V2 Phase Research Articles

Coupling in vitro cell culture with synchrotron SAXS to understand the bio-interaction of lipid-based liquid crystalline nanoparticles with vascular endothelial cells.

Nonlamellar lipid-based liquid crystalline (LLC) nanoparticles possessing different internal nanostructures, specifically the 3D-ordered cubosomes (V2 phase) and the 2D-ordered hexosomes (H2 phase), are of increasing interest as drug delivery systems. To facilitate their development, it is important that we understand their interactions with healthy human umbilical vein endothelial cells (HUVECs). To this end, a 3D cells-in-a-tube model that recapitulates the basic morphology (i.e. tubular lumen) and in vivo microenvironment (i.e. physiological shear stress) of blood vessels was employed as a biomimetic testing platform, and the bio-nanoparticle interactions were compared with that of the conventional 2D planar cell culture. Confocal microscopy imaging revealed internalisation of the nanoparticles into HUVECs within 2h and that the nanoparticle-cell interactions of cubosomes and hexosomes were not significantly different from one another. Low fluid shear stress conditions (i.e. venous simulation at 0.8 dynes/cm2) were shown to impose subtle effects on the degree of nanoparticle-cell interactions as compared with the static 2D culture. The unexpected similarity of cellular interactions between cubosomes and hexosomes was clarified via a real-time phase behaviour analysis using the synchrotron-based small-angle X-ray scattering (SAXS) technique. When the nanoparticles came into contact with HUVECs under circulating conditions, the cubosomes gradually evolved into hexosomes (within 16min). In contrast, the hexosomes retained their original internal structure with minimal changes to the lattice parameters. This study highlights the need to couple cellular studies with high-resolution analytics such as time-resolved SAXS analysis to ensure that particle structures are verified in situ, enabling accurate interpretation of the dynamics of cellular interactions and potential bio-induced changes of particles intended for biomedical applications. Graphical abstract.

Bulk and dispersed aqueous behaviour of an endogenous lipid, selachyl alcohol: Effect of Tween 80 and Pluronic F127 on nanostructure.

Tween 80 has been reported to provide a means of targeting drug nanocarriers to the blood- brain barrier. This study investigated the influence of addition of Tween 80 on the formation of different bulk and dispersed lyotropic liquid crystalline phases in selachyl alcohol-based systems. The effect of increasing concentrations of Tween 80 and Pluronic F127 (as a control) (0-25% w/w relative to SA) on the bulk phase behaviour and dispersions of selachyl alcohol (SA) were investigated using small angle X-ray scattering, dynamic light scattering, and cryogenic transmission electron microscopy. The addition of Tween 80 to SA bulk phase samples triggered concentration-dependent phase changes with the structure sequentially evolving from a reverse hexagonal phase (H2) to a mixed H2 and inverse bicontinuous cubic (V2) then a V2 phase alone. In contrast, the addition of Pluronic F127 resulted in a phase change from H2 phase to a mixed lamellar and H2 phase system. The mean particle size of internally structured particles was 125-190 nm with low polydispersity indices (0.1-0.2). Nanoparticles retained the bulk phase internal structure in the presence of Tween 80, whereas in the presence of Pluronic F127, the additional lamellar phase that formed in bulk phase systems was not observed. Cryo-TEM revealed the formation of cubosomes and hexosomes by SA in excess water in the presence of Tween 80 and Pluronic F127 respectively. In summary, it was shown that stabilisation of SA dispersions using Tween 80 resulted in a decrease in negative curvature leading to a change in internal structure from H2 to V2 phase. The studies provide the core understanding of particle structure to progress these structured lipid nanocarriers into delivery studies with Tween 80 as a mechanism to target the blood-brain barrier.

Self-assembly of quaternary ammonium gemini surfactants in cyclohexane upon reinforcement by simple counterions.

