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In the design of dynamic supramolecular systems used in molecular machines, it is important to understand the binding preferences between the macrocycle and stations along the thread. Here, we apply 1H NMR spectroscopy to investigate the relative stabilities of a series of linear alkylammonium templated pseudorotaxanes with the general formula [H2NRR'][Cr7CoF8(O2CCH2tBu)16] by exchanging the cation in solution. Our results show that the pseudorotaxanes are able to exchange threads via a dissociative mechanism. The position of equilibrium is dependent upon the ammonium cation and solvent used. Short chain primary ammonium cations are shown to be far less favourable macrocycle stations than secondary ammonium cations. Collision‐induced dissociation mass spectrometry (CID‐MS) has been used to look at disassembly of the pseudorotaxanes in a solvent‐free environment and stability trends compared to those in acetone‐d6. The energy needed to induce 50 % of the precursor ion loss (E50) is used and shows a similar trend to the equilibria measured by NMR. The relative stabilities of these hybrid inorganic‐organic pseudo‐rotaxanes are different to those of host‐guest compounds involving crown ethers and this may be valuable for the design of molecular machines. [ABSTRACT FROM AUTHOR]

A synthetic strategy is demonstrated to prepare two distinct trimers of antiferromagnetically coupled {Cr7Ni} rings, substantially varying the magnetic interactions between the spin centres. The interactions were studied using multi‐frequency cw EPR: in a trimer linked via non‐covalent H‐bonding interactions no measurable interaction between rings was seen, while in a trimer linked via iso‐nicotinate groups isotropic and anisotropic exchange interactions of +0.42 and −0.8 GHz, respectively, were observed. The latter are the same as those for a simpler hetero‐dimer system, showing how the spin‐spin interactions can be built in a predictable and modular manner in these systems. [ABSTRACT FROM AUTHOR]

Despite being known for decades, the solution-state molecular chemistry of heptapnictogen ([Pn7]3−; Pn = P, As) clusters is not well established. Here we study heavy element derivatives of tetrel functionalized heptapnictogen clusters towards heteroallene capture, specifically isocyanates, an isothiocyanate and CO2 are probed. Clusters (Me3Ge)3P7 (1), (Et3Ge)3P7 (2), (nBu3Sn)3P7 (3), and (Me3Si)3As7 (4) were all found to capture isocyanates between all three of their tetrel–pnictogen bonds. In the case of phenyl isocyanate insertion, tetrel coordination at the isocyanate nitrogen atoms is preferred, while in the case of p-toluenesulfonyl isocyanate insertion, tetrel coordination at oxygen is preferred. Furthermore, the reaction of (Me3Si)3P7 with CO2 gave NMR spectra consistent with the capture of the greenhouse gas. Heteroallene insertion at these clusters was also studied using density functional theory. [ABSTRACT FROM AUTHOR]

We report a method for routine crystal structure determination on very small (typically 0.1 mg or less) amounts of crystalline material using powder X-ray diffraction data from a laboratory-based single-crystal diffractometer. The solved structures span a wide range of molecular and crystallographic complexity. [ABSTRACT FROM AUTHOR]

Despite being known for decades the chemical reactivity of homoatomic seven‐atom phosphorus clusters towards small molecules remains largely unexplored. Here, we report that neutral tris(silyl) functionalised heptaphosphane (P7(SiR3)3) cages are capable of heteroallene capture between the P−Si bonds of the cluster. A range of isocyanates and an isothiocyanate were investigated. In the case of isocyanates, silyl bonding at oxygen or nitrogen is regioselectively directed by the functional group on the isocyanate and substituents on the silyl moiety. Above all, we find that captured isothiocyanate molecules can be exchanged for isocyanate molecules, indicative of small molecule catch and release. Small molecule catch and release at these Zintl‐derived clusters reveals their potential application as chemical storage materials or as reusable probes. [ABSTRACT FROM AUTHOR]

With the recent increase in research into ferroelectric, anti‐ferroelectric and piezoelectric materials, studying the solid‐state properties in situ under applied electric fields is vital in understanding the underlying processes. Where this behaviour is the result of atomic displacements, crystallographic insight has an important role. This work presents a sample environment designed to apply an electric field to single‐crystal samples in situ on the small‐molecule single‐crystal diffraction beamline I19, Diamond Light Source (UK). The configuration and operation of the cell is described as well as its application to studies of a proton‐transfer colour‐change material. [ABSTRACT FROM AUTHOR]

