On computing stress in polymer systems involving multi-body potentials from molecular dynamics simulation.

Hardy stress definition has been restricted to pair potentials and embedded-atom method potentials due to the basic assumptions in the derivation of a symmetric microscopic stress tensor. Force decomposition required in the Hardy stress expression becomes obscure for multi-body potentials. In this work, we demonstrate the invariance of the Hardy stress expression for a polymer system modeled with multi-body interatomic potentials including up to four atoms interaction, by applying central force decomposition of the atomic force. The balance of momentum has been demonstrated to be valid theoretically and tested under various numerical simulation conditions. The validity of momentum conservation justifies the extension of Hardy stress expression to multi-body potential systems. Computed Hardy stress has been observed to converge to the virial stress of the system with increasing spatial averaging volume. This work provides a feasible and reliable linkage between the atomistic and continuum scales for multi-body potential systems.

Modification of the tube-in-tube pedicled anterolateral thigh flap for total phalloplasty: the mushroom flap.

BACKGROUND: Malformation or absence of the penis can lead to physical and psychological problems for male patients. Reconstruction of the phallus should optimally be completed in a single procedure, be aesthetically pleasing, retain erogenous and tactile sensation, enable micturition in the standing position, and allow for penetrative sexual intercourse. The tube-in-tube flap was described nearly 30 years ago and forms both a urethra and an outer penile shaft with a single flap. Here we present our modification of the original tube-in-tube design with the pedicled anterolateral thigh (ALT) flap and an extension for the neoglans, which we have termed the "mushroom flap" because of its shape and design. METHODS: The flap is based on the ALT flap; however, the area that will become the neoglans is shaped with a semicircular extension, resembling the head of a mushroom. When the flap is tubularized, the neoglans has the proper anatomic landmarks such as the corona and more closely approximates a circumcised penis. When used in conjunction with the tube-in-tube design, the neophallus, neoglans, and neourethra can all be constructed in a single stage with a single flap. RESULTS: We have performed total phalloplasties in three patients using the pedicled ALT flap, and the mushroom flap design evolved as we sought to improve the aesthetics of the neoglans. In comparing the aesthetic results among our patients as well as those published in the literature, the mushroom flap design seems to provide the most natural and aesthetically pleasing appearance. CONCLUSIONS: The pedicled ALT flap can be used to reconstruct an entire penis, as well as a urethra, without the need for microsurgery. By modifying the original tube-in-tube design to include a semicircular extension (a.k.a. the "mushroom flap"), we feel that we have been able to achieve a more natural-appearing neoglans.

Modified transconjunctival lower lid approach for orbital fractures in East Asian patients: the lateral paracanthal incision revisited.

BACKGROUND: Optimal repair of an orbital fracture requires adequate exposure into the orbit. The transconjunctival approach with lateral canthotomy is a valid option in East Asian patients, who are especially sensitive to the appearance of an external skin scar, although one must also recognize the potential complications associated with eyelid aperture mechanics. The authors report the modification of the transconjunctival approach, in which a lateral paracanthal incision is made along with division of the lateral tarsal plate but not at the lateral canthus. This was developed to overcome the complications of traditional lateral cantholysis. METHODS: A retrospective chart review was performed for all patients who had received the modified transconjunctival incision. Patient demographics, injury characteristics, and surgical outcomes were evaluated. RESULTS: The baseline demographics of 30 patients in this study was typical of orbital fractures in the Korean population. A take-back operation was required in one case of preseptal hematoma. The mean follow-up period was 6 months, and no long-term functional complications were identified. Of the 30 total patients, 29 showed excellent aesthetic outcome. One patient did present with postoperative notch deformity but did not feel the need for a revision operation. CONCLUSIONS: The transconjunctival approach with a lateral paracanthal incision is an alternative approach to the orbital wall. The decoupling of the lower eyelid through the lateral portion of the tarsal plate provides excellent exposure of the orbital floor and provides a reliable and consistent landmark by which the anatomy of the eyelid can be restored. The aesthetic and functional outcomes are excellent. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.