The hyporheic zone of river ecosystems provides a habitat for a diverse macroinvertebrate community that makes a vital contribution to ecosystem functioning and biodiversity. However, effective methods for sampling this community have proved difficult to establish, due to the inaccessibility of subsurface sediments. The aim of this study was to compare the two most common semi-quantitative macr...

Both vacuum-squeezed and bright amplitude-squeezed states of light are experimentally generated from a frequency doubler with a semimonolithic Fabry-Perot configuration consisting of a type II nonlinear crystal and a concave mirror. Vacuum squeezing of 3.2 +/- 0.1 dB and amplitude squeezing of 1.3 +/- 0.2 dB are obtained simultaneously at a pump power of 8 mW. The two quadrature-squeezed optica...

The three major vacuum systems serving the two-mile accelerator, the optical alignment system light pipe, and the beam switchyard (BSY) transport vacuum chambers are located as shown in Fig. 23-1. The accelerator vacuum system must maintain a very high vacuum in the accelerator to prevent RF electrical breakdown and electron scatter. Thirtytwo subsystems evacuate the accelerator to a design pre...

In simple vacuum systems employing a' single ion pump, it is common to use the linear pump current pressure relationship to advantage, eliminating the need for a separate vacuum gauge by reading the ion pump power supply current. In large systems it becomes prohibitively expensive to install a power supply for each pump and in such systems one or more central supplies are usually used with a di...

Vacuum weighing of mass artifacts eliminates the necessity of air buoyancy correction and its contribution to the measurement uncertainty. Vacuum weighing is also an important process in the experiments currently underway for the redefinition of the SI mass unit, the kilogram. Creating the optimum vacuum environment for mass metrology requires careful design and selection of construction materi...