Filter Mats Research Articles

An Echo State Network-Based Light Framework for Online Anomaly Detection: An Approach to Using AI at the Edge

Production efficiency is used to determine the best conditions for manufacturing goods at the lowest possible unit cost. When achieved, production efficiency leads to increased revenues for the manufacturer, enhanced employee safety, and a satisfied customer base. Production efficiency not only measures the amount of resources that are needed for production but also considers the productivity levels and the state of the production lines. In this context, online anomaly detection (AD) is an important tool for maintaining the reliability of the production ecosystem. With advancements in artificial intelligence and the growing significance of identifying and mitigating anomalies across different fields, approaches based on artificial neural networks facilitate the recognition of intricate types of anomalies by taking into account both temporal and contextual attributes. In this paper, a lightweight framework based on the Echo State Network (ESN) model running at the edge is introduced for online AD. Compared to other AD methods, such as Long Short-Term Memory (LSTM), it achieves superior precision, accuracy, and recall metrics while reducing training time, CO2 emissions, and the need for high computational resources. The preliminary evaluation of the proposed solution was conducted using a low-resource computing device at the edge of the real production machine through an Industrial Internet of Things (IIoT) smart meter module. The machine used to test the proposed solution was provided by the Italian company SIFIM Srl, which manufactures filter mats for industrial kitchens. Experimental results demonstrate the feasibility of developing an AD method that achieves high accuracy, with the ESN-based framework reaching 85% compared to 80.88% for the LSTM-based model. Furthermore, this method requires minimal hardware resources, with a training time of 9.5 s compared to 2.100 s for the other model.

Efficient adsorption of aromatic and aliphatic hydrocarbons by electrospun hydrophobic PTFE-NiO composite nanofiber filter mats

Aromatic and aliphatic hydrocarbons (AAHs) are comprised of a variety of gaseous chemicals that may affect human and environmental health. To remove AAHs from air, polytetrafluoroethylene-nickel oxide (PTFE-NiO) composite nanofiber filter mats (NFMs) were synthesized and characterized for their ability to effectively adsorb AAHs. The NiO-nanoparticle-doped mats were fabricated by green electrospinning of PTFE and polyvinyl alcohol (PVA) mixtures added with nickel (II) nitrate hexahydrate in the spinning solution followed by surface heat treatment. FE-SEM FTIR, Raman spectroscopy, sessile drop and Jar methods were applied as characterization techniques. The diameter of the electrospun nanofibers without NiO dopant ranged from 0.34 ± 21.61 to 0.23 ± 10.12 µm, whereas a reduction in diameter of NiO-doped nanofibers was obtained, ranging between pristine to 0.25 ± 24.12 µm and 0.12 ± 85.75 µm with heat treatment. 6% (by weight) NiO-doped PTFE composite NFMs exhibited a high water-contact angle of 120 ± 2.20 degrees; the high hydrophobicity value aided self-cleansing property of NFMs for practical applications. UV adsorption capability for heat-treated PTFE-NiO NFMs was evaluated for three AAHs, and the results showed that 6 wt% NiO adsorbed 1.41, 0.67, and 0.73 µg/mg of toluene, formaldehyde and acetone, respectively. These findings reveal the potential applicability of the prepared filter mats for capturing various AAHs from polluted air.

