Adaptive Shaping Research Articles

Engineering the Functional Expansion of Microneedles.

Microneedles (MNs), composed of an array of micro-sized needles and a supporting base, have transcended their initial use to replace hypodermic needles in drug delivery and fluid collection, advancing toward multifunctional platforms. In this review, four major areas are summarized in interdisciplinary engineering approaches combined with MNs technology. First, electronics engineering, the most extensively researched field, enables applications in biomonitoring, electrical stimulation, and closed-loop theranostics through the generation, transmission, and transformation of electrical signals. Second, in electromagnetic engineering, the responsiveness of electromagnetic induction offers prospects for remote and programmable therapeutic applications. Third, photonic engineering endows MNs with novel functionalities, such as waveguiding and photonic manipulation to enhance optical therapeutic capabilities and facilitate the visualization of disease progression and treatment processes. Lastly, it reviewed the role of mechanical engineering in conferring shape adaptability and programmable motion features necessary for various MNs applications. This review focuses on the functionalities that emerge from the intersection of MNs with complementary engineering technologies, aiming to inspire further research and innovation in microneedle technology for biomedical applications.

Venezuelans in Peru: Adaptation attitudes, optimism and relations with host society

AbstractBy August 2023, the global population of Venezuelan migrants and refugees had reached 7.7 million. This constitutes one of the world largest migration movements in the recent decades and is arguably the most significant one in the context of South–South migration. This paper investigates adaptation attitudes of Venezuelan migrants as well as the attitudes towards their adaptation among Peruvian neighbours living in Peru. Furthermore, we explore the importance of optimism and intergroup relations for the adaptation attitudes. For this purpose, we designed and conducted a survey among Venezuelan migrants and their Peruvian neighbours in Peru between April and May 2023. Significant differences in adaptation attitudes were identified between migrants and their native neighbours. Venezuelans exhibited a greater proclivity towards positive adaptation whereas their neighbours demonstrated a tendency to marginalize or separate migrants. This can potentially lead to give rise to heightened conflict between two populations, thereby becoming a significant factor driving further migration of Venezuelans to other countries. However, optimism emerged as significant factor in shaping adaptation attitudes across both populations.

Investigating climate change adaptation strategies among informal residents in Kumasi, Ghana, through the lenses of the social action and control theories

The urban poor in informal settlements in Ghana remain exposed and vulnerable to climate--induced hazards. Their exclusion from official adaptation interventions, undeniably calls for social mechanisms to enable them to adapt to climate change hazards such as heatwaves and floods. Individuals may contribute to exacerbating climate-induced hazards or employ adaptation measures as a common practice or due to their connectedness to a group, as hypothesised by the social action and social control theories, respectively. There is, however, no known study on the empirical and theoretical contributions of these theories to influencing climate change adaptation efforts in urban Africa. At best, studies have looked at the importance of individual and community skills, and assets to adapting to climate change hazards. Underpinned by the social action and social control theories, 367 household interviews, four focus group discussions and seven relevant agency interviews in two of Kumasi’s largest informal settlements – Aboabo and Asawase - were conducted to explore how elements of the theories shape hazard reduction and adaptation efforts, and discuss the barriers to building adaptation to climate impacts. We found that most households employed several adaptation measures because they saw other residents do the same which was confirmed by the Chi-square test statistic (χ2=4.968, p<0.000) and as hypothesised by the social action theory. Similarly, as hypothesised by the social control theory, we also found differences in the adaptation measures employed by households belonging to identified environment-related groups (χ2=21.465, p<0.001). This was, largely, because among other activities, the education and training exercises undertaken by the groups influenced the knowledge levels of members about climate change hazards and adaptation measures. The groups offer emotional, monetary, material, and practical support to cope within the short-term; first to the members, and the general residents, who are hit by disasters. Generally, adopted measures to reduce adverse impacts and build adaptation were unsustainable. This study is among few studies that demonstrate the contribution of social action and social control theories to managing and adapting climate change and its associated impacts in African cities.

