Membrane Strip Research Articles

Application of pseudo-emulsion based hollow fiber strip dispersion with task-specific ionic liquids for recovery of zinc(II) from chloride solutions

Task-specific ionic liquids: 3-[1-(hydroxyimine)undecyl]-1-propylpyridinium bromide and 3-[1-(hydroxyimine)undecyl]-1-propylpyridinium chloride as the carriers in the Zn(II) extraction from chloride media through pseudo-emulsion based membrane strip dispersion (PEHFSD) have been presented. The transport of zinc(II) was investigated as a function of various experimental variables: flow rates of phases, ionic liquid structure in the organic phase, initial zinc(II) concentration and chloride ions in the feed phase. The overall mass transfer coefficient of permeation was calculated from the experimental data, the values being found in the range of 2.5×10−7–8.0 × 10−7 m/s. The recovery of Zn(II) by the stripping solution (5% w/v Na2SO4) was around 70% for most conditions tested. The results of using the task-specific ionic liquids as carrier were also compared to that obtained using the commercial extractant tributyl phosphate.

Return to the Operating Room after Macular Surgery: IRIS Registry Analysis

To investigate the rate of return to the operating room after vitrectomy surgery to treat macular hole or epiretinal membrane. A retrospective registry cohort. Individuals receiving care in ophthalmology practices participating in the Academy IRIS (Intelligent Research in Sight) Registry. Data from the IRIS Registry were analyzed for patients who underwent vitrectomy for macular holes or epiretinal membranes. Cases were identified by the combination of International Classification of Diseases, 9th revision code (362.54, 362.56) and a current procedural terminology (CPT) code for vitrectomy surgery between January 1, 2013 and June 30,2017. The eyes that underwent additional eye surgery within 1 year after initial vitrectomy for macular hole or epiretinal membrane were identified, as was the nature of the additional procedures per CPT code. A total of 41 475 eyes underwent vitrectomy for macular hole and 73 219 eyes underwent vitrectomy for epiretinal membrane during the study period. In the macular hole group, 7573 had a second surgery within 1 year, and 2827 (6.8%) had a second surgery that was not cataract related. In the epiretinal membrane group, 12 433 had a second surgery within 1 year, 4022 (5.5%) of which were not cataract related. In the macular hole group, 4.6% of eyes returned to the operating room for another macular hole repair surgery, and 2.0% returned for retinal detachment repair. In the epiretinal membrane group, 1.4% returned for a second vitrectomy with membrane stripping, and 2.5% returned for retinal detachment repair. This registry-based study encompassed a large number of patients but was limited by the inaccessibility of some information and the potential for inaccurate medical records or coding, as it obtained data from multiple electronic health records entities. Excluding cataract surgery, approximately 6% of eyes that underwent vitrectomy to address macular hole or epiretinal membrane returned for a second ophthalmic procedure within a year. In the macular hole group, most secondary non-cataract surgeries were for another macular hole repair procedure. For both macular holes and epiretinal membranes, approximately 2% of eyes required retinal detachment repair surgery within 1 year.

A Highly Sensitive Immunochromatographic Strip Test for Rapid and Quantitative Detection of Saikosaponin d.

A quantitative lateral-flow immunoassay using gold nanoparticles (AuNPs) conjugated with a monoclonal antibody (MAb) against saikosaponin d (SSd) was developed for the analysis of SSd. The AuNPs were prepared in our laboratory. The AuNPs were polyhedral, with an average diameter of approximately 18 nm. We used the conjugation between AuNPs and MAbs against SSd to prepare immunochromatographic strips (ICSs). For the quantitative experiment, the strips with the test results were scanned using a membrane strip reader, and a detection curve (regression equation, y = −0.113ln(x) + 1.5451, R2 = 0.983), representing the averages of the scanned data, was obtained. This curve was linear from 96 ng/mL to 150 μg/mL, and the IC50 value was 10.39 μg/mL. In this study, we bring the concept of POCT (point-of-care testing) to the measurement of TCM compounds, and this is the first report of quantitative detection of SSd by an ICS.

