pwc-archive/papers-with-abstracts huggingface dataset:
Small-Signal Dynamics of Lossy Inverter-Based Microgrids for Generalized Droop Controls
Authors: Abdullah Al Maruf, Anamika Dubey, Sandip Roy
Date: 2024-04-04 00:00:00

A network-level small-signal model is developed for lossy microgrids, which considers coupled angle and voltage dynamics of inverter-based microgrids and uses a more general framework of droop controls in the inverter. It is shown that when relative resistances of the lines in the microgrid are reasonably consistent and differences of voltage angles across the lines are small at the operating point, the generalized droop controls can be designed to enforce decoupling between angle dynamics and voltage dynamics. Next, structural results for the asymptotic stability of small-signal angle and voltage dynamics are given for the case when generalized droop control achieves decoupling. Simulated transient responses of a modified IEEE 9-bus system are presented to validate the theoretical findings which show the effectiveness of generalized droop controls in independently shaping the settling times of the angle and voltage responses of the lossy microgrid system.
Ambiguity in the use of SIR models to fit epidemic incidence data
Authors: B Shayak, Sana Jahedi, James A Yorke
Date: 2024-04-05 00:00:00
Tasks: parameter estimation

When fitting a multi-parameter model to a data set, computer algorithms may suggest that a range of parameters provide equally reasonable fits, making the parameter estimation difficult. Here, we prove this fact for an SIR model. We say a set of parameter values is a good fit to outbreak data if the solution has the data's three most significant characteristics: the standard deviation, the mean time, and the total number of cases. In our model, in addition to the "basic reproduction number" $R_0$, three other parameters need to be estimated to fit a solution to outbreak data. We will show that those parameters can be chosen so that each gives a linear transformation of a solution's incidence data. As a result, we show that for every choice of $R_0>1$, there is a good fit for each outbreak. We also illustrate our results by providing the least square best fits of the New York City and London data sets of the Omicron variant of COVID-19. Furthermore, we show how versions of the SIR model with $N$ compartments have far more good fits- - indeed a high dimensional set of good fits -- for each target -- showing that more complicated models may have an even greater problem in overparametrizing outbreak characteristics.
The rules of multiplayer cooperation in networks of communities
Authors: Diogo L. Pires, Mark Broom
Date: 2024-04-04 00:00:00

Community organization permeates both social and biological complex systems. To study its interplay with behavior emergence, we model mobile structured populations with multiplayer interactions. We derive general analytical methods for evolutionary dynamics under high home fidelity when populations self-organize into networks of asymptotically isolated communities. In this limit, community organization dominates over the network structure and emerging behavior is independent of network topology. We obtain the rules of multiplayer cooperation in networks of communities for different types of social dilemmas. The success of cooperation is a result of the benefits shared amongst communal cooperators outperforming the benefits reaped by defectors in mixed communities. Under weak selection, cooperation can evolve and be stable for any size (Q) and number (M) of communities if the reward-to-cost ratio (V/K) of public goods is higher than a critical value. Community organization is a solid mechanism for sustaining the evolution of cooperation under public goods dilemmas, particularly when populations are organized into a higher number of smaller communities. Contrary to public goods dilemmas relating to production, the multiplayer Hawk-Dove (HD) dilemma is a commons dilemma focusing on the fair consumption of preexisting resources. This game holds mixed results but tends to favour cooperation under larger communities, highlighting that the two types of social dilemmas might lead to solid differences in the behaviour adopted under community structure.
Cooperative Evolutionary Pressure and Diminishing Returns Might Explain the Fermi Paradox: On What Super-AIs Are Like
Authors: Daniel Vallstrom
Date: 2024-04-01 00:00:00
Tasks: Fairness

With an evolutionary approach, the basis of morality can be explained as adaptations to problems of cooperation. With 'evolution' taken in a broad sense, AIs that satisfy the conditions for evolution to apply will be subject to the same cooperative evolutionary pressure as biological entities. Here the adaptiveness of increased cooperation as material safety and wealth increase is discussed -- for humans, for other societies, and for AIs. Diminishing beneficial returns from increased access to material resources also suggests the possibility that, on the whole, there will be no incentive to for instance colonize entire galaxies, thus providing a possible explanation of the Fermi paradox, wondering where everybody is. It is further argued that old societies could engender, give way to, super-AIs, since it is likely that super-AIs are feasible, and fitter. Closing is an aside on effective ways for morals and goals to affect life and society, emphasizing environments, cultures, and laws, and exemplified by how to eat. 'Diminishing returns' is defined, as less than roots, the inverse of infeasibility. It is also noted that there can be no exponential colonization or reproduction, for mathematical reasons, as each entity takes up a certain amount of space. Appended are an algorithm for colonizing for example a galaxy quickly, models of the evolution of cooperation and fairness under diminishing returns, and software for simulating signaling development.
Forecasting with Neuro-Dynamic Programming
Authors: Pedro Afonso Fernandes
Date: 2024-04-04 00:00:00

