Ovarian cycle and scanning electron micrographs of the spawned egg of female mantis shrimp Oratosquilla massavensis (Alexandria, Egypt)

Mantis shrimp Oratosquilla massevensis is an abundant marine crustacean in Egypt. It is common among the most important predators in many shallow, tropical and subtropical marine habitats. It is poorly understood as many species spend most of their life tucked away in burrows and holes. The objective of this study is to provide information on the histological characteristics of the ovary of female mantis shrimp O. massevensis and the morphology of the spawned egg, using scanning electron microscope. The ovaries showed a pronounced macroscopic differentiation in size and color with the maturation of the ovary, in six developmental stages namely: immature stage, previtellogenesis, primary vitellogenesis, secondary vitellogenesis, maturation and spent stage. Staining affinities of different structural components, size of different oocytes and nuclear sizes, as well as the follicular cells and their association with oocytes were used to differentiate between different oocyte developmental stages. Scanning electron micrographs of the spawned egg of O. massavensis revealed spherical forms of the egg with well noticed stalk or funiculus. The chorion is ornamented as a wrinkled layer with different textures. Two different yolky materials or matrices were observed, the first one constitutes a conical shaped hard matrix with glassy appearance, while the second one appears spongy with somewhat soft appearance

Magnetic Graphene Oxide as an Efficient Adsorbent for the Separation and Preconcentration of Cu(II), Pb(II), and Cd(II) from Environmental Samples

The separation and preconcentration of copper(II), lead(II), and cadmium(II) ions on magnetic graphene oxide (MGO) by solid-phase extraction was carried out. Quantitative recovery was obtained by adsorption of analytes on MGO at pH 6 and elution of 3 M HNO3 in 10% acetone. To optimize the presented method, the effects of various parameters-including pH, eluent conditions, and vortex time-were examined. Matrix effects were also investigated. Mean recoveries of the analytes were between 95 and 105%. The proposed method was validated by applying it to certified reference materials. Addition and recovery tests were also performed. The method was applied to verify the analyte content of several water and food samples

In situ XRD and electrochemical investigation on a new intercalation-type anode for high-rate lithium ion capacitor

A new intercalation-type anode material is reported herein to improve the lithium storage kinetics for high-rate lithium ion capacitors. The crystal structure of orthorhombic NaNbO3 indicates two possible tunnels for lithium ions insertion into NaNbO3 host along the and directions. Moreover, in situ XRD is conducted to investigate the lithium storage mechanism and structural evolution of the NaNbO3 anode, demonstrating its intercalation behavior through (101) and (141) planes. Furthermore, the rGO nanosheets are introduced to facilitate the charge transfer, which also effectively prevent the aggregation of NaNbO3 nanocubes. As expected, the NaNbO3/rGO nanocomposites possess remarkable reversible capacity (465 mA h g−1 at 0.1 A g−1), superior rate capability (325 mA h g−1 at 1.0 A g−1) and cycling stability, attributed to their synergistic effect and high Li+ diffusion coefficient DLi [D(NaNbO3/rGO)/D(NaNbO3) ≈ 31.54]. Remarkably, the NaNbO3/rGO-based LIC delivers a high energy density of 166.7 W h kg−1 at 112.4 W kg−1 and remains 24.1 W h kg−1 at an ultrahigh power density of 26621.2 W kg−1, with an outstanding cycling durability (90% retention over 3000 cycles at 1.0 A g−1). This study provides new insights on novel intercalation-type anode material to enrich the materials system of LICs.This work was supported by the Natural Science Foundation of Jiangsu Province (No. BK20170549), the National Natural Science Foundation of China (No. 21706103) and Postdoctoral Science Foundation of Jiangsu Province (No. 2019K295)