© 2012 INFORMS Overflow Networks: Approximations and

Motivated by call center cosourcing problems, we consider a service network operated under an overflow mechanism. Calls are first routed to an in-house (or dedicated) service station that has a finite waiting room. If the waiting room is full, the call is overflowed to an outside provider (an overflow station) that might also be serving overflows from other stations. We establish approximations for overflow networks with many servers under a resource-pooling assumption that stipulates, in our context, that the fraction of overflowed calls is nonnegligible. Our two main results are (i) an approximation for the overflow processes via limit theorems and (ii) asymptotic independence between each of the in-house stations and the overflow station. In particular, we show that, as the system becomes large, the dependency between each in-house station and the overflow station becomes negligible. Independence between stations in overflow networks is assumed in the literature on call centers, and we provide a rigorous support for those useful heuristics. Subject classifications: overflow networks; cosourcing; heavy-traffic approximations; separation of time scales

Implications of insecticide resistance for malaria vector control with long-lasting insecticidal nets: trends in pyrethroid resistance during a WHO-coordinated multi-country prospective study.

BACKGROUND: Increasing pyrethroid resistance has been an undesirable correlate of the rapid increase in coverage of insecticide-treated nets (ITNs) since 2000. Whilst monitoring of resistance levels has increased markedly over this period, longitudinal monitoring is still lacking, meaning the temporal and spatial dynamics of phenotypic resistance in the context of increasing ITN coverage are unclear. METHODS: As part of a large WHO-co-ordinated epidemiological study investigating the impact of resistance on malaria infection, longitudinal monitoring of phenotypic resistance to pyrethroids was undertaken in 290 clusters across Benin, Cameroon, India, Kenya and Sudan. Mortality in response to pyrethroids in the major anopheline vectors in each location was recorded during consecutive years using standard WHO test procedures. Trends in mosquito mortality were examined using generalised linear mixed-effect models. RESULTS: Insecticide resistance (using the WHO definition of mortality < 90%) was detected in clusters in all countries across the study period. The highest mosquito mortality (lowest resistance frequency) was consistently reported from India, in an area where ITNs had only recently been introduced. Substantial temporal and spatial variation was evident in mortality measures in all countries. Overall, a trend of decreasing mosquito mortality (increasing resistance frequency) was recorded (Odds Ratio per year: 0.79 per year (95% CI: 0.79-0.81, P < 0.001). There was also evidence that higher net usage was associated with lower mosquito mortality in some countries. DISCUSSION: Pyrethroid resistance increased over the study duration in four out of five countries. Insecticide-based vector control may be compromised as a result of ever higher resistance frequencies

Implications of non-volatile memory as primary storage for database management systems

Traditional Database Management System (DBMS) software relies on hard disks for storing relational data. Hard disks are cheap, persistent, and offer huge storage capacities. However, data retrieval latency for hard disks is extremely high. To hide this latency, DRAM is used as an intermediate storage. DRAM is significantly faster than disk, but deployed in smaller capacities due to cost and power constraints, and without the necessary persistency feature that disks have. Non-Volatile Memory (NVM) is an emerging storage class technology which promises the best of both worlds. It can offer large storage capacities, due to better scaling and cost metrics than DRAM, and is non-volatile (persistent) like hard disks. At the same time, its data retrieval time is much lower than that of hard disks and it is also byte-addressable like DRAM. In this paper, we explore the implications of employing NVM as primary storage for DBMS. In other words, we investigate the modifications necessary to be applied on a traditional relational DBMS to take advantage of NVM features. As a case study, we have modified the storage engine (SE) of PostgreSQL enabling efficient use of NVM hardware. We detail the necessary changes and challenges such modifications entail and evaluate them using a comprehensive emulation platform. Results indicate that our modified SE reduces query execution time by up to 40% and 14.4% when compared to disk and NVM storage, with average reductions of 20.5% and 4.5%, respectively.The research leading to these results has received funding from the European Union’s 7th Framework Programme under grant agreement number 318633, the Ministry of Science and Technology of Spain under contract TIN2015-65316-P, and a HiPEAC collaboration grant awarded to Naveed Ul Mustafa.Peer ReviewedPostprint (author's final draft

Challenges for the euro area and implications for Latvia

This Policy Contribution reviews the major challenges faced by the euro area, and discusses recent initiatives and the way forward. Some implications are drawn out for Latviaâ??s euro accession, which is likely to be beneficial on balance. The euro area faces three major challenges: (1) high private and public debt in some of its parts together with a requirement for competitiveness adjustment that in some countries has barely started; (2) weak growth outlook; (3) continued banking-sector fragility that, with sovereign stress, feeds a negative feedback loop. The euro area has agreed many significant measures to overcome these problems, including the European Stability Mechanism and the fiscal compact. The 21 February agreement on Greece removes a major source of financial instability even though it is likely that further debt reductions will be needed. Significant concerns remain, the most important of which are the slow real economic adjustment and the largely unaddressed banking-sovereign fragility. The fiscal compact raises the issue of appropriate fiscal stabilisation tools at the euro-area level. Countries that will soon join the euro should actively shape the debate about the further development of the overall set-up. For Latvia, joining the euro makes sense because Latvia has kept its exchange rate fixed and has undergone internal adjustment. In its euro-area accession negotiations, Latvia should ensure that it does not participate in any of the currently ongoing financial assistance programmes. This Policy Contribution reproduces evidence given by Guntram B. Wolff to the Latvian parliamentâ??s European affairs committee, 22 February 2012.

Assessing the economic implications of Turkish accession to the EU

We explore the economic implications of Turkish accession to the European Union. We focus on three main changes associated with Turkish membership: (i) accession to the internal European Market; (ii) institutional reforms in Turkey triggered by EU-membership; and (iii) migration in response to the free movement of workers. Overall, the macroeconomic implications for EU countries are small but positive, through cheaper imports and the benefits from trade creation. Dutch exports increase by around 20% (550 million euro). Turkey experiences larger economic gains than the EU: consumption per capita is estimated to rise by about 4% as a result of accession to the internal market and free movement of labour. If Turkey would succeed in reforming its domestic institutions in response to EU-membership, economic growth in Turkey could increase more. In particular, tentative estimates suggest that consumption per capita in Turkey could rise by an additional 9%. These benefits would spill over to the EU. For instance, Dutch exports to Turkey would rise by another 1.8 billion euro and income by 500 million euro.

Rail Privatisation: Financial Implications

INTRODUCTION My aim in this brief paper is not to argue the case for or against privatisation, but rather to comment on the likely financial implications of some of the options. Nevertheless, it does not seem possible to do this without briefly reviewing the advantages and disadvantages that are claimed to flow hm privatisation. I will then consider the existing organisation and financial performance of British Rail. Following this, I will discuss alternative ways of achieving the necessary level of profitability for private investors to be interested in owning and operating the railway system

BMSSM Implications for Cosmology

The addition of non-renormalizable terms involving the Higgs fields to the MSSM (BMSSM) ameliorates the little hierarchy problem of the MSSM. We analyze in detail the two main cosmological issues affected by the BMSSM: dark matter and baryogenesis. The regions for which the relic abundance of the LSP is consistent with WMAP and collider constraints are identified, showing that the bulk region and other previously excluded regions are now permitted. Requiring vacuum stability limits the allowed regions. Based on a two-loop finite temperature effective potential analysis, we show that the electroweak phase transition can be sufficiently first order in regions that for the MSSM are incompatible with the LEP Higgs mass bound, including parameter values of \tan\beta \lsim 5, m_{\tilde{t}_{1}} > m_t, m_Q << TeV.Comment: 28 pages, 4 figures. References adde