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Precise determination of atomic structures in ferroelectric thin films and their evolution with temperature is crucial for fundamental study and design of functional materials. However, this has been impeded by the lack of techniques applicable to a thin-film geometry. Here we use cryogenic scanning transmission electron microscopy (STEM) to observe the atomic structure of a BaTiO3 film on a (111)-SrTiO3 substrate under varying temperatures. Our study explicitly proves a structure transition from a complex polymorphic nanodomain configuration at room temperature transitioning to a homogeneous ground-state rhombohedral structure of BaTiO3 below ∼250 K, which was predicted by phase-field simulation. More importantly, another unexpected transition is revealed, a transition to complex nanodomains below ∼105 K caused by an altered mechanical boundary condition due to the antiferrodistortive phase transition of the SrTiO3 substrate. This study demonstrates the power of cryogenic STEM in elucidating structure-property relationships in numerous functional materials at low temperatures.

The characteristics of typical posterior canal-benign paroxysmal positional vertigo-canalolithiasis (P-BPPV-Can) are well known. We found 10 patients with a new variant of P-BPPV-Can: Reverse (Rev)-P-BPPV-Can. The characteristics and pathophysiology of Rev-P-BPPV-Can are discussed.For 4 years and 9 months, 10 patients with Rev-P-BPPV-Can (9 women and 1 man; mean age: 73 years) visited our clinic. Within the same period, 268 patients with unilateral typical P-BPPV-Can were treated. During the Dix-Hallpike and Epley maneuvers, nystagmus was recorded using an infrared charge-coupled device camera mounted on a pair of spectacles.The patients exhibited entirely opposite direction of nystagmus from typical P-BPPV-Can in both the Dix-Hallpike head position and upright sitting position. The patients had typical characteristics of nystagmus due to canalolithiasis, such as latency, duration of1 min, linear-torsional nystagmus, and fatigability. Rev-P-BPPV-Can appeared after the Epley maneuver for typical P-BPPV-Can; in other patients, Rev-P-BPPV-Can changed to typical P-BPPV-Can. The affected sides of Rev-P-BPPV-Can were decided by those of typical P-BPPV-Can.Canalolithiasis in the non-ampullary distal portion of the posterior semicircular canal may be a potential pathophysiology of Rev-P-BPPV-Can. The Epley maneuver has little effect for treating Rev-P-BPPV-Can, but spontaneous transition to typical P-BPPV-Can or spontaneous recovery is expected.

Each natural mode of the electromagnetic field within a parabolic mirror exhibits spatial localization and polarization properties that can be exploited for the quantum control of its interaction with atomic systems. The region of localization is not restricted to the focus of the mirror leading to a selective response of atomic systems trapped on its vicinity. We report calculations of the spontaneous emission rates for an atom trapped inside the mirror accounting for all atomic polarizations and diverse trapping regions. It is shown that electric dipole transitions can be enhanced near the focus of a deep parabolic mirror with a clear identification of the few vectorial modes involved. Out of the focus the enhancement vanishes gradually, but the number of relevant modes remains small. Ultimately this represents a quantum electrodynamic system where internal and external degrees of freedom cooperate to maximize a selective exchange and detection of single excitations.

Despite decades of research, our understanding of epilepsy, including how seizures are generated and propagate, is incomplete. However, there is growing recognition that epilepsy is more than just the occurrence of seizures, with patients often experiencing comorbid deficits in cognition that are poorly understood. In addition, the available therapies for treatment of epilepsy, from pharmaceutical treatment to surgical resection and seizure prevention devices, often exacerbate deficits in cognitive function. In this review, we discuss the hypothesis that seizure generation and cognitive deficits have a similar pathological source characterized by, but not limited to, deficits in theta oscillations and their influence on interneurons. We present a new framework that describes oscillatory states in epilepsy as alternating between hyper- and hypo-synchrony rather than solely the spontaneous transition to hyper-excitability characterized by the seizures. This framework suggests that as neural oscillations, specifically in the theta range, vary their tempo from a slowed almost adagio tempo during interictal periods to faster, more rhythmic allegretto tempo preictally, they impact the function of interneurons, modulating their ability to control seizures and their role in cognitive processing. This slow wave oscillatory framework may help explain why current therapies that work to reduce hyper-excitability do not completely eliminate seizures and often lead to exacerbated cognitive deficits.

