Filter Discs Research Articles

DNA retention on depth filters

Depth filtration is a commonly-used bioprocessing unit operation for harvest clarification that reduces the levels of process- and product-related impurities such as cell debris, host-cell proteins, nucleic acids and protein aggregates. Since depth filters comprise multiple components, different functionalities may contribute to such retention, making the mechanisms by which different impurities are removed difficult to decouple. Here we probe the mechanisms by which double-stranded DNA (dsDNA) is retained on depth filter media by visualizing the distribution of fluorescently-labeled retained DNA on spent depth filter discs using confocal fluorescence microscopy. The extent of DNA displacement into the depth filter was found to increase with decreasing DNA length and with increasing operational parameters such as wash volume and buffer ionic strength. In addition, using 5-ethynyl-2′-deoxyuridine (EdU) to label DNA in dividing CHO cells, we showed that Chinese hamster ovary (CHO) cellular DNA in the lysate supernatant migrates deeper into the depth filter than the lysate re-suspended pellet, elucidating the role of the size of the DNA in its form as an impurity. Apart from aiding DNA purification and removal, our experimental approaches and findings can be leveraged in studying the transport and retention of nucleic acids and other impurities on depth filters at a small scale.

Rapid, field-deployable method for collecting and preserving plant metabolome for biochemical and functional characterization.

Study of plant metabolome is a growing field of science that catalogs vast biochemical and functional diversity of phytochemicals. However, collecting and storing samples of plant metabolome, sharing these samples across the scientific community and making them compatible with bioactivity assays presents significant challenges to the advancement of metabolome research. We have developed a RApid Metabolome Extraction and Storage (RAMES) technology that allows efficient, highly compact, field-deployable collection and storage of libraries of plant metabolome. RAMES technology combines rapid extraction with immobilization of extracts on glass microfiber filter discs. Two grams of plant tissue extracted in ethanol, using a specially adapted Dremel® rotary tool, produces 25–35 replicas of 10 mm glass fiber discs impregnated with phytochemicals. These discs can be either eluted with solvents (such as 70% ethanol) to study the metabolomic profiles or used directly in a variety of functional assays. We have developed simple, non-sterile, anti-fungal, anti-bacterial, and anti-oxidant assays formatted for 24-multiwell plates directly compatible with RAMES discs placed inside the wells. Using these methods we confirmed activity in 30 out of 32 randomly selected anti-microbial medicinal plants and spices. Seven species scored the highest activity (total kill) in the anti-bacterial (bacteria from human saliva) and two anti-fungal screens (Fusarium spp. and Saccharomyces cerevisiae), providing functional validation of RAMES technology. RAMES libraries showed limited degradation of compounds after 12 months of storage at -20°C, while others remained stable. Fifty-eight percent of structures characterized in the extracts loaded onto RAMES discs could be eluted from the discs without significant losses. Miniaturized RAMES technology, as described and validated in this manuscript offers a labor, cost, and time-effective alternative to conventional collection of phytochemicals. RAMES technology enables creation of comprehensive metabolomic libraries from various ecosystems and geographical regions in a format compatible with further biochemical and functional studies.

Antimicrobial effect of aqueous extracts from the peel, pulp and grape seed (vitis vinifera) on streptococcus mutans, in vitro study

Objective : To determine the antibacterial activity of aqueous grape extracts (Vitis vinifera) obtained from the skin, seed and pulp, on Streptococcus mutans (ATCC 35668, Ecuador), using 0.12% chlorhexidine as a positive control and distilled water as a negative control. Materials and methods : Aqueous extracts were obtained from the pulp, seeds and grape skin of the northern region of Ecuador, at a concentration of 40, 70 and 100%, which were impregnated 20 ml each in paper filter discs. and placed in Petri dishes with strains of Streptococcus mutans inoculated on blood agar, disks impregnated in 0.12% chlorhexidine and distilled water were used as control; the antimicrobial activity was evaluated considering the inhibition zones obtained at 24 and 48 hours of incubation. Results : The evaluation times 24 and 48 were different (p = 0.00) showing a greater inhibitory effect at 48 hours, where the 100% grape seed extract presented antimicrobial activity similar to 0.12% chlorhexidine, and the 70% concentration of the same extract reduced inhibition. However, peel and pulp extracts in their different concentration did not present halos of inhibition against Streptococcus mutans. Conclusions : The aqueous extract of 100% grape seeds showed antimicrobial activity similar to 0.12% chlorhexidine against Streptococcus mutans.

