Space sweep solves intersection of convex polyhedra

Summary Plane-sweep algorithms form a fairly general approach to two-dimensional problems of computational geometry. No corresponding general space-sweep algorithms for geometric problems in 3- space are known. We derive concepts for such space-sweep algorithms that yield an efficient solution to the problem of solving any set operation (union, intersection, ...) of two convex polyhedra. Our solution matches the best known time bound of O(n log n), where n is the combined number of vertices of the two polyhedra.     

Experimental determination of mechanical properties of Ni and Ni-Fe microbars

 In this study, nickel and nickel-iron alloy microsamples produced using the LIGA technique are investigated. With vibration tests and tensile tests, design parameters such as Young’s modulus, elastic limit, and failure stress are determined. A new microsample tensile test apparatus is presented, in which forces and elongation are separately measured with very high accuracy. The comparison between the Young’s modulus which is determined with vibration experiments and the Young’s modulus derived from tensile tests ensures the reliability of the measurements presented. The error sources are analysed with the help of finite element models and the uncertainty in determining the Young’s modulus is calculated. The strength values measured for LIGA specimens are about 3 times higher than for comparable macroscopic specimens. Received 27 February 1996 / Accepted: 11 March 1996     

Evaluating a strategy for maintaining nitrifier activity during long-term starvation in a moving bed biofilm reactor (MBBR) treating reverse osmosis concentrate

A two-stage moving bed biofilm reactor (MBBR) was applied at the Bundamba advanced water treatment plant (AWTP) (Queensland, Australia) to treat the reverse osmosis concentrate (ROC) for inorganic nutrient removal. One of the operational challenges for the system was to cope with the large fluctuations of the ROC flow. This study investigated the decay rates of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) and biofilm detachment in MBBR during starvation for up to one month. An intermittent aeration strategy of 15 min aeration every 6 h was applied. This study also evaluated the activity recovery of both AOB and NOB after normal operation was resumed. The results showed that the activity loss of AOB and NOB was relatively minor (<20%) within 10 days of starvation, which ensured relatively quick recovery of ammonium removal when normal operation resumed. In contrast, the AOB and NOB activity loss reached 60-80% when the starvation time was longer than 20 days, resulting in slower recovery of ammonium removal after starvation. Starvation for less than 20 days didn't result in an apparent biomass detachment from carriers.     

The inhibitory effects of free nitrous acid on the energy generation and growth processes of an enriched nitrobacter culture

The inhibitory effects of nitrite (NO2-)/free nitrous acid (HNO2-FNA) on the metabolism of Nitrobacter were investigated using a method allowing the decoupling of the growth and energy generation processes. A lab-scale sequencing batch reactor was operated forthe enrichment of a Nitrobacter culture. Fluorescent in situ hybridization (FISH) analysis showed that 73% of the bacterial population was Nitrobacter. Batch tests were carried out to assess the oxygen and nitrite consumption rates of the enriched culture at low and high nitrite levels, in the presence or absence of inorganic carbon. It was observed that in the absence of CO2, the Nitrobacter culture was able to oxidize nitrite at a rate that is 76% of that in the presence of CO2, with an oxygen consumption rate that is 85% of that measured in the presence of CO2. This enabled the impacts of nitrite/FNA on the catabolic and anabolic processes of Nitrobacter to be assessed separately. FNA rather than nitrite was likely the actual inhibitor to the Nitrobacter metabolism. It was revealed that FNA of up to 0.05 mg HNO2-N x L(-1) (3.4 microM), which was the highest FNA concentration used in this study, did not have any inhibitory effect on the catabolic processes of Nitrobacter. However, FNA initiated its inhibition to the anabolic processes of Nitrobacterat approximately 0.011 mg HNO2-N x L(-1) (0.8 microM), and completely stopped biomass synthesis at a concentration of approximately 0.023 mg HNO2-N x L(-1) (1.6 microM). The inhibitory effect could be described by an empirical inhibitory model proposed in this paper, but the underlying mechanisms remain to be revealed.     

