Filter Capsule Research Articles

Dual excitation self-balancing capacitance measurement method based on frequency adjustment

The double-ended excitation self-balancing bridge excitation method is a capacitance measurement method with rather a high measurement accuracy currently. However, the reference impedance of the electric bridge limits the traditional self-balancing excitation measurement method, making it difficult to achieve high accuracy and a wide range of capacitance sensor measurements. In the proposed paper, frequency adjustment method is introduced to enable impedance matching between the measured capacitance and the reference resistance. The measurement range is broadened as well as maintaining the accuracy of the capacitance measurement. The measurement circuit is composed of a reference resistor, a bridge in series with the measured capacitance and an operational amplifier follower circuit. First, we roughly measure the input impedance of the operational amplifier and the capacitive reactance of the capacitance under test using a two-step excitation method. Then, the best excitation frequency is calculated to match the reference resistor according to the capacitive reactance under test, and the input impedance of the operational amplifier is re-estimated with the best frequency. Finally, we complete the accurate measurement of the capacitive reactance under test through the use of dual excitation. The experimental results demonstrate the method’s high accuracy measurement within the range of 1.6 pF–16 nF, with the reference resistance set at 1 MΩ and the excitation frequency adjusted between 10 and 100 kHz. Additionally, dual excitation stability testing verifies relative standard deviations in the range of 0.01%–0.12%. Experiments on filter capsule sensing detection show that the proposed frequency adjustment measurement method can perform highly sensitive capacitive sensing measurements under the influence of parasitic effects.

Scale-up issues for commercial depth filters in bioprocessing.

Significant increases in cell density and product titer have led to renewed interest in the application of depth filtration for initial clarification of cell culture fluid in antibody production. The performance of these depth filters will depend on the local pressure and velocity distribution within the filter capsule, but these are very difficult to probe experimentally, leading to challenges in both process design and scale-up. We have used a combination of carefully designed experimental studies and computational fluid dynamics (CFD) to examine these issues in both lab-scale (SupracapTM 50) and pilot-scale (StaxTM ) depth filter modules, both employing dual-layer lenticular PDH4 media containing diatomaceous earth. The SupracapTM 50 showed a more rapid increase in transmembrane pressure and a more rapid DNA breakthrough during filtration of a Chinese Hamster Ovary cell culture fluid. These results were explained using CFD calculations which showed very different flow distributions within the modules. CFD predictions were further validated using measurements of the residence time distribution and dye binding in both the lab-scale and pilot-plant modules. These results provide important insights into the factors controlling the performance and scale-up of these commercially important depth filters as well as a framework that can be broadly applied to develop more effective depth filters and depth filtration processes.

Flow and residence time distribution in small-scale dual-layer depth filter capsules

Depth filtration is widely used for clarification of liquid feeds, including the purification of biopharmaceuticals. The performance characteristics of these depth filters can be strongly influenced by the local flow and pressure distribution within the filter capsule, but there is currently little information on these phenomena in commercial depth filter modules. This work used a combination of computational fluid dynamics (CFD), residence time distribution (RTD) measurements, and dye binding experiments to obtain detailed information on the pressure and flow distribution within a small-scale Supracap™ depth filtration capsule, containing two layers of depth filter media with different pore size, that is of high interest in bioprocessing. The results confirmed the presence of four distinct flow paths through the capsule, with less than 40% of the flow passing completely through both layers of the depth filter media and nearly 11% bypassing the large pore size prefilter layer. Model calculations were in good agreement with the measured RTD and images of dye binding, providing further confirmation of the flow phenomena. These studies provide important insights into the performance characteristics of these depth filters, while providing a framework that can be applied to analyze the pressure and flow distribution in other membrane and depth filtration modules.

Menthol, Nicotine, and Flavoring Content of Capsule Cigarettes in the US.

