Orientation State Research Articles

Orientational Ambiguity in Septin Coiled Coils and its Structural Basis

Septins are an example of subtle molecular recognition whereby different paralogues must correctly assemble into functional filaments important for essential cellular events such as cytokinesis. Most possess C-terminal domains capable of forming coiled coils which are believed to be involved in filament formation and bundling. Here, we report an integrated structural approach which aims to unravel their architectural diversity and in so doing provide direct structural information for the coiled-coil regions of five human septins. Unexpectedly, we encounter dimeric structures presenting both parallel and antiparallel arrangements which are in consonance with molecular modelling suggesting that both are energetically accessible. These sequences therefore code for two metastable states of different orientations which employ different but overlapping interfaces. The antiparallel structures present a mixed coiled-coil interface, one side of which is dominated by a continuous chain of core hydrophilic residues. This unusual type of coiled coil could be used to expand the toolkit currently available to the protein engineer for the design of previously unforeseen coiled-coil based assemblies. Within a physiological context, our data provide the first atomic details related to the assumption that the parallel orientation is likely formed between septin monomers from the same filament whilst antiparallelism may participate in the widely described interfilament cross bridges necessary for higher order structures and thereby septin function.

Hybrid Perovskites, Metal-Organic Frameworks, and Beyond: Unconventional Degrees of Freedom in Molecular Frameworks.

ConspectusThe structural degrees of freedom of a solid material are the various distortions most straightforwardly activated by external stimuli such as temperature, pressure, or adsorption. One of the most successful design strategies in materials chemistry involves controlling these individual distortions to produce useful collective functional responses. In a ferroelectric such as lead titanate, for example, the key degree of freedom involves asymmetric displacements of Pb2+ and Ti4+ cations; it is by coupling these together that the system as a whole interacts with external electric fields. Collective rotations of the polyhedral units in oxide ceramics are another commonly exploited distortion, driving anomalous behavior such as negative thermal expansion—the counterintuitive phenomenon of volume contraction on heating. An exciting development in the field has been to take advantage of the interplay between different distortion types: generating polarization by combining two different polyhedral rotations, for example. In this way, degrees of freedom act as geometric “elements” that can themselves be combined to engineer materials with new and interesting properties. Just as the discovery of new chemical elements quite obviously diversified chemical space, we might expect that identifying new and different types of structural degrees of freedom to be an important strategy for developing new kinds of functional materials. In this context, the broad family of molecular frameworks is emerging as an extraordinarily fertile source of new and unanticipated distortion types, the vast majority of which have no parallel in the established families of conventional solid-state chemistry.Framework materials are solids whose structures are assembled from two fundamental components: nodes and linkers. Quite simply, linkers join the nodes together to form scaffolding-like networks that extend from the atomic to the macroscopic scale. These structures usually contain cavities, which can also accommodate additional ions for charge balance. In the well-established systems—such as lead titanate—node, linker, and extra-framework ions are all individual atoms (Ti, O, and Pb, respectively). But in molecular frameworks, at least one of these components is a molecule.In this Account, we survey the unconventional degrees of freedom introduced through the simple act of replacing atoms by molecules. Our motivation is to understand the role these new distortions play (or might be expected to play) in different materials properties. The various degrees of freedom themselves—unconventional rotational, translational, orientational, and conformational states—are summarized and described in the context of relevant experimental examples. The much-improved prospect for generating emergent functionalities by combining these new distortion types is then discussed. We highlight a number of directions for future research—including the design and application of hierarchically structured phases of matter intermediate to solids and liquid crystals—which serve to highlight the extraordinary possibilities for this nascent field.

Elastoplastic transition in a metastable β-Titanium alloy, Timetal-18 – An in-situ synchrotron X-ray diffraction study

The elastoplastic transition of a metastable β-Ti alloy, Timetal-18, is studied using in-situ high energy synchrotron X-ray diffraction microscopy (HEDM). The measured evolutions of the complete elastic strain (and stress) tensor(s), resolved shear stress, lattice rotation and rotation of the stress state of the grains are compared with the predictions of the elasto-viscoplastic Micromechanical Analysis of Stress-Strain Inhomogeneities with fast Fourier transform (MASSIF) code instantiated with an experimentally measured microstructure which matched that of the sample. The preferred glide plane of dislocations with ½<111> Burgers vectors of the BCC alloy was explored. It was found that the polycrystalline stress-strain response could be equally well described by any of the candidate glide planes or combinations thereof (i.e., pencil glide). However, simulations involving slip on {112} planes yielded a marginally better description of the individual grain-level responses, as compared to the simulation involving only the {110} planes. The small (typically <1°) crystallographic reorientations that the grains undergo during the elastoplastic transition, are insufficient to permit discrimination between candidate slip modes. The resolved shear stress (RSS) distributions showed a sharp increase in skewness around macroscopic yield and it was found that the hardening during the elastoplastic transition is primarily due to intergranular interactions. Analysis of “hard” and “soft” grains suggests non-Schmid effects may be present, even in these low strain rate, room temperature experiments. Finally, examination of the individual responses revealed “strain softening” in some of the grains. Intragranular heterogeneity in the orientation and stress state are highlighted as important areas for future investigations, which may reveal answers to unresolved questions in this research.

