Surface-Enhanced Raman Scattering in Tunable Bimetallic Core-Shell

In this paper, optical properties of multilayer spherical core-shell nanoparticles based on quasi-static approach and plasmon hybridization theory are investigated. Calculations show that light absorption spectrum of bimetallic multilayer core-shell has three intense plasmon resonance peaks, which are more suitable for multiplex biosensing based on surface-enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR). The plasmon resonance peaks in bimetal nanshells are optimized by tuning the geometrical parameters. In addition, the optimal geometry is discussed to obtain the Raman enhancement factor in bimetallic multilayer nanoshell. SERS enhancement factor is calculated with consideration of dampings due to both the electron scattering and the radiation at the boundary and modified Drude model in dielectric function of bimetallic nanoshell. It is shown that bimetallic nanoshell with the small size exhibits strong SERS enhancement factor (~6.63 × 10⁵) with additional collision dampings and ~2.9 × 10⁹ with modified Drude model which are suitable for biosensing applications. In addition, any variation in blood concentration and oxygen level can be detected by this bimetallic core-shell nanoparticle with sensitivity of Δλ/Δn = 264.91 nm/RIU.     

Nanoscale mono- and multi-layer cylinder structures formed by recombinant S-layer proteins of mosquitocidal Bacillus sphaericus C3-41

The mature surface layer (S-layer) protein SlpC of mosquitocidal Bacillus sphaericus C3-41 comprises amino acids 31–1,176 and could recrystallize in vitro. The N-terminal SLH domain is responsible for binding function. Deletion of this part, S-layer proteins could not bind to the cell wall sacculi. To investigate the self-assembly ability of SlpC from B. sphaericus, nine truncations were constructed and their self-assembly properties were compared with the recombinant mature S-layer protein rSlpC_31–1,176. The results showed that rSbsC_31–1,176 and truncations rSlpC_211–1,176, rSlpC_278–1,176, rSlpC_31–1,100, and rSlpC_31–1,050 could assemble into multilayer cylinder structures, while N-terminal truncations rSlpC_338–1,176, rSlpC_438–1,176, and rSlpC_498–1,176 mainly showed monolayer cylinders in recombinant Escherichia coli BL21 (DE3) cells. Growth phase analysis of the self-assembly process revealed that rSlpC_498–1,176 mainly formed monolayer cylinders in the early stage (0.5 and 1 h induction of expression), but few double-layer or multilayer cylinders were also found with the cells growing, while rSlpC_31–1,176 could formed multilayer cylinders in all the growth stage in the E. coli cells. It is concluded that the deletion of the C-terminal 126 aa or the N-terminal 497 aa did not interfere with the self-assembly process, the fragment (amino acids 278 to 337) is essential for the multilayer cylinder formation in E. coli BL21 (DE3) cells in the early stage and the fragment (amino acids 338 to 497) is related to monolayer cylinder formation. The information is important for further studies on the assembly mechanism of S-layer proteins and forms a basis for further studies concerning surface display and nanobiotechnology.     

Probing the Localized Surface Plasmon Field of a Gold Nanoparticle-Based Fibre Optic Biosensor

Gold nanoparticles (GNP) have been used in a variety of localized surface plasmon resonance (LSPR)-based optical sensor systems and in a variety of forms, such as colloidal suspensions, immobilized GNP on flat surfaces or optical fibres. A key parameter affecting the sensitivity of these systems is the effective depth of penetration of the surface plasmons. This study aims to determine the plasmon penetration depth in the case of an immobilized GNP-based LSPR optical biosensor. The optical biosensor used for experimentation is a U-bend fibre optic probe of 200-μm core diameter and 1.5-mm bend diameter on which GNP is immobilized. Formation of multilayered nanostructures on the immobilized GNP was used to investigate the field of the localized surface plasmons. Two multilayered nanostructures were explored in this study, viz. a polyelectrolyte multilayer formed by layer-by-layer (LBL) deposition of oppositely charged polyelectrolytes and an immunoglobulin G (IgG) multilayer formed through sequential immobilization of two mutually specific antibodies. Measurement of LSPR absorbance change with deposition of each analyte layer was used to determine the plasmon penetration depth (d _P) of the LSPR biosensor. Probing the plasmon field with an IgG multilayer gave rise to at least twofold higher d _P compared to d _P obtained from the polyelectrolyte multilayer. The effect of GNP size was also studied, and GNP of three diameters, viz. 18, 36 and 45 nm, were used. The 36-nm-diameter GNP exhibited the highest d _P. The outcomes of this study may provide leads for optimization of LSPR-based sensors for various biosensing applications.     

