204 research outputs found
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Large-scale sea surface temperature variability from satellite and shipboard measurements
A series of satellite sea surface temperature (SST) intercomparison workshops were conducted under NASA sponsorship at the Jet Propulsion Laboratory. Three different satellite data sets were compared with each other, with routinely collected ship data, and with climatology for the months of November 1979, December 1981, March 1982, and July 1982. The three satellite data sets were (1) AVHRR-SST estimates produced operationally by the National Oceanic and Atmospheric Administration from the advanced very high resolution radiometer aboard the NOAA polar-orbiting weather satellites; (2) HIRS/MSU-SST estimates produced by a research group at the NASA Goddard Space Flight Center from the 20-channel high resolution infrared sounder and the 4-channel microwave sounding unit, also aboard the NOAA satellites; and (3) SMMR-SST estimates produced by another group at Goddard from the scanning multifrequency microwave radiometer on the NASA research satellite Nimbus 7. The satellite and ship data were differenced against an accepted climatology to produce anomalies, which in turn were spatially and temporally averaged into 2° latitude-longitude, 1-month bins. Monthly statistics on the satellite and ship bin average SST yielded rms differences ranging from 0.58° to 1.37°C and mean differences ranging from -0.48° to 0.72°C, varying substantially from month to month and sensor to sensor. The SMMR generally had the largest rms differences and time-dependent biases, while the AVHRR and HIRS/MSU had smaller more comparable values. The monthly bins were further smoother spatially to correspond to 600-km averages to further suppress the noise of individual observations, particularly for the ship data. When this was done the monthly ship data standard deviations about climatology varied between 0.35° and 0.63°C. Taking these values as true SST signal standard deviation levels, and the satellite-ship rms differences as noise levels, results in signal-to-noise variance ratios of about 0.25 for SMMR and 1.0 for AVHRR and HIRS/MSU. Maps of SST anomaly reveal a complex pattern of partial agreement and disagreement between ship and satellite data. Maps of satellite minus ship and satellite minus satellite SST differences were often dominated by coherent large-scale patterns of obvious geophysical origin related to distributions of surface wind speed, atmospheric water vapor, cloudiness, and stratospheric aerosols. Unfortunately, the spatial scales of these patterns are often quite similar to those associated with actual SST anomalies. Caution must therefore be exercised when dealing with the satellite data so that errors are not misinterpreted as true SST anomalies
Two factor saturated designs: cycles, Gini index and state polytopes
In this paper we analyze and characterize the saturated fractions of two-factor designs under the simple effect model. Using Li et al.ear algebra, we define a criterion to check whether a given fraction is saturated or not. We also compute the number of saturated fractions, providing an alternative proof of the Cayley's formula. Finally we show how, given a list of saturated fractions, Gini indexes of their margins and the associated state polytopes could be used to classify them
Nonlinear Integer Programming
Research efforts of the past fifty years have led to a development of linear
integer programming as a mature discipline of mathematical optimization. Such a
level of maturity has not been reached when one considers nonlinear systems
subject to integrality requirements for the variables. This chapter is
dedicated to this topic.
The primary goal is a study of a simple version of general nonlinear integer
problems, where all constraints are still linear. Our focus is on the
computational complexity of the problem, which varies significantly with the
type of nonlinear objective function in combination with the underlying
combinatorial structure. Numerous boundary cases of complexity emerge, which
sometimes surprisingly lead even to polynomial time algorithms.
We also cover recent successful approaches for more general classes of
problems. Though no positive theoretical efficiency results are available, nor
are they likely to ever be available, these seem to be the currently most
successful and interesting approaches for solving practical problems.
It is our belief that the study of algorithms motivated by theoretical
considerations and those motivated by our desire to solve practical instances
should and do inform one another. So it is with this viewpoint that we present
the subject, and it is in this direction that we hope to spark further
research.Comment: 57 pages. To appear in: M. J\"unger, T. Liebling, D. Naddef, G.
Nemhauser, W. Pulleyblank, G. Reinelt, G. Rinaldi, and L. Wolsey (eds.), 50
Years of Integer Programming 1958--2008: The Early Years and State-of-the-Art
Surveys, Springer-Verlag, 2009, ISBN 354068274
Tracking Official Development Assistance for Reproductive Health in Conflict-Affected Countries
Preeti Patel and colleagues report inequity in the disbursement of official development assistance for reproductive health between countries affected by conflict and those unaffected
Effects of Dietary Restriction on Cancer Development and Progression
The effects of caloric restriction on tumor growth and progression are known for
over a century. Indeed, fasting has been practiced for millennia, but just recently
has emerged the protective role that it may exert toward cells. Fasting cycles are
able to reprogram the cellular metabolism, by inducing protection against oxidative
stress and prolonging cellular longevity. The reduction of calorie intake as
well as short- or long-term fasting has been shown to protect against chronic and
degenerative diseases, such as diabetes, cardiovascular pathologies, and cancer.
