Algorithm and design improvements for indirect time of flight range imaging cameras

This thesis describes the development of a compact and modularised indirect time of flight range imaging camera. These cameras commonly use the Amplitude Modulated Continuous Wave (AMCW) technique. For this technique, an entire scene is illuminated with light modulated at a high frequency. An image sensor is also modulated and the phase shift introduced between the two modulation signals, due to the transit time of the light reflecting off objects in the scene and returning to the camera, is used to measure the distance. The system constructed for this thesis is controlled by a Cyclone III FPGA and is capable of producing full field of view range images in real time with no additional computational resources. A PMD19K-2 sensor is used as the modulatable image sensor, and is capable of modulation frequencies up to 40 MHz. One significant issue identified with this range imaging technology is that the precision of the range measurements are often dependent on the properties of the object being measured. The dynamic range of the camera is therefore very important when imaging high contrast scenes. Variable Frame Rate Imaging is a novel technique that is developed as part of this thesis and is shown to have promise for addressing this issue. Traditional theory for indirect time of flight cameras is expanded to describe this technique and is experimentally verified. A comparison is made between this technique and traditional High Dynamic Range Imaging. Furthermore, this technique is extended to provide a constant precision measurement of a scene, regardless of the properties of the objects in the scene. It is shown that the replacement of the standard phase detection algorithm with a different algorithm can both reduce the linearity error in the phase measurements caused by harmonics in the correlation waveform and ameliorate axial motion error caused by relative motion of the camera and the object being measured. The new algorithm requires a trivial increase in computational power over the standard algorithm and can be implemented without any significant changes to the standard hardware used in indirect time of flight cameras. Finally, the complete system is evaluated in a number of real world scenarios. Applications in both 3D modelling and mobile robotics are demonstrated and tests are performed for a variety of scenarios including dynamic scenes using a Pioneer 2 robot

Drug sensitivity and apoptosis in tamoxifen resistant breast cancer

Tamoxifen has long been used in the treatment of hormone responsive breast cancer. However, tumours frequently develop resistance within 2-5 years of treatment, characterised by the return of tumour growth. The epidermal growth factor receptor EGFR is an important contributing factor in allowing formerly tamoxifen sensitive tumours to grow in the presence of tamoxifen. High levels of EGFR in many tumours correlate with a poor prognosis and an increased resistance to cytotoxic drugs. It was the initial aim of this study to ascertain whether the increased EGFR signalling associated with tamoxifen resistance results in a phenotype more resistant to cytotoxic drugs, and to study the underlying mechanisms that may cause this. Rather than observing the expected increase in resistance to cytotoxic drugs upon the development of tamoxifen resistance, a greatly increased sensitivity to the radiomimetic drug bleomycin was observed. Inhibition of EGFR in either the tamoxifen sensitive or resistant cells had very little effect on bleomycin sensitivity, The rate of uptake of various drugs was measured, and found to be identical between tamoxifen sensitive cells and their tamoxifen resistant derivatives. Microarray analysis of mRNA levels of drug efflux proteins also showed no significant decrease in drug efflux pump gene expression, with two efflux pump genes MRP3 and MRP4 showing increased expression. Tamoxifen resistant cells displayed greatly increased sensitivity to the apoptosis inducer camptothecin, and showed a significant increase in the levels of activated caspases present. Immunocytochemistry revealed a significant downregulation of the anti-apoptotic protein bcl-2.. Sensitivity to bleomycin was also measured and was found to inversely correlate to bcl-2 status. Finally bcl-2 levels were modulated using oestrogens and antioestrogens, and with an siRNA directed against the oestrogen receptor. The effect on bleomycin sensitivity was examined. Reduction of bcl-2 expression by either method had no effect on bleomycin sensitivit

The role of maternal stress in early pregnancy in the aetiology of gastroschisis : An incident case control study

We wish to thank all the women who took the time to take part in this study, the research nurses who undertook interviews and data collection: Sandra Edwards-Fenton, Anne Chamberlain, Marit Bodley, Sharon Brown, Isobel Clegg, Catherine Collins and the British Isles Network of Congenital Anomaly Registers (BINOCAR) for their support in facilitating this study.Peer reviewedPublisher PD

Exercise-induced bronchoconstriction in school-aged children who had chronic lung disease in infancy

