Wavelength-agile H2O absorption spectrometer for thermometry of general combustion gases

Using a novel Fourier-domain mode-locking (FDML) laser scanning 1330-1380 nm, we have developed a gas thermometer based on absorption spectroscopy that is appropriate for combustion gases at essentially arbitrary conditions. The path-integrated measurements are particularly useful in homogeneous environments, and here we present measurements in a controlled piston engine and a shock tube. Engine measurements demonstrate a RMS temperature precision of ±3% at 1500 K and 200 kHz bandwidth; the precision is improved dramatically by averaging. Initial shock tube measurements place the absolute accuracy of the thermometer within ∼2% to 1000 K. The sensor performs best when significant H₂O vapor is present, but requires only at 300 K, at 1000 K, or at 3000 K for 2% accurate thermometry, assuming a 4 kHz measurement bandwidth (200 kHz scans with 50 averages). The sensor also provides H₂O mole fraction and shows potential for monitoring gas pressure based on the broadening of spectral features. To aid in designing other sensors based on high-temperature, high-pressure H₂O absorption spectroscopy, a database of measured spectra is included.     

Solid-phase Pd-catalysed cross-coupling methods for the construction of π-conjugated peptide nanomaterials

We describe the development of two procedures for the synthesis of peptides that are embedded with a variety of π-conjugated semi-conducting oligomers. These procedures utilise solid-phase variants of classical palladium-catalysed cross-couplings commonly used to prepare π-conjugated oligomers. The resulting peptide–π–electron hybrids are soluble in aqueous media and self-assemble to produce 1D nanostructures, simultaneously forming networks of π-stacked conduits. The procedures have allowed for the inclusion of complex chromophores including mixed aryl units, ethynylene linkers and sexithiophenes where the latter peptide's nanostructures demonstrated substantial conductivity when employed as an active layer in a field-effect transistor.     

Amplification of a cyclic mixed-metalloporphyrin tetramer from a dynamic combinatorial library through orthogonal metal coordination

A cyclic porphyrin tetramer, consisting of two bis-phosphine substituted zinc(II) porphyrin units and two Rh(III)TPP units, is selected and amplified virtually quantitatively from a dynamic combinatorial library using 4,4'-bipy as a scaffold and using orthogonal binding modes.     

Amphipols can support the activity of a membrane enzyme

Amphipathic polymers ("amphipols") were introduced several years ago (Tribet, C.; Audebert, R.; Popot, J.-L. Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 15047-15050) as an alternative method for solubilizing integral membrane proteins in stable, nativelike conformations. However, direct maintenance of full membrane protein functionality in amphipol solutions has not previously been demonstrated in the absence of added lipid or detergent. In this contribution, the first zwitterionic amphipol "PMAL-B-100" is introduced. PMAL-B-100 not only maintains membrane protein structure and solubility, but also supports the full catalytic activity of an integral membrane enzyme, diacylglycerol kinase, in the complete absence of additional lipid or detergent. All of the roles which a lipid bilayer normally plays in maintaining diacylglycerol kinase's structure and in facilitating catalysis are satisfied by the environment and interactions supplied by PMAL-B-100.     

Pseudorapidity distributions of charged particles from Au + Au collisions at the maximum RHIC energy,square root[s(NN)] = 200 GeV

We present charged-particle multiplicities as a function of pseudorapidity and collision centrality for the 197Au+197Au reaction at square root[s(NN)] = 200 GeV. For the 5% most central events we obtain dN(ch)/deta/(eta = 0) = 625+/-55 and N(ch)/(-4.7< or =eta < or =4.7) = 4630 +/- 370, i.e., 14% and 21% increases, respectively, relative to square root[s(NN)] = 130 GeV collisions. Charged-particle production per pair of participant nucleons is found to increase from peripheral to central collisions around midrapidity. These results constrain current models of particle production at the highest RHIC energy.     

Disulfide-strapped porphyrins for monolayer formation on gold

Porphyrins with a disulfide-containing strap have been prepared as an alternative to dithiols for self-assembled monolayer formation on gold surfaces. The strapped porphyrins have the advantage of greater air stability than their dithiol analogues. Cis and trans atropisomers of a strapped porphyrin were isolated. Gold electrodes modified with dithiol and disulfide porphyrins were not identical as evidenced by contact angle or electrochemical measurements.     

Acylhydroperoxide oxidations of the anticancer agent hexamethylmelamine

The clinically effective anticancer agent hexamethylmelamine undergoes an unusual acylhydroperoxide oxidative transformation to give the novel product 2,4-bis(dimethylamino)-6-[(dimethylamino)oxy]-1,3,5-triazine.     

Magnetic polariton,impurity mode enhancement,and superradiance effects in FeF2

The first clear evidence for the existence of $\text{magnetic polaritons}$ from a high resolution, far-infrared (FIR) study of the antiferromagnetic resonance (AFMR) of FeF₂ is presented. The broad (4 kOe) asymmetric structure observed in transmission is shown to be a characteristic polariton effect; the linewidth ΔH at 4.2 K is only 350 Oe. The Mn impurity mode is enhanced by ～50 in agreement with a coupled equations of motion prediction. Both host and impurity resonances are broadened by superradiance.     

Two-atom model for the calculation of surface blocking in medium and high energy ion scattering

A two-atom blocking model has been developed to analyze surface blocking patterns recently obtained in medium energy ion scattering experiments. In the model the mean square thermal vibration amplitude of a surface atom can be used as a fitting parameter in comparison with experimental results. Anisotropic surface vibrations have been taken into account by assuming a non-spherical Gaussian probability distribution for the thermal displacement of the surface atom. In addition, some analytical expressions have been derived for the effective nuber of target atoms contributing to the yield of ions backscattered into a blocking direction.