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Results of genetic analysis of three derivatives of Azospirillum brasilense Sp245 (strains BK570, SK051, and SK248) carrying cointegrates of plasmids 85-MDa and pJFF350 (the vector for omegon mutagenesis), which manifest abnormalities in flagellation and motility, are presented. It was shown for the first time that the integration of the suicide vector into one of Azospirillum resident plasmids is accompanied by the formation of various fusion products and changes in flagellation and motility of these bacteria, such as the loss of the polar (Fla) and lateral (Laf) flagella in SK051; inactivation of Fla and Laf in SK248; and Fla-dependent acceleration of expansion in semiliquid media in BK570.

Using Omegon-Km mutagenesis, six Azospirillum brasilense Sp245 mutant derivatives lacking the capability to synthesize either one of the two major O-specific polysaccharides (O-PSs) were constructed in vivo. In all of the Lps mutants obtained, single Omegon-Km insertions were shown to be located on an indigenous plasmid DNA with molecular weight 120 MDa (p120). Physical and immunochemical analyses revealed two p120 loci coding for O-PSI and two p120 loci involved in the production of O-PSII. One of the lps loci from both groups was also shown to act in the production of Calcofluor-binding polysaccharides. It was demonstrated that two Sp245 plasmid bands with apparent molecular weights of 120 and 130 MDa (as visualized by analytical gel electrophoreses) seem to be the two topological forms of the same plasmid species (p120). Transfer properties of p120 were also examined.

Nucleation from supersaturated water vapour on different liquid substrates (n-hexadecane, decalin, 2-bromotoluene and tetrachloroethylene) has been studied experimentally by the reverse Wilson chamber method in order to obtain the dependence of the critical supersaturation on the macroscopic geometry of the three-phase system. The experimental results are interpreted on the basis of the classical theory of heterogeneous nucleation as well as in the framework of the theory of barrierless heterogeneous nucleation. The discrepancy between the measured critical supersaturations and those predicted by the classical theory is explained by the effect of a negative line tension of the three-phase contact line. The influence of the macroscopic geometry on the line tension has been investigated.

The possible conformations and packing of the macromolecular fragments in Langmuir-Blodgett films from amphiphilic polyamic acid systems with side methylene groups have been studied. From the quantomechanical and conformational calculations, models of molecular packing with extended and folded arrangement of the side chains were proposed which agree with the values obtained by X-ray analysis for the thickness of the layers in the multilayered structures.

Amphiphilic polyimides with side methylene tails and various chemical structure of the backbones have been studied in the “bulk” state (cast films) and in the form of multilayered molecular films (Langmuir films) by means of calorimetry, X-ray scattering and pressure-area diagrams.

A modified version of the reverse Wilson chamber (RWC) suitable for direct observation of droplet growth and droplet (nuclei) determination is proposed. The observed independence of nuclei number per cm2 as a function of the supersaturation is in contradiction with the classical (Volmer) theory of heterogeneous nucleation. This anomalous behaviour, however, supports our previous interpretation of heterogeneous nucleation as a barrierless process.

Magnetocrystalline anisotropy of the Mm2Co17–xZr compounds is investigated in the temperature range 78 to 290 K. At room temperatures the effective anisotropy constant increases with x. The resultant uniaxial anisotropy is weakened with the decrease of the temperature. The temperature depencence of magnetization measured in weak fields normal to the c-axis shows a well expressed rise at 140 K with cooling. This behaviour is ascribed to a competition between the planar rare-earth and uniaxial cobalt anisotropies which exhibit different temperature behaviour. Im Temperaturbereich von 78 bis 290 K wird die magnetokristalline Anisotropie von Mm2Co17–xZx-Verbindungen untersucht. Bei Zimmertemperatur nimmt die effektive Anisotropiekonstante mit x zu. Die resultierende einachsige Anisotropie wird mit abnehmender Temperatur schwacher. Die Temperaturabhangigkeit der Magnetisierung, in schwachen Feldern senkrecht zur c-Achse gemessen wird, zeigt einen ausgepragten Anstieg wahrend der Abkuhlung bei 140 K. Dieses Verhalten wird der Konkurrenz zwischen der planaren Seltenerd- und einachsigen Kobalt-Anisotropie zugeschreiben, die verschiedenes Temperaturverhalten aufweisen.

