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Drop profile analysis tensiometry is applied to measure the dilational visco-elasticity of BLG at the buffered aqueous solution/tetradecane (W/TD) interface using oscillating drops of TD immersed in W at frequencies between 0.01–0.2 Hz. The buffered solutions were investigated at pH 3, pH 5 (isoelectric point) and pH 7 at different buffer concentrations (1 mM, 10 mM and 100 mM). The real part of the complex visco-elasticity shows a maximum when plotted as a function of the interfacial pressure Π. In contrast to the water/air surface (W/A) where we observe maximum elasticity values between 15 and 20 mN/m, at the W/TD interface these maximum values are up to 65–70 mM/m, which is in parallel with the much higher interfacial pressure values at the W/TD interface when compared to the W/A surface. Refereed/Peer-reviewed

The adsorption kinetics of beta-lactoglobulin (BLG) at the water/tetradecane (W/TD) interface as studied by drop profile analysis tensiometry is significantly controlled by the diffusional transport in the aqueous solution bulk. However, due to the contact with the hydrophobic oil phase the protein molecules change their conformation in order to adapt to the interfacial environment. This conformational change can be expressed via the adsorption activity constant. The analysis of the dynamic interfacial tensions leads to much lower activities at short adsorption times and low surface coverages. This allows to conclude that in the early stage of the adsorption layer formation the structure of the BLG adsorption layer at the W/TD interface is similar to that at the water/air (W/A) interface. Refereed/Peer-reviewed

The dynamic surface pressure II of air bubbles aging in buffered beta-lactoglobulin (BLG) solutions containing various protein concentrations C-BLG (10(-9)-10(-4)M), pH (3-7) and buffer concentrations C-buff (1, 10 and 100 mM) was measured as a function of time t by bubble profile analysis tensiometry. Adsorption kinetics was studied by recording II(t) data for 80 000 s and the final II-values were used to construct the surface pressure isotherm II(C-BLG) for the pH values of 3, 5, 7 (C-buff = 10 mM) and 6.3 (in pure water). On the basis of obtained kinetic and concentration dependencies the effect of pH on the protein surface activity was qualitatively analyzed. At constant Cbuff =10 mM and relatively low protein concentrations (C-BLG10(-6) M) BLG is the most surface active at pH 5 (negligible net charge in the vicinity of the isoelectric point, pI approximate to 5.1). At constant C-buff, BLG solutions with pH 3 show the lowest surface activity. The influence of the ionic strength (buffer concentration) of the solution on the dynamic II was studied at a selected protein concentration of C-BLG =10(-5) M. The kinetics of adsorption is weakly affected by C-buff for solutions with pH 5 and significantly enhanced by increasing C-buff for solutions with pH not equal pI. The effect of the chemical nature of the electrolyte was obtained for non-buffered aqueous BLG solutions (natural pH similar to 6.3) at different concentrations of NaCI or CaCI2. It is demonstrated that the adsorption kinetics and the surface pressure isotherm of BLG at the water/air surface depend strongly on the protein effective charge, which is dictated by the solution pH and ionic strength. Refereed/Peer-reviewed

Using drop profile analysis tensiometry the adsorption dynamics and the equilibrium equation of state of beta-lactoglobulin (BLG) at the water/tetradecane (W/TD) interface are studied at pH 3, 5 and 7. The data are well described by a thermodynamic adsorption model using almost identical model parameters for all three pH values except for the surface activity coefficient. The surface pressure isotherms at the water/air (W/A) surface exhibit much steeper run than interfacial pressure at the W/TD interface for any of the studied cases at pH 3, 5 and 7, and the calculated adsorption isotherm data point at smaller adsorbed amounts for these pH. This seems to be in contrast to the much larger interfacial pressure changes reached at high BLG concentrations at the W/TD interface, which are almost three times higher than those at the W/A surface. The observations can be explained by a strong interaction between BLG and the oil molecules at the interface. The dynamic interfacial tensions can be adequately described by a mixed adsorption model, assuming a diffusional transport of the protein molecules in the aqueous bulk phase and an adsorption mechanism which assumes a change of the adsorption activity parameter in dependence of the interfacial coverage. Refereed/Peer-reviewed

Reaction sintered SiC ceramics were prepared by the silicon melt infiltration method over temperatures of 1450−1550°C. The effects of the carbon and silicon contents of the starting materials as well as the sintering temperature and time on the thermal conductivities and microstructures of the ceramic materials were studied. The thermal conductivities and microstructures of the samples were characterised using thermal conductivity measurements, X-ray diffraction analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy and mercury injection porosimetry. The results showed that sintering temperature and time as well as the carbon and silicon contents of the green specimens are the main factors affecting the microstructure and porosity of reaction bonded SiC ceramics. Increasing the reaction temperature and time decreased the porosity of the ceramics. This was due to the infiltration of the silicon melt into the ceramic specimens. The thermal conductivity and porosity of the sampl...

