Hot Wind Research Articles

HOT GAS LINES IN T TAURI STARS

ABSTRACT For Classical T Tauri Stars (CTTSs), the resonance doublets of N v, Si iv, and C iv, as well as the He ii 1640 Å line, trace hot gas flows and act as diagnostics of the accretion process. In this paper we assemble a large high-resolution, high-sensitivity data set of these lines in CTTSs and Weak T Tauri Stars (WTTSs). The sample comprises 35 stars: 1 Herbig Ae star, 28 CTTSs, and 6 WTTSs. We find that the C iv, Si iv, and N v lines in CTTSs all have similar shapes. We decompose the C iv and He ii lines into broad and narrow Gaussian components (BC and NC). The most common (50%) C iv line morphology in CTTSs is that of a low-velocity NC together with a redshifted BC. For CTTSs, a strong BC is the result of the accretion process. The contribution fraction of the NC to the C iv line flux in CTTSs increases with accretion rate, from ∼20% to up to ∼80%. The velocity centroids of the BCs and NCs are such that V BC ≳ 4 V NC, consistent with the predictions of the accretion shock model, in at most 12 out of 22 CTTSs. We do not find evidence of the post-shock becoming buried in the stellar photosphere due to the pressure of the accretion flow. The He ii CTTSs lines are generally symmetric and narrow, with FWHM and redshifts comparable to those of WTTSs. They are less redshifted than the CTTSs C iv lines, by ∼10 km s−1. The amount of flux in the BC of the He ii line is small compared to that of the C iv line, and we show that this is consistent with models of the pre-shock column emission. Overall, the observations are consistent with the presence of multiple accretion columns with different densities or with accretion models that predict a slow-moving, low-density region in the periphery of the accretion column. For HN Tau A and RW Aur A, most of the C iv line is blueshifted suggesting that the C iv emission is produced by shocks within outflow jets. In our sample, the Herbig Ae star DX Cha is the only object for which we find a P-Cygni profile in the C iv line, which argues for the presence of a hot (105 K) wind. For the overall sample, the Si iv and N v line luminosities are correlated with the C iv line luminosities, although the relationship between Si iv and C iv shows large scatter about a linear relationship and suggests that TW Hya, V4046 Sgr, AA Tau, DF Tau, GM Aur, and V1190 Sco are silicon-poor, while CV Cha, DX Cha, RU Lup, and RW Aur may be silicon-rich.

SCATTERED EMISSION FROMz∼ 1 GALACTIC OUTFLOWS

Mapping Mg II resonance emission scattered by galactic winds offers a means to determine the spatial extent and density of the warm outflow. Using Keck/LRIS spectroscopy, we have resolved scattered Mg II emission to the east of 32016857, a star-forming galaxy at z =0.9392 with an outflow. The Mg II emission from this galaxy exhibits a P-Cygni profile, extends further than both the continuum and [O II] emission along the eastern side of the slit, and has a constant Doppler shift along the slit which does not follow the velocity gradient of the nebular [O II] emission. Using the Sobolev approximation, we derive the density of Mg+ ions at a radius of 12 to 18 kpc in the outflow. We model the ionization correction and find that much of the outflowing Mg is in Mg++. We estimate that the total mass flux could be as large as 330 - 500 solar masses per year, with the largest uncertainties coming from the depletion of Mg onto grains and the clumpiness of the warm outflow. We show that confining the warm clouds with a hot wind reduces the estimated mass flux of the warm outflow and indicates amass-loading factor near unity in the warm phase alone. Based on the high blue luminosities that distinguish 32016857 and TKRS 4389, described by Rubin et al. 2011, from other galaxies with P-Cygni emission, we suggest that, as sensitivity to diffuse emission improves, scattering halos may prove to be a generic property of star-forming galaxies at intermediate redshifts.

