Oxygen-poor Environments Research Articles

Solution-processed wide band gap transparent conducting Sr0.94La0.06SnO3 films

Pseudo-cubic perovskite La-doped SrSnO3 has been proposed as a promising alternative for ultra-violet (UV) transparent conductors due to its favorable electrical transport properties and UV transparency. However, the difficulty in fabricating large-size La-doped SrSnO3 films with high electrical mobility continues to hinder the development of practical applications. In this work, Sr0.94La0.06SnO3 (SLSO) thin films with wide bandgap of ∼4.5 eV were fabricated by using solution deposition route. Emphasis was placed on creating oxygen-poor environments and selecting appropriate post-annealing temperatures, which were determined based on the kinetic energy of relevant defects and second-phase impurities. Post-annealing treatment was applied to refine the microstructure and enhance electrical transport properties. As a result, a relatively high carrier mobility of 25.9 cm2 V−1 s−1 and a low resistivity of 1.15 mΩ cm at a carrier concentration of 2.08 × 1020 cm−3 were achieved. Enhanced electrical properties were attributed to the increased presence of oxygen vacancies, as confirmed by electron paramagnetic resonance results. This study presents a straightforward approach for the production of large-scale epitaxial UV transparent conducting SLSO thin films.

The Impact of Annealing Methods on the Encapsulating Structure and Storage-Stability of Freeze-Dried Pellets of Probiotic Bacteria

ObjectiveThis paper investigates the critical role of material thickness in freeze-dried pellets for enhancing the storage stability of encapsulated bacteria. Freeze dried material of varying thicknesses obtained from different annealing durations is quantified using Scanning Electron Microscopy (SEM) and X-ray microtomography (μCT), the material thickness is then correlated to the storage stability of the encapsulated cells.MethodsA formulation comprising of sucrose, maltodextrin, and probiotic cells is quenched in liquid nitrogen to form pellets. The pellets undergo different durations of annealing before undergoing freeze-drying. The material thickness is quantified using SEM and μCT. Storage stability in both oxygen-rich and oxygen-poor environments is evaluated by measuring CFU counts and correlated with the pellet structure.ResultsThe varying annealing protocols produce a range of material thicknesses, with more extensive annealing resulting in thicker materials. Storage stability exhibits a positive correlation with material thickness, indicating improved stability with thicker materials. Non-annealed pellets exhibit structural irregularities and inconsistent storage stability, highlighting the impracticality of avoiding annealing in the freeze-drying process.ConclusionsExtensive annealing not only enhances the storage stability of probiotic products but also provides greater control over the freeze-drying process, ensuring homogeneous and reproducible products. This study underscores the importance of material thickness in freeze-dried pellets for optimizing storage stability for probiotic formulations, and emphasize the necessity of annealing as a critical step in freeze-drying quenched pellets to achieve desired structural and stability outcomes.

Stability of Pt1/CeO2 single-atom catalyst in oxygen-poor environments: first-principles insights

Due to its exceptional oxygen storage/release capabilities, excellent catalytic activity, and selectivity, the single-atom Pt1/CeO2 catalyst has demonstrated significant research prospects and development promise in fuel cell applications. Investigating how the Pt1/CeO2 system behaves in oxygen-poor environments has become a focal point of current research. In the present work, the formation of oxygen vacancies as well as their impact on the stability of Pt adsorption in different Pt1/CeO2 systems under oxygen-poor conditions is systematically investigated. The research findings indicate that the ease of oxygen vacancy formation is primarily dictated by the structure of the Pt1/CeO2 system, with a higher propensity in low-stability systems (PtOB/CeO2, PfCeT/CeO2, PtOT/CeO2). Oxygen vacancies tend to form away from Pt positions (at the 2NN positions). Oxygen-poor and high-temperature environments promote the formation of oxygen vacancies in Pt1/CeO2 systems. Furthermore, in low-stability systems, oxygen vacancies, through adjustments to the system’s electronic structure, such as increasing the quantity of Ce3+ polarons and the transferred charge amount of Pt atoms, significantly enhance the adsorption strength of Pt atoms. This study aims to offer new insights and avenues for the design of fuel cell catalysts, promoting practical applications and development in fuel cells.