Insecticidal activity of essential oil from Eucalyptus globulus against Aphis nerii (Boyer) and Gynaikothrips ficorum (Marchal)

Aphids and thrips are very important pest species of many greenhouse and field plants in the world. In recent years, there have been attempts to identify plants for their insecticidal property with a view to find out suitable alternatives to the indiscriminate use of chemical pesticides, which are a risk for human health and the environment. The aim of this work was to evaluate the insecticidal effect of Eucalyptus globulus Labill essential oil (EO) against Aphis nerii Boyer de Fonscolombe (Hemiptera: Aphididae) and Gynaikothrips ficorum Marchal (Thysanoptera: Ploeothridae). The EO was extracted by hydrodistillation and the bioassay was evaluated by toxicity contact method, using solutions at different concentrations and for different time intervals. The EO was more toxic to G. ficorum (LC50 = 0.031?L cm-2) than A. nerii (LC50 = 0.099?L cm-2) on filter discs at 12 h of exposure. These results suggested that EO from E. globulus constitute a good alternative for the control of A. nerii and G. ficorum, considering their insecticidal effects at low applied concentrations and for short periods of time.

Impact of chlorination on silver elution from ceramic water filters

Applying silver nanoparticles (nAg) or silver nitrate (AgNO3) to ceramic water filters improves microbiological efficacy, reduces biofilm formation, and protects stored water from recontamination. A challenge in ceramic filter production is adding sufficient silver to achieve these goals without exceeding the maximum recommended silver concentration in drinking water. Silver release is affected by silver type, application method, and influent water chemistry. Despite a lack of data, there is an assumption that chlorinated water should not be used as influent water because it may increase silver elution. Thus, the objective of this work was to systematically evaluate the impact of chlorinated water (0–4 mg/L free chlorine residual, FCR) on silver release from ceramic filter disks painted with casein-coated nAg, painted with AgNO3, or containing fired-in nAg over a range of ionic strength (IS = 0–10 mM as NaNO3) in the presence or absence of natural organic matter (NOM). Influent deionized water containing chlorine increased silver release 2–5-fold compared to controls. However, this effect of chlorine was mitigated at higher IS (≥1 mM) or in the presence of NOM (3 mg C/L). For filter disks painted with nAg or AgNO3, silver release increased with increasing IS (with or without chlorine), and effluent concentrations remained above the World Health Organization (WHO) guideline of 0.1 mg/L even after 30 h (80 pore volumes, PVs) of flow with a background solution of 10 mM NaNO3. Silver speciation (nAg vs. Ag+) was monitored in effluent samples from painted or fired-in nAg filter disks. Results indicated that in general, greater than 90% of the eluted silver was due to Ag+ dissolution rather than nAg release. Additionally, a filter disk prepared with fired-in nAg exhibited a lower % released in the nanoparticle form (nAg = 5% of total Ag in effluent) compared to painted on nAg (nAg = 14% of total Ag in effluent). The findings of this study suggest that chlorinated influent water has minimal impact on silver elution from ceramic filters under simulated natural water conditions, and thus, the recommendation to avoid the use of chlorinated water with ceramic filters is not necessary under most conditions.

Systematic neonatal screening for congenital Chagas disease in Northeast Brazil: prevalence of Trypanosoma cruzi infection in the Southern region of Sergipe.

