Linguistics

Contains research summary and abstracts for nine theses

An optimization-based algorithm for simultaneous shaping of poles and zeros for non-collocated vibration suppression

This article presents a control design method for simultaneous shaping of the poles and zeros of linear time-invariant systems, motivated by the application of non-collocated vibration suppression to flexible multi-body systems. An entire suppression of vibrations at a target mass for a given excitation frequencies can be recast into the problem of assigning zeros of the transfer function from the excitation force to the target mass’ position. The design requirement of achieving sufficient damping in the closed loop system combined with suppressing vibrations at the target, leads to the minimization of the spectral abscissa function of the closed loop system as a function of the controller parameters, subject to zero location constraints. These constraints exhibit polynomial dependence on the controller parameters. We present two approaches to solve the optimization problem which are both based on constraint elimination followed by application of an algorithm for non-smooth unconstrained optimization. The design approach is applicable to delay-free models as well as time-delay models of retarded and neutral type. Simulations results illustrate its applicability to a spring-mass-damper system

Updated clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease

Several molecular subtypes of sporadic Creutzfeldt-Jakob disease have been identified and electroencephalogram and cerebrospinal fluid biomarkers have been reported to support clinical diagnosis but with variable utility according to subtype. In recent years, a series of publications have demonstrated a potentially important role for magnetic resonance imaging in the pre-mortem diagnosis of sporadic Creutzfeldt-Jakob disease. Magnetic resonance imaging signal alterations correlate with distinct sporadic Creutzfeldt-Jakob disease molecular subtypes and thus might contribute to the earlier identification of the whole spectrum of sporadic Creutzfeldt-Jakob disease cases. This multi-centre international study aimed to provide a rationale for the amendment of the clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease. Patients with sporadic Creutzfeldt-Jakob disease and fluid attenuated inversion recovery or diffusion-weight imaging were recruited from 12 countries. Patients referred as ‘suspected sporadic Creutzfeldt-Jakob disease' but with an alternative diagnosis after thorough follow up, were analysed as controls. All magnetic resonance imaging scans were assessed for signal changes according to a standard protocol encompassing seven cortical regions, basal ganglia, thalamus and cerebellum. Magnetic resonance imaging scans were evaluated in 436 sporadic Creutzfeldt-Jakob disease patients and 141 controls. The pattern of high signal intensity with the best sensitivity and specificity in the differential diagnosis of sporadic Creutzfeldt-Jakob disease was identified. The optimum diagnostic accuracy in the differential diagnosis of rapid progressive dementia was obtained when either at least two cortical regions (temporal, parietal or occipital) or both caudate nucleus and putamen displayed a high signal in fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging. Based on our analyses, magnetic resonance imaging was positive in 83% of cases. In all definite cases, the amended criteria would cover the vast majority of suspected cases, being positive in 98%. Cerebral cortical signal increase and high signal in caudate nucleus and putamen on fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging are useful in the diagnosis of sporadic Creutzfeldt-Jakob disease. We propose an amendment to the clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease to include findings from magnetic resonance imaging scan

A Composite Cylinder Model for the Prediction of Residual Stresses in Gamma-Titanium Composites

An experimental study of the residual stress formation and evolution in ␥-titanium-based composite material was completed for some important processing and heat treatment conditions. A concentric cylinder model based on Norton's creep law with the coefficients replaced by new terms related to time and temperature was developed by a combination of viscoplasticity and thermoelastic analysis of concentric cylinder domains representative for the matrix and the fiber. The x-ray diffraction (XRD) technique was used to measure average residual stresses at the neighborhood of Saphikon fibers. The composite was fabricated by hot isostatic pressing. The residual stress at the matrix decreased as the temperature of the heat treatment increased up to an optimum value, after which the residual stress started to build up despite the increase in the annealing temperature. This phenomenon was depicted through the numerical model as well as in the XRD

Factors that hinder and assist learning in virtual environments: a case study

Working, playing and learning in virtual environments will become increasingly important in the future. Such spaces, it is claimed, allow for realistic social interaction and present opportunities for providing motivational learning environments. For example the School of Computer Science at the University of Hertfordshire have recently established an online campus within Second Life. In this paper we present part of a four year research programme into some of the problems and issues inherent in studying and working in non-immersive virtual environments such as Second Life. We found that many learners experience difficulty with navigation in such spaces and that this may significantly affect task performance and attitude. In the first of a series of studies, important variables that affect navigation in such spaces were identified and their effects on task performance, ability to recall information and attitude to the environments were measured and are presented. In the final part of the paper we discuss how our findings are applicable to learning in virtual spaces such as Second Life

