1,197 research outputs found
Spectral triangulation molecular contrast optical coherence tomography with indocyanine green as the contrast agent
We report a new molecular contrast optical coherence tomography (MCOCT) implementation that profiles the contrast agent distribution in a sample by measuring the agent's spectral differential absorption. The method, spectra triangulation MCOCT, can effectively suppress contributions from spectrally dependent scatterings from the sample without a priori knowledge of the scattering properties. We demonstrate molecular imaging with this new MCOCT modality by mapping the distribution of indocyanine green, a FDA-approved infrared red dye, within a stage 54 Xenopus laevis
Endogenous glutathione levels modulate the frequency of both spontaneous and long wavelength ultraviolet induced mutations in human cells
Spontaneous and induced mutations at the hypoxanthine guanine phosphoribosyt transferase locus have been measured in cultured human lymphoblastoid (TK6) cell populations under conditions in which cellular glutathione has been severely depleted by overnight treatment with buthionine-S,R-sulfoximine. At maximum levels of glutathione depletion, the increase in spontaneous frequency is at least 5-fold, a finding consistent with the possibility that cellular redox state can modulate the levels of pre-mutagenic damage arising as a result of normal metabolism in cultured human cells. Glutathione depletion does not lead to a significant enhancement in the frequency of mutants that arise as a result of irradiation at 313 run but does lead to a 3-fold increase in mutations resulting from irradiation at 365 nm. These results indicate that glutathione may quench reactive intermediates that would otherwise lead to spontaneous mutations as well as a fraction of UVA radiation-induced premutagenic damag
In-Process Radiography of ARC Weld
In-process nondestructive evaluation of welds is of major importance for automated weld processing. Real-time evaluation of defect formation makes possible on-line rewelding and adjustment of process parameters. Measurements of physical parameters related to weld quality may also give information important for understanding the weld process and for improvements of weld quality. In this study we implement industrial radiography for real-time weld process monitoring and testing. X-ray penetrating radiation is used for volume observation in the welding pool and the heat-affected zone during the weld process. The advantages of such a technique are on-line testing of defect formation in the weld and the study of metal fusion and filler metal-base metal interaction, metal transfer and mass flow in the welding pool. This technique may also be used for post-service real-time remote testing of weld quality. By integrating automatic nondestructive inspection with an automatic process control system, unified manufacturing control and testing procedures can be developed. In this unit approach, the nondestructive system may be included as a part of the sensing system in the feedback loop of the process control. Research and development of such general concepts for remote weld process control using real-time radiography as a vision system was initiated in our laboratory under the sponsorship of the Edison Welding Institute
Cosmology and astrophysics from relaxed galaxy clusters - IV: Robustly calibrating hydrostatic masses with weak lensing
This is the fourth in a series of papers studying the astrophysics and
cosmology of massive, dynamically relaxed galaxy clusters. Here, we use
measurements of weak gravitational lensing from the Weighing the Giants project
to calibrate Chandra X-ray measurements of total mass that rely on the
assumption of hydrostatic equilibrium. This comparison of X-ray and lensing
masses provides a measurement of the combined bias of X-ray hydrostatic masses
due to both astrophysical and instrumental sources. Assuming a fixed cosmology,
and within a characteristic radius (r_2500) determined from the X-ray data, we
measure a lensing to X-ray mass ratio of 0.96 +/- 9% (stat) +/- 9% (sys). We
find no significant trends of this ratio with mass, redshift or the
morphological indicators used to select the sample. In accordance with
predictions from hydro simulations for the most massive, relaxed clusters, our
results disfavor strong, tens-of-percent departures from hydrostatic
equilibrium at these radii. In addition, we find a mean concentration of the
sample measured from lensing data of c_200 = . Anticipated
short-term improvements in lensing systematics, and a modest expansion of the
relaxed lensing sample, can easily increase the measurement precision by
30--50%, leading to similar improvements in cosmological constraints that
employ X-ray hydrostatic mass estimates, such as on Omega_m from the cluster
gas mass fraction.Comment: 13 pages. Submitted to MNRAS. Comments welcom
Distance-Based Habitat Associations of Northern Bobwhites in a Fescue-Dominated Landscape in Kansas
