865 research outputs found
Toward accurate quantitative photoacoustic imaging: learning vascular blood oxygen saturation in three dimensions
Significance: Two-dimensional (2-D) fully convolutional neural networks have been shown
capable of producing maps of sO2 from 2-D simulated images of simple tissue models.
However, their potential to produce accurate estimates in vivo is uncertain as they are limited
by the 2-D nature of the training data when the problem is inherently three-dimensional (3-D),
and they have not been tested with realistic images.
Aim: To demonstrate the capability of deep neural networks to process whole 3-D images and
output 3-D maps of vascular sO2 from realistic tissue models/images.
Approach: Two separate fully convolutional neural networks were trained to produce 3-D maps
of vascular blood oxygen saturation and vessel positions from multiwavelength simulated
images of tissue models.
Results: The mean of the absolute difference between the true mean vessel sO2 and the network
output for 40 examples was 4.4% and the standard deviation was 4.5%.
Conclusions: 3-D fully convolutional networks were shown capable of producing accurate sO2
maps using the full extent of spatial information contained within 3-D images generated under
conditions mimicking real imaging scenarios. We demonstrate that networks can cope with some
of the confounding effects present in real images such as limited-view artifacts and have the
potential to produce accurate estimates in vivo
Лексическое наполнение современных газет российских немцев как реализация этнической функции языка
The purpose of our study was to determine the expression of the pro-apoptotic BAX protein in relation to the mutational status of BAX and p53 (as transcriptional activator of the BAX gene) in benign and malignant thyroid tissue. In 47 patients with thyroid tumours (14 follicular and 3 papillary carcinomas, 14 adenomas and 16 goitres), the DNA was screened for mutations of BAX (exon 1-6) and p53 (exon 5-8) by single-strand conformation polymorphism polymerase chain reaction (SSCP-PCR). Furthermore, the protein expression of BAX, p53 and p21 (which is also increased transcriptionally by p53) was investigated by immunohistochemistry. Surprisingly, we observed elevated BAX levels in patients with thyroid carcinomas compared with patients with adenomas (unpaired t-test: p<0.05) or with goitres (p<0.02). This is in clear contrast to other carcinomas where BAX is frequently inactivated which correlates to a poor prognosis (Sturm et al., 1999). There were no significant differences of the BAX levels between goitres or the adenomas. In the SSCP-PCR analysis, no BAX mutations were detectable. P53 mutation analysis by SSCP-PCR did not reveal any functional p53 mutations in the patients with carcinomas, adenomas or goitres. Nevertheless, patients with carcinomas showed an overexpression (preferentially cytoplasmic) of p53 protein compared with patients with benign tumours (p<0.05). The absence of p53 mutations suggests that the overexpressed p53 is wild type. This is in line with the expression profile of BAX and p21, which showed a higher protein expression in these p53 positive tumours (p<0.05 in the carcinomas compared with the non-malignant lesions). Consequently, the overexpressed p53 might be a correlate for dysregulation without loss of function. This, in turn, might be a reason for the good outcome of some patients with thyroid cancer
On Learned Operator Correction in Inverse Problems
We discuss the possibility of learning a data-driven explicit model correction for inverse problems and whether such a model correction can be used within a variational framework to obtain regularized reconstructions. This paper discusses the conceptual difficulty of learning such a forward model correction and proceeds to present a possible solution as a forward-adjoint correction that explicitly corrects in both data and solution spaces. We then derive conditions under which solutions to the variational problem with a learned correction converge to solutions obtained with the correct operator. The proposed approach is evaluated on an application to limited view photoacoustic tomography and compared to the established framework of the Bayesian approximation error method
Multistability in the Kuramoto model with synaptic plasticity
We present a simplified phase model for neuronal dynamics with spike timing-dependent plasticity (STDP). For asymmetric, experimentally observed STDP we find multistability: a coexistence of a fully synchronized, a fully desynchronized, and a variety of cluster states in a wide enough range of the parameter space. We show that multistability can occur only for asymmetric STDP, and we study how the coexistence of synchronization and desynchronization and clustering depends on the distribution of the eigenfrequencies. We test the efficacy of the proposed method on the Kuramoto model which is, de facto, one of the sample models for a description of the phase dynamics in neuronal ensembles
Magnetic Resonance in the Spin-Peierls compound
We present results from magnetic resonance measurements for 75-350 GHz in
'-NaVO. The temperature dependence of the integrated
intensity indicates that we observe transitions in the excited state. A
quantitative description gives resonances in the triplet state at high symmetry
points of the excitation spectrum of this Spin-Peierls compound. This energy
has the same temperature dependence as the Spin-Peierls gap. Similarities and
differences with the other inorganic compound CuGeO are discussed.Comment: 2 pages, REVTEX, 3 figures. to be published in Phys.Rev.
