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Lenses
Kinds of Lenses Selected AbstractsThe shape of an accretion disc in a misaligned black hole binaryMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2009Rebecca G. Martin ABSTRACT We model the overall shape of an accretion disc in a semidetached binary system in which mass is transferred on to a spinning black hole the spin axis of which is misaligned with the orbital rotation axis. We assume the disc is in a steady state. Its outer regions are subject to differential precession caused by tidal torques of the companion star. These tend to align the outer parts of the disc with the orbital plane. Its inner regions are subject to differential precession caused by the Lense,Thirring effect. These tend to align the inner parts of the disc with the spin of the black hole. We give full numerical solutions for the shape of the disc for some particular disc parameters. We then show how an analytic approximation to these solutions can be obtained for the case when the disc surface density varies as a power law with radius. These analytic solutions for the shape of the disc are reasonably accurate even for large misalignments and can be simply applied for general disc parameters. They are particularly useful when the numerical solutions would be slow. [source] International Political Economy: Different Textbooks, Different LensesINTERNATIONAL STUDIES REVIEW, Issue 3 2003Christopher W. Scholl First page of article [source] The effect of treatment zone diameter in hyperopic orthokeratologyOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 6 2009Paul Gifford Abstract Purpose:, To investigate the time course of treatment zone (TZ) diameter changes in hyperopic orthokeratology (OK) lens wear from 1 h in the open eye through to seven nights in the closed eye. Methods:, Twelve subjects were fitted with rigid hyperopic OK lenses. Lenses were worn in the open eye for 1 h then one night in the closed eye, separated by a washout period of 4 days. Changes in best corrected visual acuity (BCVA) and corneal topography (Medmont E-300) were measured on lens removal. The TZ, comprising the central steepened zone (CSZ) and surrounding annular flattened zone (AFZ), was measured from corneal topography. Subsequently, ten subjects wore the same lens design overnight for seven nights, and measurements were taken on lens removal and 8 h later on Days 1 and 7. Results:, Both CSZ and AFZ were apparent after 1 h of hyperopic OK lens wear. CSZ decreased while AFZ increased with longer periods of lens wear. BCVA reduced with longer periods of lens wear and was associated with decreasing CSZ (r = ,0.866, p < 0.001) and increasing AFZ (r = 0.447, p < 0.05). Conclusions:, The association of changes of treatment zone size with reductions in BCVA suggests that increasing CSZ may lead to better visual outcomes in hyperopic OK. [source] AlamarBlue bioassay for cellular investigation of UV-induced crystalline lens damageOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 4 2003Olanrewaju M. Oriowo Abstract Purpose: The use of the alamarBlue fluorescence dye for cellular study of UV-induced photodamage in cultured ocular lenses was examined by comparing the results from the fluorometric assay to lens optical quality using a scanning laser system to measure the focal lengths of the lenses following UVB treatment. Methods: Excised porcine lenses were cultured in M199 supplemented with 1% antibiotics and 4% porcine serum. After 1 week of pre-incubation at 37°C, baseline measurements were taken. Treated lenses were irradiated with a range of UVB radiant exposures from 0.019 to 0.076 J cm,2. The lenses were maintained for a further 4 weeks, with measurements carried out every 48 h in the first 9 days post-UVB treatment and then once each week. At each measurement session, treated and control lenses were transferred into a 24-well plate, one lens per well containing the assay. The lenses were incubated for 50 min, after which fluorescence readings were taken with a plate reader. Results: Analyses showed significant (p < 0.05) inhibition of lens metabolic activity and optical function in the 0.038 and 0.076 J cm,2 UVB treated lenses. Lenses treated with 0.019 J cm,2 UVB did not exhibit any photodamage. Conclusions: These results suggest that the alamarBlue assay is useful for the in vitro study of UV-induced lens damage. The decrease in the capacity of treated lenses to reduce alamarBlue over time confirms that UVB photo-oxidation can cause diminution of viable lens epithelial and fibre cells. The results also suggest that the energy threshold for broadband UVB induced cataractogenesis in vitro ranges between 0.019 and 0.038 J cm,2. [source] Impairment of Eye Lens Cell Physiology and Optics by Broadband Ultraviolet A,Ultraviolet B Radiation,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2002O. M. Oriowo ABSTRACT The phototoxicity of ultraviolet A (UVA) alone and UVA plus ultraviolet B (UVB) combined on cultured porcine lenses was investigated by analyzing cellular function as measured with a fluorescence bioassay approach and optical integrity, in terms of sharpness of the lens focus as measured with a scanning laser system. The bioassay consisted of carboxyfluorescein diacetate-acetoxymethyl ester and alamarBlue fluorescent dyes. Aseptically dissected porcine lenses were maintained in modified medium 199 without phenol red supplemented with 1% penicillin,streptomycin and 4% porcine serum. At 1 week of preincubation, baseline measurements were obtained. Then the lenses were treated with single exposures of different UVA and UVB energy levels. The lenses treated with 86 J/cm2 UVA alone showed a significant (P < 0.05) decrease in cellular and optical integrity at 48 h after exposure, whereas those treated with 43 J/cm2 UVA alone did not show significant phototoxic effect. Lenses treated with 15.63 J/cm2 UVA plus 0.019 J/cm2 UVB combined showed significant adverse effects beginning from 48 h after exposure. Also, there was no recovery. These findings show that a high UVA dose alone and relatively low UVA in combination with low UVB radiant exposure can impair lens cellular and optical functions, respectively. [source] Previewing Policy Sciences: Multiple Lenses and Segmented VisionsPOLITICS & POLICY, Issue 3 2006Thomas A.P. Sinclair In setting an agenda for policy sciences, Harold Lasswell argued that the field would be shaped by its contextuality, problem orientation, and methodological diversity. The review of developments in the field in this article shows that scholars have divided into positivist and post-positivist orientations that employ multiple frameworks and models. I argue that theoretical diversity should be expected and welcomed given the complexity of policy processes and phenomena. The article encourages positivists and post-positivists alike to allow the problem being studied to drive analysis and to seek ways to integrate different theoretical