The Relationship Between Restrictive Regulation of Midwives, Practice Environment, and Professional Burnout: A 7-State Mixed-Methods Comparison of Autonomous and Restrictive State Regulation.

PURPOSE: The purpose of the study was to investigate the relationship between state regulation of the midwifery workforce, practice environment, and burnout. BACKGROUND: Burnout threatens the US midwifery workforce, with over 40% of certified nurse-midwives meeting criteria. Burnout can lead to poorer physical and mental health and withdrawal from the workforce. Burnout in midwives has been associated with lack of control and autonomy. In the United States, midwives' autonomy is restricted through state-level regulation that limits scope of practice and professional independence. METHODS: A mixed-methods study was conducted using an explanatory sequential approach. Quantitative and qualitative data were collected by online surveys and analyzed in a 2-stage process, followed by data integration. RESULTS: State regulation was not found to be independently associated with burnout (n = 248; P = .250); however, mediation analysis showed a significant association between state regulation, practice environment, and burnout. Qualitative analysis mirrored the importance of practice environment and expanded on its features. CONCLUSION: For midwives, unrestrictive practice regulation may not translate to burnout prevention without supportive practice environments. IMPLICATIONS FOR PRACTICE AND RESEARCH: Interventions should focus on promoting job flexibility, realistic demands, and professional values. While midwives' commitment to patients and the profession can help bolster the workforce, it can also amplify negative experiences of the practice environment.

The economic benefits of surgical site infection prevention in adults: a systematic review.

BACKGROUND: Surgical site infections (SSIs) present a significant burden to healthcare and patients in terms of excess length of stay, distress, disability and death. SSI risk and the associated economic burden may be reduced through adherence to prevention guidelines although the irreducible minimum is unclear. AIM: To evaluate the methods used to estimate the cost-effectiveness of prevention strategies for all SSIs. METHODS: PubMed, Medline, CINAHL, and UK National Health Service Economic Evaluation Database were searched from inception to January 2020 to identify English language economic evaluation studies, embedded economic evaluations, and studies with some analysis in relation to cost and benefit in adult patients receiving surgical care in any setting. Risk of bias was assessed using two published checklists. FINDINGS: Thirty-two studies involving 24,043 participants were included. Most studies evaluated SSI prevention in orthopaedic surgeries. Antibiotic prophylaxis, screening, treating, or decolonization of meticillin-resistant Staphylococcus aureus and surgical wound closure were the main methods evaluated. Methods ranged from cost-analyses to cost-effectiveness and cost-utility analyses. Synthesis of results was not possible due to heterogeneity. All studies reported some economic benefit associated with preventing SSI; however, measures of benefit were not reported consistently and the quality of studies was low to moderate. Limited evidence in relation to SSI impact on quality of life was identified. CONCLUSION: Current evidence in relation to the economic benefits of SSI prevention is limited. Further robust studies that utilize sound economic and epidemiological methods are required to inform future investment decisions in SSI prevention.

The experiences of midwives in integrated maternity care: A qualitative metasynthesis.

OBJECTIVES: To conduct a metasynthesis of eight qualitative studies of the experiences of midwives in integrated maternity practice; to identify common motifs among the eight studies through a thematic interpretive integration known as reciprocal translation; and to explore the effects on midwifery processes of care in the setting of integrated maternity practice. DESIGN: A qualitative metasynthesis to analyze, synthesize, and interpret eight qualitative studies on the experiences of midwives and the effect on the midwifery processes of care in the setting of integrated maternity practice. SAMPLE AND SETTING: Participants from the primary studies included a total of 160 midwives providing hospital-based intrapartum care. All primary studies were conducted in settings with midwives and obstetricians working together in an integrated or collaborative manner. FINDINGS: Three overarching themes emerged from the data: professional dissonance, functioning from a position of risk, and practicing down. KEY CONCLUSIONS: The findings indicated that integrated maternity practice affects the professional experience of midwives. Through a qualitative exploration, a clear process of deprofessionalization and deviation from the midwifery model of care is detailed. Midwives experienced decreasing opportunity to provide the quality woman-centered physiologic care that evidence shows benefits childbearing women. IMPLICATIONS FOR PRACTICE: Integrated maternity practice, where low-risk and high-risk pregnancies are managed by midwife/physician teams, have proliferated as a solution to the need for quality, safe, and efficient health care. Insufficient evidence exists detailing the success or failure of this model of care. Qualitative studies suggest that the increasing medicalization occurring in integrated maternity practices minimizes the profession of midwifery and the ability to provide evidence-based quality midwifery care.

