Unravelling colloid filter cake motions in membrane cleaning procedures.
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ABSTRACT:
SUBMITTER: Luken A
PROVIDER: S-EPMC7674421 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:During soft matter filtration, colloids accumulate in a compressible porous cake layer on top of the membrane surface. The void size between the colloids predominantly defines the cake-specific permeation resistance and the corresponding filtration efficiency. While higher fluxes are beneficial for the process efficiency, they compress the cake and increase permeation resistance. However, it is not fully understood how soft particles behave during cake formation and how their compression influences the overall cake properties. This study visualizes the formation and compression process of soft filter cakes in microfluidic model systems. During cake formation, we analyze single-particle movements inside the filter cake voids and how they interact with the whole filter cake morphology. During cake compression, we visualize reversible and irreversible compression and distinguish the two phenomena. Finally, we confirm the compression phenomena by modeling the soft particle filter cake using a CFD-DEM approach. The results underline the importance of considering the compression history when describing the filter cake morphology and its related properties. Thus, this study links single colloid movements and filter cake compression to the overall cake behavior and narrows the gap between single colloid events and the filtration process.
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Project description:In sandstone formations, the quartz particles integrate with drilling fluid solids and become part of the filter cake structure. As a result, the dissolution rate of the filter cake diminishes and reduces the removal efficiency. This paper presents a novel solution to overcome the challenges that restricts the filter cake removal process such as the presence of the quartz layer and the polymer coat. A multi-stage method for removing the filter cake from a wellbore is presented. The composition of the new formulation is; ammonium fluoride (NH4F), with a strong oxidizer, such as sodium bromate (NaBrO3) causes an exothermic reaction in the first stage, thereby removing the quartz layer and polymer coat in the filter cake by the in-situ generated HF acid. During the second stage for the barite-based filter cake, chelating agents combined with convertor catalysts were used to dissolve the barite. Solubility experiments were conducted to evaluate the efficiency at each stage in the filter cake removal process at 300 ºF and 500 psi. The experimental results showed that the formulation consisting of ammonium fluoride (NH4F), with a strong oxidizer (sodium bromate,NaBrO3), combined with exothermic reaction was able to generate HF in-situ, which in turn dissolved the quartz mineral and remove the polymer from the filter cake.
| S-EPMC7519126 | biostudies-literature
Project description:The recent COVID-19 pandemic has underscored the necessity of protecting health care providers (HCPs) against the transmission of infectious agents during dental procedures. To this end, the effectiveness of several air cleaning devices (ACDs) in reducing HCPs exposure to aerosols generated during dental procedures was estimated, separately or in combination with each other. These ACDs were a chairside unit capturing aerosols at the source of generation, and four ambient ACDs: a portable ambient ACD; a negative pressure module; a custom made, fan-operated and wall-mounted air filter (WMAF); and a smaller and passive version of the latter. The last three ACDs were intended for mobile dental clinics (MDCs) only. This assessment was performed in two different environments: in a dental clinic operatory and in a MDC. Two dental personnel, acting in the roles of dentist and dental assistant, performed on simulated patient aerosol-generating and non-aerosol-generating procedures. For each 5-minute scenario, the cumulative exposure to airborne particulate matter 10 µm in size or smaller (PM10) was determined by calculating the sum of all 1 second readings obtained with personal and ambient air monitors. The effectiveness of the ACDs in capturing PM10 was estimated based on the capability of the ACDs to keep PM10 level at or below the initial background level. In all conditions assessed in the dental clinic operatory, when both the chairside and portable ambient ACDs were functioning, an estimated effectiveness of 100% in capturing PM10 was achieved. In the MDC, in all conditions where the chairside ACD was used without the negative pressure module, an estimated effectiveness of 100% was also achieved. The simultaneous operation of the negative pressure module in the MDC, which led to a room negative pressure of -0.25 inch wc, reduced the chairside ACD's effectiveness in capturing aerosols. Conversely, the use of the WMAF in the MDC in combination with the chairside ACD further reduced exposure to PM10 below the initial background level. Nonetheless, in all conditions assessed in both settings (dental clinic operatory and MDC), larger visible aerosols were produced, often landing on the surrounding environment. A fair portion of these aerosols landed on the inside of the chairside ACD flange. This assessment suggests that the use of the tested chairside ACD, by capturing aerosols at the source of generation, had the greatest impact on reducing exposure of dental personnel to PM10 produced during dental procedures. This study also indicates that such exposure is further reduced with the addition of an ambient ACD. However, creating a negative pressure room as high as -0.25 inch wc can lead to air turbulence reducing the effectiveness of ACDs in capturing aerosols at the source. Furthermore, the presence of uncaptured droplets and spatter on the surrounding environment supports the need to complement the use of engineering controls with proper administrative controls and personal protective equipment, as recommended by governmental agencies and the scientific community for preventing the transmission of infection in health care settings.
