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The ambiguity of the Weitzenböck connection is investigated from the perspective of frames. In doing so, the pure-tetrad formalism and the formalism with an affine connection are compared with each other; it is shown that the ambiguity in the affine connection is equivalent to that of the frame. The role played by the regularization procedure is discussed, and it is argued that the frame approach gives better results than any regularization procedure, including those that make use of a suitable choice of the affine connection. It is also argued that, for consistency, the Weitzenböck torsion must be either manifesting only gravitational effects or gravitational effects plus accelerations. Two possible interpretations for the torsion tensor are present, and an application to a frame that accelerates along the same direction as that of a p p -wave is used to show the consistence of these interpretations. Finally, some possible solutions to the well-known problems of the f (T) theories are proposed. [ABSTRACT FROM AUTHOR]

In response to the unanswered relevant questions surrounding atherosclerosis, it becomes imperative to investigate arterioles using sophisticated mathematical modelling techniques to shed light on critical stress and strain patterns influenced by gravity. The primary objective of this study is to scrutinize flow characteristics and probe stress and strain distributions experienced by the intima layer of arterioles, encompassing coronary, renal, cerebral, mesenteric, and pulmonary arteries, under gravitational forces. This investigation employs a fluid-structure interaction methodology utilizing arbitrary Eulerian–Lagrangian formulation. The study delves into blood flow characteristics within coronary, renal, cerebral, mesenteric, and pulmonary arterioles using the fluid-structure interaction technique, employing an arbitrary Eulerian–Lagrangian formulation. It thoroughly examines various biomechanical parameters such as the Cauchy–Green stress tensor, Principal strain, Piola–Kirchoff stress tensor, deformation tensor, and volume strain along the intima layer under the gravitational influence, elucidating vulnerable regions prone to endothelial dysfunction. Higher values of δV are found at the left shoulder and in the intima’s post stenosis area due to the pressure gradient along the flow channel, whereas other intima regions show a null volume strain. A thorough understanding of stress distribution is essential to create focused therapies to lessen vascular health problems. The stress in the post-stenosis region seems to affect the endothelial layer to a significant extent. [ABSTRACT FROM AUTHOR]

In this study, we explore the quantum effects in the Schwarzschild spacetime for massive and massless scalar particles in the presence of an external gravitational field. The methodology involves the analytical solution of the Klein–Gordon equation for the scalar particles in the near-horizon spacetime limit, using Rindler approximation. The results show that the quantum effects differ significantly for the massive and massless cases, they possess similar characteristics near the event horizon. Bosons without mass that are distant from the event horizon undergo a reduced gravitational impact and possess a symmetric wave function that remains unchanged when they approach the event horizon. However, the symmetry is lost, indicating that the particle strives for a lower energy state and becomes erratic as it nears the event horizon. This aligns with the anticipated behavior of particles within the Schwarzschild horizon. The particles have an energy spectrum even for tremendous values of the Schwarzschild radius, which entails the validity of the Rindler approximation in the near horizon geometry. We have observed that the quantum effects of massive and massless particles differ based on the mass. Specifically, massive and massless scalars behave differently due to their geometric differences, which results in different eigenstates. Although they both tend to seek lower energy levels when they approach the event horizon, their behavior is not the same. [ABSTRACT FROM AUTHOR]

Within the framework of the modified geodetic brane gravity, conformed by the Regge–Teitelboim model and enhanced with a linear term in the extrinsic curvature of the brane, the possibility that under an FRW geometry this theory emulates the so-called dark energy is discussed. The cosmological behavior of this model displays a self-(non-self)-accelerated expansion of this universe which is caused by a combination of usual matter and gravitational geometric effects controlled by a β parameter that accompanies the correction K term. Indeed, the self-accelerated branch, provided by the trace K model raises the question of whether the extrinsic curvature correction terms might be suitable for dark energy candidates. We discuss the analytical expression obtained for ρ dark in addition to the main cosmological parameters such as the state parameter ω eff and the deceleration parameter q. Moreover, when we call for the contribution of dark radiation-like energy to be switched off, Ω d r , 0 → 0 , we find the same acceleration behavior, as well as the same dark energy content provided by the DGP theory. The relationship of our findings to the analysis for ρ dark performed by Davidson and Gurwich within the unified brane cosmology is briefly discussed. [ABSTRACT FROM AUTHOR]

We derive specific properties of electromagnetism when gravitational effects are not negligible and analyze their impact on new physics at the horizons of black holes. We show that a neutral configuration of charges in a region of high redshift, characterized by a large gtt, produces a highly localized electromagnetic field that vanishes just beyond that region. This phenomenon implies the existence of extensive families of spacetime structures generated by electromagnetic degrees of freedom that are as compact as black holes. We construct neutral bound states of extremal black holes in four dimensions and in five dimensions, where one direction is compact. These geometries are indistinguishable from a neutral black hole, referred to as distorted Schwarzschild, except in an infinitesimal region near its horizon where the entrapped electromagnetic structures start to manifest. The five-dimensional solutions satisfy various criteria for describing black hole microstructure: they increase in size with the Newton constant, are as compact as the Schwarzschild black hole, and have an entropy that scales like M2. [ABSTRACT FROM AUTHOR]

Background and Objectives: The aim of this quantitative research was to investigate the effect of gravitational forces on the marginal integrity of different bulk-fill composites by micro-CT imaging. Materials and Methods: Fifty caries-free human third molars extracted for prophylactic purposes were used in this study. Each tooth was prepared with two proximal box cavities, with dimensions of 3 mm × 3 mm × 5 mm. Five distinct groups, each comprising 20 cavities, thus totaling 100 cavities for this study: (1, Group CON): Clearfil Majesty Flow + Clearfil Majesty Esthetic (as the control); (2, Group FBR): Filtek Bulk-fill Flowable Restorative + Clearfil Majesty Esthetic; (3, Group XTB): Voco Extrabase + Clearfil Majesty Esthetic; (4, Group SDR): SDR + Clearfil Majesty Esthetic; and (5, Group SNC): Sonicfill. When restoring the mesial cavities, the occlusal surfaces of the teeth in the mold were positioned upwards, counteracting the force of gravity. In contrast, for the restoration of the distal cavities, the occlusal surfaces were aligned downwards, to be parallel with the gravitational pull. After restorative procedures, each tooth was treated with 5000 thermal cycles. A solution of ammoniacal silver nitrate (AgNO3) was employed as a tracing agent. The micro-CT scans were conducted and the total volume of silver nitrate and the total volume of restorations within the relevant region of interest were calculated in "mm3" with software. Two-way ANOVA and Tukey tests were performed at a significance level of p = 0.05 with Graphpad Prism v 8.2.1 software. Results: Both gravity effect and interaction showed no statistical differences (p > 0.05). Statistically significant differences were observed in the restorative materials (p < 0.05). Conclusions: Gravitational forces do not emerge as a major factor affecting the marginal integrity of flowable bulk-fill composites in class II restorations. The chemical composition of the composites plays a more crucial role, with the XTB composite showing higher microleakage ratios compared to the others. [ABSTRACT FROM AUTHOR]

