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Jets are a commonly observed phenomenon in post-asymptotic giant branch (post-AGB) binaries. Due to the orbital motion of the binary, the jet causes variable absorption in the Balmer profiles. In previous work, we have developed spatio-kinematic and radiative transfer models to reproduce the observed Balmer line variability and derive the spatio-kinematic structure of the jet and its mass-loss rate. Here, we apply our jet model to five post-AGB binaries with distinct H{\alpha} line variability and diverse orbital properties. Our models fit the H{\alpha} line variations very well. We estimate jet mass-loss rates between 10-8 Mdot yr-1 and 10-4 Mdot yr-1 , from which we deduce accretion rates onto the companion between 10-7 Mdot yr-1 and 10-3 Mdot yr-1 . These accretion rates are somewhat higher than can be comfortably explained with reasonable sources of accretion, but we argue that the circumbinary disc in these systems is most-likely the source feeding the accretion, although accretion from the post-AGB star cannot be ruled out. The diversity of the variability in the five objects is due to their wide ejection cones combined with a range of viewing angles, rather than inherent differences between the objects. The nature of the observations does not let us easily distinguish which jet launching model (stellar jet, disc wind, or X-wind) should be favoured. In conclusion, we show that our jet model includes the physical parameters to successfully reproduce the H{\alpha} line variations and retrieve the structure and mass-loss rates of the jet for all five objects that are representative of the diverse sample of Galactic post-AGB binaries., Comment: 20 pages, 9 figures, accepted for publication in MNRAS

Aims. We aim to determine the geometry, density gradient, and velocity structure of jets in post-asymptotic giant branch (post-AGB) binaries. Methods. Our high cadence time series of high-resolution optical spectra of jet-creating post-AGB binary systems provide us with a unique tomography of the jet. We determine the spatio-kinematic structure of the jets based on these data by fitting the synthetic spectral line profiles created by our model to the observed, orbital phase-resolved, H{\alpha}-line profiles of these systems. The fitting routine is provided with an initial spectrum and is allowed to test three configurations, derived from three specific jet launching models: a stellar jet launched by the star, an X-wind, and a disk wind configuration. We apply a Markov-chain Monte Carlo routine in order to fit our model to the observations. Our fitting code is tested on the post-AGB binary IRAS19135+3937. Results. We find that a model using the stellar jet configuration gives a marginally better fit to our observations. The jet has a wide half-opening angle of about 76 degrees and reaches velocities up to 870 km/s. Conclusions. Our methodology is successful in determining some parameters for jets in post-AGB binaries. The model for IRAS19135+3937 includes a transparent, low density inner region (for a half-opening angle < 40 degrees). The source feeding the accretion disk around the companion is most likely the circumbinary disk. We will apply this jet fitting routine to other jet-creating post-AGB stars in order to provide a more complete description of these objects., Comment: 14 pages, 12 figures, accepted for publication in A&A

Aims. In this study, we determine the morphology and mass-loss rate of jets emanating from the companion in post-asymptotic giant branch (post-AGB) binary stars with a circumbinary disk. In doing so, we also determine the mass accretion rates on to the companion and investigate the source feeding the circum-companion accretion disk. Methods. We perform a spatio-kinematic modelling of the jet of two well-sampled post-AGB binaries, BD+46442 and IRAS19135+3937, by fitting the orbital phased time series of H-alpha spectra. Once the jet geometry, velocity and scaled density structure are computed, we carry out radiative transfer modelling of the jet for the first four Balmer lines to determine the jet densities, thus allowing us to compute the jet mass-loss rates and mass accretion rates. Results. The spatio-kinematic model of the jet reproduces the observed absorption feature in the H-alpha lines. In both objects, the jets have an inner region with extremely low density. Using our radiative transfer model, we find the full three-dimensional density structure of both jets. From these results, we can compute mass-loss rates of the jets, which are of the order of 10^-7 - 10^-5 M_sol/yr. We estimate mass accretion rates onto the companion of 10^-6 - 10^-4 M_sol/yr. Conclusions. Based on the mass accretion rates found for these two objects, we conclude that the circumbinary disk is most likely the source feeding the circum-companion accretion disk. This is in agreement with the observed depletion patterns in post-AGB binaries. The high accretion rates from the circumbinary disk imply that the lifetime of the disk will be short. Mass-transfer from the post-AGB star cannot be excluded in these systems, but it is unlikely to provide a sufficient mass-transfer rate to sustain the observed jet mass-loss rates., Comment: 16 pages, 13 figures, accepted for publication in A&A

