Volume and surface propellant heating in an electrothermal radio-frequency plasma micro-thruster

The temporal evolution of neutral gas temperature over the first 5 min of operation for an electrothermal radio-frequency micro-thruster with nitrogen (N2) propellant was measured using rovibrational band matching of the second positive N2 system. Three distinct periods of gas heating were identified with time constants of τ 1 = 8 × 10⁻⁵ s, τ 2 = 8 s, and τ 3 = 100 s. The fast heating (τ 1) is attributed to volumetric heating processes within the discharge driven by ion-neutral collisions. The slow heating (τ 3) is from ion neutralization and vibrational de-excitation on the walls creating wall heating. The intermediate heating mechanism (τ 2) is yet to be fully identified although some theories are suggested.This research was partially funded by the Australian Space Research Program (APT project) and the Australian Research Council Discovery Project (No. DP140100571)

Arf6 determines tissue architecture by stabilizing intercellular adhesion

Correct cell shape is indispensable for tissue architecture, with cell shape being determined by cortical actin and surface adhesion. The role of adhesion in remodeling tissue is to counteract the deformation of cells by force, resulting from actomyosin contractility, and to maintain tissue integrity. The dynamics of this adhesion is critical to the processes of cell shape formation and maintenance. Here, we show that the trafficking molecule, Arf6, has a direct impact on cell elongation, by acting to stabilize E-cadherin-based adhesion complexes at the cell surface, in addition to its canonical role in endocytosis. We demonstrate that these functions of Arf6 are dependent on the molecule Flotillin1, which recruits Arf6 to the plasma membrane. Our data suggest that Arf6 and Flotillin1 operate in a pathway distinct from clathrin-mediated endocytosis. Altogether, we demonstrate that Arf6- and Flotillin1-dependent regulation of the dynamics of cell adhesion contributes to molding tissue in vivo

Impactful Mentoring of Women Graduate Students: Guiding the Development of Leadership Behaviors

Women graduate students continue to express interest in developing as leaders and are looking to the university to provide support for this endeavor. In classroom discussions about leadership development, women graduate students indicate strong desire for professional mentoring for leadership development. Yet, there are no uniform ideas about what mentors should do or how mentors should support women graduate students. The need for mentoring is supported in the research literature. Bowling (2018) asserts that sustainable female leadership is best supported through mentorship. Bowling (2018) further explains that mentorship is a critical component of preparing women for the workplace and continued professional development. Impactful mentorship is positive, mutual and reciprocal (Ragins, 2011). Ragins (2011) recognized that expertise fluidity among mentoring partners influences the quality of the mentoring relationship. Johnson and Smith (2018) contend that mentoring is not about rescuing women but is about building positive structures in which women can grow and thrive. The purpose of this study is to explore perspectives of women graduate students about what mentoring is needed to guide leadership development

Dynamic pinning at a Py/Co interface measured using inductive magnetometry

Broadband FMR responses for metallic single-layer and bi-layer magnetic films with total thicknesses smaller than the microwave magnetic skin depth have been studied. Two different types of microwave transducers were used to excite and detect magnetization precession: a narrow coplanar waveguide and a wide microstrip line. Both transducers show efficient excitation of higher-order standing spin wave modes. The ratio of amplitudes of the first standing spin wave to the fundamental resonant mode is independent of frequency for single films. In contrast, we find a strong variation of the amplitudes with frequency for bi-layers and the ratio is strongly dependent on the ordering of layers with respect to a stripline transducer. Most importantly, cavity FMR measurements on the same samples show considerably weaker amplitudes for the standing spin waves. All experimental data are consistent with expected effects due to screening by eddy currents in films with thicknesses below the microwave magnetic skin depth. Finally, conditions for observing eddy current effects in different types of experiments are critically examined

Ultrathin epitaxial Fe films in vicinal GaAs(001): A study by spin-resolved photoelectron spectroscopy

Thin epitaxial Fe films have been grown on vicinal GaAs(001) substrates and their remanent magnetic properties and the degree of substrate atom diffusion investigated using synchrotron-based photoelectron spectroscopy. The vicinal Fe films, though exhibiting greater As diffusion than their singular homologues, displayed better film quality both from the structural and the magnetic points of view. The spin-resolved valence spectra of the vicinal films resemble those for crystalline bulk Fe at lower film thicknesses than for singular films

IFN-γ-producing CD4+ T cells promote experimental cerebral malaria by modulating CD8+ T cell accumulation within the brain.

It is well established that IFN-γ is required for the development of experimental cerebral malaria (ECM) during Plasmodium berghei ANKA infection of C57BL/6 mice. However, the temporal and tissue-specific cellular sources of IFN-γ during P. berghei ANKA infection have not been investigated, and it is not known whether IFN-γ production by a single cell type in isolation can induce cerebral pathology. In this study, using IFN-γ reporter mice, we show that NK cells dominate the IFN-γ response during the early stages of infection in the brain, but not in the spleen, before being replaced by CD4(+) and CD8(+) T cells. Importantly, we demonstrate that IFN-γ-producing CD4(+) T cells, but not innate or CD8(+) T cells, can promote the development of ECM in normally resistant IFN-γ(-/-) mice infected with P. berghei ANKA. Adoptively transferred wild-type CD4(+) T cells accumulate within the spleen, lung, and brain of IFN-γ(-/-) mice and induce ECM through active IFN-γ secretion, which increases the accumulation of endogenous IFN-γ(-/-) CD8(+) T cells within the brain. Depletion of endogenous IFN-γ(-/-) CD8(+) T cells abrogates the ability of wild-type CD4(+) T cells to promote ECM. Finally, we show that IFN-γ production, specifically by CD4(+) T cells, is sufficient to induce expression of CXCL9 and CXCL10 within the brain, providing a mechanistic basis for the enhanced CD8(+) T cell accumulation. To our knowledge, these observations demonstrate, for the first time, the importance of and pathways by which IFN-γ-producing CD4(+) T cells promote the development of ECM during P. berghei ANKA infection