Economic forecasting is concerned with the estimation of some variable like gross domestic product (GDP) in the next period given a set of variables that describes the current situation or state of the economy, including industrial production, retail trade turnover or economic confidence. Neuro-dynamic programming (NDP) provides tools to deal with forecasting and other sequential problems with such high-dimensional states spaces. Whereas conventional forecasting methods penalises the difference (or loss) between predicted and actual outcomes, NDP favours the difference between temporally successive predictions, following an interactive and trial-and-error approach. Past data provides a guidance to train the models, but in a different way from ordinary least squares (OLS) and other supervised learning methods, signalling the adjustment costs between sequential states. We found that it is possible to train a GDP forecasting model with data concerned with other countries that performs better than models trained with past data from the tested country (Portugal). In addition, we found that non-linear architectures to approximate the value function of a sequential problem, namely, neural networks can perform better than a simple linear architecture, lowering the out-of-sample mean absolute forecast error (MAE) by 32% from an OLS model.
Judgment in macroeconomic output growth predictions: Efficiency, accuracy and persistence
Authors: Michael Pedersen
Date: 2024-04-05 00:00:00

The present study applies observations of individual predictions of the first three releases of the US output growth rate to evaluate how the applied judgment affects prediction efficiency and accuracy as well as if judgment is persistent. While the first two issues have been assessed in other studies, there is little evidence on the formation of judgment in macroeconomic projections. Most of the forecasters produce unbiased predictions, but employing the median Bloomberg projection as baseline, it turns out that judgment generally does not improve accuracy. There seems to be persistence in the judgment applied by forecasters in the sense that the sign of the adjustment in the first release prediction carries over to the projections of the two following revisions. One possible explanation is that forecasters use some kind of anchor-and-adjustment heuristic.
Subscription-Based Inventory Planning for E-Grocery Retailing
Authors: David Winkelmann, Charlotte Köhler
Date: 2024-04-05 00:00:00

The growing e-grocery sector faces challenges in becoming profitable due to heightened customer expectations and logistical complexities. This paper addresses the impact of uncertainty in customer demand on inventory planning for online grocery retailers. Given the perishable nature of grocery products and intense market competition, retailers must ensure product availability while minimising overstocking costs. We propose introducing subscription offers as a solution to mitigate these inventory challenges. Unlike existing literature focusing on uniform subscription models that may harm profitability, our approach considers the synergy between implementing product subscriptions and cost savings from improved inventory planning. We present a three-step procedure enabling retailers to understand uncertainty costs, quantify the value of gathering additional planning information, and implement profitability-enhancing subscription offers. This holistic approach ensures the development of sustainable subscription models in the e-grocery domain.
The forgotten pillar of sustainability: development of the S-assessment tool to evaluate Organizational Social Sustainability
Authors: Alessandro Annarelli, Tiziana Catarci, Laura Palagi
Date: 2024-04-05 00:00:00
Tasks: Decision Making

Pursuing sustainable development has become a global imperative, underscored adopting of the 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals (SDG). At the heart of this agenda lies the recognition of social sustainability as a pivotal component, emphasizing the need for inclusive societies where every individual can thrive. Despite its significance, social sustainability remains a "forgotten pillar," often overshadowed by environmental concerns. In response, this paper presents the development and validation of the S-Assessment Tool for Social Sustainability, a comprehensive questionnaire designed to evaluate organizations' performance across critical dimensions such as health and wellness, gender equality, decent work, and economic growth, reducing inequalities, and responsible production and consumption. The questionnaire was constructed on the critical dimensions identified through a systematic and narrative hybrid approach to the analysis of peer-reviewed literature. The framework has been structured around the values of the SDGs. It aims to empower organizations to better understand and address their social impact, fostering positive change and contributing to the collective effort towards a more equitable and sustainable future. Through collaborative partnerships and rigorous methodology, this research underscores the importance of integrating social sustainability into organizational practices and decision-making processes, ultimately advancing the broader agenda of sustainable development.
Effect of State and Local Sexual Orientation Anti-Discrimination Laws on Labor Market Differentials
Authors: Scott Delhommer, Domonkos F. Vamossy
Date: 2024-04-04 00:00:00

