CD correlation of C-2′substituted monocyclic carotenoids

The scope and limitation of circular dichroism (CD) correlations of several C-2′ substituted monocyclic monochiral, homodichiral and heterodichiral carotenoids have been investigated, aiming at the assignment of absolute configuration at C-2′ by using the diester and 2′-β-d-tetraacetylglucosyl derivative of (2′R)-plectaniaxanthin and a synthetic chiral C₄₅-carotene as key references. The correlations are based on the additivity hypothesis, the conformational rule and a comparison of CD spectra, preferably conservative ones. Quantitative aspects of the conformational rule are considered. Substituent effects at C-2′ and C-1′ have been studied. Absolute configurations are suggested for (2′)-phleixanthophyll (3S,2′S)-2′-hydroxyflexixanthin, (3R,2′S)-myxoxanthophyll, (3S,2′S-4-ketomyxoxanthophyll (3R,2′S)-myxol-2′-O-methyl methylpentoside and (2R,2′S)-Cp. 473 from relevant CD correlations. The chiralities of (2′S)-4-ketophleixanthophyll and (2R,6R,2′S)-A.g. 471 are suggested from biogenetic considerations. A chemosystematic consideration of chirality and source is included.     

应用原生动物群落评价石油废水对燕山区水系的影响

北京燕山地区的水系——周口店河、东沙河、丁家洼河、西沙河、大石河中游受到石油废水和生活污水的影响。作者在5条河流同步采用载玻片法、PFu(Polyurethane Foam Unit)法和传统的浮游生物沉淀法收集原生动物群落。对群落的种类组成、多样性指数、群集过程(Seq、G、T90％)等参数进行了测定。3种方法都能监测出周口店河有严重的毒性效应,载玻片法和PFU法能监测出含石油的废水在东沙河逐渐净化的过程,PFU法能最终判断出西沙河的有机污染比丁家洼河大。因此这5条河流的污染程度是依大石河、丁家洼河、西沙河、东沙河、周口店河的次序而递增。周口店河上游站因含强酸、强碱的废水引起的毒性已迫使原生动物无法生存。由于东沙河的汇入,大石河的中游地段优势种出现以自养性向异养性转化、丰度增加、多样性指数下降的富营养化现象,对北拒马河亦有潜在的压迫。     

Avian predation upon a mixed community of common voles (Microtus arvalis) and wood mice (Apodemus sylvaticus)

Summary Pellets of diurnal avian predators (mainly kestrels and buzzards) were analysed to prove the hypothesis of selective predation for a mixed population of small rodents. It was found that voles heavily predominated as prey over mice (up to a factor of 19 during winter). Within both prey species, predation focussed on distinct parts of the populations: during winter the heaviest specimens were preferentially captured, during summer the subadults were in an exposed position. In the voles, an additional predominance of males occurred (up to a factor of 5.2 during summer). These findings verify the assumption of Errington (1956) that speciments of a low social rank are susceptible to the highest risk of predation.     

A Microcomputer Program for Evaluating Sampling Error: an Application to Stereological Methods for Electron Microscopy

In situations where there is a need to minimize sampling error or sample size, the coefficient of variation (CV) may be used to evaluate sampling error as a function of the number of observations or subjects in a sample. For example, CV is useful for estimating the minimum number of electron micrographs (N_min) required to obtain a representative field sample for stereological analysis. To facilitate the determination of N_min, we have written a program (COEFficient) for DOS microcomputers which calculates CVs. COEF assists the user in reducing error to that which solely reflects biological variability, thereby minimizing the time and cost of subsequent analyses.     

Alternative partitioning of the genotype-by-environment interaction

Summary Alternative methods for partitioning the genotype-by-environment interaction, for an arbitrary number of genotypes or environments, were examined. Partitioning of the interaction is important in order to determine the nature of the interaction. Two methods of partitioning were examined; both separated the interaction into two types: (1) due to heterogeneous variances or (2) due to imperfect correlations. Method 1 was based on heterogeneity among environments in the scaling of differences among genotypes. Method 2 was based on heterogeneity among genotypes in the scaling of differences among environments. Any remaining interaction arises from deviations from the perfect positive correlation of genotypic rankings among environments (Method 1) or of environmental rankings among genotypes (Method 2). Method 1 is more appropriate for random genotypes that are to be tested in either fixed or random environments. With Method 1, the interactions that arise mainly from heterogeneity of genotypic scaling among environments are generally unimportant. However, if environments are fixed and interactions are mainly due to imperfect correlations of rankings, specialized lines may be indicated for each environment. Method 2 is more useful in evaluating fixed genotypes for sensitivity to random environments. A partitioning of the interaction into that due to the type of interaction within each genotype was shown to be useful in that situation.Journal Paper No. 123737 of the Purdue University Agricultural Experiment Station     

Application of photon correlation spectroscopy as a technique for detecting culture contamination

The application of photon correlation spectroscopy (PCS) to detect culture contamination in chemostats was studied. It was found that the presence of a given particle size in a population of particles of a different size could be detected, but this ability was strongly dependent on particles of a different size could be detected, but this ability was strongly dependent on particle size difference and was most sensitive when contaminants are larger than the host. The inherent polydisparity of actively growing and dividing microbial cells negates any advantage in the use of multi-angle PCS to detect contaminants.     

