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Search Results: 1 - 10 of 149117 matches for " John T. Sanders "
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Brachial artery-to-brachial vein arterio-venous fistula in a pediatric patient
Nosrahtollah Nezakatgoo,John T. Sanders,Deborah P. Jones
Nephrology Reviews , 2009, DOI: 10.4081/nr.2009.e3
Abstract: The National Kidney Foundation’s Disease Outcome Quality Initiative (NKF-DOQI) guidelines, produced in 1997, emphasized the superiority of arterio-venous fistulae (AVF) as vascular access in patients on chronic hemodialysis. Challenges in pediatric hemodialysis patients include poor superficial venous vasculature. We describe an approach to brachial artery to brachial vein AVF creation in a pediatric dialysis patient. The fistula is patent for greater than one year after creation. A great deal of passion and enthusiasm is a prerequisite for successful and technically challenging cases such as the one described.
Serum Galactose-Deficient IgA1 Level Is Not Associated with Proteinuria in Children with IgA Nephropathy
M. Colleen Hastings,Sabahat Afshan,John T. Sanders,Oulimata Kane,T. Matthew Eison,Keith K. Lau,Zina Moldoveanu,Bruce A. Julian,Jan Novak,Robert J. Wyatt
International Journal of Nephrology , 2012, DOI: 10.1155/2012/315467
Abstract: Introduction. Percentage of galactose-deficient IgA1 (Gd-IgA1) relative to total IgA in serum was recently reported to correlate with proteinuria at time of sampling and during follow-up for pediatric and adult patients with IgA nephropathy. We sought to determine whether this association exists in another cohort of pediatric patients with IgA nephropathy. Methods. Subjects were younger than 18 years at entry. Blood samples were collected on one or more occasions for determination of serum total IgA and Gd-IgA1. Gd-IgA1 was expressed as serum level and percent of total IgA. Urinary protein/creatinine ratio was calculated for random specimens. Spearman’s correlation coefficients assessed the relationship between study variables. Results. The cohort had 29 Caucasians and 11 African-Americans with a male?:?female ratio of 1.9?:?1. Mean age at diagnosis was 11.7 ± 3.7 years. No statistically significant correlation was identified between serum total IgA, Gd-IgA1, or percent Gd-IgA1 versus urinary protein/creatinine ratio determined contemporaneously with biopsy or between average serum Gd-IgA1 or average percent Gd-IgA1 and time-average urinary protein/creatinine ratio. Conclusion. The magnitude of proteinuria in this cohort of pediatric patients with IgA nephropathy was influenced by factors other than Gd-IgA1 level, consistent with the proposed multi-hit pathogenetic pathways for this renal disease. 1. Introduction IgA nephropathy (IgAN) is the most common form of chronic glomerulonephritis for individuals of European and Asian descent [1, 2]. The level of proteinuria at diagnosis of IgAN has been associated with the primary endpoint of outcome (i.e., progression to chronic dialysis or transplantation) in adults [3–7] and children [8–11]. Data from clinical and basic research in IgAN has led to the hypothesis that four hits are responsible for clinical expression of IgAN [12]. The first hit is the presence of aberrantly glycosylated O-linked glycans on the heavy-chain hinge region of circulatory IgA1 that terminate in N-acetylgalactosamine (GalNAc) rather than galactose [13]. Elevated serum levels of this galactose-deficient IgA1 (Gd-IgA1) were found in 76% of 153 Caucasian adults with IgAN in the United States [14]. IgAN patients in Japan and China also had elevated serum Gd-IgA1 levels [15, 16], as did African-American patients in the southeastern United States [17]. In addition, elevated serum Gd-IgA1 levels were found in 77% of 22 African-American and Caucasian children with IgAN [18]. The second hit is the induction of circulating IgG or IgA
Hot gas in the galaxy: what do we know for sure?
W. T. Sanders
Revista mexicana de astronomía y astrofísica , 2000,
Abstract: En la d ecada pasada se lograron grandes avances en nuestra concepci on del gas interestelar caliente de la V a L actea. El Di use X-ray Spectrometer obtuvo espectros del plano gal actico (esto es, de la Burbuja Local), en el rango 0.15{0.28 keV, que muestran l neas y mezclas de l neas de emisi on. Los espectros con rman que el fondo de rayos-X suaves, en estas energ as, es de origen t ermico a aproximadamente 106 K, pero el espectro no puede ser bien ajustado con los modelos de emisi on de plasma existentes. Los datos del sat elite ROSAT, tanto de muestreo de todo el cielo como de observaciones puntuales, restringen las distancias del gas que emite dentro de la Burbuja Local, el medio interestelar local y el halo. Los datos con rman que la Burbuja Local tiene un tama~no de 100 pc y que el halo gal actico tiene dos componentes de gas caliente; una componente muy inhomog enea de 106 K y otra componente m as caliente, de varios 106 K, cuya distribuci on es suave y sigue a la estructura general de la Galaxia. El sat elite ASCA ha detectado emisi on de plasmas a m as de 107 K en la cresta gal actica, en dos regiones del centro gal actico y en el bulbo. M as recientemente, el micro calor metro del experimento Wisconsin/Goddard con cohetes observ o el espectro de la emisi on difusa en (l; b) (90 ; 60 ), con un campo visual de 1 sr en el rango espectral 0.1{1 keV y con una resoluci on de 8 eV. Las l neas de O VII y O VIII son detectadas, pero s olo se obtienen l mites superiores para las l neas esperadas de Fe XVII.
