1,230 research outputs found
Protoplanetary and Transitional Disks in the Open Stellar Cluster IC 2395
We present new deep UBVRI images and high-resolution multi-object optical
spectroscopy of the young (~ 6 - 10 Myr old), relatively nearby (800 pc) open
cluster IC 2395. We identify nearly 300 cluster members and use the photometry
to estimate their spectral types, which extend from early B to middle M. We
also present an infrared imaging survey of the central region using the IRAC
and MIPS instruments on board the Spitzer Space Telescope, covering the
wavelength range from 3.6 to 24 microns. Our infrared observations allow us to
detect dust in circumstellar disks originating over a typical range of radii ~
0.1 to ~ 10AU from the central star. We identify 18 Class II, 8 transitional
disk, and 23 debris disk candidates, respectively 6.5%, 2.9%, and 8.3% of the
cluster members with appropriate data. We apply the same criteria for
transitional disk identification to 19 other stellar clusters and associations
spanning ages from ~ 1 to ~ 18 Myr. We find that the number of disks in the
transitional phase as a fraction of the total with strong 24 micron excesses
([8] - [24] > 1.5) increases from 8.4 +\- 1.3% at ~ 3 Myr to 46 +\- 5% at ~ 10
Myr. Alternative definitions of transitional disks will yield different
percentages but should show the same trend.Comment: accepted by the Astrophysical Journa
Cyclophosphamide-Induced Cystitis Increases Bladder CXCR4 Expression and CXCR4-Macrophage Migration Inhibitory Factor Association
BACKGROUND: Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine involved in cystitis and a non-cognate ligand of the chemokine receptor CXCR4 in vitro. We studied whether CXCR4-MIF associations occur in rat bladder and the effect of experimental cystitis. METHODS AND FINDINGS: Twenty male rats received saline or cyclophosphamide (40 mg/kg; i.p.; every 3(rd) day) to induce persistent cystitis. After eight days, urine was collected and bladders excised under anesthesia. Bladder CXCR4 and CXCR4-MIF co-localization were examined with immunhistochemistry. ELISA determined MIF and stromal derived factor-1 (SDF-1; cognate ligand for CXCR4) levels. Bladder CXCR4 expression (real-time RTC-PCR) and protein levels (Western blotting) were examined. Co-immunoprecipitations studied MIF-CXCR4 associations.Urothelial basal and intermediate (but not superficial) cells in saline-treated rats contained CXCR4, co-localized with MIF. Cyclophosphamide treatment caused: 1) significant redistribution of CXCR4 immunostaining to all urothelial layers (especially apical surface of superficial cells) and increased bladder CXCR4 expression; 2) increased urine MIF with decreased bladder MIF; 3) increased bladder SDF-1; 4) increased CXCR4-MIF associations. CONCLUSIONS: These data demonstrate CXCR4-MIF associations occur in vivo in rat bladder and increase in experimental cystitis. Thus, CXCR4 represents an alternative pathway for MIF-mediated signal transduction during bladder inflammation. In the bladder, MIF may compete with SDF-1 (cognate ligand) to activate signal transduction mediated by CXCR4
Smoothed Particle Hydrodynamics for Relativistic Heavy Ion Collisions
The method of smoothed particle hydrodynamics (SPH) is developped
appropriately for the study of relativistic heavy ion collision processes. In
order to describe the flow of a high energy but low baryon number density
fluid, the entropy is taken as the SPH base. We formulate the method in terms
of the variational principle. Several examples show that the method is very
promising for the study of hadronic flow in RHIC physics.Comment: 14 pages, 8figure
The United States' contribution of plastic waste to land and ocean
