Control of cracking in concrete by steel reinforcement : an examination of some of the mechanisms involved

The techniques tried up till now to model the problem of cracking in reinforced concrete have been largely empirical. Many relationships have been identified between certain parameters and the occurrence and size of cracks. This thesis reviews these, reports on the current state of knowledge, and discusses some of the theories proposed. Because of the great variation and complexity of the materials and stress interactions involved, the problem has to date defied completely objective theoretical modelling. The finite element method provides a powerful new modelling tool for theoretical simulation of complex real problems. Recent developments on constitutive models for concrete make this method extremely attractive for use in this case. This thesis attempts to make use of these tools by carrying out some analyses of the cracking of reinforced concrete prisms stressed in tension. The method is found to be a viable way of examining mechanisms and effects which are not ordinarily visible in laboratory experiments. These mechanisms are discussed in the light of the experimental findings recorded in the literature

Activity patterns in two rodent communities at El Cielo Biosphere Reserve, Tamaulipas, Mexico

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 25-30).Today, natural systems are undergoing drastic human-induced changes and losses of biodiversity. During this time of change it is extremely important that we understand the underlying mechanisms controlling the structure and composition of biotic communities. Small mammal communities have been studied extensively in arid regions (Brown et al. 2000), but few studies have been conducted in tropical regions. In 1957 Hutchinson proposed niche division as a means of co-existence of similar species. In 1974 Schoener proposed that the dietary, spatial, and temporal were the three main axes along which niche division may occur. This study evaluated the temporal patterns of the rodent communities at two sites in El Cielo Biosphere Reserve, Tamaulipas, Mexico. The first site was located in the Tropical Sub-Deciduous Forest (TSDF) region of the reserve. Six rodent species were trapped during interval trapping: Liomys irroratus (Heteromyidae), Peromyscus levipes (Muridae), Peromyscus leucopus (Muridae), Baiomys taylori (Muridae), Sigmodon hispidus (Muridae), and Oryzomys couesi (Muridae). All species at both sites are nocturnal and granivorous. We used chi-square and G-test analyses and rejected our null hypothesis (Time periods during the night were utilized equally) for all species except for P. leucopus, which had an extremely small sample size. We constructed a null model using Gotelli's Ecosim program against which to test Pianka's niche overlap index, and found that p (observed <= expected) = 0.91 (Gotelli and Entsminger 2001). Likewise, at the second site, located in the Cloud Forest (CF) region, we rejected our null hypothesis for both species (P. levipes and P. ochraventer (Muridae)). P (observed <=expected)=0.87. We concluded that there is a very small chance the patterns observed in either site are random, and thus there is likely an underlying mechanism shaping these patterns. We also observed that O. couesi and L. irroratus overlapped in their spatial and dietary niches, but were separated by their temporal niche utilization. The temporal niche aspect is rarely included in the many studies focusing on dietary and spatial niches. There are still many aspects of activity patterns that are poorly understood

Towards understanding how exploitation influences the wild energetic response of marine fish to temperature variability