Tendon‐Driven Stiffness‐Tunable Soft Actuator via Thermoelectric‐based Bidirectional Temperature Control

AbstractSoft robots have excellent spatial adaptability and high flexibility, but they are limited by the low stiffness of their constituent materials when faced with high‐load tasks. In recent years, there have been many works on the development of stiffness‐tunable soft actuators by introducing variable stiffness materials into soft actuators, but the existing solutions usually suffer from the problems of slow response, complex structure, and the need of many auxiliary devices to support the completion of the stiffness tuning cycle. This paper proposes a tendon‐driven stiffness‐tunable soft actuator that addresses these issues. Benefiting from the bidirectional temperature control of thermoelectric modules and the excellent in‐plane thermal conductivity of graphene, the actuator is capable of achieving the heating and cooling process by transferring the heat flow through the graphene structure into and out of the shape‐memory polymer (SMP) layer of the tendon‐driven actuator. This enables stiffness tuning via a single device, reducing the dependence on complex external cooling systems. The use of tendon‐driven actuators further eliminates the complex bellow structure of conventional pneumatic actuators and dramatically reduces the size and manufacturing difficulty of individual actuators. Finally, the high load capacity and shape adaptability of the actuator are demonstrated by a gripper equipped with three actuators, which successfully grips objects of various shapes and weights, ranging from less than 10 g to up to 1.6 kg.

Mechanical Strength of Additive Manufactured and Standard Polymeric Components Joined Through Structural Adhesives

The main aim of this work is to evaluate the mechanical properties of additive manufactured polymeric parts joined with standard plastic parts through structural adhesives. The primary advantage of this technique is its ability to significantly increase the size of the final assembly by using additive manufacturing (AM) for complex joints and inexpensive, reliable extruded plastic parts for load-bearing components. This hybrid assembly combines the flexibility and shape adaptability of AM with the structural strength and cost-effectiveness of extruded polymer parts, resulting in a final design that performs comparably to the base material. The materials used in the paper are rigid acrylic adhesive and toughened acrylic, both applicable with almost no surface preparation and fast curing. The 3D-printed parts are produced in ABS, while the standard parts are in PVC. First, the work is devoted to estimating the performance of the adhesives using pin–collar joints and a combined numerical and experimental methodology. The second section presents and discusses the results of two more realistic applications of adhesive bonding to hybrid complex joints. For the pin–collar joints, the results show failure mostly in the adhesive, with an average shear stress of 11.5 MPa and 5.22 MPa and a stiffness of 4449 N/mm and 3649 N/mm for the rigid and toughened adhesives, respectively. The results of the adhesive bonding of structural joints show that the adhesive is always capable of providing the load-carrying capacity required to achieve the strength of traditionally manufactured polymeric parts. The paper shows that adhesives are a feasible way to expand the potential of 3D-printed equipment to obtain larger hybrid parts partially realized with traditional technology, especially with inexpensive off-the-shelf bars and sections.

Self-Adaptive Magnetic Liquid Metal Microrobots Capable of Crossing Biological Barriers and Wireless Neuromodulation.

Magnetic liquid-bodied microrobots (MRs) possess nearly infinite shape adaptivity. However, they currently confront the risk of structure instability/crushes during shape-morphing in tiny biological environments. This article reports that magnetic liquid metal (LM) MRs (LMMRs) show high structure stability and robust magnetic maneuverability. In this protocol, Fe nanoparticles are encapsulated inside less-than-10-μm LM microdroplets by establishing interfacial chemical potential barriers, yielding LMMRs. Their robust magnetic maneuverability originates from the magnetically controlled assembly of Fe nanoparticles inside LM and distinct liquid-solid interaction. With the self-adaptive shape-recovering capabilities even after 50% deformation, LMMRs can implement vertical climbing over walls up to 400% of its body length and traverse channels with the size of its two-thirds. The in vitro and in vivo experiments have both verified the effective magneto-mechanical stimulation of LMMRs upon neurons after their shape-adaptive crossing the blood-brain barrier under a driven magnetic field. Our work provides a promising strategy for wireless therapies with MRs by safely and effectively overcoming biological barriers.

Stabilizing selection and adaptation shape cis and trans gene expression variation in C. elegans.

