Management of traumatic double-level spondyloptosis of the thoracic spine with posterior spondylectomy: Case report

Traumatic spondyloptosis of the thoracic spine is an uncommon injury. In most cases, spondyloptosis is confined to one vertebral body, whereas double-level spondyloptosis is extremely rare. Most patients who sustain traumatic spondyloptosis immediately become paraplegic, but in some cases neurological function is preserved. If this occurs, it is due to detachment of the pedicles from the corresponding vertebral body, resulting in spontaneous decompression of neural elements. Herein, the authors describe a case of undetected traumatic double-level spondyloptosis in the upper thoracic region in an adult male patient who was neurologically intact for 2 days but later became paraplegic. Initially, management of this pathology seemed a very challenging scenario. However, with review of the reconstructed CT images and reproduction of the injury on a plastic model, a posterior-only approach was chosen as an alternative operative solution for this catastrophic injury. Via this single-stage posterior approach, long-segment pedicle screw/rod instrumentation resulted in successful reduction, restoration of alignment, and stabilization after 1-level posterior spondylectomy. To the best of the authors knowledge, this is the first example reported in the literature of double-level spondyloptosis of the thoracic and the lumbar spine. This report describes the rationale, mechanism, and technical details afforded for reduction and stabilization of this rare injury. © AANS 2015

Mechanistic studies of the reactions of some allylic halides

Imperial Users onl

Color Image Segmentation Based on Bayesian Theorem for Mobile Robot Navigation

Image segmentation is a fundamental process in many image, video, and computer vision applications. Object extraction and object recognition are typical applications that use segmentation as a low level image processing. Most of the existing color image segmentation approaches, define a region based on color similarity. This assumption often makes it difficult for many algorithms to separate the objects of interest which consist of highlights, shadows and shading which causes inhomogeneous colors of the objects’ surface. Bayesian classification and decision making are based on probability theory and choosing the most probable or the lowest risk. A useful property of the statistical classifier like Bayesian is that, it is optimal in the sense that it minimizes the expected mis classification rate. However when the number of features increased, Bayesian classifier is quite expensive both in terms of computational time and memory. This thesis proposes a Bayesian color segmentation method which is robust and simple for real time color segmentation even in presence of environmental light effect. In this study a decision boundary equation, which is acquired from class conditional probability density function (PDF) of colors, based on Bayes decision theory has been used for desired color segmentation. The estimation of unknown PDF is a common problem and in this study Gaussian kernel function which is most widely used nonparametric density estimation method has been used for PDF calculation. Comparisons were made between the proposed method to the k-nearest neighbor (KNN) and support vector machine (SVM), methods for image segmentation. Experimental results show that the proposed algorithm works better than other two methods in terms of classifier accuracy with result of more than 99 percent successful segmentation of desired color in varying illumination. In order to show the real time ability and robustness of proposed method for color segmentation, experimental results conducted on vision based mobile robot for navigation. First the robot was trained by some training sample of desired target color in environment. The decision boundary which acquired in the teaching phase has been used for real time color segmentation as the robot move in the environment. Spatial information of desired color in segmented image has been used for calculating the robot heading angle which is used by mobile robot controller for navigation. However, all of the existing color image segmentation approaches are strongly application dependent. This study shows that proposed algorithm successfully cope with the varying illumination which causes uneven colors of the objects’ surface. The experimental results show the proposed algorithm is simple and robust, for real time application on vision based mobile robot for navigation, in spite of presence of other shapes and colors in the environmen

Remote paraparesis due to a traumatic extradural arachnoid cyst developing 2 years after brachial plexus root avulsion injury: Case report and review of the literature

Traumatic extradural arachnoid cyst is a rare entity. However, late appearance of paraparesis due to formation of an extradural arachnoid cyst as a sequel of brachial plexus injury is extremely rare and the literature regarding this issue is scarce revealing only 11 cases. Herein, we report a patient with delayed progressive spastic paraparesis appearing after a multilevel brachial plexus root avulsion injury where imaging revealed formation of a large traumatic extradural arachnoid cyst at the cervicothoracic region. Furthermore, to propose that a high-energy trauma might simultaneously result in delayed formation of an extradural arachnoid cyst. However, preganglionic root avulsion injury with pseudomeningocele formation in association with extradural arachnoid cyst is not reported previously. A case of a 36-year-old man with spastic paraparesis developing 2 years after a multilevel brachial plexus root avulsion injury is presented. Root avulsion had immediately resulted in complete paralysis of the left upper limb that had not ameliorated. Imaging studies of the cervicothoracic region disclosed left-sided multilevel pseudomeningoceles and a large extradural arachnoid cyst extending from C5 to T2. After appropriate en bloc laminotomy, the cyst was excised and the causative dural tear was closed. Subsequently, three large defects of pseudomeningoceles were obliterated with artificial dural patch for the prevention of cord herniation. This was followed with laminoplasty of the corresponding levels after dural closure. The postoperative course was uneventful and paraparesis recovered steadily within 2 months. Paraparesis even years after brachial plexus injury should be regarded as a serious event that deserves extensive imaging survey for the possibility of the formation of an extradural arachnoid cyst. Careful review of the literature disclosed that the current case is the 12th case that an extradural arachnoid cyst has developed after brachial plexus injury and the first example that the pathogenic factor that might be implicated in occurrence of this rare association could be clarified with review of the MRI features. Actually, the presence of posttraumatic pseudomeningoceles in association with an arachnoid cyst in the current case is in favor of the belief that only preganglionic root injuries that are in close proximity to the spinal canal had been the cause dural tear with remote formation of extradural arachnoid cyst. � 2015 Georg Thieme Verlag KG Stuttgart � New York

