227 research outputs found
A Formal Treatment of Generalized Preferential Attachment and its Empirical Validation
Generalized preferential attachment is defined as the tendency of a vertex to
acquire new links in the future with respect to a particular vertex property.
Understanding which properties influence link acquisition tendency (LAT) gives
us a predictive power to estimate the future growth of network and insight
about the actual dynamics governing the complex networks. In this study, we
explore the effect of age and degree on LAT by analyzing data collected from a
new complex-network growth dataset. We found that LAT and degree of a vertex
are linearly correlated in accordance with previous studies. Interestingly, the
relation between LAT and age of a vertex is found to be in conflict with the
known models of network growth. We identified three different periods in the
network's lifetime where the relation between age and LAT is strongly positive,
almost stationary and negative correspondingly
Wave propagation in stereo-lithographical (STL) bone replicas at oblique incidence
Comparisons between predictions of a Biot-Allard model allowing for angle-dependent elasticity and
angle-and-porosity dependent tortuosity and transmission data obtained at normal incidence on
water-saturated replica bones are extended to oblique incidence. The model includes two parameters
which are adjusted for best fit at normal incidence. Using the same parameter values, it is found that predictions
of the variation of transmitted waveforms with angle through two types of bone replica are in
reasonable agreement with data despite the fact that scattering is not included in the theory
On the mechanical modeling of cell components
Eukaryotic cells are complex systems which carry out a variety of different tasks. The current contribution gives insight into the modeling of some of their vital components and represents an overview of results achieved within the international D‐A‐CH project on computational modeling of transport processes in a cell. The first part of the contribution studies viscoelastic effects of cross‐linked actin network embedded in cytosol. The basic‐model is used to simulate the actin behavior at a microscopic level. It considers the influence of the physical length, the end‐to‐end distance and the stretch modulus in order to provide a relationship between the stretch of a single polymer chain and the applied tension force. The effective behavior of the cell cytoplasm is simulated by using the multiscale finite element method. Here, a standard large strain viscous approach is applied for the cytosol, while the generalized Maxwell model simulates viscous effects occurring in filaments due to deviatoric changes. The examples dealing with combinations of tension‐holding tests give insight into the effective behavior of the cytoplasm
TiO2 thin film transistor by atomic layer deposition
In this study, TiO2 films were deposited using thermal Atomic Layer Deposition (ALD) system. It is observed that asdeposited ALD TiO 2 films are amorphous and not suitable as TFT channel material. In order to use the film as channel material, a post-annealing process is needed. Annealed films transform into a polycrystalline form containing mixed anatase and rutile phases. For this purpose, devices are annealed at 475°C and observed that their threshold voltage value is 6.5V, subthreshold slope is 0.35 V/dec, Ion/Ioff ratios 2.5×106 and mobility value is 0.672 cm2/V.s. Optical response measurements showed that devices exhibits decent performance at ultraviolet region where TiO 2 has band to band absorption mechanism. © 2013 SPIE
Simple sequence repeat-based assessment of genetic diversity in 'Dimrit' and 'Gemre' grapevine accessions from Turkey
It is widely believed that Turkey has played an important role in the evolution of modern day grapes due to its unique geographical location with close proximity to the regions of grape diversity. Despite this, the rich grape germplasm found in Turkey has not been sufficiently analyzed genetically. In this study, 31 grapevine accessions from 'Dimrit' (or 'Dilmit') and 'Gemre' grape groups were genetically analyzed at eight SSR (microsatellite) loci (VVS2, VVMD5, VVMD7, VVMD24, VVMD27, VVMD28, VrZAG62 and VrZAG79) and for a number of ampeolographic characteristics. These analyses identified sufficient genetic diversity between these two grape groups that, in general, clustered separately in the dendrogram constructed based on the SSR data. However, the ecogeographical distribution and genetic relationship of the genotypes did not show any significant correlation. Two 'Gemre' accessions were determined as genetically identical. In addition, one case of synonym and several cases of homonym genotypes were identified. The results reported here are important first steps towards better characterization of these grape genotypes and would aid future germplasm management and breeding efforts.
