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1
Cameron, S. M., V. I. Nikora et M. T. Stewart. « Very-large-scale motions in rough-bed open-channel flow ». Journal of Fluid Mechanics 814 (9 février 2017) : 416–29. http://dx.doi.org/10.1017/jfm.2017.24.
Texte intégralRésumé :
Long-duration particle image velocimetry measurements in rough-bed open-channel flows (OCFs) reveal that the pre-multiplied spectra of the streamwise velocity have a bimodal distribution due to the presence of large- and very-large-scale motions (LSMs and VLSMs, respectively). The existence of VLSMs in boundary layers, pipes and closed channels has been acknowledged for some time, but strong supporting evidence for their presence in OCF has been lacking. The data reported in this paper fill this gap. Length scales of the LSMs and VLSMs in OCF exhibit different scaling properties; whereas the streamwise length of the LSM scales with the flow depth, the VLSM streamwise length does not scale purely with flow depth and may additionally depend on other scales such as the channel width, roughness height or viscous length. The transverse extent of the LSMs was found to increase with increasing elevation, but the VLSM transverse scale is anchored around two flow depths. The origin and nature of LSMs and VLSMs are still to be resolved, but differences in their scaling suggest that VLSMs in rough-bed OCFs form independently rather than as a spatial alignment of LSMs.
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Dasmen, Rahmat Novrianda. « IMPLEMENTASI METODE VLSM (VARIABLE LENGTH SUBNET MASK) PADA PEMETAAN IP ADDRESS LAN (LOCAL AREA NETWORK) STIPER SRWIGAMA PALEMBANG ». Computatio : Journal of Computer Science and Information Systems 2, no 2 (31 octobre 2018) : 112. http://dx.doi.org/10.24912/computatio.v2i2.1703.
Texte intégralRésumé :
Pemetaan IP (Internet Protocol) Address pada setiap user yang ada di LAN (Local Area Network) STIPER Sriwigama Palembang saat ini masih dilakukan secara manual dan terkadang tanpa mencatat IP address yang telah diberikan pada user-user sebelumnya sehingga terjadi kesamaan IP address yang menyebabkan bentrokan saat pengiriman data. Hal inilah yang menjadi penyebab dasar sehingga peneliti bermaksud mengimplementasikan metode VLSM (Variable Length Subnet Mask) sehingga dapat memetakan IP address untuk user ke dalam beberapa bagian. Pada STIPER Sriwigama Palembang dibagi beberapa bagian user yaitu : Ketua, Wakil Ketua, LPPM, Administrasi, Dosen, Staff, Perpustakaan dan Mahasiswa. Perhitungan pemetaan IP address dengan metode VLSM ini diawali dari jumlah user yang terbanyak dari beberapa bagian yang telah dibagi di atas. Pemetaan IP ini menjadi solusi dari permasalahan yang terjadi pada STIPER Sriwigama Palembang sehingga dengan metode VLSM tidak lagi terjadi bentrokan IP address karena setiap user telah memperoleh IP address dan subnet mask yang berbeda-beda.
3
Niki, Chiharu, Takatsune Kumada, Takashi Maruyama, Manabu Tamura, Takakazu Kawamata et Yoshihiro Muragaki. « Primary Cognitive Factors Impaired after Glioma Surgery and Associated Brain Regions ». Behavioural Neurology 2020 (25 mars 2020) : 1–9. http://dx.doi.org/10.1155/2020/7941689.
Texte intégralRésumé :
Previous studies have shown that cognitive impairments in patients with brain tumors are not severe. However, to preserve the postsurgical QOL of patients with brain tumors, it is important to identify “primary” cognitive functions and associated brain regions that are more vulnerable to cognitive impairments following surgery. The objective of this study was to investigate primary cognitive factors affecting not only simple cognitive tasks but also several other cognitive tasks and associated brain regions. Patients with glioma in the left (n=33) and the right (n=21) hemisphere participated in the study. Seven neuropsychological tasks from five cognitive domains were conducted pre- and 6 months postoperation. Factor analyses were conducted to identify “primary” common cognitive functions affecting the task performance in left and right glioma groups. Next, lesion analyses were performed using voxel-based lesion-symptom mapping (VLSM) to identify critical brain regions related to impairments of the primary cognitive functions. Factor analysis revealed two primary cognitive components in each glioma group. The first cognitive component in the left glioma group affected the digit span forward and backward tasks and concept shifting and the letter-digit substitution tasks. VLSM analysis revealed significant regions from the posterior middle temporal gyri to the supramarginal gyrus. The second cognitive component affected verbal memory, and verbal fluency tasks and VLSM analysis indicated two different significant regions, the medial temporal regions and the middle temporal gyrus to the posterior parietal lobes. The first cognitive component in the right glioma group affected positive and negative factor loadings on the task, such that the positive cognitive component affected only the Stroop color-word task. VLSM related to deficits of the Stroop task revealed significant regions in the anterior medial frontal cortex. On the other hand, the negative component affected concept shifting, word fluency, and digit span forward tasks, and VLSM revealed significant regions in the right inferior frontal cortex. It is suggested that primary cognitive functions related to specific brain regions were possibly affected by glioma resection.
4
Wang, G., et D. H. Richter. « Two mechanisms of modulation of very-large-scale motions by inertial particles in open channel flow ». Journal of Fluid Mechanics 868 (15 avril 2019) : 538–59. http://dx.doi.org/10.1017/jfm.2019.210.
Texte intégralRésumé :
Very-large-scale motions (VLSMs) and large-scale motions (LSMs) coexist at moderate Reynolds numbers in a very long open channel flow. Direct numerical simulations two-way coupled with inertial particles are analysed using spectral information to investigate the modulation of VLSMs. In the wall-normal direction, particle distributions (mean/preferential concentration) exhibit two distinct behaviours in the inner flow and outer flow, corresponding to two highly anisotropic turbulent structures, LSMs and VLSMs. This results in particle inertia’s non-monotonic effects on the VLSMs: low inertia (based on the inner scale) and high inertia (based on the outer scale) both strengthen the VLSMs, whereas moderate and very high inertia have little influence. Through conditional tests, low- and high-inertia particles enhance VLSMs following two distinct routes. Low-inertia particles promote VLSMs indirectly through the enhancement of the regeneration cycle (the self-sustaining mechanism of LSMs) in the inner region, whereas high-inertia particles enhance the VLSM directly through contribution to the Reynolds shear stress at similar temporal scales in the outer region. This understanding also provides more general insight into inner–outer interaction in high-Reynolds-number, wall-bounded flows.
5
Cameron, Stuart, Vladimir Nikora, Mark Stewart et Andrea Zampiron. « Large and very large scale motions in roughbed open-channel flow ». E3S Web of Conferences 40 (2018) : 05061. http://dx.doi.org/10.1051/e3sconf/20184005061.
Texte intégralRésumé :
Long duration PIV measurements in rough-bed (glass beads) open-channel flow (OCF) reveal that the pre-multiplied spectra of the streamwise velocity has a bimodal distribution due to the presence of large and very large scale motions (LSMs and VLSMs, respectively). The existence of VLSMs in boundary layers, pipes and closed channels has been acknowledged for some time, but strong supporting evidence for their presence in OCF has been lacking. Length scales of the large and very large scale motions in OCF exhibit different scaling properties; whereas the streamwise length of the LSM scales with the flow depth, the VLSM streamwise length does not scale purely with flow depth and may additionally depend on other scales such as the channel width, roughness height, or viscous length. Supplementary data for flows over self-affine fractal rough beds support these findings and additionally indicate that the length of VLSMs may grow along the extensive distance from the channel entrance. The origin and nature of LSMs and VLSMs are still to be resolved, but differences in their scaling suggest that VLSMs in rough-bed open-channel flows form independently rather than as a spatial alignment of LSMs.
6
Lee, Kyoung Bo, Seong Hoon Lim, Geun-Young Park et Sun Im. « Effect of Brain Lesions on Voluntary Cough in Patients with Supratentorial Stroke : An Observational Study ». Brain Sciences 10, no 9 (10 septembre 2020) : 627. http://dx.doi.org/10.3390/brainsci10090627.
Texte intégralRésumé :
Patients with stroke are known to manifest a decreased cough force, which is associated with an increased risk of aspiration. Specific brain lesions have been linked to impaired reflexive coughing. However, few studies have investigated whether specific stroke lesions are associated with impaired voluntary cough. Here, we studied the effects of stroke lesions on voluntary cough using voxel-based lesion-symptom mapping (VLSM). In this retrospective cross-sectional study, the peak cough flow was measured in patients who complained of weak cough (n = 39) after supratentorial lesions. Brain lesions were visualized via magnetic resonance imaging (MRI) at the onset of stroke. These lesions were studied using VLSM. The VLSM method with non-parametric mapping revealed that lesions in the sub-gyral frontal lobe and superior longitudinal and posterior corona radiata were associated with a weak cough flow. In addition, lesions in the inferior parietal and temporal lobes and both the superior and mid-temporal gyrus were associated with a weak peak cough flow during voluntary coughing. This study identified several brain lesions underlying impaired voluntary cough. The results might be useful in predicting those at risk of poor cough function and may improve the prognosis of patients at increased risk of respiratory complications after a stroke.
