1,751 research outputs found
Hanging the harp on the willow tree: music and national identity in postcolonial Ireland
No full textAn inquiry into how music served as a nation building tool in the early decades of the Irish Free State.M.A.Includes bibliographical referencesby Crystal N. Galyea
Modelling surface roughening during plastic deformation of metal crystals under contact shear loading
No full textDuring plastic deformation, metal surfaces roughen and this has a deleterious impact on their tribological performance. It is therefore desirable to be able to predict and control the amount of roughening caused by subsurface plasticity. As a first step, we focus on modelling plastic deformation during contact shearing of an FCC metallic single crystal, employing a finite strain Discrete Dislocation Plasticity (DDP) formulation. This formulation allows us to capture the finite lattice rotations induced in the material by shearing and the corresponding local rotation of the crystallographic slip planes. The simulations predict a pronounced material pile-up in front of the contact and a sink-in at its rear, which are strongly crystal-orientation dependent. By comparing finite and small strain DDP, we can assess the effect of slip plane rotation on surface roughening and on metal plasticity in general. Results of the simulations are also compared with crystal plasticity, which is also capable of predicting a pile-up and sink-in, but not the crystal-orientation dependency of roughening.Accepted Author Manuscript(OLD) MSE-
The optical properties of automatically darkening welding filters based on liquid crystal technology
No full textThis thesis addresses the problem of the poor optical angular properties displayed by the majority of automatically darkening welding filters currently on the market that are based on liquid crystal technology. It is shown that by reducing the twist-angle present in the liquid crystal cell to below that of 90 together with employment of a novel polariser arrangement, an optical shutter design based on a double-cell construction is obtained that boasts a reduced angular transmittance variation when in the activated phase. This gives an optical filter possessing a wide central viewing cone whilst maintaining the remaining optical parameters at a high level. The only point of compromise comes from the voltage increase requirement upon reduction of the twist- angle in order to maintain cell contrast. Although this inflates the power consumption of the system, beneficial effects upon the total light scattering provoked by the device are also observed. The final sections deal with a new mode of operation for a twisted-nematic liquid crystal cell when placed between crossed polarisers together with an interference filter possessing a high optical transmittance over the central part of the visible spectrum. This mode of operation means that the cell is in a dark state when inactivated. Application of a small stimulating voltage transmutes the unit into the light state, where upon further increment of the driving electronics beyond this point reverts the system back into a low transmittance phase. Such a mode of operation for a twisted-nematic cell offers several advantages over that of the normally white mode when considering the optical lens of an automatically darkening welding filter. In particular, a dark, fail-safe state is provided should the controlling electronics malfunction preventing the unit from holding in a potentially hazardous light phase, a property usually associated with the normally black mode of operation, whilst the fast switching speed from the light to the dark state associated with the normally white mode of operation is maintained. It is shown that there are only two cell types that display this phenomenon and the optical properties of these two systems are analysed in some detail with the view of developing an automatically darkening welding filter based on this technology. This thesis is submitted to the University of Durham for the degree of Master of Science. All work contained within this thesis was carried out by the author at Hornell Innovation AB in Sweden. No material contained within has been submitted for a previous degree and the copyright of this thesis rests with the author. No quotation from it should be published without his prior written consent and information derived from it should be acknowledged
Topological Protection in Radiative Photonic Crystal Cavities
