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This paper describes the design and fabrication of electrically controlled paper actuators that operate based on the dimensional changes that occur in paper when the moisture absorbed on the surface of the cellulose fibers changes. These actuators are called “Hygroexpansive Electrothermal Paper Actuators” (HEPAs). The actuators are made from paper, conducting polymer, and adhesive tape. They are lightweight, inexpensive, and can be fabricated using simple printing techniques. The central element of the HEPAs is a porous conducting path (used to provide electrothermal heating) that changes the moisture content of the paper and causes actuation. This conducting path is made by embedding a conducting polymer (PEDOT:PSS) within the paper, and thus making a paper/polymer composite that retains the porosity and hydrophilicity of paper. Different types of HEPAs (straight, precurved, and creased) achieved different types of motions (e.g., bending motion, accordion type motion). A theoretical model for their behavior is proposed. These actuators have been used for the manipulation of liquids and for the fabrication of an optical shutter., Chemistry and Chemical Biology

The use of omniphobic “fluoroalkylated paper” as a substrate for inkjet printing of aqueous inks that are the precursors of electrically conductive patterns is described. By controlling the surface chemistry of the paper, it is possible to print high resolution, conductive patterns that remain conductive after folding and exposure to common solvents., Chemistry and Chemical Biology, Engineering and Applied Sciences, Other Research Unit

The fields of paper microfluidics and printed electronics have developed independently, and are incompatible in many of their aspects (e.g. printed electronic thin films are not designed to tolerate the flows of liquids, and especially of water, nor are water filled-channels designed to conduct electrons). This work demonstrates monolithic integration of microfluidics and electronics on paper, by extending the use of paper microfluidics to the fabrication of electrical conductors by the wicking of aqueous conducting inks inside microfluidic channels. These conductors are unique in that they can act as wires, electrodes, and microfluidic channels at the same time. These techniques, make it possible to print both two- and three-dimensional fluidic, electrofluidic, and electrical components using simple methods, and thus to design new paper devices. This paper demonstrates the fabrication of three classes of devices: i) 3D paper “printed circuit boards”, ii) vertical-flow electroanalytical devices, and iii) foldable, all-organic paper batteries., Chemistry and Chemical Biology

Current methods of monitoring breathing require cumbersome, inconvenient, and often expensive devices; this requirement sets practical limitations on the frequency and duration of measurements. This article describes a paper-based moisture sensor that uses the hygroscopic character of paper (i.e. the ability of paper to adsorb water reversibly from the surrounding environment) to measure patterns and rate of respiration by converting the changes in humidity caused by cycles of inhalation and exhalation to electrical signals. The changing level of humidity that occurs in a cycle causes a corresponding change in the ionic conductivity of the sensor, which can be measured electrically. By combining the paper sensor with conventional electronics, data concerning respiration can be transmitted to a nearby smartphone or tablet computer for post-processing, and subsequently to a cloud server. This means of sensing provides a new, practical method of recording and analyzing patterns of breathing., Chemistry and Chemical Biology

The fabrication and properties of “fluoroalkylated paper” (“\(R^F\) paper”) by vapor-phase silanization of paper with fluoroalkyl trichlorosilanes is reported. \(R^F\) paper is both hydrophobic and oleophobic: it repels water \((θ_{app}^{H2O} > 140^{\circ})\), organic liquids with surface tensions as low as \(28 \space mN \space m^{-1}\), aqueous solutions containing ionic and non-ionic surfactants, and complex liquids such as blood (which contains salts, surfactants, and biological material such as cells, proteins, and lipids). The propensity of the paper to resist wetting by liquids with a wide range of surface tensions correlates with the length and degree of fluorination of the organosilane (with a few exceptions in the case of methyl trichlorosilane-treated paper), and with the roughness of the paper. \(R^F\) paper maintains the high permeability to gases and mechanical flexibility of the untreated paper, and can be folded into functional shapes (e.g., microtiter plates and liquid-filled gas sensors). When impregnated with a perfluorinated oil, \(R^F\) paper forms a “slippery” surface (paper slippery liquid-infused porous surface, or “paper SLIPS“) capable of repelling liquids with surface tensions as low as \(15 \space mN \space m^{-1}\). The foldability of the paper SLIPS allows the fabrication of channels and flow switches to guide the transport of liquid droplets., Chemistry and Chemical Biology, Other Research Unit

A multilayered paper-based platform is used to investigate the interactions between human lung tumor cells and fibroblasts that are isolated from primary patient tumor samples., Chemistry and Chemical Biology

This paper describes several low-cost methods for fabricating flexible electronic circuits on paper. The circuits comprise i) metallic wires (e.g., tin or zinc) that are deposited on the substrate by evaporation, sputtering, or airbrushing, and ii) discrete surface-mountable electronic components that are fastened with conductive adhesive directly to the wires. These electronic circuits—like conventional printed circuit boards—can be produced with electronic components that connect on both sides of the substrate. Unlike printed circuit boards made from fiberglass, ceramics, or polyimides, however, paper can be folded and creased (repeatedly), shaped to form three-dimensional structures, trimmed using scissors, used to wick fluids (e.g., for microfluidic applications) and disposed of by incineration. Paper-based electronic circuits are thin and lightweight; they should be useful for applications in consumer electronics and packaging, for disposable systems for uses in the military and homeland security, for applications in medical sensing or low-cost portable diagnostics, for paper-based microelectromechanical systems, and for applications involving textiles., Chemistry and Chemical Biology, Engineering and Applied Sciences

