Reducing Electricity Demand Charge for Data Centers with Partial Execution

Data centers consume a large amount of energy and incur substantial electricity cost. In this paper, we study the familiar problem of reducing data center energy cost with two new perspectives. First, we find, through an empirical study of contracts from electric utilities powering Google data centers, that demand charge per kW for the maximum power used is a major component of the total cost. Second, many services such as Web search tolerate partial execution of the requests because the response quality is a concave function of processing time. Data from Microsoft Bing search engine confirms this observation. We propose a simple idea of using partial execution to reduce the peak power demand and energy cost of data centers. We systematically study the problem of scheduling partial execution with stringent SLAs on response quality. For a single data center, we derive an optimal algorithm to solve the workload scheduling problem. In the case of multiple geo-distributed data centers, the demand of each data center is controlled by the request routing algorithm, which makes the problem much more involved. We decouple the two aspects, and develop a distributed optimization algorithm to solve the large-scale request routing problem. Trace-driven simulations show that partial execution reduces cost by $3\%--10.5\%$ for one data center, and by $15.5\%$ for geo-distributed data centers together with request routing.Comment: 12 page

Intrinsically Bent DNA in the Promoter Regions of the Yeast GAL1–10 and GAL80 Genes

Circular permutation analysis has detected fairly strong sites of intrinsic DNA bending on the promoter regions of the yeast GAL1–10 and GAL80 genes. These bends lie in functionally suggestive locations. On the promoter of the GAL1–10 structural genes, strong bends bracket nucleosome B, which lies between the UASG and the GAL1 TATA. These intrinsic bends could help position nucleosome B. Nucleosome B plus two other promoter nucleosomes protect the TATA and start site elements in the inactive state of expression but are completely disrupted (removed) when GAL1–10 expression is induced. The strongest intrinsic bend (;70°) lies at the downstream edge of nucleosome B; this places it approximately 30 base pairs upstream of the GAL1 TATA, a position that could allow it to be involved in GAL1 activation in several ways, including the recruitment of a yeast HMG protein that is required for the normally robust level of GAL1 expression in the induced state (Paull, T., Carey, M., and Johnson, R. (1996) Genes Dev. 10, 2769–2781). On the regulatory gene GAL80, the single bend lies in the non-nucleosomal hypersensitive region, between a GAL80-specific far upstream promoter element and the more gene-proximal promoter elements. GAL80 promoter region nucleosomes contain no intrinsically bent DNA

Distinguishing importation from diversification of quinolone-resistant Neisseria gonorrhoeae by molecular evolutionary analysis

<p>Abstract</p> <p>Background</p> <p>Distinguishing the recent introduction of quinolone resistant gonococci into a population from diversification of resistant strains already in the population is important for planning effective infection control strategies. We applied molecular evolutionary analyses to DNA sequences from 9 housekeeping genes and <it>gyrA</it>, <it>parC </it>and <it>porB </it>of 24 quinolone resistant <it>N. gonorrhoeae </it>(QRNG) and 24 quinolone sensitive isolates collected in Israel during 2000–2001.</p> <p>Results</p> <p>Phylogenetic and eBURST analyses and estimates of divergence time indicated QRNG were introduced on 3 separate occasions and underwent limited diversification by mutation, deletion and horizontal gene transfer. Reconstruction of <it>N. gonorrhoeae </it>demography showed a slowly declining effective strain population size from 1976 to 1993, rapid decline between 1994 and 1999, and an increase from 1999 to 2001. This is partially attributable to declining gonorrhea case rates from 1973 to 1994. Additional contributing factors are selective sweeps of antibiotic resistant gonococci and increased transmission from sex workers. The abrupt decline in the mid-1990s heralded an increased incidence of gonorrhea from 1997 to the present. The subsequent increase in effective strain population size since 1999 reflects the increased gonococcal census population and introduction of quinolone resistance strains.</p> <p>Conclusion</p> <p>Our study demonstrates the effective use of population genetic approaches to assess recent and historical population dynamics of <it>N. gonorrhoeae</it>.</p

Projections of Atmospheric Nitrogen Deposition to the Chesapeake Bay Watershed

Atmospheric deposition is among the largest pathways of nitrogen loading to the Chesapeake Bay Watershed (CBW). The interplay between future climate and emission changes in and around the CBW will likely shift the future nutrient deposition abundance and chemical regime (e.g., oxidized vs. reduced nitrogen). In this work, a Representative Concentration Pathway from the Community Earth System Model is dynamically downscaled using a recently updated Weather Research and Forecasting model that subsequently drives the Community Multiscale Air Quality model coupled to the agroeconomic Environmental Policy Integrated Climate model. The relative impacts of emission and climate changes on atmospheric nutrient deposition are explored for a recent historical period and a period centered on 2050. The projected regional emissions in Community Multiscale Air Quality reflect current federal and state regulations, which use baseline and projected emission years 2011 and 2040, respectively. The historical simulations of 2-m temperature (T2) and precipitation (PRECIP) have cool and dry biases, and temperature and PRECIP are projected to both increase. Ammonium wet deposition agrees well with observations, but nitrate wet deposition is underpredicted. Climate and deposition changes increase simulated future ammonium fertilizer application. In the CBW by 2050, these changes (along with widespread decreases in anthropogenic nitrogen oxide and sulfur oxide emissions, and relatively constant ammonia emissions) decrease total nitrogen deposition by 21%, decrease annual average oxidized nitrogen deposition by 44%, and increase reduced nitrogen deposition by 10%. These results emphasize the importance of decreased anthropogenic emissions on the control of future nitrogen loading to the Chesapeake Bay in a changing climate

The Candidate Intermediate-Mass Black Hole in the Globular Cluster M54

Ibata et al. reported evidence for density and kinematic cusps in the Galactic globular cluster M54, possibly due to the presence of a 9400 solar-mass black hole. Radiative signatures of accretion onto M54's candidate intermediate-mass black hole (IMBH) could bolster the case for its existence. Analysis of new Chandra and recent Hubble Space Telescope astrometry rules out the X-ray counterpart to the candidate IMBH suggested by Ibata et al. If an IMBH exists in M54, then it has an Eddington ratio of L(0.3-8 keV) / L(Edd) < 1.4 x 10^(-10), more similar to that of the candidate IMBH in M15 than that in G1. From new imaging with the NRAO Very Large Array, the luminosity of the candidate IMBH is L(8.5 GHz) < 3.6 x 10^29 ergs/s (3 sigma). Two background active galaxies discovered toward M54 could serve as probes of its intracluster medium.Comment: 4 pages; 2 figures; emulateapj.cls; to appear in A

Reactive astrocytes potentiate tumor aggressiveness in a murine glioma resection and recurrence model

Surgical resection is a universal component of glioma therapy. Little is known about the postoperative microenvironment due to limited preclinical models. Thus, we sought to develop a glioma resection and recurrence model in syngeneic immune-competent mice to understand how surgical resection influences tumor biology and the local microenvironment