On partitioning rectilinear polygons into star-shaped polygons

We present an algorithm for finding optimum partitions of simple monotone rectilinear polygons into star-shaped polygons. The algorithm may introduce Steiner points and its time complexity isO(n), wheren is the number of vertices in the polygon. We then use this algorithm to obtain anO(n logn) approximation algorithm for partitioning simple rectilinear polygons into star-shaped polygons with the size of the partition being at most six times the optimum.     

Integrated Modeling of Anaerobic Fluidized Bed Bioreactor for Deicing Waste Treatment. II: Simulation and Experimental Studies

This paper examines the influence of bed segregation on the performance of an anaerobic fluidized bed bioreactor (AFBR) using both an integrated mathematical model previously described in Part I of this study, and experimental data obtained from a laboratory-scale AFBR continuous flow system and batch serum vial tests. Local hydrodynamics within the bed are shown to determine mixing intensities and patterns of bioparticles thereby controlling biofilm thickness and composition along the bed height. Results of the model simulations and the experimental data indicate that shallow biofilms that allow full substrate penetration are dominantly populated with faster growing micro-organisms. The internal mass transfer resistance in thicker biofilm significantly influences population distribution resulting in the increase of population of slower growing micro-organisms in a deeper layer of the biofilm. The serum bottle tests also confirm that microbial distribution inside a multispecies biofilm is determined by the hydrodynamic condition of the reactor. This study illustrates the importance of hydrodynamic regimes in the AFBR, and demonstrates the impact of bed segregation on bioparticle properties and total system performance.     

One‐dimensional photogeneration profiles in silicon solar cells with pyramidal texture

The key metric of surface texturing is the short‐circuit current J_sc. It depends on front surface transmittance, light trapping and the spatial profiles of photogeneration G and collection efficiency η_c. To take advantage of a one‐dimensional profile of η_c(ζ), where ζ is the shortest distance to the p–n junction, we determine G(ζ) via ray tracing. This permits rigorous optical assessment of common pyramidal textures for various cell designs. When ζ is small, G(ζ) is largest beneath regular inverted pyramids, upright pyramids (regular or random) and planar surfaces, respectively. This higher G(ζ) results in superior collection of generated carriers in front‐junction cells. In simulations of a conventional screen‐print cell, 92.0% of generated carriers are collected for inverted pyramids, compared to 91.4% for upright pyramids, and 90.0% for a planar surface. Higher efficiency and rear junction devices are analysed in the paper. Despite differences in G(ζ) beneath textures, inverted pyramids achieve the highest J_sc for all cell designs examined (marginally so for high‐efficiency rear‐contact cells) due to superior front surface transmittance and light trapping. We assess a common one‐dimensional model for photogeneration beneath textured surfaces. This model underestimates G(ζ) when ζ is small, and overestimates G(ζ) when ζ is large. As a result, the generation current determined is inaccurate for thin substrates. It can be computed to within 3% error for 250 µm thick substrates. However, errors in G(ζ) can lead to 7.5% inaccuracy in calculations of J_sc. Errors are largest for lower efficiency designs, in which collection efficiency varies through the substrate. Copyright © 2011 John Wiley & Sons, Ltd.     

Bicycle injury events among older adults in Northern Sweden: A 10-year population based study

Bicycles are a common mode of transportation and injured bicyclists cause a substantial burden on the medical sector. In Sweden, about half of fatally injured bicyclists are 65 years or older. This study analyzes the injury mechanisms, injuries, and consequences among bicyclists 65 years or older and compare with younger bicyclists (≤64) and older adults as passenger car drivers, to give a basis for an injury preventive discussion for this age group. Umeå University Hospital's primary catchments area had 142,000 inhabitants in 2006. Nearly all injured road users in the well-defined geographic area are treated at this hospital and a 10-year data set (N = 456) of injured bicyclists aged 65+ from the hospital's continuous injury registration (1997-2006) was analyzed. The results show that the annual injury incidence was 2.4 and 2.2 per 1000 men and women, respectively, aged 65 or older. For men the incidence rate was constant in the three age groups 65-74, 75-84 and 85+, while it decreased strongly for women. The incidence rate for old adults as passenger car drivers and younger bicyclists was 1.0 and 4.6, respectively. Most frequent injury mechanisms were falls when getting on or off a bicycle (20%) and by potholes or irregularities on the ground, edge of a sidewalk, or similar (13%). Only 6% were hit by cars, trucks, or buses. Half of the injured suffered fractures or dislocations, and 10% suffered concussion or more serious intracranial injuries. Getting on or off the bicycle caused most fractures (especially a high fraction of the hip and femur fractures) and resulted in 27% of all inpatient days in hospital. Three individuals died. One-third of the injured were treated as inpatients for a total of 1413 days (on average 9 days), with 69% of the days being caused by fractures. The cost for out- and inpatient acute treatment was approximately USD 4700 (SEK 33,000) per injured. The results merit an interest for this target group; bicycle injuries among older adults are costly both for the individual and the medical sector. Injury mitigation strategies focused on the needs of this group are probably as well motivated as those focused on older car drivers.     

