Evolution of star clusters in a cosmological tidal field

We present a method to couple N-body star cluster simulations to a cosmological tidal field, using the Astrophysical Multipurpose Software Environment. We apply this method to star clusters embedded in the CosmoGrid dark matter-only LambdaCDM simulation. Our star clusters are born at z = 10 (corresponding to an age of the Universe of about 500 Myr) by selecting a dark matter particle and initializing a star cluster with 32,000 stars on its location. We then follow the dynamical evolution of the star cluster within the cosmological environment. We compare the evolution of star clusters in two Milky-Way size haloes with a different accretion history. The mass loss of the star clusters is continuous irrespective of the tidal history of the host halo, but major merger events tend to increase the rate of mass loss. From the selected two dark matter haloes, the halo that experienced the larger number of mergers tends to drive a smaller mass loss rate from the embedded star clusters, even though the final masses of both haloes are similar. We identify two families of star clusters: native clusters, which become part of the main halo before its final major merger event, and the immigrant clusters, which are accreted upon or after this event; native clusters tend to evaporate more quickly than immigrant clusters. Accounting for the evolution of the dark matter halo causes immigrant star clusters to retain more mass than when the z=0 tidal field is taken as a static potential. The reason for this is the weaker tidal field experienced by immigrant star clusters before merging with the larger dark matter halo.Comment: 14 pages, 14 figures, accepted for publication in MNRA

High risk of adverse events in hospitalised hip fracture patients of 65 years and older: results of a retrospective record review study

Objectives Hip fracture patients of 65 years and older are a complex patient group who often suffer from complications and difficult rehabilitation with disappointing results. It is unknown to what extent suboptimal hospital care contributes to these poor outcomes. This study reports on the scale, preventability, causes and prevention strategies of adverse events in patients, aged 65 years and older, admitted to the hospital with a primary diagnosis of hip fracture. Design, setting and outcome measures A retrospective record review study was conducted of 616 hip fracture patients (≥65 years) admitted to surgical or orthopaedic departments in four Dutch hospitals in 2007. Experienced physician reviewers determined the presence and preventability of adverse events, causes and prevention strategies using a structured review form. The main outcome measures were frequency of adverse events and preventable adverse events in hospitalised hip fracture patients of 65 years and older, and strategies to prevent them in the future. Results 114 (19%) of the 616 patients in the study experienced one or more adverse events; 49 of these were preventable. The majority of the adverse events (70%) was related to the surgical procedure and many resulted in an intervention or additional treatment (67%). Human causes contributed to 53% of the adverse events, followed by patient-related factors (39%). Training and close monitoring of quality of care and the health professional's performance were the most often selected strategies to prevent these adverse events in the future. Conclusions The high percentage of preventable adverse events found in this study shows that care for older hospitalised hip fracture patients should be improved. More training and quality assurance is required to provide safer care and to reduce the number of preventable adverse events in this vulnerable patient group

Determination of the morphological texture of the fibres in a composite material made from a textile of AISI 316L fibres using a mixed deconvolution/positivity method

The orientation distribution or 'morphological texture function' (MTF) of the fibres is determined from measurements of the crystallographic texture of the fibres themselves. From neutron diffraction pole-figure measurements of the fibres in the composite and X-ray diffraction pole figures of the individual fibres, the MTF is determined by a deconvolution. To account for errors in the expansion coefficients due to measurement uncertainties, the deconvolution is performed simultaneously with a positivity criterion in the form of a set of linear equations which may be solved by a least-squares method. This approach is validated using a model system of AISI 316L stainless-steel fibres in an Al-13 wt% Si eutectic casting alloy. The fibres had been spun into yarns and subsequently woven to form a textile. The composite was made by infiltrating a 'brick' containing several layers of the textile with the Al alloy. The results of the deconvolution procedure show that the method indeed yields the expected morphological texture. The so-determined MTF is resolved to an angular resolution not attainable by other methods. It also provides a very good estimate of the volume fractions of the different texture components.status: publishe

Determination of morphological textures of the fibres in composite materials made from textiles of carbon fibres

The orientation distribution of fibres (morphological texture) in a composite is very important in determining the properties of the material. Therefore, methods which can provide quantitative descriptions of the morphological texture are essential. One approach to determining the morphological texture function (MTF) is to measure the orientation distribution of the crystals in the fibres. Since many types of reinforcing fibres are crystalline and textured (i.e. carbon fibres, whiskers, etc.) this approach may be interesting for commercial/industrial applications. For this technique to be applied, the crystallographic texture intrinsic to the fibres must be determined and subsequently measurements of the crystallographic texture should be made in the composite. The morphological texture can then be calculated by a deconvolution of the composite texture with the fibre's intrinsic texture. In this paper, morphological textures are determined in woven fabrics made from carbon fibres embedded in a polymer matrix. Straight fibres removed from the fabric serve as the reference material for the deconvolution. It is demonstrated that this technique is applicable and can resolve the orientation distribution to an accuracy greater than is needed for determining the elastic properties.status: publishe

Determination of the morphological texture of the fibres in a composite material made from a textile of AISI 316L fibres using a mixed deconvolution/positivity method

The orientation distribution or 'morphological texture function' (MTF) of the fibres is determined from measurements of the crystallographic texture of the fibres themselves. From neutron diffraction pole-figure measurements of the fibres in the composite and X-ray diffraction pole figures of the individual fibres, the MTF is determined by a deconvolution. To account for errors in the expansion coefficients due to measurement uncertainties, the deconvolution is performed simultaneously with a positivity criterion in the form of a set of linear equations which may be solved by a least-squares method. This approach is validated using a model system of AISI 316L stainless-steel fibres in an Al-13 wt% Si eutectic casting alloy. The fibres had been spun into yarns and subsequently woven to form a textile. The composite was made by infiltrating a 'brick' containing several layers of the textile with the Al alloy. The results of the deconvolution procedure show that the method indeed yields the expected morphological texture. The so-determined MTF is resolved to an angular resolution not attainable by other methods. It also provides a very good estimate of the volume fractions of the different texture components

TEM and X-ray diffraction investigation of the structural characteristics of the microporous oxide film formed on polycrystalline Ti

The microporous TiO2 layer in the vicinity of the Ti-TiO2 interface is formed by a great amount of tiny crystallites. Bigger anatase and rutile crystals stand in the outer region of the oxide. The orientation of a proportion of the TiO2 crystals is influenced by the underlying textured Ti substrate. © 2003 Published by Elsevier Science Ltd. on behalf fo Acta Materialia Inc.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Determination of the Morphological Textures of Fibres in a Composite Material Made from a Textile of AISI 316L Fibres

NRC publication: Ye