2,727 research outputs found
Cationic Porphyrins with Large Side Arm Substituents as Resonance Light Scattering Ratiometric Probes for Specific Recognition of Nucleic Acid G-quadruplexes
Specific G-quadruplex-probing is crucial for both biological sciences and biosensing applications. Most reported probes are focused on fluorescent or colorimetric recognition of G-quadruplexes. Herein, for the first time, we reported a new specific G-quadruplex-probing technique—resonance light scattering (RLS)-based ratiometric recognition. To achieve the RLS probing of G-quadruplexes in the important physiological pH range of 7.4-6.0, four water soluble cationic porphyrin derivatives, including an unreported octa-cationic porphyrin, with large side arm substituents were synthesized and developed as RLS probes. These RLS probes were demonstrated to work well for ratiometric recognition of G-quadruplexes with high specificity against single- and double-stranded DNAs, including long double-stranded ones. The working mechanism was speculated to be based on the RLS signal changes caused by porphyrin protonation that was promoted by the end-stacking of porphyrins on Gquadruplexes. This work adds an important member in G-quadruplex probe family, thus providing a useful tool for studies on G-quadruplex-related events concerning G-quadruplex formation, destruction and changes in size, shape and aggregation. As a proofof-concept example of applications, the RLS probes were demonstrated to work well for label-free and sequence-specific sensing of microRNA. This work also provides a simple and useful way for the preparation of cationic porphyrins with high charges
The impact of hospital attributes on patient choice for first visit
The underutilization of primary care in urban China threatens the efficiency and effectiveness of
the Chinese health system. To guide patient flow to primary care, the Chinese government has
rolled out a sequence of health care reforms which improve the affordability, the infrastructure and
workforce of the primary care system. However, these measures have not yielded the desired effect
on the utilization of primary care, which is lowest in urban areas. It is unclear how the factors
identified to influence facility choice in urban China are actually impacting choice behaviour. We
conducted a discrete choice experiment to elicit the quantitative impact of facility attributes when
choosing a health care facility for first visit and analysed how the stated choice varies with these
attributes. We found that the respondents placed different weights on the identified attributes, depending
on whether they perceived their condition to be minor or severe. For conditions perceived
as minor, the respondents valued visit time, equipment and medical skill most. For conditions perceived
as severe, they placed most importance on equipment, travel time and facility size.
We found that for conditions perceived as minor, only 14% preferred visiting a facility over opting
out, a percentage which would more than double to 37% if community health centres were maximally
improved. For conditions perceived as severe, improvements in community health centres
may almost double first visits to primary care, mostly from patients who would otherwise choose
higher-level facilities. Our findings suggest that for both severity conditions, improvements to medical
equipment and medical skill at community health centres in urban China can effectively direct patient
flow to primary care and promote the efficiency and effectiveness of the urban health system
Public preferences for health care facilities in rural China: A discrete choice experiment
To successfully tackle the problems with the underutilization of primary care in rural China, it is important to align resource allocation with the preferences of the rural population. However, despite growing interest in the factors influencing the rural population's choice of facility, it is unclear how much weight should be placed on these factors, especially under different scenarios of disease severity. In the first study to elicit quantified trade-offs among influential factors in choosing health care facilities, we carried out a discrete choice experiment (DCE) in rural China. We used a Bayesian efficient design to construct 36 choice sets, and then divided them into three blocks. Each block formed one version of questionnaire that contained 12 choice questions. Each question was assigned a hypothetical perceived severity scenario of either minor or severe disease. 559 Rural residents completed the DCE through face-to-face interviews in December 2017–March 2018. We used mixed logit models to analyze the choice data. The factors regarding the availability and affordability of a facility, such as visit time, travel time, and out-of-pocket cost, were highly valued. When the facilities changed simultaneously from the worst to the best case, a huge increase (from 4.8% to 66.5%) in the predicted choice probability of choosing to visit a facility was observed under perceived minor disease scenario, whereas there was no significant change under perceived severe disease scenario. Improvements to drug availability, medical professional skill and equipment in rural primary care system can induce potential medical care seeking, and redirect patient flow from higher level hospitals to primary level. Especially, township health centers, which provide service to the residents in rural communities, have great potential to be the ideal facilities for first-contact care
Wide-field HST/ACS images of M81: The Population of Compact Star Clusters
We study the population of compact stellar clusters (CSCs) in M81, using the
HST/ACS images in the filters F435W, F606W and F814W covering, for the first
time, the entire optical extent of the galaxy. Our sample contains 435 clusters
of FWHM less than 10 ACS pixels (9 pc). The sample shows the presence of two
cluster populations, a blue group of 263 objects brighter than B=22 mag, and a
red group of 172 objects, brighter than B=24 mag. Based on the analysis of
colour magnitude diagrams and making use of simple stellar population models,
we find the blue clusters are younger than 300 Myr with some clusters as young
as few Myr, and the red clusters are as old as globular clusters. The
luminosity function of the blue group follows a power-law distribution with an
index of 2.0, typical value for young CSCs in other galaxies. The power-law
shows unmistakable signs of truncation at I=18.0 mag (M_I=-9.8 mag), which
would correspond to a mass-limit of 4x10^4 M_solar if the brightest clusters
are younger than 10 Myr. The red clusters have photometric masses between 10^5
to 2x10^7 M_solar for the adopted age of 5 Gyr and their luminosity function
resembles very much the globular cluster luminosity function in the Milky Way.
