Nonlinear dynamics of phase separation in thin films

We present a long-wavelength approximation to the Navier-Stokes Cahn-Hilliard equations to describe phase separation in thin films. The equations we derive underscore the coupled behaviour of free-surface variations and phase separation. We introduce a repulsive substrate-film interaction potential and analyse the resulting fourth-order equations by constructing a Lyapunov functional, which, combined with the regularizing repulsive potential, gives rise to a positive lower bound for the free-surface height. The value of this lower bound depends on the parameters of the problem, a result which we compare with numerical simulations. While the theoretical lower bound is an obstacle to the rupture of a film that initially is everywhere of finite height, it is not sufficiently sharp to represent accurately the parametric dependence of the observed dips or `valleys' in free-surface height. We observe these valleys across zones where the concentration of the binary mixture changes sharply, indicating the formation of bubbles. Finally, we carry out numerical simulations without the repulsive interaction, and find that the film ruptures in finite time, while the gradient of the Cahn--Hilliard concentration develops a singularity.Comment: 26 pages, 20 figures, PDFLaTeX with RevTeX4 macros. A thorough analysis of the equations is presented in arXiv:0805.103

The First Galaxies: Clues from Element Abundances

It has recently become possible to measure directly the abundances of several chemical elements in a variety of environments at redshifts up to z = 5. In this review I summarise the latest observations of Lyman break galaxies, damped Lyman alpha systems and the Lyman alpha forest with a view to uncovering any clues which these data may offer to the first episodes of star formation. The picture which is emerging is one where the universe at z = 3 already included many of the components of today's galaxies--even at these early times we see evidence for Populations I and II stars, while the `smoking gun' for Population III objects may be hidden in the chemical composition of the lowest density regions of the IGM, yet to be deciphered.Comment: 15 pages, LaTex, 8 Postscript Figures. To appear in the Philosophical Transactions of The Royal Society, Series

On Collisionless Electron-Ion Temperature Equilibration in the Fast Solar Wind

We explore a mechanism, entirely new to the fast solar wind, of electron heating by lower hybrid waves to explain the shift to higher charge states observed in various elements in the fast wind at 1 A.U. relative to the original coronal hole plasma. This process is a variation on that previously discussed for two temperature accretion flows by Begelman & Chiueh. Lower hybrid waves are generated by gyrating minor ions (mainly alpha-particles) and become significant once strong ion cyclotron heating sets in beyond 1.5 R_sun. In this way the model avoids conflict with SUMER electron temperature diagnostic measurements between 1 and 1.5 R_sun. The principal requirement for such a process to work is the existence of density gradients in the fast solar wind, with scale length of similar order to the proton inertial length. Similar size structures have previously been inferred by other authors from radio scintillation observations and considerations of ion cyclotron wave generation by global resonant MHD waves.Comment: 32 pages including 11 figures, 4 tables, accepted by Ap

Long-term interleukin-6 levels and subsequent risk of coronary heart disease: Two new prospective studies and a systematic review

