220 research outputs found
A possible role of ground-based microorganisms on cloud formation in the atmosphere
The formation of clouds is an important process for the atmosphere, the
hydrological cycle, and climate, but some aspects of it are not completely
understood. In this work, we show that microorganisms might affect cloud
formation without leaving the Earth's surface by releasing biological
surfactants (or biosurfactants) in the environment, that make their way into
atmospheric aerosols and could significantly enhance their activation into
cloud droplets.
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In the first part of this work, the cloud-nucleating efficiency of standard
biosurfactants was characterized and found to be better than that of any
aerosol material studied so far, including inorganic salts. These results
identify molecular structures that give organic compounds exceptional
cloud-nucleating properties. In the second part, atmospheric aerosols were
sampled at different locations: a temperate coastal site, a marine site, a
temperate forest, and a tropical forest. Their surface tension was measured
and found to be below 30 mN/m, the lowest reported for aerosols, to our
knowledge. This very low surface tension was attributed to the presence of
biosurfactants, the only natural substances able to reach to such low
values.
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The presence of strong microbial surfactants in aerosols would be consistent
with the organic fractions of exceptional cloud-nucleating efficiency
recently found in aerosols, and with the correlations between algae bloom
and cloud cover reported in the Southern Ocean. The results of this work
also suggest that biosurfactants might be common in aerosols and thus of
global relevance. If this is confirmed, a new role for microorganisms on the
atmosphere and climate could be identified
Three-Dimensional Cell and Tissue Patterning in a Strained Fibrin Gel System
Techniques developed for the in vitro reproduction of three-dimensional (3D) biomimetic tissue will be valuable for investigating changes in cell function in tissues and for fabricating cell/matrix composites for applications in tissue engineering techniques. In this study, we show that the simple application of a continuous strain to a fibrin gel facilitates the development of fibril alignment and bundle-like structures in the fibrin gel in the direction of the applied strain. Myoblasts cultured in this gel also exhibited well-aligned cell patterning in a direction parallel to the direction of the strain. Interestingly, the direction of cell proliferation was identical to that of cell alignment. Finally, the oriented cells formed linear groups that were aligned parallel to the direction of the strain and replicated the native skeletal muscle cell patterning. In addition, vein endothelial cells formed a linear, aligned vessel-like structure in this system. Thus, the system enables the in vitro reproduction of 3D aligned cell sets replicating biological tissue patterns
Wakefield Generation in Hydrogen and Lithium Plasmas at FACET-II: Diagnostics and First Beam-Plasma Interaction Results
Plasma Wakefield Acceleration (PWFA) provides ultrahigh acceleration
gradients of 10s of GeV/m, providing a novel path towards efficient, compact,
TeV-scale linear colliders and high brightness free electron lasers. Critical
to the success of these applications is demonstrating simultaneously high
gradient acceleration, high energy transfer efficiency, and preservation of
emittance, charge, and energy spread. Experiments at the FACET-II National User
Facility at SLAC National Accelerator Laboratory aim to achieve all of these
milestones in a single stage plasma wakefield accelerator, providing a 10 GeV
energy gain in a <1 m plasma with high energy transfer efficiency. Such a
demonstration depends critically on diagnostics able to measure emittance with
mm-mrad accuracy, energy spectra to determine both %-level energy spread and
broadband energy gain and loss, incoming longitudinal phase space, and matching
dynamics. This paper discusses the experimental setup at FACET-II, including
the incoming beam parameters from the FACET-II linac, plasma sources, and
diagnostics developed to meet this challenge. Initial progress on the
generation of beam ionized wakes in meter-scale hydrogen gas is discussed, as
well as commissioning of the plasma sources and diagnostics
Characterisation of physico-mechanical properties and degradation potential of calcium alginate beads for use in embolisation
High molecular weight alginate beads with 59% mannuronic acid content or 68% guluronic acid were prepared using a droplet generator and crosslinked in calcium chloride. The alginate beads were compared to current embolisation microspheres for compressibility and monitored over 12 weeks for size and weight change at 37°C in low volumes of ringers solutions. A sheep uterine model was used to analyse bead degradation and inflammatory response over 12 weeks. Both the in vitro and in vivo data show good delivery, with a compressibility similar to current embolic beads. In vitro, swelling was noted almost immediately and after 12 weeks the first signs of degradation were noted. No difference was noted in vivo. This study has shown that high molecular weight alginate gel beads were well tolerated by the body, but beads associated with induced thrombi were susceptible to inflammatory cell infiltration. The beads were shown to be easy to handle and were still observable after 3 months in vivo. The beads were robust enough to be delivered through a 2.7 Fr microcatheter. This study has demonstrated that high molecular weight, high purity alginate bead can be considered as semi-permanent embolisation beads, with the potential to bioresorb over time
