Geosynthetic landfill cap stability: comparison of limit equilibrium, computational limit analysis and finite-element analyses

The stability of the veneer cover soil (landfill cap) is an important issue in landfill design. Incorrect design of the landfill cap can lead to failure, which may result in the veneer cover soil sliding on an underlying geosynthetic layer, or in tension failure of the geosynthetic itself. Previous limit equilibrium (LE) analyses of veneer cover layer stability presented in the literature have generally considered whole-slope failure. In this paper, modified LE equations are proposed that (a) encompass more critical cases of localised slope failure for specific cases, and (b) are calibrated against two other methods: 2-D computational limit analysis (CLA) using LimitState:GEO and 2-D elasto-plastic finite-element (FE) analysis using PLAXIS. The scenarios examined encompass a cover of uniform thickness, a buttressed cover, a cover of tapered thickness, the effects of seepage forces, and the effects of construction equipment. It is shown that the LE method provides a reasonable estimate of veneer cover layer stability for most cases examined, although it is in general non-conservative, relative to the CLA and FE analyses. Local failure was found to be critical in the case of the construction equipment, buttress and horizontal seepage scenarios. In the latter case the LE equations previously presented in the literature significantly overestimate stability compared with the LE, CLA and FE analyses considered in this paper

The role of an extended medial column arthrodesis for Charcot midfoot neuroarthropathy

The etiology of diabetic Charcot neuroarthropathy involving the midfoot often includes an inciting traumatic event or repetitive micro-trauma from an uncompensated biomechanical imbalance that potentiates an incompletely understood pathway leading to a rocker-bottom foot deformity and ulceration. In the setting of a severe Charcot foot fracture and/or dislocation with obvious osseous instability, diagnostic delay can potentiate the limb-threatening sequelae of infected midfoot ulcerations in this patient population. In this article, the authors discuss the thought process as well as the advantages of performing an extended medial column arthrodesis for selected Charcot midfoot deformities

Application of Ni(II)-Assisted Peptide Bond Hydrolysis to Non-Enzymatic Affinity Tag Removal

In this study, we demonstrate a non-enzymatic method for hydrolytic peptide bond cleavage, applied to the removal of an affinity tag from a recombinant fusion protein, SPI2-SRHWAP-His6. This method is based on a highly specific Ni(II) reaction with (S/T)XHZ peptide sequences. It can be applied for the protein attached to an affinity column or to the unbound protein in solution. We studied the effect of pH, temperature and Ni(II) concentration on the efficacy of cleavage and developed an analytical protocol, which provides active protein with a 90% yield and ∼100% purity. The method works well in the presence of non-ionic detergents, DTT and GuHCl, therefore providing a viable alternative for currently used techniques

A Case Report of a Double Advancement Flap Closure Combined with an Ilizarov Technique for the Chronic Plantar Forefoot Ulceration.

Soft tissue closure of defects on the plantar surface of the foot continues to be a challenge for the reconstructive surgeon secondarily to the limited number of surgical options and often difficulty of replacing durable and similar soft tissue coverage. Primary closure and skin grafting may not be suitable for the weight-bearing surfaces of the plantar forefoot area, and closure may then be obtained by other means of plastic surgery techniques

Surgical Treatment of Calcaneal Fracture Malunions and Posttraumatic Deformities.

The surgical management of calcaneal fractures presents with several obstacles to the treating physician. Many experienced surgeons acknowledge a steep and significant learning curve in the operative management of calcaneal fractures. Nonoperative management of displaced intra-articular calcaneal fractures may result in malunion, thereby affecting the function of the ankle and subtalar joint. Although some calcaneal fractures can be treated conservatively, a majority of them require operative intervention. The goal of this article is to bring some insight into the realm of revisional surgery on residual deformity of the calcaneus after operative intervention and also provide a rationale approach to successfully manage failed surgeries for calcaneal fractures

Revisional Charcot Foot and Ankle Surgery.

Charcot neuroarthropathy is often a devastating diabetic foot complication that poses a great risk for limb loss and can have a significant impact on a patient\u27s quality of life in the presence of multiple existing comorbidities. It is a progressive and debilitating condition characterized by joint dislocation, pathologic fracture(s), and extensive destruction of the foot or ankle architecture secondary to dense peripheral neuropathy. This pathologic process can be idiopathic, secondary to acute trauma or previous surgery, or attributable to repetitive microinjury. Once the Charcot process has been initiated, continued ambulation results in progressive collapse and deformity. Severe deformities can have an impact on the patient\u27s ambulatory status, and when associated with instability, ulceration, or infection, there is greater risk for a major limb amputation

Plantar Foot Donor Site as a Harvest of a Split-thickness Skin Graft.

The authors present a minimally invasive procedure for harvesting a split thickness skin graft (STSG) from the plantar surface of the foot. This is another option to consider for soft tissue reconstruction of diabetic foot wounds to help restore form and function and to prevent amputation. The authors do not recommend this technique for all soft tissue wounds of the toes and plantar aspect of the foot but believe it is a viable option for selected small diabetic foot wounds that may benefit from a STSG

Complications and Revisional Hallux Valgus Surgery.

Complications with hallux valgus surgery can manifest in a variety of ways, but ultimately preventing them depends on the surgeon\u27s expertise in patient and procedural selection, ability to perform the surgery selected, and knowledge in dealing with postoperative care and complications if present. In this article, the authors discuss common diagnostic and treatment dilemmas when dealing with recurrent hallux valgus, hallux varus, malunion, and avascular necrosis following bunion surgery

Dynamic Behavior of an Intrinsically Unstructured Linker Domain Is Conserved in the Face of Negligible Amino Acid Sequence Conservation

Proteins or regions of proteins that do not form compact globular structures are classified as intrinsically unstructured proteins (IUPs). IUPs are common in nature and have essential molecular functions, but even a limited understanding of the evolution of their dynamic behavior is lacking. The primary objective of this work was to test the evolutionary conservation of dynamic behavior for a particular class of IUPs that form intrinsically unstructured linker domains (IULD) that tether flanking folded domains. This objective was accomplished by measuring the backbone flexibility of several IULD homologues using nuclear magnetic resonance (NMR) spectroscopy. The backbone flexibility of five IULDs, representing three kingdoms, was measured and analyzed. Two IULDs from animals, one IULD from fungi, and two IULDs from plants showed similar levels of backbone flexibility that were consistent with the absence of a compact globular structure. In contrast, the amino acid sequences of the IULDs from these three taxa showed no significant similarity. To investigate how the dynamic behavior of the IULDs could be conserved in the absence of detectable sequence conservation, evolutionary rate studies were performed on a set of nine mammalian IULDs. The results of this analysis showed that many sites in the IULD are evolving neutrally, suggesting that dynamic behavior can be maintained in the absence of natural selection. This work represents the first experimental test of the evolutionary conservation of dynamic behavior and demonstrates that amino acid sequence conservation is not required for the conservation of dynamic behavior and presumably molecular function