212 research outputs found
Optical Control of Field-Emission Sites by Femtosecond Laser Pulses
We have investigated field emission patterns from a clean tungsten tip apex
induced by femtosecond laser pulses. Strongly asymmetric modulations of the
field emission intensity distributions are observed depending on the
polarization of the light and the laser incidence direction relative to the
azimuthal orientation of tip apex. In effect, we have realized an ultrafast
pulsed field-emission source with site selectivity on the 10 nm scale.
Simulations of local fields on the tip apex and of electron emission patterns
based on photo-excited nonequilibrium electron distributions explain our
observations quantitatively.Comment: 4 pages, submitted to Physical Review Letter
a comprehensive and efficient analysis pipeline designed for ChIP-nexus
Background ChIP-nexus, an extension of the ChIP-exo protocol, can be used to
map the borders of protein-bound DNA sequences at nucleotide resolution,
requires less input DNA and enables selective PCR duplicate removal using
random barcodes. However, the use of random barcodes requires additional
preprocessing of the mapping data, which complicates the computational
analysis. To date, only a very limited number of software packages are
available for the analysis of ChIP-exo data, which have not yet been
systematically tested and compared on ChIP-nexus data. Results Here, we
present a comprehensive software package for ChIP-nexus data that exploits the
random barcodes for selective removal of PCR duplicates and for quality
control. Furthermore, we developed bespoke methods to estimate the width of
the protected region resulting from protein-DNA binding and to infer binding
positions from ChIP-nexus data. Finally, we applied our peak calling method as
well as the two other methods MACE and MACS2 to the available ChIP-nexus data.
Conclusions The Q-nexus software is efficient and easy to use. Novel
statistics about duplication rates in consideration of random barcodes are
calculated. Our method for the estimation of the width of the protected region
yields unbiased signatures that are highly reproducible for biological
replicates and at the same time very specific for the respective factors
analyzed. As judged by the irreproducible discovery rate (IDR), our peak
calling algorithm shows a substantially better reproducibility. An
implementation of Q-nexus is available at http://charite.github.io/Q/
Age-dependent microstructural changes of the intervertebral disc: a validation of proteoglycan-sensitive spectral CT
Objective: To analyze the two major components of the intervertebral disc (IVD) in an ex vivo phantom, as well as age-related changes in patients.
Methods: Collagen and chondroitin sulfate were imaged at different concentrations in agar solution. Age-related changes in disc density were retrospectively analyzed in normal-appearing discs in dual-energy computed tomography (DECT) images from a patient cohort with various spinal pathologies (n = 136). All computed tomography (CT) scans were acquired using single-source DECT at 80 and 135 kVp with automatic exposure calculation. In 136 patients, the attenuation of normal-appearing discs on collagen/chondroitin maps (cMaps) correlated with the patients' age with Pearson's r using standardized regions of interest in the anterior anulus fibrosus (AAF) and nucleus pulposus (NP).
Results: DECT collagen mapping revealed concentration-dependent Hounsfield units (HU) of IVD components. For collagen, we found Pearson's r = 0.9610 (95% CI 0.6789-0.9959), p = 0.0023 at 120 kVe, and r = 0.8824 (95% CI 0.2495-0.9871), p = 0.0199 in cMap. For chondroitin sulfate, Pearson's r was 0.9583 (95% CI 0.6603-0.9956), p = 0.0026 at 120 kVp, and r = 0.9646 (95% CI 0.7044-0.9963), p = 0.0019 in cMap. Analysis of normal-appearing IVDs revealed an inverse correlation of density with age in the AAF: Pearson's r = - 0.2294 at 135 kVp (95% CI - 0.4012 to - 0.04203; p=0.0141) and r = - 0.09341 in cMap (95% CI - 0.2777 to 0.09754; p = 0.0003). In the NP, age and density did not correlate significantly at 135 kVp (p = 0.9228) and in cMap (p = 0.3229).
Conclusions: DECT-based collagen mapping allows microstructural analysis of the two main intervertebral disc components-collagen and chondroitin sulfate. IVD density declines with age, presumably due to a reduction in collagen and chondroitin sulfate content. Age-related alterations of disc microstructure appear most pronounced in the AAF
Peer review analysis in the field of radiation oncology: results from a web-based survey of the Young DEGRO working group
PURPOSE To evaluate the reviewing behaviour in the German-speaking countries in order to provide recommendations to increase the attractiveness of reviewing activity in the field of radiation oncology.
METHODS In November 2019, a survey was conducted by the Young DEGRO working group (jDEGRO) using the online platform “eSurveyCreator”. The questionnaire consisted of 29 items examining a~broad range of factors that influence reviewing motivation and performance.
RESULTS A total of 281 responses were received. Of these, 154 (55%) were completed and included in the evaluation. The most important factors for journal selection criteria and peer review performance in the field of radiation oncology are the scientific background of the manuscript (85%), reputation of the journal (59%) and a~high impact factor (IF; 40%). Reasons for declining an invitation to review include the scientific background of the article (60%), assumed effort (55%) and a low IF (27%). A~double-blind review process is preferred by 70% of respondents to a single-blind (16%) or an open review process (14%). If compensation was offered, 59% of participants would review articles more often. Only 12% of the participants have received compensation for their reviewing activities so far. As compensation for the effort of reviewing, 55% of the respondents would prefer free access to the journal's articles, 45% a discount for their own manuscripts, 40% reduced congress fees and 39% compensation for expenses.
