1,436 research outputs found
An experimental investigation of leading-edge vortex augmentation by blowing
A wind tunnel test was conducted to determine the effects of over-the-wing blowing as a means of augmenting the leading-edge vortex flow of several pointed-tip, sharp-edged planforms. Arrow, delta, and diamond wings with leading-edge sweeps of 30 and 45 degrees were mounted on a body-of-revolution fuselage and tested in a low-speed wind tunnel at a Mach number of 0.2. Nozzle location data, pitch data, and flow-visualization pictures were obtained for a range of blowing rates. Results show pronounced increases in vortex lift due to the blowing
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Passive-solar design manual for the United States Navy
A passive solar design manual for single-family detached residences and dormitory-type buildings is being developed. The design procedure employed in the manual is a simplification of the original monthly solar load ratio (SLR) method. The new SLR correlations involve a single constant for each system. The correlation constant appears as a scale factor permitting the use of a universal performance curve for all passive systems. Furthermore, by providing location-dependent correlations between the annual solar heating fraction (SHF)* and the minimum monthly SHF, we have eliminated the need to perform an SLR calculation for each month of the heating season
Spectroscopic scanning tunneling microscopy insights into Fe-based superconductors
In the first three years since the discovery of Fe-based high Tc
superconductors, scanning tunneling microscopy (STM) and spectroscopy have shed
light on three important questions. First, STM has demonstrated the complexity
of the pairing symmetry in Fe-based materials. Phase-sensitive quasiparticle
interference (QPI) imaging and low temperature spectroscopy have shown that the
pairing order parameter varies from nodal to nodeless s\pm within a single
family, FeTe1-xSex. Second, STM has imaged C4 -> C2 symmetry breaking in the
electronic states of both parent and superconducting materials. As a local
probe, STM is in a strong position to understand the interactions between these
broken symmetry states and superconductivity. Finally, STM has been used to
image the vortex state, giving insights into the technical problem of vortex
pinning, and the fundamental problem of the competing states introduced when
superconductivity is locally quenched by a magnetic field. Here we give a
pedagogical introduction to STM and QPI imaging, discuss the specific
challenges associated with extracting bulk properties from the study of
surfaces, and report on progress made in understanding Fe-based superconductors
using STM techniques.Comment: 36 pages, 23 figures, 229 reference
High-coverage sequencing and annotated assemblies of the budgerigar genome
BACKGROUND: Parrots belong to a group of behaviorally advanced vertebrates and have an advanced ability of vocal learning relative to other vocal-learning birds. They can imitate human speech, synchronize their body movements to a rhythmic beat, and understand complex concepts of referential meaning to sounds. However, little is known about the genetics of these traits. Elucidating the genetic bases would require whole genome sequencing and a robust assembly of a parrot genome. FINDINGS: We present a genomic resource for the budgerigar, an Australian Parakeet (Melopsittacus undulatus) -- the most widely studied parrot species in neuroscience and behavior. We present genomic sequence data that includes over 300x raw read coverage from multiple sequencing technologies and chromosome optical maps from a single male animal. The reads and optical maps were used to create three hybrid assemblies representing some of the largest genomic scaffolds to date for a bird; two of which were annotated based on similarities to reference sets of non-redundant human, zebra finch and chicken proteins, and budgerigar transcriptome sequence assemblies. The sequence reads for this project were in part generated and used for both the Assemblathon 2 competition and the first de novo assembly of a giga-scale vertebrate genome utilizing PacBio single-molecule sequencing. CONCLUSIONS: Across several quality metrics, these budgerigar assemblies are comparable to or better than the chicken and zebra finch genome assemblies built from traditional Sanger sequencing reads, and are sufficient to analyze regions that are difficult to sequence and assemble, including those not yet assembled in prior bird genomes, and promoter regions of genes differentially regulated in vocal learning brain regions. This work provides valuable data and material for genome technology development and for investigating the genomics of complex behavioral traits
Biology and Impacts of Pacific Island Invasive Species: 8. Eleutherodactylus planirostris, the Greenhouse Frog (Anura: Eleutherodactylidae)
The greenhouse frog, Eleutherodactylus planirostris, is a direct-developing (i.e., no aquatic stage) frog native to Cuba and the Bahamas. It was introduced to Hawaii via nursery plants in the early 1990s and then subsequently from Hawaii to Guam in 2003. The greenhouse frog is now widespread on five Hawaiian Islands and Guam. Infestations are often overlooked due to the frog’s quiet calls, small size, and cryptic behavior, and this likely contributes to its spread. Because the greenhouse frog is an insectivore, introductions may reduce invertebrates. In Hawaii, the greenhouse frog primarily consumes ants, mites, and springtails, and obtains densities of up to 12,500 frogs ha-1. At this density, it is estimated that they can consume up to 129,000 invertebrates ha-1 night-1. They are a food source for the non-native brown tree snake in Guam and may be a food source for other non-native species. They may also compete with other insectivores for available prey. The greatest direct economic impacts of the invasions are to the nursery trade that must treat infested shipments. Although various control methods have been developed to control frogs in Hawaii, and citric acid, in particular, is effective in reducing greenhouse frogs, the frog’s inconspicuous nature often prevents populations from being identified and managed