In vitro models of ischemia have not historically recapitulated the cellular interactions and gradients of molecules that occur in a 3D tissue. This work demonstrates a paper-based 3D culture system that mimics some of the interactions that occur among populations of cells in the heart during ischemia. Multiple layers of paper containing cells, suspended in hydrogels, are stacked to form a layered 3D model of a tissue. Mass transport of oxygen and glucose into this 3D system can be modulated to induce an ischemic environment in the bottom layers of the stack. This ischemic stress induces cardiomyocytes at the bottom of the stack to secrete chemokines which subsequently trigger fibroblasts residing in adjacent layers to migrate toward the ischemic region. This work demonstrates the usefulness of patterned, stacked paper for performing in vitro mechanistic studies of cellular motility and viability within a model of the laminar ventricle tissue of the heart., Chemistry and Chemical Biology, Engineering and Applied Sciences, Other Research Unit

Paper works: Paper-based indirect ELISA (see picture) has been demonstrated through the detection of rabbit IgG and the HIV-1 envelope antigen gp41. This technique combines the sensitivity and specificity of ELISA with the low cost and ease-of-use of paper-based platforms., Chemistry and Chemical Biology

Field observations of major earthquake fault zones show that shear deformation is often confined to principal slipping zones that may be of order 1–100 μm wide, located within a broader gouge layer of order 10–100 mm wide. This paper examines the possibility that the extreme strain localization observed may be due to the coupling of shear heating, thermal pressurization, and diffusion. In the absence of a stabilizing mechanism shear deformation in a continuum analysis will collapse to an infinitesimally thin zone. Two possible stabilizing mechanisms, studied in this paper, are rate-strengthening friction and dilatancy. For rate-strengthening friction alone, a linear stability analysis shows that uniform shear of a gouge layer is unstable for perturbations exceeding a critical wavelength. Using this critical wavelength we predict a width for the localized zone as a function of the gouge properties. Taking representative parameters for fault gouge at typical centroidal depths of crustal seismogenic zones, we predict localized zones of order 5–40 μm wide, roughly consistent with field and experimental observations. For dilatancy alone, linearized strain rate perturbations with a sufficiently large wavelength will undergo transient exponential growth before decaying back to uniform shear. The total perturbation strain accumulated during this transient strain rate localization is shown to be largely controlled by a single dimensionless parameter E, which is a measure of the dilatancy of the gouge material due to an increase in strain rate., Earth and Planetary Sciences, Engineering and Applied Sciences

For many molecular ecologists, the mantra and mission of the field of ecological genomics could be encapsulated by the phrase ‘to find the genes that matter’ (Mitchell-Olds 2001; Rockman 2012). This phrase of course refers to the early hope and current increasing success in the search for genes whose variation underlies phenotypic variation and fitness in natural populations. In the years since the modern incarnation of the field of ecological genomics, many would agree that the low-hanging fruit has, at least in principle, been plucked: we now have several elegant examples of genes whose variation influences key adaptive traits in natural populations, and these examples have revealed important insights into the architecture of adaptive variation (Hoekstra et al. 2006; Shapiro et al. 2009; Chan et al. 2010). But how well will these early examples, often involving single genes of large effect on discrete or near-discrete phenotypes, represent the dynamics of adaptive change for the totality of phenotypes in nature? Will traits exhibiting continuous rather than discrete variation in natural populations have as simple a genetic basis as these early examples suggest (Prasad et al. 2012; Rockman 2012)? Two papers in this issue (Robinson et al. 2013; Santure et al. 2013) not only suggest answers to these questions but also provide useful extensions of statistical approaches for ecological geneticists to study the genetics of continuous variation in nature. Together these papers, by the same research groups studying evolution in a natural population of Great Tits (Parus major), provide a glimpse of what we should expect as the field begins to dissect the genetic basis of what is arguably the most common type of variation in nature, and how genome-wide surveys of variation can be applied to natural populations without pedigrees., Organismic and Evolutionary Biology

This paper examines changes in disaster response and relief efforts and recent web-based geospatial technological developments through an evaluation of the experiences of the Center for Geographic Analysis, Harvard University, of the Sichuan (2008) and Haiti (2010) earthquake responses. This paper outlines how conventional GIS (geographic information systems) disaster responses by governmental agencies and relief response organisations and the means for geospatial data-sharing have been transformed into a more dynamic, more transparent, and decentralised form with a wide participation. It begins by reviewing briefly at historical changes in the employment of geospatial technologies in major devastating disasters, including the Sichuan and Haiti earthquakes (case studies for our geospatial portal project). It goes on to assess changes in the available dataset type and in geospatial disaster responders, as well as the impact of geospatial technological changes on disaster relief effort. Finally, the paper discusses lessons learned from recent responses and offers some thoughts for future development., Other Research Unit

