Modified gravity without dark matter

On an empirical level, the most successful alternative to dark matter in bound gravitational systems is the modified Newtonian dynamics, or MOND, proposed by Milgrom. Here I discuss the attempts to formulate MOND as a modification of General Relativity. I begin with a summary of the phenomenological successes of MOND and then discuss the various covariant theories that have been proposed as a basis for the idea. I show why these proposals have led inevitably to a multi-field theory. I describe in some detail TeVeS, the tensor-vector-scalar theory proposed by Bekenstein, and discuss its successes and shortcomings. This lecture is primarily pedagogical and directed to those with some, but not a deep, background in General RelativityComment: 28 pages, 10 figures, lecture given at Third Aegean Summer School, The Invisible Universe: Dark Matter and Dark Energy, minor errors corrected, references update

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

CANDELS : constraining the AGN-merger connection with host morphologies at z ~ 2

Using Hubble Space Telescope/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we examine the role that major galaxy mergers play in triggering active galactic nucleus (AGN) activity at z ~ 2. Our sample consists of 72 moderate-luminosity (L X ~ 1042-44 erg s-1) AGNs at 1.5 < z < 2.5 that are selected using the 4 Ms Chandra observations in the Chandra Deep Field South, the deepest X-ray observations to date. Employing visual classifications, we have analyzed the rest-frame optical morphologies of the AGN host galaxies and compared them to a mass-matched control sample of 216 non-active galaxies at the same redshift. We find that most of the AGNs reside in disk galaxies (51.4+5.8 - 5.9%), while a smaller percentage are found in spheroids (27.8+5.8 - 4.6%). Roughly 16.7+5.3 - 3.5% of the AGN hosts have highly disturbed morphologies and appear to be involved in a major merger or interaction, while most of the hosts (55.6+5.6 - 5.9%) appear relatively relaxed and undisturbed. These fractions are statistically consistent with the fraction of control galaxies that show similar morphological disturbances. These results suggest that the hosts of moderate-luminosity AGNs are no more likely to be involved in an ongoing merger or interaction relative to non-active galaxies of similar mass at z ~ 2. The high disk fraction observed among the AGN hosts also appears to be at odds with predictions that merger-driven accretion should be the dominant AGN fueling mode at z ~ 2, even at moderate X-ray luminosities. Although we cannot rule out that minor mergers are responsible for triggering these systems, the presence of a large population of relatively undisturbed disk-like hosts suggests that the stochastic accretion of gas plays a greater role in fueling AGN activity at z ~ 2 than previously thought

Astronomical Distance Determination in the Space Age: Secondary Distance Indicators

The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations. © 2018, The Author(s)

Plasma lipid profiles discriminate bacterial from viral infection in febrile children

Fever is the most common reason that children present to Emergency Departments. Clinical signs and symptoms suggestive of bacterial infection ar

Health-related quality of life after burns : a prospective multicentre cohort study with 18 months follow-up.

Background: Health-related quality of life (HRQOL) is an important parameter after medical treatments. Knowledge of (predictors of) diminished quality of life can help improve medical outcome. The aim of this study was to quantify health loss in patients with burns and to assess the contribution of injury extent, age, gender, and psychologic factors to HRQOL and speed of recovery. A multicenter prospective cohort design was used to address these aims. Methods: Data were obtained from 260 adults with burns. Patients completed the EQ-5D at 3 weeks, 3, 6, 9, and 18 months after burn and psychologic questionnaires during hospitalization. Patient’s scores were compared with an age- and gender-weighted norm population. Results: Patients suffered from substantial health losses at short term, but after 18 months the majority reached a HRQOL comparable with the norm population with the exception of patients requiring two or more surgeries. The best predictor of long-term HRQOL and the speed of recovery was the number of surgeries, followed by psychologic problems. Both predicted baseline and trajectories of improvement. Symptoms of traumatic stress were most debilitating over time. Conclusions: Both injury severity and psychologic problems play a pivotal role in reduced HRQOL and the speed of recovery. The number of surgeries seems to give a practically useful indication of the expected recovery speed that could aid in decision making and provides adequate information for patients in the aftermath of their initial surgical treatment. Screening for traumatic stress is recommended

Reliability and validity of the Health Outcomes Burn Questionnaire for infants and children in The Netherlands

The Health Outcomes Burn Questionnaire (HOBQ) is a self-administered questionnaire to monitor outcome after burns in young children. This study aimed to assess feasibility, reliability and validity of the Dutch version of the HOBQ. The HOBQ was adapted into Dutch and tested in a population of children aged 0-4 years with a primary admission to a Dutch burn centre in March 2001-February 2004. Parents of 413 children were sent a questionnaire. To assess validity, a generic outcome instrument was included, the Infant Toddler Quality of Life Questionnaire (ITQOL). The response rate was 50.0% (n=196). Mean self-reported completion time was 16.7 min. The internal consistency of all the HOBQ-scales was good (Cronbach's alpha's >0.69). Test-retest results showed no differences in 7 out of 10 scales. High correlations between HOBQ-scales and conceptually equivalent ITQOL and scales were found in 5 out of 7 comparisons. The majority of the HOBQ-scales (7 out of 10) showed significant differences in the expected direction between children with a long versus short length of stay. Our data support the reliability and validity of the Dutch HOBQ. The HOBQ can be used as a research tool, to monitor functional outcome after burns in young children. Further research in other samples is recommend to fully establish the reliability and validity of the HOBQ. (C) 2005 Elsevier Ltd and ISBI. All rights reserved

Reliability and validity of the Health Outcomes Burn Questionnaire for infants and children in The Netherlands

The Health Outcomes Burn Questionnaire (HOBQ) is a self-administered questionnaire to monitor outcome after burns in young children. This study aimed to assess feasibility, reliability and validity of the Dutch version of the HOBQ. The HOBQ was adapted into Dutch and tested in a population of children aged 0-4 years with a primary admission to a Dutch burn centre in March 2001-February 2004. Parents of 413 children were sent a questionnaire. To assess validity, a generic outcome instrument was included, the Infant Toddler Quality of Life Questionnaire (ITQOL). The response rate was 50.0% (n=196). Mean self-reported completion time was 16.7 min. The internal consistency of all the HOBQ-scales was good (Cronbach's alpha's >0.69). Test-retest results showed no differences in 7 out of 10 scales. High correlations between HOBQ-scales and conceptually equivalent ITQOL and scales were found in 5 out of 7 comparisons. The majority of the HOBQ-scales (7 out of 10) showed significant differences in the expected direction between children with a long versus short length of stay. Our data support the reliability and validity of the Dutch HOBQ. The HOBQ can be used as a research tool, to monitor functional outcome after burns in young children. Further research in other samples is recommend to fully establish the reliability and validity of the HOBQ. (C) 2005 Elsevier Ltd and ISBI. All rights reserved

Factors affecting quality of dried low-rank coals

10.1080/07373930701590608Drying Technology25101601-1611DRTE