Geopolymer based brake pads

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Origin of a counterintuitive yellow light-emitting electrochemical cell based on a blue-emitting heteroleptic copper(I) complex

This work provides the synthesis, structural characterization, electrochemical and photophysical features, as well as the application in light-emitting electrochemical cells (LECs) of a novel heteroleptic copper(I) complex – [Cu(impy)(POP)][PF6], where impy is 3-(2-methoxyphenyl)-1-(pyridine-2-yl)imidazo[1,5-a]pyridine and POP is bis{2-(diphenylphosphanyl)phenyl}ether. This compound shows blue photoluminescence (PL, λ = 450 nm) in solution and solid-state and excellent redox stability. Despite these excellent features, the electroluminescence (EL) response is located at ∼550 nm. Although the EL spectrum of LECs is typically red-shifted compared to the PL of the electroluminescent material, a shift of ca. 100 nm represents the largest one reported in LECs. To date, the large shift phenomena have been attributed to (i) a change in the nature of the lowest emitting state due to a concentration effect of the films, (ii) a reversible substitution of the ligands due to the weak coordination to the Cu(I), and (iii) a change in the distribution of the excited states due to polarization effects. After having discarded these along with others like the irreversible degradation of the emitter during device fabrication and/or under operation conditions, driving conditions, active layer composition, and changes in the excited states under different external electrical stimuli, we attribute the origin of this unexpected shift to a lack of a thermally activated delayed fluorescence (TADF) process due to the solely ligand-centered character of the excited states. As such, the lack of a charge transfer character in the excited states leads to a blue-fluorescence and yellow-phosphorescence photo- and electro-responses, respectively. This corroborates recent studies focused on the design of TADF for heteroleptic copper(I) complexes. Overall, this work is a clear insight into the design of new copper(I) complexes towards the preparation of blue LECs, which are still unexplored

Friction materials for brake systems: role of the single constituent properties on the tribological behaviour

This thesis focus on the study of the single constituent effect on the friction and wear properties of brake pad, in order to obtain a systematic selection method for raw friction materials. For this purpose, three systems of commercially available raw materials (carbon, titanates and alumina), were investigated. The results allowed the comprehension of the main morphological and structural features affecting the tribological behaviour, then laying the foundation for making a preliminary selection of the raw materials based on the desired tribological behaviour, overcoming a trial and error approach. The characterization method set up can be applied on several other families of friction materials and the investigation can be extended to other applications, different from brake pads

Granular and platelet titanate as promising brake pads ingredients

Recent efforts in developing eco-friendlier and safer brake pads led to the replacement of whisker potassium hexatitanate (KTO). Granular and platelet KTO are considered promising substitutes, even if their friction and wear behaviour has not been comprehensively investigated yet. For this reason, this paper focuses on the tribological properties of granular and platelet KTO, and potassium magnesium titanate (KMTO), investigated by pin and ball on disk. Both raw materials in form of powder and composites, containing 50%wt of titanate and 50%wt of phenolic resin reinforced with aramid fibres, were analysed. Scanning Electron Microscopy, X-ray diffraction and Raman spectroscopy were employed for the morphological and structural analysis of powders and composites. Also, hardness and porosity were considered as parameters potentially affecting the tribological behaviour. As major outcomes, KMTO appears as a milder solid lubricant than KTO and platelet particles lead to superior wear resistance with respect to the granular ones

Origin of a counterintuitive yellow light-emitting electrochemical cell based on a blue-emitting heteroleptic copper(I) complex