| S-EPMC8344839 | biostudies-literature
Project description:Objective: To date, many brain-machine interface (BMI) studies have developed decoding algorithms for neuroprostheses that provide users with precise control of upper arm reaches with some limited grasping capabilities. However, comparatively few have focused on quantifying the performance of precise finger control. Here we expand upon this work by investigating online control of individual finger groups. Approach: We have developed a novel training manipulandum for non-human primate (NHP) studies to isolate the movements of two specific finger groups: index and middle-ring-pinkie (MRP) fingers. We use this device in combination with the ReFIT (Recalibrated Feedback Intention-Trained) Kalman filter to decode the position of each finger group during a single degree of freedom task in two rhesus macaques with Utah arrays in motor cortex. The ReFIT Kalman filter uses a two-stage training approach that improves online control of upper arm tasks with substantial reductions in orbiting time, thus making it a logical first choice for precise finger control. Results: Both animals were able to reliably acquire fingertip targets with both index and MRP fingers, which they did in blocks of finger group specific trials. Decoding from motor signals online, the ReFIT Kalman filter reliably outperformed the standard Kalman filter, measured by bit rate, across all tested finger groups and movements by 31.0 and 35.2%. These decoders were robust when the manipulandum was removed during online control. While index finger movements and middle-ring-pinkie finger movements could be differentiated from each other with 81.7% accuracy across both subjects, the linear Kalman filter was not sufficient for decoding both finger groups together due to significant unwanted movement in the stationary finger, potentially due to co-contraction. Significance: To our knowledge, this is the first systematic and biomimetic separation of digits for continuous online decoding in a NHP as well as the first demonstration of the ReFIT Kalman filter improving the performance of precise finger decoding. These results suggest that novel nonlinear approaches, apparently not necessary for center out reaches or gross hand motions, may be necessary to achieve independent and precise control of individual fingers.
| S-EPMC6231049 | biostudies-literature
Project description:Background Osmosis drives transcapillary ultrafiltration and water removal in patients treated with peritoneal dialysis. Crystalloid osmosis, typically induced by glucose, relies on dialysate tonicity and occurs through endothelial aquaporin-1 water channels and interendothelial clefts. In contrast, the mechanisms mediating water flow driven by colloidal agents, such as icodextrin, and combinations of osmotic agents have not been evaluated.Methods We used experimental models of peritoneal dialysis in mouse and biophysical studies combined with mathematical modeling to evaluate the mechanisms of colloid versus crystalloid osmosis across the peritoneal membrane and to investigate the pathways mediating water flow generated by the glucose polymer icodextrin.ResultsIn silico modeling and in vivo studies showed that deletion of aquaporin-1 did not influence osmotic water transport induced by icodextrin but did affect that induced by crystalloid agents. Water flow induced by icodextrin was dependent upon the presence of large, colloidal fractions, with a reflection coefficient close to unity, a low diffusion capacity, and a minimal effect on dialysate osmolality. Combining crystalloid and colloid osmotic agents in the same dialysis solution strikingly enhanced water and sodium transport across the peritoneal membrane, improving ultrafiltration efficiency over that obtained with either type of agent alone.Conclusions These data cast light on the molecular mechanisms involved in colloid versus crystalloid osmosis and characterize novel osmotic agents. Dialysis solutions combining crystalloid and colloid particles may help restore fluid balance in patients treated with peritoneal dialysis.
