Island Of Stability Research Articles

New islands of stability with double-trace deformations

We assess the role of a resonant spectrum in the AdS instability, and quantify the extent to which breaking the resonant spectrum of AdS can restore stability. Specifically, we study non-collapsing `multi-oscillator' solutions in AdS under various boundary conditions that allow for both resonant and non-resonant spectra. We find non-collapsing two mode, equal amplitude solutions in the non-resonant Robin case, and that these solutions vanish in the fully resonant Dirichlet case. This is consistent with non-resonant stability, and with the idea that stable solutions in the Dirichlet case are all single-mode dominated. Surprisingly, when the boundary condition is Neumann, we find non-collapsing solutions arbitrarily close to AdS that are not single-mode dominated, despite the spectrum being fully resonant.

Exploring the periodic table’s heaviest chemistry

Elements heavier than uranium don’t exist naturally on Earth. Researchers make these massive elements at the end of the periodic table by smashing smaller atoms together in particle accelerators. These experiments create just a handful of short-lived atoms, but researchers around the world can still investigate the chemical properties of the superheavy elements. Future experiments might yield longer-lived isotopes to help researchers probe new superheavies, elements that could challenge our knowledge of chemistry and even the periodic table itself. Join Speaking of Chemistry as we charter a tour toward this possible island of stability to learn how scientists working with elements at the end of the periodic table perform superheavy chemistry and what they hope to find out. Watch the episode at cenm.ag/islandofstability.

Human beings as islands of stability: Monitoring body states using breath profiles

By checking the reproducibility of conventional mid-infrared Fourier spectroscopy of human breath in a small test study (15 individuals), we found that a set of volatile organic compounds (VOC) of the individual breath samples remains reproducible at least for 18 months. This set forms a unique individual’s “island of stability” (IOS) in a multidimensional VOC concentration space. The IOS stability can simultaneously be affected by various life effects as well as the onset of a disease. Reflecting the body state, they both should have different characteristics. Namely, they could be distinguished by different temporal profiles: In the case of life effects (beverage intake, physical or mental exercises, smoking etc.), there is a non-monotonic shift of the IOS position with the return to the steady state, whereas a progressing disease corresponds to a monotonic IOS shift. As a first step of proving these dependencies, we studied various life effects with the focus on the strength and characteristic time of the IOS shift. In general, our results support homeostasis on a long time scale of months, allostasis on scales of hours to weeks or until smoke quitting for smokers, as well as resilience in the case of recovery from a disease.

Mixed global dynamics of forced vibro-impact oscillator with Coulomb friction.

This paper revisits a well-known model of forced vibro-impact oscillator with Amonton-Coulomb friction. In the vast majority of the existing studies, this model included also viscous friction, and its global dynamics in the state space is governed by periodic, quasiperiodic, or chaotic attractors. We demonstrate that removal of the viscous friction leads to qualitative modification of the global dynamics, namely, the state space is divided into the regions with "regular" attraction to the aforementioned special solutions and the regions with profoundly Hamiltonian dynamics. The latter regions contain structures typical for forced Hamiltonian systems: stability islands, extended nonattractive chaotic regions, etc. We prove that such local Hamiltonian behavior should occur for phase trajectories with nonvanishing velocity. Stability analysis for the periodic orbits confirms the above statement. It is demonstrated that similar mixed global dynamics can be observed in a broader class of models.

Vibration analysis of milling process with helix-angle cutter based on Euler method

The chatter vibration is the major limiting factor in increasing the metal removal rates of the machine tools. In this paper, a program for dynamic analysis of thin-walled milling process with helical milling cutter is developed, based on Euler iteration. The program can take into account the characteristics of thin-walled workpiece, the contact separation between workpiece and cutter, the helical angle of cutter teeth and other actual cutting process characteristics. Based on the stability lobe diagram obtained by semi-discrete method, the stability simulation in different cutting parameters around the stable island was carried out. The unstable form of the cutting process was determined by spectrum analysis and Poincare mapping method. The results show that the method is in good agreement with the results of stability Lobe diagram and can capture the stability island in small radial cutting process. This method can well grasp the cutting force and vibration evolution process in cutting process, and provide an effective means for stability analysis of cutting process.

