947 research outputs found
Strip-tillage and Row Cover Use in Organically and Conventionally Grown Muskmelon
Growing muskmelon in a more sustainable way involves multiple management practices. Cover crops often are incorporated into the soil before planting the cash crop. However, they also can be “rolled” and used as a ground cover throughout the growing season. The cash crop is planted in small, tilled strips within the residue. This “strip-tillage” technique provides a weed-controlling, moisture-retaining mat that does not need to be removed at the season’s end, as plastic mulch does. The reduction in tillage can improve soil structure and health
Effects of Co substitution on thermodynamic and transport properties and anisotropic in Ba(FeCo)As single crystals
Single crystalline samples of Ba(FeCo)As with
have been grown and characterized via microscopic, thermodynamic and transport
measurements. With increasing Co substitution, the thermodynamic and transport
signatures of the structural (high temperature tetragonal to low temperature
orthorhombic) and magnetic (high temperature non magnetic to low temperature
antiferromagnetic) transitions are suppressed at a rate of roughly 15 K per
percent Co. In addition, for superconductivity is stabilized,
rising to a maximum of approximately 23 K for and
decreasing for higher values. The phase diagram for
Ba(FeCo)As indicates that either superconductivity can
exist in both low temperature crystallographic phases or that there is a
structural phase separation. Anisotropic, superconducting, upper critical field
data () show a significant and clear change in anisotropy between
samples that have higher temperature structural phase transitions and those
that do not. These data show that the superconductivity is sensitive to the
suppression of the higher temperature phase transition
Strip-tillage and Row Cover Use in Organically and Conventionally Grown Summer Squash
Growing summer squash in a more sustainable way involves multiple management practices. Cover crops often are incorporated into the soil before planting a cash crop. However, they can also be “rolled” and used as a ground cover throughout the growing season. The cash crop is planted in small, tilled strips within the residue. This “strip-tillage” technique provides a weed-controlling, moisture-retaining mat that does not need to be removed at the season’s end, as plastic mulch does. The reduction in tillage can improve soil structure and health
Momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals measured by angle resolved photoemission spectroscopy
We use angle resolved photoemission spectroscopy (ARPES) to study the
momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals.
We find that the Gamma hole pocket is fully gapped below the superconducting
transition temperature. The value of the superconducting gap is 15 +- 1.5 meV
and its anisotropy around the hole pocket is smaller than 20% of this value.
This is consistent with an isotropic or anisotropic s-wave symmetry of the
order parameter or exotic d-wave symmetry with nodes located off the Fermi
surface sheets. This is a significant departure from the situation in the
cuprates, pointing to possibility that the superconductivity in the iron
arsenic based system arises from a different mechanism.Comment: 4 pages, 3 figure
Excitability and irritability in preschoolers predicts later psychopathology: The importance of positive and negative emotion dysregulation
Emotion dysregulation is a risk factor for the development of a variety of psychopathologic outcomes. In children, irritability, or dysregulated negative affect, has been the primary focus, as it predicts later negative outcomes even in very young children. However, dysregulation of positive emotion is increasingly recognized as a contributor to psychopathology. Here we used an exploratory factor analysis and defined four factors of emotion dysregulation: irritability, excitability, sadness, and anhedonia, in the preschool-age psychiatric assessment collected in a sample of 302 children ages 3-5 years enriched for early onset depression. The irritability and excitability factor scores defined in preschoolers predicted later diagnosis of mood and externalizing disorders when controlling for other factor scores, social adversity, maternal history of mood disorders, and externalizing diagnoses at baseline. The preschool excitability factor score predicted emotion lability in late childhood and early adolescence when controlling for other factor scores, social adversity, and maternal history. Both excitability and irritability factor scores in preschoolers predicted global functioning into the teen years and early adolescence, respectively. These findings underscore the importance of positive, as well as negative, affect dysregulation as early as the preschool years in predicting later psychopathology, which deserves both further study and clinical consideration
Upper and lower critical magnetic fields of superconducting NdFeAsO1−xFx single crystals studied by Hall-probe magnetization and specific heat
International audienceThe upper and lower critical fields have been deduced from specific heat and Hall-probe magnetization measurements in nonoptimally doped Nd O,F FeAs single crystals Tc 32-35 K . The anisotropy of the penetration depth is temperature independent and on the order of 4.0 1.5. Similarly specific-heat data lead to an anisotropy of the coherence length 5.5 1.5 close to Tc. Our results suggest the presence of rather large thermal fluctuations and the existence of a vortex liquid phase over a broad temperature range 5 K large at 2 T
ZFOURGE: Extreme 5007 emission may be a common early-lifetime phase for star-forming galaxies at
Using the \prospector\ spectral energy distribution (SED) fitting code, we
analyze the properties of 19 Extreme Emission Line Galaxies (EELGs) identified
in the bluest composite SED in the \zfourge\ survey at .
