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1
Bondarenko, I. N., I. Yu Bliznyuk, and Е. А. Gorbenko. "MICROWAVE IRREGULAR RESONANT STRUCTURES." Telecommunications and Radio Engineering 78, no. 5 (2019): 385–92. http://dx.doi.org/10.1615/telecomradeng.v78.i5.20.
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Houfek, Karel, Martin Čížek, and Jiří Horáček. "On irregular oscillatory structures in resonant vibrational excitation cross-sections in diatomic molecules." Chemical Physics 347, no. 1-3 (May 2008): 250–56. http://dx.doi.org/10.1016/j.chemphys.2007.11.017.
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Ni, Wenjun, Chunyong Yang, Yiyang Luo, Ran Xia, Ping Lu, Dora Juan Juan Hu, Sylvain Danto, Perry Ping Shum, and Lei Wei. "Recent Advancement of Anti-Resonant Hollow-Core Fibers for Sensing Applications." Photonics 8, no. 4 (April 19, 2021): 128. http://dx.doi.org/10.3390/photonics8040128.
Повний текст джерелаАнотація:
Specialty fibers have enabled a wide range of sensing applications. Particularly, with the recent advancement of anti-resonant effects, specialty fibers with hollow structures offer a unique sensing platform to achieve highly accurate and ultra-compact fiber optic sensors with large measurement ranges. This review presents an overview of recent progress in anti-resonant hollow-core fibers for sensing applications. Both regular and irregular-shaped fibers and their performance in various sensing scenarios are summarized. Finally, the challenges and possible solutions are briefly presented with some perspectives toward the future development of anti-resonant hollow-core fibers for advanced sensing.
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D’Acunto, Mario, Francesco Fuso, Ruggero Micheletto, Makoto Naruse, Francesco Tantussi, and Maria Allegrini. "Near-field surface plasmon field enhancement induced by rippled surfaces." Beilstein Journal of Nanotechnology 8 (April 28, 2017): 956–67. http://dx.doi.org/10.3762/bjnano.8.97.
Повний текст джерелаАнотація:
The occurrence of plasmon resonances on metallic nanometer-scale structures is an intrinsically nanoscale phenomenon, given that the two resonance conditions (i.e., negative dielectric permittivity and large free-space wavelength in comparison with system dimensions) are realized at the same time on the nanoscale. Resonances on surface metallic nanostructures are often experimentally found by probing the structures under investigation with radiation of various frequencies following a trial-and-error method. A general technique for the tuning of these resonances is highly desirable. In this paper we address the issue of the role of local surface patterns in the tuning of these resonances as a function of wavelength and electric field polarization. The effect of nanoscale roughness on the surface plasmon polaritons of randomly patterned gold films is numerically investigated. The field enhancement and relation to specific roughness patterns is analyzed, producing many different realizations of rippled surfaces. We demonstrate that irregular patterns act as metal–dielectric–metal local nanogaps (cavities) for the resonant plasmonic field. In turn, the numerical results are compared to experimental data obtained via aperture scanning near-field optical microscopy.
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Cotti, Giordano, and Davide Guzzetti. "Results on the extension of isomonodromy deformations to the case of a resonant irregular singularity." Random Matrices: Theory and Applications 07, no. 04 (October 2018): 1840003. http://dx.doi.org/10.1142/s2010326318400038.
Повний текст джерелаАнотація:
We explain some results of [G. Cotti, B. A. Dubrovin and D. Guzzetti, Isomonodromy deformations at an irregular singularity with coalescing eigenvalues, preprint (2017); arXiv:1706.04808 .], discussed in our talk [G. Cotti, Monodromy of semisimple Frobenius coalescent structures, in Int. Workshop Asymptotic and Computational Aspects of Complex Differential Equations, CRM, Pisa, February 13–17, (2017).] in Pisa, February 2017. Consider an [Formula: see text] linear system of ODEs with an irregular singularity of Poincaré rank 1 at [Formula: see text] and Fuchsian singularity at [Formula: see text], holomorphically depending on parameter [Formula: see text] within a polydisk in [Formula: see text] centered at [Formula: see text]. The eigenvalues of the leading matrix at [Formula: see text], which is diagonal, coalesce along a coalescence locus [Formula: see text] contained in the polydisk. Under minimal vanishing conditions on the residue matrix at [Formula: see text], we show in [G. Cotti, B. A. Dubrovin and D. Guzzetti, Isomonodromy deformations at an irregular singularity with coalescing eigenvalues, preprint (2017); arXiv:1706.04808 .] that isomonodromic deformations can be extended to the whole polydisk, including [Formula: see text], in such a way that the fundamental matrix solutions and the constant monodromy data are well defined in the whole polydisk. These data can be computed just by considering the system at point of [Formula: see text], where it simplifies. Conversely, if the [Formula: see text]-dependent system is isomonodromic in a small domain contained in the polydisk not intersecting [Formula: see text], and if suitable entries of the Stokes matrices vanish, then [Formula: see text] is not a branching locus for the fundamental matrix solutions. The results have applications to Frobenius manifolds and Painlevé equations.
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Tsutsumanova, Gitchka G., Neno D. Todorov, Stoyan C. Russev, Miroslav V. Abrashev, Victor G. Ivanov, and Alexey V. Lukoyanov. "Silver Flowerlike Structures for Surface-Enhanced Raman Spectroscopy." Nanomaterials 11, no. 12 (November 24, 2021): 3184. http://dx.doi.org/10.3390/nano11123184.
Повний текст джерелаАнотація:
Micro- and nanoflowers are a class of materials composed of particles with high surface-to-volume ratio. They have been extensively studied in the last decade due to simple preparation protocols and promising applications in biosensing, as drug delivery agents, for water purification, and so on. Flowerlike objects, due to their highly irregular surface, may act also as plasmonic materials, providing resonant coupling between optical waves and surface plasmon excitations. This fact allows us to infer the possibility to use micro- and nanoflowers as effective surface-enhanced Raman scattering (SERS) substrate materials. Here, we report on the design and Raman enhancement properties of silver flowerlike structures, deposited on aluminum surface. A simple and cost-effective fabrication method is described, which leads to SERS substrates of high developed surface area. The morphology of the silver flowers on a nanoscale is characterized by self-organized quasiperiodic stacks of nanosheets, which act as plasmonic cavity resonators. The substrates were tested against rhodamine-6G (R6G) water solutions of concentration varying between 10−3 M and 10−7 M. Optimal SERS enhancement factors of up to 105 were established at R6G concentrations in the 10−6–10−7 M range.
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Firdaus, Nurman, Eko Budi Djatmiko, Rudi Walujo Prastianto, and Muryadin. "Experimental Study on Coupled Motion of Floating Crane Barge and Lifted Module in Irregular Waves." IOP Conference Series: Earth and Environmental Science 972, no. 1 (January 1, 2022): 012070. http://dx.doi.org/10.1088/1755-1315/972/1/012070.
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Abstract Installation and decommissioning activities of offshore structures often applied a floating crane barge for a lifting operation. The excessive movement response of lifted module affected by the motion of floating crane barge in waves can increase a large amplitude. However, the coupled motions of a floating crane barge and lifted module are not easy to predict accurately due to the dynamic movement of a lifted module and the complex coupling system. The coupled motion responses of a floating crane barge and a lifted module during lifting operation were investigated based on time domain by experimental method in this study. The model tests are carried out at Manoeuvring and Ocean Basin of Indonesian Hydrodynamic Laboratory, BRIN. The experimental conditions include the load cases of without and with a load of lifted module in crane tip, and the lifting operation was evaluated under irregular wave conditions. The experimental results show in that the phenomena of shift resonant frequency for the dynamic responses are clearly observed on the coupled motion of multibody system. The dynamic oscillations of the lifted module have a significant effect on the motion response of the floating crane barge. And the hoisting of lifted module has an obstructed effect on the rolling motion of crane barge.
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Thejaswini, R. M., L. Govindaraju, and V. Devaraj. "Experimental and Numerical Studies on Setback Buildings Considering the SSI Effect under Seismic Response." Civil Engineering Journal 7, no. 3 (March 3, 2021): 431–48. http://dx.doi.org/10.28991/cej-2021-03091664.
Повний текст джерелаАнотація:
From the previous studies it is observed that due to the effect of the earthquake, several irregular buildings failed vulnerably. Further the effect of sub soil conditions where these buildings have been founded also play an important role on the seismic response of these buildings. In the past, experimental studies on the seismic response of different setback building configurations have not been carried out. Therefore, in the present study the seismic behaviour of setback buildings considering Soil Structure Interaction (SSI) has been evaluated by conducting experimental and numerical investigations. Buildings with various setback configurations were considered and are designed as pile foundation supported structures. The irregularity index of these building configurations have been determined as per the existing codal provisions. These piles supported buildings representing the prototype structure have been scaled down according to geometric, kinematic and dynamic scaling laws. The scaled building models are subjected to vibrations beyond resonant frequencies using shake table facility. A comparison of the results has been made between experimental and numerical investigations. Based on the study it has been observed that storey displacements of building with regular configurations are higher in comparison with the setback buildings. It is also found that asymmetrical and symmetrical setback buildings having different irregularity indices as per IS:1893-2016 indicate nearly the same displacements at resonant frequencies. Doi: 10.28991/cej-2021-03091664 Full Text: PDF
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Georgiou, I. T., I. Schwartz, E. Emaci, and A. Vakakis. "Interaction Between Slow and Fast Oscillations in an Infinite Degree-of-Freedom Linear System Coupled to a Nonlinear Subsystem: Theory and Experiment." Journal of Applied Mechanics 66, no. 2 (June 1, 1999): 448–59. http://dx.doi.org/10.1115/1.2791069.