Detection of peptidases in Trypanosoma cruzi epimastigotes using chromogenic and fluorogenic substrates

Detergent extracts of Trypanosoma cruzi epimastigotes catalysed the hydrolysis of a range of amino-acyl and peptidyl p-nitro-anilides and aminomethylcoumarins. At least three enzymes were detected that cleave Z-Phe-Arg-MCA. Two of these were optimally active at alkaline pH, the other at pH 4·0. Of the two enzymes with alkaline pH optima, one was a cysteine peptidase and was unable to cleave Bz-Arg-MCA readily, whilst the other cleaved Bz-Arg-MCA and was inhibited by diisopropyl fluorophosphate. The acidic enzyme was similar to cathespin L of other eukayrotes with respect to its pH profile, substrate-specificity and inhibitor-sensitivity. Evidence was presented that epimastigotes contain a cysteine-type dipeptidyl aminopeptidase, one or more aminopeptidases, and a serine peptidase that cleaves Boc-Ala-Ala-pNA. Digitonin solubilization of the activities from cells supports the hypothesis that the cathespin L-like enzyme and the dipeptidyl aminopeptidase are lysosomal, whilst the Bz-Arg-MCA hydrolase, the aminopeptidases and the Boc-Ala-Ala-pNA serine peptidase are cytosoli

Large Magellanic Cloud Planetary Nebula Morphology: Probing Stellar Populations and Evolution

Planetary Nebulae (PNe) in the Large Magellanic Cloud (LMC) offer the unique opportunity to study both the Population and evolution of low- and intermediate-mass stars, by means of the morphological type of the nebula. Using observations from our LMC PN morphological survey, and including images available in the HST Data Archive, and published chemical abundances, we find that asymmetry in PNe is strongly correlated with a younger stellar Population, as indicated by the abundance of elements that are unaltered by stellar evolution (Ne, Ar, S). While similar results have been obtained for Galactic PNe, this is the first demonstration of the relationship for extra-galactic PNe. We also examine the relation between morphology and abundance of the products of stellar evolution. We found that asymmetric PNe have higher nitrogen and lower carbon abundances than symmetric PNe. Our two main results are broadly consistent with the predictions of stellar evolution if the progenitors of asymmetric PNe have on average larger masses than the progenitors of symmetric PNe. The results bear on the question of formation mechanisms for asymmetric PNe, specifically, that the genesis of PNe structure should relate strongly to the Population type, and by inference the mass, of the progenitor star, and less strongly on whether the central star is a member of a close binary system.Comment: The Astrophysical Journal Letters, in press 4 figure

Congeneric predators fill discrete niches created by the relative abundances of their prey species

To what degree is niche partitioning driven by underlying patterns in resources such as food, rather than by competition itself? Do discrete niches exist? We address these questions in the context of Cooper's and Sharp-shinned Hawks, two broadly sympatric, North American, bird-eating raptors in the genus Accipiter. We find that the resource base, as quantified by body masses of birds at bird feeders, is approximately lognormal (smallest birds are most abundant), with lesser modes (peaks) in abundance at larger body mass. The predators appear to exploit peaks in the resource base, with Sharp-shinned Hawks focusing on small prey items (median of 26.5 g), and Cooper's Hawks taking prey from the two most abundant peaks (both the small body mass peak and a lesser peak at medium body mass ~90g). We tested the ability of citizen scientists to distinguish these notoriously similar species, and we determined the influence of potential false positive detections on our conclusions. We find that citizen scientists struggle to distinguish these predators from one another, and 18% of Cooper's Hawks were identified as Sharp-shinned Hawks, while 27% of Sharp-shinned Hawks were identified as Cooper's Hawks. Yet, simulations show that this uncertainty did not jeopardize our qualitative conclusions.Funding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: 1402506Data collected through the interactions add-on to Project FeederWatch. Eliot Miller tracks incoming observations, highlights unusual observations, and contacts contributors to confirm/refute such observations. This then is a cleaner and vetted version of the original FeederWatch interactions observations. User names, IDs, and email addresses are all stripped from the data

Breaking a species barrier by enabling hybrid recombination

Hybrid sterility maintains reproductive isolation between species by preventing them from exchanging genetic material1. Anti-recombination can contribute to hybrid sterility when different species' chromosome sequences are too diverged to cross over efficiently during hybrid meiosis, resulting in chromosome mis-segregation and aneuploidy. The genome sequences of the yeasts Saccharomyces cerevisiae and Saccharomyces paradoxus have diverged by about 12% and their hybrids are sexually sterile: nearly all of their gametes are aneuploid and inviable. Previous methods to increase hybrid yeast fertility have targeted the anti-recombination machinery by enhancing meiotic crossing over. However, these methods also have counteracting detrimental effects on gamete viability due to increased mutagenesis2 and ectopic recombination3. Therefore, the role of anti-recombination has not been fully revealed, and it is often dismissed as a minor player in speciation1. By repressing two genes, SGS1 and MSH2, specifically during meiosis whilst maintaining their mitotic expression, we were able to increase hybrid fertility 70-fold, to the level of non-hybrid crosses, confirming that anti-recombination is the principal cause of hybrid sterility. Breaking this species barrier allows us to generate, for the first time, viable euploid gametes containing recombinant hybrid genomes from these two highly diverged parent species