Magnetic polarons and magnetoresistance in EuB6

EuB6 is a low carrier density ferromagnet which exhibits large magnetoresistance, positive or negative depending on temperature. The formation of magnetic polarons just above the magnetic critical temperature has been suggested by spin-flip Raman scattering experiments. We find that the fact that EuB6 is a semimetal has to be taken into account to explain its electronic properties, including magnetic polarons and magnetoresistance.Comment: 6 pages, 1 figur

High-Resolution Kinoform X-Ray Optics Printed via 405 nm 3D Laser Lithography

Efficient focusing of X-rays is essential for high-resolution X-ray microscopy. Diffractive X-ray optics called kinoforms offer the highest focusing efficiencies in theory. However, they have long remained unavailable due to their challenging nanofabrication. Recently, various X-ray optic geometries including kinoforms have been realized using 3D laser lithography at near-infrared wavelengths. As the smallest features (period) of the kinoform determines the resolving power, there is a natural drive to find ways to fabricate kinoforms with ever smaller features. Here, a custom-built 3D laser lithography setup with an excitation wavelength of 405 nm is used, which allows to half the smallest period of the kinoforms compared to previous work. A 40% improvement in scanning transmission X-ray microscopy image resolution, that is, a cutoff resolution of 145 nm, and an efficiency of 7.6% at 700 eV is achieved. A reconstructed pixel size of 18.5 nm, reaching the limit imposed by the design of the microscopy set-up, is demonstrated through ptychographic imaging of a magnetic sample which has a strongly reduced contrast mechanism. Moreover, X-ray lenses manufactured by 405 nm 3D laser lithography have the potential to become much less expensive than X-ray lenses made by other means

Priming by Chemokines Restricts Lateral Mobility of the Adhesion Receptor LFA-1 and Restores Adhesion to ICAM-1 Nano-Aggregates on Human Mature Dendritic Cells

LFA-1 is a leukocyte specific β2 integrin that plays a major role in regulating adhesion and migration of different immune cells. Recent data suggest that LFA-1 on mature dendritic cells (mDCs) may function as a chemokine-inducible anchor during homing of DCs through the afferent lymphatics into the lymph nodes, by transiently switching its molecular conformational state. However, the role of LFA-1 mobility in this process is not yet known, despite that the importance of lateral organization and dynamics for LFA-1-mediated adhesion regulation is broadly recognized. Using single particle tracking approaches we here show that LFA-1 exhibits higher mobility on resting mDCs compared to monocytes. Lymphoid chemokine CCL21 stimulation of the LFA-1 high affinity state on mDCs, led to a significant reduction of mobility and an increase on the fraction of stationary receptors, consistent with re-activation of the receptor. Addition of soluble monomeric ICAM-1 in the presence of CCL21 did not alter the diffusion profile of LFA-1 while soluble ICAM-1 nano-aggregates in the presence of CCL21 further reduced LFA-1 mobility and readily bound to the receptor. Overall, our results emphasize the importance of LFA-1 lateral mobility across the membrane on the regulation of integrin activation and its function as adhesion receptor. Importantly, our data show that chemokines alone are not sufficient to trigger the high affinity state of the integrin based on the strict definition that affinity refers to the adhesion capacity of a single receptor to its ligand in solution. Instead our data indicate that nanoclustering of the receptor, induced by multi-ligand binding, is required to maintain stable cell adhesion once LFA-1 high affinity state is transiently triggered by inside-out signals.Peer ReviewedPostprint (published version

Theory of exciton-exciton correlation in nonlinear optical response

We present a systematic theory of Coulomb interaction effects in the nonlinear optical processes in semiconductors using a perturbation series in the exciting laser field. The third-order dynamical response consists of phase-space filling correction, mean-field exciton-exciton interaction, and two-exciton correlation effects expressed as a force-force correlation function. The theory provides a unified description of effects of bound and unbound biexcitons, including memory-effects beyond the Markovian approximation. Approximations for the correlation function are presented.Comment: RevTex, 35 pages, 10 PostScript figs, shorter version submitted to Physical Review

High amp; 8208;Resolution Kinoform X Ray Optics Printed via 405 nm 3D Laser Lithography

