Vibrational analyses of silacyclopentanes

The complete infrared and Raman spectra of 1,1-difluoro-1-silacyclopentane and 1,1-dichloro-1-silacyclopentane have been recorded and analyzed. Furthermore, a number of the vibrational frequencies of the silacyclopentane and silacyclopentane-1, 1-d₂ molecules have been reassigned.A normal coordinate calculation for each of these molecules was carried out and this demonstrated the validity of the assignments. Considerable mixing of the modes was found especially where ring vibrations and SiX₂ motions were involved.     

A reform in undergraduate mathematics curriculum : more emphasis on social and pedagogical skills

The paper describes the changes that are being made in the mathematics teachers' subject studies in the Department of Mathematics at the University of Joensuu, in order to provide our mathematics students both with a sufficiently deep knowledge of mathematics and science, and with present-day expertise in their profession as teachers. While the formal structure of the mathematics curriculum remains structured and taught as courses with mostly traditional names like algebra, analysis, and linear algebra, there are also totally new ‘professionally oriented’ courses. Some of the old courses—with rather traditional and rigorous contents—have been changed in a more student-driven direction. In these ‘pedagogically oriented’ courses students are encouraged, and even forced, to study co-operatively in social interaction, for example to negotiate how to solve a problem decently, or how to build a formal definition for a concept with certain wanted attributes. As an ultimate example of a pedagogical experiment we describe in more detail an abstract algebra course, where co-operative learning is combined with intensive programming in a mathematically oriented computer environment.     

The daguerreotype surface as a SERS substrate: characterization of image deterioration in plates from the 19th century studio of Southworth & Hawes

Dramatic condition changes were noted in a group of daguerreotypes during a 10 month‐long exhibition featuring masterworks of the prominent Boston‐based studio of Southworth & Hawes. The changes took the form of a hazy, extended white surface layer and of white spots that partially obscured the images after between four weeks and 10 months of exhibition. Raman spectroscopy, complemented by in situ scanning electron microscopy–energy dispersive X‐ray spectrometry (SEM–EDS), was used to nondestructively characterize this form of image deterioration in eight representative daguerreotypes from the studio. Raman proved to be a sensitive technique to noninvasively identify the compounds on the plates due to the fact that their Ag surfaces behave as surface‐enhanced Raman scattering (SERS) substrates. A band at ca 242 cm⁻¹ assigned to the Ag Cl stretching mode was observed in the areas where a white surface layer or white spots are present. In some of the areas probed, substituted aromatic compounds were also detected. The presence of Ag Cl bonds on daguerreotype surfaces has profound implications for their exhibition and preservation due to the photosensitivity of silver chloride in the ultraviolet–visible range, which can generate metallic silver that would redeposit on the surfaces. The possible sources of the compounds detected on the surfaces of the plates are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Water-soluble full-length single-wall carbon nanotube polyelectrolytes: preparation and characterization

HiPco single-wall carbon nanotubes (SWNTs) have been noncovalently modified with ionic pyrene and naphthalene derivatives to prepare water-soluble SWNT polyelectrolytes (SWNT-PEs), which are analogous to polyanions and polycations. The modified nanotubes have been characterized with UV-vis-NIR, fluorescence, Raman and X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The nanotube-adsorbate interactions consist of pi-pi stacking interactions between the aromatic core of the adsorbate and the nanotube surface and specific contributions because of the substituents. The interaction between nanotubes and adsorbates also involves charge transfer from adsorbates to SWNTs, and with naphthalene sulfonates the role of a free amino group was important. The ionic surface charge density of the modified SWNTs is constant and probably controlled by electrostatic repulsion between like charges. The linear ionic charge density of the modified SWNTs is similar to that of common highly charged polyelectrolytes.     

On the interaction of HBT with pulp lignin during mediated laccase delignification—a study using fractionated pyrolysis-GC/MS

An analytical method using fractionated pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was developed and applied for characterizing the type of interaction between 1-hydroxybenzotriazole (HBT)-mediator and pulp lignin in laccase delignification of pulp. In fractionated pyrolysis, the sample is pyrolyzed at progressively increasing temperatures in order to study particular fractions of the sample and to minimize secondary pyrolysis effects. This makes it possible to determine whether a certain pyrolysis product originates from one chemical moiety or different chemical moieties in one molecule. In the present method, samples were fractionated by thermal desorption at 200 °C followed by pyrolysis at progressively increasing temperatures from 320 to 800 °C. The products formed in each fraction were separated in a capillary GC column and detected and identified using MS. The type of interaction between HBT and pulp lignin was studied by following the formation of nitrogen-containing products during fractionated pyrolysis of a residual lignin isolated from laccase/HBT-treated oxygen-delignified softwood kraft pulp. This residual lignin was found to contain approximately 2% HBT residue. Most (87%) of this residue was covalently linked to the residual lignin. The results also strongly suggest that the HBT residue is present in two chemically different forms.     

Development of Dpa-based imidazole zinc anion receptors

A synthetic route for a new, phenolic Dpa-based aza ligand is presented and its chelation with zinc ions and imidazole were studied using UV/vis and mass spectrometry. A bathochromic shift of 30 nm was observed for the 2∗Zn complex of the ligand in UV/vis zinc titration experiments. The mass spectrum indicated formation of an imidazole anion zinc chelate complex.     

Vibrational spectra and ring-puckering of 2-cyclopenten-1-ones

The mid-infrared, far-infrared, and Raman spectra of 2-cyclopenten-1-one and 2-cyclopenten-1-one-5, 5-d₂ have been recorded. Assignments for each of the thirty vibrational fundamentals have been made for the two molecules. Several ring-puckering transitions were observed in the far-infrared spectrum of each molecule. From these were determined potential functions which establish the planarity of the ring system. The potential functions in reduced form derived for the hyride and deuteride are V = 15.0(Z⁴ + 8.0Z²) cm^?1 and V = 14.2(Z⁴ + 8.8Z²) cm^?1, respectively.     

Effect of wet spinning parameters on the properties of novel cellulosic fibres

Novel cellulose fibres (Biocelsol) were spun by traditional wet spinning technique from the alkaline solution prepared by dissolving enzyme treated pulp directly into aqueous sodium zincate (ZnO/NaOH). The spinning dope contained 6 wt.% of cellulose, 7.8 wt.% of sodium hydroxide (NaOH) and 0.84 wt.% of zinc oxide (ZnO). The fibres were spun into 5% and 15% sulphuric acid (H₂SO₄) baths containing 10% sodium sulphate (Na₂SO₄). The highest fibre tenacity obtained was 1.8 cNdtex⁻¹ with elongation of 15% and titre of 1.4 dtex. Average molecular weights and shape of molecular weight distribution curves of the celluloses from the novel wet spun cellulosic fibre and from the commercial viscose fibre were close to each other.