Adsorption and Aggregation Behavior of Mixtures of Quaternary-Ammonium-Salt-Type Amphiphilic Compounds with Fluorinated Counterions and Surfactants.

The surface adsorption and aggregation behavior of a mixture of quaternary-ammonium-salt-type amphiphilic monomeric compounds (C4 FSA, C8 FSA, and C4 NTf2) or gemini compounds (C10-2-C4 FSA) and various surfactants (nonionic hexaoxyethylene dodecyl ether (C12EO6), anionic sodium dodecyl sulfate (SDS), cationic dodecyltrimethylammonium bromide (C12TAB), and zwitterionic N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (C12Sb)) was investigated. Both types of compounds contained alkyl chains of nonidentical lengths that used bis(fluorosulfonyl)imide (FSA-) or bis(trifluoromethanesulfonyl)imide (NTf2-) as counterions. The mixtures were analyzed for surface tension, viscosity, electrical conductivity, and pyrene fluorescence, in addition to evaluation by cryogenic transmission electron microscopy, small-angle X-ray scattering, and dynamic light scattering. Our results showed that the surface tension depended on the surfactant structure. For the mixture of C8 FSA and SDS, as the SDS concentration increased, the surface tension first decreased and became constant at the critical micelle concentration (CMC). In this concentration range, C8 FSA and SDS were approximately equimolar (2.5 mmol dm-3), the mixture adsorbed efficiently at the air-water interface, and vesicles and linear-type micelles were formed in the solution owing to the decreased electrostatic repulsion between the hydrophilic groups. As the SDS concentration further increased, the surface tension increased and reached another constant value. The C8 FSA at the interface was replaced by SDS and the aggregates transformed into spherical micelles. The surface tension plot of the mixture of the amphiphilic compounds and C12Sb showed a minimum at the CMC. The lowest CMC and surface tension were observed for C10-2-C4 FSA, indicating that the gemini compounds offer excellent adsorption and orientation at the air-water interface. It was revealed that the quaternary-ammonium-salt-type amphiphilic compounds in this study acted as ionic liquids on their own and as surfactants in aqueous solution. Further, they could improve the surface activity of conventional ionic surfactants.

Acute off-target effects of neural circuit manipulations.

Rapid and reversible manipulations of neural activity in behaving animals are transforming our understanding of brain function. An important assumption underlying much of this work is that evoked behavioural changes reflect the function of the manipulated circuits. We show that this assumption is problematic because it disregards indirect effects on the independent functions of downstream circuits. Transient inactivations of motor cortex in rats and nucleus interface (Nif) in songbirds severely degraded task-specific movement patterns and courtship songs, respectively, which are learned skills that recover spontaneously after permanent lesions of the same areas. We resolve this discrepancy in songbirds, showing that Nif silencing acutely affects the function of HVC, a downstream song control nucleus. Paralleling song recovery, the off-target effects resolved within days of Nif lesions, a recovery consistent with homeostatic regulation of neural activity in HVC. These results have implications for interpreting transient circuit manipulations and for understanding recovery after brain lesions.

Surface Adsorption and Bulk Properties of Surfactants in Quaternary-Ammonium-Salt-Type Amphiphilic Monomeric and Gemini Ionic Liquids.

The physicochemical properties of ionic liquids can be readily controlled. Currently, it is necessary to investigate the properties of different surfactants to elucidate the mixtures used in quaternary-ammonium-salt-type ionic liquids. Herein, the surface adsorption and bulk properties of homogeneous polyoxyethylene (EO)-type nonionic surfactant, quaternary-ammonium-salt-type cationic surfactant, and sulfobetaine-type zwitterionic surfactant are elucidated in quaternary-ammonium-salt-type amphiphilic monomeric ionic liquids and gemini ionic liquids with bis(fluorosulfonyl)imide or bis(trifluoromethanesulfonyl)imide as counterions. The monomeric amphiphilic ionic liquids that adsorbed at the interface were replaced with CxEOy (where x and y represent alkyl and EO chain lengths, respectively) as the concentration of CxEOy increased. On the other hand, in the gemini amphiphilic ionic liquids, the surface tensions of CxEOy were lower than those of the monomeric ionic liquids. Consequently, both gemini amphiphilic ionic liquids and CxEOy adsorbed efficiently at the interface and oriented themselves because of a synergistic effect. Furthermore, for ionic liquids with short alkyl chains, an orderly bulk nanostructure was not observed at low concentrations in CxEOy, while a layer structure formed at higher concentrations; in contrast, ionic liquids with long alkyl chains formed a layer structure. The alkyl chains, which were interlocked in the bilayer structure, resulted in a densely packed layer structure.