Pesticides and pesticide-related products in ambient air in Germany

BackgroundTree bark measurements conducted between 2014 and 2017 in a biosphere reserve in Germany have indicated the presence of pesticides from conventional agriculture in ambient air. In the present study, we quantified pesticides and related substances in ambient air at 69 sites using passive air samplers and ventilation filter mats. It is, to our knowledge, so far the most comprehensive data set on pesticides and their related products in ambient air in Germany.ResultsSamples were collected in 2019 and analysed for over 500 substances. One hundred and nine (109) were detected, including 28 that are not approved for use in Germany. In each sampling site, we identified one to 36 substances, including locations such as national parks and forests. Here, the presence of pesticides is not expected, e.g., on the highest mountain top in the national park “Harz” (13 substances) and in the "Bavarian Forest" (six substances). Glyphosate was recorded in every sample. More than half of passive air samplers contained chlorothalonil, metolachlor, pendimethalin, terbuthylazine, prothioconazole-desthio, dimethenamid, prosulfocarb, flufenacet, tebuconazole, aclonifen, chlorflurenol, hexachlorobenzene (HCB), and γ-hexachlorocyclohexane (γ-HCH). Filter mats also contained boscalid. The statistical analysis showed that landscape classification and agricultural intensity were the primary factors influencing the number of substances detected in ambient air. Location, such as protected areas or regions of organic farming, had only a small effect on the number of substances recorded. Medium- and long-range transport likely accounts for these findings. Extending the current sampling method will probably detect more pesticides than the data currently suggest.ConclusionsAirborne pesticide mixtures are ubiquitous in Germany, which is particularly concerning for glyphosate, pendimethalin, and prosulfocarb. Deposition of these pesticides on organic products may disqualify them from the market, resulting in economic losses to farmers. Air concentrations of pesticides are a relevant issue and must be reduced.

Assessment of the potential release of nanomaterials from electrospun nanofiber filter media

Due to the special properties of electrospun nanofibers such as high surface area and porosity, ease of surface functionalization, low pressure drop, suitable mechanical strength, their application in the fabrication of air purifying filtration media has increased dramatically in the recent years. The release of nanomaterials from electrospun nanofibers and human exposure to these substances is one of the concerns regarding to application of nanofiber media in air purifying applications.The aims of present study were to fabricate and characterize the nanofiber filter media, and to determine the release of nanomaterials from them during their application in a filter test rig for removing potassium chloride (KCl) nanoparticles. Polyacrylonitrile, one of the most commonly used polymers in electrospun nanofiber filter media, was embedded with various nanomaterials including magnesium oxide nanoparticles and single wall carbon nanotube and was converted to nanofiber filter mats via electrospinning process. The air samples were collected at the downstream of prepared nanofiber filter mats using polycarbonate (PC) and mixed cellulose ester (MCE) filters according to NIOSH methods 7404 and 7402. The PC filters were analyzed by FE-SEM microscopy for assessing potential release of nanofibers and MCE filters were analyzed by CytoViva's Hyper Spectral Imaging System coupled with Enhanced Dark Field Microscopy (HIS-EDFM) for assessing the potential release of nanomaterials (SWNTs and MgO NPs) from the electrospun nanofiber filter mats. The findings indicated that electrospun nanofibers and their embedded nanoparticles were rarely detached and released from the filter media during normal filtration process. Therefore, it is possible to obtain a very low release by improving quality of the nanofiber filter media and applying a safe design approach.

Enhanced Capture of Particulate Matter by Molecularly Charged Electrospun Nanofibers

We introduce molecularly charged electrospun nanofibers obtained by soft chemical treatment for the capture of particulate matter (PM). These PMs, along with certain volatile organic compounds (VOCs), pose a severe threat not only to human health but also to the environment. As the concentrations of these PMs have been steadily increasing in the Southeast Asian countries, a dire need for protection against these particles is warranted. Filtering out the polluted air using various filtration media, such as face masks and nasal filters, has been the standard method for minimizing exposure to PM. Here, we demonstrate the removal of PM and VOCs by utilizing electrospun nanofibers of polystyrene (PS) and polyacrylonitrile (PAN) with molecular charges imparted on them via chemical treatment. The chemically treated fibers were successful in capturing even particles measuring 300 nm, which are considered to be the most penetrable particles. We report a filtration efficiency of ∼93% for removing such particles, which is ∼3 ± 1.5% enhancement when compared to the untreated fibers. The fibers have been subjected to extreme haze conditions (∼1413 μg m–³) of PM₂.₅ for a duration of 1 h, and the filtration efficiency was measured to be ∼99.01%. These fibers also possess the capability to capture model VOCs such as aniline, toluene, tetrahydrofuran, and chloroform. When PAN, PS, and their chemically treated counterparts were tested for their antibacterial activity, these filter mats had bactericidal effect on Escherichia coli, Bacillus subtilis, and Enterococcus faecalis. A nasal plug hosting these filter mats has been designed, which can offer personal protection from PM. Enhanced removal of residual particles is extremely important, and this difficult task is made possible with our approach. The efficiency of our approach is due to the charged nature of PM, especially of the smaller size regime.

