Cascade Transitions Research Articles

The HIV Care Cascade for Older Adults in Rural South Africa: A Longitudinal Cohort Study (2014-2019).

As people with HIV grow older, stable engagement in care is essential for healthy aging. We evaluate the HIV care cascade for older adults in rural South Africa at 2 time points cross-sectionally and assess movement in the cascade over time. We evaluated the cascade stage at waves 1 (2014-2015) and 2 (2018-2019) of Health and Aging in Africa: A Longitudinal Study of an INDPETH Community in South Africa, a population-based longitudinal cohort study in Mpumalanga Province, South Africa. Biomarker screening defined cascade stages [HIV+/no antiretroviral therapy (ART); ART+/unsuppressed viral load; ART+/suppressed viral load]. Between-wave probability of death, cascade progression, regression, cascade transitions, and sociodemographic predictors were assessed with Poisson regression. The impact of death was considered using the Fine and Gray competing risk model. We observed a higher prevalence of antiretroviral therapy with viral suppression over time (50% in wave 1 vs. 70% in wave 2). Among those alive, the oldest age group (70+ years old) was most likely to have cascade progression [adjusted risk ratio for treatment initiation vs. 40-49 years old: 1.38 (95% confidence interval: 1.02 to 1.86)]. However, there was a significant risk of death and cascade regression. Death between waves reached 40% for 70+-year-olds who were ART+/unsuppressed. In competing risk models, older age was associated with equivalent or less cascade progression. Older age groups who were unsuppressed on treatment and men had poorer cascade outcomes. Improvements observed in HIV treatment coverage over time for older adults must be interpreted in the context of the high risk of death for older HIV-positive adults, especially among those failing treatment.

Insight into Details of Chemical Exchange Kinetics Studied by NMR CPMG Method

A more detailed insight into the chemical kinetics and dynamics of chemical exchanges within a molecule or between molecules in liquids is made possible by the NMR CPMG method, which, in addition to the exchange rate, gives its power spectrum, which contains information about the underlying processes of chemical exchange. The applicability of the method is demonstrated by measuring the chemical exchange in an aqueous solutions of sucrose, whose rate spectra have shapes that cannot be explained as transitions in a double potential well, but after interpretation using the chemical Langevin equations, it can be explained as a cascading chemical transition across several intermediate potential walls.

Information cascade on networks and phase transitions

Herein, we consider a voting model for information cascades on several types of networks – a random graph, the Barabási–Albert(BA) model, and lattice networks – by using one parameter ω; ω=1,0,−1 respectively correspond to these networks. Our objective is to study the relation between the phase transitions and networks using the parameter, ω which is related to the size of hubs. We discuss the differences between the phases in which the networks depend. In ω≠−1, without a lattice, the following two types of phase transitions can be observed: information cascade transition and super-normal transition. The first is the transition between a state where most voters make correct choices and a state where most of them are wrong. This is an absorption transition that belongs to the non-equilibrium transition. In the symmetric case, the phase transition is continuous and the universality class is the same as nonlinear Pólya model. In contrast, in the asymmetric case, there is a discontinuous phase transition, where the gap depends on the network. As ω increases, the size of the hub and the gap increase. Therefore, a network that has hubs has a greater effect through this phase transition. The critical point of information cascade transition does not depend on ω. The super-normal transition is the transition of the convergence speed, and the critical point of the convergence speed transition depends on ω. At ω=1, in the BA model, this transition disappears, and the range where we can observe the phase transition is the same as that in the percolation model on the network. Both phase transitions disappear at ω=−1 in the lattice case. In conclusion, as the performance near the lattice case, ω∼−1 exhibits the best performance of the voting in all networks. As the hub size decreases, the performance improves. Finally, we show the relation between the voting model and the elephant walk model.

The hormonal control of parturition.

