Estimation of return values for significant wave height from satellite data

Estimation of extreme wave height across the oceans is important for marine safety and design, but is hampered by lack of data. Buoy and platform data are geographically limited, and though satellite observations offer global coverage, they suffer from temporal sparsity and intermittency, making application of standard methods of extreme value estimation problematical. A possible strategy in the face of such difficulty is to use extra model assumptions to compensate for lack of data. In this spirit we report initial exploration of an approach to estimation of extreme wave heights using crossings methods based on a log-Gaussian model. The suggested procedure can utilize either intermittent satellite data or regular time series data such as obtained from a buoy, and it is adapted to seasonal variation in the wave height climate. The paper outlines derivation of the method and illustrates its application to data from the Atlantic and Pacific oceans. A numerical comparison is made with the results of an annual maximum analysis for sites at which both satellite and buoy data are available. The paper concludes with a discussion of the applicability of the new approach, its relationship to other extreme value methods and desirable directions for further development.     

Influence of HF2- geometry on magnetic interactions elucidated from polymorphs of the metal-organic framework [Ni(HF2)(pyz)2]PF6 (pyz = pyrazine)

A tetragonal polymorph of [Ni(HF(2))(pyz)(2)]PF(6) (designated β) is isomorphic to its SbF(6)-congener at 295 K and features linear Ni-FHF-Ni pillars. Enhancements in the spin exchange (J(FHF) = 7.7 K), Néel temperature (T(N) = 7 K), and critical field (B(c) = 24 T) were found relative to monoclinic α-PF(6). DFT reveals that the HF(2)(-) bridges are significantly better mediators of magnetic exchange than pyz (J(pyz)), where J(FHF) ≈ 3J(pyz), thus leading to quasi-1D behavior. Spin density resides on all atoms of the HF(2)(-) bridge whereas N-donor atoms of the pyz ring bear most of the density.     

Investigation of a liposomal oxaliplatin drug formulation by capillary electrophoresis hyphenated to inductively coupled plasma mass spectrometry (CE-ICP-MS)

A capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS) method was developed for separation of the free oxaliplatin drug substance from liposome-entrapped oxaliplatin. Simultaneous determination of phosphorous and platinum opened the possibility to simultaneously monitor the liposomes (phospholipids) and platinum-based drug. In order to suppress the interferences, argon gas was used as a collision gas in ICP-MS. A detection limit of 29 ng/mL of platinum and a precision of 2.9% (for 10 μg/mL of oxaliplatin standard) were obtained. Measurement of the total concentration of free and encapsulated oxaliplatin by CE-ICP-MS was compared with total determination by ICP-MS after microwave digestion and showed a good agreement. A liposomal formulation of oxaliplatin based on PEGylated liposomes was used as a model drug formulation. Studies of accelerated drug release induced by sonication and phospholipase A₂ catalyzed hydrolysis were performed. It was demonstrated that the CE-ICP-MS was an efficient in vitro characterization method in the development and quality assurance purposes of lipsome-based formulation of metallodrugs.     

Aminolysis of resin-bound N-nosylaziridine-2-carboxylic acids

[Structure: see text] Solid-phase synthesis is a rapidly developing area of organic chemistry, of particular importance for medicinal chemistry and chemical biology. Aziridines have previously only rarely been applied in solid-phase synthesis. In the present work, aminolysis of resin-bound, spring-loaded N-nitrobenzenesulfonyl-activated aziridine-2-carboxylic acids has been optimized and employed in the synthesis of a number of open-chain and heterocyclic scaffolds, including enantiopure products.     

Resonance fluorescence from semiconductor quantum dots: beyond the Mollow triplet

We show that the resonance fluorescence spectrum of a quantum dot excited by a strong optical pulse contains multiple peaks beyond those of the Mollow triplet. We show that as the area of the optical pulse is increased, new side peaks split off the central peak and shift in frequency. A simple analytical theory has been derived, which quantitatively accounts for the appearance and position of the peaks. This theory explains the physics responsible for the multiple peaks. By considering the time-dependent spectrum we demonstrate a time ordering of the side peaks, which is further evidence for the suggested physical explanation.     

