Stable 6H organic-inorganic hybrid lead perovskite and competitive formation of 6H and 3C perovskite structure with mixed A cations

We thank the Chinese Scholarship Council for Ph.D. Studentship support (to JT). Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifique de Belgique (F.R.S.-FNRS) under grant no. 2.5020.11. D.B. is an FNRS Research Director.We report the synthesis and properties of a new organic–inorganic hybrid lead perovskite (OIHP), azetidinium lead bromide (AzPbBr3), possessing the 6H perovskite structure (space group P63/mmc with a = 8.745 Å and c = 21.329 Å). This compound has a band gap of 2.81 eV and remains stable for >6 months in the ambient environment. DFT simulations are in fairly good agreement with experiments and indicate that AzPbBr3 is a direct band gap semiconductor. A partial solid solution with the cubic (3C) perovskite methylammonium lead bromide (Az1–xMAxPbBr3) is possible. In Az-rich 6H compositions the lattice volume and band gap are invariant with x (≤0.3), whereas in the MA-rich 3C phase (0.8 ≤ x ≤ 1.0) the lattice parameters and band gap increase with increasing Az content. Although the relatively large band gap of AzPbBr3 makes it unsuitable for photovoltaic applications, the results indicate Az+ is a suitable alternative organic A cation for band gap tuning of OHIPs.PostprintPeer reviewe

Enhanced photoluminescence and reduced dimensionality via vacancy ordering in a 10H halide perovskite

H.L. would like to thank the University of St. Andrews for financial support via a St. Leonard’s scholarship. The authors acknowledge facilities access made possible through support from the EPSRC Light Element Analysis facility Grant EP/T019298/1 and the EPSRC Strategic Equipment Resource Grant EP/R023751/1.Vacancy-ordered halide perovskites have received great interest in optoelectronic applications. In this work, we report the novel inorganic halide Cs10MnSb6Cl30 with a distinctive 10H (10-layer hexagonal) perovskite polytype structure with (hcccc)2 stacking. Cs10MnSb6Cl30 has 30% B-site vacancies ordered at both corner- and face-sharing sites, resulting in [MnSb6Cl30]10–n columns, i.e., a reduction of octahedral connectivity to 1D. This results in enhanced photoluminescence in comparison to the previously reported 25% vacancy-ordered 3C polytype Cs4MnSb2Cl12 with 2D connectivity. This demonstrates not only the existence of the 10H perovskite structure in halides but also demonstrates the degree of B-site deficiency and stacking sequence variation as a direction to tune the optical properties of perovskite polytypes via vacancy rearrangements.Publisher PDFPeer reviewe

Surveillance of Arthropod Vector-Borne Infectious Diseases Using Remote Sensing Techniques: A Review

Epidemiologists are adopting new remote sensing techniques to study a variety of vector-borne diseases. Associations between satellite-derived environmental variables such as temperature, humidity, and land cover type and vector density are used to identify and characterize vector habitats. The convergence of factors such as the availability of multi-temporal satellite data and georeferenced epidemiological data, collaboration between remote sensing scientists and biologists, and the availability of sophisticated, statistical geographic information system and image processing algorithms in a desktop environment creates a fertile research environment. The use of remote sensing techniques to map vector-borne diseases has evolved significantly over the past 25 years. In this paper, we review the status of remote sensing studies of arthropod vector-borne diseases due to mosquitoes, ticks, blackflies, tsetse flies, and sandflies, which are responsible for the majority of vector-borne diseases in the world. Examples of simple image classification techniques that associate land use and land cover types with vector habitats, as well as complex statistical models that link satellite-derived multi-temporal meteorological observations with vector biology and abundance, are discussed here. Future improvements in remote sensing applications in epidemiology are also discussed

Salmonella Phage ST64B Encodes a Member of the SseK/NleB Effector Family

Salmonella enterica is a species of bacteria that is a major cause of enteritis across the globe, while certain serovars cause typhoid, a more serious disease associated with a significant mortality rate. Type III secreted effectors are major contributors to the pathogenesis of Salmonella infections. Genes encoding effectors are acquired via horizontal gene transfer, and a subset are encoded within active phage lysogens. Because the acquisition of effectors is in flux, the complement of effectors possessed by various Salmonella strains frequently differs. By comparing the genome sequences of S. enterica serovar Typhimurium strain SL1344 with LT2, we identified a gene with significant similarity to SseK/NleB type III secreted effector proteins within a phage ST64B lysogen that is absent from LT2. We have named this gene sseK3. SseK3 was co-regulated with the SPI-2 type III secretion system in vitro and inside host cells, and was also injected into infected host cells. While no role for SseK3 in virulence could be identified, a role for the other family members in murine typhoid was found. SseK3 and other phage-encoded effectors were found to have a significant but sparse distribution in the available Salmonella genome sequences, indicating the potential for more uncharacterised effectors to be present in less studied serovars. These phage-encoded effectors may be principle subjects of contemporary selective processes shaping Salmonella-host interactions