Parturition is a complex physiological process that must occur in a reliable manner and at an appropriate gestation stage to ensure a healthy newborn and mother. To this end, hormones that affect the function of the gravid uterus, especially progesterone (P4), 17β-estradiol (E2), oxytocin (OT), and prostaglandins (PGs), play pivotal roles. P4 via the nuclear P4 receptor (PR) promotes uterine quiescence and for most of pregnancy exerts a dominant block to labor. Loss of the P4 block to parturition in association with a gain in prolabor actions of E2 are key transitions in the hormonal cascade leading to parturition. P4 withdrawal can occur through various mechanisms depending on species and physiological context. Parturition in most species involves inflammation within the uterine tissues and especially at the maternal-fetal interface. Local PGs and other inflammatory mediators may initiate parturition by inducing P4 withdrawal. Withdrawal of the P4 block is coordinated with increased E2 actions to enhance uterotonic signals mediated by OT and PGs to promote uterine contractions, cervix softening, and membrane rupture, i.e., labor. This review examines recent advances in research to understand the hormonal control of parturition, with focus on the roles of P4, E2, PGs, OT, inflammatory cytokines, and placental peptide hormones together with evolutionary biology of and implications for clinical management of human parturition.

Policy as a catalyst in shaping mobility sector transition for developing countries

This paper presents a modified technology innovation system (MTIS) approach applicable to developing countries. Evidence collected over three decades 1992–2022, shows how policy plays a catalytic role in managing multidimensional low-emission mobility transitions in developing countries such as Pakistan. This paper follows policy and the network of actors, institutions and technology in compressed natural gas (CNG)-based mobility transition in Pakistan. Event-based analysis helped in mapping the development of respective functions, which is later validated by expert consultation. Between 1992 and 2002, deliberate policies for early adoption were put in place to strategically manage a desired transition path. This involved providing guidance and knowledge diffusion through demonstration to increase entrepreneurial activities and market formation. The accelerated diffusion during the take-off period during 2003–2012 was due to the entry of private businesses and multinational companies speeding up entrepreneurial activity and market-formation functions. However, there was a clear policy-driven roll-back and deceleration during 2013–2022. Policies designed to ban CNG licence issuance and renewal resulted in detrimental effects on market and entrepreneurial activities. Social struggle arising from roll-back is now caught in a dilemma if policy innovation will lead to re-emergence of CNG or will support a new transition cycle through the emergence and adoption of electric vehicles in the mobility space of Pakistan. Rapid shifts in the global landscape of innovation and market conditions are creating a need for the effective handling of cascading transition management in developing countries. This paper outlines how lessons learnt from Pakistan’s CNG-MTIS can help in shaping electric vehicle MTIS not only in Pakistan, but also in many other developing countries. It is recommended that, in order to manage cascading transitions in developing countries, new approaches and strategies for reskilling, retraining and redirecting finances to address stranded assets be employed. This can mitigate the negative impacts on those affected by transformation and create an environment for a just transition that restores trust in policy and accelerates transformative change.

Astrophysical S-factor and reaction rate for 15N(p,γ)16O within the modified potential cluster model* *Supported by the Ministry of Science and Higher Education of the Republic of Kazakhstan (AP09259174)

We study radiative capture on the ground state of 16O at stellar energies within the framework of a modified potential cluster model (MPCM) with forbidden states, including low-lying resonances. The investigation of the 15N( )16O reaction includes the consideration of resonances due to transitions and the contribution of the scattering wave in the p + 15N channel due to the transition. We calculated the astrophysical low-energy S-factor, and the extrapolated turned out to be within 34.7−40.4 keV·b. The important role of the asymptotic constant (AC) for the 15N( )16O process with interfering (312) and (962) resonances is elucidated. A comparison of our calculation for the S-factor with existing experimental and theoretical data is addressed, and a reasonable agreement is found. The reaction rate is calculated and compared with the existing rates. It has negligible dependence on the variation of AC but shows a strong impact of the interference of (312) and (962) resonances in reference to the CNO Gamow windows, especially at low temperatures. We estimate the contribution of cascade transitions to the reaction rate based on the exclusive experimental data from Phys. Rev. C. 85, 065810 (2012). The reaction rate enhancement due to the cascade transitions is observed from and reaches the maximum factor ~ 1.3 at . We present the Gamow energy window and a comparison of rates for radiative proton capture reactions 12N( )13O, 13N( ) 14O, 14N( )15O, and 15N( )16O obtained in the framework of the MPCM and provide the temperature windows, prevalence, and significance of each process.