Viral diseases of honey bees are important economically and ecologically and have been widely modelled. The models reflect the fact that, in contrast to the typical case for vertebrates, invertebrates cannot acquire immunity to a viral disease, so they are of SIS or (more often) SI type. Very often, these diseases may be transmitted vertically as well as horizontally, by vectors as well as directly, and through the environment, although models do not generally reflect all these transmission mechanisms. Here, we shall consider an important additional complication the consequences of which have yet to be fully explored in a model, namely that both infected honey bees and their vectors may best be described using more than one infection class. For honey bees, we consider three infection classes. Covert infections occur when bees have the virus under control, such that they do not display symptoms of the disease, and are minimally or not at all affected by it. Acutely overtly infected bees often exhibit severe symptoms and have a greatly curtailed lifespan. Chronically overtly infected bees typically have milder symptoms and a moderately shortened lifespan. For the vector, we consider just two infection classes which are covert infected and overt infected as has been observed in deformed-wing virus (DWV) vectored by varroa mites. Using this structure, we explore the impact of spontaneous transition of both mites and bees from a covertly to an overtly infected state, which is also a novel element in modelling viral diseases of honey bees made possible by including the different infected classes. The dynamics of these diseases are unsurprisingly rather different from the dynamics of a standard SI or SIS disease. In this paper, we highlight how our compartmental structure for infection in honey bees and their vectors impact the disease dynamics observed, concentrating in particular on DWV vectored by varroa mites. If there is no spontaneous transition, then a basic reproduction number $$R_0$$ R 0 exists. We derive a condition for $$R_0>1$$ R 0 > 1 that reflects the complexities of the system, with components for vertical and for direct and vector-mediated horizontal transmission, using the directed graph of the next-generation matrix of the system. Such a condition has never previously been derived for a honey-bee–mite–virus system. When spontaneous transitions do occur, then $$R_0$$ R 0 no longer exists, but we introduce a modification of the analysis that allows us to determine whether (i) the disease remains largely covert or (ii) a substantial outbreak of overt disease occurs.

The use of E u 3 + codoping for enhancing the H o 3 + : 5 I 5 → 5 I 6 emission in fluoroindate glasses shows that E u 3 + could depopulate the lower laser state H o 3 + : 5 I 6 while having little effect on the upper state H o 3 + : 5 I 5 , resulting in greater population inversion. The H o 3 + / E u 3 + codoped glass has high spontaneous transition probability ( 6.31 s − 1 ) together with large emission cross section ( 7.68 × 10 − 21 c m 2 ). This study indicates that codoping of H o 3 + with E u 3 + is a feasible alternative to quench the lower energy level of the 3.9 µm emission and the H o 3 + / E u 3 + codoped fluoroindate glass is a promising material for efficient 3.9 µm fiber lasers.

Two rhythmic coordinations, 0° and 180° relative phase, can be performed stably at preferred frequency (~ 1 Hz) without training. Evidence indicates that both 0° and 180° coordination entail detection of the relative direction of movement. At higher frequencies, this yields instability of 180° and spontaneous transition to 0°. The ability to perform a 90° coordination can be acquired by learning to detect and use relative position as information. We now investigate the skilled performance of 90° bimanual coordination with frequency scaling and whether 90° coordination exhibits mode switching to 0° or 180° at higher frequencies. Unlike the switching from 180° to 0°, a transition from the learned 90° coordination to the intrinsic 0° or 180° modes would entail a change in information. This would seem to require intentional decisions during performance as would correcting performance that had strayed from 90°. Relatedly, correction would seem to be an intrinsic part of the performance of 90° during learning. We investigated whether it remains so. We tested bimanual coordination at 90° under both noninterference and correcting instructions. Under correcting instructions, bimanual 90° coordination remained stable at both low and high frequencies. Noninterference instructions yielded stable performance at lower frequencies and switching to 0° or 180° at higher frequencies. Thus, correction is optional and switching to the intrinsic modes occurred. We extended the Bingham (Ecol Psychol 16:45–53, 2004a; Advances in psychology, vol. 135, Time-to-contact, Elsevier Science Publishers, 2004b) model for 0° and 180° coordination to create a dynamical, perception–action account of learned 90° bimanual coordination, in which mode switching and correction were both initiated as the information required for performance of 90° fell below threshold. This means that intentional decisions about what coordination to perform and whether to correct occurred only before performance was begun, not during performance. The extended strictly dynamical model was successfully used to simulate performance of participants in the experiments.