Abstract A032: Low non-immune stromal cell levels and high hypoxic tumor microenvironments are associated with pathologic complete response in the neoadjuvant I-SPY2 TRIAL

Abstract Background: Non-immune components of the tumor microenvironment (TME) play important roles in cancer. We explore two important components of the TME: non-immune stromal cell populations including fibroblasts, adipocytes, and endothelial cells; and hypoxic conditions. We leverage published gene expression-based biomarkers of stromal cell types and hypoxia, and molecular and clinical data from the I-SPY2 TRIAL (PMID: 35623341) – an adaptive neoadjuvant trial for locally advanced breast cancers. We assess the contribution of stromal cell populations and oxygen-poor environments at pre-treatment in shaping the landscape of immune enrichment and therapeutic response in breast cancers. Methods: We curated 14 stromal and 11 hypoxia gene sets, in addition to 35 immune gene sets from literature. Signatures scores of stromal, hypoxic, and immune TME were calculated from gene expression profiles of pre-treatment tumor samples from I-SPY2 patients (n=987) in the first 9 treatment arms of the trial plus control arms. Correlation of stromal and hypoxia signatures with immune signatures were assessed, and association of TME features with HER2/HR receptor status, I-SPY response-predictive subtype (RPS), and pathological complete response (pCR) were evaluated using non-parametric tests. All p-values were adjusted for multiple testing. Significance levels were defined at adj. p<0.05. Results: Both stromal and hypoxia signatures showed significant differential enrichment across HR/HER2 and RPS subtypes, and association with pCR. Several stromal signatures including adipocytes, endothelial cells, mesenchymal stem cells, and overall stromal score had the lowest enrichment in HR-/HER2- breast cancers, and in the RPS HER2-/immune+ subtype. Moreover, most stromal signatures showed anti-correlation with CD8+ and CD4+ T cell enrichment. Stromal signatures including endothelial cells, smooth muscle cells, and overall score were significantly lower in patients who achieved pCR. Two hypoxia gene sets demonstrated highly significant enrichment in HR- versus HR+ samples regardless of HER2 status. All hypoxia signatures varied significantly across RPS subtypes, with the highest scores in HER2-/Immune-/DRD+, especially relative to HER2-/Immune-/DRD- and HER2+/BP-Luminal subtypes. Hypoxia signatures strongly linked to hypoxia inducible factor (HIF) and angiogenesis via VEGF were positively associated with pCR. These hypoxia signatures showed treatment-specific associations with pCR, specifically in agents targeting mechanisms with known interactions with hypoxia-induced biology: trebananib (angiogenesis inhibitor), ganetespib (HSP90 inhibitor) and veliparib/carboplatin (DNA damage repair inhibitor). Conclusions: Hypoxia and stromal cell gene signatures show breast cancer subtype-specific biology. Relative absence of non-immune stromal cell types is associated with higher immune infiltration and higher pCR rates, while specific hypoxia pathways were associated with response to therapeutic agents targeting hypoxia-related pathways. Citation Format: Kailey Dubinsky, Elene Tsopurashvili, Denise M. Wolf, Zheyun Xu, Silver Al Khafaji Alkhafaji, Anna van Montfort, Christina Yau, Diane Heditsian, Allison Fiscalini, Laura J. Esserman, Laura van ‘t Veer, Rosalyn W. Sayaman. Low non-immune stromal cell levels and high hypoxic tumor microenvironments are associated with pathologic complete response in the neoadjuvant I-SPY2 TRIAL [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A032.

Study on flame retardancy of EPDM reinforced by ammonium polyphosphate.

