Nice Model Research Articles

Fields with a dense-codense linearly independent multiplicative subgroup

We study expansions of an algebraically closed field K or a real closed field R with a linearly independent subgroup G of the multiplicative group of the field or the unit circle group $${\mathbb {S}}(R)$$, satisfying a density/codensity condition (in the sense of geometric theories). Since the set G is neither algebraically closed nor algebraically independent, the expansion can be viewed as “intermediate” between the two other types of dense/codense expansions of geometric theories: lovely pairs and H-structures. We show that in both the algebraically closed field and real closed field cases, the resulting theory is near model complete and the expansion preserves many nice model theoretic conditions related to the complexity of definable sets such as stability and NIP.

Superparamagnetic enzyme-graphene oxide magnetic nanocomposite as an environmentally friendly biocatalyst: Synthesis and biodegradation of dye using response surface methodology

The unique properties of graphene oxide (GO) nanosheets were integrated with the superparamagnetic characteristics of the CuFe2O4 nanoparticles to synthesize the magnetic graphene oxide (MGO), which was chemically modified with 3-amino propyl trimethoxy silane (APTMS) to functionalize the amine group on MGO (MGO-NH2). Afterward, MGO-NH2 was activated with glutaraldehyde (GLU) as a crosslinking agent to synthesize the functionalized MGO (fMGO) and its capability toward covalent Laccase immobilization was investigated. The comprehensive structural analysis using various characterization techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) clearly confirmed the covalent attachment of laccase onto MGO. The response surface methodology (RSM), based on Central Composite Design (CCD), was applied to optimize the immobilized Laccase (nanobiocatalyst)-mediated biodegradation of Direct Red 23 (DR23), as an azo dye, by considering independent variables such as nanobiocatalyst dosage, dye concentration, and pH. The optimal conditions to obtain the maximum decolorization yield (95.33%) were nanobiocatalyst dosage = 290.23 mg/L, dye concentration = 19.60 mg/L, and pH = 4.23. The obtained correlation coefficient and the adjusted one of 0.9651 and 0.9336, respectively, imply the nice model fitness. Therefore, structural characterization along with the experimental decolorization results introduced the synthesized superparamagnetic GO as an environmentally friendly nanobiocatalyst for effective decolorization purposes.

Excitation of a Primordial Cold Asteroid Belt as an Outcome of Planetary Instability

Abstract The main asteroid belt (MB) is low in mass but dynamically excited. Here we propose a new mechanism to excite the MB during the giant planet (the “Nice model”) instability, which is expected to feature repeated close encounters between Jupiter and one or more ice giants (“jumping Jupiter” or JJ). We show that, when Jupiter temporarily reaches a high-enough level of excitation, both in eccentricity and inclination, it induces strong forced vectors of eccentricity and inclination across the MB region. Because during the JJ instability Jupiter’s orbit “jumps” around, the forced vectors keep changing both in magnitude and phase throughout the whole MB region. The entire cold primordial MB is thus excited as a natural outcome of the JJ instability. The level of such an excitation, however, is typically larger than the current orbital excitation observed in the MB. We show that the subsequent evolution of the solar system is capable of reshaping the resultant overexcited MB to its present-day orbital state, and that a strong mass depletion (∼90%) is associated with the JJ instability phase and its subsequent evolution throughout the age of the solar system.

Dynamical effects on the classical Kuiper belt during the excited-Neptune model

The link between the dynamical evolution of the giant planets and the Kuiper Belt orbital structure can provide clues and insight about the dynamical history of the Solar System. The classical region of the Kuiper Belt has two populations (the cold and hot populations) with completely different physical and dynamical properties. These properties have been explained in the framework of a sub-set of the simulations of the Nice Model, in which Neptune remained on a low-eccentricity orbit (Neptune’s eccentricity is never larger than 0.1) throughout the giant planet instability (Nesvorný 2015a,b). However, recent simulations (Gomes et al., 2018) have showed that the remaining Nice model simulations, in which Neptune temporarily acquires a large-eccentricity orbit (larger than 0.1), are also consistent with the preservation of the cold population (inclination smaller than 4°), if the latter formed in situ. However, the resulting a cold population showed in many of the simulations eccentricities larger than those observed for the real population. The purpose of this work is to discuss the dynamical effects on the Kuiper belt region due to an excited Neptune phase. We focus on a short period of time, of about six hundred thousand years, which is characterized by Neptune’s large eccentricity and smooth migration with a slow precession of Neptune’s perihelion. This phase was observed during a full simulation of the Nice Model (Gomes et al., 2018) just after the last jump of Neptune’s orbit due to an encounter with another planet. We show that if self-gravity is considered in the disk, the precession rate of the particles longitude of perihelion ϖ is slowed down, which in turn speeds up the cycle of ϖN−ϖ (the subscript N referring to Neptune), associated to the particles eccentricity evolution. This, combined with the effect of mutual scattering among the bodies, which spreads all orbital elements, allows some objects to return to low eccentricities. However, we show that if the cold population originally had a small total mass, this effect is negligible. Thus, we conclude that the only possibilities to keep at low eccentricity some cold-population objects during a high-eccentricity phase of Neptune are that (i) either Neptune’s precession was rapid, as suggested by Batygin et al. (2011) or (ii) Neptune’s slow precession phase was long enough to allow some particles to experience a full secular cycle of ϖ−ϖN.

