Using hypothesis testing on the mass-transfer effect with sulfate removal as an application

Sulfate and chemical oxygen demand removal by an anaerobic batch reactor treating of acid mine drainage is modelled. Available models are abundant but excessively complex, with large numbers of free parameters. Here, maximum likelihood and chi-squared hypothesis tests are applied to three simple models, with Malthus-Monod and Fick description, in increasing order of complexity: (i) planktonic single population (of sulfate-reducing bacteria); (ii) planktonic double-competing populations (adding fermentative bacteria); (iii) granule bound double-competing populations. The data set consists of 6 time profiles, sampled from 120 days of operation after stabilization of the reactor in pH 4. Single population is refuted by all profiles, in which the sulfate reduction is 72% larger than fermentatives. The planktonic double-competing population description is refuted at 119 days, with inner granule diffusion rate as low as 10% of the previous period. The results showed that, after an operation time, the influence of mass transfer became more evident and the incorporation of Fick's law in the model was fundamental to the description of this trend. All tests and inferences are performed at the 90% confidence interval due to large systematic uncertainties in the data.

Application of horizontal-flow anaerobic immobilized biomass reactor for bioremediation of acid mine drainage

The production of low-pH effluent with sulfate and metals is one of the biggest environmental concerns in the mining industry. The biological process for sulfate reduction has the potential to become a low-cost solution that enables the recovery of interesting compounds. The present study analyzed such a process in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor, employing ethanol as the carbon and energy source. Results showed that a maximal efficiency in the removal of sulfate and ethanol could only be obtained by reducing the applied sulfate load (225.1 ± 38 g m(-3) d(-1)). This strategy led to over 75% of chemical oxygen demand (COD) and sulfate removal. Among the COD/SO4(2-) studied ratios, 0.67 showed the most promising performance. The effluent's pH has naturally remained between 6.8 and 7.0 and the complete oxidation of the organic matter has been observed. Corrections of the influent pH or effluent recirculation did not show any significant effect on the COD and sulfate removal efficiency. Species closely related to strains of Clostridium sp. and species of Acidaminobacter hydrogenomorfans and Fusibacter paucivorans that can be related to the process of sulfate reduction were found in the HAIB reactors when the initial pH was 5 and the COD/SO4(2-) ratio increased to 1.0.

Sulfide-oxidizing bacteria establishment in an innovative microaerobic reactor with an internal silicone membrane for sulfur recovery from wastewater

A novel bioreactor, employing a silicone membrane for microaeration, was studied for partial sulfide oxidation to elemental sulfur. The objective of this study was to assess the feasibility of using an internal silicone membrane reactor (ISMR) to treat dissolved sulfide and to characterize its microbial community. The ISMR is an effective system to eliminate sulfide produced in anaerobic reactors. Sulfide removal efficiencies reached 96 % in a combined anaerobic/microaerobic reactor and significant sulfate production did not occur. The oxygen transfer was strongly influenced by air pressure and flow. Pyrosequencing analysis indicated various sulfide-oxidizing bacteria (SOB) affiliated to the species Acidithiobacillus thiooxidans, Sulfuricurvum kujiense and Pseudomonas stutzeri attached to the membrane and also indicated similarity between the biomass deposited on the membrane wall and the biomass drawn from the material support, supported the establishment of SOB in an anaerobic sludge under microaerobic conditions. Furthermore, these results showed that the reactor configuration can develop SOB under microaerobic conditions and can improve and reestablish the sulfide conversion to elemental sulfur.

Medial displacement calcaneal tuberosity osteotomy in the treatment of posterior tibial insufficiency

The loss of function of the posterior tibial tendon has been associated with a progressive deformity in adults, resulting in a painful flatfoot. Patients who have a painful flatfoot usually develop a valgus deformity of the hindfoot and an abduction deformity of the forefoot. If these deformities are supple, a medial displacement calcaneal tuberosity osteotomy together with a soft tissue repair by talonavicular capsulorraphy and repair of the spring ligament associated with a flexor digitorum tendon transfer to the posterior tibial can result in a satisfactory outcome.

Surgical reconstruction of the paralytic flaccid foot

Flaccid paralytic deformities are secondary to muscular imbalances. Conditions affecting the muscle itself or the neurogenic control of the muscle produce muscular imbalance. Once the origin of the flaccid paralytic foot is established, factors contributing to the deformity can be identified and addressed. It is imperative to understand the natural history of the underlying disorder that causes the deformity. The treatment of the patient with a flaccid paralysis depends primarily on a thorough knowledge and understanding of the normal function of the foot gait and secondarily on a thorough understanding of the natural history of the condition to be treated. A systematic, well-planned course of treatment, either surgical or nonsurgical, needs to be developed for each patient.

Amputation surgery and prostheses

Wide surgical margins in surgery for a bone tumor can be accomplished either by local excision or by amputation surgery. Amputation surgery has less morbidity than limb salvage surgery. Prosthetic replacement in the lower-extremity amputation should provide an artificial limb that will be comfortable and stable for weight bearing. Retention of the anatomic knee joint is critical for better ambulation and less energy expenditure. Upper-extremity prosthesis should be functional and cosmetically acceptable.