The quaternary ammonium gemini surfactants 12-s-12 (s = 2, 6, and 10) can produce homogeneous cyclohexane solutions with the assistance of salts, sodium benzoate (NaBez), sodium salicylate (NaSal), or sodium 2-bromoethanesulphonate (NaBres). In these samples, 12-s-12/salt formed aggregates and their structures were assigned by SAXS measurements together with POM observations. Among the three salts, both NaBez and NaBres had similar effects on assisting aggregate formation, but NaSal favoured the generation of aggregates of 12-s-12 with lower interface curvature. For example, both 12-2-12/NaBez and 12-2-12/NaBres formed an I2 liquid crystalline (LC) phase with an Fm3m structure, but 12-2-12/NaSal generated a H2 LC phase. Both 12-6-12/NaBez and 12-6-12/NaBres generated a H2 LC phase, while 12-6-12/NaSal yielded both H2 and V2 phases with Pn3m symmetry, both of which co-existed in solution. The special effect of NaSal was attributed to its ortho-hydroxyl in the benzene ring. This favoured the formation of intermolecular hydrogen bonds among the NaSal molecules attracted to the quaternary ammonium head of 12-s-12. The water molecules joined between the NaSal molecules to build hydrogen-bonding bridges, which further increased the size of the 12-s-12 head. This benefited the formation of aggregates with lower surface curvature. In the systems of both NaBez and NaBres, the spacer length of the gemini surfactants dominated the morphology of the formed aggregates, wherein the effect of the salt was significantly weaker. Finally, the visco-elasticity of samples with similar aggregates was measured and the rheological behaviour discussed.

Self-assembly of imidazolium-based surface active ionic liquids in aqueous solution: The role of different substituent group on aromatic counterions

Self-assembly behavior of 1-dodecyl-3-methylimidazolium o-anisate (C12mimA) and 1-dodecyl-3-methylimidazolium o-bromobenzoate (C12mimB) in aqueous solution was systematically explored, respectively. Combined with the concerning results of 1-dodecyl-3-methylimidazolium salicylate (C12mimSal) reported previously, impact of aromatic counterions with various substituent group on the aggregation behavior of surface active ionic liquids (SAILs) was demonstrated. Compared with C12mimSal, inferior surface activity of C12mimA and C12mimB can be attributed to deficiency of H-bonding. Lower critical micelle concentration (cmc) of C12mimB than C12mimA may result from the less negative interaction energy between it and water molecule, testified by density functional theory (DFT) calculations. An investigation of temperature effect on cmc reveals that, micellization processes of these two SAILs are entropic-driven within the range of temperature studied. Polarized optical microscopy (POM) and small angle X-ray scattering (SAXS) were employed to determine the generation of lyotropic liquid crystals (LLCs). Similar to C12mimSal, a hexagonal liquid crystalline phase (H1) and a cubic liquid crystalline phase (V2) appear successively with the increasing concentration of C12mimA and C12mimB. While only at higher concentration than C12mimSal, they can exhibit V2 phase. Structural parameters calculated from SAXS patterns suggest that higher concentration or temperature can lead to a closer alignment of SAIL molecules. Rheological results of LLC formed by the two SAILs show traits of general H1 phase analogous to C12mimSal. This work can provide insights into the self-assembly behavior of SAILs and facilitate their potential applications in some fields, e.g. nanomaterial preparation and drug delivery, etc.

Влияние гербицидов на численность микроорганизмов и биологическую активность почвы в агроценозах сои

