End State Research Articles

A computational theory of the subjective experience of flow

Flow is a subjective state characterized by immersion and engagement in one’s current activity. The benefits of flow for productivity and health are well-documented, but a rigorous description of the flow-generating process remains elusive. Here we develop and empirically test a theory of flow’s computational substrates: the informational theory of flow. Our theory draws on the concept of mutual information, a fundamental quantity in information theory that quantifies the strength of association between two variables. We propose that the mutual information between desired end states and means of attaining them — I({M;E}) — gives rise to flow. We support our theory across five experiments (four preregistered) by showing, across multiple activities, that increasing I({M;E}) increases flow and has important downstream benefits, including enhanced attention and enjoyment. We rule out alternative constructs including alternative metrics of associative strength, psychological constructs previously shown to predict flow, and various forms of instrumental value.

Role of Gauss-Bonnet corrections in a DGP brane gravitational collapse

An Oppenheimer-Snyder (OS)-type collapse is considered for a Dvali-Gabadadze-Porrati (DGP) brane, whereas a Gauss-Bonnet (GB) term is provided for the bulk. We study the combined effect of the DGP induced gravity plus the GB curvature, regarding any modification of the general relativistic OS dynamics. Our paper has a twofold objective. On the one hand, we investigate the nature of singularities that may arise at the collapse end state. It is shown that all dynamical scenarios for the contracting brane would end in one of the following cases, depending on conditions imposed: either a central shell-focusing singularity or what we designate as a "sudden collapse singularity." On the other hand, we also study the deviations of the exterior spacetime from the standard Schwarzschild geometry, which emerges in our modified OS scenario. Our purpose is to investigate whether a black hole always forms regarding this brane world model. We find situations where a naked singularity emerges instead.

How not to extract information from black holes: Cosmic censorship as a guiding principle

Black holes in general relativity are commonly believed to evolve towards a Schwarzschild state as they gradually lose angular momentum and electrical charge under Hawking evaporation. However, when Kim and Wen applied quantum information theory to Hawking evaporation and argued that Hawking particles with maximum mutual information could dominate the emission process, they found that charged black holes tend towards extremality. In view of some evidence pointing towards extremal black holes being effectively singular, this would violate the cosmic censorship conjecture. Nevertheless, since the Kim-Wen model is too simplistic (e.g. it assumes a continuous spectrum of particles with arbitrary charge-to-mass ratio), one might hope that a more realistic model could avoid this problem. In this work, we show that having only a finite species of charged particles would actually worsen the situation, with some end states becoming a naked singularity. With this model as an example, we emphasize the need to study whether charged black holes can violate cosmic censorship under a given model of Hawking evaporation.

A Model of Homologous Confined and Ejective Eruptions Involving Kink Instability and Flux Cancellation

In this study, we model a sequence of a confined and a full eruption, employing the relaxed end state of the confined eruption of a kink-unstable flux rope as the initial condition for the ejective one. The full eruption, a model of a coronal mass ejection, develops as a result of converging motions imposed at the photospheric boundary, which drive flux cancellation. In this process, parts of the positive and negative external flux converge toward the polarity inversion line, reconnect, and cancel each other. Flux of the same amount as the canceled flux transfers to a flux rope, increasing the free magnetic energy of the coronal field. With sustained flux cancellation and the associated progressive weakening of the magnetic tension of the overlying flux, we find that a flux reduction of ≈11% initiates the torus instability of the flux rope, which leads to a full eruption. These results demonstrate that a homologous full eruption, following a confined one, can be driven by flux cancellation.

Majorana-like end states in one-dimensional dimerized Kitaev topolectrical circuit

Majorana zero modes (MZMs) have attracted tremendous attention in condensed matter and materials physics communities due to the implications in topological quantum computation. One-dimensional (1D) dimerized Kitaev chain is a prototype model for MZMs, but its realization remains a challenge in material systems. Here, we develop a distinctive approach to achieve Majorana-like end states (MESs) by implementing practical dimerized Kitaev topolectrical circuits. Specifically, two arrays of inductors are arranged to simulate particles and antiparticles, while intra- and inter-array capacitive connections are used to model hopping and superconducting pairing. Three topological phases can be achieved by tuning the capacitance, i.e. the trivial phase, Su–Schrieffer–Heeger topological phase and Kitaev phase, with distinct field strength distributions in real space. Majorana splitting is observed around a domain wall in the circuit, and we propose an efficient experimental observable-edge distance-to characterize the process as premonition of topological phase transition. Remarkably, dynamics of the Gaussian wave packet in time domain provide an excellent signal to detect MESs in experiments, as only MESs allow nonlocal propagation in circuit network. Our results not only manifest the superiorities of topolectrical circuits for exotic topological states, but also pave the way for possible applications in electrical engineering and signal processing.