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Ruggieri, Serena, Fulvia Fanelli, Letizia Castelli, Nikolaos Petsas, Laura De Giglio et Luca Prosperini. « Lesion symptom map of cognitive–postural interference in multiple sclerosis ». Multiple Sclerosis Journal 24, no 5 (24 mars 2017) : 653–62. http://dx.doi.org/10.1177/1352458517701313.
Texte intégralRésumé :
Objective: To investigate the disease-altered structure–function relationship underlying the cognitive–postural interference (CPI) phenomenon in multiple sclerosis (MS). Methods: We measured postural sway of 96 patients and 48 sex-/age-matched healthy controls by force platform in quiet standing (single-task (ST)) while performing the Stroop test (dual-task (DT)) to estimate the dual-task cost (DTC) of balance. In patient group, binary T2 and T1 lesion masks and their corresponding lesion volumes were obtained from magnetic resonance imaging (MRI) of brain. Normalized brain volume (NBV) was also estimated by SIENAX. Correlations between DTC and lesion location were determined by voxel-based lesion symptom mapping (VLSM) analyses. Results: Patients had greater DTC than controls ( p < 0.001). Among whole brain MRI metrics, only T1 lesion volume correlated with DTC ( r = −0.27; p < 0.01). However, VLSM analysis did not reveal any association with DTC using T1 lesion masks. By contrast, we found clusters of T2 lesions in distinct anatomical regions (anterior and superior corona radiata, bilaterally) to be correlated with DTC ( p < 0.01 false discovery rate (FDR)-corrected). A multivariable stepwise regression model confirmed findings from VLSM analysis. NBV did not contribute to fit the model. Conclusion: Our findings suggest that the CPI phenomenon in MS can be explained by disconnection along specific areas implicated in task-switching abilities and divided attention.
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BAILEY, SEAN C. C., et ALEXANDER J. SMITS. « Experimental investigation of the structure of large- and very-large-scale motions in turbulent pipe flow ». Journal of Fluid Mechanics 651 (24 mars 2010) : 339–56. http://dx.doi.org/10.1017/s0022112009993983.
Texte intégralRésumé :
Multi-point velocity measurements have been performed in turbulent pipe flow at ReD = 1.5 × 105 and combined with cross-spectral and proper orthogonal decomposition analysis to elucidate information on the structure of the large- and very-large-scale motions in the outer layer of wall-bounded flows. The results indicate that in the outer layer the large-scale motions (LSM) may be composed of detached eddies with a wide range of azimuthal scales, whereas in the logarithmic layer they are attached. The very-large-scale motions (VLSM) have large radial scales, are concentrated around a single azimuthal mode and make a smaller angle with the wall compared to the LSM. The results support a hypothesis that only the detached LSM in the outer layer align to form the VLSM.
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Lee, Jin, Jae Hwa Lee, Jung-Il Choi et Hyung Jin Sung. « Spatial organization of large- and very-large-scale motions in a turbulent channel flow ». Journal of Fluid Mechanics 749 (23 mai 2014) : 818–40. http://dx.doi.org/10.1017/jfm.2014.249.
Texte intégralRésumé :
AbstractDirect numerical simulations were carried out to investigate the spatial features of large- and very-large-scale motions (LSMs and VLSMs) in a turbulent channel flow ($\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mathit{Re}_{\tau }=930$). A streak detection method based on the streamwise velocity fluctuations was used to individually trace the cores of LSMs and VLSMs. We found that both the LSM and VLSM populations were large. Several of the wall-attached LSMs stretched toward the outer regions of the channel. The VLSMs consisted of inclined outer LSMs and near-wall streaks. The number of outer LSMs increased linearly with the streamwise length of the VLSMs. The temporal features of the low-speed streaks in the outer region revealed that growing and merging events dominated the large-scale (1–$3\delta $) structures. The VLSMs $({>}3\delta )$ were primarily created by merging events, and the statistical analysis of these events supported that the merging of large-scale upstream structures contributed to the formation of VLSMs. Because the local convection velocity is proportional to the streamwise velocity fluctuations, the streamwise-aligned structures of the positive- and negative-$u$ patches suggested a primary mechanism underlying the merging events. The alignment of the positive- and negative-$u$ structures may be an essential prerequisite for the formation of VLSMs.
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Lee, Kyoung Bo, Sang Won Yoo, Eun Kyu Ji, Woo Seop Hwang, Yeun Jie Yoo, Mi-Jeong Yoon, Bo Young Hong et Seong Hoon Lim. « Is Lateropulsion Really Related with a Specific Lesion of the Brain ? » Brain Sciences 11, no 3 (10 mars 2021) : 354. http://dx.doi.org/10.3390/brainsci11030354.
Texte intégralRésumé :
Lateropulsion (pusher syndrome) is an important barrier to standing and gait after stroke. Although several studies have attempted to elucidate the relationship between brain lesions and lateropulsion, the effects of specific brain lesions on the development of lateropulsion remain unclear. Thus, the present study investigated the effects of stroke lesion location and size on lateropulsion in right hemisphere stroke patients. The present retrospective cross-sectional observational study assessed 50 right hemisphere stroke patients. Lateropulsion was diagnosed and evaluated using the Scale for Contraversive Pushing (SCP). Voxel-based lesion symptom mapping (VLSM) analysis with 3T-MRI was used to identify the culprit lesion for SCP. We also performed VLSM controlling for lesion volume as a nuisance covariate, in a multivariate model that also controlled for other factors contributing to pusher behavior. VLSM, combined with statistical non-parametric mapping (SnPM), identified the specific region with SCP. Lesion size was associated with lateropulsion. The precentral gyrus, postcentral gyrus, inferior frontal gyrus, insula and subgyral parietal lobe of the right hemisphere seemed to be associated with the lateropulsion; however, after adjusting for lesion volume as a nuisance covariate, no lesion areas were associated with the SCP scores. The size of the right hemisphere lesion was the only factor most strongly associated with lateropulsion in patients with stroke. These results may be useful for planning rehabilitation strategies of restoring vertical posture and understanding the pathophysiology of lateropulsion in stroke patients.
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Jang, Jae-Yeol, et No-Whan Kim. « The case study for Implementation and verification of Network based on VLSM ». Journal of the Korea institute of electronic communication sciences 9, no 11 (30 novembre 2014) : 1267–76. http://dx.doi.org/10.13067/jkiecs.2014.9.11.1267.
Texte intégral
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Lee, Myoungkyu, et Robert D. Moser. « Spectral analysis of the budget equation in turbulent channel flows at high Reynolds number ». Journal of Fluid Mechanics 860 (14 décembre 2018) : 886–938. http://dx.doi.org/10.1017/jfm.2018.903.
Texte intégralRésumé :
The transport equations for the variances of the velocity components are investigated using data from direct numerical simulations of incompressible channel flows at friction Reynolds number ($Re_{\unicode[STIX]{x1D70F}}$) up to$Re_{\unicode[STIX]{x1D70F}}=5200$. Each term in the transport equation has been spectrally decomposed to expose the contribution of turbulence at different length scales to the processes governing the flow of energy in the wall-normal direction, in scale and among components. The outer-layer turbulence is dominated by very large-scale streamwise elongated modes, which are consistent with the very large-scale motions (VLSM) that have been observed by many others. The presence of these VLSMs drives many of the characteristics of the turbulent energy flows. Away from the wall, production occurs primarily in these large-scale streamwise-elongated modes in the streamwise velocity, but dissipation occurs nearly isotropically in both velocity components and scale. For this to happen, the energy is transferred from the streamwise-elongated modes to modes with a range of orientations through nonlinear interactions, and then transferred to other velocity components. This allows energy to be transferred more-or-less isotropically from these large scales to the small scales at which dissipation occurs. The VLSMs also transfer energy to the wall region, resulting in a modulation of the autonomous near-wall dynamics and the observed Reynolds number dependence of the near-wall velocity variances. The near-wall energy flows are more complex, but are consistent with the well-known autonomous near-wall dynamics that gives rise to streaks and streamwise vortices. Through the overlap region between outer- and inner-layer turbulence, there is a self-similar structure to the energy flows. The VLSM production occurs at spanwise scales that grow with$y$. There is transport of energy away from the wall over a range of scales that grows with$y$. Moreover, there is transfer of energy to small dissipative scales which grows like$y^{1/4}$, as expected from Kolmogorov scaling. Finally, the small-scale near-wall processes characterised by wavelengths less than 1000 wall units are largely Reynolds number independent, while the larger-scale outer-layer processes are strongly Reynolds number dependent. The interaction between them appears to be relatively simple.
