Stability analysis of the Eulerian-Lagrangian finite volume methods for nonlinear hyperbolic equations in one space dimension

In this paper, we construct a novel Eulerian-Lagrangian finite volume (ELFV) method for nonlinear scalar hyperbolic equations in one space dimension. It is well known that the exact solutions to such problems may contain shocks though the initial conditions are smooth, and direct numerical methods may suffer from restricted time step sizes. To relieve the restriction, we propose an ELFV method, where the space-time domain was separated by the partition lines originated from the cell interfaces whose slopes are obtained following the Rakine-Hugoniot junmp condition. Unfortunately, to avoid the intersection of the partition lines, the time step sizes are still limited. To fix this gap, we detect effective troubled cells (ETCs) and carefully design the influence region of each ETC, within which the partitioned space-time regions are merged together to form a new one. Then with the new partition of the space-time domain, we theoretically prove that the proposed first-order scheme with Euler forward time discretization is total-variation-diminishing and maximum-principle-preserving with {at least twice} larger time step constraints than the classical first order Eulerian method for Burgers' equation. Numerical experiments verify the optimality of the designed time step sizes.Comment: Submitted to Mathematics of Computatio

3D MR Ventricle Segmentation in Pre-term Infants with Post-Hemorrhagic Ventricle Dilation

Intraventricular hemorrhage (IVH) or bleed within the brain is a common condition among pre-term infants that occurs in very low birth weight preterm neonates. The prognosis is further worsened by the development of progressive ventricular dilatation, i.e., post-hemorrhagic ventricle dilation (PHVD), which occurs in 10-30% of IVH patients. In practice, predicting PHVD accurately and determining if that specific patient with ventricular dilatation requires the ability to measure accurately ventricular volume. While monitoring of PHVD in infants is typically done by repeated US and not MRI, once the patient has been treated, the follow-up over the lifetime of the patient is done by MRI. While manual segmentation is still seen as a gold standard, it is extremely time consuming, and therefore not feasible in a clinical context, and it also has a large inter-and intra-observer variability. This paper proposes an segmentation algorithm to extract the cerebral ventricles from 3D T1-weighted MR images of pre-term infants with PHVD. The proposed segmentation algorithm makes use of the convex optimization technique combined with the learned priors of image intensities and label probabilistic map, which is built from a multi-atlas registration scheme. The leave-one-out cross validation using 7 PHVD patient T1 weighted MR images showed that the proposed method yielded a mean DSC of 89.7% +/- 4.2%, a MAD of 2.6 +/- 1.1 mm, a MAXD of 17.8 +/- 6.2 mm, and a VD of 11.6% +/- 5.9%, suggesting a good agreement with manual segmentations

Differences in Expression of EGFR, Ki67 and p-EPK in Oral Cavity Squamous Cell Carcinoma

Purpose: To evaluate the expression of EGFR, Ki67, and p-EPK in oral cavity and oropharyngeal cancers, and to investigate their clinical significance as prognostic markers.Methods: One hundred patients who underwent curative surgery for oral cavity or oropharyngeal squamous cell carcinoma in a Chinese People’s Liberation Army General Hospital between March 1999 and October 2010 were evaluated. The level of protein expression of EGFR, Ki67 and p-EPK was assessed by immunohistochemistry. In situ hybridization was used to detect the existence of human papillomavirus (HPV).Results: Nineteen of 75 patients with oropharyngeal cancer showed HPV-positive tumors, and two of 72 patients with oral cavity cancer showed HPV-positive tumors. EGFR and Ki67 expression was significantly higher in oral cavity cancers than in oropharyngeal cancers (p = 0.005 and p = 0.001, respectively). Loss of p-EPK occurred significantly more frequently in oral cavity cancers than in oropharyngeal cancers (p = 0.004). Overexpression of EGFR and Ki67 and loss of p-EPK were observed more frequently in HPV negative tumors. Multivariate Cox regression analysis showed that Ki67 expression had a significantly unfavorable impact on relapse free survival in oropharyngeal cancer.Conclusion: The expression levels of EGFR, Ki67, and p-EPK differ between oropharyngeal and oral cavity cancer and it may be attributed to HPV-related molecular pathogenesis. The expression of Ki67 might be an unfavorable prognostic marker for relapse-free survival in oropharyngeal cancer.Keywords: EGFR; Ki67; p-EPK; Oral cavity squamous cell carcinoma, Expression differenc

Study the build-up, initiation and acceleration of 2008 April 26 coronal mass ejection observed by STEREO

In this paper, we analyze the full evolution, from a few days prior to the eruption to the initiation, and the final acceleration and propagation, of the CME that occurred on 2008 April 26 using the unprecedented high cadence and multi-wavelength observations by STEREO. There existed frequent filament activities and EUV jets prior to the CME eruption for a few days. These activities were probably caused by the magnetic reconnection in the lower atmosphere driven by photospheric convergence motions, which were evident in the sequence of magnetogram images from MDI (Michelson Doppler Imager) onboard SOHO. The slow low-layer magnetic reconnection may be responsible for the storage of magnetic free energy in the corona and the formation of a sigmoidal core field or a flux rope leading to the eventual eruption. The occurrence of EUV brightenings in the sigmoidal core field prior to the rise of the flux rope implies that the eruption was triggered by the inner tether-cutting reconnection, but not the external breakout reconnection. During the period of impulsive acceleration, the time profile of the CME acceleration in the inner corona is found to be consistent with the time profile of the reconnection electric field inferred from the footpoint separation and the RHESSI 15-25 keV HXR flux curve of the associated flare. The full evolution of this CME can be described in four distinct phases: the build-up phase, initiation phase, main acceleration phase, and propagation phase. The physical properties and the transition between these phases are discussed, in an attempt to provide a global picture of CME dynamic evolution.Comment: 28 pages, 8 figures, accepted for publication in Ap

