The response of coral skeletal nano-structure and hardness to ocean acidification conditions

Funding: Scottish Funding Council - HR09011; UK Natural Environment Research Council - NE/I022973/1.Ocean acidification typically reduces coral calcification rates and can fundamentally alter skeletal morphology. We use atomic force microscopy (AFM) and microindentation to determine how seawater pCO2 affects skeletal structure and Vickers hardness in a Porites lutea coral. At 400 µatm, the skeletal fasciculi are composed of tightly packed bundles of acicular crystals composed of quadrilateral nanograins, approximately 80–300 nm in dimensions. We interpret high adhesion at the nanograin edges as an organic coating. At 750 µatm the crystals are less regular in width and orientation and composed of either smaller/more rounded nanograins than observed at 400 µatm or of larger areas with little variation in adhesion. Coral aragonite may form via ion-by-ion attachment to the existing skeleton or via conversion of amorphous calcium carbonate precursors. Changes in nanoparticle morphology could reflect variations in the sizes of nanoparticles produced by each crystallization pathway or in the contributions of each pathway to biomineralization. We observe no significant variation in Vickers hardness between skeletons cultured at different seawater pCO2. Either the nanograin size does not affect skeletal hardness or the effect is offset by other changes in the skeleton, e.g. increases in skeletal organic material as reported in previous studies.Publisher PDFPeer reviewe

Growth speeds and growth modes of sodium chloride : a quantitative two-dimensional phase-field study

The understanding of crystal growth is beneficial to many different sectors, such as crystal engineering, drug manufacturing and life sciences. This phenomenon can be studied computationally on the molecular level, providing insights into the atomistic interactions of growth particles occurring at the solid-liquid interface. However, a significant amount of effort is often required to reveal information on spatial and temporal scales that are relevant in crystal growth experiments that are (usually) mesoscopic in nature. The Phase-field (PF) approach is a phenomenological model that can simulate, efficiently, the evolution of microstructures on length and time scales that are directly comparable to experiments but not many quantitative studies of precipitation crystal growth using the PF method are reported in the literature. In this study, the precipitation PF model was employed to simulate and investigate, quantitatively, the crystal growth of sodium chloride, NaCl, in supersaturated solutions. More specifically, the accuracy of the model over a wide range of time scales is revealed by comparing the one-dimensional growth speeds of NaCl (simulated over periods of a few milliseconds up to several minutes) with experimental results from the literature. In addition, by simulating two-dimensional growth using circular crystals of different radii, it is shown that the PF model can be used to demonstrate the influence of curvature of a crystal surface on the growth speed. Lastly, by simulating anisotropic crystal growth of NaCl in two dimensions for a range of concentrations, the model predicted the transition from compact to non-compact growth to occur at a supersaturation coefficient of ~1.4, which is in good agreement with experimental observations of NaCl grown in microchannels. The work described in this thesis demonstrates that the PF model can provide information about crystal growth on length and time scales that are not easily accessible with molecular methods

Phase field modelling of crystal growth of NaCl in two dimensions

Modelling crystal growth is important for example in crystal engineering, materials science, and the life sciences. Molecular modelling techniques can provide fundamental insights into the atomic processes underlying crystal growth but do not always give direct information about growth rates and growth modes on spatial and temporal scales relevant in nature and for applications. The phase-field (PF) approach is a relatively simple model that can provide results on length and time scales directly comparable to experiments, but it has not extensively been employed to investigate crystallization of ionic solids, and not many quantitative results have been reported. In the present study we model the growth of cubic NaCl crystals in two dimensions. We have used small crystal seeds with an appropriate anisotropy term to investigate both the growth speed and the growth mode. Results are compared to experimental data from the literature. The PF model displays the concentration dependent transition from compact to non-compact growth of NaCl reasonably well on spatial and temporal scales that are not easily accessible with other theoretical models

