A deep narrowband survey for planetary nebulae at the outskirts of M33

Context: Planetary nebulae (PNe) are excellent tracers of stellar populations with low surface brightness, and therefore provide a powerful method to detect and explore the rich system of substructures discovered around the main spiral galaxies of the Local Group. Aims: We searched the outskirts of the Local Group spiral galaxy M33 (the Triangulum) for PNe to gain new insights into the extended stellar substructure on the northern side of the disc and to study the existence of a faint classical halo. Methods: The search is based on wide field imaging covering a 4.5 square degree area out to a maximum projected distance of about 40 kpc from the centre of the galaxy. The PN candidates are detected by the combination of images obtained in narrowband filters selecting the [OIII]$\lambda5007\AA$ and H$\alpha$ + [NII] nebular lines and in the continuum g' and r' broadband filters. Results:Inside the bright optical disc of M33, eight new PN candidates were identified, three of which were spectroscopically confirmed. No PN candidates were found outside the limits of the disc. Fourteen additional sources showing [OIII] excess were also discovered. Conclusions:The absence of bright PN candidates in the area outside the galaxy disc covered by this survey sets an upper limit to the luminosity of the underlying population of $\mathrm{\sim1.6\cdot10^{7}L_{\odot}}$, suggesting the lack of a massive classical halo, which is in agreement with the results obtained using the RGB population.Comment: 13 pages, 18 figure

Point defects on graphene on metals

Understanding the coupling of graphene with its local environment is critical to be able to integrate it in tomorrow's electronic devices. Here we show how the presence of a metallic substrate affects the properties of an atomically tailored graphene layer. We have deliberately introduced single carbon vacancies on a graphene monolayer grown on a Pt(111) surface and investigated its impact in the electronic, structural and magnetic properties of the graphene layer. Our low temperature scanning tunneling microscopy studies, complemented by density functional theory, show the existence of a broad electronic resonance above the Fermi energy associated with the vacancies. Vacancy sites become reactive leading to an increase of the coupling between the graphene layer and the metal substrate at these points; this gives rise to a rapid decay of the localized state and the quenching of the magnetic moment associated with carbon vacancies in free-standing graphene layers

The cadherin–catenin complex in nasopharyngeal carcinoma

Abnormal Wnt signaling and impaired cell–cell adhesion due to abnormal E-cadherin and b-catenin func tion have been implicated in many cancers, but have not been fully explored in nasopharyngeal carcinoma. The aim of this study was to analyze b-Catenin cellular location and E-cadherin expression levels in nasopharyngeal carcinoma. E-cadherin expression levels were also correlated with clinical data and underlying pathology. b-Catenin and E-cadherin expression were examined in 18 nasopharyn geal carcinoma and 7 non-tumoral inflammatory pharynx tissues using immunohistochemical methods. Patient clin ical data were collected, and histological evaluation was performed by hematoxylin/eosin staining. b-catenin was detected in membrane and cytoplasm in all cases of naso pharyngeal carcinoma, regardless of histological type; in non-tumoral tissues, however, b-catenin was observed only in the membrane. As for E-cadherin expression levels, strong staining was observed in most non-tumoral tissues, but staining was only moderate in nasopharyngeal carci noma tissues. E-cadherin expression was associated with b-catenin localization, study group, metastatic disease, and patient outcomes. Reduced levels of E-cadherin protein observed in nasopharyngeal carinoma may play an important role in invasion and metastasis. Cytoplasmic b-catenin in nasopharyngeal carcinoma may impair cell– cell adhesion, promoting invasive behavior and a metastatic tumor phenotype