Background The relevance to coronary heart disease (CHD) of cytokines that govern inflammatory cascades, such as interleukin-6 (IL-6), may be underestimated because such mediators are short acting and prone to fluctuations. We evaluated associations of long-term circulating IL-6 levels with CHD risk (defined as nonfatal myocardial infarction [MI] or fatal CHD) in two population-based cohorts, involving serial measurements to enable correction for within-person variability. We updated a systematic review to put the new findings in context. Methods and Findings Measurements were made in samples obtained at baseline from 2,138 patients who had a first-ever nonfatal MI or died of CHD during follow-up, and from 4,267 controls in two cohorts comprising 24,230 participants. Correction for within-person variability was made using data from repeat measurements taken several years apart in several hundred participants. The year-to-year variability of IL-6 values within individuals was relatively high (regression dilution ratios of 0.41, 95% confidence interval [CI] 0.28-0.53, over 4 y, and 0.35, 95% CI 0.23-0.48, over 12 y). Ignoring this variability, we found an odds ratio for CHD, adjusted for several established risk factors, of 1.46 (95% CI 1.29-1.65) per 2 standard deviation (SD) increase of baseline IL-6 values, similar to that for baseline C-reactive protein. After correction for within-person variability, the odds ratio for CHD was 2.14 (95% CI 1.45-3.15) with long-term average ("usual'') IL-6, similar to those for some established risk factors. Increasing IL-6 levels were associated with progressively increasing CHD risk. An updated systematic review of electronic databases and other sources identified 15 relevant previous population-based prospective studies of IL-6 and clinical coronary outcomes (i.e., MI or coronary death). Including the two current studies, the 17 available prospective studies gave a combined odds ratio of 1.61 (95% CI 1.42-1.83) per 2 SD increase in baseline IL-6 (corresponding to an odds ratio of 3.34 [95% CI 2.45-4.56] per 2 SD increase in usual [long-term average] IL-6 levels). Conclusions Long-term IL-6 levels are associated with CHD risk about as strongly as are some major established risk factors, but causality remains uncertain. These findings highlight the potential relevance of IL-6-mediated pathways to CH

Soil ecosystem services of the under different uses in the Colombian Amazonia

Agroforestry systems (AFs), where agricultural and livestock crops are associated with woody plants, are known as sustainable systems, that conserve biodiversity and improve the provision of ecosystem services without compromising productivity. This work focuses mainly on cacao AFs, which have been related to different ecosystem services in tropical regions. Especially, our study focuses on the ability of the cacao AFs to improve soil ecosystem services in the Colombian Amazon region. We focused on soil ecosystems ecosystem services in the Colombian Amazonia because: of the social importance of cacao production system in the study region, specifically within the post conflict context; the lack of knowledge on the capacity of cacao AFs to offer soil ecosystem services in the study zone and its capacity in restoring ecosystem services in degraded soils. Aim The objective of our work was to evaluate the soil quality in different cacao agroforestry systems in the Colombian Amazonia, and to compare these evaluated soil quality of soil quality in Forest and Pasture. Material and methods The study was conducted at the Macagual Amazon Research Center, located west of the Colombian Amazon. We evaluated soil quality in four types of AFs Cacao, presenting different establishment, composition and structural characteristics; but also in a plot of native forest composed of characteristic species of the area, and in a plot of pasture composed of grasses. In the different plot of each land use, we evaluated the diversity of macrofauna, the morphology of aggregate, the physical properties and the soil chemistry. We summarized these variables in a General Indicator of Soil Quality GISQ, characterizing soil quality in the different land uses. Major results and Conclusion It was found that the level of intensification among land uses (Bosque>AFs>Pasture) affects the decrease of the macrofauna populations, which was related to soil compaction (physical properties). Chemical fertility improved with the establishment of AFs influenced by the application of amendments and organic fertilizers. When establishing agroforestry systems from pasture areas at a certain level of degradation, the GISQ scale was found to increase by 42%. Our results indicate that AFs practices can definitely be used as a restoration strategy, for the recovery of degraded areas

The VLT-FLAMES Tarantula Survey XIX. B-type Supergiants - Atmospheric parameters and nitrogen abundances to investigate the role of binarity and the width of the main sequence