Efficient focusing of X rays is essential for high resolution X ray microscopy. Diffractive X ray optics called kinoforms offer the highest focusing efficiencies in theory. However, they have long remained unavailable due to their challenging nanofabrication. Recently, various X ray optic geometries including kinoforms have been realized using 3D laser lithography at near infrared wavelengths. As the smallest features period of the kinoform determines the resolving power, there is a natural drive to find ways to fabricate kinoforms with ever smaller features. Here, a custom built 3D laser lithography setup with an excitation wavelength of 405 nm is used, which allows to half the smallest period of the kinoforms compared to previous work. A 40 improvement in scanning transmission X ray microscopy image resolution, that is, a cutoff resolution of 145 nm, and an efficiency of 7.6 at 700 eV is achieved. A reconstructed pixel size of 18.5 nm, reaching the limit imposed by the design of the microscopy set up, is demonstrated through ptychographic imaging of a magnetic sample which has a strongly reduced contrast mechanism. Moreover, X ray lenses manufactured by 405 nm 3D laser lithography have the potential to become much less expensive than X ray lenses made by other mean

Determination of the Michel Parameters rho, xi, and delta in tau-Lepton Decays with tau --> rho nu Tags

Using the ARGUS detector at the $e^+ e^-$ storage ring DORIS II, we have measured the Michel parameters $\rho$, $\xi$, and $\xi\delta$ for $\tau^{\pm}\to l^{\pm} \nu\bar\nu$ decays in $\tau$-pair events produced at center of mass energies in the region of the $\Upsilon$ resonances. Using $\tau^\mp \to \rho^\mp \nu$ as spin analyzing tags, we find $\rho_{e}=0.68\pm 0.04 \pm 0.08$, $\xi_{e}= 1.12 \pm 0.20 \pm 0.09$, $\xi\delta_{e}= 0.57 \pm 0.14 \pm 0.07$, $\rho_{\mu}= 0.69 \pm 0.06 \pm 0.08$, $\xi_{\mu}= 1.25 \pm 0.27 \pm 0.14$ and $\xi\delta_{\mu}= 0.72 \pm 0.18 \pm 0.10$. In addition, we report the combined ARGUS results on $\rho$, $\xi$, and $\xi\delta$ using this work und previous measurements.Comment: 10 pages, well formatted postscript can be found at http://pktw06.phy.tu-dresden.de/iktp/pub/desy97-194.p

Towards high performance living manufacturing systems ‒ A new convergence between biology and engineering

This paper reports on a highly ambitious international study undertaken in the period 2018–2020 on the topic of convergence between biology and advanced manufacturing systems. The international team (authors of this paper) worked together to analyse the status of this convergence through the assessment of concrete examples, referred to here as demonstrators, within advanced manufacturing systems. Four independent demonstrators from different sections of the manufacturing value chain and involving bio-inspiration, bio-integration and/or bio-intelligence were selected to test the following hypothesis: “That Future Manufacturing Systems will incorporate Components, Features, Characteristics and Capabilities that enable the convergence towards Living Systems”. Each of these four demonstrators have succeeded in supporting this hypothesis and in providing clear evidence to confirm that significant performance benefits may be derived through the “biologicalisation” of advanced manufacturing systems. This conclusion is of great significance for the next phases of development of manufacturing science and engineering globally. The evidence reported in this paper provides a robust basis for recommending that a deeper analysis of the implications of biologicalised manufacturing systems be undertaken. As a result of this early stage work, it is concluded that there is a high likelihood that this new convergence will lead to a major paradigm shift in advanced manufacturing. Outstanding opportunities exist for high levels of innovation in the next stages of development of advanced manufacturing processes and systems from the biological perspective. The relationship between the human and the physical manufacturing system will also change and the world of advanced manufacturing will be confronted with many new challenges including important ethical questions

Search based software engineering: Trends, techniques and applications

© ACM, 2012. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version is available from the link below.In the past five years there has been a dramatic increase in work on Search-Based Software Engineering (SBSE), an approach to Software Engineering (SE) in which Search-Based Optimization (SBO) algorithms are used to address problems in SE. SBSE has been applied to problems throughout the SE lifecycle, from requirements and project planning to maintenance and reengineering. The approach is attractive because it offers a suite of adaptive automated and semiautomated solutions in situations typified by large complex problem spaces with multiple competing and conflicting objectives. This article provides a review and classification of literature on SBSE. The work identifies research trends and relationships between the techniques applied and the applications to which they have been applied and highlights gaps in the literature and avenues for further research.EPSRC and E