Microwave Pretreatment of Backsawn Messmate Boards to Improve Drying Quality: Part 1

The findings of an investigation into the microwave (MW) modification and conventional kiln drying of backsawn/flatsawn messmate stringybark (Eucalyptus obliqua L'Herit) are summarized. The project was conducted in two parts. Part 1, the subject of this article, investigates whether low-intensity microwave modification results in more or less check formation than occurs during conventional drying of eucalypts. Part 2 of the investigation will determine the acceleration in kiln drying that can be achieved through microwave modification of the wood structure and in turn improving permeability.

Significant improvement in microwave modified samples compared to controls in relation to check (internal/honeycombing and surface) formation during drying was observed, with Schedule 1 (70 kWh/m³) having 55% of samples without checks compared to the control samples at 31%.

The study also found that there is a significant reduction in surface checking (number and depth) in MW modified boards compared to the controls. The control samples exhibited the highest proportion of surface checking, with 65% possessing one or more surface checks, of which 82% extended more than one quarter the width of the sample. This was in marked contrast to Schedule 2 (75 kWh/m3), which resulted in 43% having one or more surface checks, of which 25% extended more than one quarter the width of the sample.

The control samples also returned the highest rate of internal/honeycombing checking with 28% of samples affected, while samples pretreated according to MW Schedule 2 yielded the lowest rate, with 11% affected.     

Microwave treatment of <Emphasis Type="Italic">Eucalyptus macrorhyncha</Emphasis> timber for reducing drying defects and its impact on physical and mechanical wood properties

Microwave is a useful and proven tool for increasing permeability of refractory wood and, thereby, it can be used for reducing drying time and defects. However, strength loss is always a concern. In this study, green timber boards were treated with microwave in two intensities, low microwave (LMW), 89 kWh/m³, and high microwave (HMW), 95 kWh/m³, and compared with control boards. Samples of all three treatments were kiln dried together. Density and selected mechanical properties were also assessed after drying. LMW, the treatment which presented the best results, showed reduction in some drying defects, such as collapse (20%), surface check length (84%), internal check length (50%) and internal check width (70%). Density, MOE and MOR on static bending were unchanged, whereas reductions in shear strength (13%) and compression strength parallel to grain (10%) were observed. HMW, on the other hand, produced higher strength reductions and more drying defects than LMW. Fine adjustments of LMW microwave power might bring drying benefits without strength losses.     

The response of a glassy polymer in a loading/unloading deformation: The stress memory experiment

A ‘stress memory’ experiment was designed to expose the nonlinear viscoelastic relaxation processes in a glassy epoxy polymer. The stress memory experiment consists of (i) constant strain rate uniaxial loading to a pre-yield, yield or post-yield condition, (ii) unloading at the same strain rate to zero stress, (iii) holding the strain constant and (iv) monitoring the subsequent stress memory response, where the stress first increases to a maximum and then relaxes to an equilibrium value for that strain. This is an analog to the classic volume memory experiment by Kovacs (Fortschr Hochpolym Forsch, 3, 394, 1964). The stress memory response showed a strong dependence on the loading/unloading strain rate which cannot be predicted by linear viscoelasticity and also provides a significant challenge to a current nonlinear constitutive models. A recently developed Stochastic Constitutive Model (J Rheol, 57(3), 949, 2013) qualitatively predicts the effect of strain rate on the stress memory response.     

(7<Emphasis Type="Italic">Z</Emphasis>,9<Emphasis Type="Italic">E</Emphasis>)-2-Methyl-7,9-Octadecadiene: A Sex Pheromone Component of <Emphasis Type="Italic">Lymantria Bantaizana</Emphasis>

Our objective was to identify the sex pheromone of Lymantria bantaizana (Lepidoptera: Lymantriidae) whose larvae feed exclusively on walnut, Juglans spp., in China, and Japan. Coupled gas chromatographic–electroantennographic detection (GC-EAD) analyses of pheromone gland extracts revealed a single EAD-active component. Retention index calculations of this compound on four GC columns suggested that it was a methyl-branched octadecadiene with conjugated double bonds. In GC-EAD analyses of 2-methyloctadecenes, (Z)-2-methyl-7-octadecene and (E)-2-methyl-7-octadecene elicited the strongest antennal responses, suggesting that the double bond positions were at C7 and C9. In comparative GC-EAD analyses of pheromone gland extract and stereoselectively synthesized isomers (E,E; E,Z; Z,E; Z,Z) of 2-methyl-7,9-octadecadiene, the (E,Z)- and (Z,E)-isomer had retention times identical to that of the candidate pheromone, but only the latter isomer elicited strong EAD activity. Results of field experiments in Japan substantiated that (7Z,9E)-2-methyl-7,9-octadecadiene is the L. bantaizana sex pheromone, a compound previously unknown in the Lepidoptera. Detection surveys in North America for exotic Eurasian forest defoliators could include traps baited with the L. bantaizana pheromone.     

