Precessing microblazars and unidentified gamma-ray sources

The recent discovery by Paredes et al. (2000) of a persistent microquasar that is positionally coincident with an unidentified gamma-ray source has open the possibility that other sources in the Third EGRET Catalog could be interpreted as microquasars as well. In this letter we show that some variable unidentified EGRET sources in the galactic plane could be produced by faint, otherwise undetected microquasars with precessing jets. When the jet points towards the observer, gamma-ray emission resulting from upscattered stellar photons could be detectable yielding a variable source with weak or undetectable counterpart at longer wavelengths. Strategies for detecting these``microblazars'' with forthcoming satellites are briefly discussed.Comment: 4 pages, 3 figures, Astronomy & Astrophysics Letters in press, typing errors correctio

Gamma-ray and neutrino emission from misaligned microquasars

Microquasars are accreting X-ray binary systems with non-thermal radio jets. In some of these systems the jet is expected to be strongly misaligned with the perpendicular to the orbital plane. If the donor star is an early-type star, the jet could collide with the stellar wind producing a standing shock between the compact object and the stellar surface. Relativistic particles injected by the jet can be re-accelerated and isotropized at the colliding region. If the jet has hadronic content, TeV protons will diffuse into the inner, dense wind leading to gamma-ray and neutrino production from interactions with the matter of the wind. In the case of very powerful jets, the wind pressure can be overbalanced and the jet might impact directly onto the stellar surface. We present estimates of the gamma-ray and neutrino luminosities for different sets of parameters in these scenarios and we briefly discuss the effects of this radiation on the donor star and its detectability with current instruments.Comment: 8 pages, 2 figures, accepted for publication in A&

Child maltreatment in the "children of the nineties" : a cohort study of risk factors

Aim: To analyze the multiple factors affecting the risk of maltreatment in young children within a comprehensive theoretical framework. Methods: The research is based on a large UK cohort study, the Avon Longitudinal Study of Parents and Children. Out of 14,256 children participating in the study, 293 were investigated by social services for suspected maltreatment and 115 were placed on local child protection registers prior to their 6th birthday. Data on the children have been obtained from obstetric data and from a series of parental questionnaires administered during pregnancy and the first 3 years of life. Risk factors have been analyzed using an hierarchical approach to logistic regression analysis. Results: In the stepwise hierarchical analysis, young parents, those with low educational achievement, and those with a past psychiatric history or a history of childhood abuse were all more likely to be investigated for maltreatment, or to have a child placed on the child protection register, with odds ratios between 1.86 and 4.96 for registration. Examining strength of effect, the highest risks were found with indicators of deprivation (3.24 for investigation and 11.02 for registration, after adjusting for parental background factors). Poor social networks increased the risk of both investigation (adjusted OR 1.93) and registration (adjusted OR 1.90). Maternal employment seemed to reduce the risk of both outcomes but adjusted odds ratios were no longer significant for registration. After adjusting for higher order confounders, single parents and reordered families were both at higher risk of registration. Reported domestic violence increased the risk of investigation and registration but this was no longer significant after adjusting for higher order variables. Low birthweight children were at higher risk of registration as were those whose parents reported few positive attributes of their babies. Conclusions: This study supports previous research in the field demonstrating that a wide range of factors in the parental background, socio-economic and family environments affect the risk of child maltreatment. By combining factors within a comprehensive ecological framework, we have demonstrated that the strongest risks are from socio-economic deprivation and from factors in the parents' own background and that parental background factors are largely, but not entirely, mediated through their impact on socio-economic factors

Relationship between muscle stress and intramuscular pressure during dynamic muscle contractions

Intramuscular pressure (IMP) has been used to estimate muscle stress indirectly. However, the ability of this technique to estimate muscle stress under dynamic conditions is poorly characterized. Therefore, the purpose of this study was to determine the extent to which IMP is a valid surrogate for muscle stress during dynamic contractions. IMP and muscle stress were compared under steady-state isotonic conditions and during complex dynamic length changes. During concentric contractions the shape of the IMP–velocity curve mimicked the basic shape of the force–velocity curve but with much higher variability. For eccentric contractions, a precipitous drop in IMP was observed despite increased muscle stress. The dissociation between muscle stress and IMP during dynamic contractions was partially explained by sensor movement. When the muscle was not moving, IMP explained 89% ± 5% of the variance in muscle force. However, when transducer movement occurred the linear relationship between IMP and stress was no longer observed. These findings demonstrate the difficulty in interpreting IMP under dynamic conditions when sensor movement occurs. They also illustrate the need to control transducer movement if muscle stress is to be inferred from IMP measurements such as might be desired during clinical gait testing. Muscle Nerve, 2007Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56124/1/20828_ftp.pd

Calibration of the 14C time scale to >40 ka by 234U–230Th dating of Lake Lisan sediments (last glacial Dead Sea)

