Which Came First, IT or Productivity? The Virtuous Cycle of Investment and Use in Enterprise Systems

While it is now well established that IT intensive firms are more productive, a critical question remains: Does IT cause productivity or are productive firms simply willing to spend more on IT? We address this question by examining the productivity and performance effects of enterprise systems investments in a uniquely detailed and comprehensive data set of 623 large, public U.S. firms. The data represent all U.S. customers of a large vendor during 1998–2005 and include the vendor’s three main enterprise system suites: Enterprise Resource Planning (ERP), Supply Chain Management (SCM), and Customer Relationship Management (CRM). A particular benefit of our data is that they distinguish the purchase of enterprise systems from their installation and use. Since enterprise systems often take years to implement, firm performance at the time of purchase often differs markedly from performance after the systems “go live.” Specifically, in our ERP data, we find that purchase events are uncorrelated with performance while go-live events are positively correlated. This indicates that the use of ERP systems actually causes performance gains rather than strong performance driving the purchase of ERP. In contrast, for SCM and CRM, we find that performance is correlated with both purchase and golive events. Because SCM and CRM are installed after ERP, these results imply that firms that experience performance gains from ERP go on to purchase SCM and CRM. Our results are robust against several alternative explanations and specifications and suggest that a causal relationship between ERP and performance triggers additional IT adoption in firms that derive value from their initial investment. These results provide an explanation of simultaneity in IT value research that fits with rational economic decision-making: Firms that successfully implement IT, react by investing in more IT. Our work suggests replacing “either-or” views of causality with a positive feedback loop conceptualization in which successful IT investments initiate a “virtuous cycle” of investment and gain. Our work also reveals other important estimation issues that can help researchers identify relationships between IT and business value.NYU, Stern School of Business, IOMS Department, Center for Digital Economy Researc

Implicit Chain Particle Model for Polymer Grafted Nanoparticles

Matrix-free nanocomposites made from polymer grafted nanoparticles (PGN) represent a paradigm shift in materials science because they greatly improve nanoparticle dispersion and offer greater tunability over rheological and mechanical properties in comparison to neat polymers. Utilizing the full potential of PGNs requires a deeper understanding of how polymer graft length, density, and chemistry influence interfacial interactions between particles. There has been great progress in describing these effects with molecular dynamics (MD). However, the limitations of the length and time scales of MD make it prohibitively costly to study systems involving more than a few PGNs. Here, we address some of these challenges by proposing a new modeling paradigm for PGNs using a strain-energy mapping framework involving potential of mean force (PMF) calculations. In this approach, each nanoparticle is coarse-grained into a representative particle with chains treated implicitly, namely, the implicit chain particle model (ICPM). Using a chemistry-specific CG-MD model of PMMA as a testbed, we derive the effective interaction between particles arranged in a closed-packed lattice configuration by matching bulk dilation/compression strain energy densities. The strain-rate dependence of the mechanical work in ICPM is also discussed. Overall, the ICPM model increases the computational speed by approximately 5-6 orders of magnitude compared to the CG-MD models. This novel framework is foundational for particle-based simulations of PGNs and their blends and accelerates the understanding and predictions of emergent properties of PGN materials

Assessing global-scale organic matter reactivity patterns in marine sediments using a lognormal reactive continuum model

Organic matter (OM) degradation in marine sediments is largely controlled by its reactivity and profoundly affects the global carbon cycle. Yet, there is currently no general framework that can constrain OM reactivity on a global scale. In this study, we propose a reactive continuum model based on a lognormal distribution (l-RCM), where OM reactivity is fully described by parameters μ (the mean reactivity of the initial OM bulk mixture) and σ (the variance of OM components around the mean reactivity). We use the l-RCM to inversely determine μ and σ at 123 sites across the global ocean. The results show that the apparent OM reactivity (〈k〉=μ⋅exp⁡(σ2/2)) decreases with decreasing sedimentation rate (ω) and that OM reactivity is more than 3 orders of magnitude higher in shelf than in abyssal regions. Despite the general global trends, higher than expected OM reactivity is observed in certain ocean regions characterized by great water depth or pronounced oxygen minimum zones, such as the eastern–western coastal equatorial Pacific and the Arabian Sea, emphasizing the complex control of the depositional environment (e.g., OM flux, oxygen content in the water column) on benthic OM reactivity. Notably, the l-RCM can also highlight the variability in OM reactivity in these regions. Based on inverse modeling results in our dataset, we establish the significant statistical relationships between 〈k〉 and ω and further map the global OM reactivity distribution. The novelty of this study lies in its unifying view but also in contributing a new framework that allows predicting OM reactivity in data-poor areas based on readily available (or more easily obtainable) information. Such a framework is currently lacking and limits our abilities to constrain OM reactivity in global biogeochemical or Earth system models

