Unusual Environment Research Articles

SN 2021adxl: A luminous nearby interacting supernova in an extremely low-metallicity environment

SN 2021adxl is a slowly evolving, luminous, Type IIn supernova with asymmetric emission line profiles, similar to the well-studied SN 2010jl. We present extensive optical, near-ultraviolet, and near-infrared photometry and spectroscopy covering ∼1.5 years post discovery. SN 2021adxl occurred in an unusual environment, atop a vigorously star-forming region that is offset from its host galaxy core. The appearance of Lyα and O II, as well as the compact core, would classify the host of SN 2021adxl as a “Blueberry” galaxy, analogous to higher redshift, low-metallicity, star-forming dwarf “Green Pea” galaxies. Using several abundance indicators, we find a metallicity of the explosion environment of only ∼0.1 Z⊙, the lowest reported metallicity for a Type IIn SN environment. SN 2021adxl reaches a peak magnitude of Mr ≈ −20.2 mag and since discovery, SN 2021adxl has faded by only ∼4 magnitudes in the r band with a cumulative radiated energy of ∼1.5 × 1050 erg over 18 months. SN 2021adxl shows strong signs of interaction with a complex circumstellar medium, seen by the detection of X-rays, revealed by the detection of coronal emission lines, and through multi-component hydrogen and helium profiles. In order to further understand this interaction, we model the Hα profile using a Monte Carlo electron scattering code. The blueshifted high-velocity component is consistent with emission from a radially thin spherical shell resulting in the broad emission components due to electron scattering. Using the velocity evolution of this emitting shell, we find that the SN ejecta collide with circumstellar material of at least ∼5 M⊙ assuming a steady-state mass-loss rate of ∼4 − 6 × 10−3 M⊙ yr−1 for the first ∼200 days of evolution. SN 2021adxl was last observed to be slowly declining at ∼0.01 mag d−1, and if this trend continues, SN 2021adxl will remain observable after its current solar conjunction. Continuing the observations of SN 2021adxl may reveal signatures of dust formation or an infrared excess, similar to that seen for SN 2010jl.

Cosmological Inference from within the Peculiar Local Universe

The existence of ‘peculiar’ velocities due to the formation of cosmic structure marks a point of discord between the real universe and the usually assumed Friedmann–Lemaítre–Robertson–Walker metric, which accomodates only the smooth Hubble expansion on large scales. In the standard ΛCDM model framework, Type Ia supernovae data are routinely “corrected” for the peculiar velocities of both the observer and the supernova host galaxies relative to the cosmic rest frame, in order to infer evidence for acceleration of the expansion rate from their Hubble diagram. However, observations indicate a strong, coherent local bulk flow that continues outward without decaying out to a redshift z≳0.1, contrary to the ΛCDM expectation. By querying the halo catalogue of the Dark Sky Hubble-volume N-body simulation, we find that an observer placed in an unusual environment like our local universe should see correlations between supernovae in the JLA catalogue that are 2–8 times stronger than seen by a typical or Copernican observer. This accounts for our finding that peculiar velocity corrections have a large impact on the value of the cosmological constant inferred from supernova data. We also demonstrate that local universe-like observers will infer a downward biased value of the clustering parameter S8 from comparing the density and velocity fields. More realistic modelling of the peculiar local universe is thus essential for correctly interpreting cosmological data.

A new chemosymbiotic bivalve species of the genus Acharax Dall, 1908 (Bivalvia, Solemyida, Solemyidae) from the Haima cold seep of the South China Sea.

Solemyidae is an ancient group of protobranch bivalves that typically inhabit unusual environments, such as deep-sea chemosynthetic environments, and are symbiotic with chemoautotrophic and gill-hosted bacteria. In May 2018, a living solemyid bivalve was collected using a remotely operated vehicle at a depth of 1,390 m from the Haima cold seep in the northwestern slope of the South China Sea. Through a comprehensive taxonomic approach combining morphological observations and molecular phylogeny reconstruction of concatenated mitochondrial COI,16S rRNA and 18S rRNA gene sequences, a new species, Acharaxhaimaensissp. nov. is identified and described. The discovery of this new species contributes to the diversity of known solemyids in deep-sea chemosynthetic environments.

