515 research outputs found

    Remotely-Operated Vehicle Animal Tracking Telemetry System

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    This paper’s design focus is a Remotely Operated Vehicle (ROV) payload receiver system. An ROV is a remote control vehicle operated from a nearby position. This project’s ROV is an aerial vehicle flown by a crew of at least four operators. The ROV receiver is needed to The receiver system receives a 165 MHz collar beacon signal, upconverts the signal to 3.4 GHz, then transmits the 3.4 GHz signal to the ROV operator. The collar beacon signal indicates the location of a tracking collar placed on an animal, fishers in this instance. The transmitted signal is received by the ROV operator and indicates the beacon signal’s direction. The ROV is directed by the operator toward the beacon signal’s location. This improves animal tracking efficiency, saving hours. The result of the project is a transceiver system capable of receiving a signal from approximately 3,500 meters maximum range, processing the signal, and transmitting the signal a maximum 915 meters (1000 yards) back to the ROV operator. The maximum distance between the operator and ROV is 1000 yards due to remote control limitations

    Solvent Synergists for Improved Kinetic Hydrate Inhibitor Performance of Poly(N-vinylcaprolactam)

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    The synergetic effect of a range of different solvents on the kinetic hydrate inhibitor (KHI) performance of poly(N-vinylcaprolactam) (PVCap) has been investigated. The equipment used was a high-pressure (76 bar) rocking cell apparatus using slow constant cooling (approximately 1 °C/h from 20.5 °C) and a synthetic natural gas mixture forming structure II hydrate. The synergetic effect was investigated by adding 5000 ppm of a range of alcohols, glycol ethers, and ketones to a solution of 2500 ppm of PVCap (Mw = 10 000 g/mol). For many of the additives, the ranking of the synergetic effect can be explained with reference to the size, shape, and hydrophobicity of the main alkyl group (“tail”) in the molecule as well as the presence of a glycol ether group. Among all of the solvents investigated, the best synergetic effect was achieved by 4-methyl-1-pentanol. When 5000 ppm of 4-methyl-1-pentanol was added to 2500 ppm of PVCap, no hydrate formation occurred down to the minimum test temperature of 3 °C (subcooling at ca. 16.3 °C) in 15 parallel experiments compared to 10.4 °C for pure PVCap. Predictions for improved glycol ether synergists are given.publishedVersio

    Regression models for linking patterns of growth to a later outcome:Infant growth and childhood overweight

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    Abstract Background Regression models are widely used to link serial measures of anthropometric size or changes in size to a later outcome. Different parameterisations of these models enable one to target different questions about the effect of growth, however, their interpretation can be challenging. Our objective was to formulate and classify several sets of parameterisations by their underlying growth pattern contrast, and to discuss their utility using an expository example. Methods We describe and classify five sets of model parameterisations in accordance with their underlying growth pattern contrast (conditional growth; being bigger v being smaller; becoming bigger and staying bigger; growing faster v being bigger; becoming and staying bigger versus being bigger). The contrasts are estimated by including different sets of repeated measures of size and changes in size in a regression model. We illustrate these models in the setting of linking infant growth (measured on 6 occasions: birth, 6 weeks, 3, 6, 12 and 24 months) in weight-for-height-for-age z-scores to later childhood overweight at 8y using complete cases from the Norwegian Childhood Growth study (n = 900). Results In our expository example, conditional growth during all periods, becoming bigger in any interval and staying bigger through infancy, and being bigger from birth were all associated with higher odds of later overweight. The highest odds of later overweight occurred for individuals who experienced high conditional growth or became bigger in the 3 to 6 month period and stayed bigger, and those who were bigger from birth to 24 months. Comparisons between periods and between growth patterns require large sample sizes and need to consider how to scale associations to make comparisons fair; with respect to the latter, we show one approach. Conclusion Studies interested in detrimental growth patterns may gain extra insight from reporting several sets of growth pattern contrasts, and hence an approach that incorporates several sets of model parameterisations. Co-efficients from these models require careful interpretation, taking account of the other variables that are conditioned on