This study aims to investigate the strong gravitational lensing effects in f (T) gravity. We present the theoretical analytic expressions for the lensing effects in f (T) gravity, including deflection angle, magnification, and time delay. On this basis, we also take the plasma lensing effect into consideration. We compare the lensing effects between the General Relativity in a vacuum environment and the f (T) gravity in a plasma environment. From a strongly lensed fast radio burst, the results indicate that in a plasma environment, General Relativity and f (T) gravity can generate indistinguishable image positions, but the magnification and time delay on these positions are significantly different, which can be distinguished by current facilities in principle. Therefore, the discrepancies between observational results and theoretical expectations can serve as clues for a modified gravity theory and provide constraints on f (T) gravity. [ABSTRACT FROM AUTHOR]

Progress in mechanobiology allowed us to better understand the important role of mechanical forces in the regulation of biological processes. Space research in the field of life sciences clearly showed that gravity plays a crucial role in biological processes. The space environment offers the unique opportunity to carry out experiments without gravity, helping us not only to understand the effects of gravitational alterations on biological systems but also the mechanisms underlying mechanoperception and cell/tissue response to mechanical and gravitational stresses. Despite the progress made so far, for future space exploration programs it is necessary to increase our knowledge on the mechanotransduction processes as well as on the molecular mechanisms underlying microgravity-induced cell and tissue alterations. This white paper reports the suggestions and recommendations of the SciSpacE Science Community for the elaboration of the section of the European Space Agency roadmap "Biology in Space and Analogue Environments" focusing on "How are cells and tissues influenced by gravity and what are the gravity perception mechanisms?" The knowledge gaps that prevent the Science Community from fully answering this question and the activities proposed to fill them are discussed. [ABSTRACT FROM AUTHOR]

A novel dual quaternion modeling and control approach is introduced as a better alternative to traditional modeling methods for formation flying spacecraft utilized for gravity recovery missions. The new formulation for the equations of motion for the relative dynamics of formation flying spacecraft and an interior test mass results in two coupled six degree-of-freedom models that show superior performance over traditional linearized and uncoupled methodologies. Utilizing data products from the Gravity Recovery and Climate Experiment Follow-On mission, a comparison of modeling methods is presented which demonstrates the advantage of the proposed dual quaternion-based modeling approach. Also, a dual quaternion-based Lyapunov controller is formulated and proven to control a test mass within specified gravitational reference sensor development requirements. Additional fidelity is added to the simulation by modeling the voltage-to-force and-torque equations of electrodes located within an electrode housing with appropriate white noise added to the commanded voltages. Equations are also derived and presented for modeling the coupling between the spacecraft and the test mass, and for modeling the density of the atmosphere so that the simulations of the spacecraft and test mass include both gravitational and nongravitational effects. This research ultimately lays the ground work and shows the need for, dual quaternions on future gravity recovery missions. • Formulated dual quaternion-based equations of motion for gravity recovery missions. • Conducted a comparison between dual quaternion and traditional modeling methods. • Formulated a dual quaternion-based Lyapunov controller for test mass pose control. • Modeled test mass actuator noise and presented actuator mapping. [ABSTRACT FROM AUTHOR]

The main objective of this study is to investigate the stability and viability of anisotropic compact stellar objects using the Krori–Burua solutions in f () gravity, where is a nonmetricity scalar that explains the gravitational effects. We use a static spherical metric in the inner region and Schwarzschild spacetime in the outer region of the Her X-I, SAX J 1808.4-3658 and 4U1820-30 compact stars to investigate their physical properties. By using observed values of the radius and mass of the considered compact stars, the unknown parameters are determined. We use a particular model of this theory to examine the behavior of energy density, pressure components, anisotropy, equation of state parameters and energy constraints in the interior of the proposed stellar objects. The Tolman–Oppenheimer–Volkoff equation is used to analyze the equilibrium state of these stars and causality condition, Herrera cracking method, adiabatic index methods are used to determine their stability. It is found that revolutionary technique sheds new light on the development of observationally accurate gravity model. [ABSTRACT FROM AUTHOR]

Despite the significant accomplishments of general relativity, numerous unresolved issues persist in our understanding of the cosmos. One of the most perplexing challenges is the ongoing accelerated expansion of the Universe, which continues to elude a complete explanation. Consequently, scientists have proposed various alternative theories to general relativity in pursuit of a deeper understanding. In our analysis, we delve into the recently proposed modified f(Q) gravity, where Q represents the nonmetricity scalar responsible for gravitational effects. Specifically, we investigate a cosmological model characterized by the functional form f(Q) =  Q  + α Q n , where α (with α ≠ 0) and n serve as free parameters. Utilizing this functional form, we construct our Hubble rate, incorporating a specific equation of state to describe the cosmic fluid. Furthermore, we leverage a dataset consisting of 31 data points from Hubble measurements and an additional 1048 data points from the Pantheon dataset. These data serve as crucial constraints for our model parameters, and we employ the Markov Chain Monte Carlo (MCMC) method to explore the parameter space and derive meaningful results. With our parameter values constrained, our analysis yields several noteworthy findings. The deceleration parameter suggests a recent accelerated phase in the cosmic expansion. In addition, the EoS parameter paints a portrait of dark energy exhibiting phantom-like characteristics. Furthermore, we delve into the application of cosmological diagnostic tools, specifically the statefinder and the Om (z) diagnostics. Both of these tools align with our previous conclusions, confirming the phantom-like behavior exhibited by our cosmological model. These results collectively contribute to our understanding of the dynamic interplay between gravity, dark energy, and the expanding cosmos. [ABSTRACT FROM AUTHOR]

