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"Stevens, Mark"
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Lost treasure of the emerald eye
The discovery of an old map by his sister Thea leads Geronimo and his family to search for buried treasure on a faraway island.
Book
Understanding of alkaline pretreatment parameters for corn stover enzymatic saccharification
Doc number: 8 Abstract Background: Previous research on alkaline pretreatment has mainly focused on optimization of the process parameters to improve substrate digestibility. To achieve satisfactory sugar yield, extremely high chemical loading and enzyme dosages were typically used. Relatively little attention has been paid to reduction of chemical consumption and process waste management, which has proven to be an indispensable component of the bio-refineries. To indicate alkali strength, both alkali concentration in pretreatment solution (g alkali/g pretreatment liquor or g alkali/L pretreatment liquor) and alkali loading based on biomass solids (g alkali/g dry biomass) have been widely used. The dual approaches make it difficult to compare the chemical consumption in different process scenarios while evaluating the cost effectiveness of this pretreatment technology. The current work addresses these issues through pretreatment of corn stover at various combinations of pretreatment conditions. Enzymatic hydrolysis with different enzyme blends was subsequently performed to identify the effects of pretreatment parameters on substrate digestibility as well as process operational and capital costs. Results: The results showed that sodium hydroxide loading is the most dominant variable for enzymatic digestibility. To reach 70% glucan conversion while avoiding extensive degradation of hemicellulose, approximately 0.08 g NaOH/g corn stover was required. It was also concluded that alkali loading based on total solids (g NaOH/g dry biomass) governs the pretreatment efficiency. Supplementing cellulase with accessory enzymes such as α-arabinofuranosidase and β-xylosidase significantly improved the conversion of the hemicellulose by 6-17%. Conclusions: The current work presents the impact of alkaline pretreatment parameters on the enzymatic hydrolysis of corn stover as well as the process operational and capital investment costs. The high chemical consumption for alkaline pretreatment technology indicates that the main challenge for commercialization is chemical recovery. However, repurposing or co-locating a biorefinery with a paper mill would be advantageous from an economic point of view.
Journal Article
Analysis of the role of the QseBC two-component sensory system in epinephrine-induced motility and intracellular replication of Burkholderia pseudomallei
Burkholderia pseudomallei is a facultative intracellular bacterial pathogen that causes melioidosis, a severe invasive disease of humans. We previously reported that the stress-related catecholamine hormone epinephrine enhances motility of B . pseudomallei , transcription of flagellar genes and the production of flagellin. It has been reported that the QseBC two-component sensory system regulates motility and virulence-associated genes in other Gram-negative bacteria in response to stress-related catecholamines, albeit disparities between studies exist. We constructed and whole-genome sequenced a mutant of B . pseudomallei with a deletion spanning the predicted qseBC homologues ( bpsl0806 and bpsl0807 ). The Δ qseBC mutant exhibited significantly reduced swimming and swarming motility and reduced transcription of fliC . It also exhibited a defect in biofilm formation and net intracellular survival in J774A.1 murine macrophage-like cells. While epinephrine enhanced bacterial motility and fliC transcription, no further reduction in these phenotypes was observed with the Δ qseBC mutant in the presence of epinephrine. Plasmid-mediated expression of qseBC suppressed bacterial growth, complicating attempts to trans -complement mutant phenotypes. Our data support a role for QseBC in motility, biofilm formation and net intracellular survival of B . pseudomallei , but indicate that it is not essential for epinephrine-induced motility per se .
Journal Article
Jenny Saville
\"Thirteen years after her first Rizzoli monograph, British artist Jenny Saville, an original member of the Young British Artists, releases her most definitive book, including never-before-published paintings from her most recent exhibition at Gagosian in New York. This much-anticipated volume unites new work with many of Saville's paintings and drawings to date, accompanied by essays that explore Saville's continuing fascination with the human body within a broad art-historical context. The book also features Saville in an extensive conversation with acclaimed American photographer Sally Mann. An illustrated chronology of Saville's career completes this elegant volume. This beautifully produced monograph is an important addition to the library on one of the world's most influential and enduring living painters.\" -- Publisher's description
Book
High-throughput measurement of single-cell growth rates using serial microfluidic mass sensor arrays
Heterogeneity in growth phenotypes and drug susceptibility in bacterial and mammalian cells are assayed at the single-cell level using multiplexed resonant mass sensors.
Methods to rapidly assess cell growth would be useful for many applications, including drug susceptibility testing, but current technologies have limited sensitivity or throughput. Here we present an approach to precisely and rapidly measure growth rates of many individual cells simultaneously. We flow cells in suspension through a microfluidic channel with 10–12 resonant mass sensors distributed along its length, weighing each cell repeatedly over the 4–20 min it spends in the channel. Because multiple cells traverse the channel at the same time, we obtain growth rates for >60 cells/h with a resolution of 0.2 pg/h for mammalian cells and 0.02 pg/h for bacteria. We measure the growth of single lymphocytic cells, mouse and human T cells, primary human leukemia cells, yeast,
Escherichia coli
and
Enterococcus faecalis
. Our system reveals subpopulations of cells with divergent growth kinetics and enables assessment of cellular responses to antibiotics and antimicrobial peptides within minutes.
