Influence of Calcium Sulfoaluminate Cement on the Pullout Performance of Reinforcing Fibers: An Evaluation of the Micro-Mechanical Behavior

The objective of this research was to determine the influence of calcium sulfoaluminate (CSA) cement on reinforcing fibers by evaluating the fiber pullout behavior, and bonding characteristics, of a single fiber embedded in a cementitious paste matrix. Four types of fibers commonly used in industry were evaluated: 1) Polyvinyl alcohol; 2) Polypropylene; 3) Coated Steel; and 4) Plain Steel. Upward trends in energy costs and potential greenhouse gas regulations favor an increased use of construction materials that require lower energy and lower CO2 emissions to fabricate, such as CSA cement, as opposed to the production of ordinary portland cement (OPC), which is more energy intensive and produces more CO2 emissions. However, widespread use of CSA cement requires a more in-depth understanding of the engineering characteristics that govern its performance, including interaction with reinforcing fibers. The overarching objective of this research was to provide the engineering base needed for the utilization of reinforcing fibers in CSA cement-based construction materials. The aims of the research were (1) to develop an ettringite-rich calcium sulfoaluminate cement, and (2) evaluate the pullout characteristics of reinforcing fibers embedded in a CSA-cement matrix. Key elements of the strategy included (1) Compare the performance of a laboratory-fabricated CSA cement to a commercial CSA cement and OPC, (2) Evaluate the peak load, and toughness of reinforcing fibers in CSA cement and OPC, (3) Evaluate the debonding-energy density and multiple-cracking behavior of fibers in CSA cement and OPC, and (4) Evaluate the shear bond strength of reinforcing fibers in CSA cement and OPC. Based on the findings of this PhD dissertation, calcium sulfoaluminate cement has a significant influence on the characteristics and behavior of embedded reinforcing fibers. An important factor contributing to the bond strength between fiber and matrix was the ability to transfer interfacial stresses from fiber to matrix. The more rigid-dense morphology of the CSA cement paste related to the ettringite crystal structure yielded higher peak loads, toughness, debonding-energy densities and shear-bond strengths for both steel and synthetic fibers. In addition to cement phase morphology, the reduction of the fiber/matrix elastic modulus ratio was found to be a primary factor affecting the performance and behavior of fibers embedded in a cementitious matrix

Scalable Bayesian modeling, monitoring and analysis of dynamic network flow data

Traffic flow count data in networks arise in many applications, such as automobile or aviation transportation, certain directed social network contexts, and Internet studies. Using an example of Internet browser traffic flow through site-segments of an international news website, we present Bayesian analyses of two linked classes of models which, in tandem, allow fast, scalable and interpretable Bayesian inference. We first develop flexible state-space models for streaming count data, able to adaptively characterize and quantify network dynamics efficiently in real-time. We then use these models as emulators of more structured, time-varying gravity models that allow formal dissection of network dynamics. This yields interpretable inferences on traffic flow characteristics, and on dynamics in interactions among network nodes. Bayesian monitoring theory defines a strategy for sequential model assessment and adaptation in cases when network flow data deviates from model-based predictions. Exploratory and sequential monitoring analyses of evolving traffic on a network of web site-segments in e-commerce demonstrate the utility of this coupled Bayesian emulation approach to analysis of streaming network count data.Comment: 29 pages, 16 figure

Geochemistry and paleoceanographic setting of Central Nevada bedded barites

Journal ArticleThe bedded barite deposits of central Nevada are hosted by rocks of the Roberts Mountains allochthon and constitute the largest barite reserves in North America. Detailed geochemical studies of three barite deposits in the Devonian Slaven Chert indicate that rocks surrounding the barite have elevated concentrations of carbon and phosphorousr elative to nonbarite-bearing rocks. Rare earth element data suggest that the barites were deposited in oxygenated seawater far from a spreading center. Ratios of Al, Ti, Fe, and Mn indicate that hydrothermal input to the sediment was minor relative to detrital input. The assembled data suggest a biogenic rather than a hydrothermal origin for the barite deposits. A model is proposed in which the barites were deposited at the O2-H2S transition of a coastal upwelling system in the Late Devonian ocean. This model is consistent with recent paleoceanographica nalyses of rocks in the Roberts Mountains allochthon, and studies indicating that the Late Devonian marked the transition from an anoxic to an oxic deep ocean

Global coverage of cetacean line-transect surveys : status quo, data gaps and future challenges