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Law, K. L., Starr, N., Siegler, T. R., Jambeck, J. R., Mallos, N. J., & Leonard, G. H. The United States' contribution of plastic waste to land and ocean. Science Advances, 6(44), (2020): eabd0288, doi:10.1126/sciadv.abd0288.Plastic waste affects environmental quality and ecosystem health. In 2010, an estimated 5 to 13 million metric tons (Mt) of plastic waste entered the ocean from both developing countries with insufficient solid waste infrastructure and high-income countries with very high waste generation. We demonstrate that, in 2016, the United States generated the largest amount of plastic waste of any country in the world (42.0 Mt). Between 0.14 and 0.41 Mt of this waste was illegally dumped in the United States, and 0.15 to 0.99 Mt was inadequately managed in countries that imported materials collected in the United States for recycling. Accounting for these contributions, the amount of plastic waste generated in the United States estimated to enter the coastal environment in 2016 was up to five times larger than that estimated for 2010, rendering the United States’ contribution among the highest in the world.This work was funded by Ocean Conservancy through support from the Arthur Vining Davis Foundations
Spitzer 24 micron Survey of Debris Disks in the Pleiades
We performed a 24 micron 2 Deg X 1 Deg survey of the Pleiades cluster, using
the MIPS instrument on Spitzer. Fifty four members ranging in spectral type
from B8 to K6 show 24 micron fluxes consistent with bare photospheres. All Be
stars show excesses attributed to free-free emission in their gaseous
envelopes. Five early-type stars and four solar-type stars show excesses
indicative of debris disks. We find a debris disk fraction of 25 % for B-A
members and 10 % for F-K3 ones. These fractions appear intermediate between
those for younger clusters and for the older field stars. They indicate a decay
with age of the frequency of the dust-production events inside the planetary
zone, with similar time scales for solar-mass stars as have been found
previously for A-stars.Comment: accepted to Ap
Thrombin Induces Macrophage Migration Inhibitory Factor Release and Upregulation in Urothelium: A Possible Contribution to Bladder Inflammation
Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine expressed by urothelial cells that mediates bladder inflammation. We investigated the effect of stimulation with thrombin, a Protease Activated Receptor-1 (PAR1) agonist, on MIF release and MIF mRNA upregulation in urothelial cells.MIF and PAR1 expression was examined in normal human immortalized urothelial cells (UROtsa) using real-time RT-PCR, Western blotting and dual immunostaining. MIF and PAR1 immunostaining was also examined in rat urothelium. The effect of thrombin stimulation (100 nM) on urothelial MIF release was examined in UROtsa cells (in vitro) and in rats (in vivo). UROtsa cells were stimulated with thrombin, culture media were collected at different time points and MIF amounts were determined by ELISA. Pentobarbital anesthetized rats received intravesical saline (control), thrombin, or thrombin +2% lidocaine (to block nerve activity) for 1 hr, intraluminal fluid was collected and MIF amounts determined by ELISA. Bladder or UROtsa MIF mRNA was measured using real time RT-PCR.UROtsa cells constitutively express MIF and PAR1 and immunostaining for both was observed in these cells and in the basal and intermediate layers of rat urothelium. Thrombin stimulation of urothelial cells resulted in a concentration- and time-dependent increase in MIF release both in vitro (UROtsa; 2.8-fold increase at 1 hr) and in vivo (rat; 4.5-fold) while heat-inactivated thrombin had no effect. In rats, thrombin-induced MIF release was reduced but not abolished by intravesical lidocaine treatment. Thrombin also upregulated MIF mRNA in UROtsa cells (3.3-fold increase) and in the rat bladder (2-fold increase) where the effect was reduced (1.4-fold) by lidocaine treatment.Urothelial cells express both MIF and PAR1. Activation of urothelial PAR1 receptors, either by locally generated thrombin or proteases present in the urine, may mediate bladder inflammation by inducing urothelial MIF release and upregulating urothelial MIF expression
The Wide Brown Dwarf Binary Oph 1622-2405 and Discovery of A Wide, Low Mass Binary in Ophiuchus (Oph 1623-2402): A New Class of Young Evaporating Wide Binaries?
