Trace Elements in the Human Milk

Human breast milk is considered to be the perfect food for infants, specifically adapted to their needs. Before birth, the mother transfers all the nutrients and bioactive components to the fetus through the placenta. After birth, these substances have to be transferred through colostrum and milk. In particular, human breast milk is supposed to provide all the essential trace elements that are required by the normal term newborn infant. Therefore, the composition of human breast milk and its changes during lactation is a topic of major importance and has been the subject for intensive research. Conversely, human milk can also be a transfer medium of undesirable (toxic) elements from the mother to the infant. An extensive review of the most recent literature was carried out focusing on the current trace elements levels and their changes during lactation. For several elements, there is a consistent knowledge of their characteristic concentrations throughout the various stages of lactation, their dependence on maternal nutritional status, inter-individual and geographical variability, metabolic pathways, inter-elemental relationships, and effects on child development. For many other elements, this knowledge does not exist or is quite limited

Two Experimental Approaches of Looking at Buoyancy

In our teaching practice, we find that a large number of first-year university physics and chemistry students exhibit some difficulties with applying Newton's third law to fluids because they think fluids do not react to forces. (c) 2013 American Association of Physics Teachers

Chemical safety of children's play paints: Focus on selected heavy metals

Children's play paints are widely used as didactic products in preschool activities. Besides direct skin contact, a great risk of oral exposure exists during its normal and foreseeable use. Due to the ubiquitous nature of most metals, their presence as impurities in all products is recognized as unavoidable. However, the toxic potential of most of them requires that their levels are kept as low as possible. The present study aimed to assess the content of selected heavy metals (Pb, Cd, Cr, Co, Ni, Mn, Cu and Zn) in “artist paints” (n = 54) and “face paints” (n = 12) commonly used in preschool establishments and available at low cost stores. Determinations were carried out by GFAAS (for Pb, Cd, Co, Cr and Ni) and FAAS (for Mn, Cu and Zn). The levels obtained [mean ± SD (maximum)] were: 0.48 ± 0.44 (1.98) μg g− 1 for Pb; 0.04 ± 0.04 (0.30) μg g− 1 for Cd; 0.17 ± 0.20 (1.47) μg g− 1 for Co; 1.36 ± 2.18 (9.40) μg g− 1 for Cr; 0.63 ± 0.56 (3.10) μg g− 1 for Ni; 19.8 ± 88.2 (718) μg g− 1 for Mn; 108 ± 260 (1458) μg g− 1 for Cu; and 130 ± 564 (3478) μg g− 1 for Zn. A safety assessment considering the estimated potential exposure and health-based limits (tolerable daily intakes) was performed. Overall, the results showed no reasons for safety concerns regarding the studied elements.info:eu-repo/semantics/publishedVersio

Magentically-Induced Lattice Distortions and Ferroelectricity in Magnetoelectric GdMnO3

In this work we investigate the magnetic field dependence of Ag octahedra rotation (tilt) and B2g symmetric stretching modes frequency at different temperatures. Our field-dependent Raman investigation at 10K is interpreted by an ionic displacive nature of the magnetically induced ferroelectric phase transition. The frequency change of the Ag tilt is in agreement with the stabilization of the Mn-Gd spin arrangement, yielding the necessary conditions for the onset of ferroelectricity on the basis of the inverse Dzyaloshinskii-Moriya interaction. The role of the Jahn-Teller cooperative interaction is also evidenced by the change of the B2g mode frequency at the ferroelectric phase transition. This frequency change allows estimating the shift of the oxygen position at the ferroelectric phase transition and the corresponding spontaneous polarization of 480 {\mu}C/m2, which agrees with earlier reported values in single crystals. Our study also confirms the existence of a large magnetic hysteresis at the lowest temperatures, which is a manifestation of magnetrostiction.Comment: 5 pages, 3 figure

Structural and insulator-to-metal phase transition at 50 GPa in GdMnO3

We present a study of the effect of very high pressure on the orthorhombic perovskite GdMnO3 by Raman spectroscopy and synchrotron x-ray diffraction up to 53.2 GPa. The experimental results yield a structural and insulator-to-metal phase transition close to 50 GPa, from an orthorhombic to a metrically cubic structure. The phase transition is of first order with a pressure hysteresis of about 6 GPa. The observed behavior under very high pressure might well be a general feature in rare-earth manganites.Comment: 4 pages, 3 figures and 2 table