2,539 research outputs found
Word Embeddings for Wine Recommender Systems Using Vocabularies of Experts and Consumers
This vision paper proposes an approach to use the most advanced word embeddings techniques to bridge the gap between the discourses of experts and non-experts and more specifically the terminologies used by the twocommunities. Word embeddings makes it possible to find equivalent terms between experts and non-experts, byapproach the similarity between words or by revealing hidden semantic relations. Thus, these controlledvocabularies with these new semantic enrichments are exploited in a hybrid recommendation system incorporating content-based ontology and keyword-based ontology to obtain relevant wines recommendations regardless of the level of expertise of the end user. The major aim is to find a non-expert vocabulary from semantic rules to enrich the knowledge of the ontology and improve the indexing of the items (i.e. wine) and the recommendation process
TLR2 Controls Intestinal Carcinogen Detoxication by CYP1A1
Intestinal cytochrome P450 subclass 1A1 (CYP1A1) contributes to a metabolic âshieldâ protecting the host from ingested carcinogens such as polycyclic aromatic hydrocarbons (PAH). The expression of CYP1 (including CYP1A2 and CYP1B1) is considered to depend solely on a heterodimeric transcription factor consisting of the arylhydrocarbon receptor (AHR) and the AHR nuclear translocator (ARNT). So far, no interference has been noted between the regulation of CYP1 and the activation of Toll-like receptor 2 (TLR2), which modulates the inflammatory response to bacterial cell wall components in immune cells and enterocytes. Here we report that intestinal CYP1A1 is silenced in TLR2-deficient mice, even when under exposure to the carcinogenic PAH benzo[a]pyrene (BaP). In contrast, hepatic CYP1A1 was moderately induced in TLR2-deficient mice without restoring their ability to clear BaP from systemic circulation, as present in wild-type animals. After feeding of BaP for 21 days, only TLR2â/â mice, but not their wild type littermates developed polyps in the colon. Gene expressions and protein concentrations of AHR and ARNT in the intestine did not differ between the genotypes. In conclusion, the presence of ligands for TLR2 of bacterial origin seems to be crucial for detoxication of luminal carcinogens by CYP1A1 in the intestine. This unprecedented finding indicates a complex interplay between the immune system of the host and intestinal bacteria with detoxication mechanisms. This highlights the relevance of intestinal microbiota when trying to unravel pathways present in mammals and opens new perspectives for research in human health
Low-velocity impacts into granular material: application to small-body landing
With the flourishing number of small body missions that involve surface interactions,
understanding the mechanics of spacecraft - surface interactions is crucial for improving our
knowledge about the landing phases of space missions, for preparing spacecraft operations,
and for interpreting the results of measurements made during the surface interactions. Given
their regolith-covered surfaces, the process of landing on a small body can be considered as
an impact at low-velocity onto a granular material in reduced-gravity.
In order to study the influence of the surface material, projectile shape, and gravity on
the collision dynamics we used two experimental configurations (one for terrestrial gravity
experiments and one for reduced-gravity experiments) to perform low-velocity collisions into
different types of granular materials: quartz sand, and two different sizes of glass beads (1.5
and 5 mm diameter). Both a spherical and a cubic projectile (with varying impact orientation)
were used.
The experimental data support a drag model for the impact dynamics composed of both a
hydrodynamic drag force and quasi-static resistance force. The hydrodynamic and quasi-static
contributions are related to the material frictional properties, the projectile geometry, and the
gravity.