Currently, the most widely used material for solid rocket motor (SRM) insulation is ethylene propylene diene monomer (EPDM) filled with flame-retardant and ablation-resistant fillers. Researchers have been working hard to find a flame-retardant filler that can simultaneously meet the complex requirements of mechanical strength, density, flame retardancy and ablative performance of the insulation layer. This requires research on the flame retardant properties of flame retardants in oxygen-poor environments. In this paper, ammonium polyphosphate (APP) is used as a flame retardant filler, which is filled into an EPDM premix (p-EPDM) containing fumed silica and aluminum hydroxide to prepare composite materials. By creating an anoxic environment, the flame retardant behavior of APP under anoxic conditions on EPDM was studied. The results show that composites prepared with APP show better flame retardant properties in tests such as limiting oxygen index and UL-94, with less impact on mechanical strength and density. The surface morphology and elemental composition of the composite combustion residues were studied using Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). In an oxygen-depleted environment, APP will thermally decompose to form ammonia, water vapor and phosphorus-containing acidic substances. These gases dilute the flammable gas and reduce the thermal conductivity. The acidic substances containing phosphorus are concentrated on the surface of the pyrolysis layer to promote the formation of the carbon layer. This provides guidance for us to design insulation layer materials with properties that are more in line with actual use requirements.

Anaerobic pathogens associated with OSA may contribute to pathophysiology via amino-acid depletion

The human microbiome is linked to multiple metabolic disorders such as obesity and diabetes. Obstructive sleep apnoea (OSA) is a common sleep disorder with several metabolic risk factors. We investigated the associations between the gut microbiome composition and function, and measures of OSA severity in participants from a prospective community-based cohort study: the Hispanic Community Health Study/Study of Latinos (HCHS/SOL). Bacterial-Wide Association Analysis (BWAS) of gut microbiome measured via metagenomics with OSA measures was performed adjusting for clinical, lifestyle and co-morbidities. This was followed by functional analysis of the OSA-enriched bacteria. We utilized additional metabolomic and transcriptomic associations to suggest possible mechanisms explaining the microbiome effects on OSA. Several uncommon anaerobic human pathogens were associated with OSA severity. These belong to the Lachnospira, Actinomyces, Kingella and Eubacterium genera. Functional analysis revealed enrichment in 49 processes including many anaerobic-related ones. Severe OSA was associated with the depletion of the amino acids glycine and glutamine in the blood, yet neither diet nor gene expression revealed any changes in the production or consumption of these amino acids. We show anaerobic bacterial communities to be a novel component of OSA pathophysiology. These are established in the oxygen-poor environments characteristic of OSA. We hypothesize that these bacteria deplete certain amino acids required for normal human homeostasis and muscle tone, contributing to OSA phenotypes. Future work should test this hypothesis as well as consider diagnostics via anaerobic bacteria detection and possible interventions via antibiotics and amino-acid supplementation. Described in methods.

Stability and mixing behavior of vanadium-iron oxide monolayers on Pt(111) and Ru(0001) substrates

Cation mixing is a well-recognized means to obtain oxides of desired functionality with predetermined structure and stoichiometry, which yet has been only little analyzed at the nanoscale. In this context, we present a comparative analysis of the stability and mixing properties of O-poor and O-rich two-dimensional V–Fe oxides grown on Pt(111) and Ru(0001) surfaces, with the aim of gaining an insight into the role of substrate and oxygen conditions on the accessible Fe contents. We find that due to the high oxygen affinity of the Ru substrate, the mixed O-rich layers are highly stable while the stability of O-poor layers is limited to inaccessibly oxygen-poor environments. In contrast, on the Pt surface, O-poor and O-rich layers coexist with, however, a much lower Fe content in the O-rich phase. We show that cationic mixing (formation of mixed V–Fe pairs) is favored in all considered systems. It results from local cation–cation interactions, reinforced by a site effect in O-rich layers on the Ru substrate. In O-rich layers on Pt, Fe–Fe repulsion is so large that it precludes the possibility of substantial Fe content. These findings highlight the subtle interplay between structural effects, oxygen chemical potential, and substrate characteristics (work function and affinity towards oxygen), which governs the mixing of complex 2D oxide phases on metallic substrates.

