Evolution of galaxy groups in the Illustris simulation

We present the first study of evolution of galaxy groups in the Illustris simulation. We focus on dynamically relaxed and unrelaxed galaxy groups representing dynamically evolved and evolving galaxy systems, respectively. The evolutionary state of a group is probed from its luminosity gap and separation between the brightest group galaxy and the center of mass of the group members. We find that the Illustris simulation, over-produces large luminosity gap galaxy systems, known as fossil systems, in comparison to observations and the probed semi-analytical predictions. However, this simulation is equally successful in recovering the correlation between luminosity gap and luminosity centroid offset, in comparison to the probed semi-analytic model. We find evolutionary tracks based on luminosity gap which indicate that a large luminosity gap group is rooted in a small luminosity gap group, regardless of the position of the brightest group galaxy within the halo. This simulation helps, for the first time, to explore the black hole mass and its accretion rate in galaxy groups. For a given stellar mass of the brightest group galaxies, the black hole mass is larger in dynamically relaxed groups with a lower rate of mass accretion. We find this consistent with the latest observational studies of the radio activities in the brightest group galaxies in fossil groups. We also find that the IGM in dynamically evolved groups is hotter for a given halo mass than that in evolving groups, again consistent with earlier observational studies.Comment: 10 pages, 10 figures. Accepted for publication in Ap

L2pB1 cells are essential for the inhibition of 3D tumor spheroids by syngeneic peritoneal immune cells

INTRODUCTION: Programmed Death Ligand 2 positive B1 cells (L2pB1) cells have a unique immunoglobulin repertoire that is poly-reactive to self-antigens and have previously been shown to have an essential role in autoimmunity. The active accumulation of L2pB1 cells inside tumors grown in vivo led us to hypothesize that this subpopulation of B1a cells may play a role in the immunosurveillance of cancer. Here, we report our investigation of the role of L2pB1 cells in the antitumor response using a three dimensional (3D) murine melanoma and colon cancer models. Our results showed that the depletion of L2pB1 cells rendered the loss of tumor inhibition effects of the syngeneic peritoneal immune cells. METHODS: Lymphocytes were collected from L2pB1 cell depleted and non-depleted peritoneal cavity washout (PCW) from an inducible knockout mouse model. Then tumor spheroids were incubated with PCW cells. Spheroid cross-sectional area (CSA) and volume were measured using a Celigo plate imager and Keyence fluorescence microscope. RESULTS: Tumor spheroid growth was significantly inhibited following incubation with syngeneic PCW but not with splenocytes. Depletion of L2pB1 significantly attenuated the tumor-inhibition effect and showed a negligible difference from the untreated control. This loss of tumor inhibition indicated that L2pB1 cells are essential for the tumor-inhibition effects of autologous peritoneal immune cells. CONCLUSIONS: These findings demonstrate the robust anti-tumor function of L2pB1 cells. In particular, peritoneal L2pB1 cells play an essential role in cancer inhibition. Future studies into the activation and antigen presentation pathways of L2pB1 cells could lead to novel immunotherapy of cancer

Refractory myasthenia gravis: the more we learn, the less we know.

Refractory myasthenia gravis identifies the group of patients that have inadequate symptom control and persistent muscle weakness and fatigability despite the use of multiple immune modulatory therapies. This manuscript highlights what is currently known about refractory myasthenia gravis and underlines major knowledge gaps, drawing attention to the unmet needs in our understanding of this disease subset. This review raises questions about our current understanding of refractory disease and how emerging data as well as therapies may alter our thinking and patients’ disease course

Estimation of Modified Measure of Skewness

It is well known that the classical measures of skewness are not reliable and their sampling distributions are not known for small samples. Therefore, we consider the modified measure of skewness that is defined in terms of cumulative probability function. The main advantage of this measure is that its sampling distribution is derived from sample data as the sum of dependent Bernoulli random variables. Moreover, its variance and confidence interval are obtained based on multiplicative binomial distribution. Comparison with classical measures using simulation and an application to actual data set are given