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Tejada Neyra, Miguel Angel, Ulf Neuberger, Annekathrin Reinhardt, Gianluca Brugnara, David Bonekamp, Martin Sill, Antje Wick et al. « Voxel-wise radiogenomic mapping of tumor location with key molecular alterations in patients with glioma ». Neuro-Oncology 20, no 11 (9 août 2018) : 1517–24. http://dx.doi.org/10.1093/neuonc/noy134.
Texte intégralRésumé :
Abstract Background This study aims to evaluate the impact of tumor location on key molecular alterations on a single voxel level in patients with newly diagnosed glioma. Methods A consecutive series of n = 237 patients with newly diagnosed glioblastoma and n = 131 patients with lower-grade glioma was analyzed. Volumetric tumor segmentation was performed on preoperative MRI with a semi-automated approach and images were registered to the standard Montreal Neurological Institute 152 space. Using a voxel-based lesion symptom mapping (VLSM) analysis, we identified specific brain regions that were associated with tumor-specific molecular alterations. We assessed a predefined set of n = 17 molecular characteristics in the glioblastoma cohort and n = 2 molecular characteristics in the lower-grade glioma cohort. Permutation adjustment (n = 1000 iterations) was used to correct for multiple testing, and voxel t-values that were greater than the t-value in >95% of the permutations were retained in the VLSM results (α = 0.05, power > 0.8). Results Tumor location predilection for isocitrate dehydrogenase (IDH) mutant tumors was found in both glioblastoma and lower-grade glioma cohorts, each showing a concordant predominance in the frontal lobe adjacent to the rostral extension of the lateral ventricles (permutation-adjusted P = 0.021 for the glioblastoma and 0.013 for the lower-grade glioma cohort). Apart from that, the VLSM analysis did not reveal a significant association of the tumor location with any other key molecular alteration in both cohorts (permutation-adjusted P > 0.05 each). Conclusion Our study highlights the unique properties of IDH mutations and underpins the hypothesis that the rostral extension of the lateral ventricles is a potential location for the cell of origin in IDH-mutant gliomas.
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Pillay, Sara B., Jeffrey R. Binder, Colin Humphries, William L. Gross et Diane S. Book. « Lesion localization of speech comprehension deficits in chronic aphasia ». Neurology 88, no 10 (8 février 2017) : 970–75. http://dx.doi.org/10.1212/wnl.0000000000003683.
Texte intégralRésumé :
Objective:Voxel-based lesion-symptom mapping (VLSM) was used to localize impairments specific to multiword (phrase and sentence) spoken language comprehension.Methods:Participants were 51 right-handed patients with chronic left hemisphere stroke. They performed an auditory description naming (ADN) task requiring comprehension of a verbal description, an auditory sentence comprehension (ASC) task, and a picture naming (PN) task. Lesions were mapped using high-resolution MRI. VLSM analyses identified the lesion correlates of ADN and ASC impairment, first with no control measures, then adding PN impairment as a covariate to control for cognitive and language processes not specific to spoken language.Results:ADN and ASC deficits were associated with lesions in a distributed frontal-temporal parietal language network. When PN impairment was included as a covariate, both ADN and ASC deficits were specifically correlated with damage localized to the mid-to-posterior portion of the middle temporal gyrus (MTG).Conclusions:Damage to the mid-to-posterior MTG is associated with an inability to integrate multiword utterances during comprehension of spoken language. Impairment of this integration process likely underlies the speech comprehension deficits characteristic of Wernicke aphasia.
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Lee, Jae Hwa, Hyung Jin Sung et Ronald J. Adrian. « Space–time formation of very-large-scale motions in turbulent pipe flow ». Journal of Fluid Mechanics 881 (25 octobre 2019) : 1010–47. http://dx.doi.org/10.1017/jfm.2019.786.
Texte intégralRésumé :
We examine the origin of very-large-scale motions (VLSMs) in fully developed turbulent pipe flow at friction Reynolds number, $\mathit{Re}_{\unicode[STIX]{x1D70F}}=934$, using data from a direct numerical simulation. The VLSMs and the packet-like large-scale motions (LSMs) found in this study are very similar to those found in earlier studies. Three-dimensional time-evolving instantaneous fields show that one component of the process leading to the large streamwise length of VLSMs is the concatenation of adjacent streamwise LSMs caused by the continuous elongation of LSMs due to the strain component of the mean shear. Spatial organization patterns of the VLSMs and LSMs and their properties are studied by separating auto-correlation of the streamwise velocity fluctuations into the components of the VLSM and the LSM defined by low-pass/high-pass filtering in the streamwise direction. The structures of the two-point spatial correlations of the streamwise velocity component of the VLSMs and the LSMs in the streamwise-azimuthal plane are characterized by multiple maxima and complex patterns that beg explanation in terms of patterned coherent arrangements of the LSMs. Using proper orthogonal decomposition (POD), it is found that the X-shape correlation pattern of the VLSMs results from the superposition of very long helically inclined structures and streamwise-aligned structures. Further explanation of the patterns in the correlations of the VLSMs and LSMs is provided through the study of synthetically constructed arrangements of simple hairpin packet models of the LSM. Head-to-tail alignment of the model packets along streamwise and helical directions suggested by the eigenvalues of the POD creates a pair of long roll-cells centred above the logarithmic layer, and bracketing the LSMs. These roll-cells are pure kinematic consequences of the induction within the LSM packets, but they may also serve to organize smaller packets.
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Guarracino, Ilaria, Tamara Ius, Cinzia Baiano, Serena D’Agostini, Miran Skrap et Barbara Tomasino. « Pre-Surgery Cognitive Performance and Voxel-Based Lesion-Symptom Mapping in Patients with Left High-Grade Glioma ». Cancers 13, no 6 (23 mars 2021) : 1467. http://dx.doi.org/10.3390/cancers13061467.
Texte intégralRésumé :
(1) Background: The literature on the effects of high-grade glioma (HGG) growth on cognition is still scarce. (2) Method: A consecutive series of 85 patients with HGG involving the left hemisphere underwent an extended neuropsychological evaluation prior to surgery. Voxel-based lesion-symptom mapping (VLSM) was used to identify regions related to cognitive performance. (3) Results: The patients’ mean level of pre-surgery accuracy was overall high. They showed the greatest difficulties in language with tasks such as naming (42.1% of patients impaired on nouns and 61.4% on verbs), reading (36.3% on words and 32.7% on pseudo-words), auditory lexical decisions (43.9%) and writing (41.3%) being most frequently impaired. VLSM analysis revealed anatomically separated areas along the temporal cortex and the white matter related to impairments on the different tasks, with voxels commonly shared by all tasks restricted to a small region in the ventral superior and middle temporal gyrus. (4) Conclusions: High-grade glioma affects cognition; nonetheless, lesions do not cause diffuse deficits but selectively impact the different language sub-domains along the ventral stream and the dorsal stream for language processing.
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Kim, M. J., H. A. Jeon et K. M. Lee. « Impairments of Syntactic Comprehension in Korean and the Location of Ischemic Stroke Lesions : A Voxel-Based Lesion-Symptom Mapping Study ». Behavioural Neurology 22, no 1-2 (2010) : 3–10. http://dx.doi.org/10.1155/2010/180852.
Texte intégralRésumé :
In order to assess the capacity of neurological patients to process syntactic features unique to Korean, such as the heavy dependence of parsing on syntactic morphemes rather than the word order in a sentence, the Korean Syntactic Comprehension Test (KSCT) was newly developed. To examine the correlation between lesion locations and the test performance, we did voxel-based lesion-symptom mapping (VLSM) analysis in a group of 39 patients with ischemic stroke. As a result, KSCT scores of the aphasic patients were significantly lower than those of 18 normal subjects. Within the patient group, VLSM analysis showed significant association between lower KSCT performance and the lesions mainly located in left perisylvian area and anterior temporal lobe. The KSCT results were also closely correlated with the results of two subtests in the Korean version-the Western Aphasia Battery. We conclude therefore that brain localization of syntactic comprehension in Korean native speakers is similar to that in other language speakers, despite the unique features of the Korean syntax, and that the KSCT will be of diagnostic value in assessing left fronto-temporal functions in Korean patients.
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Cameron, S. M., V. I. Nikora et I. Marusic. « Drag forces on a bed particle in open-channel flow : effects of pressure spatial fluctuations and very-large-scale motions ». Journal of Fluid Mechanics 863 (25 janvier 2019) : 494–512. http://dx.doi.org/10.1017/jfm.2018.1003.
