Children's Perspectives on Food Allergy in Schools: A Qualitative Study.

Approximately 7% of children live with food allergy, a condition that requires dietary avoidance to prevent an allergic reaction. In this qualitative study, we aimed to understand food allergy-related experiences, beliefs and learning preferences among children with and without food allergies, to inform a school-based, food allergy education program. Data were analysed thematically. We virtually interviewed children in Kindergarten-Grade 8 in Manitoba, Canada, with (n = 7) and without (n = 9) parent-reported, physician-diagnosed food allergies. We identified three themes: Naive reliance on peers and school staff to assist with food allergy management; Limited food allergy knowledge; and, Recommended food allergy curricula: complementary perspective. Our findings will help inform the development of a school-based, food allergy education program, with a long-term goal of minimizing food allergy-related worries and optimizing safety for children with food allergy. Ongoing, school-based food allergy education is needed.

Thermodynamic Evidence of Structural Transformations in CO2-Loaded Metal-Organic Framework Zn(MeIm)2 from Heat Capacity Measurements.

Metal-organic frameworks are a class of porous compounds with potential applications in molecular sieving, gas sequestration, and catalysis. One family of MOFs, zeolitic imidizolate frameworks (ZIFs), is of particular interest for carbon dioxide sequestration. We have previously reported the heat capacity of the sodalite topology of the zinc 2-methylimidazolate framework (ZIF-8), and in this Article we present the first low-temperature heat capacity measurements of ZIF-8 with various amounts of sorbed CO2. Molar heat capacities from 1.8 to 300 K are presented for samples containing up to 0.99 mol of CO2 per mol of ZIF-8. Samples with at least 0.56 mol of CO2 per mol of ZIF-8 display a large, broad anomaly from 70 to 220 K with a shoulder on the low-temperature side, suggesting sorption-induced structural transitions. We attribute the broad anomaly partially to a gate-opening transition, with the remainder resulting from CO2 rearrangement and/or lattice expansion. The measurements also reveal a subtle anomaly from 0 to 70 K in all samples that does not exist in the sorbate-free material, which likely reflects new vibrational modes resulting from sorbate/ZIF-8 interactions. These results provide the first thermodynamic evidence of structural transitions induced by CO2 sorption in the ZIF-8 framework.

New Insights about CuO Nanoparticles from Inelastic Neutron Scattering.

Inelastic Neutron Scattering (INS) spectroscopy has provided a unique insight into the magnetodymanics of nanoscale copper (II) oxide (CuO). We present evidence for the propagation of magnons in the directions of the ordering vectors of both the commensurate and helically modulated incommensurate antiferromagnetic phases of CuO. The temperature dependency of the magnon spin-wave intensity (in the accessible energy-range of the experiment) conforms to the Bose population of states at low temperatures (T ≤ 100 K), as expected for bosons, then intensity significantly increases, with maximum at about 225 K (close to TN), and decreases at higher temperatures. The obtained results can be related to gradual softening of the dispersion curves of magnon spin-waves and decreasing the spin gap with temperature approaching TN on heating, and slow dissipation of the short-range dynamic spin correlations at higher temperatures. However, the intensity of the magnon signal was found to be particle size dependent, and increases with decreasing particle size. This "reverse size effect" is believed to be related to either creation of single-domain particles at the nanoscale, or "superferromagnetism effect" and the formation of collective particle states.

Gallium Arsenate Dihydrate under Pressure: Elastic Properties, Compression Mechanism, and Hydrogen Bonding.

