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

SiO Masers In Variable-Stars

NSF MPS 05070-76Astronom

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

Remuneration for Representation: Legislative Pay in Comparative and Long Term Perspective

One of the most important changes to legislative politics in the last century has been payment of ordinary legislators. Initially an aspect of broadening representation, politicians’ pay has more recently been related to professionalisation of parliamentary roles. As such, it also acts as a flashpoint for public distrust of the political class. In spite of its importance for central questions in political science, however, scholars have shown little sustained interest in the topic. While scholars have investigated some of the effects of varying pay levels on legislative bodies, no systematic account of legislative pay setting has emerged. In this context, this thesis makes both a theoretical and empirical contribution to the existing literature. First, it develops a theoretical framework to explain how variation in regulatory regimes for legislative pay affects the level, composition and dynamics of legislative compensation. The framework focuses on the role of reforms which take decisions on pay and allowances out of legislators’ hands – hypothesising that pay will be more transparent, but also higher, when politicians give up control. This framework is then analysed in the context of both comparative and longitudinal data on legislative compensation in a selection of countries, taking into account both legislators’ salaries, and less-visible earnings through allowances. Results emphasise the role of regulatory regimes in determining the composition of legislative pay in particular, while questioning previous accounts that associated more independent regulation with a constraining influence over the level of pay. Instead, the analysis indicates that politicians may often alienate decisions over their pay precisely in order to overcome democratic pressures which lead to excessive self-restraint. More broadly, the thesis contributes to accounts of how legislative work professionalised over the course of the twentieth century – becoming a full-time, professionally remunerated career for politicians.Economic and Social Research Council (ESRC

Visual control of flight speed in Drosophila melanogaster

Flight control in insects depends on self-induced image motion (optic flow), which the visual system must process to generate appropriate corrective steering maneuvers. Classic experiments in tethered insects applied rigorous system identification techniques for the analysis of turning reactions in the presence of rotating pattern stimuli delivered in open-loop. However, the functional relevance of these measurements for visual free-flight control remains equivocal due to the largely unknown effects of the highly constrained experimental conditions. To perform a systems analysis of the visual flight speed response under free-flight conditions, we implemented a `one-parameter open-loop' paradigm using `TrackFly' in a wind tunnel equipped with real-time tracking and virtual reality display technology. Upwind flying flies were stimulated with sine gratings of varying temporal and spatial frequencies, and the resulting speed responses were measured from the resulting flight speed reactions. To control flight speed, the visual system of the fruit fly extracts linear pattern velocity robustly over a broad range of spatio–temporal frequencies. The speed signal is used for a proportional control of flight speed within locomotor limits. The extraction of pattern velocity over a broad spatio–temporal frequency range may require more sophisticated motion processing mechanisms than those identified in flies so far. In Drosophila, the neuromotor pathways underlying flight speed control may be suitably explored by applying advanced genetic techniques, for which our data can serve as a baseline. Finally, the high-level control principles identified in the fly can be meaningfully transferred into a robotic context, such as for the robust and efficient control of autonomous flying micro air vehicles

Spacelab Ground Operations

The Spacelab, which is designed and built principally by the European Space Agency and its contractor, ERNO, with certain elements provided by the McDonnell Douglas Technical Services Company, under contract to NASA, will be operated by NASA as a key element of the Space Transportation System. Like the Shuttle, the operational base for the Spacelab will be the Kennedy Space Center in Florida. The Spacelab modular design and\u27its operational interrelationship among the Shuttle, the Spacelab Payload and the ground facilities dictate a particular approach to the ground turnaround in order to achieve the projected mission model. Spacelab facilities and GSE are being prepared at KSC and intense planning is under way to develop a disciplined, systematic operational scheme which is key to the quick turnaround required of all STS elements. A certain portion of the Spacelab ground operational cycle will be almost totally dependent upon the Shuttle turnaround functions, such as the period after Spacelab installation into the Orbiter for pre-launch processing, and the period immediately after landing, prior to removal of the Spacelab. During these times, the Spacelab is operationally an extension of the Orbiter systems and is functionally under Orbiter control

VLA 1.4GHz observations of the GOODS-North Field: Data Reduction and Analysis

We describe deep, new, wide-field radio continuum observations of the Great Observatories Origins Deep Survey -- North (GOODS-N) field. The resulting map has a synthesized beamsize of ~1.7" and an r.m.s. noise level of ~3.9uJy/bm near its center and ~8uJy/bm at 15', from phase center. We have cataloged 1,230 discrete radio emitters, within a 40' x 40' region, above a 5-sigma detection threshold of ~20uJy at the field center. New techniques, pioneered by Owen & Morrison (2008), have enabled us to achieve a dynamic range of 6800:1 in a field that has significantly strong confusing sources. We compare the 1.4-GHz (20-cm) source counts with those from other published radio surveys. Our differential counts are nearly Euclidean below 100uJy with a median source diameter of ~1.2". This adds to the evidence presented by Owen & Morrison (2008) that the natural confusion limit may lie near ~1uJy. If the Euclidean slope of the counts continues down to the natural confusion limit as an extrapolation of our log N - log S, this indicates that the cutoff must be fairly sharp below 1uJy else the cosmic microwave background temperature would increase above 2.7K at 1.4 GHz.Comment: Accepted for publication in ApJS. 16 pages, 19 figures. Radio data and source list can be found at http://www.ifa.hawaii.edu/~morrison/GOODSN

Modelling the spinning dust emission from LDN 1780

We study the anomalous microwave emission (AME) in the Lynds Dark Nebula (LDN) 1780 on two angular scales. Using available ancillary data at an angular resolution of 1 degree, we construct an SED between 0.408 GHz to 2997 GHz. We show that there is a significant amount of AME at these angular scales and the excess is compatible with a physical spinning dust model. We find that LDN 1780 is one of the clearest examples of AME on 1 degree scales. We detected AME with a significance > 20$\sigma$. We also find at these angular scales that the location of the peak of the emission at frequencies between 23-70 GHz differs from the one on the 90-3000 GHz map. In order to investigate the origin of the AME in this cloud, we use data obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) that provides 2 arcmin resolution at 30 GHz. We study the connection between the radio and IR emissions using morphological correlations. The best correlation is found to be with MIPS 70$\mu$m, which traces warm dust (T$\sim$50K). Finally, we study the difference in radio emissivity between two locations within the cloud. We measured a factor $\approx 6$ of difference in 30 GHz emissivity. We show that this variation can be explained, using the spinning dust model, by a variation on the dust grain size distribution across the cloud, particularly changing the carbon fraction and hence the amount of PAHs.Comment: 14 pages, 11 figures, submitted to MNRA