Non-monotonic Fashion Research Articles

Spatial interactions and cooperation can change the speed of evolution of complex phenotypes.

Complex traits arise from the interactions among multiple gene products. In the case where the complex phenotype is separated from the wild type by a fitness valley or a fitness plateau, the generation of a complex phenotype may take a very long evolutionary time. Interestingly, the rate of evolution depends in nontrivial ways on various properties of the underlying stochastic process, such as the spatial organization of the population and social interactions among cells. Here we review some of our recent work that investigates these phenomena in asexual populations. The role of spatial constraints is quite complex: there are realistic cases where spatial constrains can accelerate or delay evolution, or even influence it in a nonmonotonic fashion, where evolution works fastest for intermediate-range constraints. Social interactions among cells can be studied in the context of the division-of-labor games. Under a range of circumstances, cooperation among cells can lead to a relatively fast creation of a complex phenotype as an emerging (distributed) property. If we further assume the presence of cheaters, we observe the emergence of a fully mutated population of cells possessing the complex phenotype. Applications of these ideas to cancer initiation and biofilm formation in bacteria are discussed.

0224 Direct exposure to metalworking fluid aerosols and chronic obstructive pulmonary disease in a cohort of U.S. automotive industry workers

ObjectivesExposure to metalworking fluid (MWF) causes respiratory outcomes such as asthma and chronic bronchitis, as well as symptoms including phlegm and wheezing. Chronic obstructive pulmonary disease (COPD) encompasses these outcomes,...

Melody Recognition in Dichotic Listening With or Without Frequency-Place Mismatch

The purpose of the study was to examine recognition of degraded melodic stimuli in dichotic listening with or without frequency-place mismatch. Melodic stimuli were noise vocoded with various number-of-channel conditions in a dichotic and monaural processor. In the dichotic zipper processor, the odd-indexed channels were tonotopically matched and presented to the left ear while the even-indexed channels were tonotopically matched or upward shifted in frequency and presented to the right ear. In the monaural processor, all channels either unshifted or shifted were presented to the left ear alone. Familiar melody recognition was measured in 16 normal-hearing adult listeners. Performance for dichotically presented melodic stimuli did not differ from that for monaurally presented stimuli even with low spectral resolution (8 channels). With spectral shift introduced in one ear, melody recognition decreased with increasing spectral shift in a nonmonotonic fashion. With spectral shift, melody recognition in dichotic listening was either not different or superior in a few cases relative to the monaural condition. With no spectral shift, cohesive fusion of dichotically presented melodic stimuli did not seem to depend on spectral resolution. In spectrally shifted conditions, listeners may have suppressed the partially shifted channels in the right ear and selectively attended only to the unshifted ones, resulting in dichotic advantages for melody recognition in some cases.

Temperature Dependence of Hydrophobic Hydration Dynamics: From Retardation to Acceleration

The perturbation induced by a hydrophobic solute on water dynamics is essential in many biochemical processes, but its mechanism and magnitude are still debated. A stringent test of the different proposed pictures is provided by recent NMR measurements by Qvist and Halle (J. Am. Chem. Soc. 2008, 130, 10345-10353) which showed that, unexpectedly, the perturbation changes in a non-monotonic fashion when the solution is cooled below room temperature. Here we perform and analyze molecular dynamics simulations of a small paradigm amphiphilic solute, trimethylamine N-oxide (TMAO), in dilute aqueous solutions over the 218-350 K temperature range. We first show that our simulations properly reproduce the non-monotonic temperature dependence. We then develop a model which combines our previously suggested entropic excluded-volume effect with a perturbation factor arising from the difference between local structural fluctuations in the shell and the bulk. Our model provides a detailed molecular understanding of the hydrophobic perturbation over the full temperature range investigated. It shows that the excluded-volume factor brings a dominant temperature-independent contribution to the perturbation at all temperatures, and provides a very good approximation at room temperature. The non-monotonic temperature dependence of the perturbation is shown to arise from the structural factor and mostly from relative shifts between the shell and bulk distributions of local structures, whose amplitude remains very small compared to the widths of those distributions.

