1,193 research outputs found
Suppression of cell-spreading and phagocytic activity on nano-pillared surface: in vitro experiment using hemocytes of the colonial ascidian Botryllus schlosseri.
Nano-scale nipple array on the body surface has been described from various invertebrates including endoparasitic and mesoparasitic copepods, but the functions of the nipple array is not well understood. Using the hydrophilized nanopillar sheets made of polystyrene as a mimetic material of the nipple arrays on the parasites\u2019 body surface, we assayed the cell spreading and phagocytosis of the hemocytes of the colonial ascidian Botryllus schlosseri. On the pillared surface, the number of spreading amebocytes and the number of phagocytizing hemocytes per unit area were always smaller than those on the flat surface (Mann-Whitney test, p < 0.05 - 0.001), probably because the effective area for the cell attachment on the pillared surface is much smaller than the area on the flat sheet. The present results supports the idea that the nipple array on the parasites' body surface reduces the innate immune reaction from the host hemocytes
Densest Diverse Subgraphs: How to Plan a Successful Cocktail Party with Diversity
Dense subgraph discovery methods are routinely used in a variety of
applications including the identification of a team of skilled individuals for
collaboration from a social network. However, when the network's node set is
associated with a sensitive attribute such as race, gender, religion, or
political opinion, the lack of diversity can lead to lawsuits.
In this work, we focus on the problem of finding a densest diverse subgraph
in a graph whose nodes have different attribute values/types that we refer to
as colors. We propose two novel formulations motivated by different realistic
scenarios. Our first formulation, called the densest diverse subgraph problem
(DDSP), guarantees that no color represents more than some fraction of the
nodes in the output subgraph, which generalizes the state-of-the-art due to
Anagnostopoulos et al. (CIKM 2020). By varying the fraction we can range the
diversity constraint and interpolate from a diverse dense subgraph where all
colors have to be equally represented to an unconstrained dense subgraph. We
design a scalable -approximation algorithm, where is
the number of nodes. Our second formulation is motivated by the setting where
any specified color should not be overlooked. We propose the densest
at-least--subgraph problem (DalS), a novel generalization of
the classic DalS, where instead of a single value , we have a vector
of cardinality demands with one coordinate per color class. We
design a -approximation algorithm using linear programming together with
an acceleration technique. Computational experiments using synthetic and
real-world datasets demonstrate that our proposed algorithms are effective in
extracting dense diverse clusters.Comment: Accepted to KDD 202
Finding Densest -Connected Subgraphs
Dense subgraph discovery is an important graph-mining primitive with a
variety of real-world applications. One of the most well-studied optimization
problems for dense subgraph discovery is the densest subgraph problem, where
given an edge-weighted undirected graph , we are asked to find
that maximizes the density , i.e., half the weighted
average degree of the induced subgraph . This problem can be solved
exactly in polynomial time and well-approximately in almost linear time.
However, a densest subgraph has a structural drawback, namely, the subgraph may
not be robust to vertex/edge failure. Indeed, a densest subgraph may not be
well-connected, which implies that the subgraph may be disconnected by removing
only a few vertices/edges within it. In this paper, we provide an algorithmic
framework to find a dense subgraph that is well-connected in terms of
vertex/edge connectivity. Specifically, we introduce the following problems:
given a graph and a positive integer/real , we are asked to find
that maximizes the density under the constraint that
is -vertex/edge-connected. For both problems, we propose
polynomial-time (bicriteria and ordinary) approximation algorithms, using
classic Mader's theorem in graph theory and its extensions
Mathematical modeling of atopic dermatitis reveals "double switch" mechanisms underlying 4 common disease phenotypes