Semiclassical Mechanics of Rotons
T. M. Sanders Jr
Physics , 2001, DOI: 10.1080/00107510110052250
Abstract: The elementary excitations in superfluid liquid He-4 named rotons have an unusual dispersion curve. The energy is an approximately quadratic function of (p-p_0), the difference between the magnitude of the momentum p and a characteristic value p_0. As a result, while for p>p_0 a roton has its (group) velocity parallel to its momentum, when p
HST ultraviolet spectral energy distributions for three ultraluminous infrared galaxies
Neil Trentham,John Kormendy,David Sanders
Physics , 1999, DOI: 10.1086/300831
Abstract: We present HST Faint Object Camera ultraviolet (230 nm and 140 nm) images of three ultraluminous infrared galaxies (ULIG: L_ir > 10^12 L_sun) selected from the IRAS Revised Bright Galaxy Sample. The purpose is to estimate spectral energy distributions (SEDs) to facilitate the identification of similar objects at high redshift in deep optical, infrared, and submm surveys. All three galaxies (VII Zw031 = IRAS F12112+0305, and IRAS F22491-1808) were well detected at 230 nm. Two of the three were marginally detected at 140 nm. The fluxes, together with ground-based optical and infrared photometry, are used to compute SEDs over a wide wavelength range. The measured SEDs drop from the optical to the ultraviolet, but the magnitude of the drop ranges from a factor of ~3 in IRAS F22491-1808 to a factor of ~100 in VIIZw031. This is most likely due to different internal extinctions. Such an interpretation is also suggested by extrapolating to ultraviolet wavelengths the optical internal extinction measured in VIIZw031. K-corrections are calculated to determine the colors of the sample galaxies as seen at high redshifts. Galaxies like VIIZw031 have very low observed rest-frame UV fluxes which means that such galaxies at high redshift will be extremely red or even missing in optical surveys. On the other hand, galaxies like IRAS F12112+0305 and IRAS F22491-1808, if seen at high redshift, would be sufficiently blue that they would not easily be distinguished from normal field galaxies, and therefore, identified as ULIGs. The implication is then that submillimeter surveys may be the only means of properly identifying the majority of ULIGs at high redshift.
The W51 Giant Molecular Cloud
John M. Carpenter,D. B. Sanders
Physics , 1998, DOI: 10.1086/300534
Abstract: We present 45"-47" angular resolution maps at 50" sampling of the 12CO and 13CO J=1-0 emission toward a 1.39 deg x 1.33 deg region in the W51 HII region complex. These data permit the spatial and kinematic separation of several spectral features observed along the line of sight to W51, and establish the presence of a massive (1.2 x 10^6 Mo), large (83 pc x 114 pc) giant molecular cloud (GMC), defined as the W51 GMC, centered at (l,b,V) = (49.5 deg, -0.2 deg, 61 km/s). A second massive (1.9 x 10^5 Mo), elongated (136 pc x 22 pc) molecular cloud is found at velocities of about 68 km/s along the southern edge of the W51 GMC. Of the five radio continuum sources that classically define the W51 region, the brightest source at lambda 6cm (G49.5-0.4) is spatially and kinematically coincident with the W51 GMC and three (G48.9-0.3, G49.1-0.4, and G49.2-0.4) are associated with the 68 km/s cloud. Published absorption line spectra indicate that the fifth prominent continuum source (G49.4-0.3) is located behind the W51 molecular cloud. The W51 GMC is among the upper 1% of clouds in the Galactic disk by size and the upper 5-10% by mass. While the W51 GMC is larger and more massive than any nearby molecular cloud, the average H2 column density is not unusual given its size and the mean H2 volume density is comparable to that in nearby clouds. The W51 GMC is also similar to other clouds in that most of the molecular mass is contained in a diffuse envelope that is not currently forming massive stars. We speculate that much of the massive star formation activity in this region has resulted from a collision between the 68 km/s cloud and the W51 GMC.
