Human milk macro- and trace-elements: Simultaneous analysis in sub-milliliter amounts by ICP-MS and application to assessing acute supplementation effects.

Adequate concentrations of human milk (HM) nutrients, including macro- and trace-elements, are essential for healthy growth and development of exclusively breastfed (EBF) infants. To monitor potential risk of deficiencies, and evaluate the effects of interventions like supplementation, accurate analysis is crucial. Even recent methods reporting on HM macro- and/or trace-elements describe multiple methodological approaches and the need for several milliliters. We optimized and validated a comprehensive method for simultaneous analysis of 13 macro- and trace-elements for simultaneous analysis by inductively-coupled plasma-mass spectrometry. 100-600 μL HM were microwave digested with ≤1.5 mL HNO3 (70 %). The digest was diluted to 5 % final acid concentration. He-Kinetic Energy Discrimination (KED; Na, K, P, Ca, Mg, Fe, Cu, Zn, Cr, Mo) and O2-Dynamic Reaction Cell (DRC; As, Mn, Se) modes minimized remaining interferences. Accuracy (NIST SRM 1869 infant formula; n = 15, 4 weeks) varied from 93.2 to 103 % (CV: 2.8-8.5 %) with trueness ranging from 93.9 to 104 %. Inter-day variation of a HM-pool (n = 20, 3 weeks) varied between 4.1 and 8.5 % for most elements; Cr, Mo, Mn (all<5 μg L-1) had higher variation, up to 25 %. Analyzing HM from 18 Bangladeshi mothers (2-4 months postpartum; day 1 = baseline, n = 17; day 2/3 = supplementation, n = 21 each) revealed higher concentrations for P, Ca, and Zn post-supplementation (p < 0.05, Friedmans Chi-Square Test). Na, Mg, Zn, and Se had the highest number of samples (>80 %) with concentrations below the Adequate Intake. Our method allows for simultaneous and reproducible analysis of macro- and trace-elements with concentrations ranging over 6 orders of magnitude, without the need for separate analytics and sample preparations, and requiring only sub-milliliter amounts of HM. Additional elements may be included after optimization and validation. The results from Bangladeshi HM samples indicate selective supplementation effects and concerningly low concentrations for some elements, which could adversely affect the EBF infant

Direct tunneling through high-κ\kappa amorphous HfO2_2: effects of chemical modification

We report first principles modeling of quantum tunneling through amorphous HfO$_2$ dielectric layer of metal-oxide-semiconductor (MOS) nanostructures in the form of n-Si/HfO$_2$/Al. In particular we predict that chemically modifying the amorphous HfO$_2$ barrier by doping N and Al atoms in the middle region - far from the two interfaces of the MOS structure, can reduce the gate-to-channel tunnel leakage by more than one order of magnitude. Several other types of modification are found to enhance tunneling or induce substantial band bending in the Si, both are not desired from leakage point of view. By analyzing transmission coefficients and projected density of states, the microscopic physics of electron traversing the tunnel barrier with or without impurity atoms in the high-$\kappa$ dielectric is revealed.Comment: 5 pages, 5 figure

Electronic and Thermoelectric Properties of van der Waals Materials with Ring-shaped Valence Bands

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Infant Serum and Maternal Milk Vitamin B-12 Are Positively Correlated in Kenyan Infant-Mother Dyads at 1-6 Months Postpartum, Irrespective of Infant Feeding Practice.

BackgroundVitamin B-12 is an essential nutrient required for many functions including DNA synthesis, erythropoiesis, and brain development. If maternal milk vitamin B-12 concentrations are low, infants may face elevated risks of deficiency when exclusively breastfed.ObjectiveWe evaluated cross-sectional associations between infant serum vitamin B-12 concentrations and maternal milk vitamin B-12 concentrations at 1-6 mo postpartum among an unsupplemented population in rural western Kenya, and assessed biological demographic, and dietary characteristics associated with adequate infant serum vitamin B-12.MethodsWe modeled 1) infant serum vitamin B-12 using maternal milk vitamin B-12 concentration with linear regression; and 2) adequate (>220 pmol/L) infant serum vitamin B-12 using hypothesized biological, demographic, and dietary predictors with logistic regression. In both models, we used generalized estimating equations to account for correlated observations at the cluster-level.ResultsThe median (quartile 1, quartile 3) infant serum vitamin B-12 concentration was 276 pmol/L (193, 399 pmol/L) and approximately one-third of infants had serum vitamin B-12 ≤220 pmol/L, indicating that they were vitamin B-12 depleted or deficient. There was a positive correlation between maternal milk and infant serum vitamin B-12 (r = 0.36, P < 0.001) and in multivariable analyses, maternal milk vitamin B-12 concentration was significantly associated with infant serum vitamin B-12 adequacy (P-trend = 0.03).ConclusionsDespite a high prevalence (90%) of maternal milk vitamin B-12 concentrations below the level used to establish the Adequate Intake (<310 pmol/L), there was a low prevalence of infant vitamin B-12 deficiency. We found few factors that were associated with infant vitamin B-12 adequacy in this population, including infant feeding practices, although maternal vitamin B-12 status was not measured. The contribution of maternal milk to infant vitamin B-12 status remains important to quantify across populations, given that maternal milk vitamin B-12 concentration is modifiable with supplementation. This trial was registered at clinicaltrials.gov as NCT01704105