Background: The skin barrier acts as the first line of defense against constant exposure to biological, microbial, physical and chemical environmental stressors. Dynamic interplay between defects in the skin barrier, dysfunctional immune responses, and environmental stressors are major factors in the development of atopic dermatitis (AD). A systems-biology modeling approach can yield significant insights into these complex and dynamic processes through integration of prior biological data. Objective: To develop a multi-scale mathematical model of AD pathogenesis that describes the dynamic interplay between the skin barrier, environmental stress and immune dysregulation, and use it to achieve a coherent mechanistic understanding of onset, progression and prevention of AD. Methods: We mathematically investigated synergistic effects of known genetic and environmental risk factors on the dynamic onset and progression of the AD phenotype, from a mostly asymptomatic mild phenotype to a severe treatment-resistant form. Results: Our model analysis identified a âdouble switchâ, with two concatenated bistable switches, as a key network motif that dictates AD pathogenesis: The first switch is responsible for the reversible onset of inflammation; The second switch is triggered by long-lasting or frequent activation of the first switch, causing the irreversible onset of systemic Th2 sensitization and worsening of AD symptoms. Conclusions: Our mathematical analysis of the bistable switch predicts that genetic risk factors lower the threshold of environmental stressors to trigger systemic Th2 sensitization. This analysis predicts and explains four common clinical AD phenotypes from a mild and reversible phenotype through to severe and recalcitrant disease and provides a mechanistic explanation for clinically-demonstrated preventive effects of emollient treatments against development of AD
Photometric Properties of Kiso Ultraviolet-Excess Galaxies in the Lynx-Ursa Major Region
We have performed a systematic study of several regions in the sky where the
number of galaxies exhibiting star formation (SF) activity is greater than
average. We used Kiso ultraviolet-excess galaxies (KUGs) as our SF-enhanced
sample. By statistically comparing the KUG and non-KUG distributions, we
discovered four KUG-rich regions with a size of . One of these regions corresponds spatially to a filament of length
Mpc in the Lynx-Ursa Major region (). We call this ``the Lynx-Ursa
Major (LUM) filament''. We obtained surface photometry of 11 of
the KUGs in the LUM filament and used these to investigate the integrated
colors, distribution of SF regions, morphologies, and local environments. We
found that these KUGs consist of distorted spiral galaxies and compact galaxies
with blue colors. Their star formation occurs in the entire disk, and is not
confined to just the central regions. The colors of the SF regions imply that
active star formation in the spiral galaxies occurred yr ago,
while that of the compact objects occurred yr ago. Though the
photometric characteristics of these KUGs are similar to those of interacting
galaxies or mergers, most of these KUGs do not show direct evidence of merger
processes.Comment: 39 pages LaTeX, using aasms4.sty, 20 figures, ApJS accepted. The
Title of the previous one was truncated by the author's mistake, and is
corrected. Main body of the paper is unchange
Performance of the Charge Injection Capability of Suzaku XIS
A charge injection technique is applied to the X-ray CCD camera, XIS (X-ray
Imaging Spectrometer) onboard Suzaku. The charge transfer inefficiency (CTI) in
each CCD column (vertical transfer channel) is measured by the injection of
charge packets into a transfer channel and subsequent readout. This paper
reports the performances of the charge injection capability based on the ground
experiments using a radiation damaged device, and in-orbit measurements of the
XIS. The ground experiments show that charges are stably injected with the
dispersion of 91eV in FWHM in a specific column for the charges equivalent to
the X-ray energy of 5.1keV. This dispersion width is significantly smaller than
that of the X-ray events of 113eV (FWHM) at approximately the same energy. The
amount of charge loss during transfer in a specific column, which is measured
with the charge injection capability, is consistent with that measured with the
calibration source. These results indicate that the charge injection technique
can accurately measure column-dependent charge losses rather than the
calibration sources. The column-to-column CTI correction to the calibration
source spectra significantly reduces the line widths compared to those with a
column-averaged CTI correction (from 193eV to 173eV in FWHM on an average at
the time of one year after the launch). In addition, this method significantly
reduces the low energy tail in the line profile of the calibration source
spectrum.Comment: Paper contains 18 figures and 15 tables. Accepted for publication in
PAS
Water formation at low temperatures by surface O2 hydrogenation I: characterization of ice penetration
Water is the main component of interstellar ice mantles, is abundant in the
solar system and is a crucial ingredient for life. The formation of this
