Effects Of Group Density Research Articles

Effects of group density, hunting, and temperature on the singing patterns of eastern hoolock gibbons (Hoolock leuconedys) in Gaoligongshan, Southwest China.

Many non-human primates produce species-specific loud calls to communicate within and between groups over long distances. Understanding these calling patterns can provide insights into how individuals modify their behavior in response to environmental variables as well as help to design efficient bioacoustic survey techniques. Eastern hoolock gibbons in Gaoligongshan inhabit the coldest habitat of all gibbon populations, but both conservation and research efforts on this population have been minimal. We studied singing patterns of two habituated and two unhabituated groups at two sites in Gaoligongshan between July 2010 and June 2015. We systematically collected data of their calls, and its relationship to temperature, group density, and hunting pressure over at least 1 year for each group. Our goal was to elucidate how these factors affect singing patterns of eastern hoolock gibbons. We found that adult pairs coordinated their singing to produce duet bouts that lasted for an average of 25.5 min. The singing rate (number of bouts/number on monitoring days*100%: 7.5-31.4%) was notably lower than other gibbon populations, presumably due to low group density (about 0.5 groups/km(2) ) and prevalence of hunting at the study site. Cold temperature also affected gibbons' singing behavior. Our study groups called, on average, 2.5 hr after sunrise, probably foraging first in the early morning after long nights in this cold habitat delayed singing. Furthermore, mean temperatures in the morning (8:00-12:00 am) were higher on singing days than on non-singing days, and one group called less frequently when monthly mean temperature was below 10°C. Our findings indicate that both hunting pressure from humans and low temperatures suppress calling behavior in hoolock gibbons. Such information is critical in evaluating the use of duetting as a monitoring technique for this endangered gibbon species. Am. J. Primatol. 78:861-871, 2016. © 2016 Wiley Periodicals, Inc.

Transition from Bioinert to Bioactive Material by Tailoring the Biological Cell Response to Carboxylated Nanocellulose.

This work presents an insight into the relationship between cell response and physicochemical properties of Cladophora cellulose (CC) by investigating the effect of CC functional group density on the response of model cell lines. CC was carboxylated by electrochemical TEMPO-mediated oxidation. By varying the amount of charge passed through the electrolysis setup, CC materials with different degrees of oxidation were obtained. The effect of carboxyl group density on the material's physicochemical properties was investigated together with the response of human dermal fibroblasts (hDF) and human osteoblastic cells (Saos-2) to the carboxylated CC films. The introduction of carboxyl groups resulted in CC films with decreased specific surface area and smaller total pore volume compared with the unmodified CC (u-CC). While u-CC films presented a porous network of randomly oriented fibers, a compact and aligned fiber pattern was depicted for the carboxylated-CC films. The decrease in surface area and total pore volume, and the orientation and aggregation of the fibers tended to augment parallel to the increase in the carboxyl group density. hDF and Saos-2 cells presented poor cell adhesion and spreading on u-CC, which gradually increased for the carboxylated CC as the degree of oxidation increased. It was found that a threshold value in carboxyl group density needs be reached to obtain a carboxylated-CC film with cytocompatibility comparable to commercial tissue culture material. Hence, this study demonstrates that a normally bioinert nanomaterial can be rendered bioactive by carefully tuning the density of charged groups on the material surface, a finding that not only may contribute to the fundamental understanding of biointerface phenomena, but also to the development of bioinert/bioactive materials.

Facile crosslinking synthesis of hyperbranch-substrate nanonetwork magnetite nanocomposite for the fast and highly efficient removal of lead ions and anionic dyes from aqueous solutions

The aim of the present work was to investigate the effect of surface functional group density on the adsorption behaviors of functionalized mesoporous Fe3O4.

Flocking of multi-agent systems with multiplicative and independent measurement noises

We investigate the effect of noise and group density on the emergence of flocking in a stochastic Cucker–Smale type system. We consider the independent and multiplicative measurement noise and derive sufficient conditions for flocking and non-flocking in terms of the noise intensity and group density. We report that, in noise environments, it is rather easy for the group with high density to form and maintain ordered group motion. Moreover, we find that, under the perturbation of multiplicative noise, systems with weak coupling can tolerate relatively strong perturbation of noise.

