High-Magnesium Calcite Mesocrystals: Formation in Aqueous Solution under Ambient Conditions.

Mesocrystals of high-magnesian calcites are commonly found in biogenic calcites. Under ambient conditions, it remains challenging to prepare mesocrystals of high-magnesian calcite in aqueous solution. We report that mesocrystals of calcite with magnesium content of about 20 mol % can be obtained from the phase transformation of magnesian amorphous calcium carbonate (Mg-ACC) in lipid solution. The limited water content on the Mg-ACC surface would reduce the extent of the dissolution-reprecipitation process and bias the phase transformation pathway toward solid-state reaction. We infer from the selected area electron diffraction patterns and the dark-field transmission electron microscopic images that the formation of Mg-calcite mesocrystals occurs through solid-state secondary nucleation, for which the phase transformation is initiated near the mineral surface and the crystalline phase propagates gradually toward the interior part of the microspheres of Mg-ACC.

Development of a water refractive index-matched microneedle integrated into a light sheet microscopy system for continuous embryonic cell imaging.

In this study, microneedle-integrated light sheet microscopy (LSM) was developed for trapping and continuously imaging embryos of Caenorhabditis elegans with subcellular resolution. To reduce aberrations when the light sheet was propagated into the device, a microneedle was fabricated using a transparent, water refractive index-matched polymer. It was proven that when the light sheet emerged from the water-immersed objective and penetrated through the microneedle with a circular surface, even with a non-perpendicular incident angle, fewer aberrations were found. An embryo was injected into and trapped at the tip of the microneedle, which was positioned at the interrogation window of the LSM apparatus with the image plane perpendicular to the light sheet, and this setup was used to sequentially acquire embryo images. By applying the light sheet, higher-resolution, higher-contrast images were obtained. The system also showed low photobleaching and low phototoxicity to embryos of C. elegans. Furthermore, three-dimensional embryo images with a whole field of view of the microneedle could be achieved by stitching together images and reconstructing sequential two-dimensional embryo images.

Occurrence of thermally induced glycidyl esters and 3-monochloropropane-1,2-diol esters in refined oils and pressed oils manufactured by different processes and associated with human health risks in Taiwan.

Glycidyl esters (GEs) and 3-monochloropropane-1,2-diol esters (3-MCPDEs) are heat-induced contaminants mainly formed during oil refining. Information on the occurrence of these contaminants in pressed oils is still limited. In this study, 16 oilseeds pressed with a screw press and a hydraulic press had extremely low concentrations of GEs and 3-MCPDEs. Seed-roasting at high temperatures was the principal factor that significantly increased contents of GEs and 3-MCPDEs in pressed oils, in which higher precursor levels were observed. Occurrence data of GE and 3-MCPDE concentrations in refined oils (n = 25) and pressed oils (n = 26) marketed in Taiwan showed that hot-pressed oils had higher concentrations than their cold-pressed counterparts, and average concentrations of refined oils were > 10-fold higher than those of pressed oils. Risk assessment using the margin of exposure (MOE) approach indicated the presence of GEs in edible oils was of concern for food safety, especially for people who frequently use refined oils.

Application of OXITEST for Prediction of Shelf-Lives of Selected Cold-Pressed Oils.

