A Coloured Spin Trap which works as a pH Sensor

Nitration of 4-hydroxybenzaldehyde afforded 2,6-dinitro-4-hydroxybenzaldehyde 2, which in the presence of thionyl chloride is converted to 4-chloro-2,6-dinitrobenzaldehyde 3. This compound is very reactive towards nucleophiles, and reacts easily with methoxyamine, affording the intermediate 4-aminomethoxy-2,6-dinitrobenzaldehyde 4. Reaction of 4 with N-t-butylhydroxylamine led to a new spin trap of the nitrone type, namely 4-aminomethoxy-3,5-dinitrophenyl-1-t-butylnitrone 6. The spin-trapping capabilities of the new compound have been tested in a classical system, in which short-lived radicals were generated by irradiation. The new compound 6 contains an acidic proton with a pKa value of 7.8, and removal of this by a base induces a colour change, from yellow to green-blue. In a similar way, a new stable nitronyl-nitroxide radical 8 has been obtained from the intermediate 4.Keywords: Synthesis; free radical; spin-trapping; pH sensor; nitron

Electron spin resonance study of puff-resolved free radical formation in mainstream cigarette smoke

Puff-by-puff resolved gas phase free radicals were measured in mainstream smoke from Kentucky 2R4F reference cigarettes using ESR spectroscopy. Three spin-trapping reagents were evaluated: PBN, DMPO and DEPMPO. Two procedures were used to collect gas phase smoke on a puff-resolved basis: i) the accumulative mode, in which all the gas phase smoke up to a particular puff was bubbled into the trap (i.e., the 5th puff corresponded to the total smoke from the 1st to 5th puffs). In this case, after a specified puff, an aliquot of the spin trap was taken and analysed; or, ii) the individual mode, in which the spin trap was analysed and then replaced after each puff. Spin concentrations were determined by double-integration of the first derivative of the ESR signal. This was compared with the integrals of known standards using the TEMPO free radical. The radicals trapped with PBN were mainly carbon-centred, whilst the oxygen-centred radicals were identified with DMPO and DEPMPO. With each spin trap, the puff-resolved radical concentrations showed a characteristic pattern as a function of the puff number. Based on the spin concentrations, the DMPO and DEPMPO spin traps showed better trapping efficiencies than PBN. The implication for gas phase free radical analysis is that a range of different spin traps should be used to probe complex free radical reactions in cigarette smoke

Electron paramagnetic resonance investigation of the free radicals in the gas and particulate phases of cigarette smoke using spin-trapping techniques

Free radicals in cigarette smoke have been studied using spin trapping EPR techniques. 2R4F reference cigarettes were smoked using 35 ml puff volumes of 2 seconds duration, once every 60 seconds. The particulate phase of the smoke was separated from the gas phase by passing the smoke through a Cambridge filter pad. For both phases, free radicals were measured and identified. A range of spin-traps was employed: PBN, DMPO, DEPMPO, and DPPH-PBN. In the gas-phase, short-lived carbon- and oxygen- centered radicals were identified; the ratios between them changed during the smoking runs. For the first puffs, C-centered radicals predominated while for the later puffs, O-centered radicals were mainly observed. The particulate phase and the ‘tar’ were studied as well

September Arctic sea ice minimum prediction – a skillful new statistical approach

Sea ice in both polar regions is an important indicator of the expression of global climate change and its polar amplification. Consequently, broad interest exists on sea ice coverage, variability and long-term change. However, its predictability is complex and it depends strongly on different atmospheric and oceanic parameters. In order to provide insights into the potential development of a monthly/seasonal signal of sea ice evolution, we applied a robust statistical model based on different oceanic and atmospheric parameters to calculate an estimate of the September sea ice extent (SSIE) on a monthly timescale. Although previous statistical attempts of monthly/seasonal SSIE forecasts show a relatively reduced skill, when the trend is removed, we show here that the September sea ice extent has a high predictive skill, up to 4 months ahead, based on previous months' oceanic and atmospheric conditions. Our statistical model skillfully captures the interannual variability of the SSIE and could provide a valuable tool for identifying relevant regions and oceanic and atmospheric parameters that are important for the sea ice development in the Arctic and for detecting sensitive/critical regions in global coupled climate models with a focus on sea ice formation.</p

Human Bone-Marrow-Derived Stem-Cell-Seeded 3D Chitosan–Gelatin–Genipin Scaffolds Show Enhanced Extracellular Matrix Mineralization When Cultured under a Perfusion Flow in Osteogenic Medium

Tissue-engineered bone tissue grafts are a promising alternative to the more conventional use of natural donor bone grafts. However, choosing an appropriate biomaterial/scaffold to sustain cell survival, proliferation, and differentiation in a 3D environment remains one of the most critical issues in this domain. Recently, chitosan/gelatin/genipin (CGG) hybrid scaffolds have been proven as a more suitable environment to induce osteogenic commitment in undifferentiated cells when doped with graphene oxide (GO). Some concern is, however, raised towards the use of graphene and graphene-related material in medical applications. The purpose of this work was thus to check if the osteogenic potential of CGG scaffolds without added GO could be increased by improving the medium diffusion in a 3D culture of differentiating cells. To this aim, the level of extracellular matrix (ECM) mineralization was evaluated in human bone-marrow-derived stem cell (hBMSC)-seeded 3D CGG scaffolds upon culture under a perfusion flow in a dedicated custom-made bioreactor system. One week after initiating dynamic culture, histological/histochemical evaluations of CGG scaffolds were carried out to analyze the early osteogenic commitment of the culture. The analyses show the enhanced ECM mineralization of the 3D perfused culture compared to the static counterpart. The results of this investigation reveal a new perspective on more efficient clinical applications of CGG scaffolds without added GO

Moisture transport and Antarctic sea ice: austral spring 2016 event

In austral spring 2016 the Antarctic region experienced anomalous sea ice retreat in all sectors, with sea ice extent in October and November 2016 being the lowest in the Southern Hemisphere over the observational period (1979–present). The extreme sea ice retreat was accompanied by widespread warming along the coastal areas as well as in the interior of the Antarctic continent. This exceptional event occurred along with a strong negative phase of the Southern Annular Mode (SAM) and the moistest and warmest spring on record, over large areas covering the Indian Ocean, the Ross Sea and the Weddell Sea. In October 2016, the positive anomalies of the totally integrated water vapor (IWV) and 2 m air temperature (T2m) over the Indian Ocean, western Pacific, Bellingshausen Sea and southern part of Ross Sea were unprecedented in the last 39 years. In October and November 2016, when the largest magnitude of negative daily sea ice concentration anomalies was observed, repeated episodes of poleward advection of warm and moist air took place. These results suggest the importance of moist and warm air intrusions into the Antarctic region as one of the main contributors to this exceptional sea ice retreat event.</p