THE INFLUENCE OF HERBICIDES ON THE NUMBER OF MICROORGANISMS AND THE BIOLOGICAL ACTIVITY OF THE SOIL IN THE SOYBEAN AGROCENOSIS I. S. Brovko , V. U. Jashchuk , Y. V. Chabaniuk The use of pesticides and agrochemicals in agriculture affects not only the productivity of crops and the quality of their crops, but also the ecological state of the soil, and as a consequence the quantity and diversity of vegetation cover and soil biota, which is an indicator of the safety of the use of substances in agriculture. Each species of organisms in the biogeocenosis (even insignificant) has multiple connections with a significant number of other species. The disappearance of any species of animals or plants can cause unpredictable consequences and even the destruction of the entire biogeocenosis. Biodiversity can be attributed to objective factors of assessing the state of the environment and the stability of ecosystems. Biological diversity is the basis of the structural and functional organization of living matter of the biosphere, determines the stability and sustainability of ecosystems. It fulfills a regulating function in the implementation of all biogeochemical, climatic and other processes on Earth. Pesticides can influence plant-microbial interactions through their effect on the pathogen or on other soil biota. For soil microorganisms, a certain selective sensitivity to herbicides and pesticides in general is characteristic. Chemical treatments mainly lead to the death of sensitive species and genera of microorganisms, the activation of resistant mutants, and the herbicide used as an energy material. As a consequence, there is a disturbance in the state of equilibrium of the soil ecosystem and, accordingly, the soil self-purification conditions resulting from the activity of successive successive microbial races, the narrowing of the spectrum of microbiological activity due to both the direct microbicidal action of herbicides and through changes in the ecological environment. Purpose of the study. Establish the dependence of changes in the numbers of microorganisms of different ecological-trophic groups on the use of herbicides, the phase of development of soybean plants and the sampling period for the natural ecosystem. In view of the fact that biological diversity, being the basis of living matter of the biosphere, determines the sustainability of ecosystems on the Earth, it is relevant to monitor and evaluate all factors that can influence the state of the agrosphere, identify risk factors, and identify links between them. In the work, generally accepted methods of conducting field experiments, methods of soil microbiology, methods of biochemistry were used. In the field experiments, the effect of herbicides imazamox and clomazone on the number of microorganisms of the main ecology-trophic and taxonomic groups in the soy rhizosphere was studied. The regular effect of preparations in the V2 phase of soybean plants as compared to the soil of the natural ecosystem has been established. It has been suggested that bacteria belonging to the clomazone preparation can use the mineral nitrogen of the soil. The number of mycelial microorganisms (streptomycetes and micromycetes) increased in the phases V 2 and R 2 for soybean plants by 30-40% and 10-15%, respectively. More sensitive to the effects of herbicides were indicators of biological activity of the soil. Thus, the influence of herbicides imazamox and clomazone was significant at the initial stages of plant development, since the R 2 phase, the effect on the indices of the number of microorganisms, the biological activity of the soil and the activity of the symbiotic system was significantly reduced and leveled at the end of the vegetation. A representative index is the phytotoxicity of the soil when using the drugs under study. Thus, the influence of herbicides imazamox and clomazone was significant at the initial stages of plant development, since the R 2 phase, the effect on the indices of the number of microorganisms, the biological activity of the soil and the activity of the symbiotic system was significantly reduced and leveled at the end of the vegetation. A representative index is the phytotoxicity of the soil when using the drugs under study. So, for ecological rationing and ecological expertise of growing technologies, it is necessary to search for and develop more sensitive methods for assessing the impact of pesticides on soil biota. Keywords: soil microbiota, soil biological activity, herbicides, imazamox, clomazone

Effects of Oscillatory Shear on the Orientation of the Inverse Bicontinuous Cubic Phase in a Nonionic Surfactant/Water System.

The bicontinuous inverse cubic phase (V2 phase) formed in amphiphilic systems consists of bilayer networks with a long-range order. We have investigated effects of oscillatory shear on the orientation of the V2 phase with space group Ia3d formed in a nonionic surfactant (C12E2)/water system by using simultaneous measurements of rheology/small-angle X-ray scattering. It is shown that grain refining occurs by applying the large amplitude oscillatory shear (LAOS) with a strain amplitude (γ0) of ∼20, which gives the ratio of the loss modulus (G″) to the storage modulus (G') (G″/G' = tan δ) of ∼100. On the other hand, orientation of the cubic lattice occurs when the small amplitude (γ0 ≈ 0.0004) oscillatory shear (SAOS) in the linear regime is applied to the sample just after the LAOS. Interestingly, the orientation is strongly enhanced by the "medium amplitude" (γ0 ≈ 0.05) oscillatory shear ("MAOS") after the SAOS. When the MAOS is applied before applying the LAOS, orientation to a particular direction is not observed, indicating that the grain refining process by the LAOS is necessary for the orientation during the MAOS. The results of additional experiments show that the shear sequence "LAOS-MAOS" is effective for the orientation of the cubic lattice. When the LAOS and MAOS are applied to the sample alternatively, grain refining and orientation occur during the LAOS and MAOS, respectively, indicating reversibility of the orientation. It is shown that (i) the degree of the orientation is dependent on γ0 and the frequency (ω) of the MAOS and (ii) relatively higher orientation can be obtained for the combination of γ0 and ω, which gives tan δ = 2-3. The lattice constant does not change throughout all the shearing processes and is equal to that before shearing within the experimental errors, indicating that the shear melting does not occur. These results suggest a possibility to control the orientation of the cubic lattice only by changing the conditions of oscillatory shear without using the epitaxial transition from other anisotropic phases, such as the hexagonal and lamellar phases.