Study on particle and cluster decay of superheavy nuclei Z = 130–144 using Cubic plus Proximity potential with improved transfer matrix method

The one-proton emission, alpha decay and cluster decay using a Cubic Plus Proximity model with improved transfer-matrix method are executed for the first time for the study of decay properties of 368 isotopes of nuclei, far from the beta stability line and beyond the islands of stability [Formula: see text] superheavy nuclei are studied within the range [Formula: see text]. The calculated decay half-lives are in good agreement with other theoretical approaches. The signature of neutron shell closure at [Formula: see text] and proton shell closure at [Formula: see text] obtained from half-life curves for emission of different clusters pronounces the previous predictions. Investigation of competition between various decay modes brings out the dominant decay mode associated with an isotope; for a given [Formula: see text] with increasing [Formula: see text] the dominant decay mode is seen to shift from proton decay to alpha decay and finally spontaneous fission. The decay modes and half-lives which are within the limit of experimental detection [Formula: see text] are presented.

Why Trump is Right to Pull American Troops from Syria

On December 19, 2018, President Donald Trump called for a “full” and “rapid” withdrawal of U.S. forces from the Syrian civil war, declaring on Twitter: “We have defeated ISIS in Syria, my only reason for being there.” This decision was in line with his campaign promise to bring American forces home from a messy and prolonged entanglement in the Middle East. Nonetheless, it set off a flurry of responses, beginning with General James Mattis’ subsequent resignation as Secretary of Defense. The Washington establishment reacted to these announcements in a typical fashion, condemning Trump’s decision and expressing shock over Mattis’ resignation. Senator Mark Warner (D-VA) declared: “This is scary. Secretary Mattis has been an island of stability amidst the chaos of the Trump administration.” Senator Lindsay Graham called the decision an “Obama-like mistake” and a “big win for ISIS, Iran, Bashar al Assad…and Russia.” Scholars from the Foundation for Defense of Democracies, the Atlantic Council, the Council on Foreign Relations, and the Center for a New American Security echoed that sentiment.

Stable X-islands of quadrupole mass filter.

Quadrupole mass filters are normally operated as narrow band pass filters by appropriate choices of rf and DC voltages corresponding to Mathieu a and q values near the apex of the first stability region. We add an auxiliary quadrupole excitation potential to the main drive voltage. As a result, stability islands appear on the () plane. The method of the islands mapping on the () plane is discussed in detail. The DC electric field's effect responsible for removing "shadowing" islands has been studied using a combination of analytic theory and computer modeling. We call a narrow stability region elongated along an iso- line an X-island. Two such stability islands were found where operation is possible without mass spectra interference when the DC potential is used. Those islands are formed by quadrupole potentials with relative excitation frequencies and , where Many other stability X-islands are presented in detail and illustrated by their transmission contours. This data is necessary for experimental testing of the separation mode at those islands. The study demonstrates how to use X-islands to achieve relatively high resolution 4000-12,000 at the transmission of about 28-15%, respectively.

