Biomineralisation by earthworms: an investigation into the stability and distribution of amorphous calcium carbonate

Background Many biominerals form from amorphous calcium carbonate (ACC), but this phase is highly unstable when synthesised in its pure form inorganically. Several species of earthworm secrete calcium carbonate granules which contain highly stable ACC. We analysed the milky fluid from which granules form and solid granules for amino acid (by liquid chromatography) and functional group (by Fourier transform infrared (FTIR) spectroscopy) compositions. Granule elemental composition was determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) and electron microprobe analysis (EMPA). Mass of ACC present in solid granules was quantified using FTIR and compared to granule elemental and amino acid compositions. Bulk analysis of granules was of powdered bulk material. Spatially resolved analysis was of thin sections of granules using synchrotron-based μ-FTIR and EMPA electron microprobe analysis. Results The milky fluid from which granules form is amino acid-rich (≤ 136 ± 3 nmol mg−1 (n = 3; ± std dev) per individual amino acid); the CaCO3 phase present is ACC. Even four years after production, granules contain ACC. No correlation exists between mass of ACC present and granule elemental composition. Granule amino acid concentrations correlate well with ACC content (r ≥ 0.7, p ≤ 0.05) consistent with a role for amino acids (or the proteins they make up) in ACC stabilisation. Intra-granule variation in ACC (RSD = 16%) and amino acid concentration (RSD = 22–35%) was high for granules produced by the same earthworm. Maps of ACC distribution produced using synchrotron-based μ-FTIR mapping of granule thin sections and the relative intensity of the ν2: ν4 peak ratio, cluster analysis and component regression using ACC and calcite standards showed similar spatial distributions of likely ACC-rich and calcite-rich areas. We could not identify organic peaks in the μ-FTIR spectra and thus could not determine whether ACC-rich domains also had relatively high amino acid concentrations. No correlation exists between ACC distribution and elemental concentrations determined by EMPA. Conclusions ACC present in earthworm CaCO3 granules is highly stable. Our results suggest a role for amino acids (or proteins) in this stability. We see no evidence for stabilisation of ACC by incorporation of inorganic components

Microscopic structure of the polymer-induced liquid precursor for calcium carbonate

Many biomineral crystals form complex non-equilibrium shapes, often via transient amorphous precursors. Also in vitro crystals can be grown with non-equilibrium morphologies, such as thin films or nanorods. In many cases this involves charged polymeric additives that form a polymer-induced liquid precursor (PILP). Here, we investigate the CaCO3 based PILP process with a variety of techniques including cryoTEM and NMR. The initial products are 30–50 nm amorphous calcium carbonate (ACC) nanoparticles with ~2 nm nanoparticulate texture. We show the polymers strongly interact with ACC in the early stages, and become excluded during crystallization, with no liquid–liquid phase separation detected during the process. Our results suggest that “PILP” is actually a polymer-driven assembly of ACC clusters, and that its liquid-like behavior at the macroscopic level is due to the small size and surface properties of the assemblies. We propose that a similar biopolymer-stabilized nanogranular phase may be active in biomineralization

Transmutation operators as a solvability concept of abstract singular equations

One of the methods of studying differential equations is the transmutation operators method. Detailed study of the theory of transmutation operators with applications may be found in the literature. Application of transmutation operators establishes many important results for different classes of differential equations including singular equations with Bessel operato

"I feel it is not enough…" Health providers' perspectives on services for victims of intimate partner violence in Malaysia.

BACKGROUND: This study explores the views and attitudes of health providers in Malaysia towards intimate partner violence (IPV) and abused women and considers whether and how their views affect the provision or quality of services. The impact of provider attitudes on the provision of services for women experiencing violence is particularly important to understand since there is a need to ensure that these women are not re-victimised by the health sector, but are treated sensitively. METHODS: In-depth interviews were conducted with 54 health care providers responsible for providing services to survivors of IPV and working in health care facilities in two Northern States in Malaysia. A thematic framework analysis method was employed to analyse the emerging themes. Interviews were coded and managed by using NVIVO (N7), a qualitative software package. RESULTS: We found that when providers follow the traditional role of treating and solving IPV as "medical problem", they tend to focus on the physical aspect of the injury, minimise the underlying cause of the problem and ignore emotional care for patients. Providers frequently felt under-trained and poorly supported in their role to help women beyond merely treating their physical injuries. What emerged from the findings is that time shortages may well impact on the ability of medical officers to identify cases of abuse, with some saying that time limitations made it more difficult to detect the real problem behind the injury. However, data from the interviews seem to suggest that time constraints may or may not end up resulting in limited care, depending on the individual interest of medical professionals on violence issues. CONCLUSIONS: Promoting empathetic health care provision is challenging. More awareness training and sensitisation could help, especially if courses focus on women's needs and strengths and how health providers can validate these and contribute to a longer term process of change for victims of violence. Clear guidance on how to record history of abuse, ask questions sensitively and validate experiences is also important together with training on good communication skills such as listening and being empathetic