Improved characterization of silicon-silicon-dioxide interfaces

Silicon is the heart of modern semiconductor devices. The dominance of Si in semiconductor technology depends on the superior quality and properties of thermally grown SiO(,2) compared with the oxide that can be placed on any other semiconductor. For this reason, Si-SiO(,2) interface has been an interesting and important research subject for many years.;The well established quasistatic and conductance methods used in the study of the Si-SiO(,2) interface are improved by using (i) an effectively thin composite insulator, (ii) low carrier concentration substrates, and most importantly (iii) low-level illumination at a wavelength that creates electron-hole pairs. Accurate measurements of both the total density of interface states and its major components as a function of energy in the forbidden gap have been made over four decades (10(\u2710) - 10(\u2714) states/eV-cm(\u272)) due to items (i) and (ii). Item (iii) decreases the response time of the slow states (those in the lower half of the band gap for n-type samples), so the quasistatic condition is well satisfied and the conductance method can be used to study the interface states throughout the band gap on a single sample. Without illumination, the quasistatic condition is not satisfied even for ramp rates on the lower side of those used previously and complementary n- and p-type samples are needed for the conductance method.;The samples investigated have a thermally grown oxide prepared in dry oxygen. They were never exposed to H(,2) or H(,2)O at an elevated temperature. We speculate that this processing provides an abrupt Si-SiO(,2) interface. The composite gate insulator was completed by having an e-gun deposited 250(ANGSTROM) layer on LaF(,3). The resulting interface, subjected to the improved experimental method, yields a wealth of distinctive structure rather than the often-reported featureless U-shaped interface-state density

Mediated voyeurism on social networking sites: The Possible social needs and potential motivations of the voyeurs on Facebook

Previous studies on social networking sites have failed to comprehensively address the mediated voyeurism in the Internet. The features of Facebook enable millions to follow their friends, which can contribute to mediated voyeurism online. The purpose of this study is to explain the voyeuristic tendencies of Facebook users. An online survey was used to obtain self-reported levels of voyeuristic tendencies and both the social needs (social comparison and social identity) and motivations (surveillance, uncertainty reduction, and uses and gratifications) of Facebook users. Findings suggest that the voyeuristic tendencies on Facebook were positively related to the aforementioned social needs and motivations

Urban Farming Design in Los Angeles: An Adaptive Reuse Project in Response to Food Crisis and Housing Crisis

As the world population is constantly growing and will reach 9 billion people by 2050, the current danger to the world\u27s food supply system creates a severe challenge. By 2050, more populations will be living in the cities and creating higher demand on food supply, but the farmable lands on our planet could be much less because of climate change and urbanization. Agricultural leaders have argued that cities will need to produce food internally to respond to demand by increasing population and to avoid harmful pollution and unaffordable food prices. Architecture, as the most influential element affecting our daily life, should react to this food crisis. Today, high-tech indoor farming systems have become more and more common and are easily accessible. It significantly increases the opportunity of growing food internally in the cities. This project will be proposing an architectural response to the food crisis and urban issues occurring now and in the future. The project will select proper indoor farming technology and its applications to implement on an abandoned hotel building. It will merge urban farms with support facilities for the local homeless population. The support will include general assistance, clinical treatment, farming education, and occupational therapy, reducing homelessness in this area. This project will predominantly focus on how farming and occupational therapy combine to improve sustainable urban living for both the general and homeless population in the Los Angeles metropolitan area

Joint Subcarrier Pairing and Power Allocation for OFDM Transmission with Decode-and-Forward Relaying

In this paper, a point-to-point Orthogonal Frequency Division Multiplexing (OFDM) system with a decode-and-forward (DF) relay is considered. The transmission consists of two hops. The source transmits in the first hop, and the relay transmits in the second hop. Each hop occupies one time slot. The relay is half-duplex, and capable of decoding the message on a particular subcarrier in one time slot, and re-encoding and forwarding it on a different subcarrier in the next time slot. Thus each message is transmitted on a pair of subcarriers in two hops. It is assumed that the destination is capable of combining the signals from the source and the relay pertaining to the same message. The goal is to maximize the weighted sum rate of the system by jointly optimizing subcarrier pairing and power allocation on each subcarrier in each hop. The weighting of the rates is to take into account the fact that different subcarriers may carry signals for different services. Both total and individual power constraints for the source and the relay are investigated. For the situations where the relay does not transmit on some subcarriers because doing so does not improve the weighted sum rate, we further allow the source to transmit new messages on these idle subcarriers. To the best of our knowledge, such a joint optimization inclusive of the destination combining has not been discussed in the literature. The problem is first formulated as a mixed integer programming problem. It is then transformed to a convex optimization problem by continuous relaxation, and solved in the dual domain. Based on the optimization results, algorithms to achieve feasible solutions are also proposed. Simulation results show that the proposed algorithms almost achieve the optimal weighted sum rate, and outperform the existing methods in various channel conditions.Comment: 33 pages, 11 figure

Understanding the Structural Basis for Transmembrane Signaling in the CLR-RAMP1 Heterodimer

