A systems evaluation on the effectiveness of a catalyst retrofit program in China.

A low-cost, rare-earth oxide (REO) catalyst has been recommended as part of China's retrofit program for Chinese carbureted vehicles. This study evaluated: (1) the emission reduction efficiency of the REO catalyst during chassis dynamometer testing on the FTP cycle; (2) the effect that fuel properties had on tailpipe emissions and catalyst efficiency; (3) the importance of vehicle premaintenance as part of a retrofit protocol; and (4) the emission reductions obtained following implementation of the program. Results also show that current in-use Chinese noncatalyst, carbureted vehicles operate excessively rich, resulting in extremely high emissions of CO, gaseous toxic compounds, and other non-methane hydrocarbon species (NMHC). Preretrofit maintenance alone has the potential to reduce these emissions by approximately 50%. Dynamometer emission tests showed emissions reductions of >95% for hydrocarbons, CO, and gaseous toxics after retrofit of the REO catalyst. In particular, the relative unit health risk associated with the decrease in emissions of airborne toxic compounds using unleaded Chinese fuel was reduced from 6.33 to 0.30. (Use of low-sulfur California Phase II gasoline rather than current in-use Chinese fuel reduced emissions further.) Following implementation of the program, a follow-up study showed that in-use emissions benefits were considerably less than anticipated, primarily because of poor quality control at the retrofit service centers, a less aggressive preretrofit maintenance procedure, and unauthorized modification to the recommended retrofit control system. Overall results indicate that a carefully controlled retrofit program using REO catalyst technology can reduce emissions significantly. However, well-defined implementation guidelines, and strict adherence to these guidelines are needed to achieve maximum benefits.

Time-resolved characterization of diesel particulate emissions. 2. Instruments for elemental and organic carbon measurements.

The measurement of elemental carbon (EC) and organic carbon (OC) mass for particles emitted by diesel vehicles is currently accomplished using particle collection on filters, followed by analysis using the thermal/optical reflectance carbon analysis method (TOR) or one of its variations. Such filter methods limit time resolution to a minimum of several minutes, making it impossible to study emissions during transient operating conditions. Testing of five different measurement methods has demonstrated that fast response measurement of diesel exhaust particulate EC and OC concentrations, consistent with TOR filter measurements, is feasible using existing technology. EC mass concentrations are best measured through determination of particulate light absorption with a photoacoustic instrument or determination of light extinction with a smoke meter. The photoacoustic instrument has the better dynamic range and sensitivity, whereas the smoke meter is a simpler instrument. Fast response OC measurements cannot be made with any single instrument tested. However, a combination of real time weighing as implemented in the tapered element oscillating microbalance with the photoacoustic instrument has been shown to be capable of determining OC concentrations with good time response. The addition of a nephelometer to the OC measurement could potentially improve time resolution, freedom from interferences, and sensitivity.

Time resolved characterization of diesel particulate emissions. 1. Instruments for particle mass measurements.

The measurement of diesel vehicle exhaust particulate mass is currently accomplished using filter collection methods according to the Code of Federal Regulations (CFR). Such filter methods limit time resolution to a minimum of several minutes, making it impossible to study emissions during transient operating conditions. Extensive testing of five different measurement methods has demonstrated that fast response measurements of diesel exhaust particulate mass concentrations, consistent with CFR filter measurements, are feasible using existing technology. The measurement principles of choice are the real time weighing of exhaust samples as implemented in the tapered element oscillating microbalance (TEOM) and the measurement of light scattering from exhaust particles as implemented in the DustTrak nephelometer. Each of these two instruments has distinctive strengths. The TEOM excels in the area of constant calibration, independent of vehicle. For the DustTrak, this calibration varies by vehicle. On the other hand, the DustTrak has an excellent signal-to-noise ratio, freedom from interference due to other exhaust sample properties, good time resolution, and simplicity. The strengths of the two measurement methods are complimentary, so an obvious suggestion is to integrate them. The nephelometer would obtain a fast response signal, with near real time calibration provided by the microbalance.

Incidence of mammary intra-arterial calcification: an age-matched control study.

Mammary intra-arterial calcification (MIAC) was seen on the mammograms of 13 of 150 (8.7%) known diabetic patients and 21 of 300 (7.0%) age-matched control patients. Statistical analysis verified no significant difference between the rate of occurrence of MIAC in the diabetic group of patients and the control group. Therefore, contrary to previous reported studies, our study does not support the conclusion of an increased frequency of MIAC in diabetic patients. MIAC is a manifestation of peripheral vascular disease resulting from a variety of causes, one of which may be diabetes.

Association between mammographic parenchymal pattern classification and incidence of breast cancer.

Wolfe has suggested that the mammographic parenchymal patterns can be used to identify a group with high incidence of breast cancer. To evaluate this claim, mammograms of women with breast cancer that was detected at the University of Michigan Breast Cancer Detection Demonstration Project have been classified and compared with a randomly selected control group from the same project. The basic mammographic classifications as defined by Wolfe were used with further refinements made in the DY and QDY groups. The mammographic classifications have been grouped according to the degree of density and age. For all ages combined, our dense classifications (DY1, DY2, DYC-, QDY2) show a higher incident rate, 22/1000,than the lucent classification (N1, P1, and QDY1),9/1000,(P less than .01), although not to the degree suggested by Wolfe. This difference is statistically significant (P less than .01); the higher risk is markedly increased for women under 50 years of age (P less than .005). After age 50 the higher risk associated with the dense breast seems to disappear (P less than .13). However, this might be a consequence of women who were in a dense classification at an earlier age who subsequently changed to a lucent classification later in life. Because the percentage of lucent breasts increases with age there is a higher absolute number of cancers (55%) in this group of women past 50; these women cannot be neglected in screening. Our results suggest the following guidelines for clinical evaluation: (1) Careful mammographic and clinical follow-up for any woman with a dense breast at any age. (2) Careful mammographic and clinical follow-up past 50 regardless of breast classification. (3) Women with lucent breasts under age 50 represent a low risk category and may not require as frequent a follow-up as the other mammographic types.