Maternal risk factors for oral clefts: A case-control study

Introduction: A cleft lip with or without a cleft palate is one of the major congenital anomalies observed in newborns. This study explored the risk factors for oral clefts in Gorgan, Northern Iran. Materials and Methods: This hospital-based case-control study was performed in three hospitals in Gorgan, Northern Iran between April 2006 and December 2009. The case group contained 33 newborns with oral clefts and the control group contained 63 healthy newborns. Clinical and demographic factors, including date of birth, gender of the newborns, type of oral cleft, consanguinity of the parents, parental ethnicity, and the mother's parity, age, education and intake of folic acid were recorded for analysis. Results: A significant association was found between parity higher than 2 and the risk of an oral cleft (OR= 3.33, CI 95% [1.20, 9.19], P> 0.02). According to ethnicity, the odds ratio for oral clefts was 0.87 in Turkmens compared with Sistani people (CI 95% [0.25, 2.96]) and 1.11 in native Fars people compared with Sistani people (CI 95% [0.38, 3.20]). A lack of folic acid consumption was associated with an increased risk of oral clefts but this was not statistically significant (OR = 1.42, CI 95% [0.58, 3.49]). There were no significant associations between sex (OR boy/girl = 0.96, CI 95% [0.41, 2.23]), parent familial relations (OR = 1.07, CI 95% [0.43, 2.63]), mother's age and oral clefts. Conclusions: The results of this study indicate that higher parity is significantly associated with an increased risk of an oral cleft, while Fars ethnicity and a low intake of folic acid increased the incidence of oral clefts but not significantly

An improved analytic solution for analysis of particle trajectories in fibrous, two‐dimensional filters

The Kuwabara solution for creeping fluid flow through periodic arrangement of cylinders is widely used in analytic and numerical studies of fibrous filters. Numerical solutions have shown that the Kuwabara solution has systematic errors, and when used for the particle trajectories in filters it results in some error in the predicted filter efficiency. The numerical solutions, although accurate, preclude further analytic treatments, and are not as compact and convenient to use as the Kuwabara solution. By reexamining the outer boundary conditions of the Kuwabara solution, a correction term to the Kuwabara solution has been derived to obtain an extended solution that is more accurate and improves prediction of the filter efficiency. By comparison with the numerical solutions, it is shown that the Kuwabara solution is the high porosity asymptote, and that the extended solution has an improved porosity dependence. A rectification is explained that can make particle collection less efficient for periodic, in‐line arrangements of fibers with particle diffusion or body force. This rectification also results in the alignment of particles with inertia (i.e., high Stokes number particles).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70636/2/PHFLE6-6-2-507-1.pd

Funicular state in drying of a porous slab

Drying of a non-hygroscopic porous slab initially saturated with liquid, up to the time of the first appearance of dried patches (critical time), is studied experimentally using glass beads and convective heating, and analytically using the volume averaged conservation equations for capillary driven liquid flow and empirical constitutive relations. Good agreement has been found between the predicted and measured results and the results show that: 1. (a) The surface mass transfer rate depends on the surface saturation. This surface saturation coefficient, which is also a function of both surface geometry and the free stream velocity, is determined experimentally.2. (b) The critical time is a ratio of the internal liquid transport conductance (Peclet number) to the external vapor transport conductance (Biot number).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26671/1/0000215.pd

Adiabatic reverse combustion in a packed bed

Downward propagation of a combustion front in a packed bed of wood particles, with air supply from below, is examined theoretically and experimentally. Using a single-step reaction, with a kinetic model of char oxidation as the dominant mechanism, and assuming local thermal equilibrium, but allowing a local chemical nonequilibrium between the solid and gas phases, the front speed uF, the adiabatic temperature Tr, and the extent of solid consumption rs/ns are determined as functions of the entering air pole-velocity u>ng. Both oxygen-limited and fuel-limited regimes, with the boundary marked by the stoichiometric burning, are examined. In the oxygen-limited regime, Tr, uF, rs/ns, and the thickness of the front [delta]F all increase with u>ng. In the fuel-limited regime, the reverse occurs and the extinction at high u>ng is predicted. In the oxygen-limited regime, where the bed is not yet fluidized, the experimental results are in good agreement with the predictions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31263/1/0000169.pd

Slip and no-slip temperature boundary conditions at interface of porous, plain media: conduction

The phase distribution nonuniformities near bounding surfaces result in anisotropy and nonuniformity of the effective thermal conductivity tensor. For a two-dimensional porous medium made of cylindrical particles, we evaluate the properties of this tensor for cases where the medium is bounded by the fluid saturating it or by a solid surface. The use of a uniform effective conductivity, such as the bulk (far from the surface) value, along with the near surface temperature distribution results in an error in the calculated heat flux. We examine this error and the errors resulting from the use of other approximations of the effective conductivity near the surface. We also point out a slip in the surface temperature occurring when the bulk effective conductivity and the temperature distribution away from the surface are used to extrapolate the temperature at the interface. A slip coefficient is used to account for this slip in temperature.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30959/1/0000631.pd

