909 research outputs found
Triphilic ionic-liquid mixtures: fluorinated and non-fluorinated aprotic ionic-liquid mixtures
We present here the possibility of forming triphilic mixtures from alkyl- and fluoroalkylimidazolium ionic liquids, thus, macroscopically homogeneous mixtures for which instead of the often observed two domainspolar and nonpolarthree stable microphases are present: polar, lipophilic, and fluorous ones. The fluorinated side chains of the cations indeed self-associate and form domains that are segregated from those of the polar and alkyl domains. To enable miscibility, despite the generally preferred macroscopic separation between fluorous and alkyl moieties, the importance of strong hydrogen bonding is shown. As the long-range structure in the alkyl and fluoroalkyl domains is dependent on the composition of the liquid, we propose that the heterogeneous, triphilic structure can be easily tuned by the molar ratio of the components. We believe that further development may allow the design of switchable, smart liquids that change their properties in a predictable way according to their composition or even their environment
Hellenistische und kaiserzeitliche Weihreliefs aus dem nördlichen Mysien:Ikonographie und Typologie einer DenkmĂ€lergruppe und ihre Bedeutung fĂŒr die Religionsgeschichte einer antiken Landschaft
Die vorliegende Arbeit untersucht die spĂ€thellenistischen und kaiserzeitlichen Weihreliefs aus dem nördlichen Mysien unter stilistischen, ikonographischen und typologischen Gesichtspunkten. Die DenkmĂ€ler werden zudem auf ihre AbhĂ€ngigkeit von den klassischen attischen Weihreliefs und ihre Beziehungen zu den Grabreliefs der gleichen Zeit hin ĂŒberprĂŒft. Die Auswertung zeigt, wie sehr die klassischen VorlĂ€ufer ikonographisch und typologisch prĂ€gend waren, die ihrerseits aber auch mit einheimischen Stil- und Darstellungselementen verbunden werden konnten. Weihreliefs und Grabreliefs nĂ€hern sich dabei typologisch an. ErgĂ€nzt wird die archĂ€ologische Bewertung der DenkmĂ€ler durch epigraphische, topographische und historische Aspekte. Die aus den Untersuchungsparametern gewonnenen Ergebnisse beleuchten nicht nur die StilphĂ€nomene spĂ€thellenistischer und kaiserzeitlicher Reliefplastik, sondern leisten einen wesentlichen Beitrag zur Religionsgeschichte dieser kleinasiatischen Landschaft
Serial protein crystallography in an electron microscope
Serial X-ray crystallography at free-electron lasers allows to solve biomolecular structures from sub-micron-sized crystals. However, beam time at these facilities is scarce, and involved sample delivery techniques are required. On the other hand, rotation electron diffraction (MicroED) has shown great potential as an alternative means for protein nano-crystallography. Here, we present a method for serial electron diffraction of protein nanocrystals combining the benefits of both approaches. In a scanning transmission electron microscope, crystals randomly dispersed on a sample grid are automatically mapped, and a diffraction pattern at fixed orientation is recorded from each at a high acquisition rate. Dose fractionation ensures minimal radiation damage effects. We demonstrate the method by solving the structure of granulovirus occlusion bodies and lysozyme to resolutions of 1.55âĂ
and 1.80âĂ
, respectively. Our method promises to provide rapid structure determination for many classes of materials with minimal sample consumption, using readily available instrumentation
Infrared spectroscopy and nano-imaging of the insulator-to-metal transition in vanadium dioxide
We present a detailed infrared study of the insulator-to-metal transition
(IMT) in vanadium dioxide (VO2) thin films. Conventional infrared spectroscopy
was employed to investigate the IMT in the far-field. Scanning near-field
infrared microscopy directly revealed the percolative IMT with increasing
temperature. We confirmed that the phase transition is also percolative with
cooling across the IMT. We present extensive near-field infrared images of
phase coexistence in the IMT regime in VO2. We find that the coexisting
insulating and metallic regions at a fixed temperature are static on the time
scale of our measurements. A novel approach for analyzing the far-field and
near-field infrared data within the Bruggeman effective medium theory was
employed to extract the optical constants of the incipient metallic puddles at
the onset of the IMT. We found divergent effective carrier mass in the metallic
puddles that demonstrates the importance of electronic correlations to the IMT
in VO2. We employ the extended dipole model for a quantitative analysis of the
observed near-field infrared amplitude contrast and compare the results with
those obtained with the basic dipole model.Comment: 18 pages including 8 figure
Range extension of Boeckella bergi Richard, 1897 (Crustacea: Copepoda: Centropagidae), with comments on the taxonomy of the species
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DNA binds to a specific site of the adhesive blood-protein von Willebrand factor guided by electrostatic interactions.
