On the interpretation of dark matter self-interactions in Abell 3827

Self-interactions of dark matter particles can potentially lead to an observable separation between the dark matter halo and the stars of a galaxy moving through a region of large dark matter density. Such a separation has recently been observed in a galaxy falling into the core of the galaxy cluster Abell 3827. We estimated the DM self-interaction cross section needed to reproduce the observed effects and find that the sensitivity of Abell 3827 has been significantly overestimated in a previous study. Our corrected estimate is $\tilde{\sigma}/m_\text{DM} \sim 3\:\text{cm}^2\:\text{g}^{-1}$ when self-interactions result in an effective drag force and $\sigma/m_\text{DM} \sim 1.5\:\text{cm}^2\:\text{g}^{-1}$ for the case of contact interactions, in some tension with previous upper bounds.Comment: 5 pages, 3 figures; v2: matches published versio

Life Out of Balance

The common theme in the videos I have produced is life out of balance. The world is a beautiful place to live in . All the things I need to live by are here: water, air, earth, plants, and the animals. Yet my home is being destroyed by the social- political system in which I live, and I am forced to live second-hand. Instead of planting a garden , my time is taken up with regulations that have nothing to do with life or living life. When the natural world is threatened, then so am I as well as my art.&nbsp; I have often heard the phrase, ' the real world' to preface a position . My question is, which real world? i.e., the world that grows things on its own unaided by many or the world of business and finance with its man-made laws? I must live in both worlds . When the natural world is threatened by the world of finance and politics, then both worlds are threatened. The natural world can survive without me. When I realize this, I understand that the grass is not my enemy, neither i s the wolf, nor do they seek to destroy me or my home or my art .&nbsp; As an artist, I cannot change what has happened, but history has not told the truth . This is where the artist goes in and takes a stand on the side of life. This is not an easy choice since the dominant culture supports superficiality which leaves art in the position of having only one function which is not to enlighten but to increase in value (money). I am sorry that the news is not good news for art , but neither is then ews good for living . Oneperson cannot change this. A change can only occur within a community of people who decide to live differently. &nbsp;</p

Creating a Taxonomy of Corporate Social Responsibility, Sustainability, Stakeholders, Environment, Green IS, and Green IT: A Literature Review

The main goal of this article is to link Green Information Systems (Green IS) and Green Information Technology (Green IT) to the overall sustainability topic. Therefore, the authors provide a taxonomy in the form of a matrix to relate the relevant concepts to each other. The quest is to identify missing relationships and establish concepts relationships. Papers from six major journals and one conference between 2006 and 2010 were examined in order to shed light on the relationship matrix. The article delivers definitions, insights into usage of terminology and existing boundaries and links amongst definitions. Besides the comprehensive overview, the authors were able to identify new links between the relevant terms. This was done by reversing given relationship definitions between the relevant terms and by using analogies

Associations between physical activity, physical fitness, and body composition in adults living in Germany: A cross-sectional study

Background & aims Body composition (BC) changes with age and is associated with morbidity and mortality. A physically active lifestyle influences BC and represents an important predictor of successful aging. To emphasize this, the World Health Organization established activity recommendations for all age groups. We describe BC during adulthood using a cross-sectional sample from a German community and investigate the associations between physical activity (PA), physical fitness (PF), and BC. Methods Data from 329 men and women aged 35 to 86 years were analyzed. PA was measured by questionnaire and classified into sport activity and habitual activity. PF was measured through physical performance tests and BC by bioelectrical impedance analysis. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated to represent height-adjusted BC. Associations between PA, PF, and BC were analyzed using linear regression models. Results For both sexes, strength was positively associated with FFMI (♂: ß = 0.313; ♀: ß = 0.213) and phase angle (♂: ß = 0.357; ♀: ß = 0.409). For FMI, a significant negative association with strength was found only in women (ß = -0.189). Cardiorespiratory fitness showed a negative association with FMI (ß = -0.312) and FFMI (ß = -0.201) for men, while in women a positive association was found for FFMI (ß = 0.186). For coordination, a significant association with FMI was observed only in women (ß = -0.190). Regarding PA only one significant relationship between sport activity and FMI among women (ß = -0.170) was found

Simulations of core formation for frequent dark matter self-interactions

We present the first $N$-body simulations that adapt the equations of smoothed particle hydrodynamics to capture the effect of dark matter self-interactions which are too frequent to be resolved explicitly. The relevant energy transfer equations are derived, the appropriate thermal conductivity is determined and the effects of different smoothing kernels are studied. We apply our framework to simulate the formation of isothermal cores in isolated dark matter haloes and determine the core growth rate as a function of the self-scattering cross section. Our approach may be combined with explicit simulations of rare scatterings in order to simulate accurately the effects of arbitrary dark matter self-interactions in future cosmological simulations.Comment: 11 pages, 6 figures; v2: matches version published in MNRA