An outstanding question in the evolution of gene expression is the relative influence of neutral processes versus natural selection, including adaptive change driven by directional selection as well as stabilizing selection, which may include compensatory dynamics. These forces shape patterns of gene expression variation within and between species, including the regulatory mechanisms governing expression in cis and trans . In this study, we interrogate intraspecific gene expression variation among seven wild C. elegans strains, with varying degrees of genomic divergence from the reference strain N2, leveraging this system's unique advantages to comprehensively evaluate gene expression evolution. By capturing allele-specific and between-strain changes in expression, we characterize the regulatory architecture and inheritance mode of gene expression variation within C. elegans and assess their relationship to nucleotide diversity, genome evolutionary history, gene essentiality, and other biological factors. We conclude that stabilizing selection is a dominant influence in maintaining expression phenotypes within the species, and the discovery that genes with higher overall expression tend to exhibit fewer expression differences supports this conclusion, as do widespread instances of cis differences compensated in trans . Moreover, analyses of human expression data replicate our finding that higher expression genes have less variable expression. We also observe evidence for directional selection driving expression divergence, and that expression divergence accelerates with increasing genomic divergence. To provide community access to the data from this first analysis of allele-specific expression in C. elegans , we introduce an interactive web application, where users can submit gene-specific queries to view expression, regulatory pattern, inheritance mode, and other information: https://wildworm.biosci.gatech.edu/ase/ .

A transforming flexahedron origami inspired gripper actuated by shape memory alloy

Abstract The transforming flexahedron origami (TFO) is a unique origami that combines the functions of fingers and palm, with a symmetrical distribution of four-finger structures and good shape adaptability. In this paper, inspired by the TFO configuration, a new type of reconfigurable gripper is designed. The kinematics and mechanics of the gripper are analyzed theoretically, and paper folding is used as the skeleton, thin film as the skin, shape memory alloy spring as the actuator, and active cooling is used to enhance the actuator efficiency. Different kinds of objects are used to test the gripping performance of the gripper, including shape adaptive ability and gripping robustness test, and the test results show that the gripper is with good gripping performance. The reconfigurable capability of the TFO configuration allows the hand gripper to have two gripping modes, adapting to the adaptive gripping of thin rod-like objects and curved objects, which is difficult to achieve with a single gripping mode. The TFO gripper provides a new way of thinking for the design of flexible and origami grippers in the future.

Applications of Metal-Organic Frameworks (MOFs) in Drug Delivery, Biosensing, and Therapy: A Comprehensive Review.

The porous materials known as metal-organic frameworks (MOFs) stand out for their enormous surface area, adaptable pore size and shape, and structural variety. These characteristics make them well-suited for various applications, especially in healthcare. This review thoroughly summarizes recent studies on the use of MOFs in drug delivery, biosensing, and therapeutics. MOFs may encapsulate medications, target certain cells or tissues, and regulate their release over time. Additionally, MOFs have the potential to be used in biosensing applications, allowing for the selective detection of chemical and biological substances. MOFs' optical or electrical characteristics may be modified to make biosensors that track physiological data. MOFs show potential for targeted drug delivery and the regulated release of therapeutic substances in cancer treatment. In addition, they may work as potent antibacterial agents, providing a less dangerous option than traditional antibiotics that increase antibiotic resistance. For practical applications, further research is required as well as more consideration for the problems with toxicity and biocompatibility. In addition to addressing the difficulties and promising possibilities in this area, this study intends to provide insights into the potential of MOFs in healthcare for drug delivery, biosensing, and treatment. Despite several essential reviews in this area, it was necessary to look into the most recent research on drug delivery, biosensing, and therapy as a combined concept.

Force-compensation-based adaptive thermal shape correction method for XFEL optics

Force-compensation-based adaptive thermal shape correction method for XFEL optics

Towards Autonomous Retail Stocking and Picking: Methods Enabling Robust Vacuum-Based Robotic Manipulation in Densely Packed Environments.

With the advent of robotics and artificial intelligence, the potential for automating tasks within human-centric environments has increased significantly. This is particularly relevant in the retail sector where the demand for efficient operations and the shortage of labor drive the need for rapid advancements in robot-based technologies. Densely packed retail shelves pose unique challenges for robotic manipulation and detection due to limited space and diverse object shapes. Vacuum-based grasping technologies offer a promising solution but face challenges with object shape adaptability. The study proposes a framework for robotic grasping in retail environments, an adaptive vacuum-based grasping solution, and a new evaluation metric-termed grasp shear force resilience-for measuring the effectiveness and stability of the grasp during manipulation. The metric provides insights into how retail objects behave under different manipulation scenarios, allowing for better assessment and optimization of robotic grasping performance. The study's findings demonstrate the adaptive suction cups' ability to successfully handle a wide range of object shapes and sizes, which, in some cases, overcome commercially available solutions, particularly in adaptability. Additionally, the grasp shear force resilience metric highlights the effects of the manipulation process, such as in shear force and shake, on the manipulated object. This offers insights into its interaction with different vacuum cup grasping solutions in retail picking and restocking scenarios.

