Over-limiting Current and Control of Dendritic Growth by Surface Conduction in Nanopores

Understanding over-limiting current (faster than diffusion) is a long-standing challenge in electrochemistry with applications in desalination and energy storage. Known mechanisms involve either chemical or hydrodynamic instabilities in unconfined electrolytes. Here, it is shown that over-limiting current can be sustained by surface conduction in nano pores, without any such instabilities, and used to control dendritic growth during electrodeposition. Copper electrode posits are grown in anodized aluminum oxide membranes with polyelectrolyte coatings to modify the surface charge. At low currents, uniform electroplating occurs, unaffected by surface modification due to thin electric double layers, but the morphology changes dramatically above the limiting current. With negative surface charge, growth is enhanced along the nanopore surfaces, forming surface dendrites and nanotubes behind a deionization shock. With positive surface charge, dendrites avoid the surfaces and are either guided along the nanopore centers or blocked from penetrating the membrane

The Impact of Public Reporting Schemes and Market Competition on Hospital Efficiency

In the wake of growing attempts to assess the validity of public reporting, much research has examined the effectiveness of public reporting regarding cost or quality of care. However, relatively little is known about whether transparency through public reporting significantly influences hospital efficiency despite its emerging expectations for providing value-based care. This study aims to identify the dynamics that transparency brought to the healthcare market regarding hospital technical efficiency, taking the role of competition into account. We compare the two public reporting schemes, All-Payer Claims Database (APCD) and Hospital Compare. Employing Data Envelopment Analysis (DEA) and a cross-sectional time-series Tobit regression analysis, we found that APCD is negatively associated with hospital technical efficiency, while hospitals facing less competition responded significantly to increasingly transparent information by enhancing their efficiency relative to hospitals in more competitive markets. We recommend that policymakers take market mechanisms into consideration jointly with the introduction of public reporting schemes in order to produce the best outcomes in healthcare

Development of an ex vivo model for the study of cerebrovascular function utilizing isolated mouse olfactory artery

OBJECTIVE: Cerebral vessels, such as intracerebral perforating arterioles isolated from rat brain, have been widely used as an ex vivo model to study the cerebrovascular function associated with cerebrovascular disorders and the therapeutic effects of various pharmacological agents. These perforating arterioles, however, have demonstrated differences in the vascular architecture and reactivity compared with a larger leptomeningeal artery which has been commonly implicated in cerebrovascular disease. In this study, therefore, we developed the method for studying cerebrovascular function utilizing the olfactory artery isolated from the mouse brain. METHODS: The olfactory artery (OA) was isolated from the C57/BL6 wild-type mouse brain. After removing connective tissues, one side of the isolated vessel segment (approximately -500 µm in length) was cannulated and the opposite end of the vessel was completely sealed while being viewed with an inverted microscope. After verifying the absence of pressure leakage, we examined the vascular reactivity to various vasoactive agents under the fixed intravascular pressure (60 mm Hg). RESULTS: We found that the isolated mouse OAs were able to constrict in response to vasoconstrictors, including KCl, phenylephrine, endothelin-1, and prostaglandin PGH(2). Moreover, this isolated vessel demonstrated vasodilation in a dose-dependent manner when vasodilatory agents, acetylcholine and bradykinin, were applied. CONCLUSION: Our findings suggest that the isolated olfactory artery would provide as a useful ex vivo model to study the molecular and cellular mechanisms of vascular function underlying cerebrovascular disorders and the direct effects of such disease-modifying pathways on cerebrovascular function utilizing pharmacological agents and genetically modified mouse models

Information Overload and its Consequences in the Context of Online Consumer Reviews

An online consumer review is the information including experiences, evaluations and opinions on products from the consumer perspective. An online consumer review plays two roles - informant and recommender. Considering two factors of review structure (the number of reviews and review type), this study analyzes the effect of online consumer reviews on consumers’ information processing depending on their levels of involvement. Generally, more positive reviews seem better from the perspective of online consumer reviews as recommenders. However, from the perspective of online consumer reviews as information providers, consumers may be confronted with too much information when a large number of reviews are offered, which results in information overload. We investigate when information overload occurs in the context of online consumer reviews, what strategies against the information overload consumers use depending on their levels of involvement, and how the product attitude and purchasing intention are changed. Our findings have implications for online sellers in terms of how to manage online consumer reviews contents

The Effect of Site Trust on Trust in the Sources of Online Consumer Review and Trust in the Sources of Consumer Endorsement in Advertisement

Consumer endorsements have along been used as an advertising strategy, and now, it is also easy to see consumer endorsements in online shopping sites. A positive Online Consumer Review (OCR) is a consumer endorsement in the web site. Although the sources of both OCR and consumer endorsement in advertisement (CEA) are typical consumers, trust in the source of OCR could be perceived differently from trust in the source of CEA. Trust in the information source ensures that consumers comfortably accept the endorsement. In e-commerce, how is a consumer’s judgment involving trust based on endorsements made by other consumers? This experimental study investigates whether trust in a web site is transferred to trust in the source of OCR and CEA. Moreover, it also tests which source credibility could be more influenced by site trust

Overlimiting Current and Shock Electrodialysis in Porous Media

Most electrochemical processes, such as electrodialysis, are limited by diffusion, but in porous media, surface conduction and electro-osmotic flow also contribute to ionic fluxes. In this paper, we report experimental evidence for surface-driven over-limiting current (faster than diffusion) and deionization shocks (propagating salt removal) in a porous medium. The apparatus consists of a silica glass frit (1 mm thick with 500 nm mean pore size) in an aqueous electrolyte (CuSO$_4$ or AgNO$_3$) passing ionic current from a reservoir to a cation-selective membrane (Nafion). The current-voltage relation of the whole system is consistent with a proposed theory based on the electro-osmotic flow mechanism over a broad range of reservoir salt concentrations (0.1 mM - 1.0 M), after accounting for (Cu) electrode polarization and pH-regulated silica charge. Above the limiting current, deionized water ($\approx 10 \mu$ $M$) can be continuously extracted from the frit, which implies the existence of a stable shock propagating against the flow, bordering a depleted region that extends more than 0.5mm across the outlet. The results suggest the feasibility of "shock electrodialysis" as a new approach to water desalination and other electrochemical separations.Comment: 39 pages, 9 fig

Database Applications in Science Data Systems for Low-Cost Satellite Missions

As in financial and business applications. satellite systems accumulate data sets over some time period. Certain portions of this data lend themselves to storage within a commercial database system. The advantages and disadvantages of using commercial database systems for storage of data related to satellite systems are discussed. The types of data stored in satellite science data systems are outlined. Case studies from MSX. NEAR and TIMED. three satellite missions developed at The Johns Hopkins University Applied Physics Laboratory. are reviewed. An example of database logical architecture to support science data queries is presented. Implementation lessons in INGRES and ORACLE are noted. Issues related to the user community in each case are discussed. In conclusion. a summary of the lessons learned from all case studies is presented