Enhanced Charge Carrier Transport in 2D Perovskites by Incorporating Single-Walled Carbon Nanotubes or Graphene

Two-dimensional (2D) organic-inorganic (hybrid) perovskites are considered promising candidates to replace conventional three-dimensional (3D) perovskites for solar cell applications as they have good resistance against moisture and UV light. However, the use of 2D perovskite is associated with a significant decrease in power efficiency resulting from their low photogenerated charge carrier density and poor charge transport. To improve power efficiency in 2D perovskites, highly crystalline films (near-single-crystal quality) of 2D perovskite need to be synthesized where the alignment of the inorganic perovskite components is controlled to have vertical alignment with respect to the contacts to improve charge transport. In this work, we explored strategies to overcome this limitation by integrating 2D perovskite with single-walled carbon nanotubes or graphene to enable more efficient extraction of charge carriers toward electric contacts. Longer carrier lifetimes were achieved after the incorporation of the carbon nanostructures in the films, and at the cell level, power efficiency increased by 2-fold

Diffusion tensor-based fiber tracking in cervical spinal cord with a 3T MRI

The protocol for spinal DTI nntl tractography with high SNR and spatial resolution has been developed arid tested on G healthy subjects and 1 CSM patient in a 3T system. Fiber bundlex were traced and were found running parallel to the cervical spinal cord correlating with the neuronal anatomy in normal subjects. The FA maps showed consistent low FA region connecting all spinal levels, which corresponded lo the grey matter structure in anatomical imaging, Spinal DTI in CSM showed diffusivity increase at compression sites. The proposed diffusion eigenvector-based method was able to differentiate between λa and λr even when there was a draxtic diffusivity change at compressed regions in CSM, which may facilitate better understanding of the pathophysiology of CSM. Our results indicated that using the current imaging and post-procensing protocols, spinal DTI can fm achieved with better grey white matter contrast, high inter-subject reproducibility and diagnostic ability. © 2006 IEEE.published_or_final_versio

A survey of machine learning approaches to analysis of large corpora

Corpus-based Machine Learning of linguistic annotations has been a key topic for all areas of Natural Language Processing. This paper presents a survey, along three dimensions of classification. First we outline different linguistic level of analysis: Tokenisation, Part-of-Speech tagging, Parsing, Semantic analysis and Discourse annotation. Secondly, we introduce alternative approaches to Machine Learning applicable to linguistic annotation of corpora: N-gram and Markov models, Neural Networks, Transformation-Based Learning, Decision Tree learning, and Vector-based classification. Thirdly, weexamine a range of Machine Learning systems for the most challenging level of linguistic annotation, discourse analysis; these illustrate the various Machine Learning approaches. Our overall aim is to provide an ontology or framework for further development of our research

Proton Density-weighted Spinal fMRI Comparison between Sensorimotor Task and Acupoint Stimulation

Proton density-weighted fMRI studies have been carried out in spinal cord in the current study. We compared the spinal cord activation produced by handgripping sensorimotor task and electro-acupuncture stimulation. Activation was detected in both cases localized at spinal levels C6-C7 (11/14 in sensorimotor and 7/11 in acupuncture stimulation). It was observed that the amount of activation in sensorimotor task was in general greater than in electroacupuncture stimulation. The percentage signal changes were found to be similar. Our results indicate that proton density-weighted fMRI in low field MRI system can be used for sensorimotor and acupuncture pathway research.published_or_final_versio

Functional MRI of the spinal cord at low field

A second contrast mechanism SEEP was reported to co-exist with BOLD during fMRI activation. The mechanism was based on the task-induced signal change of extravascular water protons and was primarily shown in the spinal cord at high field. Recently, a preliminary study was reported at 0.2T showing SEEP contrast in the brain while the BOLD effect was negligible. The present study is to investigate the presence of SEEP in the spinal cord at 0.2T using proton density-weighted imaging with motor task. Bilateral activations were obtained in the anterior grey horns consistently across C6-C8 levels, which correlated with the neural anatomy.published_or_final_versio

In vivo diffusion tensor imaging in rat model of chronic spinal cord compression

Session 64: Advanced Spinal Cord Imaging - Oral presentationWe have employed DTI to investigate the pathophysiology of chronic spinal cord compression in this study. Average diffusion characteristic curves and fiber tracking have been done to evaluate the lesion and intact regions. DTI is sensitive to the damage and it is potential to monitor the progressive structural and functional changes in such chronic spinal cord diseases.published_or_final_versionThe 17th Scientific Meeting & Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM), Honolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 2009, p. 63

Detection of ipsilateral and contralateral activation components in unilateral fingers-tapping using spinal BOLD fMR

Ipsilateral activation component has been reported in brain fMRI studies using unilateral finger motion. However, the ipsilateral component is usually taskdependent and sparsely distributed. In this study, spinal BOLD fMRI has been performed on 4 healthy right-handed volunteers performing unilateral fingerstapping to investigate the ipsilateral and contralateral activation inside the cervical spinal cord. Our results showed that more activation were found at the spinal level C5-C6/C7. Bilateral activation was observed in all subjects both in left/right hand fingers-tapping. Spinal fMRI was sensitive to detect bilateral firing in fingers-tapping using dominant or non-dominant hands.published_or_final_versio

In vivo diffusion tensor imaging of chronic spinal cord compression in rat model

Conference Theme: Engineering the Future of BiomedicineChronic spinal cord compression induced cervical myelopathy is a comon cause of spinal cord dysfunction. The exact mechanisms of underlying progressive cell death remain to be elucidated. In this study, in vivo diffusion tensor imaging (DTI) has been applied to investigate the microstructural changes of white matter (WM) in this neurodegenerative disease. Compared with conventional MRI techniques, DTI is believed to be more specific to pathological changes. Radial diffusivity (λ⊥) is higher in the ipilesional region, suggesting demyelination or axonal degradation may occur after prolonged compression. Near the epicenter of lesion, axial diffusivity (λ∥) is lower. Also, caudal-rostral asymmetry has been observed in λ∥. Feasibility of using DTI to detect microstructural changes in chronic disease has been demonstrated. ©2009 IEEE.published_or_final_versionThe 31st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2009), Minneapolis, MN., 3-6 September 2009. In Proceedings of the 31st EMBC, 2009, p. 2715-271

Multi-valued, singular stochastic evolution inclusions

We provide an abstract variational existence and uniqueness result for multi-valued, monotone, non-coercive stochastic evolution inclusions in Hilbert spaces with general additive and Wiener multiplicative noise. As examples we discuss certain singular diffusion equations such as the stochastic 1-Laplacian evolution (total variation flow) in all space dimensions and the stochastic singular fast diffusion equation. In case of additive Wiener noise we prove the existence of a unique weak-* mean ergodic invariant measure.Comment: 39 pages, in press: J. Math. Pures Appl. (2013