High resolution MRI for preoperative work-up of neonates with an anorectal malformation: a direct comparison with distal pressure colostography/fistulography

OBJECTIVE: To compare MRI and colostography/fistulography in neonates with anorectal malformations (ARM), using surgery as reference standard. METHODS: Thirty-three neonates (22 boys) with ARM were included. All patients underwent both preoperative high-resolution MRI (without sedation or contrast instillation) and colostography/fistulography. The Krickenbeck classification was used to classify anorectal malformations, and the level of the rectal ending in relation to the levator muscle was evaluated. RESULTS: Subjects included nine patients with a bulbar recto-urethral fistula, six with a prostatic recto-urethral fistula, five with a vestibular fistula, five with a cloacal malformation, four without fistula, one with a H-type fistula, one with anal stenosis, one with a rectoperineal fistula and one with a bladderneck fistula. MRI and colostography/fistulography predicted anatomy in 88 % (29/33) and 61 % (20/33) of cases, respectively (p = 0.012). The distal end of the rectal pouch was correctly predicted in 88 % (29/33) and 67 % (22/33) of cases, respectively (p = 0.065). The length of the common channel in cloacal malformation was predicted with MRI in all (100 %, 5/5) and in 80 % of cases (4/5) with colostography/fistulography. Two bowel perforations occurred during colostography/fistulography. CONCLUSIONS: MRI provides the most accurate evaluation of ARM and should be considered a serious alternative to colostography/fistulography during preoperative work-up. KEY POINTS: • High-resolution MRI is feasible without the use of sedation or anaesthesia. • MRI is more accurate than colostography/fistulography in visualising the type of ARM. • MRI is as reliable as colostography/fistulography in predicting the level of the rectal pouch. • Colostography/fistulography can be complicated by bowel perforation

The calculations of thermodynamic and opto-electronics properties of Pb1-xCaxSe semiconducting ternary Alloys

The ab initio full potential linearized augmented plane wave (FP-LAPW) method within density functional theory was applied to study the effect of composition on the structural and electronic properties Pbl-xCaxSe temary alloys. The effect of composition on lattice parameter, bulk modulus, band gap was investigate. Deviations of the lattice constant from Vegard’s law and the bulk modulus from linear concentration dependence were observed. In addition, the microscopic origins of compositional disorder were explained by using the approach of Zunger and co-workers. The disorder parameter (gap bowing) was found to be strong and was mainly caused by the chemical charge transfer effect. The volume deformation contributions for all alloys were also found to be significant, while the structural relaxation contributions to the gap bowing parameter were relatively smaller. On the other hand, the thermodynamic stability and optical properties are attempted in the calculations. The calculated refractive indices and optical dielectric constants for the parent compounds show better agreement with the known data when the Moss relation is used. Compositional dependence of the optical and electronic properties studied is also investigated

The calculations of thermodynamic and opto-electronics properties of Pb1-xCaxSe semiconducting ternary Alloys

The ab initio full potential linearized augmented plane wave (FP-LAPW) method within density functional theory was applied to study the effect of composition on the structural and electronic properties Pbl-xCaxSe temary alloys. The effect of composition on lattice parameter, bulk modulus, band gap was investigate. Deviations of the lattice constant from Vegard’s law and the bulk modulus from linear concentration dependence were observed. In addition, the microscopic origins of compositional disorder were explained by using the approach of Zunger and co-workers. The disorder parameter (gap bowing) was found to be strong and was mainly caused by the chemical charge transfer effect. The volume deformation contributions for all alloys were also found to be significant, while the structural relaxation contributions to the gap bowing parameter were relatively smaller. On the other hand, the thermodynamic stability and optical properties are attempted in the calculations. The calculated refractive indices and optical dielectric constants for the parent compounds show better agreement with the known data when the Moss relation is used. Compositional dependence of the optical and electronic properties studied is also investigated

Structural, electronic, elastic, and thermal properties of CaNiH3 perovskite obtained from first-principles calculations

A theoretical study of the structural, elastic, electronic, mechanical, and thermal properties of the perovskite-type hydride CaNiH3 is presented. This study is carried out via first-principles full potential (FP) linearized augmented plane wave plus local orbital (LAPW+lo) method designed within the density functional theory (DFT). To treat the exchange-correlation energy/potential for the total energy calculations, the local density approximation (LDA) of Perdew-Wang (PW) and the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) are used. The three independent elastic constants (C 11, C 12, and C 44) are calculated from the direct computation of the stresses generated by small strains. Besides, we report the variation of the elastic constants as a function of pressure as well. From the calculated elastic constants, the mechanical character of CaNiH3 is predicted. Pertaining to the thermal properties, the Debye temperature is estimated from the average sound velocity. To further comprehend this compound, the quasi-harmonic Debye model is used to analyze the thermal properties. From the calculations, we find that the obtained results of the lattice constant (a 0), bulk modulus (B 0), and its pressure derivative () are in good agreement with the available theoretical as well as experimental results. Similarly, the obtained electronic band structure demonstrates the metallic character of this perovskite-type hydride

