more massive lake clay deposited during a period of reduced water supply and rising water levels after the drawdown of the high-level glacial lakes (Iroquois and successors); and (E) modern lake clay less than 10 m thick that began accumulating around 6-8 ka with the subsequent return of upper Great Lakes drainage through the Ontario basin. Seismic reflections also define the configuration of the bedrock surface and pre-glacial stream valleys incised in the bedrock surface. Several anomalous bottom and subbottom features in the surficial sediments are mapped, such as discontinuous and offset reflections, furrows, gas pockets, and areas of large subbottom relief. None of these features appear to be spatially correlative with the diffuse seismicity that characterizes the lake area or with deeper structures such as Paleozoic bedrock faults or crustal-penetrating faults in the Precambrian basement.On a interprété et étalonné environ 2550 km de profils de sismique réflexion monocanal à haute résolution selon les données lithologiques et géochronologique de quatre sondages représentatifs faits par carottier à piston et un échantillon prélevé avec une benne afin d'établir le cadre stratigraphique des dépôts accumulés sous le fond du lac Ontario. Cinq unités recouvrant le substratum paiéozoïque ont été identifées et cartographiées. Ces unités informelles, de la plus ancienne à la plus jeune, sont : (A) un till sous-glaciaire (?) déposé par les glaces de Port Huron à la fin de la glaciation wisconsienne; (B) une unité de limite glaciaire (?) confinée à la partie ouest du lac et qui a probablement été déposée pendant le retrait des glaces de Port Huron, peu après 13 ka; (C) une unité d'étendue régionale d'argile glaciolacustre feuilletée qui s'est accumulée jusqu'à environ 11 ka; (D) une argile lacustre, de faiblement feuilletée à massive, mise en place au cours d'une période où il y eut approvisionnement en eau réduit et hausse du niveau de l'eau après l'abaissement des lacs glaciaires (Iroquois et ultérieurs); et (E) une argile lacustre moderne de moins de 10 m d'épaisseur qui a commencé à s'accumuler à partir de 6-8 ka après la reprise du drainage des Grands Lacs par le bassin Ontario. La sismique réflexion a aussi permis de délimiter la configuration de la surface du socle et des vallées pré-glaciaires qui y sont entaillées. Plusieurs éléments des sédiments de surface du fond du lac et sous le fond ont été cartographies, comme des réflexions de discontinuités et de décalages, des rainures, des poches de gaz et des zones de grandes formes enfouies. Aucun de ces éléments ne semble correspondre spatialement à la sis-micité diffuse qui caractérise la région du lac ou aux structures profondes comme les failles de substratum paiéozoïque ou celle du socle précambrien.Ungefàhr 2550 km seismischer Reflexionsprofile wurden interpretiert und kalibiriert mit lithologischen und geochronologischen Informationen von vier repràsentativen Kolbenbohrkernen und einer ausges-chùrften Probe, um den regionalen stratigraphischen Rahmen fur die unter dem Bett des Ontariosees gelegenen Ablagerungen zu erhalten. Man hat fùnf Einheiten, die das anstehende Gestein aus dem Palàozoikum ùberlagern, identifiziert und kartographiert: (A) eine subglaziale Grundmoràne (?), die durch das Eis von Port Huron am Ende der Wisconsin-Vereisung abgelagert wurde; (B) eine auf den westlichen Teil des Sees begrenzte Eisrand (?)-Einheit, die wahrs-cheinlich wàhrend des Rùckzugs des Port Huron-Eises kurz nach 13ka abgelagert wurde; (C) eine regional ausgedehnte Einheit von blâttrigem glaziallimnischem Lehm, die sien bis etwa 11 ka ansammelte, (D) ein schwachbis massivblàttriger Seelehm, der wàhrend einer Période verminderter Wasserzufuhr und steigenden Wasserspiegeln sich ansammelte; und (E) moderner Seelehm von weniger als 10 m Dicke, der sich um etwa 6-8 ka anzusammeln begann, mit der Rùckkehr der Drainage der oberen GroRen Seen durch das Ontariobecken. Seismische Reflexionen las-sen auch die Konfiguration der Sockeloberflàche und der pràglazialen in die Sockeloberflàche eingeschnittenen FluBtàler erkennen. Mehrere unregelmàfîige Grundund Untergrunderscheinungen der Oberflàchensedimente wurden kartographiert, wie Diskontinuitàt und Hôhenunschiede der Reflexionen, Mulden, Gastaschen und Gebiete mit breitem Untergrundrelief. Keine dieser Erscheinungen scheint ràumlich mit der fur das Seen-Gebiet charakteristischen Seismik zu korrelieren oder mit tieferen Strukturen, wie die Verwerfungen des anstehenden Gestems aus dem Palàozoikum order durch die Kruste dringende Verwergungen im pràkambrischen Untergrund

