C hyperfine interactions in the ground state of the negatively charged nitrogen vacancy ͑NV − ͒ center have been investigated using electron-paramagnetic-resonance spectroscopy. The previously published parameters for the 14 N hyperfine interaction do not produce a satisfactory fit to the experimental NV − electron-paramagnetic-resonance data. The small anisotropic component of the NV − hyperfine interaction can be explained from dipolar interaction between the nitrogen nucleus and the unpaired-electron probability density localized on the three carbon atoms neighboring the vacancy. Optical spin polarization of the NV − ground state was used to enhance the electron-paramagnetic-resonance sensitivity enabling detailed study of the hyperfine interaction with 13 C neighbors. The data confirmed the identification of three equivalent carbon nearest neighbors but indicated the next largest 13 C interaction is with six, rather than as previously assumed three, equivalent neighboring carbon atoms.

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Infra-red (IR) absorption results on irradiated and annealed synthetic diamond are presented which confirm an earlier proposal that a component found in the defect-induced one-phonon region of some diamonds arises from positively charged single-substitutional nitrogen . The concentration ratio of to neutral substitutional nitrogen centres may be changed by shining light of various energies onto the examined samples. By correlating changes in absorption of the IR component associated with centres with changes in the component, and using a previously determined relation between the concentration of centres and peak absorption coefficient at 1130 , the relationship between peak absorption at 1332 and concentration of centres has been derived, namely 1 of absorption is produced by ppm centres. Other defects may also give rise to absorption at 1332 , but the component is uniquely identified by further peaks at 1046 and 950 . The significance of this component is demonstrated by the fact that some samples can contain in excess of 80 ppm centres, and this must consequently be accounted for when assaying the total nitrogen concentration in such samples. Using the above relationship useful parameters relating the concentration of neutral vacancies, negative vacancies and negatively charged nitrogen-vacancy centres to their respective zero-phonon line integrated absorptions have been derived.

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Evidence for natural selection, positive or negative, on gene encoding antigens may indicate variation or functional constraints that are immunologically relevant. Most malaria surface antigens with high genetic diversity have been reported to be under positive-diversifying selection. However, antigens with limited genetic variation are usually ignored in terms of the role that natural selection may have in generating such patterns. We investigated orthologous genes encoding two merozoite proteins, MSP8 and MSP10, among several mammalian Plasmodium spp. These antigens, together with MSP1, are among the few MSPs that have two epidermal growth factor-like domains (EGF) at the C-terminal. Those EGF are relatively conserved (low levels of genetic polymorphism) and have been proposed to act as ligands during the invasion of RBCs. We use several evolutionary genetic methods to detect patterns consistent with natural selection acting on MSP8 and MSP10 orthologs in the human parasites P. falciparum and P. vivax, as well as closely related malarial species found in non-human primates (NHPs). Overall, these antigens have low polymorphism in the human parasites in comparison with the orthologs from other Plasmodium species. We found that the MSP10 gene polymorphism in P. falciparum only harbor non-synonymous substitutions, a pattern consistent with a gene under positive selection. Evidence of purifying selection was found on the polymorphism observed in both orthologs from P. cynomolgi, a non-human primate parasite closely related to P. vivax, but it was not conclusive in the human parasite. Yet, using phylogenetic base approaches, we found evidence for purifying selection on both MSP8 and MSP10 in the lineage leading to P. vivax. Such antigens evolving under strong functional constraints could become valuable vaccine candidates. We discuss how comparative approaches could allow detecting patterns consistent with negative selection even when there is low polymorphism in the extant populations.

Plasmodium vivax is the most prevalent human malaria parasite outside of Africa. Yet, studies aimed to identify genes with signatures consistent with natural selection are rare. Here, we present a comparative analysis of the pattern of genetic variation of five sequenced isolates of P. vivax and its divergence with two closely related species, Plasmodium cynomolgi and Plasmodium knowlesi, using a set of orthologous genes. In contrast to Plasmodium falciparum, the parasite that causes the most lethal form of human malaria, we did not find significant constraints on the evolution of synonymous sites genome wide in P. vivax. The comparative analysis of polymorphism and divergence across loci allowed us to identify 87 genes with patterns consistent with positive selection, including genes involved in the “exportome” of P. vivax, which are potentially involved in evasion of the host immune system. Nevertheless, we have found a pattern of polymorphism genome wide that is consistent with a significant amount of constraint on the replacement changes and prevalent negative selection. Our analyses also show that silent polymorphism tends to be larger toward the ends of the chromosomes, where many genes involved in antigenicity are located, suggesting that natural selection acts not only by shaping the patterns of variation within the genes but it also affects genome organization.

Oxidative stress is preempted by an adequate level of antioxidants, which scavenge oxidants when they are produced in excess by different sources, including leukocytes and immature spermatozoa. Enzymatic antioxidants, such as superoxide dismutase, catalase and glutathione peroxidase, and several nonenzymatic antioxidants (pro teins, vitamins and minerals), working as oxidant scavengers and cofactors of en zymatic antioxidants have been identified in seminal plasma. The total antioxidant capacity (TAC) is a diagnostic test that can be utilised in the male infertility workup. TAC measures the amount of total antioxidants in seminal plasma. Therefore, it pro vides an assessment of the reductive potential in seminal plasma. Several studies have investigated the diagnostic application of TAC in various andrology conditions. There is substantial evidence in the literature to show that infertile patients have lower seminal TAC in comparison with fertile men. Moreover, there is a positive cor relation between TAC and seminal parameters, such as sperm concentration, motility and morphology. Evaluation of TAC together with reactive oxygen species (ROS) and sperm DNA fragmentation index (DFI) may be beneficial in the diagnosis of male infertility.

Results from spectroscopic analyses of GE POL high-pressure high-temperature (HPHT) annealed nominally type IIa diamonds are presented, and these spectral characteristics are compared with those of untreated diamonds of similar appearance and type. Absorption spectroscopy reveals that any yellow coloration in such HPHT-treated diamonds is due to low concentrations of single nitrogen, which have not been observed in untreated type IIa diamonds. Laser-excited photoluminescence spectroscopy reveals the presence of nitrogen-vacancy centers in most, but not all, HPHT-treated stones. When these centers are present, the ratio of the 575:637 nm luminescence intensities offers a potential means of separating HPHT-treated from untreated type IIa diamonds. The total absence of luminescence may be another important indicator of HPHT treatment.