A primer on open-source, experimental social media simulation software: Opportunities for misinformation research and beyond

Social media simulation software (SMSS) allows researchers to collect behavioural data on how participants to engage with researcher-specified social media content using natural, interactive social media user interfaces. A notable subset of SMSS allow for experimental observation of how people engage with different types of content or user interfaces. Providing an avenue for collecting causal evidence on how algorithmic recommendation systems and design affordances of social media platforms impact behaviour; particularly online harms like misinformation. This article reviews key similarities and differences between three notable SMSS (The (Mis)information Game, the Mock Social Media Website Tool, and the Truman Platform), provides recommendations for use, and perspectives on the future of SMSS.

Paint marking using CO2 anaesthetization does not affect exploratory and recruitment behaviours in the rock ant, Temnothorax rugatulus

The study of animal behaviour sometimes requires unique identification of individuals, especially in the study of social behaviours involving the interactions of multiple individuals. To this end, researchers have developed many different methods of marking individuals. For small animals like insects, paint marks are often applied to their bodies by anaesthetizing them using low temperature or carbon dioxide. Despite this procedure being ubiquitous when studying social insects, the effect of paint and anaesthetics on their behaviour has not been well investigated, especially their effect on performance during a collective task. In our study, we investigate how paint marks and anaesthetics affect the movement and recruitment behaviours of the ant Temnothorax rugatulus in a house hunting context. We painted two thirds of colony members, half of them using CO2 and the other half using low temperature as methods of anaesthetization, and left the one third unpainted as a control group. We then measured their exploratory behaviour prior to house hunting and their recruitment behaviours during house hunting. We found that neither paint marks nor anaesthetics reduce activity levels of these behaviours. However, low-temperature anaesthetized ants performed a higher number of recruitment behaviours than control ants. Because CO2 anaesthetized ants performed all tasks at the same level as control ants, our data suggest that this is a good technique for paint marking ants, especially T. rugatulus. This is the first study empirically testing negative effects of paint marking on individual and collective outcomes in social insects. Our study represents an important step towards routine validation of individual identification methods used in the study of animal behaviour.

A novel method for simulating ex vivo tooth extractions under varying applied loads

BACKGROUND

Tooth extraction is a common surgical procedure where the invasiveness of the surgery can affect the nature of the dentoalveolar remodelling which follows. However, there is very little biomechanical data relating the loading applied during tooth extraction to the outcomes of the procedure. The purpose of this pilot study is to present a novel ex vivo experimental method for measuring tooth extraction mechanics and to explore preliminary metrics for predicting extraction success.

METHODS

A custom experimental apparatus was developed in-house to extract central incisors from ex vivo swine mandible samples. Twenty-five (n = 25) incisors were extracted at different rates in displacement- and force-control, along with an intermittent ramp-hold scheme for a total of five schemes. Peak forces and extraction success were recorded for each test. Video analysis assisted in determining the instantaneous stiffnesses of the dental complex during continuous extractions, which were compared using the K-means clustering algorithm.

FINDINGS

Tooth extraction forces ranged from 102 N to 309 N, with higher-rate tests tending towards higher peak forces (141 N - 308 N) than the lower-rate tests (102 N-204 N) for displacement- and force-controlled schemes. The K-means algorithm clearly identified load rates among tests, indicating that higher-rate loading increased system stiffness relative to the lower-rate tests.

INTERPRETATION

The developed experimental method demonstrated a desirable degree of control. The preliminary results suggest the influence of load rate on the mechanical response of the dental complex and extraction outcome. Future work will further investigate the biomechanics of tooth extraction and relate them to tissue damage to improve future tooth extraction procedures.

