Development and evaluation of automatic landing control laws for light wing loading STOL aircraft

Automatic flare and decrab control laws were developed for NASA's experimental Twin Otter. This light wing loading STOL aircraft was equipped with direct lift control (DLC) wing spoilers to enhance flight path control. Automatic landing control laws that made use of the spoilers were developed, evaluated in a simulation and the results compared with these obtained for configurations that did not use DLC. The spoilers produced a significant improvement in performance. A simulation that could be operated faster than real time in order to provide statistical landing data for a large number of landings over a wide spectrum of disturbances in a short time was constructed and used in the evaluation and refinement of control law configurations. A longitudinal control law that had been previously developed and evaluated in flight was also simulated and its performance compared with that of the control laws developed. Runway alignment control laws were also defined, evaluated, and refined to result in a final recommended configuration. Good landing performance, compatible with Category 3 operation into STOL runways, was obtained

Analytical study of the origin and behavior of asymmetric vortices

An hypothesis advanced originally to explain computational observations is supported by theoretical considerations: The asymmetric mean flow observed on bodies of revolution at moderate to high angles of attack is the result of a convective instability of an originally symmetric flow to a time-invariant space-fixed disturbance. Additionally, the time-dependent fluctuations characteristic of the flow at higher angles of attack (up to 90 deg) are the result of an absolute instability of an originally steady flow to a small temporal disturbance of finite duration. Within a common domain, the instability mechanisms may coexist. The experimentally confirmed existence of bistable states, wherein the side-force variation with nose roll angle approaches a square-wave distribution, is attributed to the dominant influence of a pair of trailing vortices from the ogival forebody. Their existence is made possible by the appearance of foci of separation in the skin-friction line pattern beyond a critical angle of attack. The extreme sensitivity of the asymmetric flow orientation to nose geometry, demonstrated experimentally, is attributed to the presence of an indeterminate phase in the family of possible solutions for the three-dimensional wave system

Dielectric mismatch and shallow donor impurities in GaN/HfO2 quantum wells

In this work we investigate electron-impurity binding energy in GaN/HfO$_2$ quantum wells. The calculation considers simultaneously all energy contributions caused by the dielectric mismatch: (i) image self-energy (i.e., interaction between electron and its image charge), (ii) the direct Coulomb interaction between the electron-impurity and (iii) the interactions among electron and impurity image charges. The theoretical model account for the solution of the time-dependent Schr\"odinger equation and the results shows how the magnitude of the electron-impurity binding energy depends on the position of impurity in the well-barrier system. The role of the large dielectric constant in the barrier region is exposed with the comparison of the results for GaN/HfO$_2$ with those of a more typical GaN/AlN system, for two different confinement regimes: narrow and wide quantum wells.Comment: 6 Pages, 7 figure

MOLECULAR CHARACTERIZATION OF MEMBRANE-BOUND GLYCOPROTEINS INVOLVED IN HUMAN DISEASES AND POTENTIAL TARGETS FOR NEW THERAPIES

The present thesis is focused on the molecular characterization of two eukaryotic membrane glycoproteins that are promising candidates for new therapeutic approaches to human diseases. The first glycoprotein is the human Receptor for the Advanced Glycation End products (hRAGE), a member of the immunoglobulin superfamily. RAGE is a type I transmembrane glycoprotein that is beneficial in normal physiological conditions but it is also a key player in the etiology and progression of several chronic pathologies such as neurodegenerative disorders (Alzheimer), atherosclerosis, cancer and complications of metabolic diseases such as diabetes, by exacerbating the inflammatory response. A variety of ligands sharing an acidic charge, as the advanced glycation End products (AGEs), S100 proteins, HMGB1, A\u3b2-amyloids, bind to the extracellular V or VC1 domains of RAGE. These domains are N-glycosylated and stabilized by disulphide bonds. To overcome the tendency to aggregate of the V and VC1 domains expressed in bacteria, in this work V and VC1 domains were expressed as secreted proteins in the methylotrophic yeast Pichia pastoris. While VC1 was secreted into the culture medium and was functional, the V domain was retained intracellularly, providing the first in vivo indication that V requires C1 to fold into a structurally stable domain. The glycosylation pattern of VC1 reflects the glycosylation of RAGE isolated from mammalian sources. A simple procedure for the purification to homogeneity of VC1 from the medium was generated and the folded state of the purified protein was assessed by thermal shift assays. The protein showed a remarkable improved thermal stability compared to VC1 expressed in bacteria. The stability and full solubility of glycosylated VC1 may be beneficial for in vitro studies aimed at the identification of new ligands or inhibitors of RAGE. The second object of this thesis was the Phr family of Candida albicans, a dimorphic fungal pathogen responsible of life-threatening invasive infections. These glycoproteins are anchored to the plasma membrane through a GPI. Phr proteins belong to family GH72 of cell wall glucan remodelling enzymes that are unique to fungi and essential for morphogenesis, cell wall integrity and virulence. For these reasons, these enzymes are targets for inhibitors of the cell wall formation to be used in therapy, similarly to what penicillins have been for bacteria. The catalytic properties of Phr proteins were studied using a new fluorescent assay. Phr1p and Phr2p are specific for \u3b2-1,3-glucan, the pH optimum was 5.8 for Phr1p and 3 for Phr2p and the temperature optimum was 30\ub0C. Pga4p was inactive suggesting that it turned out into a structural cell wall protein. Finally, we studied the transcriptome of cells lacking \u3b2-1,3-glucan remodelling (phr1\u394 cells) after induction of growth as hypha, the invasive form of this pathogen. About 310 genes were modulated and genetic analysis showed that chitin synthesis by the Chs3p isoform is essential for viability of phr1\u394 cells

