High-density Operations Research Articles

Residential proximity to high-density poultry operations associated with campylobacteriosis and infectious diarrhea.

Poultry carry zoonotic bacteria that can cause gastroenteritis in humans. Environmental transmission of pathogens from poultry operations may increase gastrointestinal infection risk in surrounding communities. To evaluate associations between residential proximity to high-density poultry operations and individual-level diarrheal illnesses, we conducted a nested case-control study among 514,488 patients in Pennsylvania (2006-2015). Using electronic health records, we identified cases of five gastrointestinal outcomes: three pathogen-specific infections, including Escherichia coli (n = 1425), Campylobacter (n = 567), and Salmonella (n = 781); infectious diarrhea (n = 781); and non-specific diarrhea (2012-2015; n = 28,201). We estimated an inverse-distance squared activity metric for poultry operations based on farm and patient addresses. Patients in the second and fourth (versus first) quartiles of the poultry operation activity metric had increased odds of Campylobacter (AOR [CI], Q2: 1.36 [1.01, 1.82]; Q3: 1.38 [0.98, 1.96]; Q4: 1.75 [1.31, 2.33]). Patients in the second, third, and fourth quartiles had increased odds of infectious diarrhea (Q2: 1.76 [1.29, 2.39]; Q3: 1.76 [1.09, 2.85]; Q4: 1.60 [1.12, 2.30]). Stratification revealed stronger relations of fourth quartile and both Campylobacter and infectious diarrhea in townships, the most rural community type in the study geography. Increasing extreme rainfall in the week prior to diagnosis strengthened fourth quartile Campylobacter associations. The poultry operation activity metric was largely unassociated with E. coli, Salmonella, and non-specific diarrhea. Findings suggest high-density poultry operations may be associated with campylobacteriosis and infectious diarrhea in nearby communities, highlighting additional public health concerns of industrial agriculture.

Engineering the Ionic Polymer Phase Surface Properties of a PEM Fuel Cell Catalyst Layer

During high power density operations, the performance of polymer electrolyte membrane fuel cells (PEMFCs) may be limited by high water saturation levels in the cathode catalyst layer due to high wettability of the ionic polymer phase. A new heat-treatment method was used to create and lock-in the surface structure of Nafion 212. Several surface characterization techniques were used to verify the membrane's surface after heat-treatment, including contact angle, atomic force microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. We found that specific heat-treatment conditions led to the formation of either a hydrophobic or hydrophilic surface. The modified membrane's surface remained intact even after the membranes were boiled in water for 1 h. Next, a 4-point conductivity technique was used to verify that the heat-treatment conditions which led to a hydrophobic surface did not negatively impact the membrane's internal conductivity. Finally, this novel heat-treatment method was applied to the cathode catalyst layer of a H2-Air PEMFC to create a hydrophobic polymer-gas interface inside the gas pores of the cathode catalyst layer. Preliminary results showed 33% increase in peak power. The results of this research will guide the design of a new class of PEMFC catalyst layers.

(Industrial Electrochemistry and Electrochemical Engineering Division Student Achievement Award) Engineering the Ionic Polymer Phase Surface Properties of a PEM Fuel Cell Catalyst Layer

During high power density operations, the performance of polymer electrolyte membrane fuel cells (PEMFCs) is limited by high water saturation levels in the cathode catalyst layer due to high wettability of the ionic polymer phase. A new heat treatment was used to create and permanently lock-in the surface structure of a biphasic membrane (Nafion® 212). Several surface characterization techniques were used to verify the engineered membrane’s surface after heat treatment, including contact angle, multi-mode atomic force microscopy (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). We found that specific heat treatment conditions will lead to the formation of either a hydrophobic or hydrophilic surface layer. The results of this research will guide the design of a new class of PEMFC catalyst layers. Engineered PEMFC catalyst layers are expected to prevent electrode flooding, therefore leading to higher performance and efficiency during high power density operations.

