LM radar reflectivity simulation Final report

Ultrasonic simulation of lunar module radar reflectivit

Is the Yb2Ti2O7 pyrochlore a quantum spin ice?

We use numerical linked cluster (NLC) expansions to compute the specific heat, C(T), and entropy, S(T), of a quantum spin ice model of Yb2Ti2O7 using anisotropic exchange interactions recently determined from inelastic neutron scattering measurements and find good agreement with experimental calorimetric data. In the perturbative weak quantum regime, this model has a ferrimagnetic ordered ground state, with two peaks in C(T): a Schottky anomaly signalling the paramagnetic to spin ice crossover followed at lower temperature by a sharp peak accompanying a first order phase transition to the ferrimagnetic state. We suggest that the two C(T) features observed in Yb2Ti2O7 are associated with the same physics. Spin excitations in this regime consist of weakly confined spinon-antispinon pairs. We suggest that conventional ground state with exotic quantum dynamics will prove a prevalent characteristic of many real quantum spin ice materials.Comment: 8 pages (two-column), 9 figure

Semi-field evaluation of a volatile transfluthrin-based intervention reveals efficacy as a spatial repellent and evidence of other modes of action

Presently, the most common malaria control tools-i.e., long lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS)-are limited to targeting indoor biting and resting behaviors of Anopheles mosquito species. Few interventions are targeted towards malaria control in areas where transmission is driven or persists due to outdoor biting behaviors. This study investigated a volatile pyrethroid-based spatial repellent (VPSR) designed to bridge this gap and provide protection from mosquito bites in outdoor spaces. Southern Province, Zambia, is one such environment where outdoor biting is suspected to contribute to malaria transmission, where people are active in the evening in open-walled outdoor kitchens. This study assessed the VPSR in replica kitchens within a controlled semi-field environment. Endpoints included effects on mosquito host seeking, immediate and delayed mortality, deterrence, blood feeding inhibition, and fertility. Host-seeking was reduced by approximately 40% over the course of nightly releases in chambers containing VPSR devices. Mosquito behavior was not uniform throughout the night, and the modeled effect of the intervention was considerably higher when hourly catch rates were considered. These two observations highlight a limitation of this overnight semi-field design and consideration of mosquito circadian rhythms is recommended for future semi-field studies. Additionally, deterrence and immediate mortality were both observed in treatment chambers, with evidence of delayed mortality and a dose related response. These results demonstrate a primarily personal protective mode of action with possible positive and negative community effects. Further investigation into this primary mode of action will be conducted through a field trial of the same product in nearby communities

The pluripotency factor Nanog regulates pericentromeric heterochromatin organization in mouse embryonic stem cells.

An open and decondensed chromatin organization is a defining property of pluripotency. Several epigenetic regulators have been implicated in maintaining an open chromatin organization, but how these processes are connected to the pluripotency network is unknown. Here, we identified a new role for the transcription factor NANOG as a key regulator connecting the pluripotency network with constitutive heterochromatin organization in mouse embryonic stem cells. Deletion of Nanog leads to chromatin compaction and the remodeling of heterochromatin domains. Forced expression of NANOG in epiblast stem cells is sufficient to decompact chromatin. NANOG associates with satellite repeats within heterochromatin domains, contributing to an architecture characterized by highly dispersed chromatin fibers, low levels of H3K9me3, and high major satellite transcription, and the strong transactivation domain of NANOG is required for this organization. The heterochromatin-associated protein SALL1 is a direct cofactor for NANOG, and loss of Sall1 recapitulates the Nanog-null phenotype, but the loss of Sall1 can be circumvented through direct recruitment of the NANOG transactivation domain to major satellites. These results establish a direct connection between the pluripotency network and chromatin organization and emphasize that maintaining an open heterochromatin architecture is a highly regulated process in embryonic stem cells.We thank Ludovic Vallier for constitutive Nanog-EpiSC, Gabrielle Brons for 129S2 EpiSC, Prim Singh for H3K9me3 antibody, Maria Elena Torres Padilla for TALE-mClover and luciferase plasmids, Wellcome Trust Sanger Institute for pCyL43 plasmid and Andras Nagy for PB-TET and rtTA plasmids. We are grateful to David Oxley and Judith Webster Novo et al. for mass spectrometry support, Simon Walker for imaging support and Anne Segonds- Pichon for statistical advice. We thank Wolf Reik and Jon Houseley for comments on the manuscript and members of Wolf Reik’s group for helpful discussions. P.J.R.-G. is supported by the Wellcome Trust [WT093736], BBSRC [M022285] and the European Commission Network of Excellence EpiGeneSys [HEALTH-F4-2010-257082]. The work was also supported with funds from the Canadian Institutes of Health Research to J.E. [Team Grant EPS-129129] and D.P.B.-J. D.P.B-J. holds the Canada Research Chair in Molecular and Cellular Imaging. I.C. is supported by the MRC

