1,026 research outputs found
Small Footprint Multilayered Millimeter-Wave Antennas and Feeding Networks for Multi-Dimensional Scanning and High-Density Integrated Systems
This paper overviews the state-of-the-art of substrate integrated waveguide (SIW) techniques in the design and realization of innovative low-cost, low-profile and low-loss (L3) millimeter-wave antenna elements, feeding networks and arrays for various wireless applications. Novel classes of multilayered antenna structures and systems are proposed and studied to exploit the vertical dimension of planar structures to overcome certain limita-tions in standard two-dimensional (2-D) topologies. The developed structures are based on two techniques, namely multi-layer stacked structures and E-plane corners. Differ-ent E-plane structures realised with SIW waveguide are presented, thereby demonstrating the potential of the proposed techniques as in multi-polarization antenna feeding. An array of 128 elements shows low SLL and height gain with just 200g of the total weight. Two versions of 2-D scanning multi-beam are presented, which effectively combine frequency scanning with beam forming networks. Adding the benefits of wide band performance to the multilayer structure, two bi-layer structures are investigated. Different stacked antennas and arrays are demonstrated to optimise the targeted antenna performances in the smallest footprint possible. These structures meet the requirement for developing inexpensive compact millimeter-wave antennas and antenna systems. Different structures and architectures are theoretically and experimentally studied and discussed for specific space- and ground-based appli-cations. Practical issues such as high-density integration and high-volume manufacturability are also addressed
Comparison of Three Different Techniques of Inverted Internal Limiting Membrane Flap in Treatment of Large Idiopathic Full-Thickness Macular Hole.
Purpose: To evaluate and compare three different techniques of inverted internal limiting membrane (ILM) flap in the treatment of large idiopathic full-thickness macular hole.
Methods: In a comparative interventional case series, 72 eyes from 72 patients with large (\u3e 400 µm) full-thickness macular hole were randomly enrolled into three different groups: group A - hemicircular ILM peel with temporally hinged inverted flap; group B - circular ILM peel with temporally hinged inverted flap; and group C - circular ILM peel with superior inverted flap. Best-corrected visual acuity (BCVA), anatomical closure rate, and ellipsoid zone (EZ) or external limiting membrane (ELM) defects were evaluated preoperatively, at week 1, and months 1, 3 and 6 after surgery.
Results: There were 24 eyes in group A, 23 in group B, and 25 in group C. In all three groups, larger diameter macular hole was associated with worse preoperative visual acuity (r=0.625, P\u3c0.001). Mean BCVA improved significantly in all three groups 6 months after surgery (0.91vs 0.55, p\u3c0.001). 6 months after surgery, mean BCVA improved from 0.91 logMAR to 0.52±0.06 in group A, 0.90 to 0.53±0.06 in group B, and 0.91 to 0.55±0.11 in group C. In group A vs. B vs. C, improvement of BCVA was 0.380±0.04 vs. 0.383±0.04 vs. 0.368±0.11 logMAR, with no statistically significant difference between groups (P=0.660). The rate of successful hole closure was 87.5% vs. 91.3% vs. 100%. Although the closure rate was 100% in Group C (circular ILM peel with superiorly hinged inverted flap), this difference was not statistically significant (P=0.115).
Conclusion: ILM peel with an inverted flap is a highly effective procedure for the treatment of large, full-thickness macular hole. Different flap techniques have comparable results, indicating that the technique can be chosen based on surgeon preference
Ground states of Heisenberg spin clusters from a cluster-based projected Hartree-Fock approach
Recent work on approximating ground states of Heisenberg spin clusters by
projected Hartree-Fock theory (PHF) is extended to a cluster-based ansatz
(cPHF). Whereas PHF variationally optimizes a site-spin product state for the
restoration of spin- and point-group symmetry, cPHF groups sites into discrete
clusters and uses a cluster-product state as the broken-symmetry reference.
