Reliability of wavefront shaping based on coherent optical adaptive technique in deep tissue focusing

Wavefront shaping can compensate the wavefront distortions in deep tissue focusing, leading to an improved penetration depth. However, when using the backscattered signals as the feedback, unexpected compensation bias may be introduced, resulting in focusing position deviations or even no focus in the illumination focal plane. Here we investigated the reliability of wavefront shaping based on coherent optical adaptive technique in deep tissue focusing by measuring the position deviations between the foci in the illumination focal plane and the epi‐detection plane. The experimental results show that when the penetration depth reaches 150 μm in mouse brain tissue (with scattering coefficient ~22.42 mm^?1) using a 488 nm laser and an objective lens with 0.75 numerical aperture, the center of the real focus will deviate out of one radius range of the Airy disk while the optimized focus in the epi‐detection plane maintained basically at the center. With the penetration depth increases, the peak to background ratio of the focus in the illumination focal plane decreases faster than that in the epi‐detection plane. The results indicate that when the penetration depth reaches 150 μm, feedback based on backscattered signals will make wavefront shaping lose its reliability, which may provide a guidance for applications of non‐invasive precise optogenetics or deep tissue optical stimulation using wavefront shaping methods. A, Intensity distribution in the epi‐detection plane and the illumination focal plane before and after correction, corresponding to brain sections with 250 and 300 μm thickness, respectively. Scale bar is 2 μm. B, Averaged focusing deviations in the epi‐detection plane (optimized) and the illumination focal plane (monitored) after compensation. The unit of the ordinate is one Airy disk diameter. Black dashed line represents one Airy disk radius. Bars represent the SE of each measurement set.      

贵州白鹇湖沉积物中孢粉记录的5.5kaB.P.以来的气候变化

通过对白鹇湖沉积物柱芯孢粉组合的剖面变化分析,在有机质14C定年基础上,探讨了白鹇湖地区过去5.5 ka calB.P.以来的植被演替和气候变化过程.研究结果表明,5500-4500 aB.P.期间,各类植被比较丰富,气候温暖湿润;4500-2750 aB.P.期间,干旱草本和蕨类植物开始出现,是气候转变过渡期;2750-1500 aB.P.期间,木本植物组合类型发生明显变化,喜湿草本减少,耐旱草本增加,气候向温凉干旱化发展;1500 aB.P.至今,木本植被和喜湿草本继续减少,中生耐旱草本和蕨类植物数量继续大幅增加,干旱化趋势明显,植被组合向典型石漠化植被组合类型发展.白鹇湖沉积物剖面孢粉组合变化表明,该地区近5000a来气候变化以温度下降、降水减少为主要趋势,并存在明显的陆地植被退化现象.研究还揭示了自然气候变化事件(如气候持续干旱)可导致喀斯特地区发生石漠化,证实了喀斯特地区生态环境具先天脆弱性.科学评估白鹇湖地区气候干旱化趋势及其生态环境影响对指导该地区科学应对气候变化具重要意义,亟待加强.     

Pollen discounting and the evolution of selfing in Arenaria uniflora (caryophyllaceae)

Although most models of mating system evolution assign a central role to the male transmission advantage of selfing genotypes, empirical data on the male fitness consequences of increased self-pollination are still uncommon. Here, I use measures of pollen import and export by focal plants in genotyped arrays to investigate the effects of floral morphology and pollination environment on self and outcross male function. Plants from an autogamous population of Arenaria uniflora (Caryophyllaceae) exhibit complete pollen discounting relative to closely related outcrossers, as do morphologically intermediate F1 hybrids between the two populations. However, the low cumulative male fitness of hybrids probably results from reduced pollen number or competitive ability, rather than a nonlinear relationship with floral morphology. When surrounded by selfers, plants from the outcrosser population self-fertilize at nearly the same rate as selfers (>80%), but have much lower self male fitness due to reduced fruit set. Because outcross siring success is also extremely low (<8%) in this treatment, these mate-limited outcrossers are at male fitness disadvantage to both pseudocleistogamous selfers and nonlimited outcrossers. The relative male fitness of plants with different mating systems appears dependent on the ecological context, as well as on morphological trade-offs.     

