Field comparison of a roof bolter dry dust collection system with an original designed wet collection system for dust control.

Dust collectors for roof bolting machines generally use a dry box to collect the roof bolting material. Recently, an underground mining operation converted a dry box dust collector to a wet box dust collector with a unique exception from MSHA for testing purposes. Water is routed to the roof bolter from the main water line of the continuous miner. The wet box utilizes a water spray to wet the incoming material. Testing was conducted comparing the two different collector types. Respirable dust concentrations surrounding the roof bolter with the different collection boxes were similar. The main difference in respirable dust concentrations occurred when cleaning the dust boxes. The average respirable dust concentration during cleaning of the wet box was 0.475 mg/m3, and during the cleaning of the dry box, the average respirable dust concentration was 1.188 mg/m3, a 60% reduction in respirable dust concentration. The quartz content of the roof material was high, ranging from 28.9 to 52.7% during this study. The results from this study indicate that using the wet box as a collector reduced exposure to respirable dust up to 60% when cleaning the collector boxes.

A field study of a roof bolter canopy air curtain (2nd generation) for respirable coal mine dust control.

A 2nd generation roof bolter canopy air curtain (CAC) design was tested by National Institute for Occupational Safety and Health (NIOSH) at a Midwestern underground coal mine. During the study, the roof bolter never operated downwind of the continuous miner. Using a combination of personal Data Rams (pDR) and gravimetric samplers, the dust control efficiency of the roof bolter CAC was ascertained. Performance evaluation was determined using three methods: (1) comparing roof bolter operator concentrations underneath the CAC to roof bolter concentrations outside the CAC, (2) comparing roof bolter operator concentrations underneath the CAC to the concentrations at the rear of the bolter, and finally, (3) using the gravimetric data directly underneath the CAC to correct roof bolter operator concentrations underneath the CAC and comparing them to the concentrations at the rear of the bolter. Method 1 dust control efficiencies ranged from -53.9% to 60.4%. Method 2 efficiencies ranged from -150.5% to 52.2%, and Method 3 efficiencies ranged from 40.7% to 91%. Reasons for negative and low dust control efficiencies are provided in this paper and include: incorrect sampling locations, large distance between CAC and operator, and contamination of intake air from line curtain. Low dust concentrations encountered during the testing made it difficult to discern whether differences in concentrations were due to the CAC or due to variances inherent in experimental dust measurement. However, the analyses, especially the Method 3 analysis, show that the CAC can be an effective dust control device.

Field investigation to measure airflow velocities of a ram dump car using circular routing at a Midwestern underground coal mine: a case study.

Due to the successful application of roof bolter canopy air curtains (CACs) to protect roof bolter operators from high levels of coal mine respirable dust, a shuttle car CAC is currently being developed. Since a shuttle car consistently trams from the continuous miner to the feeder and back at a speed up to 9.66 kph (6 mph) or 2.68 m/s (528 fpm), it is thought that the shuttle car may encounter very high air velocities (mine ventilation air velocity + max shuttle speed (2.68 m/s (528 fpm)). Past research and preliminary lab testing showed that CAC protection in high interference air velocities is difficult to achieve. Therefore, testing was conducted at a Midwestern US coal mine to determine the air velocities their shuttle car actually encounters. This mine used ram dump cars as their shuttle cars. Results showed that coal mine dust exposure is generally very low at the feeder and when tramming. Elevated concentrations are encountered at the ram dump car operator position when the car is being loaded by the continuous miner. Recorded air velocities while tramming did not reach the max air velocity of mine ventilation air velocity + 2.68 m/s (528 fpm) calculated as 3.32 m/s (653 fpm). High velocities, while encountered, were of low frequency and associated with low respirable coal mine dust concentrations. Therefore, using this new information, designing the shuttle car CAC for maximum interference air velocity may not be as important as previously thought.

Field investigation to measure airflow velocities of a shuttle car using independent routes at a central Appalachian underground coal mine.

Canopy air curtains on roof bolting machines have been proven to protect miners from respirable dust, preventing their overexposure to dust. Another desired application for canopy air curtains is in the compartments of shuttle cars. The challenges faced in developing the design of canopy air curtains for shuttle cars include mine ventilation rates in tandem with the shuttle car tram speeds. The resulting cab airspeeds may exceed 182 m/min (600 fpm), as found in the present study conducted in a central Appalachian underground coal mine by U.S. National Institute for Occupational Safety and Health (NIOSH) researchers. Prior research and laboratory testing had indicated that successfully protecting a miner in high air velocities is difficult, because the clean air from the canopy air curtain is unable to penetrate through the high-velocity mine air. In this study, the dust concentrations to which a shuttle car operator was exposed were measured, and air velocities experienced by the operator were measured as well using a recording vane anemometer. The results indicate that the highest exposure to respirable dust, 2.22 mg/m3, occurred when the shuttle car was loading at the continuous miner, where the average airspeed was 48 m/min (157 fpm). While tramming, the operator was exposed to 0.77 mg/m3 of respirable dust with an average airspeed of 62 m/min (203 fpm). This study indicates that a canopy air curtain system can be designed to greatly reduce an operator's exposure to respirable dust by providing clean air to the operator, as the majority of the operator's dust exposure occurs in air velocities slower than 61 m/min (200 fpm).

