On-demand or Spot? Selling the cloud to risk-averse customers

In Amazon EC2, cloud resources are sold through a combination of an on-demand market, in which customers buy resources at a fixed price, and a spot market, in which customers bid for an uncertain supply of excess resources. Standard market environments suggest that an optimal design uses just one type of market. We show the prevalence of a dual market system can be explained by heterogeneous risk attitudes of customers. In our stylized model, we consider unit demand risk-averse bidders. We show the model admits a unique equilibrium, with higher revenue and higher welfare than using only spot markets. Furthermore, as risk aversion increases, the usage of the on-demand market increases. We conclude that risk attitudes are an important factor in cloud resource allocation and should be incorporated into models of cloud markets.Comment: Appeared at WINE 201

Patterned Arrays of Supramolecular Microcapsules

Micropatterning of hydrogel has brought innovative outcomes in fundamental and applied material sciences. Previous approaches have mainly been dedicated to fabricate arrays of bulk hydrogel beads, which have inherent challenges including loading ability, scalability, specificity and versatility. Here we present a methodology to create hollow microcapsule arrays from sessile microdroplets. The difference in wettability between hydrophilic and hydrophobic surfaces enables self-partitioning of liquid into microdroplet arrays, serving as microreservoirs to load complementarily-functionalized host-guest polymers, cucurbit[8]uril-threaded highly-branched polyrotaxanes (HBP-CB[8]) and naphthyl-functionalized hydroxyethyl cellulose (HEC-Np). The interfacial dynamic complexation between positively-charged HBP-CB[8] and HECNp occurred in the presence of negatively-charged surfactants, resulting in condensed supramolecular hydrogel skins. The hydrogel microcapsules were uniform in size, and were developed to encapsulate target cargos in a robust and well-defined manner. Moreover, the microcapsule substrates were further used for surface enhanced Raman spectroscopy (SERS) sensing upon loading of gold nanoparticles. This facile assembly of microcapsule arrays has potential applications in controlled cargo delivery, bio-sensing, high throughput analysis and sorting

The metrics and correlates of physician migration from Africa

<p>Abstract</p> <p>Background</p> <p>Physician migration from poor to rich countries is considered an important contributor to the growing health workforce crisis in the developing world. This is particularly true for Africa. The perceived magnitude of such migration for each source country might, however, depend on the choice of metrics used in the analysis. This study examined the influence of choice of migration metrics on the rankings of African countries that suffered the most physician migration, and investigated the correlates of physician migration.</p> <p>Methods</p> <p>Ranking and correlational analyses were conducted on African physician migration data adjusted for bilateral net flows, and supplemented with developmental, economic and health system data. The setting was the 53 African birth countries of African-born physicians working in nine wealthier destination countries. Three metrics of physician migration were used: total number of physician émigrés; emigration fraction defined as the proportion of the potential physician pool working in destination countries; and physician migration density defined as the number of physician émigrés per 1000 population of the African source country.</p> <p>Results</p> <p>Rankings based on any of the migration metrics differed substantially from those based on the other two metrics. Although the emigration fraction and physician migration density metrics gave proportionality to the migration crisis, only the latter was consistently associated with source countries' workforce capacity, health, health spending, economic and development characteristics. As such, higher physician migration density was seen among African countries with relatively higher health workforce capacity (0.401 ≤ <it>r </it>≤ 0.694, <it>p </it>≤ 0.011), health status, health spending, and development.</p> <p>Conclusion</p> <p>The perceived magnitude of physician migration is sensitive to the choice of metrics. Complementing the emigration fraction, the physician migration density is a metric which gives a different but proportionate picture of which African countries stand to lose relatively more of its physicians with unchecked migration. The nature of health policies geared at health-worker migration can be expected to depend on the choice of migration metrics.</p

Microcapsule Buckling Triggered by Compression-Induced Interfacial Phase Change

There is an emerging trend towards the fabrication of microcapsules at liquid interfaces. In order to control the parameters of such capsules, the interfacial processes governing their formation must be understood. Here, poly(vinyl alcohol) films are assembled at the interface of water-in-oil microfluidic droplets. The polymer is cross-linked using cucurbit[8]uril ternary supramolecular complexes. It is shown that compression-induced phase change causes the onset of buckling in the interfacial film. On evaporative compression, the interfacial film both increases in density and thickens, until it reaches a critical density and a phase change occurs. We show that this increase in density can be simply related to the film Poisson ratio and area compression.This description captures fundamentals of many compressive interfacial phase changes and can also explain the observation of a fixed thickness-to-radius ratio at buckling, $\left(\frac TR\right)$$_{buck}$

