Computer-aided position planning of miniplates to treat facial bone defects

In this contribution, a software system for computer-aided position planning of miniplates to treat facial bone defects is proposed. The intra-operatively used bone plates have to be passively adapted on the underlying bone contours for adequate bone fragment stabilization. However, this procedure can lead to frequent intra-operatively performed material readjustments especially in complex surgical cases. Our approach is able to fit a selection of common implant models on the surgeon's desired position in a 3D computer model. This happens with respect to the surrounding anatomical structures, always including the possibility of adjusting both the direction and the position of the used osteosynthesis material. By using the proposed software, surgeons are able to pre-plan the out coming implant in its form and morphology with the aid of a computer-visualized model within a few minutes. Further, the resulting model can be stored in STL file format, the commonly used format for 3D printing. Using this technology, surgeons are able to print the virtual generated implant, or create an individually designed bending tool. This method leads to adapted osteosynthesis materials according to the surrounding anatomy and requires further a minimum amount of money and time.Comment: 19 pages, 13 Figures, 2 Table

Detection of alkali path in a pilot-scale combustor using laser spectroscopy and surface ionization — From vapor to particles

Alkali species have been under intensive research in thermal conversion applications due to their abundance especially in biomass fuels. Alkali metals, sodium (Na) and potassium (K), are known to cause severe operational problems in combustion units, such as slagging, fouling, and corrosion. In this work, we present a monitoring method to follow alkali behavior from vapor to particles in a pilot-scale reactor. In our approach we combine Tunable Diode Laser Atomic Spectroscopy (TDLAS) for atomic potassium monitoring, Collinear Photofragmentation and Atomic Absorption Spectroscopy (CPFAAS) for KCl and KOH detection, and Surface Ionization Detection (SID) for monitoring of total flue gas and aerosol alkali content. Experiments were carried out in the Chalmers 100 kW oxy-fuel combustion unit that, during these experiments, used propane as fuel. Alkali species were injected as a water solution directly to the flame. In addition, SO2 was used to alter the conditions for alkali species formation injecting it directly to the combustion feed gas. Due to the alkali monitoring system described, we were able to monitor the alkali behavior during nucleation and sulfation processes. The conditions for dimer formation and heterogeneous nucleation were observed when the temperature conditions were changed by lowering the thermal input to the unit

A stochastic Lagrangian representation of the 3-dimensional incompressible Navier-Stokes equations

In this paper we derive a representation of the deterministic 3-dimensional Navier-Stokes equations based on stochastic Lagrangian paths. The particle trajectories obey SDEs driven by a uniform Wiener process; the inviscid Weber formula for the Euler equations of ideal fluids is used to recover the velocity field. This method admits a self-contained proof of local existence for the nonlinear stochastic system, and can be extended to formulate stochastic representations of related hydrodynamic-type equations, including viscous Burgers equations and LANS-alpha models.Comment: v4: Minor corrections to bibliography, and final version that will apear in CPAM. v3: Minor corrections to the algebra in the last section. v2: Minor changes to introduction and refferences. 14 pages, 0 figure

Characterization of Minkowski measurability in terms of surface area

The $r$-parallel set to a set $A$ in Euclidean space consists of all points with distance at most $r$ from $A$. Recently, the asymptotic behaviour of volume and the surface area of parallel sets as $r$ tends to 0 has been studied and some general results regarding their relations have been established. In this paper we complete this picture. In particular, we show that a set is Minkowski measurable if and only if it is S-measurable, i.e. if its S-content is positive and finite, and that positivity and finiteness of lower and upper Minkowski content implies the same for the S-contents and vice versa. The results are formulated in the more general setting of Kneser functions. Furthermore, the relations between Minkowski and S-contents are studied for more general gauge functions. The results are also applied to simplify the proof of the Modified Weyl-Berry conjecture in dimension one.Comment: slightly revised original versio

Dynamic Simulation of a solar tower system with open volumetic receiver - a review on the vICERP project

The paper presents an overview on the modeling and simulation activities of the virtual institute for central receiver power plants (vICERP). Within a three years launch period models and tools for dynamic simulation of central receiver power plants have been developed by the five research institutes involved. The models are based on the Modelica modeling language. Today, models for the heliostat field, the receiver, the air cycle, the thermal storage, and the water-steam cycle are available within the consortium. As a first application, the Solar Tower Jülich technology was used as a reference. Models are validated with real operational data from the Solar Tower Jülich

Helping behaviour during cooperative learning and learning gains

Is helping behaviour (i.e., solicited help and peer tutoring) during cooperative learning (CL) related to subsequent learning gains? And can teachers influence pupils’ helping behaviour? One hundred one 5th grade pupils from multiethnic schools, 10-12 years old, participated in the study. Forty two pupils (31 immigrant) worked in an experimental condition, characterized by the stimulation of solicited high quality help and 59 (24 immigrant) worked in a control condition. It was found that learning gains were predicted positively by pupils’ unsolicited helping behaviour (i.e., peer tutoring) and negatively by solicited help. Furthermore, teachers were able to affect pupils’ low quality solicited help only. Lastly, immigrant pupils used less helping behaviour than local pupils, irrespective of CL setting

Physical fitness and nutritional anthropometric status of children from disadvantaged communities in the Nelson Mandela Bay region

Background: Information about the relationships between physical fitness, body composition and nutrition has increased in recent years; however, little is known about physical fitness and the coexistence of under-/overnutrition among children living in disadvantaged areas. Objectives: To determine the physical fitness status and its association with body composition, growth and selected socio- demographics in primary schoolchildren from disadvantaged communities in the Nelson Mandela Bay region. Methods: Nine hundred and sixty-five children (49% girls, M=9.5 years) participated in this cross-sectional study. Height and weight were measured to establish body mass index, and height-for-age z-scores. Physical fitness was assessed using tests from the Eurofit Physical Fitness test battery (flexibility, upper/lower body muscular strength and cardiorespiratory fitness). Between- group differences and cross-sectional associations were examined with univariate (Chi2-tests, analyses of variance) and multivariate methods (mixed linear/logistic regression). Results: Most children had normal weight (76.7%), while 4.5% were underweight and 18.7% were overweight/obese. Underweight children and children with stunted growth (11.5%) had lower average upper body strength (p<0.001). Overweight/obese children had lower scores in weight-bearing activities (p<0.001). Children with higher socio-economic status were more likely to be overweight and obese (p<0.001). In the multivariate analyses, sex, age, body mass index, and stunting were associated with children’s physical fitness. Conclusion: Fitness assessments seem to be a relevant measure of the current health status of children in disadvantaged settings. Compared to international norms, the children in this study had relatively low scores for both upper- and lower body muscular strength. Therefore, effective school-based intervention programmes should be developed to improve children’s physical fitness in disadvantaged schools