Light optical deformation measurements in microbars with nanometer resolution

 In a microsample tensile test the deformation of the testing region is observed with a light microscope. Using a new vision algorithm, elongations are determined with nanometer resolution. The image analysis system operates with adaptive least squares correlation and contains a diagnostic tool which provides information about the computational precision and determinability of the parameters to be estimated. Various tests are performed to verify the reliability and sensitivity of the presented method and to show its potential in the field of micromechanics. Received: 18 August 1995/Accepted: 20 December 1995     

Light optical deformation measurements in microbars with nanometer resolution

In a microsample tensile test the deformation of the testing region is observed with a light microscope. Using a new vision algorithm, elongations are determined with nanometer resolution. The image analysis system operates with adaptive least squares correlation and contains a diagnostic tool which provides information about the computational precision and determinability of the parameters to be estimated. Various tests are performed to verify the reliability and sensitivity of the presented method and to show its potential in the field of micromechanics. This paper was not presented at the International Conference on High Aspect-Ratio Microstructure Technology HARMST '95 in July 1995.     

Experimental determination of mechanical properties of Ni and Ni-Fe microbars

In this study, nickel and nickel-iron alloy microsamples produced using the LIGA technique are investigated. With vibration tests and tensile tests, design parameters such as Young’s modulus, elastic limit, and failure stress are determined. A new microsample tensile test apparatus is presented, in which forces and elongation are separately measured with very high accuracy. The comparison between the Young’s modulus which is determined with vibration experiments and the Young’s modulus derived from tensile tests ensures the reliability of the measurements presented. The error sources are analysed with the help of finite element models and the uncertainty in determining the Young’s modulus is calculated. The strength values measured for LIGA specimens are about 3 times higher than for comparable macroscopic specimens. This paper was not presented at the International Conference of High Aspect-Ratio Microstructure Technology HARMST ’95 in July 1995.     

Implication of Melanocortin Receptor Genes in the Familial Comorbidity of Type 2 Diabetes and Depression

The melanocortin receptors are G-protein-coupled receptors, which are essential components of the hypothalamic–pituitary–adrenal axis, and they mediate the actions of melanocortins (melanocyte-stimulating hormones: α-MSH, β-MSH, and γ-MSH) as well as the adrenocorticotropin hormone (ACTH) in skin pigmentation, adrenal steroidogenesis, and stress response. Three melanocortin receptor genes (MC1R, MC2R, and MC5R) contribute to the risk of major depressive disorder (MDD), and one melanocortin receptor gene (MC4R) contributes to the risk of type 2 diabetes (T2D). MDD increases T2D risk in drug-naïve patients; thus, MDD and T2D commonly coexist. The five melanocortin receptor genes might confer risk for both disorders. However, they have never been investigated jointly to evaluate their potential contributing roles in the MDD-T2D comorbidity, specifically within families. In 212 Italian families with T2D and MDD, we tested 11 single nucleotide polymorphisms (SNPs) in the MC1R gene, 9 SNPs in MC2R, 3 SNPs in MC3R, 4 SNPs in MC4R, and 2 SNPs in MC5R. The testing used 2-point parametric linkage and linkage disequilibrium (LD) (i.e., association) analysis with four models (dominant with complete penetrance (D1), dominant with incomplete penetrance (D2), recessive with complete penetrance (R1), and recessive with incomplete penetrance (R2)). We detected significant (p ≤ 0.05) linkage and/or LD (i.e., association) to/with MDD for one SNP in MC2R (rs111734014) and one SNP in MC5R (rs2236700), and to/with T2D for three SNPs in MC1R (rs1805007 and rs201192930, and rs2228479), one SNP in MC2R (rs104894660), two SNPs in MC3R (rs3746619 and rs3827103), and one SNP in MC4R genes (Chr18-60372302). The linkage/LD/association was significant across different linkage patterns and different modes of inheritance. All reported variants are novel in MDD and T2D. This is the first study to report risk variants in MC1R, MC2R, and MC3R genes in T2D. MC2R and MC5R genes are replicated in MDD, with one novel variant each. Within our dataset, only the MC2R gene appears to confer risk for both MDD and T2D, albeit with different risk variants. To further clarity the role of the melanocortin receptor genes in MDD-T2D, these findings should be sought among other ethnicities as well.