A Pockels cell enabled heterodyne phase contrast imaging diagnostic for detection of ion cyclotron emission.

This work describes a novel optical heterodyne detection scheme that significantly extends the frequency response of the phase contrast imaging method to detect electron density fluctuations in tens of megahertz frequency range. The system employs a variable frequency electro-optic modulator to allow operation at any frequency in the range 10-40 MHz without the need to realign the system. The frequency coverage of the system makes it suitable to measure the radial structure of the electron density component of ion cyclotron emission on devices having confining magnetic field of a few tesla, thus extending the purely temporal measurements provided so far by magnetic probes.

Spotted Lanternfly (Hemiptera: Fulgoridae) Nymphal Dispersion Patterns and Their Influence on Field Experiments.

The spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae) (White, 1845), is an invasive pest in the Mid-Atlantic region of the United States. Understanding this pest's dispersion patterns is fundamental for development of management and surveillance programs. To address this knowledge gap, we quantified spotted lanternfly nymph dispersion patterns by instar for rural and urban/suburban habitats, and we compared the number of sample units required for sticky traps and in situ visual counts to estimate population densities at several precisions. In addition, we assessed the ability of two experimental designs (completely random and randomized complete block) to detect management practices' impacts in the field. All instars typically followed an aggregated dispersion pattern. Sample size and time requirements for checking and replacing sticky traps and for conducting in situ counts were similar, but in situ counts do not require purchasing traps, installation time, or delays before treatment, and do not remove insects. Although the cost for using in situ counts is likely less than for sticky traps, early instar spotted lanternfly nymph populations are harder to visually detect than later instars because of their small size, which may negate any cost advantage when treatments are applied early. In general, using a randomized complete block design resulted in higher statistical power than a completely random design, allowing detection of proportional population reductions of 10-20% less with equal replication. Studies aiming to evaluate treatments that reduce spotted lanternfly numbers by less than 60% will require researchers to evaluate the feasibility of using the required large sample sizes.

Dispersion Patterns and Sample Size Estimates for Egg Masses of Spotted Lanternfly (Hemiptera: Fulgoridae).

The spotted lanternfly, Lycorma delicatula (White), is a new invasive pest in the United States. To quantify spotted lanternfly population abundance, one must understand this pest's dispersion pattern, that is, the spatial arrangement of individuals within a population. Spotted lanternflies overwinter in egg masses from late fall to May, making this life stage suitable for population assessments. We measured the dispersion pattern of egg masses at two types of sites: a suburban housing development, where we used individual trees as the sampling unit, and rural woodlots, where we used individual trees and also plots with 5.64 m radius as sampling units. Plots were the same size as those recommended for monitoring the gypsy moth, a well-studied pest with similar egg laying habit to the spotted lanternfly. Egg masses in both sampling units were counted up to a height of 3 m. With trees as the sampling unit, egg masses were aggregated in 12 of 20 rural sampling universes, randomly dispersed at 6, and completely absent at 2. Similar patterns were seen when using the 5.64-m radius rural sampling units and for suburban sampling universes. We calculated sample size requirements for a range of mean densities at a precision of 25 and 30%. Additionally, the vertical distribution of egg masses was characterized on the invasive tree of heaven [Ailanthus altissima (Mill.) Swingle], a preferred host for spotted lanternflies. For small trees, there was a positive relationship between number of egg masses in the bottom 3 m of the tree and the total count.

Parametrization of energy sharing distributions in direct double photoionization of He.

We present experimental results on the characteristic sharing of available excess energy, ranging from 11-221 eV, between two electrons in single-photon direct double ionization of He. An effective parametrization of the sharing distributions is presented along with an empirical model that describes the complete shape of the distribution based on a single experimentally determinable parameter. The measured total energy sharing distributions are separated into two distributions representing the shake-off and knock-out parts by simulating the sharing distribution curves expected from a pure wave collapse after a sudden removal of the primary electron. In this way, empirical knock-out distributions are extracted and both the shake-off and knock-out distributions are parametrized. These results suggest a simple method that can be applied to other atomic and molecular systems to experimentally study important aspects of the direct double ionization process.

