5,493 research outputs found
Diffusive Migration of Low-Mass Proto-planets in Turbulent Disks
Torque fluctuations due to magnetorotational turbulence in proto-planetary
disks may greatly influence the migration patterns and survival probabilities
of nascent planets. Provided that the turbulence is a stationary stochastic
process with finite amplitude and correlation time, the resulting diffusive
migration can be described with a Fokker-Planck equation, which we reduce to an
advection-diffusion equation. We calibrate the coefficients with existing
turbulent-disk simulations and mean-migration estimates, and solve the equation
both analytically and numerically. Diffusion tends to dominate over advection
for planets of low-mass and those in the outer regions of proto-planetary
disks, whether they are described by the Minimum Mass Solar Nebula (MMSN) or by
T-Tauri alpha disks. Diffusion systematically reduces the lifetime of most
planets, yet it allows a declining fraction of them to survive for extended
periods of time at large radii. Mean planet lifetimes can even be formally
infinite (e.g. in an infinite steady MMSN), though median lifetimes are always
finite. Surviving planets may linger near specific radii where the combined
effects of advection and diffusion are minimized, or at large radii, depending
on model specifics. The stochastic nature of migration in turbulent disks
challenges deterministic planet formation scenarios and suggests instead that a
wide variety of planetary outcomes are possible from similar initial
conditions. This would contribute to the diversity of (extrasolar) planetary
systems.Comment: 31 pages, 7 figures, accepted for publication in Ap
Quantum Dots in Strong Magnetic Fields: Stability Criteria for the Maximum Density Droplet
In this article we discuss the ground state of a parabolically confined
quantum dots in the limit of very strong magnetic fields where the electron
system is completely spin-polarized and all electrons are in the lowest Landau
level. Without electron-electron interactions the ground state is a single
Slater determinant corresponding to a droplet centered on the minimum of the
confinement potential and occupying the minimum area allowed by the Pauli
exclusion principle. Electron-electron interactions favor droplets of larger
area. We derive exact criteria for the stability of the maximum density droplet
against edge excitations and against the introduction of holes in the interior
of the droplet. The possibility of obtaining exact results in the strong
magnetic field is related to important simplifications associated with broken
time-reversal symmetry in a strong magnetic field.Comment: 17 pages, 5 figures (not included), RevTeX 3.0. (UCF-CM-93-002
Mapping the optical properties of slab-type two-dimensional photonic crystal waveguides
We report on systematic experimental mapping of the transmission properties
of two-dimensional silicon-on-insulator photonic crystal waveguides for a broad
range of hole radii, slab thicknesses and waveguide lengths for both TE and TM
polarizations. Detailed analysis of numerous spectral features allows a direct
comparison of experimental data with 3D plane wave and finite-difference
time-domain calculations. We find, counter-intuitively, that the bandwidth for
low-loss propagation completely vanishes for structural parameters where the
photonic band gap is maximized. Our results demonstrate that, in order to
maximize the bandwidth of low-loss waveguiding, the hole radius must be
significantly reduced. While the photonic band gap considerably narrows, the
bandwidth of low-loss propagation in PhC waveguides is increased up to 125nm
with losses as low as 82dB/cm.Comment: 10 pages, 8 figure
PseudoFuN: Deriving functional potentials of pseudogenes from integrative relationships with genes and microRNAs across 32 cancers
BACKGROUND:
Long thought "relics" of evolution, not until recently have pseudogenes been of medical interest regarding regulation in cancer. Often, these regulatory roles are a direct by-product of their close sequence homology to protein-coding genes. Novel pseudogene-gene (PGG) functional associations can be identified through the integration of biomedical data, such as sequence homology, functional pathways, gene expression, pseudogene expression, and microRNA expression. However, not all of the information has been integrated, and almost all previous pseudogene studies relied on 1:1 pseudogene-parent gene relationships without leveraging other homologous genes/pseudogenes.
RESULTS:
We produce PGG families that expand beyond the current 1:1 paradigm. First, we construct expansive PGG databases by (i) CUDAlign graphics processing unit (GPU) accelerated local alignment of all pseudogenes to gene families (totaling 1.6 billion individual local alignments and >40,000 GPU hours) and (ii) BLAST-based assignment of pseudogenes to gene families. Second, we create an open-source web application (PseudoFuN [Pseudogene Functional Networks]) to search for integrative functional relationships of sequence homology, microRNA expression, gene expression, pseudogene expression, and gene ontology. We produce four "flavors" of CUDAlign-based databases (>462,000,000 PGG pairwise alignments and 133,770 PGG families) that can be queried and downloaded using PseudoFuN. These databases are consistent with previous 1:1 PGG annotation and also are much more powerful including millions of de novo PGG associations. For example, we find multiple known (e.g., miR-20a-PTEN-PTENP1) and novel (e.g., miR-375-SOX15-PPP4R1L) microRNA-gene-pseudogene associations in prostate cancer. PseudoFuN provides a "one stop shop" for identifying and visualizing thousands of potential regulatory relationships related to pseudogenes in The Cancer Genome Atlas cancers.
