4,440 research outputs found
Presence of the “Threatened” \u3ci\u3eTrimerotropis Huroniana\u3c/i\u3e (Orthoptera: Acrididae) in Relation to the Occurrence of Native Dune Plant Species and the Exotic \u3ci\u3eCentaurea Biebersteinii\u3c/i\u3e
Trimerotropis huroniana Wlk. is a “Threatened” species in Michigan and Wisconsin with a distribution limited to open dune systems in the northern Great Lakes region of North America. Pitfall traps were utilized in the Grand Sable Dunes of Pictured Rocks National Lakeshore, MI, along with an herbaceous plant survey, to identify the relationship of T. huroniana with native dune plant species, Ammophila breviligulata Fern. (American beachgrass, Poaceae), Artemisia campestris L. (field sagewort, Asteraceae), and the exotic invasive plant Centaurea biebersteinii DC. [=Centaurea maculosa, spotted knapweed, Lamarck] (Asteraceae). The absence of C. biebersteinii resulted in an increased likelihood of capturing T. huroniana. This was most likely due to the increased likelihood of encountering A. campestris in areas without C. biebersteinii. The occurrence of A. breviligulata was independent of C. biebersteinii presence. A significant positive linear relationship occurred between the percent cover of A. campestris and the traps that captured T. huroniana. There was no significant relationship between A. breviligulata percent cover and the traps that captured T. huroniana. The occurrence and distribution of T. huroniana is closely related to the presence and abundance of A. campestris. Habitat conservation and improvement for T. huroniana should include increases in A. campestris populations through the removal of C. biebersteinii
Predicting Emerald Ash Borer, \u3ci\u3eAgrilus Planipennis\u3c/i\u3e (Coleoptera: Buprestidae), Landing Behavior on Unwounded Ash
Detection of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive forest pest, is difficult in low density populations war- ranting continual development of various trapping techniques and protocols. Understanding and predicting landing behavior of A. planipennis may assist in the further development of trapping techniques and improvement of trapping protocols for widespread survey programs in North America. Three multiple regression models were developed using ash tree vigor and crown light exposure to predict the landing behavior of A. planipennis. These models were then used to predict the landing density of A. planipennis at separate sites and in separate years. Successful prediction of A. planipennis capture density at the test sites was limited. Even though the multiple regression models were not effective at predicting landing behavior of A. planipennis, tree characteristics were used to predict the likelihood of A. planipennis landing. Trees predicted as having high likelihood of landing had 3.5 times as many A. planipennis adults/m2 on stem traps than trees predicted as having low likelihood of landing. While the landing density of A. planipennis may not be efficiently predicted, the utility of these predictions may be in the form of identifying trees with a high likelihood of A. planipennis landing. Those high likelihood trees may assist in improving existing detection programs and techniques in North American forests
Weak values and the Leggett-Garg inequality in solid-state qubits
An implementation of weak values is investigated in solid-state qubits. We
demonstrate that a weak value can be non-classical if and only if a
Leggett-Garg inequality can also be violated. Generalized weak values are
described, where post-selection on a range of weak measurement results.
