Sense Of Gravity Research Articles

Modulation of vestibular input by short-term head-down bed rest affects somatosensory perception: implications for space missions.

On Earth, self-produced somatosensory stimuli are typically perceived as less intense than externally generated stimuli of the same intensity, a phenomenon referred to as somatosensory attenuation (SA). Although this phenomenon arises from the integration of multisensory signals, the specific contribution of the vestibular system and the sense of gravity to somatosensory cognition underlying distinction between self-generated and externally generated sensations remains largely unknown. Here, we investigated whether temporary modulation of the gravitational input by head-down tilt bed rest (HDBR)-a well-known Earth-based analog of microgravity-might significantly affect somatosensory perception of self- and externally generated stimuli. In this study, 40 healthy participants were tested using short-term HDBR. Participants received a total of 40 non-painful self- and others generated electrical stimuli (20 self- and 20 other-generated stimuli) in an upright and HDBR position while blindfolded. After each stimulus, they were asked to rate the perceived intensity of the stimulation on a Likert scale. Somatosensory stimulations were perceived as significantly less intense during HDBR compared to upright position, regardless of the agent administering the stimulus. In addition, the magnitude of SA in upright position was negatively correlated with the participants' somatosensory threshold. Based on the direction of SA in the upright position, participants were divided in two subgroups. In the subgroup experiencing SA, the intensity rating of stimulations generated by others decreased significantly during HDBR, leading to the disappearance of the phenomenon of SA. In the second subgroup, on the other hand, reversed SA was not affected by HDBR. Modulation of the gravitational input by HDBR produced underestimation of somatosensory stimuli. Furthermore, in participants experiencing SA, the reduction of vestibular inputs by HDBR led to the disappearance of the SA phenomenon. These findings provide new insights into the role of the gravitational input in somatosensory perception and have important implications for astronauts who are exposed to weightlessness during space missions.

Living donor liver transplant: A strategy to increase transplant access

Living donor liver transplant: A strategy to increase transplant access

Review: Louis Kahn: The Importance of Drawing and Our Days Are Like Full Years: A Memoir with Letters from Louis Kahn

Review: <i>Louis Kahn: The Importance of Drawing</i> and <i>Our Days Are Like Full Years: A Memoir with Letters from Louis Kahn</i>

AdS Euclidean wormholes

We explore the construction and stability of asymptotically anti-de Sitter Euclidean wormholes in a variety of models. In simple ad hoc low-energy models, it is not hard to construct two-boundary Euclidean wormholes that dominate over disconnected solutions and which are stable (lacking negative modes) in the usual sense of Euclidean quantum gravity. Indeed, the structure of such solutions turns out to strongly resemble that of the Hawking–Page phase transition for AdS–Schwarzschild black holes, in that for boundary sources above some threshold we find both a ‘large’ and a ‘small’ branch of wormhole solutions with the latter being stable and dominating over the disconnected solution for large enough sources. We are also able to construct two-boundary Euclidean wormholes in a variety of string compactifications that dominate over the disconnected solutions we find and that are stable with respect to field-theoretic perturbations. However, as in classic examples investigated by Maldacena and Maoz, the wormholes in these UV-complete settings always suffer from brane-nucleation instabilities (even when sources that one might hope would stabilize such instabilities are tuned to large values). This indicates the existence of additional disconnected solutions with lower action. We discuss the significance of such results for the factorization problem of AdS/CFT.

