417 research outputs found
Translational and rotational diffusion coefficients in nanofluids from polarized dynamic light scattering
Nanofluids representing nanometer-sized solid particles dispersed in liquids are of interest in many
fields of process and energy engineering, e.g., heat transfer, catalysis, and the design of functionalized
materials [1]. The physical, chemical, optical, and electronic properties of nanofluids are strongly driven
by the size, shape, surface potential, and concentration of the nanoparticles. For the analysis of diffusive
processes in nanofluids allowing access to, e.g., particle size and its distribution, dynamic light scattering
(DLS) is the state-of-the-art technique. It is based on the analysis of microscopic fluctuations originating
from the random thermal movement of particles in the continuous liquid phase at macroscopic
thermodynamic equilibrium. For anisotropic particles or particle aggregates, besides translational
diffusion also rotational diffusion occurs. To obtain the sum of the orientation-averaged translational
(DT) and rotational (DR) diffusivities by depolarized DLS [2], a homodyne detection scheme is usually
applied which can hardly be fulfilled in the experimental realization. Furthermore, the experiments are
restricted to limited ranges for temperature, particle concentration, and viscosity
Comments on the European Commission’s Proposal for a Regulation on the Law Applicable to Contractual Obligations („Rome I“) of December 15, 2005 and the European Parliament Committee on Legal Affairs’ Draft Report on the Proposal of August 22, 2006
The behaviour of political parties and MPs in the parliaments of the Weimar Republic
Copyright @ 2012 The Authors. This is the author's accepted manuscript. The final published article is available from the link below.Analysing the roll-call votes of the MPs of the Weimar Republic we find: (1) that party competition in the Weimar parliaments can be structured along two dimensions: an economic left–right and a pro-/anti-democratic. Remarkably, this is stable throughout the entire lifespan of the Republic and not just in the later years and despite the varying content of votes across the lifespan of the Republic, and (2) that nearly all parties were troubled by intra-party divisions, though, in particular, the national socialists and communists became homogeneous in the final years of the Republic.Zukunftskolleg, University of Konstan
Mg-chelatase of tobacco: The role of the subunit CHL D in the chelation step of protoporphyrin IX
Versatile strategy for homogeneous drying patterns of dispersed particles
After spilling coffee, a tell-tale stain is left by the drying droplet. This universal phenomenon, known as the coffee ring effect, is observed independent of the dispersed material. However, for many technological processes such as coating techniques and ink-jet printing a uniform particle deposition is required and the coffee ring effect is a major drawback. Here, we present a simple and versatile strategy to achieve homogeneous drying patterns using surface-modified particle dispersions. High-molecular weight surface-active polymers that physisorb onto the particle surfaces provide enhanced steric stabilization and prevent accumulation and pinning at the droplet edge. In addition, in the absence of free polymer in the dispersion, the surface modification strongly enhances the particle adsorption to the air/liquid interface, where they experience a thermal Marangoni backflow towards the apex of the drop, leading to uniform particle deposition after drying. The method is independent of particle shape and applicable to a variety of commercial pigment particles and different dispersion media, demonstrating the practicality of this work for everyday processes
Biophysical Investigation of the Mode of Inhibition of Tetramic Acids, the Allosteric Inhibitors of Undecaprenyl Pyrophosphate Synthase
Undecaprenyl pyrophosphate synthase (UPPS) catalyzes the consecutive condensation of eight molecules of isopentenyl pyrophosphate (IPP) with farnesyl pyrophosphate (FPP) to generate the C(55) undecaprenyl pyrophosphate (UPP). It has been demonstrated that tetramic acids (TAs) are selective and potent inhibitors of UPPS, but the mode of inhibition was unclear. In this work, we used a fluorescent FPP probe to study possible TA binding at the FPP binding site. A photosensitive TA analogue was designed and synthesized for the study of the site of interaction of TA with UPPS using photo-cross-linking and mass spectrometry. The interaction of substrates with UPPS and with the UPPS.TA complex was investigated by protein fluorescence