Dynamic critical behavior of the classical anisotropic BCC Heisenberg antiferromagnet

Using a recently implemented integration method [Krech et. al.] based on an iterative second-order Suzuki-Trotter decomposition scheme, we have performed spin dynamics simulations to study the critical dynamics of the BCC Heisenberg antiferromagnet with uniaxial anisotropy. This technique allowed us to probe the narrow asymptotic critical region of the model and estimate the dynamic critical exponent $z=2.25 \pm 0.08$. Comparisons with competing theories and experimental results are presented.Comment: Latex, 3 pages, 5 figure

Evaluation et auto-évaluation des niveaux et des variations de l'attention de l'enfant à l'adulte: approche chronopsychologique

International audienceLes variations journalières des processus cognitifs en situation d'apprentissage ont fait l'objet de nombreux travaux chez l'enfant scolarisé. Parmi ces processus, l'implication majeure de l'attention depuis la perception jusqu'à l'action est acquise. Concernant les rythmicités cognitives de l'adulte en formation, la littérature présente peu de travaux repérables dans ce milieu de vie et de développement. Par ailleurs, si les performances mesurées ont largement été investies dans l'étude des rythmicités cognitives de l'enfant à l'adulte, l'auto estimation reste elle-même peu étudiée. Le but poursuivi était d'évaluer les niveaux et les variations journalières de l'attention mesurée et auto-estimée de l'enfant à l'adulte selon une perspective développementale et d'investir les écarts entre mesures objectives et subjectives. Participants : 262 enfants scolarisés du CP au CM2 : 134 filles (âge moyen : 9 ± 2) ; 128 garçons (âge moyen : 9 ± 1), et 166 adultes en formation : 130 femmes (âge moyen : 31;2 ± 10) et 36 hommes (âge moyen : 27;10 ± 8). Matériel et déroulement : Tests de barrage et échelles visuelles analogiques (fatigue et vigilance) en passation collective à quatre moments d'une même journée (début et fin de matinée ; début et fin d'après-midi) au mois de mai. Les données ont été traitées par ANOVA à mesures répétées, analyses corrélationnelles et typologiques. Les analyses suggèrent la mise en place progressive d'un profil journalier de l'attention avec élévation des performances du début de la journée jusqu'en fin d'après-midi pour l'adulte. Ainsi le profil classique défini chez l'enfant constituerait une étape dans le développement de l'attention de l'enfant à l'adulte. Le creux post prandial observé dans la littérature chez les enfants semble disparaître avec l'avancée en âge et l'existence de profils différenciés chez les plus jeunes contraste avec la typologie des adultes principalement caractérisée par des différences de niveau d'attention sans différenciation de profil. Aucun effet du genre n'a été relevé quel que soit l'âge considéré. Si la mesure subjective de la vigilance n'est pas prédictive des performances attentionnelles et de leurs variations, elle est en lien avec l'autoévaluation de la fatigue suggérant l'effort fourni et ressenti pour maintenir les performances. Les relations entre mesures objectives et subjectives et leurs variations journalières ouvrent un champ nouveau à investir pour les travaux en chronopsychologie dans une perspective life span

Coincidental Occurrence of Acute In-stent Thrombosis and Iatrogenic Vessel Perforation During a Wingspan Stent Placement: Management with a Stent In-stent Technique

We presented a case that an acute in-stent thrombosis after the deployment of a Wingspan stent was successfully managed with a stent in-stent technique. Because vessel perforation and subarachnoid hemorrhage were iatrogenically developed during the procedure, we were unable to use the thrombolytic agents to correct the in-stent thrombosis. When a thrombotic complication following an intracranial stent placement occurs with a coincidentally hemorrhagic complication, the stent in-stent technique should be considered as a treatment option

Polchinski equation, reparameterization invariance and the derivative expansion

The connection between the anomalous dimension and some invariance properties of the fixed point actions within exact RG is explored. As an application, Polchinski equation at next-to-leading order in the derivative expansion is studied. For the Wilson fixed point of the one-component scalar theory in three dimensions we obtain the critical exponents \eta=0.042, \nu=0.622 and \omega=0.754.Comment: 28 pages, LaTeX with psfig, 12 encapsulated PostScript figures. A number wrongly quoted in the abstract correcte