International audience; Anoxic spreading depolarization (aSD) has been hypothesized as a terminal event during oxygen-glucose deprivation (OGD) in submerged cortical slices in vitro. However, mechanical artifacts caused by aSD-triggered edema may introduce error in the assessment of neuronal viability. Here, using continuous patch-clamp recordings from submerged rat cortical slices, we first confirmed that vast majority of L4 neurons permanently lost their membrane potential during OGD-induced aSD. In some recordings, spontaneous transition from whole-cell to outside out configuration occurred during or after aSD, and only a small fraction of neurons survived aSD with reperfusion started shortly after aSD. Secondly, to minimize artifacts caused by OGD-induced edema, cells were short-term patched following OGD episodes of various duration. Nearly half of L4 cells maintained membrane potential and showed the ability to spike-fire if reperfusion started less than 10 min after aSD. The probability of finding live neurons progressively decreased at longer reperfusion delays at a rate of about 2% per minute. We also found that neurons in L2/3 show nearly threefold higher resistance to OGD than neurons in L4. Our results suggest that in the OGD ischemia model, aSD is not a terminal event, and that the "commitment point" of irreversible damage occurs at variable delays, in the range of tens of minutes, after OGD-induced aSD in submerged cortical slices. Duration of ischemia is the key factor determining neuronal survival, neurological, and behavioral outcome. During global brain ischemia caused by cardiac arrest, irreversible loss of brain function and legal death are conventionally thought to occur within 5-10 min of cardiac arrest 1. Paradoxically, however, neuronal function can be restored even after much longer periods of global ischemia under several experimental settings including extracorporeal reperfusion with special cytoprotective reperfusate up to 4 h after cardiac arrest in pigs 2 or maintenance of rat brain slices that were prepared 1-6 h after cardiac arrest 3 , or after 30 min middle cerebral artery occlusion 4 , in ACSF. These observations raised the hypothesis that neurons may survive much longer episodes of ischemia than traditionally thought, thus opening questions for further research on the possibility of expanding the time window for resuscitation. Development of brain injury during ischemia proceeds through the initial phase of compensation, during which brain activity ceases but neurons maintain their membrane potential, and recovery of cardiovascular function restores brain activity without major damage to the brain 1,5,6. Passage to the decompensation phase is associated with a wave of collective and nearly complete neuronal depolarization, so-called anoxic spreading depolarization (aSD) occurring at ~ 5 min after the onset of ischemia 5,7,8. Generation of aSD is caused by depletion of intracellular reserves of energy metabolites, loss of function of the energy-dependent active ion transporters and rupture in transmembrane ionic gradients 5,7,8. aSD is a highly energy-demanding event which severely aggravates metabolic status 9. Considerable evidence indicates that aSD is the key ischemic event that triggers cascades of intracellular reactions leading to acute and delayed neuronal death 5,7,8. Similarly, periinfarct depolarizations (PIDs) severely compromise the metabolic state in the penumbra and cause expansion of the ischemic core during the development of the focal ischemic injury 10. The oxygen-glucose deprivation (OGD) model of an ischemia-like condition has been extensively used to explore acute changes in neuronal function during metabolic insult in brain slices in vitro. In this model, metabolite deprivation causes a series of events largely recapitulating the development of ischemic injury OPEN

Transport of water in narrow nanochannels as a single-file chain is involved in various biological activities and nanofluidic applications. However, although the consistent dipole orientation of the water molecules is intensively studied, its effect upon the transport behavior is still unknown. In this Rapid Communication, we find two states of slow and fast transport coexist in the single-file water in the presence of channel defects that break the collective dipole orientation. A low diffusive mobility is found for the dipole orientation inconsistent configurations while mobility approximately two times higher is found for the consistent ones. The two-state diffusion process relies on the different hydrogen bond connections, which possess overlapped structures, enabling a spontaneous transition. The slow state is insensitive to the increased defect number while the fast state is reduced accordingly. The two states exhibit different lifetime and temperature dependences that demonstrate a possibility for manipulation. Our result implies the possibility of two-state diffusion process of water in nanofluid phenomena due to the common presence of defects in nanochannels.