The brightest GC in M81 has M_B^0=-10.3 mag, which is ~0.9 mag brighter than
w-Cen, the most massive GC in the Milky Way.Comment: Accepted by MNRAS. The paper contains 10 figures and 3 tables. Table
3 will be published in full online onl
An Oxygen Abundance Gradient into the Outer Disk of M81
The extended HI disk and tidal tails of M81 present an interesting
environment to study the effects of galaxy interaction on star formation and
chemical evolution of the outer disk of a large spiral galaxy. We present
H{\alpha} imaging of the outer disk of M81 and luminosities for 40 HII regions
out to about 3 times the optical radius. We have also obtained MMT spectra for
21 HII regions out to more than twice the optical radius. We derive strong line
oxygen abundances for all HII regions using R_{23} based and [NII]/[OII] based
calibrations and electron temperature abundances for seven regions spanning a
galactocentric distance between 5.7 and 32 kpc. We also comment on the
abundances of HII regions near KDG 61 and the "tidal dwarf" candidate HoIX. Our
results constitute the most radially extended metallicity study for M81 to
date. With this extended data set, we find an overall oxygen abundance gradient
of -0.013 dex/kpc over the entire radial range. This is significantly flatter
than what has been found in previous studies which were limited to the optical
disk. From our temperature based abundances, we find a gradient of -0.020
dex/kpc and present the possibility of a broken gradient from these data, but
note the need to obtain more temperature based abundances at intermediate
galactocentric distances (~10-20 kpc) to verify whether or not this may be the
case. We discuss our main result of a rather flat gradient for M81 in the
context of simulations and observations of abundance gradients in other
galaxies. We find that the shallow abundance gradient of M81 is likely a result
of the interaction history of this galaxy.Comment: 41 pages, 11 figures, accepted for publication in MNRA
Spectroscopic study of blue compact galaxies IV. Star formation rates and gas depletion timescales
This is the fourth paper in a series studying star formation rates, stellar
components, metallicities, and star formation histories of a blue compact
galaxy (BCG) sample. Using Ha, [OII]3727, IR, radio (1.4GHz) luminosities and
neutral hydrogen gas masses, we estimated star formation rates(SFR) and gas
depletion timescales of 72 star-forming BCGs. The SFRs of the BCGs in our
sample span nearly four orders of magnitude, from approximately 10^-2 to
10^2M_sun/yr, with a median SFR of about 3M_sun/yr. The typical gas depletion
timescale of BCGs is about one billion years.
We found that subtracting underlying stellar absorption is very important to
calculate both dust extinction and SFR of galaxies. Otherwise, the intrinsic
extinction will be overestimated, the SFRs derived from [OII] and Ha will be
underestimated (if the underlying stellar absorption and the internal
extinction were not corrected from the observed luminosity) or overestimated
(if an overestimated internal extinction were used for extinction correction).
After both the underlying stellar absorption and the dust extinction were
corrected, a remarkably good correlation emerges among Ha, [OII], IR and radio
SFR indicators. Finally, we find a good correlation between the measured SFR
and the absolute blue magnitude, metallicity, interstellar extinction of BCGs.
