The genesis of Hurricane Nate and its interaction with a nearby environment of very dry air

The Supplement related to this article is available online at https://doi.org/10.5194/acp-17-10349-2017-supplementThe article of record as published may be found at http://dx.doi.org/10.5194/acp-17-10349-2017The interaction of a tropical disturbance with its environment is thought to play an important role in whether a disturbance will develop or not. Most developing disturbances are somewhat protected from the intrusion of environmental dry air at mid-levels. For African easterly wave (AEW) disturbances, the protective boundary is approximated by closed streamlines in the wave-relative frame, and their interior is called the wave pouch. The dynamic and thermodynamic processes of spin-up occur inside the pouch. In this study, we define the kinematic boundaries for a nonAEW disturbance in the Bay of Campeche that originated along a sharp frontal boundary in a confluent region of low pressure. We examine these boundaries during the genesis of Hurricane Nate (2011) to show how a pouch boundary on isobaric levels in the Lagrangian frame may allow for some transport into the pouch along the frontal boundary while still protecting the innermost development region. This result illustrates a generic property of weakly unsteady flows, including the time-dependent critical layer of AEWs, that lateral exchange of air occurs along a segment of the boundary formed by the instantaneous, closed translating streamlines. Transport in the Lagrangian frame is simplest when measured with respect to the stable and unstable manifolds of a hyperbolic trajectory, which are topologically invariant. In this framework, an exact analysis of vorticity transport identifies the primary source as the advection of vorticity through the entrainment and expulsion of bounded material regions called lobes. We also show how these Lagrangian boundaries impact the concentration of moisture, influence convection, and contribute to the pouch vertical structure.NSFNASAAGS-1313948AGS-1439283AGS-0733380NNG11PK02

Chiral magnetization configurations in magnetic nanostructures in the presence of Dzyaloshinski-Moriya interactions

Many low-dimensional systems, such as nanoscale islands, thin films, and multilayers, as well as bulk systems, such as multiferroics, are characterized by the lack of inversion symmetry, a fact that may give rise to a Dzyaloshinskii-Moriya (DM) interaction. For sufficient strength, the DM interaction will favor spiral spin configurations of definite chirality. In order to harness such systems for applications, it is important to understand the conditions under which these spiral spin configurations form and how they can be controlled via an external field. Here, we present exact solutions of the 1D magnetization profiles in such systems for arbitrary material parameters in closed form. Determining the energy per unit length exactly, we are able to present the critical strength of the DM interaction, at which spiral solutions are energetically favorable. These magnetization profiles, in general, take the form of a domain wall or soliton lattice, with all solitons having the same chirality, whose sign is dictated by DM interaction. Conversely, given an energetically favorable spiral solution, we determine quantitatively how the magnetization profile changes as a function of the applied field

Gas Rich Dwarf Spheroidals

We present evidence that nearly half of the dwarf spheroidal galaxies (dSph and dSph/dIrr) in the Local Group are associated with large reservoirs of atomic gas, in some cases larger than the stellar mass. The gas is sometimes found at large distance (~10 kpc) from the center of a galaxy and is not necessarily centered on it. Similarly large quantities of ionized gas could be hidden in these systems as well. The properties of some of the gas reservoirs are similar to the median properties of the High-Velocity Clouds (HVCs); two of the HI reservoirs are catalogued HVCs. The association of the HI with the dwarf spheroidals might thus provide a link between the HVCs and stars. We show that the HI content of the Local Group dSphs and dIrrs exhibits a sharp decline if the galaxy is within 250 kpc of either the Milky Way or M31. This can be explained if both galaxies have a sufficiently massive x-ray emitting halo that produces ram-pressure stripping if a dwarf ventures too close to either giant spiral. We also investigate tidal stripping of the dwarf galaxies and find that although it may play a role, it cannot explain the apparent total absence of neutral gas in most dSph galaxies at distances less than 250 kpc. For the derived mean density of the hot gas, n_0 = 2.5e-5 cm^-2, ram-pressure stripping is found to be more than an order of magnitude more effective in removing the gas from the dSph galaxies. The hot halo, with an inferred mass of 1e10 solar masses, may represent a reservoir of ~1000 destroyed dwarf systems, either HVCs or true dwarf galaxies similar to those we observe now.Comment: AASTex preprint style, 27 pages including 12 figures. Submitted to ApJ. See also http://astro.berkeley.edu/~robisha

The Physical Parameters of the Retired A Star HD185351

We report here an analysis of the physical stellar parameters of the giant star HD185351 using Kepler short-cadence photometry, optical and near infrared interferometry from CHARA, and high-resolution spectroscopy. Asteroseismic oscillations detected in the Kepler short-cadence photometry combined with an effective temperature calculated from the interferometric angular diameter and bolometric flux yield a mean density, rho_star = 0.0130 +- 0.0003 rho_sun and surface gravity, logg = 3.280 +- 0.011. Combining the gravity and density we find Rstar = 5.35 +- 0.20 Rsun and Mstar = 1.99 +- 0.23 Msun. The trigonometric parallax and CHARA angular diameter give a radius Rstar = 4.97 +- 0.07 Rsun. This smaller radius,when combined with the mean stellar density, corresponds to a stellar mass Mstar = 1.60 +- 0.08 Msun, which is smaller than the asteroseismic mass by 1.6-sigma. We find that a larger mass is supported by the observation of mixed modes in our high-precision photometry, the spacing of which is consistent only for Mstar =~ 1.8 Msun. Our various and independent mass measurements can be compared to the mass measured from interpolating the spectroscopic parameters onto stellar evolution models, which yields a model-based mass M_star = 1.87 +- 0.07 Msun. This mass agrees well with the asteroseismic value,but is 2.6-sigma higher than the mass from the combination of asteroseismology and interferometry. The discrepancy motivates future studies with a larger sample of giant stars. However, all of our mass measurements are consistent with HD185351 having a mass in excess of 1.5 Msun.Comment: ApJ accepte

