Close-coupling Research Articles

Elastic and inelastic low-energy electron collisions with PH2, PF2 and PCl2 radicals

Ab initio scattering calculations for low-energy electron collisions with PH2, PF2, and PCl2 are performed using the R-matrix method in this study. The elastic integral, differential, and momentum transfer cross sections and the excitation cross sections from the ground state to the five low-lying electron excited states are presented in the energy region of 0.01–15 eV. The target states are represented by including correlations via a configuration interaction technique. The resonant states are detected and identified. The sensitivity of the results to changes in the theoretical model is checked by comparing predictions from a variety of approximations including static exchange, one state close-coupling (CC), and many-state CC approximations. The similarities and differences among the resonances of these three radicals are discussed.

Targeting BKCa Channels in Migraine: Rationale and Perspectives.

Large (big)-conductance calcium-activated potassium (BKCa) channels are expressed in migraine-related structures such as the cranial arteries, trigeminal ganglion and trigeminal spinal nucleus, and they play a substantial role in vascular tonus and neuronal excitability. Using synthetic BKCa channels openers was associated with headache as a frequent adverse effect in healthy volunteers. Additionally, BKCa channels are downstream molecules in migraine signalling pathways that are activated by several compounds known to provoke migraine, including calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP) and glyceryl trinitrate (GTN). Also, there is a high affinity and a close coupling between BKCa channels and ATP-sensitive potassium (KATP) channels, the role of which has recently been established in migraine pathophysiology. These observations raise the question as to whether direct BKCa channel activation can provoke migraine in migraine patients, and whether the BKCa channel could be a potential novel anti-migraine target. Hence, randomized and placebo-controlled clinical studies on BKCa channel openers or blockers in migraine patients are needed.

Sensing Actin Dynamics through Adherens Junctions

We study punctate adherens junctions (pAJs) to determine how short-lived cadherin clusters and relatively stable actin bundles interact despite differences in dynamics. We show that pAJ-linked bundles consist of two distinct regions-the bundle stalk (AJ-BS) and a tip (AJ-BT) positioned between cadherin clusters and the stalk. The tip differs from the stalk in a number of ways: it is devoid of the actin-bundling protein calponin, and exhibits a much faster F-actin turnover rate. While F-actin in the stalk displays centripetal movement, the F-actin in the tip is immobile. The F-actin turnover in both the tip and stalk is dependent on cadherin cluster stability, which in turn is regulated by F-actin. The close bidirectional coupling between the stability of cadherin and associated F-actin shows how pAJs, and perhaps other AJs, allow cells to sense and coordinate the dynamics of the actin cytoskeleton in neighboring cells-a mechanism we term "dynasensing."

A scientometric review of blockchain research

As a new and rapidly developing distributed technology, blockchain has shown substantial impact on the fields of cryptocurrency and e-commerce and thus has attracted the interests of governments, enterprises, and research institutions. As such, it is important to understand the state of blockchain research in order for those institutions to plan their research effectively. Towards this goal, we first integrate two search strategies to construct a representative dataset. Then we analyze the blockchain literature between 2013 and 2018 in this dataset with a science mapping approach and Latent Dirichlet Allocation model. Based on the results of the analysis, we found the following insights: (1) the evolution of blockchain research involves many disciplines while two major disciplines—computer science and business—lead the way. (2) The current research can be divided into four research areas: underlying technology architecture, privacy and security, financial application, and smart scene applications. (3) The evolution of blockchain research has gone through three stages: basic blockchain technology, various business applications, and integration with advanced technologies such as fog computing, Internet of things, and artificial intelligence. (4) We also discovered a close coupling of two research issues that have transformative power, i.e., the potential by the application of cryptocurrency in the real world and the improvement of blockchain technology based on the application requirements. Overall, our study uses multiple complementary scientometric methods to generate a panoramic view of the recent developments in blockchain research. Future research directions and some limitations are discussed.

