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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