Methodological Guidelines for Prevention of Destruction of Parallel Filter Cartridges Located in One Vessel at Maximum Pressure Drop

Technical literature lacks scientific foundations for prevention of destruction of parallel filter cartridges within one vessel in gas purification devices at maximum pressure drop. In order to prevent filter net damage caused by solid particles, which can be found in the raw (non-purified) gas stream at the inlet to the gas purification device, we have developed principles and technical solutions for installation of a protective plate with perforated holes, the size of which excludes entry of debris capable of destroying the outer surface of the filter net. In order to prevent the destruction of fully-clogged filter net from the impact occurring as the result of pressure drop in the filter cartridge, we have developed solutions for transferring gas pressure from the clogged net to the supporting rectangular plate perforated with openings. An equation is proposed for finding the maximum opening diameter in rectangular support plates, which prevent damage to the clogged filter mats adjacent to them in the event of an increase in the pressure drop to the maximum value in the cartridge.

Enhanced Aerosol Particle Filtration Efficiency of Nonwoven Porous Cellulose Triacetate Nanofiber Mats.

Aerosol particle filtration in most penetrating particle size (MPPS) region is of great challenge for conventional nonwoven filter mats. The present work, therefore, redesigns conventional filter mats by introducing porous structure. A combination of thermally induced phase separation and breath figure mechanism was employed to synthesize porous cellulose triacetate fibers, in conjunction with the volatile solvent methylene chloride. The ambient humidity, the concentration of the polyvinylpyrrolidone (PVP) secondary polymer, and the ethanol cosolvent were all adjusted to modify the Taylor cone formation, jet stability, and fiber porosity. After fiber formation, the PVP was removed to obtain a superhydrophobic material. To distinguish the effect of pores, the performance of porous and nonporous nanofibers having similar sizes was conducted. Tests were performed using various dust particle sizes, and the results show that the collection efficiency of the porous fibers, resulting from particle diffusion, inertial impaction, and interception, was improved. Interestingly, the efficiency of the porous fibers in the MPPS region was exceptionally enhanced (up to 95%), demonstrating that the presence of dynamic pores greatly contributes to particle capture.

Filter media properties of mineral fibres produced by plasma spray

ABSTRACTThe purpose of this study was to determine the properties of fibrous gas filtration media produced from mineral zeolite. Fibres were generated by direct current plasma spray. The paper characterizes morphology, chemical composition, geometrical structure of elementary fibres, and thermal resistance, as well as the filtration properties of fibre media. The diameter of the produced elementary fibres ranged from 0.17 to 0.90 μm and the length ranged from 0.025 to 5.1 mm. The release of fibres from the media in the air stream was noticed, but it was minimized by hot-pressing the formed fibre mats. The fibres kept their properties up to the temperature of 956°C, while further increase in temperature resulted in the filter media becoming shrunk and brittle. The filtration efficiency of the prepared filter mats ranged from 95.34% to 99.99% for aerosol particles ranging in a size between 0.03 and 10.0 μm. Unprocessed fibre media showed the highest filtration efficiency when filtering aerosol particles smaller than 0.1 µm. Hot-pressed filters were characterized by the highest quality factor values, ranging from 0.021 to 0.064 Pa−1 (average value 0.034 Pa−1).

