Tunability in 3-Site Electronic Excitation Transfer Dynamics: Insights into the Role of Perturbative Coupling.

Electronic excitation transfer dynamics in photosynthetic systems, including the Fenna-Matthews-Olson complex, are often modeled using the interaction picture of three two-level systems, also known as the 3-site system. Among the two possible configurations, uphill and downhill, a recent publication reported an intriguing correlation between population dynamics and the intersite coupling. Specifically, the uphill configuration has been shown to have a pronounced dependence on perturbations in the intersite coupling, whereas the downhill configuration displays negligible dependence. In this study, we consider a generic 3-site configuration and model site interactions through the Markovian master equation. Through this approach, we derive succinct analytical expressions for the population dynamics between the sites, shedding light on the differences in behavior between the two configurations. Using these analytical expressions, we demonstrate the range of tunability in population dynamics achievable with minimal changes in intersite coupling, and we validate these findings through simulation results. These insights into the population dynamics of a 3-site system are expected to play a crucial role in facilitating the design of efficient energy-transfer pathways in molecular systems.

Unilateral Hemilaminectomy for the Excision of Intradural Extramedullary Spinal Tumors: A Beginner's Challenges.

AIM: To analyze retrospectively our experience of unilateral hemilaminectomy in intradural extramedullary (IDEM) tumors. MATERIAL AND METHODS: This study included 28 patients with IDEM tumors who underwent unilateral hemilaminectomies during the period 2011?2016. The preoperative clinicoradiological data, intraoperative findings, and postoperative outcomes were analyzed using a Microsoft Excel database. RESULTS: The mean age of the patients was 49.14 ± 12.23 years, and the average duration of symptoms was 11.82 weeks. The tumor distribution in the spine was as follows: cervical spine (14.2%), cervicodorsal spine (3.6%), dorsal spine (39.3%), dorsolumbar spine (10.7%), and lumbar spine (32.1%). Twenty patients (71%) underwent two-level laminectomies, and three-level laminectomies were performed on eight patients (29%). The mean operative time was 4 hours and 40 minutes. CONCLUSION: Unilateral hemilaminectomy is a safe, minimally invasive procedure for the excision of IDEM tumors. Beginners may face difficulties with this procedure and should ideally take more time than with a conventional total laminectomy because of the narrow operating corridor. As more experience is gained, this procedure will become easier in selected cases.

Craniotomy with Ridges: A Time and Cost-Efficient Technique for Unwavering Fixation of Bone Flap.

After advent of the power driven tools, the ease of surgeons and pace of surgery has been enhanced. Nowadays, most of the neurosurgeons are tend to use the motorized drills for elevating a bone flap to make a craniotomy. The bone cutting by the craniotome is wide and nonbeveled, which mandates the fixation of bone flap at closure, either by wiring, miniplates, or other fixation techniques. This not only lengthens the duration of surgery but also adds extra cost of miniplates to the patient. Here we are presenting a novel technique of elevating a bone flap where fixation at the end of surgery is not obligatory, without any risk of sinking of bone flap into the craniotomy defect.