Differences between species in seed bank and vegetation helps to hold functional diversity in a floodable Neotropical savanna

种子库和植被物种之间的差异有助于保持新热带稀树草原的功能多样性 本研究的目的是量化种子库和建立的植被对物种组成、功能组成和多样性的贡献,并讨论这些差异对冲积平原植物群落更新和稳定性的影响。我们在巴西潘塔纳尔湿地的一个周期性洪水泛滥的稀树大草原上,在旱季和雨季对分布在5个地点的25个地块(10 m × 1 m)的1.5 m高度的地面覆盖植被和种子库进行了采样。采用出苗法对土壤种子库进行了评价。研究结果表明,种子库物种具有赋予群落更新的特征,而植被则具有稳定性特征。种子库的功能丰富度高于植被,而功能均匀度则低于植被。由于种子库和植被的植物特征不同,使得具有不同功能稳定性和更新特性的物种得以共存,这将有助于维持植物的功能多样性。这可能会让植物种群在应对干旱、火灾和洪水等不同的环境选择时更具有弹性。     

Hybridization and speciation

Hybridization has many and varied impacts on the process of speciation. Hybridization may slow or reverse differentiation by allowing gene flow and recombination. It may accelerate speciation via adaptive introgression or cause near‐instantaneous speciation by allopolyploidization. It may have multiple effects at different stages and in different spatial contexts within a single speciation event. We offer a perspective on the context and evolutionary significance of hybridization during speciation, highlighting issues of current interest and debate. In secondary contact zones, it is uncertain if barriers to gene flow will be strengthened or broken down due to recombination and gene flow. Theory and empirical evidence suggest the latter is more likely, except within and around strongly selected genomic regions. Hybridization may contribute to speciation through the formation of new hybrid taxa, whereas introgression of a few loci may promote adaptive divergence and so facilitate speciation. Gene regulatory networks, epigenetic effects and the evolution of selfish genetic material in the genome suggest that the Dobzhansky–Muller model of hybrid incompatibilities requires a broader interpretation. Finally, although the incidence of reinforcement remains uncertain, this and other interactions in areas of sympatry may have knock‐on effects on speciation both within and outside regions of hybridization.     

Culture And Staining of Pollen Grains of Ricinus communis

Germinating and growing pollen grains (male gametophytes) of Ricinus communis L. in liquid culture is achieved as follows: Pollen is collected over a 10-15 min period from mature anther clusters which have been removed from the male flowers and which have been kept at 25° C and 40-60% relative humidity. Samples weighing between 2.5 and 5.0 mg are brought as quickly as possible into a Desicote treated vial containing 17% sucrose and 30 ppm H₃BO₃ in boiled distilled water. The proportion (w/v) of pollen to culture solution should be 1:100. Shed pollen is kept in a humidity chamber whenever it is not being handled. The air in the culture vial is replaced by O₂ at the pressure of 1 atmosphere plus 5 lb and the sealed vials are shaken gently for 8-10 hr while partially immersed in a waterbath kept at 30° C. The pollen is fixed by the addition to the incubation suspension of an absolute alcohol-lactic acid (4:1) fixing fluid. The proportion used is 36 parts of fixing fluid to 1 part of culture solution. The fixed pollen can be stored in the fixative. Smears are prepared by applying single drops of the constantly agitated suspension of fixed pollen to a microscope slide. After each drop has spread out and dried, an additional drop is added until 10-20 have been applied. The preparations are stained by adding a drop of 1% acetic-orcein and are sealed with fingernail lacquer. The method is well adapted to the following types of studies: pollen germination, physiology of pollen tube growth, morphology of the male gametocyte, and physiology and cytology of the generative cell and nucleus.     

Introgressive hybridization of Senecio hercynicus and S. ovatus (Compositae,Senecioneae) along an altitudinal gradient in Harz National Park (Germany)

Introgressive hybridization of Senecio hercynicus and S. ovatus (Compositae, Senecioneae) was studied in a hybrid zone on the southern slopes of Mt Brocken (Harz Mountains, Germany). A total of 415 plants representing 10 stands along an altitudinal gradient were investigated using multivariate statistical analyses of morphological characters and molecular markers (random amplified polymorphic DNA[RAPD]). Both types of traits detected pure S. hercynicus stands on the summit plateau, pure S. ovatus stands at the lowest elevations, and hybrid swarms at intermediate elevations. While morphological and molecular patterns coincided, some individuals in hybrid stands combined morphological patterns typical of S. ovatus with RAPD patterns typical of S. hercynicus, and vice versa. In general, introgression was symmetrical within stands, though one stand combined S. ovatus characters with the glandular hair typical for S. hercynicus, and two stands combined a S. hercynicus typical RAPD genotype with morphological characters shifted towards S. ovatus. Because pure stands of S. hercynicus occurred only on the summit plateau of Mt Brocken, and markers typical for S. ovatus were detectable in stands up to 1040 m a.s.l., future fusion or assimilation of the rare form, S. hercynicus, by the more widespread S. ovatus appears possible at Mt Brocken.     

Synthesis and Evaluation of Pyrrole Polyamide- 2′-Deoxyguanosine 5′-Phosphate Hybrid

Pyrrole polyamide-2′-deoxyguanosine 5′-phosphate hybrid (Hybrid 4) was synthesized and evaluated in terms of the inhibition of mouse mammary carcinoma FM3A cell growth. Hybrid 4 was found to exhibit dose-dependent inhibition of cell growth.     