Eye infection risks from Pseudomonas aeruginosa via hand soap and eye drops.

Eye infections from bacterial contamination of bulk-refillable liquid soap dispensers and artificial tear eye drops continue to occur, resulting in adverse health outcomes that include impaired vision or eye enucleation. Pseudomonas aeruginosa (P. aeruginosa), a common cause of eye infections, can grow in eye drop containers and refillable soap dispensers to high numbers. To assess the risk of eye infection, a quantitative microbial risk assessment for P. aeruginosa was conducted to predict the probability of an eye infection for two potential exposure scenarios: (i) individuals using bacteria-contaminated eye drops and (ii) contact lens wearers washing their hands with bacteria-contaminated liquid soap prior to placing the lens. The median risk of an eye infection using contaminated eye drops and hand soap for both single and multiple exposure events (per day) ranged from 10-1 to 10-4, with contaminated eye drops having the greater risk. The concentration of P. aeruginosa was identified as the parameter contributing the greatest variance on eye infection risk; therefore, the prevalence and level of bacterial contamination of the product would have the greatest influence on health risk. Using eye drops in a single-use container or with preservatives can mitigate bacterial growth, and using non-refillable soap dispensers is recommended to reduce contamination of hand soap. Given the opportunistic nature of P. aeruginosa and its ability to thrive in unique environments, additional safeguards to mitigate bacterial growth and exposure are warranted.IMPORTANCEPseudomonas aeruginosa (P. aeruginosa) is a pathogen that can persist in a variety of unusual environments and continues to pose a significant risk for public health. This quantitative microbial risk assessment (QMRA) estimates the potential human health risks, specifically for eye infections, associated with exposure to P. aeruginosa in bacteria-contaminated artificial tear eye drops and hand soap. This study applies the risk assessment framework of QMRA to evaluate eye infection risks through both consumer products. The study examines the prevalence of this pathogen in eye drops and soap, as well as the critical need to implement measures that will mitigate bacterial exposure (e.g., single-use soap dispensers and eye drops with preservatives). Additionally, limitations and challenges are discussed, including the need to incorporate data regarding consumer practices, which may improve exposure assessments and health risk estimates.

The right stuff: Salutogenic and pathogenic responses over a year in Antarctica

IntroductionEver since the first human reached the South Pole, studies have sought to explore the impact of an isolated, confined, and unusual environment on human adaptation. The findings have highlighted both negative and salutogenic effects on crews. Although several studies have focused on adaptation in the polar regions, we still do not fully understand its mechanisms. Thus, the objectives of the present study are: (1) to investigate the impact of a one-year stay in Antarctica on health adaptation; and (2) to assess recovery from this experience two days later. MethodSeventeen healthy participants were recruited to stay for one year at the French Dumont d’Urville station in Antarctica. Psychological, physiological, and exteroceptive measures were recorded on the day of arrival at the station (baseline), during each quarter of the wintering season (M4, M7, M10, M12), and two days after the return to the continent (D+2). Subjects were allocated to two groups according to their scores on the General Health Questionnaire at baseline, as follows: very limited or no existence of minor non-psychiatric or psychotic disorders (higher than normal, HN); and standard values for non-psychiatric or minor psychotic disorders within the general population (ordinary range, OR). ResultsOur results highlight both an adaptative response during the winter months, and pathogenic states during the last quarter of the mission and at recovery (D+2), which are still below normal values for psychological disorders and stress. The analysis of OR and HN groups during overwintering highlights a decrease in psychosensory responses, and thus poorer adaptation. ConclusionSpending a year in Antarctica no longer has harmful consequences (except during the third quarter of the mission), and the harshness of the environment in midwinter does not seem to be an aggravating factor for the winterers included in this study. Nevertheless, the General Health Questionnaire indicates two levels of adaptation during the mission. The latter observation suggests that there is a need to select the most-adaptable crews to maintain high performance during overwintering, and to prepare for the return to the continent. Taken together, our results contribute to a better understanding of adaptation in extreme environments, notably future dark space exploration.

