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101.
《Wood material science & engineering》2013,8(3-4):125-130
Abstract The transmission of footfall-excited impact sound is commonly reduced using floating wood floors. These constructions contain three layers: a load-bearing wood floor, a resilient material and a floating wood slab. For wood construction excited by transient load (e.g. footsteps), sound reduction estimations may contain uncertainties due to inadequate modelling of footsteps and floor components. This paper presents a multiple degree-of-freedom system model using Working Model 2D® (WM2D). The model includes orthotropic behavior of wood and equivalent spring stiffness determination of the resilient layer. Sound reduction is determined and it is shown that larger reductions are possible through the inclusion of floating wood slabs in the load-bearing floor. 相似文献
102.
Digestive enzymes of Cirrhinus mrigala (Ham.) were studied during ontogenic development. Specific amylase activity was detected in first feeding fish. The enzyme activity decreased up to day‐18 and then it increased with the age of fish to reach the highest level on day‐34. Protease activity was 28.61 ± 8.90 mU mg protein?1 min?1 on day‐4 and increased with the age throughout the study period. Trypsin activity was 31.86 ± 1.12 mU mg protein?1 min?1 on day‐4. The activity decreased up to day‐10 and from day‐12 onwards increased up to day‐26. Chymotrypsin activity was 14.56 ± 2.74 mU mg protein?1 min?1on day‐4 and constantly increased up to day‐26. A significant increase in lipase activity was observed between days‐24 and 34. SDS‐PAGE and substrate SDS‐PAGE showed the diversity of protein (17.4–127.8 kDa) and protease activity bands (16.6–88.8 kDa) during ontogenesis. Soybean trypsin inhibitor, phenyl methyl sulphonyl fluoride, N‐α‐p‐tosyl‐l ‐lysine chloromethylketone and N‐tosyl‐l ‐phenylalanine chloromethylketone inhibited the protease activity up to 79.72–97.21, 65.55–94.83, 45.41–75.31 and 40.78–64.72%, respectively. Inhibition study in substrate SDS‐PAGE revealed the abundance of serine proteases and the presence of isoforms of trypsin and chymotrypsin. Ethylenediamine‐tetraacetate showed 5.56–22.78% inhibition of metal ion‐specific enzyme activity. 相似文献
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为了研究不同水平ZnSO4和Met-Zn对家兔生产性能及组织Zn沉积的影响,选用2.5月龄布列塔尼亚肉兔120只,随机分成10组,基础日粮中分别以ZnSO4和Met-Zn形式添加70、105、140、1752、10 mg/kgZn,预试期7 d,正试期30 d。结果表明,在Zn添加量为70~140 mg/kg时,Met-Zn对家兔生产性能的影响优于ZnSO4。日粮Zn含量在70~210 mg/kg时,肉兔肝脏、肾脏、脾脏及背最长肌的Zn含量不呈现明显的变化趋势。 相似文献
105.
《Communications in Soil Science and Plant Analysis》2012,43(1):79-86
Abstract The bismuth sulfide and methylene blue colorimetric finishes for soil sulfate determination by the Johnson‐Nishita distillation method were examined and compared. Both procedures gave comparable results when applied to soils and soil extracts, but the bismuth method was more rapid and more reliable. Nitrogen flow rate over the range 100–500 ml/min was not critical for the bismuth method, provided appropriate distillation times were employed. However, the release and transfer of hydrogen sulfide in the bismuth method was effected in one‐third of the time required for the méthylène blue finish, largely due to the elimination of a gas‐washing step. Predrying of soil extract samples increased recovery of hydrogen sulfide with the bismuth procedure arid could be used to increase sensitivity. Nitrate interference was observed with the bismuth procedure but attributed to interference during the reduction step. The bismuth procedure can readily be adapted for microdetermination in the 0–40 ppm sulfate‐S range. 相似文献
106.
Yoshikazu Kiriiwa Sunao Osumi Masanobu Endo Akira Nukaya Akio Morita Hiromi Yokota 《Soil Science and Plant Nutrition》2013,59(7):1119-1124
Abstract In alkaline soils, plant growth is impaired mainly by high pH and high concentration of bicarbonates. The bicarbonate concentration increases the pH value, and causes deficiency of iron. A bicarbonate-resistant cell line (BR line) of tobacco (Nicotiana tabacum L. cv. Burley21) was selected by adding excess bicarbonate ions (20 mmol L?1) to the culture medium. The pH of the medium was buffered 8.0 to 8.3. Under these conditions, about 80% of iron in the medium became insoluble. However, under such conditions, the BR line grew well. In this report, we examined some characteristics of the growth and iron uptake in the BR line under iron-deficient (i.e. high pH or no-iron) condition. At pH 5.8, the Fe3+ reduction activity was not significantly different between the non-selected line and the BR line. At pH 8.0, however, the Fe3+ reduction activity of the BR line was higher than that of the non-selected line. In no-iron condition, the growth of the non-selected line was markedly reduced after 2 weeks, while the BR line was not affected. The content of malic acid in both lines increased with the medium pH, and the content in the BR line was higher than that in the non-selected line. The BR line was able to adapt to the conditions, which restricted iron uptake, such as high bicarbonate concentration, high pH, and low iron conditions. The high ability of Fe3+ reduction was maintained at even high pH conditions. Further, the BR line may be able to improve the utilization of iron in the cells. 相似文献
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109.
针对受硫酸盐溶液长期浸泡作用的混凝土,制备对应于混凝土所处环境类别和作用等级中度、严重和非常严重的硫酸钠溶液,硫酸根浓度分别为800、6 000、50 000 mg/L。将强度等级为C40的混凝土试块在硫酸钠溶液中浸泡至不同龄期,采用钻芯、分层切片、研磨提取水泥石粉末样本进行化学分析,研究了硫酸根离子在混凝土内的分散和传输规律。结果表明,硫酸根离子在混凝土中的传输与侵蚀溶液浓度和侵蚀龄期存在较复杂的相关性。在侵蚀龄期较短时,硫酸根离子在混凝土中的传输速度较快,侵蚀深度较大。随着侵蚀龄期的增长,硫酸根离子主要集中在混凝土浅层范围内,且随着侵蚀溶液浓度的增加浅层混凝土中的硫酸根离子含量明显增大。 相似文献
110.
以史氏鲟鱼软骨为原料,按碱提-酶解-乙醇沉淀工艺流程进行提取硫酸软骨素的各主要工序工艺的研究.通过单因素试验及正交试验,得出最佳碱提工艺为以两倍量6%的NaOH为溶剂,于40℃的水浴中搅拌提取4 h.通过正交试验,得出最佳酶解工艺条件是先将浸提液调节pH至8.6,加入胰酶0.5%,50℃保温水解3 h;后降温至40℃,调pH至5.7,加入胃蛋白酶0.3%,保温水解2h.通过单因素试验,得出最佳的乙醇沉淀工艺条件是将滤液pH调为6.5,加入95%的乙醇至醇沉浓度为70%,静置过夜.制备的硫酸软骨素经检测符合WS1-C3-0030-2000(硫酸软骨素口服片)和WS-10001-(HD-0892)-2002(硫酸软骨素注射品)标准的要求. 相似文献