pwc-archive/papers-with-abstracts huggingface dataset:
Tournaments, Contestant Heterogeneity and Performance
Authors: Enzo Brox, Daniel Goller
Date: 2024-01-10 00:00:00

Tournaments are frequently used incentive mechanisms to enhance performance. In this paper, we use field data and show that skill disparities among contestants asymmetrically affect the performance of contestants. Skill disparities have detrimental effects on the performance of the lower-ability contestant but positive effects on the performance of the higher-ability contestant. We discuss the potential of different behavioral approaches to explain our findings and discuss the implications of our results for the optimal design of contests. Beyond that, our study reveals two important empirical results: (a) affirmative action-type policies may help to mitigate the adverse effects on lower-ability contestants, and (b) the skill level of potential future contestants in subsequent tournament stages can detrimentally influence the performance of higher-ability contestants but does not affect the lower-ability contestant.
Can unions impose costs on employers in education strikes? Evidence from pension disputes in UK universities
Authors: Nils Braakmann, Barbara Eberth
Date: 2024-01-10 00:00:00

The impact of strikes in educational institutions, specifically universities, on employers remains understudied. This paper investigates the impact of education strikes in UK universities from 2018 to 2022, primarily due to pension disputes. Using data from the Guardian University Guide and the 2014 and 2021 Research Excellence Frameworks and leveraging difference-in-differences and regression discontinuity approaches, our findings suggest significant declines in several student related outcomes, such as student satisfaction, and a more mixed picture for student attainment and research performance. These results highlight the substantial, albeit indirect, cost unions can impose on university employers during strikes.
Is there a size premium for nations?
Authors: Jože P. Damijan, Sandra Damijan, Osiris Jorge Parcero
Date: 2024-01-10 00:00:00

This paper examines whether there is a premium in country size. We study whether there are significant gains from being a small or a large country in terms of certain socioeconomic indicators and how large this premium is. Using panel data for 200 countries over 50 years, we estimate premia for various sizes of nations across a variety of key economic and socioeconomic performance indicators. We find that smaller countries are richer, have larger governments, and are more prudent in terms of fiscal policies than larger ones. On the other hand, smaller countries seem to be subject to higher absolute and per capita costs for the provision of essential public goods, which may lower their socioeconomic performance in terms of health and education. In terms of economic performance, small countries seem to do better than large countries, compensating for smallness by relying on foreign trade and foreign direct investment. The latter comes at the cost of higher vulnerability to external shocks, resulting in higher volatility of growth rates. This paper's findings offer essential guidance to policymakers, international organizations, and business researchers, especially those assessing a country's economic or socioeconomic performance or potential. The study implies that comparisons with medium-sized or large countries may be of little utility in predicting the performance of small countries.
Behind the Eastern-Western European convergence path: the role of geography and trade liberalization
Authors: Adolfo Cristobal Campoamor, Osiris Jorge Parcero
Date: 2024-01-10 00:00:00

This paper proposes a two blocks and three regions economic geography model that can account for the most salient stylized facts experienced by Eastern European transition economies during the period 1990 2005. In contrast to the existing literature, which has favored technological explanations, trade liberalization is the only driving force. The model correctly predicts that in the first half of the period, trade liberalization led to divergence in GDP per capita, both between the West and the East and within the East. Consistent with the data, in the second half of the period, this process was reversed and convergence became the dominant force.
Revealed comparative advantages in scientific and technological disciplines in Uruguay
Authors: Nestor Gandelman, Osiris Jorge Parcero, Matilde Pereira, Flavia Roldan
Date: 2024-01-09 00:00:00
Tasks: Articles, Econometrics

