From the individual element test to finite element templates: Evolution of the patch test

This paper starts a sequence of three articles that follow an unconventional approach in finite element research. The ultimate objective is to construct high-performance elements and element-level error estimators for those elements. The approach takes off from our previous work in high-performance elements and culminates with the development of finite element templates. The present paper concentrates on the patch test and evolved versions of the test that have played a key role in this research. Following a brief review of the historical roots, we present the Individual Element Test (IET) of Bergan and Hanssen in an expanded context that encompasses several important classes of new elements. The relationship of the IET to the multielement forms A, B and C of the patch test and to the single-element test are investigated. An important consequence of the IET application is that the element stiffness equations decompose naturally into basic and higher-order parts. The application of this decomposition to the “sanitization” of the non-convergent BCIZ element is described and verified with numerical experiments. Two sequel papers in preparation are subtitled ‘the algebraic approach’ and ‘element-level error estimation’. These apply the fundamental decomposition to the derivation of templates for specific mechanical elements and to the construction of element-level error estimators, respectively.     

The effect of the scale of horizontal subsurface flow constructed wetlands on flow and transport parameters.

Horizontal subsurface flow constructed wetlands have proven their efficiency in treating wastewater and removing the pollutants of concern. Treatment efficiency depends on the wastewater residence time, which is a function of the hydraulic loading and the physical conditions of the constructed filter system, which can be described with effective parameters such as: hydraulic conductivity, porosity, dispersivity etc. Because spatial variability is often scale dependent, these effective parameters may be affected by the scale of the system being studied. In this paper the results of tracer experiments in constructed filters using saturated horizontal flow at three scales (small and medium lab scales and full-scale system) using the same filter media is reported. Light-weight aggregate (filter media termed Filtralite-P) was used at all scales. Increasing the scale was associated with increasing dispersivity, meanwhile hydraulic conductivity experienced dramatic reduction and variation by increasing the examined scale. Observed changes in the hydraulic parameters indicate that heterogeneity at different scales should be taken into account when the performance of LWA filters are evaluated from small-scale experiments.     

Consumption of fish from a contaminated lake strongly affects the concentrations of polybrominated diphenyl ethers and hexabromocyclododecane in serum

Very high concentrations of polybrominated diphenyl ethers (PBDE) have been reported in fish from Lake Mj?sa in Norway. This study was performed to examine the serum concentrations of PBDE and hexabromocyclododecane (HBCD) in consumers of fish from this lake and to investigate possible relationships between serum concentrations, self-reported fish intake and calculated total dietary PBDE exposure. Serum concentrations of the sum of the seven PBDE (BDE-28, 47, 99, 100, 153, 154 and 183) were significantly higher than those of a reference group of Norwegians eating only food with background levels of contamination (medians: 18 ng/g lipids men, 8.4 ng/g lipids women). The median dietary intake of Sum 7 PBDE was 2549 ng/day (30 ng/kg body weight/day), the highest dietary intake of PBDE reported. The contribution from fish caught from the contaminated lake comprised 98.7% of the total dietary exposure. For men, serum levels of PBDE were strongly correlated with the calculated dietary exposure, except for BDE-209. This suggests that sources other than the diet are important for human BDE-209 exposure. The median serum HBCD concentration was 4.1 and 2.6 ng/g lipids for men and women, respectively, and was also found to be associated with consumption of fish from Lake Mj?sa.     

Impact of understory vegetation on forest canopy reflectance and remotely sensed LAI estimates

Forest leaf area index (LAI), is an important variable in carbon balance models. However, understory vegetation is a recognized problem that limits the accuracy of satellite-estimated forest LAI. A canopy reflectance model was used to investigate the impact of the understory vegetation on LAI estimated from reflectance values estimated from satellite sensor data. Reflectance spectra were produced by the model using detailed field data as input, i.e. forest LAI, tree structural parameters, and the composition, distribution and reflectance of the forest floor. Common deciduous and coniferous forest types in southern Sweden were investigated. A negative linear relationship (r² = 0.6) was observed between field estimated LAI and the degree of understory vegetation, and the results indicated better agreement when coniferous and deciduous stands were analysed separately. The simulated spectra verified that the impact of the understory on the reflected signal from the top of the canopy is important; the reflectance values varying by up to ± 18% in the red and up to ± 10% in the near infra-red region of the spectra due to the understory. In order to predict the variation in LAI due to the understory vegetation, model inversions were performed where the input spectra were changed between the minimum, average and maximum reflectance values obtained from the forward runs. The resulting variation in LAI was found to be 1.6 units on average. The LAI of the understory could be predicted indirectly from simple stand data on forest characteristics, i.e. from allometric estimates, as an initial step in the process of estimating LAI. It is suggested here that compensation for the effect of the understory would improve the accuracy in the estimates of canopy LAI considerably.     

Radiation of water waves from an oscillating source located at a slope of angle π/4

An analytical investigation is performed of the linear radiation problem for water waves generated by an oscillating normal velocity distribution along a sloping beach with slope angle /4. The distribution of normal velocity is arbitrary, and it oscillates with a given frequency. The solution is expressed in terms of the Green function which represents a source of unit oscillatory flux located at an arbitrary position along the slope. At infinity the radiation condition is applied to determine the outgoing wave. As a simple example of integrating the Green function, the reflection of an incoming sinusoidal wave is calculated.     

