Effects Of Group Density Research Articles

Adsorption of nickel (II) from aqueous solutions with clay-supported nano-scale zero-valent iron synthesized from green tea extract

Nano zerovalent iron (nZVI) supported adsorbents have been reported as suitable candidates for adsorption of water contaminants. However, the role of and interplay between surface chemistry, functional group density and textural properties has largely been unexplored. In this work, green tea derived nano zerovalent iron (nZVI) supported clay hybrid material (CnZVI) was used as a novel adsorbent for the removal of Ni2+ ions from water. The unmodified natural clay (Arg) and the CnZVI composite were characterized using FTIR, SEM, TGA and BET techniques. Incorporation of nZVI ameliorated the specific surface area from 16.88 to 30.46 m2/g, translating to ∼80 % increase. This translated to ∼69 % increase in maximum adsorption capacity from 8.47 to 14.38 mg/g, respectively. The addition of nZVI in the clay decreased the affinity (KF) for Ni2+ by ∼48 %. The disparity between the percent increase in surface area (∼80 %) and the adsorption capacity (∼69 %) implies the adsorption of Ni2+ was significantly controlled by textural properties compensating for the antagonistic effects of functional group density. The kinetic rates were best predicted by the pseudo-first-order and Elovich’s models for the Arg and CnZVI, respectively, implicit evidence of the role of surface chemistry. A maximum adsorption capacity of 14 mg/g was achieved for 100 mg Ni2+/L in 120 min for CnZVI.

Effect of surface hydroxyl group density of support membrane on water permeance of polyamide thin-film composite membrane

Polyamide-based thin-film composite (TFC) membranes are widely used in water treatment processes. Recently, the influence of support membranes on the performance of polyamide layers has garnered considerable attention. Regarding the chemical properties of the support membranes, the surface wettability and the interaction between the amine monomer used for interfacial polymerization and the membrane surface are considered to play crucial roles. In this study, we investigated the effect of the wettability of the support membrane surface and its interaction with the amine monomer on the water permeance of TFC membranes. We prepared TFC membranes on polyketone support membranes with varying surface hydroxyl group densities and aqueous solution wettabilities. While no clear correlation was observed between the support membrane's wettability and the water permeance of the TFC membrane, an increase in hydroxyl group density did result in higher water permeance. The hydroxyl groups interact with PIP, inhibiting PIP diffusion and potentially leading to the formation of a thinner polyamide layer, which enhances water permeance. Therefore, the interaction between the amine monomer and support membrane surface strongly affects the formation of the polyamide layer.

Effect of Polymer Architecture and Acidic Group Density on the Degree of Salt Formation in Amorphous Solid Dispersions.

Recent work has shown that an amorphous drug-polymer salt can be highly stable against crystallization under hot and humid storage conditions (e.g., 40 °C/75% RH) and provide fast release and that these advantages depend on the degree of salt formation. Here, we investigate the salt formation between the basic drug lumefantrine (LMF) and several acidic polymers: poly(acrylic acid) (PAA), hypromellose phthalate (HPMCP), hypromellose acetate succinate (HPMCAS), cellulose acetate phthalate (CAP), Eudragit L100, and Eudragit L100-55. Salt formation was performed by "slurry synthesis" where dry components were mixed at room temperature in the presence of a small quantity of an organic solvent, which was subsequently removed. This method achieved more complete salt formation than the conventional methods of hot-melt extrusion and rotary evaporation. The acidic group density of a polymer was determined by nonaqueous titration in the same solvent used for slurry synthesis; the degree of LMF protonation was determined by X-ray photoelectron spectroscopy. The polymers studied show very different abilities to protonate LMF when compared at a common drug loading, following the order PAA > (HPMCP ∼ CAP ∼ L100 ∼ L100-55) > HPMCAS, but the difference largely disappears when the degree of protonation is plotted against the concentration of the available acidic groups for reaction. This indicates that the extent of salt formation is mainly controlled by the acidic group density and is less sensitive to the polymer architecture. Our results are relevant for selecting the optimal polymer to control the degree of ionization in amorphous solid dispersions.

