SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Centrifugation

280

Balance arises from the interplay of external forces acting on the body and internally generated movements. Many animal bodies are inherently unstable, necessitating corrective locomotion to maintain stability. Understanding how developing animals come to balance remains a challenge. Here we study the interplay among environment, sensation, and action as balance develops in larval zebrafish. We first model the physical forces that challenge underwater balance and experimentally confirm that larvae are subject to constant destabilization. Larvae propel in swim bouts that, we find, tend to stabilize the body. We confirm the relationship between locomotion and balance by changing larval body composition, exacerbating instability and eliciting more frequent swimming. Intriguingly, developing zebrafish come to control the initiation of locomotion, swimming preferentially when unstable, thus restoring preferred postures. To test the sufficiency of locomotor-driven stabilization and the developing control of movement timing, we incorporate both into a generative model of swimming. Simulated larvae recapitulate observed postures and movement timing across early development, but only when locomotor-driven stabilization and control of movement initiation are both utilized. We conclude the ability to move when unstable is the key developmental improvement to balance in larval zebrafish. Our work informs how emerging sensorimotor ability comes to impact how and why animals move when they do.

Concepts: Force, Fish, Centrifugation, Instability, Stability, Developmental biology

144

More than 35 years and 11 000 publications after the discovery of quasicrystals by Dan Shechtman, quite a bit is known about their occurrence, formation, stability, structures and physical properties. It has also been discovered that quasiperiodic self-assembly is not restricted to intermetallics, but can take place in systems on the meso- and macroscales. However, there are some blank areas, even in the centre of the big picture. For instance, it has still not been fully clarified whether quasicrystals are just entropy-stabilized high-temperature phases or whether they can be thermodynamically stable at 0 K as well. More studies are needed for developing a generally accepted model of quasicrystal growth. The state of the art of quasicrystal research is briefly reviewed and the main as-yet unanswered questions are addressed, as well as the experimental limitations to finding answers to them. The focus of this discussion is on quasicrystal structure analysis as well as on quasicrystal stability and growth mechanisms.

Concepts: System, Structure, Centrifugation, Need, Model theory, Quasiperiodicity, Dan Shechtman, Quasicrystal

64

The Mg-Si-O system is the major Earth and rocky planet-forming system. Here, through quantum variable-composition evolutionary structure explorations, we have discovered several unexpected stable binary and ternary compounds in the Mg-Si-O system. Besides the well-known SiO2 phases, we have found two extraordinary silicon oxides, SiO3 and SiO, which become stable at pressures above 0.51 TPa and 1.89 TPa, respectively. In the Mg-O system, we have found one new compound, MgO3, which becomes stable at 0.89 TPa. We find that not only the (MgO)x·(SiO2)y compounds, but also two (MgO3)x·(SiO3)y compounds, MgSi3O12 and MgSiO6, have stability fields above 2.41 TPa and 2.95 TPa, respectively. The highly oxidized MgSi3O12 can form in deep mantles of mega-Earths with masses above 20 M⊕ (M⊕:Earth’s mass). Furthermore, the dissociation pathways of pPv-MgSiO3 are also clarified, and found to be different at low and high temperatures. The low-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ SiO2 + Mg2SiO4 ⇒ MgO + SiO2, while the high-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ MgO + MgSi2O5 ⇒ MgO + SiO2. Present results are relevant for models of the internal structure of giant exoplanets, and for understanding the high-pressure behavior of materials.

Concepts: Centrifugation, Chemical compound, Extrasolar planet, Oxides, Oxygen, Silicon, Oxide, Silicon dioxide

28

Resection of the ulnar head in cases of debilitating pain owing to arthrosis of the distal radioulnar joint can provide satisfying relief. However, there is mounting evidence that pain with heavier use, instability, and torque-generating weakness in more active individuals may result in less satisfying outcomes. Implant arthroplasty can provide a means to stabilize the radius to the ulna after ulnar head resection, but it requires significant attention to requisite soft tissue stabilization and alignment of the distal radius to the implant to be successful.

Concepts: Centrifugation, Ulna, Distal radioulnar articulation

28

BACKGROUND: Dynamic postural stability is defined as the ability to transition from a dynamic movement to a stable condition over one’s base of support. Measures of dynamic stability have been used extensively to classify ankle instability status and assist clinicians with ankle injury interventions. Therefore, the purpose of this study was to determine if current methods of quantifying dynamic stability are accurate in differentiating among healthy, coper, and unstable ankles. METHODS: One hundred ninety four Division-I collegiate athletes (football, volleyball, field hockey, men’s/women’s soccer, men’s/women’s lacrosse, men’s/women’s basketball) volunteered for this study. Participants were categorized into healthy, coper, and stable groups by a self-reported questionnaire and previous history of ankle injuries. Dynamic postural stability was assessed using the Multi-Directional Dynamic Stability Protocol by jumping and landing single-legged onto a force platform from four different directions. Receiver operator curves were used to analyze the accuracy of current techniques of calculating dynamic stability among groups. FINDINGS: None of the existing methods were found to be accurate in differentiating ankle instability status in any of the jump landings. INTERPRETATION: Researchers have commonly used these existing methods to quantify dynamic postural stability. None of the current calculation techniques worked with our jump landing protocol. Researchers need to pay attention to the protocol and calculation technique pairings in that using inaccurate measures of dynamic postural stability makes any findings of that research ineffective. Therefore, this challenges researchers to develop a more accurate calculation to quantify dynamic postural stability, or develop a jump landing protocol that exposes sensorimotor deficits in the more able-bodied population.