Arsenic biomineralization and selenium nanoparticles biosynthesis by Halomonas boliviensis strain H-10 isolated from the high-altitude Salar de Huasco salt flat (Chile)

High-altitude Andean wetlands of the Atacama Desert (Chile), including the Salar de Huasco salt flat, are unusual environments characterized by a great variability of physical-chemical conditions, often combined with a high concentration of heavy metals, including arsenic (As) and semimetals, such as selenium (Se). Microorganisms present in these environments evolved adaptative strategies to cope with environmental stresses, with biotechnological potentials. The present work investigated the natural bacterial community composition in sediments collected from the Salar de Huasco salt flat, by high-throughput Illumina sequencing, and to isolate bacterial strains able to remove As and biosynthesize Se nanoparticles (SeNPs). Dominant taxonomic groups (abundance ≥1%) were affiliated to Proteobacteria (mainly consisting in Delta- and Alfa- Gamma-proteobacteria) Bacteriodetes, Firmicutes, Acidobacteria, Spirochaetes, Deinococcus-Thermus, Gemmatimonadetes and Verrucomicrobia. Halomonas boliviensis strain H-10 was able to both biomineralize As and biosynthesise SeNPs; therefore, the characteristics of H. boliviensis strain H-10 could be used for biotechnological purposes, including As bioremediation from water and bioproduction of SeNPs.

The effect of urbanization and temperature on thermal tolerance, foraging performance, and competition in cavity-dwelling ants.

Human disturbance including rapid urbanization and increased temperatures can have profound effects on the ecology of local populations. Eusocial insects, such as ants, have adapted to stressors of increasing temperature and urbanization; however, these evolutionary responses are not consistent among populations across geographic space. Here we asked how urbanization and incubation temperature influence critical thermal maximum (CTmax) and various ecologically relevant behaviors in three ant species in urban and rural locations in Worcester, MA, USA. We did this by incubating colonies of three species of cavity dwelling ant (Aphaenogaster picea, Tapinoma sessile, and Temnothorax longispinosus) from 2 habitat types (Rural and Urban), for 60-days at multiple temperatures. We found that incubation temperature, urbanization, and species of ant all significantly affected overall colony critical thermal maximum. We also found that recruitment time, colonization time, and defense response were significantly affected by incubation temperature and varied between species of ant, while recruitment and colonization time were additionally affected by urbanization. These variable changes in performance and competitive traits across species suggest that responses to urbanization and shifting temperatures are not universal across species. Changes in behavioral responses caused by urbanization may disrupt biodiversity, creating unusual competitive environments as a consequence of natural adaptations and cause both direct and indirect mechanisms for which human disturbance can lead to local species extinction.

Using Element/Ca Response to Cleaning in Foraminifera From Endmember Depositional Environments to Infer Contaminants and Inform Pretreatment

AbstractPast ocean conditions are often reconstructed using the elemental composition of foraminiferal calcite. However, foraminiferal remains are often impacted by post‐depositional contaminants; thus, they require cleaning prior to element/Ca (El/Ca) analysis. To explore the impact of sample pretreatment on foraminiferal El/Ca ratios (Li, Na, Mg, Al, Mn, Fe, Zn, Sr, I, Ba, and U) we performed six cleaning procedures on four foraminifera populations from distinct depositional environments: Two from South Pacific carbonate ooze (ELT25‐11) and two from the hemi‐pelagic sediments of the California Margin (ODP1017E, SPR0901‐04BC). Despite differences in regional oceanography, sample type (i.e., surface‐ or deep‐dwelling planktic, benthic), and cleaning procedure, the main driver of El/Ca variability in the data set is the sedimentary depositional environment, suggesting site‐specific differences in element concentrations and contaminants. This finding challenges the notion that sample cleaning procedures should be informed by the El/Ca of paleoclimate interest, as elements may be found in different contaminants and/or elemental abundances in unique environments. Our data also show that traditional cleaning methods which use a combination of rinsing, sonication, oxidation/reduction, and complexation reactions effectively remove contaminants found on foraminifera in either depositional environment. However, even after contaminant removal, some elements (i.e., U and Fe) remain higher in California Margin foraminifera relative to South Pacific foraminifera. This suggests that the range of acceptable El/Ca values in the literature must be expanded when working with foraminifera from unusual depositional environments (i.e., hemipelagic, siliciclastic sites with high sedimentation regimes) versus values associated with more typical sites (i.e., a pelagic carbonate ooze).