Possible Mechanism for Formation and Regulation of the Palmitate-Induced Cyclosporin A-Insensitive Mitochondrial Pore

The mechanism of the palmitate-induced opening of the mitochondrial Ca2+-dependent cyclosporin A (CsA)-insensitive pore was studied, as well as the influence on this process of well-known modulators of the CsA-sensitive Ca2+-dependent pore. Palmitic acid, which can bind Ca2+ with high affinity, induced the cyclosporin A-insensitive swelling of mitochondria, whereas palmitoleic and 2-bromopalmitic acids, which have no such affinity for Ca2+, failed to induce the pore opening. The palmitate-induced Ca2+-dependent swelling of mitochondria was not affected by a well-known inhibitor of the CsA-sensitive pore (ADP) and an activator of this pore (inorganic phosphate, P(i)). However, this swelling was inhibited by physiological concentrations of ATP ([I]50 = 1.3 mM), but 100 microM ATP increased by 30% the rate of mitochondria swelling if Ca2+ had been added earlier. The effects of ATP (inhibition and activation) manifested themselves from different sides of the inner mitochondrial membrane. Mg2+ inhibited the palmitate-induced Ca2+-dependent swelling of mitochondria with [I]50 = 0.8 mM. It is concluded that palmitic acid induces the opening of the CsA-insensitive pore due to its ability for complexing with Ca2+. A possible mechanism of the pore formation and the influence of some modulators on this process are discussed.     

The effect of non-algal turbidity on the relationship of Secchi depth to chlorophyll a

Data from four reservoirs representative of different trophic states and with different apparent optical properties were analyzed to determine the relationship of Secchi depth to algal biomass as measured by chlorophyll a. In the eutrophic reservoir Secchi depth was determined partially by the chlorophyll a content (r² = 0.31) but only when chlorophyll a data from bloom conditions are included. In the two mesotrophic reservoirs, Secchi depth was entirely determined by non-algal turbidity. In the oligotrophic reservoir, Secchi depth was determined neither by chlorophyll a nor non-algal turbidity and was probably determined by dissolved color. When data from the four reservoirs were pooled (N = 205), 53% of the variation in Secchi depth was explained by: SD = 2.55–0.52 ln (Turbidity) + 0.005 (Chlorophyll a). It is apparent that attempts to estimate algal biomass for trophic state classification or other management practices from Secchi depth data are inappropriate even where moderate amounts of non-algal turbidity are present.     

俄罗斯北部平原(VYCHEGDA河盆地)全新世植物群和植被

对Vychegda河流域靠近Baika村(61°16'N,46°44'E)洪积平原的一个剖面进行了孢粉学研究.化石点位于泰加林带中部,靠近欧洲云杉林和亚乌拉尔-西伯利亚云、冷杉-西伯利亚松林界限附近.该河流盆地森林覆盖率高达98%.根据放射性碳年代测定,沉积涵盖了全新世大约自9000 yrs B.P.以来的大部分地层.主要运用化石植物群组成来恢复这一地区全新世以来的植被和气候变化,通过某些化石植物群的全部植物种类的现代地理分布的分析,可以发现与过去植被最接近的现代对应植被类型的位置,通过确定所有植物种现代生长地区的景观和气候来推测与古环境最接近的景观和气候.整个孢粉组合序列中云杉、松和桦占统治地位,但是植物群的成分和植被有变化.暖温带树种,如椴、榆及栎等在森林中的含量有变化,在全新世最暖期,相当于中晚大西洋期(6000-4500 yrs B.P.)达到最高.这些变化通过对应的现代植物群在俄罗斯平原的"迁移"反映出来,从中、南乌拉尔向西至Sukhona河盆地然后再返回到研究区的Vychegda河下游.运用古植物群的方法定量恢复的主要气候指标表明在大西洋期7月份月均温比现代高2.5℃,1月份月均温比现在高出1℃,年降雨量和现在接近.这段时间可以认为是本地区全新世的气候最适宜期.     