This paper presents the first quasi-experimental research examining the effect of both local and state anti-discrimination laws on sexual orientation on the labor supply and wages of lesbian, gay, and bisexual (LGB) workers. To do so, we use the American Community Survey data on household composition to infer sexual orientation and combine this with a unique panel dataset on state and local anti-discrimination laws. Leveraging variation in law implementation across localities over time and between same-sex and different-sex couples, we find that anti-discrimination laws not only significantly narrow gaps in labor force participation and employment for male same-sex couples relative to men in different-sex couples, but also boost their percentile rank in the wage distribution. Our analysis reveals mostly null effects for female same-sex couples; however, in metropolitan areas these laws significantly reduce their employment compared to women in different-sex couples. One explanation for the reduced labor supply is that female same-sex couples begin to have more children in response to the laws. Finally, we present evidence that state anti-discrimination laws significantly and persistently increased support for same-sex marriage. This research shows that anti-discrimination laws can be an effective policy tool for reducing labor market inequalities across sexual orientation and improving sentiment toward LGB Americans.
Productivity and quality-adjusted life years: QALYs, PALYs and beyond
Authors: Kristian S. Hansen, Juan D. Moreno-Ternero, Lars P. Østerdal
Date: 2024-04-05 00:00:00

We develop a unified framework for the measurement and valuation of health and productivity. Within this framework, we characterize evaluation functions allowing for compromises between the classical quality-adjusted life years (QALYs) and its polar productivity-adjusted life years (PALYs). Our framework and characterization results provide a new normative basis for the economic evaluation of health care interventions, as well as occupational health and safety policies, aimed to impact both health and productivity of individuals.
A first passage model of intravitreal drug delivery and residence time, in relation to ocular geometry, individual variability, and injection location
Authors: Patricia Lamirande, Eamonn A. Gaffney, Michael Gertz, Philip K. Maini, Jessica R. Crawshaw, Antonello Caruso
Date: 2024-04-05 00:00:00

Purpose: Standard of care for various retinal diseases involves recurrent intravitreal injections. This motivates mathematical modelling efforts to identify influential factors for drug residence time, aiming to minimise administration frequency. We sought to describe the vitreal diffusion of therapeutics in nonclinical species used during drug development assessments. In human eyes, we investigated the impact of variability in vitreous cavity size and eccentricity, and in injection location, on drug elimination. Methods: Using a first passage time approach, we modelled the transport-controlled distribution of two standard therapeutic protein formats (Fab and IgG) and elimination through anterior and posterior pathways. Detailed anatomical 3D geometries of mouse, rat, rabbit, cynomolgus monkey, and human eyes were constructed using ocular images and biometry datasets. A scaling relationship was derived for comparison with experimental ocular half-lives. Results: Model simulations revealed a dependence of residence time on ocular size and injection location. Delivery to the posterior vitreous resulted in increased vitreal half-life and retinal permeation. Interindividual variability in human eyes had a significant influence on residence time (half-life range of 5-7 days), showing a strong correlation to axial length and vitreal volume. Anterior exit was the predominant route of drug elimination. Contribution of the posterior pathway displayed a small (3%) difference between protein formats, but varied between species (10-30%). Conclusions: The modelling results suggest that experimental variability in ocular half-life is partially attributed to anatomical differences and injection site location. Simulations further suggest a potential role of the posterior pathway permeability in determining species differences in ocular pharmacokinetics.
The effects of HIV self-testing on HIV incidence and awareness of status among men who have sex with men in the United States: Insights from a novel compartmental model
Authors: Alex Viguerie, Chaitra Gopalappa, Cynthia M. Lyles, Paul G. Farnham
Date: 2024-04-05 00:00:00

The OraQuick In-Home HIV self-test represents a fast, inexpensive, and convenient method for users to assess their HIV status. If integrated thoughtfully into existing testing practices, accompanied by efficient pathways to formal diagnosis, self-testing could both enhance HIV awareness and reduce HIV incidence. However, currently available self-tests are less sensitive, particularly for recent infection, than gold-standard laboratory tests. It is important to understand the impact if some portion of standard testing is replaced by self-tests. We introduced a novel compartmental model to evaluate the effects of self-testing among gay, bisexual and other men who have sex with men (MSM) in the United States for the period 2020 to 2030. We varied the model for different screening rates, self-test proportions, and delays to diagnosis for those identified through self-tests to determine the potential impact on HIV incidence and awareness of status. When HIV self-tests are strictly supplemental, self-testing can decrease HIV incidence among MSM in the US by up to 10% and increase awareness of status among MSM from 85% to 91% over a 10-year period, provided linkage to care and formal diagnosis occur promptly following a positive self-test (90 days or less). As self-tests replace a higher percentage laboratory-based testing algorithms, increases in overall testing rates were necessary to ensure reductions in HIV incidence. However, such increases were small (under 10% for prompt engagement in care and moderate levels of replacement). Improvements in self-test sensitivity and/or decreases in the detection period may further reduce any necessary increases in overall testing. Our study suggests that, if properly utilized, self-testing can provide significant long-term reductions to HIV incidence and improve awareness of HIV status.
The Origin of Mutational Epistasis
Authors: Jorge A. Vila
Date: 2024-04-05 00:00:00
Tasks: Protein Folding

