2,343 research outputs found
The Shape of LITTLE THINGS Dwarf Galaxies DDO 46 and DDO 168: Understanding the stellar and gas kinematics
We present the stellar and gas kinematics of DDO 46 and DDO 168 from the
LITTLE THINGS survey and determine their respective Vmax/sigma_z,0 values. We
used the KPNO's 4-meter telescope with the Echelle spectrograph as a long-slit
spectrograph. We acquired spectra of DDO 168 along four position angles by
placing the slit over the morphological major and minor axes and two
intermediate position angles. However, due to poor weather conditions during
our observing run for DDO 46, we were able to extract only one useful data
point from the morphological major axis. We determined a central stellar
velocity dispersion perpendicular to the disk, sigma_z,0, of 13.5+/-8 km/s for
DDO 46 and of 10.7+/-2.9 km/s for DDO 168. We then derived the
maximum rotation speed in both galaxies using the LITTLE THINGS HI data. We
separated bulk motions from non-circular motions using a double Gaussian
decomposition technique and applied a tilted-ring model to the bulk velocity
field. We corrected the observed HI rotation speeds for asymmetric drift and
found a maximum velocity, Vmax, of 77.4 +/- 3.7 and 67.4 +/- 4.0 km/s for DDO
46 and DDO 168, respectively. Thus, we derived a kinematic measure,
Vmax/sigma_z,0, of 5.7 +/- 0.6 for DDO 46 and 6.3 +/- 0.3 for DDO 168.
Comparing these values to ones determined for spiral galaxies, we find that DDO
46 and DDO 168 have Vmax/sigma_z,0 values indicative of thin disks, which is in
contrast to minor-to-major axis ratio studies
The Stellar and Gas Kinematics of the LITTLE THINGS Dwarf Irregular Galaxy NGC 1569
In order to understand the formation and evolution of dIm galaxies, one needs
to understand their three-dimensional structure. We present measurements of the
stellar velocity dispersion in NGC 1569, a nearby post-starburst dIm galaxy.
The stellar vertical velocity dispersion, , coupled with the
maximum rotational velocity derived from \ion{H}{1} observations, , gives a measure of how kinematically hot the galaxy is, and, therefore,
indicates its structure. We conclude that the stars in NGC 1569 are in a thick
disk with a = 2.4 0.7. In addition to the
structure, we analyze the ionized gas kinematics from \ion{O}{3} observations
along the morphological major axis. These data show evidence for outflow from
the inner starburst region and a potential expanding shell near supermassive
star cluster (SSC) A. When compared to the stellar kinematics, the velocity
dispersion of the stars increase in the region of SSC A supporting the
hypothesis of an expanding shell. The stellar kinematics closely follow the
motion of the gas. Analysis of high resolution \ion{H}{1} data clearly reveals
the presence of an \ion{H}{1} cloud that appears to be impacting the eastern
edge of NGC 1569. Also, an ultra-dense \ion{H}{1} cloud can be seen extending
to the west of the impacting \ion{H}{1} cloud. This dense cloud is likely the
remains of a dense \ion{H}{1} bridge that extended through what is now the
central starburst area. The impacting \ion{H}{1} cloud was the catalyst for the
starburst, thus turning the dense gas into stars over a short timescale,
1 Gyr. We performed a careful study of the spectral energy distribution using
infrared, optical, and ultraviolet photometry producing a state-of-the-art mass
model for the stellar disk. This mass modeling shows that stars dominate the
gravitational potential in the inner 1 kpc.Comment: 49 pages, 25 figures, accepted in A
Recommended from our members
Understanding the roles of mutations in the amyloid precursor protein in Alzheimer disease
Many models of disease progression in Alzheimer’s disease (AD) have been proposed to help guide experimental design and aid the interpretation of results. Models focussing on the genetic evidence include the amyloid cascade (ACH) and presenilin (PSH) hypotheses and the amyloid precursor protein (APP) matrix approach (AMA), of which the ACH has held a dominant position for over two decades. However, the ACH has never been fully accepted and has not yet delivered on its therapeutic promise. We review the ACH, PSH and AMA in relation to levels of APP proteolytic fragments reported from AD-associated mutations in APP. Different APP mutations have diverse effects on the levels of APP proteolytic fragments. This evidence is consistent with at least three disease pathways that can differ between familial and sporadic AD and two pathways associated with cerebral amyloid angiopathy. We cannot fully evaluate the ACH, PSH and AMA in relation to the effects of mutations in APP as the APP proteolytic system has not been investigated systematically. The confounding effects of sequence homology, complexity of competing cleavages and antibody cross reactivities all illustrate limitations in our understanding of the roles these fragments and the APP proteolytic system as a whole in normal aging and disease play. Current experimental design should be refined to generate clearer evidence, addressing both aging and complex disorders with standardised reporting formats. A more flexible theoretical framework capable of accommodating the complexity of the APP proteolytic system is required to integrate available evidence.CB and SH are supported by a National Institute of Health Research Senior Investigator award
Little Things
We present LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes,
The HI Nearby Galaxy Survey) that is aimed at determining what drives star
formation in dwarf galaxies. This is a multi-wavelength survey of 37 Dwarf
Irregular and 4 Blue Compact Dwarf galaxies that is centered around HI-line
data obtained with the National Radio Astronomy Observatory (NRAO) Very Large
Array (VLA). The HI-line data are characterized by high sensitivity (less than
