2,283 research outputs found
Bubble transport by electro-magnetophoretic forces at anode bottom of aluminium cells
Electrically conducting and nonconducting particles and bubbles experience additional forcing in a liquid which carries electric current. These so called electro-magnetophoretic forces are well known in metallurgical applications, like metal purification in vacuum-arc remelting, electro-slag processes, impurity removal or
concentration change in special castings. However, the effect of electro-magnetophoretic forces has never been considered for aluminium cells where the gas bubbles evolving in the liquid electrolyte are surrounded by an electric current and significant magnetic fields. We present models to estimate the effect of electric current flow in the vicinity of the bubbles and the additional
pressure distribution resulting from the magnetic forces in the surrounding liquid electrolyte. According to the estimates, this force becomes important for bubbles exceeding 2 mm in size, and could be sufficient to overcome the typical drag force associated with electrolyte flow thereby opposing motion of the bubble along the base of the anode when it is inclined at a slight angle. The effect
could explain certain features of the anode effect onset.
Mathematical models and numerical results are presented and a further implementation in the general MHD code for the aluminium cell design is discussed
Angiogenically active vascular endothelial growth factor is over-expressed in malignant human and rat prostate carcinoma cells
Vascular endothelial growth factor (VEGF) is one of the most potent factors for stimulating angiogenesis, an essential process required for expansion of primary tumour and dissemination of malignant cells. To investigate the possible role of VEGF in facilitating metastasis of prostate cancer via stimulating angiogenesis, we have used Northern and slot blotting, reverse transcription polymerase chain reaction, nucleotide sequence analysis and enzyme-linked immunosorbent assay to compare the VEGF expression in series of human and rat cell lines with either benign or malignant characteristics. We have also employed the chick chorioallantoic membrane (CAM) assay to measure the angiogenic activity of the VEGF derived from both benign and malignant cells. The level of VEGF mRNA expressed in the seven malignant human and rat cell lines is 3.5- to 10-fold higher than that expressed in the benign cell lines. The three metastatic variants, generated by transfection of a benign cell line with DNA extracted from prostate carcinoma cells, expressed 2.5 to 5 times more VEGF mRNA than their parental benign cells. While VEGF 121 and 165 were predominantly expressed by both the benign and malignant cells, the transcript representing VEGF 189 isoform was only detected in the malignant cells. At protein level, three human malignant cell lines produced more VEGF (2.7â7.9 ng mlâ1) than the benign cell line (1.3 ng mlâ1). CAM assay detected a VEGF-dependent angiogenic activity in the medium from malignant cells, but only a relatively weak VEGF-independent activity in the medium from benign cells. These results demonstrated that malignant cells did over-express VEGF and only the VEGF derived from malignant cells was angiogenically active. Thus, we suggest that the VEGF produced by malignant cells might play an important role in facilitating metastasis of prostatic cancer. © 2000 Cancer Research Campaig
Role of Interleukin 17 in arthritis chronicity through survival of synoviocytes via regulation of synoviolin expression
Background:
