8,307 research outputs found
Neural activity of the anterior insula in emotional processing depends on the individuals' emotional susceptibility
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Neocerebellar Crus I abnormalities associated with a speech and language disorder due to a mutation in FOXP2
No full textBilateral volume reduction in the caudate nucleus has been established as a prominent brain abnormality associated with a FOXP2 mutation in affected members of the ‘KE family’, who present with developmental orofacial and verbal dyspraxia in conjunction with pervasive language deficits. Despite the gene’s early and prominent expression in the cerebellum and the evidence for reciprocal cerebellum-basal ganglia connectivity, very little is known about cerebellar abnormalities in affected KE members. Using cerebellum-specific voxel-based morphometry (VBM) and volumetry, we provide converging evidence from subsets of affected KE members scanned at three time points for grey matter (GM) volume reduction bilaterally in neocerebellar lobule VIIa Crus I compared with unaffected members and unrelated controls. We also show that right Crus I volume correlates with left and total caudate nucleus volumes in affected KE members, and that right and total Crus I volumes predict the performance of affected members in non-word repetition
and non-verbal orofacial praxis. Crus I also shows bilateral hypo-activation in functional MRI in the affected KE members relative to controls during non-word repetition. The association of Crus I with key aspects of the behavioural phenotype of this FOXP2 point mutation is consistent with recent evidence of cerebellar involvement in complex motor sequencing. For the first time, specific cerebello-basal ganglia loops are implicated in the execution of complex oromotor sequences needed for human speech
Changes in white matter microstructure during adolescence
No full textPostmortem histological studies have demonstrated that myelination in human brain white matter (WM) continues throughout adolescence and well into adulthood. We used in vivo diffusion-weighted magnetic resonance imaging to test for age-related WM changes in 42 adolescents and 20 young adults. Tract-Based Spatial Statistics (TBSS) analysis of the adolescent data identified widespread age-related increases in fractional anisotropy (FA) that were most significant in clusters including the body of the corpus callosum and right superior corona radiata. These changes were driven by changes in perpendicular, rather than parallel, diffusivity. These WM clusters were used as seeds for probabilistic tractography, allowing us to identify the regions as belonging to callosal, corticospinal, and prefrontal tracts. We also performed voxel-based morphometry-style analysis of conventional T1-weighted images to test for age-related changes in grey matter (GM). We identified a cluster including right middle frontal and precentral gyri that showed an age-related decrease in GM density through adolescence and connected with the tracts showing age-related WM FA increases. The GM density decrease was highly significantly correlated with the WM FA increase in the connected cluster. Age-related changes in FA were much less prominent in the young adult group, but we did find a significant age-related increase in FA in the right superior longitudinal fascicle, suggesting that structural development of this pathway continues into adulthood. Our results suggest that significant microstructural changes in WM continue throughout adolescence and are associated with corresponding age-related changes in cortical GM regions
Bilateral brain abnormalities associated with dominantly inherited verbal and orofacial dyspraxia.