MFM-722(Pb)-DMA undergoes a single-crystal-to-single-crystal (SCSC) transformation to give MFM-722(Pb)-H2O via ligand substitution upon exposure to water vapour. In situ single crystal impedance spectroscopy reveals an increase in proton conductivity due to this structural transition, with MFM-722(Pb)-H2O showing a proton conductivity of 6.61 × 10−4 S cm−1 at 50 °C and 98% RH. The low activation energy (Ea = 0.21 eV) indicates that the proton conduction follows a Grotthuss mechanism. [ABSTRACT FROM AUTHOR]

The effects of sea level rise are now beginning to be detected in seagrass ecosystems. The present work deals with how sea level rise translates into changes on seagrass distribution at local scale and how to provide reliable information and tools to predict the vulnerability of shallow coastal ecosystems to the expected effects. To evaluate mid- and long-term changes in the habitat suitability of Zostera noltei a combination of clustering techniques—Self organizing maps and K means—considering RCP and high-end projections was used. The study, developed at the Bay of Santander, provides evidence indicating that sea level rise will highly affect meadows of Zostera noltei. This species will experience an important spatial variability, mainly in deeper areas, where moderate rising levels will substantially reduce the availability of suitable habitats for this species. This process will intensify over time and seagrass meadows are expected to be severely affected in the long term. A rising level of 0.63 m by 2100 will result in a 14.2% reduction in suitable habitats, while a 51% loss will occur with a sea level rise of 2 m. Our results indicate that large areas of seagrass in the Bay of Santander will be lost with future sea level rise, especially in the absence of major changes to sediment dynamics. However, a review of the main feedbacks and self-amplifying mechanisms regulating their adaptation allows us to be confident about Zostera noltei's capacity to adapt to changing conditions in the near future. In the long term, there are more doubts regarding this ability and possible responses remain highly uncertain. [ABSTRACT FROM AUTHOR]

Reduction of copper(II) chloride using sodium ascorbate in the presence of pure sodium 5-nitro-tetrazolate (NaNT) forms copper(I) 5-nitrotetrazolate – a known initiatory explosive (DBX-1) – and the novel mixed-ligand copper(I) chloride 5-nitrotetrazolate coordination polymer Cu3Cl(N4C-NO2)2, as well as mixtures of both. The reaction is controlled by the presence of seed crystals and transition metal compounds other than CuCl2. Cu3Cl(N4C-NO2)2 is obtained as a wine-red, air stable, water-insoluble, crystalline and highly sensitive explosive material with a greater crystal density, lower thermal stability and a higher sensitivity toward hydrolysis and shock than DBX-1. Efforts to obtain the stable and pure starting material are improved by crystallisation of NaNT as a tetrahydrate. Cu3Cl(N4C-NO2)2 and Na(H2O)4(NT) were characterised by single crystal and powder XRD, IR spectroscopy, magnetic and thermal measaurements, elemental analysis, particle size measurements, mass spectrometry, and by drop weight testing. [ABSTRACT FROM AUTHOR]

We present conductivity data for a newly synthesised metal–organic framework FeQ, Fe(C14H6O4).H2O demonstrating significant electronic transport. The electrical conductivity of the material is expected to be through the π–π interaction of the ligand-quinizarin and is measured to be 1.73 × 10−2 Scm−1. Its potential role as supercapacitor electrodes is discussed. [ABSTRACT FROM AUTHOR]

Historic coastal structures have played a key role in small- to medium-size ports, being the driving force for the local development of coastal communities. Because coastal managers require reliable risk-based analysis of the whole life cycle of these coastal structures, previous lifetimes should be studied. This is a differentiating factor with respect to the newly built breakwaters. For this reason, in this work, a methodology for assessing how the hydraulic performance of an expired lifetime has evolved over the years is presented. It is performed following a probabilistic approach due to the uncertainty related to both the involved variables (wave climate, geometrical and structural breakwater variables) and the hydraulic response of the structure. The first ones are characterized by reliable probability distribution functions. The second ones are characterized by reliable formulae for the analysis of the hydraulic response. However, their non-conventional designs located in shallow-water locations require site-dependent formulae. To overcome this problem, a novel methodology to apply CFD numerical models is presented. Finally, it is integrated in a high-resolution time-dependent probabilistic methodology which takes into account the stochastic behaviour of all the involved variables, coastal and structural processes with a good uncertainty level. This article is part of the theme issue 'Environmental loading of heritage structures'. [ABSTRACT FROM AUTHOR]

