Sensitivity to initial conditions in self-organized critical systems

We discuss sensitivity to initial conditions in a model for avalanches in granular media displaying self-organized criticality. We show that damage, due to a small perturbation in initial conditions, does not spread. The damage persists in a statistically time-invariant and scale-free form. We argue that the origin of this behavior is the Abelian nature of the model, which generalizes our results to all Abelian models, including the BTW model and the Manna model. An ensemble average of the damage leads to seemingly time dependent damage spreading. Scaling arguments show that this numerical result is due to the time lag before avalanches reach the initial perturbation.Comment: 4 pages, 4 figures, submitted to Physical Review Letter

Chronic Inflammation, Cardiorespiratory Fitness, and Dietary Inflammatory Index in Cancer Survivors

Chronic inflammation has been linked to the development and progression of cancer. Age, body composition, cardiorespiratory fitness, and dietary factors are associated with a global marker of inflammation, c-reactive protein (CRP), in healthy populations. However, few studies have explored the relationship between these variables with physically active cancer survivors. PURPOSE: To examine differences in fitness, and dietary characteristics of active cancer survivors when grouped according to serum CRP (Low vs. Moderate to High). METHODS: Cancer survivors (N = 14, mean age = 66 ± 15 years) were evaluated for body mass index (BMI), body composition, and cardiorespiratory fitness (VO2peak). Diet logs (3 day) were analyzed and the dietary inflammatory index (DII) for each subject was obtained. Serum CRP was evaluated with an enzyme linked immunosorbent assay (ELISA). Subjects were assigned to one of two groups based on their serum CRP concentrations: Low CRP (= 1 mg/L) (LO) (N = 7) or Moderate to High (CRP \u3e 1 mg/L) (MH) (N = 7). A t-test was used to compare LO and MH groups. Data are presented as mean ± SD. RESULTS: MH had significantly higher BMI (kg/m2) (HM 30 ± 5.2 vs. LO 24 ± 8.8, p = 0.02), higher body fat percentage (40.3 ± 7.77 vs. 32.4 ± 5.34, p = 0.05), and lower VO2peak values (mL/kg/min) (19.4 ± 5.54 vs. 31.8 ± 2.70, p = 0.0002). There were no significant differences between LO and HM with respect to age, caloric intake, or DII. CONCLUSION: Cancer survivors with moderate to high serum concentrations of CRP had higher BMI, more body fat and lower cardiorespiratory fitness. These data suggest that interventions aimed at reducing body fat and improving cardiorespiratory fitness may be useful in controlling chronic inflammation as defined by serum CRP concentrations in cancer survivors

The 1868 St. Landry Massacre: Reconstruction\u27s Deadliest Episode of Violence

The St. Landry Massacre is representative of the pervasive violence and intimidation in the South during the 1868 presidential canvass and represented the deadliest incident of racial violence during the Reconstruction Era. Southern conservatives used large scale collective violence in 1868 as a method to gain political control and restore the antebellum racial hierarchy. From 1865-1868, these Southerners struggled against the federal government, carpetbaggers, and Southern black populations to gain this control, but had largely failed in their attempts. After the First Reconstruction Act of March, 1867 forced Southern governments to accept universal male suffrage, Southern conservatives utilized violence and intimidation to achieve their goals, which escalated as the 1868 presidential election neared. Violence was nearly omnipresent in Louisiana during the presidential canvass and was the primary reason behind the Democratic victory in the state. This violence not only succeeded in its initial goal of securing a victory for the Democratic Party during the 1868 presidential election, but long term consequences also arose. Louisiana responded to the violence with a series of election laws, one creating the Returning Board on Elections, a potentially corrupt committee that could decide elections in the state by invalidating votes it deemed to be obtained by fraud. Nationally, the First Enforcement Act protected black voters and rights granted by previous reconstruction legislation. St. Landry Parish illustrates the local shift of power after 1868, where an instance of conservative boss rule occurred and the parish Republican Party was unable to fully recover for the remainder of Reconstruction. By 1874, conservative Democratic control was so complete in St. Landry that it became home to Louisiana\u27s first White League. Although 1868 was the peak of Reconstruction Era violence, conservative Democrats resorted to force when other attempts at regional control failed for the remainder of the period

Universality Class of One-Dimensional Directed Sandpile Models

A general n-state directed `sandpile' model is introduced. The stationary properties of the n-state model are derived for n < infty, and analytical arguments based on a central limit theorem show that the model belongs to the universality class of the totally asymmetric Oslo model, with a crossover to uncorrelated branching process behavior for small system sizes. Hence, the central limit theorem allows us to identify the existence of a large universality class of one-dimensional directed sandpile models.Comment: 4 pages, 2 figure

Microphysical and macrophysical responses of marine stratocumulus polluted by underlying ships

