Evaluation of Multiple Corrosion Protection Systems for Reinforced Concrete Bridge Decks

Chloride-induced corrosion is one of the leading causes of premature serviceability failure in reinforced concrete bridge decks. In an effort to mitigate the effect of corrosion on the longevity of concrete bridge decks, several corrosion protection systems have been developed. The current study evaluates the effectiveness of multiple corrosion protection strategies when used in conjunction with epoxycoated reinforcement (ECR). The epoxy coating in all test bars is penetrated with either four or ten 3-mm (1/8-in.) diameter holes. The systems evaluated include three corrosion inhibitors (DCI-S, Rheocrete 222+, and Hycrete DSS) in concrete with a w/c ratio of 0.45 and 0.35, an ECR containing a primer of microencapsulated calcium nitrite between the epoxy and the steel in concrete with a w/c ratio of 0.45 and 0.35, three types of increased adhesion ECR (ECR pretreated with chromate prior to the application of the epoxy coating, and ECR with increased adhesion epoxies developed by DuPont and Valspar) evaluated in concrete with a w/c ratio of 0.45, as well as in concrete containing DCI-S corrosion inhibitor, and multiple-coated reinforcement that contains a zinc layer between the steel and the DuPont 8-2739 epoxy coating in concrete with a w/c ratio of 0.45. Conventional steel and epoxy-coated reinforcement serve as control specimens; the performance of the epoxy-coated reinforcement is compared to the performance of the conventional steel reinforcement. Each corrosion protection system is evaluated using the Southern Exposure and cracked beam tests. Macrocell and microcell corrosion losses, mat-to-mat resistances, top and bottom mat corrosion potentials, and critical chloride concentrations are measured during the test. Upon completion of the study, each specimen is autopsied and any disbondment of the epoxy coating from the steel is measured. Of the systems evaluated in this study, conventional steel exhibits the greatest amount of corrosion. ECR, whether in uncracked or cracked concrete, exhibits low corrosion losses; well below the magnitude required to cause corrosion-induced surface deterioration. A lower w/c ratio provides additional protection in uncracked concrete, but affords little to no protection in cracked concrete. Corrosion inhibitors, while effective in uncracked concrete, afford no additional protection against corrosion in cracked concrete. All three improved adhesion ECR systems exhibit corrosion performance that is similar to conventional ECR. Multiple-coated reinforcement exhibits greater corrosion losses than conventional ECR, but the corrosion losses are below the magnitude of corrosion loss required to cause corrosion-induced surface deterioration. The effective critical chloride threshold for epoxy-coated reinforcement is several times higher than that of conventional reinforcement. A relationship exists between microcell and macrocell corrosion loss, and between both microcell and macrocell corrosion loss and the disbonded area of epoxy observed on the bar. The cathodic disbondment test (ASTM A775) does not appear to be a reliable indicator of corrosion disbondment performance of in-service epoxycoated reinforcement

Influence of Pacing Strategy on Oxygen Uptake During Treadmill Middle-Distance Running

The oxygen uptake (V·O2) attained during a constant speed 800-m pace trial on a treadmill is less than the maximal V·O2 (V·O2max) in male middle-distance runners with a high V·O2max (i.e., > 65 ml · kg-1 · min-1). We therefore investigated whether the V·O2 attained was influenced by the pacing strategy adopted. Eight male middle-distance runners (age 25.8 ± 3.3 years; height 1.78 ± 0.10 m; mass 67.8 ± 4.7 kg) with a personal best 800-m time of 112.0 ± 3.3 s volunteered to participate. Subjects undertook a speed ramped progressive test to determine V·O2max and three 800-m pace runs to exhaustion all in a randomised order. The three 800-m pace runs included constant speed, acceleration, and race simulation runs. Oxygen uptake was determined throughout each test using 15-s Douglas bag collections. Following the application of a 30-s rolling average, the highest V·O2 during the progressive test (i.e., V·O2max) and the highest V·O2 during the 800-m pace runs (i.e., V·O2peak) were compared. For the eight runners, V·O2max was 67.2 ± 4.3 ml · kg-1 · min-1. V·O2peak was 60.1 ± 5.1 ml · kg-1 · min-1, 61.1 ± 5.2 ml · kg-1 · min-1, and 62.2 ± 4.9 ml · kg-1 · min-1, yielding values of 89.3 ± 2.4 %, 90.8 ± 2.8 %, and 92.5 ± 3.1 % V·O2max for the constant speed, acceleration and race simulation runs, respectively. Across runs, repeated measures ANOVA revealed a significant effect (p = 0.048). Trend analysis identified a significant linear trend (p = 0.025) with the % V·O2max attained being higher for the acceleration run than the constant speed run, and higher still for the race simulation run. These results demonstrate that in middle-distance runners a) pacing strategy influences the V·O2 attained, with a race simulation run elevating the V·O2 attained compared with other pacing strategies, and b) regardless of pacing strategy the V·O2 attained in an 800-m pace run on a treadmill is less than V·O2max

