354 research outputs found
Collision centrality and dependence of the emission of thermal photons from fluctuating initial state in ideal hydrodynamic calculation
Fluctuations in the initial QCD matter density distribution are found to
enhance the production of thermal photons significantly in the range 2 \leq pT
\leq 4 GeV/c compared to a smooth initial state averaged profile in ideal
hydrodynamic calculation for 200 AGeV Au+Au collisions at the Relativistic
Heavy Ion Collider (RHIC) and 2.76 ATeV Pb+Pb collisions at the Large Hadron
Collider (LHC). The thermal emission of photons is strongly dependent on the
initial temperature of the system where the presence of 'hotspots' in the
initial state translates into enhanced production of photons compared to a
smooth profile. The effect of fluctuations in the initial state is found to be
stronger for peripheral collisions and for lower beam energies. The pT spectra
are found to be quite sensitive to the value of the initial formation time of
the plasma which is not known unambiguously and which may vary with collision
centralities at a particular beam energy. Increase in the value of the
formation time lowers the production of thermal photons compared to the results
from a shorter formation time. However, the relative enhancement from
fluctuating initial tates (compared to a smooth initial state) is found to be
stronger for the larger values of formation time. The pT spectra alone are
found to be insufficient to quantify the fluctuations in the initial density
distribution due to the uncertainties in the initial conditions. A suitably
normalized ratio of central-to-peripheral yield as a function of collision
centrality and pT can be a useful measure of the fluctuation size scale.Comment: 10 pages, 10 figure
Developmental regulation of linkers of the nucleoskeleton to the cytoskeleton during mouse postnatal retinogenesis
Harmonic current injection for torque ripple reduction with optimum current trajectory for minimum induced voltage
Electric drives often do not have a smooth torque. In most cases they are coupled with mechanical systems. These tend to have natural frequencies. Therefore, it is advisable to eliminate harmonics from the torque pulsation if they are close to a natural frequency. One possibility to do this is harmonic current injection or HCI for short. However, the question arises, how exactly this harmonic current should be. The fact that a harmonic in the torque can be influenced by the d and q current results in a greater degree of freedom. This paper presents a method to investigate all possible solutions. Furthermore, two optimization possibilities for the current trajectory are presented. The effect of this selection on the maximum torque speed curve is shown. It has been found that the method which minimizes the induced voltage achieves an up to 8% larger range of application in this example
Microconstriction Arrays for High-Throughput Quantitative Measurements of Cell Mechanical Properties
AbstractWe describe a method for quantifying the mechanical properties of cells in suspension with a microfluidic device consisting of a parallel array of micron-sized constrictions. Using a high-speed charge-coupled device camera, we measure the flow speed, cell deformation, and entry time into the constrictions of several hundred cells per minute during their passage through the device. From the flow speed and the occupation state of the microconstriction array with cells, the driving pressure across each constriction is continuously computed. Cell entry times into microconstrictions decrease with increased driving pressure and decreased cell size according to a power law. From this power-law relationship, the cell elasticity and fluidity can be estimated. When cells are treated with drugs that depolymerize or stabilize the cytoskeleton or the nucleus, elasticity and fluidity data from all treatments collapse onto a master curve. Power-law rheology and collapse onto a master curve are predicted by the theory of soft glassy materials and have been previously shown to describe the mechanical behavior of cells adhering to a substrate. Our finding that this theory also applies to cells in suspension provides the foundation for a quantitative high-throughput measurement of cell mechanical properties with microfluidic devices
Generating spectral dental panoramic images from single energy computed tomography volumes
Purpose: To implement a framework generating synthetic spectral panoramic
images from single energy CT volumes. Using the framework output to compare the
synthetic images against experimental spectral panoramic images for
cross-verification. Methods: A simulation framework for generating synthetic
spectral panoramic images from CT volumes is described. A cone beam CT scan of
an anthropomorphic head phantom is used as input. An experimental spectral
panoramic image of the same phantom is acquired. Results: The output of the
framework of an anthropomorphic head phantom is compared against an
experimental spectral panoramic image of the same phantom. The synthetic and
experimental spectral panoramic images resemble each other considerably,
especially the bone features. In the soft tissue images, there are some
deviations, which are a result of the differences between the experimental and
synthetic processing pipelines. Conclusions: It is demonstrated that generating
synthetic spectral panoramic images from single energy CT volumes is possible.