The use of TNF inhibitors has been a major progress in the treatment of chronic inflammation. However, not all patients respond. In addition, response will be often lost when treatment is stopped. These clinical aspects indicate that other cytokines might be involved and we focus here on the role of IL-17. In addition, the chronic nature of joint inflammation may contribute to reduced response and enhanced chronicity. Therefore we studied the capacity of IL-17 to regulate synoviolin, an E3 ubiquitin ligase implicated in synovial hyperplasia in human rheumatoid arthritis (RA) FLS and in chronic reactivated streptococcal cell wall (SCW)-induced arthritis.<p></p>
Methodology/Principal Findings:
Chronic reactivated SCW-induced arthritis was examined in IL-17R deficient and wild-type mice. Synoviolin expression was analysed by real-time RT-PCR, Western Blot or immunostaining in RA FLS and tissue, and p53 assessed by Western Blot. Apoptosis was detected by annexin V/propidium iodide staining, SS DNA apoptosis ELISA kit or TUNEL staining and proliferation by PCNA staining. IL-17 receptor A (IL-17RA), IL-17 receptor C (IL-17-RC) or synoviolin inhibition were achieved by small interfering RNA (siRNA) or neutralizing antibodies. IL-17 induced sustained synoviolin expression in RA FLS. Sodium nitroprusside (SNP)-induced RA FLS apoptosis was associated with reduced synoviolin expression and was rescued by IL-17 treatment with a corresponding increase in synoviolin expression. IL-17RC or IL-17RA RNA interference increased SNP-induced apoptosis, and decreased IL-17-induced synoviolin. IL-17 rescued RA FLS from apoptosis induced by synoviolin knockdown. IL-17 and TNF had additive effects on synoviolin expression and protection against apoptosis induced by synoviolin knowndown. In IL-17R deficient mice, a decrease in arthritis severity was characterized by increased synovial apoptosis, reduced proliferation and a marked reduction in synoviolin expression. A distinct absence of synoviolin expressing germinal centres in IL-17R deficient mice contrasted with synoviolin positive B cells and Th17 cells in synovial germinal centre-like structures.<p></p>
Conclusion/Significance:
IL-17 induction of synoviolin may contribute at least in part to RA chronicity by prolonging the survival of RA FLS and immune cells in germinal centre reactions. These results extend the role of IL-17 to synovial hyperplasia.<p></p>
Shell model description of Ge isotopes
A shell model study of the low energy region of the spectra in Ge isotopes
for is presented, analyzing the excitation energies,
quadrupole moments, values and occupation numbers. The theoretical
results have been compared with the available experimental data. The shell
model calculations have been performed employing three different effective
interactions and valence spaces.We have used two effective shell model
interactions, JUN45 and jj44b, for the valence space
without truncation. To include the proton subshell in valence space
we have employed the effective interaction due to Sorlin {\it et al.},
with Ca as a core and a truncation in the number of excited particles.Comment: 10 pages, 10 figures, Proc. of the XXXV Nuclear Physics Symposium,
January 3-6 2012, Cocoyoc, Morelos, Mexico. IOP Journal of Physics:
Conference Series (in press
A Simple Model for Anisotropic Step Growth
We consider a simple model for the growth of isolated steps on a vicinal
crystal surface. It incorporates diffusion and drift of adatoms on the terrace,
and strong step and kink edge barriers. Using a combination of analytic methods
and Monte Carlo simulations, we study the morphology of growing steps in
detail. In particular, under typical Molecular Beam Epitaxy conditions the step
morphology is linearly unstable in the model and develops fingers separated by
deep cracks. The vertical roughness of the step grows linearly in time, while
horizontally the fingers coarsen proportional to . We develop scaling
arguments to study the saturation of the ledge morphology for a finite width
and length of the terrace.Comment: 20 pages, 12 figures; [email protected]
Novel components of the Toxoplasma inner membrane complex revealed by BioID.
