Propagation of terahertz radiation in non-homogeneous materials and structures

The work undertaken is concerned with looking at how terahertz frequency radiation (here defined as 300 GHz -10 THz) propagates through media which have a random structure ("non-homogeneous materials"). Materials of this type are important in a wide range of applications, but are of particular interest in security and surveillance. Propagation of terahertz radiation through non-homogeneous materials is not well understood: both interference and scattering effects become important in this spectral range, where the wavelength and size and separation of the scattering centres are often commensurable. A simple model, which uses the phase change of a wave to describe its transmission through media having relatively small changes in refractive index is developed and compared with both exact theories and experimentally obtained measurements. Overall, a satisfactory agreement between the experimental data for transmission through arrays of cylinders, textiles and powders is seen. It is well known that pulses of terahertz radiation from optoelectronic sources have a complex shape. Post detection signal processing routines can be used to clean up the experimentally determined signals. The development of such algorithms is described, before they are applied to experimental results to determine: the minimum size of gaps between slabs to mimic voids in media; and the response of various compounds to a sharply terminated input pulse. The investigation of scattering from random structures requires the construction of a spectrometer having the capability to measure THz pulses scattered at different angles. Such a system ideally requires fibre-fed detection schemes to be used. The construction of a scattering spectrometer is described and its performance outlined. Pulses of terahertz which have been scattered by a sample of interest can be reconstructed, using methods from conventional tomography, to produce images of the phantom under test. Such measurements are outlined here. To our knowledge, this is the first time that tomography has been undertaken using a fixed sample and rotating detector arrangement

La confianza organizacional como variable mediadora entre el capital psicológico y la conducta de compartir conocimiento

Trabajo de investigaciónLa presente investigación se orientó a determinar si la confianza organizacional se comportaba como mediadora de la relación entre el capital psicológico y la conducta de compartir conocimiento, para lo cual se realizó un estudio cuantitativo con un diseño transversal correlacional, con una muestra de 156 participantes, entre gerentes y empleados de empresas públicas y privadas del Departamento de Boyacá. Se evidenciaron correlaciones positivas entre las variables objeto de estudio y en virtud de los análisis de regresión lineal se encontró que la confianza organizacional media la relación entre el capital psicológico y la conducta de compartir conocimiento. Dado que la mediación encontrada fue parcial, se puede colegir que la confianza organizacional no es la única determinante de la relación entre estas variables; pueden existir otros factores igualmente considerables como el liderazgo. En conclusión, el presente documento visualiza el papel significativo de la confianza en entornos organizacionales, que finalmente se consolidará como una ventaja competitiva.1. RESUMEN 2. MARCO TEÓRICO 3. JUSTIFICACIÓN 4. PLANTEAMIENTO DEL PROBLEMA DE INVESTIGACIÓN 5. OBJETIVOS 6. VARIABLES 7. HIPÓTESIS 8. METODO 9. RESULTADOS 10. DISCUSIÓN 11. REFERENCIAS 12. APÉNDICESMaestríaMagister en Psicologí

Diammonium biphenyl-4,4′-disulfonate

In the title salt, 2NH4 +·C12H8O6S2 2−, the dianion has crystallographic inversion symmetry. A three-dimensional framework is formed from primary hydrogen-bonded sheet structures comprising ammonium N—H⋯Osulfonate inter­actions and is linked peripherally through the biphenyl residues of the anions. This open framework has 43 Å3 solvent-accessible voids

Ludwig: A parallel Lattice-Boltzmann code for complex fluids

This paper describes `Ludwig', a versatile code for the simulation of Lattice-Boltzmann (LB) models in 3-D on cubic lattices. In fact `Ludwig' is not a single code, but a set of codes that share certain common routines, such as I/O and communications. If `Ludwig' is used as intended, a variety of complex fluid models with different equilibrium free energies are simple to code, so that the user may concentrate on the physics of the problem, rather than on parallel computing issues. Thus far, `Ludwig''s main application has been to symmetric binary fluid mixtures. We first explain the philosophy and structure of `Ludwig' which is argued to be a very effective way of developing large codes for academic consortia. Next we elaborate on some parallel implementation issues such as parallel I/O, and the use of MPI to achieve full portability and good efficiency on both MPP and SMP systems. Finally, we describe how to implement generic solid boundaries, and look in detail at the particular case of a symmetric binary fluid mixture near a solid wall. We present a novel scheme for the thermodynamically consistent simulation of wetting phenomena, in the presence of static and moving solid boundaries, and check its performance.Comment: Submitted to Computer Physics Communication

Survey of Australians using cannabis for medical purposes

BACKGROUND: The New South Wales State Government recently proposed a trial of the medical use of cannabis. Australians who currently use cannabis medicinally do so illegally and without assurances of quality control. Given the dearth of local information on this issue, this study explored the experiences of medical cannabis users. METHODS: Australian adults who had used cannabis for medical purposes were recruited using media stories. A total of 147 respondents were screened by phone and anonymous questionnaires were mailed, to be returned by postage paid envelope. RESULTS: Data were available for 128 participants. Long term and regular medical cannabis use was frequently reported for multiple medical conditions including chronic pain (57%), depression (56%), arthritis (35%), persistent nausea (27%) and weight loss (26%). Cannabis was perceived to provide "great relief" overall (86%), and substantial relief of specific symptoms such as pain, nausea and insomnia. It was also typically perceived as superior to other medications in terms of undesirable effects, and the extent of relief provided. However, nearly one half (41%) experienced conditions or symptoms that were not helped by its use. The most prevalent concerns related to its illegality. Participants reported strong support for their use from clinicians and family. There was almost universal interest (89%) in participating in a clinical trial of medical cannabis, and strong support (79%) for investigating alternative delivery methods. CONCLUSION: Australian medical cannabis users are risking legal ramifications, but consistent with users elsewhere, claim moderate to substantial benefits from its use in the management of their medical condition. In addition to strong public support, medical cannabis users show strong interest in clinical cannabis research, including the investigation of alternative delivery methods