The State in Chinese Economic History

We survey the recent economics and history literature on the Chinese state to investigate its role in China's long-term socioeconomic development. We highlight three insights. First, unlike in Europe, where interstate competition helped give rise to capitalist states with high capacity, the Chinese state emerged from a different historical context. Second, the eighteenth- and nineteenth-century Chinese state does not fit into the mold of a strong and extractive Oriental despotic state as once commonly believed. By conventional measures, early modern China had a weak state. Third, state building and center-local relations are two useful dimensions to understand development and change in China's recent history and political economy. To adapt China to a changing world, Chinese state builders embarked on a long process of state building from the late-nineteenth century through the Republican and Communist eras. Facilitated partly by regional decentralization, the process now sees the Chinese state playing a substantially larger role in the economy and everyday life than any previous time in history.

The Doctor and Mrs. A.: Ethics and Counter-Ethics in an Indian Dream Analysis by Sarah Pinto

Reviewed by: The Doctor and Mrs. A.: Ethics and Counter-Ethics in an Indian Dream Analysis by Sarah Pinto Sean M. Dowdy Sarah Pinto, The Doctor and Mrs. A.: Ethics and Counter-Ethics in an Indian Dream Analysis. New York: Fordham University Press, 2020. 256 pp. Sarah Pinto's latest book, The Doctor and Mrs. A., is a soaring re-analysis of a psychoanalytic case study, a mere 40 pages lodged in an obscure text published in Lahore during India's Partition. Dev Satya Nand's The Objective Method of Dream Interpretation: Derived from Researches in the Oriental Reminiscence State (1947), though largely forgotten, argues for a regenerative process of transforming and reconceiving one's desires through their re-experience in dream states. As Pinto in turn argues, the experimental nature of the text, especially in its accidental ambulations and openness to new ways of living, affords a framework for theorizing the flipside of ethics, or what she dubs "counter-ethics"—i.e., departures from or reversals/reorganizations of ethical formulations. Pinto's entire book can be read as a fleshing-forth of this concept in its gendered, decolonial, and socio-cosmic implications—all the while keeping its defining contours fluid and open enough to do the work that counter-ethics is supposed to do. Being "indifferent to content…a position not a set of principles" (193), a counter-ethic responds to ethical claims with a modest, yet indomitable rejoinder: "Don't get too comfortable" (181). So, let's get a little uncomfortable and dive into the voices of a small and strange conversation once lost to the archives… The Doctor Dev Satya Nand was an Indian psychiatrist trained at the University of Edinburgh who later assumed psychoanalytic training under the supervision [End Page 163] of Owen Berkeley-Hill. While employed at the Punjabi Mental Hospital in the early 1940s he began work on his "objective method." Satya Nand's effort to re-work Freudian dream analysis—unscientific "mumbo-jumbo," in his words (89)—was meant to be both a correction and an elaboration. A correction in the sense that Satya Nand was trying to bypass the partial insights of free-association in order to impartially observe the rock-bottom truth of psychical reality. For the eponymous case re-analyzed by Pinto, the case of Mrs. A., Dr. Satya Nand had the analysand "promise to tell 'the whole truth and nothing but the truth' about whatever 'came into her mind during our investigations'" (7). This overhaul of Freud's "fundamental rule" in the incongruous language of legalist oath-taking removes the "free" from "association," but in doing so it—almost ironically, and perhaps counter to the intentions of Satya Nand—shifts analytic attention away from intrapsychic content and toward the dynamic forms of mutual interpretation. Thus, as an elaboration, elements of Satya Nand's approach were way ahead of their time. His technique for analyzing dreams (a day-dream in the case of Mrs. A.) was to parse and fragment "stories" of the analysand into "dream smudges," divide them up with elliptic gaps of silence (which he called "dream spaces"), then offer an interpretation with the intention of encouraging the analysand to reflect on the soundness of his interpretation as well as its unvoiced connections. Interpretation as an anti-authoritative offering, a proposal for the analysand to accept, refute, reinterpret, or fill in the blanks—this is a technical innovation most often attributed to D. W. Winnicott (1976), a quarter of a century later! And while Satya Nand's approach seems to avoid the transference/countertransference—i.e., the analytically essential, unconscious tango of projections, identifications, etc. stirred up between therapist and patient—his dialogical and narrativefocused technique is strikingly original enough to hold our attention. For Pinto, this technique became central to her conceptual development of counter-ethics. Mrs. A.'s "small arguments," her rebuttals and refutations of Satya Nand's interpretations, all demonstrate counter-ethics through "the choreographies of transformation, the forms taken by ethical imaginaries in their encounters with one another and with the world…often in moments when the terms of ethical formulations are revalued, or their meanings parsed" (27–28). Additionally, as Pinto historicizes in...