Ability of polyurethane foams to support placenta-derived cell adhesion and osteogenic differentiation: preliminary results

In bone tissue reconstruction, the use of engineered constructs created by mesenchymal stem cells (MSCs) that differentiate and proliferate into 3D porous scaffolds is an appealing alternative to clinical therapies. Human placenta represents a possible source of MSCs, as it is readily available without invasive procedures and because of the phenotypic plasticity of many of the cell types isolated from this tissue. The scaffold considered in this work is a slowly degradable polyurethane foam (EF PU foam), synthesized and characterized for morphology and in vitro interaction with chorion mesenchymal cells (CMCs). These cells were isolated from human term placenta and cultured onto the EF PU foam using two different culture media (EMEM and NH osteogenic differentiation medium). Synthesized EF PU foam showed homogeneous pore size and distribution, with 89% open porosity. In vitro tests showed CMCs scaffold colonization, as confirmed by Scanning Electron Microscopy (SEM) observations and hematoxylin–eosin staining. Alizarin Red staining revealed the presence of a small amount of calcium deposition for the samples treated with the osteogenic differentiation medium. Therefore, the proposed EF PU foam appears to stimulate cell adhesion in vitro, sustaining CMCs growth and differentiation into the osteogenic lineage.     

Efficient and robust three‐phase split computations

The combination of successive substitution and the Newton method provides a robust and efficient algorithm to solve the nonlinear isofugacity and mass balance equations for two‐phase split computations. The two‐phase Rachford–Rice equation may sometimes introduce complexity, but the Newton and bisection methods provide a robust solution algorithm. For three‐phase split calculations, the literature shows that the computed three‐phase region is smaller than measured data indicate. We suggest that an improved solution algorithm for the three‐phase Rachford–Rice equations can address the problem. Our proposal is to use a two‐dimensional bisection method to provide good initial guesses for the Newton algorithm used to solve the three‐phase Rachford–Rice equations. In this work, we present examples of various degree of complexity to demonstrate powerful features of the combined bisection‐Newton method in three‐phase split calculations. To the best of our knowledge, the use of the bisection method in two variables has not been used to solve the three‐phase Rachford–Rice equations in the past. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Processing of highly porous TiO2 bone scaffolds with improved compressive strength

In the present study, the effect of sintering time and recoating procedures on the pore architectural parameters and compressive strength of highly porous ceramic TiO₂ foams were investigated. Long sintering times (>5 h) at 1500 °C led to an inward collapse of one wall of the triangular voids typically found in the strut interior of foams prepared using the replication method. This strut folding led to increased compressive strength, while the pore architectural features were not significantly affected. Furthermore, majority of the internal porosity of the foam struts was partially eliminated and became accessible for infiltration with TiO₂ slurry. Recoating procedures were found to markedly reduce the flaw size and number in the TiO₂ foam struts, which led to significant strengthening of the ceramic structure (0.7 → 3.4 MPa) by improved structural uniformity and slightly increased strut diameter.     

High concentrations of essential and toxic elements in infant formula and infant foods – A matter of concern

This study assessed concentrations in and intake of toxic and essential elements from formulas and foods intended for infants during their first 6 months of life. Concentrations of the essential elements Ca, Fe, Zn, Mn and Mo were significantly higher in most formulas than in breast milk. Daily intake of Mn from formula varies from ten up to several hundred times the intake of the breast fed infant, levels that may be associated with adverse health effects. One portion of infant food provided significantly more Fe, Mn, Mo, As, Cd, Pb and U than one feeding of breast milk, but less Ca, Cu and Se. Rice-based products in particular contained elevated As concentrations. Drinking water used to mix powdered formula may add significantly to the concentrations in the ready-made products. Evaluation of potentially adverse effects of the elevated element concentrations in infant formulas and foods are warranted.     

Treatment of pre-invasive conditions during opportunistic screening and its effectiveness on cervical cancer incidence in one Norwegian county

OBJECTIVE: To identify a correlation between dialysis treatment duration and severity of acquired cystic disease of the end-stage kidney measured by cyst sizes; and assess its effect on spontaneous improvement of anemia. MATERIALS AND METHODS: Ten patients, 6 males and 4 females were selected, who have been on hemodialytic treatment for more than 5 years. There was no patient selected with autosomal dominant polycystic kidney disease. The renal evaluation has been made through ultrasonographic studies. Acquired cystic disease of the end-stage kidney was characterized by finding four or more cysts in both kidneys. The largest cysts were measured for correlation effect. The diagnosis of anemia was established by hematocrit and hemoglobin serum values. It has also been analyzed serum urea, creatinine, albumin, iron, total iron-binding capacity and the per cent saturation of serum transferrin were tested. RESULTS: The patients were properly dialysed (serum urea and creatinine = 98.7 +/- 35 mg/dL e 9.7 +/- 2.7 mg/dL, respectively). There were in good nutritional shape (serum albumin = 4.5 +/- 0.5 g/dL) and had normal serum iron level (serum iron = 80 +/- 34 mg/dL). The prevalence of acquired renal cystic disease was 80%. No finding of malignancy has been detected in these cysts. There was a significant correlation between time on dialysis treatment and hematocrit values (R = 0.70; p < 0.05). Cyst sizes had a direct and significant correlation with hematocrit levels (R = 0.74; p < 0.05). CONCLUSION: These results show that spontaneous improvement on anemia seen in patients on chronic dialysis has a significant correlation with the severity of acquired cystic disease of the end-stage kidney. Our data suggest a functional role of acquired kidney cysts on endogenous erythropoietin production.