Texte intégralRésumé :
The fluctuating drag forces acting on spherical roughness elements comprising the bed of an open-channel flow have been recorded along with synchronous measurements of the surrounding velocity field using stereoscopic particle image velocimetry. The protrusion of the target particle, equipped with a force sensor, was systematically varied between zero and one-half diameter relative to the hexagonally packed adjacent spheres. Premultiplied spectra of drag force fluctuations were found to have bimodal shapes with a low-frequency (${\approx}0.5~\text{Hz}$) peak corresponding to the presence of very-large-scale motions (VLSMs) in the turbulent flow. The high-frequency ($\gtrapprox 4~\text{Hz}$) region of the drag force spectra cannot be explained by velocity time series extracted from points around the particle, but instead appears to be dominated by the action of pressure gradients in the overlying flow field. For small particle protrusions, this high-frequency region contributes a majority of the drag force variance, while the relative importance of the low-frequency drag force fluctuations increases with increasing protrusion. The amplitude of high-frequency drag force fluctuations is modulated by the VLSMs irrespective of particle protrusion. These results provide some insight into the mechanics of bed particle stability and indicate that the optimum conditions for particle entrainment may occur when a low-pressure region embedded in the high-velocity portion of a VLSM overlays a particle.
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Lukic, Sladjana, Elena Barbieri, Xue Wang, David Caplan, Swathi Kiran, Brenda Rapp, Todd B. Parrish et Cynthia K. Thompson. « Right Hemisphere Grey Matter Volume and Language Functions in Stroke Aphasia ». Neural Plasticity 2017 (2017) : 1–14. http://dx.doi.org/10.1155/2017/5601509.
Texte intégralRésumé :
The role of the right hemisphere (RH) in recovery from aphasia is incompletely understood. The present study quantified RH grey matter (GM) volume in individuals with chronic stroke-induced aphasia and cognitively healthy people using voxel-based morphometry. We compared group differences in GM volume in the entire RH and in RH regions-of-interest. Given that lesion site is a critical source of heterogeneity associated with poststroke language ability, we used voxel-based lesion symptom mapping (VLSM) to examine the relation between lesion site and language performance in the aphasic participants. Finally, using results derived from the VLSM as a covariate, we evaluated the relation between GM volume in the RH and language ability across domains, including comprehension and production processes both at the word and sentence levels and across spoken and written modalities. Between-subject comparisons showed that GM volume in the RH SMA was reduced in the aphasic group compared to the healthy controls. We also found that, for the aphasic group, increased RH volume in the MTG and the SMA was associated with better language comprehension and production scores, respectively. These data suggest that the RH may support functions previously performed by LH regions and have important implications for understanding poststroke reorganization.
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Tobyne, Sean M., Wilson B. Ochoa, J. Daniel Bireley, Victoria MJ Smith, Jeroen JG Geurts, Jeremy D. Schmahmann et Eric C. Klawiter. « Cognitive impairment and the regional distribution of cerebellar lesions in multiple sclerosis ». Multiple Sclerosis Journal 24, no 13 (21 septembre 2017) : 1687–95. http://dx.doi.org/10.1177/1352458517730132.
Texte intégralRésumé :
Background: Cerebellar lesions are often reported in relapsing-remitting multiple sclerosis (RRMS) and have been associated with impaired motor function and cognitive status. However, prior research has primarily focused on summary measures of cerebellar involvement (e.g. total lesion load, gray/white matter volume) and not on the effect of lesion load within specific regions of cerebellar white matter. Objective: Spatially map the probability of cerebellar white matter lesion (CWML) occurrence in RRMS and explore the relationship between cognitive impairment and lesion (CWML) location within the cerebellum. Methods: High-resolution structural magnetic resonance imaging (MRI) was acquired on 16 cognitively impaired (CI) and 15 cognitively preserved (CP) RRMS subjects at 3T and used for lesion identification and voxel-based lesion-symptom mapping (VLSM). Results: CI RRMS demonstrated a predilection for the middle cerebellar peduncle (MCP). VLSM results indicate that lesions of the MCP are significantly associated with CI in RRMS. Measures of cerebellar lesion load were correlated with age at disease onset but not disease duration. Conclusion: A specific pattern of cerebellar lesions involving the MCP, rather than the total CWML load, contributes to cognitive dysfunction in RRMS. Cerebellar lesion profiles may provide a biomarker of current or evolving risk for cognitive status change in RRMS.
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Yang, Jimmy C., Daniel T. Ginat, Darin D. Dougherty, Nikos Makris et Emad N. Eskandar. « Lesion analysis for cingulotomy and limbic leucotomy : comparison and correlation with clinical outcomes ». Journal of Neurosurgery 120, no 1 (janvier 2014) : 152–63. http://dx.doi.org/10.3171/2013.9.jns13839.
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Object Cingulotomy and limbic leucotomy are lesioning surgeries with demonstrated benefit for medically intractable psychiatric illnesses. They represent significant refinements of the prefrontal lobotomy used from the 1930s through the 1950s. However, the associations between anatomical characterization of these lesions and outcome data are not well understood. To elucidate these procedures and associations, the authors sought to define and compare the neuroanatomy of cingulotomy and limbic leucotomy and to test a method that uses neuroanatomical data and voxel-based lesion–symptom mapping (VLSM) to reveal potential refinements to modern psychiatric neurosurgical procedures. Methods T1-weighted MR images of patients who had undergone cingulotomy and limbic leucotomy were segmented and registered onto the Montreal Neurological Institute T1-weighted template brain MNI152. Using an atlas-based approach, the authors calculated, by case, the percentage of each anatomical structure affected by the lesion. Because of the infrequency of modern lesion procedures and the requirement for higher-resolution clinical imaging, the sample size was small. The pilot study correlated cingulotomy and limbic leucotomy lesion characteristics with clinical outcomes for patients with obsessive-compulsive disorder. For this study, preoperative and postoperative Yale-Brown Obsessive Compulsive Scale scores for 11 cingulotomy patients and 8 limbic leucotomy patients were obtained, and lesion masks were defined and compared anatomically by using an atlas-based method. Statistically significant voxels were additionally calculated by using VLSM techniques that correlated lesion characteristics with postoperative scores. Results Mean lesion volumes were 13.3 ml for cingulotomy and 11.8 ml for limbic leucotomy. As expected, cingulotomy was isolated to the anterior cingulum. The subcaudate tractotomy portion of limbic leucotomy additionally affected Brodmann area 25, the medial orbitofrontal cortex, and the nucleus accumbens. Initial results indicated that the dorsolateral regions of the cingulotomy lesion and the posteroventral regions of the subcaudate tractotomy lesion were associated with improved postoperative Yale-Brown Obsessive Compulsive Scale scores. Conclusions Cingulotomy and limbic leucotomy are lesioning surgeries that target pathological circuits implicated in psychiatric disease. Lesion analysis and VLSM contextualize outcome data and have the potential to be useful for improving lesioning neurosurgical procedures.
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Liu, Xiangyu, Ping Zhang et Guanglong Du. « Hybrid adaptive impedance-leader-follower control for multi-arm coordination manipulators ». Industrial Robot : An International Journal 43, no 1 (18 janvier 2016) : 112–20. http://dx.doi.org/10.1108/ir-05-2015-0093.
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Purpose – The purpose of this paper is to provide a hybrid adaptive impedance-leader-follower control algorithm for multi-arm coordination manipulators, which is significant for dealing with the problems of kinematics inconsistency and error accumulation of interactive force in multi-arm system. Design/methodology/approach – This paper utilized a motion mapping theory in Cartesian space to establish a centralized dynamic leader-follower control algorithm which helped to reduce the possibility of kinematics inconsistency for multiple manipulators. A virtual linear spring model (VLSM) was presented based on a recognition approach of characteristic marker. This paper accomplished an adaptive impedance control algorithm based on the VLSM, which took into account the non-rigid contact characteristic. Experimentally demonstrated results showed the proposed algorithm guarantees that the motion and interactive forces asymptotically converge to the prescribed values. Findings – The hybrid control method improves the accuracy and reliability of multi-arm coordination system, which presents a new control framework for multiple manipulators. Practical implications – This algorithm has significant commercial applications, as a means of controlling multi-arm coordination manipulators that could serve to handle large objects and assemble complicated objects in industrial and hazardous environment. Originality/value – This work presented a new control framework for multiple coordination manipulators, which can ensure consistent kinematics and reduce the influence of error accumulation, and thus can improve the accuracy and reliability of multi-arm coordination system.
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Cheon, SeongKwon, DongXue Jin, YoungRag Kim et ChongGun Kim. « An IP Subnet Address Calculation and Management method on VLSM ». KIPS Transactions:PartC 12C, no 1 (1 février 2005) : 97–104. http://dx.doi.org/10.3745/kipstc.2005.12c.1.097.
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Riccardi, Nicholas, Chris Rorden, Julius Fridriksson et Rutvik H. Desai. « Canonical Sentence Processing and the Inferior Frontal Cortex : Is There a Connection ? » Neurobiology of Language 3, no 2 (2022) : 318–44. http://dx.doi.org/10.1162/nol_a_00067.
