Demetra Schermerhorn | University of North Carolina at Chapel Hill (original) (raw)

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Papers by Demetra Schermerhorn

Background: Both mood and anxiety disorders are more prevalent in women than men with the onset t... more Background: Both mood and anxiety disorders are more prevalent in women than men with the onset typically occurring during adolescence or early childbearing years. These disorders are particularly prevalent during pregnancy and the postpartum period. While depression during the perinatal period has received significant attention recently, anxiety has not received the same amount of attention. Methods: The current study was a secondary analysis of a prospective cohort study that followed 91 women with mood disorders through pregnancy and the postpartum period. Our objective was to determine if a correlation existed between anxiety and suicidality. We hypothesized that pregnant women with a history of a mood disorder and comorbid anxiety are more likely to be suicidal than those without comorbid anxiety. The presence of anxiety was determined using the anxiety subscale of the Edinburgh Postnatal Depression Scale, EPDS; a cut off score of six or greater was used to indicate significant...

Mineralogical Magazine, 2015

ABSTRACT Carbonated strontium fluor-, hydroxyl- and chlorapatites (carbonated Sr10(PO4)6X2 = CSrA... more ABSTRACT Carbonated strontium fluor-, hydroxyl- and chlorapatites (carbonated Sr10(PO4)6X2 = CSrApX, where X= OH, Cl and F) were synthesized in aqueous solution. The substitution mode of carbonate was determined from infrared (IR) stretching frequencies for carbonate and from the variation in unit-cell axial lengths as a function of carbonate content. The a-axis lengths of CSrApF and CSrApCl decrease, whereas the a-axis length of CSrApOH increases slightly with increasing carbonate substitution. The carbonate IR stretching region from ∼1390 to 1590 cm–1 contains two doublets for both CSrApOH and CSrApCl, indicating the presence of both A- and B-type carbonate. The carbonate spectral region for CSrApF is reminiscent of that for CCaApF, which contains one doublet for B-type carbonate with a small shoulder attributable to A-type carbonate. Activity-based K sp values (assuming B-type substitution) were determined for all three series of carbonated Sr apatites and show that the solubilities of CSrApOH and CSrApCl increase at higher carbonate values, whereas those of CSrApF stay constant. The K sp values for uncarbonated SrApOH, SrApCl and SrApF were determined by extrapolation to zero percent carbonate (10–120, 10–112 and 10–113 for SrApOH, SrApCl and SrApF, respectively).

American Mineralogist, 2014

ABSTRACT Confirmation of structural H2O in apatites using 2H solid state NMR spectroscopy has bee... more ABSTRACT Confirmation of structural H2O in apatites using 2H solid state NMR spectroscopy has been followed by the determination of the number of molecules of H2O per unit cell (MPUC) using thermal gravimetric analysis (TGA) in 10 series of carbonated apatites [CMApX; M10(PO4)6X2 = MApX] containing the divalent cations (M) calcium, strontium, barium, and lead, and monovalent anions (X) OH−, F−, and Cl−. For many of the series, the average MPUC ranges from ca. 1.5-2.5 and is independent of the concentration (wt%) of carbonate. For other series, the average MPUC is as low as ca. 0.8 or as high as ca. 4.0. We have found for six of the series, i.e., those in which carbonate predominantly (>90%) substitutes for phosphate that the average MPUC correlates with cation and anion atomic radii, with unit-cell axial lengths, and, especially, with our calculations of the void space available in the c-axis channels. We speculate that the volume of the channels in apatites affects the ability of H2O to occupy channel sites. In most low-temperature apatites of the type M10(PO4)6X2 that have been studied, carbonate prefers to substitute for phosphate (B-type substitution) rather than for monovalent anions in channel sites (A-type substitution), although computer simulations indicate that carbonate is more thermodynamically stable in the channel sites rather than the phosphate sites. In apatites with nearly total B-type carbonate substitution, there is no relationship between the number of molecules of H2O in the channels and the weight percent carbonate in the apatite. This lack of correlation would be expected when there is no competition within the channel between H2O and carbonate occupancy. In apatites with greater channel volumes, however, we infer that increased ease of carbonate incorporation in the channels also increases competition between H2O and carbonate. The originally incorporated amount of H2O is diminished to accommodate the thermodynamically favored carbonate ion substitution in the channels. We further speculate that these scenarios are most easily rationalized by incorporation of H2O early in the formation of nascent crystallites of apatites formed in aqueous solution, with carbonate entering the newly formed channels later and, in some cases, with difficulty.