Moth Scale-Derived Kairomones Used by Egg–Larval Parasitoid Ascogaster quadridentata to Locate Eggs of Its Host, Cydia pomonella

We determined that location of host (Cydia pomonella) eggs by Ascogaster quadridentata is mediated by kairomones, investigated potential sources of the kairomones and identified a blend of kairomones from the source that was attractive to A. quadridentata. In Y-tube olfactometer bioassays, female A. quadridentata were attracted to Porapak Q-collected volatiles from female C. pomonella scales and eggs, but not to C. pomonella sex pheromone. Scales of C. pomonella were also attractive to male A. quadridentata. Coupled gas chromatographic–electroantennographic detection analysis of scale volatile extracts revealed numerous compounds that elicited responses from male or female A. quadridentata antennae, including heptanal, octanal, nonanal, decanal, undecan-2-one, dodecanal, pentadecan-2-one, (Z)-6-pentadecen-2-one, (Z)-9-hexadecenal, (Z)-6-heptadecen-2-one, and 3,7,11-trimethyl-2E,6E,10-dodecatrien-1-ol acetate. A synthetic blend of these compounds at quantities and ratios equivalent to Porapak Q scale volatile extract was attractive to female A. quadridentata in a Y-tube olfactometer bioassay.     

Idempotent Interval Analysis and Optimization Problems

Many problems in optimization theory are strongly nonlinear in the traditional sense but possess a hidden linear structure over suitable idempotent semirings. After an overview of "Idempotent Mathematics" with an emphasis on matrix theory, interval analysis over idempotent semirings is developed. The theory is applied to construction of exact interval solutions to the interval discrete stationary Bellman equation. Solution of an interval system is typically NP-hard in the traditional interval linear algebra; in the idempotent case it is polynomial. A generalization to the case of positive semirings is outlined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Detection of DNA sequences using an alternating electric field in a nanopore capacitor

Molecular dynamics simulations revealed that back-and-forth motion of DNA strands through a 1 nm diameter pore exhibits sequence-specific hysteresis that arises from the reorientation of the DNA bases in the nanopore constriction. Such hysteresis of the DNA motion results in detectable changes of the electrostatic potential at the electrodes of the nanopore capacitor and in a sequence-specific drift of the DNA strand under an oscillating transmembrane bias. A strategy is suggested for sequencing DNA in a nanopore using the electric field that alternates periodically in time.     

(1S)-1-Ethyl-2-Methylpropyl 3,13-Dimethylpentadecanoate: Major Sex Pheromone Component of Paulownia Bagworm, Clania variegata

The Paulownia bagworm, Clania variegata Snell. (Lepidoptera: Psychidae), is one of the most significant forest defoliators in China. In gas chromatographic (GC)–electroantennographic detection analyses of pheromone gland extracts of female C. variegata on three GC columns (DB-5, DB-23, DB-210), two compounds (A and B) elicited strong responses from male antennae. The more abundant component B was isolated by high-performance liquid chromatography and identified as 1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate by transesterification, GC-mass spectrometry (MS), and comparison of its spectral and GC retention characteristics with those of synthetic compounds. In field trapping experiments in China, racemic and (1S)-1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate [but not the (1R)-stereoisomer] attracted male C. variegata. The absolute configuration of B (a molecule with three chiral centers) and the structure of component A remain to be determined.     

Does the Stereochemistry of Methylated Cuticular Hydrocarbons Contribute to Mate Recognition in the Egg Parasitoid Wasp Ooencyrtus kuvanae?

Close-range sexual communication of the egg parasitoid wasp Ooencyrtus kuvanae (Hymenoptera: Encyrtidae) takes place on host gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae), egg masses. We tested the hypothesis that mate recognition in O. kuvanae is mediated, in part, by low-volatility cuticular hydrocarbon (CHC) pheromone components. Gas chromatographic and GC-mass spectrometric analyses of body surface extracts of male and female wasps revealed no sex-specific components, but 5-methylheptacosane (5-me-27Hy) and 5,17-dimethylheptacosane (5,17-dime-27Hy) were consistently more abundant in extracts of males. The ratio of 5-me-27Hy and 5,17-dime-27Hy was similar in extracts of males and females, and quantitative differences alone seemed insufficient to impart sex-specific CHC profiles. Therefore, we further hypothesized that the absolute configuration of 5-me-27Hy and 5,17-dime-27Hy contributes to mate recognition or attraction. As the stereoisomers of 5-me-27Hy and 5,17-dime-27Hy cannot currently be separated chromatographically, we could not determine the stereochemistry of the insect-produced components. Instead, we synthesized all stereoisomers and bioassayed synthetic blends in laboratory experiments. Of eight 2-component blends, each blend containing one of the two enantiomers of 5-me-27Hy and one of the four stereoisomers of 5,17-dime-27Hy, the blend of (5S)-methylheptacosane and (5R,17S)-dimethylheptacosane attracted males, whereas the blend of (5R)-methylheptacosane and (5R,17R)-dimethylheptacosane repelled males. Apparent recognition of both pheromone components and pheromone antagonists by males supports the hypothesis that the stereochemistry of 5-me-27Hy and 5,17-dime-27Hy, and possibly other methylated CHCs, may differ between male and female O. kuvanae, and that these differences may serve in mate attraction and recognition.