2,874 research outputs found
Skeletal Micro-RNA Responses to Simulated Weightlessness
Astronauts lose bone structure during long-duration spaceflight. These changes are due, in part, to insufficient bone formation by the osteoblast cells. Little is known about the role that small (approximately 22 nucleotides), non-coding micro-RNAs (miRNAs) play in the osteoblast response to microgravity. We hypothesize that osteoblast-lineage cells alter their miRNA status during microgravity exposure, contributing to impaired bone formation during weightlessness. To simulate weightlessness, female mice (C57BL/6, Charles River, 10 weeks of age, n = 7) were hindlimb unloaded up to 12 days. Age-matched and normally ambulating mice served as controls (n=7). To assess the expression of miRNAs in skeletal tissue, the tibia was collected ex vivo and cleaned of soft-tissue and marrow. Total RNA was collected from tibial bone and relative abundance was measured for miRNAs of interest using quantitative real time PCR array looking at 372 unique and well-characterized mature miRNAs using the delta-delta Ct method. Transcripts of interest were normalized to an average of 6 reference RNAs. Preliminary results show that hindlimb unloading decreased the expression of 14 miRNAs to less than 0.5 times that of the control levels and increased the expression of 5 miRNAs relative to the control mice between 1.2-1.5-fold (p less than 0.05, respectively). Using the miRSystem we assessed overlapping target genes predicted to be regulated by multiple members of the 19 differentially expressed miRNAs as well as in silico predicted targets of our individual miRNAs. Our miRsystem results indicated that a number of our differentially expressed miRNAs were regulators of genes related to the Wnt-Beta Catenin pathway-a known regulator of bone health-and, interestingly, the estrogen-mediated cell-cycle regulation pathway, which may indicate that simulated weightlessness modulated systemic hormonal levels or hormonal transduction that additionally contributed to bone loss. We plan to follow up these findings by measuring gene expression of miRNA-regulated genes within these two pathways with the aim of furthering our understanding of the function of miRNAs in the skeletal response to spaceflight
Accurate, Fast and Scalable Kernel Ridge Regression on Parallel and Distributed Systems
We propose two new methods to address the weak scaling problems of KRR: the
Balanced KRR (BKRR) and K-means KRR (KKRR). These methods consider alternative
ways to partition the input dataset into p different parts, generating p
different models, and then selecting the best model among them. Compared to a
conventional implementation, KKRR2 (optimized version of KKRR) improves the
weak scaling efficiency from 0.32% to 38% and achieves a 591times speedup for
getting the same accuracy by using the same data and the same hardware (1536
processors). BKRR2 (optimized version of BKRR) achieves a higher accuracy than
the current fastest method using less training time for a variety of datasets.
For the applications requiring only approximate solutions, BKRR2 improves the
weak scaling efficiency to 92% and achieves 3505 times speedup (theoretical
speedup: 4096 times).Comment: This paper has been accepted by ACM International Conference on
Supercomputing (ICS) 201
Perceived Dangerousness Mediates Punitive Attitudes Toward Sex Offenders: Results From a Vignette Experiment
The current study used an experimental vignette (n = 1,093) to examine the effects of perpetrator sex and age, and victim sex and age, on simulated juror sentencing recommendations for individuals convicted of sexual offenses (ICSO). Path analyses were used to see if differences in punitive attitudes could be explained by perceptions of dangerousness participants attached to experimentally manipulated variables, as hypothesized by attribution theorists. Results show that participants consistently recommended longer sentences, higher fines, and indicated greater support for post-release sanctions for male offenders, older perpetrators, and for offenders who victimized younger adolescents. Path analysis demonstrated that perceptions of dangerousness partially mediated the relationship between experimentally manipulated predictor variables and recommended sentence length, providing partial support for attribution theory
Development and validation of a dynamic metamodel based on stochastic radial basis functions and uncertainty quantification
Phonon drag thermopower and weak localization
Previous experimental work on a two-dimensional (2D) electron gas in a
Si-on-sapphire device led to the conclusion that both conductivity and phonon
drag thermopower are affected to the same relative extent by weak
localization. The present paper presents further experimental and theoretical
results on these transport coefficients for two very low mobility 2D electron
gases in doped GaAs/GaAlAs quantum wells. The experiments
were carried out in the temperature range 3-7K where phonon drag dominates the
thermopower and, contrary to the previous work, the changes observed in the
thermopower due to weak localization were found to be an order of magnitude
less than those in the conductivity. A theoretical framework for phonon drag
thermopower in 2D and 3D semiconductors is presented which accounts for this
insensitivity of to weak localization. It also provides transparent
physical explanations of many previous experimental and theoretical results.Comment: 19 page Revtex file, 3 Postscript figur
Active Tension Network model suggests an exotic mechanical state realized in epithelial tissues.