and methodological approaches. [source] Communicating throughout Katrina: Competing and Complementary Conceptual Lenses on Crisis CommunicationPUBLIC ADMINISTRATION REVIEW, Issue 2007James L. Garnett Hurricane Katrina was as much a communication disaster as it was a natural and bureaucratic disaster. Communication gaps, missed signals, information technology failures, administrative buffering, turf battles, and deliberate and unintentional misinterpretations delayed and handicapped both the recognition of the crisis that Katrina posed and the response to its devastation. This essay views crisis communication through four conceptual lenses: (1) crisis communication as interpersonal influence, (2) crisis communication as media relations, (3) crisis communication as technology showcase, and (4) crisis communication as interorganizational networking. A conceptual framework is presented that compares these lenses with regard to agency, transparency, technology, and chronology. The planning, response, and recovery stages of the Hurricane Katrina disaster are viewed through these communication conceptual lenses, illustrating key facets of each perspective and adding to our deepening understanding of the events. Many of the problems we have identified can be categorized as "information gaps",or at least problems with information-related implications, or failures to act decisively because information was sketchy at best. Better information would have been an optimal weapon against Katrina. Information sent to the right people at the right place at the right time. Information moved within agencies, across departments, and between jurisdictions of government as well. Seamlessly. Securely. Efficiently , One would think we could share information by now. But Katrina again proved we cannot. ,U.S. House Select Bipartisan Committee With the floodwalls gashed and hemorrhaging billions of gallons of water into the city, it was only a matter of a few hours on Monday before the communications citywide began to fail , Communication was about to become the biggest problem of the catastrophe. ,Christopher Cooper and Robert Block, Disaster: Hurricane Katrina and the Failure of Homeland Security Truth became a casualty, news organizations that were patting their own backs in early September were publishing protracted mea culpas by the end of the month. ,Matt Welch, "They Shoot Helicopters, Don't They?" [source] Light scattering in the C57BL/6 mouse lensACTA OPHTHALMOLOGICA, Issue 2 2007Linda M. Meyer Abstract. Purpose:, To characterize inherent light scattering in the C57BL/6 mouse lens. Methods:, Lenses from 20 6-week-old female C57BL/6 mice were extracted from freshly enucleated globes and microsurgically cleaned of remnants of the ciliary body. Lens light scattering was measured quantitatively with a light dissemination meter (LDM). Morphological properties of the mouse lenses were documented using grid- and dark-field illumination photography. Analysis of variance was performed to establish variance for animals, variance between left and right eyes and variance for measurements. Results:, Average inherent light scattering in the C57BL/6 mouse lens is 0.16 ± 0.02 tEDC (transformed equivalent diazepam concentration). The mean size of a mouse lens at 6 weeks is 1.9 mm in diameter. Two lenses featured pre-existing cortical lens opacities. Variance for animals was assessed to be 7.9 10, 4 tEDC2, variance for measurements was 1.6 10, 4 tEDC2, and variance between left and right eyes was 8.8 10, 4 tEDC2. The tolerance limit for non-pathological light scattering was determined to 0.26 tEDC. No significant difference in light scattering between left and right mouse lenses was found. The minimum number of C57BL/6 mice required for detection of a 10% experimentally induced change in light scattering intensity was estimated to be 50 for independent group experiments and 25 for paired design experiments. Conclusions:, The C57BL/6 mouse is a suitable animal in which to conduct experiments on light scattering or cataractogenesis with high precision at reasonable sample sizes. Before including C57BL/6 mice into a study on cataractogenesis, pre-existing lens opacities such as congenital cataract must be excluded. [source] Allergic Conjunctivitis and Contact Lenses: Experience with Olopatadine Hydrochloride 0.1% TherapyACTA OPHTHALMOLOGICA, Issue 2000M. Brodsky ABSTRACT. Objective: The efficacy of Patanol®, a topically applied anti-allergic agent, was evaluated in a group of patients with allergic conjunctivitis due to contact lens wear (GROUP I) and a group comprised of seasonal allergic conjunctivitis patients, vernal conjunctivitis patients and atopic keratoconjunctivitis patients (GROUP II). Methods: One drop of Patanol® was administered to each eye twice daily. Signs and symptoms were assessed 7, 14, and 28 days after initiation of drug therapy. Results: Itching/burning, tearing, hyperemia and papillary reaction were reduced to scores of 0/1 (absent/mild) in 85%, 90%, 81% and 62%, respectively, of GROUP I patients at Day 28. The allergic conditions in GROUP II patients also improved with Patanol® treatment. Itching/burning, tearing, hyperemia and papillary reactions were absent/mild in 60%, 76%, 96% and 90%, respectively, of these patients at Day 28. Conclusion: Patanol® treatment effectively and rapidly alleviated the signs and symptoms of allergic conjunctivitis due to contact lens wear as well as vernal conjunctivitis, atopic keratoconjunctivitis and the common seasonal allergic conjunctivitis. Patanol® allowed allergic patients to be more comfortable while permitting them to continue using contact lenses. [source] Possible Environmental Factors Underlying Amphibian Decline in Eastern Puerto Rico: Analysis of U.S. Government Data ArchivesCONSERVATION BIOLOGY, Issue 4 2001Robert F. Stallard I examined changes in environmental conditions by examining time-series data sets that extend back at least into the 1980s, a period when frog populations were declining. The data include forest cover; annual mean, minimum, and maximum daily temperature; annual rainfall; rain and stream chemistry; and atmospheric-dust transport. I examined satellite imagery and air-chemistry samples from a single National Aeronautics and Space Administration aircraft flight across the Caribbean showing patches of pollutants, described as thin sheets or lenses, in the lower troposphere. The main source of these pollutants appeared to be fires from land clearing and deforestation, primarily in Africa. Some pollutant concentrations were high and, in the case of ozone, approached health limits set for urban air. Urban pollution impinging on Puerto Rico, dust generation from Africa ( potential soil pathogens), and tropical forest burning ( gaseous pollutants) have all increased during the last three decades, overlapping the timing of amphibian declines in eastern Puerto Rico. None of the data sets pointed directly to changes so extreme that they might