1,458 research outputs found
Can \u3cem\u3eDarapsa myron\u3c/em\u3e (Lepidoptera: Sphingidae) Successfully Use the Invasive Plant \u3cem\u3eAmpelopsis brevipedunculata\u3c/em\u3e as a Food Resource?
Although biological invasions are generally thought to negatively impact native fauna, native herbivores that can utilize invasive plants may benefit. The East Coast of the United States has been invaded by the vitaceous plant Ampelopsis brevipedunculata. The invaded range of A. brevipedunculata overlaps with that of the native Vitis labrusca, a closely-related species that is a host plant for the native moth Darapsa myron (Lepidoptera: Sphingidae). We reared D. myron larvae on either V. labrusca or A. brevipedunculata to assess whether development and survival differed on the two plant species. Larval growth and survival to pupation was only 5% on A. brevipedunculata compared to 30% on V. labrusca, suggesting that the invasive species is an unsuitable hostplant for D. myron
A Time-Orbiting Potential Trap for Bose-Einstein Condensate Interferometry
We describe a novel atom trap for Bose-Einstein condensates of 87Rb to be
used in atom interferometry experiments. The trap is based on a time-orbiting
potential waveguide. It supports the atoms against gravity while providing weak
confinement to minimize interaction effects. We observe harmonic oscillation
frequencies omega_x, omega_y, omega_z as low as 2 pi times (6.0,1.2,3.3) Hz. Up
to 2 times 10^4 condensate atoms have been loaded into the trap, at estimated
temperatures as low as 850 pK. We anticipate that interferometer measurement
times of 1 s or more should be achievable in this device.Comment: 9 pages, 3 figure
Moir\'e Intralayer Excitons in a MoSe/MoS Heterostructure
Spatially periodic structures with a long range period, referred to as
moir\'e pattern, can be obtained in van der Waals bilayers in the presence of a
small stacking angle or of lattice mismatch between the monolayers. Theoretical
predictions suggest that the resulting spatially periodic variation of the band
structure modifies the optical properties of both intra and interlayer excitons
of transition metal dichalcogenides heterostructures. Here, we report on the
impact of the moir\'e pattern formed in a MoSe/MoS heterobilayer
encapsulated in hexagonal boron nitride. The periodic in-plane potential
results in a splitting of the MoSe exciton and trion in both emission and
absorption spectra. The observed energy difference between the split peaks is
fully consistent with theoretical predictions.Comment: just accepted in Nano Letters (10.1021/acs.nanolett.8b03266
On phase-space integrals with Heaviside functions
We discuss peculiarities that arise in the computation of real-emission contributions to observables that contain Heaviside functions. A prominent example of such a case is the zero-jettiness soft function in SCET, whose calculation at next-to-next-to-next-to-leading order in perturbative QCD is an interesting problem. Since the zero-jettiness soft function distinguishes between emissions into different hemispheres, its definition involves θ-functions of light-cone components of emitted soft partons. This prevents a direct use of multi-loop methods, based on reverse unitarity, for computing the zero-jettiness soft function in high orders of perturbation theory. We propose a way to bypass this problem and illustrate its effectiveness by computing various non-trivial contributions to the zero-jettiness soft function at NNLO and N3LO in perturbative QCD
Datana drexelii (Lepidoptera: Notododontidae) occurrence and larval survival on highbush blueberry cultivars
Plant genotype influences plant suitability to herbivores; domesticated plants selected for properties such as high fruit yield may be particularly vulnerable to herbivory. Cultivated strains of highbush blueberry, Vaccinium corymbosum L. can be high-quality hosts for larvae of the gregariously-feeding notodontid Datana drexelii (Hy. Edwards). We conducted an experiment assessing D. drexelii larval survival and pupal weight when fed foliage from five blueberry cultivars: ‘Bluecrop’, ‘Bluetta’, ‘Blueray’, ‘Lateblue’, and ‘Jersey’. We complemented this experimental work with repeated bush-level surveys of a managed blueberry patch for naturally occurring D. drexelii larval clusters. Larval survival and pupal weight were significantly higher on ‘Lateblue’ foliage than from the ‘Bluecrop’, ‘Bluetta’, and ‘Jersey’ cultivars. The blueberry patch surveys found more D. drexelii larval clusters on ‘Bluehaven’, ‘Collins’, and ‘Darrow’ bushes than on the cultivars ‘Earliblue’ and ‘Jersey’. The low D. drexelii occurrence and performance on the ‘Jersey’ cultivar suggests that this variety may be appropriate for areas where this pest is common; conversely, their high occurrence on ‘Bluehaven’ ‘Collins’, and ‘Darrow’ suggests that these cultivars may be particularly vulnerable. Cultivar-level variation in herbivore vulnerability highlights how understanding plant-pest interactions can help manage agricultural species
Probing the inter-layer exciton physics in a MoS/MoSe/MoS van der Waals heterostructure
Stacking atomic monolayers of semiconducting transition metal dichalcogenides
(TMDs) has emerged as an effective way to engineer their properties. In
principle, the staggered band alignment of TMD heterostructures should result
in the formation of inter-layer excitons with long lifetimes and robust valley
polarization. However, these features have been observed simultaneously only in
MoSe/WSe heterostructures. Here we report on the observation of long
lived inter-layer exciton emission in a MoS/MoSe/MoS trilayer van
der Waals heterostructure. The inter-layer nature of the observed transition is
confirmed by photoluminescence spectroscopy, as well as by analyzing the
temporal, excitation power and temperature dependence of the inter-layer
emission peak. The observed complex photoluminescence dynamics suggests the
presence of quasi-degenerate momentum-direct and momentum-indirect bandgaps. We
show that circularly polarized optical pumping results in long lived valley
polarization of inter-layer exciton. Intriguingly, the inter-layer exciton
photoluminescence has helicity opposite to the excitation. Our results show
that through a careful choice of the TMDs forming the van der Waals
heterostructure it is possible to control the circular polarization of the
inter-layer exciton emission.Comment: 19 pages, 3 figures. Just accepted for publication in Nano Letters
(http://pubs.acs.org/doi/10.1021/acs.nanolett.7b03184
The Pattern of CP Asymmetries in Transitions
New CP violating physics in transitions will modify the CP
asymmetries in B decays into final CP eigenstates (, , , , and ) from their
Standard Model values. In a model independent analysis, the pattern of
deviations can be used to probe which Wilson coefficients get a significant
contribution from the new physics. We demonstrate this idea using several
well-motivated models of new physics, and apply it to current data.Comment: 20 pages, 3 figures, 6 tables. v3: Discussion of higher order
corrections extended; Version appearing in JHE
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