Chagas disease is caused by the flagellate protozoan Trypanosoma cruzi, being one of the leading causes of morbidity and mortality in the Americas with an estimated six to seven million infected people worldwide. In Brazil, the improvement in vector control and blood donor screening has evidenced the important epidemiological role of congenital transmission of Chagas disease. A serological survey for Chagas disease was performed in 3,952 newborns in the southern region of Sergipe using paper filter disks of dried blood samples. The newborns were screened using the Sergipe State Neonatal Screening Program between July 2015 and July 2016, and 3,749 and 750 blood samples were obtained for the IgG enzyme-linked immunosorbent assay and indirect immunofluorescence assay, respectively. In addition, mothers of the children who presented initial reagent serology were examined. Among 3,749 blood samples, samples of two children were positive for the enzyme-linked immunosorbent assay; however, their confirmation test results were negative, suggesting passive transfer of the mother's antibody. One puerpera was identified with Chagas disease, with a prevalence of 0.02%. Congenital Chagas disease was not observed in newborns in the Southern region of Sergipe. However, Chagas disease was observed in women of reproductive age. Therefore, effective measurements for monitoring and systematic evaluation should be conducted. The Neonatal Screening Program proved to be an effective public health strategy for the prevention and control of Chagas disease.

Isolation and Enrichment of Bacteriophages by Membrane Filtration Immobilization Technique

The method described here enables rapid bacteriophage isolation and enrichment of host-specific bacteriophages from an environmental sample. This is achieved by using a simple 0.45-µm Millipore membrane where a specific host is immobilized on the membrane and a sample suspected of containing bacteriophages is exposed to the immobilized cells with the help of a membrane filtration unit. This filtration step facilitates host-specific interaction of bacteriophages with the host and maximization of this interaction using a classic membrane filtration method. Under the effect of vacuum from a vacuum pump, a filter assembly provides a chance for every bacteriophage in the sample to interact with the specific host on the membrane filter. Our technique allows retaining specific bacteriophages on the membrane along with its host cells via adsorption; these adsorbed bacteriophages (along with their hosts) on a filter disc are then enriched in regular nutritive broth, tryptone soya broth (TSB), by incubation. With help of a plaque assay method, host-specific phages of various bacterial species can be isolated, segregated, and enriched. © 2018 by John Wiley & Sons, Inc.

Potential of Plant Extracts to Inhibit the Ichthyophonus sp. Infection in Blue Tilapia: A Preliminary Study in vitro

We studied in vitro the potential of plant extracts to inhibit the infection caused by Ichthyophonus sp. in blue tilapia (Oreochromis aureus). We inoculated Ichthyophonus sp. on agar plates where we placed the filter discs that were prepared by filtering the aqueous extracts (five concentrations) of ginger (Zingiber officinale), linseed (Linum usitatissimum), henna (Lawsonia inermis) and white turmeric (Curcuma zedoaria). All plants inhibited the growth of Ichthyophonus sp. in the highest concentration (20%); Z. officinale appeared to be the most effective, whereas C. zedoaria was the least effective. This study suggests that widely available and inexpensive plant extracts might be effective natural agents to prevent the Ichthyophonus sp. infection in fish. More research is needed in order to ascertain the efficiency of the plant extracts in vivo as well as to find a proper practice used in aquaculture.

A Susceptibility Screen of Phytochemicals Against Staphylococcus aureus

Given the current and emerging levels of bacterial resistance to existing antimicrobic agents, evaluative assessment of plant‐derived compounds for antibacterial potential was deemed important and timely. The focus of this research was to determine the effect of phytochemicals on Staphylococcus aureus using the Kirby‐Bauer susceptibility assay, a method widely used in clinical laboratories as standard operating procedure for determination of bacterial susceptibility to antibiotics. Whatman filter disks were saturated with phytochemical and placed onto a Mueller Hinton agar plate swabbed with bacteria using the standard 3‐way streak method. Bacterial plates were incubated and then susceptibility was determined by measurement of resultant zones of inhibition. Antibiotic disks were assessed in parallel with phytochemical‐impregnated disks. The hypothesis was that specific phytochemicals inhibit bacterial growth. S. aureus (n=4 ATCC strains) displayed large zones of inhibition for cinnamaldehyde (31±12 mm: mean±SD), epigallocatechin gallate (14±1 mm) and plumbagin (16±3 mm). Inclusion of cinnamaldehyde, epigallocatechin gallate or plumbagin as anti‐Staphylococcus agents as direct therapeutic agents or as combination treatment strategies with current antimicrobial drugs may offer treatment options for patients with multi‐drug resistant bacterial infections.Support or Funding InformationFinancial support for VPM was received from the DeNardo Education and Research Foundation.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