Concepts: Landing, Foot, Accuracy and precision, Centrifugation, Stability, Sprained ankle, Instability, Ankle

27

Abstract Previous studies show that the concept of escapism needs to be clarified and that its relation to problematic online gaming and other factors needs further examination. This study uses well-established, basic learning theory to clarify the concept of escapism, and examines its relation to problematic gaming, psychological distress, and satisfaction with life among players of massively multiplayer online role-playing games (MMORPGs). MMORPG players (n=201) answered an online questionnaire where these factors were measured and correlated with a previously developed scale on motivation to play (MTPI), including extra items to cover positive and negative aspects of escapism. Factor analysis and construct validation show that positive aspects of escapism are theoretically and empirically unstable and that escapism is best clarified as purely “negative escapism,” corresponding to playing being negatively reinforced as a way of avoiding everyday hassles and distress. Negative escapism had a stronger relationship to symptoms of Internet addiction, psychological distress, and life satisfaction than other variables and other more positive motivations to play. Future studies should use the revised subscale for escapism (in the MTPI-R) presented in the present study, for example when screening for Internet addiction.

Concepts: Role-playing game, Centrifugation, Factor analysis, Video game genres, World of Warcraft, Learning, Online game, Massively multiplayer online game

27

STUDY DESIGN:: A retrospective case series describing teardrop fracture of the axis. OBJECT:: The purpose of the study was to clarify the clinical features, the mechanism of injury and the potential instability of extension teardrop fractures of the axis, so as to emphasize the importance of recognizing this injury as a separate entity. SUMMARY OF BACKGROUND DATA:: Teardrop fractures of the axis are rare spinal fractures, comprising only a small percentage of all injuries of the cervical spine. The stability of this fracture pattern has been a matter of debate leading to controversy regarding treatment strategies and the need for stabilization. METHODS:: We retrospectively reviewed data from 16 patients to document mechanism of injury, neurological deficit, treatment and clinical outcome, and imaging findings. RESULTS:: Extension teardrop fractures accounted for approximately 8.9% of upper cervical spinal injuries and 12.7% of axis fractures at the authors' institution over the same period. Six patients (4 males and 2 females) underwent surgery (4 via an anterior approach, 2 cases via a posterior approach). Ten cases underwent Halo-vest immobilization for a period between 6 and 12 weeks. At final follow-up, fourteen cases achieved excellent results, while two patients complained of mild residual neck pain. Maximum cranial-caudal dimensions of the fragments were between 5 and 24 mm (average, 12.9 mm), and the transverse dimensions were between 5 and 22 mm (average, 11.1 mm). Fragment displacement ranged from 1 to 9 mm (average, 3.5 mm) while fragment rotation ranged from 10 to 52 degrees (average, 24.4 deg) in the sagittal plane. CONCLUSIONS:: Most patients with an extension teardrop fracture of the axis can be treated conservatively. Based on this case series, the authors suggest that large fragment size, displacement or angulation, intervertebral disc injury, neurologic deficit or signs of instability are reasonable indications for surgical treatment.

Concepts: Intervertebral disc, Surgery, Physical trauma, Axis, Flexion, Centrifugation, Cervical vertebrae, Vertebral column

23

Nanostructured lipid carrier (NLC) was fabricated from rambutan (Nephelium lappaceum L.) kernel fat stabilized with Tween 80 in this present work. The influence of the Tween 80 concentration (0.025, 0.05, 0.1, 0.2, 0.5 and 1.0wt%) and solidification temperature (5 and 25°C) on the characteristics and stability of the NLC were investigated. The results showed that an increase in the Tween 80 concentration caused decreased zeta-potential (ζ-potential) and particle size (Z-average) with no significant effect on the polydispersity index (PDI). Lipid particles in the NLC at all Tween 80 concentrations had a tendency to grow and the PDI tended to increase due to Ostwald ripening upon storage over 28days. At least 0.2wt% Tween 80 concentrations could be used to stabilize 1wt% rambutan NLC. The solidification temperature affected the microstructure, melting behavior and stability of rambutan NLC. Pre-solidification at 5°C could create stable NLC with monodispersed-spherical lipid particles. Consequently, these stable NLC particles produced from rambutan kernel fat may serve as useful carriers for the delivery of bioactive lipophilic nutraceuticals.

Concepts: Centrifugation, Solution, Lychee, Stability, Pulasan, Nephelium, Saturation, Rambutan

6

To clarify whether deaths associated with hot and cold days are among the frail who would have died anyway in the next few weeks or months.

Concepts: Centrifugation, Reincarnation, Death, Life

5

What influences how people feel about and behave toward their romantic partners? Extending beyond features of the partners, relationship experiences, and social context, the current research examines whether benign, relationship-irrelevant factors-such as one’s somatic experiences-can influence relationship perceptions and interpersonal behavior. Drawing on the embodiment literature, we propose that experiencing physical instability can undermine perceptions of relationship stability. Participants who experienced physical instability by sitting at a wobbly workstation rather than a stable workstation (Study 1), standing on one foot rather than two (Study 2), or sitting on an inflatable seat cushion rather than a rigid one (Study 3) perceived their romantic relationships to be less likely to last. Results were consistent with risk-regulation theory: Perceptions of relational instability were associated with reporting lower relationship quality (Studies 1-3) and expressing less affection toward the partner (Studies 2 and 3). These findings indicate that benign physical experiences can influence perceptions of relationship stability, exerting downstream effects on consequential relationship processes.

Concepts: Centrifugation, Perception, Relationship, Stability, Mind, Experience, Interpersonal relationship, Psychology