Morphologic Measurements of Anatomic Landmarks in Pulp Chambers of Human First Molars: A Study of Bitewing Radiographs

INTRODUCTION: Knowledge of the anatomic location and dimension of the molar pulp chamber may preserve healthy pulp during operative procedure and reduce risk of perforation of chamber during access preparation. A review of literatures regarding the morphology of pulp chamber however revealed very little information; so the aim of this in vivo study was to measure the dimensions of first molar pulp chambers as seen on bitewing (BW) radiographs. MATERIALS AND METHODS: In this cross-sectional study molar's BW radiographs of 130 subjects in two age groups were taken under standardized conditions (group of 18-25 years old subjects and group of 50-65 years old subjects). The films were digitized and nine anatomical landmarks were evaluated from the image of each first molar as follow: A; mesial to distal pulp horn distance, B; mesial to distal walls at the middle of pulp chamber, C; mesial to distal orifices, D; mesial cusp tip to its horn, E; distal cusp tip to its horn, F; pulp chamber height, G; pulp chamber floor to furcation, H; pulp chamber ceiling to furcation, I; cusp tips to furcation. The data were evaluated by using AUTOCAD (2007) software with 0.00 precision. Two way ANOVA test (Uni-variant analysis) were used to determine the interaction between restoration and age on pulp chamber dimensions. RESULTS: There was no significant difference in pulp chamber dimensions between the genders. Although there was significant reduction in the size of pulp chamber with advancing age, no significant differences were found in the restored and non restored teeth. CONCLUSION: The finding of this study showed size reduction and changes of pulp chamber with age so may enhance knowledge to minimize errors during endodontics treatments

3-Ethyl­sulfanyl-5-methyl-1-phenyl-7-(pyrrolidin-1-yl)-1H-pyrimido[4,5-e][1,3,4]thia­diazine

In the crystal structure of the title compound, C18H21N5S2, the thia­diazine six-membered ring and pyrrolidine five-membered ring display boat and envelope conformations, respectively. The crystal structure contains weak C—H⋯N and C—H⋯S hydrogen bonding

The Effect of Lecturing in Student-generated Photomontage on EFL Learners’ Fluency, Accuracy and Complexity

This study examines if the two tasks exploited, model-based lecture and the photomontage one, have been effective in upgrading students’ speaking skills in CAF domain. From a methodological point of view an independent samples t-test design is used to obtain data from 33 subjects consisting of both male and female studying EFL in Guilan University. Group one and two are Oral II students and group three are Oral I, each consisting of 11 members. The video recorded data are transcribed and coded for later analysis. Measures include areas of CAF. Results of t-tests show that lecturing on photomontage generated higher fluency and some trend in accuracy with no effect on complexity. The results are discussed in the light of Skehan’s CAF triad, as well as competing theories of attention allocation during task performance. The findings provide insight into impact of task use and present suggestions for EFL/ESL teachers and materials developers

A New Topological Perspective on Quantization in Physics

We propose a new characterization of classical quantization in physics in terms of sheaf cohomology on the site of spacetime as a smooth 4-manifold. The perspective of sheaf cohomology is motivated by a presentation of the Aharonov-Bohm effect in terms of the integration of differential forms

Engineering toughening mechanisms in architectured ceramic-based bioinspired materials

Abstract Ceramics offer many attractive properties including low-density, high compressive strength, remarkable thermal stability, and high oxidation/corrosion resistance. However, these materials suffer from brittleness, which substantially limits the range of their applications, where high toughness is required. This investigation draws inspiration from a concept of architectures with three-dimensional (3D) networks of weak interfaces targeting high toughness ceramics. In this study, a comprehensive method combining an advanced computational model with 3D digital image correlation (DIC) was developed to engineer bioinspired multilayered architectured ceramics and assesses their toughening and deformation mechanisms when subjected to a low-velocity impact load regime. A complete finite element (FE) analysis was conducted to precisely evaluate the crack growth and displacement field of the architectured ceramics and is compared to those of plain ceramics. The damage and displacement evolution results from FE analysis and experimental testing revealed that the primary source of toughening of the architectured ceramic systems is extrinsic, resulting from extensive crack deflection and delamination. Crack propagation along an irregular long path at the weak interfaces of architectured layers increased the toughness of the plain ceramics by two orders of magnitude. Based on the DIC data, both extrinsic and intrinsic toughening mechanisms were captured: sliding of the tiles in the architectured ceramics and channel plastic deformation in adhesive interlayers, respectively