[1] Opportunity has been traversing the Meridiani plains since 25 January 2004 (sol 1), acquiring numerous observations of the atmosphere, soils, and rocks. This paper provides an overview of key discoveries between sols 511 and 2300, complementing earlier papers covering results from the initial phases of the mission. Key new results include (1) atmospheric argon measurements that demonstrate the importance of atmospheric transport to and from the winter carbon dioxide polar ice caps; (2) observations showing that aeolian ripples covering the plains were generated by easterly winds during an epoch with enhanced Hadley cell circulation; (3) the discovery and characterization of cobbles and boulders that include iron and stony-iron meteorites and Martian impact ejecta; (4) measurements of wall rock strata within Erebus and Victoria craters that provide compelling evidence of formation by aeolian sand deposition, with local reworking within ephemeral lakes; (5) determination that the stratigraphy exposed in the walls of Victoria and Endurance craters show an enrichment of chlorine and depletion of magnesium and sulfur with increasing depth. This result implies that regional-scale aqueous alteration took place before formation of these craters. Most recently, Opportunity has been traversing toward the ancient Endeavour crater. Orbital data show that clay minerals are exposed on its rim. Hydrated sulfate minerals are exposed in plains rocks adjacent to the rim, unlike the surfaces of plains outcrops observed thus far by Opportunity. With continued mechanical health, Opportunity will reach terrains on and around Endeavour's rim that will be markedly different from anything examined to date., Earth and Planetary Sciences

In response to Arroyo, I explain my position on the concept of “natural goodness” and how my use of that concept compares to that of Geach and Foot. An Aristotelian or functional notion of goodness provides the material for Kantian endorsement in a theory of value that avoids a metaphysical commitment to intrinsic values. In response to Cummiskey, I review reasons for thinking Kantianism and consequentialism incompatible, especially those objections to aggregation that arise from the notion of the natural good previously described. In response to Moland, I explain why I think Hegelian worries about the supposed emptiness of the Kantian self do not apply to my account. And in response to both Moland and Bird-Pollan, I argue that, contrary to the view of some Hegelians, the intersubjective normativity of reason is not something developed through actual social relations; rather, it is something essential to an individual's relations with himself or herself. I want to begin by thanking Christopher Arroyo, David Cummiskey, Lydia Moland, and Stefan Bird-Pollan for their interesting and provocative comments in this symposium. There's more in their papers than I can possibly respond to in a reasonable space, so I'm just going to pick and choose. “The Origin of the Good and Our Animal Nature” spells out some of my current thinking on the good, so a summary of that paper will put me in a position to begin by addressing some of Arroyo's and Cummiskey's points., Philosophy

This paper studies competition in a network industry with a stylized two layered network structure, and examines: (i) price and connectivity incentives of the upstream networks, and (ii) incentives for vertical integration between an upstream network provider and a downstream firm. The main result of this paper is that vertical integration occurs only if the initial installed-base difference between the upstream networks is sufficiently small, and in that case, industry is configured with two vertically integrated networks, which yields highest incentives to invest in quality of interconnection. When the installed-base difference is sufficiently large, there is no integration in the industry, and neither of the firms have an incentive to invest in quality of interconnection. An industry configuration in which only the large network integrates and excludes (or raises cost of) its downstream rival does not appear as an equilibrium outcome: in the presence of a large asymmetry between the networks, when quality of interconnection is a strategic variable, the large network can exercise a substantial market power without vertical integration. Therefore, a vertically separated industry structure does not necessarily yield procompetitive outcomes.

The euro has arisen as a credible eventual competitor to the dollar as leading international currency, much as the dollar rose to challenge the pound 70 years ago. This paper uses econometrically-estimated determinants of the shares of major currencies in the reserve holdings of the world’s central banks. Significant factors include: size of the home country, rate of return, and liquidity in the relevant home financial center (as measured by the turnover in its foreign exchange market). There is a tipping phenomenon, but changes are felt only with a long lag (we estimate a weight on the preceding year’s currency share around .9). The equation correctly predicts out-of-sample a (small) narrowing in the gap between the dollar and euro over the period 1999-2007. This paper updates calculations regarding possible scenarios for the future. We exclude the scenario where the United Kingdom joins euroland. But we do take into account of the fact that London has nonetheless become the de facto financial center of the euro, more so than Frankfurt. We also assume that the dollar continues in the future to depreciate at the trend rate that it has shown on average over the last 20 years. The conclusion is that the euro may surpass the dollar as leading international reserve currency as early as 2015.

Motivated by the need to meaningfully implement the Institute of Medicine's (IOM's) definition of health care disparity, this paper proposes statistical frameworks that lay out explicitly the needed causal assumptions for defining disparity measures. Our key emphasis is that a scientifically defensible disparity measure must take into account the direction of the causal relationship between allowable covariates that are not considered to be contributors to disparity and non-allowable covariates that are considered to be contributors to disparity, to avoid flawed disparity measures based on implausible populations that are not relevant for clinical or policy decisions. However, these causal relationships are usually unknown and undetectable from observed data. Consequently, we must make strong causal assumptions in order to proceed. Two frameworks are proposed in this paper, one is the conditional disparity framework under the assumption that allowable covariates impact non-allowable covariates but not vice versa. The other is the marginal disparity framework under the assumption that non-allowable covariates impact allowable ones but not vice versa. We establish theoretical conditions under which the two disparity measures are the same and present a theoretical example showing that the difference between the two disparity measures can be arbitrarily large. Using data from the Collaborative Psychiatric Epidemiology Survey, we also provide an example where the conditional disparity is misled by Simpson's paradox, whereas the marginal disparity approach handles it correctly., Statistics

State test score trends are widely interpreted as indicators of educational improvement. To validate these interpretations, state test score trends are often compared to trends on other tests such as the National Assessment of Educational Progress (NAEP). These comparisons raise serious technical and substantive concerns. Technically, the most commonly used trend statistics – for example, the change in the percent of proficient students – are misleading in the context of cross-test comparisons. Substantively, it may not be reasonable to expect that NAEP and state test score trends should be similar. This paper motivates then applies a “scale-invariant” framework for cross-test trend comparisons to compare “high-stakes” state test score trends from 2003 to 2005 to NAEP trends over the same period. Results show that state trends are significantly more positive than NAEP trends. The paper concludes with cautions against the positioning of trend discrepancies in a framework where only one trend is considered “true.”

