Sea level change in the Malaysian seas from multi-satellite altimeter data

Seas from satellite altimetry data of the Topex, Jason-1, ERS-1, ERS-2 and Envisat missions. During the past two decades, satellite altimeter has provided its capability in measuring the global mean of sea level with precision better than 1 mm/year. Sea level data retrieval and reduction were carried out using Radar Altimeter Database System (RADS). In RADS data processing, the recently updated environmental and geophysical corrections were applied. Sixth 1° × 1° areas were chosen for the altimeter data comparison and to find the best ocean tide model for Malaysian Seas, where the altimeter tracks are nearby to tide gauge locations. Similarity in the pattern of sea level variations indicated good agreements between tide gauge data and altimeter data using FES2004 ocean tide model. It also showed that the altimeter data can be used to investigate sea level rise for Malaysian Seas. Here, sea level variations for four areas in the Malaysian Seas have been investigated using 15 years of altimeter data. The altimeter sea level time series revealed that since 1993, the mean sea level in Malaysian Seas has been rising at a rate of between 1.42 – 4.08 mm/year. This information is important to study alternative energy extraction and environmental issues related to flood investigations and global warming

User-Defined Key Pair Protocol

E-commerce applications have flourished on the Internet because of their ability to perform secure transactions in which the identities of the two parties could be verified and the communications between them encrypted. The Transport Layer Security (TLS) protocol is implemented to make secure transactions possible by creating a secure tunnel between the user\u27s browser and the server with the help of Certificate Authorities (CAs). CAs are a third party that can be trusted by both the user\u27s browser and the server and are responsible for establishing secured communication between them. The major limitation of this model is the use of CAs as single points of trust that can introduce severe security breaches globally. In my thesis, I provide a high-level design for a new protocol in the application layer of the TCP/IP suite that will build a secure tunnel between the user\u27s browser and the server without the involvement of any third party. My proposed protocol is called User-Defined Key Pair (UDKP), and its objective is to build a secure tunnel between the user\u27s browser and the server using a public/private key pair generated for the user on the fly inside the user\u27s browser based on the user credential information. This key pair will be used by the protocol instead of the server certificate as the starting point for creating the secure tunnel

Paroxetine is Pro-inflammatory in Human Brain Microvascular Endothelial Cells

BACKGROUND: Paroxetine is an antidepressant that is widely used. However, Paroxetine possesses anticholinergic properties which may contribute to cognitive decline in older adults. Surprisingly, the mechanisms of the cognitive decline of anticholinergic drugs in older adults remains elusive. A hypothesis is that a loss of cholinergic signaling is pro-inflammatory in the brain. We designed experiments to determine if Paroxetine is pro-inflammatory in Normal Human Brain Microvascular Endothelial Cells (NHBMECs). METHOD: NHBMECs were grown at 5% CO2, 37C and 95% relative humidity until 90% confluent. NHBMECs were treated with the RNA free water as control, Paroxetine as 1.67x 10 4 mM/mol, IL1B 2ng/ml for 24 hours. RNA was isolated, converted into CDNA, and gene expression determined via RT-PCR. Statistical analysis was performed via ANOVA and post-hoc Tukey’s with a significant p-value \u3c 0.05. Experiments were completed on 10-04-19. The mRNA expression studies were performed on 11-01-19. RESULTS: NHBMECs exposed to Paroxetine for 24 hours demonstrated elevated expression of CCL2 and CXCL5. NHBMECs exposed to Paroxetine + IL1B demonstrated synergistic elevations in CCL2 and CXCL5. CONCLUSION: Our result suggests that Paroxetine may have pro-inflammatory properties within this subset of human brain cells. Therefore, our preliminary data suggests the possibility of pathological pro- inflammatory mechanisms associated with Paroxetine. Further evaluation of different populations of normal human brain cells are warranted.https://scholarscompass.vcu.edu/gradposters/1096/thumbnail.jp

Ecological risk assessment based on land cover change: A case of Zanzibar-Tanzania, 2003-2027

