Near-infrared transmittance spectroscopy for radiochemical ageing of EPDM

The feasibility of using near-infrared spectroscopy as a sensitive technique to follow the influence of gamma-irradiation upon ageing of different EPDM (ethylene propylene diene monomer) elastomers has been evaluated. Although identification is difficult, differences can be observed between the non-irradiated and irradiated materials for total integrated doses from 50 to 450 kGy using a dose rate of 1 kGy h(-1) under an oxygen flow. The decrease in intensity of bands at 7040, 4610 and 4910 cm(-1) are linked to the disappearance of additives present in the elastomer such as excess of vulcanising or antioxidant agents and occur for the lowest irradiation dose. This disappearance is confirmed by TGA (thermogravimetric analysis). The increase in band intensities assigned to the formation of hydroxyl and carbonyl groups (5100, 4860 and 4670 cm(-1)) irradiation indicates an increase in oxidation with irradiation in the presence of oxygen. No bands linked to the presence of C=C from the diene have been detected, probably owing to the low concentration in the material and the weak intensity in near-infrared region. For strong irradiation doses (450 kGy), the three formulations studied show no difference in their NIR spectra, which is confirmed by the TGA of these irradiated materials. PCA performed at 5000-4600 cm(-1) or 7090-6980 cm(-1) shows efficient discrimination.     

Specific applications of capillary electrochromatography to biopolymers, including proteins, nucleic acids, peptide mapping, antibodies, and so forth

Separation of biopolymers is an obvious application of capillary electrochromatography (CEC) technology, since speed and resolution should increase significantly over high-performance liquid chromatography (HPLC). All too often, HPLC chromatograms of polymers show poorly resolved envelopes of overlapping peaks from oligomers. The practical limitation of column length and pressure drop has hindered development of high resolution separations of many polymers in HPLC. However, this generally applies only to packed beds of small particles, and not to continuous (or monolithic) beds, as introduced by Hjerten et al. [S. Hjerten, Ind. Eng. Chem. Res. 38 (1999) 1205; S. Hjerten, C. Ericson, Y.-M. Li, R. Zhang, Biomed. Chromatogr. 12 (1998) 120; C. Ericson, S. Hjerten, Anal. Chem. 71 (1999) 1621; J.-L. Liao, N. Chen, C. Ericson, S. Hjerten, Anal. Chem. 68 (1996) 3468; S. Hjerten, A. Vegvari, T. Srichaiyo, H.-X. Zhang, C. Ericson, D. Eaker, J. Capillary. Elec. 5 (1998) 13; C. Ericson, J.-L. Liao, K. Nakazato, S. Hjerten, J. Chromatogr. A 767 (1997) 33; S. Hjerten, D. Eaker, K. Elenbring, C. Ericson, K. Kubo, J.-L. Liao, C.-M. Zeng, P.-A. Lidstrom, C. Lindh, A. Palm, T. Srichiayo, L. Valtcheva, R. Zhang, Jpn. J. Electroph. 39 (1995) 1]. Throughout this review we will refer to such packings as monolithic or continuous beds, but they are identical type packings, formed by the in situ polymerization in the capillary or column. CEC capillaries can be much longer, and contain smaller particles than is practical for HPLC. This improves resolution significantly. CEC is able to capitalize on existing mobile phase technology developed over 30 years to improve separations. The requirement that the mobile phase simultaneously promote the separation and mobile phase mobility needs to be considered. In RPLC, this dual role is not much of a problem. It may be much more important in other modes, particularly ion-exchange (IEC). As the field develops, it is becoming clear that CEC is not just a simple extension of HPLC. Instruments, column technology and operating optima are clearly different than HPLC. CEC will develop into its own unique field. Open tubular HPLC is almost precluded by the high pressures required for forcing liquids through 10 microm or smaller capillaries. Electroosmotic pumping (EOF) avoids the pressure constraints and provides better flow profiles. Compared to HPCE, the ability to interact with the stationary phase may enable separations that would be difficult with electrophoresis alone. Since the mobile phase can be less complex than micellar electrokinetic chromatography (MEKC), CEC also avoids the problem of high background signals from the micelle forming compounds. Thus CEC-MS (mass spectrometry) is expected to be even more powerful than HPCE-MS. The fortuitous, simultaneous development of matrix assisted laser desorption-time of flight MS (MALDI-TOF-MS) technology will enable extension of the mass range to above 100 000 Da. Lack of familiarity is the perhaps the largest liability of CEC compared to other techniques. This paper critically compares the state-of-the-art of CEC with HPLC and HPCE, with a particular emphasis on separation of biopolymers. The goal is to help the reader overcome the fear of the unknown, in this case, CEC.     