Knowledge of abundance, trends and distribution of cetacean populations is needed to inform marine conservation efforts, ecosystem models and spatial planning. We compiled a geo-spatial database of published data on cetacean abundance from dedicated visual line-transect surveys and encoded >1100 abundance estimates for 47 species from 430 surveys conducted worldwide from 1975-2005. Our subsequent analyses revealed large spatial, temporal and taxonomic variability and gaps in survey coverage. With the exception of Antarctic waters, survey coverage was biased toward the northern hemisphere, especially US and northern European waters. Overall, <25% of the world’s ocean surface was surveyed and only 6% had been covered frequently enough (≥ 5 times) to allow trend estimation. Almost half the global survey effort, defined as total area (km2) covered by all survey study areas across time, was concentrated in the Eastern Tropical Pacific (ETP). Neither the number of surveys conducted nor the survey effort had increased in recent years. Across species, an average of 10% of a species’ predicted range had been covered by at least one survey, but there was considerable variation among species. With the exception of three delphinid species, <1% of all species’ ranges had been covered frequently enough for trend analysis. We use a data-rich species, sperm whale, as an example to illustrate the challenges of using available data from line-transect surveys for the detection of trends or for spatial planning. Finally, we propose and contrast several field and analytical methods to fill in data gaps to improve future cetacean conservation management efforts.Publisher PDFPeer reviewe

Cementitious Compositions

The invention provides a cementitious composition comprising a cement component comprising (i) an accelerant, (ii) a calcium sulphate source and (iii) an ettringite forming cement; an aggregate; and optionally water; wherein the cement has a minimum unconfined compressive strength of 1500 psi when tested in accordance with ASTM C1140 and/or C1604 at 15 minutes after placement; methods for its use and concrete formed from it

Social Workers Who Left the Profession: An Exploratory Study

Why professional social workers leave the field of social work for other types of employment has implications for social work practice and education. The study suggests that economic advantage is but one of the factors involved in choosing other employment

A New Geographic Locality and Three New Host Records for Neobenedenia melleni (MacCallum) (Monogenea: Capsalidae)

A new geographic locality record and three new host records for Neobenedenia melleni (MacCallum, 1921) (Monogenea: Capsalidae) are provided. Specimens of N. melleni were collected from the skin of three Florida pompano, Trachinotus carolinus (Linnaeus, 1166)(Carangidae),caught in the northern Gulf of Mexico off Horn Island, Mississippi; from the skin of a bluering angelfish, Pomacanthus annularis (Bloch, 1157) (Pomacanthidae), in the Shark Reef Aquarium at Mandalay Bay, Las Vegas, Nevada; from the skin of a rock greenling, Hexagrammos lagocephalus (Pallas, 1810) (Hexagrammidae), in the Alaska SeaLife Center, Seward, Alaska; and from the skin of two blue-barred ribbon gobies, Oxymetopon cyanoctenosum Klausewitz and Condé, 1981 (Microdesmidae), in a tropical fish clearinghouse in Hayward, California. This is the first published record of the parasite from a microdesmid or wild carangid. Prior to this report, no specimen of N. melleni had been reported from a wild-caught fish in the Gulf of Mexico. The presence of N. melleni in the Gulf of Mexico is particularly noteworthy because this monogenean is a known pathogen of cultured fishes in netpens and recirculating seawater systems

Dissecting regulatory T cell expansion using polymer microparticles presenting defined ratios of self-antigen and regulatory cues

Biomaterials allow for the precision control over the combination and release of cargo needed to engineer cell outcomes. These capabilities are particularly attractive as new candidate therapies to treat autoimmune diseases, conditions where dysfunctional immune cells create pathogenic tissue environments during attack of self-molecules termed self-antigens. Here we extend past studies showing combinations of a small molecule immunomodulator co-delivered with self-antigen induces antigen-specific regulatory T cells. In particular, we sought to elucidate how different ratios of these components loaded in degradable polymer particles shape the antigen presenting cell (APC) -T cell interactions that drive differentiation of T cells toward either inflammatory or regulatory phenotypes. Using rapamycin (rapa) as a modulatory cue and myelin self-peptide (myelin oligodendrocyte glycoprotein- MOG) – self-antigen attacked during multiple sclerosis (MS), we integrate these components into polymer particles over a range of ratios and concentrations without altering the physicochemical properties of the particles. Using primary cell co-cultures, we show that while all ratios of rapa:MOG significantly decreased expression of co-stimulation molecules on dendritic cells (DCs), these levels were insensitive to the specific ratio. During co-culture with primary T cell receptor transgenic T cells, we demonstrate that the ratio of rapa:MOG controls the expansion and differentiation of these cells. In particular, at shorter time points, higher ratios induce regulatory T cells most efficiently, while at longer time points the processes are not sensitive to the specific ratio. We also found corresponding changes in gene expression and inflammatory cytokine secretion during these times. The in vitro results in this study contribute to in vitro regulatory T cell expansion techniques, as well as provide insight into future studies to explore other modulatory effects of rapa such as induction of maintenance or survival cues