1,075 research outputs found
Flexoelectric effect in finite samples
Static flexoelectric effect in a finite sample of a solid is addressed in
terms of phenomenological theory for the case of a thin plate subjected to
bending. It has been shown that despite an explicit asymmetry inherent to the
bulk constitutive electromechanical equations which take into account the
flexoelectric coupling, the electromechanical response for a finite sample is
"symmetric". "Symmetric" means that if a sensor and an actuator are made of a
flexoelectric element, performance of such devices can be characterized by the
same effective piezoelectric coefficient. This behavior is consistent with the
thermodynamic arguments offered earlier, being in conflict with the current
point of view on the matter in literature. This result was obtained using
standard mechanical boundary conditions valid for the case where the
polarization vanishes at the surface. It was shown that, for the case where
there is the polarization is nonzero at the surface, the aforementioned
symmetry of electromechanical response may be violated if standard mechanical
boundary conditions are used, leading to a conflict with the thermodynamic
arguments. It was argued that this conflict may be resolved when using modified
mechanical boundary conditions. It was also shown that the contribution of
surface piezoelectricity to the flexoelectric response of a finite sample is
expected to be comparable to that of the static bulk contribution (including
the material with high values of the dielectric constant) and to scale as the
bulk value of the dielectric constant (similar to the bulk contribution). This
finding implies that if the experimentally measured flexoelectric coefficient
scales as the dielectric constant of the material, this does not imply that the
measured flexoelectric response is controlled by the static bulk contribution
to the flexoelectric effect
Relationship between cyclooxygenase-2 and human epidermal growth factor receptor 2 in vascular endothelial growth factor C up-regulation and lymphangiogenesis in human breast cancer
Both cyclooxygenase (COX)-2 and human epidermal growth factor receptor (HER)-2 promote breast cancer progression; however, the relationship between the two molecules remains unclear. We utilized human breast cancer tissues and cell lines to examine whether COX-2 and HER-2 played independent or interdependent roles in vascular endothelial growth factor (VEGF)-C up-regulation and lymphangiogenesis. A paired correlation of immunodetectable levels of COX-2, VEGF-C, and HER-2 proteins and lymphovascular density (LVD; D2-40-immunolabeled) in 55 breast cancer specimens revealed a positive correlation between COX-2 and HER-2 irrespective of clinicopathological status. However COX-2 alone positively correlated with LVD. In 10 independent specimens, mRNA levels showed a positive correlation between HER-2 and COX-2 or VEGF-C but not LYVE-1 (lymphovascular endothelial marker). These findings implicate COX-2, but not HER-2, in breast cancer-associated lymphangiogenesis. Manipulation of the COX-2 or HER-2 genes in breast cancer cell lines varying widely in COX-2 and HER-2 expression revealed a direct role of COX-2 and an indirect COX-2 dependent role of HER-2 in VEGF-C up-regulation: (i) high VEGF-C expression in high COX-2/low HER-2 expressing MDA-MB-231 cells was reduced by siRNA-mediated down-regulation of COX-2, but not HER-2; (ii) integration of HER-2 in these cells simultaneously up-regulated COX-2 protein as well as VEGF-C secretion; and (iii) low VEGF-C secretion by high HER-2/low COX-2 expressing SK-BR-3 cells was stimulated by COX-2 overexpression. These findings of the primary role of COX-2 and the COX-2-dependent role of HER-2, if any, in VEGF-C up-regulation and lymphangiogenesis suggest that COX-2 inhibitors may abrogate lymphatic metastasis in breast cancer irrespective of HER-2 status. © 2010 Japanese Cancer Association
O-GlcNAcylation and Regulation of Galectin-3 in Extraembryonic Endoderm Differentiation
The regulation of proteins through the addition and removal of O-linked ÎČ-N-acetylglucosamine (O-GlcNAc) plays a role in many signaling events, specifically in stem cell pluripo-tency and the regulation of differentiation. However, these post-translational modifications have not been explored in extraembryonic endoderm (XEN) differentiation. Of the plethora of proteins regulated through O-GlcNAc, we explored galectin-3 as a candidate protein known to have various intracellular and extracellular functions. Based on other studies, we predicted a reduction in global O-GlcNAcylation levels and a distinct galectin expression profile in XEN cells relative to embryonic stem (ES) cells. By conducting dot blot analysis, XEN cells had decreased levels of global O-GlcNAc than ES cells, which reflected a disbalance in the expression of genes encoding O-GlcNAc cycle enzymes. Immunoassays (Western blot and ELISA) revealed that although XEN cells (low O-GlcNAc) had lower concentrations of both intracellular and extracellular galectin-3 than ES cells (high O-GlcNAc), the relative secretion of galectin-3 was significantly increased by XEN cells. Inducing ES cells toward XEN in the presence of an O-GlcNAcase inhibitor was not sufficient to inhibit XEN differentiation. However, global O-GlcNAcylation was found to decrease in differentiated cells and the extracellular localization of galectin-3 accompanies these changes. Inhibiting global O-GlcNAcylation status does not, however, impact pluripotency and the ability of ES cells to differentiate to the XEN lineage