Objectives: To assess for exercise-induced bronchoconstriction in 8- to 12-year-old children who had chronic lung disease (CLD) in infancy, and to evaluate the response of bronchoconstriction to bronchodilation with albuterol in comparison with preterm and term controls. Study design: Ninety-two children, including 29 with CLD, 33 born preterm at ≤32 weeks' gestation, and 30 born at term, underwent lung spirometry before and after cycle ergometry testing and after postexercise bronchodilation with albuterol. Results: Doctor-diagnosed asthma and exercise-induced wheeze were reported more frequently in the CLD group than in the preterm and term groups, but only 10% were receiving a bronchodilator. There were no differences among the groups in peak minute ventilation, oxygen uptake, or carbon dioxide output at maximum exercise. After maximal exercise, predicted forced expiratory volume in 1 second (FEV1) decreased from a mean baseline value of 81.9% (95% CI, 76.6-87.0%) to 70.8% (95% CI, 65.5-76.1%) after exercise in the CLD group, from 92.0% (95% CI, 87.2-96.8%) to 84.3% (95% CI, 79.1-89.4%) in the preterm group, and from 97.5% (95% CI, 92.5-102.6%) to 90.3% (95% CI, 85.1-95.5%) in the term group. After albuterol administration, FEV1 increased to 86.8% (95% CI, 81.7-92.0%) in the CLD group, 92.1% (95% CI, 87.3-96.9%) in the preterm group, and 97.1% (95% CI, 92.0-102.3%) in the term group. The decrease in predicted FEV1 after exercise and increase in predicted FEV1 after bronchodilator use were greatest in the CLD group (−11.0% [95% CI, −18.4 to −3.6%] and 16.0% [95% CI, 8.6-23.4%], respectively; P < .005 for both), with differences of <8% in the 2 control groups. Conclusion: School-age children who had CLD in infancy had significant exercise-induced bronchoconstriction that responded significantly to bronchodilation. Reversible exercise-induced bronchoconstriction is common in children who experienced CLD in infancy and should be actively assessed for and treated

Measurement of vulnerability to water stress-induced cavitation in grapevine: a comparison of four techniques applied to a long-vesseled species

Among woody plants, grapevines are often described as highly vulnerable to water-stress induced cavitation with emboli forming at slight tensions. However, we found native embolism never exceeded 30% despite low xylem water potentials (Ψx) for stems of

Measurement of vulnerability to water-stress induced cavitation in grapevine: a comparison of four techniques applied to a long-vesseled species

Among woody plants, grapevines are often described as highly vulnerable to water-stress induced cavitation with emboli forming at slight tensions. However, we found native embolism never exceeded 30% despite low xylem water potentials (Ψx) for stems of field grown vines. The discrepancy between native embolism measurements and those of previous reports led us to assess vulnerability curve generation using four separate methods and alterations (i.e. segment length and with/without flushing to remove embolism prior to measurement) of each. Centrifuge, dehydration and air-injection methods, which rely on measurement of percentage loss of hydraulic conductivity (PLC) in detached stems, were compared against non-invasive monitoring of xylem cavitation with nuclear magnetic resonance (NMR) imaging. Short segment air-injection and flushed centrifuge stems reached >90 PLC at Ψx of-0.5 and −1.5 MPa, respectively, whereas dehydration and long-segment air-injection measurements indicated no significant embolism at Ψx > −2.0 MPa. Observations from NMR agreed with the dehydration and long segment air-injection methods, showing the majority of vessels were still water-filled at Ψx > −1.5 MPa. Our findings show V. vinifera stems are far less vulnerable to water stress-induced cavitation than previously reported, and dehydration and long segment air-injection techniques are more appropriate for long-vesseled species and organs

The role of maternal nutrition in the aetiology of gastroschisis: an incident case-control study

