Abstract
The capacity-limited human brain is constantly confronted with a huge amount of sensory information. Selective attention is needed for biasing neural processing towards relevant information ...and consequently allows meaningful interaction with the environment. Activity in the alpha-band has been proposed to be related to top-down modulation of neural inhibition and could thus represent a viable candidate to control the priority of stimulus processing. It is, however, unknown whether modulations in the alpha-band directly relate to changes in the sensory gain control of the early visual cortex. Here, we used a spatial cueing paradigm while simultaneously measuring ongoing alpha-band oscillations and steady-state visual evoked potentials (SSVEPs) as a marker of continuous early sensory processing in the human visual cortex. Thereby, the effects of spatial attention for both of these signals and their potential interactions were assessed. As expected, spatial attention modulated both alpha-band and SSVEP responses. However, their modulations were independent of each other and the corresponding activity profiles differed across task demands. Thus, our results challenge the view that modulations of alpha-band activity represent a mechanism that directly alters or controls sensory gain. The potential role of alpha-band oscillations beyond sensory processing will be discussed in light of the present results.
Leukocyte inflammatory responses require integrin cell-adhesion molecule signaling through spleen tyrosine kinase (Syk), a non-receptor kinase that binds directly to integrin β-chain cytoplasmic ...domains. Here, we developed a high-throughput screen to identify small molecule inhibitors of the Syk-integrin cytoplasmic domain interactions. Screening small molecule compound libraries identified the β-lactam antibiotics cefsulodin and ceftazidime, which inhibited integrin β-subunit cytoplasmic domain binding to the tandem SH2 domains of Syk (IC
range, 1.02-4.9 µM). Modeling suggested antagonist binding to Syk outside the pITAM binding site. Ceftazidime inhibited integrin signaling
Syk, including inhibition of adhesion-dependent upregulation of interleukin-1β and monocyte chemoattractant protein-1, but did not inhibit ITAM-dependent phosphorylation of Syk mediated by FcγRI signaling. Our results demonstrate a novel means to target Syk independent of its kinase and pITAM binding sites such that integrin signaling
this kinase is abrogated but ITAM-dependent signaling remains intact. As integrin signaling through Syk is essential for leukocyte activation, this may represent a novel approach to target inflammation.
We observed the in situ growth of a grain during recrystallization in the bulk of a deformed sample. We used the three-dimensional x-ray diffraction microscope located at the European Synchrotron ...Radiation Facility in Grenoble, France. The results showed a very heterogeneous growth pattern, contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. This type of in situ bulk measurement opens up the possibility of obtaining experimental data on scientific topics that before could only be analyzed theoretically on the basis of the statistical characterization of microstructures. For recrystallization, the in situ method includes direct measurements of nucleation and boundary migration through a deformed matrix.
Mg2NiH4 synthesis and decomposition reactions Polanski, M.; Nielsen, T.K.; Kunce, I. ...
International journal of hydrogen energy,
04/2013, Letnik:
38, Številka:
10
Journal Article
Recenzirano
A ternary Mg2NiH4 hydride was synthesized using method that relies on a relatively short mechanical milling time (one hour) of a 2:1 MgH2–Ni powder mixture followed by sintering at a sufficiently ...high hydrogen pressure (>85 bar) and temperature (>400 °C). The ternary hydride forms in less than 2.5 h (including the milling time) with a yield of ∼90% as a mixture of two polymorphic forms. The mechanisms of formation and decomposition of ternary Mg2NiH4 under different hydrogen pressures were studied in detail using an in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and high pressure DSC. The obtained experimental results are supported by morphological and microstructural investigations performed using SEM and high resolution STEM. Additionally, effects occurring during the desorption reaction were studied using DSC coupled with mass spectrometry.
► Mg2NiH4 synthesis by ball milling (MgH2 + Ni) followed by sintering is presented. ► In situ SR-PXD data is presented for synthesis and decomposition. ► High pressure DSC data is presented for synthesis and decomposition. ► High resolution microstructural data is presented.
Activation of the integrin family of cell adhesion receptors on progenitor cells may be a viable approach to enhance the effects of stem cell-based therapies by improving cell retention and ...engraftment. Here, we describe the synthesis and characterization of the first small molecule agonist identified for the integrin α4β1 (also known as very late antigen-4 or VLA-4). The agonist, THI0019, was generated via two structural modifications to a previously identified α4β1 antagonist. THI0019 greatly enhanced the adhesion of cultured cell lines and primary progenitor cells to α4β1 ligands VCAM-1 and CS1 under both static and flow conditions. Furthermore, THI0019 facilitated the rolling and spreading of cells on VCAM-1 and the migration of cells toward SDF-1α. Molecular modeling predicted that the compound binds at the α/β subunit interface overlapping the ligand-binding site thus indicating that the compound must be displaced upon ligand binding. In support of this model, an analog of THI0019 modified to contain a photoreactive group was used to demonstrate that when cross-linked to the integrin, the compound behaves as an antagonist instead of an agonist. In addition, THI0019 showed cross-reactivity with the related integrin α4β7 as well as α5β1 and αLβ2. When cross-linked to αLβ2, the photoreactive analog of THI0019 remained an agonist, consistent with it binding at the α/β subunit interface and not at the ligand-binding site in the inserted (“I”) domain of the αL subunit. Co-administering progenitor cells with a compound such as THI0019 may provide a mechanism for enhancing stem cell therapy.
