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Toward a physiological explanation of juvenile growth curves
Juvenile growth curves are generally sigmoid in shape: Growth is initially nearly exponential, but it slows to near zero as the animal approaches maturity. The dropâoff in growth rate is puzzling because, everything else being equal, selection favors growing as fast as possible. Existing theory posits sublinear scaling of resource acquisition with juvenile body mass and linear scaling of the requirement for maintenance, so the difference, fuel for growth, decreases as the juvenile increases in size. Experimental evidence, however, suggests that maintenance metabolism increases sublinearly not linearly with size. Here, we develop a new theory consistent with the experimental evidence. Our theory is based on the plausible assumption that there is a tradeâoff in the capacity of capillaries to supply growing and developed cells. As the proportion of nonâgrowing cells increases, they take up more macromolecules from the capillaries, leaving fewer to support growing cells. The predicted growth curves are realistic and similar to those of previous models (Bertalanffy, Gompertz, and Logistic) but have the advantage of being derived from a plausible physiological model. We hope that our focus on resource delivery in capillaries will encourage new experimental work to identify the detailed physiological basis of the tradeâoff underlying juvenile growth curves
Paradoxical popups: Why are they hard to catch?
Even professional baseball players occasionally find it difficult to
gracefully approach seemingly routine pop-ups. This paper describes a set of
towering pop-ups with trajectories that exhibit cusps and loops near the apex.
For a normal fly ball, the horizontal velocity is continuously decreasing due
to drag caused by air resistance. But for pop-ups, the Magnus force (the force
due to the ball spinning in a moving airflow) is larger than the drag force. In
these cases the horizontal velocity decreases in the beginning, like a normal
fly ball, but after the apex, the Magnus force accelerates the horizontal
motion. We refer to this class of pop-ups as paradoxical because they appear to
misinform the typically robust optical control strategies used by fielders and
lead to systematic vacillation in running paths, especially when a trajectory
terminates near the fielder. In short, some of the dancing around when
infielders pursue pop-ups can be well explained as a combination of bizarre
trajectories and misguidance by the normally reliable optical control strategy,
rather than apparent fielder error. Former major league infielders confirm that
our model agrees with their experiences.Comment: 28 pages, 10 figures, sumitted to American Journal of Physic
Physical State of Molecular Gas in High Galactic Latitude Translucent Clouds
The rotational transitions of carbon monoxide (CO) are the primary means of
investigating the density and velocity structure of the molecular interstellar
medium. Here we study the lowest four rotational transitions of CO towards
high-latitude translucent molecular clouds (HLCs). We report new observations
of the J = (4-3), (2-1), and (1-0) transitions of CO towards eight
high-latitude clouds. The new observations are combined with data from the
literature to show that the emission from all observed CO transitions is
linearly correlated. This implies that the excitation conditions which lead to
emission in these transitions are uniform throughout the clouds. Observed
13CO/12CO (1-0) integrated intensity ratios are generally much greater than the
expected abundance ratio of the two species, indicating that the regions which
emit 12CO (1-0) radiation are optically thick. We develop a statistical method
to compare the observed line ratios with models of CO excitation and radiative
transfer. This enables us to determine the most likely portion of the physical
parameter space which is compatible with the observations. The model enables us
to rule out CO gas temperatures greater than 30K since the most likely
high-temperature configurations are 1 pc-sized structures aligned along the
line of sight. The most probable solution is a high density and low temperature
(HDLT) solution. The CO cell size is approximately 0.01 pc (2000 AU). These
cells are thus tiny fragments within the 100 times larger CO-emitting extent of
a typical high-latitude cloud. We discuss the physical implications of HDLT
cells, and we suggest ways to test for their existence.Comment: 19 pages, 13 figures, 2 tables, emulateapj To be published in The
Astrophysical Journa
Providing Feedback Following Leadership Walkrounds is Associated with Better Patient Safety Culture, Higher Employee Engagement and Lower Burnout
Background There is a poorly understood relationship between Leadership WalkRounds (WR) and domains such as safety culture, employee engagement, burnout and work-life balance. Methods This cross-sectional survey study evaluated associations between receiving feedback about actions taken as a result of WR and healthcare worker assessments of patient safety culture, employee engagement, burnout and work-life balance, across 829 work settings. Results 16â797 of 23â853 administered surveys were returned (70.4%). 5497 (32.7% of total) reported that they had participated in WR, and 4074 (24.3%) reported that they participated in WR with feedback. Work settings reporting more WR with feedback had substantially higher safety culture domain scores (first vs fourth quartile Cohenâs d range: 0.34â0.84; % increase range: 15â27) and significantly higher engagement scores for four of its six domains (first vs fourth quartile Cohenâs d range: 0.02â0.76; % increase range: 0.48â0.70). Conclusion This WR study of patient safety and organisational outcomes tested relationships with a comprehensive set of safety culture and engagement metrics in the largest sample of hospitals and respondents to date. Beyond measuring simply whether WRs occur, we examine WR with feedback, as WR being done well. We suggest that when WRs are conducted, acted on, and the results are fed back to those involved, the work setting is a better place to deliver and receive care as assessed across a broad range of metrics, including teamwork, safety, leadership, growth opportunities, participation in decision-making and the emotional exhaustion component of burnout. Whether WR with feedback is a manifestation of better norms, or a cause of these norms, is unknown, but the link is demonstrably potent
Safeguarding children in dentistry: 1. Child protection training, experience and practice of dental professionals with an interest in paediatric dentistry
* Few dental professionals with child protection training have experience of making referrals.
* There is a wide gap in practice between recognising signs of child abuse and neglect and responding effectively.
* This may indicate missed opportunities to save children from continuing abuse.
* There is a need for improved child protection information, support and training for dental professionals.
Abstract
Following several highly publicised inquiries into the deaths of children from abuse and neglect, there has been much recent interest in the role and responsibility of all health professionals to protect children at risk of maltreatment. The findings of a postal questionnaire, sent in March 2005 to 789 dentists and dental care professionals with an interest in paediatric dentistry working in varied settings in the UK, are presented in a two-part report and discussed in the context of current multi-agency good practice in safeguarding and promoting the welfare of children. This first part explores reported child protection training, experience and practice. There was a significant gap between recognising signs of abuse and responding effectively: 67% of respondents had suspected abuse or neglect of a child patient at some time in their career but only 29% had ever made a child protection referral. The dental profession is alerted to the need to ensure necessary appropriate action to safeguard children is always taken when child abuse or neglect are suspected
Angular analysis and branching fraction measurement of the decay B0âK*0ÎŒ+ÎŒâ
The angular distributions and the differential branching fraction of the decay B0âK*(892)0ÎŒ+ÎŒâ are studied using a data sample corresponding to an integrated luminosity of 5.2 fbâ1collected with the CMS detector at the LHC in pp collisions at âs=7 TeV. From more than 400 signal decays, the forwardâbackward asymmetry of the muons, the K*(892)0 longitudinal polarization fraction, and the differential branching fraction are determined as a function of the square of the dimuon invariant mass. The measurements are in good agreement with standard model predictions
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