Rapid Lignin Thermal Property Prediction through Attenuated Total Reflectance-Infrared Spectroscopy and Chemometrics

To expedite the valorisation of lignin as a sustainable component in materials applications, rapid and generally available analytical methods are essential to overcome the bottleneck of lignin characterisation. Where features of a lignin's chemical structure have previously been found to be predicted by Partial Least Squares (PLS) regression models built on Infrared (IR) data, we now show for the first time that this approach can be extended to prediction of the glass transition temperature (Tg), a key physicochemical property. This methodology is shown to be convenient and more robust for prediction of Tg than prediction through empirically derived relationships (e. g., Flory-Fox). The chemometric analysis provided root mean squared errors of prediction (RMSEP) as low as 10.0 °C for a botanically, and a process-diverse set of lignins, and 6.2 °C for kraft-only samples. The PLS models could separately predict both the Tg as well as the degree of allylation (%allyl) for allylated lignin fractions, which were all derived from a single lignin source. The models performed exceptionally well, delivering RMSEP of 6.1 °C, and 5.4 %, respectively, despite the conflicting influences of increasing molecular weight and %allyl on Tg. Finally, the method provided accurate determinations of %allyl with RMSEP of 5.2 %.

Expanding lignin thermal property space by fractionation and covalent modification

To fully exploit kraft lignin's potential in material applications, we need to achieve tight control over those key physicochemical lignin parameters that ultimately determine, and serve as proxy for, the properties of lignin-derived materials. Here, we show that fractionation combined with systematic (incremental) modification provides a powerful strategy to expand and controllably tailor lignin property space. In particular, the glass transition temperature (Tg) of a typical kraft lignin could be tuned over a remarkable and unprecedented 213 °C. Remarkably, for all fractions the Tg proved to be highly linearly correlated with the degree of derivatisation by allylation, offering such tight control over the Tg of the lignin and ultimately the ability to 'dial-in' this key property. Importantly, such control over this proxy parameter indeed translated well to lignin-based thiol-ene thermosetting films, whose Tgs thus covered a range from 2-124 °C. This proof of concept suggests this approach to be a powerful and generalisable one, allowing a biorefinery or downstream operation to consciously and reliably tailor lignins to predictable specifications which fit their desired application.

Tuning the Properties of Biobased PU Coatings via Selective Lignin Fractionation and Partial Depolymerization

Polyurethane (PU) coatings with high lignin content and tunable properties were made using a combination of fractionation and partial catalytic depolymerization as a novel strategy to tailor lignin molar mass and hydroxyl group reactivity, the key parameters for use in PU coatings. Acetone organosolv lignin obtained from pilot-scale fractionation of beech wood chips was processed at the kilogram scale to produce lignin fractions with specific molar mass ranges (M_w 1000-6000 g/mol) and reduced polydispersity. Aliphatic hydroxyl groups were distributed relatively evenly over the lignin fractions, allowing detailed study of the correlation between lignin molar mass and hydroxyl group reactivity using an aliphatic polyisocyanate linker. As expected, the high molar mass fractions exhibited low cross-linking reactivity, yielding rigid coatings with a high glass transition temperature (T_g). The lower M_w fractions showed increased lignin reactivity, extent of cross-linking, and gave coatings with enhanced flexibility and lower T_g. Lignin properties could be further tailored by lignin partial depolymerization by reduction (PDR) of the beech wood lignin and its high molar mass fractions; excellent translation of the PDR process was observed from laboratory to the pilot scale necessary for coating applications in prospective industrial scenarios. Lignin depolymerization significantly improved lignin reactivity, and coatings produced from PDR lignin showed the lowest T_g values and highest coating flexibility. Overall, this study provides a powerful strategy for the production of PU coatings with tailored properties and high (>90%) biomass content, paving the path to the development of fully green and circular PU materials.