UNLABELLED:The inner membrane complex (IMC) of Toxoplasma gondii is a peripheral membrane system that is composed of flattened alveolar sacs that underlie the plasma membrane, coupled to a supporting cytoskeletal network. The IMC plays important roles in parasite replication, motility, and host cell invasion. Despite these central roles in the biology of the parasite, the proteins that constitute the IMC are largely unknown. In this study, we have adapted a technique named proximity-dependent biotin identification (BioID) for use in T. gondii to identify novel components of the IMC. Using IMC proteins in both the alveoli and the cytoskeletal network as bait, we have uncovered a total of 19 new IMC proteins in both of these suborganellar compartments, two of which we functionally evaluate by gene knockout. Importantly, labeling of IMC proteins using this approach has revealed a group of proteins that localize to the sutures of the alveolar sacs that have been seen in their entirety in Toxoplasma species only by freeze fracture electron microscopy. Collectively, our study greatly expands the repertoire of known proteins in the IMC and experimentally validates BioID as a strategy for discovering novel constituents of specific cellular compartments of T. gondii. IMPORTANCE:The identification of binding partners is critical for determining protein function within cellular compartments. However, discovery of protein-protein interactions within membrane or cytoskeletal compartments is challenging, particularly for transient or unstable interactions that are often disrupted by experimental manipulation of these compartments. To circumvent these problems, we adapted an in vivo biotinylation technique called BioID for Toxoplasma species to identify binding partners and proximal proteins within native cellular environments. We used BioID to identify 19 novel proteins in the parasite IMC, an organelle consisting of fused membrane sacs and an underlying cytoskeleton, whose protein composition is largely unknown. We also demonstrate the power of BioID for targeted discovery of proteins within specific compartments, such as the IMC cytoskeleton. In addition, we uncovered a new group of proteins localizing to the alveolar sutures of the IMC. BioID promises to reveal new insights on protein constituents and interactions within cellular compartments of Toxoplasma
Determining the representative factors affecting warning message dissemination in VANETs
In this paper, we present a statistical analysis based on the 2k factorial methodology
to determine the representative factors affecting traffic safety applications in Vehicular
ad hoc networks (VANETs). Our purpose is to determine what are the key factors affecting
Warning Message Dissemination (WMD) in order to concentrate on such parameters,
thus reducing the amount of required simulation time when evaluating VANETs. Simulation
results show that the key factors affecting warning messages delivery are: (i) the transmission
range, (ii) the radio propagation model used, and (iii) the density of vehicles. Based on this
statistical analysis, we evaluate a compound key factor: neighbor density. This factor combines
the above-mentioned factors into a single entity, reducing the number of factors that
must be taken into account for VANET researchers to evaluate the benefits of their proposals.This work was partially supported by the Ministerio de Educacion y Ciencia, Spain, under Grant TIN2008-06441-C02-01, and by the Fundacion Antonio Gargallo, under Grant 2009/B001.MartĂnez DomĂnguez, FJ.; Toh, CK.; Cano EscribĂĄ, JC.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2012). Determining the representative factors affecting warning message dissemination in VANETs. Wireless Personal Communications. 67(2):295-314. https://doi.org/10.1007/s11277-010-9989-4S295314672Eichler, S. (2007). Performance evaluation of the IEEE 802.11p WAVE communication standard. In Proceedings of the vehicular technology conference (VTC-2007 Fall), USA.Fall, K., & Varadhan, K. (2000). ns notes and documents. The VINT Project. UC Berkeley, LBL, USC/ISI, and Xerox PARC. Available at http://www.isi.edu/nsnam/ns/ns-documentation.html .Fasolo, E., Zanella, A., & Zorzi, M. (2006). An effective broadcast scheme for alert message propagation in vehicular ad hoc networks. In Proceedings of the IEEE International Conference on Communications, Istambul, Turkey.Korkmaz, G., Ekici, E., Ozguner, F., & Ozguner, U. (2004). Urban multi-hop broadcast protocols for inter-vehicle communication systems. In Proceedings of First ACM Workshop on Vehicular Ad Hoc Networks (VANET 2004).Martinez, F. J., Toh, C.-K., Cano, J.-C., Calafate, C. T., & Manzoni, P. (2009). Realistic radio propagation models (RPMs) for VANET simulations. In IEEE wireless communications and networking conference (WCNC), Budapest, Hungary.Martinez, F. J., Cano, J.-C., Calafate, C. T., & Manzoni, P. (2008). CityMob: A mobility model pattern generator for VANETs. In IEEE vehicular networks and applications workshop (Vehi-Mobi, held with ICC), Beijing, China.Martinez, F. J., Cano, J.