be considered a direct lethal cause of amphibian declines in Puerto Rico. More experimental research is required to link any of these environmental factors to this problem. Resumen: Las pasadas tres décadas han visto grandes disminuciones poblacionales de especies de anfibios en altas elevaciones de Puerto Rico oriental, una región única en los trópicos húmedos debido al grado de monitoreo ambiental que se ha llevado a cabo mediante los esfuerzos de las agencias de gobierno de los Estados Unidos. Examiné los cambios en condiciones ambientales mediante el análisis de datos de series de tiempo que se extienden hasta los 1980s, un periodo en el que las poblaciones de ranas estaban declinando. Los datos incluyen cobertura forestal; temperatura diaria media, mínima y máxima anual; precipitación anual; química de la lluvia y arroyos; y el transporte atmosférico de polvo. Examiné imágenes de satélite y muestras de química del aire obtenidos de un solo vuelo de una nave de la NASA a lo largo del Caribe que mostraba parches de contaminantes descritas como capas delgadas de lentes en la inferior troposfera. La mayor fuente de contaminantes parece ser los incendios de tierras clareadas y la deforestación, principalmente en África. Algunas concentraciones de contaminantes fueron altas y en el caso del ozono, se aproximó a los límites de salud establecidos para aire urbano. La contaminación urbana afectando a Puerto Rico, la generación de polvo en África ( patógenos del suelo potenciales) y la quema de bosque tropical (contaminantes gaseosos) han incrementado durante las últimas tres décadas, superponiéndose con el periodo en que oturrieron las disminuciones de anfibios en Puerto Rico oriental. Ninguno de estos conjuntos de datos señaló directamente hacia cambios tan extremos que debieran ser considerados como una causa letal directa de las disminuciones en Puerto Rico. Se requiere de más investigación experimental que vincule a estos factores ambientales con este problema. [source] Stories of Schools/Teacher Stories: A Two-Part Invention on the Walls ThemeCURRICULUM INQUIRY, Issue 1 2000Cheryl J. Craig Patterned in the style of a musical invention, this work adopts Clandinin and Connelly's metaphor of a professional knowledge landscape (1995), Olson's conceptualization of the narrative authority (1993, 1995) of teacher knowledge, and my idea that teachers develop their knowledge in knowledge communities (Craig 1992, 1995a, 1995b, 1998). The first invention outlines the stories of school (Clandinin & Connelly 1996) that Riverview School and Evergreen School were given and the changes that take place over time. The second invention features beginning teacher, Benita Dalton, and her narratives of experience lived and told in the two school contexts. Relating the teacher's stories to the narrative accounts of the two campuses illustrates the extent to which context shapes teachers' practices and bounds their knowing. The work sheds much light on the subtle complexities of teachers' professional knowledge landscapes and adds to the conceptual base of a line of inquiry that focuses on the shaping effect of context on teachers' knowledge developments. An invention, loosely defined, involves the creation, through thought and/or action, of something that did not exist before. Written in the style of a musical invention, this piece is composed of two parts featuring the stories of two schools played against the evolving stories of a teacher who worked in both contexts. While the two parts of the invention both develop the walls theme, each unfolds in a different manner. The two variations which constitute the first part of the invention center on the stories of school (Clandinin & Connelly 1996) that Riverview School and Evergreen School were given and examines how these stories changed over time. The two variations that comprise the second part of the invention highlight beginning teacher, Benita Dalton, her stories of experience (Connelly & Clandinin 1990) lived and told at the two schools, and shifts that took place in her knowledge development. Connecting the fine-grained accounts of an individual with the coarse-grained accounts of schools reveals the extent to which stories of school influence teachers' practices, set the horizons of what is available for teachers to come to know, and adds to the conceptual base of a line of research that examines the how teachers' knowledge developments are influenced by context. The work begins with introductions to Benita Dalton and me, the teacher and the researcher in the study. Discussions of the research method and the theoretical framework appear next. These preliminary sketches prepare the reader for the two-part invention that follows. They lay the methodological groundwork as well as provide lenses with which to view, and a language with which to describe, contextual experiences. The next segment of the piece is Part I of the Invention comprised of Variation I: A Narrative Account of Riverview School, Variation II: A Narrative Account of Evergreen School, and a reflective coda on stories of schools. These passages bring the first part of the invention to closure. Next comes Invention II, the second movement of the piece, featuring Variation I: A Story of Benita's Experience at Riverview and Variation II: A Story of Benita's Experience at Evergreen. As with the first part of the invention, a reflective coda appears at the end of Benita's stories of experience that concludes the second part of the invention. The article ends with a grand finale, where the parallel stories developed in the invention's two parts are intentionally brought together for practical and theoretical purposes. These closing passages specifically address the principle question, the simple melody around which this two-part inquiry/invention has been constructed/composed: How does context affect teachers' knowledge developments? [source] Risky Business: Economic Uncertainty, Market Reforms and Female Livelihoods in Northeast GhanaDEVELOPMENT AND CHANGE, Issue 5 2000Brenda Chalfin This article examines the implications of economic uncertainty for rural markets and the livelihoods of female traders. It does so through a case study of a community in northern Ghana caught in the throes of a structural adjustment-driven privatization initiative. In order to fully comprehend the nature of the economic uncertainties in which rural economic actors are enmeshed and the manner in which they resist, engage or engender these conditions, two theoretical lenses are interposed. One, focusing on structural dissolution and an overall process of rural, and especially female, disempowerment, is drawn from recent approaches to African political economy. The other, gleaned from the field of economic anthropology, attends to the agency and knowledge of rural entrepreneurs in the face of unstable and imperfect market conditions. By bringing together these different analytic traditions, the critical significance