Background: Gastroschisis, a congenital anomaly involving a defect in the fetal abdominal wall, has increased in prevalence in many countries, but the aetiology is uncertain. We tested the hypothesis that high maternal alcohol consumption and poor diet in the first trimester are risk factors in a case–control study in the UK (1 July 2007 to 28 February 2010). Methods: Gastroschisis cases and three controls per case (matched for maternal age) were identified at 18- to 20-week routine anomaly screening ultrasound scan (USS). Interviews were carried out during the antenatal period (median 24 weeks' gestation) using a piloted questionnaire. Conditional logistic regression was used to describe the associations between exposure variables and gastroschisis, adjusted for known confounding variables. Results: The response rate was 73% for cases (n = 91) and 70% for controls (n = 217). High consumption of fruits and vegetables during the first trimester (aOR 0.2; 95% CI 0.04–0.6), taking folic acid for at least 6 weeks during the first trimester (aOR 0.3; 95% CI 0.1–0.7) and increasing body fat percentage of total maternal body weight (aOR 0.9; 95% CI 0.8–0.9 per 1% increase) were independently associated with reduced risk. Cigarette smoking (aOR 2.7; 95% CI 1.1–6.8) was an independent risk factor. Conclusion: We report for the first time that higher intake of fruits and vegetables during the first trimester, longer duration of folic acid supplementation and higher body fat percentage are associated with reduced risk of fetal gastroschisis, independent of cigarette smoking. The increased risk of cigarette smoking is greatest in older women and in high socio-economic groups

Centrifuge technique consistently overestimates vulnerability to water stress-induced cavitation in grapevines as confirmed with high-resolution computed tomography

Vulnerability to cavitation is a key variable defining the limits to drought resistance in woody plants (Kursar et al., 2009). This trait is typically assessed by a vulnerability curve, which can be generated by a range of methods, including dehydration (Sperry et al., 1988), air injection (Cochard et al., 1992), and centrifugation (Alder et al., 1997). Results from two recent papers suggest that one of the most widely used methods, the centrifuge technique, overestimates vulnerability to cavitation in species with very long vessels (Choat et al., 2010; Cochard et al., 2010). Typically, the centrifuge technique produces characteristic ‘R shaped’ curves for long-vesseled species, compared with ‘S shaped’ curves produced by the dehydration method (Cochard et al., 2010). Both research groups proposed that open vessels contained in the centrifuged samples were responsible for this artifact. Grapevine (Vitis vinifera L.), a liana species known to have unusually long and wide vessels, appears to be particularly susceptible to artifacts with the centrifuge method (Choat et al., 2010), but the conclusions of this paper have been challenged by Jacobsen & Pratt (2012). They contend the dehydration technique actually underestimates vulnerability to cavitation in grapevine because the production of gels and ⁄ or tyloses causes a decline in maximum specific hydraulic conductivity (Ks max) over time. On the basis of their results and previously published hydraulic data, they concluded that the centrifuge technique is the most appropriate technique for estimating vulnerability to embolism (see details in Jacobsen & Pratt, 2012). Here we demonstrate that declining Ks max did not influence the results of Choat et al. (2010) and present new evidence from high-resolution computed tomography (HRCT) to support our original conclusions and refute those of Jacobsen & Pratt (2012). We also contend that the analysis of previous literature presented in Jacobsen & Pratt (2012) was oversimplified and obscured the specific comparison of cavitation resistance in current year shoots of grapevine. Overall, the findings presented in Jacobsen & Pratt (2012) for V. vinifera cv Glenora are in direct contrast to published and unpublished results generated by our research groups for other V. vinifera varieties

Biallelic Mutations in p16(INK4a) Confer Resistance to Ras- and Ets-Induced Senescence in Human Diploid Fibroblasts

The INK4a/ARF tumor suppressor locus is implicated in the senescence-like growth arrest provoked by oncogenic Ras in primary cells. INK4a and ARF are distinct proteins encoded by transcripts in which a shared exon is decoded in alternative reading frames. Here we analyze dermal fibroblasts (designated Q34) from an individual carrying independent missense mutations in each copy of the common exon. Both mutations alter the amino acid sequence of INK4a and functionally impair the protein, although they do so to different degrees. Only one of the mutations affects the sequence of ARF, causing an apparently innocuous change near its carboxy terminus. Unlike normal human fibroblasts, Q34 cells are not permanently arrested by Ras or its downstream effectors Ets1 and Ets2. Moreover, ectopic Ras enables the cells to grow as anchorage-independent colonies, and in relatively young Q34 cells anchorage independence can be achieved without addition of telomerase or perturbation of the p53 pathway. Whereas ARF plays the principal role in Ras-induced arrest of mouse fibroblasts, our data imply that INK4a assumes this role in human fibroblasts

Hypothesised pathway diagram for Stress, Social support, Lifestyle and Nutrition in the aetiology of Gastroschisis.

<p>Hypothesised pathway diagram for Stress, Social support, Lifestyle and Nutrition in the aetiology of Gastroschisis.</p