This work provides the synthesis, structural characterization, electrochemical and photophysical features, as well as the application in light-emitting electrochemical cells (LECs) of a novel heteroleptic copper(I) complex – [Cu(impy)(POP)][PF6], where impy is 3-(2-methoxyphenyl)-1-(pyridine-2-yl)imidazo[1,5-a]pyridine and POP is bis{2-(diphenylphosphanyl)phenyl}ether. This compound shows blue photoluminescence (PL, λ = 450 nm) in solution and solid-state and excellent redox stability. Despite these excellent features, the electroluminescence (EL) response is located at ∼550 nm. Although the EL spectrum of LECs is typically red-shifted compared to the PL of the electroluminescent material, a shift of ca. 100 nm represents the largest one reported in LECs. To date, the large shift phenomena have been attributed to (i) a change in the nature of the lowest emitting state due to a concentration effect of the films, (ii) a reversible substitution of the ligands due to the weak coordination to the Cu(I), and (iii) a change in the distribution of the excited states due to polarization effects. After having discarded these along with others like the irreversible degradation of the emitter during device fabrication and/or under operation conditions, driving conditions, active layer composition, and changes in the excited states under different external electrical stimuli, we attribute the origin of this unexpected shift to a lack of a thermally activated delayed fluorescence (TADF) process due to the solely ligand-centered character of the excited states. As such, the lack of a charge transfer character in the excited states leads to a blue-fluorescence and yellow-phosphorescence photo- and electro-responses, respectively. This corroborates recent studies focused on the design of TADF for heteroleptic copper(I) complexes. Overall, this work is a clear insight into the design of new copper(I) complexes towards the preparation of blue LECs, which are still unexplored

Strategies to increase the quantum yield: Luminescent methoxylated imidazo[1,5-a]pyridines

A series of methoxylated imidazo[1,5-a]pyridines is presented and their optical and electrochemical properties investigated and interpreted on the basis of density functional theory calculations. The photophysical properties are discussed in relation to the chemical structure. The key role of the 1,3 substitutions on the imidazo[1,5-a] pyridine nucleus on rotational barriers and on frontier molecular orbitals is discussed in relation to the experimental hyperchromic effect, photoemission quantum yield and electrochemical properties. Depending on the position of the introduced methoxy substituents on the imidazo[1,5-a]pyridine nucleus, we are able to tune the Stokes shift and to increase the emission quantum yield from 22% to 50%.Web of Science192art. no. 10945

SMN deficiency perturbs monoamine neurotransmitter metabolism in spinal muscular atrophy

Beyond motor neuron degeneration, homozygous mutations in the survival motor neuron 1 (SMN1) gene cause multiorgan and metabolic defects in patients with spinal muscular atrophy (SMA). However, the precise biochemical features of these alterations and the age of onset in the brain and peripheral organs remain unclear. Using untargeted NMR-based metabolomics in SMA mice, we identify cerebral and hepatic abnormalities related to energy homeostasis pathways and amino acid metabolism, emerging already at postnatal day 3 (P3) in the liver. Through HPLC, we find that SMN deficiency induces a drop in cerebral norepinephrine levels in overt symptomatic SMA mice at P11, affecting the mRNA and protein expression of key genes regulating monoamine metabolism, including aromatic L-amino acid decarboxylase (AADC), dopamine beta-hydroxylase (D beta H) and monoamine oxidase A (MAO-A). In support of the translational value of our preclinical observations, we also discovered that SMN upregulation increases cerebrospinal fluid norepinephrine concentration in Nusinersen-treated SMA1 patients. Our findings highlight a previously unrecognized harmful influence of low SMN levels on the expression of critical enzymes involved in monoamine metabolism, suggesting that SMN-inducing therapies may modulate catecholamine neurotransmission. These results may also be relevant for setting therapeutic approaches to counteract peripheral metabolic defects in SMA.SMN deficiency causes age-dependent reduction of cerebral norepinephrine levels in mice by influencing the expression of genes regulating monoamine metabolism. In severe SMA1 patients, the SMN-inducing drug, Nusinersen, rescues CSF norepinephrine levels

Production of an induced pluripotent stem cell line CSSi018-A (14192) from a patient with hypomyelinating leukodystrophy 7 (HLD7) carrying biallelic variants of POLR3A (c.1802 T > A; c.4072G > A)

Hypomyelinating leukodystrophies (HLD) are a group of heterogeneous genetic disorders characterized by a deficit in myelin deposition during brain development. Specifically, 4H-Leukodystrophy is a recessive disease due to biallelic mutations in the POLR3A gene, which encodes one of the subunits forming the catalytic core of RNA polymerase III (PolIII). The disease also presents non-neurological signs such as hypodontia and hypogonadotropic hypogonadism. Here, we report the generation of a human induced pluripotent stem cell (hiPSC) line from fibroblasts of the first identified carrier of the biallelic POLR3A variants c.1802 T > A and c.4072G > A