Magnetization reversal of ferromagnetic nanowires studied by magnetic force microscopy

The magnetization reversal of two-dimensional arrays of parallel ferromagnetic Fe nanowires embedded in nanoporous alumina templates has been studied. By combining bulk magnetization measurements (superconducting quantum interference device magnetometry) with field-dependent magnetic force microscopy (MFM), we have been able to decompose the macroscopic hysteresis loop in terms of the irreversible magnetic responses of individual nanowires. The latter are found to behave as monodomain ferromagnetic needles, with hysteresis loops displaced (asymmetric) as a consequence of the strong dipolar interactions between them. The application of field-dependent MFM provides a microscopic method to obtain the hysteresis curve of the array, by simply registering the fraction of up and down magnetized wires as a function of applied field. The observed deviations from the rectangular shape of the macroscopic hysteresis loop of the array can be ascribed to the spatial variation of the dipolar field through the inhomogeneously filled membrane. The system studied proves to be an excellent example of the two-dimensional classical Preisach model, well known from the field of hysteresis modeling and micromagnetism.

Force-free twisted magnetospheres of neutron stars

Context. The X-ray spectra observed in the persistent emission of magnetars are evidence for the existence of a magnetosphere. The high-energy part of the spectra is explained by resonant cyclotron upscattering of soft thermal photons in a twisted magnetosphere, which has motivated an increasing number of efforts to improve and generalize existing magnetosphere models. Aims. We want to build more general configurations of twisted, force-free magnetospheres as a first step to understanding the role played by the magnetic field geometry in the observed spectra. Methods. First we reviewed and extended previous analytical works to assess the viability and limitations of semi-analytical approaches. Second, we built a numerical code able to relax an initial configuration of a nonrotating magnetosphere to a force-free geometry, provided any arbitrary form of the magnetic field at the star surface. The numerical code is based on a finite-difference time-domain, divergence-free, and conservative scheme, based of the magneto-frictional method used in other scenarios. Results. We obtain new numerical configurations of twisted magnetospheres, with distributions of twist and currents that differ from previous analytical solutions. The range of global twist of the new family of solutions is similar to the existing semi-analytical models (up to some radians), but the achieved geometry may be quite different. Conclusions. The geometry of twisted, force-free magnetospheres shows a wider variety of possibilities than previously considered. This has implications for the observed spectra and opens the possibility of implementing alternative models in simulations of radiative transfer aiming at providing spectra to be compared with observations.

The influence of magnetic field geometry on magnetars X-ray spectra

Nowadays, the analysis of the X-ray spectra of magnetically powered neutron stars or magnetars is one of the most valuable tools to gain insight into the physical processes occurring in their interiors and magnetospheres. In particular, the magnetospheric plasma leaves a strong imprint on the observed X-ray spectrum by means of Compton up-scattering of the thermal radiation coming from the star surface. Motivated by the increased quality of the observational data, much theoretical work has been devoted to develop Monte Carlo (MC) codes that incorporate the effects of resonant Compton scattering (RCS) in the modeling of radiative transfer of photons through the magnetosphere. The two key ingredients in this simulations are the kinetic plasma properties and the magnetic field (MF) configuration. The MF geometry is expected to be complex, but up to now only mathematically simple solutions (self-similar solutions) have been employed. In this work, we discuss the effects of new, more realistic, MF geometries on synthetic spectra. We use new force-free solutions [14] in a previously developed MC code [9] to assess the influence of MF geometry on the emerging spectra. Our main result is that the shape of the final spectrum is mostly sensitive to uncertain parameters of the magnetospheric plasma, but the MF geometry plays an important role on the angle-dependence of the spectra.

With or without you...judging politically in the field of Area of Freedom, Security and Justice? Research Papers in Law, 3/2007

