Application of the discontinuous Galerkin time domain method in the simulation of the optical properties of dielectric particles

A Discontinuous Galerkin Time Domain method (DGTD), using a fourth order Runge-Kutta time-stepping of Maxwell's equations, was applied to the simulation of the optical properties of dielectric particles in two-dimensional (2-D) geometry. As examples of the numerical implementation of this method, the single-scattering properties of 2D circular and hexagonal particles are presented. In the case of circular particles, the scattering phase matrix was computed using the DGTD method and compared with the exact solution. For hexagonal particles, the DGTD method was used to compute single-scattering properties of randomly oriented 2-D hexagonal ice crystals, and results were compared with those calculated using a geometric optics method. Both shortwave (visible) and longwave (infrared) cases are considered, with particle size parameters 50 and 100. Ice in shortwave and longwave cases is absorptive and non-absorptive, respectively. The comparisons between DG solutions and the exact solutions in computing the optical properties of circular ice crystals reveal the applicability of the DG method to calculations of both absorptive and non-absorptive particles. In the hexagonal case scattering results are also presented as a function of both incident and scattering angles, revealing structure apparently not reported before. Using the geometric optics method we are able to interpret this structure in terms of contributions from varying numbers of internal reflections within the crystal

Decomposing Atmospheric Versus Oceanic Contributions to the High-To-Low Latitude Teleconnection during a Freshwater Triggered Abrupt Climate Change

In this dissertation we study the high-to-low latitude teleconnection during Younger Dryas-like abrupt climate events using models. The teleconnection considered here is between climate change induced by a freshwater input in high-latitude North Atlantic and global response over the Northern Hemisphere and in the tropics. We focus on three primary questions: (1) What is the relative importance of oceanic vs. atmospheric processes in the teleconnection? (2) What are the respective mechanisms of the atmospheric and oceanic controlled teleconnection? (3) How important is sea surface temperature to the teleconnection, particularly in tropical climate responses. To answer these questions we performed a series of model experiments using an Atmospheric General Circulation Model coupled to a thermodynamic slab ocean model. Previous studies identified a teleconnection between the high-latitude fresh-waterforced abrupt climate change and the low-latitude climate response during a Younger Dryas-like abrupt climate change using coupled Atmosphere-Ocean General Circulation Models. In this study we attempt to separate and compare the atmospheric and oceanic contributions to this teleconnection. The results show that these contributions have comparable climate response magnitudes, but different spatial characteristics with the atmospheric contribution being more zonally symmetric than the oceanic counterpart. Physical atmospheric and oceanic processes are also analyzed to address the second question. It is found that the equator ward propagation of the high-latitude surface cooling is induced by increasing surface sensible heat flux in northern mid-latitudes and subtropics and surface latent heat flux in northern equatorial region. The increase in sensible heat flux is due to cooling of near surface air temperatures, whereas latent heat response is caused by strengthening of the surface trade winds linked to an increase in meridional surface temperature gradient. The oceanic contribution in the North Atlantic is through changes in the oceanic circulation caused by freshwater forcing. To address the third question, we performed additional modelling experiments with same high-latitude forcing but different oceanic mixed layer depths. It is found that change in sea surface temperature is necessary for the high-to-low latitude teleconnection and the tropical precipitation response. To determine the importance of sea surface temperature in Intertropical Convergence Zone (ITCZ) response, we further performed an experiment using a simple model developed by Lindzen and Nigam (1987) and found that the change in sea surface temperature, in concert with lower-tropospheric vertical mixing and surface drag, largely contributes to the simulated ITCZ shift

Application of the discontinuous Galerkin time domain method in the simulation of the optical properties of dielectric particles

A Discontinuous Galerkin Time Domain method (DGTD), using a fourth order Runge-Kutta time-stepping of Maxwell's equations, was applied to the simulation of the optical properties of dielectric particles in two-dimensional (2-D) geometry. As examples of the numerical implementation of this method, the single-scattering properties of 2D circular and hexagonal particles are presented. In the case of circular particles, the scattering phase matrix was computed using the DGTD method and compared with the exact solution. For hexagonal particles, the DGTD method was used to compute single-scattering properties of randomly oriented 2-D hexagonal ice crystals, and results were compared with those calculated using a geometric optics method. Both shortwave (visible) and longwave (infrared) cases are considered, with particle size parameters 50 and 100. Ice in shortwave and longwave cases is absorptive and non-absorptive, respectively. The comparisons between DG solutions and the exact solutions in computing the optical properties of circular ice crystals reveal the applicability of the DG method to calculations of both absorptive and non-absorptive particles. In the hexagonal case scattering results are also presented as a function of both incident and scattering angles, revealing structure apparently not reported before. Using the geometric optics method we are able to interpret this structure in terms of contributions from varying numbers of internal reflections within the crystal

Using microneedle array electrodes for non-invasive electrophysiological signal acquisition and sensory feedback evoking

