Action Approach Research Articles

Future ecosystem business model tool: Design science and field test in the efuel ecosystem towards the sustainability transition

This paper presents a novel business model design tool called Future ecosystem business model (FEBM). The FEBM aims to address the lack of managerial tools linking business models, foresight, and ecosystem strategizing in the context of systemic technological changes, as those characterizing the sustainability transition in a multi-level perspective. The tool has been shaped through a design science approach building on a structured review of the literature. A field test was conducted through a case study to test the proposed tool. The empirical context was that of a publicly funded project in the field of electrofuels (efuels). The project foresaw the development and integration of several technologies, whose adoption was likely to have significant implications within and across industries. The proposed approach contributes to the literature on business model design in the context of technology-driven transformations characterized by high uncertainty and interdependence, such as those related to the sustainability transition. Strategy and innovation managers may find in the proposed FEBM tool an actionable approach to shape decision-making against far-reaching technological and societal challenges.

A Reasoned Action Approach to Increase Asian Americans’ Counseling Intention Upon Pet Loss

A Reasoned Action Approach to Increase Asian Americans’ Counseling Intention Upon Pet Loss

A scoping review of health models for the community mental health needs of the United Arab Emirates: Nurturing the social determinants of mental health through social prescribing in the Middle East

Despite the growing interest in social prescribing the diversification of health and social care strategies to support the well-being of patients has remained entrenched with a focus on the hospital setting within the Middle East. The United Arab Emirates has commenced progressing community mental health care to lead changes in how care and treatment are delivered within the United Arab Emirates. The authors adopted the use of the framework of Arksey and O’Malley (2005) to provide a systematic approach to searching the literature and creating a comprehensive foundation to guide the review. This scoping review provides a better understanding of the compatibility, content and outcomes of a selection of health models. The scoping review findings will inform the proposed use of social prescribing as an actionable approach to create a focus on the need to include and empower the social determinants of mental health. This article proposes an evidence-based health strategy that supports and enhances recent additions to national legislation on the inclusion of the Mental Health Law within the United Arab Emirates to meditate and prevent inequities in addressing the mental health needs of citizens and residents within the nation’s diverse communities.

Selective Bribery: When Do Citizens Engage in Corruption?

Corruption often persists not only because public officials take bribes, but also because many citizens are willing to pay them. Yet even in countries with endemic corruption, few people always pay bribes. Why do citizens bribe in some situations but not in others? Integrating insights from both principal-agent and collective action approaches to the study of corruption, we develop and empirically evaluate an analytical framework for understanding selective bribery. Our framework reveals how citizens’ motivations, costs, and risks influence their willingness to engage in corruption. A conjoint experiment conducted in Ukraine in 2020 predominantly corroborates our pre-registered predictions. By shedding light on conditions that dampen citizens’ readiness to pay bribes, our findings offer insights into the types of institutional reforms that may reduce corruption and ultimately help countries to escape self-reinforcing corruption cycles.

Correcting misperceptions about very low nicotine cigarettes for cigarette-only smokers, dual/poly smokers, other tobacco users, and non-tobacco users

BackgroundThe U.S. Food and Drug Administration authorized the sale and marketing of two very low nicotine cigarettes (VLNC) as modified risk tobacco products. The misperception that VLNC are healthier than regular cigarettes is common. This study explores effective message strategies to inform the public about health risks associated with VLNC use, encourage cigarette smokers to try VLNC, and prevent other tobacco users and non-users from product initiation. MethodsFollowing the Reasoned Action approach, a VLNC educational message was developed based on the salient beliefs associated with behavioral intention. The message was tested in an online survey conducted in 2018, where 410 participants were randomly assigned to one of the two message conditions (no-message, VLNC message). Message effects were assessed across four tobacco-use groups (non-tobacco users, cigarette-only smokers, cigarette dual/poly smokers, other tobacco users). ResultsCompared to the no-message control, the VLNC message condition showed lower nicotine risk perception for all participants, lower misbelief in VLNC safety for non-users and cigarette-only smokers, higher belief in VLNC carcinogenicity for other tobacco users, stronger belief in second-hand smoke harm for cigarette dual/poly smokers and other tobacco users, and higher VLNC intention for cigarette-only smokers. ConclusionsDifferent messages are needed for different types of tobacco users. Both cigarette smokers and other tobacco users could benefit from messages that acknowledge the non-addictiveness but emphasize the health risks of VLNC. Regulators could consider making physical harm statements a requirement for VLNC packaging and marketing. New strategies need to be explored to inform cigarette dual/poly smokers.