Importance of otorhinolaryngology and vestibulogy for posture and balance of the human body

The vestibular system provides the human brain with information about the angular and linear deviation of the head and body in space, as well as the sense of gravity. It is essential for maintaining adequate body position, orientation and performance of motor acts. Synchronous work with other systems – visual and proprioceptive - is observed. Disorientation, staggering and dizziness are provoked by a conflict of the information received by the different sensors. The vestibular system is a constantly engaged system. Scientific databases - PubMed, SCOPUS and MEDLINE - were used to find appropriate studies in English and other languages on the topic of this review, with the following keywords: vestibular disorder, balance, posture, adenoid hypertrophy, hearing loss. A time period of 2010-2021 was set to trace the latest discoveries in the scientific field. Fundamental pieces of scientific research from the second half of the 20th century were also included. In addition to information from the mentioned scientific databases and articles such as clinical trials and review articles, we included information and paid attention to the work of Bulgarian authors on the problems of the topic, including information from articles, abstracts of dissertations. It can be clearly concluded, based on the analyzed literature, that the ability to maintain balance is due to specific information acquired through several sensory processing systems. While vision is important for posture and balance, the ability to hear, the absence of vestibular deficits, the lack of hypertrophic processes in the adenoids contribute to the fine control and regulation of balance. Disorders in one system - visual, audio-vestibular, stomatognathic - affect others, including the whole body, because they are all connected. Patients should be offered a comprehensive diagnosis because, as has been shown many times, the pathology is interrelated and requires appropriate diagnostic methods and treatment plan. This is done in order to improve the quality of life of the patients and reduce the consequences of the disease.

The effect of head roll and soft surface on Virtual SVV in healthy subjects: A normalization study

Objective: The utricle is a crucial structure for a sense of gravity, but the contribution of proprioceptive receptors is also essential. This study aimed to measure the effect of head roll and soft surface on subjective visual vertical (SVV) in healthy subjects to determine the effect of neck and plantar proprioceptive inputs.

Trauma, Memory, History and its Counter Narration in Thi Bui’s Graphic Memoir The Best We Could Do

ABSTRACT The idea of graphics has long been associated with entertainment, thus underlying the sense of gravity that graphic narratives attempt to portray. But lately this perception has changed and the scholarship in the field of graphic narratives has emerged tremendously, owing much to the texts by Eisner, Spiegelman, McCloud, and Chute, among many others. Bui’s sombre narrative presents the dreadful and horrifying reality of the Vietnam War and brings attention to the alternate representations which are mostly negated by the dominant discourse. Her aim is to locate the marginalised and give a material form to the absent. Loss, absence, trauma, history, and memories are rooted in the framework of the narrative. The choice of the graphic novel as a medium to narrate her story provides a dynamism to the understanding of the above-mentioned ideas. The very structure of the graphic novel is capable of vivifying these ideas. This paper, therefore, attempts to analyse Thi Bui’s debut graphic memoir, The Best We Could Do, in order to understand the ideas of intergenerational trauma and counter narration of history as presented in the text and how she uses the medium of graphic novel to elaborate such ideas.

Time Course of Sensory Substitution for Gravity Sensing in Visual Vertical Orientation Perception following Complete Vestibular Loss.

Loss of vestibular function causes severe acute symptoms of dizziness and disorientation, yet the brain can adapt and regain near to normal locomotor and orientation function through sensory substitution. Animal studies quantifying functional recovery have yet been limited to reflexive eye movements. Here, we studied the interplay between vestibular and proprioceptive graviception in macaque monkeys trained in an earth-vertical visual orientation (subjective visual vertical; SVV) task and measured the time course of sensory substitution for gravity perception following complete bilateral vestibular loss (BVL). Graviceptive gain, defined as the ratio of perceived versus actual tilt angle, decreased to 20% immediately following labyrinthectomy, and recovered to nearly prelesion levels with a time constant of approximately three weeks of postsurgery testing. We conclude that proprioception accounts for up to 20% of gravity sensing in normal animals, and is re-weighted to substitute completely perceptual graviception after vestibular loss. We show that these results can be accounted for by an optimal sensory fusion model.

