Consuming Information Systems: An Economic Model of User Satisfaction

This paper has two major objectives. The first objective intends to answer the following question which is of significant interest to information system (IS) researchers and practitioners: How does user satisfaction (satisfaction) respond to changes in system use and system attributes? The second and more ambitious objective is to promote the application of economic theories in user behavior research. In contrast to prior research that conceived the development of user satisfaction as an information valuation and integration process, we consider such development to be embedded in the IS consumption process, that is, users gain utility (satisfaction) from consuming (using) the system. This perspective enables us to re-conceptualize user satisfaction as a proxy of utility and apply utility research in economics to study user satisfaction. An economic model of user satisfaction was developed. Two empirical studies were conducted to examine the research model. The findings confirmed the consumptive nature of user satisfaction. Apart from enriching our understanding of user satisfaction, this research demonstrates the usefulness of economic theories in user behavior research

The slow death (or rebirth?) of extended star formation in z∼0.1z \sim 0.1 green valley early-type galaxies

UV observations in the local universe have uncovered a population of early-type galaxies with UV flux consistent with low-level recent or ongoing star formation. Understanding the origin of such star formation remains an open issue. We present resolved UV-optical photometry of a sample of 19 Sloan Digital Sky Survey (SDSS) early-type galaxies at $z \sim 0.1$ drawn from the sample originally selected by Salim & Rich to lie in the bluer part of the green valley in the UV-optical color-magnitude diagram as measured by the $\textit{Galaxy Evolution Explorer (GALEX)}$. Utilizing high-resolution $\textit{Hubble Space Telescope (HST)}$ far-UV imaging provides unique insight into the distribution of UV light in these galaxies, which we call "extended star-forming early-type galaxies" (ESF-ETGs) because of extended UV emission that is indicative of recent star formation. The UV-optical color profiles of all ESF-ETGs show red centers and blue outer parts. Their outer colors require the existence of a significant underlying population of older stars in the UV-bright regions. An analysis of stacked SDSS spectra reveals weak LINER-like emission in their centers. Using a cross-matched SDSS DR7/$GALEX$ GR6 catalog, we search for other green valley galaxies with similar properties to these ESF-ETGs and estimate that $\approx 13$ of dust-corrected green valley galaxies of similar stellar mass and UV-optical color are likely ESF-candidates, i.e., ESF-ETGs are not rare. Our results are consistent with star formation that is gradually declining in existing disks, i.e., the ESF-ETGs are evolving onto the red sequence for the first time, or with rejuvenated star formation due to accreted gas in older disks provided that the gas does not disrupt the structure of the galaxy and the resulting star formation is not too recent and bursty. ESF-ETGs may typify an important subpopulation of galaxies that can linger in the green valley for up to several Gyrs, based on their resemblance to nearby gas-rich green valley galaxies with low-level ongoing star formation

Can Social Capital be Transferred Cross the Boundary of the Real and Virtual Worlds? An Empirical Investigation of Twitter

Micro-blogs like Twitter are playing increasingly important roles in social life. Some key users of Twitter have drawn huge attention from other people. Their opinions have had significant influence on the rest of Twitter users. In other words, these people are highly reputable and have more social capital in the Twitter world. But what factors contribute to the social capital in a part of the virtual world like Twitter is still largely unknown. This paper investigates the source of social capital in the Twitter world. We identify two types of sources that influence a user’s social capital in the Twitter world: (1) inherited capital from outside the Twitter world; and (2) social activities conducted within the Twitter world. The results show that both inherited capital from outside, and activities within, the Twitter world, have positive influence on a user’s social capital in the Twitter world. Our results suggest that social capital can be transferred from the real world to the virtual one. Meanwhile the inherited social capital of a user from outside the Twitter world significantly impacts the level of activities the user undertakes in the Twitter world. For ordinary people, inherited social capital positively associates with the level of their social activities in the Twitter world. But for the most well known Twitter users, who are usually celebrities, this relationship is negative. Implications for research and practice are further discussed