Physical aspects of the fire and explosion hazard of combustible dust. Part 2. Self-wave modes of combustion

In present review, based on the authors' long-term research, generalized ideas about the ignition patterns andmetal dust wave burning are given. The first part discusses patterns of ignition as a result of the action of non-linearthermokinetic type factors (Arrhenius dependence). The second part analyzes the flame propagation patterns in dust caused by the presence of hydrodynamic nonlinearities in the active system, which lead to the existence of laminar, vibrational, and turbulent flames. The influence of physico-chemical parameters (type, dispersion, concentration of fuel) andflame propagation hydrodynamic conditions (reaction pipes of different diameters and lengths, dust clouds with a volume of 10 ÷ 40 m3) on theindicated modes implementation and their characteristics are discussed.
 For laminar flames, the main focus is on the problem of normal flame speed and flame propagation concentration limits. For a vibrating flame (reaction tubes were ignited at the open end of a semi-closed tube), the regularities of cascade transitions are analyzed – laminar flame ↔ vibrational type I ↔ vibrational type II ↔ turbulent flame.

Statistical methods applied for the assessment of the HIV cascade and continuum of care: a systematic scoping review

ObjectivesThis scoping review aims to identify and synthesise existing statistical methods used to assess the progress of HIV treatment programmes in terms of the HIV cascade and continuum of care...

Modular tipping points: How local network structure impacts critical transitions in networked spin systems

Critical transitions describe a phenomenon where a system abruptly shifts from one stable state to an alternative, often detrimental, stable state. Understanding and possibly preventing the occurrence of a critical transition is thus highly relevant to many ecological, sociological, and physical systems. In this context, it has been shown that the underlying network structure of a system heavily impacts the transition behavior of that system. In this paper, we study a crucial but often overlooked aspect in critical transitions: the modularity of the system’s underlying network topology. In particular, we investigate how the transition behavior of a networked system changes as we alter the local network structure of the system through controlled changes of the degree assortativity. We observe that systems with high modularity undergo cascading transitions, while systems with low modularity undergo more unified transitions. We also observe that networked systems that consist of nodes with varying degrees of connectivity tend to transition earlier in response to changes in a control parameter than one would anticipate based solely on the average degree of that network. However, in rare cases, such as when there is both low modularity and high degree disassortativity, the transition behavior aligns with what we would expected given the network’s average degree. Results are confirmed for a diverse set of degree distributions including stylized two-degree networks, uniform, Poisson, and power-law degree distributions. On the basis of these results, we argue that to understand critical transitions in networked systems, they must be understood in terms of individual system components and their roles within the network structure.

Shake-off effect on the portions of energy reemitted by gold atom upon the cascade decay of vacancies in its K to O shells

Abstract Cascade decays of single vacancies in K to O shells of the gold atom are simulated by straightforward construction and analysis of the cascade decay trees. Portions of energies (a) absorbed by initially ionized Au atom, (b) reemitted by cascade-produced electrons, and (c) reemitted by cascade-produced photons are calculated with taking into account the shake-off processes caused by the change of atomic core potential during cascade transitions. Au atom absorbs noticeable amount of energy acquired in photoionization act only when ionized in its N and O shells, 33%–45% and 41%–54%, respectively. Except for the case of K-ionization, most of the energy is reemitted by cascade electrons: 57%–64%, 77%–85%, 55%–67%, and 46%–59% during the decay of vacancies in L, M, N, and O shells. Energies carried away by the cascade photons are only important for initial vacancies in K (89%) and L (29%–39%) shells. Inclusion of the shake-off branches in the decay trees increase substantially their complexity, however it leads to comparatively small corrections to calculated portions of energy redistributed through channels a, b, and c. This supports earlier qualitative prediction of small possible effect of the SO processes on the cascades in heavy atoms.