Integrating taphonomy and facies analysis to assess the palaeoecology of Oligocene Kuphus-beds (Prebetic, Southeastern Spain)

ABSTRACT Kuphus is a genus of teredinid bivalves whose modern counterpart, K. polythalamius, colonises oxygen-poor and restricted marine environments enriched in plant remains. In the Oligocene, Kuphus colonies are quite abundant worldwide, but their depositional setting has never been studied in detail. We describe the first report of Oligocene Kuphus beds from the Iberian Peninsula, cropping out in platform deposits of the Prebetic (Southeastern Spain). By means of anterior endings and taphonomic characters as orientation of Kuphus tubes, fragmentation, packing and mixing with other fauna, four skeletal concentrations were distinguished: SkC A represents in situ colonies with anterior endings well preserved and with local dolomitisation around the tubes and was recorded in the inner lagoon; SkC B, with parallel and horizontally reoriented tubes, was formed by tidal currents; SkC C records high-energy events breaking down the tubes and resedimenting them close to the source area; SkC D is characterised by fragmented tubes mixed with other bioclasts, deposited by storms in the outer platform. The recorded skeletal concentrations are consistent with the environmental setting of K. polythalamius, but the morphological differences and the absence of data on the presence of plant remains could possibly reflect adaptations to higher variety of palaeoenvironments.

Quantitative PCR reveals the frequency and distribution of 3 indigenous yeast species across a range of specialty cheeses.

Indigenous microorganisms are important components of the complex ecosystem of many dairy foods including cheeses, and they are potential contributors to the development of a specific cheese's sensory properties. Among these indigenous microorganisms are the yeasts Cyberlindnera jadinii, Pichia kudriavzevii, and Kazachstania servazzii, which were previously detected using traditional microbiological methods in both raw milk and some artisanal specialty cheeses produced in the province of Québec, Canada. However, their levels across different cheese varieties are unknown. A highly specific and sensitive real-time quantitative PCR assay was developed to quantitate these yeast species in a variety of specialty cheeses (bloomy-rind, washed-rind, and natural-rind cheeses from raw, thermized, and pasteurized milks). The specificity of the quantitative PCR assay was validated, and it showed no cross-amplification with 11 other fungal microorganisms usually found in bloomy-rind and washed-rind cheeses. Cyberlindnera jadinii and P. kudriavzevii were found in the majority of the cheeses analyzed (25 of 29 and 24 of 29 cheeses, respectively) in concentrations up to 104 to 108 gene copies/g in the cheese cores, which are considered oxygen-poor environments, and 101 to 104 gene copies/cm2 in the rind. However, their high abundance was not observed in the same samples. Whereas C. jadinii was present and dominant in all core and rind samples, P. kudriavzevii was mostly present in cheese cores. In contrast, K. servazzii was present in the rinds of only 2 cheeses, in concentrations ranging from 101 to 103 gene copies/cm2, and in 1 cheese core at 105 gene copies/g. Thus, in the ecosystems of specialty cheeses, indigenous yeasts are highly frequent but variable, with certain species selectively present in specific varieties. These results shed light on some indigenous yeasts that establish during the ripening of specialty cheeses.

The Effects of Hypoxia on Threshold Food Concentrations in Different Daphnia Species

Numerous studies have revealed a negative correlation between the body size and temperature among a variety of aquatic ectotherms. Many studies at individual and population levels indicated that this mechanism may be explained by the decrease of competitive abilities of larger- over smaller-bodied individuals, as the production of larger-bodied individuals is more limited due to greater susceptibility to decreased oxygen concentrations (i.e., environmental hypoxia) at elevated temperatures. However, this hypothesis is still not tested at the community level. To test this, we performed several experiments on the food thresholds (which is a proxy for competitive ability) of 6 zooplankton (Daphnia) species varying in body size, at high or low oxygen concentrations. Contrary to the hypothesis tested, hypoxia increased threshold food concentrations to a relatively greater extent in smaller species than in larger ones. This may be attributed to the better evolutionary adaptations of larger-bodied daphnids to oxygen-poor environments manifested in higher production of haemoglobin. The results obtained in this study cannot exclude the possibility that environmental hypoxia is responsible for the temperature-size pattern in aquatic ectotherms, as our experiments did not take into account the long-term energetic costs of expedited haemoglobin synthesis, which could shift size-dependent competitive power.