A combined phase contrast imaging and heterodyne interferometer system for multiscale fluctuation measurements (invited).

In this work, a novel combined diagnostic capable of measuring multiscale density fluctuations that extend from magnetohydrodynamic (MHD) to the lower range of electron temperature gradient turbulence has been designed, installed, and operated at DIII-D. The combined diagnostic was constructed by adding a heterodyne interferometer to the pre-existing phase contrast imaging (PCI) system, both of which measure line-integrated electron density fluctuations. The port-space footprint is minimized via use of a single 10.6 µm probe beam. With temporal bandwidths in excess of 1 MHz, the PCI measures high-k (1.5 cm-1 < |k R | ≤ 25 cm-1) fluctuations with sensitivity 3 × 1 0 13 m - 2 / kHz , while the interferometer simultaneously measures low-k (|k R | < 5 cm-1) fluctuations with sensitivity 3 × 1 0 14 m - 2 / kHz . The intentional mid-k overlap has been empirically verified with sound-wave calibrations and allows quantitative investigation of multiscale effects that are predicted to be significant in the reactor-relevant T e ∼ T i regime. Furthermore, via correlation with the primary DIII-D interferometer, the toroidal mode numbers of core-localized MHD can be measured.

Quantum dynamics of long-range interacting systems using the positive-P and gauge-P representations.

We provide the necessary framework for carrying out stochastic positive-P and gauge-P simulations of bosonic systems with long-range interactions. In these approaches, the quantum evolution is sampled by trajectories in phase space, allowing calculation of correlations without truncation of the Hilbert space or other approximations to the quantum state. The main drawback is that the simulation time is limited by noise arising from interactions. We show that the long-range character of these interactions does not further increase the limitations of these methods, in contrast to the situation for alternatives such as the density matrix renormalization group. Furthermore, stochastic gauge techniques can also successfully extend simulation times in the long-range-interaction case, by making using of parameters that affect the noise properties of trajectories, without affecting physical observables. We derive essential results that significantly aid the use of these methods: estimates of the available simulation time, optimized stochastic gauges, a general form of the characteristic stochastic variance, and adaptations for very large systems. Testing the performance of particular drift and diffusion gauges for nonlocal interactions, we find that, for small to medium systems, drift gauges are beneficial, whereas for sufficiently large systems, it is optimal to use only a diffusion gauge. The methods are illustrated with direct numerical simulations of interaction quenches in extended Bose-Hubbard lattice systems and the excitation of Rydberg states in a Bose-Einstein condensate, also without the need for the typical frozen gas approximation. We demonstrate that gauges can indeed lengthen the useful simulation time.

A phase contrast imaging-interferometer system for detection of multiscale electron density fluctuations on DIII-D.

Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI-interferometer. The combined system uses a single 10.6 µm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz

Switching Exciton Pulses Through Conical Intersections.

Exciton pulses transport excitation and entanglement adiabatically through Rydberg aggregates, assemblies of highly excited light atoms, which are set into directed motion by resonant dipole-dipole interaction. Here, we demonstrate the coherent splitting of such pulses as well as the spatial segregation of electronic excitation and atomic motion. Both mechanisms exploit local nonadiabatic effects at a conical intersection, turning them from a decoherence source into an asset. The intersection provides a sensitive knob controlling the propagation direction and coherence properties of exciton pulses. The fundamental ideas discussed here have general implications for excitons on a dynamic network.

Single-photon multiple detachment in fullerene negative ions: absolute ionization cross sections and the role of the extra electron.

We have obtained experimental photo-double- and photo-triple-detachment cross sections for the fullerene negative ion using Advanced Light Source photons of 17-90 eV. The cross sections are 2 and 2.5 times larger than those for C60 and appear to be compressed and shifted in photon energy as compared to C60. Our analysis reveals that the additional electron in C60- primarily produces screening which is responsible for the modification of the spectrum. Both screening effects, the shift and the compression, can be quantitatively accounted for by a linear transformation of the energy axis. Applying the transformation allows us to map the neutral and negative ion cross sections onto each other, pointing out the close relationship of correlated few-electron dynamics in neutral and negatively charged extended systems. In contrast, dynamics of neutral and negatively charged atoms or small molecules are typically not closely related.

