Effects of rhizopodin and latrunculin B on the morphology and on the actin cytoskeleton of mammalian cells

The effects of the novel myxobacterial compound rhizopodin on mammalian cells were studied and compared with those of latrunculin B. Both substances induced adherently growing L929 mouse fibroblasts and PtK2 potoroo kidney cells to produce long, narrow, branched extensions or runners. Rhizopodin was more efficient than latrunculin B in that respect (minimal inhibitory concentration with L929 cells 5 nM vs 50 nM), and, in contrast to latrunculin B, its effects were permanent. Rhizopodin-treated cells became much larger than normal cells and were multinucleate, yet stayed alive and biochemically active for several weeks. Latrunculin B-treated cells returned to a quasi-normal state within 3-4 days. But latrunculin B acted faster, with the first effects becoming visible almost immediately upon the addition of the drug, while the first rhizopodin effects were seen 10 min later. Both substances caused reorganization of the actin cytoskeleton. When 100 nM rhizopodin was added to PtK2 cells, the stress fibers began to decay after just 10 min and had disappeared completely after about 3 h. Later there was a gradual restitution of F-actin. Long F-actin fibers were seen within the runners, and only there; in fact, these fibers may be responsible for the development and extension of the runners. The microtubuli network adjusted itself to the new cell morphology, but was not directly impaired by the compound.     

Mixed meshless formulation for analysis of shell-like structures

An efficient mixed meshless computational method based on the Local Petrov–Galerkin approach for analysis of plate and shell structures is presented. A concept of a three-dimensional solid is applied allowing the use of complete three-dimensional constitutive equations, and exact shell geometry can be described. Discretization is carried out by using both the moving least square approximation and the polynomial functions. Independent field variables are the strain and stress tensor components expressed in terms of the nodal values, which are then replaced by the nodal displacements by using the independent displacement interpolation. A closed global system of equations with only nodal displacements as unknown variables is derived. The undesired locking phenomena are fully suppressed. The proposed mixed formulation is numerically more efficient than the available meshless fully displacement approach, as demonstrated by the numerical examples.     

Small-kernel superresolution methods for microscanning imaging systems

Two computationally efficient methods for superresolution reconstruction and restoration of microscanning imaging systems are presented. Microscanning creates multiple low-resolution images with slightly different sample-scene phase shifts. The digital processing methods developed here combine the low-resolution images to produce an image with higher pixel resolution (i.e., superresolution) and higher fidelity. The methods implement reconstruction to increase resolution and restoration to improve fidelity in one-pass convolution with a small kernel. One method uses a small-kernel Wiener filter and the other method uses a parametric cubic convolution filter. Both methods are based on an end-to-end, continuous-discrete-continuous microscanning imaging system model. Because the filters are constrained to small spatial kernels they can be efficiently applied by convolution and are amenable to adaptive processing and to parallel processing. Experimental results with simulated imaging and with real microscanned images indicate that the small-kernel methods efficiently and effectively increase resolution and fidelity.     

Manufacture and application of ultra-small micro end mills

The use of micro parts and micro structured elements has constantly grown over the past decade. Milling with micro end-mills belongs to the manufacturing technologies which offer a high potential for competitive micro machining. However, the design criteria for the micro end-mills and their manufacture pose many challenges. In this paper, first the design and manufacture of single-edge micro end-mills with diameters between 10 and 50 μm and a variable helix angle is described. Second, the use of these end-mills in titanium and polymethyl methacrylate (PMMA) is described to demonstrate their potential.     

Revisiting the Ziegler–Nichols process dynamics characterization

The Ziegler–Nichols process dynamics characterization is based on the estimation of the ultimate gain k_u and ultimate frequency ω_u. The angle φ of the tangent to the Nyquist curve at the frequency ω_u is introduced, as an additional parameter in the frequency domain. The essential dynamic characteristics of the process can be captured by using the tangent rule, proposed here as an extension of the Ziegler–Nichols approach. The validity of the tangent rule is confirmed by using the PID controller optimization on a test batch consisting of stable, integrating and unstable processes, including dead-time. Parameters k_u, ω_u and φ can be determined from the sustained oscillations, using the phase-locked loop identifier module.     

