Signatures of quantum criticality in hole-doped and chemically pressurized EuFe_2As_2 single crystals

We study the effect of hole-doping and chemical pressure (isovalent doping) in single crystals of K$_x$Eu$_{1-x}$Fe$_2$As$_2$ and EuFe$_2$(As$_{1-y}$P$_y$)$_2$, respectively, by measurements of the thermopower, $S(T)$, and electrical resistivity, $\rho(T)$. The evolution of $S(T)$ upon doping indicates drastic changes of the electronic configuration at critical values $x_{\mathrm{cr}}=0.3$ and $y_{\mathrm{cr}}=0.21$, respectively, as the spin-density-wave transition is completely suppressed and superconductivity (SC) emerges. For the case of chemical pressure, the comparison with published ARPES measurements indicates a Lifshitz transition at $y_{cr}$. The temperature dependences $S(T)/T\propto \log T$ and $\Delta\rho\propto T$ observed in the normal state above the SC transition suggest quantum criticality in both systems.Comment: PRB accepte

Persistent detwinning of iron pnictides by small magnetic fields

Our comprehensive study on EuFe$_2$As$_2$ reveals a dramatic reduction of magnetic detwinning fields compared to other AFe$_2$As$_2$ (A = Ba, Sr, Ca) iron pnictides by indirect magneto-elastic coupling of the Eu$^{2+}$ ions. We find that only 0.1T are sufficient for persistent detwinning below the local Eu$^{2+}$ ordering; above $T_\text{Eu}$ = 19K, higher fields are necessary. Even after the field is switched off, a significant imbalance of twin domains remains constant up to the structural and electronic phase transition (190K). This persistent detwinning provides the unique possibility to study the low temperature electronic in-plane anisotropy of iron pnictides without applying any symmetrybreaking external force.Comment: accepted by Physical Review Letter

Upper critical magnetic field in K0.83Fe1.83Se2 and Eu0.5K0.5Fe2As2 single crystals

The H-T phase diagrams of single crystalline electron-doped K0.83Fe1.83Se2 (KFS1), K0.8Fe2Se2 (KFS2) and hole-doped Eu0.5K0.5Fe2As2 (EKFA) have been deduced from tunnel diode oscillator-based contactless measurements in pulsed magnetic fields up to 57 T for the inter-plane (H//c) and in-plane (H//ab) directions. The temperature dependence of the upper critical magnetic field Hc2(T) relevant to EFKA is accounted for by the Pauli model including an anisotropic Pauli paramagnetic contribution (\mu_BHp=114 T for H//ab and 86 T for H//c). This is also the case of KFS1 and KFS2 for H//ab whereas a significant upward curvature, accounted for by a two-gap model, is observed for H//c. Despite the presence of antiferromagnetic lattice order within the superconducting state of the studied compounds, no influence of magnetic ordering on the temperature dependence of Hc2(T) is observed.Comment: 9 pages, 5 figures. arXiv admin note: text overlap with arXiv:1104.561

Modeling time delay in the NFκB signaling pathway following low dose IL-1 stimulation

Stimulation of human epithelial cells with IL-1 (10 ng/ml) + UVB radiation results in sustained NFκB activation caused by continuous IKKβ phosphorylation. We have recently published a strictly reduced ordinary differential equation model elucidating the involved mechanisms. Here, we compare model extensions for low IL-1 doses (0.5 ng/ml), where delayed IKKβ phosphorylation is observed. The extended model including a positive regulatory element, most likely auto-ubiquitination of TRAF6, reproduces the observed experimental data most convincingly. The extension is shown to be consistent with the original model and contains very sensitive processes which may serve as potential intervention targets

Gewisse morphologische, physiognomische und antropologische Merkmale bei einwohnern eines jugoslawischen Küstengebiets

