Environmental effects on vibrational properties of carotenoids: experiments and calculations on peridinin

Carotenoids are employed in light-harvesting complexes of dinoflagellates with the two-fold aim to extend the spectral range of the antenna and to protect it from radiation damage. We have studied the effect of the environment on the vibrational properties of the carotenoid peridinin in different solvents by means of vibrational spectroscopies and QM/MM molecular dynamics simulations. Three prototypical solvents were considered: cyclohexane (an apolar/aprotic solvent), deuterated acetonitrile (a polar/aprotic solvent) and methanol (a polar/protic solvent). Thanks to effective normal mode analysis, we were able to assign the experimental Raman and IR bands and to clarify the effect of the solvent on band shifts. In the 1500-1650 cm(-1) region, seven vibrational modes of the polyene chain were identified and assigned to specific molecular vibrations. In the 1700-1800 cm(-1) region a strong progressive down-shift of the lactonic carbonyl frequency is observed passing from cyclohexane to methanol solutions. This has been rationalized here in terms of solvent polarity and solute-solvent hydrogen bond interactions. On the basis of our data we propose a classification of non-equivalent peridinins in the Peridinin-Chlorophyll-Proteins, light-harvesting complexes of dinoflagellates.     

Phenol transformation photosensitised by quinoid compounds

The phototransformation of phenol in aqueous solution was studied with different quinoid compounds, which are usually detected on atmospheric particulate matter: 2-ethylanthraquinone (EtAQ), benzanthracene-7,12-dione (BAD), 5,12-naphthacenequinone (NQ), 9,10-anthraquinone (AQ), and 2,6-dihydroxyanthraquinone (DAQ). All the studied quinones were able to sensitise the phototransformation of phenol. Under blue-light irradiation the approximated, polychromatic quantum yields for phenol photodegradation were in the order AQ > BAD > EtAQ > NQ > DAQ. Quantum mechanical calculations showed that AQ and DAQ have a very different spin distribution in the triplet state (largely located on the carbonyl oxygen and delocalised over the aromatic ring, respectively) that could account for the difference in reactivity. The spin distribution of EtAQ is similar to that of AQ. Under simulated sunlight, EtAQ induced the highest rate of phenol degradation. Radiation-excited EtAQ would oxidise both ground-state EtAQ and phenol; a kinetic model that excludes the ˙OH radical and singlet oxygen as reactive species is supported by the experimental data. Quinones were also able to oxidise nitrite to nitrogen dioxide, thereby inducing phenol nitration. Such a process is a potential source of nitrogen dioxide and nitrophenols in the atmospheric aerosols.     

Uniqueness and symmetry results for solutions of a mean field equation on 𝕊2 via a new bubbling phenomenon

Motivated by the study of gauge field vortices, we consider a mean field equation on the standard sphere 𝕊² involving a Dirac distribution supported at a point P ∈ 𝕊². Consistently with the physical applications, we show that solutions “concentrate” precisely around the point P for some limiting value of a given parameter. We use this fact to obtain symmetry (about the axis ) and uniqueness property for the solution. The presence of the Dirac measure makes such a task particularly delicate to handle from the analytical point of view. In fact, the bubbling phenomenon about the singularity allows the existence of solution sequences with a double‐peak profile near P. The new and more delicate part of this paper is to exclude this possibility by using the method of moving planes together with the Alexandrov‐Bol inequality. © 2011 Wiley Periodicals, Inc.     

A general framework for pricing Asian options under stochastic volatility on parallel architectures

In this paper, we present a transform-based algorithm for pricing discretely monitored arithmetic Asian options with remarkable accuracy in a general stochastic volatility framework, including affine models and time-changed Lévy processes. The accuracy is justified both theoretically and experimentally. In addition, to speed up the valuation process, we employ high-performance computing technologies. More specifically, we develop a parallel option pricing system that can be easily reproduced on parallel computers, also realized as a cluster of personal computers. Numerical results showing the accuracy, speed and efficiency of the procedure are reported in the paper.     