Plasma is an ionized gas that is typically formed under high-temperature laboratory conditions. Recent progress in atmospheric plasmas has led to cold atmospheric plasma (CAP) devices with ion temperatures close to room temperature. The unique chemical and physical properties of CAP have led to its use in various biomedical applications including cancer therapy. CAP exhibits a spontaneous transition from a spatially homogeneous state to a modifiable pattern that is subject to self-organization. In this Opinion article, we discuss some new applications for plasma in cancer therapy based on plasma self-organization, which enables adaptive features in plasma-based therapeutic systems.

Human locomotion is a fundamental skill that is required for daily living, yet it is not completely known how human gait is regulated in a manner that seems so effortless. Gait transitions have been analyzed to gain insight into the control mechanisms of human locomotion since there is a known change that occurs as the speed of locomotion changes. Specifically, as gait speed changes, there is a spontaneous transition between walking and running that occurs at a particular speed. Despite the growing body of research on the determinants of this preferred transition speed and thus the triggering mechanisms of human gait transitions, a clear consensus regarding the control mechanisms of gait is still lacking. Therefore, this article reviews the determinants of the preferred transition speed using concepts of the dynamic systems theory and how these determinants contribute to four proposed triggers (i.e. metabolic efficiency, mechanical efficiency, mechanical load and cognitive and perceptual) of human gait transitions. While individual anthropometric and strength characteristics influence the preferred transition speed, they do not act to trigger a gait transition. The research has more strongly supported the mechanical efficiency and mechanical load determinants as triggering mechanisms of human gait transitions. These mechanical determinants, combined with cognitive and perceptual processes may thus be used to regulate human gait patterns through proprioceptive and perceptual feedback as the speed of locomotion changes.

Vertical MoO2/MoS2 core–shell structures were synthesized on an amorphous surface (SiO2) by chemical vapor deposition at a high heating rate using a configuration in which the vapor phase was confined. The confined reaction configuration was achieved by partially covering the MoO3-containing boat with a substrate, which allowed rapid buildup of the partially reduced MoO3–x crystals in an early stage (below 680 °C). Rapid temperature ramping to 780 °C enabled spontaneous transition of the reaction environment from sulfur-poor to sulfur-rich, which induced a sequential phase transition from MoO3–x to intermediate MoO2 and finally to MoO2/MoS2 core–shell structures. The orthorhombic crystal structure of MoO3–x contributed to the formation of vertical crystals on the amorphous substrate, whereas the nonvolatility of the subsequently formed MoO2 enabled layer-by-layer sulfurization to form MoS2 on the oxide surface with minimal resublimation loss of MoO2. By adjustment of the sulfurization temperature and time...

The ground state properties of β and ω phases in Ti-(0–30 at%)V alloys were calculated, and subsequently thermodynamics and energy barriers of the displacive β to ω transition were investigated by first-principles. The results show that the lattice parameters of β and ω phases decreases with increasing V content in Ti-V alloys. The principal lattice strains for the β to ω transition are highly compositional dependent, and the volume variation decreases with increasing V content. The mechanical stability of the ω phase increases initially at the V content around 10 at% and then decreases with increasing V content. Based on the quasiharmonic Debye model, a metastable diffusionless phase diagram has been established, showing that the ω phase is thermodynamically more stable than the β phase at room temperature, anticipating a spontaneous transition from β to ω phases in Ti-V alloys. The calculations of energy pathways indicate that there is an energy barrier during the displacive β to ω transition in Ti-V alloys at temperatures from 100 to 500 K, but not at 0 K.