The improved prognosis of hypoplastic left heart:A Population-Based Register Study of 343 Cases in England and Wales

Background: Hypoplastic Left Heart Syndrome (HLHS) is a severe congenital heart defect (CHD) characterised by the underdevelopment of the left side of the heart with varying levels of hypoplasia of the left atrium, mitral valve, left ventricle, aortic valve and aortic arch. In the UK, age 12 survival for cases born between 1991 and 1993 was 21%. UK survival estimates corresponding to cases born between 2000 and 2015 were improved at 56%, but survival was examined up to age five only. Contemporary long-term survival estimates play a crucial role in counselling parents following diagnosis. The aim of this study was to report survival estimates up to age 15 for children born with HLHS or hypoplastic left ventricle with additional CHD in England and Wales between 1998 and 2012. Methods: Cases of HLHS notified to four congenital anomaly registers in England and Wales during 1998–2012, matched to Office for National Statistics mortality information, were included. Kaplan-Meier survival estimates to age 15 were reported. Cox regression models were fitted to examine risk factors for mortality. Results: There were 244 cases of HLHS and 99 cases of hypoplastic left ventricle co-occurring with other CHD, with traced survival status. Kaplan-Meier survival estimates for HLHS were 84.4% at age 1 week, 76.2% at 1 month, 63.5% at age 1 year, 58.6% at age 5 years, 54.6% at age 10 years, and 32.6% to age 15 years. The Kaplan-Meier survival estimates for cases of hypoplastic left ventricle co-occurring with additional CHD were 90.9% at age 1 week, 84.9% at 1 month, 73.7% at age 1 year, 67.7% to age 5 years, 59.2% to age 10 years, and 40.3% to age 15 years. Preterm birth (p = 0.007), low birth weight (p = 0.005), and female sex (p = 0.01) were associated with mortality. Conclusions: We have shown that prognosis associated with HLHS in the twenty first century exceeds that of many previous population-based studies, likely due to improvements in intensive care technologies and advances in surgical techniques over the last few decades

Influence of Pacing Strategy on Oxygen Uptake During Treadmill Middle-Distance Running

The oxygen uptake (V·O2) attained during a constant speed 800-m pace trial on a treadmill is less than the maximal V·O2 (V·O2max) in male middle-distance runners with a high V·O2max (i.e., > 65 ml · kg-1 · min-1). We therefore investigated whether the V·O2 attained was influenced by the pacing strategy adopted. Eight male middle-distance runners (age 25.8 ± 3.3 years; height 1.78 ± 0.10 m; mass 67.8 ± 4.7 kg) with a personal best 800-m time of 112.0 ± 3.3 s volunteered to participate. Subjects undertook a speed ramped progressive test to determine V·O2max and three 800-m pace runs to exhaustion all in a randomised order. The three 800-m pace runs included constant speed, acceleration, and race simulation runs. Oxygen uptake was determined throughout each test using 15-s Douglas bag collections. Following the application of a 30-s rolling average, the highest V·O2 during the progressive test (i.e., V·O2max) and the highest V·O2 during the 800-m pace runs (i.e., V·O2peak) were compared. For the eight runners, V·O2max was 67.2 ± 4.3 ml · kg-1 · min-1. V·O2peak was 60.1 ± 5.1 ml · kg-1 · min-1, 61.1 ± 5.2 ml · kg-1 · min-1, and 62.2 ± 4.9 ml · kg-1 · min-1, yielding values of 89.3 ± 2.4 %, 90.8 ± 2.8 %, and 92.5 ± 3.1 % V·O2max for the constant speed, acceleration and race simulation runs, respectively. Across runs, repeated measures ANOVA revealed a significant effect (p = 0.048). Trend analysis identified a significant linear trend (p = 0.025) with the % V·O2max attained being higher for the acceleration run than the constant speed run, and higher still for the race simulation run. These results demonstrate that in middle-distance runners a) pacing strategy influences the V·O2 attained, with a race simulation run elevating the V·O2 attained compared with other pacing strategies, and b) regardless of pacing strategy the V·O2 attained in an 800-m pace run on a treadmill is less than V·O2max