TECHNOLOGY OF OBTAINING POLYRIBOSYLRIBITOL PHOSPHATE AS AN ACTIVE PHARMACEUTICAL INGREDIENT FOR THE PRODUCTION OF POLYSACCHARIDE VACCINES

Despite the world practice, in the Russian Federation immunization against hemophilic infection is carried out only for the children from risk groups, which may be due to the lack of production of this vaccine in the Russian Federation. Therefore, the development of technology for the preparation of polyribosylribitol phosphate (PRP, the active substance of the Hib vaccine) remains relevant. Earlier, the employees of the federal state unitary enterprise “Saint-Petersburg scientific research institute of vaccines and serums and the enterprise for the production of bacterial preparations” of Federal medical and biologic agency of Russia isolated and identified the strain of Haemophilus influenzae SPB type b B-7884. The conditions for cultivation of the strain B-7884 and primary isolation of PRP from the culture liquid were arranged. The aim of the work was to study the possibility of excluding the centrifugation stage for separating H. influenzae SPB type b B-7884 biomass before clarification on the cascade of filter discs, and the development of subsequent stages of PRP isolation from the obtained intermediate product. Materials and methods. PRP isolation from an inactivated culture liquid of strain B-7884 was carried out by centrifugation, filtration, precipitation, homogenization, extraction under various conditions. The concentration of PRP in the intermediate products was determined by the orcinol method, the identity was determined by the latex agglutination test. Results and discussion. The optimal scheme for isolation and purification of the active pharmaceutical ingredient PRP, including filtration through the cascade of deep filters Zeta plus LP 60 (0.3–0.6 μm) and Zeta plus LP 90 (0.1–0.3 μm), concentration and diafiltration on ultrafiltration cassettes with nominal molecular weight cut-off of 30 kDa, precipitation with 10% cetyltrimethylammonium bromide solution (5% v/v), with subsequent homogenization of the obtained precipitate (in the presence of 12.5% of ethanol from the concentrate volume) and extraction (32.5% ethanol), filtration through depth filters Zeta Plus SP 30 and carbon filters Zeta Plus Carbon R53, and precipitation by 1.0% (v/v) 4.0 M sodium chloride solution and freezing at –(20 ± 2)°C, was developed. Conclusion. The obtained results will become the basis for the further development of the polysaccharide substance and allow us to proceed to the next stage in the development of the vaccine against Haemophilus influenzae type b – conjugation with the carrier protein.

Nitrogen mustard-induced corneal injury involves the sphingomyelin-ceramide pathway

PurposeNitrogen mustard (NM), which simulates the effects of sulfur mustard (SM), is a potent vesicant known to cause irreversible corneal damage. This study investigates the mechanisms by which NM induces corneal damage by examining the impact of NM exposure on the morphology and lipidome of the cornea. MethodsIntact ex vivo rabbit eyes were placed in serum-free DMEM organ culture. NM (0, 1, 2.5, 5 or 10 mg/ml) was applied to the central cornea for 5, 10 or 15 min using a 5 mm filter disk and subsequently rinsed with DMEM. Corneas were then cultured for 3, 24, or 48 h before being fixed for morphological analysis or for 24 h before being snap frozen for lipidomic analysis. ResultsNo morphological changes were detected 3 h after NM exposure. Twenty-four h after exposure, 1 mg/ml NM caused erosion of the corneal epithelium, but no damage to the underlying stroma. Damage caused by 2.5 mg/ml NM extended almost two thirds through the corneal stroma, while 5 mg/ml completely penetrated the corneal stroma. An altered lipid profile occurred 24 h after corneas were exposed to NM. Specific sphingomyelins, ceramides, and diacylglycerols were increased up to 9-, 60- and 10-fold, respectively. ConclusionsNM induces concentration- and exposure time-dependent damage to the cornea that increases in severity over time. Alterations in the sphingomyelin-ceramide pathway may contribute to the damaging effects of NM exposure.