Systematic literature review of cold-formed steel at elevated temperature scenario

Cold-formed steels (CFS) or light gauge steels (LGS) are steel sections created through processes without heat application, such as roll forming or press-braking. In the past few decades, the utilization of CFS as a structural material has expanded due to its advantages over the other materials used in the construction industry, consequently increasing the number of studies conducted by many researchers. CFS studies have focused on many research areas, including designing, and analyzing members and systems, connections, sustainability, residual stresses, and post-fire data. As a result, several authors have also conducted a literature review involving these areas. However, a literature review for more recent studies involving elevated temperature exposure of CFS has not been conducted. This paper seeks to compile and review the recent publications regarding CFS behavior and performance at high temperatures events. Sixty-nine (69) journal articles published from 2017 to 2023 were retrieved from the Scopus database and systematically reviewed through text mining with the aid of VOS Viewer. Prior studies utilizing finite element analysis and experimental methods to investigate the performance at elevated temperature events of varying CFS sections, systems, and steel grades have been summarized. In addition, this paper also briefly discussed the findings of the recent research works involving member connections of CFS. Key points from the literature review have been emphasized such as the outcome of experimental and numerical validation of existing design rules from different codes such as American Iron and Steel Institute (AISI), Eurocodes, and Australian codes which could vary depending on the CFS section and steel grades. Important points of previous studies regarding the CFS walls, insulations, and screwed connections have also been noted in this paper. Based on the review, research gaps in the prior studies involving elevated temperature exposure of CFS have been identified, such as lack of CFS investigation under fatigue and cyclic loading. These were then recommended as future direction and concentration of CFS at elevated temperatures research works.

Unmasking racial avoidance: Experimental evidence on parental school choice and public health policies during the Covid-19 pandemic

BACKGROUND

COVID-19 drastically changed the school choice landscape as families considered schools with varying public health protocols as well as academic and demographic characteristics. Our understanding of families' preferences during the pandemic is limited, however, because it primarily derives from surveys asking parents about a single school characteristic.

OBJECTIVE

We aimed to understand how families' preferences for schools' racial composition and public health policies may interdepend.

METHODS

We conducted an original school choice survey experiment with U.S. White parents in August 2021. Parents indicated their willingness to enroll their student in hypothetical schools with experimentally randomized school quality ratings, racial and socioeconomic demographics, and COVID mitigation strategies (i.e. instructional modalities, mask and vaccination mandates).

RESULTS

We find novel causal evidence that White parents' preferences for schools' racial demographics and public health policies are interdependent. Among otherwise similar schools, parents expressed stronger preferences to avoid Black, Latinx, and Asian schools when there were fewer COVID mitigation policies. Relatedly, parents required more stringent COVID protocols for their children to attend predominantly Black, Latinx, and Asian schools while showing no preferences for COVID policies among predominantly White schools. The interdependence of preferred racial demographics and public health polices was amplified among White parents who held stigmatizing beliefs about Asian populations carrying the COVID virus and pro-White sentiments. Although Democrats expressed stronger preferences for schools with more COVID mitigation strategies than Republicans, for White parents across the political spectrum school racial composition and COVID mitigation preferences interdepended.

CONCLUSIONS

This study suggests families may leverage flexible student assignment policies and schools of choice to enroll in or avoid schools based on both preferred public health policies and racial demographics. Districts should consider how adopting strong public health policies during infectious disease outbreaks may help mitigate hardened racial avoidance and school racial segregation.

Practical Aspects of NMR-Based Metabolomics

While NMR-based metabolomics is only about 20 years old, NMR has been a key part of metabolic and metabolism studies for >40 years. Historically, metabolic researchers used NMR because of its high level of reproducibility, superb instrument stability, facile sample preparation protocols, inherently quantitative character, non-destructive nature, and amenability to automation. In this chapter, we provide a short history of NMR-based metabolomics. We then provide a detailed description of some of the practical aspects of performing NMR-based metabolomics studies including sample preparation, pulse sequence selection, and spectral acquisition and processing. The two different approaches to metabolomics data analysis, targeted vs. untargeted, are briefly outlined. We also describe several software packages to help users process NMR spectra obtained via these two different approaches. We then give several examples of useful or interesting applications of NMR-based metabolomics, ranging from applications to drug toxicology, to identifying inborn errors of metabolism to analyzing the contents of biofluids from dairy cattle. Throughout this chapter, we will highlight the strengths and limitations of NMR-based metabolomics. Additionally, we will conclude with descriptions of recent advances in NMR hardware, methodology, and software and speculate about where NMR-based metabolomics is going in the next 5-10 years.