Studies on the orientations of the mitochondrial redox carriers I. Orientation of the hemes of cytochrome c oxidase with respect to the plane of a cytochrome oxidase-lipid model membrane

The liganded derivatives of mitochondrial cytochrome c oxidase have been prepared in hydrated oriented multilayers of membranous cytochrome c oxidase. The optical spectra of the liganded derivatives recorded at an angle of 45° between the incident light beam and the normal to the planes of the membranes in the multilayers show dichroic ratios of almost 2 in the visible region and 1.2–1.4 in the Soret region. The dichroic ratios were found to be similar for both cytochromes a and a₃. Electron paramagnetic resonance spectra of the azide, sulfide, and formate complexes of cytochrome c oxidase obtained as a function of the orientation of the applied magnetic field relative to the planes of the membranes in the multilayer confirm the optical data and demonstrate that both hemes of cytochrome c oxidase are oriented such that the angle between the heme normal and the membrane normal is approximately 90°.     

Structurally and functionally characterized in vitro model of rabbit vocal fold epithelium

In this paper, we describe a method for primary culture of a well differentiated electrically tight rabbit vocal fold epithelial cell multilayer and the measurement of transepithelial electrical resistance (TEER) for the evaluation of epithelial barrier function in vitro. Rabbit larynges were harvested and enzymatically treated to isolate vocal fold epithelial cells and to establish primary culture. Vocal fold epithelial cells were co-cultured with mitomycin C-treated feeder cells on collagen-coated plates. After 10–14 days in primary culture, cells were passaged and cultured until they achieved 70–90% confluence on collagen-coated plates. Epithelial cells were then passaged onto collagen-coated cell culture inserts using 4.5 cm² membrane filters (1.0 μm pore size) with 10% fetal bovine serum or 30 μg/mL bovine pituitary extract to investigate the effects of growth-promoting additives on TEER. Additional experiments were performed to investigate optimal seeding density (1.1, 2.2, 4.4, or 8.9 × 10⁵ cells/cm²), the effect of co-culture with feeder cells, and the effect of passage number on epithelial barrier function. Characterization of in vitro cultures was performed using hematoxylin and eosin staining and immunostaining for vocal fold epithelial cell markers and tight junctions. Results revealed higher TEER in cells supplemented with fetal bovine serum compared to bovine pituitary extract. TEER was highest in cells passaged at a seeding density of 2.2 × 10⁴ cells/cm², and TEER was higher in cells at passage two than passage three. Ultrastructural experiments revealed a well-differentiated epithelial cell multilayer, expressing the epithelial cell markers CK13, CK14 and the tight junction proteins occludin and ZO-1.     

A dilatometric investigation of the effects of general anaesthetics,alcohols and hydrostatic pressure on the phase transition in smectic mesophases of dipalmitoyl phosphatidylcholine

The effect of general anaesthetics, alcohols and hydrostatic pressure on the thermal transition in dipalmitoyl phosphatidylcholine multilayer liposomes has been measured using dilatometry. The volume increasse at the transition (ΔV_t) is 0.0350 ± 0.0003 ml/g. the transition temperature (T_t) 41.84 ± 0.09°C and the width of the transition 1.025 ± 0.18°C. ΔH calculated by the Clapeyron-Clausius equation is 8.4 kcal/mol. The n-alcohols C₃C₅ reduced the transition temperature without affecting the transition width which was however, increased by n-hexanol. Trichloroethylene, the fluorescent probe N-phenyl-1-naphthyl-amine, and methoxyflurane all increased the transition width (reduced the cooperativity of the transition) with a simultaneous depression of T_t. Methoxyflurane caused a two-stage transition expansion. Diethyl ether's effect has similarities with both the C₃ and C₆ alcohols. Generally ΔV_t was unaffected by the agents.Pressure increased T_t by 0.0238°C/atm linearly over the range 1–300 atm in both treated and untreated liposomes, and therefore cannot be said to antagonize anaesthetics. In both treated and untreated liposomes ΔV_t and the width of the transition were unaffected by pressure. Pressure thus reverses the effects of anaesthetics on T_t but not their spread of the transition width.     

