3,357 research outputs found
Polymer multimode waveguide optical and electronic PCB manufacturing
No full textThe paper describes the research in the £1.3 million IeMRC Integrated Optical and Electronic Interconnect PCB Manufacturing (OPCB) Flagship Project in which 8 companies and 3 universities carry out collaborative research and which was formed and is technically led by the author. The consortium’s research is aimed at investigating a range of fabrication techniques, some established and some novel, for fabricating polymer multimode waveguides from several polymers, some formulations of which are being developed within the project. The challenge is to develop low cost waveguide manufacturing techniques compatible with commercial PCB manufacturing and to reduce their alignment cost. The project aims to take the first steps in making this hybrid optical waveguide and electrical copper track printed circuit board disruptive technology widely available by establishing and incorporating waveguide design rules into commercial PCB layout software and transferring the technology for fabricating such boards to a commercial PCB manufacturer. To focus the research the project is designing an optical waveguide backplane to tight realistic constraints, using commercial layout software with the new optical design rules, for a demonstrator into which 4 daughter cards are plugged, each carrying an aggregate of 80 Gb/s data so that each waveguide carries 10 Gb/s
Two-beam energy exchange in a hybrid photorefractive-flexoelectric liquid-crystal cell
No full textWe develop a semiquantitative theory to describe the experimentally observed energy gain when two light beams intersect in hybrid organic-inorganic photorefractives. These systems consist of a nematic liquid-crystal LC layer placed between two photorefractive windows. A periodic space-charge field is induced by the interfering light beams in the photorefractive windows. The field penetrates into the LC, interacting with the nematic director and giving rise to a diffraction grating. LC flexoelectricity is the principal physical mechanism driving the grating structure. Each light beam diffracts from the induced grating, leading to an apparent energy gain and loss within each beam. The LC optics is described in the Bragg regime. In the theory the exponential
gain coefficient is a product of a beam interference term, a flexoelectricity term and a space-charge term. The theory has been compared with results of an experimental study on hybrid cells filled with the LC mixture TL 205. Experimentally the energy gain is maximal at much lower grating wave numbers than is predicted by naïve theory. However, if the director reorientation is cubic rather than linear in the space-charge field term, then good agreement between theory and experiment can be achieved using only a single fitting parameter. We provide a semiquantitative argument to justify this nonlinearity in terms of electric-field-induced local phase
separation between different components of the liquid crystal
Hospital food service: a comparative analysis of systems and introducing the ‘Steamplicity’ concept
No full textBackground Patient meals are an integral part of treatment hence the provision and consumption of a balanced diet, essential to aid recovery. A number of food service systems are used to provide meals and the Steamplicity concept has recently been introduced. This seeks, through the application of a static, extended choice menu, revised patient ordering procedures, new cooking processes and individual patient food heated/cooked at ward level, to address some of the current hospital food service concerns. The aim of this small-scale study, therefore, was to compare a cook-chill food service operation against Steamplicity. Specifically, the goals were to measure food intake and wastage at ward level; ‘stakeholders’ (i.e. patients, staff, etc.) satisfaction with both systems; and patients’ acceptability of the food provided.
Method The study used both quantitative (self-completed patient questionnaires, n = 52) and qualitative methods (semi-structured interviews, n = 16) with appropriate stakeholders including medical and food service staff, patients and their visitors.
Results Patients preferred the Steamplicity system overall and in particular in terms of food choice, ordering, delivery and food quality. Wastage was considerably less with the Steamplicity system, although care must be taken to ensure that poor operating procedures do not negate this advantage. When the total weight of food consumed in the ward at each meal is divided by the number of main courses served, at lunch, the mean intake with the cook-chill system was 202 g whilst that for the Steamplicity system was 282 g and for the evening meal, 226 g compared with 310 g.
Conclusions The results of this small study suggest that Steamplicity is more acceptable to patients and encourages the consumption of larger portions. Further evaluation of the Steamplicity system is warranted.