VO2 Attained During Treadmill Running: The Influence of a Specialist (400-m or 800-m) Event

Purpose: Previously it has been observed that, in well-trained 800-m athletes, VO(2)max is not attained during middle-distance running events on a treadmill, even when a race-type pacing strategy is adopted. Therefore, the authors investigated whether specialization in a particular running distance (400-m or 800-m) influences the VO(2) attained during running on a treadmill. Methods: Six 400-m and six 800-m running specialists participated in the study. A 400-m trial and a progressive test to determine VO(2)max were completed in a counterbalanced order. Oxygen uptakes attained during the 400-m trial were compared to examine the influence of specialist event. Results: A VO(2) plateau was observed in all participants for the progressive test, demonstrating the attainment of VO(2)max. The VO(2)max values were 56.2 +/- 4.7 and 69.3 +/- 4.5 mL . kg(-1) min(-1) for the 400-m- and 800-m-event specialists, respectively (P = .0003). Durations for the 400-m trial were 55.1 +/- 4.2 s and 55.8 +/- 2.3 s for the 400-m- and 800-m-event specialists, respectively. The VO(2) responses achieved were 93.1% +/- 2.0% and 85.7% +/- 3.0% VO(2)max for the 400-m- and 800-m-event specialists, respectively (P = .001). Conclusions: These results demonstrate that specialist running events do appear to influence the percentage of VO(2)max achieved in the 400-m trial, with the 800-m specialists attaining a lower percentage of VO(2)max than the 400-m specialists. The 400-m specialists appear to compensate for a lower VO(2)max by attaining a higher percentage VO(2)max during a 400-m trial

Influence of test duration on oxygen uptake attained during treadmill running

Previous investigations have revealed that in well-trained middle-distance runners, oxygen uptake (VO2) does not attain maximal values (VO2max) in exhaustive treadmill trials where the VO2 demand exceeds VO2max. To date, this shortfall in the VO2 attained has been demonstrated in trials as short as 2 min in duration. In this study, we investigated whether a reduction in exhaustive test duration influences the VO2 attained during running on a treadmill. Six middle-distance runners participated in the study, completing an exhaustive 400 m and 800 m trial. These trials, together with a progressive test to determine VO2max, were completed in a counterbalanced order. Oxygen uptakes attained during the 400 m and 800 m trials were compared to examine the influence of exhaustive test duration. A plateau in VO2 was observed in all participants for the progressive test, demonstrating the attainment of VO2max. The mean speed, duration, and resulting distance in the constant-speed exhaustive trials were 25.8 km h(-1) (s=1.2), 55.8 s (s=2.3), and 400.2 m (s=20.2) for the 400 m trial, and 24.3 km h(-1) (s=0.8), 108.4 s (s=21.2), and 730.1 m (s=129.1) for the 800 m trial, respectively. A paired-samples t-test revealed a significantly different (P=0.018)%VO2max was attained for the 400 m (85.7%, s=3.0) and 800 m (89.1%, s=5.0) trials. In conclusion, VO2 did not reach VO2max during the exhaustive constant-speed 400 m and 800 m trials, but the test duration does influence the%VO2max achieved. Specifically, the VO2 attained becomes progressively further below VO2max as trial duration is reduced, such that 89% and 86% VO2max is achieved in exhaustive 800 m and 400 m constant-speed trials, respectively