Scale up of the learning circles: a participatory action approach to support local food systems in four diverse First Nations school communities within Canada

BackgroundAddressing Indigenous food security and food sovereignty calls for community-driven strategies to improve access to and availability of traditional and local food. Participatory approaches that integrate Indigenous leadership have supported successful program implementation. Learning Circles: Local Healthy Food to School is a participatory program that convenes a range of stakeholders including food producers, educators and Knowledge Keepers to plan, implement and monitor local food system action. Pilot work (2014–2015) in Haida Gwaii, British Columbia (BC), showed promising results of the Learning Circles (LC) approach in enhancing local and traditional food access, knowledge and skills among youth and adolescents. The objective of the current evaluation was therefore to examine the process of scaling-up the LC vertically within the Haida Nation; and horizontally across three diverse First Nations contexts: Gitxsan Nation, Hazelton /Upper Skeena, BC; Ministikwan Lake Cree Nation, Saskatchewan; and Black River First Nation, Manitoba between 2016 and 2019.MethodsAn implementation science framework, Foster-Fishman and Watson’s (2012) ABLe Change Framework, was used to understand the LC as a participatory approach to facilitate community capacity building to strengthen local food systems. Interviews (n = 52), meeting summaries (n = 44) and tracking sheets (n = 39) were thematically analyzed.ResultsThe LC facilitated a collaborative process to: (1) build on strengths and explore ways to increase readiness and capacity to reclaim traditional and local food systems; (2) strengthen connections to land, traditional knowledge and ways of life; (3) foster community-level action and multi-sector partnerships; (4) drive actions towards decolonization through revitalization of traditional foods; (5) improve availability of and appreciation for local healthy and traditional foods in school communities; and (6) promote holistic wellness through steps towards food sovereignty and food security. Scale-up within Haida Gwaii supported a growing, robust local and traditional food system and enhanced Haida leadership. The approach worked well in other First Nations contexts, though baseline capacity and the presence of champions were enabling factors.ConclusionsFindings highlight LC as a participatory approach to build capacity and support iterative planning-to-action in community food systems. Identified strengths and challenges support opportunities to expand, adopt and modify the LC approach in other Indigenous communities with diverse food systems.

Effect of nonzero temperature to non-condensed fraction of a homogeneous dilute weakly interacting Bose gas

This study aims to investigate the effect of nonzero temperature to the non-condensed fraction of a homogeneous repulsive weakly interacting Bose gas in region of sufficiently low temperature. Within improved Hartree-Fock approximation, the Cornwall–Jackiw–Tomboulis effective action approach shows that the thermal fluctuations make the non-condensed fraction increase as a second and fourth-order power law of temperature. Indeed, the effect of non-infinite size of the trap is also integrated. The result is compared with experimental data.

Youth Participatory Action Communication Research: A Model for Developing Youth-Driven Health Campaigns

ABSTRACT Youth offer valuable insight on health communication needs and solutions in their communities. We propose youth participatory action communication research (YPACR) as a model for health campaign development that engages youth perspectives in applying systematic theory-informed communication research to addressing youth-identified health priorities. YPACR informed a series of paid high school internship programs in West Philadelphia, in which youth interns identified mental health help-seeking communication as a need among peers. In Phase 1, guided by the reasoned action approach and Hornik & Woolf method, youth interns conducted a survey measuring behavioral beliefs, normative beliefs, and control beliefs associated with mental health help-seeking, as well as trusted sources of mental health information, among local high school students. Survey results suggested control (self-efficacy) was an important message target and peers were trusted mental health information sources. In Phase 2, youth interns developed TikTok-style messages focused on strengthening control beliefs and promoting a youth-selected mental health support resource. Youth interns distributed an online survey experiment to test whether youth-created messages shown alongside resource information increased help-seeking self-efficacy compared to an information-only control. The YPACR framework contributed to youth-relevant campaign goals, study measurements, recruitment approaches, data interpretation, and message design. We discuss the benefits and challenges of this youth-driven health campaign development model and recommendations for future research.

