Influence of Structure Parameters on the Information Diffusion Process in Virtual Networks

This paper examines the effects of composition, size and structure of virtual networks on the diffusion of information. The research extends the Axelrod cultural model (ACM), an established theory rooted in political science research, to explain information dissemination among social actors in ICT-enabled virtual networks (Axelrod 1997). The investigation is focused on the impact of network structure parameters and gives insight on how a manipulation of those parameters influences the diffusion of information in virtual networks

EBAY’s Acquisition of Skype SA: Valuing the Voice of the Buyer

This set of teaching cases deals with the surprising acquisition of VOIP provider Skype SA by e-commerce giant eBay in the fall of 2005. The initial case examines two distinct topics: First, it introduces VOIP technology and traces the development of commercial applications from 1995 to 2003. Second, it considers issues of strategic alignment by raising the question of whether eBay should have allied with or acquired Skype SA. The second case provides an epilogue set two years after the acquisition that examines the intermediate outcomes of the Skype integration

CHEP: The Net of Things

PART A: Forced by operational inefficiencies in its own business model, CHEP, the market leader in the rental pallet business, became an early adopter of Radio Frequency Identification (RFID) technology. Having proven the effectiveness of the technology for internal operations with a pilot test, CHEP now had to find clients who want to adopt the technology-enabled services in order to pay for a large scale roll out. The case traces CHEP’s challenges associated with the development and deployment RFID in its own operation and raises questions of how to proceed with potential IT-enabled change at the enterprise and supply chain level, without spoiling relationships with current clients and maintaining its core business. PART B: In fall 2007, Brian Beattie and Puneet Sawhney looked back at CHEP’s RFID initiative and the progress that has been made since the 2003 decision to further incorporate the technology into its assets. While the original intent of tagging all pallets did not materialize, considerable progress had been made into quantifying the benefits of RFID adoption. Industry-wide developments had changed the scope of the RFID initiative from simply tagging the asset pool to creating value added service for CHEP’s clients. Overall, RFID had yet to revolutionize the supply chain, but the evolution of technology and the innovation of RFID related products and services had aided CHEP in maintaining its market leadership in the pallet business and enabled CHEP to created new lines of business

Physicians' working conditions and job satisfaction : does hospital ownership in Germany make a difference?

Background: A growing number of German hospitals have been privatized with the intention of increasing cost effectiveness and improving the quality of health care. Numerous studies investigated what possible qualitative and economic consequences these changes issues might have on patient care. However, little is known about how this privatization trend relates to physicians' working conditions and job satisfaction. It was anticipated that different working conditions would be associated with different types of hospital ownership. To that end, this study's purpose is to compare how physicians, working for both public and privatized hospitals, rate their respective psychosocial working conditions and job satisfaction. Methods: The study was designed as a cross-sectional comparison using questionnaire data from 203 physicians working at German hospitals of different ownership types (private for-profit, public and private nonprofit). Results: The present study shows that several aspects of physicians' perceived working conditions differ significantly depending on hospital ownership. However, results also indicated that physicians' job satisfaction does not vary between different types of hospital ownership. Finally, it was demonstrated that job demands and resources are associated with job satisfaction, while type of ownership is not. Conclusion: This study represents one of a few studies that investigate the effect of hospital ownership on physicians work situation and demonstrated that the type of ownership is a potential factor accounting for differences in working conditions. The findings provide an informative basis to find solutions improving physicians' work at German hospitals

Scoliosis : density-equalizing mapping and scientometric analysis

Background: Publications related to scoliosis have increased enormously. A differentiation between publications of major and minor importance has become difficult even for experts. Scientometric data on developments and tendencies in scoliosis research has not been available to date. The aim of the current study was to evaluate the scientific efforts of scoliosis research both quantitatively and qualitatively. Methods: Large-scale data analysis, density-equalizing algorithms and scientometric methods were used to evaluate both the quantity and quality of research achievements of scientists studying scoliosis. Density-equalizing algorithms were applied to data retrieved from ISI-Web. Results: From 1904 to 2007, 8,186 items pertaining to scoliosis were published and included in the database. The studies were published in 76 countries: the USA, the U.K. and Canada being the most productive centers. The Washington University (St. Louis, Missouri) was identified as the most prolific institution during that period, and orthopedics represented by far the most productive medical discipline. "BRADFORD, DS" is the most productive author (146 items), and "DANSEREAU, J" is the author with the highest scientific impact (h-index of 27). Conclusion: Our results suggest that currently established measures of research output (i.e. impact factor, h-index) should be evaluated critically because phenomena, such as self-citation and co-authorship, distort the results and limit the value of the conclusions that may be drawn from these measures. Qualitative statements are just tractable by the comparison of the parameters with respect to multiple linkages. In order to obtain more objective evaluation tools, new measurements need to be developed

Quantifying Selection Bias in Cross-Sectional Studies of Ovarian Hormones

Most studies of ovarian hormones in adult women collect data from a cross-sectional sample of participants meeting various selection criteria including not having been pregnant or breastfeeding for several months. Although this approach is intended to eliminate the effects of these factors on hormonal variation, it introduces a selection bias of unknown magnitude: in a non-contracepting population, those women with the highest fecundity are more likely to be either pregnant or lactating, and so not included in a study sample. Thus a cross-sectional sample disproportionately represents women with the lowest fecundity (and potentially the lowest hormone levels). Here we present a preliminary evaluation of the magnitude of this selection bias, focusing on progesterone ($P$) levels near the luteal peak. We use data from Project REPA, a longitudinal study of reproductive functioning in rural Bolivians, recruited without regard to reproductive status (Vitzthum, Spielvogel, and Thornburg \textit{Proceedings of the U.S. National Academy of Sciences/} 101, 1443 (2004)). Drawing from 542~non-conception cycles in 144~women, we construct simulated cross-sectional samples meeting various inclusion criteria and compare their anovulation rates and progesterone levels.National Science Foundation, University of California, Binghamton University, Indiana Universit

