In regulated monopoly services, consumers lack effective exit options, making complaint systems a central mechanism for expressing dissatisfaction and generating regulatory information about service performance. However, complaint rates are not direct or unbiased indicators of service failures, as the decision to complain involves informational, procedural, and behavioral costs, reflecting both service problems and heterogeneous access barriers. Because administrative data record filed complaints rather than adjudicated outcomes, complaint rates are interpreted as noisy signals of perceived billing anomalies rather than direct measures of confirmed service failures, firm misconduct, or regulatory noncompliance. This paper reinterprets billing-related complaints as endogenous regulatory signals in essential public services. We develop a microeconomic framework in which households decide whether to complain when facing an atypical bill under uncertainty about its origin-whether it reflects a firm billing error or household-specific factors. The model's predictions are tested using sector-month administrative data from Sedapal, the public water utility serving Metropolitan Lima (Peru), covering January 2022-June 2023. We estimate a dynamic panel model (System GMM) to identify persistence in complaint behavior and its response to unanticipated tariff shocks. We find strong persistence in complaint rates and a significant response to unexpected tariff increases. These patterns suggest structural frictions in service provision or communication and a critical role for tariff transparency. Overall, the results imply that regulators should strengthen tariff communication and incorporate complaint data into monitoring systems as screening and triage indicators, rather than as mechanical evidence of confirmed billing errors or firm misconduct.
Diaphorina citri is the primary vector of Huanglongbing (HLB), a devastating disease that affects global citrus production. Effective biological control using the parasitoid Tamarixia radiata represents a sustainable alternative to chemical insecticides, but its efficacy depends heavily on environmental variables and resource availability. In this work, we develop a four-compartment mathematical model to analyze the dynamics of D. citri in the presence of T. radiata, a known parasitoid. Our model incorporates the cyclical and periodic behavior of citrus flushing (new shoots), providing a qualitative representation of resource-limited dynamics broadly consistent with field observations. Through comparative simulations of three scenarios, without parasitoid, a single initial introduction, and periodic augmentative releases, we characterize and compare the impact of T. radiata as a biological control agent. Our results show that periodic releases maintain pest suppression, whereas a single introduction produces a substantial but incomplete reduction in pest pressure that persists without fully dissipating over the simulated horizon. A sensitivity analysis over the release period and magnitude, together with an invasion-exponent stability criterion, delineates the region of the release-schedule parameter space predicted to achieve eradication rather than mere suppression. Additional checks confirm that this suppression is robust to imperfect release synchrony and quantify the conditions under which the model’s boundedness and mass-action assumptions hold. By aligning theoretical modeling with ecological reality, this framework supports the role of T. radiata in pest suppression and provides a baseline for future work on optimal and cost-effective release strategies. We frame this model explicitly as a qualitative first-approximation theoretical tool rather than a field-validated predictive one, given the absence of empirical calibration and independent validation against laboratory or empirical data. Within this scope, the predicted suppression of D. citri density is best read as a proxy for reduced HLB transmission risk, since vector control remains the standard management strategy for the disease in the absence of a direct treatment for the causal bacterium.
In this work, the effects of seawater exposure and specimen geometry on the mechanical performance of 3D-printed Acrylonitrile Butadiene Styrene (ABS) and carbon fiber-reinforced ABS (ABS/CF) were investigated. Enclosed 3D printers were used to avoid shrinkage and warping of ABS and ABS/CF. The standard specimen types in this research work were ASTM D638 type IV, ISO 527-2 type 1BA, and ASTM D3039 full-section specimens. The tensile tests were strain-controlled tests with a strain rate of 0.1 min− 1. Firstly, the effects of the different specimen types on the tensile strength and Young’s modulus of unaged (as-printed) ABS and ABS/CF were analyzed. Secondly, the three types of specimens were immersed in seawater for 1, 2, and 3 weeks to evaluate moisture absorption and the degradation of the mechanical properties. The results indicated that the test specimen type had a statistically significant effect on the mechanical properties of ABS and ABS/CF, with the ISO 527 specimen exhibiting the lowest tensile strength and Young’s modulus. Moreover, all ABS and ABS/CF specimens showed moisture uptake of less than 1
This study examines, through a feminist empowerment lens, the trajectories that lead Peruvian adolescent mothers into institutional care following pregnancies resulting from sexual violence, and their lived experiences within these settings. Using a qualitative case study design, the research was conducted in a state-accredited protection institution in Lima. Nine adolescent mothers aged 13 to 17 participated in structured observations and group interviews conducted together with in-depth interviews with one adolescent and two institutional authorities. The findings identified three key moments across a continuum of violence and care: sexual violence within the family, disclosure and engagement with legal and health systems, and life inside the institution. Across these phases, participants encountered multiple forms of revictimization, including within institutions meant to provide care. At the same time, the study documents expressions of resistance and agency, including disclosure, peer solidarity, and collective care. These practices illustrate forms of "power from within" and "power with" that emerge under conditions of profound constraint. Rather than positioning institutionalization as protective by default, the analysis shows how care is often delivered through paternalistic and controlling logics that limit autonomy. The study contributes to feminist psychology by conceptualizing empowerment as relational, situated, and negotiated within institutional contexts.
We extend the Standard Model (SM) by introducing a U(1)' gauge boson and a real pseudo-scalar field, both odd under a & Zopf;2 symmetry. The resulting low-energy spectrum consists of a stable vector as the dark matter candidate, and a pseudo-scalar mediator, which interacts with the SM via a Higgs portal coupling and a dimension-five portal connecting it to both the dark and visible photons. We explore the freeze-in of both particles at low reheating temperature, finding a rich yield evolution dynamics in the early Universe. This setup brings a consistent dark matter scenario in which the dark photon relic abundance is generated through freeze-in at low reheating temperatures. In addition to its cosmological viability, the model can be tested at the LHC: Higgs bosons can decay into dark photons and displaced visible photons via the long-lived mediator. These signatures allow us to constrain the Higgs portal coupling using recent searches for non-pointing photons and limits on invisible or undetected Higgs decays. We derive meaningful constraints on the dark matter parameter space, in particular excluding a thermalized mediator in the region compatible with the observed relic abundance.
