Dynamics of dissolved organic matter and disinfection byproduct precursors along a low elevation gradient in woody wetlands - an implication of hydrologic impacts of climate change on source water quality.

Foliar litter is an important terrestrial source of dissolved organic matter (DOM) and disinfection byproducts (DBPs) in the source water supply. Climate changes could alter precipitation patterns and hydroperiods in woody wetlands, resulting in a hydrologic shift along the low elevation gradient and change the productions of DOC and DBP precursors and their exports to source water. Here, we conducted an 80-week field decomposition study using fresh-fallen leaves along an elevation gradient, representing well-drained, relatively moist, and inundated environments, in Congaree National Park, South Carolina.

A multirod collimator for neutron therapy.

Purpose: To design, construct, and commission a multirod collimator for producing irregularly shaped fields in neutron radiation therapy. To demonstrate the reliability and applicability of this device to routine use with a superconducting cyclotron for neutron therapy.

Methods And Materials: A multirod collimator has been designed, constructed, and thoroughly tested to investigate its radiological properties; neutron transmission characteristics, beam profiles, and penumbral widths as a function of field size and depth in a phantom, and the spatial resolution of the rod array, have been measured.

Calculations of x-ray and neutron transmission through multirod arrays.

Multirod arrays can be used to produce irregularly shaped irradiation fields for use in external beam photon and neutron radiation therapy. Two prototype multirod collimators have been built for use with high energy photon beams. A practical multirod collimator is in routine use with the fast neutron beam at a superconducting cyclotron based neutron therapy facility.

Radiological properties of a prototype multi-rod collimator for producing irregular fields in photon radiation therapy.

A prototype multi-rod collimator for producing irregular fields in photon radiation therapy has been designed and built. The mechanical details of the design and operation of the multi-rod collimator are discussed. Beam profiles for an approximately 10 x 10 cm2 field have been measured at various depths in phantom, and compared with profiles obtained using the secondary collimator jaws alone and with cast metal blocks.

Transmission measurements in multi-rod arrays: a design study for a multi-rod collimator.

The results of transmission measurements for neutrons, cobalt-60 gamma-rays, and 10 and 15 MV photons made with close-packed arrays of tungsten rods are presented. These results indicate that tungsten rod arrays of reasonable thickness can provide for primary or secondary collimation of all these radiation beams. Development work on a collimation system utilizing the multi-rod concept which is capable of producing irregularly shaped fields and suitable for use in photon or neutron radiation therapy is described.