Excavations at a salt-production site named Zhongba in the Three Gorges region of China document a complex system of intersecting activities that changed gradually over a long period of time. As the salt production became much larger in scale during the Bronze Age, the context of this production shifted from one for which there is no archaeological evidence for attachment between producers and those who control the products to a situation in which the exchange of salt to other regions seems to have been controlled, or at least directed, by an emergent elite whose authority was based in part on divinatory ability and the control of ritual knowledge. This study examines the concept of context in relation to the organization of salt production at this site and argues that multiple lines of evidence must be considered if we are to avoid simplified assumptions concerning the nature of products and the production processes through which they are made., Anthropology

This paper contributes to the study of social change by considering boundary work as a dimension of cultural change. Drawing on the computer-assisted qualitative analysis of 73 formal speeches made by Donald Trump during the 2016 electoral campaign, we argue that his political rhetoric, which led to his presidential victory, addressed the white working classes’ concern with their declining position in the national pecking order. He addressed their concern by raising the moral status of this group, that is, by 1) emphatically describing them as hard working Americans who are victims of globalization; 2) voicing their concerns about ‘people above’ (professionals, the rich, and politicians); 3) drawing strong moral boundaries toward undocumented immigrants, refugees and Muslims; 4) presenting African American and (legal) Hispanic Americans as workers who also deserve jobs; 5) stressing the role of working class men as protectors of women and LGBTQ people. This particular case study of cultural resonance provides a novel, distinctively sociological approach for capturing dynamics of social change., African and African American Studies, History of Science, Sociology

This paper builds a stochastic model of the processes that give rise to observed patterns of representation and bias in congressional and state legislative elections. The analysis demonstrates that partisan swing and incumbency voting, concepts from the congressional elections literature, have determinate effects on representation and bias, concepts from the redistrictihg literature. The model shows precisely how incumbency and increased variability of partisan swing reduce the responsiveness of the electoral system and how partisan swing affects whether the system is biased toward one party or the other. Incumbency, and other causes of unresponsive representation, also reduce the effect of partisan swing on current levels of partisan bias. By relaxing the restrictive portions of the widely applied "uniform partisan swing" assumption, the theoretical analysis leads directly to an empirical model enabling one more reliably to estimate responsiveness and bias from a single year of electoral data. Applying this to data from seven elections in each of six states, the paper demonstrates that redistricting has effects in predicted directions in the short run: partisan gerrymandering biases the system in favor of the party in control and, by freeing up seats held by opposition party incumbents, increases the system's responsiveness. Bipartisan-controlled redistricting appears to reduce bias somewhat and dramatically to reduce responsiveness. Nonpartisan redistricting processes substantially increase responsiveness but do not have as clear an effect on bias. However, after only two elections, prima facie evidence for redistricting effects evaporate in most states. Finally, across every state and type of redistricting process, responsiveness declined significantly over the course of the decade. This is clear evidence that the phenomenon of "vanishing marginals," recognized first in the U.S. Congress literature, also applies to these different types of state legislative assemblies. It also strongly suggests that redistricting could not account for this pattern., Government

To investigate the phenomenon of patient–physician mistrust in China, a qualitative study involving 107 physicians, nurses and health officials in Guangdong Province, southern China, was conducted through semi-structured interviews and focus groups. In this paper we report the key findings of the empirical study and argue for the essential role of medical professionalism in rebuilding patient-physician trust. Health professionals are trapped in a vicious circle of mistrust. Mistrust (particularly physicians’ distrust of patients and their relatives) leads to increased levels of fear and self-protection by doctors which exacerbate difficulties in communication; in turn, this increases physician workloads, adding to a strong sense of injustice and victimization. These factors produce poorer healthcare outcomes and increasingly discontented and angry patients, escalate conflicts and disputes, and result in negative media coverage, all these ultimately contributing to even greater levels of mistrust. The vicious circle indicates not only the crisis of patient-physician relationship but the crisis of medicine as a profession and institution. Underlying the circle is the inherent conflict of interest in the healthcare system by which health professionals and hospitals have become profit-driven. This institutional conflict of interest seriously compromises the fundamental principle of medical professionalism—the primacy of patient welfare—as well as the traditional Chinese ideal of “medicine as the art of humanity”. Patient trust can be restored through rectifying this institutional conflict of interest and promoting medical professionalism via a series of recommended practical measures.

Trust is indispensable not only for interpersonal relationships and social life, but for good quality healthcare. As manifested in the increasing violence and tension in patient-physician relationships, China has been experiencing a widespread and profound crisis of patient–physician trust. And globally, the crisis of trust is an issue that every society, either developing or developed, has to face in one way or another. Yet, in spite of some pioneering works, the subject of patient-physician trust and mistrust – a crucial matter in healthcare especially because there are numerous ethical implications – has largely been marginalized in bioethics as a global discourse. Drawing lessons as well as inspirations from China, this paper demonstrates the necessity of a trust-oriented bioethics and presents some key theoretical, methodological and philosophical elements of such a bioethics. A trust-oriented bioethics moves beyond the current dominant bioethical paradigms through putting the subject of trust and mistrust in the central agenda of the field, learning from the social sciences, and reviving indigenous moral resources. In order for global bioethics to claim its relevance to the things that truly matter in social life and healthcare, trust should be as vital as such central norms like autonomy and justice and can serve as a potent theoretical framework.