SMYD3 plays a key role in cancer cell viability, adhesion, migration and invasion. SMYD3 promotes formation of inducible regulatory T cells and is involved in reducing autoimmunity. However, the nearly “closed” substrate-binding site and poor in vitro H3K4 methyltransferase activity have obscured further understanding of this oncogenically related protein. Here we reveal that SMYD3 can adopt an “open” conformation using molecular dynamics simulation and small-angle X-ray scattering. This ligand-binding-capable open state is related to the crystal structure-like closed state by a striking clamshell-like inter-lobe dynamics. The two states are characterized by many distinct structural and dynamical differences and the conformational transition pathway is mediated by a reversible twisting motion of the C-terminal domain (CTD). The spontaneous transition from the closed to open states suggests two possible, mutually non-exclusive models for SMYD3 functional regulation and the conformational selection mechanism and allostery may regulate the catalytic or ligand binding competence of SMYD3. This study provides an immediate clue to the puzzling role of SMYD3 in epigenetic gene regulation.

The violation of Leggett-Garg-type inequalities (LGtIs) is studied on a two-level atom, driven by an external field in the presence of a squeezed thermal reservoir. The violations are observed in the underdamped regime where the spontaneous transition rate is much smaller compared to the Rabi frequency. An increase in thermal effects is found to decrease the extent of violation as well as the time over which the violation lasts. With the increase in the value of the squeezing parameter the extent of violation of LGtIs is seen to reduce. The violation of LGtIs is favored by an increase in the driving frequency. Further, the interplay of the degree of violation and strength of the measurements is studied. It is found that the maximum violation occurs for ideal projective measurements.

Cardiac electrical alternans (CEA), manifested as T-wave alternans in ECG, is a clinical biomarker for predicting cardiac arrhythmias and sudden death. However, the mechanism underlying the spontaneous transition from CEA to arrhythmias remains incompletely elucidated. In this study, multiscale rabbit ventricular models were used to study the transition and a potential role of INa in perpetuating such a transition. It was shown CEA evolved into either concordant or discordant action potential (AP) conduction alternans in a homogeneous one-dimensional tissue model, depending on tissue AP duration and conduction velocity (CV) restitution properties. Discordant alternans was able to cause conduction failure in the model, which was promoted by impaired sodium channel with either a reduced or increased channel current. In a two-dimensional homogeneous tissue model, a combined effect of rate- and curvature-dependent CV broke-up alternating wavefronts at localised points, facilitating a spontaneous transition from CEA to re-entry. Tissue inhomogeneity or anisotropy further promoted break-up of re-entry, leading to multiple wavelets. Similar observations have also been seen in human atrial cellular and tissue models. In conclusion, our results identify a mechanism by which CEA spontaneously evolves into re-entry without a requirement for premature ventricular complexes or pre-existing tissue heterogeneities, and demonstrated the important pro-arrhythmic role of impaired sodium channel activity. These findings are model-independent and have potential human relevance., Author summary T-wave alternans (TWA), manifested as beat to beat alterations between large and small T-wave amplitudes on the electrocardiogram (ECG) is one of the prevalent clinical observations that are closely associated with cardiac arrhythmias and sudden death. TWA is believed to be underlined by cardiac alternans at the cellular level, but the extract mechanism for the transition from cellular alternans to that at the tissue level, and how this further spontaneously evolves into cardiac arrhythmias remains incompletely elucidated. In this study, multiscale rabbit ventricular computational models were used to address this issue by investigating the underlying mechanism(s) for the arrhythmogenesis of cardiac alternans, as well as a possible role of sodium channel on perpetuating cardiac arrhythmias. Our results demonstrated a spontaneous development of re-entry from cellular alternans, arising from a combined action of APD and CV restitution properties with the curvature-dependence of CV. Tissue inhomogeneity and anisotropy further promoted break-up of excitation waves, leading to multiple re-entrant excitation waves. It was also found impaired sodium channel with either increased or decreased channel current facilitated the arrhythmogenesis. This study provides new insights into underlying the mechanism, by which cellular cardiac alternans spontaneously evolves into cardiac arrhythmias. Similar results were observed in human atrial tissue models, suggesting our major findings are model-independent and of potential clinical relevance.