No full textThe KE family is a large three-generational pedigree in which half of the members suffer from a verbal and orofacial dyspraxia in association with a point mutation in the FOXP2 gene. This report extends previous voxel-based morphometric analyses of magnetic resonance imaging (MRI) scans (Watkins et al. [2002] Brain 125:465-478) using a bilateral conjunction analysis. This searches specifically for areas of grey matter density that differ bilaterally in the affected members compared with both matched controls and the unaffected family members. 3-D T1-weighted MRI datasets of 17 family members (10 affected, 7 unaffected) and matched controls were compared. The most significant findings were reduced grey matter density bilaterally in the caudate nucleus, the cerebellum, and the left and right inferior frontal gyrus in the affected members. In addition, increased grey matter density was found bilaterally in the planum temporale. These results confirm that a point mutation in FOXP2 is associated with several bilateral grey matter abnormalities in both motor and language related regions. The results also demonstrate the advantages of using a conjunction analysis when bilateral abnormalities are suspected
The Design and Implementation of a Key Performance Indicator Dashboard for KE-chain
No full textKE-works is a six years old company which aims to optimise the product development process in industrial applications. To accomplish this, KE-works deploys a web-application called KE-chain. KEchain is an engineering workflow management system with the objective to increase the efficiency of the product development process through better control, more efficient distribution, access and use of product-related information. Users have the possibility to set-up a project, manage the tasks belonging to this project, and control the workflow and information distribution. With KE-chain users are able to create structure in the heap of information that composes their product and, when used right, improve the process of their project development. One of the key elements in optimising the product development process is the monitoring of the available data to give users insight in the status of the project. Currently it is difficult to get a good overview of a project within KE-chain and it is not possible to see what tasks are cirtical at a certain moment. A common way of showing the status or performance of systems is the use of Key Performance Indicators (KPI’s). These indicators, for example in the form of a graph or a table, can quickly give information about the performance of a system. KE-works has decided that it wants to give its users an overview in the formof a project-specific dashboard with KPI widgets. Therefore the assignment is to design and develop an integrated KPI dashboard into KE-chain. To design the KPI dashboard, which we named KE-board, we shortly researched the field of Performance Measurement to get an overview of the different approaches for the design of KPI’s. As a basis for the design we have adopted the Lean methodology [1] which has been used by KE-works in the past. In our research we have actually connected the Lean wastes to measures in KE-chain. To do this, we have chosen a bottom-up approach, which means we started by identifying the available data, after which we extracted several groups of measures. We have interviewed several clients of KEworks, the users of KE-chain. From these interviews we deducted which groups of measures were important for which user roles. To verify which measures are of importance for these dashboards, we have questioned and interviewd the consultants of KE-works. By combining the results of the interviews and the questionnaires we designed 7 KPI widgets. Finally, we created KE-board and integrated it into KE-chain in five weeks of implementation. After that we have evaluated the complete dashboard by interviewing the consultants of KE-works. On top of that, we have sent them a questionnaire in which they rated the functionality of the widgets to see if they contribute to their purpose and achieve the goals that we set for them. KE-board has been received well by the management and employees of KE-works and according to the extensive evaluation we can state that it definitely contributes to the optimization of the product development process in KE-chain.Computer ScienceComputer ScienceElectrical Engineering, Mathematics and Computer Scienc
Optimal upper bound for the infinity norm of eigenvectors of random matrices
No full textLet be a random Hermitian (or symmetric) matrix whose upper diagonal and diagonal entries are independent random variables with mean zero and variance one. It is well known that the empirical spectral distribution (ESD) converges in probability to the semicircle law supported on . In this thesis we study the local convergence of ESD to the semicircle law. One main result is that if the entries of are bounded, then the semicircle law holds on intervals of scale . As a consequence, we obtain the delocalization result for the eigenvectors, i.e., the upper bound for the infinity norm of unit eigenvectors corresponding to eigenvalues in the bulk of spectrum, is . The bound is the same as the infinity norm of a vector chosen uniformly on the unit sphere in . We also study the local version of Marchenko-Pastur law for random covariance matrices and obtain the optimal upper bound for the infinity norm of singular vectors. This is joint work with V. Vu. In the last chapter, we discuss the delocalization properties for the adjacency matrices of ErdH{o}s-R'{e}nyi random graph. This is part of some earlier results joint with L. Tran and V. Vu.Ph. D.Includes bibliographical referencesIncludes vitaby Ke Wan
Development of zein-based ice nucleator films for frozen food applications