Analysis of levitation of saturated liquid droplets on permeable surfaces

Steady-state evaporation of a saturated liquid droplet and its levitation over a solid surface due to momentum-induced pressure in the vapor film is studied by solving the axisymmetric governing equation numerically. A previous one-dimensional analysis shows that the distance (or gap) between the solid surface and the droplet decreases when the vapor can penetrate the solid. For porous layers, this onedimensional analysis which is based on Brinkman's extension to Darcy's law predicts momentum boundary layer thicknesses of the order of the square root of the permeability. In typical porous solids, this thickness is smaller than the pore or particle size. In the present study the Beavers-Joseph semi-empirical boundary condition at the interface of the plain (i.e. vapor underneath the droplet) and permeable layers is used instead of this one-dimensional model. The reduction in the gap size with respect to variations in permeability and thickness of the porous layer is determined for the ranges where this boundary condition is valid. The effect of vapor escape through the bottom surface of the porous layer is also studied. This axisymmetric model predicts an asymptotic value for the slip velocity and the gap size as the permeability increases beyond a certain value. This failure of the model to predict the collapse of the droplet is due to the breakdown of the Beavers-Joseph interfacial condition for high permeabilities. However, for practical applications the surface roughness is expected to dominate when the gap size approaches zero. The onedimensional model, i.e. the Brinkman extension, on the other hand, predicts an unrealistic rapid drop of the gap size when the permeability is increased beyond a certain value, because of the assumption of equal pressure gradients in the porous and plain layers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28611/1/0000423.pd

Natural convection heat transfer from a vertical plate to high permeability porous media: an experiment and an approximate solution

The heat transfer rate from an isothermal vertical plate placed next to saturated high permeability porous media is studied experimentally and analytically. The media used are polyurethane foams saturated with air. An integral method is applied in predicting the heat transfer rate by including the non-Darcy effects, which are expected to be significant for high permeabilities and high Rayleigh numbers. Good agreement is found between the experimental and predicted results except when the permeability is relatively low and the Peclet number becomes very small. Although some of the permeabilities encountered are large, for the experimental conditions considered in this study the Rayleigh numbers are not very high; therefore, the non-Darcy effects are not significant.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26726/1/0000276.pd

Slip and no-slip velocity boundary conditions at interface of porous, plain media

The hydrodynamic boundary condition at the interface between a porous and a plain medium is examined by direct simulation of the two-dimensional flow field near the interface of a porous medium made of cylinders. The existing slip boundary condition, which contains a slip coefficient [alpha], and the noslip boundary condition, which contains an effective viscosity [mu]', are examined. The dependence of [alpha] on the direction of the flow (with respect to the interfacial plane), the porosity, the Reynolds number (based on the unit cell length and the Darcean velocity), the selection of the interfacial location, and the arrangement of the cylinders (structure) is examined in detail. The numerical results show that [alpha] is not only a function of the structure but also depends on the flow direction, the Reynolds number, the extent of the plain medium, and the nonuniformities in the arrangement of the surface particles. It is also shown that for an accurate prediction of the local velocity near the interface (inside the porous medium), [mu]' must vary within the porous medium. This shows that the Brinkman extension based on a uniform [mu]', and the associated screening distance, do not satisfactorily model the flow field in the porous medium.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30141/1/0000518.pd

Phonon Band Structure and Thermal Transport Correlation in a Layered Diatomic Crystal

To elucidate the relationship between a crystal's structure, its thermal conductivity, and its phonon dispersion characteristics, an analysis is conducted on layered diatomic Lennard-Jones crystals with various mass ratios. Lattice dynamics theory and molecular dynamics simulations are used to predict the phonon dispersion curves and the thermal conductivity. The layered structure generates directionally dependent thermal conductivities lower than those predicted by density trends alone. The dispersion characteristics are quantified using a set of novel band diagram metrics, which are used to assess the contributions of acoustic phonons and optical phonons to the thermal conductivity. The thermal conductivity increases as the extent of the acoustic modes increases, and decreases as the extent of the stop bands increases. The sensitivity of the thermal conductivity to the band diagram metrics is highest at low temperatures, where there is less anharmonic scattering, indicating that dispersion plays a more prominent role in thermal transport in that regime. We propose that the dispersion metrics (i) provide an indirect measure of the relative contributions of dispersion and anharmonic scattering to the thermal transport, and (ii) uncouple the standard thermal conductivity structure-property relation to that of structure-dispersion and dispersion-property relations, providing opportunities for better understanding of the underlying physical mechanisms and a potential tool for material design.Comment: 30 pages, 10 figure