Effect of Exercise-Induced Reductions in Blood Volume on Cardiac Output and Oxygen Transport Capacity

We wanted to demonstrate the relationship between blood volume, cardiac size, cardiac output and maximum oxygen uptake ([Formula: see text] O(2max)) and to quantify blood volume shifts during exercise and their impact on oxygen transport. Twenty-four healthy, non-smoking, heterogeneously trained male participants (27 ± 4.6 years) performed incremental cycle ergometer tests to determine [Formula: see text] O(2max) and changes in blood volume and cardiac output. Cardiac output was determined by an inert gas rebreathing procedure. Heart dimensions were determined by 3D echocardiography. Blood volume and hemoglobin mass were determined by using the optimized CO-rebreathing method. The [Formula: see text] O(2max) ranged between 47.5 and 74.1 mL⋅kg(–1)⋅min(–1). Heart volume ranged between 7.7 and 17.9 mL⋅kg(–1) and maximum cardiac output ranged between 252 and 434 mL⋅kg(–1)⋅min(–1). The mean blood volume decreased by 8% (567 ± 187 mL, p = 0.001) until maximum exercise, leading to an increase in [Hb] by 1.3 ± 0.4 g⋅dL(–1) while peripheral oxygen saturation decreased by 6.1 ± 2.4%. There were close correlations between resting blood volume and heart volume (r = 0.73, p = 0.002), maximum blood volume and maximum cardiac output (r = 0.68, p = 0.001), and maximum cardiac output and [Formula: see text] O(2max) (r = 0.76, p < 0.001). An increase in maximum blood volume by 1,000 mL was associated with an increase in maximum stroke volume by 25 mL and in maximum cardiac output by 3.5 L⋅min(–1). In conclusion, blood volume markedly decreased until maximal exhaustion, potentially affecting the stroke volume response during exercise. Simultaneously, hemoconcentrations maintained the arterial oxygen content and compensated for the potential loss in maximum cardiac output. Therefore, a large blood volume at rest is an important factor for achieving a high cardiac output during exercise and blood volume shifts compensate for the decrease in peripheral oxygen saturation, thereby maintaining a high arteriovenous oxygen difference

Cardiac stroke volume in females and its correlation to blood volume and cardiac dimensions

We aimed to continuously determine the stroke volume (SV) and blood volume (BV) during incremental exercise to evaluate the individual SV course and to correlate both variables across different exercise intensities. Twenty-six females with heterogeneous endurance capacities performed an incremental cycle ergometer test to continuously determine the oxygen uptake (V̇O(2)), cardiac output (Q̇) and changes in BV. Q̇ was determined by impedance cardiography and resting cardiac dimensions by 2D echocardiography. Hemoglobin mass and BV were determined using a carbon monoxide-rebreathing method. V̇O(2max) ranged from 32 to 62 mL·kg(−1)·min(−1). Q̇(max) and SV(max) ranged from 16.4 to 31.6 L·min(−1) and 90–170 mL, respectively. The SV significantly increased from rest to 40% and from 40% to 80% V̇O(2max). Changes in SV from rest to 40% V̇O(2max) were negatively (r = −0.40, p = 0.05), between 40% and 80% positively correlated with BV (r = 0.45, p < 0.05). At each exercise intensity, the SV was significantly correlated with the BV and the cardiac dimensions, i.e., left ventricular muscle mass (LVMM) and end-diastolic diameter (LVEDD). The BV decreased by 280 ± 115 mL (5.7%, p = 0.001) until maximum exercise. We found no correlation between the changes in BV and the changes in SV between each exercise intensity. The hemoglobin concentration [Hb] increased by 0.8 ± 0.3 g·dL(−1), the capillary oxygen saturation (ScO(2)) decreased by 4.0% (p < 0.001). As a result, the calculated arterial oxygen content significantly increased (18.5 ± 1.0 vs. 18.9 ± 1.0 mL·dL(−1), p = 0.001). A 1 L higher BV at V̇O(2max) was associated with a higher SV(max) of 16.2 mL (r = 0.63, p < 0.001) and Q̇(max) of 2.5 L·min(−1) (r = 0.56, p < 0.01). In conclusion, the SV strongly correlates with the cardiac dimensions, which might be the result of adaptations to an increased volume load. The positive effect of a high BV on SV is particularly noticeable at high and severe intensity exercise. The theoretically expected reduction in V̇O(2max) due to lower SV as a consequence of reduced BV is apparently compensated by the increased arterial oxygen content due to a higher [Hb]