Experimental verification of principal losses in a regulatory particulate matter emissions sampling system for aircraft turbine engines.

A sampling system for measuring emissions of nonvolatile particulate matter (nvPM) from aircraft gas turbine engines has been developed to replace the use of smoke number and is used for international regulatory purposes. This sampling system can be up to 35 m in length. The sampling system length in addition to the volatile particle remover (VPR) and other sampling system components lead to substantial particle losses, which are a function of the particle size distribution, ranging from 50 to 90% for particle number concentrations and 10-50% for particle mass concentrations. The particle size distribution is dependent on engine technology, operating point, and fuel composition. Any nvPM emissions measurement bias caused by the sampling system will lead to unrepresentative emissions measurements which limit the method as a universal metric. Hence, a method to estimate size dependent sampling system losses using the system parameters and the measured mass and number concentrations was also developed (SAE 2017; SAE 2019). An assessment of the particle losses in two principal components used in ARP6481 (SAE 2019) was conducted during the VAriable Response In Aircraft nvPM Testing (VARIAnT) 2 campaign. Measurements were made on the 25-meter sample line portion of the system using multiple, well characterized particle sizing instruments to obtain the penetration efficiencies. An agreement of ± 15% was obtained between the measured and the ARP6481 method penetrations for the 25-meter sample line portion of the system. Measurements of VPR penetration efficiency were also made to verify its performance for aviation nvPM number. The research also demonstrated the difficulty of making system loss measurements and substantiates the E-31 decision to predict rather than measure system losses.

New paradigm for suppression of gyrokinetic turbulence by velocity shear.

The shear in the mean field velocity Doppler shift is shown to suppress the amplitude of electric potential fluctuations by inducing a shift in the peak of the radial wave number spectrum. An analytic model of the process shows that the fluctuation spectrum shifts in the direction where the velocity shear is linearly destabilizing but that nonlinear mixing causes a recentering of the spectrum about a shifted radial wave number at reduced amplitude A model for the 2D nonlinear spectrum is used in a quasilinear calculation of the transport that is shown to accurately reproduce the suppression of energy and particle transport and the Reynolds stress due to the velocity shear.

Chemical characterization of the fine particle emissions from commercial aircraft engines during the Aircraft Particle Emissions eXperiment (APEX) 1 to 3.

This paper addresses the need for detailed chemical information on the fine particulate matter (PM) generated by commercial aviation engines. The exhaust plumes of seven turbofan engine models were sampled as part of the three test campaigns of the Aircraft Particle Emissions eXperiment (APEX). In these experiments, continuous measurements of black carbon (BC) and particle surface-bound polycyclic aromatic compounds (PAHs) were conducted. In addition, time-integrated sampling was performed for bulk elemental composition, water-soluble ions, organic and elemental carbon (OC and EC), and trace semivolatile organic compounds (SVOCs). The continuous BC and PAH monitoring showed a characteristic U-shaped curve of the emission index (EI or mass of pollutant/mass of fuel burned) vs fuel flow for the turbofan engines tested. The time-integrated EIs for both elemental composition and water-soluble ions were heavily dominated by sulfur and SO(4)(2-), respectively, with a ∼2.4% median conversion of fuel S(IV) to particle S(VI). The corrected OC and EC emission indices obtained in this study ranged from 37 to 83 mg/kg and 21 to 275 mg/kg, respectively, with the EC/OC ratio ranging from ∼0.3 to 7 depending on engine type and test conditions. Finally, the particle SVOC EIs varied by as much as 2 orders of magnitude with distinct variations in chemical composition observed for different engine types and operating conditions.

Diverse styles of submarine venting on the ultraslow spreading Mid-Cayman Rise.