Transformative Ethics and Moving Toward “Greatness” – Problems and Realities

The purpose of this paper is to emphasize the role of Transformative Ethics as leaders and organizations move toward the achievement of greatness. It is a conceptual paper that explains the key importance of the pursuit of greatness and the role of Transformative Ethics in that pursuit. The paper suggests that each of the twelve perspectives that comprise Transformative Ethics supports the pursuit of greatness and that the pursuit of excellence is necessary for individuals and firms in today’s global marketplace. The research implications from this study support the importance of Transformative Ethics as a contributing ethical perspective for leaders and organizations. As leaders and organizations interact with others, the need for ethical leadership is critical for establishing trust and earning follower commitment This paper is one of the first to address the practical implications of Transformative Ethics for leaders and organizations

A statistical study of the luminosity gap in galaxy groups

The luminosity gap between the two brightest members of galaxy groups and clusters is thought to offer a strong test for the models of galaxy formation and evolution. This study focuses on the statistics of the luminosity gap in galaxy groups, in particular fossil groups, e.g. large luminosity gap, in an analogy with the same in a cosmological simulation. We use spectroscopic legacy data of seventh data release (DR7) of SDSS, to extract a volume limited sample of galaxy groups utilizing modified friends-of-friends (mFoF) algorithm. Attention is paid to galaxy groups with the brightest group galaxy (BGG) more luminous than \Mr = -22. An initial sample of 620 groups in which 109 optical fossil groups, where the luminosity gap exceeds 2 magnitude, were identified. We compare the statistics of the luminosity gap in galaxy groups at low mass range from the SDSS with the same in the Millennium simulations where galaxies are modeled semi-analytically. We show that the BGGs residing in galaxy groups with large luminosity gap, i.e. fossil groups, are on average brighter and live in lower mass halos with respect to their counter parts in non-fossil systems. Although low mass galaxy groups are thought to have recently formed, we show that in galaxy groups with 15 galaxies brighter than $M_r\ge -19.5$, evolutionary process are most likely to be responsible for the large luminosity gap. We also examine a new probe of finding fossil group. In addition we extend the recently introduced observational probe based on the luminosity gap, the butterfly diagram, to galaxy groups and study the probe as a function of halo mass. This probe can, in conjunction with the luminosity function, help to fine tune the semi-analytic models of galaxies employed in the cosmological simulations.Comment: 11 pages, 11 figures, accepted to PASP journa

Probability distribution theory, generalisations and applications of l-moments

In this thesis, we have studied L-moments and trimmed L-moments (TL-moments) which are both linear functions of order statistics. We have derived expressions for exact variances and covariances of sample L-moments and of sample TL-moments for any sample size n in terms of first and second-order moments of order statistics from small conceptual sample sizes, which do not depend on the actual sample size n. Moreover, we have established a theorem which characterises the normal distribution in terms of these second-order moments and the characterisation suggests a new test of normality. We have also derived a method of estimation based on TL-moments which gives zero weight to extreme observations. TL-moments have certain advantages over L-moments and method of moments. They exist whether or not the mean exists (for example the Cauchy distribution) and they are more robust to the presence of outliers. Also, we have investigated four methods for estimating the parameters of a symmetric lambda distribution: maximum likelihood method in the case of one parameter and L-moments, LQ-moments and TL-moments in the case of three parameters. The L-moments and TL-moments estimators are in closed form and simple to use, while numerical methods are required for the other two methods, maximum likelihood and LQ-moments. Because of the flexibility and the simplicity of the lambda distribution, it is useful in fitting data when, as is often the case, the underlying distribution is unknown. Also, we have studied the symmetric plotting position for quantile plot assuming a symmetric lambda distribution and conclude that the choice of the plotting position parameter depends upon the shape of the distribution. Finally, we propose exponentially weighted moving average (EWMA) control charts to monitor the process mean and dispersion using the sample L-mean and sample L-scale and charts based on trimmed versions of the same statistics. The proposed control charts limits are less influenced by extreme observations than classical EWMA control charts, and lead to tighter limits in the presence of out-of-control observations