16 research outputs found
Recommended from our members
Practical Considerations for High Spatial and Temporal Resolution Dynamic Transmission Electron Microscopy
Although recent years have seen significant advances in the spatial resolution possible in the transmission electron microscope (TEM), the temporal resolution of most microscopes is limited to video rate at best. This lack of temporal resolution means that our understanding of dynamic processes in materials is extremely limited. High temporal resolution in the TEM can be achieved, however, by replacing the normal thermionic or field emission source with a photoemission source. In this case the temporal resolution is limited only by the ability to create a short pulse of photoexcited electrons in the source, and this can be as short as a few femtoseconds. The operation of the photo-emission source and the control of the subsequent pulse of electrons (containing as many as 5 x 10{sup 7} electrons) create significant challenges for a standard microscope column that is designed to operate with a single electron in the column at any one time. In this paper, the generation and control of electron pulses in the TEM to obtain a temporal resolution <10{sup -6} s will be described and the effect of the pulse duration and current density on the spatial resolution of the instrument will be examined. The potential of these levels of temporal and spatial resolution for the study of dynamic materials processes will also be discussed
Recommended from our members
Recent Advances in Kicker Pulser Technology for Linear Induction Accelerators
Recent progress in the development and understanding of linear induction accelerator have produced machines with 10s of MeV of beam energy and multi-kiloampere currents. Near-term machines, such as DARHT-2, are envisioned with microsecond pulselengths. Fast beam kickers, based on cylindrical electromagnetic stripline structures, will permit effective use of these extremely high-energy beams in an increasing number of applications. In one application, radiography, kickers were an essential element in resolving temporal evolution of hydrodynamic events by cleaving out individual pulses from long, microsecond beams. Advanced schemes are envisioned where these individual pulses are redirected through varying length beam lines and suitably recombined for stereographic imaging or tomographic reconstruction. Recent advances in fast kickers and their pulsed power technology are described. Kicker pulsers based on both planar triode and all solid-state componentry are discussed and future development plans are presented
Chemical Attribution of Fentanyl Using Multivariate Statistical Analysis of Orthogonal Mass Spectral Data
Attribution of the origin of an illicit
drug relies on identification
of compounds indicative of its clandestine production and is a key
component of many modern forensic investigations. The results of these
studies can yield detailed information on method of manufacture, starting
material source, and final product, all critical forensic evidence.
In the present work, chemical attribution signatures (CAS) associated
with the synthesis of the analgesic fentanyl, <i>N</i>-(1-phenylethylpiperidin-4-yl)-<i>N</i>-phenylpropanamide, were investigated. Six synthesis methods,
all previously published fentanyl synthetic routes or hybrid versions
thereof, were studied in an effort to identify and classify route-specific
signatures. A total of 160 distinct compounds and inorganic species
were identified using gas and liquid chromatographies combined with
mass spectrometric methods (gas chromatography/mass spectrometry (GC/MS)
and liquid chromatography–tandem mass spectrometry-time of-flight
(LC–MS/MS-TOF)) in conjunction with inductively coupled plasma
mass spectrometry (ICPMS). The complexity of the resultant data matrix
urged the use of multivariate statistical analysis. Using partial
least-squares-discriminant analysis (PLS-DA), 87 route-specific CAS
were classified and a statistical model capable of predicting the
method of fentanyl synthesis was validated and tested against CAS
profiles from crude fentanyl products deposited and later extracted
from two operationally relevant surfaces: stainless steel and vinyl
tile. This work provides the most detailed fentanyl CAS investigation
to date by using orthogonal mass spectral data to identify CAS of
forensic significance for illicit drug detection, profiling, and attribution
Motivation in rehabilitation and acquired brain injury: can theory help us understand it?
Rehabilitation of emergent awareness of errors post traumatic brain injury: A pilot intervention
Recent trends in rehabilitation interventions for visual neglect and anosognosia for hemiplegia following right hemisphere stroke
A theoretical view on the thermodynamic cis–trans equilibrium of dihalo ruthenium olefin metathesis (pre-)catalysts
Interventions for improving self-awareness following acquired brain injury
Accurate self-awareness in clients who have had an acquired brain injury (ABI) has been associated with positive outcomes. However, providing intervention that improves clients' self-awareness is a challenging task for occupational therapists. The present paper provides an overview of the literature regarding models to guide intervention, intervention considerations, descriptions of interventions, and research evidence for interventions. Professionals can draw upon cognitive rehabilitation models and specific models of self-awareness. Facilitatory interventions, such as education, feedback, behaviour therapy and psychotherapy have been recommended to a greater extent than compensatory interventions. The development of interventions for improving self-awareness is at an early stage, and research on the effectiveness of interventions is limited. Future research is required into the effectiveness of interventions to improve clients' self-awareness before structured intervention guidelines can be developed
Synthesis of Ferrocenyl and Ruthenocenyl Thioamide derivatives using a single-step three-component reaction
The efficient syntheses of various metallocenyl thioamides using a single-step three-component condensation reaction between the commercially available (dimethylaminomethyl)ferrocene or aminomethylferrocene and another organic amine in the presence of elemental sulfur are described. All new organometallic thioamide derivatives were unambiguously characterized by 1H and 13C NMR spectroscopy and mass spectrometry. Furthermore, the structures of five ferrocenyl thioamides determined by X-ray crystallography are presented