High-sensitivity cassette for reducing limit of detection for diesel particulate matter sampling.

NIOSH researchers designed a high-sensitivity (HS) cassette to improve the limit of detection of the National Institute for Occupational Safety and Health's (NIOSH) method 5040 and the Airtec near real-time diesel particulate matter (DPM) monitor. This was achieved by reducing the size of the diesel particulate matter deposition spot from 8.0 cm2 (NIOSH method 5040 mining samples) and 7.6 cm2 (Airtec samples) to 0.5 cm2. When compared with the standard cassette, the new high-sensitivity cassette improves the limit of detection of NIOSH method 5040 by approximately five times, and the differences between the elemental carbon results from the HS cassette and the standard three-piece cassette were within statistical error. The limit of detection for Airtec measurements improved by approximately 15 times, and the elemental carbon results with the HS cassette between the Airtec and NIOSH method 5040 were within statistical agreement. When used in the Airtec monitor, the high-sensitivity cassette showed promise for measuring short-duration spot checks of ambient concentrations but was limited when performing some long-term sampling due to the resultant loss of dynamic range. Only up to 7 µg of elemental carbon was collected onto the HS cassette before the increase in pump backpressure caused the flow fluctuations to exceed targeted values by unacceptable levels. The HS cassette shows promise for effective engineering evaluations of control technologies and strategies and near real-time diesel particulate matter measurements for a variety of occupations.

Comparison of MERV 16 and HEPA filters for cab filtration of underground mining equipment.

Significant strides have been made in optimizing the design of filtration and pressurization systems used on the enclosed cabs of mobile mining equipment to reduce respirable dust and provide the best air quality to the equipment operators. Considering all of the advances made in this area, one aspect that still needed to be evaluated was a comparison of the efficiencies of the different filters used in these systems. As high-efficiency particulate arrestance (HEPA) filters provide the highest filtering efficiency, the general assumption would be that they would also provide the greatest level of protection to workers. Researchers for the U.S. National Institute for Occupational Safety and Health (NIOSH) speculated, based upon a previous laboratory study, that filters with minimum efficiency reporting value, or MERV rating, of 16 may be a more appropriate choice than HEPA filters in most cases for the mining industry. A study was therefore performed comparing HEPA and MERV 16 filters on two kinds of underground limestone mining equipment, a roof bolter and a face drill, to evaluate this theory. Testing showed that, at the 95-percent confidence level, there was no statistical difference between the efficiencies of the two types of filters on the two kinds of mining equipment. As the MERV 16 filters were less restrictive, provided greater airflow and cab pressurization, cost less and required less-frequent replacement than the HEPA filters, the MERV 16 filters were concluded to be the optimal choice for both the roof bolter and the face drill in this comparative-analysis case study. Another key finding of this study is the substantial improvement in the effectiveness of filtration and pressurization systems when using a final filter design.

Effects of MERV 16 filters and routine work practices on enclosed cabs for reducing respirable dust and DPM exposures in an underground limestone mine.

An effective technique to minimize miners' respirable dust and diesel exposure on mobile mining equipment is to place mine operators in enclosed cabs with designed filtration and pressurization systems. Many factors affect the performance of these enclosed cab systems, and one of the most significant factors is the effectiveness of the filtration system. High-efficiency particulate air (HEPA)-type filters are typically used because they are highly efficient at capturing all types and sizes of particles, including those in the submicron range such as diesel particulate matter (DPM). However, in laboratory tests, minimum efficiency reporting value (MERV) 16 filters have proven to be highly efficient for capturing DPM and respirable dust. Also, MERV 16 filters can be less restrictive to cab airflow and less expensive than HEPA filters. To verify their effectiveness in the field, MERV 16 filters were used in the enclosed cab filtration system on a face drill and roof bolting mining machine and tested at an underground limestone mine. Test results showed that DPM and respirable dust concentrations were reduced by more than 90% when the cabs were properly sealed. However, when the cab door was opened periodically throughout the shift, the reduction efficiency of the MERV 16 filters was reduced to 80% on average.

Investigation of induced recirculation during planned ventilation system maintenance.