Ultra-luminous X-ray sources as supercritical accretion disks: Spectral energy distributions

We describe a model of spectral energy distribution in supercritical accretion disks (SCAD) based on the conception by Shakura and Sunyaev. We apply this model to five ultra-luminous X-ray sources (ULXs). In this approach, the disk becomes thick at distances to the center less than the spherization radius, and the temperature dependence is T ∝ r −1/2. In this region the disk luminosity is L bol ∼ L Edd $$\ln \left( {{{\dot M} \mathord{\left/ {\vphantom {{\dot M} {\dot M_{Edd} }}} \right. \kern-\nulldelimiterspace} {\dot M_{Edd} }}} \right)$$ , and strong wind arises forming a wind funnel above the disk. Outside the spherization radius, the disk is thin and its total luminosity is Eddington, L Edd. The thin disk heats the wind from below. From the inner side of the funnel the wind is heated by the supercritical disk. In this paper we do not consider Comptonization in the inner hot winds which must cover the deep supercritical disk regions. Our model is technically similar to the DISKIR model of Gierlinski et al. The models differ in disk type (standard—supercritical) and irradiation (disk—wind).We propose to distinguish between these two models in the X-ray region of about 0.3–1 keV, where the SCAD model has a flat νF ν spectrum, and the DISKIR model never has a flat part, as it is based on the standard α-disk. An important difference between the models can be found in their resulting black hole masses. In application to the ULX spectra, the DISKIR model yields black hole masses of a few hundred solar masses, whereas the SCAD model produces stellar-mass (about 10M⊙) black holes.

DETECTION OF DIFFUSE X-RAY EMISSION FROM PLANETARY NEBULAE WITH NEBULAR O VI

The presence of O VI ions can be indicative of plasma temperatures of a few times 10^5 K that is expected in heat conduction layers between the hot shocked stellar wind gas at several 10^6 K and the cooler (~10,000 K) nebular gas of planetary nebulae (PNe). We have used FUSE observations of PNe to search for nebular O VI emission or absorption as a diagnostic of conduction layer to ensure the presence of hot interior gas. Three PNe showing nebular O VI, namely IC 418, NGC 2392, and NGC 6826, have been selected for Chandra observations and diffuse X-ray emission is indeed detected in each of these PNe. Among the three, NGC 2392 has peculiarly high diffuse X-ray luminosity and plasma temperature compared with those expected from its stellar wind's mechanical luminosity and terminal velocity. The limited effects of heat conduction on the plasma temperature of a hot bubble at the low terminal velocity of the stellar wind of NGC 2392 may partially account for its high plasma temperature, but the high X-ray luminosity needs to be powered by processes other than the observed stellar wind, probably caused by the presence of an unseen binary companion of the CSPN of NGC 2392. We have compiled relevant information on the X-ray, stellar, and nebular properties of PNe with a bubble morphology and found that the expectations of bubble models including heat conduction compare favorably with the present X-ray observations of hot bubbles around H-rich CSPNe, but have notable discrepancies for those around H-poor [WR] CSPNe. We note that PNe with more massive central stars can produce hotter plasma and higher X-ray surface brightness inside central hot bubbles.

Use of alumina phosphate waste to produce building materials

Abstract The generation of a fine fraction of sedimentary alumina phosphate before the manufacturing process of phosphoric acid –used as fertilizer– poses a crucial environmental issue related to the large quantities of fines stored for a long time in the wildlife without treatment or recycling in the region of Thiès in Sénégal by the Industries Chimiques du Sénégal (ICS) and the Société Sénégalaise des Phosphates de Thiès (SSPT). This work deals with the use of the fines particles of phosphate generated by the physical processing (crushing, transport and screening) of the raw material by the both mining companies. These fines particles of phosphates cover all the fauna and flora surrounding the sector with whitish dust particularly during the Harmattan, a hot and dry wind, while they can be leached during the rainy season to contaminate groundwater and then cause diseases to the populations who drink that water. Indeed, these materials, which are stored in large quantities as “waste”, and which pollute, the space and the environment, can be recycled as refractory materials useful in manufacturing such as bricks or paving blocks. The purpose of this study is to find, from these discarded fines that are not yet processed, a good and new material in terms of physical and mechanical characteristics that will meet a customary standard. This will allow not only to reduce their potential hazard by reducing the pollution for the consumption of the fines in order to generate a useful material especially in the surrounding villages of the mining sector, but also to employ young people in working age in this fines recycling process, to create jobs and therefore additional economic resources that allow a better life because the majority of the youngsters from these areas are unemployed. The formulation of a well-known mixture containing fines of sedimentary alumina phosphate of particles size ranging between 0.063 mm to 5 mm, with chemical composition similar to that of volcanic slag, sodium silicate called water-glass as binder of mineral elements; and water, led to the manufacturing of geomaterials blocks with 20×10×6 cm3 size by baking them several hours on an oven at the constant temperature of 225°C. The sodium silicate density was 1.4. Good mechanical and physical characteristics were achieved through systematic testing. Strength splitting rupture tests, total water content determination, size measurements of the blocks (length, width and thickness) as well as the loss on ignition on ambient atmosphere were achieved on the blocks after treatment for a complete identification. Average values of 3.03 MPa and 2.5% were obtained as results respectively for the splitting rupture strength and for the total water content. Negative variations of −2.05 mm, −0.59 mm and 1.69 mm on average values were obtained respectively on their length, their width and their thickness for a value of 5.30% of loss on ignition. The blocks are exposed on the fire on their upper surface whilst the heating effect falls of rapidly at the other side. The deduction of the compressive resistance strength from the average value of splitting rupture gave a value of 40.5 MPa. This value testifies very good mechanical resistance strength of the material which is made by the fines of phosphate. These characteristics obtained are compared here to the European Standard values EN 1338 for paving blocks. The values obtained for all the tests attest good manufacturing material. This new material can also be used as refractory materials in the ovens and in pottery materials.

