Thermal and IR-induced conformer interconversion processes for 2-chloroallyl alcohol in Low-temperature matrices: Wavelength-dependent conformer steady states

2-chloroallyl alcohol has been studied in low-temperature Ar, Kr, Xe, N₂ and CH₄ matrices. An IR-induced process was found in all media except CH₄ and resulted in a steady state dependent on the Wavelength of the irradiation. At elevated temperatures thermal conformer interconversions occurred. The energetics of the processes are discussed and their potential barriers determined. No mode selectivity was found.     

The bar spectral sequence converging toh *(SO(2n+1))

We study the bar spectral sequence converging toh _*(SO(2n+1)), whereh is an algebra theory overBP. The differentials are determined completely ifh=P(l) andn<2 ^l . These results will be used in a future paper on the MoravaK-theories ofSO(2n+1), with no restriction onn. As another application, we determineBP _*(Spin(7)) including much of its algebra structure.AMS Subject Classification: 57T10, 57T30, 55N22     

Hadronization of quark systems

Hadronization in simple models of quark systems is discussed with emphasis on the combinatorial aspects. The numberN of quarks and the numberN _c of colours are the relevant variables. In onedimension and in the meson and baryon sector the problem is completely soluble. When multiquark hadrons are included an iterative procedure still allows a complete solution. Higher dimensions are difficult to treat but global hadronization, without dimensionality constraints, is again soluble. As a general result the baryon/meson ratio is, for large quark densities, rather large, ?1/3 and may grow without limit asN→∞.     

Label-free selective DNA detection with high mismatch recognition by PNA beacons and ion exchange HPLC

Two 11mer peptide nucleic acid (PNA) beacons were synthesized and tested for the detection of full-matched or single mismatched DNA. Fluorescent measurements carried out in solution showed only partial discrimination of the mismatched sequence, while using anion-exchange HPLC, in combination with fluorimetric detection, allowed DNA analysis to be performed with high sensitivity and extremely high sequence selectivity. Up to >90 : 1 signal discrimination in the presence of one single mismatched base was observed. The analysis was tested on both short and long DNA oligomers. Detection of DNA obtained from PCR amplification was also performed allowing the selective detection of the target sequence in complex mixtures. Label free detection of the DNA with high sequence selectivity is therefore possible using the present approach.     

Paradigms in isotope dilution mass spectrometry for elemental speciation analysis

Isotope dilution mass spectrometry currently stands out as the method providing results with unchallenged precision and accuracy in elemental speciation. However, recent history of isotope dilution mass spectrometry has shown that the extent to which this primary ratio measurement method can deliver accurate results is still subject of active research. In this review, we will summarize the fundamental prerequisites behind isotope dilution mass spectrometry and discuss their practical limits of validity and effects on the accuracy of the obtained results. This review is not to be viewed as a critique of isotope dilution; rather its purpose is to highlight the lesser studied aspects that will ensure and elevate current supremacy of the results obtained from this method.     

Characterization of estuarine sediments by near infrared diffuse reflectance spectroscopy

It has been developed a partial least squares near infrared (PLS-NIR) method for the determination of estuarine sediment physicochemical parameters. The method was based on the chemometric treatment of first order derivative reflectance spectra obtained from samples previously lyophilized and sieved through a lower than 63 μm grid. Spectra were scanned from 833 to 2976 nm, averaging 36 scans per spectrum at a resolution of 8 cm⁻¹, using chromatographic glass vials of 9.5 mm internal diameter as measurement cells. Models were built using reference data of 31 samples selected through the use of a hierarchical cluster analysis of NIR spectra of sediments obtained from the Ria de Arousa estuary and prediction parameters were established from a validation set of 50 samples of the same area. pH, redox potential (Eh), carbon (C), nitrogen (N) and hydrogen (H) content together with Sn, Pb, Cd, As, Sb and total Cr and also acid soluble, reducible and oxidable Cr fractions were employed as characteristic parameters of the studied sediments. Standard error of prediction values for C and N content were of the order of 4 and 1.3 mg g⁻¹ for H. Prediction errors for pH and Eh were 0.15 units and 37 mV, respectively, thus indicating the good prediction capabilities of the method. Regarding trace metal concentrations PLS-NIR provided prediction error levels for unknown samples around 20% for Sn, Pb, As and Sb and root mean square errors of prediction around 40% for concentration levels of 400 ng g⁻¹ Cd and 100 μg g⁻¹ Cr. For the different extractable fractions of Cr the residual prediction deviation varied from 1.3 to 1.7 but relative errors found for samples of the validation set were only useful for screening purposes.     

Transamidation reactions of 2-(2-sulfonylguanidino)acetamides

The reactivity of a series of sulfonylguanidinoacetamides 2A-E towards amines is reported. Guanidinoacetamides 2A-C, containing the arylsulfonylimino moiety, undergo a facile transamidation to give substituted carboxamides 4A-C, through the imidazolidinone intermediate 3. Acetamide 2D, having a methanesulfonylimino substituent, affords the imidazolidinone 3D and no transamidated carboxamides 4 are detected. In the case of guanidinoacetamide 2E, with a p-nitrobenzenesulfonylimino substituent, a Smiles rearrangement was observed.