\prospector\ includes a physical model for nebular emission and returns
probability distributions for stellar mass, stellar metallicity, dust
attenuation, and nonparametric star formation history (SFH). The EELGs show
evidence for a starburst in the most recent 50 Myr, with the median EELG having
a specific star formation rate (sSFR) of 4.6 Gyr and forming 15\% of its
mass in this short time. For a sample of more typical star-forming galaxies
(SFGs) at the same redshifts, the median SFG has a sSFR of 1.1 Gyr and
forms only of its mass in the last 50 Myr. We find that virtually all of
our EELGs have rising SFHs, while most of our SFGs do not. From our analysis,
we hypothesize that many, if not most, star-forming galaxies at
undergo an extreme H+[\hbox{{\rm O}\kern 0.1em{\sc iii}}] emission
line phase early in their lifetimes. In a companion paper, we obtain
spectroscopic confirmation of the EELGs as part of our {\sc MOSEL} survey. In
the future, explorations of uncertainties in modeling the UV slope for galaxies
at are needed to better constrain their properties, e.g. stellar
metallicities.Comment: 11 pages, 5 figures (main figure is fig 5), accepted for publication
in Ap
Evaluation of Trapping to Reduce Monk Parakeet Populations at Electric Utility Facilities
Through accidental and intentional introductions, the monk parakeet, native to South America, is now established in several parts of the United States. In Florida, it occurs in 21 of 67 counties. Monk parakeets build a bulky nest structure of sticks, and they often build on electric utility substations and support structures for distribution and transmission lines. This nesting activity is incompatible with reliable electric service because nest material creates short circuits that cause power outages. Nest removal by electric utility personnel is ongoing but provides only short-term relief, as buds readily rebuild their nests. In h s study, we evaluated passive and active methods to trap monk parakeets, and we documented the effectiveness of trapping to reduce rates of nest rebuilding on distribution poles. At electric substations, we tested two passive trap designs: a drop-in style trap, and a walk-in style trap. Monk parakeets were wary of traps, however, and were not easily captured even with extensive pre-baiting and the use of decoy birds. At distribution poles, we actively trapped birds at 47 nest sites using specially designed nets placed over nest entrances at night while birds roosted. Birds were then caught as they flew out of the nests into the net. Capture success at individual nest sites ranged from 0 to 100% with an overall average of 51%. Of the 47 sites where birds were trapped at night, 43 nests were removed immediately or shortly after netting. Subsequent monitoring revealed that higher nest site capture rates resulted in slower rates of nest rebuilding. We conclude that while more research is needed to design an effective passive trapping system, monk parakeets can be readily trapped from distribution pole nests at night thereby enhancing nest removal efforts
Flux pinning in (1111) iron-pnictide superconducting crystals
Local magnetic measurements are used to quantitatively characterize
heterogeneity and flux line pinning in PrFeAsO_1-y and NdFeAs(O,F)
superconducting single crystals. In spite of spatial fluctuations of the
critical current density on the macroscopic scale, it is shown that the major
contribution comes from collective pinning of vortex lines by microscopic
defects by the mean-free path fluctuation mechanism. The defect density
extracted from experiment corresponds to the dopant atom density, which means
that dopant atoms play an important role both in vortex pinning and in
quasiparticle scattering. In the studied underdoped PrFeAsO_1-y and NdFeAs(O,F)
crystals, there is a background of strong pinning, which we attribute to
spatial variations of the dopant atom density on the scale of a few dozen to
one hundred nm. These variations do not go beyond 5% - we therefore do not find
any evidence for coexistence of the superconducting and the antiferromagnetic
phase. The critical current density in sub-T fields is characterized by the
presence of a peak effect, the location of which in the (B,T)-plane is
consistent with an order-disorder transition of the vortex lattice.Comment: 12 pages, submitted to Phys Rev.
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