Piecing together the puzzle of NGC 5253: abundances, kinematics and WR stars

We present Gemini-S/GMOS-IFU optical spectroscopy of four regions near the centre of the nearby (3.8 Mpc) dwarf starburst galaxy NGC 5253. This galaxy is famous for hosting a radio supernebula containing two deeply embedded massive super star clusters, surrounded by a region of enhanced nitrogen abundance that has been linked to the presence of WR stars. We detected 11 distinct sources of red WR bump (CIV) emission over a 20" (~350 pc) area, each consistent with the presence of ~1 WCE-type star. WC stars are not found coincident with the supernebula, although WN stars have previously been detected here. We performed a multi-component decomposition of the H\alpha\ line across all four fields and mapped the kinematics of the narrow and broad (FWHM = 100-250 km/s) components. These maps paint a picture of localised gas flows, as part of multiple overlapping bubbles and filaments driven by the star clusters throughout the starburst. We confirm the presence of a strong H\alpha\ velocity gradient over ~4.5" (~80 pc) coincident with the region of N/O enhancement, and high gas density known from previous study, and interpret this as an accelerating ionized gas outflow from the supernebula clusters. We measure the ionized gas abundances in a number of regions in the outer IFU positions and combine these with measurements from the literature to assess the radial abundance distribution. We find that the O/H and N/H profiles are consistent with being flat. Only the central 50 pc exhibits the well-known N/O enhancement, and we propose that the unusually high densities/pressures in the supernebula region have acted to impede the escape of metal-enriched hot winds from the star clusters and allow them to mix with the cooler phases, thus allowing these freshly processed chemicals to be seen in the optical.

HST FUV C iv observations of the hot DG Tauri jet

Protostellar jets are tightly connected to the accretion process and regulate the angular momentum balance of accreting star-disk systems. The DG Tau jet is one of the best-studied protostellar jets and contains plasma with temperatures ranging over three orders of magnitude within the innermost 50 AU of the jet. We present new Hubble Space Telescope (HST) far ultraviolet (FUV) long-slit spectra spatially resolving the C IV emission (T~1e5 K) from the jet for the first time, and quasi-simultaneous HST observations of optical forbidden emission lines ([O I], [N II], [S II] and [O III]) and fluorescent H2 lines. The C IV emission peaks at 42 AU from the stellar position and has a FWHM of 52 AU along the jet. Its deprojected velocity of around 200 km/s decreases monotonically away from the driving source. In addition, we compare our HST data with the X-ray emission from the DG Tau jet. We investigate the requirements to explain the data by an initially hot jet compared to local heating. Both scenarios indicate a mass loss by the T~1e5 K jet of ~1e-9 Msun/year, i.e., between the values for the lower temperature jet (T~1e4 K) and the hotter X-ray emitting part (T>1e6 K). However, a simple initially hot wind requires a large launching region (~1 AU), and we therefore favor local heating.

