Hot Wind Research Articles

English

Irrigation and varietal improvement are two major ways of increasing and stabilizing durum wheat (Triticum durum Desf.) production in semi-arid Mediterranean countries. A 3-year study was conducted in Khemis-Miliana (Upper Chelif, Algeria) to evaluate the yield response of six durum wheat genotypes to deficit irrigation. Grain yield in the unirrigated treatment ranged from 2.0 t.ha-1 (2008) to 2.8 t.ha-1 (2009). In rainfed conditions, the local variety Mohammed Ben Bachir (MBB) was the least productive (yield < 2.0 t.ha-1) but the most stable, being the most insensitive to early drought. Yields of Bousselem exceeded 3.0 t.ha-1 whereas Mexicali and Vitron had more variable and lower yields. Rainwater productivity (RWPg, the ratio of grain yield to precipitation) ranged from 0.5 (MBB) to 1.1 kg.m-3 for Bousselem, Chen’s, and Waha, three varieties known to be drought-tolerant. Deficit irrigation (140 mm) resulted in an increase in grain yield of 0.4 to 3.2 t.ha-1 depending on weather conditions and variety, with a mean response of 1.1 t.ha-1. Irrigating between shooting and booting increased straw production by 23% and grain production by 46% on average. The most explanatory components of final yield under rainfed management were the number of ears.m-² and the number of grains per ear, while under irrigated management the number of grains per ear and the thousand grain weight were more critical for yield determination. The development of irrigation on durum wheat could help to close the gap between current and attainable grain yields in semi-arid Algeria, provided groundwater is available and the flowering period escapes desiccating hot winds. Wheat breeding should be focused on developing genotypes with stable behavior under drought but which respond well to irrigation. Key words: Irrigation, drought, yield components.

식물 코팅 소재 선발법과 작물들에 대한 콩 오일의 증산 억제 효과

Plants as well as crops are damaged by a combination of the hot and dry winds that has been a major factor in the reduction of crop production. A means to protect them from damaging conditions is to consider a coating material. In this study, we established laboratory screening methods to find a coating material to protect a crop from rapid transpiration caused by various factors. In a test measuring the weight loss of kidney bean seedlings for 6 days, Avion treatments decreased its weight loss (P=0.05). Owing to long-time spend in completing this assay, we performed a more simple method using a cobalt chloride paper strip, which changes from blue to red colors under water condition. Beewax, guagum, paraffin liquid, soybean oil, and PE-635 gave a waterproofing effect above 37 and 43% at 0.5 and 1 h after treatment, respectively. However, these tested materials did not show significant waterproofing results at 2 h. Although the methods produced reasonable results, a screening method to obtain more objective data is needed. An alternative is to use an instrument that can detect the transpiration of crop leaves. In a preliminary test using barley leaves, a portable photosynthesis system showed transpiration inhibition of 2% soybean oil and 10 times-diluted Avion under field conditions. In another test using the leaves of maize seedlings and apricot tree, 2% liquid paraffin and plant oils such as apricot oil, linseed oil, olive oil, and soybean oil showed significant transpiration inhibition (P=0.05). Especially, paraffin liquid and soybean oil selected from above tests gave good transpiration inhibitory effects against rice at 2%. In addition, the mixture of 2% soybean oil and a spreader showed more elevated inhibition results comparing with soybean oil or the spreader alone indicating that the spreader may be attributed to more uniform diffusion of the hydrophobic material onto the leaf surface of maize seedlings. The hydrophobic material coated physically the stomata and cuticle layers on leaf surfaces of rice. These hydrophobic materials screened in this study are expected to be used as plant coating materials.

Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars

Our understanding of massive star evolution is in flux due to recent upheavals in our view of mass loss and observations of a high binary fraction among O-type stars. Mass-loss rates for standard metallicity-dependent winds of hot stars are lower by a factor of 2–3 compared with rates adopted in modern stellar evolution codes, due to the influence of clumping on observed diagnostics. Weaker hot star winds shift the burden of H-envelope removal to the winds, pulsations, and eruptions of evolved supergiants, as well as binary mass transfer. Studies of stripped-envelope supernovae, in particular, require binary mass transfer. Dramatic examples of eruptive mass loss are seen in Type IIn supernovae, which have massive shells ejected just a few years earlier. These eruptions are a prelude to core collapse, and may signify severe instabilities in the latest nuclear burning phases. We encounter the predicament that the most important modes of mass loss are also the most uncertain, undermining the predictive power of single-star evolution models. Moreover, the influence of winds and rotation has been evaluated by testing single-star models against observed statistics that, it turns out, are heavily influenced by binary evolution. Altogether, this may alter our view about the most basic outcomes of massive-star mass loss—are Wolf-Rayet stars and Type Ibc supernovae the products of winds, or are they mostly the result of binary evolution and eruptive mass loss? This is not fully settled, but mounting evidence points toward the latter. This paradigm shift impacts other areas of astronomy, because it changes predictions for ionizing radiation and wind feedback from stellar populations, it may alter conclusions about star-formation rates and initial mass functions, it affects the origin of compact stellar remnants, and it influences how we use supernovae as probes of stellar evolution across cosmic time.

Mass loss from inhomogeneous hot star winds

[Abridged] We develop and benchmark a fast and easy-to-use effective-opacity formalism for line and continuum radiative transfer in an accelerating two-component clumpy medium. The formalism bridges the limits of optically thin and thick clumps, and is here used to i) design a simple vorosity-modified Sobolev with exact integration (vmSEI) method for analyzing UV wind resonance lines in hot, massive stars, and ii) derive simple correction factors to the line force driving the outflows of such stars. We show that (for a given ionization factor) UV resonance doublets may be used to analytically predict the upward corrections in empirically inferred mass-loss rates associated with porosity in velocity space (a.k.a. velocity-porosity, or vorosity), but that severe solution degeneracies exist. For an inter-clump density set to 1 % of the mean density, we for O and B supergiants derive upward empirical mass-loss corrections of typically factors of either ~5 or ~50, depending on which of the two applicable solutions is chosen. Overall, our results indicate this solution dichotomy severely limits the use of UV resonance lines as direct mass-loss indicators of clumped hot stellar winds. We next apply the effective-opacity formalism to the standard CAK theory of line-driven winds. By analytic and numerical hydrodynamics calculations, we show that in cases where vorosity is important at the critical point setting the mass-loss rate, the reduced line-force leads to a lower theoretical mass loss, by a factor scaling with the normalized velocity filling factor fvel. On the other hand, if vorosity is important only above this critical point, the predicted mass loss is not affected, but the wind terminal speed is reduced. This shows that porosity in velocity space can have a significant impact not only on the diagnostics, but also on the dynamics and theory of radiatively driven winds.

Soluble starch synthase activity in relation to thermal tolerance of developing wheat (Triticum aestivum, Triticum durum) and maize (Zea mays) grains

Triticum aestivum (var HD 2987), T. durum (var HD 4719) and Zea mays (var HQPM 7) were exposed to control (C) and elevated (E) temperature (2.1-3.8°C higher) in open top chambers during post anthesis period. Soluble starch synthase (SSS) activity in the developing grains and grain yield components at maturity were determined in C and E grown plants. Excised developing grains at 20 DAA (days after anthesis) of ambient grown T. aestivum (var HD 2987), T. durum (var HD 4719) and Zea mays (var HQPM 7, HM 10 and DHM 117) were also incubated at 25, 35 and 45°C for 2 hours and then analysed for the activities of SSS. The kinetic parameters of SSS in the grains of ambient grown plants were also determined. The study revealed a higher catalytic efficiency and relatively thermostable SSS in maize grains compared to wheat. Among tested wheat varieties, aestivum wheat showed a better thermostability of SSS in vitro and in vivo than durum wheat. An association of thermostability of SSS and thermotolerance for grain growth was indicated. The above observation of a highly efficient and relatively thermostable SSS in maize grains may possibly be utilized for improving thermotolerance of SSS and grain growth in wheat. The improved thermotolerance for grain growth in wheat will go a long way in enhancing wheat productivity, which suffers heavy losses due to frequent hot winds during grain filling period.

