2,730 research outputs found
Standard model plethystics
We study the vacuum geometry prescribed by the gauge invariant operators of the minimal supersymmetric standard model via the plethystic program. This is achieved by using several tricks to perform the highly computationally challenging Molien-Weyl integral, from which we extract the Hilbert series, encoding the invariants of the geometry at all degrees. The fully refined Hilbert series is presented as the explicit sum of 1422 rational functions. We found a good choice of weights to unrefine the Hilbert series into a rational function of a single variable, from which we can read off the dimension and the degree of the vacuum moduli space of the minimal supersymmetric standard model gauge invariants. All data in Mathematica format are also presented
Detection of Extended He II Reionization in the Temperature Evolution of the Intergalactic Medium
We present new measurements of the temperature of the intergalactic medium
(IGM) derived from the Lyman-alpha forest over 2.0 < z < 4.8. The small-scale
structure in the forest of 61 high-resolution QSO spectra is quantified using a
new statistic, the curvature, and the conversion to temperature calibrated
using a suite of hydrodynamic simulations. At each redshift we focus on
obtaining the temperature at an optimal overdensity probed by the Lyman-alpha
forest, T(Delta), where the temperature is nearly a one-to-one function of the
curvature regardless of the slope of the temperature-density relation. The
median 2-sigma statistical uncertainty in these measurements is 8 per cent,
though there may be comparable systematic errors due to the unknown amount of
Jeans smoothing in the IGM. We use our T(Delta) results to infer the
temperature at the mean density, T0. Even for a maximally steep
temperature-density relation, T0 must increase from ~8000 K at z ~ 4.4 to
>~12000 K at z ~ 2.8. This increase is not consistent with the monotonic
decline in T0 expected in the absence of He II reionization. We therefore
interpret the observed rise in temperature as evidence of He II reionization
beginning at z >~ 4.4. The evolution of T0 is consistent with an end to He II
reionization at z ~ 3, as suggested by opacity measurements of the He II
Lyman-alpha forest, although the redshift at which T0 peaks will depend
somewhat on the evolution of the temperature-density relation. These new
temperature measurements suggest that the heat input due to the reionization of
He II dominates the thermal balance of the IGM over an extended period with
Delta_z >~ 1.Comment: 19 pages, 15 figures, accepted to MNRA
Small Unmanned Aircraft Systems Integration into the National Airspace System Visual-Line-of-Sight Human-in-the-Loop Experiment
As part of the Unmanned Aircraft Systems (UAS) in the National Airspace System (NAS) project, research on integrating small UAS (sUAS) into the NAS was underway by a human-systems integration (HSI) team at the NASA Langley Research Center. Minimal to no research has been conducted on the safe, effective, and efficient manner in which to integrate these aircraft into the NAS. sUAS are defined as aircraft weighing 55 pounds or less. The objective of this human system integration team was to build a UAS Ground Control Station (GCS) and to develop a research test-bed and database that provides data, proof of concept, and human factors guidelines for GCS operations in the NAS. The objectives of this experiment were to evaluate the effectiveness and safety of flying sUAS in Class D and Class G airspace utilizing manual control inputs and voice radio communications between the pilot, mission control, and air traffic control. The design of the experiment included three sets of GCS display configurations, in addition to a hand-held control unit. The three different display configurations were VLOS, VLOS + Primary Flight Display (PFD), and VLOS + PFD + Moving Map (Map). Test subject pilots had better situation awareness of their vehicle position, altitude, airspeed, location over the ground, and mission track using the Map display configuration. This configuration allowed the pilots to complete the mission objectives with less workload, at the expense of having better situation awareness of other aircraft. The subjects were better able to see other aircraft when using the VLOS display configuration. However, their mission performance, as well as their ability to aviate and navigate, was reduced compared to runs that included the PFD and Map displays
Fibroblast Activation Protein (FAP) Accelerates Collagen Degradation and Clearance from Lungs in Mice
Idiopathic pulmonary fibrosis is a disease characterized by progressive, unrelenting lung scarring, with death from respiratory failure within 2–4 years unless lung transplantation is performed. New effective therapies are clearly needed. Fibroblast activation protein (FAP) is a cell surface-associated serine protease up-regulated in the lungs of patients with idiopathic pulmonary fibrosis as well as in wound healing and cancer. We postulate that FAP is not only a marker of disease but influences the development of pulmonary fibrosis after lung injury. In two different models of pulmonary fibrosis, intratracheal bleomycin instillation and thoracic irradiation, we find increased mortality and increased lung fibrosis in FAP-deficient mice compared with wild-type mice. Lung extracellular matrix analysis reveals accumulation of intermediate-sized collagen fragments in FAP-deficient mouse lungs, consistent with in vitro studies showing that FAP mediates ordered proteolytic processing of matrix metalloproteinase (MMP)-derived collagen cleavage products. FAP-mediated collagen processing leads to increased collagen internalization without altering expression of the endocytic collagen receptor, Endo180. Pharmacologic FAP inhibition decreases collagen internalization as expected. Conversely, restoration of FAP expression in the lungs of FAP-deficient mice decreases lung hydroxyproline content after intratracheal bleomycin to levels comparable with that of wild-type controls. Our findings indicate that FAP participates directly, in concert with MMPs, in collagen catabolism and clearance and is an important factor in resolving scar after injury and restoring lung homeostasis. Our study identifies FAP as a novel endogenous regulator of fibrosis and is the first to show FAP's protective effects in the lung