The transition from a quasi-static to a hydrodynamical regime is shown to occur at lower
impact velocities in reduced-gravity trials than in terrestrial gravity trials, indicating that
regolith has a more fluid-like behaviour in low-gravity. The reduced quasi-static regime of a
granular material under low-gravity conditions leads to a reduction in the strength, resulting
in a decreased resistance to penetration and larger penetration depths
Tapered Optical Fiber Sensor for Label-Free Detection of Biomolecules
This paper presents a fast, highly sensitive and low-cost tapered optical fiber biosensor that enables the label-free detection of biomolecules. The sensor takes advantage of the interference effect between the fiberâs first two propagation modes along the taper waist region. The biomolecules bonded on the taper surface were determined by demodulating the transmission spectrum phase shift. Because of the sharp spectrum fringe signals, as well as a relatively long biomolecule testing region, the sensor displayed a fast response and was highly sensitive. To better understand the influence of various biomolecules on the sensor, a numerical simulation that varied biolayer parameters such as thickness and refractive index was performed. The results showed that the spectrum fringe shift was obvious to be measured even when the biolayer was only nanometers thick. A microchannel chip was designed and fabricated for the protection of the sensor and biotesting. Microelectromechanical systems (MEMS) fabrication techniques were used to precisely control the profile and depth of the microchannel on the silicon chip with an accuracy of 2 ÎŒm. A tapered optical fiber biosensor was fabricated and evaluated with an Immune globulin G (IgG) antibody-antigen pair
Rotational velocities of nearby young stars
Stellar rotation is a crucial parameter driving stellar magnetism, activity
and mixing of chemical elements. Furthermore, the evolution of stellar rotation
is coupled to the evolution of circumstellar disks. Disk-braking mechanisms are
believed to be responsible for rotational deceleration during the accretion
phase, and rotational spin-up during the contraction phase after decoupling
from the disk for fast rotators arriving at the ZAMS. We investigate the
projected rotational velocities vsini of a sample of young stars with respect
to the stellar mass and disk evolutionary state to search for possible
indications of disk-braking mechanisms. We analyse the stellar spectra of 220
nearby (mostly <100pc) young (2-600 Myr) stars for their vsini, stellar age,
Halpha emission, and accretion rates. The stars have been observed with FEROS
and HARPS in La Silla, Chile. The spectra have been cross-correlated with
appropriate theoretical templates. We build a new calibration to be able to
derive vsini values from the cross-correlated spectra. Stellar ages are
estimated from the LiI equivalent width at 6708 Ang. The equivalent width and
width at 10% height of the Halpha emission are measured to identify accretors
and used to estimate accretion rates. The vsini is then analysed with respect
to the evolutionary state of the circumstellar disks to search for indications
of disk-braking mechanisms in accretors. We find that the broad vsini
distribution of our targets extends to rotation velocities of up to more than
100 km/s and peaks at a value of 7.8+-1.2 km/s, and that ~70% of our stars show
vsini<30 km/s. Furthermore, we can find indications for disk-braking in
accretors and rotational spin-up of stars which are decoupled from their disks.
In addition, we show that a number of young stars are suitable for precise
radial-velocity measurements for planet-search surveys.Comment: 16 pages, 6 figures, accepted for publication in A&
Importance of data structure in comparing two dimension reduction methods for classification of microarray gene expression data
BACKGROUND: With the advance of microarray technology, several methods for gene classification and prognosis have been already designed. However, under various denominations, some of these methods have similar approaches. This study evaluates the influence of gene expression variance structure on the performance of methods that describe the relationship between gene expression levels and a given phenotype through projection of data onto discriminant axes. RESULTS: We compared Between-Group Analysis and Discriminant Analysis (with prior dimension reduction through Partial Least Squares or Principal Components Analysis). A geometric approach showed that these two methods are strongly related, but differ in the way they handle data structure. Yet, data structure helps understanding the predictive efficiency of these methods. Three main structure situations may be identified. When the clusters of points are clearly split, both methods perform equally well. When the clusters