Education And Small Business Growth: A Gender Perspective Of Two Divergent Provinces In South Africa

The article attempts to identify whether the level of education and gender has an impact on the business growth of SMMEs in a developing economy. The study furthermore looks at the contribution made by the SMME sector from a spatial perspective. The Western Cape is seen as a more affluent province and a bigger contributor to the countrys GDP as opposed to KwaZulu-Natal, which comprises of the former province of Natal and the Zululand homelands. Entrepreneurship can be considered as one of the means of creating an enabling environment conducive to reducing poverty, stimulating economic growth, and creating employment opportunities, particularly in a South African context. Hence, activities in the SMME sector are often considered to be the bedrock of an economy and a key driver of growth and development. This holds most true for women assuming the role of entrepreneur, especially in developing countries. This study aims to explore and test this delicate relationship between women entrepreneurs and SMME sustainability, and to conduct empirical investigations into high-density SMME operations in two South African provinces. Survey data were collected from SMME owners/managers in the Western Cape and KwaZulu-Natal provinces of South Africa. In building on previous academic literature on SMME sustainability and women in business, various measures are developed and tested for reliability and validity. The study is cross-sectional in design, making use of trained fieldworkers to administer face-to-face surveys to a diverse set of SMMEs. A structured questionnaire was used to collect data from 465 owners/managers in the two provinces. The findings show (i) a positive relationship between a business owners/managers level of education and business growth, (ii) no correlation between a business owners/managers education and employment, and (iii) no relationship between gender and business growth. The findings of the study can benefit the South African Government in directing policy, SMME owners, educators and women in business by increasing awareness of the nature of sustainable SMMEs, and the effect of operational skills, gender and education on the development thereof. This study focuses on the growing sector of women in business and the impact of education in SMMEs linked toward business sustainability. A contribution is made toward theory development through empirical research.

Methicillin-ResistantStaphylococcus aureus

Despite the availability of effective preventative and therapeutic strategies, methicillin-resistant Staphylococcus aureus (MRSA) remains amajor cause of health care–associated and, more recently, community-acquired infections. Since the introduction of methicillin in 1959, epidemics due to different clones ofMRSAhave occurred in diverse geographic regions.1 The result has been the persistence of MRSA as an important pathogen worldwide. In the United States, themost recentMRSA epidemic has been due to the clone USA300. USA300 has been responsible for themajorityof communityandhealth care–associatedoutbreaks since the early 1990s.1 Until recently, thenumber of infections has continued to rise, especially in urban centers. While themajority of these have been skin and soft-tissue infections (SSTIs), a notable minority have been invasive and life-threatening.1 Two articles in this issueof JAMAInternalMedicineprovide additional insight into both the incidence and the risks associatedwithdevelopmentofMRSA infections.Danteset al2provide evidence that the overall incidence of invasiveMRSA infections nationally is declining. Casey et al3 perform an ecological investigation; they find that individuals livingnear high-density farming operations (ie, farms having an animal density of 2 animals or 1000-lbs live weight per acre) or near crop fieldsusingmanure exported from thehigh-density livestock farms are at increased risk of developingMRSA or other bacterial SSTIs. Both studies raise questions thatwarrant further investigation. Dantes et al2 useddata from theActiveBacterial Core Surveillance Program (ABCSP) to compare the national incidence rate of invasive MRSA infections for the years 2005 through 2011. The findings are of special importance because of the surveymethods that areusedand the size of the sample population (approximately 15 million). The ABCSP is an active surveillance program that is population based and includes a reviewofmedical records. It serves as amodel for this type of surveillance. The results show that the incidence of health care–associated community-onset and hospital-onset invasive MRSA infections have declined by 27.7% and 54.2%, respectively. The findings are consistent with several earlier reports including one from the same group. This impressive declinemaywellbeduetothe implementationof infectioncontrol efforts at thehospital level; however, it is alsopossible that the epidemic MRSA strains circulating in the health care setting have evolved, becoming less virulent. In contrast to the decline inhealth care–associatedMRSA, the estimated reduction in incidence of community-associated infections was a modest 5%. In addition to the evidence that the incidenceofMRSA infections is declining, the study highlights 2 important points. The first is the observation that there is an increased risk of recurrent infection among recentlyhospitalizedpatientswith healthcare–associatedcommunity-onset infections.Thesepatients had a 64% risk of infection at 3 months or less followingdischarge.Others have also reported ahigh risk of reinfection in discharged patients either infected or colonized with MRSA.4 Possible explanations for the patients’ increased risk include underlyingmedical comorbidities, persistent colonizationor recolonizationwithMRSA,orexposure tosimilar risks of MRSA infection following discharge. This subset of patients would appear to be candidates for studies directed at reducing their high risk of recurrent infection. The second finding is the limited change in the incidence of communityassociated infections. This is in marked contrast with the reduction in the incidence of health care–associated infections. As noted by the authors, the study highlights the need for a greater understanding of how these epidemic MRSA strains spread and initiate infection within the community. Related articles pages 1970 and 1980 Research Original Investigation National Burden of Invasive MRSA Infections

