A closer look at water-related geologic activity on Mars

Water has supposedly marked the surface of Mars and produced characteristic landforms. To understand the history of water on Mars, we take a close look at key locations with the High-Resolution Imaging Science Experiment on board the Mars Reconnaissance Orbiter, reaching fine spatial scales of 25 to 32 centimeters per pixel. Boulders ranging up to approximately 2 meters in diameter are ubiquitous in the middle to high latitudes, which include deposits previously interpreted as finegrained ocean sediments or dusty snow. Bright gully deposits identify six locations with very recent activity, but these lie on steep (20 degrees to 35 degrees) slopes where dry mass wasting could occur. Thus, we cannot confirm the reality of ancient oceans or water in active gullies but do see evidence of fluvial modification of geologically recent mid-latitude gullies and equatorial impact craters.     

曲霉属真菌发酵提取物对奶牛生产性能影响的试验研究

中低产奶牛生产性能的提高及奶牛体况调整是奶牛生产健康发展的关键。试验在中低产奶牛干奶期、泌乳初期及泌乳高峰前期饲料中添加曲霉属真菌发酵提取物“保增乐”（商品名）；对奶牛干乳期体重、泌乳初期产奶性能改变及奶牛机体代谢情况进行检测。试验结果：饲喂“保增乐”奶牛干乳期体重显著增加（P〈0．05），奶牛泌乳初期产奶性能显著增强（P〈0．05），奶牛泌乳初期隐性酮病状况以及机体代谢内环境的酸碱平衡都有明显的改善。研究表明．添加“保增乐”对奶牛生产性能的提高及机体代谢状况的改善有显著作用。     

输气管道中缓蚀剂雾化浓度分布及加注量计算

利用液体雾化流动理论，对缓蚀剂在天然气管道内的雾化过程，雾化浓度分布及其保护管道的机理进行了研究。研究中发现，缓蚀剂的雾化在喷流状态下最为充分，且可形成均匀的保护膜；而雾化角、雾化细度、雾化均匀度和浓度分布等评定缓蚀剂雾化质量的，又可以用来检验管道是否得到了有效保护。     

Biscrolling nanotube sheets and functional guests into yarns

Multifunctional applications of textiles have been limited by the inability to spin important materials into yarns. Generically applicable methods are demonstrated for producing weavable yarns comprising up to 95 weight percent of otherwise unspinnable particulate or nanofiber powders that remain highly functional. Scrolled 50-nanometer-thick carbon nanotube sheets confine these powders in the galleries of irregular scroll sacks whose observed complex structures are related to twist-dependent extension of Archimedean spirals, Fermat spirals, or spiral pairs into scrolls. The strength and electronic connectivity of a small weight fraction of scrolled carbon nanotube sheet enables yarn weaving, sewing, knotting, braiding, and charge collection. This technology is used to make yarns of superconductors, lithium-ion battery materials, graphene ribbons, catalytic nanofibers for fuel cells, and titanium dioxide for photocatalysis.     

Development of transgenic fungi that kill human malaria parasites in mosquitoes

Metarhizium anisopliae infects mosquitoes through the cuticle and proliferates in the hemolymph. To allow M. anisopliae to combat malaria in mosquitoes with advanced malaria infections, we produced recombinant strains expressing molecules that target sporozoites as they travel through the hemolymph to the salivary glands. Eleven days after a Plasmodium-infected blood meal, mosquitoes were treated with M. anisopliae expressing salivary gland and midgut peptide 1 (SM1), which blocks attachment of sporozoites to salivary glands; a single-chain antibody that agglutinates sporozoites; or scorpine, which is an antimicrobial toxin. These reduced sporozoite counts by 71%, 85%, and 90%, respectively. M. anisopliae expressing scorpine and an [SM1](8):scorpine fusion protein reduced sporozoite counts by 98%, suggesting that Metarhizium-mediated inhibition of Plasmodium development could be a powerful weapon for combating malaria.     

绵羊实验性变异黄芪和黄花棘豆中毒的比较

 利用饲喂试验比较了变异黄芪和黄花棘豆对绵羊的毒性作用.结果表明,变异黄芪和黄花棘豆的毒性作用极为相似.主要临床症状为沉郁、被毛粗乱、消瘦、体重减轻、僵硬,采食时头部水平震颤,神经机能紊乱及心律不齐.从试验的第18d开始,两组的循环淋巴细胞中出现胞浆空泡,血清碱性磷酸酶活性、谷草转氨酶活性及血清尿素氮含量均明显升高.各组的血糖、肌酐、血钙、血钾、总蛋白、谷丙转氨酶均无明显变化.2组E-玫瑰花环形成率均显着降低(P<0.05).2组的特征病理组织学变化均为神经细胞及实质细胞胞浆空泡化.电镜观察表明,空泡是由溶酶体样结构及线粒体肿胀所致.变异黄芪中毒和黄花棘豆中毒的症状、病理变化、临床病理学及细胞免疫功能变化的相似性充分说明,变异黄芪中毒亦可归属于疯草中毒.     

