645 research outputs found
The evolution of a writer's voice: Gloria Naylor reads and reflects on her own work
No full textRecorded in Ithaca, NY by Cornell University., Sponsored by: Society for the Humanities., Speaker(s): Author of The Women of Brewster Place, Mama Day and Linden Hills., Reading, November 21, 1988.Naylor describes the development of her literary voice and suggests that the legion of voices which have preceded her have molded hers into what it is today.1_k80p6ida1_cmmq69o
Impairment of cerebral autoregulation in the first hours after carotid endarterectomy (CEA)
No full textMeasurement of cerebral blood flow autoregulation from spontaneous changes in arterial blood pressure
No full textA parametric approach to measuring cerebral blood flow autoregulation from spontaneous variations in blood pressure
No full textAutoregulation maintains cerebral blood flow (CBF) almost constant in the face of changes in arterial blood pressure (ABP). Tests for impairment of this process using only spontaneous fluctuations in ABP, without provoking large variations, are of great clinical interest, and a range of different approaches have previously been applied. Extending earlier work based on linear filters, we propose a simple parametric method using a first order finite impulse response filter. We evaluate the method on ABP and CBF velocity [(CBFV), from trancranial Doppler ultrasound] signals collected in 60 patients with stenosis or occlusion of the carotid arteries. Data were collected during the inspiration of ambient air, a 5% CO2/air mixture, and finally the return to ambient air. Equivalent data were collected in 15 normal subjects. The filters estimated from the data segments with constant inspiratory pCO2 showed the expected high-pass characteristic, which was reduced during hypercapnia and also in patients. Highly significant correlation between the filter parameters and cerebrovascular reactivity (percent increase in CBFV per unit change in end-tidal pCO2) gives further evidence that the filters reflect autoregulation. The method allows simple parametrization of the dynamic autoregulatory responses in CBFV, and the analysis of short (1 min) data segments
Parametric modeling of arterial blood pressure and blood flow velocity, for measuring cerebral autoregulation
No full textPerspectives on Critical Design: a Conversation with Ralph Ball and Maxine Naylor
No full textThis paper features an edited conversation with designers Ralph Ball and Maxine Naylor. It explores their thinking in relation to critical design.
In the preface to 'Form Follows Idea' (Ball & Naylor, 2005) Jeremy Myerson describes Ball and Naylor as being regarded among Britain’s most thoughtful furniture designers.
In 1985 Ball formed a design partnership with Maxine Naylor a reputable experimental designer maker. Together they began to challenge the boarders between art, craft and design. They have exhibited work internationally and held teaching positions in colleges in the UK and USA. Over the course of a decade from 1985 Ball taught on Furniture, Jewellery and Industrial design at the Royal College of Art where Naylor taught on Furniture Design, directing the course between 1995 and 1998. Today Ralph Ball is Professor of Design at Central Saint Martins University of the Arts London and Maxine Naylor is Professor of Design and Director of the Design Research Institute University of Brighton.
Through practice and academic tenure they have developed a distinctive approach to practice based research and refined their critical perspectives. They describe themselves as critical designers and use design as a critical, visual discourse to communicate ideas about design culture and society today. Taking experimentation as a research method they subject their ideas to a critical process of refutation. They question the work through a scholarly approach that challenges protocols of design to enhance the design profession.
In this conversation the designer’s concepts of ‘open-process’ and ‘design poetics’ are discussed. They describe their role acting as critics of design from within design practice. They outline their thoughts on the increasingly un-ideological culture of industrial design. They describe how through playful experiment they question the value of repetition in design and mass production of products. They do this by taking modernist axioms to extremes and ‘embedding narrative’ into objects as commentary on the state of contemporary design.
