1,221 research outputs found
Locating Planetesimal Belts in the Multiple-planet Systems HD 128311, HD 202206, HD 82943, and HR 8799
In addition to the Sun, six other stars are known to harbor multiple planets and debris disks: HD 69830, HD 38529, HD 128311, HD 202206, HD 82943, and HR 8799. In this paper, we set constraints on the location of the dust-producing planetesimals around the latter four systems. We use a radiative transfer model to analyze the spectral energy distributions of the dust disks (including two new Spitzer IRS spectra presented in this paper), and a dynamical model to assess the long-term stability of the planetesimals' orbits. As members of a small group of stars that show evidence of harboring a multiple planets and planetesimals, their study can help us learn about the diversity of planetary systems
Effect of Commonly Prescribed Liquid Medications on Streptococcus mutans Biofilm. An in vitro study
Objective: This study addressed the effect of pediatric liquid antibiotic medications on Streptococcus mutans UA159. These suspensions commonly contain sugars such as sucrose to make them more palatable for children. The study was designed to evaluate the effects of oral liquid antibiotics on Streptococcus mutans growth and biofilm formation. Study Design: A 24 hour culture of S. mutans was treated with various concentrations of liquid medications commonly prescribed to children for odontogenic or fungal infections– amoxicillin, penicillin VK, clindamycin, and nystatin. The study was conducted in sterile 96-well flat bottom microtiter plates. The minimum inhibitory and biofilm inhibitory concentrations (MIC/MBIC) of S. mutans were determined for each medication. S. mutans was cultured with and without the test drugs, the amount of total growth measured, the biofilms washed, fixed, and stained with crystal violet. The absorbance was determined to evaluate biofilm formation. Results: Higher concentrations of amoxicillin, penicillin VK and clindamycin had decreased biofilm and overall growth than the control. The MICs were 1:2,560 (1.95 ug/ml), 1:2,560 (1.95 ug/ml) and 1:40 (9.375 ug/ml), while the MBIC were 1:640 (7.8 ug/ml), 1:1,280 (3.9 ug/ml) and 1:20 (18.75 ug/ml), respectively. Lower concentrations provided increased biofilm and overall growth. Nystatin induced significantly more biofilm and overall growth than the control at all concentrations. Conclusion: At high concentrations, approximately at the levels expected to be present in the oral cavity of children, amoxicillin, penicillin, and clindamycin inhibited S. mutans biofilm and overall growth due to their antibiotic activity, while at lower concentrations the three antibiotics demonstrated an increase in biofilm and growth. The increase in S. mutans biofilm and overall growth is most likely attributed to the sugar content in the medications. Nystatin provided an increase in biofilm and growth at each concentration tested
The debris disk around gamma Doradus resolved with Herschel
We present observations of the debris disk around gamma Doradus, an F1V star,
from the Herschel Key Programme DEBRIS (Disc Emission via Bias-free
Reconnaissance in the Infrared/Submillimetre). The disk is well-resolved at 70,
100 and 160 micron, resolved along its major axis at 250 micron, detected but
not resolved at 350 micron, and confused with a background source at 500
micron. It is one of our best resolved targets and we find it to have a
radially broad dust distribution. The modelling of the resolved images cannot
distinguish between two configurations: an arrangement of a warm inner ring at
several AU (best-fit 4 AU) and a cool outer belt extending from ~55 to 400 AU
or an arrangement of two cool, narrow rings at ~70 AU and ~190 AU. This
suggests that any configuration between these two is also possible. Both models
have a total fractional luminosity of ~10^{-5} and are consistent with the disk
being aligned with the stellar equator. The inner edge of either possible
configuration suggests that the most likely region to find planets in this
system would be within ~55 AU of the star. A transient event is not needed to
explain the warm dust's fractional luminosity.Comment: 12 pages, 6 figures, accepted for publication in Ap
A prospective, longitudinal, observational cohort study examining how glaucoma affects quality of life and visually-related function over 4Â years: design and methodology
Effect of developmental stage of HSC and recipient on transplant outcomes