Dissertation submitted in partial fulfilment of the requirements for the degree of Master of Science in Geospatial TechnologiesLand use under improper land management is a major challenge in sub-Saharan Africa, and this has drastically affected ecological security. Addressing environmental impacts related to this major challenge requires faster and more efficient planning strategies that are based on measured information on land-use patterns. This study was employed to access the ecological risk index of Zanzibar using land cover change. We first employed Random Forest classifier to classify three Landsat images of Zanzibar for the year 2003, 2009 and 2018. And then the land change modeler was employed to simulate the land cover for Zanzibar City up to 2027 from land-use maps of 2009 and 2018 under business-as-usual and other two alternative scenarios (conservation and extreme scenario). Next, the ecological risk index of Zanzibar for each land cover was assessed based on the theories of landscape ecology and ecological risk model. The results show that the built-up areas and farmland of Zanzibar island have been increased constantly, while the natural grassland and forest cover were shrinking. The forest, agricultural and grassland have been highly fragmented into several small patches relative to the decrease in their patch areas. On the other hand, the ecological risk index of Zanzibar island has appeared to increase at a constant rate and if the current trend continues this index will increase by up to 8.9% in 2027. In comparing the three future scenarios the results show that the ERI for the conservation scenario will increase by only 4.6% which is at least 1.6% less compared to 6.2% of the business as usual, while the extreme scenario will provide a high increase of ERI of up to 8.9%. This study will help authorities to understand ecological processes and land use dynamics of various land cover classes, along with preventing unmanaged growth and haphazard development of informal housing and infrastructure

Perceptual biases are inconsistent with Bayesian encoding of speed in the human visual system

The notion that Bayesian processes are fundamental to brain function and sensory processing has recently received much support, and a number of Bayesian accounts of how the brain encodes the speed of moving objects have been proposed that challenge earlier mechanistic models. We measured the perceived speed of low contrast patterns at both low (2.5 cd m2) and high (25 cd m2) luminance in order to assess these competing models of how the human visual system encodes speed. At both luminance levels low contrast stimuli are perceptually biased such that they appear slower at slow (, 8 Hz) speeds but faster at higher (16 Hz) speeds. However, we find that the reversal of the perceptual bias from under- to overestimation occurred at slower speeds at low luminance. We also found that the bias was greater at slow speeds at high luminance but greater at fast speeds at low luminance. Moreover, discrimination thresholds were found to be similar at high and low luminance. These findings can be predicted by models in which speed is encoded by the relative activity within two broadly tuned temporal channels but are inconsistent with Bayesian models of speed encoding. We conclude that Bayesian processes cannot adequately account for speed encoding in the human visual system

A case of Zanzibar (Tanzania)

Omar, H., & Cabral, P. (2020). Ecological risk assessment based on land cover changes: A case of Zanzibar (Tanzania). Remote Sensing, 12(19), 1-24. [3114]. https://doi.org/10.3390/RS12193114Land use and land cover (LULC) under improper land management is a major challenge in sub-Saharan Africa and has drastically affected ecological security. Addressing environmental impacts related to this challenge requires efficient planning strategies based on the measured information of land use patterns. This study assessed the ecological risk index (ERI) of Zanzibar based on LULC. A random forest classifier was used to classify three Landsat images of Zanzibar for the years 2003, 2009, and 2018. Then, a land change model was employed to simulate the LULC changes for 2027 under a business-as-usual (BAU), conservation, and extreme scenarios. Results showed that the built-up areas and farmland of Zanzibar Island have increased constantly, while the natural grassland and forest cover have decreased. The forest, agricultural, and grassland were highly fragmented into several small patches. The ERI of Zanzibar Island increased at a constant rate and, if the current trend continues, this index will increase by up to 8.9% in 2027 under an extreme scenario. If a conservation scenario is adopted, the ERI will increase by 4.6% whereas if a BAU policy is followed, this value will increase by 6.2%. This study provides authorities with useful information to understand better the ecological processes and LULC dynamics and prevent unmanaged growth and haphazard development of informal housing and infrastructure.publishersversionpublishe

