Introduction to PNET special issue on “Resilience in future 5G photonic networks”

Photonic Network Communications -     

Large Power Increase Enabled by High-Q Diamond-Loaded Cavities for Terahertz Gyrotrons

Journal of Infrared, Millimeter, and Terahertz Waves - A new operation scheme is proposed to enable large increase in output power of terahertz gyrotrons. In this scheme, the gyrotron operates in...     

Travelling wave ion mobility mass spectrometry studies of protein structure: biological significance and comparison with X-ray crystallography and nuclear magnetic resonance spectroscopy measurements

The three-dimensional conformation of a protein is central to its biological function. The characterisation of aspects of three-dimensional protein structure by mass spectrometry is an area of much interest as the gas-phase conformation, in many instances, can be related to that of the solution phase. Travelling wave ion mobility mass spectrometry (TWIMS) was used to investigate the biological significance of gas-phase protein structure. Protein standards were analysed by TWIMS under denaturing and near-physiological solvent conditions and cross-sections estimated for the charge states observed. Estimates of collision cross-sections were obtained with reference to known standards with published cross-sections. Estimated cross-sections were compared with values from published X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy structures. The cross-section measured by ion mobility mass spectrometry varies with charge state, allowing the unfolding transition of proteins in the gas phase to be studied. Cross-sections estimated experimentally for proteins studied, for charge states most indicative of native structure, are in good agreement with measurements calculated from published X-ray and NMR structures. The relative stability of gas-phase structures has been investigated, for the proteins studied, based on their change in cross-section with increase in charge. These results illustrate that the TWIMS approach can provide data on three-dimensional protein structures of biological relevance.     

Evaluating a Cumaean Sibyl: Domenichino or later? A multi analytical approach

The purpose of this study is to clarify important details about a Cumaean Sibyl painting that is preserved in a private collection. This work, bearing neither signature nor date, has never undergone conservation. It was executed after Domenichino's Cumaean Sibyl, a work known to have been used as a model by many 18th century painters.Investigation of the anonymous artist's painting technique and identification of its constituent materials were facilitated by employing optical microscopy (OM), scanning electron microscopy (SEM/EDS), FTIR and microRaman spectroscopies and high performance liquid chromatography with diode array detection (HPLC-DAD). The painter's palette comprised lead white, yellow ochre, lead-antimonate yellow (Naples yellow), cinnabar, cochineal lake, madder lake, haematite, Prussian blue and carbon black.The detection of Prussian blue (synthesized in 1704 and widely used as artist's pigment after 1750) was decisive in establishing the work's authenticity for, as such, it cannot be attributed either to Domenico Zampieri (1581-1641) or to his apprentices. In addition, the identification of Naples yellow, which prevailed in the period from 1750 to 1850, supports this statement. Nevertheless, its elaborate painting technique strongly suggests an artist greatly influenced by the Renaissance masters. A comparison of its stylistic features with those of the Cumaean Sibyl of Angelica Kauffmann (1741-1807), a prolific 18th century artist known to have studied and to have copied Domenichino's Sibyl, reveals significant similarities between the two in composition and palette. The unsigned Sibyl, therefore, could well be by Kauffmann.     

Accurate Interaction Energies of CO2 with the 20 Naturally Occurring Amino Acids

We have performed a series of highly accurate calculations between CO₂ and the 20 naturally occurring amino acids for the investigation of the attractive noncovalent interactions. Different nucleophilic groups present in the amino acid structures were considered (α-NH₂, COOH, side groups), and the stronger binding sites were identified. A database of accurate reference interactions energies was compiled as computed by explicitly-correlated coupled-cluster singles-and-doubles, together with perturbative triples extrapolated to the complete-basis-set limit. The CCSD(F12)(T)/CBS reference values were used for comparing a variety of popular density functionals with different basis sets. Our results show that most density functionals with the triple-zeta basis set def2-TZVPP align with the CCSD(F12)(T)/CBS reference values, but errors range from 0.1 kcal/mol up to 1.0 kcal/mol.     

Tuning Charge Transfer in Ion–Surface Collisions at Hyperthermal Energies

Charge exchange in ion–surface collisions may be influenced by surface adsorbates to alter the charge state of the scattered projectiles. We show here that the positive‐ion yield, observed during ion scattering on metal surfaces at low incident energies, is greatly enhanced by adsorbing electronegative species onto the surface. Specifically, when beams of N⁺ and O⁺ ions are scattered off of clean Au surfaces at hyperthermal energies, no positive ions are observed exiting. Partial adsorption of F atoms on the Au surface, however, leads to the appearance of positively charged primary ions scattering off of Au, a direct result of the increase in the Au work function. The inelastic energy losses for positive‐ion exits are slightly larger than the corresponding ionization energies of the respective N and O atoms, which suggest that the detected positive ions are formed by surface reionization during the hard collision event.     

Road to Next Generation Mobile Networks: An Evolutionary Dynamics Approach

One of the major challenges that mobile operators (MOs) are faced with nowadays is the transition to 4th Generation (4G) mobile communication technologies. The main reason for this lies on the reluctance of MOs to invest in a new technology without being sure about its success. The current paper investigates the decision-making procedures of a MO that wishes to migrate from its current technology type to 4G. Traditionally, the decision of deploying a new technology has been based on the analysis of similar implementations in other countries. However, such approaches can be inefficient and time consuming, as there are discrepancies concerning the technological progress among different countries. To this end, the authors employ evolutionary game theory to model the interactions of the MO’s decisions and the subscribers’ needs, and propose a practical and efficient qualitative model that identifies the circumstances under which the transition towards 4G networking can be facilitated. Specifically, the mathematical foundation of the decision making process is provided and the key role of the charging price and the quality of experience by the subscribers for using 4G connectivity is proven. With the process of 4G deployment still ongoing, this paper aims to present an analysis that can be used supplementary to the decision process of a MO that aims to evolve his network.     

Direct Hydrogenation of Dinitrogen and Dioxygen via Eley–Rideal Reactions

Most Eley–Rideal abstraction reactions involve an energetic gas‐phase atom reacting directly with a surface adsorbate to form a molecular product. Molecular projectiles are generally less reactive, may dissociate upon collision with the surface, and thus more difficult to prove that they can participate intact in abstraction reactions. Here we provide experimental evidence for direct reactions occurring between molecular N₂⁺ and O₂⁺ projectiles and surface‐adsorbed D atoms in two steps: first, the two atoms of the diatomic molecule undergo consecutive collisions with a metal surface atom without bond rupture; and second, the rebounding molecule abstracts a surface D atom to form N₂D and O₂D intermediates, respectively, detected as ions. The kinematics of the collisional interaction confirms product formation by an Eley–Rideal reaction mechanism and accounts for inelastic energy losses commensurate with surface re‐ionization. Such energetic hydrogenation of dinitrogen may provide facile activation of its triple bond as a first step towards bond cleavage.     

Synthesis of (R)-dihydropyridones as key intermediates for an efficient access to piperidine alkaloids

The efficient transformation of D-glucal to (2R)-hydroxymethyldihydropyridinone 5 in seven steps and 35 % overall yield is reported. Dihydropyridone 5 constitutes a versatile chiral building block for the synthesis of various piperidine alkaloids. In this regard, 5 was converted to piperidinol 13 and piperidinone 15, that may be further elaborated for the syntheses of (+)-desoxoprosophylline (1) and deoxymannojirimycin (3) or D-mannolactam (4), respectively.