TEM TOMOGRAPHY AND HOLOGRAPHY OF LOW DIMENSIONAL OXIDE STRUCTURES

Ph.DDOCTOR OF PHILOSOPH

Estimation of high-dimensional brain connectivity networks using functional magnetic resonance imaging data

Recent studies in neuroimaging show increasing interest in mapping the brain connectivity. It can be potentially useful as biomarkers in identifying neuropsychiatric diseases as well as tool for psychological studies. This study considers the problem of modeling high-dimensional brain connectivity using statistical approach and estimate the connectivity between functional magnetic resonance imaging (fMRI) time series data measured from brain regions. The high-dimension of fMRI data (N) corresponding to the number of brain regions, is typically much larger than sample size or the number of time points taken (T). In this setting, the conventional connectivity estimators such as sample covariance and least-square (LS) estimator are no longer consistent and reliable. In addition, the traditional analysis assumes the brain network to be timeinvariant but recent neuroimaging studies show brain connectivity is changing over the experimental time course. This study developed a novel shrinkage approach to characterize directed brain connectivity in high-dimension. The shrinkage method is involved in incorporating shrinkage-based estimators (Ledoit-Wolf (LW) and Rao- Blackwell LW (RBLW)) in the covariance matrix and LS-based linear regression fitting of vector autoregressive (VAR) model, to reduce the mean squared error of estimates in both high-dimensional functional and effective connectivity. This allows better conditioned and invertible estimated matrix which is important to generate a reliable estimator. Then, the shrinkage-based VAR estimator has been extended to estimate time-evolving effective brain connectivity. The shrinkage-based methods are evaluated via simulations and applied to fMRI resting-state data. Simulation results show reduced mean squared error of estimated connectivity matrix in LW and RBLWbased estimators as compared to conventional sample covariance and LS estimators in both static and dynamic connectivity analysis. These estimators show robustness towards the increasing dimension. Result on real resting-state fMRI data showed that the proposed methods are able to identify functionally-related resting-state brain connectivity networks and evolution of connectivity states across time. It provides additional insights into human whole-brain connectivity during at rest as compared to previous finding particularly in the directionality of connectivity in high-dimensional brain networks

Protective effect of ginkgolide B against isoproterenolinduced chronic heart failure in rats via modulation of Nrf2 and HO-1 signaling pathways

Purpose: To determine the protective effect of ginkgolide B (GB) against isoproterenol (ISO)-induced chronic heart failure in a rat model. Methods: A total of 32 male Wistar rats were randomly divided into 4 groups. Rats in control group received only saline, while rats in GB alone group were injected with GB at a dose of 20 mg/kg body weight (bwt) intraperitoneally (i.p). Another group of rats was injected with ISO  subcutaneously (s.c.) at a dose of 85 mg/kg for 2 days (ISO group). Rats in the GB+ISO group were administered GB at a dose of 20 mg/kg, i.p., for 7 days prior to exposure to ISO s.c. at a dose of 85 mg/kg. Results: Rats pre-treated with GB for 7 days prior to ISO exposure showed a significant decrease in cardiac infarct size, and marked decreases in the levels of cardiac biomarkers, inflammatory and apoptotic biomarkers, and lipid peroxidation (p < 0.05), but significant improvement in the levels ofendogenous antioxidants (p < 0.05). In addition, GB administration resulted in marked increases in the protein expression levels of heme  oxygenase-1 (HO-1) and Nrf2 in cardiac tissue (p < 0.05). Conclusion: These results indicate that pre-treatment of chronic heart failure rats with GB for 7 consecutive days considerably lowered inflammatory and apoptotic markers via upregulation of Nrf2/HO-1 signaling pathway. Thus, GB has cardioprotective potential in humans. Keywords: Ginkgolide B, Nrf2/HO-1, Inflammatory markers, Apoptotic markers, Antioxidant

