Holocene Emergence of the South and East Coasts of Melville Island, Queen Elizabeth Islands, Northwest Territories, Canada

Twenty-five radiocarbon dates from the coast of Melville Island show that there has been up to 100 m of Holocene emergence. This evidence of post-glacial rebound suggests there was significant late-Wisconsin glacier cover on or near the island. The Winter Harbour moraine on the south coast is thought to mark the maximum northward advance of the Laurentide ice. However, emergence for this area appears to be essentially complete, whereas the northeast coast is still recovering at a rate of approximately 0.35 cm/yr. Ice cover in the region to the northeast must, therefore, have been thicker and/or lasted longer than in the peripheral areas of the Laurentide ice, lending support to the concept of an Innuitian Ice Sheet, rather than local ice masses over the central Queen Elizabeth Islands. Unfortunately, there is an absence of fresh glacial landforms and stratigraphy that can be attributed to the Innuitian Ice Sheet. We suggest that this ice sheet may have had a thermal regime below the pressure melting point, thus depriving the ice of much of its erosive and depositional capabilities, but with a sufficient mass to account for the observed pattern of emergence

Sensitivity of Surface Materials and Vegetation to Disturbance in the Queen Elizabeth Islands: An Approach and Commentary

Concern about potential and actual disturbance of surface materials, vegetation and wildlife of the Queen Elizabeth Islands has risen sharply in the last few years. The purpose of this paper is to outline an approach to the problem, based on terrain studies, and to offer a commentary on the recent paper by T.A. Babb and L.C. Bliss in Arctic. … For a rational assessment of the problem, information is required on: a) surface materials - ice content, texture, engineering properties; b) topography and landforms; c) geomorphic processes; d) drainage - seasonal change and single events; e) vegetation - percentage cover and composition by species; f) summer temperatures, and moisture balance in soil; g) wildlife. … Surface materials are very significant elements of the terrain, especially when potential for disturbance is being considered. Hence, surface materials are used by the present writers as a nucleus around which other elements of the terrain are grouped. … Two of the present writers undertook in 1972 an exercise in the mapping of sensitivity at a scale of 1:500,000 of the Queen Elizabeth Islands, based primarily on bedrock maps and extensive personal communications, but found it unsatisfactory because the degree of detail was insufficient to reflect the variability in the sensitivity of the terrain. … [In evaluating the paper by Babb and Bliss, the present authors conclude that]: The overall objective of these authors in emphasizing the "susceptibility of the soils and vegetation to surface disturbance" is good. However the methods used to achieve this objective are inconsistent, and in several cases the results are inaccurate. A serious deficiency is that the criteria for determining categories of "susceptibility" are obscure. … The "Polar Desert" category is described as an area with 10% or less plant cover, low susceptibility to disturbance and low ground ice content. One interpretation of this seems to be that poorly-vegetated areas are less susceptible to disturbance of vegetation than are more densely vegetated areas. Only in so far as a low plant density lessens the probability of direct impact of vehicles on plants is this interpretation obviously true. A sparsely vegetated area may be an important, or even critical, range for ungulates; therefore the effect of disturbance of it could be great. The type of vegetation - such as willow, sedge, saxifrage, grass or bryophyte - is a vital consideration. An alternative interpretation is that unvegetated areas (90% of the Polar Desert category, classed as "soils") have a low sensitivity to surface disturbance. This is not true for some major areas of both eastern Melville Island and Western Ellesmere Island where highly sensitive surfaces, almost devoid of vegetation, are subject to extensive slope failure or thermokarst development, even without disturbance. Where the authors have left their major field of expertise and have commented on geology and geomorphology, weaknesses are evident. They appear to draw a direct relationship between active-layer soil moisture and "susceptibility". For overland travel this is generally true, but if excavation penetrates the shallow active layer and the frost table, then the relationship certainly no longer holds. Furthermore, the implication of a relationship between susceptibility, ice content and vegetation cover is simplistic and can be misleading. The assertion that "10% or more vegetation cover indicates the existence of sufficient moisture for the segregation of horizontal ice layers" is without basis. The present writers have drilled over 300 shallow (1-6 m) holes in eastern Melville Island and western Ellesmere Island to evaluate ice content and have found the relationship between vegetation, ground ice and materials to be complex. &hellip

Lyapunov exponent of many-particle systems: testing the stochastic approach

The stochastic approach to the determination of the largest Lyapunov exponent of a many-particle system is tested in the so-called mean-field XY-Hamiltonians. In weakly chaotic regimes, the stochastic approach relates the Lyapunov exponent to a few statistical properties of the Hessian matrix of the interaction, which can be calculated as suitable thermal averages. We have verified that there is a satisfactory quantitative agreement between theory and simulations in the disordered phases of the XY models, either with attractive or repulsive interactions. Part of the success of the theory is due to the possibility of predicting the shape of the required correlation functions, because this permits the calculation of correlation times as thermal averages.Comment: 11 pages including 6 figure

Proposal of an experimental scheme for realising a translucent eavesdropping on a quantum cryptographic channel

Purpose of this paper is to suggest a scheme, which can be realised with today's technology and could be used for entangling a probe to a photon qubit based on polarisation. Using this probe a translucent or a coherent eavesdropping can be performed.Comment: in pres

