18 research outputs found
Hemifacial spasm in a patient with neurofibromatosis and Arnold-Chiari malformation: a unique case association
A model of feedback control for the charge-balanced suppression of epileptic seizures
Here we present several refinements to a model of feedback control for the suppression of epileptic seizures. We utilize a stochastic partial differential equation (SPDE) model of the human cortex. First, we verify the strong convergence of numerical solutions to this model, paying special attention to the sharp spatial changes that occur at electrode edges. This allows us to choose appropriate step sizes for our simulations; because the spatial step size must be small relative to the size of an electrode in order to resolve its electrical behavior, we are able to include a more detailed electrode profile in the simulation. Then, based on evidence that the mean soma potential is not the variable most closely related to the measurement of a cortical surface electrode, we develop a new model for this. The model is based on the currents flowing in the cortex and is used for a simulation of feedback control. The simulation utilizes a new control algorithm incorporating the total integral of the applied electrical potential. Not only does this succeed in suppressing the seizure-like oscillations, but it guarantees that the applied signal will be charge-balanced and therefore unlikely to cause cortical damage
Comprehensive in vivo Mapping of the Human Basal Ganglia and Thalamic Connectome in Individuals Using 7T MRI
Basal ganglia circuits are affected in neurological disorders such as Parkinson's disease (PD), essential tremor, dystonia and Tourette syndrome. Understanding the structural and functional connectivity of these circuits is critical for elucidating the mechanisms of the movement and neuropsychiatric disorders, and is vital for developing new therapeutic strategies such as deep brain stimulation (DBS). Knowledge about the connectivity of the human basal ganglia and thalamus has rapidly evolved over recent years through non-invasive imaging techniques, but has remained incomplete because of insufficient resolution and sensitivity of these techniques. Here, we present an imaging and computational protocol designed to generate a comprehensive in vivo and subject-specific, three-dimensional model of the structure and connections of the human basal ganglia. High-resolution structural and functional magnetic resonance images were acquired with a 7-Tesla magnet. Capitalizing on the enhanced signal-to-noise ratio (SNR) and enriched contrast obtained at high-field MRI, detailed structural and connectivity representations of the human basal ganglia and thalamus were achieved. This unique combination of multiple imaging modalities enabled the in-vivo visualization of the individual human basal ganglia and thalamic nuclei, the reconstruction of seven white-matter pathways and their connectivity probability that, to date, have only been reported in animal studies, histologically, or group-averaged MRI population studies. Also described are subject-specific parcellations of the basal ganglia and thalamus into sub-territories based on their distinct connectivity patterns. These anatomical connectivity findings are supported by functional connectivity data derived from resting-state functional MRI (R-fMRI). This work demonstrates new capabilities for studying basal ganglia circuitry, and opens new avenues of investigation into the movement and neuropsychiatric disorders, in individual human subjects
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Organizational innovation in the multinational enterprise: internalization theory and business history
This article engages in a methodological experiment by using historical evidence to challenge a common misperception about internalization theory. The theory has often been criticized for maintaining that it assumes a hierarchically organized MNE based on knowledge flowing from the home country. This is not an accurate description of how global firms operate in recent decades, but this article shows it has never been true historically. Using longitudinal data on individual firms from the nineteenth century onwards, it reveals evidence of how entrepreneurs and firms with multinational activity faced with market imperfections changed the design of their headquarters and their organizational structures
Comparative use of turkey and chicken wing brachial artery models for microvascular anastomosis training
Comparing fourth ventricle shunt survival after placement via stereotactic transtentorial and suboccipital approaches
Infecções relacionadas Ă assistĂŞncia em saĂşde e gravidade clĂnica em uma unidade de terapia intensiva
Objetivou-se verificar a possĂvel associação entre a severidade clĂnica e a ocorrĂŞncia de infecções relacionadas Ă assistĂŞncia em saĂşde. Conduziu-se uma coorte prospectiva em uma unidade de terapia intensiva de um hospitaluniversitário, de agosto de 2009 a fevereiro de 2010. Utilizou-se o Average Severity Index Score para avaliar a severidadeclĂnica. Os dados foram coletados por vigilância ativa e processados no SPSS. Realizou-se análise univariada econsiderou-se significância estatĂstica de p<0,05, com intervalo de confiança de 95%. O Ăndice de severidade esteverelacionado Ă ocorrĂŞncia de infecções, assim como tempo de permanĂŞncia na unidade de terapia intensiva, tipo depaciente, uso de procedimento invasivo, antimicrobiano, colonização e desfecho do paciente (p<0,05). A presençade infecções foi um fator preditivo para a ocorrĂŞncia de Ăłbitos (p=0,000). Tais achados reforçam a ideia de que aocorrĂŞncia de infecção constitui uma complexa cadeia, multifatorial, com destaque para a severidade clĂnica do paciente