2,709 research outputs found
Amsler Extensometer
No full textThis extensometer was designed by the Alfred J. Amsler Co. of Schaffhausen, Switzerland. An extensometer is a mechanical device designed to measure small deformations in materials.13 x 10 x 7 c
Macroalgae
No full textResearch on Antarctic macroalgae began with the expeditions of Gaudichaud,
Bory, Montagne, Hooker and Harvey as early as 1817 (Godley 1965). A second
notable period in the exploration of macroalgae from the Southern Ocean and
the cold-temperate regions of South America was around the turn of the 19th to
the 20th century. The most important studies during this time were conducted by
Hariot, Reinsch, Gain, Skottsberg and Kylin (Wiencke & Clayton 2002). These
taxonomic and biogeographical studies enabled Papenfuss (1964) to produce
the first catalogue of Antarctic and sub-Antarctic benthic marine macroalgae.
The introduction of SCUBA diving into the methodological portfolio by Neushul
(1965), Zaneveld (1966a, b, 1968) and Delépine et al. (1966) opened a new
era. Later on, Moe (Moe & DeLaca 1976), Lamb & Zimmermann (1976),
Amsler (Amsler et al., 1995) and Klöser and co-workers (Klöser et al. 1996)
conducted numerous diving studies allowing for the first time more precise
descriptions of the depth distribution of Antarctic macroalgae. In subsequent
years a major attempt was made to investigate the life history of Antarctic
species (Wiencke et al. 2007). In this period scientific knowledge of Antarctic
macroalgae was considerably broadened and the first monograph of these
ecologically important species was compiled (Wiencke & Clayton 2002).
Moreover, in-depth studies on the physiological thallus anatomy (Wiencke et
al. 2007), phenology (Wiencke et al. 2011) as well as on the temperature and
light requirements (Gómez et al. 2011, Wiencke & Amsler 2012) of Antarctic
species became possible. Detailed investigations on trophic relations between
macroalgae and herbivores began in the last decade of the 20th century (Iken
1996, 1999). Recent studies focus on the defenses between macroalgae and
herbivores, defences against diatom fouling (Amsler et al. 2005a, 2008, 2011,
Iken et al. 2011, Wiencke & Amsler 2012) as well as on the effect of global
climate changes on geographic distribution (Müller et al. 2011) and depth
zonation (Zacher et al. 2007a, Campana et al. 2011)
Comparison of amsler–krumeich and sandali classifications for staging eyes with keratoconus
No full textKeratoconus (KC) is the most common corneal ectasia characterized by progressive corneal thinning, protrusion, and irregular astigmatism. The Amsler–Krumeich classification based on the analysis of corneal topography, corneal thickness, refraction and biomicroscopy is the most commonly used; recently, a new classification based on anterior segment Optical Coherence Tomography was introduced by Sandali and colleagues. Since there is no information about the possible agreement between these two classifications, the aim of this study is to compare the stratification of consecutive KC patients using the Amsler–Krumeich and Sandali classifications, and to further ascertain KC cases in which one classification is preferred over the other. Overall, 252 eyes of 137 patients (41.45 ± 16.93 years) were analyzed: in 156 eyes (61.9%), the Amsler and Sandali staging differed in one stage while in 75 cases (29.8%) it differed in two or more stages. In 222 eyes (88.1%), the Sandali staging was higher compared to the Amsler one. These results show that the two classifications are not fully interchangeable: the Amsler–Krumeich classification is more appropriate in identifying and longitudinally monitoring patients with early stages of KC, while the Sandali classification for the diagnosis and follow-up of patients with more advanced stages, particularly when a surgical planning has to be chosen
Diagnostic Accuracy of the Amsler Grid Test for Detecting Neovascular Age-Related Macular Degeneration: A Systematic Review and Meta-analysis
No full textImportance: Patients with nonneovascular age-related macular degeneration (AMD) are encouraged to use the Amsler grid test for self-assessment to facilitate early diagnosis. The test is widely recommended, suggesting a belief that it signals worsening AMD, warranting its use in home monitoring. Objective: To systematically review studies of the diagnostic test accuracy of the Amsler grid in the diagnosis of neovascular AMD and to perform diagnostic test accuracy meta-analyses. Data Sources: A systematic literature search was conducted in 12 databases for relevant titles from database inception until May 7, 2022. Study Selection: Studies included those with groups defined as having (1) neovascular AMD and (2) either healthy eyes or eyes with nonneovascular AMD. The index test was the Amsler grid. The reference standard was ophthalmic examination. After removal of obviously irrelevant reports, 2 authors (J.B. and M.S.) independently screened the remaining references in full text for potential eligibility. Disagreements were resolved by a third author (Y.S.). Data Extraction and Synthesis: Two authors (J.B. and I.P.) independently extracted all data and evaluated quality and applicability of eligible studies using the Quality Assessment of Diagnostic Accuracy Studies 2. Disagreements were resolved by a third author (Y.S.). Main Outcomes and Measures: Sensitivity and specificity of the Amsler grid for detecting neovascular AMD with comparators being either healthy control participants or patients with nonneovascular AMD. Results: Of 523 records screened, 10 studies were included with a total of 1890 eyes (mean participant age ranging from 62 to 83 years). Sensitivity and specificity to diagnose neovascular AMD were 67% (95% CI, 51%-79%) and 99% (95% CI, 85%-100%), respectively, when comparators were healthy control participants and 71% (95% CI, 60%-80%) and 63% (95% CI, 49%-51%), respectively, when control participants were patients with nonneovascular AMD. Overall, potential sources of bias were low across studies. Conclusions and Relevance: Although the Amsler grid is easy and inexpensive to use for detection of metamorphopsia, its sensitivity may be at levels typically not recommended for monitoring. Coupling this lower sensitivity with only moderate specificity to identify neovascular AMD in a population at risk, these findings suggest that such patients typically should be encouraged to undergo ophthalmic examination regularly, regardless of any results of Amsler grid self-assessment
