2,224 research outputs found
Inflammatory angiogenesis as a target for prevention and therapy: Kaposi's sarcoma and HIV tat as models
Large-scale quantum-emitter arrays in atomically thin semiconductors
This is the final version. Available on open access from Nature Research via the DOI in this recordData availability:
The data that supports the findings of this study are available from the corresponding author upon request.Quantum light emitters have been observed in atomically thin layers of transition metal dichalcogenides. However, they are found at random locations within the host material and usually in low densities, hindering experiments aiming to investigate this new class of emitters. Here, we create deterministic arrays of hundreds of quantum emitters in tungsten diselenide and tungsten disulphide monolayers, emitting across a range of wavelengths in the visible spectrum (610–680 nm and 740–820 nm), with a greater spectral stability than their randomly occurring counterparts. This is achieved by depositing monolayers onto silica substrates nanopatterned with arrays of 150-nm-diameter pillars ranging from 60 to 190 nm in height. The nanopillars create localized deformations in the material resulting in the quantum confinement of excitons. Our method may enable the placement of emitters in photonic structures such as optical waveguides in a scalable way, where precise and accurate positioning is paramount.European CommissionEuropean Research Council (ERC)Engineering and Physical Sciences Research Council (EPSRC)National Science Foundation (NSF
Uniaxial strain in graphene by Raman spectroscopy: G peak splitting, Grüneisen parameters, and sample orientation
Graphene is the two-dimensional building block for carbon allotropes of every
other dimensionality. Since its experimental discovery, graphene continues to
attract enormous interest, in particular as a new kind of matter, in which
electron transport is governed by a Dirac-like wave equation, and as a model
system for studying electronic and phonon properties of other, more complex,
graphitic materials[1-4]. Here, we uncover the constitutive relation of
graphene and probe new physics of its optical phonons, by studying its Raman
spectrum as a function of uniaxial strain. We find that the doubly degenerate
E2g optical mode splits in two components, one polarized along the strain and
the other perpendicular to it. This leads to the splitting of the G peak into
two bands, which we call G+ and G-, by analogy with the effect of curvature on
the nanotube G peak[5-7]. Both peaks red shift with increasing strain, and
their splitting increases, in excellent agreement with first-principles
calculations. Their relative intensities are found to depend on light
polarization, which provides a useful tool to probe the graphene
crystallographic orientation with respect to the strain. The singly degenerate
2D and 2D' bands also red shift, but do not split for small strains. We study
the Gruneisen parameters for the phonons responsible for the G, D and D' peaks.
These can be used to measure the amount of uniaxial or biaxial strain,
providing a fundamental tool for nanoelectronics, where strain monitoring is of
paramount importance[8, 9
Value of multidetector computed tomography image segmentation for preoperative planning in general surgery
Using practical examples, this report aims to highlight the clinical value of patient-specific three-dimensional (3D) models, obtained segmenting multidetector computed tomography (MDCT) images, for preoperative planning in general surgery.In this study, segmentation and 3D model generation were performed using a semiautomatic tool developed in the authors' laboratory. Their segmentation procedure is based on the neighborhood connected region-growing algorithm that, appropriately parameterized for the anatomy of interest and combined with the optimal segmentation sequence, generates good-quality 3D images coupled with facility of use. Using a touch screen monitor, manual refining can be added to segment structures unsuitable for automatic reconstruction. Three-dimensional models of 10 candidates for major general surgery procedures were presented to the operating surgeons for evaluation. A questionnaire then was administered after surgery to assess the perceived added value of the new technology.The questionnaire results were very positive. The authors recorded the diffuse opinion that planning the procedure using a segmented data set allows the surgeon to plan critical interventions with better awareness of the specific patient anatomy and consequently facilitates choosing the best surgical approach.The benefit shown in this report supports a wider use of segmentation software in clinical practice, even taking into account the extra time and effort required to learn and use these systems
The impact of vitamin D status on changes in bone mineral density during treatment with bisphosphonates and after discontinuation following long-term use in post-menopausal osteoporosis
BACKGROUND: It is still unclear whether addition of calcium/vitamin D supplements leads to an incremental benefit in patients taking bisphosphonates and whether achievement of serum level of 25 (OH) vitamin D of at least 70 nmol/L has an impact on the skeletal response to bisphosphonates. Moreover the maintenance of BMD after bisphosphonates withdrawal with the continuation of calcium/vitamin D supplements only, remains uncertain. The aims were to assess the impact of vitamin D status on changes in bone mineral density (BMD) in firstly patients with post-menopausal osteoporosis on bisphosphonates and secondly following discontinuation of bisphosphonates after long-term use. METHODS: Two patient groups were recruited. The first study population comprised of 112 women treated with a bisphosphonate. The second study population consisted of 35 women who had been on bisphosphonates for > 5 years in whom the treatment agent was discontinued. Baseline BMD, changes in BMD following treatment, duration of treatment, serum 25 (OH) vitamin D, parathyroid hormone (PTH), urine C-terminal telopeptides of type 1 collagen (CTX) were obtained on the study participants. RESULTS: In the first study group, subjects with serum vitamin D concentrations (> 70 nmol/L) had a significantly lower serum PTH level (mean [SEM] 41 [2] ng/L). PTH concentrations of 41 ng/L or less was associated with a significantly higher increase in BMD at the hip following treatment with bisphosphonates compared to patients with PTH > 41 ng/L (2.5% [0.9] v/s -0.2% [0.9], P = 0.04). In the second study group, discontinuation of bisphosphonate for 15 months after long-term treatment did not result in significant bone loss at the lumbar spine and total hip, although a trend towards gradual decline in BMD at the femoral neck was observed. CONCLUSION: the data suggest that optimal serum 25 (OH) vitamin D concentration may lead to further reduction in bone loss at the hip in patients on bisphosphonates. A prospective controlled trial is needed to evaluate whether the response to bisphosphonates is influenced by vitamin D status. BMD is preserved at the lumbar spine and total hip following discontinuation of bisphosphonate for a short period following long-term treatment, although a gradual loss occurs at the femoral neck
On form factors in N=4 sym
In this paper we study the form factors for the half-BPS operators
and the stress tensor supermultiplet
current up to the second order of perturbation theory and for the
Konishi operator at first order of perturbation theory in
SYM theory at weak coupling. For all the objects we observe the
exponentiation of the IR divergences with two anomalous dimensions: the cusp
anomalous dimension and the collinear anomalous dimension. For the IR finite
parts we obtain a similar situation as for the gluon scattering amplitudes,
namely, apart from the case of and the finite part has
some remainder function which we calculate up to the second order. It involves
the generalized Goncharov polylogarithms of several variables. All the answers
are expressed through the integrals related to the dual conformal invariant
ones which might be a signal of integrable structure standing behind the form
factors.Comment: 35 pages, 7 figures, LATEX2
A practical approach to assess leg muscle oxygenation during ramp-incremental cycle ergometry in heart failure
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