Continuous Flow Photooxidative Degradation of Azo Dyes with Biomass-Derived Carbon Dots

The presence of persistent organic pollutants in industrial wastewaters is becoming a problem of major concern. In the present study we explored the degradation of azo dyes, wellknown common hazardous contaminants, by a green and efficient procedure using continuous flow photooxidative degradation. In particular, carbon dots synthesized from fishery waste (bass-CDs) were used as a cheap and readily available photocatalyst in combination with oxygen and UV light. Methyl orange, acid red 18, amaranth, sunset yellow and chromotrope were chosen as model substrates and their degradation was studied both in batch and in continuous flow conditions. All the azo dyes were fully degraded with both techniques highlighting the suitability of bass-CDs for the decontamination of wastewater. The main advantages are of using a “disposable” photocatalyst, in aqueous solvent and in continuous flow. In particular, continuous flow operation allowed faster decompositions: circa 2 min versus 1–3 hours needed in batc

CO2-assisted hydrolytic hydrogenation of cellulose and cellulose-based waste into sorbitol over commercial Ru/C

A single-step protocol was developed for the hydrolytic hydrogenation of microcrystalline cellulose into sorbitol over commercial carbon-supported Ru, in the presence of gaseous CO2 as an acid source and molecular hydrogen as a reductant. Under these conditions, cellulose was first hydrolysed to glucose by reversibly formed carbonic acid in water and then instantaneously hydrogenated on Ru/C. By tuning the reaction parameters, such as temperature, time and the relative pressure of CO2 and hydrogen gas, cellulose was fully converted at 220 & DEG;C in 18 h under 30 and 40 bar of H-2 and CO2, respectively, with a sorbitol yield of 81%. Blank experiments revealed that without a catalyst and hydrogen, the reaction exhibited <5% conversion and glucose was the only detected product when the reaction was performed under CO2 pressure. XRD measurements on CO2-treated cellulose surprisingly revealed no noticeable changes in the crystallinity index (<10% with respect to microcrystalline cellulose), suggesting that hydrolytic hydrogenation took place on crystalline, not amorphous, cellulose. Furthermore, not only several cellulosic feedstocks, including filter paper, cotton wool, and cotton fiber, but also typical cellulose-based wastes such as a cardboard pizza box were also tested and under the optimized conditions sorbitol was obtained with yields ranging from 56% up to 72% in all cases. No less significant was the Ru/C catalyst stability, which could be recycled at least six times without any noticeable activity loss

reactions of p coumaryl alcohol model compounds with dimethyl carbonate towards the upgrading of lignin building blocks

Cinnamyl alcohol 1 and 4-(3-hydroxypropyl)phenol 2, two compounds resembling the lignin building block p-coumaryl alcohol, can be selectively transformed into different products by catalytic methodologies based on dimethyl carbonate (DMC) as a green solvent/reagent. Selectivity can be tuned as a function of the reaction temperature and of the nature of the catalyst. Basic catalysts such as K2CO3, trioctylmethylphosphonium methylcarbonate ([P8881][CH3OCOO]), and CsF/αAl2O3 promote selective transesterification of the aliphatic hydroxyl group at 90 °C. However, amphoteric solids such as alkali metal-exchanged faujasites, NaX and NaY, selectively yield the corresponding alkyl ethers at higher temperatures (165–180 °C). The phenolic hydroxyl group of 2 can be methylated similarly with the faujasites at high temperatures. This preliminary screening for selectivity illustrates reactivity trends and delineates some of what might be among the most promising synthetic pathways to upgrade lignin-derived chemical building blocks

Bridging the gap of storage ring light sources and linac-driven free-electron lasers

High-gain free-electron lasers (FELs) are driven by short, high-charge density electron beams as only produced at dedicated single pass or recirculating linear accelerators. We describe new conceptual, technical, and modeling solutions to produce subpicosecond, up to 100 \u3bcJ energy extreme ultra-violet and soft x-ray FEL pulses at high- and tunable repetition rates, from diffraction-limited storage ring light source. In contrast to previously proposed schemes, we show that lasing can be simultaneous to the standard multibunch radiation emission from short insertion devices, and that it can be obtained with limited impact on the storage ring infrastructure. By virtue of the high-average power but moderate pulse energy, the storage ring-driven high-gain FEL would open the door to unprecedented accuracy in time-resolved spectroscopic analysis of matter in the linear response regime, in addition to inelastic scattering experiments

