Online Scheduling on Identical Machines using SRPT

Due to its optimality on a single machine for the problem of minimizing average flow time, Shortest-Remaining-Processing-Time (\srpt) appears to be the most natural algorithm to consider for the problem of minimizing average flow time on multiple identical machines. It is known that \srpt achieves the best possible competitive ratio on multiple machines up to a constant factor. Using resource augmentation, \srpt is known to achieve total flow time at most that of the optimal solution when given machines of speed $2- \frac{1}{m}$. Further, it is known that \srpt's competitive ratio improves as the speed increases; \srpt is $s$-speed $\frac{1}{s}$-competitive when $s \geq 2- \frac{1}{m}$. However, a gap has persisted in our understanding of \srpt. Before this work, the performance of \srpt was not known when \srpt is given (1+\eps)-speed when 0 < \eps < 1-\frac{1}{m}, even though it has been thought that \srpt is (1+\eps)-speed $O(1)$-competitive for over a decade. Resolving this question was suggested in Open Problem 2.9 from the survey "Online Scheduling" by Pruhs, Sgall, and Torng \cite{PruhsST}, and we answer the question in this paper. We show that \srpt is \emph{scalable} on $m$ identical machines. That is, we show \srpt is (1+\eps)-speed O(\frac{1}{\eps})-competitive for \eps >0. We complement this by showing that \srpt is (1+\eps)-speed O(\frac{1}{\eps^2})-competitive for the objective of minimizing the $\ell_k$-norms of flow time on $m$ identical machines. Both of our results rely on new potential functions that capture the structure of \srpt. Our results, combined with previous work, show that \srpt is the best possible online algorithm in essentially every aspect when migration is permissible.Comment: Accepted for publication at SODA. This version fixes an error in a preliminary versio

Characterizing Transition Temperature Gas in the Galactic Corona

We present a study of the properties of the transition temperature (T~10^5 K) gas in the Milky Way corona, based on measurements of OVI, NV, CIV, SiIV and FeIII absorption lines seen in the far ultraviolet spectra of 58 sightlines to extragalactic targets, obtained with Far-Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph. In many sightlines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly-ionized atoms are distributed irregularly in a layer with a scaleheight of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60 km/s. On average the integrated column densities are log N(OVI)=14.3, log N(NV)=13.5, log N(CIV)=14.2, log N(SiIV)=13.6 and log N(FeIII)=14.2, with a dispersion of just 0.2 dex in each case. In sightlines around the Galactic Center and Galactic North Pole all column densities are enhanced by a factor ~2, while at intermediate latitudes in the southern sky there is a deficit in N(OVI) of about a factor 2, but no deficit for the other ions. We compare the column densities and ionic ratios to a series of theoretical predictions: collisional ionization equilibrium, shock ionization, conductive interfaces, turbulent mixing, thick disk supernovae, static non-equilibrium ionization (NIE) radiative cooling and an NIE radiative cooling model in which the gas flows through the cooling zone. None of these models can fully reproduce the data, but it is clear that non-equilibrium ionization radiative cooling is important in generating the transition temperature gas.Comment: 99 pages, 11 figures, with appendix on Cooling Flow model; only a sample of 5 subfigures of figure 2 included - full set of 69 available through Ap

Plasma Leptin Levels and Incidence of Heart Failure, Cardiovascular Disease, and Total Mortality in Elderly Individuals

OBJECTIVE: Obesity predisposes individuals to congestive heart failure (CHF) and cardiovascular disease (CVD). Leptin regulates energy homeostasis, is elevated in obesity, and influences ventricular and vascular remodeling. We tested the hypothesis that leptin levels are associated with greater risk of CHF, CVD, and mortality in elderly individuals. RESEARCH DESIGN AND METHODS: We evaluated 818 elderly (mean age 79 years, 62% women) Framingham Study participants attending a routine examination at which plasma leptin was assayed. RESULTS: Leptin levels were higher in women and strongly correlated with BMI (P < 0.0001). On follow-up (mean 8.0 years), 129 (of 775 free of CHF) participants developed CHF, 187 (of 532 free of CVD) experienced a first CVD event, and 391 individuals died. In multivariable Cox regression models adjusting for established risk factors, log-leptin was positively associated with incidence of CHF and CVD (hazard ratio [HR] per SD increment 1.26 [95% CI 1.03–1.55] and 1.28 [1.09–1.50], respectively). Additional adjustment for BMI nullified the association with CHF (0.97 [0.75–1.24]) but only modestly attenuated the relation to CVD incidence (1.23 [1.00–1.51], P = 0.052). We observed a nonlinear, U-shaped relation between log-leptin and mortality (P = 0.005 for quadratic term) with greater risk of death evident at both low and high leptin levels. CONCLUSIONS: In our moderate-sized community-based elderly sample, higher circulating leptin levels were associated with a greater risk of CHF and CVD, but leptin did not provide incremental prognostic information beyond BMI. Additional investigations are warranted to elucidate the U-shaped relation of leptin to mortality.National Institutes of Health's National Heart, Lung, and Blood Institute (N01-HC25195, N01-HV28178, K24-HL04334, R01-DK080739