Allowing time for 8+ hours of sleep: identification and validation of important beliefs using the reasoned action approach.

The present studies advance research using the Reasoned Action Approach to understand sleep behavior. Identification of the modal salient beliefs that individuals hold regarding their sleep habits is necessary to understand the attitudes, perceived normative pressure, and perceived behavioral control (PBC) that individuals hold. Belief elicitation (Study 1) and follow-up validation (Study 2) studies of undergraduates at a Midwestern USA university were conducted to identify readily accessible and important beliefs regarding allowing time for 8+ hours of sleep each night. Important attitude relevant beliefs included positive effects on mood, thinking, health, and productivity. Important normative beliefs were perceived injunctive pressure from family, health professionals, and significant others. Because of the strong influence of PBC on intentions/behavior, most important were control beliefs about the need for good time management. The present studies increased our understanding why many individuals do not allow time to obtain adequate sleep. Identification of the beliefs that distinguish between those who intend to allow time for adequate sleep and those who do not is a necessary step toward the design of effective interventions to improve sleep duration. The results indicate that a focus on increasing time management skills and PBC may be an effective approach for sleep interventions.

Mitigating data quality challenges in ambulatory wrist-worn wearable monitoring through analytical and practical approaches

Chronic disease management and follow-up are vital for realizing sustained patient well-being and optimal health outcomes. Recent advancements in wearable technologies, particularly wrist-worn devices, offer promising solutions for longitudinal patient monitoring, replacing subjective, intermittent self-reporting with objective, continuous monitoring. However, collecting and analyzing data from wearables presents several challenges, such as data entry errors, non-wear periods, missing data, and wearable artifacts. In this work, we explore these data analysis challenges using two real-world datasets (mBrain21 and ETRI lifelog2020). We introduce practical countermeasures, including participant compliance visualizations, interaction-triggered questionnaires to assess personal bias, and an optimized pipeline for detecting non-wear periods. Additionally, we propose a visualization-oriented approach to validate processing pipelines using scalable tools such as tsflex and Plotly-Resampler. Lastly, we present a bootstrapping methodology to evaluate the variability of wearable-derived features in the presence of partially missing data segments. Prioritizing transparency and reproducibility, we provide open access to our detailed code examples, facilitating adaptation in future wearable research. In conclusion, our contributions provide actionable approaches for improving wearable data collection and analysis.

A scoping review of health models for the community mental health needs of the United Arab Emirates: Nurturing the social determinants of mental health through social prescribing in the Middle East

Despite the growing interest in social prescribing the diversification of health and social care strategies to support the well-being of patients has remained entrenched with a focus on the hospital setting within the Middle East. The United Arab Emirates has commenced progressing community mental health care to lead changes in how care and treatment are delivered within the United Arab Emirates. The authors adopted the use of the framework of Arksey and O’Malley (2005) to provide a systematic approach to searching the literature and creating a comprehensive foundation to guide the review. This scoping review provides a better understanding of the compatibility, content and outcomes of a selection of health models. The scoping review findings will inform the proposed use of social prescribing as an actionable approach to create a focus on the need to include and empower the social determinants of mental health. This article proposes an evidence-based health strategy that supports and enhances recent additions to national legislation on the inclusion of the Mental Health Law within the United Arab Emirates to meditate and prevent inequities in addressing the mental health needs of citizens and residents within the nation’s diverse communities.

Penerapan Metode Role Palying dalam Pembelajaran PAI Untuk Meningkatkan Kemampuan Hafalan Siswa pada Siswa Kelas VII MTsS Jam’iyah Mahmudiyah Tanjung Pura

This research aims to improve the ability to memorize the Qur'an of grade VII MTsS Jam'iyah Mahmudiyah students through the Role Playing method. The research uses a classroom action approach (Classroom Action Research) with two cycles, each cycle includes the stages of planning, implementation, observation, and reflection. In the pre-cycle, only 31% of students achieved completeness with KKM 75. After the application of the Role Playing method in cycle I, the completeness increased to 71%. In cycle II, the percentage of completion increased significantly to 91%. These results show that the Role Playing method is effective in improving students' ability to memorize the Qur'an, increase their active participation, and motivation to learn.

