4,305 research outputs found
Synthesis and characterization of hybrid organic-inorganic materials based on sulphonated polyamideimide and silica
The preparation of hybrid organicβinorganic
membrane materials based on a sulphonated polyamideimide
resin and silica filler has been studied. The method
allows the solβgel process to proceed in the presence of a
high molecular weight polyamideimide, resulting in well
dispersed silica nanoparticles (<50 nm) within the polymer
matrix with chemical bonding between the organic and
inorganic phases. Tetraethoxysilane (TEOS) was used as
the silica precursor and the organosilicate networks were
bonded to the polymer matrix via a coupling agent
aminopropyltriethoxysilane (APTrEOS). The structure and
properties of these hybrid materials were characterized via a
range of techniques including FTIR, TGA, DSC, SEM and
contact angle analysis. It was found that the compatibility
between organic and inorganic phases has been greatly
enhanced by the incorporation of APTrEOS. The thermal
stability and hydrophilic properties of hybrid materials have
also been significantly improved
Standing waves for acoustic levitation
Standing waves are the most popular method to achieve acoustic trapping. Particles with greater acoustic impedance than the propagation medium will be trapped at the pressure nodes of a standing wave. Acoustic trapping can be used to hold particles of various materials and sizes, without the need of a close-loop controlling system. Acoustic levitation is a helpful and versatile tool for biomaterials and chemistry, with applications in spectroscopy and lab-on-a-droplet procedures. In this chapter, multiple methods are presented to simulate the acoustic field generated by one or multiple emitters. From the acoustic field, models such as the Gor'kov potential or the Flux Integral are applied to calculate the force exerted on the levitated particles. The position and angle of the acoustic emitters play a fundamental role, thus we analyse commonly used configurations such as emitter and reflector, two opposed emitters, or arrangements using phased arrays
An AUC-based Permutation Variable Importance Measure for Random Forests
The random forest (RF) method is a commonly used tool for classification with high dimensional data as well as for ranking candidate predictors based on the so-called random forest variable importance measures (VIMs). However the classification performance of RF is known to be suboptimal in case of strongly unbalanced data, i.e. data where response class sizes differ considerably. Suggestions were made to obtain better classification performance based either on sampling procedures or on cost sensitivity analyses. However to our knowledge the performance of the VIMs has not yet been examined in the case of unbalanced response classes. In this paper we explore the performance of the permutation VIM for unbalanced data settings and introduce an alternative permutation VIM based on the area under the curve (AUC) that is expected to be more robust towards class imbalance. We investigated the performance of the standard permutation VIM and of our novel AUC-based permutation VIM for different class imbalance levels using simulated data and real data. The results suggest that the standard permutation VIM loses its ability to discriminate between associated predictors and predictors not associated with the response for increasing class imbalance. It is outperformed by our new AUC-based permutation VIM for unbalanced data settings, while the performance of both VIMs is very similar in the case of balanced classes. The new AUC-based VIM is implemented in the R package party for the unbiased RF variant based on conditional inference trees. The codes implementing our study are available from the companion website: http://www.ibe.med.uni-muenchen.de/organisation/mitarbeiter/070_drittmittel/janitza/index.html
Nonlinear vortex light beams supported and stabilized by dissipation
We describe nonlinear Bessel vortex beams as localized and stationary
solutions with embedded vorticity to the nonlinear Schr\"odinger equation with
a dissipative term that accounts for the multi-photon absorption processes
taking place at high enough powers in common optical media. In these beams,
power and orbital angular momentum are permanently transferred to matter in the
inner, nonlinear rings, at the same time that they are refueled by spiral
inward currents of energy and angular momentum coming from the outer linear
rings, acting as an intrinsic reservoir. Unlike vortex solitons and dissipative
vortex solitons, the existence of these vortex beams does not critically depend
on the precise form of the dispersive nonlinearities, as Kerr self-focusing or
self-defocusing, and do not require a balancing gain. They have been shown to
play a prominent role in "tubular" filamentation experiments with powerful,
vortex-carrying Bessel beams, where they act as attractors in the beam
propagation dynamics. Nonlinear Bessel vortex beams provide indeed a new
solution to the problem of the stable propagation of ring-shaped vortex light
beams in homogeneous self-focusing Kerr media. A stability analysis
demonstrates that there exist nonlinear Bessel vortex beams with single or
multiple vorticity that are stable against azimuthal breakup and collapse, and
that the mechanism that renders these vortexes stable is dissipation. The
stability properties of nonlinear Bessel vortex beams explain the experimental
observations in the tubular filamentation experiments.Comment: Chapter of boo
Plasmonically Enhanced Reflectance of Heat Radiation from Low-Bandgap Semiconductor Microinclusions
Increased reflectance from the inclusion of highly scattering particles at
low volume fractions in an insulating dielectric offers a promising way to
reduce radiative thermal losses at high temperatures. Here, we investigate
plasmonic resonance driven enhanced scattering from microinclusions of
low-bandgap semiconductors (InP, Si, Ge, PbS, InAs and Te) in an insulating
composite to tailor its infrared reflectance for minimizing thermal losses from
radiative transfer. To this end, we compute the spectral properties of the
microcomposites using Monte Carlo modeling and compare them with results from
Fresnel equations. The role of particle size-dependent Mie scattering and
absorption efficiencies, and, scattering anisotropy are studied to identify the
optimal microinclusion size and material parameters for maximizing the
reflectance of the thermal radiation. For composites with Si and Ge
microinclusions we obtain reflectance efficiencies of 57 - 65% for the incident
blackbody radiation from sources at temperatures in the range 400 - 1600
{\deg}C. Furthermore, we observe a broadbanding of the reflectance spectra from
the plasmonic resonances due to charge carriers generated from defect states
within the semiconductor bandgap. Our results thus open up the possibility of
developing efficient high-temperature thermal insulators through use of the
low-bandgap semiconductor microinclusions in insulating dielectrics.Comment: Main article (8 Figures and 2 Tables) + Supporting Information (8
Figures
Triad3a induces the degradation of early necrosome to limit RipK1-dependent cytokine production and necroptosis.