Cellular compartments are membrane-enclosed, spatially distinct microenvironments which confine and protect biochemical reactions in the biological cell. On the early Earth, the autonomous formation of compartments is thought to have led to the encapsulation of nucleotides, thereby satisfying a starting condition for the emergence of life. Recently, surfaces have come into focus as potential platforms for the self-assembly of prebiotic compartments, as significantly enhanced vesicle formation was reported in the presence of solid interfaces. The detailed mechanism of such formation at the mesoscale is still under discussion. We report here on the spontaneous transformation of solid surface-adhered lipid deposits to unilamellar membrane compartments through a straightforward sequence of topological changes, proceeding via a network of interconnected lipid nanotubes. We show that this transformation is entirely driven by surface-free energy minimization and does not require hydrolysis of organic molecules, or external stimuli such as electrical currents or mechanical agitation. The vesicular structures take up and encapsulate their external environment during formation, and can subsequently separate and migrate upon exposure to hydrodynamic flow. This may link, for the first time, the self-directed transition from weakly organized bioamphiphile assemblies on solid surfaces to protocells with secluded internal contents.SignificanceThe nature of the physical and chemical mechanisms behind the formation, growth and division of the earliest protocells is among the key questions concerning the origin of life. Establishing a simple pathway for the assembly of protocell structures from the primordial soup is a particular challenge. Emerging evidence supporting the assumption that solid surfaces have a governing role in protocell formation has recently expanded the scope, and created new inspiration for investigation. By presenting a physical path from self-assembled amphiphile-based membranes on solid surfaces to spherical single-membrane compartments via a consistent sequence of transformations, solely driven by the materials properties of the interfaces, a direct link between the presence of functional biomolecules and the development of protocells can be established.

We analyze the breakdown of causality for the perfect fluid limit in a medium with polarizeability. We show that to restore causality a relaxation term linking vorticity and polarization, analogous to the Israel-Stewart term linking viscous forces and gradients,is required. This term provides a minimum amount of dissipation a locally thermalized relativistic medium with polarizeability must have, independently of its underlying degrees of freedom. For ferromagnetic materials an infrared acausal mode remains, which we interpret as a Banks-Casher mode signaling spontaneous magnetization. With these ingredients, we propose a candidate for a fully causal Lagrangian of a relativistic polarizeable system near the perfect fluid limit., Version accepted for publication, Phys.Rev.D

Different cell lineages growing in microgravity undergo a spontaneous transition leading to the emergence of two distinct phenotypes. By returning these populations in a normal gravitational field, the two phenotypes collapse, recovering their original configuration. In this review, we hypothesize that, once the gravitational constraint is removed, the system freely explores its phenotypic space, while, when in a gravitational field, cells are "constrained" to adopt only one favored configuration. We suggest that the genome allows for a wide range of "possibilities" but it is unable per se to choose among them: the emergence of a specific phenotype is enabled by physical constraints that drive the system toward a preferred solution. These findings may help in understanding how cells and tissues behave in both development and cancer.

The goal of this study was to select and test some analysis tools to identify and characterize precursors to the onset of thermo-acoustic pulsation in a gas turbine combustor. The target flame was a turbulent, swirl-stability ethylene-air flame operated at ϕ = 0.91, and 5 bars pressure. 3-component stereo-particle image velocimetry (PIV) measurements, acquired at 9.3 kHz over periods of approximately 4 seconds were used to characterize the flow-field near the exit plane of the combustor. Acoustic measurements and OH*-chemiluminescence images were acquired synchronously, with OH* images acquired at every third cycle of the PIV measurement system. Analysis revealed the presence of two characteristic frequencies in the data for the stable flame; a 475 Hz oscillation associated with the shear-layer dynamics and a weak thermo-acoustic oscillation 610 Hz. In the excited state, a 720 Hz self-excited thermo-acoustic oscillation dominated combustor dynamics. A possible precursor event was identified in the form of a 635 Hz oscillation that appeared in the data 0.15s prior to transition. Bandpass filtering of the velocity data at this frequency showed this oscillation originates in the outer recirculation zone of the combustor.

International audience; When a high power output is required in cycling, a spontaneous transition by the cyclist from a seated to a standing position generally occurs. In this study, by varying the cadence and cyclist bodyweight, we tested whether the transition is better explained by the greater power economy of a standing position or by the emergence of mechanical constraints that force cyclists to stand. Ten males participated in five experimental sessions corresponding to different bodyweights (80%, 100%, or 120%) and cadences (50 RPM, 70 RPM, or 90 RPM). In each session, we first determined the seat-to-stand transition power (SSTP) in an incremental test. The participants then cycled at 20%, 40%, 60%, 80%, 100%, or 120% of the SSTP in the seated and standing positions, for which we recorded the saddle forces and electromyogram (EMG) signals of eight lower limb muscles. We estimated the cycling cost using an EMG cost function (ECF) and the minimal saddle forces in the seated position as an indicator of the mechanical constraints.Our results show the SSTP to vary with respect to both cadence and bodyweight. The ECF was lower in the standing position above the SSTP value (i.e., at 120%) in all experimental sessions. The minimal saddle forces varied significantly with respect to both cadence and bodyweight.These results suggest that optimization of the muscular cost function, rather than mechanical constraints, explain the seat-to-stand transition in cycling.