| S-EPMC6050940 | biostudies-literature
Project description:We evaluated the effect of phosphorus application rates from various sources and in the presence or absence of filter cake on soil phosphorus, plant phosphorus, changes in acid phosphatase activity, and sugarcane productivity grown in Eutrophic Red Ultisol. Three P sources were used (triple superphosphate, Araxa rock phosphate, and Bayovar rock phosphate) and four application rates (0, 90, 180, and 360 kg ha(-1) of P2O5) in the presence or absence of filter cake (7.5 t ha(-1), dry basis). The soil P, the accumulated plant P, the leaf acid phosphatase activity and straw, the stalk productivity, the concentration of soluble solids in the juice (Brix), the juice sucrose content (Pol), and the purity were the parameters evaluated. We found that P applications increased levels of soil, leaf, and juice phosphorus and led to higher phosphorus accumulation and greater stalk and straw productivity. These levels were highest in the presence of filter cake. Acid phosphatase activity decreased with increasing plant phosphorus concentration. Phosphate fertilization did not show effect on sugarcane technological quality. We concluded that P application, regardless of source, improved phosphorus nutrition and increased productivity in sugarcane and, when associated with filter cake, reduced the need for mineral fertilizer.
| S-EPMC4442304 | biostudies-other
Project description:BACKGROUND:Bioaerosols are defined as airborne particles of liquid or volatile compounds that contain living organisms or have been released from living organisms. The creation of bioaerosols is a recognized consequence of certain types of dental treatment and represents a potential mechanism for the spread of infection. OBJECTIVES:The aims of the present study were to assess the bioaerosols generated by certain dental procedures and to evaluate the efficiency of a commercially available Air Cleaning System (ACS) designed to reduce bioaerosol levels. METHODS:Bioaerosol sampling was undertaken in the absence of clinical activity (baseline) and also during treatment procedures (cavity preparation using an air rotor, history and oral examination, ultrasonic scaling and tooth extraction under local anaesthesia). For each treatment, bioaerosols were measured for two patient episodes (with and without ACS operation) and between five and nine bioaerosol samples were collected. For baseline measurements, 15 bioaerosol samples were obtained. For bioaerosol sampling, environmental air was drawn on to blood agar plates using a bioaerosol sampling pump placed in a standard position 20 cm from the dental chair. Plates were incubated aerobically at 37°C for 48 hours and resulting growth quantified as colony forming units (cfu/m³). Distinct colony types were identified using standard methods. Results were analysed statistically using SPSS 12 and Wilcoxon signed rank tests. RESULTS:The ACS resulted in a significant reduction (p = 0.001) in the mean bioaerosols (cfu/m³) of all three clinics compared with baseline measurements. The mean level of bioaerosols recorded during the procedures, with or without the ACS activated respectively, was 23.9 cfu/m³ and 105.1 cfu/m³ (p = 0.02) for cavity preparation, 23.9 cfu/m³ and 62.2 cfu/m³ (p = 0.04) for history and oral examination; 41.9 cfu/m³ and 70.9 cfu/m³ (p = 0.01) for ultrasonic scaling and 9.1 cfu/m³ and 66.1 cfu/m³ (p = 0.01) for extraction. The predominant microorganisms isolated were Staphylococcus species and Micrococcus species. CONCLUSION:These findings indicate potentially hazardous bioaerosols created during dental procedures can be significantly reduced using an air cleaning system.
| S-EPMC7091833 | biostudies-literature
Project description:The effect of wet environments on the dust cake of filter media was studied. The collapse angles of dust particles and the collapse angles between dust particles and filter media increase with increasing dust moisture content, relative humidity, and spray rate. The smallest growth rate of collapse was observed under dust moisture content, while the largest growth rate occurred under the spray rate condition. The collapse angles between dust particles and filter media of coated filter media were smaller compared to those of mechanical filter media under different wet environments. The dust cake drag coefficients of both filter media initially increase and then decrease with an increase in the dust moisture content, decrease with the acceleration of the relative humidity, and show a pattern of first decreasing and then increasing as the spray rate increases. The dust loading capacity of both filter media follows an opposite trend to that of the dust cake drag coefficients.
| S-EPMC10564904 | biostudies-literature