Structural characterization of linear isomalto-/malto-oligomer products synthesized by the novel GTFB 4,6-α-glucanotransferase enzyme from Lactobacillus reuteri 121

Recently, a novel glucansucrase (GS)-like gene (gtfB) was isolated from the probiotic bacterium Lactobacillus reuteri 121 and expressed in Escherichia coli. The purified recombinant GTFB enzyme was characterized and turned out to be inactive with sucrose, the natural GS substrate. Instead, GTFB acted on malto-oligosaccharides (MOSs), thereby yielding elongated gluco-oligomers/polymers containing besides (α1→4) also (α1→6) glycosidic linkages, and it was classified as a 4,6-α-glucanotransferase. To gain more insight into its reaction specificity, incubations of the GTFB enzyme with a series of MOSs and their corresponding alditols [degree of polymerization, DP2(-ol)–DP7 (-ol)] were carried out, and (purified) products were structurally analyzed with matrix-assisted laser desorption ionization time-of-flight mass spectrometry and one-/two-dimensional 1H and 13C nuclear magnetic resonance spectroscopy. With each of the tested malto-oligomers, the GTFB enzyme yielded series of novel linear isomalto-/malto-oligomers, in the case of DP7 up to DP >35.

Kinetics of accelerated degradation of historic iron gall ink-containing paper

Although degradation of iron gall ink containing paper has been scientifically studied for almost 250 years, we still do not have a good understanding of the kinetics of the process. While many studies focussed on model samples to avoid the inhomogeneity of real historic samples or the need for sampling, this research was conducted on a selection of real documents. Accelerated degradation experiments were performed at six combinations of temperature and relative humidity (RH) in the intervals 50–80 °C/20–80% RH. The analytical methods were optimised such that sample consumption was minimised and errors and uncertainties were evaluated. The results show that the rate of degradation, measured as change in the degree of polymerisation of cellulose in paper beneath ink, can be described in Arrhenius terms, and that the apparent activation energy for the process depends on the moisture content in the material. The variation is consistent with the process of hydrolysis becoming less prominent at lower moisture content values, although the results indicate that hydrolytic degradation predominates during natural ink-induced degradation. In the context of the historic samples used in the study, the presence of ink accelerated the degradation of paper by a constant factor of 1.59 in comparison to paper without ink, across the range of experimental T and RH. This indicates that a dose-response function could be developed for ink-induced degradation of paper

Damage function for poly(vinyl chloride) in heritage collections

Yellowing of plastic objects as a consequence of chemical degradation is a common heritage conservation challenge. In the case of poly(vinyl chloride) elimination of hydrogen chloride leads to the formation of polyene sequences that act as chromophores. The objective of this work was to quantitatively evaluate the rate of degradation observed as yellowing, as relevant to room conditions during long-term storage of heritage collections. Degradation was quantified as increase in the b* colour coordinate during accelerated degradation at 50 and 70 °C as a function of temperature, relative humidity, plasticizer content, and polymer molecular weight. The significance of each variable was investigated with multiple linear regression. Lower temperature, lower relative humidity, higher polymer molecular weight and higher plasticizer content were associated with lower degradation rates. The activation energy of 86 kJ/mol was calculated. The concept of ‘1- °C-equivalent’ is introduced to enable variable prioritisation from a heritage management aspect. The resulting model can be used to shape environmental management guidelines and identify the most vulnerable objects in heritage collections

Volatile aldehydes in libraries and archives

Volatile aldehydes are produced during degradation of paper-based materials. This may result in their accumulation in archival and library repositories. However, no systematic study has been performed so far. In the frame of this study, passive sampling was carried out at ten locations in four libraries and archives. Despite the very variable sampling locations, no major differences were found, although air-filtered repositories were found to have lower concentrations while a non-ventilated newspaper repository exhibited the highest concentrations of volatile aldehydes (formaldehyde, acetaldehyde, furfural and hexanal). Five employees in one institution were also provided with personal passive samplers to investigate employees’ exposure to volatile aldehydes. All values were lower than the presently valid exposure limits. The concentration of volatile aldehydes, acetic acid, and volatile organic compounds (VOCs) in general was also compared with that of outdoor-generated pollutants. It was evident that inside the repository and particularly inside archival boxes, the concentration of VOCs and acetic acid was much higher than the concentration of outdoor-generated pollutants, which are otherwise more routinely studied in connection with heritage materials. This indicates that further work on the pro-degradative effect of VOCs on heritage materials is necessary and that monitoring of VOCs in heritage institutions should become more widespread

Computational studies of history-dependence in nematic liquid crystals in random environments

