Biomedical subjects

C A Ortiz

Publications and source records attributed to C A Ortiz.

6 recordsLinked to original sources

PubMed1999

A generic mixing system for achieving conditions suitable for single point representative effluent air sampling.

The U.S. EPA has approved Alternate Reference Methodologies for sampling radionuclide aerosol particles from stacks and ducts of U.S. DOE facilities. The approach allows use of single point sampling with shrouded probes from locations where both fluid momentum and contaminant concentration are well mixed across the flow cross section. For existing stacks and ducts that do not have locations where there is adequate mixing, we have developed a generic mixing system that will generate conditions suitable for single point sampling. The coefficients of variation of the velocity, tracer gas, and 10 microm aerodynamic diameter aerosol particles profiles are all less than 10%, which are well within the EPA limit of 20%. Mixing is affected neither by size of the system nor by flow rate, provided the flow is turbulent.

Air Pollution, Radioactive↗

PubMed1996

Single point aerosol sampling: evaluation of mixing and probe performance in a nuclear stack.

Alternative reference methodologies have been developed for sampling of radionuclides from stacks and ducts, which differ from the methods previously required by the United States Environmental Protection Agency. These alternative reference methodologies have recently been approved by the U.S. EPA for use in lieu of the current standard techniques. The standard EPA methods are prescriptive in selection of sampling locations and in design of sampling probes whereas the alternative reference methodologies are performance driven. Tests were conducted in a stack at Los Alamos National Laboratory to demonstrate the efficacy of some aspects of the alternative reference methodologies. Coefficients of variation of velocity, tracer gas, and aerosol particle profiles were determined at three sampling locations. Results showed that numerical criteria placed upon the coefficients of variation by the alternative reference methodologies were met at sampling stations located 9 and 14 stack diameters from the flow entrance, but not at a location that was 1.5 diameters downstream from the inlet. Experiments were conducted to characterize the transmission of 10 microns aerodynamic diameter liquid aerosol particles through three types of sampling probes. The transmission ratio (ratio of aerosol concentration at the probe exit plane to the concentration in the free stream) was 107% for a 113 L min-1 (4-cfm) anisokinetic shrouded probe, but only 20% for an isokinetic probe that follows the existing EPA standard requirements. A specially designed isokinetic probe showed a transmission ratio of 63%. The shrouded probe performance would conform to the alternative reference methodologies criteria; however, the isokinetic probes would not.

Aerosols↗

PubMed1992

A continuous sampler with background suppression for monitoring alpha-emitting aerosol particles.

A continuous air monitor has been developed that includes provisions for improving the detection of alpha-emitting aerosol particles in the presence of radon/thoron progeny that are unattached to ambient aerosol particles. Wind tunnel tests show that 80% of 10-microns aerodynamic equivalent diameter particles penetrate the flow system from the ambient air to the collection filter when the flow rate is 57 L min-1 (2 cfm) and the wind speed is 1 m s-1. Uniformity of aerosol collection on the filter, as characterized by the coefficient of variation of the areal density deposits, is less than 15% for 10-microns aerodynamic-equivalent-diameter aerosol particles. Tests with unattached radon daughters in a flow-through chamber showed that approximately 99% of the 218Po was removed by an inlet screen that is designed to collect radon daughters that are in the size range of molecular clusters. The inlet screen offers the opportunity to improve the signal-to-noise ratio of energy spectra in the regions of interest (subranges of the energy spectrum) of transuranic elements and thereby enhance the performance of background compensation algorithms.

Aerosols↗

PubMed1991

A CAM (continuous air monitor) sampler for collecting and assessing alpha-emitting aerosol particles.

A new continuous air monitor (CAM) sampler for assessing alpha-emitting transuranic aerosol particles has been developed. The system has been designed to permit collection of particles that can potentially penetrate into the thoracic region of the human respiratory system. Wind tunnel testing of the sampler has been used to characterize the penetration of aerosol to the collection filter. Results show that greater than or equal to 50% of 10-micrograms aerodynamic equivalent diameter (AED) particles are collected by the filter at wind speeds of 0.3 to 2 m s-1 and at sampling flow rates of 28 to 113 L min-1 (1 to 4 cfm). The deposition of 10-microns AED particles takes place primarily in the center of the filter, where the counting efficiency of the detector is highest.

Aerosols↗

PubMed1990

Performance evaluation of continuous air monitor (CAM) sampling heads.

Continuous air monitor (CAM) samplers are used to detect radioactive aerosol particles in nuclear facilities and to provide alarm signals should the concentrations exceed a multiple of the derived air concentration (DAC) of the radionuclide of concern in a set amount of time. Aerosol particles are drawn into a CAM sampler where collection is to take place upon a filter. Radioactivity of the particles is determined with a detector that is placed in close proximity to the filter face. An important determinant of CAM performance is the ability of the inlet and body of the CAM to transport particulate matter in the inhalable-size range (less than or equal to 10 microns aerodynamic diameter) to the filter without substantial loss or bias with respect to particulate size. Three types of CAM samplers were tested in a low-velocity aerosol wind tunnel to determine the degree to which particles penetrate through the flow systems to the collection filter under conditions typical of normal room air exchange rates. Two air velocities were used: 0.3 and 1.0 m s-1. The CAM samplers were primarily operated at a flow rate of 56.6 L min-1, although some tests were conducted at a flow rate of 28.3 L min-1. The CAM units were prototypes manufactured by Kurz Instruments, Eberline Instrument Corporation, and Victoreen Inc. These three units represent three different approaches to CAM head design. At an air speed of 1 m s-1, aerosol penetration to the filters of the Kurz unit was essentially 100% for particle sizes of 3 and 7-microns aerodynamic diameter and was 86% for a size of 15 microns. For the Eberline sampler, the penetration was over 80% for 3-microns particles but was reduced to less than 2% for 7-microns particles. The victoreen sampler showed penetration values of 98% for 3-microns aerodynamic diameter particles, 88% for 7-microns particles and 4% for a size of 15 microns. Air speed had little effect on the penetration results for the two speeds which were tested. Tests were conducted to determine the uniformity of deposits on the filters of the CAM samplers. For a particle size of 10 microns, the deposits were nonuniform for all three of the instruments.

Aerosols↗

PubMedDate not supplied

A non-invasive technique for the control of intestinal parasites in rhesus macaques (Macaca mulatta).

Control of intestinal parasites is a major concern in maintaining the health and well-being of captive primates. This study established that percutaneous application of ivermectin was as effective as subcutaneous administration for the control of nematodes in captive rhesus macaques. The method is less intrusive than the standard subcutaneous or oral delivery routes and did not adversely affect the health of any of the study subjects.

Administration, Cutaneous↗