Background: Activation of integrins may improve cell retention rates in stem cell transplantation.
Results: The first small molecule agonist of integrin α4β1 is generated and enhances cell adhesion mechanisms in vitro.
Conclusion: The agonist binds at the subunit interface, inducing ligand binding with consequent displacement of compound.
Significance: The agonist may improve progenitor cell retention as an adjunct to cell-based therapy.
Abstract Multi-material structures in the automotive industry hold great potential for lightweight design, body construction, and functionalization due to their favorable mechanical properties and ...reduced structural weight. The combination of metal and plastic, in particular, is commonly used to enhance the overall properties of the end product when compared to single-material structures. This paper describes a process development with a hot-stamping and an extrusion tool. By means of this tool, a thermally assisted extrusion process can be used to join GMT (Glass Mat reinforced Thermoplastics) and 22MnB5 steel in a single process step. Through adhesion, the GMT adheres to the rough surface of the AlSi(aluminum-silicon)-coated 22MnB5. Test components were manufactured and through static tests the influence of process parameters was evaluated. Assuming that the parameters determined for the reference component are already sufficient for a design in the vehicle, the reduction of the steel thickness of the structure from 1.5 mm to 1.2 mm can be recommended on the basis of the results obtained. This is accompanied by a reduction in the mass of the test structure used while maintaining or improving its dynamic and static properties. Further weight savings appear possible through further component and process optimization.
In this work the effect of a partial replacement of CaH2 with CaF2 on the sorption properties of the system CaH2 + MgB2 has been studied. The first five hydrogen absorption and four desorption ...reactions of the CaH2 + MgB2 and 3CaH2 + CaF2 + 4MgB2 systems were investigated by means of volumetric measurements, high-pressure differential scanning calorimetric technique (HP-DSC), 11B and 19F MAS NMR spectroscopy, and in situ synchrotron radiation powder X-ray diffraction (SR-PXD). It was observed that already during the mixing of the reactants formation of a nonstoichiometric CaF2–x H x solid solution takes place. Formation of the CaF2–x H x solid solution sensibly affects the overall hydrogen sorption reactions of the system CaH2 + MgB2.
Green rust is a naturally occurring layered mixed-valent ferrous–ferric hydroxide, which can react with a range of redox-active compounds. Sulfate-bearing green rust is generally thought to have ...interlayers composed of sulfate and water. Here, we provide evidence that the interlayers also contain monovalent cations, using X-ray photoelectron spectroscopy and synchrotron X-ray scattering. For material synthesized with Na+, K+, Rb+, or Cs+, interlayer thickness derived from basal plane spacings correlates with the radius of the monovalent cation. In addition, sequential washing of the materials with water showed that Na+ and K+ were structurally fixed in the interlayer, whereas Rb+ and Cs+ could be removed, resulting in a decrease in the basal layer spacing. The incorporation of cations in the interlayer opens up new possibilities for the use of sulfate green rust for exchange reactions with both anions and cations: e.g., radioactive Cs.
Here we present the first four dimensional (time and three dimensional space resolved) experiment on a strongly deformed geological material. Results show that even complicated microstructures with ...large continuous and discontinuous changes in crystallographic orientation can be resolved quantitatively. The details that can be resolved are unprecedented and therefore the presented technique promises to become influential in a wide range of geoscientific investigations. Grain and subgrain scale processes are fundamental to mineral deformation and associated Earth Dynamics, and time resolved observation of these processes is vital for establishing an in‐depth understanding of the latter. However, until recently, in situ experiments were restricted to observations of two dimensional surfaces. We compared experimental results from two dynamic, in situ annealing experiments on a single halite crystal; a 2D experiment conducted inside the scanning electron microscope and a 3D X‐ray diffraction experiment. This allowed us to evaluate the possible effects of the free surface on grain and subgrain processes. The extent to which surface effects cause experimental artifacts in 2D studies has long been questioned. Our study shows that, although the nature of recovery processes are the same, the area swept by subgrain boundaries is up to 5 times larger in the volume than observed on the surface. We suggest this discrepancy is due to enhanced drag force on subgrain boundaries by thermal surface grooving. Our results show that while it is problematic to derive absolute mobilities from 2D experiments, derived relative mobilities between boundaries with different misorientation angles can be used.
Key Points
The 3DXRD technique is applicable for crystalline geological materials
Complicated microstructures can be resolved quantitatively
Thermal grooving in 2D experiments results in retardation of boundary movement
A 30% deformed aluminum sample was mapped non-destructively using three-dimensional X-ray diffraction (3DXRD) before and after annealing to nucleation of recrystallization. Nuclei appeared in the ...bulk of the sample. Their positions and volumes were determined, and the crystallographic orientations were compared with the orientations of the deformed grains. It was found that nuclei with new orientations can form and their orientations have been related to the dislocation structure in the deformed grains.
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