of uncertainty within the complex process of rural economic transformation and reproduction becomes evident. Rather than functioning as a diagnostic of economic crisis and insecurity, uncertainty can be a strategic resource integral to the constitution of markets, livelihoods and economic coalitions. Such a perspective, privileging the institutional potentials of local social practice, makes apparent the forceful role played by female traders in the structuring of rural marketing systems even in the face of externally-induced and sometimes dramatic shifts in material conditions. [source] Gene expression profiles of lens regeneration and development in Xenopus laevisDEVELOPMENTAL DYNAMICS, Issue 9 2009Erica L. Malloch Abstract Seven hundred and thirty-four unique genes were recovered from a cDNA library enriched for genes up-regulated during the process of lens regeneration in the frog Xenopus laevis. The sequences represent transcription factors, proteins involved in RNA synthesis/processing, components of prominent cell signaling pathways, genes involved in protein processing, transport, and degradation (e.g., the ubiquitin/proteasome pathway), matrix metalloproteases (MMPs), as well as many other proteins. The findings implicate specific signal transduction pathways in the process of lens regeneration, including the FGF, TGF-beta, MAPK, Retinoic acid, Wnt, and hedgehog signaling pathways, which are known to play important roles in eye/lens development and regeneration in various systems. In situ hybridization revealed that the majority of genes recovered are expressed during embryogenesis, including in eye tissues. Several novel genes specifically expressed in lenses were identified. The suite of genes was compared to those up-regulated in other regenerating tissues/organisms, and a small degree of overlap was detected. Developmental Dynamics 238:2340,2356, 2009. © 2009 Wiley-Liss, Inc. [source] Targeted deletion of Dicer disrupts lens morphogenesis, corneal epithelium stratification, and whole eye developmentDEVELOPMENTAL DYNAMICS, Issue 9 2009Yan Li Abstract Dicer, a ribonuclease essential for miRNA processing, is expressed abundantly in developing mouse cornea and lens. We studied the roles of Dicer and miRNAs in eye development by conditionally deleting the Dicer gene in the mouse lens and corneal epithelium. Adult Dicer conditional null (DicerCN) mice had severe microphthalmia with no discernible lens and a poorly stratified corneal epithelium. Targeted deletion of Dicer effectively inhibited miRNA processing in the developing lens at 12.5 day of embryogenesis (E12.5). Lens development initiated normally but underwent progressive dystrophy between E14.5 and E18.5. Microarray analysis revealed activation of P53 signaling in DicerCN lenses at E13.5, consistent with increased apoptosis and reduced cell proliferation between E12.5 and E14.5. Expression of Pax6 and other lens developmental transcription factors were not greatly affected between E12.5 and E14.5 but decreased as the lens degenerated. Our data indicated an indispensible role for Dicer and miRNAs in lens and corneal development. Developmental Dynamics 238:2388,2400, 2009. © 2009 Wiley-Liss, Inc. [source] A peek inside the neurosecretory brain through Orthopedia lensesDEVELOPMENTAL DYNAMICS, Issue 9 2008Luca Del Giacco Abstract The wealth of expression and functional data presented in this overview discloses the homeogene Orthopedia (Otp) as critical for the development of the hypothalamic neuroendocrine system of vertebrates. Specifically, the results depict the up-to-date portrait of the regulation and functions of Otp. The development of neuroendocrine nuclei relies on Otp from fish to mammals, as demonstrated for several peptide and hormone releasing neurons. Additionally, the activity of Otp is essential for the induction of the dopaminergic phenotype in the hypothalamus of vertebrates. Recent insights into the pathways required for Otp regulation have revealed the implication of the main extracellular signals acting during hypothalamic development. Alterations in these pathways are involved in several neuronal disorders, and the resultant downstream misregulation of Otp might impair the development of the hypothalamus, and be therefore responsible for the neuroendocrine dysfunctions that typify these diseases. Developmental Dynamics 237:2295,2303, 2008. © 2008 Wiley-Liss, Inc. [source] Selective expression of the small GTPase RhoB in the early developing mouse lensDEVELOPMENTAL DYNAMICS, Issue 3 2001Rupalatha Maddala Abstract This report describes the expression and distribution pattern of RhoB GTPase in the developing mouse lens. RhoB expression was confirmed by sequencing an reverse transcriptase-polymerase chain reaction,generated DNA fragment of RhoB. Immunohistochemical analysis of RhoB revealed expression in the lens vesicle (both anterior and posterior vesicle) at embryonic day (E) 11.5, and in the epithelium and primary fibers of the E14.5 lens. Compared with the neonatal stage (day 1), where RhoB is detected in the entire lens (epithelium, primary, and secondary fibers), expression of this protein is restricted to the epithelial and outer cortical secondary fibers in postnatal lenses (from day 7 to day18). Interestingly, in E11.5 and E14.5 lenses, RhoB is localized predominantly in the lens, but not detectable in the retina, cornea, or other ocular tissues. RhoB expression appears to be down-regulated in the postnatal lens with concomitant up-regulation in the retina and cornea, compared with earlier stages of development (eyes of E11.5, E14.5, and neonatal mice). This study reveals the selective expression of RhoB in the lens during early eye development and suggests a potential role for this small GTPase in cytoskeletal reorganization associated with lens epithelial cell elongation and differentiation. © 2001 Wiley-Liss, Inc. [source] Reduced accommodative function in dyskinetic cerebral palsy: a novel management strategyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 10 2000Linda M Ross MBCh B MRCP MRCPCH A9-year-old boy with dyskinetic cerebral palsy secondary to neonatal encephalopathy is described. He presented with blurring of near vision which had begun to impact on his school work. Objective assessment of accommodation showed that very little was present, although convergence was almost normal. The near-vision symptoms were completely removed and reading dramatically improved with the provision of varifocal spectacles. Varifocal lenses provide an optimal correction for far, intermediate (i.e. for computer screens), and near distances (i.e. for reading). Managing this type of patient with varifocal spectacles has not been previously reported. It is clearly very important to prescribe an optimal spectacle correction to provide clear vision to optimize learning. [source] Cataracts in experimentally diabetic mouse: morphological and apoptotic changesDIABETES OBESITY & METABOLISM, Issue 2 