The purpose of this study was to directly compare selected aspects (food wastage at ward level; satisfaction with systems and food provided) of a traditional cook-chill food service operation against ‘Steamplicity’. Results indicate that patients preferred the ‘Steamplicty’ system in all areas: food choice, ordering, delivery, food quality and overall. Wastage was considerably less with the ‘Steamplicity’ system; although care must be taken to ensure that poor operating procedures do not negate this advantage. When the total weight of food consumed in the ward at each meal is divided by the number of main courses served, results show that at lunch, mean intake with the cook-chill system was 202g whilst that for the ‘Steamplicity’ system was 282g and for the evening meal, 226g compared with 310g
Beam coupling in hybrid photorefractive inorganic-cholesteric liquid crystal cells: impact of optical rotation
No full textWe develop a theoretical model to describe two-beam energy exchange in a hybrid photorefractive inorganic-cholesteric cell. A cholesteric layer is placed between two inorganic substrates. One of the substrates is photorefractive (Ce:SBN). Weak and strong light beams are incident on the hybrid cell. The interfering light beams induce a periodic space-charge field in the photorefractive window. This penetrates into the cholesteric liquid crystal (LC), inducing a diffraction grating written on the LC director. In the theory, the flexoelectric mechanism for electric field-director coupling is more important than the LC static dielectric anisotropy coupling. The LC optics is described in the Bragg regime. Each beam induces two circular polarized waves propagating in the cholesteric cell with different velocities. The model thus includes optical rotation in the cholesteric LC. The incident light beam wavelength can fall above, below, or inside the cholesteric gap. The theory calculates the energy gain of the weak beam, as a result of its interaction with the pump beam within the diffraction grating. Theoretical results for exponential gain coefficients are compared with experimental results for hybrid cells filled with cholesteric mixture BL038/CB15 at different concentrations of chiral agent CB15. Reconciliation between theory and experiment requires the inclusion of a phenomenological multiplier in the magnitude of the director grating. This multiplier is cubic in the space-charge field, and we provide a justification of the q-dependence of the multiplier. Within this paradigm, we are able to fit theory to experimental data for cholesteric mixtures with different spectral position of cholesteric gap relative to the wavelength of incident beams, subject to the use of some fitting parameters
Additional bryophyte taxa from the Cook Islands
No full textIt is evident that the bryophyte flora of the Cook Islands remains poorly documented. Here, ten moss species and five liverwort species of Lepidoziaceae are newly reported for the Cook Islands. These records include Calomnion denticulatum, previously known only from Samoa, Ectropothecium viridifolium, previously known only from Hawai’i, and Tricholepidozia quadriseta, previously known only from Australia. Also, thirteen new island records of mosses are reported for Outer Islands of the group and additional information is provided for some previously published report
Two-beam energy exchange in a hybrid photorefractive inorganic-cholesteric cell
No full textWe develop a theoretical model to describe two-beam energy exchange in a hybrid photorefractive inorganic-cholesteric cell. A cholesteric LC cell is placed between two inorganic photorefractive windows. Weak and strong light beams are incident on the LC cell. The interfering light beams induce a periodic space-charge field in the photorefractive windows. This penetrates into the LC, inducing a diffraction grating written on the LC director. The theory calculates the energy gain of the weak beam, as a result of its interaction with the pump beam within the diffraction grating. In the theory, the flexoelectric mechanism for electric field-director coupling is a more important than the LC static dielectric anisotropy coupling. The flexoelectric polarization in the bulk LC follows from the initial director pretilt at the cell substrates and is the main physical mechanism governing the magnitude of the director grating and the two-beam coupling. The LC optics is described in the Bragg regime. Theoretical results for exponential gain coefficients have been compared with experimental results for hybrid cells filled with cholesteric mixtures TL205/CB15 and BL038/CB15. In order to reconcile theory and experiment, we require that (a) the magnitude of the director grating must be cubic rather than linear in the space-charge field, and (b) near the cell surface, nematic ordering must dominate. Within this paradigm, we are able to fit experimental data to theory for both cholesteric mixtures, subject to the use of some fitting parameters
Hydrodroma tonapii Cook
No full text<i>Hydrodroma tonapii</i> Cook <p>(Table 5)</p> <p> <b>Material compared</b>: “ Holotype Ψ India, Kerala St. 2 m. W. Vayitri ex. stream 15 February 1963, D.R. Cook IND 81” (FMNH). State of conservation: mounting medium slightly darkened and turbid, right palp missing.</p> <p> <b>Remarks</b>: <i>H. tonapii</i> was described by Cook (1967) from a single female specimen taken in Kerala State (India). The description of this species did not include a discussion of affinities. Furthermore Cook gave no information about the presence and number of swimming setae on II/III-L. The number and distribution of swimming setae on legs (see Table 5), makes <i>H. tonapii</i> similar to <i>H. reinhardi</i> Pesic (Mediterranean) and <i>H. wilesi</i> <b>sp. nov.</b> (see above). For a clearer separation of <i>H. reinhardi</i> and <i>H. tonapii</i>, information on general variability of measurements in additional specimens of <i>H. tonapii</i> is necessary (Pesic 2002).</p> <p> <b>Distribution:</b> India.</p> <p> <b>Habitat:</b> stream.</p> <p> <i>H.tonapii</i> female holotype</p> <p>II-L-5 posterior 0</p> <p>III-L-4 posterior 3</p> <p>III-L-5 posterior 3</p> <p>IV-L-4 anterior 2</p> <p>IV-L-4 posterior 3</p> <p>IV-L-5 anterior 0</p> <p>IV-L-5 posterior 2</p>Published as part of <i>Pesic, Vladimir & Smit, Harry, 2007, Water mite species of the genus Hydrodroma Koch (Acari: Hydrachnidia, Hydrodromidae) from Australia. Part II, pp. 41-50 in Zootaxa 1509</i> on pages 49-50, DOI: <a href="http://zenodo.org/record/177223">10.5281/zenodo.177223</a>
The Chance and Probability Concepts Project
No full textThis article, created by D.R. Green, describes an investigation of what concepts and intuitions concerning random processes are present in the minds of children of varying abilities across the 11-16 age range. The ability to list permutations, combinations and arrangements is also being investigated. The author states, "Over the past two decades the topic of 'Probabilityâ has been brought into the mathematics curriculum but it may be that this is more an empty gesture rather than a sound strategy." This article can help to alleviate many of the struggles in teaching probability concepts. The article is pitched at a more elementary audience, but is still a perfect resource for almost anyone teaching in the field
Geology field trip by train. University of Idaho. [250-6]
No full text1953 photograph of Geology. l-r: Dean J.D. Forrester, Earl F. Cook, Harry H. Caldwell, D.R. Theophilus, H. Walter Steffans. Donor: Publications Dept. [PG1_250-06
Achieving 10 ps coincidence time resolution in TOF-PET is an impossible dream
No full textGreen 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.RST/Radiation, Science and TechnologyRST/Medical Physics & Technolog
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