Automated Visual Database Creation For A Ground Vehicle Simulator

This research focuses on extracting road models from stereo video sequences taken from a moving vehicle. The proposed method combines color histogram based segmentation, active contours (snakes) and morphological processing to extract road boundary coordinates for conversion into Matlab or Multigen OpenFlight compatible polygonal representations. Color segmentation uses an initial truth frame to develop a color probability density function (PDF) of the road versus the terrain. Subsequent frames are segmented using a Maximum Apostiori Probability (MAP) criteria and the resulting templates are used to update the PDFs. Color segmentation worked well where there was minimal shadowing and occlusion by other cars. A snake algorithm was used to find the road edges which were converted to 3D coordinates using stereo disparity and vehicle position information. The resulting 3D road models were accurate to within 1 meter

Beyond Nuclear Pasta: Phase Transitions and Neutrino Opacity of Non-Traditional Pasta

In this work, we focus on different length scales within the dynamics of nucleons in conditions according to the neutron star crust, with a semiclassical molecular dynamics model, studying isospin symmetric matter at subsaturation densities. While varying the temperature, we find that a solid-liquid phase transition exists, that can be also characterized with a morphology transition. For higher temperatures, above this phase transition, we study the neutrino opacity, and find that in the liquid phase, the scattering of low momenta neutrinos remain high, even though the morphology of the structures differ significatively from those of the traditional nuclear pasta.Comment: 12 pages, 10 figure

Anticipated Synchronization in a Biologically Plausible Model of Neuronal Motifs

Two identical autonomous dynamical systems coupled in a master-slave configuration can exhibit anticipated synchronization (AS) if the slave also receives a delayed negative self-feedback. Recently, AS was shown to occur in systems of simplified neuron models, requiring the coupling of the neuronal membrane potential with its delayed value. However, this coupling has no obvious biological correlate. Here we propose a canonical neuronal microcircuit with standard chemical synapses, where the delayed inhibition is provided by an interneuron. In this biologically plausible scenario, a smooth transition from delayed synchronization (DS) to AS typically occurs when the inhibitory synaptic conductance is increased. The phenomenon is shown to be robust when model parameters are varied within physiological range. Since the DS-AS transition amounts to an inversion in the timing of the pre- and post-synaptic spikes, our results could have a bearing on spike-timing-dependent-plasticity models

Classification of sagittal imbalance based on spinal alignment and compensatory mechanisms

Sagittal balance is an independent predictor of clinical outcomes in spinal care. Surgical treatment is challenging and jeopardized by frequent complications. Guidelines for surgical treatment are currently not based on a classification of the disease. A comprehensive classification of sagittal balance based on regional deformities and compensatory mechanisms combined in deformity patterns is proposed. Though the sagittal shape of the spine can change due to degeneration or trauma, correlations between sagittal shape parameters and pelvic incidence (PI) have been described. Pelvic incidence is not changed by degeneration, thus representing a permanent source of information on the original sagittal shape of the spine.One hundred and twenty-eight full-spine lateral standing radiographs of patients with different spinal conditions were evaluated and classified by one rater. One random subseries of 35 patients was evaluated by two raters for calculation of inter-rater agreement. Spinopelvic parameters were measured in all the radiographs. Internal validity of the classification system was evaluated comparing the values of regional sagittal parameters that distinguish one category from the others.Eight different patterns were identified regarding the site of the deformity and the presence of compensatory mechanisms: cervical, thoracic, thoracolumbar junction, lumbar, lower lumbar, global and pelvic kyphosis and normal sagittal alignment. Inter-rater agreement was almost perfect (κ = 0.963). Statistically significant differences were found comparing the means of selected sagittal spinopelvic parameters that conceptually divide pairs or groups of categories: C2-C7 SVA for cervical kyphosis vs all other patients, TK-PI mismatch for thoracic kyphosis vs all other patients, T11-L2 kyphosis for thoracolumbar kyphosis vs all other patients, global alignment (LL+TK-PI) and SVA for lumbar kyphosis vs global kyphosis and pelvic tilt for pelvic kyphosis vs lumbar, lower lumbar and global kyphosis.A comprehensive classification of sagittal imbalance is presented. This classification permits a better interpretation of the deformity and muscle forces acting on the spine, and helps surgical planning. Preliminary validation has been provided

Assessment of the corrosion behaviour of alloys 825 and 625 in stagnant seawater-effect of temperature and welding