A novel procedure to investigate social anxiety using videoconferencing software: A proof-of-concept study

Social anxiety disorder (SAD) is very common and can be significantly disabling. New treatments are needed as the remission rate for SAD is the lowest of all the anxiety disorders. Experimental medicine models, in which features resembling a clinical disorder are experimentally induced, are a cost-effective and timely approach to explore potential novel treatments for psychiatric disorders. Following the emergence of SARS-CoV-2, there is a need to develop experimental medicine models that can be carried out remotely. We developed a novel procedure to investigate SAD (the InterneT-based Stress test for Social Anxiety Disorder; ITSSAD) that can be carried out entirely online by a single investigator, potentially reducing costs and maximising internal reliability. The procedure involves an anticipatory period followed by a naturalistic social interaction task. In a sample of 20 non-treatment-seeking volunteers with symptoms of SAD, the ITSSAD induced significant subjective anxiety and reduced positive affect. Further, increased social anxiety symptoms at baseline predicted increased anxiety during the social interaction task. This protocol needs further validation with physiological measures. The ITSSAD is a new tool for researchers to investigate mechanisms underlying social anxiety disorder.

Deliberating Inequality: A Blueprint for Studying the Social Formation of Beliefs about Economic Inequality

In most contemporary societies, people underestimate the extent of economic inequality, resulting in lower support for taxation and redistribution than might be expressed by better informed citizens. We still know little, however, about how understandings of inequality arise, and therefore about where perceptions and misperceptions of it might come from. This methodological article takes one step toward filling this gap by developing a research design-a blueprint-to study how people's understandings of wealth and income inequality develop through social interaction. Our approach combines insights from recent scholarship highlighting the socially situated character of inequality beliefs with those of survey experimental work testing how information about inequality changes people's understandings of it. Specifically, we propose to use deliberative focus groups to approximate the interactional contexts in which individuals process information and form beliefs in social life. Leveraging an experimental methodology, our design then varies the social makeup of deliberative groups, as well as the information about inequality we share with participants, to explore how different types of social environments and information shape people's understandings of economic inequality. This should let us test, in particular, whether the low socioeconomic diversity of people's discussion and interaction networks relates to their tendency to underestimate inequality, and whether beliefs about opportunity explain people's lack of appetite for redistributive policies. In this exploratory article we motivate our methodological apparatus and describe its key features, before reflecting on the findings from a proof-of-concept study conducted in London in the fall of 2019.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11211-022-00389-0.

Allosteric binding on nuclear receptors: Insights on screening of non-competitive endocrine-disrupting chemicals

Endocrine-disrupting chemicals (EDCs) can compete with endogenous hormones and bind to the orthosteric site of nuclear receptors (NRs), affecting normal endocrine system function and causing severe symptoms. Recently, a series of pharmaceuticals and personal care products (PPCPs) have been discovered to bind to the allosteric sites of NRs and induce similar effects. However, it remains unclear how diverse EDCs work in this new way. Therefore, we have systematically summarized the allosteric sites and underlying mechanisms based on existing studies, mainly regarding drugs belonging to the PPCP class. Advanced methods, classified as structural biology, biochemistry and computational simulation, together with their advantages and hurdles for allosteric site recognition and mechanism insight have also been described. Furthermore, we have highlighted two available strategies for virtual screening of numerous EDCs, relying on the structural features of allosteric sites and lead compounds, respectively. We aim to provide reliable theoretical and technical support for a broader view of various allosteric interactions between EDCs and NRs, and to drive high-throughput and accurate screening of potential EDCs with non-competitive effects.

Popularity and Gender Prototypicality: An Experimental Approach

Despite the growing scientific understanding of peer popularity, there are few theories that explicitly address the development of peer popularity in adolescence. The studies reported here present a preliminary test of the theory that popularity is associated with gender prototypicality. Popularity is associated with physical attractiveness, as well as with attributes (e.g., athletic involvement for boys, having stylish clothes for girls) that often reflect gender-based expectations. After being exposed to either a high school popularity priming condition or a neutral control condition, 1st-year college students rated photographs (Study 1, N = 368, 34% male, 66% female; M_age = 19.30, SD = 1.78, range 17-35), vignettes (Study 2, N = 249, 16.4% males, 83.2% females, 0.4% other; M_age = 18.71, SD = 2.31, range 17-40), and social media profiles (Study 3, N = 218, 30.3% male, 69.3% female, 0.5% other; Mage = 19.40, SD = 2.31, range 18-39) depicting gender-typical and gender-atypical adolescents' appearance and interests on a number of popularity-related characteristics. These results indicated that gender prototypicality in both appearance and interests is associated with popularity.