Electrochemical Stripping to Recover Nitrogen from Source-Separated Urine.

Recovering nitrogen from separately collected urine can potentially reduce costs and energy of wastewater nitrogen removal and fertilizer production. Through benchtop experiments, we demonstrate the recovery of nitrogen from urine as ammonium sulfate using electrochemical stripping, a combination of electrodialysis and membrane stripping. Nitrogen was selectively recovered with 93% efficiency in batch experiments with real urine and required 30.6 MJ kg N-1 in continuous-flow experiments (slightly less than conventional ammonia stripping). The effects of solution chemistry on nitrogen flux, electrolytic reactions, and reactions with electro-generated oxidants were evaluated using synthetic urine solutions. Fates of urine-relevant trace organic contaminants, including electrochemical oxidation and reaction with electro-generated chlorine, were investigated with a suite of common pharmaceuticals. Trace organics (<0.1 μg L-1) and elements (<30 μg L-1) were not detected at appreciable levels in the ammonium sulfate fertilizer product. This novel approach holds promise for selective recovery of nitrogen from concentrated liquid waste streams such as source-separated urine.

Capacitive Membrane Stripping for Ammonia Recovery (CapAmm) from Dilute Wastewaters

A novel cost-effective flow-electrode capacitive deionization unit combined with a hydrophobic gas-permeable hollow fiber membrane contactor (designated “CapAmm”) is described here and used for efficient recovery of ammonia from dilute synthetic wastewaters. During operation, ammonia migrates across a cation exchange membrane and selectively accumulates in the cathode chamber of a flow electrode followed by transformation to dissolved NH3 with subsequent stripping via a membrane contactor and recovery as ammonium sulfate. Our results demonstrate that the CapAmm process can achieve an ammonia removal efficiency of ∼90% and a recovery efficiency of ∼60%. At current densities of 5.8 and 11.5 A m–2 (normalized by the effective cation exchange membrane area) and a hydraulic retention time of 1.48 min, the energies required for ammonia recovery were 9.9 and 21.1 kWh (kg of N)−1, respectively, with these values being comparable with those of other similar electrochemical ammonia recovery systems. These findings ...

White light reflectance spectroscopy biosensing system for fast quantitative prostate specific antigen determination in forensic samples

A label-free biosensor based on white light reflectance spectroscopy for the determination of PSA as semen indicator in forensic samples is presented. The sensor is based on a two-step immunoassay which employs the same polyclonal anti-PSA antibody as capture and detection antibody followed by reaction with streptavidin as a signal enhancement step. The whole assay time was set to 10min; 5min reaction of immobilized antibody with the PSA calibrators or the samples, 3min reaction with the biotinylated anti-PSA antibody and 2min reaction with streptavidin. Following this protocol, a detection limit of 0.5ng/mL was achieved and the assay's linear response range extended up to 500ng/mL. Thus, taking into account the quantification limit of 1.0ng/mL and the average PSA concentration in semen (0.2–5.5mg/mL), semen quantities of a few nanoliters could be detected. The accuracy of the sensor developed was demonstrated through recovery (% recovery ranged from 89.6 to 106) and semen dilution experiments. A linear correlation was found for semen dilutions ranging from 5000 to 360,000. The lack of interference by other bodily fluids was confirmed by analysing stains of blood, urine and saliva prior to and after the addition of semen. Finally, the sensor was evaluated by analysing 51 forensic casework samples which were also analysed with a semi-quantitative membrane strip test (Seratec® PSA), through microscopic detection of spermatozoa, and male DNA identification through detection of Y chromosome. The results obtained with the sensor were in excellent agreement with those provided by an immunoradiometric assay kit (PSA-RIACT) and in complete agreement with the findings using the membrane strip assay, spermatozoa and Y chromosome detection. The excellent analytical performance and small size of the instrument make the sensor developed an attractive tool for use in forensic evidence screening for semen detection.