-C., Calafate, C. T., & Manzoni, P. (2009). A performance evaluation of warning message dissemination in 802.11p based VANETs. In IEEE local computer networks conference (LCN 2009), ZĂŒrich, Switzerland.Torrent-Moreno, M., Santi, P., & Hartenstein, H. (2005). Fair sharing of bandwidth in VANETs. In Proceedings of the 2nd ACM international workshop on vehicular ad hoc networks, Germany.Tseng Y.-C., Ni S.-Y., Chen Y.-S., Sheu J.-P. (2002) The broadcast storm problem in a mobile ad hoc network. Wireless Networks 8: 153â167Wisitpongphan N., Tonguz O., Parikh J., Mudalige P., Bai F., Sadekar V. (2007) Broadcast storm mitigation techniques in vehicular ad hoc networks. Wireless Communications IEEE 14(6): 84â94. doi: 10.1109/MWC.2007.4407231Yang, X., Liu, J., Zhao, F., & Vaidya, N. H. (2004). A vehicle-to-vehicle communication protocol for cooperative collision warning. In Proceedings of the first annual international conference on mobile and ubiquitous systems: Networking and services (MobiQuitousâ04).Yoon, J., Liu, M., & Noble, B. (2003). Random waypoint considered harmful. Proceedings of IEEE INFOCOMM 2003, San Francisco, California, USA.Zang, Y., Stibor, L., Cheng, X., Reumerman, H.-J., Paruzel, A., & Barroso, A. (2007). Congestion control in wireless networks for vehicular safety applications. In Proceedings of the 8th European Wireless Conference, Paris, France
GPU-based Iterative Cone Beam CT Reconstruction Using Tight Frame Regularization
X-ray imaging dose from serial cone-beam CT (CBCT) scans raises a clinical
concern in most image guided radiation therapy procedures. It is the goal of
this paper to develop a fast GPU-based algorithm to reconstruct high quality
CBCT images from undersampled and noisy projection data so as to lower the
imaging dose. For this purpose, we have developed an iterative tight frame (TF)
based CBCT reconstruction algorithm. A condition that a real CBCT image has a
sparse representation under a TF basis is imposed in the iteration process as
regularization to the solution. To speed up the computation, a multi-grid
method is employed. Our GPU implementation has achieved high computational
efficiency and a CBCT image of resolution 512\times512\times70 can be
reconstructed in ~5 min. We have tested our algorithm on a digital NCAT phantom
and a physical Catphan phantom. It is found that our TF-based algorithm is able
to reconstrct CBCT in the context of undersampling and low mAs levels. We have
also quantitatively analyzed the reconstructed CBCT image quality in terms of
modulation-transfer-function and contrast-to-noise ratio under various scanning
conditions. The results confirm the high CBCT image quality obtained from our
TF algorithm. Moreover, our algorithm has also been validated in a real
clinical context using a head-and-neck patient case. Comparisons of the
developed TF algorithm and the current state-of-the-art TV algorithm have also
been made in various cases studied in terms of reconstructed image quality and
computation efficiency.Comment: 24 pages, 8 figures, accepted by Phys. Med. Bio
Solitary waves of nonlinear nonintegrable equations
Our goal is to find closed form analytic expressions for the solitary waves
of nonlinear nonintegrable partial differential equations. The suitable
methods, which can only be nonperturbative, are classified in two classes.
In the first class, which includes the well known so-called truncation
methods, one \textit{a priori} assumes a given class of expressions
(polynomials, etc) for the unknown solution; the involved work can easily be
done by hand but all solutions outside the given class are surely missed.
In the second class, instead of searching an expression for the solution, one
builds an intermediate, equivalent information, namely the \textit{first order}
autonomous ODE satisfied by the solitary wave; in principle, no solution can be
missed, but the involved work requires computer algebra.
We present the application to the cubic and quintic complex one-dimensional
Ginzburg-Landau equations, and to the Kuramoto-Sivashinsky equation.Comment: 28 pages, chapter in book "Dissipative solitons", ed. Akhmediev, to
appea
Projection methods in conic optimization
There exist efficient algorithms to project a point onto the intersection of
a convex cone and an affine subspace. Those conic projections are in turn the
work-horse of a range of algorithms in conic optimization, having a variety of
applications in science, finance and engineering. This chapter reviews some of
these algorithms, emphasizing the so-called regularization algorithms for
linear conic optimization, and applications in polynomial optimization. This is
a presentation of the material of several recent research articles; we aim here
at clarifying the ideas, presenting them in a general framework, and pointing
out important techniques
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