When Antibiotics Fail: The Expert Panel on the Potential Socio-Economic Impacts of Antimicrobial Resistance in Canada

Antimicrobials are life savers in Canada, enabling modern healthcare and playing a central role in agriculture. They have reduced the economic, medical, and social burden of infectious diseases and are part of many routine medical interventions, such as caesarean sections, joint replacements, and tonsillectomies. As use of antimicrobials has increased, bacteria evolved to become resistant, resulting in drugs that are no longer effective at treating infections. Antimicrobial resistance (AMR) is increasing worldwide, and with widespread trade and travel, resistance can spread quickly, posing a serious threat to all countries. For Canada, the implications of AMR are stark. When Antibiotics Fail examines the current impacts of AMR on our healthcare system, projects the future impact on Canada’s GDP, and looks at how widespread resistance will influence the day-to-day lives of Canadians. The report examines these issues through a One Health lens, recognizing the interconnected nature of AMR, from healthcare settings to the environment to the agriculture sector. It is the most comprehensive report to date on the economic impact of AMR in Canada

The bashful and the boastful : prestigious leaders and social change in Mesolithic Societies

The creation and maintenance of influential leaders and authorities is one of the key themes of archaeological and historical enquiry. However the social dynamics of authorities and leaders in the Mesolithic remains a largely unexplored area of study. The role and influence of authorities can be remarkably different in different situations yet they exist in all societies and in almost all social contexts from playgrounds to parliaments. Here we explore the literature on the dynamics of authority creation, maintenance and contestation in egalitarian societies, and discuss the implications for our interpretation and understanding of the formation of authorities and leaders and changing social relationships within the Mesolithic

The Death Effector Domains of Caspase-8 Induce Terminal Differentiation

The differentiation and senescence programs of metazoans play key roles in regulating normal development and preventing aberrant cell proliferation, such as cancer. These programs are intimately associated with both the mitotic and apoptotic pathways. Caspase-8 is an apical apoptotic initiator that has recently been appreciated to coordinate non-apoptotic roles in the cell. Most of these functions are attributed to the catalytic domain, however, the amino-terminal death effector domains (DED)s, which belong to the death domain superfamily of proteins, can also play key roles during development. Here we describe a novel role for caspase-8 DEDs in regulating cell differentiation and senescence. Caspase-8 DEDs accumulate during terminal differentiation and senescence of epithelial, endothelial and myeloid cells; genetic deletion or shRNA suppression of caspase-8 disrupts cell differentiation, while re-expression of DEDs rescues this phenotype. Among caspase-8 deficient neuroblastoma cells, DED expression attenuated tumor growth in vivo and proliferation in vitro via disruption of mitosis and cytokinesis, resulting in upregulation of p53 and induction of differentiation markers. These events occur independent of caspase-8 catalytic activity, but require a critical lysine (K156) in a microtubule-binding motif in the second DED domain. The results demonstrate a new function for the DEDs of caspase-8, and describe an unexpected mechanism that contributes to cell differentiation and senescence

Involvement of Noradrenergic Neurotransmission in the Stress- but not Cocaine-Induced Reinstatement of Extinguished Cocaine-Induced Conditioned Place Preference in Mice: Role for β-2 Adrenergic Receptors

The responsiveness of central noradrenergic systems to stressors and cocaine poses norepinephrine as a potential common mechanism through which drug re-exposure and stressful stimuli promote relapse. This study investigated the role of noradrenergic systems in the reinstatement of extinguished cocaine-induced conditioned place preference by cocaine and stress in male C57BL/6 mice. Cocaine- (15 mg/kg, i.p.) induced conditioned place preference was extinguished by repeated exposure to the apparatus in the absence of drug and reestablished by a cocaine challenge (15 mg/kg), exposure to a stressor (6-min forced swim (FS); 20–25°C water), or administration of the α-2 adrenergic receptor (AR) antagonists yohimbine (2 mg/kg, i.p.) or BRL44408 (5, 10 mg/kg, i.p.). To investigate the role of ARs, mice were administered the nonselective β-AR antagonist, propranolol (5, 10 mg/kg, i.p.), the α-1 AR antagonist, prazosin (1, 2 mg/kg, i.p.), or the α-2 AR agonist, clonidine (0.03, 0.3 mg/kg, i.p.) before reinstatement testing. Clonidine, prazosin, and propranolol failed to block cocaine-induced reinstatement. The low (0.03 mg/kg) but not high (0.3 mg/kg) clonidine dose fully blocked FS-induced reinstatement but not reinstatement by yohimbine. Propranolol, but not prazosin, blocked reinstatement by both yohimbine and FS, suggesting the involvement of β-ARs. The β-2 AR antagonist ICI-118551 (1 mg/kg, i.p.), but not the β-1 AR antagonist betaxolol (10 mg/kg, i.p.), also blocked FS-induced reinstatement. These findings suggest that stress-induced reinstatement requires noradrenergic signaling through β-2 ARs and that cocaine-induced reinstatement does not require AR activation, even though stimulation of central noradrenergic neurotransmission is sufficient to reinstate