Antenna Array Enabled Space/Air/Ground Communications and Networking for 6G

Antenna arrays have a long history of more than 100 years and have evolved closely with the development of electronic and information technologies, playing an indispensable role in wireless communications and radar. With the rapid development of electronic and information technologies, the demand for all-time, all-domain, and full-space network services has exploded, and new communication requirements have been put forward on various space/air/ground platforms. To meet the ever increasing requirements of the future sixth generation (6G) wireless communications, such as high capacity, wide coverage, low latency, and strong robustness, it is promising to employ different types of antenna arrays with various beamforming technologies in space/air/ground communication networks, bringing in advantages such as considerable antenna gains, multiplexing gains, and diversity gains. However, enabling antenna array for space/air/ground communication networks poses specific, distinctive and tricky challenges, which has aroused extensive research attention. This paper aims to overview the field of antenna array enabled space/air/ground communications and networking. The technical potentials and challenges of antenna array enabled space/air/ground communications and networking are presented first. Subsequently, the antenna array structures and designs are discussed. We then discuss various emerging technologies facilitated by antenna arrays to meet the new communication requirements of space/air/ground communication systems. Enabled by these emerging technologies, the distinct characteristics, challenges, and solutions for space communications, airborne communications, and ground communications are reviewed. Finally, we present promising directions for future research in antenna array enabled space/air/ground communications and networking

Geosynchronous magnetopause crossings and their relationships with magnetic storms and substorms

The paper investigates the strengthening of magnetospheric activity related to geosynchronous magnetopause crossings (GMCs). We make a list of GMC events using the empirical magnetopause model (Lin et al., 2010) and hourly averaged OMNI data and find which solar wind and magnetospheric conditions accompany and follow the GMCs. The GMCs are mostly caused by the impact of interplanetary coronal mass ejections (ICMEs) and/or interplanetary shocks often with a strong increase in the density and a moderate increase in velocity. The average solar wind density during the first GMC hour is higher than 20 cm−3 in 70 % cases, while the velocity is higher than 500 km/s in 56 % cases. The hourly interplanetary magnetic field (IMF) BZ is negative in 87 % cases. The average over all events SMU (SML), Kp, and PC indices reach maxima (minima) in 1 hour after the GMC beginning, while the delay of the minimum of the Dst index is usually 3–8 hours. These average time delays do not depend on the strength of the storms and substorms. The SML (Dst) minimum is less than -500 nT (-30 nT) in the next 24 hours in 95 % (99 %) cases, i.e. the GMC events are mostly followed by magnetic storms and substorms. We compare solar wind and magnetospheric conditions for GMCs connected with ICMEs and stream interaction regions (SIRs). Our study confirms that the ICME-related events are characterized by stronger ring current and auroral activity than the SIR-related events. The difference might be explained by the different behavior of the solar wind velocity

Toward a versatile toolbox for cucurbit[n]uril-based supramolecular hydrogel networks through in situ polymerization

The success of exploiting cucurbit[n]uril (CB[n] )-based molecular recognition in self-assembled systems has sparked a tremendous interest in polymer and materials chemistry. In this study, polymerization in the presence of host-guest complexes is applied as a modular synthetic approach toward a diverse set of CB[8]-based supramolecular hydrogels with desirable properties, such as mechanical strength, toughness, energy dissipation, self-healing, and shear-thinning. A range of vinyl monomers, including acrylamide-, acrylate-, and imidazolium-based hydrophilic monomers, could be easily incorporated as the polymer backbones, leading to a library of CB[8] hydrogel networks. This versatile strategy explores new horizons for the construction of supramolecular hydrogel networks and materials with emergent properties in wearable and self-healable electronic devices, sensors, and structural biomaterials.This work was supported by the Marie Curie FP7 SASSYPOL ITN (607602) programme (to J.L.), Ministry of Education of Malaysia and Universiti Teknologi MARA, Malaysia (to C.S.Y.T.), and EPRSC (EP/F0355351 and EP/G060649/1) and the ERC (ASPiRe, 240629) (to O.A.S.)