Context. Some RV Tauri stars show a long-term photometric variability in their mean magnitudes. DF Cygni (DF Cyg), the only RV Tauri star in the original Kepler field, and the prototype RV Tauri (RV Tau) are two such stars. Aims. The focus of this paper is on two famous but still poorly understood RV Tauri stars: RV Tau and DF Cyg. We aim to confirm their suspected binary nature and derive their orbital elements to investigate the impact of their orbits on the evolution of these systems. This research is embedded in a wider endeavour to study binary evolution of low- and intermediate-mass stars. Methods. The high amplitude pulsations were cleaned from the radial-velocity data to better constrain the orbital motion, allowing us to obtain accurate orbital parameters. We also analysed the photometric time series of both stars using a Lomb-Scargle periodogram. We used Gaia Data Release 2 (DR2) parallaxes in combination with the spectral energy distributions (SEDs) to compute their luminosities. These luminosities were complemented with the ones we computed using a period-luminosity-colour (PLC) relation for RV Tauri stars. The ratio of the circumstellar infrared (IR) flux to the photospheric flux obtained from the SEDs was used to estimate the orbital inclination of each system. Results. DF Cyg and RV Tau are binaries with spectroscopic orbital periods of 784 ± 16 days and 1198 ± 17 days, respectively. These orbital periods are found to be similar to the long-term periodic variability in the photometry, indicating that binarity indeed explains the long-term photometric variability. The SEDs of these systems indicate the presence of a circumbinary disc. Our line of sight grazes the dusty disc, which causes the photometric flux from the star to extinct periodically with the orbital period. Our derived orbital inclinations enabled us to obtain accurate companion masses for DF Cyg and RV Tau, and these were found to be 0.6 ± 0.1 M⊙ and 0.7 ± 0.1 M⊙ ,respectively. The derived luminosities suggest that RV Tau is a post asymptotic giant branch (post-AGB) binary, while DF Cyg is likely a post red giant branch (post-RGB) binary. Analysis of the Kepler photometry of DF Cyg revealed a power spectrum with side lobes around the fundamental pulsation frequency. This modulation corresponds to the spectroscopic orbital period and hence to the long-term photometric period. Finally we report on the evidence of high velocity absorption features related to the Hα profile in both objects, indicating outflows launched from around the companion., SCOPUS: ar.j, info:eu-repo/semantics/published

In this study the growth mechanism of {111 tabular silver halide crystals will be examined. The side-face structure and aspect ratio of tabular silver bromide crystals grown from different concentrations of silver bromide dissolved in dimethylsulphoxide (DMSO) were established in situ and ex situ. For tabular silver bromide crystals grown by the industrial double―jet precipitation method, transmission electron microscopy images of ultramicrotomed sections of the side faces were analysed. Also for tabular silver bromide and tabular silver chloride crystals grown from the vapour phase the relation between the aspect ratio and side-face structure was studied. Using the result of the different crystallization techniques it is shown that there is a strong relation between the aspect ratio and the side-face structure. For tabular crystals grown from DMSO, by industrial double-jet precipitation and from the vapour phase the same relation between the aspect ratio and side-face structure is observed. This provides evidence to support the idea that the growth mechanism of 111} tabular crystals is universal and independent of the crystal growth technique or crystallization medium. The preferential lateral growth of the tabular crystals can be explained by the substep mechanism proposed by Ming and co-workers in an earlier study. This mechanism explains the increase in growth rate of a {111} side face linked via a twin plane to a faster growing { 100} side face.