Interpocket polarization model for magnetic structures in rare-earth hexaborides

The origin of peculiar magnetic structures in cubic rare-earth (R) hexaborides RB_6 is traced back to their characteristic band structure. The three sphere-like Fermi surfaces induce interpocket polarization of the conduction band as a part of a RKKY-type interaction. It is shown for the free-electron-like model that the interpocket polarization gives rise to a broad maximum in the intersite interaction I(q) around q=(1/4,1/4,1/2) in the Brillouin zone. This maximum is consistent with the superstructure observed in R=Ce, Gd and Dy. The wave-number dependence of I(q) is independently extracted from analysis of the spin-wave spectrum measured for NdB_6. It is found that I(q) obtained from fitting the data has a similarly to that derived by the interpocket polarization model, except that the absolute maximum now occurs at (0,0,1/2) in consistency with the A-type structure. The overall shape of I(q) gives a hint toward understanding an incommensurate structure in PrB_6 as well.Comment: 5 pages, 3 figures, submitted to J.Phys.Soc.Jp

Quadrupolar Kondo Effect in Non-Kramers Doublet System PrInAg2

We performed ultrasonic measurement on the rare-earth intermetallic compound PrInAg_2 to examine the quadrupolar Kondo effect associated with the non-Kramers Gamma_3 doublet ground state. The characteristic softening of the elastic constant (c_{11}-c_{12})/2 below 10 K in PrInAg_2 is attributed to a Curie term in quadrupolar susceptibility for the quadrupole O_2^2=J_x^2-J_y^2 of the stable Gamma_3 ground state. (c_{11}-c_{12})/2 turns to a slight increase with the -lnT dependence below 0.1 K, which suggests the quenching of the quadrupolar moment in the quadrupolar Kondo state. Under applied magnetic fields of 10 T and 15 T above 8.7 T corresponding to the Kondo temperature T_K of ~ 0.86 K, the behavior of (c_{11}-c_{12})/2 is described in terms of quadrupolar susceptibility for the stable 4f^2 state.Comment: PDF, 10pages + 5figures, Strongly Correlated Electron

Crystal growth, structure and ferromagnetic properties of a Ce3Pt23Si11 single crystal

A high-quality single crystal of Ce3Pt23Si11 has been grown using the Czochralski method. The crystal structure is presented and the chemical composition has been checked using an electron microprobe analyzer. Measurements of the electrical resistivity and magnetic susceptibility performed at low temperature show a ferromagnetic transition at Tc = 0.44 K.Comment: 12 pages, 9 figure

Tug-of-war between corrugation and binding energy: revealing the formation of multiple moiré patterns on a strongly interacting graphene-metal system

The formation of multidomain epitaxial graphene on Rh(111) under ultra-high vacuum (UHV) conditions has been characterized by scanning tunnelling microscopy (STM) measurements and density functional theory (DFT) calculations. At variance with the accepted view for strongly interacting graphene-metal systems, we clearly demonstrate the formation of different rotational domains leading to multiple moiré structures with a wide distribution of surface periodicities. Experiments reveal a correlation between the STM apparent corrugation and the lattice parameter of the moiré unit cell, with corrugations of just 30-40 pm for the smallest moirés. DFT calculations for a relevant selection of these moiré patterns show much larger height differences and a non-monotonic behaviour with the moiré size. Simulations based on non-equilibrium Green's function (NEGF) methods reproduce quantitatively the experimental trend and provide a detailed understanding of the interplay between electronic and geometric contributions in the STM contrast of graphene systems. Our study sheds light on the subtle energy balance among strain, corrugation and binding that drives the formation of the moiré patterns in all graphene/metal systems and suggests an explanation for the success of an effective model only based on the lattice mismatch. Although low values of the strain energy are a necessary condition, it is the ability of graphene to corrugate in order to maximize the areas of favourable graphene-metal interactions that finally selects the stable configurationsWe acknowledge financial support from Spanish grants MAT2013-41636-P, MAT2011-23627, MAT2011-26534, CSD2010-00024 (MINECO, Spain) and S2009/MAT-1467 (CAM, Spain). A.J.M.G. was supported by a Marie Curie action under the Seventh Framework Programme. P.P. was supported by the Ramón y Cajal Progra

