Scanning near-field optical microscopy of a cell membrane in liquid

The applications of scanning near‐field optical microscopy to biological specimens under physiological conditions have so far been very rare since common techniques for a probe–sample distance control are not as well suited for operation in liquid as under ambient conditions. We have shown previously that our own approach for a distance control, based on a short aperture fibre probe and a tuning fork as force sensor in a tapping mode, works well even on soft material in water. By means of an electronic self‐excitation circuit, which compensates for changes of the resonance frequency due to evaporation of liquid, the stability of the force feedback has now been further improved. We present further evidence for the excellent suitability of the tapping‐mode‐like distance control to an operation in liquid, for example, by force‐imaging of double‐stranded DNA. Moreover, we demonstrate that a nuclear envelope in liquid can be imaged with a high optical resolution of ～70 nm without affecting its structural integrity. Thereby, single nuclear pores in the nuclear envelope with a nearest neighbour distance of ～120 nm have been optically resolved for the first time.     

Transmissive x-ray beam position monitors with submicron position- and submillisecond time resolution

We present the development of fast transmissive center-of-mass x-ray beam position monitors with a large active area, based on a thinned position sensitive detector in both a duo- and a tetra-lateral variant. The detectors were tested at BESSY beamlines BL14.1, KMC-1, and KMC-2 and yielded signal currents of up to 3 microA/100 mA ring current at 10 keV photon energy using the monochromatic focused beam of BL14.1. The active area sizes were 1 x 1 and 3 x 3 mm(2) for the duo-lateral and 5 x 5 mm(2) for the tetra-lateral devices, with the duo-lateral detectors currently being available in sizes from 1 x 1 to 10 x 10 mm(2) and thicknesses between 5 and 10 microm. The presented detectors' thicknesses were measured to be 5 and 8 microm with a corresponding transmission of up to 93% at 10 keV and 15% at 2.5 keV. Up to a detection bandwidth of 10 kHz, the monitors provide submicron position resolution. For lower detection bandwidths, the signal-to-noise reaches values of up to 6 x 10(4) at 10 Hz, corresponding to a position resolution of better than 50 nm for both detector sizes. As it stands, this monitor design approach promises to be a generic solution for automation of state-of-the-art crystal monochromator beamlines.     

Renal cell culture

Methods for the establishment and growth of renal cell types in culture are reviewed, with emphasis on current trends. General techniques available for the isolation and culture of glomerular cells have progressed from explant to enzyme dissociation and cloning techniques. The growth characteristics and properties of cultured glomerular endothelial, epithelial, mesangial, and bone-marrow-derived cells are discussed. Studies are described in which cultures of contractile mesangial cells have led to an elucidation of their role both in normally functioning glomeruli and in disease states. Renal tubule culture techniques also have progressed from mixed tissue explants and cell isolates to fractionation of enriched tubule populations and growth of specific, individually microdissected proximal convoluted, proximal straight, thick ascending limb of Henle's loop, and collecting tubules. The differentiated tubule epithelial-specific properties of such primary cultures are discussed in relation to those of permanently growing cell lines such as MDCK and LLC-PK1. Renal tubule cultures will be invaluable for the study of the role of hormones and extracellular matrix in epithelial growth and polarity of normal structure and function. In addition, in vitro models of cultured renal tubules have been established to study the effects of age, nephrotoxins, and anoxic injury.     

Graphical enhancement to support PCA-based process monitoring and fault diagnosis

Principal component analysis (PCA) for process modeling and multivariate statistical techniques for monitoring, fault detection, and diagnosis are becoming more common in published research, but are still underutilized in practice. This paper summarizes an in-depth case study on a chemical process with 20 monitored process variables, one of which reflects product quality. The analysis is performed using the PLS - Toolbox 2.01 with MATLAB, augmented with software which automates the analysis and implements a statistical enhancement that uses confidence limits on the residuals of each variable for fault detection rather than just confidence limits on an overall residual. The newly developed graphical interface identifies and displays each variable's contribution to the faulty behavior of the process; and it aids greatly in analyzing results. The case study analyzed within shows that using the statistical enhancement can reduce the fault detection time, and the automated graphical interface implements the enhancement easily.     