We use a numerical model, already validated for this purpose, to simulate the effect of wave frequency spread on wave transformation and swash amplitudes. Simulations are performed for planar beach slope cases and for offshore wave spectra whose frequency spread changes over realistic values. Results indicate that frequency spread, under normally approaching waves, affects swash amplitudes. For moderately dissipative conditions, the significant infragravity swash increases for increasing values of the offshore frequency spread. The opposite occurs under extremely dissipative conditions. The numerical analysis suggests that this inverted pattern is driven by the effect that different distributions of incoming long‐wave energy have on low‐frequency wave propagation and dissipation. In fact, with large frequency spreads, wave groups force relatively short subharmonic waves that are strongly enhanced in the shoaling zone. This process leads to an infragravity swash increase for increasing frequency spread under moderately dissipative conditions in which low‐frequency energy dissipation in shallow water is negligible or small. However, under extremely dissipative conditions, the significant low‐frequency energy dissipation associated with large frequency spreads overturns the strong energy growth in the shoaling zone eventually yielding an infragravity swash decrease for increasing frequency spread. Key Points: Numerical simulations reveal that frequency spread affects swash amplitudes with a pattern that inverts over two Iribarren number rangesAn infragravity swash increase for increasing frequency spread is observed under moderately dissipative conditionsThe infragravity swash increases for decreasing frequency spread under extremely dissipative conditions [ABSTRACT FROM AUTHOR]

Abstract: [2] and [3] hybrid rotaxanes are reported based on {Ti7M} rings (M is a trivalent metal such as FeIII or GaIII). NMR studies show that [2]rotaxanes can act as molecular shuttles, while EPR studies of [3]rotaxanes show weak interactions between the paramagnetic components of the supramolecular assemblies. [ABSTRACT FROM AUTHOR]

Abstract: [2] and [3] hybrid rotaxanes are reported based on {Ti7M} rings (M is a trivalent metal such as FeIII or GaIII). NMR studies show that [2]rotaxanes can act as molecular shuttles, while EPR studies of [3]rotaxanes show weak interactions between the paramagnetic components of the supramolecular assemblies. [ABSTRACT FROM AUTHOR]

A family of heterometallic [Cat][TixMO(x+1)(O2CtBu)2x+2] rings is reported where Cat=a secondary or tertiary alkyl ammonium ion, x=7, 8 or 9, and M=FeIII, GaIII, CrIII, InIII and AlIII. The structures are regular polygons with eight, nine or ten vertices with each edge bridged by an oxide and two pivalates. The size of the ring formed is controlled by the alkylammonium cation present. In each case a homometallic by-product is found [Cat][TixO(x+1)(O2CtBu)2x−1]. [ABSTRACT FROM AUTHOR]

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The mathematical modeling of the interaction of water waves with porous coastal structures has continuously been among the most relevant challenges in coastal engineering research and practice. Finding a tool to better predict essential processes, relevant to the functionality and stability of breakwaters and jetties, and how they are affected by permeability, has been hampered by computational limitations that are being overcome. Over the last 60 years, the Journal of Waterway, Port, Coast, and Ocean Engineering has witnessed gradual developments leading from linearized solutions based on wave theories and constant friction coefficients to very sophisticated Eulerian or Lagrangian solvers of the Navier-Stokes (NS) equations, including turbulence within porous media. Today, although not without difficulty, the first steps are being made toward addressing the simulation of a fully three-dimensional interaction of complete sea states with porous structures at prototype scale. In this paper, after posing the mathematical foundations of the problem, the solution techniques available in the literature are reviewed. Linear solutions based on potential theory; depth-integrated solutions, including Boussinesq approximations; and solutions based on the NS equations, in both the Eulerian and Lagrangian frameworks, are covered. Then, turbulence modeling on porous media is discussed. Conclusions and a discussion of future research directions close the paper. It is shown that, after so many years, some fundamental questions still remain unanswered, leaving challenges open for future research. [ABSTRACT FROM AUTHOR]

The first regular homometallic ring containing an odd number of metal centers is reported. The ring was synthesized by means of amine-templated self-assembly. Extensive physical characterization studies, including magnetic measurements, powder inelastic neutron scattering (INS), and DFT calculations, show that the molecule has a near perfect match to the expected behavior for a frustrated system with the lowest energy pair of S=1/2 spin states separated by only 0.1 meV (0.8 cm−1). [ABSTRACT FROM AUTHOR]

The first regular homometallic ring containing an odd number of metal centers is reported. The ring was synthesized by means of amine-templated self-assembly. Extensive physical characterization studies, including magnetic measurements, powder inelastic neutron scattering (INS), and DFT calculations, show that the molecule has a near perfect match to the expected behavior for a frustrated system with the lowest energy pair of S=1/2 spin states separated by only 0.1 meV (0.8 cm−1). [ABSTRACT FROM AUTHOR]