Calcified Tissue International, 2012

Water is well recognized as an important component in bone, typically regarded as a constituent o... more Water is well recognized as an important component in bone, typically regarded as a constituent of collagen, a pore-filling fluid in bone, and an adsorbed species on the surface of bone crystallites. The possible siting and role of water within the structure of the apatite crystallites have not been fully explored. In our experiments, carbonated hydroxyl- and fluorapatites were prepared in D(2)O and characterized by elemental analysis, thermal gravimetric analysis, powder X-ray diffraction, and infrared and Raman spectroscopy. Two hydroxylapatites and two fluorapatites, with widely different amounts of carbonate were analyzed by solid state (2)H NMR spectroscopy using the quadrupole echo pulse sequence, and each spectrum showed one single line as well as a low-intensity powder pattern. The relaxation time of 7.1 ms for 5.9 wt% carbonated hydroxylapatite indicates that the single line is likely due to rapid, high-symmetry jumps in translationally rigid D(2)O molecules, indicative of structural incorporation within the lattice. Discrimination between structurally incorporated and adsorbed water is enhanced by the rapid exchange of surface D(2)O with atmospheric H(2)O. Moreover, a (2)H resonance was observed for samples dried under a variety of conditions, including in vacuo heating to 150°C. In contrast, a sample heated to 500°C produced no deuterium resonance, indicating that structural water had been released by that temperature. We propose that water is located in the c-axis channels. Because structural water is observed even for apatites with very low carbonate content, some of the water molecules must lie between the monovalent ions.

Background: Both mood and anxiety disorders are more prevalent in women than men with the onset t... more Background: Both mood and anxiety disorders are more prevalent in women than men with the onset typically occurring during adolescence or early childbearing years. These disorders are particularly prevalent during pregnancy and the postpartum period. While depression during the perinatal period has received significant attention recently, anxiety has not received the same amount of attention. Methods: The current study was a secondary analysis of a prospective cohort study that followed 91 women with mood disorders through pregnancy and the postpartum period. Our objective was to determine if a correlation existed between anxiety and suicidality. We hypothesized that pregnant women with a history of a mood disorder and comorbid anxiety are more likely to be suicidal than those without comorbid anxiety. The presence of anxiety was determined using the anxiety subscale of the Edinburgh Postnatal Depression Scale, EPDS; a cut off score of six or greater was used to indicate significant...

Mineralogical Magazine, 2015

ABSTRACT Carbonated strontium fluor-, hydroxyl- and chlorapatites (carbonated Sr10(PO4)6X2 = CSrA... more ABSTRACT Carbonated strontium fluor-, hydroxyl- and chlorapatites (carbonated Sr10(PO4)6X2 = CSrApX, where X= OH, Cl and F) were synthesized in aqueous solution. The substitution mode of carbonate was determined from infrared (IR) stretching frequencies for carbonate and from the variation in unit-cell axial lengths as a function of carbonate content. The a-axis lengths of CSrApF and CSrApCl decrease, whereas the a-axis length of CSrApOH increases slightly with increasing carbonate substitution. The carbonate IR stretching region from ∼1390 to 1590 cm–1 contains two doublets for both CSrApOH and CSrApCl, indicating the presence of both A- and B-type carbonate. The carbonate spectral region for CSrApF is reminiscent of that for CCaApF, which contains one doublet for B-type carbonate with a small shoulder attributable to A-type carbonate. Activity-based K sp values (assuming B-type substitution) were determined for all three series of carbonated Sr apatites and show that the solubilities of CSrApOH and CSrApCl increase at higher carbonate values, whereas those of CSrApF stay constant. The K sp values for uncarbonated SrApOH, SrApCl and SrApF were determined by extrapolation to zero percent carbonate (10–120, 10–112 and 10–113 for SrApOH, SrApCl and SrApF, respectively).