Improved thermodynamic stability and visible light absorption in Zr+X codoped (X = S, Se and Te) BaTiO3 photocatalysts: A first-principles study

Band gap tuning of titanium based perovskite oxides through chalcogen doping is an attractive avenue for realizing visible light driven photocatalysis for hydrogen production. Unfortunately, accommodating a chalcogen atom at an O-site of BaTiO3 is thermodynamically challenging owing to large differences in the atomic radii and electronegativities of oxygen and chalcogen atoms. In the present study we employ first-principles density functional theory calculations to examine the influence of Zr codoping on the structural, thermodynamic, opto-electronic properties and photocatalytic performance of X-doped (X = S, Se and Te) BaTiO3 systems. The atomic structure and energetic properties are computed using SCAN meta-GGA functional of density functional theory, while the electronic and optical properties are computed using the TB-mBJ meta-GGA potential functional. Within the valid limits of the atomic chemical potentials, we find that chalcogen doping in BaTiO3 lattice would be experimentally difficult despite a clear reduction in the electronic band gap of this system useful for application in visible light driven photocatalysis. In order to improve the synthesis feasibility of X-doped BaTiO3 under oxygen-rich as well as oxygen-poor chemical environments, we propose Zr as a codopant at a Ti-site in X-doped BaTiO3 which improves the thermodynamic stability and also retains the reduction in the electronic band gap of cubic BaTiO3 caused by the presence of chalcogen atom. Our results suggest that Zr+X (X = S, Se and Te) codoped BaTiO3 offer great opportunities as practical photocatalysts for hydrogen production through overall splitting of the water molecule.

Central-line associated bloodstream infections secondary to strict anaerobes: Time for A definition change?

Background: Central-line–associated bloodstream infections (CLABSIs) arise from bacteria migrating from the skin along the catheter, by direct inoculation, or from pathogens that form biofilms on the interior surface of the catheter. However, given the oxygen-poor environments that obligate anaerobes require, these organisms are unlikely to survive long enough on the skin or on the catheter after direct inoculation to be the true cause of a CLABSI. Although some anaerobic CLABSIs may meet the definition for a mucosal-barrier-injury, laboratory-confirmed, bloodstream infection (MBI-LCBI), some may be not. We sought to determine the proportion of CLABSIs attributed to obligate anaerobic bacteria, and we sought to determine the pathophysiologic source of these infections. Methods: We performed a retrospective analysis of prospectively collected CLABSI data at 54 hospitals (academic and community) in the southeastern United States from January 2015 to December 2020. We performed chart reviews on a convenient sample for which medical records were available. We calculated the proportion of CLABSIs due to obligate anaerobes, and we have described a subset of anaerobic CLABSI cases. Results: We identified 60 anaerobic CLABSIs of 2,430 CLABSIs (2.5%). Of the 60 anaerobic CLABSIs, 7 were polymicrobial with nonanaerobic bacteria. The most common species we identified were Bacteroides, Clostridium, and Lactobacillus (Table 1). The proportion of anaerobic CLABSIs per year varied from 1.2% to 3.7% (Fig. 1). Of 60 anaerobic CLABSIs, 29 (48%) occurred in the only quaternary-care academic medical center in the database. In contrast, an average of 0.6 (SD, 0.6) anaerobic CLABSIs occurred in the 53 community hospitals over the 6-year study period. Of these 29 anaerobic CLABSIs, 23 (79%) were clinically consistent with secondary bloodstream infections (BSIs) due to gastrointestinal or genitourinary source, but they lacked appropriate documentation to meet NHSN criteria for secondary BSI or MBI-LCBI based on case reviews by infection prevention physicians. The other 6 anaerobic CLABSIs did not have a clear clinical etiology and did not meet MBI-LCBI criteria. In addition, 27 (93%) of 29 anaerobic CLABSIs occurred in patients who were either solid-organ transplant recipients, were stem-cell transplant recipients, or were receiving chemotherapy. Lastly, 27 (93%) of 29 anaerobic CLABSIs were treated with antibiotics. Conclusions: Anaerobic CLABSIs are uncommon events, but CLABSI may disproportionately affect large, academic hospitals caring for a high proportion of medically complex patients. Additional criteria could be added to the MBI-LCBI to better classify anaerobic BSI.Funding: NoneDisclosures: None

Metabolic Reconstruction Elucidates the Lifestyle of the Last Diplomonadida Common Ancestor.

