论松木刨切单板的最佳厚度

论松木刨切单板的最佳厚度［俄］Ａ．Ａ．巴尔塔舍维奇等用作家具生产饰面材料的刨切单板，制造成各种厚度（毫米）：０．６（核桃木、桃花心木），０．８（山毛榉、水曲柳、赤杨、桦木），１．０（松木）。为了节约原料在家具制造中用薄单板，尤其是０．４毫米的单板进行...     

Bioactive saponins from the fruits of Aesculus pavia L

Continued chemical investigation on the fruits of Aesculus pavia L. resulted in theisolation and identification of two new oleanolic acid saponins, namely vaccaroside A (1) andvaccaroside B (2). The isolated furostanol saponins were evaluated for cytotoxic activity againsthuman normal amniotic and human lung carcinoma cell lines using neutral red and MTT assays.In vitro experiments showed significant cytotoxicity in a dose dependent manner with IC50 valuesin the range of 27.80–79.02 μM.     

Trypanocidal activity of extracts and fractions of Bertholletia excelsa

Crude extracts and fractions of Bertholletia excelsa stem barks were tested for trypanocidal activity. Acetone and methanol extracts showed significant in vitro trypanocidal activity against trypomastigote form of Trypanosoma cruzi since in the concentration of 500 microg/ml, the parasites were reduced in 100% and 90.3% respectively, whereas the triterpene betulinic acid pure isolated from hexane extract presented 75.4%.     

Grapefruit and oroblanco enhance hepatic detoxification enzymes in rats: possible role in protection against chemical carcinogenesis

Citrus fruits are considered to be functional foods that promote good health. This study was carried out to assess the effect of oroblanco and grapefruit consumption on hepatic detoxification enzymes. Male Sprague-Dawley rats were provided with either regular drinking water (control) or experimental treatments of oroblanco juice, grapefruit juice, or a sugar mix for 6 weeks. After 1 week of treatment, half the animals in each group were injected with the procarcinogen 1,2-dimethylhydrazine. Grapefruit juice significantly increased activity and expression of the hepatic phase I enzyme, cytochrome P450 CYP1A1, with a marked trend toward enhanced NAD(P)H:quinone reductase (QR) activity. Oroblanco juice significantly increased glutathione S-transferase phase II enzyme activity along with CYP1A1 expression and a notable trend toward increased activity of both CYP1A1 and QR. These results suggest that these citrus fruits are bifunctional inducers, modulating both phase I and phase II drug-metabolizing enzymes to enhance hepatic detoxification.     

台湾省木材工业近况

台湾省的木材工业,自从60年代成功地开拓国外市场以来,得到了顺利的发展,且保持着增长的趋势。然而,台湾的木材工业所必需的木材资源依赖于进口,制品的销售也依赖于国外市场,为省内厂商所能控制的只有工艺方法而已。1986年新台币与美元的     

用木质废料制造木质片材

以锯屑、树皮等细小的废料为原料,用水系而容易凝胶化的可形成橡胶状弹性体的聚氨酯作为阻水剂,可制造出一种新型材料。按成型条件的不同,和有无二次热压,可制出从比较柔软到相当硬的片材产品,因而有很宽的使用范围,如用作包装材料、地板材料、各种绝缘材料、植物栽培筒罐、干燥农业用地的隔水板等等。原料柔软片材要使用20～80目的锯屑,用19号带锯条的锯屑大体可以符合其粒级要求,有少量通过80目的微粉也不会给成型带来困难。使用排锯机、元锯机的锯屑,需要筛去大于10目的锯屑;必要时可粉碎后加以利用。树皮要去掉硬质表皮的咖啡渣,单独     

Carbon dioxide and water vapor exchange by young and old ponderosa pine ecosystems during a dry summer

We investigated key factors controlling mass and energy exchange by a young (6-year-old) ponderosa pine (Pinus ponderosa Laws.) plantation on the west side of the Sierra Nevada Mountains and an old-growth ponderosa pine forest (mix of 45- and 250-year-old trees) on the east side of the Cascade Mountains, from June through September 1997. At both sites, we operated eddy covariance systems above the canopy to measure net ecosystem exchange of carbon dioxide and water vapor, and made concurrent meteorological and ecophysiological measurements. Our objective was to understand and compare the controls on ecosystem processes in these two forests. Precipitation is much higher in the young plantation than in the old-growth forest (1660 versus 550 mm year-1), although both forests experienced decreasing soil water availability and increasing vapor pressure deficits (D) as the summer of 1997 progressed. As a result, drought stress increased at both sites during this period, and changes in D strongly influenced ecosystem conductance and net carbon uptake. Ecosystem conductance for a given D was higher in the young pine plantation than in the old-growth forest, but decreased dramatically following several days of high D in late summer, possibly because of xylem cavitation. Net CO2 exchange generally decreased with conductance at both sites, although values were roughly twice as high at the young site. Simulations with the 3-PG model, which included the effect of tree age on fluxes, suggest that, during the fall through spring period, milder temperatures and ample water availability at the young site provide better conditions for photosynthesis than at the old pine site. Thus, over the long-term, the young site can carry more leaf area, and the climatic conditions between fall and spring offset the more severe limitations imposed by summer drought.     

Morphinandienone alkaloids from Dehaasia longipedicellata

Five morphinoid alkaloids have been isolated from Dehaasia longipedicellata, namely (-) pallidine, a new alkaloid (+) pallidinine (1), (+)-milonine, (-) 8,14-dehydrosalutaridine and (-) sinoacutine.