Laws can be written along a spectrum of specificity, ranging from vague standards to more detailed rules with particular examples. Behavioral and legal scholarship each present conflicting views about the optimal degree of specificity with which laws should be designed. From a behavioral standpoint, specificity is important to help people understand their goals and use their cognitive resources in a focused manner. At the same time, ambiguity in the law can even encourage good people to engage in creative interpretations of legal requirements, allowing them to justify unethical behavior, with limited awareness of the meaning of that behavior. By contrast, theories of crowding out, trust, and cooperation suggest that specificity can create resentment and lead to under-compliance and under-performance. These conflicting views about the effects of specificity serve as the background for this experimental project. This paper studies the effects of specificity on behavior in response to a directive that shares important features with the law. First, we examine the effect of specificity on compliance (following a directive) versus performance (beyond a minimum threshold). Second, we compare the controlling, limiting effects of specificity with its instructive, informative effects by comparing the interaction between specificity and monitoring with the interaction between specificity and good faith. We hypothesized that the combination of specificity and monitoring enhances the effect of specificity on compliance but harms performance and trust, whereas the combination of specificity and good faith enhances both the informative goal-setting aspects of specificity and people’s sense of commitment. The study employs an experimental design in which subjects edit a document after being exposed to detailed (vague) instructions, with (without) a reference to good faith, and with (without) monitoring (through sanctioning). The assignments were designed in such a way that people could engage in various levels of editing (both required and not required, reasonable and more than reasonable), allowing us to measure distinctly both compliance and performance. Our results suggest that when participants require information and guidance, as in the case of editing a document, specificity increases performance even beyond what is required relative to a vague standard condition.

Abating climate change is an enormous international public goods problem with a classical "free rider" structure. But it is also a global "free driver" problem because geoengineering the stratosphere with reflective particles to block incoming solar radiation is so cheap that it could essentially be undertaken unilaterally by one state perceiving itself to be in peril. This exploratory paper develops the main features of a "free driver" externality in a simple model motivated by the asymmetric consequences of type-I and type-II errors. I propose a social-choice decision architecture embodying the solution concept of a supermajority voting rule and derive its basic properties., Economics

We study optimal government debt maturity in a model where investors derive monetary services from holding riskless short-term securities. In a setting where the government is the only issuer of such riskless paper, it trades off the monetary premium associated with short-term debt against the refinancing risk implied by the need to roll over its debt more often. We then extend the model to allow private financial intermediaries to compete with the government in the provision of short-term, money-like claims. We argue that if there are negative externalities associated with private money creation, the government should tilt its issuance more towards short maturities. The idea is that the government may have a comparative advantage relative to the private sector in bearing refinancing risk and, hence, should aim to partially crowd out the private sector's use of short-term debt.

In this paper, we solve a dynamic model of households' mortgage decisions incorporating labor income, house price, inflation, and interest rate risk. Using a zero-profit condition for mortgage lenders, we solve for equilibrium mortgage rates given borrower characteristics and optimal decisions. The model quantifies the effects of adjustable versus fixed mortgage rates, loan-to-value ratios, and mortgage affordability measures on mortgage premia and default. Mortgage selection by heterogeneous borrowers helps explain the higher default rates on adjustable-rate mortgages during the recent U.S. housing downturn, and the variation in mortgage premia with the level of interest rates., Economics

In this paper, we propose an extension of the productivity decomposition method developed by Olley & Pakes (1996). This extension provides an accounting for the contributions of both firm entry and exit to aggregate productivity changes. It breaks down the contribution of surviving firms into a component accounting for changes in the firm-level distribution of productivity and another accounting for market share reallocations among those firms - following the same methodology as the one proposed by Olley & Pakes (1996). We argue that the other decompositions that break-down aggregate productivity changes into these same four components introduce some biases in the measurement of the contributions of entry and exit. We apply our proposed decomposition to the large measured increases of productivity in Slovenian manufacturing during the 1995-2000 period and contrast our results with those of other decompositions. We find that, over a 5-year period, the measurement bias associated with entry and exit is substantial, accounting for up to 10 percentage points of aggregate productivity growth. We also find that market share reallocations among surviving firms played a much more important role in driving aggregate productivity changes., Economics

Despite the growth of research in universities on point-of-care (POC) diagnostics for global health, most devices never leave the laboratory. The processes that move diagnostic technology from the laboratory to the field—the processes intended to evaluate operation and performance under realistic conditions—are more complicated than they might seem. Two case studies illustrate this process: the development of a paper-based device to measure liver function, and the development of a device to identify sickle cell disease based on aqueous multiphase systems (AMPS) and differences in the densities of normal and sickled cells. Details of developing these devices provide strategies for forming partnerships, prototyping devices, designing studies, and evaluating POC diagnostics. Technical and procedural lessons drawn from these experiences may be useful to those designing diagnostic tests for developing countries, and more generally, technologies for use in resource-limited environments., Chemistry and Chemical Biology

Jean Tirole was awarded the 2014 Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel for his analysis of market power and regulation. This paper provides an overview of some of that work, and of his related contributions to game theory., Economics

This paper investigates whether individual venture capitalists have repeatable investment skill and to what extent their skill is impacted by the VC firm where they work. We examine a unique dataset that tracks the performance of individual venture capitalists' investments across time and as they move between firms. We find evidence of skill and exit style differences even among venture partners investing at the same VC firm at the same time. Furthermore, our estimates suggest the partner's human capital is two to five times more important than the VC firm's organizational capital in explaining performance.