2005K. R. Hegde Aim:, The objective of these investigations was to extend our earlier study on the induction of cataracts in diabetic mice, a low aldose reductase (AR) animal model at morphological level. Previous studies were done primarily at biochemical level. Methods:, Diabetes was induced by intraperitoneal administration of streptozotocin. The lenses isolated after the establishment of diabetes were then subjected to histologic and electron microscopic studies. Results:, Morphological alterations were characterized by shrinkage, elongation and lobulization of the nuclei of the epithelial cells. This was associated with chromatin condensation and its margination. Similar structural aberrations were also observed in a significant number of the subepithelial fibre cells representing defect in fibre maturation. More interestingly, unlike that in other common animal models of diabetic cataract, such abnormally nucleated cells were also found to be prevalent in the posterior subcapsular region, a finding common in human diabetics also. Conclusion:, The present studies further affirm the suitability of the mouse model for a study of cataractogenesis induced by diabetes. Because of the findings reported herein, as well as the known biochemical similarity between the lenses of the mice and humans in respect of AR deficiency, contrary to the rat model where it is very high, use of this species is considered more useful towards understanding the basic aetiology as well as for evaluating the efficacy of various referred nutritional and metabolic antioxidants against such cataracts. [source] Testing etching hypothesis for the shaping of granite dome structures beneath lateritic weathering landsurfaces using ERT methodEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2003Anicet Beauvais Abstract An Erratum has been published for this article in Earth Surface Processes and Landforms 28(13) 2003, 1491. Granite domes, boulders and knobs buried within saprolite have been detected beneath lateritic weathering landsurfaces using 2D electrical resistivity tomography (ERT). This technique provides a valuable means of mapping the bedrock topography and the regolith structures underneath landsurfaces, as it is intrinsically very sensitive to the electrical properties of superimposed pedological, hydrological and geological layers, allowing the determination of their relative geometry and spatial relationships. For instance, 2D inverse electrical resistivity models including topographic data permit the de,nition of lithostratigraphic cross-sections. It shows that resistive layers, such as the more or less hardened ferruginous horizons and/or the bedrock, are generally well differentiated from poorly resistive layers, such as saprolite, including water-saturated lenses, as has been corroborated by past and actual borehole observations. The analysis of the 2D geometrical relations between the weathering front, i.e. the bedrock topography, and the erosion surface, i.e. the landsurface topography, documents the weathering and erosion processes governing the development of the landforms and the underlying structures, thus allowing the etching hypothesis to be tested. The in,ltration waters are diverted by bedrock protrusions, which behave as structural thresholds compartmentalizing the saprolite domain, and also the regolith water table, into distinct perched saturated subdomains. The diverted waters are thus accumulated in bedrock troughs, which behave like underground channels where the saprolite production rate may be enhanced, provided that the water drainage is ef,cient. If the landsurface topography controls the runoff dynamics, the actual bedrock topography as depicted by ERT imaging in,uences the hydrodynamics beneath the landsurface. In some way, this may control the actual weathering rate and the shaping of bedrock protrusions as granite domes and knobs within thick saprolite, before their eventual future exposure. Copyright © 2003 John Wiley & Sons, Ltd. [source] EDUCATING COMMUNAL AGENTS: BUILDING ON THE PERSPECTIVISM OF G.H. MEADEDUCATIONAL THEORY, Issue 4 2007Jack Martin In this essay, Jack Martin aims to remedy such oversight by interpreting Mead's social-psychological and educational theorizing of selfhood and agency through the lenses of the perspectival realism Mead developed in the last decade of his life. This interpretation understands education as concerned with the cultivation and coordination of cultural, societal, interpersonal, and personal perspectives. Within this framework, communal agency is understood as a self-interpreting, self-determining capability of persons. This agentive capability derives from immersion and participation with others within sociocultural practices and perspectives, but also includes reactivity to those same practices and perspectives. The education of communal agents as envisioned here emphasizes the social nature of education, students' experience and development, and the critical role of the teacher as a mediator between student development and social process. Such an education is grounded in the immediate experiences and perspectives of learners, but increasingly assists learners to move beyond their own experiences through engaged interaction with others and with resources for acquiring broader, more organized perspectives on themselves, others, and the world. [source] Light-emitting diode-induced fluorescence detection of native proteins in capillary electrophoresisELECTROPHORESIS, Issue 21 2005Chanan Sluszny Abstract A continuous-wave 280 nm light-emitting diode (LED) was used as the excitation source for native fluorescence detection of proteins in CE. The operating current and temperature of the LED were optimized in order to achieve high luminescence power. It was found that a forward current of 30,mA and a temperature of approximately 5°C gave the best S/N. By using a set of two ball lenses to focus light from the LED, we achieved a spot of approximately 200,,m with a power of 0.1,0.2,mW on the detection window. Fluorescence was collected with a ball lens at 90° angle through a bandpass filter onto a photomultiplier tube. In CZE an LOD of 20,nM for conalbumin was reached. In capillary gel electrophoresis all eight proteins from a commercial standard kit were detected with high S/N. For a 10,,g/mL total protein mixture, S/N was better than 3 for all proteins in solution. Further improvement in LOD should be possible on utilization of an LED with higher luminescence power. [source] The brain weights body-based cues higher than vision when estimating walked distancesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2010Jennifer L. Campos Abstract Optic flow is the stream of retinal information generated when an observer's body, head or eyes move relative to their environment, and it plays a defining role in many influential theories of active perception. Traditionally, studies of optic flow have used artificially generated flow in the