Staff expectations for the implementation of an electronic health record system: a qualitative study using normalisation process theory

Background: Global evidence suggests a range of benefits for introducing electronic health record (EHR) systems to improve patient care. However, implementing EHR within healthcare organisations is complex and, in the United Kingdom (UK), uptake has been slow. More research is needed to explore factors influencing successful implementation. This study explored staff expectations for change and outcome following procurement of a commercial EHR system by a large academic acute NHS hospital in the UK. Methods: Qualitative interviews were conducted with 14 members of hospital staff who represented a variety of user groups across different specialities within the hospital. The four components of Normalisation Process Theory (Coherence, Cognitive participation, Collective action and Reflexive monitoring) provided a theoretical framework to interpret and report study findings. Results: Health professionals had a common understanding for the rationale for EHR implementation (Coherence). There was variation in willingness to engage with and invest time into EHR (Cognitive participation) at an individual, professional and organisational level. Collective action (whether staff feel able to use the EHR) was influenced by context and perceived user-involvement in EHR design and planning of the implementation strategy. When appraising EHR (Reflexive monitoring), staff anticipated short and long-term benefits. Staff perceived that quality and safety of patient care would be improved with EHR implementation, but that these benefits may not be immediate. Some staff perceived that use of the system may negatively impact patient care. The findings indicate that preparedness for EHR use could mitigate perceived threats to the quality and safety of care. Conclusions: Health professionals looked forward to reaping the benefits from EHR use. Variations in level of engagement suggest early components of the implementation strategy were effective, and that more work was needed to involve users in preparing them for use. A clearer understanding as to how staff groups and services differentially interact with the EHR as they go about their daily work was required. The findings may inform other hospitals and healthcare systems on actions that can be taken prior to EHR implementation to reduce concerns for quality and safety of patient care and improve the chance of successful implementation

General practitioners' evaluation of community psychiatric services: responsiveness to change of the General Practitioner Experiences Questionnaire (GPEQ)

<p>Abstract</p> <p>Background</p> <p>Instruments have been developed to assess professional views of the quality of care but have rarely been tested for responsiveness to change. The objective of this study was to test the responsiveness of the General Practitioner Experiences Questionnaire (GPEQ) for the measurement of Community Mental Health Centres in Norway.</p> <p>Methods</p> <p>National surveys were conducted in Norway in 2006 (n = 2,415) and 2008 (n = 2,209) to measure general practitioners' evaluation of community mental health centres. GPs evaluated the centres by means of a postal questionnaire, consisting of questions focused on centre quality and cooperation with GPs. As part of the national surveys 75 GPs in 2006 and 66 GPs in 2008 evaluated Hamar community mental health centre. Between the surveys, several quality improvement initiatives were implemented which were directed at cooperation with and guidance for GPs in Stange municipality, one of eight municipalities in Hamar centre catchment area. The main outcome measures were changes in GPEQ scores from 2006 to 2008 for GPs evaluating Hamar community mental health centre from Stange municipality, and changes in scores for GPs in the other seven municipalities and nationally which were assessed for statistical significance.</p> <p>Results</p> <p>GPs in Stange municipality rated Hamar community mental health centre significantly better on the guidance scale in 2008 than in 2006; on a 0-100 scale where 100 represents the best possible experiences the score was 26.5 in 2006 and 58.3 in 2008 (p < 0.001). Apart from one item about workforce situation, none of the other scales and items showed significant changes. The control group from the other seven municipalities gave significantly poorer rating for the emergency situation scale, the workforce situation scale and seven items in 2008 than in 2006. The national results showed small differences between 2006 and 2008, even though several scales and items were significantly different. A question about changes in centre performance over the last 2-3 years showed that 82% of GPs from Stange municipality reported that Hamar community mental health centre had improved, compared to only 36% from the other seven municipalities and 40% nationally which was statistically significant.</p> <p>Conclusions</p> <p>Following the implementation of an initiative designed to enhance service quality, the GPEQ identified expected changes in the guidance scale for the intervention group, indicating that the instrument is responsive to change. The worsening of services for GPs in the control group evaluating Hamar centre warrants further study.</p