3,759 research outputs found
Stable divisorial gonality is in NP
Divisorial gonality and stable divisorial gonality are graph parameters,
which have an origin in algebraic geometry. Divisorial gonality of a connected
graph can be defined with help of a chip firing game on . The stable
divisorial gonality of is the minimum divisorial gonality over all
subdivisions of edges of .
In this paper we prove that deciding whether a given connected graph has
stable divisorial gonality at most a given integer belongs to the class NP.
Combined with the result that (stable) divisorial gonality is NP-hard by
Gijswijt, we obtain that stable divisorial gonality is NP-complete. The proof
consist of a partial certificate that can be verified by solving an Integer
Linear Programming instance. As a corollary, we have that the number of
subdivisions needed for minimum stable divisorial gonality of a graph with
vertices is bounded by for a polynomial
Quantized spin wave modes in magnetic tunnel junction nanopillars
We present an experimental and theoretical study of the magnetic field
dependence of the mode frequency of thermally excited spin waves in rectangular
shaped nanopillars of lateral sizes 60x100, 75x150, and 105x190 nm2, patterned
from MgO-based magnetic tunnel junctions. The spin wave frequencies were
measured using spectrally resolved electrical noise measurements. In all
spectra, several independent quantized spin wave modes have been observed and
could be identified as eigenexcitations of the free layer and of the synthetic
antiferromagnet of the junction. Using a theoretical approach based on the
diagonalization of the dynamical matrix of a system of three coupled, spatially
confined magnetic layers, we have modeled the spectra for the smallest pillar
and have extracted its material parameters. The magnetization and exchange
stiffness constant of the CoFeB free layer are thereby found to be
substantially reduced compared to the corresponding thin film values. Moreover,
we could infer that the pinning of the magnetization at the lateral boundaries
must be weak. Finally, the interlayer dipolar coupling between the free layer
and the synthetic antiferromagnet causes mode anticrossings with gap openings
up to 2 GHz. At low fields and in the larger pillars, there is clear evidence
for strong non-uniformities of the layer magnetizations. In particular, at zero
field the lowest mode is not the fundamental mode, but a mode most likely
localized near the layer edges.Comment: 16 pages, 4 figures, (re)submitted to PR
Deep Learning-Based Natural Language Processing in Radiology:The Impact of Report Complexity, Disease Prevalence, Dataset Size, and Algorithm Type on Model Performance
In radiology, natural language processing (NLP) allows the extraction of valuable information from radiology reports. It can be used for various downstream tasks such as quality improvement, epidemiological research, and monitoring guideline adherence. Class imbalance, variation in dataset size, variation in report complexity, and algorithm type all influence NLP performance but have not yet been systematically and interrelatedly evaluated. In this study, we investigate these factors on the performance of four types [a fully connected neural network (Dense), a long short-term memory recurrent neural network (LSTM), a convolutional neural network (CNN), and a Bidirectional Encoder Representations from Transformers (BERT)] of deep learning-based NLP.Β Two datasets consisting of radiologist-annotated reports of both trauma radiographs (nβ=β2469) and chest radiographs and computer tomography (CT) studies (nβ=β2255) were split into training sets (80%) and testing sets (20%). The training data was used as a source to train all four model types in 84 experiments (Fracture-data) and 45 experiments (Chest-data) with variation in size and prevalence. The performance was evaluated on sensitivity, specificity, positive predictive value, negative predictive value, area under the curve, and F score.Β After the NLP of radiology reports, all four model-architectures demonstrated high performance with metrics up toβ>β0.90.Β CNN, LSTM, and Dense were outperformed by the BERT algorithm because of its stable results despite variation in training size and prevalence. Awareness of variation in prevalence is warranted because it impacts sensitivity and specificity in opposite directions. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10916-021-01761-4
The Birthday Party Test (BPT); A new picture description test to support the assessment of simultanagnosia in patients with acquired brain injury
There is broad consensus on the utility of complex pictures in the assessment of simultanagnosia in patients with acquired brain injury (ABI). To overcome various shortcomings of current instruments, we have developed the Birthday Party Test (BPT); a picture description test that contains a neutral scene, a balanced representation of events, and provides clear instructions and a scoring-aid. We have applied the BPT in a large group of patients with ABI (nβ=β502) and in an age-matched healthy control group (nβ=β194). Our results show that performance on the BPT was associated with a range of descriptive, neuropsychological and clinical characteristics and that poor test performance appeared to be more common in patients with etiologies that have an increased risk of bilateral damage. Furthermore, we assume a high correspondence between test performance on the BPT and the assessorβs clinical judgment of likely having simultanagnosia in preliminary analyses. This study shows the potential usefulness of the BPT to support diagnostic decision making in simultanagnosia. The BPT is made freely available to facilitate its broad application in the clinical assessment of patients with visual impairment and to enable a further evaluation of its utility and validity in future studies