A Wizard-of-Oz experimental approach to study the human factors of automated vehicles: Platform and methods evaluation

OBJECTIVES

Driving simulation is an important platform for studying vehicle automation. There are different approaches to using this platform - with most using scripting or programmatic tools to simulate vehicle automation. A less frequently used approach, the Wizard-of-Oz method, has potential for increased flexibility and efficiency in designing and conducting experiments. This study designed and evaluated an experimental setup to examine the feasibility of this approach as an alternative for conducting automation studies.

METHODS

Twenty-four participants experienced simulated vehicle automation in two platforms, one where the automation was controlled by algorithms, and the other where the automation was simulated by an external operator. Surveys were administered after each drive and the drivers' takeover performance after the automation disengaged was measured.

RESULTS

Results indicate that while the kinematic parameters of the driving differed significantly for the two platforms, there were no significant differences in the perceptions of participants and in their takeover performance between the two platforms.

CONCLUSION

These results provide evidence for the use of alternative approaches for the conduct of human factors studies on vehicle automation, potentially lowering barriers to undertaking such experiments while increasing flexibility in designing more complex studies.

Biomechanics of stomach tissues and structure in patients with obesity

Even though bariatric surgery is one of the most effective treatment option of obesity, post-surgical weight loss is not always ensured, especially in the long term, when many patients experience weight regain. Bariatric procedures are largely based on surgeon's expertise and intra-operative decisions, while an integrated in-silico approach could support surgical activity. The effects of bariatric surgery on gastric distension, which activates the neural circuitry promoting satiety, can be considered one of the main factors in the operation success. This aspect can be investigated trough computational modelling based on the mechanical properties of stomach tissues and structure. Mechanical tests on gastric tissues and structure from people with obesity are carried out, as basis for the development of a computational model. The samples are obtained from stomach residuals explanted during laparoscopic sleeve gastrectomy interventions. Uniaxial tensile and stress relaxation tests are performed in different directions and inflation tests are carried out on the entire stomach residual. Experimental results show anisotropic, non-linear elastic and time-dependent behavior. In addition, the mechanical properties demonstrate to be dependent on the sample location within the stomach. Inflation tests confirm the characteristics of time-dependence and non-linear elasticity of the stomach wall. Experimental activities developed provide a unique set of data about the mechanical behavior of the stomach of patients with obesity, considering both tissues and structure. This data set can be adopted for the development of computational models of the stomach, as support to the rational investigation of biomechanical aspects of bariatric surgery.

A Methodical Quantification of Needle Visibility and Echogenicity in Ultrasound Images

During ultrasound-guided percutaneous interventions, needle localization can be a challenge. To increase needle visibility, enhancements of both the imaging methods and the needle surface properties have been investigated. However, a methodical approach to compare potential solutions is currently unavailable. The work described here involves automated image acquisition, analysis and reporting techniques to collect large amounts of data efficiently, delineate relevant factors and communicate effects. Data processing included filtering, line fitting and image intensity analysis steps. Foreground and background image samples were used to compute a contrast-to-noise ratio or a signal ratio. The approach was evaluated in a comparative study of commercially available and custom-made needles. Varied parameters included needle material, diameter and surface roughness. The shafts with kerfed patterns and the trocar and chiba tips performed best. The approach enabled an intuitive polar depiction of needle visibility in ultrasound images for a large range of insertion angles.

A coupled approach for identification of nonlinear and compressible material models for soft tissue based on different experimental setups - Exemplified and detailed for lung parenchyma