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The interaction dynamics of a cantilever linear beam coupled to a nonlinear pendulum, a prototype for linear/nonlinear coupled structures of infinite degrees-of-freedom, has been studied analytically and experimentally. The spatio-temporal characteristics of the dynamics is analyzed by using tools from geometric singular perturbation theory and proper orthogonal decompositions. Over a wide range of coupling between the linear beam and the nonlinear pendulum, the coupled dynamics is dominated by three proper orthogonal (PO) modes. The first two dominant PO modes stem from those characterizing the reduced slow free dynamics of the stiff/soft (weakly coupled) system. The third mode appears in all interactions and stems from the reduced fast free dynamics. The interaction creates periodic and quasi-periodic motions that reduce dramatically the forced resonant dynamics in the linear substructure. These regular motions are characterized by four PO modes. The irregular interaction dynamics consists of low-dimensional and high-dimensional chaotic motions characterized by three PO modes and six to seven PO modes, respectively. Experimental tests are also carried out and there is satisfactory agreement with theoretical predictions.
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Tarucha, Seigo. "Transport in Quantum Dots: Observation of Atomlike Properties." MRS Bulletin 23, no. 2 (February 1998): 49–53. http://dx.doi.org/10.1557/s0883769400031274.
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Recent advances in nanofabrication technologies have enabled us to fabricate semiconductor quantum dots in which electrons are three-dimensionally confined. These quantum dots are often referred to as artificial atoms since their electronic properties—for example the ionization energy and discrete excitation spectrum—resemble those of real atoms. Electrons bound to a nucleus potential encounter sufficiently strong effects of quantum-mechanical confinement and mutual Coulomb interactions that they are well arranged in ordered states, and this leads to the arrangement of atoms in the periodic table. It is well known in atom physics that the threedimensional spherically symmetric potential around atoms gives rise to the shell structure 1s, 2s, 2p, 3s, 3p,…. The ionization energy has a large maximum for atomic numbers 2, 10, 18,…. Up to atomic number 23, these shells are filled sequentially. Hund's rule determines whether a spin-down or a spin-up electron is added. This article describes how closely we can approach the electronic properties of real atoms through the use of semiconductor quantum dots.Both the effects of quantum confinement and Coulomb interaction become strong in quantum dots when the dot size is comparable to the electron wavelength and contains just a few electrons. The consequence of these factors on transport have only recently been studied in vertical-dot devices, which contain a dot located between source and drain contacts by means of heterostructure tunnel barriers because the few-electron regime is only accessible in the vertical-dot device. Studies include transport measurements through submicron resonant tunneling devices and submicron gated resonant-tunneling devices, and capacitance measurements on submicron double-barrier structures. However quantum-dot devices usually contain some disorder—for instance because of impurities or when the shape of the dot is irregular—which readily causes sample specific inhomogeneity in the electronic properties. Clean quantum dots, in the form of regular disks, have only recently been fabricated in a semiconductor heterostructure (Figure 1), and have been used to study the atomlike properties of artificial atoms.
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Nesvorný, David. "Dynamical Evolution of the Early Solar System." Annual Review of Astronomy and Astrophysics 56, no. 1 (September 14, 2018): 137–74. http://dx.doi.org/10.1146/annurev-astro-081817-052028.
Повний текст джерелаАнотація:
Several properties of the Solar System, including the wide radial spacing of the giant planets, can be explained if planets radially migrated by exchanging orbital energy and momentum with outer disk planetesimals. Neptune's planetesimal-driven migration, in particular, has a strong advocate in the dynamical structure of the Kuiper belt. A dynamical instability is thought to have occurred during the early stages with Jupiter having close encounters with a Neptune-class planet. As a result of the encounters, Jupiter acquired its current orbital eccentricity and jumped inward by a fraction of an astronomical unit, as required for the survival of the terrestrial planets and from asteroid belt constraints. Planetary encounters also contributed to capture of Jupiter Trojans and irregular satellites of the giant planets. Here we discuss the dynamical evolution of the early Solar System with an eye to determining how models of planetary migration/instability can be constrained from its present architecture. Specifically, we review arguments suggesting that the Solar System may have originally contained a third ice giant on a resonant orbit between Saturn and Uranus. This hypothesized planet was presumably ejected into interstellar space during the instability. The Kuiper belt kernel and other dynamical structures in the trans-Neptunian region may provide evidence for the ejected planet. We favor the early version of the instability where Neptune migrated into the outer planetesimal disk within a few tens of millions of years after the dispersal of the protosolar nebula. If so, the planetary migration/instability was not the cause of the Late Heavy Bombardment. Mercury's orbit may have been excited during the instability.
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Lin, Y‐J, and Suresh V. Venna. "A novel method for piezoelectric transducers placement for passive vibration control of geometrically non‐linear structures." Sensor Review 28, no. 3 (June 27, 2008): 233–41. http://dx.doi.org/10.1108/02602280810882599.
Повний текст джерелаАнотація:
PurposeThe purpose of this paper is to propose an effective and novel methodology to determine optimal location of piezoelectric transducers for passive vibration control of geometrically complicated structures and shells with various curvatures. An industry‐standard aircraft leading‐edge structure is considered for the actuator placement analysis and experimental verification.Design/methodology/approachThe proposed method is based on finite element analysis of the underlying structure having a thin layer of piezoelectric elements covering the entire inner surface with pertinent boundary conditions. All the piezoelectric properties are incorporated into the elements. Specifically, modal piezoelectric analysis is performed to provide computed tomography for the evaluations of the electric potential distributions on these piezoelectric elements attributed by the first bending and torsional modes of structural vibration. Then, the outstanding zone(s) yielding highest amount of electric potentials can be identified as the target location for the best actuator placement.FindingsSix piezoelectric vibration absorbers are determined to be placed alongside both of the fixed edges. An experimental verification of the aluminum leading edge's vibration suppression using the proposed method is conducted exploiting two resistive shunt circuits for the passive damping. A good agreement is obtained between the analytical and experimental results. In particular, vibration suppression around 30 and 25 per cent and Q‐factor reduction up to 15 and 10 per cent are obtained in the designated bending and torsional modes, respectively. In addition, some amount of damping improvement is observed at higher modes of vibration as well.Research limitations/implicationsThe frequency in the proposed approach will be increased slowly and gradually from 0 to 500 Hz. When the frequency matches the natural frequency of the structure, owing to the resonant condition the plate will vibrate heavily. The vibrations of the plate can be observed by connecting a sensor to an oscilloscope. Owing to the use of only one sensor, not all the modes can be detected. Only the first few modes can be picked up by the sensor, because of its location.Practical implicationsThis method can also be used in optimizing not only the location but also the size and shape of the passive vibration absorber to attain maximum amount of damping. This can be achieved by simply changing the dimensions and shape of the piezoelectric vibration absorber in the finite element model on an iterative basis to find the configuration that gives maximum electric potential.Originality/valueThe determination of optimal location(s) for piezoelectric transducers is very complicated and difficult if the geometry of structures is curved or irregular. Therefore, it has never been reported in the literature. Here an efficient FEA‐based electric potential tomography method is proposed to identify the optimized locations for the PZT transducers for passive vibration control of geometrically complicated structures, with minimal efforts. In addition, this method will facilitate the determination of electric potentials that would be obtained at all the possible locations for piezoelectric transducers and hence makes it possible to optimize the placement and configurations of the candidate transducers on complex shape structures.
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Szachniuk, M. "Assigning NMR spectra of irregular RNAs by heuristic algorithms." Bulletin of the Polish Academy of Sciences Technical Sciences 63, no. 1 (March 1, 2015): 329–38. http://dx.doi.org/10.1515/bpasts-2015-0037.
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Abstract Computer-aided analysis and preprocessing of spectral data is a prerequisite for any study of molecular structures by Nuclear Magnetic Resonance (NMR) spectroscopy. The data processing stage usually involves a considerable dedication of time and expert knowledge to cope with peak picking, resonance signal assignment and calculation of structure parameters. A significant part of the latter step is performed in an automated way. However, in peak picking and resonance assignment a multistage manual assistance is still essential. The work presented here is focused on the theoretical modeling and analyzing the assignment problem by applying heuristic approaches to the NMR spectra recorded for RNA structures containing irregular regions.
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Liu, Yao, Yong-Hwan Cho, Norimi Mizutani, and Tomoaki Nakamura. "Study on the Resonant Behaviors of a Bottom-Hinged Oscillating Wave Surge Converter." Journal of Marine Science and Engineering 10, no. 1 (December 21, 2021): 2. http://dx.doi.org/10.3390/jmse10010002.
Повний текст джерелаАнотація:
This paper studied the resonant behaviors of a bottom-hinged oscillating wave surge converter (OWSC) as well as the relationship of resonance with the response and capture width ratio (CWR). The time-domain dynamic equation of an OWSC in shallow water based on the boundary element method (BEM) was solved by a Python code, considering the corrected wave surface and the nonlinearities of restoring moment, drag, and friction. The unknown factors, such as wave surface corrected factor and drag coefficient, were effectively calibrated with computational fluid dynamics (CFD) method. An intermediate initial angle in free decay is appropriate for use to determine the natural period. Under regular waves, the resonance occurs near the natural period for the uniform wave amplitude, rather than the uniform wave torque amplitude, and can disappear due to the amplification of Power Take-Off (PTO) friction. Under unit-amplitude regular waves, the period of maximum CWR is relatively close to the period of maximum velocity, but far from the resonant period. Under irregular waves, no stable resonance is observed because the maximum equivalent pitch angle appears at different peak periods of wave spectra with the variation in PTO damping. When the period of a regular wave or the peak period of an irregular wave is close to the natural period, a phase hysteresis of velocity relative to wave torque always occurs.
