Biomedical subjects

M Jeppesen

Publications and source records attributed to M Jeppesen.

4 recordsLinked to original sources

PubMed2006

Achieving peak brightness in an atom laser.

In this Letter we present experimental results and a simple analytic theory on the first continuous (long pulse) Raman atom laser. We analyze the flux and brightness of a generic two state atom laser with an analytic model that shows excellent agreement with our experiments. We show that, for the same source size, the brightness achievable with a Raman atom laser is at least 3 orders of magnitude greater than achievable in any other demonstrated continuously outcoupled atom laser.

Journal Article↗

PubMed2006

Blue five-level frequency-upconversion system in rubidium.

We demonstrate production of continuous coherent blue laser light by using a five-level system in rubidium vapor. Two low-power lasers, at 780 and 776 nm, induce strong atomic coherence in the 5S-5P-5D states. The atoms decay to the 6P excited state, from which stimulated emission produces a coherent blue (420 nm) beam. We have coupled both ground-state hyperfine levels, effecting coherence between four levels. The coherent blue output is enhanced by several mechanisms, including stronger coupling to a larger fraction of the atomic population, operation at a detuning such that the vapor is nominally transparent to the 780 nm pump field, reduced losses owing to optical pumping, and optimal phase matching. We report experimental findings and compare them with results from a semiclassical Maxwell-Bloch model.

Journal Article↗

PubMed2000

Splenocytes cultured in low concentrations of IL-2 generate NK cell specificities toward syngenic and allogenic targets.

Splenocytes cultured in the presence of 30-60 units/ml IL-2 for 5 days develop natural killer activity toward syngeneic and allogeneic tumor cell targets. The IL-2 activated splenocytes, themselves, are partially resistant, whereas concanavalin A-activated T blast cells are completely resistant to killing. Surprisingly, major histocompatibility complex (MHC)-I-negative target cells are also resistant to natural killer (NK)-cell-mediated killing. Cells resistant to killing were unable to block NK-cell-mediated killing of sensitive targets as judged from cold target cell inhibition experiments, and one type of target cells sensitive to killing did generally not cross-block killing of other killing-sensitive target cell types. Alloantigen exposure of splenocytes, i.e., one-way mixed lymphocyte cultures, partially prevents the development of NK-cell activity. Our data suggest that target structures which trigger killing activity of NK cells are determined by the phenotype of the target cell and are dependent on its MHC class I expression disregarding the haplotype of the cell.

Animals↗

PubMed1993

Bristle end-rounding in children's toothbrushes: a comparative study.

Animal and clinical studies have shown that sharp, unpolished toothbrush bristles can injure gingival tissues and that substantial variation exists in the degree of end-roundness of commercially available toothbrushes. In this study, eight brands of children's toothbrushes were assessed for their relative potential to cause oral tissue injury based upon the degree of end-roundness of their bristles. The brands studied were: Blend-a-dent Jr., Butler GUM Jr., Colgate Plus Jr., Johnson & Johnson Prevent Jr., Johnson & Johnson Reach Child, Lever Bros. Disney, Oral-B P20, and Sensodyne Jr. Brushes were ranked on the basis of three criteria: the percentage of bristles with sharp ends (89% roundness or less), the percentage of bristles with smooth edges (96% roundness or greater), and the average roundness of bristle ends. The Oral-B P20 brush had significantly more (p < 0.05) bristles with a roundness of 96% or greater; it also was in the group having the lowest number of bristles with sharp edges and had the highest average roundness. Based on these criteria, the Oral-B P20 showed the least potential for oral tissue damage, whereas the Johnson & Johnson Reach Child and Butler GUM Jr. showed the most potential for tissue injury. The other brands investigated were intermediate in end-rounding values and damage potential.

Child↗