Results of computer simulation studies of crystal surfaces and related crystal growth mechanisms as well as statistical mechanical roughening transition theories of these surfaces are reviewed. The implications of these theories for crystal growth mechanisms, such as the spiral growth mechanism and the substep mechanism, recently described by Ming and co-workers, are treated briefly. Relations between roughening theories and recent developments in the crystallographic morphological theory of Hartman and Perdok are introduced. It is shown how this integrated theory can be applied to crystals having an NaCI structure, such as AgBr and AgCl crystals. The most stable faces are the {100} and {111} faces respectively. The {111} faces will be stable only if the high dipole moment can be removed by reconstruction or interaction with the solvent. Supersaturation is the key parameter that determines the growth morphology. At low supersaturations, only {100} faces are present. At higher supersaturations, {111 faces will become dominant. On these faces, formation of twins will occur at even higher supersaturations, leading, as a result of the substep mechanism, to tabular and needle-like crystals. The detailed understanding of all kinds of tabular and needle-like AgBr and AgCl crystals will be the subject of a subsequent paper.

This study deals with the morphology and growth mechanism of multiply twinned Ag crystals grown from the vapor phase. Ag crystals were grown under sublimation conditions for small growth rates as a function of the driving force and sublimation temperature. At relatively low driving force and low temperature cubooctahedrons and single twinned crystals appeared. At higher driving forces also {111} tabular crystals (containing multiple parallel twin planes) and 5-fold twinned structures resulting in decahedrons, icosahedrons, and elongated decahedrons bounded by {100} sides faces, were observed together with other nonparallel twinned crystals. Increasing the driving force further led to tabular crystals with higher aspect ratios and different side-face structures; the preferential unidirectional growth of the elongated decahedrons was also increased. The growth mechanism of {111} tabular Ag crystals and other multiply twinned Ag crystals is for the first time studied in detail. The influence of the driving f...

In this study the morphology and growth mechanism of AgX (X=Cl, Br) needle crystals will be revealed. The silver halide needles are grown by two different techniques. AgBr needles are grown with an extractive crystallization in a dimethylsulfoxide–water mixture and AgCl needles are grown from the vapor phase. All needles contain nonparallel twin planes. The morphology of the AgBr needles grown from dimethylsulfoxide is the same as the needles grown in the industrial precipitation process in water. The side faces of these solution grown needles are built up of relatively slowly growing {1 1 1} faces. Both needle tops are composed of three relatively fast growing {1 0 0} faces making a ridge structure. The vapor-grown needles have two different morphologies. For both types the side faces consist of four {1 1 1} and two {1 0 0} faces. All {1 1 1} faces are linked via twin planes to a fast growing {1 0 0} face. The preferential unidirectional growth of all needles is caused by cross-twinning. The preferential growth occurs along the intersection line of the twin planes. Between the twin planes a rough growing face appears on the needle top. This face is capable of increasing the growth rate of the other top faces owing to the substep mechanism.

Crystals of pure AgX (X = Cl, Br) were grown from the vapour phase on copper and quartz substrates. For both AgBr and AgCl the same morphologies appear namely, cubic, {100} tabular, {100} tabular with (411) twinning, cubooctahedral, {111} tabular and needle shaped. These morphologies are the same as obtained for pure silver bromide from precipitation. So, the role of the solvent in the growth process could be examined. The vapour growth morphology turns out to depend strongly on the temperature difference between the furnace and the substrate. At low temperature difference the {100} faces were observed, whereas at higher driving force the {111} faces became more visible. At a critical temperature difference twin planes parallel to the {111} faces were formed resulting in tabular crystals (multi-parallel twinning) and needle shaped crystals (also non-parallel twinning). Due to the occurrence of {111} tabular crystals for both AgBr and AgCl and the constant driving force during the experiments, con...

The morphology of crystals precipitated from silver bromide complex solutions in organic solvents has been studied by scanning electron microscopy. {1 0 0}, {1 1 1}, {1 1 0} and {3 3 1} were the main forms found in these crystals. The crystals could adopt a large variety of shapes similar to those found in aqueous precipitation. The large size of the crystals allowed a clear observation of the side faces on tabular crystals. The expected ridge-trough disposition of {1 1 1} faces on the sides was very rarely observed and only as a result of crystal fracturing or re-dissolution. On the contrary, the sides were formed by a continuous plane from top to bottom forming an acute dihedral angle alternatively with the top and bottom face in the hexagonal crystals, and, by two planes with an outward inclination meeting at some middle point in the case of triangular crystals. {1 0 0} faces were also observed on the sides of relatively thick tabular crystals sitting on the acute edges.