In this paper, a coupled inverse analysis is proposed to identify nonlinear compressible hyperelastic material models described by two sets of experiments. While the overall approach is applicable for different materials, here it will be presented for viable lung parenchyma. Characterizing the material properties of lung parenchyma is essential to describe and predict the mechanical behavior of the respiratory system in health and disease. During breathing and mechanical ventilation, lung parenchyma is mainly subjected to volumetric deformations along with isochoric and asymmetric deformations that occur especially in diseased heterogeneous lungs. Notwithstanding, most studies examine lung tissue in predominantly isochoric tension tests. In this paper, we investigate the volumetric material behavior as well as the isochoric deformations in two sets of experiments: namely, volume-pressure-change experiments (performed with 287 samples of 26 rats) and uniaxial tension tests (performed with 30 samples of 5 rats). Based on these sets of experiments, we propose a coupled inverse analysis, which simultaneously incorporates both measurement sets to optimize the material parameters. Accordingly, we determine a suitable material model using the experimental results of both sets of experiments in one coupled identification process. The identified strain energy function with the corresponding material parameters [Formula: see text] is validated to model both sets of experiments precisely. Hence, this constitutive model describes the complex volumetric and isochoric nonlinear material behavior of lung parenchyma. This derived material model can be used for nonlinear finite element simulations of lung parenchyma and will help to quantify the stresses and strains of lung tissue during spontaneous and artificial breathing; thus, allowing new insights into lung function and biology.

Computational Models for the Mechanical Investigation of Stomach Tissues and Structure

Bariatric surgery is performed on obese people aiming at reducing the capacity of the stomach and/or the absorbing capability of the gastrointestinal tract. A more reliable and effective approach to bariatric surgery may integrate different expertise, in the areas of surgery, physiology and biomechanics, availing of a strong cooperation between clinicians and engineers. This work aimed at developing a computational model of the stomach, as a computational tool for the physio-mechanical investigation of stomach functionality and the planning of bariatric procedures. In this sense, coupled experimental and numerical activities were developed. Experimental investigations on pig and piglet stomachs aimed at providing information about stomach geometrical configuration and structural behavior. The computational model was defined starting from the analysis of data from histo-morphometric investigations and mechanical tests. A fiber-reinforced visco-hyperelastic constitutive model was developed to interpret the mechanical response of stomach tissues; constitutive parameters were identified considering mechanical tests at both tissue and structure levels. Computational analyses were performed to investigate the pressure-volume behavior of the stomach. The developed model satisfactorily interpreted results from experimental activities, suggesting its reliability. Furthermore, the model was exploited to investigate stress and strain fields within gastric tissues, as the stimuli for mechanoreceptors that interact with the central nervous system leading to the feeling of satiety. In this respect, the developed computational model may be employed to evaluate the influence of bariatric intervention on the stimulation of mechanoreceptors, and the following meal induced satiety.

Comparisons of spark-charge bubble dynamics near the elastic and rigid boundaries

The objective of this paper is to apply experimental methods to investigate the dynamics of spark-induced bubbles in the vicinity of the elastic and rigid boundary. In the experiment, the temporal evolution of the bubble is recorded by the high-speed camera at the 25,000 frames per second, as well as corresponding data such as normalized collapse position, the time of bubble collapse, and the velocity of the high-speed liquid jet. Results are presented for a single bubble generated over the elastic and rigid plates, under a wide range of normalized standoff distance from 0.5 to 3.0. The results show that the high-speed jet emitted by non-spherical bubble collapse near the boundary is one of the important factors to cause the destructive erosion pit. With the increase of the standoff distance, the expansion, shrink, jet formation, and rebound of the bubbles vary evidently adjacent to the different boundary conditions. Compared with the rigid boundary cases, the normalized first collapsed position and the time of bubble collapse are much smaller near the elastic boundary. The formation of the high-speed liquid jet in the neighborhood of the elastic/rigid boundary is founded in two different mechanisms. Furthermore, the normalized maximum velocity near the rigid plate is always larger than that near the elastic plate.

Context matters

Eliciting the level of risk aversion of experimental subjects is of crucial concern to experimenters. In the literature there are a variety of methods used for such elicitation; the concern of the experiment reported in this paper is to compare them. The methods we investigate are the following: Holt-Laury price lists; pairwise choices, the Becker-DeGroot-Marschak method; allocation questions. Clearly their relative efficiency in measuring risk aversion depends upon the numbers of questions asked; but the method itself may well influence the estimated risk-aversion. While it is impossible to determine a 'best' method (as the truth is unknown) we can look at the differences between the different methods. We carried out an experiment in four parts, corresponding to the four different methods, with 96 subjects. In analysing the data our methodology involves fitting preference functionals; we use four, Expected Utility and Rank-Dependent Expected Utility, each combined with either a CRRA or a CARA utility function. Our results show that the inferred level of risk aversion is more sensitive to the elicitation method than to the assumed-true preference functional. Experimenters should worry most about context.