This paper makes the case that when wishful thinking ill-founds belief, the belief depends on the desire in ways can be recapitulated at the level of perceptual experience. The relevant kinds of desires include motivations, hopes, preferences, and goals. I distinguish between two modes of dependence of belief on desire in wishful thinking: selective or inquiry-related, and responsive or evidence-related. I offers a theory of basing on which beliefs are badly-based on desires, due to patterns of dependence that can found in the relationship between experiences and desires as well. This conclusion brings us a large part of the way to the conclusion that like beliefs, experiences can be ill-founded by depending on a desire., Philosophy

This paper uses a series of experiments with commercial bank loan officers to test the effect of performance incentives on risk assessment and lending decisions. We first show that while high-powered incentives lead to greater screening effort and more profitable lending, their power is muted by both deferred compensation and the limited liability typically enjoyed by credit officers. Second, we present direct evidence that incentive contracts distort judgment and beliefs, even among trained professionals with many years of experience. Loans evaluated under more permissive incentive schemes are rated significantly less risky than the same loans evaluated under pay-for-performance.

This paper describes the fabrication of 3D soft, inflatable structures from thin, 2D tiles fabricated from elastomeric polymers. The tiles are connected using soft joints that increase the surface area available for gluing them together, and mechanically reinforce the structures to withstand the tensile forces associated with pneumatic actuation. The ability of the elastomeric polymer to withstand large deformations without failure makes it possible to explore and implement new joint designs, for example “double-taper dovetail joints,” that cannot be used with hard materials. This approach simplifies the fabrication of soft structures comprising materials with different physical properties (e.g., stiffness, electrical conductivity, optical transparency), and provides the methods required to “program” the response of these structures to mechanical (e.g., pneumatic pressurization) and other physical (e.g., electrical) stimuli. The flexibility and modularity of this approach is demonstrated in a set of soft structures that expanded or buckled into distinct, predictable shapes when inflated or deflated. These structures combine easily to form extended systems with motions dependent on the configurations of the selected components, and, when fabricated with electrically conductive tiles, electronic circuits with pneumatically active elements. This approach to the fabrication of hollow, 3D structures provides routes to new soft actuators., Chemistry and Chemical Biology

This paper describes adaptive composites that respond to mechanical stimuli by changing their Young's modulus. These composites are fabricated by combining a shorter layer of elastic material (e.g., latex) and a longer layer of stiffer material (e.g., polyethylene and Kevlar), and fixing them together at their ends. Tension along the layered composite increases its length, and as the strain increases, the composite changes the load-bearing layer from the elastic to the stiff material. The result is a step in the Young's modulus of the composite. The characteristics of the step (or steps) can be engineered by changing the constituent materials, the number of layers, and their geometries (e.g., sinusoidal, hierarchical, two-dimensional web-like, rod-coil, embedded, and ring structures). For composites with more than two steps in modulus, the materials within the composites can be layered in a hierarchical structure to fit within a smaller volume, without sacrificing performance. These composites can also be used to make structures with tunable, stepped compressive moduli. An adaptation of these principles can generate an electronic sensor that can monitor the applied compressive strain. Increasing or decreasing the strain closes or opens a circuit and reversibly activates a light-emitting diode., Chemistry and Chemical Biology

Over the last decade the World Management Survey (WMS) has collected firm-level management practices data across multiple sectors and countries. We developed the survey to try to explain the large and persistent TFP differences across firms and countries. This review paper discusses what has been learned empirically and theoretically from the WMS and other recent work on management practices. Our preliminary results suggest that about a quarter of cross-country and within-country TFP gaps can be accounted for by management practices. Management seems to matter both qualitatively and quantitatively. Competition, governance, human capital, and informational frictions help account for the variation in management.

This paper compares rates of charge transport by tunneling across junctions with the structures AgTSX(CH2)2nCH3 //Ga2O3 /EGaIn (n=1–8 and X= [BOND]SCH2[BOND] and [BOND]O2C[BOND]); here AgTS is template-stripped silver, and EGaIn is the eutectic alloy of gallium and indium. Its objective was to compare the tunneling decay coefficient (β, Å−1) and the injection current (J0, A cm−2) of the junctions comprising SAMs of n-alkanethiolates and n-alkanoates. Replacing AgTSSCH2-R with AgTSO2C-R (R=alkyl chains) had no significant influence on J0 (ca. 3×103 A cm−2) or β (0.75–0.79 Å−1)—an indication that such changes (both structural and electronic) in the AgTSXR interface do not influence the rate of charge transport. A comparison of junctions comprising oligo(phenylene)carboxylates and n-alkanoates showed, as expected, that β for aliphatic (0.79 Å−1) and aromatic (0.60 Å−1) SAMs differed significantly., Chemistry and Chemical Biology