A qualitative meta-synthesis of women's experiences of labor dystocia.

PROBLEM: Researchers have prioritized understanding and differentiating the pathophysiologic mechanisms to improve precision in diagnosis and individualization of care, however the experiences of women with labor dystocia have been underexamined. BACKGROUND: Management of labor dystocia has been identified as an opportunity for reducing the rate of unnecessary cesarean births and the associated risks to women and their infants. This meta-synthesis explores women's experiences of labor dystocia to enrich the discussion of care practices and contextualize discussions of shared decision making in what is most meaningful to women. QUESTIONS: How does prolonged labor influence women's experience of birth and motherhood? What are women's experiences with decision-making about labor augmentation during prolonged labor? METHODS: Sandelowski and Barroso's meta-synthesis approach was used to analyze primary qualitative studies of women's experiences of labor dystocia. Through inductive thematic synthesis and reciprocal translation, themes identified in qualitative research, quotations, and coded meaning units were aggregated and interpreted into derived categories and themes. FINDINGS: Fourteen qualitative studies were analyzed. Women experienced labor dystocia as a transition from healthy labor to abnormal labor requiring medical support consistent with Transition Theory by Meleis. Six new categories and thirty themes were identified. Each category and theme reflects a distinct component of the experience of labor dystocia. DISCUSSION/CONCLUSION: There is wide variation in the way women experience labor dystocia. Facilitation of the transition from healthy labor to labor dystocia can be supported by a fluid, adaptable method of caring for women in the face of uncertainty and loss of choice.

Examining nurse/patient relationships in care coordination: A qualitative metasynthesis.

BACKGROUND: The combination of education, experience, skill mix, and frequency of nursing care provided has not been broadly studied from a systems theory perspective, in the care coordination process, or within transitions of care. PURPOSE: To examine nurse/patient relationships (as a proxy for nurse dose) in the care coordination experience through a qualitative metasynthesis using a systems theory approach. DESIGN: The study was a qualitative metasynthesis with four sequential processes; (1) a systematic literature search to answer the structured research question, (2) formal quality appraisal and data immersion, (3) interpretive synthesis of the data within and across studies, and (4) re-situating the derived themes through reciprocal translation to each of the primary studies. CINHAL, Cochrane Library, Embase and PubMed were searched, and 159 articles retrieved. Eight articles remained after inclusion/exclusion criteria and quality review criteria were applied. RESULTS: Key themes were organized using a systems theory perspective (Structure, Process and Outcomes). The need for a coordinated nurse-patient relationship and the ability of the nurse to calm the complexity that occurs forms the structure of the relationship. The process includes having an awareness of challenges of the coordinated nurse-patient relationship and the transitions that occur, nurses going above and beyond, providing meaningful communication, and navigating system complexity. The outcomes are the value of a coordinated nurse-patient relationship and managing the illness/wellness journey. CONCLUSIONS: The information from this metasynthesis provides an integrated view for nursing leaders and insight into factors that promote an effective and coordinated nurse-patient relationship.

Estimating excess length of stay due to healthcare-associated infections: a systematic review and meta-analysis of statistical methodology.

