772 research outputs found

    Modeling Land-Cover Types Using Multiple Endmember Spectral Mixture Analysis in a Desert City

    Get PDF
    Spectral mixture analysis is probably the most commonly used approach among sub-pixel analysis techniques. This method models pixel spectra as a linear combination of spectral signatures from two or more ground components. However, spectral mixture analysis does not account for the absence of one of the surface features or spectral variation within pure materials since it utilizes an invariable set of surface features. Multiple endmember spectral mixture analysis (MESMA), which addresses these issues by allowing endmembers to vary on a per pixel basis, was employed in this study to model Landsat ETM+ reflectance in the Phoenix metropolitan area. Image endmember spectra of vegetation, soils, and impervious surfaces were collected with the use of a fine resolution Quickbird image and the pixel purity index. This study employed 204 (=3x17x4) total four-endmember models for the urban subset and 96 (=6x6x2x4) total five-endmember models for the non-urban subset to identify fractions of soil, impervious surface, vegetation, and shade. The Pearson correlation between the fraction outputs from MESMA and reference data from Quickbird 60 cm resolution data for soil, impervious, and vegetation were 0.8030, 0.8632, and 0.8496 respectively. Results from this study suggest that the MESMA approach is effective in mapping urban land covers in desert cities at sub- pixel level.

    Interlaminar modelling to predict composite coiled tube failure

    Get PDF
    In a field operation that uses coiled tubing in its applications, fibre-reinforced polymer matrix composite tubing is seldom used. Fibre-composite coiled tubes offer advantages, compared to steel material, through a reduction in weight and improvement in fatigue life. The stiffness of composite material degrades progressively when increasing the number of cyclic loading. The fatigue damage and failure criteria of fibre-reinforced composite coiled tubes are more complex than that of steel; hence, failure predictions are somewhat unreliable. Among the defects in composite materials, interlaminar delamination is the foremost problem in fibre-reinforced composite material, and it leads to a reduction in strength and stiffness especially in cyclic-load conditions. Delamination causes a redistribution of the load path along the composite structure, which is unpredictable; therefore, delamination in a composite coiled tube in an oil and gas field eventually leads to final failure, which could be catastrophic. A-ply-by-ply mathematical modelling and numerical simulation method was developed to predict interlaminar delamination of filament-wound composite coiled tubes under a combination of different loading scenarios with consideration to low-cycle fatigue. The objective of this paper is to explain interlaminar delamination as an initial crack and source of stress concentration in composite coiled tubes in the framework of meso-cracking progression of matrix damage modelling of composite laminates. The paper focuses on delamination failure because the largest span of the composite lifecycle is at the crack propagation phase, which manifests itself in the form of delamination. The analysis shows that the crack front tip is not uniform, and also shows that carbon fibre possesses higher stiffness values compared to glass fibre. The paper confirms that 2D modelling cannot express the real release strain energy rate at the crack front tip. Mode-I testing, however, showed that the double cantilever beam (DCB) only represents the normal stress from the release strain energy rate. The results also indicated that there were other sources contributing to the strain energy release rate, such as inter-layer frictions and normal stress in the end notched flexure (ENF) testing mode

    Case Studies on the Exploitation of Crowd-Sourcing with Web 2.0 Functionalities

    Get PDF
    Crowd-sourcing appears more promising with Web 2.0 functionality and businesses have started using it for a wide range of activities, that would be better completed by a crowd rather than any specific pool of knowledge workers. However, relatively little is known about how a business can leverage on collective intelligence and capture the user- generated value for competitive advantage. This empirical study uses the principle of interpretive field research to validate the case findings with a descriptive multiple case study methodology. An extended theoretical framework to identify the important considerations at strategic and functional levels for the effective use of crowd-sourcing is proposed. The analytic framework uses five Business Strategy Components: Vision and Strategy, Human Capital, Infrastructure, Linkage and Trust, and External Environment. It also uses four Web 2.0 Functional Components: Social Networking, Interaction Orientation, Customization & Personalization, and User- added Value. By using these components as analytic lenses, the case research examines how successful e-commerce firms may deploy Web 2.0 functionalities for effective use of crowd-sourcing. Prioritization of these functional considerations might be favorable in some cases for the best fit of situations and limitations. In conclusion, it is important that the alignment between strategy and functional components is maintained

    Pilot study on depression among secondary school students in Selangor

    Get PDF
    A cross sectional descriptive study of 2048 subjects was conducted to determine the prevalence of depression and factors influencing depression among students in secondary school from urban and rural areas in the state of Selangor. Malaysia. The children's depression inventory (COl) developed by Maria Kovacs was used in this study. Students who participated in this study come from two urban schools and three rural schools. It was found that in the yield for scores for five factors were 9.2% have negative mood. 5% have interpersonal problems. 8.3% have ineffectiveness. 9.8% have anhedonia and 10.6% have negative self esteem. Following the interpretive guidelines for the T-scores. it was found that 10.3% of the students were much above average in the depression scale. This study also found that: 1% of students were smoking. 1.6% of students were gum sniffling. 0.9% took drugs. 4.1 % took alcohol and 9.9% took things from other people. Females were more depressed than males. The Chinese students were more depressed compared to Indian students. Students whose parents had no formal education or had only primary education were more depressed than students whose parents had secondary. college or university education. Depression increased with increasing number of siblings. Depression contributed to the habit of drug abuse. gum sniffing and stealing but not to smoking and alcohol abuse. Suicidal tendencies were more likely among the depressed students. It is imperative that not only caregivers but also teachers have to be equipped with the knowledge. attitude and skills to assist secondary school children cope with their emotions. handle conflicts and manage stress early so that a more productive society will develop in the future

