Shock conditions recorded in NWA 8159 martian augite basalt with implications for the impact cratering history on Mars

NWA 8159 is an augite-rich martian basalt, formed by cooling of a relatively evolved, Ca-rich, Ti-poor and LREE-depleted lava, under relatively oxidizing conditions, during the early Amazonian. In addition to its distinct igneous petrogenesis and high fO_2, NWA 8159 is also set apart from most martian shergottites with respect to the low degree of shock metamorphism required to preserve crystalline igneous plagioclase (An_(50–65)). In this study, mineral transformations within and adjacent to shock veins in NWA 8159 were investigated using scanning electron microscopy, Raman spectroscopy and transmission electron microscopy to better constrain the unusal shock history of this meteorite. The transformation of olivine to ahrensite (Fe-ringwoodite) along shock vein margins, and tissintite and coesiteformed from igneous mineral (labradorite and silica) grains entrained as clasts within shock veins has been documented in this study. We report on a previously unidentified mineral assemblage of Ca-Na-majoritic garnet, sodic-clinopyroxene and stishovite crystallized from shock melt. This mineral assemblage indicates a crystallization pressure of approximately 16 GPa, which is within the range of previous shock pressure estimates for this meteorite (15–23 GPa). The presence of a majoritic garnet-bearing assemblage throughout veins up to 0.6 mm wide indicates that the sample remained at high-pressure throughout the melt vein quench. Based on thermal models, the sample must have remained at high pressure for ∼100 ms. This shock duration is an order of magnitude longer than those experienced by more highly shocked shergottites such as Tissint or Zagami (>30 GPa; 10–20 ms) and would seem to imply a relatively large impact event. Recent numerical models demonstrate that a range of shock pressures and durations are realized by rocks within the ejected spall zone of a hypervelocity impact. The shock conditions experienced by NWA 8159 therefore do not require an impact event distinct from other shergottites. Rather, our findings suggest that this meteorite originated from near the martian surface at the edge of the impact site. The shock history of NWA 8159 provides a picture of Mars consistent with that derived from remote observation; that of a random cratering process that samples a geologically long-lived and complex planet

How do tree species with different successional stages affect soil organic nitrogen transformations?

Organic nitrogen (N) is the most important N component of soil organic matter.However, knowledge on how tree species with different successional stages affect its transformations in soils remains limited. To address this issue, we sampled mineral soils (0−10 cm) in monocultures composed by tree species of different successional stages, including early (black alder and silver birch), early to mid (sycamore and European ash), and late (sweet chestnut, pedunculate oak and European beech), and measured the potential protease activity, the microbial uptake and respiration of 14C-labeled organic N (L-alanine and L-trialanine), and the mineralization of L-alanine N. The activities of alanine aminopeptidase and leucine aminopeptidase (153.8−341.9 and 91.6−147.9 nmol/g/h, respectively), the half-life of the uptake of alanine and trialanine (26.7−39.6 and 60.8−78.6 min, respectively), the half-life of the mineraliztion of alanine and trialanine (1.98−2.45 and 2.98−4.13 h, respectively) by soil microbes were altered by tree species of different successional stages, systematically changing the transformation chain of soil organic N. From trees of early successional stage to that of late, the turnover rates of soil organic N appeared to decrease and the half-life appeared to increase significantly. The (carbon) C:N ratio of soil microbial biomass was positively related to the half-life of 14Clabeled alanine and trialanine mineralization, and was negatively related to the C use efficiency of alanine, suggesting that microbial demand for C could partially drive the assimilation of soil organic N. Our results suggest that the successional stage of tree species play an important role in regulating the soil organic N turnover. An improved understanding of how tree species with different successional stages influence microbial function and soil organic N cycling is beneficial to future afforestation and forest management, alleviating the impacts of global change on the ecosystem

Soybean-derived Bowman-Birk inhibitor inhibits neurotoxicity of LPS-activated macrophages

