Fundamental aspects of episodic accretion chemistry explored with single-point models

We explore a set of single-point chemical models to study the fundamental chemical aspects of episodic accretion in low-mass embedded protostars. Our goal is twofold: (1) to understand how the repeated heating and cooling of the envelope affects the abundances of CO and related species; and (2) to identify chemical tracers that can be used as a novel probe of the timescales and other physical aspects of episodic accretion. We develop a set of single-point models that serve as a general prescription for how the chemical composition of a protostellar envelope is altered by episodic accretion. The main effect of each accretion burst is to drive CO ice off the grains in part of the envelope. The duration of the subsequent quiescent stage (before the next burst hits) is similar to or shorter than the freeze-out timescale of CO, allowing the chemical effects of a burst to linger long after the burst has ended. We predict that the resulting excess of gas-phase CO can be observed with single-dish or interferometer facilities as evidence of an accretion burst in the past 10^3 - 10^4 yr.Comment: 5 pages, 3 figures, accepted by ApJ Letters (emulateapj format). May 8, 2013: added erratum to correct Eq. 1. This equation was implemented correctly in our code, so all results and conclusions are unaffected. Figure 2 is updated with minor changes to the labels above the panel

Strangeness contributions to nucleon form factors

We review a recent theoretical determination of the strange quark content of the electromagnetic form factors of the nucleon. These are compared with a global analysis of current experimental measurements in parity-violating electron scattering.Comment: 5 pages, 6 figures; Talk presented at the International Workshop "From Parity Violation to Hadronic Structure and more...", Milos, Greece, May 16-20, 200

Applying Polyacrylamide (PAM) to Reduce Seepage Loss of Water Through Unlined Canals

High molecular weight, linear, anionic polyacrylamide (PAM) is under investigation as a means of sealing unlined water delivery canals, thus potentially increasing the amount of water for downstream users. This study uses a two-layer conceptual model to explore the mechanism of reducing water loss from seepage

Support Structures and Their Impacts on Work Outcomes of Online Workers in Developing Countries

Online labor platforms (OLPs) are transforming how firms operate and how people work. While much attention has been paid to understand how OLPs use algorithms to match workers with consumers and how OLPs are different from traditional firms, little is known about how this new form of firm impacts marginalized populations. Likewise, little is known about what factors lead to online workers’ work success. This short paper aims to explore the support structures for online laborers in developing countries. Drawing on the literature, we distill two types of support structure, namely, formal support from the platform firm, and informal support from peers. The current study seeks to develop in-depth understanding of support structures for online workers in developing countries and how support structures impact their work outcomes

Topology-aware Piecewise Linearization of the AC Power Flow through Generative Modeling

Effective power flow modeling critically affects the ability to efficiently solve large-scale grid optimization problems, especially those with topology-related decision variables. In this work, we put forth a generative modeling approach to obtain a piecewise linear (PWL) approximation of AC power flow by training a simple neural network model from actual data samples. By using the ReLU activation, the NN models can produce a PWL mapping from the input voltage magnitudes and angles to the output power flow and injection. Our proposed generative PWL model uniquely accounts for the nonlinear and topology-related couplings of power flow models, and thus it can greatly improve the accuracy and consistency of output power variables. Most importantly, it enables to reformulate the nonlinear power flow and line status-related constraints into mixed-integer linear ones, such that one can efficiently solve grid topology optimization tasks like the AC optimal transmission switching (OTS) problem. Numerical tests using the IEEE 14- and 118-bus test systems have demonstrated the modeling accuracy of the proposed PWL approximation using a generative approach, as well as its ability in enabling competitive OTS solutions at very low computation order

PREDICTION OF RECESSION

The purpose of our research is to examine the predictive power of inverted yield curve for the recession in the near future. The data used in this research are between Jan 1, 1959 to Nov, 2008. There are 8 recessions during this period, including current one. We conducted two sets of tests. The first set consists of spread between 10-year Treasury bond and 3-month Treasury bill and spread between 10-year Treasury bond and 3-month LIBOR; and we find the predictive power of spread between 10-year Treasury bond and 3-month Treasury bill is much stronger than the other one. The second set consists of spread between 10-year SWAP rate and 3-month LIBOR, spread between 10-year Treasury bond and 3-month Treasury bill, as well as the spread between 10-year Treasury bond and 3 month LIBOR. For the second test, we find that although there is a couple of recession involved and data is relatively limited, predictive power of spread between 10-year T-bond and 3 month still stands out and we also find the spread between 3-month LIBOR and 10-year SWAP could be a better indicator in the future by using more data. We conclude that term spread of Treasury rate is still the most powerful tool for forecasting the recession

Emancipation Research in Information Systems: Integrating Agency, Dialogue, Inclusion, and Rationality Research

Emancipation is a key concept in critical theories. Prior work suggests that emancipation is a complex and multi-faceted concept. Many conceptualizations of emancipation exist, and emancipation is defined in different ways. Existing empirical studies mainly focus on one or few components of emancipation. To have an integrated understanding of emancipation, we review the literature on emancipation in information systems (IS), with a view toward developing a typology of components of emancipation in the IS field. The typology of emancipation components consists of four components: freedom to act, freedom to express, freedom to belong and freedom to think. These components relate to the concepts of agency, dialogue, inclusion, and rationality, respectively