The Role of Negative Emotions in the Aetiology of Non-Impact Sports Injuries: Interactions of the Stress Response and Motor Control Systems

The Role of Negative Emotions in the Aetiology of Non-Impact Sports Injuries: Interactions of the Stress Response and Motor Control Systems

Fakeons and microcausality: light cones, gravitational waves and the Hubble constant

The concept of a fake particle, or ‘fakeon’, allows us to make sense of quantum gravity as an ultraviolet complete theory, by renouncing causality at very small distances. We investigate whether the violation of microcausality can be amplified or detected in the most common settings. We show that it is actually short range for all practical purposes. Due to our experimental limitations, the violation does not propagate along the light cones or by means of gravitational waves. In some cases, the Universe even conspires to make the effect disappear. For example, the positivity of the Hubble constant appears to be responsible for the direction of time in the early Universe.

Putative Receptors for Gravity Sensing in Mammalian Cells: The Effects of Microgravity

Gravity is a constitutive force that influences life on Earth. It is sensed and translated into biochemical stimuli through the so called “mechanosensors”, proteins able to change their molecular conformation in order to amplify external cues causing several intracellular responses. Mechanosensors are widely represented in the human body with important structures such as otholiths in hair cells of vestibular system and statoliths in plants. Moreover, they are also present in the bone, where mechanical cues can cause bone resorption or formation and in muscle in which mechanical stimuli can increase the sensibility for mechanical stretch. In this review, we discuss the role of mechanosensors in two different conditions: normogravity and microgravity, emphasizing their emerging role in microgravity. Microgravity is a singular condition in which many molecular changes occur, strictly connected with the modified gravity force and free fall of bodies. Here, we first summarize the most important mechanosensors involved in normogravity and microgravity. Subsequently, we propose muscle LIM protein (MLP) and sirtuins as new actors in mechanosensing and signaling transduction under microgravity.

The quest for purely virtual quanta: fakeons versus Feynman-Wheeler particles

The search for purely virtual quanta has attracted interest in the past. We consider various proposals and compare them to the concept of fake particle, or “fakeon”. In particular, the Feynman-Wheeler propagator, which amounts to using the Cauchy principal value inside Feynman diagrams, violates renormalizability, unitarity and stability, due to the coexistence of the prescriptions ±iE. We contrast the Feynman, fakeon and Feynman- Wheeler prescriptions in ordinary as well as cut diagrams. The fakeon does not have the problems of the Feynman-Wheeler propagator and emerges as the correct concept of purely virtual quantum. It allows us to make sense of quantum gravity at the fundamental level, and places it on an equal footing with the standard model. The resulting theory of quantum gravity is perturbative up to an incredibly high energy.

Psychoeducation for children in a psychiatric ward in the immediate aftermath of the 2011 earthquake and tsunami in Japan

On 11 March 2011, Japan was struck by a massive earthquake and tsunami. There were a number of hospitals in the disaster-affected area, including some with psychiatric and children’s wards. Since all utilities were completely cut off for several days, children in the hospital had no access to information about the disaster. Therefore, they lacked a sense of the gravity of the situation and did not show any signs of panic. However, as several psychiatric hospitals located in the coastal area were severely devastated by the tsunami and therefore were unable to continue providing medical services, inpatients of these hospitals had to be accommodated in other hospitals that had children’s wards. The workers on these wards had to respond to minimise the negative psychological impact of this situation on the children in their care. On 18 March 2011, one week after the disaster, brief psychoeducation presentations were conducted with PowerPoint slides, teaching the children how to cope with the stress they were experiencing, using an original rating scale: a mood thermometer. Observations suggest that brief psychoeducation in the immediate phase after a disaster may effectively reduce the psychological trauma that children might otherwise experience.

Relative Cerebral Blood Transit Time Decline and Neurological Improvement in Patients After Internal Carotid Artery Stenting.

