A simple one-dimensional model for the explanation and analysis of GaAs MESFET behavior

The explanation of GaAs metal-semiconductor field effect transistor (MESFET) operation often involves the use of simplistic analytical formulae, which serve to obscure the more subtle physics of device action. The authors consider here a simple one-dimensional (1-D) model for GaAs MESFETs, which avoids more confusing numerical modeling schemes, yet still facilitates an analysis of the physical functionality of the device. The model takes into account current saturation due to either velocity saturation or channel pinch-off, the modulation of effective gate length and the series resistance of the regions beyond the gate. The results of the model have been compared to experimental data readily obtained from the literature, and the agreement has been shown to be goo

Genetic Diversity in the Bo\u27an, Salar, and Dongxiang : Co-Resident Muslim Populations in Gansu Province, P.R. China

Patterns s of genetic diversity within and between three co-resident Muslim populations from Gansu Provence in the Peoples Republic of China were examined and the results contrasted with historical information. This study of members of the Bo\u27an, Salar and Dongxiang communities will contribute to a clearer understanding of the origins and migratory patterns of Muslims in PR China, and more generally the effect of population subdivision on gene pool structure and composition. Ten autosomal and live Y-chromosome microsatellite loci were genotyped to determine allele distribution patterns. Subsequently, the D-loop region of mitochondrial DNA was sequenced to complement the autosomal and Y-chromosome data. To infer between- and within- population relationships, data were analysed by several alternative statistical techniques based on either the Infinite Allele Mutation model or the Stepwise Mutation model. Due to the endogamous nature of the three populations, increased levels of homozygosity at autosomal loci were observed. Y-chromosome data exhibited major differences between the study populations, whilst mitochondrial DNA suggested more consistent inter-community relationships. Demographic information was also assessed to provide a more detailed account of population structure and phylogeny

Simulation of the impact of stress induced piezoelectric charge in GaAs MESFETs

This work presents the methodology involved in applying numerical electronic device simulation, and specifically, the application of this methodology to the study of piezoelectric effects in GaAs MESFETs. Firstly, a three-dimensional (3D) numerical simulation package EVEREST, developed for the simulation of silicon electronic devices, has been enhanced by the introduction and verification of models for GaAs device physics. Then a 2D finite element program for the simulation of mechanical stresses in the MESFET structure and a program for the extraction of piezoelectric charge from the numerically calculated stresses have been produced. The force load model applied to the metal/dielectric/GaAs structure is suggested as a good mathematical representation of the physical processes involved. The impact of stress induced piezoelectric charge, substrate doping and varying gate length on the electrical characteristics of epitaxial and ion-implanted MESFETs have been determined by numerical simulation using the EVEREST device simulator. Comparison between experimental data and simulation results has been presented. Finally, conclusions and suggestions for further study have been given

Optimal Correction of The Slice Timing Problem and Subject Motion Artifacts in fMRI

Functional magnetic resonance imaging (fMRI) is an extremely popular investigative and clinical imaging tool that allows safe and noninvasive study of the functional living brain. Fundamentally, fMRI measures a physiological signal as it changes over time. The manner in which this spatio-temporal signal is acquired can create technical challenges during image reconstruction that must be corrected for if any meaningful information is to be extracted from the data. Two particular challenges that are fundamentally intertwined with each other are temporal misalignment and spatial misalignment. Temporal misalignment is due to the nature of fMRI acquisition protocols themselves: a 3D volume is created by sampling and stacking multiple 2D slices. However, these slices are not acquired simultaneously or sequentially, and therefore will always be temporally misaligned with each other. Spatial misalignment arises when subject motion is present during the scan, resulting in individual volumes being spatially misaligned with each other. Spatial and temporal misalignment are not independent from each other, and their interaction can cause additional artifacts and reconstruction challenges if not addressed properly. The purpose of this thesis is to critically examine the problem of both spatial and temporal misalignment from a signal processing perspective, while considering the physical nature and origin of the signal itself, and develop optimal correction routines for spatial and temporal misalignment and their associated artifacts. One of the most immediate problems associated with temporal misalignment is that the order in which the slices are acquired must be known in order for correction to be possible. Surprisingly, this information is rarely provided with old or shared data, meaning that this critical preprocessing step must be skipped, significantly lowering the value of the data. We use the spatio-temporal properties of the fMRI signal to develop a robust and accurate algorithm to infer the slice acquisition order retrospectively from any fMRI scan. The ability to extract the interleave parameter from any data set allows us to perform slice timing correction even if this information had been lost, or was not provided with the scan. In the next section of this work, we develop a new optimal method of slice timing correction (Filter-Shift) based on the fundamental properties of sampling theory in digital signal processing. By examining the properties of the signal of interest (The blood oxygen level depended signal: BOLD signal), we are able to design and implement an effective FIR filter to simultaneously remove noise and reconstruct the signal of interest at any shifted offset, without the need for sub-optimal interpolation. In the final section, we investigate the effects of different motion types on the MR signal based on the Bloch equation, in order to develop a theoretical foundation from which we can create an optimal correction method. We devise a novel method to remove these artifacts: Discrete reconstruction of irregular fMRI trajectory (DRIFT). Our method calculates the exact displacement of the k-space samples due to motion at each dwell time and retrospectively corrects each slice of the fMRI volume using an inverse nonuniform Fourier transform. We conclude that a hybrid approach with both prospective and retrospective components are essentially required for optimal removal of motion artifacts from the fMRI data. The combined work of this thesis provides two theoretically sound and extremely effective correction routines, that both remove artifacts and restore the underlying sampled signal. Motion correction and slice timing correction are typically the first two preprocessing steps to be applied to any fMRI data, and thus provide the foundation for any further analysis. While many other preprocessing steps can be omitted or included depending on the analysis, motion correction and slice timing correction are unequivocally beneficial and necessary for accurate and reliable results. This work provides a theoretical and quantitative framework that describes the optimal removal of artifacts associated with motion and slice timing