STRUCTURE AND DYNAMICS OF THE ACCRETION PROCESS AND WIND IN TW Hya

Time-domain spectroscopy of the classical accreting T Tauri star, TW Hya, covering a decade and spanning the far UV to the near-infrared spectral regions can identify the radiation sources, the atmospheric structure produced by accretion,and properties of the stellar wind. On time scales from days to years, substantial changes occur in emission line profiles and line strengths. Our extensive time-domain spectroscopy suggests that the broad near-IR, optical, and far-uv emission lines, centered on the star, originate in a turbulent post-shock region and can undergo scattering by the overlying stellar wind as well as some absorption from infalling material. Stable absorption features appear in H-alpha, apparently caused by an accreting column silhouetted in the stellar wind. Inflow of material onto the star is revealed by the near-IR He I 10830A line, and its free-fall velocity correlates inversely with the strength of the post-shock emission, consistent with a dipole accretion model. However, the predictions of hydrogen line profiles based on accretion stream models are not well-matched by these observations. Evidence of an accelerating warm to hot stellar wind is shown by the near-IR He I line, and emission profiles of C II, C III, C IV, N V, and O VI. The outflow of material changes substantially in both speed and opacity in the yearly sampling of the near-IR He I line over a decade. Terminal outflow velocities that range from 200 km/s to almost 400 km/s in He I appear to be directly related to the amount of post- shock emission, giving evidence for an accretion-driven stellar wind. Calculations of the emission from realistic post- shock regions are needed.

The Research and Application of the PID Controller Based on the Improved BP Network

This paper mainly introduces a PID controller, which is optimized by an improved BP algorithm, and discusses the analysis method of it. It states a way to dynamically adjust the learning rate and the momentum factor through the variety of the input and output of the PID controller to realize an intelligent control. And it connects this control method with the control of the hot winds of the gas in bar furnace of a steel plant to realize a closed-loop control and solve the problems such as the wave of the gas pressure and the insufficiency of combustion. According to the practice, the fluctuation of gas pressure is restricted within 5%, which means that this control method could largely improve the precision of furnace control and further more raise the economic and social benefits.

EXTENDED X-RAY EMISSION FROM A QUASAR-DRIVEN SUPERBUBBLE

We present observations of extended, 20-kpc scale soft X-ray gas around a luminous obscured quasar hosted by an ultra-luminous infrared galaxy caught in the midst of a major merger. The extended X-ray emission is well fit as a thermal gas with a temperature of kT ~ 280 eV and a luminosity of L_X ~ 10^42 erg/s and is spatially coincident with a known ionized gas outflow. Based on the X-ray luminosity, a factor of ~10 fainter than the [OIII] emission, we conclude that the X-ray emission is either dominated by photoionization, or by shocked emission from cloud surfaces in a hot quasar-driven wind.

Active galactic nuclei-driven outflows without immediate quenching in simulations of high-redshift disc galaxies

We study outflows driven by Active Galactic Nuclei (AGNs) using high- resolution simulations of idealized z=2 isolated disk galaxies. Episodic accretion events lead to outflows with velocities >1000 km/s and mass outflow rates up to the star formation rate (several tens of Msun/yr). Outflowing winds escape perpendicular to the disk with wide opening angles, and are typically asymmetric (i.e. unipolar) because dense gas above or below the AGN in the resolved disk inhibits outflow. Owing to rapid variability in the accretion rates, outflowing gas may be detectable even when the AGN is effectively "off." The highest velocity outflows are sometimes, but not always, concentrated within 2-3 kpc of the galactic center during the peak accretion. With our purely thermal AGN feedback model -- standard in previous literature -- the outflowing material is mostly hot (10^6 K) and diffuse (nH<10^(-2) cm-3), but includes a cold component entrained in the hot wind. Despite the powerful bursts and high outflow rates, AGN feedback has little effect on the dense gas in the galaxy disk. Thus AGN-driven outflows in our simulations do not cause rapid quenching of star-formation, although they may remove significant amounts of gas of long (>Gyr) timescales.