Integral equation method for the electromagnetic wave propagation in stratified anisotropic dielectric-magnetic materials

We investigate the propagation of electromagnetic waves in stratified anisotropic dielectric-magnetic materials using the integral equation method (IEM). Based on the superposition principle, we use Hertz vector formulations of radiated fields to study the interaction of wave with matter. We derive in a new way the dispersion relation, Snell's law and reflection/transmission coefficients by self-consistent analyses. Moreover, we find two new forms of the generalized extinction theorem. Applying the IEM, we investigate the wave propagation through a slab and disclose the underlying physics which are further verified by numerical simulations. The results lead to a unified framework of the IEM for the propagation of wave incident either from a medium or vacuum in stratified dielectric-magnetic materials.Comment: 14pages, 3figure

Hartree-Fock Theory of Skyrmions in Quantum Hall Ferromagnets

We report on a study of the charged-skyrmion or spin-texture excitations which occur in quantum Hall ferromagnets near odd Landau level filling factors. Particle-hole symmetry is used to relate the spin-quantum numbers of charged particle and hole excitations and neutral particle-hole pair excitations. Hartree-Fock theory is used to provide quantitative estimates of the energies of these excitations and their dependence on Zeeman coupling strength, Landau level quantum numbers, and the thicknesses of the two-dimensional electron layers. For the case of $\nu$ near three we suggest the possibility of first order phase transitions with increasing Zeeman coupling strength from a many skyrmion state to one with many maximally spin-polarized quasiparticles.Comment: 26 pages, 10 figure

Three-dimensional Optical-resolution Photoacoustic Microscopy

Optical microscopy, providing valuable insights at the cellular and organelle levels, has been widely recognized as an enabling biomedical technology. As the mainstays of in vivo three-dimensional (3-D) optical microscopy, single-/multi-photon fluorescence microscopy and optical coherence tomography (OCT) have demonstrated their extraordinary sensitivities to fluorescence and optical scattering contrasts, respectively. However, the optical absorption contrast of biological tissues, which encodes essential physiological/pathological information, has not yet been assessable. The emergence of biomedical photoacoustics has led to a new branch of optical microscopy optical-resolution photoacoustic microscopy (OR-PAM), where the optical irradiation is focused to the diffraction limit to achieve cellular1 or even subcellular level lateral resolution. As a valuable complement to existing optical microscopy technologies, OR-PAM brings in at least two novelties. First and most importantly, OR-PAM detects optical absorption contrasts with extraordinary sensitivity (i.e., 100%). Combining OR-PAM with fluorescence microscopy or with optical-scattering-based OCT (or with both) provides comprehensive optical properties of biological tissues. Second, OR-PAM encodes optical absorption into acoustic waves, in contrast to the pure optical processes in fluorescence microscopy and OCT, and provides background-free detection. The acoustic detection in OR-PAM mitigates the impacts of optical scattering on signal degradation and naturally eliminates possible interferences (i.e., crosstalks) between excitation and detection, which is a common problem in fluorescence microscopy due to the overlap between the excitation and fluorescence spectra. Unique for optical absorption imaging, OR-PAM has demonstrated broad biomedical applications since its invention, including, but not limited to, neurology, ophthalmology, vascular biology, and dermatology. In this video, we teach the system configuration and alignment of OR-PAM as well as the experimental procedures for in vivo functional microvascular imaging

