4,444 research outputs found
Perspective: Current advances in solid-state NMR spectroscopy
In contrast to the rapid and revolutionary impact of solution-state Nuclear Magnetic Resonance (NMR) on modern chemistry, the field of solid-state NMR has matured more slowly. This reflects the major technical challenges of much reduced spectral resolution and sensitivity in solid-state as compared to solution-state spectra, as well as the relative complexity of the solid state. In this perspective, we outline the technique developments that have pushed resolution to intrinsic limits and the approaches, including ongoing major developments in the field of Dynamic Nuclear Polarisation, that have enhanced spectral sensitivity. The information on local structure and dynamics that can be obtained using these gains in sensitivity and resolution is illustrated with a diverse range of examples from large biomolecules to energy materials and pharmaceuticals and from both ordered and highly disordered materials. We discuss how parallel developments in quantum chemical calculation, particularly density functional theory, have enabled experimental data to be translated directly into information on local structure and dynamics, giving rise to the developing field of “NMR crystallography
Spatiotemporal dispersion and wave envelopes with relativistic and pseudorelativistic characteristics
A generic nonparaxial model for pulse envelopes is presented. Classic Schro¨dinger-type descriptions of
wave propagation have their origins in slowly-varying envelopes combined with a Galilean boost to the
local time frame. By abandoning these two simplifications, a picture of pulse evolution emerges in which
frame-of-reference considerations and space-time transformations take center stage. A wide range of
effects, analogous to those in special relativity, then follows for both linear and nonlinear systems. Explicit
demonstration is presented through exact bright and dark soliton pulse solutions
Evolution of Th2 responses : Characterization of IL-4/13 in sea bass (Dicentrarchus labrax L.) and studies of expression and biological activity
Acknowledgements This research was funded by the European Commission under the 7th Framework Programme for Research and Technological Development (FP7) of the European Union (Grant Agreement 311993 TARGETFISH). T.W. received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland). MASTS is funded by the Scottish Funding Council (grant reference number HR09011) and contributing institutions.Peer reviewedPublisher PD
Thin-Film Metamaterials called Sculptured Thin Films
Morphology and performance are conjointed attributes of metamaterials, of
which sculptured thin films (STFs) are examples. STFs are assemblies of
nanowires that can be fabricated from many different materials, typically via
physical vapor deposition onto rotating substrates. The curvilinear--nanowire
morphology of STFs is determined by the substrate motions during fabrication.
The optical properties, especially, can be tailored by varying the morphology
of STFs. In many cases prototype devices have been fabricated for various
optical, thermal, chemical, and biological applications.Comment: to be published in Proc. ICTP School on Metamaterials (Augsut 2009,
Sibiu, Romania
Wave envelopes with second-order spatiotemporal dispersion : I. Bright Kerr solitons and cnoidal waves
We propose a simple scalar model for describing pulse phenomena beyond the conventional slowly-varying envelope approximation. The generic governing equation has a cubic nonlinearity and we focus here mainly on contexts involving anomalous group-velocity dispersion. Pulse propagation turns out to be a problem firmly rooted in frames-of-reference considerations. The transformation properties of the new model and its space-time structure are explored in detail. Two distinct representations of exact analytical solitons and their associated conservation laws (in both integral and algebraic forms) are presented, and a range of new predictions is made. We also report cnoidal waves of the governing nonlinear equation. Crucially, conventional pulse theory is shown to emerge as a limit of the more general formulation. Extensive simulations examine the role of the new solitons as robust attractors
Polyhedral Cosmic Strings
Quantum field theory is discussed in M\"obius corner kaleidoscopes using the
method of images. The vacuum average of the stress-energy tensor of a free
field is derived and is shown to be a simple sum of straight cosmic string
expressions, the strings running along the edges of the corners. It does not
seem possible to set up a spin-half theory easily.Comment: 15 pages, 4 text figures not include
Wave envelopes with second-order spatiotemporal dispersion: II. Modulational instabilities and dark Kerr solitons