Surface Adsorption Properties and Layer Structures of Homogeneous Polyoxyethylene-Type Nonionic Surfactants in Quaternary-Ammonium-Salt-Type Amphiphilic Gemini Ionic Liquids with Oxygen- or Nitrogen-Containing Spacers.

The amphiphilic ionic liquids containing an alkyl chain in molecules form nano-structure in the bulk, although they also show surface activity and form aggregates in aqueous solutions. Although insights into the layer structures of ionic liquids were obtained using X-ray and neutron scattering techniques, the nanostructures of ionic liquids remain unclear. Herein, the surface adsorption and bulk properties of homogeneous polyoxyethylene (EO)-type nonionic surfactants (CxEO6; x = 8, 12, or 16) were elucidated in quaternary-ammonium-salt-type amphiphilic gemini ionic liquids with oxygen or nitrogen-containing spacers [2Cn(Spacer) NTf2; (Spacer) = (2-O-2), (2-O-2-O-2), (2-N-2), (2/2-N-2), (3), (5), or (6); n = 10, 12, or 14 for (2-O-2) and n = 12 for all other spacers] by surface tension, small- and wide-angle X-ray scattering, cryogenic transmission electron microscopy, and viscosity measurements. The surface tension of C12EO6 in 2Cn(Spacer) NTf2 with oxygen-containing spacers increased with increasing concentration of C12EO6, becoming close to that of C12EO6 alone, indicating that the amphiphilic ionic liquid adsorbed at the interface was replaced with CxEO6. In contrast, both 2Cn(Spacer) NTf2 with nitrogen-containing spacers and nonionic surfactants remained adsorbed at the interface at high concentrations. In the bulk, it was found that 2Cn(Spacer) NTf2 formed layer structures, in which the spacing depended on the alkyl chain length of CxEO6. These insights are expected to advance the practical applications of amphiphilic ionic liquids such as ion permeation, drug solubilization, and energy delivery systems.

Physicochemical and solution properties of quaternary-ammonium-salt-type amphiphilic trimeric ionic liquids.

The quaternary-ammonium-salt-type amphiphilic compounds 3Cntris-s-Q X (star-type; carbon number between the central amino and ammonium groups s = 2, 3) and 3Cnlin-3-Q X (linear-type; carbon number between the hydrophilic groups s = 3), where n represents the alkyl chain length (n = 8, 10, 12, 14) and X represents a counterion [hexafluorophosphate, trifluoromethanesulfonate (OTf), bis(fluorosulfonyl)amide (FSA), and bis(trifluoromethanesulfonyl)amide (NTf2)], were synthesized. Except for 3C12tris-3-Q OTf, these trimeric compounds presented melting points lower than 100 °C and therefore are defined as ionic liquids. Among them, 3Cntris-3-Q NTf2 (n = 8, 12, 14) and 3Cnlin-3-Q NTf2 (n = 8, 10) presented melting points lower than 0 °C. The melting points of the amphiphilic trimeric ionic liquids (n = 8, 10), which were lower for the star- than for the linear-type compounds, were higher than those of the corresponding monomeric compounds but lower than those of the corresponding gemini samples. Moreover, the amphiphilic trimeric ionic liquids exhibited higher conductivities and lower viscosities than the corresponding gemini ionic liquids, while the star-type trimeric ionic liquids presented lower conductivities and higher viscosities than those of the linear-type compounds. The amphiphilic trimeric ionic liquids also readily adsorbed at the air/water interface and oriented themselves to form micelles in aqueous solution. This aggregation behavior was not observed in the monomeric and gemini ionic liquids.

Neural representations of courtship song in the Drosophila brain.

Acoustic communication in drosophilid flies is based on the production and perception of courtship songs, which facilitate mating. Despite decades of research on courtship songs and behavior in Drosophila, central auditory responses have remained uncharacterized. In this study, we report on intracellular recordings from central neurons that innervate the Drosophila antennal mechanosensory and motor center (AMMC), the first relay for auditory information in the fly brain. These neurons produce graded-potential (nonspiking) responses to sound; we compare recordings from AMMC neurons to extracellular recordings of the receptor neuron population [Johnston's organ neurons (JONs)]. We discover that, while steady-state response profiles for tonal and broadband stimuli are significantly transformed between the JON population in the antenna and AMMC neurons in the brain, transient responses to pulses present in natural stimuli (courtship song) are not. For pulse stimuli in particular, AMMC neurons simply low-pass filter the receptor population response, thus preserving low-frequency temporal features (such as the spacing of song pulses) for analysis by postsynaptic neurons. We also compare responses in two closely related Drosophila species, Drosophila melanogaster and Drosophila simulans, and find that pulse song responses are largely similar, despite differences in the spectral content of their songs. Our recordings inform how downstream circuits may read out behaviorally relevant information from central neurons in the AMMC.

