3,073 research outputs found
Finite-Time Observer Based Guidance and Control of Underactuated Surface Vehicles with Unknown Sideslip Angles and Disturbances
Suffering from complex sideslip angles, path following control of an under actuated surface vehicle (USV) becomes significantly challenging and remains unresolved. In this paper, a finite-time observer based guidance and control (FOGC) scheme for path following of an USV with time-varying and large sideslip angles and unknown external disturbances is proposed. The salient features of the proposed FOGC scheme are as follows: 1) time-varying large sideslip angle is exactly estimated by a finite-time sideslip observer, and thereby contributing to the sideslip-tangent line-of-sight guidance law which significantly enhances the robustness of the guidance system to unknown sideslip angles which are significantly large and time-varying; 2) a finite-time disturbance observer (FDO) is devised to exactly observe unknown external disturbances, and thereby implementing FDO-based surge and heading robust tracking controllers, which possess remarkable tracking accuracy and precise disturbance rejection, simultaneously; and 3) by virtue of cascade analysis and Lyapunov approach, global asymptotic stability of the integrated guidance-control system is rigorously ensured. Simulation studies and comparisons are conducted to demonstrate the effectiveness and superiority of the proposed FOGC scheme
Directional single-mode emission from coupled whispering gallery resonators realized by using ZnS microbelts
Author name used in this publication: Siu Fung Yu2012-2013 > Academic research: refereed > Publication in refereed journalpublished_fina
Ecmo-assisted carinal resection and reconstruction after left pneumonectomy
Extracorporeal Membrane Oxygenation (ECMO) has become an increasingly important technique for patients with respiratory or cardiac failure for a variety of causes. In addition, there are many reports about the use of ECMO in surgical operation on neonates and children patients with tracheal obstruction. In this report we present a case about an adult patient who underwent a carinal resection and reconstruction after left pneumonectomy with ECMO assistance successfully. To our knowledge, this case is the first of its kind to use ECMO in adult carinal resection and reconstruction after pneumonectomy. In this report, we try to illustrate that ECMO is effective in operations of this kind
The clinicopathologic observation, c-KIT gene mutation and clonal status of gastrointestinal stromal tumor in the sacrum
<p>Abstract</p> <p>Background</p> <p>It is very rare that gastrointestinal stromal tumor (GIST) occurs in the sacrum. Only one case of GIST occuring in the sacral region, with intracranial metastasis, has been reported in the literature. Moreover, only few cases have been published in literature about its clonal origin.</p> <p>Case presentation</p> <p>In this report, we present a rare case of GIST occuring in the sacrum and describe its clinicopathologic features, c-KIT gene mutation and clonal status. Microscopically, the lesion was composed of spindle cells arranged in cords, knitted and whirlpool patterns. Trabecula of bone were found in the lesion. The cytoplasm of tumor cells were abundant, and the nuclei were fusiform. Mitotic figures were rare. Immunohistochemically, the tumor cells showed positive reactivity for CD117 and CD34. On mutation analysis, a c-KIT gene mutation was found in exon 11. The result of clonal analysis demonstrated that the GIST was monoclonal.</p> <p>Conclusion</p> <p>In summary, we showed that tumor material, phenotypically identical with GISTs was found in the sacrum. It is difficult to differentiate GISTs from other spindle cell tumors, hence the need for immunohistochemistry, the examination of c-KIT gene amplification and sequencing.</p
Dusty Planetary Systems
Extensive photometric stellar surveys show that many main sequence stars show
emission at infrared and longer wavelengths that is in excess of the stellar
photosphere; this emission is thought to arise from circumstellar dust. The
presence of dust disks is confirmed by spatially resolved imaging at infrared
to millimeter wavelengths (tracing the dust thermal emission), and at optical
to near infrared wavelengths (tracing the dust scattered light). Because the
expected lifetime of these dust particles is much shorter than the age of the
stars (>10 Myr), it is inferred that this solid material not primordial, i.e.
the remaining from the placental cloud of gas and dust where the star was born,
but instead is replenished by dust-producing planetesimals. These planetesimals
are analogous to the asteroids, comets and Kuiper Belt objects (KBOs) in our
Solar system that produce the interplanetary dust that gives rise to the
zodiacal light (tracing the inner component of the Solar system debris disk).