Thin film MoS2 nanocrystal based ultraviolet photodetector
We report on the development of UV range photodetector based on molybdenum disulfide nanocrystals (MoS2-NCs). The inorganic MoS2- NCs are produced by pulsed laser ablation technique in deionized water and the colloidal MoS2-NCs are characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction and UV/VIS absorption measurements. The photoresponse studies indicate that the fabricated MoS 2- NCs photodetector (MoS2-NCs PD) operates well within 300-400 nm UV range, with diminishing response at visible wavelengths, due to the MoS2- NCs absorption characteristics. The structural and the optical properties of laser generated MoS2-NCs suggest promising applications in the field of photonics and optoelectronics. © 2012 Optical Society of America
Mutation of cancer driver MLL2 results in transcription stress and genome instability
Genome instability is a recurring feature of tumorigenesis. Mutation in MLL2, encoding a histone methyltransferase, is a driver in numerous different cancer types, but the mechanism is unclear. Here, we present evidence that MLL2 mutation results in genome instability. Mouse cells in which MLL2 gene deletion can be induced display elevated levels of sister chromatid exchange, gross chromosomal aberrations, 53BP1 foci, and micronuclei. Human MLL2 knockout cells are characterized by genome instability as well. Interestingly, MLL2 interacts with RNA polymerase II (RNAPII) and RECQL5, and, although MLL2 mutated cells have normal overall H3K4me levels in genes, nucleosomes in the immediate vicinity of RNAPII are hypomethylated. Importantly,MLL2 mutated cells display signs of substantial transcription stress, and the most affected genes overlap with early replicating fragile sites, show elevated levels ofγH2AX, and suffer frequent mutation. The requirement for MLL2 in the maintenance of genome stability in genes helps explain its widespread role in cancer and points to transcription stress as a strong driver in tumorigenesis
Spectral renormalization group theory on networks
Discrete amorphous materials are best described in terms of arbitrary
networks which can be embedded in three dimensional space. Investigating the
thermodynamic equilibrium as well as non-equilibrium behavior of such materials
around second order phase transitions call for special techniques.
We set up a renormalization group scheme by expanding an arbitrary scalar
field living on the nodes of an arbitrary network, in terms of the eigenvectors
of the normalized graph Laplacian. The renormalization transformation involves,
as usual, the integration over the more "rapidly varying" components of the
field, corresponding to eigenvectors with larger eigenvalues, and then
rescaling. The critical exponents depend on the particular graph through the
spectral density of the eigenvalues.Comment: 17 pages, 3 figures, presented at the Continuum Models and Discrete
Systems (CMDS-12), 21-25 Feb 2011, Saha Institute of Nuclear Physics,
Kolkata, Indi
Acinetobacter baumannii in intensive care unit: A novel system to study clonal relationship among the isolates
<p>Abstract</p> <p>Background</p> <p>The nosocomial infections surveillance system must be strongly effective especially in highly critic areas, such as Intensive Care Units (ICU). These areas are frequently an epidemiological epicentre for transmission of multi-resistant pathogens, like <it>Acinetobacter baumannii</it>. As an epidemic outbreak occurs it is very important to confirm or exclude the genetic relationship among the isolates in a short time. There are several molecular typing systems used with this aim. The Repetitive sequence-based PCR (REP-PCR) has been recognized as an effective method and it was recently adapted to an automated format known as the DiversiLab system.</p> <p>Methods</p> <p>In the present study we have evaluated the combination of a newly introduced software package for the control of hospital infection (VIGI@ct) with the DiversiLab system. In order to evaluate the reliability of the DiversiLab its results were also compared with those obtained using f-AFLP.</p> <p>Results</p> <p>The combination of VIGI@ct and DiversiLab enabled an earlier identification of an <it>A. baumannii </it>epidemic cluster, through the confirmation of the genetic relationship among the isolates. This cluster regards 56 multi-drug-resistant <it>A. baumannii </it>isolates from several specimens collected from 13 different patients admitted to the ICU in a ten month period. The <it>A. baumannii </it>isolates were clonally related being their similarity included between 97 and 100%. The results of the DiversiLab were confirmed by f-AFLP analysis.</p> <p>Conclusion</p> <p>The early identification of the outbreak has led to the prompt application of operative procedures and precautions to avoid the spread of pathogen. To date, 6 months after the last <it>A. baumannii </it>isolate, no other related case has been identified.</p
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