High-Density Livestock Operations, Crop Field Application of Manure, and Risk of Community-Associated Methicillin-ResistantStaphylococcus aureusInfection in Pennsylvania

Nearly 80% of antibiotics in the United States are sold for use in livestock feeds. The manure produced by these animals contains antibiotic-resistant bacteria, resistance genes, and antibiotics and is subsequently applied to crop fields, where it may put community members at risk for antibiotic-resistant infections. To assess the association between individual exposure to swine and dairy/veal industrial agriculture and risk of methicillin-resistant Staphylococcus aureus (MRSA) infection. A population-based, nested case-control study of primary care patients from a single health care system in Pennsylvania from 2005 to 2010. Incident MRSA cases were identified using electronic health records, classified as community-associated MRSA or health care-associated MRSA, and frequency matched to randomly selected controls and patients with skin and soft-tissue infection. Nutrient management plans were used to create 2 exposure variables: seasonal crop field manure application and number of livestock animals at the operation. In a substudy, we collected 200 isolates from patients stratified by location of diagnosis and proximity to livestock operations. Community-associated MRSA, health care-associated MRSA, and skin and soft-tissue infection status (with no history of MRSA) compared with controls. From a total population of 446,480 patients, 1539 community-associated MRSA, 1335 health care-associated MRSA, 2895 skin and soft-tissue infection cases, and 2914 controls were included. After adjustment for MRSA risk factors, the highest quartile of swine crop field exposure was significantly associated with community-associated MRSA, health care-associated MRSA, and skin and soft-tissue infection case status (adjusted odds ratios, 1.38 [95% CI, 1.13-1.69], 1.30 [95% CI, 1.05-1.61], and 1.37 [95% CI, 1.18-1.60], respectively); and there was a trend of increasing odds across quartiles for each outcome (P ≤ .01 for trend in all comparisons). There were similar but weaker associations of swine operations with community-associated MRSA and skin and soft-tissue infection. Molecular testing of 200 isolates identified 31 unique spa types, none of which corresponded to CC398 (clonal complex 398), but some have been previously found in swine. Proximity to swine manure application to crop fields and livestock operations each was associated with MRSA and skin and soft-tissue infection. These findings contribute to the growing concern about the potential public health impacts of high-density livestock production.

Rule derivation for arrival aircraft sequencing

At present, the conventional way to sequence aircraft in the terminal area is to follow the first-come, first-served rule. Even though such sequencing is considered fair to all airlines and is associated with no increase in the workload of air traffic controllers, it is not always the optimal solution in terms of fuel burn and runway capacity. In this research we consider a substitute to the first-come, first-served rule leading to a more optimal sequencing which would reduce the total fuel burn when aggregated by all airplanes approaching a destination airport. The approach taken is to provide air traffic controllers with a simple guideline which can help them determine the sequence without increasing their workload too much and whenever possible add up to runway capacity. Sequencing is based on fuel burn simulations of single aircraft entering the terminal area of a sample airport. First, optimal aircraft sequences and their associated flight times under high-density operations are determined by Sequential Quadratic Programming. Next, the results are analyzed considering several attributes and three sequencing rules are proposed. Their effect is verified through Monte-Carlo simulations and it is concluded that through two simple swaps significant fuel savings of up to 17% of the extra fuel needed to make adjustments to the flight profile because of congestions can be achieved.

Density fluctuations induced by MARFE on FTU

High density operations on FTU (Frascati Tokamak Upgade) are affected by strong density oscillations due to the so-called MARFE (Multifaceted Asymmetric Radiation From the Edge). An analysis of these oscillations is reported here. The MARFE on FTU occurs at the value of ρ = 0.48 (ρ is ratio between line-averaged density with averaged current density in the plasma); at the MARFE onset, the volume averaged density versus central density is almost constant, corresponding to the value of 0.8. The MARFE is observed to move up and down along the poloidal circumference on FTU. The MARFE movement causes continuous density fluctuations. Amplitude of density fluctuations decreases with edge safety factor and with electron density. The mechanism to cause MARFE movement is discussed. If amplitude exceeds a certain threshold, it may cause poloidal heat flux asymmetry between the edges of the MARFE, which will make the MARFE moving along the poloidal circumference.

