87 research outputs found
Stacking the Nanochemistry Deck: Structural and Compositional Diversity in One-Dimensional Photonic Crystals
No full textOne-dimensional photonic structures, known as Bragg stacks reflectors or Bragg mirrors, represent a well-developed subject in the field of optical science. However, because of a lack of dynamic tunablity and their dependence on complex top-down techniques for their fabrication, they have received little attention from the materials science community present recent and ongoing developments on the way to fun dimensional photonic structures obtained from simple botton-up techniques. We focus on the versatility of this new approach, which allows the incorporation of a wide range of materials into photonic structures
The role of Gpi-anchored axonal glycoproteins in neural development and neurological disorders.
No full textThis review article focuses on the Contactin (CNTN) subset of the Immunoglobulin supergene family (IgC2/FNIII molecules), whose components share structural properties (the association of Immunoglobulin type C2 with Fibronectin type III domains), as well as a general role in cell contact formation and axonal growth control. IgC2/FNIII molecules include 6 highly related components (CNTN 1-6), associated with the cell membrane via a Glycosyl Phosphatidyl Inositol (GPI)-containing lipid tail. Contactin 1 and Contactin 2 share ~50 (49.38)% identity at the aminoacid level. They are components of the cell surface, from which they may be released in soluble forms. They bind heterophilically to multiple partners in cis and in trans, including members of the related L1CAM family and of the Neurexin family Contactin-associated proteins (CNTNAPs or Casprs). Such interactions are important for organising the neuronal membrane, as well as for modulating the growth and pathfinding of axon tracts. In addition, they also mediate the functional maturation of axons by promoting their interactions with myelinating cells at the nodal, paranodal and juxtaparanodal regions. Such interactions also mediate differential ionic channels (both Na(+) and K(+)) distribution, which is of critical relevance in the generation of the peak-shaped action potential. Indeed, thanks to their interactions with Ankyrin G, Na(+) channels map within the nodal regions, where they drive axonal depolarization. However, no ionic channels are found in the flanking Contactin1-containing paranodal regions, where CNTN1 interactions with Caspr1 and with the Ig superfamily component Neurofascin 155 in cis and in trans, respectively, build a molecular barrier between the node and the juxtaparanode. In this region K(+) channels are clustered, depending upon molecular interactions with Contactin 2 and with Caspr2. In addition to these functions, the Contactins appear to have also a role in degenerative and inflammatory disorders: indeed Contactin 2 is involved in neurodegenerative disorders with a special reference to the Alzheimer disease, given its ability to work as a ligand of the Alzheimer Precursor Protein (APP), which results in increased Alzheimer Intracellular Domain (AICD) release in a γ-secretase-dependent manner. On the other hand Contactin-1 drives Notch signalling activation via the Hes pathway, which could be consistent with its ability to modulate neuroinflammation events, and with the possibility that Contactin 1-dependent interactions may participate to the pathogenesis of the Multiple Sclerosis and of other inflammatory disorders
Two-Photon Poly(phenylenevinylene) DFB Laser
No full textTwo-photon pumped lasing of a poly(phenylenevinylene)-titania-silica (PPV-TiO(2)-SiO(2)) nano-composite comprised of PPV synthesized within the void spaces of a multilayer nanoparticle TiO(2) and SiO(2) 1D photonic crystal is reported for the first time. With this distributed feedback (DFB) device, we have discovered the surprising result that two photon lasing requires only a factor of 2 higher intensity than one photon lasing thereby allowing laser excitation densities far below those that cause material degradation. The lower excitation density makes possible laser operation in the high-repetition rate regime and the use of compact and cheap NIR pump sources. All this makes our device rather interesting for optical telecommunication applications
Nanofabrication by self-assembly
No full textThe self-assembly paradigm in chemistry, physics and biology has matured scientifically over the past two-decades to a point of sophistication that one can begin to exploit its numerous attributes in nanofabrication. In what follows we will take a brief look at current thinking about self-ssembly and with some recent examples taken from our own work examine how nanofabrication has benefited from self-assembly