Effects of surface hydroxyl group density on the photocatalytic activity of Fe3+-doped TiO2

The aim of the work is to study the effects of oxygen vacancy and surface hydroxyl group density on the photocatalytic activity of Fe3+-doped TiO2, and to investigate how the titanium dioxide doped with different levels of the Fe3+ influenced their physical and chemical characterizations. The photocatalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), electron spin resonance (ESR), X-ray photoelectron spectroscope (XPS) and Fourier transform infrared (FTIR) spectra. The results revealed that adsorbed hydroxyl group density significantly influenced the photocatalytic activity, and a small amount of Fe3+ can act as a photo-generated hole and a photo-generated electron trap and inhibit the electron–hole recombination. The 0.10%-Fe3+-TiO2 with the highest surface hydroxyl group density revealed the maximum rate constant of 0.716 and the optimal photocatalytic degradation of MB. As Fe3+ doping levels are larger than 0.10%, the cluster of FeTi′–V¨O–FeTi′ generated gradually. This implied that an excessive amount of Fe3+ doped into TiO2 is detrimental to the photocatalytic activity due to the formation of FeTi′–V¨O–FeTi′ clusters and enhances the recombination of photogenerated electrons and holes.

Is ethnic density associated with risk of child pedestrian injury? A comparison of inter-census changes in ethnic populations and injury rates

Objectives. Research on inequalities in child pedestrian injury risk has identified some puzzling trends: although, in general, living in more affluent areas protects children from injury, this is not true for those in some minority ethnic groups. This study aimed to identify whether ‘group density’ effects are associated with injury risk, and whether taking these into account alters the relationship between area deprivation and injury risk. ‘Group density’ effects exist when ethnic minorities living in an area with a higher proportion of people from a similar ethnic group enjoy better health than those who live in areas with a lower proportion, even though areas with dense minority ethnic populations can be relatively more materially disadvantaged.Design. This study utilised variation in minority ethnic densities in London between two census periods to identify any associations between group density and injury risk. Using police data on road traffic injury and population census data from 2001 to 2011, the numbers of ‘White,’ ‘Asian’ and ‘Black’ child pedestrian injuries in an area were modelled as a function of the percentage of the population in that area that are ‘White,’ ‘Asian’ and ‘Black,’ controlling for socio-economic disadvantage and characteristics of the road environment.Results. There was strong evidence (p < 0.001) of a negative association between ‘Black’ population density and ‘Black’ child pedestrian injury risk [incidence (of injury) rate ratios (IRR) 0.575, 95% CI 0.515–0.642]. There was weak evidence (p = 0.083) of a negative association between ‘Asian’ density and ‘Asian’ child pedestrian injury risk (IRR 0.901, 95% CI 0.801–1.014) and no evidence (p = 0.412) of an association between ‘White’ density and ‘White’ child pedestrian injury risk (IRR 1.075, 95% CI 0.904–1.279). When group density effects are taken into account, area deprivation is associated with injury risk of all ethnic groups.Conclusions. Group density appears to protect ‘Black’ children living in London against pedestrian injury risk. These findings suggest that future research should focus on structural properties of societies to explain the relationships between minority ethnicity and risk.

Living on the edge: Effects of body size, group density and microhabitat selection on escape behaviour of southern leopard frogs Lithobates sphenocephalus

Abstract Models of optimal escape strategy predict that animals should move away when the costs of fleeing (metabolic and opportunity costs) are outweighed by the costs of remaining. These theoretical models predict that more vulnerable individuals should be more reactive, moving away when an approaching threat is further away. We tested whether escape behaviour (including ‘escape calling’) of Lithobates sphenocephalus approached by a human was influenced by body size or the initial microhabitat that the individual was found in. Irrespective of their size, frogs in the open tended to remain immobile, enhancing their crypsis. Frogs in cover showed different responses according to their body size, but, contrary to our initial predictions, larger frogs showed greater responsiveness (longer flight initiation distance and distances fled) than small frogs. Small frogs tended to remain closer to water and escaped into water, while larger individuals were more likely to jump to terrestrial cover and call during escape. Density of frogs near the focal animal had no effect on escape behaviour. This study indicates a range of escape responses in this species and points to the importance of divergent escape choices for organisms which live on the edge of different environments.

Ab initio metadynamics study on hydronium ion dynamics at acid-functionalized interfaces: effect of surface group density.

This article presents an ab initio metadynamics study of elementary hydronium ion transitions at dense arrays of surface groups with sulfonic acid head groups. Calculations simulate minimally hydrated conditions of the interfacial ionic system. The specific focus is on the influence of the surface group density on hydronium ion transport. Results reveal a high sensitivity of the activation free energy of hydronium translocations to the surface group density. A spontaneous concerted transition with low activation barrier is found at a surface group separation of 6.8 Å. When hydroniums translocate concertedly, the activation barrier of the transition drops by more than a factor of two to the value of 0.25 eV. An approach is presented to determine interaction constants of hydronium ions and anionic surface groups as well as the surface group flexibility from the analysis of frequency spectra. These properties are discussed in the context of a recently developed soliton theory of interfacial proton transport.