CCBKE — Session key negotiation for fast and secure scheduling of scientific applications in cloud computing

Instead of purchasing and maintaining their own computing infrastructure, scientists can now run data-intensive scientific applications in a hybrid environment such as cloud computing by facilitating its vast storage and computation capabilities. During the scheduling of such scientific applications for execution, various computation data flows will happen between the controller and computing server instances. Amongst various quality-of-service (QoS) metrics, data security is always one of the greatest concerns to scientists because their data may be intercepted or stolen by malicious parties during those data flows, especially for less secure hybrid cloud systems. An existing typical method for addressing this issue is to apply the Internet Key Exchange (IKE) scheme to generate and exchange session keys, and then to apply these keys for performing symmetric-key encryption which will encrypt those data flows. However, the IKE scheme suffers from low efficiency due to its asymmetric-key cryptological operations over a large amount of data and high-density operations which are exactly the characteristics of scientific applications. In this paper, we propose Cloud Computing Background Key Exchange (CCBKE), a novel authenticated key exchange scheme that aims at efficient security-aware scheduling of scientific applications. Our scheme is designed based on the randomness-reuse strategy and the Internet Key Exchange (IKE) scheme. Theoretical analyses and experimental results demonstrate that, compared with the IKE scheme, our CCBKE scheme can significantly improve the efficiency by dramatically reducing time consumption and computation load without sacrificing the level of security.

Review of stellarator/heliotron design issues towards MFE DEMO

The first review is presented for the recent stellarator designs of FFHR, HSR, ARIES-CS, which are based on the experimental device projects of LHD, W-7X, NCSX, respectively. The main advantageous features of those designs are common on (1) current-free plasmas, which leads to steady, high Q and disruption-free reactors and (2) high density operations, which largely reduces the diverter heat load. Design optimization and engineering feasibility are highlighted including maintainability, fabricability and showing future R&D key issues with prospect towards DEMO.

High-Capacity Tube Network Design Using the Hough Transform

A new airspace design concept, tube networks, could enable high-density operations with less air traffic control workload. To construct tubes optimally, it is necessary to identify the commonality of flight trajectories. This paper proposes a new strategy to cluster great circle flight trajectories for forming tubes. The Hough transform is applied to identify groups or clusters of great circle trajectories that could form the tube networks. The genetic algorithm is then applied to optimize the tube network. Results show that small deviations from great circle routes could yield tubes that accommodate significant traffic levels within feasible computational time.

Progress of design studies on an LHD-type steady state reactor

Progress of design studies on a heliotron reactor is reported. Recent experimental achievements in large helical device (LHD) are building up the physical basement. Integrated designs on LHD-type energy reactors have improved the base design of force free helical reactor and revealed economical feasibility. Large helical device is exploring a new horizon of net current free helical plasmas. Inherent characteristics demonstrate reactor relevant performances individually; steady state (1 h), high beta (5%), high density (1 × 10 21 m −3), etc. In particular, discovery of internal diffusion barrier provides a novel attractive scenario of super high density operation. It greatly facilitates physical requirements as well as mitigates engineering demands. New methods have been proposed to access and operate ignited plasmas; a long rise-up over 300 s to reduce the heating power to 30 MW and a new proportional-integration-derivative (PID) control of the fueling to handle the thermally unstable plasma at high-density operations.

Short wavelength far infrared laser polarimeter with silicon photoelastic modulators

A short wavelength far infrared laser whose wavelength lambda is about 50 microm is preferable for a polarimeter and an interferometer for high density operations in the Large Helical Device (LHD) and on future large fusion devices such as ITER. This is because the beam bending effect (proportional to lambda(2)) in a plasma, which causes fringe jump errors, is small and the Faraday and the Cotton-Mouton effects are moderate. We have developed a polarimeter with highly resistive silicon photoelastic modulators (PEMs) for the CH(3)OD laser (lambda=57.2 and 47.7 microm). We performed bench tests of the polarimeter with a dual PEM and demonstrated the feasibility for the polarimeter. Good linearity between actual and evaluated polarization angles is achieved with an angular resolution of 0.05 degrees and a temporal resolution of 1 ms. The baseline drift of the polarization angle is about 0.1 degrees for 1000 s.