Characterize physical design features of cigarette brands sold in the US according to the delivery method of menthol that may affect sensory perception among users. Twelve cigarette brands, mentholated and non-mentholated, were purchased for analyses of the physical design characteristics, quantification of nicotine and menthol, and identification of flavor additives. Physical design characteristics did not differ significantly between the various cigarette brands. However, significant differences were seen in levels of menthol. Menthol levels were greatest in products that had dual delivery methods of menthol (6.7mg/cigarette; SE=0.27) followed by products mentholated in a filter capsule only (5.7mg/cigarette; SE=0.25), and those mentholated in the tobacco only (3.8mg/cigarette; SE=0.12); products that were not mentholated had the least (0.38mg/cigarette; SE=0.31). Finally, flavor additives with a mint flavor profile other than menthol were identified, such as pulegone and limonene, and differed between cigarette brands, which are likely contributing to the menthol flavor experience associated with use of these products. The regulation of menthol delivery method, flavorings added to the capsule, and/or menthol concentration may be beneficial for the public health as these factors are likely creating unique sensory experiences.

Impact of menthol delivery methods on smoker sensory perceptions.

INTRODUCTIONMenthol can be added to cigarettes in several ways; these different delivery methods of menthol may lead to changes in sensory attributes, as well as perceived risk and appeal of these products.METHODSUsing a randomized, controlled study design, 18 current, established menthol smokers were asked to sample Camel Crush and Camel Menthol cigarette products, crushed and uncrushed. Smoking behavior, exhaled carbon monoxide, subjective ratings, and perceived risk measures were assessed for each product.RESULTSCigarette Evaluation Scale relief of craving scores for participants’ preferred brand (mean: 5.3, SE: 0.3) were significantly higher (p=0.012) than Camel Menthol crushed (mean: 4.6, SE: 0.3) as were the Sensory Scale satisfaction scores (preferred brand mean: 6.9, SE: 0.7 compared to Camel Menthol crushed mean: 5.1, SE: 0.6; p=0.004). In addition, the average Sensory Scale smoke strength scores for participants’ preferred brand (mean: 6.9, SE: 0.5) was also significantly higher than Camel Crush crushed (mean: 5.0, SE: 0.5; p=0.022). There were no significant differences in smoking topography measures, CO boosts, or perceived risk between Camel Crush or Camel Menthol products.CONCLUSIONSThe delivery method and amount of menthol present in cigarettes did not appear to affect short-term smoking behavior, sensory perceptions, or perceived product risk among a small sample of current established adult menthol smokers. It is possible that consumers of cigarette products may be attracted to the innovative technology of the crushable filter capsule as opposed to the taste experience, however, further research is needed.

Menthol Cigarettes and Smoking Cessation among Adult Smokers in the US.

Objectives: In this study, we identified differences in cessation, nicotine dependence, and quit attempts between smokers using non-menthol cigarettes and smokers using menthol cigarettes differing in menthol delivery method (eg, menthol in the tobacco only, crushable capsules only or both). Methods: We analyzed data from the Population Assessment of Tobacco and Health Study, Waves 1 and 2 (W1 and W2), to determine associations of delivery method of menthol with cessation, nicotine dependence, and quit attempts among current adult cigarette smokers. Results: Nearly 40% of US smokers reported using a mentholated cigarette product with most using a product mentholated in the tobacco only. Smokers included in this analysis had a moderate to low heaviness of smoking index score. The lowest average score was among those using products mentholated in a filter capsule only (1.3, SE = .10), and the highest among those using non-mentholated products (2.4, SE = .03). About 12% of smokers quit between W1 and W2. Cessation, nicotine dependence, and quit attempts at W2 were not associated with delivery method of menthol at W1. Conclusions: Method of menthol delivery did not impact cessation, nicotine dependence, and quit attempts.

Efficacy and Effectiveness of Showerheads Attached with Point-of-use (POU) Filter Capsules in Preventing Waterborne Diseases in a Japanese Hospital.