On the nonlinear effects of the mean wind force on the galloping onset in shallow cables

Nonlinear Dynamics - The critical aeroelastic behavior of horizontal, suspended, and shallow cables is analyzed via a continuous model accounting for both external and internal damping....     

Characterization of Basil Volatile Fraction and Study of Its Agronomic Variation by ASCA

Basil is a plant known worldwide for its culinary and health attributes. It counts more than a hundred and fifty species and many more chemo-types due to its easy cross-breeds. Each species and each chemo-type have a typical aroma pattern and selecting the proper one is crucial for the food industry. Twelve basil varieties have been studied over three years (2018–2020), as have four different cuts. To characterize the aroma profile, nine typical basil flavour molecules have been selected using a gas chromatography–mass spectrometry coupled with an olfactometer (GC–MS/O). The concentrations of the nine selected molecules were measured by an ultra-fast CG e-nose and Principal Component Analysis (PCA) was applied to detect possible differences among the samples. The PCA results highlighted differences between harvesting years, mainly for 2018, whereas no observable clusters were found concerning varieties and cuts, probably due to the combined effects of the investigated factors. For this reason, the ANOVA Simultaneous Component Analysis (ASCA) methodology was applied on a balanced a posteriori designed dataset. All the considered factors and interactions were statistically significant (p < 0.05) in explaining differences between the basil aroma profiles, with more relevant effects of variety and year.     

Modified edge finite elements for photonic crystals

We consider Maxwell’s equations with periodic coefficients as it is usually done for the modeling of photonic crystals. Using Bloch/Floquet theory, the problem reduces in a standard way to a modification of the Maxwell cavity eigenproblem with periodic boundary conditions. Following [8], a modification of edge finite elements is considered for the approximation of the band gap. The method can be used with meshes of tetrahedrons or parallelepipeds. A rigorous analysis of convergence is presented, together with some preliminary numerical results in 2D, which fully confirm the robustness of the method. The analysis uses well established results on the discrete compactness for edge elements, together with new sharper interpolation estimates.     

Behaviour of Bu(CH2—CHCH2)SnCl2 in water and water-cosolvent media: An approach to understanding the chemical degradation of organotins in aquatic environments

The behaviour of allylbutyltin dichloride in water, water–ethanol and water–hexane media, under either homogeneous or heterogeneous conditions, has been studied. 1,3-Diallyl-1,3-dibutyl-1,3-dichlorodistannoxane, butyltin di(hydroxy)chloride and butyltin trichloride arise from the solvolytic, acid–base and degradation processes. The degradation process involving the cleavage of the tin–carbon allyl bond has been interpreted to occur via an intramolecular reaction at the expense of the cation [Bu(CH₂=CHCH₂)Sn(OH)(H₂O)_n]⁺. The mechanistic pathway is ascribable to an internal interaction of the electrophilic cation with a bonded water molecule. This mechanistic proposal may be of some help with understanding of the chemical degradation of diorganotin derivatives in aquatic environments.     

A convenient synthesis of unsymmetrically substituted terphenyls of biologically active stilbenes via a double Suzuki cross-coupling protocol

A double Suzuki cross-coupling protocol has been devised as a practical route to a variety of terphenyls. Good chemoselectivity was observed. Unsymmetrically substituted triphenylenes were also easily prepared.     

Evidence of nuclear motion in H<Subscript>2</Subscript>-like molecules by means of high harmonic generation

The dynamics of hydrogen-like molecules is investigated beyond the usual fixed nuclei approximation. The nuclear motion introduces in the familiar spectrum of emitted radiation additional regular lines whose separation is essentially given by the vibrational frequency of nuclear motion. A wavelet analysis of the emitted spectrum shows that the intensity of the harmonic lines is modulated with the same period of the nuclear motion; this suggests the possibility of the real-time control of the nuclear dynamics.