Starfish saponin part LVI. Three new asterosaponins from the starfish Goniopecten demonstrans
No full textThree new steroidal sulfate pentaglycosides (asterosaponins), goniopectenosides A-C (1-3), were isolated from the polar extract of the starfish Goniopecten demonstrans. The pentasaccharide moiety linked to C-6 of 3 beta -sulfated steroidal aglycones, consists of D-xylose, D-fucose, D-quinovose, and the unprecedented 3-O-methyl-D-quinovose. Their structures were elucidated by extensive NMR experiments as well as chemical evidence. The isolated asterosaponins have been found to significantly inhibit the settlement of the biofouling marine brown macroalga Hincksia irregularis
Crystal structure prediction based on density functional theory
No full textThe atomic arrangements in solids fundamentally govern the physical properties of a material. In solid state physics, resolving the crystal structure is therefore one of the key approaches when investigating novel materials. However, experimental methods to determine the crystal structure can be very difficult, expensive, or even impossible, depending on the problem and external conditions applied to the material. Examples are high pressure experiments, where accessible pressures are limited to roughly 400 GPa, or investigations of materials with constituents that cannot be detected in X-ray diffraction experiments. Furthermore, investigating crystal structures is not only fundamental in material science, but also in chemistry, biology and pharmacy. Therefore, efficient computational methods for predicting crystal structures based solely on the system's composition would provide a powerful tool with wide scientific applications.
In 1994, Angelo Gavezzotti published an article titled ``Are Crystal Structures Predictable?'', providing simultanously the simple answer: ``no''. Meanwhile, with increasing computational resources, the situation has changed and prediction of crystal structures from first principle calculations has become feasible, while still remaining a demanding task. In 2004, the minima hopping method was developed and has there-since been successfully applied to predict structures in a wide range of non-periodic systems. In this thesis, we present an extended version of the minima hopping method for crystal structure prediction by generalizing the efficient search algorithm for finding the most stable structures within any periodic system. As applications of this approach, we investigated binary Lennard-Jones benchmark mixtures, silicon crystals, high pressure phases of carbon resulting from cold compressed graphite, superconduction phases in disilane and low energy structures in the hydrogen storage material LiAlH4
The multifocal pattern electroretinogram in chloroquine retinopathy
No full textPurpose: Optimal screening for ocular toxicity caused by chloroquine and hydroxychloroquine is still controversial. With the multifocal pattern electroretinogram (mfPERG), a new electrophysiological technique has recently become available to detect early changes of ganglion cells. In this study this new technique is applied to a series of 10 patients seen consecutively receiving long-term chloroquine medication. Methods: In 10 patients receiving chloroquine medication, clinical examination, Amsler visual field testing and computerized color vision testing were performed. If toxicity was suspected, automated perimetry was carried out. In addition, in all patients conventional pattern electroretinogram (PERG) and mfPERG testing were performed. Results: On clinical examination 8 patients showed no chloroquine-associated maculopathy, while 2 patients did. Of these 2, only 1 reported abnormalities when viewing the Amsler chart, while automated perimetry showed typical, ring-like paracentral scotomas in both affected patients and color vision was significantly abnormal. In the normal patients, 4 of 8 had a mild color vision disturbance, which correlated to age-related macular changes. The amplitudes of the PERG and the central (approximately 10degrees) responses of the mfPERG were markedly reduced in chloroquine maculopathy, while the latencies were unchanged. The peripheral rings of mfPERG (ranging to 48degrees) were not affected by chloroquine toxicity. Both PERG and mfPERG were less affected by age-related macular changes. Conclusions: The reduction of PERG and central mfPERG responses in chloroquine maculopathy may help with the early detection of toxicity. Copyright (C) 2004 S. Karger AG, Basel
Critical pedagogy/popular education group
No full textFew today doubt that English Higher Education (HE), like the wider world in which it is located, is in crisis. This is, in part, an economic crisis, as the government response to the current recession seems to be that of introducing the kind of neoliberal ‘shock doctrine’ (Klein 2007) or ‘shock therapy’ (Harvey 2005) that previously resulted in swingeing cuts in public services in Southern nations. Our aim in producing this volume is that these contributions help develop a collective response to the seeming limits of these conditions. We view the strength of these contributions in part as providing palpable evidence of how we and our colleagues are acting with critical hope under current conditions so that we might encourage others to work with us to build, together, more progressive formal and informal education systems that address and seek to redress multiple injustices of the world today
A new application of emulsions to measure the gravitational force on antihydrogen
No full textWe propose to build and operate a detector based on the emulsion film technology for the measurement of the gravitational acceleration on antimatter, to be performed by the AEgIS experiment (AD6) at CERN. The goal of AEgIS is to test the weak equivalence principle with a precision of 1% on the gravitational acceleration g by measuring the vertical position of the annihilation vertex of antihydrogen atoms after their free fall while moving horizontally in a vacuum pipe. With the emulsion technology developed at the University of Bern we propose to improve the performance of AEgIS by exploiting the superior position resolution of emulsion films over other particle detectors. The idea is to use a new type of emulsion films, especially developed for applications in vacuum, to yield a spatial resolution of the order of one micron in the measurement of the sag of the antihydrogen atoms in the gravitational field. This is an order of magnitude better than what was planned in the original AEgIS proposal
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