We imaged five objects near the star forming clouds of Ophiuchus with the
Keck Laser Guide Star AO system. We resolved Allers et al. (2006)'s #11 (Oph
16222-2405) and #16 (Oph 16233-2402) into binary systems. The #11 object is
resolved into a 243 AU binary, the widest known for a very low mass (VLM)
binary. The binary nature of #11 was discovered first by Allers (2005) and
independently here during which we obtained the first spatially resolved R~2000
near-infrared (J & K) spectra, mid-IR photometry, and orbital motion estimates.
We estimate for 11A and 11B gravities (log(g)>3.75), ages (5+/-2 Myr),
luminosities (log(L/Lsun)=-2.77+/-0.10 and -2.96+/-0.10), and temperatures
(Teff=2375+/-175 and 2175+/-175 K). We find self-consistent DUSTY evolutionary
model (Chabrier et al. 2000) masses of 17+4-5 MJup and 14+6-5 MJup, for 11A and
11B respectively. Our masses are higher than those previously reported (13-15
MJup and 7-8 MJup) by Jayawardhana & Ivanov (2006b). Hence, we find the system
is unlikely a ``planetary mass binary'', (in agreement with Luhman et al. 2007)
but it has the second lowest mass and lowest binding energy of any known
binary. Oph #11 and Oph #16 belong to a newly recognized population of wide
(>100 AU), young (<10 Myr), roughly equal mass, VLM stellar and brown dwarf
binaries. We deduce that ~6+/-3% of young (<10 Myr) VLM objects are in such
wide systems. However, only 0.3+/-0.1% of old field VLM objects are found in
such wide systems. Thus, young, wide, VLM binary populations may be
evaporating, due to stellar encounters in their natal clusters, leading to a
field population depleted in wide VLM systems.Comment: Accepted version V2. Now 13 pages longer (45 total) due to a new
discussion of the stability of the wide brown dwarf binary population, new
summary Figure 17 now included, Astrophysical Journal 2007 in pres
Discovery of Two Very Low-Mass Binaries: Final Results of an Adaptive Optics Survey of Nearby M6.0-M7.5 Stars
We present updated results of a high-resolution, magnitude limited (Ks<12
mag) imaging survey of nearby low-mass M6.0-M7.5 field stars. The observations
were carried out using adaptive optics at the Gemini North, VLT, Keck II, and
Subaru telescopes. Our sample of 36 stars consists predominantly of nearby (<30
pc) field stars, 5 of which we have resolved as binaries. Two of the binary
systems, 2MASSI J0429184-312356 and 2MASSI J1847034+552243, are presented here
for the first time. All 5 discovered binary systems have separations between
0.08"-0.53" (2-9 AU) with similar mass ratios (q>0.8, delta Ks < 1 mag). This
result supports the hypothesis that wide (a>20 AU) very low-mass (M_tot<0.19
M_sun) binary systems are rare. The projected semimajor axis distribution of
these systems peak at ~ 5 AU and we report a sensitivity-corrected binary
fraction of 9% (-3%, +4%) for stars with primaries of spectral type M6.0-M7.5
with separations >3 AU and mass ratios q>0.6. Within these instrumental
sensitivities, these results support the overall trend that both the semimajor
axis distribution and binary fraction are a function of the mass of the primary
star and decrease with decreasing primary mass. These observations provide
important constraints for low-mass binary star formation theories.Comment: 20 pages, 8 figures, accepted to Ap
Adults’ number-line estimation strategies: Evidence from eye movements
Although the development of number-line estimation ability is well documented, little is known of the processes underlying successful estimators’ mappings of numerical information onto spatial representations during these tasks. We tracked adults’ eye movements during a number-line estimation task to investigate the processes underlying number-to-space translation, with three main results. First, eye movements were strongly related to the target number’s location, and early processing measures directly predicted later estimation performance. Second, fixations and estimates were influenced by the size of the first number presented, indicating that adults calibrate their estimates online. Third, adults’ number-line estimates demonstrated patterns of error consistent with the predictions of psychophysical models of proportion estimation, and eye movement data predicted the specific error patterns we observed. These results support proportion-based accounts of number-line estimation and suggest that adults’ translation of numerical information into spatial representations is a rapid, online process
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