A Suspended Nanogap Formed by Field-Induced Atomically Sharp Tips

A sub-nanometer scale suspended gap (nanogap) defined by electric field-induced atomically sharp metallic tips is presented. A strong local electric field (\u3e109 V=m) across micro/nanomachined tips facing each other causes the metal ion migration in the form of dendrite-like growth at the cathode. The nanogap is fully isolated from the substrate eliminating growth mechanisms that involve substrate interactions. The proposed mechanism of ion transportation is verified using real-time imaging of the metal ion transportation using an in situ biasing in transmission electron microscope (TEM). The configuration of the micro/nanomachined suspended tips allows nanostructure growth of a wide variety of materials including metals, metal-oxides, and polymers. VC 2012 American Institute of Physics

An Empirical Analysis of Consumption Patterns for Mobile Apps and Web: A Multiple Discrete-Continuous Extreme Value Approach

Using a unique panel data set detailing individual-level mobile app consumption, this study develops a utility theory-based structural model for multiple discrete/continuous choices in app use. We identify the dynamics and inter-dependencies between mobile apps and jointly quantify consumers’ app choice and satiation simultaneously. The results suggest that mobile users’ baseline utility is the highest for communication apps, while the lowest for personal financing apps. In addition, users’ satiation level is the highest for the personal financing apps and the lowest for the game apps. However, a substantial heterogeneity in baseline utility and satiation is observed across diverse users. Furthermore, both positive and negative correlations exist in the baseline utility and satiation levels of mobile web and app categories. Consequently, the proposed frameworks could open new perspectives for handling large-scale, micro-level data, serving as important resources for big data analytics in general and mobile app analytics in particular

Symmetry-Protected Solitons and Bulk-Boundary Correspondence in Generalized Jackiw-Rebbi Models

We investigate the roles of symmetry and bulk-boundary correspondence in characterizing topological edge states in generalized Jackiw-Rebbi (JR) models. We show that time-reversal ($T$), charge-conjugation ($C$), parity ($P$), and discrete internal field rotation ($Z_n$) symmetries protect and characterize the various types of edge states such as chiral and nonchiral solitons via bulk-boundary correspondence in the presence of the multiple vacua. As two representative models, we consider the JR model composed of a single fermion field having a complex mass and the generalized JR model with two massless but interacting fermion fields. The JR model shows nonchiral solitons with the $Z_2$ rotation symmetry, whereas it shows chiral solitons with the broken $Z_2$ rotation symmetry. In the generalized JR model, only nonchiral solitons can emerge with only $Z_2$ rotation symmetry, whereas both chiral and nonchiral solitons can exist with enhanced $Z_4$ rotation symmetry. Moreover, we find that the nonchiral solitons have $C, P$ symmetries while the chiral solitons do not, which can be explained by the symmetry-invariant lines connecting degenerate vacua. Finally, we find the symmetry correspondence between multiply-degenerate global vacua and solitons such that ${T}$, ${C}$, ${P}$ symmetries of a soliton inherit from global minima that are connected by the soliton, which provides a novel tool for the characterization of topological solitons

Nature or Nurture? An Analysis of Rational Addiction to Mobile Social Applications

Through the lens of rational addiction theory (Becker and Murphy, 1988), this study investigates whether addiction to mobile social apps should be viewed as a rational behavior rather than an uncontrollable, irrational disorder. To derive the analytical model, this study extends the rational addiction framework to include a utility-level network effect as the key factor that regulates the inter-temporal consumption of mobile social apps. Further, to validate empirically the rational addiction model in this context, we gathered and analyzed longitudinal panel data on the weekly app usage of thousands of smartphone users. The findings suggest that consistent with the rational addiction theory, users of mobile social apps are rational and forward-looking. They determine their current consumption based on both past and future consumption and the utility derived from network effects. However, the extent of rational addiction to mobile social apps varies considerably across diverse demographic groups and app categories

The Economics of All-You-Can-Read Pricing: Tariff Choice, Contract Renewal, and Switching for E-Book Purchases

E-book markets are currently moving through a period of disequilibrium as new pricing structures (i.e., flat-fee subscriptions) are rapidly embraced by major vendors. On the basis of a novel dataset, we investigate how the availability of “all-you-can-read” pricing programs influences consumers’ tariff choice, contract renewal, and switching behaviors. Consistent with the rational choice framework, the findings suggest that most e-book consumers significantly gain from subscription-based tariffs. However, we also find some other intriguing results. Among the three subscription designs examined, the 1-week plan affords consumers more economic benefits than do 1-day or 1-month programs. The economic gains derived from subscription-based tariffs diminish as consumers renew their subscriptions under the same contract duration. Consumers who switch to other plans also suffer from reduced savings. Finally, iOS users are more inclined to select subscription models than are Android users because of the absence of in-app purchase functionalities for the former