Duplex ceramic coating produced by low temperature thermo-reactive deposition and diffusion on the cold work tool steel substrate: Thermodynamics, kinetics and modeling

Specimens of DIN 100MnCrW4 steel (type O1 tool steel) have been cut and prepared for performing a duplex surface treatment involving nitriding and low temperature vanadium thermo-reactive deposition and diffusion (TRD) technique. The TRD process was performed in a molten salt bath at different temperatures of 575, 650 and 725°C for 1–30h. The treatment formed a vanadium carbonitride coating with the thickness up to 10.5μm on a hardened diffusion zone. Characterizations by means of an optical microscope (OM), scanning electron microscope equipped with energy dispersive X-ray spectrometer (SEM–EDS) and X-ray diffraction analysis (XRD) indicated that the compact and dense coating mainly consisted of V(C,N) and V2(C,N) phases. All the growth processes of the formed vanadium carbonitride layer obtained by TRD followed a parabolic kinetics while the calculated activation energy (Q) for the treatment was 181.1kJ/mol. An artificial neural network (ANN) based model for predicting the layer thickness of ceramic coatings was presented. Constructing the model, training, validating and testing of experimental results from 72 different specimens were conducted. The data used as inputs in the proposed model were arranged in a format of five parameters that comprised of “pre-nitriding time”, “ferro-vanadium particle size”, “ferro-vanadium weight percent”, “salt bath temperature” and “coating time”. Accordingly, the thickness of duplex coating in each specimen was estimated accurately. Finally, the proposed ANN-based model showed a strong potential for predicting the layer thickness of duplex ceramic coating performed by the TRD technique on the substrate of cold work tool steel.

Computer-aided modeling for predicting layer thickness of a duplex treated ceramic coating on tool steels

Five different tool steels (DIN 1.2080, 1.2210, 1.2344, 1.2510 and 1.3343) have been targeted for a duplex surface treatment consisted of nitriding followed by vanadium thermo-reactive diffusion (TRD). TRD process was performed in molten salt bath at 575, 650 and 725°C for 1 to 15h. A duplex ceramic coating of vanadium carbonitride (VCN) with a thickness up to 10.2μm was formed on tool steel substrates. Characterization of the ceramic coating by means of scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) indicated that the diffused compact and dense layers mainly consisted of V(C,N) and V2(C,N) phases. Layer thickness of duplex coating has been modeled by gene expression programming (GEP). Recently, application of GEP as a computer-aided technique has got appreciable attraction especially for modeling and to formulate engineering demands. For GEP approaches, chemical composition of steel substrates along with different bath and processing parameters totally composed of 17 different parameters were considered as inputs to establish mathematical correlations. Finally, the training and testing results in models have shown strong potential for predicting the layer thickness of duplex treated ceramic coating on tool steels.