Mini descemet membrane stripping (m-DMES) in patients with Fuchs’ endothelial dystrophy: A new method

We present two cases with focal corneal edema due to Fuchs’ endothelial dystrophy that were successfully treated with mini Descemet membrane stripping (m-DMES) (diameter of 3–4mm; at the area of preexisting focal corneal edema) without endothelial replacement during cataract surgery. Specular microscopy demonstrated Fuchs’ endothelial dystrophy and histopathologic evaluation confirmed the diagnosis. Anterior segment optical coherence tomography and confocal microscopy were used for the evaluation of the corneal tissue recovery course after the surgical procedure. In both patients, we observed an initial aggravation of corneal edema in the area of DM removal for two months followed by gradual improvement. At four months postoperatively, corneal edema had completely regressed resulting in corneal clearance and visual acuity improvement in both cases. M-DMES without graft insertion represents a promising alternative surgical technique that could be applied in specific cases of Fuchs’ endothelial dystrophy with focal corneal edema.

Detection of environmentally hazardous pesticide in fruit and vegetable samples using gold nanoparticles

A new approach for simple, competitive and sensitive, dipstick immunoassay (DIA) was developed to detect organophosphorus pesticide. Residual pesticides such as kitazine in fruits and vegetables are one of the major food safety concerns for consumers in the world. It is the alternative method to nitrocellulose strip (NC) for the detection of harmful pesticides. The matrix effects of different food samples (tomato, cucumber, grapes and orange) were studied in flow through ELISA (Enzyme Linked Immunoassay) and DIA method. Different size morphology was synthesized from gold nanoparticles and bioconjugated to Ig G, which served as the detecting agent confirmed by AFM. The different concentration of organophosphorus in the food sample was detected by the development of purple color in the membrane strips. Among four fruit juices, the grape juice exhibits increased absorbance resulted that the bioconjugated gold nanoparticle is actively detected the kitazine present in the grape juice evidenced by ELISA method has good reproducibility and satisfactory accuracy. The interpretation of the results was visual, and these ELISAs can be used as convenient qualitative tools for the rapid screening ofkitazine residues in food samples.

Ammonia Recovery from Pig Slurry Using a Membrane Contactor—Influence of Slurry Pretreatment

Pig slurry contains sufficient amount of nitrogen, phosphorus, and potassium for plant growth. If appropriately administered, this could substitute significant amounts of fertilizer. However, excessive fertilization with slurry causes environmental problems. To reduce environmental issues, solid-liquid separation or anaerobic digestion is needed to obtain a better distribution of nutrients. Solid-liquid separation produces a solid fraction rich in phosphorus and a liquid fraction containing ammonia, potassium, and high water content. Therefore, further concentration of ammonia is desired for any practical use. In this study, ammonia membrane stripping was carried out using polypropylene membranes and the impact of temperature, flow velocities, and liquid fraction pretreatment on the membrane contactor performance was tested. Sieved liquid effluents from a decanter centrifuge, a screw press, an AL-2 system (flocculation and filtration), and an anaerobic digester were tested. Since the properties of these liquid effluents vary, they might affect ammonia recovery. Thus, it is essential to investigate which effluent is most suitable as a feed for a membrane contactor and what is the cost of preprocessing. The mean ammonia mass transfer coefficient at 30 °C was found to be equal to 17 ± 2 × 10−3 m h−1. At 50 °C, it was found to be equal to 29 ± 2 × 10−3 m h−1 for all the tested effluents. This means that sieving after slurry separation or anaerobic digestion alleviates the influence the solid-liquid separation has on ammonia membrane stripping. However, the cost evaluation showed that solid-liquid separation using a decanter centrifuge followed by sieve draining is the cheapest of the methods investigated.

