95 research outputs found
The Polariscope balloon-borne servo system
Polariscope balloon-borne servo syste
Multicolor Polarimetry of Selected Be Stars: 1995-98
A new polarimeter called AnyPol has been used at Limber Observatory for four
years to annually monitor the broadband linear polarization of a sample of
bright northern Be stars. This is the fourth report on a program started in
1985 at McDonald Observatory and the first one to come entirely from the new
installation. Although no variability was detected at the 3-sigma level during
the current reporting period, analysis of the full 13-year data set is
beginning to reveal hints of long-term variability that may provide clues for
understanding the Be phenomenon.Comment: 25 pages including 17 tables; 17 figures; aaspp4 style; accepted by
PAS
Spectropolarimetry of the Luminous Narrow-Line Seyfert Galaxies IRAS 20181-2244 and IRAS 13224-3809
We observed the narrow-line Seyfert 1 galaxies IRAS 20181-2244 and IRAS
13324-3809 with a new spectropolarimeter on the RC spectrograph at the CTIO 4m
telescope. Previously it had been suggested that IRAS 20181-2244 was a Type 2
QSO and thus might contain an obscured broad-line region which could be
detected by the presence of broad Balmer lines in the polarized flux. We found
the object to be polarized at about 2%, and constant with wavelength, (unlike
most narrow-line Seyfert 1s), but with no evidence of broad Balmer lines in
polarized flux. The spectropolarimetry indicates that the scattering material
is inside the BLR. IRAS 13224-3809, notable for its high variability in X-ray
and UV wavelengths, has a low polarization consistent with a Galactic
interstellar origin.Comment: 19 pages using (AASTEX) aaspp4.sty and 5 postscript figures To be
published in the Astrophysical Journa
Dust in the Small Magellanic Cloud: Interstellar Polarization and Extinction
To elucidate the dust properties in the SMC we have for the first time
measured linear polarization in five colors in the optical region of the
spectrum for a sample of reddened stars. For two of these stars, for which
there were no existing UV spectrophotometric measurements, but for which we
measured a relatively large polarization, we have also obtained data from the
International Ultraviolet Explorer (IUE) in order to study the extinction. The
main results are: (1) the wavelength of maximum polarization, ,
in the SMC is typically smaller than that in the Galaxy; (2) however, AZV 456,
which shows the UV extinction bump, has a typical of that in
the Galaxy, its polarization curve is narrower, its bump is shifted to shorter
wavelengths as compared to the Galaxy and its UV extinction does not conform to
the Galactic analytical interpolation curve based on the ratio of total to
selective extinction; (3) the 'typical', monotonic SMC extinction curve can be
best fit with amorphous carbon and silicate grains; (4) the extinction towards
AZV456 may only be explained by assuming a larger gas-to-dust ratio than the
observed N(HI)/A(V) value, with a small amount of the available carbon in
graphite form; (5) from an analysis of both the extinction and polarization
data and our model fits it appears that the SMC has typically smaller grains
than those in the Galaxy.Comment: To appear in the ApJ, 50 pages, latex fil
Environmental risk factors for dementia: a systematic review
Background - Dementia risk reduction is a major and growing public health priority. While certain modifiable risk factors for dementia have been identified, there remains a substantial proportion of unexplained risk. There is evidence that environmental risk factors may explain some of this risk. Thus, we present the first comprehensive systematic review of environmental risk factors for dementia.
Methods - We searched the PubMed and Web of Science databases from their inception to January 2016, bibliographies of review articles, and articles related to publically available environmental data. Articles were included if they examined the association between an environmental risk factor and dementia. Studies with another outcome (for example, cognition), a physiological measure of the exposure, case studies, animal studies, and studies of nutrition were excluded. Data were extracted from individual studies which were, in turn, appraised for methodological quality. The strength and consistency of the overall evidence for each risk factor identified was assessed.
Results - We screened 4784 studies and included 60 in the review. Risk factors were considered in six categories: air quality, toxic heavy metals, other metals, other trace elements, occupational-related exposures, and miscellaneous environmental factors. Few studies took a life course approach. There is at least moderate evidence implicating the following risk factors: air pollution; aluminium; silicon; selenium; pesticides; vitamin D deficiency; and electric and magnetic fields.
Conclusions - Studies varied widely in size and quality and therefore we must be circumspect in our conclusions. Nevertheless, this extensive review suggests that future research could focus on a short list of environmental risk factors for dementia. Furthermore, further robust, longitudinal studies with repeated measures of environmental exposures are required to confirm these associations
Working with Commercially Available Quantum Dots for Immunofluorescence on Tissue Sections
Quantum dots are semiconductor fluorescent nanocrystals that exhibit excellent characteristics compared with more commonly used organic fluorescent dyes. For many years quantum dot conjugated products have been available in multiple forms for fluorescence imaging of tissue sections under the trademark name Qdot®. They have much increased brightness, narrow emission spectrum, large Stokes shift and photostability compared with conventional organic fluorescent dyes, which together make them the fluorophores of choice for demanding requirements. Vivid Qdots are recent replacements for original Qdots, modified to improve brightness, however this has affected the fluorescence stability in commonly used conditions for immunohistochemistry. We present here our investigation of the stability of original and Vivid Qdots in solution and in immunohistochemistry, highlight the potential pitfalls and propose a protocol for stable and reliable multiplex staining with current commercially available original and Vivid Qdots
Design of compliant joints for large scale structures
Large scale structures can benefit from the design of compliant joints that can provide flexibility and adaptability. A high level of deformation is achieved locally with the design of flexures in compliant mechanisms. Additionally, by introducing contact-aided compliant mechanisms, nonlinear bending stiffness is achieved to make the joints flexible in one direction and stiff in the opposite one. All these concepts have been explored in small scale engineering design, but they have not been applied to large scale structures. In this paper the design of a large scale compliant mechanism is proposed for novel design of a foldable shipping container. The superelasticity of nickel titanium is shown to be beneficial in designing the joints of the compliant mechanism.</p
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