Biomechanical analysis of gait adaptation in the nematode Caenorhabditis elegans.

To navigate different environments, an animal must be able to adapt its locomotory gait to its physical surroundings. The nematode Caenorhabditis elegans, between swimming in water and crawling on surfaces, adapts its locomotory gait to surroundings that impose approximately 10,000-fold differences in mechanical resistance. Here we investigate this feat by studying the undulatory movements of C. elegans in Newtonian fluids spanning nearly five orders of magnitude in viscosity. In these fluids, the worm undulatory gait varies continuously with changes in external load: As load increases, both wavelength and frequency of undulation decrease. We also quantify the internal viscoelastic properties of the worm's body and their role in locomotory dynamics. We incorporate muscle activity, internal load, and external load into a biomechanical model of locomotion and show that (i) muscle power is nearly constant across changes in locomotory gait, and (ii) the onset of gait adaptation occurs as external load becomes comparable to internal load. During the swimming gait, which is evoked by small external loads, muscle power is primarily devoted to bending the worm's elastic body. During the crawling gait, evoked by large external loads, comparable muscle power is used to drive the external load and the elastic body. Our results suggest that C. elegans locomotory gait continuously adapts to external mechanical load in order to maintain propulsive thrust.

AC Electromagnetic Field Controls the Biofilms on the Glass Surface by Escherichia coli & Staphylococcus epidermidis Inhibition Effect.

Biofilms, mainly comprised of bacteria, form on materials' surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials that make up drains, and slippage. Inside of a biofilm is an environment conducive to the growth and propagation of bacteria. Problems with biofilms include the inability of disinfectants and antibiotics to act on them. Therefore, we have investigated the potential application of alternating electromagnetic fields for biofilm control. We obtained exciting results using various materials' specimens and frequency conditions. Through these studies, we gradually understood that the combination of the type of bacteria, the kind of material, and the application of an electromagnetic field with various low frequencies (4 kHz-12 kHz) changes the circumstances of the onset of the biofilm suppression effect. In this study, relatively high frequencies (20 and 30 kHz) were applied to biofilms caused by Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis), and quantitative evaluation was performed using staining methods. The sample surfaces were analyzed by Raman spectroscopy using a Laser Raman spectrometer to confirm the presence of biofilms on the surface.

Proposal for Some Affordable Laboratory Biofilm Reactors and Their Critical Evaluations from Practical Viewpoints.

Biofilms are a result of bacterial activities and are found everywhere. They often form on metal surfaces and on the surfaces of polymeric compounds. Biofilms are sticky and mostly consist of water. They have a strong resistance to antimicrobial agents and can cause serious problems for modern medicine and industry. Biofilms are composed of extracellular polymeric substances (EPS) such as polysaccharides produced from bacterial cells and are dominated by water at the initial stage. In a series of experiments, using Escherichia coli, we developed three types of laboratory biofilm reactors (LBR) to simulate biofilm formation. For the first trial, we used a rotary type of biofilm reactor for stirring. For the next trial, we tried another rotary type of reactor where the circular plate holding specimens was rotated. Finally, a circular laboratory biofilm reactor was used. Biofilms were evaluated by using a crystal violet staining method and by using Raman spectroscopy. Additionally, they were compared to each other from the practical (industrial) viewpoints. The third type was the best to form biofilms in a short period. However, the first and second were better from the viewpoint of "ease of use". All of these have their own advantages and disadvantages, respectively. Therefore, they should be properly selected and used for specific and appropriate purposes in the future.

Quantitative Analyses of Biofilm by Using Crystal Violet Staining and Optical Reflection.

Biofilms have caused many problems, not only in the industrial fields, but also in our daily lives. Therefore, it is important for us to control them by evaluating them properly. There are many instrumental analytical methods available for evaluating formed biofilm qualitatively. These methods include the use of Raman spectroscopy and various microscopes (optical microscopes, confocal laser microscopes, scanning electron microscopes, transmission electron microscopes, atomic force microscopes, etc.). On the other hand, there are some biological methods, such as staining, gene analyses, etc. From the practical viewpoint, staining methods seem to be the best due to various reasons. Therefore, we focused on the staining method that used a crystal violet solution. In the previous study, we devised an evaluation process for biofilms using a color meter to analyze the various staining situations. However, this method was complicated and expensive for practical engineers. For this experiment, we investigated the process of using regular photos that were quantified without any instruments except for digitized cameras. Digitized cameras were used to compare the results. As a result, we confirmed that the absolute values were different for both cases, respectively. However, the tendency of changes was the same. Therefore, we plan to utilize the changes before and after biofilm formation as indicators for the future.

Characterization and Solution Properties of Quaternary-Ammonium-Salt-Type Amphiphilic Gemini Ionic Liquids.