A Pitch Salience Function Derived from Harmonic Frequency Deviations for Polyphonic Music Analysis

In this paper, a novel approach for the computation of a pitch salience function is presented. The aim of a pitch (considered here as synonym for fundamental frequency) salience function is to es- timate the relevance of the most salient musical pitches that are present in a certain audio excerpt. Such a function is used in nu- merous Music Information Retrieval (MIR) tasks such as pitch, multiple-pitch estimation, melody extraction and audio features computation (such as chroma or Pitch Class Profiles). In order to compute the salience of a pitch candidate f , the classical approach uses the weighted sum of the energy of the short time spectrum at its integer multiples frequencies hf. In the present work, we pro- pose a different approach which does not rely on energy but only on frequency location. For this, we first estimate the peaks of the short time spectrum. From the frequency location of these peaks, we evaluate the likelihood that each peak is an harmonic of a given fundamental frequency. The specificity of our method is to use as likelihood the deviation of the harmonic frequency locations from the pitch locations of the equal tempered scale. This is used to cre- ate a theoretical sequence of deviations which is then compared to an observed one. The proposed method is then evaluated for a task of multiple-pitch estimation using the MAPS test-set

Perturbation theory for the one-dimensional optical polaron

The one-dimensional optical polaron is treated on the basis of the perturbation theory in the weak coupling limit. A special matrix diagrammatic technique is developed. It is shown how to evaluate all terms of the perturbation theory for the ground-state energy of a polaron to any order by means of this technique. The ground-state energy is calculated up to the eighth order of the perturbation theory. The effective mass of an electron is obtained up to the sixth order of the perturbation theory. The radius of convergence of the obtained series is estimated. The obtained results are compared with the results from the Feynman polaron theory.Comment: 9 pages, 2 figures, RevTeX, to be published in Phys. Rev. B (2001) Ap

Data from docking simulations to develop an efficient strategy able to evaluate the interactions between RAGE and MDA-induced albumin adducts

This data article contains the results of docking simulations performed in order to develop a suitable in silico strategy able to assess the stability of the putative complexes between RAGE and MDA induced adducts on human albumin as experimentally determined doi: 10.1016/j.redox.2016.12.017, (Degani et al., 2017) [1]. The docking simulations involved different approaches to give a simplified yet realistic representation of the protein adducts and their environment. With increasing complexity, simulations involved the corresponding albumin tripeptides and pentapeptides with the modified residue in the central position as well as pseudo-structures which were generated by collecting the albumin residues around the adducted residue within a sphere of 7.5 \uc5 and 5 \uc5 radius. The reliability of the tested approaches was assessed by monitoring the score differences between adducted and unmodified residues. The obtained results revealed the greater predictive power of the spherical pseudo-structures compared to the simple tri- or pentapeptidic sequences thus suggesting that RAGE recognition involves residues which are spatially close to the modified residue even though not necessarily adjacent in the primary sequence

Quantum control theory for coupled 2-electron dynamics in quantum dots

We investigate optimal control strategies for state to state transitions in a model of a quantum dot molecule containing two active strongly interacting electrons. The Schrodinger equation is solved nonperturbatively in conjunction with several quantum control strategies. This results in optimized electric pulses in the THz regime which can populate combinations of states with very short transition times. The speedup compared to intuitively constructed pulses is an order of magnitude. We furthermore make use of optimized pulse control in the simulation of an experimental preparation of the molecular quantum dot system. It is shown that exclusive population of certain excited states leads to a complete suppression of spin dephasing, as was indicated in Nepstad et al. [Phys. Rev. B 77, 125315 (2008)].Comment: 24 pages, 9 figure

Insights into the effects of N-glycosylation on the characteristics of the VC1 domain of the human receptor for advanced glycation end products (RAGE) secreted by Pichia pastoris

Advanced glycation end products (AGEs) and advanced lipoxidation end products (ALEs), resulting from non-enzymatic modifications of proteins, are potentially harmful to human health. They directly act on proteins, affecting structure and function, or through receptor-mediated mechanisms. RAGE, a type I transmembrane glycoprotein, was identified as a receptor for AGEs. RAGE is involved in chronic inflammation, oxidative stress-based diseases and ageing. The majority of RAGE ligands bind to the VC1 domain. This domain was successfully expressed and secreted by Pichia pastoris. Out of two N-glycosylation sites, one (Asn25) was fully occupied while the other (Asn81) was under-glycosylated, generating two VC1 variants, named p36 and p34. Analysis of N-glycans and of their influence on VC1 properties were here investigated. The highly sensitive procainamide labeling method coupled to ES-MS was used for N-glycan profiling. N-glycans released from VC1 ranged from Man9GlcNAc2- to Man15GlcNAc2- with major Man10GlcNAc2- and Man11GlcNAc2- species for p36 and p34, respectively. Circular dichroism spectra indicated that VC1 maintains the same conformation also after removal of N-glycans. Thermal denaturation curves showed that the carbohydrate moiety has a small stabilizing effect on VC1 protein conformation. The removal of the glycan moiety did not affect the binding of VC1 to sugar-derived AGE- or malondialdehyde-derived ALE-human serum albumin. Given the crucial role of RAGE in human pathologies, the features of VC1 from P. pastoris will prove useful in designing strategies for the enrichment of AGEs/ALEs from plasma, urine or tissues, and in characterizing the nature of the interaction