Enhanced NO, CO and C3H6 conversion on Pt/Pd catalysts: Impact of oxygen storage material and catalyst architecture

Simultaneous conversion of NO, CO and C3H6 under stoichiometric conditions was carried out on washcoated monoliths containing oxygen storage material (OSM)-promoted mixed Platinum group metals (PGM: Pt(95 %)/Pd(5 %)), to evaluate OSM promotion and to identify the best architecture. The studied OSMs include ceria-zirconia (Ce0.3Zr0.7O2; CZO) and mixed metal oxide spinel (Mn0.5Fe2.5O4; MFO). PGM supported directly on the OSM was found to be the best design for CZO, leading to a ∼70 °C simultaneous decrease in the light-off temperature (T80; feed temperature giving 80 % conversion) for NO, CO and C3H6 conversion compared to the alumina-supported PGM. Close coupling between the PGM and CZO is responsible for the activity promotion. In contrast, a dual-layer architecture (top PGM layer, bottom MFO layer) outperformed the MFO-supported PGM catalyst. The dual-layer PGM-MFO catalyst decreased the T80 by ∼50 °C for NO, CO and C3H6 conversion compared to the PGM-only catalyst. Enhancement obtained with the dual-layer PGM-MFO architecture relies on a direct catalytic contribution from the spinel. During lean/rich modulation the addition of CZO or spinel helps to mitigate the detrimental impact of modulation on NO, CO and C3H6 conversion above 400 °C. The data suggest that both CZO and MFO can buffer lean/rich modulation but exhibit preference to different reductants; CZO-supported PGM and dual-layer PGM-MFO show no conversion decrease during modulation for CO or C3H6 modulation, respectively. Dynamic oxygen storage capacity (DOSC) measurements show that the spinel exhibits ∼10 times higher DOSC than CZO for both CO and C3H6 reductants. Both CO and C3H6 are equally effective reductants for the MFO but CO is better for CZO and PGM-deposited CZO. The study provides useful insight into benefits of OSM and provides guidance for optimization of the multi-component PGM + OSM catalyst composition and architecture.

Lateral geomorphic connectivity in a fluvial landscape system: Unraveling the role of confinement, biogeomorphic interactions, and glacial legacies

The rates at which sediment from the landscape is recruited to channel networks reflect lateral geomorphic connectivity and have significant implications for biophysical river systems. By strongly influencing sediment supply regime, such inputs control the dynamics and characteristics of the channel as well as the associated habitat and biota. The main objective of this research was to disentangle the relative importance of geomorphic and biological factors which define spatial patterns in lateral connectivity by promoting or restricting bank erosion, avulsions, and slope failures. Focusing on a forested, formerly glaciated mountain basin in the interior Pacific Northwest, we combined extensive field surveys with remote sensing data (LiDAR, aerial imagery) to obtain metrics representing this complex suite of landscape characteristics. The interpretation of evidence yielded by correlations between these variables, a regime model, and qualitative observations, suggest that, at a multi-decadal timescale between major landscape disturbances, lateral connectivity patterns in Sullivan Creek may be, to a large extent, governed by a combination of biotic factors and glacial legacies. In particular, forest canopy metrics were key predictors of hillslope stability as well as bank and valley floor resistance, suggesting a pivotal influence of root reinforcement. On the other hand, instream large wood abundance was closely related to channel splitting, which reflects its role in promoting channel avulsions. More extensive bank erosion in reaches dominated by drift deposits appeared to indicate glacial legacies. Furthermore, a strong association between bank erosion and colluvial inputs suggested a close coupling within the channel-hillslope system. Lateral confinement – defined as the proportion of the channel length abutting against bedrock, terraces, fans and roads – was negatively associated with channel braiding; the relationships linking confinement with bank erosion and the magnitude of colluvial inputs (negative and positive association, respectively) were relatively weak. Taken together, findings emerging from this research suggest that better understanding of lateral geomorphic connectivity patterns in mountain river basins similar to our study site requires that both channel processes and broader, biophysical landscape system be considered.

Large eddy simulation of a partially pre-vaporized ethanol reacting spray using the multiphase DTF/flamelet model

Spray reactive flow finds application in various technical devices, and due to the complex nature, their optimization is very challenging, requiring proper modeling of turbulence/chemistry interactions as well as of the contribution from spray evaporation. This work presents a study of sub-grid scale combustion models, where relevant assumptions on multiphase coupling and their effects are analyzed in detail. For this purpose, two different flamelet approaches, i.e. progress variable spray flamelet and multi-regime gas flamelet are examined in an implementation coupled with the dynamic thickened flame model, along with which the impact of inlet inhomogeneities condition and droplet evaporation taking into account internal temperature gradient is also investigated. The numerical evaluation is carried out in large eddy simulations of a benchmark ethanol spray flame with partial pre-vaporization, where an Eulerian-Lagrangian numerical framework is adopted. The analysis demonstrated that the flame dynamics under consideration is governed by a close coupling between spray evaporation, turbulent dispersion and unsteady flame propagation at upstream shear layers. Results show that the spray flamelets built from counterflow partially-premixed spray flames achieved a better agreement with experiments, capturing the flame structure in terms of gas-phase temperature, OH mass fraction as well as spray statistics.