BIOLOGICAL STUDY OF TWO SPOTTED SPIDER MITE Tetranychus sp. (ACARI: TETRANYCHIDAE) ON THREE LEAF PHASES OF MUNG BEAN AND ADZUKI BEAN FOR MITE MASS REARING

Two-spotted spider mite (TSM) Tetranychus sp. is one of prey mites for phyotoseiid mite mass rearing. Based on previous research that TSM population developed well on Mung bean ( V igna radiata ) and Adzuki bean ( V . angularis ) as host plants, confirmed growth and development of TSM on both beans. Research was aimed to observe biology of TSM on three phases of Mung bean and Adzuki bean leaf such as at primary leaf unrolled completely (V1), at the 1 st trifoliate unrolled completely (V2), and at the 2 nd trifoliate unrolled completely (V3). Pre adult stadia, life cycle, male and female longevity, female fecundity of TSM, and trichome density were observed on petri dishes contained each leaf phase of beans. Result showed that three leaf phases of beans did not influence significantly in all biological variables, except fecundity. TSM fecundity was the highest on V3 phase of Mung bean (86.90). Trichome density on Mung bean leaf surface per mm² was lower than Adzuki bean. Trichome density of upper leaf surface of V3 phase of Mung bean (10.53) and Adzuki bean (3.07) were lower than V1 (13.20; 12.40) and V2 phase (6.20; 5.27). V3 phase of Mung bean was most suitable for TSM mass rearing. Key words: fecundity, leaf phase, mass rearing, trichome density, two-spotted spider mite

Novel Spiropyran Amphiphiles and Their Application as Light-Responsive Liquid Crystalline Components

Light-responsive materials formed by liquid crystalline lipids in water have potential application to drug delivery through inclusion of photochromic additives such as spiropyran. A series of novel analogues of spiropyran (SP) have been synthesized with an SP headgroup that possess a C8 (SP-OC), C12 (SP-L), and C16 (SP-P) tail to probe the influence of the length of the hydrophobic tail on their physicochemical properties and effect on behavior in liquid crystal matrices with a view to application as stimulus-responsive elements on ultraviolet irradiation. In addition, compounds possessing an oleyl (SP-OL) and phytanyl (SP-PHYT) tail, to mimic those of the "parent" reverse bicontinuous cubic (V2) phase forming lipids, glyceryl monooleate (GMO) and phytantriol, were also prepared. The photochromic compounds were characterized by their melting points and photophysical behavior in solution using techniques including hot stage microscopy (HSM), differential scanning calorimetry (DSC), and UV-visible spectroscopy. Their effect on the equilibrium nanostructure of bulk V2 phases and phase-switching kinetics after exposure to UV light was assessed using small-angle X-ray scattering (SAXS). The melting point of the SP derivatives decreased linearly with increasing chain length, which suggests that interactions between the head groups governed their melting point, rather than the van der Waals interactions between the tails. Changing the R group did not influence the equilibrium rate constants for the isomerization of SP. Phase transition temperatures of liquid crystalline (LC) matrices were influenced significantly by incorporation of the SP derivatives and were greatest when the photochromic compound possessed an intermediate tail length substituent compared to the short alkyl or bulkier moieties. The level of disruption of lipid packing, and hence phase structure, were dependent on the duration of UV exposure.

Revisiting β-Casein as a Stabilizer for Lipid Liquid Crystalline Nanostructured Particles

Lipid liquid crystalline nanoparticles such as cubosomes and hexosomes have unique internal nanostructures that have shown great potential in drug and nutrient delivery applications. The triblock copolymer, Pluronic F127, is usually employed as a steric stabilizer in dispersions of lipid nanostructured particles. In this study, we investigated the formation, colloidal stability and internal nanostructure and morphology of glyceryl monooleate (GMO) and phytantriol (PHYT) cubosome dispersions on substituting β-casein with F127 in increasing proportion as the stabilizer. Internal structure and particle morphology were evaluated using small-angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (cryo-TEM), while protein secondary structure was studied using synchrotron radiation circular dichroism (SRCD). The GMO cubosome dispersion stabilized by β-casein alone displayed a V(2) (Pn3m) phase structure and a V(2) to H(2) phase transition at 60 °C. In comparison, F127-stabilized GMO dispersion had a V(2) (Im3m) phase structure and the H(2) phase only appeared at higher temperature, that is, 70 °C. In the case of PHYT dispersions, only the V(2) (Pn3m) phase structure was observed irrespective of the type and concentration of stabilizers. However, β-casein-stabilized PHYT dispersion displayed a V(2) to H(2) to L(2) transition behavior upon heating, whereas F127-stabilized PHYT dispersion displayed only a direct V(2) to L(2) transition. The protein secondary structure was not disturbed by interaction with GMO or PHYT cubosomes. The results demonstrate that β-casein provides steric stabilization to dispersions of lipid nanostructured particles and avoids the transition to Im3m structure in GMO cubosomes, but also favors the formation of the H(2) phase, which has implications in drug formulation and delivery applications.

