1,753 research outputs found
Upper limits on the temperature of inspiraling astrophysical black holes
We present a method to constrain the temperature of astrophysical black holes
through detecting the inspiral phase of binary black hole coalescences. At
sufficient separation, inspiraling black holes can be regarded as isolated
objects, hence their temperature can still be defined. Due to their intrinsic
radiation, inspiraling black holes lose part of their masses during the
inspiral phase. As a result, coalescence speeds up, introducing a correction to
the orbital phase. We show that this dephasing may allow us to constrain the
temperature of inspiraling black holes through gravitational-wave detection.
Using the binary black-hole coalescences of the first two observing runs of the
Advanced LIGO and Virgo detectors, we constrain the temperature of parental
black holes to be less than about K. Such a constraint corresponds to
luminosity of about for a black hole of , which is about 20 orders of magnitude below the peak luminosity of
the corresponding gravitational-wave event, indicating no evidence for strong
quantum-gravity effects through the detection of the inspiral phase.Comment: Match the published versio
A SECI-Based Knowledge Conversion Model of Business Process Capture
Security questions are one of the mechanisms used to recover passwords. Strong answers to security questions (i.e. high entropy) are hard for attackers to guess or obtain using social engineering techniques (e.g. monitoring of social networking profiles), but at the same time are difficult to remember. Instead, weak answers to security questions (i.e. low entropy) are easy to remember, which makes them more vulnerable to cyber-attacks. Convenience leads users to use the same answers to security questions on multiple accounts, which exposes these accounts to numerous cyber-threats. Hence, current security questions implementations rarely achieve the required security and memorability requirements. This research study is the first step in the development of a model which investigates the determinants that influence usersā behavioural intentions through motivation to select strong and memorable answers to security questions. This research also provides design recommendations for novel security questions mechanisms
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Protease signaling regulates apical cell extrusion, cell contacts, and proliferation in epithelia.
Mechanisms that sense and regulate epithelial morphogenesis, integrity, and homeostasis are incompletely understood. Protease-activated receptor 2 (Par2), the Par2-activating membrane-tethered protease matriptase, and its inhibitor, hepatocyte activator inhibitor 1 (Hai1), are coexpressed in most epithelia and may make up a local signaling system that regulates epithelial behavior. We explored the role of Par2b in matriptase-dependent skin abnormalities in Hai1a-deficient zebrafish embryos. We show an unexpected role for Par2b in regulation of epithelial apical cell extrusion, roles in regulating proliferation that were opposite in distinct but adjacent epithelial monolayers, and roles in regulating cell-cell junctions, mobility, survival, and expression of genes involved in tissue remodeling and inflammation. The epidermal growth factor receptor Erbb2 and matrix metalloproteinases, the latter induced by Par2b, may contribute to some matriptase- and Par2b-dependent phenotypes and be permissive for others. Our results suggest that local protease-activated receptor signaling can coordinate cell behaviors known to contribute to epithelial morphogenesis and homeostasis
Prolonged AĪ² treatment leads to impairment in the ability of primary cortical neurons to maintain K+ and Ca2+ homeostasis
<p>Abstract</p> <p>Background</p> <p>Alzheimer's disease (AD) is a progressive neurodegenerative disease, characterised by the formation of insoluble amyloidogenic plaques and neurofibrillary tangles. Beta amyloid (AĪ²) peptide is one of the main constituents in AĪ² plaques, and is thought to be a primary causative agent in AD. Neurons are likely to be exposed to chronic, sublethal doses of AĪ² over an extended time during the pathogenesis of AD, however most studies published to date using <it>in vitro </it>models have focussed on acute studies. To experimentally model the progressive pathogenesis of AD, we exposed primary cortical neurons daily to 1 Ī¼M of AĪ²<sub>1-40 </sub>over 7 days and compared their survival with age-similar untreated cells. We also investigated whether chronic AĪ² exposure affects neuronal susceptibility to the subsequent acute excitotoxicity induced by 10 Ī¼M glutamate and assessed how Ca<sup>2+ </sup>and K<sup>+ </sup>homeostasis were affected by either treatment.</p> <p>Results</p> <p>We show that continuous exposure to 1 Ī¼M AĪ²<sub>1-40 </sub>for seven days decreased survival of cultured cortical neurons by 20%. This decrease in survival correlated with increased K<sup>+ </sup>efflux from the cells. One day treatment with 1 Ī¼M AĪ² followed by glutamate led to a substantially higher K<sup>+ </sup>efflux than in the age-similar untreated control. This difference further increased with the duration of the treatment. K<sup>+ </sup>efflux also remained higher in AĪ² treated cells 20 min after glutamate application leading to 2.8-fold higher total K<sup>+ </sup>effluxed from the cells compared to controls. Ca<sup>2+ </sup>uptake was significantly higher only after prolonged AĪ² treatment with 2.5-fold increase in total Ca<sup>2+ </sup>uptake over 20 min post glutamate application after six days of AĪ² treatment or longer (P < 0.05).</p> <p>Conclusions</p> <p>Our data suggest that long term exposure to AĪ² is detrimental because it reduces the ability of cortical neurons to maintain K<sup>+ </sup>and Ca<sup>2+ </sup>homeostasis in response to glutamate challenge, a response that might underlie the early symptoms of AD. The observed inability to maintain K<sup>+ </sup>homeostasis might furthermore be useful in future studies as an early indicator of pathological changes in response to AĪ².</p