Mechanical behavior and failure mechanism of multilayer graphene oxides with various oxygen contents and functional types: A ReaxFF molecular dynamics simulation

An in-depth understanding about the failure mechanism of graphene oxide and its relationship with structure and temperature is essentially important to improve the mechanical properties of graphene oxides. In this work, a series of comparison groups have been established to investigate the effects of oxygen-containing functional group density, the number of layers, temperature, and hydroxyl to epoxy group ratio on the mechanical properties of monolayer and multilayer graphene oxides through ReaxFF molecular dynamics simulations. It is demonstrated that the position of functional group distribution plays a decisive role in the mechanical properties of graphene oxide. Meanwhile, the active thermal motion of atoms at high temperatures leads to a more fracture-prone structure, but the multilayer graphene oxide is less sensitive to temperature compared to monolayer graphene oxide. In addition, the structure with more hydroxyl groups has better mechanical properties because the distortion energy of the carbon skeleton caused by hydrogen groups is much smaller than that of epoxy groups. This study provides directions and possibilities for the optimization of the mechanical properties of graphene oxide.

Mineralization of calcium phosphate on two-dimensional polymer films with controllable density of carboxyl groups.

Two-dimensional polymers functionalized with controllable density of carboxyl groups were constructed with the Langmuir-Blodgett method. Mineralization of calcium phosphate shows significantly different characteristics on these films, which clearly indicates that the density of carboxy groups plays a determining role in controlling the nucleation and orientated growth of calcium phosphate.

Lack of fit with the neighbourhood social environment as a risk factor for psychosis - a national cohort study.

Many studies report an ethnic density effect whereby psychosis incidence among ethnic minority groups is higher in low co-ethnic density areas. It is unclear whether an equivalent density effect applies with other types of socioeconomic disadvantages. We followed a population cohort of 2 million native Danes comprising all those born on 1st January 1965, or later, living in Denmark on their 15th birthday. Socioeconomic disadvantage, based on parents' circumstances at age 15 (low income, manual occupation, single parent and unemployed), was measured alongside neighbourhood prevalence of these indices. Each indicator was associated with a higher incidence of non-affective psychosis which remained the same, or was slightly reduced, if neighbourhood levels of disadvantage were lower. For example, for individuals from a low-income background there was no difference in incidence for those living in areas where a low-income was least common [incidence rate ratio (IRR) 1.01; 95% confidence interval (CI) 0.93-1.10 v. those in the quintile where a low income was most common. Typically, differences associated with area-level disadvantage were the same whether or not cohort members had a disadvantaged background; for instance, for those from a manual occupation background, incidence was lower in the quintile where this was least v. most common (IRR 0.83; 95% CI 0.71-0.97), as it was for those from a non-manual background (IRR 0.77; 95% CI 0.67-0.87). We found little evidence for group density effects in contrast to previous ethnic density studies. Further research is needed with equivalent investigations in other countries to see if similar patterns are observed.

Interlayer spacing of multilayer graphene oxide: Influences of oxygen-containing group density, thickness, temperature and strain

Multilayer graphene oxide (GO) has shown promising applications in ion sieving, gas separation and water purification. However, accurate control of interlayer spacing is still the bottleneck of practical application. In this paper, molecular dynamic simulations have been conducted to reveal the effects of oxygen-containing group density, thickness, temperature and applied strain on the interlayer spacing of multilayer GO sheets systematically. It is found that the interlayer spacing of multilayer GO is positively correlated with oxygen-containing group density and temperature. The interlayer spacing between the outer layer and the secondary outer layer are smaller than these between the inner layers. The distance between inner layers change little with the thickness. When the oxygen-containing group density is below 20%, the interlayer spacing decreases slightly with the increasing strains, while it reaches 30%, the interlayer space decreases first and then recovers at a turning point with an applied strain of 6% owing to the breakage of C–C bond in epoxy groups. Our results would provide a guidance for interlayer spacing controlling and separation membrane designing.