The Office of Mine Safety and Health Research (OMSHR) investigated ways to increase mine airflow to underground metal/nonmetal (M/NM) mine working areas to improve miners' health and safety. One of those areas is controlled recirculation. Because the quantity of mine air often cannot be increased, reusing part of the ventilating air can be an effective alternative, if implemented properly, until the capacity of the present system is improved. The additional airflow can be used to provide effective dilution of contaminants and higher flow velocities in the underground mine environment. Most applications of controlled recirculation involve taking a portion of the return air and passing it back into the intake to increase the air volume delivered to the desired work areas. OMSHR investigated a Nevada gold mine where shaft rehabilitation was in progress and one of the two main fans was shut down to allow reduced air velocity for safe shaft work. Underground booster fan operating pressures were kept constant to maintain airflow to work areas, inducing controlled recirculation in one work zone. Investigation into system behavior and the effects of recirculation on the working area during times of reduced primary ventilation system airflow would provide additional information on implementation of controlled recirculation into the system and how these events affect M/NM ventilation systems. The National Institute for Occupational Safety and Health monitored the ventilation district when both main fans were operating and another scenario with one of the units turned off for maintenance. Airflow and contaminants were measured to determine the exposure effects of induced recirculation on miner health. Surveys showed that 19% controlled recirculation created no change in the overall district airflow distribution and a small reduction in district fresh air intake. Total dust levels increased only modestly and respirable dust levels were also low. Diesel particulate matter (DPM) levels showed a high increase in district intake mass flow, but minor increases in exposure levels related to the recirculation percentage. Utilization of DPM mass flow rates allows input into ventilation modeling programs to better understand and plan for ventilation changes and district recirculation effects on miners' health.

Evaluation of a wearable monitor for measuring real-time diesel particulate matter concentrations in several underground mines.

The standard method for determining diesel particulate matter (DPM) exposures in underground metal/nonmetal mines provides the average exposure concentration for an entire working shift, and it can take weeks to obtain results. This approach is problematic because, although it reports that an overexposure has occurred, it fails to provide critical information about cause or prevention. Conversely, real-time measurement would provide miners with timely information to identify the major factors contributing to overexposures and would allow engineering controls to be deployed immediately. Due to these potential benefits, the National Institute for Occupational Safety and Health (NIOSH) developed a wearable instrument that measures real-time elemental carbon (EC) concentrations (EC is a DPM surrogate) via laser extinction. This instrument was later constructed into a commercial version (Airtec). This article evaluates the Airtec's performance in several underground metal/nonmetal mines by comparing it to the standard method for determining DPM exposures (NIOSH method 5040). The instrument was found to meet the NIOSH accuracy criteria and to show no statistical difference from NIOSH method 5040 results. In addition, the instrument's measurements were found to be unaffected by dust and humidity.

Relationship between elemental carbon, total carbon, and diesel particulate matter in several underground metal/non-metal mines.

Elemental carbon (EC) is currently used as a surrogate for diesel particulate matter (DPM) in underground mines since it can be accurately measured at low concentrations and diesels are the only source of submicrometer EC in underground mines. A disadvantage of using EC as a surrogate for DPM is that the fraction of EC in DPM is a function of various engine parameters and fuel formulations, etc. In order to evaluate how EC predicts DPM in the underground mining atmosphere, measurements of total carbon (TC; representing over 80% of the DPM) and EC were taken away from potential interferences in four underground metal/non-metal mines during actual production. In a controlled atmosphere, DPM mass, TC, and EC measurements were also collected while several different types of vehicles simulated production with and without different types of control technologies. When diesel particulate filters (DPFs) were not used, both studies showed that EC could be used to predict DPM mass or TC. The variability of the data started to increase at TC concentrations below 230 microg/m3 and was high (> +/- 20%) at TC concentrations below 160 microg/m3, probably due to the problem with sampling organic carbon (OC) at these concentrations. It was also discovered that when certain DPFs were used, the relationship between DPM and EC changed at lower DPM concentrations.

Phylogenetics of paniceae (poaceae).

Paniceae demonstrate unique variability of photosynthetic physiology and anatomy, including both non-Kranz and Kranz species and all subtypes of the latter. This variability suggests hypotheses of independent origin or reversals (e.g., from C(4) to C(3)). These hypotheses can be tested by phylogenetic analysis of independent molecular characters. The molecular phylogeny of 57 species of Paniceae was explored using sequences from the grass-specific insert found in the plastid locus rpoC2. Phylogenetic analyses confirmed some long-recognized alliances in Paniceae, some recent molecular phylogenetic results, and suggested new relationships. Broadly, Paniceae were found to be paraphyletic with Andropogoneae, Panicum was found to be polyphyletic, and Oplismenus hirtellus was resolved as the sister group to the remaining ingroup species. A particularly well-supported clade in the rpoC2 tree included four genera with non-Kranz species and three with distinctively keeled paleas. As previously suggested, the PCK (phosphoenol pyruvate carboxykinase) C(4) subtype arose once within Paniceae. All clades with non-Kranz species had Kranz ancestors or sister taxa suggesting repeated loss of the Kranz syndrome.

