Sedimentary process inferences from Humic substances analysis and deposition rates (Western Ross Sea,Antarctica)

The first 40?cm of sediment of three basins in the Ross Sea were sampled using a box corer. Site Y1 was located close to the coast in Terra Nova Bay; the sediment of site Y3 was collected in a more distal basin in the central sector of the Ross Sea; finally site Y5 was sampled in the deepest zone of the Joides Basin.

Sediment cores were sliced and analysed with a depth resolution of 2–4.5?cm. The distribution of humic substances and their structural features along the cores were determined and related to the pattern of Total Organic Carbon (TOC) and sedimentological data. The grain size distribution and the ²¹⁰Pb inventories allow the sediment of the study sites to be characterised.

The humic substance content in the sediment decreases, with a change in slope between 23 and 26?cm at Y1, between 12 and 15?cm at Y3 and constant values with further depth. At Y5 the depth profile of humic substance content shows constant values in the upper 17?cm and values decrease with further depth. The pattern of humic substance yield is similar to that found for TOC. The analysis of the elemental composition of the humic acids extracted from different sediment depths shows an increasing C/N atomic ratio at sites Y1 and Y3 and constant values along the Y5 core. The depth profile of the C/N atomic ratio is confirmed by the changes observed in the structural characterisation and indicates a shift from the freshly deposited organic matter on the sediment surface to more humified material (humin). The results obtained highlight a different sedimentation rate at the three sites as deduced from sedimentological analysis.     

Spin–Orbit Charge-Transfer Intersystem Crossing (ISC) in Compact Electron Donor–Acceptor Dyads: ISC Mechanism and Application as Novel and Potent Photodynamic Therapy Reagents

Spin–orbit charge-transfer intersystem crossing (SOCT-ISC) is useful for the preparation of heavy atom-free triplet photosensitisers (PSs). Herein, a series of perylene-Bodipy compact electron donor/acceptor dyads showing efficient SOCT-ISC is prepared. The photophysical properties of the dyads were studied with steady-state and time-resolved spectroscopies. Efficient triplet state formation (quantum yield Φ_T=60 %) was observed, with a triplet state lifetime (τ_T=436 μs) much longer than that accessed with the conventional heavy atom effect (τ_T=62 μs). The SOCT-ISC mechanism was unambiguously confirmed by direct excitation of the charge transfer (CT) absorption band by using nanosecond transient absorption spectroscopy and time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The factors affecting the SOCT-ISC efficiency include the geometry, the potential energy surface of the torsion, the spin density for the atoms of the linker, solvent polarity, and the energy matching of the ¹CT/³LE states. Remarkably, these heavy atom-free triplet PSs were demonstrated as a new type of efficient photodynamic therapy (PDT) reagents (phototoxicity, EC₅₀=75 nm ), with a negligible dark toxicity (EC₅₀=78.1 μm ) compared with the conventional heavy atom PSs (dark toxicity, EC₅₀=6.0 μm, light toxicity, EC₅₀=4.0 nm ). This study provides in-depth understanding of the SOCT-ISC, unveils the design principles of triplet PSs based on SOCT-ISC, and underlines their application as a new generation of potent PDT reagents.     

Tuning the Triplet Excited State of Bis(dipyrrin) Zinc(II) Complexes: Symmetry Breaking Charge Transfer Architecture with Exceptionally Long Lived Triplet State for Upconversion

Zinc(II) bis(dipyrrin) complexes, which feature intense visible absorption and efficient symmetry breaking charge transfer (SBCT) are outstanding candidates for photovoltaics but their short lived triplet states limit applications in several areas. Herein we demonstrate that triplet excited state dynamics of bis(dipyrrin) complexes can be efficiently tuned by attaching electron donating aryl moieties at the 5,5′-position of the complexes. For the first time, a long lived triplet excited state (τ_T=296 μs) along with efficient ISC ability (Φ_Δ=71 %) was observed for zinc(II) bis(dipyrrin) complexes, formed via SBCT. The results revealed that molecular geometry and energy gap between the charge transfer (CT) state and triplet energy levels strongly control the triplet excited state properties of the complexes. An efficient triplet–triplet annihilation upconversion system was devised for the first time using a SBCT architecture as triplet photosensitizer, reaching a high upconversion quantum yield of 6.2 %. Our findings provide a blueprint for the development of triplet photosensitizers based on earth abundant metal complexes with long lived triplet state for revolutionary photochemical applications.     

Weighted distance-based trees for ranking data

Advances in Data Analysis and Classification - Within the framework of preference rankings, the interest can lie in finding which predictors and which interactions are able to explain the observed...     