The presented drop and bubble micro manipulator (DBMM) is a new experimental tool for the quantitative analysis of the interaction between two drops or two bubbles or even between a single drop with a bubble in a liquid medium. For each drop or bubble, a coarse and a very fine dosing system allow controlling their size or changing it in respect to a given protocol. An accurate pressure sensor for each drop/bubble can record changes in the capillary pressure with a selected sampling rate in order to follow critical processes between the two liquid menisci, such as coalescence. The stability of liquid films between drops or bubbles can be studied also under external perturbations, i.e. a harmonic oscillation with a given frequency and amplitude can be generated in order to find critical conditions for the coalescence. The described tool can be used in different experimental protocols. Among them there are options to mimic the situation of multilayers and multiple emulsions. Recording of dynamic processes as video with a standard frame rate is possible as well. Alternatively, a fast video camera can be mounted to monitor fast processes, such as the coalescence of two drops or bubbles.

The recently described new experimental tool called Drop and Bubble Micro Manipulator (DBMM) has been applied to studies of the stability of protein covered bubbles against coalescence. Among the available protocols the time interval between the moment of bubble contact to the moment of coalescence of two contacting bubble is determined for different β-Lactoglobulin (BLG) concentrations and different ageing times. A threshold concentration of BLG is needed to prevent immediate coalescence. The longer the ageing time above this threshold concentration of BLG is the longer is the lifetime of the liquid film between the bubbles. The adsorbed amount of BLG was determined as a function of time and concentration and correlates with the observed coalescence behaviour of the contacting bubbles. Refereed/Peer-reviewed

Liquid interfaces are met everywhere in our daily life. The corresponding interfacial properties and their modification play an important role in many modern technologies. Most prominent examples are all processes involved in the formation of foams and emulsions, as they are based on a fast creation of new surfaces, often of an immense extension. During the formation of an emulsion, for example, all freshly created and already existing interfaces are permanently subject to all types of deformation. This clearly entails the need of a quantitative knowledge on relevant dynamic interfacial properties and their changes under conditions pertinent to the technological processes. We report on the state of the art of interfacial layer characterization, including the determination of thermodynamic quantities as base line for a further quantitative analysis of the more important dynamic interfacial characteristics. Main focus of the presented work is on the experimental possibilities available at present to gain dynamic interfacial parameters, such as interfacial tensions, adsorbed amounts, interfacial composition, visco-elastic parameters, at shortest available surface ages and fastest possible interfacial perturbations. The experimental opportunities are presented along with examples for selected systems and theoretical models for a best data analysis. We also report on simulation results and concepts of necessary refinements and developments in this important field of interfacial dynamics. Refereed/Peer-reviewed

Janus emulsions, formed by mixing two oil components (i.e., olive oil (OO) and silicone oil (SiO)) with water in the presence of two surface active biopolymers, i.e., gelatin and chitosan, are investigated in more detail. The stability of Janus droplets formed strongly depends on the polymer components used. The mixture of both biopolymers represents an extraordinary effect which can be related to the complex formation of gelatin and chitosan. Taken into account that under the given pH conditions, in the acidic pH range between 4 and 6, below the isoelectric point of gelatin, both polymers are polycations, one can conclude that non-Coulombic interactions are of relevance for the enhanced surface activity of the complexes. Dynamic interfacial tension (gamma) measurements by using the drop profile analysis tensiometry (PAT) indicate a strong adsorption of the polymer complexes at the olive oil/water interface in contrast to the silicone/water interface. In a first step, the polymer complexes are adsorbed at the interface, and in a second step, a more rigid skin-like polymer layer is formed. This first example of a polymer-stabilized Janus emulsion opens new perspectives for the application, e.g., in food emulsions or for making scaffold materials.

An intensive experimental study was carried out to investigate the causes of the overconsolidation phenomena in the Namak New City site, Korea. Geological events in conjunction with sea level changes, groundwater fluctuation, weathering, leaching and cementation were examined as possible causes of overconsolidation. In addition to oedometer and triaxial tests, radiocarbon dating, geochemical components and pore water chemistry were analysed. It was shown that the overconsolidation in the upper marine clay deposit was not caused by stress reductions such as erosion and groundwater fluctuation. Furthermore, weathering or leaching seemed unlikely. The apparent overconsolidation can be explained by cementation, which is indicated by profiles of the sulphate and potassium ion concentrations in the pore water. At the early stage of the Holocene marine deposition, the rate of deposition was 4·4 mm/yr; thereafter it was reduced to 1·4 mm/yr, controlling chemical processes such as sulphate reduction and ion exchanges and, in turn, apparent overconsolidation. Some mechanical and chemical properties of the apparent overconsolidated clay were compared with the geologically overconsolidated Palaeosol layer in the site.

