Simplified recording of soft contact lens fit

Purpose: To determine the critical fitting characteristics of modern soft contact lens fits and from this to devise a simplified recording scheme. Methods: Ten subjects (aged 28.1 ± 7.4 years) wore eight different modern soft contact lenses. Video was captured and analysed of blink (central and up-gaze), excursion lag (up, down, right and left gaze) and push-up movement, centration and coverage. Results: Lens centration was on average close to the corneal centre. Movement on blink was significantly smaller in up-gaze than in primary-gaze (p<0.001). Lag was greatest in down-gaze and least in up-gaze (p<0.001). Push-up test recovery speed was 1.32±0.73mm/s. Overall lens movement was determined best by assessing horizontal lag, movement on blink in up-gaze and push-up recovery speed. Steeper lens base-curves did not have a significant effect on lens fit characteristics. Contact lens material did influence lens fit characteristics, particularly silicone-hydrogels which generally had lower centration and a faster push-up speed of recovery than HEMA lenses (p<0.05). Conclusion: Lag on vertical gaze, and movement on blink in primary gaze generally provide little extra information on overall lens movement compared to horizontal lag, movement on blink in up gaze and push-up recovery speed. They can therefore be excluded from a simplified recording scheme. A simplified and comprehensive soft contact lens fit recording system could consist of a cross-hairs indicating the centre of the cornea; a circle to indicate the lens centration; a mark on the relevant position of the circle to indicate any limbal incursion; a grade (‘B’) below for movement with blink in up-gaze, a grade (‘L’) to the side for horizontal lag and a grade above (‘P’) for the assessed push-up recovery speed.

The influence of corneoscleral topography on soft contact lens fit

To evaluate the influence of peripheral ocular topography, as evaluated by optical coherence tomography (OCT), compared with traditional measures of corneal profile using keratometry and videokeratoscopy, on soft contact lens fit.

Stochastic volatility and the goodness-of-fit of the Heston model

Recently, Drǎgulescu and Yakovenko proposed an analytical formula for computing the probability density function of stock log returns, based on the Heston model, which they tested empirically. Their research design inadvertently favourably biased the fit of the data to the Heston model, thus overstating their empirical results. Furthermore, Drǎgulescu and Yakovenko did not perform any goodness-of-fit statistical tests. This study employs a research design that facilitates statistical tests of the goodness-of-fit of the Heston model to empirical returns. Robustness checks are also performed. In brief, the Heston model outperformed the Gaussian model only at high frequencies and even so does not provide a statistically acceptable fit to the data. The Gaussian model performed (marginally) better at medium and low frequencies, at which points the extra parameters of the Heston model have adverse impacts on the test statistics. © 2005 Taylor & Francis Group Ltd.

Total factor productivity and the spillover hypothesis: some new evidence

In this paper I test the spillover hypothesis of the endogenous growth literature on a sample of manufacturing firms in Italy, 1989–1994, using a new approach based on the Malmquist index. First, I measure the productivity growth registered by the high- and non-high-tech firms computing the Malmquist index with DEA. I decompose it into technical change and technical efficiency change. Then I test whether the technical change registered by high-tech firms affects productivity growth of non-high-tech firms, after controlling for factors which can potentially affect productivity growth.

The temporal binding deficit hypothesis of autism

Frith has argued that people with autism show “weak central coherence,” an unusual bias toward piecemeal rather than configurational processing and a reduction in the normal tendency to process information in context. However, the precise cognitive and neurological mechanisms underlying weak central coherence are still unknown. We propose the hypothesis that the features of autism associated with weak central coherence result from a reduction in the integration of specialized local neural networks in the brain caused by a deficit in temporal binding. The visuoperceptual anomalies associated with weak central coherence may be attributed to a reduction in synchronization of high-frequency gamma activity between local networks processing local features. The failure to utilize context in language processing in autism can be explained in similar terms. Temporal binding deficits could also contribute to executive dysfunction in autism and to some of the deficits in socialization and communication.

Language against the odds, or rather not:the weak central coherence hypothesis and language

EV is a child with a talent for learning language combined with Asperger syndrome. EV’s talent is evident in the unusual circumstances of her acquisition of both her first (Bulgarian) and second (German) languages and the unique patterns of both receptive and expressive language (in both the L1 and L2), in which she shows subtle dissociations in competence and performance consistent with an uneven cognitive profile of skills and abilities. We argue that this case provides support for theories of language learning and usage that require more general underlying cognitive mechanisms and skills. One such account, the Weak Central Coherence (WCC) hypothesis of autism, provides a plausible framework for the interpretation of the simultaneous co-occurrence of EV’s particular pattern of cognitive strengths and weaknesses. Furthermore, we show that specific features of the uneven cognitive profile of Asperger syndrome can help explain the observed language talent displayed by EV. Thus, rather than demonstrating a case where language learning takes place despite the presence of deficits, EV’s case illustrates how a pattern of strengths within this profile can specifically promote language learning.