We discuss a possibility to explain observations usually related to the existence of dark matter by passing from the general relativity (GR) theory to a modified theory of gravity, the embedding theory proposed by Regge and Teitelboim. In this approach, it is assumed that our space–time is a four-dimensional surface in a ten-dimensional flat ambient space. This clear geometric interpretation of a change of a variable in the GR action leading to a new theory distinguishes this approach from the known alternatives: mimetic gravity and other variants. After the passage to the modified theory of gravity, additional solutions that can be interpreted as GR solutions with additional fictitious matter appear besides the solutions corresponding to GR. In that theory, one can try to see dark matter, with no need to assume the existence of dark matter as a fundamental object; its role is played by the degrees of freedom of modified gravity. In the embedding theory, the number of degrees of freedom of fictitious matter is sufficiently large, and hence an explanation of all observations without complicating the theory any further can be attempted. [ABSTRACT FROM AUTHOR]

We consider the role of gravity in solute transport when a thin droplet evaporates. Under the physically relevant assumptions that the contact line is pinned and the solutal Péclet number, ${Pe}$ , is large, we identify two asymptotic regimes that depend on the size of the Bond number, ${Bo}$. When ${Bo} = O(1)$ as ${Pe}\rightarrow \infty$ , the asymptotic structure of solute transport follows directly from the surface-tension-dominated regime, whereby advection drives solute towards the contact line, only to be countered by local diffusive effects, leading to the formation of the famous 'coffee ring.' In the distinguished limit in which ${Bo} = O({Pe}^{4/3})$ as ${Pe}\rightarrow \infty$ , this interplay between advection and diffusion takes place alongside that between surface tension and gravity. In each regime, we perform a systematic asymptotic analysis of the solute transport and compare our predictions to numerical simulations. We identify the effect of gravity on the nascent coffee ring, providing quantitative predictions of the size, location and shape of the solute mass profile. In particular, for a fixed Péclet number, as the effect of gravity increases, the coffee ring is diminished in height and situated further from the contact line. Furthermore, for certain values of ${Bo}$ , ${Pe}$ and the evaporation time, a secondary peak may exist inside the classical coffee ring. The onset of this secondary peak is linked to the change in type of the critical point in the solute mass profile at the droplet centre. Both the onset and the peak characteristics are shown to be independent of ${Pe}$. [ABSTRACT FROM AUTHOR]

Symmetric teleparallel gravity offers to reformulate the gravitational formalism without the presence of curvature and torsion with the help of non-metricity tensors. Interestingly, Symmetric teleparallel gravity can be formulated equivalently to teleparallel gravity or general relativity for an appropriate setup. In this study, our aim lies in exploring the bouncing cosmologies as an alternative to the initial singularity of the Universe in the background of modified symmetric teleparallel gravity. To explore this, we adopt the reconstruction technique to present the possible reconstructed Lagrangian for various cosmological bouncing solutions in a flat Friedmann–Lemaître–Robertson–Walker spacetime with a perfect fluid matter distribution. We study the reconstructed gravitational Lagrangians, which are capable of reproducing analytical or semianalytical solutions for symmetric bounce, super-bounce, oscillatory bounce, matter bounce, and exponential bouncing model settings. Further, we examine the dark energy profiles of the models using reconstructed Lagrangians. In addition, we found that an additional term arises in each reconstructed Lagrangian compared to general relativity (GR). That extra term corrected the background GR to present bouncing cosmology in modified gravity. These newly motivated cosmological models may have an effect on gravitational phenomena at other cosmological scales. [ABSTRACT FROM AUTHOR]

Fractures are ubiquitous in geological systems. As reactive fluid flow through a fracture, dissolution of the fracture walls may occur, thus altering the fracture aperture and increasing permeability. It has been recognized that gravity plays an important role in dissolving vertical fractures due to buoyancy‐driven convection. However, the role of gravity in dissolving horizontal fractures is not well understood. Here, we combine microfluidics/Hele‐Shaw experiments and a numerical method to study how the interplay of buoyancy‐driven convection and forced convection controls dissolution dynamics and permeability increase in horizontal fractures. We first develop the micro‐continuum approach by incorporating the gravitational effects, and then, we perform experiments to validate our method, confirming that the method can well capture gravitational effects on dissolution. Through 3D simulations, we find that buoyancy‐driven convection breaks the symmetry of dissolution on the upper and lower surfaces. We employ a symmetry index to identify three dissolution regimes. As the importance of gravity increases (Ri increases), the dissolution regime shifts from forced convection to mixed convection and to natural (or buoyancy‐driven) convection. We establish a link between these dissolution regimes and permeability evolution. In the forced convection or natural convection regimes, the permeability nearly remains unchanged for various Ri. However, in the mixed convection regime, permeability increase is suppressed by the gravitational effects; the underlying mechanism is that the solid phase tends to dissolve near the fracture inlet due to gravitational instability. This work improves our understanding of the gravitational effects on dissolution regimes and permeability evolution in horizontal fractures. Plain Language Summary: Fractures are widely present in the shallow crust of the Earth. The dissolution of fractures is critical for many subsurface processes, including geological carbon sequestration and acid‐injection enhanced oil recovery. Gravity plays an important role in dissolving fractures because of the buoyancy‐driven convection, which is a heavy fluid layer due to the release of the solid phase resulting in convection cells with mushroomlike plumes. However, it remains unexplored how this buoyancy‐driven convection controls dissolution in horizontal fractures. Here, we combine flow‐visualization experiments and a numerical method to investigate gravitational effects. We find that buoyancy‐driven convection breaks the symmetry of dissolution on the upper and lower surfaces. Using a symmetry index, we identify three dissolution regimes, namely forced convection regime, natural convection regime, and mixed convection regime. We show that in the natural or forced convection regimes, the permeability nearly remains unchanged, while in the mixed regime, the permeability decreases with the increase of the importance of gravity. This work highlights the importance of the gravity‐driven dissolution even the relative density difference is down to 0.1% at slow flow rate. Gravitational effects would be amplified for lower flow rates and should be considered under reservoir conditions. Key Points: We develop a pore‐scale numerical method for flow‐dissolution processes, verified by our microfluidics and Hele‐Shaw experimentsWe identify three dissolution regimes to elucidate the role of gravity and establish a link between regimes and permeability evolutionIn mixed convection regime, permeability increase is suppressed by gravity because dissolution occurs near the inlet by convection cells [ABSTRACT FROM AUTHOR]