2012 Summer.Includes bibliographical references.Multiple sensors flying in the A-train constellation of satellites were used to determine the extent to which aerosol plumes from ships passing below marine stratocumulus alter the microphysical and macrophysical properties of the clouds. Aerosol plumes generated by ships sometimes influence cloud microphysical properties (effective radius) and, to a largely undetermined extent, cloud macrophysical properties (liquid water path, coverage, depth, precipitation, and longevity). Aerosol indirect effects were brought into focus, using observations from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and the 94-GHZ radar onboard CloudSat. To assess local cloud scale responses to aerosol, the locations of over one thousand ship tracks coinciding with the radar were meticulously logged by hand from the Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. MODIS imagery was used to distinguish ship tracks that were embedded in closed, open, and unclassifiable mesoscale cellular cloud structures. The impact of aerosol on the microphysical cloud properties in both the closed and open cell regimes were consistent with the changes predicted by the Twomey hypothesis. For the macrophysical changes, differences in the sign and magnitude of these properties were observed between cloud regimes. The results demonstrate that the spatial extent of rainfall (rain cover fraction) and intensity decrease in the clouds contaminated by the ship plume compared to the ambient pristine clouds. Although reductions of precipitation were common amongst the clouds with detectable rainfall (72% of cases), a substantial fraction of ship tracks (28% of cases) exhibited the opposite response. The sign and strength of the response was tied to the type of stratocumulus (e.g., closed vs open cells), depth of the boundary layer, and humidity in the free-troposphere. When closed cellular clouds were identified, liquid water path, drizzle rate, and rain cover fraction (an average relative decrease of 61%) was significantly smaller in the ship-contaminated clouds. Differences in drizzle rate resulted primarily from the reductions in rain cover fraction (i.e., fewer pixels were identified with rain in the clouds polluted by the ship). The opposite occurred in the open cell regime. Ship plumes ingested into this regime resulted in significantly deeper and brighter clouds with higher liquid water amounts and rain rates. Enhanced rain rates (average relative increase of 89%) were primarily due to the changes in intensity (i.e., rain rates on the 1.1 km pixel scale were higher in the ship contaminated clouds) and, to a lesser extent, rain cover fraction. One implication for these differences is that the local aerosol indirect radiative forcing was more than five times larger for ship tracks observed in the open cell regime (-59 W m-2) compared to those identified in the closed cell regime (-12 W m-2). The results presented here underline the need to consider the mesoscale structure of stratocumulus when examining the cloud dynamic response to changes in aerosol concentration. In the final part of the dissertation, the focus shifted to the climate scale to examine the impact of shipping on the Earth's radiation budget. Two studies were employed, in the first; changes to the radiative properties of boundary layer clouds (i.e., cloud top heights less than 3 km) were examined in response to the substantial decreases in ship traffic that resulted from the recent world economic recession in 2008. Differences in the annually averaged droplet effective radius and top of atmosphere outgoing shortwave radiative flux between 2007 and 2009 did not manifest as a clear response in the climate system and, was probably masked either due to competing aerosol cloud feedbacks or by interannual climate variability. In the second study, a method was developed to estimate the radiative forcing from shipping by convolving lanes of densely populated ships onto the global distributions of closed and open cell stratocumulus clouds. Closed cells were observed more than twice as often as open cells. Despite the smaller abundance of open cells, a significant portion of the radiative forcing from shipping was claimed by this regime. On the whole, the global radiative forcing from ship tracks was small (approximately -0.45 mW m-2) compared to the radiative forcing associated with the atmospheric buildup of anthropogenic CO2

A Method for Measuring Programmatic Dependency and Interdependency between DoD Acquisition Programs

There is currently no accepted method for quantitative measurement of acquisition program interdependency. While some methods exist for measuring dependency or interdependency at the component or system level, these methods do not translate well to program interdependency measurement. The objective of this thesis is to provide a model for measuring acquisition program interdependency accurately and quantitatively. The model presented in this thesis uses four Interdependency Factors to identify dependency relationships between programs. Specific Interdependency Levels are then used to measure the strengths of those dependencies. The model also accounts for measurement of dependencies upon programs that are not directly connected, i.e., programs that have a degree of separation from another program, and measurement of program criticality, or the extent to which a program is depended-upon. In this thesis, the measurement model is applied to an example program to measure program dependency characteristics. The results demonstrate that the model can be effectively used to identify and measure program dependencies. The model gives the program manager a quantitative tool to determine how much a program depends upon other programs and the potential impacts of those dependencies. With this information, program managers can better protect against vulnerabilities associated with interdependent effects from other program

Comparison of academic performance of twins and singletons in adolescence : follow-up study

Objectives To determine whether twins in recent cohorts show similar academic performance in adolescence to singletons and to test the effect of birth weight on academic performance in twins and singletons. Design Follow-up study. Setting Denmark. Participants All twins (n = 3411) and a 5% random sample of singletons (n = 7796) born in Denmark during 1986-8. Main outcome measures Test scores in ninth grade (age 15 or 16), birth weight, gestational age at birth, parents’ age, and parents’ education. Results Ninth grade test scores were normally distributed, with almost identical mean and standard deviations for twins and singletons (8.02 v 8.02 and 1.05 v 1.06) despite the twins weighing on average 908 g (95% confidence interval 886 to 930 g) less than the singletons at birth. Controlling for birth weight, gestational age at birth, age at test, and parents’ age and education confirmed the similarity of test scores for twins and singletons (difference 0.04, 95% confidence interval − 0.03 to 0.10). A significant, positive association between test score and birth weight was observed in both twins and singletons, but the size of the effect was small: 0.06-0.12 standard deviations for every kilogram increase in birth weight. Conclusions Although older cohorts of twins have been found to have lower mean IQ scores than singletons, twins in recent Danish cohorts show similar academic performance in adolescence to that of singletons. Birth weight has a minimal effect on academic performance in recent cohorts; for twins this effect is best judged relative to what is a normal birth weight for twins and not for singletons