Tectono-stratigraphic response of the Sandino Forearc Basin (N-Costa Rica and W-Nicaragua) to episodes of rough crust and oblique subduction
The southern Central American active margin is a world-class site where past and
present subduction processes have been extensively studied. Tectonic erosion/accretion
and oblique/orthogonal subduction are thought to alternate in space and time
along the Middle American Trench. These processes may cause various responses
in the upper plate, such as uplift/subsidence, deformation, and volcanic arc migration/
shut-off. We present an updated stratigraphic framework of the Late Cretaceous–
Cenozoic Sandino Forearc Basin (SFB) which provides evidence of
sedimentary response to tectonic events. Since its inception, the basin was predominantly
filled with deep-water volcaniclastic deposits. In contrast, shallow-water
deposits appeared episodically in the basin record and are considered as tectonic
event markers. The SFB stretches for about 300 km and varies in thickness from
5 km (southern part) to about 16 km (northern part). The drastic, along-basin, thickness
variation appears to be the result of (1) differential tectonic evolutions and (2)
differential rates of sediment supply. (1) The northern SFB did not experience major
tectonic events. In contrast, the reduced thickness of the southern SFB (5 km) is the
result of at least four uplift phases related to the collision/accretion of bathymetric
reliefs on the incoming plate: (i) the accretion of a buoyant oceanic plateau (Nicoya
Complex) during the middle Campanian; (ii) the collision of an oceanic plateau (?)
during the late Danian–Selandian; (iii) the collision/accretion of seamounts during
the late Eocene–early Oligocene; (iv) the collision of seamounts and ridges during
the Pliocene–Holocene. (2) The northwestward thickening of the SFB may have
been enhanced by high sediment supply in the Fonseca Gulf area which reflects
sourcing from wide, high relief drainage basins. In contrast, sedimentary input has
possibly been lower along the southern SFB, due to the proximity of the narrow,
lowland isthmus of southern Central America. Moreover, two phases of strongly
oblique subduction affected the margin, producing strike-slip faulting in the forearc
basin: (1) prior to the Farallon Plate breakup, an Oligocene transpressional phase
caused deformation and uplift of the basin depocenter, triggering shallowing-upward
of the Nicaraguan Isthmus in the central and northern SFB; (2) a Pleistocene–Holocene transtensional phase drives the NW-directed motion of a forearc sliver
and reactivation of the graben-bounding faults of the late Neogene Nicaraguan
Depression. We discuss arguments in favour of a Pliocene development of the
Nicaraguan Depression and propose that the Nicaraguan Isthmus, which is the
apparent rift shoulder of the depression, represents a structure inherited from the Oligocene
transpressional phase
Minsky and the Subprime Mortgage Crisis: The Financial Instability Hypothesis in the Era of Financialization
Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi-
gamma is measured using 232 fb-1 of data collected with the BABAR detector at
center-of-mass energies near 10.58 GeV. An observable is introduced and shown
to be very robust against detector asymmetries while keeping a large
sensitivity to the physical charge asymmetry that results from the interference
between initial and final state radiation. The asymmetry is determined as
afunction of the invariant mass of the final-state tracks from production
threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e-
--> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A
clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly
in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order
FSR production is consistent with the QED expectation for e+ e- --> mu+ mu-
gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.
Measurement of CP Asymmetries and Branching Fractions in Charmless Two-Body B-Meson Decays to Pions and Kaons
We present improved measurements of CP-violation parameters in the decays
, , and , and of
the branching fractions for and . The
results are obtained with the full data set collected at the
resonance by the BABAR experiment at the PEP-II asymmetric-energy factory
at the SLAC National Accelerator Laboratory, corresponding to
million pairs. We find the CP-violation parameter values and
branching fractions where in each case, the first uncertainties are statistical
and the second are systematic. We observe CP violation with a significance of
6.7 standard deviations for and 6.1 standard deviations for
, including systematic uncertainties. Constraints on the
Unitarity Triangle angle are determined from the isospin relations
among the rates and asymmetries. Considering only the solution
preferred by the Standard Model, we find to be in the range
at the 68% confidence level.Comment: 18 pages, 11 postscript figures, submitted to Phys. Rev.
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