The present paper contains the investigations with respect to the optical appearance, redshift distribution, and observed energy flux of the thin accretion disk described by the Novikov-Thorne model in modified gravity (MOG) proposed by Moffat. The results show that the gravity coupling parameter α plays an indispensable role in the size of direct and secondary images of the accretion disk, while the image profile is mainly affected by the observational angles. In addition, an increase of the parameter α leads to that of the redshift factor, but a decrease in the radiation energy flux of the accretion disk. These results are due to the enhancement of the parameter α that strengthens the black hole's gravitational effects. By comparing the accretion disk images of the Schwarzschild-MOG black hole, the Schwarzschild black hole, and the Reissner–Nordström black hole, we point out that the Schwarzschild-MOG black hole exhibits the largest inner shadow and the lowest luminosity. This finding provides a potential way to distinguish Schwarzschild-MOG black holes from their counterparts in General Relativity. [ABSTRACT FROM AUTHOR]

In-situ resource utilization has become a significant issue in recent space projects. For example, various studies have focused on lunar manufacturing using regoliths available on the moon's surface. Although regolith manufacturing will be conducted under lunar gravity, most studies have not considered the adverse effects of low gravity on additive manufacturing processes. This study evaluates the gravitational effect on lunar regolith powder bed fusion (PBF) by applying centrifugal acceleration to the PBF process. The experimental results show that gravitational acceleration influences the density, hardness, and transparency of the fabricated regolith blocks. [ABSTRACT FROM AUTHOR]

General relativity (GR) is an important theory that requires very stringent tests. So far, its supporting evidence comes mainly from measurements of photon gravitational effects, including light bending near the Sun, gravitational lensing in some galaxies and gravitational redshift of light. These previous experiments were designed based on a hidden assumption, namely, the gravitational mass of a photon is zero; thus, light should not be bent in a gravitational field if there is no space-time curving. In this work, we showed that the gravitational mass of a photon is not zero. Instead, it is equal to its quantum mass, which can be determined from its momentum using the de Broglie relation. Based on this understanding, the gravitational effects of light can be explained more simply using quantum physics. Our findings suggest that, in order to fully evaluate the theory of GR, more stringent experimental tests are required. Some examples of future experiments for testing the principle of equivalence are proposed here. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to study the gravity effects on a micro-elongated thermoelastic layer under a fluid load, utilizing the Lord–Shulman (L-S) theory and the dual-phase-lag (DPL) model. Design/methodology/approach: The analytical method used was the normal mode which partial differential equations transform into ordinary differential equations. Findings: Aluminum epoxy numerical computations are carried out, and the results are graphed. The DPL model and the L-S theory are compared in the complete absence and presence of gravity. Comparisons were also made for three values of and it is observed that the gravity has quite a massive influence on all physical quantities. Originality/value: In the present paper, the authors shall create the general equation for the energy equation, which includes the two theories (DPL and L-S) as well as the solution of micro-elongated thermoelasticity under fluid load. The problem is pretty important in many dynamical systems. [ABSTRACT FROM AUTHOR]

In this work we study the high-energy Higgs boson phenomenology associated to the non-metricity scale ΛQ at the LHC. Non-metricity is present in more generic non-Riemannian geometries describing gravity beyond General Relativity and exhibits nice features in astronomy and cosmology, and it can be analysed perturbatively. Using effective field theory tools, we calculate the new physics contributions to the one-loop H → γγ and gg → H processes and, together with previous bounds from Compton scattering, we obtain relevant constraints and correlations in the model's parameter space. This can help us take a step further, and no longer associate gravitational effects uniquely to astronomical phenomena, and to start analysing these effects by means of high energy experiments. In turn, this could also help us get a better grasp at quantum phenomena associated to gravity. [ABSTRACT FROM AUTHOR]

Gravity plays a crucial role in physiology. The lack of gravity, like in long duration spaceflight missions, cause pathologies in e.g., the musculoskeletal system, cardiovascular deconditioning, immune system deprivation or brain abnormalities, to just mention a few. The application of artificial gravity through short-arm human centrifugation (SAHC) has been studied as a possible countermeasure to treat spaceflight deconditioning. However, hypergravity protocols applied by using SAHC have also been used to treat different, ground-based pathologies. Such gravitational therapies have been applied in Uruguay for more than four decades now. The aim of this overview is to summarize the most important findings about the effects of gravitational therapy in different, mainly vascular based pathologies according to the experience in the Gravitational Therapy Center and to discuss the current research in the field of hypergravity applications in medicine but also as multisystem countermeasure for near weightlessness pathologies. New insight is needed on the use of hypergravity in medicine and space research and application. [ABSTRACT FROM AUTHOR]

In this work the effects of a geometrically generated post‐inflationary era on the energy spectrum of the primordial gravitational waves are considered. Specifically, a post‐inflationary constant equation of state era, generated by the synergistic effect of f(R)$f(R)$ gravity and of radiation and matter perfect fluids shall be considered. Two cases of interest shall be studied, one with equation of state parameter w=−1/3$w=-1/3$, in which case the Universe neither accelerates nor decelerates, and one with w=0$w=0$ so an early matter domination era. For the evaluation of the inflationary observational indices which is relevant for the calculation of the gravitational waves energy spectrum, the effects of the constant equation of state parameter era, on the e‐foldings number is also taken into account. In both the w=−1/3$w=-1/3$ and w=0$w=0$ cases, the energy spectrum of the primordial gravitational waves is amplified, but for the w=0$w=0$ case, the effect is stronger. [ABSTRACT FROM AUTHOR]

The gravitational redshift induced by stellar surface gravity is notoriously difficult to measure for non-degenerate stars, since its amplitude is small in comparison with the typical Doppler shift induced by stellar radial velocity. In this study, we make use of the large observational data set of the Gaia mission to achieve a significant reduction of noise caused by these random stellar motions. By measuring the differences in velocities between the components of the pairs of comoving stars and wide binaries, we are able to statistically measure the combined effects of gravitational redshift and convective blueshifting of spectral lines, and nullify the effect of the peculiar motions of the stars. For the subset of stars considered in this study, we find a positive correlation between the observed differences in Gaia radial velocities and the differences in surface gravity and convective blueshift inferred from effective temperature and luminosity measurements. The results rule out a null signal at the 5σ level for our full data set. Additionally, we study the subdominant effects of binary motion, and possible systematic errors in radial velocity measurements within Gaia. Results from the technique presented in this study are expected to improve significantly with data from the next Gaia data release. Such improvements could be used to constrain the mass–luminosity relation and stellar models that predict the magnitude of convective blueshift. [ABSTRACT FROM AUTHOR]