Broadband High Efficiency Fractal-Like and Diverse Geometry Silicon Nanowire Arrays for Photovoltaic Applications

Solar energy has many advantages over conventional sources of energy. It is abundant, clean and sustainable. One way to convert solar energy directly into electrical energy is by using the photovoltaic solar cells (PVSC). Despite PVSC are becoming economically competitive, they still have high cost and low light to electricity conversion efficiency. Therefore, increasing the efficiency and reducing the cost are key elements for producing economically more competitive PVSC that would have significant impact on energy market and saving environment. A significant percentage of the PVSC cost is due to the materials cost. For that, thin films PVSC have been proposed which offer the benefits of the low amount of material and fabrication costs. Regrettably, thin film PVSC show poor light to electricity conversion efficiency because of many factors especially the high optical losses. To enhance conversion efficiency, numerous techniques have been proposed to reduce the optical losses and to enhance the absorption of light in thin film PVSC. One promising technique is the nanowire (NW) arrays in general and the silicon nanowire (SiNW) arrays in particular. The purpose of this research is to introduce vertically aligned SiNW arrays with enhanced and broadband absorption covering the entire solar spectrum while simultaneously reducing the amount of material used. To this end, we apply new concept for designing SiNW arrays based on employing diversity of physical dimensions, especially radial diversity within certain lattice configurations. In order to study the interaction of light with SiNW arrays and compute their optical properties, electromagnetic numerical modeling is used. A commercial numerical electromagnetic solver software package, high frequency structure simulation (HFSS), is utilized to model the SiNW arrays and to study their optical properties. We studied different geometries factors that affect the optical properties of SiNW arrays. Based on this study, we found that the optical properties of SiNW arrays are strongly affected by the radial diversity, the arrangement of SiNW in a lattice, and the configuration of such lattice. The proper selection of these parameters leads to broaden and enhance the light absorption of the SiNW arrays. Inspired by natural configurations, fractal geometry and diamond lattice structures, we introduced two lattice configurations: fractal-like array (FLA) that is inspired by fractal geometry, and diamond-like array (DLA) that is inspired by diamond crystal lattice structure. Optimization, using parametric analysis, of the introduced arrays parameters for the light absorption level and the amount of used material has been performed. Both of the introduced SiNW arrays show broadband, strong light absorption coupled with reduction of the amount of the used material. DLA in specific showed significantly enhanced absorption covering the entire solar spectrum of interest, where near-unity absorption spectrum could be achieved. We studied the optical properties of complete PVSC devices that are based on SiNW array. Moreover, the performance of PVSC device that is based on SiNW has been investigated by using numerical modeling. SILVACO software package is used for performing the numerical simulation of the PVSC device performance, which can simultaneously handle the different coupled physical mechanisms contributing to the photovoltaic effect. The effect of the geometry of PVSC device that is based on SiNW is investigated, which shows that the geometry of such PVSC has a role in enhancing its electrical properties. The outcome of this study introduces new SiNW array configurations that have enhanced optical properties using a low amount of material that can be utilized for producing higher efficiency thin film PVCS. The overall conclusion of this work is that a weak absorption indirect band gap material, silicon, in the form of properly designed SiNW and SiNC arrays has the potentials to achieve near-unity ideal absorption spectrum using reduced amount of material, which can lead to produce new generation of lower cost and enhanced efficiency thin film PVSC

Design zero-voltage switching DC-DC buck converter

This report proposes an integrated, high switching frequency, zero-voltage-switching dc-dc buck converter for battery charger application. The design and analysis of dc�dc buck converter with integrated inductor is presented. The converter has been optimized to convert 12V input voltage to 5V at 1.5A maximum load current at 50MHz switching frequency. The converter has been simulated using an ORCAD 16.5 based simulation tool and result show that the switching losses using zero�voltage-switching technique is less compared to conventional buck converter