BACKGROUND: Healthcare-associated infection (HCAI) affects millions of patients worldwide. HCAI is associated with increased healthcare costs, owing primarily to increased hospital length of stay (LOS) but calculating these costs is complicated due to time-dependent bias. Accurate estimation of excess LOS due to HCAI is essential to ensure that we invest in cost-effective infection prevention and control (IPC) measures. AIM: To identify and review the main statistical methods that have been employed to estimate differential LOS between patients with, and without, HCAI; to highlight and discuss potential biases of all statistical approaches. METHODS: A systematic review from 1997 to April 2017 was conducted in PubMed, CINAHL, ProQuest and EconLit databases. Studies were quality-assessed using an adapted Newcastle-Ottawa Scale (NOS). Methods were categorized as time-fixed or time-varying, with the former exhibiting time-dependent bias. Two examples of meta-analysis were used to illustrate how estimates of excess LOS differ between different studies. FINDINGS: Ninety-two studies with estimates on excess LOS were identified. The majority of articles employed time-fixed methods (75%). Studies using time-varying methods are of higher quality according to NOS. Studies using time-fixed methods overestimate additional LOS attributable to HCAI. Undertaking meta-analysis is challenging due to a variety of study designs and reporting styles. Study differences are further magnified by heterogeneous populations, case definitions, causative organisms, and susceptibilities. CONCLUSION: Methodologies have evolved over the last 20 years but there is still a significant body of evidence reliant upon time-fixed methods. Robust estimates are required to inform investment in cost-effective IPC interventions.

Differences in statin associated neuroprotection corresponds with either decreased production of IL-1ß or TNF-α in an in vitro model of neuroinflammation-induced neurodegeneration.

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) have been associated with conflicting effects within the central nervous system (CNS), with underlying mechanisms remaining unclear. Although differences between individual statins' CNS effects have been reported clinically, few studies to date have compared multiple statins' neuroprotective effects. This study aimed to compare six statins (atorvastatin, fluvastatin, pitavastatin, pravastatin, rosuvastatin, simvastatin; 0-100 µM) using an in vitro model of lipopolysaccharide (LPS)-induced neuroinflammation and subsequent neurodegeneration. To achieve this, HAPI microglia were treated with LPS (0.1 µg/mL; 24 h), resulting in increased reactive oxygen species (ROS), nitric oxide, and IL-1ß, TNF-α and PGE2 release. Conditioned media ("HAPI-CM") was then transferred to SH-SY5Y neuroblastoma cells, and effects on cellular viability, mitochondrial membrane permeability, apoptosis, autophagy and ROS production assessed. Of the statins investigated, only atorvastatin, pravastatin and rosuvastatin protected SH-SY5Y cells from LPS-induced decreases in cellular viability; this appeared mediated through reduced caspase 3/7 activation and was associated with decreased IL-1ß (atorvastatin, pravastatin) and/or TNF-α (atorvastatin, pravastatin, rosuvastatin). Only pravastatin conferred protection at all tested concentrations. ROS production and autophagic vacuole formation was decreased by all statins, suggesting these two mechanisms are unlikely to be sole mediators of neuroprotection seen with selected statins. Ultimately, our model suggests that despite all statins reducing microglial inflammation, subsequent effects on neuronal viability and cell death signalling pathways varies between statins. Our findings highlight the need to consider individual statins as inducing discrete pharmacological effects within the CNS in future in vitro/in vivo studies and in clinical practice.

Statins Reduce Lipopolysaccharide-Induced Cytokine and Inflammatory Mediator Release in an In Vitro Model of Microglial-Like Cells.

The anti-inflammatory effects of statins (HMG-CoA reductase inhibitors) within the cardiovascular system are well-established; however, their neuroinflammatory potential is unclear. It is currently unknown whether statins' neurological effects are lipid-dependent or due to pleiotropic mechanisms. Therefore, the assumption that all statin compounds will have the same effect within the central nervous system is potentially inappropriate, with no studies to date having compared all statins in a single model. Thus, the aim of this study was to compare the effects of the six statins (atorvastatin, fluvastatin, pitavastatin, pravastatin, rosuvastatin, and simvastatin) within a single in vitro model of neuroinflammation. To achieve this, PMA-differentiated THP-1 cells were used as surrogate microglial cells, and LPS was used to induce inflammatory conditions. Here, we show that pretreatment with all statins was able to significantly reduce LPS-induced interleukin (IL)-1ß and tumour necrosis factor (TNF)-α release, as well as decrease LPS-induced prostaglandin E2 (PGE2). Similarly, global reactive oxygen species (ROS) and nitric oxide (NO) production were decreased following pretreatment with all statins. Based on these findings, it is suggested that more complex cellular models should be considered to further compare individual statin compounds, including translation into in vivo models of acute and/or chronic neuroinflammation.