Investigating effect of mutation on structure and function of G6PD enzyme: a comparative molecular dynamics simulation study.

Several natural mutants of the human G6PD enzyme exist and have been reported. Because the enzymatic activities of many mutants are different from that of the wildtype, the genetic polymorphism of G6PD plays an important role in the synthesis of nucleic acids via ribulose-5-phosphate and formation of reduced NADP in response to oxidative stress. G6PD mutations leading to its deficiency result in the neonatal jaundice and acute hemolytic anemia in human. Herein, we demonstrate the molecular dynamics simulations of the wildtype G6PD and its three mutants to monitor the effect of mutations on dynamics and stability of the protein. These mutants are Chatham (A335T), Nashville (R393H), Alhambra (V394L), among which R393H and V394L lie closer to binding site of structural NADP+. MD analysis including RMSD, RMSF and protein secondary structure revealed that decrease in the stability of mutants is key factor for loss of their activity. The results demonstrated that mutations in the G6PD sequence resulted in altered structural stability and hence functional changes in enzymes. Also, the binding site, of structural NADP+, which is far away from the catalytic site plays an important role in protein stability and folding. Mutation at this site causes changes in structural stability and hence functional deviations in enzyme structure reflecting the importance of structural NADP+ binding site. The calculation of binding free energy by post processing end state method of Molecular Mechanics Poisson Boltzmann SurfaceArea (MM-PBSA) has inferred that ligand binding in wildtype is favorable as compared to mutants which represent destabilised protein structure due to mutation that in turn may hinder the normal physiological function. Exploring individual components of free energy revealed that the van der Waals energy component representing non-polar/hydrophobic energy contribution act as a dominant factor in case of ligand binding. Our study also provides an insight in identifying the key inhibitory site in G6PD and its mutants which can be exploited to use them as a target for developing new inhibitors in rational drug design.

Solubility of Hydrophobes into Macrocyclic Hosts.

The intrinsic nature of macrocyclic molecules to preferentially absorb a specific solute has been opening up supramolecular chemistry. Nevertheless, the determinant factor with molecular perspectives in promoting host-guest complexations remains inconclusive, due to the lack of rigorous thermodynamic examination on the guest solubility inside the host. Here, we quantify the solute-solvent energetic and entropic contributions between the end states and on the docking route during inclusion of noble gases in cucurbit[5]uril, cucurbit[6]uril, and α-cyclodextrin, using molecular dynamics simulations in combination with the potential distribution theorem. Results show that in all of the pairs examined both the solute-solvent energy and entropy favor the inclusion, while the former is rather dominant. The frequency of interior drying, which pertains to the entropic contribution, differs between the hosts and is controlled by the existence of lid water at portal and the flexibility of host framework. Moreover, the hosts exhibit various types of absorption manners, involving non-, single-, and double-free-energy barriers.

Pulmonary atresia with intact ventricular septum: Intended strategies

ObjectiveNeonatal interventional strategies for pulmonary atresia with intact ventricular septum are based on tricuspid valve hypoplasia and right ventricle-dependent coronary circulation. We sought to evaluate long-term outcomes comparing biventricular (BiV) versus single-ventricle (SV) strategies. MethodsRetrospective review was performed of 119 patients diagnosed with pulmonary atresia with intact ventricular septum from 1995 to 2018. Descriptive statistics summarized patient characteristics and a multivariable Cox survival model was used to compare treatment strategies. ResultsOf 119 patients, 62 (52.1%) were male and 13 (10.9%) had a chromosomal abnormality. BiV was pursued in 53.8% (64 out of 119) and SV in 46.2% (55 out of 119) with median tricuspid valve z scores of −1.59 (interquartile range, −3.03 to 0.21) and −5.12 (interquartile range, −5.60 to −4.06), respectively. The median follow-up was 6 years (interquartile range, 2-15 years). Overall survival at 1, 3, and 10 years was 82.4% (98 out of 119), 80.6% (96 out of 119) and 79.8% (95 out of 119), respectively. End states include 36 (30.3%) BiV, 33 (27.7%) SV, 22 (18.5%) alive without definitive end state, 21 (17.6%) death before end state, 4 (3.4%) 1-and-a-half ventricle, and 3 (2.5%) transplants. No SV were converted to BiV, whereas 4 out of 64 (6.3%) BiV were converted to SV. After adjusting for gender, chromosomal abnormalities, gestational age, and birth weight, SV patients had a significantly higher hazard of mortality (hazard ratio, 9.0; 95% CI, 2.65-30.69; P < .001). Mortality was higher in those with right ventricle-dependent coronary circulation (41.9% [13 out of 31]) compared with those without right ventricle-dependent coronary circulation (7.3% [6 out of 82]) (P < .001). ConclusionsPulmonary atresia with intact ventricular septum remains a challenging lesion for those patients on the SV pathway, particularly with right ventricle-dependent coronary circulation.

