16 research outputs found
Bacteriophage ZCSE2 is a Potent Antimicrobial against Salmonella enterica Serovars: Ultrastructure, genomics and efficacy
© 2020 by the authors. Developing novel antimicrobials capable of controlling multidrug-resistant bacterial pathogens is essential to restrict the use of antibiotics. Bacteriophages (phages) constitute a major resource that can be harnessed as an alternative to traditional antimicrobial therapies. Phage ZCSE2 was isolated among several others from raw sewage but was distinguished by broad-spectrum activity against Salmonella serovars considered pathogenic to humans and animals. Lytic profiles of ZCSE2 against a panel of Salmonella were determined together with low temperature activity and pH stability. The morphological features of the phage and host infection processes were characterized using a combination of transmission electron and atomic force microscopies. Whole genome sequencing of ZCSE2 produced a complete DNA sequence of 53,965 bp. No known virulence genes were identified in the sequence data, making ZCSE2 a good candidate for phage-mediated biological control purposes. ZCSE2 was further tested against S. Enteritidis in liquid culture and was observed to reduce the target bacterium to below the limits of detection from initial concentrations of 107–108 Colony Forming Units (CFU)/mL. With a broad host-range against pathogenic Salmonella serovars, phage ZCSE2 constitutes a potential tool against a major cause of human and animal disease
Recent Results from Epitaxial Growth on Step Free 4H-SiC Mesas
This paper updates recent progress made in growth, characterization, and understanding of high quality homoepitaxial and heteroepitaxial films grown on step-free 4H-SiC mesas. First, we report initial achievement of step-free 4H-SiC surfaces with carbon-face surface polarity. Next, we will describe further observations of how step-free 4H-SiC thin lateral cantilever evolution is significantly impacted by crystal faceting behavior that imposes non-uniform film thickness on cantilever undersides. Finally, recent investigations of in-plane lattice constant mismatch strain relief mechanisms observed for heteroepitaxial growth of 3C-SiC as well as 2H-AlN/GaN heterofilms on step-free 4H-SiC mesas will be reviewed. In both cases, the complete elimination of atomic heterointerface steps on the mesa structure enables uniquely well-ordered misfit dislocation arrays to form near the heterointerfaces with remarkable lack of dislocations threading vertically into the heteroepilayers. In the case of 3C-SiC heterofilms, it has been proposed that dislocation half-loops nucleate at mesa edges and glide laterally along the step-free 3C/4H interfaces. In contrast, 3C-SiC and 2H-AlN/GaN heterofilms grown on 4H-SiC mesas with steps exhibit highly disordered interface misfit dislocation structure coupled with 100X greater density of dislocations threading through the thickness of the heteroepilayers. These results indicate that the presence of steps at the heteroepitaxial interface (i.e., on the initial heteroepitaxial nucleation surface) plays a highly important role in the defect structure, quality, and relaxation mechanisms of single-crystal heteroepitaxial films
Layer-by-Layer Assembly of Heterogeneous Modular Nanocomposites
Layer-by-layer (LbL) assembly of nanoparticles and polyelectrolyte multilayers into alternating nonrepetitive strata (modules) demonstrates an important advance in heterogeneous nanocomposites from random or repetitive distributions of nanoparticles to a versatile modular design. The morphology and composition for each module are determined by the LbL assembly conditions, as confirmed by cross-section transmission electron microscopy (TEM) and by X-ray photoelectron spectroscopy (XPS). Thickness and spacing of the modules are maintained in the 5–50 nm range relevant for nanoscale proximal interactions
Transfer of Chemically Modified Graphene with Retention of Functionality for Surface Engineering
Single-layer graphene chemically
reduced by the Birch process delaminates
from a Si/SiO<sub><i>x</i></sub> substrate when exposed
to an ethanol/water mixture, enabling transfer of chemically functionalized
graphene to arbitrary substrates such as metals, dielectrics, and
polymers. Unlike in previous reports, the graphene retains hydrogen,
methyl, and aryl functional groups during the transfer process. This
enables one to functionalize the receiving substrate with the properties
of the chemically modified graphene (CMG). For instance, magnetic
force microscopy shows that the previously reported magnetic properties
of partially hydrogenated graphene remain after transfer. We also
transfer hydrogenated graphene from its copper growth substrate to
a Si/SiO<sub><i>x</i></sub> wafer and thermally dehydrogenate
it to demonstrate a polymer- and etchant-free graphene transfer for
potential use in transmission electron microscopy. Finally, we show
that the Birch reduction facilitates delamination of CMG by weakening
van der Waals forces between graphene and its substrate