Effect of silica fume and fly ash on heat of hydration of Portland cement

Results of calorimeter tests on Portland cement-silica fume-fly ash mixtures are presented. Data indicate that silica fume accelerates cement hydration at high water/cementitious ratios and retards hydration at low water/cementitious ratios. On the other hand, fly ash retards cement hydration more significantly at high water/cementitious ratios. When silica fume and fly ash are added together with cement, the reactivity of the silica fume is hampered and the hydration of the cementitious system is significantly retarded.     

Disease Recurrence during Adjuvant Immune Checkpoint Inhibitor Treatment in Metastatic Melanoma: Clinical,Laboratory, and Radiological Characteristics in Patients from a Single Tertiary Referral Center

Despite the dramatic improvements in recurrence-free survival in patients with metastatic melanoma treated with immune checkpoint inhibitors (ICI), a number of patients develop metastases during adjuvant therapy. It is not currently possible to predict which patients are most likely to develop disease recurrence due to a lack of reliable biomarkers. Thus, we retrospectively analyzed the case records of all patients who commenced adjuvant ICI therapy between January 2018 and December 2021 in a single university skin cancer center (n = 46) (i) to determine the rates of disease recurrence, (ii) to examine the utility of established markers, and (iii) to examine whether re-challenge with immunotherapy resulted in clinical response. Twelve out of forty-six (26%) patients developed a relapse on adjuvant immunotherapy in our cohort, and the median time to relapse was 139 days. Adjuvant immunotherapy was continued in three patients. Of the twelve patients who developed recurrence during adjuvant immunotherapy, seven had further disease recurrence within the observation period, with a median time of 112 days after the first progress. There was no significant difference comparing early recurrence (<180 days after initiation) on adjuvant immunotherapy to late recurrence (>180 days after initiation) on adjuvant immunotherapy. Classical tumor markers, including serum lactate dehydrogenase (LDH) and S-100, were unreliable for the detection of disease recurrence. Baseline lymphocyte and eosinophil counts and those during immunotherapy were not associated with disease recurrence. Interestingly, patients with NRAS mutations were disproportionately represented (60%) in the patients who developed disease recurrence, suggesting that these patients should be closely monitored during adjuvant therapy.     

Neutron diffraction from fibers

The X-ray diffraction technique has greatly improved our understanding of the function and properties of filamentous systems of biological and organic polymers by providing structural information at a molecular level. Although X-ray diffraction remains the primary method for determining fiber structures, neutron diffraction is an important supplementary technique. Neutron diffraction has some distinct advantages over the X-ray technique for providing certain types of structural information. This review describes the results from neutron diffraction studies of fibers and discusses the future prospects for this emerging technology.     

A study of the hot-working behavior of SiC-Al alloy

The hot-working behavior of two metal matrix composites (7090 + 20 vol pct SiC whiskers and 6061 + 20 vol pct SiC whiskers) and their powder metallurgy matrix alloys (7090 and 6061) was studied by hot torsion testing. Flow stress (σ_o) and strain-to-failure (ε _f ) data were generated at deformation temperatures and strain rates corresponding to the potential range for commercially hot-working these alloys. Based on the hot torsion data, hot-working parameters were recommended where σ_o was low and ε _f was high. Strain rate sensitivities and activation energies of deformation were computed for the alloys. Formerly with Martin Marietta Laboratories, Baltimore, MD     

The effect of solution heat-treatment on grain boundary segregation and stress-corrosion cracking of Al-Zn-Mg alloys

The relationship between susceptibility to stress-corrosion cracking (SCC) and grain boundary (GB) chemistry was investigated to elucidate the SCC mechanism in two Al-Zn-Mg alloys (Al-6.92Zn-2.85Mg-0.13Zr, Al-4.40Zn-3.70Mg; wt pct). Grain boundary chemistry was measured by Auger electron spectroscopy (AES) fromin situ fractures on the actual GB surface. The fractures were produced by pre-exposing specimens to water-vapor-saturated air, which induced hydrogen embrittlement of the GB. Susceptibility to SCC was varied by changing either solution heat-treatment temperature (SHT) or aging time. The SCC susceptibility, as measured by plateau crack velocity or reciprocal time-to-failure in a chromate-inhibited brine solution, was shown to decrease with increasing SHT and in general, to decrease with increasing aging time. “Free Mg,”i.e., unbound in MgZn₂ precipitates and present in the region between two grains, was present on all boundaries, as shown by AES, but no correlation was observed between free Mg concentration and SCC susceptibility. Possible explanations for these results are discussed.     