The 3D secular dynamics of radial-velocity-detected planetary systems

Aims. To date, more than 600 multi-planetary systems have been discovered. Due to the limitations of the detection methods, our knowledge of the systems is usually far from complete. In particular, for planetary systems discovered with the radial velocity (RV) technique, the inclinations of the orbital planes, and thus the mutual inclinations and planetary masses, are unknown. Our work aims to constrain the spatial configuration of several RV-detected extrasolar systems that are not in a mean-motion resonance. Methods. Through an analytical study based on a first-order secular Hamiltonian expansion and numerical explorations performed with a chaos detector, we identified ranges of values for the orbital inclinations and the mutual inclinations, which ensure the long-term stability of the system. Our results were validated by comparison with n-body simulations, showing the accuracy of our analytical approach up to high mutual inclinations (∼70 ° −80°). Results. We find that, given the current estimations for the parameters of the selected systems, long-term regular evolution of the spatial configurations is observed, for all the systems, (i) at low mutual inclinations (typically less than 35°) and (ii) at higher mutual inclinations, preferentially if the system is in a Lidov-Kozai resonance. Indeed, a rapid destabilisation of highly mutually inclined orbits is commonly observed, due to the significant chaos that develops around the stability islands of the Lidov-Kozai resonance. The extent of the Lidov-Kozai resonant region is discussed for ten planetary systems (HD 11506, HD 12661, HD 134987, HD 142, HD 154857, HD 164922, HD 169830, HD 207832, HD 4732, and HD 74156).

A multi-reflection time-of-flight mass analyzer at IMP/CAS

Accurate mass data of transuranium nuclei is particularly important for the study of superheavy nuclei and the investigation of “island of stability”. A low energy mass spectrometer to provide high-precision mass measurement and isobaric separation of short-lived fusion-evaporation reaction products is planned at the Spectrometer for Heavy Atom and Nuclear Structure (SHANS). A multi-reflection time-of-flight mass analyzer for SHANS has been designed and constructed and is being tested now. In the in-trap-lift mode, the latest simulation results by using SIMION give a maximal mass resolving power of 1.6 × 105 for a TOF of 6.4 ms, and the preliminary test results by applying the simulated voltages show that its mass resolving power has reached ≈7000 for a TOF of 1.6 ms.

Resilience of BST-2/Tetherin structure to single amino acid substitutions.

Human tetherin, also known as BST-2 or CD317, is a dimeric, extracellular membrane-bound protein that consists of N and C terminal membrane anchors connected by an extracellular domain. BST-2 is involved in binding enveloped viruses, such as HIV, and inhibiting viral release in addition to a role in NF-kB signaling. Viral tethering by tetherin can be disrupted by the interaction with Vpu in HIV-1 in addition to other viral proteins. The structural mechanism of tetherin function is not clear and the effects of human tetherin mutations identified by sequencing consortiums are not known. To address this gap in the knowledge, we used data from the Ensembl database to construct and model known human missense mutations within the ectodomain to investigate how the structure of the ectodomain influences function. From the data, we identified an island of sequence stability within the ectodomain, which corresponds to a functionally and structurally important region identified in previous biochemical and biophysical studies. Most of the modeled mutations had little effect on the structure of the dimer and the coiled-coil, suggesting that the coiled-coil compensates for changes in primary structure. Thus, many of the functional defects observed in previous studies may not be due to changes in tetherin structure, but rather, due to in changes in protein-protein interactions or in aspects of tetherin not currently understood. The lack of structural effects by mutations known to decrease function further illustrates the need for more study of the structure-function connection for this system. Finally, apparent flexibility in tetherin sequence may allow for greater anti-viral activities with a larger number of viruses by reducing specific interactions with anti-tetherin proteins, while maintaining virus restriction.

Systematic study of α-decay half-lives of super-heavy nuclei with 106≤Z≤118

The α-decay half-lives of the superheavy nuclei are systematically studied using different versions of proximity potential and a exact method to calculate Coulomb potential between spherical and deformed nuclei in the framework of the double folding model. To reproduce the α-decay half-life, the experimental α-decay energy and Wentzel-Kramers-Brillouin approximation have been used. It is found that the computed values by the Ngô 80 are in good compromise with the experimental half-lives in comparison with other versions. Also, by using this version and within QWS4 for determination α-decay energies for superheavy elements, we had predicted the α-decay half-lives for superheavy nuclei which have not been reported yet. The long half-lives with magnitude about 100 seconds are predicted for the superheavy nuclei which are not in stability islands which indicating remarkable stability in comparison with their neighbors. These results are also in good agreement with the predictions of other semi-empirical formulas.