Open-air sprays for capturing and controlling airborne float coal dust on longwall faces.

Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 µm in diameter, in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity of 3.6 m/s (700 fpm). Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle should be operated at high fluid pressures to produce smaller droplets and move more air. These findings agree with past respirable dust control research, providing guidance on spray selection and spray array design in ongoing efforts to control airborne float dust over the entire longwall ventilated opening.

Characterization of airborne float coal dust emitted during continuous mining, longwall mining and belt transport.

Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. If deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coal dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float coal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float coal dust to respirable dust ranged from 10.3 to 13.8. The ratios measured on the longwall face were between 18.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8.

Crystallographic substrate binding studies of Leishmania mexicana SCP2-thiolase (type-2): unique features of oxyanion hole-1.

C: Structures of the C123A variant of the dimeric Leishmania mexicana SCP2-thiolase (type-2) (Lm-thiolase), complexed with acetyl-CoA and acetoacetyl-CoA, respectively, are reported. The catalytic site of thiolase contains two oxyanion holes, OAH1 and OAH2, which are important for catalysis. The two structures reveal for the first time the hydrogen bond interactions of the CoA-thioester oxygen atom of the substrate with the hydrogen bond donors of OAH1 of a CHH-thiolase. The amino acid sequence fingerprints ( xS, EAF, G P) of three catalytic loops identify the active site geometry of the well-studied CNH-thiolases, whereas SCP2-thiolases (type-1, type-2) are classified as CHH-thiolases, having as corresponding fingerprints xS, DCF and G P. In all thiolases, OAH2 is formed by the main chain NH groups of two catalytic loops. In the well-studied CNH-thiolases, OAH1 is formed by a water (of the Wat-Asn(NEAF) dyad) and NE2 (of the GHP-histidine). In the two described liganded Lm-thiolase structures, it is seen that in this CHH-thiolase, OAH1 is formed by NE2 of His338 (HDCF) and His388 (GHP). Analysis of the OAH1 hydrogen bond networks suggests that the GHP-histidine is doubly protonated and positively charged in these complexes, whereas the HDCF histidine is neutral and singly protonated.

Experimental study on foam coverage on simulated longwall roof.

Testing was conducted to determine the ability of foam to maintain roof coverage in a simulated longwall mining environment. Approximately 27 percent of respirable coal mine dust can be attributed to longwall shield movement, and developing controls for this dust source has been difficult. The application of foam is a possible dust control method for this source. Laboratory testing of two foam agents was conducted to determine the ability of the foam to adhere to a simulated longwall face roof surface. Two different foam generation methods were used: compressed air and blower air. Using a new imaging technology, image processing and analysis utilizing ImageJ software produced quantifiable results of foam roof coverage. For compressed air foam in 3.3 m/s (650 fpm) ventilation, 98 percent of agent A was intact while 95 percent of agent B was intact on the roof at three minutes after application. At 30 minutes after application, 94 percent of agent A was intact while only 20 percent of agent B remained. For blower air in 3.3 m/s (650 fpm) ventilation, the results were dependent upon nozzle type. Three different nozzles were tested. At 30 min after application, 74 to 92 percent of foam agent A remained, while 3 to 50 percent of foam agent B remained. Compressed air foam seems to remain intact for longer durations and is easier to apply than blower air foam. However, more water drained from the foam when using compressed air foam, which demonstrates that blower air foam retains more water at the roof surface. Agent A seemed to be the better performer as far as roof application is concerned. This testing demonstrates that roof application of foam is feasible and is able to withstand a typical face ventilation velocity, establishing this technique's potential for longwall shield dust control.

Utility of the Sindbis replicon system as an Env-targeted HIV vaccine.