Transcriptome Analyses of Tumor-Adjacent Somatic Tissues Reveal Genes Co-Expressed with Transposable Elements
Background: Despite the long-held assumption that transposons are normally only expressed in the germ-line, recent evidence shows that transcripts of transposable element (TE) sequences are frequently found in the somatic cells. However, the extent of variation in TE transcript levels across different tissues and different individuals are unknown, and the co-expression between TEs and host gene mRNAs have not been examined. Results: Here we report the variation in TE derived transcript levels across tissues and between individuals observed in the non-tumorous tissues collected for The Cancer Genome Atlas. We found core TE co-expression modules consisting mainly of transposons, showing correlated expression across broad classes of TEs. Despite this co-expression within tissues, there are individual TE loci that exhibit tissue-specific expression patterns, when compared across tissues. The core TE modules were negatively correlated with other gene modules that consisted of immune response genes in interferon signaling. KRAB Zinc Finger Proteins (KZFPs) were over-represented gene members of the TE modules, showing positive correlation across multiple tissues. But we did not find overlap between TE-KZFP pairs that are co-expressed and TE-KZFP pairs that are bound in published ChIP-seq studies. Conclusions: We find unexpected variation in TE derived transcripts, within and across non-tumorous tissues. We describe a broad view of the RNA state for non-tumorous tissues exhibiting higher level of TE transcripts. Tissues with higher level of TE transcripts have a broad range of TEs co-expressed, with high expression of a large number of KZFPs, and lower RNA levels of immune genes
NON-PERIODIC LATTICE STRUCTURE DESIGN FOR ADDITIVE MANUFACTURING
Department of Mechanical EngineeringAs manufacturability of lattice structures has been relaxed with the availability of additive manufacturing (AM) technology, the study of cellular structure optimization has seen a rapid development during the past decade. Numerous design approaches for lattice structures have been proposed to help designers fabricate efficient lattice model. Generally, these approaches demand for unbearable computational cost and prior knowledge. To overcome the drawbacks of existing methods, Choi et al. proposes a simple framework of generating non-periodic lattice structures using topologically pre-optimized building blocks. However, this method does not properly consider the manufacturability of the lattice structure by neglecting additive manufacturing constraints in the design process. This thesis suggests a strategy to consider manufacturing constraints for the AM process in a contemporary lattice structure generation framework, in this case, Choi et al. work. The proposed method is devised to take full advantage of the already existing components, i.e. building block library, in order not to add complexity in the overall process. Considering the manufacturability of the lattice designs, an algorithm derived from the STL slicing method is introduced in the selection process to replace unprintable building blocks for optimal microstructure. Finally, numerical examples are presented, and reasonable solutions have been obtained to show the feasibility of the proposed method.clos
Targeted search for the kinematic dipole of the gravitational-wave background
There is growing interest in using current and future gravitational-wave
interferometers to search for anisotropies in the gravitational-wave
background. One guaranteed anisotropic signal is the kinematic dipole induced
by our peculiar motion with respect to the cosmic rest frame, as measured in
other full-sky observables such as the cosmic microwave background. Our prior
knowledge of the amplitude and direction of this dipole is not explicitly
accounted for in existing searches by LIGO/Virgo/KAGRA, but could provide
crucial information to help disentangle the sources which contribute to the
gravitational-wave background. Here we develop a targeted search pipeline which
uses this prior knowledge to enable unbiased and minimum-variance inference of
the dipole magnitude. Our search generalises existing methods to allow for a
time-dependent signal model, which captures the annual modulation of the dipole
due to the Earth's orbit. We validate our pipeline on mock data, demonstrating
that neglecting this time dependence can bias the inferred dipole by as much as
. We then run our analysis on the full LIGO/Virgo O1+O2+O3 dataset,
obtaining upper limits on the dipole amplitude that are consistent with
existing anisotropic search results.Comment: 12 pages, 3 figure
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