From the Introduction. The study of the European Court of Justice’s (ECJ) case law of the regarding the Area of Freedom Security and Justice (AFSJ) is fascinating in many ways.1 First, almost the totality of the relevant case law is extremely recent, thereby marking the first ‘foundational’ steps in this field of law. This is the result of the fact that the AFSJ was set up by the Treaty of Amsterdam in 1997 and only entered into force in May 1999.2 Second, as the AFSJ is a new field of EU competence, it sets afresh all the fundamental questions – both political and legal – triggered by European integration, namely in terms of: a) distribution of powers between the Union and its member states, b) attribution of competences between the various EU Institutions, c) direct effect and supremacy of EU rules, d) scope of competence of the ECJ, and e) measure of the protection given to fundamental rights. The above questions beg for answers which should take into account both the extremely sensible fields of law upon which the AFSJ is anchored, and the EU’s highly inconvenient three-pillar institutional framework.3 Third, and as a consequence of the above, the vast majority of the ECJ’s judgments relating to the AFSJ are a) delivered by the Full Court or, at least, the Grand Chamber, b) with the intervention of great many member states and c) often obscure in content. This is due to the fact that the Court is called upon to set the foundational rules in a new field of EU law, often trying to accommodate divergent considerations, not all of which are strictly legal.4 Fourth, the case law of the Court relating to the AFSJ, touches upon a vast variety of topics which are not necessarily related to one another. This is why it is essential to limit the scope of this study. The content of, and steering for, the AFSJ were given by the Tampere European Council, in October 1999. According to the Tampere Conclusions, the AFSJ should consist of four key elements: a) a common immigration and asylum policy, b) judicial cooperation in both civil and penal matters, c) action against criminality and d) external action of the EU in all the above fields. Moreover, the AFSJ is to a large extent based on the Schengen acquis. The latter has been ‘communautarised’5 by the Treaty of Amsterdam and further ‘ventilated’ between the first and third pillars by decisions 1999/435 and 1999/436.6 Judicial cooperation in civil matters, mainly by means of international conventions (such as the Rome Convention of 1981 on the law applicable to contractual obligations) and regulations (such as (EC) 44/20017 and (EC) 1348/20008) also form part of the AFSJ. However, the relevant case law of the ECJ will not be examined in the present contribution.9 Similarly, the judgments of the Court delivered in the course of Article 226 EC proceedings against member states, will be omitted.10 Even after setting aside the above case law and notwithstanding the fact that the AFSJ only dates as far back as May 1999, the judgments of the ECJ are numerous. A simple (if not simplistic) categorisation may be between, on the one hand, judgments which concern the institutional setting of the AFSJ (para. 2) and, on the other, judgments which are related to some substantive AFSJ policy (para. 3).

More Union in European Defence. CEPS Task Force Report, 26 February 2015

Years of uncoordinated cuts in defence spending have eroded the EU’s role as a security actor in what is now a multipolar world. This CEPS Task Force report aims to provide member states and the EU institutions with the narrative to strengthen defence cooperation in the EU, in the face of numerous emergencies in the EU’s strategic neighbourhood and ever-present security threats. The report is a record of the deliberations over several months between high-level experts in the field of European security and defence, who conclude that the Treaty of Lisbon demands and permits a great deal more in terms of our common security and defence activities. And that member states could achieve much more value for money than the €190 billion that they spend to keep up 28 national armies, comprising roughly 1.5 million service personnel. This report suggests policy actions to further the EU’s strategic, institutional, capabilities, and resources cooperation in the field of defence. Ultimately, in the view of the Task Force experts, further integration should amount to a European Defence Union.

Morphology Change of C60 Islands on Organic Crystals Observed by Atomic Force Microscopy

Organic-organic heterojunctions are nowadays highly regarded materials for light-emitting diodes, field-effect transistors, and photovoltaic cells with the prospect of designing low-cost, flexible, and efficient electronic devices.1-3 However, the key parameter of optimized heterojunctions relies on the choice of the molecular compounds as well as on the morphology of the organic-organic interface,4 which thus requires fundamental studies. In this work, we investigated the deposition of C60 molecules at room temperature on an organic layer compound, the salt bis(benzylammonium)bis(oxalato)cupurate(II), by means of noncontact atomic force microscopy. Three-dimensional molecular islands of C60 having either triangular or hexagonal shapes are formed on the substrate following a "Volmer-Weber" type of growth. We demonstrate the dynamical reshaping of those C60 nanostructures under the local action of the AFM tip at room temperature. The dissipated energy is about 75 meV and can be interpreted as the activation energy required for this migration process.

A brief history of early Kelly Field, 1916-1918 /

Shipping list no.: 88-213-P.

Remarkable journey : the Wright Field heritage in photographs /

Shipping list no.: 91-286-P.

An analytical and experimental study of the ionized flow field about a hemisphere cylinder and its effect on the radiation pattern of a slot antenna

Mode of access: Internet.

On one-dimensional channel flow in the presence of a magnetic field.

"Prepared for the Air Force Ballistic Missile Division, Headquarters Air Research and Development Command, under contract AF 04(647)-309 advanced propulsion systems."

Rate of heat-transfer near the stagnation point of a blunt body of revolution, in the presence of a magnetic field.

"Prepared for the Air Force Ballistic Missile Division, Headquarters Air Research and Development Command, under contract AF04(647)-127, call no. 4."

Magnetic plasma propulsion by means of a travelling sinusoidal field.

"STL/TR-60-0000-09114."

A Little journey to the home of the Engineering Division, Army Air Service, McCook Field, Dayton, Ohio.

Cover title.

Some useful information for the design of air-core solenoids. Part I: Relationships between magnetic field, power, ampere-turns and current density. Part II: Homogenous magnetic fields,

"AFOSR-1525."

Boundary layer and wake modifications to compressor design systems : the effect of blade-to-blade flow variations on the mean flow field of a transonic rotor : final report, 01 September 1976-31 August 1978 /

"AFAPL-TR-79-2010."