Biotic and Abiotic Imprints on Mg-Rich Stromatolites: Lessons from Lake Salda, SW Turkey

Modern hydrated Mg rich stromatolites are actively growing along the shallow shorelines of Lake Salda (SW Turkey). An integrated approach involving isotopic, mineralogical, microscopic, and organic/geochemical techniques along with culture-independent molecular methods were applied to various lake samples to assess the role of microbial processes on stromatolite formation. This study further explores the biosignature preservation potential of fossil stromatolites by comparing with textures, lipid profiles and isotopic composition of the modern stromatolites. Similar lipid profile and δ13C isotope values in active and fossil stromatolites argue that CO2 cycling delicately balanced between photosynthetic and heterotrophic (aerobic) activity as in the active ones may have regulated stromatolite formation in the lake. A decrease in the exopolymeric substances (EPS) profile of the mat and concurrent hydromagnesite precipitation imply a critical role for EPS in the formation of stromatolite. Consistently, a discrete, discontinuous lamination and clotted micropeloidal textures with cyanobacterial remnants in the fossil stromatolites likely refer to partial degradation of EPS, creating local nucleation sites and allowing precipitation of hydrated Mg minerals and provide a link to the active microbial mat in the modern stromatolites. Our results for the first time provide strong evidence for close coupling of cyanobacterial photosynthesis and aerobic heterotrophic respiration on hydromagnesite textures involved in the stromatolite formation of Lake Salda. The creation of photosynthesis induced high-pH conditions combined with a change in the amount and properties of the EPS and the repetition of these processes over time seems to be a possible pathway for stromatolite growth in the lake. Understanding these microbial symbioses and their mineralized records may provide new insights on the formation mechanism of Mg-rich carbonates not only for terrestrial geological records but also for planetary bodies like Mars, where hydrated Mg-carbonate deposits have been identified in possible paleolake deposits at Jezero crater, the landing site of the NASA Mars 2020 rover.

Injector-coupled thermoacoustic instabilities in an experimental LOX-methane rocket combustor during start-up

This paper reports the investigation of acoustic combustion instability experienced during repetitive ignition testing of a sub-scale LOX-methane rocket thrust chamber. The occurrence of resonant coupling between the LOX injectors and the combustion chamber acoustic modes was assessed from the experimental data recorded during the highly transient phase of operation from ignition up to around 2 s. A method was developed to model the evolution of acoustic properties in both the combustion chamber and the injectors during the transient period. For the LOX injectors, the Woods equation was used to estimate the speed of sound in the two-phase flow. The models were used to identify the corresponding mode frequencies in the unsteady pressure measurements, and show that the high-amplitude instability occurred when they intersected. Very close coupling of less than 3% frequency difference is required for high amplitudes to be observed. However, the condition was necessary but not sufficient for high amplitudes to be reached.

Ecological Stoichiometry of Carbon, Nitrogen, and Phosphorus in Subtropical Paddy Soils

