225 research outputs found
Fluorescence kinetics of flavin adenine dinucleotide in different microenvironments
Fluorescence kinetics of flavin adenine dinucleotide was measured in a wide time and spectral range in different media, affecting its intra- end extramolecular interactions, and analyzed by a new method based on compressed sensing
Encodings of Range Maximum-Sum Segment Queries and Applications
Given an array A containing arbitrary (positive and negative) numbers, we
consider the problem of supporting range maximum-sum segment queries on A:
i.e., given an arbitrary range [i,j], return the subrange [i' ,j' ] \subseteq
[i,j] such that the sum of the numbers in A[i'..j'] is maximized. Chen and Chao
[Disc. App. Math. 2007] presented a data structure for this problem that
occupies {\Theta}(n) words, can be constructed in {\Theta}(n) time, and
supports queries in {\Theta}(1) time. Our first result is that if only the
indices [i',j'] are desired (rather than the maximum sum achieved in that
subrange), then it is possible to reduce the space to {\Theta}(n) bits,
regardless the numbers stored in A, while retaining the same construction and
query time. We also improve the best known space lower bound for any data
structure that supports range maximum-sum segment queries from n bits to
1.89113n - {\Theta}(lg n) bits, for sufficiently large values of n. Finally, we
provide a new application of this data structure which simplifies a previously
known linear time algorithm for finding k-covers: i.e., given an array A of n
numbers and a number k, find k disjoint subranges [i_1 ,j_1 ],...,[i_k ,j_k ],
such that the total sum of all the numbers in the subranges is maximized.Comment: 19 pages + 2 page appendix, 4 figures. A shortened version of this
paper will appear in CPM 201
Study of shock waves generation, hot electron production and role of parametric instabilities in an intensity regime relevant for the shock ignition
We present experimental results at intensities relevant to Shock Ignition
obtained at the sub-ns Prague Asterix Laser System in 2012 . We studied shock waves
produced by laser-matter interaction in presence of a pre-plasma. We used a first beam at
1ω (1315 nm) at 7 × 10 13 W/cm 2 to create a pre-plasma on the front side of the target and
a second at 3ω (438 nm) at ∼ 10 16 W/cm 2 to create the shock wave. Multilayer targets
composed of 25 (or 40 μm) of plastic (doped with Cl), 5 μm of Cu (for Kα diagnostics)
and 20 μm of Al for shock measurement were used. We used X-ray spectroscopy of Cl
to evaluate the plasma temperature, Kα imaging and spectroscopy to evaluate spatial and
spectral properties of the fast electrons and a streak camera for shock breakout measurements.
Parametric instabilities (Stimulated Raman Scattering, Stimulated Brillouin Scattering and
Two Plasmon Decay) were studied by collecting the back scattered light and analysing its
spectrum. Back scattered energy was measured with calorimeters. To evaluate the maximum
pressure reached in our experiment we performed hydro simulations with CHIC and DUED
codes. The maximum shock pressure generated in our experiment at the front side of the
target during laser-interaction is 90 Mbar. The conversion efficiency into hot electrons was
estimated to be of the order of ∼ 0.1% and their mean energy in the order ∼50 keV.
