426 research outputs found
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 for one data center, and by for geo-distributed
data centers together with request routing.Comment: 12 page
A medium voltage DC testbed for ship power system research
Medium voltage dc distribution systems are currently of interest for future naval warships. In order to provide hardware validation for research associated with the development of these systems, a low power Medium Voltage DC Testbed (MVDCT) is being constructed. This paper documents the system being constructed and provides some initial test results
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
Statistical-mechanical lattice models for protein-DNA binding in chromatin
Statistical-mechanical lattice models for protein-DNA binding are well
established as a method to describe complex ligand binding equilibriums
measured in vitro with purified DNA and protein components. Recently, a new
field of applications has opened up for this approach since it has become
possible to experimentally quantify genome-wide protein occupancies in relation
to the DNA sequence. In particular, the organization of the eukaryotic genome
by histone proteins into a nucleoprotein complex termed chromatin has been
recognized as a key parameter that controls the access of transcription factors
to the DNA sequence. New approaches have to be developed to derive statistical
mechanical lattice descriptions of chromatin-associated protein-DNA
interactions. Here, we present the theoretical framework for lattice models of
histone-DNA interactions in chromatin and investigate the (competitive) DNA
binding of other chromosomal proteins and transcription factors. The results
have a number of applications for quantitative models for the regulation of
gene expression.Comment: 19 pages, 7 figures, accepted author manuscript, to appear in J.
Phys.: Cond. Mat
Incremental testing of the Community Multiscale Air Quality (CMAQ) modeling system version 4.7
This paper describes the scientific and structural updates to the latest release of the Community Multiscale Air Quality (CMAQ) modeling system version 4.7 (v4.7) and points the reader to additional resources for further details. The model updates were evaluated relative to observations and results from previous model versions in a series of simulations conducted to incrementally assess the effect of each change. The focus of this paper is on five major scientific upgrades: (a) updates to the heterogeneous N<sub>2</sub>O<sub>5</sub> parameterization, (b) improvement in the treatment of secondary organic aerosol (SOA), (c) inclusion of dynamic mass transfer for coarse-mode aerosol, (d) revisions to the cloud model, and (e) new options for the calculation of photolysis rates. Incremental test simulations over the eastern United States during January and August 2006 are evaluated to assess the model response to each scientific improvement, providing explanations of differences in results between v4.7 and previously released CMAQ model versions. Particulate sulfate predictions are improved across all monitoring networks during both seasons due to cloud module updates. Numerous updates to the SOA module improve the simulation of seasonal variability and decrease the bias in organic carbon predictions at urban sites in the winter. Bias in the total mass of fine particulate matter (PM<sub>2.5</sub>) is dominated by overpredictions of unspeciated PM<sub>2.5</sub> (PM<sub>other</sub>) in the winter and by underpredictions of carbon in the summer. The CMAQv4.7 model results show slightly worse performance for ozone predictions. However, changes to the meteorological inputs are found to have a much greater impact on ozone predictions compared to changes to the CMAQ modules described here. Model updates had little effect on existing biases in wet deposition predictions
Long-term trends in total inorganic nitrogen and sulfur deposition in the US from 1990 to 2010
Excess deposition (including both wet and dry deposition) of nitrogen and
sulfur is detrimental to ecosystems. Recent studies have investigated the
spatial patterns and temporal trends of nitrogen and sulfur wet deposition,
but few studies have focused on dry deposition due to the scarcity of dry
deposition measurements. Here, we use long-term model simulations from the
coupled Weather Research and Forecasting and the Community Multiscale Air
Quality (WRF-CMAQ) model covering the period from 1990 to 2010 to study
changes in spatial distribution as well as temporal trends in total (TDEP),
wet (WDEP), and dry deposition (DDEP) of total inorganic nitrogen (TIN) and
sulfur (TS) in the United States (US). We first evaluate the model's
performance in simulating WDEP over the US by comparing the model results
with observational data from the US National Atmospheric Deposition Program.