The role of anaerobic methane oxidation on the carbonate authigenesis in sediments of the subtropical Beibu Gulf, South China Sea: A reactive–transport modelling approach

The formation and burial of authigenic carbonate in marine sediment significantly affect the sedimentary carbon cycle and its isotopic mass balance in geological history. Anaerobic oxidation of methane (AOM) is the primary driver of authigenic carbonate precipitation within the sulfate-methane transition zone (SMTZ). Quantitative estimations of the role of AOM on the authigenic carbonate precipitation and its carbon isotope under non-steady-state processes (e.g., changes in methane fluxes at the bottom sediment, sedimentation rates or organic fluxes in the surface sediment), however, are still limited. In this study, we use geochemical data from porewater (e.g., the concentration of sulfate, calcium, magnesium, strontium, dissolved inorganic carbon, total alkalinity) and solid sediment (e.g., organic matter content, and carbonate content) in different depositional environments of the subtropical Beibu Gulf, South China Sea, combined with a diagenetic reactive-transport modelling approach, to estimate the mineralogy of authigenic carbonate, the relationship between AOM and authigenic carbonate precipitation, and the impact of AOM rate on carbon isotope of sediment carbonate (δ13CCar). The results show that high-Mg carbonates (high-Mg calcite and dolomite) are the main type of authigenic carbonate (∼80%) formed in the methane-bearing sediments, leading to higher porewater Sr2+/Ca2+ (>0.02) and Mg2+/Ca2+ (>20) within the SMTZ. Our modelling analysis highlights that the non-steady-state induced by increased methane flux from the underlying sediments can significantly accelerate the authigenic carbonates formation within the SMTZ. Using parametric sensitivity analysis, we observed that even a 1% increase in the authigenic carbonate fraction of sediment carbonates results in significant changes in δ13CCar within the SMTZ (from −1‰ to −2‰), mainly due to lighter carbon isotopes produced by more intensive AOM processes. Noteworthily, the terrestrial-to-marine transition was identified by the sediment and porewater geochemical profiles at site SO-8. Although lower authigenic carbonate precipitation occurs in terrestrial sedimentary environments, the proportion of authigenic carbonate in terrestrial environments (11%) is much higher than that in marine environments (1%), resulting in carbon isotopes of carbonate in terrestrial sediments becoming more negative (−5‰)

Mining Face-to-Face Interaction Networks Using Sociometric Badges: Predicting Productivity in an IT Configuration Task

We integrate social network theories and information richness theory to understand which social structures are associated with effective knowledge transfer and higher productivity in face-to-face communication networks. Using novel data collection tools and methodologies, we record precise data on face-to-face interaction networks, tonal conversational variation and physical proximity among a group of IT configuration specialists over one month. By linking these data to detailed performance and productivity metrics we find that 1) network cohesion is associated with higher worker productivity, in contrast to previous findings for email data; 2) cohesion in face-to-face networks is associated with even higher performance during complex tasks, suggesting that social cohesion complements information-rich communication media when tasks are complex; 3) dominant structures for “latent” networks differ from “in-task” networks; and 4) face-to-face networks have more explanatory power than physical-proximity networks. Our research opens new avenues for the measurement of face-to-face interaction and information worker productivity

Which Came First, IT or Productivity? The Virtuous Cycle of Investment and Use in Enterprise Systems

While it is now well established that IT intensive firms are more productive, a critical question remains: Does IT cause productivity or are productive firms simply willing to spend more on IT? We address this question by examining the productivity and performance effects of enterprise systems investments in a uniquely detailed and comprehensive data set of 623 large, public U.S. firms. The data represent all U.S. customers of a large vendor during 1998–2005 and include the vendor’s three main enterprise system suites: Enterprise Resource Planning (ERP), Supply Chain Management (SCM), and Customer Relationship Management (CRM). A particular benefit of our data is that they distinguish the purchase of enterprise systems from their installation and use. Since enterprise systems often take years to implement, firm performance at the time of purchase often differs markedly from performance after the systems “go live.” Specifically, in our ERP data, we find that purchase events are uncorrelated with performance while go-live events are positively correlated. This indicates that the use of ERP systems actually causes performance gains rather than strong performance driving the purchase of ERP. In contrast, for SCM and CRM, we find that performance is correlated with both purchase and golive events. Because SCM and CRM are installed after ERP, these results imply that firms that experience performance gains from ERP go on to purchase SCM and CRM. Our results are robust against several alternative explanations and specifications and suggest that a causal relationship between ERP and performance triggers additional IT adoption in firms that derive value from their initial investment. These results provide an explanation of simultaneity in IT value research that fits with rational economic decision-making: Firms that successfully implement IT, react by investing in more IT. Our work suggests replacing “either-or” views of causality with a positive feedback loop conceptualization in which successful IT investments initiate a “virtuous cycle” of investment and gain. Our work also reveals other important estimation issues that can help researchers identify relationships between IT and business value.NYU, Stern School of Business, IOMS Department, Center for Digital Economy Researc

