Nonlinear vibrations of offshore structures under random wave excitation

An account is given of some mathematical methods which have been used to analyse the response of offshore structures to random wave excitation. The analysis of nonlinear phenomena and the assessment of related nongaussian probability distributions are emphasized. The following problems are analysed in some depth: probability distributions for Morison-type wave loading; response near resonance of nonlinearly damped systems to random excitation; parametric resonance and instability of nonlinearly damped systems with randomly fluctuating restoring force coefficient. Solutions to each of these problem areas are illustrated by practical examples.     

Secondary flows and particle centrifugation in slightly tilted rotating pipes

A theoretical analysis is presented of viscous incompressible laminar flow in a pipe which rotates around an axis held at small angle with respect to its symmetry-axis. Analogous to the results of Barua and Benton [1, 2], solutions in closed-form are given for circulatory flows in the cross-sectional plane of the pipe due to Coriolis forces in combination with Hagen-Poiseuille flow through the pipe. The solutions are used to derive analytical expressions for trajectories of solid or liquid particles entrained in the gas and being subject to centrifugation and the said secondary flows. It is shown that despite centrifugation, particles can be locked into circulatory trajectories thus remaining suspended in the gas flowing through the pipe.     

Sensitive inductively coupled plasma mass spectrometry assay for the determination of platinum originating from cisplatin, carboplatin, and oxaliplatin in human plasma ultrafiltrate

We present a highly sensitive, rapid method for the determination of platinum originating from the anticancer agents cisplatin, carboplatin, and oxaliplatin in human plasma ultrafiltrate. The method is based on the quantification of platinum by inductively coupled plasma mass spectrometry and allows quantification of 7.50 ng l-1 platinum in only 150 microl of matrix. Sample pretreatment involves dilution of samples with 1% HNO3. Validation fulfilled the most recent FDA guidelines for bioanalytical method validation. Validated ranges of quantification were 7.50 ng l-1 to 1.00x10(5) ng l-1 in plasma ultrafiltrate for all three platinum compounds. The assay is now successfully used to support pharmacokinetic studies in cancer patients treated with cisplatin, carboplatin, or oxaliplatin.     

The effect of blowing or suction on laminar free convective heat transfer on flat horizontal plates

In the present paper laminar free convective heat transfer on flat permeable horizontal plates is investigated. To assess the effect of surface suction or injection on heat transfer a correction factor, provided by the film model (or “film theory”), is applied. Comparing the film model predictions with numerical results of previous boundary layer analyses yields good agreement for a wide range of dimensionless transpiration levels.     

A simple and universal method for the separation and identification of phospholipid molecular species

One of the major challenges in lipidomics is to obtain as much information about the lipidome as possible. Here, we present a simple yet universal high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) method to separate molecular species of all phospholipid classes in one single run. The method is sensitive, robust and allows lipid profiling using full scan mass spectrometry, as well as lipid class specific scanning in positive and negative ionisation mode. This allows high-throughput processing of samples for lipidomics, even if different types of MS analysis are required. Excellent separation of isobaric and even isomeric species is achieved, and original levels of lyso-lipids can be determined without interference from lyso-lipids formed from diacyl species by source fragmentation. As examples of application of this method, more than 400 phospholipid species were identified and quantified in crude phospholipid extracts from rat liver and the parasitic helminth Schistosoma mansoni.     

Spectroscopic studies of [M(CO)5M′(CO)3(1,4-diazabuta-1,3-diene)] (M,M' = Mn,Re) and their photolysis products

Photolysis of [M(CO)₅M′(CO)₃(dab)] (M, M′ = Mn, Re; dab = 1,4-diazabuta-1,3-diene, RNCHCHNR) in 2-Me-THF leads to both homolytic and heterolytic splitting of the metalmetal bond depending on the solution temperature. In a rigid medium such as a CH₄-matrix no breaking of the metalmetal bond is observed but instead formation of [M(CO)₃M′(CO)₃(dab)] in which compound the dab-ligand is σ,σ,π,π bridging between M and M′.     