Effects of Supplemental Irrigation and Nitrogen Applied on Yield and Yield Components of Bread Wheat at the Saïs Region of Morocco

The objective of this study is to determinate the optimal growth stage for applying supplemental irrigation and nitrogen to enhance bread wheat ( Triticum aestivum L.) productivity and water use efficiency under rainfed condition in Morocco. Field trial was conducted during two years (2007-2008 and 2008-2009). Three genotypes (G) of Moroccan bread wheat; Achtar, Arrehane and an Advanced Line II were combined with five nitrogen doses (N); 0, 40, 80, 120 and 160 kg N ha ‐1 and three water treatments (I); rainfed (I 0), irrigated (60 mm) at 21 according to the Zadoks scale (I1) and irrigated (60 mm) at 59 according to the Zadoks scale (I2). Results in the drought year (2007-2008) show that I2 improves water use efficiency, grain yield and its components by 91 and 60% respectively, compared to I 0 and I1 treatments. I2 has limited the effects of the Chergui ‐hot and dry wind coming from the Sahara- which has a negative impact on growth mainly at the end of the cycle of the crop. Grain yield and other yield components increased simultaneously with the increase in nitrogen inputs during the second 2008-2009 crop year which was rainy. The 120 kg N ha ‐1 dose allowed the highest results, with no significant difference with the

A Clinical Study of Pterygium and Results of Treatment by Excision and Limbal Autograft or Augmented with Post-Op Mitomycin C

Aim: To prospectively analyze the clinical profile of pterygium and to compare results of management by excision with limbal conjunctival autograft or postoperative topical Mitomycin C drops. Methodology: Study was conducted over a period of 23 months, at a tertiary eye care hospital including 80 eyes of 80 patients who underwent surgery, out of which 40 underwent limbal conjunctival autograft and the remaining 40 underwent pterygium excision followed by Mitomycin C after fulfilling the inclusion criteria. A detailed history was taken and recorded regarding the disease with reference to age, occupation, residence, exposure to dust and hot wind. The extent of corneal involvement by the pterygium was noted. The patients were followed after one week and then monthly for a year. BCVA were noted on every visit and slit lamp examination was done for recurrence, sclera thinning and corneal vascularisation. Result: 80 eyes of 80 patients were enrolled with male preponderance, out of which 40 underwent limbal conjunctival autograft (gr. A) and the remaining 40 underwent pterygium excision followed by Mitomycin C (gr. B). All patients were in the age group of 23 to 70 years. The study showed a higher incidence of pterygium in the age group of 41-50 years with male preponderance probably due to chronic dryness, and exposure to ultraviolet light, dust, and hot winds. The right eye was more affected than the left eye, and nasal side was more involved than the temporal side. The recurrence among group A was 2 out of 40 with a recurrence rate of 5% and among group B was 3 out of 40 with a recurrence rate of 7.5%. Scleral thinning was seen in two cases (5%) in patients who underwent pterygium excision followed by Mitomycin C. Conclusion: Conjunctival limbal autograft and postoperative MMC (0.02%) are both safe and effective adjuncts to primary pterygium surgery. The main prejudices against autografting are the expertise and time required for the procedure. The recent use of biologic adhesives to fixate the autograft in place may simplify the procedure. Age of the patients was strongly associated with recurrence regardless of which procedure was used. More research needs to be done to delve into this seemingly innocuous pathology of conjunctiva to effectively manage the disease condition.

Breeding of Sistan Yaghouti Grape using Clonal Selection

Sistan Yaghouti grape belongs to the category of seedless grapes which are resistant to diseases and they have an uninterrupted growth in adverse conditions. Sistan weather usually has hot wind and salty soil. In order to increase the fruit quality, we investigated vine yards of Sistan areas such as Zahak, Dust-Mohammed and Bonjar and collected samples of Yaghouti grape. Traits of Yaghouti grape were calculated using Descriptor method. Results showed that Yaghouti grape clones had high variation in traits such as density of branch, size of berry, weight of berry, weight of branch and height of branch. Therefore, it can be said that clonal selection is suitable method for breeding of grape for good branch quality. Collected seedlings were also planted in Zahak agriculture research station for further evaluation and stability of traits with respect to location and season.