Quaternary-ammonium-salt-type amphiphilic gemini compounds (C m -2-C n X, where m and n represent the alkyl chain lengths; m = 4, 6, 8, 10; n = 2, 4, 6, 8, 10; m ≥ n; and X indicates the counterion BF4, PF6, OTf, FSA, or NTf2) were synthesized by the quaternization of N,N,N',N'-tetramethylethylenediamine and n-alkyl bromide and a subsequent ion-exchange reaction with five different counterions. For comparison, the corresponding monomeric compounds (C n X, n = 2, 4, 6, 8, and 10) were also synthesized. The melting points of the compounds were evaluated using differential scanning calorimetry, and those with melting points lower than 100 °C were treated as ionic liquids during the subsequent measurements. The amphiphilic gemini compounds exhibited the lowest melting points (44-49 °C) when bulky NTf2 - was the counterion and the degree of dissymmetry between the two alkyl chains was 0.4 < n/m < 0.75. However, their melting points were not similar to those of the monomeric compounds with NTf2 - and n = 4-10 (<29 °C). The gemini ionic liquids exhibited significantly lower conductivities and higher viscosities than those of the corresponding monomeric ionic liquids. This is because of the decrease in the mobility of the cation molecules caused by the gemini structure, in which the two monomeric compounds are connected by a spacer. The gemini ionic liquids also showed higher densities than those of the corresponding monomeric ionic liquids, owing to the dimer of the gemini structure. Further, the gemini ionic liquids were adsorbed readily at the air/water interface and oriented themselves but did not show the critical micelle concentration for the concentration range over which they could be dissolved in water. The amphiphilic monomeric and gemini ionic liquids also tended to form ion pairs in aqueous solutions, as the length of their alkyl chain was relatively short.

Rheo-SANS study on relationship between micellar structures and rheological behavior of cationic gemini surfactants in solution.

HYPOTHESIS: Gemini surfactant 12-2-12 (dimethylene-1,2-bis(dodecyl dimethylammonium bromide)) solutions are known to show shear thickening and thinning under salt-free conditions. Because the rheological behavior of the wormlike micelles formed by 12-2-12 in solution is related to their structure, we expected that changes to the precursor structure would affect their rheological behaviors. It is also important to understand the effect of the introduction of a spacer group in the 12-2-12 molecules on the rheological behavior and structure of the wormlike micelles under shear flow. EXPERIMENTS: Simultaneous small-angle neutron scattering and rheological measurements (Rheo-SANS) of the 12-2-12 solutions were performed. We exhaustively studied the structural changes in the wormlike micelles upon increasing shear rate. FINDINGS: We found that the wormlike micelles were oriented in the direction of the flow due to elongation and that changes to the precursor of the wormlike micelles did not affect the shear thickening. As a precursor structural change of shear thinning, the wormlike micelles elongated while maintaining their orientation. We found that an increase in the molecular curvature of the 12-2-12 due to the introduction of a spacer-group contributed to the unusual rheological behaviors of the wormlike micelles in a solution under shear flow.

Motor cortex is required for learning but not for executing a motor skill.

Motor cortex is widely believed to underlie the acquisition and execution of motor skills, but its contributions to these processes are not fully understood. One reason is that studies on motor skills often conflate motor cortex's established role in dexterous control with roles in learning and producing task-specific motor sequences. To dissociate these aspects, we developed a motor task for rats that trains spatiotemporally precise movement patterns without requirements for dexterity. Remarkably, motor cortex lesions had no discernible effect on the acquired skills, which were expressed in their distinct pre-lesion forms on the very first day of post-lesion training. Motor cortex lesions prior to training, however, rendered rats unable to acquire the stereotyped motor sequences required for the task. These results suggest a remarkable capacity of subcortical motor circuits to execute learned skills and a previously unappreciated role for motor cortex in "tutoring" these circuits during learning.

A fully automated high-throughput training system for rodents.

Addressing the neural mechanisms underlying complex learned behaviors requires training animals in well-controlled tasks, an often time-consuming and labor-intensive process that can severely limit the feasibility of such studies. To overcome this constraint, we developed a fully computer-controlled general purpose system for high-throughput training of rodents. By standardizing and automating the implementation of predefined training protocols within the animal's home-cage our system dramatically reduces the efforts involved in animal training while also removing human errors and biases from the process. We deployed this system to train rats in a variety of sensorimotor tasks, achieving learning rates comparable to existing, but more laborious, methods. By incrementally and systematically increasing the difficulty of the task over weeks of training, rats were able to master motor tasks that, in complexity and structure, resemble ones used in primate studies of motor sequence learning. By enabling fully automated training of rodents in a home-cage setting this low-cost and modular system increases the utility of rodents for studying the neural underpinnings of a variety of complex behaviors.