Collisions and Mergers of Disk Galaxies: Hydrodynamics of Star Forming Gas

We summarize the results of numerical simulations of colliding gas-rich disk galaxies in which the impact velocity is set parallel to the spin axes of the two galaxies. The effects of varying the impact speed are studied with particular attention to the resulting gaseous structures and shockwave patterns, and the time needed to produce these structures. The simulations employ an N-body treatment of the stars and dark matter, together with an SPH treatment of the gas, in which all components of the models are gravitationally active. The results indicate that for such impact geometries, collisions can lead to the very rapid formation of a central, rapidly rotating, dense gas disk, and that in all cases extensive star formation is predicted by the very high gas densities and prevalence of shocks, both in the nucleus and out in the galactic disks. As the dense nucleus is forming, gas and stars are dispersed over very large volumes, and only fall back towards the nucleus over long times. In the case of low impact velocities, this takes an order of magnitude more time than that needed for the formation of a dense nucleus.Comment: To be published in Proceedings of 'The Evolution of Galaxies III- From simple approaches to self-consistent models,' held in Kiel, Germany, July 2002, Astrophysics and Space Science (Kluwer), vol. 284, p. 479, 200

Designing an information system for updating land records in Bangladesh: action design ethnographic research (ADER)

Open Access. This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.This article has been made available through the Brunel Open Access Publishing Fund.Information Systems (IS) has developed through adapting, generating and applying diverse methodologies, methods, and techniques from reference disciplines. Further, Action Design Research (ADR) has recently developed as a broad research method that focuses on designing and redesigning IT and IS in organizational contexts. This paper reflects on applying ADR in a complex organizational context in a developing country. It shows that ADR requires additional lens for designing IS in such a complex organizational context. Through conducting ADR, it is seen that an ethnographic framework has potential complementarities for understanding complex contexts thereby enhancing the ADR processes. This paper argues that conducting ADR with an ethnographic approach enhances design of IS and organizational contexts. Finally, this paper aims presents a broader methodological framework, Action Design Ethnographic Research (ADER), for designing artefacts as well as IS. This is illustrated through the case of a land records updating service in Bangladesh

The Crystal Structure of OprG from Pseudomonas aeruginosa, a Potential Channel for Transport of Hydrophobic Molecules across the Outer Membrane

Background: The outer membrane (OM) of Gram-negative bacteria provides a barrier to the passage of hydrophobic and hydrophilic compounds into the cell. The OM has embedded proteins that serve important functions in signal transduction and in the transport of molecules into the periplasm. The OmpW family of OM proteins, of which P. aeruginosa OprG is a member, is widespread in Gram-negative bacteria. The biological functions of OprG and other OmpW family members are still unclear. Methodology/Principal Findings: In order to obtain more information about possible functions of OmpW family members we have solved the X-ray crystal structure of P. aeruginosa OprG at 2.4 A ˚ resolution. OprG forms an eightstranded b-barrel with a hydrophobic channel that leads from the extracellular surface to a lateral opening in the barrel wall. The OprG barrel is closed off from the periplasm by interacting polar and charged residues on opposite sides of the barrel wall. Conclusions/Significance: The crystal structure, together with recent biochemical data, suggests that OprG and other OmpW family members form channels that mediate the diffusion of small hydrophobic molecules across the OM by a latera

Expert opinion on detecting and treating depression in palliative care: A Delphi study

<p>Abstract</p> <p>Background</p> <p>There is a dearth of data regarding the optimal method of detecting and treating depression in palliative care. This study applied the Delphi method to evaluate expert opinion on choice of screening tool, choice of antidepressant and choice of psychological therapy. The aim was to inform the development of best practice recommendations for the European Palliative Care Research Collaborative clinical practice guideline on managing depression in palliative care.</p> <p>Methods</p> <p>18 members of an international, multi-professional expert group completed a structured questionnaire in two rounds, rating their agreement with proposed items on a scale from 0-10 and annotating with additional comments. The median and range were calculated to give a statistical average of the experts' ratings.</p> <p>Results</p> <p>There was contention regarding the benefits of screening, with 'routine informal asking' (median 8.5 (0-10)) rated more highly than formal screening tools such as the Hospital Anxiety and Depression Scale (median 7.0 (1-10). Mirtazapine (median 9 (7-10) and citalopram (median 9 (5-10) were the considered the best choice of antidepressant and cognitive behavioural therapy (median 9.0 (3-10) the best choice of psychological therapy.</p> <p>Conclusions</p> <p>The range of expert ratings was broad, indicating discordance in the views of experts. Direct comparative data from randomised controlled trials are needed to strengthen the evidence-base and achieve clarity on how best to detect and treat depression in this setting.</p

Aβ42 Mutants with Different Aggregation Profiles Induce Distinct Pathologies in Drosophila