The effects of semantic and phonemic prestimulation cues on picture naming in aphasia.

In this study of auditory prestimulation cues, picture naming performances under phonemic and semantic conditions were compared to picture naming performance under a neutral condition. Twenty aphasic subjects named 324 pictures (108 pictures x 3 conditions) each. Responses were scored using a coding system adapted by the investigator from classification systems used by Williams and Canter (1982) and Kohn and Goodglass (1985). Results indicated that naming accuracy was facilitated by phonemic and semantic cues. An examination of the distribution of errors under the three conditions revealed systematic effects of phonemic and semantic cues on the frequency of occurrence of specific error types. Increases in semantic paraphasia proportion scores and decreases in unrelated word error proportion scores were associated with the semantic condition, while increases in phonemic paraphasia proportion scores were associated with the phonemic condition. The finding that naming performance of aphasic adults varies as a function of the type of information provided by the cue is discussed in relation to cascade visual confrontation naming models.

Gesture recognition in patients with aphasia.

This study focuses on the controversial issue of the integrity of gestural communication abilities in subjects with aphasia. To define the ability of subjects to interpret symbolic gestures, an Amer-Ind Recognition Test (ART) was developed which required no verbal response from the examiner or the subject. The relationships between impairment of Amer-Ind signal recognition and (a) severity of aphasia, (b) listening and talking abilities and (c) the type of response picture used were investigated. Whether subjects more often chose related foils than unrelated foils in a forced-choice format was also examined. Two training tests and the ART are described. Results from administration to 15 aphasic subjects indicated that: (a) all subjects performed equally well, regardless of their aphasia severity classification; (b) action picture recognition was related to listening ability; (c) action pictures were easier to identify than object pictures; and (d) on error responses, subjects overwhelmingly chose related over unrelated foils. The possibility that gestural abilities were relatively well preserved among the subjects tested, in the presence of a wide range of listening and talking deficits, is also discussed.

TONAR calibration: a brief note.

Measurements were made of the frequency response characteristics of the microphone-separator components of TONAR II instrumentation. The results of our calibration studies revealed 1) appreciable non-uniformity in frequency response of the two microphones, 2) a considerable degree of mismatch in frequency response between the microphones and, 3) dynamic interactions among microphone, separator cavity, and talker cavity resonant characteristics. Findings are discussed in terms of their implications regarding the validity of TONAR II based nasalance ratio measures.

Auditory semantic, syntactic, and retention errors made by aphasic subjects on the Token Test.

The Token Test was administered to 25 mild aphasic and 25 matched normal subjects for the purpose of determining the linguistic nature of the auditory verbal comprehension error responses. As was expected, the aphasic subjects obtained significantly poorer scores on the Token Test than did the normal subjects, with minimal overlap between the two groups. In Parts I-IV, the errors were exclusively semantic, and reflected only the amount of required verbal memory. In Part V, the syntactic structures vary, and the aphasic subjects showed a similar pattern of difficulty as did the normal subjects. Syntactic errors were more prevalent than semantic errors in Part V, suggesting that syntactic complexity was the most important factor in verbal comprehension on this part. In comparison to previous research utilizing the Token Test with normal children, the aphasic subjects in the present study generally had high error rates on the same items as did the children.

Performance of normal six- and seven-year-old males on oral manometer tasks.

An assessment was made of oral manometric performance of normal speaking six- and seven-year-old boys. Readings of maximum, sustained, positive and negative pressure with bleed and nostrils occluded and open were obtained from each of forty subjects. It was found that the majority of normal speaking six- and seven-year-old boys had considerable difficulty generating and maintaining stable, maximal positive and negative pressure upon repeated trials of each of four manometric tasks. The findings of this project support the general hypothesis that oral manometric ratio data may be of questionable diagnostic value in predicting velopharyngeal adequacy for speech, particularly if ratio data must be interpreted dichotomously. The observations made were interpreted to support the view that there may be substantial differences even within the normal population in the ability to perform manometric tasks. The present results suggest that operational procedures commonly used during manometric testing merit rigorous scrutiny, re-examination and analysis.