ABSENCE OF POLLEN DISCOUNTING IN A GENOTYPE OF IPOMOEA PURPUREA EXHIBITING INCREASED SELFING

Throughout southeastern North America, the annual morning glory Ipomoea purpurea exhibits a polymorphism at a locus that influences the intensity of floral pigmentation. Previous studies have shown that when rare, the homozygous white genotype has a greater selfing rate than the homozygous dark genotype. In the absence of pollen discounting (a reduction in transmission of pollen to other plants by genotypes that exhibit increased selfing) and inbreeding depression, this increased selfing rate should favor the white allele. Experiments reported here confirm that the white genotype has elevated selfing rates when rare but indicate pollen discounting is not associated with elevated selfing. Rather, white genotypes contribute more pollen to the outcross pollen pool. The disparity between genotypes in both selfing rates and success at pollen contribution to other plants disappears at intermediate to high frequencies of the white allele. Pollinator movements are consistent with the pattern of selfing. These results suggest that elevated selfing and enhanced success at pollen donation contribute to maintenance of the white allele in natural populations of morning glories.     

OVULE PACKAGING IN STOCHASTIC POLLINATION AND FERTILIZATION ENVIRONMENTS

The modular morphology of plants has important consequences for reproductive strategies. Ovules are packaged in discrete structures (flowers) that usually vary stochastically in pollen capture and ovule fertilization, because of the vagaries of pollen transfer by external agents. Different ovule packaging schemes may use limited reproductive resources more or less effectively, so that some number of ovules per flower may be optimal, given the prevailing probabilities of ovule fertilization. I derive a phenotypic model for ovule number per flower that maximizes the expected total ovule fertilizations on a plant when pollination and fertilization vary randomly among individual flowers. This model predicts that, except for small or inexpensive flowers, ovules should be “oversupplied” relative to the mean receipt of pollen tubes, so that pollen limitation of seed set should be common. Published data are congruent with this prediction. Additional hypotheses on the relation of ovule packaging to floral cost, plant size, and variance in pollen receipt are suggested by the model, but few data exist to evaluate these hypotheses.     

Influences of sea level changes and volcanic eruptions on Holocene vegetation in Tonga

Here, we investigate Mid- to Late-Holocene vegetation changes in low-lying coastal areas in Tonga and how changing sea levels and recurrent volcanic eruptions have influenced vegetation dynamics on four islands of the Tongan archipelago (South Pacific). To investigate past vegetation and environmental change at Ngofe Marsh (‘Uta Vava’u), we examined palynomorphs (pollen and spores), charcoal (fire), and sediment characteristics (volcanic activity) from a 6.7-m-long sediment core. Radiocarbon dating indicated the sediments were deposited over the last 7700 years. We integrated the Ngofe Marsh data with similar previously published data from Avai’o’vuna Swamp on Pangaimotu Island, Lotofoa Swamp on Foa Island, and Finemui Swamp on Ha’afeva Island. Plant taxa were categorized as littoral, mangrove, rainforest, successional/ disturbance, and wetland groups, and linear models were used to examine relationships between vegetation, relative sea level change, and volcanic eruptions (tephra). We found that relative sea level change has impacted vegetation on three of the four islands investigated. Volcanic eruptions were not identified as a driver of vegetation change. Rainforest decline does not appear to be driven by sea level changes or volcanic eruptions. From all sites analyzed, vegetation at Finemui Swamp was most sensitive to changes in relative sea level. While vegetation on low-lying Pacific islands is sensitive to changing sea levels, island characteristics, such as area and elevation, are also likely to be important factors that mediate specific island responses to drivers of change.