δ13C and δD measurements of volatile organic compounds in a variety of emissions by thermal desorption compound specific isotope analysis

Volatile organic compounds (VOCs) can be related to different compound classes but they all have a distinct vapour pressure allowing them to enter the atmosphere under ambient conditions. VOCs can undergo various reactions in the atmosphere and are emitted by various processes (anthropogenic and natural). Compound specific isotope analysis (CSIA) has been used in many other research studies to track the fate and source of compounds in the environment and the geological record. The majority of CSIA has been applied to extracts from soil, sediment or crude oils requiring entirely different sampling techniques compared to atmospheric samples. Applying CSIA to atmospheric compounds is a growing research field but has mainly being restricted to stable isotopes of carbon.This PhD thesis presents a novel application for adsorptive sampling on TenaxTA to analyse compound specific δ13C and δD of a range of atmospheric VOCs (C6 - C10). For the first time a 2-stage thermal desorption (TD) unit was linked to gas chromatography isotope ratio mass spectrometry (GC-irMS) and instrumental conditions were thoroughly investigated and optimised. Results obtained by using a standard mix of eleven VOCs confirmed reliability of TD-GCirMS analyses with standard deviations (SD) below instrument precision. δ values showed negligible isotopic fractionation compared to results obtained from traditional GC-irMS analysis (without TD unit) demonstrating the suitability of TD for CSIA.The technique was applied to analyse VOCs from various emission sources, e.g. car exhaust, biomass combustion and an industry stack. The results obtained have provided some insight into the formation processes of the VOCs investigated. δ13C values from an alumina refinery emission support a natural origin for the VOCs (organic material in bauxite ore). The δD values (21 to - 137 ‰) of the industry emission were consistently more enriched in D compared to δD values of VOCs previously reported making the δ values of VOCs in the industrial stack unique. Car exhaust emission from a petrol engine showed significant differences in δ values for VOCs up to 2 ‰ and 25 ‰ (δ13C and δD, respectively) at different tank fuel levels when using the same fuel batch. Car exhaust emission samples from a diesel engine showed a high content of highly complex mixture of unresolved compounds thus chromatographic baseline separation of VOCs was not achieved for stable hydrogen isotope analysis and led to unreliable δ values. The results from different biomass combustion emissions (including 5 species of C3 plants and 3 species of C4 plants) confirmed significant differences in δ13C of VOCs between C3 and C4 plants due to their specific metabolic pathways for carbon fixation in photosynthesis. The δD of VOCs derived from dicotyledons were less depleted in D compared to δD of VOCs derived from grasses (differences >27 ‰) indicating that the VOCs are derived mainly from lignin/cellulose rather than from lipids since dicotyledons contain higher amounts of lignin/cellulose.Due to the unique isotopic signatures of the VOCs from the different emission sources it was possible to distinguish their origins. Furthermore, TD-GC-irMS shows great potential to establish other emission sources in the environment and may help to gain some insight into their modes of formation

Characterizing physiological and symptomatic variation in menstrual cycles using self-tracked mobile health data

The menstrual cycle is a key indicator of overall health for women of reproductive age. Previously, menstruation was primarily studied through survey results; however, as menstrual tracking mobile apps become more widely adopted, they provide an increasingly large, content-rich source of menstrual health experiences and behaviors over time. By exploring a database of user-tracked observations from the Clue app by BioWink of over 378,000 users and 4.9 million natural cycles, we show that self-reported menstrual tracker data can reveal statistically significant relationships between per-person cycle length variability and self-reported qualitative symptoms. A concern for self-tracked data is that they reflect not only physiological behaviors, but also the engagement dynamics of app users. To mitigate such potential artifacts, we develop a procedure to exclude cycles lacking user engagement, thereby allowing us to better distinguish true menstrual patterns from tracking anomalies. We uncover that women located at different ends of the menstrual variability spectrum, based on the consistency of their cycle length statistics, exhibit statistically significant differences in their cycle characteristics and symptom tracking patterns. We also find that cycle and period length statistics are stationary over the app usage timeline across the variability spectrum. The symptoms that we identify as showing statistically significant association with timing data can be useful to clinicians and users for predicting cycle variability from symptoms or as potential health indicators for conditions like endometriosis. Our findings showcase the potential of longitudinal, high-resolution self-tracked data to improve understanding of menstruation and women's health as a whole.Comment: The Supplementary Information for this work, as well as the code required for data pre-processing and producing results is available in https://github.com/iurteaga/menstrual_cycle_analysi

Toys Become Tools: From Virtual Worlds to Real Commerce

This teaching case considers the challenges and opportunities faced by an entrepreneur in Second Life, one of the more popular virtual world environments. Second Life provides the economic and technological platform required for immersion, social interaction, and the potential of private enterprise. Many entrepreneurs have taken advantage of the various business opportunities offered in Second Life, and a number have earned significant income through their in-world creations and services. Stuart O\u27Brian, the CEO and founder of VirtualCircle, was one of the early pioneers of virtual commerce. Over the last three years, his organization faced multiple business and technology challenges while negotiating the hypercompetitive and turbulent environment within Second Life. However, he now questions the sustainability of the ever-changing and agile business model that enabled the success of VirtualCircle. Stuart also faces questions regarding avenues of future growth and is grappling with issues concerning interoperability and the replication of his prior success in other virtual environments—and the real world