Fully integrated ready-to-use paper-based electrochemical biosensor to detect nerve agents

Paper-based microfluidic devices are gaining large popularity because of their uncontested advantages of simplicity, cost-effectiveness, limited necessity of laboratory infrastructure and skilled personnel. Moreover, these devices require only small volumes of reagents and samples, provide rapid analysis, and are portable and disposable. Their combination with electrochemical detection offers additional benefits of high sensitivity, selectivity, simplicity of instrumentation, portability, and low cost of the total system. Herein, we present the first example of an integrated paper-based screen-printed electrochemical biosensor device able to quantify nerve agents. The principle of this approach is based on dual electrochemical measurements, in parallel, of butyrylcholinesterase (BChE) enzyme activity towards butyrylthiocholine with and without exposure to contaminated samples. The sensitivity of this device is largely improved using a carbon black/Prussian Blue nanocomposite as a working electrode modifier. The proposed device allows an entirely reagent-free analysis. A strip of a nitrocellulose membrane, that contains the substrate, is integrated with a paper-based test area that holds a screen-printed electrode and BChE. Paraoxon, chosen as nerve agent simulant, is linearly detected down to 3µg/L. The use of extremely affordable manufacturing techniques provides a rapid, sensitive, reproducible, and inexpensive tool for in situ assessment of nerve agent contamination. This represents a powerful approach for use by non-specialists, that can be easily broadened to other (bio)systems.

Development of Immunochromatography Incorporated with Electrochemical Systems for Detecting the Activity of Labeled Enzyme

Immunochromatography is a well-established technique and widely used as a practical kit for detection of various diagnoses for the initial screening of medical diagnoses. When a solution containing target analytes is added at the end of a membrane, the solution spontaneously migrates toward the other end of the membrane by capillary force. This automatic migration of the solution is combined with the capturing of analytes by the immunorecognition events. The target moleculses in the solutions flowing in the membrane arrived at the region immobilized with antibody and captured to form immunocomplexes. The antibody conjugated with the signal source is also migrated with target molecules to concentrate the signal source. The concentrated signal source can be detected by colorimetric or fluorescent measurements within 10 - 20 min. Moreover, the unreacted signal source was spontaneously removed to downstream in the membrane strips, and automatically discriminated from the captured molecules. Thus, the immunochromatography is a simple and rapid immunosensing system. A visual colorimetric measurement by necked eye is commonly utilized for the decision of positivity or negativity, but is of low sensitivity, and thus insufficient for quantitative analysis. Complete dark box and precisely arranged optical system are required to utilize the fluorescence detection for quantitative analysis. In this presentation, the electrochemical detection system was incorporated in lateral flow immunochromatographic assays for the quantitative and automatic determination of target molecules. The working electrode was placed at the downstream from the region immobilized with antibody. The hydrogen peroxide (redox species) generated by the labeled enzyme captured on the antibody immobilized region can flow in the downstream to arrive the electrode and be detected by the amperometry. The device for electrochemical immunochromatography consisted of a test strip (nitrocellulose membrane) with the antibody immobilization area and absorbent pad and acrylic plates incorporating Pt disk electrode (50 m) and poles for supporting the membranes. The silver wire was inserted through another plate to use as a pseudo-reference/counter electrode. Cyclic voltammetry of Fe(CN)6 4− flowing in the test strip was measured by using the device for immunochromatography. The steady-state oxidation current was observed at a region of positive potential due to the continuous supply of solution flow containing Fe(CN)6 4−. In addition, the oxidation current obtained without flow in the test strip is smaller than that obtained with flow. The redox species flowing in the test strip can be detected with the present system. Amperometry was also performed in the test strip with flow at different concentrations of Fe(CN)6 4−. The obtained steady-state current increased linearly with increasing the concentration of Fe(CN)6 4− in the flowing solution. Therefore, we would determine the concentration of redox species flowing in the test strip. Hydrogen peroxide generated by the reaction of labeled enzyme (glucose oxidase, GOx) was detected to demonstrate the determination of target molecules. The solution containing different concentrations of target analyte, mouse IgG was applied to the end of the test strip. When mouse IgG and GOx-labeled antibody arrived at the region immobilized with antibody, sandwich type of immunocomplex was formed at the region. The addition of the solution containing glucose that is the substrate of the labeled enzyme allows to producing hydrogen peroxide to detect captured mouse IgG and removing unreacted labeled enzyme to downstream. When glucose was added, the oxidation current increased gradually and reached at almost a steady-state. The current response increased with increasing concentration of mouse IgG. Thus, amount of the captured mouse IgG can be determined. The total measurement time required with the present system is around 20 min, which is equivalent to conventional immunochromatographic formats.Therefore, we can incorporate electrochemical quantitation in a simple immunosensing system for immunochromatography.