The paper presents a new structural model of the granitoid intrusions of the Moldanubian plutonic complex in southern Bohemiaeast of the town of Kaplice. Valuable archival gravity data were supplemented by magnetic survey and precise profile gravity measurements to better define the gravitational effect of the granitoid body and provide an accurate model solution. Our findings, based on geophysical analyses and modelling, bring new information on the shape and deep structure of the Moldanubian plutonic complex in southern Bohemia. These results are complemented by a tectonic investigation of the Freistadt granodiorite body and the Kaplice Fault. New information on the geometry of the Kaplice Fault plane acquired from Linsser indications is discussed in relation to its possible recent seismic activity. The usefulness of the Linsser indications method for active tectonic studies is demonstrated. This is the first regional study in this insufficiently known part of the Bohemian Massif, providing new information on the extent of granites and their relationship to one of the most significant faults in this area. [ABSTRACT FROM AUTHOR]

The present study discussed the effect of rotation and gravitational on a nonlocal two-temperature thermoelastic solid with variable thermal conductivity. The problem is solved using the dual-phase-lag model, coupled theory (CD), and Lord-Shulman (L-S) theory with memory-dependent derivatives. Using suitable non-dimensional variables and normal mode analysis is considered to solve the problem. MATLAB software is used for numerical calculations. Comparisons are made with the results of three different theories predicted in the absence and presence of the gravity field and rotation. Comparisons are made with the results of three different theories predicted for different values of a nonlocal parameter. It is found that the physical quantities are affected by the rotation, gravity field, and the nonlocal parameter. [ABSTRACT FROM AUTHOR]

The motive of this work is to numerically evaluate the effect of changeable gravitational fields and varying viscosity on the beginning of convection in ferromagnetic fluid layer. The fluid layer is constrained by two free boundaries and varying gravitational fields that vary with distance across the layer. The authors hypothesized two categories of gravitational field variation, which can be subdivided into six distinct cases: (i) f (z) = z , (ii) f (z) = e z , (iii) f (z) = l o g (1 + z) , (iv) f (z) = − z , (v) f (z) = − z 2 , and (vi) f (z) = z 2 − 2 z. The normal mode method was applied, and the single term Galerkin approach was used to solve the ensuing eigenvalue problem. The results imply that, in the first three cases, the gravity variation parameter speeds up the commencement of convection, while, in the last three cases, the viscosity variation parameter and gravity variation parameter slow down the onset of convection. It was also observed that, in the absence of the viscosity variation parameter, the non-buoyancy magnetization parameter destabilizes the impact on the beginning of convection but, in the presence of the viscosity variation parameter, it destabilizes or stabilizes impact on the beginning of convection. In the case of oscillatory convection, the results illustrate that oscillatory modes are not permitted, suggesting the validity of the theory of exchange of stabilities. Additionally, it was also discovered that the system is more stable for case (vi) and more unstable for case (ii). [ABSTRACT FROM AUTHOR]

In this paper we investigate the problem of multiple expanding Newtonian stars that interact via their gravitational effect on each other. It is clear physically that if two stars at rest are separated initially, and start expanding as well as moving according to the laws of Newtonian gravity, they may eventually collide. Thus, one can ask whether each star can be given an initial position and velocity such that they can keep expanding without touching. We show that even with gravitational interaction between the bodies, a large class of initial positions and velocities give global-in-time solutions to the N Body Euler–Poisson system. To do this we use scaling mechanisms present in the compressible Euler system, shown in Parmeshwar (Quart Appl Math 79(2):273–334, 2021), gaining advantageous time weights and smallness in our estimates under the specific form of the Lagrangian flow maps, and assumption of small mass for each star, represented by a parameter δ . This is combined with a careful analysis of how the gravitational interaction between stars affects their dynamics. [ABSTRACT FROM AUTHOR]

Simulating drainage in volumetric images of porous materials is a key technique for studying multiphase flow and transport. Image‐based techniques based on sphere insertion are popular due to their computational efficiency and reasonable predictions, though they lack physical rigor. Since most tomograms are small, the impact of gravity on the fluid distributions has not been previously considered. With the advent of stochastically generated images of arbitrary size, and ever larger field‐of‐view images, the validity of neglecting gravity is becoming questionable. In this work, an image‐based technique that includes the effect of gravity during gravity stabilized displacements was developed and validated. Results compared favorably with analytical solutions of capillary rise in tubes, and to micromodel experiments in terms of the pseudo‐capillary pressure curves. The compactness of the invasion front was also shown to vary linearly with the inverse Bond number. Finally, a contour map of expected error as a function of image size and Bond number was generated to help identify when gravitational effects cannot be ignored. The presented algorithm utilizes only basic image processing tools and offers the same computational advantage as other image‐based sphere insertion methods. Key Points: The effect of gravity was incorporated in an image‐based drainage algorithmComparison to micromodel experiments from literature showed excellent agreement in pseudo‐capillary pressure curves, quantitatively predicting the slope while qualitatively matching the residual saturationExpected error for neglecting gravity was compiled into a contour plot to estimate which images and fluid pairs should consider gravity, with errors as high as 50% in some cases [ABSTRACT FROM AUTHOR]

Changes in the gravitational vector by postural changes or weightlessness induce fluid shifts, impacting ocular hemodynamics and regional pressures. This investigation explores the impact of changes in the direction of the gravitational vector on intraocular pressure (IOP), mean arterial pressure at eye level (MAPeye), and ocular perfusion pressure (OPP), which is critical for ocular health. Thirteen subjects underwent 360( of tilt (including both prone and supine positions) at 15° increments. At each angle, steady-state IOP and MAPeye were measured, and OPP calculated as MAPeye – IOP. Experimental data were also compared to a six-compartment lumped-parameter model of the eye. Mean IOP, MAPeye, and OPP significantly increased from 0° supine to 90° head-down tilt (HDT) by 20.7 ± 1.7 mmHg (P < 0.001), 38.5 ± 4.1 mmHg (P < 0.001), and 17.4 ± 3.2 mmHg (P < 0.001), respectively. Head-up tilt (HUT) significantly decreased OPP by 16.5 ± 2.5 mmHg (P < 0.001). IOP was significantly higher in prone versus supine position for much of the tilt range. Our study indicates that OPP is highly gravitationally dependent. Specifically, data show that MAPeye is more gravitationally dependent than IOP, thus causing OPP to increase during HDT and to decrease during HUT. In addition, IOP was elevated in prone position compared with supine position due to the additional hydrostatic column between the base of the rostral globe to the mid-coronal plane, supporting the notion that hydrostatic forces play an important role in ocular hemodynamics. Changes in OPP as a function of changes in gravitational stress and/or weightlessness may play a role in the pathogenesis of spaceflight-associated neuro-ocular syndrome. [ABSTRACT FROM AUTHOR]