Gallium arsenate dihydrate is a member of a class of isostructural compounds, with the general formula M(3+)AsO4·2H2O (M(3+) = Fe, Al, In, or Ga), which are being considered as potential solid-state storage media for the sequestration of toxic arsenic cations. We report the first high-pressure structural analysis of a metal arsenate dihydrate, namely, GaAsO4·2H2O. This compound crystallizes in the orthorhombic space group Pbca with Z = 8. Accurate unit cell parameters as a function of pressure were obtained by high-pressure single-crystal X-ray diffraction, and a bulk modulus of 51.1(3) GPa for GaAsO4·2H2O was determined from a third-order Birch-Murnaghan equation of state fit to the P-V data. Assessment of the pressure dependencies of the unit cell lengths showed that the compressibility of the structure along the axial directions increases in the order of [010] < [100] < [001]. This order was found to correlate well with the proposed compression mechanism for GaAsO4·2H2O, which involves deformation of the internal channel void spaces of the polyhedral helices that lie parallel to the [010] direction, and increased distortion of the GaO6 octahedra. The findings of the high-pressure diffraction experiment were further supported by the results from variable-pressure Raman analysis of GaAsO4·2H2O. Moreover, we propose a revised and more complex model for the hydrogen-bonding scheme in GaAsO4·2H2O, and on the basis of this revision, we reassigned the peaks in the OH stretching regions of previously published Raman spectra of this compound.

Non-hydrostatic behavior of KBr as a pressure medium in diamond anvil cells up to 5.63 GPa.

Non-hydrostatic stresses of KBr acting as a pressure-transmitting medium have been investigated by examining their effect on a single crystal of quartz in a diamond anvil cell (DAC). The lattice strains or distortions were measured by single-crystal x-ray diffraction methods, and the non-hydrostatic deviatoric stresses for KBr were determined up to 5.63(2) GPa. The experimental results show that differences between axial stress components in the direction normal to the DAC culet face and the radial stress components in directions parallel to the DAC culet face are about 0.063(24) GPa at pressures below 2.14 GPa, and the pressure-transmitting medium can therefore be considered as quasi-hydrostatic up to this pressure. However above 2.14 GPa, after the phase transition pressure of KBr during which it converts from the B1 phase to the B2 phase, the deviatoric stresses constantly increase with increasing pressure. At the maximum pressure of this study, 5.63(2) GPa, the difference between axial stress and radial stress components reaches 0.93(9) GPa. Different variations in the non-hydrostatic deviatoric stresses were observed during both compression and decompression of the DAC, and are mainly ascribed to the phase-transition-induced volume change of KBr.

Pressure-induced bond rearrangement and reversible phase transformation in a metal-organic framework.

Pressure-induced phase transformations (PIPTs) occur in a wide range of materials. In general, the bonding characteristics, before and after the PIPT, remain invariant in most materials, and the bond rearrangement is usually irreversible due to the strain induced under pressure. A reversible PIPT associated with a substantial bond rearrangement has been found in a metal-organic framework material, namely [tmenH2][Er(HCOO)4]2 (tmenH2(2+)=N,N,N',N'-tetramethylethylenediammonium). The transition is first-order and is accompanied by a unit cell volume change of about 10%. High-pressure single-crystal X-ray diffraction studies reveal the complex bond rearrangement through the transition. The reversible nature of the transition is confirmed by means of independent nanoindentation measurements on single crystals.

Bonded radii and the contraction of the electron density of the oxygen atom by bonded interactions.

The bonded radii for more than 700 bonded pairs of atoms, comprising more than 50 oxide crystals, extracted from experimental and theoretical electron density distributions, are averaged and compared with the ionic radii for first, second, and third row atoms. At odds with the assumption of a "fixed" ionic radius of 1.40 Å for the oxide anion, the bonded radius for the anion, r(b)(O), decreases systematically from 1.40 to 0.65 Å as the electron density distribution of the atom is progressively polarized and contracted by its bonded interactions. The radii for the more electropositive metal atoms agree with the ionic radii when the electron density distribution of the anion is largely unpolarized by its bonded interactions. However, those for the more electronegative metal atoms are progressively larger than the ionic radii as the electron density distribution of the anion is progressively polarized and contracted along the bond vectors with decreasing bond length. The progressive decrease of r(b)(O) indicates that the compilation of sets of ionic radii, based on a fixed radius for the oxide anion, is problematic and impacts the accuracy of the ionic radii for the metal atoms. The assumption of a "fixed" radius for the anion, made in the derivation of sets of radii, not only results in unrealistic negative ionic radii for the more electronegative atoms but also in ionic radii that are as much as 0.5 Å smaller than the bonded radii, particularly for the more electronegative M atoms. The lack of agreement between the ionic and the bonded radii for the more shared bonded interactions is ascribed to the progressive increase in the polarization and contraction of the electron density of the oxide anion by the bonded interactions with a concomitant decrease in the radius of the anion, a factor that was largely neglected in the compilation of the ionic radii for fluoride, oxide, sulfide, and nitride crystals. The close agreement of the bonded radii and procrystal bonded radii is consistent with the argument that the chemical forces that govern the electron density distributions and bonded radii are largely atomic in nature, resulting in comparable electron density distributions.