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Abstract The role of left inferior frontal cortex (LIFC) in canonical sentence comprehension is controversial. Many studies have found involvement of LIFC in sentence production or complex sentence comprehension, but negative or mixed results are often found in comprehension of simple or canonical sentences. We used voxel-, region-, and connectivity-based lesion symptom mapping (VLSM, RLSM, CLSM) in left-hemisphere chronic stroke survivors to investigate canonical sentence comprehension while controlling for lexical-semantic, executive, and phonological processes. We investigated how damage and disrupted white matter connectivity of LIFC and two other language-related regions, the left anterior temporal lobe (LATL) and posterior temporal-inferior parietal area (LpT-iP), affected sentence comprehension. VLSM and RLSM revealed that LIFC damage was not associated with canonical sentence comprehension measured by a sensibility judgment task. LIFC damage was associated instead with impairments in a lexical semantic similarity judgment task with high semantic/executive demands. Damage to the LpT-iP, specifically posterior middle temporal gyrus (pMTG), predicted worse sentence comprehension after controlling for visual lexical access, semantic knowledge, and auditory-verbal short-term memory (STM), but not auditory single-word comprehension, suggesting pMTG is vital for auditory language comprehension. CLSM revealed that disruption of left-lateralized white-matter connections from LIFC to LATL and LpT-iP was associated with worse sentence comprehension, controlling for performance in tasks related to lexical access, auditory word comprehension, and auditory-verbal STM. However, the LIFC connections were accounted for by the lexical semantic similarity judgment task, which had high semantic/executive demands. This suggests that LIFC connectivity is relevant to canonical sentence comprehension when task-related semantic/executive demands are high.
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Ivanova, M. V., O. Dragoy, S. V. Kuptsova, S. Yu. Akinina, A. G. Petrushevskii, O. N. Fedina, A. Turken, V. M. Shklovsky et N. F. Dronkers. « Neural mechanisms of two different verbal working memory tasks : A VLSM study ». Neuropsychologia 115 (juillet 2018) : 25–41. http://dx.doi.org/10.1016/j.neuropsychologia.2018.03.003.
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Nakada, Mitsutoshi, Riho Nakajima, Hirokazu Okita et Masashi Kinoshita. « NCOG-17. FACTORS INFLUENCING POOR INDEPENDENCE LEVEL FOLLOWING RESECTION OF THE RIGHT TEMPORO-PARIETAL GLIOBLASTOMAS ». Neuro-Oncology 23, Supplement_6 (2 novembre 2021) : vi155. http://dx.doi.org/10.1093/neuonc/noab196.608.
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Abstract In glioma surgeries, cognitive outcomes for the dominant hemisphere have gained much attention compared to the non-dominant hemisphere. For non-dominant hemispheric glioblastomas, we previously observed decreased independence level following glioblastoma resection of the posterior temporal to the parietal lobes. Here, we investigated the reason for the poor Karnofsky Performance Status (KPS) in such glioblastomas. A total of 41 patients with resection of the right cerebral hemispheric primary glioblastoma were enrolled for the study. Several kinds of neuropsychological functions and KPS of the brain regions were evaluated at pre- and postoperative 3 months by performing the Spearman’s correlation analysis and voxel-based lesion symptom mapping (VLSM). Additionally, the correlation between the resected volume of each gyrus or white matter tract and neuropsychological function score was analyzed. KPS at chronic phase (73.6) declined significantly compared with preoperation (81.0, p = 0.020). Functional factors influencing the KPS were general cognitive function, visuospatial cognition, emotion recognition, executive function, and apathy. The VLSM analysis revealed that the resection of the ventral parietal lobe and supramarginal gyrus (VPL-SMG) resulted in significantly poor KPS. Among the functional factors affecting KPS, VPL-SMG resection contributed to significantly lower scores in visuospatial cognition, emotion recognition, and apathy than those without resection (p = 0.0045, 0.047, and 0.0002, respectively). Further, we investigated whether the damage of the VPL-SMG could result in KPS related functional deficit. We found visuospatial cognition related to the posterior occipital lobe, SMG, arcuate fasciculus (AF), and dorsal superior longitudinal fasciculus, emotion recognition to the middle to inferior occipital gyrus and AF, and apathy to the inferior parietal lobe and middle temporal gyrus. We concluded that deficits of visuospatial cognition, emotion recognition, and apathy due to the damage of the cortical and white matter areas, including the VPL-SMG, were responsible for KPS of the non-dominant hemispheric glioblastomas.
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Nakajima, Riho, Masashi Kinoshita, Hirokazu Okita et Mitsutoshi Nakada. « QOLP-02. PRESERVING FUNCTIONS OF LANGUAGE, MOTOR, AND WORKING MEMORY BY AWAKE MAPPING CONTRIBUTES TO MAINTAIN QUALITY OF LIFE IN GLIOMAS ». Neuro-Oncology 21, Supplement_6 (novembre 2019) : vi197. http://dx.doi.org/10.1093/neuonc/noz175.822.
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Abstract INTRODUCTION Aims of awake surgery are considered as maximum resection and functional preservation for postoperative quality of life (QOL). However, any studies have not been focused on the fundamental hypothesis that preservation of brain functions contributes to patient’s QOL. In this study, we investigated postoperative QOL and its related factors to reveal contribution of awake surgery for maintaining QOL. METHODS A total of 63 patients who underwent awake surgery were studied. Several kinds of neuropsychological/neurological tests and SF-36 to assess QOL were performed at 6-month postoperatively. In SF-36, 3-component scores, including physical, mental, and role/social component were calculated and they were compared with healthy volunteers. Additionally, their background factors were collected from medical records. Then, influenced background and functional factors to QOL were analyzed using multiple regression analysis. Moreover, voxel-based lesion symptom (VLSM) analyses were performed to investigate relationship between resected regions and QOL. RESULTS Though physical and mental QOL scores were almost equivalent to healthy volunteers, role and social component score (RCS) were significantly declined (36.7, < .0001). Using multiple regression analysis, RCS significantly related to reinstatement among several background factors (p=0.0038). Until postoperative 6 months, 71.6% returned to professional work. Moreover, RCS correlated significantly with working memory, language, and motor function among several brain functions (p=0.019, 0.0028, 0.010, respectively). In the VLSM analysis, patients who resected following regions showed significantly low RCS; the left inferior frontal and superior to middle temporal gyri which relate to language; and right supplementary motor area and cingulate cortex which are involved in motor control or working memory. CONCLUSIONS The important factors to maintain QOL are reinstatement and preserving brain functions including language, motor, and working memory. This suggests that awake surgery aiming for preserving these functions is a benefit for postoperative QOL.
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Nakajima, Riho, Masashi Kinoshita, Hirokazu Okita et Mitsutoshi Nakada. « NCOG-41. FUNCTIONAL OUTCOME FOLLOWING NON-DOMINANT HEMISPHERIC GLIOMA SURGERY FROM THE ASPECT OF INDEPENDENCE LEVEL, COGNITIVE FUNCTION AND RETURN TO SOCIAL LIVES ». Neuro-Oncology 22, Supplement_2 (novembre 2020) : ii138. http://dx.doi.org/10.1093/neuonc/noaa215.579.
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Abstract BACKGROUND Functional outcome has been paid much attention in surgery for eloquent area or dominant hemisphere. Little is known about functional outcome following surgery for non-dominant hemispheric gliomas, although some resent reports revealed the importance of right cerebral hemisphere on glioma surgery. Here, we investigated functional outcome of right cerebral hemispheric gliomas from the aspect of independence level, cognitive function, and return to social lives. METHODS Totally 82 patients with right cerebral hemispheric gliomas who underwent surgery for resection in Kanazawa university hospital were studied. Patients were divided into two groups, WHO grade II/III and IV. Karnofsky Performance Status (KPS), Mini-mental state examination (MMSE), and whether or not to return to work at pre-operation and chronic phase were evaluated. To reveal responsible region for decline of each index, the voxel-based lesion symptom (VLSM) analyses were performed. RESULTS MMSE; no difference was found through postoperative course in grade II/III, whereas postoperative score of grade IV was declined significantly compared with pre-operation (25.1 and 21.9 point; p=0.048). KPS; preoperative independence level was maintained until chronic phase in grade II/III (94.7 and 89.5). While, in grade IV, postoperative KPS was declined significantly than that of pre-operation (82.0 and 70.0, p=0.007). Results of the VLSM analysis revealed that patients who resected temporo-parietal junction in grade IV showed significantly low KPS score. Return to social lives; Reintegration ratio of working population was 71% and 35% for grade II/III and IV, respectively. Of these, as for grade II/III gliomas, the cingulate cortex and medial orbito-frontal cortex relate to return to social lives. CONCLUSIONS Functional outcome following surgery depends on tumor grade and resected region in right cerebral hemispheric gliomas.
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Küper, Michael, Barbara Brandauer, Markus Thürling, Beate Schoch, Elke R. Gizewski, Dagmar Timmann et Joachim Hermsdörfer. « Impaired prehension is associated with lesions of the superior and inferior hand representation within the human cerebellum ». Journal of Neurophysiology 105, no 5 (mai 2011) : 2018–29. http://dx.doi.org/10.1152/jn.00834.2010.