A new comparison of 14C dates with 234U-230Th ages is presented of aragonites from Lake Lisan, the last Glacial Dead Sea, between ∼20–52 cal-ka-BP. The Lisan data are coincident with the coral based 14C-calendar age calibration through the continuous portion of the curve to 23.5 cal-ka-BP, and with the additional ‘checkpoints’ at ∼30 and ∼40 cal-ka-BP. The agreement with the corals provides evidence for the accuracy of the U-Th and 14C ages, and indicates that Lisan aragonites can potentially be used to generate a nearly continuous record of the atmospheric 14C variations through this crucial time interval. The Lisan data are compared with other records older than 25 cal-ka-BP from Lake Suigetsu, Japan, North Atlantic foraminifera, South African cave deposits and tufa from Spain. Over some age intervals the records show broad agreement, over other intervals they diverge. All agree that 14C ages were ∼2.5±0.5 ka younger than calendar ages between 20–32 cal-ka-BP. For ages >32 cal-ka-BP, the Lake Suigetsu data indicate small differences between 14C ages and calendar ages of less than 1.5 ka. The other records broadly agree that 14C ages are too young by ∼3±1 ka from 32–39 cal-ka-BP. At ∼40 cal-ka-BP, the foraminifera show equal 14C and calendar ages, while the corals, Lisan aragonites and the Spanish tufa indicate a large age difference of 4–5 ka. A recent paleomagnetic study of the Lisan Formation indicates that the high calendar-14C age difference at ∼40 cal-ka-BP may be associated with the Laschamp paleomagnetic excursion

Ageing, old age and older adults: a social media analysis of dominant topics and discourses

Whilst representations of old age and older people in traditional media have been well documented, examinations of such representations within social media discourse are still scarce. This is an unfortunate omission because of the importance of social media for communication in contemporary society. In this study, we combine content analysis and discourse analysis to explore patterns of representation on Twitter around the terms ageing, old age, older people and elderly with a sample of 1,200 tweets. Our analysis shows that ‘personal concerns/views’ and ‘health and social care’ are the predominant overall topics, although some topics are clearly linked with specific keywords. The language often used in the tweets seems to reinforce negative discourses of age and ageing that locate older adults as a disempowered, vulnerable and homogeneous group; old age is deemed a problem and ageing is considered something that needs to be resisted, slowed or disguised. These topics and discursive patterns are indeed similar to those found in empirical studies of social perceptions and traditional media portrayal of old age, which indicates that social media and Twitter in particular appears to serve as an online platform that reproduces and reinforces existing ageist discourses in traditional media that feed into social perceptions of ageing and older people.Published onlin

An exploration of tutors’ experiences of facilitating problem-based learning. Part 2: Implications for the facilitation of problem-based learning

YesThis paper is the second of two parts exploring a study that was undertaken to investigate the role of the tutor in facilitating problem-based learning (PBL). The first part focussed on the methodological underpinnings of the study. This paper aims to focus on the findings of the study and their implications for the facilitation of PBL. Six essential themes emerged from the findings that described the facilitation role. The tutors believed that their facilitation role was essentially structured around the decision of when to intervene and how to intervene in the PBL process. Modelling and non-verbal communication were seen as essential strategies for the facilitator. Underpinning these decisions was the need to trust in the philosophy of PBL. However, within many of the themes, there was a divergence of opinion as to how the role should actually be undertaken. Despite this, these findings have implications for the future role of PBL facilitators in Health Professional Education

General and specific effects of early-life psychosocial adversities on adolescent grey matter volume

AbstractExposure to childhood adversities (CA) is associated with subsequent alterations in regional brain grey matter volume (GMV). Prior studies have focused mainly on severe neglect and maltreatment. The aim of this study was to determine in currently healthy adolescents if exposure to more common forms of CA results in reduced GMV. Effects on brain structure were investigated using voxel-based morphometry in a cross-sectional study of youth recruited from a population-based longitudinal cohort. 58 participants (mean age=18.4) with (n=27) or without (n=31) CA exposure measured retrospectively from maternal interview were included in the study. Measures of recent negative life events (RNLE) recorded at 14 and 17years, current depressive symptoms, gender, participant/parental psychiatric history, current family functioning perception and 5-HTTLPR genotype were covariates in analyses. A multivariate analysis of adversities demonstrated a general association with a widespread distributed neural network consisting of cortical midline, lateral frontal, temporal, limbic, and cerebellar regions. Univariate analyses showed more specific associations between adversity measures and regional GMV: CA specifically demonstrated reduced vermis GMV and past psychiatric history with reduced medial temporal lobe volume. In contrast RNLE aged 14 was associated with increased lateral cerebellar and anterior cingulate GMV. We conclude that exposure to moderate levels of childhood adversities occurring during childhood and early adolescence exerts effects on the developing adolescent brain. Reducing exposure to adverse social environments during early life may optimize typical brain development and reduce subsequent mental health risks in adult life

Minimum Wage Channels of Adjustment

Industrial Relations, forthcoming Abstract: The effects of minimum wage increases in 2007-2009 are analyzed using a sample of restaurants from Georgia/Alabama. Store-level payroll records provide precise measures of compliance costs. Examined are multiple adjustment channels. Exploiting variation in compliance costs across restaurants, we find employment and hours responses to be variable and in most cases statistically insignificant. Channels of adjustment to wage increases and to changes in non-labor costs include prices, profits, wage compression, turnover, and performance standards

In search of theory? The workplace case study tradition in the 21st century

Workplace case studies have been valued by some for their ability to advance theory while others dismiss them as little more than descriptive stories. This paper presents a detailed content analysis of case study articles to assess the relative balance between theory, conceptual analysis and description. Drawing on a random sample of papers (n = 173) published in leading journals, I find that fewer than one in seven are descriptive papers while only one in ten are theory oriented. Using three criteria, I identify exemplars of theoretical and conceptual analysis and show how these may be used to advance the field