Computational Design of Flexible Electride with Nontrivial Band Topology

Electrides, with their excess electrons distributed in crystal cavities playing the role of anions, exhibit a variety of unique electronic and magnetic properties. In this work, we employ the first-principles crystal structure prediction to identify a new prototype of A3B electride in which both interlayer spacings and intralayer vacancies provide channels to accommodate the excess electrons in the crystal. This A3B type of structure is calculated to be thermodynamically stable for two alkaline metals oxides (Rb3O and K3O). Remarkably, the unique feature of multiple types of cavities makes the spatial arrangement of anionic electrons highly flexible via elastic strain engineering and chemical substitution, in contrast to the previously reported electrides characterized by a single topology of interstitial electrons. More importantly, our first-principles calculations reveal that Rb3O is a topological Dirac nodal line semimetal, which is induced by the band inversion at the general electronic k momentums in the Brillouin zone associated with the intersitial electric charges. The discovery of flexible electride in combining with topological electronic properties opens an avenue for electride design and shows great promises in electronic device applications

Characteristics Analysis and Measurement of Inverter-Fed Induction Motors for Stator and Rotor Fault Detection

Inverter-fed induction motors (IMs) contain a serious of current harmonics, which become severer under stator and rotor faults. The resultant fault components in the currents affect the monitoring of the motor status. With this background, the fault components in the electromagnetic torque under stator faults considering harmonics are derived in this paper, and the fault components in current harmonics under rotor faults are analyzed. More importantly, the monitoring based on the fault characteristics (both in the torque and current) is proposed to provide reliable stator and rotor fault diagnosis. Specifically, the fault components induced by stator faults in the electromagnetic torque are discussed in this paper, and then, fault components are characterized in the torque spectrum to identify stator faults. To achieve so, a full-order flux observer is adopted to calculate the torque. On the other hand, under rotor faults, the sidebands caused by time and space harmonics in the current are analyzed and exploited to recognize rotor faults, being the motor current signature analysis (MCSA). Experimental tests are performed on an inverter-fed 2.2 kW/380 V/50 Hz IM, which verifies the analysis and the effectiveness of the proposed fault diagnosis methods of inverter-fed IMs

Explanation by a putative triester-like mechanism for the thio effects and Mn2+ rescues in reactions catalyzed by a hammerhead ribozyme

AbstractDivalent metal ion-dependent hammerhead ribozymes can cleave any RNA with a NUX triplet, wherein the N can be any residue and X can be C, U or A. In recent literature on the mechanism of action of hammerhead ribozymes, one important role of divalent metal ions is generally suggested to be an electrophilic catalyst by directly coordinating with the pro-Rp oxygen of the scissile phosphate to stabilize the transition state. This proposal was made on the basis of thio effects and the proposed electrophilic catalyst is very attractive as an explanation for the catalytic activity of metalloenzymes. Reexamination of thio effects with substrates having a GUA triplet at the cleavage site shows that, in agreement with the previous finding, the cleavage rate, in the presence of Mg2+ ions, is significantly reduced in the case of the phosphorothioate substrate (RpS), wherein the pro-Rp oxygen at the scissile phosphate is replaced by sulfur, while the cleavage rate is reduced to a much lesser extent for the other isomer (SpS), wherein the pro-Sp oxygen at the scissile phosphate is replaced by sulfur. However, more careful examination of the rescue ability of Mn2+ ions with these isomers demonstrates that more thiophilic Mn2+ ions rescue the reaction not only with the RpS isomer but also with the SpS isomer and, importantly, to a greater extent for the SpS isomer. These results argue against the previous conclusion that a metal ion is directly coordinating with the pro-Rp oxygen of the scissile phosphate to stabilize the transition state. In this paper we try to elucidate the possible origin of the thio effects and propose a `triester-like' mechanism in reactions catalyzed by hammerhead ribozymes

Role of Carotenoids in Poultry Industry in China: A Review

The poultry as a rapidly growing global industry, occupies a very crucial position in the economy of China. Based on valid reason and available data, pigmentation plays a key role in attracting and convincing consumers demand on  a yellow bird, because it  is perceived as an indication of health. It was observed that broiler carcass skin and meat color affect the consumer's final judgment on the quality and values of poultry products in China, as well as in some other countries. Broiler chickens with a yellow skin color have been shown to be considered desirable by consumers while chickens with less desirable coloring have a lower market value, and are purchased less often by consumers. These compounds are not naturally synthesized by chickens, instead they are mostly derived from diet. However, for decades, carotenoid have attracted attention for promoting health, skin coloration, improve sexual behavior, vitamin A precursors and  antioxidant. As such, carotenoids are commercially important in  broiler, agriculture, food, health and the cosmetic industries. In China properly formulated feed and carotenoids are a significant part of a successful poultry industry. In this review therefore, an attempt has been made to establish the role of carotenoids. Their importance in the overall economy of the country has been highlighted. Also some constraints and illegal use of pigments in broiler diets have been discussed. However, a workable strategy for the promotion of the poultry has been outlined to strengthen the natural and approved carotenoids to improve the socioeconomic conditions of the rural and urban dweller of the country besides practical knowledge to the farmers and poultry producers. Keywords: Role of carotenoid, pigments , poultry industry, China market