Coulomb explosion of uniformly charged spheroids.

A simple, semianalytical model is proposed for nonrelativistic Coulomb explosion of a uniformly charged spheroid. This model allows us to derive the time-dependent particle energy distributions. Simple expressions are also given for the characteristic explosion time and maximum particle energies in the limits of extreme prolate and oblate spheroids as well as for the sphere. Results of particle simulations are found to be in remarkably good agreement with the model.

Dopant-induced ignition of helium nanodroplets in intense few-cycle laser pulses.

We demonstrate ultrafast resonant energy absorption of rare-gas doped He nanodroplets from intense few-cycle (~10 fs) laser pulses. We find that less than 10 dopant atoms "ignite" the droplet to generate a nonspherical electronic nanoplasma resulting ultimately in complete ionization and disintegration of all atoms, although the pristine He droplet is transparent for the laser intensities applied. Our calculations at those intensities reveal that the minimal pulse length required for ignition is about 9 fs.

A homonuclear molecule with a permanent electric dipole moment.

Permanent electric dipole moments in molecules require a breaking of parity symmetry. Conventionally, this symmetry breaking relies on the presence of heteronuclear constituents. We report the observation of a permanent electric dipole moment in a homonuclear molecule in which the binding is based on asymmetric electronic excitation between the atoms. These exotic molecules consist of a ground-state rubidium (Rb) atom bound inside a second Rb atom electronically excited to a high-lying Rydberg state. Detailed calculations predict appreciable dipole moments on the order of 1 Debye, in excellent agreement with the observations.

Conical intersections in an ultracold gas.

We find that energy surfaces of more than two atoms or molecules interacting via transition dipole-dipole potentials generically possess conical intersections (CIs). Typically only few atoms participate strongly in such an intersection. For the fundamental case, a circular trimer, we show how the CI affects adiabatic excitation transport via electronic decoherence or geometric phase interference. These phenomena may be experimentally accessible if the trimer is realized by light alkali atoms in a ring trap, whose interactions are induced by off-resonant dressing with Rydberg states. Such a setup promises a direct probe of the full many-body density dynamics near a CI.

Newton's cradle and entanglement transport in a flexible Rydberg chain.

In a regular, flexible chain of Rydberg atoms, a single electronic excitation localizes on two atoms that are in closer mutual proximity than all others. We show how the interplay between excitonic and atomic motion causes electronic excitation and diatomic proximity to propagate through the Rydberg chain as a combined pulse. In this manner entanglement is transferred adiabatically along the chain, reminiscent of momentum transfer in Newton's cradle.

Rydberg trimers and excited dimers bound by internal quantum reflection.

In a combined experimental and theoretical effort we report on two novel types of ultracold long-range Rydberg molecules. First, we demonstrate the creation of triatomic molecules of one Rydberg atom and two ground-state atoms in a single-step photoassociation. Second, we assign a series of excited dimer states that are bound by a so far unexplored mechanism based on internal quantum reflection at a steep potential drop. The properties of the Rydberg molecules identified in this work qualify them as prototypes for a new type of chemistry at ultracold temperatures.

[Pharmacokinetic MRI of the prostate: parameters for differentiating low-grade and high-grade prostate cancer]. / Pharmakokinetische MRT der Prostata: Parameter zur Unterscheidung von Low-grade- und High-grade-Prostatakarzinomen.