Direct Determination of the Structure of Barium Stearate Multilayers by X-Ray Diffraction

Diffraction of X-rays is recorded from barium stearate multilayer systems with from 2 to 60 double layers or unit cells. The generalized Patterson function P′(x) is calculated by an integral Fourier transform of observed intensity data from a specimen containing only two unit cells. The Patterson function P₀(x) of a single unit cell is determined from P′(x) and the electron density distribution of a bimolecular leaflet is obtained by a deconvolution procedure of P₀(x) after Hosemann and Bagchi. The electron density distribution is also calculated independently by a conventional Fourier synthesis with an experimentally established set of phases. The results of the two methods are consistent and fit a physical model of the bimolecular leaflet. A direct analysis, therefore, can be performed if diffraction is observed from multilayer systems with a small number of unit cells.     

Transpiration of trees in a cool temperate forest on Mt. Aso,Japan: comparison of model simulation and measurements

In the large caldera of Mt. Aso, Japan, artificial grasslands were converted into forests of different species due to the decline of the livestock industry in this region. These changes in species composition are thought to have changed not only the transpiration rates (E), but also the responses in E to variations in environmental conditions. For three introduced forest types, we monitored E using sap flux sensors and computed E with a multilayer model parameterized by independently obtained leaf-scale ecophysiological traits. Modeled E replicated the time series of measured E reasonably well, but did not reproduce a decrease in E lasting 20 days after a short rainless period in conifer plantation. Mean leaf-scale stomatal conductance of two deciduous broadleaved tree species was as low as that of trees under dry conditions in other studies, possibly an adaptation for the avoidance of excessive E during rainless periods. These results suggest that land use change influenced E and its response to the rainfall patterns of the region and that drought plays an important role in influencing species-specific E characteristics in this rainy region. The multilayer model in combination with sap flux measurements was found to be a useful tool not only for the extrapolation of E, but also for the detection of the unexpected events, as long as the measured parameter values capture the species-specific seasonality in leaf ecophysiological traits.     

Hydraulic permeability and compressive properties of porcine and human synovium

The synovium is a multilayer connective tissue separating the intra-articular spaces of the diarthrodial joint from the extra-synovial vascular and lymphatic supply. Synovium regulates drug transport into and out of the joint, yet its material properties remain poorly characterized. Here, we measured the compressive properties (aggregate modulus, Young's modulus, and Poisson's ratio) and hydraulic permeability of synovium with a combined experimental-computational approach. A compressive aggregate modulus and Young's modulus for the solid phase of synovium were quantified from linear regression of the equilibrium confined and unconfined compressive stress upon strain, respectively (H_A = 4.3 ± 2.0 kPa, E_s = 2.1 ± 0.75, porcine; H_A = 3.1 ± 2.0 kPa, E_s = 2.8 ± 1.7, human). Poisson's ratio was estimated to be 0.39 and 0.40 for porcine and human tissue, respectively, from moduli values in a Monte Carlo simulation. To calculate hydraulic permeability, a biphasic finite element model's predictions were numerically matched to experimental data for the time-varying ramp and hold phase of a single increment of applied strain (k = 7.4 ± 4.1 × 10^?15 m⁴/N.s, porcine; k = 7.4 ± 4.3 × 10^?15 m⁴/N.s, human). We can use these newly measured properties to predict fluid flow gradients across the tissue in response to previously reported intra-articular pressures. These values for material constants are to our knowledge the first available measurements in synovium that are necessary to better understand drug transport in both healthy and pathological joints.     

A unique form of light reflector and the evolution of signalling in Ovalipes (Crustacea: Decapoda: Portunidae)

The first demonstration, to our knowledge, of an evolutionary shift in communication mode in animals is presented. Some species of Ovalipes display spectacular iridescence resulting from multilayer reflectors in the cuticle. This reflector is unique in animals because each layer is corrugated and slightly out of phase with adjacent layers. Solid layers are separated from fluid layers in the reflector by side branches acting as support struts. An effect of this reflector is that blue light is reflected over a ''broad'' angle around a plane parallel to the sea floor when the host crab is resting. Species of Ovalipes all possess stridulatory structures. The shallow-water species with the best developed stridulatory structures are non-iridescent and use sound as a signal. Deep-water species possess poorly developed stridulatory structures and display iridescence from most regions of the body. In deep water, where incident light is blue, light display is highly directional in contrast to sound produced via stridulation. Sound and light display probably perform the same function of sexual signalling in Ovalipes, although the directional signal is less likely to attract predators. Deep-water species of Ovalipes appear to have evolved towards using light in conspecific signalling. This change from using sound to using light reflects the change in habitat light properties, perhaps the hunting mechanisms of cohabitees, and its progression is an indicator of phylogeny. The changes in sexual signalling mechanisms, following spatial–geographical isolation, may have promoted speciation in Ovalipes.     

