Prophylactic antioxidants and phenolics of seagrass and seaweed species: A seasonal variation study in a Southern Indian Ocean Island, Mauritius

The seasonal variations in the polyphenolic contents and potential antioxidant activities of seven seaweed species (Padina gymnospora, Gracilaria salicornia, Palisada papillosa, Galaxaura rugosa, Enteromorpha intestinalis, Codium arabicum and Dictyosphaeria cavernosa) and five seagrass species (Syringodium isoetifolium, Halodule uninervis, Thalassodendron ciliatum, Halophila ovalis and Halophila stipulacea) were assessed. In summer, the highest total phenolic content was recorded in the seaweed P. gymnospora and the lowest in G. rugosa. The total phenolic contents in the seagrass species were significantly higher than those observed in the seaweed species during both seasons. The highest flavonoid concentrations (FC) were observed in the seaweed species E. intestinalis in winter and in the seaweed P. gymnospora in summer. All tested species had higher FC in winter. The highest antioxidant activity (assessed using the Ferric ion reducing antioxidant power) was in the seaweed P. gymnospora during summer (FRAP: 9.7 ± 0.3 X10¯³ Fe²+mM/g DW). However, the seaweed P. gymnospora extract and the extracts from all 5 seagrass species had significantly different (p<0.01) antioxidant activities (assessed using the Trolox equivalent antioxidant capacity assay) in winter compared to the summer season. The collective data are indicative of the potential of Mauritian seaweeds and seagrasses as possible sources of secondary metabolites for pharmaceuticals. Further analysis using bio-efficacy models are warranted to justify the phytoceutical capacity of the seaweeds and seagrasses.Keywords: Antioxidant; Total Phenols; Total Flavonoids; FRAP; TEAC; Seagrass; Seaweed; Seasonal variation; Mauritiu

Al0.52In0.48P avalanche photodiodes for soft X-ray spectroscopy

The performance of Al0.52In0.48P avalanche photodiodes was assessed as soft X-ray detectors at room temperature. The effect of the avalanche gain improved the energy resolution and an energy resolution (FWHM) of 682 eV is reported for 5.9 keV X-rays

Al0.6Ga0.4As x-ray avalanche photodiodes for spectroscopy

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Exploring the blueprint of photoprotection in Mycosporine-like Amino Acids

Microorganisms require protection against the potentially damaging effects of ultraviolet radiation exposure. Photoprotection is, in part, provided by mycosporine-like amino acids (MAAs). Previous reports have proposed that nonradiative decay mediates the impressive photoprotection abilities of MAAs. In this letter, we present the first ultrafast dynamics study of two MAAs, shinorine and porphyra-334. We demonstrate that, in aqueous solution, these MAAs relax along their S1 coordinates toward the S1/S0 conical intersection within a few hundred femtoseconds after photoexcitation and then traverse the conical intersection and vibrationally cool in approximately 1 ps through heat transfer to the solvent. This new insight allows a quintessential component of microbial life to be unraveled and informs the development of molecular photon-to-heat converters for a myriad of applications

Spectroscopic insight on impact of environment on natural photoprotectants

Biomimicry has become a key player in researching new materials for a whole range of applications. In this study, we have taken a crude extract from the red algae Palmaria palmata containing mycosporine-like amino acids – a photoprotective family of molecules. We have applied the crude extract onto a surface to assess if photoprotection, and more broadly, light-to-heat conversion, is retained; we found it is. Considering sunscreens as a specific application, we have performed transmission and reflection terahertz spectroscopy of the extract and glycerol to demonstrate how one can monitor stability in real-world applications

High temperature AlInP X-ray spectrometers

Two custom-made Al0.52In0.48P p+-i-n+ mesa photodiodes with different diameters (217 µm ± 15 µm and 409 µm ± 28 µm) and i layer thicknesses of 6 µm have been electrically characterised over the temperature range 0 °C to 100 °C. Each photodiode was then investigated as a high-temperature-tolerant photon counting X-ray detector by connecting it to a custom-made low-noise charge-sensitive preamplifier and illuminating it with an 55Fe radioisotope X-ray source (Mn Kα = 5.9 keV; Mn Kβ = 6.49 keV). At 100 °C, the best energy resolutions (full width at half maximum at 5.9 keV) achieved using the 217 µm ± 15 µm diameter photodiode and the 409 µm ±28 µm diameter photodiode were 1.31 keV ± 0.04 keV and 1.64 keV ±0.08 keV, respectively. Noise analysis of the system is presented. The dielectric dissipation factor of Al0.52In0.48P was estimated as a function of temperature, up to 100 °C. The results show the performance of the thickest Al0.52In0.48P X-ray detectors so far reported at high temperature. The work has relevance for the development of novel space science instrumentation for use in hot space environments and extreme terrestrial applications

New Insights into Segmental Packing, Chain Dynamics and Thermomechanical Performance of Aliphatic Polyurea Composites: Comparison between Silica Oxides and Titanium (III) Oxides

Polyurea (PU) is intrinsically reinforced by its microphase-separated morphology, giving its excellent mechanical properties. In this study, it is shown how a high-index PU formulation applies easy diffusion of hard segments into the soft phase of the PU matrix and tune its chain mobility. Moreover, the interaction of micro (>100 nm), nano (<100 nm) fillers with the microdomains and their thermomechanical properties are unraveled. Herein, nanosilica oxide (NS) and micro titanium (III) oxide (Ti2O3) are incorporated at low loadings into a solvent-free two-component aliphatic PU via insitu polymerization. While NS achieves an interfacial interaction with urea groups and forms a tight hard segmental packing, the large-sized Ti2O3 assembles the interconnected PU chain network, improving its crystallinity. Strong reinforcement by NS is noticed when tensile strength increased from 26 to 31 MPa and on the maximum thermal degradation temperature by 21 °C increment from the neat PU. In contrast, the soft segmental dynamics are triggered with the presence of Ti2O3 as indicated in the reduction in glass transition temperature and the 288% improvement in the storage modulus. This study provides an insightful perspective in designing robust PU composites, effective for myriad applications including strong and flexible films in circuit boards and photovoltaic (PV) cells