Observation of photo-induced plasmon-phonon coupling in PbTe via ultrafast x-ray scattering.

We report the observation of photo-induced plasmon-phonon coupled modes in the group IV-VI semiconductor PbTe using ultrafast x-ray diffuse scattering at the Linac Coherent Light Source. We measure the near-zone-center excited-state dispersion of the heavily screened longitudinal optical (LO) phonon branch as extracted from differential changes in x-ray diffuse scattering intensity following above bandgap photoexcitation. We suggest that upon photoexcitation, the LO phonon-plasmon coupled (LOPC) modes themselves become coupled to longitudinal acoustic modes that drive electron band shifts via acoustic deformation potentials and possibly to low-energy single-particle excitations within the plasma and that these couplings give rise to displacement-correlations that oscillate in time with a period given effectively by the heavily screened LOPC frequency.

Quantifying deformations and strains in human intervertebral discs using Digital Volume Correlation combined with MRI (DVC-MRI).

Physical disruptions to intervertebral discs (IVDs) can cause mechanical changes that lead to degeneration and to low back pain which affects 75% of us in our lifetimes. Quantifying the effects of these changes on internal IVD strains may lead to better preventative strategies and treatments. Digital Volume Correlation (DVC) is a non-invasive technique that divides volumetric images into subsets, and measures strains by tracking the internal patterns within them under load. Applying DVC to MRIs may allow non-invasive strain measurements. However, DVC-MRI for strain measurements in IVDs has not been used previously. The purpose of this study was to quantify the strain and deformation errors associated with DVC-MRI for measurements in human IVDs. Eight human lumbar IVDs were MRI scanned (9.4 T) for a 'zero-strain study' (multiple unloaded scans to quantify noise within the system), and a loaded study (2 mm axial compression). Three DVC methodologies: Fast-Fourier transform (FFT), direct correlation (DC), and a combination of both FFT and DC approaches were compared with subset sizes ranging from 8 to 88 voxels to establish the optimal DVC methodology and settings which were then used in the loaded study. FFT + DC was the optimal method and a subset size of 56 voxels (2520 µm) was found to be a good compromise between errors and spatial resolution. Displacement and strain errors did not exceed 28 µm and 3000 microstrain, respectively. These findings demonstrate that DVC-MRI can quantify internal strains within IVDs non-invasively and accurately. The method has unique potential for assessing IVD strains within patients.

Propagation phase-contrast micro-computed tomography allows laboratory-based three-dimensional imaging of articular cartilage down to the cellular level.

OBJECTIVE: High-resolution non-invasive three-dimensional (3D) imaging of chondrocytes in articular cartilage remains elusive. The aim of this study was to explore whether laboratory micro-computed tomography (micro-CT) permits imaging cells within articular cartilage. DESIGN: Bovine osteochondral plugs were prepared four ways: in phosphate-buffered saline (PBS) or 70% ethanol (EtOH), both with or without phosphotungstic acid (PTA) staining. Specimens were imaged with micro-CT following two protocols: 1) absorption contrast (AC) imaging 2) propagation phase-contrast (PPC) imaging. All samples were scanned in liquid. The contrast to noise ratio (C/N) of cellular features quantified scan quality and were statistically analysed. Cellular features resolved by micro-CT were validated by standard histology. RESULTS: The highest quality images were obtained using propagation phase-contrast imaging and PTA-staining in 70% EtOH. Cellular features were also visualised when stained in PBS and unstained in EtOH. Under all conditions PPC resulted in greater contrast than AC (p < 0.0001 to p = 0.038). Simultaneous imaging of cartilage and subchondral bone did not impede image quality. Corresponding features were located in both histology and micro-CT and followed the same distribution with similar density and roundness values. CONCLUSIONS: Three-dimensional visualisation and quantification of the chondrocyte population within articular cartilage can be achieved across a field of view of several millimetres using laboratory-based micro-CT. The ability to map chondrocytes in 3D opens possibilities for research in fields from skeletal development through to medical device design and treatment of cartilage degeneration.

Heterodyne x-ray diffuse scattering from coherent phonons.

Here, we report Fourier-transform inelastic x-ray scattering measurements of photoexcited GaAs with embedded ErAs nanoparticles. We observe temporal oscillations in the x-ray scattering intensity, which we attribute to inelastic scattering from coherent acoustic phonons. Unlike in thermal equilibrium, where inelastic x-ray scattering is proportional to the phonon occupation, we show that the scattering is proportional to the phonon amplitude for coherent states. The wavevectors of the observed phonons extend beyond the excitation wavevector. The nanoparticles break the discrete translational symmetry of the lattice, enabling the generation of large wavevector coherent phonons. Elastic scattering of x-ray photons from the nanoparticles provides a reference for heterodyne mixing, yielding signals proportional to the phonon amplitude.

