Efficient radiative transfer techniques in hydrodynamic simulations

Radiative transfer is an important component of hydrodynamic simulations as it determines the thermal properties of a physical system. It is especially important in cases where heating and cooling regulate sig- nificant processes, such as in the collapse of molecular clouds, the development of gravitational instabilities in protostellar discs, disc-planet interactions, and planet migration. We compare two approximate radiative transfer methods which indirectly estimate optical depths within hydrodynamic simulations using two dif- ferent metrics: (i) the gravitational potential and density of the gas (Stamatellos et al.), and (ii) the pressure scale-height (Lombardi et al.). We find that both methods are accurate for spherical configurations e.g. in collapsing molecular clouds and within clumps that form in protostellar discs. However, the pressure scale- height approach is more accurate in protostellar discs (low and high-mass discs, discs with spiral features, discs with embedded planets). We also investigate the β-cooling approximation which is commonly used when simulating protostellar discs, and in which the cooling time is proportional to the orbital period of the gas. We demonstrate that the use of a constant β cannot capture the wide range of spatial and temporal vari- ations of cooling in protostellar discs, which may affect the development of gravitational instabilities, planet migration, planet mass growth, and the orbital properties of planets

Epidermal growth factor (EGF) withdrawal masks gene expression differences in the study of pituitary adenylate cyclase-activating polypeptide (PACAP) activation of primary neural stem cell proliferation

BACKGROUND: The recently discovered adult neural stem cells, which maintain continuous generation of new neuronal and glial cells throughout adulthood, are a promising and expandable source of cells for use in cell replacement therapies within the central nervous system. These cells could either be induced to proliferate and differentiate endogenously, or expanded and differentiated in culture before being transplanted into the damaged site of the brain. In order to achieve these goals effective strategies to isolate, expand and differentiate neural stem cells into the desired specific phenotypes must be developed. However, little is known as yet about the factors and mechanisms influencing these processes. It has recently been reported that pituitary adenylate cyclase-activating polypeptide (PACAP) promotes neural stem cell proliferation both in vivo and in vitro. RESULTS: We used cDNA microarrays with the aim of analysing the transcriptional changes underlying PACAP induced proliferation of neural stem cells. The primary neural stem/progenitor cells used were neurospheres, generated from the lateral ventricle wall of the adult mouse brain. The results were compared to both differentiation and proliferation controls, which revealed an unexpected and significant differential expression relating to withdrawal of epidermal growth factor (EGF) from the neurosphere growth medium. The effect of EGF removal was so pronounced that it masked the changes in gene expression patterns produced by the addition of PACAP. CONCLUSION: Experimental models aiming at transcriptional analysis of induced proliferation in primary neural stem cells need to take into consideration the significant effect on transcription caused by removal of EGF. Alternatively, EGF-free culture conditions need to be developed

Tools for Dataset Lifecycle Management

With a growing demand for transparency and openness around scientific research and an emphasis on the sharing of scientific workflows and datasets, there is a similarly increasing number in the variety of client and web-based tools required to manage each stage in the lifecycle of individual datasets. Datasets are produced from a variety of instruments and computations; are analyzed and manipulated; are stored and referenced within the context of a research project; and, ideally, are archived, stored, and shared with the rest of the world. Each of these efforts, however, requires a number of user actions involving a growing number of systems and interfaces. In an effort to preserve the flexibility and autonomy of the researchers, but also to minimize the logistical effort involved, we present in this paper a partial solution approach to this problem through the integration of workflow execution, project collaboration, project-based dataset management and versioning, and long-term archiving and dissemination. This example demonstrates the orchestration of a number of existing Microsoft Research projects; however, the interaction between each uses existing web interoperability protocols and can easily support the replacement of individual architectural components with related services

Tools for Dataset Lifecycle Management

With a growing demand for transparency and openness around scientific research and an emphasis on the sharing of scientific workflows and datasets, there is a similarly increasing number in the variety of client and web-based tools required to manage each stage in the lifecycle of individual datasets. Datasets are produced from a variety of instruments and computations; are analyzed and manipulated; are stored and referenced within the context of a research project; and, ideally, are archived, stored, and shared with the rest of the world. Each of these efforts, however, requires a number of user actions involving a growing number of systems and interfaces. In an effort to preserve the flexibility and autonomy of the researchers, but also to minimize the logistical effort involved, we present in this paper a partial solution approach to this problem through the integration of workflow execution, project collaboration, project-based dataset management and versioning, and long-term archiving and dissemination. This example demonstrates the orchestration of a number of existing Microsoft Research projects; however, the interaction between each uses existing web interoperability protocols and can easily support the replacement of individual architectural components with related services

Multimorbidity and socioeconomic deprivation in primary care consultations

Purpose: The influence of multimorbidity on the clinical encounter is poorly understood, especially in areas of high socioeconomic deprivation where burdensome multimorbidity is concentrated. The aim of the current study was to examine the effect of multimorbidity on general practice consultations, in areas of high and low deprivation. Methods: We conducted secondary analyses of 659 video-recorded routine consultations involving 25 general practitioners (GPs) in deprived areas and 22 in affluent areas of Scotland. Patients rated the GP’s empathy using the Consultation and Relational Empathy (CARE) measure immediately after the consultation. Videos were analyzed using the Measure of Patient-Centered Communication. Multilevel, multi-regression analysis identified differences between the groups. Results: In affluent areas, patients with multimorbidity received longer consultations than patients without multimorbidity (mean 12.8 minutes vs 9.3, respectively; P = .015), but this was not so in deprived areas (mean 9.9 minutes vs 10.0 respectively; P = .774). In affluent areas, patients with multimorbidity perceived their GP as more empathic (P = .009) than patients without multimorbidity; this difference was not found in deprived areas (P = .344). Video analysis showed that GPs in affluent areas were more attentive to the disease and illness experience in patients with multimorbidity (P < .031) compared with patients without multimorbidity. This was not the case in deprived areas (P = .727). Conclusions: In deprived areas, the greater need of patients with multimorbidity is not reflected in the longer consultation length, higher GP patient centeredness, and higher perceived GP empathy found in affluent areas. Action is required to redress this mismatch of need and service provision for patients with multimorbidity if health inequalities are to be narrowed rather than widened by primary care

Transcriptome analysis in primary neural stem cells using a tag cDNA amplification method

BACKGROUND: Neural stem cells (NSCs) can be isolated from the adult mammalian brain and expanded in culture, in the form of cellular aggregates called neurospheres. Neurospheres provide an in vitro model for studying NSC behaviour and give information on the factors and mechanisms that govern their proliferation and differentiation. They are also a promising source for cell replacement therapies of the central nervous system. Neurospheres are complex structures consisting of several cell types of varying degrees of differentiation. One way of characterising neurospheres is to analyse their gene expression profiles. The value of such studies is however uncertain since they are heterogeneous structures and different populations of neurospheres may vary significantly in their gene expression. RESULTS: To address this issue, we have used cDNA microarrays and a recently reported tag cDNA amplification method to analyse the gene expression profiles of neurospheres originating from separate isolations of the lateral ventricle wall of adult mice and passaged to varying degrees. Separate isolations as well as consecutive passages yield a high variability in gene expression while parallel cultures yield the lowest variability. CONCLUSIONS: We demonstrate a low technical amplification variability using the employed amplification strategy and conclude that neurospheres from the same isolation and passage are sufficiently similar to be used for comparative gene expression analysis

Дистанционное обучение начертательной геометрии

Appendix 1: Data dictionary. Appendix 2: Read Codes used to define the presence of intellectual disability (DOCX 21 kb