Decoherence in trapped ions due to polarization of the residual background gas

We investigate the mechanism of damping and heating of trapped ions associated with the polarization of the residual background gas induced by the oscillating ions themselves. Reasoning by analogy with the physics of surface electrons in liquid helium, we demonstrate that the decay of Rabi oscillations observed in experiments on 9Be+ can be attributed to the polarization phenomena investigated here. The measured sensitivity of the damping of Rabi oscillations with respect to the vibrational quantum number of a trapped ion is also predicted in our polarization model.Comment: 26 pdf pages with 5 figures, http://www.df.ufscar.br/~quantum

Evidence for the fourth P11 resonance predicted by the constituent quark model

It is pointed out that the third of five low-lying P11 states predicted by a constituent quark model can be identified with the third of four states in a solution from a three-channel analysis by the Zagreb group. This is one of the so-called ``missing'' resonances, predicted at 1880 MeV. The fit of the Zagreb group to the pi N -> eta N data is the crucial element in finding this fourth resonance in the P11 partial wave.Comment: 8 pages, revtex; expanded acknowledgement

Quantifying Entanglement Production of Quantum Operations

The problem of entanglement produced by an arbitrary operator is formulated and a related measure of entanglement production is introduced. This measure of entanglement production satisfies all properties natural for such a characteristic. A particular case is the entanglement produced by a density operator or a density matrix. The suggested measure is valid for operations over pure states as well as over mixed states, for equilibrium as well as nonequilibrium processes. Systems of arbitrary nature can be treated, described either by field operators, spin operators, or any other kind of operators, which is realized by constructing generalized density matrices. The interplay between entanglement production and phase transitions in statistical systems is analysed by the examples of Bose-Einstein condensation, superconducting transition, and magnetic transitions. The relation between the measure of entanglement production and order indices is analysed.Comment: 20 pages, Revte

Density functional study of Aun_n (n=2-20) clusters: lowest-energy structures and electronic properties

We have investigated the lowest-energy structures and electronic properties of the Au$_n$(n=2-20) clusters based on density functional theory (DFT) with local density approximation. The small Au$_n$ clusters adopt planar structures up to n=6. Tabular cage structures are preferred in the range of n=10-14 and a structural transition from tabular cage-like structure to compact near-spherical structure is found around n=15. The most stable configurations obtained for Au$_{13}$ and Au$_{19}$ clusters are amorphous instead of icosahedral or fcc-like, while the electronic density of states sensitively depend on the cluster geometry. Dramatic odd-even alternative behaviors are obtained in the relative stability, HOMO-LUMO gaps and ionization potentials of gold clusters. The size evolution of electronic properties is discussed and the theoretical ionization potentials of Au$_n$ clusters compare well with experiments.Comment: 6 pages, 7 figure

Soft-core baryon-baryon potentials for the complete baryon octet

SU(3) symmetry relations on the recently constructed hyperon-nucleon potentials are used to develop potential models for all possible baryon-baryon interaction channels. The main focus is on the interaction channels with total strangeness S=-2, -3, and -4, for which no experimental data exist yet. The potential models for these channels are based on SU(3) extensions of potential models for the S=0 and S=-1 sectors, which are fitted to experimental data. Although the SU(3) symmetry is not taken to be exact, the S=0 and S=-1 sectors still provide the necessary constraints to fix all free parameters. The potentials for the S=-2, -3, and -4 sectors, therefore, do not contain any additional free parameters, which makes them the first models of this kind. Various properties of the potentials are illustrated by giving results for scattering lengths, bound states, and total cross sections.Comment: 22 pages RevTex, 6 postscript figure

Poly(allylamine) magnetomicelles for image guided drug delivery.

Polymeric micelles have received considerable interest for their use as drug delivery vehicles for hydrophobic drug solubilisation. Inorganic metallic nanoparticles have already been exploited clinically in diagnostics for their contrast ability, using magnetic resonance imaging. The combination of these two platforms results in a multifunctional drug carrier for image-guided drug delivery. Here we report the synthesis and evaluation of a new class of poly(allylamine) (PAA) polymer grafted with hydrophobic oxadiazole (Ox) pendant group in a 5% molar monomer: pendant ratio. Further, the thiol-containing pendant group facilitated the attachment of hybrid iron oxide-gold nanoparticles (HNPs) via dative covalent bonding. Physicochemical characterisation of both PAA-Ox5 and PAA-Ox5-HNP polymers was carried out using elemental analysis, nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy (FTIR) and photon correlation spectroscopy (PCS). The drug loading potential of these novel aggregates was investigated, through direct conjugation of hydrophilic and encapsulation of hydrophobic drugs, respectively. The model hydrophobic drugs 2,6- diisopropylphenol (propofol) and (2S,6'R)-7-chloro-2',4,6-trimethoxy-6'-methyl-3H,4'H-spiro[1-benzofuran-2,1'- cyclohex[2]ene]-3,4'-dione (griseofulvin), and the chemotherapeutic agents bisnapthalamidopropyldiaminooctane (BNIPDaoct) and 6-Thioguanine (6-TG) were used. The data showed that the addition of HNPs onto the PAA-Ox5 structure resulted in aggregates of 175 nm in diameter. The PAA-Ox5-HNP nano-aggregates were capable of high drug solubilisation capacities (25.79 mgmL-1, 1.68 mgmL-1 and 0.92 mgmL-1) for propofol, griseofulvin and BNIPDaoct, respectively. 6-TG was also successfully conjugated into the polymer structure (2.8 mgmL-1). In vitro assays on human pancreatic adenocarcinoma cells (BxPC-3) showed increased drug uptake and decreased IC50 values using the novel formulations compared with free drug. This study highlights the potential of PAA-Ox5-HNP as a bi-functional imaging and drug delivery platform