Marcel van der Heijden.

Marcel van der Heijden.

Mars’ growth stunted by an early giant planet instability

Many dynamical aspects of the solar system can be explained by the outer planets experiencing a period of orbital instability sometimes called the Nice Model. Though often correlated with a perceived delayed spike in the lunar cratering record known as the Late Heavy Bombardment (LHB), recent work suggests that this event may have occurred much earlier; perhaps during the epoch of terrestrial planet formation. While current simulations of terrestrial accretion can reproduce many observed qualities of the solar system, replicating the small mass of Mars requires modification to standard planet formation models. Here we use 800 dynamical simulations to show that an early instability in the outer solar system strongly influences terrestrial planet formation and regularly yields properly sized Mars analogs. Our most successful outcomes occur when the terrestrial planets evolve an additional 1–10 million years (Myr) following the dispersal of the gas disk, before the onset of the giant planet instability. In these simulations, accretion has begun in the Mars region before the instability, but the dynamical perturbation induced by the giant planets’ scattering removes large embryos from Mars’ vicinity. Large embryos are either ejected or scattered inward toward Earth and Venus (in some cases to deliver water), and Mars is left behind as a stranded embryo. An early giant planet instability can thus replicate both the inner and outer solar system in a single model.

The proposed origin of our solar system with planet migration

Two new models to explain the origin and history of our solar system are reviewed from a creation perspective, the Grand Tack model and the Nice model. These new theories propose that the four outer planets formed closer to the Sun, as well as closer together, than today. Then their orbits underwent periods of migration. Theories developed in the research on extrasolar planet systems are today being applied to our own solar system. The new migration models are finding much support from the planetary science community. These new models are summarized and evaluated Biblically and scientifically. Rather than demonstrating how our solar system formed, the new migration models can be understood as supporting the intelligent design of our solar system.

Analysis of In Vivo Cell Migration in Mosaic Zebrafish Embryos.

Being optically clear, the zebrafish embryo is a nice model system to analyze cell migration in vivo. This chapter describes a combination of injection and cell transplant procedures that allows creation of mosaic embryos, containing a few cells labeled differently from their neighbors. Rapid 5D confocal imaging of these embryos permits to simultaneously track and quantify the movement of large cell groups, as well as analyze the cellular or subcellular dynamics of transplanted cells during their migration. In addition, expression of a candidate gene can be modified in transplanted cells. Comparing behavior of these cells to control or neighboring cells allows determination of the role of the candidate gene in cell migration. We describe the procedure, focusing on one specific cell population during gastrulation, but it can easily be adapted to other cell populations and other migration events during early embryogenesis.

Simulations of the Solar System's Early Dynamical Evolution with a Self-gravitating Planetesimal Disk

Abstract Over the course of the last decade, the Nice model has dramatically changed our view of the solar system’s formation and early evolution. Within the context of this model, a transient period of planet–planet scattering is triggered by gravitational interactions between the giant planets and a massive primordial planetesimal disk, leading to a successful reproduction of the solar system’s present-day architecture. In typical realizations of the Nice model, self-gravity of the planetesimal disk is routinely neglected, as it poses a computational bottleneck to the calculations. Recent analyses have shown, however, that a self-gravitating disk can exhibit behavior that is dynamically distinct, and this disparity may have significant implications for the solar system’s evolutionary path. In this work, we explore this discrepancy utilizing a large suite of Nice model simulations with and without a self-gravitating planetesimal disk, taking advantage of the inherently parallel nature of graphic processing units. Our simulations demonstrate that self-consistent modeling of particle interactions does not lead to significantly different final planetary orbits from those obtained within conventional simulations. Moreover, self-gravitating calculations show similar planetesimal evolution to non-self-gravitating numerical experiments after dynamical instability is triggered, suggesting that the orbital clustering observed in the distant Kuiper Belt is unlikely to have a self-gravitational origin.

