On the Importance of the Interclump Medium for Superionization: O VI Formation in the Wind of Zeta Pup

We have studied superionization and X-ray line formation in the spectra of Zeta Pup using our new stellar atmosphere code (XCMFGEN) that can be used to simultaneously analyze optical, UV, and X-ray observations. Here, we present results on the formation of the O VI ll1032, 1038 doublet. Our simulations, supported by simple theoretical calculations, show that clumped wind models that assume void in the interclump space cannot reproduce the observed O VI profiles. However, enough O VI can be produced if the voids are filled by a low density gas. The recombination of O VI is very efficient in the dense material but in the tenuous interclump region an observable amount of O VI can be maintained. We also find that different UV resonance lines are sensitive to different density regimes in Zeta Pup : C IV is almost exclusively formed within the densest regions, while the majority of O VI resides between clumps. N V is an intermediate case, with contributions from both the tenuous gas and clumps.Comment: Accepted for publication in ApJL, 4 pages with 3 figure

Evidence for sub-Chandrasekhar-mass progenitors of Type Ia supernovae at the faint end of the width-luminosity relation

The faster light-curve evolution of low-luminosity Type Ia supernovae (SNe Ia) suggests that they could result from the explosion of white dwarf (WD) progenitors below the Chandrasekhar mass ($M_{\rm Ch}$). Here we present 1D non-LTE time-dependent radiative transfer simulations of pure central detonations of carbon-oxygen WDs with a mass (M_\rm{tot}) between 0.88 M$_{\odot}$ and 1.15 M$_{\odot}$, and a $^{56}\rm{Ni}$ yield between 0.08 M$_{\odot}$ and 0.84 M$_{\odot}$. Their lower ejecta density compared to $M_{\rm Ch}$ models results in a more rapid increase of the luminosity at early times and an enhanced $\gamma$-ray escape fraction past maximum light. Consequently, their bolometric light curves display shorter rise times and larger post-maximum decline rates. Moreover, the higher M(^{56}\rm{Ni})/M_\rm{tot} ratio at a given $^{56}\rm{Ni}$ mass enhances the temperature and ionization level in the spectrum-formation region for the less luminous models, giving rise to bluer colours at maximum light and a faster post-maximum evolution of the $B-V$ colour. For sub-$M_{\rm Ch}$ models fainter than $M_B\approx -18.5$ mag at peak, the greater bolometric decline and faster colour evolution lead to a larger $B$-band post-maximum decline rate, $\Delta M_{15}(B)$. In particular, all of our previously-published $M_{\rm Ch}$ models (standard and pulsational delayed detonations) are confined to $\Delta M_{15}(B) < 1.4$ mag, while the sub-$M_{\rm Ch}$ models with M_\rm{tot}\lesssim 1 M$_{\odot}$ extend beyond this limit to $\Delta M_{15}(B)\approx 1.65$ mag for a peak $M_B\approx -17$ mag, in better agreement with the observed width-luminosity relation (WLR). Regardless of the precise ignition mechanism, these simulations suggest that fast-declining SNe Ia at the faint end of the WLR could result from the explosion of WDs whose mass is significantly below the Chandrasekhar limit.Comment: 10 pages, 6 figures. Accepted for publication in MNRA

On the changes in the physical properties of the ionized region around the Weigelt structures in Eta Carinae over the 5.54-yr spectroscopic cycle

We present HST/STIS observations and analysis of two prominent nebular structures around the central source of Eta Carinae, the knots C and D. The former is brighter than the latter for emission lines from intermediate or high ionization potential ions. The brightness of lines from intermediate and high ionization potential ions significantly decreases at phases around periastron. We do not see conspicuous changes in the brightness of lines from low ionization potential (<13.6 eV) that the total extinction towards the Weigelt structures is that the total extinction towards the Weigelt structures is AsubV =2/0. that the total extinction towards the Weigelt structures is AV = 2.0. Weigelt C and D are characterized by an electron density of that the total extinction towards the Weigelt structures is AV = 2.0. Weigelt C and D are characterized by an electron density of 10exp6.9 cm-3 that does not significantly change throughout the orbital cycle. The electron temperature varies from 5500 K (around periastron) to 7200 K (around apastron). The relative changes in the brightness of He I lines are well reproduced by the variations in the electron temperature alone. We found that, at phases around periastron, the electron temperature seems to be higher for Weigelt C than that of D. The Weigelt structures are located close to the Homunculus equatorial plane, at a distance of about 1240 AU from the central source. From the analysis of proper motion and age, the Weigelt complex can be associated with the equatorial structure called the Butterfly Nebula surrounding the central binary system.Comment: 19 pages, 18 figure