Designing high-caliber nonwoven filter mats for coalescence filtration of oil/water emulsions

Oily wastewater is a major problem in industries that can cause severe environmental pollution without proper treatment. In this paper, an easily fabricated, robust and durable nonwoven fibrous filter mat was prepared for coalescence filtration of four kinds of oil-in-water emulsions, namely hexadecane/water, octane/water, soybean oil/water and engine oil/water. An aromatic thermoplastic polyurethane resin (TPU) was selected to bind the fibers together for structure integrity of the mat. Special roughening treatment to the mat was conducted to deliver the required wettability for effective coalescence separation of these emulsions. The filter mat thus prepared reached a tensile strength of 2.99MPa, 20 times stronger than that of the pristine mat. The mat surface was made both hydrophilic and superoleophilic, allowing it to have separation efficiency as high as 99.61% in a single pass flow. Moreover, even pre-saturated with oil, the mat remained effective in separation and permitted high flow, proving its high caliber for potential industrial applications.

Conopeptide ρ-TIA Defines a New Allosteric Site on the Extracellular Surface of the α1B-Adrenoceptor

The G protein-coupled receptor (GPCR) superfamily is an important drug target that includes over 1000 membrane receptors that functionally couple extracellular stimuli to intracellular effectors. Despite the potential of extracellular surface (ECS) residues in GPCRs to interact with subtype-specific allosteric modulators, few ECS pharmacophores for class A receptors have been identified. Using the turkey β(1)-adrenergic receptor crystal structure, we modeled the α(1B)-adrenoceptor (α(1B)-AR) to help identify the allosteric site for ρ-conopeptide TIA, an inverse agonist at this receptor. Combining mutational radioligand binding and inositol 1-phosphate signaling studies, together with molecular docking simulations using a refined NMR structure of ρ-TIA, we identified 14 residues on the ECS of the α(1B)-AR that influenced ρ-TIA binding. Double mutant cycle analysis and docking confirmed that ρ-TIA binding was dominated by a salt bridge and cation-π between Arg-4-ρ-TIA and Asp-327 and Phe-330, respectively, and a T-stacking-π interaction between Trp-3-ρ-TIA and Phe-330. Water-bridging hydrogen bonds between Asn-2-ρ-TIA and Val-197, Trp-3-ρ-TIA and Ser-318, and the positively charged N terminus and Glu-186, were also identified. These interactions reveal that peptide binding to the ECS on transmembrane helix 6 (TMH6) and TMH7 at the base of extracellular loop 3 (ECL3) is sufficient to allosterically inhibit agonist signaling at a GPCR. The ligand-accessible ECS residues identified provide the first view of an allosteric inhibitor pharmacophore for α(1)-adrenoceptors and mechanistic insight and a new set of structural constraints for the design of allosteric antagonists at related GPCRs.

Morphology optimization of polymer nanofiber for applications in aerosol particle filtration

Polymer nanofiber mats with various morphology structures (nanofiber, beaded-nanofiber, and composite particle/nanofiber) were prepared by electrospinning for application to aerosol particle filtration. The filtration performance of these polymer nanofiber mats was evaluated based on quality factors generated from measurement of penetration through the filter by sodium chloride (NaCl) aerosol particles ranging from 20 to 300 nm. These filtration test results showed that the quality factors of beaded-nanofiber filter mats were the best, even though the aerosol particle penetration of them was the highest of the morphology structures. The results of the present study show that morphology optimization of polymer nanofibers is an effective method for improvement of filtration performance, and it must be the future direction for development of new filtration media.