Introduction: Due to the enhanced awareness of consumers concerning healthy foods, homemade expeller-pressed oils have become popular worldwide. However, an extended storage period may lead to oxidization of the oil and exposure to hazardous byproducts by consumers. Methods: In this study, 10 pressed oil samples prepared from common oilseeds using a small-scale expeller oil press were analyzed by OXITEST with a sample amount of 5 g of oil and an oxygen pressure of 800 kPa under accelerated conditions for shelf-life projections. The oil properties were investigated, including the recovery, smoke point, acid value, iodine value, "fatty acid composition, and contents of pigments and tocopherols". Results: The autoxidation reaction of various expeller-pressed oils under an accelerated testing system followed zero-order Arrhenius kinetics (R 2 > 0.99). Shelf-lives of the pressed oils at 25°C were estimated by extrapolation to range 105~1,089 days. The obtained shelf-lives were significantly correlated with log induction period (IP) values (r > 0.81, p < 0.05) and unsaturated fatty acids (UFAs) (r < -0.69, p < 0.05), but not with the iodine value, acid value, or smoke point. Scatter diagrams between shelf-lives and UFAs suggested that these pressed oils could be grouped by two linear regression curves (r > 0.98, p < 0.05). The predictive equations using multiple linear regression are presented herein, with predictor variables of UFAs and an unspecified item involving potential influencing factors such as tocopherol contents (r > 0.88, p < 0.05). Conclusions: Our findings first revealed that the UFA portion was partially correlated with the shelf-lives of selected expeller-pressed seed oils as estimated by the OXITEST. The derived equations can be applied for shelf-life predictions of expeller-pressed oils stored under dark ambient conditions based on the fatty acid profile.

Macro Photography with Lightsheet Illumination Enables Whole Expanded Brain Imaging with Single-cell Resolution.

Macro photography allows direct visualization of the enlarged whole mouse brain by a combination of lightsheet illumination and expansion microscopy with single-cell resolution.  Taking advantage of the long working distance of a camera lens, we imaged a 3.7 cm thick, transparent, fluorescently-labeled expanded brain. In order to improve 3D sectioning capability, we used lightsheet excitation confined as the depth of field of the camera lens. Using 4x sample expansion and 5x optical magnification, macro photography enables imaging of expanded whole mouse brain with an effective resolution of 300 nm, which provides the subcellular structural information at the organ level.

Formation of nano-magnesite in the calcareous spicules prepared under ambient conditions.

We report that high-Mg calcite spherulites can undergo a coarsening process to form calcareous spicules of ∼30 microns in width and several hundred microns in length after an aging process in air for a prolonged period. During the aging process, the crystallinity of the calcitic structure has been improved substantially with a significant migration of Mg ions toward the mineral surface. In a thin-foil sample of the spicule aged for 20 months, nanocrystallites of magnesite with minor substitution level of Ca ions have been found near the surface of the spicule.

Anhydrous amorphous calcium carbonate (ACC) is structurally different from the transient phase of biogenic ACC.

Amorphous calcium carbonate (ACC) is an important precursor phase of biogenic calcite. In this work, an in situ Ca L-edge X-ray absorption spectroscopic study has been carried out to monitor the phase transformation process of hydrated ACC from room temperature to 773 K in the presence of water vapor pressure at 0.4 mbar. The L2,3 crystal field splittings of the near edge X-ray absorption fine structure (NEXAFS) spectra acquired for hydrated and anhydrous ACC are indistinguishable. The transformation process from anhydrous ACC to calcite is greatly facilitated by the presence of water moisture. Our data acquired for nano-calcite are in close resemblance to those reported for "type 2" ACC in sea urchin larval spicules. We suggest that "type 2 ACC" or the "transient phase of ACC" is a disordered calcium carbonate phase with a nascent calcitic structure at the nanometer length scale.

Preparation and Structural Characterization of Free-Standing Octacalcium-Phosphate-Rich Thin Films.

Free-standing films of calcium phosphates exhibit many favorable properties for tissue engineering. In this work, a thin film of calcium phosphate is prepared in a liposome suspension using the method of ammonia gas diffusion. The thickness of the film is about 10 µm, and the lateral dimensions are on the length scale of millimeter. The results of powder X-ray diffraction and transmission electron microscopy show that the thin films contain the mineral phases of hydroxyapatite and octacalcium phosphate (OCP). Using solid-state NMR spectroscopy, in particular the technique of heteronuclear correlation spectroscopy with variable contact time, the major crystalline phase of the thin film has been confirmed to be OCP.