RSS-Based Cooperative Localization and Orientation Estimation Exploiting Antenna Directivity

In this paper, we propose a factor-graph-based cooperative positioning algorithm that uses RSS radio measurements and accounts for the directivity of the antennas. This is achieved by modeling the directivity with a parametric antenna pattern and jointly estimating position and orientation of the agents. We propose two different approaches whereas the first one uses a continuous representation of the orientation state and the second one a discrete representation. We validate our proposed methods with simulations and measurements in a static sensor network with more than 900 agents in an indoor environment and show that the positioning accuracy can be improved significantly by considering the influence of orientations.

A plausible mechanism for longitudinal lock-in of the plant cortical microtubule array after light-induced reorientation

The light-induced reorientation of the cortical microtubule array in dark-grown Arabidopsis thaliana hypocotyl cells is a striking example of the dynamical plasticity of the microtubule cytoskeleton. A consensus model, based on katanin-mediated severing at microtubule crossovers, has been developed that successfully describes the onset of the observed switch between a transverse and longitudinal array orientation. However, we currently lack an understanding of why the newly populated longitudinal array direction remains stable for longer times and re-equilibration effects would tend to drive the system back to a mixed orientation state. Using both simulations and analytical calculations, we show that the assumption of a small orientation-dependent shift in microtubule dynamics is sufficient to explain the long-term lock-in of the longitudinal array orientation. Furthermore, we show that the natural alternative hypothesis that there is a selective advantage in severing longitudinal microtubules, is neither necessary nor sufficient to achieve cortical array reorientation, but is able to accelerate this process significantly.

Ferromagnetic Ordering Theory of Colloidal Suspension of Magnetic Particles in Liquid Crystal

A molecular-statistical theory of colloidal suspension of spherical ferromagnetic particles in a nematic liquid crystal matrix is considered. A tensor expression of the suspension Hamiltonian is proposed, which contains contributions that make it possible to describe the ferromagnetic state of the studied system. Within the mean-field approximation, a system of equations is obtained that describes various orientational states of the suspension. Phase diagrams of the suspension are plotted. It is shown that depending on temperature and intensity of particles interaction with the liquid crystal matrix, the suspension can be in an ordered state with different magnetic properties, namely, in the ferromagnetic and superparamagnetic nematic phases, in addition to the isotropic phase.

Effects of Shading and Soil Compaction on the Growth, Leaf Area and Biomass Allocation of Tomatoes (Lycopersicon esculentum)

Plants are often exposed to stressors such as shading and soil compaction, influencing their morphology and physiology. This study aimed to determine the effects of shading (e.g. using black, white, and transparent cloths) and disturbance on the growth, leaf area, and biomass allocation of plants using tomatoes (Lycopersicon esculentum). The establishment of the study area and gathering of field data were conducted for one month at Davao Oriental State College of Science and Technology (DOSCST), Mati City, Davao Oriental. In the shading experiment, the leaf weight ratio (LWR) of the plants was revealed to be directly proportional to their exposure to sunlight. A similar trend was observed on the specific leaf area (SLA) and leaf area ratio (LAR) values, with the SLA and LAR values higher on the plots with the most shading and decreasing with increasing exposure to sunlight. In the disturbance experiment, the LWR and SLA were observed to be inversely proportional to the intensity of disturbance with higher values reported on the undisturbed plot. A general pattern was observed in terms of biomass allocation in the plant parts; the stems have the bulk of the weight, followed by the leaves while the roots have the least weight. In the shading experiment, the highest biomass was observed on the white fabric-covered plot and the least on the black fabric-covered plot. In the disturbance experiment, the undisturbed plot was observed to have higher biomass than the disturbed plot. These have implications in terms of crop cultivation.