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Swaliheen, Mohd. "Comparison of Analysis and Design of Regular and Irregular Configuration of Multi Story Building in Seismic Zones." International Journal for Research in Applied Science and Engineering Technology 9, no. 8 (August 31, 2021): 2395–412. http://dx.doi.org/10.22214/ijraset.2021.37765.
Повний текст джерелаАнотація:
Abstract: This paper is concerned with the effects of various vertical irregularities on the seismic response of a structure. The objective of the project is to carry out Response spectrum analysis (RSA) and Time history Analysis (THA) of vertically irregular RC building frames and to carry out the ductility based design using IS 13920 corresponding to Equivalent static analysis and Time history analysis. Comparison of the results of analysis and design of irregular structures with regular structure was done. The scope of the project also includes the evaluation of response of structures subjected to high, low and intermediate frequency content earthquakes using Time history analysis. Three types of irregularities namely mass irregularity, stiffness irregularity and vertical geometry irregularity were considered. According to our observation, the storey shear force was found to be maximum for the first storey and it decreases to minimum in the top storey in all cases. The mass irregular structures were observed to experience larger base shear than similar regular structures. The stiffness irregular structure experienced lesser base shear and has larger inter-storey drifts. The absolute displacements obtained from time history analysis of geometry irregular structure at respective nodes were found to be greater than that in case of regular structure for upper stories but gradually as we moved to lower stories displacements in both structures tended to converge. . Lower stiffness results in higher displacements of upper stories. In case of a mass irregular structure, time history analysis gives slightly higher displacement for upper stories than that in regular structures whereas as we move down lower stories show higher displacements as compared to that in regular structures. When time history analysis was done for regular as well as stiffness irregular structure, it was found that displacements of upper stories did not vary much from each other but as we moved down to lower stories the absolute displacement in case of soft storey were higher compared to respective stories in regular structure. Tall structures were found to have low natural frequency hence their response was found to be maximum in a low frequency earthquake. It is because low natural frequency of tall structures subjected to low frequency earthquake leads to resonance resulting in larger displacements. If a high rise structure (low natural frequency)is subjected to high frequency ground motion then it results in small displacements. Similarly, if a low rise structure (high natural frequency) is subjected to high frequency ground motion it results in larger displacements whereas small displacements occur when the high rise structure is subjected to low frequency ground motion.
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Xia, Weida, Yuxiang Ma, Guohai Dong, Jie Zhang, and Xiaozhou Ma. "Emergence of Solitons from Irregular Waves in Deep Water." Journal of Marine Science and Engineering 9, no. 12 (December 2, 2021): 1369. http://dx.doi.org/10.3390/jmse9121369.
Повний текст джерелаАнотація:
Numerical simulations were performed to study the long-distance evolution of irregular waves in deep water. It was observed that some solitons, which are the theoretical solutions of the nonlinear Schrödinger equation, emerged spontaneously as irregular wave trains propagated in deep water. The solitons propagated approximately at a speed of the linear group velocity. All the solitons had a relatively large amplitude and one detected soliton’s height was two times larger than the significant wave height of the wave train, therefore satisfying the rogue wave definition. The numerical results showed that solitons can persist for a long distance, reaching about 65 times the peak wavelength. By analyzing the spatial variations of these solitons in both time and spectral domains, it is found that the third-and higher-order resonant interactions and dispersion effects played significant roles in the formation of solitons.
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Bishop, S. R., L. M. Leung, and L. N. Virgin. "Predicting Incipient Jumps to Resonance of Compliant Marine Structures in an Evolving Sea-State." Journal of Offshore Mechanics and Arctic Engineering 109, no. 3 (August 1, 1987): 223–28. http://dx.doi.org/10.1115/1.3257013.
Повний текст джерелаАнотація:
When monitoring the wave-driven motions of a compliant offshore facility, be it an articulated mooring tower or a vessel, the engineer would like to be able to predict, in real time, any incipient jump to resonance that might be imminent due to the slowly evolving sea-state. We explore in this paper a study of some new possible prediction techniques for both a jump to a main fundamental resonance leading to capsize and a flip bifurcation to a subharmonic resonance. Stroboscopic Poincare´ mapping techniques based on discrete time sampling are used to give information about the approach to instability. The first application of these techniques is in the prediction of the jump in resonance and consequent capsize at a cyclic fold in the roll response of a vessel in regular beam seas. Secondly, the techniques are shown to work extremely well in a variety of computational situations when applied to the simulation of an articulated mooring tower during the approach to the potentially dangerous oscillations produced by the onset of subharmonic resonance at a flip bifurcation, in both regular and irregular ocean waves.
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CHABANOV, V. M., and B. N. ZAKHARIEV. "UNPRECEDENTED POSSIBILITY OF DISCRETE SCATTERING STATES AND THEIR CONTROL." International Journal of Modern Physics B 20, no. 28 (November 10, 2006): 4779–84. http://dx.doi.org/10.1142/s0217979206035618.
Повний текст джерелаАнотація:
The discrete states of unlimited wave motion, "antipodes" of Anderson's localization [Phys. Rev.109, 1492–1505 (1958)] ("continuum of bound states"), are presented. This newly mentioned and an unexpected kind of spectrum appeared to be attainable via a multiple combination of the remarkable phenomenon of resonance tunneling. It was found that this unusual spectral situation takes place for a quantum system of infinite irregularly distributed resonance tunneling potential traps. Generalization of this instructive phenomenon to periodic, multi-channel structures is considered.
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Nakamura, Tomoaki, Naoto Nagayama, Yong-Hwan Cho, Norimi Mizutani, Yoshinosuke Kurahara, and Masahide Takeda. "Motion of Floating Caisson with Extended Bottom Slab under Regular and Irregular Waves." Journal of Marine Science and Engineering 9, no. 10 (October 15, 2021): 1129. http://dx.doi.org/10.3390/jmse9101129.
Повний текст джерелаАнотація:
Floating caissons may oscillate primarily due to ocean waves during towing operations. Reducing the oscillation based on the extension part (footing) of the bottom slab of the caissons can efficiently increase the safety of towing maneuvers. However, the influence of the footing length on the motion of floating caissons has not been adequately studied. This study investigates this topic through hydraulic model experiments and numerical simulations. Experimental results for regular waves show that the rotational motion (pitch) of the caisson around the wave crest direction increases owing to resonance. This suggests that the pitch could be reduced by designing caissons, such that resonance may be prevented along the footing length. In the numerical simulations of irregular waves, the Fourier amplitudes of the heave and pitch show that the footings amplify their low-frequency components and reduce their high-frequency components. Furthermore, the significant total amplitudes of the heave and pitch show a different trend from that of the regular waves observed in the hydraulic model experiments. This suggests that it is essential to examine the motion of a caisson under irregular waves when assessing the effect of footings in an actual marine environment.
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Cui, Zhen Feng, and Dehui Sun. "Synthesis and Characterization of CoFe2O4 Nanoparticles." Advanced Materials Research 261-263 (May 2011): 533–36. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.533.
Повний текст джерелаАнотація:
We synthesized the magnetic CoFe2O4nanoparticles using a solution method in the presence of hexamethylenetetramine (HMTA) at 85 °C for 6 h. Their morphologies, structures, surface properties and magnetism were characterized by Field emission scanning electron microscopy (FE-SEM) images, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Vibrating sample magnetometer (VSM), respectively. FE-SEM results show that the synthesized samples are irregular nanoparticles with average size range of about 40-120 nm. XRD confirms that the samples belong to the rhombohedral crystal system. The magnetic CoFe2O4nanoparticles have the potential application in magnetic resonance imaging, high-density information storage and drug delivery.
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Yu, Haibin, Minli Zheng, Wei Zhang, Wenrui Lv, and Wanying Nie. "Research on Centroid Distribution and Dynamic Characteristics of Irregular Tooth End Milling Cutters." Applied Sciences 11, no. 21 (October 27, 2021): 10071. http://dx.doi.org/10.3390/app112110071.
Повний текст джерелаАнотація:
For irregular end milling cutters, the incomplete equality of the pitch angle and helix angle will lead to an uneven mass distribution. The problems of centroid distribution caused by this, and whether it would affect the dynamic characteristics of milling cutters, have not been systematically studied. In this paper, through the proposed mathematical model, the centroid positions of each radial section of four types of end milling cutters, with equal overall eccentricities and different structures, are calculated, respectively. The centroid distribution of end milling cutters is studied and analyzed. Combined with finite element analysis, the vibration mode, frequency, and resonance frequency band of each type of end milling cutter, under the same dynamic excitation, is obtained. Based on a study of the dynamic characteristics of various types of end milling cutters, it is found that the response displacement of the variable pitch variable helix end milling cutter is the smallest, which is 0.043800 mm. With the same level of accuracy, its dynamic performance is the best. On the premise of not changing the overall eccentricity of the end milling cutter, a new idea for the structural design to improve the dynamic characteristics of the end milling cutter is provided.