A generalized Vlasov theory for composite beams

A generalized Vlasov theory for composite beams with arbitrary geometric and material sectional properties is developed based on the variational asymptotic beam sectional analysis. Instead of invoking ad hoc kinematic assumptions, the variational-asymptotic method is used to rigorously split the geometrically-nonlinear, three-dimensional elasticity problem into a linear, two-dimensional, cross-sectional analysis and a nonlinear, one-dimensional, beam analysis. The developed theory is implemented into VABS, a general-purpose, finite-element based beam cross-sectional analysis code. Several problems are studied to compare the present theory with published results and a commercial three-dimensional finite element code. The present work focuses on the issues concerning the use of the Vlasov correction in the context of the accuracy of the resulting beam theory. The systematic comparison with three-dimensional finite element analysis results helps to quantitatively demonstrate both the advantages and limitations of the Vlasov theory.     

Determination of the bacterial processes which are sources of nitrous oxide production in marine samples

Partial denitrification and the initial step of nitrification are the main biological processes which produce nitrous oxide. In order to determine the contribution that these processes have in nitrous oxide production, the efficiency of different inhibitors on nitrifying activity has been tested, and the effect on denitrifying activity has been investigated, using culture strains and natural marine samples. A good nitrification inhibitor should not affect denitrification. A low partial pressure of C2H2 provided the best conditions, inhibiting 75%, Nitrosococcus oceanus (culture sample) and 100% (natural sample) of the nitrifying activity and having only a small inhibitory effect (12%) on denitrifying activity. These conditions have been applied on samples from the dilution plume of the Rh?ne River, an area characterized as a source of nitrous oxide. Using these inhibitors, it has been shown that in this area, incomplete denitrification is the main process producing nitrous oxide in the surface layers at the mouth of the river and in the bottom nepheloid layer, whereas in the marine surface layer the dominant process is nitrification.     

Coupling multiscale X-ray physics and micromechanics for bone tissue composition and elasticity determination from micro-CT data,by example of femora from OVX and sham rats

Due to its high resolution, micro-CT (Computed Tomograph) scanning is the key to assess bone quality of sham and OVX (ovariectomized) rats. Combination of basic X-ray physics, such as the energy- and chemistry-dependence of attenuation coefficients, with results from ashing tests on rat bones, delivers mineral, organic, and water volume fractions within the voxels. Additional use of a microelastic model for bone provides voxel-specific elastic properties. The new method delivers realistic bone mass densities, and reveals that OVX protocols may indeed induce some bone mass loss, while the average composition of the bone tissue remains largely unaltered.     

Optimal design of type-2 and type-1 fuzzy tracking controllers for autonomous mobile robots under perturbed torques using a new chemical optimization paradigm

This paper addresses the tracking problem for the dynamic model of a unicycle mobile robot. A novel optimization method inspired on the chemical reactions is applied to solve this motion problem by integrating a kinematic and a torque controller based on fuzzy logic theory. Computer simulations are presented confirming that this optimization paradigm is able to outperform other optimization techniques applied to this particular robot application.     

Effect of topology on the adhesive forces between electrospun polymer fibers using a T‐peel test

Electrospinning provides an effective methodology to obtain high aspect ratio polymer fibers for biomimetic applications. In this article, we evaluate the effect of topology on adhesion between aligned fibers. Polycaprolactone is electrospun using two different setups: (i) a tip collector and (ii) a flat collector. The tip collector enables the fibers to self‐align. When a fiber reaches the tip collector, the next fiber is repelled by the charge they carry, forcing the fibers to deposit in a parallel arrangement. The flat collector allows the fibers to deposit at random. The adhesion between the fiber mats is measured using a T‐peel test. Adhesion strength (758.7 ± 211.7 kPa) changes marginally with the peeling rate and applied pressure on the membranes. Aligned fibers exhibit higher adhesion strength between the membranes in comparison to randomly oriented nonwovens (613.1 ± 79.9 kPa). The estimated Johnson–Kendall–Roberts contact energy (83.1 ± 32.5 mJ/m²) is consistent with the range of van der Waals adhesion forces. This work shows how the adhesion between two polymer membranes can be modulated by surface topology, based on a T‐peel testing setup. POLYM. ENG. SCI., 53:2219–2227, 2013. © 2013 Society of Plastics Engineers     

Bioinformatics in the post-genomic age

The sequencing of several genomes, including the human genome, has provided a vast amount of information which must be exploited if new drugs are to be provided. Bioinformatics is essentially the science of taking this and other biological information and applying advanced IT techniques to it so as to identify protein targets and therefore suitable drug candidates. Databases, software and research and development tools are all being created with a view to efficient search and interrogation.The author, in emphasising the need for obtaining appropriate monopoly protection, highlights the problems associated with the patenting of computer program related patents and refers to database rights as an alternative form of protection.