Recently we discovered that in developed integrated flow cytometry using combination high resolution transmission and two beam (pump-probe) of photothermal microscopy with flow module the temporal fluctuation of probe beam even without pump laser pulse are very sensitive to functional states of single cells (e.g. with 2-3 differences in average fluctuation amplitude for live and dead cells). In this paper we are focusing on theoretical and experimental studies of these new phenomena using thermolens schematics with highly stabilized continuous-wave He-Ne laser and photodiode/photomultiplier with pinhole. This scheme allows to study both random and laser-induced thermolens effects in passive and active mode including short and long term monitoring of scattered light fluctuation in transillumination mode at single cellular and even sub-cellular levels in vitro, and in vivo. We demonstrate these schematics has some potential to monitor intracellular dynamics including change in cell metabolism, and necrosis, especially, under pump laser impacts in vitro in stationary condition. Besides, we present some relevant data obtained with other similar schematics, including evaluation of bacterial motility by dynamic light scattering.We discuss further potential developing this approach for flow cytometry with fast speed photodetector and digital camera and the multi- wavelength statistical and correlation analysis of speckle-related signals in applications to analysis of complex motions and functional properties of cells in bioflows including the evaluation of the rotational and translational components of the motion of individual live and dead cells.

The easy- and hard-axis magnetization behaviour has been studied in detail in a Mm 2 Co 16.5 Zr 0.5 pseudomonocrystal, where Mm is cerium misch-metal, in the temperature range 4.2–290 K. At room temperature, the magnetocrystalline anisotropy of the compounds is uniaxial with the easy direction along the c -axis of the hexagonal cell. However, when the temperature decreases the anisotropy becomes cone-like, with the easy directions forming at 8 K a cone with an angle of 70° with respect to the c -axis. This transition is explained in terms of the competition between the anisotropies of the Co and R sublattices.

Azospirillum brasilense Sp245 has a mixed type of flagellation: a single polar flagellum (Fla) is synthesized constitutively, and abundant lateral flagella (Laf) are produced only in solid and semisolid media. In the present study, Omegon-Km Fla-Laf-, Fla-Laf+, Fla-/Mot-Laf-. Fla-/Mot-Laf+, Mot-Laf-, and Che- mutants of Sp245 were constructed in vivo. In some of the mutants, a number of cells possessed from 1 to 5 subpolar long flagella (Sfl). These Sfl provided the host cells with unusual motility patterns. Mutants producing shortened Fla and Laf were also detected. In the mutants still producing Laf, their expression retained the wild-type inducibility. However, all the mutants described were unable to form swarm rings in semisolid media. The results suggest the existence of common control or structural elements in assembly and rotation apparatus of both Fla and Laf systems. Single Omegon-Km insertions were localized in 85 MD (in two mutants) and in 120 MD (in one mutant) indigenous plasmids, as well as to least in two different regions of chromosomal DNA (in other mutants).

The critical supersaturation for water condensation on hexadecane as a function of the initial water vapor pressure was determined by the adiabatic compression pulse method [ Scheludko et al., J. Colloid Interface Sci. 82, 83 (1981) ]. An improvement of the method is described. The higher the initial partial water pressure the lower was the critical supersaturation. With a decrease in the initial relative humidity the critical supersaturation (Sc) approached a constant value (ln Sc ≈ 0.14) which was reached at a humidity of about 80%. This asymptotic value was interpreted in terms of droplet formation from gas phase on a support, taking into consideration negative line tension on the perimeter of the water lens-nucleus on hexadecane. The value of −3 × 10−5 dyn was obtained for the line tension in the system studied. An extension of the heterogeneous phase formation theory (Scheludko, Colloids Surfaces, in press) allowed us to assume that the low critical supersaturation value obtained by Mitchell (Thesis, Clarkson Institute of Technology, 1976) was related to the formation of droplets from an unstable water layer already present on the support surface.

The effect of the line tension κ on condensation of liquid from supersaturated vapors onto solid spherical nuclei is studied. A negative line tension, which is considered here, leads to a decrease in critical supersaturation and a new mechanism of barrierless phase formation. Critical supersaturation is interpreted as the supersaturation corresponding to the onset of such barrierless condensation. The result is presented graphically, in dimensionless coordinates, for three different wetting angles θ ∞ of an infinitely large drop. Numerical values of critical supersaturation as a function of nucleus radius R 0 are presented for κ = −1.5 × 10 −5 dyn and surface tension for water σ = 72 dyn/cm at 25°C. The most important conclusion is that in a very wide range of R 0 the critical supersaturation remains constant and equals the critical supersaturation at condensation on a flat substrate (i.e., at R 0 = ∞).