Final ion yields upon the cascade decay of single K, L, M, and N vacancies in atomic silver

Final ion yields and mean final ion charges upon the cascade decay of single vacancies in the K, L, M, and N shells of atomic silver are calculated using the method of construction and analysis of the decay trees with accounting for the shake-offs caused by the change of atomic core potential due to cascade transitions. The shake-off effect on the final ion yields is found to be comparatively small, the largest increase of the mean final ion charge being 0.20e in the case of initial 2s vacancy. Total semi-relativistic Pauli–Fock energies of cascade-produced ionic configurations were used to calculate cascade transition energies, which made it possible to accurately account for the closing of some non-radiative transitions in multivacancy cascade configurations. For the transitions with overlapping multiplets of initial and final ionic configurations, only energetically allowed transitions between the multiplet components were counted when calculating mean transition energies and transitions branching ratios. Comparison of calculated charge spectra with those reported earlier by other authors demonstrated crucial importance of accurate calculation of transition energies and accounting for multiplet splitting in simulation of cascades in heavy atoms.

Energy reemission and possible radiosensitizing effect caused by the cascade decay of single vacancies in the K, L, M, and N shells of atomic silver

Cascade decays of single vacancies in the K, L, M, and N shells of the silver atom are studied using the method of straightforward construction and analysis of the cascade de-excitation trees with inclusion of additional shake-off ejections of outer-shell electrons caused by the change of atomic core potential due to cascade transitions. The spectra of the cascade-produced electrons and photons emitted upon the decay of single vacancies in 1s1/2 to 4p3/2 subshells are calculated. For each initial vacancy, the energies absorbed by the silver atom itself, and those carried away by cascade electrons and photons, are calculated. Absorption of energy by the silver atom itself is only significant upon N- and M-shell ionization (49–66% and 18–36%, respectively), i.e. in the UV to soft X-ray range. After L- to N-ionization, most of the acquired energy is reemitted with cascade electrons, respective portions making 81–85% during L-ionization, 62–82% during M-ionization, and 34–51% during N-ionization. Reemission of energy with cascade photons is dominant after K-ionization (76%). When silver atoms are used as radiosensitizing agents in radiotherapy, cascade electrons play the principal role in the energy transfer to organism tissues. Due to small free paths in the organic medium, they give their energy to the environment in rather small volumes inside a particular cell where they are placed. As for the photons emitted after K-ionization, they transfer energy to the medium in much larger volumes, and with much smaller absorbed doses.

Coupling of magnetism, crystal lattice, and transport in EuCuP and EuCuAs

EuCuP and EuCuAs are members of a family of materials with candidates for realizing magnetically tuned electronic topology. In this work, the magnetic phase transitions and magnetoelastic coupling of EuCuP and EuCuAs have been investigated. Around the Curie temperature, the thermal expansion coefficient and specific-heat capacity of EuCuP are found to have two closely spaced features, at approximately 30 and 31.3 K, which may indicate a cascading magnetic transition or perhaps an electronic transition closely coupled to the magnetic ordering. The zero-field magnetoelastic coupling appears to be stronger in EuCuP than in EuCuAs, and field-dependent measurements suggest this is due to the dominant ferromagnetic interaction in EuCuP as opposed to antiferromagnetic order in EuCuAs below ${T}_{\mathrm{N}}=13.5\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. Thermal expansion is anisotropic around ${T}_{\mathrm{N}}$ in EuCuAs, with a maximum expansion along [001] occurring above ${T}_{\mathrm{N}}$ prior to a stiffening of this $c$-axis component on cooling through ${T}_{\mathrm{N}}$; the expansion of the basal plane has a lambda-like peak centered slightly above ${T}_{\mathrm{N}}$. Matching these behaviors, the ac susceptibility data for EuCuAs suggest the presence of strong ferromagnetic correlations above ${T}_{\mathrm{N}}$ in the vicinity where the $c$-axis expansion peaks. Both compounds possess similar electrical and thermoelectric transport behaviors, with short-range magnetic order likely playing an important role above ${T}_{\mathrm{C}}$ or ${T}_{\mathrm{N}}$. Transport properties suggest these are predominantly hole doped due to intrinsic defects, and narrow-gap semiconducting or semimetallic behavior may be achievable if the underlying defects can be tuned.