In complex, multicomponent systems, polymers often undergo phase transitions between distinct conformations. This paper reports a millimeter-scale granular model of coil-to-globule transitions: one “polymer” chain—a cylinders-on-a-string “pearl necklace”—and many spheres, all shaken on a horizontal surface. It is possible to describe the behavior of this granular system by using formalisms generally used in statistical physics of polymers. Two sets of experiments allowed the observation of first- and second-order coil-to-globule transitions. The model shows that the competition between long- and short-range interactions leads to a first-order transition. Well-designed granular system represents another kind of approach to the study of polymer phase transitions and might inspire future designs of polymer-like mesoscale systems., Chemistry and Chemical Biology

This paper demonstrates the enrichment of reticulocytes by centrifuging whole blood through aqueous multiphase systems (AMPSs)—immiscible phases of solutions of polymers that form step-gradients in density. The interfaces of an AMPS concentrate cells; this concentration facilitates the extraction of blood enriched for reticulocytes. AMPS enrich reticulocytes from blood from both healthy and hemochromatosis donors. Varying the osmolality and density of the phases of AMPS provides different levels of enrichment and yield of reticulocytes. A maximum enrichment of reticulocytemia of 64 ± 3% was obtained from donors with hemochromatosis. When used on peripheral blood from normal donors, AMPS can provide a higher yield of enriched reticulocytes and a higher proportion of reticulocytes expressing CD71 than differential centrifugation followed by centrifugation over Percoll. Blood enriched for reticulocytes by AMPS could be useful for research on malaria. Several species of malaria parasites show a preference to invade young erythrocytes and reticulocytes; this preference complicates in vitro cultivation of these species in human blood. Plasmodium knowlesi malaria parasites invade normal human blood enriched for reticulocytes by AMPSs at a rate 2.2 times greater (P < 0.01) than they invade unenriched blood. Parasite invasion in normal blood enriched by AMPS was 1.8 times greater (P < 0.05) than in blood enriched to a similar reticulocytemia by differential centrifugation followed by centrifugation over Percoll. The enrichment of reticulocytes that are invaded by malaria parasites demonstrates that AMPSs can provide a label-free method to enrich cells for biological research., Chemistry and Chemical Biology

We explore the phenomenon of co-authorship by economists who share a surname. Prior research has included at most two economist co-authors who share a surname. Ours is the first paper to have three economist co-authors who share a surname, as well as the first where such co-authors are unrelated by marriage or blood., Economics

Field and laboratory observations indicate that at seismic slip rates most shearing is confined to a very narrow zone, just a few tens to hundreds of microns wide, and sometimes as small as a few microns. Rice et al. (2014) analyzed the stability of uniform shear in a fluid-saturated gouge material. They considered two distinct mechanisms to limit localization to a finite thickness zone, rate-strengthening friction, and dilatancy. In this paper we use numerical simulations to extend beyond the linearized perturbation context in Rice et al. (2014), and study the behavior after the loss of stability. Neglecting dilatancy we find that straining localizes to a width that is almost independent of the gouge layer width, suggesting that the localized zone width is set by the physical properties of the gouge material. Choosing parameters thought to be representative of a crustal depth of 7 km, this predicts that deformation should be confined to a zone between 4 and 44 μm wide. Next, considering dilatancy alone we again find a localized zone thickness that is independent of gouge layer thickness. For dilatancy alone we predict localized zone thicknesses between 1 and 2 μm wide for a depth of 7 km. Finally, we study the impact of localization on the shear strength and temperature evolution of the gouge material. Strain rate localization focuses frictional heating into a narrower zone, leading to a much faster temperature rise than that predicted when localization is not accounted for. Since the dynamic weakening mechanism considered here is thermally driven, this leads to accelerated dynamic weakening., Earth and Planetary Sciences, Engineering and Applied Sciences

This paper compares rates of charge transport by tunneling across junctions with the structures \(Ag^{TS}X(CH_2)_{2n}CH_3 //Ga_2O_3 /EGaIn \space\) (n=1–8 and \(X= -SCH_2-\) and \(O_2C-\)); here \(Ag^{TS}\) is template-stripped silver, and EGaIn is the eutectic alloy of gallium and indium. Its objective was to compare the tunneling decay coefficient (\(\beta\), Å\(^{−1}\)) and the injection current (\(J_0\), A cm\(^{−2}\)) of the junctions comprising SAMs of n-alkanethiolates and n-alkanoates. Replacing \(Ag^{TS}SCH_2-R\) with \(Ag^{TS}O_2C-R\) (R=alkyl chains) had no significant influence on \(J_0\) (ca. \(3\times10^3 A cm^{−2}\)) or \(\beta\) (0.75–0.79 Å\(^{−1}\))—an indication that such changes (both structural and electronic) in the \(Ag^{TS}XR\) interface do not influence the rate of charge transport. A comparison of junctions comprising oligo(phenylene)carboxylates and n-alkanoates showed, as expected, that \(\beta\) for aliphatic (0.79 Å\(^{−1}\)) and aromatic (0.60 Å\(^{−1}\)) SAMs differed significantly., Chemistry and Chemical Biology, Other Research Unit