Effects of global O-GlcNAcylation on galectin gene-expression profiles in human cancer cell lines
Background/Aim: The effects of O-linked ÎČ-N-acetyl-D-glucosamine (O-GlcNAc) transferase (OGT) and O-GlcNAcase (OGA) inhibitors on galectin gene expression profiles were examined in MCF7, HT-29, and HL-60 cancer cell lines. Materials and Methods: Cell cultures were treated for 24 h with OGA inhibitor thiamet G or OGT inhibitor 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-5-thio-α-D-glucopyranose, and global O-GlcNAc levels and expression of galectin genes were determined using an immunodot blot assay and real-time quantitative polymerase chain reaction. Results: Two galectin genes, LGALS3 in MCF7 cells and LGALS12 in HL-60 cells, were up-regulated by O-GlcNAc, whereas other cell-specific galectins were unresponsive to changes in O-GlcNAc level. Of interest, basal levels of O-GlcNAc in resting HL-60 and HT-29 cells were significantly higher than those in cells differentiated into neutrophilic or enterocytic lineages, respectively. Conclusion: O-GlcNAc-mediated signaling pathways may be involved in regulating the expression of only a limited number of galectin genes. Additional O-GlcNAc-dependent mechanisms may work at the protein level (galectin secretion and intracellular localization) and warrant further investigation
Management of space surveillance radar temporal resource on fuzzy set theory
This paper addresses the problem of optimizing the use of temporal resources of a radar station (RS) under limited time
resources. Special attention is given to the necessity of considering a multitude of compensatory optimality criteria
when allocating the RS operating time. The proposed approach is based on the use of fuzzy set theory which represents
an innovative solution in the context of this task. The task of managing the RS temporal resources is formulated as the
search for an optimal work schedule among all potentially possible options. This schedule should minimize the values
of all partial optimality criteria. Fuzzy set theory is applied to solve this problem, allowing for the consideration of
uncertainty and variability in task execution conditions. An algorithm for managing the RS temporal resources was
presented. The review results confirm the probable increase in efficiency, especially in conditions of acute shortage
of temporal resources, ensuring their optimal distribution among current tasks. Furthermore, the algorithm enables
decisions to be made about the possibility of performing special or additional tasks without compromising the main
monitoring functions. The review of the proposed algorithm provides a basis for hypothesizing its advantages over
traditional methods of managing the RS temporal resources. In particular, the use of fuzzy set theory allows for more
flexible responses to changes in task execution conditions and enhances the overall adaptability of the system. In the
future, this approach could be adapted and applied in other areas where there is a need for resource optimization under
conditions of limitation and uncertainty of external factors
Algorithm for promptly maintaining the temperature regime of power amplification units of the radar transmitting complex based on a thermal model
The development trends of modern electronic equipment included in radar stations consist of a constant increase in the
output radiated power. This leads to a significant increase in heat generation of power amplification units as the most
heat-loaded ones. To reduce failures of these units associated with overheating, this work proposes an original algorithm
for quickly maintaining the temperature regime. The algorithm is based on a thermal model, which allows, unlike the
known ones, to calculate the temperature distribution in the block in real time, taking into account telemetry from
temperature sensors installed inside the block. The novelty of the proposed algorithm lies in the real-time control of the
cooling system based on the block temperature forecast obtained using a thermal model. The thermal model is based
on the mathematical formalization of thermal processes using the anisotropic body method, which allows minimizing
the computational costs of calculations by representing the power amplification unit as a quasi-homogeneous body.
