Photoproduction of H2 by wildtype Anabaena PCC 7120 and a hydrogen uptake deficient mutant: from laboratory experiments to outdoor culture

We have analyzed the filamentous cyanobacterium Anabaena PCC 7120 (wildtype) containing one nitrogenase, one uptake hydrogenase and one bidirectional hydrogenase and its hydrogen uptake deficient mutant AMC 414 for their H₂ production capacities. Anabaena PCC 7120 and AMC 414 had similar growth rates in turbidostat mode with increased growth rates at higher light intensity. Rates of C₂H₂ reduction were similar for both strains. In contrast to the wildtype, AMC 414 produced H₂ in a PhotoBioReactor (PhBR) using air as the lifting gas. The rate of H₂ production increased with light intensity and was not even saturated at 456 μEm⁻² s⁻¹. H₂ production increased significantly when replacing the air with argon. The maximal H₂ production during outdoor conditions was recorded using AMC 414 with a peak at 14.9 ml H₂ h⁻¹ l⁻¹. Despite the relatively high production, maximal efficiency of solar energy to H₂ conversion was only 0.042%. A molecular method was developed to analyze the relative abundancies of weight and mutant in competition experiments in the PhBR.     

Oil whip-induced wear in journal bearings

This paper investigates the effect of oil whirl and oil whip in fluid film radial bearings due to possible metallic contact. The degree of metallic contact and thereby wear and tear between rotating shafts and bearing bushes is assessed by measuring electric currents through the oil film. The current as well as the voltage varied in accordance with the contact ratio between the shaft and bush in the fluid film radial bearing. The gauge signal thus indicates the degree of metallic contact based on the thickness of the oil film in the load zone. Some experimental results are provided to illustrate that at low normalised loads involving oil whirl and oil whip, no electric current is detected, while high levels of electric current are registered at high load levels when no oil whirl or oil whip occurred. It is therefore concluded that at low loads, oil whirl and oil whip have little influence on wear and tear in a journal bearing.     

The effect of hybrid nanoparticle additives on epoxy‐nanocomposite behavior and morphology

Amine modified polyhedral oligomeric silsesquioxane (POSS‐NH₂) was used to modify sodium montmorillonite (MMT) nanoclays for improved dispersion in epoxy resin. The dispersion of the clay particles was inspected using scanning electron microscopy, energy dispersive spectroscopy (EDS) and X‐Ray diffraction and the thermal properties compared using differential scanning calorimetry (DSC) and thermogravametric analysis. The introduction of the amine‐POSS was found to have a positive effect on the dispersion of the MMT clays and prevented agglomeration. The absence of clay agglomerates lead to an increase in glass transition temperature (T_g) from 44°C in the samples with the untreated clay up to 54°C in the samples with 10% additional POSS‐NH₂. The addition of POSS‐NH₂ initial increase of the weight loss (T_{d 5%}) but slowed down the rate of degradation due to the formation of an inert silica layer and eventually leading to an increased charyield. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Meeting a demand vs. enhancing protections in homogeneous parallel systems

The article considers defense resource allocation in a system exposed to planned and forced losses. The defender distributes its limited resource between deploying identical system elements and their protection from attacks. Planned losses arise if there are not enough elements to meet the demand. Forced losses arise if an external attack reduces the performance below the demand. The attacker distributes its effort evenly among all the elements or among elements from a chosen subset. The vulnerability of each element is determined by an attacker–defender contest success function. The expected damage caused by the attack is proportional to the system performance reduction below a planned level of demand satisfaction.     

Towards automatic adaptive geometrically non-linear shell analysis. Part I: Implementation of an h-adaptive mesh refinement procedure

Effective methods leading to automated adaptive numerical solutions to geometrically non-linear shell-type problems are studied in this work. In particular, procedures for improving the accuracy, the reliability and the computational efficiency of the finite element solutions are of primary interest here. This is addressed using h-adaptive mesh refinement based on a posteriori error estimation, self-adaptive methods in global incremental/iterative processes, as well as smart algorithms and heuristic approaches based on methods of knowledge engineering. Seemless integration of h-adaptive finite element methods with adaptive step-length control makes it possible to maintain a prescribed accuracy while maintaining the solution efficiency without user intervention throughout the process of a non-linear analysis. Several examples illustrate the merit and potential of the approach studied herein and confirm the feasibility of developing an automatic adaptive environment for geometrically non-linear analysis of shell structures.     