A new method for determination of the surface tension by measuring the maximum weight at the pull of a small vitreous sphere from the liquid is proposed The exact solution of the problem is found and is shown how the wetting of the sphere must be taken into account through the central angle formed between the sphere radius passing through the perimeter of wetting and the horizontal surface. A set for measuring the maximum weight and the central angle is described. The accuracy of determination of the surface tension and of the angle of wetting is estimated to be thousandths of dyn/cm and a few minutes, respectively. Some limitations of the method are discussed as well as the possibilities to overcome them. Various approximate solutions are treated and, in particular, it has been shown that the approximation previously used in the flotation model is satisfactorily accurate in that case.

The pressure in the Reverse Wilson Chamber (RWC) was directly measured at different rates of compression of the gas mixture. It was shown that at compression time Τ in the range from 0.06 to 0.3 s an intermediate, between adiabatic and isothermal, process took place in the chamber. To obtain the relative pressure increaseδ Pm/Pat from the values of the relative gas compressionδ V/V, a calibration of the experimental set-up was carried out. The calibration showed that the values of critical supersaturationSc for water condensation on hexadecane, estimated for intermediate regime of the gas compression, were reduced with respect to the values calculated when the adiabatic regime was assumed. This fact confirmed the conclusions made earlier [1–3] that the classical theory was not applicable in this case of heterogeneous phase formation and that the line tensionκ < 0 should be taken into account. Moreover, in an atmosphere of very pure argon (instead of room air [1–3]) the critical supersaturation turned out to be independent of the initial state of undersaturationSo. The more accurate values obtained for condensation of water on hexadecane were: lnSc=0.204 (instead of the maximum value obtained earlier: lnSc=0.26) andκ=−1.9×10−5 dyne (instead ofκ=−1.5×10−5 dyne).

It is shown that an increase in surfactant concentration at first causes the critical thicknesses of rupture on microscopic films to decrease but gradually a nearly constant value is reached. With films of aqueous solutions of fatty acids (valeric, caproic, caprylic and capric acids), this dependence correlates well with the effect of the surfactant concentration on the damping of capillary waves. With surfactants of the detergent type (OPE-7, OPE-20) in addition to the change of the critical thickness, the transition from rupture to formation of black spots is described, as the surfactant concentration exceedsC bl. The remarkable fact in the latter case is the independence of the critical thickness of the final state, be it rupture or formation of first or second black films. On the basis of the experimental data the assumption is put forward that the critical thickness of rupture or the critical thickness of formation of black spots is substantially affected by macroscopic non-uniformities in the film thickness. Thus the conclusion is reached that the critical thickness of an ideally plane parallel film which is the object of the theory, must be obtained by extrapolation of the measured value toward extremely small radii.

For the purpose of applying the result of Gibbs onto heterogeneous phase formation as well as to incorporate the effect of line tension in that case and elucidate the problem of nuclei participation in Brownian motion, we shall consider in greater detail the work of formation of a new phase nucleus from supersaturated vapors.

The magnetic properties of single crystals of the alloys Dy0.1Y0.9 and Dy0.3Y0.7 are investigated in the temperature range from 4.2 to 150 K in magnetic fields up to 11 × 103kA/m, along the hard axis and in the basal plane. The magnetic structure of the investigated alloys is helical antiferromagnetic with the helix axis along “c”. The Neel points are established to be 40 and 90 K. At a critical field a magnetic transition is observed. The helical structure deformates in a “fan” one. The energy of magnetic anisotropy is calculated and compared with the exchange energy. Die magnetischen Eigenschaften der Einkristalle der Legierungen Dy0,1Y0,9 and Dyo,3Yo,7 werden im Temperaturbereich von 4,2 bis 150 K in Magnetfeldern bis zu 11 × 103 kA/m in Richtung der harten Achse der Basisebene untersucht. Die inagnetische Struktur der untersuehten Legierungen ist helikal antiferromagnetisch mit der Helix-Achse in Richtung„c”. Die Neelpunkte werden zu 40 und 90 K bestimmt. Bei einem kritischen Feld wird ein magnetischer Ubergang beobachtet. Die helikale Struktur deformiert sich zu einer wannenformigen Struktur. Die Energie der magneti-schen Anisotropie wird berechnet und mit der Austauschenergie verglichen.

