267 research outputs found
The Steiner Formula for Minkowski Valuations
A Steiner type formula for continuous translation invariant Minkowski
valuations is established. In combination with a recent result on the symmetry
of rigid motion invariant homogeneous bivaluations, this new Steiner type
formula is used to obtain a family of Brunn-Minkowski type inequalities for
rigid motion intertwining Minkowski valuations
Identification and simulation of surface alpha events on passivated surfaces of germanium detectors and the influence of metalisation
Events from alpha interactions on the surfaces of germanium detectors are a
major contribution to the background in germanium-based searches for
neutrinoless double-beta decay. Surface events are subject to charge trapping,
affecting their pulse shape and reconstructed energy. A study of alpha events
on the passivated end-plate of a segmented true-coaxial n-type high-purity
germanium detector is presented. Charge trapping is analysed in detail and an
existing pulse-shape analysis technique to identify alpha events is verified
with mirror pulses observed in the non-collecting channels of the segmented
test detector. The observed radial dependence of charge trapping confirms
previous results. A dependence of the probability of charge trapping on the
crystal axes is observed for the first time. A first model to describe charge
trapping effects within the framework of the simulation software
SolidStateDetectors.jl is introduced. The influence of metalisation on events
from low-energy gamma interactions close to the passivated surface is also
presented
Temperature Dependence of the Electron-Drift Anisotropy and Implications for the Electron-Drift Model
The electron drift in germanium detectors is modeled making many assumptions.
Confronted with data, these assumptions have to be revisited. The temperature
dependence of the drift of electrons was studied in detail for an n-type
segmented point-contact germanium detector. The detector was mounted in a
temperature controlled, electrically cooled cryostat. Surface events were
induced with collimated 81 keV photons from a Ba source. A detailed
analysis of the rise time of pulses collected in surface scans, performed at
different temperatures, is presented. The longitudinal anisotropy of the
electron drift decreases with rising temperature. A new approach, making use of
designated rise-time windows determined by simulations using
SolidStateDetectors.jl, was used to isolate the longitudinal drift of electrons
along different axes to quantify this observation. The measured temperature
dependence of the longitudinal drift velocities combined with the standard
electron drift model as widely used in relevant simulation packages results in
unphysical predictions. A first suggestion to modify the electron-drift model
is motivated and described. The results of a first implementation of the
modified model in SolidStateDetectors.jl are shown. They describe the data
reasonably well. A general review of the model and the standard input values
for mobilities is suggested
Correlation of Perfusion MRI and F-18-FDG PET Imaging Biomarkers for Monitoring Regorafenib Therapy in Experimental Colon Carcinomas with Immunohistochemical Validation
Objectives To investigate a multimodal, multiparametric perfusion MRI/F-18-fluoro-deoxyglucose (F-18-FDG)-PET imaging protocol for monitoring regorafenib therapy effects on experimental colorectal adenocarcinomas in rats with immunohistochemical validation. Materials and Methods Human colorectal adenocarcinoma xenografts (HT-29) were implanted subcutaneously in n = 17 (n = 10 therapy group;n = 7 control group) female athymic nude rats (Hsd: RH-Foxn1(mu)). Animals were imaged at baseline and after a one-week daily treatment protocol with regorafenib (10 mg/kg bodyweight) using a multimodal, multiparametric perfusion MRI/F-18-FDG-PET imaging protocol. In perfusion MRI, quantitative parameters of plasma flow (PF, mL/100 mL/min), plasma volume (PV,%) and endothelial permeability-surface area product (PS, mL/100 mL/min) were calculated. In F-18-FDG-PET, tumor-to-background-ratio (TTB) was calculated. Perfusion MRI parameters were correlated with TTB and immunohistochemical assessments of tumor microvascular density (CD-31) and cell proliferation (Ki-67). Results Regorafenib significantly (p<0.01) suppressed PF (81.1 +/- 7.5 to 50.6 +/- 16.0 mL/100mL/min), PV (12.1 +/- 3.6 to 7.5 +/- 1.6%) and PS (13.6 +/- 3.2 to 7.9 +/- 2.3 mL/100mL/min) as well as TTB (3.4 +/- 0.6 to 1.9 +/- 1.1) between baseline and day 7. Immunohistochemistry revealed significantly (p<0.03) lower tumor microvascular density (CD-31, 7.0 +/- 2.4 vs. 16.1 +/- 5.9) and tumor cell proliferation (Ki-67, 434.0 +/- 62.9 vs. 663.0 +/- 98.3) in the therapy group. Perfusion MRI parameters Delta PF, Delta PV and Delta PS showed strong and significant (r = 0.67-0.78;p<0.01) correlations to the PET parameter Delta TTB and significant correlations (r = 0.57-0.67;p<0.03) to immunohistochemical Ki-67 as well as to CD-31-stainings (r = 0.49-0.55;p<0.05). Conclusions A multimodal, multiparametric perfusion MRI/PET imaging protocol allowed for non-invasive monitoring of regorafenib therapy effects on experimental colorectal adenocarcinomas in vivo with significant correlations between perfusion MRI parameters and F-18-FDG-PET validated by immunohistochemistry