Tap water contamination is a growing concern in healthcare facilities, and despite chlorination, tap water in these facilities contains several pathogenic microorganisms causing healthcare-associated waterborne infections or nosocomial outbreaks. Shower units are particularly prone to contamination as they are conducive for bacterial growth and can even produce bioaerosols containing pathogenic bacteria. Shower units coupled with point-of-use (POU) water filters are a simple and safe option; however, their efficacy has been under-reported. Therefore, we determined the efficacy of showerheads attached with a POU filter capsule in preventing infections in our hospital. We investigated the presence of pathogenic bacteria in water sampled from three shower units. After replacing the original shower units with new ones incorporated with a sterile-grade water filter capsule (0.2 µm; QPoint™), the water samples were analyzed for up to 2 months. The POU filters removed several pathogenic bacteria (Mycobacterium, Pseudomonas, Stenotrophomonas, Aeromonas, and Klebsiella spp.). Filter effectiveness depends on regional water quality and we believe that effective tap water treatment combined with the use of POU filters (introduced at a reasonable cost in healthcare facilities) can considerably minimize waterborne diseases in hospitals and improve patient care.

Using Extractables Data of Sterile Filter Components for Scaling Calculations.

Users of single-use (SU) components need extractables data to demonstrate material safety for regulatory bodies before incorporation in the biopharmaceutical process. In this context, the correct use of such extractables data is key to deriving realistic risk assessments for SU devices. In this paper, a standardized extractables approach was used that provides comprehensive extractables information including identity and quantity. The combination of extractables data obtained from different components of a sterile filter capsule, such as the filter cartridge and housing, and the scaling thereof is presented. A sterile filter type including polyethersulfone membrane was extracted with pure water and pure ethanol at 40°C for 24 h. The organic extractables were identified and their concentration quantified using state-of-the-art analytical methods such as gas chromatography-mass spectrometry for semivolatile compounds together with headspace sampling for volatile compounds, and liquid chromatography coupled with high-resolution mass spectrometry. The extractables detected were assigned to the materials of filter construction. The evaluation showed that the extractables quantities per device depended on the surface areas of the contact materials, such as the filter membrane, and also on the plastic parts. This paper confirms the validity of a so-called component approach and a scaling concept to calculate extractables data for SU filters of different sizes with short-term contact.LAY ABSTRACT: In the biopharmaceutical industry, a large number of SU system combinations with a variety of different sizes are used. Suppliers of such diverse SU systems and assemblies cannot perform extraction studies for all of the different configurations and sizes individually. It is acceptable in this industry to use component approaches and scaling concepts to provide extractables data for SU systems and assemblies derived from a dedicated extraction experiment. This paper shows the applicability of a so-called component approach and of a scaling concept to calculate extractables data for sterile polyethersulfone membrane filters and filter capsules of different sizes. Selected extraction conditions allow scaling calculations according to underlying physical principles. The extractions were performed under short-term contact, for example, 24 h, to ensure that the release of extractables was diffusion-controlled. The results demonstrated that extractables quantities depend on the surface area of the contact material. Membrane-related compounds were scalable with the membrane area, whereas polypropylene (PP)-related compounds were scalable with the PP contact area.

Comparison of capture and storage methods for aqueous macrobial eDNA using an optimized extraction protocol: advantage of enclosed filter

Summary Aqueous environmental DNA (eDNA) is an emerging efficient non‐invasive tool for species inventory studies. To maximize performance of downstream quantitative PCR (qPCR) and next‐generation sequencing (NGS) applications, quality and quantity of the starting material is crucial, calling for optimized capture, storage and extraction techniques of eDNA. Previous comparative studies for eDNA capture/storage have tested precipitation and ‘open’ filters. However, practical ‘enclosed’ filters which reduce unnecessary handling have not been included. Here, we fill this gap by comparing a filter capsule (Sterivex‐GP polyethersulfone, pore size 0·22 μm, hereafter called SX) with commonly used methods. Our experimental set‐up, covering altogether 41 treatments combining capture by precipitation or filtration with different preservation techniques and storage times, sampled one single lake (and a fish‐free control pond). We selected documented capture methods that have successfully targeted a wide range of fauna. The eDNA was extracted using an optimized protocol modified from the DNeasy® Blood & Tissue kit (Qiagen). We measured total eDNA concentrations and Cq‐values (cycles used for DNA quantification by qPCR) to target specific mtDNA cytochrome b (cyt b) sequences in two local keystone fish species. SX yielded higher amounts of total eDNA along with lower Cq‐values than polycarbonate track‐etched filters (PCTE), glass fibre filters (GF) or ethanol precipitation (EP). SX also generated lower Cq‐values than cellulose nitrate filters (CN) for one of the target species. DNA integrity of SX samples did not decrease significantly after 2 weeks of storage in contrast to GF and PCTE. Adding preservative before storage improved SX results. In conclusion, we recommend SX filters (originally designed for filtering micro‐organisms) as an efficient capture method for sampling macrobial eDNA. Ethanol or Longmire's buffer preservation of SX immediately after filtration is recommended. Preserved SX capsules may be stored at room temperature for at least 2 weeks without significant degradation. Reduced handling and less exposure to outside stress compared with other filters may contribute to better eDNA results. SX capsules are easily transported and enable eDNA sampling in remote and harsh field conditions as samples can be filtered/preserved on site.