Angular correlation of the two gamma rays produced in the thermal neutron capture on gadolinium-155 and gadolinium-157

Abstract The ANNRI-Gd collaboration studied in detail the single γ-ray spectrum produced from the thermal neutron capture on 155Gd and 157Gd in our previous publications. Gadolinium targets were exposed to a neutron beam provided by the Japan Spallation Neutron Source (JSNS) in J-PARC, Japan. In the present analysis, one new additional coaxial germanium crystal was used in combination with the 14 germanium crystals in the cluster detectors to study the angular correlation of the two γ rays emitted in the same neutron capture. We present for the first time angular correlation functions for two γ rays produced during the electromagnetic cascade transitions in the (n, γ) reactions on 155Gd and 157Gd. As expected, we observe mild angular correlations for the strong, but rare transitions from the resonance state to the two energy levels of known spin-parities. Contrariwise, we observe negligibly small angular correlations for arbitrary pairs of two γ rays produced in the majority of cascade transitions from the resonance state to the dense continuum states.

Exclusive Effect in Rydberg Atom-Based Multi-Band Microwave Communication

We have demonstrated a Rydberg atom-based two-band communication with the optically excited Rydberg state coupled to another pair of Rydberg states by two microwave fields, respectively. The initial Rydberg state is excited by a three-color electromagnetically-induced absorption in rubidium vapor cell via cascading transitions, with all of them located in infrared bands: a 780 nm laser servers as a probe to monitor the optical transmittancy via transition 5S1/2→5P3/2, 776 nm and 1260 nm lasers are used to couple the states 5P3/2 and 5D5/2 and states 5D5/2 and 44F7/2. Experimentally, we show that two channel communications carried on the two microwave transitions influence each other irreconcilably, so that they cannot work at their most sensitive microwave-optical conversion points simultaneously. For a remarkable communication quality for both channels, the two microwave fields both have to make concessions to reach a common microwave-optical gain. The optimized balance for the two microwave intensities locates at EMW1=6.5 mV/cm and EMW2=5.5 mV/cm in our case. This mutual exclusive influence is theoretically well-explained by an optical Bloch equation considering all optical and microwave field interactions with atoms.

Final ion charge spectra upon cascade decay of inner-shell vacancies in atomic Au

Final ion charge spectra produced by the cascade de-excitations of 1s- to 5p 3/2-vacancies of the gold atom are calculated by direct construction and analysis of the cascade decay trees. The energies of multivacancy configurations arising in the course of the cascade development, and the partial widths of radiation and radiationless cascade transitions are calculated using the Pauli–Fock approximation. The energies of the cascade transitions are calculated as the differences of total Pauli–Fock energies of initial and final ionic configurations which allowed excluding energy-forbidden radiationless transitions in numerous multivacancy configurations. Partial widths of transitions are expressed in the form that allowed accounting for the effect of electron subshell populations on the transition widths. The partial widths of the transitions between the states of the overlapping initial and final state multiplets are corrected so as to exclude energy-forbidden transitions between the multiplet states. It is demonstrated that accurate accounting for possible forbiddance of transitions between cascade configurations and the exclusion of energy-forbidden term-to-term transitions between the multiplets’ states are crucial in deep-initial-vacancy cascade simulations.

