Finite element modeling (FEM) simulation of interactions between wood and microwaves

The aim of this study was to use finite element modeling (FEM) as a tool to analyze microwave scattering in wood and to verify the model by measurements with a microwave scanner. A medical computed tomography scanner was used to measure distribution of density and moisture content in a piece of Scots pine (Pinus sylvestris). Dielectric properties were calculated from measured values for cross sections from the piece and used in the model. Images describing the distribution of the electric field and phase shift were obtained from the FEM simulation. The model was verified by measurements with a scanner based on a microwave sensor. The results show that simulated values correspond well to measured values. Furthermore, discontinuities in the material caused scattering in both the measured and the simulated values. The greater the discontinuity in the material, the greater was the need for computational power in the simulation.     

Characterization of resistance to Aphis glycines in soybean accessions

The soybean aphid, Aphis glycines Matsumura, is a pest of soybean [Glycine max L. (Merrill)] in Asia, and its recent establishment in North America has led to large, recurring outbreaks that have challenged pest management practitioners there to seek environmentally responsible means for its control. Growth-chamber experiments were conducted to determine and characterize host-plant resistance among several soybean accessions. Soybean plants were first screened for resistance by rating the population growth of A. glycines in two tests. All plants of PI 230977 and 25% of PI 71506 plants were resistant (≤100 aphids per plant) in the first screening test. All ‘Dowling’, PI 71506 and PI 230977 were resistant (≤150 aphids per plant), and 50% of plants of line ‘G93-9223’ were resistant in the second test. Follow-up experiments showed that antixenosis was a modality of resistance based on reduced nymphiposition by A. glycines on Dowling, PI 230977 and PI 71506 in no-choice tests and on fewer numbers of A. glycines on Dowling, PI 230977, PI 71506 and G93-5223 in distribution tests. Antixenosis in Dowling and PI 230977 was stronger in the unifoliolate leaves than in other shoot structures, whereas distribution of A. glycines within plants of PI 71506 and G93-5223 suggested comparable suitability between unifoliolate leaves and other shoot structures of these accessions. Antibiosis to A. glycines was evident as a lower proportion of aphids that reproduced on PI 230977 and from fewer progeny on PI 230977 and Dowling than on 91B91. The number of days from birth to reproduction by A. glycines did not differ among accessions. Results confirmed Dowling and PI 71506 as strong sources of resistance to A. glycines. The levels of antixenosis and antibiosis to A. glycines in PI 230977 and antixenosis to A. glycines in G93-9223 suggest that these accessions may also be valuable to soybean breeding programs as sources of resistance.     

Initial reactions in sapwood of Norway spruce and Scots pine after wounding and infection by Heterobasidion parviporum and H. annosum

The xylem surface of seedlings, stem material and roots of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) were inoculated with strains of Heterobasidion annosum s. str. and H. parviporum s. str. The depth of necrosis in wounded spruce increased at a linear rate for at least seven weeks of incubation, but the rate of necrotic spread was significantly faster in infected wounds. In wounded pine the necrosis was maintained at a more superficial level for several weeks. Both spruce and pine sapwood were initially infected by hyphae of both species. In spruce, the hyphae advanced at a constant rate behind the necrotic front. On the contrary, after 1–2 weeks living H. parviporum hyphae were rare in pine rays. Heterobasidion annosum hyphae survived in pine rays, phloem and tracheids, despite a heavy accumulation of phenolics and resins and were able to penetrate into the sapwood at a linear rate although slower than infections in spruce. Histochemistry and quantitative estimates demonstrated that peroxidase activity was initially higher in spruce sapwood than in pine. Within three days of incubation, the activity in spruce sapwood disappeared concurrently with deepening necrosis. However, in pine, in both control and infected samples, there was a significant increase in peroxidase activity in the area surrounding the superficial necrosis, up to the wound surface and in the cambium and phloem around the wound. After wounding and infection, the content of soluble protein increased significantly in wood of older trees but not in seedlings. Infection resulted in an increased formation of lipophilic extractives in both spruce and pine but to a significantly greater degree in the latter, whereas the amount of hydrophilic compounds decreased in both. High‐performance liquid chromatography (HPLC) analyses of lipophilic extracts showed that inoculation of pine with the two species of Heterobasidion increased the amounts of pinosylvin, its monomethylether and several other phenolics as also resinous compounds. The results obtained may be relevant in explaining the known higher resistance of Scots pine to H. parviporum.     

Choosing green sawing dimensions for Norway spruce from stochastic simulations

The high accuracy of log positioning and the stability of saw blades in breakdown machinery in modern sawmills have reduced the need to add margins for sawing variations. Oversize green sawing dimensions are still needed, but mainly to allow for drying shrinkage. This has put a new focus on better adapting green sawing dimensions to the shrinkage behavior of wood. In this study, a method for optimization of green sawing dimensions using stochastic simulation is presented. Normal distributions were generated for planed dry dimensions, kerf width, and target moisture content. The minimum share of boards exceeding the specified dry dimensions was decided, and deformations in boards from all positions in the cross section in a number of logs were simulated. The simulated shrinkage allowance from stochastic simulations was compared to experimental results from an industry test and to finite element results based on material data for Norway spruce. The results showed that the green width of the sawn boards should increase when the number of boards in the center yield increases. The green thickness of boards should be thinner for center boards and outer boards than for inner boards.     