The thermodynamic properties of hydrated γ-Al2O3 nanoparticles.

In this paper we report a combined calorimetric and inelastic neutron scattering (INS) study of hydrated γ-Al2O3 (γ-alumina) nanoparticles. These complementary techniques have enabled a comprehensive evaluation of the thermodynamic properties of this technological and industrially important metal oxide to be achieved. The isobaric heat capacity (C(p)) data presented herein provide further critical insights into the much-debated chemical composition of γ-alumina nanoparticles. Furthermore, the isochoric heat capacity (C(v)) of the surface water, which is so essential to the stability of all metal-oxides at the nanoscale, has been extracted from the high-resolution INS data and differs significantly from that of ice-Ih due to the dominating influence of strong surface-water interactions. This study also encompassed the analysis of four γ-alumina samples with differing pore diameters [4.5 (1), 13.8 (2), 17.9 (3), and 27.2 nm (4)], and the results obtained allow us to unambiguously conclude that the water content and pore size have no influence on the thermodynamic behaviour of hydrated γ-alumina nanoparticles.

High-pressure crystal structure of elastically isotropic CaTiO3 perovskite under hydrostatic and non-hydrostatic conditions.

The structural evolution of orthorhombic CaTiO3 perovskite has been studied using high-pressure single-crystal x-ray diffraction under hydrostatic conditions up to 8.1 GPa and under a non-hydrostatic stress field formed in a diamond anvil cell (DAC) up to 4.7 GPa. Under hydrostatic conditions, the TiO6 octahedra become more tilted and distorted with increasing pressure, similar to other 2:4 perovskites. Under non-hydrostatic conditions, the experiments do not show any apparent difference in the internal structural variation from hydrostatic conditions and no additional tilts and distortions in the TiO6 octahedra are observed, even though the lattice itself becomes distorted due to the non-hydrostatic stress. The similarity between the hydrostatic and non-hydrostatic cases can be ascribed to the fact that CaTiO3 perovskite is nearly elastically isotropic and, as a consequence, its deviatoric unit-cell volume strain produced by the non-hydrostatic stress is very small; in other words, the additional octahedral tilts relevant to the extra unit-cell volume associated with the deviatoric unit-cell volume strain may be totally neglected. This study further addresses the role that three factors--the elastic properties, the crystal orientation and the pressure medium--have on the structural evolution of an orthorhombic perovskite loaded in a DAC under non-hydrostatic conditions. The influence of these factors can be clearly visualized by plotting the three-dimensional distribution of the deviatoric unit-cell volume strain in relation to the cylindrical axis of the DAC and indicates that, if the elasticity of a perovskite is nearly isotropic as it is for CaTiO3, the other two factors become relatively insignificant.

The structural variation of rhombohedral LaAlO3 perovskite under non-hydrostatic stress fields in a diamond-anvil cell.

The structural variation of LaAlO(3) perovskite under non-hydrostatic stress developed in the pressure medium within a diamond-anvil cell was determined using single-crystal x-ray diffraction. The experimental results show that the lattice of LaAlO(3) becomes more distorted and deviates from the hydrostatic behavior as pressure is increased up to 7.5 GPa. The determination of the crystal structure further confirms that the octahedral AlO(6) groups become more distorted, but the octahedral rotation around the threefold axis decreases as under hydrostatic conditions. These experimental results can be reproduced from knowledge of the elastic tensor of the sample at ambient conditions and the stress state within the pressure medium. Further calculations for two other orientations also indicate that non-hydrostatic stress has only a small effect on the rotation of the AlO(6) octahedra towards zero, but non-hydrostatic stress inevitably leads to distortions in the crystal lattice and the AlO(6) octahedra. As a result, the crystal structure is eventually driven away from cubic symmetry under non-hydrostatic conditions, whereas it evolves towards cubic symmetry under hydrostatic pressure.

