城市绿地中的声景观对精神复愈的作用

当前针对声景观的研究多数是以探索人们喜好的声音为主,而很少考虑声景观与视觉景观的相互作用。为探讨城市绿地中声景观与视觉景观相互作用对于精神复愈的作用,选取了8个具有代表性的城市绿地。以能够反映样地景观特点的视频作为复愈能力评测的媒介,通过计算机技术将选取的5种声音（单一鸟鸣声、多种鸟鸣声、蛙叫声、流水声和中国古典音乐）与在所选样地上录制的8段视频进行组合,选择191位大学生作为评价人员,对城市绿地的精神复愈性能力进行评价;并邀请5位景观专业的研究生对城市绿地的景观特征进行定量分析。结果显示：城市绿地中存在水流声或蛙叫声会降低绿地的精神复愈能力;把单一鸟鸣声和多种鸟类鸟鸣声设置在地形起伏较平坦的环境中能够更加有效地提高精神复愈能力。     

保鲜剂对天门冬切叶的保鲜效应

以150 mg·L-1柠檬酸+500 mg·L-1 CaCl2+1 mg·L-1 6-BA为基础液,加入不同浓度蔗糖和青霉素进行瓶插试验,研究天门冬(Asparagus cochinchinensis)切叶瓶插寿命、黄化程度及生理变化。结果表明,基础液添加100 mg·L-1青霉素+0.25%蔗糖保鲜液对天门冬切叶保鲜效果最好,与对照比,瓶插寿命延长11.3 d;比对照推迟4 d出现黄化现象;叶绿素含量推迟3 d达到峰值;鲜重变化率比对照推迟2 d达到峰值,且维持在较高水平;相对电导率和MDA维持较低水平;POD活性推迟3 d出现峰值,且POD活性比对照高,CAT活性推迟6 d出现峰值,且CAT活性维持较高水平。说明适宜浓度的蔗糖和青霉素能减缓叶绿素含量和叶片鲜重下降,抑制叶片内膜脂过氧化产物MDA产生,维持叶片膜结构相对稳定,增强POD和CAT活性,保持天门冬切叶观赏品质并延长瓶插寿命。     

Evaluating the wind cooling potential on outdoor thermal comfort in selected Iranian climate types

Wind is one of the main factors affecting people's outdoor thermal sensation. Ongoing urbanization and urban densification are transforming the urban climate and complicating the pedestrian-level wind environment. Therefore, the main aim of this research is to evaluate the potential wind-cooling effect on human outdoor thermal conditions. Accordingly, the current research attempts determine the best wind directions for thermal comfort at the studied stations and how these factors will be changed under the effects of global warming. Outdoor thermal conditions were modeled based on the physiologically equivalent temperature (PET) thermal index using RayMan software for the decades of the 2000s and the 2040s in different climate types of Iran (Csb, BWh, Csa, and BSh) To estimate the potential cooling effect of wind, the PET was calculated (1) under actual wind conditions, and (2) under calm wind (0.05 m/s) conditions. Then, the ΔPET for these two conditions, which indicates the cooling potential effect (CPE) of the wind, was calculated for four representative stations (Ardebil, Bandar Abbas, Gorgan, and Shiraz). In comparison with the 2000s, the results indicated that by the 2040s, the predicted wind cooling potential will have increased in Ardebil, Shiraz, Bandar Abbas and Gorgan (CPE of 13.2 °C, 13.1 °C, 11.2 °C, and 11 °C, respectively). Based on the overall average of two climate change scenarios (A2 and B1) used in this study, the occurrence of “comfortable” conditions by the 2040s will have increased in Bandar Abbas, Shiraz, and Ardebil by 1.1%, 0.4%, and 0.3%, respectively, while it will have decreased in Gorgan by 1.5%. Accounting for the cooling effect of wind, the comfort cooling potential of wind is predicted to rise by an average of 1.6 °C in the 2040s compared with the 2000s in all the studied stations. Therefore, this will affect the microclimates positively and could reduce the urban heat island effects.     

Density functional calculations of 15N chemical shifts in solvated dipeptides

We performed density functional calculations to examine the effects of solvation, hydrogen bonding, backbone conformation, and the side chain on 15N chemical shielding in proteins. We used N-methylacetamide (NMA) and N-formyl-alanyl-X (with X being one of the 19 naturally occurring amino acids excluding proline) as model systems. In addition, calculations were performed for selected fragments from protein GB3. The conducting polarizable continuum model was employed to include the effect of solvent in the density functional calculations. Our calculations for NMA show that the augmentation of the polarizable continuum model with the explicit water molecules in the first solvation shell has a significant influence on isotropic 15N chemical shift but not as much on the chemical shift anisotropy. The difference in the isotropic chemical shift between the standard beta-sheet and alpha-helical conformations ranges from 0.8 to 6.2 ppm depending on the residue type, with the mean of 2.7 ppm. This is in good agreement with the experimental chemical shifts averaged over a database of 36 proteins containing >6100 amino acid residues. The orientation of the 15N chemical shielding tensor as well as its anisotropy and asymmetry are also in the range of values experimentally observed for peptides and proteins.     

