A number of recent observations by probe and X-ray methods on the behaviour of crossbridges during contraction is considered in relation to the energetics of the process. It is shown that a self-consistent picture of the crossbridge cycle, compatible with these observations and involving strongly and weakly attached crossbridges, can be obtained providing that the tension-generating part of the crossbridge stroke is only about 40 A i.e. about one-third of the usually accepted value. The myosin head subunits in the tension-generating bridges could have a configuration close to that of rigor. A mechanism is suggested whereby rapid tension recovery after quick releases up to 120 A could still be produced by such a system.

Crossbridge behaviour during muscle contraction

Muscle structure, sarcomere length and influences on meat quality: A review

The results of a series of radio sounding observations on (a) transient bursts of atmospheric ionization, and (b) abnormal or sporadic E-layer ionization, are described and discussed. Special observations during the recent Giacobinid meteor shower of 10 October 1946 confirm that the ionization bursts which can be observed at all hours of the day are due to sporadic meteors. A statistical study of abnormal or sporadic E-layer ionization gives strong support to the view that, in temperate latitudes, this phenomenon is also largely ascribable to the same cause.

http://iopscience.iop.org/article/10.1088/0959-5309/59/3/313/pdf

The radio detection of meteor trails and allied phenomena

The results of the effects of a solar eclipse of magnitude 0.88 at Huancayo, Peru, on the various components of the E-, F1-, and F2-layers of the ionosphere are described. Minima in ion-density were observed for the E- and F1-layers near the time of maximum eclipse. A delayed effect on the decrease of F2-layer ion-density was observed. An effect on F2-layer ion-density, which may be attributed to a corpuscular eclipse, is described. (Other suggestions regarding this effect are given in a separate report by H. W. Wells and A. H. Shapley.) The results of signal-intensity variations, WWV, are also noted.

Effects on the ionosphere at Huancayo, Peru, of the solar eclipse, January 25, 1944

The confusion which has existed for decades about the relationship between temperate zone sporadic E, as seen on an ionosonde, and meteor incidence has been resolved by identifying three classes of meteor-produced Es (herein called Em)) Class 1 Em is the instantaneous partially reflecting ionosonde echo due to a single meteor trail. Correspondence in height and time of single echoes has long been established, but no statistical work relating these echoes directly to meteor occurrence rates has yet been done. Class 2 Em defines the cases where meteor occurrence is of sufficient strength to produce control of fEs on the simultaneous ionogram. This is a rare occurrence and has accounted for much of the ambiguity in the literature where direct relationships have been sought between meteor rate and Es occurrence from tabulated ionosonde data. Class 3 Em is the production of Es layers by the subsequent action of wind shear on residual meteor ion concentrations. This is identified statistically by the probability of occurrence of Es above at least 4 MHz or preferably above somewhat higher frequencies. A major conclusion which emerges is that much temperate zone Es, but not necessarily all, is of this type.

Relationship of meteors to sporadic E , 1. A sorting of facts

OF the various agencies responsible for producing and maintaining ionisation of the ionosphere, bombardment of the upper atmosphere by meteors has been suggested as one. Skellett1 has carried out a calculation of the energy received by the earth due to impact of the meteors and finds that during a meteoric shower it might be so high as a fourteenth of that due to ultra-violet light from the sun. He therefore concludes that meteoric showers might be one of the factors disturbing the ionisation of the upper atmosphere. In order to find if any correlation exists between the occurrence of the two phenomena, Schafer and Goodall2 measured the height of the E-region during the Leonid meteoric shower of 1931. They found that on some nights the ionic density attained high values. Unfortunately, their observations were vitiated by a magnetic storm which was in progress at that time. Though they were unable to draw any definite conclusion regarding the correlation, they summarise their observations by saying that there is reason to believe that the presence of meteors in unusual numbers can cause increased ionisation of an intermittent nature in the region of the lower layer.

Effect of a Meteoric Shower on the Ionosphere

IT has been definitely established that the ionosphere responsible for carrying radio waves round the curved surface of the earth is divided into two clearly distinguishable regions1,2 The lower—the classical Kennelly-Heaviside or the E layer—is situated at a height of about 90 km, and the upper —the Appleton or the F layer—is situated at a height of about 200 km The nature of the ionising agencies producing these two different layers is, however, not yet definitely known

B. N. Ghose

Papers

Effect of a Meteoric Shower on the Ionosphere

Effect of the Solar Eclipse on the Ionosphere