Heat transfer effects on hydropneumatic suspension systems

One of the problems experienced on hydropneumatic suspension systems, is the effect of temperature change on the spring characteristic, resulting in variations in spring rate and ride height. This problem can be analysed using an appropriate heat transfer model. Two major heat transfer modes are investigated, i.e. heat transfer between the gas and its surroundings and heat transfer between the damper oil and the gas. The analyses performed include the determination of the dynamic spring force characteristic, the effect of heat build-up on the spring force characteristic and the effect of heat build-up on the performance of the hydropneumatic spring and damper unit during vehicle tests. Mathematical modelling of the spring characteristic is performed by solving the energy equation for a gas in a closed container using the thermal time constant approach. The Benedict–Webb–Rubin equation of state is used for real gas behaviour. The mathematical model is verified against experimental data and good correlation is achieved. It is shown that hydropneumatic suspension systems have a significant amount of inherent damping due to heat transfer which produces no nett temperature change or heat build-up. The effect of heat build-up in the damper on the spring force characteristic is determined by laboratory tests. It is shown that heat generation in the damper, accompanied by a rise in gas temperature, has a detrimental effect on the spring force characteristic. Tests performed on experimental hydropneumatic spring and damper systems fitted to a test vehicle indicate that the effect is smaller in practice than anticipated. Heat build-up is strongly influenced by terrain roughness, vehicle speed, mission profile and damping levels.     

Affinity Study of Novel Gelatin Cell Carriers for Fibronectin

In the present work, the gelatin/fibronectin affinity was evaluated using SPR, QCM and radiolabelling. The results indicate that type A gelatin films possess a higher affinity for Fn compared to type B gelatin. This is due to a combined hydrophobic and electrostatic interaction between gelatin type A and Fn. In a second part, the affinity of Fn for porous gelatin scaffolds was evaluated. The scaffolds were prepared by a cryogenic treatment and subsequent freeze‐drying yielding type I and type II scaffolds which possess different pore geometries/sizes. The results indicate that the Fn density on the scaffolds can be fine‐tuned by varying the Fn concentration, the gelatin type (A vs. B), the pore size/geometry (type I vs. type II scaffolds).

     

Odd random phase multisine EIS as a detection method for the onset of corrosion of coated steel

In this work, odd random phase multisine Electrochemical Impedance Spectroscopy (ORP-EIS) was used as a detection method for the onset of corrosion of coated steel. The possibility to use ORP-EIS as a rapid-screening test for corrosion was investigated. It is concluded that the detection of a non-linear behavior combined with a non-stationary behavior during the onset of corrosion can be used as a criterion in a rapid-screening test for corrosion of coated steel.     

Purification of 3-indolylacetic acid by solid phase extraction

This paper deals with the use of solid-phase extraction (SPE) for the extraction and purification of 3-indolylacetic acid (IAA), the main and most important representative of the plant growth regulators auxins. The procedure is based on the use of C18-SPE columns in two steps. In the first one, raw extract in methanol:water (4:1) is applied on the column in order to remove neutral ballast. In the second step the eluate is diluted with water to a final methanol concentration of 20% (to decrease the elution strength of the solvent) and acidified with formic acid to a final concentration of 1% (to convert the IAA from the anionic to the neutral form). Neutral IAA is then retained on the second SPE column, eluted by (acidified) methanol, and subjected to final analysis. Scintillation counting of tritium labeled IAA standard was used for the investigation and optimization of the SPE procedure. Gas chromatography with mass spectrometric detection was suggested as a convenient method for routine determination of IAA after its methylation with diazomethane. Overall recovery of the procedure was estimated as 89-94% and a physiological level of IAA equal to 0.48 nmol/g (84 ng/g) fresh weight was found using an optimized SPE-GC-MS method.     

Single-molecule surface enhanced resonance Raman spectroscopy of the enhanced green fluorescent protein

In the present contribution, we demonstrated that surface-enhanced resonance Raman scattering spectra from single green fluorescent proteins (GFPs) were obtained. The most important findings are the direct detection of the conversion between a deprotonated and a protonated form of the chromophore at the single-molecule level via the corresponding vibrational fingerprints, and the fact that the enhanced green fluorescent protein (EGFP) also shows a high surface enhanced resonance Raman scattering (SERRS) signal. Our findings show the potential of the technique to study structural dynamics of protein molecules at a single-molecule level.     

Synchronization of delay-coupled oscillators: a study of semiconductor lasers

Two delay-coupled semiconductor lasers are studied in the regime where the coupling delay is comparable to the time scales of the internal laser oscillations. Detuning the optical frequency between the two lasers, novel delay-induced scenarios leading from optical frequency locking to successive states of periodic intensity pulsations are observed. We demonstrate and analyze these dynamical phenomena experimentally using two distinct laser configurations. A theoretical treatment reveals the universal character of our findings for delay-coupled systems.     

Tailoring wave chaos in vertical-cavity surface-emitting lasers via polarization control

We demonstrate that polarization control in combination with the geometrical shape affects wave chaos phenomena in vertical-cavity surface-emitting lasers (VCSELs). In a grating-polarization-stabilized VCSEL, we demonstrate wave chaos in one polarization mode and a transition from wave chaos to regular behavior in the other orthogonal polarization mode. We quantify the amount of chaoticity via the Brody nearest-neighbor distribution. Comparing with a reference VCSEL without a surface-grating, we explain these results and their injection current dependence by the surface-grating-induced mode selection and a change in the effective resonator shape.