Imposing classical weak values permits the derivation of Leggett-Garg
inequalities for bounded operators. Our analysis is presented in terms of
kicked quantum nondemolition measurements on a quantum double-dot charge qubit.Comment: 4 pages, 2 figure
Migration as Adaptation? Exploring The Scope for Co-ordinating Environmental and Migration Policies in the European Union
Precision frequency measurements with interferometric weak values
We demonstrate an experiment which utilizes a Sagnac interferometer to
measure a change in optical frequency of 129 kHz per root Hz with only 2 mW of
continuous wave, single mode input power. We describe the measurement of a weak
value and show how even higher frequency sensitivities may be obtained over a
bandwidth of several nanometers. This technique has many possible applications,
such as precision relative frequency measurements and laser locking without the
use of atomic lines.Comment: 4 pages, 3 figures, published in PR
Ultrasensitive Beam Deflection Measurement via Interferometric Weak Value Amplification
We report on the use of an interferometric weak value technique to amplify
very small transverse deflections of an optical beam. By entangling the beam's
transverse degrees of freedom with the which-path states of a Sagnac
interferometer, it is possible to realize an optical amplifier for polarization
independent deflections. The theory for the interferometric weak value
amplification method is presented along with the experimental results, which
are in good agreement. Of particular interest, we measured the angular
deflection of a mirror down to 560 femtoradians and the linear travel of a
piezo actuator down to 20 femtometers
Optimizing the Signal to Noise Ratio of a Beam Deflection Measurement with Interferometric Weak Values
The amplification obtained using weak values is quantified through a detailed
investigation of the signal to noise ratio for an optical beam deflection
measurement. We show that for a given deflection, input power and beam radius,
the use of interferometric weak values allows one to obtain the optimum signal
to noise ratio using a coherent beam. This method has the advantage of reduced
technical noise and allows for the use of detectors with a low saturation
intensity. We report on an experiment which improves the signal to noise ratio
for a beam deflection measurement by a factor of 54 when compared to a
measurement using the same beam size and a quantum limited detector
Revisiting two-step Forbush decreases
Interplanetary coronal mass ejections (ICMEs) and their shocks can sweep out galactic cosmic rays (GCRs), thus creating Forbush decreases (FDs). The traditional model of FDs predicts that an ICME and its shock decrease the GCR intensity in a two-step profile. This model, however, has been the focus of little testing. Thus, our goal is to discover whether a passing ICME and its shock inevitably lead to a two-step FD, as predicted by the model. We use cosmic ray data from 14 neutron monitors and, when possible, high time resolution GCR data from the spacecraft International Gamma Ray Astrophysical Laboratory (INTEGRAL). We analyze 233 ICMEs that should have created two-step FDs. Of these, only 80 created FDs, and only 13 created two-step FDs. FDs are thus less common than predicted by the model. The majority of events indicates that profiles of FDs are more complicated, particularly within the ICME sheath, than predicted by the model. We conclude that the traditional model of FDs as having one or two steps should be discarded. We also conclude that generally ignored small-scale interplanetary magnetic field structure can contribute to the observed variety of FD profiles
Presence of the “Threatened” \u3ci\u3eTrimerotropis Huroniana\u3c/i\u3e (Orthoptera: Acrididae) in Relation to the Occurrence of Native Dune Plant Species and the Exotic \u3ci\u3eCentaurea Biebersteinii\u3c/i\u3e
Trimerotropis huroniana Wlk. is a “Threatened” species in Michigan and Wisconsin with a distribution limited to open dune systems in the northern Great Lakes region of North America. Pitfall traps were utilized in the Grand Sable Dunes of Pictured Rocks National Lakeshore, MI, along with an herbaceous plant survey, to identify the relationship of T. huroniana with native dune plant species, Ammophila breviligulata Fern. (American beachgrass, Poaceae), Artemisia campestris L. (field sagewort, Asteraceae), and the exotic invasive plant Centaurea biebersteinii DC. [=Centaurea maculosa, spotted knapweed, Lamarck] (Asteraceae). The absence of C. biebersteinii resulted in an increased likelihood of capturing T. huroniana. This was most likely due to the increased likelihood of encountering A. campestris in areas without C. biebersteinii. The occurrence of A. breviligulata was independent of C. biebersteinii presence. A significant positive linear relationship occurred between the percent cover of A. campestris and the traps that captured T. huroniana. There was no significant relationship between A. breviligulata percent cover and the traps that captured T. huroniana. The occurrence and distribution of T. huroniana is closely related to the presence and abundance of A. campestris. Habitat conservation and improvement for T. huroniana should include increases in A. campestris populations through the removal of C. biebersteinii
Gap theory of rectification in ballistic three-terminal conductors
We introduce a model for rectification in three-terminal ballistic
conductors, where the central connecting node is modeled as a chaotic cavity.
For bias voltages comparable to the Fermi energy, a strong nonlinearity is
created by the opening of a gap in the transport window. Both noninteracting
cavity electrons at arbitrary temperature as well as the hot electron regime
are considered. Charging effects are treated within the transmission formalism
using a self-consistent analysis. The conductance of the third lead in a
voltage probe configuration is varied to also model inelastic effects. We find
that the basic transport features are insensitive to all of these changes,
indicating that the nonlinearity is robust and well suited to applications such
as current rectification in ballistic systems. Our findings are in broad
agreement with several recent experiments.Comment: 8 pages, 6 figure
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