Two oppositely charged surfactants in an aqueous solution interact with each other via electrostatic interactions and produce surfactant complexes-catanionics. However, their quantitative influence on the interfacial tension at the solution/air and solution/oil interfaces is still unknown. We have measured the interfacial tension of sodium dodecyl sulphate (SDS) and dodecyltrimethylammonium bromide (DoTAB) aqueous mixtures using the du Nouy ring tensiometer and drop profile analysis tensiometry (PAT-1). For the oil phase, we used hexane. The obtained kinetic and equilibrium experimental results were fitted with the common theoretical Frumkin adsorption model. We found that SDS + DoTAB complexes show much higher surface activity than the single surfactants. At solution/air and solution/oil interfaces, SDS and DoTAB produce ion pairs with low water affinity and relatively low oil solubility. SDS + DoTAB partition coefficient between hexane and water phases is 0.32. Such surfactant complexes with advanced surface characteristics may be beneficial in different industrial branches nowadays. Refereed/Peer-reviewed

Single drops or bubbles are frequently used for the characterization of liquid− fluid interfaces. Their advantage is the small volume and the various protocols of their formation. Thus, several important methods are based on single drops and bubbles, such as capillary pressure and profile analysis tensiometry. However, these methods are often applied under dynamic conditions, although their principles are defined under equilibrium conditions. Thus, specific attention has to be paid when these methods are used beyond certain limits. In many cases, computational fluid dynamics (CFD) simulations have allowed researchers, to extend these limits and to gain important information on the interfacial dynamics. Examples discussed here are the capillary pressure tensiometry used for short time and profile analysis tensiometry for long time dynamic interfacial tension measurements, the oscillating drop methods for measuring dilational visco-elasticity. For measuring the coalescence of two drops the liquid dynamics of the subsequently formed liquid bridges have to be considered. In this paper, a thorough review of important experimental and computational findings, related to the dynamics of drops, including its formation, growth, oscillation, detachment, and coalescence is presented. Emphasis is however on some selected important developments. In addition, the paper tries to predict the main directions of advancement in interfacial research for the near future.

Due to the complicated artefacts in SIMS depth profiling, SIMS depth resolution is difficult to evaluate. For evaluation of the SIMS depth resolution, delta-doped layers are more useful than sharp interfaces, because the matrix effect and the sputtering rate change can be minimized in profiling through delta layers. The GaAs delta-doped layers in Si were grown and proposed as a reference material for the evaluation of SIMS depth resolution. The SIMS depth resolution was estimated using the analytical expression based on a double exponential with a Gaussian, and its dependence on SIMS analysis conditions such as ion energy, ion species and incidence angle was studied with the proposed GaAs delta-doped multilayers in Si. Copyright © 2000 John Wiley & Sons, Ltd.

In this paper, a bulk-micromachined corner cube retroflector (CCR) with ultra-low voltage operation and negligible power consumption has been newly designed and fabricated for free space optical communication applications. The proposed CCR was comprised of bulk-micromachined vertical mirror which has two mutually orthogonal reflective surfaces and one piezoelectrically actuating horizontal mirror. The fabricated CCR has 300µm × 300µm of reflective surfaces. The vertical mirror with two orthogonal reflective surfaces can be obtained by using double SOI-wafer and anisotropic wet etching of (110) silicon wafer. The horizontal bottom mirror was comprised of two supporting and one actuating PZT cantilevers with meander shaped hinges. The supporting cantilevers and the meander hinges were used for accurate angular alignment of mirror by balancing and isolating the residual stresses occurred in the released PZT cantilevers after fabrication. The bottom actuated mirror exhibited a angular displacement of 1.87° at 5 volts applied with on-off switching in 276µs. The fabricated CCR can be digitally modulated up to 1kb/s.