Two-parameter areal scaling in the Hénon map

We study a bifurcation cascade whose proper unfolding requires tuning more than one parameter simultaneously. Specifically, we investigate metric properties of extended self-similar triangular areas observed recently in the control parameter space of flows (lasers and electronic circuits), and maps. Such areas are delimited by shrimplike stability islands, seem to arise in unbounded quantities, and to accumulate in narrow intervals of control parameters. Numerically, we find their asymptotic rate of accumulation to be unity. The asymptotic properties of triangle vertices and their centroids are also investigated.

Extension of the nuclear landscape to hyperheavy nuclei

The properties of hyperheavy nuclei and the extension of nuclear landscape to hyperheavy nuclei are extensively studied within covariant density functional theory. Axial reflection symmetric and reflection asymmetric relativistic Hartree-Bogoliubov (RHB) calculations are carried out. The role of triaxiality is studied within triaxial RHB and triaxial relativistic mean field + BCS frameworks. With increasing proton number beyond Z~130 the transition from ellipsoidal-like nuclear shapes to toroidal ones takes place. The description of latter shapes requires the basis which is typically significantly larger than the one employed for the description of ellipsoidal-like shapes. Many hyperheavy nuclei with toroidal shapes are expected to be unstable towards multifragmentation. However, three islands of stability of spherical hyperheavy nuclei have been predicted for the first time in Ref. [1]. Proton and neutron densities, charge radii, neutron skins and underlying shell structure of the nuclei located in the centers of these islands have been investigated in detail. Large neutron shell gaps at N=228, 308 and 406 define approximate centers of these islands in neutron number. On the contrary, large proton gap appear only at Z=154 in the (Z~156, N~310) island. As a result, this is the largest island of stability of spherical hyperheavy nuclei found in the calculations. The calculations indicate the stability of the nuclei in these islands with respect of octupole and triaxial distortions. Fission barriers in neutron-rich superheavy nuclei are studied in triaxial RHB framework; the impact of triaxiality on the heights of fission barriers is substantial in some parts of this region. Based on the results obtained in the present work, the extension of nuclear landscape to hyperheavy nuclei is provided.

Twisted states in nonlocally coupled phase oscillators with frequency distribution consisting of two Lorentzian distributions with the same mean frequency and different widths.

In globally coupled phase oscillators, the distribution of natural frequency has strong effects on both synchronization transition and synchronous dynamics. In this work, we study a ring of nonlocally coupled phase oscillators with the frequency distribution made up of two Lorentzians with the same center frequency but with different half widths. Using the Ott-Antonsen ansatz, we derive a reduced model in the continuum limit. Based on the reduced model, we analyze the stability of the incoherent state and find the existence of multiple stability islands for the incoherent state depending on the parameters. Furthermore, we numerically simulate the reduced model and find a large number of twisted states resulting from the instabilities of the incoherent state with respect to different spatial modes. For some winding numbers, the stability region of the corresponding twisted state consists of two disjoint parameter regions, one for the intermediate coupling strength and the other for the strong coupling strength.

Characteristic times in the standard map.

We study and compare three characteristic times of the standard map: the Lyapunov time t_{L}, the Poincaré recurrence time t_{r}, and the stickiness (or escape) time t_{st}. The Lyapunov time is the inverse of the Lyapunov characteristic number (L) and in general is quite small. We find empirical relations for the L as a function of the nonlinearity parameter K and of the chaotic area A. We also find empirical relations for the Poincaré recurrence time t_{r} as a function of the nonlinearity parameter K, of the chaotic area A, and of the size of the box of initial conditions ε. As a consequence, we find relations between t_{r} and L. We compare the distributions of the stickiness time and the Poincaré recurrence time. The stickiness time inside the sticky regions at the boundary of the islands of stability is orders of magnitude smaller than the Poincaré recurrence time t_{r} and this affects the diffusion exponent μ, which converges always to the value μ=1. This is shown in an extreme stickiness case. The diffusion is anomalous (ballistic motion) inside the accelerator mode islands of stability with μ=2 but it is normal everywhere outside the islands with μ=1. In a particular case of extreme stickiness, we find the hierarchy of islands around islands.