No full textWe study the signatures of topological light confinement in the leakage radiation of two-dimensional topological photonic crystal cavities that feature the quantum spin Hall effect at telecom wavelengths. The mode profiles in real and momentum space are retrieved using far field imaging and Fourier spectropolarimetry. We examine the scaling behavior of mode spectra, observe band-inversion-induced confinement, and demonstrate hallmarks of topological protection in the loss rates, which are largely unaffected by cavity shape and size. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.QN/Kuipers LabQN/Quantum Nanoscienc
Suppression of turbulent diffusion on the water surface by viscoelastic nano layer
No full textWe study effects of thin (10 nm) layers of adsorbed proteins on the water surface hydrodynamics. We show that extremely small concentrations of protein (less than 1 ppm) form strong viscoelastic layer at the water-air interface. This layer greatly reduces single particle dispersion on the surface perturbed by Faraday waves and turns disordered surface waves into a square stationary oscillating crystal. The viscoelastic film is destroyed by minute addition of surfactant which leads to the recovery of the horizontal mobility of fluid particles and the restoration of the Faraday wave driven turbulence
Investigation of Mn-implanted n-type Ge
No full textMn+ irons were implanted to n-type Ge(1 1 1) single crystal at room temperature with an energy of 100 keV and a dose of 3 x 10(16) cm(-2). Subsequently annealing was performed at 400degreesC for 1 h under flowing nitrogen gas. X-ray diffraction measurements show that as-implanted sample is amorphous and the structure of crystal is restored after annealing. Polycrystalline germanium is formed in annealed sample. There are no new phases found except germanium. The samples surface morphologies indicate that annealed sample has island-like feature while there is no such kind of characteristic in as-implanted sample. The elemental composition of annealed sample was analyzed by Auger electron spectroscopy. It shows that manganese ions are deeply implanted into germanium substrate and the highest manganese atomic concentration is 8% at the depth of 120 nm. The magnetic properties of samples were investigated by an alternating gradient magnetometer. The annealed sample shows ferromagnetic behavior at room temperature. (C) 2004 Elsevier B.V. All rights reserved
Modification of Loop 1 Affects the Nucleotide Binding Properties of Myo1c, the Adaptation Motor in the Inner Ear
No full textMyo1c is one of eight members of the mammalian myosin I family of actin-associated molecular motors. In stereocilia of the hair cells in the inner ear, Myo1c presumably serves as the adaptation motor, which regulates the opening and closing of transduction channels. Although there is conservation of sequence and structure among all myosins in the N-terminal motor domain, which contains the nucleotide- and actin-binding sites, some differences include the length and composition of surface loops, including loop 1, which lies near the nucleotide-binding domain. To investigate the role of loop 1, we expressed in insect cells mutants of a truncated form of Myo1c, Myo1c1IQ, as well as chimeras of Myo1c1IQ with the analogous loop from other myosins. We found that replacement of the charged residues in loop 1 with alanines or the whole loop with a series of alanines did not alter the ATPase activity, transient kinetics properties, or Ca2+ sensitivity of Myo1c1IQ. Substitution of loop 1 with that of the corresponding region from tonic smooth muscle myosin II (Myo1c1IQ-tonic) or replacement with a single glycine (Myo1c1IQ-G) accelerated the release of ADP from A.M 2?3-fold in Ca2+, whereas substitution with loop 1 from phasic muscle myosin II (Myo1c1IQ-phasic) accelerated the release of ADP 35-fold. Motility assays with chimeras containing a single ?-helix, or SAH, domain showed that Myo1cSAH-tonic translocated actin in vitro twice as fast as Myo1cSAH-WT and 3-fold faster than Myo1cSAH-G. The studies show that changes induced in Myo1c via modification of loop 1 showed no resemblance to the behavior of the loop donor myosins or to the changes previously observed with similar Myo1b chimeras
Two Systems of [DabcoH(2)](2+)/[PipH(2)](2+)-Uranyl-Oxalate Showing Reversible Crystal-to-Crystal Transformations Controlled by the Diammonium/Uranyl/Oxalate Ratios in Aqueous Solutions ([DabcoH(2)](2+)=1,4-Diazabicyclo-[2.2.2]-octaneH(2) and [Pi