A generic logic model for physical activity interventions for the cardiac population using intervention mapping

Abstract Introduction Regular physical activity is important in the secondary prevention of cardiovascular disease. But many cardiac patients have difficulty establishing lifelong physical activity habits, even after completion of an exercise-based cardiac rehabilitation programme. There is a need for effective interventions to support cardiac patients' physical activity. Such interventions are often complex behaviour change interventions whose design should be grounded in programme theory, i.e., a description of how the intervention is expected to lead to its effects and under what conditions. A logic model is often used to communicate programme theory [1]. Purpose The purpose of this work was to describe a generic logic model for behaviour change interventions to increase and maintain physical activity among patients who have had an acute cardiac event. Methods We applied the Intervention Mapping approach [2] to develop a generic logic model that is both data- and theory-driven, i.e. informed by research evidence and behaviour change theory. The at-risk behaviour for the individual cardiac patient was defined as "insufficient independent long-term maintenance of heart-healthy physical activity", compounded by the environmental factor "lack of support provision for long-term independent physical activity" from the healthcare providers and people in the patient’s interpersonal environment. We defined performance objectives by asking the questions: "What do people who had an acute cardiac event need to do to increase and maintain their heart-healthy physical activity?" and "What do the healthcare providers and people in the patient’s interpersonal environment need to do to encourage and support the patient in being physically active?" The performance objectives specify what actions are required of the individuals targeted in the intervention. We selected determinants corresponding to performance objectives based on empirical evidence from systematic reviews and based on behaviour change theory such as the Reasoned Action Approach (RAA) and the Health Action Process Approach (HAPA). Results Central elements of the logic model are presented in table 1. The logic model includes 18 performance objectives and 13 determinants, supported by empirical evidence from 40 scientific publications. Conclusion The generic logic model serves as a collection of current knowledge regarding increasing and maintaining physical activity among the cardiac population and can be used for a number of purposes: as a foundation for developing new interventions; as a blueprint against which to compare and/or solidify the programme theory of existing interventions; as a conceptual framework for designing evaluations of interventions; as a current evidence map from which to identify research gaps; and as a point of reference for reflecting on one’s own health behaviour.Table 1.Elements of the logic model.

Novel Sleep Phenotypic Profiles Associated With Incident Atrial Fibrillation in a Large Clinical Cohort

BackgroundWhile sleep disorders are implicated in atrial fibrillation (AF), the interplay of physiologic alterations and symptoms remains unclear. Sleep-based phenotypes can account for this complexity and translate to actionable approaches to identify at-risk patients and therapeutic interventions. ObjectivesThis study hypothesized discrete phenotypes of symptoms and polysomnography (PSG)-based data differ in relation to incident AF. MethodsData from the STARLIT (sleep Signals, Testing, And Reports LInked to patient Traits) registry on Cleveland Clinic patients (≥18 years of age) who underwent PSG from November 27, 2004, to December 30,2015, were retrospectively examined. Phenotypes were identified using latent class analysis of symptoms and PSG-based measures of sleep-disordered breathing and sleep architecture. Phenotypes were included as the primary predictor in a multivariable-adjusted Cox proportional hazard models for incident AF. ResultsIn our cohort (N = 43,433, age 51.8 ± 14.5 years, 51.9% male, 74.9% White), 7.3% (n = 3,166) had baseline AF. Over a 7.6- ± 3.4-year follow-up period, 8.9% (n = 3,595) developed incident AF. Five phenotypes were identified. The hypoxia subtype (n = 3,245) had 48% increased incident AF (HR: 1.48; 95% CI: 1.34-1.64), the apneas + arousals subtype (n = 4,592) had 22% increased incident AF (HR: 1.22; 95% CI: 1.10-1.35), and the short sleep + nonrapid eye movement subtype (n = 6,126) had 11% increased incident AF (HR: 1.11; 95% CI: 1.01-1.22) compared with long sleep + rapid eye movement (n = 26,809), the reference group. The hypopneas subtype (n = 2,661) did not differ from reference (HR: 0.89; 95% CI: 0.77-1.03). ConclusionsConsistent with prior evidence supporting hypoxia as an AF driver and cardiac risk of the sleepy phenotype, this constellation of symptoms and physiologic alterations illustrates vulnerability for AF development, providing potential value in enhancing our understanding of integrated sleep-specific symptoms and physiologic risk of atrial arrhythmogenesis.

