Electron-Hole Asymmetry in GdBaCo_{2}O_{5+x}: Evidence for Spin Blockade of Electron Transport in a Correlated Electron System

In RBaCo_{2}O_{5+x} compounds (R is rare earth) variability of the oxygen content allows precise doping of CoO_2 planes with both types of charge carriers. We study transport properties of doped GdBaCo_{2}O_{5+x} single crystals and find a remarkable asymmetry in the behavior of holes and electrons doped into a parent insulator GdBaCo_{2}O_{5.5}. Doping dependences of resistivity, Hall response, and thermoelectric power reveal that the doped holes greatly improve the conductivity, while the electron-doped samples always remain poorly conducting. This doping asymmetry provides strong evidence for a spin blockade of the electron transport in RBaCo_{2}O_{5+x}.Comment: 4 pages, 5 figures, accepted for publication in PR

Assessment of in vitro antitumoral and antimicrobial activities of marine algae harvested from the eastern Mediterranean sea

Antitumoral activities of five algal extracts obtained from the marine algae Scytosiphon lomentaria, Padina pavonica, Cystoseira mediterranea (Phaeophyceae), Hypnea musciformis and Spyridia filamentosa (Rhodophyta) were assessed against the human breast adenocarcinoma cell line MCF–7 and the human prostate carcinoma epithelium like cell lines DU 145, LNCaP, PC3 using the cytotoxic assay, in vitro. The crude extract of S. filamentosa showed strong cytotoxic activity against the DU-145 cell line, and it showed less than 10% cell viability after treatment. Antimicrobial activities of the crude extracts of algae (with the exception of H. musciformis) were also tested by disc diffusion assay against three Gram positive and five Gram negative bacterial strains and against the yeast pathogen Candida albicans. Among the extraxts, S. lomentaria extract (prepared with methanol) inhibited highly Gram negative bacterium Salmonella typhimurium growth while C. albicans growth was only inhibited by C.mediterrranea extract

First report of the North Atlantic myrionematoid brown alga Ulonema rhizophorum Foslie (Phaeophyceae, Chordariaceae) in the Mediterranean Sea

The myrionematoid brown alga Ulonema rhizophorum Foslie (Phaeophyceae, Chordariaceae) is reported for the first time from the Mediterranean Sea. This species was collected growing as an epiphyte on Ulva sp. from the Dardanelles (Sea of Marmara, Turkey) in the midlittoral zone. Ulonema rhizophorum is characterized by downwardly produced rhizoids from the basal system. A key to the Mediterranean related genera of Ulonema is provided

First report of the alien brown alga Scytosiphon dotyi M.J. Wynne (Phaeophyceae, Scytosiphonaceae) in Turkey

The alien brown alga Scytosiphon dotyi M.J. Wynne (Phaeophyceae, Scytosiphonaceae) is reported for the first time in Turkey. This species was collected growing epilithically in the midlittoral zone in the Dardanelles (Sea of Marmara, Turkey)

Additional Evidence for the Surface Origin of the Peculiar Angular-Dependent Magnetoresistance Oscillations Discovered in a Topological Insulator Bi_{1-x}Sb_{x}

We present detailed data on the unusual angular-dependent magnetoresistance oscillation phenomenon recently discovered in a topological insulator Bi_{0.91}Sb_{0.09}. Direct comparison of the data taken before and after etching the sample surface gives compelling evidence that this phenomenon is essentially originating from a surface state. The symmetry of the oscillations suggests that it probably comes from the (111) plane, and obviously a new mechanism, such as a coupling between the surface and the bulk states, is responsible for this intriguing phenomenon in topological insulators.Comment: 5 pages, 4 figures, Proceedings manuscript for the 19th International Conference on the Application of High Magnetic Fields in Semiconductor Physics and Nanotechnology (HMF-19

Ising-like Spin Anisotropy and Competing Antiferromagnetic - Ferromagnetic Orders in GdBaCo_{2}O_{5.5} Single Crystals

In RBaCo_{2}O_{5+x} compounds (R is rare earth), a ferromagnetic-antiferromagnetic competition is accompanied by a giant magnetoresistance. We study the magnetization of detwinned GdBaCo_{2}O_{5.5} single crystals, and find a remarkable uniaxial anisotropy of Co^{3+} spins which is tightly linked with the chain oxygen ordering in GdO_{0.5} planes. Reflecting the underlying oxygen order, CoO_2 planes also develop a spin-state order consisting of Co^{3+} ions in alternating rows of S=1 and S=0 states. The magnetic structure appears to be composed of weakly coupled ferromagnetic ladders with Ising-like moments, which gives a simple picture for magnetotransport phenomena.Comment: 5 pages, 4 figures, accepted to Phys.Rev.Let