A new theory of the critical state of the thin liquid film, at which it either ruptures or forms a black spot, is propounded. The concept of the spontaneous growth of the surface fluctuational waves at the critical state, proposed by A. Scheludko [ Proc. K. Ned. Akad. Wet. Ser. B 65 , 76 and 87 (1962)], is employed. The consistent application of the Brownian motion theory infers that the rate-determining process is that of attaining the state of instability and not, as assumed by A. Vrij [ Disc. Faraday Soc. 42 , 23 (1966)], the consequent evolution of the instability. The theory is confirmed by new experimental data on the critical thickness of formation of black spots in films from aqueous solutions of sodium dodecyl sulfate + NaCl. In contrast to the previous studies [E. Manev, A. Scheludko, and D. Exerowa, Colloid Polym. Soc. 252 , 586 (1974); A. Scheludko, loc cit. ] where the mean critical thickness of the films is determined, in the present study the thickness in the thinnest part of the critical film is measured. In the same manner the rate of thinning at the critical state is obtained. The agreement of experiment with theory confirms the estimate of the van der Waals-Hamaker function according to Lifshitz's theory.

This paper specifies the method for determination of the critical supersaturation at heterogeneous phase formation for the case when line tension x is taken into account, especially when it is negative. All considerations are on the basis of the theory treated before [1, 2]. By analogy to the case of homogeneous condensation on ions [5, 6] it is shown that at < 0 the critical supersaturation has a maximum value; it corresponds to a barrier-free phase formation and to the maximum in the dependence of the vapour pressure on the drop size.

The experimental data of ref. 3 on electrolytic deposition of mercury from a concentrated solution of mercurous nitrate on a non-structured platinum microcathode are interpreted according to the theory of phase formation on a substrate, taking into account the line tension of the wetting perimeter of the drop-nucleus [1]. It is shown that a value of that line tension of about—2.5 × 10 −5 dyne explains the experimental results. The analysis leads also to the generalization that at negative line tension, the formation of the new phase corresponds to supersaturations at which the work of nucleus formation is annulled. The experimental results of ref. 4 are discussed from this point of view.

A new method has been developed for the investigation of the condensation from supersaturated vapor on substrates by the adiabatic compression of a saturated vapor gas. The condensation was detected by light scattering, measured with a photomultiplier. A maximum critical supersaturation of about 42% at room temperature (t = 20°C) was found for water condensation on hexadecane. This value was shown to be 2.5 times less than the value to be expected according to the prevailing interpretation of heterogeneous phase formation, following Volmer's pattern. But, when taking into account the linear tension of the nucleus lens perimeter, good agreement was obtained with the critical supersaturation found at a linear tension of about −0.8 × 10−5 dyne. Equations for the work of formation of a liquid nucleus on a liquid substrate, deduced in the paper, underlie the discussion.

The interpretation of the critical supersaturation at water condensation on hexadecane, put forward in [3], is now completed with the treatment of the barrier mechanism of a new phase formation in the case of negative line tension (κ

A new method for experimental determination of the line tension at the contact line between a Newton black (NB) film and the bulk solution, “the critical bubble method,” has been developed. The theoretical basis of the method is discussed. In a special device small bubbles of radii R = 10–100 μm are generated and observed. The smallest bubbles do not form NB films. Bubbles of radii greater than the “critical radius” Rc always form NB films. It is assumed that the formation of NB films is hindered by a force barrier due to a positive line tension. The buoyancy force of the bubbles of radii greater than Rc overcomes this barrier. On this basis values of the line tension ϰ are calculated from the experimentally obtained Rc. The dependence of ϰ on the electrolyte concentration is studied in the small CNacl range in which the ϰ values are positive for sodium lauryl sulfate aqueous solutions.

The film tension of curved (spherical) Newton black foam films having radii of curvature between 70 and 700 μm has been studied experimentally. Measurements with films from sodium dodecyl sulfate aqueous solutions have been carried out using a method developed previously for direct measurement of the film tension at different capillary pressures. The results are discussed in comparison with the results of other authors for film tensions of curved and of plane Newton black films. The line tension values, determined with the different experimental film tension values, as well as their comparison with the theory are also discussed. It is concluded that there is no noticeable dependence of the film tension on the film curvature, or on the capillary pressure, in the whole range of film curvature radii covered by this study.

