436 research outputs found
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 KEuFeAs and
EuFe(AsP), respectively, by measurements of the
thermopower, , and electrical resistivity, . The evolution of
upon doping indicates drastic changes of the electronic configuration at
critical values and , 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
. The temperature dependences and
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 EuFeAs reveals a dramatic reduction of
magnetic detwinning fields compared to other AFeAs (A = Ba, Sr, Ca)
iron pnictides by indirect magneto-elastic coupling of the Eu ions. We
find that only 0.1T are sufficient for persistent detwinning below the local
Eu ordering; above = 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
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Thermal Neutron Radiography With the Plutonium Recycle Critical Facility.
Modeling time delay in the NFÎșB signaling pathway following low dose IL-1 stimulation
Stimulation of human epithelial cells with IL-1 (10 ng/ml) + UVB radiation results in sustained NFÎșB activation caused by continuous IKKÎČ 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 IKKÎČ 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 KĂŒstengebiets
Autori su obavili analizu nalaza 498 ispitanika obaju spolova djece starosjedilaca (najmanje jedna generacija) u Solinu i KaĆĄtelima. Ispitivanja su provedena kod djece stare 10â14 godina, s namjerom da se pridonese prikupljanju podataka nacionalnih obiljeĆŸja. Ispitivanja su po karakteru sondaĆŸna. Problematika se je sastojala u tome da se utvrdi postoje li signifikantni nalazi i njihove meÄusobne korelacije. Ispitivanja su obavljena u podruÄju identiÄne geografske ĆĄirine, u kojoj je obavljao ispitivanja i Francuz Pont30, s namjerom da se ustanovi da li utvrÄeni indeks odgovara onom spomenutog autora. Mjerenja, su izvedena standardnim instrumentarijem, a vrĆĄila ih je ekipa od triju Älanova, koautora ovog rada, koja je prethodno proĆĄla blind test, konstruiran za ispitivanja te vrsti. UnoĆĄenje i obrada podataka uÄinjeno je na obrascima za ortodontske sistematske preglede (rubno buĆĄene kartice br. 1226/038). Rezultati su komparirani s nalazima stranih autora. UtvrÄeno je izmeÄu ostalog da je SI i parametar Zy-Zy veÄi kod muĆĄkih ispitanika. PĆ i SĆ su u cijelosti veÄe kod ispitanika bez anomalija. Usporedbene vrijednosti dobivenog indeksa za PĆ i SĆ vrlo su blizu mjerama po Pontu30, ĆĄto potvrÄuje pretpostavku, da se je radilo o ispitanicima sa ĆĄirokim Äeljustima. StatistiÄka obrada vlastitih podataka prikazana je na tab. 1., dok ostale tablice prikazuju rezultate stranih autora. Tab. 2 i 4 sadrĆŸe i vlastite rezultate zbog preglednije komparacije. Autori se kritiÄki osvrÄu na pomanjkanje standardne metodike u ispitivanjima te vrsti u nacionalnoj stomatoloĆĄkoj literaturi NjemaÄke 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 KaĆĄtela. 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 KaĆĄtela auf gewisse Merkmale, durchgefĂŒhrt. Die Untersuchungen wurden an Kindern im Alter von 10 bis 14 Jahren gemacht, mit der Absicht BeitrĂ€ge fĂŒr nationale Merkmale zu sammeln. Es sollte festgestellt werden ob deutliche Befunde erhoben werden können, und ihre gegen seitigen ZusammenhĂ€nge geprĂŒft werden. Die Untersuchungen wurden in Gebieten der gleichen geographischen Breite durchgefĂŒhrt, 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 ausgefĂŒhrt. Die Resultate wurden mit Befunden anderer Autoren verglichen. Unter Anderem wurde festgestellt, dass die Sl und der Parameter Zy-Zy bei mĂ€nnlichen 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 fĂŒr die angefĂŒhrten Breiten sind den Pont - Werten sehr nahe, was die Vorraussetzung bestĂ€tigt, dass es sich um Probanden mit breiten Kiefern handelt. Die statistische Bearbeitung der eigenen Befunde ist auf Tabelle 1 dargestellt, wĂ€hrend die ĂŒbrigen Tabellen Resultate anderer Autoren zeigen. Die Tabellen 2 und 4 behalten auch eigene Resultate, wegen besserer Ăbersicht bei der Vergleichung. Die Autoren beanstĂ€nden das Fehlen einer Standard- -Methode fĂŒr 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.
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