Comparison of Lead and Tin Concentrations in Air at a Solder Manufacturer from the Closed-Face 37-mm Cassette With and Without a Custom Cellulose-Acetate Cassette Insert

A polyvinyl chloride (PVC) cassette insert with PVC filter (ACCU-CAP) in a 37-mm closed-face cassette (CFC) was designed for gravimetric analysis. A customized version of the ACCU-CAP, also to be used in the CFC, was manufactured from an acid-digestible cellulose-acetate cassette insert joined to a mixed cellulose ester (MCE) filter for wet chemical analysis. The aim of this study was to compare metal particle concentrations as sampled by the customized insert (CI) in a CFC sampler with the traditional sampling method using only a MCE filter in the CFC. Thirty-nine personal and 13 area samples were taken using paired filter-based CFC and the CI in CFC samplers at a solder manufacturing plant. The CI was removed from its CFC, and digested and analyzed as a whole. The MCE filter from the typical CFC was removed for analysis and then the interior of the cassette was wiped with Ghost Wipe for a separate analysis. The MCE filter only, Ghost Wipe, and CI were separately dissolved in heated nitric acid for ICP-MS analysis. Overall, the geometric mean concentration of the filter-only (FO) samples was considerably lower than that of the CI samples, by 53% for lead and 32% for tin. However, if the FO analysis was added to the corresponding Ghost Wipe analysis, i.e., filter+interior wipe (FW), the geometric mean concentrations of the FW results were similar to those of the CI results (by 113% for lead and 98% for tin). For both lead and tin the comparison of (log-transformed) metal concentrations between the FW and CI results showed no statistically significant difference (p-value = 0.3009 for lead and 0.800 for tin), while the comparison between the FO and CI results shows statistically significant differences (all p-values < 0.05). In conclusion, incorporating the sampler internal non-filter deposits by wiping or use of an internal filter capsule gave higher results than analyzing only the filter. Close agreement between the two methods of including non-filter deposits is an indication of general equivalency.

Is nudge an effective public health strategy to tackle obesity? Yes

Users of single-use (SU) components need extractables data to demonstrate material safety for regulatory bodies before incorporation in the biopharmaceutical process. In this context, the correct use of such extractables...

Solid-state time-gated luminescence microscope with ultraviolet light-emitting diode excitation and electron-multiplying charge-coupled device detection

Many naturally occurring materials are autofluorescent, a property that can reduce the discriminative ability of fluorescence methods, sometimes to the point where they cannot be usefully applied. Shifting from the spectral to the temporal domain, it is possible to discriminate fluorophores on the basis of their fluorescence decay lifetime. Luminophores with sufficiently long lifetimes can be discriminated from short-lived autofluorescence using time-gated luminescence (TGL). This technique relies upon the application of a brief excitation pulse followed by a resolving period to permit short-lived autofluorescence to decay, after which detection is enabled to capture persistent emission. In our studies, a high-power UV LED was mounted in the filter capsule of an Olympus BX51 microscope to serve as the excitation source. The microscope was fitted with an Andor DV885 electron-multiplying CCD (EM-CCD) camera with the trigger input synchronized to UV LED operation. Giardia lamblia cysts labeled with the europium chelate BHHST were analyzed against an autofluorescent background with the TGL microscope. The EM-CCD camera captured useful TGL images in real time with a single exposure cycle. With 4x frame averaging, images acquired in TGL mode showed a 30-fold improvement in SNR compared with conventional fluorescence microscopy.