Intracluster correlation is thus already included at the mean-field level and
intercluster correlation is introduced through symmetry projection. Variants of
cPHF differing in the broken and restored symmetries are evaluated for ground
states and singlet-triplet gaps of antiferromagnetic spin rings for various
cluster sizes, where cPHF in general affords a significant improvement over
ordinary PHF, although the division into clusters lowers the cyclical symmetry.
On the other hand, certain two- or three-dimensional spin arrangements permit
cluster groupings compatible with the full spatial symmetry. We accordingly
demonstrate that cPHF yields approximate ground states with correct spin and
point-group quantum numbers for honeycomb lattice fragments and symmetric
polyhedra.Comment: 41 page
C3G mediated suppression of malignant transformation involves activation of PP2A phosphatases at the subcortical actin cytoskeleton
In previous work, we demonstrated that C3G suppresses Ras oncogenic transformation by a mechanism involving inhibition of ERK phosphorylation. Here we present evidences indicating that this suppression mechanism is mediated, at least in part, by serine/threonine phosphatases of the PP2A family. Thus: (i) ectopic expression of C3G or C3GΔCat (mutant lacking the GEF activity) increases specific ERK-associated PP2A phosphatase activities; (ii) C3G and PP2A interact, as demonstrated by immunofluorescence and co-immunoprecipitation experiments; (iii) association between PP2A and MEK or ERK increases in C3G overexpressing cells; (iv) phosphorylated-inactive PP2A level decreases in C3G expressing clones and, most importantly, (v) okadaic acid reverts the inhibitory effect of C3G on ERK phosphorylation. Moreover, C3G interacts with Ksr-1, a scaffold protein of the Ras-ERK pathway that also associates with PP2A. The fraction of C3G involved in transformation suppression is restricted to the subcortical actin cytoskeleton where it interacts with actin. Furthermore, the association between C3G and PP2A remains stable even after cytoskeleton disruption with cytochalasin D, suggesting that the three proteins form a complex at this subcellular compartment. Finally, C3G- and C3GΔCat-mediated inhibition of ERK phosphorylation is reverted by incubation with cytochalasin D. We hypothesize that C3G triggers PP2A activation and binding to MEK and ERK at the subcortical actin cytoskeleton, thus favouring ERK dephosphorylation. © 2007 Elsevier Inc. All rights reserved.This work was supported by grants SAF2003-04177 andGEN2003- 20239-C06-02 from MEC, Spain, FIS-FEDERPI030651, PI041324 and PI061274 from ISCIII,MSC, Spain, as well as institutional support from Redes Temáticas (C03/10 and RD06/0020/0000) de investigación en cáncer from ISCIII, MSC, Spain. S. M-E is a postodoctoral fellow supported by grant GEN2003-20239-C06-02. C.G. was supported by the Ramón y Cajal Program from the Spanish Ministry of Education.Peer Reviewe
Determining a piston's top dead center (TDC) in an automobile using installed piezoelectric on a vibrating beam
Smart structures and MEMS are considered important field recently, due to the importance and high capabilities in measurement and the power of reaction and response to changes of the surroundings. This research concerns two fields of practical vision in the automotive industry and discuss the energy recycled industrial vibrations. The goal is to use the PVDF piezoelectric elements in car flywheel for energy harvesting, and compare and replace it with the revolution sensor. This research is totally based on empirical tests data and the result that the use of piezoelectric polymer sensors can harvest energy, was find performing far better than inductive sensors.Keywords: Piezoelectric element; Vibration energy harvesting; smart structures; Revolution sensor; Flywhee
Complete Resection of Ampullary Paragangliomas Confined to the Submucosa on Endoscopic Ultrasound May Be Best Achieved by Radical Surgical Resection
Paragangliomas of the gastrointestinal tract generally are benign tumors usually found in the second portion of the duodenum. We present a case of paraganglioma of the ampulla of Vater confined to the submucosa on endoscopic ultrasound examination. This was initially treated by endoscopic resection, followed by pancreaticoduodenectomy after local resection margins were positive. Histopathology showed a well-differentiated ampullary paraganglioma confined to the submucosa, but with involvement of one regional lymph node. Only 25 prior cases of paraganglioma at the ampulla of Vater have been reported, and nine of these have demonstrated local or distant metastases. Because of their malignant potential, ampullary paragangliomas should be treated with radical resection if the goal is to achieve complete resection, even if preoperative imaging shows local confinement