Transport and magnetic properties of GdBaCo_{2}O_{5+x} single crystals: A cobalt oxide with square-lattice CoO_2 planes over a wide range of electron and hole doping

Single crystals of the layered perovskite GdBaCo_{2}O_{5+x} (GBCO) have been grown by the floating-zone method, and their transport, magnetic, and structural properties have been studied in detail over a wide range of oxygen contents. The obtained data are used to establish a rich phase diagram centered at the "parent'' compound GdBaCo_{2}O_{5.5} -- an insulator with Co ions in the 3+ state. An attractive feature of GBCO is that it allows a precise and continuous doping of CoO_{2} planes with either electrons or holes, spanning a wide range from the charge-ordered insulator at 50% electron doping (x=0) to the undoped band insulator (x=0.5), and further towards the heavily hole-doped metallic state. This continuous doping is clearly manifested in the behavior of thermoelectric power which exhibits a spectacular divergence with approaching x=0.5, where it reaches large absolute values and abruptly changes its sign. At low temperatures, the homogeneous distribution of doped carriers in GBCO becomes unstable, and both the magnetic and transport properties point to an intriguing nanoscopic phase separation. We also find that throughout the composition range the magnetic behavior in GBCO is governed by a delicate balance between ferromagnetic (FM) and antiferromagnetic (AF) interactions, which can be easily affected by temperature, doping, or magnetic field, bringing about FM-AF transitions and a giant magnetoresistance (MR) phenomenon. An exceptionally strong uniaxial anisotropy of the Co spins, which dramatically simplifies the possible spin arrangements, together with the possibility of continuous ambipolar doping turn GBCO into a model system for studying the competing magnetic interactions, nanoscopic phase separation and accompanying magnetoresistance phenomena.Comment: 31 pages, 32 figures, submitted to Phys. Rev.

The effects of leptin on F-actin remodelling in type 1 diabetes

Background: The aim of the current study is to investigate the effect of leptin on cytoskeleton structures in both in vivo and in vitro model of diabetes. Materials and methods: For in vivo studies, leptin in different doses (240, and 480 mg/kg) was injected to the diabetic rats after 1-week of streptozotocin (STZ, 55 mg/kg) treatment. Leptin levels were analysed in serum, liver, and pancreas samples. Hepatic and pancreatic F- and G-actin expressions were determined by Western blotting. For in vitro studies, hepatic and pancreatic primary cell lines were obtained from the control rats. To these cultures, STZ (15 and 30 mM), leptin (50, 60 and 100 ng/mL), and their combinations were applied for 1, 3, and 4 weeks. After the treatment period, F-actin was visualised by the Alexa-fluor fluorescent dye.  Results: Streptozotocin decreased the G-actin in both tissues in vivo. However, leptin caused a dose-dependent increase in G-actin levels while F-actin decreased in both tissues. Moreover, leptin caused the perimembranous condensation of actin filaments and amelioration of F-actin structures in vivo. A dose-dependent corruption of F-actin filament structures was observed in leptin-treated primary cells in vitro, while STZ also caused corruption of these filaments. Co-exposure of STZ and leptin caused the amelioration of F-actin filaments, while the peri- membranous condensation was also observed as was in vivo study.  Conclusions: Leptin therapy could be a candidate for diabetes, but it should not be ruled out as being important the severity of diabetes and leptin doses.

Management and Organization in the work of Michel Houellebecq

Research in management and organization may only gain by being inspired from arts, culture and humanities in order to rethink practices but also to nourish its own perspectives. Life in organizations is artificially separate from ordinary life: all of mundane objects are thus conducive to astonishment, inspiration, and even problematization. The unplugged subsection “voices” gives the opportunity to academics and non-academics to deliver an interpretation about an object from the cultural or artistic world. Interpreted objects are or not directly related to organizational life, resonate or not with the moment, but share some intriguing features. These interpretations suggest a patchwork of variations on the same object

Room-temperature ferromagnetism in Sr_(1-x)Y_xCoO_(3-delta) (0.2 < x < 0.25)

We have measured magnetic susceptibility and resistivity of Sr$_{1-x}$Y$_x$CoO$_{3-\delta}$ ($x=$ 0.1, 0.15, 0.2, 0.215, 0.225, 0.25, 0.3, and 0.4), and have found that Sr$_{1-x}$Y$_x$CoO$_{3-\delta}$ is a room temperature ferromagnet with a Curie temperature of 335 K in a narrow compositional range of 0.2 $\leq x\leq$ 0.25. This is the highest transition temperature among perovskite Co oxides. The saturation magnetization for $x=$ 0.225 is 0.25 $\mu_B$/Co at 10 K, which implies that the observed ferromagnetism is a bulk effect. We attribute this ferromagnetism to a peculiar Sr/Y ordering.Comment: 5 pages, 4 figure