Calcified soft tissue leiomyoma of the shoulder mimicking a chondrogenic tumor

A case of leiomyoma with prominent calcification in the deep soft tissue of the shoulder is reported. The tumor showed mulberry-like calcifications on radiographs and computed tomography scans. Magnetic resonance imaging (MRI) showed well-circumscribed solid tumor with multiple signal voids. Although the signal intensity characteristics of the tumor matrix on plain MRI resembled those of chondroid matrix, the entire tumor was enhanced by gadopentetate dimeglumine and could be differentiated from chondrogenic tumors. MRI was also useful in evaluating the tumor extent.

A comparison of computed tomography-myelography, magnetic resonance imaging, and myelography in the diagnosis of herniated nucleus pulposus and spinal stenosis

The sensitivity, specificity, and accuracy of computed tomography (CT)-myelography, magnetic resonance imaging (MRI), and myelography in making the diagnosis of herniated nucleus pulposus (HNP) and spinal stenosis were compared in a retrospective study involving 59 surgical procedures in 57 patients who had all three tests performed preoperatively. One hundred nineteen levels were surgically explored for evidence of HNP and spinal stenosis. The results of each test were correlated with what was found at each surgical level explored. Overall, myelo-CT was the most accurate test for diagnosing HNP (76.4%) as well as the most sensitive (77.8%), whereas myelography was the most specific (89.2%). In making the diagnosis of spinal stenosis, myelo-CT and MRI were equally accurate (85.3%) and sensitive (87.2%), whereas myelography was the most specific (88.9%). In a special subset of patients who had revision surgery, the accuracy rate in diagnosing spinal stenosis or HNP was highest with MRI (84.9%), as was the sensitivity (69.2%) and specificity (95%). According to the results obtained from this series of patients, myelo-CT seems to be the most sensitive and accurate test in diagnosing HNP and spinal stenosis, whereas myelography is the most specific, although no statistical significance was noted in this study. However, because MRI did compare favorably with myelo-CT in most instances, particularly in revision surgery; it may be the procedure of choice due to its noninvasiveness and relative lack of side effects.

Giant cell tumor of the plantar tendon sheath: role of MR imaging in diagnosis. Case report

Giant cell tumor of the tendon sheath with characteristic magnetic resonance imaging findings is reported. The tumor was low intensity on T1-weighted and T2-weighted images, and showed strong homogeneous enhancement. These findings were considered to represent the pathological features of fine hemosiderin granules and collagenization.

The Bridle procedure in the treatment of paralysis of the foot

The Bridle procedure consists of a posterior tibial tendon transfer through the interosseous membrane to the dorsum of the foot with a dual anastomosis to the tendon of the anterior tibial and a rerouted peroneus longus in front of the lateral malleolus. This procedure is performed to restore loss of dorsiflexion and to balance the foot, preventing a secondary varus or valgus deformity. The procedure was performed in 10 patients with 11 feet with paralysis of dorsiflexion of the foot. All are brace-free. The results are better in patients with peroneal nerve palsy secondary to trauma.

An evaluation of the mechanical failure modalities of a rotating hinge knee prosthesis

The clinical and metallurgical performance of 12 retrieved Noiles total knee prostheses was investigated. Clinical histories and serial roentgenograms were used in conjunction with the American Society for Testing and Materials (ASTM) standard implant retrieval and analysis techniques to assess device performance. All of the devices were removed because of implant loosening with pain, while two devices also had a late infection. The average time in situ for all devices was four years. Roentgenographically, all of the devices showed signs of progressive radiolucencies. Ten (83%) of the devices migrated proximally within the femur. A marked varus drift was observed in eight (67%) of the retrieved prostheses. Hypertrophy of the femoral cortex was observed in eight (67%) of the cases. Seventy-three percent of the polyethylene tibial stems exhibited extensive wear on the anterior and medial aspects of the articulating surface. Extensive wear was also seen on the anterior and extreme posterior aspects in 92% of the polyethylene tibial plateau bearings. This wear was a consequence of the migration of the femoral component leading to buttressing of the plastic components against bone or bone cement. This study indicates serious design flaws in the Noiles knee prosthesis that unless corrected would question the use of the device in either primary or revision knee surgery.

Segmental spinal instrumentation in the management of fractures of the thoracic and lumbar spine

Eleven cases of fracture of the thoracic and lumbar spine were treated with segmental spinal instrumentation (Luque rods). The majority of these injuries occurred in motor vehicular accidents or falls from a height and were usually associated with multisystem trauma. This method of instrumentation provided immediate rigid internal fixation, which obviated the need for postoperative orthoses, allowed easier nursing care and early ambulation, and facilitated rehabilitation of patients with spinal cord injury. At 13 months' average follow-up, there have been no instances of wire breakage, rod deformation, or deterioration of neurologic status. This favorable experience suggests that segmental spinal instrumentation should be considered as an alternative mode of spinal instrumentation in fractures of the thoracic and lumbar spine.

Internal fixation of the femur in patients with osteogenesis imperfecta

The operation of fragmentation and intramedullary rod fixation of the femur with an extensible device has proved valuable for children with osteogenesis imperfecta because it permits these children to remain ambulatory. The use of an extensible rather than a solid rod has greatly decreased the need for reoperation.