4,477 research outputs found
Uncovering Cryptic Parasitoid Diversity in Horismenus (Chalcidoidea, Eulophidae)
The file attached is the Published/publisher’s pdf version of the article.© 2015 Kenyon et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
The TAOS Project: Upper Bounds on the Population of Small KBOs and Tests of Models of Formation and Evolution of the Outer Solar System
We have analyzed the first 3.75 years of data from TAOS, the Taiwanese
American Occultation Survey. TAOS monitors bright stars to search for
occultations by Kuiper Belt Objects (KBOs). This dataset comprises 5e5
star-hours of multi-telescope photometric data taken at 4 or 5 Hz. No events
consistent with KBO occultations were found in this dataset. We compute the
number of events expected for the Kuiper Belt formation and evolution models of
Pan & Sari (2005), Kenyon & Bromley (2004), Benavidez & Campo Bagatin (2009),
and Fraser (2009). A comparison with the upper limits we derive from our data
constrains the parameter space of these models. This is the first detailed
comparison of models of the KBO size distribution with data from an occultation
survey. Our results suggest that the KBO population is comprised of objects
with low internal strength and that planetary migration played a role in the
shaping of the size distribution.Comment: 18 pages, 16 figures, Aj submitte
The Stellar-Disk Electric (Short) Circuit: Observational Predictions for a YSO Jet Flow
We discuss the star-disk electric circuit for a young stellar object (YSO)
and calculate the expected torques on the star and the disk. We obtain the same
disk magnetic field and star-disk torques as given by standard
magnetohydrodynamic (MHD) analysis. We show how a short circuit in the
star-disk electric circuit may produce a magnetically-driven jet flow from the
inner edge of a disk surrounding a young star.
An unsteady bipolar jet flow is produced that flows perpendicular to the disk
plane. Jet speeds of order hundreds of kilometres per second are possible,
while the outflow mass loss rate is proportional to the mass accretion rate and
is a function of the disk inner radius relative to the disk co-rotation radius.Comment: 6 pages, 8 figures, Accepted for publication in Astrophysics & Space
Scienc
Random on-board pixel sampling (ROPS) X-ray Camera
Recent advances in compressed sensing theory and algorithms offer new
possibilities for high-speed X-ray camera design. In many CMOS cameras, each
pixel has an independent on-board circuit that includes an amplifier, noise
rejection, signal shaper, an analog-to-digital converter (ADC), and optional
in-pixel storage. When X-ray images are sparse, i.e., when one of the following
cases is true: (a.) The number of pixels with true X-ray hits is much smaller
than the total number of pixels; (b.) The X-ray information is redundant; or
(c.) Some prior knowledge about the X-ray images exists, sparse sampling may be
allowed. Here we first illustrate the feasibility of random on-board pixel
sampling (ROPS) using an existing set of X-ray images, followed by a discussion
about signal to noise as a function of pixel size. Next, we describe a possible
circuit architecture to achieve random pixel access and in-pixel storage. The
combination of a multilayer architecture, sparse on-chip sampling, and
computational image techniques, is expected to facilitate the development and
applications of high-speed X-ray camera technology.Comment: 9 pages, 6 figures, Presented in 19th iWoRI
Vacancy localization in the square dimer model
We study the classical dimer model on a square lattice with a single vacancy
by developing a graph-theoretic classification of the set of all configurations
which extends the spanning tree formulation of close-packed dimers. With this
formalism, we can address the question of the possible motion of the vacancy
induced by dimer slidings. We find a probability 57/4-10Sqrt[2] for the vacancy
to be strictly jammed in an infinite system. More generally, the size
distribution of the domain accessible to the vacancy is characterized by a
power law decay with exponent 9/8. On a finite system, the probability that a
vacancy in the bulk can reach the boundary falls off as a power law of the
system size with exponent 1/4. The resultant weak localization of vacancies
still allows for unbounded diffusion, characterized by a diffusion exponent
that we relate to that of diffusion on spanning trees. We also implement
numerical simulations of the model with both free and periodic boundary
conditions.Comment: 35 pages, 24 figures. Improved version with one added figure (figure
9), a shift s->s+1 in the definition of the tree size, and minor correction
Resident Corneal Cells Communicate with Neutrophils Leading to the Production of IP-10 during the Primary Inflammatory Response to HSV-1 Infection
In this study we show that murine and human neutrophils are capable of secreting IP-10 in response to communication from the HSV-1 infected cornea and that they do so in a time frame associated with the recruitment of CD8+ T cells and CXCR3-expressing cells. Cellular markers were used to establish that neutrophil influx corresponded in time to peak IP-10 production, and cellular depletion confirmed neutrophils to be a significant source of IP-10 during HSV-1 corneal infection in mice. A novel ex vivo model for human corneal tissue infection with HSV-1 was used to confirm that cells resident in the cornea are also capable of stimulating neutrophils to secrete IP-10. Our results support the hypothesis that neutrophils play a key role in T-cell recruitment and control of viral replication during HSV-1 corneal infection through the production of the T-cell recruiting chemokine IP-10
Pretransplant Immune Parameters Associate With Islet Allograft Outcome: Implications for Transplant Strategy?