Molecular and electronic structure of chromium(V) nitrido complexes with azide and isothiocyanate ligands

The first use of [Cr(N)Cl4]2- as a starting material in chromium(v) nitrido chemistry is demonstrated in simple, high yield, metathesis reactions with the pseudohalogens SCN- and N3- yielding five-coordinate, labile complexes: [Cr(N)(NCS)4]2- and [Cr(N)(N3)4]2-, which have been crystallized and characterized by single-crystal X-ray diffraction. Reaction of [Cr(N)(NCS)4]2- with 1,10-phenanthroline furnishes six-coordinate [Cr(N)(NCS)3(phen)]- wherein phenanthroline coordinates to the position trans to the nitrido ligand. The trans influence of the nitrido ligand leads to a bond length difference of 0.223 A between the axial and equatorial ligators from the phenanthroline ligand. The absorption band with lowest energy in these pseudo-linear complexes is assigned as the electric dipole forbidden transition d(xy) --> d(x-y) based on intensities and its variation with the nature of the equatorial ligators. This absorption provides the spectrochemical series for the equatorial ligands, which is found to be numerically almost identical to that determined for chromium(III). DFT calculations reproduce the observed structures and corroborate the ligand field picture of the electronic structure of these complexes.     

A triptycene-based approach to solubilising carbon nanotubes and C60

We describe herein the synthesis of a triptycene-based surfactant designed with the ability to solubilise single-walled carbon nanotubes (SWNTs) and C(60) in water through non-covalent interactions. Furthermore, an amphiphilic naphthalene-based surfactant with the same ability to solubilise SWNTs and C(60) has also been prepared. The compounds synthesised were designed with either two ionic or non-ionic tails to ensure a large number of supramolecular interactions with the solvent, thereby promoting strong solubilisation. The surfactants produced stable suspensions in which the SWNTs are dispersed and the surfactant/SWNT complexes formed are stable for more than one year. UV/Vis/NIR absorption spectroscopy, TEM and AFM were employed to probe the solubilisation properties of the dispersion of surfactants and SWNTs in water.     

Interaction of Amino Acid and Dipeptide β-Naphthylamide Derivatives with Hyaluronic Acid and Human Serum Albumin Studied by Capillary Electrophoresis Frontal Analysis

Interactions of drug candidates with the biomacromolecules of the synovial fluid affect drug targeting to the articular cartilage as well as clearance from the synovial space upon intra-articular administration. Hyaluronic acid (HA) and human serum albumin (HSA) are two main components existing in the synovial fluid. To this end, we investigated the affinity of seven cationic amino acid and dipeptide β-naphthylamide derivatives towards HA and HSA in order to shed light on possible relationships between physicochemical properties, in particular charge state, and biomacromolecular interactions to increase the joint residence time. Capillary electrophoresis frontal analysis was used for characterization of the binding of the derivatives to hyaluronic acid and HSA at 25 °C in acetate buffer (pH 4.65) and phosphate buffer (pH 7.40), respectively. Linear binding isotherms were observed for the ligand–hyaluronic acid interactions and the obtained binding constants ranged from 43 to 133 M^?1. The average fraction of bound ligand towards hyaluronic acid increased with increasing the net charge of the ligands but was less than 67 % for all investigated ligands. The obtained binding constants of the ligands with HSA varied in the range of 10³–10⁶ M^?1. The interactions of low-molecular weight derivatives with hyaluronic acid were highly dependent on the ligand charge state. This trend was not observed for the interactions with HSA. The obtained affinity data may provide useful information in the design of cartilage adhesive prodrugs with extended residence time in the synovial cavity.     

The trans influence in mer‐tri­chloro­nitridobis­(tri­phenyl­arsine)­ruthenium(VI)

The title compound, mer‐[RuCl₃N(C₁₈H₁₅As)₂], is the first structurally characterized example of a nitride complex in which ruthenium is six‐coordinated to monodentate ligands only. The Ru[triple‐bond]N bond length [1.6161 (15) Å] is relatively long, and the trans influence of the nitride ligand is reflected by the difference between the Ru—Cl_trans and Ru—Cl_cis bond lengths [0.1234 (4) Å]. The N—Ru—Cl_trans axis is sited on a twofold axis.