absence of the body-based cues typically coincident with self-motion (e.g. proprioceptive, efference copy, and vestibular). While optic flow alone can be used to judge the direction, speed and magnitude of self-motion, little is known about the precise extent to which it is used during natural locomotor behaviours such as walking. In this study, walked distances were estimated in an open outdoor environment. This study employed two novel complementary techniques to dissociate the contributions of optic flow from body-based cues when estimating distance travelled in a flat, open, outdoor environment void of distinct proximal visual landmarks. First, lenses were used to magnify or minify the visual environment. Second, two walked distances were presented in succession and were either the same or different in magnitude; vision was either present or absent in each. A computational model was developed based on the results of both experiments. Highly convergent cue-weighting values were observed, indicating that the brain consistently weighted body-based cues about twice as high as optic flow, the combination of the two cues being additive. The current experiments represent some of the first to isolate and quantify the contributions of optic flow during natural human locomotor behaviour. [source] Sol,Gel Derived Nanocomposites for Optical ApplicationsADVANCED ENGINEERING MATERIALS, Issue 5 2010Peter W. de Oliveira This paper provides a selective description of the development of nanostructured materials and the fabrication of the devices for optical applications. Examples are interference coatings, refractive and diffractive lenses, and macro- and micro-GRIN (graded refractive index) optical elements. Hybrid materials containing nanoparticles are of particular interest for the production of optical elements because, by exploiting the intrinsic solid state properties of the nanoparticles, nanocomposites can be tailored to exhibit the desired properties. A particular advantage of wet chemical processing lies in its great flexibility for depositing functional coatings. [source] Geoarchaeology of the Kostenki,Borshchevo sites, Don River Valley, RussiaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2007Vance T. Holliday The Kostenki,Borshchevo localities include 26 Upper Paleolithic sites on the first and second terraces along the west bank of the Don River, near Voronezh on the central East European Plain. Geoarchaeological research from 2001 through 2004 focused on sites Kostenki 1, 12, and 14, with additional work at Kostenki 11 and 16, and Borshchevo 5. The strata are grouped into three units (bottom up): Unit 1, > 50 ka, consists of coarse alluvium (representing upper terrace 2 deposits) and colluvium, overlain by fine-grained sediments. Unit 2 includes archaeological horizons sealed within two sets of thin lenses of silt, carbonate, chalk fragments, and organic-rich soils (termed the Lower Humic Bed and Upper Humic Bed) dating 50,30 ka. Separating the humic beds is a volcanic ash lens identified as the Campanian Ignimbrite Y5 tephra, dated elsewhere by Ar/Ar to ca. 40 ka. The humic beds appear to result from the complex interplay of soil formation, spring deposition, slope action, and other processes. Several horizons buried in the lower part of Unit 2 contain Upper Paleolithic assemblages. The springs and seeps, which are still present in the area today, emanated from the bedrock valley wall. Their presence may account for the unusually high concentration of Upper Paleolithic sites in this part of the central East European Plain. Unit 3, < 30 ka, contains redeposited loess with a buried soil (Gmelin Soil) overlain by a primary full-glacial loess with an associated Chernozem (Mollisol), forming the surface of the second terrace. © 2007 Wiley Periodicals, Inc. [source] Growth and albitization of K-feldspar in crystalline rocks in the shallow crust: a tracer for fluid circulation during exhumation?GEOFLUIDS (ELECTRONIC), Issue 2 2003M. B. Holness Abstract A general feature of medium- to coarse-grained, sheet-silicate bearing, quartzo-feldspathic rocks of either metamorphic or igneous affinity is the retrograde development of lenses of pure K-feldspar at the grain boundaries between sheet silicate (0 0 1) faces and original feldspar grains. The growth of these lenses acts to displace and deform the sheet silicate grain by a force of crystallization, although the substrate feldspar and adjacent quartz are not deformed. Subsequent to the growth of the lenses they are replaced to variable degrees by pure albite, which grows into the lens from the substrate feldspar behind an irregular replacement front. The composition and texture of both K-feldspar and replacive albite suggest a strong affinity with authigenic feldspars, although it is considered likely that the K-feldspar of the lenses is derived from low-temperature biotite-breakdown reactions. A model is proposed whereby the lenses grow into open pores at dilatant sites in response to infiltration of aqueous fluids as the crystalline rocks are exhumed under brittle conditions. Continued circulation of infiltrating fluids in a temperature gradient results in the replacement of K-feldspar by albite via an alkali exchange process. The lenses point to a significant grain-scale permeability in crystalline rock at shallow levels in the crust. [source] Development Section, April 2008GEOGRAPHY COMPASS (ELECTRONIC), Issue 3 2008Cheryl McEwan EDITORIAL It is a great privilege to serve as Editor for the Development section of Geography Compass. The journal is an exciting new venture in electronic publishing that aims to publish state-of-the-art peer-reviewed surveys of key contemporary issues in geographical scholarship. As the first Editor of this section, it is my responsibility to establish the key aims and innovations for this section of the journal. These include: publishing reviews of scholarship on topics of contemporary relevance that are accessible and useful to researchers, teachers, students and practitioners; developing the range of topics covered across the spectrum of development geography; helping to set agendas in development geography by identifying gaps in existing empirical and conceptual research; commissioning articles from both established and graduate/early career researchers who are working at the frontiers of development geography; and communicating the distinctiveness of Geography Compass. Part of this distinctiveness is in publishing articles that are both of scholarly excellence and accessible to a wide audience. The first volume of Geography Compass was published in 2007, covering a wide range of topics (e.g. migration, children, technology, grassroots women's organizations, civil society, biodiversity, tourism, inequality, agrarian change, participatory development, disability, spirituality) in a number of specific geographical areas (e.g. Africa/southern Africa, Caribbean, China, Peru). Forthcoming in 2008/2009 are