    Core wettability reproduction: A new solvent cleaning and core restoration strategy for chalk cores

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    Laboratory core restoration procedures include different core cleaning solvents, establishment of initial water saturation (Swi) by diverse techniques and processes of crude oil exposure that influence the final core wetting properties.In carbonate reservoirs, the acidic Polar Organic Components (POC) in crude oil are the main components dictating the wettability of the carbonate surface. Negatively charged carboxylates strongly attach to the positively charged CaCO3 surface, thus acting as anchor molecules for the oil phase.During core cleaning with organic solvents, some of the adsorbed POC will be detached from the mineral surfaces, thereby changing the wetting conditions. However, cores are not expected to become completely water-wet even when using strong solvents.The main aim of this paper is to develop core cleaning and core restoration procedures to reproduce initial core wettability.Fractional-wet outcrop chalk cores were exposed to two different core cleaning procedures, (1) mild kerosene-heptane cleaning, or (2) standard toluene-methanol cleaning. Chromatographic wettability tests showed that both cleaning methods increased the fraction of water-wet surface area to a similar extent, but neither of them removed all adsorbed POC from the rock surface. Wettability tests by spontaneous imbibition showed that the kerosene-heptane cleaned core behaved slightly water-wet, while the toluene-methanol cleaned core behaved very water-wet, even though the cores had similar fractions of water-wet surface areas. Increased amount of crude oil exposure during core restoration reduced the water wetness below the initial fractional core wetting.Initial core wettability was successfully reproduced by combining mild cleaning solvents preserving initial adsorbed POC, and minimizing the amount of crude oil exposure during core restoration. Only a 1.5–3.6 %OOIP variation in ultimate recovery during spontaneous imbibition in four different core systems was observed.publishedVersio

    Peak oxygen uptake and breathing pattern in COPD patients – a four-year longitudinal study

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    Background: Activities of daily living in patients with chronic obstructive pulmonary disease (COPD) are limited by exertional dyspnea and reduced exercise capacity. The aims of the study were to examine longitudinal changes in peak oxygen uptake (V̇O2peak), peak minute ventilation (V̇Epeak) and breathing pattern over four years in a group of COPD patients, and to examine potential explanatory variables of change. Methods: This longitudinal study included 63 COPD patients, aged 44-75 years, with a mean forced expiratory volume in one second (FEV1) at baseline of 51 % of predicted (SD = 14). The patients performed two cardiopulmonary exercise tests (CPETs) on treadmill 4.5 years apart. The relationship between changes in V̇ O2peak and V̇Epeak and possible explanatory variables, including dynamic lung volumes and inspiratory capacity (IC), were analysed by multivariate linear regression analysis. The breathing pattern in terms of the relationship between minute ventilation (V̇E) and tidal volume (VT) was described by a quadratic equation, VT = a + b∙V̇ E + c∙V̇E2, for each test. The VTmax was calculated from the individual quadratic relationships, and was the point where the first derivative of the quadratic equation was zero. The mean changes in the curve parameters (CPET2 minus CPET1) and VTmax were analysed by bivariate and multivariate linear regression analyses with age, sex, height, changes in weight, lung function, IC and inspiratory reserve volume as possible explanatory variables. Results: Significant reductions in V̇ O2peak (p < 0.001) and V̇ Epeak (p < 0.001) were related to a decrease in resting IC and in FEV1. Persistent smoking contributed to the reduction in V̇O2peak. The breathing pattern changed towards a lower VT at a given V̇ E and was related to the reduction in FEV1. Conclusion: Increasing static hyperinflation and increasing airway obstruction were related to a reduction in exercise capacity. The breathing pattern changed towards more shallow breathing, and was related to increasing airway obstruction.publishedVersio

    Biodegradation of the Alkaline Cellulose Degradation Products Generated during Radioactive Waste Disposal.

