Antenatal imaging diagnosis of thoraco-omphalopagus conjoined twins.

Conjoined twins occur in an estimated one in every 200,000 live births. The etiology remains largely speculative, with genetic and environmental factors being considered. The thoraco-omphalopagus type accounts for approximately 40% of cases, making it a focal point for clinical and radiological research. Radiological imaging plays a pivotal role in delineating anatomical details, offering insights into the feasibility of surgical interventions and informing parental counselling regarding prognosis and management options. We present a case of thoracoomphalogus conjoined twins diagnosed during the third trimester of pregnancy in a 19-year-old woman. The detailed radiological assessment using ultra-sound and MRI provided crucial information on organ sharing and vascular anatomy, which is critical for management strategies. This case underscores the critical role of prenatal imaging in detecting complex congenital anomalies, facilitating informed decision-making by healthcare providers and families.

Vibrational and thermal properties of ScN and YN: quasi-harmonic approximation calculations and anharmonic effects.

The structural, vibrational and thermal properties of rocksalt ScN and YN are investigated by using a first-principles plane-wave approach. The results are discussed in comparison with the similarly calculated results for rocksalt MgO and zincblende AlN. The thermal expansivity (α(V)) computed within the quasi-harmonic approximation shows that there are significant anharmonic effects in ScN and YN, which are comparable to those in MgO. Since no experimental results are available for α(V) of either ScN or YN, the anharmonic effects are accounted for by a variant of the very recently introduced effective semiempirical ansatz (Phys. Rev. B 2009 79 104304) for calculating anharmonic free energy, which does not require any input from experiment. The validity of this very simple approach is demonstrated first by applying it to MgO. For the considered phase of AlN, the quasi-harmonic approximation is valid up to very high temperatures, and the thus obtained α(V) is in good agreement with experiment. The values of α(V) for semiconductor transition metal nitrides that crystallize in the rocksalt phase are higher than those for the zincblende phase of group-IIIB nitrides, and a major part of these differences is due to the crystal structure.