Multiple Supersonic Phase Fronts Launched at a Complex-Oxide Heterointerface.

Selective optical excitation of a substrate lattice can drive phase changes across heterointerfaces. This phenomenon is a nonequilibrium analogue of static strain control in heterostructures and may lead to new applications in optically controlled phase change devices. Here, we make use of time-resolved nonresonant and resonant x-ray diffraction to clarify the underlying physics and to separate different microscopic degrees of freedom in space and time. We measure the dynamics of the lattice and that of the charge disproportionation in NdNiO_{3}, when an insulator-metal transition is driven by coherent lattice distortions in the LaAlO_{3} substrate. We find that charge redistribution propagates at supersonic speeds from the interface into the NdNiO_{3} film, followed by a sonic lattice wave. When combined with measurements of magnetic disordering and of the metal-insulator transition, these results establish a hierarchy of events for ultrafast control at complex-oxide heterointerfaces.

Three-dimensional imaging of dislocation dynamics during the hydriding phase transformation.

Crystallographic imperfections significantly alter material properties and their response to external stimuli, including solute-induced phase transformations. Despite recent progress in imaging defects using electron and X-ray techniques, in situ three-dimensional imaging of defect dynamics remains challenging. Here, we use Bragg coherent diffractive imaging to image defects during the hydriding phase transformation of palladium nanocrystals. During constant-pressure experiments we observe that the phase transformation begins after dislocation nucleation close to the phase boundary in particles larger than 300 nm. The three-dimensional phase morphology suggests that the hydrogen-rich phase is more similar to a spherical cap on the hydrogen-poor phase than to the core-shell model commonly assumed. We substantiate this using three-dimensional phase field modelling, demonstrating how phase morphology affects the critical size for dislocation nucleation. Our results reveal how particle size and phase morphology affects transformations in the PdH system.

Bragg coherent diffraction imaging and metrics for radiation damage in protein micro-crystallography.

The proliferation of extremely intense synchrotron sources has enabled ever higher-resolution structures to be obtained using data collected from smaller and often more imperfect biological crystals (Helliwell, 1984). Synchrotron beamlines now exist that are capable of measuring data from single crystals that are just a few micrometres in size. This provides renewed motivation to study and understand the radiation damage behaviour of small protein crystals. Reciprocal-space mapping and Bragg coherent diffractive imaging experiments have been performed on cryo-cooled microcrystals of hen egg-white lysozyme as they undergo radiation damage. Several well established metrics, such as intensity-loss and lattice expansion, are applied to the diffraction data and the results are compared with several new metrics that can be extracted from the coherent imaging experiments. Individually some of these metrics are inconclusive. However, combining metrics, the results suggest that radiation damage behaviour in protein micro-crystals differs from that of larger protein crystals and may allow them to continue to diffract for longer. A possible mechanism to account for these observations is proposed.

Laboratory evaluation of a novel anaesthesia delivery device.

Here, we describe proof of concept of a novel method for delivering volatile anaesthetics, where the liquid anaesthetic (sevoflurane or isoflurane) is formulated into an emulsion that is contained in a compact, lightweight device through which carrier gas flows. Release of anaesthetic is achieved by stirring of the formulation, allowing controlled and responsive release of anaesthetic at a variety of fixed flow rates between 0.5 l.min-1 and 5 l.min-1 , with ventilated, non-ventilated and draw-over breathing systems. Anaesthetic release was evaluated using target anaesthetic concentrations ranging from 0.5% v/v to 8% v/v to mimic those typically required for induction and maintenance of anaesthesia, and lower concentrations suitable for sedation. Under all conditions, output could be maintained within 0.1% v/v of the intended setting, and the device could deliver a controlled level of anaesthetic for at least 60 min, with compensation for different ambient temperatures (10-30 °C) and carrier gas flow rates. This device offers a simple, inexpensive method of delivering safe concentrations of volatile anaesthetics for a wide range of applications.

BATTERIES. Topological defect dynamics in operando battery nanoparticles.

Topological defects can markedly alter nanomaterial properties. This presents opportunities for "defect engineering," where desired functionalities are generated through defect manipulation. However, imaging defects in working devices with nanoscale resolution remains elusive. We report three-dimensional imaging of dislocation dynamics in individual battery cathode nanoparticles under operando conditions using Bragg coherent diffractive imaging. Dislocations are static at room temperature and mobile during charge transport. During the structural phase transformation, the lithium-rich phase nucleates near the dislocation and spreads inhomogeneously. The dislocation field is a local probe of elastic properties, and we find that a region of the material exhibits a negative Poisson's ratio at high voltage. Operando dislocation imaging thus opens a powerful avenue for facilitating improvement and rational design of nanostructured materials.

Radiation damage in a micron-sized protein crystal studied via reciprocal space mapping and Bragg coherent diffractive imaging.