Oxidation of tertiary amine-derivatized surfaces to control protein adhesion

Selective oxidation of omega-tertiary amine self-assembled thiol monolayers to tertiary amine N-oxides is shown to transform the adhesion of model proteins lysozyme and fibrinogen upon them. Efficient preparation of both secondary and tertiary linker amides as judged by X-ray photoelectron spectroscopy (XPS) and water droplet contact angle was achieved with an improved amide bond formation on gold quartz crystal microbalance (QCM) sensors using 2-(1H-7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyl hexafluorophosphate methanaminium uronium (HATU). Oxidation with hydrogen peroxide was similarly assessed, and adhesion of lysozyme and fibrinogen from phosphate buffered saline was then assayed by QCM and imaged by AFM. Tertiary amine-functionalized sensors adsorbed multilayers of aggregated lysozyme, whereas tertiary amine N-oxides and triethylene glycol-terminated monolayers are consistent with small protein aggregates. The surface containing a dimethylamine N-oxide headgroup and ethyl secondary amide linker showed the largest difference in adsorption of both proteins. Oxidation of tertiary amine decorated surfaces therefore holds the potential for selective deposition of proteins and cells through masking and other patterning techniques

Addition of Inflammatory Biomarkers Did Not Improve Diabetes Prediction in the Community: The Framingham Heart Study

Background: Prior studies have reported conflicting findings with regard to the association of biomarkers in the prediction of incident type 2 diabetes. We evaluated 12 biomarkers as possible diabetes predictors in the Framingham Heart Study. Methods and results: Biomarkers representing inflammation (C-reactive protein, interleukin-6, monocyte chemoattractant protein-1, tumor necrosis factor receptor 2, osteoprotegerin, and fibrinogen), endothelial dysfunction (intercellular adhesion molecule-1), vascular damage (CD40-ligand, P-selectin, and lipoprotein-associated phospholipase A2 mass and activity), and oxidative stress (urinary isoprostanes) were measured in participants without diabetes attending the Offspring seventh (n=2499) or multiethnic Omni second (n=189) examination (1998–2001). Biomarkers were loge transformed and standardized. Multivariable logistic regression tested each biomarker in association with incident diabetes at a follow-up examination (the Offspring eighth and Omni third examination; mean 6.6 years later), with adjustment for age, sex, cohort, body mass index, fasting glucose, systolic blood pressure, high-density lipoprotein cholesterol, triglycerides, and smoking. C statistics were evaluated with and without inflammatory markers. In 2638 participants (56% women, mean age 59 years), 162 (6.1%) developed type 2 diabetes. All biomarkers, excluding osteoprotegerin, were associated with the outcome with adjustment for age, sex, and cohort; however, none remained significant after multivariable adjustment (all P>0.05). The c statistic from the model including only clinical covariates (0.89) did not statistically significantly improve after addition of biomarkers (all P>0.10). Conclusions: Biomarkers representing different inflammatory pathways are associated with incident diabetes but do not remain statistically significant after adjustment for established clinical covariates. Inflammatory biomarkers might not be an effective resource to predict type 2 diabetes in community-based samples

Systematic Blueshift of Line Profiles in the Type IIn Supernova 2010jl: Evidence for Post-Shock Dust Formation?

Type IIn SNe show spectral evidence for strong interaction between their blast wave and dense circumstellar material (CSM) around the progenitor star. SN2010jl was the brightest core-collapse SN in 2010, and it was a Type IIn explosion with strong CSM interaction. Andrews et al. recently reported evidence for an IR excess in SN2010jl, indicating either new dust formation or the heating of CSM dust in an IR echo. Here we report multi-epoch spectra of SN2010jl that reveal the tell-tale signature of new dust formation: emission-line profiles becoming systematically more blueshifted as the red side of the line is blocked by increasing extinction. The effect is seen clearly in the intermediate-width (400--4000 km/s) component of H$\alpha$ beginning roughly 30d after explosion. Moreover, we present near-IR spectra demonstrating that the asymmetry in the hydrogen-line profiles is wavelength dependent, appearing more pronounced at shorter wavelengths. This evidence suggests that new dust grains had formed quickly in the post-shock shell of SN 2010jl arising from CSM interaction. Since the observed dust temperature has been attributed to an IR echo and not to new dust, either (1) IR excess emission at $\lambda < 5 \mu$m is not a particularly sensitive tracer of new dust formation in SNe, or (2) some assumptions about expected dust temperatures might require further study. Lastly, we discuss one possible mechanism other than dust that might lead to increasingly blueshifted line profiles in SNeIIn, although the wavelength dependence of the asymmetry argues against this hypothesis in the case of SN2010jl.Comment: 6 pages, 4 figures, submitted to A