In this study we hypothesized that the alleviation of neurological symptoms long after internal carotid artery (ICA) stenting may be related to sustained improvement of cerebral perfusion. Thirty-four subjects (F/M; 15/19) with >70% stenosis of a single internal carotid artery and neurological symptoms, who underwent a carotid artery stenting procedure, were studied. Brain computed tomography perfusion (CTP) imaging was performed before and 3years after ICA stenting. The following relative variables were compared: cerebral blood flow (rCBF), cerebral blood volume (rCBV), mean transit time (rMTT), time to peak (rTTP), and permeability surface area product (rPS). A survey also was conducted to compare the patients' clinical symptoms. Overall, we found that a trend toward rMTT decline was the only persisting change after ICA stenting. We then stratified the patients into the subgroups of <2%, 2-5%, and>5% rMTT decline and found that those with a rMTT decline >2% reported a prominent reduction in subjective clinical symptoms such as headache, dizziness, tinnitus, blurred vision, transient blindness, a sense of gravity of the head, and pain in the eyeballs. We conclude that a shortened mean rMTT, likely reflecting improved cerebral microcirculation, underlies the improvement of neurological symptoms in patients with ICA stenosis.

Noxious geopolitics, festering populaces and transmutable pasts: reframing the limits of acceptable politics through European refugee crises

ABSTRACTPavlovich's article sheds light on how recent interventions in Libya and Syria have facilitated a mass influx of Others in Europe (that is, refugees, migrants and asylum-seekers from the Middle East and Africa), thereby exacerbating already-existing frustrations and anxieties among local populations. This scenario is prompting many Europeans to look to their own collective pasts—through the prism of the present—where they find meaning in far-right, nationalist or populist narratives. These narratives are then used to legitimate political platforms that threaten the foundations of a multi-ethnic, multiracial and multiconfessional cosmopolitan society. Applying insights gleaned from ethnographic fieldwork in the Balkans, Pavlovich sheds light on how geopolitical manoeuvrings have sparked refugee crises, and subsequently impacted local politics across Europe. Ultimately, foreign intervention, refugee crises and the rise of right-leaning populism can be utilized as a heuristic prism to better understand the processes of social and political transformation in Europe. The lessons that can be learned import a sense of gravity in facing the future, given that the bounds and limits of international order and acceptable political action that were shaped in the post-Second World War era are becoming unhinged.

Session on Goldwater Rule Elicits Diverse Reactions From Participants

Session on Goldwater Rule Elicits Diverse Reactions From Participants

Fabrication, Modeling, and Evaluation of a Digital Output Tilt Sensor With Conductive Microspheres

Recent advances in wearable computing ask for bendable and conformable electronic circuits and sensors, allowing an easy integration into everyday life objects. Here, we present a novel flexible tilt sensor on plastic using conductive microspheres as gravity sensitive pendulum. The sensor provides a digital output of the measurement signal without the need for any additional electronics (e.g., amplifiers) close to the sensing structure. The sensor is fabricated on a free-standing polyimide foil with SU-8 photoresist defining the cavity for the pendulum. The pendulum consists of freely movable conductive microspheres which, depending on the sense of gravity, connect different electric contacts patterned on the polyimide foil. We develop a model of the sensor and identify the amount of microspheres as one of the key parameters in the sensor design, which influences the performance of the sensor. The presented tilt sensor with eight contacts achieves an angular resolution of 22.5° with a hysteresis of 10° and less at a tilt of the sensor plane of 50°. Analysis of the microsphere movements reveals a response time of the sensor at ~ 50 ms.

Hong Kong, Grounded

Hong Kong, Grounded Photographs of the contact zones between the mountain and the multilevel metropolis. Karl Kullmann 2017. Places Journal. https://doi.org/10.22269/170502 Hong Kong is relentlessly vertical, a city of towers and skyways, elevators and ladder streets, built on a mountainside — a city without ground, according to the architects Adam Frampton, Jonathan D. Solomon, and Clara Wong. In their guidebook to the three- dimensional circulatory networks of downtown Hong Kong, they draw a city that has radically abrogated its relationship with the ground plane. [1] It’s a beautiful, insightful book, but its sense of gravity is all wrong. For no matter how deeply you lose yourself in the aerial labyrinth, how many escalators you ascend from sea level, how many building portals you pass through, inevitably the mountainous terrain of Hong Kong Island rises up at a faster rate. The levitating pedestrian bumps into the hillside and is brought back to earth. In Hong Kong, the ground is everywhere. The photographs in this slideshow examine contact zones between the multilevel metropolis and the mountain. Rocks and soils that in other cities would be buried or obscured here are integral to the setting. The terrain that weaves between streets, under buildings, and through public spaces reminds pedestrians of the tenuous relation between the city and its geology. To guard against landslides,