The interconnected processes of protein folding, mutations, epistasis, and evolution have all been the subject of extensive analysis throughout the years due to their significance for structural and evolutionary biology. The origin (molecular basis) of epistasis (the non-additive interactions between mutations) is still, nonetheless, unknown. The existence of a new perspective on protein folding (a problem that needs to be conceived as an analytic whole) will enable us to shed light on the origin of mutational epistasis at the simplest level (within proteins) while also uncovering the reasons on why the genetic background in which they occur (a key component of molecular evolution) could foster changes in epistasis effects. Additionally, because mutations are the source of epistasis, more research is needed to determine the impact of posttranslational modifications (which have the potential to increase the diversity of the proteome by several orders of magnitude) on both mutational epistasis and protein evolvability. Finally, a protein evolution thermodynamic-based analysis that does not consider specific mutational steps or epistasis effects will be discussed. Our study explores the complex processes behind the evolution of proteins upon mutations, clearing up some previously unresolved issues and providing direction for further research in this area.
A Comprehensive System for Secondary Structure Analysis of Protein Models
Authors: Vedh Kannan
Date: 2024-02-18 00:00:00
Tasks: Outlier Detection

In protein structure analysis, the accurate characterization of secondary structure elements is crucial for understanding protein function and dynamics. This paper presents a software system designed for the comprehensive analysis of the secondary structure of protein models. Leveraging phi ({\phi}) and psi ({\psi}) torsion angles, the system utilises K-means clustering and outlier detection techniques to identify and classify folding structures within protein models. Through the visualisation of the Ramachandran plot, the software enables the differentiation of various secondary structure motifs, including alpha-helices, beta-sheets, and other structural elements. The incorporation of customisable threshold values facilitates the identification of outliers, providing insights into potential structural anomalies or misalignments within protein models. Overall, this software system offers researchers a powerful tool for comprehensive secondary structure analysis, to aid in enhancing understanding of protein structures created using both traditional methods such as X-Ray Diffraction and contemporary methods such as Artificial Intelligence.
Modulation of metastable ensemble dynamics explains optimal coding at moderate arousal in auditory cortex
Authors: Lia Papadopoulos, Suhyun Jo, Kevin Zumwalt, Michael Wehr, David A. McCormick, Luca Mazzucato
Date: 2024-04-05 00:00:00
Tasks: Decision Making

Performance during perceptual decision-making exhibits an inverted-U relationship with arousal, but the underlying network mechanisms remain unclear. Here, we recorded from auditory cortex (A1) of behaving mice during passive tone presentation, while tracking arousal via pupillometry. We found that tone discriminability in A1 ensembles was optimal at intermediate arousal, revealing a population-level neural correlate of the inverted-U relationship. We explained this arousal-dependent coding using a spiking network model with a clustered architecture. Specifically, we show that optimal stimulus discriminability is achieved near a transition between a multi-attractor phase with metastable cluster dynamics (low arousal) and a single-attractor phase (high arousal). Additional signatures of this transition include arousal-induced reductions of overall neural variability and the extent of stimulus-induced variability quenching, which we observed in the empirical data. Our results elucidate computational principles underlying interactions between pupil-linked arousal, sensory processing, and neural variability, and suggest a role for phase transitions in explaining nonlinear modulations of cortical computations.
Non-local impact of distal airway constrictions on patterns of inhaled particle deposition
Authors: James D. Shemilt, Alex Horsley, Jim M. Wild, Oliver E. Jensen, Alice B. Thompson, Carl A. Whitfield
Date: 2024-04-04 00:00:00

Airway constriction and blockage in obstructive lung diseases cause ventilation heterogeneity and create barriers to effective drug deposition. Established computational particle-deposition models have not accounted for these impacts of disease. We present a new particle-deposition model that calculates ventilation based on the resistance of each airway, such that ventilation responds to airway constriction. The model incorporates distal airway constrictions representative of cystic fibrosis, allowing us to investigate the resulting impact on patterns of deposition. Unlike previous models, our model predicts how constrictions affect deposition in airways throughout the lungs, not just in the constricted airways. Deposition is reduced in airways directly distal and proximal to constrictions. When constrictions are clustered together, central-airways deposition can increase significantly in regions away from constrictions, but distal-airways deposition in those regions remains largely unchanged. We use our model to calculate lung clearance index (LCI), a clinical measure of ventilation heterogeneity, after applying constrictions of varying severities in one lobe. We find an increase in LCI coinciding with significantly reduced deposition in the affected lobe. Our results show how the model provides a framework for development of computational tools that capture the impacts of airway disease, which could significantly affect predictions of regional dosing.