309 research outputs found
Analysis of fluidization behavior in the loop-seal of a circulating fluidized bed gasifier using particle-in-cell method
No full textThe loop-seal (LS) of a circulating fluidized bed (CFB) reactor is the heart of the system and is still under consideration due to complexities in both two-phase flow and the geometry. The LS controls the solid circulation rate (SCR) of particles that is crucial for the stable operation of a CFB system. In this study, the effect of the aeration rate on the circulation rate of two-chamber LS for a 10 MWth CFB gasification system is examined. The influence of aeration rate supplied to the recycle and the supply chambers of the LS is investigated in detail with 44 different cases using computational particle fluid dynamics (CPFD) method. Barracuda VR software is used to model the whole CFB system with non-reacting isothermal flow assumption. The solid circulation rates are investigated for various aeration rates corresponding to different operating regimes. The stable and unstable operating conditions are identified according to monitored pressure fluctuations. Moreover, three regimes are revealed based on the analysis of differential pressure between two chambers of LS. It is found that the region for the stable operation, corresponding to higher SCR and lower pressure fluctuations, exists for a certain range of aeration rates and the aeration ratio between two chambers of LS
Combination of Luque instrumentation with polyaxial screws in the treatment of myelomeningocele kyphosis
No full textRigid congenital kyphosis in myelomeningocele is associated with an important morbidity with skin breakdown, recurrent infection, and decreased function. Kyphectomy is the classic treatment to restore spinal alignment; however, surgery is associated with morbidity and long-term complications. The purpose of this retrospective study was to examine the authors' experience using combination of Luque instrumentation with posterolaterally placed polyaxial screws in. the treatment of myelomeningocele kyphosis. From June 1999 to June 2003, 7 patients were treated and followed up for an average of 68.6 months. The average age at the time of the operation was 7 year and I month. All patients underwent vertebral excision from just above the apex of vertebral deformity to realign the sagittal deformity. Posterolaterally placed polyaxial screws were used in combination with segmental Luque instrumentation. Kyphotic deformity averaged 104 degrees before surgery, 15.2 degrees after surgery, and 18.5 degrees at the latest follow-up. The average loss of correction was 3.3 degrees. The average blood loss was 611 mL. Complications occurred in 2 of 7 patients were superficial wound breakdown and deep wound infection that required rotational flap closure. Kyphectomy with posterior instrumentation by using Luque technique in the combination with polyaxial screws is reliable method for correcting rigid kyphotic deformity in patients with myelomeningocele. Rigidity of the construct, greater correction capacity, and low profile instrumentation by the help of posterolateral insertion of the polyaxial screws and wiring were the distinct advantages of this technique
Preventing blood-induced joint damage with the use of intra-articular iron chelators: an experimental study in rabbits
No full textThis animal model was designed to evaluate the effect of intra-articular iron-chelator treatment in the prevention of blood-induced joint disease. Thirty domestic male rabbits were divided into three equal groups. One milliliter of homologous blood was injected into the left knee of each rabbit in groups 1 and 2. In the second group, 0.1 ml desferroxamine mesilate (DM) was also injected to the blood. In group 3, the animals received injections of 0.1 DM which was mixed with equal amounts of sterile saline solution. The joints were injected three times each week for 12 weeks. At the end of 12 weeks, the knee joints of each rabbit were examined. The synovium in group 1 was found statistically significantly thicker than in group 2. Obvious erosion and ulceration of the cartilage were seen in all joints in group 1 and absent in group 2. Iron-chelator treatment reduced the formation of blood-induced joint damage in rabbit knees by inhibiting the iron-catalyzed formation of destructive oxygen metabolites that has an effect on joint cartilage and synovium
Conservative treatment of Charcot artroparthy in a series of spina bifida patients: the experience of one center and review of the literature
No full textThe present study was performed to evaluate the use of patellar tendon-bearing ankle foot orthesis for the treatment of Charcot arthropathy in a series of patients with spina bifida. A cohort of 350 spina bifida patients, ages ranging between 12 months and 22 years were evaluated in our clinic between June 1993 and March 2004. Charcot arthropathy was seen in five of these children. Treatment was initiated with nonsteroidal anti-inflammatory drugs, oral bisphosphonates and immobilization. No change was observed in the patients' symptoms after a month of treatment. At this time, a patellar tendon-bearing ankle foot orthesis was prescribed and used for a period of 6 to 24 months. All patients improved within 2 months. At the end of 2 years of follow-up, three patients are still using the brace without any complaints. One patient still has symptoms, although she is wearing her brace, but she has had significant improvement compared with the initiation of therapy. Non-weight-bearing, immobilization and surgery are the known treatment choices in Charcot arthropathy. Little experience exists about this entity and its treatment. Our experience reveals that the patellar tendon-bearing ankle foot orthesis leads to significant improvement in children with Charcot arthropathy without surgery and immobilization
Molecular orientation behavior of poly (vinyl chloride) as influenced by the nanoparticles and plasticizer during uniaxial film stretching in the rubbery stage
No full textThe structural evolution during uniaxial stretching of poly(vinyl chloride) films was studied using our real time spectral birefringence stretching machine. The effect of clay loading and the amount of plasticizer as well as the rate effects on the birefringence development and true mechanical response are presented with a final model summarizing the molecular phenomena during stretching. Mechano-optical studies revealed that birefringence correlated with mechanical response (stress, strain, work) nonlinearly. This was primarily attributed to the preexisting strong network of largely amorphous chains connected via small crystallites that act as physical crosslinking points. These crystallites are not easily destroyed during the high-speed stretching process as evidenced from the birefringence–true strain curves along with the X-ray crystallinity measurements. At high speeds, the amorphous chains do not have enough time to relax and hence attain higher orientation levels. The crystallites, however, orient more efficiently when stretched at slow speeds. Apparently, some relaxation of the surrounding amorphous chains helps rotate the crystallites in the stretching direction. Overall birefringence is higher at high stretching speeds for a given true strain value. When the nanoparticles are incorporated, the orientation levels are increased significantly for both the crystalline and amorphous phases. Nanoplatelets increase the continuity of the network because they have strong interaction with the amorphous chains and/or crystallites. This in turn helps transfer the local stresses to the attached chains and increase the orientation levels of the chains
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