molecule in the interstellar medium cannot be explained by gas-phase chemistry
only and its surface hydrogenation formation routes at low temperatures (O, O2,
O3 channels) are still unclear and most likely incomplete. In a previous paper
we discussed an unexpected zeroth-order H2O production behavior in O2 ice
hydrogenation experiments compared to the first-order H2CO and CH3OH production
behavior found in former studies on hydrogenation of CO ice. In this paper we
experimentally investigate in detail how the structure of O2 ice leads to this
rare behavior in reaction order and production yield. In our experiments H
atoms are added to a thick O2 ice under fully controlled conditions, while the
changes are followed by means of reflection absorption infrared spectroscopy
(RAIRS). The H-atom penetration mechanism is systematically studied by varying
the temperature, thickness and structure of the O2 ice. We conclude that the
competition between reaction and diffusion of the H atoms into the O2 ice
explains the unexpected H2O and H2O2 formation behavior. In addition, we show
that the proposed O2 hydrogenation scheme is incomplete, suggesting that
additional surface reactions should be considered. Indeed, the detection of
newly formed O3 in the ice upon H-atom exposure proves that the O2 channel is
not an isolated route. Furthermore, the addition of H2 molecules is found not
to have a measurable effect on the O2 reaction channel.Comment: 1 page, 1 figur
Measurement of Stresses in Fixed-Bridge Restorations Using a Brittle Coating Technique
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67230/2/10.1177_00220345650440042201.pd
A Compensatory Mutation Provides Resistance to Disparate HIV Fusion Inhibitor Peptides and Enhances Membrane Fusion
Fusion inhibitors are a class of antiretroviral drugs used to prevent entry of HIV into host cells. Many of the fusion inhibitors being developed, including the drug enfuvirtide, are peptides designed to competitively inhibit the viral fusion protein gp41. With the emergence of drug resistance, there is an increased need for effective and unique alternatives within this class of antivirals. One such alternative is a class of cyclic, cationic, antimicrobial peptides known as Ξ-defensins, which are produced by many non-human primates and exhibit broad-spectrum antiviral and antibacterial activity. Currently, the Ξ-defensin analog RC-101 is being developed as a microbicide due to its specific antiviral activity, lack of toxicity to cells and tissues, and safety in animals. Understanding potential RC-101 resistance, and how resistance to other fusion inhibitors affects RC-101 susceptibility, is critical for future development. In previous studies, we identified a mutant, R5-tropic virus that had evolved partial resistance to RC-101 during in vitro selection. Here, we report that a secondary mutation in gp41 was found to restore replicative fitness, membrane fusion, and the rate of viral entry, which were compromised by an initial mutation providing partial RC-101 resistance. Interestingly, we show that RC-101 is effective against two enfuvirtide-resistant mutants, demonstrating the clinical importance of RC-101 as a unique fusion inhibitor. These findings both expand our understanding of HIV drug-resistance to diverse peptide fusion inhibitors and emphasize the significance of compensatory gp41 mutations. © 2013 Wood et al
Synthesis of titanate nanostructures using amorphous precursor material and their adsorption/photocatalytic properties
This paper reports on a new and swift hydrothermal chemical route to prepare
titanate nanostructures (TNS) avoiding the use of crystalline TiO2 as starting
material. The synthesis approach uses a commercial solution of TiCl3 as
titanium source to prepare an amorphous precursor, circumventing the use of
hazardous chemical compounds. The influence of the reaction temperature and
dwell autoclave time on the structure and morphology of the synthesised
materials was studied. Homogeneous titanate nanotubes with a high
length/diameter aspect ratio were synthesised at 160^{\circ}C and 24 h. A band
gap of 3.06\pm0.03 eV was determined for the TNS samples prepared in these
experimental conditions. This value is red shifted by 0.14 eV compared to the
band gap value usually reported for the TiO2 anatase. Moreover, such samples
show better adsorption capacity and photocatalytic performance on the dye
rhodamine 6G (R6G) photodegradation process than TiO2 nanoparticles. A 98%
reduction of the R6G concentration was achieved after 45 minutes of irradiation
of a 10 ppm dye aqueous solution and 1 g/L of TNS catalyst.Comment: 29 pages, 10 figures, accepted for publication in Journal of
Materials Scienc
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