Research on Identification Method for Interface Flange in Automatic Docking System of Fluid Loading and Unloading Arm for Bottom Loading

The automatic docking system of the loading and offloading arm of a tank car is the key link to realizing the unmanned operation of tank car loading and unloading. The spatial position detection of the flange port of a tank car can guide the automatic docking of the fluid loading and offloading arm and flange port of the tank car. In this paper, a flange position detection method based on image recognition was proposed. Firstly, the end state of the loading arm was analyzed to determine the expression mode of the loading arm’s spatial pose so as to form a unified expression with the flange position and docked pose on the tank car. Then, for the image processing of the flange port of the tank car, this paper binarized the edge of the flange end face based on the Otsu algorithm, used the Canny algorithm for edge detection, used the least squares method to fit the image edge coordinates into a spatial circle, calculated the center coordinates and normal vector of the flange end face, and used these parameters to guide the end of the loading arm to adjust the position and attitude so that it was consistent with the position and pose of the flange port to realize docking. Then, a circular object center detection and calibration experiment, a flange end face image experiment, and an automobile tank car flange port physical detection experiment were carried out. The test results show that the spatial coordinate accuracy of the flange port diameter and center detected by this method meets the requirements of the loading arm automatic docking system, providing a research idea for the design of an automatic docking system for the loading and unloading arm of a tank car.

The Grey Orchestra

The UK response to the Salisbury poisoning attacks of 2018 was a triumph and provides valuable lessons in information advantage and grey-zone competition for the national security establishment. From the poisoning of the Skripals in March to the unravelling of the GRU’s operations in October, the UK conducted a phased, managed confrontation, reaching a defined end state. Characterised by the need to establish clarity, authority and authenticity, the UK used an ‘elastic communications strategy’, which blunted Kremlin disinformation and leveraged the full spectrum of government powers into a potent ‘second strike’ communications response. The case demonstrates that successful and innovative grey-zone competition can be achieved without sacrificing moral authority.◼

Reconstruction and fire risk assessment of arc‐tracking at a plug‐outlet connection point

SummaryPolyvinyl chloride (PVC), a typical plug insulating material, is an organic material with high tracking resistance. However, the tracking resistance of PVC gets considerably reduced by thermal degradation. In this study, a phenol resin with low tracking resistance was implanted between plug blades as an insulating material that simulated the thermally degraded insulating material of the plug, and a method that could efficiently and reliably reconstruct the arc‐tracking was proposed. Also, arc‐tracking experiments using the proposed method were conducted to evaluate fire risk at the plug‐outlet connection caused by arc‐tracking. To reconstruct the end state of insulation failure in which the tracking resistance of the plug insulation material deteriorated due to thermal degradation, the insulation material between the blades of a 12 A, 125 V rated PVC plug was cut out. Then, a phenol resin piece (6 or 3 mm width) was implanted in the entire, upper or lower halves between the plug blades. The end state of insulation failure was accelerated by applying carbon grease to the phenol resin surface. The implanted plug was inserted into a 15 A, 125 V rated outlet connected to a 100 V AC commercial power supply, and the arc‐tracking at the plug‐outlet connection was observed. When the width of the phenol resin to be implanted was 3 mm, we found that the outlet plate and plug could ignite due to the longer electrical discharge duration. The plug was often extinguished immediately after the end of the electrical discharge due to the self‐extinguishing properties of PVC, but when an acrylonitrile butadiene styrene resin outlet plate ignited, the combustion continued for several minutes. Even though PVCs have self‐extinguishing properties, they burn temporarily during arc‐tracking. From the results, the flame from the electric fire outbreak is believed to spread to the outlet plate and eventually developed into a fire.