Glassy liquid crystalline systems are expected to show significant history-dependent effects. Two model glassy systems are the RAN and SSS (sprinkled silica spin) lattice models. The RAN model is a Lebwohl-Lasher lattice model with locally coupled nematic spins, together with uncorrelated random anisotropy fields at each site, while the SSS model has a finite concentration of impurity spins frozen in random directions. Here Brownian simulation is used to study the effect of different sample histories in the low temperature regime in a three-dimensional (d=3) model intermediate between SSS and RAN, in which a finite concentration p<pc (pc the percolation threshold) of frozen spins interacts with neighboring nematic spins with coupling W. Simulations were performed at temperature T?TNI/2 (TNI the bulk nematic-isotropic transition temperature) for temperature-quenched and field-quenched histories (TQH and FQH, respectively), as well as for temperature-annealed histories (AH). The first two of these limits represent extreme histories encountered in typical experimental studies. Using long-time averages for equilibrated systems, we calculate orientational order parameters and two-point correlation functions. Finite-size scaling was used to determine the range of the orientational ordering, as a function of coupling strength W,p and sample history. Sample history plays a significant role; for given concentration p, as disorder strength W is increased, TQH systems sustain quasi-long-range order (QLRO) and short-range order (SRO). The data are also consistent with a long-range order (LRO) phase at very low disorder strength. By contrast, for FQH and p?0.1, only LRO and QLRO occur within the range of parameters investigated. The crossover between regimes depends on history, but in general, the FQH phase is more ordered than the AH phase, which is more ordered than the TQH phase. However, at temperatures close to the isotropic-nematic phase transition of pure samples we observe SRO for p=0.1 even for FQH. We detect also in the QLRO phase a domain-type structural pattern, consistent with ideas introduced by Giamarchi and Doussal [Phys. Rev. B 52, 1242 (1995)] on superconducting flux lattices. In the weak-disorder limit the orientational correlation length obeys the Larkin-Imry-Ma scaling ??D?2/(4?d)

Patient-reported outcomes following flexible sigmoidoscopy screening for colorectal cancer in a demonstration screening programme in the UK

<p>OBJECTIVES: Flexible sigmoidoscopy (FS) screening for colorectal cancer will be introduced into the National Cancer Screening Programmes in England in 2013. Patient-reported outcome measures (PROMs) from trial participants indicate high acceptability and no adverse physical or psychological consequences, but this may not generalize to routine screening in the community. This study examined PROMs in a community-based FS screening programme.</p> <p>METHODS: Eligible adults aged 58-59 (n = 2016) registered at 34 London general practices were mailed a National Health Service-endorsed invitation to attend FS screening. Pain and side-effects were assessed in a 'morning-after' questionnaire, and satisfaction was assessed in a three-month follow-up questionnaire. Anxiety, self-rated health and colorectal symptoms were assessed at prescreening and follow-up.</p> <p>RESULTS: In total, 1020 people attended screening and were included in the current analyses, of whom 913 (90%) returned the morning-after questionnaire, and 674 (66%) the follow-up questionnaire. The prescreening questionnaire had been completed by 751 (74%) of those who attended. The majority (87%) of respondents reported no pain or mild pain, and the most frequent side-effect (wind) was only experienced more than mildly by 16%. Satisfaction was extremely high, with 98% glad they had the test; 97% would encourage a friend to have it. From prescreening to follow-up there were no changes in anxiety or self-rated health, and the number of colorectal symptoms declined. Satisfaction and changes in wellbeing were not moderated by gender, deprivation, ethnicity or screening outcome.</p> <p>CONCLUSIONS: PROMs indicate high acceptability of FS screening in 58-59 year olds, with no adverse effects on colorectal symptoms, health status or psychological wellbeing.</p&gt

History-Dependent Patterns in Randomly Perturbed Nematic Liquid Crystals

We study the characteristics of nematic structures in a randomly perturbed nematic liquid crystal (LC) phase. We focus on the impact of the samples history on the universal behavior. The obtained results are of interest for every randomly perturbed system exhibiting a continuous symmetry-breaking phase transition. A semimicroscopic lattice simulation is used where the LC molecules are treated as cylindrically symmetric, rod-like objects interacting via a Lebwohl-Lasher (LL) interaction. Pure LC systems exhibit a first order phase transition into the orientationally ordered nematic phase at T=Tc on lowering the temperature T. The orientational ordering of LC molecules is perturbed by the quenched, randomly distributed rod-like impurities of concentration p. Their orientation is randomly distributed, and they are coupled with the LC molecules via an LL-type interaction. Only concentrations below the percolation threshold are considered. The key macroscopic characteristics of perturbed LC structures in the symmetry-broken nematic phase are analyzed for two qualitatively different histories at T≪Tc. We demonstrate that, for a weak enough interaction among the LC molecules and impurities, qualitatively different history-dependent states could be obtained. These states could exhibit either short-range, quasi-long-range, or even long-range order

Machine learning-assisted non-destructive plasticizer identification and quantification in historical PVC objects based on IR spectroscopy

Non-destructive spectroscopic analysis combined with machine learning rapidly provides information on the identity and content of plasticizers in PVC objects of heritage value. For the first time, a large and diverse collection of more than 100 PVC objects in different degradation stages and of diverse chemical compositions was analysed by chromatographic and spectroscopic techniques to create a dataset used to construct classification and regression models. Accounting for this variety makes the model more robust and reliable for the analysis of objects in museum collections. Six different machine learning classification algorithms were compared to determine the algorithm with the highest classification accuracy of the most common plasticizers, based solely on the spectroscopic data. A classification model capable of the identification of di(2-ethylhexyl) phthalate, di(2-ethylhexyl) terephthalate, diisononyl phthalate, diisodecyl phthalate, a mixture of diisononyl phthalate and diisodecyl phthalate, and unplasticized PVC was constructed. Additionally, regression models for quantification of di(2-ethylhexyl) phthalate and di(2-ethylhexyl) terephthalate in PVC were built. This study of real-life objects demonstrates that classification and quantification of plasticizers in a general collection of degraded PVC objects is possible, providing valuable data to collection managers