Based on bibliometric information from Scopus for the period 1996-2019, this document characterizes the evolution of Uruguayan scientific production and establishes the areas in which the country has a revealed comparative advantage (RCA). Methodologically, it is proposed that there is a RCA in an area if this area has a greater share in national scientific production than the share of the area in world scientific production. The evidence presented considers two measurements of scientific production (published articles and citations) and three levels of aggregation in the areas (a minor one with 5 large areas, a more detailed one with 27 disciplines and another even more granular with more than 300 disaggregations). Within Health Sciences there is a RCA in Veterinary, Nursing and Medicine. Within Life Sciences there is a RCA in Agricultural and Biological Sciences, Immunology and Microbiology and Biochemistry, Genetics and Molecular Biology. In Physical Sciences there is only a RCA in Environmental Science and in Social Sciences only in Economics, Econometrics and Finance.
Partition-form Cooperative Games in Two-Echelon Supply Chains
Authors: Gurkirat Wadhwa, Tushar Shankar Walunj, Veeraruna Kavitha
Date: 2024-01-10 00:00:00
Tasks: Form

Competition and cooperation are inherent features of any multi-echelon supply chain. The interactions among the agents across the same echelon and that across various echelons influence the percolation of market demand across echelons. The agents may want to collaborate with others in pursuit of attracting higher demand and thereby improving their own revenue. We consider one supplier (at a higher echelon) and two manufacturers (at a lower echelon and facing the customers) and study the collaborations that are `stable'; the main differentiator from the existing studies in supply chain literature is the consideration of the following crucial aspect -- the revenue of any collaborative unit also depends upon the way the opponents collaborate. Such competitive scenarios can be modeled using what is known as partition form games. Our study reveals that the grand coalition is not stable when the product is essential and the customers buy it from any of the manufacturers without a preference. The supplier prefers to collaborate with only one manufacturer, the one stronger in terms of market power; further, such collaboration is stable only when the stronger manufacturer is significantly stronger. Interestingly, no stable collaborative arrangements exist when the two manufacturers are nearly equal in market power.
Comparison of linear and nonlinear methods for decoding selective attention to speech from ear-EEG recordings
Authors: Mike Thornton, Danilo Mandic, Tobias Reichenbach
Date: 2024-01-10 00:00:00
Tasks: EEG

Many people with hearing loss struggle to comprehend speech in crowded auditory scenes, even when they are using hearing aids. It has recently been demonstrated that the focus of a listener's selective attention to speech can be decoded from their electroencephalography (EEG) recordings, raising the prospect of smart EEG-steered hearing aids which restore speech comprehension in adverse acoustic environments (such as the cocktail party). To this end, we here assess the feasibility of using a novel, ultra-wearable ear-EEG device to classify the selective attention of normal-hearing listeners who participated in a two-talker competing-speakers experiment. Eighteen participants took part in a diotic listening task, whereby they were asked to attend to one narrator whilst ignoring the other. Encoding models were estimated from the recorded signals, and these confirmed that the device has the ability to capture auditory responses that are consistent with those reported in high-density EEG studies. Several state-of-the-art auditory attention decoding algorithms were next compared, including stimulus-reconstruction algorithms based on linear regression as well as non-linear deep neural networks, and canonical correlation analysis (CCA). Meaningful markers of selective auditory attention could be extracted from the ear-EEG signals of all 18 participants, even when those markers were derived from relatively short EEG segments of just five seconds in duration. Algorithms which related the EEG signals to the rising edges of the speech temporal envelope (onset envelope) were more successful than those which made use of the temporal envelope itself. The CCA algorithm achieved the highest mean attention decoding accuracy, although differences between the performances of the three algorithms were both small and not statistically significant when EEG segments of short durations were employed.
An event-based implementation of saliency-based visual attention for rapid scene analysis
Authors: Camille Simon Chane, Ernst Niebur, Ryad Benosman, Sio-Hoi Ieng
Date: 2024-01-10 00:00:00