Multidimensional Gas Chromatography−Olfactometry for the Identification and Prioritization of Malodors from Confined Animal Feeding Operations

Odor profiling efforts were directed at applying to high-density livestock operations some of the lessons learned in resolving past, highly diverse, odor-focused investigations in the consumer product industry. Solid-phase microextraction (SPME) was used for field air sampling of odorous air near and downwind of a beef cattle feedyard and a swine finisher barn in Texas. Multidimensional gas chromatography-olfactometry (MDGC-O) was utilized in an attempt to define and prioritize the basic building blocks of odor character associated with these livestock operations. Although scores of potential odorant volatiles have been previously identified in high-density livestock operations, the odor profile results developed herein suggest that only a very few of these may constitute the preponderance of the odor complaints associated with these environments. This appeared to be especially true for the case of increasing distance from both cattle feedyard and swine barn facilities, with p-cresol consistently taking on the dominant odor impact role with ever increasing distance. In contrast, at- or near-site odor profiles were shown to be much more complex, with many of the well-known lower tier odorant compounds rising in relative significance. For the cattle feedyard at- or near-site odor profiles, trimethylamine was shown to represent a significantly greater individual odor impact relative to the more often cited livestock odorants such as hydrogen sulfide, the organic sulfides, and volatile fatty acids. This study demonstrates that SPME combined with a MDGC-O-mass spectrometry system can be used for the sampling, identification, and prioritization of odors associated with livestock.

Feedback Control of Braking Deceleration on Railway Vehicle

AbstractAn increase of the deceleration in high-speed and high-density train operations degrades riding comfort and frequently causes wheel skids. This requires an introduction of the control technology to upgrade the control performance of brake systems on railway vehicles. We are now studying control methods for a mechanical brake that uses friction and pneumatic pressure, including nonlinear elements as the basis of a brake force. Furthermore, the system itself has certain “dead time,” which is not negligible and makes control difficult. One of our targets is to develop a brake control device that can control the deceleration in accordance with a decelerating pattern that optimizes the riding comfort of trains and prevents wheel skids. In this paper, a design method of the controller for the deceleration tracking control and the system compensating the dead time are proposed. Finally, the effects of them are confirmed through computer simulations and experimental results on a dynamo test stand.

A dual infection by infectious cuticular epithelial necrosis virus and a Chlamydia -like organism in cultured Litopenaeus vannamei (Boone) in Ecuador

During 1996, microscopic examinations of post larvae and juveniles of moribund Litopenaeus vannamei showed multifocal necrosis in the cuticular epithelial tissues. In addition to these severe degenerative alterations in the epithelial cells typical of infectious cuticular epithelial necrosis virus (ICENV), columnar cells of the epithelium displayed small round intracytoplasmic inclusions in the necrotic tissue. Examination by electron microscopy of affected tissues demonstrated prokaryotic organisms in the cytoplasm of epithelial cells delineated by a distinct cytoplasmic vesicle; the prokaryotic organisms were morphologically similar to the genus Chlamydia. The necrotic tissue also showed the presence of particles of ICENV; the double infection by two different organisms in cuticular epithelial cells has not been reported previously. Two distinct stages in the intracellular development of a Chlamydia-like organism were recognized: (1) pleomorphic elementary bodies (EBs) that were spherical to oval were often observed in the process of division or in forming a common chain of three cells, the cells were surrounded by a rigid cell envelope and the presence of a cap or plaque hexagonally arrayed; (2) the reticular bodies (RBs) were forms often in the process of division. These cells had an electron-dense cytoplasm and contained a loose network of nuclear fibrils and a more fragile cell envelope. Regardless of the development stages of the Chlamydia-like organism within the cytoplasmic vesicles, ICENV particles were observed, either dispersed or in clusters, surrounded or inside the vesicles. The potential adverse impact of this dual infection on shrimp culture should be considered, especially in high-density operations.

Current profile control and magnetohydrodynamic stability in Tore Supra discharges with edge-plasma control by the ergodic divertor

Although ergodic divertors are primarily designed to control particle and heat fluxes at the plasma edge, they also happen to affect the MHD stability of tokamak discharges. On Tore Supra, the ergodic divertor has long been known to stabilize the m/n = 2/1 tearing mode induced, for instance, by edge radiation and detachment processes, thus allowing safe high-current and high-density operations. More recently, though, in discharges where ergodic divertor operations were optimized relative to the control of the edge-plasma (i.e. with large divertor perturbation), a detrimental increase in the disruptivity has been observed. The action that the ergodic divertor has on the MHD activity is interpreted in terms of a redistribution of the current profile. The latter results from a large increase in the edge resistivity, primarily induced by the degradation of the electron energy confinement in the ergodic layer. The possibility that a transport barrier develops in the vicinity of the separatrix strongly affects the considered modelling.

