1,898 research outputs found
On the angular anisotropy of the randomly averaged magnetic neutron scattering cross section of nanoparticles
The magnetic small-angle neutron scattering (SANS) cross section of dilute
ensembles of uniformly magnetized and randomly oriented Stoner–Wohlfarth
particles is calculated using the Landau–Lifshitz equation. The focus of this
study is on the angular anisotropy of the magnetic SANS signal as it can be seen
on a two-dimensional position-sensitive detector. Depending on the symmetry
of the magnetic anisotropy of the particles (e.g. uniaxial, cubic), an anisotropic
magnetic SANS pattern may result, even in the remanent state or at the coercive
field. The case of inhomogeneously magnetized particles and the effects of a
particle-size distribution and interparticle correlations are also discussed
Fingerprint of vortex-like flux closure in isotropic Nd-Fe-B bulk magnet
Taking advantage of recent progress in neutron instrumentation and in the
understanding of magnetic-field-dependent small-angle neutron scattering, here,
we study the three-dimensional magnetization distribution within an isotropic
Nd-Fe-B bulk magnet. The magnetic neutron scattering cross section of this
system features the so-called spike anisotropy, which points towards the
presence of a strong magnetodipolar interaction. This experimental result
combined with a damped oscillatory behavior of the corresponding correlation
function and recent micromagnetic simulation results on spherical nanoparticles
suggest an interpretation of the neutron data in terms of vortex-like flux
closure patterns. The field-dependent correlation length is very well
reproduced by a power-law model used to describe the London penetration depth
in the vortex state of type-II superconductors and suggests the 'pairing'
(interaction) of magnetic vortices.Comment: 14 pages, 5 figure
Micromagnetic simulation of neutron scattering from spherical nanoparticles: Effect of pore-type defects
We employ micromagnetic simulations to model the effect of pore-type
microstructural defects on the magnetic small-angle neutron scattering cross
section and the related pair-distance distribution function of spherical
magnetic nanoparticles. Our expression for the magnetic energy takes into
account the isotropic exchange interaction, the magnetocrystalline anisotropy,
the dipolar interaction, and an externally applied magnetic field. The
signatures of the defects and the role of the dipolar energy are highlighted
and the effect of a particle-size distribution is studied. The results serve as
a guideline to the experimentalist.Comment: arXiv admin note: text overlap with arXiv:2205.0755
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D3.8 Comparative evaluation of the MAZI pilots (version 1)
This deliverable is the first of three reporting on the MAZI pilots’ comparative evaluation. We report on progress towards developing a comparative evaluation approach that will draw from the four MAZI pilots to inform the project, to understand progress and enable lessons learned to be applied across MAZI and beyond.In this report we introduce our approach to a comparative meta evaluation strategy in the context of MAZI, taking into account the rich diversity of the consortium partners, their wide range of disciplines, and the different contexts of the pilots. Given this diversity, we emphasise a participatory approach to evaluation, drawing from partners’ academic disciplines and practitioner fields to inform the development of an evaluation framework. Each partner brings with them their own paradigms and methodologies for analysing progress, and a ‘one size fits all’ approach to evaluation applied to all pilots risks losing the richness each has to offer. Therefore, we have found it necessary to begin the process through negotiating a set of high level, lightweight instruments that can initially engage each pilot team in the activity, and elicit data while enabling the reporting of local diversity.We briefly describe the diversity of contexts, then introduce our participatory approach to engaging with partners. We introduce the first set of tools used to gather data and report on initial data gathered from the two pilots that are underway, Nachbarschafts-Akademie / Neighbourhood Academy (NAk, Berlin) and CreekNet (London).We conclude by outlining the coverage of the second version of this deliverable (D3.9, to be reported in M26) and the third version (D3.10, to be reported in M36)
Virtual Machine Support for Many-Core Architectures: Decoupling Abstract from Concrete Concurrency Models
The upcoming many-core architectures require software developers to exploit
concurrency to utilize available computational power. Today's high-level
language virtual machines (VMs), which are a cornerstone of software
development, do not provide sufficient abstraction for concurrency concepts. We
analyze concrete and abstract concurrency models and identify the challenges
they impose for VMs. To provide sufficient concurrency support in VMs, we
propose to integrate concurrency operations into VM instruction sets.
Since there will always be VMs optimized for special purposes, our goal is to
develop a methodology to design instruction sets with concurrency support.