Collisional Cascades in Planetesimal Disks II. Embedded Planets
We use a multiannulus planetesimal accretion code to investigate the growth
of icy planets in the outer regions of a planetesimal disk. In a quiescent
minimum mass solar nebula, icy planets grow to sizes of 1000--3000 km on a
timescale t = 15-20 Myr (a/30 AU)^3 where a is the distance from the central
star. Planets form faster in more massive nebulae. Newly-formed planets stir up
leftover planetesimals along their orbits and produce a collisional cascade
where icy planetesimals are slowly ground to dust.
The dusty debris of planet formation has physical characteristics similar to
those observed in beta Pic, HR 4796A, and other debris disks. We derive dust
masses for small particles, 1 mm and smaller, and large particles, 1 mm and
larger, as a function of the initial conditions in the planetesimal disk. The
dust luminosities derived from these masses are similar to those observed in
Vega, HR 4796A, and other debris disks. The calculations produce bright rings
and dark gaps. Bright rings occur where 1000 km and larger planets have
recently formed. Dark gaps are regions where planets have cleared out dust or
shadows where planets have yet to form.Comment: to be published in the Astronomical Journal, January 2004; 7 pages of
text; 17 figures at
http://cfa-www.harvard.edu/~kenyon/pf/emb-planet-figures.pdf; 2 animations at
http://cfa-www.harvard.edu/~kenyon/pf/emb-planet-movies.htm
Improving the Care Pathway for Women who Request Caesarean Section: An Experience-Based Co-Design Study
Background
Maternal request for Caesarean section is controversial and yet the NICE Caesarean section Guideline recommends that that if this is requested, following discussion of the risks and benefits, women should be supported in their choice. There was a desire to improve the pathway at Birmingham Women’s NHS Foundation Trust.
Methods
Experience-based co-design methodology uses service user and clinicians experiences collected using qualitative methods to jointly re-design services. Firstly semi-structured interviews were conducted to elicit the views and experiences of health care professionals and women who requested Caesarean section (with and without medical indication). Analysis identified key themes arising from the health care professionals’ interviews and ‘touch points’ (key moments or events related to the experience of care) arising from the interviews with women.. Separate workshops were then held with each group to ensure these resonated and to identify key areas for service improvement. At the first joint workshop a pathway using ‘audio clips’ demonstrating women’s agreed ‘touch points’ prompted discussion and joint working began to change the pathway. A final second workshop was held to agree changes to the pathway.
Results
Interviews were conducted with health care professionals (n = 22, 10 consultant obstetricians and 12 midwives) and women (n = 15). The women’s ‘touch points’ included repetition of request, delay in the decision for Caesarean section to be made, feeling judged, and that information was poor with similar findings identified from the health care professionals. Joint working resulted in a revised pathway for women who request Caesarean section.
Changes to the pathway for women as a result of the work include written information about ‘The way your baby may be born’ which is given to the woman followed by a discussion about mode of birth around the 16 week appointment. If the woman wishes to have a Caesarean section, referral is made to appropriate health care professionals (e.g., Consultant Midwife, counsellor) only if support and information would be useful. If Caesarean section is requested, woman is referred to a consultant obstetrician for an appointment at 20/40, with a decision by 28/40. Recording this in the notes minimises repeated challenge described by women. Final consent and timing of Caesarean section remain as recommended.
Conclusion
This has resulted in changes to the pathway agreed by a co-design process and which are acceptable to both health care professionals and women. Use of such methodologies should be considered more frequently when implementing service change
Constraints on the disk geometry of the T Tauri star AA Tau from linear polarimetry
We have simultaneously monitored the photometric and polarimetric variations
of the Classical T Tauri star AA Tau during the fall of 2002. We combine these
data with previously published polarimetric data covering two earlier epochs.
The phase coverage is complete, although not contiguous. AA Tau clearly shows
cyclic variations coupled with the rotation of the system. The star-disk system
produces a repeatable polarisation curve where the polarisation increases with
decreasing brightness. The data fit well with the model put forward by Bouvier
et al. (1999) where AA Tau is viewed almost edge-on and its disk is actively
dumping material onto the central star via magnetospheric accretion. The inner
edge of the disk is deformed by its interaction with the tilted magnetosphere,
producing eclipses as it rotates and occults the photosphere periodically. From
the shape of the polarisation curve in the QU-Plane we confirm that the
accretion disk is seen at a large inclination, almost edge-on, and predict that
its position angle is PA~90 deg., i.e., that the disk's major axis is oriented
in the East-West direction.Comment: Astron. Astrophys., in pres
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