Soft robots actuated by pressurization and inflation of a pneumatic network (a “pneu-net”) of small channels in elastomeric materials are appealing for their ability to produce sophisticated motions with simple controls. Although current designs of pneu-nets achieve motion with large amplitudes, they do so relatively slowly (that is, over seconds). This paper describes a new design for pneu-nets that reduces the amount of gas that must be transported for inflation of the pneu-net, and thus increases its speed of actuation. A simple actuator can bend from a linear shape to a quasi-circular shape in 50 milliseconds when pressurized at ΔP = 345 kPa. At high rates of pressurization and inflation, the path along which the actuator bends depends on this rate. When inflated fully, the channels and chambers of this new pneu-net design experience only one-tenth the change in volume of that required for a motion of equal amplitude using the previous design. This small change in volume requires comparably low levels of strain in the material at maximum amplitudes of actuation, and commensurately low rates of fatigue and failure. This actuator can operate over a million cycles without significant degradation of performance. This design for soft robotic actuators combines high rates of actuation with high reliability of the actuator, and opens new areas of application for them., Chemistry and Chemical Biology

This paper characterizes the ability of soft pneumatic actuators and robots to resist mechanical insults that would irreversibly damage or destroy hard robotic systems—systems fabricated in metals and structural polymers, and actuated mechanically—of comparable sizes. The pneumatic networks that actuate these soft machines are formed by bonding two layers of elastomeric or polymeric materials that have different moduli on application of strain by pneumatic inflation; this difference in strain between an extensible top layer and an inextensible, strain-limiting, bottom layer causes the pneumatic network to expand anisotropically. While all the soft machines described here are, to some extent, more resistant to damage by compressive forces, blunt impacts, and severe bending than most corresponding hard systems, the composition of the strain-limiting layers confers on them very different tensile and compressive strengths., Chemistry and Chemical Biology, Other Research Unit

Reaching for yield—the propensity to buy riskier assets in order to achieve higher yields—is believed to be an important factor contributing to the credit cycle. This paper analyses this phenomenon in the corporate bond market. Specifically, we show evidence for reaching for yield among insurance companies, the largest institutional holders of corporate bonds. Insurance companies have capital requirements tied to the credit ratings of their investments. Conditional on ratings, insurance portfolios are systematically biased toward higher yield, higher CDS bonds. This behavior appears to be related to the business cycle, being most pronounced during economic expansions. It is also more pronounced for the insurance firms for which regulatory capital requirements are more binding. The results hold both at issuance and for trading in the secondary market and are robust to a series of bond and issuer controls, including issuer fixed effects as well as liquidity and duration. Comparison of the ex-post performance of bonds acquired by insurance companies does not show outperformance but higher volatility of realized returns.

How do rankings affect demand? This paper investigates the impact of college rankings, and the visibility of those rankings, on students' application decisions. Using natural experiments from U.S. News and World Report College Rankings, we present two main findings. First, we identify a causal impact of rankings on application decisions. When explicit rankings of colleges are published in U.S. News, a one-rank improvement leads to a 1-percentage-point increase in the number of applications to that college. Second, we show that the response to the information represented in rankings depends on the way in which that information is presented. Rankings have no effect on application decisions when colleges are listed alphabetically, even when readers are provided data on college quality and the methodology used to calculate rankings. This finding provides evidence that the salience of information is a central determinant of a firm's demand function, even for purchases as large as college attendance.

The Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS) is a multi-component epidemiological and neurobiological study designed to generate actionable recommendations to reduce U.S. Army suicides and increase knowledge about determinants of suicidality. Three Army STARRS component studies are large-scale surveys: one of new soldiers prior to beginning Basic Combat Training (BCT; n=50,765 completed self-administered questionnaires); another of other soldiers exclusive of those in BCT (n=35,372); and a third of three Brigade Combat Teams about to deploy to Afghanistan who are being followed multiple times after returning from deployment (n= 9,421). Although the response rates in these surveys are quite good (72.0-90.8%), questions can be raised about sample biases in estimating prevalence of mental disorders and suicidality, the main outcomes of the surveys based on evidence that people in the general population with mental disorders are under-represented in community surveys. This paper presents the results of analyses designed to determine whether such bias exists in the Army STARRS surveys and, if so, to develop weights to correct for these biases. Data are also presented on sample inefficiencies introduced by weighting and sample clustering and on analyses of the trade-off between bias and efficiency in weight trimming., Psychology

The Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS) is a multi-component epidemiological and neurobiological study of unprecedented size and complexity designed to generate actionable evidence-based recommendations to reduce U.S. Army suicides and increase basic knowledge about determinants of suicidality by carrying out coordinated component studies. A number of major logistical challenges were faced in implementing these studies. The current report presents an overview of the approaches taken to meet these challenges, with a special focus on the field procedures used to implement the component studies. As detailed in the paper, these challenges were addressed at the onset of the initiative by establishing an Executive Committee, a Data Coordination Center (the Survey Research Center [SRC] at the University of Michigan), and study-specific design and analysis teams that worked with staff on instrumentation and field procedures. SRC staff, in turn, worked with the Office of the Deputy Under Secretary of the Army (ODUSA) and local Army Points of Contact (POCs) to address logistical issues and facilitate data collection. These structures, coupled with careful fieldworker training, supervision, and piloting contributed to the major Army STARRS data collection efforts having higher response rates than previous large-scale studies of comparable military samples., Psychology

This paper provides the first formal model of business model innovation. Our analysis focuses on sponsor-based business model innovations where a firm monetizes its product through sponsors rather than setting prices to its customer base. We analyze strategic interactions between an innovative entrant and an incumbent where the incumbent may imitate the entrant's business model innovation once it is revealed. The results suggest that an entrant needs to strategically choose whether to reveal its innovation by competing through the new business model or conceal it by adopting a traditional business model. We also show that the value of business model innovation may be so substantial that an incumbent may prefer to compete in a duopoly rather than to remain a monopolist.