Details of Resonant Structures within a Nice Model Kuiper Belt: Predictions for High-perihelion TNO Detections

Abstract We analyze a detailed Nice model simulation of Kuiper Belt emplacement from Brasser & Morbidelli, where Neptune undergoes a high-eccentricity phase and migrates outward. In this work, which follows from Pike et al., we specifically focus on the details of structures within Neptune’s mean-motion resonances and in the high-pericenter population of simulated trans-Neptunian objects (TNOs). We find several characteristics of these populations that should be observable in the distant solar system in future large-scale TNO surveys as a diagnostic of whether or not this mode of Neptune migration occurred in the early solar system. We find that the leading asymmetric libration islands of the n:1 resonances are generally much more populated than the trailing islands. We also find the nonresonant high-q population of TNOs should have higher inclinations than the low-q population due to the importance of Kozai cycling during their emplacement histories. Finally, high-q TNOs should be present in roughly equal numbers on either side of distant mean-motion resonances. These predictions contrast with predictions from other Kuiper Belt emplacement simulations and will be testable by upcoming surveys.

90 Head-to-head comparison shows poor performance of both diamond-forrester and pryor models in predicting coronary artery disease in chest pain patients: a single centre experience in a large cohort of patients

BackgroundAn optimal investigation strategy for patients with suspected angina pectoris (AP) remains elusive. UK and ESC guidelines use historical prediction models to guide management after the likelihood of coronary artery...

Main photophysical properties of oxyblepharismin

Oxyblepharismin is the photo-oxidized form of blepharismin, the chromophore responsible for the photophobic response of heterotrich ciliate Blepharisma japonicum, and represents a nice model for the study of photo-transduction. In this work, we focused on the photophysical characterization of OxyBP, in view of highlighting the main features related to excitation and emission. By a combined experimental and computational approach we identified the main features of absorption and fluorescence emission of the molecule in solvents of different properties, identifying the nature of transitions as well as the possible heterogeneity at ground/excited state. The thorough photophysical characterization of OxyBP is meant to provide the starting point for the elucidation of the photo-transduction pathway in vivo.

8-5-3 NICE モデルによるエネルギー将来試算

8-5-3 NICE モデルによるエネルギー将来試算

The Structure of the Distant Kuiper Belt in a Nice Model Scenario

Abstract This work explores the orbital distribution of minor bodies in the outer Solar System emplaced as a result of a Nice model migration from the simulations of Brasser and Morbidelli. This planetary migration scatters a planetesimal disk from between 29 and 34 au and emplaces a population of objects into the Kuiper Belt region. From the 2:1 Neptune resonance and outward, the test particles analyzed populate the outer resonances with orbital distributions consistent with trans-Neptunian object (TNO) detections in semimajor axis, inclination, and eccentricity, while capture into the closest resonances is too efficient. The relative populations of the simulated scattering objects and resonant objects in the 3:1 and 4:1 resonances are also consistent with observed populations based on debiased TNO surveys, but the 5:1 resonance is severely underpopulated compared to population estimates from survey results. Scattering emplacement results in the expected orbital distribution for the majority of the TNO populations; however, the origin of the large observed population in the 5:1 resonance remains unexplained.

Cometary impact rates on the Moon and planets during the late heavy bombardment

Context. The Nice model predicts that the trans-planetary planetesimal disk made a large or even dominant contribution to the cratering in the inner solar system during the late heavy bombardment (LHB). In the presence of evidence that lunar craters and mare basins may be mainly of asteroidal origin, there is a dilemma of the missing comets that is not yet resolved.Aims. We aim to revisit the problem of cometary impact rates on the Moon and the terrestrial planets during the LHB with a flexible model, allowing us to study the influences of physical destruction of comets, the mass of the primordial disk, and the distribution of this mass over the entire size range.Methods. We performed a Monte Carlo study of the dynamics of the cometary LHB projectiles and derive the impact rates by calculating individual collision probabilities for a huge sample of projectile orbits. We used Minimum Orbit Intersection Distances (MOIDs) according to a new scheme introduced here. Different calculations were performed using different models for the physical evolution of comet nuclei and for the properties of the primordial, trans-planetary disk.Results. Based on the capture probability of Jupiter Trojans, we find a best fit radius of the largest LHB comet impacting the Moon for a low-mass primordial disk. For this disk mass, the LHB cratering of the Moon, Mercury and Mars were dominated by asteroids. However, some smaller lunar maria were likely preceded by comet impacts. The volatile delivery to the Earth and Mars by LHB comets was much less than their water inventories.Conclusions. There is no excessive cometary cratering, if the LHB was caused by a late planetary instability in the Nice Model. The Earth and Mars obtained their water very early in their histories. The Noachian water flows on Mars cannot be attributed to the arrival of LHB-related H2 O or CO2 .