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributio
Contribution to understanding the mathematical structure of quantum mechanics
Probabilistic description of results of measurements and its consequences for
understanding quantum mechanics are discussed. It is shown that the basic
mathematical structure of quantum mechanics like the probability amplitudes,
Born rule, commutation and uncertainty relations, probability density current,
momentum operator, rules for including the scalar and vector potentials and
antiparticles can be obtained from the probabilistic description of results of
measurement of the space coordinates and time. Equations of motion of quantum
mechanics, the Klein-Gordon equation, Schrodinger equation and Dirac equation
are obtained from the requirement of the relativistic invariance of the
space-time Fisher information. The limit case of the delta-like probability
densities leads to the Hamilton-Jacobi equation of classical mechanics. Many
particle systems and the postulates of quantum mechanics are also discussed.Comment: 21 page
X-ray microscopy of living multicellular organisms with the Prague Asterix Iodine Laser System
Soft X-ray contact microscopy (SXCM) experiments have been performed
using the Prague Asterix Iodine Laser System (PALS). Laser wavelength
and pulse duration were λ = 1.314 μm and τ (FWHM) = 450 ps,
respectively. Pulsed X rays were generated using teflon, gold, and
molybdenum targets with laser intensities I ≥
1014 W/cm2. Experiments have been performed
on the nematodes Caenorhabditis elegans. Images were recorded
on PMMA photo resists and analyzed using an atomic force microscope
operating in contact mode. Our preliminary results indicate the
suitability of the SXCM for multicellular specimens
Shock pressure induced by 0.44 [mu]m laser radiation on aluminum targets
Shock pressure generated in aluminum targets due to the interaction
of 0.44 μm (3 ω of iodine laser) laser radiation has been
studied. The laser intensity profile was smoothed using phase zone
plates. Aluminum step targets were irradiated at an intensity
I ≈ 1014 W/cm2. Shock velocity in
the aluminum target was estimated by detecting the shock luminosity
from the target rear using a streak camera to infer the shock pressure.
Experimental results show a good agreement with the theoretical model
based on the delocalized laser absorption approximation. In the present
report, we explicitly discuss the importance of target thickness on the
shock pressure scaling
Fundamental limitations of LIGA x-ray lithography: sidewall offset, slope and minimum feature size
Human Health Risk Assessment For Arsenic: A Critical Review
Millions of people are exposed to arsenic resulting in a range of health implications.This paper provides an up-to-date review of the different sources of arsenic (water, soil and food), indicators of human exposure (biomarker assessment of hair, nail, urine and blood), epidemiological and toxicological studies on carcinogenic and non-carcinogenic health outcomes, and risk assessment approaches. The review demonstrates a need for more work evaluating the risks of different arsenic species such as; arsenate, arsenite monomethylarsonic acid, monomethylarsonous acid, dimethylarsinic acid and dimethylarsinous acid as well as a need to better integrate the different exposure sources in risk assessments
Two-Photon Microscopy for Non-Invasive, Quantitative Monitoring of Stem Cell Differentiation
BACKGROUND: The engineering of functional tissues is a complex multi-stage process, the success of which depends on the careful control of culture conditions and ultimately tissue maturation. To enable the efficient optimization of tissue development protocols, techniques suitable for monitoring the effects of added stimuli and induced tissue changes are needed. METHODOLOGY/PRINCIPAL FINDINGS: Here, we present the quantitative use of two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) as a noninvasive means to monitor the differentiation of human mesenchymal stem cells (hMSCs) using entirely endogenous sources of contrast. We demonstrate that the individual fluorescence contribution from the intrinsic cellular fluorophores NAD(P)H, flavoproteins and lipofuscin can be extracted from TPEF images and monitored dynamically from the same cell population over time. Using the redox ratio, calculated from the contributions of NAD(P)H and flavoproteins, we identify distinct patterns in the evolution of the metabolic activity of hMSCs maintained in either propagation, osteogenic or adipogenic differentiation media. The differentiation of these cells is mirrored by changes in cell morphology apparent in high resolution TPEF images and by the detection of collagen production via SHG imaging. Finally, we find dramatic increases in lipofuscin levels in hMSCs maintained at 20% oxygen vs. those in 5% oxygen, establishing the use of this chromophore as a potential biomarker for oxidative stress. CONCLUSIONS/SIGNIFICANCE: In this study we demonstrate that it is possible to monitor the metabolic activity, morphology, ECM production and oxidative stress of hMSCs in a non-invasive manner. This is accomplished using generally available multiphoton microscopy equipment and simple data analysis techniques, such that the method can widely adopted by laboratories with a diversity of comparable equipment. This method therefore represents a powerful tool, which enables researchers to monitor engineered tissues and optimize culture conditions in a near real time manner
- …