Biomass Pre-Extraction as a Versatile Strategy to Improve Biorefinery Feedstock Flexibility, Sugar Yields, and Lignin Purity

Feedstock flexibility is highly advantageous for the viability of (solvent-based) biorefineries but comes with the considerable challenge of having to cope with the varying nature and typically high abundance of nonlignocellulose compounds in the most readily available residual biomass streams. Here, we demonstrate that mild aqueous acetone organosolv fractionation of various complex lignocellulosic raw materials (roadside grass, wheat straw, birch branches, almond shells, and a mixed stream thereof) is indeed negatively affected by these compounds and present a versatile strategy to mitigate this bottleneck in biorefining. A biomass pre-extraction approach has been developed to remove the detrimental extractives with (aqueous) acetone prior to fractionation. Pre-extraction removed organic extractives as well as minerals, primarily reducing acid dose requirements for fractionation and loss of hemicellulose sugars by degradation and improved the purity of the isolated lignin. We show how pre-extraction affects the effectiveness of the biorefinery process, including detailed mass balances for pretreatment, downstream processing, and product characteristics, and how it affects solvent and energy use with a first conceptual process design. The integrated biorefining approach allows for the improved compatibility of biorefineries with sustainable feedstock supply chains, enhanced biomass valorization (i.e., isolation of bioactive compounds from the extract), and more effective biomass processing with limited variation in product quality.

A phase III study of recombinant human interferon gamma to prevent opportunistic infections in advanced HIV disease

The efficacy and safety of recombinant human interferon gamma (rIFN-gamma) in the reduction of opportunistic disease in patients with advanced HIV-1 infection are assessed. A 12-month double-blind, placebo-controlled, multicenter, Phase III trial of rIFN-gamma in HIV-positive patients with CD4 < 100 x 10(9)/liter on stable antiretroviral therapy. Eighty-four patients were allocated treatment on a 1:1 basis to rIFN-gamma or placebo. Patients received rIFN-gamma 0.05 mg/m(2) or 0.9% saline subcutaneously three times weekly for 48 weeks (optional extension to 18 months). The primary end point was the incidence of opportunist infections (CDC categories B/C). Secondary end points included mortality, immunological, and virological parameters. Patients on placebo had a mean of 3.45 opportunist infections (OIs) in the first 48 weeks. Patients treated with rIFN-gamma had a mean of 1.71 OIs (p = 0.04). However, the model showed overdispersion and the inclusion of a dispersion factor raised the p value to 0.13. rIFN-gamma appeared to have a particular effect on the incidence of Candida, herpes simplex, and cytomegalovirus infections. Three-year survival in the rIFN-gamma arm was 28% compared to 18% in the placebo group (not significant). rIFN-gamma-associated side-effects of headache, fatigue, rigors, influenza-like symptoms, depression, myalgia, and granulocytopenia were reversible. There was no evidence for HIV activation. Although not significant, the trend towards decreased opportunistic infections and increased survival warrants consideration of further trials of rIFN-gamma. The study gives additional information on the safety profile of this cytokine.

Chlamydia trachomatis detection--is it doctor dependent?

The accuracy of tests for chlamydia depends, among other things, upon the quality of the clinical specimen. Most chlamydia tests do not allow comment on specimen quality. It has been shown that examination of Papanicolaou stains or Diff-Quik stains of endocervical secretions can be used to assess the quality of endocervical sampling. This study has found that by analysing surrogate markers, such as the rates of inadequate cervical cytology and chlamydia detection rates in patients not identified as chlamydia contacts, it is possible to identify doctors performing less well in cervical sampling without the need for extra tests.

Blood-borne virus infection: the occupational risks

Healthcare workers who are in contact with patients and/or clinical material are at continuous risk of acquiring blood-borne viral infections, in particular, infection with hepatitis B virus, hepatitis C virus and the human immunodeficiency virus (HIV). Prevention of occupational exposure is dependent on education. Prevention strategies include immunization, exposure avoidance by the use of universal precautions at all times, and post-exposure advice and prophylaxis. This article will review the risks to healthcare workers associated with exposure to hepatitis B, hepatitis C, and HIV. It will discuss post-exposure management in the United Kingdom (UK) and briefly outline the risks to patients from infected healthcare workers.

'Get it on' in the millennium

Over the Christmas and New Year period the Health Education Authority launched a sexual health promotion campaign aimed at increasing the awareness of and reducing the incidence of sexually transmitted infections (STIs) and unwanted pregnancy. We undertook a study to assess the effect of this campaign locally in 2 genitourinary medicine (GUM) clinics. From our study we concluded the following: (1) Although rarely performed, it is possible to assess the effectiveness of health promotion campaigns. (2) Genitourinary medicine clinics provide a good forum for the assessment of such campaigns. (3) The information obtained from such assessments can be valuable for effective targeting of future campaigns.