Sexual Dichromatism of the Damselfly Calopteryx japonica Caused by a Melanin-Chitin Multilayer in the Male Wing Veins

Mature male Calopteryx japonica damselflies have dark-blue wings, due to darkly coloured wing membranes and blue reflecting veins. The membranes contain a high melanin concentration and the veins have a multilayer of melanin and chitin. Female and immature C. japonica damselflies have brown wings. We have determined the refractive index of melanin by comparing the differently pigmented wing membranes and applying Jamin-Lebedeff interference microscopy. Together with the previously measured refractive index of chitin the blue, structural colour of the male wing veins could be quantitatively explained by an optical multilayer model. The obtained melanin refractive index data will be useful in optical studies on melanized tissues, especially where melanin is concentrated in layers, thus causing iridescence.     

Phospholipid arrangements in multilayers and artificial membranes: quantitative analysis of the X-ray diffraction data from a multilayer of 1,2-dimyristoyl-DL-phosphatidylethanolamine.

The X-ray diffraction data from a multilayer of 1,2-dimyristoyl-dl-phosphatidylethanolamine is interpreted quantitatively (R₁ = 0.20) from a single crystal analysis of the molecular structure of 1,2-dilauroyl-dl-phosphatidylethanolamine.     

Architecture and Assembly of the Bacillus subtilis Spore Coat

Bacillus spores are encased in a multilayer, proteinaceous self-assembled coat structure that assists in protecting the bacterial genome from stresses and consists of at least 70 proteins. The elucidation of Bacillus spore coat assembly, architecture, and function is critical to determining mechanisms of spore pathogenesis, environmental resistance, immune response, and physicochemical properties. Recently, genetic, biochemical and microscopy methods have provided new insight into spore coat architecture, assembly, structure and function. However, detailed spore coat architecture and assembly, comprehensive understanding of the proteomic composition of coat layers, and specific roles of coat proteins in coat assembly and their precise localization within the coat remain in question. In this study, atomic force microscopy was used to probe the coat structure of Bacillus subtilis wild type and cotA, cotB, safA, cotH, cotO, cotE, gerE, and cotE gerE spores. This approach provided high-resolution visualization of the various spore coat structures, new insight into the function of specific coat proteins, and enabled the development of a detailed model of spore coat architecture. This model is consistent with a recently reported four-layer coat assembly and further adds several coat layers not reported previously. The coat is organized starting from the outside into an outermost amorphous (crust) layer, a rodlet layer, a honeycomb layer, a fibrous layer, a layer of “nanodot” particles, a multilayer assembly, and finally the undercoat/basement layer. We propose that the assembly of the previously unreported fibrous layer, which we link to the darkly stained outer coat seen by electron microscopy, and the nanodot layer are cotH- and cotE- dependent and cotE-specific respectively. We further propose that the inner coat multilayer structure is crystalline with its apparent two-dimensional (2D) nuclei being the first example of a non-mineral 2D nucleation crystallization pattern in a biological organism.     

Modulation of Visible and Near-Infrared Surface Plasmon Resonance of Au Nanoparticles Based on Highly Doped Graphene

We study an active modulation of surface plasmon resonance (SPR) of Au nanoparticles based on highly doped graphene in visible and near-infrared regions. We find that compared to the traditional metal SPR, the SPR of Au nanoparticles based on graphene causes a remarkable blue shift. The field intensity in the gap is redistributed to standing wave. The field intensity of standing wave is about one order of magnitude higher than the traditional model. Moreover, the SPR of Au nanoparticles can be actively modulated by varying the graphene Fermi energy. We find the maximum modulation of field intensity of absorption spectra is more than 21.6 % at λ?=?822?nm and the amount of blue shift is 17.4 nm, which is about 2.14 % of the initial wavelength λ ₀?=?813.4?nm, with increasing monolayer graphene Fermi energy from 1.0 to 1.5 ev. We find that the SPR sensitivity to the refractive index n of the environment is about 642 nm per refractive index unit (RIU). The SPR wavelengths have a big blue shift, which is about 33 nm, with increasing number of graphene layers from 1 to 3, and some shoulders on the absorption spectra are observed in the models with multilayer graphene. Finally, we study the Au nanorod array based on monolayer graphene. We find that the blue shift caused by the graphene increases from 14 to 24 nm, with increasing gap g _y from 10 to 20 nm. Then, it decreases from 24 to 14 nm, with increasing gap g _y from 20 to 50 nm. This study provides a new way for actively modulating the optical and optoelectronic devices.     

