Series Of Natural Experiments Research Articles

Modeling the Stress–Strain State of a Filled Human Bladder

In this paper, the problems of modeling the human bladder and its stress–strain state under an external static influence are considered. A method for the identification of the anisotropic biomechanical characteristics of the bladder tissue is proposed. An FEM model was created, which takes into account the fact that the bladder is surrounded by fiber, affected by surrounding organs, and partially protected by pelvic bones. The model considers the presence of constant hydrostatic pressure on the walls of the bladder when it is full. It has been shown that the isotropic mechanical characteristics of biological tissue can be used for studying the deformed state of a filled bladder if a filled bladder of 300 mL is considered as the initial non-deformed stage. This was shown by the modeling and verification of the effect of the external static force on the bladder. Numerical experiments were conducted based on the constructed model. To validate the results obtained, a series of natural experiments on the effect of external pressure on the bladder under ultrasound control were conducted. In the future, there are plans to use the constructed model to study rupture deformations of the bladder under the influence of static and dynamic loads.

LABORATORY STUDIES OF MATHEMATICAL MODELS THERMAL OBJECTS

Is devoted to the development and analysis of mathematical models of thermal objects. The extruder adopted as a thermal object is a vivid example of multi-zone pass-through technological units, the value of which is enormous for the domestic economy. In the article, the replacement of a real industrial object with a laboratory sample is carried out to work out the methodology of practical identification when obtaining a mathematical model with its subsequent analysis. A positive result is able to transfer the obtained results to a real technological unit. In the article, the object of research was selected, possible representations of mathematical models of industrial objects were analyzed, methods of practical identification were reviewed, the method of practical identification of thermal objects was selected, a series of natural experiments was prepared in laboratory conditions and numerical results were obtained, numerical parameters of coefficients were determined transmission and transport delay of mathematical models, time constants of mathematical models were found, analysis of mathematical models of a laboratory installation from the angle of optimization was carried out. The obtained results made it possible to correctly approach the identification of the working zone of a multi-zone pass-through technological unit using the example of an extruder, which carries out the technological process of processing agricultural raw materials by separating product fractions. Namely, decide on the type of primary converter (temperature sensor), the location of the sensors on the object, evaluate the cross effects of the heating zones in statics, choose the structure and parameters of PI (proportional, integrating components) and PID (proportional, integrating, differential components) regulators to maintain the temperature specified by the technical task in the working area of the extruder.

Appellate court assignments as a natural experiment: Gender panel effects in sex discrimination cases

AbstractThis paper argues that estimating causal effects on US Appellate Court panels can be advanced by analyzing the data as a series of natural experiments, fully exploiting the as‐if random assignment of judges to cases. As a template, this paper reanalyzes Boyd et al.'s data on sex‐discrimination cases. The question is the impact on the votes by male judges from having a female judge on their panel. Leverage from as‐if random assignment can be exploited only by restricting comparisons of treatments cases (in the example, female co‐panelist) exclusively to control cases (all‐male panels) from the same period and time period from which the treatment cases are drawn. With as‐if random assignment reducing the possibility of a biased estimate, the results confirms a gender panel effect similar in size to the claim by Boyd et al. Restricting comparisons to within the same circuit and time period further advances understanding of the causal mechanism. When male or female judges side with female plaintiffs, the females are more persuasive at swaying the votes of their male co‐panelists' votes.

Humans tend to share food more generously than money and other objects: Preliminary evidence

AbstractFood‐sharing is an especially important component of human cooperation, trust and altruism, and certain characteristics of food as compared to other objects may increase the likelihood of food transfers to other individuals. Consequently, people should exhibit higher generosity when sharing food than when sharing other goods (like money or inedible items). We tested this prediction in a series of natural experiments. In Study 1, we found that people (N = 114) were more likely to buy a bread roll for a confederate dressed up as a poor‐looking person than to give money for a bread roll or money to this person. In Study 2, 239 participants were more likely to donate food than non‐food items such as hygienic products or school accessories to a social welfare center. Finally, in Study 3, 226 subjects could share perishable, edible items (apples), coupons for apples or inedible items (pens) with fellow students, and there were no significant differences in generosity between these conditions. Overall, our results suggest that humans might exhibit a food‐sharing preference in certain conditions, especially when they share objects that belong to them and when they have a choice between sharing food and non‐food items. However, further studies are necessary to confirm this notion, to explore the characteristics of food that make sharing it particularly probable, and to understand potential mechanisms underlying this tendency.

Echoes: What Happens when Football Is Played behind Closed Doors?