spectroscopy. Our results suggested that tetramic acid binds to UPPS at an allosteric site adjacent to the FPP binding site. TA binds to free UPPS enzyme but not to substrate-bound UPPS. Unlike Escherichia coli UPPS which follows an ordered substrate binding mechanism, Streptococcus pneumoniae UPPS appears to follow a random-sequential substrate binding mechanism. Only one substrate, FPP or IPP, is able to bind to the UPPS.TA complex, but the quaternary complex, UPPS.TA.FPP.IPP, cannot be formed. We propose that binding of TA to UPPS significantly alters the conformation of UPPS needed for proper substrate binding. As the result, substrate turnover is prevented, leading to the inhibition of UPPS catalytic activity. These probe compounds and biophysical assays also allowed us to quickly study the mode of inhibition of other UPPS inhibitors identified from a high-throughput screening and inhibitors produced from a medicinal chemistry program
Image quality assessment of the right ventricle with three different delayed enhancement sequences in patients suspected of ARVC/D
Histopathologic findings in arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) are replacement of the normal myocardium with fatty and fibrous elements with preferential involvement of the right ventricle. The right ventricular fibrosis can be visualised by post-gadolinium delayed enhancement inversion recovery imaging (DE imaging). We compared the image quality of three different gradient echo MRI sequences for short axis DE imaging of the right ventricle (RV). We retrospectively analysed MRI scans performed between February 2005 and December 2008 in 97 patients (mean age: 41.2 years, 67% men) suspected of ARVC/D. For DE imaging either a 2D Phase Sensitive (PSIR), a 2D (2D) or a 3D (3D) inversion recovery sequence was used in respectively 38, 32 and 27 MRI-examinations. The RV, divided in 10 segments, was assessed for image quality by two radiologists in random sequence. A consensus reading was performed if results differed between the two readings. Image quality was good in 24% of all segments in the 3D group, 66% in the 2D group and 79% in the PSIR group. Poor image quality was observed in 51% (3D), 10% (2D), and 2% (PSIR) of all segments. Exams were considered suitable for clinical use in 7% of exams in the 3D group, 75% of exams in the 2D group and 90% of exams of the PSIR group. Breathing-artifacts occurred in 22% (3D), 59% (2D) and 53% (PSIR). Motion-artifacts occurred in 56% (3D), 28% (2D) and 29% (PSIR). Post-gadolinium imaging using the PSIR sequence results in better and more consistent image quality of the RV compared to the 2D and 3D sequences
The Max b-HLH-LZ Can Transduce into Cells and Inhibit c-Myc Transcriptional Activities
The inhibition of the functions of c-Myc (endogenous and oncogenic) was recently shown to provide a spectacular therapeutic index in cancer mouse models, with complete tumor regression and minimal side-effects in normal tissues. This was achieved by the systemic and conditional expression of omomyc, the cDNA of a designed mutant of the b-HLH-LZ of c-Myc named Omomyc. The overall mode of action of Omomyc consists in the sequestration of Max and the concomitant competition of the Omomyc/Max complex with the endogenous c-Myc/Max heterodimer. This leads to the inhibition of the transactivation of Myc target genes involved in proliferation and metabolism. While this body of work has provided extraordinary insights to guide the future development of new cancer therapies that target c-Myc, Omomyc itself is not a therapeutic agent. In this context, we sought to exploit the use of a b-HLH-LZ to inhibit c-Myc in a cancer cell line in a more direct fashion. We demonstrate that the b-HLH-LZ domain of Max (Max*) behaves as a bona fide protein transduction domain (PTD) that can efficiently transduce across cellular membrane via through endocytosis and translocate to the nucleus. In addition, we show that the treatment of HeLa cells with Max* leads to a reduction of metabolism and proliferation rate. Accordingly, we observe a decrease of the population of HeLa cells in S phase, an accumulation in G1/G0 and the induction of apoptosis. In agreement with these phenotypic changes, we show by q-RT-PCR that the treatment of HeLa cells with Max* leads to the activation of the transcription c-Myc repressed genes as well as the repression of the expression of c-Myc activated genes. In addition to the novel discovery that the Max b-HLH-LZ is a PTD, our findings open up new avenues and strategies for the direct inhibition of c-Myc with b-HLH-LZ analogs
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