DISCOVERY OF X-RAY EMISSION FROM THE FIRST Be/BLACK HOLE SYSTEM

MWC 656 (= HD 215227) was recently discovered to be the first binary system composed of a Be star and a black hole (BH). We observed it with \textit{XMM-Newton}, and detected a faint X-ray source compatible with the position of the optical star, thus proving it to be the first Be/BH X-ray binary. The spectrum analysis requires a model fit with two components, a black body plus a power law, with $k_{\rm B}T = 0.07^{+0.04}_{-0.03}$~keV and a photon index $\Gamma= 1.0\pm0.8$, respectively. The non-thermal component dominates above $\simeq$0.8 keV. The obtained total flux is $F(0.3$--$5.5~{\rm keV}) = (4.6^{+1.3}_{-1.1})\times10^{-14}$ erg cm$^{-2}$ s$^{-1}$. At a distance of $2.6\pm0.6$~kpc the total flux translates into a luminosity $L_{\rm X} = (3.7\pm1.7)\times10^{31}$ erg s$^{-1}$. Considering the estimated range of BH masses to be 3.8--6.9 $M_{\odot}$, this luminosity represents $(6.7\pm4.4)\times10^{-8}~L_{\rm Edd}$, which is typical of stellar-mass BHs in quiescence. We discuss the origin of the two spectral components: the thermal component is associated with the hot wind of the Be star, whereas the power law component is associated with emission from the vicinity of the BH. We also find that the position of MWC~656 in the radio versus X-ray luminosity diagram may be consistent with the radio/X-ray correlation observed in BH low-mass X-ray binaries. This suggests that this correlation might also be valid for BH high-mass X-ray binaries (HMXBs) with X-ray luminosities down to $\sim10^{-8} L_{\rm Edd}$. MWC~656 will allow the accretion processes and the accretion/ejection coupling at very low luminosities for BH~HMXBs to be studied.

Connecting the Sun and the solar wind: the self-consistent transition of heating mechanisms

We have performed a 2.5 dimensional magnetohydrodynamic simulation that resolves the propagation and dissipation of Alfven waves in the solar atmosphere. Alfvenic fluctuations are introduced on the bottom boundary of the extremely large simulation box that ranges from the photosphere to far above the solar wind acceleration region. Our model is ab initio in the sense that no corona and no wind are assumed initially.The numerical experiment reveals the quasi-steady solution that has the transition from the cool to the hot atmosphere and the emergence of the high speed wind. The global structure of the resulting hot wind solution fairly well agree with the coronal and the solar wind structure inferred from observations. The purpose of this study is to complement the previous paper by Matsumoto & Suzuki (2012) and describe the more detailed results and the analysis method. These results include the dynamics of the transition region and the more precisely measured heating rate in the atmosphere. Particularly, the spatial distribution of the heating rate helps us to interpret the actual heating mechanisms in the numerical simulation.Our estimation method of heating rate turned out to be a good measure for dissipation of Alfven waves and low beta fast waves.

HOT GALACTIC WINDS CONSTRAINED BY THE X-RAY LUMINOSITIES OF GALAXIES

Galactic superwinds may be driven by very hot outflows generated by overlapping supernovae within the host galaxy. We use the Chevalier & Clegg (CC85) wind model and the observed correlation between X-ray luminosities of galaxies and their SFRs to constrain the mass loss rates (\dot{M}_hot) across a wide range of star formation rates (SFRs), from dwarf starbursts to ultra-luminous infrared galaxies. We show that for fixed thermalization efficiency and mass loading rate, the X-ray luminosity of the hot wind scales as L_X ~ SFR^2, significantly steeper than is observed for star-forming galaxies: L_X ~ SFR. Using this difference we constrain the mass-loading and thermalization efficiency of hot galactic winds. For reasonable values of the thermalization efficiency (<~ 1) and for SFR >~ 10 M_sun/yr we find that \dot{M}_hot/SFR <~ 1, significantly lower than required by integrated constraints on the efficiency of stellar feedback in galaxies, and potentially too low to explain observations of winds from rapidly star-forming galaxies. In addition, we highlight the fact that heavily mass-loaded winds cannot be described by the adiabatic CC85 model because they become strongly radiative.