Nitrification in hybrid bioreactors treating simulated domestic wastewater

Aim

To provide deeper insights into nitrification process within aerobic bioreactors containing supplemental physical support media (hybrid bioreactors).

Methods and Results

Three bench‐scale hybrid bioreactors with different media size and one control bioreactor were operated to assess how biofilm integrity influences microbial community conditions and bioreactor performance. The systems were operated initially at a 5‐day hydraulic retention time (HRT), and all reactors displayed efficient nitrification and chemical oxygen demand (COD) removal (>95%). However, when HRT was reduced to 2·5 days, COD removal rates remained high, but nitrification efficiencies declined in all reactors after 19 days. To explain reduced performance, nitrifying bacterial communities (ammonia‐oxidizing bacteria, AOB; nitrite‐oxidizing bacteria, NOB) were examined in the liquid phase and also on the beads using qPCR, FISH and DGGE. Overall, the presence of the beads in a reactor promoted bacterial abundances and diversity, but as bead size was increased, biofilms with active coupled AOB–NOB activity were less apparent, resulting in incomplete nitrification.

Conclusions

Hybrid bioreactors have potential to sustain effective nitrification at low HRTs, but support media size and configuration type must be optimized to ensure coupled AOB and NOB activity in nitrification.

Significance and Impact of the Study

This study shows that AOB and NOB coupling must be accomplished to minimize nitrification failure.     

Detection of Architectural Distortion in Prior Mammograms via Analysis of Oriented Patterns

We demonstrate methods for the detection of architectural distortion in prior mammograms of interval-cancer cases based on analysis of the orientation of breast tissue patterns in mammograms. We hypothesize that architectural distortion modifies the normal orientation of breast tissue patterns in mammographic images before the formation of masses or tumors. In the initial steps of our methods, the oriented structures in a given mammogram are analyzed using Gabor filters and phase portraits to detect node-like sites of radiating or intersecting tissue patterns. Each detected site is then characterized using the node value, fractal dimension, and a measure of angular dispersion specifically designed to represent spiculating patterns associated with architectural distortion.Our methods were tested with a database of 106 prior mammograms of 56 interval-cancer cases and 52 mammograms of 13 normal cases using the features developed for the characterization of architectural distortion, pattern classification via quadratic discriminant analysis, and validation with the leave-one-patient out procedure. According to the results of free-response receiver operating characteristic analysis, our methods have demonstrated the capability to detect architectural distortion in prior mammograms, taken 15 months (on the average) before clinical diagnosis of breast cancer, with a sensitivity of 80% at about five false positives per patient.     

A Novel High‐Energy Hybrid Supercapacitor with an Anatase TiO2–Reduced Graphene Oxide Anode and an Activated Carbon Cathode

A hybrid supercapacitor with high energy and power densities is reported. It comprises a composite anode of anatase TiO₂ and reduced graphene oxide and an activated carbon cathode in a non‐aqueous electrolyte. While intercalation compounds can provide high energy typically at the expense of power, the anatase TiO₂ nanoparticles are able to sustain both high energy and power in the hybrid supercapacitor. At a voltage range from 1.0 to 3.0 V, 42 W h kg^?1 of energy is achieved at 800 W kg^?1. Even at a 4‐s charge/discharge rate, an energy density as high as 8.9 W h kg^?1 can be retained. The high energy and power of this hybrid supercapacitor bridges the gap between conventional batteries with high energy and low power and supercapacitors with high power and low energy.     

Quantum Dot Based Heterostructures for Unassisted Photoelectrochemical Hydrogen Generation

TiO₂ hollow nanowires (HNWs) and nanoparticles (NPs) constitute promising architectures for QDs sensitized photoanodes for H₂ generation. We sensitize these structures with CdS/CdSe quantum dots by two different methods (chemical bath deposition, CBD and succesive ionic layer adsorption and reaction, SILAR) and evaluate the performance of these photoelectrodes. Remarkable photocurrents of 4 mA·cm and 8 mA·cm^?2 and hydrogen generation rates of 40 ml·cm^?2·day^?1 and 80 ml·cm^?2·day^?1 have been obtained in a three electrode configuration with sacrificial hole scavengers (Na₂S and Na₂SO₃), for HNWs and NPs respectively, which is confirmed through gas analysis. More importantly, autonomous generation of H₂ (20 ml·cm^?2·day^?1 corresponding to 2 mA·cm^?2 photocurrent) is obtained in a two electrode configuration at short circuit under 100 mW·cm^?2 illumination, clearly showing that these photoanodes can produce hydrogen without the assistance of any external bias. To the best of the authors' knowledge, this is the highest unbiased solar H₂ generation rate reported for these of QDs based heterostructures. Impedance spectroscopy measurements show similar electron density of trap states below the TiO₂ conduction band while the recombination resistance was higher for HNWs, consistently with the much lower surface area compared to NPs. However, the conductivity of both structures is similar, in spite of the one dimensional character of HNWs, which leaves some room for improvement of these nanowired structures. The effect of the QDs deposition method is also evaluated. Both structures show remarkable stability without any appreciable photocurrent loss after 0.5 hour of operation. The findings of this study constitute a relevant step towards the feasibility of hydrogen generation with wide bandgap semiconductors/quantum dots based heterostructures.