Supplementing the conversation the author offers his reflections. Primarily this exposes a form of critical design that differs significantly from popular and often technologically orientated notions of critical design
Enhancement of effective electro-optic coefficient in domain engineered UV-written waveguides in LiNbO<sub>3</sub>
No full textUV laser-induced poling-inhibition produces inverted domains in LiNbO3 which overlap significantly with waveguide modes. We have observed a 26% enhancement of the effective electro-optic coefficient in such domain-engineered waveguides
Electro-optic coefficient enhancement in poled LiNbO<sub>3</sub> waveguides
No full textLithium niobate crystals (LN) show a significant electro-optic (EO) response which contributes to the fabrication of low-voltage operation, high speed integrated optical modulators routinely used in optical telecommunication and integrated optics [1]. A UV laser direct writing method for the fabrication of optical channel waveguides has been proposed and characterized recently [2-4]. Here we report on the enhancement of the electro-optic response of these UV laser-written LN waveguides as a result of a post-poling process. More specifically we have observed a 26% increase of the r33 coefficient compared to the bulk in LN waveguides, fabricated by direct UV writing, that have been subjected to poling inhibition [5]. Poling inhibition produces inverted ferroelectric domains which are only a few microns deep. These domains are formed exactly in the same place as the UV written tracks which are responsible for the waveguide formation, and they overlap significantly with the propagating waveguide mode as is illustrated schematically in Fig. 1. Due to the polarization-selective transmission in the UV-written waveguides only the r33 coefficient could be investigated. Fig. 1 Schematic of the cross section of a) a UV-written waveguide on a single domain substrate, and b) the tail-to-tail domain arrangement overlapping with the waveguide after poling-inhibition. Optical channel waveguides were fabricated by direct UV laser focused writing on the +z face of a z-cut undoped congruent LN substrate [4]. The sample was subsequently subjected to electric field poling using an externally applied electric field (~19.5 kV/mm) which resulted in local poling-inhibited domains of limited depth that overlap with the waveguides as shown in Fig. 1b [5,6]. The electro-optic response was evaluated interferometrically by placing the waveguides in one branch of a Mach-Zehnder interferometer [3]. A set of titanium in-diffused waveguides was used as a control sample to provide the background measurement of the bulk for the r33 coefficient. The measured values of the electro-optic coefficient (r33) in the poling-inhibited samples proved to be systematically higher than the value obtained with the control sample of unpoled titanium in-diffused waveguides which was 35 pm/V. The highest value of the r33 coefficient that was measured in the poling-inhibited waveguides was 44.2 pm/V, which corresponds to an enhancement of 26% as compared to the reference Ti indiffused waveguide sample. The observed enhancement in the value of the EO coefficient is attributed to the strain which is associated with the presence of a tail-to-tail domain boundary that surrounds the optical waveguide channel as illustrated in Fig. 1b. The enhancement of the EO coefficient varied for waveguides which were fabricated under different UV irradiation conditions. The irradiation conditions affect both the waveguide mode confinement and the depth of the poling-inhibited domains. This suggests that the enhancement can be further optimized and even applied to other waveguide systems such as titanium in-diffused and proton exchanged channel guides
Local electro-optic coefficient enhancement in LiNbO<sub>3</sub> channel waveguides by domain engineering
No full textUV laser-induced poling-inhibition produces opposite domains in LiNbO3 which overlap significantly with waveguide modes. A 55% enhancement of the effective electro-optic coefficient was observed in such domain-engineered waveguides
Transatlantic Debate. Asymptomatic Carotid Artery Stenosis – Medical Therapy Alone Versus Medical Therapy Plus Carotid Endarterectomy or Stenting
No full textVascular surgery has matured to the point that there exists robust bodies of literature exploring many of our therapies. However, this evidence is but one of the factors that dictate medical practice. Others include local patient demographics, the practical implications of healthcare delivery, and an individual surgeon's interpretation of this evidence, which can be somewhat subjective. As a result, there are numerous examples of vascular specialists' practice patterns differing depending on their geographic location. Recognizing this, the Editors of the Journal of Vascular Surgery and the European Journal of Vascular and Endovascular Surgery have developed a series of Trans-Atlantic Debates to explore these instances. The inaugural debate explores the controversial question of how best to manage asymptomatic carotid artery stenoses. Our debators, Peter Schneider and Ross Naylor, offer reasoned and passionate arguments to defend their differing approaches. We trust that this addition to our journals will prove enlightening and, perhaps, entertaining
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