Nivolumab and ipilimumab in the real-world setting in patients with mesothelioma
Objectives: Nivolumab (anti-PD-1) plus ipilimumab (anti-CTLA-4) is a new first-line treatment combination for patients with pleural mesothelioma. Nivolumab-ipilimumab improved the survival, however, 30.3% of the patients suffered from grade 3β4 treatment related adverse events (TRAE's) and TRAE's led to discontinuation in 23.0% of all patients. Here, we present the first real-world data of nivolumab plus ipilimumab in patients with malignant mesothelioma treated in two mesothelioma expert centers. Methods: Clinical data of patients with mesothelioma treated with nivolumab and ipilimumab were prospectively collected. Clinical parameters were obtained every visit, CT scans were evaluated every 12 weeks and adverse events were assessed continuously during the treatment. Data on grade 2β5 TRAE's and activity (overall response rate (ORR), duration of response (DOR), disease control rate (DCR), median progression-free survival (mPFS) and median overall survival (mOS) were reported. Results: Between January 2021 and August 2022, 184 patients were treated with nivolumab plus ipilimumab. The median follow-up was 12.1 months (95 %CI 11.1 β 13.1). Grade 3β4 TRAEs were seen in 27.7 % of the patients and 25.0 % discontinued immunotherapy treatment early because of TRAE's. ORR was 21.7 % (95 % CI 15.7β27.7), median DOR was 5.7 months (IQR 3.2β8.7) and DCR at 12 weeks 56.0 % (95 % CI 48.8β63.2). The mPFS was 5.5 months (95 %CI 4.1β6.9), mOS was 14.1 months (95 % CI 11.1β18.2). Conclusions: Nivolumab plus ipilimumab had an equal efficacy in a real-world comparable population but also a high risk of TRAE's, leading to discontinuation of treatment in 25% of the patients.</p
Electrically controlled long-distance spin transport through an antiferromagnetic insulator
Spintronics uses spins, the intrinsic angular momentum of electrons, as an
alternative for the electron charge. Its long-term goal is in the development
of beyond-Moore low dissipation technology devices. Recent progress
demonstrated the long-distance transport of spin signals across ferromagnetic
insulators. Antiferromagnetically ordered materials are however the most common
class of magnetic materials with several crucial advantages over ferromagnetic
systems. In contrast to the latter, antiferromagnets exhibit no net magnetic
moment, which renders them stable and impervious to external fields. In
addition, they can be operated at THz frequencies. While fundamentally their
properties bode well for spin transport, previous indirect observations
indicate that spin transmission through antiferromagnets is limited to short
distances of a few nanometers. Here we demonstrate the long-distance, over tens
of micrometers, propagation of spin currents through hematite (\alpha-Fe2O3),
the most common antiferromagnetic iron oxide, exploiting the spin Hall effect
for spin injection. We control the spin current flow by the interfacial
spin-bias and by tuning the antiferromagnetic resonance frequency with an
external magnetic field. This simple antiferromagnetic insulator is shown to
convey spin information parallel to the compensated moment (N\'eel order) over
distances exceeding tens of micrometers. This newly-discovered mechanism
transports spin as efficiently as the net magnetic moments in the best-suited
complex ferromagnets. Our results pave the way to ultra-fast, low-power
antiferromagnet-insulator-based spin-logic devices that operate at room
temperature and in the absence of magnetic fields
Nile perch distribution in south-east Lake Victoria is more strongly driven by abiotic factors, than by prey densities
Abstract We studied the effects of environmental driving factors (maximum depth, visibility, oxygen, temperature, and prey densities) on the distribution and diet composition of Nile perch (Lates niloticus) in south-east Lake Victoria from 2009 to 2011. We tested the hypotheses that (i) Nile perch distribution is regulated by the same environmental factors on a local scale (Mwanza Gulf) and on a regional scale (Mwanza Gulf, Speke Gulf and the open lake in Sengerema district), and (ii) driving factors act differently on different Nile perch size classes. Fish were sampled with gillnets. Nile perch densities were highest in the shallow part of the Mwanza Gulf and during the wet seasons, mainly caused by high densities of juveniles. The environmental driving factors explained Nile perch distributions on both regional and local scales in a similar way, often showing non-linear relationships. Maximum depth and temperature were the best predictors of Nile perch densities. Prey densities of shrimp and haplochromines did not strongly affect Nile perch distributions, but did explain Nile perch diet on a local and regional scale. We conclude that abiotic variables drive Nile perch distributions more strongly than prey densities and that feeding takes place opportunistically
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ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ Π½ΠΎΠ²ΡΠΉ ΡΠΎΡΠΌΠ°Π»ΠΈΠ·ΠΌ ΡΠΈΠΏΠΈΠ·ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ Ξ·-ΠΈΡΡΠΈΡΠ»Π΅Π½ΠΈΡ Π² ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅ ΡΠ΅ΠΎΡΠ΅ΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΎΡΠ½ΠΎΠ²Ρ Π΄Π»Ρ ΠΏΠΎ-ΡΡΡΠΎΠ΅Π½ΠΈΡ ΡΠΏΠ΅ΡΠΈΠ°Π»ΡΠ½ΡΡ
ΠΊΠ»Π°ΡΡΠΎΠ² ΡΠΈΡΡΠ΅ΠΌ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ ΠΏΠ΅ΡΠ΅ΠΏΠΈΡΡΠ²Π°ΡΡΠΈΡ
ΠΏΡΠ°Π²ΠΈΠ». Π€ΠΎΡΠΌΠ°-Π»ΠΈΠ·ΠΌ ΠΈΡΠΏΠΎΠ»ΡΠ·ΡΠ΅Ρ ΡΠΏΠΎΡΡΠ΄ΠΎΡΠ΅Π½Π½ΡΠ΅ Π½Π΅ΠΊΠΎΠ½ΡΠ»ΡΡΠ½ΡΠ½ΡΠ΅ ΠΌΠ½ΠΎΠΆΠ΅ΡΡΠ²Π° ΠΏΡΠ°Π²ΠΈΠ» ΠΏΠ΅ΡΠ΅ΠΏΠΈΡΡΠ²Π°Π½ΠΈΡ ΠΈ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΠ΅ Ρ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠ½ΡΠΌ ΠΎΠΊΡΡΠΆΠ΅Π½ΠΈΠ΅ΠΌ, ΡΡΠΎ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ ΡΠ°ΡΡΠΈΡΠΈΡΡ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΠΈ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
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