Effect of Annealing Temperature on Microstructure and Resistivity of TiC Thin Films

Titanium carbide (TiC) thin films were prepared by non-reactive simultaneous double magnetron sputtering. After deposition, all samples were annealed at different temperatures under high-vacuum conditions. This paper mainly discusses the influence of deposition methods and annealing temperatures on microstructure, surface topography, bonding states and electrical resistivity of TiC films. XRD (X-ray diffraction) results show that TiC thin films can still form crystals without annealing, and the crystallinity of thin films is improved after annealing. The estimated grain size of the TiC films varies from 8.5 nm to 14.7 nm with annealing temperature. It can be seen from SEM (scanning electron microscope) images that surfaces of the films are composed of irregular particles, and when the temperature reaches to 800 °C, the shape of the particles becomes spherical. Growth rate of film is about 30.8 nm/min. Oxygen-related peaks were observed in XPS (X-ray photoelectron spectroscopy) spectra, which is due to the absorption of oxygen atoms on the surface of the film when exposed to air. Raman spectra confirm the formation of TiC crystals and amorphous states of carbon. Resistivity of TiC films decreases monotonically from 666.73 to 86.01 μΩ·cm with the increase in annealing temperature. In brief, the TiC thin films prepared in this study show good crystallinity, thermal stability and low resistivity, which can meet the requirements of metal gate applications.

Influence of Lithium Oxide on the Characteristics and Mechanical Property in Willemite Crystal Glazes

The effect of lithium Oxide content on the characteristics and mechanical property of willemite (2ZnO.SiO2) under a heating condition in Na2O-K2O-Li2O-CaO-(ZnO)-Al2O3-SiO2 glazing system used in stoneware, sintered at a maximum at temperature 1250 °C by a heating rate of 2.6 °C/min for 8 hours is the firing process of the glazes and clay to melt. After 15 minutes, the temperature dropped to 1100 °C for 40 minutes was stimulated crystallization and soaked in kiln at 1100 °C for 4 hours. This result was consistent with the chemical compositions from the XRF technique indicated that the glaze comprised ZnO and SiO2 were the main compositions and compared to the mineral composition after sintering of the glazed crystal which revealed 2ZnO.SiO2 as the main component and the result from the XRD technique. The microstructure of the glazed crystals after sintering was needle shaped and had spherical growth. The analytical results from Vickers hardness technique showed that microhardness by adding 3-5 % of Li2O of the glazes S1, S2, S3, S4 and S5 as 105.96 ± 4.58, 112.30 ± 9.95, 153.90 ± 7.29, 244.80 ± 5.42 and 382.62 ± 9.20, respectively. More willemite crystals in the glaze results in more strength of the glaze as well.

A growing microcolony can survive and support persistent propagation of virulent phages

Bacteria form colonies and secrete extracellular polymeric substances that surround the individual cells. These spatial structures are often associated with collaboration and quorum sensing between the bacteria. Here we investigate the mutual protection provided by spherical growth of a monoclonal colony during exposure to phages that proliferate on its surface. As a proof of concept we exposed growing colonies of Escherichia coli to a virulent mutant of phage P1. When the colony consists of less than ∼50,000 members it is eliminated, while larger initial colonies allow long-term survival of both phage-resistant mutants and, importantly, colonies of mostly phage-sensitive members. A mathematical model predicts that colonies formed solely by phage-sensitive bacteria can survive because the growth of bacteria throughout the colony exceeds the killing of bacteria on the surface and pinpoints how the critical colony size depends on key parameters in the phage infection cycle.

A Growing Microcolony can Survive and Support Persistent Propagation of Virulent Phages

Bacteria form colonies and secrete extracellular polymeric substances that surround the individual cells. These spatial structures are often associated with collaboration and quorum sensing between the bacteria. Here we investigate the mutual protection provided by spherical growth of a monoclonal colony during exposure to phages that proliferate on its surface. As a proof of concept we exposed growing colonies ofEscherichia colito a virulent mutant of phage P1. When the colony consists of less than ~ 50000 members it is eliminated, while larger initial colonies allow long-term survival because the growth of bacteria throughout the spherical colony exceeds the killing of bacteria on the surface. A mathematical model pinpoints how this critical colony size depends on key parameters in the phage infection cycle. Surprisingly, we predict that a higher phage adsorption rate would allow substantially smaller colonies to survive a virulent phage.Significance StatementBacteria are repeatedly exposed to an excess of phages, and carry evidence of this in terms of multiple defense mechanisms encoded in their genome. In addition to molecular mechanisms, bacteria may exploit the defense of spatial refuges. Here we demonstrate how bacteria can limit the impact of a virulent phage attack by growing as a colony which only exposes its surface to phages. We identify a critical size of the initial colony, below which the phages entirely eliminates the colony, and above which the colony continues to grow despite the presence of phages. Our study suggests that coexistence of phages and bacteria is strongly influenced by the spatial composition of microcolonies of susceptible bacteria.

DISTRIBUCIÓN DE ESPONJAS SOBRE LA PLATAFORMA CONTINENTAL DE LA GUAJIRA, CARIBE COLOMBIANO

During the exploration of the soft calcareous bottoms of the continental shelf of La Guajira Department, 47 different species of sponges were identified in the classes Demospongiae and Calcarea. From bottom trawling carried out throughout the continental shelf on the bathymetric fringes of 10 and 50 m, it was found that the number of species is larger at 50 m depth, mainly in areas to the north and south where sand and mud sediments prevail. However, the patterns are not consistent in all the cases, owing to the low similarities between stations, based on the presence-absence of sponges, indicating a rather heterogeneous faunal composition. The soft bottoms allow the growth of non-sessile and sessile sponges; collected species show massive, incrusting ramified and spherical growth, all loosely attached but agglutinating large substratum fragments to which they hold.