Spin dependent quantum interference in non-local graphene spin valves
Spin dependent electron transport measurements on graphene are of high
importance to explore possible spintronic applications. Up to date all spin
transport experiments on graphene were done in a semi-classical regime,
disregarding quantum transport properties such as phase coherence and
interference. Here we show that in a quantum coherent graphene nanostructure
the non-local voltage is strongly modulated. Using non-local measurements, we
separate the signal in spin dependent and spin independent contributions. We
show that the spin dependent contribution is about two orders of magnitude
larger than the spin independent one, when corrected for the finite
polarization of the electrodes. The non-local spin signal is not only strongly
modulated but also changes polarity as a function of the applied gate voltage.
By locally tuning the carrier density in the constriction we show that the
constriction plays a major role in this effect and indicates that it can act as
a spin filter device. Our results show the potential of quantum coherent
graphene nanostructures for the use in future spintronic devices
Magnetic bound states in the quarter-filled ladder system }
Raman scattering in the quarter-filled spin ladder system alpha'-NaV_2O_5
shows in the dimerized singlet ground state () an unexpected
sequence of three magnetic bound states. Our results suggest that the recently
proposed mapping onto an effective spin chain for has to be given
up in favor of the full topology and exchange paths of a ladder in the
dimerized phase for . As the new ground state we propose a dynamic
superposition of energetically nearly degenerate dimer configurations on the
ladder.Comment: 5 pages, 4 figures, to be published in PRB, brief reports, Dec. 199
Spintronic magnetic anisotropy
An attractive feature of magnetic adatoms and molecules for nanoscale
applications is their superparamagnetism, the preferred alignment of their spin
along an easy axis preventing undesired spin reversal. The underlying magnetic
anisotropy barrier --a quadrupolar energy splitting-- is internally generated
by spin-orbit interaction and can nowadays be probed by electronic transport.
Here we predict that in a much broader class of quantum-dot systems with spin
larger than one-half, superparamagnetism may arise without spin-orbit
interaction: by attaching ferromagnets a spintronic exchange field of
quadrupolar nature is generated locally. It can be observed in conductance
measurements and surprisingly leads to enhanced spin filtering even in a state
with zero average spin. Analogously to the spintronic dipolar exchange field,
responsible for a local spin torque, the effect is susceptible to electric
control and increases with tunnel coupling as well as with spin polarization.Comment: 6 pages with 4 figures + 26 pages of Supplementary Informatio
Определение факторов, влияющих на азимут развития трещины гидроразрыва пласта на Приобском нефтяном месторождении (ХМАО)
Цель работы – определение факторов, влияющих на азимут развития трещины гидроразрыва пласта на П нефтяном месторождении
В процессе работы были проведены различные мероприятия по анализу эффективности ГРП, горного напряжение и ориентации трещин в пласте. В работе рассмотрен вопрос о охране труда и окружающей среды. Бакалаврская работа выполнена с учетом современных достижений в области техники и технологии.
Выпускная квалификационная работа выполнена в текстовом редакторе Microsoft Word.Purpose – to determine factors influencing the azimuth of the development of the crack hydraulic fracturing for P oil field
In the process, various events were carried out to analyze efficiency of hydraulic fracturing, rock stress and orientation of cracks in the formation. The paper discusses the issue of labor protection and the environment.
Undergraduate work is performed taking into account modern achievements in the field of engineering and technology.
Final qualifying work is executed in a text editor of Microsoft Word
- …