The synthetic images have many similarities with the experimental results,
increasing the confidence in the correctness of the information contained
within experimental spectral panoramic images and indicating that the synthetic
images could be useful in further research
Effect of nozzle up-scaling on coaxial, gas-assisted atomization
Mass flow scaling of gas-assisted coaxial atomizers from laboratory to industrial scale is of major interest for a wide field of applications. However, there is only scarce knowledge and research concerning the effect of atomizer scale-up on liquid breakup and spray characteristics. The main objective of this study is therefore to derive basic principles for liquid jet breakup using upscaled nozzles to increase the liquid mass flow rate M_ liq. For that purpose, atomizers with the same geometrical setup but increased sizes have been designed and experimentally investigated for M_ liq ¼ 20, 50, 100, and 500 kg/h, while the aerodynamic Weber number Weaero and gas-to-liquid ratio GLR have been kept constant. The primary jet breakup was recorded via high-speed imaging, and the liquid core length LC and the frequency of the Kelvin–Helmholtz instability fK were extracted. Applying these results as reference data, highly resolved numerical simulations have been performed to gain a deeper understanding of the effect of mass flow scaling. In the case of keeping Weaero and GLR constant, it has been shown by both experiments and simulations that the breakup morphology, given by a pulsating liquid jet with the disintegration of fibertype liquid fragments, remains almost unchanged with the degree of upscaling n. However, the normalized breakup length LC=dliq has been found to be considerably increased with increasing n. The reason has been shown to be the decreased gas flow velocity vgas at the nozzle exit with n, which leads to a decreased gas-to-liquid momentum flux ratio j and an attenuated momentum exchange between the phases. Accordingly, the calculated turbulence kinetic energy of the gas flow and the specific kinetic energy in the liquid phase decrease with n. This corresponds to a decreased fKHI with n or M_ liq, respectively, which has been confirmed by both experiments and simulations. The same behavior has been shown for two liquids with different viscosities and at different Weaero. The obtained results allow a first-order estimate of the liquid breakup characteristics, where the influence of nozzle upscaling can be incorporated into j and Reliq in terms of n
Effect of elevated pressure on air-assisted primary atomization of coaxial liquid jets : Basic research for entrained flow gasification
Highly resolved numerical simulations have been conducted for a generic, coaxial air-blast atomizer designed for fundamental research of entrained flow gasification processes. Objective of the work is to gain a detailed knowledge of the influence of elevated reactor pressure on the primary atomization behaviour of high-viscous liquid jets. In agreement with measured breakup morphology and breakup regimes proposed in literature, the simulations yield a pulsating mode instability of liquid jet, along with disintegrations of fibre-type liquid fragments for different pressures. From the mechanism point of view, the breakup process has been shown to be triggered by concentric, axisymmetric ring vortices, which disturb the liquid jet surface in a first stage and penetrate further into the intact core, leading to interfacial instabilities and pinch-off of liquid ligaments. The liquid jet breaks up faster at elevated pressure, leading to a shorter core length L. The calculated exponent (b -0.5) of the power law for fitting the decrease of L with p agrees well with measured correlations from literature in terms of varied momentum flux ratio M and Weber number We, although water jets, atmospheric pressure and different air-assisted, external mixing nozzles were used in these works. Therefore, the effect of elevated pressure is equivalent to that of increased M or We , which scale linearly with p or the gas density for the current setup. The specific kinetic energy of liquid k has been found to be increased with p, which is particularly pronounced in the high frequency range. A first-order estimate has been proposed, which can be used for the evaluation of liquid kinetic energy or droplet velocity within the spray. The results have been validated by simulations with twice-refined resolution, yielding a grid-independence behaviour with respect to the primary breakup characteristics. However, the follow-up processes with secondary breakup and spray dispersion are reproduced better by using the finer grid
Systematic Comparison of Jet Energy-Loss Schemes in a realistic hydrodynamic medium
We perform a systematic comparison of three different jet energy-loss
approaches. These include the Armesto-Salgado-Wiedemann scheme based on the
approach of Baier-Dokshitzer-Mueller-Peigne-Schiff and Zakharov (BDMPS-Z/ASW),
the Higher Twist approach (HT) and a scheme based on the approach of
Arnold-Moore-Yaffe (AMY). In this comparison, an identical medium evolution
will be utilized for all three approaches: not only does this entail the use of
the same realistic three-dimensional relativistic fluid dynamics (RFD)
simulation, but also includes the use of identical initial parton-distribution
functions and final fragmentation functions. We are, thus, in a unique
position, not only to isolate fundamental differences between the various
approaches, but also to make rigorous calculations for different experimental
measurements using "state of the art" components. All three approaches are
reduced to a version which contains only one free tunable parameter, this is
then related to the well known transport parameter . We find that the
parameters of all three calculations can be adjusted to provide a good
description of inclusive data on versus transverse momentum. However,
we do observe slight differences in their predictions for the centrality and
azimuthal angular dependence of vs. . We also note that the value
of the transport coefficient in the three approaches to describe the
data differs significantly.Comment: 15 pages, 12 figures, revtex, minor changes in model nomenclature and
reference
Comparing the value of mono- vs coculture for high-throughput compound screening in hematological malignancies
Large-scale compound screens are a powerful model system for understanding variability of treatment response and discovering druggable tumor vulnerabilities of hematological malignancies. However, as mostly performed in a monoculture of tumor cells, these assays disregard modulatory effects of the in vivo microenvironment. It is an open question whether and to what extent coculture with bone marrow stromal cells could improve the biological relevance of drug testing assays over monoculture. Here, we established a high-throughput platform to measure ex vivo sensitivity of 108 primary blood cancer samples to 50 drugs in monoculture and coculture with bone marrow stromal cells. Stromal coculture conferred resistance to 52% of compounds in chronic lymphocytic leukemia (CLL) and 36% of compounds in acute myeloid leukemia (AML), including chemotherapeutics, B-cell receptor inhibitors, proteasome inhibitors, and Bromodomain and extraterminal domain inhibitors. Only the JAK inhibitors ruxolitinib and tofacitinib exhibited increased efficacy in AML and CLL stromal coculture. We further confirmed the importance of JAK-STAT signaling for stroma-mediated resistance by showing that stromal cells induce phosphorylation of STAT3 in CLL cells. We genetically characterized the 108 cancer samples and found that drug-gene associations strongly correlated between monoculture and coculture. However, effect sizes were lower in coculture, with more drug-gene associations detected in monoculture than in coculture. Our results justify a 2-step strategy for drug perturbation testing, with large-scale screening performed in monoculture, followed by focused evaluation of potential stroma-mediated resistances in coculture
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