Nitrogen-vacancy color centers created by proton implantation in a diamond

We present an experimental study of the longitudinal and transverse relaxation of ensembles of negatively charged nitrogen-vacancy (NV−) centers in a diamond monocrystal prepared by 1.8 MeV proton implantation. The focused proton beam was used to introduce vacancies at a 20 µµm depth layer. Applied doses were in the range of 1.5×1013 to 1.5×1017 ions/cm2. The samples were subsequently annealed in vacuum which resulted in a migration of vacancies and their association with the nitrogen present in the diamond matrix. The proton implantation technique proved versatile to control production of nitrogen-vacancy color centers in thin films

Data coding tools for color-coded vector nanolithography

We propose and demonstrate the ability and efficiency of using a universal file format for a nanolithography pattern. A problem faced by the physicists working in the field of nanolithography is a lack of a flexible pattern design software (possibly open–source) that could be applied in combination with a broad range of commercial scanning probe microscope (SPM) systems. The current nanolithography software packages are device–specific and not portable. Therefore, it is impossible to make a lithography pattern and share it with fellow physicists working on a networked sub-system. In this paper we describe the software designed to read and interpret a nanolithography pattern stored in a Windows Metafile (WMF) standard graphic format and next to draw it on a substrate using an SPM tip. The nanolithography parameters like height, velocity, feedback force, etc. are coded in the color of the WMF onto the RGB channels of the image establishing a distinct relation between a graphical feature (color) and the used nanolithography scheme (voltage, height, etc.). The concept enables preparation of complex patterns using any standard graphic software and aids an intuitive recognition of the mode and parameters set for a pattern. The advantages of using a WMF over other approaches and the universal scope of the software are discussed

Ammonium Hydroxide Mediated Hydrothermal Crystallization of Hydroxyapatite Coatings on Titanium Substrate

Controlled growth of hydroxyapatite (HAp) coatings on titanium substrate plays an important role in the fabrication of the composites for bone tissue engineering. We describe the synthesis of the crystalline hydroxyapatite coatings on the Ti/TiO2 substrate through a hydrothermal method by using ethylenediamine tetraacetic acid disodium salt (Na2EDTA) and varying concentrations of ammonium hydroxide (NH4OH) in calcium-phosphate precursor solution. Na2EDTA serves as a chelating agent, while NH4OH is used as an alkaline source and crystal growth modifier. We characterized the HAp coatings using x-ray diffraction, scanning electron microscopy, and Raman spectroscopy. We also performed the elemental chemical analysis by means of a particle induced x–ray emission method. Our results show that there is a pH limit for which the hydrothermal deposition of HAp on titanium occurs. Moreover, we observed that NH4OH had a measurable influence on the coating thickness as well as on the size and shape of the HAp crystals. We found that with the increase of NH4OH concentration, the thickness of the Hap layer increases and its morphology changes from irregular flakes to well-defined hexagonal rods

Application of Spectroscopic Methods for the Identification of Superoxide Dismutases in Cyanobacteria

Superoxide dismutases (SODs) belong to the group of metalloenzymes that remove superoxide anion radicals and they have been identified in three domains of life: Bacteria, Archaea and Eucarya. SODs in Synechocystis sp. PCC 6803, Gloeobacter violaceus CCALA 979, and Geitlerinema sp. ZHR1A were investigated. We hypothesized that iron (FeSOD) and/or manganese (MnSOD) dominate as active forms in these cyanobacteria. Activity staining and three different spectroscopic methods of SOD activity bands excised from the gels were used to identify a suitable metal in the separated samples. FeSODs or enzymes belonging to the Fe-MnSOD superfamily were detected. The spectroscopic analyses showed that only Fe is present in the SOD activity bands. We found FeSOD in Synechocystis sp. PCC 6803 while two forms in G. violaceus and Geitlerinema sp. ZHR1A: FeSOD1 and FeSOD2 were present. However, no active Cu/ZnSODs were identified in G. violaceus and Geitlerinema sp. ZHR1A. We have shown that selected spectroscopic techniques can be complementary to the commonly used method of staining for SOD activity in a gel. Furthermore, the occurrence of active SODs in the cyanobacteria studied is also discussed in the context of SOD evolution in oxyphotrophs

Novel Approach to Tooth Chemistry. Quantification of the Dental-Enamel Junction

The dentin-enamel junction (DEJ) is known for its special role in teeth. Several techniques were applied for the investigation of the DEJ in human sound molar teeth. The electron (EPMA) and proton (PIXE) microprobes gave consistent indications about the variability of elemental concentrations on this boundary. The locally increased and oscillating concentrations of Mg and Na were observed in the junction, in the layer adhering to the enamel and covering roughly half of the DEJ width. The chemical results were compared with the optical profiles of the junction. Our chemical and optical results were next compared with the micromechanical results (hardness, elastic modulus, friction coefficient) available in the world literature. A strong correlation of both result sets was proven, which testifies to the self-affinity of the junction structures for different locations and even for different kinds of teeth and techniques applied for studies. Energetic changes in tooth strictly connected with crystallographic transformations were calculated, and the minimum energetic status was discovered for DEJ zone. Modeling of both walls of the DEJ from optical data was demonstrated. Comparing the DEJ in human teeth with the same structure found in dinosaur, shark, and alligator teeth evidences the universality of dentin enamel junction in animal world. The paper makes a contribution to better understanding the joining of the different hard tissues

Influence of proton irradiation on the magnetic properties of two-dimensional Ni(II) molecular magnet

Abstract The influence of 1.9 MeV proton irradiation on structural and magnetic properties has been explored in the two-dimensional (2D) NiSO4(1,3-phenylenediamine)2 coordination ferrimagnet. The X-ray powder diffraction and IR spectroscopy revealed that the octahedrons with Ni ion in the center remain unchanged regardless of the fluence a sample received. In contrast, proton irradiation greatly influences the hydrogen bonds in the flexible parts in which the 1,3-phenylenediamine is involved. Dc magnetic measurements revealed that several magnetic properties were modified with proton irradiation. The isothermal magnetization measured at T = 2.0 K varied with the proton dose, achieving a 50% increase in magnetization in the highest measured field µ0 H dc = 7 T or a 25% decrease in remanence. The most significant change was observed for the coercive field, which was reduced by 90% compared to the non-irradiated sample. The observed results are accounted for the increased freedom of magnetic moments rotation and the modification of intralayer exchange couplings