Dynamic Sensorimotor Planning during Long-Term Sequence Learning: The Role of Variability, Response Chunking and Planning Errors

Many everyday skills are learned by binding otherwise independent actions into a unified sequence of responses across days or weeks of practice. Here we looked at how the dynamics of action planning and response binding change across such long timescales. Subjects (N = 23) were trained on a bimanual version of the serial reaction time task (32-item sequence) for two weeks (10 days total). Response times and accuracy both showed improvement with time, but appeared to be learned at different rates. Changes in response speed across training were associated with dynamic changes in response time variability, with faster learners expanding their variability during the early training days and then contracting response variability late in training. Using a novel measure of response chunking, we found that individual responses became temporally correlated across trials and asymptoted to set sizes of approximately 7 bound responses at the end of the first week of training. Finally, we used a state-space model of the response planning process to look at how predictive (i.e., response anticipation) and error-corrective (i.e., post-error slowing) processes correlated with learning rates for speed, accuracy and chunking. This analysis yielded non-monotonic association patterns between the state-space model parameters and learning rates, suggesting that different parts of the response planning process are relevant at different stages of long-term learning. These findings highlight the dynamic modulation of response speed, variability, accuracy and chunking as multiple movements become bound together into a larger set of responses during sequence learning. © 2012 Verstynen et al

What on Earth have we been burning? Deciphering sedimentary records of pyrogenic carbon

Humans have interacted with fire for thousands of years, yet the utilization of fossil fuels marked the beginning of a new era. Ubiquitous in the environment, pyrogenic carbon (PyC) arises from incomplete combustion of biomass and fossil fuels, forming a continuum of condensed aromatic structures. Here we develop and evaluate 14C records for two complementary PyC molecular markers, benzene-polycarboxylic-acids (BPCAs) and polycyclic-aromatic-hydrocarbons (PAHs) preserved in aquatic sediments from a sub-urban and a remote catchment in the United States (U.S.) from mid-1700s to 1998. Results show that the majority of PyC stems from local sources and is transferred to aquatic sedimentary archives on sub-decadal to millennial time scales. Whereas a small portion stems from near-contemporaneous production and sedimentation, the majority of PyC (<90%) experiences delayed transmission due to ‘pre-aging’ on millennial timescales in catchment soils prior to its ultimate deposition. BPCAs (soot) and PAHs (precursors of soot) trace fossil fuel-derived PyC. Both markers parallel historical records of the consumption of fossil fuels in U.S., yet never account for more than 19% total PyC. This study demonstrates that isotopic characterization of multiple tracers is necessary to constrain histories and inventories of PyC, and that sequestration of PyC can markedly lag its production

Phosphorus desorption and isotope exchange kinetics in agricultural soils

To improve phosphorus (P) fertilization and environmental assessments, a better understanding of release kinetics of solid-phase P to soil solution is needed. In this study, Fe (hydr)oxide-coated filter papers (Fh papers), isotopic exchange kinetics (IEK) and chemical extractions were used to assess the sizes of fast and slowly desorbing P pools in the soils of six long-term Swedish field experiments. The P desorption data from the Fh-paper extraction of soil (20 days of continual P removal) were fitted with the Lookman two-compartment desorption model, which estimates the pools of fast (Q(1)) and slowly (Q(2)) desorbing P, and their desorption rates k(1) and k(2). The amounts of isotope-exchangeable P (E) were calculated (E-1min to E->3 months) and compared with Q(1) and Q(2). The strongest relationship was found between E-1 min and Q(1) (r(2) = .87, p < .01). There was also an inverse relationship between the IEK parameter n (the rate of exchange) and k(1) (r(2) = .52, p < .01) and k(2) (r(2) = .52, p < .01), suggesting that a soil with a high value of n desorbs less P per time unit. The relationships between these results show that they deliver similar information, but both methods are hard to implement in routine analysis. However, Olsen-extractable P was similar in magnitude to Q(1) (P-Olsen = 1.1 x Q(1) + 2.3, r(2) = .96), n and k(1) were related to P-Olsen/P-CaCl2, while k(2) was related to P-oxalate/P-Olsen. Therefore, these extractions can be used to estimate the sizes and desorption rates of the different P pools, which could be important for assessments of plant availability and leaching

Sarcoidosis of the Mandibular Condyle: A Rare Disease That Can Mimic Malignancy

Sarcoidosis can involve any of the organs, however intraosseous involvement is rare and ranges from 5 to 15%, with lesions of the mandible being even rarer – currently with few known cases reported. Intraosseous lesions involving the mandible have been noted to be asymptomatic or associated with chronic jaw pain. Additionally, mandibular involvement can present as a lytic bone lesion mimicking osseous malignancy. Chronic polyarthritis is commonly associated with the progression of sarcoidosis and intraosseous involvement has been considered a late-stage sequelae. We report a case of biopsy-proven sarcoidosis within the mandibular condyle in an asymptomatic 56-year-old Caucasian female who had no preceding polyarthritis or symptomatic progression of disease, discuss the imaging features, and report management