On the generation of internal waves by tidal flow over a sill----a possible nonlinear mechanism

The generation of internal waves in a two layer tidal channel containing a sill is considered. The distorted free surface associated with the locally accelerated tidal flow in the vicinity of the sill is assumed to be the driving force for internal waves. A simplified, nonrigorous model, which incorporates this forcing mechanism, is developed and predicts that internal waves should be generated at twice the tidal frequency as well as at the tidal frequency...

Physical Electronics

Contains research objectives and reports on one research project

A Review of Scanning Tunneling Microscope and Atomic Force Microscope Imaging of Large Biological Structures: Problems and Prospects

The application of the scanning tunneling microscope (STM) and the atomic force microscope (AFM) to the study of small biological molecules, such as DNA and smaller molecules, has received considerable attention in the literature. This paper reviews STM and AFM studies of larger biological structures such as bacterial membranes, bacteriophages, viruses, antibodies, etc. The problems encountered in these applications are emphasized, with particular reference to the unknown conduction mechanism, tip-sample interaction forces, and tip-sample convolution artifacts in the images. The latter problem is illustrated by new results from IgG antibody complexes attached to a bacterial sheath layer. A new conduction mechanism involving a graphite film overlayer is suggested. The future prospects are discussed, with emphasis on the unique capabilities of these microscopes compared to conventional electron microscopes

A Density Matrix-based Algorithm for Solving Eigenvalue Problems

A new numerical algorithm for solving the symmetric eigenvalue problem is presented. The technique deviates fundamentally from the traditional Krylov subspace iteration based techniques (Arnoldi and Lanczos algorithms) or other Davidson-Jacobi techniques, and takes its inspiration from the contour integration and density matrix representation in quantum mechanics. It will be shown that this new algorithm - named FEAST - exhibits high efficiency, robustness, accuracy and scalability on parallel architectures. Examples from electronic structure calculations of Carbon nanotubes (CNT) are presented, and numerical performances and capabilities are discussed.Comment: 7 pages, 3 figure

A New Atomic Force Microscopy Technique for the Measurement of the Elastic Properties of Biological Materials

We developed a new technique to measure elastic properties by using the atomic force microscope (AFM) tip to press samples into grooves etched in a GaAs substrate. We measured the Young\u27s modulus of β-chitin fibres with cross-sections less than 40 nm X 20 nm to be 1-2 X 1011 N/m2. In the isotropic approximation, the Young\u27s modulus of the S-layer sheath of the archaeobacterium Methanospirillum hungatei was 1-3 X 1010 N/m2. By testing the sheath to breaking strength we estimated the bacterium can sustain an internal pressure as high as 100-200 atmospheres (1-2 x 107 N/m2)

Direct Observation by Scanning Tunneling Microscopy of the Two-Dimensional Lattice Structure of the S-Layer Sheath of the Archaeobacterium Methanospirillum hungatei GP1

Observation of the two-dimensional (2-D) 3 nm x 3 nm lattice structure of the S-layer sheath of the archaeobacterium Methanospirillum hungatei is reported for the first time by scanning tunneling microscopy. The samples consisted of sheath fragments deposited on a TaSe2 substrate and coated with a Pt/Ir film. In addition to confirming the 2-D structure, the images reveal some new information about the nano-scale details of the sheath structure. A lateral resolution of 1 nm was achieved, suggesting that the grain size of the Pt/Ir films was much less than for similar films deposited on a smooth metal surface

R-matrix Floquet theory for laser-assisted electron-atom scattering

A new version of the R-matrix Floquet theory for laser-assisted electron-atom scattering is presented. The theory is non-perturbative and applicable to a non-relativistic many-electron atom or ion in a homogeneous linearly polarized field. It is based on the use of channel functions built from field-dressed target states, which greatly simplifies the general formalism.Comment: 18 pages, LaTeX2e, submitted to J.Phys.

Association of acute myeloid leukemias most immature phenotype with risk groups and outcomes

The precise phenotype and biology of acute myeloid leukemia stem cells remain controversial, in part because the “gold standard” immunodeficient mouse engraftment assay fails in a significant fraction of patients and identifies multiple cell-types in others. We sought to analyze the clinical utility of a novel assay for putative leukemia stem cells in a large prospective cohort. The leukemic clone’s most primitive hematopoietic cellular phenotype was prospectively identified in 109 newly-diagnosed acute myeloid leukemia patients, and analyzed against clinical risk groups and outcomes. Most (80/109) patients harbored CD34+CD38− leukemia cells. The CD34+CD38− leukemia cells in 47 of the 80 patients displayed intermediate aldehyde dehydrogenase expression, while normal CD34+CD38− hematopoietic stem cells expressed high levels of aldehyde dehydrogenase. In the other 33/80 patients, the CD34+CD38− leukemia cells exhibited high aldehyde dehydrogenase activity, and most (28/33, 85%) harbored poor-risk cytogenetics or FMS-like tyrosine kinase 3 internal tandem translocations. No CD34+ leukemia cells could be detected in 28/109 patients, including 14/21 patients with nucleophosmin-1 mutations and 6/7 acute promyelocytic leukemia patients. The patients with CD34+CD38− leukemia cells with high aldehyde dehydrogenase activity manifested a significantly lower complete remission rate, as well as poorer event-free and overall survivals. The leukemic clone’s most immature phenotype was heterogeneous with respect to CD34, CD38, and ALDH expression, but correlated with acute myeloid leukemia risk groups and outcomes. The strong clinical correlations suggest that the most immature phenotype detectable in the leukemia might serve as a biomarker for “clinically-relevant” leukemia stem cells. ClinicalTrials.gov: {"type":"clinical-trial","attrs":{"text":"NCT01349972","term_id":"NCT01349972"}}NCT01349972

Modern and fossil non-pollen palynomorphs from the Basque mountains (western Pyrenees, France): the use of coprophilous fungi to reconstruct pastoral activity

International audienceThis paper presents results from a modern dataset of non-pollen palynomorphs and its application to aca. 2,000 year peat record from the same area in the western Pyrenees (Basque Country, France). The modern dataset is composed of 35 surface samples (moss polsters) from a mountainous pasture-woodland landscape. Airborne fungal spores (ascospores and conidia), found dominant in the dataset, are linked to the degree of landscape openness and grazing pressure. The complete spectrum of 13 selected spore-types of dung-related Ascomycetes is positively linked with grazing pressure. However, different dung affinities between the spore-types have been identified. These are types clearly related to high grazing pressure and types with no or unclear dung indicative value. The modern dataset is used to aid interpretation of the local fossil pollen record as an independent 'proxy' to assess past pastoral dynamics. This study confirms the utility of modern nonpollen palynomorphs from terrestrial ecosystems in the reconstruction of historical local pastoral activities but also shows their limitation. It may be necessary to extend such study to wetland ecosystems and to investigate the spatial dimension of some fungal spores