No full textWe present here two systems of [dabcoH(2)](2+)-uranyl-oxalate and [pipH(2)](2+)-uranyl-oxalate in which [dabcoH(2)](2+) and [pipH(2)](2+) are cations of doubly protonated 1,4-diazabicyclo-[2.2.2]-octane (dabco) and peperazine (pip), respectively. Each system yielded two different crystals and showed the reversible crystal-to-crystal transformations between them in aqueous solutions, controlled by the ratio of reactants or building blocks in the reaction systems. The four compounds in pairs are [dabcoH(2)][UO2-(C2O4)(2)(H2O) (dabco1) and [dabcoH(2)][(UO2)(2)(C2O4)(3)-(H2O)(2)]center dot 2H(2)O (dabco2), and [pipH(2)][UO2(C2O4)(H2O)]center dot 4H(2)O (pip1) and [pipH(2)][(UO2)(2)(C2O4)(3)(H2O)(2)]center dot 2H(2)O (pip2). Besides the cations and lattice water, dabco1 and pip1 contain mononuclear anions of [UO2-(C2O4)(2)(H2O)](2-), whereas dabco2 and pip2 posses dinuclear anions of [(UO2)(2)(C2O4)(3)(H2O)](2-), and in all structures, the uranium ion shows a pentagonal bipyramid environment made up of equatorial oxalate, water, and apical oxygen. The needle crystal of sabco1 belong to the chiral space group P6(5)22. In the structure, the [UO2(C2O4)(2)(H2O)](2-) anions form anionic helixes along the 6(5) axis and they are further linked by N-H center dot center dot center dot O hydrogen bonds between the interhelix [dabcoH(2)](2+) cation and oxalates of the anion. Disorder of lattice water and [dabcoH(2)](2+) cation is observed in dabco1. The thin plate crystals of pip1 in space group P (1) over bar possess a lamellar structure, with dense layers of [pipH(2)](2+)center dot 2[CO(C2O4)(2)(H2O)]2- pillared by other crystallographically unique [pipH(2)](2+) cations, and the structure contains lattice water forming branched zigzag water chains. Block crystals of dabco2 and pip2, in monoclinic space groups C2/c and P2(1)/c, respectively, are of similar layer-like structures, possessing the dinuclear [(UO2)(2)(C2O4)(3)(H2O)(2)](2-) anion with one tetradentate oxalate bridge. The anions and ammonium cations form chains by N-H center dot center dot center dot O hydrogen bonds between them and then further form stacked layers via O-H center dot center dot center dot O hydrogen bonds among the coordinated and lattice water and the oxalate ligands. The ratio of diammonium/uranyl/oxalate in the reaction systems controlled transformation. The thermal stability; UV-vis, IR, and Raman spectra; and luminescence were also investigated.Chemistry, MultidisciplinaryCrystallographyMaterials Science, MultidisciplinarySCI(E)EI7ARTICLE62597-26061
p-n Junction Formation in i-Ge Crystal by Laser Radiation
No full textP-n junction is the main component of many semiconductor devices. Thermodiffusion, ion implantation and molecular beam epitaxy are only a few methods to form a p-n junction. The main drawback for these methods is high cost per p-n junction since the equipment for these methods is expensive. A possibility of p-n junction formation by laser radiation was shown in several p- and n-type semiconductors: p-Si[1,2], p-CdTe[3], p-InSb[4,5], p-InAs[6], p-PbSe[7] and p-Ge[8] due to inversion of conductivity type. Unfortunately, the mechanism of p-n junction formation by laser radiation is not clear until now.
In the present research rectification effect of current-voltage characteristic in pure intrinsic Ge crystal after irradiation by Nd:YAG laser was observed. The effect is characterised by threshold intensity of the laser radiation. Increase of rectification ratio of current-voltage characteristics and barrier height with intensity of the laser radiation, energy of laser radiation quanta and number of pulses was observed in this experiment. The mechanism of this phenomenon is explained by generation and redistribution of intrinsic point defects in temperature gradient field, which causes strongly absorbed laser radiation. The redistribution of defects takes place because interstitial atoms drift towards the irradiated surface, but vacancies drift in the opposite direction – in the bulk of semiconductor according to Thermogradient effect. Since interstitials in Ge crystal are of n-type and vacancies are known to be of p-type, a p-n junction is formed.
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Acknowledgments.
The author gratefully acknowledges financial support in part by Europe Project in the Framework of MATERA+ project, European Regional Development Fund within the project “Sol-gel and laser technologies for the development of nanostructures and barrier structures”, the ESF Projects No. 1DP/1.1.1.2.0/09/ APIA/VIAA/142 and «Support for the implementation of doctoral studies at Riga Technical University»
Anti-cancer agents .1. N,N,N',N'-Tetraacetylhexamethylenediamine
No full textThe centrosymmetric molecule N,N,N',N'-tetraacetylhexamethylenediamine, C14H24N2O4, occupies a special position, with only half of the molecule in the asymmetric unit. Each terminal N,N-bisacetylamine group is planar but not twofold symmetric.CrystallographySCI(E)EI6ARTICLEPt 51238-12395
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