Understanding the molecular signaling in programmed cell death is vital to a practical understanding of inflammation and immune cell function. Here we identify a previously unrecognized mechanism that functions to downregulate the necrosome, a central signaling complex involved in inflammation and necroptosis. We show that RipK1 associates with RipK3 in an early necrosome, independent of RipK3 phosphorylation and MLKL-induced necroptotic death. We find that formation of the early necrosome activates K48-ubiquitin-dependent proteasomal degradation of RipK1, Caspase-8, and other necrosomal proteins. Our results reveal that the E3-ubiquitin ligase Triad3a promotes this negative feedback loop independently of typical RipK1 ubiquitin editing enzymes, cIAPs, A20, or CYLD. Finally, we show that Triad3a-dependent necrosomal degradation limits necroptosis and production of inflammatory cytokines. These results reveal a new mechanism of shutting off necrosome signaling and may pave the way to new strategies for therapeutic manipulation of inflammatory responses
Topology optimization for human proximal femur considering bi-modulus behavior of cortical bones
Β© Springer International Publishing Switzerland 2015. The material in the human proximal femur is considered as bi-modulus material and the density distribution is predicted by topology optimization method. To reduce the computational cost, the bi-modulus material is replaced with two isotropic materials in simulation. The selection of local material modulus is determined by the previous local stress state. Compared with density prediction results by traditional isotropic material in proximal femur, the bi-modulus material layouts are different obviously. The results also demonstrate that the bi-modulus material model is better than the isotropic material model in simulation of density prediction in femur bone
Characteristics of transposable element exonization within human and mouse
Insertion of transposed elements within mammalian genes is thought to be an
important contributor to mammalian evolution and speciation. Insertion of
transposed elements into introns can lead to their activation as alternatively
spliced cassette exons, an event called exonization. Elucidation of the
evolutionary constraints that have shaped fixation of transposed elements
within human and mouse protein coding genes and subsequent exonization is
important for understanding of how the exonization process has affected
transcriptome and proteome complexities. Here we show that exonization of
transposed elements is biased towards the beginning of the coding sequence in
both human and mouse genes. Analysis of single nucleotide polymorphisms (SNPs)
revealed that exonization of transposed elements can be population-specific,
implying that exonizations may enhance divergence and lead to speciation. SNP
density analysis revealed differences between Alu and other transposed
elements. Finally, we identified cases of primate-specific Alu elements that
depend on RNA editing for their exonization. These results shed light on TE
fixation and the exonization process within human and mouse genes.Comment: 11 pages, 4 figure
The incidence of liver injury in Uyghur patients treated for TB in Xinjiang Uyghur autonomous region, China, and its association with hepatic enzyme polymorphisms nat2, cyp2e1, gstm1 and gstt1.
BACKGROUND AND OBJECTIVE: Of three first-line anti-tuberculosis (anti-TB) drugs, isoniazid is most commonly associated with hepatotoxicity. Differences in INH-induced toxicity have been attributed to genetic variability at several loci, NAT2, CYP2E1, GSTM1and GSTT1, that code for drug-metabolizing enzymes. This study evaluated whether the polymorphisms in these enzymes were associated with an increased risk of anti-TB drug-induced hepatitis in patients and could potentially be used to identify patients at risk of liver injury. METHODS AND DESIGN: In a cross-sectional study, 2244 tuberculosis patients were assessed two months after the start of treatment. Anti-TB drug-induced liver injury (ATLI) was defined as an ALT, AST or bilirubin value more than twice the upper limit of normal. NAT2, CYP2E1, GSTM1 and GSTT1 genotypes were determined using the PCR/ligase detection reaction assays. RESULTS: 2244 patients were evaluated, there were 89 cases of ATLI, a prevalence of 4% 9 patients (0.4%) had ALT levels more than 5 times the upper limit of normal. The prevalence of ATLI was greater among men than women, and there was a weak association with NAT2*5 genotypes, with ATLI more common among patients with the NAT2*5*CT genotype. The sensitivity of the CT genotype for identifying patients with ATLI was 42% and the positive predictive value 5.9%. CT ATLI was more common among slow acetylators (prevalence ratio 2.0 (95% CI 0.95,4.20) )compared to rapid acetylators. There was no evidence that ATLI was associated with CYP2E1 RsaIc1/c1genotype, CYP2E1 RsaIc1/c2 or c2/c2 genotypes, or GSTM1/GSTT1 null genotypes. CONCLUSIONS: In Xinjiang Uyghur TB patients, liver injury was associated with the genetic variant NAT2*5, however the genetic markers studied are unlikely to be useful for screening patients due to the low sensitivity and low positive predictive values for identifying persons at risk of liver injury
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