TLUSTY non-LTE model atmosphere calculations have been used to determine atmospheric parameters and nitrogen (N) abundances for 34 single and 18 binary B-type supergiants (BSGs). The effects of flux contribution from an unseen secondary were considered for the binary sample. We present the first systematic study of the incidence of binarity for a sample of BSGs across the theoretical terminal age main sequence (TAMS). To account for the distribution of effective temperatures of the BSGs it may be necessary to extend the TAMS to lower temperatures. This is consistent with the derived distribution of mass discrepancies, projected rotational velocities (vsini) and N abundances, provided that stars cooler than this temperature are post RSG objects. For the BSGs in the Tarantula and previous FLAMES surveys, most have small vsini. About 10% have larger vsini (>100 km/s) but surprisingly these show little or no N enhancement. All the cooler BSGs have low vsini of <70km/s and high N abundance estimates, implying that either bi-stability braking or evolution on a blue loop may be important. A lack of cool binaries, possibly reflects the small sample size. Single star evolutionary models, which include rotation, can account for the N enhancement in both the single and binary samples. The detailed distribution of N abundances in the single and binary samples may be different, possibly reflecting differences in their evolutionary history. The first comparative study of single and binary BSGs has revealed that the main sequence may be significantly wider than previously assumed, extending to Teff=20000K. Some marginal differences in single and binary atmospheric parameters and abundances have been identified, possibly implying non-standard evolution for some of the sample. This sample as a whole has implications for several aspects of our understanding of the evolution of BSGs. Full abstract in paperComment: 21 pages, 15 figures, 11 table

Muscle recruitment patterns during the prone leg extension

BACKGROUND: The prone leg extension (PLE) is a clinical test used to evaluate the function of the lumbopelvis. It has been theorized that a normal and consistent pattern of muscle activation exists. Previous research has found two contradictory patterns of muscle activation during PLE in normal individuals. One study shows an almost simultaneous activation of the lower erector spinae and hamstring muscle group with a delayed activation of the gluteus maximus, while the second describes the order of activation being ipsilateral erector spinae (to the leg being extended), hamstrings, contralateral erector spinae and gluteus maximus. Due to the different conclusions from these two studies and the lack of quantified muscle onset times, expressed in absolute time this study attempted to quantify the muscle onset times (in milliseconds) during the prone leg extension, while noting if a consistent order of activation exists and whether a timing relationship also exists between the gluteus maximus and contralateral latissimus dorsi. METHODS: 10 asymptomatic males (Average height: 175.2 cm (SD 6.5), Average Weight 75.9 kg (SD 6.5), Average Age: 27.1(SD 1.28)) and 4 asymptomatic females (Average height 164.5 (SD 2.9), weight: 56.2 (SD 8.9), Average Age: 25 (SD 1)) performed the prone leg extension task while the myoelectric signal was recorded from the bilateral lower erector spinae, gluteus maximus and hamstring muscle groups. Activation onsets were determined from the rectified EMG signal relative to the onset of the hamstrings muscle group. RESULTS: No consistent recruitment patterns were detected for prone leg extension among the hamstring muscle group and the erector spinae. However, a consistent delay in the Gluteus Maximus firing of approximately 370 ms after the first muscle activated was found. Five out of 14 asymptomatic subjects showed a delay in gluteus maximus firing exceeding the average delay found in previous research of subjects considered to have a dysfunctional firing pattern. CONCLUSION: A consistent pattern of activation was not found. Variability was seen across subjects. These findings suggest the PLE is not sufficient for a diagnostic test due to the notable physiological variation. An overlap between normal and potentially abnormal activation patterns may exist

Faint Blue Objects in the Hubble Deep Field South Revealed: White Dwarfs, Subdwarfs, and Quasars

We explore the nature of the faint blue objects in the Hubble Deep Field South. We have derived proper motions for the point sources in the Hubble Deep Field South using a 3 year baseline. Combining our proper motion measurements with spectral energy distribution fitting enabled us to identify 4 quasars and 42 stars, including 3 white dwarf candidates. Two of these white dwarf candidates, HDFS 1444 and 895, are found to display significant proper motion, 21.1 $\pm$ 7.9 mas/yr and 34.9 $\pm$ 8.0 mas/yr, and are consistent with being thick disk or halo white dwarfs located at ~2 kpc. The other faint blue objects analyzed by Mendez & Minniti do not show any significant proper motion and are inconsistent with being halo white dwarfs; they do not contribute to the Galactic dark matter. The observed population of stars and white dwarfs is consistent with standard Galactic models.Comment: ApJ accepted, 39 pages, 13 figure