A "dose on demand" Biomarker Generator for automated production of [(18)F]F(-) and [(18)F]FDG.

The University of Oklahoma-College of Pharmacy has installed the first Biomarker Generator (BG75) comprising a self-shielded 7.5-MeV proton beam positive ion cyclotron and an aseptic automated chemistry production and quality control module for production of [(18)F]F(-) and clinical [(18)F]FDG. Performance, reliability, and safety of the system for the production of "dose on demand" were tested over several months. No-carrier-added [(18)F]F(-) was obtained through the (18)O(p,n)(18)F nuclear reaction by irradiation (20-40 min) of a >95% enriched [(18)O]H2O target (280 µl) with a 7.5-MeV proton beam (3.5-5.0 µA). Automated quality control tests were performed on each dose. The HPLC-based analytical methods were validated against USP methods of quality control. [(18)F]FDG produced by BG75 was tested in a mouse tumor model implanted with H441 human lung adenocarcinoma cells. After initial installment and optimization, the [(18)F]F(-) production has been consistent since March 2011 with a maximum production of 400 to 450 mCi in a day. The average yield is 0.61 mCi/min and 0.92 mCi/min at 3.8 µA and 5 µA, respectively. The current target window has held up for over 25 weeks against >400 bombardment cycles. [(18)F]FDG production has been consistent since June 2012 with an average of six doses/day in an automated synthesis mode (RCY≈50%). The release criteria included USP-specified limits for pH, residual solvents (acetonitrile/ethanol), kryptofix, radiochemical purity/identity, and filter integrity test. The entire automated operation generated minimal radiation exposure hazard to the operator and environment. As expected, [(18)F]FDG produced by BG75 was found to delineate tumor volume in a mouse model of xenograft tumor. In summary, production and quality control of "[(18)F]FDG dose on demand" have been accomplished in an automated and safe manner by the first Biomarker Generator. The implementation of a cGMP quality system is under way towards the ANDA submission and first clinical use of [(18)F]FDG produced by BG75.

c-Myc and Her2 cooperate to drive a stem-like phenotype with poor prognosis in breast cancer.

The HER2 (ERBB2) and MYC genes are commonly amplified in breast cancer, yet little is known about their molecular and clinical interaction. Using a novel chimeric mammary transgenic approach and in vitro models, we demonstrate markedly increased self-renewal and tumour-propagating capability of cells transformed with Her2 and c-Myc. Coexpression of both oncoproteins in cultured cells led to the activation of a c-Myc transcriptional signature and acquisition of a self-renewing phenotype independent of an epithelial-mesenchymal transition programme or regulation of conventional cancer stem cell markers. Instead, Her2 and c-Myc cooperated to induce the expression of lipoprotein lipase, which was required for proliferation and self-renewal in vitro. HER2 and MYC were frequently coamplified in breast cancer, associated with aggressive clinical behaviour and poor outcome. Lastly, we show that in HER2(+) breast cancer patients receiving adjuvant chemotherapy (but not targeted anti-Her2 therapy), MYC amplification is associated with a poor outcome. These findings demonstrate the importance of molecular and cellular context in oncogenic transformation and acquisition of a malignant stem-like phenotype and have diagnostic and therapeutic consequences for the clinical management of HER2(+) breast cancer.

Vocalizations produced by humpback whale (Megaptera novaeangliae) calves recorded in Hawaii.

Although humpback whale (Megaptera novaeangliae) calves are reported to vocalize, this has not been measurably verified. During March 2006, an underwater video camera and two-element hydrophone array were used to record nonsong vocalizations from a mother-calf escort off Hawaii. Acoustic data were analyzed; measured time delays between hydrophones provided bearings to 21 distinct vocalizations produced by the male calf. Signals were pulsed (71%), frequency modulated (19%), or amplitude modulated (10%). They were of simple structure, low frequency (mean=220 Hz), brief duration (mean=170 ms), and relatively narrow bandwidth (mean=2 kHz). The calf produced three series of "grunts" when approaching the diver. During winters of the years 2001-2005 in Hawaii, nonsong vocalizations were recorded in 109 (65%) of 169 groups with a calf using an underwater video and single (omnidirectional) hydrophone. Nonsong vocalizations were most common (34 of 39) in lone mother-calf pairs. A subsample from this dataset of 60 signals assessed to be vocalizations provided strong evidence that 10 male and 18 female calves vocalized based on statistical similarity to the 21 verified calf signals, proximity to an isolated calf (27 of 28 calves), strong signal-to-noise ratio, and/or bubble emissions coincident to sound.