Thirty years after the first discovery of high-temperature submarine venting, the vast majority of the global mid-ocean ridge remains unexplored for hydrothermal activity. Of particular interest are the world's ultraslow spreading ridges that were the last to be demonstrated to host high-temperature venting but may host systems particularly relevant to prebiotic chemistry and the origins of life. Here we report evidence for previously unknown, diverse, and very deep hydrothermal vents along the approximately 110 km long, ultraslow spreading Mid-Cayman Rise (MCR). Our data indicate that the MCR hosts at least three discrete hydrothermal sites, each representing a different type of water-rock interaction, including both mafic and ultramafic systems and, at approximately 5,000 m, the deepest known hydrothermal vent. Although submarine hydrothermal circulation, in which seawater percolates through and reacts with host lithologies, occurs on all mid-ocean ridges, the diversity of vent types identified here and their relative geographic isolation make the MCR unique in the oceans. These new sites offer prospects for an expanded range of vent-fluid compositions, varieties of abiotic organic chemical synthesis and extremophile microorganisms, and unparalleled faunal biodiversity--all in close proximity.

Characterization of fine particle and gaseous emissions during school bus idling.

The particulate matter (PM) and gaseous emissions from six diesel school buses were determined over a simulated waiting period typical of schools in the northeastern U.S. Testing was conducted for both continuous idle and hot restart conditions using a suite of on-line particle and gas analyzers installed in the U.S. Environmental Protection Agency's Diesel Emissions Aerosol Laboratory. The specific pollutants measured encompassed total PM-2.5 mass (PM < or = 2.5 microm in aerodynamic diameter), PM-2.5 number concentration, particle size distribution, particle-surface polycyclic aromatic hydrocarbons (PAHs), and a tracer gas (1,1,1,2,3,3,3-heptafluoropropane) in the diluted sample stream. Carbon monoxide (CO), carbon dioxide, nitrogen oxides (NO(x)), total hydrocarbons (THC), oxygen, formaldehyde, and the tracer gas were also measured in the raw exhaust. Results of the study showed little difference in the measured emissions between a 10 min post-restart idle and a 10 min continuous idle with the exception of THC and formaldehyde. However, an emissions pulse was observed during engine restart. A predictive equation was developed from the experimental data, which allows a comparison between continuous idle and hot restart for NO(x), CO, PM2.5, and PAHs and which considers factors such as the restart emissions pulse and periods when the engine is not running. This equation indicates that restart is the preferred operating scenario as long as there is no extended idling after the engine is restarted.

DNA methylation inhibits expression and transposition of the Neurospora Tad retrotransposon.

Tad is a LINE-like retrotransposon of the filamentous fungus Neurospora crassa. We have analyzed both expression and transposition of this element using strains with a single copy of Tad located in the 5' noncoding sequences of the am (glutamate dehydrogenase) gene. Tad in this position has been shown to carry a de novo cytosine methylation signal which causes reversible methylation of both Tad and am upstream sequences. Here we find that methylation of the Tad sequences inhibits both Tad expression and transposition. This inhibition can be relieved by the use of 5-azacytidine, a drug which reduces cytosine methylation, or by placing the Tad/am sequences in a dim-2 genetic background.

Elimination of active tad elements during the sexual phase of the Neurospora crassa life cycle.

Tad is an active LINE-like retrotransposon isolated from the Adiopodoumé strain of Neurospora crassa. Extensive analysis of other Neurospora strains has revealed no other strain with active Tad, but all strains tested have multiple copies of defective Tad elements. We have examined the ability of Tad to survive during the sexual cycle of Neurospora and find that active Tad is rapidly eliminated. The characteristics of this elimination suggest that the repeat-induced point mutation (RIP) mechanism was responsible. By the use of transformation to switch the mating type of the Adiopodoumé strain we concluded that this strain is not defective in the RIP process. Analysis of defective Tad elements isolated from a variety of strains indicates that the major difference between these elements and active Tad is due to the presence of a large number of G-C to A-T transition mutations. This would be expected if the changes were due primarily to the RIP process. Mapping of a selection of defective Tad elements reveals that they are present on all of the chromosomes; however, many of the elements are not widely shared among strains. This suggests that repeated introduction and elimination of Tad elements has occurred. Mechanisms that might be responsible for this repeated introduction are discussed.

Dynamic modeling of stepwise internal transport barrier formation in DIII-D negative-central-shear discharges.