Current advances in synchrotron radiation instrumentation for MX experiments

Following pioneering work 40 years ago, synchrotron beamlines dedicated to macromolecular crystallography (MX) have improved in almost every aspect as instrumentation has evolved. Beam sizes and crystal dimensions are now on the single micron scale while data can be collected from proteins with molecular weights over 10 MDa and from crystals with unit cell dimensions over 1000 Å. Furthermore it is possible to collect a complete data set in seconds, and obtain the resulting structure in minutes. The impact of MX synchrotron beamlines and their evolution is reflected in their scientific output, and MX is now the method of choice for a variety of aims from ligand binding to structure determination of membrane proteins, viruses and ribosomes, resulting in a much deeper understanding of the machinery of life. A main driving force of beamline evolution have been advances in almost every aspect of the instrumentation comprising a synchrotron beamline. In this review we aim to provide an overview of the current status of instrumentation at modern MX experiments. The most critical optical components are discussed, as are aspects of endstation design, sample delivery, visualisation and positioning, the sample environment, beam shaping, detectors and data acquisition and processing.

Alcohol Use Predicts Sexual Decision-Making: A Systematic Review and Meta-Analysis of the Experimental Literature

Alcohol is associated with HIV and other sexually transmitted infections through increased sexual risk-taking behavior. Establishing a causal link between alcohol and sexual behavior has been challenging due to methodological limitations (e.g., reliance on cross-sectional designs). Experimental methods can be used to establish causality. The purpose of this meta-analysis was to evaluate the effects of alcohol consumption on unprotected sex intentions. We searched electronic bibliographic databases for records with relevant keywords; 26 manuscripts (k = 30 studies) met inclusion criteria. Results indicate that alcohol consumption is associated with greater intentions to engage in unprotected sex (d +s = 0.24, 0.35). The effect of alcohol on unprotected sex intentions was greater when sexual arousal was heightened. Alcohol consumption is causally linked to theoretical antecedents of sexual risk behavior, consistent with the alcohol myopia model. Addressing alcohol consumption as a determinant of unprotected sex intentions may lead to more effective HIV interventions.

Experimental physical methods and theories--then and now

INTRODUCTION

A first evaluation of fundamental research into the physics and physiology of Ultra high dilutions (UHDs) was conducted by the author in 1994(1). In this paper we revisit methods and theories from back then and follow their paths through their evolution and contribution to new knowledge in UHD research since then.

METHOD

Physical methods and theories discusses in our anthology on UHD in 1994(1) form the basis for tracing ideas and findings along their path of further development and impact on new knowledge in UHD.

RESULTS

Experimental approaches to probe physical changes in homeopathic preparations have become more sophisticated over past two decades, so did the desire to report results to a scientific standard that is on par with those in specialist literature. The same cannot be said about underlying supporting theoretical models and simulations.

CONCLUSION

Grant challenges in science often take a more targeted and more concerted approach to formulate a research question and then look for answers. A concerted effort to focus on one hypothesized physical aspect of a well-defined homeopathic preparation may help aligning experimental methods with theoretical models and, in doing so, help to gain a deeper understanding of the whole body of insights and data produced.

Bench Models for Assessing the Mechanics of Mitral Valve Repair and Percutaneous Surgery

Rapid preclinical evaluations of mitral valve (MV) mechanics are currently best facilitated by bench models of the left ventricle (LV). This review aims to provide a comprehensive assessment of these models to aid interpretation of their resulting data, inform future experimental evaluations, and further the translation of results to procedure and device development. For this review, two types of experimental bench models were evaluated. Rigid LV models were characterized as fluid-mechanical systems capable of testing explanted MVs under static and or pulsatile left heart hemodynamics. Passive LV models were characterized as explanted hearts whose left side is placed in series with a static or pulsatile flow-loop. In both systems, MV function and mechanics can be quantitatively evaluated. Rigid and passive LV models were characterized and evaluated. The materials and methods involved in their construction, function, quantitative capabilities, and disease modeling were described. The advantages and disadvantages of each model are compared to aid the interpretation of their resulting data and inform future experimental evaluations. Repair and percutaneous studies completed in these models were additionally summarized with perspective on future advances discussed. Bench models of the LV provide excellent platforms for quantifying MV repair mechanics and function. While exceptional work has been reported, more research and development is necessary to improve techniques and devices for repair and percutaneous surgery. Continuing efforts in this field will significantly contribute to the further development of procedures and devices, predictions of long-term performance, and patient safety.