Phase field modelling of crystal growth of NaCl in two dimensions

Financial support from the University of St. Andrews under a St Leonard's College Scholarship (CDT) is gratefully acknowledged.Modelling crystal growth is important for example in crystal engineering, materials science, and the life sciences. Molecular modelling techniques can provide fundamental insights into the atomic processes underlying crystal growth but do not always give direct information about growth rates and growth modes on spatial and temporal scales relevant in nature and for applications. The phase-field (PF) approach is a relatively simple model that can provide results on length and time scales directly comparable to experiments, but it has not extensively been employed to investigate crystallization of ionic solids, and not many quantitative results have been reported. In the present study we model the growth of cubic NaCl crystals in two dimensions. We have used small crystal seeds with an appropriate anisotropy term to investigate both the growth speed and the growth mode. Results are compared to experimental data from the literature. The PF model displays the concentration dependent transition from compact to non-compact growth of NaCl reasonably well on spatial and temporal scales that are not easily accessible with other theoretical models.Publisher PDFPeer reviewe

Phase field modelling of crystal growth of NaCl in two dimensions (dataset)

Data set for the publication titled "Phase field modelling of crystal growth of NaCl in two dimensions" in CrystEngComm

Growth Speeds and Growth Modes of Sodium Chloride: a Quantitative Two-Dimensional Phase-Field Study (thesis data)

Research data output from the precipitation Phase-field model simulate during the PhD. The data files are embargoed until 13/04/202

The response of coral skeletal nano-structure and hardness to ocean acidification conditions

Ocean acidification typically reduces coral calcification rates and can fundamentally alter skeletal morphology. We use atomic force microscopy (AFM) and microindentation to determine how seawater pCO2 affects skeletal structure and Vickers hardness in a Porites lutea coral. At 400 µatm, the skeletal fasciculi are composed of tightly packed bundles of acicular crystals composed of quadrilateral nanograins, approximately 80–300 nm in dimensions. We interpret high adhesion at the nanograin edges as an organic coating. At 750 µatm the crystals are less regular in width and orientation and composed of either smaller/more rounded nanograins than observed at 400 µatm or of larger areas with little variation in adhesion. Coral aragonite may form via ion-by-ion attachment to the existing skeleton or via conversion of amorphous calcium carbonate precursors. Changes in nanoparticle morphology could reflect variations in the sizes of nanoparticles produced by each crystallization pathway or in the contributions of each pathway to biomineralization. We observe no significant variation in Vickers hardness between skeletons cultured at different seawater pCO2. Either the nanograin size does not affect skeletal hardness or the effect is offset by other changes in the skeleton, e.g. increases in skeletal organic material as reported in previous studies

Electronic supplementary data from The response of coral skeletal nano structure and hardness to ocean acidification conditions

Raw data for figures 3, 7 and 8. r2 between adhesion and either sample height or roughness in Figures 5 and 6. Images of sample indents

Melatonin Promotes Superovulation in Sika Deer (Cervus nippon)

In this study, the effects of melatonin (MT) on superovulation and reproductive hormones (melatonin, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and PRL) were investigated in female sika deer. Different doses (40 or 80 mg/animal) of melatonin were subcutaneously implanted into deer before the breeding season. Exogenous melatonin administration significantly elevated the serum FSH levels at the time of insemination compared with levels in control animals. During superovulation, the serum LH levels in donor sika deer reached their highest values (7.1 ± 2.04 ng/mL) at the point of insemination, compared with the baseline levels (4.98 ± 0.07 ng/mL) in control animals. This high level of LH was sustained until the day of embryo recovery. In contrast, the serum levels of PRL in the 80 mg of melatonin-treated group were significantly lower than those of control deer. The average number of corpora lutea in melatonin-treated deer was significantly higher than that of the control (p < 0.05). The average number of embryos in the deer treated with 40 mg of melatonin was higher than that of the control; however, this increase did not reach significant difference (p > 0.05), which may be related to the relatively small sample size. In addition, embryonic development in melatonin-treated groups was delayed