1D graphene-like silicon systems: silicene nano-ribbons

Through this review we can follow the various phases that have led to the discovery of the new allotrope form of silicon: silicene. This is a one-atom thick silicon sheet arranged in a honeycomb lattice, similar to graphene. For silicon, which usually is sp3 hybridized, it represents an unusual and rare structure. First, silicene was theoretically hypothesized and subsequently its structure calculated as a possible candidate for nano-ribbons of Si grown on the anisotropic Ag(110) surface. It was only later, when the physical and chemical properties of this peculiar form of silicon, demonstrating the presence of π and π* bands giving the so-called Dirac cones at the K corners of the Brillouin zone, the sp2-like nature of the valence orbitals of the Si-Si bonds and its strong resistance towards oxygen were reported, that the real existence of silicene became recognized in the scientific community. This review is essentially focused on the experimental work performed on 1D isolated silicene nano-ribbons and their 1D dense array grown on Ag(110) surfaces.     

Ugi reaction-assisted rapid assembly of affinity-based probes against potential protein tyrosine phosphatases

The multi-component Ugi reaction has been employed to assemble a small library of affinity-based probes (AfBPs) that target potential protein tyrosine phosphatases. The probes showed good labelling of PTP1B and MptpB, and were subsequently used to label endogenous PTP1B in MCF-7 cell lysates.     

Synthesis and preliminary biological evaluation of carba analogues from Neisseria meningitidis A capsular polysaccharide

The Gram-negative encapsulated bacterium Neisseria meningitidis type A (MenA) is a major cause of meningitis in developing countries, especially in the sub-Saharan region of Africa. The development and manufacture of an efficient glycoconjugate vaccine against MenA is greatly hampered by the poor hydrolytic stability of its capsular polysaccharide, consisting of (1→6)-linked 2-acetamido-2-deoxy-α-d-mannopyranosyl phosphate repeating units. The replacement of the ring oxygen with a methylene group to get a carbocyclic analogue leads to the loss of the acetalic character of the phosphodiester and consequently to the enhancement of its chemical stability. Here we report the synthesis of oligomers (mono-, di- and trisaccharide) of carba-N-acetylmannosamine-1-O-phosphate as candidates for stabilized analogues of the corresponding fragments of MenA capsular polysaccharide. Each of the synthesized compounds contains a phosphodiester-linked aminopropyl spacer at its reducing end to allow for protein conjugation. The inhibition abilities of the synthetic molecules were investigated by a competitive ELISA assay, showing that only the carba-disaccharide is recognized by a polyclonal anti-MenA serum with an affinity similar to a native MenA oligosaccharide with average polymerization degree of 3.     

On negative eigenvalues of selfadjoint eztensions of band matrices

The method of one-step extension is used here to analyse the number of negative eigenvalues of an extension of a selfadjoint band matrix in terms of the entries in the band matrix and the nature of the extension. Applications art; given to selfadjoint Toeplitz matrices and to the problem of determining the size of the singular values of an extension of a lower-triangular matrix.     

The curvature measurement of the human eyeball

The curvature of the cornea in the ophthalmology field is essential data, especially for humans when they are being tested for wearing contact lenses, or for patients undergoing refractive surgery by either knife or laser. It is extremely difficult to measure the curvature of the eye precisely because the measurement of the cornea, using a contact tool, is not possible. In this paper, we propose a method to measure the curvature using lens aberration theory and an image processing technique. We project a circular grating, known as a Placido disc, on to the cornea. The reflective image does not have equal divisions and this distortion value contains the curvature information.     

Subsurface As-layer formation in Au films deposited on GaAs(001)

Au deposited at room temperature on MBE grown GaAs (001) has been studied by UPS, XPS and AES. At Au coverages below ～2Å the adsorption interaction spreads the Au (6s) states density over the width of the GaAs valence band, while at higher coverages the Au overlayer has metallic properties. For the thick Au overlayers a subsurface As-rich region is established. It is suggested that this has a stabilizing influence on the continuous Au overlayer.     

An image-based LCD positioning system utilizing the modified FHT method

In this paper, a LCD positioning system based on an image processing method is described. This method is effective in finding the angle of the geometric features in the cross registration mask. However, when two marks appear in the same frame, the problem of situation verification becomes more complex. We use an algorithm that assists with calculating the location and rotation angle for two marks precisely and quickly using the Fast Hough Transform (FHT). This method determines the locations of two masks and calculates the rotation angle from a blurred edge to adjust the LCD position and orientation.     

Towards empirical EPR parameters for characterizing V(IV) complexes

Improved empirical techniques are described for determining the solution structures (coordination numbers and ligand donor groups) of oxoV(IV) complexes from isotropic EPR parameters. These methods will enable more detailed structural information to be obtained than was available previously from such empirical correlations. Assignments of the structures of the V(IV)/oxalate complexes were found to differ from those proposed in the literature and have been important in developing the empirical parameters reported here. In acidic solutions (pH≤1), V(V) oxalate complexes decay slowly to yield three V(IV) complexes, [V(O)(ox)₂]^2?, [V(O)(ox)(OH₂)₃]⁰ andcis-[V(O)(ox)₂(OH₂)]^2? (ox=oxalato(2-)), which have been characterized by EPR spectroscopy. These same three complexes are obtained from the direct reaction of V(IV) with oxalic acid. The structures of these complexes were assigned on the basis of the pH and [oxH₂] dependences of the EPR signals and differ significantly to those reported in the literature. The equilibria among the five- and six-coordinate complexes, and the protonation/deprotonation equilibrium of the six-coordinate species are consistent with the well-studied isoelectronic Cr(V) system.     

High-resolution synchrotron radiation core-level spectroscopy of semiconductor surfaces

Thanks to recent technical developments (optics and detection systems), at several synchrotron radiation facilities in the world, it is possible to perform photoemission spectroscopy studies with very high resolution. In the present report, we will review the new insights gained from high-resolution core-level spectroscopy on the structural and electronic properties of different semiconductor surfaces, such as InAs(110), Si and Ge (100) and (111), as well as clean and adsorbate covered Si and Ge(111) surfaces.