The price elasticity of demand for heroin: Matched longitudinal and experimental evidence

This paper reports estimates of the price elasticity of demand for heroin based on a newly constructed dataset. The dataset has two matched components concerning the same sample of regular heroin users: longitudinal information about real-world heroin demand (actual price and actual quantity at daily intervals for each heroin user in the sample) and experimental information about laboratory heroin demand (elicited by presenting the same heroin users with scenarios in a laboratory setting). Two empirical strategies are used to estimate the price elasticity of demand for heroin. The first strategy exploits the idiosyncratic variation in the price experienced by a heroin user over time that occurs in markets for illegal drugs. The second strategy exploits the experimentally induced variation in price experienced by a heroin user across experimental scenarios. Both empirical strategies result in the estimate that the conditional price elasticity of demand for heroin is approximately -0.80.

Networks of ProteinProtein Interactions: From Uncertainty to Molecular Details

Proteins are the bricks and mortar of cells. The work of proteins is structural and functional, as they are the principal element of the organization of the cell architecture, but they also play a relevant role in its metabolism and regulation. To perform all these functions, proteins need to interact with each other and with other bio-molecules, either to form complexes or to recognize precise targets of their action. For instance, a particular transcription factor may activate one gene or another depending on its interactions with other proteins and not only with DNA. Hence, the ability of a protein to interact with other bio-molecules, and the partners they have at each particular time and location can be crucial to characterize the role of a protein. Proteins rarely act alone; they rather constitute a mingled network of physical interactions or other types of relationships (such as metabolic and regulatory) or signaling cascades. In this context, understanding the function of a protein implies to recognize the members of its neighborhood and to grasp how they associate, both at the systemic and atomic level. The network of physical interactions between the proteins of a system, cell or organism, is defined as the interactome. The purpose of this review is to deepen the description of interactomes at different levels of detail: from the molecular structure of complexes to the global topology of the network of interactions. The approaches and techniques applied experimentally and computationally to attain each level are depicted. The limits of each technique and its integration into a model network, the challenges and actual problems of completeness of an interactome, and the reliability of the interactions are reviewed and summarized. Finally, the application of the current knowledge of protein-protein interactions on modern network medicine and protein function annotation is also explored.

Experimental methods in neuroscience: an undergraduate neuroscience laboratory course for teaching ethical issues, laboratory techniques, experimental design, and analysis

We have developed and recently taught a 200 level undergraduate course entitled, 'Experimental Methods in Neuroscience'. This is a required course in an increasingly popular Neuroscience major at Smith College. Students are introduced initially to issues of animal ethics and experimentation, and are familiarized with our Animal Care Facility. Using an open field and rotarod apparatus, and the elevated plus and Barnes mazes, they conduct behavioral testing of two strains of mice, C57/BL/6J and 129S1/SvImJ, known to exhibit distinct behavioral traits. The group then employs histological techniques to prepare brain sections for observing neuroanatomical variation between strains (for example, 129S1/SvImJ mice are occasionally acallosal). In the final laboratory exercise, they assay the acetylcholinesterase activity in fore- and hindbrains from each strain. The experiments enable the students to gain confidence in collecting data, compiling large data sets, handling spreadsheets and graphing, applying appropriate statistics, and writing accurate and concise scientific reports in journal article format. The course concludes with pairs of students conducting self-designed independent projects using the acquired behavioral, histological or neurochemical techniques. Experimental Methods in Neuroscience is proving particularly successful as it is relatively straightforward for students to design interesting experiments, gain experience in neuroscience experimentation without excessive use of animals, gather substantial data sets, and develop skills in scientific report writing and presentation at an early stage in their neuroscience curricula. Furthermore, the course has emerged as a centralizing focus for our neuroscience program and is suitable for transfer to and adaptation by other institutions.