Differential production cross section of Z bosons as a function of transverse momentum at sqrt

We present a measurement of the transverse momentum distribution of Z bosons produced in p&pmacr; collisions at sqrt[s] = 1.8 TeV from data collected by the DO experiment at the Fermilab Tevatron Collider. We find good agreement between our results and current resummation calculations, and also use our data to extract nonperturbative parameters for a particular version of the resummation formalism. The resulting values are significantly more precise than obtained in previous determinations.     

Hydroxymethylphenylnaphthoie acid lactones

Reduction of 1-phenylnaphthalene-2,3-dicarboxylic anhydride (I) with zinc and acetic acid or lithium aluminium hydride yields a mixture of 1-phenyl-3-hydroxymethyl-2-naphthoie acid lactone (II) and 1-phonyl-2-hydroxymethyl-3-naphthoie acid lactone (III). Catalytic hydrogenation of (I) gave the tetrahydronaphthalene dicarboxylic anhydride (IV). Oxidation of the phenyldihydronaphthofuran (X), prepared by base-catalyzed cyclization of the ether (IX), also yielded lactones (II) and (III). The phenyltetrahydronaphthofuran (XII) was similarly prepared by cyclization of the phenylpropargyl cinnamyl ether (XI).     

The photo-ionization of mono- and di-sodium tetracene in 2-MTHF at room temperature by nanosecond ruby laser pulses

The photo-ionization of di-sodium tetracene in MTHF at room temperature by ns ruby laser pulses is a bi-photonic process in which the ejected electrons are captured in the vicinity of one of the Na⁺ ions forming the Na⁺;e ion-pair. The life time of the lowest excited singlet state is at least 7.5 ns. The probability of electron ejection from one of the higher excited states is of the order 1% or less. The results confirm earlier work by Giling et al. Mono-sodium tetracene shows a similar behaviour. The life time of its lowest excited double state is at least 2.3 ns.     

N,N'-dimethyl-N,N'-diarylurea anion radicals: an intramolecular reductive elimination

The one-electron reduction of tertiary N,N'-dimethyl-N,N'-diarylureas (aryl = phenyl, beta-naphthyl, alpha-naphthyl), in HMPA, results in anion radicals that undergo novel intramolecular reductive elimination reactions leading to the formation of the anion radicals of the corresponding biaryls. These results are due to face to face pi-pi stacking interactions involving the two aromatic rings in the urea systems. The overlapping p(pi)() orbitals on the ipso carbons of opposing aryl groups evolve into a sigma bond leading to the formation of the biaryl anion radical. In the case of the N,N'-dimethyl-N,N'-di-2-pyrenylurea system, there is a node in the LUMO of the number 2 carbon, and the parent anion radical remains intact.     

Industrial scale production of stable isotopes employing the technique of plasma separation

Calutrons, centrifuges, diffusion and distillation processes are some of the devices and techniques that have been employed to produce substantial quantities of enriched stable isotopes. Nevertheless, the availability of enriched isotopes in sufficient quantities for industrial applications remains very restricted. Industries such as those involved with medicine, semiconductors, nuclear fuel, propulsion, and national defense have identified the potential need for various enriched isotopes in large quantities. Economically producing most enriched (non-gaseous) isotopes in sufficient quantities has so far eluded commercial producers. The plasma separation process is a commercial technique now available for producing large quantities of a wide range of enriched isotopes. Until recently, this technique has mainly been explored with small-scale (proof-of-principle) devices that have been built and operated at research institutes. The new Theragenics^TM facility at Oak Ridge, TN houses the only existing commercial scale PSP system. This device, which successfully operated in the 1980's, has recently been re-commissioned and is planned to be used to produce a variety of isotopes. This report will summarize the progress and the capabilities of this device and it's potential for impacting the world's supply of stable isotopes in the future. This technique now holds promise of being able to open the door to allowing new and exciting applications of these isotopes in the future.     

Natural benzofurans: Synthesis of isopterofuran

A synthesis of the fungistatic phytoalexin, isopterofuran is described. In the key step, the benzofuran heterocycle is constructed by reaction of an o-iodophenol with a cuprous arylacetylide.