Discontinuous thermotropic response of Tetrahymena membrane lipids correlated with specific lipid compositional changes

Steady-state fluorescence polarization measurements of 1,6-diphenyl-1,3,5-hexatriene in microsomal lipids from Tetrahymena pyriformis cells grown at 39 or 15°C revealed discrete slope discontinuities in plots of polarization vs. temperature. Two well-defined ‘break points’ were present in the 0–40°C temperature range examined and their precise location was dependent upon the growth temperature of the cells. By mixing phospholipids from cells grown at different temperatures, the break points at 17.5 and 32°C in 39°C-lipid multilayer preparations were shown to correlate with the breaks at 12 and 27°C, respectively, in similar preparations from 15°C-grown cells. The discrete break points were also present, but at slightly different characteristic temperatures, in a phosphatidylcholine fraction and a phosphatidylethanolamine plus 2-aminoethylphosphonolipid fraction purified from the phospholipids and in total microsomal lipids (phospholipids plus the sterol-like triterpenoid, tetrahymanol). However, catalytic hydrogenation of the phospholipid fatty acids or mixing the non-hydrogenated phospholipids with increasing proportions of synthetic dipalmitoyl phosphatidylcholine eliminated the break points. We interpret this discontinuous thermotropic response in microsomal lipids as signalling a lipid phase separation of importance in regulating physiological events.     

Comparative Assessment of the Artificial Neural Network and Response Surface Modelling Efficiencies for Biohydrogen Production on Sugar Cane Molasses

This study comparatively evaluates the modelling efficiency of the Response Surface Methodology (RSM) and the Artificial Neural Network (ANN). Twenty-nine biohydrogen fermentation batches were carried out to generate the experimental data. The input parameters consisted of a concentration of molasses (50–150 g/l), pH (4–8), temperature (35–40 °C) and inoculum concentration (10–50 %). The obtained data were used to develop the RSM and ANN models. The ANN model was a committee of networks with a topology of 4-(6-10)-1 structured on multilayer perceptrons. RSM and ANN models gave R ² values of 0.75 and 0.91, respectively, with predicted optimum conditions of 150 g/l, 8 and 35 °C for molasses, pH and temperature, respectively, with differences in inoculum concentrations (10.11 and 15 %) for RSM and ANN, respectively. Upon validation, 15.12 and 119.08 % prediction errors on hydrogen volume were found for ANN and RSM, respectively. These findings suggest that ANN has greater accuracy in modelling the relationships between the considered process inputs for fermentative biohydrogen production and thus, is more reliable to navigate the optimization space.     

A method of water-soluble solid fraction saturation concentration evaluation in dry thalli of Antarctic lichenized fungi,in vivo

BackgroundAt initial steps of rehydration from cryptobiosis of anhydrobiotic organisms or at rehydration of dry tissues the liquid ¹H NMR signal increased anomaly. The surplus in liquid signal may appear if some solid constituents dissolved, or if they were decomposed by enzymatic action.MethodsHydration kinetics, sorption isotherm, ¹H NMR spectra and high power relaxometry were applied to monitor gaseous phase rehydration of Antarctic lichen Cetraria aculeata. Tightly and loosely bound water signal were distinguished, and the upper hydration limit for dissolution of water soluble solid fraction was not observed. A simple theoretical model was proposed.ResultsThe hydration courses showed a very tightly bound water fraction, a tightly bound water, and a loosely bound water fraction. Sigmoidal in form sorption isotherm was fitted well by multilayer sorption model. ¹H NMR showed one Gaussian signal component from solid matrix of thallus and one or two Lorentzian line components from tightly bound, and from loosely bound water. The hydration dependency of liquid signal was fitted by rational function.ConclusionsAlthough in dehydrated C.aculeata the level of carbohydrates and polyols was low, the lichenase action during rehydration process increased it; the averaged saturation concentration c_s=(57.3±12.0)%, which resembled that for sucrose.General significanceThe proposed method of water soluble solid fraction saturation concentration, c_s, calculation from ¹H NMR data may be applied for other organisms experiencing extreme dehydration or for dry tissues. We recalculated the published elsewhere data for horse chestnut (Aesculus hippocastanum) bast [water-soluble solid fraction recognized as sucrose, c_s=(74.5±5.1)%]; and for Usnea antarctica, where c_s=0.81±0.04.     