The Evolution of Age-Dependent Plasticity

When organisms encounter environments that are heterogeneous in time, phenotypic plasticity is often favored by selection. The degree of such plasticity can vary during an organism's lifetime, but the factors promoting differential plastic responses at different ages or life stages remain poorly understood. Here we develop and analyze an evolutionary model to investigate how environmental information is optimally collected and translated into phenotypic adjustments at different ages. We demonstrate that plasticity must often be expected to vary with age in a nonmonotonic fashion. Early in life, it is generally optimal to delay phenotypic adjustments until sufficient information has been collected about the state of the environment to warrant a costly phenotypic adjustment. Toward the end of life, phenotypic adjustments are disfavored as well because their beneficial effects can no longer be fully reaped before death. Our analysis clarifies how patterns of age-dependent plasticity are shaped by the interplay of environmental uncertainty, the accuracy of perceived information, and the costs of phenotypic adjustments with life-history determinants such as the relative strengths of fecundity and viability selection experienced by the organism over its lifetime. We conclude by comparing our results with expectations for alternative mechanisms, including developmental constraints, that promote age-dependent plasticity.

Circulating levels of perfluoroalkyl substances and prevalent diabetes in the elderly

Several environmental contaminants, such as polychlorinated biphenyls, dioxins, bisphenol A and phthalates, have been linked to diabetes. We therefore investigated whether other kinds of contaminants, perfluoroalkyl substances (PFAS), also called perfluorinated compounds (PFCs), are also associated with diabetes. The Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study investigated 1,016 men and women aged 70 years. Seven PFAS were detected in almost all participant sera by ultra-high performance liquid chromatograph/tandem mass spectrometry. Diabetes was defined as use of hypoglycaemic agents or fasting glucose >7.0 mmol/l. 114 people had diabetes. In the linear analysis, no significant relationships were seen between the seven PFAS and prevalent diabetes. However, inclusion of the quadratic terms of the PFAS revealed a significant non-linear relationship between perfluorononanoic acid (PFNA) and diabetes, even after adjusting for multiple confounders (OR 1.96, 95% CI 1.19, 3.22, p = 0.008 for the linear term and OR 1.25, 95% CI 1.08, 1.44, p = 0.002 for the quadratic term). Perfluorooctanoic acid (PFOA) also showed such a relationship (p = 0.01). PFOA was related to the proinsulin/insulin ratio (a marker of insulin secretion), but none of the PFAS was related to the HOMA-IR (a marker of insulin resistance) following adjustment for multiple confounders. PFNA was related to prevalent diabetes in a non-monotonic fashion in this cross-sectional study, supporting the view that this perfluoroalkyl substance might influence glucose metabolism in humans at the level of exposure seen in the general elderly population.

Nonstatistical dynamics on potentials exhibiting reaction path bifurcations and valley-ridge inflection points

We study reaction dynamics on a model potential energy surface exhibiting post-transition state bifurcation in the vicinity of a valley ridge inflection (VRI) point. We compute fractional yields of products reached after the VRI region is traversed, both with and without dissipation. It is found that apparently minor variations in the potential lead to significant changes in the reaction dynamics. Moreover, when dissipative effects are incorporated, the product ratio depends in a complicated and highly non-monotonic fashion on the dissipation parameter. Dynamics in the vicinity of the VRI point itself play essentially no role in determining the product ratio, except in the highly dissipative regime.

Clustering of modifiable biobehavioral risk factors for chronic disease in US adults: a latent class analysis

Examining the co-occurrence patterns of modifiable biobehavioral risk factors for deadly chronic diseases (e.g. cancer, cardiovascular disease, diabetes) can elucidate the etiology of risk factors and guide disease-prevention programming. The aims of this study were to (1) identify latent classes based on the clustering of five key biobehavioral risk factors among US adults who reported at least one risk factor and (2) explore the demographic correlates of the identified latent classes. Participants were respondents of the National Epidemiologic Survey of Alcohol and Related Conditions (2004-2005) with at least one of the following disease risk factors in the past year (N = 22,789), which were also the latent class indicators: (1) alcohol abuse/dependence, (2) drug abuse/dependence, (3) nicotine dependence, (4) obesity, and (5) physical inactivity. Housing sample units were selected to match the US National Census in location and demographic characteristics, with young adults oversampled. Participants were administered surveys by trained interviewers. Five latent classes were yielded: 'obese, active non-substance abusers' (23%); 'nicotine-dependent, active, and non-obese' (19%); 'active, non-obese alcohol abusers' (6%); 'inactive, non-substance abusers' (50%); and 'active, polysubstance abusers' (3.7%). Four classes were characterized by a 100% likelihood of having one risk factor coupled with a low or moderate likelihood of having the other four risk factors. The five classes exhibited unique demographic profiles. Risk factors may cluster together in a non-monotonic fashion, with the majority of the at-risk population of US adults expected to have a high likelihood of endorsing only one of these five risk factors.