Exploitation of fish populations can exacerbate the effects of climate change, yet our understanding of their synergistic effects remains limited. As fish are increasingly exposed to temperatures on the edges of their optimal thermal performance window, their physiological response is expected to shape their future performance. It is therefore concerning that exploitation can select for specific physiological phenotypes, as this may affect fished populations’ physiological response to temperature change. A recent laboratory study revealed fewer high-performance metabolic-scope phenotypes in an exploited population of the marine Sparid Chrysoblepus laticeps across a range of experimental temperatures in comparison to an unexploited population. This suggested that individuals in exploited populations may have less available energy for aerobic performance at thermal extremes, which may reduce the resilience of the population to changes in temperature. However, since laboratory experiments exclude numerous other variables that fish encounter in the wild, it was necessary to test this finding in a natural setting. This thesis aimed to further develop the laboratory study by assessing whether exploitation effects the wild energetic response of C. laticeps to thermal variability. To achieve this, the field metabolic rate of C. laticeps, a resident and endemic South African fish, from a near-pristine population (Tsitsikamma National Park) and a heavily exploited population (Port Elizabeth) was compared using acoustic accelerometry. A laboratory-based study using a swim-tunnel respirometer and accelerometer transmitters was conducted to develop a model to predict metabolic rate from acceleration data at temperatures from 10 to 22⁰C. Acceleration, temperature, mass and population (exploited/unexploited) were found to be the best predictors of the metabolic rate of C. laticeps and were incorporated into the model to estimate the field metabolic rate of fish tagged with acoustic accelerometers in the wild. To examine the combined effects of temperature and exploitation on the field metabolic rate of C. laticeps in their natural state, two fine-scale telemetry arrays with temperature loggers were used to assess the acceleration of the fish across different temperatures in the wild for three months during a period of high thermal variability. Ten fish from the exploited and unexploited populations were caught, surgically implanted with accelerometer transmitters and released back into the wild. Close to 500 000 and 400 000 acceleration estimates were recorded from wild exploited and unexploited fish, respectively. The field metabolic rate of both populations was estimated by combining the field acceleration and temperature data with the laboratory calibration model. The field metabolic rate of C. laticeps from the exploited population was constrained near cold and warm extremes compared to no constraints observed in the unexploited population. This was attributed to reduced inter-individual variability in the field metabolic rate-temperature relationship within the exploited population. There appeared to be a greater proportion of individuals that maintained a high field metabolic rate at extreme temperatures in the unexploited population. In contrast, all but one fish from the exploited population did not maintain a high field metabolic rate at extreme temperatures. These findings aligned with the laboratory-based metabolic-scope study on both populations of C. laticeps and demonstrate that passive-fishing may be removing thermally tolerant individuals and rendering exploited populations less resilient to thermal change. These findings are discussed in the context of fisheries management and particularly on the role that marine protected areas could play in maintaining physiological diversity, and therefore the resilience of fish in the Anthropocene. This study highlights the importance of applied conservation physiology in understanding the consequences of fisheries-induced evolution in an increasingly variable climate

Poultry virus isolates and method

Infectious bursal disease viruses were isolated from broiler chickens experiencing proventriculitis in, for example, Oklahoma, Texas, West Virginia, and California. Chicken virus isolates Texas RB 3, Texas RB 4, HBS, F57-7, W/L 39, GAR 1, and the like have been isolated. These viruses are some of the major causes of this condition and can be utilized as or in a vaccine to prevent the disease condition. The viruses are a significant finding in the search for a causative agent for proventriculitis in broiler chickens and as such may be utilized in the development of a vaccine or vaccines. The viruses can be attenuated to be used as a modified live vaccine or utilized in an inactivated form in a killed vaccine

Marine heatwaves exceed cardiac thermal limits of adult sparid fish (Diplodus capensis, Smith 1884)

Climate change not only drives increases in global mean ocean temperatures, but also in the intensity and duration of marine heatwaves (MHWs), with potentially deleterious effects on local fishes. A first step to assess the vulnerability of fishes to MHWs is to quantify their upper thermal thresholds and contrast these limits against current and future ocean temperatures during such heating events. Heart failure is considered a primary mechanism governing the upper thermal limits of fishes and begins to occur at temperatures where heart rate fails to keep pace with thermal dependency of reaction rates. This point is identified by estimating the Arrhenius breakpoint temperature (TAB), which is the temperature where maximum heart rate (fHmax) first deviates from its exponential increase with temperature and the incremental Q10 breakpoint temperature (TQB), which is where the Q10 temperature coefficient (relative change in heart rate for a 10◦C increase in temperature) for fHmax abruptly decreases during acute warming. Here we determined TAB, TQB and the temperature that causes cardiac arrhythmia (TARR) in adults of the marine sparid, Diplodus capensis, using an established technique. Using these thermal indices results, we further estimated adult D. capensis vulnerability to contemporary MHWs and increases in ocean temperatures along the warm-temperate south-east coast of South Africa. For the established technique, we stimulated fHmax with atropine and isoproterenol and used internal heart rate loggers to measure fHmax under conditions of acute warming in the laboratory. We estimated average TAB, TQB, and TARR values of 20.8◦C, 21.0◦C, and 28.3◦C. These findings indicate that the physiology of D. capensis will be progressively compromised when temperatures exceed 21.0◦C up to a thermal end-point of 28.3◦C. Recent MHWs along the warm-temperate south-east coast, furthermore, are already occurring within the TARR threshold (26.6–30.0◦C) for cardiac function in adult D. capensis, suggesting that this species may already be physiologically compromised by MHWs. Predicted increases in mean ocean temperatures of a conservative 2.0◦C, may further result in adult D. capensis experiencing more frequent MHWs as well as a contraction of the northern range limit of this species as mean summer temperatures exceed the average TARR of 28.3◦C.National Research Foundation (NRF) Research Development Grants for y-rated researchers: 93382; NRF Extension Doctoral Scholarship 95092, 111071info:eu-repo/semantics/publishedVersio