Es wird der zusatzliche Druck in Schaumfilmen aus wasserigen Saponinlosungen bei verschiedenem Elektrolytgehalt gemessen. Dabei wird gute Ubereinstimmung mit der Theorie der langsamen Koagulation der suspensoiden Kolloide gefunden. Die Konstante in der Abhangigkeit dervan der Waalsschen Komponente des zusatzlichen Druckes von der Filmdicke wird fur Wasser zu ca. 4·10−14 experimentell bestimmt.

Es werden die Methode der zylindrischen stehenden Wellen sowie der Einflus von oberflachenaktiven Stoffen (losliche und unlosliche Fettsaure und Triton X 100) auf die Dampfung dieser Wellen beschrieben. Die experimentelle Untersuchung der tangentialen Bewegung der Oberflache in Anwesenheit des Oberflachenfilmes bestatigt die Aussagen der hydrodynamischen Theorie der Dampfung. Fur die untersuchten Oberflachenfilme werden Oberflachendruck und dynamische Elastizitat berechnet. Der Unterschied zwischen den ermittelten dynamischen Elastizitaten und den aus der Zustandsgleichung berechneten statischen Elastizitaten wird diskutiert.

Die spontane Verringerung der Dicke von horizontalen Schaumfilmen, die wegen Ausfliesen der Losung aus den flachen Teilen zu den verdickten konkaven Randteilen stattfindet, wird theoretisch und experimentell untersucht. Die Dicke von Schaumfilmen, die aus verdunnten Losungen von Na-Oleat, Saponin oder Isoamylalkohol erhalten wurden, wird konduktometrisch oder interferometrisch bestimmt. In Anwesenheit von KCl stimmen die experimentellen Ergebnisse mit den theoretisch zu erwartenden gut uberein. Die untersuchten Schaumfilme hatten eine grosere Dicke als 0,2Μ.

Es werden Daten uber die Dicke von Gleichgewichtsschaumfilmen aus wasserigen Saponinlosungen (5·10−4%) bei Anwesenheit von KCl verschiedener Konzentration gegeben. Der experimentell gefundene Zusammenhang zwischen Filmdicke und Elektrolytkonzentration stimmt sehr gut mit der Theorie der elektrostatischen Abstosung zwischen den diffusen elektrischen Schichten uberein.

Preliminary experiments have been carried out which measure the variation in the intensity of the light scattered by DNA solutions under the influence of an electric field. Data have been collected on the length of DNA molecules, their electric polarizability, and their dispersion behavior.

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On the basis of the theory of capillarity, the process of formation of a wetting perimeter when a spherical particle touches a planar liquid surface is analysed taking into account the line energy of this perimeter. The minimum size of particle which can float is calculated and an accurate estimate is made for the minimum time of touching of particle and surface. The kinetic energy of collision between an air bubble and the particles is used to calculate the maximum size of particles which can remain attached for flotation. Flotation data suggest that a lower limit for the size of isolated particles which can be floated is of the order of 1 µm and a comparison of this radius with the theoretical limit gives a value of 10–4 to 10–5 dyn for the line energy of the wetting perimeter. Predictions of the flotation region in terms of particle size and contact angle using this energy do not conflict with practical findings.

On the basis of Navier-Stokes equations, the theory of the spontaneous rupture of thin liquid films is generalized by taking into account the influence of the surfactant on the hydrodynamics of the film. Our measurements of the critical thicknesses of rupture of aniline films, stabilized with C12H25OH, confirm the theory at low surfactant concentrations. The discussion of the discrepancy between theory and experiment at higher surfactant concentrations shows that the surfactant influences the properties of the thin liquid films in a specific manner.

The critical thickness of rupture of circular microscopic foam films with diameter from 3 × 10–3 to 2.57 × 10–2 cm of chlorbenzene (+ 2 × 10–4 g/cm3 aerosol MA) and aniline (+ 10–3 g/cm3 lauric alcohol) was measured. The isotherms of the disjoining pressure/foam thickness for both solutions9,10 permit a comparison to be made of the experimental critical thickness data with the predictions of the theory. 2,3. Good agreement was found for the influence of the surface tension on the critical thickness and for the independence of the critical thickness on the viscosity. However, the absolute values of the critical thickness are lower than (though close to) those, predicted by the theory. It seems that they do not tend to zero when the film radius decreases, as might be expected theoretically. An attempt was made to determinary the smallest critical thickness, which was found to be about 100–150 A. A preliminary investigation was made about the most probable distribution of the critical thickness data.