No full textThis research aimed at developing zein-based ice nucleation films for the applications of frozen foods. Acetic acid was chosen as the solvent to cast zein films with flawless surface. Tributyl citrate (TBC) was mixed into zein films to various proportions and 10% TBC was most effective on improving mechanical properties resulting in 2.3-fold more flexibility and 5.8-fold more toughness compared to unplasticized zein films. But incorporation of 20% TBC significantly decreased the water absorption by 19% compared to 10% TBC. Thus, zein films with 20% TBC with good flexibility and water resistance was used in following experiments. The activity of ECINs was stable at pH between 4.0 and 9.0 and ionic strength between 0.01 M and 0.10 M. In the development of INFs, the optimum adsorption of ECINs on zein films surface occurred through layer-by-layer method at pH 7.0 and ionic strength of 0.05 M on UV/ozone-treated zein. A novel method was developed to quantify the activity of INFs, which revealed that the highest activity of zein-based INFs reached 175 units/mm2. The zein-based ice nucleation films (INFs) were used to wrap frozen bread dough during five freeze/thaw cycles. The high-activity INF was as effective as blending ECINs in improving the yeast survival by 40%, and consequently increased the specific volume of bread loaf by 25%. Furthermore, high-activity INFs prevented the dehydration of frozen dough and thus significantly reduced the crumb hardness by 36% and increased the crumb springiness by 1.25 times. On energy saving, zein-based INFs were less potential than blended ECINs. INFs only reduced the time of freezing by 6% compared to the 20% by blended ECINs. However, the total amount of ECINs used on wrapping a piece of dough was only about 1/200 of the amount through blending. In addition, ECINs immobilized on the zein films showed desirable stability to sustain at least fifteen repetitive uses on freezing water.Ph. D.Includes bibliographical referencesIncludes vitaby Ke Sh
Integrating centralized and decentralized approaches for multi-robot coordination
No full textAutonomous multi-robot systems play important roles in many areas such as industrial applications for repetitive tasks, explorations in hazardous environments, and military missions in extreme conditions. Many existing coordination strategies are developed for two general types of multi-robot systems including strongly centralized systems and completely decentralized systems. For strongly centralized systems, the global information including the environment as well as the locations of all the robots is shared. It is typical for small number of robots in well structural environments and is not robust to dynamic environment or failures in communications and other uncertainties. For completely decentralized systems, each robot is executing its own control schemes completely autonomously. There are no specified leaders throughout the mission, and the team organization does not have a set structure. In many real-world applications, it is beneficial to use so-called weakly centralized systems, in which the leader robot is not specified a priori, but it is selected dynamically during the mission to guide the robot team through dynamic environments or other uncertainties. It is very challenging to develop coordination strategies for this type of systems because of the dynamic nature of the team structures. The strategies should not only allow for on-line leader role selection but also enable formation decomposition and reconfiguration whenever necessary. In this thesis, we describe a general coordination framework for weakly centralized multi-robot systems that integrates the features from both strongly centralized and completely decentralized coordination strategies at the individual robot level. The framework allows the robots to reconfigure the formation dynamically in the presence of obstacles or other uncertainties in the environment, and promotes the main advantages of multi-robot systems such as flexibility and modularity. Since the control schemes can be decentralized and this framework allows for the selection of the motion planner and local controller for a given task, the framework can be naturally applied to multi-robot systems with larger scales. We have implemented this framework on a team of two-wheeled differential driven mobile robots. Significant results from numerical simulations and experiments have been obtained to demonstrate that the coordination schemes are effective and robust, and the framework is viable and can be scaled to relative large scale multi-robot systems.Ph.D.Includes bibliographical referencesIncludes vitaby Ke X
Longitudinal changes in grey and white matter during adolescence.
No full textBrain development continues actively during adolescence. Previous MRI studies have shown complex patterns of apparent loss of grey matter (GM) volume and increases in white matter (WM) volume and fractional anisotropy (FA), an index of WM microstructure. In this longitudinal study (mean follow-up=2.5+/-0.5 years) of 24 adolescents, we used a voxel-based morphometry (VBM)-style analysis with conventional T1-weighted images to test for age-related changes in GM and WM volumes. We also performed tract-based spatial statistics (TBSS) analysis of diffusion tensor imaging (DTI) data to test for age-related WM changes across the whole brain. Probabilistic tractography was used to carry out quantitative comparisons across subjects in measures of WM microstructure in two fiber tracts important for supporting speech and motor functions (arcuate fasciculus [AF] and corticospinal tract [CST]). The whole-brain analyses identified age-related increases in WM volume and FA bilaterally in many fiber tracts, including AF and many parts of the CST. FA changes were mainly driven by increases in parallel diffusivity, probably reflecting increases in the diameter of the axons forming the fiber tracts. FA values of both left and right AF (but not of the CST) were significantly higher at the end of the follow-up than at baseline. Over the same period, widespread reductions in the cortical GM volume were found. These findings provide imaging-based anatomical data suggesting that brain maturation in adolescence is associated with structural changes enhancing long-distance connectivities in different WM tracts, specifically in the AF and CST, at the same time that cortical GM exhibits synaptic "pruning"
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