Diffusing an Innovation: Clinician Perceptions of Continuous Predictive Analytics Monitoring in Intensive Care

Background The purpose of this article is to describe neonatal intensive care unit clinician perceptions of a continuous predictive analytics technology and how those perceptions influenced clinician adoption. Adopting and integrating new technology into care is notoriously slow and difficult; realizing expected gains remain a challenge. Methods Semistructured interviews from a cross-section of neonatal physicians (n ¼ 14) and nurses (n ¼ 8) from a single U.S. medical center were collected 18 months following the conclusion of the predictive monitoring technology randomized control trial. Following qualitative descriptive analysis, innovation attributes from Diffusion of Innovation Theory-guided thematic development. Results Results suggest that the combination of physical location as well as lack of integration into work flow or methods of using data in care decisionmaking may have delayed clinicians from routinely paying attention to the data. Once data were routinely collected, documented, and reported during patient rounds and patient handoffs, clinicians came to view data as another vital sign. Through clinicians’ observation of senior physicians and nurses, and ongoing dialogue about data trends and patient status, clinicians learned how to integrate these data in care decision making (e.g., differential diagnosis) and came to value the technology as beneficial to care delivery. Discussion The use of newly created predictive technologies that provide early warning of illness may require implementation strategies that acknowledge the risk–benefit of treatment cliniciansmust balance and take advantage of existing clinician trainingmethods

Different Domains of the RNA Polymerase of Infectious Bursal Disease Virus Contribute to Virulence

BACKGROUND: Infectious bursal disease virus (IBDV) is a pathogen of worldwide significance to the poultry industry. IBDV has a bi-segmented double-stranded RNA genome. Segments A and B encode the capsid, ribonucleoprotein and non-structural proteins, or the virus polymerase (RdRp), respectively. Since the late eighties, very virulent (vv) IBDV strains have emerged in Europe inducing up to 60% mortality. Although some progress has been made in understanding the molecular biology of IBDV, the molecular basis for the pathogenicity of vvIBDV is still not fully understood. METHODOLOGY, PRINCIPAL FINDINGS: Strain 88180 belongs to a lineage of pathogenic IBDV phylogenetically related to vvIBDV. By reverse genetics, we rescued a molecular clone (mc88180), as pathogenic as its parent strain. To study the molecular basis for 88180 pathogenicity, we constructed and characterized in vivo reassortant or mosaic recombinant viruses derived from the 88180 and the attenuated Cu-1 IBDV strains. The reassortant virus rescued from segments A of 88180 (A88) and B of Cu-1 (BCU1) was milder than mc88180 showing that segment B is involved in 88180 pathogenicity. Next, the exchange of different regions of BCU1 with their counterparts in B88 in association with A88 did not fully restore a virulence equivalent to mc88180. This demonstrated that several regions if not the whole B88 are essential for the in vivo pathogenicity of 88180. CONCLUSION, SIGNIFICANCE: The present results show that different domains of the RdRp, are essential for the in vivo pathogenicity of IBDV, independently of the replication efficiency of the mosaic viruses