48,204 research outputs found
Molar mass and solution conformation of branched alpha(1 - 4), alpha(1 - 6) Glucans. Part I: Glycogens in water
Solution molar masses and conformations of glycogens from different sources (rabbit, oyster, mussel and bovine) were analysed using sedimentation velocity in the analytical ultracentrifuge, size-exclusion chromatography coupled to multi-angle laser light scattering (SEC-MALLS), size-exclusion chromatography coupled to a differential pressure viscometer and dynamic light scattering. Rabbit, oyster and mussel glycogens consisted of one population of high molar mass (weight averages ranging from 4.6 x 106 to 1.1 x 107 g/mol) as demonstrated by sedimentation velocity and SEC-MALLS, whereas bovine glycogen had a bimodal distribution of significantly lower molar mass (1.0 x 105 and 4.5 x 105 g/mol). The spherical structure of all glycogen molecules was demonstrated in the slopes of the Mark-Houwink-Kuhn-Sakurada-type power-law relations for sedimentation coefficient (s20,wo), intrinsic viscosity ([η]), radius of gyration (rg,z) and radius of hydration (rH,z), respectively, and was further supported by the � (=rg,z/rH,z) function, the fractal dimension and the Perrin function. The degree of branching was estimated to be ∼10% from the shrinking factors, g′ (=[η]branched/[η]linear) and also h (=(f/fo)branched/(f/fo)linear), respectively, where (f/fo) is the translational frictional ratio, consistent with expectation. © 2007 Elsevier Ltd. All rights reserved
Preferences for Prenatal Tests for Cystic Fibrosis: A Discrete Choice Experiment to Compare the Views of Adult Patients, Carriers of Cystic Fibrosis and Health Professionals
As new technologies enable the development of non-invasive prenatal diagnosis (NIPD) for cystic fibrosis (CF), research examining stakeholder views is essential for the preparation of implementation strategies. Here, we compare the views of potential service users with those of health professionals who provide counselling for prenatal tests. A questionnaire incorporating a discrete choice experiment examined preferences for key attributes of NIPD and explored views on NIPD for CF. Adult patients (n = 92) and carriers of CF (n = 50) were recruited from one children’s and one adult NHS specialist CF centre. Health professionals (n = 70) were recruited via an e-mail invitation to relevant professional bodies. The key attribute affecting service user testing preferences was no miscarriage risk, while for health professionals, accuracy and early testing were important. The uptake of NIPD by service users was predicted to be high and includes couples that would currently decline invasive testing. Many service users (47%) and health professionals (55.2%) thought the availability of NIPD for CF would increase the pressure to undergo prenatal testing. Most service users (68.5%) thought NIPD for CF should be offered to all pregnant women, whereas more health professionals (68.2%) thought NIPD should be reserved for known carrier couples. The implications for clinical practice are discussed
The Near-Infrared Broad Emission Line Region of Active Galactic Nuclei -- I. The Observations
We present high quality (high signal-to-noise ratio and moderate spectral
resolution) near-infrared (near-IR) spectroscopic observations of 23 well-known
broad-emission line active galactic nuclei (AGN). Additionally, we obtained
simultaneous (within two months) optical spectroscopy of similar quality. The
near-IR broad emission line spectrum of AGN is dominated by permitted
transitions of hydrogen, helium, oxygen, and calcium, and by the rich spectrum
of singly-ionized iron. In this paper we present the spectra, line
identifications and measurements, and address briefly some of the important
issues regarding the physics of AGN broad emission line regions. In particular,
we investigate the excitation mechanism of neutral oxygen and confront for the
first time theoretical predictions of the near-IR iron emission spectrum with
observations.Comment: 45 pages, 17 figures, accepted by ApJ
Annular electroconvection with shear
We report experiments on convection driven by a radial electrical force in
suspended annular smectic A liquid crystal films. In the absence of an
externally imposed azimuthal shear, a stationary one-dimensional (1D) pattern
consisting of symmetric vortex pairs is formed via a supercritical transition
at the onset of convection. Shearing reduces the symmetries of the base state
and produces a traveling 1D pattern whose basic periodic unit is a pair of
asymmetric vortices. For a sufficiently large shear, the primary bifurcation