Intracystic Malignant Adenomyoepithelioma of the Breast: A Case Report and Review of Literature

Adenomyoepithelioma (AME) of the breast is a rare neoplasm with a biphasic proliferation of epithelial and myoepithelial cells. The authors report an unusual case of AME of 51-year-old woman. The AME was located in a cystic structure 6 cm in diameter as a solid nodular lesion with 2cm size. Immunohistochemically, the nodule was comprised with 2 cell population of tubular structures. First population of the glandular epithelial cells with dark cytoplasm showed the activity of CK7(+), CAM5.2(+), CK5/6(partly +), p63(-), CD10(-), S-100(-), αSMA(-). Second population of outer myoepithelial cells with clear cytoplasm displayed the activity of p63(+), CD10(+), CK14(+) CK5/6 (partly +), CK7(weakly +), CAM5.2(weakly +), S-100(+), αSMA(+). Beside them, cellular cluster of the inner epithelial cells with prominent nuclear as well as cellular atypia, and atypical spindle cell proliferation emanating from the myoepithelial component were also present. Thus, the nodule was diagnosed as malignant AME. One year after the lumpectomy, pulmonal metastasis of the breast tumor was also found. So far as we are concerned, such case of intracystic malignant AME of the breast has never been described. Regarding histogenesis of the neoplasm growing under the unusual environment, a consideration with review of literature was done.

Unravelling molecular interaction of the uranyl(VI) complex with bovine serum albumin.

Interest in the biotoxicology of uranium resulting from its inherent radioactive as well as chemical properties has been growing intensely in recent years. Indeed, uranium in its stable form as UO22+ species is ubiquitously found on earth, and this form is commonly known as the uranyl(VI) ion. The unusual electronic environment at the core of the uranyl(VI) complex plays an important role in its interaction with biomacromolecules. Based on the spectroscopic and computational studies, we have explored the interaction of the uranyl(VI) complex with BSA. The results showed that the fluorescence intensity of BSA was quenched upon interaction with the uranyl(VI) complex largely through dynamic mode, which was authenticated by Stern-Volmer calculations and fluorescence lifetime measurements at different temperatures. Fluorescence anisotropy and synchronous fluorescence spectroscopy were performed to understand the micro-environments of the fluorophores. Furthermore, the binding constant, standard free energy and number of binding sites were also calculated. Thermodynamic parameters such as ΔH° and ΔS° revealed that the non-covalent interactions played a principal role in the binding of the uranyl(VI) complex to BSA, and the value of ΔG° indicated the spontaneity of the interaction. Using the site marker fluorescent probes, the binding location of the uranyl(VI) complex at the BSA site was established. This was further supported by the molecular docking technique with a docking free energy of -38.91 kJ mol-1, indicating the non-covalent binding of the uranyl(VI) complex with BSA active sites. This piece of work may contribute mostly to understanding the pharmacokinetics of the uranyl(VI) complex and provide fundamental data on its safe usage.

Revisiting the phosphonium salt chemistry for P-doped carbon synthesis: toward high phosphorus contents and beyond the phosphate environment.

The introduction of phosphorus and nitrogen atoms in carbo-catalysts is a common way to tune the electronic density, and thereby the reactivity, of the material, as well as to introduce surface reactive sites. Numerous environments are reported for the N atoms, but the P-doping chemistry is less explored and focuses on surface POx groups. A one-step synthesis of P/N-doped carbonaceous materials is presented here, using affordable and industrially available urea and tetrakis(hydroxymethyl)phosphonium chloride (THPC) as the N and P sources, respectively. In contrast to most of the synthetic pathways toward P-doped carbonaceous materials, the THPC precursor only displays P-C bonds along the carbon backbone. This resulted in unusual phosphorus environments for the materials obtained from direct thermal treatment of THPC-urea, presumably of type C-P-N according to 31P NMR and XPS. Alternatively, the in situ polymerization and calcination of the precursors were run in calcium chloride hydrate, used as a combined reaction medium and porogen agent. Following this salt-templating strategy led to particularly high phosphorus contents (up to 18 wt%), associated with porosities up to 600 m2 g-1. The so-formed P/N-doped porous materials were employed as metal-free catalysts for the mild oxidative dehydrogenation of N-heterocycles to N-heteroarenes at room temperature and in air.