A simple scalar model for describing spatiotemporal dispersion of pulses, beyond the classic “slowly-varying envelopes + Galilean boost” approach, is studied. The governing equation has a cubic nonlinearity and we focus here mainly on contexts with normal group-velocity dispersion. A complete analysis of continuous waves is reported, including their dispersion relations and modulational instability characteristics. We also present a detailed derivation of exact analytical dark solitons, obtained by combining direct-integration methods with geometrical transformations. Classic results from conventional pulse theory are recovered as-ymptotically from the spatiotemporal formulation. Numerical simulations test new theoretical predictions for modulational instability, and examine the robustness of spatiotemporal dark solitons against perturbations to their local pulse shape
Economic liberalization and the antecedents of top management teams: evidence from Turkish 'big' business
There has been an increased interest in the last two decades in top management teams (TMTs) of business firms. Much of the research, however, has been US-based and concerned primarily with TMT effects on organizational outcomes. The present study aims to expand this literature by examining the antecedents of top team composition in the context of macro-level economic change in a late-industrializing country. The post-1980 trade and market reforms in Turkey provided the empirical setting. Drawing upon the literatures on TMT and chief executive characteristics together with punctuated equilibrium models of change and institutional theory, the article develops the argument that which firm-level factors affect which attributes of TMT formations varies across the early and late stages of economic liberalization. Results of the empirical investigation of 71 of the largest industrial firms in Turkey broadly supported the hypotheses derived from this premise. In the early stages of economic liberalization the average age and average organizational tenure of TMTs were related to the export orientation of firms, whereas in later stages, firm performance became a major predictor of these team attributes. Educational background characteristics of teams appeared to be under stronger institutional pressures, altering in different ways in the face of macro-level change
Early Reduction of MRI Activity During 6 Months of Treatment With Cladribine Tablets for Highly Active Relapsing Multiple Sclerosis MAGNIFY-MS
BACKGROUND AND OBJECTIVES
The onset of action for high-efficacy immunotherapies in multiple sclerosis (MS) is an important parameter. This study (MAGNIFY-MS) evaluates the onset of action of cladribine tablets by observing changes in combined unique active (CUA) MRI lesion counts during the first 6 months of treatment in patients with highly active relapsing MS.
METHODS
MRI was performed at screening, baseline, and at months 1, 2, 3, and 6 after initiating treatment with cladribine tablets 3.5 mg/kg. CUA lesion counts, defined as the sum of T1 gadolinium-enhancing (Gd+) lesions and new or enlarging active T2 lesions (without T1 Gd+), were compared between postbaseline and the baseline period and standardized to the period length and the number of MRIs performed.
RESULTS
Included in this analysis were 270 patients who received ≥1 dose of cladribine tablets. After treatment initiation, significant reductions in mean CUA lesion counts were observed from month 1 onward compared with the baseline period (-1.193 between month 1 and month 6, -1.500 between month 2 and month 6, and -1.692 between month 3 and month 6; all p < 0.0001). Mean T1 Gd+ lesion counts were decreased from month 2 onward compared with baseline (-0.857 at month 2, -1.355 at month 3, and -1.449 at month 6; all p < 0.0001), whereas the proportion of patients without any CUA lesions increased from 52.0% between month 1 and month 6 to 80.5% between month 3 and month 6.
DISCUSSION
Findings suggest an early onset of action for cladribine tablets, with an increasing reduction in active MRI lesions over time.
TRIAL REGISTRATION INFORMATION
NCT03364036; Date registered: December 06, 2017.
CLASSIFICATION OF EVIDENCE
Using frequent MRI assessments of the brain over the first 6 months of the MAGNIFY-MS study (NCT03364036), we aimed to determine the onset of action of cladribine tablets 3.5 mg/kg in adult patients with highly active relapsing MS. This study provides Class IV evidence that, in such patients, treatment with cladribine tablets is associated with an early onset of action with reductions in active MRI lesion counts from month 2 (day 60) onward, with an increasing reduction in such lesions over time
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