On the location of the ring around the dwarf planet Haumea

The recently discovered ring around the dwarf planet (136108) Haumea is located near the 1:3 resonance between the orbital motion of the ring particles and the spin of Haumea. In the current work is studied the dynamics of individual particles in the region where is located the ring. Using the Poincar\'e Surface of Section technique, the islands of stability associated with the 1:3 resonance are identified and studied. Along all its existence this resonance showed to be doubled, producing pairs of periodic and quasi-periodic orbits. The fact of being doubled introduces a separatrix, which generates a chaotic layer that significantly reduces the size of the stable regions of the 1:3 resonance. The results also show that there is a minimum equivalent eccentricity ($e_{1:3}$) for the existence of such resonance. This value seems to be too high to keep a particle within the borders of the ring. On the other hand, the Poincar\'e Surface of Sections show the existence of much larger stable regions, but associated with a family of first kind periodic orbits. They exist with equivalent eccentricity values lower than $e_{1:3}$, and covering a large radial distance, which encompasses the region of the Haumea's ring. Therefore, this analysis suggests the Haumea's ring is in a stable region associated with a first kind periodic orbit instead of the 1:3 resonance.

Investigation on the onset voltage and stability island of electrospray in the cone-jet mode using curved counter electrode

The objective of this study was to examine the effect of curved counter electrodes on the onset voltage and the stability island of the electrohydrodynamic atomization (EHDA) in the cone-jet mode. Five types of counter electrodes, regarding their curvature, and seven capillary nozzles with different diameters were used. Therefore, the effect of geometrical parameters on the onset voltage is investigated. Dimensionless numbers are used to help to generalize the results. These results are compared to the theoretical equation for the onset voltage. The results show the dependency of the onset coefficient on various parameters, specifically the counter electrode curvature. In addition, for a given configuration, the use of curved counter electrode led to about a 50% increase in the stability island area.

Approaching the Island of Stability --- Walking on Firm Grounds

The research in the field of superheavy elements started in the sixties of the last century triggered by the prediction of a region of enhanced nuclear stability at the next closed proton and neutron shells beyond 208Pb. Adam Sobiczewski was one of the first predicting proton and neutron numbers for these shell closures at Z = 114 and N = 184, respectively. In the following decades, extensive efforts led to the synthesis of isotopes of elements up to Z = 118 in a fruitful competition of the leading laboratories in the field with FLNR/JINR in Dubna, Russia, LBNL in Berkeley, USA, GSI in Darmstadt, Germany and most recently RIKEN in Wako (Tokyo), Japan. Beyond the synthesis of new elements and isotopes, substantial activities were dedicated to nuclear structure studies, laying the basis for the understanding of this exotic nuclear matter. In-beam spectroscopy as well as decay spectroscopy after separation (DSAS) together with the support by theory have the potential to lay the basis for a successful approach of the so-called island of stability, the firm grounds, the creation of which had been started by pioneers like Adam Sobiczewski in the beginning of the second half of last century. In this paper, some of the achievements mainly of DSAS will be presented, with an emphasis on the guidance by theory and the work of Adam Sobiczewski, to whom this paper is dedicated.

New Constraints on Classical de Sitter: Flirting with the Swampland

AbstractWe study the existence and stability of classical de Sitter solutions of type II supergravities with parallel ‐branes and orientifold ‐planes. Together with the dilaton and volume scalar fields, we consider a third one that distinguishes between parallel and transverse directions to the . We derive the complete scalar potential for these three fields. This formalism allows us to reproduce known constraints obtained in 10d, and to derive new ones. Specifying to group manifolds with constant fluxes, we exclude a large region of parameter space, forbidding de Sitter solutions on nilmanifolds, semi‐simple group manifolds, and some solvmanifolds (at least in some standard algebra basis). In the small remaining region, we identify a stability island, where the three scalars could be stabilized in any de Sitter solution. We discuss these results in the swampland context.