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Search Results: 1 - 10 of 225270 matches for " Janet R Sparrow "
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A Method of Drusen Measurement Based on the Geometry of Fundus Reflectance
R Theodore Smith, Takayuki Nagasaki, Janet R Sparrow, Irene Barbazetto, Caroline CW Klaver, Jackie K Chan
BioMedical Engineering OnLine , 2003, DOI: 10.1186/1475-925x-2-10
Abstract: An interactive semi-automated procedure was developed to level the macular background reflectance for the purpose of morphometric analysis of drusen. 12 color fundus photographs of patients with age-related macular degeneration and drusen were analyzed. After digitizing the photographs, the underlying background pattern in the green channel was leveled by an algorithm based on the elliptically concentric geometry of the reflectance in the normal macula: the gray scale values of all structures within defined elliptical boundaries were raised sequentially until a uniform background was obtained. Segmentation of drusen and area measurements in the central and middle subfields (1000 μm and 3000 μm diameters) were performed by uniform thresholds. Two observers using this interactive semi-automated software measured each image digitally. The mean digital measurements were compared to independent stereo fundus gradings by two expert graders (stereo Grader 1 estimated the drusen percentage in each of the 24 regions as falling into one of four standard broad ranges; stereo Grader 2 estimated drusen percentages in 1% to 5% intervals).The mean digital area measurements had a median standard deviation of 1.9%. The mean digital area measurements agreed with stereo Grader 1 in 22/24 cases. The 95% limits of agreement between the mean digital area measurements and the more precise stereo gradings of Grader 2 were -6.4 % to +6.8 % in the central subfield and -6.0 % to +4.5 % in the middle subfield. The mean absolute differences between the digital and stereo gradings 2 were 2.8 +/- 3.4% in the central subfield and 2.2 +/- 2.7% in the middle subfield.Semi-automated, supervised drusen measurements may be done reproducibly and accurately with adaptations of commercial software. This technique for macular image analysis has potential for use in clinical research.Color fundus photographs have been routinely employed for diagnostic purposes for many years, and fundus photo gradings are c
A Novel Source of Methylglyoxal and Glyoxal in Retina: Implications for Age-Related Macular Degeneration
Kee Dong Yoon, Kazunori Yamamoto, Keiko Ueda, Jilin Zhou, Janet R. Sparrow
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041309
Abstract: Aging of retinal pigment epithelial (RPE) cells of the eye is marked by accumulations of bisretinoid fluorophores; two of the compounds within this lipofuscin mixture are A2E and all-trans-retinal dimer. These pigments are implicated in pathological mechanisms involved in some vision-threatening disorders including age-related macular degeneration (AMD). Studies have shown that bisretinoids are photosensitive compounds that undergo photooxidation and photodegradation when irradiated with short wavelength visible light. Utilizing ultra performance liquid chromatography (UPLC) with electrospray ionization mass spectrometry (ESI-MS) we demonstrate that photodegradation of A2E and all-trans-retinal dimer generates the dicarbonyls glyoxal (GO) and methylglyoxal (MG), that are known to modify proteins by advanced glycation endproduct (AGE) formation. By extracellular trapping with aminoguanidine, we established that these oxo-aldehydes are released from irradiated A2E-containing RPE cells. Enzyme-linked immunosorbant assays (ELISA) revealed that the substrate underlying A2E-containing RPE was AGE-modified after irradiation. This AGE deposition was suppressed by prior treatment of the cells with aminoguanidine. AGE-modification causes structural and functional impairment of proteins. In chronic diseases such as diabetes and atherosclerosis, MG and GO modify proteins by non-enzymatic glycation and oxidation reactions. AGE-modified proteins are also components of drusen, the sub-RPE deposits that confer increased risk of AMD onset. These results indicate that photodegraded RPE bisretinoid is likely to be a previously unknown source of MG and GO in the eye.
Modulated-Power Implantable Neuromodulation Devices and Their Impact on Surrounding Tissue Temperatures  [PDF]
John R. Stark, Sergio R. Romero, John M. Gorman, John P. Abraham, Ephraim M. Sparrow
Journal of Biomedical Science and Engineering (JBiSE) , 2016, DOI: 10.4236/jbise.2016.912048
Abstract: This project was intended to determine whether the preprogrammed time-varying recharge protocol for a battery incased in a neuromodulation implant can give rise to tissue temperatures that surpass a safe level or are otherwise benign. The study included the development of a highly accurate model of all the thermal processes that are activated by the recharging of the battery contained within the neuromodulation implant. The model was implemented by numerical simulations performed for several realistic operating conditions. The computed spatial and temporal tissue temperature distributions were employed to estimate possible tissue damage by making use of two independent methodologies. Independent calorimeter-based experiments were performed to provide validation for the calculated rates of heat generation in the coils of the implant. Spatial and temporal tissue temperature distributions extracted from the numerical simulations revealed the thermal effects associated with several realistic operating protocols. None of the operating protocols gave rise to temperatures above 42. Numerical values of thermal tissue damage metrics were determined and compared with accepted values which correspond to the absence and the presence of tissue damage. The experimentally determined rate of heat generation in the implant coils validated that from electrical measurements to within 2%. Both the tissue temperature results and the thermal damage metrics found no evidence of tissue injury when time-varying preprogrammed protocols are used in the recharging of neuromodulation implant-encased batteries.