The GLF23 transport model is used to dynamically follow bifurcations in the energy and toroidal momentum confinement in DIII-D discharges with an internal transport barrier. The temperatures and toroidal velocity profiles are evolved while self-consistently computing the effects of E x B shear stabilization during the formation and expansion of internal transport barriers. The barrier is predicted to form in a stepwise fashion through a series of sudden jumps in the core-electron and ion temperatures and toroidal rotation velocity. These results are consistent with experimental observations. In the simulations, the step transitions are a direct result of local E x B driven transport bifurcations.

The Neurospora am gene and NADP-specific glutamate dehydrogenase: mutational sequence changes and functional effects--more mutants and a summary.

A further series of mutant am alleles, encoding potentially active NADP-specific glutamate dehydrogenase (GDH) and capable of complementation in heterocaryons, have been characterized with respect to both GDH properties and DNA sequence changes. Several mutants previously studied, and some of their same-site or second-site revertants, have also been sequenced for the first time. We present a summary of what is known of the properties of all am mutants that have been defined at the sequence level.

Do advanced practice nurses and physician assistants benefit small rural hospitals?

Advanced practice nurses and physician assistants have offered small, rural hospitals an alternative to scarce primary care physicians for 30 years. This paper uses survey data from 285 small rural hospitals and case studies of 36 of these hospitals to answer questions about the extent to which advanced practice nurses and physician assistants provide primary care in small, rural hospitals, the benefits that might bring to the hospitals as well as the reactions of the public. The study used survey data collected as part of an evaluation of 285 hospitals, which received a Rural Health Care Transition grant from the Health Care Financing Administration in 1993 and 1994. Most of the hospitals used the practitioners; 70 percent used nurse practitioners; 30 percent used physician assistants; and 20 percent used both. There were some negative reactions to the use of the practitioners, but, overall, there was acceptance and benefits to the hospitals in the form of reduced recruitment costs, increased revenues and increased service offerings. These practitioners are beneficial to rural hospitals, and mechanisms to encourage their acceptance should be developed and implemented.

Sulfate content correlates with iron concentrations in ambient air pollution particles.

Current levels of air pollution particles in American cities can increase human mortality. Both the mechanism of injury and the responsible components are not known. We have postulated that injury following air pollution particle exposure is produced through a generation of oxygen-based free radicals catalyzed by metals present in the particles. As a result of its abundance in the atmosphere, sulfate appears to potentially be the most successful ligand to complex metal cations. We tested the hypothesis that (1) some portion of iron in ambient air pollution particles is present as sulfate and (2) this relationship between iron and sulfate results from the capacity of the latter to function as a ligand to mobilize the metal from the oxide. Concentrations of sulfate and iron in acid extracts of 20 filters (total suspended particles) from Utah were measured using inductively coupled plasma emission spectroscopy. In vitro oxidant generation was also measured using thiobarbituric acid-reactive products of deoxyribose. There were significant correlations between sulfate content, iron concentrations, and oxidant generation. Agitation of calcium sulfate with iron(III) oxide produced concentrations of water-soluble, catalytically active iron. We conclude that some portion of iron in the atmosphere is present as a sulfate. This relationship between sulfate and iron concentrations is likely the product of SO42- functioning as a ligand for the meal after its mobilization from an oxide by photoreduction. There were also associations between sulfate content, iron concentrations, and oxidant generation. However, sulfates had no capacity to support electron transport unless they were present with iron.

Effects of puzzle feeders on pathological behavior in individually housed rhesus monkeys.