Evaluating the link between self-assembled mesophase structure and drug release

Lipid-based liquid crystalline materials are of increasing interest for use as drug delivery systems. The intricate nanostructure of the reversed bicontinuous cubic (V2) and inverse hexagonal (H2) liquid crystal matrices have been shown to provide diffusion controlled release of actives of varying size and polarity. In this study, we extend the understanding of release to other self-assembled phases, the micellar cubic phase (I2) and inverse micelles (L2). The systems are comparable as they were all prepared from the one lipid, glyceryl monooleate (GMO), which sequentially forms all four phases with increasing hexadecane (HD) content in excess water. Phase identity was confirmed by small angle X-ray scattering (SAXS). SAXS data indicated that four mesophases were formed with increasing HD content at 25°C: V2 phase (Pn3m space group) formed at 0–4% (w/w) HD, H2 phase formed at 4–25% (w/w) HD, I2 phase (Fd3m space group) formed at 25–40% (w/w) HD and finally L2 phase formed at >40% (w/w) HD. Analogous compositions using phytantriol rather than GMO as the core lipid did not produce the I2 phase, with only V2 to H2 to L2 transitions being apparent with increasing HD concentration. In order to relate the liquid crystal phase structure to drug release rate, in vitro release tests were conducted by incorporating radio-labelled glucose as a model hydrophilic drug into the four GMO-based mesophases. It was found that the drug release followed first-order diffusion kinetics and was fastest from V2 followed by L2, H2, and I2. Drug release was shown to be significantly faster from bicontinuous cubic phase than the other mesophases, indicating that the state of the water compartments, whether open or closed, has a great influence on the rate of drug release. It is envisioned that liquid crystalline mesophases with slower release characteristics will more likely have potential applications as sustained release drug delivery systems, and hence that the bicontinuous cubic phase is not necessarily the best choice for a sustained release matrix.

Lyotropic Liquid-Crystalline Phases Formed by Pluronic P123 in Ethylammonium Nitrate

Aggregation of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymer, Pluronic P123, is promoted in a room temperature ionic liquid, ethylammonium nitrate (EAN). A series of lyotropic mesophases including normal micellar cubic (I1), normal hexagonal (H1), lamellar (Lalpha), and reverse bicontinuous cubic (V2) are identified at 25 degrees C by using polarized optical microscopy and small-angle X-ray scattering techniques. Such self-assembly behavior of P123 in EAN is similar to those observed in H2O or 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMim(+)][PF6(-)]) systems except for the presence of the V2 phase in EAN and the absence of the I 1 phase in [BMim(+)][PF6(-)]. This suggests that the ionic solvent of EAN plays similar roles as H2O and [BMim(+)][PF6(-)] during the aggregation process and solvates the PEO blocks through hydrogen-bond interaction. Furthermore, the hydrogen bonds are considered to form between the ethylammonium cations and oxygen atoms of the PEO blocks as confirmed by Fourier transform infrared spectra of P123-EAN assemblies. This deduction is also consistent with the results from differential scanning calorimetry and thermogravimetric analysis. The additional V2 phase appearing in the P123-EAN system is attributed to the higher affinity for the relatively hydrophobic PPO blocks to EAN than to water, which might reduce the effective area of the solvophilic headgroup and increase the volume of the solvophobic part. The obtained results may help us to better understand the self-assembly process for amphiphilic block copolymers in protic solvents.