A low-cost time-hopping impulse radio system for high data rate transmission

We present an efficient, low-cost implementation of time-hopping impulse radio that fulfills the spectral mask mandated by the FCC and is suitable for high-data-rate, short-range communications. Key features are: (i) all-baseband implementation that obviates the need for passband components, (ii) symbol-rate (not chip rate) sampling, A/D conversion, and digital signal processing, (iii) fast acquisition due to novel search algorithms, (iv) spectral shaping that can be adapted to accommodate different spectrum regulations and interference environments. Computer simulations show that this system can provide 110Mbit/s at 7-10m distance, as well as higher data rates at shorter distances under FCC emissions limits. Due to the spreading concept of time-hopping impulse radio, the system can sustain multiple simultaneous users, and can suppress narrowband interference effectively.Comment: To appear in EURASIP Journal on Applied Signal Processing (Special Issue on UWB - State of the Art

XMM-Newton and NuSTAR Observations of the Compact Millisecond Pulsar Binary PSR J1653–0158

We have presented the first joint XMM-Newton and NuSTAR analysis of the millisecond pulsar (MSP) binary PSR J1653−0158. The 75 minute orbital period inferred from optical and gamma-ray observations together with the 1.97 ms pulsation in the gamma-rays indicate that this system is the most compact Black Widow MSP system known to date. The orbital period was not detected in the XMM-Newton and NuSTAR data, probably due to insufficient photon counts obtained in the observations. Fitting the joint X-ray spectrum of PSR J1653−0158 with a power law gives a photon index Γ = 1.71 ± 0.09. The X-ray luminosity of the source in the (0.2–40) keV band is deduced to be 1.18 × 1031 erg s−1, for an adopted distance of 0.84 kpc. We have shown that the broadband X-ray spectrum can be explained by synchrotron radiation from electrons accelerated in the intrabinary shock, and the gamma-rays detected in the Fermi data are curvature radiations from electrons and positrons in the pulsar magnetosphere. Our kinematic analysis of the Tidarren systems PSR J1653–0158 and PSR J1311–3430 indicates that the two Tidarren systems are likely to have originated in the Galactic disk

Comprehensive quantification of height dependence of entrainment mixing between stratiform cloud top and environment

Different entrainment-mixing processes of turbulence are crucial to processes related to clouds; however, only a few qualitative studies have been concentrated on the vertical distributions of entrainment-mixing mechanisms with low vertical resolutions. To quantitatively study vertical profiles of entrainment-mixing mechanisms with a high resolution, the stratiform clouds observed in the Physics of Stratocumulus Top (POST) project are examined. The unique sawtooth flight pattern allows for an examination of the vertical distributions of entrainment-mixing mechanisms with a 5ĝ€¯m vertical resolution. Relative standard deviation of volume mean radius divided by relative standard deviation of liquid water content is introduced to be a new estimation of microphysical homogeneous mixing degree, to overcome difficulties of determining the adiabatic microphysical properties required in existing measures. The vertical profile of this new measure indicates that entrainment-mixing mechanisms become more homogeneous with decreasing altitudes and are consistent with the dynamical measures of Damköhler number and transition scale number. Further analysis shows that the vertical variation of entrainment-mixing mechanisms with decreasing altitudes is due to the increases of turbulent dissipation rate in cloud and relative humidity in droplet-free air and the decrease of size of droplet-free air. The results offer insights into the theoretical understanding and parameterizations of vertical variation of entrainment-mixing mechanisms

Time Protection: the Missing OS Abstraction

Timing channels enable data leakage that threatens the security of computer systems, from cloud platforms to smartphones and browsers executing untrusted third-party code. Preventing unauthorised information flow is a core duty of the operating system, however, present OSes are unable to prevent timing channels. We argue that OSes must provide time protection in addition to the established memory protection. We examine the requirements of time protection, present a design and its implementation in the seL4 microkernel, and evaluate its efficacy as well as performance overhead on Arm and x86 processors