Self-injurious behavior (SIB) occurs in about 10% of individually housed monkeys. Monkeys with SIB bite their own bodies frequently, occasionally inflicting wounds as a result. At present, there is no standard treatment for this phenomenon. We examined the effectiveness of puzzle feeders in alleviating SIB in monkeys with a veterinary record of self-inflicted wounding. Two groups of monkeys (SIB and controls) were exposed to puzzle feeders for a 6 week period. Three levels of maze difficulty were examined. All monkeys used the feeders, but manipulation was confined to a brief period immediately after the feeders were loaded each day (1000 h) and was infrequent during the later sampling periods (1100 and 1400 h). The most difficult maze yielded a slight increase in usage at 1100 h. During the puzzle feeder phase, whole body stereotypies, including pacing and rocking, were reduced substantially in all monkeys at 1000 h when feeder manipulation was at its highest. However, self-biting in the SIB group was unchanged. Some monkeys actually bit themselves while manipulating the feeder. Long-term effects on abnormal behavior were assessed by comparing behavior during the feeder phase to baseline periods and to a phase in which the monkeys were provisioned with treats placed directly into their food box. Whole body stereotypies, including pacing, were reduced during both treatment phases; however, the reduction was associated only with the 1000 h observation. Puzzle feeders were more effective than treats alone in alleviating whole body stereotypies. Self-biting was unchanged through all phases. Puzzle feeders are beneficial from the perspective of eliciting manipulation. They also yield transient reductions in whole body stereotypy, an effect that does not extend beyond the direct manipulation of the feeder. Puzzle feeders are ineffective in alleviating self-injurious behavior.

Efficacy of topical nonsteroidal drops as pain relief after excimer laser photorefractive keratectomy.

PURPOSE: To compare the efficacy of topical aqueous indomethacin and ketorolac for pain relief following excimer laser photorefractive keratectomy (PRK). METHODS: We conducted a double masked, randomized trial involving 120 patients. All patients received a standard regimen of one of the trial drugs and chloramphenicol ointment to be used four times daily for 2 days. Pain levels and quality were assessed on a 10 cm linear analogue scale prior to each instillation of the topical medication with the McGill pain questionnaire. Pain threshold was evaluated using a modified State Trait Anxiety Inventory questionnaire. Patients were advised to use paracetomol for additional pain relief but were allowed to use any oral analgesic (except nonsteroidal agents) which they documented (type and quantity). RESULTS: There was no significant difference in pain scores between the groups using indomethacin and ketoralac. CONCLUSION: We found no significant difference between topical ketoralac and aqueous indomethacin as pain relief following excimer laser PRK. Both drugs seemed to significantly reduce pain.

The Neurospora aab-1 gene encodes a CCAAT binding protein homologous to yeast HAP5.

The expression of the am (glutamate dehydrogenase) gene is dependent upon two upstream activating sequences, designated URSam(alpha) and URSam(beta). A heteromeric nuclear protein Am Alpha Binding protein (AAB) binds specifically to a CCAAT box within the URSam(alpha) element. AAB appears to be composed of three components. We used polyclonal antiserum raised against the highly purified AAB1 subunit to isolate a partial aab-1 cDNA clone, which was then used to isolate a full-length cDNA and a genomic clone. The full-length cDNA has the potential to encode a 272 amino acid protein with a calculated molecular weight of 30 kD. Amino acid sequence obtained by Edman analysis of the AAB1 protein confirmed that the aab-1 gene had been cloned. AAB-1 shows similarity to the HAP5 protein of yeast and the CBF-C protein of rat. Each of these proteins is an essential subunit of their respective heteromeric CCAAT binding proteins. The aab1 gene maps on linkage group III of Neurospora crassa near the trp-1 locus. Disruption of the aab-1 gene results in pleiotropic effects on growth and development as well as a 50% reduction in glutamate dehydrogenase levels. Transformation of the aab-1 disruption mutant strain with the cloned genomic copy of the aab-1 gene rescued all of the phenotypic alterations associated with the aab-1 mutation.

Utilisation of domiciliary dental services.

OBJECTIVES: To develop undergraduate dental student understanding of the attitudes of elderly people towards dentistry and of the barriers which prevent them from seeking treatment. DESIGN: Each student interviewed a) an elderly person already known to them and b) an elderly person at a Day Rehabilitation Unit using a questionnaire. Students were not trained nor standardised. SETTING: a) in the student's home locality, b) in a Rehabilitation Unit in Sheffield. SUBJECTS: 161 people were interviewed with mean ages a) 78 years and b) 85 years. MAIN OUTCOME MEASURES: Perceptions of treatment need and domiciliary treatment by these elderly people. The results are summarised but not analysed because of the inherent limitations of data derived by unsupervised students. CONCLUSIONS: This educational exercise successfully engaged the studentsí minds and, for some, generated enthusiasm. They achieved valuable insight into the topic and realised that many people who inevitably have dental problems either feel that this is acceptable or do not know that they can obtain domiciliary dental care.