Controlling the rate of penetration of a therapeutic drug into the wall of an artery by means of a pressurized balloon  [PDF]
John R. Stark, John M. Gorman, Ephraim M. Sparrow, John P. Abraham, Rob E. Kohler
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.65067

The focus of this paper is to propose, model, and characterize a means of accelerating the rate of delivery of therapeutic drugs to human tissues. The investigated means is a pressurized, permeable-walled balloon filled with a homogeneous mixture of the drug and the carrier fluid. The fluid mixture, driven by pressure, traverses the thickness of the balloon wall through laser-drilled pores. The number and deployment of the pores can be controlled to a high degree of precision. As a consequence, the wall of the balloon can be regarded as a homogeneous porous medium, and the traversing fluid flow can be analyzed by means of porous media models. When the balloon is in intimate contact with the surface of a tissue bed, the therapeutic fluid flows in series as it passes through the balloon wall and penetrates the tissue. The flow rate can be controlled by proper selection of the balloon permeability, the viscosity of the flowing medium, and the pressure internal to the balloon. The delivered concentration of the drug was predicted by coupling the present balloon-focused theory with a previously developed tissue-bed model that includes both diffusion and advection processes. The tribologic interaction of the pressurized balloon with an artery wall was investigated experimentally to assess the possible formation of aneurysms.

2-Amino-1-(2-carboxylatoethyl)pyrimidin-1-ium monohydrate
Christopher R. Sparrow,Edwin H. Walker Jr,Frank R. Fronczek
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810045332
Abstract: In the title structure, C7H9N3O2·H2O, there are two formula units in the asymmetric unit. The molecule is a zwitterion, containing a quaternary N atom and a deprotonated carboxyl group, with C—O distances in the range 1.256 (2)–1.266 (3) . The two independent molecules form a hydrogen-bonded R22(16) dimer about an approximate inversion center via N—H...O hydrogen bonds, with N...O distances of 2.766 (2) and 2.888 (2) . O—H...O hydrogen bonds involving the water molecules and additional N—H...O hydrogen bonds link these dimers, forming double chains.
Christopher R. Sparrow,Frank R. Fronczek,Steven F. Watkins
Acta Crystallographica Section E , 2012, DOI: 10.1107/s160053681203663x
Abstract: The title compound, C24H26O2Si2, has C2 crystallographic symmetry. The dihedral angle between the aromatic rings is 84.5 (2)°. The acetylene group is slightly non-linear, with angles at the acetylene C atoms of 175.7 (2) and 177.0 (2)°. In the crystal structure, only van de Waals interactions occur.
3-(2-Acetylanilino)propanoic acid
Christopher R. Sparrow,Edwin H. Walker Jr,Frank R. Fronczek
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536808035277
Abstract: The title molecule, C11H13NO3, has its propanoic acid group in an extended conformation, such that the molecule is nearly planar, with a mean deviation of 0.036 [the maxima being 0.106 (1) and 0.110 (1) for the two methylene C atoms]. The NH group forms an intramolecular hydrogen bond with the acetyl group; in the crystal COOH group forms a centrosymmetric hydrogen-bonded dimer.
Bodies in Transit: The Plastic Subject of Alphonso Lingis
Tom Sparrow
Perspectives : International Postgraduate Journal of Philosophy , 2009,
Abstract: Alphonso Lingis is the author of many books and renowned for his translations of Levinas, Merleau-Ponty, and Klossowski. By combining a rich philosophical training with an extensive travel itinerary, Lingis has developed a distinctive brand of phenomenology that is only now beginning to gain critical attention. Lingis inhabits a ready-made language and conceptuality, but cultivates a style of thinking which disrupts and transforms the work of his predecessors, setting him apart from the rest of his field. This essay sketches Lingis’ phenomenology of sensation in order to give expression to some dimensions of Lingisian travel. As we see, Lingis deploys a theory of the subject which features the plasticity of the body, the materiality of affect, and the alimentary nature of sensation.
Response to Workplace Violence in Health Care: Recognized but not Regulated by Kathleen M. McPhaul and Jane A. Lipscomb (September 30, 2004)
Janet R. Cooper
Online Journal of Issues in Nursing , 2005,
Planar Bragg Grating Sensors—Fabrication and Applications: A Review
I. J. G. Sparrow,P. G. R. Smith,G. D. Emmerson,S. P. Watts,C. Riziotis
Journal of Sensors , 2009, DOI: 10.1155/2009/607647
Abstract: We discuss the background and technology of planar Bragg grating sensors, reviewing their development and describing the latest developments. The physical operating principles are discussed, relating device operation to user requirements. Recent performance of such devices includes a planar Bragg grating sensor design which allows refractive index resolution of 1.9×10?6 RIU and temperature resolution of 0.03°C. This sensor design is incorporated into industrialised applications allowing the sensor to be used for real time sensing in intrinsically safe, high-pressure pipelines, or for insertion probe applications such as fermentation. Initial data demonstrating the ability to identify solvents and monitor long term industrial processes is presented. A brief review of the technology used to fabricate the sensors is given along with examples of the flexibility afforded by the technique.
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