Energetics of formation and hydration of functionalized silica nanoparticles: An atomistic computational study

The energetics of formation and hydration of functionalized silica nanoparticles were studied using a combination of first-principles calculations based on density functional theory with van der Waals dispersion correction and molecular dynamics. The energetics and effects of group density were evaluated in both; hydrophilic (ethylene-glycol) and hydrophobic (sulfonic) organosilane functional groups, and the optimum group density were obtained in vacuum and aqueous environment. The functional group bounded in a geminal silanol site was found to be more stable than silanol one, by ∼1.30 and ∼1.32eV for hydrophilic and hydrophobic groups, respectively. In vacuum, an optimum graft density of 4.2 and 4.5groups/nm2 was obtained for hydrophobic and hydrophilic coverage, based on molecular dynamics calculations. Interestingly, a double well energy profile is obtained when functionalized nanoparticles are placed within aqueous media, and those minima for hydrophilic groups appear at lower coverage compared to hydrophobic one. The double energy minima is explained by the H2O molecules arrangement as function of the group density on nanoparticles surface. At low coverage, H2O molecules surround the groups while at high coverage, the functional groups shield the molecules to penetrate within the groups and the size effect of the functional group studied here was found to be negligible on the stability.

Mechanical reinforcement of polyethylene using n- alkyl group-functionalized multiwalled carbon nanotubes: Effect of alkyl group carbon chain length and density

Polyethylene (PE) is one of the most produced synthetic resins in the world. Functionalized multiwalled carbon nanotube (MWCNT) is a potential nanoscale filler to realize the next generation strong and multifunctional PE composites. We demonstrate that MWCNTs grafted with short n-alkyl groups are effective nanofillers for mechanical reinforcement of PE composites. At 1 wt% filler loading, the yield stress and Young’s modulus improve significantly up to 54 and 63% compared with neat PE, respectively. Among ductile properties, tensile strength increases up to 30%; ultimate strain is preserved; and toughness increases up to 33%. More important, we show that short n-alkyl groups can be grafted on MWCNTs much easier than long chain polymers. Further, we find that alkyl groups of C14‐C18 chains have the optimum length for reinforcement. The optimum density of grafted alkyl groups is around 0.390‐0.423 lmol/mg when the C14 alkyl groups are used. Overall, the results manifest that MWCNTs grafted with n-alkyl groups with suitable length and density are efficient nanoscale fillers for high-performance PE composites. POLYM. ENG. SCI., 54:336‐344, 2014. a 2013 Society of Plastics Engineers

Improved Antifouling Properties of Polyamide Nanofiltration Membranes by Reducing the Density of Surface Carboxyl Groups

Carboxyls are inherent functional groups of thin-film composite polyamide nanofiltration (NF) membranes, which may play a role in membrane performance and fouling. Their surface presence is attributed to incomplete reaction of acyl chloride monomers during the membrane active layer synthesis by interfacial polymerization. In order to unravel the effect of carboxyl group density on organic fouling, NF membranes were fabricated by reacting piperazine (PIP) with either isophthaloyl chloride (IPC) or the more commonly used trimesoyl chloride (TMC). Fouling experiments were conducted with alginate as a model hydrophilic organic foulant in a solution, simulating the composition of municipal secondary effluent. Improved antifouling properties were observed for the IPC membrane, which exhibited lower flux decline (40%) and significantly greater fouling reversibility or cleaning efficiency (74%) than the TMC membrane (51% flux decline and 40% cleaning efficiency). Surface characterization revealed that there was a substantial difference in the density of surface carboxyl groups between the IPC and TMC membranes, while other surface properties were comparable. The role of carboxyl groups was elucidated by measurements of foulant-surface intermolecular forces by atomic force microscopy, which showed lower adhesion forces and rupture distances for the IPC membrane compared to TMC membranes in the presence of calcium ions in solution. Our results demonstrated that a decrease in surface carboxyl group density of polyamide membranes fabricated with IPC monomers can prevent calcium bridging with alginate and, thus, improve membrane antifouling properties.