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Impairment of patients with cerebellar disease in prehension is well recognized. So far specific localizations within the human cerebellum associated with the impairment have rarely been assessed. To address this question we performed voxel-based lesion symptom mapping (VLSM) in patients with chronic focal cerebellar lesions in relation to specific deficits in prehensile movements. Patients with stroke within the posterior inferior cerebellar artery territory ( n = 13) or the superior cerebellar artery (SCA) territory ( n = 7) and corresponding control subjects were included in the study. Participants reached out, grasped, and lifted an object with either the left or right hand and with fast or normal movement speed. Both kinematic and grip-force parameters were recorded. Magnetic resonance imaging anatomical scans of the cerebellum were acquired, and lesions were marked as regions of interest. For VLSM analysis, a nonparametric test (Brunner-Munzel) was applied. Cerebellar patients showed clear abnormalities in hand transport (impaired movement speed and straightness) and, to a lesser degree, in hand shaping (increased finger touch latencies) while grip function was preserved. Deficits were most prominent in patients with SCA lesions and for ipsilesional, fast movements. Disorders in hand transport may be more difficult to compensate than deficits in hand shaping and grip-force control in chronic focal lesions of the cerebellum because of higher demands on predictive control of interaction torques. Lesions of the superior cerebellar cortex (lobules IV, V, VI) were associated with slower hand transport, whereas lesions of both superior (lobules VI, V, VI) and inferior cerebellar cortex (lobules VII, VIII) were associated with impaired movement straightness. These findings show that both the superior and inferior hand representations within the cerebellum contribute to hand transport during prehensile movements; however, they may have a different functional role.
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Al-Yahya, Ibtesam Mohammed. « The Effect of a Task-Based, Curriculum-Enrichment Program for Vocabulary Learning Strategies on Saudi University Students ». International Journal of Linguistics 13, no 5 (24 septembre 2021) : 111. http://dx.doi.org/10.5296/ijl.v13i5.19112.
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The current study set to investigate the effect of introducing particular vocabulary learning strategies (VLSs) to Saudi, female students. The strategies implemented were six: 'grouping words together to study them' (GW); 'putting English labels on physical objects' (LO); 'using scales for gradable words'(SC); 'using semantic maps'(SM); 'using the keyword method' (KW) and 'studying words with a pictorial representation of their meaning' (PR). The participants were a group of 90 level-one students studying in the Department of English Language and Translation at Imam Muhammad Ibn Saud Islamic University, Riyadh. They were assigned to two groups: control (N= 44) and experimental (N=46); only the experimental group received instructions on those strategies in a form of task-based, curriculum-enrichment materials. To assess the effectiveness of such a VLS instruction (VLSI) program, three areas were examined: the students' vocabulary learning (VL), the frequency of strategy-use, and their VLS repertoire. The data of the study were derived from three instruments: pre-post vocabulary achievement test (VAT), pre-post questionnaire and semi-structured interviews. The analysis of the data revealed the effectiveness of the VSBI program in the areas identified above. First, it improved the students' vocabulary achievement as well as their VL, in general. Second, it increased the frequency of using general categories of VLSs (i.e. VLSs altogether, consolidation strategies, metacognitive strategies). It also increased the frequency of using five of the taught strategies which were GW, LO, SC, KW, and PR. Third, the VSBI program proved to be positive in that it changed and improved the students' VLS repertoire.
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Rabadi, Reem Ibrahim. « Vocabulary Learning Strategies Employed by Undergraduate EFL Jordanian Students ». English Language and Literature Studies 6, no 1 (26 février 2016) : 47. http://dx.doi.org/10.5539/ells.v6n1p47.
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<p>The present study investigates the various vocabulary learning strategies (VLSs) used by undergraduate Jordanian students majoring English Language and Literature in Jordanian universities. The five categories of the vocabulary learning strategies (Memory, Determination, Social, Cognitive, and Metacognitive) were used in this study following Schmitt’s taxonomy. For this purpose, a questionnaire containing forty items selected from Schmitt’s (1997) Vocabulary Learning Strategies Questionnaire (VLSQ) was administered to a pool of 110 Jordanian students majoring in English Language and Literature from eight Jordanian universities. This testing instrument was used to reveal the types of vocabulary learning strategies used by the participants, to discover the most and least frequently used VLS employed by them, and to know the main patterns of variation of the participants’ choice of VLSs if they are high, medium, or low VLS users. The descriptive analysis of the study showed that Jordanian EFL learners were “medium” strategy users overall. With regard to strategy categories, the results revealed that Memory strategies were the most frequently employed by them and Metacognitive strategies were the least frequently used strategies among them. Although the participants were medium strategy users, the results of the VLSQ revealed that some individual strategies were employed at a low level. This result leads to adopt the learners’ individual vocabulary learning strategy as an important variable in future research. The findings of this study will be advantageous to language instructors to improve effective vocabulary teaching techniques and curriculum designers to provide learners with preferable vocabulary learning strategies.</p>
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Jung, Soojin, Ha Ra Jeon, Hea-Eun Yang, Si-Nae Kim et Ri-La Lim. « Voxel Based Lesion-Symptom Brain Mapping (VLSM) Study of Swallowing Control in Stroke Patients ». Archives of Physical Medicine and Rehabilitation 97, no 10 (octobre 2016) : e56-e57. http://dx.doi.org/10.1016/j.apmr.2016.08.171.
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Rosenberg, B. J., M. Hultmark, M. Vallikivi, S. C. C. Bailey et A. J. Smits. « Turbulence spectra in smooth- and rough-wall pipe flow at extreme Reynolds numbers ». Journal of Fluid Mechanics 731 (14 août 2013) : 46–63. http://dx.doi.org/10.1017/jfm.2013.359.
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AbstractWell-resolved streamwise velocity spectra are reported for smooth- and rough-wall turbulent pipe flow over a large range of Reynolds numbers. The turbulence structure far from the wall is seen to be unaffected by the roughness, in accordance with Townsend’s Reynolds number similarity hypothesis. Moreover, the energy spectra within the turbulent wall region follow the classical inner and outer scaling behaviour. While an overlap region between the two scalings and the associated${ k}_{x}^{- 1} $law are observed near${R}^{+ } \approx 3000$, the${ k}_{x}^{- 1} $behaviour is obfuscated at higher Reynolds numbers due to the evolving energy content of the large scales (the very-large-scale motions, or VLSMs). We apply a semi-empirical correction (del Álamo & Jiménez,J. Fluid Mech., vol. 640, 2009, pp. 5–26) to the experimental data to estimate how Taylor’s frozen field hypothesis distorts the pseudo-spatial spectra inferred from time-resolved measurements. While the correction tends to suppress the long wavelength peak in the logarithmic layer spectrum, the peak nonetheless appears to be a robust feature of pipe flow at high Reynolds number. The inertial subrange develops around${R}^{+ } \gt 2000$where the characteristic${ k}_{x}^{- 5/ 3} $region is evident, which, for high Reynolds numbers, persists in the wake and logarithmic regions. In the logarithmic region, the streamwise wavelength of the VLSM peak scales with distance from the wall, which is in contrast to boundary layers, where the superstructures have been shown to scale with boundary layer thickness throughout the entire shear layer. Moreover, the similarity in the streamwise wavelength scaling of the large- and very-large-scale motions supports the notion that the two are physically interdependent.
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Geva, Sharon, Jean-Claude Baron, P. Simon Jones, Cathy J. Price et Elizabeth A. Warburton. « A comparison of VLSM and VBM in a cohort of patients with post-stroke aphasia ». NeuroImage : Clinical 1, no 1 (2012) : 37–47. http://dx.doi.org/10.1016/j.nicl.2012.08.003.
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Walker, Grant M., Myrna F. Schwartz, Daniel Y. Kimberg, Olufunsho Faseyitan, Adelyn Brecher, Gary S. Dell et H. Branch Coslett. « Support for anterior temporal involvement in semantic error production in aphasia : New evidence from VLSM ». Brain and Language 117, no 3 (juin 2011) : 110–22. http://dx.doi.org/10.1016/j.bandl.2010.09.008.
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Chousianitis, K., A. Ganas, M. Papanikolaou, P. Argyrakis, G. Drakatos et K. Makropoulos. « Time series analysis of the NOANET CGPS stations ». Bulletin of the Geological Society of Greece 47, no 2 (24 janvier 2017) : 508. http://dx.doi.org/10.12681/bgsg.11078.
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The National Observatory of Athens has begun installing permanent GPS stations on February 2006 including a EUREF permanent station in Attica, NOA1. Currently the National Observatory of Athens operates 20 continuous GPS stations around Greece all sampling at 1-s and transmitting real-time data to Athens. Several stations also sample at 0.2-s (5 Hz) and record the data in the ring buffer for a period of 1-2 days. Their location is carefully selected so that both geological and seismotectonic criteria are fulfilled. All stations are situated close to major seismogenic structures of Greece such as the Cephalonia Transform Fault (CTF) in the Ionian Sea (VLSM, PONT, SPAN, KIPO), and the two North Anatolian Fault branches in the North Aegean Sea (PRKV, LEMN ). We describe the CGPS data archiving and processing procedures, used to combine into a uniform velocity solution the observations of all the NOANET stations, accounting for the seasonal (annual and semiannual) signals, and considering the off-sets in the coordinate time-series.