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Zhang, Deng-Bo, You-Qi Tang, and Li-Qun Chen. "Irregular instability boundaries of axially accelerating viscoelastic beams with 1:3 internal resonance." International Journal of Mechanical Sciences 133 (November 2017): 535–43. http://dx.doi.org/10.1016/j.ijmecsci.2017.08.052.
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Serhir-Taleb, Najat, and Claude Marche. "Une analyse numérique des possibilités de résonance d'un bassin portuaire de profondeur variable." Canadian Journal of Civil Engineering 16, no. 4 (August 1, 1989): 467–76. http://dx.doi.org/10.1139/l89-076.
Повний текст джерелаАнотація:
Creating, enlarging and excavating a harbour can modify the dynamic response of the basin. A verification of the resonance modes is common practice before undertaking the related work. This can be done numerically if the necessary assumptions are justifiable. It can be done on a small-scale model if the basin has an irregular shape or if the depth varies from one area to the other.A computer-programmed analytical method of resonance modes is presented. It is derived from the direct measure principle of successive oscillation superposition used in the laboratory. Validation is obtained by applying the method to existing theoretical solutions and to the analysis of a small creek of the Gaspe Peninsula where the importance of refraction in the analytical results is demonstrated. Key words: harbour, vibration, agitation, ocean waves, diffraction, refraction, numerical model, application. [Journal translation]
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Fuse, Honoka, Masaya Ito, Kosuke Takemura, Shuzo Ikuta, Toru Motoi, Tomotake Okuma, Madoka Kataoka, and Fumitaka Koga. "Renal Angiomyolipoma Mimicking a Well-Differentiated Retroperitoneal Liposarcoma." Case Reports in Urology 2020 (September 24, 2020): 1–5. http://dx.doi.org/10.1155/2020/8812057.
Повний текст джерелаАнотація:
A 37-year-old Burmese woman presented with an incidentally found retroperitoneal fat-containing tumor. The tumor was 9 cm in the longest diameter, surrounding the right kidney, and composed of homogenous adipose tissue with thickened septum-like structures and spotty nonadipose structures, which were enhanced on contrast-enhanced computed tomography and magnetic resonance imaging. The tumor did not show either a beak sign or synchronous angiomyolipoma-like lesion in the kidneys. The tumor had irregular septa, thin blood vessels, and spotty small soft-tissue nodules. The tumor did not contain any heterogeneously enhanced solid lesions suspicious for dedifferentiated liposarcomas. Based on these imaging findings, a clinical diagnosis of a well-differentiated liposarcoma was made. Under the consensus of a multidisciplinary cancer board, she was recommended to undergo core-needle biopsy to confirm the clinical diagnosis. However, she declined to undergo biopsy for financial reasons. She underwent kidney-sparing retroperitoneal tumor resection. Histopathologically, the tumor was an angiomyolipoma with positive immunostaining for HMB45 and Melan A. The present case suggests the importance of core-needle biopsy prior to surgical intervention for retroperitoneal fat-containing tumors.
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Bartczyk, Mateusz, Andrzej Suchanowski, and Marta Woldańska-Okońska. "STOCHASTIC RESONANCE METHOD IN PHYSIOTHERAPY − A REVIEW OF THE LITERATURE." Wiadomości Lekarskie 72, no. 7 (2019): 1364–70. http://dx.doi.org/10.36740/wlek201907125.
Повний текст джерелаАнотація:
Non-linearity is an important feature of many human body structures that may result from deterministic properties of the body and noise. Noise is defined as accidental or irregular fluctuations or disturbances that are not part of the signal. Stochastic resonance (SR), the term originally used in a very specific context, is now widely used to describe any phenomenon in which the presence of noise in a nonlinear system is better for the quality of the output signal than its absence. The conducted research for the needs of physiotherapy consists in assessing the impact of the platform generating forced mechanical vibrations with specific parameters in selected disease entities, sports disciplines, as well as prevention. The aim of the work is to discuss the stochastic resonance method and to analyze the results of the most important works discussing the use and effectiveness of therapeutic impact on the human body. The use of the stochastic resonance method enforces mechanical vibrations, which are characterized by the variability of rhythm, amplitude and direction of vibrations, which enforces postural adjustment regulated by the CNS and response to stimuli that disturb the body’s balance. The analysis of the effectiveness of therapeutic impact in the field of body balance disorders, reeducation of locomotion in people with partial spinal cord injury, motor motility and changes in hormonal concentrations was carried out. Stochastic resonance therapy can reduce or eliminate dysfunction in many disease entities, however, further studies are needed to assess the effectiveness of the therapy.
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Kumar, Ashutosh, Salman Rashid, Sumit Singh, Rong Li, and Leon S. Dure. "Spinal Cord Diffuse Midline Glioma in a 4-Year-Old Boy." Child Neurology Open 6 (January 1, 2019): 2329048X1984245. http://dx.doi.org/10.1177/2329048x19842451.
Повний текст джерелаАнотація:
Objective: We report a child presenting with spinal myelopathy secondary to H3K27M mutant diffuse midline glioma. Case Report: A 4-year-old boy presented with a 3-week history of progressive gait difficulty. Examination revealed bilateral hand and lower extremity weakness, left leg hypertonia with ankle clonus, and a right hemisensory deficit. Magnetic resonance imaging of neuroaxis showed cervical and thoracic spinal cord with expansion and irregular areas of enhancement. Serum and cerebrospinal fluid studies were unremarkable for infectious, autoimmune, inflammatory, and neoplastic causes but showed mild cerebrospinal fluid pleocytosis, hypoglycorrhachia, and high protein level. A thoracic cord biopsy revealed a diffuse midline glioma (World Health Organization grade IV). Consequently, the tumor involved intracranial structures and patient died within 4 months after diagnosis. Conclusion: High-grade spinal cord gliomas are very rare but should be considered in the differential diagnosis of pediatric myelopathy. Tissue biopsy is recommended in indeterminate cases to facilitate diagnosis and to guide management.
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Zielińska, Beata, Ewa Mijowska, and Ryszard J. Kalenczuk. "Synthesis and Characterization of K-Ta Mixed Oxides for Hydrogen Generation in Photocatalysis." International Journal of Photoenergy 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/525727.
Повний текст джерелаАнотація:
K-Ta mixed oxides photocatalysts have been prepared by impregnation followed by calcination. The influence of the reaction temperature (450°C–900°C) on the phase formation, crystal morphology, and photocatalytic activity in hydrogen generation of the produced materials was investigated. The detailed analysis has revealed that all products exhibit high crystallinity and irregular structure. Moreover, two different crystal structures of potassium tantalates such as KTaO3and K2Ta4O11were obtained. It was also found that the sample composed of KTaO3and traces of unreacted Ta2O5(annealed at 600°C) exhibits the highest activity in the reaction of photocatalytic hydrogen generation. The crystallographic phases, optical and vibronic properties were examined by X-ray diffraction (XRD) and diffuse reflectance (DR) UV-vis and resonance Raman spectroscopic methods, respectively. Morphology and chemical composition of the produced samples were studied using a high-resolution transmission electron microscope (HR-TEM) and an energy dispersive X-ray spectrometer (EDX) as its mode.
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Siebermair, Johannes, Eugene G. Kholmovski, Douglas Sheffer, Joyce Schroeder, Leif Jensen, Mobin Kheirkhahan, Alex A. Baher, et al. "Saturation recovery-prepared magnetic resonance angiography for assessment of left atrial and esophageal anatomy." British Journal of Radiology 94, no. 1123 (July 1, 2021): 20210048. http://dx.doi.org/10.1259/bjr.20210048.
Повний текст джерелаАнотація:
Objectives: Magnetic resonance angiography (MRA) has been established as an important imaging method in cardiac ablation procedures. In pulmonary vein (PV) isolation procedures, MRA has the potential to minimize the risk of severe complications, such as atrio-esophageal fistula, by providing detailed information on esophageal position relatively to cardiac structures. However, traditional non-gated, first-pass (FP) MRA approaches have several limitations, such as long breath-holds, non-uniform signal intensity throughout the left atrium (LA), and poor esophageal visualization. The aim of this observational study was to validate a respiratory-navigated, ECG-gated (EC), saturation recovery-prepared MRA technique for simultaneous imaging of LA, LA appendage, PVs, esophagus, and adjacent anatomical structures. Methods: Before PVI, 106 consecutive patients with a history of AF underwent either conventional FP-MRA (n = 53 patients) or our new EC-MRA (n = 53 patients). Five quality scores (QS) of LA and esophagus visibility were assessed by two experienced readers. The non-parametric Mann–Whitney U-test was used to compare QS between FP-MRA and EC-MRA groups, and linear regression was applied to assess clinical contributors to image quality. Results: EC-MRA demonstrated significantly better image quality than FP-MRA in every quality category. Esophageal visibility using the new MRA technique was markedly better than with the conventional FP-MRA technique (median 3.5 [IQR 1] vs median 1.0, p < 0.001). In contrast to FP-MRA, overall image quality of EC-MRA was not influenced by heart rate. Conclusion: Our ECG-gated, respiratory-navigated, saturation recovery-prepared MRA technique provides significantly better image quality and esophageal visibility than the established non-gated, breath-holding FP-MRA. Image quality of EC-MRA technique has the additional advantage of being unaffected by heart rate. Advances in knowledge: Detailed information of cardiac anatomy has the potential to minimize the risk of severe complications and improve success rates in invasive electrophysiological studies. Our novel ECG-gated, respiratory-navigated, saturation recovery-prepared MRA technique provides significantly better image quality of LA and esophageal structures than the traditional first-pass algorithm. This new MRA technique is robust to arrhythmia (tachycardic, irregular heart rates) frequently observed in AF patients.