changes from supercritical to subcritical. We describe measurements of the
resulting hysteresis as a function of the shear at radius ratio . This simple pattern forming system has an unusual combination of
symmetries and control parameters and should be amenable to quantitative
theoretical analysis.Comment: 12 preprint pages, 3 figures in 2 parts each. For more info, see
http://mobydick.physics.utoronto.c
Pump less wearable microfluidic device for real time pH sweat monitoring
This paper presents the fabrication and the performance of a novel, wearable, robust, flexible and disposable
microfluidic device which incorporates micro-Light Emitting Diodes (μ-LEDs) as a detection system, for
monitoring in real time mode the pH of the sweat generated during an exercising period
Adaptive Optics Near-Infrared Spectroscopy of the Sgr A* Cluster
We present K-band ~ 2600 spectroscopy of five stars
(K ~ 14 - 16 mag) within 0.''5 of Sgr A*, the radio source associated with the
compact massive object suspected to be a 2.6 x 10 \msun black hole at the
center of our Galaxy. High spatial resolution of ~ 0.''09, and good strehl
ratios of ~ 0.2 achieved with adaptive optics on the 10-meter Keck telescope
make it possible to measure moderate-resolution spectra of these stars
individually for the first time. Two stars (S0-17 and S0-18) are identified as
late-type stars by the detection of CO bandhead absorption in their spectra.
Their absolute K magnitudes and CO bandhead absorption strengths are consistent
with early K giants. Three stars (S0-1, S0-2, and S0-16), with r
0.0075 pc (~ 0.''2) from Sgr A*, lack CO bandhead absorption, confirming the
results of earlier lower spectral and lower spatial resolution observations
that the majority of the stars in the Sgr A* Cluster are early-type stars. The
absolute K magnitudes of the early-type stars suggest that they are late O -
early B main sequence stars of ages 20 Myr. The presence of young stars in
the Sgr A* Cluster, so close to the central supermassive black hole, poses the
intriguing problem of how these stars could have formed, or could have been
brought, within its strong tidal field.Comment: 19 pages, 8 figures, 2 tables. Accepted for publication in Ap
Assessment of Variable-cycle Engines for Mach 2.7 Supersonic Transports
Three proposed SCAR propulsion systems in terms of aircraft range for a fixed payload and take-off gross weight with a design cruise Mach number 2.7 are evaluated. The effects of various noise and operational restraints are determined and sensitivities to some of the more important performance variables are presented for the most probable design noise and operational restraint case. Critical areas requiring new or improved technology for each cycle are delineated
Lewis Research Center spin rig and its use in vibration analysis of rotating systems
The Lewis Research Center spin rig was constructed to provide experimental evaluation of analysis methods developed under the NASA Engine Structural Dynamics Program. Rotors up to 51 cm (20 in.) in diameter can be spun to 16,000 rpm in vacuum by an air motor. Vibration forcing functions are provided by shakers that apply oscillatory axial forces or transverse moments to the shaft, by a natural whirling of the shaft, and by an air jet. Blade vibration is detected by strain gages and optical blade-tip motion sensors. A variety of analogy and digital processing equipment is used to display and analyze the signals. Results obtained from two rotors are discussed. A 56-blade compressor disk was used to check proper operation of the entire spin rig system. A special two-blade rotor was designed and used to hold flat and twisted plates at various setting and sweep angles. Accurate Southwell coefficients have been obtained for several modes of a flat plate oriented parallel to the plane of rotation
Strong coupling of magnons in a YIG sphere to photons in a planar superconducting resonator in the quantum limit
We report measurements of a superconducting coplanar waveguide resonator
(CPWR) coupled to a sphere of yttrium-iron garnet. The non-uniform CPWR field
allows us to excite various magnon modes in the sphere. Mode frequencies and
relative coupling strengths are consistent with theory. Strong coupling is
observed to several modes even with, on average, less than one excitation
present in the CPWR. The time response to square pulses shows oscillations at
the mode splitting frequency. These results indicate the feasibility of
combining magnonic and planar superconducting quantum devices.Comment: 5 pages, 4 figure
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