Due to an ease of reprogramming in the process of nuclear transfer (NT), undifferentiated stem cells may support greater development of cloned embryos compared with differentiated cell types. Hence, stem cells may be more suitable as nuclear donor cells for NT procedures than somatic cells. In pigs, comparative studies of NT using stem cells and their differentiated descendant cells have not yet been reported. Embryonic germ (EG) cells are undifferentiated stem cells isolated from cultured primordial germ cells (PGC) and can differentiate into several cell types. In this study, in vitro development of NT embryos using porcine EG cells and their derivative neural precursor (NP) cells was investigated. Porcine EG cells were isolated from cultured PGC collected from embryos on Day 23 of gestation (Shim et al. 1997 Biol. Reprod. 57, 1089–1095). Neural precursor cells, based on morphology of neural rosettes or neurospheres, were differentiated from porcine EG cells by sequential culture of the cells on gelatinized dishes in N2B27 medium with and without 10 µm retinoic acid for 7 days each. Since porcine EG cells and NP cells differentiated from the same EG cells were used in the present study, the genetic makeup of nuclear donor cells was identical, eliminating any genetic variation between undifferentiated and differentiated cells in the comparison. The efficiencies of NT using the two different cell populations were compared. The rates of fusion were not different between NT embryos from EG and NP cells. However, the rate of cleavage in NT embryos from EG cells was significantly higher (P < 0.05) than that from NP cells (141/247, 57.1% v. 105/228, 46.1%). Similarly, the rate of blastocyst development was significantly higher (P < 0.05) in NT using EG cells than that using NP cells (43/247, 17.4% v. 18/228, 7.9%). The effects on NT efficiency using either stem cells or their differentiated progeny is still controversial. The rates of blastocyst development using somatic stem cells were either reduced in mice (Sung et al. 2006 Nat. Genet. 38, 1323–1328) or remained the same in deer (Berg et al. 2007 Biol. Reprod. 77, 384–394) and cattle (Green et al. 2007 Biol. Reprod. 77, 395–406). However, the results obtained from the present study in pigs demonstrate a reduced capability for nuclear donor cells to be reprogrammed following the differentiation of porcine EG cells. This suggests that the effect on NT efficiency by using stem cells and their differentiated progeny may vary depending upon the species and cell types involved.

Constitutive expression of A transgene often results in serious physiological disturbances in transgenic animals. For instance, systemic overexpression of human growth hormone in transgenic pigs has resulted in detrimental side effects in general health and reproductive performance. One of the solutions to such problem would be inducible expression of a transgene that may restrict production of foreign proteins from transgenic animals only when needed. In this study, a retrovirus vector was designed to express the green fluorescent protein (GFP) gene under the control of the tetracycline-inducible promoter. Transformation of porcine fetal fibroblast cells was achieved by infection of the cells with the vector and subsequent antibiotic selection. To induce transgene expression, transformed porcine fetal fibroblast cells were cultured in medium supplemented with doxycycline for 48 h. Induction of the GFP gene was verified by the emission of fluorescence from transformed cells. Nuclei of transformed cells with or without doxycycline treatment were transferred into enucleated oocytes, and the induction efficiency was analyzed by monitoring fluorescent emission during development of reconstituted embryos to the blastocyst stage. In addition, differences in the rates of blastocyst development between experimental groups were analyzed by Student's t-test. Blastocyst formation of nuclear transfer embryos using transformed cells with tetracycline-inducible retrovirus vector (12.0%, 128/1072) was not significantly different (P > 0.05) from that with non-inducible control vectors (13.7%, 41/300), suggesting that an introduction of tetracycline-inducible retrovirus vector was not particularly harmful to the development of nuclear transfer embryos. Also, the blastocyst development rate of nuclear transfer embryos after induction of transgene by doxycycline (12.1%, 99/815) was not significantly different (P > 0.05) from that of the non-induced counterparts (11.3%, 29/257), suggesting that the induction of transgene did not affect the development of transgenic clone embryos. In a majority of embryos, high expression of the GFP gene was observed in cloned embryos with transgene induction, whereas poor or no GFP expression was detected in non-induced controls. The results from this study suggest that tetracycline-inducible expression of transgenes in nuclear transfer embryos may be used for production of foreign proteins in transgenic animals in a more controlled manner than with conventional procedures. Further experiments on transfer of cloned embryos carrying such an inducible transgene to recipients may enable production of transgenic pigs with fewer side effects from unregulated expression of the transgene.

To meet the demand for shallow junction secondary ion mass spectrometry (SIMS) profiling, the surface transient Si sputtering effect should be corrected in addition to the improvement of depth resolution. With low-energy grazing incident ions, the SIMS depth resolution can be improved better than 1 nm. For the correction of the surface transient effect, we report that multiple As delta-layer Si thin films characterized with high-resolution transmission electron microscopy and medium-energy ion scattering spectroscopy can be used as a reference thin film. With the reference thin films, the depth scale shift in the surface transient region can be calibrated under each analysis condition. For low-energy Cs+ ion bombardment, the average Si sputtering yield in the surface 5 nm layer can be 70% higher than that in the steady state, which corresponds to a depth scale shift of 2.0 nm to the shallower direction.