Evidence for the utricular origin of the vestibular short-latency-evoked potential (VsEP) to bone-conducted vibration in guinea pig

Previous studies have shown that the vestibular short-latency-evoked potential (VsEP) in response to the brief head acceleration stimulus is a compound action potential of neurons innervating the otolith organs. However, due to the lack of direct evidence, it is currently unclear whether the VsEP is primarily generated by the activity of utricular or saccular afferent neurons, or some mixture of the two. Here, we investigated the origin of the VsEP evoked by brief bone-conducted vibration pulses in guinea pigs, using selective destruction of the cochlea, semicircular canals (SCCs), saccule, or utricle, along with neural blockade with tetrodotoxin (TTX) application, and mechanical displacements of the surgically exposed utricular macula. To access each end organ, either a dorsal or a ventral surgical approach was used. TTX application abolished the VsEP, supporting the neurogenic origin of the response. Selective cochlear, SCCs, or saccular destruction had no significant effect on VsEP amplitude, whereas utricular destruction abolished the VsEP completely. Displacement of the utricular membrane changed the VsEP amplitude in a non-monotonic fashion. These results suggest that the VsEP evoked by BCV in guinea pigs represents almost entirely a utricular response. Furthermore, it suggests that displacements of the utricular macula may alter its response to bone-conduction stimuli.

Quasistatic rheology and microstructural description of sheared granular materials composed of platy particles

This is the first paper of a series devoted to the micro-mechanical modeling of clayey soils, by means of discrete element simulations. We specifically focus here on the effect of the platy shape of particles by reducing the interactions between particles to mechanical contact forces (i.e., neither electrostatic repulsion nor van der Waals forces are taken into account). The particles are three-dimensional square plates, approximated as spheropolyhedra. Several samples composed of particles of different levels of platyness (related to the ratio of length to thickness) were numerically prepared and sheared up to large deformations. We analyzed the shear strength, packing fraction, orientation of the particles, connectivity, fabric of the interactions network, and interaction forces as functions of the platyness. We find that both the mechanical behavior and microstructure are strongly dependent on the degree of platyness. The principal underlying phenomenon is the alignment of particle faces along a particular direction. This ordering phenomenon, which emerges even for shapes that deviate only slightly from that of a sphere, enhances the ability of the packing to develop an anisotropic structure leading to large shear strength, especially as a consequence of the fabric and mobilization of friction forces. Moreover, the connectivity of the packings and their packing fraction also evolve with the platyness. In particular, the packing fraction evolves in a nonmonotonic fashion, as observed in other granular materials composed of elongated or angular particles.

The shape and free energy of a lipid bilayer surrounding a membrane inclusion

Membrane inclusion interactions are studied within the scope of continuum theory. We show that the free energy functional for the membrane thickness can be rewritten as a constant times a dimensionless integral. For cylindrical inclusions, the resulting differential equation gives a thickness profile that depends on the radius of the cylinder and one single lipid property, a correlation length that is determined by the ratio of the thickness compressibility and bending moduli. The solutions decay in a non-monotonic fashion with one single observable minimum. A solution for planar geometry may either be explicitly constructed or obtained by letting the radius of the cylinder go to infinity. In dimensionless units the initial derivative of the thickness profile is universal and equal to −1/2. In physical units, the derivative depends on the size of the hydrophobic mismatch as well as the membrane correlation length and will usually be fairly small but clearly non-zero. The line tension between the protein inclusion and a fluid phase membrane will depend on the hydrophobic mismatch and be of the order of 10pN (larger for the gel phase). This results in free energy costs for the inclusion that will be up to tens of kJ/mol (in the fluid phase).

The Shape and Free Energy of a Lipid Bilayer Surrounding a Membrane Inclusion

Membrane inclusion interactions are studied within the scope of continuum theory. We show that the free energy functional for the membrane thickness can be rewritten as a constant times a dimensionless integral. For cylindrical inclusions, the resulting differential equation gives a thickness profile that depends on the radius of the cylinder and one single lipid property, a correlation length that is determined by the ratio of the thickness compressibility and bending moduli. The solutions decay in a non-monotonic fashion with one single observable minimum. A solution for planar geometry may either be explicitly constructed or obtained by letting the radius of the cylinder go to infinity. In dimensionless units the initial derivative of the thickness profile is universal and equal to −1/√2. In physical units, the derivative depends on the size of the hydrophobic mismatch as well as the membrane correlation length and will usually be fairly small but clearly non-zero. The line tension between the protein inclusion and a fluid phase membrane will depend on the hydrophobic mismatch and be of the order of 10 pN (larger for the gel phase). This results in free energy costs for the inclusion that will be up to tens of kJ/mol (in the fluid phase)