First principles calculations of structural, electronic and thermodynamic properties of SrS, SrSe, SrTe compounds and SrS1−xSex alloy

AbstractThe ab initio full potential linearized augmented plane wave (FP-LAPW) method within density functional theory was applied to study the structural and electronic properties of the compounds SrS, SrSe, SrTe and their alloy SrS1−xSex in the NaCl structure. Results are obtained using both the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange-correlation potentials. The ground-state properties, like lattice constant and bulk modulus obtained from our calculations agree very well with experimental and other theoretical calculations. We present the main features of electronic properties, where the electronic band structure shows that the fundamental energy gap is indirect (Γ→X). Moreover the alternative form of GGA proposed by Engel and Vosko (GGA-EV) is also used for band structure calculations. Results obtained with this approximation show that significant improvement over other theoretical work are closer to the experimental data. The effect of composition on lattice parameter and bulk modulus was investigated.Deviations of the lattice constant from Vegard’s law and the bulk modulus from linear concentration dependence were observed for the alloy. Moreover, the microscopic origins of the gap bowing were explained. In addition the thermodynamic stability of the alloy was investigated by calculating the critical temperature for SrS1−xSex alloy

Ab initio calculations of the structural, electronic, thermodynamic and thermal properties of BaSe1-xTe x alloys

The alkaline earth metal chalcogenides are being intensively investigated because of their advanced technological applications, for example in photoluminescent devices. In this study, the structural, electronic, thermodynamic and thermal properties of the BaSe1-xTe x alloys at alloying composition x = 0, 0.25, 0.50, 0.75 and 1 are investigated. The full potential linearized augmented plane wave plus local orbital method designed within the density functional theory was used to perform the total energy calculations. In this research work the effect of the composition on the results of the parameters and bulk modulus as well as on the band gap energy is analyzed. From our results, we found a deviation of the obtained results for the lattice constants from Vegard's law as well as a deviation of the value of the bulk modulus from the linear concentration dependence. We also carried out a microscopic analysis of the origin of the band gap energy bowing parameter. Furthermore, the thermodynamic stability of the considered alloys was explored through the measurement of the miscibility critical temperature. The quasi-harmonic Debye model, as implemented in the Gibbs code, was used to predict the thermal properties of the BaSe1-xTe x alloys, and these investigations comprise our first theoretical predictions concerning the BaSe1-xTe x alloys

First-principles computational study on structural, elastic, magnetic, electronic, and thermoelectric properties of Co

In this research work, first-principles computational study is performed on the structural, elastic, thermal, magnetic, electronic, and thermoelectric properties of the ternary Heusler compound Co2MnGe in its cubic phase. For this purpose, the “full potential linearized augmented plane-wave FP-L(APW + lo)” approach realized in the WIEN2k code is employed. To determine total energy, the exchange–correlation energy/potential part is treated within the “Perdew–Burke–Ernzerhof (PBE)” parameterized approach of “generalized gradient approximation (GGA) and modified Becke–Johnson (mBJ)” schemes. The magnetic phase stability was predicted via quantum mechanically total energy calculations for both non-magnetic and magnetic phases. Our obtained results for total energy show that the title material is stable in the ferromagnetic phase. The analysis of the profile of density of states (DOS), band structure plots, and the calculations of spin magnetic moment endorse the semi-metallic nature of the title compound. Calculations of the elastic constants, Cij, and results of the elastic moduli, such as bulk modulus (B), shear modulus (G), Young modulus (E), Poisson ratio (ν), and ratio B/G, are reported and analyzed as well. Gibbs computational code based on the “quasi-harmonic Debye model” is used to explore thermal properties, whereas parameters to understand the thermoelectric behavior, BoltzTrap code based on Boltzmann theory for transport properties is applied. Besides that, the chemical potential effect on the Seebeck coefficient and power factor is also analyzed at temperatures 300, 600, and 900 K. The results of thermoelectric parameters of the title Heusler compound, for the spin-down channel, are found good; hence, the obtained results highlight the title compound as a potential candidate for thermoelectric devices