PURPOSE: To investigate whether pharmacokinetic MRI parameters "perfusion, blood volume, mean transit time (MTT), interstitial volume, permeability, extraction coefficient, delay, and dispersion" allow the differentiation of low-grade (Gleason score < or = 6) and high-grade (Gleason score > or = 7) prostate cancer. MATERIALS AND METHOD: Forty-two patients with prostate cancer verified by biopsy (PSA 2.7 to 31.4 ng/ml) and scheduled for prostatectomy underwent MRI at 1.5 Tesla using the dynamic contrast-enhanced inversion-prepared dual-contrast gradient echo sequence (temporal resolution, 1.65 s) and a combined endorectal body phased array coil. Parametric maps were computed using a sequential 3-compartment model and the corresponding post-processing algorithms. A total of 41 areas of prostate cancer (15 low-grade, 26 high-grade cancers) in 32 patients were able to be correlated with the prostatectomy specimens and were included in the analysis. RESULTS: Low-grade prostate cancers had a higher mean blood volume (1.76 % vs. 1.64 %, p = 0.039), longer MTT (6.39 s vs. 3.25 s, p < 0.001), and lower mean permeability (2.57 min (-1) vs. 3.86 min (-1), p = 0.011) than high-grade cancers. No statistically significant difference was found for perfusion (p = 0.069), interstitial volume (p = 0.849), extraction coefficient (p = 0.615), delay (p = 0.489), and dispersion (p = 0.306). CONCLUSIONS: Blood volume, MTT, and permeability allow the differentiation of low-grade and high-grade prostate cancer. They may be used to detect cancer progression by MRI in patients managed by active surveillance.

Localized measurement of short wavelength plasma fluctuations with the DIII-D phase contrast imaging diagnostic.

A novel rotating mask system has been designed and implemented on the DIII-D phase contrast imaging (PCI) diagnostic to produce the first spatially localized PCI measurements of a tokamak plasma. The localization technique makes use of the variation in the magnetic field component perpendicular to the viewing chord as a function of chord height. This new capability provides measurements in the range of 2

Antiblockade in Rydberg excitation of an ultracold lattice gas.

It is shown that the two-step excitation scheme typically used to create an ultracold Rydberg gas can be described with an effective two-level rate equation, greatly reducing the complexity of the optical Bloch equations. This allows us to efficiently solve the many-body problem of interacting cold atoms with a Monte Carlo technique. Our results reproduce the observed excitation blockade effect. However, we demonstrate that an Autler-Townes double peak structure in the two-step excitation scheme, which occurs for moderate pulse lengths as used in the experiment, can give rise to an antiblockade effect. It is most pronounced for atoms arranged on a lattice. Since the effect is robust against a large number of lattice defects it should be experimentally realizable with an optical lattice created by CO2 lasers.

Treatment of scaphoid non-unions by a palmar approach with vascularised bone graft harvested from the thumb.

Ten patients with scaphoid non-unions which had been present for longer than 2 years were treated using a vascularised bone graft harvested from the thumb and pedicled on the first dorsal metacarpal artery. Bone harvesting and grafting were performed by a single palmar approach. Concomitant cancellous bone graft was not used. Bone healing was confirmed by CT scans in nine of the ten patients. Persistence of the non-union was observed in one patient who was the oldest in this series, had the longest standing non-union and was a heavy smoker. Twelve months after surgery, nine of the ten patients had significant pain relief with an improved range of motion and grip strength.

Origin of chaos in soft interactions and signatures of nonergodicity.

The emergence of chaotic motion is discussed for hard-point like and soft collisions between two particles in a one-dimensional box. It is known that ergodicity may be obtained in hard-point like collisions for specific mass ratios gamma=m(2)/m(1) of the two particles and that Lyapunov exponents are zero. However, if a Yukawa interaction between the particles is introduced, we show analytically that positive Lyapunov exponents are generated due to double collisions close to the walls. While the largest finite-time Lyapunov exponent changes smoothly with gamma , the number of occurrences of the most probable one, extracted from the distribution of finite-time Lyapunov exponents over initial conditions, reveals details about the phase-space dynamics. In particular, the influence of the integrable and pseudointegrable dynamics without Yukawa interaction for specific mass ratios can be clearly identified and demonstrates the sensitivity of the finite-time Lyapunov exponents as a phase-space probe. Being not restricted to two-dimensional problems such as Poincaré sections, the number of occurrences of the most probable Lyapunov exponents suggests itself as a suitable tool to characterize phase-space dynamics in higher dimensions. This is shown for the problem of two interacting particles in a circular billiard.