A thermodynamic framework for the magnesium-dependent folding of RNA

The goal of this review is to present a unified picture of the relationship between ion binding and RNA folding based on recent theoretical and computational advances. In particular, we present a model describing how the association of magnesium ions is coupled to the tertiary structure folding of several well-characterized RNA molecules. This model is developed in terms of the nonlinear Poisson–Boltzmann (NLPB) equation, which provides a rigorous electrostatic description of the interaction between Mg 2+ and specific RNA structures. In our description, most of the ions surrounding an RNA behave as a thermally fluctuating ensemble distributed according to a Boltzmann weighted average of the mean electrostatic potential around the RNA. In some cases, however, individual ions near the RNA may shed some of their surrounding waters to optimize their Coulombic interactions with the negatively charged ligands on the RNA. These chelated ions are energetically distinct from the surrounding ensemble and must be treated explicitly. This model is used to explore several different RNA systems that interact differently with Mg 2+ . In each case, the NLPB equation accurately describes the stoichiometric and energetic linkage between Mg 2+ binding and RNA folding without requiring any fitted parameters in the calculation. Based on this model, we present a physical description of how Mg 2+ binds and stabilizes specific RNA structures to promote the folding reaction. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 118–136, 2003Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34328/1/10353_ftp.pd

Emergence of a peak in early infant mortality due to HIV/AIDS in South Africa

Objectives: South Africa has among the highest levels of HIV prevalence in the world. Our objectives are to describe the distribution of South African infant and child mortality by age at fine resolution, to identify any trends over recent time and to examine these trends for HIV-associated and non HIV-associated causes of mortality. Methods: A retrospective review of vital registration data was conducted. All registered postneonatal deaths under 1 year of age in South Africa for the period 1997–2002 were analysed by age in months using a generalized linear model with a log link and Poisson family. Results: Postneonatal mortality increased each year over the period 1997–2002. A peak in HIV-related deaths was observed, centred at 2–3 months of age, rising monotonically over time. Conclusion: We interpret the peak in mortality at 2–3 months as an indicator for paediatric AIDS in a South African population with high HIV prevalence and where other causes of death are not sufficiently high to mask HIV effects. Intrauterine and intrapartum infection may contribute to this peak. It is potentially a useful surveillance tool, not requiring an exact cause of death. The findings also illustrate the need for early treatment of mother and child in settings with very high HIV prevalence

Application of Intervention Mapping to develop a community-based health promotion pre-pregnancy intervention for adolescent girls in rural South Africa: Project Ntshembo (Hope).

BACKGROUND: South Africa (SA) is undergoing multiple transitions with an increasing burden of non-communicable diseases and high levels of overweight and obesity in adolescent girls and women. Adolescence is key to addressing trans-generational risk and a window of opportunity to intervene and positively impact on individuals' health trajectories into adulthood. Using Intervention Mapping (IM), this paper describes the development of the Ntshembo intervention, which is intended to improve the health and well-being of adolescent girls in order to limit the inter-generational transfer of risk of metabolic disease, in particular diabetes risk. METHODS: This paper describes the application of the first four steps of IM. Evidence is provided to support the selection of four key behavioural objectives: viz. to eat a healthy, balanced diet, increase physical activity, reduce sedentary behaviour, and promote reproductive health. Appropriate behaviour change techniques are suggested and a theoretical framework outlining components of relevant behaviour change theories is presented. It is proposed that the Ntshembo intervention will be community-based, including specialist adolescent community health workers who will deliver a complex intervention comprising of individual, peer, family and community mobilisation components. CONCLUSIONS: The Ntshembo intervention is novel, both in SA and globally, as it is: (1) based on strong evidence, extensive formative work and best practice from evaluated interventions; (2) combines theory with evidence to inform intervention components; (3) includes multiple domains of influence (community through to the individual); (4) focuses on an at-risk target group; and (5) embeds within existing and planned health service priorities in SA

The Effect of Prior Exposures on the Notched Fatigue Behavior of Disk Superalloy ME3

Environmental attack has the potential to limit turbine disk durability, particularly in next generation engines which will run hotter; there is a need to understand better oxidation at potential service conditions and develop models that link microstructure to fatigue response. More efficient gas turbine engine designs will require higher operating temperatures. Turbine disks are regarded as critical flight safety components; a failure is a serious hazard. Low cycle fatigue is an important design criteria for turbine disks. Powder metallurgy alloys, like ME3, have led to major improvements in temperature performance through refractory additions (e.g. Mo,W) at the expense of environmental resistance (Al, Cr). Service conditions for aerospace disks can produce major cycle periods extending from minutes to hours and days with total service times exceeding 1,000 hours in aerospace applications. Some of the effects of service can be captured by extended exposures at elevated temperature prior to LCF testing. Some details of the work presented here have been published