The detailed chemical composition of 25 milks from different breeds of cow, sheep and goat were related to their properties of rennet clotting, coagulum development and syneresis at pH 6-4. Experiments in which concentrations of fat and whey proteins in milk were manipulated, and in which milks were homogenized at different pressures, were also carried out and the effects observed were related to the above processes.The composition of milks varied widely and many relations between concentrations of components could be related to their known modes of secretion from the alveolus or to their structural functions in the colloidal phase of milk. Rennet clotting was related to total Ca concentration and also to the proportions of

SummaryThe chemical composition and rennet coagulation properties at pH 6·4 of milks from 2 commercial herds of Friesian cows were monitored during the change from winter diet to spring grazing. There was considerable variation both in composition and in coagulation properties during this period. There were significant trends for increasing concentrations of casein, Na and lactose, and decreasing concentrations of fat, citrate, K and Mg following the change. Many correlations occurred between concentrations of components, some of which may have physiological significance. Coagulum strength increased after the change to spring grazing and was related to the concentrations of casein, citrate and some of the minerals. Syneresis time did not follow any trend during this period, but was significantly related to concentrations of fat, Na and K. Rennet clotting time did not follow a significant trend immediately after the dietary change, but tended to increase as the summer progressed; it was significantly related to concentrations of Ca, PiNa and K, as well as to the original pH of the milk. When the concentration of lactose in milk was adjusted, variations in lactose concentration did not affect the coagulation properties of milk.

Differentiable simulators provide an avenue for closing the sim-to-real gap by enabling the use of efficient, gradient-based optimization algorithms to find the simulation parameters that best fit the observed sensor readings. Nonetheless, these analytical models can only predict the dynamical behavior of systems for which they have been designed. In this work, we study the augmentation of a novel differentiable rigid-body physics engine via neural networks that is able to learn nonlinear relationships between dynamic quantities and can thus learn effects not accounted for in traditional simulators. Such augmentations require less data to train and generalize better compared to entirely data-driven models.Through extensive experiments, we demonstrate the ability of our hybrid simulator to learn complex dynamics involving frictional contacts from real data, as well as match known models of viscous friction, and present an approach for automatically discovering useful augmentations. We show that, besides benefiting dynamics modeling, inserting neural networks can accelerate model-based control architectures. We observe a ten-fold speedup when replacing the QP solver inside a model-predictive gait controller for quadruped robots with a neural network, allowing us to significantly improve control delays as we demonstrate in real-hardware experiments. We publish code, additional results and videos from our experiments on our project webpage at https://sites.google.com/usc.edu/neuralsim.

The detailed composition, pH, and the properties of rennet clotting, coagulum development and syneresis at pH 6-4 were estimated in milks from 4 Friesian cows during the first 9 weeks of lactation. The concentrations of casein, fat, citrate, Ca, Mg, Pj and Na decreased significantly during early lactation whilst the pH and concentration of lactose increased. Levels of whey protein and K and the casein:fat ratio were unaltered. Considerable variation occurred in the relative proportions of a s -, yff-and /c-casein. These changes in composition were associated with decreasing coagulum strength and an increased rate of whey drainage although rennet clotting time (RCT) did not follow a significant trend. RCT was positively related to levels of Na and whey protein but negatively correlated with Pj, K and lactose. There were significant positive correlations between coagulum strength and casein, fat, nonprotein nitrogen, P 4 , Ca, Mg and citrate. The correlation with a s -casein was stronger than that with /?-or /c-casein. Syneresis time was positively related to fat, Ca and coagulum strength, but negatively related to the concentration of lactose.Seasonal changes in milk composition give rise to unfavourable variations in the yield and quality of dairy products. Feeding, stage of lactation and breeding are the major controllable factors which affect milk composition. Recent studies on milks from different breeds and species of ruminant (Storry et al. 1983) and from Friesian herd milks during the change from winter rations to spring grazing (Grandison et al. 1984) have demonstrated that the coagulation of milk by rennet is radically affected by milk composition. In the latter report and the present study we have attempted to assess individually the effects of nutritional changes and stage of lactation on the composition and rennet coagulating properties of milk. Previous reports (e.g. Chapman & Burnett, 1972;O'Keeffe et al. 1982) have described the variation in composition and properties of milk with season but have not dissociated the effects of nutrition and lactation.The present paper describes studies of the detailed composition and rennet coagulation properties of milks from four Friesian cows during the first 9 weeks of lactation.

A system is described in which a graphite rod electrothermal vaporisation device is employed for the introduction of microlitre liquid samples, after desolvation, into an inductively coupled argon plasma source for atomisation and excitation for optical emission spectrometry. The analytical performance of the system has been studied and detection limits for 16 elements a t the sub-nanogram level are presented.