Effects of Phase Aberration and Noise on Extended High Frame Rate Imaging

Based on the high frame rate (HFR) imaging theories, an extended HFR imaging method has been developed recently in our lab where multiple limited-diffraction array beams or steered plane waves are used in transmissions to reconstruct a high quality image of an equivalent dynamic focusing in both transmissions and receptions. The method has the potential to simplify imaging systems because the fast Fourier transform and square-wave aperture weightings can be used. The method is also flexible in using different numbers of transmissions for a continuous trade-off between image quality and frame rate. In this paper, we study the effects of phase aberration and noise on the extended HFR imaging method with in vitro experiments and compare the results with those obtained with a conventional delay-and-sum (D&S) method of a fixed-transmission focus and a dynamically-focused reception. In the experiments, an ATS539 tissue-mimicking phantom and an Acuson V2 phase array transducer (128 elements, 2.5 MHz, and 0.15-mm pitch) were used. The transducer was driven by a homemade general-purpose HFR imaging system that was capable of producing both the limited-diffraction array beams and steeredplane waves and echo data were acquired with the same system and then transferred to a personal computer via a universal serial bus (USB) 2.0 link for image reconstructions. The phase aberration was introduced by adding random phase shifts to both transmission and reception beams. The random noise was added to the received radiofrequency echo data. Results show that the phase aberration and noise degrade both the extended HFR and the conventional delay-and-sum (D&S) imaging method. However, images reconstructed with the extended HFR imaging method have an overall higher quality than those with the D&S method given the phase aberration and noise models studied.

Dye Method to Identify the Types of Cubic Phases

Cubic phases formed in surfactant or copolymer solutions are optically-isotropic and highly viscous liquid crystals. They are mainly categorized to four types; normal micellar discontinuous (I1), reverse micellar discontinous (I2), normal bicontinuous (V1), reverse bicontinuous (V2) cubic phases. We used both water- and oil-soluble dye solutions to specify the type of cubic phase by a simple dyeing method. Water-soluble dye (Tartrazine) colors I1 phase, whereas it remains on the top of I2 phase. Oil-soluble dye (Sudan III) shows the opposite phenomena. Both dyes do color the V1 and V2 phases in binary water-surfactant systems. In the presence of oil, the water-soluble dye colors the V1 phase faster than the V2 phase. The oil-soluble dye shows the opposite rate of dyeing to bicontinuous cubic phases.

Theory of Surface-Induced Magnetism in Adsorbed 3He Films. III: Possibility of Anisotropic Phase

Within a three-layer model proposed by the author, the adsorbed 3He is shown to admit a ground state (V2 phase) which is the same as that of a 2-d Heisenberg antiferromagnet on a triangular lattice. The V2 phase is found to be possible only at high coverages. Its phase diagram is obtained and its Néel temperature and critical field are found to be 0.37 mK and 20.1 G respectively. In the V2 phase, the system has a uniaxial anisotropy and NMR signals have positive frequency shifts at low fields (4.52 kHz at zero applied field) in the case of the vertical applied field. The results are compared with the experiments by Friedman et al.

Control of locomotion in marine mollusc Clione limacina. IV. Role of type 12 interneurons.

Type 12 interneurons in pedal ganglia of Clione limacina exerted a strong influence upon the locomotor generator during "intense" swimming. These neurons generated "plateau" potentials, i.e. their membrane potential had two stable states: the "upper" one when a neuron was depolarized, and the "down" one, separated by 30-40 mV. The interneurons could remain in each state for a long time. Short depolarizing and hyperpolarizing current pulses, as well as excitatory and inhibitory postsynaptic potentials, could transfer the interneurons from one state to another. When the pedal ganglia generated the locomotory rhythm, type 12 neurons received an EPSP and passed to the "upper" state in the V2-phase of a locomotor cycle. They remained at this state until the beginning of the D1-phase when they received an IPSP and passed to the "down" state. The EPSP in type 12 neurons was produced by type 8d neurons, and the IPSP by type 7 neurons. Type 12 neurons exerted inhibitory influences upon many neurons active in the V1 and V2 phases, and excitatory influences upon the D-phase interneurons (type 7). The functional role of type 12 neurons was to limit the activity of neurons discharging in the V-phase of a locomotory cycle. In addition, they enhanced the excitation of the D-phase neurons and promoted, thus, the transition from the V-phase to the D-phase.