Can fractal dimensions objectivize gastropod shell morphometrics? A case study from Lake Lugu (SW China)

1. Morphometrics are fundamental for the analysis of size and shape in fossils, particularly because soft parts or DNA are rarely preserved and hard parts such as shells are commonly the only source of information. Geometric morphometrics, that is, landmark analysis, is well established for the description of shape but it exhibits a couple of shortcomings resulting from subjective choices during landmarking (number and position of landmarks) and from difficulties in resolving shape at the level of micro-sculpture. 2. With the aid of high-resolution 3D scanning technology and analyses of fractal dimensions, we test whether such shortcomings of linear and landmark morphometrics can be overcome. As a model group, we selected a clade of modern viviparid gastropods from Lake Lugu, with shells that show a high degree of sculptural variation. Linear and landmark analyses were applied to the same shells in order to establish the fractal dimensions. The genetic diversity of the gastropod clade was assessed. 3. The genetic results suggest that the gastropod clade represents a single species. The results of all morphometric methods applied are in line with the genetic results, which is that no specific morphotype could be delimited. Apart from this overall agreement, landmark and fractal dimension analyses do not correspond to each other but represent data sets with different information. Generally, the fractal dimension values quantify the roughness of the shell surface, the resolution of the 3D scans determining the level. In our approach, we captured the micro-sculpture but not the first-order sculptural elements, which explains that fractal dimension and landmark data are not in phase. 4. We can show that analyzing fractal dimensions of gastropod shells opens a window to more detailed information that can be considered in evolutionary and ecological contexts. We propose that using low-resolution 3D scans may successfully substitute landmark analyses because it overcomes the subjective landmarking. Analyses of 3D scans with higher resolution than used in this study will provide surface roughness information at the mineralogical level. We suggest that fractal dimension analyses of a combination of differently resolved 3D models will significantly improve the quality of shell morphometrics

Ground and Airborne U.K. Measurements of Nitryl Chloride: An Investigation of the Role of Cl Atom Oxidation at Weybourne Atmospheric Observatory

Nitryl chloride (ClNO2) measurements from the Weybourne Atmospheric Observatory (WAO) are reported from March to April 2013 using a quadruple chemical ionization mass spectrometer with the I− ionization scheme. WAO is a rural coastal site with generally low NOx concentrations, a type of location poorly studied for ClNO2 production. Concentrations of ClNO2 exceeded that of the limit of detection (0.8 ppt) on each night of the campaign, as did concentrations of N2O5, which was also measured simultaneously with the Cambridge Broadband Cavity Enhanced Absorption Spectrometer. A peak concentration of 65 ppt of ClNO2 is reported here. Vertical profiles of ClNO2 from early- to middle-morning flights in close proximity to WAO are also reported, showing elevated concentrations at low altitude. The photolysis of observed ClNO2 and a box model utilizing the Master Chemical Mechanism modified to include chlorine chemistry was used to calculate Cl atom concentrations. This model utilized numerous VOCs from the second Tropospheric Organic Chemistry project in 2004, at the same location and time of year. From this the relative importance of the oxidation of three groups of measured VOCs (alkanes, alkenes, and alkynes) by OH radicals, Cl atoms, and O3 is compared. Cl atom oxidation was deemed generally insignificant at this time and location for total oxidation due to the much lower concentration of ClNO2 observed, even following the night of greatest ClNO2 production

The Dixmier property and tracial states for C*-algebras

A.T. was partially supported by an NSERC Postdoctoral Fellowship and through the EPSRC grant EP/N00874X/1. Acknowledgements We are grateful to Luis Santiago for helpful discussions at an early stage of this investigation. We would also like to thank the referee for providing helpful comments, which have led to a number of improvements.Peer reviewedPublisher PD

Single-source-precursor synthesis of high temperature stable SiC/C/Fe nanocomposites from a processable hyperbranched polyferrocenylcarbosilane with high ceramic yield