Beyond the aspect hypothesis:tense-aspect development in advanced L2 French

The Aspect Hypothesis (AH) claims that the association of any verb category (lexical aspect) with any grammatical aspect (perfective or imperfective) constitutes the endpoint of acquisition. The present book evaluates the explanatory power of the Aspect Hypothesis for the acquisition of French past tenses, which constitutes a serious stumbling block for foreign learners, even at the highest levels of proficiency. The present research applies the Aspect Hypothesis to the production of 61 Anglophone 'advanced learners' in a tutored environment. In so doing, it tests concurrent explanations, including the influence of the input, the influence of chunking, and the hypothesis of cyclic development. It discusses the cotextual and contextual factors that still provoke «non-native glitches» at the final stage of the Aspect Hypothesis. The book shows that the AH fails to account for the complex phenomenon of past tense development, as it adopts a local and linear approach.

Color categories: confirmation of the relativity hypothesis

The question of whether language affects our categorization of perceptual continua is of particular interest for the domain of color where constraints on categorization have been proposed both within the visual system and in the visual environment. Recent research (Roberson, Davies, & Davidoff, 2000; Roberson et al., in press) found substantial evidence of cognitive color differences between different language communities, but concerns remained as to how representative might be a tiny, extremely remote community. The present study replicates and extends previous findings using additional paradigms among a larger community in a different visual environment. Adult semi-nomadic tribesmen in Southern Africa carried out similarity judgments, short-term memory and long-term learning tasks. They showed different cognitive organization of color to both English and another language with the five color terms. Moreover, Categorical Perception effects were found to differ even between languages with broadly similar color categories. The results provide further evidence of the tight relationship between language and cognition.

Hypothesis: is Alzheimer's disease a metal-induced immune disorder?

A hypothesis that a metal-induced immune disorder may be involved in the pathogenesis of some forms of Alzheimer's disease (AD) is presented. The classical complement pathway is activated in AD and T cells and reactive microglia appear in the brain. Studies of metal induced autoimmunity and the use of compounds containing aluminium as vaccine adjuvants suggest that metals can activate complement and can be taken up by antigen presenting cells. The consequent immune response could contribute to neuronal damage, beta-amyloid deposition and cell death. The strengths and weaknesses of this hypothesis are discussed and tests of some aspects are proposed.

Statnote 19: non-linear regression: fitting an exponential curve to data

Non-linear relationships are common in microbiological research and often necessitate the use of the statistical techniques of non-linear regression or curve fitting. In some circumstances, the investigator may wish to fit an exponential model to the data, i.e., to test the hypothesis that a quantity Y either increases or decays exponentially with increasing X. This type of model is straight forward to fit as taking logarithms of the Y variable linearises the relationship which can then be treated by the methods of linear regression.

Data methods in optometry. Part 10: non-linear regression analysis

1. The techniques associated with regression, whether linear or non-linear, are some of the most useful statistical procedures that can be applied in clinical studies in optometry. 2. In some cases, there may be no scientific model of the relationship between X and Y that can be specified in advance and the objective may be to provide a ‘curve of best fit’ for predictive purposes. In such cases, the fitting of a general polynomial type curve may be the best approach. 3. An investigator may have a specific model in mind that relates Y to X and the data may provide a test of this hypothesis. Some of these curves can be reduced to a linear regression by transformation, e.g., the exponential and negative exponential decay curves. 4. In some circumstances, e.g., the asymptotic curve or logistic growth law, a more complex process of curve fitting involving non-linear estimation will be required.

The 'hard problem' and the quantum physicists. Part 2: modern times

This is the second part of a review of the work of quantum physicists on the ‘hard part’ of the problem of mind. After an introduction which sets the scene and a brief review of contemporary work on the neural correlates of consciousness (NCC) the work of four prominent modern investigators is examined: J.C. Eccles/Friedrich Beck; Henry Stapp; Stuart Hameroff/Roger Penrose; David Bohm. With the exception of David Bohm, all attempt to show where in the brain’s microstructure quantum affects could make themselves felt. It is reluctantly concluded that none have neurobiological plausibility. They are all instances, to paraphrase T.H. Huxley, of a beautiful hypothesis destroyed by ugly facts. David Bohm does not attempt to fit his new quantum physics to contemporary neurobiology but instead asks for a radical rethink of our conventional scientific paradigm. He suggests that we should look towards developing a ‘pan-experientialism’ or ‘dual-aspect monism’ where consciousness goes ‘all the way down’ and that the ‘hard problem’ is not soluble within the framework of ideas provided by ‘classical’ natural science.