First-principles study on thermodynamic properties and phase transitions in TiS(2).

Structural and vibrational properties of TiS(2) with the CdI(2) structure have been studied to high pressures from density functional calculations with the local density approximation (LDA). The calculated axial compressibility of the CdI(2)-type phase agrees well with experimental data and is typical of layered transition-metal dichalcogenides. The obtained phonon dispersions show a good correspondence with available experiments. A phonon anomaly is revealed at 0 GPa, but is much reduced at 20 GPa. The thermodynamic properties of this phase were also calculated at high pressures and high temperatures using the quasi-harmonic approximation. Our LDA study on the pressure-induced phase transition sequence predicts that the CdI(2)-type TiS(2), the phase stable at ambient conditions, should transform to the cotunnite phase at 15.1 GPa, then to a tetragonal phase (I4/mmm) at 45.0 GPa. The tetragonal phase remains stable to at least 500 GPa. The existence of the tetragonal phase at high pressures is consistent with our previous findings in NiS(2) (Yu and Ross 2010 J. Phys.: Condens. Matter 22 235401). The cotunnite phase, although only stable in a narrow pressure range between 15.1 and 45.0 GPa, displays the formation of a compact S network between 100 and 200 GPa, which is evidenced by a kink in the variation of unit cell lengths with pressure. The electron density analysis in cotunnite shows that valence electrons are delocalized from Ti atoms and concentrated near the S network.

Prediction of high-pressure polymorphism in NiS2 at megabar pressures.

A sequence of pressure-induced phase transitions of vaesite, NiS(2), with pyrite structure, has been established from static LDA calculations. A dozen AX(2) candidate structures have been studied at high pressures including cotunnite (α-PbCl(2)), which is commonly observed in other AX(2) compounds at high pressures. At 150 GPa, vaesite transforms to a tetragonal phase (P4(2)/n) rather than cotunnite. This tetragonal structure is characterized by layers of Ni atoms in eight-fold coordination with S atoms rather than the nine-fold coordination observed in cotunnite. With further compression to about 7.5 Mbar, the tetragonal phase transforms into a hexagonal AlB(2)-type structure (P6/mmm) which is characterized by planar hexagonal layers of S intercalated by Ni atoms where each Ni atom is 12-fold coordinated by S atoms. Calculated band structures and valence electron density maps show S-S and Ni-S bonded interactions for NiS(2) under these extremely compressed conditions. The tetragonal phase may have geophysical implications if present in the Earth's core.

Pressure-induced cooperative bond rearrangement in a zinc imidazolate framework: a high-pressure single-crystal X-ray diffraction study.

The pressure-dependent structural evolution of a neutral zinc-imidazolate framework [Zn(2)(C(3)H(3)N(2))(4)](n) (ZnIm) has been investigated. The as-synthesized three-dimensional ZnIm network (alpha-phase) crystallizes in the tetragonal space group I4(1)cd (a = 23.5028(4) A, c = 12.4607(3) A). The ZnIm crystal undergoes a phase transition to a previously unknown beta-phase within the 0.543(5)-0.847(5) GPa pressure range. The tetragonal crystal system is conserved during this transformation, and the beta-phase space group is I4(1) (a = 22.7482(3) A, c = 13.0168(3) A). The physical mechanism by which the transition occurs involves a complex cooperative bond rearrangement process. The room-temperature bulk modulus for ZnIm is estimated to be approximately 14 GPa. This study represents the first example of a high-pressure single-crystal X-ray diffraction analysis of a metal-organic framework.

Inelastic neutron scattering study of confined surface water on rutile nanoparticles.