Gravitational instabilities of uniform black strings in AdS space

Locally AdS$_{d-1}\times\mathbb{R}$ uniform black strings (UBS) in the presence of a massless scalar field are believed to avoid the onset of the Gregory-Laflamme (GL) instability in $d\ge4$ as no tachyonic modes exist in the spectrum of the Laplace-Beltrami operator. We present analytic and numerical evidence of GL modes in the Lichnerowicz spectrum indicating that AdS$_{d-1}$ UBSs are classically and thermodynamically unstable at the linear level in $d>4$. In $d=4$, we confirm that uniform BTZ$_3$ strings are indeed stable as previously suggested. We propose that linear instabilities of black strings are triggered if and only if a tachyonic mode exists in the Lichnerowicz spectrum. At the end state of the instability, AdS$_{d-1}$ UBSs of finite length may tunnel to a SAdS$_d$ black hole or converge onto a novel non-uniform AdS$_d$ black string. We conjecture that weak cosmic censorship is violated if the non-uniform solution is an exact AdS$_d$ black funnel and compute entropy estimates in $d>4$ as evidence.

PH-induced insertion of pHLIP into a lipid bilayer: In-situ SEIRAS characterization of a folding intermediate at neutral pH

The pH low insertion peptide (pHLIP) is a pH-sensitive cell penetrating peptide that transforms from an unstructured coil on the membrane surface at pH > 7, to a transmembrane (TM) α-helix at pH < 5. By exploiting this unique property, pHLIP attracts interest as a potential tool for drug delivery and visualisation of acidic tissues produced by various maladies such as cancer, inflammation, hypoxia etc. Even though the structures of initial and end states of pHLIP insertion have been widely accepted, the intermediate structures in between these two states are less clear. Here, we have applied in situ Surface-Enhanced Infrared Absorption spectroscopy to examine the pH-induced insertion and folding processes of pHLIP into a solid-supported lipid bilayer. We show that formation of partially helical structure already takes place at pH only slightly below 7.0, but with the helical axis parallel to the membrane surface. The peptide starts to reorientate its helix from horizontal to vertical direction, accompanied by the insertion into the TM region at pH < 6.2. Further insertion into the TM region of the peptide results in an increase of inherent α-helical structure and complete secondary structure formation at pH 5.3. Analysis of the changes of the carboxylate vibrational bands upon pH titration shows two distinctive groups of aspartates and glutamates with pKa values of 4.5 and 6.3, respectively. Comparison to the amide bands of the peptide backbone suggests that the latter Asp/Glu groups are directly involved in the conformational changes of pHLIP in the respective intermediate states.

Intrinsic topological magnons in arrays of magnetic dipoles

We study a simple magnetic system composed of periodically modulated magnetic dipoles with an easy axis. Upon adjusting the geometric modulation amplitude alone, chains and two-dimensional stacked chains exhibit a rich magnon spectrum where frequency gaps and magnon speeds are easily manipulable. The blend of anisotropy due to dipolar interactions between magnets and geometrical modulation induces a magnetic phase with fractional Zak number in infinite chains and end states in open one-dimensional systems. In two dimensions it gives rise to topological modes at the edges of stripes. Tuning the amplitude in two-dimensional lattices causes a band touching, which triggers the exchange of the Chern numbers of the volume bands and switches the sign of the thermal conductivity.

Effects of the N-terminal dynamics on the conformational states of human dopamine transporter

Dopamine transporter mediates the neurotransmitter dopamine homeostasis in a sodium-dependent manner. The transport process involves an alternating access of a substrate to the extracellular and intracellular spaces, which is associated with different conformational states of the transporter. However, the underlying mechanism of modulation of the state transition remains elusive. Here we present a computational simulation study of human dopamine transporter to explore its two end states (outward-facing open and inward-facing open) that have not been determined experimentally. We show that the full-length transporter may tend to adopt the inward-facing open state in its free state. The binding of an amphetamine may not trap the transporter in the outward-facing open state with increasing length of the N-terminal. Furthermore, we identify distinct patterns in the interaction networks between the N-terminal and the intracellular region that could stabilize the state of the transporter, independent of substrate binding and phosphorylation. Our results reveal the essential role of the N-terminal dynamics in modulating the functional states of the dopamine transporter, providing molecular insights into the coupling of conformational transition and substrate passage in neurotransmitter transporters.

Quantum Magnetism and Topological Superconductivity in Yu-Shiba-Rusinov Chains.

Chains of magnetic adatoms on superconductors have been discussed as promising systems for realizing Majorana end states. Here, we show that dilute Yu-Shiba-Rusinov (YSR) chains are also a versatile platform for quantum magnetism and correlated electron dynamics, with widely adjustable spin values and couplings. Focusing on subgap excitations, we derive an extended t-J model for dilute quantum YSR chains and use it to study the phase diagram as well as tunneling spectra. We explore the implications of quantum magnetism for the formation of a topological superconducting phase, contrasting it to existing models assuming classical spin textures.

