Avaliação da resistência à tração perpendicular às fibras da madeira nas direções radial e tangencial

<p class="Normal1"><span>A discussão sobre a importância do conhecimento da resistência à tração perpendicular às fibras para uma melhor compreensão do comportamento mecânico da madeira em diversas situações, tais como na análise de retração, na análise de falhas de peças de madeira laminadas coladas ou na formulação de critérios de resistência para materiais anisotrópicos aplicados à madeira, torna evidente que a investigação dos valores dessas resistências é necessária. Neste trabalho foi avaliada a resistência à tração perpendicular às fibras para as direções radial e tangencial, considerando-se uma amostra de 83 corpos de prova da espécie de madeira <em>Acer saccharinum</em>, comumente conhecida como <em>Sugar Maple</em>. A metodologia usada para o ensaio de tração seguiu a norma americana ASTM D143. Além disso, foi analisada a influência da densidade nos valores de resistência para cada direção. Os modos de ruptura verificados nos corpos de prova nas direções pesquisadas são acompanhados por uma simulação numérica via software Ansys. A partir da análise estatística realizada, pode-se concluir que os resultados experimentais de resistências à tração perpendicular às fibras nas direções radial e tangencial apresentam uma diferença estatística significativa. Observou-se também que a densidade não teve influência estatisticamente relevante nos valores de resistência nas duas direções avaliadas.</span></p>

Bioactive Glucitol-Core Containing Gallotannins and other Phytochemicals from Silver Maple (Acer saccharinum) Leaves

In the course of our group's investigation of members of the maple ( Acer) genus, a series of glucitol-core containing gallotannins (GCGs) were isolated and identified (by NMR and HREISMS). Among higher plants, only certain maple species are known to produce GCGs, compounds with potential nutraceutical and cosmetic applications due to their reported antioxidant, antidiabetic, anti-α-glucosidase, anti-glycation, anticancer, and skin health promoting effects. Herein, we sought to investigate whether the previously un-investigated silver maple (Acer saccharinum) species was also a source of GCGs. Nine phenolic compounds, including six GCGs, were identified (by HPLC-DAD analyses using previously isolated standards) as ginnalins A-C (1-3), maplexins B, D, and F (4-6), methyl syringate (7), methyl gallate (8), and 3-methoxy-4-hydroxyphenol-1-β-D-(6-galloyl)-glucopyranoside (9). In addition, one sesquiterpenoid, namely, pubineroid A (10), was isolated and identified (by NMR).

ОСОБЛИВОСТІ ОТРИМАННЯ АСЕПТИЧНОЇ КУЛЬТУРИ ACER SACCHARINUM L. В УМОВАХ IN VITRO

Обґрунтовано актуальність мікроклонального розмноження Acer saccharinum L. Наведено особливості морфогенезу при введенні в культуру in vitro Acer saccharinum L. Проведено підбір оптимального часу відбору та тип експлантів. Встановлено оптимальні концентрації стерилянтів і час експозиції для ефективного (95 %) отримання асептичної культури Acer saccharinum L. Підібрано основні компоненти живильного середовища з додаванням регуляторів росту цитокінінового типу дії. Встановлено найефективніше середовище з додаванням 0,2 мг∙л-1 тідіазурону для успішного отримання морфогенно активних мікропагонів клена сріблястого в умовах in vitro.

A Study of Branch Dynamics on an Open-Grown Tree

This study investigates the dynamic properties of branches on an open-grown tree, where most of the mass is in the branches rather than in the trunk. When large branches on open-grown trees sway in winds, they individually and collectively influence how the whole tree sways. If branches are removed, as in pruning, the effect on tree sway has not yet been studied and the literature is almost nonexistent regarding recommendations for pruning open-grown trees to reduce wind damage. Trees come in many shapes and sizes and in urban areas, usually grow in open spaces and develop many branches. In forests, and particularly in closely spaced plantations, trees grow with an upright central trunk and develop significantly less branch mass. Forest conifers have been studied to identify their dynamic properties in winds, but the results may be different for open-grown trees. A 19.7 m tall silver maple (Acer saccharinum) with four codominant branches was tested by pulling and then releasing each branch to determine the dynamic properties. Branches were progressively removed and the tests repeated. The sway response was recorded with strain instruments attached to the trunk and accelerometers attached to each branch. The dynamic properties of frequency and damping were determined for all tests. The tree with all branches attached, in full foliage was difficult to sway because of damping from the branches. Significant changes in oscillating frequency and damping were observed only after most of the branches (greater than 80%) were removed. The results support the concept that branches provide damping, which dissipates energy from the wind as a mechanism to help trees survive.

Stolon Growth and Tillering of Experimental Zoysiagrasses in Shade

Zoysiagrass (Zoysia spp.) grown under shade on golf courses and in home lawns is slow to recover from damage and declines in quality over time. We evaluated stolon growth and tillering of ‘Meyer’ and Chinese Common (both Z. japonica Steud.); ‘Zorro’, ‘Diamond’, and ‘Cavalier’ [all Z. matrella L. (Merr.)]; ‘Emerald’ (Z. matrella × Z. pacifica Goudsw.); and six experimental progeny from ‘Emerald’ × Z. japonica and reciprocal crosses of Z. japonica × Z. matrella under silver maple (Acer saccharinum L.) shade and in full sun in 2008 and 2009 in Manhattan, KS. A single 6-cm diameter plug was planted in the center of 1.2 m × 1.2-m plots, and data were collected weekly on the number of stolons, stolon elongation, and number of stolon branches. Tiller number was collected at the start and end of each study period, and biomass (excluding roots) was determined at the end of each season. Zoysiagrasses under an average of 76% tree shade exhibited reductions of 38% to 95% in stolon number; 9% to 70% in stolon length; 10% to 93% in stolon branching; and 56% to 98% in biomass. Seven of the 10 grasses exhibited a decline in tiller number in each experiment; none of the grasses differed from ‘Meyer’ in percentage change in tiller number under shade. ‘Emerald’, ‘Cavalier’, ‘Zorro’, and several progeny from crosses between ‘Emerald’ × Z. japonica or reciprocal crosses of Z. matrella × Z. japonica produced more, longer, or more highly branched stolons than ‘Meyer’, suggesting they may have improved recovery potential in shade.