The presence of these "debris disks" around stars with a wide range of masses,
luminosities, and metallicities, with and without binary companions, is
evidence that planetesimal formation is a robust process that can take place
under a wide range of conditions. This chapter is divided in two parts. Part I
discusses how the study of the Solar system debris disk and the study of debris
disks around other stars can help us learn about the formation, evolution and
diversity of planetary systems by shedding light on the frequency and timing of
planetesimal formation, the location and physical properties of the
planetesimals, the presence of long-period planets, and the dynamical and
collisional evolution of the system. Part II reviews the physical processes
that affect dust particles in the gas-free environment of a debris disk and
their effect on the dust particle size and spatial distribution.Comment: 68 pages, 25 figures. To be published in "Solar and Planetary
Systems" (P. Kalas and L. French, Eds.), Volume 3 of the series "Planets,
Stars and Stellar Systems" (T.D. Oswalt, Editor-in-chief), Springer 201
Adolescent brain maturation and cortical folding: evidence for reductions in gyrification
Evidence from anatomical and functional imaging studies have highlighted major modifications of cortical circuits during adolescence. These include reductions of gray matter (GM), increases in the myelination of cortico-cortical connections and changes in the architecture of large-scale cortical networks. It is currently unclear, however, how the ongoing developmental processes impact upon the folding of the cerebral cortex and how changes in gyrification relate to maturation of GM/WM-volume, thickness and surface area. In the current study, we acquired high-resolution (3 Tesla) magnetic resonance imaging (MRI) data from 79 healthy subjects (34 males and 45 females) between the ages of 12 and 23 years and performed whole brain analysis of cortical folding patterns with the gyrification index (GI). In addition to GI-values, we obtained estimates of cortical thickness, surface area, GM and white matter (WM) volume which permitted correlations with changes in gyrification. Our data show pronounced and widespread reductions in GI-values during adolescence in several cortical regions which include precentral, temporal and frontal areas. Decreases in gyrification overlap only partially with changes in the thickness, volume and surface of GM and were characterized overall by a linear developmental trajectory. Our data suggest that the observed reductions in GI-values represent an additional, important modification of the cerebral cortex during late brain maturation which may be related to cognitive development
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ALMaQUEST. IV. The ALMA-MaNGA QUEnching and STar Formation (ALMaQUEST) Survey
The ALMaQUEST (ALMA-MaNGA QUEnching and STar formation) survey is a program
with spatially-resolved CO(1-0) measurements obtained with the Atacama
Large Millimeter Array (ALMA) for 46 galaxies selected from the Mapping Nearby
Galaxies at Apache Point Observatory (MaNGA) DR15 optical integral-field
spectroscopic survey. The aim of the ALMaQUEST survey is to investigate the
dependence of star formation activity on the cold molecular gas content at kpc
scales in nearby galaxies. The sample consists of galaxies spanning a wide
range in specific star formation rate (sSFR), including starburst (SB),
main-sequence (MS), and green valley (GV) galaxies. In this paper, we present
the sample selection and characteristics of the ALMA observations, and showcase
some of the key results enabled by the combination of spatially-matched stellar
populations and gas measurements. Considering the global (aperture-matched)
stellar mass, molecular gas mass, and star formation rate of the sample, we
find that the sSFR depends on both the star formation efficiency (SFE) and the
molecular gas fraction (), although the correlation with the
latter is slightly weaker. Furthermore, the dependence of sSFR on the molecular
gas content (SFE or ) is stronger than that on either the atomic
gas fraction or the molecular-to-atomic gas fraction, albeit with the small HI
sample size. On kpc scales, the variations in both SFE and
within individual galaxies can be as large as 1-2 dex thereby demonstrating
that the availability of spatially-resolved observations is essential to
understand the details of both star formation and quenching processes.STFC
ER
Prenylation inhibitors stimulate both estrogen receptor α transcriptional activity through AF-1 and AF-2 and estrogen receptor β transcriptional activity
INTRODUCTION: We showed in a previous study that prenylated proteins play a role in estradiol stimulation of proliferation. However, these proteins antagonize the ability of estrogen receptor (ER) α to stimulate estrogen response element (ERE)-dependent transcriptional activity, potentially through the formation of a co-regulator complex. The present study investigates, in further detail, how prenylated proteins modulate the transcriptional activities mediated by ERα and by ERβ. METHODS: The ERE-β-globin-Luc-SV-Neo plasmid was either stably transfected into MCF-7 cells or HeLa cells (MELN cells and HELN cells, respectively) or transiently transfected into MCF-7 cells using polyethylenimine. Cells deprived of estradiol were analyzed for ERE-dependent luciferase activity 16 hours after estradiol stimulation and treatment with FTI-277 (a farnesyltransferase inhibitor) or with GGTI-298 (a geranylgeranyltransferase I inhibitor). In HELN cells, the effect of prenyltransferase inhibitors on luciferase activity was compared after transient transfection of plasmids coding either the full-length ERα, the full-length ERβ, the AF-1-deleted ERα or the AF-2-deleted ERα. The presence of ERα was then detected by immunocytochemistry in either the nuclei or the cytoplasms of MCF-7 cells. Finally, Clostridium botulinum C3 exoenzyme treatment was used to determine the involvement of Rho proteins in ERE-dependent luciferase activity. RESULTS: FTI-277 and GGTI-298 only stimulate ERE-dependent luciferase activity in stably transfected MCF-7 cells. They stimulate both ERα-mediated and ERβ-mediated ERE-dependent luciferase activity in HELN cells, in the presence of and in the absence of estradiol. The roles of both AF-1 and AF-2 are significant in this effect. Nuclear ERα is decreased in the presence of prenyltransferase inhibitors in MCF-7 cells, again in the presence of and in the absence of estradiol. By contrast, cytoplasmic ERα is mainly decreased after treatment with FTI-277, in the presence of and in the absence of estradiol. The involvement of Rho proteins in ERE-dependent luciferase activity in MELN cells is clearly established. CONCLUSIONS: Together, these results demonstrate that prenylated proteins (at least RhoA, RhoB and/or RhoC) antagonize the ability of ERα and ERβ to stimulate ERE-dependent transcriptional activity, potentially acting through both AF-1 and AF-2 transcriptional activities
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