Sindbis replicon-based vaccine vectors are designed to combine the immunostimulatory properties of replicating viruses with the superior safety profile of non-replicating systems. In this study we performed a detailed assessment of Sindbis (SIN) replicon vectors expressing HIV-1 envelope protein (Env) for the induction of cell-mediated and humoral immune responses in a small animal model. SIN-derived virus-like particles (VLP) elicited Env-specific antibody responses that were detectable after boosting with recombinant Env protein. This priming effect could be mediated by replicon activity alone but may be enhanced by Env attached to the surface of VLP, offering a potential advantage for this mode of replicon delivery for Env based vaccination strategies. In contrast, the Env-specific CTL responses that were elicited by SIN-VLP were entirely dependent on replicon activity. SIN-VLP priming induced more durable humoral responses than immunization with protein only. This is important from a vaccine perspective, given the intrinsic tendency of Env to induce short-lived antibody responses in the context of vaccination or infection. These results indicate that further efforts to enhance the magnitude and durability of the HIV-1 Env-specific immune responses generated by Sindbis vectors, either alone or as part of prime-boost regimens, are justified.

Induction of HIV-1 subtype B and AE-specific neutralizing antibodies in mice and macaques with DNA prime and recombinant gp140 protein boost regimens.

We developed highly expressing clade B and AE DNA and envelope protein (Env) vaccines for evaluation in mice and macaques as DNA prime/protein boost regimens. High levels of Env-specific antibodies were induced in mice, albeit with limited neutralizing activity in vitro. A combined clade B and AE regimen induced high titer Env-specific antibody in two pigtail macaques that neutralized several strains of HIV-1. However, upon mucosal challenge with SHIV(SF162P3) no protection from infection was observed. Although the vaccines tested provide a platform for inducing robust humoral immunity, further refinements to broaden coverage against divergent strains and induce mucosal immunity are needed.

Small interfering RNAs against the TAR RNA binding protein, TRBP, a Dicer cofactor, inhibit human immunodeficiency virus type 1 long terminal repeat expression and viral production.

RNA interference (RNAi) is now widely used for gene silencing in mammalian cells. The mechanism uses the RNA-induced silencing complex, in which Dicer, Ago2, and the human immunodeficiency virus type 1 (HIV-1) TAR RNA binding protein (TRBP) are the main components. TRBP is a protein that increases HIV-1 expression and replication by inhibition of the interferon-induced protein kinase PKR and by increasing translation of viral mRNA. After HIV infection, TRBP could restrict the viral RNA through its activity in RNAi or could contribute more to the enhancement of viral replication. To determine which function will be predominant in the virological context, we analyzed whether the inhibition of its expression could enhance or decrease HIV replication. We have generated small interfering RNAs (siRNAs) against TRBP and found that they decrease HIV-1 long terminal repeat (LTR) basal expression 2-fold, and the LTR Tat transactivated level up to 10-fold. In the context of HIV replication, siRNAs against TRBP decrease the expression of viral genes and inhibit viral production up to fivefold. The moderate increase in PKR expression and activation indicates that it contributes partially to viral gene inhibition. The moderate decrease in micro-RNA (miRNA) biogenesis by TRBP siRNAs suggests that in the context of HIV replication, TRBP functions other than RNAi are predominant. In addition, siRNAs against Dicer decrease viral production twofold and impede miRNA biogenesis. These results suggest that, in the context of HIV replication, TRBP contributes mainly to the enhancement of virus production and that Dicer does not mediate HIV restriction by RNAi.

Alteration of the proline at position 7 of the HIV-1 spacer peptide p1 suppresses viral infectivity in a strain dependent manner.

The HIV-1 spacer peptide p1 is located in the C-terminus of the Gag polyprotein and separates the nucleocapsid (NC) and p6(Gag). Research centered on p1 has been limited and as yet no function has been ascribed to this spacer peptide. We have previously found that the conserved p1 proline residues (position 7 and 13) are critical for replication in the HIV-1 strain HXB2-BH10. In this study we have focused on the proline rich p1-p6(Gag) C-terminus of HIV-1. We individually examined the role of p1 proline's in multiple strains of HIV-1 and investigated the role of three proline residues in p6(Gag) (P24, P25 and P30). Assessment of the HXB2-BH10 based mutants revealed that Gag-Pol incorporation relative to Gag decreased in the p1 mutant virions, with the double proline mutant the most impaired. Mutating both p1 proline residues was found to abolish infectivity in multiple strains of HIV-1. Independent mutation of the p1 proline at position 7 resulted in a strain-dependent suppression of viral infectivity. This defect correlates with the presence of a tyrosine residue at position 9 of p1 and occurs in the early phase of the HIV-1 replication cycle. The p1 proline residues were found to be functionally distinct from P24, P25 and P30 in p6(Gag). This work affords novel insights into our understanding of the role of p1 in HIV-1 replication.

Virion-associated cholesterol is critical for the maintenance of HIV-1 structure and infectivity.