An introduction to the physics of Cartan gravity

A distance can be measured by monitoring how much a wheel has rotated when rolled without slipping. This simple idea underlies the mathematics of Cartan geometry. The Cartan-geometric description of gravity consists of a SO(1,4) gauge connection AAB(x) and a gravitational Higgs field VA(x) which breaks the gauge symmetry. The clear similarity with symmetry-broken Yang–Mills theory suggests strongly the existence of a new field VA in nature: the gravitational Higgs field. By treating VA as a genuine dynamical field we arrive at a natural generalization of General Relativity with a wealth of new phenomenology. Importantly, General Relativity is reproduced exactly in the limit that the SO(1,4) norm V2(x) tends to a positive constant. We show that in regions wherein V2 varies–but has a definite sign–the Cartan-geometric formulation is a particular version of a scalar–tensor theory (in the sense of gravity being described by a scalar field ϕ, metric tensor gμν, and possibly a torsion tensor Tμνρ). A specific choice of action yields the Peebles–Ratra quintessence model whilst more general actions are shown to exhibit propagation of torsion. Regions where the sign of V2 changes correspond to a change in signature of the geometry. Specifically, a simple choice of action with FRW symmetry imposed yields, without any additional ad hoc assumptions, a classical analogue of the Hartle–Hawking no-boundary proposal with the big bang singularity replaced by signature change. Cosmological solutions from more general actions are described, none of which have a big bang singularity, with most solutions reproducing General Relativity, or its Euclidean version, for late cosmological times. Requiring that gravity couples to matter fields through the gauge prescription forces a fundamental change in the description of bosonic matter fields: the equations of motion of all matter fields become first-order partial differential equations with the scalar and Dirac actions taking on structurally similar first-order forms. All matter actions reduce to the standard ones in the limit V2→const. We argue that Cartan geometry may function as a novel platform for inspiring and exploring modified theories of gravity with applications to dark energy, black holes, and early-universe cosmology. We end by listing a set of open problems.

Visiting Richard Serra's "Promenade" sculpture improves postural control and judgment of subjective visual vertical.

Body sway while maintaining an upright quiet stance reflects an active process of balance based on the integration of visual, vestibular, somatosensory, and proprioceptive inputs. Richard Serra’s Promenade sculpture featured in the 2008 Monumenta exhibition at the Grand Palais in Paris, France is herein hypothesized to have stimulated the body’s vertical and longitudinal axes as it showcased five monumental rectangular solids pitched at a 1.69° angle. Using computerized dynamic posturography we measured the body sway of 23 visitors when fixating a cross, or when observing the artwork (fixating it or actively exploring it with eye movements) before and after walking around and alongside the sculpture (i.e., before and after a promenade). A first fixation at the sculpture increased medio-lateral stability (in terms of spectral power of body sway). Eye movement exploration in the depth of the sculpture increased antero-posterior stability [in terms of spectral power and canceling time (CT) of body sway] at the expense of medio-lateral stability (in terms of CT). Moreover, a medio-lateral instability associated with eye movement exploration before the promenade (in terms of body sway sensu stricto) was canceled after the promenade. Finally, the overall medio-lateral stability (in terms of spectral power) increased after the promenade. Fourteen additional visitors were asked to stand in a dark room and adjust a luminous line to what they considered to be the earth-vertical axis. The promenade executed within the sculpted environment afforded by Serra’s monumental statuary works resulted in significantly improved performances on the subjective visual vertical test. We attribute these effects to the sculpted environment provided by the exhibition which may have acted as a kind of physiologic “training ground” thereby improving the visitors’ overall sense of visual perspective, equilibrium, and gravity.