Shear induced rigidity in athermal materials: a unified statistical framework

Recent studies of athermal systems such as dry grains and dense, non-Brownian suspensions have shown that shear can lead to solidification through the process of shear jamming in grains and discontinuous shear thickening in suspensions. The similarities observed between these two distinct phenomena suggest that the physical processes leading to shear-induced rigidity in athermal materials are universal. We present a non-equilibrium statistical mechanics model, which exhibits the phenomenology of these shear-driven transitions: shear jamming and discontinuous shear thickening in different regions of the predicted phase diagram. Our analysis identifies the crucial physical processes underlying shear-driven rigidity transitions, and clarifies the distinct roles played by shearing forces and the density of grains.Comment: Comments welcom

Design of conditions for emergence of self-replicators

A self-replicator is usually understood to be an object of definite form that promotes the conversion of materials in its environment into a nearly identical copy of itself. The challenge of engineering novel, micro- or nano-scale self-replicators has attracted keen interest in recent years, both because exponential amplification is an attractive method for generating high yields of specific products, and also because self-reproducing entities have the potential to be optimized or adapted through rounds of iterative selection. Substantial steps forward have been achieved both in the engineering of particular self-replicating molecules, and also in characterizing the physical basis for possible mechanisms of self-replication. At present, however, there is need for a theoretical treatment of what physical conditions are most conducive to the emergence of novel self-replicating structures from a reservoir of building blocks on a desired time-scale. Here we report progress in addressing this need. By analyzing the dynamics of a generic class of heterogeneous particle mixtures whose reaction rates emerge from basic physical interactions, we demonstrate that the spontaneous discovery of self-replication is controlled by relatively generic features of the chemical space, namely: the dispersion in the distribution of reaction timescales and bound-state energies. Based on this analysis, we provide quantitative criteria that may aid experimentalists in designing a system capable of producing self-replicators, and in estimating the likely timescale for exponential growth to start.Comment: Supplementary Information is under the Ancillary Files ---

New Perspectives on Implementing Health Information Technology

The importance of studying challenges in implementing information technology solutions in health care organizations is highlighted by the huge investments in health care information technology (HIT) which has been spurred by recent government mandates. Information technology can help improve health care delivery cost by facilitating the standardization of work processes or routines and reducing variations among them. Set in a premier 950+ bed hospital in the south eastern part of US, this dissertation consists of two studies examining the challenges involved in implementing HIT solutions. In the first study, we seek to gain deep insights into how the process of creating a patient’s chart evolves over time in a health care institution. The second study focuses on the users of Electronic Health Records (EHR) system, investigating the compliance behavior of various providers with respect to patient records in the system. In the first study, through the lens of Activity theory our results show that the charting routine is implicated by the following environmental factors: (1) Tools, (2) Rules, (3) Community, and (4) Roles, and by individual factors: (5) Computer Self-Efficacy and (6) Risk Propensity. In the second study, our results indicate that there is a substantial effect of subculture of the different occupational groups on IT security compliance intent and behavior in a health care institution

THE DYNAMICS OF INFORMATION SECURITY POLICY ADOPTION

We argue that most organizations fail to internalize information security policies (ISPs) and only ceremonially adopt them because the adoption decision is generally driven by external legitimization purposes rather than efficiency gains. Based on the data collected from semi structured interviews of senior executives, our preliminary findings reveal that ISPs are not integrated to the existing organizational routines until there is an external jolt such as a security breach. However, given the sudden nature of these jolts, ISPs do not gain internal legitimacy. We propose that after the implementation and before the internalization of ISPs, organizations need to actively integrate ISPs into their existing routines, with the aim of internal legitimization in the eyes of the organizational members

Patient Generated Health Data: Framework for Decision Making

Patient information is a major part of healthcare decision making. Although currently scattered due to multiple sources and diverse formats, decision making can be improved if the patient information is readily available in a unified manner. Mobile technologies can improve decision making by integrating patient information from multiple sources. This study explores how patient generated health data (PGHD) from multiple sources can lead to improved healthcare decision making. A semi-systematic review is conducted to analyze research articles for transparency, clarity, and complete reporting. We conceptualize the data generated by healthcare professional as primarily from EHR/EMR and the data generated by patient as primarily from mobile apps and wearables. Eight themes led to the development of Convergence Model for Patient Data (CMPD). A framework was developed to illustrate several scenarios, to identify quality and timeliness requirements in mobile healthcare environment, and to provide necessary decision support

Using Secondary Data to Tell a New Story: A Cautionary Tale in Health Information Technology Research

Through the growth of big data and open data, new opportunities have presented themselves for information systems (IS) researchers who want to investigate phenomena they cannot easily study using primary data. As a result, many scholars have “retooled” their skills to leverage the large amount of readily available secondary data for analysis. In this confessional account, we share the story about how the first and second authors faced challenges when using secondary data for a research project in the health information technology domain. Through additional analysis of studies on health information technology that have used secondary data, we identified several themes of potential pitfalls that can occur when collecting, appropriating, and analyzing secondary data for a research project. We share these themes and relevant exemplars to help IS researchers avoid mistakes when using secondary data

Shear-induced organization of forces in dense suspensions: signatures of discontinuous shear thickening

Dense suspensions can exhibit an abrupt change in their viscosity in response to increasing shear rate. The origin of this discontinuous shear thickening (DST) has been ascribed to the transformation of lubricated contacts to frictional, particle-on-particle contacts. Recent research on the flowing and jamming behavior of dense suspensions has explored the intersection of ideas from granular physics and Stokesian fluid dynamics to better understand this transition from lubricated to frictional rheology. DST is reminiscent of classical phase transitions, and a key question is how interactions between the microscopic constituents give rise to a macroscopic transition. In this paper, we extend a formalism that has proven to be successful in understanding shear jamming of dry grains to dense suspensions. Quantitative analysis of the collective evolution of the contact-force network accompanying the DST transition demonstrates clear changes in the distribution of microscopic variables, and leads to the identification of an "order parameter" characterizing DST.Comment: 4 pages. We welcome comments and criticism

Shear-induced rigidity of frictional particles: Analysis of emergent order in stress space

Solids are distinguished from fluids by their ability to resist shear. In traditional solids, the resistance to shear is associated with the emergence of broken translational symmetry as exhibited by a non-uniform density pattern, which results from either minimizing the energy cost or maximizing the entropy or both. In this work, we focus on a class of systems, where this paradigm is challenged. We show that shear-driven jamming in dry granular materials is a collective process controlled solely by the constraints of mechanical equilibrium. We argue that these constraints lead to a broken translational symmetry in a dual space that encodes the statistics of contact forces and the topology of the contact network. The shear-jamming transition is marked by the appearance of this broken symmetry. We extend our earlier work, by comparing and contrasting real space measures of rheology with those obtained from the dual space. We investigate the structure and behavior of the dual space as the system evolves through the rigidity transition in two different shear protocols. We analyze the robustness of the shear-jamming scenario with respect to protocol and packing fraction, and demonstrate that it is possible to define a protocol-independent order parameter in this dual space, which signals the onset of rigidity.Comment: 14 pages, 17 figure