Spatio-temporal impacts of roads on the persistence of populations: analytic and numerical approaches

Roads can have drastic impacts on wildlife populations. Although there is wide recognition of the negative impacts caused by roads and a wealth of practical studies, there is a lack of theoretical work that can be used to predict the impact of road networks or to implement mitigation measures. Here, using Skellam’s diffusion model, we develop analytic and numerical approaches to analyze the impact of road networks on the survival of populations. Our models show that the viability of a population is determined not only by road density but also by the size and shape of patches. Accordingly, we studied the minimum size of a patch to sustain a population with given diffusion and growth parameters. We provide simple formulas to estimate the minimum patch size, and illustrate the importance of shape with square and rectangular patches. Our models also allow the estimation of time to extinction after road construction for a population in a patch smaller than that of the minimum size. Finally, using numerical computations we illustrate how the spatial arrangement of fences strongly affects both the equilibrium density and the spatial distribution of populations, and that not all fence layouts are equally effective. We anticipate that our methods provide a tool to assess the impact of geometrical features of road networks on wildlife and that they can be used to design mitigation measures to prevent the decline and extinction of populations in an anthropogenically disturbed landscape.     

Metanephric cell microenvironment induces embryonic stem cells to differentiate toward renal cells

AIM: To explore the effects of metanephric cell microenvironment on inducing embryonic stem cells (ESCs) to differentiate toward renal cells.METHODS: Embryoid bodies (EBs) of D3 mouse embryonic stem cells were prepared by hanging drop culture, and the EBs were co-cultured indirectly with metanephric cells derived from E12.5 d mouse embryo. The EBs cell with spontaneous differentiation was used as the control. The proteins of Pax2 and WT-1 were analyzed by immunofluorescence assay. The mRNA expression of Pax2, WT-1, Lim1, Sall1, Emx2, GDNF, Wnt4, BMP7, Nephl, Nephrin, KSP and CD24 genes was detected by RT- PCR.RESULTS: The genes related to kidney development were expressed in the EBs cells after co-culture on day 3, and the mRNA expression of Pax2, WT-1, Emx2, GDNF, Nephl, Nephrin, KSP and CD24 was stronger than those in control group. Pax2 positive cells were found on day 3 in the co-cultured EBs cells, and the positive cells increased on day 5 and day 7. WT-1 protein positive cells were found in the co-cultured EBs cells on day 5. No Pax2 or WT-1 positive cell was observed in control group.CONCLUSION: Metanephric cell microenvironment promotes ESCs differentiation toward renal cells.     

Influence of land use on water quality in a tropical landscape: a multi-scale analysis

There is a pressing need to understand the consequences of human activities, such as land transformations, on watershed ecosystem services. This is a challenging task because different indicators of water quality and yield are expected to vary in their responsiveness to large versus local-scale heterogeneity in land use and land cover (LUC). Here we rely on water quality data collected between 1977 and 2000 from dozens of gauge stations in Puerto Rico together with precipitation data and land cover maps to (1) quantify impacts of spatial heterogeneity in LUC on several water quality indicators; (2) determine the spatial scale at which this heterogeneity influences water quality; and (3) examine how antecedent precipitation modulates these impacts. Our models explained 30–58% of observed variance in water quality metrics. Temporal variation in antecedent precipitation and changes in LUC between measurements periods rather than spatial variation in LUC accounted for the majority of variation in water quality. Urbanization and pasture development generally degraded water quality while agriculture and secondary forest re-growth had mixed impacts. The spatial scale over which LUC influenced water quality differed across indicators. Turbidity and dissolved oxygen (DO) responded to LUC in large-scale watersheds, in-stream nitrogen concentrations to LUC in riparian buffers of large watersheds, and fecal matter content and in-stream phosphorus concentration to LUC at the sub-watershed scale. Stream discharge modulated impacts of LUC on water quality for most of the metrics. Our findings highlight the importance of considering multiple spatial scales for understanding the impacts of human activities on watershed ecosystem services.