Gel and liquid-crystal phase structures of the trioxyethylene glycol monohexadecyl ether/water system

Optical microscopy, differential scanning calorimetry, small-angle X-ray diffraction and nuclear magnetic resonance spectroscopy have been used to study the lyotropic phases formed by trioxyethylene glycol monohexadecyl ether with water (2H2O). The phase diagram exhibits regions corresponding to lamellar (Lα), inverse cubic [V2(1), V2(2)], gel (Lβ) and isotropic liquid phases (W, L2, L3). The two V2 phases were identified by both optical microscopy and small-angle X-ray measurements. The gel phase exhibits a large melting entropy, and part of the molecule has a much restricted mobility. Low-angle X-ray data indicate that the alkyl chains are ordered, with a thickness equivalent to one hydrocarbon chain length. Taken together these data confirm a monolayer ‘interdigitated’ alkyl chain structure for the gel. In the presence of water the gel is stable (at thermodynamic equilibrium) below 40 °C. Anhydrous C16EO3 exhibits polymorphic phase behaviour. After melting the crystalline surfactant, a metastable gel structure forms on cooling and the crystalline solid reforms only after lengthy storage at low temperature. The maximum water-layer thickness of the Lα phase is larger than that of Lβ despite the expected weaker inter-layer attractions in the latter case. This implies the existence of an additional repulsion in Lα, possibly arising from elastic undulations of liquid bilayers.

ChemInform Abstract: PROPERTIES OF MOLTEN CARBOXYLATES. PART 8. A.C. IMPEDANCE OF MESOPHASES OF SOME EVEN CHAIN LENGTH LEAD(II) N‐ALKANOATES

Measurements have been made of the conductance of lead(II) n-alkanoates of even carbon chain length from hexanoate to octadecanoate inclusive in the liquid crystalline region. Phase transitions are reproduced in agreement with previous d.t.a. studies. There is only a small change in conductance on transition of the liquid to the V2 phase and activation energies for these phases are similar to those in the liquid. The activation energies for conductance in the laminar G phases are chain length dependent indicating that the charge transporting species may contain the carboxylate group. Conductance and capacitance are frequency dependent in all phases. In the liquid and V2 phases the effect of frequency on conductance is small and on capacitance large. It may be explained by the linearised space charge polarisation theory (LSCPT), if there are two charge carriers the discharge of the minor of which is blocked at the electrode whilst the other carrier is free. In the G phases the effect on conductance is large whilst that on capacitance relatively small. The data are inconsistent with the LSCPT and can not be fitted by a single relaxation time. Similar effects are observed for the solid phases and for solid sodium isovalerate. A model is proposed that may qualitatively explain the observations.

Properties of molten carboxylates. Part 8.—A.c. impedance of mesophases of some even chain length lead(II) n-alkanoates

Measurements have been made of the conductance of lead(II) n-alkanoates of even carbon chain length from hexanoate to octadecanoate inclusive in the liquid crystalline region. Phase transitions are reproduced in agreement with previous d.t.a. studies. There is only a small change in conductance on transition of the liquid to the V2 phase and activation energies for these phases are similar to those in the liquid. The activation energies for conductance in the laminar G phases are chain length dependent indicating that the charge transporting species may contain the carboxylate group. Conductance and capacitance are frequency dependent in all phases. In the liquid and V2 phases the effect of frequency on conductance is small and on capacitance large. It may be explained by the linearised space charge polarisation theory (LSCPT), if there are two charge carriers the discharge of the minor of which is blocked at the electrode whilst the other carrier is free. In the G phases the effect on conductance is large whilst that on capacitance relatively small. The data are inconsistent with the LSCPT and can not be fitted by a single relaxation time. Similar effects are observed for the solid phases and for solid sodium isovalerate. A model is proposed that may qualitatively explain the observations.