Regulation of neuraminidase expression in Streptococcus pneumoniae

The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2180/12/200 Extent: 12p.BackgroundSialic acid (N-acetylneuraminic acid; NeuNAc) is one of the most important carbohydrates for Streptococcus pneumoniae due of its role as a carbon and energy source, receptor for adhesion and invasion and molecular signal for promotion of biofilm formation, nasopharyngeal carriage and invasion of the lung.ResultsIn this work, NeuNAc and its metabolic derivative N-acetyl mannosamine (ManNAc) were used to analyze regulatory mechanisms of the neuraminidase locus expression. Genomic and metabolic comparison to Streptococcus mitis, Streptococcus oralis, Streptococcus gordonii and Streptococcus sanguinis elucidates the metabolic association of the two amino sugars to different parts of the locus coding for the two main pneumococcal neuraminidases and confirms the substrate specificity of the respective ABC transporters. Quantitative gene expression analysis shows repression of the locus by glucose and induction of all predicted transcriptional units by ManNAc and NeuNAc, each inducing with higher efficiency the operon encoding for the transporter with higher specificity for the respective amino sugar. Cytofluorimetric analysis demonstrated enhanced surface exposure of NanA on pneumococci grown in NeuNAc and ManNAc and an activity assay allowed to quantify approximately twelve times as much neuraminidase activity on induced cells as opposed to glucose grown cells.ConclusionsThe present data increase the understanding of metabolic regulation of the nanAB locus and indicate that experiments aimed at the elucidation of the relevance of neuraminidases in pneumococcal virulence should possibly not be carried out on bacteria grown in glucose containing media.Luciana Gualdi, Jasvinder Kaur Hayre, Alice Gerlini, Alessandro Bidossi, Leonarda Colomba, Claudia Trappetti, Gianni Pozzi, Jean-Denis Docquier, Peter Andrew, Susanna Ricci and Marco R Oggion

Understanding transmission and control of Cystic Echinococcosis and other taeniid infections in the Falkland Islands