Mechanical interactions play a crucial role in epithelial morphogenesis, yet understanding the complex mechanisms through which stress and deformation affect cell behavior remains an open problem. Here we formulate and analyze the Active Tension Network (ATN) model, which assumes that the mechanical balance of cells within a tissue is dominated by cortical tension and introduces tension-dependent active remodeling of the cortex. We find that ATNs exhibit unusual mechanical properties. Specifically, an ATN behaves as a fluid at short times, but at long times supports external tension like a solid. Furthermore, an ATN has an extensively degenerate equilibrium mechanical state associated with a discrete conformal - "isogonal" - deformation of cells. The ATN model predicts a constraint on equilibrium cell geometries, which we demonstrate to approximately hold in certain epithelial tissues. We further show that isogonal modes are observed in the fruit y embryo, accounting for the striking variability of apical areas of ventral cells and helping understand the early phase of gastrulation. Living matter realizes new and exotic mechanical states, the study of which helps to understand biological phenomena
Optical Properties of (162173) 1999 JU3: In Preparation for the JAXA Hayabusa 2 Sample Return Mission
We investigated the magnitude-phase relation of (162173) 1999 JU3, a target
asteroid for the JAXA Hayabusa 2 sample return mission. We initially employed
the international Astronomical Union's H-G formalism but found that it fits
less well using a single set of parameters. To improve the inadequate fit, we
employed two photometric functions, the Shevchenko and Hapke functions. With
the Shevchenko function, we found that the magnitude-phase relation exhibits
linear behavior in a wide phase angle range (alpha = 5-75 deg) and shows weak
nonlinear opposition brightening at alpha< 5 deg, providing a more reliable
absolute magnitude of Hv = 19.25 +- 0.03. The phase slope (0.039 +- 0.001
mag/deg) and opposition effect amplitude (parameterized by the ratio of
intensity at alpha=0.3 deg to that at alpha=5 deg, I(0.3)/I(5)=1.31+-0.05) are
consistent with those of typical C-type asteroids. We also attempted to
determine the parameters for the Hapke model, which are applicable for
constructing the surface reflectance map with the Hayabusa 2 onboard cameras.
Although we could not constrain the full set of Hapke parameters, we obtained
possible values, w=0.041, g=-0.38, B0=1.43, and h=0.050, assuming a surface
roughness parameter theta=20 deg. By combining our photometric study with a
thermal model of the asteroid (Mueller et al. in preparation), we obtained a
geometric albedo of pv = 0.047 +- 0.003, phase integral q = 0.32 +- 0.03, and
Bond albedo AB = 0.014 +- 0.002, which are commensurate with the values for
common C-type asteroids.Comment: 27 pages, 4 figure, accepted for publication in the Astrophysical
Journa
The Simons Observatory: Magnetic Shielding Measurements for the Universal Multiplexing Module
The Simons Observatory (SO) includes four telescopes that will measure the
temperature and polarization of the cosmic microwave background using over
60,000 highly sensitive transition-edge bolometers (TES). These multichroic TES
bolometers are read out by a microwave RF SQUID multiplexing system with a
multiplexing factor of 910. Given that both TESes and SQUIDs are susceptible to
magnetic field pickup and that it is hard to predict how they will respond to
such fields, it is important to characterize the magnetic response of these
systems empirically. This information can then be used to limit spurious
signals by informing magnetic shielding designs for the detectors and readout.
This paper focuses on measurements of magnetic pickup with different magnetic
shielding configurations for the SO universal multiplexing module (UMM), which
contains the SQUIDs, associated resonators, and TES bias circuit. The magnetic
pickup of a prototype UMM was tested under three shielding configurations: no
shielding (copper packaging), aluminum packaging for the UMM, and a
tin/lead-plated shield surrounding the entire dilution refrigerator 100 mK cold
stage. The measurements show that the aluminum packaging outperforms the copper
packaging by a shielding factor of 8-10, and adding the tin/lead-plated 1K
shield further increases the relative shielding factor in the aluminum
configuration by 1-2 orders of magnitude.Comment: 7 pages, 4 figure, conference proceedings submitted to the Journal of
Low Temperature Physic
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