Precise Gravitational Tests via the SEE Mission: A Proposal for Space-Based Measurements
Alvin J. Sanders,George T. Gillies
Physics , 2010,
Abstract: The objective of a SEE mission is to support development of unification theory by carrying out sensitive gravitational tests capable of determining whether various alternative theories are compatible with nature. Gravitation is a key "missing link" in unification theory. Nearly all unification theories incorporate gravity at a fundamental level, and therefore precise measurements of gravitational forces will place important constraints on unification theories. Ground-based gravitational measurements to the accuracy required are impossible due to the many sources of noise present in the terrestrial environment. The proposed space-based Satellite Energy Exchange (SEE) mission will measure several important parameters to an accuracy between 100 and 10,000 times better than current or planned measurement capabilities. It will test for time variation of the gravitational "constant" G and for violations of the weak equivalence principle (WEP) and the inverse-square-law (ISL), and it will determine G. It is well-known that the discovery of breakdowns in WEP or ISL and the possible determination of a time-varying G would have significant consequences on virtually all aspects of unification theory.
Radiating dipoles in photonic crystals
Kurt Busch,Nipun Vats,Sajeev John,Barry C. Sanders
Physics , 2000, DOI: 10.1103/PhysRevE.62.4251
Abstract: The radiation dynamics of a dipole antenna embedded in a Photonic Crystal are modeled by an initially excited harmonic oscillator coupled to a non--Markovian bath of harmonic oscillators representing the colored electromagnetic vacuum within the crystal. Realistic coupling constants based on the natural modes of the Photonic Crystal, i.e., Bloch waves and their associated dispersion relation, are derived. For simple model systems, well-known results such as decay times and emission spectra are reproduced. This approach enables direct incorporation of realistic band structure computations into studies of radiative emission from atoms and molecules within photonic crystals. We therefore provide a predictive and interpretative tool for experiments in both the microwave and optical regimes.
The Role of Starburst-AGN composites in Luminous Infrared Galaxy Mergers: Insights from the New Optical Classification Scheme
T. -T. Yuan,L. J. Kewley,D. B. Sanders
Physics , 2009, DOI: 10.1088/0004-637X/709/2/884
Abstract: We investigate the fraction of starbursts, starburst-AGN composites, Seyferts, and LINERs as a function of infrared luminosity (L_IR) and merger progress for ~500 infrared-selected galaxies. Using the new optical classifications afforded by the extremely large data set of the Sloan Digital Sky Survey, we find that the fraction of LINERs in IR-selected samples is rare (< 5%) compared with other spectral types. The lack of strong infrared emission in LINERs is consistent with recent optical studies suggesting that LINERs contain AGN with lower accretion rates than in Seyfert galaxies. Most previously classified infrared-luminous LINERs are classified as starburst-AGN composite galaxies in the new scheme. Starburst-AGN composites appear to "bridge" the spectral evolution from starburst to AGN in ULIRGs. The relative strength of the AGN versus starburst activity shows a significant increase at high infrared luminosity. In ULIRGs (L_IR >10^12 L_odot), starburst-AGN composite galaxies dominate at early--intermediate stages of the merger, and AGN galaxies dominate during the final merger stages. Our results are consistent with models for IR-luminous galaxies where mergers of gas-rich spirals fuel both starburst and AGN, and where the AGN becomes increasingly dominant during the final merger stages of the most luminous infrared objects.
Gaussian quantum marginal problem
J. Eisert,T. Tyc,T. Rudolph,B. C. Sanders
Physics , 2007, DOI: 10.1007/s00220-008-0442-4
Abstract: The quantum marginal problem asks what local spectra are consistent with a given spectrum of a joint state of a composite quantum system. This setting, also referred to as the question of the compatibility of local spectra, has several applications in quantum information theory. Here, we introduce the analogue of this statement for Gaussian states for any number of modes, and solve it in generality, for pure and mixed states, both concerning necessary and sufficient conditions. Formally, our result can be viewed as an analogue of the Sing-Thompson Theorem (respectively Horn's Lemma), characterizing the relationship between main diagonal elements and singular values of a complex matrix: We find necessary and sufficient conditions for vectors (d1, ..., dn) and (c1, ..., cn) to be the symplectic eigenvalues and symplectic main diagonal elements of a strictly positive real matrix, respectively. More physically speaking, this result determines what local temperatures or entropies are consistent with a pure or mixed Gaussian state of several modes. We find that this result implies a solution to the problem of sharing of entanglement in pure Gaussian states and allows for estimating the global entropy of non-Gaussian states based on local measurements. Implications to the actual preparation of multi-mode continuous-variable entangled states are discussed. We compare the findings with the marginal problem for qubits, the solution of which for pure states has a strikingly similar and in fact simple form.
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