Behaviour of fire weather indices in the 2009–10 New Zealand wildland fire season

The Weather Research and Forecasting mesoscale atmospheric model was used to investigate fire weather conditions during the 2009–10 New Zealand wildland fire season. The analysis considered New Zealand's version of the Fire Weather Index used in the Canadian Forest Fire Danger Rating System, the Haines Index (HI) and the Continuous Haines Index (CHI). This represents the first investigation in New Zealand of the HI and CHI, which rate the potential for extreme fire behaviour or large fire growth based on the lower tropospheric atmospheric stability and humidity. The wildland fire activity during the 2009–10 fire season was typical of New Zealand, and there was considerable spatial and temporal variability in the fire weather conditions. The most frequent severe fire weather conditions as quantified by the fire weather indices occurred to the east of the dividing mountain ranges in both the North Island and South Island, and were associated with the hot, dry and windy north-westerly foehn winds that commonly affect New Zealand. The 36 wildland fires greater in area than 5 ha during the 2009–10 fire season occurred under a range of fire weather conditions, and no correlation was found between the wildland fire size and each individual weather variable.

Cool, warm and hot outflows from CTTS: The FUV view of DG Tau

Classical T Tauri stars (CTTSs) drive strong outflows with temperatures from about 103 K up to a few 106 K. These outflows regulate the angular momentum balance and are therefore tightly related to the accretion process. However, the outflow driving and heating mechanisms are not well understood. We present new HST data of the “prototypical” jet-driving CTTS DG Tau tracing the low-temperature outflow with fluorescently excited far-UV molecular hydrogen emission and the high-temperature part with C IV emission. We find that the spatial distribution of the low-temperature plasma is V-shaped consistent with molecular disk-wind models. Low-velocity shocks (vshock ~ 30 km s−1 ) are probably the pumping source for the FUV H 2 lines. The hot plasma (T > 105 K) is located close to the jet axis at a distance of 40 AU from the driving source and spatially offset from standard (optical) jet-tracers like [S II] or [O I]. It does not show any hints for proper-motion contrasting typical jet properties. The high-temperature plasma is unlikely caused by a hot stellar wind and we propose that the stationary heating is caused by internal shocks or magnetic reconnection.

On the spatial structure and time evolution of shamal winds over the Arabian Sea – a case study through numerical modelling

ABSTRACTShamal events are extra‐tropical weather systems which occur in winter (cold and dry winds) as well as summer (hot and humid winds) with strong northwesterly or northerly winds blowing over the Arabian Peninsula. We have used Weather Research and Forecasting (WRF) model to simulate a major winter shamal event (having duration of 3–5 days), which occurred in 2008 and analysed the spatial structure and time evolution of shamal winds over the Arabian Sea (AS). The study reveals that horizontally, shamal winds extend upto 14°N and bring out significant changes in the atmospheric temperature—longitudinally from Arabian coast to west coast of India; its vertical extension is upto to approximately 8 km near Oman and approximately 3 km near Ratnagiri coast. Along the Arabian coast a temperature drop of 12 °C is observed and along west coast of India a drop of 5 °C. It gets dissipated when northeast monsoon winds dominate. Its speed reduces from 15 m s−1 (Oman coast) to 9 m s−1 (central AS) as it propagates into AS. However, it must be noted that the present work is limited to a case study and hence, the southerly extension of the phenomenon and the associated changes in air temperature should not be considered a climatological reference. The shamal events may influence the wind induced circulation, heat flux and stratification in the AS, and these need to be analysed further.