Rapid microwave-assisted fabrication of Al-doped zinc oxide nanorods on a glass substrate for photocatalytic degradation of phenol under visible light irradiation

A rapid microwave-assisted process was used to synthesize a quasi-aligned Al-doped ZnO nanorods on a glass substrate. X-ray diffraction and scanning electron microscopy were used to investigate the crystal structure and morphological properties while the optical properties of the prepared materials have been examined by UV–visible and photoluminescence spectroscopy. Two different Al concentrations, 1% and 5%, were used to dope ZnO nanorods. The prepared Al-doped ZnO samples were annealed at 350 °C–550 °C temperature range. 1% AZO sample annealed at 550 °C showed the highest visible light absorption. Synthesized NRs surface chemistry have been characterized using X-ray photoelectron spectroscopy. Samples morphology, NRs density and diameter significantly changed with Al doping. Results show that the crystal orientation and surface oxidation states are dependent on Al content. Overall, Al-doping of ZnO NRs enhanced the photocatalytic degradation of phenol, especially at 1% Al due to bandgap narrowing and enhancement of visible light absorption.

Decomposers found on a partially decomposed Caimito (Chrysophyllum caimito): Example of a log ecosystem

Decomposers are integral parts of our ecosystem, breaking down matter and releasing it back into the soil for other living things to utilize instead of remaining unused in the tissues of dead animals and plants. This research focused on identifying the decomposers found in Chrysophyllum cainito, commonly known as the star apple. Additionally, it aimed to recognize the non-living elements that influence the small ecosystem within a decomposing log. The study was conducted on August 14, 2017, at the Davao Oriental State College of Science and Technology (DOSCTS) main campus, with the observation lasting one day. A total of eight decomposers were discovered, including lichens, mosses, fungi, polychaete worms, earthworms, termites, woodlice, and ants. The study also documented various abiotic factors such as sunlight, soil, oxygen, water, temperature, and the decomposition log itself. These findings indicate that the sampled area displayed a high diversity of decomposers.

Structure and rheology of soft hybrid systems of magnetic nanoparticles in liquid-crystalline matrices: results from particle-resolved computer simulations

Abstract Hybrid mixtures composed of magnetic nanoparticles (MNP) in liquid crystalline (LC) matrices are a fascinating class of soft materials with intriguing physical properties and a wide range of potential applications, e.g., as stimuli-responsive and adaptive materials. Already in the absence of an external stimulus, these systems can display various types of orientationally disordered and ordered phases, which are enriched by self-assembled structures formed by the MNPs. In the presence of external fields, one typically observes highly nonlinear macroscopic behavior. However, an understanding of the structure and dynamics of such systems on the particle level has, so far, remained elusive. In the present paper we review recent computer simulation studies targeting the structure, equilibrium dynamics and rheology of LC-MNP systems, in which the particle sizes of the two components are comparable. As a numerically tractable model system we consider mixtures of soft spherical or elongated particles with a permanent magnetic dipole moment and ellipsoidal non-magnetic particles interacting via a Gay-Berne potential. We address, first, equilibrium aspects such as structural organization and self-assembly (cluster formation) of the MNPs in dependence of the orientational state of the matrix, the role of the size ratio, the impact of an external magnetic field, and the translational and orientational diffusion of the two components. Second, we discuss the non-equilibrium dynamics of LC-MNP mixtures under planar shear flow, considering both, spherical and non-spherical MNPs. Our results contribute to a detailed understanding of these intriguing hybrid materials, and they may serve as a guide for future experiments.

Influence of Cholesterol on the Orientation of the Farnesylated GTP-Bound KRas-4B Binding with Anionic Model Membranes.