For laboratory and synchrotron based X-ray sources, radiation damage has posed a significant barrier to obtaining high-resolution structural data from biological macromolecules. The problem is particularly acute for micron-sized crystals where the weaker signal often necessitates the use of higher intensity beams to obtain the relevant data. Here, we employ a combination of techniques, including Bragg coherent diffractive imaging to characterise the radiation induced damage in a micron-sized protein crystal over time. The approach we adopt here could help screen for potential protein crystal candidates for measurement at X-ray free election laser sources.

Ultrafast three-dimensional imaging of lattice dynamics in individual gold nanocrystals.

Key insights into the behavior of materials can be gained by observing their structure as they undergo lattice distortion. Laser pulses on the femtosecond time scale can be used to induce disorder in a "pump-probe" experiment with the ensuing transients being probed stroboscopically with femtosecond pulses of visible light, x-rays, or electrons. Here we report three-dimensional imaging of the generation and subsequent evolution of coherent acoustic phonons on the picosecond time scale within a single gold nanocrystal by means of an x-ray free-electron laser, providing insights into the physics of this phenomenon. Our results allow comparison and confirmation of predictive models based on continuum elasticity theory and molecular dynamics simulations.

High-resolution three-dimensional partially coherent diffraction imaging.

The wave properties of light, particularly its coherence, are responsible for interference effects, which can be exploited in powerful imaging applications. Coherent diffractive imaging relies heavily on coherence and has recently experienced rapid growth. Coherent diffractive imaging recovers an object from its diffraction pattern by computational phasing with the potential of wavelength-limited resolution. Diminished coherence results in reconstructions that suffer from artefacts or fail completely. Here we demonstrate ab initio phasing of partially coherent diffraction patterns in three dimensions, while simultaneously determining the coherence properties of the illuminating wavefield. Both the dramatic improvements in image interpretability and the three-dimensional evaluation of the coherence will have broad implications for quantitative imaging of nanostructures and wavefield characterization with X-rays and electrons.

An in-vacuum x-ray diffraction microscope for use in the 0.7-2.9 keV range.

A dedicated in-vacuum coherent x-ray diffraction microscope was installed at the 2-ID-B beamline of the Advanced Photon Source for use with 0.7-2.9 keV x-rays. The instrument can accommodate three common implementations of diffractive imaging; plane wave illumination; defocused-probe (Fresnel diffractive imaging) and scanning (ptychography) using either a pinhole, focused or defocused probe. The microscope design includes active feedback to limit motion of the optics with respect to the sample. Upper bounds on the relative optics-to-sample displacement have been measured to be 5.8 nm(v) and 4.4 nm(h) rms/h using capacitance micrometry and 27 nm/h using x-ray point projection imaging. The stability of the measurement platform and in-vacuum operation allows for long exposure times, high signal-to-noise and large dynamic range two-dimensional intensity measurements to be acquired. Finally, we illustrate the microscope's stability with a recent experimental result.

Use of a complex constraint in coherent diffractive imaging.

We demonstrate use of a complex constraint based on the interaction of x-rays with matter for reconstructing images from coherent X-ray diffraction. We show the complementary information provided by the phase and magnitude of the reconstructed wavefield greatly improves the quality of the resulting estimate of the transmission function of an object without the need for a priori information about the object composition.

Quantitative phase measurement in coherent diffraction imaging.

We demonstrate high spatial resolution phase retrieval of a non-periodic gold nano-structure using the method of Fresnel coherent diffractive imaging. The result is quantitative to better than 10% and does not rely on any a priori knowledge of the sample.

Efficacy of an ivermectin and pyrantel pamoate combination against adult hookworm, Ancylostoma braziliense, in dogs.

A chewable tablet incorporating ivermectin and pyrantel was tested in 12 Beagle dogs for efficacy against the adult hookworm, Ancylostoma braziliense. The dogs were administered infective larvae of A braziliense orally. Twenty-one days after infection the dogs were weighed and allocated randomly to receive either an oral treatment with ivermectin and pyrantel in a beef-based chewable tablet or no treatment. The chewable tablet was a commercially available product, which was made to deliver ivermectin at 6 micrograms/kg and pyrantel at 5.0 mg/kg to each dog. Seven days after treatment the dogs were euthanased, necropsied, and examined for adult hookworms. At necropsy, no adult A braziliense was observed in any of the 6 treated dogs and all 6 dogs that had been left untreated were infected with adult A braziliense (range, 48 to 161). It was concluded that this combination product is 100% efficacious against adult A braziliense.

Activity of a novel nonpeptidyl growth hormone secretagogue, L-700,653, in swine.