The identification of ancestral traits is essential to understanding the evolution of any group. In the case of parasitic groups, this helps us understand the adaptation to this lifestyle and a particular host. Most diplomonads are parasites, but there are free-living members of the group nested among the host-associated diplomonads. Furthermore, most of the close relatives within Fornicata are free-living organisms. This leaves the lifestyle of the ancestor unclear. Here, we present metabolic maps of four different diplomonad species. We identified 853 metabolic reactions and 147 pathways present in at least one of the analyzed diplomonads. Our study suggests that diplomonads represent a metabolically diverse group in which differences correlate with different environments (e.g., the detoxification of arsenic). Using a parsimonious analysis, we also provide a description of the putative metabolism of the last Diplomonadida common ancestor. Our results show that the acquisition and loss of reactions have shaped metabolism since this common ancestor. There is a net loss of reaction in all branches leading to parasitic diplomonads, suggesting an ongoing reduction in the metabolic capacity. Important traits present in host-associated diplomonads (e.g., virulence factors and the synthesis of UDP-N-acetyl-d-galactosamine) are shared with free-living relatives. The last Diplomonadida common ancestor most likely already had acquired important enzymes for the salvage of nucleotides and had a reduced capacity to synthesize nucleotides, lipids, and amino acids de novo, suggesting that it was an obligate host-associated organism.IMPORTANCE Diplomonads are a group of microbial eukaryotes found in oxygen-poor environments. There are both parasitic (e.g., Giardia intestinalis) and free-living (e.g., Trepomonas) members in the group. Diplomonads are well known for their anaerobic metabolism, which has been studied for many years. Here, we reconstructed whole metabolic networks of four extant diplomonad species as well as their ancestors, using a bioinformatics approach. We show that the metabolism within the group is under constant change throughout evolutionary time, in response to the environments that the different lineages explore. Both gene losses and gains are responsible for the adaptation processes. Interestingly, it appears that the last Diplomonadida common ancestor had a metabolism that is more similar to extant parasitic than free-living diplomonads. This suggests that the host-associated lifestyle of parasitic diplomonads, such as the human parasite G. intestinalis, is an old evolutionary adaptation.

From yellow to silver: Transforming cranial morphology in European eel (Anguilla anguilla).

The European eel (Anguilla anguilla) has been extensively studied, especially because of its highly specialized migratory behaviour associated with substantial phenotypic transformations. During this migration, one of those transformations the eel undergoes is from yellow to silver eel, a process known as silvering. Although the cranial morphology during the earlier glass, elver and yellow eel stages are well studied, little is known about actual morphological changes during the transformation process from the yellow to the silver eel stage. Yet, literature suggests drastic changes in musculoskeletal anatomy. Here, we investigated the cranial musculoskeletal morphology of 11 male European eels at different stages during silvering, resulting both from natural and artificial maturation. Using 3D-reconstructed µCT data of the head, the skull and cranial muscles associated with jaw closing and respiration were studied. Eye size was used as a proxy for the silvering stage. Size-adjusted jaw muscle volumes increased during silvering, although insignificantly. Accordingly, a near-significant increase in bite force was observed. Respiratory muscles size did increase significantly during silvering, however. Considering the eel's long migration, which often includes deep and thus potentially oxygen-poor environments, having a better performing respiratory system may facilitate efficient migration. Both overall skull dimensions and specifically orbit size increased with eye index, suggesting they play a role in accommodating the enlarging eyes during silvering. Finally, artificially matured eels had a wider and taller skull, as well as larger jaw muscles than wild silver eels. This could be caused (a) by different conditions experienced during the yellow eel stage, which are maintained in the silver eel stage, (b) by side effects of hormonal injections or (c) be part of the maturation process as artificially induced silver eels had a higher eye index than the wild silver eels.

Surface structure and energetics of low index facets of bismuth ferrite.