Coulomb dissociation of <SUP>20,21</SUP>N

Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N20,21 are reported. Relativistic N20,21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the N19(n,γ)N20 and N20(n,γ)N21 excitation functions and thermonuclear reaction rates have been determined. The N19(n,γ)N20 rate is up to a factor of 5 higher at T<1GK with respect to previous theoretical calculations, leading to a 10% decrease in the predicted fluorine abundance

IMECE2005-81122 ADHESION ENERGY OF SINGLE WALL CARBON NANOTUBE-POLYETHYLENE COMPOSITE: EFFECT OF MAGNETIC FIELD

ABSTRACT In this paper, we investigate the adhesion energy at the interface between single wall carbon nanotubes and polyethylene matrix with and without an external magnetic field. The carbon nanotubes are of two different chiralities --armchair (10,10), and zigzag (10,0), and the external high magnetic field is of 25 Tesla intensity. The study employs molecular dynamics simulations and concludes that the magnetic field decreases the interfacial adhesion energy although it increases the individual potential energies of the nanotubes, the polyethylene, and the composite

Biopsychosocial Aspects in Individuals with Acute and Chronic Rotator Cuff Related Shoulder Pain: Classification Based on a Decision Tree Analysis

Biopsychosocial aspects seem to influence the clinical condition of rotator cuff related shoulder pain (RCRSP). However, traditional bivariate and linear analyses may not be sufficiently robust to capture the complex relationships among these aspects. This study determined which biopsychosocial aspects would better classify individuals with acute and chronic RCRSP and described how these aspects interact to create biopsychosocial phenotypes in individuals with acute and chronic RCRSP. Individuals with acute (<six months of pain, n = 15) and chronic (≥six months of pain, n = 38) RCRSP were included. Sociodemographic data, biological data related to general clinical health status, to shoulder clinical condition and to sensory function, and psychosocial data were collected. Outcomes were compared between groups and a decision tree was used to classify the individuals with acute and chronic RCRSP into different phenotypes hierarchically organized in nodes. Only conditioned pain modulation was different between the groups. However, the tree combined six biopsychosocial aspects to identify seven distinct phenotypes in individuals with RCRSP: three phenotypes of individuals with acute, and four with chronic RCRSP. While the majority of the individuals with chronic RCRSP have no other previous painful complaint besides the shoulder pain and low efficiency of endogenous pain modulation with no signs of biomechanical related pain, individuals with acute RCRSP are more likely to have preserved endogenous pain modulation and unilateral pain with signs of kinesiophobia

Prions in the urine of patients with variant Creutzfeldt-Jakob disease

BACKGROUND: Prions, the infectious agents responsible for transmissible spongiform encephalopathies, consist mainly of the misfolded prion protein (PrPSc). The unique mechanism of transmission and the appearance of a variant form of Creutzfeldt-Jakob disease, which has been linked to consumption of prion-contaminated cattle meat, have raised concerns about public health. Evidence suggests that variant Creutzfeldt-Jakob disease prions circulate in body fluids from people in whom the disease is silently incubating. METHODS: To investigate whether PrPSc can be detected in the urine of patients with variant Creutzfeldt-Jakob disease, we used the protein misfolding cyclic amplification (PMCA) technique to amplify minute quantities of PrPSc, enabling highly sensitive detection of the protein. We analyzed urine samples from several patients with various transmissible spongiform encephalopathies (variant and sporadic Creutzfeldt-Jakob disease and genetic forms of prion disease), patients with other degenerative or nondegenerative neurologic disorders, and healthy persons. RESULTS: PrPSc was detectable only in the urine of patients with variant Creutzfeldt-Jakob disease and had the typical electrophoretic profile associated with this disease. PrPSc was detected in 13 of 14 urine samples obtained from patients with variant Creutzfeldt-Jakob disease and in none of the 224 urine samples obtained from patients with other neurologic diseases and from healthy controls, resulting in an estimated sensitivity of 92.9% (95% confidence interval [CI], 66.1 to 99.8) and a specificity of 100.0% (95% CI, 98.4 to 100.0). The PrPSc concentration in urine calculated by means of quantitative PMCA was estimated at 1×10-16 g per milliliter, or 3×10-21 mol per milliliter, which extrapolates to approximately 40 to 100 oligomeric particles of PrPSc per milliliter of urine. CONCLUSIONS: Urine samples obtained from patients with variant Creutzfeldt-Jakob disease contained minute quantities of PrPSc

IMECE2002-33401 FABRICATION OF NdFeB THIN FILM AND ITS APPLICATION IN MEMS

ABSTRACT The paper measures the magnetic properties of NdFeB thin films developed under the effects of magnetic field. The samples exhibited a larger residual inductance, saturation magnetization and energy product than those treated without field or with weaker field. Magnetic MEMS was introduced with application of the NdFeB film to micro device such as pumps and gear transmission system