A quantum adiabatic evolution algorithm applied to random instances of an NP-complete problem

A quantum system will stay near its instantaneous ground state if the Hamiltonian that governs its evolution varies slowly enough. This quantum adiabatic behavior is the basis of a new class of algorithms for quantum computing. We tested one such algorithm by applying it to randomly generated hard instances of an NP-complete problem. For the small examples that we could simulate, the quantum adiabatic algorithm worked well, providing evidence that quantum computers (if large ones can be built) may be able to outperform ordinary computers on hard sets of instances of NP-complete problems.     

HPLC method for analysis of secoisolariciresinol diglucoside in flaxseeds

A method was developed for the analysis of secoisolariciresinol diglucoside (SDG) in flaxseeds. The analytical method involves extraction of defatted flaxseed flour with dioxane/ethanol, aqueous base-hydrolysis, solid-phase purification of an SDG-containing fraction, and quantitative analysis by high-performance liquid chromatography (HPLC). Pure SDG was isolated from flaxseed using different column chromatographic methods and used, as external standard, for the calibration of the method and for quantification. The method was then applied to study the variation in SDG content in flaxseeds from 14 cultivars grown in Sweden and 15 cultivars grown in Denmark. The SDG content varied between 11.7 and 24.1 mg/g in defatted flaxseed flour and between 6.1 and 13.3 mg/g in whole flaxseeds.     

Effects of neonicitinoid seed treatments on soybean aphid and its natural enemies

Insecticidal seed treatments are increasingly being applied to soybeans in North America, and several recent studies question what they add to current pest management. Here, we examine the effects of two neonicotinoid insecticidal seed treatments on insect populations (pest and natural enemies) in SD soybeans over 2 years. Moreover, we conducted laboratory experiments to determine the duration that seed treatments remained effective against the soybean aphid (Aphis glycines, Hemiptera: Aphididae) and how thiamethoxam affected survival of one of the aphid’s predators, Orius insidiosus (Hemiptera: Anthocoridae) on soybean. Soybean aphids, thrips, and grasshopper populations were unaffected by the insecticidal seed treatments in the field. The laboratory trial revealed that all bioactivity of the seed treatments against soybean aphids was gone within 46 days after planting, prior to aphid populations damaging the crop. Bean leaf beetles, a sporadic pest in our area, were reduced by the seed treatments. But, there were no yield benefits of insecticidal seed treatments over the 2 years of the study at this location. Natural enemy communities were significantly reduced by thiamethoxam seed treatments relative to the untreated control, particularly populations of Nabis americoferus (Hemiptera: Nabidae). Chrysoperla (Neuroptera: Chrysopidae) adults were reduced in the imidacloprid-treated plots. In the laboratory, rearing O. insidiosus on soybean plants treated with thiamethoxam resulted in higher mortality for both the nymphs and the adult stage. Offering the predator insect prey on the thiamethoxam-treated plants improved survival of the adult stage, but not the nymphal stage. This work confirms that insecticidal seed treatments offer little benefit to soybean producers of the Northern Great Plains and adds to the discussion by suggesting that generalist predators are adversely affected by the insecticides.     

Distribution, density and abundance of the western Baltic herring (Clupea harengus) in the Sound (ICES Subdivision 23) in relation to hydrographical features

Biomass and duration of the over-wintering period of the Rügen spring spawning herring stock (RHS) in the Sound (ICES Subdivison 23) were investigated as well as possible hydrographical factors affecting relative distribution and triggering southwards migration towards the spawning grounds. Monitoring was performed during 27 surveys over a 6-year period (1993–1998). Abundance of 45–165 000 t in August–February, 5–60 000 t in March–May, and <2000 t in June–July was found. This indicates a longer over-wintering period than hitherto assumed. The year classes 1988, 1991 and 1994 were relatively strong occurring in the Sound from age 2 (winter-rings) and abundance in autumn 1993 and 1996–1997 was relatively high. Relative year class strengths are in accordance with variations in larval indices at the spawning grounds. Decreasing abundance in late spring in the Sound was concordant with observed peaks in commercial landings and (subsequent) peak larval indices at the spawning grounds. Larger size groups seem to migrate southwards in spring before smaller herring size groups. Peak herring densities occur in the northern Sound in autumn and they do not concentrate near the southern Drogden threshold in spring before southwards spawning migration. Highest densities were found from 8 to 22 m below sea surface, and just below or in the halocline in areas with stratified water column. Indications of inflows to the Baltic triggering southwards migration can be observed at some occasions, however, these results are not conclusive because of relatively few biomass estimates in 1996–1998. The identified patterns in herring occurrence agree with some conclusions on migration routes for RHS from previously reported tagging studies, but the present investigations indicate prolonged over-wintering in the Sound. This report quantifies the abundance and distribution of herring in the Sound over the year on basis of repeated investigations, and investigates possible influence of hydrographical factors on distribution and migration.