2,315 research outputs found
Competition between Kondo screening and indirect magnetic exchange in a quantum box
Nanoscale systems of metal atoms antiferromagnetically exchange coupled to
several magnetic impurities are shown to exhibit an unconventional re-entrant
competition between Kondo screening and indirect magnetic exchange interaction.
Depending on the atomic positions of the magnetic moments, the total
ground-state spin deviates from predictions of standard
Ruderman-Kittel-Kasuya-Yosida perturbation theory. The effect shows up on an
energy scale larger than the level width induced by the coupling to the
environment and is experimentally verifiable by studying magnetic field
dependencies.Comment: 5 pages, 2 figures, v3 with minor change
Autowaves in a dc complex plasma confined behind a de Laval nozzle
Experiments to explore stability conditions and topology of a dense
microparticle cloud supported against gravity by a gas flow were carried out.
By using a nozzle shaped glass insert within the glass tube of a dc discharge
plasma chamber a weakly ionized gas flow through a de Laval nozzle was
produced. The experiments were performed using neon gas at a pressure of 100 Pa
and melamine-formaldehyde particles with a diameter of 3.43 {\mu}m. The
capturing and stable global confining of the particles behind the nozzle in the
plasma were demonstrated. The particles inside the cloud behaved as a single
convection cell inhomogeneously structured along the nozzle axis in a tube-like
manner. The pulsed acceleration localized in the very head of the cloud
mediated by collective plasma-particle interactions and the resulting wave
pattern were studied in detail.Comment: 6 pages, 4 figure
Experimental investigation of dynamical structures formation due to flowing complex plasma past an obstacle
We report the experimental observation of dynamical behavior of flowing
complex plasma past a spherical obstacle. The experiment has been carried out
in a -shaped DC glow discharge experimental device using kaolin particles
as the dust component in a background of Argon plasma. A stationary dust cloud
is formed by maintaining the pumping speed and gas flow rate. A spherical
obstacle vertically mounted on the cathode tray acts as an obstacle to the flow
of dust particles. The controlled dust flow is generated by reducing the mass
flow of the neutrals through a mass flow controller. The flowing dust particles
are repelled by the electrostatic field of the negatively charged sphere and a
microparticle free region (dust void) is formed surrounding the obstacle. The
far particles are attracted towards the floating obstacle and reflected back
when they have arrived at a minimum distance, causing a ring shaped structure
around the obstacle. We characterize the shape of this structure over a range
of dust flow speeds and obstacle biases. For a supersonic flow of dust fluid
around a negatively biased obstacle, a bow shock is formed on the upstream side
of the sphere, while the generation of wave structures is observed on the
downstream side for a particular range of flow velocities. Reynolds numbers in
this case is estimated as . This wave structure reminds of the
beginning of the formation of a Von-K\'arm\'an vortex street. A physical
picture for the observed structure based on ion-drag, neutral streaming and
electric forces is discussed.Comment: 9 pages, 7 figure
Dynamical mean-field theory of indirect magnetic exchange
To analyze the physical properties arising from indirect magnetic exchange
between several magnetic adatoms and between complex magnetic nanostructures on
metallic surfaces, the real-space extension of dynamical mean-field theory
(R-DMFT) appears attractive as it can be applied to systems of almost arbitrary
geometry and complexity. While R-DMFT describes the Kondo effect of a single
adatom exactly, indirect magnetic (RKKY) exchange is taken into account on an
approximate level only. Here, we consider a simplified model system consisting
of two magnetic Hubbard sites ("adatoms") hybridizing with a non-interacting
tight-binding chain ("substrate surface"). This two-impurity Anderson model
incorporates the competition between the Kondo effect and indirect exchange but
is amenable to an exact numerical solution via the density-matrix
renormalization group (DMRG). The particle-hole symmetric model at half-filling
and zero temperature is used to benchmark R-DMFT results for the magnetic
coupling between the two adatoms and for the magnetic properties induced in the
substrate. In particular, the dependence of the local adatom and the nonlocal
adatom-adatom static susceptibilities as well as the magnetic response of the
substrate on the distance between the adatoms and on the strength of their
coupling with the substrate is studied. We find both, excellent agreement with
the DMRG data even on subtle details of the competition between RKKY exchange
and the Kondo effect but also complete failure of the R-DMFT, depending on the
parameter regime considered. R-DMFT calculations are performed using the
Lanczos method as impurity solver. With the real-space extension of the