articles on the Gambia, Latin America, the Philippines, Southeast Asia, Bangladesh and South Africa, focusing on topics such as food security, comparative post-socialism, foreign aid and fair trade. Building on these diverse and excellent articles, I plan to communicate the distinctiveness of Development in a number of ways. First, I encourage an ecumenical approach to the notion of ,development geography' and welcome contributions from scholars across a range of social science disciplines whose work would be useful to a geography audience. This is important, not least because both development and geography, in disciplinary terms, are largely European inventions. Many scholars in Latin America, Africa and Asia, for example, do not refer to themselves as either development specialists or geographers but are producing important research in areas of direct relevance to students and researchers of ,development geography'. As the first editions illustrate, I also seek to publish articles that reflect ,development' in its broadest sense, encompassing economic, (geo)political, social, cultural and environmental issues. 2008 will be an interesting year for development, with a number of important issues and events shaping discourse and policy. These include: the Beijing Olympics and increasing focus on China's role in international development; political change in a number of African countries (Kenya, Zimbabwe, South Africa); the US presidential elections and potential shifts in policy on climate change, trade and security; the impacts of the Bali roadmap on climate change in the current economic context; the increasing number of impoverished people in Asia (notably China and India), sub-Saharan Africa and Latin America (notably Brazil) that even the World Bank has acknowledged; the implications of the increasing role of philanthropic foundations (e.g. the Gates Foundation and those emerging in India and Russia) in international development. I hope to see some of these issues covered in this journal. Second, I am keen to break down the association between ,development' and parts of the world variously categorized as ,Third World', ,Global South' or ,Developing World' by publishing articles that cut across North and South, East and West. The intellectual and disciplinary practices within (Western) geography that separate those researching issues in the South and post-socialist contexts from those researching similar issues in advanced capitalist economies are, it seems, no longer sustainable or sensible. Moreover, while studies of transnational and ethical trade, neoliberalism, household economies and ,commodity chains', for example, incorporate a multitude of case studies from across the world, these tend to be understood through conceptual lenses that almost always have their theoretical antecedents in Western theorization. The notion of ,learning from' debates, policy and practice in other parts of the world is still relatively alien within the discipline. There are thus issues in how we research and teach ethically and responsibly in and about different parts of the world, and in which this journal might make a contribution. Third, and related, part of my responsibility is to ensure that Compass reflects the breadth of debate about ,development' by publishing articles written by a truly international range of scholars. This has proved to be a challenge to date, in part reflecting the newness of the journal and the difficulties posed by English language publication. However, an immediate aim is to publish the work and ideas of scholars based outside of Anglophone contexts, in the Global South and in post-socialist contexts, and to use international referees who are able to provide valuable commentaries on the articles. A longer-term aim is to also further internationalize the Editorial Board. Currently, one-third of the Editorial Board is non-UK and I plan to increase this to at least 50% in future. Fourth, I plan to ensure that the Development section takes full advantage of electronic publication and the opportunities this offers. Thus, while I am keen to retain a word limit in the interest of publishing accessible articles, the lack of constraint regarding page space enables authors to include a wide range of illustrative and other material that is impossible in print journals. I plan to encourage authors to make greater use of visual materials (maps, photographs/photo-essays, video, sound recordings, model simulations and datasets) alongside text as well as more innovative forms of presentation where this might be appropriate. Finally, in the coming year, I intend to work more closely with other Compass section Editors to realize the potential for fostering debate that cuts across subdisciplinary and even disciplinary boundaries. The journal publishes across the full spectrum of the discipline and there is thus scope for publishing articles and/or special issues on development-related topics that might best be approached through dialogue between the natural and social sciences. Such topics might include resources (e.g. water, oil, bio-fuels), hazard and risk (from environmental issues to human and state security), and sustainability and quality of life (planned for 2008). Part of the distinctiveness of Compass is that electronic-only publication ensures that articles are published in relatively quick time , in some cases less than 3 months from initial submission to publication. It thus provides an important outlet for researchers working in fast-changing contexts and for those, such as graduate and early-career researchers, who might require swift publication for career purposes. Of course, as Editor I am reliant on referees both engaging with Manuscript Central and providing reports on articles in a relatively short space of time to fully expedite the process. My experience so far has been generally very positive and I would like to thank the referees for working within the spirit of the journal. Editing a journal is, of course, a collaborative and shared endeavour. The Development Editorial Board has been central to the successful launch of Development by working so generously to highlight topics and potential authors and to review articles; I would like to take this opportunity to thank Tony Bebbington, Reg Cline-Cole, Sara Kindon, Claire Mercer, Giles Mohan, Warwick Murray, Richa Nagar, Rob Potter, Saraswati Raju, Jonathan Rigg, Jenny Robinson and Alison Stenning. The Editors-in-Chief , Mike Bradshaw and Basil Gomez , have provided invaluable advice while adding humour (and colour) to the editorial process. Colleagues at Wiley-Blackwell have provided superb support, in particular, Helen Ashton who is constantly on hand to provide advice and assistance. I look forward to working closely with these people again in the coming year, as well as with the authors and readers who are vital to ensuring that Geography Compass fulfils its remit. [source] Development of Saline Ground Water