1.1 mJy/beam per channel), high spectral resolution (less than or equal to 2.6
km/s), and high angular resolution (~6 arcseconds. The LITTLE THINGS sample
contains dwarf galaxies that are relatively nearby (less than or equal to 10.3
Mpc; 6 arcseconds is less than or equal to 300 pc), that were known to contain
atomic hydrogen, the fuel for star formation, and that cover a large range in
dwarf galactic properties. We describe our VLA data acquisition, calibration,
and mapping procedures, as well as HI map characteristics, and show channel
maps, moment maps, velocity-flux profiles, and surface gas density profiles. In
addition to the HI data we have GALEX UV and ground-based UBV and Halpha images
for most of the galaxies, and JHK images for some. Spitzer mid-IR images are
available for many of the galaxies as well. These data sets are available
on-line.Comment: In press in A
Asymmetric triplex metallohelices with high and selective activity against cancer cells
Small cationic amphiphilic α-helical peptides are emerging as agents for the treatment of cancer and infection, but they are costly and display unfavourable pharmacokinetics. Helical coordination complexes may offer a three-dimensional scaffold for the synthesis of mimetic architectures. However, the high symmetry and modest functionality of current systems offer little scope to tailor the structure to interact with specific biomolecular targets, or to create libraries for phenotypic screens. Here, we report the highly stereoselective asymmetric self-assembly of very stable, functionalized metallohelices. Their anti-parallel head-to-head-to-tail ‘triplex’ strand arrangement creates an amphipathic functional topology akin to that of the active sub-units of, for example, host-defence peptides and p53. The metallohelices display high, structure-dependent toxicity to the human colon carcinoma cell-line HCT116 p53++, causing dramatic changes in the cell cycle without DNA damage. They have lower toxicity to human breast adenocarcinoma cells (MDA-MB-468) and, most remarkably, they show no significant toxicity to the bacteria methicillin-resistant Staphylococcus aureus and Escherichia coli.
At a glanc
Predicting the Collapse of Pain Medicine Using the Economic Recession of 2008 as a Comparator: Lessons Remain Unlearned
Sayed E Wahezi,1 Corey W Hunter,2 Farshad M Ahadian,3 Charles E Argoff,4 Michael E Schatman5,6 1Department of Physical Medicine & Rehabilitation, Montefiore Medical Center, Bronx, NY, USA; 2Ainsworth Institute of Pain Management, New York, NY, USA; 3Department of Anesthesiology, Center for Pain and Palliative Medicine, University of California, San Diego Medical Center, San Diego, CA, USA; 4Department of Neurology, Albany Medical Center, Albany, NY, USA; 5Department of Anesthesiology, Perioperative Care and Pain Medicine, NYU Grossman School of Medicine, New York, NY, USA; 6Department of Population Health – Division of Medical Ethics, NYU Grossman School of Medicine, New York, NY, USACorrespondence: Sayed E Wahezi, Department of Physical Medicine and Rehabilitation, Montefiore Medical Center, 1250 Waters Place, Tower #2 8th Floor, Bronx, NY, 10461, USA, Tel +1 718-920-7246, Fax +1 929-263-3950, Email [email protected]: The last decade has seen a boom in pain medicine, basic science and interventional pain management. Concomitantly, there is a need to educate trainees, young attendings, and seasoned attendings on these innovations. There has been a growth in the number of societies that represent pain medicine physicians, each with its own philosophy and guiding principles. The variety of thought within pain management, within the various groups that practice this field, and amongst the societies which protect those missions inherently creates divergence and isolation within these different communities. There is the enormous opportunity for our field to grow, but we need the voices of all different specialties and sub-specialties which practice pain medicine to collectively design the future of our emerging field. The explosion of revolutionary percutaneous surgeries, medications, psychotherapy, and research and development in our field has outpaced the ability of payers to fully embrace them. There is an increased number of pain practitioners using novel therapies, postgraduate training programs do not adequately train users in these techniques thereby creating a potential for sub-optimal outcomes. In part, this is a reason why payers for many of our more novel treatments have decreased patient access or eliminated remuneration for some of them. We believe that society-based collaborative regulation of education, research, and treatment guidelines is needed to improve visibility for payers and end users who provide these treatments. Furthermore, postgraduate chronic pain fellowship education has been deemed by many to be insufficient to educate on all of the necessary requirements needed for the independent practice of pain medicine, especially the consummation of newer technologies. Here, we draw comparison with this tenuous stage in pain management history with the last United States recession to remind us of how poor institutional regulation and neglect for long-term growth hampers a community.Keywords: fellowship, training, futur
The effectiveness of public health interventions to reduce the health impact of climate change:a systematic review of systematic reviews
Climate change is likely to be one of the most important threats to public health in the coming years. Yet despite the large number of papers considering the health impact of climate change, few have considered what public health interventions may be of most value in reducing the disease burden. We aimed to evaluate the effectiveness of public health interventions to reduce the disease burden of high priority climate sensitive diseases
- …