Cystic echinococcosis, caused by the larval form of the cestode parasite Echinococcus granulosus, has been identified as an important public health risk in the Falkland Islands since the early 1940s. This prompted the instigation of an intensive control scheme in the mid-1960s, comprised of regular dosing of domestic dogs with the anthelmintic praziquantel and education of local people about safe disposal of potentially infected offal. This scheme has remained in place to the current day and is generally considered to be a successful programme– resulting in a reduction in the prevalence of infection in sheep has reduced from >50% in the 1950s to less than 1 % now and there has not been a case of human hydatid disease for more than 20 years. However, concerns remain that hydatid cysts are still identified in a small number of sheep at slaughter (0.004% in 2017) and occurring every year subsequently suggesting transmission is still occurring. This is also supported by the observation that sheep continue to be infected at higher levels with the (non-zoonotic) cestode Taenia hydatigena, also transmitted by dogs. In 2010, all dogs on the Falkland Islands were tested by Copro-PCR, resulting in eight dogs (1.4%) testing positive. The dog population was tested again in 2012, where there were no cases but when tested in 2014 by Coproantigen testing, six (1.04%) were positive for E. granulosus coproantigens. This project used questionnaires, coproantigen and coproPCR analysis, abattoir data surveillance, DNA sequencing, environmental sample analysis and mathematical modelling to study Echinococcus granulosus and other taeniids endemic in the Falklands and investigate how their continued transmission can occur in the face of the prolonged intensive control programme. A questionnaire survey identified possible methods of disposal of offal that in a previous study, were associated with canine coproantigen positivity. The entire dog population was analysed via coproantigen techniques in 2018, and four (0.68%) dogs were coproantigen positive, though none of these were confirmed by PCR. From 2018 to 2020, five cases of CE were identified in sheep at the Sand Bay abattoir in the Falklands (0.01%), with one of the cases coming from a positive farm in 2018. There were two cases from farms with positive dogs in 2010 and one from a farm with a positive dog in 2014. To investigate environmental contamination on farms and potentially identify historical dog infections, soil samples taken from kennel sites were analysed for the presence of coproantigens, with five farms having positive results, one farm matching with a positive dog in 2018. To identify key processes fuelling the transmission of E. granulosus in the Falklands, a mechanically informed compartmental model was created, estimating the basic reproduction number (R0) for the parasite, and identifying scenarios where this estimate increased above one suggesting continued transmission could occur. Seven scenarios where lapses in control measures could result in the R0 estimate increasing above one and continued transmission of E. granulosus could occur. The results of this project show clear evidence of dogs still being involved in the transmission of taeniid parasites in the Falklands, with key areas of the eradication programme such as the inadequate disposal of offal and dogs gaining access to offal allowing the transmission cycle to be completed and transmission of E. granulosus and other taeniids to occur. Rectifying these lapses in control measures and focussing control and surveillance to a more localised control approach will help strengthen the control programme and move the Falklands closer towards the complete eradication of Cystic Echinococcosis

Delineation of the visual pathway in paediatric optic pathway glioma patients using probabilistic tractography, and correlations with visual acuity

BACKGROUND: Radiological biomarkers which correlate with visual function are needed to improve the clinical management of optic pathway glioma (OPG) patients. Currently, these are not available using conventional magnetic resonance imaging (MRI) sequences. The aim of this study was to determine whether diffusion MRI could be used to delineate the entire optic pathway in OPG patients, and provide imaging biomarkers within this pathway which correlate with a patient's visual acuity (VA). METHODS: Multi-shell diffusion MRI data were acquired in a cohort of paediatric OPG patients, along with VA measurements in each eye. Diffusion MRI data were processed using constrained spherical deconvolution and probabilistic fibre tractography, to delineate the white matter bundles forming the optic pathway in each patient. Median fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were measured in the optic nerves, tracts, and radiations, and correlated against each patient's VA. RESULTS: In the optic nerves, median FA significantly correlated with VA (R2adj = 0.31, p = 0.0082), with lower FA associated with poorer vision. In the optic radiations, both lower FA and higher ADC were significantly associated with poorer vision (R2adj = 0.52, p = 0.00075 and R2adj = 0.50, p = 0.0012 respectively). No significant correlations between VA and either FA or ADC were found in the optic tracts. CONCLUSIONS: Multi-shell diffusion MRI provides in vivo delineation of the optic pathway in OPG patients, despite the presence of tumour invasion. This technique provides imaging biomarkers which are sensitive to microstructural damage to the underlying white matter in this pathway, which is not always visible on conventional MRI

Roadmap on exsolution for energy applications

Over the last decade, exsolution has emerged as a powerful new method for decorating oxide supports with uniformly dispersed nanoparticles for energy and catalytic applications. Due to their exceptional anchorage, resilience to various degradation mechanisms, as well as numerous ways in which they can be produced, transformed and applied, exsolved nanoparticles have set new standards for nanoparticles in terms of activity, durability and functionality. In conjunction with multifunctional supports such as perovskite oxides, exsolution becomes a powerful platform for the design of advanced energy materials. In the following sections, we review the current status of the exsolution approach, seeking to facilitate transfer of ideas between different fields of application. We also explore future directions of research, particularly noting the multi-scale development required to take the concept forward, from fundamentals through operando studies to pilot scale demonstrations