Simulation of the temperature distribution process in the power amplification unit was performed in the COMSOL.
To evaluate the efficiency of the algorithm and the ability to operate in real time at the operational stage of the radar
station, a computational experiment was performed using model data. The simulation results confirmed the possibility
of calculating the temperature distribution in the block in real time. Unlike existing algorithms for maintaining the
temperature regime of a block, based on the readings of temperature sensors that determine the temperature at the current
moment in time, the developed algorithm implements a temperature forecast. This allows you to take measures to cool
the unit before the onset of critical emergency situations
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
Co-Expression of α9ÎČ1 Integrin and VEGF-D Confers Lymphatic Metastatic Ability to a Human Breast Cancer Cell Line MDA-MB-468LN
INTRODUCTION AND OBJECTIVES: Lymphatic metastasis is a common occurrence in human breast cancer, mechanisms remaining poorly understood. MDA-MB-468LN (468LN), a variant of the MDA-MB-468GFP (468GFP) human breast cancer cell line, produces extensive lymphatic metastasis in nude mice. 468LN cells differentially express α9ÎČ1 integrin, a receptor for lymphangiogenic factors VEGF-C/-D. We explored whether (1) differential production of VEGF-C/-D by 468LN cells provides an autocrine stimulus for cellular motility by interacting with α9ÎČ1 and a paracrine stimulus for lymphangiogenesis in vitro as measured with capillary-like tube formation by human lymphatic endothelial cells (HMVEC-dLy); (2) differential expression of α9 also promotes cellular motility/invasiveness by interacting with macrophage derived factors; (3) stable knock-down of VEGF-D or α9 in 468LN cells abrogates lymphangiogenesis and lymphatic metastasis in vivo in nude mice. RESULTS: A comparison of expression of cyclo-oxygenase (COX)-2 (a VEGF-C/-D inducer), VEGF-C/-D and their receptors revealed little COX-2 expression by either cells. However, 468LN cells showed differential VEGF-D and α9ÎČ1 expression, VEGF-D secretion, proliferative, migratory/invasive capacities, latter functions being stimulated further with VEGF-D. The requirement of α9ÎČ1 for native and VEGF-D-stimulated proliferation, migration and Erk activation was demonstrated by treating with α9ÎČ1 blocking antibody or knock-down of α9. An autocrine role of VEGF-D in migration was shown by its impairment by silencing VEGF-D and restoration with VEGF-D. 468LN cells and their soluble products stimulated tube formation, migration/invasiveness of HMVEC-dLy cell in a VEGF-D dependent manner as indicated by the loss of stimulation by silencing VEGF-D in 468LN cells. Furthermore, 468LN cells showed α9-dependent stimulation of migration/invasiveness by macrophage products. Finally, capacity for intra-tumoral lymphangiogenesis and lymphatic metastasis in nude mice was completely abrogated by stable knock-down of either VEGF-D or α9 in 468LN cells. CONCLUSION: Differential capacity for VEGF-D production and α9ÎČ1 integrin expression by 468LN cells jointly contributed to their lymphatic metastatic phenotype
Measurement of the flavour composition of dijet events in pp collisions at root s=7 TeV with the ATLAS detector
This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at √s=7 TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39Â pbâ1. Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40Â GeV to 500Â GeV and jet rapidity |y|<2.1. The fit results agree with the predictions of leading- and next-to-leading-order calculations, with the exception of the dijet fraction composed of bottom and light flavour jets, which is underestimated by all models at large transverse jet momenta. The ability to identify jets containing two b-hadrons, originating from e.g. gluon splitting, is demonstrated. The difference between bottom jet production rates in leading and subleading jets is consistent with the next-to-leading-order predictions
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