Mental health consequences of minority political positions: The case of brexit

The group density effect, where a group member's psychiatric risk is associated with the proportion of the local population their group comprises, demonstrates the importance of minority group status to mental health. Previous research, focusing on ethnicity, has been correlational, but newly-formed identities provide opportunities for natural experiments, with greater scope for causal inference. This study examines whether such a group density effect can be found for the novel Brexit identities of 'leaver' and 'remainer' following the UK's divisive 2016 referendum on EU membership. Mixed effects models were fitted to the Understanding Society panel survey series (N=25,555, 19,767 for analyses controlling for pre-referendum mental health data), predicting mental health as a function of individual opinion on EU membership and local referendum results. These interacted such that those holding the local majority opinion had better mental health (Odds ratio (OR):875 [0.766- 0.9995]), compared to those in the minority. This result survived adjustment for individual and area-level economic circumstances (OR:866 [0.758-0.989]), and, strikingly, pre-referendum mental health (OR: 0.841 [0.709-0.998]), as well as a number of other potential confounding variables. The results provide evidence for rapidly forming group density effects based on de novo identities, and suggest that identity may be a causal mechanism for group density effects more broadly. They also speak to the extent of polarisation in the Brexit-era UK, and its public health consequences.

Free thiol groups on poly(aspartamide) based hydrogels facilitate tooth-derived progenitor cell proliferation and differentiation.

Cell-based tissue reconstruction is an important field of regenerative medicine. Stem and progenitor cells derived from tooth-associated tissues have strong regeneration potential. However, their in vivo application requires the development of novel scaffolds that will provide a suitable three-dimensional (3D) environment allowing not only the survival of the cells but eliciting their proliferation and differentiation. Our aim was to study the viability and differentiation capacity of periodontal ligament cells (PDLCs) cultured on recently developed biocompatible and biodegradable poly(aspartamide) (PASP)-based hydrogels. Viability and behavior of PDLCs were investigated on PASP-based hydrogels possessing different chemical, physical and mechanical properties. Based on our previous results, the effect of thiol group density in the polymer matrix on cell viability, morphology and differentiation ability is in the focus of our article. The chemical composition and 3D structures of the hydrogels were determined by FT Raman spectroscopy and Scanning Electron Microscopy. Morphology of the cells was examined by phase contrast microscopy. To visualize cell growth and migration patterns through the hydrogels, two-photon microscopy were utilized. Cell viability analysis was performed according to a standardized protocol using WST-1 reagent. PDLCs were able to attach and grow on PASP-based hydrogels. An increase in gel stiffness enhanced adhesion and proliferation of the cells. However, the highest population of viable cells was observed on the PASP gels containing free thiol groups. The presence of thiol groups does not only enhance viability but also facilitates the osteogenic direction of the differentiating cells. These cell-gel structures seem to be highly promising for cell-based tissue reconstruction purposes in the field of regenerative medicine.

Effect of Functional Group Density of Anion Exchange Resins on Removal of p-Toluene Sulfonic Acid from Aqueous Solution

Adsorption using anion exchange resins is an efficient method for the removal of aromatic sulfonic acids (ASAs) from industrial wastewater. In this study, a series of weak-base anion exchangers (SD1–SD5) were synthesized to investigate the effect of functional group density of resins on the adsorption of ASAs from wastewater containing competitive inorganic anions. p-Toluene sulfonic acid (PTSA) was selected as a target pollutant, and Na2SO4 was chosen as the competitive inorganic salt because of its widespread existence in industrial wastewater. Adsorption performances of these resins were evaluated and compared in terms of selectivity, kinetics, isotherms, regeneration, and dynamic adsorption behavior. Importantly, the PTSA uptake increased with the raising content of functional groups on resins in the absence of Na2SO4; however, in the presence of a high level of Na2SO4 (for example, ≥1%), a decrease in the functional group density could improve the adsorption capacity of resins for PTSA. Moreover, desorption and fixed bed column experiments were conducted in all resins, thereby confirming the effect of functional group density of resins on the PTSA adsorption in actual application. In brief, this research will provide a better understanding for the design and preparation of anion exchangers for the effective removal of ASA from wastewater.