Autori su obavili analizu nalaza 498 ispitanika obaju spolova djece starosjedilaca (najmanje jedna generacija) u Solinu i Kaštelima. Ispitivanja su provedena kod djece stare 10—14 godina, s namjerom da se pridonese prikupljanju podataka nacionalnih obilježja. Ispitivanja su po karakteru sondažna. Problematika se je sastojala u tome da se utvrdi postoje li signifikantni nalazi i njihove međusobne korelacije. Ispitivanja su obavljena u području identične geografske širine, u kojoj je obavljao ispitivanja i Francuz Pont30, s namjerom da se ustanovi da li utvrđeni indeks odgovara onom spomenutog autora. Mjerenja, su izvedena standardnim instrumentarijem, a vršila ih je ekipa od triju članova, koautora ovog rada, koja je prethodno prošla blind test, konstruiran za ispitivanja te vrsti. Unošenje i obrada podataka učinjeno je na obrascima za ortodontske sistematske preglede (rubno bušene kartice br. 1226/038). Rezultati su komparirani s nalazima stranih autora. Utvrđeno je između ostalog da je SI i parametar Zy-Zy veći kod muških ispitanika. PŠ i SŠ su u cijelosti veće kod ispitanika bez anomalija. Usporedbene vrijednosti dobivenog indeksa za PŠ i SŠ vrlo su blizu mjerama po Pontu30, što potvrđuje pretpostavku, da se je radilo o ispitanicima sa širokim čeljustima. Statistička obrada vlastitih podataka prikazana je na tab. 1., dok ostale tablice prikazuju rezultate stranih autora. Tab. 2 i 4 sadrže i vlastite rezultate zbog preglednije komparacije. Autori se kritički osvrću na pomanjkanje standardne metodike u ispitivanjima te vrsti u nacionalnoj stomatološkoj literaturi Njemačke i Jugoslavije.The authors published an analysis of the findings in 498 test subjects of both sexes, children of the indigenes (at least one generation) of Solin and Kaštela. The testing was carried out in children aged between 10 to 14 for the purpose of contributing to the collection of data on national characteristics. The tests had a probing character and were meant to investigate the problem whether there existed any significant findings and to establish their mutual correlation. Testings were carried out in a region of identical geographical latitude to that in which the Frenchman Pont made his investigations (30). The aim was to establish whether the index obtained corresponded to that of the mentioned author. Measuring was carried out by means of standard instruments and a team consisting of three members, coauthors of this paper, was engaged in the task. The team had previously undergone the blind test for investigations of that kind. The elaboration and entry of data was made on forms for ortodontic systematic examinations (punch cards no. 1226/038). The results were compared1 to^ the findings of the foreign authors. It was ascertained that the width of the upper incisors and the distance Zy-Zy were higher in boys. Anterior and posterior widths of the upper dental arch were higher in subjects without malocclusions. The obtained values for both widths of the dental arch were very close to those of Pont, thus confirming the hypothesis that the test subjects had wide jaws. The statistical elaboration of our own data is shown in Table 1, while the other tables show the results of foreign authors. Table 2 and 4 contain also our own results for easier comparison. The authors point out at the lack of standard methods in investigations of that kind in the national German and Yugoslav dental literature.Die Autoren haben eine Befunderhebung bei 498 Kindern beiderlei Geschlechts von Alteingesessenen in Solin und Kaštela auf gewisse Merkmale, durchgeführt. Die Untersuchungen wurden an Kindern im Alter von 10 bis 14 Jahren gemacht, mit der Absicht Beiträge für nationale Merkmale zu sammeln. Es sollte festgestellt werden ob deutliche Befunde erhoben werden können, und ihre gegen seitigen Zusammenhänge geprüft werden. Die Untersuchungen wurden in Gebieten der gleichen geographischen Breite durchgeführt, in welchen auch der Franzose Pont seine Untersuchungen anstellte, mit der Absicht festzustellen ob der erhaltene Index dem Pontschen-Index gleich ist. Die Messungen wurden von den drei Koautoren dieser Arbeit mit standardisierten Methoden ausgeführt. Die Resultate wurden mit Befunden anderer Autoren verglichen. Unter Anderem wurde festgestellt, dass die Sl und der Parameter Zy-Zy bei männlichen Probanaen grösser ist. Die vordere und die hintere obere Zahn bogen breite ist im Ganzen grösser bei Untersuchten die keine Anomalien aufwiesen. Der Vergleichswert der erhaltenen Indexe für die angeführten Breiten sind den Pont - Werten sehr nahe, was die Vorraussetzung bestätigt, dass es sich um Probanden mit breiten Kiefern handelt. Die statistische Bearbeitung der eigenen Befunde ist auf Tabelle 1 dargestellt, während die übrigen Tabellen Resultate anderer Autoren zeigen. Die Tabellen 2 und 4 behalten auch eigene Resultate, wegen besserer Übersicht bei der Vergleichung. Die Autoren beanständen das Fehlen einer Standard- -Methode für Untersuchungen dieser Art in der nationalen stomatologischen Literatur Deutschlands und Jugoslawiens

Spatially-resolved potential measurement with ion crystals

We present a method to measure potentials over an extended region using one-dimensional ion crystals in a radio frequency (RF) ion trap. The equilibrium spacings of the ions within the crystal allow the determination of the external forces acting at each point. From this the overall potential, and also potentials due to specific trap features, are calculated. The method can be used to probe potentials near proximal objects in real time, and can be generalized to higher dimensions.Comment: 7 pages (double spaced), 3 figure

Generation of a wave packet tailored to efficient free space excitation of a single atom

We demonstrate the generation of an optical dipole wave suitable for the process of efficiently coupling single quanta of light and matter in free space. We employ a parabolic mirror for the conversion of a transverse beam mode to a focused dipole wave and show the required spatial and temporal shaping of the mode incident onto the mirror. The results include a proof of principle correction of the parabolic mirror's aberrations. For the application of exciting an atom with a single photon pulse we demonstrate the creation of a suitable temporal pulse envelope. We infer coupling strengths of 89% and success probabilities of up to 87% for the application of exciting a single atom for the current experimental parameters.Comment: to be published in Europ. Phys. J.