NSFC [50802079, 51072169]; Natural Science Foundation of Fujian Province of China [2011J01330]Hydrosilylation of vinyl ferrocene with allylhydridopolycarbosilane was used to synthesize a processable hyperbranched polyferrocenylcarbosilane (HBPFCS), which was characterized by combination of gel permeation chromatography, Fourier transform infrared (FT-IR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation of the HBPFCSs was then investigated by FT-IR and C-13 MAS NMR spectroscopy as well as by thermal gravimetric analysis (TGA). A self-catalytic effect of ferrocenyl units in the HBPFCS skeleton on dehydrocoupling was found during a curing process at 170 degrees C resulting in a high ceramic yield of ca. 80% at 1200 degrees C in Ar. Finally, microstructures and magnetic properties of the final ceramics were studied by techniques such as X-ray diffraction, energy dispersive spectroscopy, Raman spectroscopy, transmission electron microscopy and vibrating sample magnetometry. The final ceramic (pyrolysis temperature >= 900 degrees C) is characterized by a microstructure comprised of a SiC/C/Fe nanocomposite. Turbostratic carbon layers located at the segregated alpha-Fe crystal boundary avoid interdiffusion and explain the exclusive existence of alpha-Fe in a SiC/C matrix even at 1300 degrees C. Variations of the iron content in the HBPFCSs and of the pyrolysis conditions facilitate the control of the composition and ceramic micro/nanostructure, influencing in particular magnetic properties of the final SiC/C/Fe nanocomposite ceramic

Spin-Nematic Squeezed Vacuum in a Quantum Gas

Using squeezed states it is possible to surpass the standard quantum limit of measurement uncertainty by reducing the measurement uncertainty of one property at the expense of another complementary property. Squeezed states were first demonstrated in optical fields and later with ensembles of pseudo spin-1/2 atoms using non-linear atom-light interactions. Recently, collisional interactions in ultracold atomic gases have been used to generate a large degree of quadrature spin squeezing in two-component Bose condensates. For pseudo spin-1/2 systems, the complementary properties are the different components of the total spin vector , which fully characterize the state on an SU(2) Bloch sphere. Here, we measure squeezing in a spin-1 Bose condensate, an SU(3) system, which requires measurement of the rank-2 nematic or quadrupole tensor as well to fully characterize the state. Following a quench through a nematic to ferromagnetic quantum phase transition, squeezing is observed in the variance of the quadratures up to -8.3(-0.7 +0.6) dB (-10.3(-0.9 +0.7) dB corrected for detection noise) below the standard quantum limit. This spin-nematic squeezing is observed for negligible occupation of the squeezed modes and is analogous to optical two-mode vacuum squeezing. This work has potential applications to continuous variable quantum information and quantum-enhanced magnetometry

β2-Adrenoceptors on tumor cells play a critical role in stress-enhanced metastasis in a mouse model of breast cancer

© 2016 The Authors Chronic stress accelerates metastasis – the main cause of death in cancer patients – through the activation of β-adrenoceptors (βARs). We have previously shown that β2AR signaling in MDA-MB-231HM breast cancer cells, facilitates invadopodia formation and invasion in vitro. However, in the tumor microenvironment where many stromal cells also express βAR, the role of β2AR signaling in tumor cells in metastasis is unclear. Therefore, to investigate the contribution of β2AR signaling in tumor cells to metastasis in vivo, we used RNA interference to generate MDA-MB-231HM breast cancer cells that are deficient in β2AR. β2AR knockdown in tumor cells reduced the proportion of cells with a mesenchymal-like morphology and, as expected, reduced tumor cell invasion in vitro. Conversely, overexpression of β2AR in low metastatic MCF-7 breast cancer cells induced an invasive phenotype. Importantly, we found that knockdown of β2AR in tumor cells significantly reduced the impact of stress on metastasis in vivo. These findings highlight a crucial role for β2AR tumor cell signaling in the adverse effects of stress on metastasis, and indicate that it may be necessary to block β2AR on tumor cells to fully control metastatic progression