Selective attention is an essential mechanism to filter sensory input and to select only its most important components, allowing the capacity-limited cognitive structures of the brain to process them in detail. The saliency map model, originally developed to understand the process of selective attention in the primate visual system, has also been extensively used in computer vision. Due to the wide-spread use of frame-based video, this is how dynamic input from non-stationary scenes is commonly implemented in saliency maps. However, the temporal structure of this input modality is very different from that of the primate visual system. Retinal input to the brain is massively parallel, local rather than frame-based, asynchronous rather than synchronous, and transmitted in the form of discrete events, neuronal action potentials (spikes). These features are captured by event-based cameras. We show that a computational saliency model can be obtained organically from such vision sensors, at minimal computational cost. We assess the performance of the model by comparing its predictions with the distribution of overt attention (fixations) of human observers, and we make available an event-based dataset that can be used as ground truth for future studies.
Adaptive-avg-pooling based Attention Vision Transformer for Face Anti-spoofing
Authors: Jichen Yang, Fangfan Chen, Rohan Kumar Das, Zhengyu Zhu, Shunsi Zhang
Date: 2024-01-10 00:00:00
Tasks: Avg, Face Anti-Spoofing

Traditional vision transformer consists of two parts: transformer encoder and multi-layer perception (MLP). The former plays the role of feature learning to obtain better representation, while the latter plays the role of classification. Here, the MLP is constituted of two fully connected (FC) layers, average value computing, FC layer and softmax layer. However, due to the use of average value computing module, some useful information may get lost, which we plan to preserve by the use of alternative framework. In this work, we propose a novel vision transformer referred to as adaptive-avg-pooling based attention vision transformer (AAViT) that uses modules of adaptive average pooling and attention to replace the module of average value computing. We explore the proposed AAViT for the studies on face anti-spoofing using Replay-Attack database. The experiments show that the AAViT outperforms vision transformer in face anti-spoofing by producing a reduced equal error rate. In addition, we found that the proposed AAViT can perform much better than some commonly used neural networks such as ResNet and some other known systems on the Replay-Attack corpus.
Pseudorange Rigidity and Solvability of Cooperative GNSS Positioning
Authors: Colin Cros, Pierre-Olivier Amblard, Christophe Prieur, Jean-François da Rocha
Date: 2024-01-10 00:00:00

Global Navigation Satellite Systems (GNSS) are a widely used technology for positioning and navigation. GNSS positioning relies on pseudorange measurements from satellites to receivers. A pseudorange is the apparent distance between two agents deduced from the time-of-flight of a signal sent from one agent to the other. Because of the lack of synchronization between the agents' clocks, it is a biased version of their distance. This paper introduces a new rigidity theory adapted to pseudorange measurements. The peculiarity of pseudoranges is that they are asymmetrical measurements. Therefore, unlike other usual rigidities, the graphs of pseudorange frameworks are directed. In this paper, pseudorange rigidity is proved to be a generic property of the underlying undirected graph of constraints. The main result is a characterization of rigid pseudorange graphs as combinations of rigid distance graphs and connected graphs. This new theory is adapted for GNSS. It provides new insights into the minimum number of satellites needed to locate a receiver, and is applied to the localization of GNSS cooperative networks of receivers. The interests of asymmetrical constraints in the context of formation control are also discussed.
Mapping Information in Feature Extraction Transformation for Chirp Signal
Authors: Shuyi Gu, Zhenghua Luo, Lin Hu, Yilin Zhang, Junxiong Guo
Date: 2024-01-10 00:00:00

Chirp signals have established diverse applications caused by the capable of producing time-dependent linear frequencies. Most feature extraction transformation methods for chirp signals focus on enhancing the performance of transform methods but neglecting the information derived from the transformation process. Consequently, they may fail to fully exploit the information from observations, resulting in decreased performance under conditions of low signal-to-noise ratio and limited observations. In this work, we develop a novel post-processing method called mapping information model to addressing this challenge. The model establishes a link between the observation space and feature space in feature extraction transform, enabling interference suppression and obtain more accurate information by iteratively resampling and assigning weights in both spaces. Analysis of the iteration process reveals a continual increase in weight of signal samples and a gradual stability in weight of noise samples. The demonstration of the noise suppression in the iteration process and feature enhancement supports the effectiveness of the mapping information model. Furthermore, numerical simulations also affirm the high efficiency of the proposed model by showcasing enhanced signal detection and estimation performances without requiring additional observations. This superior model allows amplifying performance within feature extraction transformation for chirp signal processing under low SNR and limited observation conditions, opens up new opportunities for areas such as communication, biomedicine, and remote sensing.
Reply to 'Comments on Graphon Signal Processing' [arXiv:2310.14683]
Authors: Luana Ruiz, Luiz F. O. Chamon, Alejandro Ribeiro
Date: 2024-01-05 00:00:00
Tasks: LEMMA, valid