Photodynamic therapy for early stage squamous cell carcinoma of the lung.

OBJECTIVE: To study the effectiveness of photodynamic therapy (PDT) as a therapeutic strategy in roentgenographically occult squamous cell carcinoma of the lung. MATERIAL AND METHODS: A carefully selected group of 21 patients (with 23 cancers) who had early stage squamous cell carcinoma of the lung and were eligible for surgical treatment were offered PDT as an alternative to resection. Patients underwent close follow-up with bronchoscopic surveillance and were offered resection if cancer persisted after no more than two sessions of PDT. RESULTS: A complete response was identified in 15 patients (16 cancers) after an initial PDT session. A complete response that lasted longer than 12 months was noted in 11 patients (52%). After PDT, the minimal follow-up period was 24 months. A subsequent primary lung cancer developed in 5 of the 21 patients (24%). Ten patients ultimately had surgical treatment, in 3 (30%) of whom N1 disease was identified at the time of resection. Two patients refused a surgical procedure and received alternative therapy. Therefore, nine patients (43%) were spared an operation (95% confidence interval, 21.8 to 66.6%). The mean duration of follow-up for these nine patients was 68 months (range, 24 to 116). CONCLUSION: On the basis of this investigation, we can conclude with 95% confidence that at least 22% of patients with early stage squamous cell lung cancer who are candidates for PDT can be spared surgical resection.

Tad, a Neurospora LINE-like retrotransposon exhibits a complex pattern of transcription.

Tad is a LINE-like element from Neurospora. Inactive Tad elements have been found in all strains of Neurospora examined; however, active copies of Tad were initially found in a single strain (Adiopodoumé) collected from nature. Active Tad elements can be transferred to laboratory strains by means of crosses, heterokaryons or by transformation with cloned active elements. We have analyzed the pattern of transcripts from Tad elements present in strains derived from Adiopodoumé containing either high or low copy numbers of active Tad. In both kinds of strains we found a complex set of discrete polyadenylated transcripts. As expected, a full-length transcript was detected with 5' and 3' ends that coincide with the consensus 5' and 3' ends of the Tad element. Two additional transcripts with the same polarity as the full-length transcript were identified. One of these plus-strand transcripts is 2.0 kb in length with a 5' end identical to that of the full-length transcript and an internal polyadenylation site. The other (4.2 kb) has an internal start site with termination occurring at the 3' consensus end of the element. The 2.0-kb transcript encodes all of ORF1. The 4.2 kb transcript could encode a 5' truncated version of ORF2. Two minusstrand transcripts were also consistently identified. These represent overlapping transcripts from the 3' tail of Tad. These transcripts share a small intron and 3' polyadenylation site. Their 5' start sites are both internal to the consensus 3' end of Tad. Possible functions of this complex array of transcripts are discussed.

Epigenetic control of a transposon-inactivated gene in Neurospora is dependent on DNA methylation.

An unstable allele of the Neurospora am (GDH) gene resulting from integration of the retrotransposon Tad3-2 into 5' noncoding sequences was found in previous work. We report that reversion to Am+ depends on DNA methylation within and upstream of Tad. Levels of methylation were correlated with the proportion of Am+ conidia, whether the cultures were derived from Am- or Am+ isolates. Reversion to Am+ did not occur when conidia were plated on 5-azacytidine, which reduces DNA methylation. The mutation dim-2, which appears to abolish DNA methylation, also prevented reversion to Am+. The native am allele, in a strain that lacked Tad elements, was replaced with am::Tad3-2 or with a deletion derivative that prevents transposition of Tad. Transformants of both classes showed instability comparable with that of the original isolates, which contain multiple Tad elements. Deletion of the upstream enhancer-like sequences, URSam alpha and beta, did not prevent the instability of am::Tad3-2. The results suggest that am expression is dependent on DNA methylation but not on proliferation or transposition of the Tad element and that the instability does not require the upstream sequences of am.