Bismuth ferrite (BiFeO3) is a multiferroic material that has received significant interest due to its functional properties which could lead to potential novel applications in microelectronics, spintronics, and controlled catalytic reactions. Here, we provide the results of an extensive theoretical study to understand the surface structure and describe the energetics of differently terminated BiFeO3 surfaces. We specifically evaluate low index crystal facets and surface level atomic terminations via density functional theory and ab initio thermodynamics techniques. Our findings indicate that surface stability with varying terminations is strongly dependent on the oxygen partial pressure and chemical potentials of bismuth and iron. In oxygen rich environments, the results suggest that (100)-O and (110)-O and terminated surfaces are more stable compared to other surface terminations and facets. On the other hand, in a relatively oxygen poor environments, we observe that (110)-Bi and (110)-Fe are more stable. The calculations also show that the majority of BFO surfaces exhibit metallic behavior with the exception of the O-terminated (100) and (110) surfaces.

Archaeorhynchus preserving significant soft tissue including probable fossilized lungs

We describe a specimen of the basal ornithuromorph Archaeorhynchus spathula from the Lower Cretaceous Jiufotang Formation with extensive soft tissue preservation. Although it is the fifth specimen to be described, unlike the others it preserves significant traces of the plumage, revealing a pintail morphology previously unrecognized among Mesozoic birds, but common in extant neornithines. In addition, this specimen preserves the probable remnants of the paired lungs, an identification supported by topographical and macro- and microscopic anatomical observations. The preserved morphology reveals a lung very similar to that of living birds. It indicates that pulmonary specializations such as exceedingly subdivided parenchyma that allow birds to achieve the oxygen acquisition capacity necessary to support powered flight were present in ornithuromorph birds 120 Mya. Among extant air breathing vertebrates, birds have structurally the most complex and functionally the most efficient respiratory system, which facilitates their highly energetically demanding form of locomotion, even in extremely oxygen-poor environments. Archaeorhynchus is commonly resolved as the most basal known ornithuromorph bird, capturing a stage of avian evolution in which skeletal indicators of respiration remain primitive yet the lung microstructure appears modern. This adds to growing evidence that many physiological modifications of soft tissue systems (e.g., digestive system and respiratory system) that characterize living birds and are key to their current success may have preceded the evolution of obvious skeletal adaptations traditionally tracked through the fossil record.

Formation law of hydrocarbon index gases during coal spontaneous combustion in an oxygen-poor environment

ABSTRACTThe disaster of coal spontaneous combustion mainly occurs in a concealed oxygen-poor environment in the underground coal mine. The formation law of hydrocarbon index gases can accurately reflect the degree of coal spontaneous combustion. In this paper, the influence of oxygen-poor degree on the formation law of hydrocarbon index gases was investigated by the program heating experiment of coal spontaneous combustion in different oxygen-poor environments. The results reveal that the rising tendency of the alkane index gas volume fraction can be reduced by the increase in oxygen-poor degree. Olefin index gases can predict the disaster of coal spontaneous combustion more reliably than alkane index gases in the oxygen-poor environment. As the optimal predictive index of coal spontaneous combustion in the oxygen-poor environment, the volume fraction ratios of olefins to alkanes can be used which increase steadily with the oxygen-poor degree.

Space travel in a high-altitude environment: One more step in human BioSpaceForming

