5,683 research outputs found
Gut microbial activity as influenced by fiber digestion: dynamic metabolomics in an in vitro colon simulator
Understanding the interaction between the gut microbial activity and the host is essential, and in vitro models are being used to test and develop hypotheses regarding the impact of food components/drugs on the human gut ecosystem. However, while in vitro models provide excellent possibilities for dynamic investigations, studies have commonly been restricted to analyses of few, targeted metabolites. In the present study, we employed NMR-based metabolomics combined with multilevel data analysis as a tool to characterize the impact of polydextrose (PDX) fiber on the in vitro derived fecal metabolome. This approach enabled us to identify and quantify the fiber-induced response on several fecal metabolites; we observed higher levels of butyrate, acetate, propionate, succinate, N-acetyl compound and a lower level of amino acids (leucine, valine, isoleucine, phenylalanine, and lysine), valerate, formate, isovalerate and trimethylamine among the PDX-treated sample compared to the control samples. In addition, by the application of multilevel data analysis we were able to examine the specific inter-individual variations, and caprylic acid was identified to be the main marker of distinct microbial compositions among the subjects. Our work is expected to provide a useful approach to understand the metabolic impact of potential prebiotic compounds and get deeper insight into the molecular regulation of gut-microbe activities in the complex gut system
Measuring Relations Between Concepts In Conceptual Spaces
The highly influential framework of conceptual spaces provides a geometric
way of representing knowledge. Instances are represented by points in a
high-dimensional space and concepts are represented by regions in this space.
Our recent mathematical formalization of this framework is capable of
representing correlations between different domains in a geometric way. In this
paper, we extend our formalization by providing quantitative mathematical
definitions for the notions of concept size, subsethood, implication,
similarity, and betweenness. This considerably increases the representational
power of our formalization by introducing measurable ways of describing
relations between concepts.Comment: Accepted at SGAI 2017 (http://www.bcs-sgai.org/ai2017/). The final
publication is available at Springer via
https://doi.org/10.1007/978-3-319-71078-5_7. arXiv admin note: substantial
text overlap with arXiv:1707.05165, arXiv:1706.0636
Macroscopic self standing SWCNT fibers as efficient electron emitters with very high emission current for robust cold cathodes
A novel of self-standing nanotube-based cold cathode is described. The electron emitter is
a single macroscopic fibre spun from neat single wall carbon nanotubes and consists of an
ensemble of nanotube bundles held together by van der Waals forces. Field emission measurements
carried out using two different types of apparatus demonstrated the long working
life of the realised cathode. The system is able to emit at very high current densities, up
to 13 A/cm2, and shows very low values of both turn on and threshold field, 0.12 V/lm and
0.21 V/lm, respectively. Such easy to handle self-standing electron sources assure good
performances and represent an enabling technology for a scalable production of cold
cathodes.
2012 Elsevier Ltd. All rights reserved.
1. Introduction
Due to a unique combination of properties, including high
electrical and thermal conductivity, and high mechanical/
chemical/thermal stability, carbon nanotubes (CNTs) have
been recognised as ideal candidate materials for application
in microelectronics [1]. Moreover, the high aspect ratio characterising
this intriguing material makes possible to significantly
strengthen electric fields into the vicinity of
nanotubes tips
The association between attention-deficit/hyperactivity disorder and retinal nerve fiber/ganglion cell layer thickness measured by optical coherence tomography: a systematic review and meta-analysis
Purpose: Retinal nerve fiber/ganglion cell layer (RNFL/GCL) thickness measured using optical coherence tomography has been proposed as an ocular biomarker for children with attention-deficit/hyperactivity disorder (ADHD), but findings varied in different studies. This study aims to determine the association between RNFL/GCL thickness and ADHD in children by systematic review and meta-analysis. / Methods: We performed a literature search in Embase, PubMed, Medline, Web of Science, and PsycINFO for relevant articles published up to February 29, 2020. All studies with original data comparing RNFL/GCL thickness in ADHD and healthy children were included. The Newcastle Ottawa Scale was used to assess bias risk and quality of evidence. Pooled estimates of the differences in thickness of RNFL or GCL between ADHD and healthy subjects were generated using meta-analysis with a random-effect model due to significant inter-study heterogeneity. Sensitivity analysis was also performed. / Results: We identified four eligible studies involving a total of 164 ADHD and 150 control subjects. Meta-analysis revealed that ADHD in children was associated with a reduction in global RNFL thickness (SMD, − 0.23; 95% CI − 0.46, − 0.01; p = 0.04). The global GCL thickness was examined in two studies with 89 ADHD and 75 control subjects, but the pooled difference in global GCL thickness between ADHD children and controls was not statistically significant (SMD, − 0.34; 95% CI − 1.25, 0.58; p = 0.47). / Conclusion: Existing evidence suggests a possible association between ADHD and RNFL thinning in children. In view of the limited number of reports, further studies in large cohorts should be warranted
Impact of N-myc amplification on median survival in children with neuroblastoma
Background: Neuroblastoma is the most common extracranial malignant solid tumor
in children under 5 years, and it is characterized by wide clinical and biological heterogeneity.
N-myc oncogene amplification is considered to be one of the most important
prognostic factors used to evaluate survival in these patients.