Catalytic CO2 Reduction with Heptacoordinated Polypyridine Complexes: Switching the Selectivity via Metal Replacement.

The discovery of molecular catalysts for the CO2 reduction reaction (CO2 RR) in the presence of water, which are both effective and selective towards the generation of carbon-based products, is a critical task. Herein we report the catalytic activity towards the CO2 RR in acetonitrile/water mixtures by a cobalt complex and its iron analog both featuring the same redox-active ligand and an unusual seven-coordination environment. Bulk electrolysis experiments show that the cobalt complex mainly yields formate (52 % selectivity at an applied potential of -2.0 V vs Fc+ /Fc and 1 % H2 O) or H2 (up to 86 % selectivity at higher applied bias and water content), while the iron complex always delivers CO as the major product (selectivity >74 %). The different catalytic behavior is further confirmed under photochemical conditions with the [Ru(bpy)3 ]2+ sensitizer (bpy=2,2'-bipyridine) and N,N-diisopropylethylamine as electron donor, where the cobalt complex leads to preferential H2 formation (up to 89 % selectivity), while the iron analog quantitatively generates CO (up to 88 % selectivity). This is ascribed to a preference towards a metal-hydride vs. a metal-carboxyl pathway for the cobalt and the iron complex, respectively, and highlights how metal replacement may effectively impact on the reactivity of transition metal complexes towards solar fuel formation.

Modeling mate choice in a small-scale community: Applying couple simulation in the U.S. and Conambo, Ecuador

The near totality of human mate choice research occurs in large-scale, urban, industrial populations. It is unclear to what extent lessons learned from such populations reflect generalizable features of human mating psychology as opposed to localized responses to the demands of these historically unusual environments. Here, we use couple simulation, an agent-based modeling technique, to compare models of mate choice across both a U.S. sample (n = 1678) and a sample of k = 15 couples from Conambo, Ecuador—a relatively remote community of horticultural-foragers in the Ecuadorian Amazon. The Conambo sample provides a unique opportunity to evaluate models of mate choice in that (1) this sample represents approximately 50% of the households within this community and (2) all of the participants in this sample are acquainted with one another. Participants in Conambo completed a ranking task in which each participant ranked each opposite-sex adult in the community in terms of their quality as a spouse. We used these rankings to simulate the mating market in Conambo under alternative models of mate choice. We find that these models are able to reproduce Conambo marriages at a high degree of accuracy and perform comparably across both the Conambo sample and U.S. samples. Specifically, the resource allocation model performs best in reproducing mate choices in both the U.S. and Conambo samples. These results suggest that at least some aspects of human mating psychology generalize across both large-scale industrialized and small-scale populations.

Taxonomic characterization of Pseudomonas hygromyciniae sp. nov., a novel species discovered from a commercially purchased antibiotic.

In an attempt to identify novel bacterial species, microbiologists have examined a wide range of environmental niches. We describe the serendipitous discovery of a novel gram-negative bacterial species from a different type of extreme niche: a purchased vial of antibiotic. The vial of antibiotic hygromycin B was found to be factory contaminated with a bacterial species, which we designate Pseudomonas hygromyciniae sp. nov. The proposed novel species belongs to the P. fluorescens complex and is most closely related to P. brenneri, P. proteolytica, and P. fluorescens. The type strain Pseudomonas hygromyciniae sp. nov. strain SDM007T (SDM007T) harbors a novel 250 kb megaplasmid which confers resistance to hygromycin B and contains numerous other genes predicted to encode replication and conjugation machinery. SDM007T grows in hygromycin concentrations of up to 5 mg/mL but does not use the antibiotic as a carbon or nitrogen source. While unable to grow at 37°C ruling out its ability to infect humans, it grows and survives at temperatures between 4 and 30°C. SDM007T can infect plants, as demonstrated by the lettuce leaf model, and is highly virulent in the Galleria mellonella infection model but is unable to infect mammalian A549 cells. These findings indicate that commercially manufactured antibiotics represent another extreme environment that may support the growth of novel bacterial species. IMPORTANCE Physical and biological stresses in extreme environments may select for bacteria not found in conventional environments providing researchers with the opportunity to not only discover novel species but to uncover new enzymes, biomolecules, and biochemical pathways. This strategy has been successful in harsh niches such as hot springs, deep ocean trenches, and hypersaline brine pools. Bacteria belonging to the Pseudomonas species are often found to survive in these unusual environments, making them relevant to healthcare, food, and manufacturing industries. Their ability to survive in a variety of environments is mainly due to the high genotypic and phenotypic diversity displayed by this genus. In this study, we discovered a novel Pseudomonas sp. from a desiccated environment of a sealed antibiotic bottle that was considered sterile. A close genetic relationship with its phylogenetic neighbors reiterated the need to use not just DNA-based tools but also biochemical characteristics to accurately classify this organism.