Aggregation of the amyloid-β-42 (Aβ42) peptide in the brain parenchyma is a pathological hallmark of Alzheimer's disease (AD), and the prevention of Aβ aggregation has been proposed as a therapeutic intervention in AD. However, recent reports indicate that Aβ can form several different prefibrillar and fibrillar aggregates and that each aggregate may confer different pathogenic effects, suggesting that manipulation of Aβ42 aggregation may not only quantitatively but also qualitatively modify brain pathology. Here, we compare the pathogenicity of human Aβ42 mutants with differing tendencies to aggregate. We examined the aggregation-prone, EOFAD-related Arctic mutation (Aβ42Arc) and an artificial mutation (Aβ42art) that is known to suppress aggregation and toxicity of Aβ42 in vitro. In the Drosophila brain, Aβ42Arc formed more oligomers and deposits than did wild type Aβ42, while Aβ42art formed fewer oligomers and deposits. The severity of locomotor dysfunction and premature death positively correlated with the aggregation tendencies of Aβ peptides. Surprisingly, however, Aβ42art caused earlier onset of memory defects than Aβ42. More remarkably, each Aβ induced qualitatively different pathologies. Aβ42Arc caused greater neuron loss than did Aβ42, while Aβ42art flies showed the strongest neurite degeneration. This pattern of degeneration coincides with the distribution of Thioflavin S-stained Aβ aggregates: Aβ42Arc formed large deposits in the cell body, Aβ42art accumulated preferentially in the neurites, while Aβ42 accumulated in both locations. Our results demonstrate that manipulation of the aggregation propensity of Aβ42 does not simply change the level of toxicity, but can also result in qualitative shifts in the pathology induced in vivo

Using direct observations on multiple occasions to measure household food availability among low-income Mexicano residents in Texas colonias

BACKGROUND: It has been recognized that the availability of foods in the home are important to nutritional health, and may influence the dietary behavior of children, adolescents, and adults. It is therefore important to understand food choices in the context of the household setting. Considering their importance, the measurement of household food resources becomes critical.Because most studies use a single point of data collection to determine the types of foods that are present in the home, which can miss the change in availability within a month and when resources are not available, the primary objective of this pilot study was to examine the feasibility and value of conducting weekly in-home assessments of household food resources over the course of one month among low-income Mexicano families in Texas colonias. METHODS: We conducted five in-home household food inventories over a thirty-day period in a small convenience sample; determined the frequency that food items were present in the participating households; and compared a one-time measurement with multiple measurements.After the development and pre-testing of the 252-item culturally and linguistically- appropriate household food inventory instrument that used direct observation to determine the presence and amount of food and beverage items in the home (refrigerator, freezer, pantry, elsewhere), two trained promotoras recruited a convenience sample of 6 households; administered a baseline questionnaire (personal info, shopping habits, and food security); conducted 5 in-home assessments (7-day interval) over a 30-day period; and documented grocery shopping and other food-related activities within the previous week of each in-home assessment. All data were collected in Spanish. Descriptive statistics were calculated for mean and frequency of sample characteristics, food-related activities, food security, and the presence of individual food items. Due to the small sample size of the pilot data, the Friedman Test and Kendall's W were used to assess the consistency of household food supplies across multiple observations. RESULTS: Complete data were collected from all 6 Mexicano women (33.2y +/- 3.3; 6.5 +/- 1.5 adults/children in household (HH); 5 HH received weekly income; and all were food insecure. All households purchased groceries within a week of at least four of the five assessments. The weekly presence and amounts of fresh and processed fruits and vegetables, dairy, meats, breads, cereals, beverages, and oils and fats varied. Further, the results revealed the inadequacy of a one-time measurement of household food resources, compared with multiple measures. The first household food inventory as a one-time measure would have mistakenly identified at least one-half of the participant households without fresh fruit, canned vegetables, dairy, protein foods, grains, chips, and sugar-sweetened beverages. CONCLUSIONS: This study highlights the value of documenting weekly household food supplies, especially in households where income resources may be more volatile. Clearly, the data show that a single HFI may miss the changes in availability--presence and amount--that occur among low-income Mexicano households who face challenges that require frequent purchase of foods and beverages. Use of multiple household food inventories can inform the development and implementation of nutrition-related policies and culturally sensitive nutrition education programs

Selective Release of MicroRNA Species from Normal and Malignant Mammary Epithelial Cells

MicroRNAs (miRNAs) in body fluids are candidate diagnostics for a variety of conditions and diseases, including breast cancer. One premise for using extracellular miRNAs to diagnose disease is the notion that the abundance of the miRNAs in body fluids reflects their abundance in the abnormal cells causing the disease. As a result, the search for such diagnostics in body fluids has focused on miRNAs that are abundant in the cells of origin. Here we report that released miRNAs do not necessarily reflect the abundance of miRNA in the cell of origin. We find that release of miRNAs from cells into blood, milk and ductal fluids is selective and that the selection of released miRNAs may correlate with malignancy. In particular, the bulk of miR-451 and miR-1246 produced by malignant mammary epithelial cells was released, but the majority of these miRNAs produced by non-malignant mammary epithelial cells was retained. Our findings suggest the existence of a cellular selection mechanism for miRNA release and indicate that the extracellular and cellular miRNA profiles differ. This selective release of miRNAs is an important consideration for the identification of circulating miRNAs as biomarkers of disease

Buffering and the evolution of chromosome-wide gene regulation

Copy number variation (CNV) in terms of aneuploidies of both entire chromosomes and chromosomal segments is an important evolutionary driving force, but it is inevitably accompanied by potentially problematic variations in gene doses and genomic instability. Thus, a delicate balance must be maintained between mechanisms that compensate for variations in gene doses (and thus allow such genomic variability) and selection against destabilizing CNVs. In Drosophila, three known compensatory mechanisms have evolved: a general segmental aneuploidy-buffering system and two chromosome-specific systems. The two chromosome-specific systems are the male-specific lethal complex, which is important for dosage compensation of the male X chromosome, and Painting of fourth, which stimulates expression of the fourth chromosome. In this review, we discuss the origin and function of buffering and compensation using Drosophila as a model