Exploring the Stability and Cardiolipin Affinity of Cytochrome C's Domain Swapped Dimer Conformation

Cytochrome c's (cytc) oxidation of the lipid cardiolipin (CL) is a proposed switch involved in initiation of the intrinsic pathway of apoptosis. Recently, there has been an increased number of reports in the literature of cytc domain-swapped dimers (DSD). The Hirota lab has reported that the horse DSD has increased peroxidase activity compared to the monomeric form. The Bowler lab has solved DSD crystal structures with various detergents binding in the hydrophobic tube of the proposed “C” cytc-CL binding site. We postulate that the DSD conformation of cytc is an evolutionary switch allowing for tighter regulation of the intrinsic pathway of apoptosis. In order to examine the stability of the DSD, samples were incubated temporally at fixed temperatures and then analyzed using size-exclusion chromatography. The data, presented here, indicate that the human DSD is more kinetically stable than horse or yeast DSD, suggesting evolution of a more kinetically stable conformation in primates. Additionally, fluorescence correlation spectroscopy (FCS) data, also presented, show the binding of Zn-cytc to CL nanodiscs (ND). ND are discoidal lipid bilayers maintained by two alpha helical belt proteins and provide a nice model system to study protein-lipid interactions. Initial FCS results indicate that the Kd of cytc for CL NDs is in the micromolar range. This poster will compare the relative CL binding affinities of monomer and DSD cytc.

Shedding light on interictal epileptic spikes: An in vivo study using fast optical signal and electrocorticography.

Interictal epileptic spikes (IESs), apart from being a key marker of epileptic neuronal networks, constitute a nice model of the widespread endogenous phenomenon of neuronal hypersynchronization. Many questions concerning the mechanisms that drive neurons to hypersynchronize remain unresolved, but synaptic as well as nonsynaptic events are likely to be involved. In this study, changes in optical properties of neural tissues were observed in rats with penicillin-induced IES using fast optical signal (FOS) concomitantly with electrocorticography (ECoG). In this study, near-infrared optical imaging was used with ECoG to investigate variations in the optical properties of cortical tissue directly associated with neuronal activity in 15 rats. FOS changes correspond to variations of scattered light from neuronal tissue when neurons are activated. To independently evaluate our method, a control experiment on somatosensory was designed and applied to seven different rats. Time-frequency analysis was also used to track variations of (de)synchronization concomitantly with changes in optical signals during IES. FOS responses revealed that changes in optical signals occurred 320 msec before to 370 msec after the IES peak. These changes started before any changes in ECoG signal. In addition, time-frequency domain electrocorticography revealed an alternating decrease-increase-decrease in the ECoG spectral power (pointing to desynchronization-synchronization-desynchronization), which occurred concomitantly with an increase-decrease-increase in relative optical signal during the IES. These results suggest a relationship between (de)synchronization and optical changes. These changes in the neuronal environment around IESs raise new questions about the mechanisms that induce changes in optical properties of neural tissues before the IES, which may provide suitable conditions for neuronal synchronization during IESs. FOS-ECoG constitutes a multimodal approach and opens new avenues to study the mechanisms of neuronal synchronization in the pathologic brain, which has clinical implications, at least in epilepsy.

Phototaxis Assay for Chlamydomonas reinhardtii.

Phototaxis is a behavior in which organisms move toward or away from the light source (positive or negative phototaxis, respectively). It is crucial for phototrophic microorganisms to inhabit under proper light conditions for phototaxis. The unicellular green alga Chlamydomonas reinhardtii rapidly changes its swimming direction upon light illumination, and thus is a nice model organism for phototaxis research. Here we show two methods to assay Chlamydomonas phototaxis; one is a quick, easy and qualitative analysis, so-called the dish assay; and the other is a quantitative single-cell analysis.