<p>Abstract</p> <p>Background</p> <p>Lipopolysaccharide (LPS), the major component of the outer membrane of gram-negative bacteria, can activate immune cells including macrophages. Activation of macrophages in the central nervous system (CNS) contributes to neuronal injury. Bowman-Birk inhibitor (BBI), a soybean-derived protease inhibitor, has anti-inflammatory properties. In this study, we examined whether BBI has the ability to inhibit LPS-mediated macrophage activation, reducing the release of pro-inflammatory cytokines and subsequent neurotoxicity in primary cortical neural cultures.</p> <p>Methods</p> <p>Mixed cortical neural cultures from rat were used as target cells for testing neurotoxicity induced by LPS-treated macrophage supernatant. Neuronal survival was measured using a cell-based ELISA method for expression of the neuronal marker MAP-2. Intracellular reactive oxygen species (ROS) production in macrophages was measured via 2', 7'-dichlorofluorescin diacetate (DCFH₂DA) oxidation. Cytokine expression was determined by quantitative real-time PCR.</p> <p>Results</p> <p>LPS treatment of macrophages induced expression of proinflammatory cytokines (IL-1β, IL-6 and TNF-α) and of ROS. In contrast, BBI pretreatment (1-100 μg/ml) of macrophages significantly inhibited LPS-mediated induction of these cytokines and ROS. Further, supernatant from BBI-pretreated and LPS-activated macrophage cultures was found to be less cytotoxic to neurons than that from non-BBI-pretreated and LPS-activated macrophage cultures. BBI, when directly added to the neuronal cultures (1-100 μg/ml), had no protective effect on neurons with or without LPS-activated macrophage supernatant treatment. In addition, BBI (100 μg/ml) had no effect on N-methyl-D-aspartic acid (NMDA)-mediated neurotoxicity.</p> <p>Conclusions</p> <p>These findings demonstrate that BBI, through its anti-inflammatory properties, protects neurons from neurotoxicity mediated by activated macrophages.</p

Shock conditions recorded in NWA 8159 martian augite basalt with implications for the impact cratering history on Mars

NWA 8159 is an augite-rich martian basalt, formed by cooling of a relatively evolved, Ca-rich, Ti-poor and LREE-depleted lava, under relatively oxidizing conditions, during the early Amazonian. In addition to its distinct igneous petrogenesis and high fO_2, NWA 8159 is also set apart from most martian shergottites with respect to the low degree of shock metamorphism required to preserve crystalline igneous plagioclase (An_(50–65)). In this study, mineral transformations within and adjacent to shock veins in NWA 8159 were investigated using scanning electron microscopy, Raman spectroscopy and transmission electron microscopy to better constrain the unusal shock history of this meteorite. The transformation of olivine to ahrensite (Fe-ringwoodite) along shock vein margins, and tissintite and coesiteformed from igneous mineral (labradorite and silica) grains entrained as clasts within shock veins has been documented in this study. We report on a previously unidentified mineral assemblage of Ca-Na-majoritic garnet, sodic-clinopyroxene and stishovite crystallized from shock melt. This mineral assemblage indicates a crystallization pressure of approximately 16 GPa, which is within the range of previous shock pressure estimates for this meteorite (15–23 GPa). The presence of a majoritic garnet-bearing assemblage throughout veins up to 0.6 mm wide indicates that the sample remained at high-pressure throughout the melt vein quench. Based on thermal models, the sample must have remained at high pressure for ∼100 ms. This shock duration is an order of magnitude longer than those experienced by more highly shocked shergottites such as Tissint or Zagami (>30 GPa; 10–20 ms) and would seem to imply a relatively large impact event. Recent numerical models demonstrate that a range of shock pressures and durations are realized by rocks within the ejected spall zone of a hypervelocity impact. The shock conditions experienced by NWA 8159 therefore do not require an impact event distinct from other shergottites. Rather, our findings suggest that this meteorite originated from near the martian surface at the edge of the impact site. The shock history of NWA 8159 provides a picture of Mars consistent with that derived from remote observation; that of a random cratering process that samples a geologically long-lived and complex planet

Functional magnetic resonance imaging providing the brain effect mechanism of acupuncture and moxibustion treatment for depression

The efficacy of acupuncture and moxibustion in the treatment of depression has been fully recognized internationally. However, its central mechanism is still not developed into a unified standard, and it is generally believed that the central mechanism is regulation of the cortical striatum thalamic neural pathway of the limbic system. In recent years, some scholars have applied functional magnetic resonance imaging (fMRI) to study the central mechanism and the associated brain effects of acupuncture and moxibustion treatment for depression. This study reviews the acupuncture and moxibustion treatment of depression from two aspects: (1) fMRI study of the brain function related to the acupuncture treatment of depression: different acupuncture and moxibustion methods are summarized, the fMRI technique is elaborately explained, and the results of fMRI study of the effects of acupuncture are analyzed in detail, and (2) fMRI associated “brain functional network” effects of acupuncture and moxibustion on depression, including the effects on the hippocampus, the amygdala, the cingulate gyrus, the frontal lobe, the temporal lobe, and other brain regions. The study of the effects of acupuncture on brain imaging is not adequately developed and still needs further improvement and development. The brain function networks associated with the acupuncture treatment of depression have not yet been adequately developed to provide a scientific and standardized mechanism of the effects of acupuncture. For this purpose, this study analyzes in-depth the clinical studies on the treatment of anxiety and depression by acupuncture and moxibustion, by depicting how the employment of fMRI technology provides significant imaging changes in the brain regions. Therefore, the study also provides a reference for future clinical research on the treatment of anxiety and depression