测定叶片蒸腾系数的封闭系统

光合测定系统内附装一控制定温的定量吸湿装置,使这系统在测定叶片光合(或呼吸)过程中,湿度保持恒定,可以测得蒸腾量及蒸腾速率,从而得到蒸腾系数。文中还介绍CO_2的标定方法。     

Joint species distribution modelling for spatio‐temporal occurrence and ordinal abundance data

Aim

Species distribution models are important tools used to study the distribution and abundance of organisms relative to abiotic variables. Dynamic local interactions among species in a community can affect abundance. The abundance of a single species may not be at equilibrium with the environment for spreading invasive species and species that are range shifting because of climate change. Innovation : We develop methods for incorporating temporal processes into a spatial joint species distribution model for presence/absence and ordinal abundance data. We model non‐equilibrium conditions via a temporal random effect and temporal dynamics with a vector‐autoregressive process allowing for intra‐ and interspecific dependence between co‐occurring species. The autoregressive term captures how the abundance of each species can enhance or inhibit its own subsequent abundance or the subsequent abundance of other species in the community and is well suited for a ‘community modules’ approach of strongly interacting species within a food web. R code is provided for fitting multispecies models within a Bayesian framework for ordinal data with any number of locations, time points, covariates and ordinal categories.

Main conclusions

We model ordinal abundance data of two invasive insects (hemlock woolly adelgid and elongate hemlock scale) that share a host tree and were undergoing northwards range expansion in the eastern U.S.A. during the period 1997–2011. Accounting for range expansion and high inter‐annual variability in abundance led to improved estimation of the species–environment relationships. We would have erroneously concluded that winter temperatures did not affect scale abundance had we not accounted for the range expansion of scale. The autoregressive component revealed weak evidence for commensalism, in which adelgid may have predisposed hemlock stands for subsequent infestation by scale. Residual spatial dependence indicated that an unmeasured variable additionally affected scale abundance. Our robust modelling approach could provide similar insights for other community modules of co‐occurring species.     

Insights into the helix‐sense inversion of poly(β‐phenethyl‐L‐aspartate) by two‐dimensional Raman correlation spectroscopy

In this study, the transition process of the helix‐sense inversion of poly(β‐phenethyl‐L‐aspartate) was investigated by Raman scattering and 2‐dimensional correlation spectroscopy. Temperature‐dependent Raman spectra were obtained during the helix‐sense inversion. The results of 2‐dimensional correlation analysis in the spectral regions of 1600‐1800 and 3200‐3400 cm^?1 showed that the intensity changes of the side‐chain ester C═O stretching bands occurred prior to those of amide A and amide I bands in the unwinding process of αR‐helix on heating. The sequential order of the intensity changes for amide A, amide I, and the side‐chain ester C═O stretching bands during the inversion process was determined. It was found that the conformation change of the side chain occurred prior to that of the main chain for the αR‐helix on heating. Thus, we concluded that the transformation of the backbone chain from right‐handed to left‐handed is triggered by the conformational change of the side chains.     

Observation of Pseudocapacitive Effect and Fast Ion Diffusion in Bimetallic Sulfides as an Advanced Sodium‐Ion Battery Anode

Sodium‐ion batteries (SIBs) are promising next‐generation alternatives due to the low cost and abundance of sodium sources. Yet developmental electrodes in SIBs such as transition metal sulfides have huge volume expansion, sluggish Na⁺ diffusion kinetics, and poor electrical conductivity. Here bimetallic sulfide (Co₉S₈/ZnS) nanocrystals embedded in hollow nitrogen‐doped carbon nanosheets are demonstrated with a high sodium diffusion coefficient, pseudocapacitive effect, and excellent reversibility. Such a unique composite structure is designed and synthesized via a facile sulfidation of the CoZn‐MOFs followed by calcination and is highly dependant on the reaction time and temperature. The optimized Co₁Zn₁‐S(600) electrode exhibits excellent sodium storage performance, including a high capacity of 542 mA h g^?1 at 0.1 A g^?1, good rate capability at 10 A g^?1, and excellent cyclic stability up to 500 cycles for half‐cell. It also shows potential in full‐cell configuration. Such capabilities will accelerate the adoption of sodium‐ion batteries for electrical energy applications.