A Critical Period for Robust Curriculum‐Based Deep Reinforcement Learning of Sequential Action in a Robot Arm

Many everyday activities are sequential in nature. That is, they can be seen as a sequence of subactions and sometimes subgoals. In the motor execution of sequential action, context effects are observed in which later subactions modulate the execution of earlier subactions (e.g., reaching for an overturned mug, people will optimize their grasp to achieve a comfortable end state). A trajectory (movement) adaptation of an often‐used paradigm in the study of sequential action, the serial response time task, showed several context effects of which centering behavior is of special interest. Centering behavior refers to the tendency (or strategy) of subjects to move their arm or mouse cursor to a position equidistant to all stimuli in the absence of predictive information, thereby reducing movement time to all possible targets. In the current study, we investigated sequential action in a virtual robotic agent trained using proximal policy optimization, a state‐of‐the‐art deep reinforcement learning algorithm. The agent was trained to reach for appearing targets, similar to a serial response time task given to humans. We found that agents were more likely to develop centering behavior similar to human subjects after curricularized learning. In our curriculum, we first rewarded agents for reaching targets before introducing a penalty for energy expenditure. When the penalty was applied with no curriculum, many agents failed to learn the task due to a lack of action space exploration, resulting in high variability of agents' performance. Our findings suggest that in virtual agents, similar to infants, early energetic exploration can promote robust later learning. This may have the same effect as infants' curiosity‐based learning by which they shape their own curriculum. However, introducing new goals cannot wait too long, as there may be critical periods in development after which agents (as humans) cannot flexibly learn to incorporate new objectives. These lessons are making their way into machine learning and offer exciting new avenues for studying both human and machine learning of sequential action.

Language Dominance Modulates Transposed-Letter N400 Priming Effects in Bilinguals

Models of visual word recognition differ as to how print exposure modulates orthographic precision. In some models, precision is the optimal end state of a lexical representation; the associations between letters and positions are initially approximate and become more precise as readers gain exposure to the word. In others, flexible orthographic coding that allows for rapid access to semantics (i.e., ‘good enough’ orthographic processing) is the optimal end state. To adjudicate between these trajectories, we compared the size of transposed-letter ERP priming effects on two ERP components thought to reflect orthographic and lexico-semantic processing across languages in late English-Spanish bilinguals. Words that are represented precisely should be less susceptible to activation by transposed-letter primes (e.g., shpae-SHAPE) than words that are not, and should therefore yield smaller priming effects. Overall, targets elicited smaller N250s and N400s and faster responses when preceded by transposed-letter primes compared to substitution primes (e.g., shgue-SHAPE). The only effect that significantly differed between languages was N400 priming, which was larger in English, the dominant language. We suggest that these results favor models of learning to read according to which ‘good enough’ orthographic processing increases with print exposure.

Outcomes of advance care directives after admission to a long-term care home: DNR the DNH?

BackgroundResidents of long-term care homes (LTCH) often experience unnecessary and non-beneficial hospitalizations and interventions near the end-of-life. Advance care directives aim to ensure that end-of-life care respects resident needs and wishes.MethodsIn this retrospective cohort study, we used multistate models to examine the health trajectories associated with Do-Not-Resuscitate (DNR) and Do-Not-Hospitalize (DNH) directives of residents admitted to LTCH in Ontario, Alberta, and British Columbia, Canada. We adjusted for baseline frailty-related health instability. We considered three possible end states: change in health, hospitalization, or death. For measurements, we used standardized RAI-MDS 2.0 LTCH assessments linked to hospital records from 2010 to 2015.ResultsWe report on 123,003 LTCH residents. The prevalence of DNR and DNH directives was 71 and 26% respectively. Both directives were associated with increased odds of transitioning to a state of greater health instability and death, and decreased odds of hospitalization. The odds of hospitalization in the presence of a DNH directive were lowered, but not eliminated, with odds of 0.67 (95% confidence interval 0.65–0.69), 0.63 (0.61–0.65), and 0.47 (0.43–0.52) for residents with low, moderate and high health instability, respectively.ConclusionEven though both DNR and DNH orders are associated with serious health outcomes, DNH directives were not frequently used and often overturned. We suggest that policies recommending DNH directives be re-evaluated, with greater emphasis on advance care planning that better reflects resident values and wishes.

Controllability problems for the heat equation with variable coefficients on a half-axis

In the paper, the problems of controllability and approximate controllability are studied for the heat equation wt = 1/ρ (kwx)x + γw, x &gt; 0, t ∈ (0, T), controlled by the Dirichlet boundary condition. Control is considered in L∞(0, T). It is proved that each initial state of this system is approximately controllable to any its end state in a given time T &gt; 0.