343 research outputs found
Probing the stability and magnetic properties of magnetosome chains in freeze-dried magnetotactic bacteria
Embracing Defects and Disorder in Magnetic Nanoparticles
Iron oxide nanoparticles have tremendous scientific and technological
potential in a broad range of technologies, from energy applications to
biomedicine. To improve their performance, single-crystalline and defect-free
nanoparticles have thus far been aspired. However, in several recent studies
defect-rich nanoparticles outperform their defect-free counterparts in magnetic
hyperthermia and magnetic particle imaging. Here, an overview on the
state-of-the-art of design and characterization of defects and resulting spin
disorder in magnetic nanoparticles is presented with a focus on iron oxide
nanoparticles. The beneficial impact of defects and disorder on intracellular
magnetic hyperthermia performance of magnetic nanoparticles for drug delivery
and cancer therapy is emphasized. Defect-engineering in iron oxide
nanoparticles emerges to become an alternative approach to tailor their
magnetic properties for biomedicine, as it is already common practice in
established systems such as semiconductors and emerging fields including
perovskite solar cells. Finally, perspectives and thoughts are given on how to
deliberately induce defects in iron oxide nanoparticles and their potential
implications for magnetic tracers to monitor cell therapy and immunotherapy by
magnetic particle imaging
Kartenbasierte Verhaltensentscheidung und Manöverplanung für automatische Fahrzeuge
Assistenzsysteme erschließen sich immer größere Teile des öffentlichen Verkehrsraumes und die aktuelle Entwicklung steuert in Richtung automatischer Fahrzeuge. Diese Systeme nehmen die Position des Fahrers ein, müssen Entscheidungen treffen und Aktionen auslösen. Hierfür ist es notwendig, die Situation zu verstehen, Entscheidungsmöglichkeiten zu identifizieren und für eine getroffene
Entscheidung Steuersignale zu generieren.
In dieser Arbeit wird eine Kartenrepräsentation (Lanelet-Karten) und eine deterministische Verhaltensgenerierung vorgestellt. Die Verhaltensgenerierung bezieht die für das Verhalten relevante Information aus der Karte und setzt sie mit
Beobachtungen aus der Sensorik in Beziehung. Das gewünschte Verhalten wird in Form von Nebenbedingungen an einen dem Stand der Technik entliehenen Trajektorienplaner übergeben.
Die Verhaltensentscheidung wird anhand einer vollautomatisierten Fahrt
im realen Straßenverkehr erprobt. Basierend auf den Ergebnissen wird untersucht, wie ein lokales Lösungsverfahren zur Trajektorienplanung so erweitert werden kann, dass auch Situationen beherrschbar sind, in denen sich mehrere – aber nicht ineinander überführbare – Optionen eröffnen. Es werden zwei Problemformulierungen und -lösungen vorgestellt und simulativ evaluiert
Advanced analysis of magnetic nanoflower measurements to leverage their use in biomedicine
Magnetic nanoparticles are an important asset in many biomedical applications ranging from the local heating of tumours to targeted drug delivery towards diseased sites. Recently, magnetic nanoflowers showed a remarkable heating performance in hyperthermia experiments thanks to their complex structure leading to a broad range of magnetic dynamics. To grasp their full potential and to better understand the origin of this unexpected heating performance, we propose the use of Kaczmarz' algorithm in interpreting magnetic characterisation measurements. It has the advantage that no a priori assumptions need to be made on the particle size distribution, contrasting current magnetic interpretation methods that often assume a lognormal size distribution. Both approaches are compared on DC magnetometry, magnetorelaxometry and AC susceptibility characterisation measurements of the nanoflowers. We report that the lognormal distribution parameters vary significantly between data sets, whereas Kaczmarz' approach achieves a consistent and accurate characterisation for all measurement sets. Additionally, we introduce a methodology to use Kaczmarz' approach on distinct measurement data sets simultaneously. It has the advantage that the strengths of the individual characterisation techniques are combined and their weaknesses reduced, further improving characterisation accuracy. Our findings are important for biomedical applications as Kaczmarz' algorithm allows to pinpoint multiple, smaller peaks in the nanostructure's size distribution compared to the monomodal lognormal distribution. The smaller peaks permit to fine-tune biomedical applications with respect to these peaks to e.g. boost heating or to reduce blurring effects in images. Furthermore, the Kaczmarz algorithm allows for a standardised data analysis for a broad range of magnetic nanoparticle samples. Thus, our approach can improve the safety and efficiency of biomedical applications of magnetic nanoparticles, paving the way towards their clinical use
Deep Learning for Survival Analysis: A Review
The influx of deep learning (DL) techniques into the field of survival
analysis in recent years, coupled with the increasing availability of
high-dimensional omics data and unstructured data like images or text, has led
to substantial methodological progress; for instance, learning from such
high-dimensional or unstructured data. Numerous modern DL-based survival
methods have been developed since the mid-2010s; however, they often address
only a small subset of scenarios in the time-to-event data setting - e.g.,
single-risk right-censored survival tasks - and neglect to incorporate more
complex (and common) settings. Partially, this is due to a lack of exchange
between experts in the respective fields.
In this work, we provide a comprehensive systematic review of DL-based
methods for time-to-event analysis, characterizing them according to both
survival- and DL-related attributes. In doing so, we hope to provide a helpful
overview to practitioners who are interested in DL techniques applicable to
their specific use case as well as to enable researchers from both fields to
identify directions for future investigation. We provide a detailed
characterization of the methods included in this review as an open-source,
interactive table: https://survival-org.github.io/DL4Survival. As this research
area is advancing rapidly, we encourage the research community to contribute to
keeping the information up to date.Comment: 24 pages, 6 figures, 2 tables, 1 interactive tabl
Overstretching Expectations May Endanger the Success of the “Millennium Surgery”
Total hip arthroplasty (THA) is an extremely successful treatment strategy. Patient expectations, however, have increased; if not properly guided by surgeons, at present, patients expect next to pain-free restoration of the joint and a fast return to work and sports. While the revision rates after THA also increased in younger patients, knowledge on musculoskeletal loads still remains sparse, and the current recommendations on postoperative rehabilitation are based on expert opinions only. The aim of this study was to unravel biomechanical contact conditions in "working age" (60 years, 67.7 +/- 8.6 years) patients during activities recommended post-THA. We hypothesized that working age patients would show substantially increased hip contact loads compared to older patients. The in vivo joint contact force (F-res) and torsion torque (M-tors), reflecting the main contact load situation, experienced during activities of daily living and sports activities were measured in a unique group of 16 patients with instrumented THA. We summarized patient activities and sports recommendations after THA mentioned within the literature using PubMed (without claim of completeness). The measurements showed that younger working age patients experienced significant (p = 0.050) increased M-tors (21.52 +/- 9.11 Nm) than older retirement age patients (13.99 +/- 7.89 Nm) by walking. Bowling, as a recommended low-impact sport, was associated with F-res of up to 5436 N and M-tors of up to 108 Nm in the working age group, which were higher than the F-res (5276 N) and M-tors (71 Nm) during high-impact soccer. Based on our results, age was proven to be a discriminator in joint loading, with working age patients presenting with increased loads compared to retirement age patients, already during daily activities. The current patient recommendations have led to further increased joint loadings. If THA cannot be delayed in a patient, we propose counselling patients on a carefully considered return to sports, focusing on low-impact activities, as indicated hereby. The findings from this work illustrate the need to provide critical feedback to patient expectations when returning to work and sports activities. Patients returning to more intensive sports activities should be carefully monitored and advised to avoid as much overloading as possible
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