A Realistic Growth Path for Solar Wind Power

Until today, the biggest solar updraft tower power plant ever built and tested was the 50 kW Spain plant in Manzanares. Since then no real plant has been built, whilst many grand plans have been drawn and given up. Solar Wind Power (SWP) is an energy form in search of its destiny: it is time to find a real market for SWP. This market is currently forming and we call it ‘evening power’. SWP transforms sunlight into heat, heat into hot artificial wind, and this wind into electricity. The three steps of transformation allow SWP to delay the generation of electricity from the daily peak of solar radiation into the evening. In the evening, the greater power demand cannot be met with other renewable CO2-free energies like wind and photovoltaic. SWP has been tested once, thirty years ago - it is time for a second trial: the Intermediate Solar Wind Power Plant (ISWiPP). The goal is to develop, test and measure SWP’s potential for heat-storage and evening power output. The technology for constructing a light steel-tower with a concrete base will be tested under real-life conditions and technologies for heat storage will be developed. The ISWiPP will enable investors to prepare for large SWiPP with hybrid (concrete and steel) towers of 1000 m height or more. This development growth path is realistic and adequate to overcome the current impasse. Like all CO2-free energy forms SWP depends very much on the location chosen. Locations with strong winds, or sand- and dust-storms, are inadequate for SWP. A good location for a SWiPP is a hot, flat and rocky desert, not too far from a city with a demand for evening power.

ACTIVE GALACTIC NUCLEUS OBSCURATION FROM WINDS: FROM DUSTY INFRARED-DRIVEN TO WARM AND X-RAY PHOTOIONIZED.

We present calculations of AGN winds at ~parsec scales, along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L=0.05 - 0.6Ledd, the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72° - 75° regardless of the luminosity. At L ≳ 0.1 the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations θ ≳ 70° and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR supported flow. At luminosities ≤0.1Ledd episodes of outflow are followed by extended periods when the wind switches to slow accretion.

THE UNUSUAL TEMPORAL AND SPECTRAL EVOLUTION OF SN2011ht. II. PECULIAR TYPE IIn OR IMPOSTOR?

SN2011ht has been described both as a true supernova (SN) and as an impostor. In this paper, we conclude that it does not match some basic expectations for a core-collapse event. We discuss SN2011ht's spectral evolution from a hot dense wind to a cool dense wind, followed by the post-plateau appearance of a faster low density wind during a rapid decline in luminosity. We identify a slow dense wind expanding at only 500–600 km s−1, present throughout the eruption. A faster wind speed V ∼ 900 km s−1 occurred in a second phase of the outburst. There is no direct or significant evidence for any flow speed above 1000 km s−1; the broad asymmetric wings of Balmer emission lines in the hot wind phase were due to Thomson scattering, not bulk motion. We estimate a mass-loss rate of order 0.05 M☉ yr−1 during the hot dense wind phase of the event. The same calculations present difficulties for a hypothetical unseen SN blast wave. There is no evidence that the kinetic energy greatly exceeded the luminous energy, roughly 3 × 1049 erg; so the radiative plus kinetic energy was small compared to a typical SN. We suggest that SN2011ht may have been a giant eruption driven by super-Eddington radiation pressure, perhaps beginning a few months before the discovery. A strongly non-spherical SN might also account for the data at the cost of more free parameters.

Influence of extreme ultraviolet radiation on the P vionization fraction in hot star winds

Different diagnostics of hot star wind mass-loss rates provide results that are difficult to reconcile with each other. The widely accepted presence of clumping in hot star winds implies a significant reduction of observational mass-loss rate estimates from diagnostics that depend on the square of the density. Moreover, the ultraviolet Pv resonance lines indicate a possible need for even stronger reduction of hot star mass-loss rates, provided that Pv is a dominant ionization stage of phosphorus at least in some hot stars. The latter assumption is challenged by a possible presence of the XUV radiation. Here we study the influence of the XUV radiation on the Pv ionization fraction in the hot star winds. By a detailed solution of the hydrodynamical, radiative transfer, and statistical equilibrium equations we confirm that sufficiently strong XUV radiation source may decrease the Pv ionization fraction, possibly depreciating the Pv lines as a reliable mass-loss rate indicator. On the other hand, the XUV radiation influences also the ionization fraction of heavier ions that drive the wind, leading to a decrease of the wind terminal velocity. Consequently, we conclude that the XUV radiation alone can not bring theory and observations in accord. We fit our predicted wind mass-loss rates by a suitable formula and compare the results with the observational mass-loss rate diagnostics. We show that for supergiants and giants the theoretical predictions do not contradict the mass-loss rate estimates based on X-ray line profiles or density squared diagnostics. On the other hand, for main-sequence stars the predicted mass-loss rates are still significantly higher than that inferred from Pv or X-ray lines. This indicates that the "weak wind problem" recently detected in low-luminosity main-sequence stars may occur to some extent also for the stars with higher luminosity.