superpose, both methods fail to give interesting predictions. In intermediate situations, the configuration of the clusters of points has to be handled by the projection to improve prediction. For this, we recommend Discriminant Analysis. Besides, an innovative way of simulation generated the three main structures by modelling different partitions of the whole variance into within-group and between-group variances. These simulated datasets were used in complement to some well-known public datasets to investigate the methods behaviour in a large diversity of structure situations. To examine the structure of a dataset before analysis and preselect an a priori appropriate method for its analysis, we proposed a two-graph preliminary visualization tool: plotting patients on the Between-Group Analysis discriminant axis (x-axis) and on the first and the second within-group Principal Components Analysis component (y-axis), respectively. CONCLUSION: Discriminant Analysis outperformed Between-Group Analysis because it allows for the dataset structure. An a priori knowledge of that structure may guide the choice of the analysis method. Simulated datasets with known properties are valuable to assess and compare the performance of analysis methods, then implementation on real datasets checks and validates the results. Thus, we warn against the use of unchallenging datasets for method comparison, such as the Golub dataset, because their structure is such that any method would be efficient
Genetically directed production of recombinant, isosteric and non-hydrolyzable ubiquitin conjugates
We describe the genetically directed incorporation of aminooxy functionality into recombinant proteins by using a mutant Methanosarcina barkeri pyrrolysylâtRNA synthetase/tRNA(CUA) pair. This allows the general production of nonhydrolysable ubiquitin conjugates of recombinant origin by bioorthogonal oxime ligation. This was exemplified by the preparation of nonhydrolysable versions of diubiquitin, polymeric ubiquitin chains and ubiquitylated SUMO. The conjugates exhibited unrivalled isostery with the native isopeptide bond, as inferred from structural and biophysical characterisation. Furthermore, the conjugates functioned as nanomolar inhibitors of deubiquitylating enzymes and were recognised by linkageâspecific antibodies. This technology should provide a versatile platform for the development of powerful tools for studying deubiquitylating enzymes and for elucidating the cellular roles of diverse polyubiquitin linkages
Body Mass Index and Waist Circumference According to Glucose Tolerance Status in Korea: The 2005 Korean Health and Nutrition Examination Survey
The purpose of this study was to investigate the stage of glucose intolerance in which persons showed a maximum obesity in Korea. A total of 4,479 participants, who were involved in the 2005 Korean National Health and Nutrition Examination Survey, was examined. The participants were divided into 5 groups by fasting plasma glucose (FPG); normal fasting glucose (NFG)1, FPG < 90 mg/dL; NFG2, FPG 90-99 mg/dL; impaired fasting glucose (IFG)1, FPG 100-109 mg/dL; IFG2, FPG 110-125 mg/dL; and diabetes mellitus, FPG ℠126 mg/dL or with anti-diabetes drugs. In those with FPG < 110 mg/dL, body mass index (BMI) and waist circumference (WC) were increased with increase of FPG (BMI in men; NFG1, 23.3 ± 0.1; NFG2, 24.4 ± 0.1; IFG1, 25.0 ± 0.2 kg/m2, in women; NFG1, 23.0 ± 0.1; NFG2, 24.0 ± 0.1; IFG1, 24.8 ± 0.2 kg/m2, WC in men; NFG1, 82.1 ± 0.3; NFG2, 85.3 ± 0.3; IFG1, 86.7 ± 0.5 cm, in women; NFG1, 77.1 ± 0.2; NFG2, 79.4 ± 0.3; IFG1, 81.8 ± 0.6 cm). In IFG2 and diabetes range, there was no more increase of BMI and WC with increase of FPG in each sex. The data suggest that degree of obesity increases with an increase of FPG in range of FPG < 100 mg/dL, peaked in FPG of 100-109 mg/dL, and then plateaus in higher FPG range in general Korean population
Implications of MMP9 for Blood Brain Barrier Disruption and Hemorrhagic Transformation Following Ischemic Stroke.
Numerous studies have documented increases in matrix metalloproteinases (MMPs), specifically MMP-9 levels following stroke, with such perturbations associated with disruption of the blood brain barrier (BBB), increased risk of hemorrhagic complications, and worsened outcome. Despite this, controversy remains as to which cells release MMP-9 at the normal and pathological BBB, with even less clarity in the context of stroke. This may be further complicated by the influence of tissue plasminogen activator (tPA) treatment. The aim of the present review is to examine the relationship between neutrophils, MMP-9 and tPA following ischemic stroke to elucidate which cells are responsible for the increases in MMP-9 and resultant barrier changes and hemorrhage observed following stroke
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