This technical note addresses an issue [arXiv:2310.14683] with the proof (but not the statement) of [arXiv:2003.05030, Proposition 4]. The statement of the proposition is correct, but the proof as written in [arXiv:2003.05030] is not and due to a typo in the manuscript, a reference to the correct proof is effectively missing. In the sequel, we present [arXiv:2003.05030, Proposition 4] and its proof. The proof follows from results in [2] that we reproduce here for clarity of exposition. Since the statement of the proposition remains correct, no change in the results of [arXiv:2003.05030] are required. In particular, Lemma 3 and Lemma 4 showing spectral convergence of graphs to graphons, Theorem 1 showing convergence of the GFT to the WFT, and Theorems 3 and 4 showing convergence of graph to graphon filters, remain valid.
A Mean Field Game between Informed Traders and a Broker
Authors: Philippe Bergault, Leandro Sánchez-Betancourt
Date: 2024-01-10 00:00:00

We find closed-form solutions to the stochastic game between a broker and a mean-field of informed traders. In the finite player game, the informed traders observe a common signal and a private signal. The broker, on the other hand, observes the trading speed of each of his clients and provides liquidity to the informed traders. Each player in the game optimises wealth adjusted by inventory penalties. In the mean field version of the game, using a G\^ateaux derivative approach, we characterise the solution to the game with a system of forward-backward stochastic differential equations that we solve explicitly. We find that the optimal trading strategy of the broker is linear on his own inventory, on the average inventory among informed traders, and on the common signal or the average trading speed of the informed traders. The Nash equilibrium we find helps informed traders decide how to use private information, and helps brokers decide how much of the order flow they should externalise or internalise when facing a large number of clients.
Markowitz Portfolio Construction at Seventy
Authors: Stephen Boyd, Kasper Johansson, Ronald Kahn, Philipp Schiele, Thomas Schmelzer
Date: 2024-01-10 00:00:00

More than seventy years ago Harry Markowitz formulated portfolio construction as an optimization problem that trades off expected return and risk, defined as the standard deviation of the portfolio returns. Since then the method has been extended to include many practical constraints and objective terms, such as transaction cost or leverage limits. Despite several criticisms of Markowitz's method, for example its sensitivity to poor forecasts of the return statistics, it has become the dominant quantitative method for portfolio construction in practice. In this article we describe an extension of Markowitz's method that addresses many practical effects and gracefully handles the uncertainty inherent in return statistics forecasting. Like Markowitz's original formulation, the extension is also a convex optimization problem, which can be solved with high reliability and speed.
Electrostatics of Salt-Dependent Reentrant Phase Behaviors Highlights Diverse Roles of ATP in Biomolecular Condensates
Authors: Yi-Hsuan Lin, Tae Hun Kim, Suman Das, Tanmoy Pal, Jonas Wessén, Atul Kaushik Rangadurai, Lewis E. Kay, Julie D. Forman-Kay, Hue Sun Chan
Date: 2024-01-10 00:00:00