Scorpion envenomation in Bagh-E Malek, Iran –a 5 year study
Scorpionism is a major health problem in many tropical countries including Iran. The aim of this study was to describe the epidemiological and demographic information among whom stung by scorpions in Bagh-E Malek, Iran. In this retrospective cross-sectional study the information were gathered through evaluation of the records of stung patients referring to Shahid Tabatabai hospital of Bagh-E Malek April 2008 to April 2012. A total of 132 cases stung by scorpion were recorded including 3115 males (43%) and 4121 females (57%).Approximately 42.1 percent of the sting cases occurred in the summer followed by spring with 35.9% of stings. About 59.8% of stings happened in people by the age of 15-44 years old. Most of the stings happened in exposed extremities (78.5%) with most of it in upper limbs (41.8%). The scorpions’ species were unknown but 60.4% of them were yellow, 34.0% black and 5.6% were “other colors”. Since the highest rate of scorpionism cases were reported in rural areas (74.2%), it is suggested that the main focus should be considered for education of rural people, especially women who play a major role in the family. Additionally, evaluation of residential houses and surrounding environment and giving information on method of cleaning up the environment from the equipment and the factors from which scorpion may use as shelter, can also be effective in reducing the incidence of Scorpionism.Keywords: Scorpion sting; Epidemiology; Bagh-E Malek; Ira
A Process Calculus for Dynamic Networks
In this paper we propose a process calculus framework for dynamic networks in which the network topology may change as computation proceeds. The proposed calculus allows one to abstract away from neighborhood-discovery computations and it contains features for broadcasting at multiple transmission ranges and for viewing networks at different levels of abstraction. We develop a theory of confluence for the calculus and we use the machinery developed towards
the verification of a leader-election algorithm for mobile ad hoc networks
Calculation of molecular g-tensors by sampling spin orientations of generalised Hartree-Fock states
The variational inclusion of spin-orbit coupling in self-consistent field
(SCF) calculations requires a generalised two-component framework, which
permits the single-determinant wave function to completely break spin symmetry.
The individual components of the molecular g-tensor are commonly obtained from
separate SCF solutions that align the magnetic moment along one of the three
principal tensor axes. However, this strategy raises the question if energy
differences between solutions are relevant, or how convergence is achieved if
the principal axis system is not determined by molecular symmetry. The present
work resolves these issues by a simple two-step procedure akin to the generator
coordinate method (GCM). First, a few generalised Hartree Fock (GHF) solutions
are converged, applying, where needed, a constraint to the orientation of the
magnetic-moment or spin vector. Then, superpositions of GHF determinants are
formed through non-orthogonal configuration interaction. This procedure yields
a Kramers doublet for the calculation of the complete g-tensor. Alternatively,
for systems with weak spin-orbit effects, diagonalisation in a basis spanned by
spin rotations of a single GHF determinant affords qualitatively correct
g-tensors by eliminating errors related to spin contamination. For small
first-row molecules, these approaches are evaluated against experimental data
and full configuration interaction results. It is further demonstrated for two
systems (a fictitious tetrahedral CH4+ species, and a CuF4(2-) complex) that a
GCM strategy, in contrast to alternative mean-field methods, can correctly
describe the spin-orbit splitting of orbitally-degenerate ground states, which
causes large g-shifts and may lead to negative g-values.Comment: 33 pages, 5 figur
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