The z=0.8596 Damped Lyman Alpha Absorbing Galaxy Toward PKS 0454+039

We present {\it Hubble Space Telescope} and ground--based data on the $z_{abs}=0.8596$ metal line absorption system along the line of sight to PKS 0454+0356. The system is a moderate redshift damped Lyman alpha system, with ${\rm N(HI)}=(5.7\pm0.3)\times10^{20}$~cm$^{-2}$ as measured from the {\it Faint Object Spectrograph} spectrum. We also present ground--based images which we use to identify the galaxy which most probably gives rise to the damped system; the most likely candidate is relatively underluminous by QSO absorber standards ($M_B \sim -19.0$ for $q_0=0.5$ and $H_0=50$ \kms Mpc$^{-1}$), and lies $\sim 8.5h^{-1}$ kpc in projection from the QSO sightline. Ground--based measurements of Zn~II, Cr~II, and Fe~II absorption lines from this system allow us to infer abundances of [Zn/H]=$-1.1$, [Cr/H]=$-1.2$, and [Fe/H]=$-1.2$, indicating overall metallicity similar to damped systems at $z >2$, and that the depletion of Cr and Fe onto dust grains may be even {\it less} important than in many of the high redshift systems of comparable metallicity. Limits previously placed on the 21-cm optical depth in the $z=0.8596$ system, together with our new N(H~I) measurement, suggest a very high spin temperature for the H~I, $T_S >> 580$ K.Comment: changed uuencode header to produce .Z file so that unix uncompress command will work without modifying file nam

Structure of Micro-instabilities in Tokamak Plasmas: Stiff Transport or Plasma Eruptions?

Solutions to a model 2D eigenmode equation describing micro-instabilities in tokamak plasmas are presented that demonstrate a sensitivity of the mode structure and stability to plasma profiles. In narrow regions of parameter space, with special plasma profiles, a maximally unstable mode is found that balloons on the outboard side of the tokamak. This corresponds to the conventional picture of a ballooning mode. However, for most profiles this mode cannot exist and instead a more stable mode is found that balloons closer to the top or bottom of the plasma. Good quantitative agreement with a 1D ballooning analysis is found provided the constraints associated with higher order profile effects, often neglected, are taken into account. A sudden transition from this general mode to the more unstable ballooning mode can occur for a critical flow shear, providing a candidate model for why some experiments observe small plasma eruptions (Edge Localised Modes, or ELMs) in place of large Type I ELMs.Comment: 11 pages, 3 figure

Producing graphite with desired properties

Isotropic or anisotropic graphite is synthesized with precise control of particle size, distribution, and shape. The isotropic graphites are nearly perfectly isotropic, with thermal expansion coefficients two or three times those of ordinary graphites. The anisotropic graphites approach the anisotropy of pyrolytic graphite

Using the local gyrokinetic code, GS2, to investigate global ITG modes in tokamaks. (I) s-α{\alpha} model with profile and flow shear effects

This paper combines results from a local gyrokinetic code with analytical theory to reconstruct the global eigenmode structure of the linearly unstable ion-temperature-gradient (ITG) mode with adiabatic electrons. The simulations presented here employ the s-${\alpha}$ tokamak equilibrium model. Local gyrokinetic calculations, using GS2 have been performed over a range of radial surfaces, x, and for ballooning phase angle, p, in the range -${\pi} {\leq} p {\leq\pi}$, to map out the complex local mode frequency, ${\Omega_0(x, p) = \omega_0(x, p) + i\gamma_0(x, p)}$. Assuming a quadratic radial profile for the drive, namely ${\eta_i = L_n/L_T}$, (holding constant all other equilibrium profiles such as safety factor, magnetic shear etc.), ${\Omega_0(x, p)}$ has a stationary point. The reconstructed global mode then sits on the outboard mid plane of the tokamak plasma, and is known as a conventional or isolated mode, with global growth rate, ${\gamma}$ ~ Max[${\gamma_0(x, p)}$], where ${\gamma_0(x, p)}$ is the local growth rate. Taking the radial variation in other equilibrium profiles (e.g safety factor q(x)) into account, removes the stationary point in ${\Omega_0(x, p)}$ and results in a mode that peaks slightly away from the outboard mid-plane with a reduced global growth rate. Finally, the influence of flow shear has also been investigated through a Doppler shift, ${\omega_0 \rightarrow \omega_0 + n\Omega^{\prime}x}$, where n is the toroidal mode number and ${\Omega^{\prime}}$ incorporates the effect of flow shear. The equilibrium profile variation introduces an asymmetry to the growth rate spectrum with respect to the sign of ${\Omega^{\prime}}$, consistent with recent global gyrokinetic calculations.Comment: 10 pages, 8 figures and 1 tabl