In vitro and in vivo preclinical models showed that different restriction dietary
regimens may be effective against cancer onset and progression, by enhancing
therapy response and reducing its toxic side effects. Fasting-mediated beneficial
effects seem to be due to the reduction of inflammatory response and downregulation
of nutrient-related signaling pathways able to modulate cell proliferation
and apoptosis. In this chapter, we will discuss the most significant studies
present in literature regarding the molecular mechanisms by which dietary
restriction may contribute to prevent cancer onset, reduce its progression, and
positively affect the response to the treatments
Leadership and style in the French Fifth Republic:Nicolas Sarkozy’s presidency in historical and cultural perspective
This article contributes to the body of the developing theoretical research in leadership and presidential studies by adding analysis of what I have termed ‘comportmental style’ as a factor in leader/follower relations. Within institutionalism and the wider structure/agency debate in political science, one of the challenges as regards the study of leadership is to identify factors that offer scope to or else militate against leaders’ performance. The comportmental style of Nicolas Sarkozy (President of the French Republic 2007–2012), deployed in the context of the – changing – institution of the presidency, was a major factor in his extreme unpopularity, and contributed to his defeat in 2012. What this tells us about the nature of the changing French presidency and the role of style will be discussed in the conclusion
Effects of social approval bias on self-reported fruit and vegetable consumption: a randomized controlled trial
<p>Abstract</p> <p>Background</p> <p>Self-reports of dietary intake in the context of nutrition intervention research can be biased by the tendency of respondents to answer consistent with expected norms (social approval bias). The objective of this study was to assess the potential influence of social approval bias on self-reports of fruit and vegetable intake obtained using both food frequency questionnaire (FFQ) and 24-hour recall methods.</p> <p>Methods</p> <p>A randomized blinded trial compared reported fruit and vegetable intake among subjects exposed to a potentially biasing prompt to that from control subjects. Subjects included 163 women residing in Colorado between 35 and 65 years of age who were randomly selected and recruited by telephone to complete what they were told would be a future telephone survey about health. Randomly half of the subjects then received a letter prior to the interview describing this as a study of fruit and vegetable intake. The letter included a brief statement of the benefits of fruits and vegetables, a 5-A-Day sticker, and a 5-a-Day refrigerator magnet. The remainder received the same letter, but describing the study purpose only as a more general nutrition survey, with neither the fruit and vegetable message nor the 5-A-Day materials. Subjects were then interviewed on the telephone within 10 days following the letters using an eight-item FFQ and a limited 24-hour recall to estimate fruit and vegetable intake. All interviewers were blinded to the treatment condition.</p> <p>Results</p> <p>By the FFQ method, subjects who viewed the potentially biasing prompts reported consuming more fruits and vegetables than did control subjects (5.2 vs. 3.7 servings per day, p < 0.001). By the 24-hour recall method, 61% of the intervention group but only 32% of the control reported eating fruits and vegetables on 3 or more occasions the prior day (p = 0.002). These associations were independent of age, race/ethnicity, education level, self-perceived health status, and time since last medical check-up.</p> <p>Conclusion</p> <p>Self-reports of fruit and vegetable intake using either a food frequency questionnaire or a limited 24-hour recall are both susceptible to substantial social approval bias. Valid assessments of intervention effects in nutritional intervention trials may require objective measures of dietary change.</p
Political leadership and the politics of performance:France, Syria and the chemical weapons crisis of 2013
This article draws upon developments in UK research on political rhetoric and political performance in order to examine the incident in 2013 when French President François Hollande committed French forces to a US-led punitive strike against Syria, after the use of chemical weapons in a Damascus suburb on 21 August. The US-led retaliation did not take place. This article analyses Hollande's declaration on 27 July and his TV appearance on 15 September. His rhetoric and style are best understood as generic to the nature of the presidential office of the Fifth Republic. The article concludes by appraising how analysis of the French case contributes to the developing literature on rhetoric, celebrity and performance
Adiponectin Haploinsufficiency Promotes Mammary Tumor Development in MMTV-PyVT Mice by Modulation of Phosphatase and Tensin Homolog Activities
Background: Adiponectin is an adipokine possessing beneficial effects on obesity-related medical complications. A negative association of adiponectin levels with breast cancer development has been demonstrated. However, the precise role of adiponectin deficiency in mammary carcinogenesis remains elusive. Methodology/Principal Findings: In the present study, MMTV-polyomavirus middle T antigen (MMTV-PyVT) transgenic mice with reduced adiponectin expressions were established and the stromal effects of adiponectin haploinsufficiency on mammary tumor development evaluated. In mice from both FVB/N and C57BL/6J backgrounds, insufficient adiponectin production promoted mammary tumor onset and development. A distinctive basal-like subtype of tumors, with a more aggressive phenotype, was derived from adiponectin haplodeficient MMTV-PyVT mice. Comparing with those from control MMTV-PyVT mice, the isolated mammary tumor cells showed enhanced tumor progression in re-implanted nude mice, accelerated proliferation in primary cultures, and hyperactivated phosphatidylinositol-3-kinase (PI3K)/Akt/beta-catenin signaling, which at least partly attributed to the decreased phosphatase and tensin homolog (PTEN) activities. Further analysis revealed that PTEN was inactivated by a redox-regulated mechanism. Increased association of PTEN-thioredoxin complexes was detected in tumors derived from mice with reduced adiponectin levels. The activities of thioredoxin (Trx1) and thioredoxin reductase (TrxR1) were significantly elevated, whereas treatment with either curcumin, an irreversible inhibitor of TrxR1, or adiponectin largely attenuated their activities and resulted in the re-activation of PTEN in these tumor cells. Moreover, adiponectin could inhibit TrxR1 promoter-mediated transcription and restore the mRNA expressions of TrxR1. Conclusion: Adiponectin haploinsufficiency facilitated mammary tumorigenesis by down-regulation of PTEN activity and activation of PI3K/ Akt signalling pathway through a mechanism involving Trx1/TrxR1 redox regulations. © 2009 Lam et al.published_or_final_versio
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