A “by-productless” cellulose foaming agent for use in imidazolium ionic liquids

Cellulose foams, or sponges, are produced from solutions in ionic liquids by the aqueous acid mediated decomposition of 1-alkyl-3- methylimidazolium-2-carboxylates, where the alkyl group and acid may be selected such that the by-product is the ionic liquid solvent: a by-productless foaming

The Role of the Striatum in Learning to Orthogonalize CD Action and Valence: A Combined PET and 7 T MRI Aging Study

Pavlovian biases influence instrumental learning by coupling reward seeking with action invigoration and punishment avoidance with action suppression. Using a probabilistic go/no-go task designed to orthogonalize action (go/no-go) and valence (reward/punishment), recent studies have shown that the interaction between the two is dependent on the striatum and its key neuromodulator dopamine. Using this task, we sought to identify how structural and neuromodulatory age-related differences in the striatum may influence Pavlovian biases and instrumental learning in 25 young and 31 older adults. Computational modeling revealed a significant age-related reduction in reward and punishment sensitivity and marked (albeit not significant) reduction in learning rate and lapse rate (irreducible noise). Voxel-based morphometry analysis using 7 Tesla MRI images showed that individual differences in learning rate in older adults were related to the volume of the caudate nucleus. In contrast, dopamine synthesis capacity in the dorsal striatum, assessed using [18F]-DOPA positron emission tomography in 22 of these older adults, was not associated with learning performance and did not moderate the relationship between caudate volume and learning rate. This multiparametric approach suggests that age-related differences in striatal volume may influence learning proficiency in old age

Experimental evidence of intrabeam scattering in a free-electron laser driver

Abstract The effect of multiple small-angle Coulomb scattering, or intrabeam scattering (IBS) is routinely observed in electron storage rings over the typical damping time scale of milliseconds. So far, IBS has not been observed in single pass electron accelerators because charge density orders of magnitude higher than in storage rings would be needed. We show that such density is now available at high brightness electron linacs for free-electron lasers (FELs). We report measurements of the beam energy spread in the FERMI linac in the presence of the microbunching instability, which are consistent with a revisited IBS model for single pass systems. We also show that neglecting the hereby demonstrated effect of IBS in the parameter range typical of seeded VUV and soft x-ray FELs, results in too conservative a facility design, or failure to realise the accessible potential performance. As an example, an optimization of the FERMI parameters driven by an experimentally benchmarked model, opens the door to the extension of stable single spectral line emission to the water window (2.3–4.4 nm), with far-reaching implications for experiments in a variety of disciplines, ranging from physics and chemistry to biology and material sciences, and including nonlinear x-ray optics based on the four-wave-mixing approach.</jats:p

Hippocampal vascularization patterns exert local and distant effects on brain structure but not vascular pathology in old age

The hippocampus within the medial temporal lobe is highly vulnerable to age-related pathology such as vascular disease. We examined hippocampal vascularization patterns by harnessing the ultra-high resolution of 7 Tesla magnetic resonance angiography. Dual-supply hemispheres with a contribution of the anterior choroidal artery to hippocampal blood supply were distinguished from single-supply ones with a sole dependence on the posterior cerebral artery. A recent study indicated that a dual vascular supply is related to preserved cognition and structural hippocampal integrity in old age and vascular disease. Here, we examined the regional specificity of these structural benefits at the level of medial temporal lobe sub-regions and hemispheres. In a cross-sectional study with an older cohort of 17 patients with cerebral small vessel disease (70.7 ±  9.0 years, 35.5% female) and 27 controls (71.1 ±  8.2 years, 44.4% female), we demonstrate that differences in grey matter volumes related to the hippocampal vascularization pattern were specifically observed in the anterior hippocampus and entorhinal cortex. These regions were especially bigger in dual-supply hemispheres, but also seemed to benefit from a contralateral dual supply. We further show that total grey matter volumes were greater in people with at least one dual-supply hemisphere, indicating that the hippocampal vascularization pattern has more far-reaching structural implications beyond the medial temporal lobe. A mediation analysis identified total grey matter as a mediator of differences in global cognition. However, our analyses on multiple neuroimaging markers for cerebral small vessel disease did not reveal any evidence that an augmented hippocampal vascularization conveys resistance nor resilience against vascular pathology. We propose that an augmented hippocampal vascularization might contribute to maintaining structural integrity in the brain and preserving cognition despite age-related degeneration. As such, the binary hippocampal vascularization pattern could have major implications for brain structure and function in ageing and dementia independent of vascular pathology, while presenting a simple framework with potential applicability to the clinical setting