11,618 research outputs found

    Anisotropy and nonlinearity in superlattices

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    This paper uses analytical expressions for the nonlinear optical absorption of superlattices by treating them as anisotropic media. The controllable system shows that the nonlinearities increase with anisotropy suggesting that strongly anisotropic materials such as those used for solar cells may also be useful for nonlinear optical applications

    Sample entropy analysis of EEG signals via artificial neural networks to model patients' consciousness level based on anesthesiologists experience.

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    Electroencephalogram (EEG) signals, as it can express the human brain's activities and reflect awareness, have been widely used in many research and medical equipment to build a noninvasive monitoring index to the depth of anesthesia (DOA). Bispectral (BIS) index monitor is one of the famous and important indicators for anesthesiologists primarily using EEG signals when assessing the DOA. In this study, an attempt is made to build a new indicator using EEG signals to provide a more valuable reference to the DOA for clinical researchers. The EEG signals are collected from patients under anesthetic surgery which are filtered using multivariate empirical mode decomposition (MEMD) method and analyzed using sample entropy (SampEn) analysis. The calculated signals from SampEn are utilized to train an artificial neural network (ANN) model through using expert assessment of consciousness level (EACL) which is assessed by experienced anesthesiologists as the target to train, validate, and test the ANN. The results that are achieved using the proposed system are compared to BIS index. The proposed system results show that it is not only having similar characteristic to BIS index but also more close to experienced anesthesiologists which illustrates the consciousness level and reflects the DOA successfully.This research is supported by the Center forDynamical Biomarkers and Translational Medicine, National Central University, Taiwan, which is sponsored by Ministry of Science and Technology (Grant no. MOST103-2911-I-008-001). Also, it is supported by National Chung-Shan Institute of Science & Technology in Taiwan (Grant nos. CSIST-095-V301 and CSIST-095-V302)

    Exploring critical issues faced by Chinese immigrant entrepreneurs in the U.K

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    Despite the significant contributions of Chinese immigrant entrepreneurs in the U.K. (Lin, 2015), their unique challenges and how they manage these challenges have not been well documented. Extant literature notes that facing challenges hinders acculturation, negatively affects an enterprise's growth (Zolin et al., 2016) and causes stress to the migrant. Immigrant entrepreneurs with limited cross-cultural competencies face additional challenges (Mathews et al., 2015). Furthermore, per literature, co-ethnic enclaves can assist new immigrants by offering financial and advisory support and bringing new opportunities (Zhang et al., 2016; Zolin et al., 2016). Extant literature chronicles local language skills (e.g., Azmat & Fujimoto, 2016; Sui et al., 2015) and cross-cultural intelligence (Aslam et al., 2016; Alon et al., 2016) are essential for easing the acculturative journey of immigrant entrepreneurs. An exploratory qualitative enquiry for extracting rich contextual data (Babin et al., 2019) using a mono method, semi-structured interview methodology was applied to capture diverse viewpoints. An exploratory, investigative research strategy is best suited when little prior research is available on this topic (Bougie & Sekaran, 2019). Purposive sampling was used along with the snowball method to get suitable respondents (Saunders et al., 2016) till the point of data saturation was achieved (Saunders et al., 2017). In total, 25 interviews were taken until no further information was gathered. Resultant data were coded to recognise themes (Belotto, 2018). The findings of this research made a significant theoretical contribution to the extant literature on this subject area which has been relatively unstructured so far (Aliaga Isla & Rialp, 2013; Malerba & Ferreira, 2020) . Moreover, current literature does not explicitly address the point of view of Chinese immigrant entrepreneurs in the U.K. and their challenges, which were covered comprehensively in this research. The findings of this study indicated that, despite the documented importance of cross-cultural competencies in literature, Chinese immigrant entrepreneurs in the U.K. displayed low levels of local language skills and cross-cultural awareness, which increased their challenges. Moreover, contrary to extant literature (Sullivan & Ford, 2014), ethnic enclaves did not offer adequate entrepreneurial support, business opportunities or networking prospects for Chinese immigrant entrepreneurs in the U.K. as per the results of this study. It was theorised that ethnic enclaves could potentially be losing their importance as financial and business support structures for newly incoming Chinese immigrant entrepreneurs because of the lack of support being available to them (Kye, 2018). This lack of support could also be because ethnic enclaves are no longer limited to highly concentrated ethnic business centres in the middle of cities. They have begun to spread out to suburbs due to city centre real estate limitations, making them less unified and easy to access. Further research was recommended for assessing the current role of ethnic enclaves due to these research findings that indicated that ethnic enclaves are no longer the support structures for immigrants as they were earlier (Kye, 2018)

    Prolonged membrane potential depolarization in cingulate pyramidal cells after digit amputation in adult rats