Northern bobwhites (Colinus virginianus) have a wide distribution across North America which influences its’ associations with habitats in a variety of landscapes. We used radio-marked bobwhites and Euclidean distance to characterize land cover associations of bobwhites at generalized level 1 and specific level 2 land cover classifications during the reproductive (15 Apr-14 Oct) and covey (15 Oct-14 Apr) periods in southeastern Kansas from 2003 to 2005. Habitat associations occurred during the reproductive (Wilkes’ k 1⁄4 0.04, F6,36 1⁄4 143.682, P , 0.001) and covey (Wilkes’ k 1⁄4 0.056, F6, 29 1⁄4 81.99, P , 0.001) periods. Ranking of the reproductive period habitats indicated bobwhites preferred locations in close proximity to fescue (Festuca spp.) over all other habitats. Coveys preferred locations in close proximity to woody cover. Bobwhites were found to associate with specific habitats at the level 2 land cover classification during the reproductive (Wilkes’ k 1⁄4 0.006, F16, 26 1⁄4 284.483, P , 0.001) and covey (Wilkes’ k 1⁄4 0.004, F16, 19 1⁄4 276.037, P , 0.001) periods. Bobwhites preferred locations in close proximity to fescue pastures and roads equally over all other habitats during the reproductive period. Coveys preferred locations in close proximity to roads and Conservation Reserve Program lands during the covey period. Fescue pastures may be avoided by bobwhites during the covey period, provided adequate cover is not provided, but bobwhites are strongly associated with them during the reproductive period because they meet nesting and brooding needs not met by other habitats
Packing While Traveling: Mixed Integer Programming for a Class of Nonlinear Knapsack Problems
Packing and vehicle routing problems play an important role in the area of
supply chain management. In this paper, we introduce a non-linear knapsack
problem that occurs when packing items along a fixed route and taking into
account travel time. We investigate constrained and unconstrained versions of
the problem and show that both are NP-hard. In order to solve the problems, we
provide a pre-processing scheme as well as exact and approximate mixed integer
programming (MIP) solutions. Our experimental results show the effectiveness of
the MIP solutions and in particular point out that the approximate MIP approach
often leads to near optimal results within far less computation time than the
exact approach
Three-dimensional relationship between high-order root-mean-square wavefront error, pupil diameter, and aging
We report root-mean-square (RMS) wavefront error (WFE) for individual aberrations and cumulative highorder
(HO) RMS WFE for the normal human eye as a function of age by decade and pupil diameter in 1 mm
steps from 3 to 7 mm and determine the relationship among HO RMS WFE, mean age for each decade of life,
and luminance for physiologic pupil diameters. Subjects included 146 healthy individuals from 20 to 80 years
of age. Ocular aberration was measured on the preferred eye of each subject (for a total of 146 eyes through
dilated pupils; computed for 3, 4, 5, 6, and 7 mm pupils; and described with a tenth-radial-order normalized
Zernike expansion. We found that HO RMS WFE increases faster with increasing pupil diameter for any given
age and pupil diameter than it does with increasing age alone. A planar function accounts for 99% of the variance
in the 3-D space defined by mean log HO RMS WFE, mean age for each decade of life, and pupil diameter.
When physiologic pupil diameters are used to estimate HO RMS WFE as a function of luminance and age, at
low luminance 9 cd/m2 HO RMS WFE decreases with increasing age. This normative data set details (1) the
3-D relationship between HO RMS WFE and age for fixed pupil diameters and (2) the 3-D relationship among
HO RMS WFE, age, and luminance for physiologic pupil diameters
Electroweak baryogenesis induced by a scalar field
A cosmological pseudoscalar field coupled to hypercharge topological number
density can exponentially amplify hyperelectric and hypermagnetic fields while
coherently rolling or oscillating, leading to the formation of a time-dependent
condensate of topological number density. The topological condensate can be
converted, under certain conditions, into baryons in sufficient quantity to
explain the observed baryon asymmetry in the universe. The amplified
hypermagnetic field can perhaps sufficiently strengthen the electroweak phase
transition, and by doing so, save any pre-existing baryon number asymmetry from
extinction.Comment: 8 pages, 4 figure
Filamented Light (FLight) Biofabrication of Highly Aligned Tissue-Engineered Constructs.
Cell-laden hydrogels used in tissue engineering generally lack sufficient 3D topographical guidance for cells to mature into aligned tissues. A new strategy called filamented light (FLight) biofabrication rapidly creates hydrogels composed of unidirectional microfilament networks, with diameters on the length scale of single cells. Due to optical modulation instability, a light beam is divided optically into FLight beams. Local polymerization of a photoactive resin is triggered, leading to local increase in refractive index, which itself creates self-focusing waveguides and further polymerization of photoresin into long hydrogel microfilaments. Diameter and spacing of the microfilaments can be tuned from 2 to 30 µm by changing the coherence length of the light beam. Microfilaments show outstanding cell instructive properties with fibroblasts, tenocytes, endothelial cells, and myoblasts, influencing cell alignment, nuclear deformation, and extracellular matrix deposition. FLight is compatible with multiple types of photoresins and allows for biofabrication of centimeter-scale hydrogel constructs with excellent cell viability within seconds (<10 s per construct). Multidirectional microfilaments are achievable within a single hydrogel construct by changing the direction of FLight projection, and complex multimaterial/multicellular tissue-engineered constructs are possible by sequentially exchanging the cell-laden photoresin. FLight offers a transformational approach to developing anisotropic tissues using photo-crosslinkable biomaterials
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