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

Incidence of cleft lip and palate in Gorgan - Northern Iran: An epidemiological study

Objective: Cleft lip with or without cleft palate is the most common orofacial congenital anomaly among live births. This study was carried out to determine the incidence rate of oral clefting in Gorgan, Northern Iran during 2004-2009. Methods: This descriptive hospital-based study was performed on 35,009 live newborns in Dezyani Hospital in Gorgan, Northern Iran during 2004-2009. All newborns were screened for oral clefts. Data including birth date, gender, type of oral clefts, parents' consanguinity, parental ethnicity and presence of other congenital anomalies were recorded for analysis. Result: The overall incidence rate of oral clefts during this 6-year period was 1.05 per 1000, or 1 per 946 live births. The incidence of cleft lip and isolated cleft palate was 0.08 and 0.37 per 1,000 live births, respectively. The ratio for different cleft types was 1:7:4 (CL: CLP: CP). The incidence of oral clefting was 1.2 per 1,000 male births and 0.86 per 1,000 female births (RR=1.40; 95% CI: 0.73-2.71). According to parental ethnicity, the incidence of oral clefting was 0.7, 1.7 and 1.26 per 1,000 in Native Fars, Turkman and Sistani, respectively. The relative risk for oral clefting in Turkman to native Fars group was 2.56 (p<0.02). In this study, 56.7% of clefts were CL+P, 8.1% were CL and 35.1% of cases were CP. CP was more common among girls (54%) than among boys (46%) but CL was more common among boys. Conclusion: The results showed that the incidence of oral clefts in the study population as being 1.05 per 1,000 live births, which has increased from 0.97 per 1,000 live births reported in an earlier study in this area. © OMSB, 2012

Structural metrics of high-temperature lattice conductivity

An atomic structure-based model for high-temperature lattice conductivity is developed for both compact crystals and cage-bridge crystals. For compact crystals, where long-range acoustic phonons dominate, the Debye temperature TDTD and Grüneisen parameter γγ are estimated using interatomic potentials to arrive at the lattice conductivity relation. Under the assumption of homogeneous deformation, TDTD is estimated according to a simplified force constant matrix and a phenomenological combinative rule for force constants, which is applicable to an arbitrary pair of interacting atoms. Also, γγ is estimated from a general Lennard-Jones potential form and the combination of the bonds. The results predicted by the model are in close agreement with the experimental results. For cage-bridge crystals, where both short-range acoustic phonons and optical phonons may be important, a simple mean-free path model is proposed: The phonon mean-free path of such a crystal at high temperatures is essentially limited by its structure and is equal to the cage size. This model also shows good agreement with the results of experiments and molecular dynamics simulations. Based on this atomic-level model, the structural metrics of crystals with low or high lattice conductivity are discussed, and some strategies for thermal design and management are suggested.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87699/2/123507_1.pd

Optimized ZT of Bi2Te3-GeTe compounds from first principles guided by homogeneous data

We predict the thermoelectric properties of layered [GeTe](m)[Bi2Te3](n) (GBT) compounds ( 1 <= m <= 8, 1 <= n <= 3), using first-principles-Boltzmann transport calculations of the homogeneous (Bi2Te3 and GeTe) data. The lattice strain and the quantum-confinement effects of compounds evolve the band-gap structures, resulting in asymmetric and large Seebeck coefficient, at high GeTe content. Using semiempirical calculations of electron scattering rate 1/tau(e), dominated by electron-acoustic phonon scattering, we reproduce reported TE properties of GBT compounds. We predict that, due to small Seebeck coefficient, the GBT compounds with high n- and p-type doping (similar to 10(20) cm(-3)), do not have high ZT near room temperature. However, we predict that the moderately doped (similar to 10(19) cm(-3)), p-type GBT compounds have enhanced ZT approximate to 1.4 near room temperature.1132Ysciescopu

Low phonon conductivity of layered BiCuOS, BiCuOSe, and BiCuOTe from first principles

Combining the effect of layer mixing, mass mismatch, and intrinsic defects, we have investigated the origin of very low phonon conductivity k(p) in thermoelectric (TE) BiCuOQ (Q: S, Se, Te) compounds. Based on the first-principles anharmonic, lattice dynamics calculations, we use the single-mode relaxation time approximation of the linearized phonon Boltzmann equation, which shows good agreement with experiments. Here, we found that the most important parameter for low k(p) is the interlayer interaction between the BiO and CuQ layers. By analyzing the phonon linewidth distribution, which indicates the phonon scattering rate, we propose that the interlayer interactions play a critical role on suppressing k(p), i.e., the heterolayered crystal controls these interlayer interactions, achieving low k(p) and optimal TE properties.1133Ysciescopu

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

Thermal conditions affecting heat transfer in FDM/FFE: a contribution towards the numerical modelling of the process

The performance of parts produced by Free Form Extrusion (FFE), an increasingly popular additive manufacturing technique, depends mainly on their dimensional accuracy, surface quality and mechanical performance. These attributes are strongly influenced by the evolution of the filament temperature and deformation during deposition and solidification. Consequently, the availability of adequate process modelling software would offer a powerful tool to support efficient process set-up and optimisation. This work examines the contribution to the overall heat transfer of various thermal phenomena developing during the manufacturing sequence, including convection and radiation with the environment, conduction with support and between adjacent filaments, radiation between adjacent filaments and convection with entrapped air. The magnitude of the mechanical deformation is also studied. Once this exercise is completed, it is possible to select the material properties, process variables and thermal phenomena that should be taken in for effective numerical modelling of FFE.This work was supported by Strategic Project - LA 25 - 2013–2014 [PEst-C/CTM/LA0025/2013]

Temperature dependent band gap in PbX (X=S, Se, Te)

PbTe is an important thermoelectric material for power generation applications due its high conversion efficiency and reliability. Its extraordinary thermoelectric performance is attributed to band convergence of the light L and heavy Σ bands. However, the temperature at which these bands converge is disputed. In this letter, we provide direct experimental evidence combined with ab initio calculations that confirm an increasing optical gap up to 673 K and predict a band convergence temperature of 700 K, much higher than previous measurements showing saturation and band convergence at 450 K