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    The anterior cingulate cortex (ACC) plays an important role in higher brain functions including learning, memory, and persistent pain. Long-term potentiation of excitatory synaptic transmission has been observed in the ACC after digit amputation, which might contribute to plastic changes associated with the phantom pain. Here we report a long-lasting membrane potential depolarization in ACC neurons of adult rats after digit amputation in vivo. Shortly after digit amputation of the hind paw, the membrane potential of intracellularly recorded ACC neurons quickly depolarized from ~-70 mV to ~-15 mV and then slowly repolarized. The duration of this amputation-induced depolarization was about 40 min. Intracellular staining revealed that these neurons were pyramidal neurons in the ACC. The depolarization is activity-dependent, since peripheral application of lidocaine significantly reduced it. Furthermore, the depolarization was significantly reduced by a NMDA receptor antagonist MK-801. Our results provide direct in vivo electrophysiological evidence that ACC pyramidal cells undergo rapid and prolonged depolarization after digit amputation, and the amputation-induced depolarization in ACC neurons might be associated with the synaptic mechanisms for phantom pain

    Quantitative brain-derived neurotrophic factor lateral flow assay for point-of-care detection of glaucoma

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    Glaucoma, a ruinous group of eye diseases with progressive degeneration of the optic nerve and vision loss, is the leading cause of irreversible blindness. Accurate and timely diagnosis of glaucoma is critical to promote secondary prevention and early disease-modifying therapies. Reliable, cheap, and rapid tests for measuring disease activities are highly required. Brain-derived neurotrophic factor (BDNF) plays an important role in maintaining the function and survival of the central nervous system. Decreased BDNF levels in tear fluid can be seen in glaucoma patients, which indicates that BDNF can be regarded as a novel biomarker for glaucoma. Conventional ELISA is the standard method to measure the BDNF level, but the multi-step operation and strict storage conditions limit its usage in point-of-care settings. Herein, a one-step and a portable glaucoma detection method was developed based on the lateral flow assay (LFA) to quantify the BDNF concentration in artificial tear fluids. The results of the LFA were analyzed by using a portable and low-cost system consisting of a smartphone camera and a dark readout box fabricated by 3D printing. The concentration of BDNF was quantified by analyzing the colorimetric intensity of the test line and the control line. This assay yields reliable quantitative results from 25 to 300 pg mL-1 with an experimental detection limit of 14.12 pg mL-1. The LFA shows a high selectivity for BDNF and high stability in different pH environments. It can be readily adapted for sensitive and quantitative testing of BDNF in a point-of-care setting. The BDNF LFA strip shows it has great potential to be used in early glaucoma detection

    The spectral variability of FSRQs

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    The optical variability of 29 flat spectrum radio quasars in SDSS Stripe 82 region are investigated by using DR7 released multi-epoch data. All FSRQs show variations with overall amplitude ranging from 0.24 mag to 3.46 mag in different sources. About half of FSRQs show a bluer-when-brighter trend, which is commonly observed for blazars. However, only one source shows a redder-when-brighter trend, which implies it is rare in FSRQs. In this source, the thermal emission may likely be responsible for the spectral behavior.Comment: 4 pages, 1 figure, to be published in Journal of Astrophysics and Astronomy, as a proceeding paper of the conference "Multiwavelength Variability of Blazars", Guangzhou, China, September 22-24, 201

    Measures of disease activity in glaucoma

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    Glaucoma is the leading cause of irreversible blindness globally which significantly affects the quality of life and has a substantial economic impact. Effective detective methods are necessary to identify glaucoma as early as possible. Regular eye examinations are important for detecting the disease early and preventing deterioration of vision and quality of life. Current methods of measuring disease activity are powerful in describing the functional and structural changes in glaucomatous eyes. However, there is still a need for a novel tool to detect glaucoma earlier and more accurately. Tear fluid biomarker analysis and new imaging technology provide novel surrogate endpoints of glaucoma. Artificial intelligence is a post-diagnostic tool that can analyse ophthalmic test results. A detail review of currently used clinical tests in glaucoma include intraocular pressure test, visual field test and optical coherence tomography are presented. The advanced technologies for glaucoma measurement which can identify specific disease characteristics, as well as the mechanism, performance and future perspectives of these devices are highlighted. Applications of AI in diagnosis and prediction in glaucoma are mentioned. With the development in imaging tools, sensor technologies and artificial intelligence, diagnostic evaluation of glaucoma must assess more variables to facilitate earlier diagnosis and management in the future

    One Monopole with k Singularities

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    We present all charge one monopole solutions of the Bogomolny equation with k prescribed Dirac singularities for the gauge groups U(2), SO(3), or SU(2). We analyze these solutions comparing them to the previously known expressions for the cases of one or two singularities.Comment: 12 pages, LaTe
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