L-700,653 is a potent nonpeptidyl GH secretagogue consisting of a benzolactam structure: (4'-[[3(R)-[[3-[(2(S),3-dihydroxypropyl) amino]3-methyl-1-oxobutyl]amino]2,3,4,5-tetrahydro-2-oxo-1H-1-benzaze pin- 1-yl]methyl][1,1'-biphenyl]2-carboxamide hydrochloride). When administered sc by a Medi-Jector device at 0, 0.003, 0.01, 0.03, and 0.1 mg/kg BW to male castrated swine (approximately 50 kg BW), L-700,653 stimulated dose-related increases in peak plasma GH concentrations by 20% (P = NS), 150% (P = NS), 250% (P < 0.05), and 340% (P < 0.05), respectively, over the saline vehicle control value (11.3 +/- 6.5 ng/ml) and stimulated increases in GH areas under the curve (AUCs) by 10% (P = NS), 30% (P = NS), 90% (P < 0.05), and 100% (P < 0.01), respectively, over the saline vehicle control value (799 +/- 145 ng/min.ml). After sc administration of L-700, 653, there were no significant changes in plasma LH levels. Subcutaneous dose of 0.03 or 0.1 mg/kg increased plasma cortisol AUCs by 60% (P = NS) and 150% (P < 0.03) over the control value (2461 +/- 935 ng/min.ml) and increased cortisol peaks by 80% (P = NS) and 200% (P < 0.01), respectively, over the control value (38.3 +/- 12.3 ng/ml). Repeated sc administration of L-700,653 (0.03 or 0.1 mg/kg) at 0800, 1400, and 2000 h daily over 3 days consistently increased mean GH peak and GH AUC at each treatment period, with minimal and maximal increases of 40% and 190% in GH peak level at the 0.03 mg/kg dose and 100% and 400% increases in GH peak level at the 0.01 mg/kg dose, respectively. Continuous i.v. infusion of L-700,653, at either 0.01 or 0.1 mg/kg BW.h over a 180-min period, increased GH AUCs by 60% (P = NS) or 470% (P < 0.01) and GH peaks by 190% (P = NS) or 1520% (P < 0.01), respectively, over the control value (589 +/- 313 ng/min.ml; 7.0 +/- 11.1 ng/ml). After a 180- to 300-min saline infusion, an iv bolus dose of 0.1 mg/kg L-700,653 resulted in GH responses inversely proportional to the previous infusion dose, i.e. 0, 0.01, or 0.1 mg/kg.(ABSTRACT TRUNCATED AT 400 WORDS)

Efficacy of ivermectin and pyrantel pamoate combined in a chewable formulation against heartworm, hookworm, and ascarid infections in dogs.

Eight trials were conducted in dogs to document the efficacy of ivermectin (6 micrograms/kg of body weight) and pyrantel pamoate (5 mg of active pyrantel/kg) in a beef-based chewable formulation against Dirofilaria immitis, Ancylostoma caninum, Uncinaria stenocephala, Toxocara canis, and Toxascaris leonina. Three studies involved induced infection with D immitis, and 5 studies involved induced or natural infection with hookworms and ascarids. In 3 intestinal parasite trials, the efficacy of the combination chewable tablet was compared with each of its components. Results indicated that 1 component did not interfere with the activity of the other. In 1 heartworm and 2 intestinal parasite trials, the efficacy of pyrantel, ivermectin/pyrantel combination, or ivermectin with pyrantel dosage of 10 mg/kg was evaluated. The ivermectin/pyrantel combination was 100% effective in preventing development of D immitis larvae. Efficacy of the combined product against T canis, Toxascaris leonina, A caninum, and U stenocephala was 90.1, 99.2, 98.5, and 98.7%, respectively. In the intestinal parasite trials, each individual component was found not to interfere with the anthelmintic action of the other. Increasing the dosage of pyrantel to 10 mg/kg (2 x that in the combination) did not interfere with the efficacy of ivermectin against heartworm or increase the activity of pyrantel against intestinal parasites.

Safety study of a beef-based chewable tablet formulation of ivermectin and pyrantel pamoate in growing dogs, pups, and breeding adult dogs.

To determine the safety of a new combination of ivermectin and pyrantel (as pamoate salt) in a novel beef-based chewable tablet formulation, 3 tolerance trials were conducted and included growing dogs, pups, and breeding adult dogs. Growing dogs, given the combination orally for 5 consecutive days at recommended dosages (5 mg of pyrantel/kg of body weight, 6 micrograms of ivermectin/kg) or at twice the pyrantel dosage in combination with the recommended dosage of ivermectin, had no adverse effects. The combination also was administered to 6-week-old pups at 1, 3, and 5 times the recommended dose on 3 successive days for 3 times in 1 month. Compared with age-matched controls, treatment had no effect on clinical status, growth rate, or gross or histologic features. Breeding male and female dogs given the combination at 3 times the recommended dose for extended periods had no adverse effects, and prevalence of abnormalities in the offspring was not greater than that in nonmedicated controls.