This study aims to understand the existence of stable soil organic carbon (C), nitrogen (N), and phosphorus (P) ratios in paddy soil. Based on a field soil survey database, the ecological stoichiometry of the C:N:P ratio of 110 subtropical paddy soil profiles and 587 genetic horizons were analyzed at a regional scale. Relevant analysis and redundancy analysis (RDA) are used to study the relationships between C:N:P ratios and soil-environmental factors (topography, parent materials, soil genetic horizons, soil groups, soil physical, and chemical properties). The results showed that the weighted averages of C:N, C:P, and N:P in paddy soils of subtropical regions were 12.6, 49, and 3.9, respectively, and C:N:P was 38:3.2:1. The C:N of paddy soil did not vary significantly with parent materials, soil groups, or genetic horizons. However, the C:P and N:P variations were significantly different, and the mean values of the two were much lower than global ratios (186 and 13.1) and average levels of C:P and N:P in Chinese soils (136 and 9.3). Although the C:N:P ratio in the paddy soil profile was relatively unstable, the topsoil C:N (14.2) was relatively stable due to the strong interaction between the topsoil and the environment. This reflects the close coupling of C and N in the topsoil of paddy fields under long-term anthrostagnic maturation. However, in the paddy soil profile, C:P and N:P were not stable, and there was no significant correlation between soil organic carbon (SOC) and total P content, total N, or total P content, which suggests that environmental changes may lead to soil C:N:P decoupling. It was found that topography, soil texture, iron oxide, and bulk density are all key soil-environmental factors that regulate the soil profile of rice paddy C:N:P.

Microbial Life in Impact Craters.

Asteroid and comet impacts are known to have caused profound disruption to multicellular life, yet their influence on habitats for microorganisms, which comprise the majority of Earth's biomass, is less well understood. Of particular interest are geological changes in the target lithology at and near the point of impact that can persist for billions of years. Deep subsurface and surface-dwelling microorganisms are shown to gain advantages from impact-induced fracturing of rocks. Deleterious changes are associated with impact-induced closure of pore spaces in rocks. Superimposed on these long-term geological changes are post-impact alterations such as changes in the hydrological system in and around a crater. The close coupling between geological changes and the conditions for microorganisms yields a synthesis of the fields of microbiology and impact cratering. We use these data to discuss how craters can be used in the search for life beyond Earth.

Low-energy electron scattering from methylene radicals: multichannel-coupling effects

SynopsisWe reported elastic and excitation cross sections for electron collisions with methylene radical using R-matrix method for electron energies ranging from 0.01 to 15 eV in close-coupling (CC) approximation. We discuss the multi-channel-coupling effects on the calculated cross sections and resonances, and how the number of excited states included in the target state impacts the convergence of the elastic and the X3B1 → 11A1 and X3B1 → 11B1 excitation cross sections, especially at higher impact energy. Finally, we estimate the accuracy of the 11A1and 11B1 excitation cross sections.

Dual Hidden Failure Model for Cyber Physical Power System

With the increasingly close coupling between the cyber network and the physical power grid in Cyber Physical Power System (CPPS), the failure of cyber network has become an important cause of blackout. Equipment failure or abnormal operation state will be appeared without alarm in complex cyber network, which brings hidden failures not been diagnosed and dealt with in time. The invisibility and harmfulness of hidden failures pose a significant threat to the safe, reliable, and stable operation of CPPS. The dual hidden cascading failure model for CPPS is proposed to reveal the failure characteristics of CPPS accurately, considering not only the hidden faults in the power grid, but also the hidden failures in the cyber network. With the different coupled relationships between power systems and cyber networks, the cyber network topology with corresponding failure threshold is obtained according to the simulation of the model with different hidden failure rates of cyber network nodes. When the hidden failure rate is lower than the failure threshold, the scale-free topology cyber network coupled mode is adopted between power grids and cyber networks, otherwise the small-world topology cyber network coupled mode is adopted, which can effectively reduce the risk of power system blackouts. The method proposed in this paper is tested by using IEEE-118 power system and its cyber network. The results show that the method is effective.

Interplay between morphogen-directed positional information systems and physiological signaling.

The development of an organism from an undifferentiated single cell into a spatially complex structure requires spatial patterning of cell fates across tissues. Positional information, proposed by Lewis Wolpert in 1969, has led to the characterization of many components involved in regulating morphogen signaling activity. However, how morphogen gradients are established, maintained, and interpreted by cells still is not fully understood. Quantitative and systems-based approaches are increasingly needed to define general biological design rules that govern positional information systems in developing organisms. This short review highlights a selective set of studies that have investigated the roles of physiological signaling in modulating and mediating morphogen-based pattern formation. Similarities between neural transmission and morphogen-based pattern formation mechanisms suggest underlying shared principles of active cell-based communication. Within larger tissues, neural networks provide directed information, via physiological signaling, that supplements positional information through diffusion. Further, mounting evidence demonstrates that physiological signaling plays a role in ensuring robustness of morphogen-based signaling. We conclude by highlighting several outstanding questions regarding the role of physiological signaling in morphogen-based pattern formation. Elucidating how physiological signaling impacts positional information is critical for understanding the close coupling of developmental and cellular processes in the context of development, disease, and regeneration.

