Single-photon emitters in hexagonal boron nitride: a review of progress.

This report summarizes progress made in understanding properties such as zero-phonon-line energies, emission and absorption polarizations, electron-phonon couplings, strain tuning and hyperfine coupling of single photon emitters in hexagonal boron nitride. The primary aims of this research are to discover the chemical nature of the emitting centres and to facilitate deployment in device applications. Critical analyses of the experimental literature and data interpretation, as well as theoretical approaches used to predict properties, are made. In particular, computational and theoretical limitations and challenges are discussed, with a range of suggestions made to overcome these limitations, striving to achieve realistic predictions concerning the nature of emitting centers. A symbiotic relationship is required in which calculations focus on properties that can easily be measured, whilst experiments deliver results in a form facilitating mass-produced calculations

Role of plant growth regulators in preservation of Pyrus germplasm in vitro

In vitro established shoots of nine pear genotypes namely; Khurolli, Bagugosha, Pathar nakh, Desi nakh, Kotharnul, Btangi, Frashishi, Kashmiri nakh, and Raj btung, were preserved by lowering concentration of growth regulators [(0.00, 0.25 or 0.50mg l-1 6-benzyaminopurine (BAP) or adding growth retardants, 10 mg L-1 Alar (diaminazide or B-9), or abscisic acid (ABA)] in the culture medium. The cultures were assessed for their survival and regenerability percentages after 3, 6, 9 and 12 months of storage. The genotypes differed significantly for survival and regeneration percentage. The culture medium supplemented with 0.50 mg L-1 BAP was comparatively more effective and resulted in higher survival rate and re-growth after transferring onto the fresh medium. Storage for short duration (3 months) resulted in significantly higher survival and regeneration rates than other storage periods. As storage period was prolonged, survival and regenerability of shoots progressively decreased. Overall results indicated that the shoots of Desi nakh had the highest survival (73.33 %) and Pathar nakh showed the maximum regenerability (67.66 %) when cultured on the medium supplemented with 0.50 mg L-1 BAP and stored for 3 months. However, no shoots of Kotharnul survived when cultured on the medium without any growth regulator and kept for 12 months.Key words: Growth retardants, in vitro preservation, pear genotypes, slow growth

Theoretical spectroscopy of the v N N B defect in hexagonal boron nitride

© 2020 American Physical Society. The VNNB defect in hexagonal boron nitride (h-BN), comprising a nitrogen vacancy adjacent to a nitrogen-for-boron substitution, is modelled in regard to its possible usefulness in a nanophotonics device. The modelling is done on both a simple model compound and on a 2D periodic representation of the defect, considering its magnetic and spectroscopic properties. The electronic distribution in most excited states of VNNB is found to be very open-shell in nature, and to deal with this two new computational methods are developed: one allows standard density-functional theory (DFT) calculations to be employed to evaluate state energies for doublet states with three unpaired electrons, the other introduces techniques needed to apply the vasp computational package to these and many other problems involving excited states. Also of general use, results from DFT calculations are then calibrated against those from the ab initio methods MRCI, CASPT2, CCSD, EOM-CCSD, and CCSD(T), seeking robust computational schemes. This complements previous work to reveal quite different properties for systems with odd and even numbers of electrons. These innovations allow 45 electronic states of the defect in its neutral, +1 and -1 charged forms to be considered. The charged forms of the defect are predicted to display properties of potential interest to nanophotonics

Filarial Lymphedema Is Characterized by Antigen- Specific Th1 and Th17 Proinflammatory Responses and a Lack of Regulatory T Cells

Background: Lymphatic filariasis can be associated with development of serious pathology in the form of lymphedema, hydrocele, and elephantiasis in a subset of infected patients. Methods and Findings: To elucidate the role of CD4+ T cell subsets in the development of lymphatic pathology, we examined specific sets of cytokines in individuals with filarial lymphedema in response to parasite antigen (BmA) and compared them with responses from asymptomatic infected individuals. We also examined expression patterns of Toll-like receptors (TLR1–10) and Nod-like receptors (Nod1, Nod2, and NALP3) in response to BmA. BmA induced significantly higher production of Th1-type cytokines—IFN-c and TNF-a—in patients with lymphedema compared with asymptomatic individuals. Notably, expression of the Th17 family of cytokines—IL-17A, IL-17F, IL-21, and IL-23—was also significantly upregulated by BmA stimulation in lymphedema patients. In contrast, expression of Foxp3, GITR, TGFb, and CTLA-4, known to be expressed by regulatory T cells, was significantly impaired in patients with lymphedema. BmA also induced significantly higher expression of TLR2, 4, 7, and 9 as well Nod1 and 2 mRNA in patients with lymphedema compared with asymptomatic controls. Conclusion: Our findings implicate increased Th1/Th17 responses and decreased regulatory T cells as well as regulation of Toll- and Nod-like receptors in pathogenesis of filarial lymphedema