The coupled model generally underestimates the WDEP of both TIN (including
both the oxidized nitrogen deposition, TNO3, and the reduced
nitrogen deposition, NHx) and TS, with better performance in
the eastern US than the western US. The underestimation of the wet deposition
by the model is mainly caused by the coarse model grid resolution, missing
lightning NOx emissions, and the poor temporal and spatial
representation of NH3 emissions. TDEP of both TIN and TS shows
significant decreases over the US, especially in the east, due to the large
emission reductions that occurred in that region. The decreasing trends of
TIN TDEP are caused by decreases in TNO3, and the increasing trends
of TIN deposition over the Great Plains and Tropical Wet Forests (Southern
Florida Coastal Plain) regions are caused by increases in NH3
emissions, although it should be noted that these increasing trends are not
significant. TIN WDEP shows decreasing trends throughout the US, except for
the Marine West Coast Forest region. TIN DDEP shows significant decreasing
trends in the Eastern Temperate Forests, Northern Forests, Mediterranean
California, and Marine West Coast Forest and significant increasing trends in the Tropical Wet Forests,
Great Plains and Southern Semi-arid Highlands. For the other three regions
(North American Deserts, Temperate Sierras, and Northwestern Forested
Mountains), the decreasing or increasing trends are not significant. Both the WDEP and DDEP of TS have
decreases across the US, with a larger decreasing trend in the DDEP than that
in the WDEP. Across the US during the 1990–2010 period, DDEP of TIN
accounts for 58–65 % of TDEP
of TIN. TDEP of TIN over the US is
dominated by deposition of TNO3 during the first decade, which then
shifts to reduced nitrogen
(NHx) dominance after 2003, resulting from a combination of
NOx emission reductions and NH3 emission
increases. The sulfur DDEP is
usually higher than the sulfur WDEP until recent years, as the sulfur DDEP
has a larger decreasing trend than
WDEP
How ready are communities to implement actions to improve diets of adolescent girls and women in urban Ghana?
Background
Ghana has reached an advanced stage of nutrition transition, contributing to an increase in nutrition-related non-communicable diseases, particularly amongst urban women. Community involvement is an important factor in the success of efforts to promote healthy eating. The readiness of populations to accept a range of interventions needs to be understood before appropriate interventions can be implemented. Therefore, this study assessed how ready urban communities are to improve diets of women of reproductive age in Ghana.
Methods
Using the Community Readiness Model (CRM), in-depth interviews were conducted with 24 key informants from various sectors in low income communities across two cities in Ghana: Accra and Ho. The CRM consists of 36 open questions addressing five readiness dimensions (community knowledge of efforts, leadership, community climate, knowledge of the issue and resources). Interviews were scored using the CRM protocol with a maximum of 9 points per dimension (from 1 = no awareness to 9 = high level of community ownership). Thematic analysis was undertaken to gain insights of community factors that could affect the implementation of interventions to improve diets.
Results
The mean community readiness scores indicated that both communities were in the “vague awareness stage” (3.35 ± 0.54 (Accra) and 3.94 ± 0.41 (Ho)). CRM scores across the five dimensions ranged from 2.65–4.38/9, ranging from denial/resistance to pre-planning. In both communities, the mean readiness score for ‘knowledge of the issue’ was the highest of all dimensions (4.10 ± 1.61 (Accra); 4.38 ± 1.81 (Ho)), but was still only at the pre-planning phase. The lowest scores were found for community knowledge of efforts (denial/resistance; 2.65 ± 2.49 (Accra)) and resources (vague awareness; 3.35 ± 1.03 (Ho)). The lack of knowledge of the consequences of unhealthy diets, misconceptions of the issue partly from low education, as well as challenges faced from a lack of resources to initiate/sustain programmes explained the low readiness.
Conclusions
Despite recognising that unhealthy diets are a public health issue in these urban Ghanaian communities, it is not seen as a priority. The low community readiness ratings highlight the need to increase awareness of the issue prior to intervening to improve diets
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