Characterization of the Transport Mechanism and Permeant Binding Profile of the Uridine Permease Fui1p of Saccharomyces cerevisiae

The uptake of Urd into the yeast Saccharomyces cerevisiae is mediated by Fui1p, a Urd-specific nucleoside transporter encoded by the FUI1 gene and a member of the yeast Fur permease family, which also includes the uracil, allantoin, and thiamine permeases. When Fui1p was produced in a double-permease knock-out strain (fur4Deltafui1Delta) of yeast, Urd uptake was stimulated at acidic pH and sensitive to the protonophore carbonyl cyanide m-chlorophenylhydrazone. Electrophysiological analysis of recombinant Fui1p produced in Xenopus oocytes demonstrated that Fui1p-mediated Urd uptake was dependent on proton cotransport with a 1:1 stoichiometry. Mutagenesis analysis of three charged amino acids (Glu(259), Lys(288), and Asp(474) in putative transmembrane segments 3, 4, and 7, respectively) revealed that only Lys(288) was required for maintaining high Urd transport efficiency. Analysis of binding energies between Fui1p and different Urd analogs indicated that Fuip1 interacted with C(3')-OH, C(2')-OH, C(5)-H, and N(3)-H of Urd. Fui1p-mediated transport of Urd was inhibited by analogs with modifications at C-5', but was not inhibited significantly by analogs with modifications at C-3', C-5, and N-3 or inversions of configuration at C-2' and C-3'. This characterization of Fui1p contributes to the emerging knowledge of the structure and function of the Fur family of permeases, including the Fui1p orthologs of pathogenic fungi.

Fluorescent Indicators Distributed throughout the Pharmacophore of Cholecystokinin Provide Insights into Distinct Modes of Binding and Activation of Type A and B Cholecystokinin Receptors

Ligand probes with fluorescent indicators positioned throughout the pharmacophoric domain can provide important insights into the molecular basis of receptor binding and activation as reflected in the microenvironment of each indicator while docked at a receptor. We developed three cholecystokinin-like probes with Aladan situated at the N terminus, in the mid-region, and at the C terminus (positions 24, 29, and 33, respectively). These were studied in solution and docked at type A and B cholecystokinin receptors. This study demonstrated clear differences in mechanisms of cholecystokinin binding and activation of these structurally related receptors with distinct agonist structure-activity relationships. The fluorescence characteristics of Aladan are highly sensitive to the polarity of its microenvironment. The mid-region probe was least accessible to the aqueous milieu as determined by fluorescence emission spectra and iodide quenching, which was not altered by changes in conformation from active to inactive. Accessibility of the N- and C-terminal probes was affected by receptor conformation. The position 24 probe was more easily quenched in the active than in the G protein-uncoupled conformation for both receptors. However, the position 33 probe docked at the type A cholecystokinin receptor was more easily quenched in the active conformation, whereas the same probe docked at the type B cholecystokinin receptor was more easily quenched in the inactive conformation. Fluorescence anisotropy and red edge excitation shift determinations confirmed these observations and supported the proposed movements. Although both type A and B cholecystokinin receptors bind cholecystokinin with high affinity, resulting in fully efficacious biological responses, these receptors utilize distinct molecular modes of binding.

Identification and Mutational Analysis of Amino Acid Residues Involved in Dipyridamole Interactions with Human and Caenorhabditis elegans Equilibrative Nucleoside Transporters

The equilibrative nucleoside transporters, hENT1 and CeENT1 from humans and Caenorhabditis elegans, respectively, are inhibited by nanomolar concentrations of dipyridamole and share a common 11-transmembrane helix (TM) topology. Random mutagenesis and screening by functional complementation in yeast for clones with reduced sensitivities to dipyridamole yielded mutations at Ile429 in TM 11 of CeENT1 and Met33 in TM 1 of hENT1. Mutational analysis of the corresponding residues of both proteins suggested important roles for these residues in competitive inhibition of hENT1 and CeENT1 by dipyridamole. To verify the roles of these residues in dipyridamole interactions, hENT2, which naturally exhibits low dipyridamole sensitivity, was mutated to contain side chains favorable for high affinity dipyridamole binding (i.e. a Met at the TM 1 and/or an Ile at the TM 11 positions). The single mutants exhibited increased hENT2 sensitivity to inhibition by dipyridamole, and the double mutant was the most sensitive, with an IC50 value that was only 2% of that of wild type. Functional analysis of the TM 1 and 11 mutants of hENT1 and CeENT1 revealed that Ala and Thr in the TM 1 and 11 positions, respectively, impaired uridine and adenosine transport and that Leu442 of hENT1 was involved in permeant selectivity. Mechanistic and structural models of dipyridamole interactions with the TM 1 and 11 residues are proposed. This study demonstrated that the corresponding residues in TMs 1 and 11 of hENT1, hENT2, and CeENT1 are important for dipyridamole interactions and nucleoside transport.