Predicting and understanding teacher use of school consultation services

Special education services offered to students and teachers in Ontario schools have changed dramatically within the past twenty years. Special education service delivery has evolved from a focus on the school psychologist as a psychometrist to the formation of multidisciplinary teams to deal with the needs of special students and their teachers. Students with special needs are no longer always segregated or left to fade into the wallpaper. By recent legislation, all students with special needs are entitled to special education programs suited to their needs. This often results in students being placed into the “least restrictive environment” which is often the regular classroom. Teachers sometimes find themselves in classrooms where several students need special attention and programming. Not having the necessary skills, knowledge or time to deal with these students, teachers need outside support to help them manage and cope with their own needs as well as those of special students. With the help of available consultation services, for example multidisciplinary resource teams, a teacher can learn to understand the needs of special students and plan, in collaboration with resource personnel, programs/curriculum suited to the students’ needs and the teacher’s abilities. However, research has shown that teachers have difficulties referring to and using the consultation services offered by resource personnel and/or School Based Teams. Much of the research to date on teacher use of consultation services focuses on teacher and school related variables, such as sex, teaching experience, class size and school climate. Ajzen and Fishbein’s (1980) theory of reasoned action provides an alternative approach to predicting and understanding teacher use of school consultation services. Through the application of the theory of reasoned action, this research examined the beliefs that affect teacher utilization of available resources, specifically by measuring teachers’ behavioral beliefs, the extent to which consultation is associated with various positive and negative outcomes, and normative beliefs, the extent to which teachers believe that important others think they should consult. In addition to the use of the theory of reasoned action, a Work Environment Scale was used to examine the extent to which teachers’ perceptions of their work environment affects their use of consultation services. Teachers’ intention to consult was significantly determined by their attitude towards consultation and the beliefs (behavioral) that they have about consultation. The beliefs teachers have about consultation include: consultation aids in program planning, benefits students and defines their needs. Teachers also believe that consultation wastes time and involves a lot of red tape. Behavioral beliefs influenced intention to consult more so than normative beliefs. However, teachers’ perceptions of what their principal wanted them to do and their motivation to comply with them was statistically significant. Teachers’ perceptions of their work environment was found to influence teacher use of consultation services. Teachers indicated an above average amount of work pressure and encouragement for them to be self-sufficient and make their own decisions. The discussion examines further teacher intention to consult, their beliefs and attitudes towards consulting and external variables, such as school environment, consultant role and presenting problem. The implications and applications of this study are discussed as well as recommendations for changing teacher use of consultation services

Grinding theory

This report presents a review and extension of current grinding theory. Grinding operations are classified on the basis of (a) the cutting action of the grit, (b) the geometry of wheel and work, (c) the type of chip produced, (d) the existence or otherwise of a continuous lateral traverse of the wheel. The theory is developed using the above method of classification. Recent experimental work by Purcell(12) on the wear of the wheel in surface grinding is reinterpreted in the light of the theory. It is shown to be consistent with the postulate of a constant task per grit. A method of calculation is suggested by which a satisfactory surface grinding technique may be applied to the form grinding of gears, where the task per grit is not independent of the imposed grinding conditions

Studies of the superconducting properties of Sn1-xInxTe (x=0.38 to 0.45) using muon-spin spectroscopy

The superconducting properties of Sn1-xInxTe (x = 0.38 to 0.45) have been studied using magnetization and muon-spin rotation or relaxation (muSR) measurements. These measurements show that the superconducting critical temperature Tc of Sn1-xInxTe increases with increasing x, reaching a maximum at around 4.8 K for x = 0.45. Zero-field muSR results indicate that time-reversal symmetry is preserved in this material. Transverse-field muon-spin rotation has been used to study the temperature dependence of the magnetic penetration depth lambda(T) in the mixed state. For all the compositions studied, lambda(T) can be well described using a single-gap s-wave BCS model. The magnetic penetration depth at zero temperature lambda(0) ranges from 500 to 580 nm. Both the superconducting gap Delta(0) at 0 K and the gap ratio Delta(0)/kBTc indicate that Sn1-xInxTe (x = 0.38 to 0.45) should be considered as a superconductor with intermediate to strong coupling.Comment: 7 pages, 6 figures, 3 table

Grinding theory

This report presents a review and extension of current grinding theory. Grinding operations are classified on the basis of (a) the cutting action of the grit, (b) the geometry of wheel and work, (c) the type of chip produced, (d) the existence or otherwise of a continuous lateral traverse of the wheel. The theory is developed using the above method of classification. Recent experimental work by Purcell(12) on the wear of the wheel in surface grinding is reinterpreted in the light of the theory. It is shown to be consistent with the postulate of a constant task per grit. A method of calculation is suggested by which a satisfactory surface grinding technique may be applied to the form grinding of gears, where the task per grit is not independent of the imposed grinding conditions

Construction of Cell-Resistant Surfaces by Immobilization of Poly(ethylene glycol) on Gold

Considerable effort has been expended in efforts to create surfaces that resist the adsorption of proteins and cells for biomedical applications. The majority of such work has focused on surfaces constructed from bulk polymers or thin polymer films. However, the fabrication of surfaces via self-assembled monolayers (SAMs) has attracted considerable interest because of the robustness, versatility, and wide-ranging applicability of these materials. SAMs are particularly appealing for biological systems where well-defined surface chemistries can be created to facilitate coupling, biorecognition, or cell adhesion along with a host of other applications in biochemistry and biotechnology