1,995 research outputs found
Mathieu beams as versatile light moulds for 3D micro particle assemblies
We present tailoring of three dimensional light fields which act as light moulds for elaborate particle micro structures of variable shapes. Stereo microscopy is used for visualization of the 3D particle assemblies. The powerful method is demonstrated for the class of propagation invariant beams, where we introduce the use of Mathieu beams as light moulds with non-rotationally-symmetric structure. They offer multifarious field distributions and facilitate the creation of versatile particle structures. This general technique may find its application in micro fluidics, chemistry, biology, and medicine, to create highly efficient mixing tools, for hierarchical supramolecular organization or in 3D tissue engineering
Synthesis of perfluorinated polyethers
A series of highly fluorinated acetylenes was prepared and their cyclization reactions were studied. A series of perfluoropolytriazines with -CF2I pendent groups were prepared. These materials can be cured thermally or photochemically to an elastomeric gum. Perfluoropolytriazines with -CN pendent groups were prepared. These materials can be crosslinked by reaction with terephthalonitrile oxide
Mammographic image restoration using maximum entropy deconvolution
An image restoration approach based on a Bayesian maximum entropy method
(MEM) has been applied to a radiological image deconvolution problem, that of
reduction of geometric blurring in magnification mammography. The aim of the
work is to demonstrate an improvement in image spatial resolution in realistic
noisy radiological images with no associated penalty in terms of reduction in
the signal-to-noise ratio perceived by the observer. Images of the TORMAM
mammographic image quality phantom were recorded using the standard
magnification settings of 1.8 magnification/fine focus and also at 1.8
magnification/broad focus and 3.0 magnification/fine focus; the latter two
arrangements would normally give rise to unacceptable geometric blurring.
Measured point-spread functions were used in conjunction with the MEM image
processing to de-blur these images. The results are presented as comparative
images of phantom test features and as observer scores for the raw and
processed images. Visualization of high resolution features and the total image
scores for the test phantom were improved by the application of the MEM
processing. It is argued that this successful demonstration of image
de-blurring in noisy radiological images offers the possibility of weakening
the link between focal spot size and geometric blurring in radiology, thus
opening up new approaches to system optimization.Comment: 18 pages, 10 figure
Topological phase for spin-orbit transformations on a laser beam
We investigate the topological phase associated with the double connectedness
of the SO(3) representation in terms of maximally entangled states. An
experimental demonstration is provided in the context of polarization and
spatial mode transformations of a laser beam carrying orbital angular momentum.
The topological phase is evidenced through interferometric measurements and a
quantitative relationship between the concurrence and the fringes visibility is
derived. Both the quantum and the classical regimes were investigated.Comment: 4 pages, 4 figure
Hypusinated eIF5A is expressed in the pancreas and spleen of individuals with type 1 and type 2 diabetes
The gene encoding eukaryotic initiation factor 5A (EIF5A) is found in diabetes-susceptibility loci in mouse and human. eIF5A is the only protein known to contain hypusine (hydroxyputrescine lysine), a polyamine-derived amino acid formed post-translationally in a reaction catalyzed by deoxyhypusine synthase (DHPS). Previous studies showed pharmacologic blockade of DHPS in type 1 diabetic NOD mice and type 2 diabetic db/db mice improved glucose tolerance and preserved beta cell mass, which suggests that hypusinated eIF5A (eIF5AHyp) may play a role in diabetes pathogenesis by direct action on the beta cells and/or altering the adaptive or innate immune responses. To translate these findings to human, we examined tissue from individuals with and without type 1 and type 2 diabetes to determine the expression of eIF5AHyp. We detected eIF5AHyp in beta cells, exocrine cells and immune cells; however, there was also unexpected enrichment of eIF5AHyp in pancreatic polypeptide-expressing PP cells. Interestingly, the presence of eIF5AHyp co-expressing PP cells was not enhanced with disease. These data identify new aspects of eIF5A biology and highlight the need to examine human tissue to understand disease
Mini-Survey Of SDSS of [OIII] AGN With Swift
The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work (e.g. Ferrarese and Merritt 2000) strongly suggests every massive galaxy has a central black hole. However, most of these objects either are not radiating or have been very difficult to detect. We are now in the era of large surveys, and the luminosity function (LF) of AGN has been estimated in various ways. In the X-ray band, Chandra and XMM surveys (e.g., Barger et al. 2005; Hasinger, et al. 2005) have revealed that the LF of Hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(x) (at al z). This is seen for all types of AGN, but is stronger for the broad-line objects (e.g., Steffen et al. 2004). In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects (Hao et al. 2005). If, as been suggested, hard X-ray and optical emission line can both be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs
Spitzer Space Telescope Spectroscopy of Ices toward Low-Mass Embedded Protostars
Sensitive 5-38 μm Spitzer Space Telescope and ground-based 3-5 μm spectra of the embedded low-mass protostars B5 IRS1 and HH 46 IRS show deep ice absorption bands superposed on steeply rising mid-infrared continua. The ices likely originate in the circumstellar envelopes. The CO_2 bending mode at 15 μm is a particularly powerful tracer of the ice composition and processing history. Toward these protostars, this band shows little evidence for thermal processing at temperatures above 50 K. Signatures of lower temperature processing are present in the CO and OCN^- bands, however. The observed CO2 profile indicates an intimate mixture with H_(2)O, but not necessarily with CH_(3)OH, in contrast to some high-mass protostars. This is consistent with the low CH_(3)OH abundance derived from the ground-based L-band spectra. The CO_2 : H_(2)O column density ratios are high in both B5 IRS1 and HH 46 IRS (~35%). Clearly, the Spitzer spectra are essential for studying ice evolution in low-mass protostellar environments and for eventually determining the relation between interstellar and solar system ices
Video recording true single-photon double-slit interference
As normally used, no commercially available camera has a low-enough dark
noise to directly produce video recordings of double-slit interference at the
photon-by-photon level, because readout noise significantly contaminates or
overwhelms the signal. In this work, noise levels are significantly reduced by
turning on the camera only when the presence of a photon has been heralded by
the arrival, at an independent detector, of a time-correlated photon produced
via parametric down-conversion. This triggering scheme provides the improvement
required for direct video imaging of Young's double-slit experiment with single
photons, allowing clarified versions of this foundational demonstration.
Further, we introduce variations on this experiment aimed at promoting
discussion of the role spatial coherence plays in such a measurement. We also
emphasize complementary aspects of single-photon measurement, where imaging
yields (transverse) position information, while diffraction yields the
transverse momentum, and highlight the roles of transverse position and
momentum correlations between down-converted photons, including examples of
"ghost" imaging and diffraction. The videos can be accessed at
http://sun.iwu.edu/~gspaldin/SinglePhotonVideos.html online.Comment: 7 pages, 8 figure
On Exchange of Orbital Angular Momentum Between Twisted Photons and Atomic Electrons
We obtain an expression for the matrix element for a twisted
(Laguerre-Gaussian profile) photon scattering from a hydrogen atom. We consider
photons incoming with an orbital angular momentum (OAM) of ,
carried by a factor of not present in a plane-wave or pure
Gaussian profile beam. The nature of the transfer of units of OAM from
the photon to the azimuthal atomic quantum number of the atom is investigated.
We obtain simple formulae for these OAM flip transitions for elastic forward
scattering of twisted photons when the photon wavelength is large
compared with the atomic target size , and small compared the Rayleigh range
, which characterizes the collimation length of the twisted photon beam.Comment: 16 page
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