Characterization of cerebral microangiopathy using 3 Tesla MRI: Correlation with neurological impairment and vascular risk factors

To investigate whether clinical and neuropsychological impairment in cerebral small-vessel disease (CSVD) can be evaluated by means of morphological magnetic resonance imaging (MRI). Materials and Methods MRI at 3 Tesla in T2- and T1-weighted sequences was evaluated in 44 patients with cerebral microangiopathy, and 30 patients with combined cerebral micro- and macroangiopathy. The MR characteristics were correlated to clinical data, attentional impairment, and the patients' individual vascular risk factor profiles. Fifteen healthy age-matched control subjects participated in the study to assess MR signal changes in nonhypertensive elderly subjects. Results Patients and normal controls differed significantly in the extent of MR signal changes. A close relation between age, obesity, hypertension, and MR signal abnormalities was evident in all patients. Patients with pure CSVD additionally showed an association between their MR-defined severity of disease and their degree of neurological impairment, and their vascular risk score. In contrast, attentional impairment did not relate to the MR-defined severity of CSVD. Conclusion MR signal changes in CSVD show a close relationship to some risk factors of individual patients. J. Magn. Reson

Modified two-potential approach to tunneling problems

One-body quantum tunneling to continuum is treated via the two-potential approach, dividing the tunneling potential into external and internal parts. We show that corrections to this approach can be minimized by taking the separation radius inside the interval determined by simple expressions. The resulting two-potential approach reproduces the resonance energy and its width, both for narrow and wide resonances. We also demonstrate that, without losing its accuracy, the two-potential approach can be modified to a form resembling the R-matrix theory, yet without any uncertainties of the latter related to the choice of the matching radius.Comment: 7 two-column pages, 3 figures, extra-explanation added, Phys. Rev. A, in pres

Quantum tunneling across spin domains in a Bose-Einstein condensate

Quantum tunneling was observed in the decay of metastable spin domains in gaseous Bose-Einstein condensates. A mean-field description of the tunneling was developed and compared with measurement. The tunneling rates are a sensitive probe of the boundary between spin domains, and indicate a spin structure in the boundary between spin domains which is prohibited in the bulk fluid. These experiments were performed with optically trapped F=1 spinor Bose-Einstein condensates of sodium.Comment: 5 pages, 4 figure

Effective-field-theory approach to persistent currents

Using an effective-field-theory (nonlinear sigma model) description of interacting electrons in a disordered metal ring enclosing magnetic flux, we calculate the moments of the persistent current distribution, in terms of interacting Goldstone modes (diffusons and cooperons). At the lowest or Gaussian order we reproduce well-known results for the average current and its variance that were originally obtained using diagrammatic perturbation theory. At this level of approximation the current distribution can be shown to be strictly Gaussian. The nonlinear sigma model provides a systematic way of calculating higher-order contributions to the current moments. An explicit calculation for the average current of the first term beyond Gaussian order shows that it is small compared to the Gaussian result; an order-of-magnitude estimation indicates that the same is true for all higher-order contributions to the average current and its variance. We therefore conclude that the experimentally observed magnitude of persistent currents cannot be explained in terms of interacting diffusons and cooperons.Comment: 12 pages, no figures, final version as publishe

Concern-driven integrated approaches to nanomaterial testing and assessment - report of the NanoSafety Cluster Working Group