The Ras family of proteins is tethered to the inner leaflet of the cell membranes which plays an essential role in signal transduction pathways that promote cellular proliferation, survival, growth, and differentiation. KRas-4B, the most mutated Ras isoform in different cancers, has been under extensive study for more than two decades. Here we have focused our interest on the influence of cholesterol on the orientations that KRas-4B adopts with respect to the plane of the anionic model membranes. How cholesterol in the bilayer might modulate preferences for specific orientation states is far from clear. Herein, after analyzing data from in total 4000 ns-long molecular dynamics (MD) simulations for four KRas-4B systems, properties such as the area per lipid and thickness of the membrane as well as selected radial distribution functions, penetration of different moieties of KRas-4B, and internal conformational fluctuations of flexible moieties in KRas-4B have been calculated. It has been shown that high cholesterol content in the plasma membrane (PM) favors one orientation state (OS), exposing the effector-binding loop for signal transduction in the cell from the atomic level. We confirm that high cholesterol in the PM helps KRas-4B mutant stay in its constitutively active state, which suggests that high cholesterol intake can increase mortality and may promote cancer progression for cancer patients. We propose that during the treatment of KRas-4B-related cancers, reducing the cholesterol level in the PM and sustaining cancer progression by controlling the plasma cholesterol intake might be taken into account in anti-cancer therapies.

Understanding heterogeneous metal-mediated interfacial enhancement mechanisms in graphene-embedded copper matrix composites

Graphene-embedded Cu matrix composites (GE-CMCs), as one of typical versatile functional composite materials, have great potential to be widely utilized in many engineering fields. Unfortunately, one of major issues is the weak interfacial interactions between metallic matrix and carbonaceous graphene, leading to the rapid mechanical failure. In this work, some heterogeneous alloying elements, including Ni, Ti, Mn and Al, are proposed to be incorporated into Cu matrix to re-construct graphene-Cu interface with the attempt to improve tensile properties of GE-CMCs via first-principles calculations. Meanwhile, a systematical investigation is given on the atomic orientation arrangement states to identify the preferable conditions, which reveal that alloying Mn element with Cu matrix with an equal atomic arrangement over the graphene-Cu interface delivers the most robust interfacial bonding ability, thus resulting in obvious strength (364%) and elongation increasement (415%) in comparison with the pristine graphene-Cu interface in GE-CMCs. Furthermore, the electronic structures and the underlying deformation and enhancement mechanisms of Mn-alloyed GE-CMCs are analyzed to verify the presence of enhanced Mn-C bonds over graphene-Cu interfaces as the external strain increases. It is expected that this work opens an avenue to understand the interfacial enhancement mechanisms and offers an effective interfacial optimization strategy via tuning the atomic arrangement orientation states to achieve high-performance tensile performance for GE-CMCs or other graphene-metal composites.

Multicriteria Decision Analysis on Information Security Policy: A Prioritization Approach

Security is the most serious concern in the digital environment. To provide a sound and firm security policy, a multi-holistic approach must be considered when making strategic decisions. Thus, the objective of this study was to evaluate the information security (IS) and decision making of Davao Oriental State University (DORSU) using the analytic hierarchy process (AHP) approach. The four aspects of IS, namely, the technology, management, economy, and culture were used with the three IS components consisting of confidentiality, integrity, and availability to implement the AHP. The results showed that the technology and management have higher significant values than the economic and cultural aspects. Meanwhile, for the IS components, the integrity signifies the highest priority followed by confidentiality, lastly, and availability. These results emphasize an imbalance in implementing IS policy, which must be addressed to ensure that the data integrity, confidentiality, and availability are balanced, particularly during the information exchange transactions.

Comparing fiber orientation evolution between startup of shear and nonlubricated squeeze flow

AbstractLight weighting has become an integral part of vehicle design. This strategy makes use of fiber‐reinforced thermoplastics, which can be injection molded into complex shapes. Composite design work requires knowledge of the orientation state throughout a part to predict properties like stiffness and strength. Although evolution models for the orientation state have been developed, each requires empirical parameters, and no standard method for obtaining these exists. This work continues efforts to find such a test, particularly for long (average length &gt; 1 mm) glass fiber composites. Here, a polypropylene loaded with 30, 40, and, 50 wt% long glass fiber is subjected to startup of shear and nonlubricated squeeze flow (NLSF). The orientation evolution was reported for both flows and an attempt was made at fitting several orientation models to the data. The measured orientation evolution from startup of shear was slower than expected, and this slower evolution appears to result from the combination of the initial orientation state and fiber concentration. On the other hand, the measured orientation profile from NLSF was found to be essentially independent of fiber concentration. However, the NLSF orientation profile could not be replicated with a single set of parameters. Rather, shear‐like parameters made reasonable predictions in shear‐dominated regions, and extension‐like parameters made reasonable predictions in extension‐dominated areas, in concordance with results from short glass fiber composites.