Unsteady MHD Casson Fluid Flow through a Parallel Plate with Hall Current

AbstractUnsteady MHD Casson fluid flow through a parallel plate with hall current is investigated. The uniform magnetic field is applied perpendicular to the plates and the fluid motion is subjected to a uniform suction and injection. The lower plate is stationary and the upper plate is moving. Explicit Finite Difference technique has been used to solve the momentum and energy equations. The effect of pressure gradient, the Hall parameter and other parameters describing in the equations are shown graphically. Effect of decaying parameter with different Casson number on primary velocity, secondary velocity and temperature distributions are illustrated in the form of the graph

Hydro-Magnetic Convection Heat Transfer in a Micropolar Fluid over a Vertical Plate

The combined effect of Hall current, Ohmic heating and suction/injection on the hydro-magnetic free convective heat transfer in a micropolar boundary layer flow past a vertical plate is analyzed. The fluid is assumed to be viscous, incompressible and electrically conducting with a strong magnetic field. Using the modified Ohm’s law and the Bossinesq approximation the governing equations of the problem are transformed into a system of non-linear ordinary differential equations by introducing a suitable similarity transformation. The resulting boundary value problem is solved numerically by Nachtsheim-Swigert shooting technique with a sixth order Runge- Kutta iteration scheme. The results are obtained to study the effects of the governing parameters, suction/injection parameter , magnetic parameter , Hall current parameter , material parameter , microrotational parameter , the Prandtl number and the Brinkman number( ) on the transport behaviors of the fluid. That is a parametric study is performed to illustrate the influence of these parameters on the velocity and temperature distribution as well as the local skin-friction and the local Nusselt number. Furthermore, the numerical solutions obtained in this study are compared with the existing results in the literature for some special values of and the results are found to be in a good agreement

Biomathematical model for gyrotactic free-forced bioconvection with oxygen diffusion in near-wall transport within a porous medium fuel cell

Bioconvection has shown significant promise for environmentally friendly, sustainable “green” fuel cell technologies. The improved design of such systems requires continuous refinements in biomathematical modelling in conjunction with laboratory and field testing. Motivated by exploring deeper the near-wall transport phenomena involved in bioinspired fuel cells, in the present article, we examine analytically and numerically the combined free-forced convective steady boundary layer flow from a solid vertical flat plate embedded in a Darcian porous medium containing gyrotactic microorganisms. Gyrotaxis is one of many taxes exhibited in biological microscale transport, and other examples include magneto-taxis, photo-taxis, chemotaxis and geo-taxis (reflecting the response of micro-organisms to magnetic field, light, chemical concentration or gravity, respectively). The bioconvection fuel cell also contains diffusing oxygen species which mimics the cathodic behavior in a proton membrane exchange (PEM) system. The vertical wall is maintained at iso-solutal (constant oxygen volume fraction and motile micro-organism density) and iso-thermal conditions. Wall values of these quantities are sustained at higher values than the ambient temperature and concentration of oxygen and biological micro-organism species. Similarity transformations are applied to render the governing partial differential equations for mass, momentum, energy, oxygen species and micro-organism species density into a system of ordinary differential equations. The emerging eight order nonlinear coupled, ordinary differential boundary value problem features several important dimensionless control parameters, namely Lewis number (Le), buoyancy ratio parameter i.e. ratio of oxygen species buoyancy force to thermal buoyancy force (Nr), bioconvection Rayleigh number (Rb), bioconvection Lewis number (Lb), bioconvection Péclet number (Pe) and the mixed convection parameter spanning the entire range of free and forced convection. The transformed non-linear system of equations with boundary conditions is solved numerically by a finite difference method with central differencing, tridiagonal matrix manipulation and an iterative procedure. Computations are validated with the symbolic Maple 14.0 software. The influence of buoyancy and bioconvection parameters on the dimensionless temperature, velocity, oxygen concentration and motile microorganism density distribution, Nusselt, Sherwood and gradient of motile microorganism density are studied. The work clearly shows the benefit of utilizing biological organisms in fuel cell design and presents a logical biomathematical modelling framework for simulating such systems. In particular, the deployment of gyrotactic micro-organisms is shown to stimulate improved transport characteristics in heat and momentum at the fuel cell wall