Herein, the authors demonstrate a heterostructured NiFe LDH-NS@DG10 hybrid catalyst by coupling of exfoliated Ni-Fe layered double hydroxide (LDH) nanosheet (NS) and defective graphene (DG). The catalyst has exhibited extremely high electrocatalytic activity for oxygen evolution reaction (OER) in an alkaline solution with an overpotential of 0.21 V at a current density of 10 mA cm , which is comparable to the current record (≈0.20 V in Fe-Co-Ni metal-oxide-film system) and superior to all other non-noble metal catalysts. Also, it possesses outstanding kinetics (Tafel slope of 52 mV dec ) for the reaction. Interestingly, the NiFe LDH-NS@DG10 hybrid has also exhibited the high hydrogen evolution reaction (HER) performance in an alkaline solution (with an overpotential of 115 mV by 2 mg cm loading at a current density of 20 mA cm ) in contrast to barely HER activity for NiFe LDH-NS itself. As a result, the bifunctional catalyst the authors developed can achieve a current density of 20 mA cm by a voltage of only 1.5 V, which is also a record for the overall water splitting. Density functional theory calculation reveals that the synergetic effects of highly exposed 3d transition metal atoms and carbon defects are essential for the bifunctional activity for OER and HER.

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Lead‐based perovskite light‐emitting diodes (PeLEDs) have exhibited excellent purity, high efficiency, and good brightness. In order to develop nontoxic, highly luminescent metal halide perovskite materials, tin, copper, germanium, zinc, bismuth, and other lead‐free perovskites have been developed. Here, a novel 0D manganese‐based (Mn‐based) organic–inorganic hybrid perovskite with the red emission located at 629 nm, high photoluminescence quantum yield of 80%, and millisecond level triplet lifetime is reported. When applied as the emissive layer in the PeLEDs, the maximum recording brightness of devices after optimization is 4700 cd m−2, and the peak external quantum efficiency is 9.8%. The half‐life of the device reaches 5.5 h at 5 V. The performance and stability of Mn‐based PeLEDs are one order of magnitude higher than those of other lead‐free PeLEDs. This work clearly shows that the Mn‐based perovskite will provide another route to fabricate stable and high‐performance lead‐free PeLEDs.

The distributions of coalescence times and ancestral lineage numbers play an essential role in coalescent modeling and ancestral inference. Both exact distributions of coalescence times and ancestral lineage numbers are expressed as the sum of alternating series, and the terms in the series become numerically intractable for large samples. More computationally attractive are their asymptotic distributions, which were derived in Griffiths (1984) for populations with constant size. In this article, we derive the asymptotic distributions of coalescence times and ancestral lineage numbers for populations with temporally varying size. For a sample of size n, denote by T m the mth coalescent time, when m + 1 lineages coalesce into m lineages, and A n (t) the number of ancestral lineages at time t back from the current generation. Similar to the results in Griffiths (1984), the number of ancestral lineages, A n (t), and the coalescence times, T m , are asymptotically normal, with the mean and variance of these distributions depending on the population size function, N(t). At the very early stage of the coalescent, when t / 0, the number of coalesced lineages n 2 A n (t) follows a Poisson distribution, and as m / n, nðn 2 1ÞT m =2Nð0Þ follows a gamma distribution. We demonstrate the accuracy of the asymptotic approximations by comparing to both exact distributions and coalescent simulations. Several applications of the theoretical results are also shown: deriving statistics related to the properties of gene genealogies, such as the time to the most recent common ancestor (TMRCA) and the total branch length (TBL) of the genealogy, and deriving the allele frequency spectrum for large genealogies. With the advent of genomic-level sequencing data for large samples, the asymptotic distributions are expected to have wide applications in theoretical and methodological development for population genetic inference. COALESCENT theory provides a fundamental framework for stochastic modeling and likelihood inference in population genetic studies (Griffiths 1980;Kingman 1982a;Hudson 1990;Nordborg 2001). A coalescent process can be decomposed into two independent processes: the topology of the gene genealogy and the sequential process of intercoalescence times (Kingman 1982a). In this article, we aim to investigate the latter process and two important random quantities associated with this process: the coalescence times and the number of ancestral lineages (Kingman 1982a). Studying the two quantities is both biologically and theoretically meaningful. First, inferring the coalescence times and the number of ancient lineages of a contemporary sample or population helps to elucidate ancient demographic history, including population admixture, migration, and founder effect. It can also provide insights into medical studies regarding the origin and genetic architecture of inherited diseases in different populations, as well as to ecological studies, for example, on investigating the process of species invasion (Risch et al. 2003;...

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Crystalline/ionic liquid crystalline block copolymers (BCPs) with various compositions have been successfully prepared by sequential reactions. The effect of corona liquid crystalline order on self-assembly of BCPs in selective solvent is investigated in detail. It is found that two-dimensional single crystals with well-developed shapes are formed when the liquid crystalline order is present. By contrast, ill-developed platelets with small size or one-dimensional worm-like micelles are assembled if the liquid crystalline order of the corona segments is lost. It is speculated that the preferred parallel arrangement of liquid crystalline block enables it to expose more growth front of crystals. Accordingly, epitaxial crystallization will proceed readily, leading to fabrication of the well-defined single crystals.

BackgroundLife expectancy at birth (LE) is a comprehensive measure that accounts for age-specific death rates in a population. Shanghai has ranked first in LE in China mainland for decades. Understanding the reasons behind its sustained gain in LE provides a good reflection of many other cities in China. The aim of this study is intended to explore temporal trend in age- and cause-specific gains in LE in Shanghai and the probable reasons lay behind.MethodsJoinpoint regression was applied to evaluate temporal trend in LE and the long time span was then divided accordingly. Contributions to change in LE (1973–2015) were decomposed by age and cause at corresponding periods.ResultsLE in Shanghai could be divided into four phases ie., descent (1973–1976), recovery (1976–1998), rapid rise (1998–2004) and slow rise (2004–2015). The growing LE was mainly attributed to reductions in mortality from the elderly populations and chronic diseases such as cerebrovascular disease, chronic lower respiratory disease, and gastrointestinal cancers (stomach, liver and esophageal cancer).ConclusionsThe four-decade sustained gain in LE in Shanghai is due to the reductions in mortality from the elderly and chronic diseases such as cerebrovascular disease, chronic lower respiratory disease, and gastrointestinal cancers. Further growth momentum still comes from the elderly population.Electronic supplementary materialThe online version of this article (10.1186/s12889-018-5112-7) contains supplementary material, which is available to authorized users.