Membrane proteins comprise of 50% of all pharmaceutical targets in the human genome. These proteins reside in equilibrium between resting and active states that are responsible for various intracellular signaling. We are interested in studying a type of membrane protein belonging to the G-protein coupled receptor (GPCR) family named calcitonin receptor-like receptor (CLR). When associated with a single pass membrane protein called receptor activity modifying protein 1 (RAMP1), the CLR-RAMP1 complex forms a specific receptor for calcitonin gene-related peptide (CGRP). Dysregulation of this receptor complex is linked to various disease states including migraine and acute coronary syndrome (ACS). Small molecule antagonists targeting CLR-RAMP1 complex have been shown to be effective in treating acute migraines, however, they are only limited to intravenous delivery. Therefore, it is very important to obtain a detail understanding on how these receptors interact to form the functional receptor for superior drug design. Membrane proteins are extremely difficult to study due to their water insoluble nature. To overcome this limitation, we developed several tools to assist our research. One important mechanism that regulates membrane protein activation is receptor oligomerization. In order to gain an understanding and identify residues that govern receptor oligomerization in a straightforward and high throughput fashion, we developed E. coli transcription factor AraC-based methods named AraTM and DN-AraTM which look at receptor homo- and heterodimerization respectively. By using AraTM assay, we were able to identify a specific juxtamembrane region within the cytosolic domain (A375-P394) of receptor for advanced glycation endproducts (RAGE) which mediates its homodimerization. Moreover, we also developed a T7-based expression vector (pOmpF) using an engineered fragment of outer membrane protein F (OmpF) as the fusion protein to direct full-length membrane protein overexpression in E. coli for high-resolution structure determination. Utilizing pOmpF vector, we successfully purified thermally stable RAMP1 protein in detergent Fos-choline 15 (FC15). By using circular dichroism, dynamic light scattering, and tryptophan fluorescence spectroscopy, we were able to show that the purified RAMP1 protein has a native tertiary structure consisting of disulfide bonds with 90% helical content. Finally, using sequence-directed searches of transmembrane structural databases, we identified a P-x-x-x-T motif interface that is conserved in RAMP1 among different species as well as between different human RAMPs. By applying cAMP signaling assay, in vivo bioluminescent resonance energy transfer assay, and zebrafish RAMP1 phenotypic knockdown and rescue experiments, we were able to show that this predicted P-x-x-x-T motif plays a critical role in CLR-RAMP1 association and function. Altogether, this work not only provides innovative tools to improve membrane protein research but also sheds light on understanding the structural basis for CLR-RAMP1 receptor signaling

Filter and nested-lattice code design for fading MIMO channels with side-information

Linear-assignment Gel'fand-Pinsker coding (LA-GPC) is a coding technique for channels with interference known only at the transmitter, where the known interference is treated as side-information (SI). As a special case of LA-GPC, dirty paper coding has been shown to be able to achieve the optimal interference-free rate for interference channels with perfect channel state information at the transmitter (CSIT). In the cases where only the channel distribution information at the transmitter (CDIT) is available, LA-GPC also has good (sometimes optimal) performance in a variety of fast and slow fading SI channels. In this paper, we design the filters in nested-lattice based coding to make it achieve the same rate performance as LA-GPC in multiple-input multiple-output (MIMO) channels. Compared with the random Gaussian codebooks used in previous works, our resultant coding schemes have an algebraic structure and can be implemented in practical systems. A simulation in a slow-fading channel is also provided, and near interference-free error performance is obtained. The proposed coding schemes can serve as the fundamental building blocks to achieve the promised rate performance of MIMO Gaussian broadcast channels with CDIT or perfect CSITComment: submitted to IEEE Transactions on Communications, Feb, 200

Clean relaying aided cognitive radio under the coexistence constraint

We consider the interference-mitigation based cognitive radio where the primary and secondary users can coexist at the same time and frequency bands, under the constraint that the rate of the primary user (PU) must remain the same with a single-user decoder. To meet such a coexistence constraint, the relaying from the secondary user (SU) can help the PU's transmission under the interference from the SU. However, the relayed signal in the known dirty paper coding (DPC) based scheme is interfered by the SU's signal, and is not "clean". In this paper, under the half-duplex constraints, we propose two new transmission schemes aided by the clean relaying from the SU's transmitter and receiver without interference from the SU. We name them as the clean transmitter relaying (CT) and clean transmitter-receiver relaying (CTR) aided cognitive radio, respectively. The rate and multiplexing gain performances of CT and CTR in fading channels with various availabilities of the channel state information at the transmitters (CSIT) are studied. Our CT generalizes the celebrated DPC based scheme proposed previously. With full CSIT, the multiplexing gain of the CTR is proved to be better (or no less) than that of the previous DPC based schemes. This is because the silent period for decoding the PU's messages for the DPC may not be necessary in the CTR. With only the statistics of CSIT, we further prove that the CTR outperforms the rate performance of the previous scheme in fast Rayleigh fading channels. The numerical examples also show that in a large class of channels, the proposed CT and CTR provide significant rate gains over the previous scheme with small complexity penalties.Comment: 30 page

Is Robustness the Cost of Accuracy? -- A Comprehensive Study on the Robustness of 18 Deep Image Classification Models

The prediction accuracy has been the long-lasting and sole standard for comparing the performance of different image classification models, including the ImageNet competition. However, recent studies have highlighted the lack of robustness in well-trained deep neural networks to adversarial examples. Visually imperceptible perturbations to natural images can easily be crafted and mislead the image classifiers towards misclassification. To demystify the trade-offs between robustness and accuracy, in this paper we thoroughly benchmark 18 ImageNet models using multiple robustness metrics, including the distortion, success rate and transferability of adversarial examples between 306 pairs of models. Our extensive experimental results reveal several new insights: (1) linear scaling law - the empirical $\ell_2$ and $\ell_\infty$ distortion metrics scale linearly with the logarithm of classification error; (2) model architecture is a more critical factor to robustness than model size, and the disclosed accuracy-robustness Pareto frontier can be used as an evaluation criterion for ImageNet model designers; (3) for a similar network architecture, increasing network depth slightly improves robustness in $\ell_\infty$ distortion; (4) there exist models (in VGG family) that exhibit high adversarial transferability, while most adversarial examples crafted from one model can only be transferred within the same family. Experiment code is publicly available at \url{https://github.com/huanzhang12/Adversarial_Survey}.Comment: Accepted by the European Conference on Computer Vision (ECCV) 201