Slack-based tunable damping leads to a trade-off between robustness and efficiency in legged locomotion.

Animals run robustly in diverse terrain. This locomotion robustness is puzzling because axon conduction velocity is limited to a few tens of meters per second. If reflex loops deliver sensory information with significant delays, one would expect a destabilizing effect on sensorimotor control. Hence, an alternative explanation describes a hierarchical structure of low-level adaptive mechanics and high-level sensorimotor control to help mitigate the effects of transmission delays. Motivated by the concept of an adaptive mechanism triggering an immediate response, we developed a tunable physical damper system. Our mechanism combines a tendon with adjustable slackness connected to a physical damper. The slack damper allows adjustment of damping force, onset timing, effective stroke, and energy dissipation. We characterize the slack damper mechanism mounted to a legged robot controlled in open-loop mode. The robot hops vertically and planarly over varying terrains and perturbations. During forward hopping, slack-based damping improves faster perturbation recovery (up to 170%) at higher energetic cost (27%). The tunable slack mechanism auto-engages the damper during perturbations, leading to a perturbation-trigger damping, improving robustness at a minimum energetic cost. With the results from the slack damper mechanism, we propose a new functional interpretation of animals' redundant muscle tendons as tunable dampers.

A modified posterior pelvic exenteration technique in a woman: (a simplified method with using transvaginal way).

We represent a simplified surgical method for posterior pelvic exenteration in a woman by using the transvaginal way in addition to classic abdominal approach. A modified posterior pelvic exenteration technique was performed in a patient with bulky pelvic tumor. The transvaginal way was used for the deep perineal dissection when the abdominal dissection was arrested. An ultralow coloanal anastomosis was completed by using the transvaginal way. After the recovery period, the patient was discharged from hospital without any complication. The transvaginal access should be reminded in the circumstances of the abdominal dissection arrested in posterior pelvic exenteration operations in women.

Stereolithographic volume evaluation of healing and shaping after rhinoplasty operations.

Nasal edema and volume changes are unavoidable processes during the healing period after rhinoplasty. Various applications were reported regarding the prevention of early edema; however, the literature shows no study focused on the course of the nasal edema and volume changes up-to-date. We aimed to study the nasal volume changes during the first year of postoperative healing period and to form a recovery and volume change diagram with the obtained data. We prepared standard frames and nasal molds of 7 rhinoplasty patients at regular time intervals (preoperative period and at the postoperative 1st, 2nd, 4th, 8th, 12th, 24th, and 52nd weeks). Plaster nasal models were created by using these molds. Volumes of models were measured by computed tomographic scanning and three-dimensional image processing programs. According to our results, the nasal edema reaches its maximum level at the postoperative fourth week and then rapidly decreases until its minimum level at the eighth week. In contrast with the general opinion, the nasal volume begins to increase smoothly reaching to a level minimally below the preoperative value by the end of the first year.

Pore structure engineering for carbon foams as possible bone implant material.

In this study authors aim to produce carbon foams with controllable pore size and distribution with high ratio of open porosity and to determine the cytotoxicity, and the bio-compatibility of the carbon foams by controlled experiments on the Dawley rats. Carbon foams are produced from Mitsubishi AR pitch at different pressures, temperatures, pressure release times, and additives for the purpose of using it as a bone implant material. Carbon foams with controllable range of pore sizes and distribution by using temperatures between 283 and 300 degrees C, pressures between 38 and 78 bar, and pressure release times between 5 and 600 s. The highest total porosity was found to be 86%. This porosity level was also complemented by the highest density, and compressive strength. Addition of isotropic pitch, graphite powder and THF, toluene and xylene solvents resulted in higher pore volumes compared with no additives. In the case of exploiting this result, it should be noted that higher pore volumes are realized with drastic drop in porosity and strength. The ability of porous foam to provide scaffold to tissue in vivo was finally investigated after 3 months of implantation in adequate pockets in the nude mice for insertion. Histological examination of the engineered constructs revealed that the tissue adaptation and bone compatibility of the carbon foam material studies on rats was found to be satisfactory. Progression of connective tissue formation into the carbon implant was observed without any sign of cytotoxicity and incompatibility during the postoperative follow-ups.

A new nerve-muscle unit model for peripheral nerve studies in rats.

Ischiatic, femoral and tibial nerves are commonly utilized in the studies of peripheral nerve surgery in rats. The authors present a new nerve-muscle unit model in which the nerve is distal enough to minimize morbidity and the muscle is convenient for all electromyographic studies. Twenty-five Wistar-Albino rats were used. In the control group; normal electromyography and histology were demonstrated in the lateral tibial nerve (LTN) and in the flexor digiti quinti brevis (FDQB) muscle. In experimental group I; a 0.5 cm nerve gap was made in the LT nerve and the proximal end was buried in the muscle in order to prevent reinnervation. In experimental group II, the LTN was cut and repaired primarily. In both groups I and II, electromyographic and histologic studies were performed at 6 and 12 weeks. In study group I, atrophic and degenerative findings were observed and in study group II, only regenerative findings were observed. The authors concluded that the LT nerve-FDQB muscle unit is a convenient model for peripheral nerve studies, with the advantages of easy dissection, wide exposure, and minimal morbidity. This model is also convenient for electromyographic and histologic evaluation.