Amorphous interface layer in thin graphite films grown on the carbon face of SiC

Cross-sectional transmission electron microscopy (TEM) is used to characterize an amorphous layer observed at the interface in graphite and graphene films grown via thermal decomposition of C-face 4H-SiC. The amorphous layer does not to cover the entire interface, but uniform contiguous regions span microns of cross-sectional interface. Annular dark field scanning transmission electron microscopy (ADF-STEM) images and electron energy loss spectroscopy (EELS) demonstrate that the amorphous layer is a carbon-rich composition of Si/C. The amorphous layer is clearly observed in samples grown at 1600{\deg}C for a range of growth pressures in argon, but not at 1500{\deg}C, suggesting a temperature-dependent formation mechanism

Negative curves on algebraic surfaces

We study curves of negative self-intersection on algebraic surfaces. We obtain results for smooth complex projective surfaces X on the number of reduced, irreducible curves C of negative self-intersection C^2. The only known examples of surfaces for which C^2 is not bounded below are in positive characteristic, and the general expectation is that no examples can arise over the complex numbers. Indeed, we show that the idea underlying the examples in positive characteristic cannot produce examples over the complex number field. The previous version of this paper claimed to give a counterexample to the Bounded Negativity Conjecture. The idea of the counterexample was to use Hecke translates of a smooth Shimura curve in order to create an infinite sequence of curves violating the Bounded Negativity Conjecture. To this end we applied Hirzebruch Proportionality to all Hecke translates, simultaneously desingularized by a version of Jaffee's Lemma which exists in the literature but which turns out to be false. Indeed, in the new version of the paper, we show that only finitely many Hecke translates of a special subvariety of a Hilbert modular surface remain smooth. This new result is based on work done jointly with Xavier Roulleau, who has been added as an author. The other results in the original posting of this paper remain unchanged.Comment: 14 pages, X. Roulleau added as author, counterexample to Bounded Negativity Conjecture withdrawn and replaced by a proof that there are only finitely many smooth Shimura curves on a compact Hilbert modular surface; the other results in the original posting of this paper remain unchange

MEDT 330 Clinical Laboratory Science: Medical Technology Practicum II

Course syllabus for MEDT 330 Clinical Laboratory Science: Medical Technology Practicum II Course description: The student will review basic microbiology skills and perform identification of additional micro-organisms. The emphasis will be on gram negative enteric bacilli, non-fermentative gram negative bacilli and acid-fast bacilli. The identification and isolation of pathogenic organisms from clinical specimens will also be stressed

Functional analyses of pSer and pThr binding domains

Since the discovery of the phosphotyrosine binding SH2 domain, many classes of phospho-recognition domains have been described which mediate many of the diverse cellular functions of protein kinases. Among those, FHA domains are unique in their ability to exclusively recognise pThr epitopes. The genome of the human pathogen Mycobacterium tuberculosis encodes 5 FHA domains, along with 11 Ser/Thr protein kinases. In the first part of this thesis, it is shown that Ser/Thr protein kinase PknB phosphorylates a threonine residue in an intrinsically unstructured region of protein FhaA. FhaA contains an FHA domain through which it interacts with and presumably inhibits MviN, a muropeptide flippase essential for cell-wall synthesis. Upon phosphorylation, the FHA domain binds the pThr epitope in an intra-molecular interaction occluding the MviN binding surface and alleviating its inhibition. Although the pThr-FHA interaction is relatively weak and nonspecific, the phosphorylated molecule nonetheless assumes a ‘closed’ conformation 99% of the time and is therefore able to outcompete the 2 orders of magnitude stronger bimolecular FHA-MviN interaction. In the second part, the phospho-binding capabilities of the human PIH1D1 protein were characterised. PIH1D1 has been shown to interact with a central chaperone assembly comprising the R2TP complex and Hsp90. It has also been shown to interact with co-factor Tel2 in a phospho-dependent manner essential for the stability of the ‘giant’ PI3-kinase-like kinases mTOR and SMG1. PIH1D1 is shown to function as a novel phospho-reader domain with a consensus binding sequence of D-pS-D-D, agreeing well with the substrate specificity of casein kinase 2. A mutant that abolishes phospho-binding was identified and used in binding experiments which showed that PIH1D1 interacts with the chaperone complex phospho-independently and that its phospho-binding capacity is utilised to recruit a subset of CK2 substrates to the chaperone complex

Nanometer-scale sharpness in corner-overgrown heterostructures

A corner-overgrown GaAs/AlGaAs heterostructure is investigated with transmission and scanning transmission electron microscopy, demonstrating self-limiting growth of an extremely sharp corner profile of 3.5 nm width. In the AlGaAs layers we observe self-ordered diagonal stripes, precipitating exactly at the corner, which are regions of increased Al content measured by an XEDS analysis. A quantitative model for self-limited growth is adapted to the present case of faceted MBE growth, and the corner sharpness is discussed in relation to quantum confined structures. We note that MBE corner overgrowth maintains nm-sharpness even after microns of growth, allowing the realization of corner-shaped nanostructures.Comment: 4 pages, 3 figure

Evolution and stabilization of subnanometric metal species in confined space by in situ TEM

Understanding the behavior and dynamic structural transformation of subnanometric metal species under reaction conditions will be helpful for understanding catalytic phenomena and for developing more efficient and stable catalysts based on single atoms and clusters. In this work, the evolution and stabilization of subnanometric Pt species confined in MCM-22 zeolite has been studied by in situ transmission electron microscopy (TEM). By correlating the results from in situ TEM studies and the results obtained in a continuous fix-bed reactor, it has been possible to delimitate the factors that control the dynamic agglomeration and redispersion behavior of metal species under reaction conditions. The dynamic reversible transformation between atomically dispersed Pt species and clusters/nanoparticles during CO oxidation at different temperatures has been elucidated. It has also been confirmed that subnanometric Pt clusters can be stabilized in MCM-22 crystallites during NO reduction with CO and H2

Development of an electrochemical immunosensor for Phakopsora pachyrhizi detection in the early diagnosis of soybean rust

Soybean rust is a disease that occurs on soybean leaves and is considered very aggressive, reducing product quality. Early identification of fungus in the plants prevents severe farming losses as well as spreading to neighboring cultures. In this paper, a label-free immunosensor was developed based on impedance measurements to detect Asian rust on soybean leaf extract at the early stages of the disease. The antibody anti-mycelium of Phakopsora pachyrhizi fungus (disease agent) was immobilized on a gold substrate via a self-assembled monolayer (SAM) of thiols using covalent cysteamine coupling. This immunosensor presents a limit of detection of 385 ng mL-1. The optimization of experimental conditions and surface blocking to minimize non-specific adsorption on the immunosensor response were evaluated. These studies, based on electrochemical impedance spectroscopy (EIS), provide new perspectives on using this method for early diagnosis of soybean rust

Statistical Approach to Fuzzy Cognitive Maps

Fuzzy cognitive maps are studied from statistical standpoint. An analogy between these maps and linear regression and logistic regression models is drawn. Practical examples are also provided.Peer reviewe

Correlation of pre-operative cancer imaging techniques with post-operative gross and microscopic pathology images

In this paper, different algorithms for volume reconstruction from tomographic cross-sectional pathology slices are described and tested. A tissue-mimicking phantom made with a mixture of agar and aluminium oxide was sliced at different thickness as per pathological standard guidelines. Phantom model was also virtually sliced and reconstructed in software. Results showed that shape-based spline interpolation method was the most precise, but generated a volume underestimation of 0.5%