In vivo dose threshold effect of adenovirus-mediated factor VIII gene therapy in hemophiliac mice.

While much is known about adenovirus biology from its development as a therapeutic gene delivery vehicle, an important question remains regarding the appropriate in vivo vector dose. We describe here an in vivo dose threshold effect with an adenoviral vector expressing human Factor VIII (FVIII) in hemophiliac mice. Upon administration of vector doses between 6 x 10(10) and 2 x 10(10) vector particles per mouse, FVIII was expressed linearly, whereas a dose of 1 x 10(10) vector particles per mouse did not result in detectable levels of FVIII activity. In contrast, in vitro transduction studies demonstrated linear transgene expression over 2 to 3 log units. To further define this dose threshold effect, a vector-mixing study was performed. Mice were injected with a total vector dose of 6 x 10(10) particles containing admixtures of FVIII vector plus a control vector lacking a transgene (null vector). With the admixture, FVIII activity was detected in mice that received 1 3 1010 particles of the FVIII vector, indicating that maintenance of the total viral input at 6 x 10(10) particles per mouse circumvented the threshold dose effect. This threshold dose effect could not be attributed to dose-dependent differences in liver toxicity nor to dose-dependent induction of cellular and humoral immune responses. Southern blot analysis of livers revealed that mice receiving the vector admixture contained FVIII DNA, accounting for the observed FVIII expression, whereas mice receiving 1 x 10(10) particles of FVIII vector had barely detectable FVIII DNA. These results suggest that the threshold effect is an in vivo phenomenon that will have important implications in defining the therapeutic window of adenoviral vectors for clinical applications.

An automated filtration assay for protein kinase C ligands

[ 3H]Phorbol dibutyrate ([ 3H]PDBu) binding to soluble mouse brain protein kinase C (PKC) was established in a 96-well microtiter plate assay. [ 3H]PDBu-PKC receptor complexes were rapidly aspirated from wells, filtered, and washed onto glass fiber filter mats using an automated cell harvester. Results were compared to a modification of a previously described assay in which components were incubated in tubes, and manually delivered and washed onto filters with a manifold filtration apparatus. Both 96-well plate and tube assays gave qualitatively and quantitatively similar results since: (i) [ 3H]PDBu binding to PKC was phosphatidylserine (PS) dependent and calcium stimulatable; (ii) the amounts of [ 3H]PDBu bound by filters with each technique at receptors excess were similar, 3.2 ± 0.3 and 3.1 ± 0.4 pmol respectively; and (iii) the affinities of [ 3H]PDBu for PKC were comparable; K d's were 1.95 ± 0.3 and 2.2 ± 0.55 n m, respectively. The 96-well plate assay was more accurate and rapid than the tube assay. The microtiter plate assay was adapted for use with [ N,N-dimethyl- 3H] N,N-dimethylstaurosporine ([ 3H]DMS). With [ 3H]PDBu and [ 3H]DMS as ligands, the 96-well plate method was used for the rapid discrimination of agents which bound selectively at the regulatory and/or catalytic domains of PKC.