Interactive visuo-motor therapy system for stroke rehabilitation
We present a virtual reality (VR)-based motor neurorehabilitation system for stroke patients with upper limb paresis. It is based on two hypotheses: (1) observed actions correlated with self-generated or intended actions engage cortical motor observation, planning and execution areas ("mirror neurons”); (2) activation in damaged parts of motor cortex can be enhanced by viewing mirrored movements of non-paretic limbs. We postulate that our approach, applied during the acute post-stroke phase, facilitates motor re-learning and improves functional recovery. The patient controls a first-person view of virtual arms in tasks varying from simple (hitting objects) to complex (grasping and moving objects). The therapist adjusts weighting factors in the non-paretic limb to move the paretic virtual limb, thereby stimulating the mirror neuron system and optimizing patient motivation through graded task success. We present the system's neuroscientific background, technical details and preliminary result
Interactive visuo-motor therapy system for stroke rehabilitation
We present a virtual reality (VR)-based motor neurorehabilitation system for stroke patients with upper limb paresis. It is based on two hypotheses: (1) observed actions correlated with self-generated or intended actions engage cortical motor observation, planning and execution areas ("mirror neurons"); (2) activation in damaged parts of motor cortex can be enhanced by viewing mirrored movements of non-paretic limbs. We postulate that our approach, applied during the acute post-stroke phase, facilitates motor re-learning and improves functional recovery. The patient controls a first-person view of virtual arms in tasks varying from simple (hitting objects) to complex (grasping and moving objects). The therapist adjusts weighting factors in the non-paretic limb to move the paretic virtual limb, thereby stimulating the mirror neuron system and optimizing patient motivation through graded task success. We present the system's neuroscientific background, technical details and preliminary results.info:eu-repo/semantics/publishedVersio
Remote sensing for cost-effective blue carbon accounting
Blue carbon ecosystems (BCE) include mangrove forests, tidal marshes, and seagrass meadows, all of which are currently under threat, putting their contribution to mitigating climate change at risk. Although certain challenges and trade-offs exist, remote sensing offers a promising avenue for transparent, replicable, and cost-effective accounting of many BCE at unprecedented temporal and spatial scales. The United Nations Framework Convention on Climate Change (UNFCCC) has issued guidelines for developing blue carbon inventories to incorporate into Nationally Determined Contributions (NDCs). Yet, there is little guidance on remote sensing techniques for monitoring, reporting, and verifying blue carbon assets. This review constructs a unified roadmap for applying remote sensing technologies to develop cost-effective carbon inventories for BCE – from local to global scales. We summarise and discuss (1) current standard guidelines for blue carbon inventories; (2) traditional and cutting-edge remote sensing technologies for mapping blue carbon habitats; (3) methods for translating habitat maps into carbon estimates; and (4) a decision tree to assist users in determining the most suitable approach depending on their areas of interest, budget, and required accuracy of blue carbon assessment. We designed this work to support UNFCCC-approved IPCC guidelines with specific recommendations on remote sensing techniques for GHG inventories. Overall, remote sensing technologies are robust and cost-effective tools for monitoring, reporting, and verifying blue carbon assets and projects. Increased appreciation of these techniques can promote a technological shift towards greater policy and industry uptake, enhancing the scalability of blue carbon as a Natural Climate Solution worldwide
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