Single-Copy Certification of Two-Qubit Gates without Entanglement

A quantum state transformation can be generally approximated by single- and two-qubit gates. This, however, does not hold with noisy intermediate-scale quantum technologies due to the errors appearing in the gate operations, where errors of two-qubit gates such as controlled-NOT and SWAP operations are dominated. In this work, we present a cost efficient single-copy certification for a realization of a two-qubit gate in the presence of depolarization noise, where it is aimed to identify if the realization is noise-free, or not. It is shown that entangled resources such as entangled states and a joint measurement are not necessary for the purpose, i.e., a noise-free two-qubit gate is not needed to certify an implementation of a two-qubit gate. A proof-of-principle demonstration is presented with photonic qubits.Comment: 8 pages. arXiv admin note: text overlap with arXiv:1812.0208

Fabrication of pyramidal probes with various periodic patterns and a single nanopore

The nanometer-scale patterned pyramidal probe with an electron beam-induced nanopore on the pyramid apex is an excellent candidate for an optical biosensor. The nanoapertures surrounded with various periodic groove patterns on the pyramid sides were fabricated using a focused ion beam technique, where the optical characteristics of the fabricated apertures with rectangular, circular, and elliptical groove patterns were investigated. The elliptical groove patterns on the pyramid were designed to maintain an identical distance between the grooves and the apex for the surface waves and, among the three patterns, the authors observed the highest optical transmission from the elliptically patterned pyramidal probe. A 103-fold increase of the transmitted optical intensity was observed after patterning with elliptical grooves, even without an aperture on the pyramid apex. The nanopore on the apex of the pyramid was fabricated using electron beam irradiation and was optically characterized

Inhibitory effect of a tyrosine-fructose Maillard reaction product, 2,4-bis(p-hydroxyphenyl)-2-butenal on amyloid-β generation and inflammatory reactions via inhibition of NF-κB and STAT3 activation in cultured astrocytes and microglial BV-2 cells

<p>Abstract</p> <p>Background</p> <p>Amyloidogenesis is linked to neuroinflammation. The tyrosine-fructose Maillard reaction product, 2,4-bis(<it>p</it>-hydroxyphenyl)-2-butenal, possesses anti-inflammatory properties in cultured macrophages, and in an arthritis animal model. Because astrocytes and microglia are responsible for amyloidogenesis and inflammatory reactions in the brain, we investigated the anti-inflammatory and anti-amyloidogenic effects of 2,4-bis(<it>p</it>-hydroxyphenyl)-2-butenal in lipopolysaccharide (LPS)-stimulated astrocytes and microglial BV-2 cells.</p> <p>Methods</p> <p>Cultured astrocytes and microglial BV-2 cells were treated with LPS (1 μg/ml) for 24 h, in the presence (1, 2, 5 μM) or absence of 2,4-bis(<it>p</it>-hydroxyphenyl)-2-butenal, and harvested. We performed molecular biological analyses to determine the levels of inflammatory and amyloid-related proteins and molecules, cytokines, Aβ, and secretases activity. Nuclear factor-kappa B (NF-κB) DNA binding activity was determined using gel mobility shift assays.</p> <p>Results</p> <p>We found that 2,4-bis(<it>p</it>-hydroxyphenyl)-2-butenal (1, 2, 5 μM) suppresses the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) as well as the production of nitric oxide (NO), reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) in LPS (1 μg/ml)-stimulated astrocytes and microglial BV-2 cells. Further, 2,4-bis(<it>p</it>-hydroxyphenyl)-2-butenal inhibited the transcriptional and DNA binding activity of NF-κB--a transcription factor that regulates genes involved in neuroinflammation and amyloidogenesis via inhibition of IκB degradation as well as nuclear translocation of p50 and p65. Consistent with the inhibitory effect on inflammatory reactions, 2,4-bis(<it>p</it>-hydroxyphenyl)-2-butenal inhibited LPS-elevated Aβ₄₂levels through attenuation of β- and γ-secretase activities. Moreover, studies using signal transducer and activator of transcription 3 (STAT3) siRNA and a pharmacological inhibitor showed that 2,4-bis(<it>p</it>-hydroxyphenyl)-2-butenal inhibits LPS-induced activation of STAT3.</p> <p>Conclusions</p> <p>These results indicate that 2,4-bis(<it>p</it>-hydroxyphenyl)-2-butenal inhibits neuroinflammatory reactions and amyloidogenesis through inhibition of NF-κB and STAT3 activation, and suggest that 2,4-bis(<it>p</it>-hydroxyphenyl)-2-butenal may be useful for the treatment of neuroinflammatory diseases like Alzheimer's disease.</p