CONCLUSIONS:
Thousands of new PGG associations can be explored in the context of microRNA-gene-pseudogene co-expression and differential expression with a simple-to-use online tool by bioinformaticians and oncologists alike
Learning Styles of Farmers and Others Involved with the Maine Potato Industry
The article reports on the learning preferences of Maine Potato Industry representatives. Using the Gregorc Mind Stylesâ„¢ approach to examine learning styles, we categorized potato farmers, university/government employees, allied industry personnel, and others involved in the potato industry into four learning styles: Concrete Sequential, Concrete Random, Abstract Sequential, and Abstract Random. The plurality of potato farmers were Concrete Sequential, while the plurality of university/government employees and allied industry personnel were Abstract Random. The difference in learning styles of the deliverers and the recipients of the information can result in poor communication and a less than optimum learning environment
Critical Mindset as a 21st Century Skill: Challenging Heteronormative Assumptions through Teaching High School Biology
This study focuses on the lived experience of an experienced biology teacher and their desire/ability to develop a gender-inclusive curriculum. Grounding on a narrative inquiry methodology, the narratives of our genderqueer high school biology teacher illustrate their beliefs about biology teaching and advancing students’ knowledge in ways that empower the students. The study highlights a need to teach biology in a way that develops students\u27 critical mindset as part of a 21st-century skill by emphasizing and weaving sociopolitical issues into their curriculum
Hot Training Conditions Inhibit Adequate Ad Libitum Recovery Fluid Intake of Runners
International Journal of Exercise Science 12(6): 1322-1333, 2019. This study examined voluntary fluid intake, hydration descriptors, and sweat loss estimation accuracy following runs in wet bulb globe temperatures of 18 (TEMP) and 26 ºC (HOT). Twelve male runners completed 1-h runs at 65% of VO2 max with access to water during runs and a variety of beverages for the following 24-h. Urine specific gravity (USG), body mass, fluid intake, and urine output were assessed at 12 and 24-h. Runners lost 1.355 ± 0.263 and 1.943 ± 0.485 L during TEMP and HOT, respectively. Sweat loss volume was underestimated by approximately one-third during both conditions. Cumulative fluid intake from start until 1-h post-run was greater in HOT, but not at 12-h (2.202±0.600 vs 2.265±0.673 L) or 24-h (3.602±0.807 vs 3.742±1.205 L). Runners replaced a lower percentage of sweat losses and displayed higher USG (p \u3c 0.001) for HOT (119±34%; 1.027±0.004) versus TEMP (166±51%; 1.018±0.004) at 12-h while exhibiting repeatable rehydration patterns within runners (ICC = 0.89) between trials. Absolute body mass was unable to differentiate the substantial differences in fluid replacement percentage. Seven runners replace
Development of Dual-Gain SiPM Boards for Extending the Energy Dynamic Range
Astronomical observations with gamma rays in the range of several hundred keV
to hundreds of MeV currently represent the least explored energy range. To
address this so-called MeV gap, we designed and built a prototype CsI:Tl
calorimeter instrument using a commercial off-the-shelf (COTS) SiPMs and
front-ends which may serve as a subsystem for a larger gamma-ray mission
concept. During development, we observed significant non-linearity in the
energy response. Additionally, using the COTS readout, the calorimeter could
not cover the four orders of magnitude in energy range required for the
telescope. We, therefore, developed dual-gain silicon photomultiplier (SiPM)
boards that make use of two SiPM species that are read out separately to
increase the dynamic energy range of the readout. In this work, we investigate
the SiPM's response with regards to active area ( and
) and various microcell sizes (, , and ). We read out CsI:Tl chunks
using dual-gain SiPMs that utilize microcells for both
SiPM species and demonstrate the concept when tested with high-energy gamma-ray
and proton beams. We also studied the response of $17 \times 17 \times 100 \
\mathrm{mm}^30.25-400 \ \mathrm{MeV}2.5-30 \ \mathrm{MeV}$. This development aims to demonstrate
the concept for future scintillator-based high-energy calorimeters with
applications in gamma-ray astrophysics
Addition Spectra of Quantum Dots in Strong Magnetic Fields
We consider the magnetic field dependence of the chemical potential for
parabolically confined quantum dots in a strong magnetic field. Approximate
expressions based on the notion that the size of a dot is determined by a
competition between confinement and interaction energies are shown to be
consistent with exact diagonalization studies for small quantum dots. Fine
structure is present in the magnetic field dependence which cannot be explained
without a full many-body description and is associated with ground-state level
crossings as a function of confinement strength or Zeeman interaction strength.
Some of this fine structure is associated with precursors of the bulk
incompressible states responsible for the fractional quantum Hall effect.Comment: 11 pages, 3 figures (available from [email protected]). Revtex
3.0. (IUCM93-010
- …