Analysis of Frequency Locking in Optically Driven MEMS Resonators

Thin, planar, radio frequency microelectromechanical systems (MEMS) resonators have been shown to self-oscillate in the absence of external forcing when illuminated by a direct current (dc) laser of sufficient amplitude. In the presence of external forcing of sufficient strength and close enough in frequency to that of the unforced oscillation, the device will become frequency locked, or entrained, by the forcing. In other words, it will vibrate at the frequency of the external forcing. Experimental results demonstrating entrainment for a disk-shaped oscillator under optical and mechanical excitation are reviewed. A thermomechanical model of the system is developed and its predictions explored to explain and predict the entrainment phenomenon. The validity of the model is demonstrated by the good agreement between the predicted and experimental results. The model equations could also be used to analyze MEMS limit-cycle oscillators designed to achieve specific performance objectives     

Immunity of electronic and transport properties of phosphorene nanoribbons to edge defects

We present an extensive study of the electronic properties and carrier transport in phosphorene nanoribbons (PNRs) with edge defects by using rigorous atomistic quantum transport simulations. This study reports on the size- and defect-dependent scaling laws governing the transport gap, and the mean free path and carrier mobility in the PNRs of interest for future nanoelectronics applications. Our results indicate that PNRs with armchair edges (aPNRs) are more immune to defects than zig-zag PNRs (zPNRs), while both PNR types exhibit superior immunity to defects relative to graphene nanoribbons (GNRs). An investigation of the mean free path demonstrated that even in the case of a low defect density the transport in PNRs is diffusive, and the carrier mobility remains a meaningful transport parameter even in ultra-small PNRs. We found that the electron–hole mobility asymmetry (present in large-area phosphorene) is retained only in zPNRs for W > 4 nm, while in other cases the asymmetry is smoothed out by edge defect scattering. Furthermore, we showed that aPNRs outperform both zPNRs and GNRs in terms of carrier mobility, and that PNRs generally offer a superior mobility-bandgap trade-off, relative to GNRs and monolayer MoS₂. This work identifies PNRs as a promising material for the extremely scaled transistor channels in future post-silicon electronic technology, and presents a persuasive argument for experimental work on nanostructured phosphorene.

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High Enthalpy Geothermal Potential of the Deep Gas Fields in Central Drava Basin,Croatia

In Croatia there is an urgent need to improve energy balance with more efficient methods of energy resources exploitation. There are approximately 3,000 wells drilled on oil, gas/condensate and geothermal reservoirs, of which only 50 were primarily drilled for purpose of geothermal exploitation. Over 10,000 seismic measurements were conducted. The most of drilled wells are scheduled for permanent abandonment in the near future, because of economical reasons and technological limitations of production. However, oil and gas wells which are near the end of production might be reassigned into geothermal wells, if aquifer water temperature and flow were satisfactory.     

Representing soil pollution by heavy metals using continuous limitation scores

The paper suggests a methodology to represent overall soil pollution in a sampled area using continuous limitation scores. The interpolated heavy metal concentrations are first transformed to limitation scores using the exponential transfer function determined by using two threshold values: permissible concentration (0 limitation points) and seriously polluted soil (4 limitation points). The limitation scores can then be summed to produce the map of cumulative limitation scores and visualize the most critically polluted areas. The methodology was illustrated using the 784 soil samples analyzed for Cd, Cr, Cu, Ni, Pb and Zn in the central region of Croatia. The samples were taken at 1×1 and grids and at fixed depths of 20 cm. Heavy metal concentrations in soil were determined by ICP-OES after microwave assisted aqua regia digestion. The sampled concentrations were interpolated using block regression-kriging with geology and land cover maps, terrain parameters and industrialization parameters as auxiliary predictors. The results showed that the best auxiliary predictors are geological map, ground water depth, NDVI and slope map and distance to urban areas. The spatial prediction was satisfactory for Cd, Ni, Pb and Zn, and somewhat less satisfactory for Cu and Cr. The final map of cumulative limitation scores showed that 33.5% of the total area is suitable for organic agriculture and 7.2% of the total area is seriously polluted by one or more heavy metals. This procedure can be used to assess suitability of soils for agricultural production and as a basis for possible legal commitments to maintain the soil quality.