Production of Small, Monodispersed Alginate Beads for Cell Immobilization

Gel entrapment retains suspension cells in a bioreactor for high-density operations without the difficulties of cell separation. To achieve and sustain high cell densities in animal cell culture, beads under 1 mm in diameter are desirable to minimize diffusional limitations. The challenge is to develop a controllable, scaleable process to produce small, monodispersed beads for cell immobilization. In this work, alginate bead populations were produced in the 0.5–1 mm size range with less than 10% standard deviation by destabilizing a viscous jet with a controlled disturbance. Systematic study of the drop formation with this “vibration” method demonstrated that Weber's theory for the instability of viscous jets qualitatively applies to the alginate system and provides a predictive tool for selecting the wavelength of disturbance for controlled bead formation. Nonlinear theory also provided guidance in establishing proper operating conditions to avoid satellite drop formation which decreases bead uniformity. A viscosity range 150–500 cp was found to be optimum for bead formation and served to rapidly establish the appropriate alginate concentration for the wide variety of commercial alginates. Through an understanding of the interaction of viscosity, linear velocity, nozzle diameter, and frequency of disturbance used to destabilize the jet, the predictable formation of small, uniform alginate beads was demonstrated with this method. As an example of scaleup, a 10-nozzle manifold can process 3–50 L of alginate/h, depending on the desired bead size.

Laser Material Interaction: Absorption Coefficient in Welding and Surface Treatment

Summary Efficient energy coupling between beam and material is fundamental for any effective application of laser technology. Qualitative a quantitative experimental assessments on laser radiation absorption phenomena during both high power density (welding) and low power density operations (surface treatments) are providing useful information on process energy balance in order to achieve a deeper understanding of the absorption mechanism and to collect a wide amount of data, a starting point for any consistent modelling of results.

Applications of Weighted Acid-Soluble Workover Fluids

This paper describes the composition and properties of a completion and workover fluid that can be weighted to 18.0 lb/gal (2157 kg/m) with an acid-soluble weighting agent. Several field case histories where these fluids were used in high-density gravel-packing operations are described. Property measurements demonstrate the stability, and highly pumpable flow characteristics of the weighted pumpable flow characteristics of the weighted fluids. Introduction Clear, solids-free brines have been used extensively in completion and workover operations, and, where applicable, these have proven quite effective. There are several reasons, however, why a solids-free brine may not meet the requirements of a particular completion or remedial operation. It then is necessary to add solids to improve or to impart certain properties to the fluids - i.e., improved hole cleaning. Rig hydraulics may be inadequate to clean cuttings or sand satisfactorily from the well using the brine alone; therefore, it is necessary to add a viscosifier to increase the brine's lifting capacity. At other times, the addition of bridging materials may be required to control loss of brine to the formation. Excessive loss of brine to the formation may result in formation damage, failure to maintain sufficient hydrostatic head, or unacceptable brine costs.Another reason for adding solids to a clear brine is to increase fluid density to control formation pressures. However, this is not widely practiced. Saturated sodium chloride provides a fluid density of 10.0 lb/gal (1198 kg/m) and calcium chloride brines are usable up to 11. 7 lb/gal (1402 kg/m) at ambient temperatures above 60 deg. F (15.6 deg. C). In the past few years, calcium bromide brines with densities up to 15.0 lb/gal (1797 kg/m3) have been used, but because of the high cost of this brine, its use cannot always be justified. Because of these limitations of the clear brines, other means would be needed to meet the higher density requirements of completion and workover. This paper describes the requirements, composition, and properties of a solids-laden brine system that has proven successful in field application. Requirements of a Solids-Laden Brine Solids-laden fluids often are considered undesirable as completion and workover fluids because these fluids could transport particles into the formation, resulting in particle plugging. This effect has been shown to exist by particle plugging. This effect has been shown to exist by several investigators and is a source of formation damage. However, several design criteria can be used to prevent, or at least minimize, particle invasion. prevent, or at least minimize, particle invasion. One design consideration is to form a particle bridge at the sand face as quickly and effectively as possible. This can be done by selecting the particle-size distribution and concentration of solids for the workover or completion fluid. Abrams concluded that to minimize particle invasion, the bridging materials should be equal to or greater than one-third the median pore size of the formation and should be present in quantities of at least 5% vol of the solids.Ultrafine particles are more apt to be transported into the formation as discrete particles, such as would occur in a deflocculated state. For this reason, a flocculating environment is desirable since the fines tend to exist as aggregates and are more likely to be retained by the bridging particles. Salt brines are, of course, highly flocculating to particles. Salt brines are, of course, highly flocculating to dispersed solids and are, therefore, highly desirable as the water phase. JPT P. 35