Neighboring group density is more important than forest stand age to a threatened social woodpecker population

Effective conservation of group-living forest wildlife requires information on how forest age moderates population parameters. Relationships between forest age and demographics can guide long-term management for wildlife populations that are expanding in relatively young second-growth forests in response to ongoing habitat management. We examined how forest age moderates effects of group density on long-term trends in group size and fledgling production in the endangered red-cockaded woodpecker Dryobates borealis (RCW) on the Savannah River Site, SC (SRS). We used 32 years of RCW monitoring data and generalized additive models to: 1) model long-term changes in average RCW group size and fledgling production; and 2) model effects of neighboring group density and neighboring group sizes across a gradient of forest age within 800 m of a group's cavity tree cluster. Average fledgling production oscillated over 2–3 year periods, but longer term evaluation indicated oscillations dampened and average fledgling production slightly decreased over time. Average group size fluctuated abruptly over 2–3 year periods from 1985 to 1994, but longer term evaluation indicated a general increase in group sizes from 1985 to 1994, followed by declines from 1995 to 2007, and a steady increase after 2010. Average fledgling production increased in response to neighboring group density but decreased as neighboring group sizes increased. In contrast, average group sizes increased in response to greater neighboring group density and neighboring group sizes. Stand age did not affect these relationships. Collectively, these results suggest forest age does not directly moderate effects of neighboring group density or group sizes on long-term average group size and fledgling production in the SRS RCW population. Although forest structure has been linked to increased RCW group sizes and productivity, our results suggest that with ongoing habitat management, long-term changes in group size and fledgling production will be driven primarily by group density conditions rather than changing forest age.

Effects of group size and group density on trade‐offs in resource selection by a group‐territorial central‐place foraging woodpecker

Trade‐offs in resource selection by central‐place foragers are driven by the need to balance the benefits of selecting resources against the costs of travel from the central place. For group‐territorial central‐place foraging birds, trade‐offs in resource selection are likely to be complicated by a competitive advantage for larger groups at high group density that may limit accessibility of high‐quality distant resources to small groups. We used the group‐territorial, central‐place foraging Red‐cockaded Woodpecker Leuconotopicus borealis (RCW) as a case study to test predictions that increases in group density lead to differences in foraging distances and resource selection for groups of different sizes. We used GPS tracking and LiDAR‐derived habitat data to model effects of group size on foraging distances and selection for high‐quality pines (≥ 35.6 cm diameter at breast height (dbh)) and lower quality pines (25.4–35.6 cm dbh) by RCW groups across low (n = 14), moderate (n = 10) and high group density (n = 10) conditions. At low and moderate group density, all RCW groups selected distant high‐quality pines in addition to those near the central place because competition for resources was low. In contrast, at high group density, larger groups travelled further to select high‐quality pines, whereas smaller groups selected high‐quality pines only when they were close to the central place and, conversely, were more likely to select lower quality pines at greater distances from the central place. Selection for high‐quality pines only when close to the cavity tree cluster at high group density is important to long‐term fitness of small RCW groups because it allows them to maximize benefits from both territorial defence and selecting high‐quality resources while minimizing costs of competition. These relationships suggest that intraspecific competition at high group density entails substantive costs to smaller groups of territorial central‐place foragers by limiting accessibility of distant high‐quality foraging resources.

Evolutionary Cooperation in Networked Public Goods Game with Dependency Groups

Either in microlevel organizations or macrolevel societies, the individuals acquire benefits or payoffs by forming interdependency groups linked by common interests. Conducting research on the effects of interdependency groups on the evolution of cooperation could have a better understanding of the social dilemma problem. In this paper, we studied a spatial public goods game with nonlocal interdependency groups where each of participants is located in a two‐dimensional square lattice or Watts–Strogatz small‐world network with payoffs obtaining from the interactions with nearest neighbors. In terms of the enhancement factor, the effects of group density on the evolutionary cooperation can be quite different. For a low enhancement factor, the cooperation level is a nonmonotonic function with the varying density of interdependency groups in the system, which means a proper density of interdependency groups can best promote the cooperative level. For a moderate enhancement factor, a higher density of interdependency groups can always correspond to a higher cooperative level. However, if the enhancement factor is too high, a high density of interdependency groups can impede the evolutionary cooperation. We give the explanations for the different roles of group density of interdependency by using the transition probabilities of C players into D players as well as the reverse. Our findings are very helpful for the understanding of emergence cooperation as well as the cooperation regulation in the selfish individuals.