OBJECTIVE: HIV-1 particles are enriched with cholesterol; however, the significance of this cholesterol enrichment is unknown. This study examines the structural and functional roles of cholesterol in HIV-1 replication. METHODS: Using methyl-beta-cyclodextrin (CD) to remove cholesterol from the HIV-1 envelope, buoyant density and infectivity of the cholesterol-deficient HIV-1 particles were compared with the untreated control. The specificity and requirement of cholesterol as an HIV-1-associated lipid were investigated by replenishing cholesterol-deficient HIV-1 with cholesterol, cholestenone (a cholesterol structural analogue) or sphingomyelin (a structurally unrelated yet virion-associated lipid). RESULTS: CD-mediated removal of virion cholesterol increased the buoyant density of virion particles and reduced HIV-1 infectivity. Trans-supplementation of exogenous cholesterol rescued the defects associated with CD-induced cholesterol depletion in HIV-1. However, the restoration of viral infectivity could not be achieved by trans-supplementation of either cholestenone or sphingomyelin. CONCLUSION: This study provides the first direct evidence that HIV-1-associated cholesterol is important for the maintenance of virion structure and infectivity. While the buoyant density of cholesterol-defective HIV-1 can be restored by a cholesterol structural analogue, cholestenone, the requirement for cholesterol is essential for HIV-1 infectivity.

An overview of a feasibility study for the production of industrial enzymes in transgenic alfalfa.

The overall aims of the research are to develop genetically engineered alfalfa producing high levels of industrially important enzymes and to develop rapid methods for extracting and purifying these enzymes from alfalfa juice. Using a reporter gene beta-glucuronidase (GUS) as a model system, we were able to demonstrate production of a foreign protein in alfalfa and gain valuable insight into the molecular approaches required for the expression and accumulation of foreign proteins in leaf tissue. GUS activity varied among individual transformants, and GUS was expressed in all plant tissues. GUS activity was shown to segregate in sexual progeny. There was no correlation between copy number of the GUS gene and activity. We have recently demonstrated the production of Mn-dependent lignin peroxidase and alpha-amylase in transgenic alfalfa. Concurrent research in the agricultural engineering aspects of this feasibility study focused on extraction strategies for the recovery of alfalfa juice, and on an evaluation of methods for processing and concentrating the juice. Thus, we are in a position to use plants expressing enzymes that have current or potential industrial importance to complete a feasibility study, and determine whether we can indeed economically recover target enzymes from field-grown transgenic alfalfa plants. The technology developed for these enzymes can be used to extract other value-added products from plants in the future.

The effect of chlorhexidine irrigation on tensile wound strength.

Chlorhexidine in an alcohol vehicle with flavoring agents has been used as a mouthrinse to reduce plaque accumulation in periodontal surgery patients. The purpose of this study was to evaluate the effects of a chlorhexidine-containing mouthrinse on the early tensile wound strength of healing surgical wounds in the rat. Standardized transdermal incisions were made on each lateral abdominal wall of 40 Sprague-Dawley rats. Wounds were irrigated with 10 ml of 0.12% chlorhexidine or 10 ml of normal saline prior to closure. Animals were sacrificed at 48 hours and 96 hours, and the wound area was excised by a standardized protocol. Wound strength was measured using constant speed tensiometry to determine the tensile strength of the healing incision. Results revealed a significantly reduced tensile wound strength at 48 hours for the chlorhexidine-treated group (127 +/- 18.5 gm) compared to the saline irrigation group (150 +/- 32.3 gm) (P < 0.001). However, by 96 hours a significantly increased tensile wound strength was demonstrated by the chlorhexidine treated group (202.1 +/- 21.7 gm) compared to the saline irrigation group (183.2 +/- 37.3 gm) (P < 0.05). These data suggest that chlorhexidine-containing mouthrinse irrigation of wounds produced a reduced early tensile wound strength, but ultimately resulted in shorter healing time.

Lack of utility of a Limulus amoebocyte lysate assay in the diagnosis of urethral discharges in men.

We evaluated a Limulus amoebocyte lysate assay (LALA) test kit for the diagnosis of gonorrhea in 883 unselected men with urethral discharge. Results were compared with those of Gram-stained smears and Martin-Lewis cultures. Of 331 men with gonococcal urethritis and 552 men with nongonoccal urethritis, 125 (37.8%) and 503 (91.1%), respectively, could not be evaluated by LALA owing either to insufficient discharge specimen to perform the test (569 or 64.4%) or to other exclusion criteria (59 or 6.7%). Of 255 LALA-evaluable discharges, LALA correctly diagnosed 252 (98.8%), compared with 244 (95.7%) for the Gram-stained smear. However, the Gram-stained smear also correctly diagnosed 96.5% of 456 men with insufficient discharge for LALA testing. The clinical utility of the LALA test kit is severely limited by performance criteria that exclude the majority of unselected men with urethritis. In addition, it is more technically cumbersome, time consuming, and costly than Gram-stained smears. Further test modifications are unlikely to overcome these inherent disadvantages of LALA.