Decreased atrioventricular plane displacement after acute myocardial infarction yields a concomitant decrease in stroke volume.

Acute myocardial infarction (AMI) can progress to heart failure, which has a poor prognosis. Normally, 60% of stroke volume (SV) is attributed to the longitudinal ventricular shortening and lengthening evident in the atrioventricular plane displacement (AVPD) during the cardiac cycle, but there is no information on how the relationship changes between SV and AVPD before and after AMI. Therefore, the aim of this study was to determine how SV depends on AVPD before and after AMI in two swine models. Serial cardiac magnetic resonance imaging was carried out before and 1–2 h after AMI in a microembolization model (n = 12) and an ischemia-reperfusion model (n = 14). A subset of pigs (n = 7) were additionally imaged at 24 h and at 7 days. Cine and late gadolinium enhancement images were analyzed for cardiac function, AVPD measurements and infarct size estimation, respectively. AVPD decreased (P < 0.05) in all myocardial regions after AMI, with a concomitant SV decrease (P < 0.001). The ischemia-reperfusion model affected SV to a higher degree and had a larger AVPD decrease than the microembolization model (−29 ± 14% vs. −15 ± 18%; P < 0.05). Wall thickening decreased in infarcted areas (P < 0.001), and A-wave AVPD remained unchanged (P = 0.93) whereas E-wave AVPD decreased (P < 0.001) after AMI. We conclude that AVPD is coupled to SV independent of infarct type but likely to a greater degree in ischemia-reperfusion infarcts compared with microembolization infarcts. AMI reduces diastolic early filling AVPD but not AVPD from atrial contraction. These findings shed light on the physiological significance of atrioventricular plane motion when assessing acute and subacute myocardial infarction.NEW & NOTEWORTHY The link between cardiac longitudinal motion, measured as atrioventricular plane displacement (AVPD), and stroke volume (SV) is investigated in swine after acute myocardial infarction (AMI). This cardiac magnetic resonance study demonstrates a close coupling between AVPD and SV before and after AMI in an experimental setting and demonstrates that this connection is present in ischemia-reperfusion and microembolization infarcts, acutely and during the first week. Furthermore, AVPD is equally and persistently depressed in infarcted and remote myocardium after AMI.

Benchmark Quantum Kinetics at Low Temperatures toward Absolute Zero and Role of Entrance Channel Wells on Tunneling, Virtual States, and Resonances: The F + HD Reaction

This paper reports a study of the quantum reaction dynamics and kinetics of the F + HD reaction at low and ultralow temperatures, focusing on the range from the Wigner limit up to 50 K. Close coupling time-independent quantum reactive scattering calculations for the production of HF and DF molecules have been carried out on two potential energy surfaces differing in the description of the reaction entrance channel. This case is computationally more demanding than the cases of F with H2 and D2 ( De Fazio et al. Frontiers in Chemistry 2019 , 7 , 328 ) but offers a wider phenomenology regarding the roles of quantum mechanical effects of tunneling, of virtual states, and of resonances. The results show that at the temperatures in the cold and ultracold regimes small changes in the entrance channel long-range interaction induce surprising near threshold features. The presence of a virtual state close to the reactive threshold gives rise to a marked anti-Arrhenius behavior of the rate constants below 100 mK. This effect enhances reaction rates by about 2 orders of magnitude, making them of the same order as those at room temperature and confining the onset of the Wigner regime in the microkelvin region.

From Local to Global Modeling for Characterizing Calcium Dynamics and Their Effects on Electrical Activity and Exocytosis in Excitable Cells.