In this study the growth of {1 1 1} tabular silver bromide crystals will be examined in situ under different conditions to determine a general growth mechanism. We established the side-face structure and aspect ratio of the tabular crystals for different concentrations of silver bromide dissolved in DMSO during the growth. The morphology of non-twinned crystals was studied to examine the relative growth rate of the {1 0 0} faces as compared to the {1 1 1} faces. It will be shown that there is a strong dependency between the relative growth rate of the {1 0 0} faces and the aspect ratio and side-face structures of the {1 1 1} tabular crystals. Relative fast growth of the {1 0 0} faces in comparison to the {1 1 1} faces leads to high aspect ratios and side-face structures with acute edges built up by {1 1 1} side faces. Relative slower growth leads to lower aspect ratios and ridge side-face structures built up by stable {1 1 1} and {1 0 0} faces. The lateral growth for all conditions can be explained by the substep mechanism proposed in an earlier study. This mechanism explains the increase of growth rate of a {1 1 1} side face that is linked via a twin plane to a faster growing {1 0 0} side face. From this mechanism and the observations it will be shown that the faces between the twin planes for double-twinned tabular crystals can be determined. The results presented here are not only valid for tabular crystals grown in the DMSO system but also for tabular crystals grown from the vapour phase and in the industrial precipitation method.

AgCl(I) crystals with (1 0 0) surfaces are studied with conventional transmission electron microscopy for their microstructure in relation with their growth habits. The crystals are prepared according to two different growth methods which give slightly different results. The presence of dislocations of mixed character that end at only two surfaces are in both cases responsible for the tabular growth, but the formation of these dislocations is different. In the first case, a stacking fault is formed which is eliminated by dislocations. In the second case, the incorporation of iodide impurities is at the origin of the formation of dislocations.

Nucleation and growth of silver bromide tabular crystals has been observed insitu for the first time by optical microscopy. Crystals were precipitated by a new method, from solutions of silver bromide and potassium bromide in DMSO. Thin tabular crystals were preferentially produced in a narrow range of silver concentration, after long nucleation periods. A twinning process occurred, generally, in a very early stage of the precipitation. Tabular crystals could appear in a single spot in the absence of other particles and they grew with a very high initial rate. Coalescence of particles was practically discarded as the main mechanism for twinning. Most tabular crystals were initially circular and then were transformed into hexagons or triangles as they developed six or three straight edges. A fast growth rate was associated with rough sides, while straight edges moved more slowly. Changes in crystal shape occurred during the growth process in a way similar to that found by Maskasky in aqueous systems by indirect mapping methods. Changes in crystal shape occurred by roughening on one, three or six crystal edges.

Recently, it has become possible to grow large tabular silver bromide crystals from organic solvents, which makes direct observation of the side faces possible. Solving the side-face structure is a key to understanding the (lateral) growth mechanism of tabular silver bromide crystals. The side-face structure of 42 tabular crystals was determined in detail. The side-face structure of the tabular crystals is built up by flat {111} and {100} cubo-octahedral faces and there are three different kinds of tabular morphology. In all observations, ridge structures were found showing no acute lips. From these determinations, the number of parallel twin planes of the tabular crystals was directly reduced from the side-face structure. The lateral growth of the tabular crystals is described by a substep mechanism. This mechanism explains the increase of growth rate of a {111} side face that is linked with a twin plane to a {100} side face. The proposed substep mechanism is based on a theory of Ming, which is universal and not only valid for the case of silver bromide. The interpretation assumes the presence of only cubo-octahedral faces and the absence of acute lips as observed.