Determination of ruthenium originating from the investigational anti-cancer drug NAMI-A in human plasma ultrafiltrate, plasma, and urine by inductively coupled plasma mass spectrometry

We present a highly sensitive, rapid method for the determination of ruthenium originating from the investigational anti-cancer drug NAMI-A in human plasma ultrafiltrate, plasma, and urine. The method is based on the quantification of ruthenium by inductively coupled plasma mass spectrometry and allows quantification of 30 ng L(-1) ruthenium in plasma ultrafiltrate and urine, and 75 ng L(-1) ruthenium in human plasma, in 150 microL of matrix. The sample pretreatment procedure is straightforward and only involves dilution with appropriate diluents. The performance of the method, in terms of accuracy and precision, fulfilled the most recent FDA guidelines for bioanalytical method validation. Validated ranges of quantification were 30.0 to 1 x 10(4) ng L(-1) for ruthenium in plasma ultrafiltrate and urine and 75.0 to 1 x 10(4) ng L(-1) for ruthenium in plasma. The applicability of the method and its superiority to atomic-absorption spectrometry were demonstrated in two patients who were treated with intravenous NAMI-A in a phase I trial. The assay is now successfully used to support pharmacokinetic studies in cancer patients treated with NAMI-A.     

Langevin equation of a fluid particle in wall-induced turbulence

We derive the Langevin equation describing the stochastic process of fluid particle motion in wall-induced turbulence (turbulent flow in pipes, channels, and boundary layers including the atmospheric surface layer). The analysis is based on the asymptotic behavior at a large Reynolds number. We use the Lagrangian Kolmogorov theory, recently derived asymptotic expressions for the spatial distribution of turbulent energy dissipation, and also newly derived reciprocity relations analogous to the Onsager relations supplemented with recent measurement results. The long-time limit of the derived Langevin equation yields the diffusion equation for admixture dispersion in wall-induced turbulence.     

The mean condensate heat resistance of dropwise condensation with flowing,inert gases

The quantification of the condensate heat resistance is studied for dropwise condensation from flowing air-steam mixtures. Flows are essentially laminar and stable with gas Reynolds numbers around 900 and 2000. The condensate shaping up as hemispheres on a plastic plane wall and the presence of inert gases make it possible that thermocapillary convection occurs making the resistance less than the mean condensate thickness (ca. 0.185 mm) divided by the heat conduction coefficient. The analysis of experiments shows that the effective mean condensate resistance might indeed be less, by a factor of 0.8±0.2. The analysis takes account of the sensible heat transfer which may be as large as 35% of the total heat transfer if inlet vapor concentration,c _in, is low (ca. 0.07). A method is presented to determine the gas-condensate interface temperature,t _i , that is needed in the analysis of the heat resistance. The highest temperature differences(t _i –t _w ),t _w being the mean temperature of the condenser plate at the gas side, have been found to occur for relatively high values ofc _in (ca. 0.3).Es wird der thermische Kondensationswiderstand bei Tropfenkondensation aus einem strömenden Luft-Dampf-Gemisch untersucht. Die Strömung ist laminar und stationär mit Gas Reynolds-Zahlen zwischen 900 und 2000. In Anwesenheit von Intertgas kann thermokapillare Konvektion am halbkugelförmigen Kondensattropfen auftreten, wobei der thermische Widerstand kleiner ist, als der Quotient aus der mittleren Kondensatdicke (ca. 0,185 mm) und dem Wärmeübergangskoeffizienten. Die Analyse der Experimente zeigt, daß der effektive mittlere Kondensatwiderstand tatsächlich um einen Faktor 0,8±0,2 kleiner sein kann. Der Energieanteil infolge Kondensatunterkühlung wird berücksichtigt, er kann bis zu 35% der gesamten Wärmeübertragung ausmachen, falls die Dampfkonzentrationc _in am Eintritt klein ist (ca. 0,07). Zur Bestimmung der in die Berechnung des thermischen Widerstandes eingehende Temperatur an der Grenzfläche zwischen Gas und Kondensatt _i , wird eine spezielle Methode entwickelt. Die größte Temperaturdifferenz (t _i –t _w ) ergibt sich bei relativ hohenc _in-Werten (ca. 0,3), wobeit _w die mittlere Temperatur der Kondensatorplatte auf der Gasseite ist.