The effects of colloidal nanotopography on initial fibroblast adhesion and morphology

Colloidal lithography offers a simple, inexpensive method of producing irregular nanotopographies, a pattern not easily attainable utilizing conventional serial writing processes. Colloids with 20- or 50-nm diameter were utilized to produce such an irregular topography and were characterized by calculating the percentage area coverage of particles. Interparticle and nearest neighbor spacing were also assessed for the individual colloids in the pattern. Two-way analysis of variance (ANOVA) indicated significant differences between the number of fibroblasts adhering to planar, 20-, and 50-nm-diameter colloidal topographies, the number of fibroblasts adhering to the substrates at the time intervals studied, namely 20 min, 1 h, and 3 h and significant interaction between time and topography on fibroblast adhesion (P<0.01). Tukey tests were utilized for sensitive identification of the differences between the sample means and compounded ANOVA results. Cytoskeletal and general cell morphology were investigated on planar and colloidal substrates, and indicated cells in contact with irregular nanotopographies exhibit many peripheral protrusions while such protrusions are absent in cells on planar control surfaces. These protrusions are rich in microtubules on 20-nm-diameter colloidal surfaces while microfilaments are prevalent on 50-nm-diameter surfaces. Moreover, by 3 h, cells on the colloidal substrates initiate cell-cell adhesions, also absent in controls

A new test procedure to validate tensile dynamic mechanical properties of sheet metals and alloys in automotive crash applications

A thin walled open channel beam subjected to a 3-point bend and constant velocity boundary condition is investigated to establish its potential to validate material performance for automotive crash applications. Specifically quantitative validation of material data determined from high speed tensile testing and qualitative validation of material resistance to fracture in crash components. Open channel beams are fabricated from structural grade sheet steel and aluminium alloy and tested at quasi-static and higher speeds up to 10 m/s and in all cases, deformation develops a plastic hinge. This paper describes development of the validation test procedure, specifically design of specimen, system of measurement and boundary conditions using numerical and experimental techniques. The new test procedure will increase confidence in materials modelling and reduce the risk to introduce new advanced high strength materials into automotive crash structures

Effects of mechanically separated dairy cow slurry on grazing performance

No abstract available

Modelling self-piercing riveted joint failures in automotive crash structures

This paper describes a new model and method to predict Self-Piercing Riveted (SPR) joint interlock failures in aluminium sheet at crash speeds using explicit finite element simulation. SPR interlock failure is dependent on rivet direction, which is included in the model. A mesh independent approach is adopted for connection model which is capable of industrial application at the full vehicle crash analysis level. The paper provides an overview of the approach to validate connection model; typically by developing detailed physics based models of various joint configurations supported with high speed experimental data, through to model capable of industrial application. The framework to validate connection model for use in crash simulation tools is expected to have broader applicatio

Validating dynamic tensile mechanical properties of sheet steels for automotive crash applications

A thin-wall open channel beam, fabricated from high strength Dual Phase sheet steel, subjected to 3-point bending and constant velocity boundary condition, is investigated to validate material performance for automotive crash applications. Specifically quantitative validation of material tensile data determined from high speed tests and component models, and qualitative validation of materials resistance to fracture. The open channel beam is subjected to quasi-static and increasing loading speed and in all cases, large displacement in which deformation involves formation of a plastic hinge. This paper describes development of test procedure, notably beam specimen design, measurement system and boundary conditions, using both experimental and numerical techniques. The new test procedure, as a compliment to crush testing, will increase confidence in the modeling and application of new advanced higher strength materials in automotive crash structure

On a problem of Andersson and Perlman

We present a simple solution to a problem posed recently by Andersson and Perlman. This solution allows us to find the conditional independence assumptions necessary to permit maximum likelihood estimation of the parameters of a multivariate normal distribution, when certain observations are missing

Adaptive modulation of antibiotic resistance through intragenomic coevolution

Bacteria gain antibiotic resistance genes by horizontal acquisition of mobile genetic elements (MGEs) from other lineages. Newly acquired MGEs are often poorly adapted causing intragenomic conflicts; these are resolved by either compensatory adaptation—of the chromosome or the MGE—or reciprocal coadaptation. The footprints of such intragenomic coevolution are present in bacterial genomes, suggesting an important role promoting genomic integration of horizontally acquired genes, but direct experimental evidence of the process is limited. Here we show adaptive modulation of tetracycline resistance via intrage- nomic coevolution between Escherichia coli and the multidrug resistant plasmid RK2. Tetracycline treatments, including mono- therapy or combination therapies with ampicillin, favoured de novo chromosomal resistance mutations coupled with mutations on RK2 impairing the plasmid-encoded tetracycline efflux pump. These mutations together provided increased tetracycline resistance at reduced cost. Additionally, the chromosomal resistance mutations conferred cross-resistance to chloramphenicol. Reciprocal coadaptation was not observed under ampicillin-only or no antibiotic selection. Intragenomic coevolution can create genomes comprising multiple replicons that together provide high-level, low-cost resistance, but the resulting co-dependence may limit the spread of coadapted MGEs to other lineages

Experimental determination of the 6s^2 ^1S_0 -> 5d6s ^3 D_1 magnetic-dipole transition amplitude in atomic ytterbium

We report on a measurement of the highly forbidden 6s^2 ^1S_0 \to 5d6s ^3 D_1 magnetic-dipole transition in atomic ytterbium using the Stark-interference technique. This amplitude is important in interpreting a future parity nonconservation experiment that exploits the same transition. We find $| | ~ = ~ 1.33(6)_{Stat}(20)_{\beta} \times 10^{-4} \mu_0$, where the larger uncertainty comes from the previously measured vector transition polarizability $\beta$. The $M1$ amplitude is small and should not limit the precision of the parity nonconservation experiment.Comment: 4 pages, 5 figures Paper resubmitted with minor corrections and additions based on comments from referee

Modeling and Characterization of a Novel, Low-Cost, Direct-Write Waveguide

Both the current long-term telecommunication trends toward optical networking and the recent growth in information bandwidth have pushed the necessity for improved optical communications. Our fabrication approach, which leverages our expertise in solid freeform fabrication in conjunction with sol-gel technology, has advantages over these other methods because of the inherent benefits of using a direct-write philosophy, such as design flexibility and minimal post-processing. However, fabrication of such novel optical components requires extensive knowledge of their light guidance capabilities. This paper will show the technical issues involved in both modeling and characterizing small optical components fabricated by locally densifying sol-gels in a modified directwrite process.Mechanical Engineerin