The spontaneous scalarization during the stellar core collapse in the massive scalarâ€"tensor theories of gravity introduces extra polarizations (on top of the plus and cross modes) in gravitational waves, whose amplitudes are determined by several model parameters. Observations of such scalarization-induced gravitational waveforms therefore offer valuable probes into these theories of gravity. Considering a triple-scalar interactions in such theories, we find that the self-coupling effects suppress the magnitude of the scalarization and thus reduce the amplitude of the associated gravitational wave signals. In addition, the self-interacting effects in the gravitational waveform are shown to be negligible due to the dispersion throughout the astrophysically distant propagation. As a consequence, the gravitational waves observed on the Earth feature the characteristic inverse-chirp pattern. Although not with the on-going ground-based detectors, we illustrate that the scalarization-induced gravitational waves may be detectable at a signal-to-noise ratio level of O (100) with future detectors, such as Einstein Telescope and Cosmic Explorer. [ABSTRACT FROM AUTHOR]

Our sensorimotor control is well adapted to normogravity environment encountered on Earth and any change in gravity significantly disturbs our movement. In order to produce appropriate motor commands for aimed arm movements such as pointing or reaching, environmental changes have to be taken into account. This adaptation is crucial when performing successful movements during microgravity and hypergravity conditions. To mitigate the effects of changing gravitational levels, such as the changed movement duration and decreased accuracy, we explored the possible beneficial effects of gravity compensation on movement. Local gravity compensation was achieved using a motorized robotic device capable of applying precise forces to the subject's wrist that generated a normogravity equivalent torque at the shoulder joint during periods of microgravity and hypergravity. The efficiency of the local gravity compensation was assessed with an experiment in which participants performed a series of pointing movements toward the target on a screen during a parabolic flight. We compared movement duration, accuracy, movement trajectory, and muscle activations of movements during periods of microgravity and hypergravity with conditions when local gravity compensation was provided. The use of local gravity compensation at the arm mitigated the changes in movement duration, accuracy, and muscle activity. Our results suggest that the use of such an assistive device helps with movements during unfamiliar environmental gravity. [ABSTRACT FROM AUTHOR]

We analyse spatiotemporal gravity changes observed on the Ischia island (Italy) accompanying the destructive earthquake of 21 August 2017. The 29 May 2016 to 22 September 2017 time-lapse gravity changes observed at 18 benchmarks of the Ischia gravimetric network are first corrected for the gravitational effect of the surface deformation using the deformation-induced topographic effect (DITE) correction. The co-seismic DITE is computed by Newtonian volumetric integration using the Toposk software, a high-resolution LiDAR DEM and the co-seismic vertical displacement field derived from Sentinel-1 InSAR data. We compare numerically the DITE field with its commonly used Bouguer approximation over the island of Ischia with the outcome that the Bouguer approximation of DITE is adequate and accurate in this case. The residual gravity changes are then computed at gravity benchmarks by correcting the observed gravity changes for the planar Bouguer effect of the elevation changes at benchmarks over the same period. The residual gravity changes are then inverted using an inversion approach based on model exploration and growing source bodies, making use of the Growth-dg inversion tool. The found inversion model, given as subsurface time-lapse density changes, is then interpreted as mainly due to a co-seismic or post-seismic disturbance of the hydrothermal system of the island. Pros and weak points of such interpretation are discussed. [ABSTRACT FROM AUTHOR]

The aim of this study was to describe how major leg muscle activities are altered after learning a novel one-legged pedaling task. Fifteen recreational cyclists practiced one-legged pedaling trials during which they were instructed to match their applied pedal force to a target direction perpendicular to the crank arm. Activity in 10 major leg muscles was measured with surface electromyography electrodes. Improved upstroke task performance was obtained by greater activity in the hip and ankle flexor muscles, counteracting the negative effects of gravity. Greater quadriceps activities explained improved targeting near top dead center. Reduced uniarticular knee and ankle extensor downstroke activities were necessary to prevent freewheeling. Greater hamstring and tibialis anterior activities improved targeting performance near the bottom of the pedal stroke. The activity patterns of the biarticular plantarflexors changed little, likely due to their contributions as knee flexors for smooth upstroke pedaling motion. These results add to our understanding of how the degrees of freedom at the muscle level are altered in a cooperative manner to overcome gravitational effects in order to achieve the learning goal of the motor task while satisfying multiple constraints—in this case, the production of smooth one-legged pedaling motion at the designated mechanical task demands. [ABSTRACT FROM AUTHOR]

This work is focused on the study of charged wormholes in the following two aspects: (i) to obtain exotic matter free effective charged wormhole solutions and (ii) to determine deflection angle for gravitational lensing effect. We have defined a novel redshift function, obtained wormhole solutions using the background of f (R) theory of gravity and found the regions obeying the weak energy condition. Further, the gravitational lensing effect is analyzed by determining the deflection angle in terms of strong field limit coefficients. [ABSTRACT FROM AUTHOR]

This paper aims to analyzing the characteristics of a spherically symmetric relativistic star in the context of massive Brans-Dicke gravity. The system of field equations is derived for specific forms of coupling and potential functions by employing the MIT bag model. The unknown metric tensors are evaluated through a well-behaved function along with Karmarkar condition for class-one embedding. The value of the bag constant is computed with the help of junction conditions for the strange star candidate Her X-1. We examine trends of energy density and anisotropic pressure of the constructed model for specific values of the coupling parameter and corresponding predicted values of the bag constant. Finally, we discuss the physical viability and stability of the model through various tests. It is concluded that the obtained celestial structure is in agreement with the physical viability and stability criteria under the effect of a gravitational scalar field. [ABSTRACT FROM AUTHOR]