Bioaerosol concentrator performance: comparative tests with viable and with solid and liquid nonviable particles.

AIMS: Generally it is more economical to first characterize a concentrator system with nonbiological particles followed by more rigorous bioaerosol testing. This study compares sampling system performance for various particle types and sizes. METHODS AND RESULTS: Performances of five concentrators were characterized with five nonviable and viable laboratory aerosols, although not every concentrator was tested with all aerosol types. For particle sizes less than c. 6 microm aerodynamic diameter, similar efficiencies are obtained for all test particles; however, for larger sizes there is a significant difference between liquid and dry particles. CONCLUSIONS: Aluminium oxide particles provide results over a broad range of sizes with a single test, but the method is less reproducible than other methods. A combination of monodisperse polystyrene spheres and oleic acid droplets provides an accurate representation of the system performance, but ultimately biological particle tests are needed. SIGNIFICANCE AND IMPACT OF THE STUDY: Devices are being developed for concentrating bioaerosol particles in the size range of 1-10 microm aerodynamic diameter and this study provides insight into data quality for different test methodologies. Also, the results show some current concentrators perform quite poorly.

Assessment of manure phosphorus export through turfgrass sod production in Erath County, Texas.

A best management practice (BMP) for exporting manure phosphorus (P) in turfgrass sod from the North Bosque River (NBR) watershed in central Texas was assessed using a geographic information system (GIS). The NBR watershed has a mandate to reduce the total annual P load to the NBR by 50% as a result of total maximum daily load regulation. Since dairy waste applications to fields are identified as the major nonpoint source of P to the river, innovative BMPs, such as export of manure P in turfgrass, will be needed to achieve the 50% reduction. However, methods are needed to evaluate the feasibility of these innovative management practices prior to their implementation. A geospatial database of suitable turfgrass production sites was developed for Erath County using GIS. Erath County largely encompasses the upper portion of the NBR watershed. Information from field experiments, production practices, and ground-truthing was used to search, analyze, and verify a geospatial database developed from national and regional sources. The integration and analyses of large databases supports the search by turf producers for sites suitable for turfgrass sod production in Erath County. In addition, GIS enables researchers and regulators to estimate manure P exports and reduced P loading due to implementation of the manure export BMP on a county scale. Under optimal conditions 198,000 kg manure P yr(-1) could be used and 114,840 kg manure P yr(-1) exported from the NBR watershed through implementation of a system using dairy manure to produce turfgrass sod. This is the equivalent of the manure P applied from 10,032 dairy cows yr(-1) and exported from 5808 dairy cows yr(-1). Application of GIS to large-scale planning and decision-making transcends traditional field-scale applications in precision agriculture.

Environmental benefits and economic costs of manure incorporation on dairy waste application fields.

Model simulations performed representing dairies in a 93000 ha watershed in north central Texas suggest that manure incorporation results in reduced phosphorus (P) losses at relatively small to moderate cost to producers. Simulated manure incorporation with a tandem disk on fields double-cropped with sorghum/winter wheat resulted in up to 33, 45, and 37% reductions in per hectare sediment-bound, soluble, and total P losses in edge-of-field runoff, relative to simulated surface manure applications. The effects of incorporation were evaluated at three different manure application rates. On aggregate across all three manure application rates, significant declines in P losses were obtained with incorporation except for sediment-bound P losses under the N-based manure application rate scenario. We found that the practice of incorporating manure shortly after it has been broadcast on the soil surface could help reduce P losses in such situations where P-based rates alone prove inadequate. The cost the producer incurs when manure is incorporated is on average about 1% of net returns when manure is applied at the N rate and 2-3% when it is applied at alternative P-based rates. In practice the costs could be lower because producers may substitute the manure incorporation operation for a tandem disk operation performed prior to manure application. As more and more dairy producers switch to the use of sorghum and corn silage in dairy rations and consequent on-farm production of these forages, the practice of manure incorporation may help to reduce phosphorus losses resulting from dairy manure applications to fields with these forage crops.