The Evolution of Extreme Genetic Variability in a Parasite-Resistance Complex.

Genomic regions that play a role in parasite defense are often found to be highly variable, with the MHC serving as an iconic example. Single nucleotide polymorphisms may represent only a small portion of this variability, with Indel polymorphisms and copy number variation further contributing. In extreme cases, haplotypes may no longer be recognized as orthologous. Understanding the evolution of such highly divergent regions is challenging because the most extreme variation is not visible using reference-assisted genomic approaches. Here we analyze the case of the Pasteuria Resistance Complex (PRC) in the crustacean Daphnia magna, a defense complex in the host against the common and virulent bacterium Pasteuria ramosa. Two haplotypes of this region have been previously described, with parts of it being non-homologous, and the region has been shown to be under balancing selection. Using pan-genome analysis and tree reconciliation methods to explore the evolution of the PRC and its characteristics within and between species of Daphnia and other Cladoceran species, our analysis revealed a remarkable diversity in this region even among host species, with many non-homologous hyper-divergent-haplotypes. The PRC is characterized by extensive duplication and losses of Fucosyltransferase (FuT) and Galactosyltransferase (GalT) genes that are believed to play a role in parasite defense. The PRC region can be traced back to common ancestors over 250 million years. The unique combination of an ancient resistance complex and a dynamic, hyper-divergent genomic environment presents a fascinating opportunity to investigate the role of such regions in the evolution and long-term maintenance of resistance polymorphisms. Our findings offer valuable insights into the evolutionary forces shaping disease resistance and adaptation, not only in the genus Daphnia, but potentially across the entire Cladocera class.

Reinforcement Learning for Fuselage Shape Control during Aircraft Assembly

Critical safety requirements necessitate ultra-high precision quality control during the assembly of large aerospace components to reduce the mismatch between parts to be joined. Traditional methods use heuristic shape adjustment or surrogate model-based control. These methods are limited by reliance on accurate model learning and inadequate robustness to varying initial assembly conditions. To address these limitations, this paper proposes a model-free reinforcement learning approach for adaptive fuselage shape control during aircraft assembly. The trained reinforcement learning agent directly adjusts the aircraft components in response to their part variations and enables an autonomous system (like AlphaGo) to learn the optimal shape control policy. Specifically, the reinforcement learning environment is built on the finite element simulator. A reward function is developed to capture the optimization objective and introduces a scheme to enforce the original constraints. The proximal policy optimization algorithm is modified to speed up the learning progress and achieve better final performance. In the case study, the root-mean-square gap between components is reduced by 98.4% on average compared with their initial shape mismatch. Our proposed method outperforms the benchmark methods with smaller final shape errors, smaller maximum forces, and lower variations across different test samples.

Caffeic acid-mediated photodynamic multifunctional hyaluronic acid-gallic acid hydrogels with instant and enduring bactericidal potency accelerate bacterial infected wound healing

The emergence of drug-resistant bacteria poses significant challenges in wound treatment. Antimicrobial photodynamic therapy has emerged as an effective approach to eliminating bacteria by inducing oxidative stress without causing drug resistance. Here, we developed a natural hyaluronic acid (HA)-gallic acid (GA) conjugation-based hydrogel combined with herbal photosensitizer-caffeic acid (CA), which exhibits self-healing ability, shape adaptability, biodegradability, and robust tissue adhesion. Under exposure to 400 nm light, caffeic acid acts as a photosensitizer, generating reactive oxygen species and oxidative damage to bacterial cell membranes. Furthermore, the presence of GA and CA displayed a continuous inhibitory effect on bacterial growth, along with antioxidant properties that promote wound healing even after the cessation of light exposure. The antibacterial mechanism of the HA-GA/CA hydrogel against MRSA, S. aureus, and E. coli was investigated through various assays measuring ATP levels, Zeta potential, hydroxyl radicals (·OH) generated by light irradiation, and biofilm clearance rate. Additionally, hydrogel's application in treating MRSA-infected wounds in mice under light irradiation demonstrated rapid wound-healing effects and biocompatibility. Overall, HA-GA/CA hydrogel provides a sustainable, antibiotic-free alternative for treating MRSA-infected wounds.