The vibrational density of states (VDOS) for water confined on the surface of rutile-TiO(2) nanoparticles has been extracted from low temperature inelastic neutron scattering spectra. Two rutile-TiO(2) nanoparticle samples that differ in their respective levels of hydration, namely TiO(2) x 0.37 H(2)O (1) and TiO(2) x 0.22 H(2)O (2) have been studied. The temperature dependency of the heat capacities for the two samples has been quantified from the VDOS. The results from this study are compared with previously reported data for water confined on anatase-TiO(2) nanoparticles.

High-pressure crystallography of rhombohedral PrAlO(3) perovskite.

The evolution of the crystal structure of rhombohedral PrAlO(3) perovskite with pressure has been investigated by single-crystal x-ray diffraction and Raman scattering experiments. The structural evolution as indicated by lattice strains, octahedral tilts, and the distortions of the octahedral AlO(6) and polyhedral PrO(12) groups with increasing pressure, is controlled by the relative compressibilities of the AlO(6) octahedra and the PrO(12) site. Because the AlO(6) octahedra are more compressible than the PrO(12) sites, up to 7.4 GPa the structure evolves towards the high-symmetry cubic phase like any other rhombohedral perovskite. The variation of volume of the rhombohedral phase with pressure can be represented by a third-order Birch-Murnaghan equation of state with bulk modulus K(0) = 193.0(1.2) GPa and K' = 6.6(4). Above 7.4 GPa the evolution towards a cubic phase is interrupted by a phase transition. Observations are consistent with the assignment of Imma symmetry to the high-pressure phase. Comparison with the low-temperature [Formula: see text] to Imma transition confirms that electronic interactions stabilize the Imma phase.

Dynamics of water confined on a TiO2 (anatase) surface.

Inelastic neutron scattering has been employed to probe the vibrational density of states of water confined by an oxide surface, namely, nanoparticles of the anatase polymorph of TiO2. The heat capacity of confined water has been measured by adiabatic calorimetry and compared with values derived from the vibrational density of states. Both inelastic neutron scattering and calorimetry demonstrate restricted mobility and lower heat capacity and entropy of confined water as compared to the bulk.

A population-based study of the effects of birth weight on early developmental delay or disability in children.

Improving medical treatment of extremely low-birth-weight infants over the last 20 to 30 years resulted in increased survival rates. The developmental sequela of salvaged infants is of great interest to perinatologists. The primary purposes of the current study were to assess the effect of birth weight (BW) on developmental delay or disability (DDD) in the first three years of life and determine whether there is a BW threshold below which all infants should be evaluated to determine if intervention services for children with DDD should be received. Three statewide databases were merged: 1998 Birth Vital Statistics; 1997-1998 Medicaid eligibility files; and 1998-2001 Children's Medical Services' Early Intervention Program (CMS-EIP) data. Infants who died within the first year of life and plural births were excluded. The final dataset consisted of 170,874 records. A child was determined to have a DDD if a developmental delay, or an established condition, such as sensory impairment, genetic, metabolic, neurological, or severe attachment disorders, was diagnosed through a multidisciplinary evaluation. Logistic regression models were used to relate BW to DDD, controlling for sociodemographic, behavioral, and perinatal variables. Adjusted odds ratios (OR) were calculated to describe the effects of BW on DDD. There was a significant effect of BW on DDD (Adjusted OR &equals 97.50, 40.01, 15.84, 3.29, 1.39, 1.00, 1.52 for BW categories 450-749, 750-999, 1000-1499, 1500- 2499, 2500-2999, 3000-4749, 4750-6050 g, respectively). In these categories, 70%, 56%, 36%, 11%, 4%, 3%, and 6% of surviving singleton infants, respectively, suffered a DDD in their first 3 years of life. Four medical, five sociodemographic, and two behavioral factors were significant in addition to BW. An equation for predicting the probability of DDD given these factors was obtained, and its use exemplified. BW is strongly associated with DDD. Over 60% of infants weighing < 1000 g and nearly half (46%) of those weighing < 1500 g at birth are diagnosed with a DDD before 3 years of age. The probability of DDD for a specific infant also varies by sociodemographic, other perinatal, and behavioral factors. The results of this paper suggest that all surviving infants of BW < 1000 g, and perhaps < 1500 g, should be automatically referred for evaluation.