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Bogopolskiy, Oleg E. "Instrumental Diagnosis and Preoperative Planning of Hip Arthroscopy in Femoroacetabular Impingement Syndrome: Lecture." Traumatology and Orthopedics of Russia 27, no. 4 (December 29, 2021): 155–68. http://dx.doi.org/10.21823/2311-2905-1636.
Повний текст джерелаАнотація:
Femoroacetabular impingement syndrome (FAI) is essentially a mechanical conflict that occurs when the acetabulum edge of the pelvic bone interacts with femur head and neck with clinical symptoms. In a basis of this conflict, as a rule, is a single or bilateral anatomical bone defect that causes an irregular shape of the hip joint with congenital or acquired etiology. Radiography, performed in a direct projection and in 45 Dunn position with external rotation of 40, is traditionally considered as basic tool for the radiological diagnosis of hip joint pathology. It allows to assess the anatomical and morphological structure of joint surfaces and their relationship. Detection of severe hip deformations may require computed tomography (CT). Magnetic resonance imaging (MRI) or magnetic resonance arthrography (MRA) is used to assess the condition of soft tissue structures of hip joint, its damage is often found in patients with FAI. The modern method of treating patients with FAI is hip arthroscopy, the undeniable advantage of which is low traumatic nature of the operation, low level of intraoperative complications and short postoperative rehabilitation period. For its successful implementation, it is necessary to take into account the complexity of performing hip arthroscopy, its duration, the necessity for good technical equipment and a high skill level of the operating surgeon. However, this operation has a number of limitations, which must be taken into account when selecting patients.
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Jiang, Chuandong, Xinlei Shang, Tingting Lin, Qingming Duan, and Jun Lin. "Quasi-2D block inversion of large-scale surface nuclear magnetic resonance profile data using a laterally constrained model." GEOPHYSICS 82, no. 2 (March 1, 2017): JM1—JM14. http://dx.doi.org/10.1190/geo2015-0455.1.
Повний текст джерелаАнотація:
The water content of underground structures can be imaged using surface nuclear magnetic resonance (NMR) in one dimension, two dimensions, or recently, three dimensions. The maximum efficiency can be obtained with a coincident loop configuration in a large-scale area, although the resolution is limited. We have developed a quasi-2D block inversion to characterize a horizontal continuous underground aquifer using a laterally constrained model to improve the resolution of thin aquifers and deep aquifers. Through the simulation of flat surface and irregular surface models, a horizontally layered aquifer with continuously variable water content and [Formula: see text] can be imaged through quasi-2D block inversion, which is more optimized than the traditional 1D block or 1D or 2D smooth inversion methods. Finally, using a series of profile data obtained from surface NMR field measurements in Mongolia, we determine that quasi-2D block inversion based on a laterally constrained model can significantly improve the discontinuity and heterogeneity caused by splicing images in a 1D block inversion and can provide a reliable result of the distribution of continuous aquifers for hydrogeology surveys over a large-scale area.
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Pols, Alana, Eric Gubesch, Nagi Abdussamie, Irene Penesis, and Christopher Chin. "Mooring Analysis of a Floating OWC Wave Energy Converter." Journal of Marine Science and Engineering 9, no. 2 (February 20, 2021): 228. http://dx.doi.org/10.3390/jmse9020228.
Повний текст джерелаАнотація:
This investigation focuses on the modelling of a floating oscillating water column (FOWC) wave energy converter with a numerical code (ANSYS AQWA) based on potential flow theory. Free-floating motions predicted by the numerical model were validated against experimental data extrapolated from a 1:36 scale model device in regular and irregular sea states. Upon validation, an assessment of the device’s motions when dynamically coupled with a four-line catenary mooring arrangement was conducted at different incident wave angles and sea states ranging from operational to survivable conditions, including the simulation of the failure of a single mooring line. The lack of viscosity in the numerical modelling led to overpredicted motions in the vicinity of the resonant frequencies; however, the addition of an external linear damping coefficient was shown to be an acceptable method of mitigating these discrepancies. The incident wave angle was found to have a limited influence on the magnitudes of heave, pitch, and surge motions. Furthermore, the obtained results indicated that the mooring restoring force is controlled by the forward mooring lines under the tested conditions.
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Lobão, Carlos Augusto Ferreira, Ulysses de Oliveira Sousa, Diego Arthur Castro Cabral, and Fernanda Myllena Sousa Campos. "Hemifacial Spasm Associated with Chiari Type I Malformation: Surgical Considerations and Case Report." Arquivos Brasileiros de Neurocirurgia: Brazilian Neurosurgery 39, no. 02 (April 24, 2020): 136–41. http://dx.doi.org/10.1055/s-0040-1708893.
Повний текст джерелаАнотація:
AbstractHemifacial spasm (HS) is a movement disorder characterized by paroxysmal and irregular contractions of the muscles innervated by the facial nerve. Chiari malformation type I (CM I) is a congenital disease characterized by caudal migration of the cerebellar tonsils, and surgical decompression of foramen magnum structures has been used for treatment. The association of HS with CM I is rare, and its pathophysiology and therapeutics are speculative. There are only a few cases reported in the literature concerning this association. The decompression of the posterior fossa for the treatment of CM I has been reported to relieve the symptoms of HS, suggesting a relation between these diseases. However, the possible complications of posterior fossa surgery cannot be underrated. We report the case of a 66-year-old patient, in ambulatory follow-up due to right HS, no longer responding to botulinum toxin treatment. Magnetic resonance imaging (MRI) of the skull revealed compression of the facial nerve and CM I. The patient underwent surgery for HS by neurovascular microdecompression of the facial nerve via right lateral suboccipital craniectomy, but presented significant clinical worsening in the postoperative period even though the cerebellum edema related to surgical manipulation was mild. Due to the clinical worsening, the patient underwent a median suboccipital craniectomy with decompression of the foramen magnum structures. After this second surgery, the patient had progressive improvement and was discharged from the hospital for ambulatory care.
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Tillashayhov, Mirzagolib, Akbar Khasanov, Latifjon Nishonboev, Anvar Amonov, Rahimjon Bekmirzaev, Zohir Shukurov, and Murod Hudoyorov. "Huge parapharyngeal space tumor: Case report and short literature review." Romanian Journal of Rhinology 12, no. 46 (April 1, 2022): 94–99. http://dx.doi.org/10.2478/rjr-2022-0014.
Повний текст джерелаАнотація:
Abstract The parapharyngeal space (PPS) has a special anatomical and clinical importance from the point of view of its content, communication and vicinity with major and vital structures. Tumors of the parapharyngeal space are uncommon, the most incriminated being the salivary gland tumors, neurogenic tumors, especially Schwannomas and paragangliomas, and lymphoreticular lesions. The correct diagnosis of the PPS tumors must include the radiologic evaluation represented by the computed tomography (CT) and the magnetic resonance imaging (MRI). The therapeutic plan depends on the imagistically identified aspect. We report a case of a 40-year-old male, who initially noted a massive tumor of the left side of the neck within 15 years. The cervical CT scan revealed, in the upper third of the left side of the neck, in the projection of the parotid and masticatory space and the submandibular region, under the lower jaw, medially at the level of cervical vertebrae C1 – C4, to the front of the sternocleidomastoid muscle, a volumetric formation irregular in shape, with clear and uneven contours, dimensions 40x65x85 mm, uniform density +30H. Transverse cervical approach was chosen for the surgical investigation.
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Tajima-Pozo, Kazuhiro, Miguel Yus, Gonzalo Ruiz-Manrique, Adrian Lewczuk, Juan Arrazola, and Francisco Montañes-Rada. "Amygdala Abnormalities in Adults With ADHD." Journal of Attention Disorders 22, no. 7 (March 10, 2016): 671–78. http://dx.doi.org/10.1177/1087054716629213.
Повний текст джерелаАнотація:
Objective: The suggested neurobiological bases of ADHD focus on the amygdala as a center of emotions processing. Therefore, we hypothesize that patients with ADHD will show an irregular pattern of emotional-related activity of the amygdala region as well as some structural abnormalities. Method: Nine adult patients with ADHD and nine group-matched healthy volunteers were studied using a 1.5-T magnetic resonance imaging (MRI) scanner. Morphometric measurements were obtained manually, and they were later processed and compared. Absolute volumes of several structures and nuclei were calculated with FSL-FIRST. For the functional magnetic resonance examination, a set of two paradigms was prepared, using a block design, incorporating images of the International Affective Picture System (IAPS). The patients were unmedicated at the time of the MRI scan. Results: Negative correlation was found between the right amygdala volume and Barrat’s impulsivity scores ( r = −.756, p = .018). The age of patients did not turn out to be a significant factor. No significantly higher activation areas were found in patients with unpleasant content images. For the left amygdala, an Region Of Interest (ROI)-based analysis showed moderately higher level of activation in the patients than in the controls with pleasant content images. Conclusion: Patients with ADHD tend to have smaller amygdala volumes. ADHD patients presented less activation in the area of the left frontal pole than the controls. There was no amygdala activation stated when presenting the pleasant images. Whereas bigger activation of the left amygdala was found in patients while presenting them unpleasant images. These results might suggest that lower emotional processing and less control of impulsivity is associated with dysfunctional amygdala in ADHD patients.
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Kunigelis, Katherine, Alexander Yang, and A. Youssef. "Endoscopic Assisted Retrosigmoid Approach for Cerebellopontine Angle Epidermoid Tumor." Journal of Neurological Surgery Part B: Skull Base 79, S 05 (September 25, 2018): S413—S414. http://dx.doi.org/10.1055/s-0038-1669978.