We study the critical behavior of a general contagion model where nodes are either active (e.g. with opinion A, or functioning) or inactive (e.g. with opinion B, or damaged). The transitions between these two states are determined by (i) spontaneous transitions independent of the neighborhood, (ii) transitions induced by neighboring nodes and (iii) spontaneous reverse transitions. The resulting dynamics is extremely rich including limit cycles and random phase switching. We derive a unifying mean-field theory. Specifically, we analytically show that the critical behavior of systems whose dynamics is governed by processes (i-iii) can only exhibit three distinct regimes: (a) uncorrelated spontaneous transition dynamics (b) contact process dynamics and (c) cusp catastrophes. This ends a long-standing debate on the universality classes of complex contagion dynamics in mean-field and substantially deepens its mathematical understanding., 11 pages, 8 figures

2.7 μm fluorescence has been achieved for the first time in Er 3+ doped novel germanosilicate glasses. Thermal stability, spectroscopic properties and energy transfer mechanism have been investigated in detail. Moreover, the spontaneous transition probability ( A rad ) and emission cross section of samples were calculated and analyzed. The prepared Er 3+ doped germanosilicate glasses possessing excellent thermal stability, high A rad (33.75 s −1 ) and emission cross section of 2.7 μm (1.90 × 10 −20 cm 2 ) provide a new material for the realization of mid-infrared fiber lasers.

In this Letter we report on controllable transition of aggregated γ-Cyclodextrins (γ-CDs) nanostructures by tuning the concentration of a long chain ionic liquid, 1-dodecyl-3-methyl imidazolium chloride (C 12 mimCl) added to the aqueous solution of γ-CDs. The gradual increase in concentration of C 12 mimCl first results in the breaking of γ-CDs aggregates by the formation of inclusion complexes with C 12 mimCl and then self-organizes into a new supramolecular aggregate. This spontaneous transition from one nanostructure to another has been established by spectroscopic and microscopic studies. It is worth to mention that addition of 1-octyl-3-methyl imidazolium chloride (C 8 mimCl) does not lead to any such transition.

A surface with Ni micro–nano cones array (MCA) was fabricated with electro-deposition method and exhibited super-hydrophilic nature when freshly prepared. Spontaneous transition from super-hydrophilicity to super-hydrophobicity was observed when the surface was exposed in air at room temperature. The special surface structure of MCA played an important role in amplifying the surface wettability. Since the surface structure remained the same as the freshly prepared Ni MCA films during the storage, the transition was proved to be attributed to the change of surface chemical composition. Such wettability transition property of Ni MCA films might shed light on the high-tech areas of self-cleaners, anti-corrosion materials, anti-contamination materials, etc.

2.7 μm emission from the Er3 + and Er3 +/Pr3 + ions doped oxyfluorotellurite glasses was detected when pumped with a 980 nm laser diode and their results were compared. It is found that 2.7 μm emission from Er3 + is enhanced by codoped with Pr3 + in the oxyfluoride tellurite glass. The emission characteristic at 2.7 μm and energy transfer (ET) have been investigated. The fabricated glass possesses a larger calculated emission cross section (1.01 × 10− 20 cm2) along with a higher spontaneous transition probability (60.92 s− 1) corresponding to the Er3 +: 4I11/2 → 4I13/2 transition. Additionally, large ET efficiency of 85% indicates the more efficient ET process from Er3 + to Pr3 + (Er3 +:4I13/2 + Pr3 +:3H4 → Er3 +:4I15/2 + Pr3 +:3F3). Therefore, codoping with Pr3 + ions can further improve the 2.7 μm emission of Er3 + via ET and the investigation of the materials in this study could help to find potential application of 2.7 μm laser.