A modular and interactive OLED-based lighting system

The concept of a flexible, large-area, organic light emitting diode (OLED)-based lighting system with a modular structure and built-in intelligent light management is introduced. Such a flexible, thin, portable lighting system with discreetly integrated electronics is important in order to allow the implementation of the lighting system into a variety of places, such as cars and temporary expedition areas. A modular construction of an OLED lighting panel makes it possible to control each OLED cell individually. This not only enables us to counteract aging or degradation effects in the OLED cells but it also allows individual OLED module brightness control to support human or ambient interaction based on integrated or centralized sensors. Moreover, integrating the driving electronics in the backplane of an OLED module improves the energy efficiency of operating large OLED panels. The thin, modular construction and individual, dynamic control are successfully demonstrated

Tackling the undeclared economy in Croatia

To evaluate how undeclared work is being tackled in Croatia this paper reports an e-survey and in-depth interviews with key stakeholders in Croatia. It is revealed that, compared with the European Economic Area countries, Croatia has a weak institutional infrastructure for tackling undeclared work and pursues a narrower range of policy measures. The outcome is a call to develop a single body to better coordinate actions to tackle the undeclared economy in Croatia and for a shift towards an approach that seeks to provide gateways to formalisation. Furthermore, Croatia needs to modernise its work and welfare regime through higher levels of state expenditure in the labour market and social protection, coupled with redistribution via social transfers so as to construct a more equal society

An introduction to two norm spaces

In this paper I present some of the concepts that result when one considers a linear space with two norms on it

Political implications of economic inequality : a literature survey

This survey documents the different arguments discussed in the academic literature on whether and how economic inequality and the emergence and stability of democratic political systems are connected. While early research in this domain has often focused on new and emerging democracies, this paper also provides an overview of the more recent literature in economics and neighboring fields that discusses democratization as well as established democracies stability and other institutional traits. In doing so, the survey contains a critical review of both theoretical and empirical contributions on the topic. The different arguments are systematically evaluated and their core hypotheses are distilled in order to document the main lines of argumentation prevalent in the literature. Together with a summary of the theoretical arguments, the main findings of related empirical research are also documented and shortly discussed. Whereas taken together, research so far generally does not suggest any conclusive results concerning economic inequality and the emergence of democracies, the survey indicates that the stability and institutional quality of established democracies can be negatively affected by economic inequality, and it outlines the conditions for this to occur. However, additional research especially on some of the more tentative hypotheses is required to allow for a more profound understanding of the different channels and relationships. Therefore, points of departure for further research, e. g. on how to operationalize specific theoretical constructs of interest and thereby on how to get a better understanding of the relations, are also suggested

Temporal shifts of Bois Noir phytoplasma types infecting grapevine in South Tyrol (Northern Italy)

Research Not

Recombination, Reservoirs, and the Modular Spike: Mechanisms of Coronavirus Cross-Species Transmission

Over the past 30 years, several cross-species transmission events, as well as changes in virus tropism, have mediated significant animal and human diseases. Most notable is severe acute respiratory syndrome (SARS), a lower respiratory tract disease of humans that was first reported in late 2002 in Guangdong Province, China. The disease, which quickly spread worldwide over a period of 4 months spanning late 2002 and early 2003, infected over 8,000 individuals and killed nearly 800 before it was successfully contained by aggressive public health intervention strategies. A coronavirus (SARS-CoV) was identified as the etiological agent of SARS, and initial assessments determined that the virus crossed to human hosts from zoonotic reservoirs, including bats, Himalayan palm civets (Paguma larvata), and raccoon dogs (Nyctereutes procyonoides), sold in exotic animal markets in Guangdong Province. In this review, we discuss the molecular mechanisms that govern coronavirus cross-species transmission both in vitro and in vivo, using the emergence of SARS-CoV as a model. We pay particular attention to how changes in the Spike attachment protein, both within and outside of the receptor binding domain, mediate the emergence of coronaviruses in new host populations