Active Infrared Sensing of Impact Damage in Carbon Fibre Reinforced Polymer

With the growing demand of carbon fibre reinforced plastic (CFRP) in aerospace, marine and automobile industries, much attention is devoted to characterizing the material strength and characteristics of failure. This paper demonstrated the feasibility to estimate the internal damage non-destructively as a result of a quantified impact applied on 16-ply fabric CFRP. On thermography images at different heating time, differences were observed between intact area and area with internal damage. The estimation of 1D extent of damage using thermographic analysis was compared with images observed with cross sectional microscopic. The results suggest that qualitative analysis using thermography shows potential to be used as a tool for measuring impact damage

Statistical parametric evaluation on new corpus design for Malay speech articulation disorder early diagnosis

Speech-to-Text or always been known as speech recognition plays an important role nowadays especially in medical area specifically in speech impairment. In this study, a Malay language speech-to-Text system was been designed by using Hidden Markov Model (HMM) as a statistical engine with emphasizing the way of Malay speech corpus design specifically for Malay articulation speech disorder. This study also describes and tests the correct number of state to analyze the changes in the performance of current Malay speech recognition in term of recognition accuracy. Statistical parametric representation method was utilized in this study and the Malay corpus database was constructed to be balanced with all the phonetic placed and manner of articulation sample appeared in Malay speech articulation therapy. The results were achieved by conducting few experiments by collecting sample from 80 patient speakers (child and adult) and contain for almost 30,720 sample training data

Enhancement of polar phases in PVDF by forming PVDF/SiC nanowire composite

Different contents of silicon carbide (SiC) nanowires were mixed with Poly(vinylidene fluoride) (PVDF) to facilitate the polar phase crystallization. It was shown that the annealing temperature and SiC content affected on the phase and crystalline structures of PVDF/SiC samples. Furthermore, the addition of SiC nanowire enhanced the transformation of non-polar α phase to polar phases and increased the relative fraction of β phase in PVDF. Due to the nucleating agent mechanism of SiC nanowires, the ion-dipole interaction between the negatively charged surface of SiC nanowires and the positive CH2 groups in PVDF facilitated the formation of polar phases in PVDF

Duration of untreated bipolar disorder: A multicenter study

Little is known about the demographic and clinical differences between short and long duration of untreated bipolar disorder (DUB) in Chinese patients. This study examined the demographic and clinical features of short (≤2 years) and long DUB (\u3e2 years) in China. A consecutively recruited sample of 555 patients with bipolar disorder (BD) was examined in 7 psychiatric hospitals and general hospital psychiatric units across China. Patients’ demographic and clinical characteristics were collected using a standardized protocol and data collection procedure. The mean DUB was 3.2 ± 6.0 years; long DUB accounted for 31.0% of the sample. Multivariate analyses revealed that longer duration of illness, diagnosis of BD type II, and earlier misdiagnosis of BD for major depressive disorder or schizophrenia were independently associated with long DUB. The mean DUB in Chinese BD patients was shorter than the reported figures from Western countries. The long-term impact of DUB on the outcome of BD is warranted

A Literature Review on the Impact in Usurping Sex Appeal Advertising on the Consumers

This article examines the literatures concerning consumer

All-Electrical Skyrmionic Bits in a Chiral Magnetic Tunnel Junction

Topological spin textures such as magnetic skyrmions hold considerable promise as robust, nanometre-scale, mobile bits for sustainable computing. A longstanding roadblock to unleashing their potential is the absence of a device enabling deterministic electrical readout of individual spin textures. Here we present the wafer-scale realization of a nanoscale chiral magnetic tunnel junction (MTJ) hosting a single, ambient skyrmion. Using a suite of electrical and multi-modal imaging techniques, we show that the MTJ nucleates skyrmions of fixed polarity, whose large readout signal - 20-70% relative to uniform states - corresponds directly to skyrmion size. Further, the MTJ exploits complementary mechanisms to stabilize distinctly sized skyrmions at zero field, thereby realizing three nonvolatile electrical states. Crucially, it can write and delete skyrmions using current densities 1,000 times lower than state-of-the-art. These results provide a platform to incorporate readout and manipulation of skyrmionic bits across myriad device architectures, and a springboard to harness chiral spin textures for multi-bit memory and unconventional computing.Comment: 8 pages, 5 figure