    Residual brain injury after early discontinuation of cooling therapy in mild neonatal encephalopathy

    Get PDF
    We examined the brain injury and neurodevelopmental outcomes in a prospective cohort of 10 babies with mild encephalopathy who had early cessation of cooling therapy. All babies had MRI and spectroscopy within 2 weeks after birth and neurodevelopmental assessment at 2 years. Cooling was prematurely discontinued at a median age of 9 hours (IQR 5-13) due to rapid clinical improvement. Five (50%) had injury on MRI or spectroscopy, and two (20%) had an abnormal neurodevelopmental outcome at 2 years. Premature cessation of cooling therapy in babies with mild neonatal encephalopathy does not exclude residual brain injury and adverse long-term neurodevelopmental outcomes. This study refers to babies recruited into the MARBLE study (NCT01309711, pre-results stage)

    Towards precision medicine for pain: diagnostic biomarkers and repurposed drugs

    Get PDF
    We endeavored to identify objective blood biomarkers for pain, a subjective sensation with a biological basis, using a stepwise discovery, prioritization, validation, and testing in independent cohorts design. We studied psychiatric patients, a high risk group for co-morbid pain disorders and increased perception of pain. For discovery, we used a powerful within-subject longitudinal design. We were successful in identifying blood gene expression biomarkers that were predictive of pain state, and of future emergency department (ED) visits for pain, more so when personalized by gender and diagnosis. MFAP3, which had no prior evidence in the literature for involvement in pain, had the most robust empirical evidence from our discovery and validation steps, and was a strong predictor for pain in the independent cohorts, particularly in females and males with PTSD. Other biomarkers with best overall convergent functional evidence for involvement in pain were GNG7, CNTN1, LY9, CCDC144B, and GBP1. Some of the individual biomarkers identified are targets of existing drugs. Moreover, the biomarker gene expression signatures were used for bioinformatic drug repurposing analyses, yielding leads for possible new drug candidates such as SC-560 (an NSAID), and amoxapine (an antidepressant), as well as natural compounds such as pyridoxine (vitamin B6), cyanocobalamin (vitamin B12), and apigenin (a plant flavonoid). Our work may help mitigate the diagnostic and treatment dilemmas that have contributed to the current opioid epidemic

    The cost of inbreeding in a socially polymorphic ant population

    Get PDF
    Trabalho de projecto de mestrado em Medicina (Gastroenterologia), apresentado á Faculdade de Medicina da Universidade de CoimbraA encefalopatia hepática é uma das principais complicações da doença hepática crónica e pode estar presente em 50 a 70% de todos os pacientes cirróticos, incluindo aqueles com alterações demonstráveis apenas por testes psicométricos, sendo uma complicação de grande relevância clínica. Na insuficiência hepática aguda, os doentes podem sucumbir a uma morte neurológica, com edema cerebral e hipertensão intracraniana. A sobrevida em pacientes com doença hepática crónica depende da avaliação dos critérios da classificação de Child-Pugh que reconhece a importância prognóstica da encefalopatia hepática. Esta complicação da doença hepática, aguda ou crónica, resulta da diminuição da actividade hepática com incapacidade marcada de eliminação de determinadas toxinas do organismo. Hoje sabe-se que os astrócitos, nomeadamente as células de Alzheimer tipo II, tem um papel importante na fisiopatologia da encefalopatia hepática. A epidemiologia e a fisiopatologia da encefalopatia hepática permanecem ainda apenas parcialmente esclarecidas, tornando este tema fonte importante de estudos constantes. O trabalho proposto tem como objectivo uma actualizada revisão bibliográfica, centrando-se nos últimos avanços científicos sobre esta alteração neuropsiquiátrica. Com este trabalho, propõe-se estudar os diferentes métodos de diagnóstico, indicações das diferentes opções terapêuticas, comparando-as entre si, identificar o impacto económico e social da encefalopatia hepática, assim como perceber os mecanismos fisiopatológicos que contribuem para esta grave alteraçãoHepatic encephalopathy is one of the main complications of chronic liver disease and can occur in 50 to 70% of all cirrhotic patients, including those with alterations demonstrated only through psychometric tests, being a complication of great clinical relevance. In severe liver failure, patients can perish due to neurological death, with brain swelling and intracranial hypertension. Chronic liver disease patients’ survival time depends on the evaluation of Child- Pugh classification criteria that recognizes the prognostic importance of hepatic encephalopathy. This liver disease complication, chronic or severe, is a result of the reduction of liver activity with marked incapacity to eliminate certain toxins from the organism. Today it is known that astrocytes, namely Alzheimer type II cells, have an important role in hepatic encephalopathy physiopathology. The epidemiology and physiopathology of hepatic encephalopathy still remain partially clarified, becoming this subject an important source of constant studies. The main goal of this study is to make an actualized bibliographical revision, grounded on the last scientific advances on this neuropsychiatric abnormality. Through this work, one considers studying the different diagnostic methods, the different therapeutic option indications, by comparing them, identifying the economic and social impact of hepatic encephalopathy, as well as understanding the physiopathological mechanisms that contribute for this serious abnormalit
    corecore