Ring formation around giant planets by tidal disruption of a single passing large Kuiper belt object

The origin of rings around giant planets remains elusive. Saturn’s rings are massive and made of 90–95% of water ice with a mass of ∼1019 kg. In contrast, the much less massive rings of Uranus and Neptune are dark and likely to have higher rock fraction. According to the so-called “Nice model”, at the time of the Late Heavy Bombardment, giant planets could have experienced a significant number of close encounters with bodies scattered from the primordial Kuiper Belt. This belt could have been massive in the past and may have contained a larger number of big objects (Mbody=1022 kg) than what is currently observed in the Kuiper Belt. Here we investigate, for the first time, the tidal disruption of a passing object, including the subsequent formation of planetary rings. First, we perform SPH simulations of the tidal destruction of big differentiated objects (Mbody=1021 and 1023 kg) that experience close encounters with Saturn or Uranus. We find that about 0.1–10% of the mass of the passing body is gravitationally captured around the planet. However, these fragments are initially big chunks and have highly eccentric orbits around the planet. In order to see their long-term evolution, we perform N-body simulations including the planet’s oblateness up to J4 starting with data obtained from the SPH simulations. Our N-body simulations show that the chunks are tidally destroyed during their next several orbits and become collections of smaller particles. Their individual orbits then start to precess incoherently around the planet’s equator, which enhances their encounter velocities on longer-term evolution, resulting in more destructive impacts. These collisions would damp their eccentricities resulting in a progressive collapse of the debris cloud into a thin equatorial and low-eccentricity ring. These high energy impacts are expected to be catastrophic enough to produce small particles. Our numerical results also show that the mass of formed rings is large enough to explain current rings including inner regular satellites around Saturn and Uranus. In the case of Uranus, a body can go deeper inside the planet’s Roche limit resulting in a more efficient capture of rocky material compared to Saturn’s case in which mostly ice is captured. Thus, our results can naturally explain the compositional difference between the rings of Saturn, Uranus and Neptune.

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

We investigate the formation and evolution of comet nuclei and other trans-Neptunian objects (TNOs) in the solar nebula and primordial disk prior to the giant planet orbit instability foreseen by the Nice model. Aims. Our goal is to determine whether most observed comet nuclei are primordial rubble-pile survivors that formed in the solar nebula and young primordial disk or collisional rubble piles formed later in the aftermath of catastrophic disruptions of larger parent bodies. We also propose a concurrent comet and TNO formation scenario that is consistent with observations. Methods. We used observations of comet 67P/Churyumov-Gerasimenko by the ESA Rosetta spacecraft, particularly by the OSIRIS camera system, combined with data from the NASA Stardust sample-return mission to comet 81P/Wild 2 and from meteoritics; we also used existing observations from ground or from spacecraft of irregular satellites of the giant planets, Centaurs, and TNOs. We performed modeling of thermophysics, hydrostatics, orbit evolution, and collision physics. Results. We find that thermal processing due to short-lived radionuclides, combined with collisional processing during accretion in the primordial disk, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles like CO and CO2; they contain little to no amorphous water ice, and have experienced extensive metasomatism and aqueous alteration due to liquid water. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. Contrarily, comet nuclei have low density, high porosity, weak strength, are rich in supervolatiles, may contain amorphous water ice, and do not display convincing evidence of in situ metasomatism or aqueous alteration. We outline a comet formation scenario that starts in the solar nebula and ends in the primordial disk, that reproduces these observed properties, and additionally explains the presence of extensive layering on 67P/Churyumov-Gerasimenko (and on 9P/Tempel 1 observed by Deep Impact), its bi-lobed shape, the extremely slow growth of comet nuclei as evidenced by recent radiometric dating, and the low collision probability that allows primordial nuclei to survive the age of the solar system. Conclusions. We conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles. We argue that TNOs formed as a result of streaming instabilities at sizes below ~400 km and that ~350 of these grew slowly in a low-mass primordial disk to the size of Triton, Pluto, and Eris, causing little viscous stirring during growth. We thus propose a dynamically cold primordial disk, which prevented medium-sized TNOs from breaking into collisional rubble piles and allowed the survival of primordial rubble-pile comets. We argue that comets formed by hierarchical agglomeration out of material that remained after TNO formation, and that this slow growth was a necessity to avoid thermal processing by short-lived radionuclides that would lead to loss of supervolatiles, and that allowed comet nuclei to incorporate ~3 Myr old material from the inner solar system.