Introduction: Bidirectional transmission of information is needed to realize a closed-loop human-machine interaction (HMI), where electrophysiological signals are recorded for man-machine control and electrical stimulations are used for machine-man feedback. As a neural interface (NI) connecting man and machine, electrodes play an important role in HMI and their characteristics are critical for information transmission.Methods: In this work, we fabricated a kind of microneedle array electrodes (MAEs) by using a magnetization-induced self-assembly method, where microneedles with a length of 500–600 μm and a tip diameter of ∼20 μm were constructed on flexible substrates. Part of the needle length could penetrate through the subjects’ stratum corneum and reach the epidermis, but not touch the dermis, establishing a safe and direct communication pathway between external electrical circuit and internal peripheral nervous system.Results: The MAEs showed significantly lower and more stable electrode-skin interface impedance than the metal-based flat array electrodes (FAEs) in various testing scenarios, demonstrating their promising impedance characteristics. With the stable microneedle structure, MAEs exhibited an average SNR of EMG that is more than 30% higher than FAEs, and a motion-intention classification accuracy that is 10% higher than FAEs. The successful sensation evoking demonstrated the feasibility of the MAE-based electrical stimulation for sensory feedback, where a variety of natural and intuitive feelings were generated in the subjects and thereafter objectively verified through EEG analysis.Discussion: This work confirms the application potential of MAEs working as an effective NI, in both electrophysiological recording and electrical stimulation, which may provide a technique support for the development of HMI

Identification of miRs-143 and -145 that Is Associated with Bone Metastasis of Prostate Cancer and Involved in the Regulation of EMT

The principal problem arising from prostate cancer (PCa) is its propensity to metastasize to bone. MicroRNAs (miRNAs) play a crucial role in many tumor metastases. The importance of miRNAs in bone metastasis of PCa has not been elucidated to date. We investigated whether the expression of certain miRNAs was associated with bone metastasis of PCa. We examined the miRNA expression profiles of 6 primary and 7 bone metastatic PCa samples by miRNA microarray analysis. The expression of 5 miRNAs significantly decreased in bone metastasis compared with primary PCa, including miRs-508-5p, -145, -143, -33a and -100. We further examined other samples of 16 primary PCa and 13 bone metastases using real-time PCR analysis. The expressions of miRs-143 and -145 were verified to down-regulate significantly in metastasis samples. By investigating relationship of the levels of miRs-143 and -145 with clinicopathological features of PCa patients, we found down-regulations of miRs-143 and -145 were negatively correlated to bone metastasis, the Gleason score and level of free PSA in primary PCa. Over-expression miR-143 and -145 by retrovirus transfection reduced the ability of migration and invasion in vitro, and tumor development and bone invasion in vivo of PC-3 cells, a human PCa cell line originated from a bone metastatic PCa specimen. Their upregulation also increased E-cadherin expression and reduced fibronectin expression of PC-3 cells which revealed a less invasive morphologic phenotype. These findings indicate that miRs-143 and -145 are associated with bone metastasis of PCa and suggest that they may play important roles in the bone metastasis and be involved in the regulation of EMT Both of them may also be clinically used as novel biomarkers in discriminating different stages of human PCa and predicting bone metastasis

Heterostructure Manipulation via in Situ Localized Phase Transformation for High-Rate and Highly Durable Lithium Ion Storage

Recently, heterostructures have attracted much attention in widespread research fields. By tailoring the physicochemical properties of the two components, creating heterostructures endows composites with diverse functions due to the synergistic effects and interfacial interaction. Here, a simple in situ localized phase transformation method is proposed to transform the transition-metal oxide electrode materials into heterostructures. Taking molybdenum oxide as an example, quasi-core-shell MoO3@MoO2heterostructures were successfully fabricated, which were uniformly anchored on reduced graphene oxide (rGO) for high-rate and highly durable lithium ion storage. The in situ introduction of the MoO2shell not only effectively enhances the electronic conductivity but also creates MoO3@MoO2heterojunctions with abundant oxygen vacancies, which induces an inbuilt driving force at the interface, enhancing ion/electron transfer. In operando synchrotron X-ray powder diffraction has confirmed the excellent phase reversibility of the MoO2shell during charge/discharge cycling, which contributes to the excellent cycling stability of the MoO3@MoO2/rGO electrode (1208.9 mAh g-1remaining at 5 A g-1after 2000 cycles). This simple in situ heterostructure fabrication method provides a facile way to optimize electrode materials for high-performance lithium ion batteries and possibly other energy storage devices

Grading Distress of Different Animal Models for Gastrointestinal Diseases Based on Plasma Corticosterone Kinetics

Comparative studies for evaluating distress in established animal models are still rare. However, this issue is becoming more important as a consequence of worldwide appreciation of animal welfare. One good parameter for evaluating distress is the quantification of corticosterone. We hypothesized that not just the absolute value but also the duration of increased corticosterone concentration in the blood is an important aspect for evaluating animal distress. Therefore, we analyzed plasma corticosterone concentrations 30, 60, 120, and 240 min after induction of pancreatitis by cerulein, liver damage by carbon tetrachloride, liver damage by bile duct ligation, and after orthotopic injection of pancreatic cancer cells. We also evaluated corticosterone kinetics after injection of distinct carrier substances. Compared to phosphate buffered saline, dimethyl sulfoxide leads to dose-dependent higher and longer-lasting circulating corticosterone concentrations. In all disease models, we observed significantly increased corticosterone concentration 30 min after stress induction. However, the corticosterone kinetics differed among the animal models. Both the absolute value of corticosterone concentration and the duration correlated positively with the quantification of animal distress by a score sheet. This suggests that both variables of corticosterone kinetics might provide a solid basis for comparing and grading distress of different animal models