Nonlinear prediction of crown–of–thorns outbreaks on the great barrier reef

The Zakai form of nonlinear prediction theory is used to estimate yearto-year state changes in crown-of-thorns starfish populations of the Great Barrier Reef. Taking the previously defined coral-state diffusion as observation process and the starfish-state diffusion as signal process, a least squares polynomial regression curve recently derived for simultaneously collected starfish/coral state data is used to set up the prediction preliminaries, Numerical results are not inconsistant with starfish outbreak values of the last 5 years and yield an expected high value for 1987. However, because of large error in the data it is doubtful that a more refined mesh for the Mihlstein approximations used to evaluate the Îto stochastic integrals involved in Zakai theory would improve the accuracy of predictions.     

Synthesis and Characterization of Far‐Red/NIR‐Fluorescent BODIPY Dyes,Solid‐State Fluorescence,and Application as Fluorescent Tags Attached to Carbon Nano‐onions

A series of π‐extended distyryl‐substituted boron dipyrromethene (BODIPY) derivatives with intense far‐red/near‐infrared (NIR) fluorescence was synthesized and characterized, with a view to enhance the dye’s performance for fluorescence labeling. An enhanced brightness was achieved by the introduction of two methyl substituents in the meso positions on the phenyl group of the BODIPY molecule; these substituents resulted in increased structural rigidity. Solid‐state fluorescence was observed for one of the distyryl‐substituted BODIPY derivatives. The introduction of a terminal bromo substituent allows for the subsequent immobilization of the BODIPY fluorophore on the surface of carbon nano‐onions (CNOs), which leads to potential imaging agents for biological and biomedical applications. The far‐red/NIR‐fluorescent CNO nanoparticles were characterized by absorption, fluorescence, and Raman spectroscopies, as well as by thermogravimetric analysis, dynamic light scattering, high‐resolution transmission electron microscopy, and confocal microscopy.     

Molecular design of polymer coatings capable of photo-triggered stress relaxation via dynamic covalent bond exchange

Polymer coatings are frequently used to modify surface properties of inorganic substrates. However, the disparity in physical properties between polymer film and substrate often leads to residual stress development, which can be deleterious to the overall performance of coated materials. This work reports the molecular design of polymer films that dissipate stress upon irradiation with ultraviolet (UV) light. These polymers are synthesized by post-polymerization modification of the reactive polymer, poly(2-vinyl-4,4-dimethyl azlactone), to introduce dynamic crosslinks capable of light-initiated addition transfer fragmentation chemistry. Using a custom-built optical cantilever, contrasting film stress responses are observed between films containing dynamic bonds and analogous control films after UV light irradiation, which indicate successful stress relaxation. Further experiments demonstrate the complete relaxation of residual stress in dynamic films after an extended exposure, thereby generating a “stress-free” film. Films fabricated using this approach can be easily tailored to incorporate additional moieties to introduce desired surface properties for future application in a wide array of coatings.     

The Sodium Borohydride and Sodium Cyanoborohydride Reduction of Unsymmetrically Substituted 3-Chloro-2-propeniminium Salts

A series of 3-substituted-3-chloro-2-propeniminium salts have been reacted with sodium borohydride and/or sodium cyanoborohydride to produce 1-substituted-1-chloro-3-N, N-dimethylamino-1-propenes in good yield.     

Microwave-assisted organic synthesis of a high-affinity pyrazolo-pyrimidinyl TSPO ligand

We herein report a dramatically improved total synthesis of the high-affinity translocator protein (TSPO) ligand DPA-714, featuring microwave-assisted organic synthesis (MAOS). Compared with previously described approaches, our novel MAOS method dramatically reduces overall reaction time without adversely effecting reaction yields. We envision that the described MAOS protocol may be suitably applied to high-throughput, diversity-oriented synthesis of novel compounds based on the pyrazolo-pyrimidinyl scaffold. Such an approach could accelerate the development of focused libraries of novel TSPO ligands with potential for future development as molecular imaging and therapeutic agents.     

Mercury induced reorientation of alkanethiolates adsorbed on gold

3 -(CH₂)₂₁-SH) were investigated by IR-vis sum frequency generation (SFG). Well-ordered monolayers and films with submonolayer coverage with a high number of gauche conformations were prepared on polycrystalline gold substrates. Exposure to a saturated mercury atmosphere induces a major reorganization of the adsorbate phase indicated by a decrease of the average cant angle. Additionally, well-ordered films show an increase of gauche defects upon amalgamation. In contrast, films with submonolayer coverage exhibit an improvement of molecular order. The experiments suggest that amalgamation flattens the corrugation potential of the substrate and yields a separation of the thiol layer into areas of low thiol density with highly disordered alkyl chains and of higher density than on gold with an orientation of the molecules similar to what is observed on silver substrates. Received: 13 November 1998     

A high voltage asymmetric waveform generator for FAIMS

High field asymmetric waveform ion mobility spectrometry (FAIMS) has been used increasingly in recent years as an additional method of ion separation and selection before mass spectrometry. The FAIMS electrodes are relatively simple to design and fabricate for laboratories wishing to implement their own FAIMS designs. However, construction of the electronics apparatus needed to produce the required high magnitude asymmetric electric field oscillating at a frequency of several hundred kilohertz is not trivial. Here we present an entirely custom-built electronics setup capable of supplying the required waveforms and voltages. The apparatus is relatively simple and inexpensive to implement. We also present data acquired on this system demonstrating the use of FAIMS as a gas-phase ion filter interface to an ion trap mass spectrometer.     

Vibrational spectroscopy of size-selected sodium-doped water clusters

The vibrational OH stretch spectra have been measured for Na(H2O)n clusters in the size range from n = 8 to 60. The complete size selection is achieved by coupling the UV radiation of a dye laser below the ionization threshold with the tunable IR radiation of an optical parametric oscillator. The spectra are dominated by intensity peaks around 3400 cm(-1) which we attribute to an increased transition dipole moment of delocalized electrons in this type of doped cluster. Aside from the positions of free (3715 cm(-1)) and double donor (3560 cm(-1)) bonds which are known from pure water clusters, specific transitions are observed at 3640 cm(-1) and in the range of the single donor bonds between 3000 and 3200 cm(-1).