Objectives: The aim of our study was to determine amplification of the N-myc oncogene
using real-time quantitative polymerase chain reaction (PCR) and to show the influence
of N-myc amplified tumors on the overall survival rate.
Patients and Methods: This study is an analytical historical cohort study of forty children
with neuroblastoma admitted to the Shafa Hospital, Iran from 1999 to 2010. Paraffined
blocks of tumoral tissue were analyzed for N-myc amplification by a PCR. The
degree of N-myc amplification was derived from the ratio of the N-myc oncogene and
the single copy reference gene, NAGK. In the statistical analysis, a Kaplan-Meier survival
analysis was used.
Results: We found a variable degree of N-myc amplification, from 3 to 2 200, in 32 of
the 40 neuroblastomas (80%). NMYC amplification was seen more frequently in patients
older than 2.5 years (71.9%), stage 4 (65.6%) and female (53.1%). Median survival time in the
males was significantly longer than in the females (P = 0.03). The overall median survival
for N-myc amplified tumor patients was 20 months, and 30 months for the non amplified
tumors.
Conclusions: The N-myc amplified tumors may increase the probability of more aggressive
behavior and rapid tumor progression, especially in advanced stages of neuroblastoma.
This study confirmed the importance of obtaining correct measurements of oncogene
amplification in the early evaluation of neuroblastomas in order to target more
aggressive therapies in patients with a higher risk of cancer progression
Purification and characterization of the bacteriophage T7 gene 2.5 protein : a single-stranded DNA-binding protein
Bacteriophage T7 gene 2.5 protein has been purified to homogeneity from cells overexpressing its gene. Native gene 2.5 protein consists of a dimer of two identical subunits of molecular weight 25,562. Gene 2.5 protein binds specifically to single-stranded DNA with a stoichiometry of approximately 7 nucleotides bound per monomer of gene 2.5 protein; binding appears to be noncooperative. Electron microscopic analysis shows that gene 2.5 protein is able to disrupt the secondary structure of single-stranded DNA. The single-stranded DNA is extended into a chain of gene 2.5 protein dimers bound along the DNA. In fluorescence quenching and nitrocellulose filter binding assays, the binding constants of gene 2.5 protein to single-stranded DNA are 1.2 x 10(6) M-1 and 3.8 x 10(6) M-1, respectively. Escherichia coli single-stranded DNA-binding protein and phage T4 gene 32 protein bind to single-stranded DNA more tightly by a factor of 25. Fluorescence spectroscopy suggests that tyrosine residue(s), but not tryptophan residues, on gene 2.5 protein interacts with single-stranded DNA
Building resilience in practice to support coral communities in the Western Indian Ocean
Global environmental change and other site specific pressures (e.g. over fishing and pollution) are threating
coral reefs and the livelihoods of dependent coastal communities. Multiple strategies are used to build the
resilience of both coral reefs and reef dependent communities but the effectiveness of these strategies is largely
unknown. Using the Western Indian Ocean (WIO) as a case study, this paper combines published literature and
expert opinion elicited through a multi-stakeholder workshop to assess the intended and realised social and
ecological implications of strategies commonly applied in the region. Findings suggest that all strategies can
contribute to building social and ecological resilience, but this varies with context and the overall strategy
objectives. The ability of strategies to be successful in the future is questioned. To support effective resilience
policy development more nuanced lesson learning requires effective monitoring and evaluation as well as a
disaggregated understanding of resilience in terms of gender, agency and the interaction between ecological and
social resilience. Opportunities for further lesson sharing between experts in the region are needed
Trapped lipopolysaccharide and LptD intermediates reveal lipopolysaccharide translocation steps across the Escherichia coli outer membrane
Lipopolysaccharide (LPS) is a main component of the outer membrane of Gram-negative bacteria, which is essential for the vitality of most Gram-negative bacteria and plays a critical role for drug resistance. LptD/E complex forms a N-terminal LPS transport slide, a hydrophobic intramembrane hole and the hydrophilic channel of the barrel, for LPS transport, lipid A insertion and core oligosaccharide and O-antigen polysaccharide translocation, respectively. However, there is no direct evidence to confirm that LptD/E transports LPS from the periplasm to the external leaflet of the outer membrane. By replacing LptD residues with an unnatural amino acid p-benzoyl-L-phenyalanine (pBPA) and UV-photo-cross-linking in E.coli, the translocon and LPS intermediates were obtained at the N-terminal domain, the intramembrane hole, the lumenal gate, the lumen of LptD channel, and the extracellular loop 1 and 4, providing the first direct evidence and “snapshots” to reveal LPS translocation steps across the outer membrane
Interval valued (\in,\ivq)-fuzzy filters of pseudo -algebras
We introduce the concept of quasi-coincidence of a fuzzy interval value with
an interval valued fuzzy set. By using this new idea, we introduce the notions
of interval valued (\in,\ivq)-fuzzy filters of pseudo -algebras and
investigate some of their related properties. Some characterization theorems of
these generalized interval valued fuzzy filters are derived. The relationship
among these generalized interval valued fuzzy filters of pseudo -algebras
is considered. Finally, we consider the concept of implication-based interval
valued fuzzy implicative filters of pseudo -algebras, in particular, the
implication operators in Lukasiewicz system of continuous-valued logic are
discussed
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