Band Calculations for Ce Compounds with AuCu3_{3}-type Crystal Structure on the basis of Dynamical Mean Field Theory I. CePd3_{3} and CeRh3_{3}

Band calculations for Ce compounds with the AuCu$_{3}$-type crystal structure were carried out on the basis of dynamical mean field theory (DMFT). The auxiliary impurity problem was solved by a method named NCA$f^{2}$vc (noncrossing approximation including the $f^{2}$ state as a vertex correction). The calculations take into account the crystal-field splitting, the spin-orbit interaction, and the correct exchange process of the $f^{1} \rightarrow f^{0},f^{2}$ virtual excitation. These are necessary features in the quantitative band theory for Ce compounds and in the calculation of their excitation spectra. The results of applying the calculation to CePd$_{3}$ and CeRh$_{3}$ are presented as the first in a series of papers. The experimental results of the photoemission spectrum (PES), the inverse PES, the angle-resolved PES, and the magnetic excitation spectra were reasonably reproduced by the first-principles DMFT band calculation. At low temperatures, the Fermi surface (FS) structure of CePd$_{3}$ is similar to that of the band obtained by the local density approximation. It gradually changes into a form that is similar to the FS of LaPd$_{3}$ as the temperature increases, since the $4f$ band shifts to the high-energy side and the lifetime broadening becomes large.}Comment: 12 pasges, 13 figure

Application of the Doehlert Design to Optimize the Signal Obtained in Photochemically Induced Fluorescence for the Determination of Eight Phenylureas

Abstract This work describes the optimization of a photochemically induced method for the detection of eight phenylureas has been developed by response surface methodology (RSM). These pesticides do not show native fluorescence but they were photolyzed into strongly fluorescent photoproducts under UV irradiation. The effect of the main variables affecting the yield of the photoderivatization reaction, and hence the fluorescence intensity, such as solvent, UV irradiation time and pH were optimized for each pesticide. A Doehlert design was applied in order to obtain maximum intensity fluorescence using response surface methodology. In general, a maximum was found for all pesticides using MeOH as organic solvent, except for diuron, whereas the effect of pH and irradiation time was different, according to each pesticide. Finally, the addition of β-cyclodextrin upon the photochemically induced fluorescence intensity was investigate. The fluorescence intensity was only improved for monolinuron at a concentration of 4×10 −3 M of β-cyclodextrin

Magnetic Phase Diagram of GdNi2B2C: Two-ion Magnetoelasticity and Anisotropic Exchange Couplings

Extensive magnetization and magnetostriction measurements were carried out on a single crystal of GdNi2B2C along the main tetragonal axes. Within the paramagnetic phase, the magnetic and strain susceptibilities revealed a weak anisotropy in the exchange couplings and two-ion tetragonal-preserving alpha-strain modes. Within the ordered phase, magnetization and magnetostriction revealed a relatively strong orthorhombic distortion mode and rich field-temperature phase diagrams. For H//(100) phase diagram, three field-induced transformations were observed, namely, at: Hd(T), related to the domain alignment; Hr(T), associated with reorientation of the moment towards the c-axis; and Hs(T), defining the saturation process wherein the exchange field is completely counterbalanced. On the other hand, For H//(001) phase diagram, only two field-induced transformations were observed, namely at: Hr(T) and Hs(T). For both phase diagrams, Hs(T) follows the relation Hs[1-(T/Tn)^2]^(1/2)kOe with Hs(T-->0)=128.5(5) kOe and Tn(H=0)=19.5 K. In contrast, the thermal evolution of Hr(T) along the c-axis (much simpler than along the a-axis) follows the relation Hr[1-T/Tr]^(1/3) kOe where Hr(T-->0)=33.5(5) kOe and Tr(H=0)=13.5 K. It is emphasized that the magnetoelastic interaction and the anisotropic exchange coupling are important perturbations and therefore should be explicitly considered if a complete analysis of the magnetic properties of the borocarbides is desired