2,673 research outputs found
Tumor growth with a necrotic core as an obstacle problem in pressure
Motivated by the incompressible limit of a cell density model, we propose a
free boundary tumor growth model where the pressure satisfies an obstacle
problem on an evolving domain , and the coincidence set
captures the emerging necrotic core. We contribute to the analytical
characterization of the solution structure in the following two aspects. By
deriving a semi-analytical solution and studying its dynamical behavior, we
obtain quantitative transitional properties of the solution separating phases
in the development of necrotic cores and establish its long time limit with the
traveling wave solutions. Also, we prove the existence of traveling wave
solutions incorporating non-zero outer densities outside the tumor bulk,
provided that the size of the outer density is below a threshold
AT2019 avd: A tidal disruption event with a two-phase evolution
Tidal disruption events (TDEs) can uncover the quiescent super-massive black
holes (SMBHs) at the center of galaxies and also offer a promising method to
study them. After the disruption of a star by a SMBH, the highly elliptical
orbit of the debris stream will be gradually circularized due to the
self-crossing, and then the circularized debris will form an accretion disk.
The recent TDE candidate AT 2019avd has double peaks in its optical light
curve, and the X-ray emerges near the second peak. The durations of the peaks
are about 400 and 600 days, respectively, and the separation between them is ~
700 days. We fit and analyse its spectral energy distribution (SED) in
optical/UV, mid-infrared, and X-ray bands. We find that this source can be
interpreted as the circularization process in the first phase plus the delayed
accretion process in the second phase. Under this two-phase scenario, we use
the succession of self-crossing circularization model to fit the first peak,
and the delayed accretion model to fit the second peak. The fitting results are
consistent with the partial disruption of a 0.9 M_sun star by a 7 * 10^6 M_sun
SMBH with the penetration factor \beta ~ 0.6. Furthermore, we find the
large-amplitude (by factors up to ~ 5) X-ray variability in AT 2019avd can be
interpreted as the rigid-body precession of the misaligned disk due to the
Lense-Thirring effect of a spinning SMBH, with the disk precession period of 10
- 25 days.Comment: 14 pages, 11 figures, 4 tables, Submitted to Ap
Combined cloud:a mixture of voluntary cloud and reserved instance marketplace
Voluntary cloud is a new paradigm of cloud computing.It provides an alternative selection along with some well-provisioned clouds.However,for the uncertain time span that participants share their computing resources in voluntary cloud,there are some challenging issues,i.e.,fluctuation,under-capacity and low-benefit.In this paper,an architecture is first proposed based on Bittorrent protocol.In this architecture,resources could be reserved or requested from Reserved Instance Marketplace and could be accessed with a lower price in a short circle.Actually,these resources could replenish the inadequate resource pool and relieve the fluctuation and under-capacity issue in voluntary cloud.Then,the fault rate of each node is used to evaluate the uncertainty of its sharing time.By leveraging a linear prediction model,it is enabled by a distribution function which is used for evaluating the computing capacity of the system.Moreover,the cost optimization problem is investigated and a computational method is presented to solve the low-benefit issue in voluntary cloud.At last,the system performance is validated by two sets of simulations.And the experimental results show the effectiveness of our computational method for resource reservation optimization
Exact analytical solution to ultrasonic interfacial reflection enabling optimal oil film thickness measurement
The ultrasonic reflection from a lubricated interface has been widely analyzed to measure fluid film thickness, with different algorithms being applied to overcome measurement accuracy and resolution issues. Existing algorithms use either the amplitude or the phase angle of the ultrasonic interfacial reflection. In this paper, a new algorithm (named the âexact model â complexâ) that simultaneously utilizes both the amplitude and the phase of the complex ultrasonic reflection coefficient is proposed and mathematically derived. General procedures for theoretical analysis in terms of measurement accuracy and uncertainty are proposed and applied to the new algorithm, the beneficial features of which (as compared to other existing algorithms) can be summarized as: 1) a direct calculation, instead of an iterative approximation, 2) guaranteed maximum measurement accuracy, and 3) acceptable measurement uncertainty. None of the existing methods have showed this combination of benefits. Moreover, two groups of raw data from previous experimental studies are utilized to further validate the practical feasibility of the new algorithm. Overall, the proposed âexact model â complexâ algorithm fully exploits the potential of ultrasonic reflection for oil film thickness measurement, with an accurate and a convenient calculation suited to practical implementation
Male Populus cathayana than female shows higher photosynthesis and less cellular injury through ABA-induced manganese transporting inhibition under high manganese condition
High Mn poisoned male and female Populus cathayana. The toxicity could be alleviated by exogenous ABA application. Intriguingly, ABA granted higher resistance to males than to females under high Mn stress because ABA could induce more blocking of Mn translocation to leaf in males than in females. Abscisic acid (ABA) is involved in plants' adaptive responses to various environmental stresses. However, little is known about the sex-related detoxification of ABA in plants under excess manganese (Mn) conditions. To reveal potentially different ABA detoxification mechanisms between Populus cathayana males and females against excess Mn exposure, photosynthesis performance, Mn2+ concentrations and morphologic changes were investigated. High Mn stress led to a more severe chloroplast destruction and, thus, greater reduction in the photosynthesis of P. cathayana females when compared to males. Under high Mn conditions, Mn reallocated mainly to leaves in females, while in males, it was distributed equally to roots and leaves. With the application of ABA, photosynthesis was restored more in males and more integrated grana in males than in females. It should be noted that Mn concentrations in males were lower in leaves and higher in roots and stems than those in females when treated with the combination of Mn and ABA. Conclusively, due to the reduction of root-shoot Mn transportation induced by ABA in P. cathayana males, males experienced less physiological injuries than do females, which suggest that males possess greater ABA-inducible resistance to Mn stress than do females.Peer reviewe
SelfâSacrificial TemplateâDirected Synthesis of MetalâOrganic FrameworkâDerived Porous Carbon for EnergyâStorage Devices
Metalâorganic framework (MOF)âderived carbon materials exhibit large surface areas, but dominant micropore characteristics and uncontrollable dimensions. Herein, we propose a selfâsacrificial templateâdirected synthesis method to engineer the porous structure and dimensions of MOFâderived carbon materials. A porous zinc oxide (ZnO) nanosheet solid is selected as the selfâsacrificial template and twoâdimensional (2D) nanostructureâdirecting agent to prepare 2D ZIFâ8âderived carbon nanosheets (ZCNs). The asâprepared ZCN materials exhibit a large surface area with hierarchical porosity. These intriguing features render ZCN materials advanced electrode materials for electrochemical energyâstorage devices, demonstrating large ionâaccessible surface area and high ionâ/electronâtransport rates. This selfâsacrificial templateâdirected synthesis method offers new avenues for rational engineering of the porous structure and dimensions of MOFâderived porous carbon materials, thus exploiting their full potential for electrochemical energyâstorage devices.On the surface: A selfâsacrificial templateâdirected synthesis method is proposed to engineer the porosity and dimensions of MOFâderived carbon materials. By using a porous nanosheet solid as the selfâsacrificial template and twoâdimensional (2D) nanostructureâdirecting agent, 2D ZIFâ8âderived carbon nanosheets are prepared, which exhibit a large ionâaccessible surface area and rapid ion transport as the electrode materials for electrochemical energyâstorage devices.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137193/1/celc201500536-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137193/2/celc201500536.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137193/3/celc201500536_am.pd
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