6,952 research outputs found
A high resolution, adjustable, lockable laser mirror mount
A prototype high resolution, adjustable, lockable mirror mount is described, suitable for use as a resonator end mirror mount in fieldable lasers. The prototype was vibrated to 15g levels, 10-2000 Hz, and was shown to be stable to within 1 arc second and settable to an accuracy of 10 arc seconds. Improvements to be made to the prototype are outlined which will significantly improve the accuracy without sacrificing the other attributes of the prototype
The body as image: image as body
Pain consultations are often contested spaces where patient and clinician compete for the roles of speaker. Often patients are searching for mechanical explanations and clinicians for psychological ones - creating an impasse and causing distress to both parties. Meanwhile, as technology advances and we have increasing means of seeing inside a person’s body we seem to have less and less ability to see inside another’s world – to understand what it means to live with pain, the significance of that pain for that individual in their social context. In this paper we explore the potential for images of pain, co-created with patients, to intervene in this unproductive patient dynamic and bring the full experience of pain - social, emotional, physical - into focus. Narrative analysis is used on a series of transcripts of pain consultations
Mountain goat ecology : logging relationships in the Bunker Creek drainage of western Montana
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Vitamin B12 measurements across neurodegenerative disorders.
Background:Vitamin B12 deficiency causes a number of neurological features including cognitive and psychiatric disturbances, gait instability, neuropathy, and autonomic dysfunction. Clinical recognition of B12 deficiency in neurodegenerative disorders is more challenging because it causes defects that overlap with expected disease progression. We sought to determine whether B12 levels at the time of diagnosis in patients with Parkinson's disease (PD) differed from those in patients with other neurodegenerative disorders. Methods:We performed a cross-sectional analysis of B12 levels obtained around the time of diagnosis in patients with PD, Multiple System Atrophy (MSA), Dementia with Lewy Bodies (DLB), Alzheimer's disease (AD), Progressive Supranuclear Palsy (PSP), Frontotemporal Dementia (FTD), or Mild Cognitive Impairment (MCI). We also evaluated the rate of B12 decline in PD, AD, and MCI. Results:In multivariable analysis adjusted for age, sex, and B12 supplementation, we found that B12 levels were significantly lower at time of diagnosis in patients with PD than in patients with PSP, FTD, and DLB. In PD, AD, and MCI, the rate of B12 decline ranged from - 17 to - 47 pg/ml/year, much greater than that reported for the elderly population. Conclusions:Further studies are needed to determine whether comorbid B12 deficiency affects progression of these disorders
Experimental verification of an Oseen flow slender body theory
Consider uniform flow past four slender bodies with elliptical cross-section of
constant ellipticity along the length of 0, 0.125, 0.25 and 0.375, respectively, for each
body. Here, ellipticity is defined as the ratio of the semiminor axis of the ellipse to
the semimajor axis. The bodies have a pointed nose which gradually increases in
cross-section with a radius of curvature 419mm to a mid-section which then remains
constant up to a blunt end section with semimajor axis diameter 160 mm, the total
length of all bodies being 800 mm. The bodies are side-mounted within a low-speed
wind tunnel with an operational wind speed of the order 30ms−1. The side force (or
lift) is measured within an angle of attack range of −3◦ to 3◦ such that the body is
rotated about the major axis of the ellipse cross-section. The lift slope is determined
for each body, and how it varies with ellipticity. It is found that this variance follows
a straight line which steadily increases with increasing ellipticity. It is shown that
this result is predicted by a recently developed Oseen flow slender body theory, and
cannot be predicted by either inviscid flow slender body theory or viscous crossflow
theories based upon the Allen and Perkins method
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Evolutionary Signatures In The Formation Of Low-Mass Protostars. II. Toward Reconciling Models And Observations
A long-standing problem in low-mass star formation is the "luminosity problem," whereby protostars are underluminous compared to the accretion luminosity expected both from theoretical collapse calculations and arguments based on the minimum accretion rate necessary to form a star within the embedded phase duration. Motivated by this luminosity problem, we present a set of evolutionary models describing the collapse of low-mass, dense cores into protostars. We use as our starting point the evolutionary model following the inside-out collapse of a singular isothermal sphere as presented by Young & Evans. We calculate the radiative transfer of the collapsing core throughout the full duration of the collapse in two dimensions. From the resulting spectral energy distributions, we calculate standard observational signatures (L(bol), T(bol), L(bol)/L(smm)) to directly compare to observations. We incorporate several modifications and additions to the original Young & Evans model in an effort to better match observations with model predictions; we include (1) the opacity from scattering in the radiative transfer, (2) a circumstellar disk directly in the two-dimensional radiative transfer, (3) a two-dimensional envelope structure, taking into account the effects of rotation, (4) mass-loss and the opening of outflow cavities, and (5) a simple treatment of episodic mass accretion. We find that scattering, two-dimensional geometry, mass-loss, and outflow cavities all affect the model predictions, as expected, but none resolve the luminosity problem. On the other hand, we find that a cycle of episodic mass accretion similar to that predicted by recent theoretical work can resolve this problem and bring the model predictions into better agreement with observations. Standard assumptions about the interplay between mass accretion and mass loss in our model give star formation efficiencies consistent with recent observations that compare the core mass function and stellar initial mass function. Finally, the combination of outflow cavities and episodic mass accretion reduces the connection between observational class and physical stage to the point where neither of the two commonly used observational signatures (T(bol) and L(bol)/L(smm)) can be considered reliable indicators of physical stage.NASA 1224608, 1288664, 1288658, RSA 1377304, NNX 07-AJ72GNSF AST0607793UT Austin University Continuing FellowshipAstronom
A "Starless" Core that Isn't: Detection of a Source in the L1014 Dense Core with the Spitzer Space Telescope
We present observations of L1014, a dense core in the Cygnus region previously thought to be starless, but data from the Spitzer Space Telescope show the presence of an embedded source. We propose a model for this source that includes a cold core, heated by the interstellar radiation field, and a low-luminosity internal source. The low luminosity of the internal source suggests a substellar object. If L1014 is representative, other "starless" cores may turn out to harbor central sources
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