The Mars Exploration Rover Opportunity touched down at Meridiani Planum in January 2004 and since then has been conducting observations with the Athena science payload. The rover has traversed more than 5 km, carrying out the first outcrop-scale investigation of sedimentary rocks on Mars. The rocks of Meridiani Planum are sandstones formed by eolian and aqueous reworking of sand grains that are composed of mixed fine-grained siliciclastics and sulfates. The siliciclastic fraction was produced by chemical alteration of a precursor basalt. The sulfates are dominantly Mg-sulfates and also include Ca-sulfates and jarosite. The stratigraphic section observed to date is dominated by eolian bedforms, with subaqueous current ripples exposed near the top of the section. After deposition, interaction with groundwater produced a range of diagenetic features, notably the hematite-rich concretions known as "blueberries." The bedrock at Meridiani is highly friable and has undergone substantial erosion by wind-transported basaltic sand. This sand, along with concretions and concretion fragments eroded from the rock, makes up a soil cover that thinly and discontinuously buries the bedrock. The soil surface exhibits both ancient and active wind ripples that record past and present wind directions. Loose rocks on the soil surface are rare and include both impact ejecta and meteorites. While Opportunity's results show that liquid water was once present at Meridiani Planum below and occasionally at the surface, the environmental conditions recorded were dominantly arid, acidic, and oxidizing and would have posed some significant challenges to the origin of life. Copyright 2006 by the American Geophysical Union.

A five-year national education program for HIV/AIDS has brought into focus many issues in continuing education and has evolved models worthy of consideration by colleagues in other fields.

AUSTRALIANS ARE BEING encouraged to take greater responsibility for their own health care. The concept of self-care is being promoted widely, including the recent paper released by the National Health and Hospitals Reform Commission1 and, more commercially, by the Australian Self Medication Industry (ASMI).2 Self-care in health refers to the activities individuals, families and communities undertake with the intention of enhancing health, preventing disease, limiting illness, and restoring health. These activities are derived from knowledge and skills from the pool of both professional and lay experience. They are undertaken by lay people on their own behalf, either separately or in participative collaboration with professionals.3 To enable Australian consumers to assume this responsibility, they should have the right to know and have access to the evidence-based status of any treatment they are considering, to enable them to make well-informed choices. This especially applies to medicines.

In the England of 1840, as Professor Chadwick observes, the idea of mission pertained to the lapsed at home as well as the heathen overseas. This article, in discussing connexions between the English Churches and the Australian colonies, deals with a third meaning: colonial mission. The seventeenth-century association of religion and colonisation is well known. The bearing of religion (heathen missions excepted) on the imperialism of the late-eighteenth and early-nineteenth centuries, and the response of English Christianity to settlement colonies in this period, have occasioned less discussion. Most familiar are the points where religion was drawn into imperial policy, as in British North America after the Revolution. Promotion of the Church of England was part of an overhaul of imperial administration in New South Wales as well. But in the new century this method of achieving political and social stability ran into difficulties at home. In Australia it was ineffective and little more popular than in the Canadas. By 1830 religion was ceasing to be an instrument of imperial policy. The new bearers of British Christianity overseas, the evangelical missionary societies, had been founded with the heathen in view and generally avoided other engagements. The missionary fervour of the post-Napoleonic period thus coincided with indifference to the religious needs of emigrants and colonists. A response came in the 1830s in the form of colonial missionary societies and a quickening of the older Church societies. Though never a match for the home and heathen enterprises of Victorian Christianity, the colonial missions had roots in the nation's past. They expressed the various aspirations of the home Churches and were part of the phenomenon of empire.

Poly (ethylene terephthalate) (PET) film was extruded and then successively biaxially stretched and thermofixed to obtain a high-strength film with stable dimensions. Next, the film was shear cut by two rotating circular knives. In the first part of this paper, a microscopic evaluation of the sheared edges of films, cut under a variety of parameters, i.e. cutting speed, film thickness and knife angle, is given. A particular cutting defect, namely the formation of fibres, is discussed. In the second part, a theory for the shear cutting process of PET film and the related fibre formation is presented. Special attention is paid to the influence of the film manufacturing parameters (applied in this study) on the behaviour of the material during shear cutting.