Ineffective and non-nodulating mutant strains of Rhizobium japonicum

Mutant strains of Rhizobium japonicum that were unable to allow the Corsoy cultivar of soybean to reduce acetylene or fix N2 were isolated. These strains grow as well as the wild type in a variety of media. Mutant strains SM1 and SM2 did not form nodules on the host plant; however, they reduced acetylene in the nonsymbiotic assay. Strains SM3 and SM4 produced nodules that did not have the characteristic pink pigment caused by leghemoglobin. The nodules formed by these strains also were small. One mutant strain, SM5, produced large pink nodules. The lesion in this strain seems to be in the gene that specifies nitrogenase component II.     

Allgemeine Untersuchungsverfahren und Laboratoriumstechnik

Ohne Zusammenfassung     

Molecular changes during learning: Behavioral strategy: A comment on Gaito and Bonnet.

Discusses J. Gaito and K. Bonnet's (see record 1971-07612-001) recent review which suggests that there is no conclusive evidence linking macromolecular changes to learning and memory. It is contended that current experiments in this field are not properly designed to test the hypothesis that a general macromolecular process underlies learning and memory, since the control group designated "nonlearning" is not achieved with the typical control procedures. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intracellular localisation of urea-cycle enzymes in liver (author's transl)

Enzymes of the Krebs-Henseleit urea-cycle were localized by means of differential centrifugation and fractional tissue extraction in rat liver and in human liver. Argininosuccinatlyase (ASAL) and Argininosuccinatsynthetase (ASAS) represent enzymes of the soluble cytoplasmic fraction. Ornithine-ketoacid-transaminase(OKT), carbamyl-phosphate-synthetase (CPS) and ornithine-carbamyl-transferase (OCT) are localized in the mitochondrial and nuclei fractions of the liver cell. Most of the arginase activity is bound to subcellular structures (probably to nuclei). A small portion of arginase-activity was found in the soluble cytoplasmatic fraction. The enzymes of the Krebs-Henseleit urea-cycle are equally distributed in rat liver and in human liver. Differences in the subcellular localisation of (mitochondrial) enzymes in human liver could be attributed to mitochondrial breakage during tissue preparation and do not represent in-vivo conditions.     

Comparative investigation of the biocompatibility of various silicon nitride ceramic qualities in vitro

There is a controversy about the biocompatibility of silicon nitride ceramics contained in the literature, which appears to be related to a factor of the individual chemical composition of different qualities of silicon nitride ceramics and of the different surface properties. This study attempts to investigate the cytotoxicity of different qualities of industrial silicon nitride ceramics applying an L929-cell culture model in a direct contact assay combined with a cell viability assessment. Five different qualities of industrial standard silicon nitride ceramics were chosen for in vitro testing. The chemical composition was determined by EDS analysis. Different biomedically approved aluminium oxide qualities, a titanium alloy, glass and polyvinylchloride (PVC) served as control materials. L929 mice fibroblasts were incubated directly on the materials for 24 h, stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy to control cell morphology, viability and cell counts compared to empty well values. Scanning electron microscopy was applied to additionally investigate cell morphology. There was no observation of cytotoxic effects on the silicon nitride ceramic samples; moreover cell morphology remained the same as on aluminium oxide and titanium. Viability testing revealed the presence of avital cells exclusively on PVC, which served as a negative control. Cell counts on all polished surfaces showed significantly higher numbers, whereas some rough surface samples showed significantly lower numbers. We conclude that silicon nitride ceramics show no cytotoxic effects and should be considered for biomedical application owing to its favourable physiochemical properties, especially its superior resistance to mechanical stress, which would be useful for compression loaded conditions. Polished surfaces would appear to promote advanced biocompatibility.     

Component-based end-user database design for ecologists

To solve today’s ecological problems, scientists need well documented, validated, and coherent data archives. Historically, however, ecologists have collected and stored data idiosyncratically, making data integration even among close collaborators difficult. Further, effective ecology data warehouses and subsequent data mining require that individual databases be accurately described with metadata against which the data themselves have been validated. Using database technology would make documenting data sets for archiving, integration, and data mining easier, but few ecologists have expertise to use database technology and they cannot afford to hire programmers. In this paper, we identify the benefits that would accrue from ecologists’ use of modern information technology and the obstacles that prevent that use. We describe our prototype, the Canopy DataBank, through which we aim to enable individual ecologists in the forest canopy research community to be their own database programmers. The key feature that makes this possible is domain-specific database components, which we call templates. We also show how additional tools that reuse these components, such as for visualization, could provide gains in productivity and motivate the use of new technology. Finally, we suggest ways in which communities might share database components and how components might be used to foster easier data integration to solve new ecological problems.     

Structural Engineering with NiTi. II: Mechanical Behavior and Scaling

This paper continues to address the overarching goal to provide a more unified understanding of NiTi shape memory alloys intended for use in structural applications by attempting to link standard processing practice and basic materials characterization to the deformation behavior of large diameter bars. Results from cyclic tensile tests performed on large diameter Ni-rich polycrystalline NiTi bars are presented. Coupon specimens taken from deformation processed bars with diameters of 12.7, 19.1, and 31.8?mm are tested along with their respective full-scale specimens. The coupon tests results reveal small and highly variable differences between specimens taken from the different size bars. The full-scale specimen tests continue to show the presence of the R phase, but lack a Lüders-like transformation. A comparison of the results suggests that coupon specimens provide only limited information in terms of the full-scale behavior. Full-scale tests using an earthquake-type loading then show similar behavior to the tensile cyclic tests suggesting the ability to use NiTi in structural applications. Overall, this paper and Tyber et al. 2007 provide a multiscale analysis of NiTi shape memory alloys to be used by both material scientist and civil engineers in the development of applications for NiTi.     

Experimental and Numerical Analysis of Composite Folded Sandwich Core Structures Under Compression

The characterisation of the mechanical behaviour of folded core structures for advanced sandwich composites under flatwise compression load using a virtual testing approach is presented. In this context dynamic compression test simulations with the explicit solvers PAM-CRASH and LS-DYNA are compared to experimental data of two different folded core structures made of aramid paper and carbon fibre-reinforced plastic (CFRP). The focus of the investigations is the constitutive modelling of the cell wall material, the consideration of imperfections and the representation of cell wall buckling, folding or crushing phenomena. The consistency of the numerical results shows that this can be a promising and efficient approach for the determination of the effective mechanical properties and a cell geometry optimisation of folded core structures.