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    The anoxic, alkaline hydrolysis of cellulosic materials generates a range of cellulose degradation products (CDP) including α and β forms of isosaccharinic acid (ISA) and is expected to occur in radioactive waste disposal sites receiving intermediate level radioactive wastes. The generation of ISA's is of particular relevance to the disposal of these wastes since they are able to form complexes with radioelements such as Pu enhancing their migration. This study demonstrates that microbial communities present in near-surface anoxic sediments are able to degrade CDP including both forms of ISA via iron reduction, sulphate reduction and methanogenesis, without any prior exposure to these substrates. No significant difference (n = 6, p = 0.118) in α and β ISA degradation rates were seen under either iron reducing, sulphate reducing or methanogenic conditions, giving an overall mean degradation rate of 4.7×10−2 hr−1 (SE±2.9×10−3). These results suggest that a radioactive waste disposal site is likely to be colonised by organisms able to degrade CDP and associated ISA's during the construction and operational phase of the facility

    Maternal and infant vitamin B12 status during infancy predict linear growth at 5 years

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    BACKGROUND: Many children worldwide have poor vitamin B12 status. The objective of this study was to estimate association between maternal and infant vitamin B12 status and long-term growth. METHODS: We randomly selected 500 Nepali mother-infant pairs and measured maternal intake and infant and maternal vitamin B12 status using plasma cobalamin, total plasma homocysteine, and methylmalonic acid concentrations. We revisited available children when they were 5 years old and measured growth. The associations between intake and maternal and infant markers of vitamin B12 and growth were estimated in multiple linear regression models adjusting for relevant confounders (n = 331). RESULTS: Maternal vitamin B12 intake and status and vitamin B12 status in infancy predicted linear growth at 5 years of age, but not during infancy. Each microgram increase in the vitamin B12 intake of the mother during infancy was associated with an increase in height of 0.4 (0.2, 0.6) height-for-age z-scores and 1.7 (0.7, 2.7) cm around the child's fifth birthday. CONCLUSION: Vitamin B12 status and intake in early life is an important determinant for linear growth at school age. Our findings should be verified in randomized, placebo controlled trials before translated into public health recommendations.We are grateful for the contributions of the field supervisor Chandrawati Chitrakar and data managers Pravin Rajbhandari and Uma Regmi, and the children and mothers for their invaluable contribution to the study. The present study was funded through grants from the Research Council of Norway (project no. 234495), from the GCRieber Funds, and the South-Eastern Norway Regional Health Authority (grant no. 2012090).publishedVersio

    Do Children Who Move Home and School Frequently Have Poorer Educational Outcomes in Their Early Years at School? An Anonymised Cohort Study

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    Frequent mobility has been linked to poorer educational attainment. We investigated the association between moving home and moving school frequently and the early childhood formal educational achievement. We carried out a cohort analysis of 121,422 children with anonymised linked records. Our exposure measures were: 1) the number of residential moves registered with a health care provider, and 2) number of school moves. Our outcome was the formal educational assessment at age 6–7. Binary regression modeling was used to examine residential moves within the three time periods: 0 – ,1 year; 1 – ,4 years and 4 – ,6 years. School moves were examined from age 4 to age 6. We adjusted for demographics, residential moves at different times, school moves and birth related variables. Children who moved home frequently were more likely not to achieve in formal assessments compared with children not moving. Adjusted odds ratios were significant for 3 or more moves within the time period 1 –,4 years and for any number of residential moves within the time period 4– ,6 years. There was a dose response relationship, with increased odds ratios with increased frequency of residential moves (2 or more moves at 4–,6 years, adjusted odds ratio 1.16 (1.03, 1.29). The most marked effect was seen with frequent school moves where 2 or more moves resulted in an adjusted odds ratio of 2.33 (1.82, 2.98). This is the first study to examine the relationship between residential and school moves in early childhood and the effect on educational attainment. Children experiencing frequent mobility may be disadvantaged and should be closely monitored. Additional educational support services should be afforded to children, particularly those who frequently change school, in order to help them achieve the expected educational standards
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