Our results indicate that faint, low-mass BCGs have lower star formation rates.Comment: 11 pages, 9 figures, be published in Astronomy and Astrophysics,
v.425, p.417-427 (2004
Extending PLE models into the mid-IR, far-IR & sub-mm
Simple pure luminosity evolution (PLE) models, in which galaxies brighten at
high redshift due to increased star-formation rates (SFRs), are known to
provide a good fit to the colours and number counts of galaxies throughout the
optical and near-infrared. We show that optically defined PLE models, where
dust reradiates absorbed optical light into infrared spectra composed of local
galaxy templates, fit galaxy counts and colours out to 8um and to at least
z=2.5. At 24-70um, the model is able to reproduce the observed source counts
with reasonable success if 16% of spiral galaxies show an excess in mid-IR flux
due to a warmer dust component and a higher SFR, in line with observations of
local starburst galaxies. There remains an under-prediction of the number of
faint-flux, high-z sources at 24um, so we explore how the evolution may be
altered to correct this. At 160um and longer wavelengths, the model fails, with
our model of normal galaxies accounting for only a few percent of sources in
these bands. However, we show that a PLE model of obscured AGN, which we have
previously shown to give a good fit to observations at 850um, also provides a
reasonable fit to the Herschel/BLAST number counts and redshift distributions
at 250-500um. In the context of a LCDM cosmology, an AGN contribution at
250-870um would remove the need to invoke a top-heavy IMF for high-redshift
starburst galaxies, although the excellent fit of the galaxy PLE model at
shorter wavelengths would still need to be explained.Comment: 14 pages, 11 figures; submitted to MNRA
An overview of the first 5 years of the ENIGMA obsessive–compulsive disorder working group: The power of worldwide collaboration
Abstract Neuroimaging has played an important part in advancing our understanding of the neurobiology of obsessive?compulsive disorder (OCD). At the same time, neuroimaging studies of OCD have had notable limitations, including reliance on relatively small samples. International collaborative efforts to increase statistical power by combining samples from across sites have been bolstered by the ENIGMA consortium; this provides specific technical expertise for conducting multi-site analyses, as well as access to a collaborative community of neuroimaging scientists. In this article, we outline the background to, development of, and initial findings from ENIGMA's OCD working group, which currently consists of 47 samples from 34 institutes in 15 countries on 5 continents, with a total sample of 2,323 OCD patients and 2,325 healthy controls. Initial work has focused on studies of cortical thickness and subcortical volumes, structural connectivity, and brain lateralization in children, adolescents and adults with OCD, also including the study on the commonalities and distinctions across different neurodevelopment disorders. Additional work is ongoing, employing machine learning techniques. Findings to date have contributed to the development of neurobiological models of OCD, have provided an important model of global scientific collaboration, and have had a number of clinical implications. Importantly, our work has shed new light on questions about whether structural and functional alterations found in OCD reflect neurodevelopmental changes, effects of the disease process, or medication impacts. We conclude with a summary of ongoing work by ENIGMA-OCD, and a consideration of future directions for neuroimaging research on OCD within and beyond ENIGMA
ACCESS III: The Nature of Star Formation in the Shapley Supercluster
We present a joint analysis of panoramic Spitzer/MIPS mid-infrared and GALEX
ultraviolet imaging of the Shapley supercluster at z=0.048. Combining this with
spectra of 814 supercluster members and 1.4GHz radio continuum maps, this
represents the largest complete census of star-formation (both obscured and
unobscured) in local cluster galaxies to date, reaching SFRs~0.02Msun/yr. We
take advantage of this comprehensive panchromatic dataset to perform a detailed
analysis of the nature of star formation in cluster galaxies, using several
quite independent diagnostics of the quantity and intensity of star formation
to develop a coherent view of the types of star formation within cluster
galaxies. We observe a robust bimodality in the infrared (f_24/f_K) galaxy
colours, which we are able to identify as another manifestation of the broad
split into star-forming spiral and passive elliptical galaxy populations seen
in UV-optical surveys. This diagnostic also allows the identification of
galaxies in the process of having their star formation quenched as the infrared
analogue to the UV "green valley" population. The bulk of supercluster galaxies
on the star-forming sequence have specific-SFRs consistent with local field
specific-SFR-M* relations, and form a tight FIR-radio correlation confirming
that their FIR emission is due to star formation. We show that 85% of the
global SFR is quiescent star formation within spiral disks, as manifest by the
observed sequence in the IRX-beta relation being significantly offset from the
starburst relation of Kong et al. (2004), while their FIR-radio colours
indicate dust heated by low-intensity star formation. Just 15% of the global
SFR is due to nuclear starbursts. The vast majority of star formation seen in
cluster galaxies comes from normal infalling spirals who have yet to be
affected by the cluster environment.Comment: 17 pages, 9 figures. Accepted for publication in MNRA
Resolving the Stellar Outskirts of M81: Evidence for a Faint, Extended Structural Component
We present a wide field census of resolved stellar populations in the
northern half of M81, conducted with Suprime-Cam on the 8-m Subaru telescope
and covering an area ~ 0.3 square degrees. The resulting color-magnitude
diagram reaches over one magnitude below the red giant branch (RGB) tip,
allowing a detailed comparison between the young and old stellar spatial
distributions. The surface density of stars with ages <~ 100 Myr is correlated
with that of neutral hydrogen in a manner similar to the disk-averaged
Kennicutt-Schmidt relation. We trace this correlation down to gas densities of
~ 2 x 10^20 cm^{-2}, lower than typically probed with H-alpha flux. Both
diffuse light and resolved RGB star counts show compelling evidence for a
faint, extended structural component beyond the bright optical disk, with a
much flatter surface brightness profile. The star counts allow us to probe this
component to significantly fainter levels than is possible with the diffuse
light alone. From the colors of its RGB stars, we estimate this component has a
peak global metallicity [M/H] ~ -1.1 +/- 0.3 at deprojected radii 32 - 44 kpc
assuming an age of 10 Gyr and distance of 3.6 Mpc. The spatial distribution of
its RGB stars follows a power-law surface density profile, I(r) ~ r^{-gamma},
with gamma ~ 2. [Abridged]Comment: 17 pages including 2 tables and 20 figures, accepted to AJ, version
with high resolution figures available at
http://www.roe.ac.uk/~mkb/astroph/m81hires.pd
- …