Analysis of atmospheric pollutant metals by laser ablation inductively coupled plasma mass spectrometry with a radial line-scan dried-droplet approach

A novel method has been improved for analyzing atmospheric pollutant metals (Be, Mn, Fe, Co, Ni, Cu, Zn, Se, Sr, Cd, and Pb) by laser ablation inductively coupled plasma mass spectrometry. In this method, solid standards are prepared by depositing droplets of aqueous standard solutions on the surface of a membrane filter, which is the same type as used for collecting atmospheric pollutant metals. Laser parameters were optimized, and ablation behaviors of the filter discs were studied. The mode of radial line scans across the filter disc was a representative ablation strategy and can avoid error from the inhomogeneous filter standards and marginal effect of the filter disc. Pt, as the internal standard, greatly improved the correlation coefficient of the calibration curve. The developed method provides low detection limits, from 0.01ng m−3 for Be and Co to 1.92ngm−3 for Fe. It was successfully applied for the determination of atmospheric pollutant metals collected in Lhasa, China. The analytical results showed good agreement with those obtained by conventional liquid analysis. In contrast to the conventional acid digestion procedure, the novel method not only greatly reduces sample preparation and shortens the analysis time but also provides a possible means for studying the spatial distribution of atmospheric filter samples.

Direct Analysis of Aerosolized Chemical Warfare Simulants Captured on a Modified Glass-Based Substrate by "Paper-Spray" Ionization.

Paper spray ionization mass spectrometry offers a rapid alternative platform requiring no sample preparation. Aerosolized chemical warfare agent (CWA) simulants trimethyl phosphate, dimethyl methylphosphonate, and diisopropyl methylphosphonate were captured by passing air through a glass fiber filter disk within a disposable paper spray cartridge. CWA simulants were aerosolized at varying concentrations using an in-house built aerosol chamber. A custom 3D-printed holder was designed and built to facilitate the aerosol capture onto the paper spray cartridges. The air flow through each of the collection devices was maintained equally to ensure the same volume of air sampled across methods. Each approach yielded linear calibration curves with R2 values between 0.98-0.99 for each compound and similar limits of detection in terms of disbursed aerosol concentration. While the glass fiber filter disk has a higher capture efficiency (≈40%), the paper spray method produces analogous results even with a lower capture efficiency (≈1%). Improvements were made to include glass fiber filters as the substrate within the paper spray cartridge consumable. Glass fiber filters were then treated with ammonium sulfate to decrease chemical interaction with the simulants. This allowed for improved direct aerosol capture efficiency (>40%). Ultimately, the limits of detection were reduced to levels comparable to current worker population limits of 1 × 10-6 mg/m3.

Rotating Ceramic Water Filter Discs System for Water Filtration

This work aimed to design, construct and operate a new laboratory scale water filtration system. This system was used to examine the efficiency of two ceramic filter discs as a medium for water filtration. These filters were made from two different ceramic mixtures of local red clay, sawdust, and water. The filtration system was designed with two rotating interfered modules of these filters. Rotating these modules generates shear force between water and the surfaces of filter discs of the filtration modules that works to reduce thickness of layer of rejected materials on the filters surfaces. Each module consists of seven filtration units and each unit consists of two ceramic filter discs. The average measured hydraulic conductivity of the first module was 13.7mm/day and that for the second module was 50mm/day. Results showed that the water filtration system can be operated continuously with a constant flow rate and the filtration process was controlled by a skin thin layer of rejected materials. The ceramic water filters of both filtration modules have high removal efficiency of total suspended solids up to 100% and of turbidity up to 99.94%.

Chitosan-Modified Filter Paper for Nucleic Acid Extraction and “in Situ PCR” on a Thermoplastic Microchip