A study of ZnFe2O4 nanoparticles modified by ferric nitrate

Transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) revealed that ZnFe2O4 particles treated with an Fe(NO3)3 solution had a three-shell structure, comprising a ZnFe2O4 core, an external γ-Fe2O3 shell, and an outer, mixed Fe(NO3)3·9H2O and ZnO layer. The concentration of the Fe(NO3)3 solution played an important role in the treatment; it determined the ratio of the chemical species and the size of the particles. The magnetization of the treated particle was related to the concentration in a non-monotonic fashion, because of the competition between the ferrimagnetic γ-Fe2O3 phase and the nonmagnetic Fe(NO3)3·9H2O/ZnO mixture. The experiments showed that only below a concentration of 0.5M was the magnetization of the treated particle enhanced with increasing concentration of the Fe(NO3)3 solution.

Spatio-Temporal Analysis of Competition between Independent and Affiliate Movie Theaters

This study presents a semi-parametric spatio-temporal regression model to understand how theater level differentiation affects the performance of independent and affiliate movie theaters. Independent movie theaters are privately owned and managed retail establishments, while affiliate theaters are managed by national-level chains such as AMC and Regal. Theater-level performance is measured using two standard industry metrics – theater-level daily revenue and theater-level daily revenue per screen. In our proposed model, we analyze how theater-level differences such as ticket price, movie assortment, geographic location, and theater format (independent vs. affiliate) affect a theater’s competitiveness. Our semi-parametric specification allows us to flexibly estimate how both time- and location-varying competitive effects (due to theater-level differentiation) influence the performance of independent and affiliate movie theaters. Our empirical analysis yields several interesting and novel findings for movie theaters. Some own differentiation strategies affect independent and affiliate theaters differently. For example, contrary to industry belief, none of the independent theaters benefit from the strategy of decreasing ticket price or increasing assortment breadth. However, the majority of affiliate theaters gain from decreasing ticket price and increasing assortment breadth. There also exist some own differentiation strategies that affect independent and affiliate theaters similarly. For example, most independent and affiliate theaters are better off increasing their number of screens. These findings also suggest that the performance impact of theater-level differentiation varies even within theaters of the same format. Furthermore, the effect of competitors' differentiation strategies on theaters’ performance varies by theater format. For example, when a competing affiliate theater increases its assortment breadth, independent theaters face losses whereas other affiliates stand to gain. Another interesting result suggests that the relationship between the individual dimensions of differentiation and the intensity of competition varies substantially across differentiation dimensions. For instance, while competitive intensity decreases almost linearly with assortment breadth, contrary to previous research it changes in a nonlinear and non-monotonic fashion with geographic distance. Armed with our proposed model, independent and affiliate movie theater managers can better understand the impact of theater-level differentiation on their own and competitors’ revenues, and they can use this to make more informed marketing investments.

Optimal Bank and Regulatory Capital Reserve Strategies Under Loan-Loss Uncertainty

We formulate a continuous-time model of a deposit taking bank, operating subject to capital adequacy regulation, where the bank's loans are exposed to default risk. The bank's objective is to maximise their market value of equity by appropriately controlling loan and equity issuance, dividend payments, and endogenous closure. We show how the bank responds to the span of capital adequacy requirements and default variances. Of interest to regulators, we also show how to find the capital requirement for which the probability of early closure (through either insolvency or endogenous closure) is minimised, and a level at which lending is maximised. An analytical formula is provided to help approximate the location of these points. Furthermore, we find that, whilst the bank's optimal capital structure varies in a non-monotonic fashion with default variance, the level of capital requirement that minimises the probability of early closure and maximises lending is fairly robust to changes in the bank's default variance/risk.