Edge reconstruction in the fractional quantum Hall regime

The interplay of electron-electron interaction and confining potential can lead to the reconstruction of fractional quantum Hall edges. We have performed exact diagonalization studies on microscopic models of fractional quantum Hall liquids, in finite size systems with disk geometry, and found numerical evidence of edge reconstruction under rather general conditions. In the present work we have taken into account effects like layer thickness and Landau level mixing, which are found to be of quantitative importance in edge physics. Due to edge reconstruction, additional nonchiral edge modes arise for both incompressible and compressible states. These additional modes couple to electromagnetic fields and thus can be detected in microwave conductivity measurements. They are also expected to affect the exponent of electron Green's function, which has been measured in tunneling experiments. We have studied in this work the electric dipole spectral function that is directly related to the microwave conductivity measurement. Our results are consistent with the enhanced microwave conductivity observed in experiments performed on samples with an array of antidots at low temperatures, and its suppression at higher temperatures. We also discuss the effects of the edge reconstruction on the single electron spectral function at the edge.Comment: 19 pages, 12 figure

Microwave Inter-Connections and Switching by means of Carbon Nano-tubes

In this work, carbon nanotube (CNT) based interconnections and switches will be reviewed, discussing the possibility to use nanotubes as potential building blocks for signal routing in microwave networks. In particular, theoretical design of coplanar waveguide (CPW), micro‐strip single‐pole‐single‐throw (SPST) and single‐pole‐double‐throw (SPDT) devices has been performed to predict the electrical performances of CNT‐based RF switching configurations. Actually, by using the semiconductor‐conductor transition obtained by properly biasing the CNTs, an isolation better than 30 dB can be obtained between the ON and OFF states of the switch for very wide bandwidth applications. This happens owing to the shape deformation and consequent change in the band‐gap due to the external pressure caused by the electric field. State‐of‐art for other switching techniques based on CNTs and their use for RF nano‐interconnections is also discussed, together with current issues in measurement techniques

Application of UV Visible Light Absorption and Scattering technique to low absorption fuels under diesel-like conditions

Light Absorption and Scattering technique (LAS) has been applied for the measurement of fuel vapour distribution in diesel-type sprays. This technique is usually limited to fuels with relatively high absorptivity, which are sometimes not commonly used as surrogate fuels. In the present paper, a comparison of fuels with very different absorptive properties has been made to determine the range of application of the methodology. A calibration procedure has been applied to n-decane (DEC), a binary blend of n-decane and n-hexadecane (50DEC) and three blends of n-heptane with a highly-absorpting fuel (HEPB1, HEPB2 and HEPB3). This methodology enables the in-situ quantification of absorption coefficients at high pressure and temperature by creating a uniform mixture inside the cylinder. Results have been later applied for the quantification of fuel vapour distribution in sprays for DEC, 50DEC and HEPB3. Results obtained with these range of fuels have enabled to establish the limit in terms of absorption coefficient needed to get consistent results with the technique.This work was partially funded by the Government of Spain through Project TRA2011-26359 and Grant BES-2012-059721. In addition, the authors acknowledge that some equipment used in this work has been partially supported by FEDER project funds (FEDER-ICTS-2012-06), framed in the operational program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain.Pastor Soriano, JV.; García Oliver, JM.; López, JJ.; Micó Reche, C. (2016). Application of UV Visible Light Absorption and Scattering technique to low absorption fuels under diesel-like conditions. Fuel. 179:258-266. https://doi.org/10.1016/j.fuel.2016.03.080S25826617

Bulk-sensitive photoemission spectroscopy of A_2FeMoO_6 double perovskites (A=Sr, Ba)

Electronic structures of Sr_2FeMoO_6 (SFMO) and Ba_2FeMoO_6 (BFMO) double perovskites have been investigated using the Fe 2p->3d resonant photoemission spectroscopy (PES) and the Cooper minimum in the Mo 4d photoionization cross section. The states close to the Fermi level are found to have strongly mixed Mo-Fe t_{2g} character, suggesting that the Fe valence is far from pure 3+. The Fe 2p_{3/2} XAS spectra indicate the mixed-valent Fe^{3+}-Fe^{2+} configurations, and the larger Fe^{2+} component for BFMO than for SFMO, suggesting a kind of double exchange interaction. The valence-band PES spectra reveal good agreement with the LSDA+U calculation.Comment: 4 pages, 3 figure