Plastic microfluidic devices with embedded chitosan-modified Fusion 5 filter paper (unmodified one purchased from GE Healthcare) have been successfully developed for DNA extraction and concentration, utilizing two different mechanisms for DNA capture: the physical entanglement of long-chain DNA molecules with the fiber matrix of the filter paper and the electrostatic adsorption of DNA to the chitosan-modified filter fibers. This new method not only provided a high DNA extraction efficiency at a pH of 5 by synergistically combining these two capture mechanisms together, but also resisted the elution of DNA from filters at a pH > 8 due to the entanglement of DNA with fibers. As a result, PCR buffers can be directly loaded into the extraction chamber for "in situ PCR", in which the captured DNA were used for downstream analysis without any loss. We demonstrated that the capture efficiencies of a 3-mm-diameter filter disc in a microchip were 98% and 95% for K562 human genomic DNA and bacteriophage λ-DNA, respectively. The washes with DI water, PCR mixture, and TE buffer cannot elute the captured DNA. In addition, the filter disc can enrich 62% of λ-DNA from a diluted sample (0.05 ng/μL), providing a concentration factor more than 30-fold. Finally, a microdevice with a simple two-chamber structure was developed for on-chip cell lysis, DNA extraction, and 15-plex short tandem repeat amplification from blood. This DNA extraction coupled with "in situ PCR" has great potential to be utilized in fully integrated microsystems for rapid, near-patient nucleic acid testing.

Modeling of filtration and mudcake buildup: An experimental investigation

This paper presents an experimental investigation and modeling of filtration and mudcake buildup during wellbore drilling. Extensive studies have been performed on this topic over the past seven decades and their general findings are summarized. In particular, the filtration model proposed in Dewan and Chenevert (2001) is discussed along with recommended methods for determining the model's parameters. New static filtration data were obtained using permeable filter discs manufactured from sand-cement mixtures to generate controlled formation material. The experimental results, consisting of fluid loss vs. time, mudcake porosity, and thickness at the end of the test, were used to evaluate the validity of the proposed methods and investigate the model's ability to predict the actual mudcake properties. Using the experimental results, some limitations of this model were identified. Therefore, modifications to Dewan and Chenevert's model were suggested to allow it to better capture the measured data, leading to the development of a new Wider Windows Filtration Model. Last, the effects of differential pressure, solids content of the mud, and filtration control agent on filtration and mudcake properties are presented and discussed.

Membrane filtration immobilization technique-a simple and novel method for primary isolation and enrichment of bacteriophages.

To develop a method for the isolation and enrichment of bacteriophages selectively against specific bacteria coupled with a membrane filtration technique. Rapid isolation and concentration of host-specific bacteriophages was achieved by exposure of the sample suspected to contain bacteriophages to a specific host immobilized on a 0·45μm membrane in a membrane filtration unit. The principle behind this method is the exploitation of host-specific interaction of bacteriophages with their host and maximizing this interaction using a classic membrane filtration method. This provides a chance for each bacteriophage in the sample to interact with the specific host on the membrane filter fitted with a vacuum pump. Specific bacteriophages of the host are retained on the membrane along with its host cells due to the effect of adsorption and these adsorbed bacteriophages (along with their hosts) on the filter disc are then amplified and enriched in regular nutritive broth tryptose soya broth by incubation. With the help of the plaque assay method, host-specific phages of various bacterial species were isolated, segregated and enriched. The phage concentration method coupled with membrane filtration immobilization of host bacteria was able to isolate and enrich the host-specific bacteriophages by several fold using a lower quantity of an environmental water sample, or other phage suspensions. Enrichment of phages from single plaques was also achieved. The isolation and detection of host-specific bacteriophages from a low density bacteriophage water sample in a single step by the use of a simple and basic microbiological technique can be achieved. Enrichment of phages from low phage titre suspensions is also achieved very effectively.

The effects of input materials on ceramic water filter efficacy for household drinking water treatment

Locally manufactured ceramic filters can improve drinking water quality and reduce diarrheal disease burden in developing countries; however, production methods and quality control protocols vary at the >50 factories. We manufactured filter disks with varied clay, burn-out material, burn-out material sieved with different mesh sizes, and burn-out material to clay ratios and calculated filter characteristics, including porosity, density, shrinkage, and flow rate. Water was run through filters daily for 4 weeks, and flow rate and Escherichia coli reduction, as measured by log reduction value (LRV), were tested twice weekly. Our results suggest: (1) the first and last LRV test results do not correlate strongly (R2 = 0.38, p < 0.010); (2) there is not a strong association between flow rate and first, average, or last LRV results (R2 = 0.17, p = 0.090; R2 = 0.30, p = 0.020; R2 = 0.24, p = 0.040); and (3) first and average LRV are associated with burn-out material (R2 = 0.68, p < 0.001; R2 = 0.60, p < 0.001), and last LRV is associated with burn-out material and mesh size (R2 = 0.54, p < 0.050). Recommendations for filter factories, are to: (1) verify filtration efficacy with repeated bacteria reduction tests when materials, processing, or filter characteristics vary; (2) carefully control production variables; and (3) continue flow rate testing each filter to evaluate within and across batch production consistency.