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Zhang, Jing-Ren, et Steven J. Norris. « Genetic Variation of the Borrelia burgdorferi Gene vlsE Involves Cassette-Specific, Segmental Gene Conversion ». Infection and Immunity 66, no 8 (1 août 1998) : 3698–704. http://dx.doi.org/10.1128/iai.66.8.3698-3704.1998.
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ABSTRACT The Lyme disease spirochete Borrelia burgdorferipossesses 15 silent vls cassettes and a vlsexpression site (vlsE) encoding a surface-exposed lipoprotein. Segments of the silent vls cassettes have been shown to recombine with the vlsE cassette region in the mammalian host, resulting in combinatorial antigenic variation. Despite promiscuous recombination within the vlsE cassette region, the 5′ and 3′ coding sequences of vlsE that flank the cassette region are not subject to sequence variation during these recombination events. The segments of the silent vlscassettes recombine in the vlsE cassette region through a unidirectional process such that the sequence and organization of the silent vls loci are not affected. As a result of recombination, the previously expressed segments are replaced by incoming segments and apparently degraded. These results provide evidence for a gene conversion mechanism in VlsE antigenic variation.
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Zhu, Xiangqi, Jiyu Wang, Ning Lu, Nader Samaan, Renke Huang et Xinda Ke. « A Hierarchical VLSM-Based Demand Response Strategy for Coordinative Voltage Control Between Transmission and Distribution Systems ». IEEE Transactions on Smart Grid 10, no 5 (septembre 2019) : 4838–47. http://dx.doi.org/10.1109/tsg.2018.2869367.
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PIRAS, FABRIZIO, et PAOLA MARANGOLO. « When “Crack walnuts” lies in different brain regions : Evidence from a voxel-based lesion-symptom mapping study ». Journal of the International Neuropsychological Society 16, no 3 (24 février 2010) : 433–42. http://dx.doi.org/10.1017/s1355617710000068.
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AbstractTheories of lexical processing differ as to how multimorphemic words, such as compounds, are mentally processed. The most recent findings seem to support the dual route hypothesis, which assumes that complex words can be stored and retrieved either whole or by decomposition into their constituents. Despite great efforts to investigate the cognitive mechanisms involved in processing complex words, very little is known about how compounds are represented in the brain. The present study was designed to address this issue in a group of 20 left-hemispheric stroke patients who were submitted to four picture-naming tasks involving nouns, verbs, noun-noun (NN) and verb-noun (VN) compounds. To determine the brain lesions implicated in these tasks, we analyzed patients’ performances together with their lesions using Voxel-based Lesion Symptom Mapping (VLSM). Results showed that while NN involved the same temporal areas as nouns, VN (although they belong to the noun category) involved different fronto-temporal regions. This latter finding is discussed within the view that distinct mechanisms process the different constituents of complex words. (JINS, 2010, 16, 433–442.)
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Lawrenz, Matthew B., R. Mark Wooten et Steven J. Norris. « Effects of vlsE Complementation on the Infectivity of Borrelia burgdorferi Lacking the Linear Plasmid lp28-1 ». Infection and Immunity 72, no 11 (novembre 2004) : 6577–85. http://dx.doi.org/10.1128/iai.72.11.6577-6585.2004.
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ABSTRACT The loss of linear plasmid lp28-1, which contains the vls antigenic variation locus, is associated with reduced infectivity of Borrelia burgdorferi in immunocompetent mice. The recombinant shuttle vector pBBE22, which includes the virulence determinant BBE22 from lp25 and restores infectivity to readily transformable B. burgdorferi lacking lp25 and lp56, was used to determine the effect of trans expression of vlsE on virulence. Spirochetes lacking lp28-1 were complemented with the plasmid pBBE22:vlsE, containing both BBE22 and vlsE. VlsE protein produced by this construct was expressed and surface accessible in in vitro-cultured B. burgdorferi, as determined by surface proteolysis and immunoblot analysis. Clones lacking lp25 but containing lp28-1 and either pBBE22 or pBBE22:vlsE were reisolated consistently from immunocompetent mice 8 weeks after infection. In contrast, a clone lacking both lp25 and lp28-1 and complemented with pBBE22:vlsE was isolated from only a single tissue of one of six C3H/HeN mice 8 weeks postinfection. These results indicate that either an intact vls antigenic variation locus or another determinant on lp28-1 is required to restore complete infectivity. In addition, an isogenic clone that retained lp28-1 was complemented with the vlsE shuttle plasmid and was examined for vlsE sequence variation and infectivity. Sequence variation was not observed for the shuttle plasmid, indicating that the cis arrangement of vlsE and the vls silent cassettes in lp28-1 facilitate vlsE gene conversion. Lack of vlsE sequence variation on the shuttle plasmid thus did not result in clearance of the trans-complemented strain in immunocompetent mice under the conditions tested.
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Bykowski, Tomasz, Kelly Babb, Kate von Lackum, Sean P. Riley, Steven J. Norris et Brian Stevenson. « Transcriptional Regulation of the Borrelia burgdorferi Antigenically Variable VlsE Surface Protein ». Journal of Bacteriology 188, no 13 (1 juillet 2006) : 4879–89. http://dx.doi.org/10.1128/jb.00229-06.
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ABSTRACT The Lyme disease agent Borrelia burgdorferi can persistently infect humans and other animals despite host active immune responses. This is facilitated, in part, by the vls locus, a complex system consisting of the vlsE expression site and an adjacent set of 11 to 15 silent vls cassettes. Segments of nonexpressed cassettes recombine with the vlsE region during infection of mammalian hosts, resulting in combinatorial antigenic variation of the VlsE outer surface protein. We now demonstrate that synthesis of VlsE is regulated during the natural mammal-tick infectious cycle, being activated in mammals but repressed during tick colonization. Examination of cultured B. burgdorferi cells indicated that the spirochete controls vlsE transcription levels in response to environmental cues. Analysis of PvlsE::gfp fusions in B. burgdorferi indicated that VlsE production is controlled at the level of transcriptional initiation, and regions of 5′ DNA involved in the regulation were identified. Electrophoretic mobility shift assays detected qualitative and quantitative changes in patterns of protein-DNA complexes formed between the vlsE promoter and cytoplasmic proteins, suggesting the involvement of DNA-binding proteins in the regulation of vlsE, with at least one protein acting as a transcriptional activator.
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Chaconas, George, Mildred Castellanos et Theodore B. Verhey. « Changing of the guard : How the Lyme disease spirochete subverts the host immune response ». Journal of Biological Chemistry 295, no 2 (21 novembre 2019) : 301–13. http://dx.doi.org/10.1074/jbc.rev119.008583.
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Lyme disease, also known as Lyme borreliosis, is the most common tick-transmitted disease in the Northern Hemisphere. The disease is caused by the bacterial spirochete Borrelia burgdorferi and other related Borrelia species. One of the many fascinating features of this unique pathogen is an elaborate system for antigenic variation, whereby the sequence of the surface-bound lipoprotein VlsE is continually modified through segmental gene conversion events. This perpetual changing of the guard allows the pathogen to remain one step ahead of the acquired immune response, enabling persistent infection. Accordingly, the vls locus is the most evolutionarily diverse genetic element in Lyme disease–causing borreliae. Small stretches of information are transferred from a series of silent cassettes in the vls locus to generate an expressed mosaic vlsE gene version that contains genetic information from several different silent cassettes, resulting in ∼1040 possible vlsE sequences. Yet, despite its extreme evolutionary flexibility, the locus has rigidly conserved structural features. These include a telomeric location of the vlsE gene, an inverse orientation of vlsE and the silent cassettes, the presence of nearly perfect inverted repeats of ∼100 bp near the 5′ end of vlsE, and an exceedingly high concentration of G runs in vlsE and the silent cassettes. We discuss the possible roles of these evolutionarily conserved features, highlight recent findings from several studies that have used next-generation DNA sequencing to unravel the switching process, and review advances in the development of a mini-vls system for genetic manipulation of the locus.
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Liu, Bo, Lina Tang, Qian Chen, Liming Zhu, Xianwu Zou, Botao Li, Qin Zhou, Yuejin Fu et Yun Lu. « Lignin Distribution on Cell Wall Micro-Morphological Regions of Fibre in Developmental Phyllostachys pubescens Culms ». Polymers 14, no 2 (13 janvier 2022) : 312. http://dx.doi.org/10.3390/polym14020312.
