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

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

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

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

Contribution to the knowledge of early geotechnics during the twentieth century: Ralph Peck

Ralph B. Peck (1912–2008), graduate and doctor of philosophy in civil engineering (1934 and 1937 respectively) from the Rensselaer Polytechnic Institute, was one of the major contributors to the development of geotechnics in the twentieth century. Born in Winnipeg (Manitoba) as an American national, he was influenced from childhood by the world of civil engineering through his father, Orwin K. Peck, who was a civil engineer, mainly as a structural engineer in the railway sector. In the absence of job offers as a structural engineer, Ralph Peck arrived at Harvard University in 1938 to attend the soil mechanics courses taught by Arthur Casagrande, which guided Peck's professional career towards geotechnics. In addition to Casagrande, Peck had the opportunity to meet and work with other very important people related to geotechnics: Albert E. Cummings, Laurits Bjerrum, Alec W. Skempton and especially Karl Terzaghi, with whom he established a great friendship, in addition to providing support, professional advice and performing important work, such as the Chicago Subway Works. Peck actively dedicated himself to consulting work, which led him to visit 44 states within the United States and 28 countries on five continents. In addition, he also participated in research work where he was asked and was a committed lecturer at the University of Illinois, where he was a professor for 32 years. The objective of this paper is to analyse, through Peck's biography, his contribution to the field of geotechnics based on his research, teaching and consultancy work, and through the influence of Peck on other important people in the field, such as Karl Terzaghi.</p