We find that tracer material can be concentrated into invariant regions of flows due exclusively to transient effects, as are produced when tracers temporarily become more buoyant than the surrounding fluid. This can occur either as a single event, e.g., if the tracer is initially weakly buoyant, or under periodic forcing, e.g., when external effects (such as solar heating) change the tracer de...

In an intriguing recent paper, Crittenden and Turok proposed cross-correlating the cosmic microwave background (CMB) with tracers of the matter density to probe the existence of a cosmological constant. Here I emphasize that a similar cross-correlation arises in an open Universe and, depending on the redshift distribution of the tracer population and the matter density, may be comparable to or ...

We use 3-dimensional numerical simulations of self-gravitating compressible turbulent gas in combination with Lagrangian tracer particles to investigate the mixing process of molecular hydrogen (H2) in interstellar clouds. Tracer particles are used to represent shock-compressed dense gas, which is associated with H2. We deposit tracer particles in regions of density contrast in excess of 10ρ0, ...

The present study examines subcortical connections of paraventricular thalamic nucleus (Pa) following small anterograde and retrograde tracer injections in cynomolgus monkeys (Macaca fascicularis). An anterograde tracer injection into the dorsal midline thalamus revealed strong projections to the accumbens nucleus, basal amygdala, lateral septum, and hypothalamus. Retrograde tracer injections i...

It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred ...

We present a 55-year old male patient who was subjected to whole body skeletal scintigraphy for metastatic work up of urinary bladder cancer. Whole body 99mTc-methylene diphosphonate (MDP) skeletal scintigraphy was performed. That revealed no skeletal metastasis in the entire body skeleton and normally visualized left kidney with empty right renal fossa. Additionally tracer activity ...

Cholesteryl ethers are nonhydrolyzable tracers of cholesteryl esters. We report here that the ethers are not legitimate tracers of esters in systems involving plasma cholesteryl ester transfer activity. On intravenous injection of doubly labeled high density lipoproteins into rabbits, cholesteryl ester tracer was more rapidly transferred to other lipoprotein fractions than was cholesteryl ether...

A tracer kinetic method is developed for the in vivo estimation of high-affinity radioligand binding to central nervous system receptors. Ligand is considered to exist in three brain pools corresponding to free, nonspecifically bound, and specifically bound tracer. These environments, in addition to that of intravascular tracer, are interrelated by a compartmental model of in vivo ligand distri...