Floral symmetry: pollinator-mediated stabilizing selection on flower size in bilateral species

Pollinator-mediated stabilizing selection (PMSS) has been proposed as the driver of the evolutionary shift from radial to bilateral symmetry of flowers. Studies have shown that variation in flower size is lower in bilateral than in radial species, but whether bilateral flowers experience more stabilizing selection pressures by employing fewer, more specialized pollinators than radial flowers remains unclear. To test the PMSS hypothesis, we investigate plant–pollinator interactions from a whole community in an alpine meadow in Hengduan Mountains, China, to examine: (i) variance in flower size and level of ecological generalization (pollinator diversity calculated using functional groups) in 14 bilateral and 13 radial species and (ii) the role pollinator diversity played in explaining the difference of variance in flower size between bilateral and radial species. Our data showed that bilateral species had less variance in flower size and were visited by fewer pollinator groups. Pollinator diversity accounted for up to 40 per cent of the difference in variance in flower size between bilateral and radial species. The mediator effect of pollinator diversity on the relationship between floral symmetry and variance in flower size in the community is consistent with the PMSS hypothesis.     

Overyielding among plant functional groups in a long-term experiment

A recent debate among ecologists has focused on mechanisms by which species diversity might affect net primary productivity. Communities with more species could use a greater variety of resource capture characteristics, leading to greater use of limiting resources (complementarity) and therefore greater productivity (overyielding). Recent experiments, however, have shown a variety of relationships between diversity and productivity. In an experiment on serpentine grassland communities spanning 8 years, we found that overyielding increased several years after plot establishment. Overyielding varied greatly depending on the functional characteristics of the species involved and the biotic and abiotic environment (particularly water availability). While functional differences among species led to strong complementarity and facilitation, these effects were not sufficient to cause significant transgressive overyielding or consistent increases in productivity with increased plant diversity. These results suggest that greater absolute production with greater diversity may be restricted to particular species combinations or environmental conditions.     

Cdc2 and Cdk2 play critical roles in low dose doxorubicin-induced cell death through mitotic catastrophe but not in high dose doxorubicin-induced apoptosis

In Huh-7 hepatoma cells, low dose (LD) doxorubicin treatment induces cell death through mitotic catastrophe accompanying the formation of large cells with multiple micronuclei, whereas high dose (HD) doxorubicin induces apoptosis. In this study, we investigated the role of Cdc2 and Cdk2 kinase in the regulation of the two modes of cell death induced by doxorubicin. During HD doxorubicin-induced apoptosis, the histone H1-associated activities of Cdc2 and Cdk2 both progressively declined in parallel with reductions in cyclin A and cyclin B protein levels. In contrast, during LD doxorubicin-induced cell death through mitotic catastrophe, the Cdc2 and Cdk2 kinases were transiently activated 1 day post-treatment, with similar changes seen in the protein levels of cyclin A, cyclin B, and Cdc2. Treatment with roscovitine, a specific inhibitor of Cdc2 and Cdk2, significantly blocked LD doxorubicin-induced mitotic catastrophe and cell death, but did not affect HD doxorubicin-induced apoptosis in Huh-7, SNU-398, and SNU-449 hepatoma cell lines. Our results demonstrate that differential regulation of Cdc2 and Cdk2 activity by different doses of doxorubicin may contribute to the induction of two distinct modes of cell death in hepatoma cells, either apoptosis or cell death through mitotic catastrophe.     

稀土元素对植物的生物效应及其作用机理

综述了稀土元素对植物根系发育、生物量、品质和抗逆性的影响.适量稀土浓度可促进植物生长,提高种子萌发能力和根系发育,提高植物生物量,并改善植物果实的品质.施用适量稀土元素还可以增强植物的抗逆性并且对一些植物病害有一定防治作用.介绍了植物对稀土元素的吸收特性和稀土元素在植物体内的含量、分布、存在形式及细胞定位.重点探讨了稀土元素对植物光合作用、叶绿素形成、植物吸收营养元素、稀土元素与钙相关性和稀土元素对细胞膜及酶的作用机理,内容包括稀土元素可提高植物叶绿素含量,增强光合效率,从而增加植物生物量.适量的稀土元素能够促进植物对营养元素的吸收、转化和利用.稀土元素有类似钙的功能,可置换出酶中的钙离子而参与酶的反应.稀土离子可以维持细胞膜的透性和稳定性,提高膜的保护功能,增强植物对不良环境的抵御能力.最后,对稀土元素的研究前景进行了展望.