Evaluation of Human Semenogelin Membrane Strip Test for Species Cross-reactivity in Dogs.

Semenogelins are proteins originating in the seminal vesicle and are useful markers for the presumptive identification of human semen. Detection of semenogelin can be done with a commercially available membrane test. In this study, a commercially available membrane test for human semenogelin proteins was used to assess for cross-reactivity in dog bodily fluids to allow for the potential utilization for detection of human semen in dog bodily fluids. The authors analyzed canine semen and other bodily fluids, including urine, saliva, vaginal secretions, fecal material, and blood. They also examined the distribution of human semenogelin I transcripts in the canine testis, prostate, and several bodily fluids by reverse transcription polymerase chain reaction. No cross-reactivity was observed in the canine bodily fluids tested except for a single rectal swab, which was negative on a second test. Further testing should be done to validate the use of this kit for screening samples from dogs suspected to have been victims of sexual abuse.

Polydiacetylene-coated polyvinylidene fluoride strip aptasensor for colorimetric detection of zinc(II)

We report a new polydiacetylene (PDA) sensor strip for simple visual detection of zinc ions in aqueous solution. The specificity of this sensor comes from Zn2+ DNA aptamer probes conjugated onto PDA. Effects of aptamer length and structure on the sensitivity of PDA’s color transition were first investigated. PDA conjugated with the optimal aptamer sequence was then coated onto a strip of polyvinylidene fluoride membrane and photopolymerized by UV exposure. The newly developed sensor successfully exhibited a blue-to-red chromatic change in a semi-quantitative manner in response to zinc ions. No discernable change was observed in solutions containing other common ions. Advantages of this sensor include its ease of fabrication, high specificity, and equipment-free detection, all of which are desirable for in-field applications and use in resource-limited settings.

The efficacy of proliferative membrane stripping combined with retinal laser photocoagulation for the treatment of proliferative vitreoretinopathy on silicone oil-filled eyes

Objective To evaluate the efficacy of proliferative membrane stripping combined with retinal laser photocoagulation for the treatment of proliferative vitreoretinopathy ( PVR ) on silicone oil-filled eyes. Methods The data of 66 eyes of 66 patients with PVR after vitrectomy combined with silicone oil tamponade surgery from January 2013 to June 2015 in our hospital were retrospectively analyzed. These patients received proliferative membrane stripping combined with retinal laser photocoagulation. The visual acuity before and after the surgery, central macular thickness, retinal reattachment, the timing of silicone oil removal and postoperative complications were observed and analyzed. Results The retinas were reattached in all 66 eyes after the surgery and no serious complication occurred. The removal of the silicone oil was within 3 months in 39 eyes ( 59.09% ) and 4 to 6 months in 27 eyes (40.91%). The membrane stripping operation was performed 2 to 4 times in 10 eyes ( 15.15% ). The recurrent retinal detachment occurred after the oil removal in 2 eyes (3.03%) and the silicone oil tamponade surgery was performed again to reattach the retina. The postoperative visual acuity improved significantly compared with preoperative visual acuity and the difference was statistically significant (χ2=14.85, P=0.0019 ). Before the surgery the mean thickness of central macular area was (352.70 ± 55.52) μm. Three months after the surgery the thickness reduced to (324.37±49.74) μm and the difference was statistically significant (t=7.591, P=0.000 ). Conclusion Proliferative membrane stripping combined with retinal laser photocoagulation for PVR on silicone oil-filled eyes is exactly effective. Key words: Proliferative membrane stripping; Laser photocoagulation, retinal; Vitreoretinopathy, proliferative; Silicone oil-filled eyes; Efficacy