A [2]rotaxane was produced through the assembly of a picolinaldehyde, an amine, and a bipyridine macrocycle around a CuI template by imine bond formation in close-to-quantitative yield. An analogous [3]rotaxane is obtained in excellent yield by replacing the amine with a diamine, thus showing the suitability of the system for the construction of higher order interlocked structures. The rotaxanes are formed within a few minutes simply through mixing the components in solution at room temperature and they can be isolated through removal of the solvent or precipitation. [ABSTRACT FROM AUTHOR]

A [2]rotaxane was produced through the assembly of a picolinaldehyde, an amine, and a bipyridine macrocycle around a CuI template by imine bond formation in close-to-quantitative yield. An analogous [3]rotaxane is obtained in excellent yield by replacing the amine with a diamine, thus showing the suitability of the system for the construction of higher order interlocked structures. The rotaxanes are formed within a few minutes simply through mixing the components in solution at room temperature and they can be isolated through removal of the solvent or precipitation. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of the uranium(III) triamide complex [UIII(N**)3] [ 1, N**=N(SiMe2 tBu)2−]. Surprisingly, complex 1 exhibits a trigonal planar geometry in the solid state, which is unprecedented for three-coordinate actinide complexes that have exclusively adopted trigonal pyramidal geometries to date. The characterization data for [UIII(N**)3] were compared with the prototypical trigonal pyramidal uranium(III) triamide complex [UIII(N')3] (N'=N(SiMe3)2−), and taken together with theoretical calculations it was concluded that pyramidalization results in net stabilization for [UIII(N')3], but this can be overcome with very sterically demanding ligands, such as N**. The planarity of 1 leads to favorable magnetic dynamics, which may be considered in the future design of UIII single-molecule magnets. [ABSTRACT FROM AUTHOR]

Tsunami wave interaction with coastal regions is responsible for very important human and economic losses. In order to properly design coastal defenses against these natural catastrophes, new numerical models need to be developed that complement existing laboratory measurements and field data. The use of numerical models based on the Navier-Stokes equations appears as a reasonable approach due to their ability to evaluate complex flow patterns around coastal structures without the inherent limitations of the classical depth-averaged models. In the present study, a Navier-Stokes-based model, IH-3VOF, is applied to study the interaction of tsunami waves with porous and impermeable structures. IH-3VOF is able to simulate wave flow within the porous structures by means of the volume-averaged Reynolds-averaged Navier-Stokes VARANS equations. The equations solved by the model and their numerical implementation are presented here. A numerical analysis of the interaction of a tsunami wave with both an impermeable and porous vertical breakwater is carried out. The wave-induced three-dimensional wave pattern is analysed from the simulations. The role paid by the porous media is also investigated. Finally, flow around the breakwater is analyzed identifying different flow behaviors in the vicinity of the breakwater and in the far field of the structure. [ABSTRACT FROM AUTHOR]

Posidonia oceanica, the most abundant seagrass species in the Mediterranean, supports a highly bio-diverse habitat and is crucial in protecting against coastal erosion. In this work, experiments in a large-scale facility have been performed, for the measurement of wave attenuation, transmission and energy dissipation over artificial Posidonia oceanica. The effects of submergence ratio corresponding to the seagrass height divided by water depth, and seagrass density as the number of stems per square metre on the above characteristics are investigated. Measurements of wave height at different locations along the vegetation meadow indicate the wave attenuation along the Posidonia oceanica for three different submergence ratios and two seagrass densities. Results are also analysed with regard to the wave-induced flow within the meadow, and the effects of the submergence ratio and the seagrass density on the mean flow characteristics, based on data of mean velocities taken at three locations within the seagrass. [ABSTRACT FROM AUTHOR]

This paper presents the numerical modelling of the cross shore propagation of infragravity waves induced by a transient focused short wave group over a sloping bottom. A dataset obtained through new laboratory experiments in the wave flume of the University of Cantabria is used to validate the Reynolds averaged Navier-Stokes type model IH- 2VOF. A new boundary condition based on the wave maker movement used in the experiments is implemented in the model. Shoaling and breaking of short waves as well as the enhancement of long waves and the energy transfer to low-frequency motion are well addressed by the model, proving the high accuracy in the reproduction of surf zone hydrodynamics. Under the steep slope regime, a long wave trough is radiated offshore from the breakpoint. Numerical simulations conducted for different bottom slopes and short wave steepness suggest that this low-frequency breakpoint generated wave is controlled by both the bed slope parameter and the Iribarren number. Moreover, the numerical model is used to investigate the influence that a large flat bottom induces on the propagation pattern of long waves. [ABSTRACT FROM AUTHOR]