One-step fabrication of a novel fiber-based absorber for flexible, tunable and boosted microwave absorption

The increasingly intricate electromagnetic environment necessitates higher anti-electromagnetic interference capabilities for electronic devices, thereby demanding a flexible absorbing material that can adapt to multiple forms, is lightweight, and exhibits excellent electromagnetic wave (EMW) absorption properties. In this study, we have developed a novel flexible absorbing material (FAM) based on glass-coated amorphous magnetic fibers (SFs) and Dallenbach-like absorbing structures through wet forming technology. By combining high-performance absorbing fiber with textile structures, the FAM demonstrates EMW absorption performance along with lightweight flexibility and shape adaptability. This paper explores the influence of process parameters in wet forming technology on FAM formation; as well as examines the construction of broadband absorbers through structural optimization. A single-layer FAM with a thickness of 1.7 mm (SFs length 8 mm, content 3 g/m2) achieves an impressive reflection loss (RL) value of −60.1 dB at 11.6 GHz. Furthermore, optimized multi-layer FAM attains effective absorption bandwidth (EAB: RL ≤ −5 dB) across a wide range from 3–14 GHz. This work presents a new approach for developing ’lightweight, thin, wide, and strong’ absorbing materials based on fiber and textile structures which holds significant implications for civilian electromagnetic interference protection as well as military electromagnetic stealth technology.

Drivers of phenotypic variation and plasticity to drought in populations of a Mediterranean shrub along an environmental gradient

Assessing the factors driving intraspecific phenotypic variation is crucial to understand the evolutionary trajectories of plant populations and predict their vulnerability to climate change. Environmental gradients often lead to phenotypic divergence in functional traits and their plasticity across populations. We studied the entire environmental range of the Mediterranean gypsum endemic shrub Helianthemum squamatum to evaluate the factors underlying quantitative population differentiation and phenotypic plasticity to drought, using a common garden with 16 populations that covered the main geographic and the entire climatic range of the species. Sampling followed a hierarchical approach to assess trait genetic variation within and among four distinct geographical regions. We found high but similar plastic responses across populations, which were consistent with adaptive plasticity to drought, including advanced phenology, more sclerophyllous leaves, higher water use efficiency and larger seeds in dry conditions. Despite these generally similar plastic responses, we found significant population differentiation in quantitative traits, part of which was structured at the regional scale. Such differentiation was not associated with environmental variation, including differences in climate and soil conditions. This suggests that non-adaptive processes might have had a role on genetic differentiation in H. squamatum, likely due to the island-like configuration of gypsum habitats and the lack of effective seed dispersal of the study species. Our results emphasize the role of phenotypic plasticity in adaptive drought response and the importance of considering both adaptive and non-adaptive processes shaping intraspecific phenotypic variation, which is crucial for predicting plant population vulnerability to climate change.

Perspectives on Intelligence in Soft Robotics

Engineers frequently aim to streamline environmental factors to facilitate the effective operation of robots. However, in nature, environmental considerations play a crucial role in shaping the embodiment of organisms. To comply robots with the complexity of real‐world environments, embedding similar intelligence is key. In the field of soft robotics, various approaches offer insight into how intelligence can be integrated into artificial agents. A discussed topic is the intricate relationship between the brain and the body at the core of intelligence in robots. The goal of this article is, therefore, to unravel the strategies to implement different types of intelligence currently adopted in soft robots. A classification is made by making a distinction between agents that adapt to their environment by 1) their adaptive shape, 2) their adaptive functionality, and 3) their adaptive mechanics. Additionally, the perspectives on intelligence based on their computational approach are distinguished: centralized computation, decentralized computation, or embedded computation. It is concluded that a tailored robotic design approach attuned to specific environmental demands is needed. To unlock the full potential of soft robots, a fresh perspective on embodied intelligence is described, so‐called mechanical intelligence, emphasizing the robot's responsiveness to changing external conditions of a real‐world environment.