American Mineralogist, 2014

ABSTRACT Confirmation of structural H2O in apatites using 2H solid state NMR spectroscopy has bee... more ABSTRACT Confirmation of structural H2O in apatites using 2H solid state NMR spectroscopy has been followed by the determination of the number of molecules of H2O per unit cell (MPUC) using thermal gravimetric analysis (TGA) in 10 series of carbonated apatites [CMApX; M10(PO4)6X2 = MApX] containing the divalent cations (M) calcium, strontium, barium, and lead, and monovalent anions (X) OH−, F−, and Cl−. For many of the series, the average MPUC ranges from ca. 1.5-2.5 and is independent of the concentration (wt%) of carbonate. For other series, the average MPUC is as low as ca. 0.8 or as high as ca. 4.0. We have found for six of the series, i.e., those in which carbonate predominantly (>90%) substitutes for phosphate that the average MPUC correlates with cation and anion atomic radii, with unit-cell axial lengths, and, especially, with our calculations of the void space available in the c-axis channels. We speculate that the volume of the channels in apatites affects the ability of H2O to occupy channel sites. In most low-temperature apatites of the type M10(PO4)6X2 that have been studied, carbonate prefers to substitute for phosphate (B-type substitution) rather than for monovalent anions in channel sites (A-type substitution), although computer simulations indicate that carbonate is more thermodynamically stable in the channel sites rather than the phosphate sites. In apatites with nearly total B-type carbonate substitution, there is no relationship between the number of molecules of H2O in the channels and the weight percent carbonate in the apatite. This lack of correlation would be expected when there is no competition within the channel between H2O and carbonate occupancy. In apatites with greater channel volumes, however, we infer that increased ease of carbonate incorporation in the channels also increases competition between H2O and carbonate. The originally incorporated amount of H2O is diminished to accommodate the thermodynamically favored carbonate ion substitution in the channels. We further speculate that these scenarios are most easily rationalized by incorporation of H2O early in the formation of nascent crystallites of apatites formed in aqueous solution, with carbonate entering the newly formed channels later and, in some cases, with difficulty.

Calcified Tissue International, 2012

Water is well recognized as an important component in bone, typically regarded as a constituent o... more Water is well recognized as an important component in bone, typically regarded as a constituent of collagen, a pore-filling fluid in bone, and an adsorbed species on the surface of bone crystallites. The possible siting and role of water within the structure of the apatite crystallites have not been fully explored. In our experiments, carbonated hydroxyl- and fluorapatites were prepared in D(2)O and characterized by elemental analysis, thermal gravimetric analysis, powder X-ray diffraction, and infrared and Raman spectroscopy. Two hydroxylapatites and two fluorapatites, with widely different amounts of carbonate were analyzed by solid state (2)H NMR spectroscopy using the quadrupole echo pulse sequence, and each spectrum showed one single line as well as a low-intensity powder pattern. The relaxation time of 7.1 ms for 5.9 wt% carbonated hydroxylapatite indicates that the single line is likely due to rapid, high-symmetry jumps in translationally rigid D(2)O molecules, indicative of structural incorporation within the lattice. Discrimination between structurally incorporated and adsorbed water is enhanced by the rapid exchange of surface D(2)O with atmospheric H(2)O. Moreover, a (2)H resonance was observed for samples dried under a variety of conditions, including in vacuo heating to 150°C. In contrast, a sample heated to 500°C produced no deuterium resonance, indicating that structural water had been released by that temperature. We propose that water is located in the c-axis channels. Because structural water is observed even for apatites with very low carbonate content, some of the water molecules must lie between the monovalent ions.