The first hematopoietic stem cells (HSCs) that engraft irradiated adult mice arise in the aorta-gonad-mesonephros (AGM) on embryonic day 11.5 (E11.5). However, at this stage, there is a discrepancy between the apparent frequency of HSCs depicted with imaging and their rarity when measured with limiting dilution transplant. We have attempted to reconcile this difference using neonatal recipients, which are more permissive for embryonic HSC engraftment. We found that embryonic HSCs from E9.5 and E10.5 preferentially engrafted neonates, whereas developmentally mature, definitive HSCs from E14.5 fetal liver or adult bone marrow (BM) more robustly engrafted adults. Neonatal engraftment was enhanced after treating adult BM-derived HSCs with interferon. Adult BM-derived HSCs preferentially homed to the liver in neonatal mice yet showed balanced homing to the liver and spleen in adults. These findings emphasize the functional differences between nascent and mature definitive HSCs
A KRAS GTPase K104Q Mutant Retains Downstream Signaling by Offsetting Defects in Regulation
The KRAS GTPase plays a critical role in the control of cellular growth. The activity of KRAS is regulated by guanine nucleotide exchange factors (GEFs), GTPase-activating proteins (GAPs), and also post-translational modification. Lysine 104 in KRAS can be modified by ubiquitylation and acetylation, but the role of this residue in intrinsic KRAS function has not been well characterized. We find that lysine 104 is important for GEF recognition, because mutations at this position impaired GEF-mediated nucleotide exchange. Because the KRAS K104Q mutant has recently been employed as an acetylation mimetic, we conducted a series of studies to evaluate its in vitro and cell-based properties. Herein, we found that KRAS K104Q exhibited defects in both GEF-mediated exchange and GAP-mediated GTP hydrolysis, consistent with NMR-detected structural perturbations in localized regions of KRAS important for recognition of these regulatory proteins. Despite the partial defect in both GEF and GAP regulation, KRAS K104Q did not alter steady-state GTP-bound levels or the ability of the oncogenic KRAS G12V mutant to cause morphologic transformation of NIH 3T3 mouse fibroblasts and of WT KRAS to rescue the growth defect of mouse embryonic fibroblasts deficient in all Ras genes. We conclude that the KRAS K104Q mutant retains both WT and mutant KRAS function, probably due to offsetting defects in recognition of factors that up-regulate (GEF) and down-regulate (GAP) RAS activity
Subcellular dynamics and functional activity of the cleaved intracellular domain of the Na+ channel β1 subunit
Case 2--1994 management of a cardiac pheochromocytoma in two patients
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31664/1/0000599.pd
Transforming Environmental Water Management to Adapt to a Changing Climate
Environmental water management has become a global imperative in response to environmental degradation and the growing recognition that human well-being and livelihoods are critically dependent on freshwater ecosystems and the ecological functions and services they provide. Although a wide range of techniques and strategies for planning and implementing environmental flows has developed, many remain based on assumptions of hydrologic stationarity, typically focusing on restoring freshwater ecosystems to pre-development or “natural” conditions. Climate change raises major challenges to this conventional approach, in part because of increasing uncertainties in patterns of water supply and demand. In such a rapidly changing world, the implementation of, and capacity of water managers to deliver flow regimes resembling historical hydrological patterns may be both unfeasible and undesirable. Additionally, as emphasis shifts from species-focused water allocation plans toward a greater appreciation of freshwater ecological functions and services, many of which will be influenced by climate change, a thorough re-evaluation of the conventional objectives, planning, delivery and monitoring of environmental water, including its role in the broader context of water and environmental management, is essential. Here, we identify the major challenges posed by climate change to environmental water management and discuss key adaptations and research needed to meet these challenges to achieve environmental and societal benefits and avoid maladaptation
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