Повний текст джерелаАнотація:
This case is a 20-year-old male, who presented with 1 month of right facial weakness (HB4) and complaints of ipsilateral eye dryness. He was initially treated for Bell's palsy with steroids and antiviral agents, but subsequently developed diplopia with right lateral gaze and underwent an MRI (magnetic resonance imaging). MRI demonstrated a 4.5 cm irregular lesion in the right cerebellopontine angle consistent with an epidermoid cyst. Because the tumor had grown with the development of the central nervous system, it has extended into different compartments, including the tentorial incisura and pineal region. A predefined surgical corridor created by the tumor facilitated access to the majority of the tumor through a retrosigmoid approach. Angled endoscopes (30-degree up and down) provided further visualization of tumor away from the line of sight of the microscope, thus allowing for gross total resection of the lesion. This video also demonstrates a sharp dissection technique necessary for safe removal of adherent tumor from critical neurovascular structures, including the basilar artery and several cranial nerves. The ipsilateral auditory evoked responses (ABRs) showed slight improvement from baseline toward the end of the case. A gross total resection was achieved, as shown by the MRI. The patient remained at his baseline cranial nerve (CN) V, VII, and VIII deficits during the immediate postoperative period.The link to the video can be found at: https://youtu.be/vCq5juJh8hk.
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Rognebakke, Olav F., and Odd M. Faltinsen. "Coupling of Sloshing and Ship Motions." Journal of Ship Research 47, no. 03 (September 1, 2003): 208–21. http://dx.doi.org/10.5957/jsr.2003.47.3.208.
Повний текст джерелаАнотація:
The coupled effect between ship motions and sloshing is studied. Two-dimensional experiments of a hull section containing tanks filled with different levels of water excited in sway by regular waves have been conducted. Steady-state results are obtained for the sway amplitude. Even if violent sloshing occurs in the tanks, the steady-state motion is almost linear and sinusoidal with the frequency of the linear incident waves. This implies that higher-order harmonics of the sloshing force are filtered out by the system. Simulations of the modeled case are performed using a linear and a nonlinear sloshing model and mainly assuming linear external flow. For steady-state motion, a convolution formulation does not improve the results relative to using constant coefficients in the equation of motion. However, in order to properly model the transient behavior in an irregular sea, a convolution formulation must be included. The treatment of the retardation function for the external problem is discussed in detail. A good agreement between experiments and computations is reported. The calculated coupled motion is sensitive to the damping of the sloshing motion in a certain frequency range where the coupled sloshing and ship motions cause resonant ship motions. A quasilinear frequency domain analysis is used to explain this by introducing the sloshing loads as a frequency dependent spring.
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Streitparth, F., P. Schöttle, K. Schlichting, H. Schell, F. Fischbach, T. Denecke, G. N. Duda, and R. J. Schröder. "Osteochondral defect repair after implantation of biodegradable scaffolds: indirect magnetic resonance arthrography and histopathologic correlation." Acta Radiologica 50, no. 7 (September 2009): 765–74. http://dx.doi.org/10.1080/02841850902980272.
Повний текст джерелаАнотація:
Background: Biodegradable scaffolds have become an important option in the treatment of osteochondral defects. Therefore, accurate and reproducible monitoring of scaffold repair tissue is crucial. Purpose: To assess the feasibility of indirect magnetic resonance (MR) arthrography in determining the quality of osteochondral repair after scaffold implantation using an MR imaging (MRI) scoring and grading system with histology as reference. Material and Methods: Osteochondral defects created at ovine condylar facets were treated with either a commercial poly (DL-lactide-co-glycolide) (PLG) scaffold or a modified softer one ( n=6/group; 87% and 55% of the elastic modulus of ovine subchondral bone, respectively). Empty defects at the contralateral condyle served as control group. A 1.5T MRI scan was performed after 6 months with proton density (PD)-weighted (w) fat-saturated (fs) fast spin-echo (FSE), T1-w two-dimensional (2D), and 3D fs gradient echo (GE) sequences 30min after intravenous Gd-DTPA administration and passive joint movement. Two independent radiologists evaluated the repair tissue. The MR findings were correlated with histological findings. Results: MRI and histological grading correlated well (10/12 cases). The stiff-scaffold group showed significantly superior repair in comparison to the control group ( P<0.05). The 3D fs GE sequence proved to be most valuable in evaluating morphologic status. Complete defect filling and integration, intact surface and isointense signal to the adjacent native cartilage, subchondral incorporation with bone marrow edema, and graft plug enhancement were associated with a good histological outcome. Histologically, we found a smooth fibrocartilaginous layer and osseous replacement of the scaffold. Incomplete cartilage repair and irregular subchondral structures on the MRI correlated histologically with fibrocartilage-like repair and subchondral sclerosis, due to substantial degradation of the scaffold. Conclusion: Indirect MR arthrography is an accurate, noninvasive monitoring tool in the follow-up of scaffold implants. The MRI scoring and grading system allows reliable assessment of normal and pathological repair, with high correlation to histological findings.
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Katoh, Hiroyuki, Shuhei Shibukawa, Keiko Yamaguchi, Akihiko Hiyama, Tomohiko Horie, Masato Sato, and Masahiko Watanabe. "A Combination of Magnetic Resonance Imaging Techniques to Localize the Dural Defect in a Case of Superficial Siderosis—A Case Report." Medicines 7, no. 6 (June 25, 2020): 36. http://dx.doi.org/10.3390/medicines7060036.
Повний текст джерелаАнотація:
Background: Superficial siderosis is a progressively disabling disease caused by recurrent subarachnoid hemorrhage with accumulation of hemosiderin in the surface of the central nervous system. Although a wide variety of conditions may cause superficial siderosis, approximately half of the cases are reported to be associated with a defect in the ventral spinal dura mater, in which case treatment entails surgical repair of the defect. Here, we report a case of superficial siderosis and report on our method to pinpoint the dural defect using a combination of magnetic resonance imaging (MRI) techniques. Methods and Results: A 74-year-old female presented suffering from hearing loss and progressive ataxia over a duration of seven years. A T2-weighted MRI study revealed hypointensity in the superficial areas of the central nervous system, leading to the diagnosis of superficial siderosis, and the presence of a fluid-filled collection in the anterior spinal canal of C7 to T10 suggested that a dural defect was the cause of the repeated hemorrhage. A balanced turbo field echo (BTFE) MRI sequence revealed possible dural defects at T1–T2 and T5–T6, and a dynamic improved motion-sensitized driven-equilibrium steady-state free precession (dynamic iMSDE SSFP) sequence revealed an irregular flow of cerebrospinal fluid through the dura at the T5–T6 level. The dural defect was confirmed and sutured through a minimal T5–T6 laminectomy without neurological consequences, and the patient reported mild improvement in gait one year after surgery. Conclusions: A combination of MRI sequences provided the necessary information to confidently perform minimal surgery to repair the dural defect. We recommend coupling a balanced steady-state free precession (SSFP) sequence to provide high resolution, high contrast images of anatomical structures and a dynamic iMSDE SSFP sequence to confirm cerebrospinal fluid motion through the defect.
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Xue, Hongkun, Xiaohan Zhu, Jiaqi Tan, Linlin Fan, Qian Li, Jintian Tang та Xu Cai. "Counter-Current Fractionation-Assisted Bioassay-Guided Separation of Active Compound from Blueberry and the Interaction between the Active Compound and α-Glucosidase". Foods 10, № 3 (1 березня 2021): 509. http://dx.doi.org/10.3390/foods10030509.
Повний текст джерелаАнотація:
An efficient strategy for the selection of active compounds from blueberry based on counter-current fractionation and bioassay-guided separation was established in this study. Blueberry extract showed potential α-glucosidase inhibitory activity. After extraction by different solvents, the active components were enriched in water. The water extract was divided into six fractions via high-speed counter-current chromatography to further track the active components. Results indicated that the α-glucosidase inhibition rate of F4 was remarkable higher than the others. Cyanidin-3-glucoside (C3G) with a purity of 94.16% was successfully separated from F4 through column chromatography, and its structure was identified by ultraviolet spectral, Fourier-transformed infrared spectroscopy, high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry, 1H nuclear magnetic resonance (NMR), and 13C NMR. The interaction mechanism between C3G and α-glucosidase was clearly characterized and described by spectroscopic methods, including fluorescence and circular dichroism (CD) in combination with molecular docking techniques. C3G could spontaneously bind with α-glucosidase to form complexes by hydrogen bonds. The secondary structure of α-glucosidase changed in varying degrees after complexation with C3G. The α-helical and β-turn contents of α-glucosidase decreased, whereas the β-sheet content and the irregular coil structures increased. Molecular docking speculated that C3G could form hydrogen bonds with α-glucosidase by binding to the active sit (Leu 313, Ser 157, Tyr 158, Phe 314, Arg 315, and two Asp 307). These findings may be useful for the development of functional foods to tackle type 2 diabetes.
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Park, Jungyul, and Hee-Young Choi. "Chondroid Syringoma Involving the Sub-brow Area." Journal of the Korean Ophthalmological Society 62, no. 7 (July 15, 2021): 983–88. http://dx.doi.org/10.3341/jkos.2021.62.7.983.