Biological Designer Self-Assembling Peptide Nanofiber Scaffolds Significantly Enhance Osteoblast Proliferation, Differentiation and 3-D Migration
A class of self-assembling peptide nanofiber scaffolds has been shown to be an excellent biological material for 3-dimension cell culture and stimulating cell migration into the scaffold, as well as for repairing tissue defects in animals. We report here the development of several peptide nanofiber scaffolds designed specifically for osteoblasts. We designed one of the pure self-assembling peptide scaffolds RADA16-I through direct coupling to short biologically active motifs. The motifs included osteogenic growth peptide ALK (ALKRQGRTLYGF) bone-cell secreted-signal peptide, osteopontin cell adhesion motif DGR (DGRGDSVAYG) and 2-unit RGD binding sequence PGR (PRGDSGYRGDS). We made the new peptide scaffolds by mixing the pure RAD16 and designer-peptide solutions, and we examined the molecular integration of the mixed nanofiber scaffolds using AFM. Compared to pure RAD16 scaffold, we found that these designer peptide scaffolds significantly promoted mouse pre-osteoblast MC3T3-E1 cell proliferation. Moreover, alkaline phosphatase (ALP) activity and osteocalcin secretion, which are early and late markers for osteoblastic differentiation, were also significantly increased. We demonstrated that the designer, self-assembling peptide scaffolds promoted the proliferation and osteogenic differentiation of MC3T3-E1. Under the identical culture medium condition, confocal images unequivocally demonstrated that the designer PRG peptide scaffold stimulated cell migration into the 3-D scaffold. Our results suggest that these designer peptide scaffolds may be very useful for promoting bone tissue regeneration
GeneTools – application for functional annotation and statistical hypothesis testing
BACKGROUND: Modern biology has shifted from "one gene" approaches to methods for genomic-scale analysis like microarray technology, which allow simultaneous measurement of thousands of genes. This has created a need for tools facilitating interpretation of biological data in "batch" mode. However, such tools often leave the investigator with large volumes of apparently unorganized information. To meet this interpretation challenge, gene-set, or cluster testing has become a popular analytical tool. Many gene-set testing methods and software packages are now available, most of which use a variety of statistical tests to assess the genes in a set for biological information. However, the field is still evolving, and there is a great need for "integrated" solutions. RESULTS: GeneTools is a web-service providing access to a database that brings together information from a broad range of resources. The annotation data are updated weekly, guaranteeing that users get data most recently available. Data submitted by the user are stored in the database, where it can easily be updated, shared between users and exported in various formats. GeneTools provides three different tools: i) NMC Annotation Tool, which offers annotations from several databases like UniGene, Entrez Gene, SwissProt and GeneOntology, in both single- and batch search mode. ii) GO Annotator Tool, where users can add new gene ontology (GO) annotations to genes of interest. These user defined GO annotations can be used in further analysis or exported for public distribution. iii) eGOn, a tool for visualization and statistical hypothesis testing of GO category representation. As the first GO tool, eGOn supports hypothesis testing for three different situations (master-target situation, mutually exclusive target-target situation and intersecting target-target situation). An important additional function is an evidence-code filter that allows users, to select the GO annotations for the analysis. CONCLUSION: GeneTools is the first "all in one" annotation tool, providing users with a rapid extraction of highly relevant gene annotation data for e.g. thousands of genes or clones at once. It allows a user to define and archive new GO annotations and it supports hypothesis testing related to GO category representations. GeneTools is freely available through www.genetools.n
Cell‐ and Gene‐Based Therapeutic Strategies for Periodontal Regenerative Medicine
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142086/1/jper1223.pd
Molecular mechanics of mineralized collagen fibrils in bone
Bone is a natural composite of collagen protein and the mineral hydroxyapatite. The structure of bone is known to be important to its load-bearing characteristics, but relatively little is known about this structure or the mechanism that govern deformation at the molecular scale. Here we perform full-atomistic calculations of the three-dimensional molecular structure of a mineralized collagen protein matrix to try to better understand its mechanical characteristics under tensile loading at various mineral densities. We find that as the mineral density increases, the tensile modulus of the network increases monotonically and well beyond that of pure collagen fibrils. Our results suggest that the mineral crystals within this network bears up to four times the stress of the collagen fibrils, whereas the collagen is predominantly responsible for the material’s deformation response. These findings reveal the mechanism by which bone is able to achieve superior energy dissipation and fracture resistance characteristics beyond its individual constituents.United States. Office of Naval Research (N000141010562)United States. Army Research Office (W991NF-09-1-0541)United States. Army Research Office (W911NF-10-1-0127)National Science Foundation (U.S.) (CMMI-0642545
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