two-site DMFT, we also benchmark a simplified R-DMFT variant.Comment: 14 pages, 8 figure
Use of Hypermedia Tools for End-User Development
Software development tools aimed at end-users tend to employ various forms of visual programming because these users find textual programming very difficult to learn. However, visual programming has known scalability issues. As an alternative, we propose hypertextual programming; a technique that represents the program as hypertext and allows the user to both browse it and manipulate it mainly by using navigation. This technique leverages the users' ability to navigate in hyperspace, a widely available skill, to edit the program under development. In order to reap the benefits of this technique, adequate hypertextual editors must be built. Many of the lessons learned in the web engineering area can be used to deal with this problem. This paper discusses the state of the current research efforts behind this novel programming technique.Publicado en Lecture Notes in Computer Science book series (LNCS, vol. 6385).Laboratorio de Investigación y Formación en Informática Avanzad
Use of Hypermedia Tools for End-User Development
Software development tools aimed at end-users tend to employ various forms of visual programming because these users find textual programming very difficult to learn. However, visual programming has known scalability issues. As an alternative, we propose hypertextual programming; a technique that represents the program as hypertext and allows the user to both browse it and manipulate it mainly by using navigation. This technique leverages the users' ability to navigate in hyperspace, a widely available skill, to edit the program under development. In order to reap the benefits of this technique, adequate hypertextual editors must be built. Many of the lessons learned in the web engineering area can be used to deal with this problem. This paper discusses the state of the current research efforts behind this novel programming technique.Publicado en Lecture Notes in Computer Science book series (LNCS, vol. 6385).Laboratorio de Investigación y Formación en Informática Avanzad
Emotional, cognitive and behavioral self-regulation in forensic psychiatric patients:Changes over time and associations with childhood trauma, identity and personality pathology
The construct of self-regulation is of particular interest to the forensic psychiatric practice due to its associations with both clinical and criminal outcomes, as well as recidivism. However, research on different components of self-regulation within forensic psychiatric practice is rare. The current study aimed to gain knowledge on the construct of self-regulation in a sample of forensic psychiatric patients (N = 94). Firstly, by investigating change of emotional, behavioral and cognitive self-regulation over the course of 12 months in state-mandated care in a treatment facility. Secondly, by looking at the associations between these three elements of self-regulation and childhood trauma, identity dysfunction and personality pathology. Repeated measures ANOVA showed little to no difference in average self-regulation over time (only for behavioral regulation), and rank-order stability was relatively high in most cases. Path analysis showed that: emotion regulation was associated with all outcomes; behavioral regulation with all except childhood trauma and detachment; and cognitive regulation only with antagonism and negative affectivity. Findings suggest short-term changes are unlikely and indicate relative importance of emotional, and to some extent behavioral regulation for clinical practice. However, due to sample size restrictions, interpretations should be made with caution
Fibroblasts in liver cancer: functions and therapeutic translation
Accumulation of fibroblasts in the premalignant or malignant liver is a characteristic feature of liver cancer, but has not been therapeutically leveraged despite evidence for pathophysiologically relevant roles in tumour growth. Hepatocellular carcinoma is a largely non-desmoplastic tumour, in which fibroblasts accumulate predominantly in the pre-neoplastic fibrotic liver and regulate the risk for hepatocellular carcinoma development through a balance of tumour-suppressive and tumour-promoting mediators. By contrast, cholangiocarcinoma is desmoplastic, with cancer-associated fibroblasts contributing to tumour growth. Accordingly, restoring the balance from tumour-promoting to tumour-suppressive fibroblasts and mediators might represent a strategy for hepatocellular carcinoma prevention, whereas in cholangiocarcinoma, fibroblasts and their mediators could be leveraged for tumour treatment. Importantly, fibroblast mediators regulating hepatocellular carcinoma development might exert opposite effects on cholangiocarcinoma growth. This Review translates the improved understanding of tumour-specific, location-specific, and stage-specific roles of fibroblasts and their mediators in liver cancer into novel and rational therapeutic concepts.Copyright © 2023 Elsevier Ltd. All rights reserved
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