Gas mixing for achieving suitable conditions for single point aerosol sampling in a straight tube: experimental and numerical results.

Experimental measurements of velocity and tracer gas concentration are taken in a straight tube to evaluate the effectiveness of mixing in achieving conditions as required by ANSI N13.1-1999 for single point extractive sampling from stacks and ducts of nuclear facilities. Mixing is evaluated for inlet turbulent intensities of 1.5%, 10%, and 20%, achieved by introducing various bi-plane grids, and for conditions generated by a commercial static gas mixer. The data obtained (at Reynolds number = 15,000) highlight the importance of inlet turbulence intensity in the process of turbulent dispersion of a dilute gas. The gas mixer does not introduce significant pressure losses and unlike bi-plane grids, the turbulence downstream of the mixer is not homogenous. A judicious choice of the release location that uses the large scale eddies and inhomogeneity of the turbulence ensures that the specified ANSI N13.1-1999 criteria are attained within 7 diameters downstream of the duct inlet. This is significantly more effective than a bi-plane grid where even with 20% inlet intensity the criteria are met only at 21 diameters downstream. The predictions of a proposed semi-empirical correlation match favorably with data. For example, at 18 diameters downstream with inlet intensities of 1.5% and 10%, the predicted coefficients of variation (COVs) of 150% and 65% are close to the actual values of 154% and 50%; where the COV of a set of measurements is the ratio of the standard deviation of the set to its mean value. The corresponding results obtained using commercially available software are 141% and 12%. Results from a particle-tracking model show good qualitative trends, but they should not be used to determine compliance with the requirements of the ANSI standard.

Retinal pericytes control expression of nitric oxide synthase and endothelin-1 in microvascular endothelial cells.

Pericytes are known to communicate with endothelial cells by direct contact and by releasing cytokines such as TGF-beta. There is also strong evidence that pericytes act as regulators of endothelial cell proliferation and differentiation. We have investigated the effect of pericyte-conditioned medium (PCM) on proliferation of human microvascular endothelial cells in vitro, together with the expression of the vasoregulatory molecules, constitutive and inducible nitric oxide synthases (ecNOS and iNOS), and endothelin-1 (ET-1). Expression was measured at the mRNA level using semiquantitative RT-PCR for all three genes and at the protein level for ecNOS and iNOS using Western blotting. Growth curves for HMECs showed that PCM inhibits proliferation, eventually leading to cell death. Exposure to PCM repressed iNOS mRNA expression fivefold after 6 h. A similar, though delayed, reduction in protein levels was observed. ecNOS mRNA was slightly induced at 6 h, though there was no significant change in ecNOS protein. By contrast, ET-1 mRNA was induced 2.3-fold after 6 h exposure to PCM. We conclude that pericytes release a soluble factor or factors that are potent inhibitors of endothelial cell growth and promote vasoconstriction by up-regulating endothelin-1 and down-regulating iNOS.

Suitability of air sampling locations downstream of bends and static mixing elements.

The revised standard for sampling effluent air from stacks and ducts of the nuclear industry places limits on the non-uniformity of velocity and contaminant profiles at the sampling location; namely, the coefficients of variation must not exceed 20% over an area that encompasses at least the center 2/3 of the cross sectional area. Tests were conducted to characterize the degree of mixing at downstream locations as affected by several types of flow disturbances, including 90 degree elbows and commercial static mixing devices. Flow straighteners were incorporated into the ducting upstream of the mixer to be tested to simulate the dampening of flow turbulence that might occur because of upstream HEPA filters. The coefficients of variation of velocity and tracer gas concentration measured in a straight tube at a distance of 3 diameters downstream from a 90 degree elbow were 17% and 69%, respectively. The mixing is impacted by the upstream flow turbulence. Without a flow straightener, the tracer gas concentration coefficient of variation was reduced to 33% at the 3-diameter location. The use of static mixing elements can greatly enhance the mixing process. A ring placed just downstream of a 90 degree elbow, which blocks the outer 56% of the cross sectional area, results in a coefficient of variation of 19% for tracer gas concentration at the 3-diameter location. Pressure loss across the elbow with the ring is about nine times that of the basic elbow. One of the commercially available static mixers provides coefficients of variation that are less than 10% for both velocity and tracer gas concentration at 4 diameters downstream from the mixer with a pressure loss that is only about 3.5 times as large as that of a 90 degree elbow.