CONCLUSION The scientific content of the manuscript, reputation of the journal and a~high IF determine the attractiveness for peer reviewing in the field of radiation oncology. The majority of participants prefer a~double-blind peer review process and would conduct more reviews if compensation was available. Free access to journal articles, discounts for publication costs or congress fees, or an expense allowance were identified to increase attractiveness of the review process
Light-induced photoisomerization of a diarylethene molecular switch on solidsurfaces
Diarylethenes are molecular switches, the state of which can efficiently be
controlled by illumination with ultraviolet or visible light. To use the
change in the molecular properties when switching between the two states for a
specific function, direct contact with solid surfaces is advantageous as it
provides immobilization. Here we present a study of a diarylethene derivate
(T-DAE, 1,2-bis(5-methyl-2-phenylthiazol-4-yl)cyclopent-1-ene) in direct
contact with highly ordered graphite as well as with semimetallic Bi(1 1 1)
surfaces by x-ray photoelectron spectroscopy, x-ray absorption spectroscopy
and simulated spectra based on density functional theory. On both surfaces,
the molecule can be switched from its open to its closed form by 325–475 nm
broadband or ultraviolet illumination. On the other hand, back isomerization
to the ring-open T-DAE was not possible
Fully printed origami thermoelectric generators for energy-harvesting
Energy-harvesting from low-temperature environmental heat via thermoelectric generators (TEG) is a versatile and maintenance-free solution for large-scale waste heat recovery and supplying renewable energy to a growing number of devices in the Internet of Things (IoT) that require an independent wireless power supply. A prerequisite for market competitiveness, however, is the cost-effective and scalable manufacturing of these TEGs. Our approach is to print the devices using printable thermoelectric polymers and composite materials. We present a mass-producible potentially low-cost fully screen printed flexible origami TEG. Through a unique two-step folding technique, we produce a mechanically stable 3D cuboidal device from a 2D layout printed on a thin flexible substrate using thermoelectric inks based on PEDOT nanowires and a TiS2:Hexylamine-complex material. We realize a device architecture with a high thermocouple density of 190 per cm² by using the thin substrate as electrical insulation between the thermoelectric elements resulting in a high-power output of 47.8 µWcm−² from a 30 K temperature difference. The device properties are adjustable via the print layout, specifically, the thermal impedance of the TEGs can be tuned over several orders of magnitudes allowing thermal impedance matching to any given heat source. We demonstrate a wireless energy-harvesting application by powering an autonomous weather sensor comprising a Bluetooth module and a power management system
Validation of nonlinear PCA
Linear principal component analysis (PCA) can be extended to a nonlinear PCA
by using artificial neural networks. But the benefit of curved components
requires a careful control of the model complexity. Moreover, standard
techniques for model selection, including cross-validation and more generally
the use of an independent test set, fail when applied to nonlinear PCA because
of its inherent unsupervised characteristics. This paper presents a new
approach for validating the complexity of nonlinear PCA models by using the
error in missing data estimation as a criterion for model selection. It is
motivated by the idea that only the model of optimal complexity is able to
predict missing values with the highest accuracy. While standard test set
validation usually favours over-fitted nonlinear PCA models, the proposed model
validation approach correctly selects the optimal model complexity.Comment: 12 pages, 5 figure
Expression of 3q Oncogene SEC62 Predicts Survival in Head and Neck Squamous Cell Carcinoma Patients Treated with Primary Chemoradiation
Primary chemoradiotherapy (CRT) is an established treatment option for locally advanced
head and neck squamous cell carcinomas (HNSCC) usually combining intensity modified radiotherapy with concurrent platinum-based chemotherapy. Though the majority of patients can be
cured with this regimen, treatment response is highly heterogeneous and can hardly be predicted.
SEC62 represents a metastasis stimulating oncogene that is frequently overexpressed in various
cancer entities and is associated with poor outcome. Its role in HNSCC patients undergoing CRT
has not been investigated so far. A total of 127 HNSCC patients treated with primary CRT were
included in this study. The median follow-up was 5.4 years. Pretherapeutic tissue samples of the
primary tumors were used for immunohistochemistry targeting SEC62. SEC62 expression, clinical
and histopathological parameters, as well as patient outcome, were correlated in univariate and
multivariate survival analyses. High SEC62 expression correlated with a significantly shorter overall
survival (p = 0.015) and advanced lymph node metastases (p = 0.024). Further significant predictors
of poor overall and progression-free survival included response to therapy (RECIST1.1), nodal status,
distant metastases, tobacco consumption, recurrence of disease, and UICC stage. In a multivariate
Cox hazard proportional regression analysis, only SEC62 expression (p = 0.046) and response to therapy (p < 0.0001) maintained statistical significance as independent predictors of the patients’ overall
survival. This study identified SEC62 as an independent prognostic biomarker in HNSCC patients
treated with primary CRT. The role of SEC62 as a potential therapeutic target and its interaction with
radiation-induced molecular alterations in head and neck cancer cells should further be investigated
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