BACKGROUND: Currently, space programs use sea-level pressures (760 mmHg) and normoxia (21% oxygen fraction) in space capsules. When astronauts need to go for a spacewalk, the pressure has to be reduced to 1/3 that of sea level (240 mmHg). This implies that in order to avoid decompression sickness (DCS) and acute mountain sickness (AMS), complex and time-consuming procedures need to be carried out. Furthermore, space suits have to sustain such pressure and protect them from radiation. A cooling vest is also used in order to keep the body temperature within normal values. This makes the space suits very voluminous and hence with rigid structures in order to sustain the pressure in space. Astronauts suffer, among many other complex microgravity alterations, anemia, that upon return to sea level, has to be correspondingly normalized to preflight levels. The reason that anemia presents is in part due to a lower requirement of oxygen by orthostatic muscles in microgravity. Exercise in space, reduces bone and muscle wasting. Over 200 million high-altitude residents live above 2000 m (6560 ft) of altitude and have adapted perfectly to life in the mountains. They live their life as if they were at sea level. They reproduce and practice sports, all this with a higher hematocrit. They even have proved extended longevity. METHODS: The knowledge acquired during 47 years of medical practice at high altitude, is applied to a proposal for a most efficient capsule environment for the human exploration of space. RESULTS: A cabin pressure similar to the city of La Paz, Bolivia (495 mmHg), that is, 2/3 that of sea level (760 mmHg) would not only maintain the hematocrit for reentry, but furthermore, could significantly accelerate the preparation for extravehicular activity that currently takes up several hours. High-altitude residents can tolerate lower levels of oxygen (hypoxia) providing them with an advantage of survival in oxygen poor environments. We likewise propose that a lower pressure (149 mmHg) be used in space suits, making them more flexible and thereby reducing the risks of DCS and AMS. This implies only 346 mmHg in pressure difference, from space capsule to space suit, as compared to 520 mmHg in the current methodology. CONCLUSIONS: The laws of physics in relation to pressure changes cannot be broken. However, human biology with adaptation to lower pressures and lower levels of oxygen and carbon dioxide, which is the case of high-altitude residents, can reduce the pressure gap significantly. Thereby, biology breaks the limitations of the laws of physics. Space travel will always have hypoxia as a fundamental threat, hence a hypobaric, normoxic space capsule environment results beneficial, practical, and one more step in “BioSpaceForming” of human beings.

MicroRNAs regulate survival in oxygen-deprived environments

Some animals must endure prolonged periods of oxygen deprivation to survive. One such extreme model is the northern crayfish (Orconectes virilis), that regularly survives year-round hypoxic and anoxic stresses in its warm stagnant summer waters and in its cold, ice-locked winter waters. To elucidate the molecular underpinnings of anoxia resistance in this natural model, we surveyed the expression profiles of 76 highly conserved microRNAs in crayfish hepatopancreas and tail muscle from normoxic, acute 2 h anoxia, and chronic 20 h anoxia exposures. MicroRNAs are known to regulate a diverse array of cellular functions required for environmental stress adaptations, and here we explored their role in anoxia tolerance. The tissue-specific anoxia responses observed herein, with 22 anoxia-responsive microRNAs in the hepatopancreas and only four in muscle, suggest that microRNAs facilitate a reprioritization of resources to preserve crucial organ functions. Bioinformatic microRNA target enrichment analysis predicted that the anoxia-downregulated microRNAs in hepatopancreas targeted Hippo signalling, suggesting that cell proliferation and apoptotic signalling are highly regulated in this liver-like organ during anoxia. Compellingly, miR-125-5p, miR-33-5p and miR-190-5p, all known to target the master regulator of oxygen deprivation responses HIF1 (hypoxia inducible factor-1), were anoxia downregulated in the hepatopancreas. The anoxia-increased transcript levels of the oxygen-dependent subunit HIF1α highlight a potential critical role for miRNA-HIF targeting in facilitating a successful anoxia response. Studying the cytoprotective mechanisms in place to protect against the challenges associated with surviving in oxygen-poor environments is critical to elucidating the vast and substantial role of microRNAs in the regulation of metabolism and stress in aquatic invertebrates.

Metabolic properties of the osteoclast.

Osteoclasts are defined as cells capable of excavating 3-dimensional resorption pits in bone and other mineralised tissues. They are derived from the differentiation/fusion of promonocytic precursors, and are usually large, multinucleated cells. In common with other cells from this myeloid lineage such as macrophages and dendritic cells, they are adapted to function in hypoxic, acidic environments. The process of bone resorption is rapid and is presumably highly energy-intensive, since osteoclasts must actively extrude protons to dissolve hydroxyapatite mineral, whilst secreting cathepsin K to degrade collagen, as well as maintaining a high degree of motility. Osteoclasts are well known to contain abundant mitochondria but they are also able to rely on glycolytic (anaerobic) metabolism to generate the ATP needed to power their activity. Their primary extracellular energy source appears to be glucose. Excessive accumulation of mitochondrial reactive oxygen species in osteoclasts during extended periods of high activity in oxygen-poor environments may promote apoptosis and help to limit bone resorption - a trajectory that could be termed "live fast, die young". In general, however, the metabolism of osteoclasts remains a poorly-investigated area, not least because of the technical challenges of studying actively resorbing cells in appropriate conditions.