Therefore, we also propose a list of trade-offs that have to be investigated to
advise the design of such instruction sets.
As a first experiment, we implemented one instruction set extension for
shared memory and one for non-shared memory concurrency. From our experimental
results, we derived a list of requirements for a full-grown experimental
environment for further research
Catching Element Formation In The Act
Gamma-ray astronomy explores the most energetic photons in nature to address
some of the most pressing puzzles in contemporary astrophysics. It encompasses
a wide range of objects and phenomena: stars, supernovae, novae, neutron stars,
stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays
and relativistic-particle acceleration, and the evolution of galaxies. MeV
gamma-rays provide a unique probe of nuclear processes in astronomy, directly
measuring radioactive decay, nuclear de-excitation, and positron annihilation.
The substantial information carried by gamma-ray photons allows us to see
deeper into these objects, the bulk of the power is often emitted at gamma-ray
energies, and radioactivity provides a natural physical clock that adds unique
information. New science will be driven by time-domain population studies at
gamma-ray energies. This science is enabled by next-generation gamma-ray
instruments with one to two orders of magnitude better sensitivity, larger sky
coverage, and faster cadence than all previous gamma-ray instruments. This
transformative capability permits: (a) the accurate identification of the
gamma-ray emitting objects and correlations with observations taken at other
wavelengths and with other messengers; (b) construction of new gamma-ray maps
of the Milky Way and other nearby galaxies where extended regions are
distinguished from point sources; and (c) considerable serendipitous science of
scarce events -- nearby neutron star mergers, for example. Advances in
technology push the performance of new gamma-ray instruments to address a wide
set of astrophysical questions.Comment: 14 pages including 3 figure
The global meningitis genome partnership.
Genomic surveillance of bacterial meningitis pathogens is essential for effective disease control globally, enabling identification of emerging and expanding strains and consequent public health interventions. While there has been a rise in the use of whole genome sequencing, this has been driven predominately by a subset of countries with adequate capacity and resources. Global capacity to participate in surveillance needs to be expanded, particularly in low and middle-income countries with high disease burdens. In light of this, the WHO-led collaboration, Defeating Meningitis by 2030 Global Roadmap, has called for the establishment of a Global Meningitis Genome Partnership that links resources for: N. meningitidis (Nm), S. pneumoniae (Sp), H. influenzae (Hi) and S. agalactiae (Sa) to improve worldwide co-ordination of strain identification and tracking. Existing platforms containing relevant genomes include: PubMLST: Nm (31,622), Sp (15,132), Hi (1935), Sa (9026); The Wellcome Sanger Institute: Nm (13,711), Sp (> 24,000), Sa (6200), Hi (1738); and BMGAP: Nm (8785), Hi (2030). A steering group is being established to coordinate the initiative and encourage high-quality data curation. Next steps include: developing guidelines on open-access sharing of genomic data; defining a core set of metadata; and facilitating development of user-friendly interfaces that represent publicly available data
Chemical PARP Inhibition Enhances Growth of Arabidopsis and Reduces Anthocyanin Accumulation and the Activation of Stress Protective Mechanisms
Poly-ADP-ribose polymerase (PARP) post-translationally modifies proteins through the addition of ADP-ribose polymers, yet its role in modulating plant development and stress responses is only poorly understood. The experiments presented here address some of the gaps in our understanding of its role in stress tolerance and thereby provide new insights into tolerance mechanisms and growth. Using a combination of chemical and genetic approaches, this study characterized phenotypes associated with PARP inhibition at the physiological level. Molecular analyses including gene expression analysis, measurement of primary metabolites and redox metabolites were used to understand the underlying processes. The analysis revealed that PARP inhibition represses anthocyanin and ascorbate accumulation under stress conditions. The reduction in defense is correlated with enhanced biomass production. Even in unstressed conditions protective genes and molecules are repressed by PARP inhibition. The reduced anthocyanin production was shown to be based on the repression of transcription of key regulatory and biosynthesis genes. PARP is a key factor for understanding growth and stress responses of plants. PARP inhibition allows plants to reduce protection such as anthocyanin, ascorbate or Non-Photochemical-Quenching whilst maintaining high energy levels likely enabling the observed enhancement of biomass production under stress, opening interesting perspectives for increasing crop productivity
Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles
We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, "Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles
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