Vibrational raman spectra of lipid systems containing amphotericin B

Resonance-enhanced and normal vibrational Raman spectra were observed for both multilamellar and single-wall vesicle assemblies of dimyristoyl phosphatidylcholine containing amphotericin B, a channel-forming polyene antibiotic, and cholesterol. The decrease in the frequency of the polyene antibiotic C  C stretching mode at 1556 cm^?1 and the increase in intensity of the CCH in-plane deformation mode at 1002 cm^?1 indicate that amphotericin B is ordered in a lipid-cholesterol medium similarly to the solid, but is surrounded by a slightly more polar environment. The intensity of the C  C stretching mode I₁₅₅₆ decreases 4-fold during the broadened gel to liquid crystalline phase transition (16–32°C) of dimyristoyl lecithin-cholesterol (4 : 1) multilayers. Other resonance-enhanced vibrations of amphotericin B exhibit similar behavior. For amphotericin B in pure dimyristoyl lecithin multilayer or vesicle systems, however, the vibrational intensity associated with the C  C stretching mode remains constant during the melting of lipid hydrocarbon chains. In addition, a third effect occurs in liquid crystalline egg lecithin-cholesterol (4 : 1, mol ratio) multilayers in which I₁₅₅₆ first increases by 25% between 3 and 25°C, in parallel with the loss of active channels, and then remains constant as the temperature increases from 25 to 42°C. This latter intensity pattern is masked in the dimyristoyl lecithin-cholesterol system by the overwhelming effect upon the C  C mode from changes in the lipid chain packing characteristics which occur during the phase transition.The broadened phase transition in 4 : 1 dimyristoyl lecithin-cholesterol multilayers (16–32°C), as followed by the ratio of intensities at 2880 and 2850 cm^?1 (asymmetric and symmetric methylene C-H stretching modes, respectively) is slightly narrowed by the addition of amphotericin B, and effect from which a binding stoichiometry at 24° of 1 : 1 amphotericin B : cholesterol is estimated. This stoichiometry was confirmed by differential calorimetric scans, which also show the presence of a peak proportional to cholesterol content.Raman I_2880/2850 peak height ratios in pure dimyristoyl lecithin bilayers were increased over the 14–38°C range by amphotericin B, a spectral effect which suggests an ordering of the lipid matrix perhaps as a consequence of the polyene binding to the bilayer surface. For bilayers containing cholesterol, the ratios of intensities of the 2935 cm^?1 feature, composed mainly of acyl chain terminal methyl and underlying methylene C-H stretching modes, to the 2850 cm^?1 feature are significantly increased by amphotericin B. This effect indicates that the antibiotic penetrates the bilayer in the lipid-sterol system.     

Estimation of <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> biomass concentration from chord length distribution data

A novel method to estimate the concentration of Chlamydomonas reinhardtii biomass was developed. The method employs the chord length distribution information gathered by means of a focused beam reflectance probe immersed in the culture sample and processes the data through a feedforward multilayer perceptron. The multilayer perceptron architecture was systematically optimised through the application of a simulated annealing algorithm. The method developed can predict the concentration of microalgae with acceptable accuracy and, with further development, it could be implemented online to monitor the aggregation status and biomass concentration of microalgal cultures.     

Formidable females redux:male social integration into female networks and the value of dynamic multilayer networks

The development of multilayer network techniques is a boon for researchers who wish to understand how different interaction layers might influence each other,and how these in turn might influence group dynamics.Here,we investigate how integration between male and female grooming and aggression interaction networks influences male power trajectories in vervet monkeys Chlorocebus pygerythrus.Our previous analyses of this phenomenon used a monolayer approach,and our aim here is to extend these analyses using a dynamic multilayer approach.To do so,we constructed a temporal series of male and female interaction layers.We then used a multivariate multilevel autoregression model to compare cross-lagged associations between a male's centrality in the female grooming layer and changes in male Elo ratings.Our results confirmed our original findings:changes in male centrality within the female grooming network were weakly but positively tied to changes in their Elo ratings.However,the multilayer network approach offered additional insights into this social process,identifying how changes in a male's centrality cascade through the other network layers.This dynamic view indicates that the changes in Elo ratings are likely to be short-lived,but that male centrality within the female network had a much stronger impact throughout the multilayer network as a whole,especially on reducing intermale aggression(i.e.,aggression directed by males toward other males).We suggest that multilayer social network approaches can take advantage of increased amounts of social data that are more commonly collected these days,using a variety of methods.Such data are inherently multilevel and multilayered,and thus offer the ability to quantify more precisely the dynamics of animal social behaviors.