The correlation between wing kinematics and steering muscle activity in the blowfly Calliphora vicina

Determining how the motor patterns of the nervous system are converted into the mechanical and behavioral output of the body is a central goal in the study of locomotion. In the case of dipteran flight, a population of small steering muscles controls many of the subtle changes in wing kinematics that allow flies to maneuver rapidly. We filmed the wing motion of tethered Calliphora vicina at high speed and simultaneously recorded multi-channel electromyographic signals from some of the prominent steering muscles in order to correlate kinematics with muscle activity. Using this analysis, we found that the timing of each spike in the basalare muscles was strongly correlated with changes in the deviation of the stroke plane during the downstroke. The relationship was non-linear such that the magnitude of the kinematic response to each muscle spike decreased with increasing levels of stroke deviation. This result suggests that downstroke deviation is controlled in part via the mechanical summation of basalare activity. We also found that interactions among the basalares and muscles III2–III4 determine the maximum forward amplitude of the wingstroke. In addition, activity in muscle I1 appears to participate in a wingbeat gearing mechanism, as previously proposed. Using these results, we have been able to correlate changes in wing kinematics with alteration in the spike rate, firing phase and combinatorial activity of identified steering muscles

Neuromuscular control of aerodynamic forces and moments in the blowfly, Calliphora vicina

Flies are among the most agile of flying insects, a capacity that ultimately results from their nervous system's control over steering muscles and aerodynamic forces during flight. In order to investigate the relationships among neuromuscular control, musculo-skeletal mechanics and flight forces, we captured high-speed, three-dimensional wing kinematics of the blowfly, Calliphora vicina, while simultaneously recording electromyogram signals from prominent steering muscles during visually induced turns. We used the quantified kinematics to calculate the translational and rotational components of aerodynamic forces and moments using a theoretical quasi-steady model of force generation, confirmed using a dynamically scaled mechanical model of a Calliphora wing. We identified three independently controlled features of the wingbeat trajectory – downstroke deviation, dorsal amplitude and mode. Modulation of each of these kinematic features corresponded to both activity in a distinct steering muscle group and a distinct manipulation of the aerodynamic force vector. This functional specificity resulted from the independent control of downstroke and upstroke forces rather than the independent control of separate aerodynamic mechanisms. The predicted contributions of each kinematic feature to body lift, thrust, roll, yaw and pitch are discussed

A sectoral analysis of Italy's development : 1861 -2010

Italy‘s economic growth over its 150 years of unified history did not occur at a steady pace nor was it balanced across sectors. Relying on an entirely new input (labour and capital) database by us built and presented in the Appendix, together with new Banca d‘Italia estimates of GDP by sector, this paper evaluates the different labour productivity growth trends within the Italian economy‘s sectors, as well as the contribution of structural change to productivity growth. Italy‘s performance is then set in an international context: a comparison of sectoral labour productivity growth rates and levels within a selected sample of countries (UK, US, Germany, Japan, India) allows us to better time, quantify and gauge the causes of Italy‘s catching-up process and subsequent more recent slowdown. Finally, the paper analyses the proximate sources of Italy‘s growth, relative to the other countries, in a standard growth accounting framework, in an attempt also to disentangle the contribution of both total factor productivity growth and capital deepening to the country‘s labour productivity dynamics

Testing the presence of multiple photometric components in nearby early-type galaxies using SDSS

We investigate two-dimensional image decomposition of nearby, morphologically selected early-type galaxies (ETGs). We are motivated by recent observational evidence of significant size growth of quiescent galaxies and theoretical development advocating a two-phase formation scenario for ETGs. We find that a significant fraction of nearby ETGs show changes in isophotal shape that require multi-component models. The characteristic sizes of the inner and outer component are $\sim 3$ and $\sim 15$ kpc. The inner component lies on the mass-size relation of ETGs at $z \sim 0.25-0.75$, while the outer component tends to be more elliptical and hints at a stochastic buildup process. We find real physical differences between the single- and double-component ETGs, with the double-component galaxies being younger and more metal-rich. The fraction of double component ETGs increases with increasing $\sigma$ and decreases in denser environments. We hypothesize that double-component systems were able to accrete gas and small galaxies until later times, boosting their central densities, building up their outer parts, and lowering their typical central ages. In contrast, the oldest galaxies, perhaps due to residing in richer environments, have no remaining hints of their last accretion episode.Comment: resubmitted to ApJ after referee's repor

Bisphosphonate-related bilateral atypical femoral fractures : be aware and beware

Although bisphosphonates have a well established therapeutic role in the prevention of osteoporosis-related fractures, several reports published over the past 5-6 years suggest a possible causative relationship between long-term use of bisphosphonates and development of ‘atypical’ subtrochanteric and femoral diaphyseal fractures. A high level of clinical suspicion and prompt imaging when these patients present with groin/thigh pain should lead to a timely diagnosis. Appropriate elective management to mitigate against the increased risks of these fractures becoming complete could then be instituted. We present a case of complete bilateral atypical subtrochanteric fractures in a patient on long-term bisphosphonates for osteoporosis. Our objective is to highlight the fracture risk of this patient population; present the current knowledge; and discuss the dilemmas in management of both femora.peer-reviewe

Threat and Punishment in Public Good Experiments

Experimental studies of social dilemmas have shown that while the existence of a sanctioning institution improves cooperation within groups, it also has a detrimental impact on group earnings in the short run. Could the introduction of pre-play threats to punish have enough of a beneficial impact on cooperation, while not incurring the cost associated with actual punishment, so that they increase overall welfare? We report an experiment in which players can issue non-binding threats to punish others based on their contribution levels to a public good. After observing others’ actual contributions, they choose their actual punishment level. We find that threats increase the level of contributions significantly. Efficiency is improved, but only in the long run. However, the possibility of sanctioning differences between threatened and actual punishment leads to lower threats, cooperation and welfare, restoring them to levels equal to or below the levels attained in the absence of threats.threats, cheap talk, sanctions, public good, experiment

Characterisation of damage mechanisms in oxide ceramics indented at dynamic and quasi-static strain rates

Ceramic materials are known to display rate dependent behaviour under impact. Tests to establish the strain-rate dependent variations in damage mechanisms have been carried out on debased alumina, an alumina-zirconia composite, and 3Y-TZP. Materials were indented dynamically and quasi-statically using identical sharp hardened steel projectiles while recording the load profile. Characteristics typical of both sharp and blunt indentation types were observed using scanning electron microscopy and piezospectroscopic mapping. At dynamic strain rates both the depth of the indentation and the residual stress in the material were lower than for quasi-static tests. This was attributed to temperature-induced softening of the projectile. Unusual behaviour was observed in the 3Y-TZP samples due to the reversible transformation from tetragonal to monoclinic crystal structures during mechanical loading. These effects and the observed superior mechanical strength against impact suggest that zirconia or zirconia-composite materials may have advantages over debased alumina for application as ceramic armour materials