External power frequency magnetic field-induced jitter on computer monitors

Power frequency magnetic fields with flux densities greater than 0.5 μT are not uncommon in offices. This level has been shown to induce jitter on VDT monitors. In the present project, these magnetic field-induced disturbances have been studied in the laboratory in order to establish a firm technical basis for future studies of the disturbance's influence on eye strain in VDT workers. Eight volunteers judged the occurrence of distortion when an applied external magnetic field was varied both in amplitude and frequency for 8 investigated VDT screens. The level of the external 50 Hz magnetic field when the distortion was detectable ranged from 0.6 to 1.1 μT. If the screen was viewed through a stereomicroscope (25 × magnification), the corresponding level was in the order of 0.2 μT. If the frequency difference between the external magnetic field and the refresh rate of the screen is only ±1-2 Hz, the disturbance is noticeable at even lower flux densities.     

Multiple Causes of Difficulty in Insight: The Case of the Nine-Dot Problem.

Theories of insight problems are often tested by formulating hypotheses about the particular difficulties of individual insight problems. Such evaluations often implicitly assume that there is a single difficulty. We argue that the quantitatively small effects of many studies arise because the difficulty of many insight problems is determined by multiple factors, so the removal of 1 factor has limited effect on the solution rate. Difficulties can reside either in problem perception, in prior knowledge, or in the processing of the problem information. We support this multiple factors perspective through 3 experiments on the 9-dot problem (N.R.F. Maier, 1930). Our results lead to a significant reformulation of the classical hypothesis as to why this problem is difficult. The results have general implications for our understanding of insight problem solving and for the interpretation of data from studies that aim to evaluate hypotheses about the sources of difficulty of particular insight problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the growth hormone/insulin-like growth factor I axis in stimulation of protein synthesis in skeletal muscles following oral refeeding

The mechanisms behind stimulation of protein synthesis in skeletal muscles following oral feeding are not well understood. Previous research has not confirmed that insulin is a major factor behind this stimulation. In the present study we have used genetically altered mice, with either a lack of GH secretion due to a mutational gene inactivation [GH (-/-) dwarf, DW/JOrlBom-dw] or mice with a homozygous site-specific insertion mutation in the insulin-like growth factor-1 gene [IGF-I (m/m)], leading to a deficient IGF-I production. These gene knock-outs were used in comparison to their normal wild types for evaluation of the role that the GH/IGF-I axis may have in activation of nutritionally induced stimulation of protein synthesis in skeletal muscles during oral refeeding. Weight stable adult C57B16 mice served as an additional normal control group. Protein synthesis was measured by a modified flooding dose technique with radioactive L-[14C-U]phenylalanine incorporation into acid precipitated muscle proteins. Fractional protein synthesis in skeletal muscles after an overnight fast was comparable among C57B16 (0.076 +/- 0.009%/h), wild-type IGF-I(+/+) (0.061 +/- 0.008) and IGF-I(m/m) deficient mice (0.068 +/- 0.006%/h), whereas GH(-/-) incompetent mice had a lower fractional synthesis rate compared with GH(+/+) competent mice (0.045 +/- 0.006 vs. 0.068 +/- 0.007, P < 0.05). Refeeding with standard chow diet stimulated protein synthesis in muscles by more than 60% in all animal groups. This response was independent of circulating GH, total IGF-I concentrations in blood, as well as up-regulation of locally produced IGF-I messenger RNA (mRNA) in skeletal muscles.     

Active fixation for scene exploration

It is well-known that active selection of fixation points in humans is highly context and task dependent. It is therefore likely that successful computational processes for fixation in active vision should be so too. We are considering active fixation in the context of recognition of man-made objects characterized by their shapes. In this situation the qualitative shape and type of observed junctions play an important role. The fixations are driven by a grouping strategy, which forms sets of connected junctions separated from the surrounding at depth discontinuities. We have furthermore developed a methodology for rapid active detection and classification of junctions by selection of fixation points. The approach is based on direct computations from image data and allows integration of stereo and accommodation cues with luminance information. This work form a part of an effort to perform active recognition of generic objects, in the spirit of Malik and Biederman, but on real imagery rather than on line-drawings.