In
this work, we utilize bifurcation diagrams to study the role
of mathematical artifacts in deteriorating the physical behavior in
statistical mechanically based equations of state of pure fluids.
We study the impact of common empirical approximations usually employed
to overcome some of the mathematical and physical challenges such
as the parametrization of mean field models or pair correlations functions
at contact. The proposed diagrams elucidate how the reduced molar
volume bifurcates with the variation of temperature at constant pressure.
We generate bifurcation diagrams for the modified van der Waals equation
of state (EOS) of Poole et al, SAFT-VR Mie, Soft-SAFT, CK-SAFT, and
the original SAFT EOSs for spherical and nonspherical molecules. We
find that the bifurcation diagram can serve as a useful schematic
tool to reveal the unphysical PVT behavior, demonstrate the existence
of physical and spurious two-phase separation regions, and illustrate
how the number of molar volume roots vary with temperatures. Our method
shows that the presence of unphysical branches can cause spurious
two-phase separation regions and create erroneous behavior in the
stability limit of vapor–liquid equilibrium. We demonstrate
that the existence of customary and spurious phase envelopes is accompanied
by S-shaped behavior in the volume-temperature bifurcation diagrams.
The study reveals that none of the SAFT models is free from producing
unphysical behavior. While the SAFT-VR Mie EOS exhibits solid–liquid-like
behavior for nonspherical molecules, the CK-SAFT EOS shows liquid–liquid
demixing behavior for spherical and nonspherical compounds. For the
soft-SAFT EOS, three different two-phase separation regions are observed
in addition to the common vapor–liquid phase separation region.
Diazaphospholenes have emerged as a promising class of metal-free hydride donors and have been implemented as molecular catalysts in several reduction reactions. Recent studies have also verified their radical reactivity...
Congenital solitary myofibroma is an exceptional tumor of newborn period and presents as solitary or multiple lesions usually confined to soft tissues. It induces intestinal obstruction or perforation, which most frequently involves the jejunum and ileum. However, jejunoileal atresia is the most frequently encountered cause of small bowel obstruction in the neonatal period. We report a new case of solitary myofibroma located in the wall of the ileum, measuring 2×3 cm2 in size, about 25 cm from the ileocecal junction, in a 17-day-old baby girl who presented with abdominal distention and bilious vomiting. Laparotomy was performed on the patient and the tumor was removed; the patient did well after surgery. Despite all the common causes of intestinal obstruction—intestinal atresia, Hirschsprung disease, anorectal anomaly, malrotation, and meconium passage problem in the neonatal period—myofibroma of the small bowel has to be considered because treatment is fairly easy and prognosis is excellent.
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