Interviewer-driven Variability in Social Network Reporting: Results from Health and Aging in Africa: a Longitudinal Study of an INDEPTH community (HAALSI) in South Africa

Social network analysis depends on how social ties to others are elicited during interviews, a process easily affected by respondent and interviewer behaviors. We investigate how the number of self-reported important social contacts varied within a single data collection round. Our data come from Health and Aging in Africa: a Longitudinal Study of an INDEPTH community (HAALSI), a comprehensive population-based survey of individuals aged 40 years and older conducted over 13 months at the Agincourt health and demographic surveillance site in rural South Africa. As part of HAALSI, interviewers elicited detailed egocentric network data. The average number of contacts reported by the 5,059 respondents both varied significantly across interviewers and fell over time as the data collection progressed, even after adjusting for respondent, interviewer, and respondent–interviewer dyad characteristics. Contact numbers rose substantially after a targeted interviewer intervention. We conclude that checking (and adjusting) for interviewer effects, even within one data collection round, is critical to valid and reliable social network analysis. Measurements of social networks depend on the number and type of social ties to others (Berkman et al. 2000; Smith and Christakis 2008). These ties are typically elicited through interviews, a process easily affected by respondent or interviewer characteristics and behaviors. Understanding social network structure and composition requires substantial amounts of information from respondents (“egos”) about the people (“alters”) they have relationships with (Marsden 1990). Notably, the survey burden associated with network data collection depends heavily on the number of alters elicited through “name generator” questions: Each alter named leads to the repetition of all follow-up questions characterizing the ego–alter relationship (“name interpreters”; Burt 1984). Interviewers have been identified as a key source of variation in survey responses, particularly for questions that are attitudinal, ambiguous, or have complex skip patterns (West and Blom 2016). Several studies have previously identified interviewer effects on network size (Brüderl et al. 2013; Josten and Trappmann 2016; Marsden 2003; Paik and Sanchagrin 2013; van Tilburg 1998). These interviewer effects may arise from differential understanding of survey questions, and therefore how questions are presented to respondents. Interviewers can also affect which alters are elicited due to their own characteristics (e.g., sex, race, age, or experience), or the nature of the interviewer–respondent dyad (e.g., gender, race, or age homophily), leading to different lines of enquiry, levels of probing, or expectations of social acceptability (Collins 1980; Hox 1994; Marsden 2003; Phung et al. 2015). Furthermore, if respondents or interviewers are aware that naming more alters substantially increases survey length, then either group may consciously or unconsciously seek to minimize the number of alters named (Eagle and Proeschold-Bell 2015; van der Zouwen and van Tilburg 2001). In cross-sectional surveys, the opportunities for respondents to learn are limited, but those for interviewers will increase as the survey period progresses. Interviewers may try to reduce survey burden, either for themselves or for respondents, by favoring language or probes that decrease the number of alters elicited. Indeed, past studies in Europe have found evidence of interviewers intentionally filtering out questions by entering fewer responses that would trigger more questions. Such filtering behavior has been seen in Europe for interviewers who are being compensated by the interview rather than by the hour (Josten and Trappmann 2016; Kosyakova et al. 2014), for interviewers with prior experience using the relevant screening tool (Matschinger et al. 2005), and where interviewers are under substantial pressure to complete more interviews (Schnell and Kreuter 2000). We aim to extend this literature by assessing how the number of alters elicited systematically changed over the course of a cross-sectional social network survey of older adults in rural South Africa. We show a substantial drop in alter numbers over time, and a swift reversal following retraining, providing substantial evidence for interviewer effects

Social interaction, noise and antibiotic-mediated switches in the intestinal microbiota

The intestinal microbiota plays important roles in digestion and resistance against entero-pathogens. As with other ecosystems, its species composition is resilient against small disturbances but strong perturbations such as antibiotics can affect the consortium dramatically. Antibiotic cessation does not necessarily restore pre-treatment conditions and disturbed microbiota are often susceptible to pathogen invasion. Here we propose a mathematical model to explain how antibiotic-mediated switches in the microbiota composition can result from simple social interactions between antibiotic-tolerant and antibiotic-sensitive bacterial groups. We build a two-species (e.g. two functional-groups) model and identify regions of domination by antibiotic-sensitive or antibiotic-tolerant bacteria, as well as a region of multistability where domination by either group is possible. Using a new framework that we derived from statistical physics, we calculate the duration of each microbiota composition state. This is shown to depend on the balance between random fluctuations in the bacterial densities and the strength of microbial interactions. The singular value decomposition of recent metagenomic data confirms our assumption of grouping microbes as antibiotic-tolerant or antibiotic-sensitive in response to a single antibiotic. Our methodology can be extended to multiple bacterial groups and thus it provides an ecological formalism to help interpret the present surge in microbiome data.Comment: 20 pages, 5 figures accepted for publication in Plos Comp Bio. Supplementary video and information availabl

Characterisation of tyre wear particle transport from roads runoff to sea in coastal environments

Data on the fate of tyre wear particles (TWPs) within aquatic environments is limited. This study quantified TWPs entering estuaries in stormwater drainage and atmospheric fallout, and once they have reached the marine environment, within surface waters and sediments. TWPs were found at concentrations of 0.4 mg/L, 2.55 mg/m2/d, 0.00063 mg/L, and 0.96 g/kg respectively. Samples were partitioned by size to examine the distribution of TWP mass. 80-90% of TWP mass entering marine systems (stormwater and atmospheric fallout) lay between 31-125 \ub5m. Larger particles preferentially accumulated in sediments where ∼50 % of TWP mass was >250 μm, compared to surface waters where the size class 15-63 μm accounted for ∼80 %. This study provides novel data on the sizes and concentrations of TWP pollution in coastal environments. Such data are of importance in determining biological exposures. Notably, the presence of TWPs in surface waters demonstrates their potential for transport over longer distances