Role of Higgs and Leggett modes for the third harmonic response in noncentrosymmetric superconductors

The amplitude and phase of the third harmonic response in superconductors provide important insights into collective Higgs and Leggett modes, respectively, in the superconducting state. In particular, for twice the incident frequency equal to the binding energy (2ω=2Δ), one finds a resonance of the amplitude and a corresponding phase jump in the third harmonic response, respectively. We generalize these concepts to superconductors without an inversion symmetry, which can be effectively described by a two-band model with an order parameter consisting of spin-singlet (even parity) and spin-triplet (odd parity) components. In our work we use an effective action approach for the derivation of the nonlinear response and assign the underlying physical processes to their respective Feynman diagrams. We calculate the third harmonic signal exemplary for the noncentrosymmetric compound CePt3Si, showing that it contains contributions from three distinguishable sources, namely the Higgs mode, the Leggett mode, and quasiparticles (broken Cooper-pairs). Only in the clean limit diamagnetic Raman-like processes contribute to the third harmonic signal, whereas the quasiparticle contributions dominate the collective modes for all triplet-singlet ratios of the gap structure. In the dirty limit, we find a significant enhancement of the Higgs mode contributions to the third harmonic response, due to the inclusion of nonvanishing paramagnetic diagrams. Finally, we argue that the phase difference between the third harmonic and the fundamental signal might reveal a jump, where its size is dependent on the light-matter coupling. Published by the American Physical Society 2024

Restricted health service utilization and subsequent positive self-care behavior during the early COVID-19 pandemic in China.

The reallocation of health resources, epidemic prevention and control measures during the COVID-19 pandemic triggered widespread restricted health service utilization, some residents and patients tried positive self-care behavior to maintain their health, yet the efficacy of this intervention remains unclear. Based on the reasoned action approach (RAA) theory, this study aimed to investigate the correlation between self-care behavior and restricted health service utilization among adults in China, trying to discover the vulnerable groups and external and intrinsic factors that affect self-care behavior among Chinese adults. Data on demographics, socioeconomic, health status, and self-care behavior were collected in "The Early China COVID-19 Survey," a cross-sectional anonymous online survey of the general population in China. Self-care behavior was measured by four indicators: weight control (WC), physical activity (PA), prevention behavior (PB), and online medical consultation (OMC). The multiple linear models and binary logistic regression were used to examine whether restricted health service utilization (RHSU) is associated with self-care behaviors; also, adjusted multivariate logistic regression was used to analyze subgroup heterogeneity. In total, 8,428 adult participants completed the survey, the mean OMC score was 1.51 (SD 1.34), the mean PB score was 18.17 (SD 3.44), and the proportion of participants who engaged in WC and PA was 42.30 and 62.57%, respectively. According to the multiple regression model, the RHSU was significantly positively correlated with all four indicators of self-care (WC: OR = 1.34, p < 0.001, PA: OR = 1.34, p < 0.05, MC: OR = 1.30, p < 0.001, PB: coef = 0.16, p < 0.05). We also observed some significant differences in the intensity of this relationship by subgroup analysis, precisely, OMC (high vs. moderate vs. low infection-risk level: OR = 1.48; 1.41; 1.19, p < 0.1), PA (male vs. female: OR = 1.27;1.06; p < 0.05, high vs. Moderate and low infection-risk level: OR = 1.51; 1.17; 1.02, p < 0.05), PB (Chronic disease groups vs. no: coef = 0.46; 0.1, p < 0.05). Restricted health service utilization predicts more positive self-care behavior, and the intensity of partial correlation was significantly different in the subgroups of sex, actual infection risk level of the living area, and chronic diseases. These findings highlight the urgent demand for self-care behavior among Chinese adults during the pandemic and provide new insights for developing self-care and reducing the burden on the healthcare system in the long term.

Stabilization of TGF-β Receptor 1 by a Receptor-Associated Adaptor Dictates Feedback Activation of the TGF-β Signaling Pathway to Maintain Liver Cancer Stemness and Drug Resistance.