Rapid lateral-flow immunoassay for the quantum dot-based detection of puerarin

In this study, a rapid (within 10min) quantitative lateral-flow immunoassay using a quantum dots (QDs)-antibody probe was developed for the analysis of puerarin (PUE) in water and biological samples. The competitive immunoassay was based on anti-PUE monoclonal antibody conjugated with QDs (detection reagent). Secondary antibody was immobilized on one end of a nitrocellulose membrane (control line) and PUE-bovine serum albumin conjugate was immobilized on the other end (test line). In the quantitative experiment, the detection results were scanned using a membrane strip reader and a detection curve (regression equation: y=−0.11ln(x)+0.979, R2=0.9816) representing the averages of the scanned data was obtained. This curve was linear from 1 to 10μg/mL. The IC50 value was 75.58ng/mL and the qualitative detection limit of PUE was 5.8ng/mL. The recovery of PUE added to phosphate-buffered saline and biological samples was in the range of 97.38–116.56%. To our knowledge, this is the first report of the quantitative detection of a natural product by QDs-based immunochromatography, which represents a powerful tool for rapidly screening PUE in plant materials and other biological samples.

P-B12 Comparison of HPV genotyping using roche linear array with Spf10-Deia Lipa 25 Version 1 in Nigerian women presenting for cervical cancer screening

Background: There is need for accurate genotyping of Human Papillomavirus (HPV) infections because persistent infection with High- Risk HPV (hrHPV) is a necessary cause for CIN2+. It is essential therefore to evaluate various genotyping assays that have been developed for this very important endeavor within the context of epidemiological studies of HPV infections in different parts of the world. In this study, we compare HPV genotyping using the SPF10 DEIA LiPA25 version 1 with Roche Linear Array HPV genotyping assays in Nigerian women attending cervical cancer screening program. Methods: One hundred and five women were tested for HPV infection using Roche Linear array HPV genotyping test, a PCR amplification technique on target DNA followed by hybridization using reverse line blot system and SPF10 DEIA genotyping system followed by LiPA25 version 1 genotyping, a 28 oligonucleotide probes that recognize 25 different types tailed with poly (dT) and immobilized as parallel lines onto membrane strips. Results: HPV genotypes were detected in 36% (38/105) of the samples using SPF10 and 23% (24/105) of the samples using linear array. Some 65% (68/105) samples showed absolute agreement between the assays (concordant), 27% (28/105) samples were discordant while 9% (9/105) samples showed correspondence for some but not all genotypes detected on both strips (compatible). Conclusions: There was 65% absolute agreement between the two assays and the SPF10/LiPA assay detected more HPV infections than the linear array.

Porous membrane strip microsampling: a dried biofluid collection format and application for quantitative enzyme immunoassay

Applicability of a new and simple membrane-strip microsampling format for the analysis of human blood serum in a strip-dried form for the presence of a range of model low and high molecular weight analytes by ELISA was demonstrated.

Antepartum Membrane Stripping in GBS Carriers, Is It Safe? (The STRIP-G Study).