The field of quantum communication has gradually expanded to include satellites in Earth's orbit. However, for long-distance communication protocols, gravity and its effect on quantum states must be taken into account. By applying the equivalence principle, we can consider that the gravitational effects are equivalent to the acceleration that observers possess. A comprehensive method is proposed to find out the effect of gravity on the performance of the four-state continuous-variable quantum key distribution (CV-QKD) protocol. Finally, the effects of gravity on the QKD of each protocol are discussed, and the associated factors are also analyzed. The performance of the CV-QKD protocol under the effects of gravity is deeply analyzed by taking acceleration into consideration. Both the asymptotic key rate and the finite-size key rate are analyzed in this paper. Furthermore, significant room exists for improving the security and efficiency of space quantum communication. • The effects of gravity have a significant negative impact on the QKD protocols. • Performance differences between asymptotic and finite-size key rates under the influence of acceleration. • Discrete modulation QKD scheme breaks through the limitations of transmission over long distances. [ABSTRACT FROM AUTHOR]

Discussing the problem of the external gravitational potential of the rotating Earth, we have to consider the fundamental postulate of the finite speed of the propagation of gravitation. This can be done using the expressions for the gravitational aberration compared to the Liénard-Wiechert solution of the retarded potentials. The term gravitational counteraberration or co-aberration is introduced to describe the pattern of the propagation of the gravitational signal emitted by the rotating Earth. It is proved that in the first approximation, the classic theory of the aberration of light can be applied to calculate this effect. Some effects of the gravitational aberration on the external gravity field of the rotating Earth may influence the orbit determination of the Earth artificial satellites. [ABSTRACT FROM AUTHOR]

The superconducting gravimeter (SG) GWR C025 has monitored the time variation in gravity at the Conrad Observatory (Austria) since autumn 2007. Two tiltmeters have operated continuously since spring 2016, namely a 5.5 m long interferometric water level tiltmeter and a Lippmann-type 2D pendulum tilt sensor. The co-located and co-oriented set up enables a wide range of investigations because the tilts are sensitive to both geometrical solid Earth deformations and to gravity potential changes. The tide-free residuals of the SG and both tiltmeters clearly reflect the gravity and/or deformation effects associated with short- and long-term environmental processes and reveal a complex water transport process at the observatory site. Water accumulation on the terrain surface causes short-term (a few hours) effects which are clearly imaged by the SG gravity and N–S tilt residuals. Long-term (> a few days/weeks) tilt and gravity variations occur frequently after long-lasting rain, heavy rain or rapid snowmelt. Gravity and tilt residuals are associated with the same hydrological process but have different physical causes. SG gravity residuals reveal the gravitational effect of water mass transport, while modelling results exclude a purely gravitational source of the observed tilts. Tilt residuals show the response on surface loading instead. Tilts can be strongly affected by strain–tilt coupling (cavity effect). N–S tilt signals are much stronger than those of the E–W component, which is most probably due to the cavity effect of the 144 m long tunnel being oriented in an E–W direction. [ABSTRACT FROM AUTHOR]

Within F (B 2) modified Weyl gravity, we consider a model of a spin- 1 / 2 electric charge consisting of interior and exterior regions. The interior region is determined by quantum gravitational effects whose approximate description is carried out using Weyl gravity nonminimally coupled to a massless Dirac spinor field. The interior region is embedded in exterior Minkowski spacetime, and the joining surface is a two-dimensional torus. It is shown that mass, electric charge, and spin of the object suggested may be the same as those for a real electron. [ABSTRACT FROM AUTHOR]

Gravity-induced quantum interference is an experiment that exhibits how a gravitational effect appears in quantum mechanics.1 In this famous experiment, gravity was added to the system just classically. In our study, we will do the related calculations on a gravitational wave background. We will argue that the effect of gravitational wave would be detectable in this quantum mechanical effect. [ABSTRACT FROM AUTHOR]

The aim of this work is to present an easy-to-use Python code to calculate the gravitational effect due to lateral variations in the thermal structure of oceanic lithospheric plates, necessary to appropriately isolate the contribution of the variations in crustal thickness. The model is applied to calculate the Moho depth in the West Philippine Basin, and the results are compared with seismic data. The estimations of the Moho depth taking into account the thermal correction presented a better fit with the seismic data and smoother geographical variations than the model without thermal correction. [ABSTRACT FROM AUTHOR]

In this paper, the strong gravitational lensing is explored for traversable wormholes in f (R , T) theory of gravity with minimally-coupled massless scalar field. First, the effective wormhole solutions are obtained using the model f (R , T) = R + 2 λ T , where λ is constant, R is scalar curvature and T is the trace of stress-energy tensor. Furthermore, three different shape functions namely, b (r) = r 0 exp (r − r 0) (Ref. 36), b (r) = r 0 (log (r + 1)) log (r 0 + 1) (Refs. 35 and 37) and b (r) = r 0 r r 0 γ , 0 < γ < 1 (Refs. 34, 35, 39, 73) are considered and studied their qualitative behavior for the construction of wormhole geometry respectively. Subsequently, gravitational lensing effect is implemented to detect the existence of photon spheres at or outside the throat of wormholes. [ABSTRACT FROM AUTHOR]

We consider modified Weyl gravity where a Dirac spinor field is nonminimally coupled to gravity. It is assumed that such modified gravity is some approximation for the description of quantum gravitational effects related to the gravitating spinor field. It is shown that such a theory contains solutions for a class of metrics which are conformally equivalent to the Hopf metric on the Hopf fibration. For this case, we obtain a full discrete spectrum of the solutions and show that they can be related to the Hopf invariant on the Hopf fibration. The expression for the spin operator in the Hopf coordinates is obtained. It is demonstrated that this class of conformally equivalent metrics contains the following: (a) a metric describing a toroidal wormhole without exotic matter; (b) a cosmological solution with a bounce and inflation and (c) a transition with a change in metric signature. A physical discussion of the results is given. [ABSTRACT FROM AUTHOR]

The effect of gravity on the dynamics of flow boiling channels is studied using linear and non-linear stability analysis tools. The developed tools are used to predict experimental results showing good agreement. The linear stability analysis shows that gravity enhances the density wave instability mechanism, enlarging the linear unstable region. Non-linear effects are then investigated by using Hopf bifurcation characterization, allowing identifying meta-stable operating conditions, associated with subcritical bifurcations. In addition, different dynamic basins have been found numerically, which correspond to sub and supercritical Hopf bifurcations. From the results obtained with the model presented here, it is concluded the gravitational effect is found to enhance the density wave instability mechanism, for both the linear and the non-linear domain. This result indicates neglecting gravity in stability studies may lead to non-conservative results. Furthermore, the gravitational effect tends to expand the region where the system exhibits a subcritical behavior. [ABSTRACT FROM AUTHOR]