Effect of the gas layer evolution on electrolytic plasma polishing of stainless steel

In recent years, electrolytic plasma polishing technology has attracted wide attention due to its advantages of shape adaptability, high efficiency, better precision, environmental friendliness, and non-contact polishing. However, the lack of research on the evolution mechanism of the gas layer at the anode interface restricts the improvement of the material removal mechanism and the regulation of the polishing effect. Firstly, the thermodynamic conditions of gas layer formation were analyzed based on the Clapeyron-Clausius equation, and the key parameters affecting the gas layer were identified. Secondly, the laws of voltage and electrolyte temperature on the dynamic evolution of the gas layer and its polishing effect were revealed. Additionally, the influence of the gas layer on the voltage-current characteristics was also investigated by analyzing the experimental phenomena. The results indicate that the optimal polishing effect is achieved at a voltage level of 300 V resulting in a decrease in Ra from 0.451 μm to 0.076 μm. Similarly, superior polishing results are obtained when the electrolyte temperature is 80 °C, with a decrease in Ra from 0.451 μm to 0.075 μm. This study provides theoretical guidance for the further development and application of electrolytic plasma polishing technology.

Towards active health: A study on the relationship between physical activity and body image among college students

AimsActive health is a new concept, model, and system for maintaining a state of whole-person health. In the context of the increasing severity of college students' mental health, it is of great significance to explore the relationship between physical activity and college students' body image based on an active health perspective. MethodsA survey was conducted among 853 college students in Zhejiang province using the physical activity rating scale, body image scale, sense of acquisition of sports body shaping scale and social adjustment scale. Using SPSS25.0 and Amos 24.0 software for data processing and analysis. Results(1) There is a significant positive correlation between physical activity, body image, sense of acquisition of sports body shaping, and social adjustment. There is a significant positive correlation between physical activity and body image among college students; The sense of acquisition of sports body shaping a significant mediating role between physical activity and the promotion of college students' body image. The effects of physical activity on body image were mainly achieved through the following three mediating pathways: (1) physical activity → sense of acquisition of sports body shaping → body image, the mediating effect value of this pathway was 0.18, which accounted for 31.6 % of the total effect, with a confidence interval of [0.08, 0.28], (2) physical activity → social adaptation → body image, the mediating effect value of this pathway was 0.09, which accounted for 15.8 % of the total effect of 15.8 %, with a confidence interval of [0.03, 0.15], and (3) physical activity → sense of acquisition of sports body shaping → social adaptation → body image, a pathway with a mediated effect value of 0.09, accounting for 15.8 % of the total effect, with a confidence interval of [0.01, 0.17]. ConclusionsPhysical activity is an important factor in promoting the body image of college students, and there is a chain intermediary effect between physical activity and body image. School sport has its own disciplinary value and unique strengths in advancing the development of body image in adolescents, and the significant mediating effects of sense of acquisition of sports body shaping and social adaptation in this process provide theoretical support for the body image turn to move from theory to practice in the field of school sport.

Local adaptation can cause both peaks and troughs in nucleotide diversity within populations.

The amount of standing variation present within populations is a fundamental quantity of interest in population genetics, commonly represented by calculating the average number of differences between pairs of nucleotide sequences (nucleotide diversity, π). It is well understood that both background and positive selection can cause reductions in nucleotide diversity, but less clear how local adaptation affects it. Depending on the assumptions and parameters, some theoretical studies have emphasized how local adaptation can reduce nucleotide diversity, while others have shown that it can increase it. Here, we explore how local adaptation shapes genome-wide patterns in within-population nucleotide diversity, extending previous work to study the effects of polygenic adaptation, genotypic redundancy, and population structure. We show that local adaptation produces two very different patterns depending on the relative strengths of migration and selection, either markedly decreasing or increasing within-population diversity at linked sites at equilibrium. At low migration, regions of depleted diversity can extend large distances from the causal locus, with substantially more diversity eroded than expected with background selection. With higher migration, peaks occur over much smaller genomic distances but with much larger magnitude changes in diversity. Across spatially extended environmental gradients, both patterns can be found within a single species, with increases in diversity at the center of the range and decreases towards the periphery. Our results demonstrate that there is no universal diagnostic signature of local adaptation based on within-population nucleotide diversity, so it will not be broadly useful for explaining increased FST. However, given that neither background nor positive selection inflate diversity, when peaks are found they suggest local adaptation may be acting on a causal allele in the region.