An oversized, late-surviving reticulosan sponge from the Carboniferous of Ireland

Cyathophycus is one of the most widespread reticulosan sponges in Ordovician to Devonian rocks, but was mostly limited to the Iapetus region during the Ordovician and Silurian periods. Having an unfused skeleton, these sponges require an element of exceptional preservation (abrupt burial as a minimum) to enter the fossil record. Most species are a few centimetres in size, and found in muddy offshore environments. A new species of Cyathophycus, C. balori nov. sp., from the Kilkee Cyclothem of the Namurian Central Clare Group of County Clare, Ireland, substantially extends the stratigraphic range of the genus into the upper Palaeozoic. At more than 50 cm in height, the new species is the largest known Cyathophycus, and one of the largest reticulosan sponges. The sponges are found abundantly as monospecific assemblages in a particular band of laminated mudstone in prodelta cyclothem deposits. This unexpected discovery reveals a new component to Carboniferous prodeltaic ecosystems, and is further evidence that early sponge groups persisted in some unusual and marginal environments.

Early onset of heavy rainfall on the northern coast of Ecuador in the aftermath of El Niño 2015/2016

In January 2016, a high-precipitation event (HPE) affected northwestern Ecuador, leading to devastating flooding in the Esmeraldas River Basin. The HPE appeared in the aftermath of the 2015/16 El Niño as an early onset of heavy rainfalls, normally expected in the peak rainy season between March and April. We investigate the local HPE atmospheric setting and the regional “weather-within-climate” characteristics of the growing-season rainfall between December and January using gauge data, satellite imagery, and reanalysis. The unusual convective environment in late January 2016 involved local and synoptic drivers leading the development of a mesoscale convective complex (MCC) during the nighttime of 24th January. The genesis of the MCC was related to an early-arriving thermal weather state and orographic lifting; the Andean ranges acted as both a channel boosting upslope flow and convective updrafts and as a heavy rain divide for inner valleys. The synoptic controls were associated with 1) a southern boundary of the inter-tropical convergence zone, abnormally displaced to 4°N as response to the 2015/16 El Niño where eastward air surges merge upward vertical mass fluxes; 2) the arrival to the Ecuadorian coast of an equatorially propagating Kelvin wave; and 3) a low-mid level moisture influx coming from the Amazon associated with ascent due to changes in the Walker circulation. Lastly, we suggest that the convective environment in late January was also favored by cross-time-scale interference of the very strong El Niño event and a strong and persistent Madden-Julian oscillation (MJO) in the central Pacific.

Kinematics of Galactic Centre clouds shaped by shear-seeded solenoidal turbulence

ABSTRACT The Central Molecular Zone (CMZ; the central ∼500 pc of the Galaxy) is a kinematically unusual environment relative to the Galactic disc, with high-velocity dispersions and a steep size–linewidth relation of the molecular clouds. In addition, the CMZ region has a significantly lower star formation rate (SFR) than expected by its large amount of dense gas. An important factor in explaining the low SFR is the turbulent state of the star-forming gas, which seems to be dominated by rotational modes. However, the turbulence driving mechanism remains unclear. In this work, we investigate how the Galactic gravitational potential affects the turbulence in CMZ clouds. We focus on the CMZ cloud G0.253+0.016 (‘the Brick’), which is very quiescent and unlikely to be kinematically dominated by stellar feedback. We demonstrate that several kinematic properties of the Brick arise naturally in a cloud-scale hydrodynamics simulation, that takes into account the Galactic gravitational potential. These properties include the line-of-sight velocity distribution, the steepened size–linewidth relation, and the predominantly solenoidal nature of the turbulence. Within the simulation, these properties result from the Galactic shear in combination with the cloud’s gravitational collapse. This is a strong indication that the Galactic gravitational potential plays a crucial role in shaping the CMZ gas kinematics, and is a major contributor to suppressing the SFR, by inducing predominantly solenoidal turbulent modes.