Understanding effects of topical ingredients on electrical measurement of skin hydration.

Methods that assess skin hydration based on changes in its electrical properties are widely used in both cosmetic and medical research. However, the devices themselves often give results which are significantly different to each other. Although some work has previously been carried out to try and understand what these devices are actually reading, it was based on a technique for measuring the devices' responses to filter discs impregnated with different liquids, which could in itself be influencing the measurements. Presented here is a new method for measuring the devices' direct responses to different materials and solutions which removes any other confounding effects, thereby providing a clearer insight into their operation. The responses of a variety of different liquids and solutions were measured using the Corneometer® and Skicon® . A new method is presented, based on the use of a custom-designed PTFE block to hold the liquids, allowing their measurement without using a filter paper. This method was developed and tested against the existing filter paper-based approach. Differences were observed in results between filter paper- and PTFE block-based approach, indicating that the filter paper itself is capable of influencing the measurements and as such is not to be recommended for assessing how different liquids impact on results from the devices. A positive correlation was observed between Corneometer® and Skicon® readings for certain solutions and under certain conditions. A large influence of salt concentration was noted for the Skicon® device with no or minimal impact from the actual water itself, humectants and emollients. Salts, emollients, water and humectants were observed to have an effect on Corneometer® readings. Both the Corneometer® and Skicon® were influenced to different extents by chemicals other than water and therefore cannot be seen purely as measures of skin 'hydration'. Although there is strong evidence that the devices do correlate with expert assessment of skin dryness, the level of water in the skin is only part of the story when it comes to understanding the benefits of topical moisturizing products applied to the skin. An alternative approach would be to consider skin 'moisturization' as a property which is influenced by water, salts and other materials such as humectants and emollients, which is more consistent with how the stratum corneum itself helps to maintain its plasticity and flexibility. In the work presented here, the Corneometer® was more suited to providing a measurement which reflects the impact of multiple different components.

Investigation of mud density and weighting materials effect on drilling fluid filter cake properties and formation damage

Drilling fluid density/type is an important factor in drilling and production operations. Most of encountered problems during rotary drilling are related to drilling mud types and weights. This paper aims to investigate the effect of mud weight on filter cake properties and formation damage through two experimental approaches. In the first approach, seven water-based drilling fluid samples with same composition are prepared with different densities (9.0–12.0 lb/gal) and examined to select the optimum mud weight that has less damage. The second approach deals with investigating the possible effect of the different weighting materials (BaSO4 and CaCO3) on filter cake properties. High pressure/high temperature loss tests and Scanning Electron Microscopy (SEM) analyses were carried out on the filter cake (two selected samples).Data analysis has revealed that mud weigh of 9.5 lb/gal has the less reduction in permeability of ceramic disk, among the seven used mud densities. Above 10.5 ppg the effect of the mud weight density on formation damage is stabilized at constant value. Fluids of CaCO3-based weighting material, has less reduction in the porosity (9.14%) and permeability (25%) of the filter disk properties than the BaSO4-based fluid. The produced filter cake porosity increases (from 0.735 to 0.859) with decreasing of fluid density in case of drilling samples of different densities. The filtration loss tests indicated that CaCO3 filter cake porosity (0.52) is less than that of the BaSO4 weighted material (0.814). The thickness of the filter cake of the BaSO4-based fluid is large and can cause some problems.The SEM analysis shows that some major elements do occur on the tested samples (Ca, Al, Si, and Ba), with dominance of Ca on the expense of Ba for the CaCO3 fluid sample and vice versa. The less effect of 9.5 lb/gal mud sample is reflected in the well-produced inter-particle pore structure and relatively crystal size. A general recommendation is given to minimize the future utilization of Barium Sulfate as a drilling fluid.