Influence of Nanoscale Particle Roughness on the Stability of Pickering Emulsions

The wetting behavior of solid surfaces can be altered dramatically by introducing surface roughness on the nanometer scale. Some of nature's most fascinating wetting phenomena are associated with surface roughness; they have inspired both fundamental research and the adoption of surface roughness as a design parameter for man-made functional coatings. So far the attention has focused primarily on macroscopic surfaces, but one should expect the wetting properties of colloidal particles to be strongly affected by roughness, too. Particle wettability, in turn, is a key parameter for the adsorption of particles at liquid interfaces and for the industrially important use of particles as emulsion stabilizers; yet, the consequence of particle roughness for emulsion stability remains poorly understood. In order to investigate the matter systematically, we have developed a surface treatment, applicable to micrometer-sized particles and macroscopic surfaces alike, that produces surface coatings with finely tunable nanoscale roughness and identical surface chemistry. Coatings with different degrees of roughness were characterized with regard to their morphology, charging, and wetting properties, and the results were correlated with the stability of emulsions prepared with coated particles of different roughness. We find that the maximum capillary pressure, a metric of the emulsions' resistance to droplet coalescence, varies significantly and in a nonmonotonic fashion with particle roughness. Surface topography and contact angle hysteresis suggest that particle roughness benefits the stability of our emulsions as long as wetting occurs homogeneously (Wenzel regime), whereas the transition toward heterogeneous wetting (Cassie-Baxter regime) is associated with a loss of stability.

Quantifying Aggregation Dynamics during Myxococcus xanthus Development

Under starvation conditions, a swarm of Myxococcus xanthus cells will undergo development, a multicellular process culminating in the formation of many aggregates called fruiting bodies, each of which contains up to 100,000 spores. The mechanics of symmetry breaking and the self-organization of cells into fruiting bodies is an active area of research. Here we use microcinematography and automated image processing to quantify several transient features of developmental dynamics. An analysis of experimental data indicates that aggregation reaches its steady state in a highly nonmonotonic fashion. The number of aggregates rapidly peaks at a value 2- to 3-fold higher than the final value and then decreases before reaching a steady state. The time dependence of aggregate size is also nonmonotonic, but to a lesser extent: average aggregate size increases from the onset of aggregation to between 10 and 15 h and then gradually decreases thereafter. During this process, the distribution of aggregates transitions from a nearly random state early in development to a more ordered state later in development. A comparison of experimental results to a mathematical model based on the traffic jam hypothesis indicates that the model fails to reproduce these dynamic features of aggregation, even though it accurately describes its final outcome. The dynamic features of M. xanthus aggregation uncovered in this study impose severe constraints on its underlying mechanisms.

Crowding-Induced Structural Alterations of Random-Loop Chromosome Model

We investigate structural alterations of random-loop polymers due to changes in the crowding condition, as a model to study environmental effects on the structure of chromosome subcompartments. The polymer structure is changed in a nonmonotonic fashion with an increasing density of crowders: condensed at small volume fractions; decondensed at high crowding volume fractions. The nonmonotonic behavior is a manifestation of the nontrivial distance dependence of the depletion interactions. We also show that crowding-induced structural alterations affect the access of binding proteins to the surface of polymer segments and are distinguished from structural changes due to the increased number of specific polymer loops.

The constitutive relation of an axisymmetric detached coating on a rigid substrate

In this work, the constitutive relation between the external force ( P) and central deflection ( w 0) of the coating in a blister test is studied by elasticity theory. The studied cases are that the coating in the presence of the residual tensile stress is deflected by a concentrated force on the central area of the coating surface. Closed-form solutions for force and deflection are obtained, and used to analyze the feature of the constitutive relations without and with delamination. The results show that the constitutive relation expresses as P ∝ w 0 n with n=1–3 for the case without delamination, while it expresses in a non-monotonic fashion for the case with delamination. The details of the constitutive relation are influenced by the radius of detached coating, residual tensile stress and interfacial toughness.

Sanctification of Marriage and General Religiousness as Buffers of the Effects of Marital Inequity

Theory suggests that relationship inequity will be associated with less marital and personal distress among the more religious, and that this interaction effect will be stronger for women than men. Data are from 178 married couples experiencing the third trimester of pregnancy of their first biological child. Five outcome variables were assessed for each spouse: marital satisfaction, love, marital conflict, depression, and anxiety. Consistent with equity theory, perceived relative advantage was related in a non-monotonic fashion to all outcomes, with increasing advantage predicting better outcomes up to the equity point, but worse outcomes afterwards. Sanctification of marriage appeared to be a more important moderator of inequity effects than general religiousness. In particular, relative advantage had weaker effects among higher sanctifiers. The influence of relative advantage was also conditioned by gender. Wives' psychological well-being appeared to be more adversely affected than men's due to considering oneself overbenefited in the relationship. Moreover, the interaction between sanctification and relative advantage was somewhat stronger for wives.