Trace adsorption of positively charged proteins onto Sepharose FF and Sepharose FF-based anion exchangers

Agarose-based matrices have been widely used in ion exchange chromatography (IEC). We have herein observed that positively charged proteins (lysozyme and cytochrome c) are adsorbed on the agarose-based anion-exchangers (Q and DEAE Sepharose FF gels) in a capacity of 10–40μg/mL. In contrast, negatively charged protein (bovine serum albumin) is not adsorbed to Sepharose FF and SP Sepharose FF gels. Elemental analysis of the gel indicated that the residual anionic sulfate groups in agarose would have worked as the cation exchange groups for the positively charged proteins. The trace adsorption behavior of lysozyme onto Sepharose FF and Sepharose FF-based anion exchangers was studied and the effects of NaCl concentration and cation group density on the adsorption were examined for better understanding of the trace adsorption in chromatographic processes. At NaCl concentrations less than 0.05mol/L, which is the normal adsorption condition in IEC, the trace adsorption kept at a high level, so this trace adsorption cannot be avoided in the ionic strength range of routine IEC operations. Grafting poly(ethylenimine) (PEI) chain of 60kDa to a cation group density of 700mmol/L could reduce the adsorption capacity to about 20μg/mL, but further reduction was not possible by increasing the cation group density to 1200mmol/L. Therefore, attentions need to be paid to the phenomenon in protein purification practice using agarose-based matrices. The research is expected to call attentions to the trace adsorption on agarose-based matrices and to the importance in the selection of the suitable solid matrices in the production of high-purity protein products in large-scale bioprocesses.

Assessing food appeal and desire to eat: the effects of portion size & energy density.

BackgroundVisual presentation of food provides considerable information such as its potential for palatability and availability, both of which can impact eating behavior.MethodsWe investigated the subjective ratings for food appeal and desire to eat when exposed to food pictures in a fed sample (n = 129) using the computer paradigm ImageRate. Food appeal and desire to eat were analyzed for the effects of food group, portion size and energy density of the foods presented as well as by participant characteristics.ResultsFood appeal ratings were significantly higher than those for desire to eat (57.9 ± 11.6 v. 44.7 ± 18.0; p < 0.05). Body mass index was positively correlated to desire to eat (r = 0.20; p < 0.05), but not food appeal. Food category analyses revealed that fruit was the highest rated food category for both appeal and desire, followed by discretionary foods. Additionally, overweight individuals reported higher ratings of desire to eat large portions of food compared to smaller portions (p < 0.001), although these effects were relatively small. Energy density of the foods was inversely correlated with ratings for both appeal and desire (r's = - 0.27; p's < 0.01).ConclusionsResults support the hypothesis that individuals differentiate between food appeal and desire to eat foods when assessing these ratings using the same type of metric. Additionally, relations among food appeal and desire to eat ratings and body mass show overweight individuals could be more responsive to visual foods cues in a manner that contributes to obesity.

Effect of amino group density for prevention of mammary gland tissue detachment from coated glass surface

Tissue detachment from histological glass slides coated with different amino group densities was investigated during heat treatment for immunohistochemical staining. In both sow and piglet mammary gland tissues, the results clearly showed strong adhesion and high retention on self-assembled monolayers with high amino group density.

Effect of Chelating Group Density of Crosslinked Graft Chain on Dynamic Binding Capacity for Metal Ions

多孔性シートにグラフトした架橋高分子鎖にイミノ二酢酸（IDA）基を導入した。エポキシ基をもつモノマーとしてグリシジルメタクリレートおよび架橋剤としてエチレングリコールジメタクリレートを多孔性シートに共グラフト重合し，引き続きイミノ二酢酸二ナトリウムによってエポキシ基を開環した。エチレングリコールジメタクリレートの仕込みモル分率を 1.0～6.0% の範囲で変えた。500 mg/L 塩化銅イオン溶液を，得られたキレート多孔性シートに滞留時間 10 秒で透過した。IDA 基密度 1.7 mmol/g である架橋型キレート多孔性シートの銅イオンの動的吸着容量は，非架橋型キレート多孔性シートのそれの 1.7 倍となった。この動的吸着容量の向上は，グラフト鎖の架橋によって，吸着した銅イオンが吸着量勾配にしたがってシート厚方向に拡散移動する現象を抑制するためである。架橋型キレート多孔性シートの動的吸着容量は，空間速度の増加とともに減少した。これは，細孔内での銅イオンの細孔半径方向の拡散移動時間が，多孔性シート内での銅イオン溶液の滞留時間と比較して無視できないことを示している。

Expanding the Scope of Conflict: Interest Groups and Interstate Compacts*

Objective. This study looks at how the characteristics of states' interest group environments affect state participation in interstate compacts. Drawing on prominent theories of interest system characteristics, we hypothesize that interest group density and concentration will influence a state's propensity to join compacts. Method. Using pooled cross-sectional time-series event-count models, we test our hypotheses for 48 states over a 30-year period. Results. We find that states with denser interest group systems are more likely to join interstate compacts, but that greater concentration of organized interests in a few economic sectors impedes compact formation. Additional analyses show that the effects of state interest group systems vary across types of interest groups and compacts. In particular, the effects of interest group density appear to be driven primarily by not-for-profit groups generating increased state participation in noneconomic compacts. Conclusion. Interstate cooperation is influenced in important ways by characteristics of interest group environments.