Operation and performance of the ATLAS Tile Calorimeter in Run 1

The Tile Calorimeter is the hadron calorimeter covering the central region of the ATLAS experiment at the Large Hadron Collider. Approximately 10,000 photomultipliers collect light from scintillating tiles acting as the active material sandwiched between slabs of steel absorber. This paper gives an overview of the calorimeter’s performance during the years 2008–2012 using cosmic-ray muon events and proton–proton collision data at centre-of-mass energies of 7 and 8TeV with a total integrated luminosity of nearly 30 fb−1. The signal reconstruction methods, calibration systems as well as the detector operation status are presented. The energy and time calibration methods performed excellently, resulting in good stability of the calorimeter response under varying conditions during the LHC Run 1. Finally, the Tile Calorimeter response to isolated muons and hadrons as well as to jets from proton–proton collisions is presented. The results demonstrate excellent performance in accord with specifications mentioned in the Technical Design Report

Biology and ecology of the world’s largest invertebrate, the colossal squid (Mesonychoteuthis hamiltoni): a short review

The colossal squid Mesonychoteuthis hamiltoni (Robson 1925) is the largest (heaviest) living invertebrate and although it is preyed upon by many top predators, its basic biology and ecology remain one of the ocean’s great mysteries. The present study aims to review the current biological knowledge on this squid. It is considered to be endemic in the Southern Ocean (SO) with a circumpolar distribution spreading from the Antarctic continent up to the Sub-Antarctic Front. Small juveniles (<40 mm mantle length) are mainly found from the surface to 500 m, and the late juvenile stages are assumed to undergo ontogenetic descent to depths reaching 2000 m. Thus, this giant spends most of its life in the meso- and bathypelagic realms, where it can reach a total length of 6 m. The maximum weight recorded so far was 495 kg. M. hamiltoni is presently reported from the diets of 17 different predator species, comprising penguins and other seabirds, fishes and marine mammals, and may feed on various prey types, including myctophids, Patagonian toothfish, sleeper sharks and other squid. Stable isotopic analysis places the colossal squid as one of the top predators in the SO. It is assumed that this squid is not capable of high-speed predator–prey interactions, but it is rather an ambush predator. Its eyes, the largest on the planet, seem to have evolved to detect very large predators (e.g., sperm whales) rather than to detect prey at long distances. The study of this unique invertebrate giant constitutes a valuable source of insight into the biophysical principles behind body-size evolution

Thermal conductivity and thermal boundary resistance of nanostructures

International audienceWe present a fabrication process of low-cost superlattices and simulations related with the heat dissipation on them. The influence of the interfacial roughness on the thermal conductivity of semiconductor/semiconductor superlattices was studied by equilibrium and non-equilibrium molecular dynamics and on the Kapitza resistance of superlattice's interfaces by equilibrium molecular dynamics. The non-equilibrium method was the tool used for the prediction of the Kapitza resistance for a binary semiconductor/metal system. Physical explanations are provided for rationalizing the simulation results

Intracellular chloride concentration influences the GABAA receptor subunit composition

GABAA receptors (GABAARs) exist as different subtype variants showing unique functional properties and defined spatio-temporal expression pattern. The molecular mechanisms underlying the developmental expression of different GABAAR are largely unknown. The intracellular concentration of chloride ([Cl−]i), the main ion permeating through GABAARs, also undergoes considerable changes during maturation, being higher at early neuronal stages with respect to adult neurons. Here we investigate the possibility that [Cl−]i could modulate the sequential expression of specific GABAARs subtypes in primary cerebellar neurons. We show that [Cl−]i regulates the expression of α3-1 and δ-containing GABAA receptors, responsible for phasic and tonic inhibition, respectively. Our findings highlight the role of [Cl−]i in tuning the strength of GABAergic responses by acting as an intracellular messenger

FtsK-Dependent Dimer Resolution on Multiple Chromosomes in the Pathogen Vibrio cholerae

Unlike most bacteria, Vibrio cholerae harbors two distinct, nonhomologous circular chromosomes (chromosome I and II). Many features of chromosome II are plasmid-like, which raised questions concerning its chromosomal nature. Plasmid replication and segregation are generally not coordinated with the bacterial cell cycle, further calling into question the mechanisms ensuring the synchronous management of chromosome I and II. Maintenance of circular replicons requires the resolution of dimers created by homologous recombination events. In Escherichia coli, chromosome dimers are resolved by the addition of a crossover at a specific site, dif, by two tyrosine recombinases, XerC and XerD. The process is coordinated with cell division through the activity of a DNA translocase, FtsK. Many E. coli plasmids also use XerCD for dimer resolution. However, the process is FtsK-independent. The two chromosomes of the V. cholerae N16961 strain carry divergent dimer resolution sites, dif1 and dif2. Here, we show that V. cholerae FtsK controls the addition of a crossover at dif1 and dif2 by a common pair of Xer recombinases. In addition, we show that specific DNA motifs dictate its orientation of translocation, the distribution of these motifs on chromosome I and chromosome II supporting the idea that FtsK translocation serves to bring together the resolution sites carried by a dimer at the time of cell division. Taken together, these results suggest that the same FtsK-dependent mechanism coordinates dimer resolution with cell division for each of the two V. cholerae chromosomes. Chromosome II dimer resolution thus stands as a bona fide chromosomal process