Liquid-liquid phase separation (LLPS) involving intrinsically disordered protein regions (IDRs) is a major physical mechanism for biological membraneless compartmentalization. The multifaceted electrostatic effects in these biomolecular condensates are exemplified here by experimental and theoretical investigations of the different salt- and ATP-dependent LLPSs of an IDR of messenger RNA-regulating protein Caprin1 and its phosphorylated variant pY-Caprin1, exhibiting, e.g., reentrant behaviors in some instances but not others. Experimental data are rationalized by physical modeling using analytical theory, molecular dynamics, and polymer field-theoretic simulations, indicating that interchain ion bridges enhance LLPS of polyelectrolytes such as Caprin1 and the high valency of ATP-magnesium is a significant factor for its colocalization with the condensed phases, as similar trends are observed for other IDRs. The electrostatic nature of these features complements ATP's involvement in $\pi$-related interactions and as an amphiphilic hydrotrope, underscoring a general role of biomolecular condensates in modulating ion concentrations and its functional ramifications.
Redox Poise during Rhodospirillum rubrum Phototrophic Growth Drives Large-scale Changes in Macromolecular Synthesis Pathways
Authors: William R. Cannon, Ethan King, Katherine A. Huening, Justin A. North
Date: 2024-01-10 00:00:00

During photoheterotrophic growth on organic substrates, purple nonsulfur photosynthetic bacteria like Rhodospirillum rubrum can acquire electrons by multiple means, including oxidation of organic substrates, oxidation of inorganic electron donors (e.g. H$_2$), and by reverse electron flow from the photosynthetic electron transport chain. These electrons are stored in the form of reduced electron-carrying cofactors (e.g. NAD(P)H and ferredoxin). The ratio of oxidized to reduced redox cofactors (e.g. ratio of NAD(P)+:NAD(P)H), or 'redox poise` is difficult to understand or predict, as are the the cellular processes for dissipating these reducing equivalents. Using physics-based models that capture mass action kinetics consistent with the thermodynamics of reactions and pathways, a range of redox conditions for heterophototrophic growth are evaluated, from conditions in which the NADP+/NADPH levels approached thermodynamic equilibrium to conditions in which the NADP+/NADPH ratio is far above the typical physiological values. Modeling results together with experimental measurements of macro molecule levels (DNA, RNA, proteins and fatty acids) indicate that the redox poise of the cell results in large-scale changes in the activity of biosynthetic pathways. Phototrophic growth is less coupled than expected to producing reductant, NAD(P)H, by reverse electron flow from the quinone pool. Instead, it primarily functions for ATP production (photophosphorylation), which drives reduction even when NADPH levels are relatively low compared to NADP+. The model, in agreement with experimental measurements of macromolecule ratios of cells growing on different carbon substrates, indicate that the dynamics of nucleotide versus lipid and protein production is likely a significant mechanism of balancing oxidation and reduction in the cell.
Beyond Michaelis-Menten: Allosteric Rate Control of Chaos
Authors: Tjeerd V. olde Scheper
Date: 2024-01-09 00:00:00

The method developed by Michaelis and Menten was foundational in the development of our understanding of biochemical reaction kinetics. Extended models of metabolism encapsulated by reaction rate theory, stochastic reaction models, and dynamic flux estimation, amongst others, address aspects of this fundamental idea. The limitations of these approaches are well understood, and efforts to overcome those issues so far have been plentiful but with limited success. The known issues can be summarised as the sole dependent relation with substrate concentration, the encapsulation of rate in a single relevant scalar, and the subsequent lack of functional control that results from this assumption. The Rate Control of Chaos (RCC) is a nonlinear control method that has been shown to be effective in controlling the dynamic state of biological oscillators based on the concept of rate limitation of the exponential growth in chaotic systems. Extending RCC with allosteric properties allows robust control of the enzymatic process, and replicates the Michaelis-Menten kinetics. The emergent dynamics is robust to perturbations and noise but susceptible to regulatory adjustments. This control method adapts the control parameters dynamically in the presence of a ligand, and permits introduction of energy relations into the control function. The dynamic nature of the control eliminates the steady-state requirements and allows the modelling of large-scale dynamic behaviour, potentially addressing issues in metabolic disorder and failure of metabolic control.