Space-time worms

A technique for visualizing the dynamics should allow for the comparison of dynamical relationships. These comparisons should include factors such as inherent variability between replicates or samples and an indication of the rate of change in variables. We have developed a method for this purpose which we call "space-time worms."... 

Space-time worms (STW) were developed to more easily visualize the dynamic relationships between the variables in microcosm experiments (Landis, Matthews, and Matthews 1996). G. Matthews and M. Roze developed the software that enables a three-dimensional viewing of the microcosm experiments. 

Construction of a space-time worm (STW). In A, the average values for the variables ankistrodesmus and ostracod are plotted along with a box plot to represent one standard deviation. Each treatment group can be represented and compared. If time is added (B), then a plot for each sampling date can be represented but the diagram becomes much harder to interpret. 

A space-time worm (STW) construction. In A, time is added as a third axis and the measurements for the two sampling days connected. When this is done for an entire experiment (B) the relative dynamics of the systems becomes readily apparent. 

To provide quantitative predictions about how to detect the superfluid-insulator transition in these experiments, Kashurnikov, Prokofev and Svistunov performed quantum Monte Carlo simulations of the singleparticle density matrix p,y = (I I /). They used the Bose-Hubbard model with harmonic confining potential and carried out world-line Monte Carlo simulations with the continuous-time Worm algorithm. The diagonal elements of the density matrix provide the real-space particle density, and... 

Here we are then enjoying the temporary expansion of space and time in which all our chemistry can occur and in which evolution has occurred by the laws of chemistry. The space between galaxies is not empty (virtual particles can appear in a vacuum), and it appears not to be unstructured, and the physicists are speaking about a worm-hole configuration whereas anyone with a sense of esthetics would have wished they had thought of Swiss cheese to go along with quarks (Farmers cheese in German) which appear to be the fundamental particles of matter. But no such luck, our life has developed in wormholes if they will be confirmed. Terms like this have a tendency to... 

In addition to body fossils, paleoecologists study trace fossils. These are things like footprints, gopher burrows, or worm trails preserved in sediments. Trace fossils indicate the behavior of the organism that made the trace and physical factors about the environment. For example, a trail of dinosaur footprints preserved in stream bed sediments provides evidence of how fast the dinosaur was moving, based on spacing of the prints. The depth of the footprints suggests how soft the sediments were, and hence, whether the stream bed was dry at the time the dinosaur traversed it. 

Molecular clocks make use of the genetic differences between present-day species to predict the time since their divergence from a common ancestor. When an ancestral species splits off new species, these new species and their descendants all gradually accumulate different genetic changes — mutations in the DNA — over time, that eventually make them very different from each other. As different, for example, as humans are now from fruit flies. The basic assumption is that species drift away from one other, in terms of their shared genetic inheritance, at a steady rate. At face value, this assumption is of course nonsense — we have crossed a lot more evolutionary space over the last 600 million years than have worms, for example. The difficulty is to specify a distance across evolutionary space on the basis of averaging the rate of evolution in dif-... 

Claims have been made from time to time that the construction of worm tunnels in fine-textured soils increases the ease of water movement. This is true if pore space is increased appreciably by worm activity but, as Barley (1959b) points out, freshly constructed tuimels are too wide to conduct water at the tensions encountered during infiltration. He considers that plant roots are probably more important than worms in modifying pore space distribution. 

DNA stretches that are thousands of base pairs long, this model becomes too computationally expensive. Thus, larger simulation units must be chosen, e.g., beads representing 37 base pairs spaced by 127 A and with radii of 25.75 A (which results in hydrodynamic properties jcorresponding to those of the worm-like chain model). Such models may be used to examine superhelical coiling of dlosed circular DNA chains on time scales up to hundreds of microseconds. These simulations require additional torsional and excluded-volume... 

---