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.

A constant flow filter air sampler for workplace environments.

A filter air sampler has been developed for sampling radionuclide aerosol particles from the workplace environment. It provides easy filter changing, constant flow sampling, and a visual display to indicate proper operation. An experimental study was conducted to characterize the collection efficiency of the sampler as affected by variations in room air velocity, particle size, sampling flow rate, inlet geometry, and inlet orientation to the free stream. Tests were carried out in a wind tunnel at velocities between 0.3 m s(-1) and 2.0 m s(-1), which is a range that covers anticipated velocities in the typical highly ventilated workplace environment of a nuclear facility. Nearly monodisperse aerosols with sizes between 5 and 20 microm aerodynamic diameter were sampled at flow rates between 28.3 and 84.9 L min(-1). Inlet orientations of 0 degrees, 90 degrees, and 180 degrees from the horizontal were selected for evaluation. When the sampler was oriented at 0 degrees over various ranges of free stream velocities, sampling flow rates and particle sizes, the transmission efficiency of aerosol was typically greater than 95%. The transmission efficiencies varied from 80% to 106% for 10-microm aerodynamic diameter particles over the previously noted range of free stream velocities and inlet orientations. Uniformity of deposits of 10 microm aerodynamic diameter particles on collection filters was examined for a sampling rate of 57 L min(-1), a sampler orientation of 90 degrees into the wind and wind speeds of 0.3-2 m s(-1). The coefficients of variation for the areal density of the deposits ranged from 6.1% to 37.2%. A miniature critical flow venturi with a constant sampling flow rate of 57 L min(-1) was developed for application to the new filter air sampler. It was demonstrated that the performance of the new filter air sampler is quite acceptable over a wide range of conditions. Overall the new filter air sampler design has been shown to provide enhanced performance with regard to sample handling, constant calibrated volumetric sample flow rate, and relatively unbiased sample aspiration performance compared with a traditional filter air sampler design.

An experimental study of aerosol penetration through horizontal tubes and Strom-type loops.

Because some designers of aerosol transport systems use the assumption that aerosol penetration through a system is maximized if the flow Reynolds number is 2,800, we have conducted tests to determine if such an assumption is appropriate. Although we do not believe that optimal performance of an aerosol sample transport system can be presented solely in terms of the Reynolds number, we have presented our results in terms of that parameter to compare our work with the results of an earlier study. Two types of experiments were performed. First, the penetration of liquid aerosol particles through horizontal tubes was experimentally investigated for a range of design and operational conditions. For a particle size of 10 microm aerodynamic diameter, the maximum penetration through a 6.7 mm diameter tube was associated with a Reynolds number of approximately 2,000; the maximum penetration through a tube of 15.9 mm occurred at a Reynolds number of about 3,000; and the maximum penetration through a 26.7 mm diameter tube occurred at about 4,000. It was also experimentally demonstrated that for a fixed flow rate through a horizontal tube, there is an optimum tube diameter for which the aerosol penetration is a maximum. An early study dealing with aerosol particle penetration through a 16.8 mm inside diameter loop of tubing (two vertical tubes, two horizontal tubes and three 90 degrees bends) suggested there was a fixed Reynolds number for optimal aerosol penetration independent of particle size. Those experiments were repeated here and the agreement with those tests is excellent; namely, the maximum penetration through a loop of 15.9 mm diameter tube occurs at a Reynolds number of approximately 2,800, independent of particle size. However, when the tube diameter of the transport system layout was changed to 26.7 mm, the Reynolds number associated with maximum penetration varied for different particle sizes, occurring at Reynolds numbers of approximately 5,600 for 8 microm AD particles, 3,800 for 10 microm particles and 3,000 for 15 microm particles.