Distributed Feedback Lasing from a Composite Poly(phenylene vinylene)-Nanoparticle One-Dimensional Photonic Crystal
No full textNanoparticle one-dimensional photonic crystals exhibit intense, broadband reflectivity coupled with a unique mesoporosity. The latter property allows for infiltration of the one-dimensional photonic crystal with functional materials, such as emitting polymers, which in turn can lead to the fabrication of composites whereby the emitter's emission can be modulated by the photon density of states of the photonic crystal. We exploit this interaction in order to produce efficient distributed feedback lasing from a composite poly(phenylene vinylene)-infiltrated nanoparticle one-dimensional photonic crystal
ADnet - Un network regionale per i pazienti Alzheimer
No full text<p>Presentazione del caso d'uso "ADnet".</p>
Blockade of dopamine D3 receptors improves hippocampal synaptic function and rescues age-related cognitive phenotype
No full textDopamine D3 receptors (D3Rs) modulate neuronal activity in several brain regions including the hippocampus. Although previous studies reported that blocking D3Rs exerts pro-cognitive effects, their involvement in hippocampal synaptic function and memory in the healthy and aged brain has not been thoroughly investigated. We demonstrated that in adult wild type (WT) mice, D3R pharmacological blockade or genetic deletion as in D3 knock out (KO) mice, converted the weak form of long-term potentiation (LTP1) into the stronger long-lasting LTP (LTP2) via the cAMP/PKA pathway, and allowed the formation of long-term memory. D3R effects were mainly mediated by post-synaptic mechanisms as their blockade enhanced basal synaptic transmission (BST), AMPAR-mediated currents, mEPSC amplitude, and the expression of the post-synaptic proteins PSD-95, phospho(p)GluA1 and p-CREB. Consistently, electron microscopy revealed a prevalent expression of D3Rs in post-synaptic dendrites. Interestingly, with age, D3Rs decreased in axon terminals while maintaining their levels in post-synaptic dendrites. Indeed, in aged WT mice, blocking D3Rs reversed the impairment of LTP, BST, memory, post-synaptic protein expression, and PSD length. Notably, aged D3-KO mice did not exhibit synaptic and memory deficits. In conclusion, we demonstrated the fundamental role of D3Rs in hippocampal synaptic function and memory, and their potential as a therapeutic target to counteract the age-related hippocampal cognitive decline
Effect of Silver Nanoparticle Coatings on Mycobacterial Biofilm Attachment and Growth: Implications for Ceramic Water Filters
No full textSilver is a natural, broad-spectrum antibacterial metal and its toxicity can be enhanced when surface area is maximized. As a result, silver nanoparticles (AgNP) have been investigated for use in novel water treatment technologies. The hypothesis of this work is that deposited AgNPs can enhance water treatment technologies by inhibiting growth of planktonic bacteria and biofilms. This was investigated by evaluating the antibacterial efficacy of AgNPs both in solution and as deposited on surfaces. AgNPs were found to be toxic to three species of environmental mycobacteria, M. smegmatis, M. avium, and M. marinum and the level of susceptibility varied widely, probably owing to the varying levels of silver that each species is exposed to in its natural environment. When cultured in a AgNP enriched environment M. smegmatis developed resistance to the toxic effects of both the nanoparticles and silver ions. The resistant mutant was as viable as the unmodified strain and was also resistant to antibiotic isoniazid. However, the strain was more susceptible to other toxic metal ions from ZnSO4 and CuSO4.
AgNPs were deposited on silicon wafer substrates by vertical colloidal deposition (VCD). Manipulating deposition speed and also concentration of AgNPs in the depositing liquid led to a range of AgNP coatings with distinctive deposition lines perpendicular to the motion of the meniscus. Experimental results for areal coverage, which was measured from SEM images of AgNP coatings, were compared to Diao’s theory of VCD but did not show agreement due to a stick-slip mechanism that is not accounted for by the theory. Durability of AgNP coatings is critical for antibacterial efficacy and to mitigate the risks of exposing the environment to nanomaterials and it was measured by exposing AgNP coatings to liquid flow in a flow cell. Durability was improved by modifying processing to include a heat treatment after deposition.
Finally, the antibiofilm efficacy of deposited AgNPs was demonstrated by culturing M. smegmatis on porous membrane filters and Si substrates that were coated with AgNP. In both cases AgNP inhibited biofilm growth with an effect that was concentration or areal coverage dependent
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