• Alterations in gravitational fluid-pressure gradients during parabolic flight pose unique challenges for the human brain. • Posterior cerebral blood flow increased during the most marked gravitational transition from micro- to hypergravity. • Systemic formation of free radicals increased and vascular bioavailability of nitric oxide decreased after parabolic flight. • Glial fibrillary acidic protein and S100 ß also increased despite no evidence for structural neuronal-axonal damage. • Repeated gravitational transitions may promote minor blood–brain barrier disruption. The present study examined if repeated bouts of micro- and hypergravity during parabolic flight (PF) alter structural integrity of the neurovascular unit (NVU) subsequent to free radical-mediated changes in regional cerebral perfusion. Six participants (5♂, 1♀) aged 29 ± 11 years were examined before, during and after a 3 h PF and compared to six sex and age-matched (27 ± 6 years) normogravity controls. Blood flow was measured in the anterior (middle cerebral artery, MCA; internal carotid artery, ICA) and posterior (vertebral artery, VA) circulation (duplex ultrasound) in-flight over the course of 15 parabolas. Venous blood was assayed for free radicals (electron paramagnetic resonance spectroscopy), nitric oxide (NO, ozone-based chemiluminescence) and NVU integrity (chemiluminescence/ELISA) in normogravity before and after exposure to 31 parabolas. While MCA velocity did not change (P > 0.05), a selective increase in VA flow was observed during the most marked gravitational transition from micro- to hypergravity (P < 0.05). Increased oxidative-nitrosative stress defined by a free radical-mediated reduction in NO and elevations in glio-vascular GFAP and S100 ß were observed after PF (P < 0.05), the latter proportional to the increase in VA flow (r = 0.908, P < 0.05). In contrast, biomarkers of neuronal-axonal damage (neuron-specific enolase, neurofilament light-chain, ubiquitin carboxy-terminal hydrolase L1 and tau) did not change (P > 0.05). Collectively, these findings suggest that the cumulative effects of repeated gravitational transitions may promote minor blood–brain barrier disruption, potentially related to the combined effects of haemodynamic (posterior cerebral hyperperfusion) and molecular (systemic oxidative-nitrosative) stress. [ABSTRACT FROM AUTHOR]

Satellite gravity data are widely used in the field of geophysics to study deep structures at the regional and global scales. These data comprise free-air gravity anomaly data, which usually need to be corrected to a Bouguer gravity anomaly for practical application. Bouguer reduction approaches can be divided into two methods based on the coordinate system: the spherical coordinates method (SBG) and the Cartesian coordinates method; the latter is further divided into the CEBG and CBG methods, which do and do not include the Earth's curvature correction. In this paper, free-air gravity anomaly data from the eastern Tibetan Plateau and its adjacent areas were used as the basic data to compare the CBG, CEBG, and SBG Bouguer gravity correction methods. The comparison of these three Bouguer gravity correction methods shows that the effect of the Earth's curvature on the gravitational effect increases with increasing elevation in the study area. We want to understand the inversion accuracy for the data obtained by different Bouguer gravity reduction approaches. The depth distributions of the Moho were obtained by the interface inversion of the Bouguer gravity anomalies obtained by the CBG, CEBG, and SBG, and active seismic profiles were used as references for comparison and evaluation. The results show that the depths of the Moho obtained by the SBG inversion are more consistent with the measured seismic profile depths. Therefore, the SBG method is recommended as the most realistic approach in the process of global or regional research employing gravity data. [ABSTRACT FROM AUTHOR]

We consider the presence of odd powers of the speed of light c in the covariant nonrelativistic expansion of General Relativity (GR). The term of order c in the relativistic metric is a vector potential that contributes at leading order in this expansion and describes strong gravitational effects outside the (post-)Newtonian regime. The nonrelativistic theory of the leading order potentials contains the full non-linear dynamics of the stationary sector of GR. [ABSTRACT FROM AUTHOR]

The article discusses that nearly 300-year success of the Newtonian gravitation theory has always been based on the implicit assumption that the gravitational force. It mentions the motivation of computer simulation was to prove the validity of the dynamic gravity force Expression 7 of pendulum experiment; and also mentions that both the measurement and the simulation gave pendulum amplitude of about 10 millimeters contrary to the calculation with the Newtonian gravity.

In this work, we investigate wormhole configurations described by a constant redshift function in Einstein-Cubic gravity (ECG). We derive analytical wormhole geometries by assuming a particular equation of state (EoS) and investigate the possibility that these solutions satisfy the standard energy conditions. We introduce exact asymptotically flat and anti-de Sitter (AdS) spacetimes that admit traversable wormholes. These solutions are obtained by imposing suitable values for the parameters of the theory so that the resulted geometries satisfy the weak energy condition (WEC) in the vicinity of the throat, due to the presence of higher-order curvature terms. Moreover, we find that AdS solutions satisfy the WEC throughout the spacetime. A description of the geodesic motion of time-like and null particles is presented for the obtained wormhole solutions. Also, using gravitational lensing effects, observational features of the wormhole structure are discussed. [ABSTRACT FROM AUTHOR]

Gravity is one of the most ubiquitous environmental effects on living systems: Cellular and organismal responses to gravity are of central importance to understanding the physiological function of organisms, especially eukaryotes. Gravity has been demonstrated to have strong effects on the closed cardiovascular systems of terrestrial vertebrates, with rapidly responding neural reflexes ensuring proper blood flow despite changes in posture. Invertebrates possess open circulatory systems, which could provide fewer mechanisms to restrict gravity effects on blood flow, suggesting that these species also experience effects of gravity on blood pressure and distribution. However, whether gravity affects the open circulatory systems of invertebrates is unknown, partly due to technical measurement issues associated with small body size. Here we used X-ray imaging, radio-tracing of hemolymph, and micropressure measurements in the American grasshopper, Schistocerca americana, to assess responses to body orientation. Our results show that during changes in body orientation, gravity causes large changes in blood and air distribution, and that body position affects ventilation rate. Remarkably, we also found that insects show similar heart rate responses to body position as vertebrates, and contrasting with the classic understanding of open circulatory systems, have flexible valving systems between thorax and abdomen that can separate pressures. Gravitational effects on invertebrate cardiovascular and respiratory systems are likely to be widely distributed among invertebrates and to have broad influence on morphological and physiological evolution. [ABSTRACT FROM AUTHOR]