Analysis of egg-based model wall paintings by use of an innovative combined dot-ELISA and UPLC-based approach

The chemical analysis of egg-based wall paintings—the mezzo fresco technique—is an interesting topic in the characterisation of organic binders. A revised procedure for a dot-enzyme-linked immunosorbent assay (dot-ELISA) able to detect protein components of egg-based wall paintings is reported. In the new dot-ELISA procedure we succeeded in maximizing the staining colour by adjusting the temperature during the staining reaction. Quantification of the colour intensity by visible reflectance spectroscopy resulted in a straight line plot of protein concentration against reflectance in the wavelength range 380–780 nm. The modified dot-ELISA procedure is proposed as a semi-quantitative analytical method for characterisation of protein binders in egg-based paintings. To evaluate its performance, the method was first applied to standard samples (ovalbumin, whole egg, egg white), then to model specimens, and finally to real samples (Giotto’s wall paintings). Moreover, amino acid analysis performed by innovative ultra-performance liquid chromatography was applied both to standards and to model samples and the results were compared with those from the dot-ELISA tests. In particular, after protein hydrolysis (24 h, 114 °C, 6 mol L^?1 HCl) of the samples, amino acid derivatization by use of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate enabled reproducible analysis of amino acids. This UPLC amino acid analysis was rapid and reproducible and was applied for the first time to egg-based paintings. Because the painting technique involved the use of egg-based tempera on fresh lime-based mortar, the study enabled investigation of the effect of the alkaline environment on egg-protein detection by both methods.

Long-Lived Charge-Transfer State Induced by Spin-Orbit Charge Transfer Intersystem Crossing (SOCT-ISC) in a Compact Spiro Electron Donor/Acceptor Dyad

We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long-lived triplet charge-transfer (³CT) state, based on the electron spin control using spin-orbit charge transfer intersystem crossing (SOCT-ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT-ISC takes 8 ns to produce the ³NI* state. Then the slow secondary CS (125 ns) gives the long-lived ³CT state (0.94 μs in deaerated n-hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as ¹NI*→¹CT→³NI*→³CT. With time-resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron-spin polarization pattern was observed for the naphthalimide-localized triplet state. Our spiro compact dyad structure and the electron spin-control approach is different to previous methods for which invoking transition-metal coordination or chromophores with intrinsic ISC ability is mandatory.     

Effect of nitrogen plasma treatment on the crystallinity and self‐bonding of polyetheretherketone (PEEK) for biomedical applications

Polyetheretherketone (PEEK) is a thermoplastic material with outstanding properties and high potential for biomedical applications, including hermetic encapsulation of active implantable devices. Different biomedical grade PEEK films with initial degree of crystallinity ranging from 8% to 32% (with or without mineral filling) were inspected. PEEK surfaces were treated with nitrogen RF plasma and the effects on materials crystallinity and self‐bonding were evaluated. In particular, the relationship between auto‐adhesive properties and crystalline content of PEEK before and after plasma treatment was examined. PEEK samples showed different bonding strength depending on their degree of crystallinity, with higher self‐bonding performance of mineral‐filled semi‐crystalline films. XRD did not show any modification of the PEEK microstructure as a result of plasma treatment, excluding a significant influence of crystallinity on the self‐bonding mechanisms. Nevertheless, plasma surface treatment successfully improved the self‐bonding strength of all the PEEK films tested, with larger increase in the case of semi‐crystalline unfilled materials. This could be interpreted to the increase in chain mobility that led to interfacial interpenetration of the amorphous phase.     

Long‐Lived Charge‐Transfer State Induced by Spin‐Orbit Charge Transfer Intersystem Crossing (SOCT‐ISC) in a Compact Spiro Electron Donor/Acceptor Dyad

We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long‐lived triplet charge‐transfer (³CT) state, based on the electron spin control using spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT‐ISC takes 8 ns to produce the ³NI* state. Then the slow secondary CS (125 ns) gives the long‐lived ³CT state (0.94 μs in deaerated n‐hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as ¹NI*→¹CT→³NI*→³CT. With time‐resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron‐spin polarization pattern was observed for the naphthalimide‐localized triplet state. Our spiro compact dyad structure and the electron spin‐control approach is different to previous methods for which invoking transition‐metal coordination or chromophores with intrinsic ISC ability is mandatory.     

Infrared intensities of methane and ethane. A starting set of electrooptical parameters for n-hydrocarbons

Sets of electrooptical parameters (eop's), suitable for longer n-paraffins and less constrained than those already used to fit the IR intensities of CH₄ and C₂H₆ and their deuterated derivatives, are presented and discussed. The technique adopted in the least-squares refinement of eop's from experimental data is discussed in detail.     

Solvent and TMEDA effects on the configurational stability of chiral lithiated aryloxiranes

The employment of hexane/N,N,N',N'-tetramethylethylenediamine (TMEDA) dramatically hinders the racemization of those lithiated styrene oxides (trifluoromethyl-, chloro-, and phenylthio-substituted) that have been proven to be configurationally unstable in THF on the timescale of their reactions. The barriers to inversion and the activation parameters, calculated (Eyring equation) for reactions performed in THF, THF/TMEDA, and hexane/TMEDA, suggest the intervention of particular enantiomerization mechanisms for each case. The role of TMEDA in both coordinating and noncoordinating solvents has also been questioned and discussed in light of the kinetic data gathered and a model for deprotonation in hexane/TMEDA has also been proposed. The synthetic benefits of our results became apparent on establishing an asymmetric synthesis of an industrially important antifungal agent.