Novel electrical properties of moiré graphene systems

In this review, we discuss the electronic structures, topological properties, correlated states, nonlinear optical responses, as well as phonon and electron-phonon coupling effects of moiré graphene superlattices. First, we illustrate that topologically non-trivial flat bands and moiré orbital magnetism are ubiquitous in various twisted graphene systems. In particular, the topological flat bands of magic-angle twisted bilayer graphene can be explained from a zeroth pseudo-Landau-level picture, which can naturally explain the experimentally observed quantum anomalous Hall effect and some of the other correlated states. These topologically nontrivial flat bands may lead to nearly quantized piezoelectric response, which can be used to directly probe the valley Chern numbers in these moiré graphene systems. A simple and general chiral decomposition rule is reviewed and discussed, which can be used to predict the low-energy band dispersions of generic twisted multilayer graphene system and alternating twisted multilayer graphene system. This review further discusses nontrivial interaction effects of magic-angle TBG such as the correlated insulator states, density wave states, cascade transitions, and nematic states, and proposes nonlinear optical measurement as an experimental probe to distinguish the different “featureless” correlated states. The phonon properties and electron-phonon coupling effects are also briefly reviewed. The novel physics emerging from band-aligned graphene-insulator heterostructres is also discussed in this review. In the end, we make a summary and an outlook about the novel physical properties of moiré superlattices based on two-dimensional materials.

Влияние дополнительных монопольных выбросов электронов на зарядовые спектры конечных ионов при каскадном распаде электронных вакансий в атоме золота

The probabilities of the formation of final ions produced by the cascade decays of vacancies in the K, L, M, N, and O shells of the gold atom are calculated. Simulation of the cascade decays of vacancies is performed by direct construction and analysis of decay trees using branching ratios and transition energies calculated in the Pauli–Fock approximation for multivacancy electron configurations arising in the course of the cascade decay. Accounting for additional monopole ejections of electrons (shake-off) accompanying the cascade transitions leads to a slight increase in the average charges of the final ions, by 0.15–0.23e. The largest relative increase in the calculated average charges of the final ions (by 3.6–3.9%) is observed upon the cascade decay of vacancies in 4p3/2, 4d3/2, and 4d5/2 subshells, and the smallest (by 0.8%) occurs in the decay of 4f-vacancy. Despite insignificant changes in the average ion charges, the structure of the charge spectra in some cases changes noticeably enough when additional electron ejections are taken into account. It is expected that in simulation of the cascade energy reemission processes when heavy atoms are used as radiosensitizers, the effect of accounting for shake-off processes will be insignificant.

Risky cascading transitions in international relationships.

Changing attitudes in diplomatic relations is a common feature of international politics. However, such changes may trigger risky domino-like cascades of "friend-to-enemy" transitions among other counties and yielding catastrophic damage that could reshape the global network of international relationships. While previous attention has been focused on studying single pairs of international relationships, due to the lack of a systematic framework, it remains still unknown whether, and how, a single transition of attitude between two countries could trigger a cascade of attitude transitions among other countries. Here, we develop such a framework and construct a global evolving network of relations between country pairs based on 70,756,728 international events between 1,225 country pairs from January 1995 to March 2020. Our framework can identify and quantify the cascade of transitions following a given original transition. Surprisingly, weaker transitions are found to initiate most of the largest cascades. We also find that transitions are not only related to the balance of the local environment, but also global network properties such as betweenness centrality. Our results suggest that these transitions have a substantial impact on bilateral trade volumes and scientific collaborations. Our results reveal reaction chains of international relations, which could be helpful for designing early warning signals and mitigation methods for global international conflicts.

Signature of Cascade Transitions between Interlayer Excitons in a Moiré Superlattice.

A moiré superlattice in transition metal dichalcogenides heterostructure provides an exciting platform for studying strongly correlated electronics and excitonic physics, such as multiple interlayer exciton (IX) energy bands. However, the correlations between these IXs remain elusive. Here, we demonstrate the cascade transitions between IXs in a moiré superlattice by performing energy- and time-resolved photoluminescence measurements in the MoS_{2}/WSe_{2} heterostructure. Furthermore, we show that the lower-energy IX can be excited to higher-energy ones, facilitating IX population inversion. Our finding of cascade transitions between IXs contributes to the fundamental understanding of the IX dynamics in moiré superlattices and may have important applications, such as in exciton condensate, quantum information protocols, and quantum cascade lasers.