Повний текст джерелаАнотація:
Purpose: Chondroid syringoma of the skin is a rare subcutaneous tumor and localization in the eyelid and orbital region that has rarely been described. We report a case of chondroid syringoma that involved the sub-brow region and was accompanied by hair loss. Case summary: A 57-year-old women presented with a mass on the lateral side of the left sub-brow region which was observed 25 years earlier. The mass, which recurred 2 months after surgery at another hospital through a skin incision was accompanied by an itching sensation. The mass was not tender or ulcerated but was reddish with superficial blood vessels and had a smooth surface with hair loss at the site of the mass. The mass showed high signal intensity on a T2-weighted magnetic resonance image and a round echogenic nodule with an irregular hypoechoic portion was observed on ultrasonography. A full-thickness excision including the adjacent normal tissue of the sub-brow mass and direct closure were subsequently performed. The pathological diagnosis was chondroid syringoma which was revealed as numerous tubular structures with various lumens in a collagenous stroma. Mucinous and fibrous findings were also observed. No recurrence was detected during the first 2 years after surgery. Conclusions: Chondroid syringoma in the eyelid and sub-brow region is uncommon. Complete resection is required to differentiate it from a malignancy and reduce the possibility of recurrence. Incomplete resection or capsular rupture during removal of the tumor could induce recurrence or a malignant change in the tumor.
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Gueydon, Sebastien, Frances M. Judge, Michael O’Shea, Eoin Lyden, Marc Le Boulluec, Julien Caverne, Jérémy Ohana, et al. "Round Robin Laboratory Testing of a Scaled 10 MW Floating Horizontal Axis Wind Turbine." Journal of Marine Science and Engineering 9, no. 9 (September 10, 2021): 988. http://dx.doi.org/10.3390/jmse9090988.
Повний текст джерелаАнотація:
This paper documents the round robin testing campaign carried out on a floating wind turbine as part of the EU H2020 MaRINET2 project. A 1/60th scale model of a 10 MW floating platform was tested in wave basins in four different locations around Europe. The tests carried out in each facility included decay tests, tests in regular and irregular waves with and without wind thrust, and tests to characterise the mooring system as well as the model itself. For the tests in wind, only the thrust of the turbine was considered and it was fixed to pre-selected levels. Hence, this work focuses on the hydrodynamic responses of a semi-submersible floating foundation. It was found that the global surge stiffness was comparable across facilities, except in one case where different azimuth angles were used for the mooring lines. Heave and pitch had the same stiffness coefficient and periods for all basins. Response Amplitude Operators (RAOs) were used to compare the responses in waves from all facilities. The shape of the motion RAOs were globally similar for all basins except around some particular frequencies. As the results were non-linear around the resonance and cancellation frequencies, the differences between facilities were magnified at these frequencies. Surge motions were significantly impacted by reflections leading to large differences in these RAOs between all basins.
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Yaşargil, M. Gazi, Chad D. Abernathey, and Ali ç. Sarioglu. "Microneurosurgical Treatment of Intracranial Dermoid and Epidermoid Tumors." Neurosurgery 24, no. 4 (April 1, 1989): 561–67. http://dx.doi.org/10.1227/00006123-198904000-00012.
Повний текст джерелаАнотація:
ABSTRACT Forty-three patients with intracranial, intradural dermoid (8) and epidermoid (35) tumors underwent radical surgical resection utilizing strict microneurosurgical technique. The average age was 37.3 years for the patients with epidermoid tumors and 36.2 years for the patients with dermoid tumors. The male to female ratio was 3:2 for the epidermoid group and 3:1 for the dermoid group. Common clinical presentations included cerebellar dysfunction, cranial nerve impairment, and seizures. Typically, computed tomography scans revealed the epidermoid tumors (30 cases studied) as nonhomogeneous hypodense lesions with irregular borders and without contrast enhancement. The dermoid tumors (7 cases studied) had a similar appearance, but with a wider range of attenuation values. Magnetic resonance imaging findings for the epidermoid tumors (6 cases studied) consisted of increased T1 and increased T2 relaxation times. Supratentorial tumors were excised by the pterional (frontosphenotemporal) approach, mesencephalic tumors by either a supratentorial posterior interhemispheric transtentorial approach or an infratentorial/supracerebellar method, and posterior fossa tumors by either a medially or laterally positioned suboccipital osteoplastic craniotomy. One epidermoid tumor and one dermoid tumor were considered to be subtotally resected because of dense adherences left attached to vital structures; the remaining 41 tumors were completely excised. The most frequent complications were aseptic/chemical meningitis and transient cranial nerve palsies. There were no perioperative deaths. Mean follow-up was 5.2 years. Eighty-six percent of patients reported good to excellent results. No patient had experienced symptomatic or radiographic evidence of recurrence. These results suggest that although dermoid and epidermoid tumors tend to cross anatomical boundaries via the subarachnoid system, in the majority of patients tumors can be resected in their entirety with relatively low morbidity by utilizing microneurosurgical techniques.
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Allolio, Bruno, and Martin Fassnacht. "Adrenocortical Carcinoma: Clinical Update." Journal of Clinical Endocrinology & Metabolism 91, no. 6 (June 1, 2006): 2027–37. http://dx.doi.org/10.1210/jc.2005-2639.
Повний текст джерелаАнотація:
Abstract Context: Adrenocortical carcinoma (ACC) is a rare and heterogeneous malignancy with incompletely understood pathogenesis and poor prognosis. Patients present with hormone excess (e.g. virilization, Cushing’s syndrome) or a local mass effect (median tumor size at diagnosis > 10 cm). This paper reviews current diagnostic and therapeutic strategies in ACC. Evidence Acquisition: Original articles and reviews were identified using a PubMed search strategy (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi) covering the time period up until November 2005. The following search terms were used in varying combinations: adrenal, adrenocortical, cancer, carcinoma, tumor, diagnosis, imaging, treatment, radiotherapy, mitotane, cytotoxic, surgery. Evidence synthesis: Tumors typically appear inhomogeneous in both computerized tomography and magnetic resonance imaging with necroses and irregular borders and differ from benign adenomas by their low fat content. Hormonal analysis reveals evidence of steroid hormone secretion by the tumor in the majority of cases, even in seemingly hormonally inactive lesions. Histopathology is crucial for the diagnosis of malignancy and may also provide important prognostic information. In stages I–III open surgery by an expert surgeon aiming at an R0 resection is the treatment of choice. Local recurrence is frequent, particularly after violation of the tumor capsule. Surgery also plays a role in local tumor recurrence and metastatic disease. In patients not amenable to surgery, mitotane (alone or in combination with cytotoxic drugs) remains the treatment of choice. Monitoring of drug levels (therapeutic range 14–20 mg/liter) is mandatory for optimum results. In advanced disease, the most promising therapeutic options (etoposide, doxorubicin, cisplatin plus mitotane, and streptozotocin plus mitotane) are currently being compared in an international phase III trial (www.firm-act.org). Adjuvant treatment options after complete tumor removal (e.g. mitotane, radiotherapy) are urgently needed because postoperative disease-free survival at 5 yr is only around 30%, but options have still not been convincingly established. National registries, international cooperations, and trials provide important new structures for patients but also for researchers aiming at systematic and continuous progress in ACC. However, future advances in the management of ACC will mainly depend on a better understanding of the molecular pathogenesis facilitating the use of modern cancer treatments (e.g. tyrosine kinase inhibitors).
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Crespo-Flores, Sergio L., Andres Cabezas, Sherouk Hassan, and Yufeng Wei. "PEA-15 C-Terminal Tail Allosterically Modulates Death-Effector Domain Conformation and Facilitates Protein–Protein Interactions." International Journal of Molecular Sciences 20, no. 13 (July 7, 2019): 3335. http://dx.doi.org/10.3390/ijms20133335.
Повний текст джерелаАнотація:
Phosphoprotein enriched in astrocytes, 15 kDa (PEA-15) exerts its regulatory roles on several critical cellular pathways through protein–protein interactions depending on its phosphorylation states. It can either inhibit the extracellular signal-regulated kinase (ERK) activities when it is dephosphorylated or block the assembly of death-inducing signaling complex (DISC) and the subsequent activation of apoptotic initiator, caspase-8, when it is phosphorylated. Due to the important roles of PEA-15 in regulating these pathways that lead to opposite cellular outcomes (cell proliferation vs. cell death), we proposed a phosphostasis (phosphorylation homeostasis) model, in which the phosphorylation states of the protein are vigorously controlled and regulated to maintain a delicate balance. The phosphostasis gives rise to the protective cellular functions of PEA-15 to preserve optimum cellular conditions. In this article, using advanced multidimensional nuclear magnetic resonance (NMR) techniques combined with a novel chemical shift (CS)-Rosetta algorithm for de novo protein structural determination, we report a novel conformation of PEA-15 death-effector domain (DED) upon interacting with ERK2. This new conformation is modulated by the irregularly structured C-terminal tail when it first recognizes and binds to ERK2 at the d-peptide recruitment site (DRS) in an allosteric manner, and is facilitated by the rearrangement of the surface electrostatic and hydrogen-bonding interactions on the DED. In this ERK2-bound conformation, three of the six helices (α2, α3, and α4) comprising the DED reorient substantially in comparison to the free-form structure, exposing key residues on the other three helices that directly interact with ERK2 at the DEF-docking site (docking site for ERK, FxF) and the activation loop. Additionally, we provide evidence that the phosphorylation of the C-terminal tail leads to a distinct conformation of DED, allowing efficient interactions with Fas-associated death domain (FADD) protein at the DISC. Our results substantiate the allosteric regulatory roles of the C-terminal tail in modulating DED conformation and facilitating protein–protein interactions of PEA-15.