Evolution of apoptosis-like programmed cell death in unicellular protozoan parasites

Apoptosis-like programmed cell death (PCD) has recently been described in multiple taxa of unicellular protists, including the protozoan parasites Plasmodium, Trypanosoma and Leishmania. Apoptosis-like PCD in protozoan parasites shares a number of morphological features with programmed cell death in multicellular organisms. However, both the evolutionary explanations and mechanisms involved in parasite PCD are poorly understood. Explaining why unicellular organisms appear to undergo 'suicide' is a challenge for evolutionary biology and uncovering death executors and pathways is a challenge for molecular and cell biology. Bioinformatics has the potential to integrate these approaches by revealing homologies in the PCD machinery of diverse taxa and evaluating their evolutionary trajectories. As the molecular mechanisms of apoptosis in model organisms are well characterised, and recent data suggest similar mechanisms operate in protozoan parasites, key questions can now be addressed. These questions include: which elements of apoptosis machinery appear to be shared between protozoan parasites and multicellular taxa and, have these mechanisms arisen through convergent or divergent evolution? We use bioinformatics to address these questions and our analyses suggest that apoptosis mechanisms in protozoan parasites and other taxa have diverged during their evolution, that some apoptosis factors are shared across taxa whilst others have been replaced by proteins with similar biochemical activities

Understanding the Role of PknJ in Mycobacterium tuberculosis: Biochemical Characterization and Identification of Novel Substrate Pyruvate Kinase A

Reversible protein phosphorylation is a prevalent signaling mechanism which modulates cellular metabolism in response to changing environmental conditions. In this study, we focus on previously uncharacterized Mycobacterium tuberculosis Ser/Thr protein kinase (STPK) PknJ, a putative transmembrane protein. PknJ is shown to possess autophosphorylation activity and is also found to be capable of carrying out phosphorylation on the artificial substrate myelin basic protein (MyBP). Previous studies have shown that the autophosphorylation activity of M. tuberculosis STPKs is dependent on the conserved residues in the activation loop. However, our results show that apart from the conventional conserved residues, additional residues in the activation loop may also play a crucial role in kinase activation. Further characterization of PknJ reveals that the kinase utilizes unusual ions (Ni2+, Co2+) as cofactors, thus hinting at a novel mechanism for PknJ activation. Additionally, as shown for other STPKs, we observe that PknJ possesses the capability to dimerize. In order to elucidate the signal transduction cascade emanating from PknJ, the M. tuberculosis membrane-associated protein fraction is treated with the active kinase and glycolytic enzyme Pyruvate kinase A (mtPykA) is identified as one of the potential substrates of PknJ. The phospholabel is found to be localized on serine and threonine residue(s), with Ser37 identified as one of the sites of phosphorylation. Since Pyk is known to catalyze the last step of glycolysis, our study shows that the fundamental pathways such as glycolysis can also be governed by STPK-mediated signaling

A Cysteine Protease Is Critical for Babesia spp. Transmission in Haemaphysalis Ticks

Vector ticks possess a unique system that enables them to digest large amounts of host blood and to transmit various animal and human pathogens, suggesting the existence of evolutionally acquired proteolytic mechanisms. We report here the molecular and reverse genetic characterization of a multifunctional cysteine protease, longipain, from the babesial parasite vector tick Haemaphysalis longicornis. Longipain shares structural similarity with papain-family cysteine proteases obtained from invertebrates and vertebrates. Endogenous longipain was mainly expressed in the midgut epithelium and was specifically localized at lysosomal vacuoles and possibly released into the lumen. Its expression was up-regulated by host blood feeding. Enzymatic functional assays using in vitro and in vivo substrates revealed that longipain hydrolysis occurs over a broad range of pH and temperature. Haemoparasiticidal assays showed that longipain dose-dependently killed tick-borne Babesia parasites, and its babesiacidal effect occurred via specific adherence to the parasite membranes. Disruption of endogenous longipain by RNA interference revealed that longipain is involved in the digestion of the host blood meal. In addition, the knockdown ticks contained an increased number of parasites, suggesting that longipain exerts a killing effect against the midgut-stage Babesia parasites in ticks. Our results suggest that longipain is essential for tick survival, and may have a role in controlling the transmission of tick-transmittable Babesia parasites

Genome of the facultative scuticociliatosis pathogen Pseudocohnilembus persalinus provides insight into its virulence through horizontal gene transfer

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