Cluster validation for unsupervised stochastic model-based imagesegmentation

Image segmentation is an important and early processing stage in many image analysis problems. Often, this must be done in an unsupervised fashion in that training data is not available and the class-conditioned feature vectors must be estimated directly from the data. A major problem in such applications is the determination of the number of classes actually present in an image. This problem, called the cluster validation problem, remains essentially unsolved. We investigate the cluster validation problem associated with the use of a previously developed unsupervised segmentation algorithm based upon the expectation-maximization (EM) algorithm. More specifically, we consider several well-known information-theoretic criteria (ICs) as candidate solutions to the validation problem when used in conjunction with this EM-based segmentation scheme. We show that these criteria generally provide inappropriate solutions due to the domination of the penalty term by the associated log-likelihood function. As an alternative we propose a model-fitting technique in which the complete data log-likelihood functional is modeled as an exponential function in the number of classes acting. The estimated number of classes are then determined in a manner similar to finding the rise time of the exponential function. This new validation technique is shown to be robust and outperform the ICs in our experiments. Experimental results for both synthetic and real world imagery are detailed.     

Abdominal assessment in the home: from A to Zzz

Conducting a through abdominal assessment in the home setting is an important part of the home care nurse's role. By using every letter of the alphabet, the tool presented in this article helps the nurse conduct a thorough health history in a concise manner. In addition, reviewing the procedure outlined in the article and using the documentation form presented, the nurse can conduct a through abdominal assessment in the home in a cost-effective manner.     

Modelling instream nitrogen variability in the Dee catchment, NE Scotland

The Integrated Nitrogen in CAtchments model (INCA) was applied to the River Dee, Aberdeenshire, NE Scotland. To a first approximation the model was able to simulate the annual mean streamwater NO3-N concentrations observed along the length of the main channel. This provided the basis for using INCA to subsequently explore the effects of N deposition and land use management on streamwater NO3-N concentrations and loads. On an annual timescale, the model predictions suggest that NO3-N concentrations will decrease by 5% following a 20% reduction in fertiliser application. Furthermore, model results also suggest that a 50% increase in N deposition will cause a 15% increase in the streamwater NO3-N concentrations. The utility of INCA as a tool for catchment management is discussed, current limitations are highlighted and possible improvements are suggested.     

Riparian zone influence on stream water chemistry at different spatial scales: a GIS-based modelling approach, an example for the Dee, NE Scotland

A geographical information system (GIS-ARC/INFO) was used to collate existing spatial data sets on catchment characteristics to predict stream water quality using simple empirical models. The study, based on the river Dee catchment in NE Scotland, found that geological maps and associated geochemical information provided a suitable framework for predicting chemical parameters associated with acidification sensitivity (including alkalinity and base cation concentrations). In particular, it was found that in relatively undisturbed catchments, the parent material and geochemistry of the riparian zone, when combined with a simple hydrological flow path model, could be used to accurately predict stream water chemistry at a range of flows (Q95 to > Q5) and spatial scales (1-1000 km2). This probably reflects the importance of the riparian zone as an area where hydrological inputs to stream systems occur via flow paths in the soil and groundwater zones. Thus, evolution of drainage water chemistry appears to retain the geochemical characteristics of the riparian area as it enters the channel network. In more intensively managed catchments, riparian land use is a further influential factor, which can be incorporated into models to improve predictions for certain base cations. The utility in providing simple hydrochemical models, based on readily available data sets, to assist environmental managers in planning land use in catchment systems is discussed.     

INFLUENCE OF SCALE ON THERMAL CHARACTERISTICS IN A LARGE MONTANE RIVER BASIN

This study monitored stream temperatures over two hydrological years at various nested scales within the large, unregulated river Dee catchment (North East Scotland). These scales were (i) the whole catchment (11 sites along main stem Dee); (ii) the tributary (single sites in main tributaries); (iii) the Girnock (five sites in one subcatchment); and (iv) the reach (26 points across single reach). The aim was to characterize the thermal regime of all locations and compare the magnitude of variation between each scale. The controls on this variation were assessed via a multiple linear regression model using Geographic Information System‐derived catchment data. Temperatures were collected at 15‐min resolution and for further analysis and discussion combined to daily means. At the catchment and subcatchment scales, a west to east gradient in mean and minimum temperatures was observed, largely paralleling changes in altitude. Temperature differences between subcatchments were generally greater than between the sites along the main stem of the Dee. Differences between tributaries reflected differences in their morphology and land use. However, some tributaries had similar thermal regimes, despite different catchment and riparian characteristics. Subcatchment differences in thermal regimes of one of the tributaries corresponded to riparian vegetation reduced diurnal variability in sections dominated by broadleaf woodland. Compared with the larger scales, reach differences in thermal regime were small (e.g. mean temperatures of riffle, pool and margin habitats were within 0.3°C). The most noticeable difference was in relation to the point samples within the backwater area, which has a more constant thermal regime, most probably reflecting its groundwater source. The regression analysis indicated that monthly mean temperatures can be predicted well using elevation and catchment area. Forest cover was a significant explanatory variable during the summer months. However, some of the empirical temperature data from the Dee indicate that similar thermal regimes can result from different physical controls and processes that have important implications for the extrapolation of such predictive models. Copyright © 2011 John Wiley & Sons, Ltd.