Review: optical fiber sensors for civil engineering applications

Optical fiber sensor (OFS) technologies have developed rapidly over the last few decades, and various types of OFS have found practical applications in the field of civil engineering. In this paper, which is resulting from the work of the RILEM technical committee “Optical fiber sensors for civil engineering applications”, different kinds of sensing techniques, including change of light intensity, interferometry, fiber Bragg grating, adsorption measurement and distributed sensing, are briefly reviewed to introduce the basic sensing principles. Then, the applications of OFS in highway structures, building structures, geotechnical structures, pipelines as well as cables monitoring are described, with focus on sensor design, installation technique and sensor performance. It is believed that the State-of-the-Art review is helpful to engineers considering the use of OFS in their projects, and can facilitate the wider application of OFS technologies in construction industry

Reliability analysis of the Ahringer Caenorhabditis elegans RNAi feeding library: a guide for genome-wide screens

<p>Abstract</p> <p>Background</p> <p>The Ahringer <it>C. elegans </it>RNAi feeding library prepared by cloning genomic DNA fragments has been widely used in genome-wide analysis of gene function. However, the library has not been thoroughly validated by direct sequencing, and there are potential errors, including: 1) mis-annotation (the clone with the retired gene name should be remapped to the actual target gene); 2) nonspecific PCR amplification; 3) cross-RNAi; 4) mis-operation such as sample loading error, <it>etc</it>.</p> <p>Results</p> <p>Here we performed a reliability analysis on the Ahringer <it>C. elegans </it>RNAi feeding library, which contains 16,256 bacterial strains, using a bioinformatics approach. Results demonstrated that most (98.3%) of the bacterial strains in the library are reliable. However, we also found that 2,851 (17.54%) bacterial strains need to be re-annotated even they are reliable. Most of these bacterial strains are the clones having the retired gene names. Besides, 28 strains are grouped into unreliable category and 226 strains are marginal because of probably expressing unrelated double-stranded RNAs (dsRNAs). The accuracy of the prediction was further confirmed by direct sequencing analysis of 496 bacterial strains. Finally, a freely accessible database named CelRNAi (<url>http://biocompute.bmi.ac.cn/CelRNAi/</url>) was developed as a valuable complement resource for the feeding RNAi library by providing the predicted information on all bacterial strains. Moreover, submission of the direct sequencing result or any other annotations for the bacterial strains to the database are allowed and will be integrated into the CelRNAi database to improve the accuracy of the library. In addition, we provide five candidate primer sets for each of the unreliable and marginal bacterial strains for users to construct an alternative vector for their own RNAi studies.</p> <p>Conclusions</p> <p>Because of the potential unreliability of the Ahringer <it>C. elegans </it>RNAi feeding library, we strongly suggest the user examine the reliability information of the bacterial strains in the CelRNAi database before performing RNAi experiments, as well as the post-RNAi experiment analysis.</p

Tin Oxide Nanorod Array-Based Electrochemical Hydrogen Peroxide Biosensor

SnO2 nanorod array grown directly on alloy substrate has been employed as the working electrode of H2O2 biosensor. Single-crystalline SnO2 nanorods provide not only low isoelectric point and enough void spaces for facile horseradish peroxidase (HRP) immobilization but also numerous conductive channels for electron transport to and from current collector; thus, leading to direct electrochemistry of HRP. The nanorod array-based biosensor demonstrates high H2O2 sensing performance in terms of excellent sensitivity (379 μA mM−1 cm−2), low detection limit (0.2 μM) and high selectivity with the apparent Michaelis–Menten constant estimated to be as small as 33.9 μM. Our work further demonstrates the advantages of ordered array architecture in electrochemical device application and sheds light on the construction of other high-performance enzymatic biosensors