We use a series of natural experiments in association football (soccer) to test whether the lack of social pressure from spectators affected behaviour and outcomes. We observe that the normal advantage to the home team from playing in their own stadium was on average eroded when they played behind closed doors, with no supporters. Among the various effects from no fans being present, visiting players were cautioned significantly less often by referees. This suggests that closed doors matches are different because referees favour the home team less in their decision making. We discuss these findings in the light of the COVID-19 pandemic that has led to the remainder of the 2019/20 European football season playing out in empty stadiums.

An experimental investigation on the relationship between perceived assembly complexity and product design complexity

Complexity is one of the main drivers inducing increased assembly cost, operational issues and increased lead time for product realisation, and continues to pose challenges to manual assembly operations. In the literature, assembly complexity is widely viewed from both objective and subjective perspectives. The objective perspective relates complexity directly to the characteristics of a process without accounting the characteristics of performers, whereas, subjective perspective considers complexity as a conjunction between process and performer characteristics. This article aims to investigate the link between perceived assembly complexity and product complexity by providing a prediction model relying on a series of natural experiments. In these experiments, the participants were asked to assemble a series of ball-and-stick models with varying degree of product complexity based on a clear 2D assembly work instruction. Complexity of each model was objectively estimated by considering structural properties associated with handling and insertion of assembly parts and their connectivity pattern. Moreover, perceived complexity is approached based on the subjective interpretations of the participants on the difficulty associated with the assembly operation of each model. The results showed that product complexity and assembly time is super-linearly correlated; an increase in the product complexity is accompanied with an increase in assembly time, rework rate and human errors. Moreover, a sigmoid curve is proposed for the relationship between perceived assembly complexity and product complexity indicating that human workers start to perceive assembly operation of a particular product as complex if the product complexity reaches a critical threshold which can vary among individuals with different skill sets, experience, training levels and assembly preferences.

The Consequences of Data Breach Disclosure Laws and Disclosed Breaches on Corporate Cash Holdings and Performance

Holding the underlying likelihood of experiencing a data breach constant, mandatory data breach disclosure laws increase risks and costs related to data breaches. This paper investigates the effects of data breach disclosure laws, and the subsequent disclosure of data breaches on the cash policies of corporations in the United States. Exploiting a series of natural experiments regarding the staggered state-level data breach disclosure laws, we show that the passage of mandatory disclosure laws leads to an increase in corporate cash holdings, particularly among financially constrained firms. This shows that data security transparency laws influence firm liquidity risk management. Further, we find firms that suffer data breaches adjust their financial policies by holding more cash, decrease their external financing as well as investment activities.

The Effect of a Low-Rate Transaction Tax on a Highly Liquid Market

This paper studies the effect of the U.S. Securities and Exchange Commission´s R31 fees, a low-rate transaction tax, on large-capitalization U.S. stock trading. The SEC altered the fee rate 15 times between 2001 and 2010, creating a series of natural experiments with which to measure the effect of transaction costs on trading volume and volatility. The main finding is a negative relationship between the SEC fee and the price volatility of stocks in the S&P 500 index. As in most previous studies, a negative relationship is also found between the fee rate and trading volume. The SEC levy´s dampening effect on both trading volume and volatility is particularly strong for more heavily traded stocks within the S&P 500, and in the years after 2007, which witnessed the rise of high-frequency trading.

Using Natural Experiments To Analyze the Impact of State Legislation on the Incidence of Abortion

A number of academic studies find that various types of state level pro-life legislation reduce the incidence of abortion. However, in these states, it is possible that changes in values and mores, and not the legislation itself, might be responsible for these abortion declines. Indeed, since the enactment of pro-life legislation is not a random occurrence, the analysis of these laws might be biased by what social scientists call “endogeneity problems.” In this study, I address these endogeneity problems through a series of natural experiments. I compare abortion trends in states that enacted pro-life legislation to abortion trends in states where pro-life laws were passed, but later nullified by a judge. All states passing pro-life laws should have experienced similar changes in values, however, the policy changed only in those states where the law took effect. Overall, the results contribute to the body of academic literature which finds that pro-life legislation reduces state abortion rates.

Nature's experiments and medical research.

The majority of human diseases are due to environmental factors and this largely determines the differences in disease pattern between different parts of the world. The situation in Africa and other developing countries, presents a series of natural experiments which, properly observed and investigated, throw light on many of the major problems of world health such as cardiovascular disease and cancer. The frequency of malnutrition and infectious disease has given a better understanding of the interplay of these two conditions and of their effects on immunological mechanisms. It is concluded that observations on natural experiments can still play an important role in medical research.