Alloy 825 has been extensively used as a cladding alloy in the gas and oil industry for process piping up to and including the manifolds, separators, wellheads, risers and valves. The outstanding corrosion resistance of alloy 825 against general and localised corrosion attack is attributed to its high Ni, Cr and Mo content. However, corrosion failures of alloy 825 equipment have been observed in offshore environments. Alloy 825 has good weldability and for applications that require exceptional resistance to corrosion, Inconel filler metal 625 is used as ''overmatching composition''. Nevertheless, there is always a threat of galvanic corrosion when two dissimilar alloys are electrically connected. In this study, the corrosion behaviour of alloy 825, alloy 625 weld and alloy 825 weldment have been investigated. Potentiodynamic polarization curves for the alloys were recorded in synthetic seawater across a range of temperatures (30 to 60°C). Mixed potential theory was applied to determine corrosion potentials, rates of corrosion and predict the galvanic effect of coupling alloy 825 to alloy 625 filler metal via welding. Three standard methods were considered to determine the critical pitting temperature (CPT) for alloy 825. Lastly, long-term immersion tests in seawater were conducted to determine the relationship between the laboratory accelerated tests results and the performance of the alloys under real service conditions. The results from the experimental tests revealed that alloy 825 and alloy 625 weld exhibit outstanding corrosion resistance to uniform corrosion, despite the effect of temperature on the corrosion rate of both alloys. The galvanic effect of coupling alloy 825 to alloy 625 via welding is insignificant. The corrosion morphology of alloy 825 and its weldment is temperature dependent. At temperatures below 45 °C, grain boundary attack was observed in alloy 825 samples, while pitting corrosion was observed at temperatures higher than 50 °C. Alloy 625 weld exhibited only one mode of corrosion attack, namely the selective dissolution of interdendritic phase throughout the test temperature range. There was no agreement between the CPT results for alloy 825 and its weldment obtained using the three standard methods. No correlation was found between CPT determined by laboratory tests and the temperature above which alloy 825 would suffer pitting corrosion in long term seawater exposure tests

Prone single-position extreme lateral interbody fusion (Pro-XLIF): preliminary results.

Abstract Background Single-position options for combined anterior and posterior fusion in the lumbar spine have been suggested to reduce the surgical time and improve the efficiency of operating room. Previous reports have focused on lateral decubitus single-position surgery. The goal of this study is to describe and evaluate the feasibility and safety of prone single-position extreme lateral interbody fusion (XLIF) with posterior fixation. Methods Design Pilot prospective non-randomized controlled study. Seven patients who underwent prone single-position XLIF and posterior fixation were evaluated (Pro-XLIF). A control group (Std-XLIF) was composed of ten patients who underwent XLIF in lateral decubitus and posterior fixation in prone position. All patients underwent interbody XLIF fusion at one level and posterior procedures at one or more levels. Duration of surgery, blood loss, complications, X-ray use and clinical outcomes were recorded. Results No major complications were observed in either group. Oswestry Disability Index, back pain and leg pain were improved in the Pro-XLIF group from 48.5, 7.7 and 8.5 to 14.5, 1.71 and 2.71, respectively, and in the Std-XLIF group from 50.8, 5.7 and 7.2 to 22.5, 3.7 and 2.5. The Pro-XLIF group had a longer time of preparation before incision (39 vs 26 min, ns), equal duration of the anterior procedure (65 vs 59 min, ns), shorter duration of surgery (133 vs 182 min, ns) and longer X-ray exposure time (102 vs 92 s, ns). The surgical technique is described. Conclusions Prone single-position XLIF is feasible and safe. In this preliminary report, the results are comparable to the standard technique. Graphic abstract These slides can be retrieved under Electronic Supplementary Material

Classification of degenerative segment disease in adults with deformity of the lumbar or thoracolumbar spine

Lumbar and thoracolumbar deformity in the adult is a condition with impairment of health status that can need surgical treatment. In contrast with adolescent deformity, where magnitude of the curve plays a significant role in surgical indication, the aspects relevant in adult deformity are pain and dysfunction that correlate with segment degeneration and imbalance. Previous classifications of adult deformity have been of little use for surgical planning.Chart review and classification of radiographic and clinical findings. A classification of degenerative disc disease based on distribution of diseased segments and balance status of the spine is presented.Four main categories are presented: Type I (limited nonapical segment disease), Type II (limited apical segment disease), Type III (extended segment disease--apical and nonapical), Type IV (imbalanced spine: IVa, sagittally imbalanced; IVb, sagittally and coronally imbalanced).Types I and II can be treated by fusion of a selective area of the curve. Type III needs fusion of all the extension of the coronal curve. Type IV usually needs aggressive corrective procedures, frequently including posterior tricolumnar osteotomies. This classification permits interpreting the extension and magnitude of the disease and can help establish a surgical plan regarding selective fusion and methods of sagittal correction. Future research is needed to validate the classification

Epidemiología de las consultas respiratorias de adultos en Santiago de Chile desde 2003 a 2008

Background: Respiratory diseases are the third cause of death, and the second cause of hospitalization among people aged 65 years or more in Chile. Aim: To analyze the distribution of consultations due to respiratory diseases among adults living in Metropolitan Santiago. Material and Methods: A daily registry of all consultations of patients older than 15 years old in seven public primary care centers, was carried out between January 2003 and December 2008. Consultations were classified as having non-respiratory or respiratory causes. The latter were broke down in upper or lower respiratory diseases, pneumonia, chronic obstructive pulmonary disease (COPD) and asthma. Results: A total of 1,170,941 consultations were registered and 19% were due to respiratory diseases. Of these, 46% were due to upper respiratory diseases, 31% due to lower respiratory diseases, 8% due to COPD, 6% due to pneumonia, 5% due to asthma and 4% due to other respiratory causes. Pneumonia and COPD were more frequent among consultants older than 65 years. Conclusions: Consultations due to respiratory diseases are approximately one fifth of all primary care consultations. Older people often have more chronic and severe diseases. Key words: Adult; Epidemiology; Morbidity; Respiratory tract diseases