Neutrophils release their intracellular content, DNA included, into the bloodstream to form neutrophil extracellular traps (NETs) that confine and kill circulating pathogens. The mechanosensitive adhesive blood protein, von Willebrand Factor (vWF), interacts with the extracellular DNA of NETs to potentially immobilize them during inflammatory and coagulatory conditions. Here, we elucidate the previously unknown molecular mechanism governing the DNA-vWF interaction by integrating atomistic, coarse-grained, and Brownian dynamics simulations, with thermophoresis, gel electrophoresis, fluorescence correlation spectroscopy (FCS), and microfluidic experiments. We demonstrate that, independently of its nucleotide sequence, double-stranded DNA binds to a specific helix of the vWF A1 domain, via three arginines. This interaction is attenuated by increasing the ionic strength. Our FCS and microfluidic measurements also highlight the key role shear-stress has in enabling this interaction. Our simulations attribute the previously-observed platelet-recruitment reduction and heparin-size modulation, upon establishment of DNA-vWF interactions, to indirect steric hindrance and partial overlap of the binding sites, respectively. Overall, we suggest electrostatics-guiding DNA to a specific protein binding site-as the main driving force defining DNA-vWF recognition. The molecular picture of a key shear-mediated DNA-protein interaction is provided here and it constitutes the basis for understanding NETs-mediated immune and hemostatic responses
Trigonometry of 'complex Hermitian' type homogeneous symmetric spaces
This paper contains a thorough study of the trigonometry of the homogeneous
symmetric spaces in the Cayley-Klein-Dickson family of spaces of 'complex
Hermitian' type and rank-one. The complex Hermitian elliptic CP^N and
hyperbolic CH^N spaces, their analogues with indefinite Hermitian metric and
some non-compact symmetric spaces associated to SL(N+1,R) are the generic
members in this family. The method encapsulates trigonometry for this whole
family of spaces into a single "basic trigonometric group equation", and has
'universality' and '(self)-duality' as its distinctive traits. All previously
known results on the trigonometry of CP^N and CH^N follow as particular cases
of our general equations. The physical Quantum Space of States of any quantum
system belongs, as the complex Hermitian space member, to this parametrised
family; hence its trigonometry appears as a rather particular case of the
equations we obtain.Comment: 46 pages, LaTe
Proteomic and Transcriptional Profiles of Human Stem Cell-Derived beta Cells Following Enteroviral Challenge
Enteroviral infections are implicated in islet autoimmunity and type 1 diabetes (T1D) pathogenesis. Significant beta-cell stress and damage occur with viral infection, leading to cells that are dysfunctional and vulnerable to destruction. Human stem cell-derived beta (SC-beta) cells are insulin-producing cell clusters that closely resemble native beta cells. To better understand the events precipitated by enteroviral infection of beta cells, we investigated transcriptional and proteomic changes in SC-beta cells challenged with coxsackie B virus (CVB). We confirmed infection by demonstrating that viral protein colocalized with insulin-positive SC-beta cells by immunostaining. Transcriptome analysis showed a decrease in insulin gene expression following infection, and combined transcriptional and proteomic analysis revealed activation of innate immune pathways, including type I interferon (IFN), IFN-stimulated genes, nuclear factor-kappa B (NF-kappaB) and downstream inflammatory cytokines, and major histocompatibility complex (MHC) class I. Finally, insulin release by CVB4-infected SC-beta cells was impaired. These transcriptional, proteomic, and functional findings are in agreement with responses in primary human islets infected with CVB ex vivo. Human SC-beta cells may serve as a surrogate for primary human islets in virus-induced diabetes models. Because human SC-beta cells are more genetically tractable and accessible than primary islets, they may provide a preferred platform for investigating T1D pathogenesis and developing new treatments
The Impact of Mixing Modes on Reliability in Longitudinal Studies
Mixed-mode designs are increasingly important in surveys, and large longitudinal studies are progressively moving to or considering such a design. In this context, our knowledge regarding the impact of mixing modes on data quality indicators in longitudinal studies is sparse. This study tries to ameliorate this situation by taking advantage of a quasi-experimental design in a longitudinal survey. Using models that estimate reliability for repeated measures, quasi-simplex models, 33 variables are analyzed by comparing a single-mode CAPI design to a sequential CATI-CAPI design. Results show no differences in reliabilities and stabilities across mixed modes either in the wave when the switch was made or in the subsequent waves. Implications and limitations are discussed. </jats:p
Collaboration scripts - a conceptual analysis
This article presents a conceptual analysis of collaboration scripts used in face-to-face and computer-mediated collaborative learning. Collaboration scripts are scaffolds that aim to improve collaboration through structuring the interactive processes between two or more learning partners. Collaboration scripts consist of at least five components: (a) learning objectives, (b) type of activities, (c) sequencing, (d) role distribution, and (e) type of representation. These components serve as a basis for comparing prototypical collaboration script approaches for face-to-face vs. computer-mediated learning. As our analysis reveals, collaboration scripts for face-to-face learning often focus on supporting collaborators in engaging in activities that are specifically related to individual knowledge acquisition. Scripts for computer-mediated collaboration are typically concerned with facilitating communicative-coordinative processes that occur among group members. The two lines of research can be consolidated to facilitate the design of collaboration scripts, which both support participation and coordination, as well as induce learning activities closely related to individual knowledge acquisition and metacognition. In addition, research on collaboration scripts needs to consider the learnersâ internal collaboration scripts as a further determinant of collaboration behavior. The article closes with the presentation of a conceptual framework incorporating both external and internal collaboration scripts
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