Axisymmetric flow simulations of fiber suspensions as described by 3D probability distribution function

Numerical models are developed to examine fiber suspension flows through axisymmetric geometries, such as a circular pipe, a center-gated disk and a die exit. The fiber orientation micro-structure is fully described by using the entire probability distribution function (PDF) in 3D instead of the second and fourth moments of the PDF, which introduce errors due to the closure approximation when using orientation tensor descriptions. A Newtonian suspending fluid is considered for the constitutive relationship and simulations are performed with and without coupling the flow and fiber orientation. Results are compared with numerical simulations obtained by using the standard evolution equation for the second-order orientation tensor and the IBOF closure approximation. It is found that the IBOF closure approximation does a relatively good job of matching the exact orientation results given by the probability distribution function. For the three explored flows, the difference between the predicted orientation results using the coupled and decoupled approaches is not significant. There is a noticeable difference in the velocity field solutions, specifically at the die exit where the coupled approach increases the die swell ratio when the fibers enter the inlet with random orientation state.

Transformations of Supported Gold Nanoparticles Observed by In Situ Electron Microscopy

Oxide supported metal nanoparticles play an important role in heterogeneous catalysis. However, understanding the metal/oxide interface and their evolution under reaction conditions remains challenging. Herein, we investigate the interface between Au nanoparticles and a CeO2 substrate by environmental transmission electron microscopy with atomic resolution. We find that the Au nanoparticles have two preferential epitaxial relationships with the substrate, i.e. Type I (111)[−110]CeO2//(111)[−110]Au and Type II (111)[−110]CeO2//(111)[1−10]Au orientation relationships, where Type I is preferred. In situ observations in the presence of O2 show that the gas can stimulate the supported Au nanoparticles to transform between these two orientations even at room temperature. Moreover, when increasing the temperature to 973 K, the transformation of an Au nanoparticle between the two orientation states and a non-crystalline state in the presence of O2 is also observed. DFT calculations of the binding between Au and CeO2 in the two relationships are strongly influenced by the presence of oxygen vacancies. For a given position of a vacancy, there is a significant energy difference between the energy of the two types. However, for some positions, Type I is preferred, and for others, Type II, but the most favourable position of the vacancy for the two types has a very similar energy. This is consistent with the observation of both types of adhesion.

Vector, bidirector, and Bloch skyrmion phases induced by structural crystallographic symmetry breaking

The 212 species of structural phase transitions which break macroscopic symmetry are analyzed with respect to the occurrence of time-reversal-invariant vector and bidirector order parameters. The possibility of discerning the orientational domain states of the low-symmetry phase by these ``vectorlike'' physical properties has been derived using a computer algorithm exploiting the concept of polar, axial, chiral, and neutral dipoles. It is argued that the presence of a pseudo-Lifshitz invariant of chiral bidirector symmetry in a Ginzburg-Landau functional of uniaxial ferroelectrics can induce electric Bloch skyrmions in the same way as the Dzyaloshinskii-Moriya interaction induces bulk magnetic Bloch skyrmions in chiral magnets. It is found that this is possible for three types of fully ferroelectric phase transitions with a chiral paraelectric phase.

TMS coil orientation and muscle activation influence lower limb intracortical excitability

IntroductionPrevious research with transcranial magnetic stimulation (TMS) indicates that coil orientation (TMS current direction) and muscle activation state (rest or active) modify corticospinal and intracortical excitability of upper limb muscles. However, the extent to which these factors influence corticospinal and intracortical excitability of lower limb muscles is unknown. This study aimed to examine how variations in coil orientation and muscle activation affect corticospinal and intracortical excitability of tibialis anterior (TA), a lower leg muscle. MethodsIn 21 young (21.6 ± 3.3 years, 11 female) adults, TMS was administered to the motor cortical representation of TA in posterior-anterior (PA) and mediolateral (ML) orientations at rest and during muscle activation. Single-pulse TMS measures of motor evoked potential amplitude, in addition to resting and active motor thresholds, were used to index corticospinal excitability, whereas paired-pulse TMS measures of short-interval intracortical inhibition (SICI) and facilitation (SICF), and long-interval intracortical inhibition (LICI), were used to assess excitability of intracortical circuits. ResultsFor single-pulse TMS, motor thresholds and test TMS intensity were lower for ML stimulation (all P < 0.05). In a resting muscle, ML TMS produced greater SICI (P < 0.001) and less SICF (both P < 0.05) when compared with PA TMS. In contrast, ML TMS in an active muscle resulted in reduced SICI but increased SICF (both P ≤ 0.001) when compared with PA TMS. ConclusionTMS coil orientation and muscle activation influence measurements of intracortical excitability recorded in the tibialis anterior, and are therefore important considerations in TMS studies of lower limb muscles.