Chandra ACIS-S imaging spectroscopy of anomalously faint X-ray emission from Comet 103P/Hartley 2 during the EPOXI encounter

We present results from the Chandra X-ray Observatory’s characterization of the X-ray emission from Comet 103P/Hartley 2, in support of NASA’s Deep Impact Extended close flyby of the comet on 04 November 2010. The comet was observed 4 times for a total on target time of ∼60ks between the 17th of October and 16th of November 2010, with two of the visits occurring during the EPOXI close approach on 04 November and 05 November 2010. X-ray emission from 103P was qualitatively similar to that observed for collisionally thin Comets 2P/Encke (Lisse, C.M. et al. [2005]. Astrophys. J. 635, 1329–1347) and 9P/Tempel 1 (Lisse, C.M. et al. [2007]. Icarus 190, 391–405). Emission morphology offset sunward but asymmetrical from the nucleus and emission lines produced by charge exchange between highly stripped C, N, and O solar wind minor ions and coma neutral gas species were found. The comet was very under-luminous in the X-ray at all times, representing the 3rd faintest comet ever detected (LX=1.1±0.3×1014ergs−1). The coma was collisionally thin to the solar wind at all times, allowing solar wind ions to flow into the inner coma and interact with the densest neutral coma gas. Localization of the X-ray emission in the regions of the major rotating gas jets was observed, consistent with the major source of cometary neutral gas species being icy coma dust particles. Variable spectral features due to changing solar wind flux densities and charge states were also seen. Modeling of the Chandra observations from the first three visits using observed gas production rates and ACE solar wind ion fluxes with a charge exchange mechanism for the emission is consistent with the temporal and spectral behavior expected for a slow, hot wind typical of low latitude emission from the solar corona interacting with the comet’s neutral coma. The X-ray emission during the 4th visit on 16 November 2010 is similar to the unusual behavior seen for Comet 17P/Holmes in 2007 (Christian, D.J. et al. [2010]. Astrophys. J. Suppl. 187, 447–459) as the solar wind became dominated by a less ionized and faster plasma, more typical of outflow from polar coronal hole regions. We postulate that the overall faintness of the comet seen during all visits is due to the unusually well mixed dust and gas content of this hyperactive comet’s coma producing Auger electrons rather than X-rays via charge exchange with the solar wind. An alternative possible explanation for the faintness of the comet’s X-ray emission, and its unusual high CV and unusually low CVI emission, is that the impinging solar wind was drastically slowed in the inner coma, below 150kms−1, before charge exchanging with cometary neutrals.

Impact of Swirl Flow on the Cooling Performance of an Effusion Cooled Combustor Liner

An experimental study on combustor liner cooling of modern direct lean injection combustion chambers using coolant ejection from both effusion cooling holes and a starter film has been conducted. The experimental setup consists of a generic scaled three sector planar rig in an open loop hot gas wind tunnel, which has been described earlier in Wurm et al. (2009, “A New Test Facility for Investigating the Interactions Between Swirl Flow and Wall Cooling Films in Combustors, Investigating the Interactions Between Swirl Flow and Wall Cooling Films in Combustors,” ASME Paper No. GT2009-59961). Experiments are performed without combustion. Realistic engine conditions are achieved by applying engine-realistic Reynolds numbers, Mach numbers, and density ratios. A particle image velocimetry (PIV) measurement technique is employed, which has been adjusted to allow for high resolution near wall velocity measurements with and without coolant ejection. As the main focus of the present study is a deeper understanding of the interaction of swirl flows and near wall cooling flows, wall pressure measurements are performed for the definition of local blowing ratios and to identify the impact on the local cooling performance. For thermal investigations an infrared thermography measurement technique is employed that allows high resolution thermal studies on the effusion cooled liner surface. The effects of different heat shield geometry on the flow field and performance of the cooling films are investigated in terms of near wall velocity distributions and film cooling effectiveness. Two different heat shield configurations are investigated which differ in shape and inclination angle of the so called heat shield lip. Operating conditions for the hot gas main flow are kept constant. The pressure drop across the effusion cooled liner is varied between 1% and 3% of the total pressure. Results show the impact of the swirled main flow on the stability of the starter film and on the effusion cooling performance. Stagnation areas which could be identified by wall pressure measurements are confirmed by PIV measurements. Thermal investigations reveal reduced cooling performance in the respective stagnation areas.