Dysregulation of the transforming growth factor-β (TGF-β)signaling pathway regulates cancer stem cells (CSCs) and drug sensitivity, whereas it remains largely unknown how feedback regulatory mechanisms are hijacked to fuel drug-resistant CSCs. Through a genome-wide CRISPR activation screen utilizing stem-like drug-resistant properties as a readout, the TGF-β receptor-associated binding protein 1 (TGFBRAP1) is identified as a TGF-β-inducible positive feedback regulator that governs sensitivity to tyrosine kinase inhibitors (TKIs) and promotes liver cancer stemness. By interacting with and stabilizing the TGF-β receptor type 1 (TGFBR1), TGFBRAP1 plays an important role in potentiating TGF-β signaling. Mechanistically, TGFBRAP1 competes with E3 ubiquitin ligases Smurf1/2 for binding to TGFΒR1, leading to impaired receptor poly-ubiquitination and proteasomal degradation. Moreover, hyperactive TGF-β signaling in turn up-regulates TGFBRAP1 expression in drug-resistant CSC-like cells, thereby constituting a previously uncharacterized feedback mechanism to amplify TGF-β signaling. As such, TGFBRAP1 expression is correlated with TGFΒR1 levels and TGF-β signaling activity in hepatocellular carcinoma (HCC) tissues, as well as overall survival and disease recurrence in multiple HCC cohorts. Therapeutically, blocking TGFBRAP1-mediated stabilization of TGFBR1 by selective inhibitors alleviates Regorafenib resistance via reducing CSCs. Collectively, targeting feedback machinery of TGF-β signaling pathway may be an actionable approach to mitigate drug resistance and liver cancer stemness.

Preventive behavior intention for a viral outbreak among college students: The case of Mpox

Objective Examine college students’ behavior intention to reduce viral outbreak transmission in the context of Mpox, and what preventive messaging strategies would be most effective in future transmissible disease outbreaks based on the Reasoned Action Approach (RAA). Participants Undergraduates at a mid-Atlantic U.S. University. Methods An online survey (n = 266) conducted at the height of the recent Mpox outbreak in the U.S., asked about five target behaviors to reduce Mpox transmission, including RAA determinants for each behavior. Results Highest intention was safe sex practices, lowest were vaccination and sexual abstinence, and sharing dishes and fabrics were in between. RAA determinants differed by target behavior, although attitudes were significantly positively associated with intention for all five behaviors. Conclusions College students are potentially open to preventative behaviors to reduce viral transmission during an outbreak. However, specific target behavior matters and messaging should focus on differing RAA determinants depending on target behavior.

Advancing advocacy communication theory: a theory grounded in undocumented college students’ motivations and strategies for challenging oppression

ABSTRACT Undocumented college students experience a myriad of stressors (e.g. fear of deportation, limited access to educational resources; Enriquez, Morales Hernandez & Ro. 2018. Deconstructing immigrant illegality: A mixed-methods investigation of stress and health among undocumented college students. Race and Social Problems, 10(3), 193–208. https://doi.org/10.1007/s12552-018-9242-4) because of systemic oppression, and they often engage in various advocacy efforts to challenge those oppressive systems. Although different persuasion (e.g. Reasoned Action Approach, Anger Activism Model; Fishbein & Ajzen. 2010. Predicting and changing behavior: The reasoned action approach. Psychology Press; Turner. 2007. Using emotion in risk communication: The anger activism model. Public Relations Review, 33(2), 114–119. https://doi.org/10.1016/j.pubrev.2006.11.013) and social movements theories (e.g. Mass Society Theory; Theory of Relative Deprivation; Bernstein & Crosby. 1980. An empirical examination of relative deprivation theory. Journal of Experimental Social Psychology, 16(5), 442–456. https://doi.org/10.1016/0022-1031(80)90050-5) can describe why minoritized group members advocate on behalf of their ingroup, these theories primarily focus on traditional advocacy efforts. rather than representing advocacy as multidimensional. Consequently, this paper introduces Advocacy Communication Theory (ACT), which argues that advocacy communication is a complex and multidimentional process consisting of advocacy strategies at the individual, interpersonal, community, organizational, and policy levels. ACT also identifies predictors of advocacy communication by drawing from communication and psychological factors, and it discusses the potential health implications associated with engaging in advocacy communication.

Effective action approach to the dynamical map

The dynamical map represents a fundamental concept in quantum field theory, providing a solution of the field equations in the Fock space of asymptotic fields. In this paper, we show how to express the dynamical map of a scalar field in the language of quantum effective action. This grants us new insights into the study of topological defects in quantum field theory by showing a connection between the usual least-action principle and Umezawa’s boson transformation method.