Simultaneous multi-wavelength observations of the TeV Blazar Mrk 421 during February - March 2003: X-ray and NIR correlated variability
In the present paper, we have reported the result of simultaneous
multi-wavelength observations of the TeV blazar Mrk 421 during February
March 2003. In this period, we have observed Mrk 421 using Pachmarhi Array of
\v{C}erenkov Telescopes (PACT) of Tata Institute of Fundamental Research at
Pachmarhi, India. Other simultaneous data were taken from the published
literature and public data archives. We have analyzed the high quality X-ray
(2-20 keV) observations from the NASA Rossi X-Ray Timing Explorer (RXTE). We
have seen a possible correlated variability between X-ray and J band (1.25
) near infrared (NIR) wavelength. This is the first case of X-ray and NIR
correlated variability in Mrk 421 or any high energy peaked (HBL) blazar. The
correlated variability reported here is indicating a similar origin for NIR and
X-ray emission. The emission is not affected much by the environment of the
surrounding medium around the central engine of the Mrk 421. The observations
are consistent with the shock-in-jet model for the emission of radiations.Comment: 11 pages, 5 figures, Accepted for Publication in ChJA
Eclipsing Binaries From the CSTAR Project at Dome A, Antarctica
The Chinese Small Telescope ARray (CSTAR) has observed an area around the
Celestial South Pole at Dome A since 2008. About light curves in the i
band were obtained lasting from March to July, 2008. The photometric precision
achieves about 4 mmag at i = 7.5 and 20 mmag at i = 12 within a 30 s exposure
time. These light curves are analyzed using Lomb--Scargle, Phase Dispersion
Minimization, and Box Least Squares methods to search for periodic signals.
False positives may appear as a variable signature caused by contaminating
stars and the observation mode of CSTAR. Therefore the period and position of
each variable candidate are checked to eliminate false positives. Eclipsing
binaries are removed by visual inspection, frequency spectrum analysis and
locally linear embedding technique. We identify 53 eclipsing binaries in the
field of view of CSTAR, containing 24 detached binaries, 8 semi-detached
binaries, 18 contact binaries, and 3 ellipsoidal variables. To derive the
parameters of these binaries, we use the Eclipsing Binaries via Artificial
Intelligence (EBAI) method. The primary and the secondary eclipse timing
variations (ETVs) for semi-detached and contact systems are analyzed.
Correlated primary and secondary ETVs confirmed by false alarm tests may
indicate an unseen perturbing companion. Through ETV analysis, we identify two
triple systems (CSTAR J084612.64-883342.9 and CSTAR J220502.55-895206.7). The
orbital parameters of the third body in CSTAR J220502.55-895206.7 are derived
using a simple dynamical model.Comment: 41 pages, 12 figures; published online in ApJ
Black hole masses and Doppler factors of -ray active galactic nuclei
The sizes of the broad-line regions (BLRs) in -ray active galactic
nuclei (AGNs) are estimated from their optical continuum luminosity by using
the empirical relation between and . Using
the broad emission line data, we derive the photon energy density in the
relativistic blobs near the massive black holes in AGNs. We calculate the power
of the broad-line photons Compton up-scattered by the relativistic electrons in
the blobs. Compared with observed -ray emission data, the Doppler
factors of the blobs for a sample of 36 -ray AGNs are derived,
which are in the range of . We estimate the central black hole
masses of these -ray AGNs from the sizes of the BLR and the broad line
widths. It is found that the black hole masses are in the range of . A significant correlation is found between the
Doppler factor and the core dominance parameter . The results are
consistent with the external radiation Compton (ERC) models for -ray
emission from AGNs. The soft seed photons are probably from the broad-line
regions.Comment: 22 pages, accepted by Ap
Genomics of post-bottleneck recovery in the northern elephant seal.
Populations and species are threatened by human pressure, but their fate is variable. Some depleted populations, such as that of the northern elephant seal (Mirounga angustirostris), recover rapidly even when the surviving population was small. The northern elephant seal was hunted extensively and taken by collectors between the early 1800s and 1892, suffering an extreme population bottleneck as a consequence. Recovery was rapid and now there are over 200,000 individuals. We sequenced 260 modern and 8 historical northern elephant seal nuclear genomes to assess the impact of the population bottleneck on individual northern elephant seals and to better understand their recovery. Here we show that inbreeding, an increase in the frequency of alleles compromised by lost function, and allele frequency distortion, reduced the fitness of breeding males and females, as well as the performance of adult females on foraging migrations. We provide a detailed investigation of the impact of a severe bottleneck on fitness at the genomic level and report on the role of specific gene systems. [Abstract copyright: © 2024. The Author(s).
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