through Transpiration of Sea WaterGROUND WATER, Issue 6 2007T. Fass As vegetation usually excludes salt during water uptake, transpiration will increase the salinity of the residual water. If the source water is sea water, then the residual water may become highly saline. In the unconfined coastal aquifer of the tropical Burdekin River delta, northeastern Australia, areas of highly saline ground water with chloride concentrations up to almost three times that of sea water occur up to 15 km from the present coastline, and are attributed to transpiration by mangrove vegetation during periods of high sea level. Radiogenic (14C) carbon isotope analyses indicate that ground water with chloride concentrations between 15,000 and 35,000 mg/L is mostly between 4000 and 6000 years old, at which time sea level was 2 to 3 m higher than present. Stable isotope analyses of oxygen-18 and deuterium show no evidence for evaporative enrichment of this water. Oxygen-18, deuterium, and stable (,13C) carbon isotope analyses of ground water and soil water point to a recharge environment beneath the mangrove forests during this postglacial sea level high stand. During that period, transpiration of the mangrove forests would have led to high chloride concentrations in the residual ground water, without inducing isotopic fractionation. Due to the higher density, this hypersaline water moved downward through the aquifer by gravity and has formed lenses of highly saline ground water at the bottom of the unconfined aquifer. [source] Recharge Through a Regional Till Aquitard: Three-Dimensional Flow Model Water Balance ApproachGROUND WATER, Issue 3 2000Richard E. Gerber In southern Ontario, vertical leakage through a regionally extensive till is the primary source of recharge to underlying aquifers used for domestic and municipal water supply. Since leakage is largely controlled by the bulk hydraulic conductivity (K) of the aquitard, accurate estimates of K are necessary to quantify the resource. Considerable controversy exists regarding estimates of K for this aquitard, which vary according to the scale of the test method. For the till matrix, estimates from core samples and slug tests consistently range from 10,11 to 10,10 m/s. Isotopic evidence (3H), on the other hand, indicates that nonmatrix structures such as sand lenses, erosional surfaces, joints, and fractures significantly enhance till permeability. This is confirmed by slug test, pump test, recharge, and water balance studies, which show that K varies over seven orders of magnitude (10,12 to 10,5 m/s). To provide a regional estimate of bulk K and a reliable estimate of vertical recharge through the Northern Till, a numerical ground water flow model was constructed for the Duffins and Petticoat Creek drainage hasin. The model was calibrated to measurements of hydraulic head and estimates and measurements of base flow throughout the basin. This model demonstrates that the vertical hydraulic conductivity (Kv) for the Northern Till ranges from 5 × 10,10 to 5 × 10,9 m/s, values that are up to 2.5 orders of magnitude greater than matrix K estimates. Regional recharge through the Northern Till is estimated to range from 30 to 35 mm/a. [source] Not Enough Science or Not Enough Learning?HIGHER EDUCATION QUARTERLY, Issue 4 2008Exploring the Gaps between Leadership Theory, Practice This paper addresses the relationships between leadership theory, practice and development, drawing on both the higher education and wider leadership literature. It explores why challenges and problems exist within the contested field of leadership theory and why gaps remain between theory and practice after more than a century of research , and indeed, with increasing levels of research, scholarship and development in the last 25 years. After highlighting the importance of context for theory, practice and development, the first section of the paper examines a range of factors that contribute to theoretical ,contests' including different starting assumptions made by researchers, the different focus of studies, examination of different causal links to explain leadership, differences in values and cultural lenses and different constructs, terminology and perspectives. The second section examines the challenges faced by leadership practitioners, as individuals, and through exercising leadership as a collective responsibility in the context of changing operating environments within higher education institutions and across sectors and countries. The author highlights three areas where some re-thinking of the links between theory and practice are necessary , at the input stage, linking research findings and recruitment practices; in terms of outcomes, by researching links between leaders, leadership and performance; and in process terms, to examine more deeply complex and relational dynamic of leadership in action. The third section offers a number of specific suggestions as to how closer alignment between theory, practice and development can be achieved. The paper concludes by arguing for greater maturity (in research, practice and development) that acknowledges that leadership is played out in complex, dynamic and changing social systems. A stronger emphasis on ,leadership learning' should deliver both better science and better outcomes for leaders and led in higher education. [source] Aesthetics of Celebration, Tension and Memory: Nigeria Urban Art HistoryHISTORY COMPASS (ELECTRONIC), Issue 5 2008Adérónké Adésolá Adésànyà This essay, among other things, addresses the question of origin of Nigerian Urban art, a genre basically found in urban spaces. It highlights the various nomenclatures by which the genre has been tagged to date and provides a robust debate on the pioneer and later urban artists in the country noting the characteristics and nuances of their art. Besides establishing the character of Nigerian urban art as compelling and significant to understanding the aesthetic sensibilities and nuances of the producer culture, issues of identity, training, authorship, patronage, social memory and social responsibility, morality and immorality and how they inform, shape and complicate the creative endeavors of urban artists are brought to the fore. In this insightful interrogation of history, people and spaces one finds the emergence of a new artistic order in which Nigerian urban artists establish and expand their own idioms, unite politics with art, engage their own audiences, cultivate their own clientele, tell their own stories and that of the society, create and endorse new identities, and increasingly expand their socioeconomic space. Their creative formats essentially transform into markets where people, products and services unite. They also serve as cultural lenses through which one gain insights into class struggle in a postcolonial society and how a critical mass of the Nigerian public interprets leadership, commerce, and culture. [source] | |||||||||||||||||||||||||||||||||||||