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Bamboo is a natural fibre reinforced composite with excellent performance which is, to a certain extent, an alternative to the shortage of wood resources. The heterogeneous distribution and molecular structure of lignin is one of the factors that determines its performance, and it is the key and most difficult component in the basic research into the chemistry of bamboo and in bamboo processing and utilization. In this study, the distribution of lignin components and lignin content in micro-morphological regions were measured in semi-quantitative level by age and radial location by means of visible-light microspectrophotometry (VLMS) coupled with the Wiesner and Maule reaction. There as guaiacyl lignin and syringyl lignin in the cell wall of the fibre. Lignin content of the secondary cell wall and cell corner increased at about 10 days, reached a maximum at 1 year, and then decreased gradually. From 17 days to 4 years, the lignin content of the secondary cell wall in the outer part of bamboo is higher than that in the middle part (which is, in turn, higher than that in the inner part of the bamboo). VLSM results of the micro-morphological regions showed that bamboo lignification developed by aging. Guaiacyl and syringl lignin units can be found in the cell wall of the fibre, parenchyma, and vessel. There was a difference in lignin content among different ages, different radial location, and different micro-morphological regions of the cell wall. The fibre walls were rich in guaiacyl lignin in the early stage of lignification and rich in syringyl units in the later stage of lignification. The guaiacyl and syringyl lignin deposition of bamboo green was earlier than that of the middle part of bamboo culm, and that of the middle part of bamboo culm was earlier than that of bamboo yellow. The single molecule lignin content of the thin layer is higher than that of thick layers, while the primary wall is higher than the secondary cell wall, showing that lignin deposition is consistent with the rules of cell wall formation. The obtained cytological information is helpful to understand the origin of the anisotropic, physical, mechanical, chemical, and machining properties of bamboo.
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Arnoux, Audrey, Monica N. Toba, Marco Duering, Momar Diouf, Joel Daouk, Jean-Marc Constans, Laurent Puy, Mélanie Barbay et Olivier Godefroy. « Is VLSM a valid tool for determining the functional anatomy of the brain ? Usefulness of additional Bayesian network analysis ». Neuropsychologia 121 (décembre 2018) : 69–78. http://dx.doi.org/10.1016/j.neuropsychologia.2018.10.003.
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Robinson, Heather, Matthew Calamia, Jan Gläscher, Joel Bruss et Daniel Tranel. « Neuroanatomical Correlates of Executive Functions : A Neuropsychological Approach Using the EXAMINER Battery ». Journal of the International Neuropsychological Society 20, no 1 (13 juin 2013) : 52–63. http://dx.doi.org/10.1017/s135561771300060x.
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AbstractExecutive functions (EF) encompass a variety of higher-order capacities such as judgment, planning, decision-making, response monitoring, insight, and self-regulation. Measuring such abilities quantitatively and establishing their neural correlates has proven to be challenging. Here, using a lesion-deficit approach, we report the neural correlates of a variety of EF tests that were developed under the auspices of the NINDS-supported EXAMINER project (Kramer, 2011;www.examiner.ucsf.edu). We administered a diverse set of EF tasks that tap three general domains—cognitive, social/emotional, and insight—to 37 patients with focal lesions to the frontal lobes, and 25 patients with lesions outside the frontal lobes. Using voxel-based lesion-symptom mapping (VLSM), we found that damage to the ventromedial prefrontal cortex (vmPFC) was predominately associated with deficits in social/emotional aspects of EF, while damage to dorsolateral prefrontal cortex (dlPFC) and anterior cingulate was predominately associated with deficits in cognitive aspects of EF. Evidence for an important role of some non-frontal regions (e.g., the temporal poles) in some aspects of EF was also found. The results provide further evidence for the neural basis of EF, and extend previous findings of the dissociation between the roles of the ventromedial and dorsolateral prefrontal sectors in organizing, implementing, and monitoring goal-directed behavior. (JINS, 2013,19, 1–12)
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Campana, Serena, Carlo Caltagirone et Paola Marangolo. « Combining Voxel-based Lesion-symptom Mapping (VLSM) With A-tDCS Language Treatment : Predicting Outcome of Recovery in Nonfluent Chronic Aphasia ». Brain Stimulation 8, no 4 (juillet 2015) : 769–76. http://dx.doi.org/10.1016/j.brs.2015.01.413.
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Fontanarosa, Donato, Luca Francioso, Maria Grazia De Giorgi et Maria Rosaria Vetrano. « MEMS Vaporazing Liquid Microthruster : A Comprehensive Review ». Applied Sciences 11, no 19 (26 septembre 2021) : 8954. http://dx.doi.org/10.3390/app11198954.
Texte intégralRésumé :
The interest in developing efficient nano and pico-satellites has grown in the last 20 years. Secondary propulsion systems capable of serving specific maneuvers are an essential part of these small satellites. In particular, Micro-Electro-Mechanical Systems (MEMS) Vaporizing Liquid Microthrusters (VLM), using water as a propellant, represent today a smart choice in terms of simplicity and cost. In this paper, we first propose a review of the international literature focused on MEMS VLM development, reviewing the different geometries and heating solutions proposed in the literature. Then, we focus on a critical aspect of these micro thrusters: the presence of unstable phenomena. In particular, the boiling instabilities and reverse channel flow substantially impact the MEMS VLMs’ performance and limit their applicability. Finally, we review the research focused on the passive and active control of the boiling instabilities, based on VLM geometry optimization and active heating strategies, respectively. Today, these ones represent the two principal research axes followed by the scientific community to mitigate the drawbacks linked to the use of MEMS VLMs.
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CHEN, SHIH-LIANG, TINGTING HWANG, SHU-MING CHANG et WEN-WEI LIN. « A FAST DIGITAL CHAOTIC GENERATOR FOR SECURE COMMUNICATION ». International Journal of Bifurcation and Chaos 20, no 12 (décembre 2010) : 3969–87. http://dx.doi.org/10.1142/s0218127410028136.
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In this paper, we propose a digitalized chaotic map, Variational Logistic Map (VLM), modified from classical logistic map to be used in secure communication. Compared with classical logistic map, VLM has large parameter space without windows and can be implemented at low hardware cost. Referring to statistical testing suites SP800-22 and TestU01, VLM with the proposed scrambling method can significantly improve the output complexity as compared with other logistic-map based generators and piecewise linear chaotic map. Experiments show that the throughput of a 32-bit VLM is up to 3200 Mbps in 0.18 μm process. Furthermore, a chaotic crypto scheme, Multi-VLM (MVLM), constructed by four 32-bit VLMs can generate an output sequence with a minimal length equal to 2128-1 by a 128-bit external key.
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Ganesan, Aparna, Adarsh Ishwar Hegde, Tushar Suvra Ghosh et Kirti Chaudhry. « Venolymphatic malformation of tongue : a prompt life saving intervention ». BMJ Case Reports 15, no 11 (novembre 2022) : e252437. http://dx.doi.org/10.1136/bcr-2022-252437.
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Venolymphatic malformations (VLMs) of the head and neck can have varied clinical presentation with associated complications. Timely diagnosis and treatment is warranted to curb the morbidity and obtain satisfactory outcomes. We present the case of a male patient in his early 20s with VLM of the tongue who received precise interventions which were executed with active contributions from a team of anaesthesiologists, interventional radiologists, oral and maxillofacial surgeons and intensivists. We highlight the importance of an immediate, comprehensive and multimodal treatment approach for VLMs of the maxillofacial region.
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McDowell, John V., Shian-Ying Sung, Linden T. Hu et Richard T. Marconi. « Evidence That the Variable Regions of the Central Domain of VlsE Are Antigenic during Infection with Lyme Disease Spirochetes ». Infection and Immunity 70, no 8 (août 2002) : 4196–203. http://dx.doi.org/10.1128/iai.70.8.4196-4203.2002.
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ABSTRACT It has been postulated that the vls system of the Lyme disease spirochetes contributes to immune evasion through antigenic variation. While it is clear that vlsE undergoes sequence change within its variable regions at a high frequency during the early stages of infection, a definitive role in immune evasion has not been demonstrated. In this report we assessed the murine and human humoral immune response to recombinant (r)-VlsE variants that originally arose during infection in mice. Immunoblot analyses of r-VlsE variants were conducted by using serum samples collected from mice infected with Borrelia burgdorferi clones that carried different vlsE variants. All of the r-VlsE variants were recognized by infection sera regardless of the identity of the infecting clone or isolate. In addition, all variants were immunoreactive with a panel of human Lyme disease patient serum samples. It is evident from these analyses that the infection-induced VlsE variants share common epitopes that reside within conserved segments of these proteins. However, preabsorption experiments revealed that the variable regions of the central domain of VlsE, which undergo rapid mutation during infection, also influence the antigenic properties of the protein. A subset of the antibodies elicited against vlsE variants that differ in the sequences of their variable regions were found to be variant specific. Hence, in spite of a robust antibody response to conserved segments of VlsE, infection-induced sequence changes within the variable regions alter the antigenicity of VlsE. These results provide the first direct evidence of antigenic variation in the VlsE protein.