Journal Article
Factors Influencing Bacterial Diversity and Community Composition in Municipal Drinking Waters in the Ohio River Basin, USA
The composition and metabolic activities of microbes in drinking water distribution systems can affect water quality and distribution system integrity. In order to understand regional variations in drinking water microbiology in the upper Ohio River watershed, the chemical and microbiological constituents of 17 municipal distribution systems were assessed. While sporadic variations were observed, the microbial diversity was generally dominated by fewer than 10 taxa, and was driven by the amount of disinfectant residual in the water. Overall, Mycobacterium spp. (Actinobacteria), MLE1-12 (phylum Cyanobacteria), Methylobacterium spp., and sphingomonads were the dominant taxa. Shifts in community composition from Alphaproteobacteria and Betaproteobacteria to Firmicutes and Gammaproteobacteria were associated with higher residual chlorine. Alpha- and beta-diversity were higher in systems with higher chlorine loads, which may reflect changes in the ecological processes structuring the communities under different levels of oxidative stress. These results expand the assessment of microbial diversity in municipal distribution systems and demonstrate the value of considering ecological theory to understand the processes controlling microbial makeup. Such understanding may inform the management of municipal drinking water resources.
Journal Article
Microglial brain region−dependent diversity and selective regional sensitivities to aging
Heterogeneity within distinct cell populations resident in the central nervous system is increasingly recognized as important for functional diversity, plasticity and sensitivity to neurological disease. The authors demonstrate genome-wide diversity of microglia dependent on brain localization in the young adult and show that aging of microglia occurs in a regionally variable manner.
Microglia have critical roles in neural development, homeostasis and neuroinflammation and are increasingly implicated in age-related neurological dysfunction. Neurodegeneration often occurs in disease-specific, spatially restricted patterns, the origins of which are unknown. We performed to our knowledge the first genome-wide analysis of microglia from discrete brain regions across the adult lifespan of the mouse, and found that microglia have distinct region-dependent transcriptional identities and age in a regionally variable manner. In the young adult brain, differences in bioenergetic and immunoregulatory pathways were the major sources of heterogeneity and suggested that cerebellar and hippocampal microglia exist in a more immune-vigilant state. Immune function correlated with regional transcriptional patterns. Augmentation of the distinct cerebellar immunophenotype and a contrasting loss in distinction of the hippocampal phenotype among forebrain regions were key features during aging. Microglial diversity may enable regionally localized homeostatic functions but could also underlie region-specific sensitivities to microglial dysregulation and involvement in age-related neurodegeneration.
Journal Article
Antarctic biodiversity predictions through substrate qualities and environmental DNA
Antarctic conservation science is crucial for enhancing Antarctic policy and understanding alterations to terrestrial Antarctic biodiversity. Antarctic conservation will have limited long-term impacts in the absence of large-scale biodiversity data, but if such data were available, it is likely to improve environmental protection regimes. To enable the prediction of Antarctic biodiversity across continental spatial scales through proxy variables, in the absence of baseline surveys, we linked Antarctic substrate-derived environmental DNA (eDNA) sequence data from the remote Antarctic Prince Charles Mountains to a selected range of concomitantly collected measurements of substrate properties. We achieved this through application of a statistical method commonly used in machine learning. Our analysis indicated that neutral substrate pH, low conductivity, and certain substrate minerals are important predictors of the presence of basidiomycetes, chlorophytes, ciliophorans, nematodes, and tardigrades. A bootstrapped regression revealed how variations in the identified substrate parameters influence probabilities of detecting eukaryote phyla across vast and remote areas of Antarctica. We believe that our work will improve future taxon distribution modeling and aid in developing more targeted surveys of biodiversity conducted under logistically challenging conditions.
Journal Article
Self-assembled highly ordered acid layers in precisely sulfonated polyethylene produce efficient proton transport
Recent advances in polymer synthesis have allowed remarkable control over chain microstructure and conformation. Capitalizing on such developments, here we create well-controlled chain folding in sulfonated polyethylene, leading to highly uniform hydrated acid layers of subnanometre thickness with high proton conductivity. The linear polyethylene contains sulfonic acid groups pendant to precisely every twenty-first carbon atom that induce tight chain folds to form the hydrated layers, while the methylene segments crystallize. The proton conductivity is on par with Nafion 117, the benchmark for fuel cell membranes. We demonstrate that well-controlled hairpin chain folding can be utilized for proton conductivity within a crystalline polymer structure, and we project that this structure could be adapted for ion transport. This layered polyethylene-based structure is an innovative and versatile design paradigm for functional polymer membranes, opening doors to efficient and selective transport of other ions and small molecules on appropriate selection of functional groups.
Journal Article