Abstract Bringing together topic-related European Union (EU)-funded projects, the so-called "NanoSafety Cluster" aims at identifying key areas for further research on risk assessment procedures for nanomaterials (NM). The outcome of NanoSafety Cluster Working Group 10, this commentary presents a vision for concern-driven integrated approaches for the (eco-)toxicological testing and assessment (IATA) of NM. Such approaches should start out by determining concerns, i.e., specific information needs for a given NM based on realistic exposure scenarios. Recognised concerns can be addressed in a set of tiers using standardised protocols for NM preparation and testing. Tier 1 includes determining physico-chemical properties, non-testing (e.g., structure-activity relationships) and evaluating existing data. In tier 2, a limited set of in vitro and in vivo tests are performed that can either indicate that the risk of the specific concern is sufficiently known or indicate the need for further testing, including details for such testing. Ecotoxicological testing begins with representative test organisms followed by complex test systems. After each tier, it is evaluated whether the information gained permits assessing the safety of the NM so that further testing can be waived. By effectively exploiting all available information, IATA allow accelerating the risk assessment process and reducing testing costs and animal use (in line with the 3Rs principle implemented in EU Directive 2010/63/EU). Combining material properties, exposure, biokinetics and hazard data, information gained with IATA can be used to recognise groups of NM based upon similar modes of action. Grouping of substances in return should form integral part of the IATA themselves

Respiratory function and respiratory complications in spinal cord injury: protocol for a prospective, multicentre cohort study in high-income countries

Introduction Pneumonia is one of the leading complications and causes of death after a spinal cord injury (SCI). After a cervical or thoracic lesion, impairment of the respiratory muscles decreases respiratory function, which increases the risk of respiratory complications. Pneumonia substantially reduces patient’s quality of life, may prolong inpatient rehabilitation time, increase healthcare costs or at worse, lead to early death. Respiratory function and coughing can be improved through various interventions after SCI, but the available evidence as to which as

Algebraic Bethe ansatz method for the exact calculation of energy spectra and form factors: applications to models of Bose-Einstein condensates and metallic nanograins

In this review we demonstrate how the algebraic Bethe ansatz is used for the calculation of the energy spectra and form factors (operator matrix elements in the basis of Hamiltonian eigenstates) in exactly solvable quantum systems. As examples we apply the theory to several models of current interest in the study of Bose-Einstein condensates, which have been successfully created using ultracold dilute atomic gases. The first model we introduce describes Josephson tunneling between two coupled Bose-Einstein condensates. It can be used not only for the study of tunneling between condensates of atomic gases, but for solid state Josephson junctions and coupled Cooper pair boxes. The theory is also applicable to models of atomic-molecular Bose-Einstein condensates, with two examples given and analysed. Additionally, these same two models are relevant to studies in quantum optics. Finally, we discuss the model of Bardeen, Cooper and Schrieffer in this framework, which is appropriate for systems of ultracold fermionic atomic gases, as well as being applicable for the description of superconducting correlations in metallic grains with nanoscale dimensions. In applying all of the above models to physical situations, the need for an exact analysis of small scale systems is established due to large quantum fluctuations which render mean-field approaches inaccurate.Comment: 49 pages, 1 figure, invited review for J. Phys. A., published version available at http://stacks.iop.org/JPhysA/36/R6

Statistical Mechanics of Elastica on Plane as a Model of Supercoiled DNA-Origin of the MKdV hierarchy-

In this article, I have investigated statistical mechanics of a non-stretched elastica in two dimensional space using path integral method. In the calculation, the MKdV hierarchy naturally appeared as the equations including the temperature fluctuation.I have classified the moduli of the closed elastica in heat bath and summed the Boltzmann weight with the thermalfluctuation over the moduli. Due to the bilinearity of the energy functional,I have obtained its exact partition function.By investigation of the system,I conjectured that an expectation value at a critical point of this system obeys the Painlev\'e equation of the first kind and its related equations extended by the KdV hierarchy.Furthermore I also commented onthe relation between the MKdV hierarchy and BRS transformationin this system.Comment: AMS-Tex Us