On the mechanism of water adsorption in carbon micropores – A molecular simulation study

Water adsorption in carbon micropores is of great practical interest because of its significant impact on the performance of carbonaceous adsorbents and because of the application of water as a molecular probe to characterize porous materials. The subject has also attracted much attention from theoreticians in the adsorption science community because of its unique adsorption behavior in contrast to that of simple gases. Here we have carried out a comprehensive Monte Carlo simulation to investigate the effects of functional group density, pore size and temperature on the adsorption of water in slit-like carbonaceous pores. The nucleation of water clusters, their growth and coalescence are the critical steps for water adsorption, and they have been studied over a wide range of conditions. We find that the transition from water clusters with a convex interface to ones with a concave interface, brought about by the coalescence of adjacent clusters, is the microscopic origin for hysteresis in water adsorption-desorption isotherms. We also find that the balance between energy and entropy, which changes in favor of entropy with increasing temperature, governs the onset of condensation and evaporation and hence the hysteresis observed in some isotherms.

Too Close to Speak Up? How Group Cohesion and Status Conflict Affect Group Voice

Although group network characteristics significantly influence a group’s capability to exchange and absorb knowledge by speaking up group members’ opinions, previous research on voice behavior has not yet fully addressed the social and relational factors in work groups that affect group- level voice. Specifically, in line with the “dark side of social capital” argument, this study examines the effects of group cohesion (i.e., network density) on group voice behavior, and further investigates when and how the effects occur. In addition, we believe these effects vary based on the group’s perception of status conflicts. Using data from 55 work groups, we found an inverted U-shaped relationship between group density and group voice behavior. Moreover, it was observed that the status conflict moderated the inverted-U effect of group density on group voice, such that: when status conflict is high, 1) overall level of group voice was reduced, 2) group voice turned to decrease faster on the downward side of the inverted-U curve. We discussed the theoretical and practical implications of these results with relation to effective group management.

Effects of Functional Group Density in Stylene-Divinylbenzene Copolymer Phase and of Supporting Electrolyte Concentration in Aqueous Phase on Performance of Iminodiacetate-type Chelating Resin in Terms of Contribution of Ion-Exchange Mechanism.

The effects of the functional group density in the stylene-divinylbenzene copoymer phase and of the supporting electrolyte concentration in the aqueous phase on the perfomance of the iminodiacetate (IDA)-type chelating resin were studied in terms of contribution of an ion-exchange mechanism. High hydrophobicity of the resin having a low functional group density interfered with penetration of aqueous solutions into the resin phase to slow the acid-base reaction and the adsorption reaction. Uptake of the cation in the supporting electrolyte into the resin phase was clearly indicated in each of two acid dissociation reactions. The high concentration of the supporting electrolyte enhanced acid dissociation of the IDA group, and a singly deprotonated species interacting with the supporting electrolyte cation strongly interfered with adsorption by the ion-exchange mechanism, while only slightly interfering with adsorption by the complexation. Both the complexed and ion-exchanged species respectively involving two or more IDA groups were destabilized to reduce the adsorption capacity of the resin having the low functional group density.

Social immunity in honeybees-Density dependence, diet, and body mass trade-offs.

Group living is favorable to pathogen spread due to the increased risk of disease transmission among individuals. Similar to individual immune defenses, social immunity, that is antiparasite defenses mounted for the benefit of individuals other than the actor, is predicted to be altered in social groups. The eusocial honey bee (Apis mellifera) secretes glucose oxidase (GOX), an antiseptic enzyme, throughout its colony, thereby providing immune protection to other individuals in the hive. We conducted a laboratory experiment to investigate the effects of group density on social immunity, specifically GOX activity, body mass and feeding behavior in caged honey bees. Individual honeybees caged in a low group density displayed increased GOX activity relative to those kept at a high group density. In addition, we provided evidence for a trade‐off between GOX activity and body mass: Individuals caged in the low group density had a lower body mass, despite consuming more food overall. Our results provide the first experimental evidence that group density affects a social immune response in a eusocial insect. Moreover, we showed that the previously reported trade‐off between immunity and body mass extends to social immunity. GOX production appears to be costly for individuals, and potentially the colony, given that low body mass is correlated with small foraging ranges in bees. At high group densities, individuals can invest less in social immunity than at low densities, while presumably gaining shared protection from infection. Thus, there is evidence that trade‐offs at the individual level (GOX vs. body mass) can affect colony‐level fitness.