The COS-Dwarfs Survey: The Carbon Reservoir Around sub-L* Galaxies

We report new observations of circumgalactic gas from the COS-Dwarfs survey, a systematic investigation of the gaseous halos around 43 low-mass z $\leq$ 0.1 galaxies using background QSOs observed with the Cosmic Origins Spectrograph. From the projected 1D and 2D distribution of C IV absorption, we find that C IV absorption is detected out to ~ 0.5 R$_{vir}$ of the host galaxies. The C IV absorption strength falls off radially as a power law and beyond 0.5 R$_{vir}$, no C IV absorption is detected above our sensitivity limit of ~ 50-100 m$\AA$. We find a tentative correlation between detected C IV absorption strength and star formation, paralleling the strong correlation seen in highly ionized oxygen for L~L* galaxies by the COS-Halos survey. The data imply a large carbon reservoir in the CGM of these galaxies, corresponding to a minimum carbon mass of $\gtrsim$ 1.2$\times 10^6$ $M_\odot$ out to ~ 110 kpc. This mass is comparable to the carbon mass in the ISM and more than the carbon mass currently in stars of these galaxies. The C IV absorption seen around these sub-L* galaxies can account for almost two-thirds of all $W_r$> 100 m$\AA$ C IV absorption detected at low z. Comparing the C IV covering fraction with hydrodynamical simulations, we find that an energy-driven wind model is consistent with the observations whereas a wind model of constant velocity fails to reproduce the CGM or the galaxy properties.Comment: 18 Pages, 11 Figures, ApJ 796 13

Numerical Study of Turbulent Mixing Layers with Non-Equilibrium Ionization Calculations

Highly ionized species such as C IV, N V, and O VI, are commonly observed in diffuse gas in various places in the universe, such as in our Galaxy's disk and halo, high velocity clouds (HVCs), external galaxies, and the intergalactic medium. One possible mechanism for producing high ions is turbulent mixing of cool gas with hotter gas in locations where these gases slide past each other. By using hydrodynamic simulations with radiative cooling and non-equilibrium ionization (NEI) calculations, we investigate the physical properties of turbulent mixing layers and the production of high ions. We find that most of the mixing occurs on the hot side of the hot/cool interface and that the mixed region separates into a tepid zone containing radiatively cooled, C IV-rich gas and a hotter zone which is rich in C IV, N V, and O VI. Mixing occurs faster than ionization or recombination, making the mixed gas a better source of C IV, N V, and O VI in our NEI simulations than in our collisional ionization equilibrium (CIE) simulations. In addition, the gas radiatively cools faster than the ions recombine, which also allows large numbers of high ions to linger in the NEI simulations. For these reasons, our NEI calculations predict more high ions than our CIE calculations predict. We also simulate various initial configurations of turbulent mixing layers and discuss their results. We compare the results of our simulations with observations and other models, including other turbulent mixing calculations. The ratios of C IV to N V and N V to O VI are in reasonable agreement with the averages calculated from observations of the halo. There is a great deal of variation from sightline to sightline and with time in our simulations. Such spatial and temporal variation may explain some of the variation seen among observations.Comment: 19 pages, 7 figures, 8 tables, Accepted for publication by Ap

GASS High Velocity Clouds in the Region of the Magellanic Leading Arm

We present a catalog of high-velocity clouds in the region of the Magellanic Leading Arm. The catalog is based on neutral hydrogen (\HI) observations from the Parkes Galactic All-Sky Survey (GASS). Excellent spectral resolution allows clouds with narrow-line components to be resolved. The total number of detected clouds is 419. We describe the method of cataloging and present the basic parameters of the clouds. We discuss the general distribution of the high-velocity clouds and classify the clouds based on their morphological type. The presence of a significant number of head-tail clouds and their distribution in the region is discussed in the context of Magellanic System simulations. We suggest that ram-pressure stripping is a more important factor than tidal forces for the morphology and formation of the Magellanic Leading Arm and that different environmental conditions might explain the morphological difference between the Magellanic Leading Arm and Magellanic Stream. We also discuss a newly identified population of clouds that forms the LA IV and a new diffuse bridge-like feature connecting the LA II and III complexes.Comment: 20 pages, 24 figures, accepted by ApJ on December 14, 201