Understanding the response of large South African companies to HIV/AIDS

This paper provides a framework analysing the response of South African companies to HIV/AIDS. Drawing on three case studies of companies, each with over 20 000 South African-based employees, we identify six ‘drivers\' that influence corporate behaviour regarding HIV/AIDS: legal requirements, voluntary regulation, business costs, social pressures, visibility of the disease, and individuals within companies.We suggest that costs calculations, while possibly underestimating indirect and macro-implications, are not key in driving company responses to HIV/AIDS.The law and voluntary regulation have influenced, but not determined, the response of companies to HIV/AIDS. Social pressures on companies are of importance, but the scale and complexity of need in South Africa has seen the deflecting of this driver. Of greater reference in determining responses has been the social pressure of other companies\' responses.The general visibility of the AIDS epidemic is also a significant factor in explaining companies\' responses to HIV/AIDS. Moreover, the visibility of HIV/AIDS within companies has influenced the responses of often relatively weak, internal agents who have been attempting to drive companies\' HIV/AIDS programmes. We conclude that external drivers – legal requirements, economic performance, and social pressures – have framed corporate responses to HIV/AIDS to a degree, but have generally been weak. Moreover, there has been relatively little synergy between these external drivers and the internal drivers – voluntary regulation, visibility, and company HIV/AIDS ‘champions\' – that could propel companies into pro-active, bold responses to HIV/AIDS. Keywords: companies, HIV response, South Africa. RÉSUMÉ Cette communication met &#224 disposition un cadre qui analyse la r&#233ponse des soci&#233t&#233s sud-africaines au VIH/SIDA. En tirant sur trois &#233tudes de cas de ces soci&#233t&#233s, chacune ayant 20 000 employ&#233s vivant en Afrique du Sud, nous identifions six conducteurs qui influencent le comportement de corporation par rapport au VIH/SIDA: des dispositions r&#233glementaires, un r&#232glement volontaire, des coûts d\'affaires, des pressions sociales, une visibilit&#233 de la maladie et des individus au sein des soci&#233t&#233s. Nous sugg&#233rons que les calculs de co&#251ts, entre temps les implications indirectes et macros sont peut-être sousestim&#233es, ne sont pas prioritaires pour diriger les r&#233ponses des soci&#233t&#233s au VIH/SIDA. La loi et le règlement volontaire ont influenc&#233, et non pas d&#233termin&#233, la r&#233ponse des soci&#233t&#233s. Les pressions sociales sur les soci&#233t&#233s ont plus d&#39importance, mais l&#39ampleur et la complexit&#233 du besoin en Afrique du Sud a d&#233tourn&#233 ce conducteur. La pression sociale des r&#233ponses des autres soci&#233t&#233s fut une r&#233f&#233rence importante qui a d&#233termin&#233 la r&#233ponse. La visibilit&#233 g&#233n&#233rale de l&#39&#233pid&#233mie du SIDA est &#233galement un facteur important dans l&#39explication des r&#233ponses de soci&#233t&#233s au VIH/SIDA. D&339autant plus que la visibilit&#233 du VIH/SIDA au sein des soci&#233t&#233s a influenc&#233 les r&#233ponses des agents, souvent relativement faibles, qui ont essay&#233 de diriger les programmes de VIH/SIDA dans les soci&#233t&#233s. Nous tirons la conclusion que les conducteurs externes – les dispositions r&#233glementaires, la performance &#233conomique et les pressions sociales – ont encadr&#233 les r&#233ponses des corporations au VIH/SIDA &#224 un certain degr&#233, mais ils ont &#233t&#233 g&#233n&#233ralement faibles. De plus, il y a eu une synergie relativement petite entre les conducteurs externes et les conducteurs internes – le r&#232glement volontaire, la visibilit&#233 et les ‘champions\' du VIH/SIDA dans la soci&#233t&#233 qui pourraient propulser les soci&#233t&#233s vers des r&#233ponses pro-actives et audacieuses au VIH/SIDA. Mots cl&#233s: soci&#233t&#233s, r&#233ponses au VIH, l&#39Afrique du Sud. Journal of Social Aspects of HIV/AIDS, Vol 2(2) 2005: 286-29

Kinetic instabilities that limit {\beta} in the edge of a tokamak plasma: a picture of an H-mode pedestal

Plasma equilibria reconstructed from the Mega-Amp Spherical Tokamak (MAST) have sufficient resolution to capture plasma evolution during the short period between edge-localized modes (ELMs). Immediately after the ELM steep gradients in pressure, P, and density, ne, form pedestals close to the separatrix, and they then expand into the core. Local gyrokinetic analysis over the ELM cycle reveals the dominant microinstabilities at perpendicular wavelengths of the order of the ion Larmor radius. These are kinetic ballooning modes (KBMs) in the pedestal and microtearing modes (MTMs) in the core close to the pedestal top. The evolving growth rate spectra, supported by gyrokinetic analysis using artificial local equilibrium scans, suggest a new physical picture for the formation and arrest of this pedestal.Comment: Final version as it appeared in PRL (March 2012). Minor improvements include: shortened abstract, and better colour table for figures. 4 pages, 6 figure

Spitzer 70 Micron Source Counts in GOODS-North

We present ultradeep Spitzer 70 μm observations of GOODS-North (Great Observatories Origins Deep Survey). For the first time, the turnover in the 70 μm Euclidean-normalized differential source counts is observed. We derive source counts down to a flux density of 1.2 mJy. From the measured source counts and fluctuation analysis, we estimate a power-law approximation of the faint 70 μm source counts of dN/dS ∝ S^−1.6, consistent with that observed for the faint 24 μm sources. An extrapolation of the 70 μm source counts to zero flux density implies a total extragalactic background light (EBL) of 7.4 ± 1.9 nW m^−2 sr^−1. The source counts above 1.2 mJy account for about 60% of the estimated EBL. From fluctuation analysis, we derive a photometric confusion level of σc = 0.30 ± 0.15 mJy (q = 5) for the Spitzer 70 μm band