ObjectiveStripping of the membranes is an established and widely utilized obstetric procedure associated with higher spontaneous vaginal delivery rates, reduced need for formal induction of labor and a lower likelihood of post-term pregnancy. Due to the theoretical concern of bacterial seeding during the procedure many practitioners choose not to sweep the membranes in Group B Streptococcus (GBS) colonized patients. We conducted ‘the STRIP-G study’ in order to determine whether maternal and neonatal outcomes are affected by GBS carrier status in women undergoing membrane stripping.Study designWe conducted a prospective study in a tertiary referral center, comparing maternal and neonatal outcomes following membrane stripping among GBS-positive, GBS-negative, and GBS-unknown patients. We compared the incidence of composite adverse neonatal outcomes (primary outcome) among the three study groups, while secondary outcome measure was composite adverse maternal outcomes.ResultsA total of 542 women were included in the study, of which 135 were GBS-positive, 361 GBS-negative, and 46 GBS-unknown status. Demographic, obstetric, and intra-partum characteristics were similar for all groups. Adverse neonatal outcomes were observed in 8 (5.9%), 31 (8.6%), and 2 (4.3%) in the GBS-positive, GBS-negative, and unknown groups, respectively (P = 0.530), (Odds Ratio between GBS-Positive vs. GBS-Negative groups 0.67 (95%, CI = 0.30–1.50)); while composite adverse maternal outcomes occurred in 9 (6.66%), 31 (8.59%), and 5 (10.87%) in the GBS-positive, GBS-negative, and unknown groups, respectively (P = 0.617).ConclusionsAntepartum membrane stripping in GBS carriers appears to be a safe obstetrical procedure that does not adversely affect maternal or neonatal outcomes.

Development of an immunochromatographic test strip for simultaneous qualitative and quantitative detection of ochratoxin A and zearalenone in cereal.

Ochratoxin A (OTA) and zearalenone (ZEN) are natural products of filamentous fungi that are harmful to humans and animals exposed to them even in extremely low concentration. The immunochromatographic test strip has become a popular diagnostic tool for detecting analytes. Its major advantages are that results can be obtained within 5-10 min, all needed reagents are included in the strip and it can be used to detect OTA and ZEN contamination in spots. In this study a colloidal gold-based immunochromatographic test strip of competitive format was developed for the rapid simultaneous qualitative and quantitative detection of OTA and ZEN in corn and other cereals. The test strip results with the naked eye showed that the sensitivities were 6 µg kg(-1) OTA and 20 µg kg(-1) ZEN in cereal, while those with a TSR3000 membrane strip reader showed that the IC50 values of OTA and ZEN were 1.7905 and 4.3514 ng mL(-1) and the lower detection limit (LDL) values were 0.7697 and 1.2000 µg kg(-1) respectively. These results were confirmed by high-performance liquid chromatography. The immunochromatographic test strip developed in this study could be used for the rapid simultaneous, qualitative and quantitative screening of OTA and ZEN in corn samples. © 2015 Society of Chemical Industry.

Limit-cycle oscillations of a pre-tensed membrane strip

The paper presents a computational and experimental study of the nonlinear aeroelastic response of a pre-tensed, high aspect-ratio, thin membrane strip. The goal of the study is to derive and validate a computational model that can be used for analysis and design of membrane strips, for the purpose of energy harvesting from flutter at low airspeeds. The mathematical model is based on a pre-tensed-beam model, accounting for bending and torsional stiffening effects due to pretension and large deformations. The aerodynamic model is a potential flow model. The equations of motion are written as a set of nonlinear ordinary differential equations, using Galerkin’s method, and are simulated numerically. The nonlinear aeroelastic model is used to study the oscillation characteristics of the membrane strip in the various stability regions. The effects of the initial pretension and non-linear stiffening on the energy-harvesting potential of the system are studied. The combined effect of the preload on the flutter onset speed, on the flutter frequency and amplitude, and on the loss of orbital stability, indicate that an optimal preload can be determined based on the intended airspeed range for energy harvesting. A series of wind tunnel tests are conducted, in which the flutter onset velocity, and the post-flutter frequencies and amplitudes are measured. Good agreement between the experimental data and computational results validate the computational model.