Electrical activity in neurons and other excitable cells is a result of complex interactions between the system of ion channels, involving both global coupling (e.g., via voltage or bulk cytosolic Ca2+ concentration) of the channels, and local coupling in ion channel complexes (e.g., via local Ca2+ concentration surrounding Ca2+ channels (CaVs), the so-called Ca2+ nanodomains). We recently devised a model of large-conductance BKCa potassium currents, and hence BKCa–CaV complexes controlled locally by CaVs via Ca2+ nanodomains. We showed how different CaV types and BKCa–CaV stoichiometries affect whole-cell electrical behavior. Ca2+ nanodomains are also important for triggering exocytosis of hormone-containing granules, and in this regard, we implemented a strategy to characterize the local interactions between granules and CaVs. In this study, we coupled electrical and exocytosis models respecting the local effects via Ca2+ nanodomains. By simulating scenarios with BKCa–CaV complexes with different stoichiometries in pituitary cells, we achieved two main electrophysiological responses (continuous spiking or bursting) and investigated their effects on the downstream exocytosis process. By varying the number and distance of CaVs coupled with the granules, we found that bursting promotes exocytosis with faster rates than spiking. However, by normalizing to Ca2+ influx, we found that bursting is only slightly more efficient than spiking when CaVs are far away from granules, whereas no difference in efficiency between bursting and spiking is observed with close granule-CaV coupling.

Coupling in situ experiments and modeling – Opportunities for data fusion, machine learning, and discovery of emergent behavior

This paper reviews recent studies, that not only includes both experiments and modeling components, but celebrates a close coupling between these techniques, in order to provide insights into the plasticity and failure of polycrystalline metals. Examples are provided of studies across multiple-scales, including, but not limited to, density functional theory combined with atom probe tomography, molecular dynamics combined with in situ transmission electron miscopy, discrete dislocation dynamics combined with nanopillars experiments, crystal plasticity combined with digital image correlation, and crystal plasticity combined with in situ high energy X-ray diffraction. The close synergy between in situ experiments and modeling provides new opportunities for model calibration, verification, and validation, by providing direct means of comparison, thus removing aspects of epistemic uncertainty in the approach. Further, data fusion between in situ experimental and model-based data, along with data driven approaches, provides a paradigm shift for determining the emergent behavior of deformation and failure, which is the foundation that underpins the mechanical behavior of polycrystalline materials.

On the Way to Efficient Analytical Measurements: The Future of Robot-Based Measurements.

The demand for efficient and qualified measurements is high. The measurements of physical parameters in industrial environments usually are automatically executed using process measurement technologies. The close coupling of the measurement system and process equipment enables in-process data acquisition (inline or online). In contrast, compound-oriented measurements for the qualitative identification and quantitative determination of chemical elements and chemical compounds, or the determination of biological behavior, are still challenging in measurement processes. Today, biological assays as well as high-content and high-throughput screening procedures are well automated. It appears quite differently if the efficiency of analytical measurements should be improved. Due to the characteristics of the samples and processes, inline or online coupling is often not possible. Therefore, atline or offline couplings are gaining in importance. In combination with robotic systems, efficient automation of analytical measurements can be reached. The book Automation Solutions for Analytical Measurements: Concepts and Applications presents and discusses suitable automation concepts and a variety of realized robot-based analytical measurement systems. In this commentary, the main findings are highlighted and discussed.

Perceptions or Actions? Grounding How Agents Interact Within a Software Architecture for Cognitive Robotics

One of the aims of cognitive robotics is to endow robots with the ability to plan solutions for complex goals and then to enact those plans. Additionally, robots should react properly upon encountering unexpected changes in their environment that are not part of their planned course of actions. This requires a close coupling between deliberative and reactive control flows. From the perspective of robotics, this coupling generally entails a tightly integrated perceptuomotor system, which is then loosely connected to some specific form of deliberative system such as a planner. From the high-level perspective of automated planning, the emphasis is on a highly functional system that, taken to its extreme, calls perceptual and motor modules as services when required. This paper proposes to join the perceptual and acting perspectives via a unique representation where the responses of all software modules in the architecture are generalized using the same set of tokens. The proposed representation integrates symbolic and metric information. The proposed approach has been successfully tested in CLARC, a robot that performs Comprehensive Geriatric Assessments of elderly patients. The robot was favourably appraised in a survey conducted to assess its behaviour. For instance, using a 5-point Likert scale from 1 (strongly disagree) to 5 (strongly agree), patients reported an average of 4.86 when asked if they felt confident during the interaction with the robot. This paper proposes a mechanism for bringing the perceptual and acting perspectives closer within a distributed robotics architecture. The idea is built on top of the blackboard model and scene graphs. The modules in our proposal communicate using a short-term memory, writing the perceptual information they need to share with other agents and accessing the information they need for determining the next goals to address.