Menendez, M., Mendez, F. J., and Losada, I. J. 2009. Forecasting seasonal to interannual variability in extreme sea levels. – ICES Journal of Marine Science, 66: 1490–1496.A statistical model to predict the probability of certain extreme sea levels occurring is presented. The model uses a time-dependent generalized extreme-value (GEV) distribution to fit monthly maxima series, and it is applied for a particular time-series record for the Atlantic Ocean (Newlyn, UK). The model permits the effects of seasonality, interannual variability, and secular trends to be identified and estimated in the probability distribution of extreme sea levels. These factors are parameterized as temporal functions (linear, quadratic, exponential, and periodic functions) or covariates (for instance, the North Atlantic Oscillation index), which automatically yield the best-fit model for the variability present in the data. A clear pattern of within-year variability and significant effects resulting from astronomical modulations (the nodal cycle and perigean tides) are detected. Modelling different time-scales helps to gain a better understanding of recent secular trends regarding extreme climate events, and it allows predictions to be made (for example, up to 2020) about the probability of the future occurrence of a particular sea level. [ABSTRACT FROM PUBLISHER]

The experience acquired in the Prestige crisis management has demonstrated the importance of forecasting oil slick trajectories to plan an effective oil spill response. To have a reliable prediction system, we need to perform a detailed calibration and validation of the oil spill transport model. In this work, the Lagrangian transport model, PICHI, developed by the University of Cantabria during the Prestige accident, is calibrated by means of an automatic calibration methodology. The shuffled complex evolution method, developed by the University of Arizona (SCE-UA), is applied to estimate the optimal coefficients of the model. The calibration of the model has been carried out using 13 buoys deployed in the Bay of Biscay during the Prestige accident as well as coetaneous meteorological and oceanographic data. Moreover, reanalysis data collected in the Spanish ESEOO project framework has also been used. Results suggest that buoys outside the continental slope were mainly driven by wind, whereas ocean currents played an important role in the motion of the buoys located over the continental slope and shelf. According to these findings, the final calibration of the coefficients is performed considering different buoy data. The methodology applied to this broad buoy database, has allowed us to calibrate the model, taking into account the relative importance of the forcings in buoy movement as well as the dynamics associated with each area. [ABSTRACT FROM AUTHOR]

This paper compares the output from four methods used to predict the mean overtopping discharge at the root of the South Breakwater of Póvoa de Varzim Harbour (Portugal): two numerical models AMAZON, based on solving the nonlinear shallow-water equations, and COBRAS-UC, based on the Reynolds averaged Navier–Stokes equations, Pedersen’s empirical formula, and the neural network tool NN_Overtopping. Output from the methods is considered alongside data from two-dimensional (2D) physical model tests. The results show that rather accurate predictions can be obtained with COBRAS-UC. Agreement between the data and the AMAZON output depends principally on the impact of porosity on overtopping: agreement is very good when the impact is limited (for high overtopping discharges) and it worsens as porosity plays a more important role (for small discharges). NN_Overtopping estimates the mean discharges with a degree of accuracy similar to AMAZON. Pedersen’s results are those which deviate more from the data, substantially overpredicting the mean discharges for the conditions analyzed. [ABSTRACT FROM AUTHOR]

A statistical model to analyze different time scales of the variability of extreme high sea levels is presented. This model uses a time-dependent generalized extreme value (GEV) distribution to fit monthly maxima series and is applied to a large historical tidal gauge record (San Francisco, California). The model allows the identification and estimation of the effects of several time scales—such as seasonality, interdecadal variability, and secular trends—in the location, scale, and shape parameters of the probability distribution of extreme sea levels. The inclusion of seasonal effects explains a large amount of data variability, thereby allowing a more efficient estimation of the processes involved. Significant correlation with the Southern Oscillation index and the nodal cycle, as well as an increase of about 20% for the secular variability of the scale parameter have been detected for the particular dataset analyzed. Results show that the model is adequate for a complete analysis of seasonal-to-interannual sea level extremes providing time-dependent quantiles and confidence intervals. [ABSTRACT FROM AUTHOR]

Presents information on a study which analyzed the influence of wave reflection and energy dissipation induced by a permeable submerged breakwaters on second-order mean quantities. Methodology of the study; Results and discussion on the study; Conclusions.

Presents information on a study which obtained an analytical solution for waves propagating through a horizontal porous plate of finite thickness. Formulation of the problem; Extension to irregular waves; Interaction of a wave group with the horizontal porous plate; Results.