EVIDENCE OF HOT HIGH VELOCITY PHOTOIONIZED PLASMA FALLING ON ACTIVELY ACCRETING T TAURI STARS

The HeII (1640 A) line and the resonance doublet of NV (UV1) provide a good diagnostic tool to constrain the excitation mechanism of hot (Te>40,000K) atmospheric/magnetospheric plasmas in T Tauri stars (TTSs). Making use of the data available in the Hubble Space Telescope Archive, this work shows that there are, at least, two distinct physical components contributing to the radiation in these tracers: the accretion flow sliding on the magnetosphere and the atmosphere. The NV profiles are symmetric and at rest with respect to the star in most sources. The velocity dispersion of the profile increases from non-accreting (40 km/s) to accreting (120 km/s) TTSs suggesting that the macroturbulence in the line formation region decreases as the stars approach the main sequence. Evidence of the NV line being formed in a hot solar-like wind has been found in RW Aur, HN Tau and AA Tau. The HeII profile has a strong narrow component that dominates the line flux; the dispersion of this component ranges from 20 to 60 km/s. The sources of this radiation is uncertain. Current data suggest that both accretion shocks and atmospheric emission might contribute to the line flux. In some sources de HeII line shows a broad and rewards shifted emission component often accompanied by semiforbidden OIII emission that has a critical density of about 3.4e10 cm-3. In spite of the different origins (inferred from the kinematics of the line formation region), NV and HeII fluxes are strongly correlated, with the possible exception of the heaviest accretors.

Effects of Roughness Strip and Acoustic Sensor Height on Subsonic Boundary Layer by Experiment

According to the measurement requirements of acoustic fatigue load on aft fuselage structure and the external installation restriction of the acoustic sensor on aircraft surface, an acoustic sensor is installed on the silencing jet test plate with reference to body type of the real aircraft. A dynamic test and analysis system combined hot wire wind speed measurement and acoustic spectrum measurement is built up for the combined experiments with different acoustic sensor height and various boundary layer flow structure at subsonic flow condition. Turbulence development of different boundary layer is analyzed. The test result can be coordinated with the local measurement to aircraft flow structure so as to estimate the effect of acoustic sensor on the flow field.

Optical IFU observations of gas pillars surrounding the super star cluster NGC 3603

We present optical integral field unit (IFU) observations of two gas pillars surrounding the Galactic young massive star cluster NGC 3603. The high S/N and spectral resolution of these data have allowed us to accurately quantify the H-alpha, [NII] and [SII] emission line shapes, and we find a mixture of broad (FWHM~70-100 km/s) and narrow (<50 km/s) components. The broad components are found close to the edges of both pillars, suggesting that they originate in turbulent mixing layers (TMLs) driven by the effect of the star cluster wind. Both pillars exhibit surprisingly high ionized gas densities of >10000 cm-3. In one pillar we found that these high densities are only found in the narrow component, implying it must originate from deeper within the pillar than the broad component. From this, together with our kinematical data, we conclude that the narrow component traces a photoevaporation flow, and that the TML forms at the interface with the hot wind. On the pillar surfaces we find a consistent offset in radial velocity between the narrow (brighter) components of H-alpha and [NII] of ~5-8 km/s, for which we were unable to find a satisfactory explanation. We urge the theoretical community to simulate mechanical and radiative cloud interactions in more detail to address the many unanswered questions raised by this study.

Soldering of solution-processed organic vertical transistor and light-emitting diode on separate glass substrates by tin micro-balls

The vertical organic space-charge-limited transistor made of P3HT and small-molecule phosphorescent organic light-emitting diode (OLED) are made on two separate glass substrate by blade coating, then soldered vertically together by tin balls with 40μm diameter. The soldering is done by hot wind of 150°C for 5min Contact resistance is only 10Ω. The vertical transistor is annealed at 150°C for 5min before soldering to enhance the output current up to 25mA/cm2 and give high thermal stability. Both OLED and the annealed vertical transistor are not affected by the soldering process. The vertical transistor has 1/4 of the OLED area and turns on the bottom-emission white OLED up to 300cd/m2 and orange OLED up to 600cd/m2. The entire operation is within 8V. OLED and transistor array can therefore be made on separate glass substrates then soldered together to form the display.

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.