Separating the impact of group size, density, and enclosure size on broiler movement and space use at a decreasing perimeter to area ratio

The goal of this study was to determine the impact of enclosure size on space use and movement patterns of domestic fowl (Gallus gallus domesticus), independent of group size and density. Research designed to estimate the effects of group size, density, or enclosure size involves inherent confounding between factors, clouding their individual effects. This experimental design enabled us to conduct multiple contrasts in order to tease apart the specific impacts. Treatments consisted of five combinations of three square enclosures: small (S; 1.5m(2)), medium (M; 3.0m(2)), and large (L; 4.5m(2)), and three group sizes of 10, 20, and 30 birds. We made comparisons while holding group size constant, holding density constant, and the third while maintaining a constant enclosure size. Nearest neighbor distances increased with enclosure size but appeared to be constrained by density. Net displacement and minimum convex polygons increased with enclosure size regardless of group size or density. We found no evidence of social restriction on space use. Results indicate that broilers adapted their use of space and movement patterns to the size of the enclosures, spreading out and utilizing a greater amount of space when it was available.

Disentangling the effects of group size and density on shoaling decisions of three-spined sticklebacks (Gasterosteus aculeatus)

Many animals live in groups most of their life. One function of this behaviour is an increased predator protection whereas larger groups provide better protection than smaller ones. A causal explanation is that due to a higher number of shoal members the individual risk of being predated will decrease (“dilution effect”). Additionally, shoaling leads to increased predator confusion. This “confusion effect” can be strengthened by an increased group density, which often correlates with group size. Many studies found that individuals prefer the larger of two groups. However, whether this preference is due to a larger group size or because of an increased density of the larger group remained unclear. To disentangle these factors we gave three-spined sticklebacks (Gasterosteus aculeatus) the choice between shoals of (1) different group size and density, (2) different group size, but equal density and (3) equal group sizes, but different densities. As expected, test fish preferred the larger and denser shoal over the smaller, less dense one. This preference was lost when shoal size differed but density was kept constant. When shoal size was equal but density differed, test fish preferred the less dense shoal. However, this was only the case when test fish chose between two relatively dense shoals. On the other hand, when overall density was low, test fish did not discriminate between shoals of different densities. This result may be explained in terms of predator avoidance. The results show that shoaling preferences might not always be influenced by a higher number of group members but also by the density and cohesiveness of the respective groups.

Disentangling the effects of group size and density on shoaling decisions of three-spined sticklebacks (Gasterosteus aculeatus)

Disentangling the effects of group size and density on shoaling decisions of three-spined sticklebacks (Gasterosteus aculeatus)

The effects of group size, leaf size, and density on the performance of a leaf‐mining moth

1. The effects of two factors, leaf size and group size, on the performance of the Tupelo leafminer, Antispila nysaefoliella (Lepidoptera: Heliozelidae), were examined by fitting growth models to mine expansion data using nonlinear mixed-effects models. 2. The rate of mine expansion served as a proxy for larval performance because of its correlation with both feeding activity and growth rate and is also the means by which a larva achieves its final mine size (or total consumption). 3. Leaf size was used as a measure of resource availability, and was expected to reduce the impact of resource competition and enhance larval performance. 4. In contrast to the unidirectional effects expected for leaf size (i.e. more resources should enhance performance), the direction for the effects of group size was expected to depend on the mechanism(s) driving the effect. For example, if there is resource competition among larvae in a group, then this could increase the feeding rates of some larvae or reduce the total consumption of others. However, if leaf mining induces host plant chemical defences, then larger groups might elicit a greater defensive response by the host plant (at the leaf), and hence, be characterized by reduced feeding and growth rates. 5. To investigate these interactions, two growth models, the Gompertz model and a modified version of the von Bertalanffy growth equation, were fitted to time series of the sizes of individual leaf mines using nonlinear mixed-effects models. Linear and nonlinear associations of each factor (group size or leaf size) with model parameters were then evaluated using a hierarchical testing procedure by determining: (i) whether inclusion of the factor produced a better-fit model, and (ii) if it did, the form of that relationship (i.e. linear or nonlinear). 6. Three patterns were detected with these analyses. (i) Leaf size had a significant positive, linear relationship with mine expansion rate. (ii) Group size had a significant quadratic relationship with mine expansion rate. (iii) The effects of leaf and group size on the maximum mine size were opposite to those found with growth rate.