Synaptic clustering during development and learning: the why, when, and how

To contribute to a functional network a neuron must make specific connections and integrate the synaptic inputs that it receives in a meaningful way. Previous modeling and experimental studies have predicted that this specificity could entail a subcellular organization whereby synapses that carry similar information are clustered together on local stretches of dendrite. Recent imaging studies have now, for the first time, demonstrated synaptic clustering during development and learning in different neuronal circuits. Interestingly, this organization is dependent on synaptic activity and most likely involves local plasticity mechanisms. Here we discuss these new insights and give an overview of the candidate plasticity mechanisms that could be involved

Single-neuron axonal reconstruction: The search for a wiring diagram of the brain

Reconstruction of the axonal projection patterns of single neurons has been an important tool for understanding both the diversity of cell types in the brain and the logic of information flow between brain regions. Innovative approaches now enable the complete reconstruction of axonal projection patterns of individual neurons with vastly increased throughput. Here, we review how advances in genetic, imaging, and computational techniques have been exploited for axonal reconstruction. We also discuss how new innovations could enable the integration of genetic and physiological information with axonal morphology for producing a census of cell types in the mammalian brain at scale.Reconstruction of the axonal projection patterns of single neurons has been an important tool for understanding both the diversity of cell types in the brain and the logic of information flow between brain regions. Innovative approaches now enable the complete reconstruction of axonal projection patterns of individual neurons with vastly increased throughput. Here, we review how advances in genetic, imaging, and computational techniques have been exploited for axonal reconstruction. We also discuss how new innovations could enable the integration of genetic and physiological information with axonal morphology for producing a census of cell types in the mammalian brain at scale.First author draf

A novel malonamide bridged silsesquioxane precursor for enhanced dispersion of transition metal ions in hybrid silica membranes

Microporous hybrid silica membranes are known to have superior (hydro)thermal and chemical stability. By incorporating metal ions, such as Ce4+ and Ni2+ into these membranes, their affinity and selectivity towards particular gases may be altered. To promote the dispersion of metal ions within the hybrid silica matrix, the sol–gel precursor N,N,N′,N′-tetrakis-(3-(triethoxysilyl)-propyl)-malonamide (TTPMA) was synthesized. The malonamide ligands clearly coordinated the Ce4+ and Ni2+ metal centers and enhanced their dispersion. During annealing these metal centers redistributed into small nanosized grains of CeO2 (<5 nm) and Ni2O3 (<15 nm). These Ce-TTPMA and Ni-TTPMA membranes showed higher H2/N2 permselectivities as compared to previously reported hybrid silica membranes based on the 1,2-bis-(triethoxysilyl)ethane precursor. The TTPMA-precursor was found suitable for membrane separation and can be a promising and versatile precursor for the incorporation of metal ions within hybrid silica matrices

Micropore structure stabilization in organosilica membranes by gaseous catalyst post-treatment

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Long-term flexibility-based structural evolution and condensation in microporous organosilica membranes for gas separation

Hybrid organosilica molecular sieving membranes with ethylene bridges are generally consolidated at 250–300 C for 2–3 hours, after which the material structure is assumed to be stabilized. This study shows that the consolidation process still continues at these temperatures after days to weeks. Ongoing condensation and structural evolution are studied in powders, films and gas permeation membranes derived from 1,2-bis(triethoxysilyl)ethane (BTESE) that are kept at temperatures up to 300 C for days and analyzed with in situ Fourier-transform infrared spectroscopy, 29Si cross-polarized magic angle spinning nuclear magnetic resonance, in situ spectroscopic ellipsometry, in situ gas permeation and in situ X-ray reflectivity. A continuously ongoing decrease in both silanol concentration and film thickness is observed, accompanied by changes in density, thermal expansion and micropore structure. The changes in the micropore structure are found to depend on pore size and affect the gas permeation performance of membranes. An important factor in the structural evolution is the network flexibility. Materials containing no organic bridges, short flexible bridges or long rigid bridges (derived from tetraethoxysilane (TEOS), bis(triethoxysilyl)methane (BTESM) and 1,4-bis(triethoxysilyl)benzene (BTESB), respectively) also show ongoing condensation, but their shrinkage rate is smaller as compared to BTESE-derived networks. A BTESE-derived film kept at 236 C for 12 days still shows no signs of approaching a structurally stabilized state