Electric field-assisted fused filament fabrication process for robust additive manufacturing in unconventional orientations

Fused filament fabrication (FFF) is one of the most widely used thermoplastic additive manufacturing techniques that have great potential for numerous applications. However, for more advanced additive manufacturing with unusual environments, such as in-space manufacturing, conventional FFF is limited by the lack of gravity and inconsistent nozzle standoff distance. Varying nozzle standoff distances in the FFF process typically result in problems with the adhesion of extruded material as well as dimensional and geometrical errors in the extruded material, which leads to a long setup time and a high failure rate. Conventional FFF typically needs continuous monitoring or human intervention to ensure successful printing. This paper innovated an electric field-assisted FFF (E-FFF) process for robust fabricating parts in unconventional printing orientations while eliminating the need for constant supervision and human intervention to maintain and adjust the z-height calibration. The E-FFF system integrates a high-voltage power supply with a conventional FFF printer to produce an electrostatic force between the nozzle and the build plate. The generated electrostatic force is capable of attracting the extruded molten polymer material towards the build plate even at larger z-heights of up to 1200 μm under unconventional printing orientations. The effectiveness of the E-FFF process was demonstrated by comparing the E-FFF and conventional FFF processes. The results affirm the assistance of gravitational force on conventional FFF processes in the normal printing orientation. The novel E-FFF process with robust printing capabilities in the vertical and reverse orientations enables much larger nozzle standoff distances than that of the conventional FFF process, which exhibits great potential to be used in the micro/zero-gravity environment in the future. A two-dimensional finite element simulation model is used to understand the effects of applied voltage on the E-FFF process and calculate the electric field intensity. The simulation results showed that the electric field intensity of E = 1.27 × 106 V/m is sufficient for successful printing in all demonstrated printing orientations.

Stop contrast acquisition in child Kriol: Evidence of stable transmission of phonology post Creole formation.

Many Aboriginal Australian communities are undergoing language shift from traditional Indigenous languages to contact varieties such as Kriol, an English-lexified Creole. Kriol is reportedly characterised by lexical items with highly variable phonological specifications, and variable implementation of voicing and manner contrasts in obstruents (Sandefur, 1986). A language, such as Kriol, characterised by this unusual degree of variability presents Kriol-acquiring children with a potentially difficult language-learning task, and one which challenges the prevalent theories of acquisition. To examine stop consonant acquisition in this unusual language environment, we present a study of Kriol stop and affricate production, followed by a mispronunciation detection study, with Kriol-speaking children (ages 4-7) from a Northern Territory community where Kriol is the lingua franca. In contrast to previous claims, the results suggest that Kriol-speaking children acquire a stable phonology and lexemes with canonical phonemic specifications, and that English experience would not appear to induce this stability.

Topotactic Transition: A Promising Opportunity for Creating New Oxides

AbstractTopotactic transition is a structural phase change in a matrix crystal lattice mediated by the ordered loss/gain and rearrangement of atoms, leading to unusual coordination environments and metal atoms with rare valent states. As early as in 1990s, low temperature hydride reduction is utilized to realize the topotactic transition. Since then, topological transformations are developed via multiple approaches. Especially, the recent discovery of the Ni‐based superconductivity in infinite‐layer nickelates has greatly boosted the topotactic transition mean to synthesizing new oxides for exploring exotic functional properties. In this review, a detailed and generalized introduction is provided to oxygen‐related topotactic transition. The main body of the review includes four parts: the structure‐facilitated effects, the mechanism of the topotactic transition, some examples of topotactic transition methods adopted in different metal oxides (V, Mn, Fe, Co, Ni) and the related applications. This study is to provide timely and thorough strategies to successfully realize topotactic transitions for researchers who are eager to create new oxide phases or new oxide materials with desired functions.