Burning Man, Desire, and the Culture of Empire

A soulful journey through the eight-day festival that claims to be both a social movement and “part of a solution to our modern malaise.”

Line transfer through clumpy, large-scale outflows: Ly α absorption and haloes around star-forming galaxies

We present constrained radiative transfer calculations of Lyman Alpha (Lya) photons propagating through clumpy, dusty, large scale outflows, and explore whether we can quantitatively explain the Lya halos that have been observed around Lyman Break Galaxies. We construct phenomenological models of large-scale outflows which consist of cold clumps that are in pressure equilibrium with a constant-velocity hot wind. First we consider models in which the cold clumps are distributed symmetrically around the galaxy, and in which the clumps undergo a continuous acceleration in its 'circumgalactic' medium (CGM). We constrain the properties of the cold clumps (radius, velocity, HI column density, & number density) by matching the observed Lya absorption strength of the CGM in the spectra of background galaxies. We then insert a Lya source in the center of this clumpy outflow, which consists of 1e5-1e6 clumps, and compute observable properties of the scattered Lya photons. In these models, the scattered radiation forms halos that are significantly more concentrated than is observed. In order to simultaneously reproduce the observed Lya absorption line strengths and the Lya halos, we require - preferably bipolar - outflows in which the clumps decelerate after their initial acceleration. This deceleration is predicted naturally in 'momentum-driven' wind models of clumpy outflows. In models that simultaneously fit the absorption and emission line data, the predicted linear polarization is ~30-40% at a surface brightness contour of S=1e-18 erg/s/cm^2/arcsec^2. Our work illustrates clearly that Lya emission line halos around starforming galaxies provide valuable constraints on the cold gas distribution & kinematics in their circumgalactic medium, and that these constraints complement those obtained from absorption line studies alone.

Unmodified small-molecule organic light-emitting diodes by blade coating

Blade coating with substrate heating and hot wind is demonstrated to be a general platform for multi-layer deposition of unmodified small-molecule organic semiconductors. Most unmodified small molecules, originally designed for vacuum evaporation, can be blade coated while the solubility is above 0.5wt.%. High uniformity is achieved for scale over 5cm. Orange devices by evaporation and blade coating are compared with 4,4′-bis(carbazol-9-yl)biphenyl (CBP) as the host, iridium(III) bis(4-(4-t-butylphenyl)thieno[3,2-c]pyridinato-N,C2′)acetylacetonate (PO-01-TB) as the emitter. The efficiency difference is within 10%. When 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) is used as the host, the current efficiencies are 40cd/A for orange, 32cd/A for green, and 20cd/A for blue. The optimized organic light-emitting diodes (OLED) structure developed for vacuum deposition can therefore be exactly copied by the low cost blade coating method in solution.

Experimental investigations on overall cooling effect of ribbed channel with air bleeds

An experimental investigation on overall heat transfer performance of a rectangular channel, in which one wall has periodically placed oblique ribs to enhance heat exchange and cylindrical film holes to bleed cooling air, has been carried out in a hot wind tunnel at different mainstream temperatures, hot mainstream Reynolds numbers, coolant Reynolds numbers and blowing ratios. To describe the cooling effect of combined external coolant film with the internal heat convection enhanced by the ribs, the overall cooling effectiveness at the surface exposed in the mainstream with high temperature was calculated by the surface temperatures measured with an infrared thermal imaging system. The total mass flow rate of cooling air through the coolant channel was regulated by a digital mass flow rate controller, and the blowing ratio passing through the total film holes was calculated based on the measurements of another digital-type mass flow meter. The detailed distributions of overall cooling effectiveness show distinctive peaks in heat transfer levels near the film holes, remarkable inner convective heat transfer effect over entire channel surface, and visible conductive heat transfer effect through the channel wall; but only when the coolant Reynolds number is large enough, the oblique rib effect can be detected from the overall cooling effectiveness; and the oblique bleeding hole effect shows the more obvious trend with increasing blowing ratios. Based on the experimental data, the overall cooling effectiveness is correlated as the functions of Rem (Reynolds number of hot mainstream) and Rec (Reynolds number of internal coolant flow at entrance) for the parametric conditions examined.