Characterisation of thermal barrier coatings and ultra high temperature composites deposited in a low pressure plasma reactor

A low pressure plasma process working at 600-800 Pa was used to deposit from aqueous solution ZrO₂-4 mol% Y₂O₃ (Yttria partially stabilized Zirconia-YpSZ) layers and stacks of Ta₂O₅/YpSZ layers for use as thermal barrier coatings (TBC). The observation of the cross section revealed a high porosity. The thermal diffusivity of the layers (1 × 10⁻⁷ m² s⁻¹) was measured by a laser flash technique and compared with values obtained on air plasma sprayed material (3 × 10⁻⁷ m² s⁻¹). The plasma reactor were also used to deposit ZrB₂-ZrO₂-SiC layers used as Ultra High Temperature Composite (UHTC) from aqueous solutions of zirconyl and Boron nitrates containing suspensions of SiC. Layers up to 100 μm thick were obtained on SiC substrates. XRD was used to study the crystallinity of the layer. The presence of ZrB₂ and SiC phases was confirmed after the deposition. XRD analysis showed that heat treatment at 1073 K under oxidizing conditions led to the loss of ZrB₂ and the appearance of ZrO₂ phases. To understand the behaviour of the layers to interaction with atomic oxygen (combustion for TBC and spacecraft re-entry phase for UHTC), we have measured the atomic oxygen recombination coefficient to determine the number of adsorption sites on the surface of the coatings. This was accomplished by using a low pressure plasma reactor coupled with optical spectroscopic measurements as a diagnostic technique.     

Effects of a hurricane on growth and morbidity in children from low-income families in Kingston, Jamaica

This is the first report of the effects of a hurricane on children's health and nutritional status in which data were available preceding and following the event. When Hurricane Gilbert struck Jamaica in 1988, a longitudinal study was in progress in which children's weights and heights were recorded every 2 months and their morbidity histories taken every week. The investigation included 127 stunted (low height-for-age) and 32 non-stunted children aged 23-44 months, living in poor areas of Kingston. The data from the 4 months before and after the hurricane were compared. There was an increase in the occurrence of respiratory symptoms including rapid or difficult breathing (P < 0.04), coughs (P < 0.001) and nasal discharges (P < 0.001) during the first 2-month period after the hurricane. However there was no significant effect on the occurrence of diarrhoea and injuries. Deficits were also found in height gain (P < 0.001) during the same period. These adverse effects were found in spite of the large amount of food aid received and the aggressive health education programme implemented after the hurricane.     

Interactions between pairs of bacteriocins from lactic bacteria

Activity of pairs of crude extracts of lactic acid bacteria (LAB) containing different bacteriocins (nisin, pediocin AcH, lacticin 481, lactacin F, and lactacin B) was measured against 10 different indicator strains. Experiments were carried out both in liquid and on solid media. Both synergisms and antagonisms were observed. Lacticin 481 produced mainly antagonistic effects whereas pediocin AcH produced mainly synergistic effects. The use of more than one LAB bacteriocin as a combination biopreservative might be envisaged.     

On partitioning rectilinear polygons into star-shaped polygons

We present an algorithm for finding optimum partitions of simple monotone rectilinear polygons into star-shaped polygons. The algorithm may introduce Steiner points and its time complexity isO(n), wheren is the number of vertices in the polygon. We then use this algorithm to obtain anO(n logn) approximation algorithm for partitioning simple rectilinear polygons into star-shaped polygons with the size of the partition being at most six times the optimum.     

Dissolution of carbon dioxide in CaO-CaF2-Al2O3 based melts containing Na2O or K2O oxide

The influence of Na₂O or K₂O on the solubility of CO₂ in CaO-CaF₂-Al₂O₃ based melts is measured by a thermogravimetric technique over a temperature range of 1250–1350°C. The values of the carbonate capacities (C'_c = wt. % ) are calculated by data on the dissolution and partial pressure of carbon dioxide. The replacement of CaO by Na₂O leads to an increase of the carbonate capacity to a maximum at 3–3.5 wt. % Na₂O and then to a decrease. The addition of Na₂O or K₂O up to 2 wt. %, to CaO-CaF₂-Al₂O₃ increases the carbonate capacity at 1300°C by 30%.