Ring-level models for predicting wood and fibre properties of Abies balsamea

Wood and fibre properties such as wood density, microfibril angle, and modulus of elasticity are industrially relevant factors in determining the mechanical properties of wood. Radial ring-level predictive models of these properties were developed using balsam fir data from a long-term trial in New Brunswick (Canada), where precommercial thinning was applied 8 years after the site was harvested. The mixed effects models developed accounted for most of the variability in wood density (68 %), microfibril angle (94 %), and modulus of elasticity (77 %) with low RMSE. This study shows that balsam fir wood and fibre properties are strongly related to distance from the pith, particularly in the first 20 mm, and much less to annual ring width. Disk height and selected weather variables related to air temperature during the growing season significantly improved the models, whereas the effect of precommercial thinning was not significant. These equations can be incorporated into computer models, such as Optitek, that simulate mill recovery and wood properties to obtain accurate information on wood products. The unexplained variation in these models is likely related in part to between-tree genetic variation, which is unknown in this study.     

The Effects of Isoflavones on Androgens and Glucocorticoids During Puberty on Male Wistar Rats

Isoflavones are the most common phytoestrogens found in human diets. However, it is still not clear whether isoflavones have effects on the reproductive and the endocrine systems under normal dietary intake and overdose. The aim of this study was to determine how the most important isoflavones, genistein and daidzein, affect androgen and glucorticoid levels on male prepuberal rats. A hundred and seventy‐five 30‐day‐old male Wistar rats were dosed orally by stomach tube every day for 35 days, with saline solution, low and high doses of genistein, daidzein and a mixture of both. Serum samples were analysed by an enzyme immunoassay for hormone determinations. In control group, there was a peak of testosterone (T) and dihydrotestosterone levels associated to the onset of puberty, at the third week. However, in low‐dose groups, the same peak was found at the fourth week (p < 0.05), indicating a delay in the onset of puberty in these groups. Moreover, high doses groups serum androgen levels were significantly lower (p < 0.05) than the control group from the first week until fifth week. This fact was supported by a epididymal histological analysis that indicate in low doses there were several content of spermatozoa at fourth week and in high doses there were few content of spermatozoa. Besides, corticosterone levels followed the same pattern of androgens in all groups. We can conclude that oral administration of isoflavones in male rats decreased the secretion of androgens and glucocorticoids causing a delay in the onset of puberty and may cause physiological and developmental problems.     

Detection and Characterization of the Cumulene Carbenes H2C5 and H2C6

Two cumulene carbenes, H2C5 and H2C6, were detected in a supersonic molecular beam by Fourier transform microwave spectroscopy. Their rotational and leading centrifugal distortion constants were determined with high accuracy, such that the entire radio spectrum can now be calculated. Like the known carbenes H2C3 and H2C4, both molecules have singlet electronic ground states and linear carbon-chain backbones. They can be produced in sufficiently high concentrations in the laboratory that their electronic spectra, expected to lie in the visible, should be readily detectable by laser spectroscopy. The microwave spectra of other, more exotic isomers may be detectable as well.     

Structures of glycoprotein Ibalpha and its complex with von Willebrand factor A1 domain

Transient interactions of platelet-receptor glycoprotein Ibalpha (GpIbalpha) and the plasma protein von Willebrand factor (VWF) reduce platelet velocity at sites of vascular damage and play a role in haemostasis and thrombosis. Here we present structures of the GpIbalpha amino-terminal domain and its complex with the VWF domain A1. In the complex, GpIbalpha wraps around one side of A1, providing two contact areas bridged by an area of solvated charge interaction. The structures explain the effects of gain-of-function mutations related to bleeding disorders and provide a model for shear-induced activation. These detailed insights into the initial interactions in platelet adhesion are relevant to the development of antithrombotic drugs.     

Identification of radical scavengers in sweet grass (Hierochloe odorata)

Extracts from aerial parts of sweet grass (Hierochloe odorata) were active DPPH free radical scavengers. The active compounds were detected in extract fractions using HPLC with on-line radical scavenging detection. After multistep fractionation of the extract, two new natural products possessing radical scavenging activity were isolated, and their structures were elucidated by NMR and MS. They were identified as 5,8-dihydroxybenzopyranone and 5-hydroxy-8-O-beta-D-glucopyranosyl-benzopyranone. Activities of the compounds isolated were tested by DPPH and ABTS free radical scavenging assays, and compared with the known natural antioxidant rosmarinic acid and Trolox.     

Estimating soil organic carbon through loss on ignition: effects of ignition conditions and structural water loss

Loss on ignition (LOI) is one of the most widely used methods for measuring organic matter content in soils but does not have a universal standard protocol. A large number of factors may influence its accuracy, such as furnace type, sample mass, duration and temperature of ignition and clay content of samples. We conducted a series of experiments to quantify these effects, which enabled us to derive (i) guidelines for ignition conditions (sample mass, duration and temperature), (ii) temperature‐specific soil organic matter (SOM) to soil organic carbon (SOC) conversion factors and (iii) clay content‐dependent correction factors for structural water loss (SWL). Bulk samples of a sandy soil (4% clay) and a silt loam soil (25% clay) were used to evaluate the effects of ignition conditions. Samples with a range of clay contents (0–50%) were used to quantify conversion and correction factors. Two furnaces, one without and one with pre‐heated air, did not show significant differences in terms of within‐batch LOI variability. In both furnaces less combustion occurred close to the door, which necessitated tray turning at half‐time as this reduced the standard deviation per batch significantly. Variation in mass loss declined exponentially with sample mass (range, 0.15–20 g). The LOI increased with duration at lower temperatures (≤ 550°C) for the sandy soil. At greater temperatures (600 and 650°C), no effect of duration was found. For the silt loam soil, LOI values increased with duration for each temperature, which was attributed to SWL. The SOM to SOC conversion factor decreased strongly with temperature at an ignition duration of 3 hours from 0.70 (350°C) to 0.57 (500°C) and stabilized around 0.55 between 550 and 650°C, indicating that at temperatures ≥ 550°C all SOM had been removed. The clay correction factor for SWL increased from 0.01 to 0.09 as the temperature of ignition increased from 350 to 650°C. To minimize within‐batch LOI variation we recommend a standard ignition duration of 3 hours, tray turning at half‐time, a sample mass ≥ 20 g and temperatures equal to or greater than 550 °C. To avoid over‐estimates of SOM through structural water loss, the presented SWL correction procedure should always be applied.