Lingual tactile sensitivity: effect of age group, sex, and fungiform papillae density.

Despite its contribution to food perception, lingual tactile sensitivity has been understudied. We hypothesized that sensitivity to threshold and suprathreshold tactile stimuli varies in the population and sought to determine proximate sources of variability. Forty-eight adults were tested for lingual threshold sensitivity via a modified letter identification task and suprathreshold sensitivity via estimation of stimulus size using magnitude estimation. In addition, taste bud density on the anterior tip of each panelist's tongue was estimated by counting the number of fungiform papillae in a 0.317cm2 circumscribed area. Lingual tactile thresholds were significantly impacted by age group as subjects 40years or older had higher thresholds than those in their 20s. Moreover, threshold sensitivity increased with increasing fungiform papillae count. Suprathreshold estimates of size were not affected by age group, sex, or fungiform papillae count.

Minority status and mental distress: a comparison of group density effects.

It has been observed that mental disorders, such as psychosis, are more common for people in some ethnic groups in areas where their ethnic group is less common. We set out to test whether this ethnic density effect reflects minority status in general, by looking at three situations where individual characteristics differ from what is usual in a locality. Using data from the South East London Community Health study (n = 1698) we investigated associations between minority status (defined by: ethnicity, household status and occupational social class) and risk of psychotic experiences, common mental disorders and parasuicide. We used a multilevel logistic model to examine cross-level interactions between minority status at individual and neighbourhood levels. Being Black in an area where this was less common (10%) was associated with higher odds of psychotic experiences [odds ratio (OR) 1.34 95% confidence interval (CI) 1.07-1.67], and attempted suicide (OR 1.84 95% CI 1.19-2.85). Living alone where this was less usual (10% less) was associated with increased odds of psychotic experiences (OR 2.18 95% CI 0.91-5.26), while being in a disadvantaged social class where this was less usual (10% less) was associated with increased odds of attempted suicide (OR 1.33 95% CI 1.03-1.71). We found no evidence for an association with common mental disorders. The relationship between minority status and mental distress was most apparent when defined in terms of broad ethnic group but was also observed for individual household status and occupational social class.

Relative Contribution of Lateral Packing Density to Albumin Adsorption on Monolayers.

The effect of functional group density on protein adsorption is systematically studied to support ongoing efforts in molecular imprinting of surfaces and bulk materials. In these applications, functional commodity chemicals are molded to complement the shape and chemistry of the target molecule. Here, we study the relationship between bovine serum albumin adsorption and ligand density for carboxylate, alcohol, and alkyl terminal groups. Control surfaces consisting of densely packed self-assembled monolayers (SAMs) are contrasted with low-density SAMs formed through thiol-yne chemistry. Direct comparison consistently yielded greater protein adsorption on low-density SAMs than conventional pure component SAMs of the same functional group. Critically, the carboxylate and alcohol low-density SAMS are more hydrophobic than their analogous dense SAMs. Mixed functional group, dense SAMs were formed with alkyl diluents to match the hydrophobicity of the low-density SAMs. Once hydrophobicity is matched, the dense carboxylate and alcohol SAMs have higher adsorption than the low-density SAMs. We conclude (1) surface charge and hydrophobicity trends dominate over surface density contributions; (2) when hydrophobicity is matched, greater adsorption occurs on dense hydrophilic groups than on lower density hydrophilic groups; (3) when hydrophobicity is matched, greater adsorption occurs on lower density hydrophobic groups than on higher density hydrophobic groups.