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Zhou, Jianxing, Wenlei Sun, and Li Cao. "Vibration and noise characteristics of a gear reducer under different operation conditions." Journal of Low Frequency Noise, Vibration and Active Control 38, no. 2 (January 25, 2019): 574–91. http://dx.doi.org/10.1177/1461348419825603.
Повний текст джерелаАнотація:
Gear system is characterized by high efficiency, compact structure, and transmission ratio stability, and it has been extensively applied in various industrial equipment. This paper presents a novel preliminary estimate method for gear reducer noise radiation and vibration characteristics, and systematic researches on radiation characteristics of gear reducer are made. In the noise analysis process, the influence of time-varying mesh stiffness, error excitation, and tooth flank contact feature are comprehensively considered, the linear vibration model and nonlinear vibro-impact model for transmission system is set up, and then the dynamic load of the gearbox is obtained by solving the model. The dynamic load of bearing is taken as an excitation, the finite element method/boundary element method is adopted to analyze vibration and noise radiation characteristics of the gear reducer. The time domain response and field point noise spectrum at sound field are obtained, and the influence of harmonic components in excitation on vibration noise radiation of gearbox are discussed. The dynamic characteristics and sound radiation characteristics of gear reducer under different operating conditions are calculated, the change pattern of frequency component of the bearing dynamic load and noise radiation based on operating condition are obtained, and some interesting conclusions are observed from research that the gearbox produce the linear vibration and noise under the heavy load condition. Meanwhile, the nonlinear vibro-impact and noise is appeared under light load condition. The distribution of the gearbox radiated nose is uniform in various conditions, but noise takes sub-harmonic components as fundamental frequency and more peaks in the noise spectrum are observed. With the increase of the rotary speed, the noise tallies with the trend described by Kato formula except that under the gear system resonance speed. The impact force between teeth flanks shall be on the increase with the increase of rotary speed, and gear pair vibration experiencing a course from irregular vibration to regular periodic rattle vibration. With the increase of load, the noise of reducer changes with load as the variation of logarithmic function. For the noise in the process with load on the increase from no-load (the load is 0), the gear reducer vibration condition experienced both sides collision, single-side collision, and normal meshing in three stages. The radiated nose is increased gradually, but the abrupt change happened in critical positions between both sides collision and single-side collision as well as single-side collision and normal meshing in the process. The conclusions of this paper will offer theoretical basis for reducer to reduce vibration and noise.
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"Seismic and Wind Analysis of Regular and Irregular RC Structures with Tuned Mass Damper." International Journal of Recent Technology and Engineering 8, no. 3 (September 30, 2019): 2263–69. http://dx.doi.org/10.35940/ijrte.b3672.098319.
Повний текст джерелаАнотація:
Latest trend in the development high rise structure demanding taller and lighter structures, which are progressively adaptable with very low damping ratio. As the structures developing vertically, they are ending up all the more affecting by powerful excitation forces, for example, wind and seismic forces. For the more safety of structure and inhabitant's solace, the vibrations of the tall structures become a major issue for both structural designers. So as to control the vibration, various methodologies are proposed out of the few systems accessible for vibration control. Out of numerous methods, TMD has been observed to be increasingly powerful in controlling the dynamic forces caused due to seismic and wind excitations. In this paper, the adequacy of TMD in controlling the dynamic reaction of structures and the impact of different ground movement parameters on the seismic viability of TMD is researched. Essentially, a TMD is a vibratory subsystem appended to a bigger scale host structure so as to lessen the dynamic reactions. The frequency of damper will tuned to essential structure's frequency, so when frequency is high, the damper will results to resonate out of phase along with structural movement. The objective of this work is to study the impact of TMD on the dynamic forces brought about by seismic tremor and wind excitations in standard just as unpredictable in tall RC building structures. For that three 22 story RC building structures are considered with a similar arrangement out of which one ordinary regular structure and the other two are irregular RC structures are demonstrated in Etabs. In irregular RC structures, Stiffness irregularity and torsional irregularity are considered. For assessing seismic and wind reactions of structures, time history analysis, and static analysis used, with and without the tuned mass damper in ETABS. The outcomes acquired from the investigation of three 22 story RC structures with and without tuned mass damper are compared
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Dorey, Patrick, Anastasia Gorina, Ilya Perapechka, Tomasz Romańczukiewicz, and Yakov Shnir. "Resonance structures in kink-antikink collisions in a deformed sine-Gordon model." Journal of High Energy Physics 2021, no. 9 (September 2021). http://dx.doi.org/10.1007/jhep09(2021)145.
Повний текст джерелаАнотація:
Abstract We study kink-antikink collisions in a model which interpolates smoothly between the completely integrable sine-Gordon theory, the ϕ4 model, and a ϕ6-like model with three degenerate vacua. We find a rich variety of behaviours, including integrability breaking, resonance windows with increasingly irregular patterns, and new types of windows near the ϕ6-like regime. False vacua, extra kink modes and kink fragmentation play important roles in the explanations of these phenomena. Our numerical studies are backed up by detailed analytical considerations.
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Ahmad, Majd, and Richard Ray. "Comparison between Ramberg-Osgood and Hardin-Drnevich soil models in Midas GTS NX." Pollack Periodica, May 29, 2021. http://dx.doi.org/10.1556/606.2021.00353.
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AbstractThis paper studies the two widely used material models for predicting the dynamic behavior of soils, the Ramberg-Osgood and Hadrin-Drnevich models. Resonant column and torsional simple shear test results on dry sand were used to calibrate and evaluate the model built in the finite element software Midas GTS NX. Both material models are already implemented by the software. This study estimates the ability and efficiency of both soil models coupled with the Masing criteria to predict the behavior of soil when subjected to irregular loading patterns, (e.g., earthquakes), and measure the two most important dynamic properties, the dynamic shear modulus, and the damping ratio.
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Bednarczyk, Dawid, Dawid Bednarczyk, Tomasz Tomala, Agata Stanek-Widera, Dariusz Lange, and Jerzy Chudek. "An Unexpected Cause of Low Back Pain - A Case Report." Case Reports In Cancer, October 27, 2020, 1–4. http://dx.doi.org/10.47496/nl.crc.2020.01.04.
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Introduction: Low back pain is rarely the first manifestation of malignancy. The symptoms may be exacerbated by coexisting inflammation and subside after antibiotic therapy. Such a clinical course may lead to a delay in the diagnosis of cancer. Case Description: 65-year-old smoking man was admitted to the Neurology Department with severe low back pain and increased serum levels of inflammatory markers. The chest X-ray was normal. Due to repeated complaints, a wide range of diagnostics of the lesion was performed. An isolated irregular infiltration penetrating the intervertebral foramina and involving the L5 spinous process and the right dorsal extensor muscle along the vertebral arch, in a total size up to 3.5 cm, in addition to the degenerative disc changes, was visualized in magnetic resonance imaging (MRI). Prolonged antibiotic therapy resulted in a significant decrease in CRP and clinical improvement. During the second exacerbation of the refractory back pain in the L-S and Th regions after 15 months, the pathological structures initially diagnosed as inflammatory infiltrations were finally recognized as a metastatic infiltration of squamous cell carcinoma (SCC) of the lung. The CT examination to the chest demonstrated a large irregular tumor in the right lung. Conclusion: The reported rare case of SCC non-small cell lung cancer metastasis to the lumbar and presacral spinal region shows limited usefulness of MRI to give a specific diagnosis of such infiltration. Despite the rarity of tumors at this site, an invasive diagnostic method should be considered first with any unclear changes.
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Vallette-Kasic, S., H. Dufour, M. Mugnier, J. Trouillas, H. Valdes-Socin, P. Caron, S. Morange, et al. "Markers of tumor invasion are major predictive factors for the long-term outcome of corticotroph microadenomas treated by transsphenoidal adenomectomy." European Journal of Endocrinology, December 1, 2000, 761–68. http://dx.doi.org/10.1530/eje.0.1430761.
Повний текст джерелаАнотація:
OBJECTIVE: To assess the postsurgical outcome of patients with corticotroph microadenomas and to define predictors of the long-term outcome, with special emphasis on markers of tumor extension. DESIGN: Prospective study of 53 corticotroph microadenomas treated by enlarged adenomectomy. Patients followed for at least 2 years were classified into two groups: those in long-term remission and uncured patients (immediate failures and recurrences). Pre-, per- and postoperative parameters were analyzed as predictors of the long-term outcome. METHODS: Baseline hormone assessments were performed preoperatively, 8 days after surgery and every 6-12 months thereafter. Pituitary magnetic resonance imaging (MRI) allowed analysis of possible tumor extension to adjacent structures. Apparent completeness of the surgical removal was determined, and fragments labeled either 'tumor' or 'surrounding pituitary tissue' were submitted to serial sectioning. RESULTS: Immediate control of hypercortisolism was achieved in 43/53 patients (81%). However, later recurrences were observed in five patients (9%). Preoperative MRI showed tumor extension into adjacent structures with good specificity (91%) for prediction of surgical failure. Evidence of local invasion at surgery was also significantly predictive of the long-term outcome. A corticotroph adenoma was found at histological examination in 96% of the patients, and 26% had irregular limits, a feature significantly correlated with a poor outcome. Immediate postoperative plasma cortisol did not allow discrimination between long-term remissions and recurrences. CONCLUSION: Surgical failure was best predicted by signs of tumor 'invasiveness' at MRI, confirmed by peroperative examination and histology.