Social change, migration and pregnancy intervals

Maternity histories from residents of a Pacific Island society, Tokelau, and migrants to New Zealand, are analysed using life table techniques. Inter-cohort differentials in patterns of family formation were found in the total Tokelau-origin population. The process of accelerated timing and spacing of pregnancies was more pronounced among migrants who tended to marry later, be pregnant at marriage, have shorter inter-pregnancy intervals at lower parities and to show evidence of family limitation occurring at higher parities. These results point to the significance of changing patterns of social control on strategies of family building

Generalized correlation measures of causality and forecasts of the VIX using non-linear models

This paper features an analysis of causal relations between the daily VIX, S & P500 and the daily realised volatility (RV) of the S & P500 sampled at 5 min intervals, plus the application of an Artificial Neural Network (ANN) model to forecast the future daily value of the VIX. Causal relations are analysed using the recently developed concept of general correlation Zheng et al. and Vinod. The neural network analysis is performed using the Group Method of Data Handling (GMDH) approach. The results suggest that causality runs from lagged daily RV and lagged continuously compounded daily return on the S & P500 index to the VIX. Sample tests suggest that an ANN model can successfully predict the daily VIX using lagged daily RV and lagged daily S & P500 Index continuously compounded returns as inputs

Generalized correlation measures of causality and forecasts of the VIX using non-linear models

This paper features an analysis of causal relations between the daily VIX, S & P500 and the daily realised volatility (RV) of the S & P500 sampled at 5 min intervals, plus the application of an Artificial Neural Network (ANN) model to forecast the future daily value of the VIX. Causal relations are analysed using the recently developed concept of general correlation Zheng et al. and Vinod. The neural network analysis is performed using the Group Method of Data Handling (GMDH) approach. The results suggest that causality runs from lagged daily RV and lagged continuously compounded daily return on the S & P500 index to the VIX. Sample tests suggest that an ANN model can successfully predict the daily VIX using lagged daily RV and lagged daily S & P500 Index continuously compounded returns as inputs

Plasma Physics

Contains reports on two research projects.U. S. Atomic Energy Commission under Contract AT(30-1)-184

Plasma Physics

Contains reports on two research projects.United States Atomic Energy Commission (Contract AT(30-1)-1842

Heavily loaded ferrite-polymer composites to produce high refractive index materials at centimetre wavelengths

A cold-pressing technique has been developed for fabricating composites composed of a polytetrafluoroethylene-polymer matrix and a wide range of volume-fractions of MnZn-ferrite filler (0%–80%). The electromagnetic properties at centimetre wavelengths of all prepared composites exhibited good reproducibility, with the most heavily loaded composites possessing simultaneously high permittivity (180 ± 10) and permeability (23±2). The natural logarithm of both the relative complex permittivity and permeability shows an approximately linear dependence with the volume fraction of ferrite. Thus, this simple method allows for the manufacture of bespoke materials required in the design and construction of devices based on the principles of transformation optics

CT dose reduction factors in the thousands using X-ray phase contrast

Phase-contrast X-ray imaging can improve the visibility of weakly absorbing objects (e.g. soft tissues) by an order of magnitude or more compared to conventional radiographs. Previously, it has been shown that combining phase retrieval with computed tomography (CT) can increase the signal-to-noise ratio (SNR) by up to two orders of magnitude over conventional CT at the same radiation dose, without loss of image quality. Our experiments reveal that as radiation dose decreases, the relative improvement in SNR increases. We discovered this enhancement can be traded for a reduction in dose greater than the square of the gain in SNR. Upon reducing the dose 300 fold, the phase-retrieved SNR was still almost 10 times larger than the absorption contrast data. This reveals the potential for dose reduction factors in the tens of thousands without loss in image quality, which would have a profound impact on medical and industrial imaging applications