Orientation of the boundary faces in nylon‐11 lamellar crystals

AbstractA semicrystalline polymer having a large repeat unit, as does nylon‐11, is particularly suitable for seeking correlation between the orientation of the lattice and the basal planes of the lamellar crystals. In filter mats of nylon‐11 single crystals, the basal planes of the lamellae are parallel to (00l) crystallographic planes; the chain axis is tilted with respect to the mat plane. By planar extrusion, bulk double oriented specimens with a nearly single texture can be prepared: the basal planes of the lamellae are parallel to (00l) planes and the chain axis is along the extrusion direction. Doubly oriented samples of nylon‐11 having a double texture have been obtained by unidirectional rolling. In these samples, the chain axes are along the rolling direction; the basal planes of the lamellar crystals are not parallel to (00l) planes. It has been proposed that lamellae consist of blocks of six hydrogen‐bonded planes shifted by one monomer unit. The parallelism between basal planes of lamellae and (00l) planes is obtained again in rolled samples annealled in contact with formic acid. Those annealed samples are similar to filter mats with respect to the orientation of the lamellar basal planes but they remain doubly oriented at the level of the unit cell; they have a long spacing larger than filter mats of single crystals.

Anisotropic swelling of doubly oriented nylon‐11 with a lamellar structure

AbstractRolled smaples of nylon‐11 annealed in formic acid (90%) at 80°C remain doubly oriented and have the same allotropic form as filter mats of single crystals. the basal planes of the crystals are parallel to (00l) planes. the long spacing is larger than in filter mats. Experimental swelling results obtained on such samples are discussed on the basis of two extreme models, the lamellar and the switchboard models. The long spacing dy and the length of the sample (along 0Y) change reversibly by the same proportion during swelling. Insertion of solvent between lamellae is invoked to explain such changes of dimension. As linear swelling ratios computed from macroscopic dimensions and SAXS measurements can reach 100%, lamellar crystals are only bonded by a few chains. The large increase of the SAXS intensity observed when annealed doubly oriented samples of nylon‐11 are wetted with allylic alcohol cannot be explained on the basis of the switchboard model but only with a three‐phase lamellar model. These three phases are the crystalline phase, the fold region, and a dilute solution of polymer in the swelling agent.

Thermal annealing of doubly oriented nylon 11 in contact with formic acid

AbstractThe most striking feature of the mechanism of thermal annealing of doubly oriented samples of low‐density polyethylene (LDPE) and probably of high‐density polyethylene (HDPE) is a progressive tilt of lamellar crystals around their crystallographic b axis. Such a rotation does not occur on thermal annealing in doubly oriented nylons. However, this rotation mechanism occurs during the thermal annealing of doubly oriented samples of nylon 11 in contact with a solvent below its dissolution temperature. As for oriented samples of polyethylene (PE), a correlation between the changes of macroscopic dimensions and long spacing obtained from the small‐angle x‐ray pattern is difficult to establish. In doubly oriented samples of nylon 11, the basal faces of the lamellar crystals are parallel to the a axis of the unit cell. Nevertheless, simple Miller indices cannot be assigned to the basal planes of the lamellae. On thermal annealing in formic acid, the basal planes of the lamellar crystals are, in some cases, parallel to (00l) planes. Annealing in formic acid at room temperature induces a phase transition: the chain c axis remains oriented along the rolling direction and the (00l) planes become parallel to the limiting planes of the lamellar crystals. Bulk doubly oriented samples of nylon 11 annealed in formic acid just below the “dissolution temperature” have the same texture of orientation as filter mats of single crystals grown from dilute solution; moreover, as these bulk specimens remain doubly oriented, they can be used for further physicochemical investigations. The usual interpretation of the small‐angle x‐ray pattern is also discussed on the basis of the results reported in this paper.

Erythropoietin assay using fetal mouse liver cell cultures: a modified technique using semi-automatic harvesting of I125 deoxyuridine labelled erythroblasts.

Modifications have been made to the fetal mouse liver cell bioassay for erythropoietin in an attempt to make the method easier and to improve specificity. Pooled human serum is used as a diluent for test serum samples, standard and control preparations in order to minimize the influence of other serum constituents on the assay results. Erythroblast proliferation is measured by incorporation of I125 deoxyuridine into DNA. The cell cultures are grown in microtitration plates and harvested semi-automatically on to glass fibre filter mats for determination of radioactivity.